Pavel G. Talalay

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My first review of mechanical drilling in ice was published more than 25 years ago as a section of a textbook for students at the St. Petersburg Mining Institute (Bobin et al. 1988). At that time ...... by a stepper motor is used to push a 5 mm diameter cone with a 60° ...... Ohio State University; About our Photos, n.d.). 4.3 Core ...
Springer Geophysics

Pavel G. Talalay

Mechanical Ice Drilling Technology

Springer Geophysics

The Springer Geophysics series seeks to publish a broad portfolio of scientific books, aiming at researchers, students, and everyone interested in geophysics. The series includes peer-reviewed monographs, edited volumes, textbooks, and conference proceedings. It covers the entire research area including, but not limited to, geodesy, planetology, geodynamics, geomagnetism, paleomagnetism, seismology, and tectonophysics.

More information about this series at http://www.springer.com/series/10173

Pavel G. Talalay

Mechanical Ice Drilling Technology

123

Pavel G. Talalay Polar Research Center, College of Construction Engineering Jilin University Changchun China

Springer Geophysics ISBN 978-981-10-0559-6 DOI 10.1007/978-981-10-0560-2

ISBN 978-981-10-0560-2

(eBook)

Jointly published with Geological Publishing House, Beijing Library of Congress Control Number: 2016931192 © Geological Publishing House, Beijing and Springer Science+Business Media Singapore 2016 This work is subject to copyright. All rights are reserved by the Publishers, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publishers, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publishers nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. Printed on acid-free paper This Springer imprint is published by SpringerNature The registered company is Springer Science+Business Media Singapore Pte Ltd.

To strive, to seek, to find, and not to yield Alfred Tennyson

Preface

This book was written for the purpose of providing a review of mechanical ice drilling technology, including the design, parameters, and performance of various tools and drills for making holes in snow, firn, and ice. Drilling in glaciers began more than 170 years ago, but incredible progress in the development of ice drilling tools and devices occurred in the period of 1950–1970, when the modern vision of ice drilling technology was developed. The past 20– 30 years have seen the expansion of new innovative solutions in ice drilling instrumentation. This seems to be an appropriate time to review older and more recent developments. My first review of mechanical drilling in ice was published more than 25 years ago as a section of a textbook for students at the St. Petersburg Mining Institute (Bobin et al. 1988). At that time, scientists in the USSR worked under conditions of limited information (even scientific), and all papers regarding different aspects of ice drilling were gleaned. For example, one of the most popular journals among ice-core scientists, the “Journal of Glaciology,” was only available in one Soviet public library, the V.I. Lenin Library in Moscow. During the last decades, I had continued to collect information, which is now much easier as a result of globalization and the availability of Internet resources, and I have moved forward to gain my own experience in ice drilling. This book does not claim to be a complete review of the devices and tools used for mechanical drilling in ice; even though the reference list contains more than 500 sources, there are undoubtedly additional published or unpublished data that could still be found. I am grateful to H. Ueda, N.I. Vasiliev, L. Augustin, S. Hansen, F. Wilhelms, V. Zagorodnov, J. Fitzpatrick, H. Motoyama, J. Schwander, J.Ö. Bjarnason, S. Kipfstuhl, J. Johnson, O. Alemany, G.P. Talalay, N. Zhang, X. Fan, and other experts for providing pictures, reports, and other materials. I would like to thank Y. Sun for the continuing support during the preparation of this book, along with Y. Yang, who provided much help with the publication procedure. The completion of the manuscript would not have been possible without financial support from the “Chinese Polar Environment Comprehensive Investigation and Assessment Programmes” (CHINARE 2014-02-02, 2014-04-02 and 2015-04-02), National Science Foundation of China (Project No. 41327804), Ministry of Land and Resources of China (Project No. 201311041) and “The Recruitment Program of Global Experts” (also called “The Thousand Talents Program”) organized by the Central Coordination Committee on the Recruitment of Talents, China. This book is dedicated to the researchers and engineers who stood at the origin of modern ice drilling technology and sadly passed away in the recent past–B.B. Kudryashov, N. Gundestrup, A.V. Krasilev, N.E. Bobin, S. Johnsen, A.M. Shkurko, and B.S. Moiseev. I was very pleased and honored to have the opportunity to work with them and appreciated their salutiferous lessons. I selected the final line of Alfred Tennyson’s poem “Ulysses” as an

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epigraph to this book because a hundred years ago it was inscribed on a cross at Observation Hill, Antarctica, to commemorate explorer Robert Scott and his party, and since that time has become a mantra for all polar explorers. Changchun, China February 2015

Pavel G. Talalay

Reference Bobin NE, Vasiliev NI, Kudryashov BB et al (1988) Mekhanicheskoye burenie skvazhin vo l’du [Mechanical Drilling in Ice]. Leningrad, Leningrad Mining Institute [In Russian]

Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction to Ice Drilling Technology . . . 1.1 Ice Drilling Targets and Aims . . . . . . 1.2 Structure of Ice Sheets and Glaciers . . 1.3 Classification of Ice Drilling Methods . References. . . . . . . . . . . . . . . . . . . . . . . . .

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Yearly History of Ice Drilling from Nineteeth to the First Half of Twentieth Century . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3

Direct-Push Drilling . . . . . . . . . . . . . . . . . . 3.1 Drive Sampling . . . . . . . . . . . . . . . . . 3.1.1 Basic Principles . . . . . . . . . . . 3.1.2 Mt. Rose Sampler . . . . . . . . . . 3.1.3 Utah Snow Sampler . . . . . . . . 3.1.4 Federal Snow Sampler . . . . . . . 3.1.5 Bowman Sampler . . . . . . . . . . 3.1.6 Rosen Sampler . . . . . . . . . . . . 3.1.7 Large Diameter Snow Samplers 3.1.8 Vibratory Drill . . . . . . . . . . . . 3.2 Penetrative Testing . . . . . . . . . . . . . . . 3.2.1 Ski Pole Penetrometer . . . . . . . 3.2.2 Ram Penetrometer. . . . . . . . . . 3.2.3 Snow Resistograph . . . . . . . . . 3.2.4 Digital Thermo-Resistograph . . 3.2.5 Snow Micro-Penetrometer . . . . 3.2.6 SABRE Probe . . . . . . . . . . . . 3.2.7 Cone Penetrometer Testing. . . . 3.3 Summary . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . .

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Hand- and Power-Driven Portable Drills . . . . . . . . . . . 4.1 Noncoring Augers. . . . . . . . . . . . . . . . . . . . . . . . 4.1.1 SFFEL Noncoring Auger . . . . . . . . . . . . . 4.1.2 SIPRE/CRREL Ice Thickness Kit . . . . . . . 4.1.3 Kovacs Ice Thickness Kit. . . . . . . . . . . . . 4.1.4 AARI Portable Sled-Mounted Drilling Rig . 4.1.5 Handheld Coal-Boring Augers . . . . . . . . . 4.1.6 Ice Augers for Winter Fishing . . . . . . . . . 4.2 Noncoring “Piston” Drills . . . . . . . . . . . . . . . . . .

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4.3

Core Augers. . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 General Principles . . . . . . . . . . . . . . 4.3.2 SFFEL Auger . . . . . . . . . . . . . . . . . 4.3.3 SIPRE Auger . . . . . . . . . . . . . . . . . 4.3.4 CRREL Auger . . . . . . . . . . . . . . . . 4.3.5 Rand Auger . . . . . . . . . . . . . . . . . . 4.3.6 Big John 12″ Auger . . . . . . . . . . . . 4.3.7 PICO Lightweight Auger . . . . . . . . . 4.3.8 Kovacs Auger. . . . . . . . . . . . . . . . . 4.3.9 IGAS Hand Auger . . . . . . . . . . . . . 4.3.10 Swiss Hand Auger . . . . . . . . . . . . . 4.3.11 UCPH Hand Auger . . . . . . . . . . . . . 4.3.12 “Prairie Dog” Auger . . . . . . . . . . . . 4.3.13 “Sidewinder” . . . . . . . . . . . . . . . . . 4.3.14 IDDO Hand Auger . . . . . . . . . . . . . 4.4 Core Drills with Teeth and Annular Bits . . . . 4.4.1 Taku Glacier Hand Drill . . . . . . . . . 4.4.2 Canadian Portable Ice Drill . . . . . . . 4.4.3 Tsykin’s Hand Drill . . . . . . . . . . . . 4.4.4 5th CAE Drill. . . . . . . . . . . . . . . . . 4.4.5 Ice Core Drill with Annular Bit PI-8 . 4.5 Mini Drills . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.1 Livingston Island Mini Drill . . . . . . . 4.5.2 Chipmunk Drill . . . . . . . . . . . . . . . 4.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Percussion Drills. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Cable-Tool Drill Rigs . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.1 IGAS Cable-Tool Rig . . . . . . . . . . . . . . . . . . . 5.1.2 Cable-Tool of California Institute of Technology 5.1.3 Star Iron Works Cable-Tool . . . . . . . . . . . . . . . 5.2 Pneumatic Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Rotary-Percussion Drills . . . . . . . . . . . . . . . . . . . . . . . 5.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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6

Conventional Machine-Driven Rotary Drill Rigs . . . . . . . . . 6.1 Dry Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.1 Expéditions Polaires Françaises in Greenland . . . 6.1.2 Baffin Island Expedition . . . . . . . . . . . . . . . . . 6.1.3 Norwegian-British-Swedish Antarctic Expedition 6.1.4 Mirny Station, Antarctica . . . . . . . . . . . . . . . . . 6.2 Auger Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.1 Mirny Station, Antarctica . . . . . . . . . . . . . . . . . 6.2.2 McMurdo Station, Antarctica . . . . . . . . . . . . . . 6.2.3 Amundsen–Scott Station, South Pole . . . . . . . . . 6.2.4 Subglacial Lake Ellsworth Camp. . . . . . . . . . . . 6.3 Commercial Drill Rigs for Ice Fishing . . . . . . . . . . . . . . 6.4 Air Rotary Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.1 Mirny, Antarctica . . . . . . . . . . . . . . . . . . . . . . 6.4.2 Site 2, Greenland . . . . . . . . . . . . . . . . . . . . . .

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6.4.3 Byrd Station, Antarctica. . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.4 Little America V, Antarctica. . . . . . . . . . . . . . . . . . . . . . . 6.4.5 Franz Josef Land, Russian Arctic . . . . . . . . . . . . . . . . . . . 6.4.6 Base Roi Baudouin, Antarctica . . . . . . . . . . . . . . . . . . . . . 6.5 Rotary Drilling with Fluid Circulation . . . . . . . . . . . . . . . . . . . . . . 6.5.1 Taku Glacier, Alaska . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.2 Mer de Glace, French Alps . . . . . . . . . . . . . . . . . . . . . . . 6.5.3 South Leduc Glacier, British Columbia . . . . . . . . . . . . . . . 6.5.4 McMurdo Station, Antarctica . . . . . . . . . . . . . . . . . . . . . . 6.6 Wire-Line Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.1 International Antarctic Glaciological Project, East Antarctica 6.6.2 Ross Ice Shelf Project . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.3 Base Druzhnaya, Antarctica . . . . . . . . . . . . . . . . . . . . . . . 6.6.4 Black Rapids Glacier, Alaska . . . . . . . . . . . . . . . . . . . . . . 6.6.5 Isua Greenstone Belt, Southwestern Greenland . . . . . . . . . . 6.6.6 Foremore Glacier, British Columbia, Western Canada . . . . . 6.6.7 Rapid Access Ice Drill (RAID) . . . . . . . . . . . . . . . . . . . . . 6.6.8 Agile Sub-ice Geological (ASIG) Drill. . . . . . . . . . . . . . . . 6.7 Drilling in Rock Glaciers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.1 Overview of Projects Using Conventional Drilling Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.2 Koci Drill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Flexible Drill-Stem Drill Rigs . . . . . . . . . . 7.1 Rapid Shallow Drill Rigs . . . . . . . . . . 7.2 Rapid-Access Drill Rigs. . . . . . . . . . . 7.2.1 Thermomechanical Drill. . . . . 7.2.2 Coiled-Tubing Drill Rigs . . . . 7.2.3 RADIX . . . . . . . . . . . . . . . . 7.2.4 SUBGLACIOR Drilling Probe 7.3 Summary . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . .

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Cable-Suspended Electromechanical Auger Drills. . . . . 8.1 Basic Principles . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 University of Iceland (UI) Drill . . . . . . . . . . . . . . 8.3 University of Bern (UB) Drills . . . . . . . . . . . . . . . 8.3.1 Rufli Drill . . . . . . . . . . . . . . . . . . . . . . . 8.3.2 Further Improved UB Drills . . . . . . . . . . . 8.4 CRREL Drill . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 Institute of Low Temperature Science (ILTS) Drills 8.5.1 First Prototypes. . . . . . . . . . . . . . . . . . . . 8.5.2 ID-140 Drill . . . . . . . . . . . . . . . . . . . . . . 8.5.3 ILTS-140 Drill . . . . . . . . . . . . . . . . . . . . 8.5.4 MID-140 Drill . . . . . . . . . . . . . . . . . . . . 8.5.5 Portable ILTS-130 and -100 Drills . . . . . . 8.5.6 ILTS-130E(F) and ILTS-150 Drills . . . . . . 8.5.7 New Portable ILTS Drill . . . . . . . . . . . . .

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8.6 8.7

University of Copenhagen (UCPH) Drill . . . . . . . . . . . . . . . . . . . Laboratoire de Glaciologie et Géophysique de l’Environnement (LGGE) Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.8 National Hydrology Research Institute (NHRI) Drill . . . . . . . . . . . 8.9 Polar Ice Coring Office (PICO) 4″ Drill. . . . . . . . . . . . . . . . . . . . 8.10 Alfred-Wegener Institute (AWI) Drills . . . . . . . . . . . . . . . . . . . . . 8.11 Australian National Antarctic Research Expedition (ANARE) Drill . 8.12 BZXJ Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.13 Geo Tecs Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.13.1 Geo Tecs Prototype Shallow Drill . . . . . . . . . . . . . . . . . . 8.13.2 Further Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . 8.13.3 Field Testing and Operations . . . . . . . . . . . . . . . . . . . . . 8.14 Hilda/Simon/Eclipse Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.14.1 Hilda/Simon Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.14.2 Eclipse Drill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.14.3 Field Testing and Coring . . . . . . . . . . . . . . . . . . . . . . . . 8.14.4 Badger-Eclipse Drill . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.15 Byrd Polar Research Center (BPRC) Drills . . . . . . . . . . . . . . . . . 8.16 British Antarctic Survey (BAS) Drills . . . . . . . . . . . . . . . . . . . . . 8.16.1 BAS/IMAU Drill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.16.2 Rapid-Access Isotope Drill . . . . . . . . . . . . . . . . . . . . . . . 8.17 FELICS Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.17.1 3″ Drill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.17.2 “Backpack Drill” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.18 Blue Ice Drill (BID) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.18.1 BID General Fescription . . . . . . . . . . . . . . . . . . . . . . . . 8.18.2 Operation and Performance . . . . . . . . . . . . . . . . . . . . . . 8.18.3 BID-Deep System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.19 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

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Cable-Suspended Electromechanical Drills with Bottom-Hole Circulation . 9.1 CRREL Electromechanical Drill . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.1 Drilling Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.2 Camp Century, Greenland . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.3 Byrd Station, Antarctica. . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 ISTUK Drill. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2.1 Drill System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2.2 Dye 3, Greenland (GISP) . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2.3 Summit, Greenland (GRIP) . . . . . . . . . . . . . . . . . . . . . . . . 9.2.4 Law Dome, Antarctica . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3 LGGE Electromechanical Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4 PICO-5.2″ Electromechanical Drill . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.1 Drill System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.2 Summit, Greenland (GISP2) . . . . . . . . . . . . . . . . . . . . . . . . 9.4.3 Taylor Dome, Antarctica . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.4 Siple Dome, Antarctica . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5 KEMS Electromechanical Drill . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.1 Drill System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.2 Severnaya Zemlya, Russian Arctic . . . . . . . . . . . . . . . . . . . 9.5.3 Vostok Station, Antarctica . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 JARE Electromechanical Drill . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9.6.1 Drill System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.2 Preliminary Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.3 First Deep Ice Coring Project at Dome F, Antarctica . . . 9.6.4 Second Deep Ice Coring Project at Dome F, Antarctica . 9.6.5 Kunlun Station (Dome A), Antarctica . . . . . . . . . . . . . 9.7 Hans Tausen (HT) Electromechanical Drill and Its Modifications 9.7.1 Basic Drill System . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7.2 Hans Tausen Ice Cap, Greenland . . . . . . . . . . . . . . . . 9.7.3 NorthGRIP, Greenland. . . . . . . . . . . . . . . . . . . . . . . . 9.7.4 EPICA Dome C, Antarctica . . . . . . . . . . . . . . . . . . . . 9.7.5 EPICA-DML, Kohnen Station, Antarctica . . . . . . . . . . 9.7.6 Berkner Island, Antarctica . . . . . . . . . . . . . . . . . . . . . 9.7.7 Talos Dome, Antarctica (TALDICE) . . . . . . . . . . . . . . 9.7.8 Flade Isblink Ice Cap, Greenland . . . . . . . . . . . . . . . . 9.7.9 NEEM Deep Ice Core Drilling, Greenland . . . . . . . . . . 9.7.10 James Ross Island, Antarctica. . . . . . . . . . . . . . . . . . . 9.7.11 Fletcher Promontory, Antarctica . . . . . . . . . . . . . . . . . 9.7.12 Roosevelt Island, Antarctica . . . . . . . . . . . . . . . . . . . . 9.7.13 NEEM, Greenland (UCPH Intermediate-Depth Ice Core Drilling System) . . . . . . . . . . . . . . . . . . . . . 9.7.14 Aurora Basin North, Antarctica. . . . . . . . . . . . . . . . . . 9.7.15 Renland Ice Cap, Greenland . . . . . . . . . . . . . . . . . . . . 9.7.16 Summit, Greenland (IDDO Intermediate-Depth Drill) . . 9.7.17 South Pole, Antarctica (SPICE). . . . . . . . . . . . . . . . . . 9.8 IDRA Drill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9 DISC Electromechanical Drill. . . . . . . . . . . . . . . . . . . . . . . . . 9.9.1 Drill System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9.2 Field Testing at Summit, Greenland . . . . . . . . . . . . . . 9.9.3 WAIS Divide, Antarctica . . . . . . . . . . . . . . . . . . . . . . 9.9.4 Replicate Coring, WAIS Divide, Antarctica . . . . . . . . . 9.10 IBED Drill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.11 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Drilling Challenges and Perspectives for Future Development . 10.1 Low-Temperature Drilling Fluids . . . . . . . . . . . . . . . . . . 10.1.1 Drilling Fluid Compositions . . . . . . . . . . . . . . . . 10.1.2 ESTISOL™ 240/COASOL™ Drilling Fluid . . . . . 10.1.3 ESTISOL™ 140 Drilling Fluid . . . . . . . . . . . . . . 10.1.4 Low-Molecular Weight Dimethyl Siloxane Oils . . 10.1.5 Low-Molecular Weight Esters. . . . . . . . . . . . . . . 10.1.6 Kerosene-Based Drilling Fluids Mixed with Fourth-Generation Foam-Expansion Agents. . 10.2 Ice Drilling Under Complicated Conditions . . . . . . . . . . . 10.2.1 Permeable Snow-Firn . . . . . . . . . . . . . . . . . . . . 10.2.2 Brittle Ice Zone . . . . . . . . . . . . . . . . . . . . . . . . 10.2.3 Warm Ice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.4 Debris-Containing Ice . . . . . . . . . . . . . . . . . . . . 10.2.5 Bedrock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.6 Elimination of Sticking Drills . . . . . . . . . . . . . . . 10.3 Advanced Drilling Systems . . . . . . . . . . . . . . . . . . . . . .

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10.3.1

Rapid-Access Ice Drilling Systems for Subglacial Bedrock Drilling . . . . . . . . . . . . . . . . . . . . . . . . 10.3.2 Sidewall Drilling. . . . . . . . . . . . . . . . . . . . . . . . 10.3.3 Automated Drilling Systems . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Appendix A: Records of Mechanical Drilling in Ice. . . . . . . . . . . . . . . . . . . . . .

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Appendix B: Abbreviations of Institutes, Organizations, and Projects . . . . . . . .

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1

Introduction to Ice Drilling Technology

1.1 Ice Drilling Targets and Aims It is well known that ice is the solid phase of water. The molecules in solid ice may be arranged in numerous different ways, called phases, depending on the temperature and pressure. At temperatures below 0 °C and above about −80 ° C, at standard atmospheric pressure, water molecules are arranged in orderly repetitive positions to form a crystalline solid with hexagonal symmetry, which is the most abundant of the varying solid phases on the Earth’s surface and is referred to as normal hexagonal ice, namely “ice Ih” (Furukawa 2011). In the natural environment, it forms ice sheets, ice caps, mountain glaciers, ice shelves, ground ice, icebergs, and river and sea ice. An ice sheet is a mass of land ice, continental or subcontinental in extent, and thick enough to cover most of the underlying bedrock topography (Bentley et al. 2007). Its shape is mainly determined by the dynamics of its outward flow. There are only two ice sheets in the modern world, on Greenland and Antarctica (Fig. 1.1). These cover approximately 11 % of the entire global surface, with the surface areas of the Greenland and Antarctic Ice Sheets measuring 1,710,000 and 14,000,000 km2, respectively (Graham 2011). They act as important stores for over 80 % of the world’s fresh water. During glacial periods, there were other ice sheets. A thick floating platform of ice that forms where an ice sheet flows down to a coastline and onto the ocean surface is called an ice shelf. Ice caps are smaller masses of perennial ice occupying parts of Arctic Russia, Canada, Iceland, and other high latitude regions (Fig. 1.2). Surface area of ice caps is less than 50,000 km2 (Bhutiyani 2011). Ice caps are not constrained by topographical features (i.e., they will lie over the top of mountains). By contrast, ice masses of similar size that are constrained by topographical features are known as ice fields. The dome of an ice cap is usually centered on the highest point of a massif. Ice flows away from this high point towards the ice cap’s periphery.

Mountain glaciers, also known as alpine glaciers, form on the crests and slopes of mountains (Fig. 1.3). There are several subtypes of mountain glaciers: (1) cirque glaciers, which are bowl-shaped hollows at the head of a valley; (2) valley glaciers, which reside in an area eroded by a stream; (3) piedmont glaciers, which are formed by multiple valley glaciers coming together; and (4) tidewater glaciers, which terminate in the sea. The term “rock glacier” has been used for various complex landforms in cold mountain areas, and can be defined as a mass of rock, ice, snow, mud, and water. Other occurrences of ice on land include the different types of ground ice associated with permafrost, which is permanently frozen soil common to very cold regions (Rafferty 2011). In the ocean waters of the polar regions, icebergs occur when large masses of ice break off from glaciers or ice shelves and drift away. The freezing of seawater in these regions results in the formation of sheets of sea ice known as pack ice. During periods of maximal extension, sea ice covers about 7 % of the Earth’s surface and about 12 % of the world’s oceans. During the winter months, similar ice bodies form on lakes and rivers in many parts of the world. Although the main content of this book describes mechanical methods of drilling in ice sheets and glaciers, some of these can also be applied to making holes in sea and water ice. The average temperature of Earth’s atmosphere and oceans from 1850–1899 to 2001–2005 increased by 0.76 °C (IPCC 2007), and the rate of warming has increased over the past 25 years, resulting in the melting of ice on land and sea. The vast polar ice sheets are shrinking as our climate becomes warmer. Global warming has led to the rapid and ubiquitous retreat of mountain glaciers, so much so that some glaciers have disappeared completely, and the existence of a great number of the remaining glaciers of the world is threatened. Reductions in the thickness and extent of Arctic sea ice have been observed over the past few decades, and the trend of shrinking Arctic sea ice cover is expected to continue.

© Geological Publishing House, Beijing and Springer Science+Business Media Singapore 2016 P.G. Talalay, Mechanical Ice Drilling Technology, Springer Geophysics, DOI 10.1007/978-981-10-0560-2_1

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Introduction to Ice Drilling Technology

Fig. 1.3 Black Rapids Glacier is a surge-type valley glacier in Alaska (Black Rapids Glacier, Alaska 2010)

Fig. 1.1 Two white spots on the Earth’s surface showing Greenland and Antarctic Ice Sheets (Transverse Mercator Projection 2013)

Fig. 1.2 Vatnajökull is typical example of ice cap in Iceland (Williams and Ferrigno 2012)

Minimizing the disruptions caused by climate change requires the ability to predict the response of the future climate to natural and anthropogenic forces on timescales of months to centuries. One of the ways the scientific community develops this understanding is studying the Earth’s climate history. By learning how and why the climate

changed in the past, we will be able to make better predictions about how the climate will change in the future. Ice sheets contain well-ordered accumulations of ancient ice that fell as snow years to millions of years ago (Fig. 1.4). The dust particles, soluble chemicals, and gases trapped in the ice are routinely used to study how the climate system operated in the past. Ice-core data have become central to our understanding of climate change in the past, and to assessments of possible future climate change. Predicting the movements of glaciers and the rate at which the ice in glaciers and ice sheets will deform under a given applied stress is important for predicting ice mass balance changes. Systematic observations using boreholes provide a means for directly studying the viscoplastic deformation (“creep”) of ice. The characteristics and behaviors of glaciers are determined to a large extent by the properties of the material from which they are made. Thus, an understanding of the properties of ice is a necessary basis for a sound understanding of glaciers. Ice cores make it possible to study the physical properties and structure of natural ice recovered from different depths, which have an influence on glacier behavior, but are also controlled by it. The visible and unseeable (but detectable by electrical resistance measurements) ash layers in an ice core are linked to volcanic eruptions and forest fires and provide an opportunity to identify and date natural catastrophes on timescales from decades to hundreds of millennia (Fig. 1.5). Another particularly exciting aspect of glacier research is the prospect of finding new forms of life inhabiting the cold ice, subglacial till, vents, or cracks in bedrock, as well as subglacial lakes. Significant numbers of viable ancient microorganisms are known to be present within the ice

1.1 Ice Drilling Targets and Aims

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Fig. 1.4 Ice sheet formation and flow (Bentley et al. 2007)

Fig. 1.5 Core recovered with naked-eye interlayer with particles of volcanic origin from depth of 1886 m at NGRIP-2 borehole, Greenland, 2000 (Photo S. Johnsen; North GRIP ice-core drilling project)

(Bobin et al. 1994). Moreover, it is possible to vivify old microorganisms because of the natural phenomenon of long-term anabiosis (Fig. 1.6). These have been isolated from cores at temperatures as low as −55 °C. The age of the cells corresponds to the longevity of the permanently frozen state of the soils, with the oldest cells dating back approximately 5 million years ago found in Antarctic ice-free areas. A unique environment can be found beneath an ice sheet, which plays a key role in the dynamics of the overlying ice sheet. Samples of basal and subglacial material contain important paleoclimatic and paleoenvironmental records, provide a unique habitat for life, and give significant information on sediment deformation beneath glaciers and its

Fig. 1.6 Microorganisms discovered in ice from depth of 2395 m, Vostok Station, Antarctica (enlarged ×14,000) (Bobin et al. 1994)

coupling to the subglacial hydraulic system, subglacial geology, and tectonics. The International Partnerships on Ice Coring Sciences (IPICS) was established in 2004 (IPICS 2005) to coordinate the scientific efforts of the ice-core community over the next decades. The IPICS is a group that represents 23 nations (Australia, Austria, Belgium, Brazil, Canada, China, Denmark, Estonia, France, Germany, India, Italy, Iceland, Japan, Korea, Netherlands, New Zealand, Norway, Russia, Sweden, Switzerland, the United Kingdom, and the United States) and is composed of ice-core scientists and drilling engineers. The IPICS has identified scientific and technical focus areas for the ice community for the next 10–20 years. The five major recommendations of the IPICS are as follows:

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1. Retrieve longest possible Antarctic ice-core climate record longer than 1.2 million years (IPICS “Oldest Ice”); this program will provide insights into the way future climate will respond to changes in the distribution of solar heating by examining how natural changes, driven by changes in the Earth’s orbit, evolved over this long time frame. 2. Retrieve longest possible Arctic ice-core climate record, with the specific goal of completely penetrating ice deposited the last time the Earth was in a warm (interglacial) state like today; this program will provide critical insights into the natural variability of our current climate and, by elucidating how the last warm period ended, may yield information on how the current warm period will end. 3. Collect a spatial 2000-year array (IPICS “2k Array”): a network of ice-core climate and climate forcing records for the last two millennia that can give answers about the present and future climate change depending on natural climate variability. 4. Collect 40,000-year network (IPICS “40k Array”) of bipolar records of climate forcing and response to understand the reasons for changes in greenhouse gas concentrations, aerosol loads, sea level, and ice masses, as well as their relationships to atmospheric and ocean circulation. 5. Improve ice coring methods with a focus on improving drilling fluids, core quality, drilling efficiency, and replicate coring methods. Water (or ice) is actually the most abundant polyatomic compound in the universe. There is a certain amount of ice on almost all of the known moons and planets. Europa, which is the sixth closest moon of the planet Jupiter, is believed to be mostly covered by water and ice with a probable thickness of several kilometers (10–30 km). Mars has two permanent polar ice caps. Radar measurements of the Martian north polar ice cap found the volume to be 821,000 km3 (Fig. 1.7) (Barlow 2008). That is nearly equal to one-third of the Earth’s Greenland Ice Sheet. The Martian south polar cap is much smaller than the one in the north. It is 400 km in diameter, compared to the 1100 km diameter of the northern cap. Extraterrestrial ice is an important target for astrobiologists for two reasons (Zacny et al. 2009). First, ice can provide a source of liquid water if the pressure and temperature conditions are suitable. Second, ice can encase and preserve biological evidence of past life. For a drill to be useful under extraterrestrial conditions, it needs to overcome the challenges that are involved with operation at such remote locations.

1

Introduction to Ice Drilling Technology

Fig. 1.7 North Polar ice cap on the Mars taken by NASA’s Mars Reconnaissance Orbiter, March 5, 2008 (Credit: NASA/JPL/Malin; Mars Reconnaissance Orbiter, 2008)

1.2 Structure of Ice Sheets and Glaciers A fall of snow on a glacier is the first step in the formation of glacier ice, a process that is often long and complex (Cuffey and Paterson 2010). How snow changes into ice, and the time the transformation takes, depends on the temperature. Snow develops into ice much more rapidly on glaciers in temperate regions, where periods of melting alternate with periods when wet-snow refreezes, compared to central Antarctica, where the temperature remains well below the freezing point throughout the year. There are two main types of glacier formation methods. Dry-snow accumulation occurs in regions where the surface never melts, even in the summer, and the snowpack remains dry. Dry-snow accumulation takes place only in the interiors of Greenland and Antarctica and near the summits of the very highest mountains elsewhere. As snow is compressed under the weight of new snow accumulating above, snowflakes turn into firn and eventually ice (Fig. 1.8). The transition between these stages is defined by density (Bertler 2011). Snow is defined as lighter than 550 kg/m3, whereas ice has a density of 830 kg/m3, and the density of firn lies between these. While snow and firn are permeable to air, below the bubble close-off depth, which lies between 800 and 830 kg/m3, ice becomes impermeable, and the crystals trap pockets of atmospheric gases in tiny bubbles between

1.2 Structure of Ice Sheets and Glaciers

Fig. 1.8 Schematic model of snow densification to firn and ice as defined by density (modified from Bertler 2011)

crystal boundaries. The transition typically occurs at depths of 50–80 m, though firn-ice transition at the South Pole was found at a depth of 115 m (Cuffey and Paterson 2010). In the percolation and wet-snow zones, air spaces are filled by meltwater and the material consists of ice layers, lenses, and glands separated by layers and patches of snow and firn. The time needed to complete the transformation into ice varies widely between different areas according to the amount of meltwater. At lower elevations, however, so much meltwater is produced that the ice layers merge to a continuous mass, called superimposed ice. A superimposed-ice zone represents the extreme case in which snow transforms to ice in a single summer.

Fig. 1.9 Typical structure of ice sheet (modified from Talalay 2013)

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A zone of extremely fragile ice, so-called “brittle” ice (Fig. 1.9), has been observed at all of the deep drilling sites at the Greenland and Antarctic Ice Sheets beginning several hundred meters below the ice surface and extending to depths of 1000–1500 m (Neff 2014). The poor ice-core quality in the brittle ice zone remains a technical challenge at all phases of intermediate-depth and deep ice-core studies. In this brittle ice, the internal gas pressure in the bubbles creates tensile stresses in the vicinity of the bubbles that exceed the strength of the ice. The phenomenological result of these stresses is a marked tendency for the ice to crack and break, with very little provocation, both during and after drilling. In extreme cases where the drill itself adds additional stresses to the ice, drill cores consist of severely cracked and broken ice pieces (Fig. 1.10). The temperature in an ice sheet increases with depth, and the lower part of the ice sheet when approaching the ice/bedrock interface is composed of so-called “warm” ice– ice with a temperature close to its pressure melting point (Augustin et al. 2007). Drilling such warm ice is extremely difficult with ordinary electromechanical drills because when the drill penetrates the warm ice, refrozen ice begins to build up on the cutters and shoes of the drill head, and the performance of the drill rapidly deteriorates to a point where penetration stops (Fig. 1.11). A debris-containing basal ice zone can be found beneath a glacier and may have a vertical extent of tens of meters (Talalay 2013). A debris-containing ice zone differs from the overlying glacier ice not only because of its debris content, but also because of its structure, properties, and composition of solutes and gases. Typically, debris particles have sizes similar to those of silt and sand, with occasional particles up to a few centimeters in diameter. It is not possible to drill debris-containing ice using conventional ice drill bits because it is composed of hard rock particles and rather soft ice.

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Introduction to Ice Drilling Technology

Beneath warm-based glaciers, free water can exist in the form of lakes, rivers, drainage pathways, and deep groundwater. Basal meltwater is confined to the pore spaces of glacial sediments immediately underlying the ice base (typically 1–10 m thick).

1.3 Classification of Ice Drilling Methods

Fig. 1.10 Ice core from brittle zone, EPICA-Dome C, Antarctica, season 2000–2001 (Credit: L. Augustin; EPICA)

Fig. 1.11 Hans Tausen drill head with buildup of ice that occurs in warm ice, EPICA-Dome C, Antarctica, season 2002–2003 (Credit: L. Augustin; EPICA)

Fig. 1.12 Classification of ice drilling methods

Drilling operations in polar regions and mountainous areas are complicated by extremely low temperatures at the surface and inboard of the glaciers, glacier flow, an absence of the roads and infrastructures, storm winds, snowfalls, etc. In principle, it would be possible to use conventional rotary drilling technology for drilling in ice, and early rotary drilling yielded acceptable drilling rates. However, considering the power consumption and weight of conventional rotary drilling rigs, they are difficult to use for glacial exploration. Special purpose-built drilling equipment and technology for ice drilling have been designed and investigated by various institutes all over the world. Depending on the nature of the ice disintegration at the borehole’s bottom, the developed methods of ice drilling can be divided into mechanical, thermal, and thermomechanical methods (Fig. 1.12). The last method has never been used in practical drilling operations on glaciers, although there are a few conceptual articles relating to the development of thermomechanical drills for making holes in ice (e.g., Das et al. 1992; Koci 1994; see Sect. 7.3). Mechanical drilling tools can use percussion or rotary fracturing of ice, but most commonly utilize cutting (Talalay 2003). Depending on their drilling ability and performance, rotary drilling tools are divided into the following groups: (1) hand- and power-driven portable drills, (2) conventional machine-driven rotary drill rigs, (3) flexible drill-stem drill rigs, (4) cable-suspended electromechanical auger drills, and

1.3 Classification of Ice Drilling Methods

(5) cable-suspended electromechanical drills with bottomhole circulation. Special thermal drills have proven to be an attractive alternative for ice drilling. There are different drilling tools that use heat to make holes in ice, including electric thermal coring drills, hot-points, hot water drilling systems, and steam drills. The specific energy required for thermal drills (590–680 MJ/m3) is two orders of magnitude higher than the energy required for mechanical systems (1.9–4.8 MJ/m3) (Koci and Sonderup 1990). In addition, the performance of a thermal drill is quite different from that of a mechanical drill and deserves a separate review. There are several other attributes used for the classification of ice drilling methods. The overall division is based on the possibility of core recovery: full-face (noncore) drilling, which produces only cuttings or melted water, and core drilling, which produces core samples and cuttings (melted water) from the kerf. Another subdivision suggests the utilization of a drilling fluid. If ice cuttings or melted water are removed from the borehole by direct lifting (augering, bailing, pumping) or air circulation, it acts, in effect, as “dry” drilling because the borehole shaft is filled with air. On the other hand, drilling deeper than 300–350 m shows significant closure in an open hole. The deepest “dry” borehole drilled by a mechanical method had a bottom depth of 411 m at Site-2, Greenland (Lange 1973). For drilling at greater depth, it is necessary to prevent borehole closure through viscoplastic deformation by filling the borehole with a fluid (Talalay and Hook 2007; Talalay et al. 2014c). Various low-temperature drilling fluids have been proposed for drilling in ice, and are broken down into three main groups: (1) two-component kerosene-based fluids with density additives, (2) alcohol compounds, and (3) ester compounds (Talalay and Gundestrup 1999, 2002; Talalay et al. 2014a). The main functions of a drilling fluid in this case are to maintain the stability of the borehole and transport cuttings (or melted water) from the bottom to the down-hole chamber or surface. Sometimes this method is referred to as “wet” drilling. In certain circumstances, in order to improve the core quality of “dry” drilling, small amounts of drilling fluid can be added to the bottom of the hole (approximately 15 m of the fluid column), which makes the drilling “semi-wet.” The material removal function is critically important to all drilling systems because the presence of excessive material at the bottom of the borehole leads to decreasing penetration rates and even to the loss of the drill. According to Mellor and Sellmann (1976), material removal systems can be grouped into the following categories: (1) direct lifting, (2) the lateral displacement of material (for example, in

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compressible snow-firn layers), (3) the lifting of cuttings by a circulation medium (air or liquids), and (4) dissolving. The first two methods, along with air circulation, are used for “dry” drilling. Ice drilling methods can be broken down into four groups based on the depth: 1. near-surface shallow drilling up to 50 m for ablation stake installation, temperature measurements at the bottom of the active layer, revealing of anthropogenic pollution, etc.; 2. shallow drilling up to 400 m for structural studies of the snow and firn zone and research on current climate variability, including interhemispheric relationships and the timing and expression of the Little Ice Age within the IPICS 2k Array; 3. intermediate drilling up to 1500 m for studying of the Antarctic and Greenland Ice Sheets, to access holes through ice shelves, and to understand the behavior and timing of the last deglaciation within the IPICS 40k Array; 4. deep drilling up to a depth of 4000 m for fundamental studies of ice-sheet dynamics and the thermal regime, to access the subglacial environment, and to recover old ice cores to reconstruct the climate of the Earth at least 1.2 million years ago and beyond within the IPICS “Oldest Ice.” Hereinafter, the different drills and tools for mechanical drilling in ice are reviewed and discussed.

References Augustin L, Motoyama H, Wilhelms F et al (2007) Drilling comparison in ‘warm ice’ and drill design comparison. Ann Glaciol 47:73–78 Barlow N (2008) Mars: an introduction to its interior, surface and atmosphere. Cambridge planetary science. Cambridge University Press, Cambridge Bentley CR, Thomas RH, Velicogna I (2007) Ice sheets. In: Global outlook for ice and snow, UNEP, pp 99–114 Bertler NAN (2011) Ice core. In: Singh VP, Singh P, Haritashya UK (eds) Encyclopedia of snow, ice and glaciers., Encyclopedia of Earth Sciences SeriesSpringer, Berlin, pp 584–589 Bhutiyani MR (2011) Ice caps. In: Singh VP, Singh P, Haritashya UK (eds) Encyclopedia of snow, ice and glaciers., Encyclopedia of Earth Sciences SeriesSpringer, Berlin, pp 582–583 Black Rapids Glacier, Alaska (2010) US Geological Survey. Available at: http://ak.water.usgs.gov/glaciology/black_rapids/. Accessed 19 July 2013 Bobin NE, Kudryashov BB, Pashkevitch VM et al (1994) Equipment and methods of microbiological sampling from deep levels of ice in central Antarctica. In: Proceedings of the fourth international workshop on ice drilling technology, Tokyo, 20–23 April 1993. Mem Nat Inst Polar Res 49:184–191

8 Cuffey KM, Paterson WSB (2010) The physics of glaciers, 4th edn. Butterworth-Heinemann, Oxford Das DK, Koci BR, Kelley JJ (1992) Development of a thermal mechanical drill for sampling ice and rock from great depths. PICO Report TJC-104 Furukawa Y (2011) Ice. In: Singh VP, Singh P, Haritashya UK (eds) Encyclopedia of snow, ice and glaciers. Encyclopedia of Earth Sciences Series. Springer, Berlin, pp 557–560 Graham AGC (2011) Ice sheet. In: Singh VP, Singh P, Haritashya UK (eds) Encyclopedia of snow, ice and glaciers., Encyclopedia of Earth Sciences SeriesSpringer, Berlin, pp 592–608 IPCC (2007) Climate change 2007: the physical science basis, contributions of Working Group 1 to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. In: Solomon S, Qin D, Manning M et al (eds) Cambridge University Press, Cambridge IPICS (2005) International partnerships in ice core sciences. Workshop Report, 13–16 March 2004, Sterling, VA, USA Koci BR (1994) The AMANDA Project: drilling precise, large-diameter holes using hot water. In: Proceedings of the fourth international workshop on ice drilling technology, Tokyo, 20–23 April 1993. Mem Nat Inst Polar Res 49:203–211 Koci BR, Sonderup JM (1990) Evaluation of deep ice core drilling system. PICO Tech Rep 90-1 Lange GR (1973) Deep rotary core drilling in ice. USA CRREL Tech, Rep 94 Mellor M, Sellmann PV (1976) General consideration for drill system design. Ice-core drilling: proceedings of the symposium, University of Nebraska, Lincoln, USA, 28–30 Aug 1974. University of Nebraska Press, Lincoln, pp 77–111 Neff PD (2014) A review of the brittle ice zone in polar ice cores. Ann Glaciol 55(68):72–82

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Introduction to Ice Drilling Technology

Rafferty JP (ed) (2011) Glaciers, sea ice and ice formation (Dynamic Earth). Britannica Educational Publishing Talalay PG (2003) Power consumption of deep ice electromechanical drills. Cold Reg Sci Technol 37:69–79 Talalay PG (2013) Subglacial till and bedrock drilling. Cold Reg Sci Technol 86:142–166 Talalay PG, Gundestrup NS (1999) Hole fluids for deep ice core drilling: a review. University of Copenhagen, Copenhagen Talalay PG, Gundestrup NS (2002) Hole fluids for deep ice core drilling. In: Proceedings of the fifth international workshop on ice drilling technology, Nagaoka, Japan, 30 Oct–1 Nov 2000. Mem Natl Inst Polar Res 56:148–170 Talalay PG, Hooke RL (2007) Closure of deep boreholes in ice sheets: a discussion. Ann Glaciol 47:125–133 Talalay PG, Fan X, Xu H et al (2014a) Drilling fluid technology in ice sheets: hydrostatic pressure and borehole closure considerations. Cold Reg Sci Technol 98:47–54 Talalay P, Hu Z, Xu H et al (2014b) Environmental considerations of low-temperature drilling fluids. Ann Glaciol 55(65):31–40 Transverse Mercator Projection (2013) Wikipedia. The free encyclopedia. Available at: http://en.wikipedia.org/wiki/Transverse_ Mercator#General_features_of_the_spherical_transverse_Mercator. Accessed 19 July 2015 Williams Jr RS, Ferrigno JG (2012) State of the Earth’s cryosphere at the beginning of the 21st century–Glaciers, global snow cover, floating ice, and permafrost and periglacial environments: US Geological Survey Professional Paper 1386–A Zacny K, Bar-Cohen Y, Davis K et al (2009) Extraterrestrial drilling and excavation. In: Bar-Cohen Y, Zacny K (eds) Drilling in extreme environments. Penetration and sampling on earth and other planets. WILEY-VCH Verlag GmbH & Co., KGaA, Weinheim, pp 347–557

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Yearly History of Ice Drilling from Nineteeth to the First Half of Twentieth Century

In the early stages of human development, making holes in ice was connected with ice fishing or accessing fresh water during winter in regions with a temperate or tundra climate, and the most popular device to use for this was a chisel-shaped blade attached to a wooden pole. Ice chisels have been used for many hundreds of years by Eskimos and the peoples of other northern nations to cut holes through ice by hand for fishing (Fig. 2.1). The ice fragments produced by the up and down chipping action of the chisel in the hole were usually removed at intervals using a spoon-shaped device to maintain the efficient action of the chisel. Ice chisels, also called “spuds,” are still used occasionally for chopping holes early in the winter season when the ice is thinner. This method of cutting a hole in the ice has the advantage that holes of practically any desired width can be made with the same simple tools. However, the hole depth is quite shallow, cores cannot be obtained, and the work is tiresome and slow if the ice is thick. To drill deeper, other drilling equipment should be used. In 1841, L. Agassiz, one of the creators of glacial theory, made his first attempt to drill to the bed of Unteraargletscher in the Alps. He transported iron rods with a total length of 50 m to the glacier and assembled a solid lance, with which he attempted to penetrate the glacier (Clarke 1987). Percussion drilling was employed, using a bit with a diameter of 80 mm. Agassiz used all his extension rods without attaining the bed. The following year he brought a few hundred meters of cable with him, which he used to suspend an iron lance, effectively rigging a rudimentary cable tool (Fig. 2.2). After 6 weeks of tedious effort, holes that were 16, 32.5, and 60 m deep had been completed. During the first 3 days of drilling in each hole, the typical drill rate was 13 m/day (with four men), but this decreased to 3–4 m/day (with eight men) as the hole depth increased. Discouraged, Agassiz made no further attempts to drill through glaciers.

The first patent related to ice-drilling technology was for an “Improvement in Ice-Augers” and was registered by W.A. Clark in the USA in 1873 (Fig. 2.3a). This patented drilling tool has the form of a screw with lips for cutting a hole of the required size. A few years later in 1883, the first patent for an ice core drilling tool, a “Machine for cutting holes through ice,” was obtained by R. Fitzgerald in the USA. This ice hand core drill was rather simple and consisted of a cylinder with a flanged edge to which cutting blades were applied (Fig. 2.3b). For shallow drilling, E. von Drygalski used a spoon-borer while wintering in Western Greenland in 1892–1893 (Kalesnik 1963). In Antarctica, in the first German South Polar expedition with the ship Gauss, he used a hand auger and spoon-borer (Fig. 2.4) (Drygalski 1904). The spoon-borer was made of a 0.75 m long steel tube with a diameter of 50 mm. Two half-moon cutters were fixed on the lower end of the tube, and a longitudinal slot helped ice cuttings to fill the internal space of the spoon. Despite being trapped by ice for nearly 14 months, the expedition discovered an adjacent area south of the Kerguelen Islands and drilled a few 30-m-deep holes in the neighboring iceberg for temperature measurements. From April 1902 to January 1903, temperature readings were taken in the air and ice one to four times per month. In August 1902, the 30-m-deep ice temperature was −10.4 °C, and in December 1902, the temperature slightly increased to −9.6 °C. In 1897, J. Vallot drilled a 25-m-deep hole in Montanvers, in the Alps, in 9 days (Bourgin 1950). At the turn of the twentieth century, A. Hamberg began an integrated study of glaciers in Swedish Lapland (Mercanton 1905). He used a driven pipe to study the inner structures of glaciers to depths of 5–6 m. Drilling a 4-m-deep hole took about 1 h. A. Blümcke and H. Hess carried out one of the most comprehensive glacier surveys of Hintereisferner (Alps) and measured the ablation rate, surface altitude, and ice velocity along a series of transverse profiles. They were the first to

© Geological Publishing House, Beijing and Springer Science+Business Media Singapore 2016 P.G. Talalay, Mechanical Ice Drilling Technology, Springer Geophysics, DOI 10.1007/978-981-10-0560-2_2

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2 Yearly History of Ice Drilling from Nineteeth to … Fig. 2.4 Drilling tools used by von Drygalski (1904): a auger; b spoon-borer; c drill pipe with threaded connection; d wrench

Fig. 2.1 Coastal Eskimo ice fisherman, Denver Museum of Nature & Science (Caribou skin clothing n.d.)

successfully drill through a glacier, and between 1895 and 1904 they drilled 11 holes with a depth range of 40–224 m, almost all of them stopping at the bed of the glacier (Blümcke and Hess 1899; Rey 1909). The deepest hole (224 m) was not completed. Their hand-powered rotary drill rig was produced by Heinrich Mayer and Co. (Tiefbau-Werkzeuge-Fabrik) (Fig. 2.5). Water circulation was used to clean ice cuttings from the bottom. Typically, holes were drilled by hand-power down to 80 m with an average drilling rate of 4–5 m/h. The total weight of the equipment was close to 2.5 t, and six men were needed to operate the drill.

Fig. 2.2 Cable tool used by L. Agassiz in 1842 (Clarke 1987)

Fig. 2.3 First-ever patented ice drills: a ice auger drill (Clark 1873); b ice core drill (Fitzgerald 1883)

Fig. 2.5 Hand-powered rotary drill used by A. Blümcke and H. Hess to drill through Hintereisferner (Rey 1909)

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Yearly History of Ice Drilling from Nineteeth to …

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Fig. 2.6 Mercanton’s design for ice drill bit (Mercanton 1905)

A. Blümcke and H. Hess measured borehole temperatures down to 148 m. However, it appears probable that their results were considerably affected by the disturbing influence on the surrounding ice of the water they were obliged to use in their drilling. A casing left in a borehole in Hintereisferner in 1901 was rediscovered in 1933, and found to have developed a forward slant, implying that the velocity was greatest at the surface (Waddington 2010). In 1900, with the help of an assistant, P.-L. Mercanton drilled in the Trient Glacier (Alps) to a depth of 12.25 m in 4 h (Mercanton 1905). Drilling the last 4.25 m took 1 h, but the rate of penetration between the 5 and 7 m depths was 6 m/h. The specifically developed drill bit had three blades that were rigidly attached to a 30-mm-diameter tube (Fig. 2.6). The outer diameter of the drill bit was 75 mm. The drill bit was connected to 2-m-long, 18-mm-diameter gas pipes rotated by the compact drill rig with a rotational speed of 30 rpm. The drill rig was suspended by a simple tripod. Ice cuttings were removed by the direct water circulation produced by a small pump with a flow rate of close to 3 L/min. In 1912, while wintering in Northeast Greenland, P. Koch and A. Wegener built a hut on the ice (Dansgaard 2005). Inside this hut, they drilled to a depth of 25 m with an auger similar to an oversized corkscrew (Fig. 2.7). They measured the temperature at various depths and its variation throughout the winter. In 1919, the first subglacial rock drilling project to approach an ore-body was successfully realized in British Columbia, Canada (Williamson 1920). The Sullivan “S” diamond drill and 20 t of supplies (a gasoline engine, three 7 m long poles for the tripod, gasoline, a zinc mud tank, and other tools) were hauled over the snow 16 miles from Laid law to the Lucky Four Mine property at an altitude of 1995 m on one of the glaciers in the Cheam Range (Fig. 2.8). The first location was on the bedrock base in a 9-m-deep snow pit with an area of 7.6 m × 7.6 m covered by a large tarpaulin. Snow water for circulation was melted using an oil stove. Drilling was done in three shifts. After drilling one hole with a depth of 213 m, an attempt was made to drill another hole at an angle of 15° to the west of the first hole, but glacial ice was encountered after going 18 m. Repeating the performance to the east, ice was again encountered at 10 m. In order to determine how deep the ice was and what the bedrock looked like, miners constructed a

Fig. 2.7 Drilling by A. Wegener (Photo gallery: Alfred Wegener, n.d.)

1.2 m × 1.8 m tunnel a distance of 25 m through the ice to the bedrock. A second drill site was located about 120 m above the first one. Philipp (1920) used a hand-operated spoon-borer with a diameter of 20 mm for glacial research (Fig. 2.9). The diameter of the spoon head was expanded to 23 mm. Connections were made using 11- and 14-mm gas pipes. After penetrating 0.2–0.25 m, the spoon needed to be retrieved to the surface, disconnected using the “quick release,” turned over, and emptied by a slight tap. In 1934, a few shallow holes to a maximum depth of 15 m were drilled by H.U. Sverdrup and H.W. Ahlmann during the course of the Norwegian–Swedish Spitsbergen Expedition (Sverdrup and Ahlmann 1935). Coring and non-coring types of drills were used. The coring drill consisted of a slit piston, one edge of which was bent slightly inward (Fig. 2.10a). The end was serrated, and the bent-in edge was sharpened so as to cut the firn when the drill was turned. The drill shaft consisted of pieces of iron piping, with a length of 1 m and wall thickness of 1 mm, which were screwed together using ordinary threads. During boring, an ordinary wooden handle was screwed in. A spoon-borer

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2 Yearly History of Ice Drilling from Nineteeth to …

Fig. 2.9 Drilling tools used by Philipp (1920): a ice spoon-borer; b “Quick release” mechanism; c, d “Quick release” mechanism inserted and locked in spoon-borer

Fig. 2.8 Hauling drill rig to site in Cheam Range, Canada, 1919 (Sullivan Machinery Company 1924)

similar to H. Philipp’s tool was used for drilling in solid ice in the lower part of the hole (Fig. 2.10b). This borer was not slit, and its end had two obliquely placed, scoop-shaped, sharp jaws. Both of the drills had high efficiency, and 1 m could easily be drilled, even in hard ice, in 10–12 min. In 1938, T. Hughes and G. Seligman drilled a few shallow holes at Jungfraujoch (Alps) for continuous temperature measurements and found that at depths near 10 m, the ice had a temperature close to the melting point, even though the mean annual air temperature was −7.3 °C (Hughes and Seligman 1939; Seligman 1941). The drilling was done using two types of augers: one with a short screw flight and another with an “enormous” leading screw and powerful cutting cheeks (Fig. 2.11a). The last one was the most successful and worked admirably in blue ice. The spoon was used to remove chips (Fig. 2.11b); this was carried out using a second set of rods to save the changing time. A smaller 15 × 1½″ spoon was principally used. The rods were drawn by hand without using a derrick. A special crown-shaped head was used to bring up undamaged shallow cores from the bottom of the hole (Fig. 2.11c). The bit had 12 teeth, eight pointing inward to hold the core, and four pointing outward to do most of the cutting.

Fig. 2.10 Drilling tools used in Spitsbergen (Sverdrup and Ahlmann 1935): a snow/firn corer; b noncore spoon-borer (“A” indicates openings through which tools are emptied)

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Yearly History of Ice Drilling from Nineteeth to …

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Fig. 2.11 Drilling tools used at Jungfraujoch, Alps, 1938 (Seligman 1941): a augers; b spoons; c coring heads

Shortly before World War II, during a reconnaissance of the glacier Mer de Glace near Chamonix, France, M. Rac– Madoux perfected another type of hand-operated ice auger that used saltwater injection to prevent the jamming of the drill hole by pieces of ice chopped off during penetration. This rig was used to drill 10 m holes in an 8 h shift, including all the operations (Nizery 1951). Although scientific research on glaciers was interrupted by World War II at the end of the 1930s, ice-drilling technology improved significantly in the following decades. The following review will start with snow samplers. Even though sampler development began in the first half of the twentieth century, the sketch includes their entire historical evolution because the old sampling tools were very similar to the new ones. Thus, the reader will gain a greater understanding by considering their development over time.

References Blümcke A, Hess H (1899) Untersuchungen am Hintereisfirner. Z. Deut. Österreich, Alpenver, Wissenschaftliche Ergänzungshefte 2 (in German) Bourgin A (1950) Technique des sondages sous-glaciaires. Revue de Géographie Alpine 38(4):623–632 (in French) Caribou skin clothing (n.d.) National Park Service. Available at: http:// www.nps.gov/gaar/historyculture/caribou-skin-clothing.htm. Accessed 4 Aug 2013 Clark WA (1873) Improvement in ice-augers. US Patent 139,769 Clarke GKC (1987) A short history of scientific investigations on glaciers. J Glaciol Spec Issue 4–24

Dansgaard W (2005) Frozen annals: Greenland Ice Cap research. Narayana Press, Copenhagen Fitzgerald R (1883) Machine for cutting holes through ice. US Patent 286: 599 Hughes TP, Seligman G (1939) The temperature, melt water movement and density increase in the névé of an alpine glacier. Mon Not R Astron Soc Geophys Suppl 4:616–647 Kalesnik SV (1963) Ocherki glatsiologii (Sketch-book about glaciology). Moscow, Geografgiz (in Russian) Mercanton PL (1905) Forages glaciaires. Archives des sciences physiques et naturelles, Series 4, vol 19, pp 367–379 (in French) Nizery A (1951) Electrothermic rig for the boring of glaciers. Trans Am Geophys Union 32(1):66–72 Philipp H (1920) Geologische Untersuchungen über den Mechanismus der Gletscherbewegung und die Entstehung der Gletschertextur. Neues Jahrbuch für Mineralogie, Geologie und Paläontologie, Beilage-Band 43, Stuttgart, pp 439–556 (in German) Rey J (ed) (1909) Études glaciologiques. Tirol Autrichien. Massif Des Grandes Rousses. Ministère de l’Agriculture. Direction de l’Hydraulique. Et Des Améliorations Agricoles. Service d’Etudes des Grandes Forces Hydrauliques (Région des Alpes). Grenoble (in French) Seligman G (1941) The structure of a temperate glacier. Geog J 97 (5):295–317 Sullivan Machinery Company (1924) Diamond drilling in a glacier and in Tropic India. Engineering and Mining Journal-Press, 12 Apr 1924, p 7 Sverdrup HU, Ahlmann HW (1935) Scientific results of the Norwegian-Swedish Spitsbergen expedition in 1934, Part I–III. Geografiska Annaler 17:22–88 von Drygalski E (1904) Zum Kontinent des eisigen su dens. Deutsche Sudpolar expedition, Fahrten und Forschungen des ‘Gauss’, 1901– 1903. G. Reimer, Berlin (in German) Waddington ED (2010) Life, death and afterlife of the extrusion flow theory. J Glaciol 56(200):973–995 Williamson AS (1920) Diamond-drilling in a glacier. Min Mag 23 (4):252–253

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Direct-Push Drilling

Direct-push drilling technology includes methods that advance a drill by pushing, hammering, or vibrating. Although these methods do not meet the proper definition of drilling, they do achieve the same result—a borehole and, if applicable, a core. Direct-push drilling tools do not remove cuttings from the hole. Rather, deepening occurs due to the compression of the formation. Properly speaking, direct-push drilling cannot be used in solid ice, but it can be considered for investigations of compressible snow-firn layers. Two direct-push methods for snow-firn drilling have recently been used: (1) drive sampling and (2) penetrative testing. Although in 1950 at Station Centrale (Greenland), a hole was excavated using a special one-ton plunger down to 30.5 m (see Sect. 6.1.1). It had a diameter of 0.8 m, which allowed a man to be lowered down and study the snow-firn stratigraphy (Heuberger 1954).

3.1

Drive Sampling

3.1.1

Basic Principles

Drive sampling is the primary method used for taking field measurements of the snow depth, depth-integrated density, and snow water equivalent (SWE) because it is considerably less destructive to the snow pack and faster to use than traditional snow pit techniques. SWE corresponds to the depth of the water that would accumulate in an area if all the snow and ice were melted in that given area. A snow sampler (also referred to as a “snow tube”) commonly consists of a metal or plastic tube (sometimes in sections for portability) with a cutter head fixed at its lower end, along with a driving wrench for operating the sampler. In most snow samplers, the cutter head has wedge-shaped teeth and is able to penetrate various types of snow, through crusted and icy layers, and in some cases, through solid ice layers of appreciable thickness that may form near the surface. On the other hand, the cutter head must not compact the

snow, which would cause an excessive amount of snow to be accepted by the interior of the cutter (Guide to Hydrological Practices 2008). Because snow samplers do not include a core catcher, the cutter head must seize the core base with sufficient adhesion to prevent the snow core from falling out when the sampler is withdrawn from the snow. Small diameter cutter heads retain the sample much better than large cutter heads, but larger samples increase the measurement accuracy. The shape of the cutter teeth should allow sufficient backfeed on the cutter to remove the ice chips and should be as thin as practical but somewhat larger than the outside diameter of the driving tube. This construction allows the chips to find a dumping area when carried backward by the feed on the cutter head. The horizontal cutting surface on the cutter blade should be sloped slightly backward to carry the chips away from the interior of the cutter head and should be kept sharp so that there is a definite separation of the snow at the inner wall. A large number of teeth provides a smooth cut and keeps the cutter head free of large chunks of ice. Because, in most cases, the inside diameter of the driving tube is larger than the inside diameter of the cutter head, the core can proceed up the tube with a minimum of interference from friction on the wall. However, in normal snow, the core will tend to move over and rub on the walls of the driving tube. Therefore, the walls should be as smooth as possible to allow the core to proceed upward without undue friction. In most cases, samplers are constructed of anodized aluminum alloy. While the surface may appear smooth, it cannot be assumed that this will ensure non-adhesion of the snow, especially when sampling wet spring snow with a coarse-grained structure. The application of wax may minimize sticking. Some samplers are provided with slots to allow the core length to be determined. In general, especially with wet snow, the core length inside may be considerably different from the true depth of the snow measured on the outer markings on the sampler. The slots also provide an entrance for a cleaning tool. Another advantage of the slot arrangement is the ability to immediately detect errors due to plugging and discard

© Geological Publishing House, Beijing and Springer Science+Business Media Singapore 2016 P.G. Talalay, Mechanical Ice Drilling Technology, Springer Geophysics, DOI 10.1007/978-981-10-0560-2_3

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Direct-Push Drilling

Fig. 3.1 Surveyor takes snow core sample and reads snow depth using gauge on tube (Credit R. Abramovich; Collins 2011)

Fig. 3.2 Weighing tube with its snow core (Credit R. Abramovich; Collins 2011)

erroneous samples. However, the slots may allow extra snow to enter the sampler and increase the measured water equivalent. Some tubes are made from transparent plastic. Thus, no slots are needed for observation, which helps to solve the problem of snow sticking inside the tube. Drilling with snow samplers involves pushing and, if necessary, rotating the sampler down through the snow pack and then extracting a core (Fig. 3.1). Very slight pressures are required to drill through the snow. The sampler should be rotated gently, with caution used to see that it remains vertical. The weight of the sampler will cause it to descend in a light snow pack. Excessive downward pressure should be avoided, because this may cause the instrument to “snow-plough” if ice layers are contained in the pack. Such blocking of the sampler tube is indicated when the snow level in the tube is observed to be well below that of the pack. A more vigorous cutting rotation is required when ice layers are encountered in the pack. If the sampler encounters crusty or icy layers, a slight clockwise rotation should be imparted to the sampler. This brings the cutter into play, which allows for penetration of the rigid layers. The amount of water in the snow pack is determined by weighing the tube with its snow core (Fig. 3.2) and

subtracting the weight of the empty tube. A balance can be graduated in either equivalent inches or centimeters of water. If a calibrated scale and/or tube is used, the SWE is obtained directly. Typically, from 5 to 10 measurements are taken at regular intervals along a snow course. The average of all the samples taken is calculated and used to represent the snow cover parameters. There are many snow samplers in use, with various diameters and cutter arrangements. As a rule, snow tube samplers capture the snow density within 5–10 % of snow pit estimates. Several density kits are commercially available and currently being used. There are others that are no longer purchasable. Historical and most common present-day snow samplers are briefly described hereinafter.

3.1.2

Mt. Rose Sampler

The first snow core sampler was developed by J.E. Church, the father of modern snow surveying. In 1905, he established a weather observatory atop the 3287 m high Mt. Rose, located in the Carson Range east of the California–Nevada border (USA). Then, during the winter of 1908–1909, he

3.1 Drive Sampling

developed procedures for measuring the depth of snow and its water equivalent. The Mt. Rose sampler consists of a seamless steel tube with an outside diameter of 1.75″ (44.5 mm) and any desired length up to 3 m (Clyde 1932). For greater snow depths, the tube is built in sections. The tube is slotted throughout its full length, with alternate slots 1.6 mm wide and 101.6 mm long. The outside of the tube is calibrated in inches. A milled steel cutter head is soldered to the bottom of the tube to facilitate drilling through hard crusts or ice layers. The inside diameter of the throat of this cutter head is 1.5″ (38.1 mm). Thus, a one inch water depth in the snow core is equivalent to slightly more than 1 oz (specifically 1.02229 oz or *30 g). Therefore, a specially calibrated scale must be used with this tube. The entire tube and cutter head is covered with a thin coat of shellac to prevent rusting and to keep the core from sticking in the tube. This simple but effective system is still used today with some modifications. In general, tests have shown that the Mt. Rose sampler provides a snow water content measurement that is slightly greater than 10 % more than the actual snow pack value (Beaumont 1967). The percentage error increases with an increase in SWE. The error found in the Mt. Rose sampler is caused by the design of the cutter head, which forces some amount of snow from the face of the head to enter the tube. Later sampler versions suitable for use in deep snow measure with an error of about 5–6 %.

3.1.3

Utah Snow Sampler

In 1932, G.D. Clyde improved the Mt. Rose sampler and developed the Utah snow sampler by reducing the inner diameter of the cutter head to 1.4872″ (37.8 mm) so that one inch of water equivalent weighed exactly 1 oz (28.35 g) (Fig. 3.3). This allowed the SWE to be measured directly without any conversion. Clyde also suggested replacing the steel tube with an aluminum one to reduce the weight of the sampler by approximately half.

Fig. 3.4 Kit with “Federal snow sampler” (Sampling instruments, n.d.)

17 Fig. 3.3 Utah snow sampler and scale (Clyde 1932)

3.1.4

Federal Snow Sampler

In 1935, the U.S. Soil Conservation Service (SCS), predecessor to the Natural Resources Conservation Service (NRCS), adopted Clyde’s basic design with the cutter head diameter rounded to 1.485″ (37.7 mm) and a cutting area of 11.2 cm2 (Work et al. 1965). The main difference compared to previous versions is that the standard Federal snow sampler has a modular design that allows the surveyor to add sections for sampling deep snow packs (Fig. 3.4). With some further small changes, the Federal snow sampler has recently

18

been produced by a few private companies (such as Rickly Hydrological, Inc. and Geo Scientific Ltd.) and is almost universally used in North America and on other continents. The design criteria for the Federal snow sampler were also adopted by the U.S. Forest Service (USFS). The Federal snow sampler is made from an anodized aluminum material and can be specified in a wide range of English and metric units, with standard section lengths of 30″ or 0.83 m. The standard set can be ordered with up to eight sections and includes a 16-tooth cutter, which is typically used for sampling snow packs or firn up to *9 m deep. Some versions of the Federal snow sampler are produced without slots. For deeper sampling or snow packs with layers of heavy ice, a thick-walled sampler (e.g., McCall sampler) is recommended (Fig. 3.5). In order to reduce the sticking of snow cores in the tube, increase the ease of sampling in deep dense snow, and maintain at least the present standard of equipment accuracy; some further improvements in snow samplers have been suggested in the USA and Canada.

3

3.1.5

Direct-Push Drilling

Bowman Sampler

This sampler was developed at Montana State College, USA, by C. Bowman in 1961. It was essentially the same as the Federal snow sampler. The difference was that it was made of Ryertex, a fiberglass material consisting of phenolic resin on a fine linen base. The wall thickness of the tubes was about 3 mm. The advantage of this fiberglass material in snow sampling was that the snow cores did not adhere to it, as in the case of the metal tube, thus permitting easier self-cleaning of the tube after sampling. The inner diameter of the cutting head was 1.485″. Initial samplings using these tubes in deep snow proved that they lacked sufficient strength (Beaumont and Work 1963). The tubes were redesigned to eliminate the slots through which the core length was viewed. The slots were replaced with 30 mm diameter holes spaced every 2″. This change increased the strength of the tubes.

3.1.6

Rosen Sampler

At the beginning of the 1960s, C. Rosen from Carpenter Machine Works of Seattle, USA, developed an original sampler. This sampler consists of heavy-gauge aluminum tubing (about twice the wall thickness of the Federal snow sampler), with each tube 30″ (0.76 m) in length just like the Federal snow sampler. The tubes are coupled together using threads cut directly into them. Thus, there are no enlarged diameters at the couplings, and the outside diameter of the tube is the same at all places above the cutter head. The inside diameter is the same as the Federal snow sampler, i.e., 1.485″. The new design permitted easier tube penetration to the ground when sampling in deep snow. The added wall thickness approximately doubled the weight of each tube. This increased the sampling effort when four to seven tubes were used in deep snow. Just like the Bowman sampler, these tubes had 30 mm diameter holes spaced every inch for reading core lengths. Many researchers prefer to use the Rosen sampler because it shows consistently less oversampling compared with the other snow samplers (only 2.9 % as reported by Work et al. 1965). This is believed to be due to the shape and sharpness of its cutter head. Moreover, the Rosen tube is unquestionably much easier to drive in deep dense snow. However, it does not release its cores as well as the Federal sampler. Moreover, because this sampler weighs twice as much as a standard Federal sampler, its use is not popular with snow surveyors on long foot trips. Fig. 3.5 Thick-walled snow sampler with 16-tooth cutter (Field Day: snow sampling and the coming of spring, 2013)

3.1 Drive Sampling

3.1.7

19

Large Diameter Snow Samplers

Extensive studies completed to characterize the errors involved in sampling with snow tubes have found that snow samples obtained with large-diameter tubes are more precise. In addition, for shallow snow depths of less than 1–1.5 m, these samplers show no significant over-measurement (Berezovskaya and Kane 2007; Goodison et al. 1987; Woo 1997; Work et al. 1965). However, for snow in excess of 1.5 m deep, they are not considered practical under field conditions. The Adirondack sampler, which was named after the Adirondack Mountains in the northeastern lobe of upstate New York, USA, is made of fiberglass (Fig. 3.6). It has a sharp stainless steel circular cutter head. The tube is 4′ (1.2 m) long, with an inner diameter of 25/8″ (66.7 mm), and can be marked in both English and metric units for measuring the depth of the snow pack. The tube meets the standards for non-contamination when the core will be retained for water quality analysis. The environment Canada ESC 30 sampler has a cutter area of 30 cm2 and uses a clear plastic tube. The specified inner/outer diameters (ID/OD) of the tube are 69.85/76.2 mm (Farnes et al. 1982). The removable driving handle collar is fixed to the top of the tube. The stainless steel cutter head has 16 teeth with lands approximately 2 mm in width and grooves close to 10 mm in width. The slope angle of the teeth is 7°. The inside lip of the cutters is ground to 61.8 mm. The overall length of the tube from the cutter teeth to the top of the driving handle is 1.26 m. The Prairie sampler, which has a hardened steel cutter and screw-in T-handles with alloy tubes, is also available. Based on the environment Canada ESC 30 design, it is 1.2 m long, with a 60 mm ID cutter head.

Fig. 3.7 Snow-hydro sampler (SWE coring tube 2013)

The MSC sampler was designed by the Meteorological Service of Canada specifically for use in snow packs that are generally less than 1.0 m deep. The inner diameter of its 16-tooth cutter head is 70.5 mm (a cutting area of 39 cm2). The tube can be produced from either aluminum or Lexan. The Snow Hydrosampler is a relatively new design fabricated by M. Sturm’s Snow-Hydro company in Fairbanks, USA (Fig. 3.7). It has a fixed length of 1.6 m and is constructed of clear Lexan, eliminating the need for observation slots (Dixon and Boon 2011). The Snow-Hydro has a 12-tooth cutter with an inner diameter of 61.8 mm (a cutting area of 30 cm2).

3.1.8

Fig. 3.6 Adirondak sampler inserted to snow/ground interface and snow depth recorded (Derry et al. 2009)

Vibratory Drill

A vibratory drill (Fig. 3.8) for drilling large diameter boreholes in snow and firn was designed by the Arctic Antarctic Research Institute (AARI) of the USSR for use in the field instead of pit excavation (Kelley et al. 1994; Morev and Zagorodnov 1992). A vibratory drill includes a core barrel with a hardened steel tip with ID/OD of 0.38 m/0.4 m and a 1.5 kW electrical motor vibrator. The length of the drill is 2.2 m, and the weight is 80 kg. The vibrator provides vertical vibration to the core barrel at a frequency of 50 Hz. The

20

3

Direct-Push Drilling

A 0.4 m diameter borehole, 6.5 m deep, was drilled with a vibratory drill at Vostok Station in Antarctica. Field tests showed a drill penetration rate of 6–8 m/min in a snow-firn layer at −50 °C. One complete drilling run took less than 5 min.

3.2

Penetrative Testing

In addition to collecting core samples, numerous penetrative instruments have been used to measure the mechanical properties (shear strength, hardness, inherent cohesion, etc.) of snow and firn.

3.2.1

Ski Pole Penetrometer

One of the simplest methods of snow avalanche observation is the estimation of the spatial extent of distinct weak snow layers or significant changes in layer hardness using a ski pole like a penetrometer (Fig. 3.9). The ski pole is placed perpendicular to the snow surface and is pushed by hand into the snow. The basket end is pushed down into soft snow, whereas the handle is used in harder snow. These measurements need to be performed by an experienced surveyor because the depth, thickness, and spatial extent are recorded based on the feeling of a change in resistance as the ski pole moves through the snowpack.

3.2.2

Ram Penetrometer

The ram penetrometer (also called the “Swiss ramsonde”) has for many years been used to test snow hardness (McClung and Schaerer 2006; Perla and Martinelli 1976). It was developed at the end of the 1930s by R. Haefeli from

Fig. 3.8 Vibratory drill for drilling large-diameter boreholes in snow and firn (modified from Morev and Zagorodnov 1992)

penetration of the drill into the snow-firn formation occurs as the tip displaces snow or firn. The vibratory action also reduces the sidewall friction, resulting in an increased rate of penetration and greater drilling depths. The compacted layer on the core surface near the tip causes the 1.2 m long core to stay inside the barrel. An electric winch and cable are used to raise and lower the drill in and out of the borehole. The total weight of the drilling equipment is less than 800 kg.

Fig. 3.9 Ski pole poke, aka ski pole penetrometer (Photo B. Tremper from Greene et al. 2010)

3.2 Penetrative Testing

penetrometers used in soil mechanics in order to determine the properties that make a snow layer a potential avalanche active layer (Bader et al. 1939). The standard ram penetrometer consists of a 1 m lead section tube with a 40 mm diameter conical tip and an apex angle of 60°, which is driven into the snow by means of a weight (2, 1, 0.5, 0.2, or 0.1 kg) dropped onto the anvil on the tube top (Fig. 3.10). Typically, a kit with a ram penetrometer includes one or two (1.0 m each) extension tubes. The procedure is quite simple. The surveyor holds the ram penetrometer in a vertical position with the guide rod attached, and then drops the hammer, counts the number of blows, and observes the depth of penetration. The ram penetrometer sensitivity is dependent on the hammer weight, particularly when used in soft and very soft snow. The magnitude of this problem may be reduced by using a lightweight hammer (0.5 kg or less) or by using a powder or Alta ram (Perla 1969). The powder ram consists of a 0.5–1.0 m lead section, an anvil weighing 0.1 kg, a guide rod, and a hammer with a mass of only 0.1 kg. The lead section cone has the same dimensions as a standard ram. A ram profile can display two different quantities: the ram number RN, which is a mass (kg), and ram resistance RR, which is a force (N):

Fig. 3.10 Schematic of ram penetrometer (Perla and Martinelli 1976)

21

RN ¼ T þ H þ RR ¼ gRN

nfH p

ð3:1Þ ð3:2Þ

where T is the mass of the tubes, including the guide rod (kg); H is the mass of the hammer (kg); n is the number of blows of the hammer; f is the fall height of the hammer (cm); and p is the increment of penetration for n blows (cm). The ram penetrometer is still used today in almost an unaltered form. However, snow is often so thinly stratified that a rammsonde can only detect the major layers. Further development of snow penetrometers focused on recording the penetration resistance continuously using digital sensors.

3.2.3

Snow Resistograph

To improve the shortcomings of the ram penetrometer, Bradley (1968) invented a snow resistograph (Fig. 3.11), which is inserted to a depth within the snow pack, rotated 90°, and then manually withdrawn. The resistance as the device is withdrawn is measured by a spring in the handle of the resistograph, and a graphical output of the hardness profile as a function of depth is generated.

Fig. 3.11 Snow resistograph (Bradley 1968): a assembled instrument; b recording head; c resistance bit

22

3

Lawrence and Bradley (1973) compared the resistograph to the ramsonde. They found a good correlation between these instruments and showed a much better resolution of soft and thin layers than possible with the ramsonde. However, the resistograph did not become widely used, perhaps because of its complicated mechanical procedure its limited maximal force range.

3.2.4

Fig. 3.13 Snow micro-penetrometer (SnowMicroPen, n.d.)

Digital Thermo-Resistograph

Dowd and Brown (1986) developed the digital thermo-resistograph, which is able to measure both strength and temperature profiles. It uses a semiconductor strain gauge load cell with a 60° cone at the end of a probe (Fig. 3.12). This instrument records the load every 5 mm. A position sensor records the position of the probe, and the measured force divided by the projected area of the cone provides a measure of the stress. The probe is driven into the snow at a constant rate via a geared mechanism powered by an electric motor. Frequent malfunctions and a lack of durability in the field are probably the reasons why it never became accepted. Brown and Birkeland (1990) described a more developed prototype of a digital resistograph with higher resolution and digital data storage and download functions. Although the results were promising, the durability of the load sensor, microprocessor, and liquid crystal display were problematic.

3.2.5

Direct-Push Drilling

Snow Micro-Penetrometer

The snow micro-penetrometer (SnowMicroPen or SMP) developed by Schneebeli and Johnson (1998) is perhaps one of the most advanced snow penetrative instruments currently used in assessing in situ snow strength. The maximum length of a penetrometer measurement is 1.25 m, with a constant penetration velocity of 20 mm/s (Fig. 3.13). The instrument dynamically measures the penetration resistance with a sampling distance of 4 μm. A geared drive rod driven

by a stepper motor is used to push a 5 mm diameter cone with a 60° included angle-sensing tip into the snow. The sensing tip is connected to a force transducer housed in a cone mounted on the end of the drive rod. The force transducer is a small-dimension piezoresistive quartz sensor with a large measurement range (0–500 N) with a high resolution 0.01–0.05 N, depending on the snow strength. The SMP force signal can be interpreted and correlated to the texture of the snow (Schneebeli et al. 1999). Two persons are able to measure more than 100 profiles within a day, which is about 20 times faster than possible for classical snow profiles.

3.2.6

Fig. 3.12 Schematic of digital thermo-resistograph probe showing cone and load column with semiconductor strain gauges (Dowd and Brown 1986)

SABRE Probe

The SABRE probe is a portable, variable-speed, digital, round-tipped penetrometer (with a diameter of 12 mm) developed by Mackenzie and Payten (2002) that measures the force resistance of snow, as well as the snow temperature, with a vertical measurement resolution of approximately 0.2 mm (Fig. 3.14). It was designed for detecting snow layers, particularly with the purpose of identifying weak layers for the assessment of slope stability. It is manually inserted into the snow at variable rates. An internal accelerometer measures the acceleration, and thus the velocity and displacement. Hence, a plot of the penetrative

3.2 Penetrative Testing

23

Fig. 3.15 Container with CPT equipment (McCallum 2014b) Fig. 3.14 SABRE probe (Floyer 2008); a close-up of body and tip; b handheld PC; c probe in use

force versus depth can be generated. Data are recorded at 500 Hz and stored on a handheld PC. The penetrometer is very portable in field, with a total weight of less than 1.5 kg. With additional memory in the handheld PC, a virtually unlimited number of profiles can be stored. A single profile takes about 10 s to perform, with an additional 30 s for data processing and storage.

3.2.7

Cone Penetrometer Testing

Cone penetrometer testing (CPT) is the most common method for collecting in situ measurements in soil. The equipment employed consists of an electrical penetrometer, hydraulic pushing system with rods, cable or transmission device, depth recorder, and data acquisition unit. CPT is usually performed to depths ranging from 15 to 30 m; however, depths as great as 100 m are attainable under ideal conditions, for example, in soft, unconsolidated sediments. The standard CPT penetrometer (or just “cone”) includes piezometric head transducers (piezocones), resistivity sleeves, nuclear logging tools, and pH indicators. Typically, the CPT equipment is mounted on a heavy truck or trailer-rig, primarily to ensure that a sufficient reaction force can be provided when driving into hard soils. The standard rate of testing is at a constant push of 20 mm/s. Schaap and Föhn (1987) tested a modified CPT developed from a commercial geotechnical instrument, with a cone diameter of 11.3 mm and a 60° included angle, which is manually driven into the snow. It has a spatial resolution

Fig. 3.16 Cone incorporating 35.6 mm diameter tip and 135 mm long cylindrical friction sleeve (McCallum 2014a)

of 1 mm in hard snow, and the data are recorded on a chart recorder. They compared the cone penetrometer hardness profile with ram hardness profiles, and the new penetrometer showed greater variations in the snow stratigraphy and snow hardness than the classical method. McCallum (2014a, b) adapted CPT equipment to allow penetrative testing in hard polar firn to depths of 10 m. To use it in Antarctica, a special container was manufactured to store and transport the CPT and ancillary equipment, and in which a CPT operator can stand (Fig. 3.15). It can be mounted on many types of typical polar vehicles, requiring connection to only hydraulics and 12 V of electricity. 35.6 mm diameter cones from GeoPoint Systems BV, with a corresponding cross-sectional area of 10 cm2 and a sleeve area of 150 cm2, were specially produced to measure the resistance on the cone tip and friction on the cone sleeve (Fig. 3.16). They also have the capacity to measure the pore pressure. Standard steel alloy rods, each with a length of 1 m, were used to transfer the penetrative force from the hydraulically driven rams to the cone at depth. Field tests proved that CPT can be used efficiently in polar environments to potentially provide estimates of physical parameters in hard firn to a substantial depth.

24

3.3

3

Summary

Although some snow cover parameters are easily monitored using satellites and passive microwave remote sensing, snow direct-push samplers are still the primary method of measuring local snow depth and SWE. All modern samplers are based on the design of the Mt. Rose sampler developed by J.E. Church a century ago and consist of a tube with a cutter head fixed at its lower end and a driving wrench for operating the sampler. Nowadays, the Federal snow sampler is the most common and is adopted by many organizations as standard equipment for snow courses. Nevertheless, this sampler only captures snow density values within 5–10 % of snow pit estimates. Snow samples obtained using large-diameter tubes (Adirondack sampler, MSC snow sampler, Snow Hydro sampler) are more precise and show no significant over-measurement. A vibration drill can be used to make large-diameter boreholes (0.4 m) in snow and firn instead of pit excavation. The basic method used to obtain a proxy for snow-firn strength is probing, in which a penetrative device is forced into a formation. At the end of the 1930s the ramsonde was developed in Switzerland and has been used for many years to test snow hardness. While this classic tool provides some characterization of the stratigraphy and mechanical properties of the snow, it is well known that the measurements are not very accurate and cannot be used to detect thin and soft layers, which are often responsible for the formation of avalanches. To overcome these limitations, several portable electric cone penetrometers have been developed. Nowadays, the lightweight SABRE probe and the more widely used SMP are the most commonly encountered tools in avalanche observations. However, the dimensions of these penetrometers make the robustness questionable if they are inserted to depths in dense polar snow. Probing with the CPT equipment used for profiling soil layers solves this problem: a modified cone can efficiently determine the strength of hard snow and firn to a depth of 5–10 m.

References Bader H, Haefeli R, Bucher E, et al (1939) Der Schnee und seine Metamorphose. Beitr. Geologie der Schweiz, Geotech. Ser. Hydrol., 3 [In German] Beaumont RT (1967) Field accuracy of volumetric snow samplers at Mt. Hood, Oregon. Proceedings of international conference on low temperature science—conference on physics of snow and ice, Sapporo, Japan, 14–19 Aug 1966. ILTS, vol 1, no 2, Hokkaido University, Sapporo, pp 1007–1013 Beaumont RT, Work RA (1963) Snow sampling results with different snow samplers. Proceedings of the 31st annual western snow conference, Yosemite National Park, California, USA, 17–19 April 1963, pp 15–19

Direct-Push Drilling

Berezovskaya S, Kane DL (2007) Strategies for measuring snow water equivalent for hydrological applications: part 1, accuracy of measurements. Proceedings of 16th northern research basin symposium, Petrozavodsk, Russia, 27 Aug–2 Sep 2007, pp 29–35 Bradley CC (1968) The resistograph and the compressive strength of snow. J Glaciol 7(51):499–506 Brown RL, Birkeland KW (1990) A comparison of the digital resistograph with the ram penetrometer. Proceedings of the fifth international snow science workshop, Big Fork, Montana, USA, 9–13 Oct 1990, pp 19–30 Clyde GD (1932) Utah snow sampler and scales for measuring water content of snow. Circular 99. Utah Agricultural Experiment Station, Logan, Utah Collins A (2011) Forecasting western waters—carrying on a tradition. United States Department of Agriculture, NRCS Idaho. Posted on 2 Mar 2011. Available at: http://blogs.usda.gov/2011/03/02/ forecasting-western-waters-%E2%80%93-carrying-on-a-tradition/. Accessed 4 July 2014 Derry J, Lilly M, Schultz G (2009) Snow data collection methods related to Tundra Travel, North Slope, Alaska: 2009. Arctic transportation network project, Rep. Number GWS.TR.09.05 Dixon D, Boon S (2011) Comparison of the SnowHydro snow sampler with existing snow tube designs in southwestern Alberta, Canada. Proceedings of the 68th eastern snow conference, McGill University, Montreal, Quebec, Canada, 14–16 June 2011, pp 207–224 Dowd T, Brown RL (1986) A new instrument for determining strength profiles in snow cover. J Glaciol 32(111):299–301 Farnes PE, Goodison BE, Peterson NR et al (1982) Metrication of manual snow sampling equipment by Western Snow Conference Metrication Committee. Proceedings of 50th annual meeting: western snow conference, Reno, Nevada, USA, 9–23 April 1982, pp 120–132 Floyer AJ (2008) Layer detection and snowpack stratigraphy characterisation from digital penetrometer signals. Ph.D. Department of Geoscience, University of Calgary, Calgary, Alberta, Canada, p 253 Goodison B, Glynn JE, Harvey KD et al (1987) Snow surveying in Canada: a perspective. Can Water Resour J 12:27–42 Greene E, Atkins D, Birkeland K et al (2010) Snow, weather and avalanches: observation guidelines for avalanche programs in the United States. Chapter 2—Snowpack observations. American Avalanche Association, Pagosa Springs, CO, Second Printing Fall 2010, pp 21–68 Guide to hydrological practices (2008) Volume I: hydrology—from measurement to hydrological information, 6th edn. World Meteorological Organization (WMO-No. 168) Heuberger JC (1954) Glaciologie. Groenland, vol I: Forages Sur L’inlandsis. Jean-Charles. Expéditions Polaires Françaises. V. Paris, Hermann & Cie (In French) Kelley JJ, Stanford K, Koci B et al (1994) Ice coring and drilling technologies developed by the Polar Ice Coring Office. Proceedings of the fourth international workshop on Ice Drilling Technology, Tokyo, 20–23 April 1993, vol 49, pp 24–40 (Mem Nat Inst Polar Res) Lawrence WS, Bradley CC (1973) Comparison of the snow resistograph with the ram penetrometer. J Glaciol 12(65):315–321 Mackenzie R, Payten W (2002) A portable, variable-speed penetrometer for snow pit evaluation. Proceedings of 11th international snow science workshop, Penticton, BC, Canada, 29 Sept–4 Oct 2002, pp 294–300 McCallum A (2014a) Cone penetration testing (CPT) in Antarctic firn: an introduction to interpretation. J Glaciol 60(219):83–93 McCallum A (2014b) A brief introduction to cone penetration testing (CPT) in frozen geomaterials. Ann Glaciol 55(68):7–14 McClung D, Schaerer PA (2006) The avalanche handbook, 3rd edn. Mountaineers books

References Morev VA, Zagorodnov VS (1992) Drilling large diameter boreholes in snow and firn. PICO Tech. Note TN-92-2 Perla RI (1969) Strength tests on newly fallen snow. J Glaciol 8:427–440 Perla RI, Martinelli M (1976) Avalanche handbook. U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station, Alpine Snow and Avalanche Research Project Sampling Instruments (n.d.) Geo Scientific Ltd. Available at: http:// www.geoscientific.com/sampling/. Accessed 3 Jul 2014 Schaap LHJ, Föhn PMB (1987) Cone penetration testing in snow. Can Geotech J 24:335–341 Schneebeli M, Johnson JB (1998) A constant-speed penetrometer for high-resolution snow stratigraphy. Ann Glaciol 26:107–111 Schneebeli M, Pielmeier C, Johnson JB (1999) Measuring snow microstructure and hardness using a high resolution penetrometer. Cold Reg Sci Technol 30:101–114

25 SnowMicroPen (n.d.) WSL Institute for Snow and Avalanche Research SLF. Available at: http://www.slf.ch/ueber/organisation/ schnee_permafrost/schneephysik/SnowMicroPen/index_EN. Accessed 20 July 2014 SWE Coring Tube (2013) SnowHydro. Available at: http://www. snowhydro.com/products/column3.html. Accessed 7 July 2014 Woo MK 1997 A guide for ground based measurement of the arctic snow cover. Canadian Snow Data CD, Meteorological Service of Canada, Downsview, Ontario Work RA, Stockwell HJ, Freeman TG et al (1965) Accuracy of field snow surveys in Western United States, including Alaska. USA CRREL Tech Rep, 163

4

Hand- and Power-Driven Portable Drills

These drills are small systems that can drill holes to maximum depths of approximately 50 m. Depending on the tasks, portable drills can be either coring or noncoring devices. They are relatively lightweight and do not require a drilling fluid. Some portable drills use a down-hole motor that drives the core barrel with or without a nonrotating outer barrel (jacket). The drill is lifted from the borehole either directly by hand or using a lightweight winch. These drills have the same structure as cable-suspended auger electromechanical drills, but are simpler and more lightweight. Thus, they are described with other heavier non-pipe auger drilling systems in Chap. 8.

4.1

Noncoring Augers

To drill holes through sea/lake/river ice for winter fishing, ice measurements, and hydrological research, various types of hand and mechanically driven noncoring augers are used. A common auger includes a rotating helical screw blade called a “flighting” that acts as a screw convey or to remove cuttings from the bottom of the hole. The rotation of the blade causes cuttings to move up in the hole being drilled. The auger is driven from the surface directly or using a series of extensions that are added as the drilling proceeds into the ice. The weight of a noncoring portable ice auger should be small enough to allow it to be transported by an individual or small vehicle. Some tools should be small and light enough to drill holes into the vertical face of a glacier (Fig. 4.1).

4.1.1

SFFEL Noncoring Auger

In 1944, the Soils, Foundation, and Frost Effects Laboratory (SFFEL) of the U.S. Army (also known as the Frost Effects Laboratory) was established by the U.S. Corps of Engineers. At the end of the 1940s, SFFEL carried out initial tests with noncoring augers such as those used for boring wood and coal (Fig. 4.2). It was found that such ordinary augers would operate satisfactorily if (1) a small hole was made on the axis

of the auger at the cutting end, (2) the cutting edge or blade was reshaped so as to work efficiently in ice, and (3) satisfactory clearance was obtained for the auger in the hole (Final report on development of ice mechanics test kit for Hydrographic Office, U.S. Navy 1950). In 1948, numerous cutting blade experiments were conducted, from which it was concluded that for hand-operated augers, the best cutting action, with reasonably small turning effort and only the weight of the auger itself supplying axial loading, could be obtained by providing a rather large clearance angle for the cutting blade. Reasonably good cutting action with very light axial loading was obtained using a blade shaped as shown in Fig. 4.3. At low temperatures, freshwater ice was so dry and frictionless that it would spiral out of an ordinary ship auger as it was being withdrawn from the hole, making progress difficult. However, this effect could be satisfactorily reduced by attaching a small metal tab (baffle) to the bottom end so that cuttings could easily slip upward and over it, but would pile up and form a block when they tended to slip back. Part of the outer helix surface was cut away to reduce the friction between the auger and hole wall. During tests, ship augers had a tendency to become bent out of alignment. This occurred fairly easily under the application of an excess turning or bending force. Once alignment was lost, the auger would jam in the hole and become difficult or impossible to operate. Taking into account that the auger diameter was too small for the operation of most oceanographic observation equipment, later SFFEL development efforts concentrated on the coring-type auger (see Sect. 4.3.2).

4.1.2

SIPRE/CRREL Ice Thickness Kit

In 1949, the U.S. Corps of Engineers established the Snow, Ice and Permafrost Research Establishment (SIPRE). A few years later, a special ice thickness kit with an auger-like “worm bit” based on a modification of the SFFEL ship auger

© Geological Publishing House, Beijing and Springer Science+Business Media Singapore 2016 P.G. Talalay, Mechanical Ice Drilling Technology, Springer Geophysics, DOI 10.1007/978-981-10-0560-2_4

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28

Fig. 4.1 Boring into 30 m high side of Taylor Glacier, Antarctica, for sensor installation (Hutchison 2004)

(Fig. 4.4a) was developed by SIPRE for the rapid manual drilling of small diameter holes to measure the thickness of lake, river, and sea ice (Ice Drills and Corers 1958). A drill with a diameter of 1″ (25.4 mm) cuts glacier ice (wet or dry) quite easily at the rate of 0.5 m/min. In 1961, SIPRE became integrated into the U.S. Army Cold Regions Research and Engineering Laboratory (USA CRREL or simply CRREL), and the ice thickness kit based on the early designs was modified (Ueda et al. 1975). A “worm bit” with a very small diameter (e.g., 1″) tended to jam easily in thick ice. Therefore, the new version of the 1 m-long auger for the ice thickness kit was enlarged in diameter to 21/8″ (47.6 mm) (Fig. 4.4b). The outside diameter of the auger was increased at the cutting edge, so as to cut a hole slightly larger than the main body of the auger.

4

Hand- and Power-Driven Portable Drills

Fig. 4.2 SFFEL 2″ modified ship auger (Final report on development of ice mechanics test kit for Hydrographic Office, U.S. Navy 1950)

Fig. 4.3 Optimal cutting angles obtained as a result of auger drilling tests (Final report on development of ice mechanics test kit for Hydrographic Office, U.S. Navy 1950)

4.1 Noncoring Augers

29

Fig. 4.4 a 1″ SIPRE “worm bit” (dimensions in inches; Ice Drills and Corers 1958); b CRREL ice thickness kit: 1 ice chisel; 2 measuring tape, with rod; 3 extension rods; 4 auger protective cap; 5 auger; 6 brace; 7 canvas cover (Ueda et al. 1975)

The “worm bit” was made from 416 stainless steel and its surface was polished. Penetration rates when the auger was turned with a hand brace ranged from 0.9 to 1.2 m/min;

the rate increased to more than 2.7 m/min when the auger was driven by an electric handheld drill using very limited thrust.

30

4.1.3

4

Kovacs Ice Thickness Kit

Recently, an improved ice thickness kit has been produced by Kovacs Enterprises, Inc., which was founded by A. Kovacs, who worked for a long time at CRREL before retiring, carrying out extensive field research in Greenland, Canada, Alaska, and Antarctica. Kovacs ice auger flights are 50 mm in diameter, 1 m long, and joined together via a patented push-button connector, which allows for the quick connection of one auger section to another (Fig. 4.5). The same connection is used to attach a 51 mm-wide ice cutting bit. This method of assembly means that there are no pins or connector bolts to lose or maintain and no bolts on which clothing can snag. A few options for driving the auger are provided, including a hand brace, a ½″ electric drill, a heavy duty electric drill, or an engine drive. The heavy duty electric drill or engine drive turns the auger at the optimum speed in the range of 550–650 rpm. A drilling rate of 4 m/min in ice is achievable with this mode of power drive. The maximum depths achieved were 24 m through a multiyear pressure ridge and 23 m through a grounded ice island (tabular iceberg) using a ½″ electric drill to power the flights.

Fig. 4.5 Shallow drilling on Shackleton Glacier, Canadian Rocky Mountains (Mechanical drilling photo gallery, n.d.)

4.1.4

Hand- and Power-Driven Portable Drills

AARI Portable Sled-Mounted Drilling Rig

In the middle of the 1950s, a portable sled-mounted drilling rig was designed at the Arctic and Antarctic Research Institute (AARI), Russia (Fig. 4.6). The drill rig was powered by a 4.4 kW gasoline engine (Korotkevich 1965). A mast with a handheld chain device was used for tripping operations. In 1960, during the 5th Complex Antarctic Expedition (CAE), eight holes with a total length of 77 m without a core were drilled at the Lazarev Ice Shelf, Antarctica. The deepest hole was 12.5 m.

4.1.5

Handheld Coal-Boring Augers

In 1957, to drill blast holes for tunneling in Northwest Greenland, the Thor Power Tool Co. EN-8C handheld electric

Fig. 4.6 AARI portable drill, Antarctica, 1959 (Korotkevich 1965)

4.1 Noncoring Augers

31

drill was used with 115/16″ (49.2 mm)-diameter augers (Abel 1961). The bits were 2″ (50.8 mm) the spearhead type and were ground, shaped, and sharpened at the tunnel site. A drilling rate of 1.5 m/min was maintained. Drilling depths of 15 m were achieved with the drill and sectional augers, with the depth limited only by the amount of drill augers available. A handheld coal-boring auger equipped with a 13/4″ (44.5 mm)-diameter bit was used with much success in 1966 (McAnerney 1970). The motor was hydraulically driven and developed high torque at a low turning speed, a combination found suitable for cutting the high-ice-content frozen silt. The penetration rate of the auger was higher than that of a rotary-percussion rock drill (see Sect. 5.3), and the auger moved rapidly in pure ice or very cold silt, provided the bits were sharp. The penetration rate in silty ice in the presence of pure ice lenses with a temperature of approximately −8.3 °C reached 3.6 m/min.

4.1.6

Ice Augers for Winter Fishing

Ice auger production for winter fishing has a long history. Businessmen K.J. Eriksson and L.A. Mattsson founded the knife factory, Eriksson & Mattssons Knivfabrik, Sweden, in 1912. The company eventually became KJ Eriksson AB and manufactured a wide range of “Mora” knives and ice fishing tools. In 2005, KJ Eriksson AB joined with Mora of Sweden, which produces hand and power ice drills under the famous Mora and Mora ICE brands, including scientific drilling equipment (e.g., 5 m-long ice augers). Minnesota-based StrikeMaster Corporation was the first to introduce to North America the “World Class” Mora hand auger in 1946. After this, StrikeMaster became the leading supplier of ice augers in the United States and introduced an array of various ice augers, including a new generation of gas and electric powered augers. In February 2012, Rapala® VMC Corporation acquired the assets of StrikeMaster Corporation and also the Mora ICE brand, which would give Rapala the global leadership position in the ice fishing category. The first ice augers were produced from strip steel, and the diameter of the cutting edges was 2–3 mm larger than the diameter of the auger (Fig. 4.7a). The lower 25–30 cm of the auger was hardened. Later, the flights became welded to the central tube to provide better transportation for the cuttings (Fig. 4.7b). At present, commercially produced augers are available for hole diameters of 4.5″, 6″, 8″, and 10″, with 8″ generally suggested. The drilling depth is limited by the length of the auger and extension, and in most cases it is not more than 1.2 m. For a hand-powered drive, a brace handle with the upper arm in-line with the auger or an offset folding handle is used. The latter arrangement makes it possible to rotate the ice auger using both hands simultaneously for added “torque,”

Fig. 4.7 a Ice auger GGI-47 of State Hydrological Institute, Russia (Bogorodsky et al. 1983); b Ice auger Mora Ice Micro 130 (max ice thickness 88 cm) in transport, along with shortest and longest working positions (Mora Ice Micro, n.d.)

ensuring fast and effortless cutting. Drilling a hole to a depth of 1 m by hand using an ice auger takes nearly 5 min in dry ice (Bogorodsky et al. 1983). Drilling in wet ice takes longer because it is necessary to retrieve the auger from the hole from time to time (every 20 cm or so) for cleaning. Even though hand augers drill relatively quickly, cutting through ice with a thickness of more than 0.3–0.4 m can get tiresome after a few holes. In the 1960s, Tomsky Rybtrest (Tomsky Fishing Trust), USSR, designed a portable easy-to-use ice drill mounted on a sled (Fig. 4.8). The drill was powered by a 2.6 kW gasoline

Fig. 4.8 Tomsky Rybtrest ice drill (Tavrizov 1966). 1 gasoline engine; 2 hand drive; 3 slideway; 4 driving rod; 5 support; 6 drill bit

32

4

Hand- and Power-Driven Portable Drills

Fig. 4.10 Drilling of 11″ (279.4 mm)-diameter hole through sea ice for deployment of autonomous ocean flux buoy near North Pole, 2002 (March 2002 deployment of autonomous ocean flux buoy at North Pole Environmental Observation Station, n.d.) Fig. 4.9 Drilling with Jiffy gasoline-powered auger through 2 m thick ice cover in Arctic lake (Photo J. Briner, University of Buffalo; Images related to Arctic environmental transformations paper, n.d.)

engine (Druzhba-60) that ran at 5200 rpm (Tavrizov 1966). It could drill a hole with a diameter of 300 mm at a maximum depth of 0.9 m with a penetration rate of 0.6 m/min. On the sled, the ice drill could be transferred from the working position to the transport position (in the figure, the transport position is portrayed by dotted lines). Nowadays, propane-, gasoline-, and electric-powered augers are becoming more and more lightweight, efficient, and widespread (Fig. 4.9). There are several options for such ice augers available today on the market, including brands like Eskimo, Jiffy, and StrikeMaster. Engine sizes vary, along with weights and performances (Table 4.1).

There are a variety of different power options: both 2-stroke and 4-stroke gasoline models are available. Propane-powered ice drills are much cleaner and can be operated even indoors. Battery powered models require less maintenance, but charging the battery is an ongoing requirement. Augers have an anti-adhesion coating (paint or Teflon coating) to prevent ice buildup. To drill holes deeper than 1.5–2 m, a simple tripod is used to raise the engine powered auger from the hole (Fig. 4.10). Some of the most important parts of ice augers are the cutters, which are fabricated from high carbon steel and are heat treated to provide a long-lasting sharp edge. Straight, round, or serrated shapes are used for the blades (Fig. 4.11). Round cutters (Fig. 4.11b) have better performance for redrilling or reaming old holes, while serrations provide a

Table 4.1 Main parameters of selected ice augers Parameters

Eskimo Mako M43Q10

Eskimo Shark 71 cc Z71Q10

Jiffy SD60i 8″ fire power

Jiffy PROII electric 8″ stealth STX™

StrikeMaster MP-825

Strike master electra lazer 12000 DP 8″

Motor type

2-stroke engine 43 cc

2-stroke engine 71 cc

2-stroke engine 49 cc

12-V electric motor

4-stroke engine 35 cc

12 V electric motor

Power/kW

1.5

2.7

1.5



1.5



Gear

1∶30

1∶25

1∶12

1∶15

1∶40

1∶40

Auger RPM

260

320

375



170

90

Weight (with auger)/kg

15.5

14.5

12.7

13.5

11.4

13.1

4.1 Noncoring Augers

33

Fig. 4.11 Cutters of ice augers. a Straight (Ledobur Mora Ice Micro 150 mm, n.d.); b round (ION Electric Ice Auger 2012); c serrated (Jiffy Ice Drills 2010)

faster, smoother cut. The blade of a cutter should be re-sharpened as necessary for optimum ice cutting efficiency. Jiffy® recommends a sharpening cutting angle of 45° for a rake angle and 15° for a clearance angle. Using a head with a central chipper tooth (Fig. 4.11c) makes it possible to drill 20 % faster than without it. In principle, the depth of portable ice auger drilling can be increased by auger extensions, but is limited by human or engine capacity. For example, such auger extensions were used to reach water through the 4–5 m permanent ice cover of Lake Fryxell, located in the Dry Valleys of Antarctica (Fig. 4.12). Drilling was the first step to opening a hole, through which the water column below was sampled (Karr et al. 2005). Normally, it takes only one person to drill a hole with a power-driven ice drill. However, scientists found a way to drill rather deep holes using a stepladder (Fig. 4.13). Although it was possible to drill using three 1 m flights at once, two assistants were need to hold the driller and stepladder. Drilling a 6″-diameter hole through 7 m of sea ice usually took about 40 min. Noncore ice drilling is also used as a mitigation method for ice jam formation during spring river floods. Holes in the ice can reduce the structural integrity of the cover, and promote increasing melt in their vicinity. Typically, the holes are drilled about one month prior to the ice-out date.

Fig. 4.12 Auger drilling through ice cover of Lake Fryxell, Antarctica (Photo J. Moore; Drilling ice: Antarctica 2004)

Fig. 4.13 Drilling through sea ice near McMurdo Station, Antarctica, for deployment of remotely operated vehicle

Holes with diameters on the order of 200 mm or more appear to be sufficient to prevent freeze back during early spring (Ice Engineering: Design, Construction and Operation Maintenance 2002). Typically, hundreds of holes spaced about 2–4 m apart are drilled around bridge piers, islands, and river bends to create shear lines for the ice to fail along. As an example, in 1992, the city of Oconto located in Northeast Wisconsin, USA, started weakening ice by drilling 220 mm-diameter holes in the ice cover of Oconto River. A posthole digger mounted on the back of a lawn and garden tractor (Fig. 4.14) was used to drill a few lines of holes spaced about 2.4–3 m apart over a distance of about 5 km. Although the unmodified posthole digger was a great improvement over handheld ice augers, the cutting speed of the auger was improved significantly by replacing the stock auger tip with a spade tip (Fig. 4.15), which made it possible to cut 150–200 holes per hour in the 35–40 cm-thick ice cover. The entire operation took about 2 weeks. Since the city of Oconto began employing this method, no ice jams have formed on that stretch of the river.

Fig. 4.14 Posthole digger mounted on the back of a tractor (Ice Engineering: Design, Construction and Operation Maintenance 2002)

34

4

Hand- and Power-Driven Portable Drills

Fig. 4.15 Modified auger tip (Ice Engineering: Design, Construction and Operation Maintenance 2002)

4.2

Noncoring “Piston” Drills

Some hand ice drills use the drill head as a piston to recover cuttings. Cutters are associated with the slotted disk and fed ice chips during cutting on the upper surface of the disk. The disk connected to the brace handle throws out cuttings when lifting. In the early 1940s, some such “piston” ice drills were patented in Sweden (e.g., SE 105141; SE 117893). In 1945, R. Green got a US design patent on a new ice “piston” drill with three chip cutters (Fig. 4.16). The hand ice drill of the Vologda Region’s Voluntary Society of Hunters and Fishermen (Bogorodsky et al. 1983), USSR, consists of handle-brace, 18 mm-diameter steel rod with a thickness of 2 mm, two grooved cross-sectional clinches, and a plate-shaped drill head made from a 3 mm-thick steel disk (Fig. 4.17). Four dismountable saw-edged 50 mm × 30 mm cutters with a thickness of 2– 3 mm produced from tool steel are attached to the disk. The cutter’s outer diameter is 170 mm,and the drill weighs 2.5 kg. The maximum drilling depth is limited to 1 m, and penetration to this depth usually takes 5–10 min. The efficiency of “piston” ice drills is less than that of auger drills, which is why there are practically none in use today.

4.3

Core Augers

4.3.1

General Principles

Portable ice core augers operate using the same principle as noncore augers, but instead of a full-diameter screw conveyor, a single core barrel with flights is used. In 1932, F. W. Brooks obtained a US patent for an ice core auger that consisted of a cylinder with flights on the outer surface (Fig. 4.18). Upwardly opening, outwardly extended,

Fig. 4.16 R. Green’s “piston” ice drill (Green 1945)

trough-shaped cutting blades were located at the lower end of the flights. This ice auger looked very similar to the modern designs that are widely used at present for shallow drilling in ice. There were a few attempts to use flights without any support or flights fixed on vertical rods instead of the barrel (Fig. 4.19), but not all of them could provide a rigid design. Most hand augers obtain cores with diameters in the range of 75–100 mm and lengths of less than 1 m. Although designed primarily as handheld tools, with hand rotation, these later became powered augers, driven by a handheld electric drill or by a light gasoline engine. In the case of hand rotation, the auger is rotated manually using either a T-handle or, for more speed but less torque, a brace handle (Bentley et al. 2009). On the surface, the extension rods are added as required and usually connected together using male-female joints and fixed with various types of retainers: some are quick-release push button types with a spring-loaded ball like Lockwell or Hartwell pins, and some have a pivoting arm or wire spring clip (Rand and Mellor 1985). The maximum drilling depth is limited by the weight of the auger and drill rods, which have to be retrieved each time

4.3 Core Augers

35

Fig. 4.17 Russian “piston” ice drill (two of four cutters are shown) (Bogorodsky et al. 1983). 1 Plate-shaped drill head; 2 slot; 3 cutter with five teeth; 4 bolts; 5 steel plate; 6 cutter with six teeth; 7 bolt holes

a core section is recovered. When the penetration depth exceeds 6 m, two or three people are needed to raise and lower the drill and to hold the string while adding or removing extension rods. A support clamp at the mouth of the hole is useful for supporting the weight of the string (Fig. 4.20a), and a tripod or gin pole helps in raising or lowering (Fig. 4.20b). A block and tackle could be used to multiply the lifting force by a factor of 2–4 or even more. The use of a tripod to assist in lifting the drill string increases the depth capacity to *50 m. The deepest hole drilled by hand drilling went as deep as 55 m in the Ward Hunt Ice Shelf, Ellesmere Island, in 1960 (Ragle et al. 1964). Almost the same depth (53.5 m) was reached in brine-saturated firn and ice using a modified SIPRE coring auger at the McMurdo Ice Shelf, Antarctica, in November 1978 (Cragin et al. 1986). The practical depth limit for hand- and engine-powered auger systems is about 30 m; most hand-coring operations are significantly shallower. Although a 50 m depth is conceivable, drilling beyond a depth of about 30 m is normally better addressed with an electromechanical drilling method because of the increasing weight and handling of the drill stem and the trip time in and out of the borehole. During the last 60 years, many different types of ice core auger have been designed and tested, and hereafter we describe some of them.

Fig. 4.18 Ice auger patented by Brooks (1932)

4.3.2

SFFEL Auger

In the late 1940s, SFFEL developed the first ice coring auger and a completed design was produced in 1950 as part of an ice mechanics test kit for the U.S. Navy’s Hydrographic Office (Fig. 4.21) (Final report on development of ice mechanics test kit for Hydrographic Office, U.S. Navy 1950). Two aggressive cutting blades with a rake angle of 30° and clearance angle of 35° were integrated into a detachable drill head (Fig. 4.22) that was fixed by screws to the lower end of the auger core barrel. The angle (30°) at which the two helices were attached to the 0.5 m-long tube with an ID/OD of 80/84.1 mm was selected to give the maximum effectiveness in moving cuttings away from the cutting edges. The cutting blades were made to cut a slightly larger hole (110.2 mm) than the outside diameter of the helices (108 mm)–enough larger to allow the auger to turn

36

4

Hand- and Power-Driven Portable Drills

Fig. 4.19 a Ice drill (Persson 1948); b ice boring device (Johnson 1954); c ice auger (Connelly 1964); d device for forming holes in ice (Medvedev 1979)

Fig. 4.20 a Working position of hand ice core auger with T-handle; b auger lifting with tripod (Koci and Kuivinen 1984)

Fig. 4.21 Original SFFEL ice auger, showing core barrel and attachment for removing cores (Final report on development of ice mechanics test kit for Hydrographic Office, U.S. Navy 1950)

freely but not enough for cuttings to pass through this clearance space in any significant amount. Sufficient clearance was also provided between the 3″ (76.2 mm) diameter core and the inside of the tube to prevent the core from

breaking off as a result of contact with the tube during drilling. To control the cutting depth and corresponding amount of turning resistance, two riding shoes were attached to the lower edge of the drill head.

4.3 Core Augers

37

4.3.3

Fig. 4.22 SFFEL coring auger drill head (Final report on development of ice mechanics test kit for Hydrographic Office, U.S. Navy 1950)

A core removal barrel was added to the top of the auger and consisted of a piece of heavy aluminum tubing with an opening along one side from which the cores could be lifted or dropped out. For operating flexibility, the upper part of the core remover was connected with a hinged cap, and if the user desired to attach the hinged cap directly to the coring auger barrel, the core removal barrel could be detached and replaced with a short adapter ring. The core removal barrel was designed for use with cores 7–12″ (178–305 mm) in length. However, in practice, it was possible to obtain cores longer than 12″. In such cases, the core removal barrel opening would be too short and the hinged cap at the top could be used to permit cores to be removed intact. The auger was turned by a modified carpenter’s bit brace. To drill deeper than the length of the core barrel, 1″ (25.4 mm) diameter aluminum extension rods with stainless steel threaded couplings were designed. The kit contained eight rods with an effective length of 3′ (0.9 m), along with two 2′ (0.6 m) rods. Although a core breaking device was not available, it was found that cores were recovered in the auger barrel about 80 % of the time. In the remaining cases, to recover the core, a separate core catcher with four pivoted teeth set in a ring at the lower end could be inserted into the hole after removing the coring auger.

SIPRE Auger

In the early 1950s SIPRE engineers modified the ACFEL ice auger, which became known worldwide as the SIPRE auger (Rand and Mellor 1985). The 3″ SIPRE auger kit includes a core barrel with drill head, driving head, five 1 m-long extensions made from 31.8 mm aluminum pipe with stainless steel sleeves and plated pins, turning brace and T-handle, starting mandrel, tools, and box (Fig. 4.23). This kit was intended for 6 m drilling and weighed *40 kg (Field Manual for the United States Antarctic Program 2001). The overall length of the SIPRE auger core barrel is approximately 1 m when the drill head is fitted. The core barrel is made from stainless steel. On the outer surface of the core barrel, two flights are welded with a helix pitch of 200 mm and an outside helix angle of 30°. In different modifications, the core barrel had a dull sand-blasted finish; some were chrome-plated, and others were Teflon-coated. The drill head is equipped by two chisel-edge mild steel cutters with a 30° rake angle and 20° clearance angle. The nominal internal diameter of the drill head is 3″ (76.2 mm), and the outer diameter is 4″ (110.9 mm) (Ice Drills and Corers 1958). The drilling speed is set by elevating screws that can be shimmed with washers and limit the angle of the helical penetration path (Fig. 4.24). The drill head does not have a core catcher, because the core is usually retained by cuttings jammed between the core and barrel wall.

Fig. 4.23 3″ SIPRE auger kit (Photo Byrd Polar Research Center, Ohio State University; About our Photos, n.d.)

38

Fig. 4.24 Drill head for SIPRE auger (Rand and Mellor 1985). A Elevating screws; B replaceable cutters

4

Hand- and Power-Driven Portable Drills

Hand rotation can give penetration rates of up to 0.5 m/min in ice when the cutters are sharp, but rates in a range of 0.15–0.35 m/min are more typical. The SIPRE auger can also be rotated using an electric motor or a gasoline engine turning at about 200–500 rpm (e.g., Hughes and Terasmae 1963). With a motor drive, penetration rates of up to 1.7 m/min have been achieved (Rand and Mellor 1985). The hand-coring SIPRE auger was first tested on Ice Island T-3, also known as Fletcher’s Ice Island, a thick tabular sheet of glacial ice that drifted throughout the central Arctic Ocean and was used as a scientific research station between 1952 and 1978. Here, in 1952–1955, nine holes were drilled, with the deepest core 32.5 m (Crary 1958). During the summer of 1954, the SIPRE auger was used at Site 2, Northwest Greenland, to retrieve a core from the bottom of a 30.5 m-deep pit (Bader et al. 1955). A 17.7 m core drill hole was sunk by hand drilling from the bottom of this pit to a total depth of 47.2 m, measured vertically. A rope over a pulley at the pit head was used to raise and lower the string of 0.9 m drill rod sections, saving time spent for assembly and disassembly the drill rods. The drill hole had the same 15° inclination from the vertical as the pit. In the same manner, Stephenson and Lister (1959) investigated firn at the inland station South ice (*82°S, *29°W) in Antarctica. To provide access to the deeper levels of firn, a pit was dug with a spade and snow saw to a depth of 14 m. From the foot of this pit, a SIPRE coring auger was used to sample a further 31 m, thereby providing a total profile of 45 m. In subsequent years, the SIPRE auger has been used to drill hundreds or even thousands of holes throughout the cold regions of the world (e.g., Bockheim et al. 2004; Nijampurkar et al. 1988; Thompson 1979; Whillans and Bolzan 1988). Even though there are many other improved versions of hand ice augers, the SIPRE auger is still popular in the ice core science community (Fig. 4.26).

Fig. 4.25 Driving head on SIPRE auger (Rand and Mellor 1985)

The upper reinforced end of the core barrel is connected to the driving head, a laminated steel block, by means of retractable pins (Fig. 4.25). The driving head provides passage for the cuttings. Cuttings are intended to fall through holes in the wall of the barrel and accumulate above the end of the core, but appreciable quantities of cuttings are conveyed above the barrel when a power drive turns the barrel at relatively high speeds. A coring run ends when the barrel is filled with a core and cuttings to a depth of about 0.6 m. If the coring run exceeds 0.6 m, the cuttings that accumulate above the barrel can jam and prevent the extraction of the core barrel.

Fig. 4.26 Drilling through Lake Joyce, Dry Valleys, Antarctica, with hand-powered SIPRE auger, 2003 (Credit B. Hall, Lake Fluctuations— Dry Valleys of Antarctica 2003)

4.3 Core Augers

4.3.4

39

CRREL Auger

A few minor changes in the SIPRE auger design were made later by CRREL specialists (Ueda et al. 1975). This is why this coring drill is sometimes referred to as the CRREL auger. These modifications included (1) a heavy duty drive head, (2) tungsten carbide cutters for drilling in permafrost (Fig. 4.27), (3) adapters for a variety of power drives, and (4) the elimination of the holes in the core barrel wall. In addition, numerous core barrels patterned after the original design have been constructed to obtain cores ranging in diameter from 25 to 150 mm.

4.3.5

Rand Auger

In 1981, CRREL undertook a sea ice study for an industry group headed by the Shell Development Corporation, and a new coring auger was designed and built by J. Rand (Rand and Mellor 1985). This drill is light enough for hand operations at depths up to 10 m. The last version of the auger has a fiberglass core barrel, 114.3 mm outside diameter, and 109.5 mm inside diameter. The cutting head (Fig. 4.28) is aluminum, with an inside diameter of 108 mm and an outside diameter of 139.7 mm. It has two helical slots for the cutters, each inclined at 45° to the face of the cutting head. The replaceable cutters are rectangular steel blanks, 38.1 mm × 17.5 mm × 4.76 mm in size. When clamped onto the drill head, the cutter has a rake angle of 45° and clearance angle of 15°. The cutters are slightly wider than the annular width of the drill head, and the cutting edge projects 3.2 mm below the face of the head. The two flights are made from nylon webbing 12.7 mm wide and 14.3 mm thick and dipped in epoxy resin. The pitch of each flight is 203 mm, giving an outside helix angle of 25°. The fiberglass barrel with the flights attached is finished with high-gloss epoxy paint. The overall length of the core barrel is 1.4, and 1 m or more of the core can be recovered. To avoid jamming the cuttings during retraction from a deep coring run, a short section (0.5 m) of flight auger with a diameter of 139.7 mm can be fitted on the top of the core barrel (Fig. 4.29).

Fig. 4.27 CRREL auger cutters (Rand and Mellor 1985). a Steel cutter for use in solid ice; b tungsten carbide cutter for use in dirty ice and frozen soil

Fig. 4.28 Drill head of Rand auger (Rand and Mellor 1985)

The Rand auger can be driven by an electric drill, which turns at 400–600 rpm with a power consumption of up to 1.2 kW. Penetration rates of 1.7–2 m/min have been measured in cold freshwater ice.

Fig. 4.29 Rand auger with section of flight auger for stirring cuttings above core barrel (Rand and Mellor 1985)

40

4.3.6

4

Big John 12″ Auger

In 1982, a 12″ auger was built by CRREL for the Shell sea ice study (Fig. 4.30) (Cox et al. 1985). The purpose of this device was to extract large cores, and 4¼″ (108 mm) diameter cores were later drilled in various directions to provide oriented test specimens. Simply stated, it is an expanded version of the Rand auger. The inside diameter of the cutting head is 304.8 mm, and its outside diameter is 342.9 mm (Rand and Mellor 1985). The fiberglass core barrel has an outside diameter of 317.5 mm, and a wall thickness of 4.76 mm. The pitch of each flight is 610 mm, and the outside helix angle is 30°. The overall length of the barrel with a cutting head is 1.26 m. The auger can drill *1 m with a maximum drilling depth of 2.4 m. The 12″ auger does not have a core catcher, and at the end of a coring run, the barrel is retracted, leaving an unbroken core in the hole. Then, the core can be broken and recovered with a separate core retrieval device, which consists of a plain cylinder fitted with spring-loaded dogs at the lower end. A small commercial drilling rig (Dig-R-Mobile,

Fig. 4.30 Big John 12″ auger (Rand and Mellor 1985)

Hand- and Power-Driven Portable Drills

Model 550, General Equipment Co.) was modified and used to operate the auger. The basic drill unit drives the drill head using a 5.1-kW air-cooled gasoline engine through a spur gear reduction, giving a maximum rotational speed of 144 rpm.

4.3.7

PICO Lightweight Auger

In the 1970s, the Polar Ice Core Office (PICO), University of Nebraska, Lincoln, USA, designed a lightweight auger particularly for use in high-alpine, remote locations that was capable of collecting firn or ice core to 50 m using a tripod to assist in raising the drill string, or to 30 m without the use of a tripod (Koci 1984; Koci and Kuivinen 1984). The 75 mm-diameter core barrel and 50-mm-diameter extensions were made of fiberglass composite pipes with an aluminum drill head and fittings. The drill extensions weighs *1 kg/m (Fig. 4.31). Two versions of the drill were produced with the core barrel and extensions available in either 1 or 2 m lengths. The drill head incorporates both a tapered annulus and core dogs to ensure positive catching of the core after each run. In the original design, extensions were screwed together, which made it slower to use than the SIPRE auger. Now, however, the extensions are held together using aluminum pins, much like the SIPRE auger (Bentley et al. 2009). For consistency, the tripod was made of pieces of the drill rod. A PICO auger kit for drilling up to 20 m weighs 40 kg, and one for 50 m weighs 95 kg (Field Manual for the United States Antarctic Program 2001). Cores in the range of 0.8–1.2 m can be retrieved in each run using the 2 m core barrel. As a result, 20 m holes can be drilled in 4 h, 30 m holes in 10 h, and 40 m holes in 15 h. The PICO auger can be driven by an electric motor with solar-generated power (Fig. 4.32). The use of a solar panel to power an electric motor attached to the topmost extensions

Fig. 4.31 Driller with PICO 9 m of extensions and 2 m core barrel (Bentley et al. 2009)

4.3 Core Augers

Fig. 4.32 PICO lightweight auger with solar-generated power (Koci 1984)

was demonstrated in Greenland and Antarctica during 1981– 1982. The solar panel performance at the South Pole was 20 % above the rated power output, exceeding results from Greenland, because of the lower ambient temperatures and higher altitude at the Pole (Kuivinen 1983). Penetration rates of 0.6 m/min were achieved in firn at a 40 m depth on a sunny day at Dye 3, Greenland, with the rate being reduced by half on a cloudy day. In 1982, the PICO lightweight auger was used to drill to a depth of 43.5 m on Mt. Wrangell, Alaska, at an altitude of *4000 m above sea level (Benson 1984). At a depth of 35 m using a 2 m-long core barrel, it took 45 min to lower the auger, drill, pull it up, and extract the core. In 1988, a set of new extensions for the PICO hand auger made of graphite and spectra was tested in Greenland (Koci 1988). Their weight is 0.36 kg/m compared to 1.1 kg/m for the fiberglass extensions first used. It seems that these extensions did not become widely used because of their low strength and high price. Even now, the PICO hand auger is one of the most widespread ice coring drills in use (Figs. 4.33 and 4.34).

4.3.8

Kovacs Auger

Kovacs Enterprises, Inc. designed three types of hand ice augers that differed generally by core diameter, including the Mark II Coring system for retrieving a 90 mm-diameter core, Mark III Coring system for a 72.5 mm-diameter core, and Mark V Coring system for a 140 mm-diameter core. These coring systems are upgraded versions of the SIPRE auger (Fig. 4.35). The core barrel is a lightweight filament wound composite tube about 1.15 m long with plastic flights (Bentley et al. 2009). The cutting head is aluminum and the cutting teeth are steel, as are the core dogs. The drive head is stainless steel and aluminum and allows for fast coupling

41

Fig. 4.33 Drilling by PICO hand auger under supervision of designer of this drill, B. Koci (behind hole) (Photo T. Wendricks, About our Photos, n.d.)

Fig. 4.34 PICO hand auger in action during Norwegian-U.S. Scientific Traverse of East Antarctica (Photo S. Tronstad, About our Photos, n.d.)

and uncoupling from the core barrel. The typical set contains two stainless steel 1 m-long extensions. A T-handle is included for turning the core barrel by hand, and an adapter is provided for turning the system using an electric drill operating at 400 rpm or less. To drill to a depth of 15 m or deeper, a tripod was designed with a small hand winch fixed on one of the tripod feet (Fig. 4.36). The Covacs auger could be drive by a gasoline engine equipped with a special low gear ratio transmission appropriate for turning the barrel at a low speed (Fig. 4.37).

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Fig. 4.35 Kovacs Mark III Coring system (Coring Systems, n.d.)

Hand- and Power-Driven Portable Drills

Fig. 4.37 Drilling into sea ice with Kovacs auger at Pegasus white ice runway, 29 km from McMurdo Station, Antarctica (Photo J. Whittington; About our Photos, n.d.)

Fig. 4.38 Core barrel and drill head of Swiss hand auger (picture was taken by author in AWI, October 2011)

4.3.10 Swiss Hand Auger

Fig. 4.36 Drilling with Kovacs auger at Larsen-C Ice Shelf, Antarctica, 2009–2010 (Shepherd et al. 2010)

4.3.9

IGAS Hand Auger

In the middle of the 1980s, the Institute of Geography, USSR Academy of Sciences (IGAS), built a hand auger that included an aluminum core barrel, extension rods, a T-handle driver, and a device at the mouth of the hole to grasp the string when connecting or disconnecting the extension rods (Arkhipov et al. 1987). The total equipment weight for a 32 m set was 38–40 kg. The drill produced up to 0.5 m cores with a diameter of 90–92 mm. In 1984–1985, the IGAS hand auger was used to drill 10 holes in Austfonna, Svalbard, with depths from 6.3 to 15.8 m. The lengths of the runs varied in the range of 0.2–0.5 m.

The Swiss hand auger was designed by H. Rufli, University of Bern in the 1980s. Extensions for this drill are connected with the help of commercially available quick-disconnecting joints. The drill head is equipped with original core catchers (Fig. 4.38). During reverse rotation of the core barrel, these core catchers engage the core and cut a shallow sub-horizontal groove. This groove decreases the surface area and produces a stress concentration, which encourages core break off.

4.3.11 UCPH Hand Auger This drill was designed in the University of Copenhagen (UCPH) to collect a 74 mm-diameter core from the top 10– 12 m of a snow–firn formation (Gundestrup et al. 1988). The core barrel was constructed using the same components as the UCPH shallow electromechanical drill (this drill is described in detail in Sect. 8.6). The drill head with three cutters is entirely the same, and the dimensions of the core barrel are unchanged,

4.3 Core Augers

43

Fig. 4.40 Basic features of “Prairie Dog” auger design (Kyne and McConnell 2007a)

Fig. 4.39 Drilling with UCPH auger 2 km west of NEEM site, Greenland, June 2011 (Photo O. Maselli; Surface Science 2011)

except for the length, which was reduced to 1.2 m. The handle, rods, and clamp between the rods and core barrel are the same as used in the Swiss hand auger. All the components of the drill system are contained in two relatively easy-to-handle boxes, weighing a total of 80 kg. To complete a 10 m-deep hole, usually close to 15 runs must be brought to the surface. The UCPH hand auger was used for the first time at Camp Century in 1986 (Clausen et al. 1988). Here, 44 holes were drilled with a total length of 358 m. Since then, the UCPH hand auger has often been used in Greenland (Fig. 4.39).

4.3.12 “Prairie Dog” Auger The “Prairie Dog” auger includes a stationary outer barrel to enable more efficient drilling—better core quality, fewer trips in and out of the hole, easier breaks from the hole bottom, better chip collection, and less energy to turn– compared to a simple single barrel (Fig. 4.40) (Kyne and McConnell 2007a).

It uses the same coring head as the PICO auger (a core diameter of 102 mm), with the same-size fiberglass–epoxy composite tubing for its inner barrel. It is completely interchangeable with the PICO auger because the outside diameter of its 3 mm-thick outer barrel is the same as the outside diameter of the flights on the PICO auger, with the flights on the “Prairie Dog” inner barrel having been shaved down a corresponding 3 mm. A lightweight anti-torque section keeps the outer barrel from rotating. When the “Prairie Dog” inner barrel is full, the chips will pack until the drill no longer turns, notifying the operator that the run is complete. The total length of the “Prairie Dog” is *2.4 m. The performance of the “Prairie Dog” is limited in very soft snow and firn. In order to overcome this limitation, the borehole is started with a PICO auger and continues to the depth where the firn is dense enough for the “Prairie Dog” anti-torque blades to grip the borehole sidewall. The depth-of-use limit is approximately 40 m. It is safe to use in warm ice where a simple core-auguring barrel could easily become stuck. Over the last decade, the “Prairie Dog” has been used to drill about 50 holes to an average depth of approximately 20 m. With fiberglass inner and outer barrels and an anti-torque section composed primarily of aluminum, the “Prairie Dog” without extensions weighs 11.3 kg. Lifting the “Prairie Dog” from the borehole can be difficult because it is heavy, long, and slick. It is helpful to have

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Hand- and Power-Driven Portable Drills

Fig. 4.42 Diagram of “Sidewinder” (Kyne and McConnell 2007b)

Fig. 4.41 The “Prairie Dog” being removed from a borehole: through the semitransparent outer barrel ice chips can be seen resting on the flights of the inner barrel (Hand Augers. Prairie Dog. Operator Manual 2010)

a second person to assist (Fig. 4.41). The anti-torque blades can be used as lifting points without risking damage to them. However, unless operators are very tall, the “Prairie Dog” cannot be lifted all the way out in this manner. Thus, it is necessary to get a second hold on the system by either clamping it between one’s knees or having someone else hold it.

reversible ¾″ electric drill that is used for both the drilling and lifting of the drill string. The electric motor uses a DC or AC current controlled by a variable transformer to obtain the correct rotation speed. A high-strength, low-stretch, synthetic-fiber rope lifts and lowers the drill string as it winds around a tube attached to the electric drill. When winding, the rope is guided onto the winding tube by cleats, which also serve as a quick way to secure the rope for drilling. The end of the winding tube connects directly to the protruding extension of the drill string for drilling. The rope always remains attached to the drill string by a rope pin that replaces the bottommost connecting pin; the winding tube holds the rope and always stays attached to the electric drill. The “Sidewinder” is compatible with the “Prairie Dog” and PICO hand augers. Even drilling to a depth of 40 m is possible using the “Sidewinder,” but the average hole depth is nearly 20 m (Fig. 4.43).

4.3.13 “Sidewinder” The “Sidewinder” (Fig. 4.42) is a hoisting system for a shallow auger system that speeds up obtaining core at depths greater than *5 m (Kyne and McConnell 2007b). The “Sidewinder” can be operated by one person. A piece of ¾″ plywood is used as a drilling platform. The cradle is hinged on the platform and swings out of the way for drilling. Power from solar cells or a small generator is fed to a

4.3.14 IDDO Hand Auger In order to improve the SIPRE/PICO augers, a new hand drill was designed by the Ice Drilling Design and Operations (IDDO) group, University of Wisconsin–Madison (Goetz and Shturmakov 2013). The drill head has three cutters and three core catchers, but the kerf is thinner than in previous modifications. Three V-belt flights are attached to the outer

4.3 Core Augers

45

Fig. 4.45 Testing of IDDO auger (Credit J. Goetz)

Fig. 4.43 “Sidewinder” retrieving PICO hand auger in Greenland (Photo T. Wendricks; About our Photos, n.d.)

surface of the core barrel with VHB tape and fixed by screws at each end. The core barrel is made from fiberglass. The drill head contains two options to break the core: conventional core dogs and a split ring collet. Planar cutters are produced from stainless steel (Fig. 4.44). Two prototypes were made and tested in firn at WAIS Divide, Antarctica, during the 2011–2012 season. These tests were largely successful, with *20 m cores recovered (Fig. 4.45). Continuous testing, improvements, and system modifications led to the production of 4 m of a good quality 78 mm-diameter core during the Antarctic 2012–2013 field season at WAIS Divide. Hand ice core augers have also been built at the Institute of Low Temperature Science (ILTS), Hokkaido University, Japan; Geo Tecs Co. Ltd., Nagoya, Japan; St. Petersburg State Mining Institute, Russia, and some other institutions, but there are no available published data about their parameters and performances.

4.4

Fig. 4.44 Coring head and cutter of IDDO hand auger (Photo J. Goetz)

Core Drills with Teeth and Annular Bits

Few other kinds of hand ice core drills were designed in Canada and the USSR in the 1950s–1970s. These drills do not use an auger for chip transportation. It should also be stated that in the very first ice experiments performed by SFFEL at the end of the 1940s, trials were conducted to determine the cutting action of steel cylinders with cutting teeth of various designs formed on the ends (Final report on development of ice mechanics test kit for Hydrographic Office, U.S. Navy 1950). It was apparent from these trials that the major deficiency of all these experimental coring devices was the absence of any means of removing the ice

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cuttings from the vicinity of the cutting blades. If the cuttings were allowed to remain and interfere with the cutting action of the following teeth or with the rotation of the corer, the device at once became inefficient or ineffective.

4.4.1

Taku Glacier Hand Drill

Similar to the Ahlmann design (see Chap. 2) a hand drill with teeth was used in the Taku Glacier, Alaska, research program in 1952–1953 (Fig. 4.46) (Miller 1954). The thick-walled core barrel was made from duraluminum. At the lower end, eight teeth were cut with a height of 12 mm and rake/clearance angles of 0°/20°. Four teeth were pointed slightly inwards and four slightly outward. To remove the ice core, two direct axis slots (10 mm × 127 mm) were cut on the core barrel. The rotation was produced by a carpenter-type hand brace. To drill to depths of a few meters, 1 m extension rods with a diameter slightly smaller than the core barrel were added.

4.4.2

Canadian Portable Ice Drill

In connection with studies in glacier physics on the Penny Ice Cap, Baffin Island, Canadian Arctic, in 1953, a portable ice drill was designed with a total equipment weight for drilling to a depth of 20 m of about 36 kg (Ward 1954). A 0.5 m-long steel coring tool is made from a piece of 44.5 mm-diameter drawn steel tube (Fig. 4.47), similar to the design suggested earlier for a conventional rotary drill rig (see Fig. 6.3). There is a mild steel adaptor on its upper end that screws onto the rods and slides a short way inside the coring tube. The heads of two set screws engage in corresponding holes in the coring tube. The saw teeth are cut and set by hand and are not hardened. To provide space for the ice cuttings, the tube wall is perforated by numerous 11.1 mm-diameter holes and spiral slots. The 0.9 m-long rods are made from extruded aluminum alloy tubes with plugs riveted in each end; one plug has a female thread and a tommy bar hole for unscrewing, the other plug has a male thread. The shoulders formed at the screw joints are advantageous when lifting the rods vertically, particularly when they are glazed with ice. The boring rods are rotated, and loaded axially if necessary, by a carpenter’s brace. The lifting rig consists basically of a light pole 6 m long, with a single pulley at the top. It is anchored to the ground by guy ropes. When the coring tool is sufficiently full and has been raised to the surface, a series of short cores separated by thin layers of ice cuttings was easily released by tapping the side of the tube with the tommy bar (with a diameter of 9.5 mm and length of 305 mm) that is used to unscrew the rods.

Hand- and Power-Driven Portable Drills

A total of about 75 m of holes, mostly in dense ice, were drilled during the 1953 summer along a 40 km course on the Penny Lee Cap. The total length of the rods taken was 18 m (20 rods), and this was the depth of the deepest hole. Drilling a 9 m-deep hole took about 2 h. The ice temperature varied down to −14 °C. This ice drill works easily through all forms of snow and dense firn below the melting point. Up to a density of 600 kg/m, the cores were relatively undisturbed. Frequent ice layers up to about 100 mm thick were no trouble, but in continuous ice, the work was more laborious. There is an art to drilling through continuous dense ice, which can only be mastered by practice.

4.4.3

Tsykin’s Hand Drill

During the International Geophysical Year (1957–1958) and near this time, specialists from IGAS carried out major temperature surveys of polar and mountain glaciers. For drilling to depths of 30 m, a special set of hand drilling equipment was designed by Tsykin (1962, 1963a, b, c). This set included a core barrel, aluminum rods with bayonet or hinged joints, a manual T-handle driver, and a tripod mast. The core barrel was made from carbon steel tubing with long slot (Fig. 4.48). Two teeth of different heights were cut on the lower part of the barrel. One higher straight tooth was designed for cutting and a second one with a curved configuration directed the ice chips inside the barrel. Three nominal sizes of core barrels with different lengths and outside diameters (OD) were designed: 1. 0.5 m length with an OD of 46 mm for drilling to depths of 8 m; 2. 0.75 m length with an OD of 52 mm for drilling to depths of 15 m; 3. 1 m length with an OD of 58 mm for drilling to depths of 30 m. Rods were made from aluminum alloy D16T. Two types of rods were produced with bayonet joints (Fig. 4.49a): 1. 1.04 m length with ID/OD of 16 mm/22 mm for drilling to depths of 6–7 m; 2. 1.54 m length with ID/OD of 16 mm/26 mm for drilling to depths of 12–15 m. The use of the rods with hinged joints eliminated the need for the assembling/disassembling of the drill string (Fig. 4.49b). In this case, the drill was hoisted from the hole strictly by hand, and the drill string was laid down directly on the surface without uncoupling. The hinged joints allowed the drill string to be deflected to an angle of 120°. To avoid a zigzag position in the hole during drilling, every

4.4 Core Drills with Teeth and Annular Bits

Fig. 4.46 Taku Glacier hand drill (Miller 1954)

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Hand- and Power-Driven Portable Drills

rod had a centralizer consisting of three cambered plates. Drilling in the firn with such rods was problematic as centralizers touched the borehole walls, and the borehole walls collapsed. Two types of aluminum handles were used: one for rods with the bayonet joints, and another one for rods with the hinged joints. In the latter case, the handle could be fixed to any place on the drill string. From 1955 to 1960, more than a hundred shallow holes were drilled using Tsykin’s drills. The drilling was quite effective. For example, the drilling of a 25 m-deep hole in the Polar Urals by a team of four people took nine working hours. The recovered ice material was represented by clumps intermixed with chips. Normally, the meter length core barrel was totally filled after a penetration of 0.5–0.6 m in cold ice. In temperate ice, the length of a run decreased to 0.25–0.3 m. From 1957 to 1959, a modified Tsykin drill was used by an expedition of the Geography Department of the Academy of Sciences of Kazakh SSR (Tsykina and Vilesov 1963; Vilesov and Shabanov 1961). Eleven holes with a total depth of 250 m were drilled on the Central Tuiuksu and Igly-Tuiuksu glaciers (Northern Tien Shan). The deepest hole, of 52.65 m, reached the bedrock beneath the glacier. The drilling of this hole took 96 h.

Fig. 4.47 Drill rod, coring tool, and adaptors of Canadian portable ice drill (Ward 1954)

4.4.4

5th CAE Drill

A special ice drill was designed and manufactured at the workshop of Mirny Station, Antarctica, by the workers of the 5th CAE (Korotkevich 1965). This drill used a special core barrel manufactured in the Institute of Earth Physics and was powered by the engine of a gasoline-powered saw (Druzhba). The total weight of the drill was 18 kg. The OD of the drill pipes was 33.5 mm. During the 5th CAE, dozens of holes (totally *190 m) were drilled at the Shackleton and Lazarev ice shelves with depths of 3–8 m and penetration rates of 0.3–0.4 m/min.

4.4.5

Fig. 4.48 Core barrel of Tsykin’s hand ice drill (Tsykin 1963c)

Ice Core Drill with Annular Bit PI-8

This drill was invented by Cherepanov, AARI (1967), and later modified by him, together with Sokolov (1975). The PI-8 drill consists of a massive metal ring with a square or rectangular cross section (Fig. 4.50). For fixing the cutter, a slot is made in the ring at an angle of 40–45°, with a width of 25–30 mm (Bogorodsky et al. 1983). This slot provides free

4.4 Core Drills with Teeth and Annular Bits

49

Fig. 4.49 Aluminum rods of Tsykin’s drill with bayonet a or hinged b joints (Tsykin 1963a, b)

Fig. 4.50 Ice core drill with annular bit (Cherepanov and Sokolov 1975)

access to the cuttings on the upper flat surface of the ring. Cuttings are cleared by lifting the ring to the surface from time to time (*5–6 cm of penetration). An excess of cuttings in the hole prevents the free rotation of the bar and may even cause the drill to stick in the hole. A groove-reinforced toothed cutter is fixed to one side of the slot, and the position of this cutter can be adjusted using two screws (the distance between the blade of the cutter and lower surface of the ring should be 2–3 mm). The blade of the cutter is wider than the ring by 5–6 mm, and the offset is 2–3 mm from both the outer and inner sides of the ring. The ring with the rod is connected to a turning brace. The diameter of the rod is less than the thickness of the ring so that it can travel freely in the kerf between the core and the borehole wall. During drilling, the rod should be as vertical as possible. Otherwise, after drilling 0.4–0.6 m, the rotation of the rod becomes difficult because of the friction of the rod on the borehole wall or core. The total length of the drill is about 1.4 m, but using additional extensions makes it possible to drill deeper, down to 3–4 m. Standard versions come in diameters of 180, 220, and 320 mm. Using the drill to break the core is not recommended because it can damage the ring and rod. To break the core, a special wooden wedge is inserted into the annular groove, and the core is recovered with the help of a stick, which is attached to the rod.

50

4.5

4

Hand- and Power-Driven Portable Drills

Mini Drills

Portable mini drills are used for sampling firn or ice from trenches or pits to a depth of a few dozen centimeters, typically for density, impurity, and other measurements.

4.5.1

Livingston Island Mini Drill

The portable Livingston Island mini-drill consists of three pieces: the drill head, core barrel, and drive nut (Fig. 4.51) (Casas et al. 1998). After several trials with different types of drill heads, a head formed by a 90 mm inner diameter aluminum ring holding three carbide teeth with a cutting angle of 80° was chosen. The aluminum core barrel is 0.46 m long, with four spiral flights having a pitch of 45°, and holes in the top. Two of these flights run the whole length of the barrel, whereas the other two run halfway up the barrel. The drive nut joins the core barrel to the power head. The drill is powered by the Pomeroy D026-GTlO model power head, which is furnished with a STIHL 48 mL gasoline motor, developing 2.6 kW at 10,000 rpm. This machine is geared down at approximately 5:1. The total weight of the engine and mini-drill is 6 kg. During the 1994–1995 Antarctic summer, ice cores were sampled at 21 sites distributed in six localities on Livingston Island, South Shetlands, Antarctica. The mini-drill worked very well and was very efficient, cutting the ice at drilling rate of 0.30–0.35 m/min. Usually, the core came out in one or two pieces, with a total length of 0.35–0.45 m. The intact core showed the original structure of the ice and ash layers, without disturbance from cutting, or ice chips. The internal diameter of the cutter head is only 1.5 mm smaller than the

Fig. 4.52 Chipmunk in use in Greenland (Photo E. Brook, Oregon State University; Bentley et al. 2009)

core tube. This causes the core to become slightly stuck in the tube, which can be an advantage in preventing the ice cores from falling out when the drill is moved up and down along the hole. Nevertheless, in some cases, difficulties arise in removing the ice cores.

4.5.2

This is perhaps the smallest hand held coring drill and collects 2″ (50.8 mm)-diameter cores in solid ice (Fig. 4.52). It consists of a coring auger driven by a standard commercial ½″ electric drill and has two barrels, one 15 cm long and another one 50 cm long (Bentley et al. 2009). This drill was used on one project (for which it was designed in IDDO) to collect samples of old ice in an ablation zone at Pakitsoq, West Greenland, in 2003 and 2004, and for several demonstrations of ice coring for the public in the U.S.

4.6

Fig. 4.51 Portable ice coring drill together with fragment of ice core containing thin tephra layer (Casas et al. 1998)

Chipmunk Drill

Summary

Noncore auger hand drills are the most efficient way to make holes up to depths of 5–6 m for access to subsea/lake/river reservoirs, for ice thickness measurements, seismic investigations, and other purposes. Manual handling is quite effective for drilling a limited number of holes to a depth of 1–2 m. To drill deeper or a larger number of holes, it is reasonable to use an engine-powered auger system. Using a “piston” noncore ice drill is not very effective, because the drill needs to be lifted repeatedly to clean cuttings from the hole. Many studies have been conducted to develop an efficient design for an ice coring auger, and basic principles suggested by SIPRE/CRREL/PICO/IDDO can be considered to

4.6 Summary

find the optimal solution. Future developments will offer refinements for easier operation and lighter weight. Although depths greater than 50 m have been achieved, drilling beyond a depth of about 30 m is normally better addressed using other drilling methods because of the increasing weight and handling of the drill stem and the trip time in and out of the borehole. The type of driving (hand or engine) and pulling-and-running equipment depends on the target depth and remoteness of the drilling site. By all accounts, when drilling holes deeper than 15–20 m, the use of a tripod and engine power is strongly recommended. Some hand ice core drills (like Tsykin’s drill) cannot provide good quality cores, which is why they are not in use at present.

References Abel Jr JF (1961) Under-ice mining techniques. USA SIPRE Technical Report 72 About our Photos (n.d.) U.S. Ice drilling program. Available at: http:// www.icedrill.org/newsmedia/images.html. Accessed 19 July 2013 Arkhipov SM, Vaykmyae RA, Vasilenko YV et al (1987) Soviet glaciological investigations on Austfonna, Nordaustlandet, Svalbard in 1984–1985. Polar Geogr Geol 11(1):25–49 Bader H, Waterhouse RW, Landauer JK et al (1955) Excavations and installations at SIPRE test site, Site 2, Greenland. USASIPRE Report 20 Benson CS (1984) Ice core drilling on Mt. Wrangell, Alaska 1982. In: Proceedings of the second international workshop/symposium on ice drilling technology (USA CRREL Special Report 84–34), Calgary, Alberta, Canada, 30–31 Aug 1982, pp 61–68 Bentley CR, Koci BR, Augustin LJM et al (2009) Ice drilling and coring. In: Bar-Cohen Y, Zacny K (eds) Drilling in extreme environments: penetration and sampling on earth and other planets. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, pp 221–308 Bockheim JG, Hinkel KM, Eisner WR et al (2004) Carbon pools and accumulation rates in an age-series of soils in drained thaw-lake basins, Arctic Alaska. Soil Sci Soc Am J 68:697–704 Bogorodsky VV, Gavrilo VP, Nedoshyvin OA (1983) Razrushenie l’da. Metody, tekhnicheskie sredstva (Destruction of ice. Methods and equipment). Leningrad, Gidrometeoizdat (In Russian) Brooks FW (1932) Ice auger. U.S. Pat. 1, 857, 585 Casas JM, Sabat F, Vilaplana JM et al (1998) New portable ice-core drilling machine: application to tephra studies. J Glaciol 44 (146):179–181 Cherepanov NV (1967) Ustroistvo dlya obrazovaniya skvazhin vo l’du vodoyemov (Device for forming holes in ice of water reservoirs). USSR Pat. 195, 474 (In Russian) Cherepanov NV, Sokolov FD (1975) Ustroistvo dlya bureniya l’da v vide ploskogo kol’tsa so s’emnym rezhushchim instrumentom. (Device for drilling ice in form of flat ring with removable cutting tool). USSR Pat. 472,237 (In Russian) Clausen HB, Stauffer B (1988) Analyses of two ice cores drilled at the ice-sheet margin in West Greenland. Ann Glaciol 10:23–27 Clausen HB, Gundestrup NS, Hansen SB et al (1988) Performance of the UCPH shallow- and hand augers. In: Proceedings of the third international workshop on ice drilling technology, Grenoble, France, 10–14 Oct 1988. LGGE, Grenoble, pp 14–20 Connelly RD (1964) Ice auger. U.S. Pat. 3,129,775

51 Coring Systems (n.d.) Kovacs enterprises. Ice drilling and coring equipment. Available at: http://www.kovacsicedrillingequipment. com/coring_systems.html. Accessed 19 July 2013 Cox GFN, Richter-Menge JA, Weeks WF et al (1985) Mechanical properties of multi-year sea ice, Phase II: test results. USA CRREL Report 85-16 Cragin JH, Gow A, Kovacs A (1986) Chemical fractionation of brine in the McMurdo Ice Shelf. Antarctica J Glaciol 32(112):307–313 Crary AP (1958) Arctic ice island and ice shelf studies Part I. Arctic 11 (1):3–42 Drilling ice: Antarctica (2004) Association for the Science of Limnology and Oceanography. Available at: http://www.aslo.org/ photopost/showphoto.php/photo/535/title/drilling-iceantarctica/cat/ 502. Accessed 21 July 2013 Field Manual for the United States Antarctic Program (2001) Raytheon Polar Services Company (RPSC). Prepared for the National Science Foundation/Office of Polar Programs (NSF/OPP) Final report on development of ice mechanics test kit for Hydrographic Office, U.S. Navy (1950) Soils, Foundation and Frost Effects Laboratory, Corps of Engineers, U.S. Army, New England Division, Boston, Mass Goetz JJ, Shturmakov AJ (2013) Design of a new IDDO hand auger. In: 7th international workshop on ice drilling technology: abstracts. Pyle Center, University of Wisconsin-Madison, Madison, USA, 9– 13 Sep 2013, p 66 Green RD (1945) Design for an ice auger. U.S. Pat. Des.,141,685 Gundestrup NS, Hansen SB, Johnsen SJ (1988) Refinements of the UCPH shallow drill. In: Proceedings of the third international workshop on ice drilling technology, Grenoble, France, 10–14 Oct 1988. LGGE, Grenoble, pp 6–13 Hand Augers. Prairie Dog. Operator Manual (2010) The University of Wisconsin. Space Science & Engineering Center. University of Wisconsin-Madison, Madison Hughes OL, Terasmae J (1963) SIPRE ice-corer for obtaining samples from permanently frozen bogs. Arctic 16(4):270–272 Hutchison K (2004) Ice cliffs a mystery. The Antarctic Sun, 12 Dec 2004, pp 1, 7–8 Ice Drills and Corers (1958) J Glaciol 3(21):30 Ice Engineering: Design, Construction and Operation Maintenance (2002) Department of the Army, U.S. Army Corps of Engineers, Washington, DC Images related to Arctic environmental transformations paper (n.d.) PEARL paleoecological environmental assessment and research laboratory, Department of Biology, Queen’s University, Kingston ON, Canada. Available at: http://post.queensu.ca/ *pearl/cf8/cf8pics.html. Accessed 31 May 2015 ION Electric Ice Auger (2012) Sportsmen’s direct: targeting outdoor innovation. Posted on 4 Sep 2012. Available at: http://www. sportsmensdirect.com/blog/ion-electric-ice-auger/. Accessed 21 July 2015 Jiffy Ice Drills (2010) U.S. Engineered for ultimate performance™. Product catalog Johnson MC (1954) Ice boring device. U.S. Pat. 2,666,623 Karr EA, Sattley WM, Rice MR et al (2005) Diversity and distribution of sulfate-reducing bacteria in permanently frozen Lake Fryxell, McMurdo Dry Valleys Antarctica. Appl Environ Microbiol 71 (10):6353–6359 Koci BR (1984) A lightweight hand coring auger. In: Proceedings of the second international workshop/symposium on ice drilling technology (USA CRREL Special Report, 84–34), Calgary, Alberta, Canada, 30–31 Aug 1982, pp 55–59 Koci B (1988) New directions in drilling and related activities. In: Proceedings of the third international workshop on ice drilling technology, Grenoble, France, 10–14 Oct 1988. LGGE, Grenoble, pp 21–23

52 Koci BR, Kuivinen KC (1984) The PICO lightweight coring auger. J Glaciol 30(105):244–245 Korotkevich YS (ed) (1965) Pyataya kontinental’naya ekspeditsiya 1959–1961 gg. Obshchee opisanye (Fifth continental expedition of 1959–1961, general description). Trudy Sovetskoy Antarkticheskoy Ekspeditsii (Transactions of Soviet Antarctic expedition), 36 (In Russian) Kuivinen KC (1983) A 237-meter ice core from South Pole Station. Antarct J US 18(5):113–114 Kyne J, McConnell J (2007a) The ‘Prairie Dog’: a double-barrel coring drill for hand augering. Ann Glaciol 47:99–100 Kyne J, McConnell J (2007b) The sidewinder for powering a hand coring auger in drilling and lifting. Ann Glaciol 47:101–104 Lake Fluctuations—Dry Valleys of Antarctica (2003) Climate Change Institute. Available at: http://climatechange.umaine.edu/Research/ Expeditions/2003/MillenialLakes/Spire.html. Accessed 22 July 2014 Ledobur Mora Ice Micro 150 mm (n.d.) On-line Magazin-Rybolov (On-line Shop-Fishman). Available at: http://zabolotskiy.ru/?page= goods&id=852&object=1652. Accessed 21 July 2013 (In Russian) March 2002 deployment of the autonomous ocean flux buoy at the North Pole Environmental Observation Station (n.d.) NPS Autonomous Ocean Flux Buoy Program. Available at: http://www.oc.nps. edu/*stanton/fluxbuoy/field/npeo_deploy.html. Accessed 19 July 2013 McAnerney JM (1970) Tunneling in a subfreezing environment. In: Rapid excavation problems and progress. Proceedings of the tunnel and shaft conference, Minneapolis, Minnesota, 15–17 May 1968. Society of Mining Engineers of the American Institute of Mining, Metallurgy, and Petroleum Engineers, Inc., New York, pp 378–394 Mechanical Drilling Photo Gallery (n.d.) Kovacs enterprises. Ice drilling and coring equipment. Available at: http:// kovacsicedrillingequipment.com/mechanicle-drilling-photo-gallery/ . Accessed 9 Mar 2015 Medvedev AG (1979) Ustroistvo dlya obrazovaniya skvazhin vo l’du (Device for forming holes in ice). USSR Pat. 641,249 (In Russian) Miller MM (1954) Mechanical core drilling in firn and ice (with a report on related investigations in the Taku Glacier, S. E. Alaska, 1950–53). Mimeographed report prepared for the E.J. Longyear Co., the Eastman Oil Well Survey Co., and the Geological Society of America Miller MM (1958) Phenomena associated with the deformation of a glacier bore-hole. Extrait des Comptes Rendus et Rapports Assemblee Genbrale de Toronto 1957 (Gentbrugge 1958), Tome IV, pp 437–452 Nijampurkar VN, Bhattacharya SK, Mukerji S et al (1988) Oxygen isotope studies in Antarctica. Fifth Indian Expedition to Antarctica, Sci. Rep., Department of Ocean Development, Tech. Publ., 5, pp 171–179 Persson RKO (1948) Isborr (Ice drill). Sweden Pat. 144,977 (In Swedish) Ragle RH, Blair RG, Persson LE (1964) Ice core studies of Ward Hunt Ice Shelf, 1960. J Glaciol 5(37):39–59 Rand J, Mellor M (1985) Ice-coring augers for shallow depth sampling. USA CRREL Report, 85–21 Shepherd A, Jenkins A, McMillan M et al (2010) AFI8/25: Isolating the Larsen-C Ice Shelf mass instability. Determining melt rates at the base of the ice shelf. Field report: Nov 2009–Jan 2010

4

Hand- and Power-Driven Portable Drills

Stephenson PJ, Lister H (1959) Preliminary results of the glaciological work on the Trans-Antarctic expedition, 1955–58. J Glaciol 3 (25):426–431 Surface Science (2011) NEEM ice core drilling project. Available at: http://www.photo.neem.dk/2011/Surface-Science/20025267_ RdrBJk#!i=1578418641&k=qQ2tQPj. Accessed 21 July 2014 Tavrizov VM (1966) Mekhanizirovannyi ledovyi bur (Power-driven ice drill). Avtomobil’nye dorogi (Automobile roads), vol 12, p 20 (In Russian) Thompson LG (1979) Ice core studies from Mt Kenya, Africa, and their relationship to other tropical ice core studies. Sea level, ice, and climatic change. In: Proceedings of the Canberra Symposium, Dec 1979. IAHS Publ., vol 131, pp 55–62 Tsykin EN (1962) Metodika izmereniya temperatury lednikov, primenyavshaysya Institutom Geografii AN SSSR v issledovaniyakh Mezhdunarodnogo geofizicheskogo goda (Methods of temperature measurements used by Institute of Geography at researches of International Geophysical Year). Akademiya nauk SSSR. Institut geografii. Materialy gliatsiologicheskikh issledovanii (Academy of Sciences of the USSR. Institute of Geography. Data of Glaciological Studies) vol 6, pp 113–127 (In Russian) Tsykin EN (1963a) L’egkie buroviye shtangi dlya bureniya na glubiny 6–7 m i 12–15 m (Light-weight drill rods for drilling to the depth of 6–7 and 12–15 m). Akademiya nauk SSSR. Institut geografii. Materialy gliatsiologicheskikh issledovanii (Academy of Sciences of the USSR. Institute of Geography. Data of glaciological studies) vol 7, pp 135–136 (In Russian) Tsykin EN (1963b) Buroviye shtangi s sharnirnym sochleneniem (Hinged drill rods). Akademiya nauk SSSR. Institut geografii. Materialy gliatsiologicheskikh issledovanii (Academy of Sciences of the USSR. Institute of Geography. Data of glaciological studies) vol 7, pp 137–139 (In Russian) Tsykin EN (1963c) Burovyie stakany dlya l’da i firna (Core barrels for ice and firn). Akademiya nauk SSSR. Institut geografii. Materialy gliatsiologicheskikh issledovanii (Academy of Sciences of the USSR. Institute of Geography. Data of glaciological studies) vol 7, pp 139–140 (In Russian) Tsykina GA, Vilesov EN (1963) O temperaturnom rezhime lednika Tuiuksu Tsentral’nyi (About temperature regime of the Central Tuiuksu Glacier). Issledovaniya lednokov i lednikovikh raionov. Akademiya nauk SSSR. Institut Geografii. Mezhduvedomstvennyi Geofizicheskyi Komitet pri Prezidiume AN SSSR (Investigations of glaciers and polar regions. Academy of Sciences of USSR. Interdepartmental) Ueda H, Sellmann P, Abele G (1975) USA CRREL snow and ice testing equipment. USA CRREL Special Report, 146 Vilesov EN, Shabanov PF (1961) Iz opyta bureniya na visokogornikh lednikakh (Drilling experiment on high-mountain glaciers). Glyatsiologicheskie issledovaniya v period MGG. Zailiiskii i Dzhungarskii Alatau (Glaciological investigations during IGY. Zailiiskii i Dzhungarskii Alatau) Alma-Ata, Izd-vo Akad. nauk Kazakhskoi SSR (Alma-Ata, Publisher: Academy of Sciences of Kazakh Soviet Socialist Republic) vol 1, pp 31–35 (In Russian) Ward WH (1954) Studies in glacier physics on the Penny ice cap, Baffin Island, 1953. Part II: portable ice-boring equipment. J Glaciol 2(16):415, 433–436 Whillans IM, Bolzan JF (1988) A method for computing shallow ice-core depths. J Glaciol 34(118):355–357

5

Percussion Drills

In a general sense, “percussion ice drilling” refers to the process of drilling boreholes by the percussive destruction of ice. The percussion drills used for ice drilling can be classed as: (1) cable-tool drill rigs, (2) pneumatic drills, and (3) rotary-percussion drills that combine rotary and percussive actions. The last two methods have been used for the shallow ice drilling (120 m through ice

NA

Mathews (1964), Walsh (1963), Wasteneys (2007)

1976

GISP drilling project

Dye 3, 65° 11′N, 43° 49′W (Greenland)

93 m

Wire-line drilling

Langway et al. (1985) (continued)

6.1 Dry Drilling

61

Table 6.1 (continued) Time

Organization

Drilling location

Depths

Hole cleaning method

References

1976–1977

RISP drilling project

J-9, Ross Ice Shelf, 82°22.5′S, 168°37.5′ W (Antarctica)

103 m; 330 m

Wire-line drilling; noncore drilling

Rand (1977)

1977–1978

RISP drilling project

J-9, Ross Ice Shelf, (Antarctica)

170.8 m

Wire-line drilling

Chiang and Langway (1978)

1982–1983

28th Soviet Antarctic Expedition

Base Druzhnaya (Antarctica)

172 m

Wire-line drilling

1983–1984

29th Soviet Antarctic Expedition

Base Druzhnaya (Antarctica)

0–47; 47–230 m

Auger drilling; wire-line drilling

Kudryashov et al. (1983, 1988), Bychenkov and Egorov (1986), Zhigalev and Shkurko (1988), Bobin et al. (1988)

1984–1985

30th Soviet Antarctic Expedition

Base Druzhnaya (Antarctica)

0–60; 60–310 m

Auger drilling; wire-line drilling

1985–1986

31st Soviet Antarctic Expedition

Base Druzhnaya (Antarctica)

55; 45; 0–40; 40–301 m

Auger drilling; wire-line drilling

1996–2002

USA CRREL

Amundsen–Scott Station, South Pole

Several shallow holes

Auger drilling

Walsh (2003)

1998

University of Alaska-Fairbanks

Black Rapids glacier (Alaska)

Four hole with maximum depth of 620 m

Water circulation

Truffer et al. (1999)

1971– 1973; 1997; 2008–2011

Various exploration companies

Isua Greenstone Belt, Greenland

*80 holes with maximum depth of 800 m

NA

Colbeck and Gow (1979), MINEX (2011)

1990; 2010

Cominco Ltd.; Roca Mines Inc.

Foremore Glacier, Canada (57° 03′N, 130° 58′W)

10 holes with maximum depth 340 m

Brine

Lee and Paterson (1991), Diamond Drilling Project: Looking Through a Glacier (2010)

A hydraulic drill rig of the S.D.H. 200 type (Fig. 6.1) was used. This was identical to that employed for diamond drilling in rocks, except for two changes: (1) the drilling spindle was modified to allow the use of tubes with an outside diameter of 47 mm, and (2) the drive pulleys were changed in order to obtain a relatively low-speed rotation. The power was supplied by a six-cylinder Studebaker generator with a nominal capacity of 55 kW. Initially, the attached winch was used for lifting the drill rods. However, from a certain depth, the capacity of this winch was insufficient, and an additional winch of the Bonneville type was installed on the machine axis. The obvious disadvantage of this winch was the drum, which was big and difficult to handle.

At Camp VI, drilling up to a depth of 100 m was accomplished using two shifts (day and night), while at deeper depths and at Station Centrale, the operations were switched to one 12–13 h shift because adding to the drill pipe length required the simultaneous presence of three men. The upper 3 m of firn was cased using an NX tube-guide with an ID/OD of 88/98 mm. In order to prevent the drill string from sticking during drilling, when the drill string was running into the hole, its surface was brush covered by a mixture of thin oil with kerosene, which remains a liquid even at low temperatures down to −30 °C. The penetration rate in firn varied in the range of 9– 24 m/h. The overall drilling speed decreased with depth, and at the depth of 100 m, it was close to 1.5 m/h. It was found

62

6 Conventional Machine-Driven Rotary Drill Rigs

Fig. 6.1 Assembling of drill rig, Greenland, 1950 (Heuberger 1954)

that the optimal rotation speed of the drill string was 200 rpm. The drill bit had eight teeth (Fig. 6.2). The height of the drill bit was 50 mm, and the inner/outer surface of the teeth had an offset of close to 1.5 mm. When adding a length of drill pipe to the drill string or re-jawing the drilling spindle, the drill rig had to lift the drill string. Otherwise, if the entire weight of the drill string was set on the bottom of the hole, the drill bit could become stuck under the high load. Such accidents occurred at depths of 96 m at Camp VI and 74 m at Station Centrale, and the recovery was very time consuming. Other types of accidents also occurred from time to time. At Camp VI, the drill string fell into the hole from a height of close to 50 m, and recovered it tooking 9 h of continuous work. Although the temperature in the hole was rather low (−14 °C at Camp VI and −27 °C at Station Centrale), immediately after penetration began, the heat dissipated by the rotation melted the surface of the ice core, which then re-froze and became stuck inside the core barrel. This is why the penetration was started with a low rotation speed, and the inner surface of the core barrel was covered by the oil lubricant Transyl. To ensure that the core did not fall during lifting, more rapid rotation was performed at the end of the drilling run, which had the wedging effect. Taking into consideration the maximum torque of the drill rig, down to 41.5 m at Camp VI and 57 m at Station Centrale, French drillers used the type AX core barrel with an ID/OD of 47/57 mm. Below 50 m, the core barrel was reduced to the EX-barrel with an ID/OD of 37/47 mm. At Station Centrale, a hole was excavated by means of a special

Fig. 6.2 Drill head with teeth used in Greenland, 1950 (Heuberger 1954)

one-ton plunger down to 30.5 m. It had a diameter of 0.8 m, which allowed a man to be lowered down and study the snow-firn stratigraphy.

6.1.2

Baffin Island Expedition

This expedition carried out a program of geological, glaciological, and biological investigations near the Clyde settlement on the east coast of Baffin Island, Canadian Arctic, in 1950. An X-ray gasoline-driven diamond drilling unit (weight 90 kg), manufactured by Boyles Bros. Drilling Co., Ltd. was used for drilling in cold ice (Ward 1952). It was considered that this drilling machine could be used conveniently for drilling to depths of about 46 m (the maximum depth achieved was not reported). The machine was equipped with its own broad skis fashioned from box-wood and bolted to the four legs. Thus, two men could tow it quite readily anywhere on the cap, through slush rivers and across lake ice submerged in water. A special saw-toothed 1½″ (38 mm) coring tool with one vertical slot was used. The ice cuttings from the set sawteeth

6.1 Dry Drilling

63

Fig. 6.4 Drilling rig at Maudheim, Antarctica (Schytt 1958)

Fig. 6.3 Coring tool designed for Baffin Island Expedition, 1950 (Ward 1952)

found their way upward into the slot and on to the top of the ice core. In later developments, the quantity and shape of the slots were modified to four spiral slots in order to improve the upward travel of ice cuttings from the sawteeth and prevent jamming of the core (Fig. 6.3). Another set of sawteeth on the upper edge of the core barrel was designed to prevent the coring tool from sticking when it was raised. The coring tool worked rather well in cold ice. Little axial load was required when drilling, other than the weight of the unit and that of the drillrods (2.4 kg/m). The coring tool tended to jam when proper care was not taken, and the cores were disturbed. To release the core from the solid drawn steel tube, it was warmed for a moment in the engine exhaust gases. Occasionally, there was a problem in raising the coring tool, even though it was quite free to rotate.

6.1.3

Norwegian-British-Swedish Antarctic Expedition

The glaciological programme of the Norwegian-BritishSwedish Antarctic Expedition, 1949–1952, included a

thorough study of the structure of the ice shelf upon which the Maudheim base was built 2.2 km from the nearest ice front of the Quar Ice Shelf, Dronning Maud Land. For this purpose, a U.G. Straitline core drilling rig powered by a 22 kW gasoline engine and equipped with an N-double hydraulic swivel head was bought from Longyear Company, North Bay, Ontario, Canada (Schytt 1958). The weight was considerable, with 1900 kg for the drilling machine, 620 kg for the pumps, 100 kg for the core barrel, and 7.9 kg/m for the drill rods (size N, 60.3-mm OD). Because dry drilling was tried, the pumps were never unpacked and used. The rig was set up on the bottom of a 1.3 m-deep pit and covered by a hut (Fig. 6.4). First, during April and May 1950, the rig was used for drilling thermometer holes to various depths between 8 and 45 m. Then, in the middle of July 1950, the deep coring was started, but had to be stopped at a depth of 50 m at the end of August because of the approaching summer season. During the second wintering, the hole was deepened from 50 m to 100 m. The drilling encountered various difficulties and complications. Once, at a depth of 63 m, the core barrel became stuck, and the drill stem broke (Giæver 1958). The standard-teeth core drill bit was modified because the teeth were too small (or there were too many), which caused the spaces between the teeth to become completely jammed with ice. This often stopped the drilling after 10 or 20 cm. After every second tooth of the best bit had been ground away, the results were better. The rate of progress varied greatly with the depth. At 30–40 m, an advance of 5 m per day was considered fair, and at a depth of 90 m, 2 m per day

64

6 Conventional Machine-Driven Rotary Drill Rigs

was good. Each individual drilling operation consisted of approximately 1 h of screwing together and lowering drill rods, a few minutes of actual drilling, and then one or several hours of hoisting and unscrewing drill rods. The run length was about 1–1.5 m when the penetration was good. The main problem involved the ice core quality: no undisturbed cores were recovered, and the ice was ground into small chips. It was impossible to free the core from the core barrel; the reaming shell and coring bit were completely stuck. This caused much trouble.

6.1.4

Mirny Station, Antarctica

During the 2nd CAE (1957–1958), several holes were drilled near Mirny Station in Antarctica using the conventional, KAM-500 mechanical drilling rig. The drill rig was installed inside a 9 m × 4.5 m wooden shack with a 14 m tall derrick (Fig. 6.5). The drilling shelter was constructed at the station workshop over a period of 4 months (Treshnikov 1960). Test hole #1 (July 7–September 10, 1957) was started at the location of the construction just at Mirny Station. No special devices for lifting the cuttings were used. Several types (16 different variants) of cutting bits were tried, along with several core barrels and various rotational speeds, but nothing resulted in cores with improved quality and length. The cores were broken up into pieces 5–15 cm in length. The first 20–30 cm of penetration on each run went well, but excessive cutter loading was required thereafter. It was possible to obtain a 0.8–1.2-m drill run. At a depth of 64.5 m, the bedrock was reached, and the hole penetrated 2.2 m into the subglacial rock using shot drilling. Prior to diamond bit drilling, this was a technique

used for hard material, in which steel or cast iron pellets are fed beneath a rotating bit. During rotation, the pellets break into small, sharp pieces, which erode the rock. The final depth of hole #1 was 66.7 m. Then, the drill rig was transported 7 km south of Mirny Station, where hole #2 was sunk (September–December 24, 1957). Up to a depth of 43 m, the drilling was accomplished without problems, and core recovery was almost complete. Deeper drilling was complicated by various accidents such as drill-string breakage and drill-rig failure. At a depth of 220 m, fluid circulation using kerosene was tested, but the experiment was stopped because of fire and health hazards. After pumping out the kerosene, dry hole drilling was continued. Finally, the drilling was stopped at a depth of 371 m because of frequent sticking of the core barrel and the risk of losing the hole. The ODs of the drill bits were as follows: 146 mm at 0–61 m, 131 mm at 62–249 m, and 112 mm at the last interval. For future temperature measurements, casings with ODs of 146 mm (0–59 m) and 108 mm (60– 355 m) were set in the hole. The total time of the drilling operations was 105 days. Afterward, the drill shelter was transported 45 km south of Mirny Station, where over four days, hole #3 was drilled to a depth of 100 m (January 17–21, 1958). The core was recovered from the whole length of the hole. The final OD of the drill bit was 112 mm.

6.2

In construction engineering, auger drilling is restricted to generally soft unconsolidated material or weak weathered rock and is used for environmental drilling, geotechnical drilling, soil engineering, and geochemistry reconnaissance work in the exploration for mineral deposits. It is relatively cheap and rather fast.

6.2.1

Fig. 6.5 Derrick of KAM-500 drill rig, 7 km from Mirny Station, 1957 (Photo M.M. Lyubarets; Treshnikov 1960)

Auger Drilling

Mirny Station, Antarctica

During the 2nd CAE (1957–1958) seismic surveying was conducted within a 225 km radius of Mirny using a conventional UShB-1 auger rig (Treshnikov 1960). The drill rig was mounted on the chassis of a ZIS-151 auto-track and driven from its engine. The chassis with the rig was fixed on the sledges, and the driver’s cabin and motor were covered by a plank-built shack (Fig. 6.6). The mast had two positions: horizontal for transportation and vertical for drilling. From February 1957 to January 1958, 98 holes with a total length of 1632 m without cores were drilled. The deepest was 102 m, 50 km from Mirny. Drilling with a commercial core auger in order to get core samples failed as the snow, firn, and ice were totally disturbed. Noncore auger

6.2 Auger Drilling

65

Fig. 6.6 UShB-1 auger drill rig, vicinity of Mirny Station, 1957 (Photo M.M. Lyubarets from Treshnikov 1960)

drilling was quite effective: in fine weather, it was possible to drill two 50 m-deep holes per day. Another drilling project was conducted during the 5th CAE (1960–1961) in conjunction with seismic investigations. A type URB-1 auger rig, weighing 485 kg, was specially built by Gyproneftemash and mounted inside a sled-mounted shack (Korotkevich 1965). The drill rig was powered by a gasoline engine (SD-44). Near Mirny Station, several holes with depths of 30–70 m were drilled, with a total length of 380 m. Drilling one hole took 6–10 h, depending on the borehole depth. From 15 to 30 % of the borehole was filled by cuttings that had fallen down during the trip out. The drill string was rotated at 75–85 rpm, and the hole diameters were 120 mm. The rate of penetration decreased with depth from 180 (sic) to 3.6 m/h. The attempt to recover a core was not successful.

6.2.2

McMurdo Station, Antarctica

Over many years, near McMurdo Station, Antarctica, conventional drill rigs were used for drilling large-diameter holes in sea ice for sampling seawater, providing access for scuba diving, deploying sub-sea remotely operated vehicles (ROVs), and other purposes. In summer seasons of 1965 to 1967, various augers were tested with a conventional B40L rotary-type drill rig in the vicinity of McMurdo Station, Antarctica (Beard and Hoffman 1967). The drill rig was hydraulically operated and had a 3.65 m folding drill tower. The hydraulic unit was driven by a gasoline-operated, 4-cylinder, water-cooled Ford industrial engine that developed 35.3 kW at 2800 rpm. The rotary spindle, driven by a hydraulic motor, was controlled through a 4-speed gear transmission that gave a speed range of 58–455 rpm. The drill rig was mounted on one-half of a 20-ton bobsled and

Fig. 6.7 Conventional B40L rotary-type drill rig on sea ice near McMurdo Station, 1973 (Antarctic Photo Library, n.d.)

required a crawler tractor for towing. Later, the drill rig was re-mounted on a rubber-tired trailer (Fig. 6.7) built on the running gear of a 5 t, 4-wheel farm trailer fitted with special hubs and 6-ply sand tires for low-ground-pressure travel (Hoffman and Moser 1967). Four augers of three different types were tested in both ice and snow: (1) 24″ (609.6 mm) medium-duty short-shaft augers with replaceable tool steel-cutting teeth (Fig. 6.8), (2) 10″ (254 mm) finger-type multi-purpose drill head with replaceable hard-faced steel teeth, and (3) 12″ (304.8 mm) and 24″ (609.6 mm) earth augers with replaceable tool steelteeth and shutter plates for retaining the drill cuttings. The operations of these four different auger-type drills in snow were quite similar. All the augers cut the snow with ease but presented problems in removing the dry, granular, sugar-like cuttings from the hole. Then, the drill rig was moved to the annual sea ice, which had a thickness of about 2.5 m. All of the augers were used for producing holes in the sea ice, with fairly similar results. No difficulties were encountered in drilling and removing cuttings in the drier ice near the surface. As the cuttings became

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Fig. 6.8 Medium-duty 24″ short-shaft auger (Beard and Hoffman 1967)

slushy wet with included brine, they again slid down the auger helix and were lost. The augers with the shutter plates retained the wet cuttings moderately well; however, they continued to spill off the sides. When these augers were pulled to the surface, shovels were needed to remove the ice cuttings, which could not be spun off by centrifugal force. The finger-type bit with a 10″ conveyor was satisfactory and could drill through the 2.5 m ice in 80 s. No problem was encountered with cuttings left in the hole because the floating sea ice was penetrated. A slower rotation speed was required for the 24″ auger than for the smaller

Fig. 6.9 Reedrill 330 auger drill making preparations for drilling through sea ice near McMurdo Station, Antarctica, October 2011 (Flickr: Sandwich 2011)

6 Conventional Machine-Driven Rotary Drill Rigs

augers. Either the first or second gear of the drive transmission could be used without chattering of the bit, provided the down pressure on the bit was not excessive. The leveling of the drill unit was found to be important to the drilling operation, and was subsequently accomplished by installing hydraulic stabilizers at the rear corners of the sled. These were operated from the control panel of the drill. The smaller type AW drill rods broke readily with all the augers. This was partially attributed to operating the drill at higher speeds in a non-level position. When this rod was replaced with the heavier NW type, no further breakage occurred. Separation of the threaded connections on the heavier drill rod was difficult and could not be accomplished with 24″ pipe wrenches in many instances, even with the threads well lubricated. Later, the B40L drill rig was changed to the hydraulic TEREX® Reedrill 330 auger drill, which was designed mainly for the foundation construction industry (Fig. 6.9). The Reedrill 330 was mounted on a tracked base moved by a snow vehicle with a top speed of 15 km/h, and it was equipped with a 4′ (1.22 m) auger bit (Sea Ice Science Support: Observation Tube, McMurdo Station 2007). The height of the mast is 7.56 m, and the weight of the drill without the chassis is 8.2 t (Terex Reedrill 330 Auger Drill 2009). The rotation speed is changed using a three-speed gearbox, with gear one providing 32.2 rpm at 71.3 kN m, gear two providing 83.7 rpm at 29 kN m, and gear three providing 238.4 rpm at 10 kN m.

6.2 Auger Drilling

This drill cannot drill through multiyear sea ice in one push. Instead it must be pushed down the length of the drill bit, brought up to dump the cuttings at the side of the hole, and then be pushed down again. This is repeated until the water underneath the ice is reached. Drilling through multiyear sea ice with a thickness of 5–6 m usually takes 5–10 min.

6.2.3

Amundsen–Scott Station, South Pole

In 1991, the USA CRREL initiated a project to design, develop, fabricate, test, build, and deploy a system for the machining of unlined tunnels at the Amundsen–Scott Station, South Pole (Walsh 2003). These tunnels are to be used for personnel passage; power, water, and sewer distribution; instrumentation, communication, and data lines; and equipment storage. The Simco 2400 SK-1 drill rig was used to drill access holes up to 12″ (304.8 mm) in diameter for the vertical chip conveyance tubing and power cord to supply power from the sled-mounted generator module on the surface to the tunneler. There was also a plan to ream these holes up to 36″ (914.4 mm) in diameter so that they can be used as an emergency exit to the surface. The Simco 2400 SK-1 drill rig is a diesel engine-powered, trailer-mounted drill with special CRREL-designed skis to allow easy transport on snow (Fig. 6.10). The controls have been slightly modified to allow speed control when operating the up-feed as well as the down-feed of the drill head traverse. Heaters have been added to the hydraulic tank to operate at the low temperatures found during the austral summer from −25 to −50 °C but have proven to be of limited value. Fig. 6.10 Simco 2400 SK-1 drill rig at South Pole (Walsh 2003)

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The drill rig is equipped with along stroke mast. The bit has the same diameter as the augers. Access holes were drilled using 12″-diameter single-flight augers. The auger was in 1 m length, and three assemblies were made up using three segments each, for a total length of 9 m. One segment was left for attachment to the auger head when starting the hole. There are two bits available for the drill, a single-cutter/single-helix bit (0.9 m long) and a double-cutter/double-helix bit (0.3 m long). The double bit head was generally used because of its superior cutting characteristics. To drill out the 36″ holes, the drill rod was inserted down the 12″ borehole, a 36″-diameter back reamer bit was attached in the snow tunnel, and the hole was drilled from the bottom up by essentially pulling the rods back up and out of the hole. A 12″ plug on the upper end of the bit keeps the bit centered in the access hole. The cuttings were dropped to the floor of the tunnel as the back reaming progressed to the surface. Because the drill rig controls were side facing, the operator was able to stand clear of the borehole as it was completed. From 1996 to 2002, a series of tunnels was driven into firn at South Pole Station, which caused a large number of problems, especially with the tunneler. Although tests with the drill system, including the 36″ back boring bit, were carried out with variable success, the project was canceled. The maximum operating depth was increased to 14 m from the surface to the tunnel roof from the original 10 m. Therefore, the amount of drill string was insufficient to reach the tunnel roof when the double cutter bit was used. Thus, the drill string had to be removed, the bits swapped, the string re-lowered into the hole, and the last 0.3 m drilled. Warm-up of the drill rig proved critical: it was very dangerous and difficult to operate, especially when cold. The

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6 Conventional Machine-Driven Rotary Drill Rigs

Fig. 6.11 Auger Torque Earth Drill TC3000, Subglacial Lake Ellsworth camp (Auger Torque Australia Pty Ltd. 2013)

drill rig had a large hydraulic reservoir with undersized heaters, and starting the drill rig was very difficult. If the drill rig was operated with cold oil, frothing occurred because the drill rotation and lift/lower hydraulic motors caused air entrainment.

6.2.4

A torque in the range of 0.96–3.12 kN m is produced by a hydraulic motor through an epicyclic gearbox. The rotation speed of the output shaft is adjusted from 7 to 46 rpm. The recommended diameters for drilling are 100–600 mm using S4 range augers. The length of a continuous-flight auger is 600–950 mm, depending on the diameter, and the maximum overall length of the drill stem with extensions is 12 m.

Subglacial Lake Ellsworth Camp

An Auger Torque Earth Drill TC3000 was used to bore through the snow and firn as part of the Subglacial Lake Ellsworth exploration project in Antarctica (Auger Torque Australia Pty Ltd. 2013). The Earth Drill TC3000 has a 73 kg top drive that hangs on a truck crane boom (Fig. 6.11). Fig. 6.12 Ice fishing at Great Slave Lake, Canada (Northwest Territories Fishermen’s Federation, n.d.)

6.3

Commercial Drill Rigs for Ice Fishing

Several decades ago, a series of movable and truck-mounted drill rigs were designed to bore large-diameter holes (typically 300 mm or more) for commercial winter net fishing. As

6.3 Commercial Drill Rigs for Ice Fishing

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Fig. 6.13 Fershtuta–Paschenko ice drill rig (Bogorodsky et al. 1983). 1 Engine; 2, 17 sleeve; 3, 14 rack; 4, 20 tongue and slot coupling; 5, 11, 12, 22, 23, 29 bearings; 6 shaft; 7 gear case; 8 driving bevel gear; 9 axle; 10 coupling element; 13 key slot of spindle; 15, 25 gear‐wheels;

16 handle; 18 tube; 19 hand hold; 21 worm gear; 24 drive hub; 26, 30 sled; 27 drilling head; 28 device for moving snow down; 31 shaft; 32, 33 warping head

an example, Fig. 6.12 shows an auger-powered drill rig mounted on a snow vehicle. Unfortunately, the data on these kinds of drilling rigs are very poor, and nowadays they are rarely used. Hereinafter, drill rigs for ice fishing designed in USSR (Bogorodsky et al. 1983) are briefly reviewed. The Fershtuta–Paschenkoice drill rig is mounted on a steel sled and powered by a 4.4 kW gasoline engine of the L-6 type running at 2200 rpm (Fig. 6.13). The rotation speed of the guide rod and drill bit is very high–1100 rpm. The drill bit has two blades with an outer diameter of 300– 350 mm in different modifications. The maximum drilling depth is 0.5–0.6 m. The driller stays on the platform and manually feeds the guide rod with the attached drill bit. During drilling, cuttings are not removed, but the hole is cleaned after completion if necessary. Drilling to a depth of 0.3 m is easily accomplished, but to drill deeper, it is necessary to significantly increase the load on the drill bit, which leads to extreme vibration of the guide rod. The drill rig weighs 350 kg. The ice drill rig LB-1 was designed in Giprorybprom (State Designing Institute of Fishing Enterprises), Moscow,

USSR, and powered by the same engine as the Fershtuta-Paschenko drill rig (Fig. 6.14). The rotation speed of the drilling bit was decreased to 665 rpm. The platform for the driller is hinged on the side. The maximum drilling depth is 0.6 m, with a hole diameter as high as 350 mm. The drill bit has been improved and has two short flights to lift cuttings upward. This is sufficient for drilling down to a depth of 0.3 m. To drill deeper, it is necessary to clean the hole by repeatedly lifting the drill assembly. The total weight of the drill rig is 470 kg. The Model 26 ice drill rig was designed by R.I. Pshenichnikov and I.N. Morozov for drilling holes with a diameter of 320 mm to a depth of 1.2 m (Fig. 6.15). This drill is powered by an engine of the ZID-4, 5 type. The 314 mm-diameter drill bit is equipped with three dismountable cutters with a rake angle of 55°, and cuttings are removed by short auger flights. The penetration rate is as much as 0.5 m/min. The lightweight ice drill OLB-42 was commercially produced in the USSR starting in 1965 (Fig. 6.16). The designed drilling depth is 0.6–0.8 m. The drill is powered by

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6 Conventional Machine-Driven Rotary Drill Rigs

Fig. 6.14 Ice drill rig LB‐1 (Bogorosky et al. 1983). 1 Steering wheel; 2 frame; 3 lever kit; 4 driller’s platform; 5 drilling bit; 6 cutters; 7 rods; 8 support; 9 sled Fig. 6.16 Ice drill rig OLB‐42 (Bogorosky et al. 1983). 1 Engine; 2 gear box; 3 drill mounting; 4 feeding device; 5 sled

Fig. 6.15 Ice drill rig of 26 model (Bogorosky et al. 1983). 1 Feeding device; 2 drill mounting; 3 warping head; 4 gear; 5 engine; 6 clamper; 7 sled; 8 drilling head

a 3.7 kW gasoline engine taken from a Vyatka motorscooter. The rotation of the drill bit can be varied using a three-speed gear box, with possible speeds of 195, 325, and 520 rpm. The weight of the OLB-42 ice drill is only 116 kg. The ice drill rig ILB-1 (ILB-2) is driven by a tractor’s power take-off shaft (Fig. 6.17). The initial feeding device was designed as a mechanical drive group with a system of

Fig. 6.17 Ice drill rig ILB‐2 (Bogorosky et al. 1983). 1 Drilling unit; 2 tractor; 3 winch; 4 base

conical and cylindrical gears. In the following modification, it was changed to a hydraulic feeding unit. The drill rig can be operated by one worker (tractor driver) because the

6.3 Commercial Drill Rigs for Ice Fishing

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Fig. 6.18 Ice drill rig PRAG‐ GPI‐56 (Bogorosky et al. 1983). 1 Vehicle; 2 drill mounting; 3 drill assembly; 4, 10 warping head; 5, 9 gear boxes; 6 hydraulic feeding device; 7 drill bit; 8 spindle

drilling control system is installed inside the cab. The rotation speed of the 350 mm-diameter drill bit is constant at 272 rpm. The maximum drilling depth is 1.5 m, with a penetration rate of close to 1 m/min. The total weight of the drill rig is 5 t. The ice drill rig PRAG-GPI-56 is mounted on a GAZ-47 tracked cross-country vehicle (Fig. 6.18) and powered by the 54.5 kW engine of the vehicle (the rotation speed of the crankshaft is 3000 rpm). The diameter of the drill bit is 350 mm, and the rotation speed can be adjusted in the range of 160–490 rpm. Continuous auger flights are used to recover cuttings from the hole. The maximum drilling depth is 2 m.

6.4

Air Rotary Drilling

When air direct circulation is used in drilling, cuttings are removed by the continuous circulation of air that flows down inside the pipe string and up-hole along the annular space between the borehole walls and the pipe string.

6.4.1

Mirny, Antarctica

The first drilling experience of Russians in Antarctica was carried out in October of 1956 just outside Mirny during the 1st CAE. Two holes to depths of 23.5 and 86.5 m were drilled using a conventional GP-1 type drilling rig (Kapitsa 1958). The drill rig was installed inside a sled-mounted shack with a 5.5 m tall derrick and powered from a 12 kW diesel generator. The drill head was made from spring steel without quench hardening. The outer diameter of the drill head was 60 mm (Fig. 6.19), no cores were retrieved, and the

Fig. 6.19 Drill bit for noncore drilling at Mirny, 1956 (Kapitsa 1958)

penetration rate was 9.5 m/h, with a rotation of 480 rpm. The cuttings were removed by the circulation of air provided by a PKS-6 portable air compressor with a maximum pressure of 0.45 MPa. The 86.5 m-deep hole penetrated into subglacial rocks. The main problems while drilling concerned the poor cutting removal and the formation of condensed water that froze on the drill pipes and borehole walls. From time to time, cuttings formed a heavy plug on the bottom of the borehole and drilling stopped. To solve this problem, hot water (80–90 °C) was dumped into the hole. When the water reached the bottom, it melted the cuttings and froze. Then, the drilling continued.

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6.4.2

6 Conventional Machine-Driven Rotary Drill Rigs

Site 2, Greenland

Ice coring operations were accomplished in Greenland during the summer seasons of 1956 and 1957 as part of the U.S. Army Corps of Engineers Greenland Research and Development Program. The drilling site, Site 2, was located in northwest Greenland, approximately 320 km east of Thule Air Base at an elevation of *2100 m a.s.l. (Langway 2008). The drilling was performed at the bottom of a 20 m × 4.5 m × 4.5 m trench (Fig. 6.20). After the rig was positioned near the end of the trench, a timber and plywood roof with a bent arch design and removable center keys was constructed over the trench. A Failing Model 314 rotary-type drill rig driven by a Buda HP-217 40 kW engine with a maximum hook load rated at 11.3 t was used (Lange 1973). The rig was modified to allow the use of the longest core barrels and drill pipe possible. The 8.5 m mast was replaced by a 11.5 m mast so that 6 m core barrels could be used continuously with 6 m lengths of drill pipe. Joy Company Sullivan model WK-80-315 cfm compressors driven by IH UD-16 diesel engines with a capacity of 8.9 m3/min were used for bottom-hole cleaning. In order to avoid melting both the hole wall and core by warm air, it was cooled using an air-to-air heat exchanger from temperatures as high as 120 °C to within −12 °C of the ambient air

Fig. 6.20 Below‐surface core drilling trench Site 2, Greenland, 1957 (Langway 2008)

temperature. The tube and fin principle was used, similar to the radiator of an internal combustion engine, except the compressed air was carried in the tubes instead of antifreeze. The radiator unit was 1.5 m × 1.5 m × 0.3 m, with three rows of tubes making five passes. Ambient air was pulled through using a 1.2 m six-blade fan driven by an 8.8 kW gasoline engine. A DCDMA double-tube core barrel with a 101.6/139.7 mm ID/OD and 6 m length was slightly modified by enlarging the annulus between the inner and outer tube extensions to reduce the air-flow constriction. The core barrel was fitted with a sludge barrel to collect cuttings that might be too large to be carried up the hole by the air stream and to collect the cuttings that would settle if the air stream suddenly failed during coring. A special 2.1 m handling sub, or length of drill pipe, was provided to avoid disassembly of the sludge barrel from the core barrel when the core barrel was connected to the drill pipe. The entire assembly, consisting of the core bit, core barrel, sludge barrel, and handling sub, was 9 m long. The coring bits carried multiple teeth of varying design; all cut a 45/8″ (98.4 mm)-diameter core and a 13¼″ (146 mm)diameter hole (Fig. 6.21). After testing and modifying, coring bits B-413-E through B-413-K were used in coring operations at Site 2 and subsequent operations in the Antarctic. Special reamers were used to guard against the possibility of hole closure by the plastic flow of the ice during drilling. They had the same tool joints as the drill pipe and could be inserted in the drill string at any point (Fig. 6.22). At the upper part of the hole, a casing with a 313/16″ (154 mm) ID followed the drilling. One shoe of the casing was made in the shape of cutting saw teeth and had the same diameter as the outside of the casing. The coring continued until circulation was lost. After this, the coring tools were pulled from the hole, and the casing was advanced by rotating and feeding weight with the hydraulic feed. Rotating and advancing the casing became increasingly difficult, and it was possible to only advance the casing to a depth of 43.5 m (48 m counting from the surface). Core drilling was done with the drill string held manually in tension, and the rotation speed was varied from 40 to 75 rpm. The rate of penetration ranged from 3.8 to 15.2 m/h. The core quality was generally fair, with cracking or disking. The core recovery was not continuous, but undisturbed samples were obtained over about 50 % of the profile (Langway 1967). The hole was advanced to 296 m by continuous coring. At this depth, progress averaged approximately two round trips per day, or about 11 m. In order to explore the problems of noncore drilling, it was decided to drill without core recovery to approximately 450 m and to attempt one or two coring runs at that depth before the end of the field season. A Hughes tricone, roller-type rock bit was substituted for the core barrel

6.4 Air Rotary Drilling

Fig. 6.21 Ice coring bits used in Greenland and Antarctica (Lange 1973). a B‐413‐E; b B‐413‐F; c B‐413‐G; d B‐413‐K; e B‐413‐J; f B‐ 413‐H

assembly, and noncore drilling was begun at 296 m. The bit shortly became stuck in the hole, and all efforts to extract it were in vain. The final depth of the hole was estimated to be 305 m from the ice sheet surface (Langway 1967). In 1957, the rig was moved 11.6 m up the trench. A noncore hole was drilled to a depth of 25 m, and the casing was set down to that depth. The plan was for the casing to run to a depth of at least 45 m, but unfortunately the shipment of the additional casing and all of the new equipment was delayed. Coring was begun with the original equipment from the 1956 season. Fairly good cores were obtained to 122 m, although regular cracking was beginning to appear. It was hoped that upward-flowing fine cuttings might seal the permeable zone below the bottom of the

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Fig. 6.22 Reamer used in Greenland and Antarctica (Lange 1973)

casing. This did not happen, and additional casing was set to 49 m shortly after it arrived. The casing was eventually advanced by under-reaming with a special cutting tool (Fig. 6.23): the blades were opened by air pressure and used to ream a 7″ (177.8 mm) hole. The utilization of the new equipment (drill bits, drill collar, and an additional compressor) that arrived in mid-season immediately improved the condition of the core. The two compressors ran continuously during drilling operations and maintained 0.4 MPa at the drill head at the maximum depth. To help prevent the ice from shattering during the coring operation, it was necessary to reduce the vibration of the core barrel and bit. This was accomplished by adding a heavy drill collar to the drill string just above the core barrel. A sludge barrel was still used above the drill collar.

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6 Conventional Machine-Driven Rotary Drill Rigs

Fig. 6.23 Failing under‐reamer (Lange 1973)

Continuous coring was terminated at 305 m, and a noncore hole was drilled to 352 m, where one coring run was made that produced a fair core. The open hole was continued to 401 m, where a final coring attempt produced some usable core. The hole was bottomed at 406.5 since the condition of the brakes no longer allowed the heavy string of tools to be safely lowered into the air-filled hole. The final depth of the hole was estimated to be 411 m from the ice sheet surface (Langway 1967). Core recovery during the 1957 operation provided nearly continuous undisturbed cores from 19 to 110 m, and about 75–85 % recovery from 110 m to 305 m; the remainder consisted of two 5-m lengths from 360 and 411 m. The core quality was considerably better than that in the previous season.

6.4.3

Byrd Station, Antarctica

The glaciological investigations at Byrd Station, West Antarctica, were a joint project of the Glaciology Panel, U.S. National Committee, International Geophysical Year (IGY),

and USA SIPRE. The drilling equipment used in Greenland was completely duplicated, with few additions. The main improvement was aimed at obtaining a more uniform feed rate that would be independent of the friction brakes of the main hoist (Lange 1973). This was eventually accomplished by the use of a truck winch driven by a small electric motor through a hydraulic transmission. The transmission allowed nearly infinitely fine variation of the ratio from 1∶1 to 100∶1. Thus, with the main hoist brake set, the electric motor would drive the truck winch at any required speed, and that speed could be very closely controlled by the hand wheel speed ratio adjustment of the transmission. The total weight of the drilling equipment delivered to Byrd Station was close to 46 t (Patenaude et al. 1959). Because there would be neither time nor equipment to construct a subsurface shelter, as was used in Greenland, a prefabricated shelter was provided for erection on the surface (Fig. 6.24). A framework of lightweight steel tubing covered by very strong fabric was designed similar to oilfield rig shelters. Drilling operations were begun on December 16, 1957, and completed on January 26, 1958. Casing was set down to

Fig. 6.24 Drilling rig in place with tubular steel frame and Naclon fabric shelter at Byrd Station, 1957–1958 (Photo A. Gow; Polar Ice Coring and IGY 1957–58 2008)

6.4 Air Rotary Drilling

a depth of 35 m. Coring was continued to 309 m without incident. The rate of penetration ranged from 4 m/h to 15 m/h. For the last few meters, a rotation speed of 50– 55 rpm and rate of penetration of 6 m/h were found to be the optimum. Two reamers were used 6 and 12 m above the drill collar to maintain the diameter of the hole by preventing cuttings from adhering to the hole walls. A core was recovered for 98 % of the distance, and most of this was good quality. The cores contained many incipient fractures roughly approximating a horizontal plane, which appeared to be tension fractures due to the release of overlying pressure. These fractures first became evident at a depth of 180–210 m and became better developed and more frequent with depth.

6.4.4

Little America V, Antarctica

The drilling equipment was transported from Byrd Station to Little America V using a surface traverse in February 1958. The drill site was located on the Ross Ice Shelf between the camp site Little America V and Crevasse Valley at an elevation of 43 m above sea level and approximately 3 km from the ice front in Kainan Bay (Gow 1968). The Ross Ice Shelf is essentially free floating at this location. Its thickness at the drill site was estimated to be 257–258 m, and the depth of seawater under it was nearly 400 m. The drilling rig (Fig. 6.25) was the same as that used at Byrd Station, with one important addition (Ragle et al. 1960). A progressive cavity 3L6-CSQ-type pump was

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provided so that liquid could be used as the circulating fluid to balance the pressure of the seawater. The pump weighed 68 kg, and at 900 rpm, it delivered 136 L/min at 1.5 MPa, which required 5.5 kW. Casing was initially set to 12 m. It became necessary to advance the casing four times to the total depth of 40 m by under-reaming before it was possible to maintain air circulation. As before, cooled compressed air was used as the circulating fluid for the upper part of the hole from the surface to 249 m. While drilling with air, the drill string was rotated at 50–60 rpm and advanced at a rate of 7.5–9 m/h. The hole was deepened from 249 m to 254.2 m, which was a few meters above the ice/seawater interface, using diesel fuel circulation. During that period, the drill string was rotated at 60–65 rpm and advanced at 9 m/h. The temperature of the diesel fuel was close to −15 °C. At the final depth, seawater began to leak into the hole (Gow 1968), and because some resistance was encountered between 183 and 189 m, it was decided to re-drill the lower part of the hole (Lange 1973). The ice cuttings had fallen to the bottom of the hole while reaming and formed a heavy slush plug. Since it was late in the season and the supply of diesel fuel had been depleted, the decision was made to shut the project down. The final depth of the open hole was measured at 221 m. Core recovery was more than 98 % of the meters cored. The core from 249 to 254.2 m, taken while using diesel fuel as the drilling fluid, did not contain the cracks normally characteristic of the cores obtained using air, but had small, irregular surficial cracks that penetrated no more than 12 mm into the core.

Fig. 6.25 Little America V drill rig, December 1958 (Photo A. Gow; Polar Ice Coring and IGY 1957–58 2008)

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6.4.5

6 Conventional Machine-Driven Rotary Drill Rigs

Franz Josef Land, Russian Arctic

In the summer seasons of 1958 and 1959, a few holes with depths of 20–82 m were drilled by the Glaciological Expedition of IGAS using a conventional SBU-150-ZIV-type self-propelled drilling rig (Fig. 6.26) in the central part and edges of the Churlyenis ice cap, Franz Joseph Land, Russian Arctic (Bazanov 1961). The drilling reached bedrock beneath the glacier and stopped after penetrating 1.5–2 m into sub-glacial rocks. The cuttings were removed by the circulation of compressed air produced by a stationary VK-3-5 single-stage compressor with a working pressure of 0.4 MPa at a discharge of 0.8–1.2 m3/min. The main part of the ice chips were collected in a 4 m-long sludge barrel placed above the core barrel. The conventional carbide-insert drill bits were ineffective for ice cutting because of small clearances. The most effective bits were handmade, six-tooth steel bits. The height of the teeth was 20–35 mm (for different bits) with rake angles of 67°–55°. On several occasions, the air condensate froze on the borehole wall, resulting in a stuck drill. Drill recovery consisted of dropping 3–5 kg portions of table salt into the hole and waiting 2–10 h before the drill was free.

Fig. 6.26 Drilling operations on Churlyenis Glacier, Franz Josef Land, 1958–1959 (Photo M. Grosvald from Bazanov 1961)

The average penetration rates depended upon the speed of the drill rotation and were 15 m/h at 72 rpm, 20 m/h at 113 rpm, and 27 m/h at 180 rpm. The optimum length of a run was found to be in the range of 1–1.5 m. The core was usually broken in pieces with lengths of 0.2–0.8 m. The average core recovery was 70–80 %.

6.4.6

Base Roi Baudouin, Antarctica

In January 1961, a collaborative drilling project of the Italian Comitato Nazionale per l’Energia Nucleare, the European Atomic Energy Community, and the Centre National de Recherches Polaires de Belgique was undertaken at Base Roi Baudouin on the ice shelf of the Princess Ragnhild Kyst (Tongiorgi et al. 1962). Commercial drilling equipment for mineral prospecting to a maximum depth of 300 m was used. A drilling machine of the XCH/60-type was manufactured in Sweden by the Craelius Company, furnished with a 7 m derrick, and powered by an 11 kW engine. The bit was hydraulically operated and advanced automatically. The drilling machine and its derrick were protected by a prefabricated 9.76 m × 3.66 m × 2.40 m wooden shelter (Fig. 6.27). The removal of cuttings was to be ensured by the circulation of compressed cooled air. To feed the air, an Atlas Copco compressor VT4Dd driven by a 33 kW diesel motor was used. It provided a maximum discharge of 4 m3/min under a pressure of 0.7 MPa. The air coming from the compressor was cooled by heat exchange with the atmosphere. It was passed through a system of 3″ (76 mm)-diameter tubes with a total length 58.5 m and fitted with two welded fins. Six straight tubes were connected to U-tubes fitted with cocks for releasing the condensed water. Before shipment to Antarctica, the equipment was tested on the Glacier du Géant in the Mont Blanc massif in October 1960. The result was quite satisfactory. Drilling at Base Roi Baudouin began on January 12, 1961, at a site 2 km south of the station. From the start,

Fig. 6.27 Shelter with tower, together with compressor and cooling system (Photo L. Goosens from Tongiorgi et al. 1962)

6.4 Air Rotary Drilling

serious difficulties were met: a slow advance, blocked core barrel after drilling several tens of centimeters, and discontinuous and partially melted cores. Over five days, all the available types of core barrels and drill bits were tried, and the drilling reached a depth of 17 m, but with useless cores. The major cause of the drilling difficulties appears to have been the loss of the circulating air in the firn. A decision was made to start a new hole, this time using the SIPRE 3″ auger driven by the drilling machine. This procedure proved efficient, the only remaining inconvenience being the short length of the core barrel (0.9 m), which necessitated withdrawing it after every 0.4–0.5 m advance. In four days, the drill reached a depth of 44 m, with a core yield of almost 100 %. Casing tubes were inserted to a depth of 43 m, and drilling was continued with the air circulation using a 3 m Craelius double-core barrel. The toothed Wydia drill bit with a 48 mm ID was altered by welding vertical ridges onto its outer side. This increased the space between the body of the core barrel and the outer wall of the drilled hole, thus facilitating the passage of the air used to carry the cuttings upward and out of the hole. In three days, the drilling reached a depth of 79.33 m, with a core recovery close to 100 %. From this depth downward, the coring was inexplicably incomplete, and the recovered core fragments rarely exceeded 0.1 m in length. On January 27, the drilling had reached a depth of 115.72 m, with an average core yield in the last interval of 55 %. Because of a technical accident, the core barrel became stuck at this depth. It was decided to abandon the rods and the core barrel because of the limited time available at the end of the season.

6.5

Rotary Drilling with Fluid Circulation

Rotary drilling with direct fluid circulation is the main method used for mineral prospecting. Cuttings are removed by the continuous circulation of the drilling fluid as the bit penetrates the formations. The drilling fluid is pumped down through the drill pipe; then the fluid flows upward in the annular space between the borehole and drill pipe, carrying the cuttings in suspension to the surface. At the surface, the drilling fluid is picked up by a mud-cleaning system, where all the solid material is removed, and the drilling fluid is then re-circulated. Drilling with fluid circulation has been used a few times in conjunction with other drilling methods, e.g., to improve the dry drilling performance 7 km from Mirny Station, Antarctica in 1957–1958 (see Sect. 6.1.4) or to balance the seawater pressure in boreholes drilled through the thickness of the ice shelves at Little America V Station in 1959 (see Sect. 6.4.4) and at Druzhnaya Base (see Sect. 6.6.3). Review of the rotary drilling with fluid circulation using wire-line drilling technology is given in the next section.

77

6.5.1

Taku Glacier, Alaska

As a part of the 1950 summer program of the American Geographical Society, a rotary Pioneer Straight-line drill rig from the Longyear Company (Fig. 6.28) was employed to obtain core samples down to a depth of 89 m on the upper Taku Glacier, Alaska, at an elevation of 1090 m a.s.l. (Miller 1951, 1954). The drill assembly with a motor and hoist was mounted on a steel frame and powered by a water-cooled, 4-cylinder Waukesha gasoline engine developing up to 7.4 kW. The engine operated at 1800 rpm and used its transmission to transmit rotating speeds of 305, 450, and 880 rpm. This equipment was capable of drilling 1.5″ (38 mm)-diameter holes in rocks to a depth of 600′ (183 m). At the maximum rated depth, cores with a diameter of 0.88″ (22 mm) can be recovered. The motor-pump assembly consisted of a Racine variable-volume oil hydraulic pump placed on the drill rig platform and a heavy-duty Fairbanks Morse deep-well pump as the source of water supply. The drilling equipment weighted more than 7 t. A total of 36 days was spent on the drilling program: 15 days were spent on drilling hole #1 (89 m), three days on hole #2 (28.6 m), and eight days on hole #3 (53.3 m). Most of the drilling was done using an NX double-core barrel and a four-tooth bit. The core quality was quite poor. The small diameter of the standard core barrel resulted in the crushing and distortion of sections, which made it difficult to remove useful cores. Most of the interval was drilled with water flushing. For procuring an abundant supply of water, it was recovered from crevasses and from the glacier surface. Problems were uncounted by the use of steel casing, include the loss of casing, rods, core barrel, and other troubles. After the termination of hole #1, a 2″ (50.8 mm) aluminum pipe was inserted into the upper 75 m of the borehole, and during three years, the changes in the azimuth and

Fig. 6.28 Pioneer Straight‐line drill rig used on upper Taku Glacier, Alaska, 1950; in foreground, deep well pump over 21‐m crevasse for water supply to drill (Glacier Institute: Brochure 2000)

78

6 Conventional Machine-Driven Rotary Drill Rigs

inclination of the tube were repeatedly measured in response to the glacier’s flow (Miller 1958).

6.5.2

Mer de Glace, French Alps

In 1950, Service Etudes de l’Electricite de France used a motor-driven rotary drill rig on the Mer de Glace in the French Alps to obtain a glacier profile (Ract-Madoux and Reynaud 1951). This glacier, like the lower elevation sectors of the Taku, is temperate during the summer months, which allowed the water to be used for flushing. A total of close to 1500 m of boreholes were drilled, mostly to the bedrock, with a maximum depth of 284 m. A drill rig from the BACHY Company was driven by a gasoline engine using a 4-speed gear transmission to provide a spindle rotation of 250–1020 rpm (Fig. 6.29). The drill rig weighed 344 kg and could be disassembled into pieces weighing 90–100 kg. A three-piston pump was driven by its own gasoline engine. The blade or auger drill bits (Fig. 6.30) were connected to standard 1.5 or 3 m drill pipes (weight of 3 m drill pipe–12 kg). In principle, the normal shift included three workers: two worked with the drill rig itself and another operated the pump. In reality, because different problems were always being encountered, seven or eight personnel worked at the site. Drilling rates of more than 10.5 m/h were realized, with a maximum penetration of 109 m during 8 h. Many different accidents happened while drilling. The most difficult and serious accidents were connected with stuck drills–many hours and even days were needed to recover the drill string to the surface, and two attempts failed. The second problem was caused by the rocks contained in the

Fig. 6.30 Drill bits used at Mer de Glace (Ract‐Madoux and Reynaud 1951)

ice. To overcome this complication, diamond drill bits were tried, but were unsuccessful because they could not penetrate the ice and sediment. At times, the circulation was lost, and ice chips collected in the borehole, forming heavy plugs. Once, on the night of August 27 to 28, 1950, a mudflow from Thendia glacier overcame Mer de Glace, and a thick mud and sand deposit covered the drill site. It took eight days to dig out the drilling equipment and restart drilling operations.

6.5.3

Fig. 6.29 Schematic of drill rig used at Mer de Glace (Ract‐Madoux and Reynaud 1951)

South Leduc Glacier, British Columbia

In 1957 an exploratory cross-cut tunnel at the mine site was driven to explore the copper zones for Granduc Mines Ltd. beneath South Leduc Glacier, Coast Mountains (British Columbia, Canada), and holes were drilled upward from the tunnel into the base of the glacier (Hunte 1995). These holes eventually became connected to the subglacier drainage network, which caused the lower level of the mine to fill with water (Mathews 1964). The inflow of water was sufficiently high in volume so that the tunnel could not be reclaimed by pumping; therefore, the underground workings were closed. A study of the ore zone indicated that access to the lower elevations of the structure was required in order for the mine’s potential to be developed. In April 1962, attempts were begun to de-water the shaft and lower workings of the mine, however, pumping alone proved insufficient; the operation of pumps at rates of more than 4500 L/min had no

6.5 Rotary Drilling with Fluid Circulation

79

Fig. 6.31 Drill bits tested in sea‐ ice drilling experiments (Hoffman and Moser 1967). a Tricone roller rock bit; b TC‐faced core drill bit

continuing effect on water level (Walsh 1963). In July and August, the end of the tunnel was partly sealed off by forcing in concrete through three 100 mm diameter holes drilled to the depths of near 150 m by a diamond drill rig vertically into it from the surface of the glacier. At the end of August the workings were finally pumped out. Two years later, the Granduc mine was put into production despite the fact that much of the Leduc Camp had been destroyed, and 26 men killed, when an avalanche hit it in February 1965. Although the mines were closed in the 1980s, the geological exploration works in this area are still in progress. In 2005 and 2006, the drilling program of Bell Resources Corp. was focused on southerly extensions of the Granduc ore deposits, which lie beneath the South Leduc Glacier and several holes were drilled through the glacier (Wasteneys 2007). Problems in glacier drilling in the 2005 Granduc drilling program were largely attributed to shallow holes and high melt rates resulting in unsupported drill strings and consequent eccentric whip which caused eventual breakage of the rods near the drill head. In spring 2006, four holes drilled on the South Leduc glacier to the maximum depth of 408 m showed depths to bedrock of over 120 meters. Holes drilled from the glacier were restricted to inclinations of greater than 70° from horizontal and involved double casing the NQ2 rods with NW and HW casing. NW casing was extended to the bedrock and the HW casing into subglacial overburden. The stability of subglacial overburden was significantly low and resulted in several instances of NW casing being sheared during advance. The best practice was to begin to overcase with HW once subglacial overburden or bedrock was reached with the NQ2-NW string. The HW casing also stiffened the drill string to reduce whip as the supporting ice melted away.

6.5.4

McMurdo Station, Antarctica

A tricone bit and special core drill bit were used for wet-drilling tests in ice, and ice with inclusions and layers of volcanic sand, gravel, and basaltic rock rubble near McMurdo Station, Antarctica, during the summer season of

1967 (Hoffman and Moser 1967). Tests were carried out with a trailer-mounted rotary B40L drill rig, the same as used in tests with ice auger drilling (see Sect. 6.2.3). A self-priming tubular mud pump with a rubber volute was used for circulating seawater as the drilling fluid; it had a maximum discharge of 382 L/min at 1.6 MPa. The standard tricone bit size, 103/4″ (120.6 mm) (Fig. 6.31a), was chosen because it was the largest recommended for a trailer-mounted drilling rig with limited weight for the reaction to the torque and down pressure. The specially fabricated core drill bit (Fig. 6.31b) consisted of a 2.74-m-long section of 14″ (355.6 mm)-diameter steel pipe with a hard-faced cutting edge. The cutting media were crushed tungsten carbide (TC) particles suspended in a metallic alloy fused to the steel body of the tool. These TC particles had a granular size of 3.2–6.4 mm and a totally random orientation within the bit crown. Both of the tested drill bits performed well in the warm (−3 °C) sea ice. The maximum drilling rates were 2.4 m/min with the tricone bit and 0.3 m/min with the core drill bit. The seawater rapidly removed the ice cuttings (6 mm or less produced by the tricone bit and the small granular cuttings produced by the core drill bit). After penetrating the sea ice covers with the TC-faced cores drill bit, the 2 m-long ice cores slipped out as the drill was pulled from the holes. These cores floated in seawater to the top of the holes, where they were removed with ice tongs.

6.6

Wire-Line Drills

In wire-line drilling, the core barrel can be removed from the bottom of the hole without removing the drill string. At the end of the run, the overshot is lowered to the borehole bottom at the wire-line end. The overshot attaches to the back of the core barrel inner tube and the wire-line is pulled to the surface with the attached core barrel. The core is then removed from the core barrel, and the empty core barrel is lowered back to its position at the bottom of the drill string.

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6.6.1

6 Conventional Machine-Driven Rotary Drill Rigs

International Antarctic Glaciological Project, East Antarctica

At the beginning of the 1970s, a lightweight wire-line core-drilling system was considered for use within the framework of the International Antarctic Glaciological Project (IAGP), East Antarctica (Hansen, 1976). A major objective of this project was to core through the East Antarctic Ice Sheet to a depth of 3000 m or more and into the bedrock beneath it. Cold air reverse circulation was chosen as the hole cleaning method for the upper 1000 m of the hole with a diameter of 178 mm. Fiberglass-reinforced epoxy pipes with a 6″ (162 mm) ID were designed to be used as casing. At a depth of about 1000 m, arctic-grade diesel fuel was proposed as the drilling fluid to reduce hole closure and remove cuttings. In November 1972, CRREL undertook the design and development of unique composite drill pipes consisting of CIBA-Geigy 512 fiberglass-reinforced epoxy pipes (3″ ID) cemented by Hydril flush joint wash-pipe connections made from N-80 steel. The weight of these pipes was only 2.87 kg/m. Thereby, the weight of the drill string could be reduced by *50 %. The weight reduction could allow the reduction of the mast weight; thus, a lighter rig could possibly be used. Over 500 m of these composite pipes were procured for use in the Ross Ice Shelf Project (see next section). However, the IAGP was not fulfilled because of organizational and financial reasons.

6.6.2

Ross Ice Shelf Project

The Ross Ice Shelf Project (RISP 1973–1979) incorporated different drilling methods to drill through the Ross Ice Shelf to examine the ice thickness, ice shelf bottom, bottom of the sub-glacier sea, water below the ice shelf, biota, and sediments below the ice. In late November 1974, during the second field season, the camp known as J-9 was established approximately 450 km from the open sea, and this site was chosen for future deep core drilling (Clough and Hansen 1979). On summer 1976, the Longyear drill rig was quickly tested at Dye 3, Greenland (93 m), and then sent to Antarctica for a penetration of the Ross Ice Shelf (Fig. 6.32). In October–December 1976, the RISP drilling project was continued with two systems using an access hole (noncore) drill (Fig. 6.33a) and a wire-line core drill designed and constructed at CRREL, which was used to drill a 187-mm hole to retrieve a 60-mm core (Fig. 6.33b). The drilling of the so-called “Bern Hole” occurred on November 5–20 (Rand 1977). Drilling was started with a wire-line drill string (the type of fluid circulation was not reported, but presumably drilling was conducted with air

Fig. 6.32 RISP wire‐line drill set up on Ross Ice Shelf, Antarctica (Photo B. Koci; Bentley et al. 2009)

reverse circulation). The major problem was the overshot, the tool used to lower the empty inner core barrel and retrieve the core-filled inner core barrel. On three separate occasions, this tool was accidentally released, causing damage to the drill bit. A core was obtained to 103 m before the third uncontrolled release of the inner tube resulted in a decision to terminate all attempts to recover the core using the wire-line system until improvements could be made to the overshot assembly. The CRREL thermal drill was set up at the “Bern hole” to attempt to drill to a depth of at least 250 m. The hole was advanced to a depth of 152 m, where the thermal drill became stuck. All attempts to recover the drill failed, and the cable was cut. Before beginning to drill an access hole, an auxiliary 7″ (177.8 mm)-diameter hole had to be drilled 60-m deep. A submersible pump was placed in this hole to pump seawater out of the access hole for use in later drilling operations. This operation was accomplished on November 26, and the drill was then moved 0.3 m sideways to start the access hole operation. Numerous problems were encountered when drilling the access hole, including the failure of the hydraulic motor for the vacuum pump, a lost drill bit, and a missing top stabilizer in the borehole. Finally, on December 13, 1976, the rotary drill became stuck at 330.3 m. During the last shift, when drilling had been resumed, a noticeable increase in the penetration rate (21 m in 4.5 h) and smooth drilling were experienced. At the end of this crew shift, drilling halted and the drill remained stationary for 30 min. At the start of the next shift’s operation, the drill could not be raised, lowered, or rotated. All attempts to recover the string were unsuccessful. During the following season (1977–1978), attempts to recover from the accident by melting out the wire-line drill with hot water failed (Bentley and Koci 2007). The drill rig was moved, and on January 5–14, 1978, drilling operations

6.6 Wire-Line Drills

81

Fig. 6.33 Bottom‐hole assembly designed at CRREL (Rand 1977). a Access hole non‐coring drill; b Wireline core drill

were continued with a cobbled-together wire-line drill (Chiang and Langway 1978; Clough 1978). While there was some difficulty with the chip removal system, the core recovery was rapid, and the core quality improved with

depth. The core hole was filled with a mixture of arctic diesel fuel and trichloroethylene at approximately 100 m, and the final depth was 170.8 m. At that depth, time ran out at the end of the season.

82

6.6.3

6 Conventional Machine-Driven Rotary Drill Rigs

Base Druzhnaya, Antarctica

During the summer seasons from 1982 to 1985, several holes were drilled by specialists from the Leningrad Mining Institute at Base Druzhnaya, which was constructed by the seaside of the Filchner Ice Shelf (Kudryashov et al. 1983, 1988; Bychenkov and Egorov 1986; Zhigalev and Shkurko 1988; Bobin et al. 1988). Later, when a few bases with the same name appeared, it was renamed Druzhnaya-1. The drilling was performed with a conventional rig of the SKB-4 type, with a MRUGU-18/20-type mast (Fig. 6.34) and SSK-59-type wire-line drilling equipment. The power was supplied from a 60-kW diesel generator. The drill rig and other equipment were installed inside a dismountable drilling shelter that was 3.7 m × 8 m × 2.5 m in size. During the summer season of 1982–1983, hole #1 was drilled to 172.3 m with 100 % core recovery. The rotational speed was 155 or 280 rpm. The rate of penetration was 60 m/h. Aviation fuel TS-1 was used as a drilling fluid (the flow rate of the NB3-120/40 pump was 40 L/min). The drilling was stopped because of a leak in the protective casing–an intolerable condition in a wire-line system–and the subsequent loss of fluid circulation. During the summer season of 1983–1984, hole #2 was drilled to 230 m without core recovery. The upper interval down to 47 m was drilled using a three-spiral coring auger with an OD of 98 mm and flight pitch of 135 mm (Fig. 6.35). Flights were welded to a steel barrel with an OD of 73 mm. The auger barrel was equipped with a core drill head on which three detachable cutters with an ID/OD of 60/100 mm were fixed by screws. The average core length in this interval was only 0.45 m because the auger flights were clogged by cuttings soon after penetration began. Several times, the screws that fixed the cutters in place were broken. After drilling the snow-firn formation and setting the casing, drilling equipment from a previous expedition was used, except for a special drill head used for full-diameter (no-core) drilling (Fig. 6.36). The ID/OD of the drill head for core drilling was 35.4/64 mm. The OD of the drill bit attached to the wire-line inner core barrel for noncore drilling was 35.2 mm. The core was only recovered from five intervals (each interval had a length of approximately 2 m). The drill string was not removed from the hole to change from core drilling to noncore drilling. Instead, the noncore drill bit was attached to the wire-line inner core barrel and lowered to the bottom of the hole through the drill string. For torque and load transmission, the bearing unit of the inner core barrel was changed to a non-rotating fixed unit. At times, the inner core barrel could not be set in the working position at the bottom of the hole. To solve this problem, deadweights were affixed to its upper part.

Fig. 6.34 Drilling shelter at Base Druzhnaya (28th SAE) (Kudryashov et al. 1983)

Fig. 6.35 Core auger used at Base Druznaya for drilling in firn (Kudryashov et al. 1988). 1 Drill head; 2 core; 3 moveable barrier; 4 window; 5 connector; 6 auger; 7 ice chips

The rate of penetration varied from 26 to 100 m/h. TS-1 aviation fuel was used as the drilling fluid. The drilling was stopped because of a problem similar to that previously

6.6 Wire-Line Drills

83

Fig. 6.36 Custom‐made drill bit KL1‐59/64 for SSK‐59 type wireline system (Bobin et al. 1988). a Drill bit attached to lower end of drill string for coring; b drill bit attached to wire‐line inner core barrel; c drill bit in assembled condition for noncore drilling

encountered, a leak in the casing and the subsequent loss of fluid circulation. Hole #3 was drilled down to 310 m in February 1985. The upper interval down to 63 m was drilled using a modified two-spiral coring auger with an OD of 98 mm and reduced flight pitch of 80 mm. The casing was fabricated from steel tubing with an OD of 89 mm. The lower part of the casing was immersed in hot water pumped directly to the bottom. After freezing, the new bottom rose to 33.4 m. Then, wire-line drilling equipment of type SSK-59 was used with special drill heads for full-diameter drilling. The rotational speed was 280 rpm. The rate of penetration varied from 53 to 66 m/h. The cuttings were removed by the circulation of compressed air produced by a 2VU-1-2, 2/13 compressor with a pressure of 0.25–0.45 MPa. At a depth of 310 m, the drill reached sub-glacial water and seawater entered the hole. During hoisting, the drill string was stuck near 160 m. During the summer season of 1985–1986 holes #4, #5, and #6 were drilled, 55.5, 44.6, and 300.5-m deep, respectively. The drilling of the first two holes was stopped because of the sticking of the two-spiral coring augers (V.M. Zubkov, personal communication 2004). The third hole was drilled to 40 m, also with a coring auger. The mean run length was 0.5 m, and the mean penetration rate was 36 m/h. Then, drilling was continued with a SSK-59-type wire-line drill with an air chip removal system. At a depth of 280 m, 3 m3 of a special emulsion (*60 % arctic-blend diesel fuel, *40 % of a CaCl2 water solution, and a small amount of stabilizer) was dumped into the hole. The drilling was continued with shortened runs using bottom circulation of the drilling fluid. At 300.5 m, the hole reached sub-glacial water. The drill was hoisted to the surface without any complications.

One of the main problems in these drilling operations was caused by icing on the surface of the drilling equipment (pump, hoses, driving stem, drill string, etc.). Sometimes, icing led to a failure of the upper drill rig collet, drill string holder, and gripping device. In May 1986, the edge of the Filchner Ice Shelf, with an area of over 13,000 km2 [(60–80) km × 230 km], broke off and was carried away in the form of three huge icebergs. Base Druzhnaya was located on one of these icebergs, and in January 1987, the Captain Kondrat’ev found the new position of the base. From January 30 to February 9, the main facilities of the base were loaded aboard the ship, and the base was closed (Savatyugin and Preobrazhenskaya 2000).

6.6.4

Black Rapids Glacier, Alaska

In 1998, a commercial wire-line drill rig was used to investigate the subglacial conditions of Black Rapids Glacier in the central Alaska Range (Truffer et al. 1999). All of the holes in the ice were pre-drilled using a hot-water drill, which was stopped a few meters above the bed. Then, rotary wire-line drilling commenced using a Longyear Super38 drill rig, making it possible to drill at least 650 m and obtain a 60-mm-diameter core (Fig. 6.37). A drill rod of the HQ size (78-mm ID) was used in the shallower holes, and one with the NQ size (60-mm ID) was used in the deepest hole. Two drill bits were used: a carbide bit to drill through the ice and soft till, and an impregnated diamond-core bit to drill through the till and bedrock. Drilling through ice with the diamond bit was as slow as 0.5 m/h, as opposed to 2–5 m/h with the carbide bit. Typical drilling rates were about 2 m/h in till and 1–1.5 m/h in

84

6 Conventional Machine-Driven Rotary Drill Rigs

at *498.5 m. Thus, no ice samples were obtained, but till was successfully recovered in the first 3 m section of core below the interface. At hole #2, wire-line drilling commenced at a depth of 336 m and continued through 12 m of ice. Further drilling was abandoned because of problems with moving the core barrel up and down the string, which resulted from the high inclination (more than 4°) of the hole drilled by the hot-water system. The last “Center Hole” was the deepest. The NQ rod was used to reduce the weight of the drill string. Wire-line ice coring began at 602 m, but was abandoned in favor of hot-water drilling at 607.5 m. The hot-water drill was lowered inside the drill rod, thus avoiding the need to pull out the entire drill string. Coring recommenced at 614.8 m and continued to 621.2 m after penetrating bedrock at 619.5 m. There were substantial difficulties in sampling the subglacial till. The penetration itself was difficult because of the clogging of the entrance of the core barrel with fragments of rock, which then prevented entry of any further material. The other problem was caused by water circulation. The stream of water caused fine sediment, sand, and even gravel to be washed away from the core barrel, and the core recovery did not exceed 25–30 %.

6.6.5 Fig. 6.37 Longyear Super 38 drill rig at Black Rapids Glacier, central Alaska Range (Truffer et al. 1999)

bedrock. Pulling out the core barrel through 600 m of drill string took about half an hour. The cuttings were removed by the circulation of water, which was recovered from the hole by a submersible pump after hot-water drilling. Four holes were drilled at three locations to a maximum depth of 620 m. Wire-line core drilling of hole #1 commenced at 488.5 m and eventually reached 510.1 m in depth. Drilling through the till presented major challenges. Equipment failure and other problems made it necessary to pull the entire drill string three times before the hole was completed, a tedious and labor-intensive undertaking. Each time the drill string was removed, the till collapsed into the uncased hole, requiring re-drilling. Because of this, the hole was cased with the wider HQ rod, and the NQ rod was used to drill inside it. In this manner, the bedrock or a large boulder was eventually reached. The hole had to be abandoned when the lowest 6 m of the string was twisted off. This could have been caused by borehole deformation and/or basal motion. At a second hole at this site, #1A, hot-water drilling was used to penetrate all the way to the ice–till interface, located

Isua Greenstone Belt, Southwestern Greenland

The Isua Greenstone Belt, hosting the Isua iron deposit about 150 km northeast of Nuuk, is concealed under the margin of the Greenland Ice Sheet (Stendal and Secher 2011). Drilling operations at the Isua deposit were started by the Marcona Corporation in 1971 (Isua Iron Ore Mine Project Greenland 2011). At this time, 13 holes were bored, totally 2719 m, from 25 to 353 m in depth, some of which were through the inland ice. Subsequently, five holes were drilled in 1972 and 1973 by Marcona for the purpose of taking temperature measurements and ice cores (Colbeck and Gow 1979). These holes were drilled using a conventional rotary-drilling rig, which circulated salt water to remove the cuttings. Although the salt water introduced many problems (the salt water was diluted or even flushed from the hole by water produced from the melting of the surrounding ice), it did provide a means for tracing the flow of surface melt water down the boreholes. Two of the five holes were drilled into the unfrozen basal layer and completed to the bedrock at depths of 265 and 299 m, respectively. In these holes, melt water from the surface drained into the hole, thus flushing out the salt water after the completion of drilling. In 1997, Rio Tinto Zinc (RTZ) Mining and Exploration Ltd. drilled another two holes through the ice and bedrock to final depths of 526 m and 800 m, respectively. In the

6.6 Wire-Line Drills

85

was based at the camp for moving personnel and equipment to and from the drill site.

Fig. 6.38 Drilling at Isua project in 2011 (Photo MT Højgaard; MINEX 2011)

summer–autumn seasons of 2008–2011, the mineral resources estimation was continued by the London Mining Plc. (contractor MT Højgaard) using 60 holes to depths from 41 to 563 m: 2008–7 holes totaling 1154 m, 2009–18 holes totaling 3859 m, 2010–17 holes totaling 5341 m, and 2011– 18 holes totaling 7656 m. A large number of holes were drilled through 100–160 m of ice before the deposit was tested (Fig. 6.38). To drill through the ore-body, the BQ, BTW, NQ, and NQ3 wire-line diamond core bits were used. The other drilling details (type of drill rig, drilling fluid, etc.) were not yet published at the time of this book’s preparation.

6.6.6

Foremore Glacier, British Columbia, Western Canada

The Foremore Glacier is located in a remote region of Northern British Columbia (BC), Canada, in the area of Galore Creek, one of the largest undeveloped copper-gold-silver deposits (Diamond Drilling Project: Looking Through a Glacier 2010). In 1987, geologists searching the area discovered a large boulder field at the toe of the Foremore Glacier (57° 03′N, 130° 58′W). The sulfide-rich mineralized boulders contained in this glacial erratic were found to contain significant quantities of zinc, copper, lead, gold, and silver. Geological and geophysical interpretations suggested that large ore bodies run under the ice. 1990 The 1990 drilling program involved testing bedrock underneath the Foremore glacier to search for a source for the base metal rich boulders found in the basal moraine at the toe of the glacier (Lee and Paterson 1991). J.T. Thomas of Smithers, B.C. was contracted to provide a Longyear 44 drill rig and personnel to carry out the program. Northern Mountain Helicopters supplied Bell 205 helicopters for drill mobilization, demobilization, and moves. A Bell 47 helicopter

Five vertical holes were drilled through Foremore Glacier between July 24 and August 28, 1990, to test geophysical and geological targets. Hole collars were located at elevations in the range of 1169–1235 m a.s.l. Approximately 1347 m of drilling was completed, including 804 m through ice and 563 m through rock. Of these five holes, three (FM 90-1, 4, and 5) were submitted as assessment work. Hole FM-90-1 was abandoned at a depth of *149 m after the rods broke at or near the ice–bedrock interface. No core was obtained. Holes FM-90-2 and FM-90-3 reached bedrock at depths of 176 and 204 m, and then were continued to 340 and 280 m, respectively. Hole FM-90-4 met bedrock at a depth of 110 m, and the ice interval was cased by HW casing to boulders in the bedrock. Core drilling was continued to the final depth of 298 m. The average length of a core was 2.86 m, with 94 % recovery. The drill core size was NQ. Hole FM-90-5 reached ice–bedrock at a depth of 149 m, and only a thin layer of till was found in the interval of 149.35–150.46 m. The hole was continued to a depth of 280 m. Holes FM 90-4 and 5 both intersected maroon and green pyroclastic schist with zones of quartz and sericite schist. No mineralization, which could account for the mineralization found in the boulders at the toe of the glacier, was encountered in either hole. 2010 Twenty years later, in 2010, drilling was resumed with the same drilling contractor (Diamond Drilling Project: Looking Through a Glacier 2010). At the beginning of the summer, all the drilling equipment was delivered to the glacier by helicopters. A Longyear 44 diamond drill rig was assembled inside of a drill shack (Fig. 6.39). At first, water as a drilling fluid was pumped from the pools of meltwater on the surface

Fig. 6.39 Longyear 44 diamond drill rig at Foremore Glacier, Western Canada, summer 2010 (Diamond Drilling Project: Looking Through a Glacier 2010)

86

of the glacier, but the amount of available water was insufficient. Therefore, a service pump was placed on a small creek just off the side of the glacier. Originally, the waterline was laid down on the ice surface, but it soon melted in and when there was a need to move it down, the waterline had to be cut. Therefore, it was necessary to heat the waterline on its 1.5 km trip to the drill rig. All of the boreholes were started using an HW-size tricone drill bit and NW-size rods. Drilling with just hot water was tested, but it did not work well. When the borehole reached the blue ice, drilling with hot water had to be stopped. Later, brine (100 g/L) was used as a drilling fluid, but when the borehole became deeper, the bottom-hole assembly often started to freeze. Although the rods could be turned, it was hard to get them to the surface. Another problem was met near the bottom of the glacier, where the drill bit often hit large boulders randomly scattered through the ice. When the drill bit started to bore a hole into a boulder, it heated up, jammed, and tried to spin the rock inside of the ice, causing problems for the drillers. When the bedrock was reached, casing was set down and rock samples were recovered through the wire-line core barrel. During the 5-week drilling season, a total of five holes were bored. A large problem was connected with melting ice during the long summer days: the surface of the glacier dropped about a meter in the week that the crew was on one site. As the ice melted, the whole drilling platform settled down, and when the casing came into contact with the ground, it bent and created a large drag on the drill string. The solution to this problem was to fly sawdust to the site before building the drilling platform to serve as insulation. This worked well, and problems with casing bending were avoided. Fig. 6.40 Conceptual, cut‐away view of wire‐line system to allow on‐the‐fly changes from coring to boring and back again (Gerasimoff 2012)

6 Conventional Machine-Driven Rotary Drill Rigs

6.6.7

Rapid Access Ice Drill (RAID)

Renewed interest in conventional rotary drill rigs comes from a wide range of interdisciplinary research goals of the international scientific community. These include the search for polar paleoclimate records in ice older than 1 million years; observation and sampling of the base of the Antarctic ice cap; recovery of rock cores from ice-covered geologic provinces of Antarctica; and measurements of the thermal gradient, heat flow, ice accumulation history, and ice deformation processes. To drill through ice sheets for core sampling and subglacial rock to depths of at least 3300 m in 200 h or less, the University of Wisconsin’s IDDO developed the concept of the Rapid Access Ice Drill (RAID), based on a conventional wire-line diamond drilling system (Gerasimoff 2012). The concept is based on an idea that was realized at Base Druzhnaya in 1983–1984 (see Sect. 6.6.3) and based on intermittent ice coring with quick switches from boring (only; no coring) to coring and back again as desired. During coring, the conventional diamond bit is replaced with a coring head with multiple sharp blades, cutting an annular groove, and drilling is conducted in the same manner as normal rock-coring operations. During boring, the inner core barrel is removed and, in its place, a barrel is inserted that is tipped with cutters that cut away all of the ice that would otherwise become the core (Fig. 6.40). In 2014, the University of Minnesota Duluth, USA, began construction of the RAID based on the modification of an industry-standard diamond rock-coring system operated in a flooded reverse-circulation mode with composite drill rods (Fig. 6.41) (Goodge and Severinghaus 2014). The RAID system is compact enough to be operated by a

6.6 Wire-Line Drills

87

Fig. 6.41 RAID operational layout (Goodge and Severinghaus 2014)

Fig. 6.42 Conceptual scale model view of the ASIG drill system as deployed to the field (Credit IDDO Engineering; Agile Sub‐Ice Geological (ASIG) drill, n.d.)

88

6 Conventional Machine-Driven Rotary Drill Rigs

3-person drilling crew. The most critical area for RAID development is how to find a way to efficiently separate the chips from the drilling fluid once the chips reach the surface. This process may ultimately limit how fast the system can penetrate ice. The separation process must be fast enough so that the drilling fluid can be pumped back down the hole. Another problem that should be solved concerns the secure isolation of the permeable near-surface snow–firn formation. DOSECC Exploration Services, LLC, a drilling and engineering company based in Salt Lake City, USA, is the lead contractor tasked with constructing and testing the RAID system. The first full-scale field trial for RAID is scheduled for 2016–2017 (Witze 2015). The projected long-term research use of the RAID system is planned for late 2017 and will involve traversing to East Antarctica via the Amundsen-Scott station at the South Pole.

6.6.8

Agile Sub-ice Geological (ASIG) Drill

To recover small rock cores near outcrops and near the ice margins in Antarctica, IDDO (University of Wisconsin-Madison) has initiated work on a new Agile Sub-Ice Geological (ASIG) drill capable of coring up to 10 m of rock core beneath few hundreds of meters of ice. Drill system is transportable by Twin Otter, or helicopter with sling load (Fig. 6.42). Maximum time at a site, including set up and core retrieval, should be at most 6 days. The conceptual design of the ASIG drill makes use of a modified commercial drill rig Discovery MP1000—Man Portable Diamond Core Drill designed for exploratory rock coring in the hard-rock minerals industry in remote areas (Fig. 6.43). The nominal capacity of the drill rig is 1220 m with B/WL size drill bit and 945 m with N/WL size drill bit. Drill bit rotation speed is continuously variable between 0 and 1200 rpm. IDDO engineers are currently designing and fabricating ice augering/drilling attachments, fluid handling and chips handling equipment, and casing setting and inflatable packer equipment. A field test of the system in North America is scheduled for summer 2016. The ASIG drill’s first in Antarctica is planned for the season 2016–2017 for recovery of rock core under several hundred meters of ice.

6.7

Drilling in Rock Glaciers

Rock glaciers are ice–rock mixtures that differ greatly from typical mountain or polar glaciers. Two types of rock glaciers, based on the internal structure, can be distinguished: (1) true glaciers covered by rock debris (“debris-covered glaciers”), and (2) periglacial glaciers on non-glacierized

Fig. 6.43 ASIG drill system inside the IDDO warehouse (Agile Sub‐ Ice Geological (ASIG) drill, n.d.)

mountain slopes consisting of a mass of rock with interstitial ice (Haeberli et al. 2006). Rock glaciers usually have very little ice visible at the surface, and they might not look at all like a glacier. The very slow movement, typically between a few centimeters and a few meters per year, also helps hide the rock glacier’s identity. Rock glaciers are typically small. A large rock glacier might be 50 m thick and a few kilometers in length. The rocks on the surface of a rock glacier can be almost any size, depending upon their source of supply. Drilling in such an environment is a challenge, since coring through inhomogeneous media, containing a range of materials, including large boulders and pure ice, necessitates the use of special drilling technologies that basically are similar to that used in permafrost drilling. Relatively few boreholes have been drilled into and through rock glaciers to permit an investigation of the thermal and other characteristics of the deeper subsurface (Haeberli et al. 2006). Cutting transportation was accomplished with drilling fluid (water) circulation, compressed air, or by an auger. Because similar problems were encountered in the course of almost all the drilling projects in rock glaciers, the technological characteristics are reviewed together in one section.

6.7 Drilling in Rock Glaciers

89

Fig. 6.45 Pieces of cores from core drilling on Gruben rock glacier, Saastal, Wallis, Swiss Alps, June 1976 (Haeberli 1985)

Fig. 6.44 Core drilling operation on Gruben rock glacier, Saastal, Wallis, Swiss Alps, June 1976 (Haeberli 1985)

6.7.1

Overview of Projects Using Conventional Drilling Equipment

RG II, Kluane Range, Canada (1969) Johnson and Nickling (1979) reported details of a 17 m borehole drilled in 1969 through the RG II rock glacier in the Kluane Range, Canada, which might be considered to be the first hole drilled through a rock glacier. Hole temperatures were re-measured 6 years after drilling, and surprisingly no negative temperatures were registered, indicating that the permafrost had melted over a relatively short period (probably supported by water advection). Murtèl-Corvatsch and Gruben, Swiss Alps (1975 and 1976) In Swiss Alps, 10.4 m-deep drilling with cores at Murtèl-Corvatsch and 7 m cored drilling at Gruben (2878.4 m a.s.l.) (Barsch et al. 1979) were performed in the 1970s. In both cases, the Minuteman drilling rig was used, which makes it possible to drill a core with a 40-mm diameter and maximum length of 0.7 m (Fig. 6.44). Whilst drilling in the rock glacier Murtèl-Corvatsch in 1975, the ice of the frozen debris often melted during the drilling procedure, which led to considerable losses of core material.

However, from the drilling rates and parts that remained in the cores, it was possible to construct a profile that showed that this section of the rock glacier is composed of frozen sediments, rich in ice, with intermittent ice lenses. The average ice content was estimated to be 50–60 %. The greatest thickness of a single (observed) ice lens was 0.3 m, but the existence of another ice lens with a thickness of about 1.5 m was suspected. The ice lenses consisted of bubble-rich ice with dirt bands. Cavities or unfrozen zones were not observed. The mean temperature in the borehole appeared to have been *−1 °C. At Gruben, the surface relief of the rock glacier was not very distinct. The boulder size on the surface ranged from 0.3 to 1.5 m in diameter. The cutting through boulders and frozen talus was done using a diamond head, which necessitated cooling with water during the drilling. No losses of circulating water were observed in the borehole during drilling, which points to the fact that the frozen debris of the rock glacier permafrost is practically impermeable to water. In spite of the cooling, warming in the borehole could not be completely avoided. Thus, parts of the core were lost due to the melting of ice (Fig. 6.45). Again, frozen debris with intermittent ice lenses was encountered. The greatest observed thickness of a single ice lens was 0.3 m, but the existence of one with a thickness of 0.6 m was not excluded. Three samples from the cores were analyzed for grain size. A maximum was observed for fine sands (23–43 %), but a considerable percentage of silt (15–34 %) was also present. Gravels (around 15 %) and clays (1–2 %) were encountered in relatively small proportions only. A total of 50–70 % of the material was classified as sand (0.063–2.00 mm). Although most of the ice had melted during the drilling operation due to thaw disturbance, the ice content of the cores was estimated visually to be about 60 % by volume. The average borehole temperature, based on 6 years of observations, was around −1 °C (Haeberli 1985).

90

Murtèl-Corvatsch, Swiss Alps (1987) One of the longest time series measurements of Alpine permafrost temperatures started when a 62.5 m-deep borehole was drilled through the Murtèl-Corvatsch rock glacier in 1987 (Haeberli et al. 1988a). Field work started in late April, 1987. In order to recover uncontaminated cores and minimize the thermal disturbance of the borehole, it had been decided to use a triple core-tube system in combination with air cooling. An Atlas 1.2 MPa screw compressor was therefore installed to deliver air at a rate of 13 m3/min through a snow-buried 2″ cooling tube to an air tank for the removal of condensed water, and then to the heavy hydraulic Longyear-34 rotational core drilling machine. The core material was automatically placed into transparent plastic liners, which remained insulated from the cold air circulating between the outer two tubes of the core barrel. A shallow experimental hole was first drilled to test the procedure. The boulders of the active layer were penetrated without coring, proving that air in the borehole could escape, and the material was highly porous and permeable. A 6 m casing was installed (Odex-system) at the top of the borehole in order to stabilize the borehole walls. Cores were taken from immediately beneath the permafrost table at about 3 m in depth. The core diameter was 70 mm, and the outer diameter of the drill bit was 106 mm. The samples came out completely dry, indicating that no melting had taken place during drilling, and that the air cooling worked efficiently. The ice was quite heavily broken, however, probably as a result of stress relief. A hard-metal drilling bit was used in the ice and ice-rich material. The last 10 cm of each individual run were done without air cooling. This allowed the lower end of the core to melt slightly at the periphery, freeze back to the core catcher and, hence, hold chips of the core material within the plastic liner. A total of about 6 m of ice-rich cores were taken in the experimental hole, which reached a depth of 21.7 m. Then, the drill rig was moved by *2 m and drilling of the deep hole was begun. Cores were taken beneath a depth of 3.6 m. Large boulders usually had to be penetrated by percussion boring, and ice-containing rock was cored using a diamond bit in combination with a double core-barrel, since rock cores tended to deform the plastic liners. No casing was used within the well ice-bonded material. Below about 45 m however, the borehole became increasingly unstable. The last piece of ice was recovered at 51 m within large boulders or severely fissured rock, with the transition between the two appearing to be gradual. Problems with unstable borehole walls continued in bedrock at greater depths. An attempt to inject concrete for stabilization was unsuccessful, because the injected mass disappeared into what was obviously highly permeable rock. Borehole

6 Conventional Machine-Driven Rotary Drill Rigs

television and caliper logging indicated that large cavities had formed in the lower part of the hole. No pressurized water was encountered. At 62.5 m, the drilling was stopped within solid bedrock. A complete set of borehole logs was run in the temporarily water-filled experimental hole. However, the high permeability of the sub-permafrost rocks made it impossible to fill the deep hole with water for borehole logging. Therefore, the experimental hole was deepened to 40 m. Here again, unfortunately, air and water were lost at a 32 m depth, where a connection with the deep hole had developed in the meantime (air loss occurring from the experimental hole to the deep hole). The drilling operation finished in early July. The ice content decreased systematically with depth down to bedrock at a depth of *50 m. However, the amount of near-surface ice was extremely high. In the upper half of the rock-glacier, the average ice content was about 80–90 % by volume. To a depth of 15 m, the average temperature was −2 to −3 °C. Both boreholes were protected with an impermeable lid against atmospheric influences and snow avalanches. They remained air-filled and initiated one of the longest measurement time series of rock glacier temperatures (Vonder Mühll and Haeberli 1990; Haeberli et al. 1998b). Pontresina-Schafberg, Swiss Alps (1990) At Pontresina-Schafberg, two boreholes were drilled in 1990 (37-and 65-m deep) as part of a project concerning snow avalanches and debris flows (Vonder Mühll and Holub 1992). The bedrock was reached at a depth of *16 m. No cores were obtained by air-lift percussion technology. In contradistinction from the Murtèl-Corvatsch borehole, no problems were encountered with the hole filling with water, which made it possible to run a complete set of logs. Logging measurements were done to determine the thickness of the perennially frozen debris layer above the bedrock and to investigate the P-wave velocity, resistivity, and ice content. The boreholes at both sites showed a high ice-content layer (80–95 %), although the temperature characteristics were quite different. Galena Creek, Wyoming (1995) Another 9.5 m core was extracted from beneath the surficial debris cover of a rock glacier at Galena Creek, Absaroka Mountains, northwestern Wyoming, USA (44° 38′ 30″N, 109° 47′ 30″W), in the summer of 1995 (Steig et al. 1998). In this glacier, the debris cover is composed of friable volcanic material, making the use of a lightweight, hand-operated SIPRE auger (see Sect. 4.3.3) feasible. In a strict sense, this drill does not belong to conventional drilling systems. However, this system, which allows continuous coring at 1 m intervals, can penetrate thin layers of silt and sand, although it cannot drill through gravel or larger clasts.

6.7 Drilling in Rock Glaciers

91

Fig. 6.46 Drilling at accumulation zone of Galena Creek rock glacier, 1995 (Photo D. Clark; Credit: J. Fitzpatrick, USGS)

Initially, an attempt was made to drill a hole in the accumulation zone just at the foot of the headwall in the wet and somewhat grabby snow using an engine-powered SIPRE auger (Fig. 6.46) (J. Fitzpatrick, personal communication 2015). Unfortunately, the drill did not work particularly well. At a central point midway down the rock glacier, a second hole was initiated, where drilling to the final depth of 9.5 m was carried out manually (Fig. 6.47). No serious problems (such as impenetrable debris layers) were encountered in the drilling; the core contained very clean ice with distinct debris-rich layers, typically 10 %) and at 15–17 m depths (>45 %). The low core recovery evidently calls into question the nature of the lost samples. Assuming that the lost core material could represent either pure ice or pure debris leads to a considerable range of uncertainty about the average ice content calculated from the recovered samples, especially in the deepest part of the DDH2010-1 borehole.

6.7.2

Fig. 6.56 Drilling on Larsbreen rock glacier, Spitsbergen, March 2008 (Photo I. Fredriksen; Juliussen 2008)

Rock Glacier #5, Choapa Valley, Andes (2010) Two boreholes (DDH2010-1 and DDH2010-2) with depths of 25 m and 20 m were drilled in the intact part of rock glacier #5 (31.88°S, 70.58°W), located in a small hanging valley called Quebrada Noroeste (NW) within the Los Pelambres mine area in the upper part of the Choapa valley, Andes, Chile, in April 2010 (Monnier and Kinnard 2013). The conventional diamond drilling technology for geological exploration was used. The ID/OD of the drill bit was 63.5 mm/96 mm. The limit of such a technique lies in the warming generated in the borehole by the rotation of the diamond drill bit; although cooling is maintained by the injection of cold water, losses of core samples are bound to occur. In both cores, the visual ice content was lower than 10 % in unsaturated frozen sediments and *40 % in layers with excess pore ice. In the DDH2010-1 borehole, the average core recovery in the first 19 m was 51 % (44 % in the frozen parts below the superficial unfrozen layer), with the lowest core recovery occurring below 15 m (>30 %). In the DDH2010-2 borehole, the average recovery rate was 57 % (67 % in the frozen parts), with the lowest rates in the

Koci Drill

The drill named after ice-drilling engineer B. Koci is an electromechanical, single-barrel, coring drill designed to operate in ice containing limited amounts of sand, silt and very small sedimentary rocks. The drill rig can drill debris-rich ice from the surface to a depth of 40 m. Although the Koci drill rig does not belong to conventional drilling systems, it was decided to provide details in this section for two reasons. First, the Koci drill was designed to perform in rock glaciers, and second, the main parts of the drill were borrowed from the conventional Husqvarna drill press: a Husqvarna DS 800 drill stand with a 2 m post and a Husqvarna Cardi D3-250S drill motor are used as the main platform (Fig. 6.57) (Green et al. 2007). The speed of the motor is controlled by a 30-A variable transformer in the range of 0–600 rpm. Power for the drill motor is supplied by a 5 kW generator. An I-beam support system is mounted to the top of the post of the drill press and centers the reaction force over the drill spindle. Hand-operated winches are attached to the ends of the I-beam and fastened either to ice screws or to rock bags. Each rock bag is designed to hold 450 kg. Because the drill itself weighs about 90 kg, a total force of nearly 10 kN can be applied to the rock drill bit. The core barrel is made from 6061-T6 aluminum tubing, and flights are welded to its inner surface (Fig. 6.58). In the first modification, a core barrel integrated with flights was milled out of the thick-walled tube stock. The drill head was made of 304 stainless steel and was connected to the core barrel using flat-head stainless-steel rivets. The drill head had an ID/OD of 80 mm/102 mm and three cutters with

96

6 Conventional Machine-Driven Rotary Drill Rigs

Fig. 6.57 Koci Drill in Beacon Valley, East Antarctica, 2009‐10 season (Photo D. Marchant; Koci drill, n.d.)

inserted cutting edges. Two different types of inserts were designed: (1) 10 V tool steel hardened to 60 HRC with a rake angle of 45° and relief angle of 15°, and (2) VM-15m+ tungsten carbide with a rake angle 30° and relief angle of 10°. Both types of inserts have rounded corners, a relief angle of 15° on the core side of the cutter and no relief on the bore wall side. The cutting pitch is controlled using penetration shoes pre-machined for a 0.8° pitch. Originally, three core dogs were used to break and hold the core, but drilling in dirty ice quickly wore the edge off the core dogs. In the modified Koci drill, a split spring-ring replaced the core dogs. A non-coring rock bit and auger can be used for penetrating larger segments of rock and gravel. The first meter is drilled by attaching the core barrel directly to the drill motor. Deeper drilling is accomplished by using PICO drill rods made of fiberglass reinforced epoxy tubing in 1.2 and 2.2 m lengths. This drill was designed to be disassembled into component parts no heavier than 30 kg (not including the generator). The total weight of the drill is 550 kg, including the packaging, tools, accessories, and spare parts. Set-up and take-down takes *3 h and *2 h, respectively. Three drillers are needed to operate the drill. The Koci drill was used for the first time on rock-covered glaciers in the Mullins and Beacon Valleys, East Antarctica,

Fig. 6.58 Core barrels from Koci drill (Koci drill, n.d.)

in the austral summer of 2006–2007, and multiple holes 1– 5 m deep were drilled, with a maximum depth of 10.25 m. The rock and sand were mostly dolerite, with an occasional sedimentary rock. After repair and modification, in 2008– 2009, the second generation of the Koci drill system was used at the same locations to drill five holes to depths of 1, 4, 16, 23, and 28 m. During the 2009–2010 season in Beacon Valley, six holes were drilled to 2, 6, 7, 14, 18, and 34 m. The drill produced acceptable-quality ice cores in unbroken lengths up to 1 m long. The surface of a core typically had a slightly rough texture. The drill equipped with tungsten carbide inserts (even chipped and dull) was able to drill through small (100

Kohshima et al. (2002)

9

UCPH (Denmark)

4 × NA

5.6

0.123

1.0

NA

300

Johnsen et al. (1980)

10

LGGE (France)

NA

NA

NA

NA

120

NA

Gillet et al. (1984)

11

NHRI, Calgary (Canada)

7 × NA

8

NA

1.5

NA

760

Holdsworth (1984)

12

PICO-4″ (USA)

7 × 0.36

10

0.42

2.5

120

6600

Litwak et al. (1984)

13

AWI-I (Germany)

7 × 0.35

10

0.27

NA

NA

NA

Jessberger and Dörr (1984) (continued)

114

8 Cable-Suspended Electromechanical Auger Drills

Table 8.1 (continued)

a

Type (country)

Cable Diameter (mm)

Weight (kg/m)

Power of winch motor (kW)

Weight (kg)

Construction (number × mm2)

Drill

Drill rig

References

14

ANARE (Australia)

NA

NA

NA

NA

NA

NA

Wehrle (1985)

15

BZXJ drill (China)

NA

NA

NA

0.3

11

127

Zhu and Han (1994), Gao et al. (2012)

16

Geo Tecs D-3 (Japan)

4 × NA

5.66

NA

1.5

50.5

NA

Zhang et al. (2014)

17

Eclipse drill (Canada)

4 × NA

4.8

0.091

0.96

50

195

Blake et al. (1998)

18

BPRC drill (USA)

2 × NA

8.1

0.118

1.5

35

356

Zagorodnov et al. (2000)

19

BAS drill (UK)

4 × NA

6.35

0.159

1.1

80

340

Mulvaney et al. (2002)

20

FELICS 3″ drill (Switzerland)

4 × 0.22

4.7

0.097

0.42

41

228

Ginot et al. (2002)

21

Blue ice drill (USA)

7 × NA

9.6

NA

4.0

NA

NA

Kuhl et al. (2014)

Values are not presented in the source: author’s estimation; NA not available

200 mm at the lower end and increases to 260 mm at the upper end. In the opinion of the designers, the increasing pitch is necessary to prevent clogging of the narrow space between the core barrel and the outer barrel by the ice chips. Two cutting bits on the lower end of the core barrel cut a 15-mm-wide kerf into the bottom of the hole (Fig. 8.6). A pair of core catchers in the form of a “dog leg” is installed in the windows of the core barrel for breaking and holding the ice core when the drill is pulled up. There was a fear that the drill might become stuck in the hole because of closure, ice chips clogging it up, or for some other reason. In order to be better able to meet such problems, three 1 kW electrical heaters could be installed in the chip chamber. It was hoped that the heat, together with the circulation of water caused by the rotation of the core barrel, would help to loosen the drill if it became stuck. These fears proved to be unfounded, and the heaters were only given a short trial. To the best of the author’s knowledge, the drill was used only once, in the summer of 1972, to drill a 415-m-deep hole into Bardarbunga on Vatnajokull Glacier, Iceland. The estimated thickness of the glacier at the drilling site was 450–500 m. In order to secure good working conditions, the drilling equipment was arranged in a pit, 7-m-long, 2.7-m-wide, and 4.2-m-deep (Fig. 8.7). This pit was covered with a roof made of polyethylene foil fastened to a wood frame. Electricity was delivered by a 15 kW gasoline power plant installed under a separate shelter outside the pit.

The expedition lasted 10 weeks, but during five of these, the drill was inoperative. The drilling was performed in two shifts with two or three men on each shift. The speed of hoisting and lowering the drill was 0.3–0.5 m/s. The drilling and breaking of the core took 5–7 min. Finally, the surface work with the drill after each run took about 15 min. The drill was designed to take a 2-m-long core on each run, but only once was a full-length core obtained. The drill would usually cut about 0.3–0.4 m easily, after which the drilling speed fell seriously, and it finally came to a halt. The mean length of the cores was 0.7–0.8 m. At a depth of 34 m below the surface of the glacier, the water table was penetrated, after which the water level stayed the same despite increasing the depth of the hole. The drill got stuck once at a depth of 17 m, and sometime later the motor burned out because of excessive load. However, the armored cable for the drill was the cause of the most serious difficulties. The drill would often sit quite tight in the hole at the end of the drilling, probably because of the clogging and partial freezing together of ice chips between the outer barrel and wall of the hole at the bottom. This might also have been because of the difficulty of breaking off the ice core. About half of the maximum allowable tension of the cable was applied in loosening the drill, but often there was a wait of several minutes until the drill became loose. On a few occasions, it was necessary to wait up to an hour, and in a single case for several hours. In spite of the limited pulling force, the conductors in the cable frequently broke, especially the signal lines.

8.2 University of Iceland (UI) Drill

115

Fig. 8.4 UI drill (Icelandic Drill) (Theodorsson 1976)

Fig. 8.5 Suspension cap of UI drill (Árnason et al. 1974)

Fig. 8.6 Lowest part of core barrel of UI drill (Árnason et al. 1974)

The cable had to be shortened four times because of breaks in the conductors, and the faulty sections were discarded. Finally, a break in one of the power lines stopped the drilling when a depth of 298 m had been reached. Fortunately, it was possible to borrow a new cable from CRREL. However, the new cable was only 425 m long. With this cable, 117 m were drilled in 8 days, stopping at a final depth of 415 m, but the bottom of the glacier was not reached. Various types of cutters were tried and some other modifications were made on the drill, but this did little to increase the drilling efficiency. Pulling the drill up a little and then releasing it quickly helped considerably, but this became less effective as the depth of the hole increased.

To avoid the refreezing of ice chips on the surface of the cutters and core barrel, an antifreeze mixture was introduced to the bottom of the water-filled hole. A closed polyethylene bag containing about 180 mL of isopropyl alcohol was tied to the inside of the lower end of the core barrel. The bag was thus lowered to the bottom of the hole with the drill and without being damaged. When the drill started and the ice core penetrated the core barrel, the bag burst, and the vigorous stirring of the rotating core barrel mixed the alcohol

116

8 Cable-Suspended Electromechanical Auger Drills

referred to as the “Rufli drill” after the principal designer, H. Rufli, was developed at the Physics Institute, University of Bern (UB), Switzerland. One of the main purposes of this new drill unit was saving as much weight as practicable (Rufli et al. 1976). As a result, no single part was heavier than 50 kg, which allowed the equipment to be transported in any type of helicopter or on a small sledge. The total weight of the complete unit was only 150 kg. This drill has a classical schematic consisting of a cable termination, anti-torque system, driving section, and coring section (Fig. 8.8). Instead of a steel armored cable, an electrical rubber-jacketed cable with a load capacity of 300 kg was used. The cable was reinforced using three hemp ropes and covered with a special rubber, which remains flexible down to −35 °C. The cable was fastened to the cable termination of the drill using epoxy resin.

Fig. 8.7 Drilling pit at Vatnajokull Glacier, Iceland, 1972 (Credit J.Ö. Bjarnason)

with the water, lowering the freezing point. This technique brought quick and positive results. After this, it was possible to drill 1.0–1.4 m in about 6 min, whereas previously it would take 30–50 min to drill 0.6–0.8 m. After drilling 1.2– 1.6 m, the drilling speed would fall seriously, probably because by then the alcohol mixture had been diluted so much that freezing on the bits began to occur. The drill had no difficulty in going through the numerous volcanic ash layers, the thickest of which was up to 9 cm. The quality of the ice cores was good. Usually, the core was in one piece, and recovery was better than 99 %.

8.3

University of Bern (UB) Drills

8.3.1

Rufli Drill

Based on experience from the SIPRE coring auger and Icelandic electromechanical drill, the lightweight drill often

Fig. 8.8 Rufli drill (Rufli et al. 1976)

8.3 University of Bern (UB) Drills

Two anti-torque systems were designed: one for firn and hard ice and another for loose snow. In the first device, four skates that are retracted during the lowering or raising of the drill are pressed radially against the wall of the borehole as soon as the drill reaches the bottom of the borehole. This device is effective in hard firn or ice, but the skates are not long enough for snow and soft firn. The second device consists of two leaf springs that press against the wall of the borehole at all times. They provide the additional restraint required in soft firn. The drill is driven by an air-cooled electric commutator motor. A friction clutch between the gear and core barrel prevents the overloading of the gear reducer and motor. Two nylon flights are attached to the core barrel, which is a 2-m-long steel tube, using screws. Only one flight goes over the upper half of the core barrel, which has four holes to admit chips to the space above the core. A movable Styrofoam disc was placed in the middle of the core barrel after each run to separate the core and chips. A steel ring is welded to the top of the core barrel to connect it to the drive section. A drill bit with two replaceable cutters is attached to the core barrel with screws. Four 2-cm-diameter holes above the bit allow chips to enter the tapered space between the core and the bit, where they provide a core-catching action. The outer barrel covers the entire length of the core barrel, except the lower 15 cm. Three ribs along the inner side provide frictional resistance between the spinning chips and the non-rotating outer barrel, which is required for the auger flights to elevate the chips to the inlet at the top of the core barrel. The bottom of the outer barrel has an inlet ring with three triangular notches. Without these notches, the chips would merely rotate with the core barrel on its open end and would get packed in front of the outer barrel, causing problems with raising the drill. In addition to the drill, the unit includes a tower, winch, and generator (Fig. 8.9). The tower consists of two aluminum tubes, each 2.3-m long with an ID/OD of 124 mm/130 mm, and it is held erect by three guy-wire cables. Each of these three cables has a pulley block with a nylon rope at the ground anchor end. The tower bottom has a ball joint. The winch is fixed to the tower. The cable on which the drill hangs goes over the sheave on the top of the tower, then down through the winch, and is spread out on the surface because there is no cable drum. The winch has no reel, but works similar to a capstan. An electric motor drives a double-gear system (a variable reduction gear and then a worm gear). The first gear is variable within a range of 0–1100 rpm, and the maximum speed after the second gear is 38 rpm. The winch also includes a control panel. An ammeter guards against an overload of the drill motor and winch motor. A two-stroke 2 kW gasoline generator is fixed on a frame, and its weight is 38 kg. Surface servicing includes the need to dig a pit near the tower about 1.5 m on a side and 1.5-m deep in order to provide space to pull the core barrel down from the drill.

117

Fig. 8.9 Entire Rufli drill unit (Rufli et al. 1976)

The first drill prototype was tested in February 1973, at Dye 2, Greenland. The electric winch was not ready, and a hand-driven winch was used to move the drill up and down. After some trouble with the coring section, it was changed to the SIPRE auger. This made it possible to obtain some experience with the driving system and drill tower. This combination was used to drill a hole to 24 m. In March 1974, a new core barrel, together with the driving unit, was tested on Plaine Morte, a glacier in the Alps, 2700 m a.s.l. Several short holes were drilled through the 3-m snow layer on the ice and down to 5 m into the ice. The penetration rates were 1.2 m/min in snow and 0.6 m/min in glacier ice. With a core barrel length of 2.1 m, the core lengths were 1.0–1.2 m in snow and 0.6–0.7 m in glacier ice. Then Rufli drill was used in the Greenland Ice Sheet Program (GISP 1971–1981), and five cores were obtained in 1974: at Summit (19 m), Crete (23 and 50 m), and Dye 2 (25 and 45 m). The drill worked well in principle. At Summit (Fig. 8.10), at a depth of 19 m, the coupling between the motor and the reduction gear broke and could not be repaired in the field. At Crete, the first hole was terminated at a depth of 23 m because the entire drill began to rotate, and even after some modifications, the drill could not penetrate

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8 Cable-Suspended Electromechanical Auger Drills

Fig. 8.10 Rufli drill assembled at Summit, Greenland, 1974 (Rufli et al. 1976)

beyond a depth of 23 m. Then, a new hole was started and successfully reached a depth of 50.5 m in 10 h. At Dye 2, the first hole was drilled to 25 m in 3 h. When the drill became stuck at the bottom of the hole, it was not possible to raise it with the winch. Some glycol was dumped into the hole, but after 2 days without results, a 200-L drum of glycol was heated to 80 °C and poured into the hole. The drill was freed very easily, and the reason why it stuck was quite visible. Two pieces of wood that were placed on the inside of the plate springs absorbed meltwater and swelled, which prevented the springs from moving inward. After a complete overhaul of the drill, it was seen that nothing was damaged by the glycol, and a new hole was started. A depth of 45 m was reached in 7.5 h without any trouble, and the average length of the cores was 0.8 m.

8.3.2

Further Improved UB Drills

UB-II Drill. A new modified drill, for our purposes referred to as the UB-II drill (taking into account that the Rufli drill

was the first drill designed at UB), was built for drilling to a 100 m depth. The complete unit weighs about 350 kg. Two winch systems were made for the drill: one was a capstan winch with 120 m of rubber cable, and the other was a conventional winch system with a drum and steel cable with three conductors. These winch systems use the same motor and gearbox. The winch speed is about 40 m/min, and the motor has a thyristor-driving unit for speed variation. In 1975, the UB-II drill was used to complete four holes in Greenland: a 94 m borehole at Dye 3, an 80-m borehole and a 30-m borehole at South Dome (about 190 km south of Dye 3), and a 60-m hole at the Hans Tausen Ice Cap. In the summer 1976 and 1977, two cores were recovered down to depths of 39 m and 65 m, respectively, at Colle Gnifetti (Monte Rosa summit range, 4450 m a.s.l., Alps) (Stauffer and Schotterer 1985). In 1978, the UB-II drill was used again in Greenland for coring at Camp III to depths of 46 and 92 m (Clausen and Stauffer 1988). Continuous cores were recovered, but they broke into disks a few centimeters thick. The first drill site was located 300 m inland from the edge of the moraine. Several small stones and some “pockets” of dirt were observed in the lower part of the ice core. At a depth of 46 m, drilling stopped due to a large boulder or bedrock. The second drill site was located 410 m farther inland. At a depth of 91 m, the ice core became wet, and all the ice chips in the core barrel were washed out, probably due to the flowing water. The last piece of the ice core contained very few visible dirt particles. The drilling was stopped because of the risk of losing the drill. In March–April 1979, three boreholes were drilled with the UB-II drill on Vernagtferner in the Oetztal Alps (Austria) to depths of 83.45, 45.1, and 34.45 m (Oerter et al. 1983). An attempt was made to drill the first borehole as deep as possible, but at a depth of 83.45 m, probably close to the glacier bed, rapidly rising water prevented further drilling. Then, the borehole was deepened by 6.20 m using an electrical hot point when it was no longer possible to penetrate the ice. After raising the drill, it was very dirty, and thus indicating contact with the bedrock or at least morainic material beneath the glacier. In the 1979–1980 season, for the first time by Western experts, the UB-II drill (“NSF-Swiss Drill”) was used to obtain ice cores at the Soviet Vostok Station in Antarctica (Marshall and Kuivinen 1981). The drill site was situated 70-m true east of the middle of the Vostok skiway, where the team from the Polar Ice Coring Office (PICO), University of Nebraska–Lincoln, drilled two boreholes to depths of 101 and 102 m. Surprisingly, in the first hole, at a depth of 100 m, a 30-mm-wide dust layer was encountered, which was not found in the subsequent 102 m and was probably due to the inclination of the hole and failure of the drill to reach the same vertical depth.

8.3 University of Bern (UB) Drills

In the 1980–1981 season, PICO prepared and loaned the NSF-Swiss Drill to the British Antarctic Survey for use in their drilling program on the Antarctic Peninsula (Kuivinen 1981). The British successfully collected cores from two holes of 30 and 83 m. Unfortunately, this drill suffered severe damage and was not recovered after being dropped off the drilling tower and falling free from the surface to the bottom of the 83-m hole. In summer 1982, the UB-II drill was again used for coring in the Alps at Colle Gnifetti, and two cores were recovered down to the bedrock of the glacier at depths of 124 and 66 m (Stauffer and Schotterer 1985). UB-III Drill. In the 1980s, the first drills were completely redesigned (Fig. 8.11) to produce better cores from greater depths (Schwander and Rufli 1988). The ID/OD of drill head cutters of the UB-III drill were increased to 105 mm/143 mm. In order to reduce the stress on the core, the drill head has four main cutters and four small cutters. The drill head is self-centering in the holes using eight 2-mm-wide helical lands, one in front and one behind each chip groove. One land slightly overlaps with the next so that the drill head touches the

Fig. 8.11 UB-III drill (Schwander and Rufli 1994)

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borehole wall on its whole circumference. The rotation of a DC motor (300 W) is electronically controlled in a range from −120 rpm (reverse rotation) to +120 rpm. The original anti-torque system has three skates that retract during the raising and lowering of the drill. These are driven out to the wall by torque and the release of the cable tension. A 9-m-high tower is equipped with a shaft encoder on the top wheel for depth measurement. A winch driven by a 4 kW DC motor provides a lowering/hoisting speed of up to 1 m/s, and 500 m of Kevlar 11-mm-diameter cable (7 mm × 0.6 mm) is spooled on the winch drum. The UB-III drill was tested at Dye 3, Greenland, in June 1988. A core of very good quality was drilled to a depth of 183 m. At this depth, considerable problems with hole closure were encountered. The lowest 10 m had to be carefully reamed every day to prevent the drill head from getting stuck in the borehole. The average core production was close to 1 m per run. During the next summer season (1989), a 304.8-m-long ice core was retrieved with the UB-III drill at Summit, Central Greenland, within the framework of the EUROCORE project (Fig. 8.12) (Schwander and Rufli 1994). No major problems

Fig. 8.12 Inside EUROCORE drill shelter at Summit, Greenland, 1989 (Schwander and Rufli 1994)

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were encountered to 130 m. Below that depth, the drilling speed was substantially reduced as a result of penetration difficulties. The motor current was unusually high, and the anti-torque section often started to rotate. The reaming action of the anti-torque section produced additional chips that fell between the jacket and the borehole wall, leading to additional torque at the drill head. In addition, the pulling force required to raise the drill was higher than normal close to the bottom of the hole, which was another sign of chips remaining above the drill head at the end of the run. Various actions were taken to improve the anti-torque section: the spring load of the anti-torque skates was increased, and the sharpness of the knives on the anti-torque skates was adjusted to prevent them from digging too easily into the borehole wall. All these measures improved the performance of the drill, but could not solve the basic problem. At a depth of 180 m, the motor current again increased considerably due to packed chips around the drill head. This was attributed to the timing of the cold drill barrels caused by the very warm and humid weather during these days. Therefore, the drilling shift was moved to the night time, when the temperatures were substantially lower. For a couple of days, this solved the problems with packed chips. In the meantime, it was decided to treat the drill barrel with a wax solution (a silicone grease-based mixture) to prevent the chips from sticking. From then on, the inner and outer barrels were heated and dried every evening, and then sprayed with this solution. In addition, the outside of the inner barrel with the auger flights was treated before each

Fig. 8.13 Ice core drill at drill site in Great Hall of Dobšinská Ice Cave in Slovakia, 2002 (Dobsina Ice Cave, n.d.)

8 Cable-Suspended Electromechanical Auger Drills

run. Then, it was able to drill at a constant rate of approximately 12 m per night, and reached the final depth of 304.8 m. The total drilling time took 29 days. At the end, it seemed that the foregoing difficulties with penetration were all linked to the problem of fine chips blocking the grooves in the drill head and auger flights. The quality of the recovered ice core was excellent to 180 m, although the first internal fissures appeared at a depth of 135 m. Down to 180 m, the length of unbroken pieces (normally about 1 m) was only limited by the core break at the end of a drilling run. When problems with penetration started, many cores were only 0.5-m long, or even shorter. Below 180 m, more and more additional fractures occurred, and the length of the unbroken pieces decreased to a range of 0.05–0.3 m. UB-IV Drill. In the early 2000s, a challenging drilling project was carried out in the Dobšinská Ice Cave in Slovakia (this cave is included on the UNESCO World Heritage list). The goal of this project was to analyze climate and environmental changes by studying continental cave ice using isotopic and chemical analysis methods (Vrana et al. 2007). Drilling was accomplished in November 2002, using the lightweight UB-IV drill, with a 3-m-tall mast designed by H. Rufli especially for the conditions of the Dobšinská Ice Cave (Fig. 8.13). Two boreholes were drilled in the so-called Great Hall of the cave: the first one to a depth of 1.62 m, which was stopped by a buried wooden pavement, and the second one to a depth of 13.93 m, which was stopped by rock inclusions.

8.3 University of Bern (UB) Drills

Fig. 8.14 Lightweight modification of UB-IV drill inside shelter, Colle Gnifetti, 2005 (Wagenbach 2006)

In the following years, the UB-IV drill with lightweight modifications was used for several drilling projects in the Alps. In 2004, a 124-m borehole was completed at Col du Fig. 8.15 Shallow drilling at Ekström Ice Shelf, Antarctica, 2006–2007 season (Credit J. Schwander, University of Bern)

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Dôme (Mont Blanc area, 4250 m a.s.l.) (Preunkert and Legrand 2013); in 2005 a 62-m borehole was drilled at Colle Gnifetti (Fig. 8.14) (Wagenbach 2006); and in 2010, 13 boreholes were drilled at the Corvatsch ice field, Col du Dôme, and Colle Gnifetti (J. Schwander, personal communication 2014). The modified UB-IV drill was also used in Antarctica. Three firn cores (B35, B36, and B37) were recovered in the vicinity of Kohnen Station (Dronning Maud Land, Antarctica) for firn air sampling and microstructural analyses during the field season of 2005–2006 (Weiler 2008). The lengths of these holes were 30, 78, and 124 m. Hole B36 was cored using a drill head with an ID/OD of 97 mm/126 mm. Because of the small radial clearance between the jacket and the borehole (1.5 mm), only short (0.2–0.6 m) cores could be drilled. Thus, in order to increase production, the cutting diameter was increased to 129.6 mm (leading to a core with a diameter of 98 mm) at a depth of 64 m in hole B36. In this way, the run length increased to 1.2 m. However, because of reaming runs and tests of the firn air pumping system, the hole stayed open for five days between 60 and 70 m and for five more days until a further sample was taken at a depth of 78 m. Because of this delay, it is likely that the hole became contaminated (indicated by much higher CO2 concentrations than expected). Thus, sampling was restarted in a new hole (B37), where drilling was terminated at a depth of 124 m, and the whole process was completed within 11 days. In January 2007, a German–Swiss team drilled four firn holes with a modified UB-IV drill on two ice ridges to the east (Halvfarryggen) and west (Søråsen) of the Ekström Ice Shelf in the region of the German Niemeyer station, Antarctica (Fig. 8.15) (Fernandoy et al. 2010). This

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8 Cable-Suspended Electromechanical Auger Drills

campaign was a pre-site survey to investigate the recent regional climate variability and potential for the future extraction of an intermediate-depth core. At Halvfarryggen, two firn cores were drilled: B38 (84 m deep) and FB0702 (42 m deep). At Søråsen, B39 (78-m deep) and FB0704 (36 m deep) were retrieved. Thus, it can be seen that starting in the early 1970s, experts from the Physics Institute, University of Bern, designed and tested several different modifications of cable-suspended electromechanical auger drills. In summary, all of the modifications worked very well in the firn and upper ice formation, but drilling deeper caused penetration and core recovery problems. Some suggested methods to solve these problems were proven to be effective and could be considered by others in future drilling activity.

8.4

CRREL Drill

Initially, the CRREL drill and related equipment was designed for continuous coring in firn and ice to a depth of 100 m (Rand 1976). Some sources refer to this drill as the “Rand drill,” based on the name of its creator. The design (Fig. 8.16) was based upon experience obtained over the many years of CRREL’s active involvement in ice-core drilling. Two cutters are connected by bolts to the drill head fixed to the bottom part of the inner core barrel. Two independent methods of catching the core are incorporated in the drill head. The first method is similar to that of the SIPRE hand auger, that is, a 1.75° taper is machined along the inside circumference of the cutting bit. This surface, along with the loose cuttings, produces a wedging effect when lifting the drill, thus breaking the core at that location. The second method uses two spring-loaded doglegs, which cut into the core when the drill is lifted upon the completion of the drilling cycle. Two nylon spirals are epoxied to the outside of the 2.5-m-long stainless steel inner barrel. The cuttings produced at the bit are transported by the auger flights to an opening at the top of this section. They are then deflected to the inside of the inner barrel. Upon entering the barrel, they fall and rest on top of the core as it enters from the bottom through the drill head. The nylon spirals also act as a bearing surface between the inner and outer barrels. The outer barrel is connected to the top of the motor and gear section enclosing the entire bottom length of the drill. The motor and gear section is composed of a submersible pump motor coupled to a planetary gear attached to the motor with a splined shaft. The anti-torque system consists of three leaf springs. The springs are 38 mm wide, and the effective length of the engagement with the wall of the hole is 760 mm. To attach the drill to the cable, a termination is

Fig. 8.16 CRREL drill (Rand 1976)

8.4 CRREL Drill

made where a small length of the armor braid is twisted around. The electrical leads continue straight through this termination. A low melting alloy (Cerro bend) is used to provide a potting compound. This material melts at 70 °C, and is poured into a cavity where the twisted armor braid is placed. A 100 m length of cable is spooled onto an aluminum drum. The drum is connected by a chain drive to a gear reducer. The hoisting speed is 1 m/s. The power for both the electric hoist motor and drill motor is provided by a 5 kW, three-phase gasoline generator. The 6.8 m tower section consists of two parts. The lower section is a telescoping square tubular section. A mechanical screw jack is connected to a variable-speed DC drive motor, which raises and lowers the internal section of this tower. This provides a method of controlling the penetration rate of the drill. The top section is made of aluminum-extruded tubing, which is split lengthwise. This section also serves as a shipping container for the drill. Markers on the telescoping tower show when 1 m has been drilled. The drill motor is stopped, and the winch is slowly raised until a core break is felt in the cable. The winch is fully engaged, and the drill rises to the surface. The entire rectangular aluminum base unit is mounted on three skis and can be towed behind a snow vehicle. The whole package can be easily disassembled and transported by a light aircraft. The entire operation was designed so that two men can assemble and operate the system. The first version of the CRREL shallow drill was tested at Station Milcent, Greenland, during the GISP-73 field season. Although the motor and anti-torque system proved to be

Fig. 8.17 CRREL drill in use during 1974–1975 summer field season, Antarctica (Rand 1976)

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undersized, the concept of the drill was valid. During the GISP-74 field season, a modified CRREL shallow drill was tested at Station Crete, Greenland. Several problems developed, which made it impossible to continue the scheduled testing. Returning to the laboratory, modifications were made to the drill’s gear reducer, reducing the final output speed to 100 rpm; several other modifications were made to the winch controls, making the overall system more adaptable for continuous drilling. In September 1974, the drill was shipped back to Greenland for a drilling test at Dye 2. After field changes to the bits, the drill successfully drilled 100 m, obtaining an excellent core. The drill was shipped directly from Dye 2 to Antarctica, where two holes were drilled (Rand 1975). The first 100-m hole was drilled in early November at the South Pole. The −30 °C temperature experienced during this operation spread the drilling over a 2.5-day period. The actual drilling time was just under 15 h. A relatively slow start was due to the drill head, which had to be reworked in the field. Heaters were added to the winch to keep the motors and gear boxes from freezing. The drill motor was stored each night in a heated shelter. The excellent cores with average lengths of 0.3–0.4 m obtained from this site had very little surface scoring. The second 100-m hole was located at J-9 on the Ross Ice Shelf (Fig. 8.17). Drilling to a 100 m depth was accomplished within a 4-day period, at the end of November, at which time the ambient air temperature ranged between −15 and −6 °C in the drilling shelter. Problems with core recovery after reaching the firn–ice transition slowed progress. The core from this site was less than perfect and

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8 Cable-Suspended Electromechanical Auger Drills

continuous, and at depths of 75–100 m, only 52 % of the core was recovered (Langway 1975). It appears that the configuration of the cutters of the CRREL shallow drill was better in firn than in ice. The firn–ice transition was not quite reached at the South Pole, whereas this boundary was reached at a depth of 47 m at J-9. In the following years, the CRREL drill was used many times in Antarctica. In the 1977–1978 season, ice cores were obtained from sites Q-13, C-16, and J-9 on the Ross Ice Shelf, as well as at the South Pole (Chiang and Langway 1978). The drilling operations at Q-13 and the South Pole proceeded smoothly and, in general, the quality of the core obtained was excellent. A total of 100 m of core was obtained at the Q-13 and C-16 sites in 4–5 days. The actual drilling time decreased as the drillers gained experience, from about 28 h at Q-13 to 14.5 h at the South Pole, even though the hole there was slightly deeper (up to 111.5 m). During the 1978–1979 austral summer, four firn cores were drilled using the CRREL drill on the McMurdo ice shelf as part of a study of brine infiltration. Because the CRREL drill’s electrical section leading to the motor was not designed to operate in liquids, it was not possible to drill deeper than *3 m into the brine layer. The deepest hole reached a depth of 59 m (Kovacs et al. 1982). Probably the last time the CRREL drill was used was at the South Pole station in the 1980–1981 season (Kuivinen 1981). Drilling proceeded to a depth of 49 m; beyond that depth, the drill could not penetrate vertically. Runs made with an inclinometer indicated that the hole was being drilled in an ever-increasing spiral; this resulted in the drill’s being wedged in the curved hole, thus preventing further penetration. In later US drilling projects, the CRREL drill was gradually replaced by the more efficient PICO-4″ drill (see Sect. 8.9).

8.5

Institute of Low Temperature Science (ILTS) Drills

8.5.1

First Prototypes

In the early 1970s, members of JARE designed, as a trial, the first-ever electromechanical auger drill. It consisted of four blocks: the cable suspension, anti-torque device, power unit, and core barrel (Suzuki 1976). The suspension was borrowed from the existing JARE 140 thermal drill. The anti-torque device was of the pantograph-type, with four pairs of arms (without skates) expanded outward by four adjustable springs. The power unit was a 100 W, 100 V, single-phase motor with a 15∶1 gear reducer. Thus, at 50 Hz, the drive shaft rotated at 100 rpm. The core barrel was 1.5 m long and was made of a steel pipe with an OD of 114.3 mm. The body of the drill head (with an ID/OD of

105 mm/150 mm) was welded to the lower end of this pipe, and three cutters were fastened to it with hexagonal bolts. Triple-spiral flights were welded all over the barrel with a uniform pitch of 150 mm. Hence, two adjacent flights were 50 mm apart vertically. In actual operation during the 12th JARE in October– November 1971, at Mizuho Station, Antarctica, the drill revealed many defects, the most serious being the ineffectiveness of the auger to move ice chips upward. Often, only 0.2–0.3 m of drilling caused ice chips to cling between the flights and the wall of the hole, overloading the motor. Even when the drill worked well, the rate of penetration was only 2–3 m/h (Suzuki and Takizawa 1978). The drill had been designed to obtain a 1-m core, but the longest core obtained was only 0.5-m long. On November 1, the drill became stuck at a depth of 41.9 m. Recovery efforts ended on November 6, when the cable slipped out from the termination. In 1973, Y. Suzuki from the Institute of Low Temperature Science (ILTS), Hokkaido University, Japan, built another electromechanical drill. This drill had no complicated suspension devices, but rather a simple hook on its top. A 200-V, 400-W, single-phase motor (3000 rpm with 50 Hz) was mounted on the upper base, while a 39∶1 gear reducer was fixed at the lower base of the anti-torque device. The motor and reducer were coupled using a spline mechanism to accommodate the change in the height of the device, which was of the pantograph-type with three pairs of arms (also without skates). The weight of the motor was considered to be sufficient to expand the arms, but in an actual test it was not. The core barrel was made of a stainless steel pipe with an ID/OD of 134 mm/139.8 mm. A drill head with an ID/OD of 131 mm/165 mm was fixed at the lower end of the core barrel. Two cutters were fixed on the drill head, each by one hexagonal bolt. The drill head was equipped with two claws for core breaking. When the drill rotated in reverse, the claws caught and struck the core to make it break. Double spiral flights with a pitch of 240 mm were welded onto the barrel, which was 2.2-m long, with the upper 1 m being a chip reservoir. The 1973, the drill was tested at the T-3 Ice Island. The rate of penetration was up to 9 m/h, but the drill usually became stuck after a penetration of 0.5–0.6 m, requiring an improvement of the chip-removing mechanism. As long as the drill proceeded smoothly, the input current was stable, showing that the motor had enough power for cutting ice. In 1977, Y. Suzuki came back to the idea of a lightweight electromechanical drill in conjunction with a shallow drilling project to depths deeper than 50 m in the Antarctic ice sheet for seismic surveys of the bedrock (Suzuki and Shiraishi 1982). In the course of the work and improvements, dozens of different drill modifications were attempted, and the parameters of the basic drills (ID-140 and MID-140) are listed in Table 8.1.

8.5 Institute of Low Temperature Science (ILTS) Drills

The outstanding feature of all these drills was the anti-torque system, which took the form of side cutters (Fig. 8.18). Three 45° spiral gears transfer the main rotation to the two horizontal axes of the side cutters, to make four grooves on the hole wall (Suzuki 1978, 1984). To help counter the torque, the guide fins placed in alignment with the side cutters fit the grooves, with a side clearance of 0.25 mm.

8.5.2

ID-140 Drill

Two drills, ID-140 and ID-140A, were completed in October 1978 (“ID-140” means “Ice Drill with 140 mm nominal outer diameter of the cutters”). These drills differed from each other only in the rotational direction of their side cutters, with that of ID-140 increasing and that of ID-140A decreasing the load on the drill head. Each drill could use either a 2-m-long barrel or a 1.4-m-long one, with the corresponding outer barrel. The primary systems were tested in a cold laboratory. The first tests showed a serious problem with the outer barrel. It had a deviation in its diameter that was so large that in spite of the nominal clearance of 1.5 mm between the barrel and the hole, the drill could not proceed without a large load being applied. Then, a stainless steel tube was hurriedly machined from a thick pipe. The tests with this outer barrel lacked sufficient results because chips were hardly transported upward, and a penetration of only 0.2–0.3 m was possible. The most probable reason was that the machined inner wall of the outer barrel was so smooth that chips rotated with the barrel without any upward motion. This is

Fig. 8.18 Mechanism of side cutters (Suzuki 1984)

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why a third outer barrel was rolled out from a thin steel sheet, in the hopes that its juncture would serve as a rib, and chips would be transported upward. The system was sent to Antarctica for use in the 20th JARE for seismic surveying at the Soya Coast (Ikami et al. 1980). A total of 200 m of cable was spooled onto the winch and weighed a total of 180 kg (Fig. 8.19). It soon transpired that the third outer barrel was very weak, and it was broken in the first run. Further drilling went on with the second outer barrel, and for all that, a 62.8-m-deep hole was drilled in 66 h. Unfortunately, the short (10-cm long) anti-torque guide fins of the ID-140 drill lost alignment with the grooves, and the drill became stuck.

8.5.3

ILTS-140 Drill

Early in 1979, in order to study the auger transportation of ice cuttings, a short drill, ILTS-140, was built for testing the influences of the flight pitch, bottom shape of the jacket, rotation speed, and other factors (Suzuki and Shiraishi 1982; Suzuki 1984, which referred to this drill as ILTS-140T). A drill head with two cutters (105 mm/146 mm) was attached to a 1-m-long double-helical inner core barrel made from a steel pipe with an ID/OD of 110.3 mm/114.3 mm. The outer barrel was made of a seamed steel pipe with an ID/OD of 135.8 mm/139.8 mm. The drive section included a 0.5 kW, single-phase, 100 V motor with a cycloidal gear with a ratio of 40:1. The rotation speed of the core barrel was 100 rpm. The anti-torque system took the form of auxiliary milling side cutters, which were rotated by an additional gear connected to the drive motor. During drilling, two plates were inserted into the grooves produced by the milling cutters and prevented the rotation of the upper part of the drill. The total length of the drill was 1.6 m, and its weight was only 36 kg.

Fig. 8.19 Drill system used in 20th JARE (Ikami et al. 1980)

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8 Cable-Suspended Electromechanical Auger Drills

It was found that chips were smoothly transported because the seam, which was only 0.2–0.3-mm high, served as a rib, stimulating upward motion of the cuttings. The test drill was later remodeled to form ILTS-140A and used by the National Institute of Polar Research (NIPR), Tokyo, in December 1979, at Allan Hills, McMurdo Sound, Antarctica, to drill blue ice down to 7 m in 5 h. A hand-driven winch was used to suspend the drill, and electric power was supplied through an independent rubber-jacketed cable from a variable transformer to control the rotation speed of the core barrel. In 1981, the drill was again remodeled to form ILTS-140B and successfully used in the 22nd JARE for coring several holes down to 30 m at East Enderby Land in Antarctica.

8.5.4

Fig. 8.20 MID‐140 drill (Suzuki and Shiraishi 1982)

MID-140 Drill

Based on test results with the ILTS-140 drill, the old ID-140 drill was modified into the MID-140 drill (the letter “M” was added to identify the new version as a “mechanical” drill). This drill can be easily disassembled into three parts: the driving unit, outer barrel, and core barrel (Fig. 8.20) (Suzuki and Shiraishi 1982). The driving unit consists of two parts. The cylindrical case of the upper part contains a relay (to reverse the rotation of the motor) and power source. There are four free-wheeling safety cutters and a connector to the slip-ring assembly at the top of the case. Four guide fins are welded to the side of the case over its entire length. Free-wheeling safety cutters behind these guide fins cut new grooves for escape when a misaligned drill is pulled up. However, the anti-torque system in the form of long fins never became misaligned during drilling. The lower part houses the main shaft, which has a plug-joint for the core barrel, barrel-release mechanism, and mechanism to drive the four side cutters. The outer barrel is attached to this lower part. The upper part can slide by 30-mm relative to the lower part, allowing a hammering action on the core barrel. A quick barrel-release mechanism operates as follows. A release ring, which can slide over the main shaft, is linked to the release shaft inside the center hole of the main shaft by a pin, through slits on the main shaft. The release shaft, in turn, is linked to joint pins in the connecting plug through a pantograph mechanism. The spring inside the main shaft pushes the release ring to its lower position, so that the joint pins protrude from the plug to connect the barrel. When the release ring is pushed up by the lever, through a hole in the main shaft housing, the joint pins retract, disconnecting the core barrel. The length of the core barrel is 1.5 m, and the length of the outer barrel is such that its end is 10 mm above the upper surface of the drill head. Three 8-mm-wide and 1.5-mm-thick ribs are spot-welded on the inner surface of the outer barrel. Both barrels are Teflon-coated.

The drill system was prepared to use in the 21st JARE (this system was referred to as MID-140B, JARE-140B, or JARE-MID-140B). Preliminary tests were carried out in July 1980, near Syowa Station at the S-22 site (30.5 and 15.6 m) and S-27-3 site (30.5 m). To facilitate drilling operations, the system was mounted on a sledge, which was 4-m long and had a canvas cabin 2.3-m long on it. The winch was set on the open space, while the generator was in the cabin. In general, the drill worked smoothly, though drill slips and core break failures occurred in several runs below 10 m. The next hole was drilled on October 18–24, 1980, at drilling site H-231 on the traverse route from Syowa Station to Mizuho Station. A 100-m-deep hole was cored in 44 h. At a depth of 68 m, a hasty reversal of the drill rotation broke the reducer, and it took 6 h to replace it using the reducer from the ID-140A drill, which had fortunately been kept at hand. After completing the hole at H-231, the drilling team moved to Mizuho Station, where during October 29– November 11, another hole was cored at the Z-140-1 site,

8.5 Institute of Low Temperature Science (ILTS) Drills

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approximately 2 km away from the station. During drilling, the weather was very severe: in the mornings, the mean temperature was −28.7 °C, with wind speeds up to 13.8 m/s, and blizzards occurred on 9 days out of the 2 weeks of operations. Despite such severe weather, drilling proceeded smoothly, except for slips of the drill, which were rather common below 65 m, where the drill usually began to slip after a penetration of 10–15 cm. After being pulled up by 0.5 m or so and lowered slowly with the motor on, the drill could resume progress for another 10–15 cm. However, this meant that it required several such procedures to drill 0.5 m. At a depth of 108 m, the core barrel was accidentally dropped to the bottom of the hole. After a laborious 6 h of work, the drillers managed to recover the barrel and resumed drilling, which was halted at 135 m because of the breakdown of the reducer. Almost 10 m was left before reaching the maximum attainable depth by the system, and the team did not give up. A mechanic of the team flew to Syowa Station with the broken driving unit to replace its reducer using the one from the ID-140 drill. He flew back the next morning with the repaired unit, and the final 8 m was drilled in that day. The 143 m hole required 81 h. Fig. 8.21 Main components of ILTS-130C drill (Suzuki 1984)

8.5.5

Portable ILTS-130 and -100 Drills

In the early 1980s, the designing of lightweight drills was continued, resulting in the ILTS-130 drill series (ILTS-130A, B, C, and D), principally for use in high mountains (Fig. 8.21) (Suzuki and Shiraishi 1982; Suzuki 1984). These differ in the power of the drive motor: 450 W for A, 220 W for B, and 350 W for C and D (Suzuki 1994). All of the drills in the ILTS-130 drill series make holes 132 mm in diameter, producing ice cores 102 mm in diameter, and 35 cm long. With a barrel 1 m long, they are shorter than 1.6 m (1.4 m for models C and D), lighter than 30 kg (21 kg for model C), and require a total of less than 1 kW of power (0.6 kW for model C). Model D weighs only 19.8 kg. The drills are suspended by a manual or small electric winch (300 W) using an ordinary 4-mm steel-wire rope, and power is supplied through an independent electric cable. The total weight of the system, consisting of the ILTS-130C drill, mast, manual winch with 40 m of 4-mm steel-wire rope and 40 m of rubber electric cable wound on a drum, controller, and 800-W generator, is about 70 kg. Replacing the winch and cable with an electric winch and armored cable increases the weight by 10 kg. Three people may backpack the system. Various field tests carried out in 1982 proved the practicability of the ILTS-130 drills. Model A has been used on a Himalayan Glacier, where a depth of 33 m was reached. Model B was used at Halley Bay, Antarctica, for coring a

22-m-deep hole. Model C was used to core to a depth of 22 m in silty ground ice at Tuktoyaktuk, N.W.T., Canada. In the mid-1980s, another version of the shallow drill ILTS-100 with a drill head with an ID/OD of 80.6 mm/106.6 mm was designed and built (Suzuki and Shimbori 1984). The triple-spiral core barrel has a length of 1.5 m intended for recovering a 0.8-m-long core. The drill length is 1.9 m, and its weight is only 13.4 kg. The drill is equipped with a W-5-60 winch, which is made to be as compact as possible. The winch, driven by 300-W DC motor, was designed to have a maximum load of 30 kg and hoisting speed of 0.5 m/s. A harmonic drive reducer (CS-32-100) is incorporated in the cable drum. The reducers only have to withstand the hoisting torque, because the core is broken by directly rotating the drum with a torque wrench. A total of 60 m of a four-conductor cable, 4.65 mm in diameter, was spooled on the winch drum. The total weight of the winch with the cable is 27 kg. The mast is made of a fiberglass pipe with an outer diameter of 70 mm. A modified version (ILTS-100S) was used for ice core drilling down to 37.6 m in the accumulation area of the San Rafael Glacier in the Northern Patagonia Icefield in November 1985 (Yamada et al. 1987). To solve the transportation problems, the total weight of the drilling system was reduced to 37 kg, including the weight of the fuel. Drilling was conducted in a 3-m-deep trench covered with a simple roof (Fig. 8.22). Eighty-four high-quality cores with a diameter of 80 mm were recovered in a total of 23 h.

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The average rate of penetration was 0.48 m/min, and the average core length was about 400 mm when using the 0.734-m-long core barrel. In 1988, the lightweight ILTS-100 drill was used in laboratory studies to obtain the basic characteristics of electromechanical drilling (Fujii et al. 1988). It was found that one-third of the total energy is consumed for ice cutting and two-thirds for barrel rotation and ice cutting transportation. From 1987 to 1995, nine ice drilling campaigns, along with specialists of the Japanese Arctic Glaciological Expedition (JAGE), operated in the Arctic region, Norway, Svalbard, and Greenland (Watanabe 1996), with the deepest hole being 210 m. Unfortunately, the details and information about the types of drilling equipment were not published.

weight of 24–29 kg. The drill was equipped with a winch of the W-6-250 type with 250 m of cable. The total weight of the winch and cable was 66 kg. During the 25th JARE, two 200 m boreholes were drilled in the course of a traverse survey over East Queen Maud Land. For the ILTS-130 series drills, the clearance of the Mk-I-type barrel (the difference between the inner radius of the jacket and the outer radius of the core barrel) was 7.4 mm (Suzuki 1994). A reduced clearance of 4.75 mm was tested in cold ice: chips literally ran up and hardly stayed along the barrel. The barrel of this diameter was called Mk-II. The narrow clearance was no problem even for the 4-m-long Mk-II barrel tested in late 1983. Unfortunately, tests in warm ice showed that wet chips could go up to the inlet but often formed a thin ice layer and did not enter the barrel. The final version of ILTS-130 (ILTS-GTBAS-130) with the Mk-II barrel and a W-5-250 winch was made for the British Antarctic Survey in April 1985. In 1983, a scaled-up version of the ILTS-150A drill was designed and produced for use in the 25th JARE (Suzuki and Shimbori 1984). The drill had a three-cutter drill head with an ID/OD of 132 mm/158 mm. It was able to obtain a core with a length of up to 0.93 m, and the total length of the drill was 2.3 m. The ILTS-150A weighed only 36.2 kg, and the plan was to suspend it by a winch of the W-12-800 type, with 800 m of cable (originally, this winch was used for thermal drilling).

8.5.6

8.5.7

Fig. 8.22 Drilling trench at San Rafael Glacier, Northern Patagonia Icefield (Yamada et al. 1987)

ILTS-130E(F) and ILTS-150 Drills

Based on the lightweight ILTS-130 drill series, two similar versions of “heavier and deeper” drill systems were designed for drilling down to 200 m (Suzuki and Shimbori 1984). The ILTS-130E drill was produced for glaciological research in the 24th JARE, with the improved ILTS-130F drill produced for the 25th JARE. Both of these drills had a four-cutter drill head with an ID/OD of 107 mm/133 mm. The drive motor had a power rating of 350 W. The drill length for the different modifications varied in the range of 2.2–2.4 m, with a Fig. 8.23 New portable ILTS drill (Kohshima et al. 2002)

New Portable ILTS Drill

A new version of a lightweight water proof drill was developed by K. Shinbori at the end of the 1990s (Kohshima et al. 2002). This drill system weighed less than 100 kg and was designed to drill at least 100-m-deep holes in logistically difficult glaciers. A newly designed pantographic-type anti-torque system and two kinds of core barrels (one for dry and another for liquid-filled holes) were produced (Fig. 8.23). The rotation speed of the drill head was changed by the voltage controller of the driven motor. The rate of

8.5 Institute of Low Temperature Science (ILTS) Drills

penetration could be varied in the range of 12–24 m/h by replacing the cutters and shoes. The winch motor also had a voltage controller, giving a tripping speed of 15 m/min on average. The drill was tested at Tyndall Glacier, South Patagonia Icefield (Chile), in November–December 1999, and basically worked well. A firn core was obtained down to a total drilling depth of 45.97 m. It comprised a 40.65 m core recovered in about 5 days, using the electromechanical drill, and a shallow core 5.47 m long obtained using a hand auger. The core length was in the range of 0.5–0.6 m at the upper part of the hole. The water-saturated firn was found at a depth close to 42 m, and the possible core length dramatically dropped to only 0.1–0.25-m per run. The pantographic anti-torque system caused problems when the drill went through horizons composed of different densities, i.e., melt-frozen layers in firn and water-soaked layers. At these horizons, the anti-torque system slipped many times, and drilling was not always easy. The length of the drill (3.13 m) was extremely disadvantageous using a mast with a height of 2.3 m. To operate the drill, it was necessary to dig a large pit, which was quite difficult at a remote glacier under bad weather conditions. Especially for drilling at Mount Wrangell, southeastern Alaska, K. Shinbori designed a new lightweight mechanical drill called the “Dokomedo (Anyplace) Drill Version 2” (Shiraiwa et al. 2004). This drill is composed of two main parts: a drill motor with an anti-torque system and a cable termination and a core barrel without a jacket. The drilling system also includes a winch with 200 m of cable, a drill mast used as a carrying case for the core barrel, a half-round pulley on the top of the mast, and a drill controller (Fig. 8.24). The total weight of the system is 100 kg, and it is back-packable by four people. It can be operated using a 0.7 kW generator, which adds 10 kg to the system’s weight. Drilling operations were conducted at the center of the summit caldera in June 2003 and June 2004. In 2003, it took 22 h over 4 days to drill to a depth of 50.3 m (Matoba et al. 2014). The length of each ice core was *0.5 m. In 2004, an ice core was drilled to 216 m (Kanamori et al. 2008).

8.6

University of Copenhagen (UCPH) Drill

The University of Copenhagen (UCPH) developed a shallow drill under the GISP Program in the middle of the 1970s (Fig. 8.25) (Johnsen et al. 1980). The total weight of the drilling equipment is close to 300 kg, including the winch, cable, mast, electronic control system, generator, fuel, and packing materials. The largest dimension is 3.5 m. All the equipment can be placed on two Nansen sledges to be towed with a ski-doo or can be carried by a small plane to less accessible drill sites.

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Fig. 8.24 ILTS drilling system used at Mount Wrangell, 2003 (Matoba et al. 2014)

The UCPH drill has a classical design with double-core barrels, which are both made of stainless steel. The outer barrel is 2.65 m long and reaches from the bottom of the anti-torque section all the way to the drill head. On the inside, the outer core barrel has 20 closely spaced grooves (0.4-mm deep) parallel to the axis, which enhance the upward transport of the chips. The inner barrel is 2.35 m long. On the outside, it is provided with three lead auger flights. The cutters are mounted on a stainless steel head fixed to the lower end of the inner core barrel. The width of the cutters is 13 mm, leaving a 1 mm clearance between the hole wall and the outer core barrel, and a 0.1 mm clearance between the core and the inner surface of the drill head (this clearance was later enlarged to 0.5 mm (Gundestrup et al. 1988). The motor-gear section of the drill is 290-mm long (including a ball-bearing support for the exit shaft) and has a 97-mm diameter. The power consumption is 230 W with no load, and 450 W when cutting ice at a penetration rate of

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Fig. 8.25 UCPH shallow drill in horizontal position for removal of core and chips (Johnsen et al. 1980)

0.5 m/min. The bottom of the motor-gear section is bolted to the outer core barrel, and the moment is transferred to the inner core barrel through a simple shaft, which is strong enough to withstand the maximum pull of 20 kN from the cable. The anti-torque system has three leaf springs that are 500-mm long, 20-mm wide, and 2-mm thick. By changing the distance between the two hinges supporting each spring, the rise of the springs can be adjusted from high values in the upper firn to low values in solid ice. In the latter case, each spring exerts a 300-N force on the hole wall, which is sufficient to prevent the rotation of the drill and low enough to ensure the necessary load on the cutters. A steel hammer block is mounted between the springs. It weighs 7 kg and glides along the three supporting rods over a distance of 100 mm. A drilled core is broken by ramming the block against the upper stopper. The same procedure serves to disengage the drill in a case of sticking. At the upper part of the drill, the electromechanical cable is fixed by a Dynagrip termination to a hammer block through a system of ball bearings, which prevents cable twisting in the case of an anti-torque failure. In such situations, three steel supporters on the rotating anti-torque system pass a micro-switch on the cable, thus producing an alarm signal at the surface. The winch is the heaviest item, weighing 140 kg, including the motor, gear, 200 m of cable, and a wooden container (later the length of the spooled cable was increased to *350 m). All parts of the winch are made of hard aluminum, except for the steel cylinder and shaft. It has a built-in 1-kW motor fixed to the cylinder. The motor-gear assembly is built principally in the same way as the drill

motor-gear section. It is bolted on the inside of the cylinder, and the gear exit shaft is fixed to one of the outer aluminum plates that carry the winch. The cone at the end of the winch contains slip rings for the winch motor and cable. The rotation of the winch can be adjusted continuously within a range of ±60 rpm, giving a maximum hoisting or lowering speed of more than 1 m/s. The drill is usually operated over a trench 0.3-m wide and 1.3-m deep. In its upright position, the device reaches from 2.3 m above to 1.2 m below the surface. The drill and mast can be turned into a horizontal position to facilitate the removal of chips and cores. The drill is normally operated by one person, while a second person logs and packs the core. A preliminary version of the drill was tested in May 1976, at Dye 3, Greenland, where the borehole was deepened to a depth of 100 m. Then, testing continued at the Hans Tausen ice cap, but the drill was lost at a depth of 60 m (Clausen et al. 1988). In 1977, an improved version of the drill was used at several locations on the Greenland ice sheet. During this season, eight boreholes were drilled to a maximum depth of 110 m, and a total of 629 m of core was recovered. At the end of the season, when the optimum shape of the cutters had been worked out, drilling a 100 m core took only 10 h. The average lengths of the core recovered per run were 1.2 m in firn and 1.0 m in ice. The quality of the core was excellent, with very few unintended breaks. The only difficulty occurred at the 110 m depth, when falling ice crystals from the upper part of the hole collected on top of the hammer block, which made it stick to the flat impact surface above. The drill was stuck for several hours, and had to be disengaged using glycol.

8.6 University of Copenhagen (UCPH) Drill

Fig. 8.26 Modified drill head of UCPH drill (Gundestrup et al. 1988)

Fig. 8.27 UCPH drill in action, NEEM Camp, Greenland, 2008. In the corner—Greenlandic postage stamp with UCPH drill (Photo H. Thing; Drilling 2008)

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Later, the system was slightly improved as follows (Gundestrup et al. 1988): (1) the material used for the slip ring electrical contacts was changed to 90 % silver with 10 % graphite; (2) the auger flights on the inner core barrel were replaced with polyethylene high-density (PEHD) flights, screwed to the inner core barrel; and (3) the drill head was modified and shoes were added to determine the penetration rate, as shown on Fig. 8.26. Since this time, the UCPH drill has remained almost unchanged and has been used for many years until now in Greenland, mainly in temperate and cold ice with temperatures between −15 and −32 °C (Fig. 8.27). The deepest hole was drilled on the Renland Ice Cap in East Greenland over a period of 9 days to a depth of 325 m in 1988 (Clausen et al. 1988). At a depth of *250 m, the core tended to create wafer-type breaks. In order to preserve the core quality, the pitch was reduced to 3 mm. This stabilized the core quality somewhat, but not all of the fine cuttings were collected inside the drill. Finally, close to the bedrock (fine clay particles were found in the core), the drill was unable to break the core and became stuck. In order to free the drill, 20 L of a 30 % glycol/water mixture was poured down the hole

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through a 50-m-long-plastic tube (the mixture was not heated). The next day, the drill was free and used to recover another 0.9-m-long core. The UCPH shallow drill can be used for reaming holes such as for casing installation. In this case, a special reaming device is fixed to the driven unit of the drill instead of the core barrel and jacket (Johnsen et al. 1980). The reaming device (Fig. 8.28) consists of a 2-m-long cylindrical container with a diameter slightly smaller than that of the drill hole. The chips cut by the knives in the top piece are collected in the cylinder. In the summer of 1978, the reaming device was attached to the motor-gear section of the drill, replacing the core barrels, and used to enlarge a 103.5-mm hole to a diameter of 135 mm down to a depth of 90 m, at a speed of 2-m per run (the reaming time was *2 min). Similar devices were later used for enlarging holes in NGRIP, NEEM, and some other intermediate and deep drilling projects.

8.7

Laboratoire de Glaciologie et Géophysique de l’Environnement (LGGE) Drills

and H. Rufli (Gillet et al. 1984). This drill consists of three main sections: a double-core barrel, a motor-gear, and an anti-torque system (Fig. 8.29). The outer jacket and inner core barrel are both made from stainless steel tubes. Three steel strips (1.5 mm thick) are fixed inside the 2.3-m-long jacket to provide better movement of the chips on their way up the flights. Two different types of inner barrels have been used. The first option employs the same two cutters (Fig. 8.30a) and core-catching system as used in the SIPRE hand auger, with two lead auger flights made from polyethylene. The second option has three round cutters (Fig. 8.30b) and three core catchers, which are tripped against the core by giving a small reverse rotation to the motor. The stainless steel spirals replace the polyethylene ones and, being thinner, increase the space available to the chips. Later, the inner core barrel was replaced by a perfectly straight auger machined from a thick-walled aluminum tube with integral flights (O. Alemany, personal communication 2015). The stainless steel jacket was replaced by a tube produced from composite materials (Kevlar, carbon, glass, and epoxy) in the LGGE workshop in the same manner as the core barrel for a deep thermal drill (Forage 4000 1986).

The original shallow drill was built in the Laboratoire de Glaciologie et Géophysique de l’Environnement (LGGE), Grenoble, France, in 1976–1977, with the help of J. Rand

Fig. 8.28 Reaming device that can be attached to UCPH drill for enlarging the diameter of a borehole (Johnsen et al. 1980)

Fig. 8.29 Schematic of LGGE drill, tower, and winch assembly (Gillet et al. 1984). 1 Electromechanical cable; 2 cable termination; 3 knocker weight; 4 spring; 5 slip-ring; 6 submersible motor; 7 gear reducer; 8 clutch; 9 chip inlets; 10 auger flights; 11 core barrel; 12 cutters; 13 sheave; 14 mast; 15 rotation axis of mast sections; 16 cable drum; 17 hydraulic motor reducer

8.7 Laboratoire de Glaciologie et Géophysique de l’Environnement (LGGE) Drills

Fig. 8.30 LGGE cutter design: a cutters borrowed from SIPRE hand drill and b rounded cutters (Gillet et al. 1984)

This outer tube had four grooves inside, and aluminum bars were placed in these grooves to improve the chip transportation. The motor-gear section has a length of 0.8 m and includes a submersible motor and gear reducer mounted in a tube filled with oil. The oil is used for lubrication and heat dissipation. The shaft going to the core barrel is supported by two bearings in order to limit the vibrations of the core barrel. The 1.1-m-long anti-torque system is equipped with four 0.72-m-long steel leaf springs. A slip ring assembly prevents the cable from twisting if the anti-torque device rotates. An 11 kg lead weight, with a 17-cm axial movement, helps to break the core by shock impact and can be used to recover the drill if it becomes slightly stuck at the bottom of the hole. The LGGE drill was first tested at Dome C, where two holes to depths of 140 and 180 m were drilled during the 1977–1978 and 1978–1979 seasons, respectively. It took about 100 h to reach 180 m with a two-man drilling team working with only one core barrel and packing the samples (Gillet and Rado 1979). Then, the drill was used at the D57 site on the Adelie Land (203 m, 1980–1981), James Ross Island (150 m, 1981), and South Pole (127 and 143 m, 1983) (Gillet et al. 1984; Gillet and Legrand 1984). The drill has never become stuck in the hole. However, in connection with the core catchers, some difficulties have occasionally been met when recovering cores. At times, it has been difficult to penetrate the ice. The main problem encountered concerned the quality of the cores. In all the drillings, this quality was excellent in the firn but deteriorated when approaching the firn/ice transition. It was unusual to recover a completely broken core. Generally, one or two pieces of the core were fractured. At depths below 150 m, the core was often broken into disks 1 or 2 cm thick. The lengths of the runs were in the range of 1.0–1.2 m in snow and firn and gradually decreased to 0.5–0.6 m in solid ice.

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From time to time, different modifications of the LGGE drill were used to recover ice cores in diverse locations of Antarctica. The drill with all its subsystems can be stowed on a skidoo sledge and quickly set up at a site. As an example, in the austral summer of 1995–1996, the LGGE shallow drill was used for coring a 49.9-m-deep hole at the top of the Bellingshausen Dome, King George Island, Antarctica (Fig. 8.31) (Simões et al. 2004). Recently, three newly developed shallow drills have been used by the LGGE (O. Alemany, personal communication 2015). The first is a 200-m shallow drill developed by A. Maneuverer. This drill provides 0.8–1.2-m-long (depending on drilling depth) and 100-mm-diameter ice core using a 138 mm borehole diameter (Duphil et al. 2014). The main characteristic of this drilling system is the manual hydraulic gearbox of the winch. The drill has been successfully used a numerous times at Dome C, Vostok station, in the traverse from Dome C to Vostok, and for casing borehole drilling within the EPICA-Dome C, Talos Dome, and SUBGLACIOR

Fig. 8.31 LGGE drill at Bellingshausen Dome, King George Island, Antarctica, 1995–1996 season (Simões et al. 2004)

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projects (Fig. 8.32). In the latter cases, the drill-core barrel was changed to a reaming head (Fig. 8.33). Unlike other reaming systems, the reaming drill design did not include a tank at the tip of the reamer to collect the ice chips generated when increasing the borehole diameter. Thus, all the ice chips produced fell to the bottom of the borehole. After several reaming runs, chips were collected using “empty core” runs with the shallow drill. A new 200 m shallow drill was built in 2005 (O. Alemany, personal communication 2015). It has a “classical” electromechanical winch with a brushless DC motor and brand new driver. The winch drum can host 200 m of 6.5-mm-diameter cable with four conductors. The drum can be easily changed in order to host cable with another diameter. The total length of the drill is 5 m, making it possible to collect 98-mm-diameter cores with a length greater than 1.5 m. The motor section is the same as that of the intermediate drill used at Berkner Island (see Sect. 9.7.6). The drill was successfully used at Dome C in 2007. However, the winch driven system needs to be improved to decrease the Fig. 8.32 Drilling of pilot-hole for casing installation with Maneuverer shallow drill, SUBGLACIOR project, Dome C, 2013–2014 (Summer season 2013/2014 at Concordia, Antarctica 2014)

8 Cable-Suspended Electromechanical Auger Drills

motor power (the running torque was not as great as planned) and increase the tripping speed in the borehole. In 2009, LGGE designed a new shallow drill in an attempt to make it more portable and lightweight and changed the heavy mast with an electrical winch to a tripod with a hand winch (Fig. 8.34). This shallow drill was designed to recover cores with a good quality even from the first meters of the soft firn (O. Alemany, personal communication 2015). Two versions of this drill were developed, one with and another without a jacket.

8.8

National Hydrology Research Institute (NHRI) Drill

Another version of shallow drill was built by the National Hydrology Research Institute (NHRI), Calgary, Canada, in 1980 (Holdsworth 1984). This drill is also referred to as the “Canadian Rufli-Rand electromechanical drill.” A special shelter in the form of a dome serves both as a structural unit

8.8 National Hydrology Research Institute (NHRI) Drill

Fig. 8.33 Shallow drill transformed into reamer (Duphil et al. 2014)

Fig. 8.34 Shallow drilling at Dome C, Antarctica, 2009/2010 (Paleoclimatic coring: high resolution and innovations, n.d.)

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to support the central fixed mast and to provide protection for the drill crew (Fig. 8.35). The shelter is constructed of 100 pieces of 25-mm-diameter aluminum tubing with flattened and individually grooved ends, which fit into key-ways on hubs situated at each node of the structure. A heavy-duty canvas canopy covers the outside of the shelter. In the crest of the canopy is a zippered fastener opening for tower access. The overall dome diameter is 4.88 m, and its height is about 2.29 m. It may easily be erected by two persons in about 1.5 h. A *1.3 m × 1.0 m × 1.3 m pit should be dug out under the shelter to extract the core barrel from the drill. A 1.2 m × 0.9 m aluminum base plate frame rests on the snow in the central part of the shelter and supports the mast, winch drum, winch motor with gear reducer, and control unit. This mast is made from two pieces of 168.3-mm-diameter aluminum tubing with a 3.4-mm wall thickness. These are joined together by an aluminum collar situated at the top of the shelter. This collar has four external lugs, which facilitate the connection of turnbuckle tie shooked onto the top ring of the dome. The top rim of the pulley rises about 2.9 m above the top of the shelter, or 5.2 m above the bottom of the base plate. The drum of the winch is made from rolled aluminum and is capable of accommodating 350 m of cable with a diameter of 8 mm. A digital counter counts the revolutions of the cable sheave, the shaft of which is connected to a direction-sensing multi-pole switch. The drill is fixed to the cable using a Rochester termination (Fig. 8.36). An U-bolt, mounted on top of the drill, accepts a clevis from the cable termination. The electrical conductors are connected to the motor through a seven-pin

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8 Cable-Suspended Electromechanical Auger Drills

Fig. 8.35 Surface equipment of NHRI drill rig (Holdsworth 1984). 1 Tubular aluminum geodesic frame and canvas cover; 2 base plate; 3 gear reducer; 4 winch motor; 5 cable drum; 6 mast; 7 pulley cover; 8 revolution counter switch housing (not shown); 9 electromechanical cable; 10 control panel; 11 snow pit

plug and bulk head connector mounted and sealed on top of the drill. Three 930 mm × 38 mm × 5.2 mm anti-torque leaf springs are arranged outside the motor. The motor output shaft is connected to a gear reducer, which is connected to a torque limiter. The torque limiter was set at *1.4 Nm, but was apparently never activated. The output shaft of the torque limiter connects to the core barrel cap by a quick-release pin. The drill can be broken down into two parts, which fit inside the tower sections for shipment. The 2.18-m-long core barrel is a seamless stainless steel tube with three stainless steel auger spirals welded to it. The separation between the cuttings and core is achieved by inserting a sliding disc inside the core barrel. Three rounded cutters are fixed to the drill head with screws. The NHRI drill was first tested at Mt. Logan, Yukon, the highest mountain in Canada, in July 1980. The camp was based on the glacier at an altitude of 5340 m a.s.l. A borehole was drilled to a depth of 103 m in ice with a temperature −29 °C. The ice core was about 96–100 mm in diameter, depending on the cutter setting, and averaged about 1 m in length. At a depth of *44 m, the accumulation of fine cuttings prevented an advance. Water was applied to solidify the bottom of the hole, and drilling continued with new sharpened cutters. The borehole was terminated because

Fig. 8.36 Schematic of NHRI drill (Holdsworth 1984). 1 Electromechanical cable; 2 electrical lead from cable termination; 3 clevis connection; 4 U-bolt; 5 Envirocon plug; 6 aluminum end cap; 7 leaf spring; 8 ice blade attachment; 9 extension tube; 10 motor tie bolts; 11 electric motor; 12 holes for mounting ice blades; 13 leaf spring; 14 keyed output shaft from motor and gear box coupler; 15 connecting link for spring attachment; 16 screwed break point for drill

disassembly; 17 gear reducer; 18 outer barrel; 19 torque limiter; 20 rotary cover on release pin access hole; 21 quick-release pin; 22 core barrel-release pin; 23 nylon bearing ring and chip seal; 24 stainless steel spiral; 25 ice cutting inlet port; 26 core barrel; 27 core cutting elevator strips and spiral bearing surface (brass, screwed to outer barrel); 28 core breaker spring; 29 core breaker; 30 drill head; 31 cap screw attachment of drill head; 32 cutters; 33 cap screw attachment of cutter

8.8 National Hydrology Research Institute (NHRI) Drill

Fig. 8.37 Drill shelter and laboratory van at South Pole, January 1982 (Photo B. Koci from Kuivinen et al. 1982)

of poor advance rates and running out of time, but in principle, the drill was still capable of obtaining a core. Cutters with different rake (30°, 35°) and relief (15°, 20°, 25°) angles were tried. The most efficient and stable relief angle was 15°. Cutters with large relief angles (20° and 25°), although satisfactory in firn, caused frequent anti-torque failures in ice. The rake angles of 30° or 35° were both satisfactory. Initially, the core dogs were only 13 mm wide. This was insufficient for firn cores, which tend to drop through the core dogs upon lifting. For drilling in firn, the width of the core breakers was increased to 19 mm, thus increasing the circumferential coverage of the blade edge to 18 %. This ensured the retention of firn cores and seemed to give cleaner core breaks. In the 1981–1982 season, the NHRI drill was used to drill a borehole down to 202.4 m at the South Pole (Kuivinen et al. 1982). The drill shelter, a core processing laboratory van, and a 6.5 kW generator were set up in the center of the station’s taxiway oval (Fig. 8.37). A core storage trench (3 m × 3 m × 6.4 m) was excavated adjacent to the drill site. Drilling continued for 22 days with a three-member drill crew and one core processor. The average working day under normal conditions was 7.5 h. The initial problems with the anti-torque system and cutting bits were overcome as drilling progressed. During drilling in the upper 60 m of the hole, the oversized anti-torque system tended to jam in the hole, thereby reducing the penetration rate and causing a “stick-slip” motion as the drill progressed down the hole. The cutters used were mainly those with a 15° relief angle, which, coupled with reduced penetration rates, produced very fine chips. After the installation of more aggressive cutters and the addition of ice skates to the anti-torque springs, drilling resumed, with a slightly increased drill current. Upon the completion of one run and winching of the drill, it was apparent from cable-blistering at the sheave and tangling above the drill/cable termination that the anti-torque section

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had failed to keep the drill from rotating down-hole. As a result, *62 m of cable had to be cut off, and the remaining 273 m of cable reterminated. The anti-torque system was completely reworked to eliminate jamming in the hole. Normal drilling resumed at a depth of 60 m, with runs averaging 0.8–0.9 m and turnaround times of 17.5 min. Below the firn/ice transition at a depth of *115 m, the turnaround times increased to 20 min per run (5 min of actual drilling time), and the core lengths were reduced to 0.7–0.8 m. The increasing hardness of the ice with depth dulled the cutter edges, and the resulting fine ice chips were difficult to transport along the drill’s auger flights. This made it necessary to sharpen the bits before each run. These problems contributed to a gradually decline in the core production (5–8 m/day) and the termination of drilling at 202.4 m. A recurring feature of core damage after the firn– ice transition was axial flaking on the sides of the core. This occurred below 80 m on Mt. Logan and below 150 m at the South Pole. The exact reason for this is not known, but because the flakes appeared to originate at the core breakers, they may have been caused by mechanical shock. Later, the NHRI drill was not used very frequently in the Canadian Arctic. One of the last examples is the Prince of Wales ice cap project, Ellesmere Island, where during April– May 2005, a 176.5 m-long surface-to-bedrock ice core was retrieved from the summit of one of the domes (1630 m a.s. l.) (Kinnard et al. 2008). The measured temperature in the borehole slightly increased from −20.9 °C at a 10 m depth to −19.6 °C at the bottom of the borehole.

8.9

Polar Ice Coring Office (PICO) 4″ Drill

This drill was constructed at the PICO, University of Nebraska–Lincoln in 1979 (Marshall and Kuivinen 1981). This unit collects a core that is 4″ (101.6 mm) in diameter. It has a classical double-core barrel design and consists of an anti-torque section, a motor, a gear reducer, an outer barrel, a rotating inner barrel, and a drill head (Litwak et al. 1984). The anti-torque system consists of three leaf springs, 120° apart. Two sets of leaf springs were produced. The primary set consists of 3.175 mm × 25.4 mm springs, with a double radius section of 355 and 406 mm, and an arc length of 815 mm. The material is 1095 carbon steel tempered to an HRC of 50–56. The second set of springs is made of 5056 steel, with an identical radial configuration and temper, but with a larger cross section of 4.57 mm × 35 mm. Both sets of springs are available with a rectangular cross section and 15° angle edges to provide options for use in various firn and ice conditions. The drill motor is regulated by a frequency controller that allows for a wide range of drill speeds (60–200 rpm) at the drill head. The motor is coupled to a reducer through a splined shaft that is coupled to the rotating inner barrel with

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two spiral flights fixed to the outside of the barrel. A reverse spiral at the upper end of this barrel forces the chips through a port, where they fall into a chamber above the core. The spirals are made of an ultra-high molecular weight polyethylene attached to the inner barrel by screws. The aluminum drill head houses three cutters and three core-catching dogs. An internal taper of the cutting head assists in gripping the ice core. The cutters and core dogs are made of 440-C stainless steel. The cable is terminated and joined to the top end of the drill by an IEC slip-ring assembly. The winch platform houses the winch, tower assembly, and control panel. The 2.36 m × 2.49 m aluminum platform is supported by three wide-flange skis, and has four leveling jacks for use in positioning and stabilizing the unit during drilling. The winch, tower, and control panel are bolted to the platform. The drum capacity of the Lebus winch is 700 m, of which 600 m is available for use down-hole, with the remaining 100 m providing a base wrap. The winch drive system for lowering and raising the drill, and the drive mechanism for controlling the penetration rate and core break, are permanently attached to the platform. The winch is driven by a 2.5 kW motor for the high-speed raising and lowering of the drill and a 1.25 kW motor for controlling the penetration and core break. The first motor provides controllable tripping speeds from 0.15 to 1 m/s. The maximum line tension at low speeds is 49 kN. The dual tubular steel tower system, 9.144 m in height, can be assembled by joining five 1.83 m sections (Fig. 8.38). The two tower sections are held together by a top connecting bridge, upon which the grooved sheave is centered. Fig. 8.38 Inside canvas-covered drill shelter at South Pole, December 1982 (Litwak et al. 1984)

8 Cable-Suspended Electromechanical Auger Drills

A two-point reactive load system provides a direct reading of the cable tension by way of a load cell on one side of the bridge. The sheave shaft is connected to a bidirectional depth counter and line speed indicator. A modified Hansen Weather Port, with arch dimensions of 4.57 m × 12.2 m × 2.05 m and covered by a six-piece canvas cover, protects the winch system and drill operators from wind and blowing snow, and provides a core processing work area. The PICO-4″ shallow drill was tested and used for the first time at the South Pole and then at Vostok Station in the 1979–1980 season. At the South Pole, a site was established 3.5 km from the station, and cores were collected to depths of 44.4 and 32 m. The holes were drilled 1 m apart in order to provide parallel samples. Then, the drill was delivered to Vostok Station, where two holes were drilled to depths of 60 and 25 m. Coring was terminated because the hole inclined, prohibiting penetration. The testing of the PICO-4″ drill was continued at the South Pole in the next season, 1980–1981 (Kuivinen 1981). The objective during this season was to test the unit to a depth of 500 m, a depth which was never reached by “dry” electromechanical auger drilling. A drill shelter and core processing laboratory van were set up in the center of the taxiway oval at the station. Four days of drilling produced promising results: cores of excellent quality averaging 1.4 m per run during the first 90 m, an average core production of 5.5 m/h, and winch line speeds of up to 2 m/s while raising the drill. At a depth of 92 m, a line tension of 18.2 kN was registered by the load cell during a core break. When the drill was brought up, two breaks in the cable’s armored

8.9 Polar Ice Coring Office (PICO) 4″ Drill

jacket were apparent, and in other places the cable’s neoprene sheath showed evidence of the cable being slightly bird-caged. The damaged 100 m portion of the cable was removed, and drilling continued to a depth of 105 m, where the cable broke again during a core break that registered over 20 kN. After this, the cable was again shortened and reterminated. On the next run, it broke again, and the drillers decided to terminate the season’s drilling because of the increasing danger to both personnel and equipment in the event of a catastrophic cable failure. The complete drill was returned to the PICO workshop for further engineering research concerning the core break, cable, and winch design. Two years later, in the 1982–1983 Antarctic field season, drilling was continued from a depth of 108 m in a hole drilled by PICO in 1980–1981 with the same down-hole drill (Kuivinen 1983). A DC drill motor replaced the AC motor and was used all season. Bits with a 45° cutting angle were used first. These produced very fine chips, which packed around the core inside the inner barrel, and caused the core to be twisted off at the base before completing a run. Attempts were made to remedy the problem by reducing the clearance between the core and inner barrel wall, increasing the cutting angle of the bits to 55°, and sharpening the cutters, but the problem persisted. Cutters with a 78° angle from horizontal and no adjustments for penetration eventually produced good cores in 0.7-m runs with penetration rates of 18 m/h to a depth of 215 m. Thereafter, the core quality deteriorated, with frequent cracks and wafering occurring, and with the length of runs reduced to 0.3 m or less. Unsuccessful attempts were made to drill using a new head configuration designed and built at the University of Bern. However, problems were encountered with this head. The penetration was limited to 0.1 m per run due to chips packing behind the cutters, and the packing around the core dogs resulted in a failure to catch the core. Drilling was finally stopped at a depth of 237 m. Drilling in this hole was continued to a depth of 353.5 m below the surface in the next season, 1983–1984 (Kuivinen and Koci 1984). The material of the cutters was changed to make them tougher and resistant to wear in the cold ice. Another modification involved giving the front of the bits a cutting angle of 50° rather than the 45° angle usually used for coring in warmer ice. The 50° cutters with a 15° clearance angle succeeded in generating the coarse chips required for chip transport up the auger barrel, while not inflicting too much damage on the core during drilling. Additionally, efforts were made to improve the core quality by minimizing the clearance between the rotating inner core barrel and stationary outer barrel by maintaining the concentricity of the head and bits to within 0.1 mm in roundness and 0.1 mm in cutting surface flatness. Although the use of heads and cutters with a 55° angle improved the core quality, it was still far from excellent. Drilling

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progressed at a rate of 12–15 m per 8-h work day in the depth interval of 300–350 m. During the same season (1983–1984), the drilling team from PICO and the University of Bern drilled, logged, and packaged a 201-m ice core from Siple Station. Drilling and core processing took place in a 3 m × 3 m × 12 m trench excavated by tractor. The trench was roofed with timbers and ½″ plywood sheets. The PICO-4″ drill and 200 m winch system were used to collect cores over a total of 12 days of operation. The core quality was excellent down to a depth of 144 m, but deteriorated beyond that depth. During the 1984–1985 austral summer, the PICO-4″ drill was used to obtain a 201-m-long core from a 2800 m high snow massif at the top of the Dominion Range close to the confluence of the Mill and Beardmore glaciers (Mayewski 1986). This core was among the first handled using ultra-clean firn/ice processing techniques (Fig. 8.39). In the same season, a 100-m core was drilled at the Upstream B site (later renamed the Whillans Ice Stream) (Alley and Bentley 1987). Unfortunately, the Upstream B core partially melted during shipment. During the 1985–1986 austral summer, another two cores (302 and 132 m) were drilled at a drill site located 1.5 km from Siple Station (Koci and Kuivinen 1986). Drilling, logging, and processing was performed in a covered trench (21 m × 3.6 m × 2.7 m). The quality of the 302-m-deep core was excellent to 200 m, after which the core was consistently wafered. Although wafered, the core recovery was very good, and the quality was adequate for micro-particle concentration, 18O isotope, conductivity, and chemistry measurements. The improved core quality was directly attributable to new asymmetrical double-angle cutters. These

Fig. 8.39 Ice-core sample handling in field, Dominion Range, 1984– 1985 austral summer (Mayewski 1986)

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cutters mounted on a drill head with an increased inner diameter produced a 10 % greater core volume than earlier cutter configurations. Drilling proceeded at 30 m per day. A second core was drilled 1.5 m from the first, with excellent quality cores obtained to a depth of 136 m. At the end of the season, a 102 m core was collected at Ridge B-C to replace the core drilled at Upstream B during 1984–1985 that melted in transit from Antarctica to the United States. During the 1987–1988 field season, an ice-core drilling project was conducted at a site called “Plateau Remote” (84° S 43°E, 3330 m a.s.l.) near the Pole of Relative Inaccessibility on the East Antarctic Plateau (Kuivinen and Koci 1987). The PICO-4″ electromechanical drill was used to collect cores to depths of 205 and 202 m. At those depths, the core began to fracture because of the removal of the overburden pressure. The actual drilling time was only 32 h for each hole. A cooperative glaciological-climatological ice-core drilling program was conducted between 1988 and 1992 on the Dyer Plateau, Antarctic Peninsula. In 1988–1989, two ice cores were drilled to depths of 104 and 108.4 m at a location 6 km west of the divide (the ice temperature at a 10 m depth is −21 °C). In 1989–1990, two cores were obtained using the PICO-4″ drill 1 m apart on the crest of the Dyer Plateau (233.8 and 235.2 m), and two 50-m cores were drilled 4 km east of the divide. The PICO-4″ drill system has been used repeatedly in Greenland and Antarctica to collect many thousands of meters of ice cores; “it has been the workhorse of the US portable drilling activity for a quarter century” (C. Bentley, personal communication 2013). The drill rig was moved from the University of Nebraska-Lincoln to the University of Alaska-Fairbanks, and then the Ice Coring and Drilling Services (ICDS), University of Wisconsin–Madison, obtained it from PICO when they took over the drilling support contract in 2000. The surface equipment (tower and winch) was redesigned several times, but the drill itself (now referred to simply as the “4-Inch Drill”) is essentially the PICO-4″ drill with no major modifications. At present, three different winches with 100, 200, and 400 m cables are available. Some of the following projects were chosen from among others to serve as examples of modern PICO-4″ drill applications. In the 2005–2006 season, one of the deepest cores (to a depth of 299.4 m) was obtained at the WAIS Divide, Antarctica (WAIS Divide Ice Core Project 2005/2006 2006). Drilling was carried out in two shifts, day and night, by the ICDS, University of Wisconsin-Madison, from December 19, 2005, to January 5, 2006. The core quality was excellent above 150 m, very good to 240 m, and good/fair between 240 and 299.4 m. During the next season (2006–2007), ICDS used the opportunity afforded by having the PICO-4″ drill at the WAIS Divide to test the effect on the core quality

8 Cable-Suspended Electromechanical Auger Drills

of using a small amount of drilling fluid as a cutting “lubricant” (WAIS Divide Ice Core Project 2006/2007 2007). The 299.4 m hole drilled during the 2005–2006 field season had closed enough during the year that it had to be reamed from approximately 250 m to the bottom. Several cores were collected by drilling without the fluid (Fig. 8.40), but the core quality did not equal that achieved during the 2005– 2006 season. Unfortunately, the use of the drilling fluid did not seem to improve the quality either. In the summer of 2007, a total of approximately 500 m of ice core was collected from four boreholes, with bottom depths ranging from 80 to 215 m at Summit Station, Greenland (Cole-Dai and Lanciki 2007). An ice coring site located approximately 5 km from the camp (Fig. 8.41) was chosen by a glaciological summer school to observe ice coring and learn how ice cores are used to study the global atmospheric environment and climate change. Although the PICO-4″ drill is quite heavy, it was successfully used many times on mountain glaciers. This system

Fig. 8.40 PICO-4″ drill at WAIS Divide to test core quality in 300-m-deep hole, 2006–2007 field season (Photo J. Souney; About our Photos, n.d.)

8.9 Polar Ice Coring Office (PICO) 4″ Drill

Fig. 8.41 PICO-4″ drill at Summit, Greenland, summer 2007 (Hickey 2014)

was brought to the Quelccaya ice cap (5670 m a.s.l.), Peru, in 1983, to core through the firn to a depth of 35 m, with two holes started (Koci 1985). Thereafter, a thermal drill was used to collect core samples to the bedrock, which was reached at depths of 163 and 154 m. The power supply was provided by a 2 kW array of solar voltaic panels. In 1987, three ice cores were recovered using the PICO-4″ drill to the bedrock at 139.8, 136.6, and 138.4 m from the Dunde ice cap summit (5325 m a.s.l.), Qinghai-Tibetan Plateau, China (Thompson et al. 1990). In 1992, at the Guliya Ice Cap, China (6200 m a.s.l.), a hole was drilled to a depth of 198 m using the PICO-4″ drill. Thereafter, the hole was continued using a thermal drill to a depth of 308 m. In 1997, two cores were obtained from Sajama, Bolivia (6542 m a.s.l.) down to depths of 132 and 132.5 m. Then again, in 1997, the PICO-4″ drill was used at the highest site ever drilled, at the Dasuopu Glacier in the central Himalayas, China, where three holes were deepened to the bedrock of the glacier (Fig. 8.42). The first core was 159.9 m long, and was drilled at 7000 m a.s.l. down the flow line from the top of the col. Two additional cores (149.2 and 167.7 m long) were drilled 100 m apart on the col at 7200 m a.s.l. (Duan and Yao 2003).

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Fig. 8.42 Drilling shelter at highest drill site ever built (7200 m a.s.l.), at Dasuopu Glacier, China, with one of highest mountains in the world —Xixabangma—shown in background (8013 m a.s.l.) (Photo V. Mikhalenko; Himalayan Ice Reveals Climate Warming, Catastrophic Drought 2000)

In July 2010, the PICO-4″ drill was used for predrilling to a depth of 55 m at Combatant col, 3000 m a.s.l., Mount Waddington, Coast Mountains, British Columbia, Canada (Neff et al. 2012). From 55 m to the final depth of 141 m, a thermal drill was used because the presence of water in the borehole prevented the evacuation of drill chips in the electromechanical drill. The ice temperature at the site was between −3 and 0 °C at depths below 20 m, with consistent temperatures of 0 ± 1 °C below 40 m. IDDO plans to replace the PICO-4″ drill with a new shallow drill to make it compatible with the Intermediate-Depth Drill (IDD), which was built in 2012– 2014 (see Sect. 9.7.15). The new shallow drill will use many of the same components as the IDD drill and will be much lighter than the PICO-4″. With the new drill, the core diameter would be 98 mm (the same diameter as the core coming from the IDD).

8.10

Alfred-Wegener Institute (AWI) Drills

The first modification of the “German intermediate ice core system” was built by the Department of Civil Engineering, Ruhr University (Bochum, Germany) in 1981, following the design of the Rufli drill and sponsored by the

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Alfred-Wegener-Institute (AWI) (Jessberger and Dörr 1984; Bässler and Kohnen 1988). The three cutters in the first version had the same shape as the SIPRE hand auger cutters (Fig. 8.43). Two asymmetric core catchers, 3 mm wide, with leaf springs are also mounted in the aluminum drill head, but during drilling, the width of the core catchers was found to be too small. The 2.2-m-long core barrel is coated with PVC, and two PVC spirals are screwed to its outside surface to transport chips to inlets at the upper end of the core barrel. Chips drop into the inner space of the core barrel, which is separated from the core by a disc that slides above the core. The outer steel barrel tube is also coated with a light colored PVC layer to prevent heating by solar radiation. The coupling between the core barrel and the motor unit consists of a lever-spring system identical to that of the Rufli drill. The anti-torque system is also the same as in the Rufli drill and consists of three steel knives. The pressure of the knives against the wall increases with the torque at the drill motor. The speed of the motor rotation is measured by a tachometer and indicated at the control panel. The seven conductors of the armored cable are used in the following way: one pair for the current to the drill motor, one pair for the speed sensor for the drill motor, one pair for the strain gauge positioned inside the anti-torque section, and one conductor for ground.

Fig. 8.43 Drill head of AWI-I shallow drill (Jessberger and Dörr 1984)

8 Cable-Suspended Electromechanical Auger Drills

The tensile strength of the cable is *36 kN. The connection between the drill and the cable is welded. Twisting of the cable is prevented by a safety hook. The total weight of the aluminum winch with the cable and ground plate is *250 kg. The base of the 5.5-m-tall mast rests on a ball joint fixed to a 0.9 m square base plate, which is connected to the winch base plate. The mast is anchored by three guy wires. The mast of the drill is composed of two aluminum tubes (114 mm/120 mm) with a length of 2.30 m and the pulley. The motor and anti-torque sections are transported inside these tubes. The drilling depth is determined by counting the passage of magnets positioned around the circumference of the pulley. An accuracy of ±10 cm was achieved, but this seems to be insufficient to satisfactorily determine the position of the drill. The electronic parts are contained in two boxes: a control unit and box with electrical circuitry. These two boxes weigh 200 kg. Because some parts of the electronic system require a temperature above 5 °C, a 2 kW thermostatically controlled heater is installed inside the second box. During operation, the electronic parts produce enough heat energy to keep the temperature above this level. The following parameters are controlled at the control panel: (1) the speed, current, and voltage of the drill motor and winch motor; (2) the depth of the drill; (3) the tension in the cable; and (4) the temperature levels inside the electrical system. During the 1981–1982 season, the AWI-I drill was tested in Antarctica at the Ekström Ice Shelf near Georg von Neumayer Station. The drilling system was installed inside a shelter. Three holes were drilled down to depths of 73.6 m (Hole B3), 51.65 m (Hole B4), and 20 m (Hole B5). During the drilling of Hole B3, the quality of the ice core was unsatisfactory below a depth of 45 m, where the core was broken into disks. Blade regrinding gave better results. These difficulties did not appear at Hole B4. Some modifications of the drill head were performed in the following years. A leaf spring anti-torque system and lighter winch with Kevlar cable were introduced to reduce the weight of the system. In January 1983, the Ekström Ice Shelf was penetrated at a depth of 203 m over a period of 15 days, but the drill became stuck at the bottom (Bässler and Kohnen 1988). In 1983, a new drill system was built, and the drill head was again modified with rounded cutters. The drill was first tested on the Jungfraujoch, Alps, and then in 1984, on the Filchner–Ronne Ice Shelf, where a 100 m core of good quality was obtained. The core quality improved from 70-m onward after replacing the angular SIPRE cutters with the rounded cutters. The greater cutting area seemed to reduce the stress in the core. In 1987, two cores with lengths of 42 and 47 m were obtained in the Ritscher Hochland, 220 km south of Georg von Neumayer Station. Because of the ineffectual core catcher design and incorrect epoxy potting

8.10

Alfred-Wegener Institute (AWI) Drills

of the Kevlar cable, the cable failed, and one drill was lost. A second drill was used to drill another hole to a depth of 204 m on the Ekström Ice Shelf, 70 km south of Georg von Neumayer Station. Since then, the drill has been modified several times, including the core catchers, cable termination with a commercially available slip ring, a grooved Lebus drum, and level winding system. Recently, the AWI drill was designed to obtain 98-mm-diameter cores and is still in use in Antarctica (S. Kipfstuhl, personal communication 2014). For instance, during the 2012–2013 season, a total of 12 shallow ice cores between 60 and 200 m in length were drilled at Kohnen Station to study the firnification process (Fig. 8.44) (Antarctic Treaty Electronic Information Exchange System 2013). Two 200 m cores were retrieved on the ice divide connecting Kohnen and Dome Fuji at sites CoFi2 and CoFi4. Camp gear and drilling equipment were left at the CoFi4 site to continue drilling operations in the 2014–2015 season further east. Following in the footsteps of earlier developments, the AWI decided to build a new shallow ice-core drill based on the classic Hans Tausen drill originally designed for wet holes (see Sect. 9.7). The new permanent magnet torque motor has 220 W of power and a constant torque (21 N m) at 0–100 rpm. Thus, the drive system does need a gear reducer (Leonhardt et al. 2013). In addition, this so-called “direct-drive high-torque motor” is more energy efficient and has been proven to be very reliable at low temperatures. The main aim of the AWI drill test at NEEM, Greenland, in the summer of 2011, was testing a new driven motor system under field conditions (Fig. 8.45; Field season report Fig. 8.44 AWI drill in field campaign of 2012–2013 season (Photo S. Kipfstuhl)

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2011). The first hole drilled with the new AWI shallow drill reached a depth of 50 m, where the drill suddenly became stuck. The cable was tensioned to 7.5 kN, and 5 L of glycol was poured down to the drill through a hose twice. It seemed that there was a slight upward movement of the cable, and the tension was left on overnight. On the next day, the drill was freed after dumping 50 L of warm glycol. Drilling resumed with the Danish Hans Tausen inner and outer core barrels using the AWI drill head and motor. The drilling went fairly well: ice chips were effectively transported away, and no packing occurred around the drill head. The core dogs also functioned well, and the core breaks were easy. A modified AWI shallow drill with a tiltable telescopic square tower was again tested at the NEEM camp in the summer of 2012 (Field season report 2012). After 29 m of drilling, a mechanical accident occurred. The steel rope holding the top of the tower broke, and the drill plunged 9 m into the hole. As the main cable snapped taught, the drill split in two, leaving only the top section attached to the cable. A borehole camera was sent down to inspect the top of the dropped part of the drill, and several plans were made to rescue it. Special fishing tools were made on site, and five 6 m-long aluminum pipes coupled together provided a means of manipulating and locking onto the device in the deep hole. In the third attempt, the tools locked onto the drill, and a 2 kN pulling force was applied. In addition, glycol was added through the pipes. After 1 h, the drill was free and slowly hoisted to the surface. Because of the damage to the drill system, the tests were terminated for the season. The third set of tests was carried out at Kohnen Station in Antarctica during the 2012–2013 season (Fig. 8.46). Two

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8 Cable-Suspended Electromechanical Auger Drills

Fig. 8.45 Digging inclined trench to depth of 2 m for new AWI shallow ice drill, NEEM Camp, Greenland, 2011 (Surface Science 2011)

Fig. 8.46 Drilling operations with new AWI ice-core shallow drill near Kohnen Station, 2012– 2013 (Photo M. Leonhardt)

boreholes were completed at the station, both to a depth of 106 m (Holes B43 and B48), with another 13 km away to a depth of 143 m (Hole B52). In general, the drilling operations were routine, and cores of good quality were obtained.

8.11

Australian National Antarctic Research Expedition (ANARE) Drill

A new drill design concept with counterrotating barrels was developed, and a drill was built in 1982 by the Antarctic Division, Department of Science, Kingston, Tasmania, for

use in the Australian National Antarctic Research Expedition (ANARE) (Wehrle 1985). By using two barrels rotating in opposite directions, the resultant torque is minimized, and the ice chip transport rate is increased. The ANARE drill consists of an upper section *1 m long containing anti-torque skates, a motor and gearbox, and a lower section *1.8 m long consisting of two counterrotating barrels (Fig. 8.47). The motor was taken from the AEG drill, and the handle was cut off to enable it to fit inside a tube with a diameter of 128 mm. The electronics contained in the handle were fit into a separate box within the same compartment. A relay is used to reverse the drilling direction.

8.11

Australian National Antarctic Research Expedition (ANARE) Drill

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The drill gearbox functioned well, although a shear pin in the drive shaft broke and was replaced with one made of a stronger material. The gap that was created between the smaller core and the inside of the inner barrel allowed cuttings to rise up and stick to the core. A ring was fitted above the cutters to reduce the inner barrel diameter by 1.3 mm, preventing the cuttings from entering the core chamber. The translucent outer barrel caused problems by allowing radiation to pass through and cause melting during and after the removal of the core and cuttings at the surface. Heating of the inner barrel caused meltwater to run down and collect at the head between the inner and outer barrels. When the drill was again lowered down the hole, the core dogs froze up and were inoperative. The drill was therefore dipped in an alcohol bath to free the “frozen” core dogs. Generally, the concept of counterrotating barrels proved to be successful. The net rotation force was almost zero. The drill could be held by hand, without leverage, as the borehole was begun. Unfortunately, there is no information available about further improvements and testing of this drill.

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Fig. 8.47 ANARE drill with counterrotating barrels (Wehrle 1985)

The motor is driven using a reduction gearbox and then another gearbox, which drives the concentric inner and outer barrels in opposite directions. The lower section of the two counterrotating barrels is designed to obtain a core 1-m long, with a chamber 0.5-m long above it where ice cuttings are stored. The outer barrel, which rotates counterclockwise, is 1.8 m long and made from a combination of fiberglass and Kevlar. On the inside, there are 24 “saw-tooth”-like ridges that run parallel to the longitudinal axis of the barrel. The inner barrel, which rotates clockwise, is 1.0-m long and is made of stainless steel, with three helical steel flights welded to it. Each of the inner and outer rotating barrels has a steel drill head with three cutters. Although the cutters for the inner and outer barrels have different shapes, both have a rake angle of 45° and a relief angle of 10°. The inner drill head also has three core-dogs. These core-dogs are spring loaded and released when the motor is reversed. The drill was tested at three sites on the Law Dome, Antarctica, during the austral summer season of 1983–1984. During tests, a 7-m-tall builders hoist, fitted to an Otaco sled, was used as a temporary tower. The hoist had a three phase, 3.7 kW electric motor with a 10 mm steel cable.

BZXJ Drills

The first version of the BZXJ drill was developed at the Lanzhou Institute of Glaciology and Geocryology in 1989 (in 1999, this institute became part of the newly formed Cold and Arid Regions Environmental and Engineering Research Institute–CAREERI), Chinese Academy of Science, and named after key Chinese characters, which mean “Electromechanical Ice Core Drill” (Zhu et al. 1991; Zhu and Han 1994). This drill does not have a jacket. Thus, the kerf width and chip volume are less than in double-core barrel drill systems (Fig. 8.48). The ice chips are stored above the core. The core barrel is made of stainless steel with a smooth surface to decrease the friction with the ice chips. Three stainless steel spirals with a width of 3 mm and height of 5 mm are welded to the core barrel. At the upper part of the core barrel, 12 windows are uniformly distributed in four vertical rows. The drill head is equipped with three straight cutters and three core catchers. It was found that 13-mm-wide cutters with a relief angle of 26° provided a smooth penetration and good ice core quality. The cutting pitch is adjusted by special screws located at the bottom end of the drill head. The drill has the best performance at a rotation speed of 30– 50 rpm and a cutting pitch of 0.3 mm. During penetration, the cutters carved a *0.5-mm-deep spiral on the core surface, and more than likely on the borehole wall. It seemed that such a crude surface assisted with chip removal. In addition, the rough surface of the core was beneficial for breaking it.

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In August 1989, the first prototype of the BZXJ-IA drill was tested on Glacier No. 1 at the Urumqi River, Tianshan (Fig. 8.49) (Gao et al. 2012). Because of the warm weather, snow and firn melted on the glacier surface, and the meltwater drained flew into the borehole. Therefore, tests were carried out during the night at subzero air temperatures, and only two short cores (10.6 and 16.4 m) were obtained. In 1990, two more improved drill systems (BZXJ-IB) were produced. The length of the cable spooled on the winch was enlarged to 300 m. This drill was again tested on Glacier No. 1, where two boreholes were drilled to depths of 57 and 92 m. The total time for drilling took 10 and 29 h, respectively. In September 1991, this drill was used for coring at King George Island, Antarctica, where 25 cores totaling 704 m were obtained, with the deepest one being 82 m. An attempt to design an intermediate drill system for coring down to 500 m based on the BZXJ drill was started in 1995, but the drilling system could not demonstrate a good performance. In October 1998, it was tested on Glacier No. 1 and then in Antarctica, with the deepest borehole slightly deeper than 50 m. In 1996, a larger diameter drill (BZXJ-IIA) was developed for use in the Chinese Antarctic Research

Fig. 8.48 Basic configuration of BZXJ drilling system (Zhu and Han 1994). 1 Generator; 2 control box; 3 collector; 4 motor; 5 winch; 6, 7 lower and upper parts of the mast; 8 cable; 9 pulley; 10 motor; 11 guide plates; 12 side milling cutters; 13 chip windows; 14 spiral; 15 core barrel; 16 drill head; 17 core catchers; 18 cutters

The anti-torque system, which has the form of side-milled cutters, was adopted from the Japanese ILTS drills (see Sect. 8.5). Four side-milled cutters create vertical grooves along the borehole and four guide plates follow these grooves and hold the counter torque. The anti-torque system of the first prototype drill provided an extra cutter load, which had an effect on the cutting process. In the further improved version of the drill, the rotation direction of the side-milled cutters was reversed, and the drilling mode for vertical holes was improved. The hoisting system consists of the following main parts: a 2.5-m-tall mast, 250-m-long armored cable, 1 kg control box, and 0.3 kW motor, which provide a drill tripping speed of 0.4 m/s and 0.6 kN of pulling force. The total weight of the winch assembly is *70 kg. The system includes a 2 kW gasoline electric generator.

Fig. 8.49 First testing of BZXJ drill on Glacier No. 1, Urumqi River, Tianshan, August 1989 (Gao et al. 2012)

8.12

BZXJ Drills

Expedition (CHINARE), and in 1997–1998, four holes were drilled in Antarctica, with depths in the range of 50–84 m. In 1998, the length of the anti-torque guide plates was increased, and two ice cores with lengths of 100 and 82 m were drilled at an inland area of the Antarctic Ice Sheet. In 2000, the next up-graded version of the drill (BZXJ-IIB) was built. Once again, the anti-torque system was modified by increasing the width of the guide plates and the diameter of the side-milling cutters. This greatly improved the torque holding ability in snow and soft firn. In 2001, BZXJ-IIB was used to drill six ice cores in Antarctica, with the deepest being 102 m. In 2001, the side-milled cutters were replaced by four leaf springs, which made drilling safer, simpler, and less power consuming. The modified drill BZXJ-IIC was tested at Glacier No. 1 in October 2001. A 72.4 m borehole was drilled in 8.6 h, with an average core length of 0.73 m. The core diameter was 92–94 mm. In 2004, the fourth version of the large-diameter ice core drill (BZXJ-IID) was developed, and can be used with different anti-torque systems, depending on the condition of the firn and snow layer. The drill weighs 21 kg, and the length of the core barrel is 1.75 m. It is capable of obtaining 0.7–0.8 m cores with a diameter *95 mm. The total weight of the drilling equipment, including the packing box and generator, is 150 kg. In 2004, a small drill team of Chinese researchers took part in ice core and climate research in the Southern Alps, New Zealand. In spite of the harsh conditions, winter is the

Fig. 8.50 BZXJ ice-core shallow drill in use at Tasman Glacier, New Zealand (NZ Ice Core Gallery 2004)

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best time of year to drill in New Zealand to prevent the ice from melting as it comes out of the glacier. Five cores were obtained from the head of the Tasman Glacier, with the longest one taken from a depth of 54 m, which represented about half of the total depth of the ice at the site (Fig. 8.50). In winter 2009, the Southern Alps were revisited, and another five cores were retrieved. A portable version of the drill (BZXJ-IC) without a mast and winch was developed based on the small-diameter (68 mm) BZXJ-IB drill. The upper part of the drill is connected to an electrical cable that is also used for lowering and raising the drill by hand (Fig. 8.51). The weight of the drill, including the batteries and control box, is only 15 kg. One set of batteries is enough to obtain 20 m of cores. The drill can also be powered by a generator (model EF1000i, weight 14 kg). The weight of the drill is too small for coring in dense firn and ice; thus, bamboo poles connected together should be used to push the drill toward the bottom of the hole (X. Fan, personal communication 2014). The BZXJ-IC drill was used several dozens of times at the Qinghai-Tibet Plateau, Arctic, and in Antarctica. The drill could be operated by one person and obtain 20 m of ice cores in 4 h. From 1989 to the end of 2012, different modifications of the BZXJ drill were used for drilling 125 shallow holes, including 37 holes to the bedrock, with a total length of 8095 m. The deepest hole was drilled to a depth of 189.4 m at the Tanggula Mountain Range, Tibetan Plateau, in May 2004. The highest drilling site was located at an altitude of 7050 m a.s.l. at the Shi Tage peak.

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Fig. 8.51 BZXJ-IC portable drill, Antarctic traverse from Zhongshan Station to Dome A, 2011–2012 season (Photo X. Fan)

8.13

Geo Tecs Drills

In the 1990s, A. Takahashi established a private enterprise called Geo Tecs Co., Ltd., in Nagoya, Japan, with the main goal of designing and producing various drilling and logging equipment for glacial research. Since then, all sorts of ice drills have been developed by this company, including shallow and deep thermal and electromechanical systems.

8.13.1 Geo Tecs Prototype Shallow Drill In 1993, the first prototype of a 200-m shallow drill was designed (Fig. 8.52) (Takahashi 1996). The total length of the drill is 3.02 m, and it has a weight of *40 kg. The 5.7-mm-outer-diameter armored cable is produced by Rochester and has four wires. This cable is attached using a standard Evergrip cable termination (No. 115-3) to the upper part of the drill. The driven unit consists of the motor, gear reducer, drive shaft, and one-touch connector. The universal 200 V, 3.5 A motor can work with either AC or DC and is controlled by adjusting the voltage. The custom-made four-stage gear reducer decreases the high-speed rotation of the motor (14,700 rpm) to an output-shaft idle speed of 70 rpm. The one-touch connector at the end of the drive shaft quickly connects to the top of the core barrel. The driven unit is placed inside a waterproof (50 kPa) housing. Three anti-torque leaf springs are fixed outside the housing and can be adjusted using the upper pivot nut. The core barrel is made of a stainless steel tube with an outside diameter of 101.6 mm and a thickness of 2.1 mm. Polyethylene spirals with a 15-mm width and 8 mm thickness are fixed to the outer surface with screws. The spiral angle is 40°. The jacket is made of a 2.5-mm-thick

stainless steel tube designed to enable a 9.2-mm clearance between the core barrel and jacket. A single strip is fixed to the inner surface of the jacket to improve chip transportation. A scraper made from a 0.3 mm spring plate is fixed to the upper part of the jacket to help the ice chips enter the windows of the core barrel (Fig. 8.53). This scraper worked extremely efficiently even in warm ice in Switzerland. The drill head is equipped with three cutters (ID/OD of 94 mm/129 mm) with shoes and three dog-leg-shaped core catchers and fixed by screws to the core barrel. The cutters have a rake angle of 40° and clearance angle of 15° and are suggested for use in temperate ice. The rake angle can be changed to 30° or 45° for cold ice or warm ice, respectively. Three shoe sizes were designed to produce pitches of 2, 4, or 6 mm.

8.13.2 Further Improvements Different types of the drills (D-1, D-2, and D-3) were developed with different lengths, weights, and drilling depth capabilities. Unlike with the D-2 and D-3 versions, the Geo Tecs D-1 drill has a so-called S-type chip chamber, in which the core barrel is rotated using a long shaft, and the space between this shaft and the jacket serves as a storage area for ice chips (Fig. 8.54) (Takahashi 2005). In addition, a series of winches with different cable lengths and motor power ratings was developed. In 2002, the drill motor was changed to a permanent magnet, DC motor (100 V, 350 W, 4000 rpm), with a diameter of 80 mm and length of 140 mm (Takahashi 2005). This made it possible to use a harmonic drive without oil and reduce the drill length by 150 mm. A harmonic drive has a

8.13

Geo Tecs Drills

149 b Fig. 8.52 Geo Tecs prototype shallow drill (Takahashi 1996). 1

Cable; 2 evergrip termination; 3 anti-torque pivot nut; 4 hinge; 5 upper waterproof seal; 6 slip rings; 7 leaf spring; 8 housing; 9 motor; 10 gear reducer; 11 O-ring; 12 shaft; 13 lower waterproof seal; 14 one-touch connector; 15 jacket; 16 window; 17 scraper; 18 core barrel; 19 flights; 20 drill head; 21, 22 cutters with shoes; 23 core catchers

longer lifetime, requires less maintenance, and has a smaller size than with a planetary reduction gear, which was used in previous models. The new cable termination reduced the drill length by another 260 mm. Thus, the drill and mast became shorter, lighter, and more convenient. In 2003, an ultra-clean modification of the drill was developed using a titanium core barrel and ceramic cutters. The main problem with the drill head design was related to icing of the space between the cutter and the shoe when drilling in warm ice. As a consequence, a special shoe (“dolphin” type) featuring a small contact area was proposed (Fig. 8.55). The shoes were attached to the middle of the cutter mount rim, and ice chips were able to flow along the space beside the shoe. The cutter mount is coated with Teflon to reduce adhesion. Especially for high-mountain applications, Geo Tecs developed a lightweight drill modification (Takeuchi et al. 2014). The ID/OD of the drill head was designed to be 95 mm/125 mm. The core barrel length was 1.35 m. This was shorter than the previous versions, which reduced the operating space and made handling easier. However, to reach the same depth, more drilling runs are needed. The maximum core length per run with this drill is 0.55 m. The power supply is provided by an inverter generator with a four-cycle gasoline engine (EF2500i, Yamaha) weighing 29 kg without fuel. The nominal power is 2.8 kW. The fuel consumption allowed 6.2–13.5 h of operation per full fuel tank (9 L).

Fig. 8.53 Working principle of scraper (modified from Takahashi 1996)

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Fig. 8.55 Cutters and shoes for drilling in warm ice (modified from Takahashi 1996)

8.13.3 Field Testing and Operations Fig. 8.54 Shallow D-1 drill (modified from Takahashi 2005)

The base and winch drum for holding 200 m of cable are made of aluminum. The winch motor is a small 750 W DC motor. The lighter weight of the drill due to the shorter barrel enables the use of 4.7-mm diameter cable, which is thinner than that used in the previous model (5.7 mm). The mast is made of aluminum tubes (80 mm × 4 mm), and can be divided into two pieces for packing. The mast height is 2.3 m (the total drill length is 2.13 m). The total weight of the drilling system, including the drill, mast, base unit, winch, and controller, is 300 kg, which is 70 kg lighter than the previous version. To ream a hole for casing installation, a special reaming head was developed to replace the core barrel assembly (Fig. 8.56). In the same manner as the UCPH shallow drill (see Sect. 8.6), the reaming head includes a container with windows on the top to allow ice chips to enter. The rotation speed of the reaming head is much slower (10–15 rpm). To avoid dropping the chips during reaming, duct tape can be wrapped around the top of the chip container to seal the clearance between it and the borehole wall (Zhang et al. 2014). Unfortunately, this action reduces the problem but cannot completely solve it. Because some of the ice cuttings drop onto the bottom of the hole during the reaming process, the recovery of the ice chips is needed after the use of each reaming size, using the standard configuration of the shallow ice-core drill.

The first tests of the Geo Tecs shallow drill were carried out in Svalbard in June–July 1993 as part of the Japanese Arctic Glaciological Expedition (JAGE-93) (Takahashi 1996). During 12 working days, a depth of 185.24 m was reached using 243 drilling runs. The anti-torque system worked very well, although slippage sometimes occurred. It was found that after drilling 0.5–0.6 m, the drill could not penetrate any further because ice chips froze inside the core barrel, preventing the core from entering. To solve this problem, (1) the drill was cooled in the hole for *5 min before

Fig. 8.56 Geo Tecs reaming head (Photo N. Zhang)

8.13

Geo Tecs Drills

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Fig. 8.57 Ice-core drilling tent at Ushkovsky ice cap, Kamchatka, Russia, 1998 (Photo T. Shiraiwa; Flickr: Ice core drilling tent 2011)

drilling began (the air temperature was 4–8 °C), (2) a plastic separator was installed on the surface at a predetermined distance from the drill head, and (3) the inner surface of the core barrel was wiped with ethylene glycol. Cutters with a rake angle of 40° were used. For comparison, cutters with 30° and 45° angles were tested, but without any difference. Shoes with a 4-mm pitch gave a reasonable rate of penetration. The measured core diameter was 93.8 mm when using cutters with an inner diameter of 94 mm. The average core length was 0.76 m, with the longest core being 1.03 m. Deeper than 140 m, the core became broken and difficult to remove from the core barrel. At a rate of 0.5 m/min, the drill consumed 304 W, including the cable losses. A shallow drill of the D-2 type, a tilting tower, an intermediate-depth winch of the W-4 type, and a 3 kW diesel generator were used for ice coring down to 118.48 m at the top of Austfonna in Nordaustlandet, Svalbard, in March– April 1998, as part of the activities of JAGE-98 (Watanabe et al. 2000). The drilling equipment was installed inside a tent (3.8 m × 5.8 m × 3.2 m). Ice coring operations were accomplished by three persons over a period of 14 days and took 118 h. The average ice core length was 0.57 m. In June 1998, the Geo Tecs D-2 shallow drill was used at Site K2 (3901 m a.s.l.) in the center of the ice cap covering the Gorshkov crater of the active Ushkovsky volcano, Kamchatka, Russia (Fig. 8.57). The last eruption of this volcano dates back to 1890. However, volcanic activities were recorded in 1980, as well as in 1983–1984. The estimated ice thickness at Site K2 is 240 m. Ice cores with a total length of 211.7 m were obtained during 307 drilling

runs in 103 h (11 days) (Shiraiwa et al. 1999). The temperatures at a depth of 10 m and the bottom of the borehole were −15.7 and −4.2 °C, respectively. The typical diameter of the ice core was 94 mm, and the average length of a run was 0.69 m. The brittle ice zone was found at a depth of 140 m. There were 328 volcanic ash layers in the ice core (Shiraiwa et al. 2001). The thickest ash layers were at least 10-mm thick. Therefore, the cutters and catchers were used in each run that included volcanic ash layers and had to be sharpened frequently. In the next year (1999), another 289.1-m-deep hole was drilled at Austfonna, Svalbard, 3 km to the north of the 1998 coring site, using the improved Geo Tecs drilling system (Motoyama et al. 2001). The following parts were modified: the cutters, cutter shoes, core catchers, core barrel, anti-torque system, chip-ice core separator, and winch-driven unit. Coring was carried out during 17 days with a maximum core production of *27 m/day. The average core length throughout the entire borehole drilling operation was 0.76 m, and the average rate of penetration was 13.8 m/h. The drill’s power consumption was quite stable, averaging 415 W. The ice became brittle deeper than 135 m, and the number of core pieces per run increased from 1–2 to 3–9. In May 2002, an ice core of 220.52 m was drilled at King Kol (60°35′20″N, 140°36′15″W; 4135 m a.s.l.), a saddle near Mt. Logan, Canada’s highest mountain (Shiraiwa et al. 2003). As the result of an ice-penetrating radar survey, the thickness of the glacier at the drill site was estimated to be 222 m. Unfortunately, the bedrock was not hit because of a shortage of winch cable. There was no clear indication in the

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bottom ice cores of whether the depth was close to the bedrock. Drilling was accomplished during 18 working days (a one-shift operation totaling 195 h). The average core production was 1.6 m/h at the upper 140 m and became as slow as 0.9 m/h below 150 m. The average core length was *0.7 m. Cores of excellent quality were recovered until a depth of 200 m, where brittle ice began. The reason for this phenomenon was unclear because, at mountain glaciers, core quality problems usually appear at shallower depths of 100– 150 m. In the summer of 2003, a 171-m-deep ice core from the surface to the bedrock was drilled by a Russia–US–Japan joint research group on the West Belukha snow–firn plateau (49°49′N, 86°34′E, 4150 m a.s.l.) in the Russian Altai Mountains (Takeuchi et al. 2014). A lightweight and short drill was placed inside a small Yoshida tent (4.5 m × 3.5 m × 2.25 m) (Fig. 8.58). To secure space for the drill system, the snow floor was lowered by 0.7 m by digging. In order to avoid working at high air temperatures in the shelter, the drilling operations were usually performed from 6 am to 12 pm, and from 4 pm to 12 am. Cutters with a 45° rake angle and 15° clearance angle and shoes with a pitch of 5 mm were mainly used. Smaller round-shaped shoes were also tried to prevent the cutters from icing in the warm ice. For more effective operation, two core barrels were used. Drilling the first hole required 87.5 h of actual working time (7 days) to core down to a depth of 171.3 m. The cutter was chipped at that depth, probably due to hitting a stone. The total number of productive runs was 324, with an average core length of 0.49 m. The cores obtained had perfect quality. A second borehole was started approximately 1 m south (downstream) of the first borehole and stopped on the

same day at a depth of 48 m due to a lack of core boxes. The working time for the second core was 12.7 h. The same Geo Tecs drill system was used at Mount Ichinsky, Kamchatka, Russia (55°46′N, 157°55′E; summit elevation 3607 m) in August 2006 (Fig. 8.59) (Matoba et al. 2007). The caldera of this mountain is covered by an ice cap that is *500 m in diameter. The core drilling was stopped at a depth of 115 m when the drill began slipping on a hard layer and could not advance any further. Rock cuttings were collected in the drill barrel. Thus, the drillers made the judgment that the drill had reached bedrock. The drilling was completed in 42.5 h with 236 drilling runs. Ice cores 90– 93 mm in diameter and *0.5 m long were consistently obtained from each drilling run. No brittle ice was found, and no thick volcanic ash layer, which had caused problems when drilling at the Ushkovsky volcano, damaged the cutters of the drill. The temperature at the 10 m depth was −13.0 °C, and the temperature at the bottom of the borehole was −3.4 °C. The air temperature in the drilling tent was higher than 0 °C. Thus, ice chips could easily melt on the drill during maintenance in the tent, and the meltwater then refroze onto the drill when the drill was reinserted into the hole. This refrozen ice caused various problems. Refrozen ice in the barrel scratched and broke the ice cores inside the barrel. Refrozen ice on the cutters and shoes caused the cutters to slip at the bottom of the hole. To prevent such problems, the maintenance time in the tent was shortened, and the drill was reinserted into the borehole as quickly as possible before ice chips melted during maintenance. In September 2007, the Geo Tecs shallow drill was brought to the top of the Grigoriev Ice Cap (41°58′33″N, 77° 54′48″E) in Kyrgyzstan (Takeuchi et al. 2014). The drill reached the bottom of the ice cap at a depth of 86.87 m and

Fig. 8.58 Drilling process at West Belukha Plateau, 2003 (Photo V. Aizen)

Fig. 8.59 Core barrel disengaged from Geo Tecs shallow drill, Mount Ichinsky, Kamchatka, Russia, 2006 (Matoba et al. 2014)

8.13

Geo Tecs Drills

Fig. 8.60 Organic soil beneath Grigoriev Ice Cap adhered to ice-drill cutters during last run, 2007 (Takeuchi et al. 2014)

penetrated a frozen organic-rich soil layer, which provided an opportunity to collect *100 g of soil material (Fig. 8.60). The lightweight Geo Tecs drilling system was again used at Aurora Peak, Alaska Range, in May and June 2008, where the borehole was terminated at 180 m as a result of restrictions on the length of the winch cable (Matoba et al. 2014). Reaching this depth took 101 h, with an average core production rate of 1.77 m/h. The total weight of the equipment transported to the glacier was 1.3 t, including 200 kg of fuel. The ice at Aurora Peak was quite “warm”: the temperature at the 10 m depth was −2.2 °C, and it was greater than −7 °C from the surface to a depth of 180 m. The slipping of the cutters at the bottom of the hole was a problem. Water-bearing ice chips became packed under the cutters, adhered to the concave section between the

Fig. 8.61 Geo Tecs shallow drill in use at Elbrus, Caucuses, Russia, 2009 (Glaciers and climate in the recent past, n.d.)

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cutters and shoes, and easily penetrated into the hole of the screw bolt fixing. These packed water-bearing ice chips prevented the cutters from biting into the ice. To prevent this, “dolphin mount” shoes were used. The average length of the ice cores was *0.5 m over the whole depth, but the number of ice-core pieces increased to 3–7 at depths below 150 m. To prevent this problem, the following actions were tried: (1) reducing the speed of the cutter rotation to reduce the shock to the ice core; (2) changing the cutter angle to make the ice chips larger, making it more difficult for them to penetrate the space between the ice core and the barrel; and (3) changing the shoe to reduce the drilling pitch. However, none of these modifications completely solved the problem. In August and September 2009, the Geo Tecs shallow drill was used for ice coring to the bedrock at a depth of 181.8 m in the central part of the Elbrus western plateau, Caucuses, Russia (43°20′54″N, 42°25′36″E; 5115 m a.s.l.) (Fig. 8.61) (Mikhalenko 2010). The total weight of the drilling equipment, tents, and packing boxes was *2 t. Drilling was accomplished in 11 days (10–12 h/day), with three personnel per shift. More recently, a Geo Tecs auger ice-core drill of the D-3 type was purchased by the Polar Research Institute of China and used to start a deep borehole at Dome A, Antarctica, in the 2011–2012 season (Zhang et al. 2014). Compared with the D-2 type, this drill is longer (3.36 m), heavier (50.5 kg), and uses a more powerful motor (permanent magnet-type DC, 200 V/500 W, 4000 rpm). The winch of the W-4 type is equipped with a three-phase AC motor (200 V, 1.5 kW) with a magnet brake and houses 600 m of 4-H-220 K armored cable

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Fig. 8.62 Removing core barrel from Geo Tecs auger ice-core drill of D-3 type, Dome A, Antarctica, January 2012 (Photo N. Zhang)

(5.66 mm in diameter, 4 lines). The drill’s tripping speed could be adjusted using an inverter control from 0.4 to 0.75 m/s. In total, 118 coring runs were undertaken using a drill bit with an ID/OD of 96.4 mm/135 mm (Fig. 8.62). Cutters with a 35° rake angle were used. The final depth of the “dry” hole was 120.8 m, with an average core run of 1.02 m. The total drilling time was 51.5 h. The core length decreased from 1.2– 1.4 to 0.5–0.9 m, deeper than the firn/ice transition (*100 m). Down to a 20 m depth, the drill bit rotation speed was maintained at *40 rpm. Beyond 20 m, it was increased to 60 rpm (the maximum was 80 rpm), and the penetration rate was controlled in the range of 6–8 m/h. At depths exceeding 100 m, the penetration rate had to be decreased to 4–6 m/h. In the upper snow formations, a core was not always obtained because of the loose formation. The anti-torque system had to be adjusted several times because the leaf springs slipped in the hole or were too tight, and the drill could not reach the bottom to cut the ice. During the drilling process, the cutters were changed twice because degradation of the penetration rate indicated that the cutting edge was blunt. Down to a 73 m depth, the obtained ice core was usually in one piece, but further down the core was broken into 2–3 pieces. In addition, there were visible fracture cracks at the surface of the core.

8.14

Hilda/Simon/Eclipse Drills

8.14.1 Hilda/Simon Drills The Hilda shallow drill was designed and built at the Glaciology Section (Terrain Sciences Division) and Instrument Development Workshop (Mineral Resources Division) of

the Geological Survey of Canada (GSC) (Blake et al. 1998). The Hilda produces 82-mm-diameter cores in roughly 0.9 m lengths. The Simon drill was also built by GSC (Zheng et al. 2006). Generally, both of these drills followed the design of the tipping-tower UCPH shallow drill (see Sect. 8.6). The barrels and cutting head of these drills were made of stainless steel. Hilda-2 was designed and built by the National Research Council of Canada. The Hilda-2 drill is identical to the Hilda, with the exception that the Hilda holds a 500 m steel cable and Hilda-2 holds a 500 m Kevlar cable. In 1992, the GSC tested the Hilda drill system on the Agassiz Ice Cap, Ellesmere Island, Northwest Territories. In subsequent years, the Hilda drill was used on the Agassiz Ice Cap to recover two 130-m cores (1993, 1994) and two ice cores 16 km apart that reached the bed of the Penny Ice Cap, Baffin Island (1995, 1996). The 333.8-m core was drilled on the central ridge of the Penny Ice Cap (1900 m a.s.l.), and the 177.9-m core was drilled at the top of a separate but joined ice dome (1810 m a.s.l.), with virtually complete core recovery. At the end of 1990s, the Simon drill was modified to recover ultra-clean ice-core samples (“Clean Simon” drill) (Zheng et al. 2006). In order to minimize the potential contamination to ice cores from the drill components during drilling, the core barrels and cutting head were made of the CP2 Ti alloy, while the cutters were made of solid tungsten carbide with a cobalt binder (Fig. 8.63). To avoid human contact during core retrieval, packing, and shipping to the laboratory, the ice core drilling system was designed to deliver ice cores directly into precleaned high-density polyethylene (HDPE) cylindrical inserts. Therefore, cores collected in this manner have no direct contact with any metal, with the exception of the titanium head and carbide

8.14

Hilda/Simon/Eclipse Drills

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Fig. 8.63 Clean Simon ice-core drill (Zheng et al. 2006). a Overview of system; b close-ups of titanium drill barrels and cutting head; c precleaned HDPE insert is placed into inner drill barrel before drilling; d cutting head is screwed in place; e cutting head is unscrewed

using titanium wrench after drilling; f insert (with core inside) is pulled out using gold plated tongs; g insert is capped with low-density polyethylene cap before being removed entirely and sealed in bag for storage and transport

cutters of the drill. Moreover, there is no human contact before the cores are processed in the laboratories. The capped inserts also served to protect the cores from breakage or other damage during transportation and to reduce sublimation during storage. The Clean Simon drill was used to retrieve a 63.7 m firn core from the summit of the Devon Island Ice Cap (75°N, 82°W; 1860 m a.s.l.), Nunavut, Canada, in early May 2000. The drill was fully wiped clean with a regular cloth in a laboratory to remove any visible dust and grease, and then was further cleaned with paper wipers. To provide additional cleaning, a shallow “clean-up” core of about 13 m was drilled before the deeper core drilling. To clean the inserts, they were first submerged in 15 % HNO3 for 24 h. After rinsing three times with distilled water, the inserts were double-bagged and transferred to a class-100 clean room, where they were further soaked in 1 % HNO3 for another 24 h, and then rinsed three times with reverse osmosis-deionized (RO-DI) water. Finally, they were placed in 0.2 % ultra-pure BASELINEs grade HNO3 for 48 h. After

acid cleaning, the inserts were rinsed again with RO-DI water and allowed to dry in a class-100 environment before being individually packaged and sealed in tubular low-density polyethylene bags. The personnel directly involved in core handling wore Tyvek clean room lab coats over their winter parkas, and used polyethylene gloves at all times. The Clean Simon drill provided excellent sample material for Pb and Cd, and potentially for other trace element analyses.

8.14.2 Eclipse Drill In 1995, Icefield Instruments Inc., Whitehorse, Yukon, Canada, began work on a lightweight, hand-portable version of the Hilda. The resulting design was named Eclipse (Fig. 8.64) after field testing at the Eclipse Dome, St Elias Range, Yukon. When dismantled, the mass of the heaviest system component (a winch drum with 250 m of cable) is 33 kg, and the length of the longest component (the outer

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8 Cable-Suspended Electromechanical Auger Drills

Fig. 8.64 Solid model of Eclipse drilling system (modified from User manual for Eclipse ice coring drill 2012)

barrel) is 2.82 m. The entire drill (including spare parts and toolkit) breaks down into eight or nine porter loads. The total mass of the drilling system is 195 kg. The Eclipse drill has three major components: a motor/anti-torque section, rotating inner barrel, and non-rotating outer barrel. Two versions of the Eclipse drill are available: one producing 82-mm-diameter cores and another producing 101-mm-diameter cores. The inner barrel is a 2.31 m long, thin-walled, stainless steel tube fitted with three nylon spirals. An aluminum cutter head is fitted to the lower end of the inner barrel, which in turn is fitted with external nylon flights and follows closely the design of the UCPH dill. The cutters are equipped with a selection of trailing shoes that set the maximum cut depth per revolution to 3, 4, 5, or 6 mm. The cutters have a cutting angle of 45°, relief angle of 15°, and rake angle of 7° (the leading edge on the inside). The cutter head also has three spring-loaded core dogs to break and hold the core. The inner barrel is attached to the drive capstan of the motor section with three bayonet-type locking pins inserted through an access port in the outer barrel. The nonrotating outer barrel has 30 straight grooves cut into its inner surface. These grooves extend from the bottom end of the barrel to the access port and serve to assist in chip transport. Chips are carried up the flights and dumped into the inner barrel through chip ports located at the top of the spiral flights. The chips fall onto a nylon core separator plug that rests on top of the ice core. The radial clearance between the inner and outer barrels is 0.6 mm. The motor section contains a DC motor, tachometer, and gear reducer in a sealed housing. The anti-torque section uses three leaf springs to provide pressure against the borehole walls. The wall pressure is adjustable using two locking nuts. The anti-torque section also contains a hammer, thrust bearing, and slip-ring assembly (Litton Poly-Scientific AC4898 series). The cable used for the drill is Vector Schlumberger 4-18P armored steel cable, which has a breaking strength of 14 kN.

The cable has four 24 AWG copper conductors. Two of the conductors are paired to supply power to the motor (with ground return through the cable sheath); the remaining conductors are used for the tachometer. An optical encoder attached to the tower sheave measures the cable travel. An anti-torque failure alarm was not included in the Eclipse design, but a condition that can be distinguished from an anti-torque failure could be detected by examining the tachometer reading. The frame consists of an open triangular base supporting a square face frame. The face frame, in turn, supports two upright L brackets that hold the winch tower. The face frame is held upright by two diagonal braces that also support the winch drum, hand winch, and winch motor. A final upright near the apex of the base members forms a support for the tipping tower when in the horizontal position. All the frame members are made from 2″ (50.8 mm) square extruded 6061-T6 aluminum tubing. The winch masses 120 kg with 250 m of cable. The winch motor is a custom-built, 3000 rpm, 24 V DC motor drawing 40 A at full load; it is equipped with an electric brake and tachometer. The output from the motor is reduced through an 80:1 Harmonic Drive transmission. The winch drum is chain-driven at a 1:1 ratio from the transmission output and is equipped with a disc brake. A hand crank drives the drum at a 4:1 ratio. A core is removed at the surface by tipping the winch tower to a horizontal position (Fig. 8.65), removing three locking pins, and extracting the inner barrel from the drill. The core and ice chips can then be removed from the top of the inner barrel. The tower height above the surface is 2.65 m. A 1.5-m-deep trench is required to accommodate the drill when in the vertical position. In its horizontal position, the drill has a slight (1.5°) downward angle to assist in removing the inner barrel. The provided control module functions include the following: (1) drill motor start, stop, direction, and speed; (2) winch-motor start, stop, direction, and speed; (3) winch

8.14

Hilda/Simon/Eclipse Drills

Fig. 8.65 Eclipse drill and tower in both horizontal and vertical (drilling) positions (Blake et al. 1998)

emergency stop switches on the winch frame; (4) tower stop switch to stop the winch motor when the drill has been raised; and (5) lockout functions for preventing motor starts when motors are turning. The provided display functions include the following: (1) drill motor current and speed, (2) winch-motor current and speed, (3) battery voltage and current draw, and (4) drill depth.

8.14.3 Field Testing and Coring In July 1996, the drill was transported to the Eclipse Dome (60°51′N, 139°47′W; 2950 m a.s.l.), a small ice rise in the Yukon. It took one person 5 h to assemble the drill and dig the drill trench. Drilling was accomplished in the open with no shelter. Because solar heating caused melting on the drill, most of the drilling was done at night, with the drill stored at depth during the day to keep it cold. A 2.2 kW Honda generator charging a 24 V, 32 A h battery bank was used for the field tests. The total depth drilled was 161.6 m below the surface over 5.5 days, with an average core length of *1 m. Aside from the *0.6 m of core lost in the upper 2 m due to soft snowpack, the core recovery was believed to be virtually complete (the calculated value was 99.7 %). The core quality from 2 m to approximately 136 m was very good to excellent; below this depth, the core quality varied from fair to good. In May 1997, a drill camp was established on the north side of Mount Everest. After vehicular transport to the Everest base camp, Tibet, at 5200 m a.s.l. the drill system was carried 10 km by yaks and a further 5 km by porters to the drill site on the Far East Rongbuk Glacier (28°06′N, 86° 58′E; 6500 m a.s.l.). Unforeseen delays resulted in a

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shortage of time, so drilling was limited to 42 m of core. The drill performed flawlessly. Later, the Eclipse drill was used many times for coring in the Canadian High Arctic (Agassiz and Penny Icecaps), Greenland (Renland), and Antarctica (Law Dome, International Trans-Antarctic Scientific Expedition–ITASE, Aurora Basin, etc.). An interesting technique for improving the core quality with the Eclipse drill was gleaned in the course of drilling a 270-m-deep core on Law Dome, East Antarctica, over the 1997–1998 season (Morgan et al. 1998). Drilling down to 90 m proceeded smoothly, with the obtained core being of very good quality. Below 90 m, the core quality started to deteriorate, and by 102 m most of the obtained core was in the form of flat disks, a few centimeters thick, with multiple internal fracture lines. Efforts to improve the core quality included drilling at different rotation speeds (75–110 rpm), varying the cutting depth (2–5 mm/rev), varying the cutter load, and drilling shorter cores (0.65 m as opposed to 1 m). Other tests involved eliminating the load of chips on the core by suspending the chip-separator plug (which normally rides on top of the core) by a string from the top of the core barrel, drilling with the core dogs retracted, and drilling with cutters, which had their inner edges reshaped to obtain a radius of *1 mm. It was also thought that friction between the core and the core barrel might tend to twist the core, so the barrel was honed to give a highly polished surface. None of these techniques or modifications had any effect on the core quality. It was finally decided that fluid would be used to lubricate the drilling process. Thus, 20 L of kerosene was lowered down the hole in a bladder and released at the bottom. The first drill run with this fluid produced no noticeable difference in the top section of the core, but the bottom section showed some improvement. A second core showed marked improvement, with only one break, but subsequent cores were not as good, and four cores after the fluid was placed in the hole, the core quality was again unacceptable. At this stage, most of the fluid had been brought back up from the hole with the cuttings, and the chips were almost dry again. Adding another 15 L of kerosene produced only a slight improvement for two cores, and three cores later the quality was again unacceptable. It was noticed that while the top third of most cores was rubble or very thin “pucks,” the bottom two-thirds was considerably less broken. It was therefore decided that instead of trying to keep the weight of the chips off the core, a weight, which simulated the top section of a core, would be placed in the core barrel above the chip-separator plug. The first test, using a 1.8 kg weight, resulted in a core with just two breaks. As a check, the following core was drilled without the weight, and its top third was again badly broken. From then on, all the cores were drilled with a weight in the core barrel (except for another check at 146 m, where the top third was again badly broken). Adding a further 1.7 kg did

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8 Cable-Suspended Electromechanical Auger Drills

Fig. 8.66 Badger-Eclipse drill in use during Norwegian—U.S. traverse of East Antarctica, 2007– 2008 season (Photo S. Tronstad; About our Photos, n.d.)

not appear to result in any further improvement, but to make a more convenient system for the remainder of the drilling down to 270 m, a 3.5 kg weight was made that took the place of the chip-separator plug. The ice cores still appeared to be very brittle, often breaking into several pieces after removal from the drill barrel, but the complete disintegration of core sections that was experienced without the weight no longer occurred. A later examination showed that cores drilled with the weight, although unbroken, still had extensive internal fracturing. In summary, applying a load of only 3.5 kg on the top of the core using a free weight in the drill-core barrel significantly improved the core quality without the use of a drilling fluid. This improvement was surprising since this load was considerably less than the overburden pressure which, for comparison at a depth of 100 m, was equivalent to a load of 350 kg on the core cross section. In 1998, a weighted separator plug was tested during drilling on Devon Island, Canadian Arctic Archipelago. It was observed that although the weight did improve the core quality, drilling in fluid was even more effective. The drill used on Devon Island incorporated a booster pump to assist in raising the fluid and chips up the spiral flights between the inner and outer tubes. In the summer of 2002, the Eclipse drill was again used by the University of New Hampshire at the Eclipse Dome and drilled the deepest core recovered in Canada. The total depth was just over 345 m, with virtually complete core recovery. Drilling was stopped because the cable ran out. Borehole closure in the rather warm ice was also becoming a concern. The top 60 m of this long core was drilled using an ultra-clean drill system.

8.14.4 Badger-Eclipse Drill Recently, the Eclipse drill was modified to make it possible to clean ice chips from the space between the core barrel and jacket using the reverse rotation of the core barrel. The modified version of the drill was named the Badger-Eclipse drill (Fig. 8.66). In 2013, IDDO increased the capabilities of the Badger-Eclipse drills by designing and fabricating a solar and wind power system for use in the operation of the drill. This new power setup was tested prior to the drill’s deployment in May 2013, and was subsequently used for shallow coring at the Mt. Hunter summit plateau (*4000 m a.s.l.), Denali National Park, Alaska Range (Fig. 8.67) (Winski 2013). Two cores all the way to the bottom at a depth of 208 m were obtained in the span of three weeks (Fig. 8.68). Its nongenerator capability will be particularly useful at field sites where environmental impact is of special concern, and where the use of a generator for drill operations is not desirable or permitted.

8.15

Byrd Polar Research Center (BPRC) Drills

In the mid-1990s, the Byrd Polar Research Center (BPRC) of Ohio State University, USA (in 2014, it was renamed the Byrd Polar and Climate Research Center–BPCRC), designed a shallow drill with a so-called S-type chip chamber (Zagorodnov et al. 2000). The drill is fully compatible with the BPRC ethanol electrothermal drill (Zagorodnov et al. 1998); the winch, cable, and other subsystems can be used for both electromechanical and thermal drilling operations.

8.15

Byrd Polar Research Center (BPRC) Drills

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Fig. 8.67 Solar and wind supply (in front) of Badger-Eclipse drill at Mt. Hunter summit plateau, Alaska Range, May 2013 (Winski 2013)

The motor-gearbox of the first version of the BPRC shallow drill also includes ball-bearing support and a top coupling unit (Fig. 8.69a). The anti-torque system is fixed to the outside of the drive unit. Two anti-torque systems were developed: a conventional anti-torque system made of four leaf springs (Fig. 8.69b) and a U-blade anti-torque system (Fig. 8.69c). A core barrel is attached to the central shaft, and Fig. 8.68 Inside drill tent with Badger-Eclipse drill at Mt. Hunter summit plateau, Alaska Range, May 2013 (Winski 2013)

the space above the core barrel is used as a chip-storage chamber. To increase the chip transportation efficiency, 18 longitudinal grooves, 6.5 mm wide, 1 mm deep, and 1.2 m long, are machined in the lower section of the aluminum jacket. Two booster augers are attached to the main shaft for chip transport above the core barrel. The shaft and core barrel, and shaft and gear, are coupled with quick-removal

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Fig. 8.69 a BPRC shallow drill: 1 drill head; 2 core barrel; 3 booster auger; 4 chip chamber; 5 coupling; 6 gearbox; 7 motor; 8 slip ring; 9 swivel; 10 cable termination; b leaf spring anti-torque; c U-blade antitorque (Zagorodnov et al. 2000)

8 Cable-Suspended Electromechanical Auger Drills

pins. The perforated-disk sweeper is attached to the top of the shaft. The coring head is equipped with three cutters and three dog-leg-shaped core catchers. The head is attached to the core barrel with screws. Originally, the cutters had 25° rack and 15° relief angles, but during the 1998 field test, the relief angle was increased to 20°. The cutters and core catchers are made of stainless steel heat-treated to an HRC of 50–55. Three flange-head screws serve as adjustable penetration limiters. The cutting pitch can be changed by adding or removing flat washers. The drilling setup includes the base frame, winch, fiberglass mast, top sheave, tilting table, and controller (Fig. 8.70). This drilling setup was designed to operate either in the open air or inside a geodesic dome. The entire system can be unpacked and assembled by one person in *4 h. The base frame is constructed of three aluminum channels bolted together and weighs 35 kg. The winch is powered by a 1.5 kW permanent magnet DC motor directly coupled to a 56:1 planetary gearbox. This motor is used for the drill’s tripping in the hole. Another small auxiliary 80 W permanent magnet geared motor is coupled to the rear shaft of the main motor and feeds the cable at a constant speed during penetration. The 500-m-long Kevlar cable, which fulfills the maximum capacity of the winch drum, weighs 56 kg. The pulling capacity of the winch is *4 kN with an empty drum, and *2 kN with a full drum. The maximum raising speed is 0.52 m/s with an empty drum, and 0.9 m/s

Fig. 8.70 General schematic of BPRC drilling system (Zagorodnov et al. 2000)

8.15

Byrd Polar Research Center (BPRC) Drills

with a full drum. The maximum gravity-lowering speed of the drill is *1.5 m/s. The mast consists of a 3.35-m-long fiberglass tube, which also serves as a drill-shipping container. A 0.3 m-diameter pulley on top of the mast is coupled to a bidirectional shaft encoder and fixed to a platform, which is supported by two load cells. The mast is fixed in a tilted (2°–3°) position by thin-wall aluminum tubes. This support structure also serves as a ladder, which the operator can climb if adjustments are needed. Standard slip-on fittings allow the fast assembly of the drilling rig. The drilling setup is vertically stable without additional support. To service the drill on the surface, a tilting table rotated on a horizontal shaft has been developed. To position the drill horizontally, it is moved over the tilting table and lowered to rest on the removable base support. With the cable free, the drill and tilting table may be turned to a slightly inclined position, where the top of the tilting table rests firmly on a support. In this position, the shaft of the core barrel can be easily separated from the gear shaft, and the core barrel can be removed from the jacket. Simultaneously, a sweeper moves all the chips from the storage chamber. Once the core barrel is disconnected from the shaft, the core is removed from the top end of the core barrel. The drill controller provides two (drill and winch) adjustable 120 V DC outputs, with a maximum current of 15 A. It also monitors the depth (1-mm resolution) in a digital format, as well as the cable tension (1 N resolution). The BPRC shallow drill was first tested in July 1997, on the Sajama Ice Cap, Bolivia (18°06′S, 68°53′W; 6542 m a.s. l.). A snow–firn–ice core 40 m in length was taken during 15 h. The drill performed well except for the anti-torque system: the thin (0.2 mm) U-blades were bent during almost every drilling run. Thicker U-blades (0.38 mm) were prepared for a second drill test on the Dasuopu Glacier, Himalayas, China (28°23′N, 85°43′E; 7200 m a.s.l.) in September 1997. Here, a 27 m ice–firn core was taken in 10 h. It was found that in layered firn–ice sequences, thicker U-blades offered substantial resistance when the drill was lowered in the borehole. Otherwise, the drill performed well. The next test of the modified BPRC drill was conducted at the Raven site, Greenland, in May 1998, where two boreholes 122 and 21 m deep were drilled in 6 days. Here, the drill was set inside a dome shelter, where the air temperature was often slightly above the melting point. Measured borehole temperatures were in the range of −14.6 to −15.4 °C. Much of the drill-test effort was focused on the optimization of the angle of the U-shaped anti-torque blades to allow penetration of the layered firn–ice sequences. Instead of four, a single pair of 0.38-mm-thick U-blades was mounted on the drill, which allowed coring from the surface down to 110 m, at which point a leaf spring anti-torque system was mounted. The second borehole was drilled using

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only this leaf spring anti-torque system. Although the U-shaped anti-torque blades worked satisfactorily, the drill performed better with the conventional anti-torque system. Below 80 m, the cutters tended to slip more frequently. To prevent this, the relief angle of the cutters was increased, and the anti-torque springs were relaxed. Both adjustments increased the bit pressure and improved the drill performance. The first sign of stress in the ice appeared near 85 m, where longitudinal fractures occurred in some ice-core sections. However, the quality of the core was quite good along its entire 122 m, and none of the core sections drilled exhibited wafering. Up to 83 m, the drill produced 1.03– 1.08-m long cores, and at greater depths, the lengths of the cores varied between 0.4 and 1.02 m, with an average length of 0.83 m. Below 85 m, long drilling runs (1.05 m) were sometimes associated with difficulties in removing the core barrel from the drill. The density of the chips in the storage chamber was *500 kg/m3. The ice-core production reached a maximum rate of 6 m/h, with an average of 3.67 m/h. In January and February of 2000, six ice cores from 9.5 to 50.9 m were drilled to bedrock (Fig. 8.71) on three remnant ice fields on the rim and summit plateau of Kilimanjaro, the highest mountain in Africa (3°04.6′S, 37°21.2′E; 5893 m a.s. l.) (Thompson et al. 2002). The temperatures in the boreholes were close to the melting point. Surprisingly, no evidence of water was observed in the boreholes, but the shallowest 9.5-m-deep hole on the small, thin, Furtwängler Glacier within the crater was water-saturated throughout. In 2000, another drilling project with the BPRC drill was carried out at Puruogangri (33°55′N, 89°05′E, 6072 m a.s.l.), the largest modern ice field in the Tibetan Plateau, China, with an area of over 400 km2 in total, where a 214.7 m-deep hole was drilled (the temperature near the bottom reached −1 °C). In the way of drill improvements, other cable termination and anti-torque system options were designed and tested, the slip-ring and swivel were removed, and the small-diameter auger in the chip chamber was replaced by a tubular shaft (V. Zagorodnov, personal communication 2015). As a result, the drill length decreased to 3 m, and the weight decreased to 27 kg. In addition, the rigidity of the drill head was increased by using a thicker section at the chip channels and heat-treated 7075 aluminum. In May–June 2002, a modified PPRC drill was used for coring down to 180 m at the saddle of Mt. Bona and Mt. Churchill in the Wrangell–St. Elias range, Alaska, USA (Fig. 8.72) (61°24′N, 141°42′W; 4200 m a.s.l.; 10-m-depth temperature: −24 °C) (Zagorodnov et al. 2005). This hole was continued using an ethanol electrothermal drill to the bedrock at a depth of 460 m. Electromechanical drilling down to a 180 m depth was done in 4.5 working days or 41 h. A few short episodes with a stuck drill (each of which

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Fig. 8.71 Ice-core drilling at Kilimanjaro, 2000 (Tanzania-Mt. Kilimanjaro 2000)

Fig. 8.72 Ice-core drilling at saddle between Mt. Bona and Mt. Churchill in southeastern Alaska, 2002 (Polar Frontier, n.d.)

8 Cable-Suspended Electromechanical Auger Drills

lasted about 3 h and required changing the cutters) occurred, mainly below 150 m. To improve the drilling performance, the drill head, exterior of the core barrel, and interior of the outer jacket were covered with antifreeze (96 % polypropylene glycol) before each drilling run. Polypropylene glycol is a viscous fluid that stays on the drill parts while lowering the drill, provides lubrication for the cuttings, and significantly improves drill performance. During drilling, the ice core is not in contact with the lubricant. Applying the antifreeze with a plastic brush adds 2–3 min to the drill surface time. Lubrication efficiently prevents chip jams when the drill is operated at air temperatures above the melting point or during sunny days when the drill is heated by solar radiation. The average glycol use is *40 mL per drilling run. In addition, tests were conducted with a new drill head having three 17.5 mL containers that carried a cutting lubricant (2:1 mixture of glycol and ethanol) (Fig. 8.73). Three valves are fixed at the bottom end of the head body and opened when the drill touches the bottom of the hole. No significant differences in the penetration rate or improvement in the core quality was noted when dry and lubricated cutters were alternated in a Bona–Churchill borehole. It is possible that the lubricant quantities were not sufficient to change the drill performance, and it is likely that the lubricant was absorbed by the cuttings. An ice-core production rate of *13 m/h was achieved during the first hour. This linearly decreased with depth, and at a 180 m depth, it was down to 1 m/h; the average core production rate throughout the drilling was 4.4 m/h. That was faster than the drilling performed at the Raven site,

8.15

Byrd Polar Research Center (BPRC) Drills

Fig. 8.73 Drill head with lubricant containers and step cutters (Zagorodnov et al. 2005)

Greenland, with the same drill. More than likely, the improved drilling performance was connected with the use of a better-machined and anodized outer jacket and to the lubrication of the core barrel. Down to a depth of 100 m, the penetration depth and average length of the core pieces was close to 1 m. At a 150 m depth, the length of the run was as short as 0.75 m. The quality of the ice cores from the Bona– Churchill borehole was significantly better than that of previous cores taken in a cold environment and in the same depth intervals. In 2003, three ice cores (168, 29, and 129 m) were obtained at two summits of the Quelccaya Ice Cap, Peru (Fig. 8.74) (13°56′S, 70°50′W; 5670 m a.s.l.; at temperatures close to the melting point), and a further three cores (34, 34, and 146 m) were obtained from Nevado Coropuna, Peru

Fig. 8.74 Drilling operations at Quelccaya Ice Cap, Peru, 2003 (Credit V. Zagorodnov)

163

(15°32′S, 72°39′W; 6450 m a.s.l.; 10-m-depth temperature: −6 °C). The top of the Quelccaya Ice Cap consisted of temperate firn with water at the firn–ice transition (at the 24– 26 m depth). A small amount of meltwater constantly ran into the borehole. The presence of capillary water in the firn complicated drilling. The water partly washed out the lubricant and wet the metal surfaces. Then, ice chips stuck to the core barrel and eventually formed a thick layer that jammed it. If the core barrel rotation was stopped before the core break, the drill became stuck at the bottom. Forward and reverse rotation would normally free the drill; otherwise, jerking and hammering were necessary. The removal of compressed cuttings from the core barrel and the bailing of water required extra effort and time. All these additional activities during the first 2 days of drilling reduced the ice-core production to 5.5 m/h, which is a production of about one-third at the same depth in cold ice. On the third day of drilling, the core production dropped to 1.34 m/h, mainly because of the frequent sticking of the drill. On the fourth day, the performance of the drill was significantly improved when step cutters (see Fig. 8.73) were introduced below 76 m. Down to a 100 m depth, the penetration depth per drilling run practically doubled, and sticking events were less frequent. However, from 100 to 124 m, the average penetration depth diminished to 0.1 m for each run, and drilling was continued with a thermal drill. Empty drilling runs (i.e., no penetration) were more frequent in this borehole than in any other holes drilled with this drill. This is attributed mainly to ice formation behind the cutters.

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A 146-m-long ice core from Nevado Coropuna was obtained in 2.5 working days, approximately 20 h, at an average core production of 7.3 m/h. The performance of the drill was close to that at the Bona–Churchill borehole. The penetration depth and length of the core pieces gradually decreased with the borehole depth. To break the core easier, a hammer was added to the upper part of the drill. In 2006, three cores from depths greater than 160 m were obtained at the Naimona’nyi Glacier, Himalayas (30°27′N, 81°20′E; 6100 m a.s.l.) during 11 days (V. Zagorodnov, personal communication 2015). In 2009, another two holes were drilled in a temperate glacier at Mt. Copa, Peru, to depths of 189.6 m and 196.2 m, with 6 working days spent on drilling operations at each borehole. During the 2009–2010 season, the BPRC drill was used in the LARsen Ice Shelf System, Antarctica (LARISSA) project on the Bruce Plateau (66°02′ S, 64°04′ W, 1975.5 m a.s.l.) (Zagorodnov et al. 2012). The first hole was drilled to a depth of 143.18 m, where the drill became stuck. Leaving that drill, a second hole was begun 1.2 m from the first one. This hole was drilled down to 178.5 m with the BPRC shallow drill, and then to the bedrock at 447.65 m using an electrothermal drill. Recently, the BPRC shallow drill was used for predrilling access boreholes at Windless Bight, McMurdo Ice Shelf, Antarctica, in November–December 2011 (Zagorodnov et al. 2014). Borehole BH1 was drilled down to a depth of 170 m. The drilling setup was then relocated to a new position (40 m north), and a second borehole, BH2, was drilled to a depth of 185 m. The temperature was measured in the BH1 hole and extrapolated to an anticipated seawater temperature of

Fig. 8.75 Ice core is dumped out of core barrel of BPRC electromechanical drill at McMurdo Ice Shelf, Antarctica, 2011 (Rejcek 2012)

8 Cable-Suspended Electromechanical Auger Drills

−1.92 °C at a depth of 193 ± 2 m. After an ice shelf thickness estimation, the drill rig was moved back to the BH1 position, and the BH1 hole was deepened down to 185.7 m. The hot-point drill was then used to penetrate to the sub-ice shelf cavity. The drilling setup was then moved back to the BH2 position and, using the shallow drill, the borehole was deepened to 190.4 m. After this, the hot-point drill was used to complete the drilling to the sub-ice-shelf cavity. Because the main purpose of the project was to install temperature sensors, the focus was to achieve a maximum production drilling rate rather than obtaining good quality ice cores (Fig. 8.75). Down to 120 m, each drilling run produced two to four pieces of ice core, but below 150 m, all the core sections consisted of only unconsolidated 2–10-mm-thick disks. The optimal penetration pitch was found to be 3.6 mm/rev, while the penetration rate was 0.72 m/min. A high-penetration pitch produced coarse cuttings that freely moved to the chip chamber and ensured an average 1 m ice-core recovery with every drilling run. The speed when lowering the drill by gravity was 1–2.2 m/s, while the average raising speed was 0.68 m/s. The core barrel’s outer surface was lubricated with propylene glycol. Lubrication was necessary starting from a depth of *60 m; otherwise, great effort was necessary to pull the core barrel off the drill jacket. Each of the two boreholes was drilled in four days (35 h of total working time), including the rig set-up and power system installation, drilling, three relocations, and the tear-down of the drill setup. The average ice-core production was *9.2 m/h. The main feature of the BPRC ice drilling technology is that the drill systems are designed to be quickly switched

8.15

Byrd Polar Research Center (BPRC) Drills

from dry hole electromechanical drilling (used to 160– 190 m) to ethanol electrothermal or hot-point drilling. This approach uses significantly lighter equipment and produces an intermediate-depth core or access boreholes rather quickly.

8.16

British Antarctic Survey (BAS) Drills

8.16.1 BAS/IMAU Drill The drill produced by the British Antarctic Survey (BAS) is very similar to the AWI drill (see Sect. 8.10), which in turn has many features of earlier Swiss designs (Fig. 8.76a, b) (Mulvaney et al. 2002). The main design changes include the following: (1) a lighter weight winch system, (2) an increase in the core diameter to 106 mm for obtaining a greater ice volume, (3) the splines on the inner surface of the outer barrel are manufactured separately and fastened to the outer barrel, (4) the inclusion of a hammer action in the head for applying a shock to the head during difficult core breaking. The anti-torque section uses three two-blade skates located and mounted at 120° centers longitudinally along the section. Allowance is made for the distance the blade protrudes from the skate to be adjusted to accommodate different firn/ice hardness values. This design allows the skates to be withdrawn into the housing under the weight of the drill hanging from the cable. Once the load on the cable decreases, as the drill reaches the bottom of the borehole, a spring on the central shaft acts to push out the upper end of the skate, forcing the blades onto the borehole wall. As the drill begins to turn, the torque reaction causes a cam, located on the lower anti-torque shaft, to force out the lower end of the skate. With this arrangement, when a greater torque is transmitted to the cam, a higher force will be exerted by the lower skate and blade against the borehole wall. Once a drilling run is complete, and the drill is lifted, the weight of the drill on the cable pulls the skates back into the housing. This section also includes a small hammer device for difficult core breaks. Located on the same shaft that drives the mechanism for withdrawing the skates, the heavy stainless steel hammer weight has a short travel of *100 mm against the skate spring before it hits against three rods, transmitting the shock via the housing to the shaft connected to the inner barrel, and on to the drill head. The driven section houses a two-pole, permanent magnet, DC motor (model DPM30X2), with a maximum continuous stall torque of 1.4 N m (peak stall torque 5 N m), and an XFCG 208-21 model gear reducer. The rotation is transmitted to the inner core barrel through a quick-release section similar to the coupling of the Rufli drill. A three-sided cone is drawn back against a spring, allowing the pins to disengage from the crown of the barrel under the force of

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individual springs. The barrel is locked onto the drive shaft when the cone is released, forcing the pins out. Positive confirmation that the barrel is locked onto the drive shaft comes from the position of the lever operating the release cone. The inner and outer barrels are both made from drawn aluminum alloy tubing (grade HT30TF). The outer barrel has a series of grooves *15-mm wide, between *25-mm-wide splines running longitudinally along the inner surface of the barrel, to aid in chip transport. Twelve splines are secured to the inner surface of the barrel with screws. Three parallel spiral flights were bonded to the inner barrel using acrylic adhesive transfer tape and then screwed. The drill head is equipped with three round cutting teeth (Fig. 8.76c), three sprung core catchers, and three small tool bits for enlarging the hole diameter (in practice this has not been needed at the depths reached so far). The rounded cutters were designed in an attempt to improve the quality of the core, by reducing radial stress cracking, but may suffer from a less efficient cutting action. Both the cutters and core catchers were machined from oil-hardened tool steel. The drill pitch setting is simply achieved by varying the number of washers on the screws on the lower, rounded, face of the head annulus, behind each cutter. The 300-m capacity winch system is built on a 1.1 m × 0.65 m aluminum base. Sledge-runners on the Fig. 8.76 BAS drill: a schematic diagram; b general layout; c drill head (Mulvaney et al. 2002)

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underside of the base make it easier to maneuver in soft snow by hand. A standard 1.1 kW, three-phase motor drives the drum shaft via a chain pulley gearing of 1.25:1, through a gear reducer with a ratio of 25:1. A motor brake is built onto the gear motor, which will stop the motor and drum instantly for emergency breaking of the winch, with panic stop switches mounted on both the controller and drum support. Finally, the winch is built with a facility for hand cranking the drum for drill recovery, should a failure of the winch motor occur during winding. A ratchet assembly can be engaged to assist in manual winding. The winch system weight, without cable, is 150 kg. The cable used is a Rochester-type 4-H-250 A cable constructed with four 22 AWG conductors with a breaking strength of 25.8 kN. DC power is fed to the drill by doubling up the conductors; the steel cable armor was not used as the return. The 5.3-m-long aluminum tower is attached at the lower end to an articulated ball joint on the base plate of the winch in front of the drum. The mast design is not intended to tilt. The drill’s motor rotation speed is controlled by a DC drive, producing a variable output of up to 180 V DC, with a full load current rating of up to 12 A. In practice, the motor can be driven as low as 30 V, or 20 rpm at the drill head. A load cell and optical encoder provide the operator with an indication of the load on the cable, cable length paid out, and tripping rate. The winch motor speed is controlled via a frequency convertor motor controller, with a maximum motor speed of 2800 rpm at 100 Hz or 12.5 rpm of the winch drum, equating to 0.23 m/s of cable speed, and a specified minimum of 25 Hz (though in practice a minimum of 12 Hz was used without experiencing problems). Power is supplied by a single standard Honda EC4000 3.4 kW generator (weight 60 kg). The total weight of the drilling system, including the winch, cable, tower, drill, and generator, is 340 kg. Two identical drills were produced: one for BAS operations and another for the Institute for Marine and Atmospheric Research Utrecht (IMAU), The Netherlands. Both drills were used under different conditions, including warm Arctic glaciers close to the melting temperature, cold polar firn and ice, and bubble-free blue ice at the following sites: Berkner Island, January 1995 (152 m); EPICA Fuel Depot, Dronning Maud Land, January 1998 (123 m); Mårmaglaciären, Sweden, April 1997 (2 × 28 m); Lomonosovfonna, Svalbard, May 1997 (121 m); Scharffenbergbotnen (85 and 52 m); Camp Maudheimvidda, Dronning Maud Land, December 1997 (2 m × 105 m); Camp Victoria, Dronning Maud Land, January 1998 (137 m); Lomonosovfonna, Svalbard, May 2000 (60 m); and EPICA, Dronning Maud Land, January 2001 (100 and 160 m). Generally, under all conditions, the drill system has worked well. In glacier ice close to melting, the sticking of cuttings on the inner barrel flights was experienced, making chip transport problematic,

8 Cable-Suspended Electromechanical Auger Drills

and providing a limit on the depth as water-soaked ice was approached. The drill head rotation speed was typically in the range of 80–95 rpm. The cutter pitch was set at about 2.5 mm, using the screws with washers on the drill head. The anti-torque section appears to work well, with no indication of cable damage from rotation of the drill in the hole, despite the absence of a slip-ring assembly between the cable and the drill. This system has the disadvantage that in the upper few meters of firn, wider blades are needed to counter the drilling torque. Below about 10 m, the blades can be changed for narrower blades, which then suffice for all further drilling. In the firn, core lengths of 0.95–1.1 m were normal, whereas in ice, the lengths were reduced to *0.85 m because more of the drill chamber was taken up with cuttings. The core quality was reasonable, with little damage to the cores at the Antarctic sites until depths in excess of about 135 m. Below this depth, some runs produced cores in several pieces, mostly broken horizontally across the core, but with occasional longitudinal slivers caused by the core catchers during breaking. Experimenting with the cutters suggested that the core quality was improved by better hardening and more regular sharpening of the cutters. It is not clear that the rounded design of the cutters led to any significant improvement in the ice-core quality. The small tools on the upper part of the head for widening the hole were not used. Core breaking was usually easy, with very few difficult breaks. More common, particularly in the firn, were grooves in the lower section of the core as the core catchers were dragged up the core before it finally broke away from the bottom. Both systems were subsequently modified by changing the chain drive cogs to give slightly faster winching speeds (*20 % faster).

8.16.2 Rapid-Access Isotope Drill Another “dry” drilling approach, proposed by BAS, is to deploy the new rapid-access isotope drill, which is able to complete a 600 m (*20 % of the ice sheet depth) borehole in just 1 week, before being redeployed at the next drilling location (Subsea World News 2014). This drill will collect only ice cuttings, which can be used for isotope analysis and climate profiling, and leave an access hole to allow the deployment of a temperature-sensing cable. Both types of investigation and analysis will be used to identify potential sites for recovering the oldest ice. All of the drilling equipment and the drilling team could be transported using two Twin Otter flights. The total length of the drill is 8.5 m, including a 5.4-m-long drill barrel. It is expected to drill at least 2.5 m of ice per run on the presumption that the density of the

8.16

British Antarctic Survey (BAS) Drills

cuttings would be 520 kg/m3. The drill consists on a spinning drill barrel with a fixed inner auger and full-diameter cutters, drive section (0.25 kW motor with planetary gearbox, epicyclical module, and motor controller), anti-torque section, and cable termination. Other drilling system components include a winch, winch controller, drill controller, 9-m-tall mast, and 5 kW generator. The entire MacArtney winch system, including a demountable cable sheave pole and an integrated sledge, is made from aluminum and designed to be extremely light and compact (Fig. 8.77). A programmable logic controller (PLC) on the winch makes sure that the winch is automatically stopped at 20 cm above the last drilling depth. Subsequently, either the operator or an automatic drill program will take control to ensure that optimal ice cutting samples are collected. When the drill is recovered, the PLC makes sure to cease winch operations 1 m before the back of the drill reaches the surface. The designed average tripping speed is 1 m/s. The first test in 2014–2015 showed problems with the ice chips transportation (R. Mulvaney, personal communication 2015). The drill design was improved and the next tests are scheduled for December 2015 at the Sky Blu station on the Antarctic Peninsula, followed by the drilling of few holes in 2016–2017 near Dome C in Antarctica.

Fig. 8.77 MacArtney winch system (Subsea World News 2014)

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8.17

FELICS Drills

8.17.1 3″ Drill The Fast Electromechanical Lightweight Ice Coring System (FELICS) was designed and manufactured by the small Swiss enterprise Icedrill.ch AG. The system is installed (within 30 min by three people) inside a commercial protective tent (Fig. 8.78) and does not require trench excavation because it is a non-tilting drill (Ginot et al. 2002). The separation of the barrels to extract ice cores and chips is performed in a vertical position. The system, including its power supply, weighs 228 kg. The heaviest component is the cable drum with 200 m of cable, which weighs 28 kg. The drill’s drive unit includes a DC motor of the Dunker GR 80 × 80 type with PLG 70 gear reduction (Fig. 8.79). Three spring-loaded skates are snugly installed into the slots of the drive-unit casing. An unusual feature of this drill is the absence of the jacket. The drive shaft is connected to the top of a chip chamber made from a thick-walled aluminum tube with two narrow machined-out parallel transporting spirals (their width continuously increases to the top). The core barrel was manufactured in the same manner. It is 0.95 m long and designed to obtain ice cores with a maximum length of 0.9 m. The chip chamber has two modifications that differ by length: the longer one (1.2 m) makes it

Fig. 8.78 Main components of 3″ FELICS drill (Ginot et al. 2002). a drive unit with motor and anti-torque system; b chip barrel; c core barrel; d drill head; e winch with cable; f winch motor; g winch base plate; h tower (inset view from top onto winch base plate)

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8 Cable-Suspended Electromechanical Auger Drills

Fig. 8.79 Cross-section of 3″ FELICS drill (Ginot et al. 2002). 1 DC motor with reduction gear; 2 circular seal (Lubroseal LM17C); 3 armored cable; 4 cable clamp; 5 electrical contactors; 6 slip ring; 7

anti-torque system; 8 jacket; 9 shaft; 10 motor support; 11 ball bearing; 12 bearing cover; 13 motor clutch; 14 clutch bolt; 15 chip container; 16 chip extractor; 17 drill clutch; 18 core barrel

possible to obtain the maximum length core in high-density ice, and the short one (0.95 m) is used for firn with a lower density. The high rotation velocity (220 rpm) of the core barrel ensures good chip transportation to the top of the chip chamber, where they fall inside through two openings. The drill can be used in the water-flooded ice because the drive unit is sealed against a maximum pressure of 50 kPa. All of the parts in contact with the core are made of anodized aluminum. An integral drill head with two cutters is fixed at the lower end of the core barrel. One of its two teeth cuts 2-mm deeper, but only forms a narrow ring around the core. The second tooth cuts the outer part of the annulus. There are no cutter shoes because the rate of penetration is controlled by the winch speed. The life of the drill head (cutters) is *150 m of drilling, after which the cutting edges of the teeth can be restored in the field with needle files. The core catchers follow the conventional core-dog design, and three different sizes are used for firn, soft ice, and hard ice. A very simple system was developed to couple the drive unit, chip chamber, and core barrel (Fig. 8.80). Two spring-loaded pistons glide radially into two holes in the thick-walled barrel. To disengage the coupling, a U-shaped tool is pushed into tangential slots of the barrel. The cores and chips are extracted from the barrels by means of a simple core pusher and chip extractor.

The winch and tower are installed on a 5-mm-thick aluminum base plate equipped with a stabilizing frame. The winch is driven by a 0.42 kW winch motor (3000 rpm) coupled to a 25:1 gear reducer, which allows a maximum drill speed of 0.5 m/s. The final version of the FELICS drill is equipped with a Schlumberger 4-18 PSS cable. For transport, the cable and current connector are separated from the drive unit by taking out six screws. The three-piece tower can be clicked together in seconds without any tools, and is mounted onto the base plate by an axis. It is stabilized with four firn-anchors outside the protective tent. The complete system is operated from a compact control box that includes an on-off current switch, a battery pack voltage meter, a solar panel/generator input current meter, and the winch and drill switches. The drill is controlled by a rotation speed regulator and rotation direction button. The winch and drill motor power are controlled by two servo-amplifiers (20 A) and are equipped with current meters. The depth of the borehole is monitored by a counter installed on the winch, but is also directly measured by a 150-m-long ballasted band meter attached to the tower. Two independent power sources are used, allowing drilling during day and night. A group of six flexible solar panels with a peak power of 190 W (USF-32, Unisolar) and a small gasoline generator (EU 10, Honda) with a nominal

Fig. 8.80 Coupling system between motor, chip chamber, and core barrel (Ginot et al. 2002)

8.17

FELICS Drills

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output of 1000 W and a weight of only 13 kg are connected to a rechargeable battery pack (capacity 840 Wh, 120 V/7 Ah) in continuous loading. The solar panels supply enough power to work with either drill or winch motor load when sufficient sunlight is available. Drilling with the battery pack can be continued for several hours without sunlight. In addition, the battery pack delivers the necessary peak power for core breaking and winch acceleration. By changing the gasoline injection nozzle, the generator functions even at altitudes above 6000 m and consumes *0.5 L/h. During the winter of 1998, test drilling to a depth of 20 m was performed on the Jungfraujoch temperate glacier (Swiss Alps, 3500 m a.s.l.). In February 1999, the first scientific drilling expedition using FELICS was conducted on the Cerro Tapado Glacier at 5536 m a.s.l. in the Chilean Andes, where the bedrock was reached at a depth of 36 m in two drilling days. In the same year, drilling was performed near the summit of Illimani, Bolivia, at 6300 m a.s.l. The simultaneous use of two FELICS drills allowed the extraction of two 136-m-long ice cores in only 6 days, including installation. In November 2000, four ice cores were obtained from the Chimborazo summit in Ecuador at 6250 m a.s.l.; one reached the bedrock at a depth of 55 m. In subsequent

Fig. 8.82 FELICS drill in Italian ITASE caravan (Photo M. Frezzotti; Paleoclimatic coring: high resolution and innovations, n.d.)

years, the FELICS drill was used a dozen times on high altitude and polar glaciers, with a typical average production of 20–25 m/day (Figs. 8.81 and 8.82).

8.17.2 “Backpack Drill”

Fig. 8.81 FELICS drill inside protective tent at Svalbard, March 2009 (Photo G. Rotschky; Ice cores, n.d.)

The “Backpack Drill” (2″ Ice Core Drill) was designed for high-mountain or preparatory expeditions, and the total weight of the drilling equipment is only *20 kg (Ginot et al. 2002). This drilling system consists of a core barrel, chip barrel, and drive unit, with no winch used (Fig. 8.83). The core diameter is 57 mm, and the maximum core length is 0.9 m. The system is attached to an electric lifting cable with a length of 20 m, which is connected to a small control box and battery pack (Fig. 8.84). The drilling depth is limited to 15–18 m. Core dogs with horizontal mobility are used to cut the core, with the knives extracted by the backward rotation of the drill. These core dogs are especially suitable for the first meters of drilling in snow and firn with densities below 600 kg/m3. Normal core catchers for solid ice are also available. Power is provided by a small solar panel (SUNLINQ, 12 Watt) via a battery pack (36 V, 3.2 A h). Drilling 15-m firn cores requires about 2–4 h. Because of the low weight of the

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8 Cable-Suspended Electromechanical Auger Drills

Fig. 8.83 “Backpack Drill” in stowed position (Ice core drills, n. d.)

drill, sometimes it is difficult to drill through solid ice. In order to apply a stronger axial load to the drill, the use of an assembly of connectable stakes attached to the top of the motor is recommended.

Fig. 8.84 Testing of “Backpack Drill” at Jungfraujoch, Alps (Ice core drills, n.d.)

8.18

Blue Ice Drill (BID)

8.18.1 BID General Fescription The Blue Ice Drill (BID) is a large-diameter, electromechanical coring drill developed by the IDDO group of the University of Wisconsin–Madison, USA, to take large-volume, near-surface (*30 m), contamination-free ice samples (Kuhl et al. 2014). The drill consists of a drill head, an inner/outer barrel assembly, and a motor/reducer section (Fig. 8.85). The subsurface equipment is supported by a tripod, winch, rope, power cable, and motor control. The stainless steel drill head with three cutters is attached to the down-hole end of the core barrel. Each cutter features a 30° rake angle and 7° clearance angle. Two widths of cutters are available: a 23.3 mm thin kerf (241 mm core, 288 mm hole) and 25.8 mm wide kerf (240 mm core, 291 mm hole). Hardened tool steel is used for the standard cutters, whereas carbide-tipped stainless steel cutters are used under dirty ice conditions. The rate of penetration is controlled by three shoes. Shoes of various sizes are available to allow pitch adjustment from 0.75 to 21 mm. Six hardened, tool-steel core dogs (sharp-tipped, teardrop-shaped pawls) of three different lengths (12.7, 15.2, and 17.8 mm intrusion depths) are available to facilitate core breaking and retrieval under various ice conditions. In the operational mode with the special core recovery tool, the core dogs are removed from the drill head, allowing the core to be drilled and left in the hole, still attached to the ice at the base, when the drill is withdrawn. The BID utilizes a double-barrel design with a rotating inner core barrel with three helical flights and a stationary

8.18

Blue Ice Drill (BID)

Fig. 8.85 Schematic view of major components of BID system (Kuhl et al. 2014)

outer barrel. Each barrel is composed of mandrel-laid fiberglass epoxy tubing, which is light, strong, tough, round, and straight. The strength of the fiberglass barrels has proved to be adequate, even for supporting the full load during core breaking. The greenhouse melting of chips occurred in the first field season because of the transparent properties of the material, but this issue was effectively addressed by painting the outer barrel white. The flights are cast in-place on the core barrel from glass-reinforced epoxy resin. The efficiency of the cutting transport is increased by five equally spaced, stainless steel strips attached axially along the inner surface of the outer barrel with adhesive and flat-head screws. Cuttings are transported to the top of the core barrel, where three windows in the tubing allow the cuttings to collect on top of the core being drilled. A plastic plug is suspended within the core barrel and used to segregate the ice cuttings from the core. Three barrel-stabilizing pads, located at the top of the outer barrel, are shimmed to the borehole diameter to keep the drill tracking straight. Power for cutting ice and transporting cuttings is provided by a custom AC induction motor through a two-stage, planetary gear reducer. A spline shaft and nut connect the gear reducer output to a drive plate with three bayonet-style, lock-pin assemblies for quickly attaching/removing the core barrel. The core barrel drive plate is supported by a slewing

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bearing. A rubber shaft seal between the motor housing and core barrel drive plate provides secondary containment for the lubricating fluids present in the motor section. The motor and reducer are housed within an aluminum and stainless steel enclosure rigidly connected to the outer barrel. Two versions of this housing exist: a model equipped with a load-triggered slide hammer for core breaks and a model without the slide hammer. The slide-hammer assembly consists of a two-piece, splined housing with 82 mm of axial travel. Up to six neodymium magnets attracted to an iron plate hold the assembly closed with a maximum force of 6.7 kN. These magnets can be removed to tune the actuation force to specific coring conditions. The motor and gear reducer are attached to the upper portion of the slide-hammer assembly. Applying an axial force in excess of the holding force of the magnets causes the upper slide-hammer assembly to actuate to the extended position against a rigid stop in a fraction of a second. This imparts an impulse force to quickly set the core dogs and propagate a crack across the ice core. The second motor housing version lacks the slide hammer, resulting in a significantly lighter, shorter motor/reducer section (46 kg, 659 mm vs. 78 kg, 903 mm). It is used in conjunction with a separate device, a core recovery tool, which is deployed to break and recover samples by tipping the core at shallow depths. The first field tests revealed drill motor failures that have been attributed to shock during the operation of the slide hammer. Modifications to shock-strengthen the drill motor have been implemented, including the addition of steel support strips in the motor housing and a change to bearings with an improved thrust-load capacity. No additional failures have been seen since these modifications were implemented. The down-hole portion of the drill is suspended via a rope attached to a swivel on the motor section top plate. The top plate also contains a mount to attach the torsion stem extensions, recovery loop, electrical connector mount, and, on the slide-hammer version, breather plugs to vent the interior during actuation. The core recovery tool is a device similar to that used in the 12″ auger built by CRREL (see Sect. 4.3.6). It consists of a 1-m-long fiberglass core barrel with three small core dogs mounted in centered housings at the bottom. A tilt mechanism (Fig. 8.86) is attached to the top of the core barrel with three bayonet-style lock-pins. The tilt mechanism transforms a vertical force from the suspending rope to a horizontal force via a cam profile/follower actuating a spring-loaded piston. A vertical force of *700 N is sufficient to actuate the tilt mechanism, breaking the core at the base. The core dogs engage in the core to resist the vertical actuation force and hold the core for retrieval to the surface. A 300-mm-long core barrel is used to break cores shorter than *0.5 m. The electrical power requirements of the BID system are supplied by a single 3.5 kW generator. A variable frequency

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Fig. 8.86 Interior model view of core recovery tool tilt mechanism (Kuhl et al. 2014)

drive (VFD) converts the 240 V, single-phase output of the generator into three-phase power to operate the drill motor, while 120 V, single-phase service is supplied to two standard outlets on the control box to power the winch motor and accessories. The VFD provides a near-constant torque at all speeds, up to the motor nameplate rpm, and soft-starts the drill motor to limit the inrush current. A 35 m, 16/4 electrical cord on a spring-energized, retracting cord reel supplies power down-hole to the drill motor. The drill motor electrical cord terminates in a watertight, strain-relieved, cord grip in the motor section top plate. The faceplate of the control box contains controls for on/off, emergency stop, rotation direction, rotation speed, local/remote, and VFD parameters. A motor load gauge and digital screen for viewing the VFD settings and inputs/outputs are also located on the faceplate. Load resistors regulated by a thermostat provide heat to keep the internal temperature of the control box above 0 °C. The drill motor rotation is controlled using either local controls on

8 Cable-Suspended Electromechanical Auger Drills

the faceplate or two interlock switches on the torsion stem handles used by the operator to anti-torque the drill. The drill is suspended from a 5.3-m-tall tripod constructed of aluminum pipe segments connected with coupler sleeves. The tripod contains two adjustable-length legs to help center the hanging drill on uneven surfaces. Two sheaves are mounted on a single axle in the tripod apex frame, allowing both the drill and core recovery tool to be suspended simultaneously via separate lines. A commercial capstan winch with a maximum pulling force of 26.7 kN is mounted in line with the fixed-length tripod leg. The winch is driven by a right-angle, two-speed electric drill motor (120 V, 13 A) controlled with a foot switch. Low-stretch ropes with diameters of 13 and 19 mm are used for the core recovery tool and drill, respectively. Each leg terminates in a hinged, triangular footplate with holes for ice screws to affix the tripod to the ice surface. For projects requiring frequent local drill moves over relatively flat terrain, the tripod is mounted on a custom HDPE plastic platform sled. The BID is operated by a minimum of two operators. A winch operator controls the descent and ascent of the drill and core recovery tool by tailing the respective ropes on the capstan winch. The winch operator also manipulates the control box to select the drill rotation direction and local or remote operation, and monitors the drill motor power. A second operator anti-torques the drill by means of two handles attached to either a barrel clamp for shallow coring or the uppermost torsion stem section for deeper cores. A reaction torque is applied from the surface via a sectioned torsion stem made of thin-walled, aluminum tubing. The drill operator controls the drill rotation by means of interlock switches on the anti-torque handles and adds or removes torsion stem sections as the drill is tripped in or out of the hole.

8.18.2 Operation and Performance The BID system was tested in a cold-room facility at the CRREL in June 2010. It was first deployed to the field in November 2010, in support of a two-season scientific project on Taylor Glacier (Fig. 8.87). During the first drilling season, a total of 560 m of core were recovered from 34 holes, the deepest of these being 21 m, in 33 (8-h) shifts. Core recovery was 100 %, with generally excellent core quality. Following this initial season, a variety of minor improvements were made to the drill system. The second season at Taylor Glacier yielded marked improvements in drilling efficiency. During the 2011/2012 season, 64 holes were drilled in 32 shifts, for a total of 931 m of core recovered. The maximum hole depth was 26 m. The drill system was next deployed to a site near Summit Station, Greenland. During this test, a 24-m-deep hole was drilled in 23 runs. The overall drill performance was satisfactory,

8.18

Blue Ice Drill (BID)

Fig. 8.87 BID at Taylor Glacier, 2010–2011 Antarctic field season (Photo J. Severinghaus; About our Photos, n.d.)

although several problems were encountered that required design modifications. The most important of these involved shallow firn core recovery and slide-hammer impact damage to the motor section. The BID system was again deployed to Taylor Glacier for the 2013/2014 field season. Approximately 1,355 m of core were recovered in 1432 drill runs from 151 separate holes. This required 34 days to complete, with two drill shifts per day for the majority of the season. Excellent coring efficiency was achieved in this season, due in part to the use of the anti-torque skates on the motor section.

8.18.3 BID-Deep System In order to recover large-volume samples from depths beyond the BID’s capability, the original rope and electrical cord were replaced by a 9.6-mm-diameter steel electromechanical cable for the BID-Deep system. This cable includes seven 20 AWG copper conductors and has a breaking strength of nearly nine times the 6.7 kN core break tension. A total of 220 m of this cable is spooled on an aluminum winch drum featuring a grooved drum to facilitate level winding. The winch is powered by a 4 kW gear motor with a 119:1 helical-bevel gear reduction capable of developing a

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maximum cable tension of 18 kN. A new crown sheave assembly with a 457-mm-diameter sheave wheel attaches to the original tripod legs. The clearance under the tripod was increased to 5.6 m by adding 29 cm extensions to each tripod leg. The tripod leg stiffness has been maintained by linking the legs together with three tie rods. The original capstan winch can still be used to operate the CRT, or other down-hole tools, via an accessory pulley mounted below the crown sheave assembly. The three-phase AC induction motor used as the winch gear motor is controlled by a VFD. A braking transistor module and resistive load bank allow the winch to safely control the weight of a sonde during lowering. Additional braking is provided by a 40 N m shaft brake mounted on the winch motor and controlled by the VFD. Speed and direction controls for the winch are housed in a weather-tight, corded pendant. Fine ascent/descent control of the drill is accomplished via a hand-wheel mounted directly to the motor shaft. A manual motor brake override switch mounted on the winch motor disengages the brake during hand-wheel operation. E-stops are located on both the pendant and winch motor body. Upgrades to the original BID motor section allow the drill to provide anti-torque cutting forces via five leaf springs mounted to an assembly surrounding the motor can. The electromechanical cable connects to a bearing-supported shaft in the motor section with a commercial mechanical cable termination. Attached to the bottom of the bearing shaft is a four-channel electrical slip-ring, which transmits power from the cable to the drill motor while allowing the sonde to rotate independently of the cable. The BID-Deep system itself is utilized for core retrieval. A tapered collet with flexible fingers is used for low-density firn cores. Core dogs are used in place of the collet when the density of the firn/ice increases. During summer 2014, the BID-Deep system was tested outside of Summit Station, Greenland (Fig. 8.88) (Cosmogenic Carbon-14 Core Project Successfully Completed Following Early Season Challenges 2014). The deepest borehole reached 187 m. The core quality was found to be an issue after *140 m. However, the fabrication of less aggressive cutters seemed to improve the core quality at these depths. Over the course of the season, a total of 59 holes were drilled in 26 days of drilling, and 1258 m of core were recovered in a total of 1151 drill runs. The tapered collet core catcher performed excellently for firn shallower than 6 m, and the core dogs were successful for core recovery below *4 m.

8.19

Summary

Starting in the beginning of the 1970s, shallow drills were used at locations from the polar ice sheets and ice caps to high-mountain glaciers. Most of these shallow drills could

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8 Cable-Suspended Electromechanical Auger Drills

Fig. 8.88 BID-Deep drill at Summit, Greenland, June 2014 (Photo B. Hmiel from Cosmogenic Carbon-14 Core Project Successfully Completed Following Early Season Challenges 2014)

obtain cores of 1.2–1.4 m in snow/firn formations, but below the firn/ice transition, the core length dramatically decreased, typically to 0.5–0.9 m. The main working parameters of augers varied from drill to drill in a range of 25°–42.3° for the auger angle and 20–220 rpm for the rotation speed (see Table 8.1). However, the rotation speed of most drills was *100 rpm. An analysis of the cutting transportation performance using the discrete element method showed that at a rotation speed of 100 rpm, an auger with 35°–40° angles had the highest axial ice cutting velocity (Hong et al. 2014). The power of the drill’s driven motor was in the range of 0.25– 1.5 kW, with an average of 0.6–0.7 kW. Cutters with 30°– 45° rack and 15° relief angles were the most common. The anti-torque systems currently being used can be divided into four types (Talalay et al. 2014): (1) leaf spring systems, (2) skate systems, (3) side milling cutters, and (4) U-shaped blade systems. To ensure that a suitable countertorque can be maintained, it has been suggested that some combination of these anti-torque systems be used (e.g., a combination leaf spring and skate system, as designed for the Rufli drill). Leaf spring and skate anti-torque systems have proven to be the most reliable designs. One of the first holes drilled to a depth of 415 m at Vatnajokull Glacier, Iceland, in 1972, is still recognized as the deepest core recovered with a cable-suspended electromechanical auger drill. It was possible to reach this depth because the subsurface water drained into the hole and remained at a constant level of 34 m despite increasing the depth of the hole, which prevented the hole from closing.

The deepest “dry” hole drilled by an electromechanical auger drill was cored at the South Pole in Antarctica. Three summer seasons were needed to accomplish this task: 1980– 1981 (108 m), 1982–1983 (237 m), and 1983–1984 (353.5 m). The weight and dimensions are not as crucial for shallow drilling systems developed to operate in Polar Regions, where airborne and ground transportation support is available. For high-mountain applications, shallow drills have to be designed to be as light as possible because transportation facilities in this case push the weight issue into the foreground. The average altitude limit for commercial helicopters is 3000–3500 m a.s.l., and they typically cruise at 200–700 m. Even though some special rescue helicopters can get up to 5000–7000 m a.s.l. (for example, a Eurocopter single-engine helicopter landed at 8850 m on the top of Mt. Everest in 2005), they cannot be considered to be a reliable means of transportation for high-mountain ice-drilling projects. Thus, drilling equipment is transported to a drill site by people using sledges and backpacks or in some cases by baggage animals (lamas or yaks). In 1997, BPRC researchers obtained the highest ice core ever drilled at the Dasuopu Glacier (7200 m a.s.l.), a 2 km-wide ice field that straddles a flat area on the flank of Xixabangma, an 8014 m peak on the Tibetan Plateau. No previous expeditions had ever drilled ice cores at such a high altitude. Yaks were used to carry the drilling equipment and ice-core shipping boxes from the glacier edge to the base camp 12 km away (Fig. 8.89).

8.19

Summary

Fig. 8.89 Yaks with ice core shipping boxes, Tibetan Plateau, 1997 (Photo L.G. Thompson; Himalayan Ice Reveals Climate Warming, Catastrophic Drought 2000)

To be lighter and conserve energy, shallow drilling systems for high-mountain applications should use small electric drives, light Kevlar cables, and aluminum drill components and subsystems. Making the shallow drill itself as small, short, and lightweight as the coring requirements permit became a challenging task for designers. Another challenging task for shallow drills is coring in temperate and polythermal glaciers. Ice-core auger drills (with rare exceptions) cannot operate efficiently at pressure-melting temperatures (Zagorodnov and Thompson 2014). Although many options to obtain good cores under these circumstances were attempted (coating the down-hole units with Teflon, lubrication by glycol, modifying the cutters and shoes, and varying the rpm, drill pitch, etc.), the intended effects were not obtained in full. An important modification introduced by the UCPH shallow drill in the 1970s and now widely (although not universally) used is to pivot the tower so that, when the drill is fully out of the hole, the tower, and drill together can be rotated to a horizontal position at a comfortable working height to make it easier to remove the core and chips. An additional advantage of this tilting action is that it reduces the needed height of the tower above the surface, although it requires a pit dug up in the glacier surface to accommodate the drill and lower part of the tower when they are tilted to the vertical. Originally designed for shallow coring, it was soon adapted to intermediate and deep coring. Economical and low-environmental-impact ice-core drilling is possible with intermediate-depth systems in which an electromechanical auger and ethanol thermal-electric drills can easily be interchanged using a single drilling platform (Zagorodnov et al. 2005). The combination of these drills makes it possible to rather quickly and effectively drill

175

boreholes partially filled with an ethanol-water solution. This drilling method has been used successfully at several sites. There is an increasing need to collect shallow cores under extremely clean conditions to conduct state-of-the-art analyses for trace element chemistry, particles, gases, and microbiology. While cores can often be decontaminated after drilling, this results in the loss of a significant volume of ice and often does not eliminate all the contamination. The “Clean Simon” shallow drill used by the GSC can be identified as a potential starting-point for a design. Clean coring also includes the use of power supplies with minimal contamination potential. Even though some shallow drilling systems showed very good performances, the further development of these drills remains an active issue today, with the goals of (1) applying the latest achievements in material/electrical engineering and computer science, (2) improving the drilling performance in “warm” ice and water-filled holes, (3) developing ergonomical drilling systems with optimal working parameters, and (4) developing the ability to interchange a rock or soil coring system to collect basal dirty ice and subglacial sediment cores.

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177 Rufli H, Stauffer B, Oeschger H (1976) Lightweight 50-meter core drill for firn and ice. In: Proceedings of the symposium (Ice-Core Drilling), University of Nebraska, Lincoln, USA, 28–30 Aug 1974. University of Nebraska Press, Lincoln, pp 139–153 Schwander J, Rufli H (1988) Electromechanical drilling in dry holes to medium depths. In: Proceedings of the third international workshop on ice drilling technology, Grenoble, France, 10–14 Oct 1988. LGGE, Grenoble, pp 32–37 Schwander J, Rufli H (1994) Electromechanical drilling of a 300-m core in a dry hole at Summit. In: Proceedings of the fourth international workshop on ice drilling technology (Memoirs of National Institute of Polar Research), Tokyo, 20–23 Apr 1993, vol 49, pp 93–98) Shiraiwa T, Nishio F, Kameda T et al (1999) Ice core drilling at Ushkovsky ice cap, Kamchatka, Russia. Seppyo J Jpn Soc Snow Ice 61(1):25–40 (In Japanese) Shiraiwa T, Murav’yev Y D, Kameda T et al (2001) Characteristics of a crater glacier at Ushkovsky volcano, Kamchatka, Russia, as revealed by the physical properties of ice cores and borehole thermometry. J Glaciol 47(158):423–432 Shiraiwa T, Goto-Azuma K, Matoba S et al (2003) Ice core drilling at King Col, Mount Logan 2002. Bull Glaciol Res 20:57–63 Shiraiwa T, Kanamori S, Benson C et al (2004) Shallow ice core drilling at Mount Wrangell. Alaska Bull Glaciol Res 21:71–77 Simões JC, Ferron FA, Bernardo RT et al (2004) Ice core study from the King George Island, South Shetlands, Antarctica. Pesquisa Antártica Brasileira 4:9–23 Stauffer B, Schotterer U (1985) Untersuchungen an eisbohrkernen von Alpengletschern. Geographica Helvetica 4:223–229 (In German) Subsea World News (2014) BAS gets improved ice core drilling winch from MacArtney. Available at: http://subseaworldnews.com/2014/ 05/07/bas-gets-improved-ice-core-drilling-winch-from-macartney/. Accessed 21 July 2013 Summer season 2013/2014 at Concordia, Antarctica (2014) Project overview. Available at: http://www.iceandlasers.org/ice-laserssubglacior-portfolios/summer-season-2013–2014-at-concordiaantarctica. Accessed 13 Sept 2014 Surface Science (2011) NEEM ice core drilling project. Available at: http://www.photo.neem.dk/2011/Surface-Science/20025267_ RdrBJk#!i=1578418641&k=qQ2tQPj. Accessed 21 July 2014 Suzuki Y (1976) Deep core drilling by Japanese Antarctic Expedition. In: Proceedings of the symposium (Ice-Core Drilling), University of Nebraska, Lincoln, USA, 28–30 Aug 1974. University of Nebraska Press, Lincoln, pp 155–166 Suzuki Y (1978) New counter-torque devices of a cable-suspended electromechanical drill. Low Temp Sci Ser A 37:163–166 (in Japanese) Suzuki Y (1984) Light weight electro-mechanical drills. In: Proceedings of the second international workshop/symposium on ice drilling technology (USA CRREL Special Report 84–34), Calgary, Alberta, Canada, 30–31 Aug 1982, pp 33–40 Suzuki Y (1994) Development of Japanese mechanical drills. Personal reminiscences. In: Proceedings of the fourth international workshop on ice drilling technology (Memoirs of National Institute of Polar Research), Tokyo, 20–23 Apr 1993, vol 49, pp 1–4 Suzuki Y, Shimbori K (1984) Mechanical drill system for the 25th Japanese Antarctic Research Expedition. In: Proceedings of the sixth symposium on polar meteorology and glaciology (Memoirs of National Institute of Polar Research), Tokyo, Japan, vol 34, pp 188–196 Suzuki Y, Shimbori K (1985) Ice core drills usable for wet ice. In: Proceedings of the seventh symposium on polar meteorology and glaciology (Memoirs of National Institute of Polar Research), Tokyo, Japan, vol 39, pp 214–218

178 Suzuki Y, Shiraishi K (1982) The drill system used by the 21st Japanese Antarctic Research Expedition and its later improvement. In: Proceedings of the fourth symposium on polar meteorology and glaciology (Memoirs of National Institute of Polar Research), Tokyo, Japan, vol 24, pp 259–273 Suzuki Y, Takizawa T (1978) Outline of the drilling operation at Mizuho Station. In: Ice-coring project at Mizuho Station (Memoirs of National Institute of Polar Research), East Antarctica, 1970– 1975, vol 10, pp 1–24 Takahashi A (1996) Development of a new shallow ice core drill. J Jpn Soc Snow Ice 58(1):29–37 (In Japanese) Takahashi A (2005) Development of an ice core drill usable for warm ice. J Jpn Soc Snow Ice 67(3):245–250 (In Japanese) Takeuchi N, Fujita K, Aizen VB et al (2014) The disappearance of glaciers in the Tien Shan Mountains in Central Asia at the end of Pleistocene. Quaternary Sci Rev 103:26–33 Talalay P, Fan X, Zheng Z et al (2014) Anti-torque systems of electromechanical cable-suspended drills and tests results. Ann Glaciol 55(68):207–218 Tanzania-Mt. Kilimanjaro (2000) The ice core drill. Available at: http:// bprc.osu.edu/Icecore/KilimanjaroDrillSystem.html. Accessed 18 Jan 2015 Theodorsson P (1976) Thermal and mechanical drilling in temperate ice in Icelandic glaciers. In: Proceedings of the symposium (Ice-Core Drilling), University of Nebraska, Lincoln, USA, 28–30 Aug 1974. University of Nebraska Press, Lincoln, pp 179–189 Thompson LG, Mosley-Thompson E, Davis ME et al (1990) Glacial stage ice-core records from the subtropical Dunde Ice Cap. China Ann Glaciol 14:288–297 Thompson LG, Mosley-Thompson E, Davis ME et al (2002) Kilimanjaro ice core records: evidence of Holocene climate change in Tropical Africa. Science 298:589–593 User manual for the Eclipse ice coring drill (2012) Icefield Instruments Inc., Whitehorse, Yukon, Canada Vrana K, Baker J, Clausen HB et al (2007) Continental ice body in Dobšiná Ice Cave (Slovakia)—Part I—project and sampling phase of isotopic and chemical study. In: Proceedings of second international workshop on ice caves, Demänovská Dolina, Liptovský Mikuláš, Slovak Republic, 8–12 May 2006, pp 24–28 WAIS Divide Ice Core Project 2005/2006 (2006) End of season field reports. Investigation of climate, ice dynamics and biology using a deep ice core from the West Antarctic ice sheet ice divide WAIS Divide Ice Core Project 2006/2007 (2007) End of season field reports. Investigation of climate, ice dynamics and biology using a deep ice core from the West Antarctic ice sheet ice divide Wagenbach D (2006) A new alpine ice core recovered for long term climate reconstructions. Institut für Umweltphysik (IUP), University Heidelberg

8 Cable-Suspended Electromechanical Auger Drills Watanabe O (1996) Japanese glaciological activities in the Arctic Region. In: Proceedings of the international symposium on environmental research in the arctic (Memories National Institute Polar Research), 19–21 July 1995, Tokyo, vol 51, pp 329–336 Watanabe O, Kamiyama K, Kameda T et al (2000) Activities of the Japanese Arctic Glaciological Expedition in 1998 (JAGE 1998). Bull Glaciol Res 17:31–35 Wehrle A (1985) A shallow core-collecting mechanical ice drill. ANARE Res Notes 28:196–201 Weiler K (2008) On the composition of firn air and its dependence on seasonally varying atmospheric boundary conditions and the firn structure. Ph.D. Faculty of Natural Sciences, University of Bern Winski D (2013) Reconstructing Central Alaskan precipitation variability and atmospheric circulation over the past millennium. In Depth 7(1):4–6 Yamada T, Kondo H, Fukuzawa T (1987) Ice core drilling operations in the Northern Patagonia Icefield. Bull Glaciol Res 4:151–155 Zagorodnov V, Thompson LG (2014) Thermal electric ice-core drills: history and new design options for intermediate-depth drilling. Ann Glaciol 55(68):322–330 Zagorodnov V, Thompson LG, Kelley JJ et al (1998) Antifreeze thermal ice core drilling: an effective approach to the acquisition of ice cores. Cold Reg Sci Technol 28:189–202 Zagorodnov V, Thompson LG, Mosley-Thompson E (2000) Portable system for intermediate-depth ice-core drilling. J Glaciol 46 (152):167–172 Zagorodnov V, Thompson LG, Ginot P et al (2005) Intermediate-depth ice coring of high-altitude and polar glaciers with a lightweight drilling system. J Glaciol 51(174):491–501 Zagorodnov V, Nagornov O, Scambos TA et al (2012) Borehole temperatures reveal details of 20th century warming at Bruce Plateau, Antarctic Peninsula. Cryosphere 6:675–686 Zagorodnov V, Tyler S, Holland D et al (2014) New technique for access-borehole drilling in shelf glaciers using lightweight drills. J Glaciol 60(223):935–944 Zhang N, An C, Fan X et al (2014) Chinese first deep ice-core drilling project DK-1 at Dome A, Antarctica (2011–2013): progress and performance. Ann Glaciol 55(68):88–98 Zheng J, Fisher D, Blake E et al (2006) An ultra-clean firn core from the Devon Island Ice Cap, Nunavut, Canada, retrieved using a titanium drill specially designed for trace element studies. J Environ Monit 8:406–413 Zhu G, Han J (1994) BZXJ super light ice core drill. In: Proceedings of the fourth international workshop on ice drilling technology (Memoirs of National Institute of Polar Research), Tokyo, 20–23 Apr 1993, vol 49, pp 87–92 Zhu G, Han J, Liang S et al (1991) BZXJ, a super light-weight core drill. J Glaciol Geocryol 13(3):261–266 (In Chinese)

9

Cable-Suspended Electromechanical Drills with Bottom-Hole Circulation

In 1947, in Oklahoma (USA), the first electromechanical cable-suspended drill, the “Electrodrill,” which was designed by A. Arutunoff (1893–1978) of the REDA Pump Co. of Bartlesville (REDA is an acronym for Russian Electrical Dynamo of Arutunoff), was tested in sedimentary rocks. In this test, numerous wells were drilled as deep as *400 m. Because of the insufficient power and low drill bit weight produced by the Electrodrill, the penetration rates did not exceed 4.2 m/h. Moreover, the friction anti-torque system caused numerous accidents involving borehole wall collapses and drill sticking, resulting in the termination of these activities. In the 1940–1950s, pipeless cable-suspended drilling technology was also developed in the Soviet Union (Minin et al. 1956). To equilibrate the counter-torque, the drill bit was alternately rotated in both directions at a certain prescribed rate, and the torque of the drill bit was balanced by the inertia of the electromechanical drill housing. This project was also terminated because the achieved hole-making capability was low. In 1964, Arutunoff’s Electrodrill was modified by CRREL for glacial research. This was a turning point in ice core drilling technology. Since the first CRREL drill was implemented, at least six different electromechanical drills with near-bottom fluid circulation have been designed in the USA, Denmark, Russia, France, Germany, Switzerland, and Japan for deep ice drilling (Table 9.1): the ISTUK, KEMS, PICO-5.2″, JARE, Hans Tausen, and DISC systems. Recent intermediate and deep ice drilling projects with cable-suspended drills have succeeded at various sites in Antarctic, the Greenland ice sheets (Figs. 9.1 and 9.2), and the Russian Arctic, including four successful penetrations into the bedrock carried out by US and Russian scientists. There have been few other designs of deep electromechanical drills, including the LGGE electromechanical drill and Italian IDRA, which had some design problems, causing their development to be terminated. These drills are also discussed to a certain extent here with an eye toward learning from past mistakes. To drill through ice and

bedrock a new version of the cable-suspended IBED drill was designed and tested in the lab in China. Field tests are planned to carry in Antarctica in season 2016–2017. Just as with auger cable-suspended drills, the only connection that these drills have to the surface is through an electromechanical cable; all the powered systems are contained within the downhole unit. The rotor of the downhole electric motor produces a rotation that is transmitted through the reducer to the core barrel with the drill head. Generally, cable-suspended electromechanical drills with bottom-hole circulation can be divided into two groups: (1) intermediatedepth drilling systems for drilling up to 400–1500 m and (2) deep drilling systems for drilling deeper than 1500 m and potentially down to 4000 m. From a generic structural point of view, these systems are the same, but the intermediate-depth systems use lighter and shorter drills, smaller winches, and simpler drilling shelters to make the logistics process of deploying drilling equipment to the field easier.

9.1

CRREL Electromechanical Drill

9.1.1

Drilling Equipment

The final version of the CRREL electromechanical drill consisted of the following main sections (Fig. 9.3): the cable termination, inclinometer housing, anti-torque section, bailer, electric motor, pump and gear reducer section, and core barrel with attached drill bit (Ueda and Garfield 1969). The drill was suspended from a double-armored electromechanical cable 25.4 mm in diameter, with 12 electrical conductors (three power and nine signal lines) and a weight of 2.1 kg/m. The cable had a breaking strength of 318 kN. The steel armor of the cable was fastened to the cable termination cylinder using a low-melt temperature Cerrobend alloy containing bismuth, lead, tin, and cadmium (melting temperature *70 °C). The inclinometer housing was

© Geological Publishing House, Beijing and Springer Science+Business Media Singapore 2016 P.G. Talalay, Mechanical Ice Drilling Technology, Springer Geophysics, DOI 10.1007/978-981-10-0560-2_9

179

180

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Cable-Suspended Electromechanical Drills …

Table 9.1 Specifications of cable-suspended electromechanical deep drills with bottom-hole circulationa Drill type

CRREL

ISTUK

PICO-5.2″

KEMS

JARE

HT (North GRIP version)

DISC

Number of cutters

8

3

3

3

3

3

4

Cutting angle (°)

90

45

45

60

50; 60; 75

42.5

50

Relief angle (°)

9

8.6

NA

5

15

10

15

Cutters OD (mm)

155.6

129.5

177.5

132; 135

135

129.6

170

Cutters ID (mm)

114.3

102.3

137

107

94

98

122

Outer barrel OD (mm)

146

Single barrel

171.3

Single barrel

122

118

Single barrel

Outer barrel ID (mm)

NA

115

113

Inner barrel OD (mm)

NA

110

143.34

127

101.6

104

157

Inner barrel ID (mm)

117.6

104

137

117

97.4

100

137

Rotation speed (rpm)

225

37.5

100

230

66

50–60

80

157.1

Pitch (mm)

*0.5

9.8

10

1–1.5

2; 3; 4; 5; 6

4.2

5.9

ROP (m/h)

*7

22

60

12–20

6-20

15

28

Swept area of the cutter (cm2)

87.5

49.4

100.0

46.9; 53.2

73.7

56.5

110.0

Outer barrel/inner barrel clearance (mm)

NA

No

13.76

No

6.7

4.5

No

Borehole walls/outer barrel clearance (mm)

4.8

9.75

3.1

2.5; 4

6

5.8

6.5

Core/inner barrel clearance (mm)

1.65

0.75

0

5

1.7

1.0

7.5

Motor

Power (kW)

13

0.6a

2.2

2.2

0.6

0.3

1.8

Rotation speed (rpm)

3600

6000

2500

2800

12,000

5000

7500

Supply voltage

2300 V

48.5 V DC

DC

220 V

270 V

60 V DC

300 V DC

Type

Planetary

Harmonic drive

Planetarya

Planetary

Planetary

Harmonic drive

Harmonic drive

Ratio

16∶1

160∶1

17∶1

12∶1

170∶1

NA

30∶1

Type

Three-stage centrifugal pump (3600 rpm)

Three independent piston pumps

Progressive cavity Moyno pump (100 rpm)

Rotary plate pump (2750 rpm)

Booster (100-mm pitch)

Dual-action piston pump (2 strokes/s)

One-stage centrifugal pump (3500 rpm)

Flow rate (L/min)

303

3 × 1.12a

135

46.6

8.5

18

400

Outlet pressure (kPa)

360

NA

NA

20

0.01

1.24

NA

Length of drill/core (m)

25/6.1

11.5/2.95

27.5/6.0

12/3

8.6/2.2 (12/3.84)

11/3.8

16/3.2

Drill weight (kg)

1180

180

730

180

190 (220a)

150

NA

References

Ueda and Garfield (1969)

Gundestrup et al. (1984)

Stanford (1994)

Kudryashov et al. (1994)

Fujii et al. (1999), Takahashi et al. (2002)

Johnsen et al. (2007)

Shturmakov et al. (2007), Johnson et al. (2007)

Gear

Pump

Note Some data were taken from Augustin et al. (2007b); NA not available information; aAuthor’s estimations

9.1 CRREL Electromechanical Drill

181

Fig. 9.1 Location of wet holes cored by cable-suspended electromechanical drills in Antarctica

fabricated from 304 stainless steel and designed to permit rapid installation and removal of the inclinometer. A Parsons Survey single-shot inclinometer, sealed in a pressure-tight container and electrically triggered from the surface, was used to measure the direction and magnitude of the hole inclination from the vertical. The anti-torque system consisted of hinged friction blades designed to be thrown out against the borehole wall upon starting the drill motor. During field tests, it was discovered that the anti-torque skates would not grab. Without an operational anti-torque system, only the large-diameter armored cable was left to provide a counter-torque. Later, additional restraint was provided by two leaf springs installed outside of the blades. The bailer was located just below the anti-torque section and was modified for drilling in ice. In the original design, the cuttings were deposited in the bottom of the bailer after being removed from the path of fluid flow. Since the density of the fluid in the hole was essentially equal to the ice chip density, this technique could not be used. It was suggested that two different fluids were used in the borehole: the lower part would be filled with an aqueous ethylene glycol solution to dissolve the chips and the upper part would use an arctic blend diesel fuel (DF-A) mixed with a densifier (trichloroethylene) to compensate for the ice overburden pressure. Concentrated glycol was sent downhole in the bailer on

each coring run, the amount depending upon the downhole temperature and volume of cuttings expected. This glycol was mixed with the dilute solution downhole with the aid of an aspirator assembly and circulated along the drill by the pump. It dissolved the cuttings and was diluted to the equilibrium concentration for the downhole temperature. The net heat required for this process was obtained from the waste heat produced during the drill operation by friction in the electrical and mechanical systems. A bailer full of dilute solution was removed on each return trip of the drill to the surface with the core. The excess solution remained downhole as it was denser than, and immiscible with, the hole fluid. In theory, the glycol consumption would be *3.23 L/m at −12 °C and 7.7 L/m at −29 °C, but in practice, more glycol was consumed, because the concentration of the solution was kept slightly rich. The drill bit and pump were powered by a three-phase, submersible induction motor. The motor interior was filled with insulating oil and sealed from the ambient hole environment. A compensating piston maintained the pressure equilibrium with the downhole pressure. The glycol solution circulated through an annular space around the motor housing. The motor output was directly coupled to the pump and gear reduction section. Ice cuttings were removed from the drill bit and placed in the circulating flow, where they were eventually dissolved. A two-stage planetary gear reducer

182

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Cable-Suspended Electromechanical Drills …

Fig. 9.2 Locations of wet holes cored by cable-suspended electromechanical drills in Greenland

was sealed from the ambient fluid and pressure-compensated with the ambient pressures. The gear reducer was coupled to the core barrel through a splined, hollow drive shaft. A 0.46-m axial movement of the shaft between the gear section and core barrel permitted the core to be broken by impact if necessary. The core barrel was a double-tube, swivel-head-type capable of holding a 6-m core. The core was removed by first breaking the connection at the top of the barrel. The barrel was removed from the hole with an auxiliary hoist and inclined at a 12° angle. The cutter and core lifter were then removed, and the core was permitted to slide into an inclined trough. Two types of drill bits were used, one with plain steel teeth and one with diamond-encrusted teeth (Fig. 9.4). The steel drill bit was used in ice; the diamond bit was used in ice, silt, or rock material. The diamond bit consisted of eight tungsten carbide inserts serving as the matrix for the surface-set diamonds (Fig. 9.5a). The diamond distribution Fig. 9.3 CRREL electromechanical drill (Ueda 2007)

9.1 CRREL Electromechanical Drill

183

was 0.22–0.28 carats/stone and 8 carats/insert. The steel drill bit consisted of eight mild steel inserts (Fig. 9.5b). Tapered split-ring core lifters with external splines were used to break the core.

9.1.2

Camp Century, Greenland

Camp Century (77°11′N, 61°08′W; 1885 m a.s.l.) was the name of a subsurface military all-year-round research station operated from 1958 to 1966 by the USA on the Greenland ice, 220 km east of Thule (Dansgaard 2005). The purpose of Camp Century was to improve the American defense capability in the Arctic. A total of 32 buildings were dug into the firn, which enabled the camp to perform all the activities of a modern town. These included power stations, workshops, offices, a radio station, garages, a dump building, shops, a hospital, living quarters, a fitness center, baths, shops, canteens, storerooms, bars, a theater, a church, and a library. The buildings were connected by galleries leading to a central main street with one-way traffic comprised of various kinds of vehicles. In June 1966, a hole at Camp Century was advanced by the CRREL electromechanical drill from 535 m, where thermal drilling had been terminated in the previous year (Hansen and Langway 1966). The average rate of penetration was 12.5–15 m/min, with a *3.2 kN weight on the bit, and consumed 11–12 kW of power (Ueda and Garfield 1968a). Less than 1 kW of power went into the cutting of the ice. The core recovery was 98 %. On July 2, at a depth of 1370.5 m, ice containing a silt band with sand and small pebbles was encountered. On July 4, after drilling through 16.9 m of this material, the interface at the bottom of the ice cap was reached at a depth of 1387.4 m. The coring continued to 1391 m, until a worn bearing in the gear prevented further penetration. Figure 9.6 shows the depth reference of the hole. The subglacial material

Fig. 9.5 Diamond (a) and steel (b) bit inserts (Ueda and Garfield 1969)

Fig. 9.4 Diamond drill bit (Ueda and Garfield 1969)

consisted of a conglomerate of frozen till and rocks of various sizes; 3.55 m of this material was recovered. In the course of the subglacial bedrock drilling, the penetration rate decreased to 1.5–2.2 m/h, and the weight on the bit increased to 8 kN, with the power input rising to 16 kW. The subglacial material was a mixture of cobbles, fragments, and dirty ice, and consisted of *50–60 % crystalline ice (Fountain et al. 1981). In the upper 600 m, the borehole was almost vertical (