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Ground Support for Underground Mines Ground Support for underground mines Yves Potvin & John Hadjigeorgiou Australian Centre for Geomechanics Copyright and Disclaimer © Copyright 2020. Australian Centre for Geomechanics, The University of Western Australia. All rights reserved. No part of this publication may be reproduced, stored or transmitted in any form without the prior permission of the Australian Centre for Geomechanics, The University of Western Australia. The information contained in this publication is for general educational and informative purposes only. Except to the extent required by law, the Australian Centre for Geomechanics, The University of Western Australia, makes no representations or warranties, express or implied, as to the accuracy, reliability or completeness of the information stored therein. To the extent permitted by law, the Australian Centre for Geomechanics, The University of Western Australia, exclude all liability for loss or damage of any kind at all (including indirect or consequential loss or damage) arising from the information in this publication or use of such information. You acknowledge that the information provided in this publication is to assist you with undertaking your own enquiries and analyses and that you should seek independent professional advice before acting in reliance on the information contained herein. While all care has been taken in presenting the information herein, no liability is accepted for errors or omissions. The views expressed in this publication are those of the authors and may not necessarily reflect those of the Australian Centre for Geomechanics, The University of Western Australia. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Production team: Paul Burnett, Garth Doig, Candice McLennan, Christine Neskudla, Josephine Ruddle and Stefania Woodward, Australian Centre for Geomechanics; Kerry Coyle, Coyle Editing Services; and Ian Pavey, Vectis Digital Graphics. Cover photograph by John Hadjigeorgiou, with permission from Agnico Eagle Mines Ltd. ISBN 978-0-9876389-5-3 Australian Centre for Geomechanics The University of Western Australia 35 Stirling Highway (M600) CRAWLEY, WESTERN AUSTRALIA AUSTRALIA 6009 Telephone: +61 8 6488 3300 [email protected] www.acg.uwa.edu.au ABN 37 882 817 280 ii Preface Recent years have seen considerable progress in In preparing the book, we have been fortunate to ground support technology and design techniques in have the support of many practising ground support underground mines, resulting in significant advances and mining engineers worldwide. Numerous in safety and productivity. This book came about as colleagues made important contributions to specific a direct recommendation from the sponsors of the chapters. In particular, Associate Professor Johan Ground Support Systems Optimisation (GSSO) Wesseloo, William Joughin and Joseph Mbenza, as research project conducted by the Australian Centre well as Philani Mpunzi and Denisha Sewnun, for Geomechanics and initiated in 2011. A strong contributed to Section 5 on ‘Probabilistic approach consensus emerged for a state-of-the-art book on to ground support design’. Professor Phil Dight ground support technology and design techniques contributed to Chapter 6 on ‘Rock stress data’, for underground mines. while Gordon Sweby co-authored Chapter 11: Ground Support for underground mines was ‘Numerical modelling for ground support design written to provide a comprehensive reference book – mining applications’. Emeritus Professor Dick for practising geotechnical and mining engineers Stacey, Dr Peter Mikula and Associate Professor faced with the task of designing ground support Johan Wesseloo reviewed the manuscript and systems in underground mines. In this context, made several insightful comments and suggestions the authors reviewed international best practices for improvement. The authors are indebted for and describe existing and novel ground support all their help and gratefully acknowledge their design methods. Throughout the book there is an contributions. We further acknowledge the many emphasis on both theory and practical tools to aid individuals, publishers and organisations who gave practising engineers in all steps of the ground support permission for the reproduction of data, figures design process. and photos. In practice, the selection of ground support Funding for the development of this book systems is not only dictated by the design process and was provided by the Ground Support Systems rock engineering criteria but also by other factors, Optimisation research project Phase 1. Major including workforce skill level, access to ground sponsors were: Minerals Research Institute of Western support supplies, local mining culture and corporate Australia (MRIWA), Codelco Chile, Glencore Mount risk tolerance. These can have a significant influence Isa Mines, IGO Limited, MMG Limited, and the on ground support strategies and installation Australian Centre for Geomechanics. Minor project practices. Nevertheless, given that ground support sponsors were: Atlas Copco Australia Pty Limited failures can have catastrophic consequences, every (now Epiroc), DSI Underground, Fero Strata Australia ground support system implemented in mines (now DSI Underground), Golder Associates Pty Ltd, should be justified by sound engineering design Geobrugg AG, and Jennmar Australia. principles. Ground Support for underground mines has been specifically written to assist practitioners in fulfilling this requirement. Yves Potvin & John Hadjigeorgiou iii Industry Sponsors The Australian Centre for Geomechanics gratefully acknowledges the industry sponsors who provided funding for the development of this book by supporting the ACG Ground Support Systems Optimisation research project Phase 1. Major Project Sponsors Minerals Research Institute of Western Australia Minor Project Sponsors ® iv Contents Preface Industry Sponsors Contents Section 1 : Ground support selection and design considerations Chapter 1 : Introduction 1.1 The principal objective of ground support ..................................................................................... 3 1.2 Ground conditions .............................................................................................................................. 5 1.2.1 Normal conditions .................................................................................................................. 6 1.2.2 High stress conditions ........................................................................................................... 8 1.2.3 Large deformations ................................................................................................................ 8 Chapter 2 : Rock mass behaviour and failure mechanisms 2.1 Introduction ....................................................................................................................................... 15 2.2 Loading and failure mechanisms ................................................................................................... 15 2.2.1 Gravity failures driven by stress relaxation ......................................................................... 18 2.2.2 Failures driven by compressive stress ............................................................................... 19 2.2.2.1 Progressive or brittle failure (stiff loading) ......................................................... 20 2.2.2.2 Sudden and violent failure (soft loading) .......................................................... 21 2.3 Summary of typical failure mechanisms in underground mines ............................................... 23 2.4 Stress path ......................................................................................................................................... 23 Chapter 3 : Rock reinforcement behaviour, anchoring mechanisms and specifications 3.1 Introduction ....................................................................................................................................... 27 3.2 Rock reinforcement behaviour ....................................................................................................... 27 3.2.1 Strong versus weak rock reinforcement ............................................................................ 28 3.2.2 Stiff versus soft reinforcement elements ............................................................................ 28 3.2.3 Post-peak behaviour: brittle versus ductile ...................................................................... 29 3.2.4 Low versus high energy absorption rock reinforcement .................................................. 30 3.2.5 Rock reinforcement and rock mass behaviour ................................................................. 30 3.3 Point anchor bolts ............................................................................................................................ 32 3.4 Continuous anchor bolts ................................................................................................................. 35 3.4.1 Continuous chemically bonded anchor bolts .................................................................... 35 3.4.1.1 Resin anchor bolts ............................................................................................ 36 3.4.1.2 Cement-grouted continuous anchor bolts ..................................................... 37 v 3.4.2 Continuous friction
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