ELSEVIER GEO-ENGINEERING BOOK SERIES VOLUME 5 Part 1 potx

The authors have placed their emphasis in exactly the right area because it ismuch more difficult to tunnel in a soft, weak rock mass than in a stiff, strong rock mass.Also, they have set

Tunnelling in Weak Rocks

Practicing Engineers, Scientists,

Academicians & Readers

Tunnelling in Weak Rocks

Bhawani Singh

Professor (Retd), IIT Roorkee

Rajnish K Goel

Scientist F CMRI Regional Centre Roorkee, India

Geo-Engineering Book Series Editor

John A Hudson FREng

Imperial College of Science, Technology and Medicine,

University of London, UK

2006

AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD

PARIS • SAN DIEGO • SINGAPORE • SYDNEY • TOKYO

P.O Box 211, 1000 San Diego, CA 92101-4495 Kidlington, Oxford London WC1X 8RR

AE Amsterdam USA OX5 1GB, UK UK

The Netherlands

© 2006 Elsevier Ltd All rights reserved.

This work is protected under copyright by Elsevier Ltd, and the following terms and conditions apply to its use: Photocopying

Single photocopies of single chapters may be made for personal use as allowed by national copyright laws Permission of the Publisher and payment of a fee is required for all other photocopying, including multiple or systematic copying, copying for advertising or promotional purposes, resale, and all forms of document delivery Special rates are available for educational institutions that wish to make photocopies for non-profit educational classroom use.

Permissions may be sought directly from Elsevier’s Rights Department in Oxford, UK: phone (+44) 1865

843830, fax (+44) 1865 853333, e-mail: permissions@elsevier.com Requests may also be completed on-line via the Elsevier homepage (http://www.elsevier.com/locate/permissions).

In the USA, users may clear permissions and make payments through the Copyright Clearance Center, Inc.,

222 Rosewood Drive, Danvers, MA 01923, USA; phone: (+1) (978) 7508400, fax: (+1) (978) 7504744, and in the UK through the Copyright Licensing Agency Rapid Clearance Service (CLARCS), 90 Tottenham Court Road, London W1P 0LP, UK; phone: (+44) 20 7631 5555; fax: (+44) 20 7631 5500 Other countries may have

a local reprographic rights agency for payments.

Derivative Works

Tables of contents may be reproduced for internal circulation, but permission of the Publisher is required for external resale or distribution of such material Permission of the Publisher is required for all other derivative works, including compilations and translations.

Electronic Storage or Usage

Permission of the Publisher is required to store or use electronically any material contained in this work, including any chapter or part of a chapter.

Except as outlined above, no part of this work may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior written permission of the Publisher.

Address permissions requests to: Elsevier’s Rights Department, at the fax and e-mail addresses noted above Notice

No responsibility is assumed by the Publisher for any injury and/or damage to persons or property as a matter

of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein Because of rapid advances in the medical sciences,

in particular, independent verification of diagnoses and drug dosages should be made.

First edition 2006

Elsevier

British Library Cataloguing in Publication Data

Singh, Bhawani

Tunnelling in weak rocks - (Elsevier geo-engineering book series; v 5)

1 Tunneling 2 Tunnels - Design 3 Rock mechanics

I Title II Goel, R K 1960-624.1’93

ISBN 13: 978-0-08-044987-6

ISBN 10: 0-08-044987-5

Typeset by Cepha Imaging Pvt Ltd, Bangalore, India

Printed in Great Britain

The objective of the Elsevier Geo-Engineering Book Series is to provide high quality books

on subjects within the broad geo-engineering subject area – e.g on engineering geology,soil mechanics, rock mechanics, civil/mining/environmental/petroleum engineering, etc.The first four books in the Series have already been published:

• “Stability Analysis and Modelling of Underground Excavations in FracturedRocks” by Weishen Zhu and Jian Zhao;

• “Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geo-systems” edited

by Ove Stephansson, John A Hudson and Lanru Jing;

• “Ground Improvement – Case Histories” edited by Buddhima Indraratna andJian Chu; and

• “Engineering Properties of Rocks” by Lianyang Zhang

Now, I am pleased to introduce “Tunnelling in Weak Rocks” by Bhawani Singh andR.K Goel The authors have placed their emphasis in exactly the right area because it ismuch more difficult to tunnel in a soft, weak rock mass than in a stiff, strong rock mass.Also, they have set their stage in the Himalayas which is an exciting setting, not only onthe surface but often even more so underground!

Readers will recall the 1999 Elsevier book written by the same authors: “Rock MassClassification: A Practical Approach in Civil Engineering” This earlier book has proved

to be a most useful reference source because all the key information relating to rockmass classification is contained in the book and so one automatically takes it off the shelfwhenever there is a question about the rock mass classification approach or the associateddetails The authors have adopted the same approach with “Tunnelling in Weak Rocks”:they provide 29 chapters covering all aspects of the subject, including theory, reviews ofrock mass classification approaches, the different types of tunnelling methods, excavationand support, hazards, instrumentation, swelling and squeezing rock conditions and manyother practical aspects of tunnelling

We hope that you enjoy the book and we welcome proposals for new books Pleasesend these to me at the email address below

Professor John A Hudson FREng

Geo-Engineering Series Editor

jah@rockeng.co.uk

“A book is a man’s best friend.”

Groucho Marx

The basic approach in the design of underground support system has been an empiricalapproach based on rock mass classification This approach was the subject of the authors’

first book, Rock Mass Classification – A Practical Approach in Civil Engineering (1999),

which has been enjoyed by the experts all over the world Lately, however, a growingneed for reliable software packages to aid engineering control of landslide and tunnelling

hazards has inspired the writing of the next book on Software for Engineering Control of

Landslide and Tunnelling Hazards based on the use of a rational approach to check the

empirical predictions to be sure of the solution

The instant liking and success of these two books further boosted our morale and

we have written this book on Tunnelling in Weak Rocks, which is based on intensive

field-oriented research work and experience It is expected that the book will generatemore confidence and interest among civil and mining design and construction engi-neers, geologists, geophysicists, managers, planners, researchers and students The set

of three complementary books that we have produced has been possible due to God’sgrace, team-work and worldwide acceptance and moral support

Emphasis is given to the practical-construction solution of tunnelling hazard trol rather than any rigorous analytical/numerical methods Practical knowledge ofthe engineering behavior of rock masses, discontinuities, the time-tested classificationapproach, tunnelling hazards, and simple analytical methods are also offered to add to theunderstanding of realistic actual construction approach

con-We have been blessed by modern tunnelling machines and shielded TBM with matic support system to bore rapidly through soils, boulders and weak rocks, etc By thegrace of God, the modern tunnel engineers have tremendous confidence now This bookalso tries to integrate the happy experience of tunnel engineers, managers, reputed fieldresearchers and famous site engineering geologists from all over the world This bookmay help in on-spot-decisions during tunnelling

auto-Himalaya is a vast region, an amazingly beautiful creation which possesses sive rejuvenating life support system It is also one of the best field laboratories for

exten-learning rock mechanics, tunnelling, engineering geology and geohazards The researchexperience gained in Himalaya is precious to the whole world.

The authors are deeply grateful to Professor J A Hudson, Imperial College of Scienceand Technology, London, and President-elect, International Society for Rock Mechanics(ISRM) for continuous encouragement and for including this book in the Elsevier Geo-Engineering Series The authors are also thankful to Elsevier Limited for publishingthe book

The authors’ foremost wish is to express their deep gratitude to: Professor CharlesFairhurst, University of Minnesota; Professor E Hoek, International ConsultingEngineer; Dr N Barton, Norway; Professor J.J.K Daemen, University of Nevada;

Dr E Grimstad, NGI, Professor G.N Pandey, University of Swansea; Professor

J Nedoma, Academy of Sciences of Czech Republic; Professor Zhao Jian, Nanyang nological University, Singapore; Professor V.D Choubey; Professor T Ramamurthy,IITD; Dr R.K Bhandari, CSIR; Mr B.B Deoja, Nepal; Mr A Wagner, Switzerland;Professor R.N Chowdhary, Australia; Professor S Sakurai, Japan; Dr R Anbalagan,IITR; Professor M Kwasniewski, Poland; Dr B Singh; Professor B.B Dhar,

Tech-Dr N.M Raju, Tech-Dr A.K Dube, Tech-Dr J.L Jethwa, Tech-Dr V.M Sharma, ATES; Late ProfessorL.S Srivastava; Professor Gopal Ranjan, COER; Professor P.K Jain, IITR; ProfessorM.N Viladkar, IITR; Dr A.K Dhawan, CSMRS; Dr V.K Mehrotra; Dr H.S Badrinath;

Dr Prabhat Kumar, CBRI; Dr P.P Bahuguna, ISM; Dr Subhash Mitra, Uttaranchal gation Department; Dr R.B Singh, Tala Hydroelectric Project, Bhutan; Dr MahendraSingh, IITR; Dr N.K Samadhiya, IITR; Mr H.S Niranjan, HBTI and Dr Rajesh

Irri-K Goel, ONGC for their constant moral support and vital suggestions and for freelysharing precious field data The authors are also grateful to the scientists and engineers

of CMRI, CSMRS, UPIRI, IIT Roorkee, IIT Delhi and ATES, AIMIL, HEICO, VSEngineering Services, New Delhi and to all project authorities for supporting the fieldresearches The authors are also grateful to Mr N.P Atterkar and Mr Sandesh Atterkar,Soilex Ltd., Roorkee for kind support Special thanks to Dr Daya Shankar, IITR and

Dr A.K Chakraborty, CMRI for sharing their research work and contributing chapters

on “Application of Geophysics .” and “Blasting for Tunnels and Roadways”,

respec-tively Thanks to Professor Yuzuru Ashdia, Kyoto University, Japan for allowing us touse his work in Chapter 2

The authors are also very grateful to their families and friends for their ficing spirit Without their support the writing of this book would have been verydifficult

sacri-The authors also thank A.A Balkema, the Netherlands; American Society of CivilEngineers (ASCE), Reston; Ellis Horwood, U.K.; Institution of Mining & Metallurgy,London; John Wiley & Sons, Inc., New York; Springer-Verlag, Germany; Trans Tech.,Germany; Wilmington Publishing House, U.K.; Van Nostrand Reinhold, New York;ICIMOD, Kathmandu; Bureau of Indian Standards, India, for their kind permission toreproduce material and also to all eminent professors, researchers and scientists whosework is referred to in the book

All engineers and geologists are requested to kindly send their precious suggestionsfor improving the book to the authors for the future editions.

2.3 Prediction ahead of tunnel face with source placed on face 12

3.4 Modified Terzaghi’s theory for tunnels and caverns 32

5.3 Updating the Q-system 58

6.5 Effect of tunnel size on support pressure 826.6 Correlations for estimating tunnel closure 856.7 Effect of tunnel depth on support pressure and closure in tunnels 866.8 Approach for obtaining ground reaction curve (GRC) 86

7.7 Dynamic shear strength of rough rock joints 997.8 Theory of shear strength at very high confining stress 997.9 Normal and shear stiffness of rock joints 101

8.2 Effect of intermediate principal stress on tangential stress at

8.3 Uniaxial compressive strength of rock mass 1068.4 Reason for strength enhancement in tunnels and a new failure theory 108

8.6 Criterion for squeezing/rock burst of rock masses 1138.7 Tensile strength across discontinuous joints 114

8.8 Dynamic strength of rock mass 115

9.2 Development of construction and lining methods 120

11.6 Parameters influencing tunnel blast results 15611.7 Models for prediction of tunnel blast results 162

12.6 Reinforcement of jointed rock mass around openings 195

13.3 Empirical approach for predicting degree of squeezing 212

14.7 Measurement of rock mass behavior around an underground

16.3 Penetration and advance rates 253

16.5 Penetration and advance rate vs QTBM 254

17.4 Building condition survey and vibration limit 263

19.6 Face advance for stabilization of broken zone 285

19.8 Strain criterion of squeezing ground condition 288

20.5 Tunnel construction and instrumentation in intra-thrust zone

23.2 Minimum overburden above a pressure tunnel 346

23.4 Cracked plain cement concrete lining 347

23.6 Hydraulic fracturing near junction of pressure tunnel

24.4 Support pressures on the wall of shaft 357

28.5 Selection of type of support system 405

28.12 Design of integrated support system 433

AI.1 Elastic stress distribution around circular tunnels 455AI.2 Proposed elasto-plastic theory of stress distribution in broken zone

Appendix II Software TM for empirical design of support system

AII.3 Experience in poor rock conditions 469

Classical books of Szechy (1967), Bienisawski (1984), Bickel et al (1997) and Hoek

et al (1995) deal with the subject of tunnelling generally in hard rocks Bieniawski(1984) have given the history of tunnelling which is very interesting Fascinating underseatunnels (immersed tube road and rail tunnels all over the world) have been described byCulverwell (1990) Himalayan region is the best field laboratory to learn Rock Mechanicsand Tunnelling Technology for weak rocks Thus, the experiences of tunnelling in thetectonically disturbed, young and fragile Himalaya are precious for the tunnel engineersall over the world The Himalaya provides the acid tests for the theories and tunnellingtechnologies Therefore, Himalaya is a boon for all of us

Prof Charles Fairhurst once said that only a strategy of tunnelling can be designed.The design of support system may not be possible in complex geological and geohydrolog-ical conditions Geologically complex and high mountains have big EGO (ExtraordinaryGeological Occurrences) problems Geological surprises are common along deep andlong tunnels (>1 km long) in young and tectonically disturbed high mountainous terrains.Geological surprises (faults/shear zones) may be discovered even after the completion

of a tunnel Thus, the designed strategy should be flexible enough to strengthen the nel locally near unexpected geological weaknesses, whenever discovered Thus planningshould be flexible and not rigid unlike in other civil engineering projects In hard rocks,the art of tunnelling has evolved into a science of tunnelling with the Grace of God

tun-Tunnelling in Weak Rocks

B Singh and R K Goel

Exploration is the weakest link in a deep long tunnelling project There are practicaldifficulties in making drill-holes along a long and deep tunnel alignment in mountainousterrain as neither drilling machine can be transported on mountain top nor water is avail-able Generally exploration pits are made to get some idea of geological cross section.But errors of extrapolation of rock layers on the basis of observed dips at the top may beserious in a folded and faulted strata Adits are generally made for geological exploration.Civil engineers need the engineering geological cross section in addition to a reliablegeological cross section Civil engineers should, therefore, drill a probe hole behind thetunnel face for an advance knowledge of the tunnelling ground conditions This probe holemay also act as drainage hole in unknown water-charged strata Engineering judgmentplays a very important role during tunnelling in the weak rocks.

The properly designed tunnel boring machine (TBM) is a good choice in the

homoge-neous rock masses in the non-squeezing ground condition (H < 350 Q1/3m) without shearzones and non-flowing rock conditions Engineers should not use TBM where engineer-ing geological investigations have not been done in detail and the rock masses are veryheterogeneous Contractors can design TBM according to the given rock mass conditionswhich are nearly homogeneous (Bhasin, 2004)

Tunnel mechanics plays an important role in planning and construction of tunnels

A deep and long tunnel should be carefully planned to avoid too high overburden causingsqueezing ground condition or rock bursts; water charged or active faults and flowingground conditions It should be realized that the same strata which is safe may pose severetunnelling problems when met again along a tunnel alignment but under a very highoverburden Tunnelling was done before tunnel mechanics was developed around 1970.Tunnelling hazards are better understood now and are tackled more effectively Rockengineers and engineering geologists should be employed at major tunnelling projectsfor safety of workers and tackling the tunnelling hazards, etc Good support will reducethe cost over-runs and delays in completion of tunnels Section 4.6 and Figs 11.2–11.6underline the importance of geological investigations in the deep and long tunnels withinthe young mountains

The combined New Austrian Tunnelling Method (NATM) and Norwegian Method ofTunnelling (NMT) have been used extensively in the conventional method of tunnelling

by drilling and blasting Tunnelling machines are very helpful in rapid excavation andsupporting The NATM (Chapter 9) gives strategy of tunnelling through various groundconditions The NMT (Chapter 10) offers a design chart for support system The steel fiberreinforced shotcrete (SFRS) is fortunately found to be generally successful in supportingweak rocks and mild to moderate squeezing grounds The full-column grouted rock bolts(grouted anchors) are better choice than pre-tensioned rock bolts in supporting weak rocks.Naturally SFRS with grouted rock bolts is the ideal choice in case of weak rocks wherefeasible It should be understood that high support pressures be reduced significantly

by allowing certain amount of tunnel closures in the case of squeezing grounds neers and geoscientists should be congratulated for safe tunnelling in the modern times.The fear of tunnelling at great depths (>1000 m) is no more there This book tries to offer

Engi-a modern integrEngi-ated strEngi-ategy of tunnelling through weEngi-ak rocks for twenty-first century(Chapter 28).

Management conditions affect the rate of tunnelling surprisingly sometimes morethan the geological conditions Therefore, improvement in the management condition

is very important The managers must make efforts to make the contractors successful

and efficient in challenging jobs like tunnelling in weak and disturbed rocks The spirit

of co-operation and commitment (i.e., mutual trust and benefit) should be created by executives Risk management is specially important in tunnelling Contractors should

insure lives of workers and TBM and tunnelling machines All the willpower of civilengineers is concentrated on the fast completion of a project Their psychology is not totolerate any hindrance in the enthusiasm of construction activity A tunnel instrumentation

is, therefore, disliked by civil engineers at the tunnelling project In fact, all that we havelearnt today about Rock mechanics is due to tunnel instrumentation The reliable andcontinuous monitoring by modern tunnel instruments is the key to success in tacklingunexpected tunnelling hazards This is shown by extensive experiences of Central MiningResearch Institute in India

The later half of twentieth century has been called as the dawn of the golden era oftunnelling all over the world Nothing succeeds like success In about 50 years, manydeep and long tunnels were built through the Alps and the Rocky mountains The 34 kmlong Loetschberg tunnel under Swiss Alps, set to open to trains in 2007 is now the longestover land tunnel Another tunnel – 58 km long Gotthard tunnel parallel to the Loetschbergtunnel will be the world’s longest tunnel when it is completed by 2020

The tunnel engineers, geologists and managers should be trained for the challenges

of the future Bieniawski (1984) suggested that the following lessons should be learntfrom the precious past field experiences

1 Tunnelling in hard rocks has now become a science from the empirical art oftunnelling

2 The great advances in tunnelling technology were due to team efforts but oftendepended upon the leadership of a single man

3 The engineer’s ingenuity has been amply proved in the past but full potential isyet to be discovered and many new inventions and breakthroughs are awaiting us

in the future A Rock engineer should be in charge of a tunnelling project for itsefficient management

4 Modern shielded tunnel boring machine may be successful in all homogeneousrocks, soils, boulders and fault zones, etc

Due to the Grace of God, the future of tunnelling and underground space nology appears to be good Under city bypass tunnels along highways is becomingpopular as in Australia Demand for multiple level underground metros with many lanes

tech-is increasing rapidly The expectation tech-is that automation in tunnelling even in weakrocks will advance rapidly Drinking water tunnel network is an immediate necessity

in over-populated nations Interlinking of rivers is also feasible on large scale Undersea tunnels are going to catch up imagination of planners A Tunnel between Londonand New York is being planned in Atlantic Ocean Underground cities may be feasibleeconomically by the end of twenty-first century United States of America invented rockmelting drilling machine in 1972 It is learnt that a TBM is developed on this principle.

It uses a tiny nuclear reactor to heat its head to about 2000◦C It thereby burns the rockmass into a gas Thus a tunnel of glassy rock is created But it is a very costly method

of tunnelling Norway is experimenting upon floating tunnels on the lakes and oceans.Vision is very good Future engineers and scientists are going to be very bold and mostefficient in using energies

The underground structures are permanent property of the people, protected from allkinds of natural disasters, unlike surface structures in the disaster prone regions which aretemporary property of the people

REFERENCES

Bhasin, R (2004) Personal communication with Prof Bhawani Singh, IIT Roorkee, India

Bickel, J O., Kuesel, T R and King, E H (1997) Tunnel Engineering Handbook 2nd edition,

Asian edition, Chapman & Hall Inc., New York and CBS Publishers, New Delhi, 544

Bieniawski, Z T (1984) Rock Mechanics Design in Mining and Tunnelling A A Balkema, 272 Hoek, E., Kaiser, P K and Bawden, W F (1995) Support of Underground Excavations in Hard

Rock A A Balkema, 215.

Szechy, K (1967) The Art of Tunnelling Akademiai Kiado, Budapest, 891.

Application of geophysics in tunnelling and

“And so geology, once considered mostly a descriptive and historical science, has in recent years taken on the aspect of an applied science Instead of being largely

speculative as perhaps it used to be, geology has become factual, quantitative, and immensely practical It became so first in mining as an aid in the search for metals; then

in the recovery of fuels and the search for oil; and now in engineering in the search for more perfect adjustment of man’s structures to nature’s limitations and for greater safety

in public works.”

Charles P Berkey, Pioneer Engineering Geologist, 1939

A modern technique in underground construction needs to use modern knowledge, which

is state-of-the-art At turn of the millennium, and with the ever increasing number ofunderground excavations, it has become all the more important that excavations are madeeconomically and are safe The modern geophysical techniques, the concept and method-ology, and its application in underground construction especially in tunnels have beendiscussed in this chapter

Initial development of geophysical techniques to determine the geological structure ofthe sub-surface was stimulated primarily by the search for potential reservoirs of petroleumand natural gas Today, geophysical techniques are being developed for application notonly to the search for deeper reservoirs of petroleum and natural gas, i.e., depths of theorder of several kilometers, but also underground openings i.e., depths of the order of

100 m or less below surface, driven by the need to make effective use of undergroundspace This trend has been promoted by recently established special regulations governingpublic use of underground space in many countries

2.1 GEOPHYSICAL EXPLORATION

Geophysical exploration may be defined as the application of non-invasive (i.e., no vations) techniques for identification of sub-surface structures and the associated physical

exca-∗Contributed by Dr Daya Shankar, Department of Earthquake Engineering, IIT Roorkee, India.

Tunnelling in Weak Rocks

B Singh and R K Goel

properties of the rocks The location and distribution of faults and fractured zones arenow routinely identified by geophysical techniques.

Table 2.1 shows the geophysical techniques currently used and the geophysical nomenon on which they are based Fig 2.1 summarizes the various techniques in terms

phe-of their application in forward and inverse analysis procedures

Forward analysis defines techniques that are designed to acquire geophysical datawith a high S/N (signal to noise amplitude) ratio, whereas inverse analysis concernstechniques designed to reconstruct the structure of the sub-surface with high resolution

by interpretation of this data The S/N ratio is defined by equation (2.1) (Ashida, 2001)

dB (decibel) = 20 log10S/N (2.1)Where dB is the ratio expressed in decibels

Resolution defines the ability to separate two features In terms of geological structure,this is measured by the ability to distinguish thin layers In the case of a reflection seismicsurvey, the resolution in the vertical direction is limited to one-quarter of the wavelength

For example, if the seismic velocity (V ) of a wave is 2000 m/s and the frequency ( f )

Table 2.1 Geophysical exploration techniques and geophysical phenomenon

Seismic exploration Reflection and refraction of seismic waves

Electric sounding Resistivity and induced polarization phenomenon

Electromagnetic method Induction phenomenon

Magnetic survey Susceptibility

Radiometric survey Scattering phenomenon of γ-ray, radon

Geothermal prospecting Geothermal phenomenon of geothermal gradient,

heat fluxWell log Geophysical prospecting using borehole

Geotomography Geophysical prospecting between boreholes

-

-Forward Problem Improvement of S/N ratio Data acquisition Data processing

Data processing & interpretation Improvement of resolution Inverse problem & inversion

Geophysical

Structure

Geophysical Data

Fig 2.1 Forward and inverse problem in geophysical techniques