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
ELSEVIER GEO-ENGINEERING BOOK SERIES VOLUME 5
2006
AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD PARIS • SAN DIEGO • SINGAPORE • SYDNEY • TOKYO
Contents
Series Preface v
Preface vii
1 Introduction 1
References 4
2 Application of geophysics in tunnelling and site survey activities 5
2.1 Geophysical exploration 5
2.2 Examples of application 7
2.3 Prediction ahead of tunnel face with source placed on face 12
2.4 Application to construction site 17
References 22
3 Terzaghi’s rock load theory 25
3.1 Introduction 25
3.2 Rock classes 25
3.3 Rock load factor 27
3.4 Modified Terzaghi’s theory for tunnels and caverns 32
References 35
4 Rock mass rating (RMR) 37
4.1 Introduction 37
4.2 Collection of field data 38
4.3 Estimation of rock mass rating 41
4.4 Applications of RMR 43
4.5 Precautions 47
4.6 Tunnel alignment 49
References 49
5 Rock mass quality Q 51
5.1 The Q-system 51
5.2 The joint orientation and the Q-system 58
5.3 Updating the Q-system 585.4 Collection of field data 59
5.5 Classification of the rock mass 61
5.6 Estimation of support pressure 61
5.7 Unsupported span 67
5.8 Rock mass characterization 69
5.9 Concluding remarks 74
References 74
6 Rock mass number 77
6.1 Introduction 77
6.2 Interrelation between Q and RMR 78
6.3 Prediction of ground conditions 81
6.4 Prediction of support pressure 81
6.5 Effect of tunnel size on support pressure 82
6.6 Correlations for estimating tunnel closure 85
6.7 Effect of tunnel depth on support pressure and closure in tunnels 86
6.8 Approach for obtaining ground reaction curve (GRC) 86
References 88
7 Strength of discontinuities 91
7.1 Introduction 91
7.2 Joint wall roughness coefficient (JRC) 92
7.3 Joint wall compressive strength (JCS) 95
7.4 Joint matching coefficient (JMC) 96
7.5 Residual angle of friction 97
7.6 Shear strength of joints 97
7.7 Dynamic shear strength of rough rock joints 99
7.8 Theory of shear strength at very high confining stress 99
7.9 Normal and shear stiffness of rock joints 101
References 101
8 Strength enhancement of rock mass in tunnels 103
8.1 Causes of strength enhancement 103
8.2 Effect of intermediate principal stress on tangential stress at
failure in tunnels 104
8.3 Uniaxial compressive strength of rock mass 106
8.4 Reason for strength enhancement in tunnels and a new failure theory 108
8.5 Critical strain of rock mass 111
8.6 Criterion for squeezing/rock burst of rock masses 113
8.7 Tensile strength across discontinuous joints 114
8.8 Dynamic strength of rock mass 115
8.9 Residual strength parameters 116
References 116
9 The new Austrian tunnelling method 119
9.1 Old tunnelling practice 119
9.2 Development of construction and lining methods 120
9.3 Modern tunnelling methods 120
9.4 Temporary supports 121
9.5 Philosophy of NATM 124
9.6 Final dimensioning by measurement 128
9.7 Concluding remarks 130
References 132
10 Norwegian method of tunnelling 133
10.1 Introduction 133
10.2 Unsupported span 134
10.3 Design of supports 135
10.4 Design of steel fiber reinforced shotcrete 136
10.5 Drainage measures 148
10.6 Experiences in poor rock conditions 148
10.7 Concluding remarks 149
References 150
11 Blasting for tunnels and roadways 151
11.1 Introduction 151
11.2 Blasting mechanics 152
11.3 Blast holes nomenclature 153
11.4 Types of cut 154
11.5 Tunnel blast performance 156
11.6 Parameters influencing tunnel blast results 156
11.7 Models for prediction of tunnel blast results 162
11.8 Blast design 167
References 177
12 Rock bolting 183
12.1 General 183
12.2 Types of rock bolts 183
12.3 Selection of rock bolts 188
12.4 Installation of rock bolts 190
12.5 Pull-out tests 192
12.6 Reinforcement of jointed rock mass around openings 195
12.7 Bolting pattern 201
12.8 Floor bolting 201
References 201
13 Tunnelling hazards 203
13.1 Introduction 203
13.2 The tunnelling hazards 205
13.3 Empirical approach for predicting degree of squeezing 212
13.4 Sudden flooding of tunnels 213
13.5 Chimney formation 214
13.6 Environmental hazards due to toxic or explosive gases and
geothermal gradient 214
13.7 Interaction between rock parameters 217
13.8 Concluding remarks 217
References 222
14 Tunnel instrumentation 223
14.1 Introduction 223
14.2 Basic considerations and requirements for the design
of an opening in rock 223
14.3 Data requirement 224
14.4 Instrumentation for tunnelling 226
14.5 Stress field 226
14.6 Support pressure in tunnels 230
14.7 Measurement of rock mass behavior around an underground
opening by borehole extensometer 233
14.8 Case histories 234
14.9 Layout of a typical test section 238
References 239
15 Tunnelling machines 241
15.1 General 241
15.2 System’s mis-match 241
15.3 Tunnel jumbo 242
15.4 Muck hauling equipment 244
15.5 Tunnel boring machine (TBM) 245
15.6 Safety during tunnelling 247
References 248
16 Rock mass quality for tunnel boring machines (QTBM) 249
16.1 Introduction 249
16.2 Q and QTBM 249
16.3 Penetration and advance rates 253
16.4 Cutter wear 253
16.5 Penetration and advance rate vs QTBM 254
16.6 Estimating time for completion 254
References 255
17 Metro tunnels 257
17.1 Introduction 257
17.2 Shielded tunnel boring machines 260
17.3 Precast lining 262
17.4 Building condition survey and vibration limit 263
17.5 Impact on the structures 263
17.6 Subsidence 265
17.7 Portal and cut slopes 265
References 266
18 Tunnelling in swelling rocks 269
18.1 Introduction 269
18.2 Support pressures in swelling ground 270
18.3 Variation of support pressure with time 272
18.4 Case histories 274
18.5 Design approach 276
References 276
19 Tunnelling through squeezing ground condition 279
19.1 Introduction 279
19.2 Criterion for squeezing ground condition 280
19.3 Elasto-plastic theory of squeezing ground 281
19.4 Displacements of tunnel walls 282
19.5 Compaction zone within broken zone 284
19.6 Face advance for stabilization of broken zone 285
19.7 Ground response curve 285
19.8 Strain criterion of squeezing ground condition 288
19.9 Support design 291
References 292
20 Case history of tunnel in squeezing ground 295
20.1 Introduction 295
20.2 Regional geology, tunnelling problems and alternative layouts 295
20.3 Tectonic activity and tunnel lining 303
20.4 Tunnel construction and instrumentation in the intra-thrust zone
at Kalawar 306
20.5 Tunnel construction and instrumentation in intra-thrust zone
at Chhibro 311
20.6 Elasto-plastic theory 313
20.7 Conclusions 320
References 322
21 Tunnels in seismic areas 325
21.1 Introduction 325
21.2 Response of an underground structure to dynamic loading 326
21.3 Observed response 327
21.4 Case history of 1991 Uttarkashi earthquake 328
21.5 Pseudo-static theory of seismic support pressure 330
21.6 Support system for blast loading 332
References 333
22 Rock burst in tunnels 335
22.1 Introduction 335
22.2 Conditions for rock burst in deep tunnels 336
22.3 Concept of strain energy release rate 338
22.4 Seismic energy released in a rock burst 339
22.5 Semi-empirical criterion of predicting rock burst 339
22.6 Suggestion for reducing severity of rock bursts 343
References 344
23 Pressure tunnels 345
23.1 Introduction 345
23.2 Minimum overburden above a pressure tunnel 346
23.3 Solid concrete lining 347
23.4 Cracked plain cement concrete lining 347
23.5 Steel liner in penstock 349
23.6 Hydraulic fracturing near junction of pressure tunnel
and penstock 352
References 352
24 Shafts 355
24.1 Introduction 355
24.2 Shapes of shaft 356
24.3 Self-supporting shaft 357
24.4 Support pressures on the wall of shaft 357
24.5 Design of support system 359
24.6 Surge shaft 360
24.7 Excavation 361
24.8 Self-compacting concrete 362
References 363
25 Half tunnels 365
25.1 Introduction 365
25.2 Application of rock mass classification 365
25.3 Wedge analysis 366
25.4 Stress distribution around half tunnel 372
References 373
26 Contractual risk sharing 375
26.1 The risk 375
26.2 Management of risk 379
26.3 Construction planning and risk 385
26.4 Time and cost estimates 386
References 386
27 Rate of tunnelling 389
27.1 Introduction 389
27.2 Classification of ground/job conditions for rate of tunnelling 390
27.3 Classification of management conditions for rate of tunnelling 390
27.4 Combined effect of ground and management conditions on rate
of tunnelling 392
27.5 Tunnel management 397
27.6 Poor tender specifications 398
27.7 Contracting practice 399
27.8 Quality management by International Tunnelling Association 400
References 401
28 Integrated method of tunnelling 403
28.1 Introduction 403
28.2 Probe holes 404
28.3 Effect of seismicity 404
28.4 Tunnel instrumentation 404
28.5 Selection of type of support system 405
28.6 Steel fiber reinforced shotcrete 406
28.7 Treatment of shear zone 411
28.8 Shotcrete 412
28.9 Rock/roof bolts 414
28.10 Steel ribs 418
28.11 Grouting in pressure tunnels 429
28.12 Design of integrated support system 433
28.13 Special requirements 439
References 442
29 Critical state rock mechanics and its applications 443
29.1 General 443
29.2 Suggested model for rock mass 445
29.3 Residual strength 449
29.4 Effect of confining pressure on friction angle 452
References 452
Appendix I Tunnel mechanics 455
AI.1 Elastic stress distribution around circular tunnels 455
AI.2 Proposed elasto-plastic theory of stress distribution in broken zone
in squeezing ground 459
AI.3 Short-term support pressure on closely spaced tunnels in squeezing
ground condition 462
AI.4 Seismic support pressures 465
References 465
Appendix II Software TM for empirical design of support system
for caverns and tunnels 467
AII.1 General 467
AII.2 Software TM 468
AII.3 Experience in poor rock conditions 469
AII.4 Concluding remarks 471
AII.5 Users manual – TM 471
References 475
Appendix III Capacity of blocked steel beam sections in the
roof of tunnel 477
References 480
Index 481
حمله
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