Guidelines for Open Pit Slope Design

cover......Page 1
Contents......Page 6
Preface and acknowledgments......Page 14
 1.2 Pit slope designs......Page 16
  1.2.2 Economic factors......Page 17
  1.2.3 Environmental and regulatory factors......Page 18
  1.3.2 Instability......Page 19
  1.4.2 Geotechnical model......Page 21
  1.4.4 Acceptance criteria (Chapter 9)......Page 23
  1.4.5 Slope design methods (Chapter 10)......Page 24
  1.4.7 Slope evaluation and monitoring (Chapter 12)......Page 25
  1.5.1 Project development......Page 26
  1.6.1 Overview......Page 27
 1.7 Conclusion......Page 29
  2.2.1 Introduction......Page 30
  2.2.2 General geotechnical logging......Page 32
  2.2.3 Mapping for structural analyses......Page 34
  2.2.4 Surface geophysical techniques......Page 37
  2.3.1 Classification......Page 38
  2.4.2 Planning and scoping......Page 41
  2.4.5 Downhole surveying......Page 42
  2.4.6 Core orientation......Page 43
  2.4.7 Core handling and documentation......Page 44
  2.4.8 Core sampling, storage and preservation......Page 46
  2.4.9 Core logging......Page 47
  2.4.10 Downhole geophysical techniques......Page 54
  2.5.1 Approach to groundwater data collection......Page 55
  2.5.2 Tests conducted during RC drilling......Page 57
  2.5.3 Piezometer installation......Page 59
  2.5.4 Guidance notes: installation of test wells for pit slope depressurisation......Page 62
  2.5.5 Hydraulic tests......Page 64
  2.5.6 Setting up pilot depressurisation trials......Page 66
 Endnotes......Page 67
 3.2 Physical setting......Page 68
  3.3.2 Porphyry deposits......Page 70
  3.3.4 Kimberlites......Page 71
  3.3.7 Stratabound deposits......Page 72
 3.4 Geotechnical requirements......Page 74
  3.5.1 Distribution of earthquakes......Page 77
  3.5.2 Seismic risk data......Page 80
 3.6 Regional stress......Page 81
  4.2.1 Major structures......Page 84
  4.2.2 Fabric......Page 90
  4.3.3 Sedimentary......Page 91
  4.4.2 Stereographic projection......Page 92
  4.4.3 Discrete fracture network modelling......Page 94
  4.5.2 Example application......Page 95
  5.2.1 Introduction......Page 98
  5.2.2 Index properties......Page 100
  5.2.3 Mechanical properties......Page 103
  5.2.4 Special conditions......Page 107
  5.3.2 Defect strength......Page 109
  5.4.2 RMR, Bieniawski......Page 132
  5.4.3 Laubscher IRMR and MRMR......Page 134
  5.4.4 Hoek-Brown GSI......Page 138
  5.5.2 Laubscher strength criteria......Page 142
  5.5.3 Hoek-Brown strength criterion......Page 143
  5.5.4 CNI criterion......Page 145
  5.5.5 Directional rock mass strength......Page 147
  5.5.6 Synthetic rock mass model......Page 153
  6.1.2 Porosity and pore pressure......Page 156
  6.1.3 General mine dewatering and localised pore pressure control......Page 161
  6.1.4 Making the decision to depressurise......Page 163
  6.2.1 Groundwater flow......Page 166
  6.2.2 Porous-medium (intergranular) groundwater settings......Page 169
  6.2.3 Fracture-flow groundwater settings......Page 171
  6.2.4 Influences on fracturing and groundwater......Page 176
  6.2.5 Mechanisms controlling pore pressure reduction......Page 178
  6.3.2 Conceptual mine scale hydrogeological model......Page 181
  6.3.3 Detailed hydrogeological model of pit slopes......Page 182
  6.4.1 Introduction......Page 183
  6.4.2 Numerical hydrogeological models for mine scale dewatering applications......Page 184
  6.4.3 Pit slope scale numerical modelling......Page 188
  6.4.4 Numerical modelling for pit slope pore pressures......Page 190
  6.4.5 Coupling pore pressure and geotechnical models......Page 194
  6.5.1 General mine dewatering......Page 195
  6.5.2 Specific programs for control of pit slope pressures......Page 196
  6.5.5 Water management and control......Page 207
  6.6.2 Relative pore pressure behaviour between high-order and low-order fractures......Page 210
  6.6.3 Standardising the interaction between pore pressure and geotechnical models......Page 211
  6.6.5 Coupled pore pressure and geotechnical modelling......Page 212
  7.2.1 Required output......Page 216
  7.2.3 Building the model......Page 217
  7.2.4 Block modelling approach......Page 220
  7.3.1 Scale effects......Page 221
  7.3.3 Hoek-Brown rock mass strength criterion......Page 225
  7.3.4 Pore pressure considerations......Page 226
 8.3 Impact of data uncertainty......Page 228
  8.4.2 Subjective assessment......Page 230
  8.5.1 Geotechnical reporting system......Page 231
 8.6 Summary and conclusions......Page 234
  9.2.1 FoS as a design criterion......Page 236
  9.3.1 PoF as a design criterion......Page 238
  9.3.2 Acceptable levels of PoF......Page 239
  9.4.1 Introduction......Page 240
  9.4.2 Cost–benefit analysis......Page 241
  9.4.3 Risk model process......Page 243
  9.4.4 Formulating acceptance criteria......Page 247
  9.4.5 Slope angles and levels of confidence......Page 249
 9.5 Summary......Page 250
  10.1.1 Design steps......Page 252
  10.1.2 Design analyses......Page 253
  10.2.1 Benches......Page 254
  10.2.2 Inter-ramp slopes......Page 259
  10.3.2 Empirical methods......Page 261
  10.3.3 Limit equilibrium methods......Page 263
  10.3.4 Numerical methods......Page 268
  10.3.5 Summary recommendations......Page 278
  11.2.2 Open pit design philosophy......Page 280
  11.2.3 Open pit design process......Page 282
  11.2.4 Application of slope design criteria in mine design......Page 283
  11.3.1 Introduction......Page 291
  11.3.2 Design terminology......Page 292
  11.3.3 Blast damage mechanisms......Page 293
  11.3.4 Influence of geology on blast-induced damage......Page 294
  11.3.5 Controlled blasting techniques......Page 297
  11.3.6 Delay configuration......Page 307
  11.3.7 Design implementation......Page 309
  11.3.8 Performance monitoring and analysis......Page 311
  11.3.9 Design refinement......Page 314
  11.3.10 Design platform......Page 320
  11.3.11 Planning and optimisation cycle......Page 321
  11.4.1 Excavation......Page 325
  11.4.2 Scaling and bench cleanup......Page 327
  11.5.1 Basic approaches......Page 328
  11.5.2 Stabilisation, repair and support methods......Page 329
  11.5.3 Design considerations......Page 330
  11.5.4 Economic considerations......Page 331
  11.5.6 Specific situations......Page 332
  11.5.7 Reinforcement measures......Page 333
  11.5.8 Rockfall protection measures......Page 340
  12.1.2 Geotechnical model validation and refinement......Page 342
  12.1.3 Bench performance......Page 344
  12.1.4 Inter-ramp slope performance......Page 352
  12.1.5 Overall slope performance......Page 354
  12.2.1 Introduction......Page 357
  12.2.2 Movement monitoring systems......Page 358
  12.2.3 Guidelines on the execution of monitoring programs......Page 378
  12.3.1 Introduction......Page 385
  12.3.2 Hazard management plan......Page 386
  13.1.2 Purpose and content of this chapter......Page 396
  13.1.3 Sources of information......Page 397
  13.2.2 General risk management process......Page 398
  13.2.3 Risk management in the minerals industry......Page 399
 13.3 Geotechnical risk management for open pit slopes......Page 400
  13.4.2 Risk identification......Page 404
  13.4.3 Risk analysis......Page 406
  13.4.4 Risk evaluation......Page 410
  13.5.1 Overview......Page 411
  13.5.3 Geotechnical control measures......Page 413
  13.5.4 Mitigation plans......Page 414
  13.5.5 Monitoring, review and feedback......Page 415
 14.1 Introduction......Page 416
  14.2.3 Closure planning for existing mines......Page 418
  14.3.1 Closure goals and criteria......Page 420
  14.3.2 Site characterisation......Page 422
  14.3.3 Ore body characteristics and mining approach......Page 423
  14.3.6 Pit lake water quality......Page 424
  14.3.8 Pit wall stability......Page 425
 14.5 Conclusions......Page 427
 Endnotes......Page 428
  Groundwater data collection......Page 430
  Essential statistical and probability theory......Page 446
  Evert Hoek, Jean Hutchinson, Kathy Kalenchuk and Mark Diederichs......Page 452
  Risk management: geotechnical hazard checklists......Page 462
  Example regulations for open pit closure......Page 474
Terminology and definitions......Page 477
References......Page 482
Index......Page 502