Contenido del Libro GUIDELINES FOR OPEN PIT SLOPE DESIGN

8/17/2019 Contenido del Libro GUIDELINES FOR OPEN PIT SLOPE DESIGN

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GUIDELINES FOR

OPEN PIT SLOPE DESIGN

EDITORS: JOHN READ, PETER STACEY

# &CSIRO J

PUBLISHING x S


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Contents

Preface and acknowledgments xiii

1 Fundamentals of slope design 1

Peter Stacey

1.1 Introduction 1

1.2 Pit slope designs 1

1.2.1 Safety/social factors 2

1.2.2 Economic factors 2

1.2.3 Environmental and regulatory factors 3

1.3 Terminology of slope design 4

1.3.1 Slope configurations 4

1.3.2 Instability 4

1.3.3 Rockfall 6

1.4 Formulation of slope designs 6

1.4.1 Introduction 6

1.4.2 Geotechnical model 6

1.4.3 Data uncertainty (Chapter 8) 8

1.4.4 Acceptance criteria (Chapter 9 ) 8

1.4.5 Slope design methods (Chapter 10) 9

1.4.6 Design implementation (Chapter 11) 10

1.4.7 Slope evaluation and monitoring (Chapter 12) 10

1.4.8 Risk management (Chapter 13) 11

1.4.9 Closure (Chapter 1 4) 11

1.5 Design requirements by project level 11

1.5.1 Project development 111.5.2 Study requirements 12

1.6 Review 12

1.6.1 Overview 12

1.6.2 Review levels 14

1.6.3 Geotechnically competent person 14

1.7 Conclusion 14

2 Field data collection 15

John Read, Jarek Jakubec and GeoffBeale

2.1 Introduction 15

2.2 Outcrop mapping and logging 15


2.2.2 General geotechnical logging 17

2.2.3 Mapping for structural analyses 19

2.2.4 Surface geophysical techniques 22

2.3 Overburden soils logging 23

2.3.1 Classification 23

2.3.2 Strength and relative density 26

2.4 Core drilling and logging 26


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vi Guidelines for Open Pit Slope Design


2.4.2 Planning and scoping 26

2.4.3 Drill hole location and collar surveying 27

2.4.4 Core barrels 27

2.4.5 Downhole surveying 27

2.4.6 Core orientation 28

2.4.7 Core handling and documentation 29

2.4.8 Core sampling, storage and preservation 31

2.4.9 Core logging 32

2.4.10 Downhole geophysical techniques 39

2.5 Groundwater data collection 40

2.5.1 Approach to groundwater data collection 40

2.5.2 Tests conducted during RC drilling 42

2.5.3 Piezometer installation 44

2.5.4 Guidance notes: installation of test wells for pit slope

depressurisation 47

2.5.5 Hydraulic tests 49

2.5.6 Setting up pilot depressurisation trials 51

2.6 Data management 52

Endnotes 52

3 Geological model 53

John Read and Luke Keeney

3.1 Introduction 53

3.2 Physical setting 53

3.3 Ore body environments 55


3.3.2 Porphyry deposits 55

3.3.3 Epithermal deposits 56

3.3.4 Kimberlites 56

3.3.5 VMS deposits 57

3.3.6 Skarn deposits 57

3.3.7 Stratabound deposits 57

3.4 Geotechnical requirements 59

3.5 Regional seismicity 62

3.5.1 Distribution of earthquakes 62

3.5.2 Seismic risk data 65

3.6 Regional stress 66

4 Structural model 69

John Read

4.1 Introduction 69

4.2 Model components 69

4.2.1 Major structures 69

4.2.2 Fabric 75

4.3 Geological environments 764.3.1 Introduction 76

4.3.2 Intrusive 76


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4.3.3 Sedimentary 76

4.3.4 Metamorphic 77

4.4 Structural modelling tools 77

4.4.1 Solid modelling 77

4.4.2 Stereographic projection 774.4.3 Discrete fracture network modelling 79

4.5 Structural domain definition 80

4.5.1 General guidelines 804.5.2 Example application 80

5 Rock mass model 83

Antonio Karzulovic and John Read

5.1 Introduction 83

5.2 Intact rock strength 83


5.2.2 Index properties 85

5.2.3 Mechanical properties 88

5.2.4 Special conditions 92

5.3 Strength of structural defects 94

5.3.1 Terminology and classification 94

5.3.2 Defect strength 94

5.4 Rock mass classification 117


5.4.2 RMR, Bieniawski 117

5.4.3 Laubscher IRMR and MRMR 119

5.4.4 Hoek-Brown GSI 123

5.5 Rock mass strength 127


5.5.2 Laubscher strength criteria 127

5.5.3 Hoek-Brown strength criterion 128

5.5.4 CNI criterion 130

5.5.5 Directional rock mass strength 132

5.5.6 Synthetic rock mass model 138

6 Hydrogeological model 141GeoffBeak

6.1 Hydrogeology and slope engineering 141


6.1.2 Porosity and pore pressure 141

6.1.3 General mine

dewatering and localised pore pressure control 1466.1.4 Making the decision to depressurise 148

6.1.5 Developing a slope depressurisation program 151

6.2 Background to groundwater hydraulics 151

6.2.1 Groundwater flow 151

6.2.2 Porous-medium (intergranular) groundwater settings 154

6.2.3 Fracture-flow groundwater settings 156

6.2.4 Influences on fracturing and groundwater 161

6.2.5 Mechanisms controlling pore pressure reduction 163


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6.3 Developing a conceptual hydrogeological model of pit slopes 166

6.3.1 Integrating the pit slope model into the regional model 166

6.3.2 Conceptual mine scale hydrogeological model 166

6.3.3 Detailed hydrogeological model of pit slopes 167

6.4 Numerical hydrogeological models 168


6.4.2 Numerical hydrogeological models for mine scale dewateringapplications 169

6.4.3 Pit slope scale numerical modelling 173

6.4.4 Numerical modelling for pit slope pore pressures 175

6.4.5 Coupling pore pressure and geotechnical models 179

6.5 Implementing a slope depressurisation program 180

6.5.1 General mine dewatering 180

6.5.2 Specific programs for control of pit slope pressures 181

6.5.3 Selecting a slope depressurisation method 192

6.5.4 Use of blasting to open up drainage pathways 192

6.5.5 Water management and control 192

6.6 Areas for future research 195


6.6.2 Relative pore pressure behaviour between high-order and low-

order fractures 195

6.6.3 Standardising the interaction between pore pressure and

geotechnical models 196

6.6.4 Investigation of transient pore pressures 197

6.6.5 Coupled pore pressure and geotechnical modelling 197

7 Geotechnical model 201

Alan Guest and John Read

7.1 Introduction 201

7.2 Constructing the geotechnical model 2017.2.1 Required output 201

7.2.2 Model development 202

7.2.3 Building the model 202

7.2.4 Block modelling approach 205

7.3 Applying the geotechnical model 206

7.3.1 Scale effects 206

7.3.2 Classification systems 210

7.3.3 Hoek-Brown rock mass strength criterion 210

7.3.4 Pore pressure considerations 211

8 Data

uncertainty 213

John Read


8.2 Causes of data uncertainty 213

8.3 Impact of data uncertainty 213

8.4 Quantifying data uncertainty 215

8.4.1 Overview 215

8.4.2 Subjective assessment 215


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8.4.3 Relative frequency concepts 216

8.5 Reporting data uncertainty 216

8.5.1 Geotechnical reporting system 216

8.5.2 Assessment criteria checklist 219

8.6 Summary and conclusions 219

9 Acceptance criteria 221

]ohan Wesseloo and John Read


9.2 Factor of safety 221

9.2.1 FoS as a design criterion 221

9.2.2 Tolerable factors of safety 223

9.3 Probability of failure 223

9.3.1 PoF as a design criterion 223

9.3.2 Acceptable levels of PoF 224

9.4 Risk model 225


9.4.2 Cost-benefit analysis 226

9.4.3 Risk model process 228

9.4.4 Formulating acceptance criteria 232

9.4.5 Slope angles and levels of confidence 234

9.5 Summary 235

10 Slope design methods 237Loren Lorig, Peter Stacey and John Read


10.1.1 Design steps 237

10.1.2 Design analyses 238

10.2 Kinematic analyses 239

10.2.1 Benches 239

10.2.2 Inter-ramp slopes 244

10.3 Rock mass analyses 246

10.3.1 Overview 246

10.3.2 Empirical methods 246

10.3.3 Limit equilibrium methods 248

10.3.4 Numerical methods 253

10.3.5 Summary recommendations 263

11 Design implementation 265

Peter Williams, John Floyd, Gideon Chitombo and Trevor Maton


11.2 Mine planning aspects of slope design 26511.2.1 Introduction 265

11.2.2 Open pi t design philosophy 265

11.2.3 Open pit design process 267

11.2.4 Application of slope design criteria in mine design 268

11.2.5 Summary and conclusions 276


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11.3 Controlled blasting 276


11.3.2 Design terminology 277

11.3.3 Blast damage mechanisms 278

11.3.4 Influence of geology on blast-induced damage 279

11.3.5 Controlled blasting techniques 282

11.3.6 Delay configuration 292

11.3.7 Design implementation 294

11.3.8 Performance monitoring and analysis 296

11.3.9 Design refinement 299

11.3.10 Design platform 305

11.3.11 Planning and optimisation cycle 306

11.4 Excavation and scaling 310

11.4.1 Excavation 310

11.4.2 Scaling and bench cleanup 312

11.4.3 Evaluation of bench design achievement 313

11.5 Artificial support 313

11.5.1 Basic approaches 313

11.5.2 Stabilisation, repair and support methods 31411.5.3 Design considerations 315

11.5.4 Economic considerations 316

11.5.5 Safety considerations 317

11.5.6 Specific situations 317

11.5.7 Reinforcement measures 318

11.5.8 Rockfall protection measures 325

12 Performance assessment and monitoring 327Mark Hawley, Scott Marisett, Geoff Beale and Peter Stacey

12.1 Assessing slope performance 327


12.1.2 Geotechnical model validation and refinement 327

12.1.3 Bench performance 329

12.1.4 Inter-ramp slope performance 337

12.1.5 Overall slope performance 339

12.1.6 Summary and conclusions 342

12.2 Slope monitoring 342


12.2.2 Movement monitoring systems 343

12.2.3 Guidelines on the execution of monitoring programs 363

12.3 Ground control management plans 370


12.3.2 Hazard management plan 371

13 Risk management 381

Ted Brown and Alison Booth


13.1.1 Background 381

13.1.2 Purpose and content of this chapter 381

13.1.3 Sources of information 382


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13.2 Overview of risk management 383

13.2.1 Definitions 383

13.2.2 General risk management process 383

13.2.3 Risk management in the minerals industry 384

13.3 Geotechnical risk management for open pit slopes 385

13.4 Risk assessment methodologies 389

13.4.1 Approaches to risk assessment 389

13.4.2 Risk identification 389

13.4.3 Risk analysis 391

13.4.4 Risk evaluation 395

13.5 Risk mitigation 396

13.5.1 Overview 396

13.5.2 Hierarchy of controls 398

13.5.3 Geotechnical control measures 398

13.5.4 Mitigation plans 399

13.5.5 Monitoring, review and feedback 400

14 Open pit closure 401Dirk van Zyl


14.2 Mine closure planning for open pits 403


14.2.2 Closure planning for new mines 403

14.2.3 Closure planning for existing mines 403

14.2.4 Risk assessment and management 405

14.3 Open pit closure planning 405

14.3.1 Closure goals and criteria 405

14.3.2 Site characterisation 407

14.3.3 Ore body characteristics and mining approach 408

14.3.4 Surface water diversion 409

14.3.5 Pit water balance 409

14.3.6 Pit lake water quality 409

14.3.7 Ecological risk assessment 410

14.3.8 Pit wall stability 410

14.3.9 Pit access 412

14.3.10 Reality of open pit closure 412

14.4 Open pit closure activities and post-closure monitoring 412

14.4.1 Closure activities 412

14.4.2 Post-closure monitoring 412

14.5 Conclusions 412

Endnotes 413

Appendix 1 415

Groundwater data collection

Appendix 2 431

Essential statistical and probability theory


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Appendix 3 437

Influence of in situ stresses on open pit design

EvertHoek, Jean Hutchinson, Kathy Kalenchuk and Mark Diederichs

App end ix 4 447

Risk management: geotechnical hazard checklists

App end ix 5 459

Example regulations for open pit closure

Terminology and definitions 462

References 467

Index 487

Contenido del Libro GUIDELINES FOR OPEN PIT SLOPE DESIGN

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