Introduction 3. Basic Mine Fill Materials 13

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1 C O N T E N T S 1 Introduction Preamble Why mine fill? Ensuring long-term regional stability Limiting excavation exposure Waste disposal Considerations for selection of mine fill systems Brief history of mine fill Australian mine fill history North American mine fill history Recent mine fill history... 9 Basic Mine Fill Materials Preamble Tailings Sizing Mineralogy Particle shape Tailings oxidation Natural sands Rock and aggregate Aggregate grading Attrition Water Cement Chemical reactions Cement contents Pozzolans Fly ash Slag Gypsum Other pozzolans Admixtures i

2 Handbook on Mine Fill 3 Geomechanics of Mine Fill Preamble Soil mechanics and mine fill Mine backfilling applications and the relevant fill parameters Dry fill (DF) Hydraulic fill (HF) Cemented hydraulic fill (CHF) Paste fill Composite fills Shotcrete Geofabrics geotextiles Sources of mine fill tailings Mine tailings Phases of backfill materials Some volumetric relationships Degree of saturation Some important unit weights of backfill materials Water content of fill Moisture content of fill Solids content Saturated fills, slurries and pastes The volumetric solids concentration C v Particle size distribution of backfill/tailings Particle size distribution curve Uniformity of fill Some important benchmarks on particle packing Relative density or density index Atterberg s limits Ultra fines in tailings (<2 µm) The fundamentals of the shear strength of backfill Fill permeability(hydraulic conductivity) Determination of coefficient of permeability Seepage gradient Quick condition and piping Development of piping in fill masses Liquefaction of mine fill Compaction and consolidation of mine fill Consolidation of fill Shear strength of fill Effective stress concept Shear strength Some general observations regarding strength development in cemented fills Measurement of shear strength Lateral earth pressure Arching in fill masses and stability analyses Stope fill mass stability analysis 3D wedge analysis ii

3 Contents 4 Fluid Mechanics of Mine Fill Preamble Transport and delivery of fill slurries Introduction to fluid mechanics principles Hydraulic fill slurry behaviour Paste fill behaviour Paste fill rheology Paste fill flow in pipes and wall shear stress Yield shear stress effect of pulp density Reticulation design Hydraulic fill reticulation design Calculating friction system losses in hydraulic fill systems Paste fill reticulation design Calculating friction factors in paste fill systems Flow control strategy Drainage through hydraulic fill Drainage analysis Saturation Testing and measurements Laboratory-scale rheology Yield shear stress and slump test Yield shear stress determined by the vane shear viscometer Viscosity measurement Pipe loop testing Introduction to Hydraulic Fill Preamble Design Demand from mining methods Cemented or uncemented hydraulic fill? Supply of materials Mill tailings Natural surface sand deposits Binders Preparation of hydraulic fill Tailings dewatering Tailings desliming Fill permeability and percolation rate Empirical relationships for permeability/percolation rate of hydraulic fill Particle size distribution curves Cautionary note on sizing criteria for hydraulic fill Hydrocyclones Spiral and rake classifiers Drum filters Elutriation tanks Storage tanks and pachucas iii

4 Handbook on Mine Fill Delivery systems from preparation site to stope Fill containment design and construction of fill barricades Placement and drainage Design principles The risk of fill inrush Erosion piping failure mechanism Mechanical defects design, construction Monitoring and performance Operational monitoring of fill and barricades Hydraulic fill summary of key issues Paste Fill Preamble Principles Advantages of paste Considerations with paste Demands from mining methods Paste fill performance Rate of filling Placement rates Supply of materials Tailings Water Binder Coarse fraction Processing of components Tailings dewatering Thickening Filtration Excavated tailings Mixing Binder addition Mix control Delivery and placement Boreholes Pipes Pumps Flushing of distribution system Retention Design Material characterisation Flow characteristics Pump test Strength gain Results Effect of yield stress at high cement contents Dewatering testwork Thickener design Filtration design Monitoring and performance Examples of paste fill applications iv

5 Contents 7 Rock Fill in Mine Fill Preamble Angle of repose Unmodified rock fill Modified rock fill Dilating fills Contracting fills Particle size optimisation Blending of rock fill Some standard rock fill gradings Binder addition Inclusion of fine-grained materials Friction angle of rock fill Rock fill production Delivery of rock fill in mining Cemented rock fill at Mount Isa Mines Fill mass stability Cement slurry rock fill trials at Mount Isa Mines (MIM) in Large cylinder testing Water content of the mix Composition of the final placed CSRF Strength Fill placement trials Rocky Paste Fill (RPF) trials at Mount Isa Mines in RPF mix components RPF strength Quality of RPF after placement Design chart for RPF Advantages of RPF Rocky paste fill at Olympic Dam Mine CSAF at George Fisher Mine Other Fill Types and Practices Preamble Fill in underground coal mines Preamble Background Ongoing development Surface subsidence mitigation and prevention Preamble Plant and equipment Fill material Water supply Fill containment Fill delivery boreholes and surface plant Fill preparation and placement Monitoring Project performance v

6 Handbook on Mine Fill vi 8.4 Filling metalliferous and coal open pits Preamble Fill materials and filling Fill materials in more detail Waste rock or coarse coal reject Tailings, fine coal reject and fly ash Co-disposal Metalliferous mining Coal mining Water management Waste rock stability Submerging tailings Mine closure Safety and hazard reduction Co-disposal of mining and municipal wastes Preamble Handling municipal waste Transportation Mine void access Co-disposal Dumped co-disposal Pumped tailings/fine reject Design Liner Underdrains Safety and hazard reduction Use of completed open pits for tailings disposal Preamble Economics Environmental requirements Physical characterisation Water removal/recovery systems Geochemical characterisation Geotechnical considerations Rehabilitation Cemented aggregate fill in complex ore bodies Preamble Geology Ground conditions Mining method Cemented aggregate fill Evaluation and test work Parameters Evaluation approach Operational issues A review of some important aspects of cemented aggregate fill Preamble Particle size distribution Fill placement Fill quality test work Aggregate quality Aggregate particle size distribution Aggregate moisture content Binder strength Slump tests CAF reference cylinder strength tests Sands and tailings In situ assessment of CAF Exposure mapping Coring Borehole pressure meter Video monitoring...137

7 Contents 9 Hazards, Risks and Environment Preamble Example of a mine fill risk Terminology Risk management Introduction Communication and consultation Establishing the context Risk identification Risk analysis Risk evaluation Risk treatment Monitoring and reviewing Recording the risk management process Some aspects of implementing risk management Establishing effective risk management Life cycle issues Limitations of risk assessment techniques Common pitfalls with risk assessments Environmental aspects of mine fill Successful use of mine fill Unsuccessful use of mine fill Mine fill risk register Preamble Risk register Suggested reading Acknowledgement Emerging Technologies and Current Research Preamble Summary of responses to requests to comment Review of content of selected papers from MINEFILL 1998, MINEFILL 2001 and MINEFILL MINEFILL MINEFILL MINEFILL Glossary 171 General terms Terms specific to chapter 6: Paste Fill Terms specific to chapter 9: Hazards, Risks and Environment vii

Table of Contents Chapter 1 Introduction to Geotechnical Engineering 1.1 Geotechnical Engineering 1.2 The Unique Nature of Soil and Rock Materials

Table of Contents Chapter 1 Introduction to Geotechnical Engineering 1.1 Geotechnical Engineering 1.2 The Unique Nature of Soil and Rock Materials 1.3 Scope of This Book 1.4 Historical Development of Geotechnical