PERUMIN 31: Nuevas tendencias de la Minería Subterránea - Planeación, operación y estabilización del macizo rocoso
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BLOQUE: OPERACIONES DE MINAS Conferencia magistral Ernesto Villaescusa, Chair in Rock Mechanics Western Australian School of Mines Miércoles 18 de setiembre, 2013
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PERUMIN 31: Nuevas tendencias de la Minería Subterránea - Planeación, operación y estabilización del macizo rocoso
- 1. Nuevas tendencias de la Minería Subterránea profunda Planeación, operación y estabilización del macizo rocoso By © Ernesto Villaescusa, PhD Chair in Rock Mechanics WA School of Mines, CRC Mining & Curtin University Australia
- 2. Western Australian School of Mines Research The overall objective is to characterize rock masses and their response to mining activities, so that stable excavations can be designed, constructed and supported. Excavation stability S801 Geological regime S802 Rock mass characterization S803 Performance prediction S804 Ground support evaluation S805 Ground support implementation S806 Backfill mining voids S808 Shotcrete support S807 New technology Rock Mass Characterization Ground Support Technology Introduction
- 3. Stope & pillar sizes Access & infrastructure Global sequences (Stress analysis) Mine planning Acceptable design NO Rock Mechanics Mine planning & Rock Mechanics Global Economics Mining method selection Orebody delineation END Document results Drill & blast design Acceptable design Detailed economics Mine planning Rock reinforcement Mine planning Extraction monitoring Operations, Mine planning Geology & Rock mechanics NO YES YES Rock mechanics Infill delineation drilling Geology Rockmass characterization Geology & rock Orebody delineation Geology Mine planning Mine planning Rockmass characterization Geology & rock mechanics Orebody Document results Mine planning Mine planning Operations, Mine planning Geology & Rock mechanics Rock mechanics Infill delineation drilling Geology G L O B A L D E S I G N D E T A I L E D D E S I G N INPUT DATA CLOSURE OF DESIGN LOOP Acceptable design Mine planning Flowchart of mine planning process (Villaescusa, 1998). Introduction
- 4. Introduction – Mining at depth Golden Grove Mine, Western Australia (Thompson, 2011) 1000m Conditions often become difficult beyond a 1000m or so
- 5. Maximum recovery – minimal dilution 0 1 2 3 4 5 6 7 8 9 0 2 4 6 8 10 12 14 Depth of Failure (m) HR Hangingwall Depth of Failure vs. Hydraulic Radius 0-1m 1-2m 3-4m 4-5m >5m Depth of Golden Grove Mine, Western Australia (Thompson, 2011) Continuous extraction sequence required to avoid pillars
- 6. Mining method selection & infrastructure SLC/SLOS SLOS 1000m Change of the mining method or infrastructure location
- 7. Geotechnical monitoring requirements Mine induced seismicity Kanowna Belle Mine, Western Australia (Morton, 2013) Seismic sensor array 1000m 1000m A need to understand the overall failure process and instability
- 8. Large scale geological discontinuities Mount Charlotte Mine, Western Australia (Corskie, 2013) 1000m The global stability may be controlled by large scale structures
- 9. Seismic response of large scale structures Fitzroy fault Kanowna Belle Mine, Western Australia (Morton, 2013) 1000m 1000m The structures may become seismically active
- 10. Mining method multiple lift - sublevel open stoping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Drill drives Cut - off s lot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cut - off s lot Used for tabular or massive – steeply dipping orebodies
- 11. Case study - sublevel open stoping at depth 1000m Callie Mine, NT Australia (Graf, 2013)
- 12. Multiple lift - Sublevel open stoping Callie Mine, NT Australia (Graf, 2013) Primary-secondary extraction sequence
- 13. Multiple lift - Sublevel open stoping Cemented rock fill of stoping voids
- 14. Callie Mine, NT Australia (Graf, 2013) In-situ stress measurements - a key requirement Acoustic Emission from oriented core samples – No access required – only deep core
- 15. Callie Mine, NT Australia (Graf, 2013) In-situ stress measurements - a key requirement Orientation and magnitude with depth determination - For all the stoping block areas planned
- 16. Callie Mine, NT Australia (Graf, 2013) Intact rock strength determination For all rock types
- 17. Callie Mine, NT Australia (Graf, 2013) Intact rock strength determination For all rock types
- 18. Callie Mine, NT Australia (Graf, 2013) Intact rock strength determination For all rock types
- 19. Callie Mine, NT Australia (Graf, 2013) Joint set number and orientation – block shape From development exposure and diamond drilled core
- 20. Callie Mine, NT Australia (Graf, 2013) Joint condition determination From development exposure and diamond drilled core
- 21. Joint set characteristics Callie Mine, NT Australia (Graf, 2013)
- 22. Callie Mine, NT Australia (Graf, 2013) RQD from exploration core Changes with depth Correlation with large scale structures
- 23. Callie Mine, NT Australia (Graf, 2013) Rock mass classification Block ABlock BBlock CBlock D
- 24. Excavation performance under increased stress 13/08/2013
- 25. Excavation performance under increased stress 13/08/2013 13/08/2013
- 26. Excavation performance under increased stress
- 27. Ground support strategy for an increasing stress 10 5 2 1 20 0.5 0.2 0.1 1 2 5 10 20 50 100 200 2.5 – 5.0 Medium confining stress Low confining stress High stress Heavy rockburst zone σ 1 = In - situ main principal stress σ c = Uniaxial Compressive Strength of intact rock Near Surface σ c σ Stress Reduction Factor (SRF) max
- 28. Ground support strategy for an increasing stress Time dependent slow deformation Sudden, violent failure The walls of the excavations become unstable due to vertical stress.
- 29. Rock bolting - with or without welded wire mesh A generalized form of support effective for shallow to moderate depths. Ground support strategy for an increasing stress
- 30. Ground support strategy for an increasing stress At greater depths bolts, shotcrete and mesh required for backs and walls.
- 31. Fibrecrete energy dissipation is not enough under high stress conditions Ground support strategy for an increasing stress
- 32. Ground support strategy for an increasing stress Fibrecrete energy dissipation is not enough under high stress conditions
- 33. Ground support strategy for an increasing stress Bolts + mesh embedded shotcrete + cables Sudden failure
- 34. (Modified from Thompson et al, 2012 ) Demand Reaction Surface Energy category pressure (KPa) displacement (mm) (KJ/m2) Low <100 <50 <5 Medium 100-150 50-100 5-15 High 150-200 100-200 15-25 Very High 200-400 200-300 25-35 Extremely High >400 >300 >35 © E. Villaescusa WA School of Mines Ground support strategy for an increasing stress Rock mass demand
- 35. Ground support strategy for an increasing stress Example of low demand – unsupported lower walls
- 36. Ground support strategy for an increasing stress Example of low to medium demand – fibrecrete and walls
- 37. Ground support strategy for an increasing stress Example of low to medium demand – fibrecrete
- 38. Ground support strategy for an increasing stress Example of high to very high demand – mesh embedded chain link
- 39. Ground support strategy for an increasing stress WASM ground support design chart
- 40. Ground support strategy for an increasing stress Excavation shape at depth will require changes
- 41. Conclusions •Rock mass characterization from exploration core. •Selection of mining method with geotechnical considerations. •Geotechnical monitoring for global stability. •Strength vs induced stress ratios become unfavourable. •Mode of failure anticipation required. •Ground support strategy for high energy dissipation. •Change of excavation shape may be required.