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Maochen Ge, Eliza Richardson, Chris Marone, Derek Elsworth, EMS, PSU & Erik Westman, VPI

A Large Block Test to Study the Energetic Failure of Rock – Application to Rock-Bursting and Earthquake Mechanics. Maochen Ge, Eliza Richardson, Chris Marone, Derek Elsworth, EMS, PSU & Erik Westman, VPI. Objectives.

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Maochen Ge, Eliza Richardson, Chris Marone, Derek Elsworth, EMS, PSU & Erik Westman, VPI

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  1. A Large Block Test to Study the Energetic Failure of Rock – Application to Rock-Bursting and Earthquake Mechanics Maochen Ge, Eliza Richardson, Chris Marone, Derek Elsworth, EMS, PSU & Erik Westman, VPI

  2. Objectives • Develop an improved understanding of the deformation and energetic failure of rock masses • Contribute to the safe design of structures (e.g. infrastructure and caverns) • Improved understanding of rock failure in space and time • Address a “big” question: Rupture mechanics and AE/MS/RB/Equake scaling

  3. Slide-Hold-Slide Friction Experiments • Hold periods of 30 – 104 [sec] @20 degree-C, peak coefficient is independent of hold periods @65 degree-C, peak value increases with increase of hold

  4. Slide-Hold-Slide Friction Experiments Frictional strengthening is likely due to augmentation in cohesion (contact area) that may result from pressure solution

  5. Scale Effects in Geo-hydrology – Space and Time Lab scale Field scale Regional scale 10-10 Permeability, m2 ? 10-14 10-18 10-1 100 102 103 101 Spatial Scale, m

  6. Constitutive Relations for Transport Behavior

  7. Approach • The Challenge – • Understanding rock-bursting and minimizing impact • The Opportunities – • Understanding failure processes at field scale and linking failure with source mechanisms • Understanding fundamental rate and state constitutive laws – and scale-up: • In space • In time

  8. Five months of seismicity at Mponeng Over 80,000 events Colors grade from cool to warm as events become more recent

  9. Creighton Mine, Canada

  10. Approach • The Challenge – • Understanding rock-bursting and minimizing impact • The Opportunities – • Understanding failure processes at field scale and linking failure with source mechanisms and event scaling • Understanding fundamental rate and state constitutive laws – and scale-up: • In space • In time

  11. Experimental Arrangement Multiple pillars (of differing dimension) constructed at multiple depths; may include discontinuities

  12. Experimental Arrangement • Monitoring Scales • Run of facility • Cavern • Test Fluid pressure Flow and reaction • Environmental Loads • Excavation • Excess fluid pressures • Monitoring and Testing • Imaging – seismics & ERT – rupture types, sizes and locations • Solid – stress, strain, extension, 4-D seismics, tilt • Fluid – liquid and gas - pressure and composition – permeability and reactive chemistry

  13. How does this experiment optimize the use of DUSEL? Time, t • Principal Attributes • Unusual spatial scale – bridges laboratory scale to field scale • Long-term access • Depth gives stress and thermal regimes…… Spatial scale, x,y,z Depth, z -> Ds; DT

  14. Important Questions • Mechanisms of the triggering of rupture • Mechanisms of strength-gain and fault-healing • Role of reactive fluids • Role of pressure solution and other mechanisms • Understanding the transition - quiescent rupture and energetic failure. • Bridging the gap between laboratory and field scales • Illuminating fundamental mechanics of Rate and State friction constitutive laws • Representation of seismic and interseismic fault behaviors • Earthquake nucleation, coseismic rupture and earthquake afterslip • Role of fault roughness and gouge on frictional properties and stability • ………………….

  15. Expected Results Address Issues Relating to: • Stability of large openings against energetic failure • Improved understanding of the energetic failure of rock • Small scale for civil and mined underground structures • Large scale (space and time) for earthquake mechanics

  16. Experimental Requirements • Contained and remote – possibly part of a “Large Experiment” Facility • Duration – Long term experiment (10y) on large volume natural fault/fracture. Subsidiary short-term expts (~1,s to ~10,s of meters edge-dimension) for short term on block periphery • Reusability – Not likely for small experiments, possible for large block. • No compatibility with physics experimentation – except monitoring of cavern excavation sequence • Needs appropriate fault/stress/strength structure

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