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F . Alvarez , J. Dávila, A. Jofré, R. Manásevich. DIM - CMM , Universidad de Chile.

Rockmass Instabilities Induced by Mining Excavations in El Teniente, a Codelco-Chile Copper Mine. F . Alvarez , J. Dávila, A. Jofré, R. Manásevich. DIM - CMM , Universidad de Chile. January 200 3. Outline. Part I: Project overview The mine and its rockmass. The caving method.

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F . Alvarez , J. Dávila, A. Jofré, R. Manásevich. DIM - CMM , Universidad de Chile.

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  1. Rockmass Instabilities Induced by Mining Excavations in El Teniente, a Codelco-Chile Copper Mine F. Alvarez, J. Dávila, A. Jofré, R. Manásevich. DIM-CMM, Universidad de Chile. January 2003.

  2. Outline • Part I: Project overview • The mine and its rockmass. • The caving method. • Rockmass instabilities and rockbursting. • Part II: Asymptotic analysis of a limit stress state.

  3. Part I Project Overview

  4. The mine • Located at2.100 masl and 80 km SSE of Santiago. • World’s largest underground copper mine. • 1.500 km of tunnels and underground excavations. • 355.000 ton/year. El Teniente

  5. The rockmass Secondary mineral: soft, near the surface and highly fragmented. Poor in copper. Primary mineral: high cohesion, deeper and much harder than the secondary ore. Rich in copper.

  6. The caving method Panel caving: the gravity force helps rock fragmentation and block extraction

  7. Evolution of the geometry

  8. Drawbacks • The excavations induce deformations and high stress conditions within the surrounding rockmass. • Consequences: • Damages to the surrounding excavations • Rockmass instabilities. • Seismic activity and rockbursting.

  9. The mathematical modelling challenge • Geomechanical properties of the rockmass • Dynamical aspects of the mining process. To develop quantitative and qualitative mathematical tools to assist the determination of mining parameters

  10. The team El Teniente Engineers S. Gaete R. Molina PDE J. Dávila R. Manásevich Optimization/Equilibrium F. Alvarez A. Jofré

  11. Part II Asymptotic analysis of the limit stress condition

  12. Elasticity theory I: stress tensor

  13. Elasticity theory II: equilibrium PDE Linear Elasticity

  14. Mixed boundary conditions rockmass cavity

  15. Shear stress evolution High stress concentrations at the underminning front

  16. Evolution

  17. Limit problem I: bilaplacian Divergence PDE (system): Domain: Plane stress Airy’s stress function: Biharmonic PDE (scalar): Boundary conditions onL:

  18. Limit problem II: conformal map Biharmonic function: Boundary conditions: Conformal map:

  19. Limit problem III: asymptotic analysis (a) Schwarz reflexion principle: (b) Variational formulation: (a) + (b) But

  20. Limit problem IV: illustration

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