Rockmass Instabilities Induced by Mining Excavations in El Teniente, a Codelco-Chile Copper Mine

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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.

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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.

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Part I Project Overview
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The mine

• Located at 2.100 masl and 80 km SSE of Santiago.
• Worlds largest underground copper mine.
• 1.500 km of tunnels and underground excavations.
• 355.000 ton/year.

El Teniente
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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.
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The caving method

• Panel caving the gravity force helps rock
  fragmentation and block extraction

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Evolution of the geometry
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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.

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The mathematical modelling challenge
To develop quantitative and qualitative mathematic
al tools to assist the determination of mining
parameters

• Geomechanical properties of the rockmass
• Dynamical aspects of the mining process.

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The team
El Teniente Engineers S. Gaete R. Molina
PDE J. Dávila R. Manásevich
Optimization/Equilibrium F. Alvarez A. Jofré
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Part II Asymptotic analysis of the limit stress
condition
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Elasticity theory I stress tensor
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Elasticity theory II equilibrium PDE
Linear Elasticity
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Mixed boundary conditions
rockmass
cavity
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Shear stress evolution

• High stress concentrations at the underminning
  front

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Evolution
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Limit problem I bilaplacian
Divergence PDE (system)
Domain
Plane stress
Airys stress function
Biharmonic PDE (scalar)
Boundary conditions on L
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Limit problem II conformal map
Biharmonic function
Boundary conditions
Conformal map
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Limit problem III asymptotic analysis
(a) Schwarz reflexion principle
(b) Variational formulation
(a) (b)
But
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Limit problem IV illustration