Authors: Sjöberg, J; Bolin, A; Sánchez Juncal, A; Wettainen, T; Mas Ivars, D; Perman, F
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Orepasses are an integral part of the mining infrastructure in sublevel caving. As part of the investigations for potential continued deeper mining in the LKAB Malmberget mine, a study on orepass design has been completed. The initial portion of the work involved numerical modelling and rock mass strength calibration of observed orepass fallouts, and spalling failure in a ventilation shaft. The calibrated numerical model was subsequently used to study different orientations and locations of orepasses for a potential haulage level at depth. The initial calibration work showed that a brittle material model — more precisely a cohesion-weakening frictionstrengthening (CWFS) model — was required to replicate both initiation and extension of stressinduced failure. A set of rock mass strength parameters was derived and further used in forward model prediction for planned orepasses. A large number of alternative scenarios were explored, in which orepass orientation and location, as well as material parameters, were varied. Orepass wear was simulated by creating a groove at the bottom of the orepass. Progressive spalling (stress-induced) failure was modelled in selected cases, by removing rock that was encapsulated by a contiguous shear band and the orepass wall in an iterative manner. The results are used in the design process for selecting suitable orepass locations.


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