Numerical investigation of effect of particle shape on isolated extracted zone (IEZ) in block caving

The block caving is one the most economical underground mining methods; the recovery ratio of resources is directly related to the quality of IEZ in block caving. The effect of particle shape on IEZ in block caving is numerically investigated through Particle Flow Code (PFC). Six categories of clumps with different shapes are created. The irregularities of clump shapes are quantitatively characterized through definition of roundness (2D) and sphericity (3D). In PFC2D, the quality of IEZ increases with decreasing of clump roundness whereas in PFC3D the quality of IEZ increases with increasing of the clump sphericity. The result of PFC simulation is calibrated and compared with the physical experiment. It is concluded that when the roundness of clump is 0.630 and the sphericity of clump is 0.973, the results of numerical simulation and physical experiment have good consistency. The Bergmark-Roos model is proper to theoretically describe the shape of IEZ in PFC3D and the kinematic model is proper to describe the shape of IEZ in PFC2D. In PFC simulation, the decreasing of clump sphericity can increase the internal friction angle and repose angle. Therefore, the friction properties of particles in PFC should both consider the assignment of friction coefficient and the effect of particle shapes.