Simulation of deformation and fracturing in potash yield pillars, Vanscoy, Saskatchewan

The deformational response of yield pillars is simulated by numerical modeling using two distinct approaches for comparison with the observed response. First, the initiation and propagation of corner shear zones are reproduced using an approach based on linear elastic fracture mechanics (LEFM) and the assumption that fractures propagate along the direction of the maximum compressive stress. Second, since the corner shear zones as observed in the mine are characterized mainly by ductile effects and are the consequence of progressive plastic deformation, elasto-viscoplastic simulations that do not incorporate discrete fracture propagation are carried out. In these models, initiation and extension of corner ductile shear zones are shown to develop as bands of plastic strain localization. After collapse of the second generation shear wedges, stresses around openings appear to be stable while deformation continues (i.e., quasi-creep stage). As pillar deformation progresses, the location of the peak vertical stress transfers from the yield pillar to the abutment pillar. Furthermore, this peak stress over the abutment continues to move away from the opening with time, signifying the progressive extension of yielding around the opening.