Investigation of Unstable Failure Potential of a Shear Slip Using DEM at an Underground Mine

Abstract

Geological structures and discontinuities subjected to the perturbations posed by mining operations in underground mining can be re-activated and cause fault-slip rockbursts. This study investigates geomechanical stability in terms of shear slip behavior along discontinuities using 3DEC with focusing on sudden changes of shear stress and shear displacement. A direct shear test is performed using a continuously yielding joint model to examine the evolution of shear stress and shear displacement on this joint. Further, this continuously yielding joint model is applied in major discontinuities of an underground mine to examine whether an unstable shear slip behavior exists, which is represented by a significant shear stress decrease and a shear displacement increase. By referring to geological mapping of this mine, four cases are developed and each case is set up with one type of major discontinuities with identically simulated mining operations. Results imply that the amplitude of shear stress decrease and shear displacement increase along discontinuities substantially increases with the depth due to higher virgin stresses and mining-induced stresses at greater depths. The discontinuity parallel to the interface between footwall and orebody is the least safe case and subjects to the largest potential of triggering seismic events. Keywords: Shear slip behavior, Unstable failure, Mining-induced seismicity, Continuously yielding joint model, DEM.