Responses of Pre-Holed Granite under Coupled Biaxial Loading and Unloading Stress Condition

Underground excavation is a necessary process for constructing mines, tunnels and depots in granite rock mass. In this study, the numerical specimens were established by discrete element method confirmed laboratory experiments order to investigate peak stress, cracking development failure properties of pre-holed under coupled biaxial loading unloading conditions. The results show that, containing D-type square holes, strengths first decrease, then increase finally decrease as inclination angles holes increase. For with elliptical increases holes. elliptical, circular, that order. cracks initially appear near crossover points between X-type shear fracturing plane pre-hole center gradually expand along direction, which indicates primarily failure. When overall length expanding direction extends size center, specimen occurs. existing connect slip vicinity hole, triggers