Abstract:The surrounding rock in rock engineering such as underground cavern excavation is usually in a state of bidirectional compressive stress. It is of practical significance to study the crack propagation under this stress state. Taking the rock mass samples with vertical cracks under low confining pressure triaxial compression or uniaxial compression as the research object, the distribution law of distal axial compressive stress and crack tip stress under different Poisson 's ratio ? and crack trace length a is analysed by numerical simulation. Based on the superposition principle, the expression of near-field stress at the tip of vertical crack / wing crack under biaxial compression is obtained, and the stress intensity factor and crack propagation direction of cracked rock mass specimen under this stress state are proposed. The results show that Poisson 's ratio and crack trace length a have a significant effect on the stress distribution at the crack tip when there is a distal axial compressive stress. The ratio of the stress at the crack tip to the axial compressive stress parallel to the crack surface has a linear function relationship with the Poisson 's ratio and a cubic function relationship with the crack trace length.