Mechanical behavior and tension-shear failure mechanism of fractured rock mass under uniaxial condition

The influence of different shapes and distribution forms of fractures on rock mass failure behavior has been extensively studied. However, the influence of the matrix arrangement and non-through-boundary distribution of fractures has not been fully reported. In this paper, four failure modes are determined by physical experiments, and then the local tensile shear failure characteristics are obtained by disassembly along the fracture surface. Discrete element (PFC2D) was used to study the local mechanical behavior and stress field evolution of specimens. The results show that the existence of fracture groups obviously weakens the compressive capacity of the specimens. As the dip angle increases, the weakening degree decreases gradually. The failure modes can be divided into diagonal inclined fracture plane, Y-shaped fracture plane, inclined axial tensile shear fracture plane, and axial split fracture plane. The mixed failure area of local tensile and shear is concentrated in the small dip fault group, while the local failure mode of the large dip joint group tends to be tensile. Influenced by the dip angle of joint group, the regional distribution patterns of tension, and pressure chains at local rock bridge are different obviously, and the transmission paths are curved chain and X-shaped connection respectively. In general, a matrix joint group is conducive to partition failure of rock mass, large dip angle is more conducive to compression, and the failure mode is more inclined to block.