Abstract: Under the condition of complex in-situ stress and mining disturbance,the rock mass is often divided into discontinuous bodies by the fracture structure plane,which causes the anisotropy of the physical and mechanical properties of the rock mass,and then changes the mechanical response and failure mode of the rock mass. In order to further study the influence of fracture geometric characteristics on the mechanical properties and failure modes of rock under uniaxial compression,combined with the results of uniaxial compression test and digital photogrammetry of structural plane,a uniaxial compression discrete element model of heterogeneous rock under multi-fracture conditions was established,and the failure mechanism and mechanical characteristics of structural plane rock were studied. The results show that the numerical simulation of uniaxial compression of fractured rock can be divided into three stages:no damage stage,crack initiation stage and crack propagation-initiation stage. With the increase of the number of cracks,the elastic modulus of the rock continues to decrease,and the peak strength tends to be stable after decreasing. In the post-peak stage of the stress-strain curve,the failure mode changes from brittle failure to plastic failure. The interaction of the fracture network forms a force-bearing framework system,inhibits local damage,and provides a relatively stable path for stress transfer and micro-crack propagation. The failure mode of fractured rock is mainly tensile failure,and the damage at the crack tip is more severe. With the increase of the number of cracks,the tendency of micro-crack dip angle decreases. Although the propagation of microcracks causes partial stress release in the stress concentration area at the crack tip,the crack tip is still the stress concentration area when the rock is unstable and destroyed. The research results can provide a reference for revealing the mechanical response mechanism between rock and fracture structural plane. 

Key words: fracture number,failure mode,mechanical properties,crack propagation,numerical simulation