Numerical simulation of shear mechanical properties of coal structural plane

In order to study the shear mechanical characteristics of coal bedding and cleat structural plane，and provide basis for surrounding rock classification and control of coal mine roadway.Taking the bedding and cleat structural planes in Jincheng Mining Area No.3 coal as the research object，the macro mechanical parameters of standard coal samples are determined by laboratory test，the numerical model containing real coal structural plane is established by PFC software，and the shear failure process of structural planes with different roughness is simulated，the results show that under the action of low normal stress，the crack mainly occurs on the surface of large convex body on the bedding structural plane，and the tensile crack is the main one; with the increase of normal stress，the cracks in the convex body gradually increase and connect，forming an obvious shear crack zone; with the increase of the roughness of the coal bedding structural plane，the structural plane will produce large dilatancy deformation，and there will be macro tensile cracks extending to the inside of the sample along the root of the convex body; the peak shear stress and the number of shear cracks and total cracks in the coal structural plane model increase obviously with the increase of roughness and normal stress.With the increase of normal stress，the proportion of shear cracks in the total cracks also increases gradually，indicating that the shear failure of the structural plane increases gradually under the action of high normal stress.The shear strength of coal structural plane is significantly reduced by cutting，with the maximum reduction of 0.3 MPa and the reduction range of 11%.However，the different distribution directions of cutting basically have no effect on the shear strength of coal structural plane.The existence of cutting will significantly increase the number of cracks when coal structural plane is damaged，and the failure form of cutting is mainly tensile failure.