As a porous medium material, coal and rock mass often contains pore defects of different sizes and shapes inside, and these defects can affect the mechanical properties of coal and rock. When coal and rock with hole defects are subjected to asymmetric loading induced by engineering excavation, it will further exacerbate the damage and fracture of coal and rock, leading to engineering instability disasters. In this paper, the particle discrete element program PFC (Particle Flow Code) was used to carry out asymmetric loading experiments on coal and rock with pore defects of different shapes, and the influence of the coupling effect of asymmetric load and pore defects on the mechanical properties and damage mechanisms of coal and rock was analyzed. The results show that pore defects can reduce the mechanical parameters of coal and rock. The degree of reduction in mechanical parameters varies with different defect shapes. Asymmetric loads can intensify the reduction of mechanical parameters of coal and rock caused by pore defects. Under asymmetric loading, microcrack propagation exhibits four-stage characteristics, and the macro failure mode is controlled by the combined influence of defect shape and asymmetric load. The location and size of the stress concentration area are greatly affected by the shape of the hole defect. Under the action of the asymmetric loading, the displacement vectors of the particles around the hole all point to the non-loading area. Tensile-shear composite failure occurs under both loading methods.
Wang et al. (Thu,) studied this question.