“…The above studies have carried out in-depth research on the stress distribution theory around the hole, the failure process of the sample with holes, the effect of the stress around the hole on the fracture evolution, and the influence mechanism of fracture evolution on permeability, but there is little research on the evolution of the coal stress and the fractures during the drilling process. In recent years, numerical simulation often has been used in the study and analysis of fracture propagation in rock materials, such as in scanning electron microscopy (SEM), atomic force microscopy (AFM), 20,21 extended finite element method (X-FEM), 22 boundary element method (BEM), 23,24 and cellular automata (CA). 25 Discontinuous medium methods, such as DEM (discrete element method), 26,27 rock failure process analysis system (RFPA), 28,29 and universal distinct element code (UDEC), have also been used.…”