###### Abstract
[27] conducted direct shear tests on double-joint rock-like specimens with different joint spacings and roughness under different normal stresses to study the influence of JRC, joint spacing, and normal stress on the shear behavior of double-joint rock masses; [PERSON] et al. [28] determined the normalized critical crack length through the analysis of the triaxial compression test results of sandstone, limestone, and siltstone samples and literature data; [PERSON] et al. [29] processed rocks of three lithologies--granite, coal, and sandstone--into single-edge notched cuboid specimens and conducted three-point bending tests to improve the accuracy of rock fracture assessment; [PERSON] et al. [30] prepared soft-hard interlayer rock (SHIR) specimens with different layer thickness ratios (LTRs) and conducted Brazilian tensile tests and numerical simulations under different interface inclination angles (\(\delta\)), LTRs, and layer sequences (LO); [PERSON] et al. [31] collected the IRT data of rocks under uniaxial compression through experiments and used methods such as wavelet denoising and reconstruction (WDRTIS) to eliminate the time noise, temperature drift, and spatial background noise in the IRT data; [PERSON] et al. [32] studied the mechanical properties and failure mechanisms of brittle rock-like samples with different combinations of two-dimensional and three-dimensional preset defects under uniaxial compression through experiments; and [PERSON] et al. [33] used the double torsion technique to conduct relaxation tests on quartz amphibolite, white sandstone, and red sandstone to study the subcritical crack growth behavior of rocks under the influence of water. However, experimental research can only obtain the \"appearance\" of rock failure and cannot reflect the internal mechanical mechanism of rock crack propagation. In addition, experimental research is highly affected by external factors and has high discreteness. Numerical simulation, as another means of scientific research, has broken through the limitations of theoretical and experimental research. Given reasonable parameters, numerical simulation can provide relatively accurate answers. Scholars initially used the finite element method to conduct numerical simulations of rock crack propagation. For example, [PERSON] et al. [34] established an improved particle-based model (GBM) of granite considering feldspar shape using a new Voronoi generation algorithm to simulate the direct shear tests of different joint persistence numerical models under different normal stresses; [PERSON] et al. [35] introduced the enrichment function of the extended finite element method (XFEM) based on the damage diffusion method (DSM) to accurately characterize cracks and holes; [PERSON] et al. [36] studied the cyclic friction response of rough rock joints under shear disturbances through laboratory experiments and numerical simulations and showed that the joint surface had significant plastic deformation and shear wear in the initial cycle. However, the finite element method has disadvantages in dealing with discontinuous problems such as cracks; that is, it is necessary to refine and remesh the grid at the crack propagation position, resulting in a large computational volume and easy calculation failure. The discrete element method is a meshless method different from the finite element method. This method discretizes the calculation domain into a series of particles and uses the contact behavior between particles to represent the complex mechanical behavior of rock crack propagation. For example, [PERSON] et al. [26] used PFC2D to simulate the rock shear process, calibrated the parameters to make the numerical curve match the experimental curve, and analyzed the microscopic force chains and failure mechanisms; [PERSON] et al. [37] simulated the rock breaking process by the impact hammer using the discrete element method (DEM) and found that the rock fragmentation was due to the formation of the crushing zone and crack propagation under the impact load; [PERSON] et al.