## 1 Introduction
Although microscopic damage in shale has been observed using techniques such as X-ray diffraction (XRD) [14], scanning electron microscopy (SEM) [13], and digital imaging correlation (DIC) [16], these methods have limitations; for example, it is difficult to observe the internal progressive damage and destruction processes. Furthermore, their high operational costs make them less suitable for large-scale applications. Additionally, controlling the bedding characteristics of natural rocks remains challenging. While rock-like materials allow bedding density and strength adjustments, the processes are complex, and the material costs are high. In contrast to laboratory experiments, numerical methods have gained popularity in recent years in geotechnical engineering due to their ability to simulate rock failure processes and visualize internal crack evolution. [PERSON] et al. [25] performed numerical simulations of three standard rock tensile strength tests (direct tensile test, Brazilian disc test, and three-point bending test) using three-dimensional (3D) rock failure process analysis (RFPA3D), revealing significant differences in the tensile strength results and emphasizing the strong influence of the size effect. [PERSON] et al. [26] conducted direct shear tests on shales with different bedding orientations using PFC3D and found that the bedding orientation significantly affected the shear strength and crack morphology. [PERSON] et al. [27] studied the impact of the bedding inclination and confining pressure on shale failure behavior using PFC\({}^{\rm 3D}\), while [PERSON] et al. [28] explored the effects of the bedding inclination, bedding density, and confining pressure on shale's mechanical properties and brittleness based on RFPA\({}^{\rm 3D}\). These studies highlight the effectiveness of numerical methods, yet most research on shale has focused on uniform bedding structures, often assuming constant bedding spacing in numerical models. However, the bedding structure of natural sedimentary shales is typically more complex, and its anisotropic effects are significant. Therefore, the distribution of bedding in numerical models, as a crucial property of the bedding structure, must be fully considered in such studies. A deep understanding of the shale fracturing mechanism and the optimization of fracturing techniques are crucial for achieving the large-scale, efficient development of deep shale gas reservoirs. To gain a deeper understanding of the influence of the bedding distribution on the mechanical properties of shale under different stress states and uncover the underlying failure mechanisms, this study employed the RFPA\({}^{\rm 3D}\) method to conduct compression and tension tests under uniaxial stress on shales with three different bedding distributions and four bedding angles, as well as compression tests under triaxial stress states on shale with a specific bedding distribution. The study obtained the mechanical characteristics, such as the strength, elastic modulus, and peak strain, of randomly distributed bedding shale under different stress paths and analyzed the anisotropic failure modes and crack propagation paths. Additionally, the research explored the effect of the bedding distribution on the anisotropic behavior under uniaxial stress and fitted shear strength parameters based on the triaxial compression test results. These findings provide a necessary theoretical basis for understanding the failure behavior of layered rock masses under various stress paths and the formation mechanisms of fracture networks.