## 3 Simulation Results and Analysis
### Uniaxial Loading Conditions
#### 3.1.2 Anisotropic Characteristics of Failure Modes  
Figure 9 illustrates the failure modes of shale under uniaxial compression at different bedding angles. Generally, the failure behavior of anisotropic rocks under compression is more complex than that of homogeneous rocks, with the crack initiation and propagation differing significantly from those in homogeneous rocks. For the three bedding orientations, the failure modes exhibit distinct anisotropic characteristics:  
Figure 8: Tensile strength under different bedding angles and bedding distributions. Figure 9: _Cont_. (1) Bedding Parallel to the Axial Force Direction: Shale experiences tensile splitting failure with a complex cross-sectional morphology in this configuration. The short cracks that form along the bedding planes intersect and develop into a more intricate crack network, leading to the specimen's splitting failure. The primary crack direction aligns with the axial force. The AE data reveal a pronounced strip-like pattern, with signals concentrated in the middle of the specimen, showing both long and short signals along the bedding. This behavior occurs because, under axial compression, the vertical bedding breaks first, producing numerous microcracks. As stress increases, these microcracks interconnect, forming a crack network that causes specimen instability. (2) Bedding at an Angle to the Principal Stress Direction: Under this condition, shear slip failure occurs along the bedding plane, causing the specimen to fracture into two larger pieces. The weak bonding of the bedding planes facilitates slip when the bedding and axial force form an angle, making it easy for cracks to propagate along the bedding plane under the applied forces. The crack initiation and growth occur along the bedding planes, resulting in a relatively simple crack morphology. At a 30\({}^{\circ}\) bedding angle, the failure path extends entirely along the bedding plane; at 60\({}^{\circ}\), the failure path also follows the bedding, but a peak-shaped protrusion appears at a certain point. Acoustic emission signals during failure are distributed in an elliptical pattern, concentrated on the bedding plane, with the primary damage represented by a crack that penetrates the bedding. (3) Bedding Perpendicular to the Axial Force Direction: In this case, a tension-shear composite failure mode develops, with cracks propagating along the bedding plane and the direction of axial force. Initially, cracks preferentially form along the weak bedding plane. As the stress increases, crack propagation gradually shifts toward the axial direction, eventually forming a serrated primary crack with high tortuosity. Acoustic emission data show that cracks parallel to the bedding direction primarily exhibit tensile failure, whereas cracks inclined to the bedding direction show increasing shear signals. Figure 9: Uniaxial compression failure modes under different bedding angles. (**a**) Bedding 0\({}^{\circ}\); (**b**) Bedding 30\({}^{\circ}\); (**c**) Bedding 60\({}^{\circ}\); (**d**) Bedding 90\({}^{\circ}\). The red AE signal represents shear failure, and the blue AE signal represents tensile failure. In summary, when the bedding angle is 0\({}^{\circ}\) or 90\({}^{\circ}\), the destruction process is characterized by the competition between the bedding planes and the matrix under axial force, leading to progressive failure and a complex crack network. When the bedding angle is 30\({}^{\circ}\) or 60\({}^{\circ}\), the bedding plane becomes the dominant failure plane under axial pressure, with destruction primarily occurring along the bedding plane, resulting in a more straightforward failure mode and lower strength. Tensile failure is a significant failure mode for deep reservoir rocks. Figure 10 illustrates the failure mode of shale under tensile stress, along with the corresponding spatial distribution of AE signals. The results indicate that the weak bedding planes significantly influence the tensile failure behavior of shale.