## 4 Numerical Results  
To study the anisotropy of fractured rock mass, the mixed model was rotated to different angles (\(\theta\) = 0\({}^{\circ}\), 30\({}^{\circ}\), 60\({}^{\circ}\), 90\({}^{\circ}\), 120\({}^{\circ}\), 150\({}^{\circ}\), 180\({}^{\circ}\)), and the same size (100 m \(\times\) 100 m) was intercepted in the same area. Thereafter, the mixed models in different directions were converted into the PFC code for the biaxial compression test. The damage mechanism and stress-strain of the compression test of the models in different directions were monitored during the test. From the perspective of the failure mode of the rock mass (as shown in Figure 9), most of the failure of the rock mass is caused by extension along the tip of the existing joints until crack formation. When the direction of the RDFN model is 30\({}^{\circ}\), the failure of the rock mass is mainly caused by the expansion and extension of linear joints until fissure formation. Although fractal joints and Fourier-type joints play a role in the destruction of the rock mass, no through joints are formed. Therefore, these joints have little effect on the damage of the rock mass. For RDFN models in other directions, the failure development mode of the rock mass is too complicated to distinguish the dominant joints that cause the failure of the rock mass. The different failure modes of the RDFN model in different directions indicate that the fractured rock mass has anisotropic mechanical characteristics. By observing the stress-strain curves in Figure 10a, the shape curves of fractured rock mass in different directions are identified to differ. Moreover, the stress-strain curve of fractured rock mass has multiple peaks that differ from the intact rocks. According to the author, multiple peaks will exist in the stress-strain curve of fractured rock mass, such as 0\({}^{\circ}\) and 60\({}^{\circ}\), which may be due to the complex distribution of structural planes of the actual fractured rock mass. In the process of compression, after the fractured rock mass bears certain external force conditions, some areas in the rock mass will first produce a small damage phenomenon in which some rock blocks slip along the mechanism. When the rock mass on both sides of these joints starts to move in a staggered manner, the stress-strain curve will have a small peak. When the rock blocks around multiple joints produce such dislocation phenomena, the stress-strain curve has multiple peaks, as shown in Figure 10a. The different shapes of the stress-strain curves in different directions further reflect the anisotropic mechanical properties of the fractured rock mass. Figure 9a,b show that the distribution of force chains and bond failure is significantly different due to the different distribution of joints during compression in different directions. According to Figure 10b, the peak compressive strengths from 0\({}^{\circ}\) to 180\({}^{\circ}\) are 17.77 MPa, 32.04 MPa, 24.51 MPa, 17.58 MPa, 13.94 MPa, 20.93 MPa, and 19.81 MPa, respectively, and the degree of  
Figure 9: Anisotropic properties of complex RDFN models. (**a**) The contact force chain distribution characteristics. (**b**) The failure modes of rock masses. anisotropy (the ratio of maximum to minimum) is approximately 2.30. Among them, the stress peak intensity of the RDFN model in the 30\({}^{\circ}\) direction is the largest, of which the stress distribution is relatively uniform, and the stress concentration area is fewer. Further, its stress-strain curve is closer to the shape of the stress-strain curve of the complete rock mass. These findings indicate that although the distribution of joints in the 30\({}^{\circ}\) direction RDFN model is as complicated as that of others, the degree of cutting by the joints is not high and no through cracks are formed, thereby indicating that its mechanical properties, such as strength and deformation, are closer to that of a complete rock mass.