## 4 Numerical Model of Bedding Slope
### Numerical Modeling  
The slope height is 164 m, and the length is 536 m. The whole model is defined as a series of geometric objects, and the type of zone is given as quadrilateral and triangle. The global zone size is 5 m, with the local mesh encryption carried out for the surface and interlayer. The post-excavation (highway) slope model has a total of 2497 nodes and 2382 zones, and the pre-excavation (natural) slope model has a total of 2512 nodes and 2396 zones. The numerical calculation model of the slope and its boundary conditions is shown in Figure 4a,b. For seepage calculations, the left and right boundaries below the initial water table are set as boundaries of the constant water head, with the hydraulic head of 136 m and 29.5 m, respectively. Moreover, the left and right boundaries above the initial water table and the bottom boundary are set as impermeable boundaries. The surface of the slope is the rainfall infiltration boundary and set as the flow boundary. The rainfall infiltration boundary needs to be considered in relation to the magnitude of the rainfall intensity and the infiltration capacity of the topsoil: when the rainfall intensity is less than the infiltration capacity of the topsoil, it is treated as the flow boundary condition; when the rainfall intensity is stronger than the infiltration capacity of the topsoil, part of the rainfall forms overland runoff, and the boundary is treated as the boundary of the fixed water level. For stress and strain calculations, the left and right boundaries are constrained in the horizontal direction, and the bottom boundary is fixed in all directions. Because the modeling conditions and influencing factors of Zhuquedong slope are complex and the theoretical analysis is difficult to apply directly, the finite-difference numerical software FLAC\({}^{\text{3D}}\) 6.0 is used to analyze the evolution process and damage mechanism of the whole process of the slope. When FLAC\({}^{\text{3D}}\) software performs seepage analysis, it automatically adjusts the negative pore water pressure to zero and is unable to determine the hydraulic conductivity based on the saturated state of the geotechnical body [25]. In this paper, we choose to import the finite element seepage calculation results of saturated-unsaturated slope geotechnical bodies into FLAC\({}^{\text{3D}}\), which mainly considers two main effects of rainfall infiltration on the slope. (1) Rainwater has a deteriorating effect on geotechnical bodies and reduces their shear strength [26]. For this purpose, the strength decay function of the geotechnical body is constructed through the FISH language, as in Equations (9) and (10), where \(c(\mu_{w})\) is the integrated cohesion value related to the pore water pressure, and in general, \(c(\mu_{w})\) decreases with the increase in pore water pressure. Based on the pore water pressure value of each node obtained by traversing, the attenuated geotechnical body shear strength value is  
Figure 3: Rainfall monitoring data. calculated and assigned to the zones according to the spatial coordinates, as shown in Figure 5.  
\[\tau_{\rm f}=c(\mu_{\rm w})+(\sigma_{\rm n}-\mu_{\rm a})_{f}\tan\varphi^{\prime} \tag{9}\]  
\[c(\mu_{\rm w})=c^{\prime}+\chi(\mu_{\rm a}-\mu_{\rm w})_{f}\tan\varphi^{\rm b} \tag{10}\]  
(2) The infiltration and recharge of rainwater increases the pore water pressure in the slope, and the presence of buoyancy forces reduces the pressure between the rock layers,  
Figure 4: Numerical model of Zhuquedong slope: (**a**) hydrogeological profile; (**b**) mesh generation and boundary conditions. Figure 5: Slope cohesion distribution after strength decay. which reduces the slip resistance of the slip surface and leads to shear damage, and rupture of the top of the slope occurs when the buoyancy force is too large [27].