# Deformation Analysis of Large-Scale Rock Slopes Considering the Effect of Microseismic Events
## 4 Numerical Simulation of the Rock Slope  
### Model Setup  
The geological profile of the slope along the arch axis at the elevations ranging from 550 m to 880 m was selected to build the numerical model, as shown in Figure 5. The software ANSYS was used to generate grids. The grid node data were imported to FLAC3D via a plug-in. The model consisted of 246,075 hexahedron elements. The numerical model had a bottom elevation of 480 m and a maximum elevation of 880 m. The model was 570 m long, perpendicular to the river, and 50 m along the river. The model mainly includes nine weak structural planes, as shown in Figure 3 (i.e., the intra formational disturbed belts LS337, LS331, LS3318, and LS3319, interlayer disturbed belts C3-1 and C3, and faults on the posterior border F17, f110, and f108). Table 3 shows the characteristics of the intra formational disturbed belts. The positive direction of the x-axis points to the right bank slope (SE 50\({}^{\circ}\)); the positive direction of the y-axis points to the river upstream (SW 40\({}^{\circ}\)); the positive direction of the z-axis is vertically downward. The x-direction normal constraints are imposed on both sides of the calculation area; the y-direction normal constraints are imposed on its front and back; the x-, y-, and z-direction constraints act on some of the key nodes at the bottom, and the free faces are free. The rock mass in the slope is classified into four categories according to the GB50287-2006 Code for Hydropower Engineering Geological Investigation in China: Class II, class III, class IV and class V, with the lithology of basalt. Moreover, the classes II, III, IV and V correspond to the values of 90-75%, 75-50%, 50-25% and below 25%, of the RQD criterion (rock quality designation) respectively [29].  
Based on the experimental results listed in Table 4, the mechanical parameters of the rock mass and structural plane in the model were set. After applying the boundary conditions to the model, the C language was applied to compile the damage constitutive model, considering the effect of the rock fracture scale. When FLAC3D software runs, the complied information is directly loaded and attached to all rock elements in the model as a dynamic link library. The excavation of the spandrel arch of the foundation slope began on 5 September 2013. The layered and segmental blasting excavation method was adopted, with each layer approximately 10 m thick. The excavation progress is shown in  
Figure 4: **(a)** Sprayed concrete cracks occurred at the sidewall of PSL2, **(b)** sprayed concrete spalling occurred at the peripheries of the entrances to WML2, **(c)** cracks occurred along fault F17 at the downstream slope of the spandrel groove, and **(d)** Sprayed shotcrete spalling occurred at the sidewall of WML1.  
Figure 6. To reflect the surrounding rock mass deformation response mechanism of the slope under layered excavation, the reinforcement and excavation were considered as truly as possible in the numerical simulation. A numerical model considering anchor cable reinforcement is shown in Figure 7. The anchor cables were adopted on-site with their prestressing force of 3000 kN. The length of the anchor cable was 30 m to 70 m (the length depends on the geological exploration conditions) and the arrangement spacing was 4 m \(\times\) 4 m. The anchoring angle was perpendicular to the slope foundation surface. Figure 8 illustrates the anchoring diagram in the numerical model.  
Figure 5. Numerical model of the rock slope.  
Figure 6. Detailed excavation schedule of the rock slope.