## 2 Numerical Simulation of CSG Dam upon Overburden
### Stress-Strain Analysis  
In the early phase of the engineering design, relevant organizations used the material mechanics method to calculate the compressive stress at the junction with the dam foundation under two working conditions: completion period and impoundment period. The result shows that the maximum compressive stress in the completion period and the impoundment period is, respectively, 0.4 MPa and 0.43 MPa, both of which meet the relevant design requirements. The assumptions about materials in the mechanics of materials method are all linear elastic, which differs from the actual situation. Therefore, it is hoped to conduct finite element numerical simulation for verification. The finite element calculation results show that the maximum compressive stress at the junction of the dam body and foundation in the completion period is 0.45 MPa, located near the heel of the dam. In the impoundment period, the maximum compressive stress is 0.46 MPa, located near the toe  
Figure 5: ANSYS calculation process. of the dam. It is found by the finite element results that due to this dam type with two stages, the compressive stress occurs at the junction of the first and second stages, different from the dam type with single stage whose maximum compressive stress is at the junction of the dam body and foundation. The following text provides a detailed analysis of the characteristic values of the dam body. The results of the completion period and the impounding period are selected for comparison. Figure 6 shows the horizontal displacement at the bottom of the dam body. The value of the horizontal axis represents the distance between the nodes at the bottom of the dam body and the centerline of the dam body. The positive direction of the horizontal axis is along the river direction, and the negative direction of the horizontal axis is against the river direction. The negative vertical axis represents displacement against the river direction, while the positive vertical axis represents displacement along the river direction. It can be seen that, with the centerline of the dam body as the boundary, the bottom of the dam body in the upstream part deviates upstream, and the closer to the centerline, the smaller the displacement value. The bottom of the dam body in the downstream part deviates downstream, and also the closer to the centerline, the smaller the displacement value. This is due to the symmetry of the cemented gravel dam body. During the impounding period, the displacement of the dam body bottom generally deviates downstream by about 0.5 mm, with larger displacement around the upstream dam heel and downstream dam toe, with the maximum displacement at the upstream dam heel position, and smaller displacement on both sides of the centerline. The characteristic values and positions of the dam body in the completion and impounding period are shown in Table 3. Maximum displacement in the X-direction in both completion and impounding periods occurs at the downstream toe of the first stage of the dam body, and the direction of displacement is along the river direction. Due to the influence of upstream water pressure, the maximum displacement in the X-direction in the impounding period is greater than that in the completion period. The maximum settlement in the Y-direction also increases under the influence of water pressure during  
Figure 6: Horizontal displacement at the bottom of the dam. the impounding period, but due to the influence of uplift pressure, some of the settlement is offset, so the final value of settlement does not change significantly, but the position of the extreme value is shifted upstream relative to the completion period. The maximum compressive stress in both completion and impounding periods occurs at the upstream dam heel where the first and second stages of the dam body meet, indicating that this is a weak point of this type of the dam with two stages.