## 4 Analysis of the Results
### Analysis on Bearing Capacity of Dam Structure  
#### 4.2.1 Calculation of Overload Capacity of Dam Body by Overload Method  
The bearing capacity of the CSGR dam of Xijiang is analyzed by comparing different types of dams and the shear strength parameters of dam bodies that are of the same type. The evaluation indexes selected are the dam crest displacement along the river, the overload failure modes of the dam body, and the vertical stress on the foundation. Drawn from the  
Figure 11: Shear stress curve of dam structure along path-3 within upstream surface. Figure 10: Shear stress curve of dam structure along path-2 within upstream surface. Figure 9: Maximum principal stress curve of dam structure along different paths with water level of check flood. displacement of the dam crest along the river in Figure 12, with the overload safety factors of the RCC gravity dam, the CSGR dam (with weathered material) and CSGR dam (without weathered material) are, respectively, 2.4, 3.1, and 4.2; the comprehensive overload capacity of the CSGR dams, either with or without the weathered material, triumphs over that of the RCC gravity dam, while the safety factor of the CSGR dam with weathered material is 26.2% smaller than that without the weathered material. The mechanism of the plastic failure mode of the CSGR dams can be seen in Figure 13, which starts with the plastic zone in the dam toe and ends with the dam heel. After expanding through both the dam toe and the heel area, at some point the plastic zone is developed into plastic failure in the dam heel, which shall spread upstream until a buckling failure is formed as a result of plastic penetrating slippage. For the CSGR dam with the weathered material, when the overload coefficient is from 1.2 to 1.8, the plastic zone appears at the dam toe first and then at the dam heel. When the overload coefficient is 2.2, the plastic zone at the dam toe begins to develop toward the upstream, and the dam body is unstable until 3.1. The entire plastic penetrating slippage line of the CSGR dams appears at a height of 13-20 m on the upstream surface or 0-3 m on the downstream surface; its plastic zone grows upstream at an angle of 13-22\({}^{\circ}\). For the CSGR dam without weathered material, when the overload coefficient is from 1.4 to 2.2, the plastic zone appears at the dam toe first and then at the dam heel. When the overload coefficient is 3.8, the plastic zone at the dam toe begins to develop towards the upstream, and at the dam heel it continues to develop towards the depth of the foundation and the foundation surface. When the overload coefficient is 4.2, the sliding line of the dam body is basically formed, and the plastic zone on the foundation surface expands rapidly. Until the overload coefficient is 4.4, the dam body is unstable. The plastic failure mode of the RCC gravity dam is different from that of the CSGR dam mentioned above as the plastic zone appears in the dam heel and keeps expanding inwardly until the plastic failure is developed, which spreads downstream and eventually causes plastic penetrating slippage. When the overload coefficient is from 1.8 to 2.4, the plastic zone occurs in the dam heel area and continues to expand until the overload coefficient is 2.5, and the dam body forms a plastic through slip line and loses stability. Compared with other dam types, the overload process of CSGR has a greater impact on the foundation. The state of vertical stress on the foundation of Figure 14 shows that as the overload coefficient increases, CSGR dams have never featured the tensile stress zone, and the fluctuation of compressive stress mostly appears in dam heel. As for the RCC gravity dam, whose vertical stress on the foundation shifts violently, the tensile stress appears and keeps spreading in the dam heel when the overload coefficient reaches 1.8, and the compressive stress zone of the dam toe is continuously tightened with the growth of the stress value. Figure 12: Displacement of two dam types. Figure 14: Vertical stress on foundation of two dam types.