Deep Stability Evaluation of High-Gravity Dam under Combining Action of Powerhouse and Dam

摘要

The rock foundation of a gravity dam is usually cut into slide blocks by the structural surfaces. Its stability is controlled by the characteristics and the combining action of these structural surfaces. The failure of a gravity dam can be caused by the destruction or large deformation of local rocks under the condition of certain loads. The coupling of continuous-discontinuous deformation is a typical characteristic of the process. As a new design idea, the powerhouse and dam are combined into an integer with one structural pattern to improve the antisliding stability of the gravity dam. The external loads are undertaken together by the powerhouse and dam. The loads acting on the dam can be transferred partly to the powerhouse, and the powerhouse weight and tail water pressure can increase the dam's stability. The optimal design of a gravity dam section can be implemented, decreasing the project quantity, and reducing construction costs. This design idea has been adopted by the Yangtze Three Gorges Project in China. The coupling methods of discontinuous deformation analysis (DDA) and FEM are used to implement the deep antisliding stability evaluation for a gravity dam under the combining action of both the powerhouse and dam. The blocks are subdivided into the finite element meshes; the displacement field and stress field in the blocks are solved by FEM, and the contacts between the deformable blocks are simulated and analyzed with the DDA method. The description ability for the block deformation can be increased, the calculation precision for the stress field in block can be improved, and the ability of DDA in solving the large deformation of a multiblock system can be inherited. Therefore, the destructive form determined by this coupling method is closer to the actual situation. As an example, the coupling methods of DDA and FEM are used to analyze and assess the deep antisliding stability of the No. 3 left powerhouse-dam section of one dam when the upstream loads are taken together by the high gravity dam and the combined powerhouse located behind dam. The effect of combining the action of the powerhouse and dam is appraised by the numerical analysis for the mechanism transferring force between the dam and powerhouse, the influence on the deformation and stress of dam and powerhouse under the combining action of powerhouse and dam, the interaction of structural planes, etc. The entire instability process of the dam is simulated and analyzed by means of reducing the mechanical parameters. Last, the qualitative and quantitative analyses are implemented to evaluate the local and the whole stability of the gravity dam under the combining action of the powerhouse and dam.