Study On The Computation Model Of Concrete Dam Reservoir Hydrodynamic Interaction

Dam-reservoir dynamic interaction is one of the most important influence factors of the dynamic response of concrete dams subjected to the strong earthquakes. Reasonable determination of the hydrodynamic pressures on the dams and its effects on the dam body during earthquakes are the basis of the safety evaluation of the dams. However, the volume of the dam is huge and the water compressibility, the absorption of the reservoir sediments, the flexibility of the foundation, the geometry of the reservoir all affect the hydrodynamic pressures. Therefore, the field test method can not be obtained the accurate value and the distribution of the hydrodynamic pressures. In terms of numerical and theory analysis, Westergaard gave the pioneer work on hydrodynamic pressures acting on rigid dam. After, many researches have extensively studied earthquake analysis of dam-reservoir system using various methods including analytical method, finite element method, and boundary method and so on. But the accurate and the efficiency of the computation model can not satisfy the demand of the engineering application and science research. So it is necessary to study a high efficient and precision numerical method for computing the hydrodynamic pressures. Based on Scaled Boundary Finite Element Method (SBFEM), this dissertation presents a computation model of dam reservoir hydrodynamic interaction and a novel radiation boundary condition for dam-reservoir systems, and also improves the coupled finite element and scaled boundary finite element approach for the earthquake response analysis of arch dam reservoir foundation systems. The major content of this dissertation is organized as follows:(1) Based on SBFEM, it presents the computation model for hydrodynamic pressures acting on the dam when the reservoir extended to infinity with uniform cross-section. It can be derived the governing equations of hydrodynamic pressure in the frequency domain by weight residual method or Hamilton variable principle. The water compressibility and absorption of reservoir sediments can be conveniently taken into consideration. Only the dam-reservoir interface needs to be discretized to model the fluid domain, the solution is automatic satisfy with the radiation condition at the infinity, and the hydrodynamic pressure in the stream direction is solved analytically. Several numerical examples including a gravity dam with an inclined upstream face and an arch dam with a reservoir of arbitrary cross-section are provided to demonstrate the computational efficiency and accuracy of the proposed model. (2) Based on SBFEM, it provides a new boundary condition of the stress on the truncation boundary suited for the complex shape of the reservoir-dam systems. The proposed approach can conveniently consider the water compressibility, the absorption of the reservoir boundary and the shape of the reservoir. Only the boundary of the dam-reservoir systems in the near field needs to be discretized. The numerical examples explain the proposed approach is not only satisfied the radiation condition boundary, but also for reducing computational efforts.(3) Coupling the SBFEM model for computing the hydrodynamic pressures on dam and the unbounded foundation with the FEM model for dam body, it improves the computation model of the dam-reservoir-foundation systems. SBFEM is good at solving the unbounded domain problems, and it can be seamlessly coupled with FEM, therefore, they can give full play to dam-reservoir-foundation problem. Besides, the computation model of hydrodynamic pressures based on SBFEM is much more accurate, and it can improve the precision of the coupled model. This paper presents the influence of dam-reservoir hydrodynamic interaction to the response of the dam, the computation model and the results can be of significant reference value for the high dam construction and the seismic safety evaluation.