Abstract: Based on the theory of fluid-structure interaction, this paper develops a dynamic simulation method that accounts for the compressibility of reservoir water and the effect of bottom sediment layers. It models water as an acoustic medium, and uses boundary impedance conditions to simulate the absorption and reflection effects of sediment layers on wave energy. Accordingly, we can transform the sediment layer problem into one-dimensional wave propagation through the foundation depth, and analytically derive the corresponding boundary parameters. Validation shows the method effectively captures the dynamic response of sediment layers with varying thicknesses. In a specific case study, we construct a three-dimensional finite element model for dam–reservoir water–sediment–foundation system of a real asphalt-concrete core rockfill dam, and simulate its dynamic behaviors at different sediment layer thicknesses. The results indicate that sediment thickness has a minor influence on dam displacement, but imposes a significant effect on the dams￠ hydrodynamic pressure, acceleration, and stress responses. Sediment layers produce suppression on the hydrodynamic pressure, and the suppression is most pronounced in the case of the sediment thickness ranges of 0.1H - 0.2H (H is the dam height). This study helps to understand the bottom sediment effect on the dynamic responses of dam–reservoir water–foundation system.

Key words: earth-rock dam, reservoir water compressibility, reflection coefficient, sediment layer, seismic response