Effect of boundary conditions on the centrifugal model of concrete gravity dams subjected to underwater explosion

Scaled-down centrifugal model testing has garnered significant attention for exploring the responses of concrete dams subjected to underwater explosions. This interest arises not only due to its cost-effectiveness compared to full-scale testing but also its ability to replicate both the internal stress distribution of dams and hydraulic pressure field of water caused by gravity. In centrifugal model tests, underwater explosions are usually carried out in a small and very strong container with stiff walls. Inevitably, reflected shock waves would be generated from these stiff walls and impose a significant effect on the damage of concrete gravity dams, leading to inaccurate prediction for prototype. However, no study has ever investigated the effect of the boundary condition on the centrifugal model of concrete gravity dams subjected to underwater explosions yet. To close this gap, a numerical model of a concrete gravity dam was developed and calibrated in this study. Numerical simulation was further performed to investigate the effect of reflected waves on the damage mode and dynamic responses of the concrete dam. It was found that concrete gravity dams with fixed boundaries suffered more severe damage and higher responses than those of dams with non-reflecting boundaries, indicating reflected shock waves have a significant influence on the dynamic responses of the concrete gravity dam. Aluminum foam layers were demonstrated better effect than rubber layers to reduce the wave reflection, e.g., reducing the peak pressure of reflected waves by up to 47%, and thus mitigate the effect of reflected waves on concrete dams.