Dynamic Pressure of Water and Sediment on Rigid Dam

Abstract

Earthquake response of reservoir sediment and its dynamic interaction with the impounded water are analyzed using a two‐dimensional model of poroelastic media. The pressure wave equation for the pore water and the sediment is solved by an implicit finite difference method coupled with a fast Poisson solver. The numerical scheme requires a conversion of the boundary condition on the rigid dam face to a Dirichlet boundary condition. For incompressible impounded water, a reduction in the dynamic pressure appears at the onset of ground motion when the bulk modulus of pore water in the sediment is compressible. The pressure rises rapidly with the celerity of pressure wave and exceeds that of Westergaard's solution for the incompressible case without the sediment. Augmentation of the pore pressure is primarily caused by the inertia of the sediment and the Stokes drag. The hydrodynamic pressures on the dam face could exceed significantly those calculated by an incompressible two‐fluid model for an idealized liquefied sediment.