Effects of porous sediments on seismic response of concrete gravity dams

A boundary-element approach for the dynamic analysis of continuous systems that may consist of water, viscoelastic, and fluid-filled poroelastic zones of arbitrary shape is applied to the study of a concrete gravity dam, which is subject to ground motion and interacts with the water, foundation, and bottom sediment. The present approach is very versatile and can be applied without difficulty to the analysis of problems in regions with very general geometries. Existing finite-element techniques are restricted to more particular geometries. The effects of sediment on the seismic response of gravity dams are evaluated for rigid and half-space viscoelastic foundation. The influence of the degree of saturation and the thickness of bottom sediment are analyzed. Some of the more remarkable conclusions obtained from the results of the present paper are: sediment compressibility has a very important effect on the dam response; the effects of fully saturated sediment are rather limited and results present very little changes with the sediment thickness when the foundation flexibility is taken into account; and partially saturated sediments produce significant changes in the system response, the influence of the thickness of the sediment layer being important in this case.