SEISMIC ANALYSIS OF GRAVITY DAMS .1. MODELING OF SEDIMENTS

A finite element technique is developed for two-dimensional dynamic analysis of systems composed of a gravity dam, the water contained in the reservoir, the sediment accumulating on the reservoir bottom, and the underlying foundation. Of particular significance in this development is the modeling of sediment as a two-phase medium, specifically, a fluid-filled poroelastic solid. It is shown that this model of the sediment can be accommodated rigorously in the derivation of a hyperelement, which recognizes the coupling between the water, sediment, and foundation and permits convenient discretization of the upstream region. The hyperelement is obtained by synthesizing the motion in the water-sediment-foundation stratum from the modes of wave propagation and a particular solution representing the applied ground motion. In the companion paper, results of an application of the present technique to the study of sediment effects on the seismic response of dams are reported and discussed.