A Probabilistic Analysis of Seismically Induced Permanent Movements in Earth Dams

Abstract

ABSTRACT The earth dams built with compacted cohesive soils or dense sandy materials are vulnerable to seismically-induced permanent displacements which in some cases may be excessive. Analysis of seismic response involves an uncertainty inherent in the specification of ground motion. In this study, a probabilistic analysis is developed for evaluating seismically-induced permanent displacements in earth dams. The ground motion is modelled as a stationary random process which is defined by the Kanai-Tajimi spectral density function. The dynamic response of the dam to vertically propagating shear waves is formulated in frequency domain. The nonlinearity in shear modulus and damping is incorporated by using an equivalent linear model for the stress strain behavior of soils. The permanent displacement in dams is assumed to be in the form of the cumulative movements of a block of soil mass detached from the body of the dam. Numerical results of an example analysis and a parametric study are presented.