SEISMIC SLOPESTABILITY ANALYSIS OF EMBANKMENTS"

Abstract

In a conventional method of slope stability analysis of dams a sliding surface is assumed and a quantitative estimate of the factor of safety is obtained by examining the equilibrium conditions at incipient failure comprising the strength of the fill material on the entire surface. These procedures indicate the factor of safety of the dam with respect to instability but provide no information regarding the deformations of the dams. Differential settlement between sections along the crest of dams may lead to development of cracks which would allow passage of water and progressive failure by erosion and piping. Differential compressibility of the core and shell of zoned embankment may result in hydraulic fracturing if the stresses at any elevation are reduced to values less than the pressure of water at the same elevation by transfer of part of the load to less compressible shells. In recent years, however there has been a growing realization of the need to determine the stress distribution and deformations inside the dam section. In this dissertation, elastic stress distributions, inside the dam section have been obtained considering plane stress condition and the results are compared with those given in literature. An earth and rock fill dam without and with foundation soil are considered. It is assumed to respond as a two dimensional system under plane stress conditions. The two dimensional assumption is also extended to model the compressible reservoir water a body impounded upstream of the dam. The foundation is also assumed as two dimensional. The dam is analyzed is analyzed for three loading cases i.e., gravity (G), gravity and hydrostatic (G + HS) and Gravity, hydrostatic and hydrodynamic loading (G +Hs + Hd). In dynamic analysis, ground acceleration record of El Centro Earthquake (1940) has been used in the time domain analysis. Stresses at heel, acceleration and displacements at the crest of dam have been presented. Finite element soft ware ANSYS 10.0 has been used for all the computation.