SEISMIC DISPLACEMENT ANALYSIS OF EARTH RETAINING STRUCTURES

Abstract

In Engineering practice, it is more logical to define failure in terms of displacements. For some important structures, even very small displacements constitute failure. Hence, there is a need to carry out displacement analysis. For retaining structures when the backfill carries sur-charge loads with considerable mechanical strength, potential failure planes have to be identified with due considerations to the mechanical strength of surcharge. Besides, it is also nece-ssary to establish the relationship between the displacements and rotations of the structure when it tends to rotate about a point above its top level under the influence of earth forces rrEsulting from relative displacements between the interfaces of sliding wedges. It is also required to establish a.relationship between the displacement of the structure and the resisting forces required to keep the structure in equilibrium and the resisting forces mobilized at the permissible displacement/ rotation. Satisfactory analytical methods are not available currently for this purpose. Seismic plastic displacements may be obtained by the method proposed by Newmark and further developed by (bodman and Seed (1966) and by Richards and Elms (1979) . These methods can not be used directly for retaining structures as no definite procedure for obtaining yield acceleration required- for such investigations has been presented. Therefore, there is an need for development of a better analytical method.