ACTIVE EARTH PRESSURE FOUNDED ON DISPLACEMENT FIELD

Abstract

This paper develops a numerical procedure for calculating the active earth pressure against a retaining wall, which allows consideration of the movements of retaining wall and backfill soil. The limit equilibrium analysis, which has been the principal concept for designing geotechnical structures, has the deficiency that the analysis cannot necessarily consider soil-structure displacements at failure. The design technique for overcoming this deficiency may have to provide a definite collapse mode like a potential slip surface, because the stability analysis subjected to a final collapse mode will keep on playing a major role in engineering practice. The proposed procedure assumes 1) Mohr-Coulomb and Coulomb yield criteria respective for backfill soil and friction interface, 2) fundamental non-associated flow rules related to the yield criteria, and 3) elastic-perfectly plastic stress-strain relationship. The procedure uses the initial stress method in FEM, and a set of yield stresses in each finite element is determined so as to minimize the total plastic work, because the procedure tries to solve the active earth pressure problem without considering the loading history. By use of these assumptions, the procedure enables to produce a definite failure region like a collapse mode supposed in the limit equilibrium analysis. The problem formulation based on these assumptions discloses an important property of Coulomb friction interface that the stresses on the interface are rather insensitive to varying some factors when keeping the initial stresses constant. The validity of the proposed procedure is verified by applying the procedure to several hypothetical case studies, where comparisons are made with Coulomb method, and where many important aspects in the earth pressure problem are clarified.