Discussion of “Applications of Limit Plasticity in Soil Mechanics”

Abstract

This paper is a discussion of the original paper by the same title. In the original paper limit analysis was used to obtain upper and lower bounds for the active earth pressure against a verticle standing smooth retaining wall. The analysis assumed Coulomb's yield criterion with constant c and phi. It was shown by the coincidence of upper and lower bounds that the Coulomb solutions for frictionless walls are exact. The analysis was extended by the upper-bound technique to include the effect of wall friction on the active earth pressure. In this discussion it is shown that the application of this analysis requires that proper stress and velocity boundary conditions should be specified so that the meaning of each solution corresponding to a problem will be clear. These were not considered in the original paper. This discussion explains why they cannot be neglected and points out the erroneous conclusions that result when they are neglected.