A Mechanical Model for The Stress-Strain Behaviour of Normally Consolidated Cohesive Soil

Abstract

ABSTRACT A mechanical model on the stress-strain behaviour of normally consolidated cohesive soil is presented in this paper based upon the experimental results. Theoretical equations are derived based on the theory of elastoplasticity. Time effect is not taken into consideration. In the analysis, strain increment is divided into two components, i. e., elastic and plastic ones. The plastic component in strain increment is further divided into two components termed here as ƞ-component and p-component. These components of plastic strain increment occur due to effective stress increments in the directions of constant mean effective principal stress and constant stress ratio, respectively. Corresponding to two components of plastic strain increment, two sets of plastic potential, yield function and hardening function are proposed, and nonassociated flow rule is formulated. The strain increments due to the effective stress increments in various directions are calculated by this theory. The model thus obtained for the stress-strain behaviour of soil reasonably explains the dependency of the direction of plastic strain increment on that of effective stress increment. This model is applied to the analyses of triaxial drained shear tests along various stress paths and satisfactory result is obtained. The stress-strain behaviour by this model is compared with those obtained by theories by Roscoe et al. (1963, 1968) and Calladine (1971). Discussion on the stress-strain behaviour of soil predicted by these theories including the author’s one is given.