A Stress-Strain Relationship of Normally consolidated Cohesive Soil Under General Stress Condition

Abstract

The author has already derived a stress-strain relationship of normally consolidated cohesive soil based upon the stress probe tests performed under axisymmetric condition (Ohmaki, 1979). The theory of elasto-plasticity is used and increments in plastic strain can be calculated using a couple of yield function, plastic potential and hardening function. In this paper, a stress-strain relationship under three dimensional stress condition is derived, which is the generalized form of the one obtained under axisymmetric condition described above. Generalization of the stress-strain relationship is based on the theory of isotropic hardening elasto-plasticity using Matsuoka and Nakai’s (1974) concept on shear and failure of soil. Using the relation between stress and strain obtained, calculated result of strain is shown when shearing is done along various stress paths (stress paths with various dq/dp keeping p and θ constant, bending stress paths on the constant p-plane, where p is the mean effective stress, q the shear stress and θ the amplitude of effective stress vector) in principal effective stress space. A stress-strain relation obtained, strain paths projected on the π-plane and strain increment vector are qualitatively explaining the experimental results acquired so far.