Analytical investigation of instability for saturated sand under triaxial condition

This paper presents the analytical investigations for the strain softening behaviour of sand found in undrained and strain controlled drained triaxial tests. The analysis is based on an isotropic hardening elasto-plastic constitutive model with a non-associated flow rule proposed by the authors. The following conclusions were reached. (1) The proposed model successfully simulates the strain softening behaviour of extremely loose sand under undrained triaxial conditions. (2) The conditions for the initiation of stain softening behaviour have been clarified. (3) The nature of the volume change and drainage conditions of a soil element have a marked influence on the occurrence of the strain softening phenomena.