EVALUATION OF BOUNDING SURFACE PLASTICITY MODEL UNDER UNSATURATED CONDITIONS

摘要

Experimental results have shown that soil behaviour,even in very small strain is not absolute in its elasticity,the plastic strain occurs during loading and its ratio and the level are a function of stress level.The ability to express those aspects of soil behaviour is one of advantage of the bounding surface.In this paper,the triaxial test results on normally consolidated silty clay soil specimens under saturated (drained shear tests) and unsaturated (constant suction) conditions were used for evaluating the bounding surface plasticity model developed by Russell and Khalili (2004).Based on the critical state,the model can well express silty clay soil behaviour on both saturated and unsaturated conditions by using the concept of effective stress.the effect of suction in the modeling is considered only with regard to its effect on the value of effective stress.Significant volumetric contraction is observed with shearing in saturated and unsaturated tests.At the same time,the stress-strain curves express hardening occurrence in the soil behaviour.The model predicts stress volumetric contraction and hardening occurrence during shearing.There is a good agreement between model simulations and experimental data from saturated and unsaturated tests.