MICROMECHANICAL ANALYSIS OF SATURATED CLAY SHEAR BEHAVIOR IN CONSOLIDATED UNDRAINED CONDITION

The experimental results under consolidated undrained condition reveal that the deformation of saturated clay exhibits the following characteristics:(1) loading shear modulus varies in loading process;(2) unloading shear modulus is constant.Based on the results,a micromechanical damage constitutive model of consolidated undrained saturated clay is presented by micromechanical analysis about every phase.This model views that the clay is composed of pore water and joint solid skeleton at the onset of loading and deforms linearly until the joint solid skeleton is subjected to damage.The damage of the joint solid skeleton is defined as the slide of clay grain interface.In the damage deformation stage,the clay specimen is composed of three phase,i.e.pore water,joint solid skeleton and sliding solid skeleton.The volume fraction and the shear modulus of the sliding phase vary in loading process.A method to calculate the volume fraction of the sliding phase in terms of Mohr-Coulomb law and the modulus decreasing curve of the sliding phase in terms of conventional triaxial test are given.The hypothesis is explored under which the nonlinear response of the clay is entirely due to the increase of the sliding phase volume fraction and the decrease of the sliding phase shear modulus.Based on Eshelby′s solution to the problem on ellipse impurity in infinite elastic body and self-consistent method,an average scheme is found to get a realistic transition from the relevant information available at the micro-scale to the overall nonlinear response at the macro-scale.In addition,an approach is given to obtain micro-parameter by conventional triaxial test.Finally,test on the versatility of the proposed model including varying hydrostatic stress and stress paths indicates that the proposed model is capable of predicting the deformation behavior for various conditions.