A DUAL-SURFACE DAMAGE MODEL AND EVALUATION FOR NATURAL SOILS WITHIN THE THERMOMECHANICAL FRAMEWORK

Naturally deposited or residual soils exhibit more complicated behavior than re-molded clays. A dual-surfarae damage model for structured soils is developed based on the ther-modynamies framework established in our first paper. The shift stresses and the transformation between the generalized dissipative stress space and actual stress space are established following a systematic procedure. The corresponding constitutive behavior of the proposed model is deter-mined, which reflects the internal structural configuration and damage behavior for geomaterials. Four evolution variables kij (i = D, R; j = V, S) and the basic parameters λ, s,v and e0 are introduced to account for the progressive loss of internal structure for natural clays. A series of fully triaxial tests and isotropic compression tests are performed for structured and reconstituted samples of Beijing and Zhengzhou natural clays. The validation of the proposed model is examined by comparing the numerical results with the experimental data.