Modeling Temperature-Dependent Behavior of Soft Clay

In this study, an anisotropic thermal-elastic-plastic (TEP) constitutive model is developed for soft clays. Two yield surfaces, namely the current yield surface and reference yield surface, are adopted to characterize the development of plastic volumetric strain (i.e., the unique internal variable of the two surfaces) due to either mechanical or thermal loading. The model is formulated based on the framework of the Modified Cam-Clay model, with only two additional parameters introduced (i.e., α and θ), to account for stress-induced anisotropy and thermal-induced translation of compression curves, respectively. Based on the model, a simplified equation is proposed to quantify the effect of drained heating on the undrained shear strength of clay. The predictive capability of the proposed model and the simplified equation for undrained shear strength are verified against published results of temperature-controlled triaxial tests on soft clay. By assessing seven different types of clays, the thermal-related parameters θ are found to almost linearly increase with the plastic index (Ip) of soil. Empirical correlations are then proposed for a quick approximation of θ, in case that data from temperature-controlled tests are not readily available.