A constitutive model of expansive clay considering thermo-hydro-mechanical coupling effect

As a possible buffer material of engineered barriers and seals, expansive clay is often subjected to the thermo-hydro-mechanical (THM) coupling actions. This paper aims to develop a constitutive model which is capable of addressing the THM coupling behavior of expansive clay. Based on the Modified Surface State Approach, two state surfaces are assumed to describe the isotropic compressing behavior of expansive clay with the support of previous works. Subsequently, the yield function and hardening law are derived from the two state surfaces. Furthermore, the yield function and flow rule for triaxial stress states are presented. Through comparing the predicted results to experimental data of the compacted MX 80 bentonite, it is demonstrated that the proposed model has capacity of capturing the typical features of THM coupling behavior of compacted expansive clay. In addition, the proposed model is used to perform triaxial shear compression behaviors of expansive clay specimen. The influences of confining pressure, suction, and temperature are analyzed through the simulated results. The results show that the proposed model is able to address the fundamental characteristics of expansive clay specimen when subjected to triaxial shear compression.