A nonlinear constitutive model for soil-structure interface with thermo-mechanical coupling

In the application of underground energy technologies, the soil-structure interface is often affected by a combination of thermodynamics effects. Therefore, establishing a practical thermo-mechanical interface model can provide an effective theoretical basis for the design of energy geo-structures. In this paper, a constitutive model of soil-structure interface with thermo-mechanical coupling is developed by the nonlinear approach. According to the critical state concept, a computational formulation is proposed that can reproduce the dynamic transition of the interface void ratio from the initial state to the critical state. And by introducing the state parameter, a state-dependent interface model of stress variation with displacement is proposed. The model embeds the nonlinear shear modulus and critical state theory. In addition, the effect of temperature and initial normal stress on the initial void ratio was obtained through normal loading tests under 10–70 °C, and relevant empirical equation was established. The model is enhanced to simulate the behaviors of sand/clay-structure interface with thermo-mechanical coupling. The model requires 11 parameters to capture the responses of temperature to the interface mechanical behaviors. The proposed model is validated with substantial performance in the prediction of interface tests with thermo-mechanical coupling under constant normal loading (CNL) and constant normal stiffness (CNS) conditions.