A review on the thermo-hydro-mechanical response of soil–structure interface for energy geostructures applications

Energy geostructures have been identified as a cost-effective mitigating strategy for the adverse impact of climate change. Operation of energy geostructures results in temperature fluctuation and subsequent water migration, particularly at the soil–structure interface, determining the shear response of soil and soil–structure interface. This state-of-the-art paper brings together experimental data from direct shear tests carried out on the soil–structure interface from several laboratory investigations, presenting a comprehensive review to gain a thorough understanding of the interface response in different thermo-hydro-mechanical states, which is critical in the analysis and design of energy geostructures. First, the evolution of shear strength parameters, i.e., adhesion and friction angle, with matric suction and temperature, are investigated. Then, a more detailed analysis of the impact of matric suction and temperature on the shear strength of the soil–structure interface is provided. Furthermore, a comprehensive discussion is provided in this section on the role of the most recent stress history in determining the non-isothermal shear strength of an interface. Data on the effect of matric suction and temperature on shear parameters of the corresponding fundamental soil is reviewed as a reference to the interface behaviour throughout the study, revealing potential underlying mechanisms. In general, a higher matric suction results in higher shear strength of the interface, whereas non-isothermal variations in adhesion and friction angle may lead to a higher or lower shear strength of a saturated interface.