Thermo-hydro-mechanical behavior of soft soils beneath energy shallow foundations subjected to thermal and mechanical loads

Energy shallow foundations represent an innovative technology that can simultaneously support structural loads and harvest geothermal energy. During geothermal operations, the underlying soils are subjected to structural loads and temperature fluctuations. Despite the potential, knowledge regarding the thermo-hydro-mechanical behavior of the multilayered soils beneath the energy foundations remains scarce. This study proposed an analytical approach to investigate the thermo-hydro-mechanical response of soft fine-grained soils beneath energy shallow foundations. The analysis focused on the evolutions of the temperature, pore water pressure, and vertical displacement of the underlying soils. The results indicate that the generation and development of the thermally induced excess pore pressure are controlled by thermal transfer processes and soil hydraulic properties. Furthermore, the mechanical load-induced ground settlement decreases upon heating and increases upon cooling, primarily due to the development of thermally induced pore pressure and the thermal volume changes of the soil skeleton. Under the considered conditions, ignoring the thermally induced mechanical effects could result in a settlement prediction error of nearly 120%. Therefore, the thermo-hydro-mechanical interactions within the soils should be appropriately considered in the analysis and prediction of the displacement behavior of the energy foundations.