Effects of Thermohydromechanical Response at the Soil–Pile Interface on the Bearing Performance of Energy Piles

Energy piles provide an innovative and efficient approach to simultaneously supporting structural loads and developing geothermal energy. During geothermal operations, the thermohydromechanical responses of the soils surrounding energy piles may influence the pile bearing performance by altering the soil–pile interaction. However, knowledge regarding this potential effect remains scarce, severely hindering the accurate assessment of the bearing capacity of energy piles. To address this issue, this study developed a numerical model to evaluate the bearing performance of energy piles under combined mechanical and cyclic thermal loading by considering the thermohydromechanical responses occurring at the soil–pile interface. Then the paper presents the measured results from field static loading tests performed on full-scale energy piles, and uses the established model to realistically capture the pile displacement behavior. Extensive comparison with full-scale experimental data thoroughly validated the effectiveness of the proposed model in capturing soil behavior and pile performance. Subsequently, by utilizing the validated model, the present study investigated the thermally induced variations in the temperature and pore water pressure of the surrounding soils, as well as evaluated their impacts on the load-displacement response of energy piles. Last, the model was used to investigate the behavior of energy piles when exposed to combined mechanical and cyclic thermal loading. The results show that thermally induced changes in the soil–pile contact pressure and thermohydromechanical interactions occurring in the soils collectively govern the evolution of the bearing capacity of energy piles. Heating can enhance pile bearing capacity by increasing the soil–pile contact pressure. However, under certain conditions, the heating-induced increase in pore water pressure may cause adverse effects on the bearing performance of energy piles. Additionally, cyclic thermal loading may induce irreversible thermomechanical responses in energy piles by coupling the mechanical head load. The thermohydromechanical interactions occurring at the soil–pile interface may exacerbate the thermally induced irreversible response of energy piles. Therefore, the thermohydromechanical response within the soils and its impact on soil–pile interaction should be appropriately considered in the analysis of energy pile foundations.