Simulation and Analysis of the Thermal-Mechanical Response of an Energy Pile

AbstractAn energy pile undertakes the functions of supporting the superstructure and controlling the indoor temperature of the building, and the thermal-mechanical coupling response of an energy pile makes its load transfer mechanism different from that of conventional engineering piles. Moreover, the thermal-mechanical coupling responses of the energy piles in summer and winter conditions are also different and need to be explored separately. Based on a ground source heat pump pile foundation workshop project in Kunshan city, Jiangsu Province, a multiphysics simulation study was carried out. The simulation results of the outlet water temperature and pile settlement are consistent with the real-world measurements, which verifies the reliability of the numerical simulation. The responses of the temperature distribution, axial stress, lateral shear stress, and settlement of the energy pile in summer and winter were analyzed, and the response laws of the energy pile in different seasons were obtained. Compared with the pure conventional load state, under the effect of thermal-mechanical coupling in winter conditions, the maximum compressive stress of the pile body is reduced by about 11.5%, but the settlement of the pile top increases by about 47.66%. Therefore, the winter conditions should be used as the design energy for the normal use of the pile. The control condition of the limit state: compared with the pure conventional load state, the maximum compressive stress of the pile increases by about 12% and the settlement of the pile top decreases by about 7.23% under the thermal-mechanical coupling effect of the summer condition. Therefore, the summer condition is the pile control conditions for the limit state of the body’s carrying capacity