Abstract: The long-term unsteady heat exchange of pile-soil makes the temperature of soil increase continuously. This phenomenon is called “heat accumulation effect” which affects the heat transfer efficiency of pile and soil, even make the energy pile system failure. In this paper, the composite phase change material was used to prepare the phase change concrete energy pile, and the thermal response model tests of the phase change pile and the ordinary pile were carried out on saturated silt. The temperature distribution around the pile, the stress and strain of the pile, the displacement of the pile top and the heat exchange efficiency of the pile were compared and anaylzed. The results show that the heat exchange direction of the phase change pile is mainly of radial exchange, and the influence area is within 2D, and the temperature change of the soil shows hysteresis effect. The change range of pile-soil temperature of phase change pile is smaller than that of ordinary pile, which can alleviate the thermal accumulation effect of soil around pile. During the temperature cycle, the phase change pile accumulates unrecoverable plastic strain. After several temperature cycles, the plastic cumulative displacement of phase change pile is smaller than that of ordinary pile. The heat transfer power of phase change pile is about 20% higher than that of ordinary pile in summer. The heat transfer power of both piles is basically the same in winter, and with the increase of operation time, the heat exchange efficiency of both piles is similar.

Key words: saturated silt, phase change material, energy pile, thermal response, model test