Abstract:Energy pile is a type of structure which can not only exchange energy with soil, but also bear the upper loading. In the seasonal frozen soil area, the upper soil layer would be frozen, and the soil in the lower part would not. The thawing settlement, frosting heave and self-deformation of the pile caused by temperature variation are the main problems to be solved for application of energy piles in this area. According to the distribution characteristics of ground temperature in seasonal frozen soil areas, the soil was divided into frozen layer and non-frozen layer, and the model tests were carried out respectively. The pile and soil temperature distribution, pore water pressure of the soil surrounding the pile and pile displacement after multiple temperature cycles in frozen and non-frozen layers were measured. The results show that irreversible settlement of the pile top would occur after multiple cycles of heat extraction in the non-frozen soil area. After 5 cycles of heat extraction, the settlement of the pile top reached 0.95%D (D is the diameter of the pile), while the settlement of the pile would not reach stable state. In the frozen layer, thawing settlement of the pile would occur in the heat injection process, and frosting heave of the pile would occur in the recovery process. The settlement caused by thawing gradually decreased with increase of thermal cycles, and disappeared after the 3rd heat injection cycle. The thawing settlement of the pile after the 1st, 2nd and 3rd heat injection reached 5.9%D, 0.93%D and 0.11%D, respectively. During each cycle, although the rising displacement caused by frosting heave decreased in each following cycle, it still existed after 5 cycles, and the displacement caused by frosting heaving rose is of a ladder shape. The pile heave was produced in the end and reached 3.8%D.