Energy pile is an innovate technology which can simultaneously support building load and acquire geothermal energy. In the practical use

expansion or contraction of the piles induced by thermal load will be restrained by the upper structure and bearing layer of pile bottom. Thus

the pile stress and displacement will be significantly influenced. However

there are only few studies focusing on this issue. Based on model test and numerical simulation methods

the thermal stress and displacement of two types of heat exchange piles (U-shaped and W-shaped) under different pile head and pile tip restraints were analyzed. Furthermore

the position of null point influenced by the pile head stiffness restraint and pile tip soil stiffness restraint were evaluated. The results show that as the pile head load stiffness restraint increased

the null point moved upwards

and the thermal stress decreased with the increasing of depth. As the pile tip soil stiffness restraint increased

the null point moved downwards

and the thermal stress increased with the increasing of depth. Compared with the case with no load

the null point will move upward with a working load.