Impact of thermal solicitations on the design of energy piles

Energy piles present a double function as bearing elements supporting the loads transferred by constructions and heat exchanger elements delivering the energy for heating and cooling. In comparison to conventional piles, they are subjected both to thermal and mechanical loadings, which affect their behaviour. Energy pile design also requires efficient and unambiguous approaches to provide the most appropriate verifications. Despite of their increasing implementation across Europe, some gaps are still present regarding their mechanical design; especially concerning the effects of the imposed cyclic thermal solicitation in the pile due to the successive periods of heating and cooling. Very few details can be found about the choice of the thermal solicitation that the designer has to consider for the design of an energy pile: number of cycles, cyclic thermal amplitude, influence of the thermal loading order, etc. In this objective, this paper includes the study of a single energy pile installed in saturated sandy soil affected by different combinations of thermal loadings. Based on the analysis of the pile displacements and the distribution of the axial forces, some recommendations are given to better appreciate the impacts of the choice of the imposed thermal solicitation in the pile.