The geothermal use of concrete geostructures (piles, walls and slabs) is an environmentally friendly way of cooling and heating buildings. With such geothermal structures, it is possible to transfer energy from the ground to fluid-filled pipes cast in concrete and then to building environments. A comprehensive research work was carried out at the EPFL (Switzerland) to improve the knowledge in the field of geothermal structures and to quantify the thermal influence on the bearing capacity of heat exchanger piles. In this paper, some features of the behaviour of a pile subjected to thermo-mechanical loads are presented. Numerical finite element results are supported by in-situ measured values.