Advances in the analysis of thermo-active foundations

Energy geostructures are foundations equipped with absorber pipes, exchanging heat with the surrounding ground. They provide a good heat source for the heating and cooling of buildings but the temperature variations they undergo bring new challenges. Thermal expansion or contraction of the foundations can lead to building movements that must be kept within acceptable limits. Therefore, a thermo-mechanical design should be adopted. This paper presents recent advances in the understanding of the behaviour of thermo-active foundations. First, contributions of in situ experiments carried out on real-scale energy piles are reviewed. The outcome of these tests is a unique numerical design tool, called Thermo-Pile, which is presented. Next, an advanced constitutive model for environmental geomechanics accounting for non-isothermal conditions is detailed as well as the experimental evidence it was based on. Examples of thermo-hydro-mechanical analyses are presented to illustrate the challenges faced when using energy geostructures. Finally, the sustainability of heat storage through particular thermo-active foundations and tunnel anchors, is assessed.