Thermo-mechanical behaviour of energy pile in underground railway construction site

The use of geothermal pile foundations is an environmental friendlyway to extract/storage energy from/in the ground. The operating principle of these innovative structures is based on energy transfer between the ground and the fluid flowing inside the probes inserted in the pile, in order to feed heat pumps dedicated to buildings heating and cooling. Nevertheless, very limited installations are recorded in Italy, and only few information are available regarding the impact of thermal processes on the structural performance of energy piles. In the present work, the geo-energy research group has analysed the thermo-hydro-mechanical behaviour of an energy pile installed in pyroclastic soils and rocks, as an element of a sheet pile wall. The developed model, solved numerically by using finite elements, is then used to forecast the behaviour of an actual pile subjected to thermo-mechanical loads and to design a proper experimental campaign in the underground railway construction site of Piazza Municipio in Napoli, Italy. The multi-pile experimental set-up is equipped with fibre optic sensors system that allows the evaluation of strains and temperature distributions along the piles during cooling and heating processes. Once the measurements will be available, the developed model will be verified and validated against on field experiments.