Thermo-mechanical behavior of a thermo-active precast pile

Abstract

[EN] A new research and development project has been launched in Spain to undertake some studies on the geothermal use of pile foundations (PITERM PROJECT). The experiment, consists of a specifically designed, constructed and fully monitored geothermal precast pile driven at Polytechnic University of Valencia. The pile is under two types of loads: mechanical and thermal. The mechanical load was applied by means of a mechanical frame anchored to the ground, as element of reaction, and three anchors used to induce an active compressive force. The thermal load was provided by a thermal installation, with a data logger to record the outflow and return temperatures. The testing set is fully instrumented in order to register the thermo-mechanical behaviour of the system in terms of thermally induced movements, thermal axial strain profiles and shaft resistance mobilized as a result of cooling and heating. The results obtained permitted the quantification of three significant effects brought about by the temperature increase: pile uplift, additional load generated in the pile by constrain of the thermal stains, and mobilization of side friction due to the relative displacement of the pile with respect to the ground. The pile strain is of the thermo-elastic type and is strongly affected by the type of surrounding soil.