Settlement Response of a Geothermal Energy Pile Group in Sand: Fid-Bau Portal

Settlement Response of a Geothermal Energy Pile Group in Sand

Saggu, Rajni / Chakraborty, Tanusree

The geothermal piles are used as a group in major construction projects. Geothermal energy piles provide sustainable energy alternative for residential and commercial buildings worldwide. In spite of the growing recognition of the benefits of energy piles, there is a still a knowledge gap about the load transfer mechanism of pile groups under thermo-mechanical loading. In the present study, thermo-mechanical response of geothermal energy pile groups in sand has been studied using three dimensional nonlinear finite element analysis procedure. A pile cap is considered on the piles. Stress-strain responses of piles and pile cap are considered linear elastic. The stress-strain response of sand is simulated using a state parameter based constitutive model CASM. The CASM model has been implemented in finite element software Abaqus through user defined material subroutine. The geothermal energy pile group has been analyzed for different combinations of thermal and non-thermal piles in the group in a single layer of Ottawa sand. Analyses have been performed by varying the spacing between the piles. Analysis results have been studied for the displacement at the base of the piles. It is observed from the results the load carried by the thermal piles increases due to heating induced excess load in the pile. For non-thermal piles however, unloading of the pile happens during heating of the thermal piles and base displacement decreases. Heating of thermal piles also causes expansion of these piles in upward direction, thus, the piles pushing the pile cap along with it in the upward direction. Differential settlement at the pile base is observed for the groups containing both thermal and non-thermal piles.