In Situ Testing of a Heat Exchanger Pile

The behavior of a pile subjected to thermo-mechanical loadings was studied in situ with the aim of quantifying the thermal influence on the bearing capacity of heat exchanger piles. A pile situated in a building under construction was equipped with a channel system to inject heat into it using a special heat pump. Load cells, deformation gauges and thermometers were installed to evaluate the behavior of the pile during seven tests with coupled thermomechanical loadings. The temperature variations applied to the pile were on the order of 15°C, and the mechanical load reached 1300 kN. The results obtained permitted the quantification of three significant effects brought about by the temperature increase: i. pile uplift, ii. mobilization of side friction due to the relative displacement of the pile with respect to the ground, and iii. additional load generated in the pile by constrain of the thermal stains.