Temperature-Dependent Load-Displacement Curves of Heat Exchanger Piles in Sand

The goal of this paper is to present the effect of heating and cooling thermal loads on the load-displacement response of heat exchanger piles in granular soils. Two-dimensional discrete element simulations were utilized to determine the changes in the shaft and toe resistances due to heating and cooling loads. The considered heat exchanger pile is 0.3 m in diameter and 20 m in length and it was installed in a homogeneous sand layer with particles ranging in size between 2.2 and 3.6 mm. The pile was divided into 5 m segments with a representative 0.5 m pile strip for each pile segment. For each modeled pile element, the vertical and lateral soil pressures were initially applied then model was left to stabilize. The strips were, then, displaced at a constant displacement rate of 10 mm/s. while measuring the developed shaft and toe resistances. The model was validated against the behavior of a reference pile without temperature changes. Upon validation, the analysis was repeated at temperatures mimicking heating and cooling conditions around heat exchanger piles. The results of the analyses performed in this study showed that the load-displacement curves for heat exchanger piles in granular soils are temperature-independent.