Effects of pile configuration on the group behavior of semi-floating energy piles

To investigate the effects of pile configuration on the group effects of semi-floating energy piles, a series of laboratory tests were performed. The tests include three distinct pile configurations, namely, a single energy pile, a 2 × 2 energy pile group, and a 3 × 3 energy pile group. Different operation modes of energy pile groups, including all energy piles being cooled and partial energy piles being cooled, were considered. The monitoring and analysis of temperature changes in energy piles and surrounding soil, axial load variation, and displacement of energy piles and non-thermally activated piles were performed. The interactions among energy piles, non-thermally activated piles, raft, and surrounding soil within semi-floating pile groups with varying numbers of energy piles and operation modes were discussed. The findings reveal that the group effects of energy piles can be attributed to two aspects, namely pile-soil interactions and pile-raft-pile interactions. Both of these interactions contribute to reduced thermally induced axial loads and increased thermally induced displacements of energy pile groups. Under similar thermal loading, the 3 × 3 energy pile group exhibits a 19% increase in displacement and a 64% decrease in maximum thermally induced axial load compared to a single energy pile. Furthermore, the group effects of an energy pile group were affected by the pile configuration and are more pronounced with an increase in the number of energy piles within a pile group. The findings presented in this paper contribute to a more precise assessment of the thermo-mechanical response exhibited by such pile foundations.