Load–displacement response and interaction behavior of energy pile groups under combined mechanical and cyclic thermal loading

Energy piles are regarded as an innovative technology that can be deployed as groups to provide structural support and geothermal energy for buildings. This study aims to investigate the load–displacement response and the interaction behavior of energy pile groups under combined thermomechanical loads. An analytical approach was developed for the thermomechanical analysis of grouped energy piles and validated against experimental data. The approach was further adopted to evaluate the effects of load levels, pile geometries, and soil–pile interface characteristics on the pile-to-pile interaction. Then, the displacement behavior of grouped piles under typical thermomechanical load paths (i.e., subjected to stepwise mechanical loads first and then cyclic thermal loads) was investigated. The results show that increasing thermomechanical load levels will decrease the displacement interaction factor between energy piles. The effects of load levels on the pile-to-pile interaction become more significant with increasing slenderness ratio. Besides, the cyclic thermal loads may cause the irreversible displacement response of energy pile groups. Due to the group action effects, the grouped energy piles experience more significant settlement than single piles after thermomechanical load paths. These results highlight the significance of accounting for the pile-to-pile interaction and the soil–pile interface behavior when addressing energy pile groups.