Thermomechanical characteristics of a thermally inactive neighboring pile of an energy soldier pile during constraint changes

•An in-situ field test has been conducted on energy soldier piles with internal support.•Temperature and constraints changes on the inactive neighboring pile is considered.•The thermal insulation effect of piles is stronger in the main structure’s construction stage.•The various construction phases gave rise to disparate constraint states around the piles.•The compressive stress corresponding to the constraints of soil on both sides is minimum. This study aims to determine whether it is worth activating energy soldier piles during the excavation and construction phases by investigating the thermomechanical response of a thermally inactive neighboring pile subjected to thermal loads resulting from an energy soldier pile in a foundation pit support system. This was achieved through a field test utilizing constant-power heating. The energy soldier piles under investigation are susceptible to constraint changes due to the installation and removal of internal supports. The impacts of temperature and constraint changes during excavation and main structure construction on thermally inactive neighboring piles are analyzed and discussed. The results indicated that the maximum temperature difference along the depth direction of the thermally inactive neighboring pile during the construction of the main structure was 9.7 °C, whereas during the excavation, it was 13.9 °C. The constraint on the excavation side transitioned from a continuous state to a concentrated state with a point-like distribution, and finally to a continuous state of restraint for the large-stiffness main structure. The maximum thermally induced stress was 0.283 MPa/°C. During the excavation stage, the degree of freedom in the middle of the pile was approximately 0.8. Following backfilling, this value decreased to 0.3. Additionally, the maximum horizontal displacement moved to below the bottom elevation of the main structure, and none of the maximum values exceeded 3 mm. Since thermal activation during the excavation and construction processes can lead to issues with no real benefit, activation of the energy piles during these phases is not necessary, and better benefits are obtained by activating the energy soldier piles during the operation phases of the internal building.