Abstract: Energy pile functions as the bearing capacity of upper load and energy transfer of shallow ground temperature, which becomes one of the most important issues for engineers. However, there is relatively little research on the thermal-mechanical coupling characteristics of energy pile in the pile-raft foundation. One new buried pipe type of energy pile was proposed in this study, in which the bottom end of the acoustic tube was connected as the heat transfer tube. Field tests on the thermal response characteristics and the stress of the raft affected by energy pile were carried out under the operation of the single energy pile in the pile-raft foundation. The temperature and stress of the pile and the stress of the raft were accurately measured. The results showed that the heat transfer efficiency of the energy pile (single U-shaped buried pipe, the effective depth of 12.8 m, pile top depth of 5.5 m) was about 80?90 W/m under the experimental conditions. The tensile stress of the raft on the top side was found during heating without dead load condition, which should be considered during the structure design.

Key words: pile-raft foundation, energy pile, thermal-mechanical coupling, thermal efficiency, field test