Abstract: The energy pile is a combination of load bearing and heat exchange. It bears the combined action of load and temperature. The bearing capacity of energy pile is very complex. Based on the energy pile engineering in Shanghai, the Brillouin optical time-domain reflectometry (BOTDR) distributed optical fiber sensing technology is used to monitor the axial force and temperature of energy pile. The axial force and side friction distribution curve of pile are obtained under the load, temperature and under the joint action of load and temperature. The bearing characteristics and load transfer characteristics of energy pile under load and temperature are analyzed. The results show that the bearing behavior of energy pile is different from the ordinary cast-in-place pile. The increase of pile temperature will cause pile deformation, and the axial force of pile will produce under the constraint of soil, which is basically linear with the change of pile temperature. Under the combined action of load and temperature, the axial force of pile is much larger than that under the action of a single factor, and the increment of axial force caused by the combined action of load and temperature can reach two times or more that of under the action of load alone. At the same time, the side negative friction of pile will be generated in a large range due to the influence of temperature rising, but the load action can obviously alleviate the generation of negative friction.

Key words: energy pile, joint action of load and temperature, BOTDR distributed optical fiber monitoring, temperature, axial force, negative friction