Analysis of the cooling effect of a concrete thermal pile in permafrost regions

The bearing capacity of a pile is significantly sensitive to ground temperature in permafrost regions. However, the cast-in-place pile foundation may disturb the thermal regime formed in a long term during construction and operation. A two-phase closed thermosyphon (TPCT) performs well in cooling permafrost engineering. This paper proposed a concrete thermal pile consisting of a concrete pile and TPCTs to control the temperature of a pile shaft. The results of an experiment conducted to analyze the cooling effect of the concrete thermal pile were presented. The influence of the length of the condenser section on the cooling effect has been discussed based on a 3-D heat transfer model of the thermal pile. The experiment results indicated that the concrete thermal pile could effectively cool the surrounding foundation soil, and the cooling rate of the thermal pile can reach 2.5 times that of the pile without the TPCT. To enhance the cooling efficiency of the thermal pile, the numerical simulation results suggested the optimal length of the condenser section should account for 44% of the total length of the TPCT. The conclusions summarized from this paper will provide valuable references and lessons to the design of the pile foundation in permafrost regions.