Effects of the pile buried pipe parameters on the thermal-mechanical coupling characteristics of energy pile under the groundwater seepage

In order to examine the influences of buried pipe parameters on the thermal-mechanical coupling characteristics of energy piles under the groundwater seepage, the numerical models of energy piles with different buried pipe parameters are established. The influences of the buried pipe number, layout of buried pipe, and diameter of buried pipe on the heat exchange rate per pile depth, daily heat exchange amount, pile body average temperature rises, displacement increment, and additional temperature load are investigated. The results show that the increasing number of buried pipes can improve the heat transfer of energy pile, but also increase the thermal interference between different buried pipes in the pile, resulting in the decrease of heat transfer performance and the increase of pile displacement and additional temperature load. Under the groundwater seepage, the layout of buried pipes has a significant effect on the heat transfer performance, but has little effect on the mechanical properties of the pile. Moreover, with the increasing seepage velocity, the difference of heat transfer rates of the energy piles corresponding to two layouts increases gradually, and the pile top displacement increment and the pile additional temperature load decrease gradually. The increasing diameter of buried pipe can improve the heat transfer of energy pile, but it will also increase the temperature rise of the pile and the soil around the pile, leading to the increase of pile displacement and additional temperature load. The research results can provide guidance for the optimal design and efficient operation of energy pile under seepage action.