Investigations on Thermomechanical Behavior of Energy Piles Considering Bearing Stratum Effects at Pile End

As a new type of energy-saving technology, energy piles have received increasing attention due to their dual functions of load bearing and heat transferring. The application of thermal load poses new challenges for the design and serviceability performance of energy piles. However, in existing theoretical studies, the stress-deformation characteristics of energy piles subjected to combined thermomechanical loading under different bearing conditions have not been fully revealed. In this study, an analytical model for energy piles under different bearing conditions was established based on the framework of elastic analysis theory, taking into account the effects of the end-bearing layer. The model was validated against the field test data. This study focuses on analyzing the effects of geotechnical conditions and geometry parameters of the piles on the load transfer and displacement behavior of energy piles. The results showed that the thermally induced axial load would increase with the stiffness of the bearing layer. Compared to floating-bearing piles, temperature variations would cause greater thermal stress in the piles bearing on stiff soil strata. The stiffnesses of the end-bearing layer, surrounding soil, and pile head are the critical factors affecting the magnitude and distribution of thermally induced stress and displacement. The normalized calculation results obtained from the analytical model can be used to estimate the thermally induced stress and displacement of energy piles in practice and provide a reference for the design and calculation of energy piles under different bearing conditions.