An efficient method for the thermo-mechanical performance of energy pipe pile groups in layered geotechnical media

Energy pipe pile groups are widely used due to their environmental and societal benefits. However, there is a lack of an accurate and efficient calculation method for them. To fill this gap, this paper proposes a framework to assess the thermo-mechanical performance of energy pipe pile groups during service. Firstly, we approximate two sets of boundary forces on pipe piles as a single set of resultant forces at the mid-radius of pipe piles to enhance computational efficiency. Then, the solution of single energy piles under thermo-mechanical loads is derived based on this assumption and further extended to pipe pile groups. Comparisons with conventional and energy pipe pile groups are made to demonstrate the rationality of the presented assumption. The robustness and convergence efficiency of the proposed method are fully discussed, indicating the feasibility for a ratio of pile thickness to outer pile radius no more than 0.4. Numerical analyses show that preventing tensile failure of pipe piles under cooling conditions becomes critical at larger pile spacings due to the enhanced independence in thermal contraction. Additionally, cooling-induced tensile stresses of pipe pile groups with a triangular arrangement are notably higher than those with a uniform layout.