A Novel Three‐Dimensional Analytical Model for the Thermomechanical Responses of Energy Piles and the Surrounding Soil Based on Thermoelastic Theory

Abstract

Owing to their dual role in utilizing geothermal energy and supporting structural loads, energy piles are affected by thermomechanical loads. Moreover, the heating/cooling of energy piles also causes non‐negligible thermal stresses in the soil around the piles. The load transfer method is commonly used to address the thermomechanical response of energy piles. However, this method has problems such as slow convergence speed, difficulty in determining parameters and neglect of the soil coupling effect. Additionally, the method is unable to be used for analysing the thermal stress and strain of the soil around the piles. To overcome the limitations of the load transfer method, in this paper, a novel three‐dimensional analytical model based on thermoelastic theory that couples the thermomechanical coupling effect between energy piles and soil is proposed. The governing equations are derived in axisymmetric coordinates, and solutions to the heat diffusion equation are applied. The Helmholtz equation is solved with undetermined coefficients determined by boundary conditions via separation of variables and recurrence relations of modified Bessel functions. By comparing the results with those of field and centrifuge tests, the solution's validity is verified. Unlike discrete load transfer methods, the continuum mechanics‐based framework eliminates iterative convergence issues and quantitatively evaluates soil thermal stress and displacement. The proposed model provides a theoretical tool for refined energy pile design under mixed geological and thermal boundary conditions, advancing multiphysical field coupling analysis for geothermal structures.