Analytical solution for heat exchange in energy pile ground considering smear effects

Abstract

Due to the installation of energy piles, the surrounding soil will be inevitably disturbed, leading to a smaller void ratio and larger thermal conductivity. This study proposes a new closed-form solution to calculate the heat exchange of energy pile foundations considering smear effects on the different soil thermal properties in the smear zone and undisturbed zone. The analytical model adopts the separation of variables to solve the governing equations. The eigenvalues are obtained according to a series of recurrence formulas and a transcendental equation. The solution is verified against existing analytical solutions in literature and numerical simulation, and an excellent agreement is obtained. The parametric study shows that a larger thermal conductivity of the soil in the smear zone results in a lower temperature at any given time. If the smear effects are not considered, the temperature will be overpredicted, especially for the pile and the soil in the smear zone. The proposed solution precisely predicts the soil temperature in the smear zone and undisturbed zone, which can contribute to the thermo-mechanical behaviour of energy pile foundations in further work.