Heat Transfer Analytical Model of Energy Soldier Piles under Air Convection Conditions

Abstract

This study proposes an analytical solution for heat transfer in energy soldier piles, considering the convective boundary conditions and temperature distribution differences in the angular direction. The problem is solved by using the separation of variables method and the Fourier–Bessel series. The proposed solution is validated by comparing the results with field test data. The field test results indicate that air convection significantly impacts temperature when the pile segment is buried shallowly. At the measurement point far away from the excavation depth (10.0 m), the temperature difference during the thermal response tests (TRTs) before excavation is 14% of the temperature difference after excavation at that point. The temperature changes for the measuring points buried in soil and the bare measuring points near the excavation face do not exceed 3°C. Heat transfer analysis using this analytical solution reveals that convective heat transfer from the surrounding environment affects the pile temperature. The further the energy pile is from the air, the more the soil temperature increases; however, the soil temperature decreases as the convective heat transfer coefficient increases. Larger diameter piles are more easily affected by this phenomenon and reach stable temperatures more slowly. The thermal influence range is 1.5–2.0 m, which decreases as the convective heat transfer coefficient of air increases. To ensure the supporting effect, burying the pipeline on the soil side and reducing the diameter of the energy soldier pile can effectively improve thermal performance.