Thermally-Induced Displacement and Stress Analysis of Geothermal Energy Piles in Sand

Design of geothermal energy piles requires consideration of the complex interaction between temperature change in the pile and induced stresses and deformations in the pile and soil, which may affect building’s performance. Hence, it is of utmost importance to understand and quantify the load transfer mechanism of energy piles under thermal and mechanical loads through rigorous numerical analysis. Thermo-mechanical response of geothermal energy piles in sand has been investigated in the present work using axisymmetric nonlinear finite element analysis procedure. Herein, the stress-strain response of piles is considered to be linear-elastic. The stress-strain response of sand has been simulated using state parameter based constitutive model CASM. Floating and end bearing geothermal energy piles of different lengths and diameters in sand have been analyzed under mechanical and thermo-mechanical loading for studying the displacements of pile and the axial stresses in pile. It is observed from the results that the relative displacement between pile and soil depends on the applied thermal load on the pile, the relative density of the sand and the end condition of the pile. Also, the piles exhibit higher axial stresses under thermo-mechanical loading as compared to that under mechanical loading.