Parametric Sensitivity Study of Energy Piles under Cyclic Thermo-mechanical Loading

In the present study, geothermal energy piles in sand subjected to long-term cyclic thermal loading with fifty heating-cooling cycles and constant mechanical loading have been analyzed numerically using the nonlinear transient finite element method and the resulting soil-structure interaction has been investigated. Analyses have been carried out for floating and end-bearing piles in both loose and dense sands subjected to different constant axial load magnitudes at the pile head. Mobilization of limit shaft resistance of the energy piles and axial stress exhibited by these piles have been investigated at the end of first heating and at the end of 50thheating. Parametric sensitivity studies have been carried out for different thermal load magnitudes, thermal conductivity values of pile and soil and thermal expansion coefficient values of soil. It is observed from the results that the limit shaft resistance of piles increases under higher thermal loading. The axial stresses generated in the pile due to thermal loading are higher than that induced due to mechanical loading and the axial stresses are sensitive to pile end conditions, soil stiffness and temperature change in the pile. However, the effect of variation of thermal parameters of pile and soil are observed to be negligible on the limit shaft resistance and axial stress exhibited by the piles.