Pile Groups Under Long-Term Cyclic Thermal Loading

This study presents the cyclic load-displacement response of thermal piles in a pile group consisting of thermal and mechanical piles. To investigate the effect of different (i) layouts of thermal piles and mechanical piles, (ii) pile spacing, and (iii) soil type on the pile displacements and axial stresses, numerical analyses were performed over 50 cycles of thermal loading and unloading of the thermal piles. The analysis outcomes show that the thermal changes in the load-displacement characteristics of the piles become complex during cyclic thermal loading and unloading of the thermal piles. The mechanical piles also exhibit uplift after thermal loading of the thermal piles, and significant differential displacements occur at the pile cap, head and base for all the piles. Higher pile spacing imposes a positive effect in terms of lower thermo-mechanical stresses in the piles compared to the case of closely spaced piles. Axial stresses in each pile are notably non-uniform after the thermal loading cycles applied on the thermal piles. Cyclic alterations in the load-displacement of thermal piles also impose alterations in load-displacement of the mechanical piles. Further, the layout of thermal piles, pile spacing, and soil type control the long-term cyclic thermo-mechanical response of the pile group.