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Estimation on bearing characteristics of a large-diameter and extra-long energy pile under various actions of mechanical and thermal loads
   

Estimation on bearing characteristics of a large-diameter and extra-long energy pile under various actions of mechanical and thermal loads

Guangzhe Zhang, Fenglei Du, Tao Wang, Shifeng Lu, Hongliang Jiang Benyi Cao
Canadian Geotechnical Journal, Vol.63, pp.1-15
2026
: https://doi.org/10.1139/cgj-2024-0685
bearing capacity Energy pile Pile settlement Strain and stress thermo-mechanical load
Energy piles, combining structural support with ground heat exchange, are increasingly used for sustainable building energy solutions. However, the thermo-mechanical behaviour of large-diameter, extra-long energy piles under real operational conditions remains inadequately understood. This study investigates the bearing characteristics of a 1.5 m diameter, 58.3 m long cast-in-place concrete energy pile installed beneath a liquefied natural gas tank, subjected to staged mechanical and thermal loading. A full-scale in situ experiment was conducted, simulating realistic load conditions, including static mechanical loading, combined thermal-mechanical loading during heating and cooling cycles, and cyclic loading effects. The results indicate that the pile exhibited high heat exchange efficiency, with rates of 115.6 and 130.3 W/m during heating and cooling, respectively. Axial expansion due to thermal loads led to the formation of a neutral plane at approximately-39 m depth, redistributing shaft resistances along the pile. Under heating, negative shaft resistance developed in the upper (-1.5 to-14 m) and lower (-39 to-51 m) parts, while positive resistance was concentrated in the mid-depth. Upon reloading, the negative resistance diminished, demonstrating mechanical dominance in pile behaviour. The pile head settlement reached-11.6 mm under maximum static loading (24 000 kN), with an additional-7.3 mm settlement observed during combined heating-loading. These findings confirm the feasibility of large-diameter energy piles for deep foundations, highlighting their stable thermo-mechanical response and informing future design optimisation for cyclic thermal and mechanical actions.

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Estimation on bearing characteristics of a large-diameter and extra-long energy pile under various actions of mechanical and thermal loads1.41 MB
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