Full-scale tests of a long energy pile subjected to separated and coupled thermo-mechanical loads

In this paper, four individual full-scale tests were carried out to study the mechanical response of a cast-in-place energy pile beneath a liquefied natural gas (LNG) tank subjected to separated and coupled thermo-mechanical loads. The results show that the temperature profiles displayed a comparable trend in response to pile heating, cooling and recovery. Specifically, the temperature at the mid-depth of the pile fluctuated rapidly, while the changes at both ends were relatively slower. During the thermal stages, when the pile had the flexibility to expand or contract, the observed strain at the pile head significantly deviated from the free thermal strain. In contrast, the strain at the pile toe was relatively aligned with the free thermal strain. The thermally induced stress obtained at the end of the coupled loading–cooling stage was found to exceed the tensile strength of the C40 reinforced concrete. However, under the actual testing conditions, both the settlement and the bearing capacity of the pile remained well within the required values, ensuring the structure of the LNG tank will not be damaged.