ABSTRACT
Previous work by the authors reviewed the reported response of full- and small-scale piles in tests in granular soils where they were subject to cyclic thermal loading. In the case of the former, largely stable behaviour has been reported but amongst the latter, the reported response consistently reveals irrecoverable settlement and increase in axial compression stress. This later is reported to be a function of the applied load with greater irrecoverable settlement occurring at lower global factor of safety and has been attributed to a variety of possible mechanisms. A hypothetical mechanism based on the initial mobilisation of the pile shaft resistance was proposed to explain this and then tested by undertaking numerical analysis. This confirmed the stable behaviour of the full-scale piles was likely due to low mobilisation (high margin of safety) with respect to the shaft resistance, while in the small-scale tests, the reverse was true. In this paper, a small-scale test on a thermally-activated pile has been back-analysed. In the test, the mechanical load-displacement behaviour along with the response to three cycles of heating and cooling were reported in sufficient detail to provide a good basis for the analytical work. It is shown that by matching the mechanical response, reasonable agreement between the thermal part of the test and finite element back-analysis can be achieved, and that the agreement can be further improved through calibration of the coefficient of thermal expansion of the pile and soil.
