Global sensitivity analysis of behavior of energy pile under thermo-mechanical loads

For the predictions and simulations of energy pile behavior under a combination of thermal and mechanical loads, with a complexity of parameters describing the energy pile, the surrounding soil and their interaction, modelers may be faced with the decision of whether it is better to spend more resource on determining the appropriate value of certain model parameters with high precision or on running more simulations to account for various uncertain input factors. In this study global sensitivity analysis is applied to explore the relative importance of the parameters of interest as model inputs and their contributions to the final results of the energy pile numerical model for different outputs. The interaction of uncertainties between different parameters is also analyzed with second order and total indices. Findings of this study indicate that the sensitivity of numerical energy pile predictions is more complex than previously thought. With a varying external forcing like the mechanical load or temperature change, the influence of input factor (e.g. model parameters) for the predictions of different spatially lumped model outputs is found to change but not always monotonically despite a monotonic variation of the output value. Spatial variability in the influence of the input factors which may be hidden by the spatially lumped analysis is also examined and inhomogeneous distribution of the input factor importance can be revealed along the whole length of the energy pile. The input factors that modelers should prioritize will not only differ depending on the assessed model output, but also on the location of the output and the surrounding circumstances which provide external loads and thermal effects. (C) 2020 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.