Modelling the mechanical behaviour of an energy pile

A finite element code, often used in pile foundation design, was applied to simulate the mechanical behaviour of an energy pile under coupled thermo-mechanical loading. The contact between the pile and the surrounding soil was assumed to be perfectly rough. The mechanical loading was applied to the pile head as it is done conventionally in practice. In order to apply thermal loading, as thermal effects are not included in the utilised code, the body of the pile was subjected to a volumetric strain that corresponds to the thermal dilation of the material of the pile. The method was evaluated by simulating two in-situ experiments and one laboratory-scale model test on an energy pile. The same temperature changes and mechanical loads as in the mentioned experiments were applied to the pile in the numerical analyses. Axial load distribution along the pile and pile head settlement obtained via simulations were compared to the experimental results in each case. A good compatibility is achieved between the results, which indicate that the decoupling procedure had been successful in predicting the behaviour of thermo- Active piles. Besides, one could conclude that in the absence of other significant mechanisms (particularly thermal diffusion into the soil and thermal expansion/contraction of the surrounding soil) and without using a soil/pile interface model, the pile volume change due to temperature change has been identified as the governing mechanism.