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Shallow geothermal heat exchangers integrated in structural pile foundations have the capability of being an efficient and costeffective solution to cater for the energy demand for heating and cooling of built structures. However, limited information is available on the effects of temperature on the geothermal energy pile load capacity. This paper discusses a field pile test aimed at assessing the impact of thermomechanical loads on the shaft capacity of a geothermal energy pile. The full-scale in situ geothermal energy pile equipped with ground loops for heating/cooling and multilevel Osterberg cells for static load testing was installed at Monash University, Melbourne, Australia in a sandy profile. Strain gauges, thermistors, and displacement transducers were also installed to study the behavior of the energy pile during the thermal and mechanical loading periods. It has been found that the pile shaft capacity increased after the pile was heated and returned to the initial capacity (i.e., initial conditions) when the pile was allowed to cool naturally. This indicated that no losses in pile shaft capacity were observed after heating and cooling cycles. A variance in average vertical thermal strains was observed along the upper section of the pile shaft at the end of the heating periods. These were almost fully recovered at the end of the cooling periods, indicating that they are of an elastic nature. Pile average circumferential strains were found to be relatively uniform at the end of the heating and cooling periods and did not change with depth. They, also, were fully recovered during the cooling period. It was also observed that the increase of temperature during the heating periods prompted the pile shaft to expand radially. Subsequently, as the pile cooled down, the pile shaft slowly contracted and returned closely to its original condition, suggesting a thermoelastic behavior

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Field observations from a heating test conducted on a geothermal energy pile, containing two Osterberg cells, installed in a dense sandy material are reported. An instrumented pile and two boreholes were installed for this purpose. The pile was heated for various time intervals and the ground heat response was observed via thermocouples installed at various depths in the two boreholes. A time lag in the diffused heat wavefront arrival was consistently observed in the borehole farthest from the heat source (i.e. pile). This suggests heat diffused slowly in the ground and its intensity reduced with distance from the heat source. Heat transfer was affected by the ground stratigraphy. The pile and the ground were allowed to cool by letting heat dissipate naturally once the heating test was completed. It was found that both the pile and the ground required at least more than twice the heating time to have full thermal recovery from the heating process. A constant heat exchange rate (or heat rejection rate) of 100–125 W/m2 was achieved, despite continuous rise in temperature of the pile and the ground