Field investigation of a geothermal energy pile: Initial observations

Shallow geothermal energy techniques integrated in structural pile foundation have the capability of being an efficient and cost effective solution to cater for the energy demand for heating and cooling of a building. 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 coupled thermo-mechanical loads on the capacity of a geothermal energy pile. The full-scale in situ geothermal energy pile equipped with ground loops for heating/cooling and multi-level Osterberg cells for static load testing was installed at Monash University in a sandy profile. Strain gauges, thermistors and displacement transducer were also installed to study the behaviour of the energy pile during the thermal and mechanical loading periods. Thermal behaviour of the surrounding soils was also examined during the heating and cooling cycles of the energy pile. It has been found the pile shaft capacity increased when the pile was heated and returned to the initial capacity (i.e initial conditions) when the pile was cooled. Thus indicating that no loss in pile shaft capacity was observed after heating and cooling cycles.