Preliminary study on the mechanical behaviour of heat exchanger pile in physical model

The effects of temperature changes on the mechanical behaviour of heat exchanger piles need to be taken into account in geotechnical design. In this preliminary study, the behaviour of an axially loaded pile under thermal cycles was investigated using a physical model. After applying the axial load on the pile head, the pile was heated from 25 degrees C to 50 degrees C and subsequently cooled to 25 degrees C. Four tests (corresponding to four values of axial load) were performed and two temperature cycles were undertaken in each test. The pile temperature and the pile head displacement were monitored. When low axial loads were applied, the heating induced heave and cooling induced settlement of the pile head. In this case, the displacement-temperature curve was found to be reversible and similar to the thermal expansion curve of the pile. However, in the case of higher axial loads, the heave of the pile head, obtained during heating, was lower than the thermal expansion of the pile, suggesting settlement of the pile toe. Irreversible settlement of the pile head was observed after these thermal cycles.