Small-scale cyclically thermally-activated pile under inclined mechanical loads

In this study, a series of 1-g physical model tests was carried out using an instrumented model energy pile installed in dry sand to characterize the influence of cyclic thermal loading on the response of energy pile subjected to inclined mechanical loading. The loading scheme considered in the model tests comprised a pre-applied axial load (10, 20, and 40% of the ultimate axial load) combined with a horizontal load (30, 50, and 70% of the ultimate horizontal load) followed by ten thermal cycles with temperature variation of +/- 1 degrees C. The results indicated that imposing thermal cycles to the pile subjected in advance to inclined mechanical loading resulted in an irreversible settlement and horizontal displacement of the pile head, which would gradually accumulate over thermal cycles. By the end of the tenth thermal cycle, the amount of accumulated irreversible settlement and horizontal displacement were generally in the range of 0.1-0.6% and 1.1-2.3% of pile diameter, respectively. Under the same horizontal load, thermal cycles at a higher axial load induced a higher irreversible settlement but a lower horizontal displacement at the pile head. Under the same axial load, thermal cycles at a higher horizontal load induced a lower settlement but a higher horizontal displacement at the pile head. Despite the fact that the ultimate horizontal bearing capacity of the pile remained unchanged after ten thermal cycles, it is recommended that due to the accumulation of irreversible horizontal displacement during the cyclic thermal loading, the long-term performance of energy pile is controlled by horizontal displacement rather than capacity.