3D finite element assessment of the effects of energy loops on the load capacity and settlement of bored piles installed in sand

摘要

Three-dimensional finite element analyses were carried out to study the geotechnical behaviour of piles fitted with high-density polyethylene (HDPE) tubes as energy loops for harnessing ground heat. The objective was to examine whether the existing analysis methods for conventional piles are applicable to energy piles. Using PLAXIS 3D software, simulations were done for 60 cases of energy piles comprising variously configured HDPE tubes. It was found that HDPE tubes inevitably interact with the soil around the pile such that 6-11 HDPE tubes decreased the load capacity by 18-70%, while 3-4 HDPE tubes had an optimum reinforcing effect on the soil, thereby increasing the load capacity by 30-75% depending on the pile size. However, the tubes had little effect on settlement at ultimate load. Thus, the work highlighted the limitation of conventional methods of analysis and the geotechnical effect of HDPE tubes installed to protrude from the base of an energy pile.