Test Construction of Cast-in-Place Concrete Energy Pile in Dredged and Reclaimed Ground

Abstract

This study evaluates the feasibility of energy piles equipped with a large-diameter drilled shaft under unfavorable ground conditions. The cast-in-place concrete energy pile was constructed at a test bed in dredged and reclaimed ground in which a confined aquifer exists. Two different configurations of heat exchange pipes (W-shape and S-shape) were designed on each side of the energy pile to compare their thermal performance. The drilled shaft reaches to a depth of 60 m whereas the heat exchange pipes are inserted to about 30 m below the ground surface. In a comparison of constructability, the S-shape heat exchanger resulted in faster installation by about 50% over the W-shape, which implies that the S-shape pipe may provide better constructability for the given construction conditions. A series of in situ thermal response tests (TRTs) were performed to compare the thermal performance of each heat exchanger. The relative heat exchange efficiency (eff) of the W-shape and the S-shape heat exchangers were determined to be 19.15 and 18.88, respectively, which means that the two different types of heat exchange pipe configurations practically yield similar thermal performance. One of the TRTs conducted in the test bed was simulated by a computational fluid dynamics (CFD) numerical model to verify the feasibility of adopting TRTs for energy piles, which reproduces quite well the TRT experimental results.