Study on the Performance of Cushion in the Rigid Pile Composite Foundation under Flexible Load

In recent years, rigid pile composite foundation has been used as a cost effective alternative to the soft ground treatment of highway and railway in China, but limited studies were conducted on the performance of the composite foundation under embankment load, especially the cushion reinforced by geosynthetics. In this paper, 3 centrifuge model tests were performed and studied on reinforced and unreinforced cushion of composite foundation. Instrumentations were applied to investigate the distributions of displacements, earth pressures in the foundations as well as tensile forces in the model geosynthetics. Following results were found: Cushion reinforced by geosynthetics can not only reduce the deformation of embankment and foundation, but also enhance the load transference to the pile cap from foundation between piles, which means cushion plays an important role in the composite foundation; Cushion works normally because of the geosynthetics in the cushion bearing tensile force. Moreover, the tensile force of geosynthetics below the shoulder of embankment is larger than that in the center of embankment and near the toe of slope because of the lateral restraint of basal reinforcement.