Vertical and horizontal bearing characteristics of model piled raft foundations supported by sheet piles

Compared with raft foundations, piled raft foundations can effectively reduce settlements caused by external loads such as superstructures, which makes them play an important role in constructions in urban areas. Recently, with the development of new piling methods, steel sheet piles can be penetrated into various types of grounds with high quality and precision. Although piles for piled raft foundations are usually pipe piles, sheet piles could become an alternative because the construction time and cost of sheet piles could be lower than those of pipe piles. Hence, a target of this research is to demonstrate the possibility of using sheet piles for piled raft foundations. In this study, a series of model tests were conducted first to investigate the load transfer behaviours of model piled raft foundations supported by three types of piles in an air-dried sand ground. Two of them were composed of sheet piles, called plate piles, and box pile respectively, and the other was a conventional pipe pile for comparison. Both vertical and horizontal load tests were conducted, and the load sharing between the raft and piles was carefully investigated. Since the plate pile foundation exhibited outstanding behaviours, finite element method (FEM) numerical analyses were then conducted to investigate the foundation-soil interaction in plate pile foundations under vertical and horizontal loading. According to the test and calculated results, a piled raft foundation supported by sheet piles would be a promising alternative to a conventional pipe pile foundation, especially in highly-seismic areas.