Study of Piled Raft Foundation on Layered Soil

Piled raft foundation is a combination of a shallow foundation (raft) and a deep foundation (pile group). In this type of foundation, the role of the raft is to provide the required bearing capacity, and the piles are used mainly as settlement reducers but can also contribute to the bearing capacity. In this paper, a numerical model was developed using the software PLAXIS 3D to analyze piled-raft foundations on layered soil. Layered soil, i.e., clay layer underlain by silty sand and then dense sand at lower layer with water table at a constant depth was assumed for the study. Here a drained condition was assumed and total vertical displacement was calculated using plastic calculations. The piles and raft were modeled using a plate element. A non-uniform vertical loading in the form of concentrated column loads has been imposed on the piled raft. The effect of some important design parameters on the performance of piled-raft foundations such as pile length, pile diameter, pile spacing, and raft thickness with varied numbers of piles on layered soil is studied. The effect of these parameters was studied in terms of their influence on the deformation of the piled raft foundation.