3D Numerical Study of the Behavior of Piled Raft Foundation on Soft Clay with Uniform and Varying Pile Lengths

Abstract

In the conventional design of a piled raft foundation, piles of uniform lengths are provided underneath the raft. However, it has been observed that in such cases, the peripheral piles either carry more loads as compared to central pile for a rigid raft, or central pile undergo more settlements than peripheral piles for a flexible raft. This paper attempts to evaluate the required length of the piles in the group for an optimum design of piled raft foundation founded on soft clay. Three-dimensional (3D) Finite Element (FE) models having different configurations of pile lengths and pile spacing were analyzed numerically using a general purpose finite element method (FEM)-based software ABAQUS. Mohr–Coulomb model is used to define the elasto-plastic soil behavior. 3 × 3 squared concrete piled raft foundations were designed with three different lengths of the piles used for the center pile, corner piles and edge piles for models with non-uniform pile lengths. The overall behavior of the piled raft foundation system is evaluated. The results have shown that the model having longest pile at center, intermediate length of piles at edges and shortest piles at the corners has the highest improvement in load-carrying capacity and maximum reduction in average and differential settlements when compared to the conventional piled raft foundation design.