FEM Analysis of Disconnected Pile Raft Foundation Under V-H-M Loading Using Plaxis-3D

Abstract

A foundation is a structural element that supports the loads of the superstructure and safely transfers them to the ground. When used in conjunction with pile groups, raft foundations can withstand extremely high loads. In recent years, disconnected pile-raft foundations (DPRF) have been viewed as a cost-effective solution for supporting heavy loads. The piles are used as settlement reducers rather than just to maintain the foundation's overall stability. These piles are separated from the raft to decrease settlement and enhance overall system rigidity. The present study examines the behaviour of disconnected pile raft foundation (DPRF) system in layered soil under vertical, horizontal, and moment(V-H-M) loading conditions using PLAXIS 3D. The use of this FEM technique to different types of loading has been presented, and findings of the model have been in agreement with the reported numerical study. A comparison between pile groups of 5x5, 3x3 and 2x2 configuration for disconnected-pile raft and connected-pile raft have been made, and results have been presented. The load settlement behaviour, axial load behaviour in a pile, and the differential settlement along the raft has been validated with the reported literature. Further, the validated model has been used for the parametric studies such as variation in pile length and diameter, cushion stiffness, and performance of raft characteristics under combined loading (V-H-M) were performed. This method has been used for the analysis of disconnected and connected pile raft foundation and a comparison between both the cases has been presented. The variation of bending moment and shear force distribution were studied for the case of combined eccentric loading conditions. The results showed that the settlement at the raft center decreases with an increase in pile length, pile diameter, and cushion stiffness. Lateral deformations observed for DPRF and unpile raft is more than the connected pile raft foundation (CPRF). The 64.37% decrease in pile load ratio has been observed if pile group changes from 5x5 to 2x2 pile configuration.