Naveen kumar.D

ABSTRACT

In modern construction, a piled-raft foundation is a composite construction which consists of piles and raft is one of the alternatives over conventional pile or raft foundations. It is used not only for reducing the settlement of soil, but also can handle large eccentric loading. The analysis of piled raft foundation is very tough and the design of piled raft with soil interaction effect is one of the major problem as the behavior of a structure is highly affected not only by the response of the superstructure, but also by the behaviour of the foundation and the soil as well. In this study, the piled raft foundation is analyzed using ANSYS (2D analysis), a popular finite element software to study the load displacement response in a sand medium of various relative densities (loose, medium dense and dense) with interaction effects. Three different pile spacing - 3d, 4d and 5d were considered for the study (where d is the pile diameter) with three different pile configuration (3x3, 4x4 and 5x5) with an objective of finding the optimum number of piles and pile spacing for various relative densities of sand. The results show that the ultimate load and settlement corresponding to ultimate load increases with the relative density. Lesser settlement is observed when the frictional angle of the sand is increased and increases when the number of piles are increasing. The rate of settlement decreases with the increase in relative density of the soil. The load settlement response of medium and dense sand is almost identical. The performance of a 4 x 4 pile group is observed to optimum. Key Words: eccentric loading, pile raft foundation, ANSYS, settlement, relative density.