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.