Serviceability-Based Finite-Element Approach on Analyzing Combined Pile–Raft Foundation

Abstract

The present study proposes a finite-element approach to focus on the load sharing and deformation aspects of combined pile–raft foundation (CPRF) in a serviceability-based framework. Soil nonlinearity was considered by depicting it as a two-parameter medium. Two concurrent analyses were carried out for raft and piles in CPRF, reckoning various soil–structure interactions and ensuring displacement compatibility at the pile–raft junction. A pivotal aspect of this approach is that under vertical loading it incorporates the effect of rotational resistance beneath the flexible raft as the second parameter of the soil medium. The proposed method was validated with available centrifuge test results. Parametric studies illustrate that with a decrease in pile spacing, the differential settlement of the system diminishes, although for higher pile load sharing optimization of spacing is vital. Raft flexibility predominantly governs the deformed shape of the system. Under lateral loading, trivial effect of pile spacing on horizontal pile load sharing is observed, while at higher lateral displacement usage of larger pile length becomes redundant.