Modeling the Response of a Piled-Raft Footing: Ultimate Bearing Capacity

Abstract

The design of pile–raft foundation is a complex problem due to pile-to-pile, pile-to-soil, pile-to-raft and raft-to-soil interaction effect; hence, a simplified and standard procedure could not be evolved so far; in spite of the fact that this type of footing finds versatile applications in the field and its use as a foundation system helps to transfer a heavy load satisfactorily and that comes with a reduced settlement, and thus, it offers an economical design without compromising the safety of the structure. The present paper presents an analytical model to predict the ultimate bearing capacity of piled-raft footings. The study has been derived using an extensive set of experimental data obtained from the studies carried out in the laboratory. Finally, the response of a full-sized raft footing, designed using the proposed model, was simulated on PLAXIS-3D for the validation purpose. The results from the model are in good agreement with the values obtained during the simulation study carried out on the PLAXIS-3D. Sensitivity analysis carried out with a soil stratum of loose and dense sand indicates that there is a significant effect of the soil properties on the load-carrying capacity of the piled-raft footing. Accordingly, a relationship is proposed to take into account the effect of the sand relative density during the analysis.