Settlement-Based Load-Sharing Ratio Variation for Large Piled-Rafts

In the piled-raft (PR) foundation design, evaluating the load shared between the raft and piles is important as both contribute to the load-carrying capacity. For the present study, three-dimensional numerical modeling has been carried out to investigate the load-sharing ratio of a large piled-raft foundation in dense sand with respect to settlement by varying parameters like spacing and length of pile and thickness of raft. Initially, the individual load–settlement responses of the raft and piles in PR are determined for all PR configurations and then compared with the individual responses of the unpiled raft and group piles. Results show that the load-carrying capacity of raft and piles in PR is found to be greater than unpiled raft and group piles, respectively, for smaller pile spacing. The load-sharing ratio increases with increase of pile spacing at all settlement levels. With increasing settlement, the load-sharing ratio decreases for smaller pile spacing, whereas, for larger pile spacing, it increases initially and then decreases. As pile length increases, the proportion of load carried by piles increases at all settlement levels for smaller pile spacing; but for larger pile spacing, the variation of the proportion of load carried by piles is not significant at smaller settlement levels. For all raft thicknesses at higher pile spacing, the proportion of load carried by piles increases initially at initial settlement and then becomes almost constant toward higher settlement.