Interaction Effects for Large Piled Rafts in Clay Soil

The behavior of a piled raft foundation (PRF) depends on complex raft–soil–pile interactions. In the present paper, the effects of pile number, pile spacing, pile length, and pile diameter on the settlement-dependent variation of raft–soil–pile interactions and load-sharing behavior of large PRFs in clay soil have been evaluated. Three-dimensional numerical analyses were performed on different foundation types such as piled raft, unpiled raft, pile group, and single pile. Results show that the piles-to-piles (P-P) interaction effect approaches unity at a particular settlement value, and the value is larger for a higher pile number, pile length, and pile diameter. With the same number of piles, at higher settlement levels, the raft-to-piles (R-P) interaction effect is slightly larger at wider pile spacing. An insignificant effect in the settlement-dependent variation of the R-P interaction effect is observed for variation in pile number, pile length, and pile diameter. The piles-to-raft (P-R) interaction effect firstly decreases within initial settlement range and then increases as PRF settlement increases. The proportion of load carried by piles in PRF initially increases and then decreases with PRF settlement. The settlement at which the pile load proportion reaches a peak is larger for a higher pile number, pile length, and pile diameter.