A Comprehensive Review of Load Distribution in Piled Raft Foundations: Effects of Pile Number and Spacing on Pile–Raft Interaction

This study provides a comprehensive review of load distribution behavior in piled raft foundations, with emphasis on the effects of pile number (n) and pile spacing (S) on the interaction between the raft and pile system. Results from analytical models, numerical simulations, and physical model experiments are synthesized to assess how these geometric parameters influence the proportion of vertical load carried by the raft and the piles. A consistent trend is observed: increasing the number of piles leads to a decrease in the load share carried by the raft (P_r/P_t) and a corresponding increase in the load carried by the piles (P_c/P_t). This indicates that, as pile density increases, the pile system gradually assumes a dominant role in supporting vertical loads. Conversely, increasing the pile spacing from 2.5D to 5D results in a higher raft load share for the same number of piles. This trend is more pronounced in configurations with fewer piles, where reduced interaction between widely spaced piles requires the raft to absorb a greater portion of the load. Comparative results also reveal that modern approaches, particularly physical modeling, finite element modeling (FEM), and advanced analytical methods, exhibit higher sensitivity to geometric variations and better capture the nonlinear nature of pile–raft interaction than simplified linear models. The convergence of results across different methods demonstrates the reliability of these approaches and their potential for improving foundation design practices. This review highlights the need to incorporate interaction effects into design guidelines to ensure accurate modeling of load sharing in piled raft systems.