Development of optimum design from static response of pile–raft interaction

Piled raft foundations are among the most commonly used support structures for offshore projects. When a raft foundation alone does not satisfy the design requirements, piles may be added to improve the ultimate load capacity and the settlement performance of the raft. In this study, design criteria were developed for the undrained behavior of a piled raft system based on an examination of average and differential settlements, raft bending moment, and pile butt load ratio. Raft settlements were evaluated by a series of three-dimensional finite element analyses. The average settlement values for the piled raft were highly influenced by the number of piles and the raft thickness. Optimal design configurations of piles for cohesive soils are discussed. Increasing the pile spacing decreased the pile butt load ratio by allowing for a more uniform load distribution between the piles.