Performance Analysis and Load Sharing of Combined Piled Raft Foundations on Cohesive Soil Using Finite Element Approach

This study investigated the load-sharing mechanism of combined piled raft foundations in cohesive soils using numerical simulations. Three-dimensional finite element analyses were conducted to evaluate the effects of raft thickness, pile spacing (S/d), aspect ratio (L/d), soil stiffness, number of piles, and pile positioning on the load-settlement response and load-sharing mechanisms under vertical loading. The results showed that increasing S/d, soil stiffness, L/d, the number of piles, and raft thickness improved the load-carrying capacity. Key factors such as soil-structure interaction, contact stresses, strain development, and pile response to varying soil stiffness were also examined. The analysis found that piles supported approximately 38–62% of the total applied vertical load, with a decrease in load sharing during the initial settlement phase. In stiff soils, this reduction occurred within 0.2% of the raft width, while in soft soils, it occurred within 1%. As soil stiffness increased, the load carried by the piles decreased. Additionally, the pile skin friction was fully mobilized when the settlement reached 0.6% of the pile diameter.