Numerical modeling of unconnected piled raft system

Grounds and foundations, underground structures
Authors:
S. Al-SaadiM. Karkush
Abstract:

In recent decades, increasing attention has been directed toward the behavior of unconnected piled raft foundations (UCPRFs) under various soil conditions. In this foundation system, a cushion layer is introduced between the pile heads and the raft, preventing direct structural contact between these components. The cushion provides an intermediate load-transfer medium and facilitates the redistribution of the applied load between the raft and the piles. Understanding this interaction is essential for evaluating the overall response of the foundation and the contribution of its individual components. This study numerically investigated the behavior of UCPRFs using the finite element method implemented in PLAXIS. The analysis considered bearing pressure, foundation settlement, axial stress distribution along the piles, and bending moment response. A parametric investigation was conducted to evaluate the effects of pile length, pile diameter, and raft stiffness on settlement reduction and foundation performance. The results showed that axial stresses in the piles increased with increasing pile length and diameter, demonstrating the influence of pile geometry on load transfer within the foundation system. Furthermore, the maximum axial load occurred at a certain depth below the pile head, indicating that load transfer continued along the upper portion of the pile rather than being concentrated at its head. Within the investigated range, changes in the raft’s modulus of elasticity had no significant effect on settlement reduction. These findings improve the understanding of load-transfer mechanisms in UCPRFs and clarify the relative influence of pile geometry and raft stiffness on their numerical response.

Key words:
unconnected piled raftcushionnumerical analysisPlaxissandy soil
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