Effect of Vertical Contact Pressure on the Lateral response of Combined Piled Raft Foundation: A Numerical Study
Keywords:
Combined pile raft foundation (CPRF), settlement, pile configuration, vertical contact pressure and PLAXIS-3DAbstract
In combined pile-raft foundations (CPRF), geotechnical engineers often assume that the lateral load is mainly supported by the piles, ignoring the contribution of the raft. This assumption can lead to a more expensive and less efficient foundation system. Various studies have examined the effects of factors such as the number of piles, pile length, pile configuration, and spacing-to-diameter ratio on the raft's contribution to lateral load. However, there is limited research on how vertical contact pressure beneath the raft affects the lateral load distribution between the raft and piles in CPRF. This study investigates the influence of vertical contact pressure on the lateral load distribution of raft and piles, focusing the impact on the front and back piles, and the effect of pile-raft configuration on lateral load distribution, while maintaining constant average vertical and lateral load per pile. In first case, a parametric study was conducted through finite element software PLAXIS-3D on small-scale piled raft model with configurations of 4 piles. A total of 14 models were created where vertical load was uniformly increased under a constant lateral load to observe the lateral response. In the second scenario, a piled raft with 4, 6 and 9 pile configurations were analysed such that average vertical and lateral load per pile across each model was maintained uniform. The results indicated that increasing vertical load enhanced the lateral response and reduced differential settlement in CPRF. The raft's lateral load contribution was found to be directly proportional to the vertical contact pressure. Additionally, at lower vertical loads, the front piles bear more lateral load than the back piles. As vertical load increased, the lateral load-bearing capacity of the back piles improved due to increased soil stiffness in front of the back piles.
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