Performance of Existing Piled Raft and Pile Group due to Adjacent Multipropped Excavation: 3D Centrifuge and Numerical Modeling

Excavation induces stress changes and soil movement on existing floating piled rafts and elevated pile groups. Limited investigation of the effects of deep excavations has resulted in an incomplete understanding of pile foundation performance at the serviceability state. A series of three-dimensional (3D) centrifuge model tests and numerical simulations are conducted in this study to investigate the influence of raft contact on the response of an existing $2\times 2$ piled raft in comparison to that of an elevated pile group when subjected to an adjacent multipropped deep excavation in dry sand. After rising $g$, an applied axial load was supported by 18% by the raft and 82% by the piles in the piled raft foundation prior to excavation. Owing to stress release and soil movement caused by the 8-m-deep excavation, the pile head load increased by 21% and 3% for the pile closer to the excavation for the piled raft and pile group foundations, respectively. Analysis of pile–soil relative settlement and raft contact pressure shows that a gap formed between the raft and ground surface in the piled raft, resulting in a load transfer from the raft to the embedded piles. A 20% larger settlement was seen in the piled raft foundation than in the pile group, to further mobilize shaft and end bearing resistances for the maintenance of vertical equilibrium. Moreover, 30% additional pile bending moment was induced due to excavation.