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Abstract

The piled-raft foundation has been commonly used in Taipei Metropolitan to solve the low bearing capacity and the excess settlement problem of the raft foundation for the high-rise building. In past studies, effects of the deep excavation, the diaphragm wall and the overburden stress of the surrounding soil on the piled-raft foundation were often ignored in the numerical simulation. In this article, a parametric study on the piled-raft foundation including four influence factors, namely, the shape of the piled-raft foundation, the arrangement of (or the number of) piles in pile group, the length of the pile, and the thickness of the raft, were carried out using three-dimensional finite element method (3-D FEM) to understand their effects on the behaviors of piledraft foundation. Parametric study results indicate that all four influence factors have significant effects on the settlement of the piled-raft foundation. Other than the settlement, the arrangement of pile has major effects on the pile head loading and the pile bending moment of the piled-raft foundation as well. In addition, the Load Carrying Ratio (LCR) of raft in piled-raft foundation is dependent on the raft settlement. A higher LCR value is constantly associated with a larger settlement of piled-raft, especially for the piled-raft with a larger PAF value (or fewer piles in pile group). Conclusively, the raft carries 20% to 35% of the total vertical load on the piled-raft system of deep excavation in Taipei Metropolitan.

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