Caisson-Bored Pile Composite Anchorage Foundation for Long-Span Suspension Bridge: Feasibility Study and Parametric Analysis

Abstract

This paper proposes a novel form of gravity foundation for long-span suspension bridges. The foundation combines a caisson with bored piles and thereafter is termed a caisson-bored pile composite anchorage (CBPCA) foundation. Based on a typical suspension bridge case study with traditional caisson foundation, the feasibility of the proposed foundation was evaluated. To further capture the performance of the CBPCA foundation, three-dimensional (3D) finite-element analyses were performed. The 3D finite-element method (FEM) was validated by comparing the simulated horizontal displacements of a nine-pile group with the reported field monitoring data. Parametric studies were also conducted to investigate the effects of various parameters associated with bored piles on the CBPCA foundation performance. The numerical analysis results indicate that increasing the pile diameter can significantly reduce the horizontal displacements of the theoretical joint point (TJP) and the structural forces of bored piles. In addition, the effect of the pile arrangement was also studied. The feasibility of reducing construction time and costs by adjusting the length of some bored piles was also discussed. Moreover, the soil strength has a great influence on the stability of the CBPCA foundation, implying that it may be not suitable for soft soil conditions, namely, a soil strength ratio smaller than 0.4 in this study.