Improved Settlement Calculation Method for Offshore Sand Compaction Pile Based on Measurements of the Hong Kong–Zhuhai–Macau Bridge

The sand compaction pile is an effective method to improve soft soil foundation. The Hong Kong–Zhuhai–Macao Bridge island-tunnel section adopts this foundation treatment method to reduce differential deformation between segments. To achieve this goal, it employs a gradually increasing replacement ratio from 42% to 70% according to the thickness changes of marine silt substratum. This study compared the settlement calculation method including the Aboshi method and Ahn’s method with the most popular prediction methods including hyperbolic, three-point, and Asaoka based on field-measured data. The results showed that the traditional settlement calculation method was not precise enough for the high replacement ratio part. Therefore, we proposed a modified settlement calculation method that considered the variation of the reduction coefficient. It was proved that the proposed method was more consistent with field results consequently. Furthermore, it was also verified by field data from the Shenzhen–Zhongshan Link. The method may be a simple and feasible one in offshore engineering practice.