Settlement Analysis of Sand Compaction Pile Composite Foundation in Transition Section of Immersed Tube Tunnel

The foundation of the immersed tube transition section of the Hong Kong-Zhu Hai-Macao Bridge Project is distributed with thick silty soil. The method of sand compaction pile + surcharge preloading is used to treat the soft soil ground. In order to determine the foundation consolidation settlement and subsequent residual settlement in the transition section of the immersed tube tunnel, a monitoring system using long wires combined with wireless transmission and long-distance data collection was developed to obtain the measured foundation settlements during the surcharge period. After comparing the measured value with the calculated value, the formula for the composite foundation of the sand compaction pile was revised to obtain a more reasonable residual settlement of the foundation, which could guide the design and construction of the immersed tube tunnel.