Abstract: The island-tunnel segment of Hong Kong-Zhuhai-Macau Bridge is featured with deep soft soil under the immersed tube foundation. Sand compaction pile together with preloading was adopted to eliminate the differential settlement between joint parts. In this paper, the technique of monitoring tube foundation settlement by liquid pressure settlement sensor is introduced in details. Satisfactory settlement data was obtained. A variety of technical approaches, including the timing of operations, protection of wire connectors and wire, were employed to improve the success rate of equipment burying. Test results showed that the technique could perform continuous stable wireless monitoring as it is of high stability, low error rate, and is less susceptible to wind and waves and construction interferences. Therefore it could realize the continuous and stable wireless monitoring of the foundation. The study is expected to provide reference for the monitoring of composite foundation under deep water conditions.

Key words: immersed tube tunnel of Hong Kong-Zhuhai-Macau Bridge, sand compaction pile, preloading, settlement calculation, in situ test