Settlement characteristics of immersed tunnel of Hong Kong–Zhuhai–Macau Bridge project

The settlement performance of an immersed tunnel in the Hong Kong–Zhuhai–Macau Bridge (HZMB) transportation project is described. The geological profile underlying the immersed tunnel is presented and the corresponding field monitoring system is introduced. The function of semi-rigid elements is analysed. The observed results related to longitudinal deformation patterns during construction (e.g. long-term settlement, differential settlement and structural behaviour) are described and analysed. Differential settlement occurred when there was a large variation in soil properties, at the joints of two adjacent elements and in different segments of the same element. Differential settlement occurred in both the longitudinal and transverse direction. During the operational period, permanent settlement was strongly related to back-silting. Tide loading and the immersion of adjacent elements may have caused transient settlement related to elastic deformation, but tide loading had less influence on the permanent settlement.