Foundation of an immersed tunnel on marine clay improved by cement deep mixing and sand compaction piles

摘要

A 3.2 km long immersed road tunnel forms part of the Busan-Geoje Fixed Link in South Korea, which connects Koreas second largest city Busan with the island of Geoje. To ensure the water tightness of the joints of the segmental tunnel structure and to limit the forces in the shear keys, the differential settlements have to be limited. This is achieved by extensive soil improvement of the marine clay below the tunnel with cement deep mixing (CDM) and sand compaction piles (SCP). This paper is concerned with the characteristics of the marine clay, the basic design principles, layout and constructional issues of the soil improvement as well as the numerical settlement and stability analyses.