Abstract: The eastern passageway project in Xiamen is the first subsea tunnel in mainland China that was ever designed and constructed by Chinese professionals. The tunnel is design to be under the shallow buried depth in completed weathered on land segment and to pass the weathered trench under the sea. The potential construction difficulties include the penetration of the saturated sand strata and the vertical shaft construction in Xiangan. In summary, the complexities of the geological conditions is more than any of the subsea tunnels ever been constructed in the world. This paper discusses the characteristic and difficult aspects of the subsea tunnel crosses the waterenriched sandy strata and the weathered trench as well as the application of the advance grouting and reinforcement technique. The results show that: (1) in different construction stages of the weathered trench, the different advance grouting should consider both the surrounding rock degrees of weathering and water contents; (2) the TSS small diameter pilot pipe the cement silicate grout can effectively reinforce the waterenriched sandy strata.

Key words: Subsea Tunnel；Eastern Passageway of Xiamen；Construction Technique；Advance Grouting, Stability Support.