Abstract: As the subsea tunnel is designed to pass through the complex strata and withstand high water pressure, the risk of shield chamber intervention tends to be higher compared to general landbased shield tunnels. Therefore, it is essential to develop a kind of safe, highly efficient and costeffective auxiliary chamber intervention technology. In this paper, typical technologies of freezing method and grouting combined with paste HDN film method are introduced and applied to the subsea tunnel projects on Lines 3 and 2 of Xiamen Metro. The recommended methods are compared in terms of adaptability and safety based on the hydrogeological characteristics and the previous application effect. The construction period and cost are divided into two stages, i.e. soil reinforcement and cutter repair, the distribution proportion of them is analyzed, and the relationship between unit repair time (cost) and workload is established. The analytical results show that: (1) With regard to the seabed sandy soil layer, the quality of the existing grouting technology fails to meet the requirements on reliability for chamber intervention under atmospheric pressure, and it is recommended to conduct hyperbaric operation with the assistance of paste HDN film in case of unstable strata and longterm chamber intervention; the freezing method demonstrates an excellent adaptability to sandy soil layer and a high level of watertightness, and which could meet the requirements of atmospheric operation under the context of close monitoring. (2) The construction period and cost required by the freezing method during the soil reinforcement and thawing stage exceed 1.6 times that as required by the grouting reinforcement method; while the efficiency of welding work under atmospheric pressure inside the chamber is 7.1 times that under hyperbaric condition; thus it could be concluded that the freezing method is more advantageous when the workload of cutter repair is high.

Key words:  , subsea tunnel, shield chamber intervention, auxiliary construction technologies, freezing method, paste HDN, grouting reinforcement