Abstract:Xiamen Xiang¢an subsea tunnel,with the total length of 5.948 km,is the first subsea tunnel designed and constructed by mainland China. According to the geological exploration data,the tunnel will pass through four deep weathered or slots troughs,F1,F2,F3,F4,where the strata are complete or strong weathered weak rocks. These strata have high permeability coefficients,huge water amount,high water pressure,and high risk of water and silt pouring in tunnel with infinite seawater supply. As a result,the safety of weathering slot F1 during tunnel construction is the key in the project. At present,the tunnel has been excavated to the weathered slot. In order to assure that the subsea tunnel can pass the weathered slot F1 successfully,the full-section curtain grouting technology is adopted to reinforce the weathered slot F1 to block up the water. The effect of the full-section curtain grouting in the first cycle is good;and the tunnel has been excavated for 18 m successfully. The geological condition,grouting mechanism,scheme and parameters,and the verification and appraisal of the construction techniques and grouting effect are introduced.