Abstract：Xiamen Xiang¢an subsea tunnel is the first subsea tunnel in China. The geological conditions of land parts of this tunnel are mostly backfill soil，sandy soil or complete weathered rock. Moreover，underground water has strong seepage characteristic. Sandy layer is enriched in water and four weathered grooves under sea directly connect with the seawater. The total water head of groundwater and seawater is between 50 m and 70 m；and the hydrostatic pressure acting on the tunnel arch crown is 0.65 MPa. Therefore，the lining waterproof is a very prominent issue. Considering the geological factors，such as water level，gushing water，erosion of framework and formation of framework，composite lining structure is adopted in Xiamen Xiang¢an subsea tunnel，and the long-time waterproof principle is main shutoff，limited discharge，multilayer proofing and rigidity-flexibility combination. Therefore，the waterproof project is set as part total-closure and limited discharge. For example，the total-closure waterproof is adopted in the parts of main tunnel，which is enriched in water；and the limited discharge project is adopted in the other parts of main tunnel where the surrounding rock is favorable. The total-closure waterproof is adopted in the service tunnel because of its little circle section. Waterproof can be reinforced through injecting pulp. Moreover，construction quality can ensure waterproof system of Xiamen Xiang¢an subsea tunnel. In fact，the waterproof design of Xiamen Xiang¢an subsea tunnel and construction effect is very well accepted. The achieved experiences can provide some references to similar projects.
