The subsea tunnels all over the world are investigated; and the three methods
such as Norway experiential method
the minimum leakage method and coal cutting experience under water
are summarized. According to above-motioned methods
the engineering analogy is used to decide the minimum rock cover of a subsea tunnel at Xiangshan Harbor. The results of three methods are thought over overall. Meanwhile its geology is considered. Then the optimal rock cover is gained. To take into account the subsea landform and geology
a profile is chosen to be the reference profile. According to the design gradient of the subsea
the tunnel motherboards and the rock covers of profiles are obtained. Comparing those with the results of engineering analogy
the shortcut of tunnel is got under the safety condition by adjusting the gradient of the part of the tunnel motherboards; so the optimal scheme to construct the subsea road tunnel is decided.