The Tokyo Wan Aqua-Line
project was aimed at the construction of a toll road of a length of
approximately 15.1
km with undersea tunnels, artificial islands and a bridge to
cross earthquakeprone Tokyo Bay. This is an expressway with two lanes each in
either direction consisting of a tunnel section of a length of approximately
9.4 km, two artificial islands (of a total length of 0.4 km), a 4.4-km bridge
and a 0.9-km land access. In the tunnel section, two highway tunnels with an
outer
diameter of 13.9 m each were driven by eight slurry shield machines with
world’s largest diameter of 14.14 m in the soft ground 9.4 to 18 m below the
sea bed under a water pressure of 0.6 MPa. This paper describes a series of
watertight lining systems including watertight and corrosion protection
segments and waterproof membranes, developed to increase the watertightness and
durability of the tunnels under the condition mentioned above.