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  Tokyo Metropolitan Subway Line No.12
(Toei Oedo Line)

The Toei Oedo Line forms a 41-km underground loop around metropolitan Tokyo. Following a construction period of 14 years, the line opened to passengers in December 2000. The new subway reinforced the cityfs complex public transport network, bringing transport convenience to many localities. In particular, the subway now links the northwest and older downtown areas with the major sub-centre of Shinjuku, where the Tokyo Metropolitan Government and major high-rise business and commercial precincts are located. The opening of the line has invigorated the economies of numerous districts located along its route.

Subway image Technical Features
Having to cope with an already densely developed underground environment, the subway is one of the deepest in the world, ranging between 15 m and 48 m below ground. To reduce construction cost, the outer diameter of the tunnel was set at only 5.3 m, some 2 m smaller than previous subway tunnels. The trains are driven by linear induction motor and are able to handle a particularly tight minimum curve radius of 102 m.
Where soil conditions were favorable, the tunnel lining used boltless construction. Lining segments were fixed to the tunnel wall with dowel, and keyed joints were used between adjacent lining segments, the first time this method of construction had been used for a railway tunnel in Japan.
Role of NCC in tunnel construction
Although the project was constructed using the design-build approach, NCC was responsible for segment lining design and construction supervision of almost half of the tunnel sections that used boltless segment joints. In addition, because of its technical experience in the design of shield tunnels, NCC was given responsibility for providing the overall design concept for these sections.
Segmental lining of the
                          Toei Oedo subway line tunnel
Segmental lining of the Toei Oedo subway line tunnel showing dowel insertion points near the centre of the pre-cast concrete segments.

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