Trans-Tokyo Bay Highway (Submarine Auto-Route)

The Trans-Tokyo Bay Highway (TTBH) on soft ground across Tokyo Bay, opened in December 1997. TTBH is a submarine auto-route of 15.1 km and consisting of two shield tunnels of about 10 km long with a diameter of 14 m situated 60 m below sea level, bridges of 4.4 km long and two man-made islands of different types on thick soft layer, 20 m below sea level, and conquered many concerned difficulties. The seismic measures unified with firm layers have succeeded to save the various structures on improved soft ground, entirely from damage from the 2011 Great East Japan Earthquake (M = 9.0).