2003 Volume 13 Pages 231-236
The Wakunami Tunnel is a binocular tunnel on the Kanazawa Sotokan Expressway. An approach-lane tunnel runs just above this binocular tunnel. This is an unprecedented structure in Japan. There is a residential zone on the surface, and the overburden is only about 12 m. In addition, the distance between the binocular tunnel and the approach-lane tunnel is merely 3 m at minimum. These severe restrictions are imposed on this tunneling project.
For construction of the binocular tunnel, a new method, named Pre Supporting System- Arch (PSS-Arch), was selected using a value engineering approach after conclusion of the contract. This method installs curved steel pipes from the central drift. This report deals with the development and construction method of this new technique.