Experiences from construction and maintenance of world's longest and deepest subsea road tunnel in Norway

The Rennesøy - Mainland connection (“Rennfast”) is located approximataly 15-20 kilometers north west of Stavanger, at the south west coast of Norway. The main parts of the project is represended by two subsea road tunnels. The longer one, The By fjord Tunnel, has a length of 5851 meters and a maximum depth of 223 meters below sea level. For the time beeing ( March, 1994 ), this tunnel is the deepest and longest subsea road tunnel in the world. This article describes experiences form construction, supplementary geological investigations, support measures, drainage and water/frost - protection. Deformations possibly caused by sqeezing rock are mentioned. Maintenance costs for a period of 12 months are given.