Submerged floating tunnels (SFTs) for Norwegian fjords

AbstractSubmerged floating tunnels (SFTs) weigh roughly the same as the surrounding water. The loads on the tunnel depend on the variation of the forces on the tunnel. The forces come from variation in traffic, current, temperature, waves, weight of water, weight of concrete, growth on the tunnel, wear of asphalt, dust and debris, relaxation of prestress and shrinkage and creep in the concrete. The last six variations are slow and can be counteracted by altering weights in the tunnel.All structures above sea level are subject to gravity, which tends to limit their spans. In SFTs buoyancy counteracts gravity. This speaks for longer spans, but the slope of roads limit the depth to raise ratio of downward arched SFTs. This tends to limit the free spans. In this article the design of SFTs is discussed. Finally there is a comparison between materials needed for two SFTs and a suspension bridge between Vallavik and Bu in Eidfjord in western Norway. The fjord is ∼500 m deep.It is many years since the author did serious research on submerged tunnels. He has written this contribution in the vain hope that some of his ideas on submerged floating tunnels might be of value to somebody. The author got the idea of SFTs at the technical university in Trondheim from his teacher Erik Ødegård [1]. However the idea is much older. E.J Reed, MP. applied for a patent in 1884. Up to 1968 the following Norwegian names are connected to the idea: Olsen 1923, Sam Lorgen 1968, Sverre Mo 1968.The author apologizes for not mentioning many other Norwegians who have done valuable work on SFTs. His best publication on submerged tunnels is [2]. It has a list of 32 references