The International Information Center for Geotechnical Engineers

Wednesday, 06 March 2019 01:00

Norway to achieve "floating tunnel" project

Norway to achieve "floating tunnel" project-Source: Norway to achieve "floating tunnel" project-Source:

Norway plans to invest in floating tunnel technology in order to facilitate motorists' transportation.

Norway's landscape, consisting of glaciers, mountains and fjords, is one of the most impressive worldwide. But, this spectacular terrain morphology makes travelling a challenging task. For example, it needs 21 hours to complete a 1,100-km trip between the city of Trondheim and the southern city of Kristiansand. Taking this route, drivers have to use 7 times ferry transportation. This journey is part of E39, a key roadway for Norway as more than 50% of the country's goods originate from this area. But the roadway "has a very low standard for a European road," Kjersti Kvalheim Dunham, a project manager at the Norwegian Public Roads Administration (NPRA), comments.

The country's government is determined to change the current situation and has come up with a sophisticated $56 billion construction plan. The project will cut the time of the aforementioned trip by half and travelling will not require ferry transportation.

The plan includes the construction of a 27km-long tunnel at a depth of 392m (which will become world's deepest and longest rock tunnel) and the erection of three suspension and five floating bridges. But, the most challenging part of the project is the development of submerged floating tunnels about 30 meters below the water surface.

Despite being beneath the sea level, the term "floating" is not accurate for this kind of constructions. Tunnels are fixed in positions with cables that are either anchored to the seabed or tethered to pontoons. In the second case, pontoons must be placed in a manner that ships would be allowed to pass through. In other respects, tunnels are constructed of concrete and operate conventionally. The effect of waves and currents must be incorporated in the design but as NPRA's chief engineer, Arianna Minoretti, explains, their impact is reduced at a depth of 30 meters below the surface.

The most severe challenges of the project include explosions, fires, overloading and submarine collisions, according to Mrs. Minoretti. The Norwegian University of Science and Technology's Center for Advanced Structural Analysis (CASA) is collaborating with NPRA to investigate the behavior of concrete constructions when subjected to internal blast loads and results show that their harmful impact is reduced due to the presence of the constant water pressure around the tunnels.

The Norwegian government plans to complete the construction by 2050. If it is realized, Norway will be the first country to achieve such a difficult project. China, South Korea and Italy are also counties that are researching and investing in similar projects.


Read 265 times Last modified on Wednesday, 06 March 2019 16:56

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