• Client / design: statens vegvesen Region vest, Askedalen 4, 6863 leikanger ID 971 032 081, Norway
• Contractor: Joint venture Metrostav – Bertelsen&Garpestad AS.
• Contrctual time period: 09/2015 – 07/2017
• Contrctual price: 352 422 365 NOK excluding VAT 35 million EUR (Approx.)

Project description

Prevention of road Rv.13 from avalanches and stone falls included excavation of a 2035 m long tunnel and 800 m of roads on the surface. The first 100 m from the eastern portal was dug using the NATM method with the implementation of its key principles: face sequencing; face stabilisation with bolts and sprayed concrete; primary lining of lattice girders, wire mesh, and sprayed concrete; pipe-roof umbrellas; geotechnical monitoring of tunnel, surface, and portal wall. The NATM excavation was done in glacial moraine with isolated inflows of water with a phyllite rock base. The rest of the tunnel, 1935 m, mostly comprised of gneiss and phyllite, was gouged using the Drill & Blast method. Water and frost insulation was made of a 45 mm PE-foam and an 80 mm shotcrete layer with PP microfibers. In the NATM section, reinforced concrete secondary lining and the intermediate membrane were constructed.

Project data

Extraordinary of the project

• The project was specific mainly by the implementation of the NATM method as it was the very first planned use of that method in Norway.

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