Bjørnegård Tunnel in Norway

AluFix and Mammut 350 overcome all challenges

Data & Facts

  • Project
    • Bjørnegård Tunnel, Norway
  • Principal
    • Statens Vegvesen, Norway
  • Contractor
    • NCC Infrastructure, Oslo (Norway)
  • MEVA systems
  • Engineering and support
    • Maxbo Teknikk, Norway

AluFix: the specialist for very confined spaces

When equipment rooms have to be integrated into new tunnel tubes as well, the available space is inevitably confined. Hence, when pouring the corresponding walls in a Norwegian road tunnel, simple handling and ease of use were important factors – and the strengths of MEVA’s AluFix system. The heavy work was tackled using Mammut 350.

The construction of the new Bjørnegård Tunnel to the west of Oslo took three-and-a-half years. The wait and the work were worthwhile. Motorists on the E16 motorway between Oslo and Bergen now make good time at this former traffic junction, and the inhabitants of the municipality of Bærum no longer suffer from the noise and traffic jams. The construction company NCC Infrastructure built a 2.3 km long tunnel with two parallel, two-lane tubes on behalf of the Norwegian road construction authority Statens Vegvesen. Maxbo Teknikk, MEVA’s Norwegian sales partner, delivered 705 m² of robust Mammut 350 frame formwork as well as 300 m² of lightweight, easy-to-handle AluFix panels.

Mammut 350 for the retaining walls
Using the modular Mammut 350 wall formwork, lateral retaining walls were poured over a length of 600 m leading up to the tunnel entrances. Maxbo Teknikk’s engineers calculated the work involved in advance and selected the strong Mammut 350 wall formwork system because of the large surface area of the walls and the fresh-concrete pressure expected. The work was performed concurrently from the north and the south ends, and the concrete was poured in 12 cycles, each with a length of about 24 m. The permissible fresh-concrete pressure load of 100 kN/m² and the robust frame design of the Mammut 350 wall formwork panels enabled the large retaining walls at the sides of the tunnel approaches to be poured quickly.

The advantages of the globally tried-and-tested system came into their own during this project. The system was quick and easy to assemble, and the large surface area of the panels of up to 8.75 m², enabled the construction work to progress rapidly. Furthermore, the required attractive surface finish was achieved, not least due to the symmetrical tie hole and joint pattern and the use of the alkus all-plastic facing. Stripping and reassembly were also carried out smoothly and swiftly thanks to the system’s ease of cleaning and the practical bump notches for simple alignment and adjustment with a crowbar.

AluFix: the specialist for very confined spaces
In the tunnels themselves the available space was significantly more confined than in front of the entrance areas. In the tubes it was necessary to build equipment rooms with a ceiling height of 5.50 m, which house, for example, drainage tanks for mountain water as well as filtration equipment. It was not possible to use lifting gear or cranes, and the low tunnels made it difficult to position the formwork and pour the concrete. Hence, NCC Infrastructure relied on the AluFix panels recommended by Maxbo Teknikk. In view of the cramped conditions, it was all the more important to be able to flexibly move the wall formwork panels by hand. The ability to produce trouble-free corner solutions for all wall thicknesses using only six panel widths and six panel heights (up to 350 cm) proved to be a huge advantage.

The lightweight modular hand-set formwork AluFix can withstand a fresh-concrete pressure of 50 kN/m². The ergonomic grip profile and the low weight of the nevertheless robust aluminium profiles made the handling easier. The power-coated profile surface is easy to clean and, far from unimportant in such a confined space, impact- and scratch-resistant. For fire prevention reasons, special, fire-resistant concrete had to be used in the entire tunnel area. The result was just as good and the surface just as smooth as usual thanks to the alkus all-plastic facing.

“The Mammut 350 formwork system has proven its worth during many a large project in Norway. In this case, during the construction of the Bjørnegård Tunnel, AluFix emphatically proved that this lightweight hand-set formwork is very well suited to concrete construction in confined spaces in technical buildings and in infrastructure,” says Pål Kjustad, sales manager at Maxbo Teknikk.

 

Photos © Maxbo Teknikk