Electric Heating for the immersed tunnel in Norway
The Bjørvika Tunnel is a motorway immersed on European Route E18 in the city center of Oslo. The tunnel links Festning tunnel in Oslo west with Ekeberg tunnel in Oslo east. The completed tunnel has an unbroken length of six kilometers. The Bjørvika Tunnel is the first immersed tunnel in Norway.
The challenge:
Ensure fast hardening of concrete during the tunnel construction under winter conditions
The immersed part of the tunnel is made up of six elements. Each element is 112.5 m long, 28–43 m wide, and 10 m high. The immersed tunnel consists of two tubes, with three lanes in each direction. The tunnel is 1,100 m long, 675 m of which are below sea level. The Bjørvika Tunnel is part of the Opera Tunnel complex, which is the interconnected system of tunnels between Ryen and Filipstad. Uniform concrete may have caused a problem, especially during the Scandinavian winter.
The solution:
Electric heating speeds up solidification in the immersed part of the tunnel
During its construction, electric heating solutions were used to harden the concrete in the roof and walls of the immersed part of the tunnel. Electric heating cables were chosen to make sure that the hardening process unfolded properly.
The result:
Normal solidification process, despite freezing temperatures
During wintertime, when temperatures drop below the freezing point, a normal concrete hardening process is difficult to reach. With electric heating solutions, the building process under harsh weather conditions was maintained uninterrupted.
Project overview
1 100 meters of tunnels
675 meters of which is immersed