Laying amongst the pristine nature of Monsastubergan and Manndalen in Northen Norway, the 5.8km K01 E6 Indre Nordnes-Skardalen double lane road tunnel is located approximately 60km East from Tromsø. This region above the Arctic Circle is popular for the Northern lights and known for its harsh, long and dark winters.
The road tunnel has been built to avoid rock falls and avalanches prone road sections and has shortened the E6 by 8km.
The client is Statens Vegvesen Region Nord (Norwegian Public Road Administration), the designers are Statens Vegvesen, EFLA and Rambøll Norge AS, the contractor for the electrical installations is Mesta AS and the contractor for the civil engineering works is Marti Nordnes DA.
The project started in December 2014 and all civil engineering works have been completed according to schedule by November 2017. The electrical installation and the final test lasted one year and the tunnel was opened to traffic on the 10th November 2018.
As a joint venture between the Swiss company Marti Tunnel AG and the Norwegian company Marti AS, Marti Nordnes DA has been awarded the E6 Indre Nordnes-Skardalen project with a contract value of EUR 55M (USD 62.4M) in October 2014. The contract type was a measured contract, based on bills of quantities, and incorporated the principle of payment by remeasurement of completed work at initially tendered rates. Slow turn-around times, changes and schedule acceleration have however influenced the project and a court case between Marti and SVV is currently ongoing.
“The main challenge was to work in a remote area on a tight schedule,” explains David Fossati, Nordnes project manager since 2017. “Fortunately, Marti has been successfully working on remote tunnelling projects in Iceland and Norway since 2008 and we could rely on our previous experience.”
The start of the project matched well with the hand over of Snekkestad tunnel site in Southern Norway and therefore most of the installation and equipment needed was available and could be moved right away.
Fossati says:“ Norway has very good sea transport possibilities. So we decided to move equipment, installations and containers for the camp by boat.”
“Another challenge was to find people willing to travel regularly to a construction site in Northern Norway, which from central Europe almost takes the same time to fly to the USA. Even though Northern landscapes are amazing, a persuasion work was required.”
The different working culture between Switzerland and Northern Norway were an additional interesting challenge.
“Of course we needed to build up trust in the beginning of the project,” says Fossati. “Coming from abroad in a remote area, it took some time to find good sub-contractors and to understand each other. I’m glad to say that through the project we managed to get some very good sub-contractors and partners.”
The bedrock along the WSW-ENE aligned tunnel route belongs to the Kåfjord nappe. This nappe consists of layers of originally sedimentary rocks that have been transformed under very high pressure and high temperature into garnet mica-schist and garnet micagneiss. The nappes are tilted towards NW and two main joint sets run NW-SE and NE-SW dipping both almost 90°.
The rock classification scheme used in Norway is Barton’s Q system. “The decision about the type of rock support is mostly a task of the client’s site engineer, who evaluates the Q-value and discusses the situation encountered at the excavation face with the miners,” says Fossati. “The close cooperation between site engineers and miners is a very good custom of the Norwegian tunnelling society.”
The road tunnel has been excavated by means of two drill and blast from both portals, with breakthrough in the middle of the tunnel. The emulsion was placed into holes as main explosive and Sandvik DT1230i were used as drill rigs. They are a three-boom electro hydraulic rig.
Fossati explains that drill and blast was the most suitable excavation method for the Nordnes tunnel mainly for the type of rock, the shape of the tunnel and the location. “This method was also good due to the tunnel design without inner lining and with a final rock support by only means of rock bolts and shotcrete,” he says.
After the start up period, the average performance of the excavation was 75m per week with peaks of up to 110m per week in two shifts of 10 hours per day for 5.5 days per week.
Rock quality was good and tool consumption was fairly typical.
In terms of spoil, most of the excavated material has been reused in land and road fillings or even avalanche barriers, while the rest was placed into the sea with a barge for sea dumping. On land, the muck was transported with dumpers and trucks.
In terms of rock support, steel fibers reinforced shotcrete was sprayed and Vikørsta CT-Bolts were installed. Additional rock support included spiling bolts and reinforced shotcrete arches. The shotcrete thickness was between 8 and 15cm and the average amount of shotcrete sprayed per meter of tunnel was 3cbm/m. Four bolts were used per each meter of the tunnel as well. This bolt is a combination of a mechanical bolt, installed as a temporary rock support and later grouted to become a permanent bolt.
Given the remote area of the project location, Marti Nordnes DA installed a Tecwill mobile batching plant on site, which delivered shotcrete and concrete for the whole project. Talking about stockpiled on site, Fossati explains that they had stocks for two or three weeks of most needed construction material. “The masses for building the road were on the other side delivered just in time by boat because we didn’t have enough space on site,” he says.
Partial “PE-Foam” water and frost protection solution was installed in the wet and damp areas of the tunnel. The system consists of an insulating PE-Foam membrane held in position by means of bolts with a reinforced concrete structure on top. Fossati explains that this is the standard Norwegian and water and frost protection system.
“The concrete lining with sealing is not common in Norwegian tunnels,” he says. “The final rock support of most tunnels only includes shotcrete and rock bolts. In presence of water, it’s required to install waterproofing and insulating foam that is covered with shotcrete. The initial investment for building such tunnels is lower as for tunnels with inner lining, as the amount of concrete needed is much lower.”
