Norway has more than 1,100 road tunnels cutting through the country's mountains and burrowing under parts of its waterways, but until now, ship traffic has had to navigate around treacherous deepwater fiords with miserable weather along the country's 18,000 mile shoreline.
Last week, Norwegian Transportation Minister Ketil Solvik-Olsen announced financing for the long discussed Stad Ship Tunnel is in place and will begin construction in early 2019.
The 5,610-foot tunnel is expected to be located at the narrowest point of the Stadlandet peninsula in northwestern Norway. Plans call for the passage to be 118-feet wide, 162-feet tall (between ground and ceiling), and be able to accommodate cruise and freight ships weighing up to 16,000 tons and 70-feet wide. Estimates are the project will cost $314 million.
Project manager Terje Andreassen said engineers will have to blast out an estimated eight million tons of rock to build the tunnel. Norway has plenty of experience and great expertise in this type of work. The upper part of the ship tunnel will be run the same way as conventional road tunnels. After that, the construction will work downwards, layer by layer. This method is called pallet blasting.
Construction will begin at opposite sides of the mountain, where workers will drill horizontally through solid rock until they meet in the middle. Once the top of the tunnel is hollowed out, they’ll reinforce the arch by applying concrete sprayed with a hose. From there workers will build service routes to transport excavated sediment from the top of the tunnel to the sea, where ships will dispose of the rock.
With the service routes established and the roof secured, workers will resume drilling and blasting through the mountain in horizontal segments, removing chunks of rock up to 44,000 pounds apiece. “You basically have to dig five tunnels on top of each other,” says Snohetta architect Hans Martin Frostad Halleraker. At the end of the process, workers will remove the nine-foot stone thresholds that prevented the sea from entering the tunnel during construction, flooding the tunnel with 36 feet of water.
Plans are the tunnel will be operational in 2023.
For more information, click on the Norwegian Coastal Administration website here: