The Faroe Islands is a chain consisting of 18 volcanic islands located between Norway and Iceland in the Atlantic Ocean.
The tunnel system will stretch beneath the sea for 11 kilometers and will connect Hvítanes, a village situated near Tórshavn, the capital city of Faroe Islands, with Eysturoy, the second largest island of the chain. In particular, the tunnel will feature two routes starting from two locations on the Eusturoy island that will be united beneath the seabed via a stunning roundabout and will continue as one route towards Hvítanes.
The underground facility will provide great benefits to people since time traveling from Tórshavn to Eysturoy Island will be reduced from 74 to just 16 minutes. The maximum inclination of the road network will be 5% while the lower point of the system will be at 187 meters below the surface of the water.
The construction of the tunnel system began in 2016. According to a study published a year later, the tunnel will pass by basalt rockmass interlayered by a glacial or post-glacial formation. Basalt is an igneous rock that is strong and durable given the absence of a network of cracks. Therefore, conditions for tunneling are good in terms of supporting the surrounding rockmass but, attention should be given to fault zones where cracks emerge so the material can be both permeable and unstable.
The same study mentions that the drill and blast technique was used for the excavation while a self-standing inner lining was proposed for supporting the surrounding rockmass. In particular, shotcrete, wire mesh and rock bolting were used for the lining of the tunnels. The maximum advance was observed in spring 2018 when the excavation proceeded with a rate of 190 meters per week.
A major challenge that the contractors tackled included the reduced mechanical properties in certain basaltic zones where a technique known as pre-excavation grouting was used. This method involves applied grout pressure in an advancing tunnel face to improve the mechanical characteristics of the rockmass and to locally reduce its permeability. According to NCC's (the construction company based in Sweden) project manager, Alf Helge Tollefsen, much more grout (about 7.500 tons) than anticipated was utilized for the accomplishment of the project.
The design of the roundabout is spectacular featuring colors and lights that change to create a glaring effect. The center of the roundabout is made of the same basalt rock within which the runnel network was excavated. It was designed by a local artist, named Trondur Patursson.
Another tunnel system in the Faroe Islands with a length of 10.9 kilometers is expected to be completed by 2023.