Finnfast Subsea Tunnel Breaks Through in NorwayMuch of Norway is covered by mountains and the western coast is gouged by deep fjords and dotted with islands. To facilitate modern communication, it has been necessary to build roads through the mountains and over - or even under - the water. Tunnels and bridges can radically reduce transit times between cities and improve traffic safety. A road passing through a mountain is safer than one winding over it, especially during the winter. As of today there are 26 subsea road tunnels in Norway, about 60 bridges longer than 500 metres and about 100 ferry connections along the western coast. The country is also building four other undersea tunnels, one of which is the Finnfast crossing. Visit http://home.no.net/lotsberg/data/norway/sub.htmlThe 8,372 m-long Finnfast crossing project on national road Rv 519 in Rogaland in southwestern Norway consists primarily of a 5,685 m single tube two-lane bidirectional tunnel under the North Sea between Hanasand on the island of Rennes and Ladstein on the island of Finn. A 1,467 m connecting single tube single-lane tunnel is also built to the island of Telgje, along with 1,220 metres of connecting roads. This connecting tunnel branches off the main tunnel from a three-lane, 250 sq m cross-sectional intersection and will be regulated with traffic lights to control alternating traffic. Other structures include a pumping sump (10,000 cubic metres, 200 m below sea level). View map here.The main tunnel has a maximum gradient of 9%, lying at -200 metres at its deepest point while the connecting tunnel is built at -150 metres at its lowest point, with 10% maximum gradient. The predicted average daily traffic is 1,000 vehicles/day. View longitudinal profile here.Through the project, the islands of Finn and Talgje in the county of Ry will gain a permanent road connection to Stavanger on the mainland before the end of 2009. Journey times from Judaberg (island of Finn) to Hanasand (island of Rennes) will be reduced from 50 to 10 minutes. Total journey times from Judaberg to Stavanger will be cut from one hour and 35 minutes to 35 minutes. The Finnfast project will be largely financed by road toll, state investment funds and the funds saved from support to ferry traffic. The construction contract has been awarded to NCC Construction by the Norwegian public roads administration, who also supervises the tunnelling works. Click no/81. Visit www.ncc.no and www.vegvesen.no/region_vest/prosjekter/finnfastDrilling and blastingThe geology is amphybolite, amphybolitic gneiss and feldspar gneiss with variable contents of mica and marble. Civil engineering work began on 12th July, 2006. Work is being carried out simultaneously from both ends. Excavation started on the island of Rennes in September 2006 and from the island of Finn in October 2006. Breakthrough of the Finnfast tunnel was celebrated on 29th May, 2008, four weeks after schedule. Actually, the Finnfast tunnel suffered a rock fall during construction in January 2007. From the intersection, 580 metres of the tunnel to Talgje has been completed to date and it is expected to make breakthrough on 15th October. Tunnelling has reached an overall advance of 88.7%. Breakthrough celebration day The main tunnel features a 64 sq m average cross-section, i.e. a Norwegian profile T8.5 (8.5 m width at road surface). The Talgje tunnel has an average cross-section of 45 square metres (T5.5 profile). Click here. Conventional drill and blast proceeded from two drives, one from the island of Rennes using an Atlas Copco XL3 drill rig and the other from the island of Finn with an Atlas Copco XE3. The XL3 boomer is being re-used for the intersection and tunnel to Talgje. Slurry explosives from Orica were used. Mechanical rock scaling was performed by using excavators equipped with hydraulic hammer. Visit www.atlascopco.com or www.boomer-rig.com and www.orica.com Atlas Copco's XL3 Boomer at the intersection After each blast, the rock is removed by Volvo loaders (a L350F from the Finn end and a L330 from the Rennes end) and 23 cu m Mercedes Benz trucks (three to six trucks at each head). Visit www.volvo.com/constructionequipment/na/en-us/products/wheelloaders/wheelloadersRock support mainly consists of Ørsta Combi Coat CT-bolts using a combination of galvanising and powder varnish for better corrosion protection below sea level, shotcrete with Propex Concrete Systems' ENDURO macro-synthetic fibres (50 mm), cement grouting, heavy steel arches and full concrete lining. Propex and BASF are partners in Norway. BASF purchased the ENDURO 600 macro-synthetic fibres from Propex and supplied to NCC. The waterproofing is made of PE foam and steel fibre-reinforced shotcrete prior to the installation of a geomembrane. The total support work has exceeded what was expected. Visit www.orsta.com or www.ct-bolt.com, www.propexinc.co.uk and www.fibermesh.com/downloads/Enduro%20600.pdfConcrete lining was performed only at places where normal support with bolts and shotcrete was considered to be insufficient. It was needed only on a 17 m portion (on Rennes side) in total for the main tunnel. A mobile steel arch formwork was placed at site with a wheel loader. A lifting work platform mounted on an AMV truck was used during shuttering of the formwork and concrete pouring. The mobile steel arch is a casting frame for 5 m-long concrete lining sequences. There was one unit at each attack if needed. Two AMV platform trucks (one at each attack) were employed for various tasks during excavation, such as grouting of bolts, mounting of ventilation duct, etc. Visit www.amv-as.no. Read more about construction of the tunnel at www.miningandconstruction.com/files//MC207_455.pdf Steel arch formwork frame for concrete lining and AMV truck and lifting platform Norwegian subsea tunnelling know-howIt is not surprising that Norwegian companies are paving the way when it comes to hard rock tunnel construction, offering technology and planning tools that make subsea tunnelling in difficult terrain the only viable, cost-effective alternative to existing ferry services or rival bridge projects. The length and depth of tunnels today has also led to new requirements concerning drainage, tunnel lining and air quality. Norwegian expertise in undersea tunnelling is increasingly in demand on the global market, with projects planned in Chile, Greenland, Russia or Scotland. To know more about Norwegian subsea tunnelling, click here. 28/08.