Breakthrough on world’s longest subsea road tunnel 23 Nov 2017

Drill+blast excavation for the world’s longest subsea road tunnel has celebrated breakthrough on the first tube of the twin tube 14.3km long Ryfylke tunnel as part of the Ryfast scheme near Stavanger in Norway. Breakthrough was celebrated when the 7.5km heading of the north lot Contract E02 by the Marti/IAV XV from Solbakk junctioned with the completed 6.8km heading of the Contract E03 south lot by AF Gruppen.

Work on the project for the national roads authority Statens Vegvesen started in August 2014 and breakthrough on the first tube was achieved at the end of October 2017. Breakthrough on the second tube on the Solbakk lot by Marti and its Icelandic JV partner IAV is expected in January 2018.

Mucking out from the long drill+blast headings is by continuous conveyor, fed by a rock crusher and at a rate of 300 tonne/hr. As the 62m² faces have advanced, excavation of the 12m-30m long cross passages at 250m intervals has progressed as has lining and fit-out activities.

At its deepest point, the tunnel is 290m below sea level making its one of the deepest subsea road tunnels. The twin tubes have a finished horseshoe-shaped profile of 4.6m high x 8.5m wide with wider profile laybys and cavern-like openings to break up monotony in the long tunnel drives.

Excavation completion on the first tube at Ryfylke also marks progress on the entire Ryfast scheme. Over the last 12 months breakthroughs have taken place on the 5.5km long Hundvåg linking tunnel into the city of Stavanger by contractor Kruse Smith/Risa and on the 3.7km long E39 Eiganes tunnel by contractor Implenia/Stangeland that links to the undersea network and comprises a warren of land-based, and relatively shallow, urban tunnels.

Assistant Project Manager Anne-Merete Gilje told TunnelTalk that the Ryfast scheme includes toll funding and is due to open to traffic in late 2019.

Aso in the Stavanger region is the 26.7km long Rogfast tunnel scheme which will become the longest undersea road tunnel when complete in 2025-26. The twin tube link below the Bokna fjord to the north of Stavanger is currently in early procurement processes or drill+blast excavation.

Gilje explained that lessons from the planning and tunnelling on Ryfylke are being taken on by the client to the preparations for Rogfast.