The Norwegian Method of Tunnelling (NMT)
Norway operates over 1,200 road tunnels totaling more than 1,500 kilometers in length, including nearly 40 sub-sea road tunnels that dip beneath saltwater fjords and coastal straits. Building that volume of underground infrastructure for a population of 5.5 million was only economically possible by rejecting the heavy cast-in-place concrete linings common in softer central European soils.
Codified through the Q-system developed at the Norwegian Geotechnical Institute (NGI) by Nick Barton and colleagues, the Norwegian Method of Tunnelling (NMT) relies on computerized multi-boom drill-and-blast jumbos, systematic probe drilling ahead of the face to inject micro-cement grouting into water-bearing fissures, tensioned steel rock bolts, and wet-process steel-fiber-reinforced sprayed concrete (shotcrete). To shield the road deck from freezing groundwater drips without pouring structural concrete walls, crews install insulated polyethylene frost-and-water protection vaults anchored inside the rock profile.
When high-speed dual-tube rail tunnels require uniform circular profiles—such as the 20-kilometer Follo Line (Blix Tunnel) south of Oslo—engineers deploy custom hard-rock Tunnel Boring Machines (TBMs) equipped with high-thrust disc cutters specifically hardened for Norwegian gneiss.
-
Lærdal Tunnel (24.51 km, E16 Aurland–Lærdal) Opened in 2000 as the world’s longest road tunnel to provide a snow-free link between Oslo and Bergen. Overburden reaches 1,400 meters, causing rock-burst stresses (bergslag) that required over 200,000 rock bolts. Three spacious caverns lit in warm amber and indirect daylight hues break the drive into four 6-kilometer segments while electrostatic precipitators scrub particulate matter and nitrogen dioxide mid-tunnel.
-
Ryfast (14.4 km Ryfylke Tunnel, -292 m) & Karmøy Tunnel Ryfast held the record as the world’s longest and deepest sub-sea road tunnel upon completion in 2019, linking Stavanger under Horgefjorden. Continuous bilge pump stations collect saline seepage water at the nadir point and pump it back to sea level.
-
Rogfast (26.7 km, -392 m below Boknafjorden) As the flagship anchor of the Coastal Highway E39 project under Statens vegvesen (Norwegian Public Roads Administration), Rogfast will surpass both Lærdal in length and Ryfast in depth. It adheres strictly to modern EU tunnel safety standards with twin tubes separated by cross-passages every 250 meters and a maximum longitudinal gradient of 5 percent.