Tanum Tunnel - Specifications

Specifications

The Tanum Tunnel is 3,590 meters (11,778 ft) long and has a cross section varying between 105 and 115 square meters (1,130 and 1,240 sq ft). The tunnel consists of a 2,718-meter-long (8,917 ft) blasted section and a 800-meter-long (2,600 ft), cut-and-cover section—the latter the easternmost part of the tunnel. It carries the double-tracked Asker Line between Jong and Åstad. The tunnel runs mostly through Cambrian-Silurian sedimentary slate, nodular limestone and shale, with local occurrences of Permian igneous rock. There is also a 400-meter-long (1,300 ft) section of less stable sedimentary rock in the Asker Group. The tunnel had a cover most of the way of between 50 and 100 meters (160 and 330 ft); however at Billingstad there was a much lower margin, laying for the most at 10 to 15 meters (33 to 49 ft) and at the least at 1.5 meters (4 ft 11 in). At Åstad, the line runs 600 meters (2,000 ft) in the open before entering the Skaugum Tunnel. The line is electrified at 15 kV 16⅔ Hz AC and allows a maximum speed of 160 kilometres per hour (100 mph). The tunnel has frost insulation 300 meters (980 ft) into the tunnel form each end. The tunnel has frost fans which ensure that the air stays put in the middle of the tunnel, thus hindering cold air from flowing past the frost isolation.