The Nuolja railway tunnel penetrates the upper nappes of the Scandinavian Caledonides. The tunnel was constructed using common drill and blast technique. After brief pre-investigations, a conservative preliminary rock support was designed. During construction, the tunnel was mapped and the rock classified. The resulting final support is considerably lighter than the preliminary design, as the rock is of a better quality than was at first anticipated.
Le tunnel de chemin de fer de Nuolja penetre les nappes superieures des Caledonides Scandinaves. II a ete construit en utilisant des techniques ordinaires de forage et de dynamitage. Après de brefs investigations, un support preliminalre des roches a ète concu. Durant la construction, le tunnel a ete cartographie et les roches classifiees. Le support final resultant est considerablement plus leger que celui qui a ete prelimlnairement adopte, surtout que les roches se sont averees de meilleure qualite.
Der Nuolja Eisenbahntunnel wurde mit den ueblichen Bohr- und Sprengtechniken errichtet. Nach kurzen Voruntersuchungen wurde ein vorlaufiger gebirgsschonender Ausbau konzipiert. Wahrend des vortriebs wurde der Tunnel kartographiert und der Fels klassifiziert. Der sich daraus ergebende endgueltige Ausbau ist wesentlich leichter als der vorlaufige Entwurf, da der Fels von besserer Qualitat ist als urspruenglich angenommen.
The Kiruna-Narvik railway was constructed in the beginning of the 20th century for transport of iron ore from the mines in Swedish Lapland to the harbour in Narvik, Norway. Mt. Nuolja is situated on the Swedish side, at about 40 km from the border. Along the mountain slope towards Lake Tornetrask, avalanches often occur during springtime. Therefore, this stretch of the railway was located in a tunnel, which is about 1.5 kilometre long.
During the years, water leakage has been a problem, particularly in the spring with formation of ice in the tunnel. In addition, the old concrete lining had started to decompose. As no stops in the ore transport was acceptable, Banverket (the Swedish State Railway Board) decided to construct a new tunnel, parallel with the old one (Figure 1).
The new tunnel is 1500 metres long, 1100 metres of which are located in rock. The width is 7 metres and the height is 9 metres with about 2 metres of blast rock at the bottom. The cross-sectional area is about 42 m2. The construction began in 1987 and the tunnel was taken into operation in the autumn 1990.
1100 metres of the tunnel are located in rock and 200 metres in each end are concrete tunnels covered with soil. Figure 2 shows a longitudinal section of the rock tunnel which is located in the Upper Allochthon of the Scandinavian Caledonides. The main rocks are quartz phyllite and phyllite, some of which carry graphite.
The general rock structure is typical for the eastern part of the mountain chain: Thrust sheets with a gentle north-westerly dip, with imbricate faults dipping 20–40 degrees west or north-west. Another important structural feature is a set of sub-vertical, extensional, water-carrying joints striking east-west.