ANSWERS: 1
  • The “Norwegian Tunnelling Method” (NMT) is a system based on expertise, cooperation, flexibility and risk sharing. The NMT includes specific techniques such as the addition of steel-fibre reinforcement to wet-process shotcrete, which has completely redefined Norwegian tunnelling technology. Instead of the traditional method of building the same support structure along the entire length of the tunnel, the Norwegian shotcreting method employs operator-guided robots to apply steel-fibre reinforced shotcrete adapted to the specific needs of each excavated area. Today, with the use of additives, it is possible to apply one layer of shotcrete that is comparable in thickness and strength to conventional in-situ concrete, and which offers exceptional flexibility and savings of up to two-thirds of the normal cost of a cast concrete arch. The Q-system for rock mass classification is a Norwegian innovation which helps engineers to determine the types and quantities of rock support techniques appropriate for any given type of project and existing geological conditions. The system was developed by the Norwegian Geotechnical Institute in 1974 and is based on data from more than 1,000 road tunnels and caverns constructed during the past two and a half decades. It is now one of the most widely-used rock classification system worldwide. Together, the Q-system and steel-fibre reinforced shotcrete have been successfully applied to all kinds of tunnel sections, even those bored in rock of extremely poor quality, such as sections of the 2.2-km-long Oslo Tunnel built beneath the city of Oslo in the early 1990s.

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