New Austrian tunneling method

The new Austrian tunneling method (NATM), also known as the sequential excavation method (SEM) or sprayed concrete lining method (SCL), Neue Österreichische Tunnelbaumethode (NÖT) in German, is a method of modern tunnel design and construction employing sophisticated monitoring to optimize various wall reinforcement techniques based on the type of rock encountered as tunneling progresses. This technique first gained attention in the 1960s based on the work of Ladislaus von Rabcewicz, Leopold Müller, and Franz Pacher between 1957 and 1965 in Austria.

Source: Wikipedia — New Austrian tunneling method (CC BY-SA 4.0)