NATM

The New Austrian Tunneling Method (NATM), also referred to as Sequential Excavation Method (SEM) or Shotcrete Method, was developed in the 1950s when shotcrete was first used systematically to stabilize squeezing ground in a water diversion tunnel at the Runserau Hydroelectric Power Project in Austria. 
After a number of successful applications in mines, water, rail and some road tunnel projects this method was adopted for the first time in urban areas in soft ground for a section of the Frankfurt Underground Subway. The construction took place in Frankfurt Clay in 1968. Because of its flexibility, economic and safe performance more than two thirds of Germany's urban mass transit tunnelling in more than 10 major cities were carried out using this method in the 1970's. These tunnels were constructed mostly in clay, silty clay, silt and soft marl or similar soft ground conditions.
In the intervening years many large cities around the world e.g. Athens, Brasilia, Dallas, Istanbul, Kyoto, Lisbon, Madrid, Paris, Rome, Sao Paulo, Seoul, Tokyo, Washington DC, amongst many others, have taken advantage of this innovative method.