The construction work must do as little as possible to affect the lives of the people in the city of millions. For this reason , the seven station and emergency exit shafts, which are up to 30 meters deep, as well as the two 1,200-meter long, single-track underground tunnels, are largely manufactured in a cover construction. The soil is first bulked out and a lid with concrete is drawn in at the depth. The excavation is then carried out under this. Advantage: The surface can be released relatively quickly for traffic and Co.
Of course, this does not work for buildings such as the university, they are subjected to cyclic propulsion by means of "NATM". Austrian tunnel specialists have developed this type of construction. However, the "new Austrian tunnel construction method" is not just the name in the Alpine Republic. The term generally describes a construction method in which the environment is considered to be an essential supporting component of the tunnel construction. Because the environment is supportive, the necessary support can be reduced. In addition, the first steps are taken in sections: The excavated rooms are first secured with sprayed concrete, the broken material is transported away, further supports such as anchors or lattice girders are inserted and the inner shell of the tunnels is produced with concrete.