ABSTRACT
NATM (the New Austrian Tunnelling Method) has become one of the main tunnelling concepts. It has originally been developed for rock conditions in the Alps. As a matter of fact, soft ground tunnelling with NATM has a shorter history than NATM tunnelling through rock. Currently, an increasing number of tunnels in urban areas is excavated according to the principles of NATM. During construction, the main aim is to preserve and improve the potential of the ground to support itself as far as possible by making use of an arching effect in the ground around the tunnel. Too large deformations should be avoided otherwise loosening in the ground will take place which significantly reduces the potential of the ground to support itself. This results in an increase of load on the tunnel lining which may cause critical situations for tunnelling safety.
