ABSTRACT
Mechanical tunnel driving with Tunnel Boring Machines (TBM) is a world-wide popular method within tunnelling, whereby the limits of its application (diameter, length, overburden, water pressure, subsoil, etc.) are being constantly pushed ahead. Frequently bedrock zones with strongly changing strength properties have to be crossed. During the excavation and transport of the material the mechanical wear often causes a loss of strength which can even lead to a complete disintegration of the composite structure.
