ABSTRACT
The face stability of shallow tunnels (cf. Fig. 1) must be guaranteed to minimise settlements at the ground surface and to prevent an uncontrolled collapse of the soil ahead of the tunnel. For this reason, a necessary support pressure, pf , must be prescribed for slurry and EPB shield machines, which needs to counteract water and earth pressure with a sufficient safety margin. For the determination of pf theoretical models as well as laboratory investigations and numerical calculations have been published.
