NATM Tunneling - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 642

Ground freezing can also be carried out by freeze pipes installed in vertical or inclined
boreholes in front of the temporary face. These boreholes may be sunk from adits driv-
en above the groundwater table or from the ground surface.
Grouting of the rock mass in front of the temporary face provides another method of
advancing support in cases where groundwater lowering is not admissible. An example
will be presented within the subsequently described case history.

20.3 Tunneling under Stuttgart Airport Runway

20.3.1 Project
The urban railway of Stuttgart was extended in 2001 by a section starting at the Air-
port station and crossing the airport to the city of Filderstadt-Bernhausen. The Airport
station (construction lot 72) and the first part of the continuation towards Bernhau-
sen (construction lot 92) were constructed by the cut-and-cover method. The following
2.15 km long tunnel section was driven according to the NATM (construction lot 601,
Fig. 20.24). Among others, the tunnel crosses below the apron and the runway of the
airport (Fig. 20.25). The approx. 500 m long tunnel section of the Filderstadt-Bern-
hausen station (construction lot 602) was again constructed by the cut-and-cover meth-
od (Fig. 20.24).

Figure 20.24 Under-tunneling of Stuttgart airport, plan (Wittke et al. 2006)