NATM Tunneling - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 645

20.3.2 Ground and Groundwater Conditions
To explore the ground and the groundwater conditions core drillings were carried out
along the tunnel alignment. Some of these boreholes were equipped as groundwater
observation wells (Section 17.8).

According to the exploration results the tunnel is located over its entire length in the
Lias

formation (Fig. 20.26). This formation consists of a layer of predominantly
claystone with embedded single layers of sandy limestone overlain by an alternating
sequence of claystone and massive sandy limestone banks (Figs. 20.26 and 20.28) as
referred to earlier (Sections 12.6, 16.7.2 and 19.2). The layer consisting predominantly
of claystone exhibits considerably lower permeability than the alternating sequence.

α

Figure 20.28 Under-tunneling of the runway of Stuttgart airport, longitudinal section with ground
profile (Wittke et al. 2006)

In the area of the airport runway, the tunnel lies completely within the predominantly
claystone layer. Adjacent to the cut-and-cover tunnel sections, that is, in the areas with
descending and ascending gradient, the tunnel crosses the alternating sequence (Fig.
20.26). Figure 20.29 shows a photograph of the temporary face in which the lowest
bank of sandy limestone of the alternating sequence, which is referred to as “main
sandstone”, is clearly visible.