W. Wittke/M. Wittke/C. Erichsen/B. Wittke-Schmitt/P. Wittke-Gattermann/D. Schmitt · AJRM as basis for design and construction of more than 70 km of tunnels of the Railway Project Stuttgart-Ulm
from back-analyses carried out for a large-scale field test in
a test gallery adjacent to the Freudenstein Tunnel   
. The given value is valid for the horizontal bedding. In
vertical direction, due to the limited jointing, the permeability
can be expected to be somewhat smaller.
According to the model presented in , the water
uptake of the intact rock and the time for transformation
from anhydrite into gypsum are described by the Diffusion
Model. The two required parameters were evaluated by
laboratory tests, back-analyses and determination of the
sulfate content   .
The relationship between swelling stress and strain is
described by an extended Huder-Amberg-Model  and
requires the two parameters given in Figure 4. These are
derived from laboratory tests and back-analyses .
The phenomena to be considered within the modelling
for tunnels in swelling rock are illustrated in Figure 5 .
Starting from the undisturbed condition (Figure 5, top
left), excavation of the tunnel leads to a stress re-distribution
around the opening which in-turn leads to dilatant
displacements due to shear along the discontinuities and
thus to an increase of the permeability (Figure 5, top right)
. If this zone of higher permeability has contact to water
bearing layers, water can penetrate due to seepage towards
the rock adjacent to the tunnel (Figure 5, bottom
right). As a consequence, swelling is initiated and leads to
a modification of the stress field and the permeability adjacent
to the tunnel (Figure 5, bottom left). The described
process is implemented in a 3D FE-program and is simulated
in iterative analyses .
The described model thus includes an elasto-viscoplastic
stress-strain-law, transient laminar seepage flow,
water consumption/capillary suction by diffusion and a
swelling law, which are fully coupled and enable consideration
of anisotropic jointed rock . All mechanical and
hydraulic parameters of the in-situ rock mass are taken as
input parameters. The construction sequence and e.g. 100
206 Geomechanics and Tunnelling 10 (2017), No. 2
years of swelling are simulated. The analyses lead to
stresses and displacements in the system and to the stress
resultants of the concrete lining. The change of permeability
as a consequence of construction and swelling results
from the analyses.
It is obvious that the swelling process only can occur
if water has access to the anhydrite-bearing rock. In order
to avoid or minimize the access of water, a number of
measures are foreseen for the project Stuttgart 21.
In order to interrupt seepage flow from water-bearing
strata through the loosened zone in the rock immediately
adjacent to the tunnel, so-called sealing structures are being
constructed. They consist of two approx. 1 m thick
and 4 to 5 m long concrete rings (Figure 6). These, because
of their limited length, lead to only minor dilation in
the rock. During optimization of the project it was decided
that these rings, which need to be water-tight throughout
the lifetime of the tunnels, will be constructed by steel
fibre-reinforced shotcrete. Sealing of the adjacent rock is
carried out by chemical grouting through radial drillholes.
For the Filder Tunnel, three of these sealing structures
are planned at the upper edge of the anhydrite-bearing
zone and one sealing structure will be constructed
near the new central station in the valley (Figure 7). Since
these sealing structures cannot be constructed early
enough from the TBM-driven tunnel, TBM tunnelling is
limited to the upper and the lower part of the Filder Tunnel
as given in Figure 7.
From the water-bearing layers above the anhydritebearing
rock in the Filder Tunnel, no water can reach the
Fig. 5. Phenomena when tunnelling in swelling rock, principle
Fig. 6. Sealing structure
Fig. 7. Longitudinal section of the Filder Tunnel