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
tion, core drillings were carried out to explore the corresponding
rock mass and to take samples from ZOP and
ZPU layers (Figure 14). A close view of horizontal cores,
which also were taken, shows that sandstone lenses are
included in the claystone of the ZOP and ZPU layers (Figure
14, left). Laboratory testing has shown that these sandstone
intercalations lead to a higher unconfined compressive
strength for loading parallel to bedding (Figure 14,
right), whereas for loading perpendicular to bedding,
practically the same strength as predicted was measured
(Figure 14, centre). Also the Young’s modulus of the intact
rock was higher than anticipated.
Abbau von Kohle
Geomechanics and Tunnelling 10 (2017), No. 2 209
Figure 12. The west section is located in the different layers
of the Brown Jurassic formation. The eastern section
of the tunnel, which is only partly represented in Figure
12, is located in White Jurassic.
The section in Aalenium 2, with a maximum overburden
of 280 m, was considered critical with regards to
squeezing rock from the beginning . The unconfined
compressive strength of the claystone layers within this
formation (ZPU and ZOP) was determined on samples
taken from the exploratory boreholes to only 3 MN/m2.
This unconfined compressive strength corresponds to an
overburden pressure resulting from an overburden of 120 m
(see Figure 12). Thus, it is much smaller than the stresses
resulting from the max. overburden of 280 m. Consequently,
in the tender, it was foreseen to excavate the corresponding
section conventionally with a yielding support.
After the contract was awarded, it was discussed
whether an exploration of the layer in question by means
of a gallery might lead to a higher strength. This would
have enabled to excavate the whole tunnel by a TBM, as it
was permitted in the tender for all other layers except the
Karstic White Jurassic   .
Thus, after the intermediate access Umpfental had
been excavated, it was decided to excavate a vertical shaft
at the intersection of adit with the main tunnel. This vertical
shaft extended down to the ZOP-layer of the Aalenium
2, in which a horizontal gallery with a yielding support
was excavated (Figure 13).
The shaft and the gallery were intensely geotechnically
mapped and monitored during construction. In addi-
Fig. 15. Aalenium 2, rock mechanical model
Fig. 16. Steinbühltunnel, longitudinal section and
Fig. 13. Exploration shaft and gallery, 3D FE-mesh
Fig. 14. Claystone of ZOP and unconfined compressive
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