Civil Engineering Reference
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Figure 8.18
Forming of a tight zone (Wittke & Wittke-Gattermann 2010)
8.8
Calibration of Model
The monitoring results obtained from a test gallery for the Freudenstein tunnel over a
period of two decades were back calculated in order to calibrate the model of Wittke
(2003). The calibration of the model was conducted by Wahlen (2009) (see also Wahlen
& Wittke 2009). The 6.8 km long Freudenstein tunnel located in unleached Gypsum
Keuper was excavated from 1984 to 1991 as part of the new high-speed railway line
from Mannheim to Stuttgart (Germany).
The exploration gallery was driven parallel to the main tunnel for investigation pur-
poses and in order to gain experience with different design concepts. Fifteen blocks with
different types of support were installed, as shown in Fig. 8.19, including the principle
of yielding support (section 1-1), the principle of resisting support (section 2-2) and the
corresponding support types with anchored slab (sections 3-3 and 4-4). Ten of these
blocks were equipped with monitoring devices (Fecker & Wullschläger 1991, Fecker
1993). From May 1987 onwards, the originally dry rock mass was irrigated underneath
the invert of the gallery by means of a grid of 6 m long boreholes to initiate swelling
(Fig. 8.20).
Sensitivity studies in which the rock mechanical parameters of the unleached Gypsum
Keuper were varied were carried out for each type of support using the coupled model.
The parameter combination specified in Table 8.1 yielded the best agreement between
monitoring results and the analyses that were carried out using the finite element pro-
gram system FEST03 of WBI (Section 10.7.1 and Wahlen 2009).
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