The project consists of a 3 km long section of the new double-track railway line between Vienna and
St. Pölten. This section also includes the construction of the Hankenfeld Tunnel (length 663 m) and
the Saladorf Tunnel (length 729 m) that were built using the cut and cover method. The project also
included the construction of two road underpasses.
In order to minimize the disruption of an ecologically valuable habitat around the tunnel, high and
steep slopes on both sides of the building pit were designed. Any failures of these slopes would have
posed extreme danger to human and property safety. Therefore, they had to be properly secured according
to a high safety-level, yet in a cost-effective manner. Despite an accurate subsoil exploration, several
uncertainties regarding the subsoil condition could not be entirely resolved. Thus, the geotechnical
safety management was of extreme importance during and after the establishment of the slope protection.
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For this section, BGG Consult was responsible for the geotechnical and hydrogeological consulting and
the geotechnical safety management. Geotechnical safety management regulates the construction and
design processes when displacements are exceeded and/or in case of stability problems. Its aim is to
minimize damage to the structures or to a third party. Regarding this, the following services were
provided:
- The expected behaviour of the system structure and subsoil were defined based on static calculations
- The type and amount of measuring instruments were determined
- The values for warning and alarm levels were determined
- The organisation, evaluation and interpretation of all measurements were conducted
- The measuring of inclinometers
- Appropriate measures and procedures were determined where discrepancies to the expected behaviour existed
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Geotechnical Safety Management of the Saladorf Tunnel:
The Saladorf Tunnel was constructed using the cut and cover method. This involved that a pit slope
with a length of 475 m and a height of up to 18 m had to be secured. This was accomplished by using
anchored shotcrete, pre-stressed anchors and grouted soil nails.
Profiles with geodetic measuring points (up to 5 points per profile) and anchor load cells were
defined every 25 m along the slope. Furthermore, five inclinometers and three 4-fold extensometers
were installed.
The data was electronically read, and regularly transmitted to the monitoring station. Thus, immediately
when warning or alarm values were exceeded, the appropriate people were automatically informed by the system
in real-time via mobile phone. This enabled safety precautions to be executed with minimal delay.
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