Design and construction of tunnels are complex issues requiring the consideration of many different aspects. IGT and Laabmayr are two renowned engineering consultancies on the international market, as evidenced by many successful projects. Here is flavour of the projects we have undertaken together.
Site supervision and coordination
St. Kanzian, Austria
IGT undertook site supervision on behalf of ÖBB Infrastruktur (Austrian Federal Railways Infrastructure). The St. Kanzian chain of tunnels includes a 620m-long cut-and-cover tunnel in Srejach, a 665m-long mined tunnel in Untersammelsdorf and the 230m-long open-cut Paratschitzen Tunnel.
Difficult ground conditions were presented by the lacustrine clay. Intricate measures such as ground improvement, jet grouting, riprap, thousands of jet-grouted piles, and bored piles were undertaken to provide ground support and waterstops.
The programme constraints presented by pre-excavation specialist underground works presented extra complexity. A reduction in the groundwater management systems was made possible by constant monitoring of the conditions on site.
The three new railway tunnels were completed successfully through intensive coordination with all parties to the project. This allowed additions and modifications to the testing, monitoring and construction measures to optimise quality and minimise risks.
S10 Mühlviertler express road, Austria
The S10 Mühlviertler express road project includes a 22km-lon new build section in Upper Austria between the end of the A7 motorway and Freistadt. The new section includes four tunnels, four cuttings and numerous further structures.
The most complex structure is the twin-tube Tunnel Götschka. The tunnel was driven through granites, which presented as fine to moderate or coarse (Weinsberger Granite) throughout the drive.
The maximum cover is 100 m. Around 725 m in, the tunnel passed underneath existing surface structures. Both tunnels are equipped with forced ventilation and smoke extraction systems, requiring a suspended ceiling slab over the whole length of the tunnel. Ventilation plant buildings are located at both portals. The tunnel was opened to traffic in December 2015.
Services provided by IGT & Laabmayr: Initial and consents design including design for the Environmental Impact Assessment, tender design, tender document preparation, detail design and provision of the on-site geotechnical engineer.
A11 Karawanken Tunnel, second bore,
The western bore of the Karawanken Tunnel was opened for two-way traffic in 1991 and is managed jointly by the Austrian (ASFINAG) and Slovenian (DARS) highway agencies. the existing bore is 7870 m long and has no emergency escapes.
IGT’s scope includes options studies, tunnel concept design consents design, tender design, detail design, on site geotechnical engineer, landfill planning, design and construction coordination and a BIM pilot project.
Based on the results of the options study, the decision was taken to add a second bore to create twin tunnels. The second bore will be 7840 m long and constructed as a mined tunnel.
Particular challenges are the difficult geotechnical conditions and the high groundwater volumes expected to be encountered during the tunnel drive. As part of the new build, the north portal service building is to be extended and the underground service rooms are to be brought into line with modern requirements. The portal areas are to be designed in coordination with the bridge designers. A suitable area for infill for disposal of excavated material is proposed in the Kanin area. The geology, tunnel and service building were included in a BIM pilot project.