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Exploration Tunnel Brixlegg East

The route section in the Tyrolean Lower Inn Valley forms the bottleneck on the rail axis via the Brenner between Munich and Verona. As from Wörgl, the 2 twin-track lines coming from Munich/Kufstein and Zell am See run together on 2 tracks. This part-section has to cope with so much international and regional goods and passenger traffic that it has reached its capacity limit. As a consequence, the greatest priority was accorded the upgrading of the Kundl/Radfeld-Baumkirchen section. This first redevelopment section is altogether 40 km long, 32 km of which runs in tunnels and subsurface routes. As tricky geological conditions were anticipated for the Brixlegg Tunnel, i.e. soft grounds and high water pressures, an exploration tunnel was driven there, which runs some 30 m to the north of the future railway tunnel. In this way, it was possible to obtain exact details about the structure and behaviour of the rock. In addition, the exploration tunnel provided 2 further advantages. Firstly, it could be used as an access for an intermediate point of attack and secondly, it enabled environmental protection measures, e. g. through blasting tests, to be planned more thoroughly. The main task of the Brixlegg exploration tunnel was to investigate the expected fault zones with vertically bedded layers of rock. Towards this end, cross-passages were driven into the route of the future rail tunnel. Furthermore, roughly 60 m long test headings were driven as required with the future cross-section of the main tunnel. The maximum overburden amounted to some 390 m. With the exception of the test headings, the excavated cross-section was up to 34 m²; it was driven by drill+blast and excavator and supported by shotcrete. Cross-sectional enlargements were produced at regular intervals in the tunnel. These served as lay-by recesses (at 250 m gaps) or turning recesses (at 1,000 m gaps).


  • Country: Austria
  • Region: Lower Inn Valley
  • Tunnel utilization: Traffic
  • Type of utilization: Main line rail
  • Client: Brenner Eisenbahn GmbH
  • Consulting Engineer: Müller+ Hereth
  • Contractor: Bilfinger Berger AG, Fröschl AG & Co KG
  • Main construction method: Trenchless
  • Type of excavation: Drill-and-blast
  • Lining: Shotcrete
  • No. of tubes: 1
  • Tunnel total length: 2,500 m
  • Cross-section: up to 34 m²
  • Contract Volume: € 15.8 million
  • Construction start/end: 1999 to 2001