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Henndorf Bypass Tunnel, Wiener Straße B 1

The Wiener Straße (B 1) is a supraregional connecting route from Salzburg via Linz to Vienna. In the Flachgau in the Salzburg catchment area, currently some 20,000 vehicles per day wend their way through the small locality of Henndorf. Thanks to the new bypass only around 25 % of local and long-distance traffic will then pass through the small town. 75 % of the current traffic volume will switch to using the bypass route. The core of the altogether 3,580 m long bypass consists of a two-lane 2,150 m road tunnel of which 732 m is driven via cut-and- cover and 1,418 m by mining means. An exploratory tunnel previously driven parallel to the main tunnel is to be developed as an evacuation and ventilation tunnel. The tunnel's spent air is to be removed via a 4 m diameter ventilation shaft with a depth of 32 m. The evacuation tunnel in its mined section is connected with the main tunnel via 5 cross-passages. In the cut-and-cover section 3 rescue shafts lead out into the open. The contract also involved roadworks to link the tunnel with the federal highway B 1 as well as the turnkey completion of the tunnel operations centre and further operating stations at the portals. The excavated cross-section varies between 85 and 100 m² and is driven by excavator and dril l+blast. The excavation cross-section is divided up into crown, bench and floor. The geological conditions in the portal zones are characterised by the prevailing ground moraine. The main part of the tunnel was driven in practically upright layers of flysch sequences. The flysch consists of a tectonically extremely deformed alternating sequence of various sedimentary rocks such as clay stone, clay marl and sandstones. The individual layers possess thicknesses of only a few decimetres. The overburden height rises from a few metres in the portal zone to more than 60 m at the centre of the tunnel. The inner lining is carried out with an umbrella seal and an unreinforced inner shell which is 30 cm thick. The formwork for the cut-and-cover section is catered for with a formwork car comprising systemised parts. In the tunnel driven by mining means a steel formwork car is used. The entire tunnel is to be provided with a concrete carriageway. A breakdown bay for affected vehicles will be installed in each direction of travel. These bays will be set up in the centre of the tunnel roughly 50 m from one another.

 

  • Country: Austria
  • Region: Land of Salzburg
  • Tunnel utilization: Traffic
  • Type of utilization: Road Tunnel
  • Client: Land Salzburg; Landesbaudirektion, Fachabteilung Straßenbau, Salzburg
  • Consulting Engineer: Geoconsult ZT GmbH, Salzburg/Spirk & Partner Ziviltechnikergesellschaft mbH, Salzburg
  • Construction monitoring: Land Salzburg
  • Contractor: Wayss & Freytag Ingenieurbau AG, Munich/Held & Francke Baugesellschaft m.b.H., Linz/Habau Hoch- und Tiefbauges. mbH, Perg
  • Main construction method: Open/Trenchless
  • Type of excavation: Drill-and-blast/Excavator
  • Lining: Shotcrete/Concrete formwork
  • No. of tubes: 1
  • Tunnel total length: 2,150 m (total), 732 m (open)
  • Cross-section: 85 to 100 m²
  • Contract Volume: 32.9 mill. Euro net.
  • Construction start/end: March 1st 2006 till June 30th, 2009
  • Opening: probably July 31st, 2009