Customer: ASFINAG
Construction period: End 2009 – autumn 2013
Location: Along the A9 Pyhrn motorway, Upper Austria, Styria
Country: Austria

The A9 Pyhrn motorway is one of the most important transit routes into South-East Europe. The Bosruck Tunnel has always been a bottleneck of the A9 Pyhrn motorway. Along this motorway, this tunnel is extended by a second tunnel (western tunnel) with an overall length of 5.5 km.

The Bosruck Tunnel (eastern tunnel) runs underneath the 1992 m high Bosruck Mountains, i.e. between the head of the Teichl Valley in Upper Austria und Enns Valley near Ardning in Styria.

A parallel tunnel called the “aeration and drainage tunnel” runs between the existing Eastern tunnel and the planned Western tunnel (length 5,425 m). The tunnel was done using the traditional tunnelling method (blasting, mechanical tunnelling) according to the Austrian Tunnelling Method using calotte driving and subsequent underhand stoping and floor construction. The method used for securing depends on the type of rock and either uses jetcrete, construction steel grids and steel arches with appropriate anchors.

The material excavated amounts to about 770,000 m³ and is mostly moved as-is to dumps. About 1/3 is reused for fills in the central parking and rest area Pyhrn-Priel that still is to be constructed.

Technical Details
Length of tunnel: approx. 5.5 km
Width of roadway: approx. 7.50 m
Roadbed: concrete road surface
Total excavation: approx. 770,000 m³ (consistency as excavated)
Construction method: New Austrian Tunnel Method