Pummersdorf Tunnel: Closing a gap in one of Austria’s most important railway lines
Within the scope of the Westbahn extension, one of the most important railway lines in Austria, a 24.7 km long gap was closed between the towns of St. Pölten and Loosdorf. The new, double tracked line runs around St. Pölten, which is located approx. 70 km west of Vienna, in order to relieve the town's train station from both transit and freight traffic. In addition to 23 bridges, three railway tunnels are being built for this project.
One of the tunnels is the approx. 3.5 km long Pummersdorf Tunnel, which is being built as a single tube double track structure. Six shafts are planned as emergency escapes from the tunnel. The shafts are to be driven to an average depth of 24 m and will be connected to the main tube via a 15 m long cross cut.
The average overburden of the tunnel is about 20 m, i.e. the tunnel is a shallow tunnel in unconsolidated ground. The geology in the area of the construction site mainly consists of medium hard to hard silt with a high degree of fine sand as well as marly clay sandstone. The main driving area for the Pummersdorf Tunnel is located in highly weathered schlier. As the tunnel is located in a very shallow area, a comprehensive pre-cut had to be carried out at both portals in order to be able to start tunnel driving.
Driving was first carried out using excavators and then continued using both excavators and blasting. DSI Austria supplied 3-bar lattice girders, expandable friction bolts, SN Anchors and anchor spiles in individual lengths of 400 cm each as well as the complete range of accessories for this project.
The main advantages of the expandable friction bolts during this project were the following:
- Immediate full load bearing capacity over the entire installed bolt length
- Low sensitivity to vibrations caused by blasting
- Ability to maintain load-bearing capacity even when undergoing deformations
- Safe, fast and easy installation
- No additional building materials required for installation
- Ability to accommodate differing or varying borehole diameters
Construction work at the Pummersdorf Tunnel began in January 2012 and had been completed in December 2014.