The St. Kanzian Tunnel Chain: DSI Underground supplies AT – Pipe Umbrella Support Systems with efficient Squeezed ConnectionThe St. Kanzian Tunnel Chain near Voelkermarkt in Carinthia, Austria, forms part of the 130km long Koralm Railway that will establish a direct connection between Graz and Klagenfurt. The tunnel chain, consisting of six tunnels, is located in the Mittlern-Althofen section in the western part of the Koralm Railway. Currently, the Untersammelsdorf, Stein and Lind Tunnels with a total length of 2,595m are being excavated.
The core parts of the approx. 5km long section are the 2,100m long Stein Tunnel – the third largest tunnel of the Koralm Railway – and the 495m long Lind Tunnel. Except for a 565m long Stein Tunnel section that is being constructed using the open cut method, the two single tube tunnels are driven in accordance with the New Austrian Tunneling Method (NATM). Approximately 350,000m³ of subsoil must be removed for the Stein Tunnel and 90,000m³ for the Lind Tunnel.
The Stein Tunnel has a maximum overburden of 39m. The tunnel is being excavated from both portals with an advanced top heading in unconsolidated ground. The Lind Tunnel has an overburden of approx. 32m. Advancement is carried out from the west portal mainly through phyllites that are overlain by a stratum of up to 15m thick lacustrine sediment.
In both tunnels, AT Pipe Umbrella Systems were used for efficient support in difficult ground. For this purpose, DSI Underground Austria supplied 6 Type AT – 139, 139.3 x 6.3mm Pipe Umbrellas with squeezed connection including an AT – Squeezing Unit.
The squeezed connection ensured the fast and safe implementation of pipe umbrella installation work. Furthermore, the squeezed connection developed by DSI Underground offers enhanced load-bearing capacity in comparison to conventional systems.
Additionally, other high quality ground support products by DSI Underground were used for stabilizing the advancement: SN Anchors, the DYWI® Drill Hollow Bar System, AT – TUBESPILE™ Self-Drilling Spiles, lattice girders and the AT – 76 Drainage System.