The use of a double shield TBM with a diameter of approximately 10 m for the advance of the longest construction lot KAT 2 of the 32.9 km long Koralm Tunnel, combined with a single lining concept – using pre-cast concrete segments with a gasket – represents a novel construction approach in the European alpine region. The cristalline rock mass is composed of various gneisses, shale gneisses, mica schists and amphibolites. Due to the presence of tectonic faults, the rock mass is locally highly heterogeneous. According to the geological report, the thickness of the faults varies between decimeters and tens of meters. Based on these boundary conditions, a construction concept has been developed in the design phase, featuring numerous normal, auxiliary and special measures. The geomechanical observations in the north and south tube of the construction lot Koralmtunnel KAT 2 are summarized and compared to the system behavior predicted during the design phase.
The Koralm tunnel is located in the south of Austria, linking the provinces of Carinthia and Styria. With its length of 32.9 km the tunnel crosses the mountain range of the Koralpe, a crystalline massif in the Eastern Alps.
The tunnel is sectioned into three construction lots: two on the Styrian side (KAT 1 and KAT 2) and one on the Carinthian side (KAT 3). The construction of the lots KAT 2 and KAT 3 is under progress, while the work on the lot KAT 1 has been finished.
The tunnel system consists of two single-track tunnels, connected every 500 m by cross-passages. Additionally, an emergency stopping area is located approx. in the middle of the tunnel.
The following chapters summarize the tender design, and compare the predicted and observed system behavior.
