Koralmtunnel Graz Klagenfurt KAT2

The Koralmtunnel, with a total length of 32.5 km, was the first and longest railway base tunnel built to date. The Koralmtunnel is the centrepiece of the new rail link between Graz and Klagenfurt.
 
The KAT2 construction lot comprised the construction of over 20 km of the twin-tube tunnel system including the associated cross-connections between the two tunnel tubes, an approx. 900 m long emergency stop and the construction of the 8 km long, double-track access section on the Styrian side.
 
Construction work on the tunnel system was carried out exclusively via an approx. 60 m deep shaft.
 
The tunnelling work was carried out over approx. 1.5 km in the sedimentary layers of the southern Graz Basin using the NATM method. Two hard rock double shield machines, each with a diameter of 10 metres, were used to excavate the crystalline rock of the Koralpe.
 
The excavated material was used to cover the entire demand for aggregates for the production of the segments and all other construction concretes. In total, material for approx. 1.1 million m³ of concrete was produced directly on site.