SITUATION

In an attempt to conform to European standards, railway routes in Austria have been designated for improvement, such as the Pontebbana axis. It represents the eastern most crossing of the Alps and links eastern Europe, Vienna, Austria’s South and northern Italy. Main efforts to improve this connection were implemented in several stretches along the line. One of these projects is the Koralm railway in the South of Austria. This new stretch will have a total length of approximately 130 km. It will decrease the travel time between the provincial capitals of Graz and Klagenfurt from the present time of three hours to one hour. The most prominent tunnel along this stretch will be the Koralm tunnel. This tunnel will have an length of approximately 32,8 km, making it Austria’s longest tunnel. The maximum overburden will reach almost 1 200 m.

GEOLOGICAL OUTLINE

The mountain range which will be crossed by the Koralm tunnel consists of a polymetamorphic crystalline basement. Predominant lithology consist of mylonitic gneisses and micaschists, with occasional marbles, amphibolites and eclogites. The crystalline basement is bounded by master faults which have generated tertiary basins on both sides of the mountain range. These occur as the Weststeirische Becken in the East, and the Lavantaler Becken in the West. The sediments of both Tertiary basins encountered by the tunnel are mainly clastic deposits of fluviatile and marine origin.

The recent morphological features of the Koralm massif were formed by Tertiary to Quaternary brittle faulting, weathering and erosion. Residual soils, generated by deep reaching in situ weathering and periglacial debris, cover the bedrock.

PROJECT STATUS

HL–AG was authorised by the Austrian government in 1995 to undertake the planning and the design of the Koralm railway including the Koralm tunnel. Meanwhile the route assessment, the tunnel system decision and the environmental impact assessment could be concluded. In a next step further investigation measures as basis for the detailed design are carried out. For that purpose in the past year a series of deep drillings, reaching depths of 1.160m, were performed successfully. This year it is expected to start with the construction of a system of investigation shafts and tunnels with an estimated length of 11 km, as schematically shown in the figure. Depending on the results of the detailed investigation and design as well as the processing by the authorities and the decision to finance the tunnel project the construction works for the Koralm tunnel could start in the years 2007/2008.