ABSTRACT: Ever since Austria became a member of the European Community, we have had to deal with an enormous increase in traffic. Also for the future, in particular because of the entry of several south-eastern European countries to the EC, a significant traffic increase is predicted. In this task, Austria's government defined, in conformity with European intentions, main railway axes to be improved for future requirements. Investments of almost 30 billion Euros in total are planned for the future improvement of Austria's railway infrastructure within the next decades. One of the key railway lines in the TEN is the so-called Pontebbana corridor. An essential part of this Pontebbana axis is the Koralm tunnel with a planned length of 32.8 km. It will underpass the Koralpe, a stretch of mountains at the border of the provinces of Carinthia and Styria. Around 30% of the tunnel will encounter tertiary sediments (clayey to silty sands) with an overburden of less than 200 m. 70% of the tunnel will pass through crystalline rockmass with a maximum overburden of up to 1.200 m.