SBT – Exploration and measures taken during tunnelling in karst terrain

In the Semmering Base Tunnel's construction lot SBT3.1, the western tunnel drives went through the large‐scale tectonic unit of the Semmering cover. The immediate area surrounding the structure is composed of karstified carbonate rocks and quartzite from the Permo‐Mesozoic era, as well as overlying mica schists and quartz phyllites from the Semmering crystalline base. In order to ensure the serviceability of the structure over its service life, it was necessary to detect the karst structures of the carbonate rocks in the surroundings of the structure and to implement rock improvement measures using appropriate methods. This article provides an overview of the karst exploration methods used for construction lot SBT3.1, the practical implementation, and the measures carried out.