The knowledge and long-standing experience of GeoZS experts made a key contribution to the construction of the Karavanke Eastern Road Tunnel, which is one of the most challenging tunnels in Slovenia due to its complex geological conditions. GeoZS activities in the planning of the eastern tunnel tube started more than ten years ago. Research work focused on uncertainties in the knowledge of the geological structure that remained unresolved after the construction of the western tunnel tube and could have affected the conditions during the construction of the eastern tunnel tube, which is only 60 metres away. A team of experts, led by Dr Bogomir Celarc and Anže Markl, has been mapping the area above the tunnel to complement the existing geological maps and to interpret the continuation of the structures into the unexplored area of the new, eastern tunnel tube. This was followed by more detailed investigations of the structural and geological conditions at depth in the tunnel, which were carried out in parallel with geomechanical and geotechnical investigations. For this purpose, several boreholes were drilled from the cross sections of the western tunnel tube and one borehole was drilled from the surface to further refine the conditions in what is expected to be the most challenging section of the tunnel route - the Mill Fault Zone. On this basis, a prognosis section was drawn up, which formed the basis for all geotechnical, hydrogeological and other measures during construction.

The excavation work was monitored by a team of experts from different disciplines, who were part of a consortium of geological-geotechnical-hydrogeological monitoring partners, in accordance with the project's technical specifications. The team also included a structural geologist, a representative of GeoZS, whose tasks included mapping of the excavation works, ongoing analysis of the structural elements and spatial location of the lithostratigraphic units. He was also involved in short-term forecasts during construction and in the production of reports. GeoZS experts also carried out palaeontological and petrological analyses, without which structural interpretation is not possible in such challenging geological conditions.

The structural-geological monitoring of the excavation works revealed only minor deviations from the conditions foreseen in the project documentation phase. A structural geological report with textual and graphical annexes was thus produced in the final post-construction phase, which forms an important part of the overall report of the consortium of partners on the geological-geotechnical-hydrogeological monitoring of the excavation works, as well as a starting point for further studies of the geological conditions in the wider area.