SBT – Tunnelling in challenging conditions: Approach to overcome a huge water inflow

Abstract An unexpected huge water inflow in one of the caverns of construction lot SBT1.1 of the Semmering Base Tunnel (SBT) triggered immediate emergency procedures to avoid a complete loss of access. The provision of safe construction conditions required the construction of large settlement basins underground to enable the temporary discharge of the water to the surface via approx. 250 m deep shafts. The final configuration of the underground structures needed to be adapted to meet the encountered conditions. Extensive preparation and injection works were caried out to create sound and safe conditions for the operational phase of the tunnel system. This was only possible by an open minded, solution oriented and common approach of all stakeholders involved in the project.