ABSTRACT
This paper presents relevant updates and worksite advancements of the Sotra Link Project (SLP), between Bergen and the island of Sotra in Western Norway). The complex 30-meters underground stretch of the two main tunnels in Kipledalen (Drotningsvik area) are discussed in detail. Design challenges arise from shallow overburden, heterogeneous geology, interferences with nearby structures. Based on the initial geological model, additional core drillings were executed to better determine local geological conditions and any geotechnical hazards. The identification of metric clayey layers within the fractured rock mass led to adjustments of the drill and blast sequence and the implementation of a permanent lining solution based on reinforced ribs of shotcrete. Moreover, jet grouting columns from the surface and extensive pre-grouting inside the tunnel have been designed. A summary of the mappings acquired during the ongoing operations is given, as a key tool to optimize drill and blast operations and lining installation.
