The application of fibre reinforced shotcrete as primary support for a tunnel in flysch

The 10 m diameter Dekani motorway tunnel was constructed using the principles of the NATM method. The tunnel was located in a flysch geological sequence, which was classified as heterogeneous weak rock. The aim of the research presented in this paper was to examine whether fibre reinforced shotcrete can be successfully used as the only material for the primary tunnel lining in these geological conditions. The interpretation of the interaction between the fibre reinforced shotcrete lining and the surrounding rock, which was based on monitoring in a 60 m long test section, is presented in the paper. The development of the new mix of steel and polypropylene fibres and shotcrete is described and the results of the laboratory testing of strength, stiffness and post-crack strength are presented. The success of the field test led to the use of the fibre reinforced shotcrete for the primary lining in a 410 m long section of the tunnel. Significant savings were made in the use of time and material without compromising the quality of the final product.