Shotcrete-Technology ´06

Sprayed concrete work at the construction sites of the Brenner Eisenbahn GmbH

Dipl.-Ing. Johann Herdina, Brenner Eisenbahn GmbH, Innsbruck

The construction of the rail link from Kundl/Radfeld to Baumkirchen calls for extensive sprayed concrete work as a preliminary safety measure to protect the tunnel excavation. As a rule the concrete is applied using the wet-mix method, with the help of non-alkaline accelerators; for the protection of sloping faces the dry-mix method may also be used. In some sections of the Vomp/Terfens tunnel, instead of wire mesh reinforcement wet-mix sprayed concrete has been applied, incorporating 35 kg per cubic metre of steel fibres, in the interest of reducing costs. Some tunnel sections are driven with the help of pressurised air, and the sprayed concrete must meet particularly high standards in terms of impermeability. The geometrical properties of the sealing materials (such as evenness of surface, demonstrated by the "lath" and "ball" method) and any profile deviations (based on the thickness of the sprayed concrete) are checked against the specifications with the help of tunnel scan shots.