Semmering Base Tunnel – Keeping shafts free of ice through the example of the Fröschnitz 2 supply shaft.

The Fröschnitz 1 and Fröschnitz 2 supply shafts of the Semmering Base Tunnel are used for the ventilation of the tunnel drives, transport of personnel, materials and machinery and as escape and rescue routes. Until the final completion of the concrete inner lining in the shafts, water still emerges repeatedly at the surface at a few locations of the shotcrete support layer. This led above all for the Fröschnitz 2 shaft to ice formation during longer periods with outside air temperatures below the freezing point of water with simultaneous operation of the fresh air supply. The effectiveness of warm air supply was investigated with thermodynamic and aerodynamic investigations and then the cost‐effectiveness of two selected systems to provide warm air were considered. The aerodynamic simulations showed that in particular the entry angle of the warm fresh air flow is decisive for the magnitude of the warm air losses. [ABSTRACT FROM AUTHOR]