4×4 SHUNTER

While being used for driving, shunting or as a train in the Cassanawald Tunnel, the Unimog has to be “wrapped up”. Although it is an incredibly resilient vehicle – with its 40 years of working life, this vintage Unimog has to be protected from the very diluted concrete which is sprayed on the walls of the tunnel. The spraying machines apply a four centimetre thick layer of fireproof mortar which can withstand temperatures of up to 2,000 °C. If there is a fire in the tunnel, this layer of mortar is supposed to prevent the concrete vault from being destroyed as the vault roof is of supreme importance for the overall stability of the tunnel structure.
The “engine” is a vintage Mercedes-Benz Unimog which used to belong to the Swiss Army and has now been fitted with road-rail equipment, so the vehicle can be operated just as easily on rails as along the road. The Unimog shunts the work train to where it is needed which means that it has to cope with a track profile with gradients of up to 3 percent within the tunnel itself.
The protective screen has really proved to be “the philosopher’s stone” for this project as on the one hand it allows work to be carried out without interruption and it also protects the continuous flow of traffic from being begrimed by the diluted fireproof mortar. This means that the traffic can at least pass the roadworks on one lane as up in the narrow Hinterrhein valley there is only the narrow canton road H13 available for a one lane diversion for on-coming traffic.