Photo: SBB
It happens fairly often in the Swiss Alps, but this one is of considerable weight: Nearly 300 meters above the railway line between Zug and Arth-Goldau, a block weighing around 500 tons has broken away from the rock face. The Swiss Federal Railways (SBB) secured the block with steel cables and is now monitoring the Rossberg area.
The Rossberg, composed of conglomerate rock, is known for its rockfall. Therefore, the Swiss Federal Railways (SBB) has always protected the railway line with numerous structures such as embankments and protective nets. With the expansion of the line to double track, additional protective nets were installed. These are already equipped with their own alarm system as a precautionary measure. In the event of a rockfall, the railway line would be closed immediately and train traffic halted. Furthermore, the area is regularly inspected and monitored by SBB specialists.
During one such inspection in April 2023, specialists discovered the boulder in the steep forest above Oberarth. The block, weighing approximately 500 tons – equivalent to five times the weight of a diesel-powered V 200 freight locomotive – had toppled from a rock face and come to rest about ten meters down onto a terrace below. The SBB is now monitoring the boulder with additional electronic systems to detect any further movement immediately. Accordingly, the railway line could be closed at any time. The safety work is currently underway.
Experts are also examining whether blasting the 180-cubic-meter conglomerate block would be advisable. If so, the railway line would have to be closed for a short time.
The reason why the block broke loose from the rock face is currently being investigated by specialists.
