Magnacun Tunnel Maintenance

The 3.7-kilometre-long section between Guarda and Ardez is located in the Lower Engadine and situated in difficult geological conditions. The RhB line runs through the western edge of the "Lower Engadine Window" in the metre gauge, where older layers of rock are overlaid by younger ones.

Maintaining and increasing railway safety is therefore necessary, plus our client has decided to carry out comprehensive rehabilitation of the Sagliains – Scuol-Tarasp section of the line. All construction work will be carried out during a six-month total closure.

Rhomberg Bahntechnik was commissioned by Rhaetian Railway to carry out local maintenance work on Magnacun tunnel masonry.

As all railway systems must function according to regulations, it is a great challenge to keep the systems intact for the entire duration of the work.

One of the most important measures is the replacement of the vaulting of a heavily stressed 8-metre shear zone, which is to be widened and reinforced with installation arches, steel grids, and shotcrete. Sections of disturbed masonry are still to be replaced by shotcrete with an average thickness of 30cm. On the rock side, a water-bearing backfill must be installed, which drains through drainage openings in the tunnel floor at the base of the wall. Although the mountain water ingress in the tunnel is not threatening, increased mountain water circulation must be expected when snow melts. Therefore, a small to large-area cleaning of the masonry and the joints has to be carried out, including a joint rehabilitation with special sprayed mortar.

• Vault replacement (8m)
• Parament replacement (46m)
• Drainage slots (340m)
• Drainage slots: ring joints reinforcement with Combiflex (55m)
• Masonry cleaning (50m)
• Joint renovation (50m)
• Repair of shotcrete wall (1970m²)