Tunnel refurbishment at the foot of the Swiss National Park

In the demanding refurbishment of Brail Tunnel I, the RSRG demonstrates how it harnesses its synergies as an international full-service provider.

The 895-metre-long metre-gauge tunnel, built in 1912, will undergo comprehensive refurbishment from April 2026 to June 2031 in order to safeguard operational safety over the long term and adapt the structure to today’s technical requirements.

A central element of the refurbishment is the renewal of the historic tunnel portals. They are carefully dismantled stone by stone, with all components recorded and stored temporarily. Following enlargement of the tunnel profile and modernisation of the substructure, they will be reconstructed true to the original, with distinctive stones returned to their original positions in order to preserve the portals’ historic character.

The location of the structure creates major logistical and safety-related demands. The tunnel can only be reached via viaducts up to 35 metres high, while construction operations in spring depend on alpine conditions. Work is authorised by the avalanche commission, as avalanches can cross the access routes to the site compounds.

The existing tunnel profile is enlarged by around one metre on each side using drill-and-blast excavation, generating approximately 15,000 m³ of excavated rock.

The subsequent internal construction is carried out using the RhB standard design with precast concrete elements. This approach has proved successful in previous projects and has been continuously developed further through RSRG initiatives. With Brail Tunnel I, the company is refurbishing the fourth of a total of seven tunnels for the Rhaetian Railway.

Work in the tunnel takes place during the night-time operational break from 20:50 to 05:00 and requires precise planning.

The sequence is standardised – after the last train has passed, the tunnel is closed, the overhead conductor rail is removed, blasting is prepared and carried out, the excavated material is transported away and the newly exposed rock surface is secured using sprayed concrete and rock anchors. The conductor rail is then reinstalled, and a temporary protection tunnel erected beneath the newly excavated section.

An RSRG specialist supports the work on the overhead conductor rail system.

The RSRG’s Digital Rail Services department supports the project with surveying and construction progress monitoring. Continuous 3D documentation allows geometry, quality and progress to be tracked precisely. The tunnel therefore grows both virtually and physically, night after night.

Each spring, the existing track system is renewed during a five-week full closure and converted from ballasted track to slab track.

Specialists from the RSRG’s mechanised track construction team are responsible for lowering the formation and installing the track.

To reduce noise and fuel emissions, the machinery fleet is being modernised, battery-powered equipment is being used more extensively and alternative fuels such as Hydrotreated Vegetable Oil (HVO) are being deployed. The installation of a photovoltaic system on the site facilities is also being examined. Rhomberg Energie is assessing the technical and economic feasibility.