Project Description
The 478 m long double-track Bommerstein Tunnel is a key part of the Zurich–Chur railway line. Over a period of approximately one and a half years, the tunnel was refurbished and upgraded to ensure reliable operation for the next 30 years.
As part of the project, a functional vault waterproofing and drainage system was installed. In addition, track and invert lowering as well as abutment underpinning using the sequential “pilgrim step” method were carried out. To maintain the required clearance profile (EBV 2), construction was secured using longitudinal support beams (longarines). Excavation works were performed using both drill-and-blast and mechanically assisted methods.
To enhance safety, additional emergency refuges were constructed within the first 25 m from the tunnel portals. Existing refuges were enlarged from 2 m² to 3 m².
In addition to the tunnel refurbishment, the project also included the rehabilitation of several engineering structures, including:
- multiple retaining walls
- both tunnel portals
- a road overpass
- mast foundations
- relocation of a stream culvert
The existing culvert was refurbished, and a new diversion including waterproofing was constructed.
The existing track superstructure was removed and reinstalled by SBB Infrastructure Maintenance after completion of the works.
Rhomberg Sersa Rail AG (formely Rhomberg Bahntechnik AG) was responsible for excavation works, substructure rehabilitation including track drainage with shoulder stabilisation, and installation of the pre-ballast layer.
The refurbishment works were carried out in stages while maintaining railway operations. First, the lakeside track was taken out of service and refurbished while train operations continued on the mountain-side track. Subsequently, the mountain-side track was taken out of service and refurbished.
At the beginning, the works were carried out during night shifts within defined time windows. Sheet pile beams were drilled to allow the installation of a total of 3,250 m² of protective wall during later possessions.
Key Personnel
- Project Manager: Stefano Cheli
- Site Manager / Deputy Project Manager: Lukas Herburger
- Construction Managers: Marco Würsch, Sven Meyer
- Site Supervisors: Manfred Warnuth, Georg Gregorincic
Special Features
- Double-track tunnel under live traffic
- Short night-time work windows
- Two-shift operation
- Rail-bound logistics
- Construction under ongoing operations
- Drill-and-blast and mechanically assisted excavation
- Restricted working space
- Challenging logistics
- High water ingress
- Excavation support systems
- Increased safety requirements
Technical Data
- Demolition of existing shotcrete lining: 250 m2
- Substructure rehabilitation with AC Rail and foundation layer: 454 m
- Substructure rehabilitation (rock section) with invert concrete: 615 m
- Profile trimming masonry: 750 m2
- Sheet pile beams: 426 units
- Cement injections: 500 t
- Anchor systems incl. longarines: 750 units
- Cable ducts: 1000 m
- Abutment underpinning: 2’000 m2
- Adaptation of refuges: 16 units
- New refuges: 4 units
- Vault drainage: 1’450 m
- New shotcrete lining (8cm): 8'100 m2
- Drainage pipelines: 1'750 m
- Manholes: 38 Stk.
- Mast and anchor foundations: 58 Stk.
- Excavation (solid material): 16'500 f m3
- New invert concrete: 470 m3
- Stream culvert (Ø 2.20 m): 25 m
- Excavation works: 690 m
