17.05.2021
SBB Line 224 / Lot 3 - CONSTRUCTION PHASE 2 - COMPLETE CLOSURE OF THE RAILWAY LINE

Status of Work
The first construction phase lasted from September to the end of February. During this phase, work could only be carried out in the Loges and Mont-Sagne tunnels during the nights from Monday to Friday.


Systematic cutting work was carried out with a special rail-bound construction to eliminate the existing undercut sections. With another construction train, safety anchors were drilled. At the end of the phase, the cut areas were profiled with road-rail excavator. 

Current work
The railway line has been completely closed since March. The rehabilitation work is being carried out at various points at the same time and should be completed by mid-September. Due to the small cross-section of the tunnels, this represents a large logistical challenge.


Considerable amounts of shotcrete are needed for the vault replacement. The shotcrete  is produced "just in time" by the company's own concrete plant in a way to be able to bring the neede quantity on time to the right place. The plant is located directly between the two tunnels of the Loges and Mont-Sagne on the main installation site.


Tunnel des Loges
In the longest of the three tunnels, the existing tunnel lining of natural stone will be demolished. The profile will then be enlarged and re-clad with a 30 cm thick layer of shotcrete. In addition to the shotcrete, the profile will be partially reinforced with metal arches. 6 niches have been blasted for the crossing of machines in the tunnel.


To ensure that train passengers can safely get out of the tunnel in an emergency in the future, an escape route is being cut into the rock on one side of the tunnel. 


At the end of the work phase,  concrete elements for the electric cables - prefabricated in Klus  - will be installed.


To ensure that the Tunnel des Loges can be handed over to the client SBB on time, work is being carried out during 24 h/day and 7 days per week.


Tunnel du Mont-Sagne
In the Mont-Sange Tunnel, as in the Loges Tunnel, the brick lining is being demolished over a distance of approx. 140m and replaced with a shotcrete lining. Somereprofiling work still have to be carried out, work which could not be done during the first phase of work due to the electric rail installations.


Tunnel de Combe Convers
The Combe-Convers tunnel will be completely renovated during the 5-month construction period. For this purpose, the two portals will be reinforced with a pipe umbrella vault, steel  girders, and a concrete vault will be constructed on the first 2 meters. The cross-section of the 250 m long tunnel will be widened between about 50cm to 1m, secured with shotcrete and sealed with a spray seal. After the building of the invert and the verges, the track ballast is already being placed again. After a snowy start, the works are on track and the various works have to be finished before the next snow falls again.


You can find more exciting facts on the reference sheet.

 
Marti Tunnel AG
Seedorffeldstrasse 21
CH-3302 Moosseedorf
+41 31 388 75 10
tunnel@martiag.ch​​​​​