It is already my second visit to the Bözberg tunnel. My first visit in June 2019 was almost two and a half years ago. At that time, cablex project manager, Urs Waldner, led me through the new 2.7-kilometre-long double tunnel with the illuminated handrail, showed me the alarm units and the five cross passageways, each with two identical technical rooms. Among other things, they have a raised floor, a transformer, a 980-volt power supply cabinet, 400-volt sub-distribution, a fire alarm system and even a control system for the illuminated handrail and a connection to the SBB control system.

Upgrading of the service and rescue tunnel.

In June 2019, the tracks had not yet been laid in the new tunnel. Now, two and a half years later, trains are already rolling through the double-track tunnel. The old railway tunnel has since been shut down and converted into a service and rescue tunnel. The work is in full swing. Implenia has already dismantled the tracks and overhead lines and installed a tarred roadway. The cross passageways between the new and old tunnels have now be cut through completely. cablex is installing the lighting and the power supply in these passageways, and a lot has been done already

I am pleased that project manager Urs Waldner is once again spending some time with me, even though the completion of a construction stage is imminent: The approval inspection of the ventilation ducts in the technical rooms. As the technical rooms are located in the cross passageways and are often not entered for extended periods of time, the ventilation should ensure that the CO2 concentration does not rise too high. On the day of my visit, the final tests are already underway.

Why is the ventilation system so important?

If an accident occurs in the Bözberg tunnel, the illuminated handrail guides passengers to the emergency exits with the escape route doors. From there, passengers enter the old Bözberg tunnel, which now serves as a rescue tunnel, through the cross passageways.

cablex is installing an airlock system with motorised gates and doors at both ends of the rescue tunnel. There is another large ventilation system has been installed on both sides. This creates overpressure in the service and rescue tunnel. "In the event of a fire, the overpressure ensures that the escape route remains free of smoke so that passengers can get out of the tunnel safely," explains project manager Urs Waldner.

Other activities of cablex in the Bözberg tunnel.

Over a distance of 2.5 kilometres, cablex is installing the lighting in the rescue tunnel as well as the escape route signals. The rescue tunnel lighting is triggered when an alarm button is pressed or the escape route door is opened in the railway tunnel.

The installation work being carried out by cablex is scheduled to be completed by the end of 2021. The inspection and approval procedure for the installations will take place in January 2022, and the handover of the tunnel to the SBB will take place in April 2022.

Infobox

The Bözberg tunnel is the largest single project of the four-metre corridor on the Gotthard axis. The expansion means that semi-trailers with a corner height of four metres can also be transported by rail. The expansion will make it possible to transport goods by rail from Hamburg to Genoa.

Some figures regarding cablex’s assignment:

• Equipment for a total of 11 technical rooms, 2 railway engineering buildings, 2 airlocks
• 5500m illuminated handrail
• 8000m 980V energy supply cable
• 12 000m ribbon cable
• 5000m ground cable
• 20 000m of various low voltage and installation cables
• 3000m cable routes
• 650 LED lamps
• 11 400-V power supply units (switchgear combinations)
• 11 980-V supply cabinets
• 10 22-kVA transformers
• 2 16-kVA transformers
• 2 132-kVA transformers
• 5 motorised cross passageway doors and 4 airlock gates
• Cooling-/air conditioning units
• Painting work
• Escape route signs and escape route lighting
• Fire alarm system
• Connection to the SBB control system LSS-CH
• Ventilation system for escape routes