Construction work
Construction work on the second Gotthard tunnel tube involves the main tunnel, access tunnels, outdoor facilities and installation sites in Göschenen and Airolo as well as the motorway cover and the redesign of the motorway junction in Airolo.
What is being constructed?
The main tunnel
The main tunnel runs parallel to the first tube about 70 metres away. Like the original tube, it will be 16.9 kilometres long. The second tube will be connected to the existing tunnel system. It has a diameter of approx. 12.3 metres. The carriageway in the tunnel plus emergency lane will be around 8 metres wide. There will be 68 connecting ducts at 250 metre intervals along the entire length of the tunnel. The cavity above the carriageway will be fitted with ventilation systems and connected to the existing ventilation shafts.
Two service ducts will be installed in the cavity under the carriageway. The first will contain all cables and pipes required for tunnel maintenance – electricity, communication and firewater. The second duct provides space for services provided by third parties, such as transmission grid owner Swissgrid, which is replacing its existing high-voltage power line over the Gotthard Pass with a new line in the road tunnel. The project to install a high-voltage power line in a road tunnel is the first of its kind Europe. Once it is up and running, the old line over the Gotthard Pass will be dismantled.
Service, infrastructure and access tunnels
The existing service and infrastructure tunnel (SISto) runs between the two main tunnels. It is connected to the main tunnel via 68 accessible cross-connecting ducts. The SISto has its own ventilation system and is at a higher pressure than the main tunnel to prevent smoke or gas entering it. Work has also had to be done on the SISto: its entrances have had to make way for those of the second tube, and have therefore been moved. In addition, FEDRO is building five new underground ventilation centres which must be connected to the SISto.
Access tunnels to the north and south lead to the fault zones. Since the TBM cannot penetrate these zones, classic blasting tunnelling methods are being employed here. Three methods are used to construct the access tunnels to the fault zones: mechanised tunnelling in unconsolidated rock, rock blasting and tunnelling using a tunnel boring machine. The northern access tunnel will be around four kilometres long. In the south, the fault zone is further away from the tunnel entrance and the tunnel is therefore longer, at five kilometres. You can find the current progress of the access tunnels on the homepage under the construction progress graphic.
Foto gallery SISto
Central ventilation centres
A total of five underground ventilation centres are planned for the second tube. These will be linked to the surface via a ventilation shaft or duct. The location of the ventilation centres is determined by the existing centres and shafts in the first tube as well as by the position and alignment of the existing SISto:
- Bäzberg
- Hospental
- Guspisbach
- Monte Prosa
- Motto di Dentro
The Bäzberg and Monte Prosa ventilation centres ensure the pressurised ventilation of the SISto and the plant duct. The Hospental, Guspisbach and Motto di Dentro centres ventilate the vehicle area.
The ventilation centres have a parking bay for breakdown vehicles and for work and maintenance vehicles. They also have technical caverns, ventilation shafts and ducts, and cross-connecting tunnels for vehicles.
Where is construction taking place?
The second tube is being constructed from the north and south at the same time. The main construction and installation sites are located in Göschenen to the north and Airolo to the south. The site management offices and accommodation for the construction workers are also located in the two villages. In Airolo, the site management offices are located at the works depot and in an SBB building near the railway station.
You can see the various sites on the following map.
Overview Göschenen
Overview Airolo
Construction work Göschenen & Airolo
How is the tunnel being constructed?
First of all, the necessary facilities and installation sites were set up in Göschenen and Airolo. Work then began on the access tunnels and the service and infrastructure tunnel. The first step in constructing the main tunnel is the so-called pre-cut. Using construction machinery, construction workers remove the loose rock and prepare for the first blast. They then blast open the start tube and the tunnel boring machine (TBM) is installed. This takes about four months. The TBM then works its way through to the fault zone. After blasting the fault zone, the TBM continues to bore through to the breakthrough point.
To make the actual breakthrough, the rock will be blasted. Once the TBM has been dismantled and removed, the tunnel vault is lined, coated and painted. Finally, the interior of the tunnel is fitted out: the carriageway is constructed, the technical installations are fitted and then everything is tested thoroughly.