The 12.3m-diameter single shield TBM has been designed to drive through the hard rock of the Alps, where granite, gneiss and slate are expected on the 7.75km-long southern tunnel section. The TBM’s cutterhead is driven by 16 motors, which have a total output of 5,600kW.
Following the FAT ceremony on July 30, the machine will now be dismantled and the components transported to the construction site in Airolo (Ticino). There, the TBM will be reassembled so Marti Tunnel AG can start driving the main tunnel from March 2025.
According to preliminary geological investigations, a geological fault zone can be expected in both the north and south of the main tunnel. Because of the rock characteristics, the two fault zone sections will be excavated using conventional blasting before starting the mechanised main tunnel drive.
To reach the fault zones in the mountain, access tunnels were driven through the rock using a TBM. Marti Tunnel AG completed the excavation of the southern access tunnel with a 7.4m-diameter Herrenknecht single shield TBM in August last year. The machines for the main tunnel will later be pulled through the two fault zones that have already been excavated.
Herrenknecht also supplied a 7m-diameter gripper TBM and a 12.2m-diameter single shield TBM to a consortium of Implenia Schweiz AG and Frutiger AG for the two northern construction lots of the main tunnel and access tunnel. The excavation of the northern access tunnel was completed in April last year and acceptance of the single shield TBM for the northern section of the main tunnel took place on July 8 this year.
The new Gotthard Tunnel will supplement the existing 16.9km tunnel between Göschenen in the Swiss canton of Uri and Airolo in the canton of Ticino. The 45-year-old tunnel needs repair so the Swiss Federal Roads Office (ASTRA) has commissioned the construction of a second, parallel tube to ensure that traffic can continue to flow during the renovation and closure of the tunnel. Once work on both tubes has been completed, one tunnel with one lane (plus emergency lane) will be available for southbound and one for northbound traffic.
Around 16,000 vehicles use the Gotthard road tunnel every day.
