12.3m diameter TBM readies for second Gotthard Road Tunnel

A high-ranking delegation from the construction company Marti Tunnel AG and the client, the Swiss Federal Roads Office (ASTRA), were present on July 30^th as Herrenknecht handed over a new 12.3m diameter Single Shield TBM for driving the southern section of the new second tube on the Gotthard road tunnel in Switzerland.

The companies commissioned with the tunnel excavation ordered one TBM for the northern and the above mentioned TBM for the southern construction sections of the main tunnel.

The TBM cutterhead is driven by 16 electric motors, with a total output of 5,600kw or around 7,600hp. The machine is specifically designed for driving through the hard rock of the Alps – granite, gneiss and slate are the main rock types to be expected along the 7,755 long southern tunnel section. Following technical acceptance, the machine will now be dismantled and the components transported to the construction site in Airolo (Ticino). There, the TBM will be reassembled so that teams from Marti Tunnel AG can start driving the main tunnel from the south as planned from March 2025.

According to preliminary geological investigations, the tunnellers will expect a geological fault zone in both the north and south sections of the planned route for the main tunnel. Due to the rock characteristics, the decision was made to excavate the two fault zones using drill and blast before starting the mechanized main tunnel drive. In order to reach the fault zones in the mountain, access tunnels were driven through the rock using mechanized tunnelling technology. Marti Tunnel AG successfully completed the excavation of the southern access tunnel using a 7.4m diameter Herrenknecht Single Shield TBM in August 2023. The machines for the main tunnel will later be pulled through the two fault zones that have already been excavated.

Herrenknecht supplied a 7m diameter Gripper TBM and a 12.2m diameter Single Shield TBM to a consortium of companies Implenia Schweiz AG and Frutiger AG for the two northern construction lots (main tunnel and access tunnel). The excavation of the northern access tunnel was completed in April 2023.

Around 16,000 vehicles pass through the existing Gotthard road tunnel every day, or six million cars and trucks per year. For 45 years, it has been a key structure for European north-south traffic through the Alps. It runs for 16.9km between Göschenen in the Swiss canton of Uri and Airolo in the canton of Ticino. The Swiss Federal Roads Office (ASTRA) is tackling necessary age-related repairs. ASTRA has subsequently commissioned the construction of a second, parallel tube to ensure that traffic can continue to flow during the renovation and the necessary closure of the existing tunnel. Once work on both tubes has been completed, one tunnel with one lane (plus emergency lane) will be available for southbound traffic and one for northbound traffic – a significant safety improvement compared to the previous operation with two-way traffic in a single tube.

Herrenknecht

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