TBM for Gotthard Tunnel drive

 A new tunnel boring machine (TBM) from Herrenknecht in Germany will be used to drive the new bore for the Gotthard Tunnel in Switzerland.  The driving work will be carried out by the construction company Marti  Tunnel while the client is the Swiss Federal Roads Office (ASTRA).  

The new tube is needed due to the growth in traffic since the original bore was built. Around 16,000 vehicle/days pass through the 16.9km Gotthard road tunnel. It is a key link for European north-south traffic through the Alps. It runs between Göschenen in the Swiss canton of Uri and Airolo in the canton of Ticino. The Swiss Federal Roads Office (ASTRA) is tackling the necessary age-related repairs after long-term and careful planning.   

ASTRA has 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 tunnel. Once all the 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, an improvement in safety  compared to the previous operation with two-way traffic in one tube.   

The diameter of the Single Shield TBM is 12.31m and the cutterhead is  driven by 16 electric motors, which have a total output of 5,600kW. As a Single Shield TBM, the machine is a specialist for driving through the hard rock of the Alps. Granite, gneiss and slate are the main types of rock to be expected on the 7.755km-long southern tunnelling section.  

Following its 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 the personnel from Marti Tunnel can start driving the main tunnel from the south as planned from March 2025. According to preliminary geological investigations, the tunnel builders expect a  geological fault zone in both the north and south of the planned route for the main tunnel. Due to the rock characteristics, the decision was made to excavate the two fault zone sections using conventional blasting before starting the mechanised main tunnel drive. In order to reach the fault zones in the mountain, access tunnels were driven through the rock. For the access tunnels, mechanized tunnelling technology was also used. Marti Tunnel successfully completed the excavation of the southern access tunnel with a 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.   

A joint venture partnership, ARGE secondo tubo, is carrying out the project and comprises Implenia Schweiz, Frutiger; Los 243 with Webuild and  CSC construzioni.