Herrenknecht TBM Achieves Breakthrough in Gotthard Road Tunnel Second Tube Project
“Up to 32 meters a day—that’s a remarkable achievement by the tunneling crews in the extremely hard Gotthard rock.” Dr.-Ing. E.h. Martin Herrenknecht, CEO of Herrenknecht AG, is proud of how well tunnel construction for the second tube of the Gotthard Road Tunnel is progressing with the tunnel boring machine (TBM) from Schwanau.
The “secondo tubo” consortium, consisting of partners Implenia and Frutiger, began tunnelling in February 2025 in Göschenen, in the Swiss canton of Uri, on behalf of the client, the Federal Roads Office (ASTRA). The tunnel construction specialists are excavating the northern section of the new second tube parallel to the road tunnel that has been in operation since 1980. To this end, Herrenknecht engineers designed and delivered on schedule a Single Shield TBM (diameter 12,225 mm) specialized for hard rock.
With the power of seven Formula 1 cars underground
The cutterhead of the machine, christened “Alessandra,” is driven by 15 motors with a total output of 5,250 kilowatts—roughly seven times the power of a current Formula 1 race car. The hydraulic thrust cylinders press the rotating cutterhead against the rock face with up to 95,000 kilonewtons—equivalent to the weight of the Eiffel Tower in Paris.
The target of the first tunnelling stage—the northern fault zone—had been excavated conventionally in advance. For this approximately 400-meter-long tunnel section, planners had predicted geological conditions in which mechanized tunnelling would not have been feasible efficiently. After the breakthrough, the tunnel builders will transport the machine, which is about 100 meters long in total, through this cavern before tackling the remaining approximately 4 kilometers to the south. In the coming weeks, the cavern will also serve to thoroughly overhaul the Herrenknecht machine after it has navigated the most challenging rock formations to date.
In addition to the sections where the miners achieved peak performance with the TBM, there were stretches with zones rich in quartz or hard, blocky granite that pushed both man and machine to their absolute limits. Johannes Faißt, Herrenknecht project manager for the Gotthard Road Tunnel, explains: “So-called disk cutters are mounted on the rotating cutterhead. As the cutterhead rotates, the disk cutters break up the rock. Depending on the geology, they are subject to specific wear and must be replaced regularly. Here, we were able to provide crucial support for the tunnelling operation with high-quality disk cutters from our Schwanau plant and a logistics process that was closely coordinated with our customer.”
Progress on the south side
Working toward the northern construction section, a tunnelling operation from the south is advancing for the second tube of the Gotthard Road Tunnel. Here, the tunnel boring machine manufactured by Herrenknecht and operated by specialists from Marti AG had been brought to a controlled stop to excavate a defined tunnel length using conventional methods. This demanding work is now largely complete, allowing mechanized tunnelling toward the north to resume in mid-May.
From 2003 to 2011, construction consortia at the Gotthard used four Herrenknecht machines to excavate a total of 85 kilometers of tunnel for what was then the world’s longest railway tunnel. The delivery for the Gotthard Base Tunnel ranks among the outstanding milestones in Herrenknecht’s corporate history. This is also confirmed by Matthias Schwärzel, the project management director in charge, for whom it means a great deal to be working with Herrenknecht technology on the Gotthard again: “Tunnel construction in the Alps, especially at the Swiss St. Gotthard, has always had an emotional component for us.”
Published on:
06 May 2026
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