Lyon-Turin: A 10-Meter ‘Monster’ Begins Drilling the World’s Longest Railway Tunnel
Lyon, Auvergne-Rhône-Alpes, France – The ambitious Lyon-Turin railway tunnel project has reached a pivotal stage with the deployment of a massive 10-meter diameter tunnel boring machine (TBM) on the Italian side. This ‘monster’ machine has commenced drilling the 57.5-kilometer base tunnel, which upon completion will be the longest railway tunnel in the world.
For years, the Lyon-Turin project was primarily a concept on paper. However, with the arrival of this extraordinary machine, the vision is rapidly transforming into a tangible reality. The TBM, with a diameter exceeding 10 meters – equivalent to a three-story building laid on its side – is poised to undertake the monumental task of excavating through the challenging Alpine terrain.
An Underground Factory: How the TBM Works
Watching the TBM operate is akin to observing a train without tracks, forging its own path. At its front, a colossal cutting wheel, equipped with dozens of steel tools, grinds and fragments the rock. Behind it, a continuous process unfolds: excavated material is removed, tunnel walls are reinforced, and concrete segments called voussoirs are installed to form the tunnel’s structure.
The most impressive aspect is the TBM’s continuous operation: it doesn’t just excavate; it constructs the tunnel as it advances. Its daily progress, which can span several tens of meters in favorable conditions, adapts to the geological nature of the terrain. In more complex zones, the machine slows down, adjusts its parameters, and navigates through the unpredictable Alpine environment.
Navigating the Unforgiving Alpine Environment
Drilling beneath the Alps is an arduous undertaking. The mountain’s geology is heterogeneous, characterized by layers, fractures, and unstable zones. Teams must contend with extremely hard rocks that rapidly wear down tools, unstable areas prone to deformation from pressure, and pressurized water that can emerge without warning.
Every meter gained in this environment demands precision and vigilance. The TBM is equipped with highly accurate guidance systems, enabling it to follow a trajectory with a tolerance of just a few centimeters over tens of kilometers. Sensors continuously analyze the geology, mechanical stresses, and the machine’s behavior, ensuring that excavation is never conducted blindly. This first giant TBM, measuring 235 meters in length with a 10.16-meter cutting wheel, was received in Germany before its transfer to Chiomonte, Italy. Designed to drill up to 2,000 meters beneath the mountain, it operates in a bimode (hard rock or soft ground) and is expected to advance approximately 10 meters per day.
A Project of Unprecedented Scale
The arrival of this initial TBM signifies a clear transition for the project. For years, the focus was on studies, surveys, and reconnaissance galleries to understand the mountain. Now, the construction enters an industrial phase, mobilizing hundreds of engineers, operators, geologists, and maintenance technicians. The organization resembles a production line, with the seemingly simple objective of continuous advancement while maintaining maximum safety.
Additional TBMs will progressively join the effort, multiplying excavation points to accelerate the drilling process and adhere to an already tight schedule.
More Than Just a Tunnel: A European Railway Link
The Lyon-Turin base tunnel is not an isolated structure; it forms the core of a railway link designed to revolutionize exchanges between France and Italy. The clear objective, despite its complex implementation, is to reduce heavy truck traffic in the Alps, shift a significant portion of freight to rail, and limit cross-border transport emissions.
The tunnel will accommodate long and heavy trains, capable of transporting substantial volumes of goods with significantly greater energy efficiency than road transport. On a European scale, it is an integral part of a corridor connecting the north and south of the continent, facilitating trade flows between the Iberian Peninsula, France, Italy, and beyond.
Impressive Mechanics, Persistent Debates
A project of this magnitude inevitably sparks discussion. The overall cost, estimated at several tens of billions of euros, regularly fuels criticism. Some view it as an excessive investment, while others highlight environmental impacts or question the project’s real utility compared to existing infrastructure.
Conversely, proponents emphasize a long-term vision: fewer trucks in Alpine valleys, modernized rail logistics, and enhanced continuity of European exchanges. The TBM, however, remains oblivious to these controversies, advancing meter by meter, indifferent to the ongoing debates.
Source: https://media24.fr/2026/03/22/dans-les-alpes-une-machine-geante-commence-a-manger-la-montagne/
