It is as long as two soccer fields, weighs thousands of tons and is designed to excavate in different geological environments with covers up to 2,000 meters of rock. The first of two maxi TBMs that will excavate the Italian side of the Mont Cenis base tunnel, the heart of the future Lyon-Turin railway line, was officially delivered today at the Herrenknecht factory in Germany where it had been built for the UXT group of companies (Itinera, Ghella and Spie Batignolles).
The TBM will be sent to the Chiomonte construction site in the Susa Valley, where it will excavate the second access adit needed to be able to continue with the excavation of the south tunnel of the base tunnel, which has already begun on the French side, advancing under the mountain towards Susa. In the next few years, when the works will be fully operational, there will be 7 TBMs excavation 75% of the base tunnel in Italy and France.
The delivery ceremony, symbolised by the rotation of the TBM cutterhead, was held in the presence of TELT President Daniel Bursaux and CEO Maurizio Bufalini, the companies of the UXT group and IS2P project management (FS Engineering, ARX, Systra, Setec), as well as the Italian consul in Freiburg Pietro Falcone and Piedmont Region Vice President Elena Chiorino. Vice Prime Minister and Minister of Infrastructure and Transport Matteo Salvini and French Minister of Transport Philippe Tabarot took the floor remotely.
Inside the mega-machine that builds the tunnel as it excavates it
The TBM has an overall length of 235 meters and consists of a 10.16-meter-diameter head and an outer shield that protects personnel and the machine during excavation, allowing safe installation of the prefabricated segments used for the tunnel lining.
The TBM is equipped with 13 engines capable of generating a total power of 4,550 kW and will advance about 10 meters per day thanks to hydraulic cylinders placed on the segments.
To specifically address the needs of this section of the tunnel, a dual mode TBM was built to cross both hard rock, operating in “open mode,” and loose ground in “closed mode.”
Digging into the heart of the mountain
The choice of this type of TBM is due to several factors: the type of geology that characterizes the excavation areas, the great depth of the tunnels to be built (up to 2,000 meters below the mountain), the need to follow reduced horizontal and vertical bending radii, and the “natural” high temperatures present at these depths, highlighted with the Maddalena exploratory tunnel in Chiomonte, which allowed this new TBM to be designed.
