Tunnel excavation begins in 1857

The Fréjus tunnel, also known as the Mont-Cenis tunnel, began construction in 1857, connecting Modane in Savoie, France, to Bardonnèche (Bardonecchia) in Italy. Work started on the Modane side at the end of August 1857, followed by the Bardonnèche side on November 14 of the same year.

Manual labor dominates early progress

Initially, miners excavated the tunnel by hand, advancing approximately 0.6 meters per day. This slow pace was due to the labor-intensive nature of the work and the lack of advanced machinery at the time.

Compressed air drills introduced in 1861

In January 1861, a compressed air drilling machine was introduced on the Bardonnèche side, marking a shift from manual labor. This innovation was developed by Savoyard engineer Germain Sommeiller, who collaborated with other engineers and inventors, including Grandis, Grattoni, Bartlett, and Colladon.

Early machine performance falls short

The initial use of the compressed air drills was disappointing, as the pace dropped to 0.47 meters per day in 1861—slower than manual labor. This was due to frequent breakdowns and the lack of experience among workers and technicians.

Improved efficiency by 1870

By 1870, the pace on the Bardonnèche side had significantly increased to 2.44 meters per day, a peak rate that was nearly four times faster than the manual rate. This improvement was achieved through experience, training, and better machine reliability.

Tunnel completion in December 1870

The two tunnel galleries met on December 25, 1870, after 12,233 meters of rock had been excavated. The final rock wall, about 4 meters thick, was destroyed by explosives during the night of December 25 to 26.

Tunnel length and modifications

The tunnel’s length between its two entrances is 12,233.55 meters, or about 12.2 kilometers. Including access connections, trains travel 12,847 meters, and after modifications in 1881, the total length increased to approximately 13.6 kilometers.

Germain Sommeiller's legacy

Germain Sommeiller, born in 1815 and a key figure in the tunnel’s development, died in 1871 before the tunnel opened. The first train passed through the tunnel on September 17, 1871, carrying 400 passengers from Bardonnèche to Fourneaux in 22 minutes.