Tunnel Boring Machine in Action

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Boring machine in action at the Mont Cenis Tunnel.

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A crew of workers operates a boring machine for the cutting of the Fréjus Rail Tunnel (also known as Mont Cenis Tunnel).
This machine, powered by compressed air, was designed to bore series of holes into the rock. It would take the crew six hours to bore between 90 and 100 holes, each 1.6 in (4 cm) wide and 31.5 in (80 cm) deep, except for a larger, center one, which would remain empty. The smaller holes were filled with powder, which was detonated in such a way that eight holes would explode simultaneously. The resulting excavation was about 27.5 in (70 cm) deep, 39 in wide, and, on average, 15.7 in (40 cm) high.

The initial fréjus Tunnel was 8 mi (12.8 km) long between Modane, France, and Bardecchia, Italy. Drilling started in August 1857 and it opened for traffic in September 1871.

The caption reads in the original French: Machine perforatrice en action au tunnel du mont Cenis.

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