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Tunnel hole-through

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Dismantling the tunnel boring machine 10 days after the hole-through on the Gotthard Base Tunnel in Switzerland.

Tunnel hole-through, also called breakthrough, is the time, during the construction of a tunnel built from both ends, when the ends meet, and the accuracy of the survey work becomes evident. Many tunnels report breakthroughs with an error of only a few inches.[citation needed]

See also

References