Tunnel hole-through
When the two sections of a tunnel under construction meet
![](http://upload.wikimedia.org/wikipedia/commons/thumb/7/70/TBM_S-210_Alptransit_Faido_East.jpg/300px-TBM_S-210_Alptransit_Faido_East.jpg)
Tunnel hole-through, also called breakthrough, is the time, during the construction of a tunnel built from both ends, when the ends meet,[1] and the accuracy of the survey work becomes evident. Many tunnels report breakthroughs with an error of only a few inches, for example:
- the 1858 Blue Ridge Tunnel – 6 inches (150 mm)
- the 1944 Blue Ridge Tunnel replacement – 4 feet (1.2 m) - 1944
- the Lötschberg Base Tunnel – 10 cm[2]
- the Holland Tunnel - 1 cm[3]
See also
- Cascade Tunnel
References
External links
Gautrain tunnel breakthrough
Brisbane Clem 7
Gotthard tunnel
Lotschberg - 10 cm
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