Tunnel hole-through
Encyclopedia
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.
See also
- Cascade TunnelCascade TunnelThe Cascade Tunnel refers to two tunnels at Stevens Pass through the Cascade Mountains, approximately to the east of Everett, Washington. The first Cascade Tunnel was a 2.63-mile long single track railroad, built by the Great Northern Railway in 1900 to avoid problems caused by heavy winter...
- Blue Ridge TunnelBlue Ridge TunnelThe Blue Ridge Tunnel, also known as the Crozet Tunnel, was the longest of four tunnels built on the Blue Ridge Railroad to cross the Blue Ridge Mountains at Rockfish Gap near Afton Mountain in central Virginia...
- 6 inches (15.2 cm) - Blue Ridge TunnelBlue Ridge TunnelThe Blue Ridge Tunnel, also known as the Crozet Tunnel, was the longest of four tunnels built on the Blue Ridge Railroad to cross the Blue Ridge Mountains at Rockfish Gap near Afton Mountain in central Virginia...
- 4 feet (1.2 m) - 1944