Encyclopedia > Tunnel

  Article Content

Tunnel

A tunnel is a passage through a mountain or under a waterway, road or railroad.

It may be for pedestrians and/or cyclists, for general road traffic, for motor vehicles only, for rail traffic, or for a canal.

Various combinations are also possible.

The central part of a metro network is usually built in tunnels. To allow non-level crossings, some lines are in deeper tunnels than others. At metro stations there are often also pedestrian tunnels to walk from one platform to another.

At train stations of ground-level railways there are often one or more pedestrian tunnels under the railway to reach the platform(s).

Construction

Shallow tunnels are of the cut-and-cover type (if under water of the immersed-tube type), deep tunnels are excavated. For intermediate levels, both methods are possible.

Cut-and-cover is a method of tunnel construction where a trench is excavated and roofed over. Strong supporting beams are necessary to avoid the danger of the tunnel collapsing.

Wartime tunnels

Castles, sappers

trench warfare: Crimea, US Civil War, WWI

Germany WWII, V2 factories, slave labor

North Korea, infiltrators, midget subs...

Japan, Corregidor, etc. (Neal Stephenson's Cryptonomicon?)

Vietnam, tunnel rats ("Platoon"?)

Examples of tunnels

See also: List of tunnels, Wind tunnel.



All Wikipedia text is available under the terms of the GNU Free Documentation License

 
  Search Encyclopedia

Search over one million articles, find something about almost anything!
 
 
  
  Featured Article
Islip Terrace, New York

... family size is 3.51. In the town the population is spread out with 29.5% under the age of 18, 6.7% from 18 to 24, 33.6% from 25 to 44, 20.6% from 45 to 64, and 9.6% ...

 
 
 
This page was created in 81.8 ms