adit, in mining, underground passage excavated nearly horizontally, with one end open to the earth's surface, usually used to service a mine. The adit end is the furthermost end from the surface, i.e., the location where miners work. The adit collar is the area where an adit opens to the surface and must be reinforced against any surface weakness.
An adit is a type of entrance to an underground mine which is horizontal or nearly horizontal. Adits are usually built into the side of a hill or mountain, and often occur when a measure of coal or an ore body is located inside the mountain but above the adjacent valley floor or coastal plain. The use of adits is generally called drift mining.

Adits have many advantages over conventional shaft mining with vertical access shafts. Less energy is required to transport miners, horses and heavy equipment into and out of the mine. It is also much easier to transport coal or ore out of the mine. Horizontal travel by means of narrow gauge tramway or cable car is also much safer and can move more people and coal than vertical elevators. In some situations, mines with adits can be drained of water by gravity alone or power-assisted gravity. Further examples of adits include:

  • Blue Hawk Mine near Kelowna, BC, Canada
  • The Snowy Hydro scheme in the Australian Snowy Mountains created during its construction.These adits are very large and used to access the central point from which the hydro tunnels were constructed.


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