Mining is an industry that pushes the envelope in engineering, and things get even more extreme when it comes to underground mining. The use of underground mines is necessary for excavating at depths greater than 60 metres (the point where surface mining turns inefficient). How Stuff Works highlighted the wide range of depths that underground mines can reach, from 750 metres for coal mines and over 2 kilometres for uranium mines.
The Mine Cage
Every underground mine has mine shafts, and each has an indispensable function. Ventilation shafts clear the toxic fumes that are by-products of blasting and drilling. Recovery shafts carry the ores from the bottom of the mine to the surface. Access shafts carry personnel and equipment to and from the surface. All shafts have crucial components, one of the most notable are mine cages.