Room and pillar mining
Horizontal excavation mining method / From Wikipedia, the free encyclopedia
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Room and pillar or pillar and stall is a variant of breast stoping. It is a mining system in which the mined material is extracted across a horizontal plane, creating horizontal arrays of rooms and pillars. To do this, "rooms" of ore are dug out while "pillars" of untouched material are left to support the roof – overburden. Calculating the size, shape, and position of pillars is a complicated procedure, and is an area of active research.[1] The technique is usually used for relatively flat-lying deposits, such as those that follow a particular stratum. Room and pillar mining can be advantageous because it reduces the risk of surface subsidence compared to other underground mining techniques.[2] It is also advantageous because it can be mechanized, and is relatively simple. However, because significant portions of ore may have to be left behind, recovery and profits can be low.[1] Room and pillar mining was one of the earliest methods used,[3] although with significantly more man-power.
The room and pillar system is used in mining coal, gypsum,[4] iron,[5] limestone,[6] and uranium[7] ores, particularly when found as manto or blanket deposits, stone and aggregates, talc, soda ash, and potash.[8] It has been used worldwide from the Czech Republic[2] to China[9] to the US.[4]