Room and pillar (variant of breast stoping) is a mining system in which the mined material is extracted across a horizontal plane making horizontal arrays of rooms and pillars. The ore is extracted in two phases, 1. Leaving "pillars" of untouched material to support the roof overburden and extracting open areas or "rooms" underground. 2. Extracting left pillars partially (in the same manner as "Bord & Pillar method"). It is usually used for relatively flat-lying deposits, such as those that follow a particular stratum.
The room and pillar system is used in mining coal, iron and base metals ores particularly when found as manto or blanket deposits, stone and aggregates, talc, soda ash and potash.
The key to the successful room and pillar mining is selecting the optimum pillar size.In general practice size of both room and pillars are kept almost equal, while in Bord & Pillar, Pillar size is much larger than bord(gallery). If the pillars are too small the mine will collapse. If the pillars are too large then significant quantities of valuable material will be left behind reducing the profitability of the mine. The percentage of material mined varies depending on many factors, including the material mined, height of the pillar, and roof conditions; typical values are: stone and aggregates 75%, coal 60%, and potash 50%.
Read more about Room And Pillar: History, Mine Layout, Retreat Mining, See Also
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