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Room and pillar mining was one of the earliest methods used, [3] although with significantly more manpower. 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 ]
Retreat mining is the removal of pillars in the underground mining technique known as room and pillar mining. In the first phase of room and pillar mining, tunnels are advanced into the coal or ore body in a rectangular pattern resembling city streets. Pillars are left between tunnels to support the weight of the overburden.
Once room and pillar mines have been developed to a stopping point limited by geology, ventilation, or economics, a supplementary version of room and pillar mining, termed second mining or retreat mining, is commonly started. Miners remove the coal in the pillars, thereby recovering as much coal from the coal seam as possible.
In many rooms and pillar mines, the pillars are taken out, starting at the farthest point from the mine haulage exit, retreating, and letting the roof come down upon the floor. Room and pillar methods are well adapted to mechanization, and are used in deposits such as coal, potash, phosphate, salt, oil shale, and bedded uranium ores.
Google Scholar is a freely accessible web search engine that indexes the full text or metadata of scholarly literature across an array of publishing formats and disciplines. . Released in beta in November 2004, the Google Scholar index includes peer-reviewed online academic journals and books, conference papers, theses and dissertations, preprints, abstracts, technical reports, and other ...
These pillars can be small-scale structures (Type A pillars) or large and throughgoing high-discharge structures (Type B pillars). Within an individual bed an increase in concavity combined with a simultaneous decrease in width of the dishes can often be observed towards the top.
Timber framing is a general term for building with wooden posts and beams. The term post is the namesake of other general names for timber framing such as post-and-beam, post-and-girt construction and more specific types of timber framing such as Post and lintel, post-frame, post in ground, and ridge-post construction.
The Natural Step is a non-profit, non-governmental organisation founded in Sweden in 1989 by scientist Karl-Henrik Robèrt.The Natural Step is also used when referring to the partially open source framework it developed.