Retreat mining is a term used to reference the final phase of an underground mining technique known as room and pillar mining. Mining is the extraction of valuable Minerals or other geological materials from the earth usually (but not always from an Ore body Room and pillar is a Mining system in which the mined material is extracted across a horizontal plane while leaving "pillars" of untouched material to support This involves excavating a room or chamber while leaving behind pillars of material for support. This excavation is carried out in a pattern advancing away from the entrance of a mine. Once a deposit has been exhausted using this method, the pillars that were left behind initially are removed, or 'pulled', retreating back towards the mine's entrance. After the pillars are removed, the roof (or back) is allowed to collapse behind the mining area. Pillar removal must occur in a very precise order in order to reduce the risks to workers, due to the high stresses placed on the remaining pillars by the abutment stresses of the caving ground.
Retreat mining is the term commonly referred to as the mining method employed by the Crandall Canyon Mine and is believed, by some, to be a factor in the August 2007 collapse which trapped six miners. The Crandall Canyon Mine, formerly Genwal Mine, was an underground Bituminous Coal mine in northwestern Emery County Utah. On November 21, 2007, the mine was sealed, entombing the deceased miners. The bureau of land management says retreat mining was being used. Robert E. Murray, CEO of Murray Energy (owner of the mine) says the technique was not being used at Crandall Canyon. Robert E Murray (born 1940 is an American CEO of Murray Energy a mining corporation based in Cleveland Ohio. [1]
See also
References
- ^ Borenstein, Seth; Talhelm, Jennifer; Vergakis, Brock. Longwall mining is a form of underground Coal mining where a long wall (typically about 250-400 m long of coal is mined in a single slice (typically 1-2 m thick "Deadly Mining Method Often Used", The Washington Post, The Associated Press, August 6, 2007. Retrieved on 2007-08-07. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 322 BC - Battle of Crannon between Athens and Macedon following the death of Alexander the Great.
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