Retreat Mining
See also: Retreat miningRetreat mining is often the final stage of room and pillar mining. 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 a particularly dangerous form of mining: according to the Mine Safety and Health Administration (MSHA), pillar recovery mining has been historically responsible for 25% of American coal mining deaths, even though it represents only 10% of the coal mining industry. Apparently retreat mining was in use at the Crandall Canyon Mine and may have caused the August 2007 collapse which trapped six miners. 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.
Read more about this topic: Room And Pillar
Famous quotes containing the words retreat and/or mining:
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—Henry David Thoreau (1817–1862)
“For every nineteenth-century middle-class family that protected its wife and child within the family circle, there was an Irish or a German girl scrubbing floors in that home, a Welsh boy mining coal to keep the home-baked goodies warm, a black girl doing the family laundry, a black mother and child picking cotton to be made into clothes for the family, and a Jewish or an Italian daughter in a sweatshop making “ladies” dresses or artificial flowers for the family to purchase.”
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