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In the second phase, once advance mining has been completed, pillars are removed "on the retreat." Removing or "pulling" pillars begins far from the entrance and proceeds toward the entrance. As the pillars are removed, the mine collapses because nothing remains to support the roof and overburden.
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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. The first phase is known as "mining on the advance," from the entrance toward the
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Tunnels only make up about 15% of the reserve, so during advance mining, only about 15% of the coal or ore is removed. During retreat mining, an additional 75% of coal or ore may be removed because pillars make up much more of the reserve, bringing the total recovery of the resource to as much as
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Removing pillars causes stresses within the mine to shift and must be planned and executed carefully to reduce danger to miners and control the amount of stress exerted on remaining pillars and the mine floor.
54:(MSHA), pillar recovery mining has been historically responsible for 25% of American coal mining deaths caused by failures of the roof or walls, even though it represents only 10% of the coal mining industry.
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20:General layout of a room-and-pillar mine.
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107:"Deep Cover Pillar Recovery in the US"
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151:Borenstein, Seth (August 6, 2007).
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153:"Deadly Mining Method Often Used"
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105:Mark, Chris (2010).
86:Directional drilling
81:Hydraulic fracturing
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113:. Retrieved
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401:Prospecting
283:Sub-surface
311:Directions
229:techniques
92:References
35:mining.
391:Automated
386:Abandoned
302:Soft rock
297:Hard rock
249:Quarrying
421:Category
361:Longwall
338:Borehole
333:Bell pit
264:Dredging
244:Open-pit
187:Archived
65:See also
366:Retreat
348:Stoping
290:Classes
236:Surface
115:13 July
259:Placer
227:Mining
29:mining
379:Other
328:Shaft
323:Slope
318:Drift
254:Strip
110:(PDF)
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138:help
117:2012
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