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modified longwall

A method used in room-and-pillar mining where the lease requires at least 80% of recovery. Basically it consists of turning the rooms on 70-ft (21.3-m) centers then working the room up 30 ft (9.1 m) wide and butting it off at its completion, then withdrawing the remaining 40 ft (12.2 m) of pillar immediately.

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  • ed.young
  • (Milwaukee, United States)

  •  (V.I.P) 21084 分数
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