The crown pillar of stope is permanent loss and not recoverable, while sill pillar and barrier pillar shall be recovered after the ore drawing work is completed.
采场的顶柱作为永久矿柱损失，采场底柱、间柱等采场大量放矿完毕后，一次性进行回收。
2
Cut-off grade method has been used to control the ore drawing in non-pillar sublevel caving mining both in and outside China.
采用无底柱分段崩落采矿法，国内外一直采用截止品位放矿法来控制出矿。
3
Population and application of the dilution ratio ore drawing method has certain social value and economic value for implementation of the sill pillar-free subdrifting method.