During mechanical longwall top coal mining, the gas permeability in top coal ahead of working face has bigger difference compared with slicemining due to the increase of mining height.
综放开采由于采高的加大，导致采场前方顶煤中瓦斯渗透性与分层开采有较大的差异。
2
The underhand slice stoping with cemented filling is the most effective mining method for incompetant orebody with complicated mining conditions.
下向分层胶结充填采矿法是矿岩破碎、开采技术条件复杂的难采矿体最有效的采矿方法。
3
The underhand slice stoping method, with reinforced concrete for roof support, is recommended to mine narrow veins where the mining technological conditions are very complicated.