mined roof

• 顶部回采

mined roof的用法和样例：

例句

1. With the increase of the depth of coal seams mined, rock bursts will easily occur in gateways with fully-mechanized sublevel caving mining.
   摘要随着煤矿开采深度增加，综放开采回采巷道易发生冲击地压危害。