短长壁综采放顶煤
shorter long-wall full-mechanized caving mining
长壁综放
long-wall full-mechanized caving mining
long-wall full-mechanized caving
长壁综采放顶煤采煤方法
longwall fully mechanized overhead caving coal mining
长壁留煤柱支撑法开采
longwall remaining coal pillars support mining
长壁留煤柱支撑法
longwall remaining coal pillars support
长壁留煤柱
long wall with coal pillar