pillar extraction meaning in Chinese

矿柱回采
煤柱回收

Research on cms - aided blast design for ore pillar extraction
辅助矿柱回采爆破设计研究
Top - coal caving technology using - steel applied for pillar extraction
型钢放顶煤技术在煤柱回收中的应用
Pillar extraction drilling
煤柱回采钻眼
Analysis of the method for constructing the cross - measures roadways of the pillar extraction face
煤柱采面过穿层巷道施工方法研究