保护层开采
protecting stratum mining
protected seam mining
protective coal seam mining
protecting seam exploitation
protective seam mining
protective coat extracted
protective layer
protected coal seam mining
protective layer mining
保护层厚度
Thickness of Coating
cover thickness
Thickness of concrete covering
depth of concrete cover layer
concrete cover
concrete cover thickness
protection thickness
thickness of concrete cover
保护层工作面
coal mining face in protected seam
保护层爆破
Protection layer blasting
protective level blasting
半导体保护器件
semiconductor protection device
版权保护管理系统
copyright protection management system