近距煤层
close coal seams
near distance coal seam group
极薄煤层开采
micro-thickness mine coal face exploitation
煤层开采地质条件
coal mining geological conditions
深部不可开采煤层
deep unminable coal seams
远距离下保护层开采
far distance lower protective seam exploitation
按煤种分层开采
mining in slices according to coal rank
采煤采气一体化
Integrated Coal Mining and Gas Extraction