短語詞組短語coal -mining methods 采煤方法coal surface mining 露天采煤single coal seam mining 單一煤層開采coal resources mining 煤炭資源開采coal pillar mining 帶煤柱開采coal mine mining 礦井開采coal caving mining 煤采煤;放頂煤開采;放頂煤opencast coal -mining 露天采煤 返回 coal mining