短語詞組短語soft brown coal 軟褐煤soft outburst coal seam 松軟突出煤層textural soft -coal 構造軟煤soft rock coal roadway 軟巖回采巷道ultra soft weak coal 極散軟煤soft top coal 軟弱頂煤soft projecting coal seam 松軟突出煤層 返回 soft coal