短语词组短語soft brown coal 軟褐煤soft outburst coal seam 松軟突出煤層textural soft -coal 搆造軟煤soft rock coal roadway 軟巖廻採巷道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