短語詞組短語asphalt cemented ballast bed 瀝青道牀integrated ballast bed 整躰道牀integral ballast bed 整躰道牀width of ballast bed 道牀寬度ballast bed finisher 平整道碴機(jī)track on ballast bed 碎石道牀軌道elastic integral ballast bed 彈性整躰道牀integrate ballast bed 整躰道牀 返回 ballast bed