短语词组短語gravel road base 碎石路基oiled gravel road 瀝青礫石路gravel road surface 砂礫路麪gravel producing for road 路用碎石生産Graded gravel road structural design 級配碎石路麪結搆設計scatter gravel on the road 把砂礫撒在路麪上 返回 gravel road