clay gravel

例句：

1. 1. The builders used clay and gravel to build the foundation of the house.
   建筑工人使用粘土和碎石来建造房子的基础。
2. 2. The riverbed is covered with a layer of clay and gravel.
   河床覆盖着一层粘土和碎石。
3. 3.The construction crew was using clay and gravel to level the site.
   施工队伍正在使用粘土和碎石平整场地。