bank gravel

例句：

1. 1.The riverbank is covered in a thick layer of gravel.
   河岸边覆盖着一层厚厚的砾石。
2. 2. The engineer carefully removed the bank gravel to make way for the construction.
   工程师小心翼翼地移除了河床上的砾石以便施工。
3. 3. The old road was paved with bank gravel, making it easy to walk on.
   这条旧路铺满了砾石，走起来很方便。