The gravel frequently is sieved and gradedsand that is packed in bags.
砾石通常是经过筛析和粒度分级的袋装砂子。
2
The river deposit, which is made up of naturally gradedsand and gravel, is characterized by its well gradation, easy control of its particle size, easy compaction and good permeability.
这种天然级配砂砾具有级配良好、粒径易控制、易碾压成型、透水性好等特点。
3
After reviewing a few design methods of sand gravel filters, a new design method of filter using broad graded materials is proposed in the paper.