filter layer的用法和樣例：
例句
- It can be the filtration layer of the dikes,river canal,seacoast,concrete and retaining walls.
可以做堤壩，河渠，海岸，混凝土，擋土墻的過(guò)濾層。 - In drainage of agricultural lands, a filter or gravel envelope is used to prevent the entrance of fine sand and silt into the drains.
在農田排水中常常采用礫石或過(guò)濾層來(lái)防止粉細砂和泥沙進(jìn)入排水溝。
