filter drains 中文意思是什麼
filter drains
解釋
濾水暗管-
In drainage of agricultural lands, a filter or gravel envelope is used to prevent the entrance of fine sand and silt into the drains.
在農田排水中常常採用礫石或過濾層來防止粉細砂和泥沙進入排水溝。
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