| 摘要 |
<p>The invention relates to a filtering element for making a liquid permeable structure on a ground surface, in a floor covering plate, in a manhole cover or a foundation ditch, for sewage or the like, with at least one pre-filtering layer in the flowing direction followed by at least one filtering layer where the free flow section of each layer increases from layer to layer in the flowing direction, the claimed filtering element being provided with a jacket surrounding it like a frame and maintaining together at least the filtering layers, each filtering layer being formed of granular material, where the grains are either in loose form or bonded to one another by a weak binder.</p> |
