| 摘要 |
The element 80 has an upper water permeable layer, e.g. of geotextile, a lower water permeable layer, e.g. of geotextile and a filter material layer provided between the upper and lower water permeable layers. The filter material may be sand or glass and can be compartmentalized by a serpentine geotextile layer or by web elements extending across the filter layer between the upper and lower layers to form elongate compartments or a grid of cells. The element can be flexible to be rolled up for transport or rigid, in panel form. The element 80 can have on one layer an elongate sealing flap 85 extending from and along one edge or two adjacent edges. The element 80 can have on its other layer a further elongate flap extending from and along one edge or two adjacent edges which is/are opposite to the first-mentioned edge(s). This provides for laying elements in grid formation with mutually overlying and underlying flaps. |
