Geotextile filter structure

摘要

The filter may be made of geotextile material (10). There is a top layer which may be thicker in the centre (16) than at the edge (14). This material may consist of a layer of e.g. felted fibrous synthetic material. The top layer rests on a thin lower layer (12) which may consist of fibrous material with a number of constrictions. There may be between 15 and 40 constrictions. This lower layer rests on a layer of soil or gravel which may be used for filtration.