Construction of inverted filters, made from mineral fibrous …
For different types of drainage arrangements, use is basically made of multilayer sand-gravel and rubble in- verted filters, the construction of which is extremely difficult and costly. ... slabs placed on an inverted filter consisting of two layers of reel glass felt (STU-77-10-215-65) with a total thick- ness of 8 era, with an underlying 75 ...