Adequate drainage is essential for achieving and maintaining soil stability in embankments and in road stability etc. Graded aggregate filters have traditionally been used for drain protection, but the problem of design , cost , placement and testing of aggregate filters makes geotextiles an attractive alternative. The drainage function of a geotextile is generally associated with its ability to transmit liquid or gas in the plane of fabric without soil loss . The major difference between filtration and drainage function is the direction of flow which makes in-plane permeability critical for the drainage function. Drainage refers to planar flow as opposed to filtration which refers to flow across the geotextile.
Waterproofing Function (Moisture barrier)
Geotextile can act as waterproof materials when impregnated with bitumen or polymeric sealing materials . After impregnation , the water and vapor permeability of the fabric become very low in both cross-plane and in plane-flow.