Geotextiles are permeable fabrics which when used in conjunction with soil, performs various basic functions including separating, filtering, strengthening, protecting or draining. Geotextiles are usually made from polypropylene or polyester and are available in four basic forms, namely woven, non-woven, needle-punched or heat bonded.
GAST uses Geotextiles for multiple applications including: filtration, subsoil drainage, sports field drainage, structural drainage, erosion control, separation and stabilisation, railway tracks, reinforcing soil slopes, liner protection, road maintenance and impermeable linings. When used in any of these applications geotextiles provide for the retention of fine particles without reducing the permeability requirements of the drain. This indicates that geotextiles perform a primary function of filtration and separation as fine soil particles are prevented from entering the drain while the water passes through.