Geotextiles are fabric materials manufactured by fusing (with chemicals or heat) or mechanically combining (needle-punched or stitch bonded) a loose web of polymer fibres. The most common are needle-punched geotextiles made of continuous long or staple fibres.

At the same surface mass (in g/m2), geotextiles are characterized by different tensile strength, porosity and permeability – depending on the fibres used (PP, PES continuous long or staple fibres) and the finishing process (calendering).

Geotextiles used for filtration, protective and drainage layers must meet two basic hydraulic criteria: permeability and clogging behaviour.

The permeability coefficient of geotextiles should be much higher than the permeability coefficient of the soil or the protected ground. The clogging criterion depends on the porosity of the geotextile and the grain size of the soil. The primary condition is that the fine soil particles do not cause clogging, i.e. sealing the filter material or silting the drainage.

Geotextiles for engineering and environmental protection applications are made mainly of polypropylene or polyester fibres.

Polypropylene and polyethene (polyolefin) geotextiles are characterized by high mechanical resistance and very good biological and chemical resistance. They are, however, weak to solar UV radiation, which should be considered by contractors working in open areas (polypropylene geotextiles should be covered). Additional agents can be added during production to make the textiles radiation resistant, which raises production costs. Polyester geotextiles are characterized by very good UV radiation resistance but have lower mechanical resistance and weaken when in contact with alkalis (e.g. cement).

Geotextiles can significantly extend the life of structures, increase their resistance and offer much better drainage than traditional methods.