Geotextile fabric

Spunbonded fabrics are effective filters in that they are layered stmctures of relatively fine fibers, the three-dimensional stmcture of which creates a torturous path. Even relatively thin spunbonded fabrics (eg, 0.2—0.25 mm) present a significant challenge to the passage of soil fines and are suitable for use in some filtration appHcations. The porosity of geotextile fabrics is classified by means of several procedures such as flux (volume flow/area per time) and equivalent opening size (EOS), which is a measure of the apparent pore size of the openings in the fabric. The flux measures the porosity to Hquid water, and the EOS measures the porosity to soHd particles of a known diameter. Literature is available on limitations of particular styles of fabrics within an apphcation (63). 

Effect of confining pressure on needle-punched hole in geotextile fabrics G1, G2, and G3 where (a) no applied stress and (b) 50 kPa applied vertical stress is Magnification 18X. 

Bentonite clays use composite sodium bentonite systems with HDPE liners and geotextile fabrics, which are more common and more effective than the traditional systems. 

Geotextile fabrics are based on woven, nonwoven and composite fabric structures whose properties are determined primarily by the fiber/yarn components present in terms of intrinsic tensile properties and chemical durability. Most geotextiles are expected to have lifetimes well in excess of 20 years and to provide varying degrees of mechanical reinforcement and containment to the civil engineering structures in which they are incorporated. 

Geotextile fabrics can be manufactured with a suitable stmcture to enable liquid or gas to flow within the plane of the fabric. The fluid s in-plane transmission property of a geotextile is also known as its transmissivity. Examples are beneath railroad ballast, to dissipate seepage water from exposed soil or rock surfaces, and drainage of pavement layers. 

Filter rules are predominandy developed for drains and other applications with unidirectional flow. Filters in coastal and riverine training and protection stmctures often experience much heavier loads with high gradients and turbulent and reversing flow. Therefore, tests are recommended to prove the filtration capability of geotextile fabric in such cases. 

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