Specification & uses of Geotextiles

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Specication according to its uses

Because of the wide variety of geosynthetics available (Fig. 24.1), along with their different polymers, filaments, bonding mechanisms, thicknesses, masses, and so on, they have a wide range of physical and mechanical properties. A further complicating factor is the variability of some properties, even within the same manufactured lot or roll. Differences may sometimes be due to the test procedures themselves. Many of our current geosynthetic tests were developed by the textile and polymer industries, often for quality control of the manufacturing process. Consequently the test values from these tests may not relate well to the civil engineering conditions of a particular application. Furthermore, soil confinement or interaction is not accounted for in most geosynthetics testing. Research is now underway to provide test procedures and soil–geosynthetic interaction properties which are more appropriate for design.

Uses of Geotextiles

1. Separation:

Commonly used for separation of aggregate-base and sub grade layers of roads.
Geo-textile prevents the sub grade materials from migrating into the aggregate base due to loads thus increasing pavement life

2. Filtration:

To retain the particles of the filtered soil, while permitting water to pass through the plane of the geo-textile
Rip rap material may be placed over geo-textile along a stream bank

3. Reinforcement: Geo-textile material under the road-bed reinforces soft soil and preserves the road embankment

4. Transmission: Some composite geo-textile materials allow water flow within the plane of the material, rather than across it such as behind a retaining wall. This function is called transmission.

5. Erosion Control:

Permanent erosion control applications: (a) slope protection, (b) diversion ditches, (c) stream and canal banks, (d) scour protection, (e) beaches, and (f ) culvert outlets. ( geocomposites is the use of prefabricated vertical (“wick”) drains to accelerate the consolidation of soft compressible cohesive soil layers. Because they are much less expensive to install, geocomposite drains have madeconventional sand drains obsolete.

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