Definition of Geotextiles | Advantages of Geotextiles | Application of Geotextiles

Advantages of Geotextiles
The geotextiles market requires bulk quantities of material. Warp-knitted weft-insertion geotextiles offer the following advantages when compared to woven geotextiles:

1. Strength-for-strength, they are lighter than woven geotextiles using the same yarn.This makes for easier handling and laying on site; thus transport and labour costs are less in real terms.

2. Knitted geotextiles have exceptional tear strength. Additional strength can be designed and built-in to the weft direction such that a bi-axial high tensile, high strength warp/weft geotextile becomes a reality; e.g. 500kNm warp and 500k Nm weft.

3. Knitted geotextiles can incorporate an additional fabric to form a true composite geotextile, the fabric being simply knitted-in.

4. The individual yarns in the warp knitted weft-insertion geotextile are straight when incorporated, so they are able to take-up the strain immediately on loading. Those in woven geotextiles are interlaced.

Uses Of Geotextiles
Construction of roads, drains, harbour works, and breakwaters, and for land reclamation and many other civil engineering purposes .

Uses of geotextile

Some importance applications of geotextile are described below:

Separation
In this function, the geotextile serves to separate two dissimilarmaterials, eg, two different soils, landfill material and the native soil, stone material and subgrade soil, old and new pavement, foundation soils and  various types of walls, or one of many other similar situations. In some instances, it is difficult to distinguish  between the separation and stabilization functions because in both situations the geotextile is serving as a  separator. However, in stabilization some additional phenomena occur.

Stabilization  

In this application, the natural soil on which the geotextile is placed is usually a wet, soft, compressible material, exhibiting very little strength. By acting as a separator, the geotextile allows water from the soft natural soil to pass from this soil into a free-draining construction soil, which in turn allows consolidation of the natural soil to take place. As a result of the consolidation process, there is a strength gain in the natural soil, which then provides an adequate foundation for construction to take place.

Reinforcement
The key difference between stabilization and reinforcement is that stabilization is accomplished by providing for drainage of water from the unstable soil, while in reinforcement the strength characteristics (stress–strain) of the geotextile provide added strength to the whole system. Another difference is that in stabilization the geotextile is placed on or around the area being stabilized and thereby also acts as a separator, whereas in the reinforcement application the geotextile is placed within the material being reinforced. This is in line with reinforcement concepts in concrete and other materials.

Filtration
Here the prime function is to retain soil or other fine materials, while allowing water to pass through. Again, it is seen that more than one function is being performed. If there were no drainage of water taking place, movement, and therefore retention of the soil, would not be of concern. Part of the mechanism by which filtration occurs is through the development of a soil filter behind the geotextile. As the water passes through, soil is filtered out and collects behind the geotextile. As buildup takes place, a natural soil filter is developed.

Drainage
In the previous sections, drainage was discussed as taking place in a direction perpendicular to the plane of the geotextile. Here, drainage parallel to the plane of the geotextile is described. The property called transmissivity is defined as flow parallel to the plane of the geotextile. This type of flow can occur to some extent in all geotextiles, but is best achieved in needle-punched nonwoven materials. This class of geotextiles can be manufactured in a range of thicknesses such that this characteristic is optimized.

Moisture Barrier
When impregnated with an asphaltic emulsion, geotextiles become impermeable and can then be used as moisture barriers. The primary application for this type of geotextile is in pavement rehabilitation.

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