As its name suggests Geotextiles refers to textiles related to earth or soil. When any permeable material used with rock, soil or earth it is termed as Geotextiles. The basic function of this technology is to prevent soil erosion to strengthening heavy concrete structures. This technology has not yet gained much attention in India, but is widely used in many countries for construction of bridges, roads, railway tracks to improve its strength. Many researchers have view that this technology is not newly developed but is in use from past thousands of years.
Formation of Geotextiles
Geotextiles can be formed of synthetic fibers, natural fibers or combination of the two. In past Geotextiles were made of natural plant fibers while today are usually formed of synthetic polymers such as polyester, polypropylene (PP), polyamides (PA) and polyamides (PA). Geotextiles made from natural fibers are less durable as they get decomposed with passage of time.
Choice of formation depends on the required properties and service life for which it is used. For example, natural fiber base Geotextiles is used for erosion control mats where durability is not a critical factor.
Natural Fiber Based Geotextiles
Natural fibers like Jute and coir have special applications. These different fibers degrade at different rates. Coir geotextiles degrade in 2 to 3 years while jute degrades in 1 to 2 years. Because of this property coir is used in situations where vegetation takes longer to establish, and jute is used in low rainfall areas as it can absorb more moisture. Also used for rural unpaved roads.
1. Natural fiber-based geotextiles are environmental friendly.
2. Its biodegradable nature has certain cost-effective applications in erosion control and re-vegetation.
3. It is helpful in quick establishment of vegetation.
4. It also helps in dust control, sand dune formation, wind erosion control and stabilization.
Synthetic Fiber Based Geotextiles
Synthetic polymers are not subject to any degradation due to any biological and chemical processes. But suffers from the main disadvantage in terms environmental friendliness as are formed from non-renewable resources as well as cause environmental pollution which may lead to health hazards.
Polypropylene is the most commonly used synthetic polymer. When high strength is desired polyester is preferred. When exceptional chemical resistance is required high density polyethylene.
Construction of Geotextiles
On the basis of construction of geotextiles, it can be classified as woven and non-woven. The arrangement of fibers in case of non-woven geotextiles is either tilting or randomly patterned in a sheet. It has special application for controlled water flow in addition to stabilization of soil. It is widely used filtration processes, roads, asphalt pavement overlays, and erosion control.
Woven geotextile is made of two sets of parallel threads or strands systematically interweaved to form a thin and flat fabric. The strands used are either slit film which are flat or monofilament that are round. The pattern of weavings depends on where its application. When high strength property is needed, woven geotextiles is the best option.
As the geotextiles is gaining application day by day, researchers are making efforts to expand and improve its scope of utility. One of the outcomes of such efforts is Geosynthetics. Natural fibers are realized insufficient to meet the tougher demands. Thus, new composites with varying properties are now being introduced which has more durability then natural fiber based geotextiles. It includes geotextiles, geonets, geogrids, geocomposites, etc. All of these have various civil engineering applications like separation, reinforcement, protection, filtration, drainage, and moisture barriers.
These are either woven or non-woven. Woven geotextiles are produced by the interweaving of yarns. Non-woven geotextiles are needle punched, heat bonded, and chemically bonded.
Geogrids are meshes, form of a regular pattern of tensile elements. Geogrids are stiffer than geotextiles. The tensile strength can prevent the degree of differential loads by spreading the load over a broader area of soil. In this way geogrids are used to strengthen fill materials in geotechnical applications. Most of all polymetric materials can be used to produce geogrids through process of interlacing, extrusion or bonding.
These are basically impervious sheets produced from polymeric materials. Geomembranes cannot be manufactured from woven methods as it leaves voids which make it permeable. Geomembranes are produced from Pp, polyvinyl chloride (PVC), HOPE and PE. Each material gives different property to it, like PVC geomembranes are much flexible while Pp geomembranes are subjected to ultra violet (UV) radiations.
These are formed of combination of geotextiles, geogrids or geomembranes.
Geotextiles in India
Though this technology has gained attention in last few years but it still lags behind on application side. In 1985, the Central Board of Irrigation and Power (CBIP) identified geosynthetics as essential and relevant to India's need for infrastructure development.
In 1988 an institute named as Indian Geosynthetic Group to promote the awareness of geosynthetics. These efforts were further strengthened by Committee for International Geosynthetics Society- India (CiGSI), established in 1992. Over the two decades, more concentration is given to extensive information dissemination on the application of geosynthetics in the field of civil engineering in India was made through training programs and publications, both at national and international levels.
Other organizations like Jute Manufacturers Development Council in Kolkata and Coir Board in Bangalore are working on R&D projects to develop diversified geotextile products from coir and jute. Also Techfab India, a private player had undertaken an experiment on use of woven tape geotextiles as reinforcement in road construction.
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