The geotextile is made of high-strength fiber bundles and non-woven fabrics. The technology is that the fiber bundles are arranged in a straight way to give full play to the force of the yarn. Under the non-woven fabric pad, warp knitting technology will wind and bind the non-woven fabric, so that the fiber bundle non-woven fabric is consolidated together, which not only maintains the anti filtration of the non-woven fabric, but also has the strength of the woven fabric. The finished geotextile is cloth like, with a width of 4-6 meters and a length of 50-100 meters.
Geotextiles are made up of polymers such as polyester or polypropylene. They are divided into 3 categories on the basis of the way they are prepared :
1. Woven Fabric Geotextile
The common geotextile is woven type, which is made by using technology similar to weaving ordinary clothing textiles. This type has the characteristic appearance of two sets of parallel threads or yarns. The yarn running along the length is called warp and the one perpendicular is called weft.
2. Non-woven Geotextile
Non-woven geotextiles are manufactured from either continuous filament yarn or short staple fiber. The bonding of fibers is done using thermal, chemical or mechanical techniques or a combination of techniques.
3. Knitted Geotextile
Knitted geotextiles are manufactured by the process of interlocking a series of loops of yarn together. All of the knitted geosynthetics are formed by using the knitting technique in conjunction with some other method of geosynthetics manufacture, such as weaving.
Apart from these three geotextiles, other geosynthetics used are geonets, geogrids, geo-cells, geomembranes, geocomposites, etc. each having their own distinct features and uses for special applications.
Functions of Geotextiles
Different soil structures are separated with geotextile to form a stable interface, so that the structures of each layer are separated and play their own characteristics and overall role as required. For example, by separating fine subgrade soil from the aggregates of the base course, the geotextile preserves the drainage and the strength characteristics of the aggregate material.
The equilibrium of geotextile-to-soil system that allows for adequate liquid flow with limited soil loss across the plane of the geotextile. Porosity and permeability are the major properties of geotextiles which involve infiltration action.
Introduction of geotextile in the soil increases the tensile strength of the soil the same amount steel does in concrete. The strength gain in soil due to the introduction of geotextile is by the following 3 mechanisms :
• Lateral restraint through interfacial friction between geotextile and soil/aggregate.
• Forcing the potential bearing surface failure plane to develop an alternate higher shear strength surface.
• Membrane type of support of the wheel loads.
Geotextile and composite geotechnical materials can prevent the leakage of liquid and the volatilization of gas, and protect the environment or the safety of buildings. A layer of non-woven geotextile is impregnated in between existing and new asphalt layers. The geotextile absorbs asphalt to become a waterproofing membrane minimising vertical flow of water into the pavement structure.