Application of Geotextiles in Civil Engineering

Application of Geotextiles:
Geotextiles are part of a wider group of civil engineering membranes called geosynthetics. They are extremely diverse in their construction and appearance. However, they are generally made from a limited number of polymers (polypropylene, polyethylene and polyester), and are mostly of five basic types: woven, heat bonded, needle punched, knitted and direct soil mixed fibers.  
 
Application of Geotextiles in Civil Engineering
 Geotextiles are used in civil engineering earthworks to reinforce vertical and steep banks of soil, to construct firm bases for temporary and permanent roads and highways, to line ground drains, so that the soil filters itself and prevents soil from filling up the drainpipes and to prevent erosion behind rock and stone facing on river banks and the coast. They have been developed since the mid 1970s, but the advent of knitted and composite fabrics has led to a revival in attempts to improve textile construction in a designed fashion. Better physical properties can be achieved by using more than one fabric and by utilizing the best features of each. Civil engineering works where geotextiles are employed can be classified into the following categories:
  1. Road Works
  2. Railway Works
  3. River Canals and Coastal Works: 
  4. Drainage
  5. Sports field construction
  6. Agriculture
Road Works: 
The basic principles of incorporating geotextiles into a soil mass are the same as those utilized in the design of reinforced concrete by incorporating steel bars. The fabrics are used to provide tensile strength in the earth mass in locations where shear stress would be generated. Moreover, to allow rapid dewatering of the roadbed, the geotextiles need to preserve its permeability without losing its separating functions. Its filtration characteristics must not be significantly altered by the mechanical loading.

Railway Works: 
The development of the railway networks is being greatly boosted by the present state of economy because of their profitability in view of increasing cost of energy and their reliability as a result of the punctuality of trains even in the adverse weather conditions. The woven fabrics or non-wovens are used to separate the soil from the sub-soil without impeding the ground water circulation where ground is unstable. Enveloping individual layers with fabric prevents the material wandering off sideways due to shocks and vibrations from running trains.

River Canals and Coastal Works: 
Geotextiles protect river banks from erosion due to currents or lapping. When used in conjunction with natural or artificial enrockments, they act as a filter. For erosion prevention, geotextile used can be either woven or nonwoven. The woven fabrics are recommended in soils of larger particle size as they usually have larger pore size. Nonwovens are used where soils such as clay silt are formed. Where hydrostatic uplift is expected, these fabrics must be of sufficiently high permeability.

Drainage: 
In civil engineering, the need for drainage has long been recognized and has created the need for filters to prevent in-situ soil from being washed into the drainage system. Such wash in soil causes clogging of the drains and potential surface instability of land adjacent to the drains. The use of geotextiles to filter the soil and a more or less single size granular material to transport water is increasingly seen as a technically and commercially viable alternative to the conventional systems. Geotextiles perform the filter mechanism for drainages in earth dams, in roads and highways, in reservoirs, behind retaining walls, deep drainage trenches and agriculture.

Sports field construction: 
Geotextiles are widely used in the construction of Caselon playing fields and AstroTurf. Caselon playing fields are synthetic grass surfaces constructed of light resistance polypropylene material with porous or nonporous carboxylated latex backing pile as high as 2.0 to 2.5 cm. AstroTurf is a synthetic turf sport surface made of nylon 6,6 pile fibre knitted into a backing of polyester yarn which provides high strength and dimensional stability. The nylon ribbon used for this is of 55 Tex. It is claimed that the surface can be used for 10 hr/day for about 10 years or more. Modern Astro Turf contains polypropylene as the base material.

Agriculture:
It is used for mud control. For the improvement of muddy paths and trails those used by cattle or light traffic, nonwoven fabrics are used and are folded by overlapping to include the pipe or a mass of grit.

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