Geotextile
Geotextiles are permeable fabrics which, when used in association with soil, have the ability to separate, filter, reinforce, protect, or drain. Typically made from polypropylene or polyester, geotextile fabrics come in three basic forms: woven (resembling mail bag sacking), needle punched (resembling felt), or heat bonded (resembling ironed felt).
Geotextile composites have been introduced and products such as geogrids and meshes have been developed. Overall, these materials are referred to as geosynthetics and each configuration—-geonets, geogrids, geotubes (such as TITANTubes) and others—-can yield benefits in geotechnical and environmental engineering design.[1]
History
Geotextiles were originally intended to be an alternative to granular soil filters. The original, and still sometimes used, term for geotextiles is filter fabrics. Work originally began in the 1950s with R.J. Barrett using geotextiles behind precast concrete seawalls, under precast concrete erosion control blocks, beneath large stone riprap, and in other erosion control situations.[2] He used different styles of woven monofilament fabrics, all characterized by a relatively high percentage open area (varying from 6 to 30%). He discussed the need for both adequate permeability and soil retention, along with adequate fabric strength and proper elongation and set the tone for geotextile use in filtration situations.
Applications
Geotextiles and related products have many applications and currently support many civil engineering applications including roads, airfields, railroads, embankments, retaining structures, reservoirs, canals, dams, bank protection, coastal engineering and construction site silt fences or geotube. Usually geotextiles are placed at the tension surface to strengthen the soil. Geotextiles are also used for sand dune armoring to protect upland coastal property from storm surge, wave action and flooding. A large sand-filled container (SFC) within the dune system prevents storm erosion from proceeding beyond the SFC. Using a sloped unit rather than a single tube eliminates damaging scour.
Erosion control manuals comment on the effectiveness of sloped, stepped shapes in mitigating shoreline erosion damage from storms. Geotextile sand-filled units provide a "soft" armoring solution for upland property protection. Geotextiles are used as matting to stabilize flow in stream channels and swales.[3][4]
Geotextiles can improve soil strength at a lower cost than conventional soil nailing.[citation needed] In addition, geotextiles allow planting on steep slopes, further securing the slope.
Geotextiles have been used to protect the fossil hominid footprints of Laetoli in Tanzania from erosion, rain, and tree roots.[5]
In building demolition, geotextile fabrics in combination with steel wire fencing can contain explosive debris.[6]
Coir (coconut fiber) geotextiles are popular for erosion control, slope stabilization and bioengineering, due to the fabric's substantial mechanical strength.[3]:App. I.E Coir geotextiles last approximately 3 to 5 years depending on the fabric weight. The product degrades into humus, enriching the soil.[7]
Design considerations
To use geotextiles to reinforce a steep slope, two components have to be calculated:
- the tension required for equilibrium
- the appropriate layout of the geotextile reinforcement.
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See also
References
- ↑ Koerner, R. M. (2012), Designing With Geosynthetics, 6th Edition, Xlibris Publishing Co., 914 pgs.
- ↑ Barrett, R. J., "Use of Plastic Filters in Coastal Structures," Proceedings from the 16th International Conference Coastal Engineers, Tokyo, September 1966, pp. 1048-1067
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- ↑ Renfrew, Colin and Paul Bahn, Archaeology. 4th ed. New York: Thames 2004. ISBN 978-0-500-28441-4.[page needed]
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