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. Geotextiles are able to withstand many things, are durable, and are able to soften a fall if someone falls down. Overall, these materials are referred to as geosynthetics and each configuration—geonets, geosynthetic clay liners, geogrids, geotextile tubes, and others—can yield benefits in geotechnical and environmental engineering design.

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.[5] 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.[6]

In building demolition, geotextile fabrics in combination with steel wire fencing can contain explosive debris.[7]

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.[8]


Portland’s Water Adaptation Initiatives with Geotextile

In many of the world's big cities, the lack of impervious surfaces is leading to water pollution, run-off, and in cases of heavy rainfall, major flooding that is affecting people's homes, businesses, and livelihoods. The city of Portland lies on the Willamette river basin, and is no stranger to this issue. Before mass development, there were original wetlands and floodplains that helped filter and naturally drain water from large rain storms or overflowing banks. However, suburbanization and urban sprawl have accelerated the construction of more impervious surfaces which have covered, drained, and filled the floodplains for transportation, agriculture, and development.[9]

Environmental Services, a government agency that manages Portland's wastewater and stormwater infrastructure, [10] recognized this phenomenon, and in 2004, partnered with the neighborhood of Westmoreland in attempt to solve this problem with road fabric, a “permeable woven geotextile that allows water on the surface to flow through the gravel to the soil beneath, but is strong enough to reduce rutting and restrict subgrade soil particles from working up into the gravel surface”.[11] They paved 1000 feet of street surface with interlocking blocks made of concrete which allow water to filtrate towards the ground through the spaces between the blocks. They then filled with gaps with fine sediment on top of a stronger base of rock. Geotextile fabric was then placed below the more solid layer to reduce pollutant flow. This reduced the amount of stormwater goes through the sewer system and the run-off that would eventually be discharged into the river.

On a larger scale, geotextile is paired with downspout disconnection, monitoring devices, vegetated infiltration areas, constructed wetlands, increased tree canopy, ecoroofs, green streets, and permeable pavement to create a wider sustainable system to work with water, not against it. The Westmoreland pilot has been repeated in several other areas with these different mechanisms, alternating between a center strip of standard asphalt and permeable pavement in both curb lanes. If applicable, this system will allow stormwater to be absorbed, filtered, and cleaned before recharging groundwater city-wide, and may become the norm if policy allows. [12]

Design methods

While many possible design methods or combinations of methods are available to the geotextile designer, the ultimate decision for a particular application usually takes one of three directions: design by cost and availability, design by specification, or design by function. Extensive literature on design methods for geotextiles has been published in the peer reviewed journal Geotextiles and Geomembranes.

See also

References

  1. Müller, W. W.; Saathoff, F. (2015). "Geosynthetics in geoenvironmental engineering". Science and Technology of Advanced Materials. 16 (3): 034605. Bibcode:2015STAdM..16c4605M. doi:10.1088/1468-6996/16/3/034605. PMC 5099829. PMID 27877792.
  2. Barrett, R. J., "Use of Plastic Filters in Coastal Structures," Proceedings from the 16th International Conference Coastal Engineers, Tokyo, September 1966, pp. 1048–1067
  3. Dane County Department of Land and Water Resources (2007). Dane County Erosion Control and Stormwater Management Manual (PDF) (Report). Madison, WI. Retrieved 2010-02-09.
  4. Massachusetts Department of Environmental Protection (2003). Massachusetts Erosion and Sediment Control Guidelines for Urban and Suburban Areas (PDF) (Report). Boston, MA. pp. 73–74.
  5. Morgan, Roy P.C.; Rickson, R.J. (2011). Slope Stabilization and Erosion Control: A Bioengineering Approach. London: Taylor & Francis. ISBN 9780419156307.
  6. Renfrew, Colin and Paul Bahn, Archaeology. 4th ed. New York: Thames 2004. ISBN 978-0-500-28441-4.
  7. WGBH Boston (December 1996). "Interview with Stacey Loizeaux". NOVA Online. Public Broadcasting Service. Retrieved 2009-04-29. Other preparatory operations involve covering/wrapping the columns first with chain link fences and then with geotextile fabric, which is very puncture resistant and has a very high tensile strength. It allows the concrete to move, but it keeps the concrete from flying. The chain link catches the bigger material and the fabric catches the smaller material from flying up and out.
  8. Richards, Davi (2006-06-02). "Coir is sustainable alternative to peat moss in the garden". Garden Hints. Corvallis, OR: Oregon State University Extension Service. Retrieved 2013-03-06.
  9. "Floodplains In Portland | Flood Information | The City of Portland, Oregon". www.portlandoregon.gov. Retrieved 2019-11-21.
  10. "PortlandOregon.gov | The City of Portland, Oregon". www.portlandoregon.gov. Retrieved 2019-11-21.
  11. https://www.portlandoregon.gov/. Retrieved 2019-11-21. Missing or empty |title= (help)
  12. "Pervious Pavement Projects | Pervious Pavement | The City of Portland, Oregon". www.portlandoregon.gov. Retrieved 2019-11-21.

Further reading

  • Koerner, R. M. (2012). Designing With Geosynthetics, 6th Edition, Xlibris Publishing Co., 914 pgs.
  • Koerner, R. M., Editor (2016). Geotextiles: From Design to Applications, Woodhead Publishing Co., AMsterdam, 617 pgs.
  • John, N. W. M. (1987). Geotextiles, Blackie Publishing Ltd., Glasgow, 347 pgs.
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