Geotextile

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Geotextile sandbags protected the historic house Kliffende on Sylt island against storms, which eroded the cliffs left and right from the sandbag barrier. Kliffende, Island Sylt, 1999.jpg
Geotextile sandbags protected the historic house Kliffende on Sylt island against storms, which eroded the cliffs left and right from the sandbag barrier.
Geotextile sandbags can be 20 m long, such as those used for the artificial reef at Narrow Neck, Queensland. Mega sand container.jpg
Geotextile sandbags can be 20 m long, such as those used for the artificial reef at Narrow Neck, Queensland.

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).

Contents

Geotextile composites have been introduced and products such as geogrids and meshes have been developed. Geotextiles 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

A silt fence on a construction site. Silt fence EPA.jpg
A silt fence on a construction site.

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]



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

Related Research Articles

Geotechnical engineering Scientific study of earth materials in engineering problems

Geotechnical engineering, also known as geotechnics, is the branch of civil engineering concerned with the engineering behavior of earth materials. It uses the principles of soil mechanics and rock mechanics for the solution of its respective engineering problems. It also relies on knowledge of geology, hydrology, geophysics, and other related sciences.

Retaining wall artificial wall used for supporting soil between two different elevations

Retaining walls are relatively rigid walls used for supporting soil laterally so that it can be retained at different levels on the two sides. Retaining walls are structures designed to restrain soil to a slope that it would not naturally keep to. They are used to bound soils between two different elevations often in areas of terrain possessing undesirable slopes or in areas where the landscape needs to be shaped severely and engineered for more specific purposes like hillside farming or roadway overpasses. A retaining wall that retains soil on the backside and water on the frontside is called a seawall or a bulkhead.

Leachate Any liquid that, in the course of passing through matter, extracts soluble or suspended solids

A leachate is any liquid that, in the course of passing through matter, extracts soluble or suspended solids, or any other component of the material through which it has passed.

Geosynthetics

Geosynthetics are synthetic products used to stabilize terrain. They are generally polymeric products used to solve civil engineering problems. This includes eight main product categories: geotextiles, geogrids, geonets, geomembranes, geosynthetic clay liners, geofoam, geocells and geocomposites. The polymeric nature of the products makes them suitable for use in the ground where high levels of durability are required. They can also be used in exposed applications. Geosynthetics are available in a wide range of forms and materials. These products have a wide range of applications and are currently used in many civil, geotechnical, transportation, geoenvironmental, hydraulic, and private development applications including roads, airfields, railroads, embankments, retaining structures, reservoirs, canals, dams, erosion control, sediment control, landfill liners, landfill covers, mining, aquaculture and agriculture.

Pond liner

A pond liner is an impermeable geomembrane used for retention of liquids, including the lining of reservoirs, retention basins, hazardous and nonhazardous surface impoundments, garden ponds and artificial streams in parks and gardens.

Landscape products refers to a group of building industry products used by garden designers and landscape architects and exhibited at trade fairs devoted to these industries. It includes: walls, fences, paving, gardening tools, outdoor lighting, water features, fountains, garden furniture, garden ornaments, gazebos, garden buildings, pond liners.

Geocomposite

The basic philosophy behind geocomposite materials is to combine the best features of different materials in such a way that specific applications are addressed in the optimal manner and at minimum cost. Thus, the benefit/cost ratio is maximized. Such geocomposites will generally be geosynthetic materials, but not always. In some cases it may be more advantageous to use a nonsynthetic material with a geosynthetic one for optimum performance and/or least cost. As seen in the following, the number of possibilities is huge — the only limits being one's ingenuity and imagination.

A geomembrane is very low permeability synthetic membrane liner or barrier used with any geotechnical engineering related material so as to control fluid migration in a human-made project, structure, or system. Geomembranes are made from relatively thin continuous polymeric sheets, but they can also be made from the impregnation of geotextiles with asphalt, elastomer or polymer sprays, or as multilayered bitumen geocomposites. Continuous polymer sheet geomembranes are, by far, the most common.

Geogrid

A geogrid is geosynthetic material used to reinforce soils and similar materials. Geogrids are commonly used to reinforce retaining walls, as well as subbases or subsoils below roads or structures. Soils pull apart under tension. Compared to soil, geogrids are strong in tension. This fact allows them to transfer forces to a larger area of soil than would otherwise be the case.

Geosynthetic clay liner Low hydraulic conductivity geomembrane with bentonite encapsulated in a geotextile

Geosynthetic clay liners (GCLs) are factory manufactured hydraulic barriers consisting of a layer of bentonite or other very low-permeability material supported by geotextiles and/or geomembranes, mechanically held together by needling, stitching, or chemical adhesives. Due to environmental laws, any seepage from landfills must be collected and properly disposed of, otherwise contamination of the surrounding ground water could cause major environmental and/or ecological problems. The lower the hydraulic conductivity the more effective the GCL will be at retaining seepage inside of the landfill. Bentonite composed predominantly (>70%) of montmorillonite or other expansive clays, are preferred and most commonly used in GCLs. A general GCL construction would consist of two layers of geosynthetics stitched together enclosing a layer of natural or processed sodium bentonite. Typically, woven and/or non-woven textile geosynthetics are used, however polyethylene or geomembrane layers or geogrid geotextiles materials have also been incorporated into the design or in place of a textile layer to increase strength. GCLs are produced by several large companies in North America, Europe, and Asia. The United States Environmental Protection Agency currently regulates landfill construction and design in the US through several legislations.

Regarding the civil engineering of shorelines, soft engineering is a shoreline management practice that uses sustainable ecological principles to restore shoreline stabilization and protect riparian habitats. Soft Shoreline Engineering (SSE) uses the strategic placement of organic materials such as vegetation, stones, sand, debris, and other structural materials to reduce erosion, enhance shoreline aesthetic, soften the land-water interface, and lower costs of ecological restoration.

Mechanically stabilized earth

Mechanically stabilized earth is soil constructed with artificial reinforcing. It can be used for retaining walls, bridge abutments, seawalls, and dikes. Although the basic principles of MSE have been used throughout history, MSE was developed in its current form in the 1960s. The reinforcing elements used can vary but include steel and geosynthetics.

Landslide mitigation refers to several man-made activities on slopes with the goal of lessening the effect of landslides. Landslides can be triggered by many, sometimes concomitant causes. In addition to shallow erosion or reduction of shear strength caused by seasonal rainfall, landslides may be triggered by anthropic activities, such as adding excessive weight above the slope, digging at mid-slope or at the foot of the slope. Often, individual phenomena join together to generate instability over time, which often does not allow a reconstruction of the evolution of a particular landslide. Therefore, landslide hazard mitigation measures are not generally classified according to the phenomenon that might cause a landslide. Instead, they are classified by the sort of slope stabilization method used:

Landfill liner

A landfill liner, or composite liner, is intended to be a low permeable barrier, which is laid down under engineered landfill sites. Until it deteriorates, the liner retards migration of leachate, and its toxic constituents, into underlying aquifers or nearby rivers, causing spoliation of the local water.

Cellular confinement

Cellular confinement systems (CCS)—also known as geocells—are widely used in construction for erosion control, soil stabilization on flat ground and steep slopes, channel protection, and structural reinforcement for load support and earth retention. Typical cellular confinement systems are geosynthetics made with ultrasonically welded high-density polyethylene (HDPE) strips or novel polymeric alloy (NPA)—and expanded on-site to form a honeycomb-like structure—and filled with sand, soil, rock, gravel or concrete.

A geonet is a geosynthetic material similar in structure to a geogrid, consisting of integrally connected parallel sets of ribs overlying similar sets at various angles for in-plane drainage of liquids or gases. Geonets are often laminated with geotextiles on one or both surfaces and are then referred to as drainage geocomposites. They are competitive with other drainage geocomposites having different core configurations.

In-Situ Capping (ISC) of Subaqueous Waste is a non-removal remediation technique for contaminated sediment that involves leaving the waste in place and isolating it from the environment by placing a layer of soil and/or material over the contaminated waste as to prevent further spread of the contaminant. In-situ capping provides a viable way to remediate an area that is contaminated. It is an option when pump and treat becomes too expensive and the area surrounding the site is a low energy system. The design of the cap and the characterization of the surrounding areas are of equal importance and drive the feasibility of the entire project. Numerous successful cases exist and more will exist in the future as the technology expands and grows more popular. In-situ capping uses techniques developed in chemistry, biology, geotechnical engineering, environmental engineering, and environmental geotechnical engineering.

Final cover is a multilayered system of various materials which are primarily used to reduce the amount of storm water that will enter a landfill after closing. Proper final cover systems will also minimize the surface water on the liner system, resist erosion due to wind or runoff, control the migrations of landfill gases, and improve aesthetics.

Robert M. Koerner was an American engineer and academic. He was Professor Emeritus at Drexel University and Director Emeritus of the Geosynthetic Institute. He died on December 1, 2019.

Ronald Kerry Rowe, FRS, FRSC, FREng is a Canadian civil engineer of Australian birth, one of the pioneers of geosynthetics.

References

  1. 1 2 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. 1 2 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. [ page needed ]
  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.

Further reading