Geotextile

Geotextiles are versatile permeable fabrics that, when used in conjunction with soil, can effectively perform multiple functions, including separation, filtration, reinforcement, protection, and drainage. Typically crafted from polypropylene or polyester, geotextile fabrics are available in two primary forms: woven, which resembles traditional mail bag sacking, and nonwoven, which resembles felt.

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. 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.

Definition

A geotextile or geofabric is a permeable and flexible fabric made ofsynthetic fibers, mainlypolypropyleneandpolyester, which can be manufactured in anon-woven(non-woven) orwoven(woven) form depending on its use or function to be performed.

Geotextiles were originally intended to be a substitute for granular soil filters. Geotextiles can also be referred to as filter fabrics. In the 1950s, R.J. Barrett began working using geotextiles behind precast concrete seawalls, under precast concrete erosion control blocks, beneath large stone riprap, and in other erosion control situations. 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 tone setting for geotextile use in filtration situations.

They are generally manufactured from 90 to 400g/m² and their main applications are: erosion control, soil reinforcement, filtration and separation between layers of materials, providing a drainage layer and protection ofgeomembranes.

The geotextile market is extremely extensive, and geotextiles are manufactured in theUnited States, Canada, Europe, and Asia. Most of the product consumed in Mexico is manufactured by local companies.

A large number of geotextiles are manufactured with the most varied characteristics:

Some geotextiles are a few millimeters thick and have a permeable structure. These can be used as drains.

Other geotextiles are impermeable, these can be used to waterproofcanalsorreservoirs, either by covering them with a layer of soil or by using them to increase the impermeability ofcementlinings.

Some geotextiles are tensile resistant and can be used to increase soil resistance to landslides, resulting in the formation of geotextile-structured slopes.

Types

In synthetic products, there are two main families: woven products and non-woven products. In the latter, a distinction is made between needle-punched non-wovens and thermally bonded non-wovens.

The main role of synthetic geotextiles is to create a permeable physical barrier between natural ground and the materials selected for the construction of structures or roads. This barrier allows water to pass through and prevents the finest parts of the natural ground from migrating and modifying the structure of the input materials (plant roots, for example). This is called a separation or filtration geotextile. This type of geotextile is also used to protect drains and drainage structures, to prevent them from clogging and therefore contribute to their sustainability.

There are also reinforcing geotextiles used in road and railway platform bases and to reinforce reinforced embankment masses.

Geotextiles made from biodegradable natural fibers are used for controlling erosion on slopes and banks as well as for mulching flower beds and hedges.

Basic concepts

Fabrics: the fibers are oriented in two directions (warpandweft).

Nonwovens: the fibers that make up the geotextile are arranged randomly.

Continuous fiber: The fibers of the nonwoven geotextile belonging to the final product are countless.

Calendered: The bond between the fibers of the nonwoven geotextile is a thermal bond where the fibers pass through two calenders.

Punching + Heat-sealing: the union between the fibers of the nonwoven geotextile is a mechanical union using needles that enter and exit at high speed, with subsequent heat fusion creating continuity of fibers in the final product.

Continuous filaments: The filaments of the nonwoven geotextile that make up the final product are countless.

Staple fibers: the geotextile filaments that make up the final product have specific lengths.

Needled, punched or needle-punched: the filaments of the nonwoven geotextile are joined by mechanical bonding through needles arranged at the bottom and top of the filament web that enter and exit the web at high speed, cohering and interlacing the filaments.

Heat-set: the filaments are joined together by heat through a thermofusion process.

Geotextiles according to their manufacturing method

Fabrics: The mesh is woven with fibers in two directions (warp and weft). They can be:

a. Flat fabrics.

b. Knitted.

Nonwovens: Randomly woven fibers bonded by mechanical, thermal, or chemical processes to a continuous filament. They can be:

a. Needled.

b. Heat-sealed.

Mixed: The mesh is composed of chopped fibers. They can be:

a. Needled.

b. Needle-punched and heat-sealed.

Types of geotextiles

Staple-stapled geotextiles not subjected to the thermofusion process are materials with minimal mechanical resistance, since there is no union between their elements and they are not linked together, they can be easily perforated by applying a perpendicular force since their fibers open without offering resistance, at the same time the tensile stresses separate them, unlinking them.

Heat-sealed geotextiles are not thick; their elongation is lower than that of needle-sealed geotextiles.

Continuous filament needle-stitched geotextiles, or needle-stitched and heat-welded geotextiles, have high mechanical resistance to prevent breakage. They also have adequate thicknesses to fulfill theirdrainage function, anti-weed geotextilefunction, geomembrane protection function and cushioning effect function.

Properties of geotextiles

Geotextile is a mesh composed of synthetic fibers whose main functions are based on its mechanical resistance to perforation and traction, and its drainage capacity.

They are used in the construction of sub-bases for roads and railways, in dams, they prevent possible erosion, they perform drainage functions in canals,retaining walls, etc.

Geotextiles are used to separate soils of different granulometries, stabilizing the ground and protecting waterproofing sheets.

Geotextiles can perform different functions:

Separation

The separation prevents contact between two surfaces with different physical properties, which prevents their mixing and contamination, although it allows the free flow of liquids by filtering them through the geotextile. This can be between two different layers of added soil or between natural and added soil.

To prevent mixing of materials, it must withstand the static and dynamic loads of the filler material and traffic during placement, as well as retain purposes. Polypropylene keeps it stable against the alkalinity of thecementand inert to the various chemical elements present in thesoil.

The following aspects must be taken into account in the separation function:

Tensilestrength.

Punchingresistance.

Elongation at break.

Dynamic cone free fall drilling.

Effective pore opening.

Thickness of the geotextile.

Filtration

Filtration is the property of a material that retains certain particles when subjected to hydrodynamic forces while allowing fluids to pass through. The filter's function must ensure its hydraulic stability.

The following parameters must be taken into account in this filtration function:

Permeability.

Effective pore opening.

Thickness of the geotextile.

Drainage

Drainage is the process by which a fluid (liquid or gas) is transferred from one location to another, evacuating it. This eliminates the fluid by evacuation within the thickness of the geotextile without washing away the ends..

The following parameters must be taken into account in this drainage function:

Permeability in the geotextile plane

Thickness of the geotextile

Booster

Geotextile reinforcement is achieved through the properties of certain geotextiles, improving their mechanical properties and reducing the level of loads on the ground because it homogenizes the loads over a large surface area.

We consider two types of reinforcements:

Tensilereinforcement, eliminating overturning forces. For example, in retaining walls, by inserting geotextile material into the wall.

Soil stabilization by particle confinement, evacuating the contained water through suppression.

The following parameters must be taken into account in this reinforcement function:

Deformation curve

Mechanical resistance totraction,punchingand tearing.

Creep, fatigue, and friction against the ground. It also helps improve the soil's support quality.

Protection

The protective function prevents the geotechnical system from deteriorating. The geotextile acts by protecting waterproof geomembranes, thereby preventing mechanical damage fromabrasionor puncture.

The following parameters must be taken into account in this protection function:

Punching resistance.

Dynamic cone free fall drilling.

Thickness (cushion effect for geomembrane protection).

Geotextile related products

Geotextile-related products are defined by NF EN ISO 10318 as flat, permeable, polymer-based materials (synthetic or natural) that do not meet the definition of a geotextile, i.e. they are neither woven, non-woven, nor knitted. Related products include geogrids, geonets, geomattresses, cellular geosynthetics, geobands, and geospacers.

Geogrid 

flat polymer -based structure, consisting of an open and regular network of tensile-resistant elements which can be assembled by extrusion, by gluing or by interlacing; the openings of which have dimensions greater than those of the constituents.

Geonet 

geosynthetic consisting of sets of parallel and superimposed rods fully connected to other similar sets at varying angles.

Geomattresses, geomats 

three-dimensional structure, consisting of filaments, and/or other elements (synthetic or natural) based on polymer, mechanically, and/or thermally and/or chemically and/or otherwise bonded. This three-dimensional structure can also be filled with coconut fibers or synthetic fibers.

Geoalveolar, geocell 

three-dimensional honeycomb or similar structure, permeable, polymer-based (synthetic or natural), consisting of strips most often made of perforated and textured HDPE welded together two by two. Used for the containment of materials with low characteristics for the creation of road or parking base, supports, bank and slope protection.

Geobanding 

polymer-based material in the form of a strip with a width not exceeding 200 mm, used in contact with the ground and/or other materials in the fields of geotechnics and civil engineering.

Geospacer 

three-dimensional polymer-based structure designed to create an air space in the soil and/or other materials, in the fields of geotechnical and civil engineering.

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 to form a geotextile tube. Geotextiles can also serve as components of other geosynthetics such as the reinforcing material in a bituminous geomembrane. 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.

Geotextiles can improve soil strength at a lower cost than conventional soil nailing. 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.

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

Coir (coconut fiber) geotextiles are popular for erosion control, slope stabilization and bioengineering, due to the fabric's substantial mechanical strength.: App. I.E  Coir geotextiles last approximately 3 to 5 years depending on the fabric weight. The product degrades into humus, enriching the soil.

Global warming

Glacial retreat

Geotextiles with reflective properties are often used in protecting the melting glaciers. In north Italy, they use Geotextiles to cover the glaciers for protection from the Sun. The reflective properties of the geotextile reflect the sun away from the melting glacier in order to slow the process. However, this process has proven to be more expensive than effective.

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.

Requirements

Geotextiles are needed for specific requirements, just as anything else in the world. Some of these requirements consist of polymers composed of a minimum of 85% by weight poly-propylene, polyesters, polyamides, polyolefins, and polyethylene. 

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