What is Geotextile Membrane used for?

A geotextile is a permeable synthetic fabric used with soil, rock or other ground materials in civil engineering. Geotextiles are one family of geosynthetics. They are often associated with high-standard, all-season roads, but they are used just as much under low-standard rural and forest roads.

Geotextile membranes are fabrics laid in the ground to separate, filter, drain or protect. They turn up in everything from landscaping to major construction, but most often in drainage and civil engineering work. In the UK they are often just called “Terram”, after a brand of geotextile, the way a vacuum cleaner gets called a “hoover”.

Their wide use comes largely from the fact that they do not biodegrade. Geotextiles are textiles, but not in the traditional sense: instead of organic fibres like cotton, wool or silk, they are made of synthetic fibres formed into a porous fabric, woven, or non-woven needle-punched felt. Water passes through them, to different degrees depending on the product.

Different Uses for Geotextile Membranes

Geotextiles are porous fabrics made from synthetic polymers: mainly polypropylene and polyester, and less often polyethylene, nylon, PVC or blends of these.

They are made in thicknesses from about 10 to 300 mils (1 mil = 1/1000 inch, so roughly 0.25 to 7.5 mm), in widths up to 30 ft and roll lengths up to 2000 ft. Their permeability ranges from that of coarse gravel to that of fine sand. Woven geotextiles are woven from monofilament, multifilament or slit-film yarns; non-wovens are made by bonding fibres mechanically (needle-punching) or thermally, then calendering through rollers in some products. Both are strong and durable even in aggressive soils. Polypropylene resists nearly the whole pH range found in soils, while polyester is normally limited to about pH 3 to 9, because it degrades in strongly alkaline ground such as lime-treated soil or next to fresh concrete.

Separating Types of Aggregates

A geotextile keeps two soils or aggregates apart that you don’t want to mix, particularly where water flows through them. When fine soil sits against coarse material, rain and seepage wash the fine particles into the gaps. The ground then becomes uneven and can sink as the fines migrate down between the larger particles.
A geotextile stops the fine particles moving, even in heavy rain. It also keeps the drainage paths in the coarser layer from clogging with fines, which reduces standing water and flooding after rain.

Protecting Against Erosion

In coastal protection, geotextiles go under the defence itself (rock armour, gabions, revetment blocks) to prevent erosion of the soil beneath. The fabric has to be strong enough not to be torn or punctured as stone and gabions are placed on it, yet permeable enough to let water drain through freely. Heavy-duty grades are normally specified for this.

Weed Membranes

Weed control fabrics are another kind of geotextile membrane. They let the plants you want grow while blocking weeds from coming up through the soil, so the plants do not compete with weeds for space and nutrients.

At landfills, geotextiles are used alongside geomembranes and clay liners as protection and drainage layers in the barrier that keeps leachate from contaminating the surrounding ground.
Ocean Global is a geosynthetics manufacturer and supplier in India, supplying geotextiles, geogrids, geomembranes, geocomposites and geonets, with more than 21 years of experience in the field.

Some Interesting facts about Geotextiles

Geotextiles are synthetic fibres made into a porous fabric that does not biodegrade, which is why they are used in so many applications in the ground around us.

Geotextiles were first used as an alternative to graded soil filters. Depending on how they are made, they separate, reinforce, filter, protect or drain, and they are used mainly in civil and environmental engineering.

1. History of Geotextile

Geotextiles were originally called filter fabrics. In the late 1950s, Robert J. Barrett began using them in erosion control work in the USA: behind precast concrete seawalls, under large stone riprap and beneath precast concrete erosion control blocks. He used woven monofilament fabrics with 6 to 30% open area. The combination of permeability, soil retention, durability and elongation made these fabrics suitable for filtration.

The idea is much older. Woven reed and grass mats mixed into soil were used to stabilise roads in ancient times, and excavations of Egyptian sites have found linen and grass mats used in construction.

2. Features of Geotextile 

A geotextile has to let water and air pass between soil layers: rainwater has to soak in, excess water has to drain out without carrying soil with it, and in landscaping roots have to grow through. That calls for the following properties:

• Physical features: specific gravity, mass per unit area, thickness and stiffness.
• Mechanical features: tensile strength, elongation, tear, burst and puncture resistance, flexibility, and friction against soil.
• Hydraulic features: porosity, permittivity (flow across the fabric), transmissivity (flow along it), apparent opening size, and resistance to biological, hydrolytic, UV, chemical and mechanical degradation.
• Endurance features: abrasion resistance, creep behaviour and long-term resistance to clogging.

3. Categories of Geotextile 

There are many kinds of geotextile, but three main types: woven, non-woven and polyspun.

Woven Geotextile

Woven geotextiles are used mainly for separation and reinforcement. They have high tensile strength and low elongation, which suits them to road construction and other load-bearing uses. They are permeable, but less so than non-wovens, so they are not the first choice for drainage.

Non-woven Geotextiles

Non-woven geotextiles are felt-like fabrics. They have lower tensile strength and stretch more than wovens, but they filter and drain well, so they are used where separation, drainage or filtration matters most: under hardscape, in drains and in erosion control.

Polyspun Geotextiles

Polyspun (spunbonded) geotextiles are lightweight non-wovens used mainly for separation. They are permeable, so they let water drain, but they add no reinforcement. They are typically used as weed barriers.

4. Fibers Used For Geotextiles

Geotextiles are made from both natural and synthetic fibres, depending on the job.

Natural geotextiles, such as jute and coir nets, paper strips, wood shavings or wool mulch, are used where the fabric is meant to biodegrade fairly quickly, for example to hold soil against erosion until vegetation takes hold.

Most geotextiles are synthetic. The 4 main polymers are polyester, polyethylene, polyamide and polypropylene.

5. Applications of Geotextiles

Put simply, a geotextile is a textile used in or under the soil: under streets, ponds, pipelines and embankments, and as reinforcement. In every application it does one or more of six jobs: separation, filtration, reinforcement, drainage, protection and containment.

Application in Dam Construction

Geotextiles are widely used in embankment dams. Their use is limited in some critical locations because they can be damaged during installation and can clog, so they should be designed and approved by experienced dam engineers who consider both design and construction.

In dams, geotextiles serve these functions:

Filtration & Drainage

Geotextiles can filter seepage through and under embankment dams, controlling the movement of soil particles carried by the seepage.

Separation and protection

The most common use in dams is as a separator between natural materials, so that one zone of the embankment does not contaminate the next.

Surface Stabilization

Geotextiles are used under armour systems to reduce erosion on dam slopes and to control sediment during dam construction.

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