Geotextile: what is it, types, characteristics, application

Technology does not stand still and very often new building or finishing materials appear. One of them is geotextile. This material has appeared quite recently, but it is already advised to use it in the construction of foundations, paths, roads, and landscaping. 

What is geotextile?

Under the name “geotextile”, a group of materials for various purposes, composition, production method and even type is hidden. Most often laid “on” or “in” the ground. The main component is synthetic threads or fibers. These materials are durable and relatively inexpensive. In some cases, fiberglass is used in production, sometimes natural materials are added to synthetics – cotton, wool. All this changes the properties and characteristics of the material, affects the area of ​​use.

Raw materials for the manufacture of geotextiles

The most common are polyester and polypropylene geosynthetics. Polypropylene has a denser structure, usually higher tensile strength, less fleecy in appearance. The disadvantage of polypropylene – it reacts poorly to ultraviolet light – becomes brittle. Therefore, as a covering material, it is better not to use it.

Polypropylene geotextile can have any color, as dyes can be added to the feedstock. The base is white, but more often the color changes due to additives that are added to obtain special properties. For example, in order for the geosynthetic to better tolerate sunlight.

Polyester geotextiles can be made from recycled materials (plastic bottles, etc.), which is why they usually cost less. Polyester threads are not long, so the material is more “hairy” and less tear-resistant. Color – any, but more often gray (Dornit brand), black, beige or brown, very rarely white. This is when it is made from virgin raw materials.

To summarize, polypropylene geotextiles should be used where high strength is needed – when constructing roads, paths, strengthening slopes, foundations, and dumps. Polyester material – suitable for beds, flower beds, slides and other landscape tricks.

Production methods and main properties

There are three different ways to make geotextiles:

• Geofabric – woven fabric made of synthetic threads with different weaving methods. By changing the thickness of the threads and their density, materials of different physical properties are obtained. Woven geotextile always has high tensile strength, therefore it is used where there may be mechanical loads – as a reinforcing, separating material. In some types of geotextile, the distance between the threads is rather big, which allows water to pass through easily, while at the same time preventing the materials from mixing. Such grades are ideal for drainage, can be used as a fraction separator.
  

• nonwoven fabric – made from short or long fibers of polyester or polypropylene connected in various ways. The connection method can be:
  • with the help of needles, geotextiles are called needle-punched;
  • during sintering from high temperature – thermally bonded;
  • using thin streams of water – hydraulically bonded.
    

• Knitted geotextile (knitting and sewing). This type of geosynthetics is produced only in Russia. Like any knitwear, it does not have as high strength as fabric, and its cost is higher than woven and non-woven types. Therefore, it is not very popular and cannot be used in places with high mechanical stress.

If the fibers are connected with needles or thin streams of water, the material looks like felt and has a fleecy surface. Thermally bonded – smoother. Different ways of connecting threads give geotextiles different properties, therefore, they are used in different areas.

If we compare all three types of non-woven geotextiles, the highest tensile strength is hydro-bonded, then thermally bonded and the “weakest” is needle-punched (needles still damage the fibers). Thermally bonded geotextiles are made from polypropylene, since polyester has a too high melting point, which dramatically increases its cost.

Impregnation and cladding

There are geotextiles with impregnations – latex, plasticizers, plastic compounds. They give the material additional properties, but almost completely deprive the filtering ability. This must be taken into account when choosing a material. For example, for a pond device, the lack of filtering capacity is a plus, for drainage – a minus.

Cladding is the re-bonding of an already finished canvas. The method of re-bonding is usually different from the primary. This gives the geotextile increased strength.

Application

Geotextiles have appeared recently, but are already used in various fields: in construction, landscape design, horticulture and horticulture, in the construction of footpaths, roads and runways. From the same material, only of low density, they make hygiene products, disposable medical clothing and underwear, and are used as rough upholstery for upholstered furniture. In general, the scope of geotextiles is very wide, and it is worth knowing which type is suitable for what purposes.

Depending on the density

The cost of geotextiles can vary significantly. As you already understood, the price is formed depending on the material and method of production. But density also plays an important role. The same materials, but with different densities, have different prices. How to find out which geotextile is needed in a particular case? You can roughly navigate by this division by density:

• Up to 60-80 g / m2 – agrotextile or covering material. It can be used for protection against germination of weeds (geotextile against weeds). Usually used non-woven polyester. To avoid confusion, they usually write like this – agrotextiles.
• A density of about 100 g / m² is for drainage, but geotextile is undesirable, as it quickly “silts up”.
• 150 g/m² and above – for separation of fractions: sand and crushed stone. You can take denser ones, but less is not worth it.
  

• Geotextiles with a weight of 100 to 200 g / m² are used for arranging footpaths, under paving slabs, under lawns, to create alpine slides, etc.
• With a density of 200 to 300 g / m², they are placed under general roads, under a car parking area.
• Above 300 g/m² – for motorways, runways, etc.

These are just approximate boundaries. It is always worth choosing geotextiles, paying attention to specific conditions. For example, for hard and rocky soil, such a characteristic as elongation at break will be important. The better the material stretches, the less the possibility of tearing when “fitting” irregularities and protrusions.

When choosing geotextiles for construction work and under roads / paths, parking lots, sites, see that there is a high breaking load (tensile strength). This characteristic can be neglected if you form uneven terrain, but there will be no load on them.

Depending on raw material and production method

Thermally bonded geotextiles have high tensile strength but only wick water away in the transverse direction. That is, it can be used in areas with low groundwater levels, on well-drained soils. It is good as a separator of different fractions and materials when arranging platforms, for footpaths made of various materials, suitable for changing the landscape. But all this – in areas with good drainage. It is not very suitable for drainage systems – water is not drained well enough.

Needle-punched is less durable, but water passes both in the longitudinal and transverse directions. It is suitable for laying on heavy soils that do not drain water well – loams, clays. The lack of strength can be compensated by laying a geogrid on the bottom – another type of geosynthetics. It will take on the main loads, and the geotextile will not allow the fractions to mix. This type can be used in drainage. The optimal density of drainage geotextile in terms of price / quality ratio is 200 g / m².

Woven geotextile is very durable, has high tensile strength. It is ideal for creating embankments, changing the landscape, creating retaining walls. And the load withstands without question. It is not recommended to use it in drainage – the gaps between the threads are quickly clogged with small particles, which worsens the drainage of water.

Примеры использования

The scope of geotextiles is wide, the following types are divided by purpose:

• Furniture. Not too dense material, which is used when lining upholstered furniture mattresses. Placed under the upholstery fabric, used to protect against dust during transportation.
• Drainage. It passes water well, thanks to its special structure it is not clogged with sand, silt, and retains a high filtering capacity for a long time.
  

• Garden or agrofibre. The main difference is that it is light-stable, that is, it does not react to ultraviolet light.
• Packing. A thin material used to make covers for packaging (for example, for shoes).
• Building. There are many different materials with different characteristics in this group. The main ones are tensile strength and degree of stretching.

When buying geotextiles, pay attention to the technical characteristics and purpose, and do not choose based only on price. If you put packaging, garden or furniture under the rubble, it will not work. Money will be wasted, as the material will tear over the course of months, and maybe even when backfilled.

Building

One of the main functions of geotextiles is to separate different layers. It can be different fractions, different materials.

• When constructing a foundation of any type, a gravel-sand cushion is laid out at the bottom of the pit. So that gravel and sand do not mix and perform their functions, geotextiles are laid between them. Its density is 160-180 g / m², but it can be more / less depending on specific conditions.
• Crushed stone is laid at the bottom of the pit when constructing roads, droshky, areas for cars, games, lawns. So that it does not mix with the soil, geotextiles are also placed under the rubble. The density is selected depending on the purpose of the object and the planned load. You also need to look at how important water drainage is.
  

• Drainage pipes are installed in the areas to divert water. They have small holes through which water seeps in, then enters the wells. So that the holes in the pipes are not clogged, they are wrapped with geotextile membranes. For better filtration, drainage pipes can be sprinkled with crushed stone. So that it does not mix with the soil, geotextiles are also used.

For all types of work, so that the materials do not “spread out” and do not mix, it is necessary to take the width of the geotextile in such a way that it rises to the entire thickness of the layer of bulk material and still wraps by 30-60 cm. With planned significant loads, twisting can be doing more will be more reliable. This applies to both construction work and landscaping, gardening, etc.

In the arrangement of the site

Work on the site involves a large amount of land work. In order for the results to please for a long time, geotextiles are used.

• When forming flower beds and beds, fertile soil is often imported. So that it does not mix with the “native” soil, the layers are separated by this material. It will also prevent the germination of plant roots from below.
• When forming hills, hills, to keep the shape, soil layers are laid with geotextiles.
• When creating artificial reservoirs, a geofabric is placed on the bottom. It is more durable, it will be better to reinforce the pit.
  

• Separation of different materials when creating rockeries, rock gardens, etc.
• The gaps between the beds can be covered with geosynthetics by pouring gravel on top. So the view is solid, and clean, and weeds do not germinate. During redevelopment, the geofabric is lifted, stones are removed. You can proceed to further work.
• For shelter from the sun, protection from frost, instead of mulch, agrofabric is placed on flower beds and beds, which is the least dense geotextile.

This is only a part of the processes in which this material can be used. There is still a rare application in our country – when creating green roofs.

Styling rules

In order for geotextiles to perform their functions, it is necessary to lay them correctly. First, let’s talk about what shouldn’t happen. First of all, you should not lay a geotextile with holes (mechanical damage). If it is not possible to replace the entire piece, lay a patch that is 50 cm larger than the size of the hole. Secondly, it cannot be dragged along. Thirdly, you can’t drive cars on the sent canvas.

The following are the general rules for laying geotextiles:

• Spread on a site previously cleared of stones, roots, construction debris. It is advisable to level the soil and, if necessary, compact. The presence of sharp protrusions or indentations is an additional risk of getting a break in this place.
  

• If several strips are laid, an “overlap” is necessary. The minimum – 30 cm – is done when arranging lawns, footpaths. When laying under roads, platforms for vehicles, etc., the minimum overlap is 50 cm.
• It is better to fasten the edges of adjacent strips. You can – sew, you can use tape. This will ensure that the edges do not wrap.

As mentioned earlier, the width of the canvas should be so large that it can be wrapped on a layer of rubble, earth, sand. And so that the “turn” was at least 30-50 cm.

There is one more question: which side to lay geotextiles correctly. There is no single answer, as it depends on the material. Some types can be laid on either side, others only on the smooth side or only on the fleecy side up. Specifically, which side to lay the geotextile is stated in the instructions for the material. If you buy not a whole roll, but only a part, check the rules for its installation with the seller.