Geotextiles – Types | Properties | Use

Geotextiles are permeable synthetic textile materials used in civil engineering for filtration, drainage, separation, reinforcement, and stabilization — applied to roads, drains, land reclamation, and harbor works. Global production reaches 1,400 million m² annually, valued at approximately $1,050 million USD. Geotextiles are manufactured primarily from polypropylene, polyester, polyamides, polyolefins, or polyethylene (minimum 85% by weight), making them highly resistant to bio-degradation, and are available in woven and nonwoven forms that allow liquid to flow across and within their thickness while performing at least one of four discrete functions: separation, reinforcement, filtration, and drainage.

What Is Geotextile?

The Textile Institute defines geotextiles as —

“Any permeable textile material used for filtration, drainage, separation, reinforcement and stabilization purposes as an integral part of civil engineering structures of earth, rock or other constructional materials.”

The Main Types of Geotextile

Based on manufacturing procedures, geotextiles fall into four categories. The table below compares their key characteristics:

1. Woven Geotextiles

Woven geotextiles are manufactured on looms with rectilinear construction that varies based on component fiber type and weave structure. These fabrics exhibit excellent stiffness properties, absorbing stress with minimal mechanical elongation—making them ideal for reinforcement applications where dimensional stability is critical.

Woven geotextiles serve two primary weight categories:

• Lighter Weight Forms (100–500 g/m²): Filters, soil separators, and erosion control textiles with percentage open area ranging from 6% to 30%.
• Heavier Weight Forms (500–2000 g/m²): Embankment support and major reinforcement applications requiring high tensile strength.

2. Knitted Geotextiles

Knitted geotextiles are primarily warp-knitted textiles produced from warp-knitting machines. They produce fine filter fabrics, medium meshes, and large-diameter soil reinforcement fabrics. Their main advantage lies in providing high strength at a relatively low cost.

These fabrics are primarily used for soil reinforcement and embankment support applications.

3. Heat-Bonded Non-Woven Geotextiles

Heat-bonded non-woven geotextiles are produced through a three-step manufacturing process:

1. Continuous fine filaments are laid randomly onto a moving belt
2. The filaments pass between heated roller systems
3. Hot rollers partially melt the filaments, creating coherence and strength through thermal bonding

This process produces thin sheets suitable for lightweight applications. The thermal bonding method limits achievable thickness to products under 5mm.

4. Needle-Punched Non-Woven Geotextiles

Needle-punched non-woven geotextiles are produced by passing blended webs of continuous or staple filaments through banks of several reciprocating barbed needles. The needles create entanglements among the filaments, providing coherence and strength through mechanical bonding rather than thermal treatment.

This process achieves thicknesses up to 10mm and weights up to 2,000 g/m²—significantly heavier than heat-bonded alternatives. The resulting fabric offers superior drainage characteristics and is widely used in filtration applications.

Geotextiles As Geosynthetics

Geotextiles are one of the two largest geosynthetic groups. Geosynthetics are defined as synthetic membranes used in contact with or within soil. Seven primary geosynthetic types exist:

1. Geomembranes
2. Geogrids
3. Geonets
4. Geocomposite
5. Geomat
6. Geocell
7. Biomat and Bionet

1. Geomembranes

Geomembranes are synthetic or bituminous manufactured sheets functioning as liquid-vapor barriers. They exhibit extremely low permeability (typically less than 1 × 10⁻¹² m/s), making them essential for landfills and waste containment facilities where seepage prevention is critical.

Geomembranes are classified into two main types:

Calendered Geomembranes

A molten viscous formulation of polypropylene or polyvinyl chloride is passed and flattened between counter-rotating rollers at temperatures typically ranging from 150°C to 200°C.

Extruded Geomembranes

Molten polymer chips are forced through a die using a screw extruder, then carried by a conveyor belt and pulled by a nip roller positioned above the die.

2. Geogrids

Geogrids are manufactured sheets (single or multi-layer) with a regular network of integrally associated parts. They are produced by extruding and stretching high-density polyethylene or polypropylene, or by weaving/kneading polyester yarns that are then coated. Their larger apertures make them particularly suitable for reinforcement materials.

Five types of geogrids are available: unidirectional, bi-directional, extruded, woven, and bonded. Tensile strength ranges from 20 kN/m to over 100 kN/m depending on the type and orientation.

1. Undirectional
2. Bi-directional
3. Extruded
4. Woven
5. Bonded

3. Geonets

Geonets are manufactured from polyethylene. A net matrix forms when molten polymer is extruded through slits in counter-rotating dies. Geonets are primarily used in drainage systems where their open structure facilitates water flow, though they lack sufficient strength for reinforcement applications.

4. Geocomposite

Geocomposites combine two or more geosynthetic materials—such as geotextile-geogrid, geotextile-geomembrane, or geogrid-geomembrane combinations—to leverage the advantages of each component. A common geocomposite drain uses 200 g/m² mass per area of polypropylene staple fibers.

5. Geomat

Geomat consists of an irregular network of fibers, yarns, or filaments manufactured in sheet form. These materials have higher open area than other geosynthetics, making them particularly effective for erosion control and drainage applications.

6. Geocell

Geocell comprises a regular open network of connected stripes linked by extrusion or adhesion. This three-dimensional cellular structure confines soil and provides effective load distribution for slope stabilization and retaining applications.

7. Biomat and Bionet

Biomat and bionet are natural and biodegradable manufactured sheets. Biomat consists of one or two layers of fiber meshes, while bionet consists of yarn structures. Coir (coconut fiber) geotextiles typically provide 3 to 5 years of functional lifespan depending on fabric weight.

The Main Properties of Geotextile

Geotextiles require three essential property categories: mechanical response, filtration ability, and chemical resistance. The key specifications for geotextile performance are summarized below:

1. Mechanical Responses

Mechanical response is the ability to perform under stressed conditions and resist damage in severe environments. Geotextiles must absorb stresses without degrading during their intended design life, which depends on material stiffness and creep resistance under sustained load.

Geotextiles are typically manufactured in composite form, where one component provides tensile strength and another provides damage protection. Tensile strength ranges from 10 kN/m to 100+ kN/m depending on material type and construction.

2. Filtration Ability

Geotextiles must hold newly prepared soil surfaces in place when water passes through them, preventing surface breakdown while allowing adequate water flow. This filtration capability is measured as permittivity (ψ), typically ranging from 0.1 to 1.0 s⁻¹ for standard geotextiles.

3. Chemical Resistance

Geotextile deterioration results from organic agents (micro- and macrofaunas), inorganic agents (extreme pH conditions below 3 or above 12), light (UV) exposure, and natural aging over time. Chemical resistance testing according to ASTM D5322 evaluates material stability in various environmental conditions.

Polyester and polypropylene geotextiles exhibit excellent chemical resistance to most acids, alkalis, and salts. When properly formulated and protected from UV exposure, these materials achieve design lifespans of 200 years or more in buried applications.

The Uses of Geotextile

Geotextiles serve multiple functional purposes: filtration, drainage, waterproofing, and separation. These materials are employed across at least 100 specific application areas in civil engineering and construction:

• Highways, flight strips, and paved surfaces
• Airport runways and taxiways
• Railroad ballasts and tracks
• River embankments and shoreline protection
• Dams, reservoirs, and canal lining systems
• Landslide mitigation and retaining structures
• Landfill liners and waste containment
• Mining heap leach pads and tailings containment
• Parks, walkways, and car parks
• Underground conduits and pipe trenches

Frequently Asked Questions

This guide covers the essential aspects of geotextiles. Below are answers to the most common queries:

1. Geotextile Serves Essential Functions in Soil Stabilization

Geotextiles are necessary for preventing soil loss in embankments, roads, and other civil engineering applications where water contacts soil and stress is applied. Without geotextile separation, aggregate layers mix with subgrade soil, reducing pavement lifespan by 30% to 50%.

2. Key Differences Between Geotextile and Geomembrane

The primary differences are:

• Geotextiles are water permeable; geomembranes are impermeable (permeability less than 1 × 10⁻¹² m/s)
• Geotextiles provide reinforcement; geomembranes provide seepage prevention
• Geotextiles are made from woven or nonwoven synthetic fabrics; geomembranes are typically high-density polyethylene sheets

3. Water Flows Through Geotextiles

Geotextiles allow water to flow through them while filtering soil particles. Their permittivity values typically range from 0.1 to 1.0 s⁻¹, enabling effective drainage and filtration in civil engineering applications.

4. Geotextile Lifespan Depends on Material and Conditions

Geotextile lifespan varies based on raw material, physical structure, manufacturing quality, and end-use conditions. Coir (coconut fiber) geotextiles provide 3 to 5 years of functional lifespan depending on fabric weight. Polyester and polypropylene geotextiles achieve 200 years or more when not exposed to UV light, according to manufacturer testing and field observations.

5. Geotextiles Function Effectively as Fabric Pots

Geotextiles serve as effective fabric grow pots. These porous fabrics provide proper drainage and soil aeration while containing growing media. The material controls water, nutrient, and oxygen flow to plant roots, creating favorable conditions for plant growth. Geotextiles are less likely to tear or puncture compared to traditional plastic pots, making them suitable for long-term container gardening applications.

6. Geotextile Fabric Installation Steps

Installation procedures vary by application, but the standard installation steps are:

• Step 1: Clear the area of vegetation and trees; remove subgrade material and fill soil voids with granular material where pockets exist
• Step 2: Level and smooth the subgrade to uniform compaction
• Step 3: Place geotextile tightly and flatly per project specifications
• Step 4: Overlap fabric edges a minimum of 300mm (12 inches) or as specified by engineering design
• Step 5: Secure overlapping areas and edges with suitable pins, staples, or adhesive
• Step 6: Fill the area loosely over the geotextile to avoid damaging the material

REFERENCES

• Hagh, A.K. (2019). Experimental Analysis of Geotextiles, Geofibers and Composites. ResearchGate.
• Wikipedia. (2024). Geotextile. Wikimedia Foundation.
• Wikipedia. (2024). Geosynthetics. Wikimedia Foundation.
• U.S. Department of Transportation, Federal Highway Administration. Geosynthetics in Transportation Infrastructure. FHWA.