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Profile Geosynthetics are synthetic, polymer-based materials placed in contact with soil, rock or earth to improve how civil engineering works perform and last. This guide covers what they are, the main types, what they are made of, the functions they serve, where they are used and why engineers specify them.
What are geosynthetics?
Geosynthetics are planar products manufactured from polymers. They are placed in or on the ground, or built into an engineered structure, to perform one or more functions. Because they are produced to a known specification, engineers can design with their measured properties rather than relying only on the variable natural materials found on site.
Types of geosynthetics
Eight main product families cover most civil and environmental works.
Geotextiles
Permeable fabrics, woven or non-woven, used for separation, filtration and drainage.
Geogrids
Polymer grids with open apertures that interlock with soil or aggregate and carry tensile load, in uniaxial or biaxial form.
Geomembranes
Impermeable polymer sheets, typically HDPE, LDPE or PVC, used as liners and barriers.
Geosynthetic clay liners (GCLs)
A layer of bentonite clay held between geotextiles or bonded to a geomembrane to form a low-permeability barrier.
Geocomposites
Products that combine two or more of the above, such as a drainage geonet bonded to geotextiles.
Geonets and geospacers
Open three-dimensional polymer structures that carry fluid flow within their plane.
Geocells
Honeycomb-shaped cellular confinement systems filled with soil or aggregate.
Geotubes and geobags
Fabric containers used to dewater sludge and to form dykes, bunds and revetments.
What are geosynthetics made of?
The main raw materials are synthetic polymers, selected for strength, durability and resistance to moisture, chemicals and biological attack.
| Polymer | Common products | Key property |
|---|---|---|
| Polypropylene (PP) | Woven and non-woven geotextiles, geobags | Strength, chemical resistance |
| Polyester (PET) | High-strength woven geotextiles, geogrids | High tensile strength, low creep |
| Polyethylene (HDPE / LDPE) | Geomembranes, geonets | Impermeable; UV-stabilised with carbon black |
| Polyvinyl chloride (PVC) | Flexible membranes, PVC-coated gabion wire | Flexibility, weather resistance |
| Polyamide and other polymers | Specialised reinforcement products | Application-specific properties |
Some temporary erosion-control products use natural fibres such as coir or jute, which biodegrade once vegetation is established.
Functions of geosynthetics
One product can perform several functions at once. The design normally depends on the function that governs the performance of the works.
| Function | What it does | Typical use |
|---|---|---|
| Stabilisation | Confines soil or aggregate so it resists deformation. | Weak ground, load-bearing platforms |
| Reinforcement | Carries tensile loads the soil cannot carry alone. | Slopes, retaining walls, embankments |
| Drainage | Conducts water within the plane of the product. | Behind walls, under pavements, landfill covers |
| Erosion control | Protects the soil surface from runoff and wind. | Slopes and riverbanks until vegetation takes hold |
| Filtration | Lets water pass while retaining soil particles. | Protecting drains from clogging |
| Separation | Keeps two dissimilar materials apart. | Aggregate on soft subgrade |
| Barrier | Restricts the movement of liquids or gases. | Liners, lagoons, containment |
| Protection | Shields another layer from puncture and abrasion. | Under geomembranes, next to sharp aggregate |
Geosynthetic applications
Roads, pavements and trafficked areas
Geotextiles separate the subgrade from the base aggregate. Geogrids stabilise the base, which can reduce the depth of granular material required and limit rutting under traffic.
Rail trackbed improvement
Geotextiles and geogrids placed beneath the ballast separate and stabilise the trackbed, which helps reduce settlement and maintenance.
Earth retaining structures and steep slopes
Geogrids placed in layers form reinforced soil walls and steep slopes, often a practical alternative to conventional retaining walls.
Embankment foundations
On soft ground, geotextiles and geogrids distribute loads and reinforce the base of the embankment, which helps control settlement and improve stability.
Drainage systems
Geocomposite drains and geonets carry water away from behind walls, under pavements and within landfill covers. Geotextile filters stop the drains from clogging.
Containment and landfill
Geomembranes and GCLs form the base and cap of landfills and lagoons. Geonets above the liner collect leachate.
Marine and coastal works
Silt curtains, geotubes and geobags are used in dredging, reclamation and shoreline protection. See our silt curtain range and geotube products.
The benefits of geosynthetics in geotechnical engineering
Less natural aggregate
Less imported fill and aggregate is needed, which lowers material cost and environmental impact.
Faster construction
Rolled products are quick to install with standard site equipment.
Predictable performance
Products are manufactured to tested specifications.
Durability
Polymer products resist rot, most chemicals and most soil conditions, supporting a long design life.
Suitable for poor ground
Projects can proceed on soft soils that would otherwise need deep excavation and replacement.
Versatile
One family of materials covers separation, reinforcement, drainage and containment.