How Do Geogrids Work?
Geogrids function by confining and reinforcing soil, effectively redistributing loads. They also interlock with soil particles, locking them in place to prevent lateral movement and improve structural performance.
Their strength comes from their ribs and junctions, which are strong enough to absorb and distribute pressure and tension across a larger area. This creates the Tension Membrane Effect that stabilises soil and alleviates issues like differential settlement.
Reinforcement
When geogrids are placed in soil, they help stabilize the soil and increase its strength. They are also able to withstand traffic loads and provide Geogrids lateral resistance which helps prevent the movement of aggregates in pavements. This feature is particularly important for roads because the stresses from wheel loading can cause lateral movements of soil. This can lead to cracking and deterioration of the road surface. Geogrids can reduce this stress by distributing the load over a large area which prevents displacement.
The aperture size of the geogrid greatly influences its mechanical behavior. Aperture shapes can vary between uniaxial and biaxial grids, knitted or woven fabrics, or composites. Triangular geogrids are becoming increasingly popular because of their more quasi-isotropic behaviors compared to uniaxial and biaxial grids. The aperture size also determines the shear strength of a material.
The tensile strength of a geogrid is very high, which makes it perfect for wall and slope applications. They can reinforce soil for slope stabilization, erosion control, and retaining walls. They can also be used in landfill liner systems and embankments over soft soils. When combined with a wall, a geogrid helps the soil act as one coherent gravity mass and can withstand more forces.
Filtration
Geogrids have filtration and stability features that make them ideal for wall or slope applications. The lateral restraint capability prevents soil movement and allows it to behave more coherently, creating a stable base for structures that would otherwise be vulnerable to crumbling or spreading.
A key feature of geogrids is their ability to transmit load across ribs and junctions, which distributes loads over a wider area. This is what makes them more resistant to strain compared to geotextiles. The strength of the ribs and junctions can also be influenced by the polymer used, as well as how they are manufactured.
Geogrids may be subjected to temperature variations in storage facilities or at the site pending installation, or from sun exposure. This can impact their tensile properties and durability. One way to increase the tensile resistance of a geogrid is to add a coating. For example, a PVC polymer with filler of carbon black (PVC/CB) was found to improve the tensile resistance and stiffness of geogrids.
Geogrids can be uniaxial, biaxial or triaxial in nature. Uniaxial geogrids have rectangular apertures and offer high tensile strengths in one direction, making them more affordable and suitable for slope or wall applications. Biaxial and triaxial geogrids have both longitudinal and transverse ribs, offering a combination of rib and junction strength for more application versatility.
Stabilization
A geogrid’s structure offers stability features in a number of ways. Its honeycomb shape allows for the drainage of water, as well as keeping wind off the surface of the soil. This also helps to prevent erosion, especially on slopes and embankments. This is because it limits the amount of movement of sand and soil particles. It is highly resistant to chemicals, bacteria and has excellent tensile strength.
The mechanical properties of a geogrid are dependent upon its physical characteristics, which include in-plane stiffness, junction efficiency and rib profile. Geogrids are generally much stiffer than geotextiles and can feel quite rigid to the touch. The stiffness of a geogrid is important as it enables it to transmit loads efficiently from the aggregate layer into the subgrade layer through lateral confinement and interlocking. This is accomplished by ensuring that the material that strikes through each aperture carries a load against its ribs, which in turn, carry the load to the adjacent ribs at their junctions.
The ability of a geogrid to transfer forces effectively across the entire area of the soil depends on its long term quality (LTQC) characteristics. These are influenced by the method of manufacture, joint type, rib profile and polymer used. The uniaxial punched, biaxial and drawn polypropylene geogrids manufactured by Tensar provide high LTQC, stability and dependability to offer base reinforcement for paved roads and foundations, working platforms on weak subgrades, construction haul roads and permanent unpaved roads.
Durability
Geogrids are durable, long-term, structures that can support heavy loads and resist seismic activity. They are often used in paved and unpaved road applications to reduce the structural cross-section of the roadway and increase service life. They can also be used to reinforce and stabilize earthworks and improve the performance of soils.
Polymer-based Geogrids are available in a range of sizes and shapes, non woven geotextile fabric suppliers providing a variety of solutions to meet specific project requirements. The most suitable type of geogrid for any particular application will depend on both the physical properties of the product and its compatibility with the surrounding soil or aggregate layers.
US Fusion’s geogrid products are designed for a wide range of stabilization and reinforcement functions. The physical characteristics of the product will influence its suitability, with four main types of geogrids available, including biaxial, unidirectional, and multiaxial. Each of these has its own unique advantages and capabilities, but how each is able to deliver on its core function will be dependent on the requirements of the site in question.