Biaxial geogrid: definition, application, and benefits of using biaxial geogrids
A bi-axial geogrid is a type of geogrid that offers soil reinforcement on two directions: longitudinal and transverse. It has high tensile strength along its length and across its width. They can be manufactured from a variety of materials such as polypropylene, polyester, or high-density polyethylene [HDPE]. At Strata Global, our biaxial geogrids [StrataGrid™ Biaxial (SGB)] is made from polyester (PET) geogrid reinforcement for soil. These high performance geogrids are constructed of high molecular weight and high knitted polyester yarns with a proprietary coating. By providing stability across two dimensions, these geogrids offer high tensile strength, and load distribution. The main benefit of using these geogrids is reduced pavement crust thickness, leading to faster and more efficient construction processes. Since a biaxial geogrid specifically is designed to improve modulus values of the base layers, it reduces the need for higher volume of in-fill material among other cost benefit accruals. A biaxial geogrid is most often used for soft soil embankments, as basal reinforcement, flexible pavement or asphalt reinforcement, below structural foundations for applications such as bridges, buildings, bridge abutments, load transfer platform or an effective void spanning solution.
When is a biaxial geogrid preferred?
A biaxial geogrid is used when the structure needs support in two directions. This is typically seen in slope reinforcement, or slope retention walls, haul road stabilization, or even for caps for leachate collection ponds and landfills. there are some soil types that demand biaxial geogrids such as granular soils, or cohesive soils due to their inherent properties. Cohesive soils are typically prone to cracking and swelling due to their low tensile strength. In this case, biaxial geogrids stabilises the soil by reducing the differential settlement and creating a uniform layer. Granular soils such as sand, or clay on the other hand come with different challenges. While they have good drainage, due to their particular size, they’re prone to localized shear failure. Geogrids instead confine this soil type, and interlock particles. Since this in turn distributes loads more evenly, reduces settlement and rutting, especially in pockets with heavy or repetitive loading.
How are biaxial geogrids made and what are its specifications?
The biaxial geogrid at Strata Global is manufactured with specific considerations in mind. Since biaxial geogrids need to withstand a range of temperature fluctuations, soil pH types, alongside moisture levels, which may change with terrain, the material needs to be inert, and unreactive through the installation phase, and post construction too, to withstand the physical pressures and chemical changes that affect the subgrade, or layers where it’s applied. A predetermined number of polyester yarn ends are pulled from a creel and are wound onto a large cylindrical beam. Post this stage, this high tenacity polyester yarn is precision-knitted into a dimensionally stable network of apertures that serves as a highly stable, high modulus precursor to the coating process. This coat is made from a proprietary styrene butadiene rubber co-polymer [SBR] optimal which makes it abrasion resistant to chemical, physical and environment factors. With different tensile strength models available, in varied aperture width, the product range allows civil engineers to choose from a list of roll types for installation. Depending on the soil type, and application, the aperture sizes and rib thickness influence the ultimate tensile strength, which are key considerations for stability of the subgrade.