What is Geogrid?

Geogrids are a subgroup of geosynthetics notable for their open apertures for use in reinforcement.  They comprise three main categories based on construction style; knitted and woven polyester or fiberglass grids that have been coated with PVC or other additives, extruded polypropylene and HDPE plastic geogrids, and welded rod or strap geogrids.  

Another way to divide geogrids is by application.  Uniaxial geogrids are commonly used for vertical reinforcement applications while biaxial geogrids are commonly used for horizontal reinforcement applications.  Uniaxial geogrids have a considerably higher tensile strength and slight elongation in the machine direction allowing them to reach peak strength under stress as the backfill settles.  Biaxial geogrids generally have the same or similar strength in both the machine and cross machine direction with very little creep allowing the geogrid to reinforce the base or sub-base in parking lots and paved and unpaved roads.  While uniaxial geogrids used in reinforced walls and slopes are needed to prevent catastrophic failure, biaxial geogrids in base reinforcement are used to reduce the amount of aggregate needed, extend the service life of the project, or provide needed reinforcement over soft soils.

Both types of geogrid work because of the open aperture construction of the geogrid.  This allows the soil or aggregate, above and below the geogrid, to fill in the gaps between the ribs giving reinforcement to the soil mass or base aggregate.  It is important to remember the benefit provided by the soil interlocking with the geogrid is only achieved when the fill is properly compacted in lifts during construction.

Be sure to check back as we go more in depth on the different styles of geogrids and how they are used in the field as well as some handy installation tips.