Geogrid is a polymeric material made up of many polymers like polyethylene, polyvinyl alcohol polypropylene etc. It is one of the most important inventions in geosynthesis which is used as a reinforcing material. They formed by joining intersecting ribs. They have large open spaces in between the ribs known as “apertures”.
The manufacturing of geogrids commercially is carried out by three ways which is explained below,
By Extrusion: In this method a flat polymeric sheet of material is made into a geogrid by extrusion and holes of desired dimensions are punched in the flat sheet to form the apertures. Then stretching is done to impart the tensile strength.
By Weaving or Knitting: As the name signifies the geogrids are manufactured by weaving fibrous yarns and apertures are formed in between the flexible joints. These types of geogrids have high tenacity.
By Welding and Extrusion: This method is similar to that of extrusion, only difference is that the extrusion of ribs is carried out by passing it through rollers, then they are sent to the welding section to form apertures. This method makes use of automated machines
Type of Geogrids
Geogrids can be classified into two types based on the stress transfer or direction of stretching during manufacture as
Type of Geogrid based on Pattern
Uniaxial geogrid – It is stretched only along longitudinal direction. Thus the stress is transferred only along that axis; even the tensile strength is more in longitudinal direction when compared to transverse direction in uniaxial geogrids.
Biaxial geogrid – It is stretched along two directions (longitudinal and transverse), thus the stress is equally distributed along both directions. In biaxial geogrids the longitudinal direction is called as machine direction (MD) and transverse direction is called cross machine direction (CMD). Since the strength is equal along both axis these geogrids are mostly preferred in construction.
2.Types of Geogrid based on manufacturing
Geogrids also have another classification based on the method of manufacturing, they are
Extruded geogrid
Woven geogrid
Bonded geogrid