Differences and Classifications of Geogrids for Construction

Preface

• Geogrids are an important branch of geosynthetic materials. Their main structure consists of vertically laid strips in both radial and latitudinal directions, forming a mesh-like material. Their primary purpose is to act as reinforcing bars in reinforced soil, with the mesh openings penetrating the soil for localized-to-overall interlocking. This addresses problems such as uneven settlement, slippage, and cracking in foundations. In recent years, engineering plastics and synthetic fibers have demonstrated high strength and high modulus compared to steel reinforcement, offering a cost-effective alternative.
• The strength of geogrids is expressed using tensile force per unit width (kN/m, i.e., "strength per meter") rather than cross-sectional area (e.g., mm²). This is mainly because their structure resembles a two-dimensional mesh. They are subjected to linear loads in reinforced soil. To standardize the calculation of strength per meter, various geogrid types, despite differences in strip width and mesh distribution, are calculated using strength per meter, thus maintaining a unified standard.

Classification of Geogrids (according to JTT1432.1 standard)

Plastic Geogrids (commonly known as PP geogrids)

Divided into stretched plastic geogrids (further divided into unidirectional and bidirectional, and made of HDPE/PP materials) and injection-molded stretched geogrids (bidirectional).

Stretched plastic geogrids: The core feature is integrated extrusion with punched holes. Available in PP and HDPE materials. Currently available are unidirectional, bidirectional, tridirectional, and four-directional geogrids. The standard only specifies unidirectional and bidirectional geogrids.

Welded steel-plastic geogrid (commonly known as steel-plastic geogrid)

PP as the main joint injection molding heat welding

Welded Fiberglass Geogrid (common materials include fiberglass, basalt, and polyester)

Fiberglass, basalt fiber, polyester fiber, and polyethylene or polypropylene are used as the main raw materials. These are extruded into composite high-strength strips, arranged at right angles along the warp and weft in a plane, and then ultrasonically welded to form a planar mesh structure geogrid with a rough, textured surface.

Unlike steel-plastic grating, its core material is fiber.

Welding of polyester geogrid

PET polyester is the main raw material

Warp-knitted polyester geogrid

Differences and Points to Note

1. For plastic geogrids, pay attention to whether the material is PP or HDPE, and whether it is unidirectional or bidirectional. Bidirectional plastic geogrids generally have low strength, only 50-50 KN/m.

2. For polyester geogrids, distinguish between welded polyester geogrids and warp-knitted polyester geogrids. The distinction is made by the presence or absence of a warp-knitting process (i.e., vertically binding yarns).

3. For steel-plastic geogrids, pay attention to the number and specifications of the steel wires inside.

4. Pay attention to mechanical properties, especially durability and strength at 2% and 5% elongation.