What is Geogrid?
A geogrid is a geosynthetic made from a polymeric material. Geogrids are formed by weaving or knitting intersecting ribs with appropriate apertures (open spaces for the ribs to fit into). Primarily, a geogrid is used for reinforcement applications in various types of construction projects but can be used for separation applications as well. They are open grids that allow the soil to strike through the apertures and the two materials interlock together to give composite behavior. There is a high demand for geogrids in construction because they are good in tension and have an increased ability to distribute loads across a large area.
Specifications:
Item | Properties | Units | MD Values1 | XMD Values1 |
---|---|---|---|---|
1 | Aperture dimensions2 | mm (in.) | 25 (1.0) | 33 (1.3) |
2 | Minimum rib thickness2 | mm (in.) | 0.76 (0.03) | 0.76 (0.03) |
3 | Tensile strength at 2% strain3 | kN/m (lb/ft.) | 4.1 (280) | 6.6 (450) |
4 | Tensile strength at 5% strain3 | kN/m (lb/ft.) | 8.5 (580) | 13.4 (920) |
5 | Ultimate tensile strength3 | kN/m (lb/ft.) | 12.4 (850) | 19.0 (1,300) |
Structural Properties | ||||
6 | Junction efficiency4 | % | MD Values1 | |
7 | Flexural stiffness5 | mg-cm | 250.000 | |
8 | Aperture stability6 | m-N/deg | 0.32 | |
Durability | ||||
9 | Resistance to installation damage7 | %SC/%SW/%GP | 95/93/90 | |
10 | Resistance to long term degradation8 | % | 100 | |
11 | Resistance to UV degradation9 | % | 100 | |
Dimensions | ||||
12 | Roll sizes | m (ft.) | 3.0 × 75.0 (9.8 × 246); 4.0 × 75.0 (13.1 × 246) |
Applications:
When geogrid is applied in high fill subgrade, the position and number of layers of geogrid shall be determined first. In the design, the main idea is to determine the layer of geogrid first, and then determine the number of layers according to the mechanical properties of geogrid. For example, in the reconstruction and expansion project of Shenyang Dalian Expressway, there are many inland river networks and most paddy fields, which is not conducive to the stability of subgrade. When using geogrid for construction, the construction party shall lay a layer of steel plastic composite belt grid 20cm below the subgrade top. At this time, the design structure and combined force of geogrid shall be designed with the longitudinal breaking load per linear meter as 60kn / M and the transverse breaking load per linear meter as 20KN / M as the control load. In the design of geogrid, we should not only ensure its sufficient strength, but also calculate the bursting strength, puncture strength, holding tensile strength, elongation, tear strength and other properties of the material. The specific project shall be determined according to the nature of engineering structure, size, use requirements, load, construction conditions and the characteristics of geosynthetics.
Construction method
Construction method of biaxial geogrid: excavate the subgrade bed, set sand cushion (height difference not more than 10 cm), roll it into a platform, and lay the grid. The longitudinal axis shall be consistent with the main stress direction. The longitudinal lap shall be 20 cm and the transverse lap shall be 10 cm. The lap joint shall be bound with plastic tape, and the paved grid shall be fixed to the ground with U-nails every two meters, The geogrid laid shall be backfilled with soil materials in time, and the number of layers of geogrid laid depends on the technical requirements.