With the development of reinforcement technology and the continuous improvement of the reinforcement theory of geosynthetic materials, new geotechnical reinforcement materials have emerged. At present, there are plastic geogrid, warp-knitted geogrid, and glass fiber geogrid. Because of the diversification of geotechnical products and the wide choice of materials, we should be careful in the choice of materials, once the choice is not appropriate, it will bring serious losses to the project.
Plastic geogrid is divided into single and bi-directional grids. In the extruded polymer sheet punching, and then longitudinal (along with the direction of the sheet) stretching will be made into a one-way grating; on the basis of this, and then in the vertical direction of its length stretching will be made into a two-way grating. The basic properties of plastic geogrids are as follows.
Mechanical properties: During the manufacturing process, the polymer molecules are arranged in the direction of stretching by directional stretching, which strengthens the linkage between molecular chains and greatly improves its tensile strength.
Temperature resistance: due to the stretching effect, its high-temperature resistance also improved.
Durability performance: Due to the addition of aging materials such as carbon black in geogrid, it has better durability such as acid resistance, alkali resistance, corrosion resistance, and aging resistance.
Construction performance: geogrid is light in weight, strong bite with soil or gravel; has acid and alkali resistance, corrosion resistance, aging resistance, softness, and easy construction.
Plastic geogrid is a plastic plane mesh with a certain flexibility, easy to cut and connect on site (can be connected by polyethylene rope or connecting rod), also can overlap and lap, easy to assemble into the required shape on-site, small bending influence, simple construction, no special construction machinery, and professional technicians are needed.
It is a kind of geogrid made of high-strength fiber or polyester, which is woven into a biaxial warp-knitted grid by lining and weft biaxial warp knitting machine, and then processed by PVC impregnated coating. Warp knitted geogrid has excellent engineering properties: high tensile strength (more than 60KN/m), small elongation (about 10%), high tear strength, small longitudinal, and transverse strength difference, and uniform deformation.
Fiberglass geogrid is a mesh structure material made of glass fiber with a certain weaving process. Strictly speaking, glass fiber grating is a kind of warp knitting grating, but due to the unique nature of the fiber used, it is classified as a separate category. Its excellent engineering properties are as follows.
Very high tensile strength and very low elongation: tensile strength can reach 100KN/m and fracture elongation is about 3%.
No long-term creep: Glass fiber grating does not creep.
High-temperature stability: the melting point of glass fiber grating is above 1000℃, and it is not affected by any influence on the hot paving asphalt concrete at 160℃.
Glass fiber geogrid has good compatibility with pavement mix: After the surface organic coating treatment, the glass fiber geogrid has good compatibility with the organic concrete mix, thus improving the shortcomings of glass fiber geogrid which is not wear-resistant and not bending-resistant.
Chemical stability: After special treatment, glass fiber geogrid can prevent all kinds of chemical erosion and resist biological erosion and climate change.
Insert lock and restrict the role: asphalt concrete mixture through the glass fiber geogrid deleted structure, forming a composite insert lock structure. Restriction to prevent the movement of asphalt concrete mixture, can get better compaction, get a greater load-bearing capacity, improve the ability to transfer the load, and reduce deformation.
The ultimate tensile strength of geogrid is from high to low: glass fiber grating, warp knitting grating, and plastic grating in order. And the ultimate elongation is from high to low: warp-knitted grating, plastic grating (the elongation of warp-knitted grating has a wide range depending on the raw material, some may be smaller than that of plastic grating), and glass fiber grating. And glass fiber grating has no creep.
The temperature resistance of glass fiber grating is obviously better than other gratings, and the temperature resistance of woven grating is improved due to impregnation by coating.
The longitudinal and transverse joints of the plastic grating are made by direct molding, so the strength is comparable with the strength of longitudinal and transverse ribs, while the joints of woven and glass fiber grating are made by weaving, so the strength is much lower than the strength of the material itself.
Plastic grating is used in single and two-way applications as follows. Unidirectional grating: One-way geogrid is suitable for reinforcement of highway and railroad roadbed, embankment, slope reinforcement, retaining wall reinforcement, bridge deck reinforcement, and shallow foundation reinforcement. It is widely used in all kinds of reinforced retaining walls. Bi-directional grating: Bi-directional grating is suitable for highway and railroad roadbed, embankment reinforcement, shallow foundation reinforcement, permanent bearing foundation reinforcement such as large square, dockyard, river roadbed reinforcement, prevention and control of reflection cracks of asphalt concrete pavement, etc.
The application range of warp-knitted geogrid is as follows: reinforcement of foundation and embankment on soft soil, homogenizing stress, improving the stability of substrate, adjusting settlement, reducing uneven settlement and improving bearing capacity: reinforcement of embankment slope, improving slope stability; reinforced bridge deck, improving the integrity and strength of bridge deck, preventing bridge head jump; preventing reflection cracks on asphalt concrete pavement, enhancing the strength of pavement base.
Glass fiber grating is suitable for asphalt and concrete pavement reinforcement, pavement reflection crack prevention, control and the connection of the old and new pavement, and other occasions where the deformation is not very large. Glass fiber grating is used in asphalt roads to play a role in fatigue cracking, low-temperature shrinkage, high-temperature rutting resistance and delayed reflection cracks.
According to the different reinforcement, situation to choose different reinforcing materials is the key to the success of engineering applications. In the selection of materials, should be more reference to the application of the same type of project, while paying more attention to the requirements of the project on the strength and elongation of the reinforcement material, do not consider only from a certain angle (such as price), so that it will be more conducive to the rapid and reasonable development of geosynthetic reinforcement technology.