At present, there are three main types of warp-knitted geotextiles: warp-knitted axial woven geotextiles, double-layer warp-knitted geotextiles, and warp-knitted and non-woven composite geotextiles. Warp-knitted geotextiles have a variety of functions. Since the high-performance yarns in the structure are arranged in parallel and straight directions, the potential of the yarns can be fully unleashed, giving them very high strength. At the same time, because high-performance yarns have special functions such as anti-corrosion and anti-aging, they have the advantage of resisting harsh environments. Warp-knitted geotextiles with high strength and environmental resistance are used in drainage, filtration, isolation and reinforcement. The function is particularly outstanding.
Types of warp-knitted geotextiles
Warp knitted axial fabric
The warp-knitted axial fabric woven through a special warp knitting machine with warp and weft lining functions is a new type of directional structure fabric. At present, the multi-axial warp knitting machines of Karl Mayer and Lipa are the most used in the world. Heguang’s multi-axial warp knitting equipment.
The yarn directions of warp knitted axial fabric interlining yarns are diverse. They can be interbedded in the warp direction and weft direction, and they can also be interbedded diagonally at almost any angle. Warp knitted axial fabrics include uniaxial, biaxial, multiaxial, grid and other organizational structures, and have advantages such as high strength, tear resistance, durability, and environmental resistance.
Biaxial warp knitted fabric
Multi-axial warp knitted fabric
Warp knitted spacer fabric
Warp knitted spacer fabrics are generally produced on double needle bed Raschel warp knitting machines. The upper and lower surface fabrics are connected through a spacer yarn system to form an overall fabric with a three-dimensional structure. The spacer system usually uses synthetic fibers to penetrate between the two surface fabrics to form a spacer layer, so that the fabric has a larger space, which is also the largest structural feature of the spacer fabric. The special spatial structure of warp-knitted spacer fabric also gives it compression resistance, breathability and moisture conduction, structural integrity and formability, etc., so it can be used in many fields. Especially as a geotechnical material, it has unique advantages in the fields of filtration and drainage.
Warp knitted spacer fabric
Warp knitted/nonwoven composite fabric
At present, the multi-axial warp knitting machine produced by Germany’s Lipa Company combines the manufacturing characteristics of non-woven fiber webs and the manufacturing characteristics of biaxial or multi-axial warp knitted fabrics to produce warp knitted/nonwoven composite fabrics. Although nonwoven geotextiles are widely used, their strength, durability and dimensional stability are relatively poor. Using warp-knitted axial fabric with high strength and good dimensional stability to composite it can greatly improve the strength and modulus of non-woven fabrics. At the same time, the composite fabric can give full play to the advantages of the two fabric structures.
Warp knitted/nonwoven composite geotextile
Application of warp-knitted geotextiles
Application on cement pipelines
High-performance cement pipes with warp-knitted axial fabric as reinforcement have significantly reduced pipe quality due to the addition of high-performance reinforcement materials. Under the technical requirements of cement concrete pipes with the same inner diameter and the same load-bearing capacity, the pipe walls of high-performance cement pipes reinforced with warp-knitted axial fabrics become significantly thinner. Relevant studies have found that when the thickness of carbon fiber reinforced cement is only 1/4 of the thickness of steel reinforced cement, it can resist the same external load as steel reinforced cement.
Comparison of the thickness of steel reinforced cement and carbon fiber reinforced cement with the same strength
The cement pipe reinforced with warp-knitted axial fabric has good load-bearing capacity and crack resistance, improves the pipe’s impermeability and durability, and provides new high-quality pipes for drainage projects. According to relevant reports, the construction of this type of pipeline in urban underground comprehensive pipeline corridors of more than 2,000km began in 2016. Therefore, warp-knitted axial fabric reinforced high-performance cement pipes will play a vital role in the construction of “sponge cities”, “underground cities”, and “underground comprehensive pipe corridors” that are being implemented by the country.
Application in road construction
As a structural form of warp-knitted axial fabric, geogrid is lined with high-performance yarns in the form of hollow threads in the warp and weft directions of the fabric. There is no gap between the warp yarns and the weft yarns.�Interweaving can form two yarn layers parallel to each other.
Key factors that affect the service life of roads and railways include environmental factors, roadbed conditions, road widening and aging, etc. As a commonly used geotechnical construction material, geogrid has high tensile strength, good stability, corrosion resistance and With advantages such as aging, it can be widely used in roadbed reinforcement fields such as roadbed reinforcement and railway roadbed reinforcement. Warp-knitted geotextiles play a vital role in the construction of new highways and the repair of old highways.
Application in dam construction and protection
The composite geotextile has excellent filtration and isolation functions. It is laid between the soil layer and gravel of the protective embankment to prevent the soil layer from mixing with the gravel, keep the soil layer under relatively small pressure, and protect the embankment from being eroded by water flow. . In addition, geotechnical materials can also be used to form geotechnical bags, and the sediment is packed in the geotechnical bag to form a flexible, erosion-resistant, heavy-weight whole that is placed in the river embankment or river channel to fix the river embankment and protect it.
Larger geotechnical pipes can be formed using warp knitted/nonwoven composite fabrics, with diameters reaching or even exceeding 0.6m and lengths of more than 10m. Filling the tubes with sediment can be used as breakwaters in the ocean to protect coastlines and seabeds. Due to the special structural characteristics of warp-knitted geotextile and its wide adaptability to raw materials, its role in high-strength and environmentally resistant geotextiles cannot be ignored.
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