Geosynthetics is a general term for synthetic materials used in civil engineering. As a civil engineering material, it uses synthetic polymers (such as plastics, chemical fibers, synthetic rubber, etc.) as raw materials to make various types of products, which are placed inside the soil, on the surface, or between various soils. , play the role of strengthening or protecting the soil.
“Technical Specifications for the Application of Geosynthetics” divides geosynthetics into geotextiles, geomembranes, special geotechnical materials and geocomposite materials, geonets, fiberglass meshes, geomatics, and other types.
Construction Engineering Terminology
Geosynthetics is a general term for various products made of synthetic materials used in geotechnical engineering and civil engineering construction. Because they are used in geotechnical engineering, they are given the word “geo” and are called “geosynthetics” to distinguish them from natural materials.
Geosynthetics used to be called “geotextile” and “geomembrane”. With the needs of engineering, new varieties of such materials continue to appear, such as geogrids, geonets and geomembrane bags, geonet pads, belts, composite geomembranes, geosynthetic clay liner, composite drainage nets, etc., the original name is impossible to cover all products, so, for a period of time thereafter, they are called “geotextiles, geomembranes, and related products (relate products)”. , such a name should not be used as a technical or academic term. To this end, in 1994 at the Fifth International Geosynthetics Academic Conference held in Singapore, the name of this type of material was determined “geosynthetics” (geosynthetics).
The raw material of geosynthetics is a polymer. They are made from chemicals extracted from coal, oil, natural gas, or limestone, which are further processed into fibers or sheets of synthetic materials, and finally made into various products. The polymers used to manufacture geosynthetics are polyethylene (PE), polyester (PET), polyamide (PER), polypropylene (PP), polyvinyl chloride (PVC), chlorinated polyethylene (CPE), polystyrene Ethylene (EPS), etc.
Another name for geotextiles is geotextiles. Early products were few, meaning a cloth-like material used in geotechnical work.
In the manufacturing process of geotextiles, polymer raw materials are first processed into filaments, staple fibers, yarns, or strips, and then geotextiles are made into planar structures. Geotextiles can be divided into woven (woven) geotextiles and non-woven (non-woven) geotextiles according to the manufacturing method. Woven geotextiles are interwoven by two sets of parallel, orthogonal or oblique warp and weft threads. Non-woven geotextiles are made by the directional or random arrangement of fibers and then processed. The different methods of connecting fibers can be divided into three types connection methods: chemical (binder) connection, thermal connection, and mechanical connection.
The outstanding advantages of geotextiles are lightweight, good continuity (can be made into a larger area), convenient construction, high tensile strength, good corrosion resistance, and resistance to microbial erosion. The disadvantage is that without special treatment, the anti-ultraviolet ability is low. If exposed to the outside, it is easy to age when exposed to direct ultraviolet rays, but if it is not exposed, the anti-aging and durability performance is still high.
Geomembranes can generally be divided into two categories: asphalt and polymers (synthetic polymers). Asphalt-containing geomembranes are composite types (including woven or non-woven geotextiles), and asphalt is used as an infiltrating binder. Polymer geomembrane is divided into plastic geomembrane, elastic geomembrane, and combined geomembrane according to different main materials.
A large number of engineering practices have shown that the geomembrane has good water impermeability, strong elasticity, and ability to adapt to deformation can be suitable for different construction conditions and working stress and has good aging resistance. Geomembrane under water and soil The durability is particularly outstanding. Geomembrane has outstanding anti-seepage and waterproof properties.
PE composite geomembrane
1. PE composite geomembrane Density: Density depends on the material it is made of. Even if the polymers that make geomembranes belong to the same class, there are often significant differences. For example, polyethylene material can be divided into different categories such as ultra-low density, low density, medium density, and high density, and the density of PE geomembrane made from this is also different. The density range of geomembrane polymer is about 0.85mg/L ~ 1.50mg/L, and the density used in engineering is generally above 0.94mg/L.
2. PE composite geomembrane Thickness: Thickness refers to the distance from the top surface to the bottom surface of the film under the normal pressure of 20kPa. For smooth geomembrane (without embossing or pattern on the surface), the measurement method of its thickness is like that of geotextile thickness, but it should be measured by a dial gauge with higher precision. Each sample should be measured at least three different locations, and the average value should be taken as the thickness of the PE composite geomembrane.
Geogrid is a major geosynthetic material with unique properties and efficacy compared with other geosynthetics. Geogrids are often used as reinforcement for reinforced soil structures or as reinforcement for composite materials. Geogrids are divided into two types: glass fiber and polyester fiber.
(1) Plastics Geogrid
This kind of geogrid is a square or rectangular polymer mesh formed by stretching and can be divided into two types: uniaxial stretching and biaxial stretching according to the different stretching directions during manufacture. It punches holes on the extruded polymer sheet (polypropylene or high-density polyethylene) and then performs directional stretching under heating conditions. The stretched grid is made by stretching only along the length of the sheet, while the stretched grid is made by continuing to stretch the stretched grid in the direction perpendicular to its length.
During the manufacture of geogrid, the polymer will be rearranged and oriented with the heating and extension process, which strengthens the bonding force between molecular chains and achieves the purpose of improving its strength. Its elongation is only 10% to 15% of the original sheet. If anti-aging materials such as carbon black are added to the geogrid, it can make it have better durability such as acid resistance, alkali resistance, corrosion resistance, and aging resistance.
(2) Glass fiber Geogrid
This kind of geogrid is made of high-strength glass fiber, sometimes with self-adhesive pressure-sensitive adhesive and surface asphalt impregnation treatment, so that the grid and the asphalt pavement are integrated. Because the interlocking force of earth and stone in the geogrid grid increases, the friction coefficient between them increases (up to 0.8 to 1.0). The frictional bite force is stronger and increased, so it is a good reinforcement material.
At the same time, the geogrid is a kind of lightweight, flexible flat mesh material, which is easy to cut and connect on-site and can also be overlapped. The construction is simple and does not need special construction machinery or professional technicians.
Geotechnical special materials
1 Geomembrane bag
A geomembrane bag is a continuous (or separate) bag-like material made of double-layer polymerized chemical fiber fabric. Concrete or mortar is poured into the film bag by a high-pressure pump to form a plate or other shape structure, which is often used for slope protection or other Ground treatment works. Film bags are divided into two categories: mechanism and simple film bags according to their materials and processing techniques. Membrane bags can be divided into reverse filtration and drainage point membrane bags, non-reverse filtration and drainage point membrane bags, concrete membrane bags without drainage points, and hinged block membranes according to whether they have reverse filtration drainage points and the shape after inflation.
Geonet is a reticulated geosynthetic material with larger holes, larger rigidity, planar structure, or three-dimensional structure, which is made of synthetic material strips, thick strands woven, or synthetic resin. It is used for soft foundation reinforcement, slope protection, grass planting, and as a base material for the manufacture of composite geomaterials.
3 Geonet pads and geocells
Geonet pads and geocells are three-dimensional structures made of synthetic materials. The former is a three-dimensional water-permeable polymer mesh pad combined with filaments, and the latter is a honeycomb or grid-like three-dimensional structure composed of geotextiles, geogrids or geomembranes, and strip polymers, which are often used for anti-erosion. Geocells with high stiffness and high confinement capacity is used in foundation reinforced cushions, subgrade beds, or track beds.
Geotextiles, geomembranes, geogrids, and some special geosynthetics are combined with two or more of them to become geocomposites. Geocomposite materials can combine the properties of different materials to better meet the needs of specific projects, and can play a variety of functions. For example, composite geomembrane is a geotextile composition made of geomembrane and geotextile according to certain requirements.
Among them, the geomembrane is used for anti-seepage, and the geotextile plays the role of reinforcement, drainage, and increasing the friction between the geomembrane and the soil surface. Another example is the geocomposite drainage material, which is a drainage material composed of non-woven geotextiles, geonets, geomembranes, or geosynthetic core materials of different shapes. Pipelines, water collection wells, drainage behind walls of supporting buildings, tunnel drainage, dam drainage facilities, etc. Plastic drainage board used in roadbed engineering is a kind of geocomposite drainage material.
A large number of geocomposite materials used for roads abroad are glass fiber polyester anti-cracking cloth and warp-knitted composite reinforced anti-cracking cloth. It can extend the service life of the road, thereby reducing the cost of repair and maintenance. Considering the long-term economic interests, it is necessary to adopt and promote geocomposite materials in China.
Geosynthetics Application field
Geosynthetics, different products have different characteristics and can be used in many engineering fields.
The fields that have been applied include geotechnical engineering, civil engineering, hydraulic engineering, environmental engineering, traffic engineering, municipal engineering, and sea reclamation engineering.
Soil erosion is a natural process caused by the action of water and wind. There are many influencing factors, such as soil types, vegetation, and landforms. Under certain conditions, human life activities will also speed up this process. If this erosion is not addressed, it can cause enormous damage to existing buildings and the environment.
Omit soil erosion control, the fields of application of geosynthetics include slope protection, water canal protection, coastline protection, tidal flat reclamation, vegetation restoration, rockfall protection net, and flood control dam construction. Depending on project characteristics and site conditions, one or more geosynthetic products may be involved in erosion control projects.
In slope protection engineering, besides using some geosynthetics, soil nails and even rock bolts are needed to ensure the stability of the protection system. In some cases, geotextile bags refilled with mortar are also used to fix the cover, and grass seeds are inserted into the gaps of the protective structure to cultivate vegetation to prevent soil erosion.
Earthshield is a manufacturer and supplier of geosynthetics (geomembrane, geotextile, geogrid, geomembrane and geomembrane bags, geomembrane mat, geonet, composite geomembrane, geosynthetic clay liner, composite drainage mesh) for over 20 years, Can provide one-stop geosynthetics solutions for your project!