wayne@sdlygccl.com

+86 538 657 5977

News

Home > News > News

What Are Geosynthetics?

May. 11, 2022
Share:

Geosynthetics is a general term for synthetic materials used in civil engineering. As a civil engineering material, it is made of synthetic polymers (such as plastics, chemical fibers, synthetic rubber, etc.) as raw materials for various products, which are placed inside the soil, on the surface or between various soils. It plays the role of reinforcing or protecting the soil.

The Technical Specification for the Application of Geosynthetic Materials divides geosynthetic materials into geotextiles, geomembranes, special geomaterials and geocomposites, geonets, glass fiber mesh, geomaterials 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 "geotextiles" and "geomembranes". With the needs of engineering, new varieties of such materials emerged, such as geogrid, geonet and geomembrane bag, geomembrane mat, belt, composite geomembrane, geosynthetic clay mat, composite drainage network, etc. The original name could not cover all products, therefore, they were called "geotextile, geomembrane and related products (related products)" for a period of time afterwards. ". Such a name should not be used as a technical or academic term. For this reason, the name of such materials was determined as "geosynthetics" (geosynthetics) at the Fifth International Geosynthetics Conference held in Singapore in 1994.

The raw materials of geosynthetics are polymers. They are made from chemical substances extracted from coal, oil, natural gas or limestone, which are further processed into fibers or sheets of synthetic materials and finally 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.

 

What Are Geosynthetics?

1.5mm and 2.0mm Landfill and Biogas Liner

 

Geomembranes

Geomembranes can generally be divided into two categories: asphalt and polymers (synthetic polymers). Bitumen-containing geomembranes are composite (including woven geotextiles or non-woven geotextiles), with asphalt as the permeation binder. Polymer geomembranes are divided into plastic geomembranes, elastic geomembranes and combined geomembranes according to different main materials.

A large number of engineering practices show that geomembranes have good impermeability, strong elasticity, the ability to adapt to deformation, can adapt to different construction conditions and working stresses, and have good anti-aging properties. The durability of geomembranes underwater and under soil is particularly outstanding. Geomembranes have outstanding impermeability and waterproof performance.

 

PE composite geomembrane

1. PE composite geomembrane density: The density depends on the material it uses. Even when the polymers used to make geomembranes belong to the same class, there are often significant differences. For example, polyethylene materials can be divided into different categories such as ultra-low density, low density, medium density, high density, etc. The density of the resulting PE geomembrane is also different. The density of geomembrane polymer ranges from about 0.85 mg/L to 1.50 mg/L, and the density used in engineering is generally above 0.94 mg/L.

2, PE composite geomembrane thickness: thickness refers to the distance from the top surface of the film to the bottom surface under normal pressure of 20kPa. For smooth geomembrane (no embossed or patterned surface), its thickness is measured in the same way as geotextile thickness, but should be measured with a higher precision micrometer. Each sample should be measured at least three different locations and the average value taken as the thickness of the PE composite geomembrane.

 

What Are Geosynthetics?

 

Geotextiles

Another name for geotextile is geotextile. There are few early products, which means cloth-like materials used in geotechnical engineering.

In the manufacturing process of geotextiles, polymeric raw materials are first processed into filaments, staple fibers, yarns or strips, and then the geotextiles are made into flat structures. Geotextiles can be divided into woven geotextiles and non-woven geotextiles according to the manufacturing method. Woven geotextiles are made by interweaving two groups of parallel, orthogonal or inclined warp and weft yarns. Nonwoven geotextiles are made of fibers that are oriented or randomly arranged and then processed. The different methods of connecting the fibers can be divided into three connection methods: chemical (adhesive) connection, thermal connection and mechanical connection.

The outstanding advantages of geotextiles are light weight, good continuity (can be made into larger areas), easy construction, high tensile strength, good corrosion resistance, and resistance to microbial erosion. The disadvantage is that it is not specially treated and has low UV resistance. If exposed, it is easily aged by direct exposure to UV rays, but if not exposed, the resistance to aging and durability remains high.

 

What Are Geosynthetics?

High Strength Road Reinforced Polyester Needle Punched Geotextile

 

Geogrids

Geogrids are a major geosynthetic material with unique properties and efficacy compared to other geosynthetics. Geogrids are commonly used as reinforcement for reinforced soil structures or as reinforcement for composite materials. There are two types of geogrids: glass fiber and polyester fiber.

(1) Plastic Geogrids  

This type of geogrid is a square or rectangular polymer grid formed by stretching, and can be classified as one-way or two-way depending on the direction of stretching at the time of manufacture. It is perforated in an extruded polymer sheet (polypropylene or HDPE) and then stretched in a directional manner under heated conditions. Stretched meshes are made by stretching only along the length of the sheet, while stretched meshes are made by continuing to stretch the stretched mesh in a direction perpendicular to its length.

During the manufacturing process of geogrids, the polymer is rearranged and reoriented as it is heated and stretched, thus strengthening the bonds between the molecular chains and achieving their strength. Its elongation is only 10% to 15% of that of the original sheet. If anti-aging materials such as carbon black are added to the geogrid, it can be made to have better durability such as acid resistance, alkali resistance, corrosion resistance and aging resistance.

 

What Are Geosynthetics?

driveway gravel grid

 

(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 grating is integrated with the asphalt pavement. Due to the increased interlocking force of soil and stone in the geogrid, the friction coefficient between them increases (up to 0.8~1.0). The frictional bite is stronger and increased, which is a good reinforcing material.

Meanwhile, geogrid is a light and flexible flat mesh material, easy to cut and connect on site, also can be lapped. Construction is simple and does not require special construction machinery or professional technicians.

 

Geotechnical special materials

1. Geomembrane bag

Geomembrane bag is a continuous (or separated) bag-like material made of double-layer polymerized chemical fiber fabric. Concrete or mortar is poured into the film bag with a high-pressure pump to form a slab or other shaped structure, often used in slope protection or other ground treatment projects. Membrane bag according to its material and processing technology is divided into two categories: mechanism bag and simple membrane bag. Membrane bag according to the shape with or without backfilter drainage point and after inflation can be divided into backfilter drainage point membrane bag, non-backfilter drainage point membrane bag, no drainage point concrete membrane bag, articulated block membrane.

2. Geonet

Geonet is made of synthetic material strips, thick strands woven or synthetic resin with larger holes, greater stiffness, flat structure or three-dimensional structure of the mesh geosynthetic material. It is used for soft foundation reinforcement, slope protection, grass planting, and as a base material for manufacturing 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 permeable polymer mat combined with fine filaments, while the latter is a honeycomb or grid-like three-dimensional structure composed of geotextile, geogrid or geomembrane, and strip polymer, commonly used for moisture control. Erosion. Geocells with high stiffness and high confinement capacity are used for foundation reinforcement mats, roadbeds or trackbeds.

 

Geocomposites

Geotextiles, geomembranes, geogrids, and some special geosynthetics combine two or more of them into geocomposites. Geocomposites can combine the properties of different materials to better meet the needs of a particular project and can perform multiple functions. For example, composite geomembranes are geotextile composites made from geomembranes and geotextiles according to certain requirements.

Among them, geomembrane is used for seepage control and geotextile plays the role of reinforcement, drainage and increasing the friction between geomembrane and soil surface. Another example is geocomposite drainage material, which is a drainage material composed of different shapes of non-woven geotextiles, geonets, geomembranes or geosynthetic cores. Pipes, catchment wells, drainage behind the walls of supporting buildings, tunnel drainage, dam drainage facilities, etc. The plastic drainage board used in roadbed projects is a geocomposite drainage material.

The geocomposite materials used in large quantities for roads abroad are glass fiber polyester ripstop and warp-knitted composite reinforced ripstop. It can extend the service life of the road and thus reduce the cost of repair and maintenance. Considering the long-term economic benefits, it is necessary to adopt and promote geosynthetics in China.

 

Application areas of geosynthetics

Geosynthetics, with different products having different properties, can be used in many engineering fields.

The fields that have been applied include geotechnical engineering, civil engineering, water conservancy engineering, environmental engineering, traffic engineering, municipal engineering, sea-perimeter engineering, etc.

 

Protection

Soil erosion is a natural process caused by the action of water and wind. There are many influencing factors, such as soil type, vegetation, and landforms. Under certain conditions, human life activities can also accelerate this process. If this erosion problem is not addressed, it may cause great damage to existing buildings and the environment.

Omitting erosion control, the application fields of geosynthetic materials include slope protection, water channel protection, shoreline protection, beach reclamation, vegetation restoration, rock fall protection network, and flood control dam construction. Depending on project characteristics and site conditions, erosion control projects may involve one or more geosynthetic products.

In slope protection projects, in addition to the use of some geosynthetic materials, soil nails and even anchors are required to ensure the stability of the protection system. In some cases, geotextile bags filled with mortar are also used to hold the cover in place and grass seeds are inserted into the gaps of the protection structure to plant vegetation to prevent soil erosion.

 

Shandong Luyuan Engineering Material Co. Limited is a manufacturer and supplier of geosynthetic materials (geomembrane, geotextile, geogrid, geomembrane and geomembrane bag, geomembrane mat, geonet, composite geomembrane, geosynthetic clay liner, composite drainage network), which can provide you with one-stop geosynthetic materials solution project!

 

What Are Geosynthetics?