1. Definition and classification
Geotextile is a water-permeable geosynthetic material made of synthetic fibers (such as polyester, polypropylene, nylon, polyethylene, and nylon) through needle punching or weaving. It is divided into two categories: woven geotextile and non-woven filament geotextile. Among them, non-woven geotextiles are needle-punched and spunlace, short fibers and long fibers. In addition, according to specific application scenarios and needs, geotextiles can be further subdivided into multiple types, such as polyester filament geotextile, singed geotextile, woven geotextile, anti-seepage geotextile, etc.

2. Characteristics and performance
High strength: Due to the use of plastic fibers, geotextiles can maintain sufficient strength and elongation in dry and wet states.
Corrosion resistance: Geotextiles can resist corrosion for a long time in soil and water with different pH values.
Good water permeability: There are gaps between fibers, which have good water permeability.
Good antimicrobial property: no damage to microorganisms and insects.
Convenient construction: Because the material is light and soft, it is very convenient to transport, lay and construct.
Complete specifications: The width can reach 9 meters, which is the widest product in China; the unit area mass is between 100~1000g/m².

3. Functions and uses
Geotextiles play a variety of important roles in civil engineering, mainly including:

Isolation: Geotextiles are used to isolate building materials with different physical properties (such as soil and sand, soil and concrete, etc.), so that two or more materials do not flow or mix, maintain the overall structure and function of the materials, and enhance the bearing capacity of the structure.
Filtration: When water flows from the fine soil layer to the coarse soil layer, the geotextile uses its good air permeability and water permeability to allow the water to pass through, while effectively intercepting soil particles, fine sand, small stones, etc., to maintain the stability of water and soil engineering.
Drainage: Geotextile is a good water-conducting material. It can form a drainage channel inside the soil to discharge excess liquid and gas in the soil structure.
Reinforcement: Geotextiles are used to enhance the tensile strength and deformation resistance of soil, increase the stability of building structures, and improve soil quality.
Protection: When water flows on soil, geotextiles can effectively diffuse, transfer or decompose concentrated stress to prevent soil from being damaged by external forces.
Sealing: Geotextiles are combined with other materials (mainly asphalt or plastic film) to form an impermeable barrier in the soil layer.
Specifically, geotextiles are widely used in engineering fields such as water conservancy, electricity, mines, roads, railways, ports, waterways, construction, and environmental protection, such as:

Water conservancy projects: used for seawalls, river embankments, lake embankments, reservoir reinforcement projects, reclamation projects, flood prevention and rescue, etc.
Highway, railway and airport projects: used for soft foundation reinforcement, slope protection, road surface anti-reflective crack structure layer, drainage system, green belt, etc.
Port and waterway projects: used for revetment, bottom protection projects, coastal moisture prevention, road slope protection, etc.
Road construction: In order to improve the smoothness of the road surface, prevent reflective cracks and act as a waterproof layer, geotextiles are laid between the base layer and the surface layer.
Landfill project: Geotextiles of a certain gram weight are selected for the lining system to protect the geomembrane and prevent it from affecting the anti-seepage function due to damage by garbage or gravel.

4. Production process
The production process of geotextiles includes steps such as raw material selection and preparation, melt extrusion, spinning into a net, needle punching reinforcement, heat setting, surface treatment, inspection and packaging. Each step has an important impact on product quality and performance, and various process parameters and operating specifications need to be strictly controlled.

5. Specifications and technical parameters
The specifications and technical parameters of geotextiles can be customized according to specific use occasions and needs. Common specifications include:

Width: Generally ranging from 2 to 6 meters, and the width can also be customized according to needs.
Length: Generally ranging from 50 to 100 meters, customized according to specific use occasions and needs.
Thickness: Generally between 0.2 and 2 mm, and can also be customized according to needs.
Tensile strength: generally between 10~150kN/m.
Elongation at break: Generally speaking, the greater the elongation at break, the better the toughness of the material.
Tear strength: generally between 100~1000N.
In addition, the waterproof performance, aging resistance, chemical corrosion resistance, etc. of geotextiles are also important technical parameters, which need to be selected and customized according to specific usage requirements.

VI. Construction and laying
During the construction of geotextiles, the following points need to be noted: