One、The following is a comprehensive introduction to geomembrane
（1）、Definition and basic concepts
Geomembrane is a kind of impervious geosynthetic material, which is composed of plastic film as impervious substrate and non-woven fabric.
（2）、 Material type and characteristics
1、Material type: Polyethylene (PE) geomembrane: This is the most widely used geotextile. It has excellent chemical resistance and can resist the erosion of a variety of chemical substances such as acid and alkali. PE geomembrane also has good weather resistance, can maintain good performance under different climatic conditions, and can adapt to a variety of environments from cold polar to hot desert.
2、Polyvinyl chloride (PVC) geomembrane: PVC geotextile has excellent flexibility and is easy to process and lay. It can adjust its flexibility and other properties by adding additives such as plasticizers
3、Other materials: chlorinated polyethylene (CPE) geomembrane, etc. CPE geomemes combine some of the characteristics of chlorinated polyethylene, such as good aging resistance and oil resistance, and are also used in specific engineering environments.
（3）、 in-depth understanding of manufacturing process
1、Extrusion blow molding method: This method is to heat the polymer raw material to a molten state, extrude a round tube blank through the extruder, and then pass compressed air into the tube blank, so that it expands to form a film.
2、Calendering method: The heated polymer is pressed through a series of calendering rollers to gradually form geomembrane. The surface of the geomembrane produced by calendering method is smooth and flat, and the thickness precision is high.
（4）、Detailed introduction of performance parameters
1、 Anti-seepage performance parameters: Permeability coefficient: This is a key index to measure the impermeability of geomembrane. It indicates the difficulty of liquid penetration in the geomembrane, the smaller the permeability coefficient, the better the anti-seepage performance.
2、Mechanical property parameters:Tensile strength: Tensile strength determines the resistance of geomembrane when subjected to tensile forces. The tensile strength of different types and thicknesses of geomembranes is different, generally between several mpa and tens of mpa. During the laying process, when the geomembrane is stretched, sufficient tensile strength can prevent its fracture.
3、Tear strength: reflects the ability of geomembrane to resist tearing. During the construction process, the geomembrane may be scratched or torn, and good tearing strength can reduce this risk.
Environmental performance parameters:
4、 Aging resistance: geomembrane will be affected by environmental factors such as ultraviolet light and temperature changes during long-term use. Good aging resistance can ensure the stability of geomembrane during many years of use.
5、 5、 Chemical resistance: In the environment of contact with different chemical substances, geomembrane needs to maintain its performance. For example, in sewage treatment plants, geomembrane should be able to resist the erosion of various chemical substances in sewage, and its chemical resistance is usually measured by immersion tests in different chemical solutions.
（5）、A wide range of application scenarios
1、 Water conservancy and hydropower projects: In the seepage control system of dam, geomembrane can effectively prevent the water in the reservoir from leaking through the dam body. For example, in earth-rock DAMS, geomembrane can be laid inside the dam body or on the surface of the dam foundation to form a continuous impermeable layer. 2、Environmental engineering field: Landfill is the key place of geomembrane application. Geomembrane is laid on the bottom and side walls of landfill sites to prevent landfill leachate from penetrating into groundwater and protect groundwater resources and soil environment.
3、Construction Project Scope: Basement waterproofing is a common application of geomembrane in construction engineering. It can be used as a part of the waterproof layer of the basement and used in conjunction with other waterproof materials to effectively prevent groundwater from penetrating into the basement and ensure the dryness and safety of the basement.
（6）、 Traffic Engineering Applications:
In the roadbed waterproofing treatment of road, railway and other traffic engineering, geomembrane can prevent the erosion of groundwater to roadbed and improve the stability of roadbed. For example, in some highway subgrade with soft soil foundation, geomembrane can be used as an isolation layer to prevent groundwater from rising and ensure the carrying capacity of the subgrade.
（7）、 construction and installation points and quality control
1、 Preparation before construction: Site cleaning is an important link before construction. To remove sharp objects in the construction site, debris, etc., to ensure that the foundation is smooth and solid.
2、 Key points of construction process: The laying of geomembrane should follow a certain sequence and method. Generally, it starts from the bottom and is laid in accordance with the direction and manner required by the design.
3、Quality control measures: The quality inspection in the construction process includes the inspection of the quality of geomembrane laying, such as checking whether there is damage and whether the splicing is good. On-site testing equipment, such as EDM detector, can be used to detect the welding quality of geomembrane.
4、Maintenance and repair measures
1)、 Daily maintenance points: Regular inspection is an important way to maintain geomembrane. In the application scenarios such as water conservancy projects and landfill sites, it is necessary to regularly check whether the surface of the geomembrane is damaged and accumulated water.
2) 、Repair method introduction: When the geomembrane is found to have a small area of damage, the patch repair method can be used. First clean up the damage, then cut a patch with the same geomembrane material, and fix the patch to the damage by welding or bonding. For larger areas of damage, part of the geomembrane may need to be replaced and re-spliced and sealed.
Two、The factors affecting the price of geomembrane mainly include the following aspects:
（1）、 raw material factors:
1、Type of raw materials:
1)、 Polyethylene raw material quality: the main raw material of geomembrane is polyethylene particles. High-quality polyethylene particles produce geomembranes with better quality and higher prices. Effect of additives: In order to improve some properties of geomembrane, such as anti-ultraviolet, anti-oxidation, etc., some special additives will be added. The use of additives with good quality and good effect will increase the production cost, which will increase the price of geomembrane.
2）、 Fluctuations in raw material prices: oil is the main source of polyethylene, and fluctuations in international oil prices will directly affect the price of polyethylene raw materials.
（2）、 Production process factors:
1、 production equipment: advanced production equipment can ensure the production quality and production efficiency of geomembrane, but the cost of equipment acquisition, maintenance and upgrade is high.
2、 process type: geomembrane according to the production process can be divided into film (casting extrusion) and blown film (blow molding flat extrusion) two. The geomembrane produced by the blown film process has the advantages of uniform thickness and stable physical indexes, but the process consumes a lot of power and the cost of the material ratio is high, so the price of the blown film process is usually slightly more expensive than that of the coated film process.
（3）、 product specification factors
1、 Thickness: In general, the thicker the thickness of the geomembrane, the more raw materials it uses, the more difficult the production, and the higher the price. For example, the price of 0.5mm thick geomembrane will be lower than that of 1.0mm thick geomembrane.
2、Width: at present, the general width of domestic geomembrane equipment is 6 meters, usually 6 meters and 6 meters of the factor of such width is the standard width, 4 meters, 4.5 meters, 5 meters and so on are not divided by 6 for special width. The special width geomembrane has a large loss in the production process, so its price is higher than that of standard width geomembrane.
3、Dimensional stability: geomembrane with good dimensional stability is easier to lay in the construction process, which can reduce the construction difficulty and material waste caused by size changes. Therefore, the price of geomembrane with good dimensional stability will be relatively high.
(4)、Quality standard factors:
1、national standards: the product standards of geomembrane are divided into new national standards, old national standards, American standards, etc. Geomembrane in line with national standards, its quality is guaranteed, and the price will be relatively high.
2、quality testing: after strict quality testing of geomembrane, its quality reliability is higher. Some regular manufacturers will test and track each roll of geotextile to ensure that the quality of the product is qualified, which will also increase the cost of the product, thus making the price rise.
(5)、 Market supply and demand factors:
1、 Market demand: When the market demand for geomembrane is large, such as in the period when large-scale water conservancy projects, landfill construction and other projects are concentrated, the price of geomembrane will rise due to short supply. On the contrary, when the market demand is small, manufacturers may reduce prices in order to promote sales.
2、 Market competition: there are many geomembrane manufacturers and fierce market competition. In order to compete for market share, some manufacturers may take the strategy of reducing prices; Some manufacturers with high brand awareness and good product quality may have relatively high product prices.
(6)、Transportation cost factors: the distance of transportation, the amount of loading, loading and unloading costs will affect the price of geomembrane. If the transportation distance is far, more transportation tools and manpower need to be used, and the transportation cost increases, the price of geomembrane will also increase accordingly.
