The geomembrane for seepage prevention

Seepage Prevention Performance: The geomembrane for seepage prevention in reservoirs has an extremely low coefficient of permeability. Generally, the coefficient of permeability of HDPE (High - Density Polyethylene) geomembrane can reach \(10^{-12}～10^{-13} cm/s\), which can effectively prevent the seepage of water and reduce the water loss of the reservoir.

Physical and Mechanical Properties: It has high tensile strength, tear strength, and puncture resistance, so as to withstand various stresses during the operation of the reservoir, such as the extrusion of the soil body and the scouring of the water flow.

Chemical Corrosion Resistance: It can resist the erosion of various chemical substances that may exist in the reservoir, including acid and alkali substances, dissolved salts, etc., ensuring long - term seepage prevention effect.

Weather Resistance: It can be used under different climatic conditions, resist the influences of factors such as ultraviolet rays and temperature changes, and has a relatively long service life, generally reaching 50 years or even longer.

HDPE Geomembrane: One of the most commonly used materials for seepage prevention in reservoirs. It has excellent seepage prevention performance, chemical resistance, and aging resistance, and is widely applied to various types of reservoirs. It has high strength, convenient construction, and mature welding technology, and can adapt to different topographic conditions.

LDPE Geomembrane: Low - Density Polyethylene geomembrane, which is relatively soft and flexible. It has certain applications in reservoirs with high deformation requirements or small - scale reservoirs. Its cost is relatively low, but its strength is slightly inferior to that of HDPE geomembrane.

EVA Geomembrane: Ethylene - Vinyl Acetate Copolymer geomembrane has good flexibility, environmental stress cracking resistance, and anti - aging performance. It performs well in the seepage prevention projects of reservoirs in cold regions and can maintain good seepage prevention effects in low - temperature environments.

Foundation Treatment: Before laying the geomembrane, the reservoir foundation needs to be strictly treated. Remove sundries such as weeds, tree roots, and sharp stones from the foundation surface, compact or reinforce the soft foundation to ensure that the foundation is flat, solid, without obvious unevenness and cracks, and avoid the geomembrane from being punctured during the laying and use process or damaged due to foundation deformation.

Laying Method: The geomembrane should be laid from the bottom of the reservoir upwards, first the bottom, and then the slopes in turn. During the laying process, ensure that the geomembrane is flat and avoid wrinkles and hanging phenomena. Manual or mechanical assistance can be used for laying, and the laying speed should be moderate to ensure that the geomembrane is closely attached to the foundation. A certain lap width, generally 10 - 20cm, should be reserved between adjacent geomembranes to ensure the welding or bonding quality.

Connection Method: The connection of the geomembrane is crucial and directly affects the seepage prevention effect. The main connection methods are welding and bonding. Welding commonly uses methods such as hot wedge welding and hot - melt extrusion welding. Before welding, clean the welding surface to remove impurities such as dust and oil. During welding, strictly control welding parameters such as temperature, speed, and pressure to ensure that the weld is firm and well - sealed. Bonding requires the use of special adhesives and should be operated according to the product instructions. Apply the adhesive evenly, apply a certain pressure after bonding, and keep it for a period of time to make the bonding firm. After welding or bonding, conduct a quality inspection on the connection part, such as using the inflation method, vacuum method, etc. to detect whether there is any leakage.

Anchoring and Fixing: To prevent the geomembrane from sliding or being washed away by the water flow, anchoring and fixing are required. Excavate an anchoring groove around the reservoir, bury the edge of the geomembrane in the groove, and backfill and compact it with soil or concrete. For the slope part, auxiliary fixing methods such as U - shaped nails and pressure strips can be used, and fix at certain intervals to ensure the stable position of the geomembrane during operation.

Protective Layer Construction: After the geomembrane is laid, a protective layer needs to be laid on its surface to protect the geomembrane from ultraviolet radiation, mechanical damage, and human damage. The protective layer materials can be clay, sand and gravel, concrete, etc. The thickness of the clay protective layer is generally 30 - 50cm, and it needs to be laid in layers and compacted; the thickness of the sand and gravel protective layer is similar, and it also needs to be compacted after laying; the strength grade of the concrete protective layer is generally not lower than C20, and the thickness is 10 - 20cm. During pouring, it should be vibrated thoroughly to ensure close combination with the geomembrane.

Quality Inspection: During the construction process, strictly inspect the geomembrane and construction quality. Sample and inspect the geomembrane materials to detect whether their physical and mechanical properties, seepage prevention performance, etc. meet the design requirements. After the construction is completed, in addition to detecting the leakage of the connection part, comprehensive non - destructive testing techniques such as spark testing can be used to check whether there is any damage to the geomembrane. After the reservoir is impounded, regularly observe the change of the reservoir water level, check whether there are any seepage signs around, and if there are any abnormalities, timely investigate and deal with them.

Maintenance Measures: Establish a regular inspection system to check whether the geomembrane and the protective layer are damaged or displaced. If a small - area damage to the geomembrane is found, it should be repaired in time. The patch method can be used, cutting the same - material geomembrane into an appropriate size and covering it on the damaged area by welding or bonding. For the damage to the protective layer, such as cracks in the clay protective layer or the scouring of the sand and gravel protective layer, repair or replenish materials in time. At the same time, prevent the damage to the reservoir seepage prevention facilities by surrounding human activities and strengthen the management of the surrounding environment of the reservoir.