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Composite geomembrane
Composite geomembrane is widely used in canal anti-seepage engineering. The large number of applications and effects of geosynthetics in civil engineering, especially in flood control and rescue engineering, have attracted the attention of engineering and technical personnel. For the application technology of geosynthetics, the state has put forward normative technical requirements in terms of anti-seepage, filtration, drainage, reinforcement, protection, etc., which has greatly accelerated the promotion and application of new materials. This material has been widely used in canal anti-seepage projects in irrigation areas. Combined with construction practice, the application technology of composite geomembrane is discussed.
Chinese name锛欳omposite geomembrane
Foreign name锛欳omposite geomembrane
Attributes锛欼mpervious material
Come source锛欸eotextile and geomembrane composite
Use the way锛欳anal seepage control project
Introduction
Composite geomembrane is an impermeable material made of geotextile and geomembrane. It is mainly used for anti-seepage. The composite geomembrane is divided into one cloth and one membrane and two cloth and one membrane. The width is 4-6m and the weight is 200- 1500g/m2, with high physical and mechanical properties such as tensile resistance, tear resistance, bursting resistance, etc., it can meet the needs of civil engineering such as water conservancy, municipal administration, construction, transportation, subway, tunnel, etc. Because of its choice of polymer materials and the addition of anti-aging agents in the production process, it can be used in unconventional temperature environments.
Application Technology
Performance
The composite geomembrane (composite impermeable membrane) is divided into one fabric and one membrane and two fabrics and one membrane, with a width of 4-6m, a weight of 200-1500g/m虏, and physical and mechanical properties such as tensile resistance, tear resistance, and bursting resistance. High, the product has the characteristics of high strength, good elongation, large deformation modulus, acid and alkali resistance, corrosion resistance, aging resistance, and good anti-seepage performance. It can meet the needs of civil engineering such as water conservancy, municipal administration, construction, transportation, subway, tunnel, and engineering construction such as seepage prevention, isolation, reinforcement, crack prevention and reinforcement. It is often used for the anti-seepage treatment of dams, drainage ditches, and the anti-fouling treatment of waste materials.
Geomembrane production workshop
Construction
The composite geomembrane is heated by the far-infrared oven on one or both sides of the film, and the geotextile and geomembrane are pressed together by a guide roller to form a composite geomembrane. With the improvement of production technology, there is also a casting method to make composite geomembrane technology. Its form includes one cloth and one film, two cloth and one film, two films and one cloth.
The geotextile is used as the protective layer of the geomembrane to protect the impermeable layer from damage. In order to reduce ultraviolet radiation and increase anti-aging performance, it is best to use the buried method for laying.
During construction, first use sand or clay with a smaller material diameter to level the base surface, and then lay the geomembrane. The geomembrane should not be stretched too tightly, and the part buried in the soil at both ends is corrugated, and finally a 10cm transition layer is spread on the geomembrane with fine sand or clay. Lay 20-30cm blocks of stone (or concrete prefabricated blocks) as a protective layer against erosion. During construction, every effort should be made to avoid stones directly hitting the geomembrane. It is best to construct the protective layer while laying the membrane. The connection between the composite geomembrane and the surrounding structures should be anchored by expansion bolts and steel plate battens, and the connection part should be coated with emulsified asphalt (2mm thick) to prevent leakage.
Composite geomembrane construction picture
Water pressure measurement
Determination of hydrostatic pressure resistance of composite geomembrane
1. The principle of hydrostatic pressure resistance of composite geomembrane After the pressure head on both sides of the composite geomembrane reaches a certain value, the composite geomembrane will rupture. Gradually increase the hydraulic pressure curing on both sides of the sample and keep it for a certain period of time. When the seepage flow increases rapidly, it means that the sample is damaged, and the hydrostatic pressure resistance value of the sample is obtained.
2. Maintain the above-mentioned pressure of the composite geomembrane for at least 2 hours, observe the change of the water level of the seepage pipe, the water level of the composite geomembrane is basically stable (seepage flow is 0), then increase the pressure step by step with 0.1-0.2mpa for the level difference, and maintain each level 2h, until there is a rapid increase in seepage flow, indicating that the sample has ruptured, and the previous first-level pressure is used as hydrostatic pressure (mpa).
3. If the composite geomembrane only needs to determine whether the geomembrane sample reaches a certain specified hydrostatic pressure resistance value, it can be directly pressurized to this pressure and maintained for 2 hours, and then it is determined to meet the requirements.
4. For each sample of the composite geomembrane, at least 3 samples shall be measured, and the lowest value shall be the hydrostatic pressure resistance of the sample.
Warp knitting
Characteristics of warp-knitted composite geomembrane: high tensile strength, low elongation, uniform vertical and horizontal deformation, high tear strength, excellent wear resistance, and strong water resistance. Warp knitted composite geomembrane.
Selection tips
The selection of composite geomembrane specifications is related to the flatness of the underlying layer, the allowable tensile stress of the material, the elastic modulus of the material, the maximum water head within the laying range and the maximum particle size of the covering layer, etc. The thickness design is mainly based on the strength required by water pressure. In addition, it is necessary to consider application conditions such as exposure, buried pressure, climate, and service life, and determine the design thickness and actual thickness in accordance with the current national standards.
Construction matters
(1) The use must be buried: the covering thickness should not be less than 30cm.
(2) The refurbished anti-seepage system should consist of cushion layer, anti-seepage layer, transition layer and protective layer.
(3) The soil should be solid to avoid uneven settlement, cracks, and turf and tree roots within the anti-seepage area should be removed. Pave the sand or clay with a small particle size as a protective layer on the contact surface with the membrane.
(4) When laying, the geomembrane should not be stretched too tightly. It is better that the two ends of the soil are buried in a corrugated shape, especially when anchored with rigid materials, there should be a certain amount of expansion and contraction.
(5) During construction, avoid stones and heavy objects directly on the geomembrane. It is best to construct, lay the membrane and cover the protective layer while constructing.
Composite geomembrane is widely used in reservoir seepage control projects
Features
1. The width of 6 meters, the widest composite film in China;
2. High puncture resistance and high friction coefficient;
3. Good aging resistance, adapt to a wide range of ambient temperature;
4. Excellent anti-drainage performance;
5. It is suitable for projects such as water conservancy, chemical industry, construction, transportation, subway, tunnel, garbage disposal plant, etc.
Composite geomembrane
Impervious bedding
Feature
The composite geomembrane uses plastic film as an impermeable base material and is composited with a non-woven fabric. Its impermeability mainly depends on the impermeability of the plastic film. The plastic films used for anti-seepage applications at home and abroad mainly include polyvinyl chloride (PVC), polyethylene (HDPE, LDPE, LLDPE), and ethylene/vinyl acetate copolymer (EVA). They are a kind of polymer chemical flexible material with relatively high specific gravity. Small size, strong extensibility, high adaptability to deformation, corrosion resistance, low temperature resistance, and good frost resistance.
There is also a new type of composite geomembrane-warp knitted composite geomembrane. Warp-knitted composite geomembrane is a new type of geotechnical material that uses synthetic fiber (or glass fiber) as the reinforcing material and is compounded with composite geomembrane. Warp knitted composite geomembrane is different from general composite geomembrane. Its biggest feature is that the intersection of warp and weft is not bent, and each is in a straight state. Tie the two firmly with a binding thread, which can be more uniform and synchronized across the board, withstand external force and distribute stress, and when the external force is applied to tear the material, the yarn will gather along the initial split to increase the tear resistance. When warp-knitting is combined, the warp-knitted binding thread is used to repeatedly pass through the fiber layers of the warp, weft and short fiber needle-punched non-woven waterproof geotextile, so that the three are knitted together. Therefore, the warp-knitted composite geomembrane not only has the characteristics of high tensile strength and low elongation, but also has the waterproof performance of the composite geomembrane. Therefore, the warp-knitted composite geomembrane is an impermeable material with the functions of reinforcement, isolation and protection. It is a high-level applied geocomposite material in the world today銆?/p>
Composite geomembrane products
Service life
In view of the fact that the composite geomembrane has certain anti-aging ability in engineering application, some documents of some countries have made relatively lenient provisions for its service life, such as the former Soviet Union BCH07-74 "Earth-rock Dam Application" "Instructions for Polyethylene Impervious Structures" stipulate that polyethylene geomembrane can be used for buildings with a service life of no more than 50 years. The conclusion in the article "Long-term Properties of Polypropylene Composite Geomembrane Geosynthetics" published by Linz Company in Austria reads: "More than 15 years of field application experience on polypropylene shows that their chemical and biological stability is high, and the fabric The biggest damage is during construction, there is no major change after laying, and the stability can be expected for more than 100 years.
Its main mechanism is to block the leakage channel of the earth dam with the impermeable plastic film, and with its large tensile strength and elongation, it can withstand the water pressure and adapt to the deformation of the dam; and the non-woven fabric is also a kind of polymer short fiber chemical The material, through needle punching or thermobonding, has high tensile strength and extensibility. After it is combined with the plastic film, it not only increases the tensile strength and puncture resistance of the plastic film, but also due to the rough surface of the non-woven fabric , Increase the friction coefficient of the contact surface, which is conducive to the stability of the composite geomembrane and protective layer. At the same time, they have good corrosion resistance to bacteria and chemical effects, are not afraid of acid, alkali, and salt erosion, and have a long service life when used in the dark.
Selection
There are many domestic manufacturers of geomembrane, and the product specifications are also varied, including one cloth and one membrane, one cloth and two membranes, two cloth and one membrane, two cloth and two membranes, and multiple cloth and multiple membranes. Models are 200g/m2~1000g/m2, etc., which can also be requested by users according to their actual conditions, and manufactured separately by the manufacturer according to requirements.
Skills requirement
鈶燩rocess
The composite geomembrane anti-seepage adopts the cyclic operation of digging, paving, ramming and protecting at the same time
鈶otective layer and surface
The 10cm-thick protective layer of the geomembrane must be sieved, and no particles larger than 6mm in diameter are allowed, otherwise the geomembrane is easy to pierce. The soil material of the protective layer must be compacted with a ram to ensure that the dry bulk density is above 1.5, and take samples for inspection at any time. When backfilling the protective layer and the masonry surface protection, it must be handled gently to avoid breaking the geomembrane. A 100mm thick crushed stone or gravel cushion should be laid under the block stone protection surface to prevent the soil protection layer from being washed out due to the influence of water level changes, wind and waves and other factors. The dry block stone shall be laid by artificial hanging lines, the stones shall be tightly embedded, the individual weight of the surface block stone shall be greater than 48kg, and all the gaps shall be filled with small stones.
鈶aying of composite geomembrane
When laying the film, it must be laid from bottom to top. The film and the film and between the film and the base surface should be flattened and tightly pressed, but the film should not be stretched too tightly, generally a little looser, but no air bubbles should be left at the bottom of the film. Because the geomembrane is relatively thin and light, it is easy to be blown by the wind after it is laid and before the protective layer is laid. Therefore, the area of the film should not be too large at one time. It is best to cover the protective layer with soil material while laying the film.
According to the information provided by the manufacturer, the composite geomembrane has a width of 1.0~1.9m. This project uses a width of 1.9m to reduce the joint material. The joints can be hot glued, glued, lapped, etc. The design of this project adopts glue, and the joint width is 50mm.
If a puncture or tear is found in the geomembrane, it must be patched with geomembrane glue three times the damaged area.
鈶ase surface cleaning
The base surface must be cleaned according to the design requirements. This is the key to ensure the anti-seepage effect, especially the sharp stones, tree roots and other debris must be thoroughly removed. The base surface must not have local unevenness. The cleaned base surface must Tamper tightly with a rammer or ramming plate to make it compact and flat.
鈶?Peripheral boundary treatment
The requirement of peripheral junction treatment is to tightly connect the composite geomembrane with the surrounding soil, block the seepage inlet, cut off the lateral leakage path, and prevent seepage water from entering the bottom surface of the geomembrane, forming blisters, and swelling and breaking the geomembrane when the reservoir water level drops. . Therefore, it is necessary to dig a water trough at the peripheral junction and bury the geomembrane in the trough. See the design drawing for specific layout.
Speaking of composite geomembrane, we must emphasize the national technical standard: GB/T17642-2008. The national standard has specific parameter requirements for various specifications of composite geomembrane. According to the process difference, the composite geomembrane is mainly divided into thermal composite geomembrane and coating composite geomembrane.
Application of composite geomembrane in engineering
Function enhancement
1. The contact surface between the composite geomembrane and the supporting material should be smooth to prevent the membrane from being punctured and losing its anti-seepage effect. Otherwise, a fine-grained cushion should be provided to protect the membrane from damage.
2. Generally in corners and deformed areas, the length of the joints should be as short as possible. Except for special requirements, on slopes with a slope greater than 1:6, within 1.5 meters from the top slope or stress concentration area, try not to install welds.
3. The connection of the composite geomembrane itself and the connection methods of the impermeable membrane can be summarized into three types, namely the bonding method, the welding method and the vulcanization method, depending on the raw materials of the impermeable membrane, and the impermeability of all joints All should be inspected to prevent leakage due to poor joint connection.
4. The connection between the composite geomembrane and the surrounding boundary. The composite geomembrane must be tightly integrated with the surrounding boundary, and anchoring grooves can be excavated between the foundation and the bank slope during construction. If the foundation is a shallow sand-gravel permeable layer, the sand and gravel should be excavated until the base rock and then the concrete base is poured , Fix the geomembrane in the concrete. If the foundation is an impervious and sticky layer, you can excavate an anchor trench with a depth of 2m and a width of about 4m, place the geomembrane in the trench, and then compactly backfill the clay; if the foundation is deep The permeable layer of sand and gravel can be covered by geomembrane to prevent seepage. Its length is determined by calculation. The covering part must be leveled, and a transition layer with a thickness of about 30cm and a maximum particle size of 20mm should be laid. The filter layer is then added with a protective layer. The periphery of the membrane should be tightly combined with the impervious layer of the bank slopes on both banks. The connection between the anti-seepage membrane and the anchor groove is determined by the allowable contact and seepage slope of the membrane and concrete. Polyvinyl chloride and butyl rubber films can be well adhered to the concrete surface with adhesives or melting agents, so the embedding length can be appropriate and shorter. Because the polyethylene film cannot adhere to the concrete surface, the length of the embedding concrete At least 0.8m.
5. After the composite geomembrane is laid, it is necessary to minimize walking and moving tools on the surface of the membrane. Anything that can cause harm to the impermeable membrane should not be placed on the membrane or carried on the membrane to avoid damage The membrane causes accidental damage.
Construction problem
1) Quality inspection of composite geomembrane materials.
2) The dyke slope is cleaned, the site is leveled, all sharp corners are removed, the under-slope is backfilled and compacted, and the rich slope is cut and flattened. After the supervision and acceptance, it provides a working surface for laying the composite geomembrane.
3) Splicing in the geomembrane field In order to facilitate the construction and ensure the splicing quality, the composite geomembrane should be as wide as possible to reduce the amount of on-site splicing. Before construction, it should be cut and spliced in the unit according to the width of the composite geomembrane and the length of the site. A block that meets the required size is formed, rolled on a steel pipe, and manually transported to the working surface for laying.
1) Laying method of composite geomembrane:
The composite geomembrane laying is divided into two parts: the bottom laying of the canal and the laying of the slope surface. Laying method: horizontal rolling along the channel axis. After the slope is laid on the slope, it is rolled along the axis of the slope and the composite geomembrane at the bottom of the canal adopts a T-shaped connection.
2) Technical requirements for laying of composite geomembrane:
Laying should be carried out in dry and warm weather. In order to facilitate splicing and prevent stress concentration, the composite geomembrane is laid in a wave-shaped relaxation method with a margin of about 1.5%. After spreading, it should be flattened and opened in time, requiring composite geomembrane and slope surface The anastomosis is smooth and there are no protrusions and wrinkles. The construction personnel should wear flat-bottomed cloth shoes or soft rubber shoes. Spike shoes are strictly prohibited to avoid stepping on the geomembrane. If the geomembrane is found to be damaged during construction, it should be repaired in time.
Do not drag or pull the composite geomembrane during transportation to avoid injury from sharp objects.
1. Extend from the bottom to the high position, don't pull it too tightly, and leave a margin of 1.50% to prepare for local sinking and stretching. Taking into account the actual situation of the project, the slope shall be laid from top to bottom;
2. The longitudinal joints of two adjacent panels should not be on the same horizontal line, and should be staggered by more than 1m;
3. The longitudinal joint should be more than 1.50m away from the dam foot and bend foot, and should be set on a plane;
4. Slope first and bottom of the field;
5. When laying on a slope, the film spreading direction should be basically parallel to the line of maximum slope.
Welding specification
鈶燣ap joint: the width of lap joint should be greater than 15cm;
鈶eat welding: suitable for a slightly thicker geomembrane substrate, and the overlap width of the weld is not less than 5CM. (Gluing is not recommended, soaking in water for a long time is easy to open the glue, and the anti-seepage effect is poor.)
Process flow
1. Foundation excavation
2. Make the mortar protection layer at the bottom of the lake (H20-30mm)
3. Slope, compact and level
4. The composite geomembrane is pasted on the vertical retaining wall
5. The base surface is leveled, cleaned, and the process is handed over
6. Sealing and stopping of underwater water pipe mouth
7. Laying and welding of composite geomembrane
8. Process handover
9. Welding and repair quality acceptance
10. Completion acceptance
Project Overview
1. The highest design water level: about 0.6m.
2. The total area of waterproof construction is about 800 square meters.
3. Ceramsite brick masonry retaining wall.
4. There are craters underwater.
Main waterproof material
1. Composite geomembrane coil, specifications: 50*4m; 150g/銕?0.5mm/150g/銕?
2. GB rubber water stop strip.
Basic condition
1. After foundation shaping and excavation, slope cutting, leveling and rolling or compaction must be carried out. Displacement and backfilling of disturbed soil shall be sprinkled or compacted in layers, each layer thickness 鈮?00mm.
2. Remove the exposed materials on the surface of the foundation with hidden dangers of puncture, such as bricks, stones, tiles, glass and metal debris; branches, plant rhizomes, etc. Clear obstacles in the field and provide necessary paving construction conditions.
3. The installation and reservation of surrounding water retaining walls, pump pits, bridge foundations, and underwater nozzles must be completed before the construction of the composite geomembrane.
Welding and laying technology
1. Welding technology
鈶燣ap width of weld bead: 80~100mm; the natural folds of the plane and vertical surface are respectively: 5%~8%; reserved expansion amount: 3%~5%; leftover amount: 2%~5%
鈶he working temperature of hot melt welding is 280~300鈩? the traveling speed is 2~3m/min; the welding mode is double bead.
鈶he method of repairing the damaged part, cutting the material of the same specification, hot-melt bonding and sealing with polyethylene glue.
鈶?There is no imitation cloth connection at the welding bead, and mechanical stitching is used.
鈶he sealing and water stop of the underwater pipe mouth is sealed with GB rubber water stop strip, metal wrapped and anti-corrosion treatment.
2. Laying technology
鈶燭he laying and unfolding direction of the composite geomembrane is from E to W or from W to E. The length of each laying, including the height of the retaining walls on both sides, is completed at one time.
鈶aying sequence, advance from the channel axis to both sides of S and N.
鈶n the construction process, first do the mortar protection layer (20-30mm) of the composite geomembrane at the bottom of the lake, and then do the paste with the vertical retaining wall.
鈶asting process of composite geomembrane and retaining wall. Apply the adhesive on the adhesive surface of the composite geomembrane and the retaining wall, dry and stand for about 5 minutes, then paste, squeeze, and flatten. The adhesive is made by mixing asphalt emulsion paint, cement and water. After the pasting is completed, the brazing nails are anchored above the water level, and waterproof and anti-corrosion treatments are done.
Quality acceptance
1. The material and construction of composite geomembrane are in compliance with the national standards for polyethylene geomembrane and composite geomembrane issued by the State Bureau of Quality and Technical Supervision.
2. Construction quality acceptance is divided into self-inspection by the construction unit and random inspection by the contractor.
3. Welding quality inspection adopts the "inflation pressure method" and the "visual inspection method" for damage repair. The inflation pressure detection index is 0.06Mpa.
4. The quality acceptance process includes the process handover procedures, completion acceptance and so on.
5. Normal leakage of artificial lake: 鈮?5mm/24h (including seasonal evaporation loss).
Construction Schedule
1. Daily efficiency, a unit is 2000~2500銕?per day according to the construction area.
2. The planned construction period is 3 days.
Suggest
1. Strengthen the protection and management of the finished composite geomembrane, improve the waterproof awareness of relevant construction personnel, and put into normal operation on schedule to ensure the quality of the project. Has a very important meaning.
2. It is recommended that the contractor should notify and send a special person to supervise. If the construction personnel related to waterproof materials find the composite geomembrane is damaged, they should promptly notify the waterproof construction personnel to repair.
3. The composite geomembrane must be prevented from sticking to oil, otherwise it will reduce the bonding strength. Storage and protection "See Introduction to Geomembrane Construction Method".
4. It is recommended that this project pay attention to the following links:
鈶燗fter the composite geomembrane is welded into a finished product, a protective layer of mortar at the bottom of the lake must be made first.
鈶he bridge foundation is waterproof, the steel bar is welded through the membrane, and the mortar protective layer is used to prevent hidden quality problems caused by electric welding.
鈶he pasting of composite geomembrane and wall shall prevent the appearance of large-area hollowing.
Specification
1. One cloth and one film (cloth: 100-1000g/m2 film thickness: 0.1-1.5mm)
2. Two cloths and one film (cloth: 80-600g/m2 film thickness: 0.2-1.5mm)
3. One cloth and two films (cloth: 100-1000g/m2 film thickness: 0.1-0.8mm)
4. Multi-cloth multi-membrane (cloth: 100-1000g/m2 film thickness: 0.1-0.8mm)
Design material
1. According to the nature of the project, category, application location, use conditions, design requirements, etc. to select the appropriate type and specifications.
2. Determine the thickness of the geomembrane according to the strength of the water pressure required by the engineering design, as well as the application conditions such as exposure, buried pressure, climate, and service life.
3. Determine the width and length of the geomembrane according to the actual size, area, construction conditions, and construction capabilities of the project, and the minimum number of joints during construction.
4. When the base layer is a concrete structure, it is advisable to choose a filament non-woven composite soil membrane that can be directly bonded to the cement base layer.
5. It is used for anti-seepage treatment in highways. Generally, 200-300g/m of one cloth and one film is used for the anti-seepage of the lower part of the central partition.Buy Composite Geomembrane
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