Technical requirements for laying HDPE geomembrane

  1. Before laying HDPE geomembrane, the corresponding qualified acceptance certificate of civil engineering shall be obtained.

  2. Before cutting the HDPE film, the relevant size should be accurately measured, and then cut according to the actual size. Generally, it is not suitable to cut according to the size shown in the figure. It should be numbered piece by piece and recorded in detail on the special form.

  3. When laying HDPE geomembrane, the welds should be minimized, and raw materials should be saved as much as possible under the premise of ensuring quality. It is also easy to ensure quality.

  4. The overlap width of the seam between the film and the film is generally not less than 10cm, usually the welding seam arrangement direction is parallel to the maximum slope, that is, arranged along the slope direction.

  5. Usually in corners and deformed areas, the length of the joint 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, there should be no welds as much as possible.

  6. When laying HDPE geomembrane, avoid artificial wrinkles. When the temperature is low, it should be tightened and flattened as much as possible.

  7. After the HDPE 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 HDPE membrane should not be placed on the membrane or carried on the membrane to avoid damage to the membrane. Cause accidental damage.

  8. Sufficient material should be reserved at the top of the slope to be fixed with anchor trenches.

  Geomembrane welding

  1. The welding process of the hot wedge welding machine is divided into: adjusting pressure → setting temperature → setting speed → welding seam overlap inspection → loading film into the machine → starting motor → pressure welding.

  2. There should be no oil and dust at the joints, and there should be no debris such as mud and sand on the overlapping section of the HDPE geomembrane. When there are debris, they must be cleaned up before welding.

  3. The welding seam is required to be neat and beautiful, without slip welding or skipping.

  4. When the length of the geomembrane is not enough, it needs to be spliced in the long direction. The transverse welding seam should be welded first, and then the longitudinal seam should be welded.

  5. Adjacent geomembrane welds should be staggered and overlapped as much as possible. The joints formed between the membrane blocks should be T-shaped, and cross-shaped should be minimized. The intersection of the longitudinal die and the weld should be reinforced with an extrusion welder.

  6. When welding the film, it is not allowed to press out dead bends. When laying HDPE geomembrane, set aside the amount of expansion and contraction caused by temperature changes according to the local temperature change range and HDPE geomembrane performance requirements.

  7. When the temperature of the welder indicated by the temperature control of the portable welder is lower than 200℃, wipe it off with a clean cloth or cotton yarn and re-solder. If necessary, it should be polished again. Do not wipe it by hand.

  8. When the joints are affected by condensation, dampness, sand, etc., they should be welded after treatment.

  9. Welding cannot be performed during rain or when there is moisture, dew, or heavy sand in the joints, unless protective measures are taken.

 10. When the temperature is lower than 5℃, construction should not be carried out in accordance with the specifications. If construction is necessary, the welding machine should be preheated before welding.

 11. During the welding process of the extrusion welding machine, the slider of the gun head should be checked frequently, and the slider should be replaced in time when the wear is serious to avoid damage to the film surface.

 12. The geomembrane should be powered by a generator with good voltage stabilization performance when welding, and a voltage stabilizer must be used when local electricity is used in special circumstances.

  Technical requirements for laying 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. The composite geomembrane and slope are required. The surface is flat and smooth, without 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 damaged during construction, it should be repaired in time.

  Splicing of composite geomembrane

  1) This project uses two-cloth and one-membrane composite geomembrane, and the welding is constructed by hot-melt welding. In order to ensure the welding quality, the welding should be carried out in the factory as much as possible, but for the convenience of construction, the width of the composite geomembrane should not be too wide. Must be spliced at the construction site.

  2) The welding quality of composite geomembrane is the key to the success or failure of composite geomembrane's anti-seepage performance. Therefore, the welding of geomembrane must be done well to ensure the welding quality. Therefore, the manufacturer of geomembrane welding should be performed by professional technicians on site. , Guidance, training, using special welding equipment for geomembrane.

  3) The welding process of two-cloth and one-membrane composite geomembrane in this project:

  4) Welding process: After the first geomembrane is laid, the second geomembrane is reversely laid on the first one, and the welding edge direction of the two films is adjusted to overlap about 7-10cm.

  5) Before welding, blow off the sand, soil and other dirt on the membrane surface with a hair dryer to ensure that the membrane surface is clean. Before the formal welding, perform trial welding according to the construction temperature to determine the walking speed and welding temperature. Generally, the walking speed is 1.5～ 4m/min, the welding temperature is 250-350 degrees. Two splicing welds, each with a width of 7-9mm, leave a cavity of 10mm between the two welds.

  Construction quality control of composite geomembrane

  Control the construction operation process Before laying the composite geomembrane, prepare the construction organization design, explain the laying method and technical measures, and use it after approval by the supervisor. The construction personnel should wear flat shoes or soft rubber-soled shoes for laying, and it is strictly forbidden to wear spiked shoes to prevent stepping on it. The geomembrane can be laid and pressed, and the laying of the composite geomembrane should be coordinated with the laying of the protective layer. In splicing, the quality of composite geomembrane welds is the key to splicing. In construction, joint inspection must be strengthened. The inspection methods include visual inspection and on-site leak detection. Visual inspection method: After the composite geomembrane is welded, observe whether there is any missing joints, whether the joints are burnt, whether there are wrinkles, whether they are evenly spliced, etc. The on-site leak detection uses the inflation method to detect the welds. The welds are double strips with a cavity of about 10mm between the two. Seal both ends of the section to be tested, insert a gas needle, and inflate to 0.05mpa～0.20mpa , Observe for 0.5min, observe the vacuum gauge, if there is no drop in the air pressure, it means that there is no leakage, weld the grid, otherwise find the reason and repair it in time. The anchoring of the upper and lower parts of the composite geomembrane is an important link, and the construction shall be carried out in strict accordance with the construction drawings and after the supervision and acceptance.

  Precautions for on-site construction

  Before going to the construction site, call the customer or related personnel to ask: the progress of the construction site and the topography (earthwork), preparations for laying and welding (number of personnel, 220 volts of electricity, cable length, insurance rope required)