Construction specification for HDPE anti-seepage membrane for sewage tanks
Construction specification for HDPE anti-seepage membrane for sewage tanks
Ⅰ The laying of HDPE anti-seepage geomembrane
Laying HDPE anti-seepage membrane is a crucial process in the entire anti-seepage system.
Before laying the film, conduct an open-package inspection on the appearance quality of HDPE anti-seepage film, record and repair any mechanical damage, production trauma, holes, folds, and other defects that have been found.
Before cutting the HDPE anti-seepage film, its relevant dimensions are measured, and then cut according to the actual situation. During the laying of the film, the overlap width between the film and the film should not be less than 100mm, so that the joint arrangement direction is parallel to the maximum slope foot line, that is, arranged along the slope direction.
When laying HDPE anti-seepage film, efforts should be made to minimize the number of welds and save raw materials as much as possible while ensuring quality. It is also easy to ensure quality.
Usually, in corners and deformed areas, the joint length should be minimized as much as possible. Unless otherwise specified, within a range of 1.5 meters from the top slope or stress concentration area on slopes with a slope greater than 1:6, welding seams should be avoided as much as possible.
During the laying of HDPE anti-seepage film, artificial wrinkles should be avoided. When the temperature is low, it should be tightened and laid flat as much as possible.
After the HDPE anti-seepage membrane is laid, walking and moving tools on the membrane surface should be minimized as much as possible. Any objects that can cause harm to the HDPE membrane should not be placed or carried on the membrane to avoid accidental damage to the membrane.
Ⅱ Welding of HDPE anti-seepage geomembrane
The welding of HDPE anti-seepage film uses a wedge welding machine and dual track hot melt welding. For areas that cannot be welded by a wedge welding machine, an extrusion hot melt welding machine should be used, accompanied by welding rods of the same quality as the raw materials, to form a single weld seam for overlay welding.
1. The welding process of the hot wedge welding machine is divided into: adjusting pressure, setting temperature, setting speed, inspecting weld overlap, installing film into the machine, and starting the motor.
2. There should be no oil stains or dust at the joints, and the overlapping surface of the HDPE anti-seepage film should not have debris such as mud, dew, or moisture. When there are debris, they must be cleaned before welding.
3. At the beginning of each day's welding, a 0.9mm x 0.3mm specimen should usually be tested on site, with an overlap width of no less than 10cm. Peel and shear tests should be carried out on site. After the specimen is qualified, it can be welded at the adjusted speed, pressure, and temperature at that time. During the welding process of the hot wedge welding machine, it is necessary to pay attention to the operation of the welding machine at all times and adjust it according to the actual situation on site
Fine tune the speed and temperature.
4.The weld seam should be neat, beautiful, and free from slipping or jumping.
5.When the length of the geotextile membrane is not enough, it needs to be longitudinally spliced. The transverse weld seam should be welded first, and then the longitudinal weld seam should be welded. The transverse weld seam should be T-shaped with a distance of more than 50cm and should not cross.
6. When welding the film, it is not allowed to press out dead folds. When laying HDPE geomembrane, the expansion and contraction deformation caused by temperature changes should be reserved according to the local temperature change amplitude and the performance requirements of HDPE geomembrane.
7. Welding cannot be carried out during rainy periods or when there is moisture, dew, or heavy sand at the joints, but protective measures should be taken Excluding.
8.When the temperature is below 5 ℃, construction should not be carried out according to the specifications. If construction is necessary, the welding machine should be preheated before welding.
9. HDPE anti-seepage geomembrane should be welded using a generator with good voltage stability for power supply. In special circumstances, when using local electricity, a voltage stabilizer must be used.
Ⅲ Anchorage of HDPE anti-seepage geomembrane
1.There are many anchoring methods, including groove anchoring, nail anchoring, expansion bolt anchoring, and embedded part fixing. Sewage tanks are usually fixed with embedded parts or expansion screw pressure strips.
2. The width of the pressure strip should not be less than 2cm, the thickness should not be less than 2mm, the spacing between expansion bolts should not exceed 600mm, and anti-corrosion measures should be taken at the exposed parts of the pressure strip.
3. The diameter of the bolts shall not be less than 4mm, and the spacing between them shall not exceed 0.5mm. During construction, the prepared sandbags shall be used to temporarily fix the membrane in place to prevent strong winds from blowing and shifting the HDPE membrane. Then, the expansion bolts shall be anchored.
4. If the embedded parts are already embedded in the pool, simply use an extrusion welding machine to weld the film onto the HDPE embedded parts.
Ⅳ Construction precautions for HDPE geomembrane
1. The power cord of the hot air gun, grinding wheel machine, and welding machine must be kept as far away as possible from their working area during use to avoid damaging the brain and causing electrical leakage.
2. Except for hot air welding, the mouth of the hot air gun must not come into contact with the HDPE film surface under any circumstances, and should be kept as far away from the film surface, human body, machinery and other objects as possible.
3. When not in use, the welding machine should not be placed directly on the HDPE film surface, but should be placed on a bracket or sandbag strap.
4.After using the film cutting knife, the blade should be immediately retracted into the knife box.
5. All kinds of temporary small tools used on site should be promptly placed in the toolbox after use.
6. It is strictly prohibited to discard the solder material removed from the extrusion welding machine gun directly on the surface of the geomembrane.
Smoking is prohibited at the HDPE geomembrane construction site, and it is not allowed to wear shoes with iron nails or high heels with hard soles to walk on the membrane surface. It is not allowed to engage in any activities that may damage the finished geomembrane product.
Ⅴ Testing and repair of finished geomembrane products
1. The inspection is carried out in three steps, namely visual inspection, inflation detection, and damage test.
2. Visual inspection is mainly a detailed inspection of the appearance, weld quality, T-shaped welding, substrate debris, etc. of the laid geotextile membrane. All construction personnel should implement this work throughout the entire construction process.
3. In addition to visual inspection, if necessary, vacuum testing and air pressure testing can also be used. The inflation strength for air pressure testing is 0.25Mpa,No air leakage for 5 minutes, considering that the roll material is relatively soft and prone to deformation, a 20% decrease in pressure is allowed.
4.When conducting a tensile test (destructive test), the standard is that during the peel and shear tests, the weld seam is not torn open and the mother is only torn apart, indicating that the welding is qualified.
5. During the appearance inspection, if any defects such as holes are found on the film surface, or if there are missed or damaged welds during the welding process, fresh base materials should be used for repair in a timely manner. Each side of the repaired scar should exceed the damaged area by 10-20cm.
