How to construct geomembranes Echo

Geomembrane laying process

SGS certificate-1.5mm(1).pdf

The construction process is carried out in the following order: laying → alignment, aligning → pressing and shaping → wiping dust → welding test → welding → inspection → repair → re-inspection → acceptance.

The seam welding method is to let the welder walk on the laid membrane, and the welding work is done in one go.

In order to facilitate construction and ensure the quality of splicing, the geomembrane should be as wide as possible to reduce the amount of splicing on site. Before construction, it should be cut in a special site according to the width and length of the geomembrane on site, and spliced into blocks of the required size, rolled on steel pipes, and manually transported to the work surface for laying. The revetment is laid from top to bottom, and horizontally from the foot of the slope to the outer end; when laying, pedestrian wooden boards are placed on both sides of the geomembrane, and attention is paid to moderate tension and relaxation. The joint surface between the geomembrane and the cushion layer must be matched and flat to avoid damage caused by humans and construction machinery. Construction workers should wear flat cloth shoes or soft rubber-soled shoes for laying. It is strictly forbidden to wear spiked shoes to prevent the geomembrane from being stepped on. The laying of geomembrane should be coordinated with the laying of the protective layer, and the geomembrane should be pressed as it is laid.

Technical requirements

(1) Manual laying should be carried out in blocks in the order of upstream first, downstream second; slope first, and trench bottom second.

(2) The membrane should be properly relaxed during laying, and a 3% to 5% margin should be reserved. A protruding wave-shaped relaxation method should be made to adapt to temperature changes and foundation settlement. And avoid artificial hard folding damage.

(3) When laying geomembranes on the slope, the joint arrangement direction should be parallel or perpendicular to the maximum slope line and should be laid from top to bottom. The membrane and the joint should be connected at the bend of the slope. The retaining walls on both sides should be laid at the same time as the trench bottom.

(4) The geomembrane should be naturally relaxed and close to the support layer, and should not be wrinkled or suspended in the air.

(5) Cut and splice according to the required size. The joints between the two pieces should be flat and wrinkle-free.

(6) The geomembrane should be pressed while being laid to prevent it from being blown away by the wind. Before covering the protective layer, a 20-40 kg sandbag should be placed every 2-5 meters at the corners of the membrane.

(7) To ensure the convenience of construction and the quality of splicing, the geomembrane should be as wide as possible to reduce the amount of splicing on site and cut in the unit as needed.

(8) When laying geomembranes, it should be laid when the outdoor temperature is above 5 degrees Celsius and the wind force is below level 4 without rain or snow. If there is rain or snow, construction should be stopped and the laid geomembrane should be covered with colored strips or plastic cloth.

Precautions during laying

(1) During the laying process, the appearance of the membrane should be checked at any time for defects such as damage, pitting, and holes.

(2) If defects or damage are found on the membrane, it should be repaired with fresh parent material in time. The scar should exceed the damaged part by 10-20 cm on each side.

Each process of geomembrane laying should be subject to "three inspections". The laying and welding of geomembrane should comply with the requirements of "Introduction to Geomembrane Construction Methods".

Welding technical requirements

(1) Double weld overlap using T welding machine

(2) Before welding, wipe the weld overlap with clean gauze or cotton cloth or blow with a hair dryer to ensure that there is no water, dust or dirt. The geomembrane is aligned parallel and overlapped appropriately with a width of 10 cm.

(3) The travel speed of the film welding machine is generally 1.5-5 m/s, and the welding temperature is 180 degrees to 200 degrees.

(4) The connection between the geomembrane and the water retaining wall is bonded with an adhesive (the adhesive is made of latex paint, cement and water). After bonding, it is anchored above the water level.

(5) The welded sample is tested by on-site tearing. The weld is not damaged by tearing and the parent material is torn, which is considered qualified.

(6) After welding is completed, it is reported for inspection and acceptance. Before acceptance, the construction unit conducts self-inspection and the contractor conducts random inspection.

Precautions for geomembrane welding

(1) The geomembrane at the welding point should be welded as a whole, and no false welding, leaking welding or excessive welding should occur.

(2) When false welding or leaking welding occurs, the weld must be cut open. Use a welding machine to weld the cut damaged part with a base material that is more than twice the diameter of the damage.

(3) The width of the double weld should be 2mm×10mm

(4) The horizontal joint misalignment size should be ≥500mm.

(5) The base material should be used to fill the T-shaped joint, and the filler size should be 300mm×300mm

Geomembrane inspection

(1) Visual inspection: carefully inspect the appearance of the laid geomembrane, welding quality, T-shaped welding, base debris, etc.

(2) On-site leak detection method: The double weld length is tested by the inflation method (inflation length 30-60m). Test method: Seal both ends of the section to be tested, insert the air needle, inflate to 0.25MPA, and observe the true air gauge after 5 minutes. If the air pressure drops by less than 20%, it indicates no leakage.

(3) Destruction test: Take a group of 1000m2 for testing on site. Its strength shall not be less than 80% of the parent material, and the specimen shall not break at the seam, otherwise the seam quality will be unqualified.

Repair of geomembrane

After the test is completed, all the inflation and pressure perforations made during the test should be immediately blocked by extrusion welding. The unqualified parts should be repaired with fresh parent material in time. After passing the re-test, the upper geomembrane should be sewn immediately. Quality requirements

(1) Main control items: Geosynthetics strength, geosynthetics elongation, and foundation bearing capacity should meet the geosynthetics foundation quality inspection standards.

(2) General items: Geosynthetics overlap length, soil and stone organic matter content, layer flatness, and each layer laying thickness should meet the geosynthetics foundation quality inspection standards.

(3) Other quality control quality requirements

The types and properties of the geosynthetics and filler soil used should be determined through field tests based on the engineering characteristics and foundation soil conditions; if geosynthetics are connected by seam joints, the connection strength in the main force direction should be no less than the tensile strength of the material used.

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