HDPE anti-seepage membrane, geomembrane landfill construction method

Qingdao Yidian Plastic Welding Equipment Co., Ltd. Technology Department

1. Requirements before construction

1. The anti-seepage construction of the landfill is the core of the whole project. Therefore, the anti-seepage construction must be completed under the joint supervision of Party A, design and supervision, and the close cooperation of the civil engineer.

2. The materials used in the project must meet the requirements.

3. The base layer after civil construction must meet the design requirements.

4. The machinery and equipment for material construction must meet the requirements.

5. Construction workers must be skilled.

2. The requirements for controlling the laying site of the civil foundation level are "four degrees"

1. Flatness: ±2cm/m2, flat and straight;

2. Compaction degree: 95%, geomembrane can be laid on it after rolling;

3. Longitudinal and transverse slopes: the longitudinal and transverse slopes should be more than 2%, and the contour boundary and structure at the bottom of the landfill must be conducive to the diversion of leachate;

4. Cleanliness: There shall be no sharp-edged debris such as tree roots, rubble, stones, and concrete particles within a vertical depth of 2.50cm.

3. Climate requirements for laying construction:

1. The temperature is 5-40℃. Considering the thermal expansion and contraction of the geomembrane, according to experience, the laying of the geomembrane should be tighter when it is cold; it should be relaxed when it is hot; of high temperature.

2. Wind and rainy days: construction should be stopped on windy levels exceeding 4 or rainy days; when the wind is small, sand bags should be used to press the geomembrane to facilitate construction.

4. Construction and installation of HDPE geomembrane

1. Cut and Ship

According to the records of the measurement of the laying base, cut the large bundles of geomembrane number records, and transport them to the laying site according to the numbers. Note that the geomembrane should not be dragged or pulled hard during transportation to avoid being stabbed by sharp objects.

2. HDPE geomembrane laying construction and installation

1) It should extend from the bottom to the high position, do not pull too tight, and leave a margin of 1.50% for local sinking and stretching. Taking into account the actual situation of the project, the slope is laid from top to bottom.

2) The longitudinal joints of two adjacent sheets should not be on a 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 the bent foot, and should be set on the plane.

4) Slope first and then the bottom of the field.

5) When laying the slope, the direction of film spreading should be basically parallel to the maximum slope line.

Slope laying control: Before the anti-seepage geomembrane is laid on the slope, first check and measure the laying area, and transport the anti-seepage membrane with the matching size in the warehouse to the first-stage anchoring ditch platform according to the measured size. According to the actual conditions of the site, a convenient way of "pushing the shop" from top to bottom is adopted. It should be cut reasonably in the fan-shaped area so that the upper and lower ends are firmly anchored.

* Bottom laying control: Before laying the anti-seepage geomembrane, first check and measure the laying area, and transport the anti-seepage membrane matching the size in the warehouse to the corresponding position according to the measured size: when laying, manually press a certain in the direction of "Pushing".

* Alignment and alignment: The laying of HDPE geomembrane, whether it is a slope or a field bottom, should be flat and straight, avoiding wrinkles and ripples, so that the two geomembranes can be aligned and aligned. The lap width is generally about 10cm according to the design requirements.

*Control of lamination: Use sand bags to press the aligned and aligned HDPE geomembrane in time to prevent it from being pulled by the wind.

*Laying control in the anchoring ditch: On the top of the anchoring ditch, a certain amount of anti-seepage membrane should be reserved according to the design requirements for local sinking and stretching.

*Longitudinal joints: the upslope section is up, the downslope section is down, and there is enough overlap length ≥15 cm, the area after the acceptance of the bentonite pad laying is laid, and the "push laying" is manually carried out in a certain direction. .

3. Welding Preparation: Experimental Welding Requirements:

1) Experimental welding was performed on HDPE geomembrane samples to inspect and adjust the welding equipment.

2) The welding equipment and welding personnel can only proceed to the next production welding after the successful completion of the experimental welding.

3) Frequency control of experimental welding: According to the change of ambient temperature, each machine shall be no less than twice a day, once before the formal operation and once in the middle shift.

4) Pilot welding is performed under the same surface and environmental conditions as production welding.

4. productive welding

1) Production welding can only be carried out by means of pilot welding.

2) Adjust the welding machine to the best parameters when welding through the experimental weldability, and automatically weld under the condition of the lap width required by the design, and the welding seam is "flat, firm and beautiful".

3) Repair with a welding torch only for repairing and where the double seam welding machine cannot operate.

5. Control of welding data

1) Whether it is production welding or experimental welding, the welding temperature, speed and pressure of the clamping stick must be maintained to achieve the best welding effect.

2) Each weld shall be inspected

6. Welding Quality Assurance Control Measures

1) When welding a slope, the length of the weld should extend along the slope and cannot cross.

2) Minimize the welding of side feet and sporadic films.

3) There should be a welding supervisor to supervise the welding operation.

4) The surface of HDPE geomembrane should be cleaned of grease, moisture, dust, garbage and other debris.

5) If welding is operated at night, there should be sufficient lighting.

6) At the lap joint of HDPE geomembrane, the wrinkles should be removed. When the size of the wrinkles is less than 10 cm, a circular or oval patch should be used, and the size of the patch should exceed the perimeter of the incision by 5 cm.

7) When the ambient temperature and unfavorable weather conditions seriously affect the welding of HDPE geomembrane, the operation should be stopped.

7. In response to the regular maintenance of the welding machine, the residues in the welding machine equipment should be cleaned frequently.

8. Welding inspection control measures

Inspection control is divided into product surface inspection and welding seam inspection.

1) Product surface inspection: When the HDPE geomembrane is unfolded, it should be checked visually for defects, and the defective or suspicious places should be marked for repair.

2) The inspection of the weld is divided into: visual inspection and leak test (non-destructive)

* Visual inspection of the weld: mainly to carefully check the appearance quality of the weld, the processing of the T-shaped weld and the cross-shaped weld, and whether there are sundries at the base layer.

*Surface of double welding seam: smooth, firm and beautiful, that is, smooth and smooth, with uniform thickness. There should be no other debris and excess scattered solder at the welding seam, and no damaged parts of the surrounding base metal should appear.

*T-welded surface: tightly combined, smooth connection.

*Cross-shaped welding seam surface: When it is really unavoidable, the cross-shaped welding can be used, but it must be covered with a patch of more than 20 cm square, which must be completed by an experienced welder.

3) Non-destructive testing: inflatable (double weld).

*Double seam gas filling detection: a non-destructive testing method to judge the quality of the welding by checking the air tightness of the double seam. The gas with a certain pressure is sealed in the air cavity, and its air tightness is judged by detecting the change of the pressure gauge attached to the needle.

*The composition of the instrument: a compression device, which can generate a pressure of 0.15--0.20Mpa, a hollow needle with a pressure gauge

* Procedure: Inflate the pressure of 0.15--0.20Mpa and keep it for more than 2 minutes to be qualified; if the pressure gauge is not stable, keep a certain pressure and apply soap liquid to the outer weld to check, if there is no air leakage It is considered qualified (ie, no treatment is performed on the other leaking weld).

4) Repair of defects: Defects found in visual inspection and positive pressure should be repaired in time; those that cannot be repaired immediately should be marked with special marks to prevent omissions.

* Repair of various voids: According to the size of the hole, when the hole is larger than 5mm, apply a 10cm round or oval liner to repair

*For small pinholes or voids, spot welding can be used.

9. Requirements for several anchoring joints

1) Anchoring ditch: It is used to fix the HDPE geomembrane and the protective layer geotextile. After the HDPE geomembrane and the protective layer geotextile are laid, they are immediately pressed with concrete plates.

2) Buffer platform: In order to stabilize the HDPE geomembrane and prevent sliding, a buffer platform is added in the center of the slope, and an anchoring ditch is set on the platform to reduce the pull-down force of the HDPE geomembrane and increase the stability. Due to the characteristics of the actual terrain, the anchoring ditch of the buffer platform in this project is small and narrow, so special attention should be paid during construction.

3) Flood intercepting ditch: Above the anchoring ditch, excavate a flood intercepting ditch to divert external rainwater to prevent water from directly entering the landfill.

The anchoring ditch in the first phase of the project also serves as a flood intercepting ditch.

10. Treatment of special parts of HDPE geomembrane welding

1) The intersection of the side slopes is the corner of the dam slope: laying and welding are special cases, and special tailoring should be made according to the actual situation to make the geomembrane close to the dam slope base, otherwise, it will cause "hanging" or "bulging" Phenomenon.

Construction points: In this area, the operator should carefully measure and cut the geomembrane into an inverted trapezoid with a wide top and a narrow bottom.

2) At the intersection of the slope of the reservoir area and the bottom of the reservoir, there are many blind ditches in the design.

Construction points: first lay the geomembrane along the dam surface at a distance of 1.5 meters from the blind ditch, and then connect it with the bottom membrane of the reservoir; the welding of the two adjacent sheets is: after welding, press into the blind ditch.

3) The connection between the dam pipe and the geomembrane: First, cut the HDPE geomembrane into a horn-shaped pipe sleeve according to the diameter of the leachate through the dam pipe, divide it into 6-8 small pieces, and then put the pipe sleeves in order from large to small. Sleeve it into the dam-piercing pipe, adjust the position of the pipe sleeve appropriately and fix it temporarily with a hot air welding torch, and the pipe sleeve must not have any suspended parts. Finally, the large and small openings of the pipe sleeve are welded to the HDPE geomembrane and the leachate dam pipe, and are reinforced with stainless steel hoop.

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