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The HDPE geomembrane construction scheme

By Jiachi June 9th, 2023 84 views
The HDPE geomembrane construction scheme

1. Pre-construction requirements

1. Anti-seepage construction is the core of the whole project. Therefore, the anti-seepage construction must be completed under the joint supervision of Party A, the design and the supervision, and under the close cooperation of the civil engineering party.
2. The materials used in the project must meet the requirements.
3. The base surface of the completed civil construction must meet the design requirements.
4. The machinery and equipment for material construction must meet the requirements.
5. Construction personnel must be skilled in the work.

2. Control of the civil engineering base surface laying site requirements "four degrees"

1. Flatness: ± 2cm / m2, smooth and straight;
2. Compaction degree: 95%, after rolling can be laid geomembrane on it;
3. Vertical and transverse slope: the vertical and transverse slope should be more than 2%, and the boundary and structure of the wheel corridor at the bottom of the landfill must be conducive to the diversion of the leachate;
4. Cleanliness: no tree roots, rubble, stones, concrete particles and other sharp debris within the vertical depth of 2.50cm.

3. Climate requirements for laying and construction

1. The temperature is 5-40℃. Considering the thermal expansion and contraction of geomembrane, according to experience, the laying of geomembrane should be tight; it should be relaxed in hot weather; however, in summer
 Avoid the high heat at noon.
2. Wind power and rainy day: the construction should be stopped if the wind power exceeds grade 4 or the rainy day; when the wind is small, the soil membrane should be pressed with sand bags to facilitate the construction.

4. Construction and installation of the HDPE geomembrane

1. Cutting and transportation

According to the record of laying base surface measurement, cut large bundles of geomembrane number record, and carry to the laying site according to the number. Note that the geomembrane avoids sharp stabbing during transport.

2. Construction and installation of HDPE geomembrane laying

1) Do not pull too tight, should leave 1.50% pieces, for local subsidence and stretching.Considering the actual situation of the project, the slope is laid from top to bottom.
2) The longitudinal joint shall be more than 1.50M away from the dam foot and the bending foot, and shall be set on the plane.
3) First side slope and then field bottom.
4) When laying the slope, the film spreading direction should be basically parallel to the maximum slope line.
 Laying control of the slope: Before the geomeme of the slope, the laying area should be checked and measured, and the membrane matching the size of the warehouse should be transported to the first phase of the anchorage trench platform. When laying, the convenient way of "pushing" from the top down is adopted according to the actual conditions of the site. In the sector area should be reasonably cut, so that the upper and lower ends are firmly anchored.
* Field bottom laying control: before laying the geomembrane, the laying area should be checked and measured, according to the size of the warehouse matching the size of the film to the corresponding position: when laying, with a certain direction, "push".
* Correct and aligned: the laying of HDPE geomembrane, whether the slope or the bottom of the field, should be smooth and straight, but some wrinkles and ripples are allowed to make the two geomembrane correct and aligned.lap width according to the design requirements, generally about 10cm.
* Control of film pressure: press the HDPE geomembrane in time to prevent the wind from blowing.
* Laying control in the anchorage ditch: on the top of the anchorage ditch, a certain amount of anti-seepage film should be reserved according to the design requirements for local sinking and stretching.
* Longitudinal joint: the uphill section is on the top, the downhill section is on the bottom, and there is enough lap length of 15m, lay the bentonite pad after acceptance, and manually "push" in a certain direction.

3. Welding preparation: Experimental welding requirements:

1) Experimental welding shall be conducted on HDPE geomembrane test samples to test and adjust the welding equipment.
2) Welding equipment and welding personnel can carry out the next productive welding only after successfully completing the experimental welding.
3) Frequency control of experimental welding: according to the change of environmental temperature, each unit shall be no less than twice a day, once before the formal operation, once in the middle shift.
4) Experimental welding is carried out under the same surface and environmental conditions as production welding.

4. Productive welding

1) Production welding can be carried out only through experimental welding.
2) Adjust the welding machine to the best parameters when passing the experimental welding, automatically under the lap width required by the design, and the weld is "smooth, firm and beautiful".
3) This is only suitable for repair and welding machine where the double seam welding machine cannot be operated.

5. Control of the welding data

1) Whether productive or experimental welding, the temperature, speed and pressure of the welding rod must be maintained to enable the welding to achieve the best effect.
2) Each weld joint shall be inspected

6. Welding quality assurance and control measures

1) When welding the slope, the weld length direction should extend along the slope and cannot be crossed.
2) minimize the welding of side feet and sporadic films.
3) During the welding operation shall be supervised by a welding supervisor.
4) The HDPE geomembrane surface shall be removed from grease, moisture, dust, garbage and other sundries.
5) If the welding is operated at night, there should be sufficient lighting.
6) At the HDPE geomembrane lap place, the wrinkle should be removed. When the wrinkle is greater than 10 cm, a round or elliptical patch should be used, and the patch size should exceed 5 cm around the incision.
7) When the ambient temperature and adverse weather conditions seriously affect the HDPE geomembrane welding, the operation shall be stopped.

7. The welding machine should be maintained regularly, and the residues in the welding machine equipment should be cleaned frequently.

8. Welding inspection and control measures

Testing control is divided into product surface detection and welding joint detection.
1) Product surface detection: when the HDPE geomembrane is deployed, use the eyes to check for defects and mark the defects or suspicious places for repair.
2) Weld inspection:: visual inspection and leak test (non-destructive)
* Visual inspection of the weld: mainly carefully check the appearance quality of the weld, the treatment of T-type weld and cross-type weld, and whether the base has sundries.
* The surface of double weld: smooth, firm, beautiful, that is, smooth and smooth, uniform thickness, there shall be no other sundries and redundant scattered solder at the weld, and the surrounding base material shall not be damaged.
* T-type weld surface: tight binding and smooth connection.
* Cross weld surface: Cross welding can only be used, but a patch above 20 cm must be covered by an experienced welder.
3) Non-destructive test: inflatable (double weld).
* Double weld inflation detection: a non-destructive detection means to judge the welding quality of the double seam by checking the air tightness of the double seam. The gas with a certain pressure closed in the air cavity can judge its air tightness by detecting the change of the accompanying pressure gauge on the needle.
* Composition of instrument: compression device, can produce 0.15--0.20Mpa pressure, hollow needle with pressure gauge
* Procedure: the pressure of 0.15--0.20Mpa is qualified for more than 2 minutes; if the pressure gauge is not stable, maintain a certain pressure, face the outside weld, if there is no leakage is qualified (that is, the other leakage weld is not treated).
4) Repair of defects: the defects found in the visual inspection and positive pressure should be repaired in time.
Composite Geomembrane Technology And Construction Precautions
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