How to Construct Geomembrane for Sewage Treatment Engineering Water Tank
How to Construct Geomembrane for Sewage Treatment Engineering Water Tank
I Compilation basis:
1. 《Design drawings for sewage treatment engineering》;
2. 《Technical specifications for the application of geosynthetic materials in water conservancy and hydropower engineering》;
3. 《 Technical Specification for Application of Geosynthetic Materials》;
4. 《Technical specifications for polyethylene (PE) geomembrane anti-seepage engineering》
Ⅱ Process flow
Temporary construction road repair → positioning and laying out → soil excavation line positioning and laying out, dam area soil stacking line positioning and laying out → excavator excavation →Bulldozers push and evenly distribute soil to the dam construction area, flatten → road rollers roll → manual excavation and trimming of slopes, transportation of surplus soil → compaction of the original soil on the surface of the soil collection area → leveling and maintenance → laying of geotextile film → positioning of joint formwork → pouring and maintenance of protective layer → compaction of expansion joints → on-site cleaning → acceptance inspection
Ⅲ Earthwork excavation
The earthwork excavation of this project mainly includes all earthwork excavation works such as trench excavation, foundation cleaning, and embankment slope adjustment, which are constructed using a combination of manual and mechanical methods. The excavated soil materials, except for those that meet the filling requirements and are directly used for earthwork filling, shall be transported and discarded externally.
Earthwork excavation must be strictly carried out in accordance with the design and construction specifications. Excavation should be carried out using a 1m3 backhoe excavator, starting from top to bottom and moving from one end to the other within a working face. The excavation slope should be formed in one go (with a reserved 20cm protective layer). The excavated soil is directly unloaded to the filling point for backfilling, and the remaining soil is transported by a 5T dump truck for disposal.
The excavation of the 20cm protective layer soil on the bottom and slope surface shall be carried out manually.
Ⅳ Earthwork filling
New excavated soil materials shall be used for backfilling, and the soil materials shall not contain harmful debris such as grass roots, cultivated soil, sand and gravel on the embankment body. After compaction, the permeability coefficient shall be less than 1 × 10-4cm/s. Earthwork filling shall be strictly carried out in accordance with relevant technical specifications for embankment engineering and earth rock dams. After the foundation cleaning work experience is qualified, earthwork filling shall be carried out. Use a 1m3 excavator to excavate soil, and use a 5T dump truck to transport it along the temporary construction road at the embankment line of the material yard to the filling point for unloading according to the advance method, ensuring that the compacted soil layer meets the design requirements. Fill the soil layer by layer and pour the soil layer by layer, starting from the lower part and gradually filling layer by layer horizontally. It is not allowed to fill along the slope. The direction of soil laying extends along the axis, and the working surface is uniformly layered and compacted. Use a 120 horsepower bulldozer to level and achieve even thickness. During the laying process, check the thickness of the soil at any time and immediately deal with any excess thickness. Use a 5-8T roller to compact. After passing the soil sample inspection, manual and mechanical roughening is used to ensure good bonding between the upper and lower soil layers. Determine the compaction parameters (soil thickness, number of compaction passes, and optimal moisture content) based on on-site sampling tests. The layer thickness should not exceed 30cm, and each layer should be compacted 4-5 times. The walking direction of the compaction machinery is parallel to the axis of the embankment.
When filling on rainy days, the earthwork filling operation surface should be covered with rain cloth. When encountering rainy days in the earthwork borrow area, rain cloth should be used to cover it to ensure that there is 2-3 days of usable work volume.
Ⅴ Composite geomembrane laying
1. Material requirements:
1.1. The PE geomembrane is used for anti-seepage in this project. The geomembrane is a composite geomembrane with a thickness of 0.2mm, and the fabric on one side of the membrane is 100g/m2. After contacting the construction unit, it was found that the material to be used in this project is produced by xxx Co., Ltd. The specification is long filament composite geotextile film with a width of 4.3m. After verification with the specifications, the technical performance indicators can meet the requirements. Now, the specifications and the technical indicators provided by xxx Co., Ltd. are shown as follows:
1.2. SL/T231-98 Technical Specification for Polyethylene (PE) Geomembrane Seepage Control Engineering stipulates:
The physical and mechanical performance indicators of PE geomembrane should meet the following requirements:
Density( ρ) Should not be less than 900 kg/;
Breaking tensile stress( σ) It should not be lower than 12MPa;
Elongation at break( ε) Should not be less than 300%;
The elastic modulus (E) should not be lower than 70MPa at 5 ℃;
The frost resistance (brittle temperature) should not be lower than -60 ℃;
The connection strength should be greater than the strength of the base material;
The tear strength should be greater than or equal to 40 N/mm;
The impermeability strength should be maintained at a water pressure of 1.05 MPa for 48 hours without water seepage;
The permeability coefficient should be less than 2.1×10-11cm/s
2. Preparation before construction:
Before the construction of PE geomembrane anti-seepage engineering, the following preparations should be made:
1) Develop a construction plan according to the construction organization design.
2) Select PE geomembrane materials according to design requirements.
3) Remove all kinds of debris inside the site that may hinder the safety of PE geomembrane.
2.2. Before construction, the PE geomembrane should be inspected in accordance with relevant specifications. If the quality is found to be unqualified or does not meet the design requirements after inspection, it shall not be put into use.
2.3. The inspection of PE geomembrane should follow the following rules:
1) Inspection, testing, and appraisal testing shall be jointly entrusted by the supply and demand parties to a third-party testing agency for testing according to standards.
2) The sampling batch for the acceptance inspection of PE geomembrane should be determined based on the continuous production of products with the same brand of raw materials, formula, specification, and process, with a weight not exceeding 5t as one batch.
3) The physical and mechanical properties in the inspection items should be inspected in accordance with the provisions of this specification. The remaining projects will be determined through negotiation between the supply and demand parties.
4) When the test results do not comply with the provisions of this specification, repeated testing should be conducted.
5) If one of the sampling test results does not meet the standard requirements, the sample is judged as unqualified; If each batch fails two sampling tests, the entire batch will be judged as unqualified.
6) When there is a dispute between the supply and demand parties regarding the quality of PE geomembrane products, they should jointly sample the unqualified batches and entrust a nationally recognized metrological certification qualified unit to conduct re inspection. The retest results can serve as the final judgment basis.
2.4 Before construction, the foundation (support layer) of the PE geomembrane anti-seepage project should be inspected according to the design requirements as follows:
1) The preliminary engineering acceptance documents signed by the construction supervision engineer for foundations, cushion layers, etc. should be complete.
2) The surface of the support layer should be flat and smooth.
3) The base should be dense and uniform. The dry density of the soil substrate shall not be less than 1.4t/m2. The uniform error shall not exceed 10%.
4) The radius of rounding for the base's internal and external corners should not be less than 50 cm.
3. Construction technology and steps:
3.1. Construction steps:
Measure and lay the edge line → Clean the foundation trench → Wet the foundation surface with water → Cut the geotextile film → Align and align it → Press and shape the film → Wipe the dust → Welding test → Welding → Testing → Repair → Re inspection → Acceptance
The construction process arrangement should comply with the following regulations:
1) The construction of PE geomembrane should be carried out after the acceptance of the foundation support layer project.
2) Each process during construction should be strictly inspected and accepted. If the previous process passes the final acceptance, the next process cannot proceed.
3) When carrying out the next process or adjacent engineering construction, the completed PE geomembrane should be properly protected and not damaged by anyone.
4) After the laying begins, it is strictly prohibited to carry out cross operations such as excavation, drilling, welding, combustion, and drainage within the range that may endanger the safety of PE geomembrane.
5) Technical points
(1) Try to minimize the amount of splicing during laying, in order to achieve satisfactory anti-seepage effect under adverse conditions.
(2) When laying geomembranes, they should extend from the lowest part to the higher position. Do not pull too tightly, leave enough space (about 1.5%) for local sinking and stretching.
(3) When laying on slopes, the principle of minimum joints, ease of construction, and reasonable cutting can be used to determine whether to lay parallel or perpendicular to the maximum slope line based on the actual situation of the project. The joint should avoid corners and be placed on a flat surface. In areas with steep slopes, a soft ladder shall be installed, and construction personnel shall carry out geomembrane welding joint construction on the soft ladder.
(4) During the laying process, welding seams, especially cross welds, should be minimized as much as possible to minimize potential leakage hazards. During the film spreading process, it is prohibited to forcefully pull the geotextile film, and it is not allowed to press out dead folds. When welding the weld seam, the floating soil on the surface must be wiped clean, otherwise the upper and lower films cannot be hot pressed together. To connect with the foundation of the building, it is necessary to flatten the geotextile film without folding, providing good operating conditions for edge sealing.
(5) The joint treatment of geomembrane is a key process that directly affects the anti-seepage effect. The general joint methods include: ① overlap: the overlap width should be greater than 15cm; ② Waterproof coating treatment after sewing; ③ Hot welding: suitable for slightly thicker non-woven fabric substrates, with a weld overlap width of no less than 10cm; ④ Adhesive: Apply pressure to the connection surface using the adhesive provided with the geotextile. The joint should be free of dust, grease, and moisture, and the length of the joint should be greater than 10cm.
3.2. Operational process requirements and quality control:
1) Before laying PE geomembrane, the following preparations should be made:
(1) Check and confirm that the basic support layer meets the conditions for laying PE geomembrane.
(2) Perform material cutting analysis and draw the sequence and cutting diagram of laying PE geomembrane.
(3) Check the appearance quality of PE geomembrane, record and repair any mechanical damage, production trauma, holes, folds and other defects that have been found.
(4) Each area and block should be equipped with sufficient screened soil or other transitional and protective layer materials according to the design requirements, and transportation roads should be left between each area and block.
(5) Conduct on-site laying tests to determine construction process parameters such as welding temperature and speed.
2) Develop a complete set of construction quality management methods and strict operating procedures based on design requirements and construction conditions, establish a sound quality assurance system, and strictly implement the "three position system" from the first process of unit project construction to ensure the quality of engineering construction.
3) Cut the slope according to the design, and remove any sharp edges or debris that may damage the geotextile membrane, such as silt, garbage, trees, grass roots, stones, etc., from the surface of the base layer within the scope of geotextile membrane laying. Smooth and compact the land, repair pits, cracks, etc., and dig anchor ditches. When there are internal and external corners on the grassroots, they should be rounded with a radius of not less than 0.5m;, Watering should be done first to moisten the soil, so that the geotextile film is tightly integrated with the foundation trench. The geotextile should not be too tight, and the two ends buried in the anchoring ditch should be corrugated. (The anchoring and connection of geomembrane are shown in the figure)
4) During construction, efforts should be made to avoid blocky objects directly hitting the geomembrane, and it is best to apply a protective layer while laying the membrane. If the composite geomembrane is connected to the structure, expansion bolts and steel plate pressure bars should be used for anchoring. The connection part should be coated with emulsified asphalt (2mm thick) for bonding to prevent leakage at that location.
5) The laying of geomembranes is carried out using segmented construction and flow operation methods. The vertical embankment axis can be divided into three sections: the horizontal section at the bottom of the pool, the sloping section, and the horizontal section at the top of the pool. Each section is 12.9 meters along the dam axis (with a geotextile membrane width of 4.3 meters as the modulus). Each section shall first carry out the construction of the horizontal section at the bottom of the pool, followed by the construction of the sloping section and the horizontal section at the top of the pool, or both at the same time. Before the construction of the slope section, the horizontal construction of the pool bottom in the adjacent section should be completed, and the construction conditions for connecting and laying the geotextile membrane should be met. Multiple parallel operations can be carried out at a certain distance along the axial direction, with a distance of 12 meters as the modulus between the two construction sections.
6) Slope PE anti-seepage membrane is laid from top to bottom. When laying, pay attention to the appropriate tension of the PE film to avoid stress concentration and human damage. Require that the contact surface between the PE film and the foundation cushion layer be consistent and flat, to prevent the phenomenon of PE film wrinkling and forming water seepage channels. Lay the PE film horizontally with the surface facing downwards and the fabric facing upwards. After laying the PE film, immediately backfill the protective layer to avoid stress concentration and human damage to the PE film.
7) The PE film adopts Shuanghan ZPR-210 or other improved automatic crawling heat welding machines. Before welding, the dirt on the film surface must be removed to ensure its cleanliness, and welding can only be carried out after the film and film are smoothly bonded. During the crawling welding process, the operator should carefully observe the quality of the welding double seam and adjust the welding temperature and walking speed according to the changes in environmental temperature at any time. The general temperature control is between 250 ℃ and 300 ℃, and the walking speed is generally 1-2 meters per minute. You can first test weld on the sample and determine reasonable process parameters before formal welding. During formal welding, the weld seam should be carefully inspected, mainly to see if the two welds are clear and transparent, and whether there are any bubbles, missing welds, melting points, or weld seam running edges. Unqualified ones need to be repaired by welding. The stitching method between fabrics is elbow joint. The optimal suture needle spacing is 6 millimeters. The suture adopts a three strand double filament polyester stranded wire with a breaking strength of Yinniu. The joint should be free of dust, grease, and moisture, and the length of the joint should be greater than 10cm. The required joint strength should not be less than 80% of the strength of the parent material, and the geotextile should be sewn with a handheld sewing machine after splicing.
The joint design of PE geomembrane should follow the following principles: minimize the number of joints and be parallel to the direction of high tensile stress; The joint should avoid corners and be set at a flat surface.
8) When there are yin and yang corners on the support layer, they should be rounded with a radius of no less than 0.5m, and a geotextile cushion layer should be added under the PE geotextile film.
9) PE geomembrane should be embedded at the top of the structure. A shallow trench with a depth of 30cm and a width of 30cm can be excavated 50cm from the slope edge, and the membrane end can be buried and filled with compacted soil. Steel bars can also be used to press and fix the nails to the top. When riveting the nails, shims should be added and rust prevention measures should be taken.
4. Other precautions:
4.1 The outdoor construction of PE geomembrane should be carried out in weather with a temperature above 5 ℃ and wind force below level 4, without rain or snow.
4.2 The following precautions should be taken during the construction of PE geomembrane:
1) When welding, the surface of the film should be dry, and the film surface should be wiped dry and cleaned with dry gauze.
2) Flames are not allowed to be brought into the construction site.
3) Do not wear spiked shoes, high heels, or hard soled shoes to step on PE film.
4) Vehicles and other machinery are not allowed to crush the geotextile surface and its protective layer.
5) During the film laying process, the appearance of the film should be checked at any time for defects such as damage, pitting, and holes.
6) If defects or damages such as holes are found on the membrane surface, fresh base materials should be used for repair in a timely manner. Each side of the scar should extend 10-20cm beyond the damaged area.
4.3 The laying construction of PE geomembrane should meet the following technical requirements:
1) The laying of large bundles of PE geomembranes should be carried out using machinery such as tractors and winches; If the conditions are not met and there are small bundles of PE film, manual laying can also be used.
2) Lay PE geomembrane in designated order and direction in sections and blocks.
3) When laying PE geomembrane, it should be relaxed appropriately and avoid artificial hard bending and damage.
4) When laying PE geomembrane, the nodes formed between the membrane blocks should be T-shaped and not cross shaped.
5) The overlap surface of the PE geomembrane weld seam shall not have impurities such as dirt, sand, accumulated water (including dew) that affect the welding quality.
6) When laying PE geomembrane, the amount of expansion and contraction deformation caused by temperature changes should be reserved according to the local temperature change amplitude and the requirements of the factory product manual.
7) The laying of PE geomembrane on the slope surface should have its joints arranged parallel or perpendicular to the maximum slope line, and should be laid in a bottom-up order.
8) At the bend of the slope, the membrane and joints should be properly attached to the slope.
9) After the laying of PE geomembrane and before covering the protective layer, a sand bag weighing 20-40kg should be placed every 2-5m at the corners of the membrane.
10) PE geomembrane should naturally relax and the supporting layer should be tightly attached, and should not be folded or suspended. When special circumstances require folding arrangement, special treatment should be made separately.
4.4 The on-site connection of PE geomembrane should comply with the following regulations:
(1) The welding form should adopt double weld lap welding.
(2) The main welding tools should use automatic temperature regulation (speed regulation) electric wedge double channel plastic heat sealing machine, hot melt extrusion welding machine, or high-temperature hot air welding machine. The plastic hot air welding gun can be used as an auxiliary tool for local repairs.
4.5. The following steps can be taken to connect PE geomembrane on site:
(1) Wipe the overlap of the weld seam with a clean gauze, ensuring that there is no water, dust, or scale; Geomembranes should be aligned parallel and overlapped appropriately.
(2) Adjust the welding equipment to the optimal working state according to the local climate conditions at that time.
(3) Conduct small sample welding tests in the adjusted working state; Test welding of 1m long PE geomembrane samples.
(4) Using on-site tearing inspection samples, if the weld seam is not damaged by tearing and the base material is torn, it is considered qualified.
(5) After passing the on-site tearing test, use a heat sealing machine that has been adjusted to its working state to perform formal welding one by one.
(6) Use an extrusion welding machine to repair T-shaped joints and weld special joints.
4.6 After welding the PE geomembrane, the welding quality of the following parts should be tested in a timely manner:
(1) All welds.
(2) Weld joints.
(3) Damaged repair area.
(4) Repair welding areas with missed or false welds.
(5) The previous inspection did not pass and the welding area was repaired again.
4.7. On site inspection can be self inspected by the construction unit (Party B) according to the welding progress. After passing the self inspection, it shall be submitted to Party A or the quality inspection department for joint sampling inspection or full inspection. The qualified reports of self inspection and joint inspection should serve as the basis for quality acceptance. In special circumstances, indoor joint testing can also be carried out according to the agreement of both parties.
4.8. The methods and equipment used for on-site testing shall comply with the following regulations:
The detection method should adopt the inflation method, namely the double weld pressure detection method and the vacuum tank method, namely the vacuum pressure leak detection method; Spark testing or ultrasonic detection methods can also be used.
4.9 The testing equipment should use pneumatic and vacuum detectors. Indoor testing should randomly take 1-2 (10-50cm) on-site weld seam samples and use indoor testing methods for testing. The welding quality should meet the following requirements:
1) The length of the double seam inflation is 30-60m, and the inflation pressure between the double welds reaches 0.15-0.2MPa, which is maintained for 1-5 minutes. If there is no significant decrease in pressure, it is considered qualified.
2) For single welds, T-joints, and repair points, a 50cm x 50cm grid should be used for vacuum testing. If the vacuum pressure is greater than or equal to 0.005 MPa and maintained for 30 seconds, and the soap solution or detergent does not bubble, it is considered qualified.
3) The spark test is used for detection, and it is considered qualified if there is no spark between the metal brushes.
4) Using ultrasonic detection, the judgment standard is based on the results displayed on the fluorescent screen of the ultrasonic emitter.
5) Indoor testing. The tensile strength of the weld seam should be greater than the strength of the base material.
4.10. On site testing shall comply with the following regulations:
1) After the inspection is completed, all inflating and pressing perforations made during the inspection should be immediately plugged using extrusion welding method.
2) The testing process and results should be recorded in detail and marked on the construction drawings.
3) The testing personnel should sign and provide clear conclusions, opinions, and suggestions on the testing records.
4) Any areas that fail quality inspection should be promptly marked and repaired with welding. The number can only be cancelled and recorded after passing the re inspection.
5) The quality assurance team should be responsible for the supervision and management of testing.
6) Qualified PE geomembranes that have been welded should be protected from any damage at all times.
7) For joints with virtual or missed welding, timely repair welding should be carried out, and vacuum testing should be carried out on the repair welding area.
8) Quality inspection should be carried out as the construction progresses. After passing the self inspection, it should be inspected or fully inspected by Party A. Only after passing the acceptance can the next process proceed.
Ⅵ Construction of concrete protective layer
Concrete construction must be strictly carried out in accordance with relevant specifications and technical requirements in the bidding documents. To ensure the construction quality of concrete, comprehensive control must be carried out from the aspects of raw materials, preparation, and pouring of concrete, in order to achieve the expected quality goals.
1. Materials
(1) Cement: Cement is ordinary Portland cement, which meets the quality standards. Each batch of cement shipped must be provided with a quality certificate by the manufacturer, and its variety, grade, packaging, and production date should be inspected and accepted. Cement that exceeds the production period of three months and cement that the construction site representative believes has doubts about its quality should be retested, otherwise it cannot be used in the project, Cement should be immediately stored on site in dry and weather proof cement tanks.
(2) Sand: The construction sand is made of natural medium coarse sand with hard particles, high strength, and good durability, which is extracted from the local gravel yard.
(3) Stones: The stones used in concrete mixing should have a hard, clean, and well graded texture, and their mechanical properties should comply with the provisions of the "Quality Standard Inspection Method for Crushed Stone or Pebble for Ordinary Concrete". Aggregates should be stacked separately according to their variety and specifications, and should not be mixed together.
(4) Water: The water used for cleaning aggregates and mixing concrete shall not contain harmful substances or chemicals and shall comply with regulatory standards.
2. Concrete pouring
(1) Construction process flow:
(2) Concrete gradation: Before starting construction, the laboratory shall conduct sampling tests and mix proportion tests on the sand and gravel aggregates (aggregates should undergo strength tests and meet the requirements) and cement to be used in the project, with sufficient guarantee rate to ensure a 100% pass rate during on-site construction. If necessary, an appropriate amount of admixtures shall be added to improve the workability and diffusion of the concrete.
3. Template: The template installation is carried out according to the procedures of layout, formwork erection, support reinforcement, lifting and leveling, size verification, gap blockage, and cleaning and cleaning, and attention is paid to the coordination with concrete pouring and compaction processes. When dismantling the formwork, non load bearing formwork should be removed when the concrete strength can ensure that its surface and edges are not damaged due to formwork removal. When dismantling, efforts should be made to avoid damaging the surface of the concrete components and the formwork itself. After the template is removed, it should be cleaned and repaired in a timely manner, and stacked according to the type and size of the template for reuse.
4. Mixing: The concrete is mixed using a 0.4m3 mixer, and the mix proportion is determined based on the grading test
Ⅶ Engineering acceptance:
After the completion of the project, timely acceptance should be organized. The members of the engineering acceptance team should include representatives from the following parties:
The owner of the construction project, namely the construction unit, and Party A of the contract;
The engineering contractor, i.e. the construction unit, Party B of the contract;
The engineering construction supervision unit, namely Party C;
Engineering design unit;
Representatives from other relevant parties.
The engineering acceptance should include the following contents:
1) Review the completeness and correctness of design and construction technical documents. Including: a complete set of design documents (including design change documents); Material factory documents; Material testing report; Construction records; Film laying, welding construction and testing, inspection records and stage acceptance reports; Completion drawings and reports; Original or photocopy of the supervising engineer's supervision report, etc.
2) The engineering acceptance should include: the appearance of the project, its performance in use, and its anti-seepage effect.
The engineering acceptance should meet the following technical requirements:
1) The design and construction units shall submit all technical documents specified in this specification to the acceptance team.
2) On site visual inspection and acceptance of the appearance quality and anti-seepage effect of the project.
3) Randomly inspect the quality of welds and joints on site.
4) If necessary, samples can be taken to test the water quality under the membrane and evaluate the anti-seepage effect.
The acceptance conclusion should be "qualified" or "unqualified", and the main basis of the conclusion should be indicated.
If either party has objections to the acceptance conclusion, they should conduct a review or request the higher-level supervisory department to review it until there is no dispute.
Ⅷ Engineering management:
1. Engineering technology management rules and regulations should be established.
All design and design change documents, construction records, observation records, and other technical data should be promptly organized and archived.
The observation of 3 PE geomembrane anti-seepage engineering should comply with the following regulations:
1) For important projects, inspection wells should be set up and regular pumping tests should be conducted to monitor the anti-seepage effect.
2) Regularly observe the water volume and water level changes under the PE geomembrane anti-seepage layer, and inspect the water quality.
3) As an important anti-seepage and pollution prevention project for groundwater environmental protection, a geomembrane monitoring system can be set up to timely monitor the integrity of PE geomembrane.
4) Geophysical exploration methods can be used to inspect and monitor the damage of PE geomembranes.
5) The impact of climate on PE geomembranes should be observed and recorded.
The management of PE geomembrane anti-seepage engineering should comply with the following regulations:
1) Do not damage the PE geomembrane anti-seepage layer.
2) The safety condition of PE geomembrane should be regularly inspected and monitored, and any leakage should be repaired in a timely manner.
3) Accumulate engineering management information and establish technical archives for PE geomembrane anti-seepage engineering management.
