1. Project Overview and Characteristics
The Nilji Water Control Project spillway project consists of five parts: diversion channel, control section, chute section, stilling tank and tailrace channel. As of October 14, 2004, the main project of the bidding section has been completed. Due to season, climate temperature and other human factors, some cracks and defects have appeared in the concrete base plate of some parts of the spillway project. The chemical grouting content of this bid section is: the bottom plate of the Woqi section (0 279.00~0 320.87); the surface of the dead sill (0 395.87~0 413.47).
Main features: Some plates in C17 of the Woqi section have relatively many cracks due to cold currents, temperatures and other irresistible factors during the concrete pouring process. C18 and C19 have relatively few cracks. The deadlock X25 Some surface cracks are mainly shrinkage cracks caused by dry weather. It has been observed that the width of the cracks is concentrated at about 0.2mm. Because the cracks are so small, the treatment technology requirements are high and the process is quite complex.
2. Chemical grouting technology
2.1 Introduction to chemical grouting
Chemical grouting generally refers to grouting prepared from chemical materials and burying grouting nozzles through drilled holes. Pressure injects it into structural cracks, causing it to spread and solidify to achieve the purpose of waterproofing, plugging, reinforcing, and strengthening. Often used to repair deep cracks in concrete structures. According to the pressure and speed of grouting, it can be divided into high-pressure fast grouting method and low-pressure slow grouting method. High-pressure chemical grouting technology uses the continuous high pressure generated by the grouting machine to inject the chemical liquid into the gaps inside the concrete, completely squeezing out the water in the gaps, and completely filling the gaps to achieve the purpose of stopping water.
2.2 Advantages of chemical grouting process
2.2.1 The pressure is high (generally up to 20MPa) and stable and reliable, allowing the chemical slurry to completely enter the deep micro-cracks of the concrete structure, and has a water-stopping effect good.
2.2.2 The grouting fluid technology is mature and the varieties are complete. The production of single-component finished products has basically been realized. It does not require on-site preparation, the quality is stable, and it can be used after opening the barrel. The slurry is chemically resistant, non-toxic, environmentally friendly and permanently waterproof after curing.
2.2.3 The construction technology is simple and easy to implement. The construction speed is fast, the water-stopping effect is immediate, and it is done once and for all. The labor intensity of workers is low, and the construction efficiency is 5 to 10 times that of traditional construction methods, which is incomparable to traditional methods.
2.2.4 Construction is not restricted by seasons or weather, and can be used for various projects, including maintenance, emergency repair projects, and drinking water projects. The comprehensive construction cost is low and the economic benefits are significant.
3. Construction method
3.1 Crack observation and description: Professional technicians will conduct on-site observation, drawing and description of the cracks in each plate and record relevant data. Observation, recording and mapping personnel are divided into separate tasks.
3.2 Selection of equipment materials
3.2.1 Crack observation instrument: JC-10 series reading microscope (Shanghai Changguang Optical Instrument Co., Ltd.)
3.2. 2 Crack grouting equipment: portable manual grouting machine. This machine does not require a power supply and the whole machine weighs 2kg. It is suitable for situations without a power supply. Since the maximum grouting pressure is only 0.3~0.5MPa, it can only be used in water leakage situations and is powerless against high-pressure slow seepage. The machine has a simple structure, is easy to use, does not require professional maintenance, and is cheap
3.2.3 Chemical materials: The most commonly used leak-stopping grouting fluid is polyurethane leak-stopping agent. It is divided into two categories: oil-soluble and water-soluble, and they are suitable for different occasions. After curing, the water-soluble polyurethane is cemented into an elastomer soft foam, which can trap water, but will shrink to its original volume after the water is lost. The advantage is that it has good elasticity and resistance to deformation, and is suitable for long-term water situations. After the oil-soluble leak plugging agent is cured, the cement becomes a hydrophobic hard foam. The cement formed after the reaction does not shrink, but has low elasticity and poor resistance to deformation. It is suitable for fields with small deformation
3.3 Auxiliary equipment:
3.3.1 High-pressure cleaning machine: used for seam cleaning. The working pressure is 6~8MPa, and the spray gun needs to be equipped with a butter head before it can be used.
3.3.2 Electric hammer and impact drill bit: For drilling, impact drill bits with a diameter of 14mm and a length of 35 to 40cm are often used.
3.3.3 Waterproof cable: 3×2.5, cable reel with power socket.
3.3.4 Acetone: used to clean grouting machines, etc., and can also be used as a diluent for grouting materials. Cement-based waterproofing materials (waterproof, leak-proofing): used for sealing joints and sealing
3.4 Specific construction sequence
3.4.1 Cleaning: detailed inspection, analysis and recording of leakage , determine the location and spacing of grouting holes. Clean the area to be constructed, remove precipitates on the concrete surface, and ensure that the surface is clean and moist.
3.4.2 Drilling: Use drilling tools such as electric hammers to drill holes along both sides of the crack. The drill bit diameter is 14mm, the drilling angle should be ≤45°, and the drilling depth should be ≤2 times the structural thickness. /3, drilling must pass through the crack. However, it is not allowed to penetrate the structure (except for grouting behind the wall). The distance between drilling holes and cracks is ≤1/2 the thickness of the structure. The distance between drilling holes is 20cm to 60cm
3.4.3 Counter-nozzle: Install a grouting nozzle (also called a water stop needle) in the drilled hole, and tighten it with a special hexagonal wrench so that the area around the grouting nozzle is in line with the drilled hole. There are no gaps between the holes and no water leakage.
3.4.4 Clean the seams: Use a high-pressure cleaner to inject clean water into the grouting nozzle at a pressure of 6MPa, observe the water outlet situation, and clean the dust in the seams.
3.4.5 Sealing surface: Use cement-based waterproofing material (No. 1 anti-permeability plugging type) to seal the surface of the crack that appears during seam cleaning in order to prevent it from leaking when the chemical slurry is poured. Pulp.
3.4.6 Grouting: Use a high-pressure grouting machine to pour chemical grouting material into the grouting holes. The order of grouting on the facade is from bottom to top; on the plane, the grouting sequence can be started from one end and the single holes can be continued one by one. When the adjacent holes start to produce grout, maintain the pressure for 3 to 5 minutes, then stop the grouting of this hole and inject the adjacent grouting holes instead.
3.4.7 Remove the nozzle: After grouting is completed, remove the exposed grouting nozzle after confirming that there is no leakage. Clean up any spilled grout that has solidified.
3.4.8 Sealing: Use cement-based waterproof material (impermeable No. 1 waterproof type) to repair and seal the grouting opening.
3.4.9 Waterproofing: Use single-component PA waterproof glue to coat the chemical irrigation part three times (primer, middle coat, top coat) with a width of 10~20cm, and a length of 20~30cm at both ends.
3.5.2 Operation points:
Because chemical grouting of cracks does not consume much slurry, just lift the pump by hand; use a hand-held electric drill to drill holes for sealing, and it is necessary to clear the cracks. Pay attention to blowing out the powder in the hole; when burying the grouting nozzle, in order to prevent the bottom of the hole from deviating from the joint surface, the distance between the bottom of the pipe and the bottom of the hole should be kept 1/3 of the hole depth. Under the premise that the structure allows, the grouting pressure should be as high as possible, usually 0.3 to 0.5pa; the grouting hole should be a hole with a large leakage and a smooth joint surface, and an exhaust and drainage hole should be reserved; the grouting procedure ranges from low to high, with one side Push to the other side in sequence; generally, two pumps are grouting at the same time. When the first hole is grouting, the adjacent hole is drained and exhausted. When the air and water in the adjacent hole are drained and the slurry is discharged, another hole is connected to continue grouting; the end standard is not The pulp discharging or continuous pulp suction rate within 15 to 30 minutes is less than 10ml/min and the pressure does not drop.
4. Requirements for construction progress:
According to the actual construction conditions, the work shall be completed according to the requirements of the owner and the supervising engineer.
5. Possible problems and solutions:
5.1 In case of hole collapse, buried drill, cavity, etc., drilling must be stopped, and then grouting, hole sweeping, etc. After the grouting of the complex hole section is completed and allowed to set for 12 hours, the next step of construction can be carried out.
5.2 If a large amount of flushing fluid is lost during the drilling process, fine sand, pisolite, sawdust or water glass can be added to the hole opening to plug the leakage. Wait for 24 hours to solidify before proceeding. 1. Construction work (when adding water glass, wait for 12 hours to set).
5.3 During the grouting process, if grout leakage, grout leakage, grout stringing, serious surface lifting, etc. are encountered, pressure reduction, flow restriction, intermittent grouting, waiting for condensation, or use of water glass can be adopted Cement mortar is grouted and left to set for treatment.
6. Quality assurance measures:
6.1 Before starting the chemical grouting project, check the equipment, materials, personnel, etc. for the grouting construction. Provide professional training to grouting recording personnel, and only those who are qualified can take up their posts.
6.2 Before starting the chemical grouting project, propose construction measures, draw a hole layout, and submit it to the supervision engineer for approval.
6.3 During construction, operations shall be organized strictly in accordance with the design construction drawings, construction measures approved by the supervision engineer, and relevant specifications.
6.4 Each process of chemical grouting strictly implements the "three inspection system" of construction quality. After the supervision engineer signs and accepts it, the next process can be carried out.
6.5 Establish a programmed quality assurance system in accordance with the quality system documents and implement it effectively to ensure that the construction process, especially key processes and special processes, are always under effective control to prevent the occurrence of unqualified processes.
6.6 As required, the following construction quality information should be available after the construction process.
6.6.1 The completed work volume and cumulative work volume of each project of drilling and grouting engineering.
6.6.2 Grouting engineering raw material testing and quality inspection results.
6.6.3 Grouting sampling test results.
6.6.4 Quality inspection records of grouting projects.
6.6.5 Quality incident handling records.
7. Construction safety assurance measures:
During the drilling and grouting processes, the following measures should be taken to ensure construction safety.
7.1 Establish the policy of "safety first, prevention first", establish and improve the safety production organization structure, set up full-time safety officers, conduct regular inspections of the construction site, and deal with problems found in a timely manner.
7.2 Provide on-the-job safety production education to personnel engaged in drilling and grouting work, so that operators can take up their posts with certificates after passing the assessment.
7.3 Distribute various necessary labor protection supplies to construction workers engaged in drilling and grouting.
7.4 Carry out safety and fire prevention work seriously at the construction site.
7.5 Ensure safe use of electricity and distribution panels at the construction site, and the distribution cabinets must have protective settings.
7.6 Safety protection devices must be installed at the operating parts of all construction machinery and equipment.
7.7 All power lines and lighting lines should be complete without any damage or leakage. They must be properly installed and maintained to avoid moisture.
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