Sprayed concrete surface layer cracking repairing construction method

Abstract

The invention relates to the technical field of tunnel construction, in particular to a construction method for repairing cracking of a sprayed concrete surface layer. Comprising the following steps: S1, observing a to-be-repaired crack, and carrying out primary treatment on the to-be-repaired crack; s2, measuring the size of the crack to be repaired after primary treatment, and preparing a repairing material and equipment for repairing construction; s3, repairing the crack to be repaired; and S4, maintaining the repaired area of the repaired crack to be repaired. The method not only provides a slope crack repairing method, but also is convenient to implement and has a light flooding application effect.

Description

Technical Field

[0001] The invention relates to the technical field of building construction, and in particular to a construction method for repairing cracks in a sprayed concrete surface layer. Background Art

[0002] With the steady development of infrastructure construction, foundation pit excavation is an essential key step. In projects with a long construction period, shotcrete slope support structures are particularly common.

[0003] The advantages of this type of slope protection structure are: simple construction process, good waterproofing effect; flexible equipment, simple operation, less construction workers; the material is ground material, low cost; the sprayed concrete surface layer is widely used in shallow foundation pit slope protection structures due to its excellent chemical properties such as high hardness, wear resistance, and waterproofness, and its mature construction process and convenient operation. However, this type of sprayed concrete surface is prone to cracking, which is also caused by its own limitations. The reasons for the cracks are as follows:

[0004] 1. During the construction process, the uneven mixing and mismatching ratio of the sprayed materials make the concrete structure insufficient in strength, and the surface cracks under the lateral pressure of the soil.

[0005] 2. The thickness of the slope protection surface layer sprayed is too large. If it exceeds 100mm and no effective anti-cracking measures are taken, the surface layer will gradually fall and crack.

[0006] 3. Due to the defects of its own technology, it is not possible to adopt the method of compartmentalization and seam division similar to floor construction, which leads to cracks due to thermal expansion and contraction.

[0007] 4. The soil pressure on the back of the slope protection is too large, which causes cracks to appear under the soil pressure after the slope protection surface layer is finally set. Therefore, it is urgent to solve this problem.

[0008] The above contents are only used to assist in understanding the technical solution of the present invention, and do not constitute an admission that the above contents are the closest prior art. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a construction method for repairing cracks in a shotcrete surface layer, which not only provides a method for repairing slope cracks, but is also easy to implement and has a wide application effect.

[0010] To achieve the above object, the technical solution of the present invention is implemented as follows: a method for repairing cracks in a shotcrete surface layer, comprising the following steps:

[0011] S1. Observe the cracks to be repaired and perform preliminary treatment on the cracks to be repaired;

[0012] S2. Measure the size of the cracks to be repaired after preliminary treatment, and prepare repair materials and equipment for repair construction;

[0013] S3, repair the cracks to be repaired;

[0014] S4. Maintain the repaired area of ​​the crack to be repaired.

[0015] Preferably, the process of performing preliminary treatment on the crack to be repaired in step S1 includes:

[0016] S11. Clean the debris in the crack to be repaired;

[0017] S12, cutting and removing the bulging concrete surface around the crack to be repaired, thereby expanding the area of ​​the crack to be repaired;

[0018] S13, excavating and cleaning the soil in the enlarged crack to be repaired;

[0019] S14. Drill holes on the side wall of the crack to be repaired after the internal soil is cleaned, and install a wire mesh.

[0020] Preferably, the repair material includes concrete and an interface agent; and the equipment used for the repair construction includes a spraying device, a spray gun and a scraper.

[0021] Preferably, the concrete includes fine aggregate, coarse aggregate, accelerator, expansive agent and cement with a grade greater than 32.5, and the cement of the concrete is slag silicate cement with a strength not less than C25.

[0022] Preferably, the ratio of cement: sand: gravel in the concrete is 1:1.4:1.9, and the water-cement ratio is 0.5; the initial setting time of the cement slurry of the concrete is less than 5 minutes, the final setting time is less than 10 minutes, and the mass ratio of the accelerator to cement is 2%-5%.

[0023] Preferably, the process of repairing the crack to be repaired in step S3 includes:

[0024] S31, the concrete is sprayed by wet spraying technology, and before the operation, the slope surface of the crack to be repaired is first moistened with water, and the slope surface is brushed with slurry using an interface agent;

[0025] S32. Pre-embed thickness control marks in the repair area of ​​the crack to be repaired;

[0026] S33. Check the injection equipment and pipelines to ensure that the equipment is operating normally and the pipelines are unobstructed;

[0027] S34. During the spraying of concrete, the distance between the spray gun and the sprayed surface should be 1-2 meters;

[0028] S35. When the crack to be repaired has a large area of ​​resection due to a large range of hollow cracking, the angle between the spray gun and the sprayed slope at the new and old junctions of the crack to be repaired should be between 30° and 60°, and the sprayed concrete should be in full contact with the hollow gaps and wire mesh on the slopes on both sides of the crack to be repaired.

[0029] S36. When the sprayed slope surface around the crack to be repaired is an inclined surface or a curved surface, the spray nozzle is perpendicular to the sprayed surface, and the sprayed concrete evenly covers the surface of the slope to be repaired;

[0030] S37. Use a scraper to level the concrete sprayed on the slope surface, and make the cracks to be repaired level with the slope surface.

[0031] Preferably, the process of curing the repaired area of ​​the crack to be repaired in step S4 includes: spraying water on the concrete surface of the repaired area of ​​the crack to be repaired once every 2 hours.

[0032] Preferably, the pre-embedded thickness control marks are arranged at equal intervals along the to-be-repaired area of ​​the crack to be repaired, and the pre-embedded thickness control marks are all perpendicular to the same plane, and adjacent pre-embedded thickness control marks are spaced about 1.5 meters apart.

[0033] Preferably, it also includes reserved concrete test blocks; the concrete test blocks are randomly selected from the repair area of ​​the crack to be repaired, and every 50m 3 of concrete and retain a group of concrete test blocks.

[0034] Preferably, the cracks to be repaired are fine cracks of about 2-5 mm, and are repaired by grouting with a patching hole. Grouting can be performed using a common injection grouting device, and the evenly stirred grouting material is injected into the gap through the patching hole until the cracks at both ends of the patching hole overflow with slurry.

[0035] The beneficial effects of the present invention are embodied in:

[0036] (1) The method provided by the present invention can quickly and effectively repair cracks and hollows in the slope protection surface layer, which not only ensures the quality of the repair, but also effectively controls the construction cost.

[0037] (2) The method provided by the present invention can effectively repair cracked and hollowed shotcrete surface layers, restore the integrity and stability of the structure, improve the safety and durability of the structure, and reduce safety risks such as foundation pit collapse caused by cracking and water seepage in the slope protection structure.

[0038] (3) The method provided by the present invention provides different repair schemes for different cracks, which not only can make the crack repair effect better, but also makes the implementation more flexible and reliable, and is easier to promote and implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic flow chart of the method is provided for the present invention. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] Example 1

[0042] like Figure 1 As shown:

[0043] The present invention provides a construction method for repairing cracks in a shotcrete surface layer, comprising the following steps:

[0044] S1, observe the cracks to be repaired and perform preliminary treatment on the cracks to be repaired. The process of performing preliminary treatment on the cracks to be repaired in step S1 includes:

[0045] S11. Clean the debris in the crack to be repaired;

[0046] S12, cutting and removing the bulging concrete surface around the crack to be repaired, thereby expanding the area of ​​the crack to be repaired;

[0047] S13, excavating and cleaning the soil in the enlarged crack to be repaired;

[0048] S14. Drill holes on the side wall of the crack to be repaired after the internal soil is cleaned, and install a wire mesh.

[0049] S2. Measure the size of the cracks to be repaired after preliminary treatment, and prepare repair materials and equipment for repair construction. Repair materials include concrete and interface agent; repair construction equipment includes spraying equipment, spray guns and scrapers.

[0050] The concrete includes fine aggregate, coarse aggregate, accelerating setting agent, expansive agent and cement with a grade greater than 32.5, and the cement of the concrete is slag silicate cement with a strength not less than C25.

[0051] The ratio of cement: sand: gravel in the concrete is 1:1.4:1.9, and the water-cement ratio is 0.5; the initial setting time of the cement slurry of the concrete is less than 5 minutes, the final setting time is less than 10 minutes, and the mass ratio of the accelerator to cement is 2% to 5%.

[0052] S3, repair the cracks to be repaired;

[0053] The process of repairing the crack to be repaired in step S3 includes:

[0054] S31. Concrete is sprayed using wet spraying technology. Before the operation, the slope surface to be repaired is first moistened with water, and the slope surface is brushed with slurry using an interface agent.

[0055] S32. Pre-embed thickness control marks in the repair area of ​​the crack to be repaired;

[0056] S33. Check the injection equipment and pipelines to ensure that the equipment is operating normally and the pipelines are unobstructed;

[0057] S34. During the spraying of concrete, the distance between the spray gun and the sprayed surface should be 1-2 meters;

[0058] S35. When the crack to be repaired has a large area of ​​resection due to a large range of hollow cracking, the angle between the spray gun and the sprayed slope at the new and old junctions of the crack to be repaired should be between 30° and 60°, and the sprayed concrete should be in full contact with the hollow gaps and wire mesh on the slopes on both sides of the crack to be repaired.

[0059] S36. When the sprayed slope surface around the crack to be repaired is an inclined surface or a curved surface, the spray nozzle is perpendicular to the sprayed surface, and the sprayed concrete evenly covers the surface of the slope to be repaired;

[0060] S37. Use a scraper to level the concrete sprayed on the slope surface, and make the cracks to be repaired level with the slope surface.

[0061] S4. Maintain the repaired area of ​​the crack to be repaired.

[0062] The process of curing the repaired area of ​​the crack to be repaired in step S4 includes: spraying water on the concrete surface of the repaired area of ​​the crack to be repaired once every 2 hours.

[0063] Example 2

[0064] 1. During specific implementation, target areas with larger cracks and hollow areas.

[0065] Clean and treat the concrete surface that needs to be repaired, cut off the larger cracked and hollow parts, remove loose materials and stains on the surface, and ensure the surface is clean.

[0066] According to the repair requirements, the original concrete materials and mix ratio are selected to ensure the quality and strength of the shotcrete, as follows.

[0067] Raw material preparation and shotcrete mix ratio:

[0068] Use slag silicate cement: its grade is greater than 32.5, the concrete strength is not less than C25 and expansion agent is added;

[0069] Fine aggregate uses medium sand with a fineness modulus of 2.0 to 3.0;

[0070] The particle size of coarse aggregate is 5-15mm;

[0071] The accelerator should be miscible with cement. The initial setting time of cement slurry mixed with the accelerator is less than 5 minutes, and the final setting time is less than 10 minutes. The dosage is 2%-5% of the cement weight (mass ratio);

[0072] The grade of plain shotcrete is generally 15-20Mpa;

[0073] Mixing ratio: cement: sand: gravel = 1: 1.4: 1.9 (C25);

[0074] Water-cement ratio 0.5.

[0075] Key points for construction of shotcrete for repairing cracks:

[0076] (1) In actual construction, the wet spraying process is used to spray concrete materials onto the concrete surface to be repaired to form a uniform and dense concrete layer. Before spraying concrete, the slope surface is first moistened with water, and ordinary grouting material is used as an interface agent, and the slope surface is brushed with the interface agent so that the sprayed concrete can better bond with the slope surface.

[0077] (2) Pre-embedded thickness control mark: If there is no minimum thickness requirement for the spray layer in the design, it should be 60 mm. The base spray thickness mark must be vertical and in the same plane, with an interval of about 1.5 meters.

[0078] (3) Spraying: During spraying, check the spraying equipment and pipelines to ensure that the equipment is operating normally and the pipelines are unobstructed. The water-cement ratio of concrete is controlled at 0.5 to ensure that the surface of the spraying layer is smooth, shiny, without dry spots, and does not flow. In addition, in order to reduce the amount of rebound generated during spraying, the spray gun should maintain an appropriate distance and angle during the spraying process. The distance between the spray gun and the sprayed surface should be 1-2 meters.

[0079] When the resection area is large due to a large range of hollowing cracks, the angle between the spray gun at the junction of the new and old surfaces and the sprayed slope should be between 30° and 60°, so that the sprayed slurry can fully contact the hollow gap between the old body and play the role of sealing the hollow cavity.

[0080] When the slope to be sprayed is an inclined or curved surface, the spray nozzle should be perpendicular to the sprayed surface to ensure that the concrete material can be fully and evenly covered on the surface to be repaired. At the same time, the construction sequence should be from bottom to top layer by layer.

[0081] (4) Leveling and calendering: When the spraying reaches a certain area, use the original slurry for leveling, scrape it with a 2-meter long scraper, and quickly repair it to make it smooth.

[0082] (5) Maintenance: After the spraying is completed, maintenance and protection should be carried out in time. After the initial setting, water should be sprayed on the concrete surface every 2 hours to ensure the strength and stability of the concrete layer and prevent cracks and hollowing.

[0083] (6) Placement of concrete test blocks: Concrete test blocks should be randomly selected from the pouring site and placed every 50m 3 Concrete, retain a group of concrete test blocks for archiving of construction records.

[0084] 2. During specific implementation, target areas with smaller cracks and local hollowing.

[0085] For small cracks of about 2-5mm, the method of grouting can be adopted for repair. Grouting can be carried out by using a common injection grouting device, and the evenly stirred grouting material is injected into the gap through the repair hole. When the cracks at both ends of the repair hole overflow with grout, it is ready. The spacing between the repair holes and the repair pressure are determined by the first trial grouting.

[0086] Through the above steps, the cracked and hollow shotcrete surface layer can be effectively repaired, the integrity and stability of the structure can be restored, the safety and durability of the structure can be improved, and the safety risks such as foundation pit collapse caused by cracking and water seepage in the slope protection structure can be reduced.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for repairing cracks in a shotcrete surface layer, characterized in that: The following steps are involved: S1. Observe the cracks to be repaired and perform preliminary treatment on the cracks to be repaired; S2. Measure the size of the cracks to be repaired after preliminary treatment, and prepare repair materials and equipment for repair construction; S3, repair the cracks to be repaired; S4. Maintain the repaired area of ​​the crack to be repaired.

2. A method for repairing cracks in a shotcrete surface layer according to claim 1, characterized in that: The process of performing preliminary treatment on the crack to be repaired in step S1 includes: S11. Clean the debris in the crack to be repaired; S12, cutting and removing the bulging concrete surface around the crack to be repaired, thereby expanding the area of ​​the crack to be repaired; S13, excavating and cleaning the soil in the enlarged crack to be repaired; S14. Drill holes on the side wall of the crack to be repaired after the internal soil is cleaned, and install a wire mesh.

3. A method for repairing cracks in a sprayed concrete surface layer according to claim 2, characterized in that: The repair material includes concrete and interface agent; the equipment used for repair construction includes spraying equipment, spray gun and scraper.

4. A method for repairing cracks in a shotcrete surface layer according to claim 1, characterized in that: The concrete comprises fine aggregate, coarse aggregate, quick-setting agent, expansive agent and cement with a grade greater than 32.5, and the cement of the concrete is slag silicate cement with a strength not less than C25.

5. A method for repairing cracks in a shotcrete surface layer according to claim 4, characterized in that: The ratio of cement: sand: gravel in the concrete is 1:1.4:1.9, and the water-cement ratio is 0.5; the initial setting time of the cement slurry of the concrete is less than 5 minutes, the final setting time is less than 10 minutes, and the mass ratio of the accelerator to cement is 2%-5%.

6. A method for repairing cracks in a shotcrete surface layer according to claim 5, characterized in that: The process of repairing the crack to be repaired in step S3 includes: S31, the concrete is sprayed by wet spraying technology, and before the operation, the slope surface of the crack to be repaired is first moistened with water, and the slope surface is brushed with slurry using an interface agent; S32. Pre-embed thickness control marks in the repair area of ​​the crack to be repaired; S33. Check the injection equipment and pipelines to ensure that the equipment is operating normally and the pipelines are unobstructed; S34. During the spraying of concrete, the distance between the spray gun and the sprayed surface should be 1-2 meters; S35. When the crack to be repaired has a large area of ​​resection due to a large range of hollow cracking, the angle between the spray gun and the sprayed slope at the new and old junctions of the crack to be repaired should be between 30° and 60°, and the sprayed concrete should be in full contact with the hollow gaps and wire mesh on the slopes on both sides of the crack to be repaired. S36. When the sprayed slope surface around the crack to be repaired is an inclined surface or a curved surface, the spray nozzle is perpendicular to the sprayed surface, and the sprayed concrete evenly covers the surface of the slope to be repaired; S37. Use a scraper to level the concrete sprayed on the slope surface, and make the cracks to be repaired level with the slope surface.

7. A method for repairing cracks in a shotcrete surface layer according to claim 6, characterized in that: The process of curing the repaired area of ​​the crack to be repaired in step S4 includes: spraying water on the concrete surface of the repaired area of ​​the crack to be repaired once every 2 hours.

8. A method for repairing cracks in a shotcrete surface layer according to claim 7, characterized in that: The pre-embedded thickness control marks are arranged at equal intervals along the to-be-repaired area of ​​the crack to be repaired, and the pre-embedded thickness control marks are all perpendicular to the same plane, and adjacent pre-embedded thickness control marks are spaced about 1.5 meters apart.

9. A method for repairing cracks in a shotcrete surface layer according to claim 8, characterized in that: It also includes reserved concrete test blocks; the concrete test blocks are randomly selected from the repair area of ​​the crack to be repaired, and every 50m 3 of concrete and retain a group of concrete test blocks.

10. A method for repairing cracks in a shotcrete surface layer according to claim 8, characterized in that: The cracks to be repaired are small cracks of about 2-5 mm, and are repaired by hole-filling grouting. Grouting can be done by using a common injection grouting device, and the evenly stirred grouting material is injected into the gap through the hole-filling hole until the cracks at both ends of the hole-filling point overflow with slurry.

Images