A process method for repairing linings using high-ductility cementitious composites

Abstract

The present invention discloses a process for repairing linings using high-ductility cement-based composite materials, comprising high-ductility cement-based composite materials, a construction process and an evaluation method. The construction process comprises the following steps: setting out and calibrating the repair area, roughening and cleaning the base of the original lining structure, applying temporary waterproof glue, laying out steel mesh, applying high-ductility cement-based composite materials in layers, leveling with fine mortar, and decorating with paint. The high-ductility cement-based composite materials are composed of cement, fly ash, silica fume, water, concrete sand, admixtures and synthetic fibers. The evaluation method uses a deformation resistance potential parameter. P This invention leverages the exceptional deformation capacity of high-ductility cement-based composite materials to achieve coordinated deformation of the repair material and the lining structure, resisting cracking and interface debonding damage caused by shrinkage. It cures water seepage from lining cracks, slows down further crack expansion, and improves the durability of the lining structure.

Description

Technical Field

[0001] The invention belongs to the technical fields of tunnel engineering and building materials, and particularly relates to a process for repairing lining by using high-ductility cement-based composite materials. Background Art

[0002] Currently operating tunnels are experiencing varying degrees of structural damage to their linings due to factors such as increasing service life, changes in surrounding rock pressure, and deterioration in material properties. These defects are primarily characterized by lining cracking and water leakage. Leakage further deteriorates the lining's health, leading to instability and catastrophic failure in severe cases. Research indicates that non-structural cracks are the primary form of lining cracking. While these cracks themselves do not threaten the lining's bearing capacity, they do provide channels for harmful gases in the tunnel to corrode the lining's steel reinforcement, accelerating lining degradation. They also provide pathways for water in the surrounding rock to migrate, migrate, and diffuse into the tunnel interior, increasing the risk of short circuits in electrical equipment such as ventilation and lighting systems.

[0003] For this type of cracks, surface sealing, grouting and groove filling are mainly used in engineering projects for treatment. Among them, the surface sealing method is favored by the engineering community due to its advantages such as wide repair area, simple construction process and rapid traffic restoration. Commonly used sealing materials include ordinary cement slurry, ordinary mortar, epoxy resin modified mortar, ordinary asphalt, epoxy resin modified asphalt, etc. In engineering practice, the above-mentioned sealing materials have achieved good repair effects in the early stage of crack treatment. However, with the increase in service time of the repair materials and the erosion of the environment in the tunnel, the durability of most repair materials has gradually deteriorated. The essence of this phenomenon is that the above-mentioned repair materials have extremely poor crack control capabilities. Once cracks occur, it is difficult to undergo continuous coordinated deformation with the lining structure, resulting in debonding and damage at the interface between the repair material and the lining, which often requires further repair.

[0004] Adding a certain amount of steel fiber, carbon fiber, basalt fiber, plant fiber and synthetic fiber to concrete or mortar can effectively improve the toughness and deformation capacity of concrete materials, such as fiber concrete and fiber reinforced mortar well known in the engineering field. However, its crack control ability is still limited, and the width can only be controlled within the order of millimeters. The material still exhibits quasi-brittle failure mode under load, and the repair effect is also poor. Summary of the Invention

[0005] This invention addresses the shortcomings of existing repair technologies by proposing a method for improving the durability of tunnel linings using a low-cost, high-ductility cement-based composite material, and also proposes a construction process for repairing cracks using this method. This method eliminates significant changes or damage to the bearing capacity of the existing lining structure, resolving the issues of incompatible degeneration between conventional repair materials and the lining structure, leading to poor repair results. It significantly improves the ability of non-structural cracks in tunnel linings to resist water seepage and carbonization, thereby effectively enhancing the impermeability and durability of the lining structure.

[0006] In order to achieve the above-mentioned repair purpose, the technical solution adopted by the present invention is as follows:

[0007] A process for repairing linings using a high-ductility cement-based composite material. A high-ductility cement-based composite material is used. The repair method adopts some specific construction methods and uses an evaluation parameter P based on the potential of the repair material to resist shrinkage and interface debonding damage to evaluate the repair effect.

[0008] The high-ductility cement-based composite material has uniaxial deformation capability, crack dispersion capability and water leakage resistance capability, and its uniaxial tensile ultimate strain is about 1%.

[0009] The above construction method specifically includes the following steps:

[0010] Step 1: Stake out and mark the repair area, mark the intended repair range, and expand the repair range to a 1-meter transition zone around the lining crack area;

[0011] Step 2: After determining the repair scope, use mechanical equipment to roughen the lining base without damaging the steel bars of the original lining structure;

[0012] Step 3: After the roughening treatment is completed, use a water gun to wash away the slurry particles on the lining surface to expose the fresh concrete bonding interface, and bury the control coating thickness mark on the lining surface;

[0013] Step 4: Use quick-setting waterproof glue to temporarily treat cracks with water seepage to prevent further water seepage;

[0014] Step 5: Lay out wire mesh in the area that needs repair. Choose HRB400 steel mesh with a wire diameter of 3mm or more and a hole diameter of 50mm to 100mm. Use expanded-bottom bolts and washers to fix the wire mesh. The spacing between the fixing bolts should be between 40cm and 60cm.

[0015] Step 6: Apply high-ductility cement-based composite materials in multiple layers. The thickness of the first application should cover the wire mesh. After the applied material has initially solidified, spray water on the applied surface every two hours for maintenance. After 24 hours, start the second application. The maintenance method after application is the same as the maintenance method after the first application. The number of applications should be no less than 3 times. The total application thickness should be controlled between 3 and 5 cm to ensure that the thickness of the applied material does not infringe the construction limit of the tunnel.

[0016] Step 7: When the high-ductility cement-based material is applied to a controlled thickness, use fine mortar to repair and level the potholes on the applied surface;

[0017] Step 8: After leveling, water the repaired area every day to soak all the repaired area surfaces. The total maintenance period is 4 weeks. In the first 2 weeks, water the area 3 times a day, and in the last 2 weeks, water the area 2 times a day.

[0018] Step 9. Use decorative paint to decorate the repaired area after maintenance.

[0019] In the above step six, before formal application, a trial application should be carried out first, and the mix ratio and construction method should be further optimized according to the site conditions and the difficulty of the application construction, and the bonding strength between the application layer and the original lining should be tested. Large-scale construction can only be carried out after the trial application effect meets the requirements; during the application process, the high-ductility cement-based material should be used as soon as it is mixed, and the dropped materials after application should not be collected and put into the next batch of fresh materials to avoid affecting the quality of the application layer; when the high-ductility cement-based composite material is applied in layers multiple times to reach 1 / 2 of the control thickness of the application, two sets of strain gauges are buried in the core area of the repair to test the axial and circumferential shrinkage strain ε of the high-ductility cement-based material along the tunnel respectively. sh .

[0020] In step six above, during the process of applying high-ductility cement-based composite materials in multiple layers, a uniaxial tensile mold is prepared, and four uniaxial tensile specimens are cast for each batch of fresh mixture. After demolding for 24 hours, the uniaxial tensile specimens are subjected to the same watering curing method as the on-site repair material coating layer, and the watering needs to soak all surfaces of the specimens.

[0021] The cured uniaxial tensile specimens were sent to the laboratory for uniaxial tensile tests, and the elastic strain ε of the specimens was measured. e and the inelastic tensile strain ε i .

[0022] The calculation formula of the above potential evaluation parameter P is as follows:

[0023] P=ε sh -(ε e +ε i +ε cp )

[0024] Where, ε sh is the shrinkage strain monitored by the embedded strain gauge, unit: %; ε e The elastic strain of the repair material measured in the experiment, unit: %; ε i is the inelastic strain of the repair material measured in the experiment, unit: %; ε cp To repair the creep of materials, high ductility cement-based composite materials ε cp Take 0.07%.

[0025] The above evaluation method is specifically as follows: when the calculated P value is less than 0, it indicates that the material deformation capacity can offset the shrinkage deformation, the high-ductility cement-based composite material has the ability to resist shrinkage damage and interface debonding, and the repair effect is good; on the contrary, the material deformation capacity cannot offset the material shrinkage deformation, the repair effect is poor, and it is necessary to readjust the mix ratio and repair again.

[0026] The components of the high-ductility cement-based composite material include: ordinary Portland cement, water, fine aggregate, Class F I fly ash, silica fume, anti-shrinkage admixture and fiber, and the component mass percentages are cement: water: fine aggregate: Class F I fly ash: silica fume = (12%~24%): (16%~17%): (21%~23%): (24%~48%): (12%~24%). The cement is one of Portland cement or ordinary Portland cement, and the strength grade of the cement is 52.5. The fine aggregate is concrete sand with a maximum particle size not exceeding 1 mm. The anti-shrinkage admixture includes a water reducer, an expansive agent and latex powder, wherein the amount of the water reducer does not exceed 0.5% of the total mass of the cementitious material, i.e., cement, fly ash and silica fume, and the amount of the expansive agent and latex powder does not exceed 10% of the cement amount. The fiber is polyvinyl alcohol fiber with a length of 8~12 mm, and its amount is 1.5~2% of the total volume of the high-ductility cement-based composite material.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] Layering a high-ductility cement-based composite material to the surface of non-structural cracks in the lining effectively prevents water leakage and reduces the rate of carbonation in the cracked area. Compared to traditional mortar or concrete repair materials, the high-ductility cement-based composite material used in this invention can deform synergistically with the lining structure, forming a strong bond. Its superior deformation capacity effectively resists shrinkage strain, preventing cracks and interfacial debonding caused by shrinkage, significantly improving the repair quality and structural service life of cracked linings.

[0029] The present invention uses a potential evaluation parameter P based on the repair material's resistance to shrinkage and interface debonding to qualitatively evaluate the repair material's ability to resist shrinkage cracking and interface debonding. It well combines field monitoring data and indoor test data, and the evaluation results are more comprehensive, easy to calculate, and convenient to implement.

[0030] The layered application of high-ductility cement-based composite materials provides a new technical means for repairing non-structural cracks in tunnel linings and has good prospects for engineering promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Cross-section of a tunnel repaired with high-ductility cement-based composite materials.

[0032] Figure 2 Process diagram of the method for repairing non-structural cracks with high-ductility cement-based materials.

[0033] Figure 3 Schematic diagram of repairing material shrinkage cracking and interface debonding failure.

[0034] In the figure, 1-high ductility cement-based composite material, 2-initial support, 3-secondary lining, 4-repair area, 5-base grooving, 6-application of temporary waterproof glue, 7-laying of wire mesh, 8-layered application of high ductility cement-based composite material, 9-fine mortar leveling, 10-paint decoration. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0036] Example

[0037] A certain highway mountain tunnel was built early and the construction technology was backward at that time. Therefore, the secondary lining was constructed using wooden formwork. As a result, the secondary lining has many joints and construction joints and poor surface flatness. In addition, the tunnel has been in operation for decades and has developed various defects to varying degrees. Among them, lining cracking and water leakage are very serious, and appropriate repair methods are urgently needed.

[0038] Tunnel concrete coring revealed that deterioration was primarily within 1 cm of the surface, with a maximum width of 0.72 mm. These cracks were non-structural and did not pose a threat to the tunnel's structural safety, requiring only durability repair. The process described herein was used to repair a network of cracks in the tunnel that was causing severe water leakage. The repair material used was the high-ductility cement-based composite material described herein, and the construction method employed was the same as described herein. The specific steps are as follows.

[0039] (1) The repair area is marked and the proposed repair range is marked. The repair range is expanded to a 1-meter transition zone on all sides based on the lining crack area.

[0040] (2) After determining the repair scope, mechanical equipment shall be used to groove and roughen the lining base, and the steel bars of the original lining structure shall not be damaged during the treatment.

[0041] (3) After the roughening treatment is completed, the slurry particles on the lining surface are washed away with a water gun to expose the fresh concrete bonding interface, and a control coating thickness mark is buried on the lining surface.

[0042] (4) Cracks with water seepage should be temporarily treated with quick-setting waterproof glue to prevent further water seepage.

[0043] (5) Lay out wire mesh in the area that needs to be repaired. Choose HRB400 steel mesh with a wire diameter of more than 3mm and a hole diameter of 50mm. The wire mesh is fixed with expanded bottom bolts and gaskets, and the spacing between the fixing bolts is kept at 50cm.

[0044] (6) Carry out trial coating to further optimize the mix ratio and construction method according to the site conditions and the difficulty of coating construction, and test the 28-day bonding strength between the coating layer and the original lining, which is generally not less than 2.0MP.

[0045] (7) Apply high-ductility cement-based composite materials in layers for multiple times. The thickness of the first application should cover the wire mesh. After the applied material is initially solidified, the applied surface is sprayed with water every two hours for maintenance. After 24 hours, the second application is started. The maintenance method after application is the same as the maintenance method after the first application. A total of 3 applications are applied, and the total application thickness is 5 cm. When the high-ductility cement-based composite materials are applied in layers for multiple times to reach 1 / 2 of the control thickness, two sets of strain gauges are buried in the core area of the repair to test the axial and circumferential shrinkage strain ε of the high-ductility cement-based materials along the tunnel. sh .

[0046] The coating process uses a high-ductility cement-based material composed of 24% ordinary Portland cement, 16% water, 21% concrete sand, 24% Class F, Type I fly ash, 12% silica fume, and an anti-shrinkage admixture. The fiber content is 2% by volume. The admixtures include a water reducer, an expansive agent, and latex powder. The water reducer content is 0.5% of the cementitious material (cement, fly ash, and silica fume), and the expansive agent and latex powder content is 8% of the cement content. The fibers are polyvinyl alcohol fibers, 12 mm in length. The high-ductility cement-based material should be used immediately after mixing. Any debris after coating should not be collected and added to the next batch of fresh material to avoid affecting the quality of the coating.

[0047] During the multiple layering and multiple application of high-ductility cement-based composite materials, a uniaxial tensile mold was prepared, and four uniaxial tensile specimens were cast for each batch of fresh mixtures; after 24 hours of demoulding, the uniaxial tensile specimens were cured in the same way as the curing method of the on-site repair material coating layer. The watering needed to soak all surfaces of the specimens. The curing cycle was set to 4 weeks. In the first 2 weeks, the curing frequency was 3 times per day, and in the last 2 weeks, the curing frequency was 2 times per day. After the curing was completed, the specimens were sent to the laboratory for uniaxial tensile testing to measure the elastic strain ε of the specimens. e and the inelastic tensile strain ε i .

[0048] (8) When the high-ductility cement-based material is applied to a controlled thickness, use fine mortar to repair and level the potholes on the applied surface;

[0049] (9) After leveling, the repair area should be watered daily for maintenance. The entire surface of the repair area should be soaked with water. The total maintenance period is 4 weeks. In the first 2 weeks, the watering maintenance should be carried out 3 times a day. In the last 2 weeks, the watering maintenance should be carried out 2 times a day.

[0050] (10) Use decorative paint to decorate the repaired area after maintenance.

[0051] After the repair work is completed, the repair effect is evaluated according to the evaluation formula proposed by the present invention. The formula is as follows:

[0052] P=ε sh -(ε e +ε i +ε cp )

[0053] Among them, the ε monitored by the on-site contraction strain gauge sh Finally, it stabilized between 225 and 250 με. The ε measured in the experiment e and ε i 0.015% and 1% respectively, ε cp With reference to the creep value of cement-based composite materials used in classic engineering projects, which is 0.07%, the final calculated P value ranges from (-1.065) to (-1.062), which is less than 0, indicating that the high-ductility cement-based composite material invented in this article has good resistance to concrete shrinkage and interface debonding.

[0054] In order to illustrate that the repair method of the present invention is more advanced, the shrinkage strain, elastic strain, inelastic strain and creep of ordinary concrete and reinforced concrete were investigated respectively, and the deformation resistance potential parameter P of the two repair materials was calculated. The calculation results are shown in the table below.

[0055]

[0056] The results show that the deformation resistance potential of ordinary concrete is positive, and the material shrinkage is prone to debonding damage. The deformation resistance potential of steel fiber concrete is partially positive, so it is difficult to ensure that the material will not debond due to shrinkage even when steel fiber concrete is used for repair; the deformation resistance potential of high-ductility cement-based repair materials is negative, which means that the shrinkage deformation of the material can be completely absorbed by the deformation capacity of the material itself, the material is unlikely to debond, and the repair effect is good.

[0057] Note: * is the creep value of cement-based composite materials used in reference classic engineering

[0058] In summary, the high-ductility cement-based repair material disclosed in the present invention provides a new technical means for the durable repair of tunnel linings.

[0059] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A process for repairing lining using high-ductility cement-based composite materials, characterized by: A high-ductility cement-based composite material was used, and some specific construction methods were used for the repair. The repair effect was evaluated using the parameter P based on the potential of the repair material to resist shrinkage and interface debonding failure. The construction method specifically comprises the following steps: Step 1: Stake out and mark the repair area, mark the intended repair range, and expand the repair range to a 1-meter transition zone around the lining crack area; Step 2: After determining the repair scope, use mechanical equipment to roughen the lining base without damaging the steel bars of the original lining structure; Step 3: After the roughening treatment is completed, use a water gun to wash away the slurry particles on the lining surface to expose the fresh concrete bonding interface, and bury the control coating thickness mark on the lining surface; Step 4: Use quick-setting waterproof glue to temporarily treat cracks with water seepage to prevent further water seepage; Step 5: Lay out wire mesh in the area that needs repair. Choose HRB400 steel mesh with a wire diameter of 3mm or more and a hole diameter of 50mm to 100mm. Use expanded-bottom bolts and washers to fix the wire mesh. The spacing between the fixing bolts should be between 40cm and 60cm. Step 6: Apply high-ductility cement-based composite materials in multiple layers. The thickness of the first application should cover the wire mesh. After the applied material has initially solidified, spray water on the applied surface every two hours for maintenance. After 24 hours, start the second application. The maintenance method after application is the same as the maintenance method after the first application. The number of applications should be no less than 3 times. The total application thickness should be controlled between 3 and 5 cm to ensure that the thickness of the applied material does not infringe the construction limit of the tunnel. Step 7: When the high-ductility cement-based material is applied to a controlled thickness, use fine mortar to repair and level the potholes on the applied surface; Step 8: After leveling, water the repaired area every day to soak all the repaired area surfaces. The total maintenance period is 4 weeks. In the first 2 weeks, water the area 3 times a day, and in the last 2 weeks, water the area 2 times a day. Step 9: Use decorative paint to decorate the repaired area after maintenance; The components of the high-ductility cement-based composite material include: ordinary Portland cement, water, fine aggregate, Class F I fly ash, silica fume, anti-shrinkage admixture and fiber, and the component mass percentages are cement: water: fine aggregate: Class F I fly ash: silica fume = (12% to 24%): (16% to 17%): (21% to 23%): (24% to 48%): (12% to 24%). The cement is one of Portland cement or ordinary Portland cement, and the strength grade of the cement is 52.

5. The fine aggregate is concrete sand with a maximum particle size not exceeding 1 mm. The anti-shrinkage admixture includes a water reducer, an expansive agent and latex powder, wherein the amount of the water reducer does not exceed 0.5% of the total mass of the cementitious materials, namely cement, fly ash and silica fume, and the amount of the expansive agent and latex powder does not exceed 10% of the cement amount. The fiber is polyvinyl alcohol fiber with a length of 8 to 12 mm, and its amount is 1.5 to 2% of the total volume of the high-ductility cement-based composite material.

2. The process for repairing lining using high-ductility cement-based composite materials according to claim 1, characterized in that: In step six, before formal application, a trial application should be carried out to further optimize the mix ratio and construction method based on site conditions and the difficulty of application. The bonding strength between the application layer and the original lining should also be tested. Large-scale construction can only be carried out after the trial application effect meets the requirements. During the application process, high-ductility cement-based materials should be mixed and used immediately. The dropped materials after application should not be collected and put into the next batch of fresh materials to avoid affecting the quality of the application layer. When the high-ductility cement-based composite material is applied multiple times in layers to reach 1 / 2 of the controlled thickness, two sets of strain gauges are buried in the core area of the repair to test the axial and circumferential shrinkage strains ε of the high-ductility cement-based material along the tunnel. sh .

3. The process for repairing lining using high ductility cement-based composite materials according to claim 2 is characterized in that In step six, during the process of applying high-ductility cement-based composite materials in layers multiple times, a uniaxial tensile mold is prepared, and four uniaxial tensile specimens are cast for each batch of fresh mixture. After demolding for 24 hours, the uniaxial tensile specimens are subjected to the same water sprinkling curing method according to the curing method of the on-site repair material coating layer. The water sprinkling needs to soak all surfaces of the specimen.

4. The process for repairing lining using high-ductility cement-based composite materials according to claim 3 is characterized in that: The cured uniaxial tensile specimens were sent to the laboratory for uniaxial tensile tests, and the elastic strain ε of the specimens was measured. e and the inelastic tensile strain ε i .

5. The process for repairing lining using high-ductility cement-based composite materials according to claim 4, characterized in that: The calculation formula of the potential evaluation parameter P is as follows: P=e sh -(e e +e i +e cp ) Where, ε sh is the contraction strain monitored by the embedded strain gauge, unit: %; ε e The elastic strain of the repair material measured in the test, unit: %; ε i is the inelastic strain of the repair material measured in the test, unit: %; ε cp To repair the creep of materials, high ductility cement-based composite materials ε cp Take 0.07%.

6. The process for repairing lining using high-ductility cement-based composite materials according to claim 5, characterized in that: The specific evaluation method is: when the calculated P value is less than 0, it indicates that the material deformation capacity can offset the shrinkage deformation, the high-ductility cement-based composite material has the ability to resist shrinkage damage and interface debonding, and the repair effect is good; on the contrary, the material deformation capacity cannot offset the material shrinkage deformation, the repair effect is poor, and it is necessary to readjust the mix ratio and repair again.

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