Concrete dam structural crack reinforcing method

Abstract

The invention relates to a concrete dam structural crack reinforcing method which comprises the specific steps of grooving, crack plugging, upstream and downstream grouting hole arrangement, grouting, dabbing and cleaning of dam bodies on the two sides of a crack, epoxy mortar leveling, carbon fiber pasting, pre-stressed anchor cable fixing and upstream face polyurea spraying. The problem of water leakage of structural through cracks of the concrete dam is solved by grouting and spraying of polyurea on the upstream face, the strength, rigidity, crack resistance and extensibility of the structure are improved through first-level carbon fibers, constraint on the two sides of the cracks is increased through the first-level carbon fibers, deformation of the cracks is limited, and the structural cracks are permanently eliminated. And the left dam body and the right dam body of the seam can normally transfer force.

Description

Technical Field

[0001] The invention relates to the technical field of concrete dam crack treatment, and in particular to a method for reinforcing structural cracks in a concrete dam. Background Art

[0002] Concrete dam cracks are generally divided into concrete temperature cracks and structural cracks. Temperature cracks themselves do not pose obvious harm to the dam structure, and you only need to pay attention to the impact of water leakage on the working properties of the dam. The key to treatment is not to eliminate the cracks themselves, but to eliminate water leakage. Therefore, only conventional grouting treatment is required. In addition to the obvious danger to the dam structure, structural cracks will also accelerate concrete aging and damage to the structure caused by frost heave. Therefore, more attention is paid to the treatment of structural cracks in engineering practice. However, structural cracks are generally difficult or impossible to eliminate, so even after grouting reinforcement, there is still the possibility of repeated cracking. The current treatment principle is to limit its development and reduce the harm caused by water leakage.

[0003] Although there are grouting, caulking, steel bars and other treatment methods for structural cracks in concrete dams in practical applications, there are still some problems that need to be solved in practical applications, especially for structural crack arch dams with through cracks. The specific problems are as follows:

[0004] 1. Leakage problem after dam cracks are treated:

[0005] After grouting reinforcement, the cracks still crack and leak repeatedly. This is mainly because the dam body on both sides of the cracks is not constrained, and a small strain can cause the grouting body to crack and deform again.

[0006] 2. Structural cracks have not been completely eliminated:

[0007] The principle of dealing with structural cracks at this stage is to limit their development and reduce the harm caused by leakage. However, for through cracks, especially through cracks in concrete arch dams, if this part cannot be permanently eliminated, the arch shoulder force cannot be effectively transmitted to the mountains on both sides through the dam body itself. When the dam block on the side of the crack reaches the limit state of bearing capacity, the dam body is prone to dangerous accidents such as "opening".

[0008] To solve the above problems, the research team proposed a method to reinforce structural cracks in concrete dams. Summary of the invention

[0009] The purpose of the present invention is to provide a method for reinforcing structural cracks in a concrete dam, which can solve the problem of water seepage in the dam body and enable the dam body on the left and right sides of the crack to transmit force normally.

[0010] A method for reinforcing structural cracks of a concrete dam comprises the following steps:

[0011] S1 Grooving: Grooving is performed along the upstream and downstream vertical cracks, and the groove shape is an inverted trapezoid;

[0012] S2 Sealing: Remove the debris in the inverted trapezoidal groove and rinse it. After the groove is completely dry, fill it with epoxy mortar to seal the seam;

[0013] S3 upstream and downstream grouting hole arrangement: both upstream and downstream adopt cross-slit arrangement of inclined holes, which pass through the seam surface and are arranged on both sides of the seam. The vertical spacing of the holes is 2m, and the spacing of the seam side holes is 3m. The angles of the inclined holes to the dam surface are 25-35° and 70-80° respectively;

[0014] S4 grouting: First flush the borehole, wash away the drilling residues in the hole and the dust in the seam, and then grout. The grouting slurry uses pure cement slurry or high-permeability modified epoxy chemical slurry, and the grouting pressure is controlled at 0.1-0.3MPa;

[0015] S5. Roughening and cleaning of the dam body on both sides of the seam: After the slurry is completely solidified, a water pressure test is carried out. After no leakage is found, the dam body on both sides of the upstream and downstream seams is roughened and cleaned. The roughening and cleaning range is the dam surface on both sides of the seam, with a length of not less than 5m. The weathered concrete and latex are removed by a pneumatic pick, the concrete base surface is cleaned with a wire brush, and the concrete base surface is cleaned with a high-pressure water gun to clean the sand and dirt;

[0016] S6 Epoxy mortar leveling: After cleaning the dam surfaces on both sides of the upstream and downstream joints, use epoxy mortar to level the roughened dam surface. The thickness of the epoxy mortar should be controlled at 15-25mm.

[0017] S7 carbon fiber bonding: After the epoxy mortar reaches 20MPa, apply AB glue on the surface and then bond the first-grade carbon fiber. The bottom of the carbon fiber should penetrate into the bedrock ≥0.5m;

[0018] S8 prestressed anchor cable fixing: In order to better fix the carbon fiber and give full play to its high-strength tensile resistance, holes are first drilled on the upstream and downstream edge surfaces, and anchor cables are installed. Steel plates are used for fixing, and prestress is applied to the upstream and downstream steel plates at the same time. The prestress is controlled at 500-1000KN;

[0019] S9 Spray polyurea on upstream surface: spray polyurea anti-seepage material on the upstream seam surface, with a spray thickness of 1 to 3 mm;

[0020] S10 crack monitoring: Install a vibrating wire crack meter on the crack surface to monitor the opening and closing degree of the crack. Check the crack treatment effect by monitoring the crack opening and closing degree. Install resistance strain gauges on the primary carbon fiber and in the crack respectively. Install resistance gauges on thin wires to measure the carbon fiber and crack strains.

[0021] Furthermore, the step S1 is to carve grooves along the upstream and downstream vertical cracks, and the groove shape is an inverted trapezoid with a bottom width of 50 mm, a top width of 100 mm, and a groove depth of 70 mm.

[0022] Preferably, in the arrangement of upstream and downstream grouting holes in step S3, the angles of the inclined holes to the dam surface are 30° and 75° respectively.

[0023] Preferably, in step S4, the grouting pressure is 0.2 MPa.

[0024] Preferably, in step S6, epoxy mortar leveling is performed, and the thickness of the epoxy mortar is 20 mm.

[0025] Preferably, in the step S7 of pasting carbon fibers, the primary carbon fibers are high-strength grade I carbon fibers, with a tensile strength of ≥3400 MPa, an elastic modulus of ≥240 GPa, and an elongation of ≥1.7%.

[0026] Preferably, in step S9, the upstream surface is sprayed with polyurea, and the thickness of the polyurea anti-seepage material sprayed is 2 mm.

[0027] Furthermore, in the crack monitoring step S10, the vibrating wire crack meter and the resistance strain gauge are installed one at the beginning and the end of the crack, and one at every 2.5 to 3 m in the middle of the crack.

[0028] The resistance strain gauges are installed in the primary carbon fiber and the cracks, respectively, with the spacing consistent with the crack gauge. The resistance gauge is installed on the thin wire to measure the strain of the carbon fiber and the crack. When the strain value obtained by measuring the extension and contraction of the carbon fiber material is consistent with the strain value measured in the crack, it means that the deformation of the left and right dam bodies is consistent, and the dam bodies and carbon fibers at both ends can transmit force normally. The dam body at one end transfers the load to the carbon fiber, which is then transferred to the other end of the dam body, and finally the load is transferred to the shore mountain. When the strain value obtained by measuring the extension and contraction of the carbon fiber material is inconsistent with the strain value measured in the crack, it means that the deformation of the left and right dam bodies is inconsistent, and the dam bodies and carbon fibers at both ends cannot transmit force normally. There will be a section of the dam body that is subjected to excessive force, which will stretch the crack open, and then the carbon fiber will be stretched until it is destroyed.

[0029] The beneficial effects of the present invention are as follows: grouting and upstream surface spraying of polyurea are used to solve the water leakage problem of structural through cracks in concrete dams; the high tensile strength of primary carbon fibers is utilized to paste them on the structure to be reinforced in a direction perpendicular to the cracks to form a new composite body, so that the reinforcing pasting material and the original dam body structure are subjected to force together, thereby increasing the crack resistance and tensile resistance of the structure, and improving the strength, rigidity, crack resistance and elongation of the structure; the primary carbon fibers are used to increase constraints on both sides of the cracks to limit their deformation, thereby ensuring that the grouting body will not crack and leak again due to the deformation of the dam body, and that the structural cracks are permanently eliminated; prestressed anchor cables are used to fix the carbon fibers to prevent them from falling off due to improper pasting or other factors and failing to achieve the corresponding effect; crack meters and resistance strain gauges are used for monitoring and on-site inspection to determine the crack treatment effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic diagram of the plan layout of embodiment 1 of the present invention;

[0031] Figure 2 This is a schematic diagram of an upstream vertical cross-section of Example 1 of the present invention;

[0032] Figure 3 It is a schematic diagram of the downstream vertical cross-section of Example 1 of the present invention.

[0033] Explanation of the reference numerals: 1. groove, 2. drilling, 3. primary carbon fiber, 4. prestressed anchor cable, 5. steel plate, 6. polyurea, 7. crack, 8. crack meter and resistance strain gauge. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0035] Example 1

[0036] Please refer to Figure 1 - Figure 3 , a method for reinforcing structural cracks of a concrete dam, comprising the following steps:

[0037] S1 Grooving: Grooving is performed along the upstream and downstream vertical cracks. The groove shape is an inverted trapezoid with a bottom width of 50 mm, a top width of 100 mm, and a groove depth of 70 mm;

[0038] S2 Sealing: Remove the debris in the inverted trapezoidal groove and rinse it. After the groove is completely dry, fill it with epoxy mortar to seal the seam;

[0039] S3 upstream and downstream grouting hole arrangement: both upstream and downstream adopt inclined holes arranged across the seams. The inclined holes pass through the seam surface and are arranged on both sides of the seam. The vertical spacing of the holes is 2m, and the spacing of the seam side holes is 3m. The angles between the inclined holes and the dam surface are 30° and 75° respectively;

[0040] S4 grouting: First flush the borehole, wash away the drilling residues in the hole and the dust in the seam, and then grout. The grouting slurry uses high-permeability modified epoxy chemical slurry, and the grouting pressure is controlled at 0.2MPa;

[0041] S5. Roughening and cleaning of the dam body on both sides of the seam: After the slurry is completely solidified, a water pressure test is carried out. After no leakage is found, the dam body on both sides of the upstream and downstream seams is roughened and cleaned. The roughening and cleaning range is the dam surface on both sides of the seam, with a length of not less than 5m. The weathered concrete and latex are removed by a pneumatic pick, the concrete base surface is cleaned with a wire brush, and the concrete base surface is cleaned with a high-pressure water gun to clean the sand and dirt;

[0042] S6 Epoxy mortar leveling: After cleaning the dam surfaces on both sides of the upstream and downstream joints, use epoxy mortar to level the roughened dam surface. The thickness of the epoxy mortar should be controlled at 20mm.

[0043] S7 carbon fiber bonding: After the epoxy mortar reaches 20MPa, apply AB glue on the surface and then bond the first-grade carbon fiber. The bottom of the carbon fiber should be ≥0.5m deep into the bedrock. The first-grade carbon fiber is high-strength grade I carbon fiber with a tensile strength of ≥3400MPa, elastic modulus ≥240GPa, and elongation ≥1.7%;

[0044] S8 prestressed anchor cable fixing: In order to better fix the carbon fiber and give full play to its high-strength tensile resistance, holes are first drilled on the upstream and downstream edge surfaces, and anchor cables are installed. Steel plates are used for fixing, and prestress is applied to the upstream and downstream steel plates at the same time. The prestress is controlled at 500-1000KN;

[0045] S9 spray polyurea on upstream surface: spray polyurea anti-seepage material on the upstream seam surface with a spray thickness of 2mm;

[0046] S10 crack monitoring: Install a vibrating-wire crack meter on the crack surface to monitor the opening and closing of the crack. Install one at the beginning and end of the crack, and one every 2.7m in the middle of the crack. The crack treatment effect is checked by monitoring the crack opening and closing. Resistance strain gauges are installed on the primary carbon fiber and in the crack respectively. The carbon fiber and crack strains are measured by installing resistance gauges on thin wires.

[0047] Example 2

[0048] S1 Grooving: Grooving is performed along the upstream and downstream vertical cracks. The groove shape is an inverted trapezoid with a bottom width of 50 mm, a top width of 100 mm, and a groove depth of 70 mm;

[0049] S2 Sealing: Remove the debris in the inverted trapezoidal groove and rinse it. After the groove is completely dry, fill it with epoxy mortar to seal the seam;

[0050] S3 upstream and downstream grouting hole arrangement: both upstream and downstream adopt inclined holes arranged across the seams. The inclined holes pass through the seam surface and are arranged on both sides of the seam. The vertical spacing of the holes is 2m, and the spacing of the seam side holes is 3m. The angles between the inclined holes and the dam surface are 25° and 70° respectively;

[0051] S4 grouting: First flush the borehole, wash away the drilling residues in the hole and the dust in the seam, and then grout. The grouting slurry uses pure cement slurry, and the grouting pressure is controlled at 0.1MPa;

[0052] S5. Roughening and cleaning of the dam body on both sides of the seam: After the slurry is completely solidified, a water pressure test is carried out. After no leakage is found, the dam body on both sides of the upstream and downstream seams is roughened and cleaned. The roughening and cleaning range is the dam surface on both sides of the seam, with a length of not less than 5m. The weathered concrete and latex are removed by a pneumatic pick, the concrete base surface is cleaned with a wire brush, and the concrete base surface is cleaned with a high-pressure water gun to clean the sand and dirt;

[0053] S6 Epoxy mortar leveling: After cleaning the dam surface on both sides of the upstream and downstream joints, use epoxy mortar to level the roughened dam surface. The thickness of the epoxy mortar is controlled at 15mm.

[0054] S7 carbon fiber bonding: After the epoxy mortar reaches 20MPa, apply AB glue on the surface and then bond the first-grade carbon fiber. The bottom of the carbon fiber should be ≥0.5m deep into the bedrock. The first-grade carbon fiber is high-strength grade I carbon fiber with a tensile strength of ≥3400MPa, elastic modulus ≥240GPa, and elongation ≥1.7%;

[0055] S8 prestressed anchor cable fixing: In order to better fix the carbon fiber and give full play to its high-strength tensile resistance, holes are first drilled on the upstream and downstream edge surfaces, and anchor cables are installed. Steel plates are used for fixing, and prestress is applied to the upstream and downstream steel plates at the same time. The prestress is controlled at 500-1000KN;

[0056] S9 spray polyurea on upstream surface: spray polyurea anti-seepage material on the upstream seam surface with a spray thickness of 1mm;

[0057] S10 crack monitoring: Install a vibrating-wire crack meter on the crack surface to monitor the opening and closing of the crack. Install one at the beginning and end of the crack, and install one every 2.5 to 3 meters in the middle of the crack to monitor the opening and closing of the crack to check the crack treatment effect. Install resistance strain gauges on the primary carbon fiber and in the crack, with the spacing consistent with the crack meter. Install resistance gauges on thin wires to measure the carbon fiber and crack strain.

[0058] Example 3

[0059] S1 Grooving: Grooving is performed along the upstream and downstream vertical cracks. The groove shape is an inverted trapezoid with a bottom width of 50 mm, a top width of 100 mm, and a groove depth of 70 mm;

[0060] S2 Sealing: Remove the debris in the inverted trapezoidal groove and rinse it. After the groove is completely dry, fill it with epoxy mortar to seal the seam;

[0061] S3 upstream and downstream grouting hole arrangement: both upstream and downstream adopt inclined holes arranged across the seams. The inclined holes pass through the seam surface and are arranged on both sides of the seam. The vertical spacing of the holes is 2m, and the spacing of the seam side holes is 3m. The angles between the inclined holes and the dam surface are 35° and 80° respectively;

[0062] S4 grouting: First flush the borehole, wash away the drilling residues in the hole and the dust in the seam, and then grout. The grouting slurry uses high-permeability modified epoxy chemical slurry, and the grouting pressure is controlled at 0.3MPa;

[0063] S5. Roughening and cleaning of the dam body on both sides of the seam: After the slurry is completely solidified, a water pressure test is carried out. After no leakage is found, the dam body on both sides of the upstream and downstream seams is roughened and cleaned. The roughening and cleaning range is the dam surface on both sides of the seam, with a length of not less than 5m. The weathered concrete and latex are removed by a pneumatic pick, the concrete base surface is cleaned with a wire brush, and the concrete base surface is cleaned with a high-pressure water gun to clean the sand and dirt;

[0064] S6 Epoxy mortar leveling: After cleaning the dam surface on both sides of the upstream and downstream joints, use epoxy mortar to level the roughened dam surface. The thickness of the epoxy mortar is controlled at 25mm.

[0065] S7 carbon fiber bonding: After the epoxy mortar reaches 20MPa, apply AB glue on the surface and then bond the first-grade carbon fiber. The bottom of the carbon fiber should be ≥0.5m deep into the bedrock. The first-grade carbon fiber is high-strength grade I carbon fiber with a tensile strength of ≥3400MPa, elastic modulus ≥240GPa, and elongation ≥1.7%;

[0066] S8 prestressed anchor cable fixing: In order to better fix the carbon fiber and give full play to its high-strength tensile resistance, holes are first drilled on the upstream and downstream edge surfaces, and anchor cables are installed. Steel plates are used for fixing, and prestress is applied to the upstream and downstream steel plates at the same time. The prestress is controlled at 500-1000KN;

[0067] S9 spray polyurea on upstream surface: spray polyurea anti-seepage material on the upstream seam surface, with a spray thickness of 3mm;

[0068] S10 crack monitoring: Install a vibrating-wire crack meter on the crack surface to monitor the opening and closing of the crack. Install one at the beginning and end of the crack, and one every 3m in the middle of the crack. Check the crack treatment effect by monitoring the crack opening and closing. Install resistance strain gauges on the primary carbon fiber and in the crack, and measure the carbon fiber and crack strains by installing resistance gauges on thin wires.

[0069] The present invention has been used in the Tuanjie Reservoir Project in Yuqing County, Guizhou Province. The reservoir dam is a concrete masonry gravity arch dam with a maximum dam height of 37.4m. There is a 24m long through crack on the right bank of the dam. The initial crack width is 2mm. After multiple grouting treatments, the crack still leaks and the crack width shows a trend of increasing year by year. The maximum crack width in the later period is 10mm. After the treatment of the scheme of the present invention, no cracks have been found to have re-cracking and leakage since the completion of June 2023. The crack opening and closing data monitored by 9 automatic crack meters installed from bottom to top upstream and downstream of the dam are ±0.01~0.14mm. 9 resistance strain gauges are installed from bottom to top in the primary carbon fiber and the crack, respectively. The currently monitored carbon fiber and crack strain values ​​are both small and the data changes of the two are basically consistent. It shows that the deformation of the left and right dam bodies is consistent, the dam bodies and carbon fibers at both ends can transmit force normally, the dam body at one end can transfer the load to the carbon fiber, and then the carbon fiber is transferred to the dam body at the other end, and finally the load is transferred to the mountain on the shore. The current monitoring data and on-site inspection results show that the present invention has a good effect in treating the through cracks in the dam and can enable the dam body on the left and right sides of the crack to transmit force normally, and has strong practicality.

[0070] Although the present invention has been described in detail above by general explanation and specific implementation methods, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, these modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for reinforcing structural cracks in a concrete dam, characterized in that: The steps include: S1 Grooving: Grooving is performed along the upstream and downstream vertical cracks, and the groove shape is an inverted trapezoid; S2 Sealing: Remove the debris in the inverted trapezoidal groove and rinse it. After the groove is completely dry, fill it with epoxy mortar to seal the seam; S3 upstream and downstream grouting hole arrangement: both upstream and downstream adopt cross-slit arrangement of inclined holes, which pass through the seam surface and are arranged on both sides of the seam. The vertical spacing of the holes is 2m, and the spacing of the seam side holes is 3m. The angles of the inclined holes to the dam surface are 25-35° and 70-80° respectively; S4 grouting: First flush the borehole, wash away the drilling residues in the hole and the dust in the seam, and then grout. The grouting slurry uses pure cement slurry or high-permeability modified epoxy chemical slurry, and the grouting pressure is controlled at 0.1-0.3MPa; S5. Roughening and cleaning of the dam body on both sides of the seam: After the slurry is completely solidified, a water pressure test is carried out. After no leakage is found, the dam body on both sides of the upstream and downstream seams is roughened and cleaned. The roughening and cleaning range is the dam surface on both sides of the seam, with a length of not less than 5m. The weathered concrete and latex are removed by a pneumatic pick, the concrete base surface is cleaned with a wire brush, and the concrete base surface is cleaned with a high-pressure water gun to clean the sand and dirt; S6 Epoxy mortar leveling: After cleaning the dam surfaces on both sides of the upstream and downstream joints, use epoxy mortar to level the roughened dam surface. The thickness of the epoxy mortar should be controlled at 15-25mm. S7 carbon fiber bonding: After the epoxy mortar reaches 20MPa, apply AB glue on the surface and then bond the first-grade carbon fiber. The bottom of the carbon fiber should penetrate into the bedrock ≥0.5m; S8 prestressed anchor cable fixing: Drill holes on the upstream and downstream edge surfaces, install anchor cables, fix them with steel plates, and apply prestress on the upstream and downstream steel plates at the same time. The prestress is controlled at 500-1000KN. S9 Spray polyurea on upstream surface: spray polyurea anti-seepage material on the upstream seam surface, with a spray thickness of 1 to 3 mm; S10 crack monitoring: A vibrating wire crack meter is installed on the crack surface to monitor the opening and closing degree of the crack. Resistance strain gauges are installed on the primary carbon fiber and in the crack respectively. The carbon fiber and crack strains are measured by installing resistance gauges on thin wires.

2. The method for reinforcing structural cracks of a concrete dam according to claim 1, characterized in that: The step S1 is to carve grooves along the upstream and downstream vertical cracks. The groove shape is an inverted trapezoid with a bottom width of 50 mm, a top width of 100 mm, and a groove depth of 70 mm.

3. The method for reinforcing structural cracks of a concrete dam according to claim 1, characterized in that: In step S3, upstream and downstream grouting holes are arranged, and the angles of the inclined holes to the dam surface are 30° and 75° respectively.

4. The method for reinforcing structural cracks of a concrete dam according to claim 1, characterized in that: The step S4 is grouting, and the grouting pressure is 0.2 MPa.

5. The method for reinforcing structural cracks of a concrete dam according to claim 1, characterized in that: The step S6 is epoxy mortar leveling, and the thickness of the epoxy mortar is 20 mm.

6. The method for reinforcing structural cracks of a concrete dam according to claim 1, characterized in that: In the step S7, carbon fibers are pasted, wherein the first-level carbon fibers are high-strength first-level carbon fibers with a tensile strength of ≥3400 MPa, an elastic modulus of ≥240 GPa, and an elongation of ≥1.7%.

7. The method for reinforcing structural cracks of a concrete dam according to claim 1, characterized in that: In step S9, the upstream surface is sprayed with polyurea, and the thickness of the polyurea anti-seepage material sprayed is 2 mm.

8. The method for reinforcing structural cracks of a concrete dam according to claim 1, characterized in that: In the crack monitoring step S10, the vibrating wire crack meter and the resistance strain gauge are installed one at the beginning and the end of the crack, and one at every 2.5 to 3 m in the middle of the crack.

Images