Early warning method for erosion and damage of underwater concrete of bridge pier column in salt concentration alternate change area

Abstract

The invention discloses an early warning method for erosion and damage of underwater concrete of a bridge pier column in a salt concentration alternating change area. The early warning method comprises the steps of arrangement of an electroosmosis system, calculation of the chloride ion erosion depth and establishment of an early warning mechanism. Through the integrated design of the electroosmosis technology and the bridge pier column structure, the drainage efficiency and the erosion and damage resistance of the bridge pier column structure are improved; obtaining a chloride ion erosion depth expression according to the condition that the chloride ion diffusion flux and the chloride ion electromigration flux are mutually balanced, and establishing a three-level early warning mechanism; the actually-measured chloride ion diffusion coefficient and the thickness of the steel bar protective layer are obtained through regular field monitoring, so that the influence of concrete stripping of the bridge pier column structure caused by water flow scouring on the electroosmosis process is corrected, and the adaptability and accuracy of early warning of underwater concrete erosion damage of the bridge pier column structure in the salinity alternating change area are improved.

Description

Technical Field

[0001] This invention relates to the field of concrete protection technology, and in particular to a method for early warning of underwater concrete erosion and damage to bridge piers in areas with alternating salt concentrations. Background Technology

[0002] Alternating salinity zones refer to areas where water salinity changes periodically over time due to factors such as tides, seasonal floods, and storm surges. These zones are characterized by uneven and highly variable salinity distribution in both time and space, and the complex and unpredictable direction and velocity of water flow caused by tidal forces. The concentration of corrosive media in the environment of in-service bridge pier concrete structures within these alternating salinity zones is influenced by multiple factors, including tides and precipitation, and the chloride erosion patterns differ from those of concrete structures in marine environments. Furthermore, the high tidal current velocity and the presence of large amounts of suspended sediment result in intense erosion of the concrete surface, easily leading to the peeling of the protective layer and accelerated exposure and corrosion of the internal reinforcing steel.

[0003] Existing methods for combating underwater concrete corrosion in bridge pier structures mainly include passive protection measures such as anti-corrosion coatings, rust inhibitors, the use of corrosion-resistant cement, and increasing the thickness of the concrete protective layer. These traditional methods have limited effectiveness in areas with fluctuating salt concentrations, require regular maintenance to preserve corrosion resistance, and cannot actively remove moisture that has seeped into the concrete pores or cracks.

[0004] Electro-osmosis technology is a seepage prevention technology based on electrochemical principles. It induces the directional migration of pore water or fissure water within concrete by applying an electric field. While currently used in soft soil drainage and tunnel seepage prevention, its application in resisting erosion damage to bridge pier structures is lacking. The existing technological gaps in applying electro-osmosis technology to underwater concrete for bridge pier structures in areas with alternating salt concentrations include: 1) Lack of integrated design: Seepage prevention measures based on electro-osmosis are not integrated with the bridge pier structure, leading to uneven electric field distribution and low drainage efficiency; 2) Lack of early warning mechanisms: Traditional electro-osmosis systems have limited monitoring methods for the electro-osmosis effect, making it difficult to provide reasonable early warnings based on structural durability; 3) Lack of dynamic control mechanisms: Traditional electro-osmosis systems rely on manual operation and adjustment, failing to link the electro-osmosis system with monitoring data, thus failing to achieve real-time monitoring and control of the electro-osmosis system.

[0005] Therefore, there is an urgent need to apply electro-osmosis technology to hollow cylindrical bridge pier structures in areas with alternating salt concentrations. This would allow for the deep integration of bridge pier structures with active drainage technology in these areas, and, combined with real-time monitoring data, enable dynamic control of the electro-osmosis system and early warning of structural durability. This would ensure effective early warning and control of underwater concrete erosion damage to bridge pier structures in areas with alternating salt concentrations. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention applies for an early warning method for underwater concrete erosion damage in bridge piers in areas with alternating salt concentrations. By deeply integrating the hollow cylindrical bridge pier structure with electro-osmosis technology and combining it with real-time monitoring data, the method achieves dynamic control of the electro-osmosis system and early warning of structural durability, thereby ensuring effective early warning and control of underwater concrete erosion damage in bridge pier structures in areas with alternating salt concentrations.

[0007] An early warning method for underwater concrete erosion damage in bridge piers in areas with alternating salt concentrations, applied to hollow cylindrical bridge pier structures in areas with alternating salt concentrations, includes the following steps:

[0008] S1. Arrangement of the electroosmosis system: An electroosmosis system, including an electroosmosis anode, an electroosmosis cathode, and a chloride ion concentration sensor, is arranged on the hollow cylindrical bridge pier structure. The electroosmosis anode is arranged vertically along the inner surface of the bridge pier structure, and the electroosmosis cathode is arranged vertically along the outer surface of the bridge pier structure. The potential difference formed by the interaction of the electroosmosis anode and the electroosmosis cathode drives water in the pores and cracks of the concrete of the bridge pier structure to migrate from the electroosmosis anode to the electroosmosis cathode. The chloride ion concentration sensor is arranged on the outer surface of the bridge pier structure to obtain chloride ion concentration data of the water in the area of ​​alternating salt concentration.

[0009] S2. Calculation of Chloride Ion Erosion Depth: Based on the equilibrium condition between chloride ion diffusion flux and chloride ion electromigration flux, the chloride ion erosion depth x of the bridge pier concrete structure in water bodies with alternating salt concentrations satisfies the following expression:

[0010]

[0011] Where D is the chloride ion diffusion coefficient, m 2 / s; s is the distance between the electroosmotic anode and the electroosmotic cathode, in meters; μ is the chloride ion mobility, in meters. 2 / (V·s); U is the potential difference between the electroosmotic anode and the electroosmotic cathode, in V; C is the chloride ion concentration in the water body in the alternating salt concentration zone, in mol / m³. 3 C minThe allowable value for chloride ion concentration in concrete structures, mol / m³ 3 The chloride ion erosion depth x reflects the chloride ion concentration at depth x exceeding the allowable chloride ion concentration C within the concrete structure. min When the chloride ion erosion depth x is negative, it is meaningless; it only reflects that the chloride ion concentration C in the water body in the area of ​​alternating salt concentration does not exceed the allowable value C of chloride ion concentration in the concrete structure. min ;

[0012] S3. Establishment of an early warning mechanism: Considering the periodic fluctuations in chloride ion concentration in water bodies caused by alternating salt concentrations due to water flow and tides, the early warning mechanism is divided into three levels based on the chloride ion erosion depth x and the thickness d of the steel reinforcement protective layer, as shown below:

[0013] 0mm≤x<10mm: Level 1 warning, indicating that the chloride ion concentration in the water body in the area of ​​alternating salt concentration is higher than the allowable value of chloride ion concentration in the concrete structure, and has begun to cause erosion and damage to the concrete.

[0014] 10mm≤x<d: Level II warning, reflecting that the erosion and damage to concrete caused by chloride ions in the water body in the area of ​​alternating salt concentration exceeds the limit of the "Standard for Chloride Ion Permeability Performance of Concrete"; where 10mm is the limit value of chloride ion erosion depth x for underwater concrete of cross-sea bridge pier structure in the "Standard for Chloride Ion Permeability Performance of Concrete"; at this time, a warning signal is sent to relevant technical personnel, and the potential difference U between the electroosmotic anode and the electroosmotic cathode is adaptively adjusted so that the expected chloride ion erosion depth x is less than 10mm;

[0015] x≥d: Level 3 warning, indicating that the chloride ion concentration around the steel bars in the concrete structure exceeds the allowable value, that is, the chloride ions in the water body in the area of ​​alternating salt concentration begin to cause corrosion damage to the steel bars in the concrete structure; at this time, a warning signal is sent to relevant technical personnel, and the potential difference U between the electroosmosis anode and the electroosmosis cathode is adjusted to the maximum value, thereby reducing the corrosion damage to the steel bars in the concrete structure caused by chloride ions in the water body in the area of ​​alternating salt concentration.

[0016] Preferably, the electroosmotic anode of the electroosmotic system is a titanium wire mesh, which is embedded in the inner surface of the bridge pier structure and has an S-shaped shape that is continuously bent and extended; the electroosmotic cathode of the electroosmotic system is a number of rod-shaped electrodes composed of pure titanium conductive cores and graphite coating layers, which are closely attached to the outer surface of the bridge pier structure.

[0017] Preferably, the electroosmosis system further includes a microcomputer control module, a switching power supply, wires, and an alarm device; the microcomputer control module controls the switching power supply and the potential difference between the electroosmosis anode and the electroosmosis cathode based on chloride ion concentration data; the wires are used for the connection between the electroosmosis anode and the electroosmosis cathode; and the alarm device is used to convey early warning information to relevant technical personnel.

[0018] Preferably, the secondary early warning in step S3, for the adaptive adjustment of the potential difference U between the electroosmotic anode and the electroosmotic cathode, satisfies the following expression:

[0019]

[0020] Where x1 is the chloride ion erosion depth limit for Level II warning, and x1 = 10 mm.

[0021] Preferably, considering the periodic fluctuations in chloride ion concentration in the water body in the alternating salt concentration zone caused by water flow and tides, when the chloride ion concentration C in the water body in the alternating salt concentration zone does not exceed the allowable value C of chloride ion concentration within the concrete structure... min When the power is turned off, the potential difference U between the electroosmotic anode and the electroosmotic cathode is reduced to 0, thereby reducing the wear and tear on the electroosmotic anode and the electroosmotic cathode during use.

[0022] Preferably, the measured chloride ion diffusion coefficient D is obtained periodically through on-site sampling and testing. a This corrects the impact of water erosion-induced concrete spalling on the chloride ion diffusion coefficient. The on-site sampling and testing steps include: after shutting off the power to the electro-osmosis system, rapidly drilling core samples from the outer surface of the bridge pier concrete structure inwards; then spraying silver nitrate solution onto the core sample surface to form a white silver chloride precipitate in the chloride ion erosion area; measuring the length of the chloride ion erosion area and obtaining the measured chloride ion erosion depth x. a The measured chloride ion diffusion coefficient D a Satisfy the following expression:

[0023]

[0024] Among them, U a C represents the potential difference between the electroosmotic anode and the electroosmotic cathode during the actual measurement. a This represents the chloride ion concentration in the water body during the measured alternating salt concentration range.

[0025] When the measured chloride ion diffusion coefficient D a Greater than 1.0×10 -12 m 2 An alert is triggered at a time of / s, sending an alert signal to relevant technical personnel.

[0026] Preferably, to correct for the impact of concrete spalling in bridge pier structures caused by water erosion on the thickness of the concrete cover for reinforcing bars, the minimum measured thickness d of the concrete cover for reinforcing bars is obtained periodically using a reinforcing bar detector. amin This updates the early warning mechanism, specifically when 10mm ≤ x < d. amin A level 2 warning is triggered when x ≥ d. amin A level-three warning was triggered.

[0027] Compared with existing technologies, the beneficial effects of this invention are as follows: For the dynamic control and early warning of underwater concrete erosion damage in bridge pier structures in areas with alternating salt concentrations, a method for early warning of underwater concrete erosion damage in bridge pier structures in areas with alternating salt concentrations is proposed. This method includes the arrangement of an electro-osmosis system, the calculation of chloride ion erosion depth, and the establishment of an early warning mechanism. Through the integrated design of electro-osmosis technology and bridge pier structure, a uniformly distributed electric field is formed in the concrete, thereby improving the drainage efficiency and erosion resistance of the bridge pier structure, and overcoming the deficiency of traditional underwater concrete erosion resistance methods that cannot actively drain water. Based on the mutual equilibrium of chloride ion diffusion flux and chloride ion electromigration flux... Under the condition of equilibrium, an expression for the chloride ion erosion depth of bridge pier concrete in water bodies with alternating salt concentrations was obtained, and a three-level early warning mechanism was established. To address the periodic fluctuations in chloride ion concentration caused by water flow and tides in areas with alternating salt concentrations, the potential difference between the electroosmotic anode and cathode was adaptively adjusted to control the chloride ion erosion depth. Regular on-site monitoring was used to obtain measured chloride ion diffusion coefficients and steel reinforcement protective layer thicknesses, thereby correcting the impact of water flow erosion on the bridge pier concrete spalling process and improving the adaptability and accuracy of the early warning system for underwater concrete erosion damage in bridge pier structures in areas with alternating salt concentrations. Attached Figure Description

[0028] Figure 1 This is a flowchart of an early warning method for underwater concrete erosion and damage to bridge piers in areas with alternating salt concentrations, as shown in an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram showing the relative relationship between the electroosmotic system and the cross-section of the bridge pier structure in an embodiment of the present invention;

[0030] Figure 3 This is a flowchart illustrating the chloride ion erosion depth calculation process and parameter update in an embodiment of the present invention.

[0031] Figure reference numerals: 1-Titanium wire mesh, 2-Rod electrode, 3-Chloride ion concentration sensor, 4-Bridge pier structure, 5-Electroosmosis direction. Detailed Implementation

[0032] The embodiments of the present invention will be described in more detail below with reference to the accompanying drawings and reference numerals, so that those skilled in the art can implement them after reading this specification. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0033] This application discloses, as follows: Figure 1-3 The method for early warning of underwater concrete erosion damage to bridge piers in areas with alternating salt concentrations, as shown, includes the following steps:

[0034] S1. Arrangement of the electroosmosis system: An electroosmosis system, including an electroosmosis anode, an electroosmosis cathode, and a chloride ion concentration sensor 3, is arranged on the hollow cylindrical bridge pier structure 4. The electroosmosis anode is arranged vertically along the inner surface of the bridge pier structure, and the electroosmosis cathode is arranged vertically along the outer surface of the bridge pier structure. The electroosmosis anode and the electroosmosis cathode work together to form a potential difference, driving water in the pores and cracks of the concrete of the bridge pier structure to migrate from the electroosmosis anode to the electroosmosis cathode. That is, the electroosmosis direction 5 is from the inner surface of the bridge pier structure to the outer surface. The chloride ion concentration sensor 3 is arranged on the outer surface of the bridge pier structure to obtain chloride ion concentration data of the water in the area where the salt concentration changes alternately.

[0035] S2. Calculation of Chloride Ion Erosion Depth: Based on the equilibrium condition between chloride ion diffusion flux and chloride ion electromigration flux, the chloride ion erosion depth x of the bridge pier concrete structure in water bodies with alternating salt concentrations satisfies the following expression:

[0036]

[0037] Where D is the chloride ion diffusion coefficient, m 2 / s; s is the distance between the electroosmotic anode and the electroosmotic cathode, in meters; μ is the chloride ion mobility, in meters. 2 / (V·s); U is the potential difference between the electroosmotic anode and the electroosmotic cathode, in V; C is the chloride ion concentration in the water body in the alternating salt concentration zone, in mol / m³. 3 C min The allowable value for chloride ion concentration in concrete structures, mol / m³ 3 The chloride ion erosion depth x reflects the chloride ion concentration at depth x exceeding the allowable chloride ion concentration C within the concrete structure. min ;

[0038] In practical implementation, the chloride ion diffusion coefficient D under typical conditions is 1.0 × 10⁻⁶. -12 m 2 / s, the distance s between the electroosmotic anode and the electroosmotic cathode is 0.5m, and the chloride ion mobility μ is 1.0×10-9 m 2 / (V·s), the potential difference U between the electroosmotic anode and the electroosmotic cathode is 0.1V, and the chloride ion concentration C in the water body in the alternating salt concentration zone is 150mol / m³. 3 According to the "Code for Durability Design of Concrete Structures" (GB / T 50476), the allowable value C for chloride ion concentration in concrete structures is... min It is 9.87 mol / m 3 The chloride ion erosion depth x is calculated according to equation (1) as follows:

[0039]

[0040] That is, under the specific implementation conditions, the chloride ion erosion depth x is 13.6 mm;

[0041] S3. Establishment of an early warning mechanism: Considering the periodic fluctuations in chloride ion concentration in water bodies in areas with alternating salt concentrations caused by tidal phenomena, the early warning mechanism is divided into three levels based on the chloride ion erosion depth x and the thickness d of the steel reinforcement protective layer, as shown below:

[0042] 0mm≤x<10mm: Level 1 warning, indicating that the chloride ion concentration in the water body in the area of ​​alternating salt concentration is higher than the allowable value of chloride ion concentration in the concrete structure, and has begun to cause erosion and damage to the concrete.

[0043] 10mm≤x<d: Level II warning, reflecting that the erosion and damage to concrete caused by chloride ions in the water body in the area of ​​alternating salt concentration exceeds the limit of the "Standard for Chloride Ion Permeability Performance of Concrete"; where 10mm is the limit value of chloride ion erosion depth x for underwater concrete of cross-sea bridge pier structure in the "Standard for Chloride Ion Permeability Performance of Concrete"; at this time, a warning signal is sent to relevant technical personnel, and the potential difference U between the electroosmotic anode and the electroosmotic cathode is adaptively adjusted so that the expected chloride ion erosion depth x is less than 10mm;

[0044] x≥d: Level 3 warning, which reflects that the chloride ion concentration around the steel bars in the concrete structure exceeds the allowable value, that is, the chloride ions in the water body in the area of ​​alternating salt concentration begin to cause corrosion damage to the steel bars in the concrete structure; at this time, a warning signal is sent to relevant technical personnel, and the potential difference U between the electroosmosis anode and the electroosmosis cathode is adjusted to the maximum value, thereby reducing the corrosion damage to the steel bars in the concrete structure caused by chloride ions in the water body in the area of ​​alternating salt concentration.

[0045] In specific implementation, for the secondary early warning in step S3, the adaptive adjustment of the potential difference U between the electroosmotic anode and the electroosmotic cathode satisfies the following expression:

[0046]

[0047] Where x1 is the chloride ion erosion depth, and x1 = 10 mm;

[0048] The chloride ion concentration C in the water body of the alternating salt concentration zone under typical conditions is 150 mol / m³. 3 The chloride ion erosion depth x is 13.6 mm, and the steel reinforcement protective layer thickness d is 70 mm, triggering a level two early warning and sending an early warning signal to relevant technical personnel. At the same time, the potential difference U between the electroosmotic anode and the electroosmotic cathode is adaptively adjusted according to formula (3) as shown in the following formula:

[0049]

[0050] In the specific implementation, U is taken as 0.15V. At this time, the chloride ion erosion depth x calculated according to formula (1) is 9.1mm, which meets the requirement of x < 10mm.

[0051] In specific implementation, the electroosmotic anode of the electroosmotic system is a titanium wire mesh 1, which is embedded in the inner surface of the bridge pier structure 4 and its shape is S-shaped and continuously curved and extended; the electroosmotic cathode of the electroosmotic system is a number of rod-shaped electrodes 2 composed of pure titanium conductive cores and graphite coating layers, which are closely attached to the outer surface of the bridge pier structure 4.

[0052] In practice, the electroosmosis system also includes a microcomputer control module, a switching power supply, wires, and an alarm device; the microcomputer control module controls the switching power supply and the potential difference between the electroosmosis anode and the electroosmosis cathode based on chloride ion concentration data; the wires are used for the connection between the electroosmosis anode and the electroosmosis cathode; and the alarm device is used to convey early warning information to relevant technical personnel.

[0053] In practice, considering the periodic fluctuations in chloride ion concentration in the water body of the alternating salt concentration zone caused by water flow and tides, when the chloride ion concentration C in the water body of the alternating salt concentration zone does not exceed the allowable value C of chloride ion concentration in the concrete structure, min When the power is turned off, the potential difference U between the electroosmotic anode and the electroosmotic cathode is reduced to 0, thereby reducing the wear and tear on the electroosmotic anode and the electroosmotic cathode during use.

[0054] In practice, the measured chloride ion diffusion coefficient D is obtained periodically through on-site sampling and testing. aThis corrects the impact of water erosion-induced concrete spalling on the chloride ion diffusion coefficient. The on-site sampling and testing steps include: after shutting off the power to the electro-osmosis system, rapidly drilling core samples from the outer surface of the bridge pier concrete structure inwards; then spraying silver nitrate solution onto the core sample surface to form a white silver chloride precipitate in the chloride ion erosion area; measuring the length of the chloride ion erosion area and obtaining the measured chloride ion erosion depth x. a The measured chloride ion diffusion coefficient D a Satisfy the following expression:

[0055]

[0056] Among them, U a C represents the potential difference between the electroosmotic anode and the electroosmotic cathode during the actual measurement. a This represents the chloride ion concentration in the water body during the measured alternating salt concentration range.

[0057] According to the "Standard for Testing and Evaluation of Concrete Durability" (JGJ / T 193-2009), concrete with a grade of C40 or higher must meet the requirement that the chloride ion diffusion coefficient is less than 1.0 × 10⁻⁶. -12 m 2 The requirement is / s; therefore, when the measured chloride ion diffusion coefficient D is... a Greater than 1.0×10 -12 m 2 An early warning is triggered at a time of / s, and an early warning signal is sent to relevant technical personnel, thereby initiating concrete surface coating repair work during maintenance.

[0058] In practice, to mitigate the impact of concrete spalling from bridge piers caused by water erosion on the thickness of the concrete cover for reinforcing bars, the minimum measured thickness d of the concrete cover for reinforcing bars is periodically obtained using a rebar detector. amin This updates the early warning mechanism, specifically when 10mm ≤ x < d. amin A level 2 warning is triggered when x ≥ d. amin A level-three warning was triggered.

[0059] Therefore, by integrating electroosmosis technology with the bridge pier structure, a uniformly distributed electric field is formed in the concrete, thereby improving the drainage efficiency and erosion resistance of the bridge pier structure. This overcomes the shortcomings of traditional underwater concrete erosion resistance methods, which cannot actively drain water. Based on the balance between chloride ion diffusion flux and chloride ion electromigration flux, an expression for the chloride ion erosion depth of the bridge pier concrete in water bodies with alternating salt concentrations is obtained, and a three-level early warning mechanism is established. By regularly monitoring the field to obtain the measured chloride ion diffusion coefficient and the thickness of the steel reinforcement protective layer, the influence of water flow scouring on the spalling of the bridge pier concrete on the electroosmosis process is corrected, improving the adaptability and accuracy of the early warning of underwater concrete erosion damage in bridge pier structures in areas with alternating salt concentrations.

[0060] The above describes one or more embodiments of the present invention in a relatively specific and detailed manner, but it should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for early warning of underwater concrete erosion and damage to bridge piers in areas with alternating salt concentrations, characterized in that, A hollow cylindrical bridge pier structure applied in a region with alternating salt concentrations includes the following steps: S1. Arrangement of the electroosmosis system: An electroosmosis system, including an electroosmosis anode, an electroosmosis cathode, and a chloride ion concentration sensor, is arranged on the hollow cylindrical bridge pier structure. The electroosmosis anode and the electroosmosis cathode are arranged vertically along the inner and outer surfaces of the bridge pier structure, respectively. By interacting, they form a potential difference, driving water in the pores and cracks of the bridge pier concrete to migrate along the direction of the electric field. The chloride ion concentration sensor is arranged on the outer surface of the bridge pier structure to obtain chloride ion concentration data of the water in the area where the salt concentration changes alternately. S2. Calculation of Chloride Ion Erosion Depth: The chloride ion erosion depth x of bridge pier concrete in water bodies with alternating salt concentrations satisfies the following expression: Where D is the chloride ion diffusion coefficient, m 2 / s; s is the distance between the electroosmotic anode and the electroosmotic cathode, in meters; μ is the chloride ion mobility, in meters. 2 / (V·s); U is the potential difference between the electroosmotic anode and the electroosmotic cathode, in V; C is the chloride ion concentration in the water body in the alternating salt concentration zone, in mol / m³. 3 C min The allowable value for chloride ion concentration in concrete structures, mol / m³ 3 ; S3. Establishment of the Early Warning Mechanism: The early warning mechanism is divided into three levels, as shown below: 0mm≤x<10mm: Level 1 warning, indicating that the chloride ion concentration in the water body in the area of ​​alternating salt concentration is higher than the allowable value of chloride ion concentration in the concrete structure, and has begun to cause erosion and damage to the concrete. 10mm≤x<d: Level II warning, reflecting that the erosion and damage to concrete caused by chloride ions in the water body in the area of ​​alternating salt concentration exceeds the limit of the "Standard for Chloride Ion Permeability Performance of Concrete"; at this time, a warning signal is sent to relevant technical personnel, and the U value is adaptively adjusted so that the expected chloride ion erosion depth x is less than 10mm. x≥d: Level 3 warning, indicating that the chloride ion concentration around the steel bars in the concrete structure exceeds the allowable value; at this time, a warning signal is sent to relevant technical personnel, and the U value is adjusted to the maximum value.

2. The method for early warning of underwater concrete erosion and damage to bridge piers in areas of alternating salt concentration as described in claim 1, characterized in that, The electroosmotic anode of the electroosmotic system is made of titanium wire mesh, which is embedded in the inner surface of the bridge pier structure and is S-shaped and continuously curved and extended. The electroosmotic cathode of the electroosmotic system is made of several rod-shaped electrodes composed of pure titanium conductive cores and graphite coating layers, which are closely attached to the outer surface of the bridge pier structure.

3. The method for early warning of underwater concrete erosion and damage to bridge piers in areas of alternating salt concentration according to claim 1, characterized in that, The electroosmosis system also includes a microcomputer control module, a switching power supply, wires, and an alarm device; the microcomputer control module controls the switching power supply and the potential difference between the electroosmosis anode and the electroosmosis cathode based on chloride ion concentration data; the wires are used for the connection between the electroosmosis anode and the electroosmosis cathode; and the alarm device is used to convey early warning information to relevant technical personnel.

4. The method for early warning of underwater concrete erosion and damage to bridge piers in areas of alternating salt concentration according to claim 1, characterized in that, In the secondary early warning process of step S3, the adaptive adjustment of the potential difference U between the electroosmotic anode and the electroosmotic cathode satisfies the following expression: Where x1 is the chloride ion erosion depth limit for Level II warning, and x1 = 10 mm.

5. The method for early warning of underwater concrete erosion and damage to bridge piers in areas of alternating salt concentration according to claim 1, characterized in that, When the chloride ion concentration C in the water body of the alternating salt concentration zone does not exceed the allowable value C of chloride ion concentration within the concrete structure. min When the power is turned off, the potential difference U between the electroosmotic anode and the electroosmotic cathode is reduced to 0, thereby reducing the wear and tear on the electroosmotic anode and the electroosmotic cathode during use.

6. The method for early warning of underwater concrete erosion and damage to bridge piers in areas of alternating salt concentration according to claim 1, characterized in that, The chloride ion diffusion coefficient D is obtained periodically through on-site sampling and testing. a This corrects the effect of concrete spalling in bridge pier structures caused by water erosion on the chloride ion diffusion coefficient. The on-site sampling and testing steps include: after turning off the power to the electro-osmosis system, quickly drilling core samples from the outer surface of the concrete of the bridge pier structure inward; then spraying silver nitrate solution onto the core sample surface to form a white silver chloride precipitate in the chloride ion erosion area; measuring the length of the chloride ion erosion area and obtaining the measured chloride ion erosion depth x. a The measured chloride ion diffusion coefficient D a Satisfy the following expression: Among them, U a C represents the potential difference between the electroosmotic anode and the electroosmotic cathode during the actual measurement. a This represents the chloride ion concentration in the water body during the measured alternating salt concentration range. When the measured chloride ion diffusion coefficient D a Greater than 1.0×10 -12 m 2 An alert is triggered at a time of / s, sending an alert signal to relevant technical personnel.

7. The method for early warning of underwater concrete erosion and damage to bridge piers in areas of alternating salt concentration according to claim 1, characterized in that, The minimum value d of the concrete cover thickness of the reinforcing bars during actual measurement is obtained periodically using a rebar detector. amin This updates the early warning mechanism, specifically when 10mm ≤ x < d. amin A level 2 warning is triggered when x ≥ d. amin A level-three warning was triggered.

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