Flood season bridge water level monitoring and early warning method and system

Abstract

The invention relates to the field of bridge operation safety, in particular to a flood season bridge water level monitoring and early warning method and system. The method comprises the following steps: constructing a flood season bridge safety water level system; setting a flood season bridge safety water level mark according to the flood season bridge safety water level line system; based on the safe water level mark of the bridge in the flood season, obtaining the water depth of a pier; acquiring a monitoring result of the water level under the bridge according to the water depth at the bridge pier; through the monitoring result, the risk early warning of the water level under the bridge in the flood season is realized. Water lines are marked in a color separation and grading mode, the warning water level prompting sign is additionally arranged, a standardized and visual water level recognition system is constructed, the function limitation of an existing water level mark is effectively made up, and the accuracy of bridge safety monitoring in the flood season and the timeliness of emergency disposal are remarkably improved; the water depth is monitored through the Karman vortex street effect and the low-concentration ion marking technology, water level over-limit real-time early warning is achieved, and a quantitative basis is provided for bridge safety assessment and emergency sealing control.

Description

Technical Field

[0001] The present invention relates to the field of bridge operation safety, and particularly to a method and system for monitoring and warning bridge water levels during flood seasons. Background Art

[0002] The water level under a bridge is one of the important indicators reflecting the safety status of a highway bridge crossing water during flood seasons. When the water level under the bridge exceeds the designed water level, the lower bridge structures such as piers and abutments may have their stress states changed due to long-term exposure to large water flow impact forces and floating object impact forces, thereby triggering potential safety hazards. In addition, too high a water level will also cause the non-water-crossing components such as bridge girders, main arches, and bearings of the bridge to be soaked, impacted, and lifted by floods, while increasing the risk of passing ships hitting the upper bridge structure, seriously affecting the overall safety of the bridge structure.

[0003] In the prior art, the water level markings under bridges mainly include two categories: navigable water levels and flood control water levels. The navigable water level is set according to the needs of ship passage to ensure that ships do not run aground at low water levels and do not hit the upper bridge structure at high water levels; the flood control water level is based on the requirements of dike safety and is used for the warning and emergency response of flood control departments. However, the above water level markings are not designed for the safety needs of the bridge itself and cannot directly reflect the safety status of the bridge structure during flood seasons, resulting in insufficient early warning of bridge water damage risks and making it difficult to provide accurate and intuitive decision-making bases for bridge safety management.

[0004] Currently, there is not much research work on the safety monitoring and warning of the water level under bridges during flood seasons, and there is no specific systematic, standardized, and refined method for monitoring and warning the water level under bridges during flood seasons. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method and system for monitoring and warning bridge water levels during flood seasons.

[0006] In a first aspect, a method for monitoring and warning the water level of a bridge during the flood season provided by the present invention includes the following steps: constructing a safety water level line system for the bridge during the flood season, where the safety water level line system for the bridge during the flood season includes the historical maximum flood level, the safety operation reference water level, and the flood control warning water level; setting safety water level marks for the bridge during the flood season based on the safety water level line system for the bridge during the flood season; obtaining the water depth at the bridge pier by using the Karman vortex street effect and the low-concentration ion marking technology based on the safety water level marks for the bridge during the flood season; obtaining the monitoring result of the water level under the bridge according to the water depth at the bridge pier; and realizing the warning of the water level under the bridge during the flood season through the monitoring result. By constructing a safety water level line system for the bridge during the flood season, the present invention incorporates the historical maximum flood level, the safety operation reference water level, and the flood control warning water level into a unified framework, realizes the quantitative grading of the water level risk under the bridge, and provides a scientific basis for warning decision-making; by setting safety water level marks for the bridge during the flood season, it intuitively shows the risk levels corresponding to different water levels, and improves the on-site personnel's ability to quickly judge the severity of the flood situation; by using the Karman vortex street effect and the low-concentration ion marking technology to obtain the water depth at the bridge pier, it breaks through the limitations of traditional water level monitoring by environmental interferences such as rapid water flow and high sediment content, and significantly improves the accuracy and reliability of data under complex hydrological conditions; by obtaining the water depth at the bridge pier in real time and analyzing the monitoring result, it realizes the dynamic tracking of water level changes and gains valuable time for warning response; by jointly analyzing the monitoring result and the safety water level line system, it realizes the refined processing from data collection to risk warning, greatly reduces the probability of human misjudgment, and effectively improves the efficiency and accuracy of the safety management of the bridge during the flood season.

[0007] Optionally, the constructing of the safety water level line system for the bridge during the flood season includes: determining the flood control warning water level; determining the safety operation reference water level; determining the historical maximum flood level; and constructing the safety water level line system for the bridge during the flood season through the flood control warning water level, the safety operation reference water level, and the historical maximum flood level. By determining the flood control warning water level, the present invention is conducive to establishing a primary warning threshold for the bridge facing flood risks during the flood season, enabling managers to take preventive measures in a timely manner at the initial stage of the flood, and reducing the potential threat of sudden floods to the bridge structure; by determining the safety operation reference water level, it clarifies the upper limit of the water level for the normal operation of the bridge, provides an objective standard for daily management and flood season safety assessment, and ensures the stable operation of the bridge within a controllable water level range; by determining the historical maximum flood level, it provides a key historical basis for the design of the bridge's flood resistance ability and the water level warning system, and enhances the ability to cope with floods exceeding the standard; by integrating the flood control warning water level, the safety operation reference water level, and the historical maximum flood level to construct the safety water level line system for the bridge during the flood season, a multi-level and progressive water level monitoring and warning framework is formed, realizing the full-process coverage from daily monitoring to emergency response, improving the systematicness and scientificity of the bridge flood control management, and providing refined and standardized decision-making support for water level monitoring and warning during the flood season.

[0008] Optionally, the determination of the flood control warning water level includes: determining the flood discharge for checking; using the flood discharge for checking to establish a calculation expression for the flow rate at the bridge site riverbed section; obtaining the hydraulic radius of the river channel and floodplain according to the calculation expression; determining the flood water level using the hydraulic radius; establishing a calculation model for the backwater height in front of the bridge based on the flood water level; obtaining the backwater height in front of the bridge according to the calculation model; and determining the flood control warning water level through the flood water level and the backwater height in front of the bridge. By determining the flood discharge for checking, the present invention provides a scientific hydrological calculation basis for bridge water level early warning, ensuring that the setting of the flood control warning water level conforms to the actual flood characteristics; by establishing a calculation expression for the flow rate at the bridge site riverbed section, it realizes the accurate simulation of the complex river channel flow, improving the accuracy of water level prediction; by calculating the hydraulic radius of the river channel and floodplain, it accurately reflects the flow resistance characteristics of different river reaches, optimizing the reliability of water level calculation; by determining the flood water level, it quantifies the potential threat degree of the flood to the bridge; by establishing a calculation model for the backwater height in front of the bridge, it effectively evaluates the blocking effect of the bridge structure on the water flow, avoiding the risk of underestimating the water level caused by the backwater effect; by determining the flood control warning water level through the flood water level and the backwater height in front of the bridge, it takes into account both the natural flood water level and the water blocking effect of the bridge, making the monitoring and early warning mechanism more targeted and secure for engineering.

[0009] Optionally, the calculation expression for the flow rate at the bridge site riverbed section is as follows: , where is the flood discharge for checking, 、 are the cross-sectional areas of the river channel and floodplain respectively, 、 are the bed roughness coefficients of the river channel and floodplain respectively, 、 are the hydraulic radii of the river channel respectively, is the riverbed slope; the calculation model for the backwater height in front of the bridge satisfies the following expression: , where is the maximum backwater height in front of the bridge, is the average velocity of the natural cross-section in front of the bridge, is the coefficient related to the pier shape, is the acceleration due to gravity, is the average velocity of the cross-section under the bridge before scouring, is the median diameter of the bed sediment, is the average flow velocity of the natural river channel. The present invention realizes the refined calculation of the flood flow of the composite cross-section river channel by constructing the flow calculation expression of the river channel and the river beach, fully considering the differences in water flow characteristics in different regions, and significantly improving the accuracy of flow distribution; by synchronously calculating the average flow velocity of the river beach, it overcomes the defect of the existing method of ignoring the influence of the river beach, and improves the full-section flow evaluation system; by establishing a pre-bridge backwater height model, the water blocking effect of the bridge is quantified; by correlating the median particle size of the bed sand with the river channel flow velocity parameters, it reflects the regulating effect of the riverbed anti-scouring characteristics on the backwater height, so that the model has both the dual theoretical support of hydraulics and sediment kinematics, and finally outputs high-precision calculation results.

[0010] Optionally, determining the safe operation reference water level includes: determining the safe operation reference water level taking into account the falling beams of the bridge superstructure to obtain a first safe operation reference water level; determining the safe operation reference water level taking into account the displacement of the bridge piers due to the dynamic water pressure and the impact of floating objects to obtain a second safe operation reference water level; determining the safe operation reference water level taking into account the collapse of the bridge piers due to the dynamic water pressure and the impact of floating objects to obtain a third safe operation reference water level; determining the safe operation reference water level taking into account the hollowing out of the bridge cone slope protection and the bridge-road transition section to obtain a fourth safe operation reference water level; determining the safe operation reference water level taking into account driving safety to obtain a fifth safe operation reference water level; and determining the minimum value of the first safe operation reference water level, the second safe operation reference water level, the third safe operation reference water level, the fourth safe operation reference water level and the fifth safe operation reference water level as the overall safe operation reference water level. The present invention constructs a systematic water level assessment system covering the safety operation failure modes of the entire bridge structure by separately determining the safe operation reference water level that takes into account five types of risks, namely, bridge superstructure beam drop, bridge pier deviation, bridge pier collapse, cone slope protection hollowing out, and driving safety, and breaks through the limitations of the traditional single water level limit. By determining the safe operation reference water level in view of the bridge superstructure beam drop risk, the instability accident caused by the excessive buoyancy of the beam body due to the excessive water level is prevented. By determining the safe operation reference water level in view of the bridge pier deviation risk, the combined destructive effect of dynamic water pressure and floating object impact on the stability of the pier column is controlled. ; By targeting the risk of pier collapse and determining the safe operating benchmark water level, the catastrophic consequences of foundation scour and structural strength failure are avoided; by targeting the risk of cone slope revetment hollowing and determining the safe operating benchmark water level, the chain damage path of the auxiliary structures caused by soil erosion is blocked; by targeting driving safety and determining the safe operating benchmark water level, the interactive safety of vehicles and bridges when driving through water is guaranteed; by selecting the minimum value of the five types of water level limits as the overall safe operating benchmark water level, it is ensured that any single risk factor will not exceed the overall safety threshold, thereby achieving the most conservative safety guarantee under the coupling of multi-dimensional risks.

[0011] Optionally, the determination of the safety operation reference water level considering the falling of the superstructure of the bridge includes: establishing a critical water level model for preventing the falling of the beam, and determining the safety operation reference water level considering the falling of the superstructure of the bridge according to the critical water level model for preventing the falling of the beam; the determination of the safety operation reference water level considering the deviation of the pier due to hydrodynamic pressure and impact of floating objects includes: establishing a critical water level model for the pier to resist deviation, and determining the safety operation reference water level considering the deviation of the pier due to hydrodynamic pressure and impact of floating objects according to the critical water level model for the pier to resist deviation; the determination of the safety operation reference water level considering the collapse of the pier due to hydrodynamic pressure and impact of floating objects includes: establishing a critical water level model for the pier to resist collapse, and determining the safety operation reference water level considering the collapse of the pier due to hydrodynamic pressure and impact of floating objects according to the critical water level model for the pier to resist collapse; the determination of the safety operation reference water level considering the erosion of the bridge slope protection and the bridge-road transition section includes: establishing a critical water level model for preventing erosion by coupling of soil and water in the bridge area, and determining the safety operation reference water level considering the erosion of the bridge slope protection and the bridge-road transition section according to the critical water level model for preventing erosion by coupling of soil and water in the bridge area; the determination of the safety operation reference water level considering driving safety includes: establishing a critical water level model for driving safety, and determining the safety operation reference water level considering driving safety according to the critical water level model for driving safety. By establishing a critical water level model for preventing the falling of the beam, the present invention ensures the stability of the superstructure of the bridge in flood; by establishing a critical water level model for the pier to resist deviation, the instability of the structural system caused by the deviation of the pier column is prevented; by establishing a critical water level model for the pier to resist collapse, catastrophic collapse accidents are avoided; by establishing a critical water level model for preventing erosion by coupling of soil and water in the bridge area, secondary disasters caused by the erosion of the slope are effectively controlled; by establishing a driving safety water level model, the driving safety during the flood season is guaranteed.

[0012] Optionally, the critical water level model for preventing the falling of the beam satisfies the following relationship: , where, represents the lateral thrust on the superstructure of the bridge when the critical water level value is , represents the lateral resistance of the superstructure of the bridge when the critical water level value is ; the critical water level model for the pier to resist deviation satisfies the following relationship: , where, represents the displacement of the top of the pier when the critical water level is , is the maximum deviation allowed for the pier during the operation of the bridge; the critical water level model for the pier to resist collapse satisfies the following relationship: , where, Indicates the critical water level is when the maximum bending moment of the pier, Indicates the designed flexural bearing capacity of the pier; the critical water level model for bridge domain water and soil coupling anti-erosion satisfies the following relationship: , wherein, Indicates the critical water level is when the vertical distance from the exit point to the toe of the back water slope; the critical water level model for driving safety satisfies the following relationship: , wherein, Indicates the critical water level, Indicates the lowest elevation of the bridge beam bottom, Indicates the clearance safety value between the designed flood level and the beam bottom elevation. Through constructing the critical water level model for preventing the falling of beams, the present invention realizes the precise balance control between the lateral thrust received by the upper structure of the bridge and the structural resistance, and ensures that the stability of the beam body is still within the safety threshold when the water level reaches the critical water level; by constructing the critical water level model for the anti-deviation of the pier, the displacement at the top of the pier is strictly limited within the allowable maximum deviation range, preventing the pier column from tilting due to the water level reaching the critical water level and causing the failure of the structural system; by constructing the critical water level model for the anti-collapse of the pier, it is ensured that the bending moment of the pier body does not exceed the designed flexural bearing capacity when the water level reaches the critical water level, eliminating the risk of pier column fracture from the strength theory level; by constructing the critical water level model for bridge domain water and soil coupling anti-erosion, with the arrival of the exit point at the slope foot as the judgment criterion, the state of soil and water loss when the water level reaches the critical water level is scientifically defined; by constructing the critical water level model for driving safety, half of the clearance safety value is reserved between the beam bottom elevation and the flood level, fully ensuring the driving safety of vehicles.

[0013] Optionally, setting the flood season bridge safety water level sign based on the flood season bridge safety water level line system includes: designing the flood season bridge safety water level sign based on the flood season bridge safety water level line system, and obtaining the design results of the font type, water level line scale text height, water level scale width, graded water level line width, graded water level line text color, background color, sign making material, water level scale accuracy, reading range requirements, setting position and fixing method of the flood season bridge safety water level sign; and setting the flood season bridge safety water level sign according to the design results. The present invention ensures the clear recognition of the sign information under complex meteorological conditions by designing the font type of the water level sign and the height of the water level line scale text; realizes the intuitive distinction of water levels of different risk levels by standardizing the water level scale width and the graded water level line width, which is convenient for rapid interpretation during the flood season; strengthens the visual warning effect of the sign and improves the visibility in extreme weather by setting the contrasting combination of the graded water level line text color and the background color; ensures the durability of the sign in a long-term sun and rain environment by optimizing the sign production materials; meets the technical requirements of high-precision water level monitoring by limiting the water level scale accuracy; ensures the accurate reading of monitoring personnel at different observation distances by clarifying the reading range requirements of the sign; and realizes the stable combination of the sign and the bridge structure by scientifically setting the sign position and fixing method, thus avoiding displacement or damage caused by flood impact.

[0014] Optionally, the obtaining of the water depth at the bridge pier based on the flood season bridge safety water level mark by using the Karman vortex street effect and low-concentration ion labeling technology includes: establishing a relationship model between the shedding frequency of the Karman vortex street and the water flow velocity at the bridge pier based on the flood season bridge safety water level mark by using the Karman vortex street effect, wherein the relationship model satisfies the following expression: , in, is the shedding frequency of the Karman vortex street, is the Strouhal number, is the width of the bridge pier projected onto the water surface, is the water flow velocity at the bridge pier; using low-concentration ion labeling technology, the shedding frequency of the Karman vortex street is obtained; according to the relationship model and the shedding frequency of the Karman vortex street, the flow velocity at the bridge pier is obtained; The relationship between the flow velocity and the hydraulic radius is established as follows: , in, is the water velocity at the bridge pier, is the hydraulic radius, is the riverbed roughness coefficient, is the riverbed slope; based on the above relationship, combined with the measurement results of the river channel dimensions at the bridge site, the water depth at the pier is obtained. By using the Karman vortex street effect to establish a relationship model between the shedding frequency and the water flow velocity, the present invention realizes non-contact flow velocity measurement based on the principle of fluid dynamics, overcomes the vulnerability problem of existing mechanical current meters under high flow velocity conditions during the flood season; by adopting the low-concentration ion labeling technology, breaks through the technical bottleneck of capturing vortex street signals in turbid water bodies, and ensures the accuracy of frequency measurement in complex hydrological environments; by establishing a relationship between the flow velocity and the hydraulic radius, expands the point flow velocity to cross-section hydraulic parameters, providing a theoretical basis for water depth calculation; by combining the measured data of the river channel dimensions, corrects the boundary condition error of the theoretical model, making the water depth calculation more in line with the actual river channel morphology; through multi-physical field coupling measurement, forms a new flood season water depth monitoring method with strong anti-interference ability, high accuracy and wide adaptability, providing reliable hydrological data support for bridge safety warning.

[0015] In a second aspect, a flood season bridge water level monitoring and warning system provided by the present invention includes an input device, a processor, an output device and a memory. The input device, the processor, the output device and the memory are interconnected. Among them, the memory is used to store a computer program, the computer program includes program instructions, the processor is configured to call the program instructions, and the system uses the above-mentioned flood season bridge water level monitoring method. The system provided by the present invention has a high degree of integration, and the information transmission between components is smooth; by constructing a multi-level water level line system, realizes dynamic hierarchical monitoring and warning of bridge flood season risks; by coupling the calculation of structural mechanics and hydrological characteristics, makes the warning threshold simultaneously meet the multiple requirements of girder drop protection, pier stability and driving safety; by integrating the Karman vortex street velocity measurement and ion labeling technology, overcomes the problem of flow velocity monitoring under complex hydrological conditions with high sediment concentration and turbulence, converts the single-point flow velocity into cross-section water depth information, and greatly improves the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flowchart of the flood season bridge water level monitoring and warning method according to an embodiment of the present invention; Figure 2 is a structural schematic diagram of the flood season bridge safety water level mark according to an embodiment of the present invention; Figure 3 is a structural schematic diagram of the flood season bridge water level monitoring and warning system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described here are only for illustrative purposes and are not used to limit the present invention. In the following description, in order to provide a thorough understanding of the present invention, a large number of specific details are set forth. However, it will be apparent to those of ordinary skill in the art that the present invention need not be practiced with these specific details. In other instances, well-known circuits, software, or methods have not been specifically described to avoid obscuring the present invention.

[0018] Throughout the specification, references to "one embodiment", "an embodiment", "one example", or "an example" mean that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present invention. Thus, the phrases "in one embodiment", "in an embodiment", "one example", or "an example" appearing throughout the specification do not necessarily all refer to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. In addition, those of ordinary skill in the art should understand that the diagrams provided herein are for illustrative purposes only and are not necessarily drawn to scale.

[0019] Please refer to Figure 1 , embodiments of the present invention provide a method for monitoring and warning the water level of a bridge during the flood season. The method includes the following steps: S1. Construct a safe water level line system for the bridge during the flood season. The safe water level line system for the bridge during the flood season includes the historical maximum flood level, the safe operation reference water level, and the flood control warning water level.

[0020] Among them, S1 further includes the following steps: S11. Determine the flood control warning water level.

[0021] The flood control warning water level refers to when the water level reaches this specific height, the wading bridge may face initial safety risks, and as the water level continues to rise or further increase, the degree of danger encountered by the bridge will increase accordingly. The calculation formula for the flood control warning water level is as follows:

[0022] Among them, is the flood control warning water level, is the flood water level, is the backwater height in front of the bridge.

[0023] In one embodiment, by calculating the flood water level and the backwater height in front of the bridge , and combining the above calculation formula for the flood control warning water level, the flood control warning water level is determined.

[0024] Specifically, first determine the flood discharge for checking the flood control warning water level. Under normal circumstances, the flood discharge for checking the flood control warning water level is calculated according to the frequency given in Table 1 in combination with the "Code for Hydrological Investigation and Design of Highway Engineering" (JTG C30-2015). For mountain bridges, the flood discharge for checking the flood control warning water level is calculated according to the frequency given in Table 2 in combination with the "Code for Hydrological Investigation and Design of Highway Engineering" (JTG C30-2015).

[0025]

[0026]

[0027] Furthermore, draw the discharge-water level curve at the riverbed cross-section of the bridge site.

[0028] Specifically, the calculation expression of the discharge at the riverbed cross-section of the bridge site is as follows:

[0029] Among them, is the flood discharge for checking, unit: , , are the cross-sectional areas of the river channel and the floodplain respectively, unit: , , are the average flow velocities of the river channel and the floodplain respectively, unit: ; satisfies the following expression:

[0030] Among them, is the roughness coefficient of the riverbed of the river channel, is the hydraulic radius of the river channel, unit: , when the ratio of the section width to the depth is greater than 10, the average water depth can be used instead, is the riverbed slope; satisfies the following expression:

[0031] Among them, is the roughness coefficient of the riverbed of the floodplain, is the hydraulic radius of the floodplain, unit: , when the ratio of the section width to the depth is greater than 10, the average water depth can be used instead, is the riverbed slope.

[0032] Furthermore, organize the above relationships to obtain: , Furthermore, obtain the hydraulic radii of the river channel and the floodplain according to the above expressions , , Further, based on the hydraulic radius of the river channel and the floodplain , , the flood water level is determined .

[0033] Further, based on the flood water level and the flood discharge for checking calculations, a discharge-water level curve at the riverbed cross-section of the bridge site is plotted.

[0034] It should be noted that the hydraulic radius of the river channel and the floodplain , can be calculated from the flood water level and the shape of the riverbed cross-section. Therefore, on the basis that the flood discharge for checking calculations has been determined, combined with the flow calculation expression at the riverbed cross-section of the bridge site, the flood water level is determined.

[0035] Further, the backwater height in front of the bridge is calculated.

[0036] Specifically, for rivers in mountainous areas and piedmont areas, where the flood rises and falls rapidly, the duration is short, and the riverbed geology is firm and not easily scoured, the backwater height under the bridge can adopt the maximum backwater value in front of the bridge. The backwater height in front of the bridge is mainly affected by the water-blocking effect of the bridge piers and is calculated according to the following relationship: , where is the maximum backwater height in front of the bridge, unit: , is the average velocity of the natural cross-section in front of the bridge, unit: , is the coefficient related to the shape of the bridge pier. For rectangular bridge piers, it takes 0.35; for circular bridge piers, it takes 0.18; for other pier shapes, it can take 0.18 - 0.35 according to the water-blocking situation, is the acceleration of gravity, is the average velocity of the cross-section under the bridge before scouring, unit: , is the median diameter of the bed sediment, unit: . When there is no data, it can be approximately taken as the average diameter, is the average velocity of the natural river channel, unit: , is the average velocity of the cross-section under the bridge, unit: .

[0037] Further, the above expression is sorted out to obtain:

[0038] Further, based on the above expression, the backwater height in front of the bridge is obtained.

[0039] S12. Determine the benchmark water level for safe operation.

[0040] The benchmark water level for safe operation is the highest water level to ensure the safe operation of the bridge crossing water. Multiple water levels should be calculated respectively according to the water damage events threatening the safe operation that may occur during the flood season of the bridge, and the minimum value among them should be taken as the benchmark water level for safe operation.

[0041] Among them, step S12 further includes the following steps: S121. Determine the benchmark water level for safe operation considering the falling of the upper structure of the bridge.

[0042] In one embodiment, the benchmark water level for safe operation is determined according to the conditions of the falling of the upper structure of the bridge.

[0043] Specifically, the falling of the upper structure of the bridge satisfies the following conditions:

[0044] Among them, is the lateral thrust on the upper structure of the bridge, unit: , is the lateral resistance of the upper structure of the bridge, unit: . The lateral thrust on the upper structure of the bridge is calculated according to the following formula:

[0045] Among them, is the impact force of floating objects, unit: , is the hydrodynamic pressure, unit: , and satisfies the following relational expression:

[0046] Among them, is the thrust coefficient, which can be obtained according to the different height-width ratios (the ratio of beam height to beam width) of the upper structure in Table 3. For slab beams and rectangular single box girders, the beam width is the bottom width; for variable-width single box girders, the beam width is the average width of the box body; for T-beams and multi-box girders, the beam width is the sum of the bottom widths of all transverse T-beams or multi-box girders; is the specific weight of water, unit: , is the acceleration of gravity, taking 9.81 , is the average velocity of the river channel, unit: , is the water-blocking area of the upper structure, unit: , and satisfies the following relational expression:

[0047] Among them, is the beam length, is the height from the beam bottom to the riverbed, is the height of the riverbed.

[0048]

[0049] Furthermore, the impact force of the floating object is calculated according to the following formula:

[0050] Among them, is the gravity of the floating object, unit: , which should be determined according to the actual situation of the floating objects in the river. When there is no survey data, it is calculated as 50 for calculation, is the average velocity of the river channel, unit: , is the acceleration of gravity, taking 9.81 , is the impact time, unit: , which should be estimated according to the actual data. When there is no actual data, it can be taken as 1 s.

[0051] Furthermore, the lateral resistance of the upper structure of the bridge is calculated according to the following formula:

[0052] Among them, is the resistance of the limiting device, unit: , and its value varies depending on the type of the limiting device and should be determined according to the specific situation. For example, for a concrete limiting block, the resistance of its limiting device is the shear bearing capacity of the limiting block; is the static friction force of the upper structure support, unit: , and is calculated according to the following formula:

[0053] Among them, is the static friction coefficient of the upper structure support, and should be taken according to the actual data of the bridge supports produced by different manufacturers; is the gravity of the beam body, unit: , and is taken according to the actual situation; is the gravity of the passing vehicles, unit: , and is taken according to the reference highway class I load standard. When taking the value, it should be reduced by 0.8 times on the basis of the highway class I load standard, is the buoyancy force on the beam body, unit: , and is calculated according to the following formula:

[0054] Among them, is the effective width of the submerged part of the superstructure, unit: For slab girders and rectangular single box girders, is the bottom width thereof, unit: For variable-width single box girders, is the average width of the submerged box part thereof; for T-girders and multi-box girders, is the sum of the bottom widths of all T-girders or multi-box girders in the transverse direction thereof, is the height of the part of the girder body submerged by water, unit: Unit, is the value of the water level under the bridge, unit: , is the unit weight of water, unit: , is the girder length, unit: .

[0055] Furthermore, to prevent the occurrence of the event of the superstructure falling and being damaged by water, the value of the water level under the bridge shall at least meet the following requirements:

[0056] Through trial calculation, there is a critical water level value such that holds, that is, the lateral thrust received by the bridge superstructure and the lateral resistance of the bridge superstructure have an equivalent relationship. The critical water level value at this time is the safety operation reference water level considering the falling of the superstructure, named the first safety operation reference water level.

[0057] S122. Determine the safety operation reference water level considering the deviation of the bridge pier due to dynamic water pressure and impact of floating objects.

[0058] In one embodiment, according to the conditions of the deviation of the bridge pier due to dynamic water pressure and impact of floating objects, the safety operation reference water level is determined.

[0059] Specifically, for continuous girders and simply supported beam bridges, the deviation of the bridge pier due to dynamic water pressure and impact of floating objects affects the structural safety and meets the following conditions:

[0060] Among them, is the displacement of the top of the bridge pier, unit: , is the maximum allowable deviation of the bridge pier during the bridge operation stage, unit: , determined by relevant design standards; Furthermore, for continuous beams and simply supported beam bridges, the displacement at the top of the pier is calculated as follows:

[0061]

[0062] where is the impact force of floating objects on the pier, unit: , is the hydrodynamic pressure on the pier, unit: , is the height of the pier, unit: , is the section stiffness of the pier, unit: , is the value of the water level under the bridge, unit: . It is calculated as follows:

[0063] where is the water-blocking area of the pier, i.e., the projected area in the water flow direction, unit: , is the average velocity of the river channel, unit: , is the specific weight of water, unit: , is the acceleration due to gravity, taking 9.81 , is the shape coefficient of the pier, which is taken according to Table 4.

[0064]

[0065] Furthermore, to prevent the pier from deflecting due to hydrodynamic pressure and impact of floating objects, the value of the water level under the bridge should at least meet the following requirements:

[0066] Through trial calculation, there is a critical water level value such that , i.e., the equivalent relationship between the displacement at the top of the pier and the maximum allowable deflection of the pier during the bridge operation stage holds. The critical water level value at this time is the safety operation reference water level considering the deflection of the pier due to hydrodynamic pressure and impact of floating objects, named the second safety operation reference water level.

[0067] S123. Determine the safety operation reference water level considering the collapse of the pier due to hydrodynamic pressure and impact of floating objects.

[0068] In one embodiment, the safety operation reference water level is determined according to the conditions under which the bridge pier collapses due to hydrodynamic pressure and impact of floating objects.

[0069] Specifically, the collapse of the bridge pier due to hydrodynamic pressure and impact of floating objects satisfies the following conditions:

[0070] Wherein, is the maximum bending moment of the bridge pier, unit: , is the designed flexural bearing capacity of the bridge pier, unit: , calculated according to the geometric shape of the bridge pier cross-section and the design value of the material strength.

[0071] Furthermore, for continuous beam and simply supported beam bridges, the maximum bending moment of the bridge pier is determined according to the following two formulas:

[0072]

[0073] Wherein, and are the bending moments calculated by the above two formulas, unit: , is the impact force of the floating object on the bridge pier, unit: , is the hydrodynamic pressure on the bridge pier, unit: , is the height of the bridge pier, unit: , is the water level value under the bridge, unit: .

[0074] Furthermore, take and the larger value of them as the maximum bending moment of the bridge pier.

[0075] Furthermore, for rigid frame bridges, the maximum bending moment of the bridge pier is calculated according to the following formula, and the larger value of them is taken as the maximum bending moment of the bridge pier:

[0076] Wherein, is the bending moment of the bridge pier, unit: , is the distance from the calculation section to the river bed, unit: , , are the bending moments generated by the impact force of the floating object and the hydrodynamic pressure at the bottom of the bridge pier respectively, unit: , , are the reaction forces generated at the bottom of the pier under the action of the impact force of floating objects and the dynamic water pressure, unit: ; , , , are calculated according to the following formula:

[0077]

[0078]

[0079]

[0080] Among them, is the impact force of floating objects on the pier, unit: , is the dynamic water pressure on the pier, unit: , is the height of the pier, unit: , is the value of the water level under the bridge, unit: .

[0081] Furthermore, take as the maximum value of the maximum bending moment of the pier.

[0082] Furthermore, to prevent the pier from collapsing under the action of dynamic water pressure and impact of floating objects, the value of the water level under the bridge should at least meet the following requirements:

[0083] Through trial calculation, there is a critical water level value , such that , that is, the equivalent relationship between the maximum bending moment of the pier and the designed flexural bearing capacity of the pier holds. At this time, is the safety operation reference water level considering the collapse of the pier under the action of dynamic water pressure and impact of floating objects, named the third safety reference water level.

[0084] S124. Determine the safety operation reference water level considering the erosion of the bridge slope protection and the bridge-road transition section.

[0085] In one embodiment, according to the conditions of the bridge slope protection and the erosion of the bridge-road transition section, the safety operation reference water level is determined.

[0086] Specifically, the hollowing out of the bridge conical slope revetment and the bridge-road transition section meets the condition for seepage to emerge from the slope body, which can be judged by the geometric position of the seepage line in the slope body. The seepage line in the slope body of the conical slope revetment and the bridge-road transition section can be calculated by the following formula:

[0087] Wherein, is the vertical distance from any point on the seepage line to the toe of the bridge conical slope revetment and the bridge-road transition section, unit: , is the horizontal distance from any point on the seepage line to the seepage emergence point, unit: , is the coefficient related to the slope body material and the water level line, unit: , is the vertical distance from the emergence point to the toe of the backwater slope, unit: , is the total seepage length, unit: . and satisfy the following relationship:

[0088] Wherein, is the water level on the upstream side of the bridge conical slope revetment and the bridge-road transition section, unit: , is the horizontal distance from the intersection point of the upstream water level line and the slope surface to the toe of the backwater slope, unit: , is the upstream slope surface angle, is the backwater slope surface angle, is the water level on the backwater side of the bridge conical slope revetment and the bridge-road transition section, unit: , satisfies the following formula:

[0089] Furthermore, to prevent the occurrence of hollowing out events in the bridge conical slope revetment and the bridge-road transition section, the water level under the bridge should at least meet the following requirements:

[0090] Through trial calculation, there is a critical water level value , such that holds, that is, the vertical distance from the emergence point to the toe of the backwater slope is equal to 0. At this time, is the safety operation reference water level considering the hollowing out of the bridge conical slope revetment and the bridge-road transition section, named the fourth safety operation reference water level.

[0091] S125. Determine the safety operation reference water level considering driving safety.

[0092] In one embodiment, considering the emergency traffic demand during the flood season and to ensure driving safety, for non-flooded bridges, the safety operation reference water level considering driving safety is calculated according to the following formula:

[0093] Wherein, represents the critical water level, unit: , represents the lowest elevation of the bridge girder bottom, unit: , represents the clearance safety value between the design flood level and the girder bottom elevation, unit: . At this time, is the operation reference water level considering driving safety, named the fifth safety operation reference water level.

[0094] S126. Determine the overall safety operation reference water level.

[0095] In one embodiment, the minimum value among the first safety operation reference water level, the second safety operation reference water level, the third safety operation reference water level, the fourth safety operation reference water level and the fifth safety operation reference water level is determined as the overall safety operation reference water level.

[0096] S13. Determine the historical maximum flood level.

[0097] The historical maximum flood level is the water level of the largest flood that has occurred historically at the bridge site.

[0098] In one embodiment, for areas with hydrological data, the historical maximum flood level is obtained according to the data provided by the water conservancy department; for areas without hydrological data, the historical maximum flood level is determined based on the flood marks left on the bridge structure, local chronicles records or the memories of the elderly nearby.

[0099] S14. Construct the flood season bridge safety water level line system.

[0100] In one embodiment, the flood season bridge safety water level line system is constructed through the flood control warning water level, the safety operation reference water level and the historical maximum flood level.

[0101] S2. Set the flood season bridge safety water level signs according to the flood season bridge safety water level line system.

[0102] In one embodiment, according to the flood season bridge safety water level line system, design the flood season bridge safety water level signs. The flood season bridge safety water level signs, also called flood control signs, are composed of a scale and graded water level lines, reflecting the distance of the water level under the bridge, such as Figure 2As shown

[0103] Furthermore, obtain the design results of the font type, water level line scale text height, water level scale width, graded water level line width, graded water level line text color, background color, identification production material, water level scale accuracy, viewing range requirements, installation location, and fixing method of the flood season bridge safety water level identification. The design results include the characteristics of the flood season bridge safety water level identification. Specifically as follows: 1. The font uses the B-type traffic sign font; the text fonts within the same flood control identification are unified.

[0104] 2. The height of the water level scale text is not less than 5 cm, and the height of the text marked on the graded water level line is not less than 7 cm.

[0105] 3. The width of the water level scale is not less than 2 cm, and the width of the graded water level line is not less than 10 cm. When the flood control identification is installed on the bridge pier, the graded water level line surrounds the bridge pier for one week.

[0106] 4. Among the text marked on the graded water level line, the text marked for the flood control warning water level is dark blue, and the abbreviation is "Warning"; the text marked for the safe operation reference water level is red, and the abbreviation is "Reference"; the text marked for the historical maximum flood water level is black, and the abbreviation is "History"; the background color is white.

[0107] 5. The identification plate is made by brushing a reflective and anti-fouling coating on the surface of a stainless steel plate, or directly brushed on the surface of the bridge pier and abutment.

[0108] 6. The minimum scale of the water level scale is not greater than 50 cm.

[0109] 7. The viewing range is more than 1.0 m above the higher of the historical maximum flood water level and the safe operation reference water level, and less than 0.5 m below the flood control warning water level.

[0110] 8. It is installed at the prominent position of the bridge pier, abutment, and the wading components of the bridgehead conical slope revetment, and faces the shore for convenient observation.

[0111] 9. It is fixed on the bridge component by bolts or welding, and the pasting method is not allowed for fixing.

[0112] Furthermore, set the flood season bridge safety water level identification according to the design results.

[0113] S3. Based on the flood season bridge safety water level identification, use the Karman vortex street effect and low-concentration ion marking technology to obtain the water depth at the bridge pier.

[0114] In one embodiment, based on the flood season bridge safety water level identification, use the Karman vortex street effect to establish a relationship model between the shedding frequency of the Karman vortex street and the water flow velocity at the bridge pier. The relationship model satisfies the following expression:

[0115] wherein, is the shedding frequency of the Karman vortex street, is the Strouhal number, is the projected width of the bridge pier's water-facing surface, is the water flow velocity at the bridge pier.

[0116] Furthermore, based on the flood-season bridge safety water level mark, an environmentally friendly and safe slow-release electrolyte layer including KCl and NaCl is coated at the position of the graded water level line on the surface of the bridge pier. When the flood-season bridge safety water level mark shows that the water level reaches the position of the graded water level line, under the scouring of the water flow, the slow-release electrolyte layer can release trace ions.

[0117] Furthermore, the low-concentration ion labeling technology is used to label the trace ions. Due to the periodic shedding characteristics of the Karman vortex street, the ion clusters washed away by the water flow also pass through a certain point downstream at the same period as the shedding of the Karman vortex street. Due to the existence of the ion clusters, the water conductivity at a certain point downstream will change.

[0118] Furthermore, a monitoring electrode is installed at a certain point downstream. By measuring the periodic fluctuation of the water conductivity through the change in the electric signal intensity, the shedding frequency of the Karman vortex street can be obtained.

[0119] Furthermore, substituting the shedding frequency of the Karman vortex street into the relational model, the water flow velocity at the bridge pier is obtained .

[0120] Furthermore, combining the measurement results of the river channel dimensions at the bridge site and the following expression, the water depth at the bridge pier is calculated. The expression is:

[0121] wherein, is the bed roughness coefficient, is the hydraulic radius. When the cross-sectional width-depth ratio is greater than 10, the average water depth can be used instead. When the foregoing conditions are not met, the hydraulic radius is the wetted perimeter of the river channel, which is related to the water depth, is the bed slope, which means that when is determined, the water depth is determined.

[0122] The advantage of this method is that it uses two ways to jointly monitor the water depth. One is the hierarchical water level trigger monitoring method. When the water level reaches a certain hierarchical water level line, the water flow generates a Karman vortex street through the bridge pier, and the characteristics of the vortex street are sensed by the monitoring electrode and quickly reflected to the backend, so as to know that the actual water level has reached a certain hierarchical water level line. The other is the continuous water level monitoring method. According to the above calculation expressions of the water flow velocity and water depth at the bridge pier, the water depth is continuously monitored, so as to know the distance between the current water level and a certain hierarchical water level line at the backend.

[0123] It should be noted that while this method monitors the water depth, it can also effectively monitor the flow velocity, which provides important parameters for calculating the stress conditions of the bridge structure under different water levels mentioned above.

[0124] S4. Obtain the monitoring result of the water level under the bridge according to the water depth at the bridge pier.

[0125] In one embodiment, based on the water depth obtained in step S3 and combined with the flood season bridge safety water level mark set in step S2, obtain the monitoring result of the water level under the bridge.

[0126] Specifically, by monitoring the change of the water depth, obtain the distance between the current water level and the "historical", "benchmark" or "warning" hierarchical water level line, so as to monitor the change of the water level and provide guidance for the bridge management department to formulate flood season emergency countermeasures.

[0127] S5. Realize the early warning of the water level under the bridge during the flood season through the monitoring result.

[0128] In one embodiment, according to the monitored water level , set three-level early warning thresholds, namely the emergency water level threshold , the dangerous water level threshold , the warning water level threshold .

[0129] Furthermore, compare the monitored water level with the three-level early warning thresholds to realize the early warning of the bridge water level during the flood season. Specifically as follows: When , the monitored water level reaches the historical maximum flood level, causing serious damage to the bridge and making the bridge unable to operate safely, flashing a red alarm light and emitting an alarm prompt sound; When , the monitored water level exceeds the safety operation benchmark water level, causing slight damage to the bridge and making the bridge unable to operate safely, flashing an orange alarm light and emitting an alarm prompt sound; When When the monitored water level does not exceed the reference water level for safe operation but reaches the warning water level, the bridge is almost undamaged and can operate safely. At this time, the water level is an abnormal water level, and enhanced attention is required. The yellow alarm light flashes, and no alarm prompt sound is emitted; When the monitored water level is below the warning water level and cannot cause damage to the bridge, and it can operate safely. At this time, the water level is a normal water level, and the alarm light does not flash, nor does the alarm prompt sound emit.

[0130] Please refer to Figure 3 , Figure 3 which is a schematic structural diagram of the flood season bridge water level monitoring and early warning system in the embodiment of the present invention. The system includes an input device, a processor, an output device, and a memory. The input device, the processor, the output device, and the memory are interconnected. Among them, the memory is used to store computer programs, and the computer programs include program instructions. The processor is configured to call the program instructions, and the system uses the above-mentioned flood season bridge water level monitoring and early warning method.

[0131] In this embodiment, the input device includes a Karman vortex street flow velocity sensor, a low-concentration ion marker detector, a riverbed cross-section scanner, a water level scale, an environmental monitor, and a user input interface.

[0132] Specifically, the Karman vortex street flow velocity sensor is installed on the upstream face of the bridge pier to detect the vortex shedding frequency; the low-concentration ion marker detector is deployed in the water area around the bridge pier to enhance the ability to identify vortex street signals; the riverbed cross-section scanner is used to measure river channel parameters, including the river channel width and the floodplain area; the water level scale has graded water level scales with a fluorescent energy storage coating for manual review; the environmental monitor collects auxiliary data, including rainfall and sediment concentration in the water flow; the user input interface is used to input bridge-related parameters.

[0133] The processor includes an edge computing unit, a core computing module, and a risk prediction module.

[0134] Specifically, the edge computing unit is deployed on-site at the bridge location for real-time data preprocessing; the core computing module runs a water level analysis algorithm; the risk prediction module is trained based on historical data to predict the water level change trend.

[0135] The output device includes an acoustic-optic alarm device, a remote monitoring platform, and an electronic water level display screen.

[0136] Specifically, the acoustic-optic alarm device is installed at both ends of the bridge and emits different alarms according to the early warning level; the remote monitoring platform is transmitted to the management center through 4G / 5G and supports viewing on a PC / mobile device; the electronic water level display screen displays the real-time water level and safety status at the bridgehead.

[0137] The memory includes a local storage unit and a cloud database.

[0138] Specifically, the local storage unit is used to cache recent monitoring data; the cloud database is used to store long-term hydrological data, warning events, and model parameters.

[0139] In summary, the present invention proposes a method for monitoring and warning the water level of a bridge during the flood season in response to possible bridge water damage events during the flood season. By constructing a safety water level line system and setting water level marks, the water level situation under the bridge is clearly and prominently displayed during the flood season; by color-coding and grading the water level lines and adding warning water level signs, a systematic and standardized water level visual recognition system is formed, effectively making up for the functional limitations of existing water level marks and significantly improving the accuracy of bridge safety monitoring and the timeliness of emergency response during the flood season; the water depth is monitored using the Karman vortex street effect and low-concentration ion marking technology to achieve real-time warning of water level overrun, providing a quantitative basis for bridge safety assessment and emergency lockdown.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

Claims

1. A flood season bridge water level monitoring and early warning method, characterized in that: The method comprises the following steps: Constructing a bridge safety water level system during the flood season, which includes the historical maximum flood level, the safe operation benchmark water level and the defense warning water level; According to the flood season bridge safety water level line system, set up flood season bridge safety water level signs; Based on the flood season bridge safety water level mark, the water depth at the bridge pier is obtained by using the Karman vortex street effect and low-concentration ion labeling technology; Obtaining monitoring results of the water level under the bridge according to the water depth at the bridge pier; Through the monitoring results, risk warning of water level under the bridge during flood season can be achieved.

2. A flood season bridge water level monitoring and early warning method according to claim 1, characterized in that: The construction of the flood season bridge safety water level system includes: Determine the warning water level; Determine the reference water level for safe operation; Determine the maximum historical flood level; A flood season bridge safety water level system is constructed through the defense warning water level, the safe operation benchmark water level and the historical maximum flood level.

3. A flood season bridge water level monitoring and early warning method according to claim 2, characterized in that: Determining the defense warning water level includes: Determine and verify flood flow; By using the verified flood flow, a calculation expression for the flow at the riverbed section at the bridge position is established; According to the calculation expression, the hydraulic radius of the river channel and the river beach is obtained; Determining the flood level using the hydraulic radius; Based on the flood water level, a calculation model for the height of the water in front of the bridge is established; According to the calculation model, the height of the water in front of the bridge is obtained; The defense warning water level is determined by the flood water level and the height of the water in front of the bridge.

4. A flood season bridge water level monitoring and early warning method according to claim 3, characterized in that: The calculation expression of the flow at the riverbed section at the bridge position is as follows: , in, To calculate flood flow, , are the water-passing areas of the river channel and river beach, , are the riverbed roughness coefficients of the river channel and river beach, , are the hydraulic radius of the river channel, is the riverbed gradient; the calculation model of the water backwater height before the bridge satisfies the following expression: ， in, is the maximum water level in front of the bridge, is the average flow velocity of the natural section before the bridge, is the coefficient related to the pier shape, is the acceleration due to gravity, is the average flow velocity under the bridge before scouring, is the median particle size of bed sand, is the average flow velocity of a natural river channel.

5. A flood season bridge water level monitoring and early warning method according to claim 2, characterized in that: Determining the safe operation reference water level includes: Determine the safe operation reference water level considering the drop of the bridge superstructure beam, and obtain the first safe operation reference water level; Determine the safe operation reference water level taking into account the displacement of the bridge piers due to dynamic water pressure and impact of floating objects, and obtain the second safe operation reference water level; Determine the safe operating reference water level that takes into account the collapse of bridge piers due to dynamic water pressure and impact of floating objects, and obtain the third safe operating reference water level; Determine the safe operating reference water level taking into account the bridge cone slope protection and the hollowing out of the bridge-road transition section, and obtain the fourth safe operating reference water level; Determine the safe operation reference water level considering driving safety and obtain the fifth safe operation reference water level; The minimum value among the first safety operation reference water level, the second safety operation reference water level, the third safety operation reference water level, the fourth safety operation reference water level and the fifth safety operation reference water level is determined as the overall safety operation reference water level.

6. A flood season bridge water level monitoring and early warning method according to claim 5, characterized in that: Determining the safe operation reference water level considering the falling beam of the bridge superstructure includes: establishing a critical water level model for preventing the falling beam, and determining the safe operation reference water level considering the falling beam of the bridge superstructure according to the critical water level model for preventing the falling beam; The determining of the safe operation reference water level considering the displacement of the bridge pier due to the dynamic water pressure and the impact of floating objects comprises: establishing a critical water level model for the bridge pier to resist displacement, and determining the safe operation reference water level considering the displacement of the bridge pier due to the dynamic water pressure and the impact of floating objects according to the critical water level model for the bridge pier to resist displacement; The determining of the safe operation reference water level considering the collapse of the bridge pier due to the dynamic water pressure and the impact of floating objects comprises: establishing a critical water level model for the anti-collapse of the bridge pier, and determining the safe operation reference water level considering the collapse of the bridge pier due to the dynamic water pressure and the impact of floating objects according to the critical water level model for the anti-collapse of the bridge pier; Determining the safe operation reference water level considering the bridge cone slope protection and the hollowing of the bridge-road transition section includes: establishing a bridge area water-soil coupling anti-erosion critical water level model, and determining the safe operation reference water level considering the bridge cone slope protection and the hollowing of the bridge-road transition section according to the bridge area water-soil coupling anti-erosion critical water level model; The determining of the safe operation reference water level considering driving safety comprises: establishing a driving safety critical water level model, and determining the safe operation reference water level considering driving safety according to the driving safety critical water level model.

7. A flood season bridge water level monitoring and early warning method according to claim 6, characterized in that: The critical water level model of the anti-fall beam satisfies the following relationship: ， in, Indicates that the critical water level is The lateral thrust on the bridge superstructure is Indicates that the critical water level is The lateral resistance of the bridge superstructure at this time; the critical water level model of the bridge pier anti-deflection satisfies the following relationship: ， in, The critical water level is The displacement of the top of the pier is is the maximum displacement of the piers allowed during the operation of the bridge; the critical water level model for the piers to resist collapse satisfies the following relationship: ， in, The critical water level is The maximum bending moment of the bridge pier is represents the design bending bearing capacity of the bridge pier; the bridge area water-soil coupled anti-corrosion critical water level model satisfies the following relationship: ， in, The critical water level is The vertical distance between the escape point and the toe of the back water surface; the critical water level model for driving safety satisfies the following relationship: ， in, Indicates the critical water level, Indicates the lowest elevation of the bridge beam bottom. It represents the clearance safety value between the design flood level and the beam bottom elevation.

8. The method for monitoring and early warning of bridge water level during flood season according to claim 1, characterized in that: The setting of flood season bridge safety water level markings according to the flood season bridge safety water level line system includes: According to the flood season bridge safety water level system, a flood season bridge safety water level sign is designed, and the font type, water level scale text height, water level scale width, graded water level width, graded water level text color, background color, sign making material, water level scale accuracy, reading range requirements, setting location and fixing method of the flood season bridge safety water level sign are obtained; According to the design results, the flood season bridge safety water level mark is set.

9. The method for monitoring and early warning of bridge water level during flood season according to claim 1, characterized in that: The method of obtaining the water depth at the bridge pier based on the flood season bridge safety water level mark and using the Karman vortex street effect and low-concentration ion labeling technology includes: Based on the flood season bridge safety water level mark, using the Karman vortex street effect, a relationship model between the shedding frequency of the Karman vortex street and the water flow velocity at the bridge pier is established, and the relationship model satisfies the following expression: ， in, is the shedding frequency of the Karman vortex street, is the Strouhal number, is the width of the bridge pier projected onto the water surface, is the water flow velocity at the bridge pier; Using low-concentration ion labeling technology, the shedding frequency of the Karman vortex street is obtained; According to the relationship model and the shedding frequency of the Karman vortex street, the flow velocity at the bridge pier is obtained; The relationship between the flow velocity and the hydraulic radius is established as follows: ， in, is the water velocity at the bridge pier, is the hydraulic radius, is the riverbed roughness coefficient, is the riverbed gradient; Based on the relationship, combined with the measurement results of the river channel dimensions at the bridge site, the water depth at the bridge pier is obtained.

10. A flood season bridge water level monitoring and early warning system, the system using a flood season bridge water level monitoring and early warning method according to any one of claims 1 to 9, characterized in that: The system includes an input device, a processor, an output device and a memory, wherein the input device, the processor, the output device and the memory are connected to each other, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is configured to call the program instructions.

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