Method and System for Hidden Danger Investigation before Flood Season and Water Damage Risk Assessment of Small and Medium-Span Bridges

Abstract

The present invention relates to the technical field of bridge engineering inspection and evaluation, specifically a method and system for hidden danger investigation before flood season and water damage risk assessment of small and medium-span bridges, which includes the following steps: obtaining bridge inundation event information and determining the flood flow of the bridge deck elevation, obtaining the risk score results and risk level situations of bridge inundation based on the flood flow and bridge inundation event information; collecting bridge structure instability information to establish a bridge structure parameter analysis model, and then obtaining the risk score results and risk level situations of the offset of the upper bridge structure and the overturning of the upper bridge structure; collecting the bridge pier and abutment collapse information set to obtain the risk score results and risk level situations of bridge pier and abutment collapse and bridgehead scouring events; analyzing the risk score results and risk level situations of bridge inundation, offset of the upper bridge structure, overturning of the upper bridge structure, bridge pier and abutment collapse, and bridgehead scouring events, and realizing hidden danger investigation before flood season and water damage risk assessment of small and medium-span bridges through a systematic evaluation method.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge engineering inspection and evaluation, and specifically to a method and system for hidden danger investigation before flood season and water damage risk assessment of small and medium-span bridges. Background Technique

[0002] Bridges are key components of the transportation network. The risks of bridges exist not only in the construction stage but also throughout the entire operation cycle. Therefore, accurately identifying, scientifically estimating, and comprehensively evaluating the safety risks of bridges are important links to ensure the safe construction of bridge projects. Bridge water damage is one of the key factors affecting the safe operation of bridges. Existing research shows that the generalized reliability analysis of bridges under flood disasters, the mechanism of bridge foundation water damage, and its reinforcement and protection strategies and targeted prevention and control measures are the core contents of bridge water damage risk assessment. Once the structural stability of the bridge is damaged, it will cause immeasurable losses. Therefore, how to efficiently and accurately carry out bridge safety risk assessment, especially for small and medium-span bridges, construct an intelligent evaluation model and system, accurately identify and evaluate the risk levels of in-service bridges, and provide scientific and reliable technical support for management personnel is an important trend and urgent need in the current technical field.

[0003] Although the existing highway engineering hydrological survey design and calculation specifications provide some bases and calculation methods, there is still a lack of a complete and systematic evaluation system and method for bridge water damage risk assessment. Therefore, it is necessary to further study bridge water damage risk assessment methods and related technologies, further construct a comprehensive and scientific evaluation system, improve the safety and smoothness of bridge projects, and overcome the subjective influence degree of traditional methods. Summary of the Invention

[0004] In view of the defects of existing methods and the deficiencies in practical applications, aiming at the limitations of the current methods for hidden danger investigation before flood season and water damage risk assessment of medium and small span bridges and their deficiencies in practical applications, the present invention proposes an evaluation system to standardize the hidden danger investigation and risk assessment of water damage of medium and small span bridges before flood season, thereby ensuring the objectivity and accuracy of the evaluation results and effectively reducing the influence degree of human subjective factors. In the first aspect, the present invention provides a method for hidden danger investigation before flood season and water damage risk evaluation of medium and small span bridges. The above method includes the following steps: obtaining bridge inundation event information, determining the flood flow of the bridge deck elevation based on the bridge inundation event information, and obtaining the risk score result and risk level situation of bridge inundation according to the flood flow and the bridge inundation event information; collecting bridge structure instability information, establishing a bridge structure parameter analysis model based on the bridge structure instability information and obtaining a parameter analysis result, and obtaining the risk score result and risk level situation of the upper structure offset and the upper structure overturning of the bridge according to the parameter analysis result; obtaining a set of bridge pier and abutment collapse information, and obtaining the risk score result and risk level situation of bridge pier and abutment collapse and bridgehead scouring events according to the set of bridge pier and abutment collapse information; comprehensively analyzing the risk score results and risk level situations of bridge inundation, upper structure offset of the bridge, upper structure overturning of the bridge, bridge pier and abutment collapse, and bridgehead scouring events to realize the hidden danger investigation and water damage risk evaluation before flood season of medium and small spans. The present invention comprehensively considers multiple risk analysis factors such as bridge inundation, upper structure offset and overturning, pier and abutment collapse, and bridgehead scouring, forming a comprehensive and systematic risk evaluation framework, which helps to accurately grasp the overall safety status of the bridge and take preventive measures in time.

[0005] Optionally, the obtaining of bridge inundation event information and determining the flood flow of the bridge deck elevation based on the bridge inundation event information includes: obtaining bridge inundation event information, where the bridge inundation event information includes information on changes in the river channel boundary of the bridge location reach, information on the compression of the bridge opening flow cross-section, and information on the investigation of curve super elevation; obtaining the flood flow of the bridge deck elevation based on the information on changes in the river channel boundary of the bridge location reach, the information on the compression of the bridge opening flow cross-section, and the information on the investigation of curve super elevation;

[0006] The flood flow satisfies the following relationship;

[0007]

[0008] Wherein, represents the typical flood flow, represents the Manning roughness coefficient, represents the average width of the river channel, represents the average water depth of the cross-section, represents the river bed slope of the reach.

[0009] The present invention analyzes flood flow and frequency through calculation formulas, which is conducive to early warning of potential flood risks and is of great significance for formulating disaster prevention and mitigation measures and ensuring the safe operation of bridges.

[0010] Optionally, obtaining the risk scoring result and risk level of bridge inundation based on the flood flow and the bridge inundation event information includes: setting a risk assessment scale for bridge inundation based on the bridge inundation event information, and obtaining the risk scoring result of bridge inundation by combining the risk assessment scale and the flood flow; determining the risk level of bridge inundation according to the risk scoring result of bridge inundation;

[0011] The risk scoring result of bridge inundation satisfies the following relationship;

[0012]

[0013] Wherein, represents the risk scoring result of bridge inundation, represents the typical flood frequency, represents the risk assessment scale of bridge inundation. The present invention quantifies the bridge inundation risk into a specific scoring result, making the risk assessment result more intuitive and easy to understand, and helping to take preventive measures and response plans in a timely manner.

[0014] Optionally, collecting bridge structural instability information, establishing a bridge structural parameter analysis model based on the bridge structural instability information and obtaining a parameter analysis result includes: constructing a bridge structural parameter analysis model based on the bridge structural instability information, and the bridge structural parameter analysis model includes a water flow average velocity calculation function, a flowing water pressure calculation function, a buoyancy calculation function, an uplift force calculation function and a floating object impact force calculation function;

[0015] The water flow average velocity calculation function satisfies the following relationship:

[0016]

[0017] Wherein, represents the water flow average velocity on the water-facing surface of the beam body, represents the lateral velocity partial coefficient, represents the first vertical distribution coefficient, represents the water depth of the channel section, represents the height of the beam body section, represents the second vertical distribution coefficient, represents the third vertical distribution coefficient, represents the average velocity of any measuring line in the section, represents the average velocity of the mid-perpendicular line in the section;

[0018] The flowing water pressure calculation function satisfies the following relationship:

[0019]

[0020] Wherein, represents the flowing water pressure, represents the bridge water resistance coefficient, represents the projected area of the bridge in the direction perpendicular to the water flow, represents the water flow density, represents the average water flow velocity on the water-facing surface of the beam body;

[0021] The buoyancy calculation function satisfies the following relationship:

[0022]

[0023] Wherein, represents the buoyancy, represents the water flow density, represents the acceleration due to gravity, represents the volume of water displaced by the bridge;

[0024] The uplift force calculation function satisfies the following relationship:

[0025]

[0026] Wherein, represents the uplift force, represents the bottom width of the bridge, represents the beam length perpendicular to the direction of flood action, represents the water flow density, represents the acceleration due to gravity, represents the backwater height in front of the bridge;

[0027] The impact force of floating objects calculation function satisfies the following relationship:

[0028]

[0029] Wherein, represents the impact force of floating objects, represents the gravity of the floating object, represents the water flow velocity, represents the acceleration due to gravity, represents the impact time.

[0030] The present invention establishes a bridge structure parameter analysis model based on multiple parameters such as the average water flow velocity, flowing water pressure, buoyancy, uplift force, and impact force of floating objects, and can thus comprehensively and precisely evaluate the structural stability of the bridge under flood conditions, which helps to identify potential structural instability risks.

[0031] Optionally, obtaining the risk scoring results and risk level conditions of the offset and overturning of the superstructure of the bridge based on the parameter analysis results includes: analyzing the horizontal force and frictional resistance acting on the bearing based on the parameter analysis results;

[0032] The horizontal force satisfies the following relationship:

[0033]

[0034] Wherein, represents the horizontal force acting on the bearing, represents the flowing water pressure, represents the impact force of floating objects;

[0035] The frictional resistance satisfies the following relationship:

[0036]

[0037] Wherein, represents the frictional resistance acting on the bearing, represents the friction coefficient, represents the number of forces perpendicular to the bearing, represents the vertical reaction force of the bearing under the total load effect.

[0038] The present invention can more accurately evaluate the offset and overturning risks of the superstructure of the bridge under flood conditions, helps to timely solve the problem of structural instability, and provides technical guarantee for the safe operation of the bridge.

[0039] Optionally, obtaining the risk scoring results and risk level conditions of the offset and overturning of the superstructure of the bridge based on the parameter analysis results includes: obtaining the risk scoring results of the offset and overturning of the superstructure of the bridge according to the horizontal force, the frictional resistance and the parameter analysis results; determining the risk level conditions of the offset and overturning of the superstructure of the bridge based on the risk scoring results of the offset and overturning of the superstructure of the bridge;

[0040] The risk scoring result of the offset of the superstructure of the bridge satisfies the following relationship;

[0041]

[0042] Wherein, represents the risk scoring result of the offset of the superstructure of the bridge, represents the typical flood frequency, represents the risk assessment scale of the offset of the superstructure of the bridge;

[0043] The risk scoring result of the overturning of the superstructure of the bridge satisfies the following relationship;

[0044]

[0045] Among them, represents the risk scoring result of the overturning of the superstructure of the bridge, represents the typical flood frequency, represents the risk assessment scale for the overturning of the superstructure of the bridge.

[0046] The present invention obtains the risk scoring result based on physical principles and mathematical formulas, further ensuring the scientificity and accuracy of the evaluation result and improving the reliability of the evaluation result.

[0047] Optionally, the obtaining of the information set of the collapse of bridge piers and abutments, and obtaining the risk scoring result and risk level situation of the collapse of bridge piers and abutments and the scour at the bridgehead include: collecting the information on the scour hazards at the pier foundation, the scour hazards at the abutment foundation, and the information on the investigation of the scour hazards at the bridgehead to obtain the information set of the collapse of bridge piers and abutments; analyzing the total scour depth, the elevation of the lowest scour line, and the safe embedment elevation of the bridge piers and abutments based on the information set of the collapse of bridge piers and abutments;

[0048] The total scour depth satisfies the following relationship:

[0049]

[0050] Among them, represents the total scour depth of the bridge piers and abutments, represents the natural scour depth of the river section at the bridge site, represents the general scour depth of the river section at the bridge site, represents the local scour depth of the river section at the bridge site;

[0051] The elevation of the lowest scour line satisfies the following relationship:

[0052]

[0053] Among them, represents the elevation of the lowest scour line, represents the elevation of the design water level, represents the local scour depth of the river section at the bridge site;

[0054] The safe embedment elevation satisfies the following relationship:

[0055]

[0056] Among them, represents the lowest safe embedment elevation of the pier and abutment foundations, represents the designed elevation of the foundation, represents the minimum embedment depth at the bottom.

[0057] The present invention conducts a quantitative analysis of the total scour depth, the elevation of the lowest scour line, and the safe embedment elevation of bridge piers and abutments, which can more accurately evaluate the risks of bridge pier and abutment collapse and bridgehead scouring events.

[0058] Optionally, obtaining the set of bridge pier and abutment collapse information and obtaining the risk score results and risk level situations of bridge pier and abutment collapse and bridgehead scouring events based on the set of bridge pier and abutment collapse information include: obtaining the risk score results of bridge pier and abutment collapse and bridgehead scouring events based on the total scour depth, the elevation of the lowest scour line, and the safe embedment elevation; analyzing the risk level situations of bridge pier and abutment collapse and bridgehead scouring events according to the risk score results of bridge pier and abutment collapse and bridgehead scouring events;

[0059] The risk score result of the bridge pier and abutment collapse satisfies the following relationship:

[0060]

[0061] wherein, represents the risk score result of the bridge pier and abutment collapse, represents the typical flood frequency, represents the risk assessment scale of the bridge pier and abutment collapse.

[0062] The present invention introduces a risk assessment scale, which improves the accuracy and reliability of the evaluation results and is conducive to early warning of the risks of bridge pier and abutment collapse and bridgehead scouring.

[0063] Optionally, the risk score result of the bridgehead scouring event satisfies the following relationship:

[0064]

[0065] wherein, represents the risk score result of the bridgehead scouring event, represents the typical flood frequency, represents the risk assessment scale of the bridgehead scouring event. The present invention sets the risk assessment scales and calculation formulas for different events, which helps to promote the standardization process in the field of bridge risk management and at the same time promotes the standardization and systematization of risk management methods.

[0066] Second aspect, the present invention also provides a hidden danger investigation and flood damage risk assessment system for small and medium - span bridges before the flood season, which can efficiently execute the hidden danger investigation and flood damage risk assessment method for small and medium - span bridges provided by the present invention. The above - mentioned system includes an input device, a processor, an output device and a memory. Among them, the input device, the processor, the output device and the memory are interconnected. The memory includes the computer - readable storage medium as described in the first aspect of the present invention. The memory is used to store a computer program, and the computer program includes program instructions. The processor is configured to call the above - mentioned program instructions. The hidden danger investigation and flood damage risk assessment system for small and medium - span bridges provided by the present invention has a compact structure and strong applicability, and greatly improves the operation efficiency. Description of the Drawings

[0067] Figure 1 It is a flowchart of the hidden danger investigation and flood damage risk assessment method for small and medium - span bridges of the present invention;

[0068] Figure 2 It is a schematic framework diagram of the flood damage risk calculation process in the hidden danger investigation and flood damage risk assessment method for small and medium - span bridges of the present invention;

[0069] Figure 3 It is a schematic diagram of the upper - structure resistance of girder bridges in the hidden danger investigation and flood damage risk assessment method for small and medium - span bridges of the present invention;

[0070] Figure 4 It is a schematic diagram of the natural scour measurement method in the hidden danger investigation and flood damage risk assessment method for small and medium - span bridges of the present invention;

[0071] Figure 5 It is a schematic diagram of the general scour and abutment scour measurement methods in the hidden danger investigation and flood damage risk assessment method for small and medium - span bridges of the present invention;

[0072] Figure 6 It is a schematic diagram of the local scour measurement method in the hidden danger investigation and flood damage risk assessment method for small and medium - span bridges of the present invention;

[0073] Figure 7 It is a schematic diagram of the encroachment of the bridge approach on the river channel in the hidden danger investigation and flood damage risk assessment method for small and medium - span bridges of the present invention;

[0074] Figure 8 It is a schematic diagram of the regulating project affecting the water flow direction in the hidden danger investigation and flood damage risk assessment method for small and medium - span bridges of the present invention;

[0075] Figure 9 It is a schematic diagram of the vortex scouring at the junction of the bridgehead and the slope protection in the hidden danger investigation and flood damage risk assessment method for small and medium - span bridges of the present invention;

[0076] Figure 10This is a schematic structural diagram of the delay selection system between blast holes in a mine for the present invention. Specific embodiments

[0077] 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 do not limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those of ordinary skill in the art that the present invention does not have to employ these specific details. In other instances, well-known circuits, software, or methods have not been specifically described in order to avoid obscuring the present invention.

[0078] Throughout the specification, the mention of "one embodiment", "an embodiment", "an example", or "an example" means 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", "an example", or "an example" appearing throughout the specification do not necessarily all refer to the same embodiment or example. In addition, the specific 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.

[0079] Please refer to Figure 1 , in view of the limitations and deficiencies of the existing methods for hidden danger investigation and flood damage risk assessment of medium and small span bridges before the flood season, the present invention proposes a systematic risk evaluation system and a quantitative analysis method, standardizes and optimizes the process of hidden danger investigation and risk assessment of medium and small span bridges before the flood season, ensures the objectivity and accuracy of the evaluation results, and at the same time reduces the influence degree of subjective factors on the evaluation results. The present invention provides a method for hidden danger investigation and flood damage risk assessment of medium and small span bridges before the flood season, and the above method includes the following steps:

[0080] S1. Obtain bridge inundation event information, determine the flood flow of the bridge deck elevation based on the above bridge inundation event information, and obtain the risk score result and risk level situation of bridge inundation according to the flood flow and bridge inundation event information. The implementation steps and specific contents are as follows:

[0081] In this embodiment, bridge flood damage events mainly include types of events such as bridge inundation, instability of the superstructure, and collapse of piers and abutments. Before the flood season arrives, hidden danger investigations and risk assessments need to be carried out for different events.

[0082] The above potential hazard investigation work mainly includes the following links: First, collect data to ensure the integrity of bridge-related information; second, conduct on-site inspections and visits to understand the current situation of the bridge and the surrounding environment; then, analyze the information and data, and analyze the different event information collected; finally, conduct flood damage event evaluation, score prediction and comprehensive judgment to further determine the flood damage risk and safety level faced by the bridge.

[0083] The process of flood damage risk assessment before the flood season for bridges includes two parts: typical flood calculation and flood damage risk calculation. For bridges where flood data information has not been updated for more than ten years, it is necessary to recalculate the typical flood flow; the process of flood damage risk calculation needs to follow a specific process. For the above flood damage risk calculation process, please refer to Figure 2 。

[0084] When using the method of potential hazard investigation and flood damage risk assessment before the flood season for small and medium-span bridges for risk assessment, the typical flood frequency should be selected with reference to the data information in Table 1.

[0085] Table 1 Recommended typical flood frequencies for bridge flood damage risk assessment

[0086] Evaluation order Typical flood frequency fn 1 1 / 10 2 1 / 25 3 1 / 50 4 1 / 75 5 1 / 100

[0087] Based on the information in Table 1, it can be seen that: the typical flood frequency is expressed as , and the typical flood flow selected during the bridge flood damage risk assessment shall not be lower than the design flood flow. If the actually selected flow is lower than the design value, then the design flood flow needs to be used for the assessment of risk events to ensure the accuracy and comprehensiveness of the assessment results.

[0088] In an optional embodiment, bridge inundation event information is obtained. The above bridge inundation event information mainly includes river channel boundary change information at the bridge site, information on the compression of the flow cross-section of the bridge opening, and information on the investigation of bend super elevation.

[0089] Collect river channel boundary change information at the bridge site.

[0090] The flood passage capacity of the river section at the bridge site is significantly affected by the riverbed boundary parameters, especially the riverbed roughness coefficient and the riverbed slope. When the riverbed roughness coefficient increases or the riverbed slope decreases, the flood passage capacity of the river section will be weakened. In order to accurately determine the riverbed roughness coefficient of the river section at the bridge site, it is necessary to investigate the riverbed overburden and vegetation characteristics in the areas 10 times the bridge length but not less than 500 meters upstream and downstream of the bridge axis. The relationship between the above characteristics and the Manning roughness coefficient of the riverbed can be obtained and confirmed by referring to the Manning roughness table. For river sections with special geological or ecological characteristics, the research results in the technical field of Manning roughness coefficient values of natural rivers at home and abroad can be used for reference to obtain more accurate roughness coefficient estimation results. Based on the above investigation and analysis methods, the flood passage characteristics of the river section at the bridge site can be more comprehensively understood, providing a favorable basis for bridge design and flood risk prediction.

[0091] To accurately determine the riverbed slope of the river section at the bridge site, it is necessary to measure the riverbed elevation at the deepest point of the cross-section at the positions 1 times the bridge length upstream and downstream of the bridge axis respectively. Subsequently, the riverbed slope of this river section is analyzed using the above two elevation values.

[0092] In the embodiment, the calculation formula of the riverbed slope of the river section satisfies the following relationship:

[0093]

[0094] Among them, represents the riverbed slope of the river section, represents the riverbed elevation at the deepest point of the cross-section through which the flow passes upstream of the bridge axis, represents the riverbed elevation at the deepest point of the cross-section through which the flow passes downstream of the bridge axis, represents the length of the river section.

[0095] Collect information on the compression of the cross-section through which the flow passes through the bridge opening.

[0096] When investigating the compression of the cross-section through which the flow passes through the bridge opening, several main factors leading to the reduction of the cross-section need to be concerned. The above factors include but are not limited to the illegal occupation of the space under the bridge by human activities, the elevation of the riverbed under the bridge due to sediment accumulation, and the blockage of the bridge opening by floating objects in the water flow. The combined action of these related factors further leads to a significant reduction in the effective cross-section through which the flow passes through the bridge opening.

[0097] Obtain information on the inspection of superelevation at the bend.

[0098] For bridge construction projects located in curved river sections, it is necessary to determine the radius of curvature of the river bend where the bridge is located and the river width at the position of the bridge axis. In addition, the superelevation phenomenon generated by the bend can be quantitatively calculated through corresponding formulas. The calculation formula of the superelevation at the bend in the embodiment is as follows:

[0099]

[0100] Among them, represents the superelevation value of the curve, represents the average width of the river channel, represents the average cross-sectional velocity, represents the acceleration due to gravity, represents the radius of the curve.

[0101] Based on the above information on the change of the river channel boundary, the compression of the flow cross-section of the bridge opening, and the inspection information of the curve superelevation, the flood flow of the bridge deck elevation is obtained.

[0102] By analyzing the current river channel boundary conditions and the current situation of the bridge, the minimum flood flow that causes the bridge deck to be flooded can be determined, and the corresponding occurrence frequency is assigned to the above flow.

[0103] Based on the current conditions of the bridge and the river channel and the typical flood frequency data in Table 1, in the embodiment, following the guiding principles of the Highway Engineering Hydrological Survey and Design Code (JTG C30-2015), the water surface elevation at the bridge site is further calculated. The relevant calculation steps and content are as follows:

[0104] For the flood level under typical flood conditions, it can be directly obtained by referring to the existing water level and flow relationship curve at the bridge site cross-section, or obtained through the typical flood flow calculation formula. The determination of the flood level needs to be based on the measurement results of the average cross-sectional water depth. The above flood level can be represented by for representation.

[0105] The above flood flow, that is, the calculation formula of the typical flood flow, satisfies the following relationship;

[0106]

[0107] Among them, represents the typical flood flow, represents the Manning roughness coefficient, represents the average width of the river channel, represents the average cross-sectional water depth, represents the bed slope of the river reach;

[0108] The calculation of the backwater height can be carried out according to the relevant content in the Highway Engineering Survey and Design Code (JTJ062-91). The above backwater height can be represented by for representation.

[0109] The water surface elevation at the bridge site can be obtained from the flood level and the backwater height. For bridges located in the river bend area, the superelevation value generated by the curve needs to be additionally considered and included to ensure the accuracy of the water surface elevation calculation. The above water surface elevation at the bridge site can be represented by for representation and satisfies the following relationship;

[0110]

[0111] Among them, represents the water surface elevation at the bridge site, represents the flood level, represents the backwater height, represents the superelevation value of the curve.

[0112] Based on the above bridge inundation event information, set the risk assessment scale for bridge inundation, combine the risk assessment scale and the flood discharge to obtain the risk score result of bridge inundation; and determine the risk level situation of bridge inundation according to the risk score result of bridge inundation.

[0113] According to the requirements of the bridge inundation risk classification and assessment standard, and combined with the bridge inundation event information, the assessment scale for evaluating the bridge inundation risk can be determined. In the embodiment, according to the classification and assessment criteria of the bridge inundation risk, and referring to the inundation event information experienced by the bridge, a set of assessment criteria and scales for quantifying the bridge inundation risk are set.

[0114] For the information on the classification and assessment standard of the bridge inundation risk in the embodiment, please refer to Table 2.

[0115] Table 2 Information Table of Bridge Inundation Risk Classification and Assessment Standard

[0116]

[0117] In Table 2, represents the typical flood frequency, represents the deck elevation, represents the water surface elevation at the bridge site, represents the bridge height, and the relevant values of the deck elevation and the bridge height can be obtained through measurement.

[0118] In Table 2, this ratio is used as the basis for evaluating the bridge inundation risk, and the assessment scale According to the ratio of the inundation risk is divided into four levels, which are represented by the values 1, 2, 3, and 4 of the assessment scale When it is 0, it is a special case, indicating that an accident has occurred.

[0119] When the ratio is greater than or equal to 0.6, the assessment scale is 1, indicating that the bridge has no inundation risk, meaning that the deck is far above the water surface, even in case of flood.

[0120] When When the ratio is between 0.2 and 0.6, the assessment scale is 2, indicating that the risk of bridge inundation is very low. At this time, the bridge deck is still at a certain distance above the water surface, but relative to the risk-free state.

[0121] When When the ratio is between 0 and 0.2, the assessment scale is 3, indicating that the risk of bridge inundation is very high, which means that the bridge deck is very close to the water surface and the flood is likely to inundate the bridge deck.

[0122] When When the ratio is less than or equal to 0, the assessment scale is 4, indicating that a bridge inundation accident has occurred, which means that the water surface is already above the bridge deck and the bridge has been inundated by the flood.

[0123] In practical applications, based on the ratio and referring to the assessment criteria in Table 2, the inundation risk level of the bridge can be quickly judged, which helps to take necessary early warning and response measures in a timely manner to ensure the safety of the bridge during floods, providing a powerful tool for bridge inundation risk assessment.

[0124] Based on the information of the bridge inundation risk classification assessment criteria provided in Table 2, the scoring results of the bridge inundation risk can be obtained. In the embodiment, the scoring results of the bridge inundation risk satisfy the following relationship;

[0125]

[0126] Among them, represents the scoring result of the bridge inundation risk, represents the typical flood frequency, represents the assessment scale of the bridge inundation risk.

[0127] The scoring result of the bridge inundation risk is determined by multiplying the typical flood frequency by the assessment scale of the bridge inundation risk. In the embodiment, standardized assessment criteria and relational expressions are adopted, which can ensure the objectivity and fairness of the bridge inundation risk assessment process, reduce the influence of human factors, be able to calculate the risk score of the bridge inundation more accurately, thereby improving the reliability of the assessment results. At the same time, quickly and accurately calculating the risk score of the bridge inundation helps decision-makers take corresponding preventive measures or formulate emergency plans according to the risk score.

[0128] The assessment of the anti-inundation risk level of the bridge should be carried out in accordance with the criteria in Table 3.

[0129] Table 3 Bridge Anti-inundation Risk Level Table

[0130]

[0131] Based on the information in Table 3, it can be known that the anti-inundation risk level of the bridge is based on the scoring result of the bridge inundation risk Determine. When the scoring result is less than or equal to 0.25, the anti-flooding risk level of the bridge is rated as level one, that is, high risk; when the scoring result is between 0.25 and 0.4, the anti-flooding risk level of the bridge is rated as level two, that is, medium risk; when the scoring result is greater than or equal to 0.4, the anti-flooding risk level of the bridge is rated as level three, that is, low risk.

[0132] Furthermore, in the method for analyzing the risk scoring and level situation of bridge flooding in this embodiment, it is only an optional condition of the present invention. In one or some other embodiments, the method for analyzing the risk scoring and level situation of bridge flooding can be adjusted according to the information characteristics and risk scoring requirements of bridge flooding events, which helps to ensure the accuracy and practicality of the evaluation results, and at the same time promotes the development and progress of risk assessment technologies in the field of bridge engineering.

[0133] S2. Collect information on bridge structure instability, establish a bridge structure parameter analysis model based on the information on bridge structure instability and obtain the parameter analysis result, and obtain the risk scoring result and risk level situation of the upper structure offset and the upper structure overturning of the bridge according to the above parameter analysis result. The specific steps and implementation contents are as follows:

[0134] First, it is necessary to collect information on bridge structure instability.

[0135] When conducting bridge safety assessment, information on bridge structure stability needs to be collected. In the embodiment, the investigation mainly focuses on the water flow velocity and density and the impact of floating objects.

[0136] If the riverbed slope of the current river channel has increased compared to the natural state before bridge construction, or the riverbed roughness coefficient has decreased, then under the same flow conditions, the water flow velocity may increase. The same method mentioned above can be used for the investigation of the riverbed slope and roughness coefficient; for bridges that have experienced debris flows before and after construction, the density of the debris flow can be estimated by measuring the volume of the debris flow residues or conducting on-site investigation and interviews.

[0137] In addition, it is also necessary to investigate the risk of floating objects hitting the bridge. If there are towns or parking lots along the river within 1 km upstream of the bridge, it is necessary to evaluate whether there is a risk of being flooded in the relevant area. If there is such a risk, it must be considered that during floods, vehicles may float with the water flow and generate additional impact forces on the bridge.

[0138] Similarly, if there is a dock within 1 km upstream of the bridge, it is necessary to estimate the impact force generated on the bridge according to the type and grade of the docked ships. At the same time, if there is a forest farm or timber storage yard upstream, it is necessary to estimate the impact force that may be generated on the bridge according to the size of the timber.

[0139] Then, based on the instability information of the bridge structure, a bridge structure parameter analysis model is constructed. In the embodiment, the above-mentioned bridge structure parameter analysis model mainly includes a water flow average velocity calculation function, a flowing water pressure calculation function, a buoyancy calculation function, an uplift force calculation function, and a floating object impact force calculation function. The specific content is as follows:

[0140] The core of the bridge impact instability risk assessment lies in analyzing the relationship between the resistance of the upper structure of the bridge and the flood acting force. If the acting force generated by the flood exceeds the resistance of the upper structure of the bridge, then when the corresponding bridge encounters the corresponding flood, there is a risk of instability events occurring in its upper structure. In the embodiment, taking the beam bridge as an example, for the schematic diagram of the resistance of the upper structure of the beam bridge, please refer to Figure 3 , where xyo is the coordinate system of the schematic diagram, represents the overturning angle.

[0141] Further analysis shows that the key factor leading to the instability of the upper structure of the bridge is the excessive water flow acting force. The loads exerted by the water flow on the upper structure of the bridge mainly include the pressure generated by the flowing water, the upward uplift force, the buoyancy that makes the structure float, and the impact force generated when the floating object impacts. In order to quantify the relevant water flow acting forces, in this embodiment, a bridge structure parameter analysis model is constructed based on the instability information of the bridge structure.

[0142] Based on the instability information of the bridge structure, analyze the average water flow velocity on the water-facing side of the beam body. The above-mentioned water flow average velocity calculation function needs to satisfy the following relationship:

[0143]

[0144] Wherein, represents the average water flow velocity on the water-facing side of the beam body, represents the lateral part coefficient of the flow velocity, represents the first vertical distribution coefficient, represents the water depth of the channel cross-section, represents the height of the beam body cross-section, represents the second vertical distribution coefficient, represents the third vertical distribution coefficient, represents the average flow velocity of any measuring line in the cross-section, represents the average flow velocity of the central vertical line in the cross-section;

[0145] Regarding the lateral part coefficient n of the flow velocity, its value range is defined between 0.975 and 1.03. The above coefficient reflects the distribution characteristics of the water flow velocity in the transverse direction in relevant calculations, that is, the lateral part coefficient of the flow velocity is between 0.975 and 1.03, which can be used to adjust or represent the change in the flow velocity of the water flow in the transverse direction on the water-facing side of the bridge beam body.

[0146] The first vertical distribution coefficient satisfies the following relationship;

[0147]

[0148] Wherein, represents the first vertical distribution coefficient, is the Froude number.

[0149] The second vertical distribution coefficient satisfies the following relationship;

[0150]

[0151] Wherein, represents the second vertical distribution coefficient, is the Froude number.

[0152] The third vertical distribution coefficient satisfies the following relationship;

[0153]

[0154] Wherein, represents the third vertical distribution coefficient, is the Froude number.

[0155] The above Froude number satisfies the following relationship;

[0156]

[0157] Wherein, represents the cross-sectional average flow velocity, represents the acceleration due to gravity, represents the water depth of the channel cross-section.

[0158] Wherein the flowing water pressure calculation function satisfies the following relationship:

[0159]

[0160] Wherein, represents the flowing water pressure, represents the bridge water resistance coefficient, represents the projected area of the bridge in the direction perpendicular to the water flow, represents the water flow density, represents the average water flow velocity on the water-facing surface of the beam body;

[0161] The numerical range of the above bridge water resistance coefficient needs to be defined between 2.0 and 2.2, which means that in the relevant water flow analysis, the obstruction of the bridge to the water flow can be quantified by the bridge water resistance coefficient K, and the coefficient value is not less than 2.0 and not higher than 2.2.

[0162] Wherein the buoyancy calculation function satisfies the following relationship:

[0163]

[0164] wherein, represents buoyancy, represents the density of the water flow, represents the acceleration due to gravity, represents the volume of water displaced by the bridge;

[0165] wherein the upward buoyant force calculation function satisfies the following relationship:

[0166]

[0167] wherein, represents the upward buoyant force, represents the width of the bridge bottom surface, represents the length of the beam perpendicular to the direction of the flood action, represents the density of the water flow, represents the acceleration due to gravity, represents the height of the water backing up in front of the bridge;

[0168] In this embodiment, the relevant data of the height of the water backing up in front of the bridge can adopt the water backing up value calculated previously.

[0169] wherein the floating object impact force calculation function satisfies the following relationship:

[0170]

[0171] wherein, represents the floating object impact force, represents the gravity of the floating object, represents the water flow velocity, represents the acceleration due to gravity, represents the impact time.

[0172] The unit of the gravity of the floating object is kilonewton (kN), and this gravity value needs to be determined according to the actual situation of the floating objects in the river or through on-site investigation.

[0173] The estimation of the impact time should preferably be determined based on existing actual data. If specific data is lacking, a reasonable time value can be set, specifically 1 second. In addition, the possible forms of instability and damage to the upper structure of the bridge caused by the water flow mainly include the offset and overturning of the bridge structure, and the specific manifestations are the offset phenomenon and the overturning risk of the structure.

[0174] Through the average water flow velocity calculation function, flowing water pressure calculation function, buoyancy calculation function, uplift force calculation function, and floating object impact force calculation function in the bridge structure parameter analysis model, based on the above parameter calculation functions, the analysis results of different bridge structure parameters can be accurately obtained. The above calculation functions are mainly based on principles such as fluid mechanics and structural mechanics, and can comprehensively consider the influence of various factors such as water flow velocity, pressure, buoyancy, and impact force on the bridge structure, thereby providing more accurate parameter analysis results. Based on this, the stress conditions of the bridge under different working conditions can be more clearly understood, which helps to improve the authenticity of the bridge stability and safety analysis results.

[0175] Then, based on the above parameter analysis results, analyze the horizontal force and frictional resistance acting on the bearing, and the specific content is as follows:

[0176] Based on the analysis results of different bridge structure parameters, further explore the relationship between the horizontal force and the frictional resistance acting on the bearing. Once the horizontal force borne by the bearing exceeds the limit of its frictional resistance, the bearing will slide, which will lead to phenomena such as the drift or dislocation of the beam body.

[0177] In the embodiment, a horizontal force analysis function is established based on the flowing water pressure, floating object impact force, and relevant data information. The above horizontal force analysis function needs to satisfy the following relationship:

[0178]

[0179] Among them, represents the horizontal force acting on the bearing, represents the flowing water pressure, represents the floating object impact force;

[0180] Furthermore, the frictional resistance satisfies the following relationship:

[0181]

[0182] Among them, represents the frictional resistance acting on the bearing, represents the friction coefficient, represents the number of forces perpendicular to the bearing, represents the vertical reaction force of the bearing under the total load effect.

[0183] Calculating the horizontal force and frictional resistance acting on the bearing can more accurately predict the behavior of the bridge under different working conditions, including but not limited to the sliding trend of the bearing and the stability of the beam body, which helps to make more reasonable decisions during the design and construction processes, and then effectively analyze the overall performance and safety of the bridge.

[0184] Finally, obtain the risk scoring results of the upper structure offset and the upper structure overturning of the bridge based on the horizontal force, friction resistance, and parameter analysis results; and determine the risk level of the upper structure offset and the upper structure overturning of the bridge according to the risk scoring results of the upper structure offset and the upper structure overturning of the bridge.

[0185] In an optional embodiment, according to the content specified in the grading and evaluation standard of the upper structure offset risk of the bridge, determine the evaluation grade of the upper structure offset risk of the bridge, and further improve the grading and evaluation information of the upper structure offset risk based on the horizontal force and friction resistance on the bearing. Please refer to Table 4.

[0186] Table 4 Grading and Evaluation Standard Table for Upper Structure Offset Risk of Bridge

[0187]

[0188] In Table 4, represents the horizontal force acting on the bearing, represents the friction resistance acting on the bearing.

[0189] Evaluation Scale According to the ratio of divide the offset risk into four grades, which are represented by the numerical values 1, 2, 3, and 4 of the evaluation scale

[0190] When the ratio of

[0191] When the ratio of

[0192] When the ratio of

[0193] When the ratio of

[0194] In practical applications, the offset risk level of the bridge can be quickly judged by calculating the horizontal force on the upper structure of the bridge and the friction resistance on the bearing, combined with the evaluation standard in Table 4, which helps to take necessary maintenance and reinforcement measures in a timely manner to ensure the stability and safety of the bridge.

[0195] Considering the typical flood frequency and the offset risk assessment scale comprehensively, the risk scoring results of the offset of the bridge superstructure satisfy the following relationship;

[0196]

[0197] Among them, represents the risk scoring result of the offset of the bridge superstructure, represents the typical flood frequency, represents the risk assessment scale of the offset of the bridge superstructure;

[0198] According to the provisions of Table 4, the offset risk assessment scale is determined, and combined with the specific flood frequency, the offset risk of the bridge superstructure when facing different flood frequencies can be analyzed, that is, the risk scoring result of the offset of the bridge superstructure can be obtained.

[0199] The grade assessment of the anti-instability risk of the bridge superstructure shall be carried out in accordance with the relevant provisions in Table 5.

[0200] Table 5 Anti-instability risk grade table of the superstructure

[0201]

[0202] Based on Table 5 and relevant information, the anti-instability risk of the bridge superstructure can be assessed.

[0203] According to the risk scoring result of the offset of the bridge superstructure, it can be compared with the scoring range in Table 5. If the risk scoring result of the offset of the bridge superstructure is less than or equal to 0.25, the anti-instability risk grade of the bridge superstructure is rated as level one; if the risk scoring result of the offset of the bridge superstructure is between 0.25 and 0.4 (including 0.25 but not including 0.4), the risk grade is rated as level two; if the risk scoring result of the offset of the bridge superstructure is greater than or equal to 0.4, the risk grade can be rated as level three. The above assessment method provides a clear and quantitative standard, which helps to accurately evaluate and predict the resistance of the bridge superstructure when facing the instability risk.

[0204] In an optional embodiment, the hydrostatic buoyancy will weaken the anti-overturning ability of the beam body, and the horizontal impact force exerted by the flood on the bridge generates a huge lateral overturning moment. At this time, the superstructure of the bridge faces the risk of overturning failure. In order to quantify the above risk, the structural stability moment and the structural overturning moment are introduced, and the assessment scale of the overturning risk of the bridge superstructure is determined according to the relevant provisions of the bridge superstructure overturning risk classification and assessment standard.

[0205] For the above-mentioned information on the risk classification and assessment of the overturning of the bridge superstructure, please refer to Table 6.

[0206] Table 6 Standard Table for Risk Classification and Assessment of the Overturning of the Bridge Superstructure

[0207]

[0208] In Table 6 represents the structural stability moment, represents the structural overturning moment.

[0209] Two moments are used in Table 6 as the basis for assessing the risk of the overturning of the bridge superstructure. The assessment scale According to the ratio of divides the overturning risk into four levels, which are represented by the numerical values 1, 2, 3, and 4 of the assessment scale

[0210] When the ratio of

[0211] When the ratio of

[0212] When the ratio of

[0213] When the ratio of

[0214] In practical applications, the risk level of the bridge overturning can be quickly judged according to the assessment criteria in Table 6, so as to take corresponding maintenance and reinforcement measures to ensure the safe operation of the bridge.

[0215] Due to the comparison relationship between the reduction of the anti-overturning moment caused by the hydrostatic buoyancy and the lateral overturning moment generated by the flood horizontal impact force, the information in Table 6 can be used in the embodiments to evaluate the magnitude of the risk of the overturning of the bridge superstructure.

[0216] The risk score result of the above-mentioned overturning of the bridge superstructure satisfies the following relationship;

[0217]

[0218] Among them, represents the risk score result of the overturning of the bridge superstructure, represents the typical flood frequency represents the risk assessment scale for the overturning of the superstructure of the bridge

[0219] The risk assessment scale for overturning was determined based on the information in Table 6 and relevant regulations

[0220] The scoring results of the risk of the superstructure of the bridge overturning are mainly determined based on the typical flood frequency and the relevant risk assessment scale. Among them, the risk scoring results of the superstructure of the bridge overturning represent the quantitative evaluation results of the risk of the superstructure of the bridge overturning when facing different flood frequencies

[0221] The grading of the risk of the superstructure of the bridge overturning should be carried out in accordance with the relevant regulations in Table 7

[0222] Table 7 Risk level table for preventing the instability of the superstructure

[0223]

[0224] Based on the information in Table 7, it can be seen that if the risk scoring result of the superstructure of the bridge overturning is less than or equal to 0.25, then the risk level of the superstructure of the bridge against overturning is rated as level one, indicating a low risk; if the risk scoring result of the superstructure of the bridge overturning is between 0.25 and 0.4 (including 0.25 but not including 0.4), then the risk level is rated as level two, indicating a moderate risk; if the risk scoring result of the superstructure of the bridge overturning is greater than or equal to 0.4, then the risk level is rated as level three, indicating a high risk. This assessment system provides a clear quantitative standard, which helps to better understand and evaluate the safety status of the bridge when facing the risk of the superstructure overturning

[0225] Furthermore, in this embodiment, the specific analysis steps for the offset and overturning of the superstructure of the bridge are only an optional condition of the present invention. In one or some other embodiments, according to the actual situation of the instability of the bridge structure and the different attribute characteristics of the bridge structure parameters, the specific analysis steps for the offset and overturning of the superstructure of the bridge can be optimized. Different bridge structures have different instability modes and structure parameters. Optimizing the analysis steps enables the method for investigating potential hazards before the flood season and evaluating the risk of water damage of small and medium - span bridges of the present invention to adapt to various complex situations, improving the applicability and practicability of the above - mentioned evaluation method

[0226] S3. Obtain the information set of the collapse of bridge piers and abutments, and obtain the risk scoring results and risk level situations of the collapse of bridge piers and abutments and the event of scouring at the bridge head according to the information set of the collapse of bridge piers and abutments. The specific implementation steps and related content are as follows

[0227] Collect information on potential scour hazards at the pier bases, potential scour hazards at the abutment foundations, and information on the investigation of scouring at the bridgeheads to obtain a set of information on bridge pier and abutment collapses; analyze the total scour depth, the elevation of the lowest scour line, and the safe embedment elevation of the bridge piers and abutments based on the above set of information on bridge pier and abutment collapses.

[0228] Collect information on potential scour hazards at the pier bases.

[0229] The core of the investigation work on potential scour hazards at the pier bases lies in identifying and addressing the risks brought about by natural scour, general scour, and local scour of the riverbed. The combined action of the above-mentioned scour phenomena forms the lowest scour line on the upstream face of the pier, and the total scour depth is the sum of the depths of the three types of scour.

[0230] Factors that need to be concerned about regarding natural scour hazards at the piers include, but are not limited to, the current situation of the scour depth, the existence of sand mining pits, changes in the erosion base level at the river section outlet, and the evolution of river bends. To effectively investigate and collect relevant potential hazard information, the following methods can be adopted:

[0231] In the embodiment, a method for measuring the natural scour depth is adopted. For details, please refer to Figure 4 .

[0232] Based on Figure 4 it can be known that this measurement method measures the elevation of the deepest point of the river channel cross-section at positions 1 times the bridge length upstream and downstream of the bridge axis respectively; then, compare the elevation with the elevation of the deepest point of the same cross-section before the bridge was built to calculate the elevation difference; finally, take the average of the elevation differences of the upstream and downstream cross-sections to obtain an estimated value of the natural scour depth.

[0233] Field surveys need to be carried out within a range of half a kilometer upstream and downstream of the bridge axis to confirm whether there are pits formed by sand mining activities. Once a sand mining pit is found, immediately measure its maximum depth to evaluate its impact on the stability of the pier.

[0234] For the riverbed within 1 kilometer downstream of the bridge axis, special attention needs to be paid to whether there are stepped non-rock riverbed elevation drop points. The above-mentioned drop points may be formed by natural processes such as water flow scouring and riverbed sediment transportation. After the drop points are found, measure the elevation difference of the riverbed upstream and downstream of the mutation point to understand the change of the riverbed morphology.

[0235] For bridges located in curved river sections, it is necessary to accurately measure the radius of curvature and the natural river width at the bend apex. The above parameters are crucial for evaluating the stability and anti-scour ability of the bridge in the curved river section.

[0236] Regarding the potential general scour hazards of bridge piers, attention should be paid to the current situation of the scour depth, whether the bridge opening is compressed, and whether the grading of the riverbed covering layer has changed. These relevant factors may all affect the scour resistance of the bridge piers. Therefore, detailed investigations and measurements are required to promptly detect and address potential scour hazards.

[0237] The general scour depth measurement method is also used in the embodiment. For details, please refer to Figure 5 , where s represents the clear span.

[0238] Based on Figure 5 Steps for measuring the general scour depth through information analysis: First, determine the position of the thalweg in the bridge opening and measure the elevation of the midpoint at this position. Then, calculate the difference between this elevation and the average elevation of the two measuring points for natural scour. The above difference is the general scour depth at the bridge pier.

[0239] The compression situation of the flow cross-section of the bridge opening needs to be investigated. The content of this investigation is the same as described above, mainly focusing on whether the bridge opening is compressed and the degree of compression.

[0240] Measurements are required to further understand the grading of the riverbed covering layer. This measurement process can be carried out with reference to the River Bed Load Sediment and Bed Sediment Measurement Regulations (SL 43-92) to further ensure the accuracy and reliability of the measurement results.

[0241] The local scour measurement method is also used in the embodiment. For details, please refer to Figure 6 .

[0242] To accurately measure the local scour depth of the bridge pier, the embodiment follows the Figure 6 shown method for measurement operations. That is, at least three measuring points are selected on the side of each bridge pier's upstream face close to the pier column, and their elevations are recorded. Subsequently, the elevation of the general scour measurement point is subtracted from the elevations of these measuring points, and the maximum value among the resulting elevation differences is recognized as the local scour depth of the bridge pier.

[0243] For non-cylindrical single-pier structures, attention should be paid to the measurement of the flow attack angle. The above measurement process involves determining the angle between the longitudinal axis of the bridge pier and the thalweg of the upstream river channel, and this angle is the flow attack angle.

[0244] For bridges whose bridge pier shapes have changed due to factors such as damage or reinforcement, in the embodiment, the pier shape coefficient and calculated width are determined with reference to the attached table information in the Highway Engineering Hydrological Survey and Design Specification (JTG C30-2015), which helps to accurately assess the scour risk of the bridge pier.

[0245] When measuring the gradation of the riverbed covering layer, the same method as that for investigating the potential hazards of general scour at bridge piers is adopted. This step aims to understand the composition and distribution of the riverbed materials in order to better predict and evaluate the scour situation of the bridge piers.

[0246] Obtain information on potential hazards of abutment foundation scour.

[0247] In the embodiment, the investigation and acquisition of information on potential hazards of abutment foundation scour involve multiple aspects, mainly including natural evolution scour of the riverbed, general scour, and local scour, which jointly determine the total scour depth of the abutment.

[0248] The factors that need to be concerned about for natural scour hazards of abutments are similar to those of bridge piers, including the current situation of scour depth, the existence of sand excavation pits, changes in the erosion base level at the river reach outlet, and the evolution of river bends. The specific implementation methods for investigating relevant hazards can refer to the investigation methods and data collection processes for natural scour hazards of bridge piers.

[0249] The investigation of potential hazards of general scour at abutments also has many similarities with that of bridge piers. Mainly, it focuses on the current situation of scour depth, whether the bridge opening is compressed, and whether the gradation of the riverbed covering layer has changed. The investigation methods and data acquisition methods for the above hazards can also refer to the potential hazards of general scour at bridge piers.

[0250] For potential hazards of local scour at abutments, more detailed investigation measures need to be taken. First, the method shown in Figure 6 can be used to measure the local scour depth of the abutment foundation, that is, to determine the elevation difference between the deepest point in the scour pit and the elevation of the riverbed outside the scour pit. Second, the attack angle of the water flow near the abutment needs to be measured. The investigation method for the above steps is the same as the measurement of the attack angle of the water flow in the investigation of potential hazards of general scour at bridge piers. For bridges whose abutment shape has changed due to damage or reinforcement, etc., the relevant tables in the Hydrological Survey and Design Code for Highway Engineering (JTG C30 - 2015) should be referred to determine its abutment shape coefficient. In addition, the flow-blocking width corresponding to the abutment and the embankment needs to be measured, and the change situation of the gradation of the riverbed covering layer needs to be evaluated. The above investigation steps and technical methods are similar to the corresponding steps of potential hazards of local scour at bridge piers.

[0251] Collect information on the investigation of potential hazards of bridgehead scouring.

[0252] For bridges that encroach on the river channel at the bridgehead in the embodiment, please refer to Figure 7 .

[0253] Figure 7The bridge shown has the problem of bridgehead encroaching the river channel, and it is necessary to investigate the hidden dangers of bridgehead scouring and collect information, which includes two aspects: on the one hand, assess the potential risk of flood scouring on the bridgehead approach, which involves analyzing whether the flood may directly impact and affect the approach roadbed of the bridgehead under a specific flow rate and velocity, thereby causing safety hazards. On the other hand, check whether the junction area between the approach and the upstream and downstream river banks is prone to form vertical axis vortices and cause scouring. The vertical axis vortex is the rotational movement generated by the water flow under specific terrain conditions. The above movement will erode the soil of the riverbank and the bridgehead, resulting in structural instability. Therefore, it is necessary to pay close attention to whether there are conditions for the formation of vortices in the junction area, and whether the vortex may cause scouring damage to the bridgehead. Based on this, the hidden dangers of bridgehead scouring can be more comprehensively assessed, and corresponding prevention and control measures can be taken to ensure the safety and stability of the bridge.

[0254] The potential risks of water flow directly impacting the bridge approach mainly include: due to the upstream river channel regulation structure or flood control facilities, especially the layout changes of groins and diversion dikes, as well as the natural swing of the main river channel, the mainstream flow direction of the flood may change. For the changes in the mainstream flow direction, please refer to Figure 8 When faced with such risks, the lowest vertical height at the toe of the approach waterfront surface should be measured.

[0255] Where the approach meets the upstream and downstream riverbanks, if there is a potential risk of whirlpool scouring, it is mainly because the necessary diversion dikes on the upstream or downstream sides are not built, or the original diversion dikes have been damaged. For a schematic diagram of whirlpool scouring, please refer to Figure 9 When faced with the above situation, it is necessary to measure the lowest vertical height where the approach road meets the river bank in order to conduct subsequent risk assessment and safety prediction.

[0256] In this embodiment, the steps for calculating the local scour depth of the river section at the bridge location based on the bridge pier collapse information set are as follows: For the local scour depth at the bridge pier, the formula in the Highway Engineering Hydrological Survey and Design Code (JTG C30-2015) can be referred to for calculation.

[0257] The local scour depth at the abutment can be calculated using the formula in the same specification.

[0258] For scour calculations under special circumstances, you can also refer to the relevant content of the specifications.

[0259] In addition, the total scour depth of bridge piers can also be obtained through corresponding calculation methods.

[0260] The total scouring depth in the embodiment satisfies the following relationship:

[0261]

[0262] in, represents the total scour depth of the bridge pier and abutment, represents the natural scour depth of the river reach at the bridge site, represents the general scour depth of the river reach at the bridge site, represents the local scour depth of the river reach at the bridge site;

[0263] The elevation of the lowest scour line satisfies the following relationship:

[0264]

[0265] Among them, represents the elevation of the lowest scour line, represents the elevation of the design water level, represents the local scour depth of the river reach at the bridge site;

[0266] The safe embedding elevation satisfies the following relationship:

[0267]

[0268] Among them, represents the lowest safe embedding elevation of the bridge pier and abutment foundation, represents the design elevation of the foundation base, represents the minimum embedding depth at the bottom.

[0269] Finally, based on the total scour depth, the elevation of the lowest scour line, and the safe embedding elevation, the risk scoring results of the bridge pier and abutment collapse and the scour at the bridgehead are obtained; at the same time, according to the risk scoring results of the bridge pier and abutment collapse and the scour at the bridgehead, the risk level of the bridge pier and abutment collapse and the scour at the bridgehead is analyzed.

[0270] In this embodiment, the risk assessment plays an important role in the prevention of bridge pier and abutment collapse events. When conducting a risk assessment of the bridge collapse under the current scour depth condition, first, it is necessary to accumulate the current depths of natural scour, general scour, and local scour experienced by the bridge pier and abutment to obtain the total scour depth, and calculate the elevation of the lowest scour line accordingly. Subsequently, the elevation is compared with the lowest safe embedding elevation. If the elevation of the lowest scour line is lower than the safety standard, it means that the current bridge is in an unsafe state and there is a high risk of collapse, and protective measures need to be taken immediately.

[0271] When conducting a risk assessment of the possible bridge pier and abutment collapse caused by excessive scour, it is necessary to calculate the natural scour depth, general scour depth, and local scour depth of the bridge pier and abutment based on the current river channel and bridge structure conditions, combined with different flood frequencies. Through the above process, the specific flood conditions leading to the bridge pier and abutment collapse can be determined.

[0272] In calculating the natural scour depth of the bridge site reach, the following principles are followed: If there are sand mining pits within half a kilometer upstream and downstream of the bridge axis, the general scour depth shall be based on the current maximum depth of the sand mining pits. If there are stepped non-rock riverbeds with sudden drops in riverbed elevation within 1 kilometer downstream of the bridge axis, the natural scour depth shall be the difference between the elevation of the current downstream natural scour measurement point and the elevation of the downstream riverbed drop point. For the natural scour depth caused by bend evolution, relevant formulas in the "Hydrological Survey and Design Code for Highway Engineering" (JTG C30-2015) can be referred to for calculation.

[0273] For the above information on the risk classification assessment of over-scouring of bridge piers and abutments that may cause pier and abutment collapses, please refer to Table 8

[0274] Table 8 Risk Classification Assessment Criteria Table for Over-Scouring of Bridge Piers and Abutments That May Cause Pier and Abutment Collapses

[0275]

[0276] In Table 8 represents the minimum safe embedment elevation of the pier and abutment foundations, represents the elevation of the lowest scour line.

[0277] Based on the analysis of the risk classification assessment information of pier and abutment collapses and the set of bridge pier and abutment collapse information, it can be seen that in the above classification assessment criteria, two key elevation ratios are used as the basis for assessing risks. According to the ratio situation, the risks are divided into four levels, and are respectively represented by the numerical values 1, 2, 3, and 4 of the assessment scale When the ratio of

[0278] When the ratio is between 0 and 0.3, the assessment scale is 1, indicating no risk, meaning that the embedment depth of the pier and abutment foundations is deep enough, and even if scour occurs, it will not pose a threat to the stability of the bridge.

[0279] When the ratio is between 0.3 and 0.6, the assessment scale is 2, indicating a very low risk. Although scour may have a certain impact on the bridge, overall, the stability of the bridge can still be guaranteed.

[0280] When the ratio is between 0.6 and 1.0, the assessment scale is 3, indicating a very high risk. At this time, it means that the scour has approached or reached the embedment depth of the pier and abutment foundations, and the stability of the bridge may be seriously threatened.

[0281] When When the ratio is greater than or equal to 1.0, the assessment scale is 4, indicating that an accident has occurred, which means that the scour has exceeded the foundation embedment depth of the bridge piers and abutments, and the bridge may have collapsed or is about to collapse.

[0282] Therefore, by comparing the ratio and referring to the risk classification assessment criteria in Table 8, the risk of bridge piers and abutments collapsing due to excessive scour can be accurately evaluated, which is crucial for the safety management and maintenance of bridges, and helps relevant personnel take timely measures to reduce risks and ensure the safe operation of bridges.

[0283] The risk score results of the above-mentioned bridge piers and abutments collapsing satisfy the following relationship:

[0284]

[0285] Among them, represents the risk score result of the bridge piers and abutments collapsing, represents the typical flood frequency, represents the risk assessment scale of the bridge piers and abutments collapsing.

[0286] According to the information in Table 8 and relevant regulations, the risk assessment scale of the piers and abutments collapsing can be determined.

[0287] The risk score result of the bridge piers and abutments collapsing is mainly determined based on the typical flood frequency and the relevant risk assessment scale. Among them, the risk score result of the bridge piers and abutments collapsing takes into account the possible flood frequencies, including low-frequency, medium-frequency, and high-frequency flood events. By comparing the flood frequency considered during the design of the bridge piers and abutments with the actual possible flood frequency, the stability and safety of the piers and abutments under extreme weather conditions can be evaluated.

[0288] The grade assessment of the bridge's resistance to the collapse risk of piers and abutments should be carried out in accordance with the relevant regulations in Table 9.

[0289] Table 9 Bridge Resistance to Pier and Abutment Collapse Risk Rating Table

[0290]

[0291] Similarly, for the risk assessment of bridgehead scouring events, the following risk assessment and analysis steps are required:

[0292] First, based on relevant information sets and methods, the water surface elevation at the bridge location under typical flood frequency can be calculated , and this step is the basis for evaluating the impact of floods on bridgehead scouring.

[0293] Next, in order to understand the susceptibility to scouring of the approach road and riverbank, the lowest elevation of the toe of the approach road's upstream slope or the lowest elevation at the junction of the approach road and the riverbank needs to be obtained through on-site measurement, and it is denoted as , the above elevation data is crucial for evaluating whether the flood will cause scouring risks to the bridgehead.

[0294] Finally, based on the obtained water surface elevation, the lowest elevation, and combined with the risk assessment criteria in Table 10, the risk assessment scale of the bridgehead scouring event can be determined, and then the risk level of the bridgehead scouring event under different flood frequencies and scouring conditions can be intuitively reflected.

[0295] For the risk classification information of the bridgehead scouring event in the embodiment, please refer to Table 10.

[0296] Table 10 Risk Classification Assessment Criteria Table for Bridgehead Scouring Events

[0297]

[0298] In Table 10 represents the lowest elevation of the toe of the approach embankment facing the water or the lowest elevation at the junction of the approach embankment and the riverbank, represents the water surface elevation at the bridge location when the typical flood frequency occurs.

[0299] In the embodiment, the risk of the bridgehead scouring event is classified and evaluated based on the information in Table 10. The above Table 10 provides clear risk classification assessment criteria for the bridgehead scouring event. This standard divides the risk level based on two key elevation ratios. According to the ratio, the risk is divided into two levels, and the assessment scales are respectively represented by the numerical values 1 and 4 of .

[0300] When the ratio is between 0 and 1.0, the assessment scale is 1, indicating that the bridgehead scouring event has not occurred, meaning that the elevation of the toe of the approach embankment facing the water or the junction of the approach embankment and the riverbank at the bridgehead is higher than or equal to the water surface elevation under the typical flood frequency, so the scouring event will not occur.

[0301] When the ratio is greater than or equal to 1.0, the assessment scale is 4, indicating that the bridgehead scouring event has occurred. Furthermore, it indicates that under the typical flood frequency, the elevation of the toe of the approach embankment facing the water or the junction of the approach embankment and the riverbank at the bridgehead is lower than the water surface elevation, so the scouring event will occur, which may cause damage to the bridge structure.

[0302] By comparing the value and referring to the risk classification assessment criteria in Table 10, it is possible to quickly and accurately judge whether the bridgehead will experience scouring events under the typical flood frequency. The above evaluation method is crucial for the safety management and maintenance of bridges because scouring events may lead to the exposure and weakening of bridge foundations, thereby threatening the overall stability of the bridge. Therefore, it is necessary to take timely necessary preventive and response measures, such as strengthening the toe of the approach embankment facing the water and improving riverbank protection, which is of great significance for reducing the risk of bridgehead scouring events.

[0303] In the embodiment, the risk score results of the above-mentioned bridgehead scouring events satisfy the following relationship:

[0304]

[0305] Among them, represents the risk score result of the bridgehead scouring event, represents the typical flood frequency, represents the risk assessment scale of the bridgehead scouring event.

[0306] The risk assessment scale of the bridgehead scouring event is determined according to the information in Table 10 and relevant regulations.

[0307] The above risk score calculation formula for the bridgehead scouring event comprehensively considers the typical flood frequency and the risk assessment scale of the bridgehead scouring event These two key factors mean that the risk score not only considers the possibility of flood occurrence, i.e., the flood frequency, but also considers the actual threat degree caused by the flood to the bridgehead, i.e., the risk assessment scale. The above calculation formula makes the risk score result more comprehensive and accurate.

[0308] Furthermore, in this embodiment, the analysis method for bridge pier collapse and bridgehead scouring events is only an optional condition of the present invention. In one or some other embodiments, the analysis method for bridge pier collapse and bridgehead scouring events can be optimized according to the actual situation of the information set and the influence degree of different risk score results. Different bridges face different risks and challenges. Optimizing the analysis method can more accurately identify potential risks and take corresponding measures, which helps to ensure the safety and reliability of the bridge.

[0309] S4. Comprehensively analyze the risk score results and risk level situations of bridge inundation, bridge superstructure offset, bridge superstructure overturning, bridge pier collapse and bridgehead scouring events to achieve hidden danger investigation and flood damage risk assessment before the flood season for small and medium-span bridges. The specific steps and related content are as follows:

[0310] In the embodiment, first, for bridge inundation, bridge superstructure offset, bridge superstructure overturning, bridge pier collapse and bridgehead scouring events, the corresponding risk assessment models are respectively applied for calculation.

[0311] Secondly, determine the risk score. According to the model calculation results, determine the risk scores of different events. The above scores respectively reflect the possibility of the event occurrence and the severity of potential consequences.

[0312] Immediately afterwards, conduct risk level division and formulate division criteria. According to the distribution of the risk scores, a reasonable risk level division criterion is formulated. In the embodiment, the above criterion fully considers the severity and occurrence frequency of the event.

[0313] Finally, the risk levels need to be classified. According to the classification criteria, the risk scores of each event are converted into corresponding risk levels, including low risk, medium risk, high risk, or extreme risk, etc.

[0314] After that, it is necessary to comprehensively collect the results of different risk scores and information on risk level analysis for comprehensive analysis and evaluation. This application adopts a multi-factor comprehensive analysis mechanism, comprehensively considering the risk scores and risk levels of bridge inundation, offset of the superstructure of the bridge, overturning of the superstructure of the bridge, collapse of bridge piers and abutments, and scouring at the bridgehead, as well as their mutual influences and correlations. At the same time, based on the results of the comprehensive analysis, the overall risk of the bridge is evaluated, including the weight allocation, priority ranking of different risk events, and the identification and assessment of potential risks.

[0315] Finally, coping strategies are formulated. According to the results of the overall risk assessment, potential hidden trouble points that may exist before the flood season of the bridge are determined, such as structural defects, poor drainage, insufficient protective facilities, etc.; specific coping measures are formulated for the identified hidden trouble points, such as strengthening the structure, improving the drainage system, adding protective facilities, etc.; implementation and monitoring need to be carried out according to the formulated measures, and the state of the bridge is continuously monitored to ensure the effectiveness of the measures.

[0316] In addition, continuous improvement and feedback are also required. Conduct an actual effectiveness evaluation. After the flood season ends, evaluate the effectiveness of the implemented measures, including but not limited to the elimination of hidden troubles, the improvement of the safety performance of the bridge, etc. It is also necessary to summarize experience, summarize the experience and lessons of this risk assessment and hidden trouble investigation, and provide reference for future bridge safety management. In terms of continuous optimization, the risk assessment model and coping strategies can be continuously optimized according to the evaluation results and summarized experience to improve the scientificity and effectiveness of the method for investigating hidden troubles before the flood season and evaluating the risk of water damage for small and medium-span bridges.

[0317] Through the above steps, the comprehensive analysis and evaluation process of the risk scores and risk levels of bridge inundation, offset of the superstructure of the bridge, overturning of the superstructure of the bridge, collapse of bridge piers and abutments, and scouring at the bridgehead can be more comprehensively understood, thus providing more scientific and comprehensive support for the investigation of hidden troubles before the flood season and the evaluation of the risk of water damage for small and medium-span bridges.

[0318] Please refer to Figure 10, in an optional embodiment, the present invention further provides a hidden danger investigation before flood and flood damage risk assessment system for medium and small span bridges. The above system includes a processor, an input device, an output device and a memory, and the processor, the input device, the output device and the memory are interconnected. Among them, the memory is used to store a computer program, and the computer program includes program instructions. The processor is configured to call the above program instructions to execute the specific steps of the method for hidden danger investigation before flood and flood damage risk assessment of medium and small span bridges provided by the present invention and related embodiments. The hidden danger investigation before flood and flood damage risk assessment system of the medium and small span bridges of the present invention has a complete structure, objectivity and stability.

[0319] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; 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 recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the 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 method for pre-flood hidden danger inspection and water damage risk assessment for small and medium-span bridges, characterized by: The steps include: Acquire bridge flooding event information, determine the flood flow at the bridge deck elevation based on the bridge flooding event information, and obtain a risk scoring result and risk level of bridge flooding according to the flood flow and the bridge flooding event information; The risk scoring result of bridge flooding satisfies the following relationship: , represents the risk score result of bridge flooding, represents the typical flood frequency, represents the risk assessment scale of bridge flooding; when When the ratio is greater than or equal to 0.6, is 1; when When the ratio is between 0.2 and 0.6, is 2; when When the ratio is between 0 and 0.2, is 3; when When the ratio is less than or equal to 0, is 4; represents the bridge deck elevation, represents the water surface elevation at the bridge location, Indicates bridge height; Collecting bridge structure instability information, establishing a bridge structure parameter analysis model based on the bridge structure instability information and obtaining parameter analysis results, and obtaining risk scoring results and risk level conditions of bridge superstructure displacement and bridge superstructure overturning according to the parameter analysis results; The risk scoring result of the bridge superstructure deviation satisfies the following relationship: ,in, represents the risk score result of the bridge superstructure deflection, represents the typical flood frequency, Represents the risk assessment scale of bridge superstructure deflection; When the ratio is between 0 and 0.3, is 1; when When the ratio is between 0.3 and 0.6, is 2; when When the ratio is between 0.6 and 1.0, is 3; when When the ratio is greater than or equal to 1.0, is 4; among them, represents the horizontal force that will act on the support, Indicates the frictional resistance acting on the support; The risk scoring result of the overturning of the bridge superstructure satisfies the following relationship: ,in, represents the risk score result of bridge superstructure overturning, represents the typical flood frequency, Indicates the risk assessment scale of overturning of bridge superstructure; When the ratio is between 0 and 0.3, is 1; when When the ratio is between 0.3 and 0.6, is 2; when When the ratio is between 0.6 and 1.0, is 3; when When the ratio is greater than or equal to 1.0, is 4; among them, represents the structural stability moment, represents the structural overturning moment; Acquire a bridge pier collapse information set, and obtain risk scoring results and risk level conditions of bridge pier collapse and bridge head scouring events based on the bridge pier collapse information set; The risk scoring result of the bridge pier collapse satisfies the following relationship: ,in, represents the risk score result of bridge pier collapse, represents the typical flood frequency, Indicates the risk assessment scale of bridge pier collapse; When the ratio is between 0 and 0.3, is 1; when When the ratio is between 0.3 and 0.6, is 2; when When the ratio is between 0.6 and 1.0, is 3; when When the ratio is greater than or equal to 1.0, is 4; Indicates the minimum safe embedding elevation of bridge piers and abutment foundations. Indicates the lowest scour line elevation; The risk scoring result of the bridgehead washing event satisfies the following relationship: ,in, It represents the risk score result of the bridgehead washing event. represents the typical flood frequency, represents the risk assessment scale of the bridgehead scouring event; When the ratio is between 0 and 1.0, is 1; when When the ratio is greater than or equal to 1.0, is 4; among them, It indicates the lowest elevation of the toe of the approach facing the water or the lowest elevation of the junction between the approach and the river bank. represents the water surface elevation at the bridge location under typical flood frequency; A comprehensive analysis is conducted on the risk scoring results and risk levels of bridge flooding, bridge superstructure displacement, bridge superstructure overturning, bridge pier collapse and bridge head scouring incidents, in order to achieve hidden danger inspection and water damage risk assessment for small and medium spans before the flood season.

2. The method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges according to claim 1 is characterized in that: The obtaining of bridge flooding event information and determining the flood flow at the bridge deck elevation based on the bridge flooding event information comprises: Obtaining bridge flooding event information, wherein the bridge flooding event information includes information on changes in river channel boundaries at the bridge location, river section compression information, and curve superelevation inspection information; Based on the river channel boundary change information of the bridge section, the bridge opening flow section compression information and the curve superelevation inspection information, the flood flow at the bridge deck elevation is obtained; The flood flow satisfies the following relationship: ， in, represents the typical flood flow, represents the Manning roughness coefficient, represents the average width of the river channel, It represents the average water depth of the section. Indicates the riverbed gradient of the river section; Water surface elevation at the bridge location Satisfies the following relationship: ， in, represents the water surface elevation at the bridge location, Indicates flood level. Indicates the height of waterlogging. Indicates the superelevation value of the curve.

3. The method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges according to claim 1 is characterized in that: The collecting of the bridge structure instability information, establishing a bridge structure parameter analysis model based on the bridge structure instability information and obtaining the parameter analysis results comprises: Constructing a bridge structure parameter analysis model based on the bridge structure instability information, the bridge structure parameter analysis model including a water flow average velocity calculation function, a water flow pressure calculation function, a buoyancy calculation function, a lifting force calculation function and a floating object impact force calculation function; The water flow average velocity calculation function satisfies the following relationship: ， in, It represents the average flow velocity of water on the water-facing surface of the beam. represents the transverse part coefficient of the flow velocity, represents the first vertical distribution coefficient, Indicates the water depth of the channel section. represents the beam section height, represents the second vertical distribution coefficient, represents the third vertical distribution coefficient, It represents the average flow velocity of any measuring line in the cross section. It represents the average flow velocity of the vertical line in the cross section; The flow water pressure calculation function satisfies the following relationship: ， in, Surface water pressure, represents the water resistance coefficient of the bridge, It represents the projected area of ​​the bridge perpendicular to the water flow direction. represents the water flow density, It indicates the average flow velocity of water on the water-facing surface of the beam; The buoyancy calculation function satisfies the following relationship: ， in, represents buoyancy, represents the water flow density, represents the acceleration due to gravity, It represents the volume of water displaced by the bridge; The lifting force calculation function satisfies the following relationship: ， in, Indicates the lifting force, Indicates the width of the bridge bottom. represents the length of the beam perpendicular to the direction of flood action, represents the water flow density, represents the acceleration due to gravity, Indicates the height of water in front of the bridge; The floating object impact force calculation function satisfies the following relationship: ， in, Indicates the impact force of floating objects, represents the gravity of floating objects, Indicates the water flow velocity, represents the acceleration due to gravity, Indicates the impact time.

4. The method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges according to claim 1 is characterized in that: The risk scoring results and risk level of bridge superstructure deviation and bridge superstructure overturning obtained according to the parameter analysis results include: Analyze the horizontal force and friction acting on the support based on the parameter analysis results; The horizontal force satisfies the following relationship: ， in, represents the horizontal force that will act on the support, Indicates the water pressure. Indicates the impact force of floating objects; The frictional resistance satisfies the following relationship: ， in, is the friction force acting on the support, represents the friction coefficient, represents the number of forces perpendicular to the support, It represents the vertical reaction of the support under the total load effect.

5. The method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges according to claim 1 is characterized in that: The acquisition of the bridge pier collapse information set and the acquisition of the risk scoring results and risk level of the bridge pier collapse and bridge head washing events according to the bridge pier collapse information set include: Collect information on hidden dangers of scouring at the base of bridge piers, hidden dangers of scouring at the abutment foundation, and hidden dangers of scouring at the bridge head to obtain a collection of information on bridge pier and abutment collapse; Analyzing the total scouring depth, the lowest scouring line elevation and the safe burial elevation of the bridge pier based on the bridge pier collapse information set; The total scouring depth satisfies the following relationship: ， in, represents the total scour depth of the bridge pier, Indicates the natural scouring depth of the river section at the bridge location. Indicates the general scouring depth of the river section at the bridge location. Indicates the local scour depth of the river section at the bridge location; The elevation of the lowest scour line satisfies the following relationship: ， in, Indicates the lowest scour line elevation, represents the design water level elevation, Indicates the total scour depth of the bridge pier; The safe embedding elevation satisfies the following relationship: ， in, Indicates the minimum safe embedding elevation of bridge piers and abutment foundations. Indicates the base design elevation, Indicates the minimum burial depth.

6. Pre-flood hidden danger inspection and water damage risk assessment system for small and medium span bridges, characterized by: The system includes a processor, an input device, an output device and a memory, wherein the processor, the input device, the output device and the memory are interconnected, 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 to execute the method for pre-flood hidden danger inspection and water damage risk assessment of small and medium-span bridges as described in any one of claims 1-5.

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