Indirect identification method for scouring depth of deepwater bridge foundation

Abstract

The invention discloses an indirect identification method for the scouring depth of a deepwater bridge foundation, and the method comprises the steps: obtaining a high-speed train-rail-sea-crossing bridge dynamic model and scouring simulation data, and solving the high-speed train-rail-sea-crossing bridge dynamic model according to the scouring simulation data, obtaining the dynamic response of each subsystem of the train, the track and the bridge; performing parameter sensitivity analysis on the dynamic response of each subsystem based on the scouring depth change, and screening characteristic indexes meeting preset conditions; fitting the characteristic indexes with the scouring depth to obtain a fitting function relational expression; and obtaining a real-time characteristic index value, and obtaining the basic scouring depth based on the fitting function relation and the real-time characteristic index value. According to the method, the foundation scour depth of the high-speed railway train-rail-sea-crossing bridge system can be well identified in the operation stage, and the method has good engineering application potential and practical value.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge health monitoring, and in particular relates to an indirect identification method for the scouring depth of a deep-water bridge foundation. Background Art

[0002] With the rapid development of my country's high-speed railway network, the number of cross-sea bridges is growing. Compared with bridges with foundations on land or in ordinary waters, the foundations of cross-sea bridges face more complex hydrological environments. The foundations of cross-sea bridges are continuously scoured under the combined effects of strong winds, huge waves, and rapids. Since scour occurs below the water surface, there is usually no sign of scour damage to the foundation of cross-sea bridges, which seriously endangers the safety performance of the bridge structure. As an important transportation hub, high-speed railway cross-sea bridges have a high proportion of time periods when high-speed trains run on them. The damage of high-speed railway cross-sea bridges due to foundation scour will bring catastrophic consequences. The scour depth can reflect the degree of scour on the bridge foundation. The prediction and monitoring of the scour depth of the foundation of high-speed railway cross-sea bridges has become the research focus of many scholars. In recent years, many new underwater monitoring equipment have emerged, such as sonar, TDR technology, multi-beam detection system, and underwater robot. However, there are many defects in using the above equipment to monitor the foundation scour depth, such as being restricted by terrain factors, high cost of single monitoring, inability to achieve long-term dynamic underwater monitoring, and difficulty in subsequent maintenance. In this context, it is particularly important to explore more efficient and economical bridge foundation scour identification methods, especially for the complex coupling system of high-speed train-track-cross-sea bridge. Most of the existing dynamic identification methods focus on the impact of scour on the characteristics of the bridge structure itself, ignoring its impact on the interaction between trains, tracks and bridges during the operation phase. Therefore, it is necessary to further study the foundation scour identification method of the high-speed train-track-bridge coupling system to achieve accurate, efficient and economical identification of the scour depth of the high-speed railway cross-sea bridge foundation, and provide technical support for the safe operation of high-speed railways. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes an indirect identification method of the scouring depth of a deep-water bridge foundation to solve the problems existing in the above prior art.

[0004] To achieve the above object, the present invention provides an indirect identification method for the scouring depth of a deep-water bridge foundation, comprising:

[0005] Obtaining a high-speed train-track-sea-crossing bridge dynamics model and scour simulation data, solving the high-speed train-track-sea-crossing bridge dynamics model according to the scour simulation data, and obtaining dynamic responses of each subsystem of the train, track, and bridge;

[0006] Conduct parameter sensitivity analysis on the dynamic response of each subsystem based on the change of scour depth, and select characteristic indicators that meet the preset conditions;

[0007] Fitting the characteristic index with the scouring depth to obtain a fitting function relationship;

[0008] A real-time characteristic index value is obtained, and a foundation scouring depth is obtained based on the fitting function relationship and the real-time characteristic index value.

[0009] Optionally, the process of obtaining a high-speed train-track-sea bridge dynamic model includes:

[0010] A train model, a track model and a bridge model are constructed respectively, and a high-speed train-track-sea-crossing bridge dynamic model is constructed based on the train model, the track model, the bridge model and the interaction between the train and the bridge, wherein a mass-spring-damper system is established as the train model, the track model adopts a three-layer elastic point support beam model to simulate the track structure, and the bridge model is constructed using the finite element method.

[0011] Optionally, the high-speed train-track-sea-crossing bridge dynamic model is expressed as:

[0012]

[0013] The subscripts v, t, and b represent the train, track, and bridge subsystems, respectively; M, C, and K represent the mass, damping, and stiffness matrices, respectively; u, u represents the displacement, velocity and acceleration column vectors respectively; P tv and P vt is the wheel-rail interaction force, P bt and P tb is the bridge-rail interaction force; P ft and P fb are the forces acting on the track and bridge foundation respectively.

[0014] Optionally, the process of obtaining flushing simulation data includes:

[0015] When foundation scour occurs, the pile side spring at the soil layer where the scour occurs is removed, and the pile side soil spring stiffness at the remaining locations is calculated based on the elevation after scour to obtain the scour simulation data.

[0016] Optionally, the process of obtaining the dynamic response of each subsystem of the train, track, and bridge includes: based on the scour simulation data, using the soil spring stiffness calculation method to obtain the force of the remaining soil around the foundation after foundation scour on the foundation of the bridge structure, substituting the force into the high-speed train-track-cross-sea bridge dynamic model, and using the explicit-implicit mixed integration method to solve, so as to obtain the dynamic response of each subsystem of the train, track, and bridge.

[0017] Optionally, the dynamic response includes multiple indicators such as mid-span train derailment coefficient, wheel weight reduction rate, wheel axle lateral force, mid-span rail displacement, mid-span displacement of the bridge and acceleration.

[0018] Optionally, a parameter sensitivity analysis is performed on the dynamic response of each subsystem based on the change in scouring depth, and the process of screening characteristic indicators that meet the preset conditions includes:

[0019] The relationship between the scouring depth and the dynamic response of each subsystem under scouring is constructed, the change rate of each dynamic response index at different scouring depths is calculated, and the index whose change rate meets the preset conditions is selected as the characteristic index.

[0020] Optionally, the process of obtaining the fitting function relationship includes: fitting all response data of the characteristic index at different scouring depths with the scouring depth to obtain the fitting function relationship.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] The present invention proposes an indirect identification method for the scour depth of deep-water bridge foundation, clarifies the correlation between the foundation scour depth and the dynamic response of the high-speed train-track-sea-crossing bridge system, finds the relationship between the foundation scour depth and the dynamic response characteristics of the high-speed train-track-sea-crossing bridge system, and achieves the purpose of determining the foundation scour depth of the high-speed train-track-sea-crossing bridge system by inputting the dynamic response characteristic value. The method avoids the underwater installation of monitoring equipment, is simple to implement, has the advantages of high result accuracy, and a simple and easy process. It can better realize the identification of the foundation scour depth of the high-speed railway train-track-sea-crossing bridge system in the operation stage, has good engineering application potential and practical value, and provides a scientific basis and technical support for solving the foundation scour problem faced by the train-track-bridge coupling system in the engineering field. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0024] Figure 1 A step diagram of an indirect identification method for the scouring depth of a deep-water bridge foundation according to an embodiment of the present invention;

[0025] Figure 2 A model diagram of a high-speed train-track-cross-sea bridge coupling system according to an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of a foundation scour depth simulation method according to an embodiment of the present invention;

[0027] Figure 4 1 is a diagram showing the train response changing with the scouring depth according to an embodiment of the present invention, (a) is a diagram showing the derailment coefficient and wheel load reduction rate changing with the scouring depth, and (b) is a diagram showing the wheel axle lateral force changing with the scouring depth;

[0028] Figure 5 This is a graph showing the variation of rail displacement with scouring depth according to an embodiment of the present invention;

[0029] Figure 6 The mid-span displacement and mid-span acceleration of the bridge according to the embodiment of the present invention vary with the scouring depth, (a) is a diagram showing the mid-span displacement varying with the scouring depth, (b) is a diagram showing the mid-span acceleration varying with the scouring depth;

[0030] Figure 7 This is a fitting curve diagram of the lateral vibration displacement and scour depth of the bridge according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0032] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0033] Embodiment 1

[0034] like Figure 1-7 As shown, this embodiment provides an indirect identification method for the scouring depth of a deep-water bridge foundation, comprising:

[0035] Obtain a high-speed train-track-cross-sea bridge dynamic model, perform scour simulation based on the high-speed train-track-cross-sea bridge dynamic model, and obtain scour simulation data; solve the high-speed train-track-cross-sea bridge dynamic model according to the scour simulation data, and obtain the dynamic response of each subsystem of the train, track, and bridge; perform parameter sensitivity analysis on the dynamic response of each subsystem based on the change of scour depth, and screen characteristic indicators that meet the preset conditions; fit the characteristic indicators with the scour depth to obtain a fitting function relationship; obtain real-time characteristic indicator values, and obtain the basic scour depth based on the fitting function relationship and the real-time characteristic indicator values.

[0036] The dynamic model of the high-speed train-track-sea-crossing bridge system is constructed by establishing the high-speed railway train-track-sea-crossing bridge coupled vibration equation based on the train, track and bridge models, and the interaction between the train and the bridge. The dynamic response of the train subsystem, track subsystem and bridge subsystem can be obtained by solving the high-speed railway train-track-sea-crossing bridge coupled vibration equation.

[0037] In the process of establishing the coupled vibration equation of high-speed railway train-track-cross-sea bridge according to the train, track and bridge models and the vehicle-bridge interaction, the train model includes several rigid bodies, dampers, springs, suspension systems and axles, and the train model is simulated as a mass-spring-damper system. The track model uses a three-layer elastic point support beam model to simulate the track structure. The rails are simplified as finite-length Eular beams on multiple elastic point supports; the sleepers are simplified as rigid bodies; the roadbed is discretized into mass blocks according to the sleeper spacing, and only the vertical degree of freedom is considered. The rails and sleepers, and the sleepers and roadbeds are connected by linear springs and damping elements, and adjacent roadbeds are connected by shear stiffness and damping. The bridge model is established by the finite element method. The main beam, bridge tower, bridge pier and foundation are simulated by beam units. The auxiliary structure and secondary loads are simulated by applying mass units. The vehicle-bridge interaction includes the force between the wheel and the rail and the force between the bridge and the rail.

[0038] The high-speed railway train-track-cross-sea bridge-foundation coupled vibration equation established based on the train, track and bridge models and the vehicle-bridge interaction is:

[0039]

[0040] Where: subscripts v, t, b represent the train, track, and bridge subsystems, respectively; M, C, K represent the mass, damping, and stiffness matrices, respectively; u, u represents the displacement, velocity and acceleration column vectors respectively; P tv and P vt is the wheel-rail interaction force. The normal contact force is solved by Hertz nonlinear contact theory, and the creep force is solved by Kalker linear theory. bt and P tb is the bridge-rail interaction force, which can be solved according to the geometric relationship between the track plate and the main beam and the static equilibrium condition; P ft and P fb It is the force of the foundation on the track and bridge foundation. The train-track-bridge coupled vibration model is a time-varying nonlinear system. It is solved by numerical methods. The explicit-implicit mixed integration method is used to solve the train-track-bridge coupled vibration equation, and the dynamic response of the train subsystem, track subsystem, and bridge subsystem can be obtained.

[0041] The method for simulating the foundation scouring effect of the high-speed railway train-track-sea-crossing bridge system and calculating the response of the high-speed railway train-track-sea-crossing bridge system under different scouring depths is to simulate the scouring effect by changing the stiffness of the soil spring unit of the soil around the bridge foundation, and to obtain the dynamic responses of the train subsystem, the track subsystem and the bridge subsystem by solving the vibration equation of the high-speed railway train-track-sea-crossing bridge coupling system.

[0042] The method of simulating scouring by changing the stiffness of the soil spring unit of the soil around the bridge foundation is to simulate foundation scouring by removing the pile side spring at the soil layer where scouring occurs and recalculating the stiffness of the pile side soil spring at the remaining positions according to the new elevation after scouring. The force of the remaining soil around the foundation on the bridge structure foundation after foundation scouring can be obtained according to the soil spring stiffness calculation method. The force is substituted into the high-speed train-track-cross-sea bridge coupled vibration equation and solved to obtain the dynamic response of the train subsystem, track subsystem and bridge subsystem under scouring.

[0043] The soil spring stiffness is calculated as follows:

[0044] According to the elastic resistance of soil in the Code for Design of Railway Bridge and Culvert Foundations (TB 10093-2017), the following calculation is carried out:

[0045] When the foundation is buried deep hour,

[0046] h m =2(d+1) (2)

[0047] Where h m It is the calculated embedment depth of the pile below the ground or local scour line, d is the average diameter of the member (m), and for reinforced concrete bored piles, d is the hole diameter.

[0048] When the foundation is buried deep hour,

[0049] h m =h (3)

[0050] Where h m is the calculated buried depth of the pile below the ground or local scour line, and h is the foundation buried depth.

[0051]

[0052] In the formula, α is the basic deformation coefficient, b0 is the basic calculation width, which can be taken according to the specifications, E is the elastic modulus of the basic material, and I is the basic average section inertia moment. For reinforced concrete components, EI=0.9E is usually used. h I, here E his the compressive elastic modulus of concrete, I is the moment of inertia of the entire section, and m is the proportional coefficient of the horizontal foundation coefficient changing with depth, which can be taken according to the specifications.

[0053] When the foundation side consists of several different soil layers, each soil layer needs to be i Convert the value of m within h to the entire depth.

[0054] When h m When there are two different soil layers at depth:

[0055]

[0056] When h m When there are three soil layers at depth:

[0057]

[0058] In formulas (5) to (6), m1, m2, and m3 represent the m value corresponding to the first soil layer, the m value corresponding to the second soil layer, and the m value corresponding to the third soil layer, respectively; h1, h2, and h3 represent the height corresponding to the first soil layer, the height corresponding to the second soil layer, and the height corresponding to the third soil layer, respectively.

[0059] The stiffness of soil spring K s :

[0060]

[0061] Where: a is the calculated thickness of the soil layer; b0 is the calculated width of the foundation side; m is the proportional coefficient of the foundation coefficient; z is the depth of the soil layer at the calculation point. The spring stiffness of the soil around the pile side can be obtained by formula (7).

[0062] The parameter sensitivity analysis of the dynamic response of the train subsystem, track subsystem, and bridge subsystem is to calculate the impact of the scouring depth on the dynamic response indicators of each subsystem and to find the dynamic response indicators that have a greater impact on the scouring depth.

[0063] The dynamic responses of the train subsystem, track subsystem and bridge subsystem include mid-span train derailment coefficient, wheel load reduction rate, wheel axle lateral force, mid-span rail displacement, bridge mid-span displacement and acceleration index, and parameter sensitivity analysis is performed on the above indexes.

[0064] Parameter sensitivity analysis is to set the scour depth as a variable, fix the parameters such as train, track, bridge, etc., assume that the scour depth increases uniformly at the set interval, and calculate the changes in the mid-span train derailment coefficient, wheel weight reduction rate, wheel axle lateral force, mid-span rail displacement, bridge mid-span displacement, and acceleration response as the scour depth changes continuously, so as to find the dynamic response indicators that are more sensitive to the scour depth.

[0065] Parameter sensitivity analysis can be specifically expressed as the following steps:

[0066] (1) The relationship between the scouring depth and the dynamic response of each subsystem under scouring is constructed as shown in the following formula:

[0067] f(Y1,Y2,Y i ……)=h (8)

[0068] Where h represents the scouring depth, Y1, Y2, Y i It represents the dynamic response index of the train subsystem, track subsystem and bridge subsystem at various scour depths.

[0069] (2) Further, it is necessary to determine Y i The response index that is more sensitive to the scouring depth can be obtained by the following formula:

[0070]

[0071] Where σ represents the mid-span train derailment coefficient, wheel load reduction rate, wheel axle lateral force, mid-span rail displacement, bridge mid-span displacement, and the rate of change of acceleration at different scour depths, and y i It represents the response values ​​of mid-span derailment coefficient, wheel load reduction rate, wheel axle lateral force, mid-span rail displacement, bridge mid-span displacement, and acceleration at different scour depths.

[0072] (3) Compare the change rates of the mid-span train derailment coefficient, wheel load reduction rate, wheel axle lateral force, mid-span rail displacement, and bridge mid-span displacement under different scour depths, and find the corresponding index with a larger σ value. The top three indexes with the highest σ value can be taken and defined as the characteristic index y of the high-speed train-track-cross-sea bridge coupling system to the change of scour depth.

[0073] The fitting of the characteristic index with the scouring depth to obtain the characteristic index and scouring depth relationship curve is to fit all the response data of the characteristic index y at different scouring depths with the scouring depth, and the functional relationship between the characteristic index y and the scouring depth h of the high-speed train-track-cross-sea bridge coupling system to foundation scouring can be obtained.

[0074] The fitting process in the above scheme can be expressed as follows: assuming that the scour depth is h and the characteristic index is y, the optimal parameters are obtained by calculation so that the relationship between h and y is as close as possible to the actual data, thereby obtaining the functional relationship between the scour depth and the characteristic index. The basic scour depth can be obtained by inputting the characteristic index value.

[0075] According to the functional relationship between the characteristic index y and the scouring depth h obtained in the above scheme, the scouring depth of the deep-water bridge foundation can be identified.

[0076] Taking a certain extra-large bridge in Fujian Province as an example, its main bridge adopts a (143.75+288+143.75)m cable-stayed continuous rigid frame with a total length of 575.5m. From left to right, the bridge has 1# pier, 2# pier, 3# pier, and 4# pier. The rock and soil layers in the bridge site are mainly classified according to their genesis: Changle Formation marine deposits (Q4m) medium sand and pebble soil, underlying the third section of the Nanyuan Formation of the Upper Jurassic System (J3n) and tuff. The rock and soil layers below the local scour line of Pier 1# are fully weathered tuff, strongly weathered tuff, and weakly weathered tuff; the rock and soil layers below the local scour line of Pier 2# are weakly weathered tuff; the rock and soil layers below the local scour line of Pier 3# are weakly weathered tuff; the rock and soil layers below the local scour line of Pier 4# are fully weathered tuff, strongly weathered tuff, and weakly weathered tuff, but Pier 4# is not in the basin and there is no scouring effect, so the scouring effect of Pier 4# is not calculated. The pile length of Pier 1# is 50m, the pile length of Pier 2# is 35m, and the pile length of Pier 3# is 58m. During the service of the bridge, it is inevitable to be subjected to long-term cyclic loads such as wind, waves, and machinery, and the changes in the structural dynamic characteristics after the foundation scouring cannot be ignored.

[0077] Using the deep water bridge foundation scour depth identification method proposed in this embodiment, Figure 1 As shown in the figure, the dynamic characteristics of deep-water bridges under foundation scouring are studied, and then the structural safety after foundation scouring is evaluated and predicted. The specific steps include the following:

[0078] Step 1: Construct a dynamic model of the high-speed train-track-cross-sea bridge system. Figure 2 The figure is a diagram of the dynamic model of the high-speed train-track-cross-sea bridge system. It can be seen from the figure that the dynamic model of the high-speed train-track-cross-sea bridge system consists of a train model, a track model, and a bridge model. According to the train, track and bridge models, and the interaction between the train and the bridge, the high-speed railway train-track-cross-sea bridge coupled vibration equation is established. Solving the high-speed railway train-track-cross-sea bridge coupled vibration equation can obtain the dynamic response of the train subsystem, track subsystem, and bridge subsystem.

[0079] In the step of establishing the high-speed railway train-track-cross-sea bridge coupled vibration equation according to the train, track and bridge models, and the vehicle-bridge interaction, the train model includes a number of rigid bodies, dampers, springs, suspension systems and axles, and the train model is simulated as a mass-spring-damping system. The track model uses a three-layer elastic point support beam model to simulate the track structure, and the rails are simplified as finite-length Eular beams on multiple elastic point supports; the sleepers are simplified as rigid bodies; the roadbed is discretized into mass blocks according to the sleeper spacing, and only the vertical degree of freedom is considered. The rails and sleepers, and the sleepers and roadbeds are connected by linear springs and damping elements, and adjacent roadbeds are connected by shear stiffness and damping. The bridge model is established by the finite element method, and the main beams, bridge towers, piers and foundations are simulated by three-dimensional beam units, and the auxiliary structures and secondary loads are simulated by applying mass units. The vehicle-bridge interaction includes the force between the wheel and the rail and the force between the bridge and the rail. The vibration equation of the high-speed train-track-cross-sea bridge coupled system is established according to the train, track and bridge models, and the vehicle-bridge interaction:

[0080]

[0081] Where: subscripts v, t, b represent the train, track, and bridge subsystems, respectively; M, C, K represent the mass, damping, and stiffness matrices, respectively; u, u represents the displacement, velocity and acceleration column vectors respectively; P tv and P vt is the wheel-rail interaction force. The normal contact force is solved by Hertz nonlinear contact theory, and the creep force is solved by Kalker linear theory. bt and P tb is the bridge-rail interaction force, which can be solved according to the geometric relationship between the track plate and the main beam and the static equilibrium condition; P ft and P fb is the force of the foundation on the track and bridge foundation. By solving the train-track-bridge-foundation system vibration equation numerically and using the explicit-implicit hybrid integration method, the dynamic response of the train subsystem, track subsystem, and bridge subsystem can be obtained. Then proceed to step 2.

[0082] Step 2: simulate the scouring effect of the high-speed railway train-track-cross-sea bridge system and calculate the dynamic response of the high-speed railway train-track-cross-sea bridge system under different scouring depths. Figure 3 As shown in the figure, when foundation scour occurs, the pile side spring at the soil layer where the scour occurs is removed, and the pile side soil spring stiffness at the remaining locations is recalculated according to the new elevation after scour to simulate foundation scour.

[0083] The soil spring stiffness is calculated as follows:

[0084] According to formula (2) to formula (7) and the Code for Design of Foundations and Subgrades for Railway Bridges and Culverts (TB 10093-2017), the pile foundation parameters of each pier can be obtained, as shown in Table 1:

[0085] Table 1

[0086] 1# d <![CDATA[h0]]> <![CDATA[L0]]> n C <![CDATA[k0]]> <![CDATA[K f ]]> k Longitudinal bridge direction 2 9 2.2 3 0.5 1.5 0.9 0.703703704 Cross Bridge 2 9 2.5 4 0.45 1.5 0.9 0.70462963 2# d <![CDATA[h0]]> <![CDATA[L0]]> n C <![CDATA[k0]]> <![CDATA[K f ]]> k Longitudinal bridge direction 2.8 11.4 3.2 4 0.45 1.36 0.9 0.707309942 Cross Bridge 2.8 11.4 3.2 4 0.45 1.36 0.9 0.707309942 3# d <![CDATA[h0]]> <![CDATA[L0]]> n C <![CDATA[k0]]> <![CDATA[K f ]]> k Longitudinal bridge direction 2.8 11.4 3.2 4 0.45 1.36 0.9 0.707309942 Cross Bridge 2.8 11.4 3.2 4 0.45 1.36 0.9 0.707309942

[0087] In the table, d is the pile diameter (m), h0 is the calculated depth of the component buried below the local scour line (m), C is a coefficient that varies with the number of components, L0 is the net distance between the two piles, k0 is the force conversion coefficient, and K f is the shape conversion factor, and k is the mutual influence coefficient.

[0088] To calculate the soil spring stiffness, it is also necessary to calculate the longitudinal and transverse calculated width b0 of each pier pile foundation. According to the specification "Code for Design of Railway Bridge and Culvert Foundations" (TB10093-2017), the calculated width b0 of each pier pile foundation is shown in Table 2.

[0089] Table 2

[0090] <![CDATA[b0]]> 1# 2# 3# Longitudinal bridge direction 1.9 2.419 2.419 Cross Bridge 1.905 2.419 2.419

[0091] Then calculate the m value of each pier pile foundation. The m value of each pier pile foundation is obtained by formula (5)-formula (6). m There are three types of soil layers within the depth, 2# and 3# piers h m There is only one soil layer within the depth. According to the soil layer type and the m value specified in the specification, the m value of each pier can be obtained. Due to the effect of foundation scouring, the remaining soil type will change with the occurrence of scouring, and the m value should also change with the change of soil type. The m values ​​of each pier are shown in Table 3.

[0092] Table 3

[0093] Pier Number Scour 2m Scour 4m Scour 6m Scour 8m Scour 10m 1# 116733 117781 118884 119815 120000 2# 120000 120000 120000 120000 120000 3# 120000 120000 120000 120000 120000

[0094] Finally, substituting into formula (7) the soil spring stiffness of the pile foundation soil layer can be calculated.

[0095] Furthermore, the calculated soil spring stiffness after scouring is input into the high-speed train-track-bridge-foundation coupling system for simulation analysis to obtain the dynamic response data of the train subsystem, track subsystem, and bridge subsystem at different scouring depths. Figure 4-Figure 6 The train derailment coefficient, wheel load reduction rate, wheel axle lateral force, rail displacement, bridge mid-span displacement and acceleration response values ​​at different scouring depths are obtained, and then step three is entered.

[0096] Step 3: Perform parameter sensitivity analysis on the dynamic response data of the train subsystem, track subsystem, and bridge subsystem, calculate the impact of scouring depth on the dynamic response indicators of each subsystem, and find the dynamic response indicators with greater impact on scouring depth. The dynamic responses of the train subsystem, track subsystem, and bridge subsystem include mid-span train derailment coefficient, wheel load reduction rate, wheel axle lateral force, mid-span rail displacement, bridge mid-span displacement, and acceleration indicators. Perform parameter sensitivity analysis on the above indicators.

[0097] According to formula (8)-formula (9), sensitivity analysis can be performed on the mid-span train derailment coefficient, wheel load reduction rate, wheel axle lateral force, mid-span rail displacement, bridge mid-span displacement, and acceleration indicators.

[0098] First, assume that the functional relationship between scour depth and characteristic index is:

[0099] h=ay+b (11)

[0100] Where h is the scouring depth, unit: m, and y is the characteristic index.

[0101] Secondly, the mid-span train derailment coefficient, wheel weight reduction rate, wheel axle lateral force, main span mid-span rail displacement, bridge mid-span displacement, and acceleration index change rate with scour depth are calculated. According to formula (9), the change rate of each response index can be obtained as shown in Table 4.

[0102] Table 4

[0103]

[0104] It can be seen from the table that the indicator with the largest rate of change is the lateral vibration displacement of the bridge. The lateral vibration displacement of the bridge is defined as the characteristic indicator y of the foundation scour of the high-speed train-track-bridge system, and then proceed to step four.

[0105] Step 4: Use software to fit the response data of characteristic index y at different scouring depths with the scouring depth h. Figure 7 This is the fitting curve of the bridge lateral vibration displacement and scour depth. It can be seen from the figure that the slope a = 78.64, the intercept b = -24.79, and substituting a and b into formula (10) to obtain the fitting curve:

[0106] h=78.64y-24.79

[0107] Depend on Figure 7 It can be seen that the determination coefficient R 2 ≈0.97.

[0108] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An indirect identification method for the scour depth of deep-water bridge foundation, characterized in that: The following steps are involved: Obtaining a high-speed train-track-cross-sea bridge dynamic model and scour simulation data; solving the high-speed train-track-cross-sea bridge dynamic model according to the scour simulation data to obtain dynamic responses of each subsystem of the train, track, and bridge; Conduct parameter sensitivity analysis on the dynamic response of each subsystem based on the change of scour depth, and select characteristic indicators that meet the preset conditions; Fitting the characteristic index with the scouring depth to obtain a fitting function relationship; A real-time characteristic index value is obtained, and a foundation scouring depth is obtained based on the fitting function relationship and the real-time characteristic index value.

2. The indirect identification method of deep-water bridge foundation scour depth according to claim 1 is characterized in that: The process of obtaining the high-speed train-track-sea bridge dynamic model includes: A train model, a track model and a bridge model are constructed respectively, and a high-speed train-track-sea-crossing bridge dynamic model is constructed based on the train model, the track model, the bridge model and the interaction between the train and the bridge, wherein a mass-spring-damper system is established as the train model, the track model adopts a three-layer elastic point support beam model to simulate the track structure, and the bridge model is constructed using the finite element method.

3. The indirect identification method of deep-water bridge foundation scour depth according to claim 2 is characterized in that: The high-speed train-track-sea-crossing bridge dynamic model is expressed as: The subscripts v, t, and b represent the train, track, and bridge subsystems, respectively; M, C, and K represent the mass, damping, and stiffness matrices, respectively; u, Represent the displacement, velocity and acceleration column vectors respectively; P tv and P vt is the wheel-rail interaction force, P bt and P tb is the bridge-rail interaction force; P ft and P fb are the forces acting on the track and bridge foundation respectively.

4. The indirect identification method of deep-water bridge foundation scour depth according to claim 1 is characterized in that: The process of obtaining scour simulation data includes: When foundation scour occurs, the pile side spring at the soil layer where the scour occurs is removed, and the pile side soil spring stiffness at the remaining locations is calculated based on the elevation after scour to obtain the scour simulation data.

5. The indirect identification method of deep-water bridge foundation scour depth according to claim 1 is characterized in that: The process of obtaining the dynamic response of each subsystem of the train, track, and bridge includes: based on the scour simulation data, using the soil spring stiffness calculation method to obtain the force of the remaining soil around the foundation after foundation scour on the bridge structure foundation, substituting the force into the high-speed train-track-cross-sea bridge dynamic model, and using the explicit-implicit mixed integration method to solve, and obtain the dynamic response of each subsystem of the train, track, and bridge.

6. The indirect identification method of deep-water bridge foundation scour depth according to claim 1 is characterized in that: The dynamic response includes multiple indicators such as mid-span train derailment coefficient, wheel load reduction rate, wheel axle lateral force, mid-span rail displacement, bridge mid-span displacement and acceleration.

7. The indirect identification method of deep-water bridge foundation scour depth according to claim 6 is characterized in that: The process of performing parameter sensitivity analysis on the dynamic response of each subsystem based on the change of scour depth and screening characteristic indicators that meet the preset conditions includes: The relationship between the scouring depth and the dynamic response of each subsystem under scouring is constructed, the change rate of each dynamic response index at different scouring depths is calculated, and the index whose change rate meets the preset conditions is selected as the characteristic index.

8. The indirect identification method of deep-water bridge foundation scour depth according to claim 1 is characterized in that: The process of obtaining the fitting function relationship includes: fitting all response data of the characteristic index at different scouring depths with the scouring depth to obtain the fitting function relationship.

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