Bridge foundation local scour depth correction method and system considering wave-current interaction

Abstract

This invention discloses a method and system for correcting the local scour depth of bridge foundations considering the combined effects of waves and currents. The method includes: calculating the depth of local scour pits on bridge piers under pure water flow; correcting the depth of local scour pits under pure water flow using an amplification factor for the local scour depth under wave influence, thus obtaining the depth of local scour pits under the combined effects of waves and currents; the amplification factor is calculated based on the tidal velocity, the maximum velocity of horizontal particles at the seabed bottom, and the KC number. This invention improves calculation accuracy, reduces the risk of local scour of cross-sea bridge foundations due to underestimation of calculated values, and ensures bridge safety.

Description

Technical Field

[0001] This invention relates to the field of marine engineering technology, and in particular to a method and system for correcting the local scour depth of bridge foundations considering the combined effects of waves and currents. Background Technology

[0002] In recent years, cross-sea bridges and offshore wind power have developed rapidly, playing an important role in local economic development. However, these marine structures generally face serious scouring problems. The local scouring of cross-sea bridge and offshore wind power foundations both domestically and internationally is often addressed using Chinese standards such as the "Specifications for Hydrological Survey and Design of Highway Engineering" (JTG C30-2015) and the "Specifications for Hydrological Survey and Design of Railway Engineering" (TB 10017-2021), as well as American standards (Evaluating Scour at Bridge - Fourth Edition). HydraulicEngi neeringCircularNo . 18 The calculation formulas for wave and current effects are provided, but none of them take into account the effect of waves. Existing physical model experiments show that the scour depth of bridge foundations under the combined action of waves and current is greater than that under the action of water flow alone. Therefore, to ensure structural safety, the scour depth of bridge foundations under the combined action of waves and current must be considered.

[0003] To account for the impact of waves, current scholars mainly rely on the calculation methods in the existing "Specifications for Hydrological Survey and Design of Highway Engineering" (JTGC30-2015) or "Specifications for Hydrological Survey and Design of Railway Engineering" (TB 10017-2021) to superimpose a given average wave velocity onto the tidal current velocity as the approach velocity in front of the pier. , Let C be the average velocity of the wave-water particles, H be the wave speed, and C be the wave height. However, this method directly uses the average velocity of the wave-water particles along the water depth and ignores the influence of the wave-structure interaction on erosion, so the accuracy of the calculation needs to be improved. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a precise method and system for correcting the local scour depth of bridge foundations that takes into account the combined effects of wave and current.

[0005] Technical solution: The method for correcting the local scour depth of bridge foundations considering the combined effect of waves and currents, as described in this invention, includes the following steps:

[0006] Calculate the depth of local scour pits on bridge piers under pure water flow;

[0007] The depth of the local scour pit on the bridge pier under the action of pure water flow is corrected by using the amplification factor of the local scour depth under the influence of waves, so as to obtain the depth of the local scour pit on the bridge pier under the combined action of waves and current.

[0008] The amplification factor is calculated based on the tidal current velocity, the maximum velocity of the horizontal wave particles at the bottom of the seabed, and the KC number.

[0009] Furthermore, the depth of the local scour pit on the bridge pier under the action of pure water flow is corrected by using the amplification factor of the local scour depth under the influence of waves, and the depth of the local scour pit on the bridge pier under the combined action of waves and current is obtained as follows:

[0010] The product of the amplification factor and the depth of the local scour pit on the pier under the action of pure water flow is the depth of the local scour pit on the pier under the combined action of wave and current.

[0011] Furthermore, the amplification factor is calculated based on the tidal current velocity, the maximum velocity of the horizontal wave particles at the seabed bottom, and the KC number, including:

[0012] ;

[0013] in, To increase the coefficient, For the speed of trends, The maximum velocity of a horizontal wave particle at the seabed bottom. For KC number, These are coefficients to be determined.

[0014] Furthermore, the undetermined coefficients were obtained through fitting tests of pure water flow scour and wave flow scour of typical bridge foundation structures. .

[0015] The bridge foundation local scour depth correction system considering the combined effect of waves and currents as described in this invention includes:

[0016] The scour depth calculation unit under pure water flow is used to calculate the depth of local scour pits on bridge piers under pure water flow.

[0017] The scour depth correction unit under the combined action of wave and current is used to correct the depth of the local scour pit of the bridge pier under the action of pure water flow by using the increase factor of the local scour depth under the influence of wave, so as to obtain the depth of the local scour pit of the bridge pier under the combined action of wave and current.

[0018] The amplification factor is calculated based on the tidal current velocity, the maximum velocity of horizontal particles at the bottom of the seabed, and the KC number.

[0019] Furthermore, in the scour depth correction unit under the combined action of waves and current, the depth of the local scour pit on the pier under the action of pure water flow is corrected by the amplification factor of the local scour depth under the influence of waves, and the depth of the local scour pit on the pier under the combined action of waves and current includes:

[0020] The product of the amplification factor and the depth of the local scour pit on the pier under the action of pure water flow is the depth of the local scour pit on the pier under the combined action of wave and current.

[0021] Furthermore, in the scour depth correction unit under the combined action of waves and currents, the amplification factor is calculated based on the tidal current velocity, the maximum velocity of horizontal particles at the seabed bottom, and the KC number, including:

[0022] ;

[0023] in, To increase the coefficient, For the speed of trends, The maximum velocity of a horizontal particle at the bottom of the seabed. For KC number, These are coefficients to be determined.

[0024] Furthermore, the undetermined coefficients were obtained through fitting tests of pure water flow scour and wave flow scour of typical bridge foundation structures. .

[0025] The computer-readable storage medium of the present invention stores a computer program, which, when executed by a processor, implements the method for correcting the local scour depth of bridge foundations considering the combined effect of wave and current.

[0026] The computer program product of the present invention includes a computer program that, when executed by a processor, implements the method for correcting the local scour depth of bridge foundations considering the combined effect of wave and current.

[0027] Beneficial effects: Compared with the prior art, the advantages of the present invention are: The present invention can quickly calculate the local scour depth of bridge foundation under the combined action of waves and currents, which can facilitate the stress verification calculation of cross-sea bridge foundations. It improves the calculation accuracy compared with the method in the current specifications, reduces the risk caused by the calculated value being too small for local scour of cross-sea bridge foundations, and ensures bridge safety. Attached Figure Description

[0028] Figure 1 This is a schematic elevation view of the foundation of the cross-sea bridge in this embodiment.

[0029] Figure 2 This is a schematic side view of the structure of the cross-sea bridge foundation in this embodiment.

[0030] Figure 3 The coefficients in this embodiment A diagram showing the comparison between calculated and experimental values. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0032] According to the current Chinese standards "Code for Hydrological Survey and Design of Railway Engineering" (TB 10017-2021) and "Code for Hydrological Survey and Design of Highway Engineering" (JTG C30-2015), the formula for calculating the local scour depth of bridge foundations is as follows.

[0033] (1) Local scour of bridge piers in non-cohesive soil riverbeds shall be calculated according to the following formula:

[0034] when hour:

[0035]

[0036] when hour:

[0037]

[0038] (2) The local scour of bridge piers in cohesive soil riverbeds shall be calculated according to the following formula:

[0039] when hour:

[0040]

[0041] when hour:

[0042]

[0043] In the above formula, The depth of the local scour pit on the bridge pier under the action of pure water flow (m). The velocity of the approach current to the pier (m / s); The initial flow velocity of riverbed sediment (m / s); The initial flow velocity in front of the pier (m / s); The pier shape coefficient; The influence coefficient of riverbed particles; Water depth (m); Calculate the width of the bridge piers; The fluidity index of cohesive soil; This is an index. For specific values ​​of each parameter, please refer to the current "Railway Engineering Hydrological Survey and Design Specifications".

[0044] However, none of the above formulas consider the effect of waves. To calculate the local scour depth of bridge foundations under the combined action of waves and currents, this invention, based on the calculation method for local scour of bridge foundations under pure water flow, introduces a local scour depth amplification factor under the influence of waves to obtain the local scour depth of bridge foundations under the combined action of waves and currents.

[0045]

[0046] in, The depth of the local scour pit on the bridge pier under the action of wave and current (m). The depth of the local scour pit on the bridge pier under the action of pure water flow (m). The local scour depth increase factor is used to account for the effects of waves.

[0047] To achieve accurate and rapid calculation of the local scour depth of bridge foundations under the combined effects of waves and currents, how can we determine the local scour depth amplification factor that considers the wave effect? This is the key. This invention introduces the maximum velocity of horizontal wave particles at the seabed bottom. Based on the KC number, a local scour depth amplification factor considering wave effects and including undetermined coefficients is proposed. Calculation formula:

[0048] Parameter 1:

[0049] Parameter 2:

[0050] in:

[0051]

[0052]

[0053] Parameter 1 reflects the amplifying effect of waves on the bottom flow velocity; parameter 2 reflects the influence of structures. In the formula, The velocity is the result of the combined action of waves and current. The maximum velocity (m / s) of a horizontal wave particle located at the bottom of the seabed. H is the tidal current velocity (m / s); H is the wave height (m), and for irregular waves, take... (i.e., the average wave height of 1 / 10 the largest wave); The wave period (s); The equivalent width (m) of the water-blocking area of ​​the bridge foundation. Width of the wave-facing surface of the bridge pier (m); Width of the wave-facing surface of the foundation (m); The thickness of the foundation (m); Water depth (m); The height (m) from the bottom of the pier to the seabed surface; This refers to the number of rows of piles perpendicular to the direction of water flow. The diameter of the pile is in meters (m).

[0054] Then consider the local scour amplification factor under the influence of waves. for:

[0055]

[0056] In the formula, For undetermined coefficients, It is the current velocity, a fundamental parameter that must be determined in engineering design and is usually verified.

[0057] The method described in this invention will be verified through specific experiments below.

[0058] 1. Conduct pure water flow scour tests and wave flow scour tests on typical bridge foundation structures to obtain the local scour depth of bridge foundations under multiple sets of pure water flow and wave flow combined effects.

[0059] The test was conducted in accordance with the current Chinese standard "Technical Specification for Simulation Test of Waterway Engineering" (JTS / T231-2021), such as... Figure 1 The image shown is a schematic elevation view of the foundation structure of the cross-sea bridge in this experiment. Figure 2 The diagram shown is a schematic side view of the foundation structure of the cross-sea bridge in this experiment, including the seabed 1, pile foundation 2, pile cap 3, and pier 4. The experimental procedure is as follows:

[0060] (1.1) Selection of model sand

[0061] Since the particle size of foundation soil varies in different regions, it is necessary to consider different particle sizes. In the experiment, the selection of model sand mainly considers the similarity with the prototype sediment initiation and the similarity with the underwater sediment repose angle.

[0062] (1.2) Calibration of test water flow and wave elements

[0063] The experiment considered the effects of different foundation dimensions, water depth, wave height, wave period, and flow velocity. First, the design flow was calibrated in the wave basin, and then the given wave elements were calibrated based on the existing flow.

[0064] The experimental water flow was a unidirectional steady flow, and the waves were irregular waves, taking into account the unidirectional effect of the wave and the flow.

[0065] The test groups are shown in Table 1 below. In Table 1, “—” indicates that this parameter is not considered, that is, this numbered group only considers the effect of water flow and does not consider the effect of waves.

[0066] Table 1. Number of Experimental Groups (Prototype Values)

[0067]

[0068] (1.3) Fabrication and installation of bridge foundation test models

[0069] Each part of the experimental model was scaled down to a specific geometric scale, maintaining geometric similarity to the prototype. All structural components were simulated as rigid structures, constructed using acrylic glass or PVC pipes with sufficient strength and rigidity.

[0070] After the test model was completed, it was installed in the test section of the wave basin. The test section was set up with a square pit with a length of 4.0m, a width of 4.0m, and a depth of 0.3m. The pit was filled with model sand. A bridge pier model was placed in the middle of the test section, and longitudinal and transverse measuring bridges were arranged around it to measure the erosion and siltation topography around the bridge pier.

[0071] (1.4) The commencement of formal trials

[0072] After the test model was installed, water was poured into the harbor basin to the target depth, and the basin was left to stand for one day to allow the foundation to fully compact before the formal test began. The incident waves and currents were input into the computer according to the calibrated parameters to generate wave and current signals. The local scour depth of the foundation was measured sequentially for each test run.

[0073] 2. Coefficient of increase in local scour depth due to wave influence Feasibility verification.

[0074] The results of the local scour depth tests for different test groups are shown in Table 2. In Table 2, “—” indicates that this parameter is not considered, that is, this test group only considers the effect of water flow and does not consider the effect of waves.

[0075] Table 2 shows that the local scour depth under the combined action of wave and current is greater than that under the action of pure water flow, indicating that waves have an amplifying effect on local scour. .

[0076] Table 2 Local scour depth

[0077]

[0078] 3. Determination of the formula for calculating the local scour depth amplification factor considering the influence of waves.

[0079] Based on experimental values, the local scour amplification factor considering the wave effect was calculated. Undetermined coefficients in Perform a fitting analysis. Based on minimizing the error, obtain the coefficients. The value is 1.1, that is:

[0080]

[0081] As shown in Table 3 and Figure 3 As shown, the comparison between the calculated and experimental values ​​indicates that the average error between the calculated and experimental values ​​is 2%, and the maximum error is within 8%. Furthermore, the calculated values ​​are generally greater than the experimental values, meaning that the calculation results obtained using the above formula are safer.

[0082] Table 3. Factors that increase the depth of local scour considering wave effects. Comparison of calculated and experimental values

[0083]

[0084] The bridge foundation local scour depth correction system considering the combined effect of waves and currents as described in this invention includes:

[0085] The scour depth calculation unit under pure water flow is used to calculate the depth of local scour pits on bridge piers under pure water flow.

[0086] The scour depth correction unit under the combined action of wave and current is used to correct the depth of the local scour pit of the bridge pier under the action of pure water flow by using the increase factor of the local scour depth under the influence of wave, so as to obtain the depth of the local scour pit of the bridge pier under the combined action of wave and current.

[0087] The amplification factor is calculated based on the tidal current velocity, the maximum velocity of horizontal particles at the bottom of the seabed, and the KC number.

[0088] The computer-readable storage medium of the present invention stores a computer program, which, when executed by a processor, implements the basic local scour depth correction method considering the combined effect of wave and current.

[0089] The computer program product of the present invention includes a computer program that, when executed by a processor, implements the method for correcting the local scour depth of bridge foundations considering the combined effect of wave and current.

[0090] The computer-readable storage medium may include RAM, ROM, EEPROM, CD-ROM or other optical disc storage devices, magnetic disk storage devices or other magnetic storage devices, flash memory or any other medium that can be used to store program code in the form of instructions or data structures and is accessible by a computer.

[0091] The processor is used to execute a computer program stored in memory to implement the various steps in the methods described in the above embodiments.

Claims

1. A method for correcting the local scour depth of bridge foundations considering the combined effects of waves and currents, characterized in that, Includes the following steps: Calculate the depth of local scour pits on bridge piers under pure water flow; The depth of the local scour pit on the bridge pier under the action of pure water flow is corrected by using the amplification factor of the local scour depth under the influence of waves, so as to obtain the depth of the local scour pit on the bridge pier under the combined action of waves and current. The amplification factor is calculated based on the tidal velocity, the maximum velocity of horizontal particles at the bottom of the seabed, and the KC number. The depth of the local scour pit on the bridge pier under the action of pure water flow is corrected by using the amplification factor of the local scour depth under the influence of waves, and the depth of the local scour pit on the bridge pier under the combined action of waves and current is obtained as follows: The product of the amplification factor and the depth of the local scour pit on the pier under the action of pure water flow is the depth of the local scour pit on the pier under the combined action of wave and current. The amplification factor is calculated based on the tidal velocity, the maximum velocity of horizontal particles at the seabed bottom, and the KC number, including: ； in, To increase the coefficient, For the speed of trends, The maximum velocity of a horizontal wave particle at the seabed bottom. For KC number, These are coefficients to be determined.

2. The method for correcting the local scour depth of bridge foundations considering the combined effects of waves and currents according to claim 1, characterized in that, The undetermined coefficients were obtained by fitting data from pure water flow scour tests and wave current scour tests on typical bridge foundation structures. .

3. A bridge foundation local scour depth correction system considering the combined effects of waves and currents, characterized in that, include: The scour depth calculation unit under pure water flow is used to calculate the depth of local scour pits on bridge piers under pure water flow. The scour depth correction unit under the combined action of wave and current is used to correct the depth of the local scour pit of the bridge pier under the action of pure water flow by using the increase factor of the local scour depth under the influence of wave, so as to obtain the depth of the local scour pit of the bridge pier under the combined action of wave and current. The amplification factor is calculated based on the tidal current velocity, the maximum velocity of the horizontal wave particles at the bottom of the seabed, and the KC number; In the scour depth correction unit under the combined action of waves and current, the depth of the local scour pit on the bridge pier under the action of pure water flow is corrected by the increase factor of the local scour depth under the influence of waves, and the depth of the local scour pit on the bridge pier under the combined action of waves and current includes: The product of the amplification factor and the depth of the local scour pit on the pier under the action of pure water flow is the depth of the local scour pit on the pier under the combined action of wave and current. In the scour depth correction unit under the combined action of waves and currents, the amplification factor is calculated based on the tidal current velocity, the maximum velocity of horizontal particles at the seabed bottom, and the KC number, including: ； in, To increase the coefficient, For the speed of trends, The maximum velocity of a horizontal wave particle at the seabed bottom. For KC number, These are coefficients to be determined.

4. The bridge foundation local scour depth correction system considering the combined effect of waves and currents according to claim 3, characterized in that, The undetermined coefficients were obtained by fitting data from pure water flow scour tests and wave current scour tests on typical bridge foundation structures. .

5. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the method for correcting the local scour depth of bridge foundations considering the combined effect of wave and current, as described in any one of claims 1-2.

6. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the method for correcting the local scour depth of bridge foundations considering the combined effect of wave and current, as described in any one of claims 1-2.

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