Method and system for determining dredging opportunity of upstream shoal of Yangtze River, terminal and medium

Abstract

The invention discloses a method for determining the dredging opportunity of an upstream shoal of the Yangtze River, a terminal and a medium. The method comprises the following steps: acquiring historical dredging data of the upstream shoal of the Yangtze River; a three-dimensional water flow mathematical model control equation is established, a Van-Rijn sediment model is adopted to calculate the gravel bed load sediment transport rate, and a riverbed evolution model is obtained through visual solving; performing water flow motion characteristic verification on the obtained riverbed evolution model; carrying out dredging opportunity influence factor analysis, and carrying out water flow and siltation amount calculation by utilizing the verified riverbed evolution model; and constructing a dredging opportunity calculation model based on the time length required for dredging, the time length required from the current to dredging completion, and the time length required from the current to dredging starting, and calculating by using the dredging opportunity calculation model to obtain the optimal dredging opportunity of the dredging area. The dredging opportunity can be accurately calculated, the dredging construction efficiency is improved, and it is ensured that a channel is safe and unblocked.

Description

Technical Field

[0001] The present invention relates to the technical field of waterway maintenance dredging, and particularly to a method, system, terminal and medium for determining the dredging timing of shoals in the upper reaches of the Yangtze River. Background Art

[0002] The maintenance dredging of the main waterway of the Yangtze River is an important part of the maintenance work. There are many shoals in the main waterway of the Yangtze River. Coupled with the influence of the clear water discharge from the Three Gorges Reservoir, the maintenance dredging work runs through the whole year with a long line and many points, resulting in a large amount of maintenance dredging work and a large investment in human, material and financial resources.

[0003] The dredging of shoals in the main waterway of the Yangtze River is the key to ensuring the smoothness of the waterway and improving the transportation efficiency. The determination of the traditional dredging timing mainly relies on experience or fixed cycles, which cannot give accurate dredging timing, and may lead to waste of resources or untimely dredging.

[0004] In the maintenance dredging work of large rivers and waterways in China, it has been noted that the dredging timing has a very important impact on the dredging effect, and there has been some exploration and research on the dredging timing. However, the actual dredging timing is affected by many complex factors such as water and sediment conditions, geological conditions, riverbed evolution, and external conditions. At present, the research mainly focuses on the impact of water level processes and the contradiction between construction and navigation on the dredging timing, and there is still a lack of systematic understanding of the influencing factors of the dredging timing, and the determination method of the dredging timing still needs to be established. Summary of the Invention

[0005] The present invention provides a method, terminal and medium for determining the dredging timing of shoals in the upper reaches of the Yangtze River, which can accurately calculate the dredging timing, improve the dredging construction efficiency, and ensure the safe and smooth waterway.

[0006] In the first aspect, the present invention provides a method for determining the dredging timing of shoals in the upper reaches of the Yangtze River, including the following steps:

[0007] Step 1, obtaining the historical dredging data of the shoals in the upper reaches of the Yangtze River;

[0008] Step 2, based on the incompressible Reynolds stress averaging, Boussinesq hypothesis and hydrostatic pressure distribution, establishing the control equations of the three-dimensional water flow mathematical model, calculating the bedload sediment transport rate by using the Van-Rijn sediment model, and obtaining the riverbed evolution model by using mike21 for visual solution of the two-dimensional plane mathematical model;

[0009] Step 3, verifying the water flow movement characteristics of the obtained riverbed evolution model;

[0010] Step 4, analyzing the influencing factors of the dredging timing, and calculating the water flow and sediment deposition amount by using the verified riverbed evolution model to determine the duration required for dredging, the duration required from the current time to the completion of dredging, and the duration required from the current time to the start of dredging;

[0011] Step 5: Construct a dredging timing calculation model based on the required duration of dredging, the duration from the current time to the completion of dredging, and the duration from the current time to the start of dredging, and use the dredging timing calculation model to calculate the optimal dredging timing for the dredging area.

[0012] Furthermore, the historical dredging data described in Step 1 includes topographic and construction data, geological condition data, and dredging vessel working capacity data, where the topographic and construction data includes the cad topographic data of the dredging and maintenance of each shoal in the upper reaches of the Yangtze River and the dredging construction time, water level, and dredging volume of each shoal in the upper reaches of the Yangtze River.

[0013] Furthermore, the control equations of the three-dimensional water flow mathematical model described in Step 2 include:

[0014] Continuity equation of water flow:

[0015]

[0016] The horizontal momentum equations in the X and Y directions are:

[0017]

[0018] where t is time; x, y, z are Cartesian coordinates; h is the total water depth, h = η + d; η is the water surface elevation; d is the still water depth; u, v, w are the velocity components in the x, y, z directions; f is the Coriolis force parameter; the shear stress T ij includes the viscous stress T xx , the eddy viscosity stress T xy and the convective gradient stress T yy , τ sx , τ sy is the wind shear stress, τ bx , τ by is the bed shear stress, c f is the drag coefficient; g is the acceleration due to gravity; ρ is the density of water; S xx , S xy , S yx , S yy are the components of the dispersion stress tensor; ν t is the vertical eddy viscosity coefficient; p a is the air atmospheric pressure; ρ0 is the reference density of water; S is the source flow rate; u s , v s are the velocity components of the source flowing to the outside; F u , F v are the horizontal stress forces.

[0019] Furthermore, the calculation formula for calculating the bed load sediment transport rate of pebbles using the Van-Rijn sediment model described in Step 2 is:

[0020]

[0021] Among them, T is a dimensionless transport parameter, T = (u′ f / u f,c ) 2 -1, the critical incipient velocity effective incipient velocity The bed surface resistance coefficient C' = 18log(4h / d 90 ), θ c is the critical Shields constant; D * is the dimensionless sediment diameter, D * = d 50 [(s - 1)g / ν 2 13 , ν is the kinematic viscosity of water; g is the acceleration due to gravity.

[0022] Furthermore, the riverbed evolution model described in step 2 includes a riverbed deformation equation and a riverbed elevation update equation.

[0023] Furthermore, the verification of the flow motion characteristics of the obtained riverbed evolution model in step 3 includes the following steps:

[0024] Step 3.1: Collect the measured data required for model verification;

[0025] Step 3.2: Determine the roughness coefficient of the river reach;

[0026] Step 3.3: Select the computational domain and generate the computational grid;

[0027] Step 3.3: Based on the measured data, conduct water level verification, velocity verification, buoy flow direction verification, and erosion and deposition volume verification respectively to determine whether the model prediction results match the measured data.

[0028] Furthermore, the mathematical expression of the dredging timing calculation model in step 5 is:

[0029]

[0030] Among them, H T represents the lowest water level for the start of dredging, H0 represents the current water level, V d represents the water level recession rate, H E represents the design water level, Q0 represents the preliminary calculated dredging volume for the first survey map after the flood season, ɑ is the correction parameter of Q0, Q c represents the siltation volume during the construction period, T d and V h represent the actual working hours and actual working efficiency of the suitable dredging vessels for each waterway respectively.

[0031] ​Second aspect, the present invention provides a system for determining the dredging timing of shoals in the upper reaches of the Yangtze River, which is used to implement the method described in the first aspect, including:

[0032] A data acquisition module, which is used to acquire the historical dredging data of the shoals in the upper reaches of the Yangtze River;

[0033] A model construction module, which is used to establish the control equations of a three-dimensional water flow mathematical model according to the incompressible Reynolds stress averaging, the Boussinesq hypothesis and the hydrostatic pressure distribution; calculate the bedload sediment transport rate by using the Van-Rijn sediment model, and use mike21 to perform the visual solution of the two-dimensional plane mathematical model to obtain the riverbed evolution model;

[0034] A model verification module, which is used to verify the water flow movement characteristics of the established riverbed evolution model;

[0035] A data analysis module, which is used to analyze the influencing factors of the dredging timing, and use the verified riverbed evolution model to calculate the water flow and sediment deposition volume, and determine the duration required for dredging, the duration required from the current time to the completion of dredging, and the duration required from the current time to the start of dredging;

[0036] A dredging timing determination module, which is used to construct a dredging timing calculation model according to the duration required for dredging, the duration required from the current time to the completion of dredging, and the duration required from the current time to the start of dredging, and use the dredging timing calculation model to calculate the best dredging timing of the dredging area.

[0037] Third aspect, the present invention provides a computer terminal, which includes a processor, a memory and a communication interface; the memory and the communication interface are coupled to the processor, and the memory is used to store computer program instructions; wherein, when the processor executes the computer program instructions, the computer terminal realizes the steps of the method described in the first aspect.

[0038] Fourth aspect, the present invention provides a computer-readable storage medium, which stores computer program instructions, and when the computer program instructions are executed by a processor, the steps of the method described in the first aspect are realized.

[0039] Beneficial effects:

[0040] 1. The present invention first collects historical dredging data, then establishes a two-dimensional plane water flow and sediment mathematical model based on the finite element method of average water depth. After that, the calculation results of this mathematical model provide scientific support for the calculation of the dredging timing, propose a new method for determining the dredging timing of shoals in the upper reaches of the Yangtze River, and use this method to calculate the latest construction water level for dredging the upper shoals, providing technical support for subsequent precise maintenance dredging.

[0041] 2. Improving the maintenance and guarantee capacity of the Yangtze River waterway is a comprehensive issue, which includes how to scientifically coordinate maintenance and dredging forces, how to improve the pre-judgment level of the Yangtze River main line waterway maintenance, etc. Traditional understanding methods are relatively one-sided, and there is no effective connection between various influencing factors. It is difficult to have a unified overall perspective to examine and analyze navigation problems, and it is difficult to meet market demands in terms of the thinking, demonstration, and expression of necessity. However, this invention innovatively links various achievements based on a two-dimensional water flow and sediment mathematical model, realizing data linkage, which can meet the requirements of the market for the discussion of project necessity. The invention results provide an overall idea for the maintenance and dredging of the upper reaches of the Yangtze River, determine reasonable dredging timing, optimize the dredging plan, and are of great significance for realizing the "smooth, efficient, safe, and green" Yangtze River shipping. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a flowchart of the method described in this invention.

[0043] Figure 2 It is a flowchart of the construction and solution of the mathematical model;

[0044] Figure 3 It is a visualization schematic diagram of the water flow and sediment model based on Mike21;

[0045] Figure 4 It is a schematic diagram of the velocity verification result;

[0046] Figure 5 It is a schematic diagram of the erosion and deposition volume verification result;

[0047] Figure 6 It is a diagram of the digital model buoy calculation results under the design flow rate, regulation flow rate, and annual average flow rate for many years;

[0048] Figure 7 It is a diagram of the digital model buoy calculation results under the medium water flow rate, common flood flow rate, and extreme flood flow rate;

[0049] Figure 8 It is a cloud map of the sediment erosion and deposition volume distribution in the typical year of the terrain in 2023;

[0050] Figure 9 It is a principle block diagram of the system described in this invention;

[0051] Figure 10 It is a principle block diagram of the terminal described in this invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The following further describes this invention in conjunction with the embodiments and the drawings.

[0053] The maintenance dredging of the waterway in the upper reaches of the Yangtze River is an important part of the maintenance work of the main line of the Yangtze River. There are many shoals in the upper reaches. The maintenance dredging work runs throughout the year, with a long line and many points. The workload of maintenance dredging is large, and the investment in human, material and financial resources is large. Since 2018, the maintenance dredging of the waterway of the main line of the Yangtze River has been implemented with market-oriented management. Using financial funds and post-Triple Gorges funds, the waterway maintenance dredging of about 20 or more shoals has been carried out in the section from Hejiangmen to Fengdu. The annual dredging volume is about 200,000 - 450,000 cubic meters. Therefore, the dredging of the shoals in the upper reaches of the Yangtze River is the key to ensuring the smoothness of the waterway and improving the transportation efficiency. The determination of the traditional dredging timing mainly relies on experience or fixed cycles, and cannot give accurate dredging timing, which may lead to waste of resources or untimely dredging.

[0054] For this reason, the embodiments of the present invention analyze the influencing factors of the dredging timing of the waterway in the upper reaches of the Yangtze River, including the water level process, riverbed scouring and silting, dredging capacity and navigation conditions, etc. By analyzing the flow and water level processes of the main hydrological stations in the upper reaches of the Yangtze River and their impacts on waterway dredging, and combining with the factors of water level process, riverbed scouring and silting, dredging capacity and navigation conditions, the main parameters for judging the dredging timing are found, so as to fit each influencing factor into an empirical formula, which can calculate the main parameters to determine the dredging timing, and thus determine the maintenance dredging timing of the waterway in the upper reaches of the Yangtze River. Specifically as follows:

[0055] Embodiment 1:

[0056] As Figure 1 shown, the embodiments of the present invention propose a method for determining the dredging timing of the shoals in the upper reaches of the Yangtze River, and the specific steps are as follows:

[0057] Step 1, obtain the historical dredging data of the shoals in the upper reaches of the Yangtze River;

[0058] In this embodiment, the historical dredging data includes topographic and construction data, geological condition data, and working capacity data of dredging vessels. Among them, the topographic and construction data includes the cad topographic data of the dredging and maintenance of each shoal in the upper reaches of the Yangtze River, as well as the dredging construction time, water level, and dredging volume of each shoal in the upper reaches of the Yangtze River. Among them:

[0059] The cad topographic data of the dredging and maintenance of each shoal in the upper reaches of the Yangtze River is selected from June 20, 2024 to July 1, 2024. The team member He Yiwei collected and sorted out the topographic data such as the cad of the recent dredging and maintenance of the upper shoals from the Yibin Waterway Bureau, Luzhou Waterway Bureau, Chongqing Waterway Bureau, etc. of the Yangtze River, as well as the relevant data such as the dredging construction time, water level, and dredging volume of each shoal collected from the Chongqing Waterway Engineering Bureau of the Yangtze River.

[0060] The geological condition data adopts the data collected from June 20, 2024 to July 1, 2024 and the results of riverbed geological exploration. According to the drilling disclosure, the strata exposed in the exploration depth range of the Yangtze River upstream riverbed are mainly sandy pebble soil layers and bedrock layers. The riverbed rock and soil are mainly sandy pebble soil layers, and the pebble content accounts for a relatively high proportion. Generally, the sandy pebble overburden layer is relatively thick. In some beach sections, the bedrock layer underlies the sandy pebble layer below the riverbed and has not been penetrated. The specific situation is shown in Table 1.

[0061] Table 1 Judgment Table for Classification of Dredged Rock and Soil and Ease of Excavation

[0062]

[0063] It can be seen from Table 1 that when the cementation degree of the sandy pebble layer on the riverbed surface is relatively good, a hard layered structure can be formed, increasing the difficulty of dredging excavation. This influencing factor should be considered in the analysis of dredging timing.

[0064] The working capacity data of the dredging vessels adopts the data collected and statistically analyzed from June 20, 2024 to July 1, 2024, and statistically analyzed the construction efficiency of different construction vessel types in different water depths for upstream shoal dredging. Among them, the statistical results of vessel efficiency are shown in Table 2:

[0065] Table 2 Statistical Table of Vessel Efficiency

[0066]

[0067] Collect and sort out the construction capabilities of various vessels used in the upper reaches of the Yangtze River in recent years, as shown in Tables 3 - 6:

[0068] Table 3 Analysis Table of Dredging Construction Efficiency of Rope Bucket Grab Dredger

[0069]

[0070] Table 4 Analysis Table of Dredging Construction Efficiency of Bucket Ladder Dredger

[0071]

[0072] Table 5 Analysis Table of Dredging Construction Efficiency of Hard Arm Grab Dredger

[0073]

[0074] Table 6 Upper and Lower Limits of Dredging Vessel Construction Operating Water Depths and Optimal Water Depths

[0075] Construction machinery Lower limit of construction water depth (m) Upper limit of construction water depth (m) Optimal water depth (m) <![CDATA[4m 3 Grab dredger]]> 4 9.5 5-6 Bucket ladder dredger 3.5 Unlimited 6-10 <![CDATA[4m 3 Bucket Ladder Dredger]]> 4.5 Unlimited The higher the water level, the lower the work efficiency

[0076] For the shoals in the upper reaches of the Yangtze River, from the analysis of the dredging medium, it is mainly the silted sand and gravel during the flood season, and the above three types of ships can all meet the construction requirements; from the analysis of the construction conditions, the flow velocity of individual shoals is above 3 m / s, and in some local areas it can reach above 4 m / s. Under such water flow conditions, the construction accuracy of the line bucket grab dredger becomes low, and it is difficult to position the ladder dredger, while the hard-arm grab dredger is the best choice for this working condition.

[0077] The hard-arm grab dredger is suitable for dredging construction with a water depth below 12 m. The construction efficiency decreases with the increase of the construction water depth. When the water level exceeds 9.5 m, the construction difficulty increases and the construction efficiency will be greatly reduced. This influencing factor should be considered during the analysis of the dredging timing.

[0078] Step 2: Based on the incompressible Reynolds stress averaging, Boussinesq hypothesis and hydrostatic pressure distribution, establish the control equations of the three-dimensional water flow mathematical model, use the Van-Rijn sediment model to calculate the sediment transport rate of pebble bed load, and use mike21 to visually solve the two-dimensional plane mathematical model to obtain the riverbed evolution model;

[0079] After comparing and analyzing the existing mathematical models and common software for calculating water flow and sediment, the present invention finally selects mike21 to construct and solve the two-dimensional plane mathematical model. As Figure 2 shown, the specific steps for model establishment and solution are as follows:

[0080] Step 2.1: Based on the incompressible Reynolds stress averaging, Boussinesq hypothesis and hydrostatic pressure distribution, establish the following control equations of the three-dimensional water flow mathematical model:

[0081] Water flow continuity equation:

[0082]

[0083] Horizontal momentum equations in the X and Y directions:

[0084]

[0085] In the formula: t is time; x, y, z are Cartesian coordinates; η is the water surface elevation; d is the static water depth; h is the total water depth, h = η + d; u, v, w are the velocity components in the x, y, z directions; f is the Coriolis force parameter, f = 2Ωsinφ (Ω is the angular velocity of rotation, φ is the geographical longitude); g is the acceleration due to gravity; ρ is the density of water; S xx 、S xy 、S yx 、S yy are the components of the dispersed stress tensor; ν t is the vertical eddy viscosity coefficient; p a is the air atmospheric pressure; ρ0 is the reference density of water; S is the source (sink) flow rate; us , v s is the velocity component of the source (sink) flowing to the outside; F u , F v is the horizontal stress. Using the velocity gradient - stress relationship, it can be simplified to

[0086]

[0087] where A is the horizontal eddy viscosity coefficient.

[0088] The velocity boundary conditions at the water surface and the riverbed bottom can be expressed as:

[0089] At the water surface (z = η):

[0090]

[0091] At the riverbed bottom (z = -d):

[0092]

[0093] In the formula, τ sx , τ sy is the wind shear stress at the water surface; τ bx , τ by is the bed shear stress, and the following relationship can be established with the depth-averaged velocity using the Chezy formula:

[0094]

[0095] where C is the Chezy coefficient.

[0096] The vertical direction adopts the depth-averaged velocity distribution, that is

[0097]

[0098] Combining the horizontal momentum equation and the continuity equation, the three-dimensional flow control equation can be simplified to two-dimensional, that is

[0099] The flow continuity equation can be rewritten as:

[0100]

[0101] The horizontal momentum equations in the X and Y directions:

[0102]

[0103] In the formula: The shear stress T ij includes viscous stress, eddy viscous stress and convective gradient stress, and the calculation formula is:

[0104]

[0105] where τ sx, τ sy is the wind shear stress, and the influence of wind is not considered in this embodiment. τ bx , τ by and τ

[0106]

[0107] where c f is the resistance coefficient. For two-dimensional problems is the average water depth flow velocity, and the friction velocity U τb has the following relationship with the bed surface resistance c f can be calculated through the Chezy coefficient C or the Manning coefficient M, that is or

[0108] When the water flow enters the river bend, due to the imbalance of the centripetal force, an outward movement will be generated near the water surface and an inward movement will be generated near the river bed. The reason is that the flow velocity in the upper part of the main flow is greater than that in the lower part, and the centrifugal force on the upper water body is greater than that on the lower water body. In order to maintain the centripetal force balance along the water depth, the streamline of the upper water body has a larger curvature radius than that of the lower water body. When a spiral flow occurs in the bend, a transverse slope (gravity component) will be generated on the water surface to maintain the balance among the lateral water pressure, the centrifugal force, and the lateral bed surface friction force. This spiral flow pattern can be considered as the sum of the longitudinal flow (main flow) and the circular motion (secondary flow) in the cross-section perpendicular to the main flow direction. The direction of the secondary flow in the cross-section points to the convex bank at the bottom of the bed surface and to the concave bank at the water surface. Due to the bending of the streamline, a small deviation is generated in the main flow near the bed surface, and at the same time, a small deviation also occurs in the bed surface shear stress. For a curved river channel, the direction of the bed surface shear stress plays a very important role in the river bed evolution.

[0109] Therefore, for Equations (4) and (5), the direction of the bed shear stress is the same as the direction of the average flow velocity. Strictly speaking, this conclusion holds only for straight rivers. For curved rivers, the following should be adopted:

[0110]

[0111] In the formula:

[0112]

[0113] where R * is the effective bending radius of the streamline, and is calculated by the following formula:

[0114]

[0115] Turbulence model:

[0116] (1) Vertical eddy viscosity coefficient νt

[0117] According to the logarithmic law, the vertical eddy viscosity coefficient can be derived as follows:

[0118]

[0119] where U τ = max(U τs , U τb ), (U τs , U τb ) are the friction velocities at the water surface and the river bed respectively; c1 and c2 are constants. For a standard parabolic cross-section, c1 = 0.41 and c2 = -0.41.

[0120] (2) Horizontal eddy viscosity coefficient A

[0121] Smagorinsky (1963) suggested using the characteristic length to calculate the influence of sub-grid eddies, and the sub-grid eddy viscosity coefficient is calculated by the following formula

[0122]

[0123] where: c s is a constant, l is the characteristic length, and S ij is the strain rate.

[0124]

[0125] Step 2.2: Use the Van - Rijn sediment model to calculate the bed load sediment transport rate and establish the sediment model:

[0126] River bed evolution is the result of the interaction between sediment and hydrodynamic forces. The sediment in the project reach mainly includes bed load, and it is appropriate to use the Van - Rijn sediment model.

[0127] Van - Rijn recommends using the following formula to calculate the bed load:

[0128]

[0129] where: T is the dimensionless transport parameter, T = (u′ f / u f,c ) 2 -1, the critical incipient velocity the effective incipient velocity the bed surface resistance coefficient C' = 18log(4h / d 90 ), θ c is the critical Shields constant (approximately equal to 0.06) and can be obtained according to Table 7; D * is the dimensionless sediment particle size, D * = d 50[(s - 1)g / ν 2 13 , where ν is the kinematic viscosity coefficient of water, and it can be approximately taken as ν = 10 -6 m 2 / s.

[0130] Table 7 Shields constant values

[0131] <![CDATA[D * range]]> <![CDATA[θ c value]]> <![CDATA[D * <4]]> <![CDATA[0.24 / D * > <![CDATA[4<D * <10]]> <![CDATA[0.14D * -0.64 <!-- 9 -->]]> <![CDATA[10<D * <20]]> <![CDATA[0.04D * -0.1 > <![CDATA[20<D * <150]]> <![CDATA[0.013D * -0.29 > <![CDATA[D * >150]]> 0.055

[0132] Step 2.3, Establish a riverbed evolution model

[0133] The riverbed evolution model combines a hydrodynamic model and a sediment transport model, and the water flow field will be continuously updated according to the changes in the riverbed topography.

[0134] (1) Riverbed deformation equation

[0135] The rate of change of the riverbed elevation at the cell center is a key parameter determining riverbed deformation, and it can be obtained from the sediment transport continuity equation

[0136]

[0137] For equilibrium sediment transport, ΔS = 0; for non - equilibrium sediment transport, ΔS = Φ0(η0)w s (c - c e ), where Φ0 is the unit - width sediment transport rate function and η0 is the standard elevation above the bed surface.

[0138] (2) Riverbed elevation update equation

[0139] The rate of change of the riverbed elevation can be calculated through Equation (17) Then the riverbed elevation at the N - th time step can be updated by the following formula

[0140]

[0141] Step 2.4, Use Mike21 for visual solution of the two - dimensional plane mathematical model.

[0142] In this embodiment, a two - dimensional water flow and sediment mathematical model is established based on the measured topographies of the Miaojiaoqi Beach section of Dongxikou Waterway during the dry, middle, and flood periods in 2015, and the visualization of the model is realized using Mike21 software, as Figure 3 shown. It can be seen from Figure 3 that the riverbed evolution model combines a hydrodynamic model and a sediment transport model. In this model, the water flow field will be continuously updated according to the changes in the riverbed topography, and it can better simulate the water flow movement under complex river boundary conditions, and can be used for numerical simulation of shoals in the upper reaches of the Yangtze River.

[0143] ​Step 3: Verify the water flow movement characteristics of the obtained riverbed evolution model;

[0144] In the embodiment of the present invention, verifying the water flow movement characteristics of the obtained riverbed evolution model includes the following steps:

[0145] Step 3.1: Collect the measured data required for model verification;

[0146] The data used for model verification in this embodiment is as follows:

[0147] (1) Topographic map of Dongxikou Waterway measured by Chongqing Shipping Engineering Survey and Design Institute of the Yangtze River in 2015, with a mapping scale of 1:2000, 1954 Beijing Coordinate System, and 1985 National Elevation Datum.

[0148] (2) Measured water surface line data, large cross-section velocity data, and measured velocity and flow direction data in 2015. The verification contents include water level, velocity distribution, and buoy flow direction.

[0149] Step 3.2: Determine the roughness coefficient of the river reach;

[0150] Calculation sections are arranged according to the specific conditions of the river. The spacing in straight sections is relatively large, and the spacing in mutation and bending sections is relatively small. Control sections are arranged at sections with sudden changes in the river channel cross-section, special terrains, and building sections, which can better control the calculation of the water surface line. During the dry season (Q Zhutuo < 5000 m 3 / s), the comprehensive roughness coefficient of the river reach is 0.024 - 0.037. During the medium water period (5000 m 3 / s ≤ Q Zhutuo ≤ 20000 m 3 / s), the comprehensive roughness coefficient of the river reach is 0.030 - 0.039. During the flood season (Q Zhutuo > 20000 m 3 / s), the comprehensive roughness coefficient of the river reach is 0.032 - 0.037.

[0151] Step 3.3: Select the calculation domain and generate the calculation grid;

[0152] The calculation grid is updated and adjusted according to the regulation plan to ensure accurate simulation of the engineering boundary. The river channel grid division of the recommended numerical simulation scheme is shown in the attached drawings, with a total of 279763 units and 562831 nodes. The grid side length of the non-key attention river reach is about 20 m, and the grid scale is about 5 m in the range from the tail of Miaojiaoqi to the reefs of Jinduizi shoal. Local encryption processing is carried out in the key attention area to more accurately simulate the effect of waterway regulation.

[0153] Step 3.3: Based on the measured data, conduct water level verification, velocity verification, buoy flow direction verification, and scouring and silting volume verification respectively, and determine whether the model prediction results are consistent with the measured data.

[0154] 1) Water level verification

[0155] By using the water surface profiles and cross-section velocities measured during the low water, medium water, and flood periods in 2015, the characteristics of water flow movement were verified. The verification results are shown in Table 8 as follows:

[0156] Table 8 Verification of water level with measured low water data in 2015, Q = 3668 m 3 / s

[0157]

[0158]

[0159] It can be seen from the verification results of the measured low water level data in the above table that the degree of conformity between the two is relatively high, the trend of the water surface profile is in good agreement, the water level deviation is within ±0.10 m, and the water level verification meets the requirements of the "Technical Specification for the Simulation of Water Flow and Sediment in Inland Waterways and Ports (JTS / T 231-4-2018)".

[0160] 2) Velocity verification

[0161] Based on the measured data and the calculated flow field, the comparison of the measured velocity and the velocity calculated by the numerical model at each flow measurement section was drawn. It can be seen from Figure 4 that the magnitude, distribution of the velocity, and the positions of the maximum and minimum values are relatively consistent with the measured data. Except for the relatively large velocity deviation at individual measurement points, the difference between the calculated velocity and the measured velocity is generally within ±0.10 m / s, and the deviation is basically controlled within ±5%. The velocity verification meets the requirements of the "Technical Specification for the Simulation of Water Flow and Sediment in Inland Waterways and Ports (JTS / T 231-4-2018)".

[0162] 3) Verification of buoy flow direction

[0163] The flow field calculated by the numerical model was compared with the measured buoy traces. It can be seen from Figure 4 that except for extremely individual places where the buoy changes suddenly, including straight sections, curved sections, confluence and bifurcation points, the flow directions of the flow fields calculated by the numerical model at each flow rate are basically consistent with the directions of the measured buoy traces.

[0164] Using the measured data in 2015, the water level, velocity, buoy flow direction, etc. of the project river section were verified, and the calculation results are in good agreement with the measured data.

[0165] 4) Verification of scouring and silting volume

[0166] Based on the measured data and the calculated flow field, the comparison of the measured velocity and the velocity calculated by the numerical model at each flow measurement section was drawn. It can be seen from Figure 5It can be seen that the flow velocity magnitude, distribution, and the positions of the maximum and minimum values are all relatively consistent with the measured data. Except for the relatively large deviation of the flow velocity at individual measuring points, the difference between the calculated flow velocity and the measured flow velocity is generally within ±0.10 m / s, and the deviation is basically controlled within ±5%. The flow velocity verification meets the requirements of the "Technical Specification for the Simulation of Water Flow, Sediment and Sand in Inland Waterways and Ports (JTS / T 231-4-2018)".

[0167] The statistical results show that the scouring and silting values of each cross-section along the way obtained by calculation and measurement are relatively close, and the overall distribution trend of the cumulative scouring and silting volume along the way is generally the same, indicating that the scouring and silting laws along the way are basically the same. The measured and calculated scouring and silting values at each time period within the year are also relatively close, and the deviation is less than ±20%, meeting the requirements of the "Technical Specification for Model Tests in Waterway Engineering (JTJ / T 231-2021)".

[0168] Through the verification of the water level, flow velocity, and scouring and silting volume of the river section, the calculation results are in good agreement with the measured data, and the verification accuracy of the model meets the requirements of the "Technical Specification for the Simulation of Water Flow, Sediment and Sand in Inland Waterways and Ports (JTS / T 231-4-2018)", indicating that the river bed evolution model can accurately simulate the water flow movement and scouring and silting changes of the actual river channel.

[0169] Step 4: Analyze the influencing factors of the dredging timing. In this embodiment, the navigation-obstructing shoal section in the upper reaches of the Yangtze River is specifically analyzed according to the influencing factors such as scouring and silting laws, dredging volume, channel geological conditions, working ability of dredging vessels, water level process, and navigation conditions.

[0170] Use the verified river bed evolution model to calculate the water flow and sediment deposition volume. Among them, the water flow calculation results are as Figure 7 and Figure 8 shown. From the mainstream distribution, the streamlines are located in the North Channel at each flow rate level. Among them, the water flow is more concentrated during the low water period, and with the increase of the flow rate level, the Miaojiaoqi and Jinduizi sandbanks pass the flow, and the mainstream gradually disperses. The sediment deposition volume calculation is shown in Table 9 and Figure 8 shown. From Table 9 and Figure 8 analysis, it is considered that under the conditions of a certain river bed, certain bed material, and the same working ability of dredging vessels, the influence of the dredging volume on the dredging timing is mainly manifested in the dredging duration. The dredging volume is proportional to the dredging duration, and the dredging volume affects the dredging time and timing by affecting the dredging duration. The dredging volume is related to the formation speed of shoal siltation, and the most important factor affecting the siltation speed is the water level drop of the river section.

[0171] Therefore, for the calculation of the dredging timing of the shoals in the upper reaches of the Yangtze River, the water level drop is ultimately mainly considered, and the evolution of the siltation body, the minimum water depth in the shallow area, and the construction water level are mainly used as variables to be obtained, that is, the minimum water depth is used as the optimal construction water level, and the calculation formula for the starting dredging timing is derived by combining the construction efficiency and the siltation change rate in the shallow area, that is, used to obtain the calculated optimal construction water level.

[0172] As analyzed above, the influencing factors for dredging timing include scouring and silting patterns, dredging volume, channel geological conditions, working capacity of dredging vessels, water level process, and navigation conditions, etc. The most basic requirement for maintenance dredging is to ensure the "smoothness" of the waterway. Therefore, based on the above analysis, in this embodiment, a dredging timing calculation model can be constructed by determining the duration required for dredging, the duration from the current time to the completion of dredging, and the duration from the current time to the start of dredging. Specifically:

[0173] Step 4.1: Determine the duration T required for dredging A

[0174] First, initially calculate the dredging volume Q through the first survey map after the flood season d , since there is a time difference between a certain survey map after the flood season and the pre-construction survey map (the survey map used for dredging design calculation of the project volume), therefore, considering the parameter ɑ, according to the scouring and silting conditions of the waterway after the flood season, the initially calculated dredging volume Q d is corrected, and then the silting volume Q during the construction period is determined according to the actual conditions of each waterway and the working experience of the designers c , that is, the actual total dredging volume Q is obtained:

[0175] Q = aQ d +Q c (19)

[0176] Through the actual working duration T d and actual working efficiency V h of the suitable dredging vessels for each waterway, combined with the actual total dredging volume Q, the duration T required for dredging is obtained A :

[0177]

[0178] Step 4.2: Determine the duration T from the current time to the completion of dredging B

[0179] According to the water level process corresponding to the current waterways, the future water level recession speed V d is deduced, combined with the current water level H0 and the predicted lowest water level H E to obtain the duration T from the current time to the completion of dredging B :

[0180]

[0181] Step 4.3: Determine the duration T from the current time to the start of dredging C

[0182] According to the duration T B from the current time to the completion of dredging AObtain the duration T required from the current time to the start of dredging C :

[0183] T C = T B - T A (22)

[0184] Step 4.4: Determine the optimal construction water level H for the start of dredging T

[0185] The current water level H0 is known, and the water level recession speed V d is known. Given the time T from the current time to the start of dredging C Combining the current water level and the water level recession speed, the optimal construction water level H for the start of work can be obtained T :

[0186] H T = H0 - V d T C (23)

[0187] Step 5: Based on the duration required for dredging, the duration required from the current time to the completion of dredging, and the duration required from the current time to the start of dredging, construct a dredging timing calculation model, and use the dredging timing calculation model to calculate the best dredging timing for the dredging area. The specific process is as follows:

[0188] By organizing each formula in Step 4, the variable to be sought for the dredging timing - the optimal construction water level - can be obtained, which is also the dredging timing calculation model. The mathematical expression is:

[0189]

[0190] Among them, H T represents the lowest water level for the start of dredging, H0 represents the current water level, V d represents the water level recession speed, H E represents the design water level, Q0 represents the preliminary calculated dredging volume from the first survey map after the flood season, ɑ is the correction parameter for Q0, Q c represents the silting volume during the construction period, T d and V h respectively represent the actual working duration and actual working efficiency of suitable dredging vessels in each waterway.

[0191] After obtaining the dredging timing calculation model, this embodiment also verified the model. The verification data used the measured data from August 15, 2024 to December 31, 2024, and verified and calculated two shoals, Xiaomi Beach and Miaojiaoqi. The results are shown in Table 10:

[0192] Table 10 Verification Table for Calculating the Dredging Timing of Shoals Based on Formulas

[0193] Calculate the start time Actual start time Calculate the start water level Actual start water level Xiaomitang 2024.11.6 2024.11.1 1.79 1.82 Miaojiaoqi 2023.12.25 2023.11.30 1.07 1.96

[0194] As can be seen from Table 10, the verification results of the dredging timing calculation model for Xiaomi Beach and Miaojiaoqi show that: the optimal construction water levels for starting work calculated for the two beaches, through actual measured water levels and construction verification, accurately judge the dredging timing for the two beaches. The calculation results are in line with the actual situation and accurate. The constructed dredging timing calculation formula is scientific and can be generally applied to the calculation of dredging timing for other key waterways in the upper reaches of the Yangtze River.

[0195] Example 2:

[0196] As Figure 9 shown, the embodiment of the present invention proposes a system for determining the dredging timing of shoals in the upper reaches of the Yangtze River. This system is used to implement the steps of the method described in Example 1 and specifically includes:

[0197] A data acquisition module, used to acquire historical dredging data of shoals in the upper reaches of the Yangtze River;

[0198] A model construction module, used to establish the control equations of the three-dimensional water flow mathematical model based on the incompressible Reynolds stress averaging, Boussinesq hypothesis, and hydrostatic pressure distribution; calculate the bed load sediment transport rate using the Van - Rijn sediment model, and use mike21 for the visual solution of the two-dimensional plane mathematical model to obtain the riverbed evolution model;

[0199] A model verification module, used to verify the water flow movement characteristics of the established riverbed evolution model;

[0200] A data analysis module, used to analyze the influencing factors of dredging timing, and use the verified riverbed evolution model to calculate water flow and sediment deposition volume, determine the duration required for dredging, the duration required from the current time to the completion of dredging, and the duration required from the current time to the start of dredging;

[0201] A dredging timing determination module, used to construct a dredging timing calculation model based on the duration required for dredging, the duration required from the current time to the completion of dredging, and the duration required from the current time to the start of dredging, and use the dredging timing calculation model to calculate the optimal dredging timing of the dredging area.

[0202] Example 3:

[0203] As Figure 10 shown, this embodiment provides a computer terminal, which includes a processor, a memory, and a communication interface; the memory and the communication interface are coupled to the processor, and the memory is used to store computer program instructions; wherein, when the processor executes the computer program instructions, the computer terminal realizes the steps of the method described in Example 1.

[0204] Example 4:

[0205] An embodiment of the present invention provides a computer-readable storage medium storing computer program instructions, which, when executed by a processor, implement the steps of the method described in Embodiment 1.

[0206] Beneficial effects: The present invention first obtains historical dredging data of shoals in the upper reaches of the Yangtze River; then, based on the incompressible Reynolds-averaged stress, the Boussinesq hypothesis, and the hydrostatic pressure distribution, a three-dimensional water flow mathematical model control equation is established, the Van-Rijn sediment model is used to calculate the pebble bed load sediment transport rate, and mike21 is used for visual solution of the two-dimensional plane mathematical model to obtain a riverbed evolution model; then, the water flow motion characteristics of the obtained riverbed evolution model are verified; next, the influencing factors of the dredging timing are analyzed, and the water flow and sediment deposition volume are calculated using the verified riverbed evolution model to determine the duration required for dredging, the duration from the current time to the completion of dredging, and the duration from the current time to the start of dredging; finally, a dredging timing calculation model is constructed based on the duration required for dredging, the duration from the current time to the completion of dredging, and the duration from the current time to the start of dredging, and the optimal dredging timing of the dredging area is calculated using the dredging timing calculation model. The calculation results can provide scientific support for the calculation of the dredging timing, propose a new method for determining the dredging timing of shoals in the upper reaches of the Yangtze River, calculate the latest construction water level for dredging of the upper shoals using this method, provide technical support for subsequent precise maintenance dredging, provide an overall idea for maintenance dredging of the upper reaches of the Yangtze River, determine a reasonable dredging timing, optimize the dredging plan, and have important significance for realizing the "smooth, efficient, safe, and green" Yangtze River shipping.

[0207] Finally, it should be noted that the above description is only the preferred embodiment of the present invention. Under the inspiration of the present invention, those of ordinary skill in the art can make various similar representations without violating the purpose and claims of the present invention, and such transformations all fall within the protection scope of the present invention.

Claims

1. A method for determining the dredging timing of shoals in the upper reaches of the Yangtze River, characterized in that, It includes the following steps: Step 1: Obtain the historical dredging data of the shoals in the upper reaches of the Yangtze River; Step 2: Based on the Reynolds-averaged Navier-Stokes equations for incompressible fluids, the Boussinesq hypothesis, and the hydrostatic pressure distribution, establish the control equations of the three-dimensional water flow mathematical model. Use the Van-Rijn sediment model to calculate the sediment transport rate of pebble bed load, and use Mike21 for the visual solution of the two-dimensional plane mathematical model to obtain the riverbed evolution model; Step 3: Verify the water flow movement characteristics of the obtained riverbed evolution model; Step 4: Analyze the influencing factors of the dredging timing, and use the verified riverbed evolution model to calculate the water flow and sediment deposition volume, and determine the duration required for dredging, the duration from the current time to the completion of dredging, and the duration from the current time to the start of dredging; Step 5: Based on the duration required for dredging, the duration from the current time to the completion of dredging, and the duration from the current time to the start of dredging, construct a dredging timing calculation model, and use the dredging timing calculation model to calculate the optimal dredging timing of the dredging area.

2. The method for determining the dredging timing of shoals in the upper reaches of the Yangtze River according to claim 1, characterized in that, The historical dredging data described in Step 1 includes topographic and construction data, geological condition data, and dredging spread working ability data. Among them, the topographic and construction data includes the cad topographic data of the dredging and maintenance of each shoal in the upper reaches of the Yangtze River, as well as the dredging construction time, water level, and dredging volume of each shoal in the upper reaches of the Yangtze River.

3. The method for determining the dredging timing of shoals in the upper reaches of the Yangtze River according to claim 1, wherein The control equations of the three-dimensional water flow mathematical model described in Step 2 include: The water continuity equation: The horizontal momentum equations in the X and Y directions are: where t is time; x, y, and z are Cartesian coordinates; h is the total water depth, h = η + d; η is the water surface elevation; d is the still water depth; u, v, and w are the velocity components in the x, y, and z directions; f is the Coriolis force parameter; the shear stress T ij includes the viscous stress T xx , the eddy viscosity stress T xy and the convective gradient stress T yy , τ sx , τ sy is the wind shear stress, τ bx , τ by is the bed shear stress, c f is the drag coefficient; g is the acceleration due to gravity; ρ is the density of water; S xx , S xy , S yx , S yy are the components of the dispersion stress tensor; ν t is the vertical eddy viscosity coefficient; p a is the air atmospheric pressure; ρ0 is the reference density of water; S is the source flow rate; u s , v s are the velocity components of the source flowing to the outside; F u , F v are the horizontal stress forces.

4. The method for determining the dredging timing of shoals in the upper reaches of the Yangtze River according to claim 1, characterized in that The calculation formula for calculating the sediment transport rate of pebble bed load using the Van-Rijn sediment model described in Step 2 is: where T is a dimensionless transport parameter, T = (u′ f / u f,c ) 2 -1, the critical incipient velocity the effective incipient velocity The bed friction coefficient C' = 18log(4h / d 90 ), θ c is the critical Shields constant; D * is the dimensionless sediment particle size, D * = d 50 [(s - 1)g / ν 2 1 / 3 , ν is the kinematic viscosity of water; g is the acceleration due to gravity.​ 5. The method for determining the dredging timing of shoals in the upper reaches of the Yangtze River according to claim 1, characterized in that The riverbed evolution model described in Step 2 includes a riverbed deformation equation and a riverbed elevation update equation.

6. The method for determining the dredging timing of shoals in the upper reaches of the Yangtze River according to claim 1, wherein The verification of the water flow movement characteristics of the obtained riverbed evolution model in Step 3 includes the following steps: Step 3.1: Collect the measured data required for model verification; Step 3.2: Determine the roughness coefficient of the river reach; Step 3.3: Select the computational domain and generate the computational grid; Step 3.3: Based on the measured data, conduct water level verification, velocity verification, buoy flow direction verification, and erosion and deposition volume verification respectively, and judge whether the model prediction results are consistent with the measured data.

7. The method for determining the dredging timing of shoals in the upper reaches of the Yangtze River according to claim 1, wherein The mathematical expression of the dredging timing calculation model described in Step 5 is: Among them, H T represents the lowest water level at the start of dredging, H0 represents the current water level, and V d represents the rate of water level decline, and H E represents the designed water level, Q0 represents the preliminary calculated dredging volume from the first survey map after the flood season, ɑ is the correction parameter for Q0, and Q c represents the silting volume during the construction period, T d and V h respectively represent the actual working hours and actual working efficiency of the suitable dredging vessels in each waterway.

8. A system for determining the dredging timing of shoals in the upper reaches of the Yangtze River, which is used to implement the method described in claims 1-7, characterized in that It includes: A data acquisition module for obtaining the historical dredging data of the shoals in the upper reaches of the Yangtze River; A model construction module for establishing the control equations of the three-dimensional water flow mathematical model according to the Reynolds-averaged Navier-Stokes equations for incompressible fluids, the Boussinesq hypothesis, and the hydrostatic pressure distribution; using the Van-Rijn sediment model to calculate the sediment transport rate of pebble bed load, and using Mike21 for the visual solution of the two-dimensional plane mathematical model to obtain the riverbed evolution model; A model verification module for verifying the water flow movement characteristics of the established riverbed evolution model; A data analysis module for analyzing the influencing factors of the dredging timing, and using the verified riverbed evolution model to calculate the water flow and sediment deposition volume, and determine the duration required for dredging, the duration from the current time to the completion of dredging, and the duration from the current time to the start of dredging; The dredging timing determination module is used to construct a dredging timing calculation model based on the duration required for dredging, the duration from the current time to the completion of dredging, and the duration from the current time to the start of dredging, and calculate the optimal dredging timing of the dredging area by using the dredging timing calculation model.

9. A computer terminal, characterized in that, The computer terminal includes a processor, a memory, and a communication interface; the memory and the communication interface are coupled to the processor, and the memory is used to store computer program instructions; wherein, when the processor executes the computer program instructions, the computer terminal implements the steps of the method according to any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer program instructions, and when the computer program instructions are executed by a processor, the steps of the method according to any one of claims 1-7 are implemented.

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