A fast calculation method for the impact of mud dumping diffusion and deposition based on analytical model

Abstract

The present invention discloses a method for rapidly calculating the impact of mud dumping diffusion and deposition based on an analytical model, the method comprising: collecting data of a mud dumping project area, and performing preprocessing to obtain water depth data; constructing a rapid calculation model for the impact of mud dumping diffusion and deposition based on a two-dimensional point source diffusion and sediment sedimentation equation, specifically comprising model establishment, grid division, terrain interpolation, source term processing, parameter selection and particle size classification; through the constructed rapid calculation model for the impact of mud dumping diffusion and deposition, the diffusion process of the sand content in the project area over time, and the mud dumping deposition process of the bottom bed of the project area are rapidly calculated under the conditions of a given mud dumping volume and mud dumping duration, and the sand content change process and bottom bed sedimentation morphology of the concerned points are obtained. The present invention can realize the rapid calculation and evaluation of the impact of mud dumping, improve the efficiency and accuracy of mud dumping operations, and is suitable for wide application in actual operations.

Description

Technical Field

[0001] The invention relates to the technical field of dredging mud dumping impact assessment, in particular to a method for quickly calculating mud dumping diffusion and deposition impact based on an analytical model. Background Art

[0002] The current mud dumping operation is often quite random, especially in offshore dumping areas. During the mud dumping operation, there is usually no sufficient calculation and evaluation, and the operation often relies on experience. This can easily lead to the spread of mud dumping and the impact on the surrounding environment cannot be estimated, or excessive local deposition affects the use of the mud dumping area. In addition, for the mud dumping process, numerical simulation and calculation are often performed through sediment mathematical models, which is cumbersome, time-consuming and labor-intensive, and has great limitations on the rapid assessment of the impact of mud dumping. Summary of the invention

[0003] In order to solve the above problems, the present invention proposes a rapid calculation method for mud dumping diffusion and sedimentation impact based on an analytical model, which can quickly calculate the diffusion distribution of sediment content and riverbed siltation.

[0004] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0005] The present invention is a method for quickly calculating the impact of mud dumping diffusion and deposition based on an analytical model, comprising the following operations:

[0006] Collect data from the mud dumping project area and pre-process it to obtain water depth data;

[0007] Construct a fast calculation model of mud diffusion and sedimentation impact based on two-dimensional point source diffusion and sediment deposition equations, including model establishment, grid division, terrain interpolation, source term processing, parameter selection and particle size classification;

[0008] By constructing a rapid calculation model for the diffusion and deposition of mud dumping, the diffusion process of sand content in the project area over time and the sedimentation process of the bottom bed in the project area can be quickly calculated under the conditions of given mud dumping volume and mud dumping duration, and the sand content change process and bottom bed sedimentation morphology of the focus points can be obtained.

[0009] A further improvement of the present invention is that the collected data includes: measured underwater terrain elevation data of the mud dumping engineering area, measured water level, flow velocity, flow direction hydrological test data of the mud dumping engineering area, porosity of mud dumping dredged soil, sediment particle density and particle grading data.

[0010] A further improvement of the present invention is that the preprocessing operation includes: unifying the measured underwater terrain elevation data and the measured water level data of the mud dumping engineering area to the same base surface, and the water depth data is the measured water level data minus the measured underwater terrain elevation data.

[0011] A further improvement of the present invention is that the expression for particle size classification is:

[0012] d=[d 1 ,d 2 ,…,d n ]

[0013] P=[p 1 ,p 2 ,…,p n ]

[0014] p 1 +p 2 +…+p n =1

[0015] Among them, d n is the median size of the particle size group, d is the median size of each particle size group, p n is the mass percentage of the particle size group, P is the calculated mass percentage of each particle size group, and n is the total number of particle size groups obtained based on the particle grading data.

[0016] A further improvement of the present invention is that the expression for source term processing is:

[0017] dM=M total / t in

[0018] C input (x 0 ,y 0 )=dM*P / (dx*dy*H(x 0 ,y 0 ))

[0019] C s (x,y) 当前时刻 =C s (x,y) 上一时刻 +C input (x,y)

[0020] Among them, M total is the total mass of the dumped mud, t in is the mud throwing time, dM is the mass thrown in each step, P is the calculated mass percentage of each particle size group, C input (x 0 ,y 0 ) is the mud throwing point during mud throwing (x 0 ,y 0 ) concentration, C s (x,y) 当前时刻 is the concentration at the current time point (x, y), C s (x,y) 上一时刻is the concentration at the previous time point (x, y), C input (x, y) is the concentration change at any point (x, y) caused by the mud dumping process, dx and dy are the length and width of the unit grid, respectively. 0 ,y 0 ) is the mud throwing point (x 0 ,y 0 ) at the depth of water.

[0021] A further improvement of the present invention is that the expression reflecting the sediment diffusion process and deposition process obtained by model establishment is:

[0022] M s (x,y)=C s (x,y)*(dx*dy*H(x,y))

[0023]

[0024]

[0025] C s (x,y)=C s' (x,y)exp(K d dt)

[0026]

[0027] Among them, C s (x,y) is the concentration at point (x,y), C s' (x, y) is the calculated transition concentration after the diffusion process and before the sedimentation process at point (x, y), M s (x,y) is the mass distribution of dredged soil at point (x,y), dx and dy are the length and width of the unit grid, G(x,y) is the Gaussian kernel function, ΔD(x,y) is the thickness of the bottom bed after settlement at point (x,y), is the convolution operator symbol, H(x,y) is the water depth at point (x,y), K L and K T are the lateral diffusion coefficient and the longitudinal diffusion coefficient, respectively, U and V are the lateral and longitudinal average velocity, respectively, η is the cloud following coefficient, K d =kw s / H is the sedimentation coefficient, H is the water depth, w s is the sediment settling velocity, k is a constant coefficient considering the combined effects of group sedimentation and density flow, λ is the porosity of the sediment on the bottom bed, ρ s is the density of sediment particles, dt is the calculation time step, x 0 ,y 0 is the coordinate position of the mud dumping point;

[0028] Sediment settling velocity w during sedimentation attenuation s for:

[0029]

[0030] Where s = ρ s / ρ is the dimensionless specific density of sediment particles, ρ is the water density, g is the acceleration of gravity, ν is the kinematic viscosity, and d is the median particle size of each particle size group.

[0031] A further improvement of the present invention is that the expression for distinguishing the cloud following coefficient η in the diffusion process of sediment with different particle sizes is:

[0032]

[0033] Among them, ω=2πf is the circular frequency, f is the turbulent pulsation frequency, ρ is the water density, d is the median particle size, μ is the dynamic viscosity, a, b, c are all transition quantities in the calculation process, u s is the moving speed of the sediment cloud, u w is the water flow speed.

[0034] The further improvement of the present invention is that the lateral diffusion coefficient K in the expression for the sediment diffusion process and the sedimentation process is L and the longitudinal diffusion coefficient K T Calculated by Elder formula, the expression is:

[0035]

[0036] Among them, C z is the Xie Cai coefficient, α and β are both constant coefficients.

[0037] A further improvement of the present invention is that the rapid calculation model of mud dumping diffusion and deposition effect adopts the fast Fourier transform calculation method to perform convolution calculation, and the calculation expression is:

[0038]

[0039] Among them, i is a complex number symbol, M s (x, y) is the mass distribution of dredged soil at point (x, y), G(x, y) is the Gaussian kernel function, C s' (x,y) is the calculated transition concentration after the diffusion process and before the sedimentation process at point (x,y), C s' The two-dimensional discrete Fourier transform form of (x,y), M sThe two-dimensional discrete Fourier transform form of (x, y), (m, l) is the frequency domain matrix element after Fourier transform of point (x, y), and X and Y are the sizes of the frequency domain matrix in two dimensions respectively. The beneficial effects of the present invention are as follows: the rapid calculation model of mud dumping diffusion and deposition effect in the present invention does not need to be calculated by the traditional planar two-dimensional hydrodynamic calculation equations, including the continuity equation, momentum equation, and sediment transport equation, bed deformation equation and other differential equations, but directly realizes the calculation of mud dumping diffusion process and deposition process through the analytical solution of the diffusion equation of the point source and the sediment deposition expression, which greatly improves the calculation efficiency of the comparative sediment mathematical model.

[0040] The present invention adopts the fast Fourier transform calculation method to perform convolution calculation, thereby greatly improving the calculation efficiency. The general diffusion process calculation is performed through point-by-point cyclic accumulation calculation in the whole field, and the execution efficiency is low. The calculation by convolution method can speed up the calculation process and improve the calculation efficiency.

[0041] In addition, in order to reflect the differences in the suspended diffusion and sedimentation processes of silt with different particle size gradations in mud throwing, the present invention classifies the different particle sizes, calculates the median particle size components of each particle size grade respectively, and finally performs weighted calculation of the influence according to the mass proportion, so as to correspond to the actual situation and improve the calculation accuracy of the mud throwing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a schematic diagram of a method flow in an embodiment of the present invention;

[0043] Figure 2 is a schematic diagram of diffusion calculation results at t = 7200 seconds in an embodiment of the present invention;

[0044] Figure 3 is a schematic diagram of diffusion calculation results at t = 7800 seconds in an embodiment of the present invention;

[0045] Figure 4 is a schematic diagram of diffusion calculation results at t=8400 seconds in an embodiment of the present invention;

[0046] Figure 5 1 is a schematic diagram comparing the actual sediment content process and the calculated sediment content process of measuring point 1 in an embodiment of the present invention;

[0047] Figure 6 2 is a schematic diagram comparing the actual sediment content process and the calculated sediment content process of measuring point 2 in an embodiment of the present invention;

[0048] Figure 7 3 is a schematic diagram comparing the actual sediment content process and the calculated sediment content process of measuring point 3 in an embodiment of the present invention;

[0049] Figure 8It is the settlement distribution calculation result in the embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0051] like Figure 1 As shown, a method for quickly calculating the impact of mud dumping diffusion and deposition based on an analytical model in this embodiment includes the following steps:

[0052] Step S1, collecting data of the mud dumping engineering area and preprocessing it to obtain water depth data;

[0053] Step S2, constructing a rapid calculation model for mud diffusion and sedimentation impact based on two-dimensional point source diffusion and sediment sedimentation equations, specifically including model establishment, grid division, terrain interpolation, source term processing, parameter selection and particle size classification;

[0054] Step S3, through the constructed rapid calculation model of mud dumping diffusion and deposition effect, the diffusion process of sand content in the project area over time and the sedimentation process of the bottom bed in the project area are quickly calculated under the conditions of given mud dumping volume and mud dumping duration, so as to obtain the change process of sand content and bottom bed sedimentation morphology of the focus points.

[0055] Step S1 specifically includes:

[0056] Collect measured underwater terrain elevation data in the mud dumping project area;

[0057] Collect the measured water level, flow velocity and flow direction hydrological test data in the mud dumping project area;

[0058] Collect data on porosity, sediment particle density and particle size distribution of dredged soil;

[0059] The collected underwater terrain elevation data Z(x,y) and measured water level W(x,y,t) of the mud dumping engineering area are processed and unified to the same base surface. The water depth data is obtained by subtracting the terrain elevation data from the water level data on the same base surface, where x and y are coordinate positions and t is the time.

[0060] Step S2 specifically includes:

[0061] Step S2.1, model construction, obtain the expression that reflects both the sediment diffusion process and the sedimentation process in the rapid calculation model of mud dumping diffusion and deposition impact:

[0062] M s (x,y)=C s (x,y)*(dx*dy*H(x,y))

[0063]

[0064] C s (x,y)=C s' (x,y)exp(K d dt)

[0065] Among them, C s (x,y) is the concentration at point (x,y), C s' (x, y) is the calculated transition concentration after the diffusion process and before the sedimentation process at point (x, y), M s (x,y) is the mass distribution of dredged soil at point (x,y), dx and dy are the length and width of the unit grid, G(x,y) is the Gaussian kernel function, ΔD(x,y) is the thickness of the bottom bed after settlement at point (x,y), is the convolution operator symbol, H(x,y) is the water depth at point (x,y), K L and K T are the lateral diffusion coefficient and the longitudinal diffusion coefficient, respectively, U and V are the lateral and longitudinal average velocities, η is the cloud following coefficient, K d =kw s / H is the sedimentation coefficient, H is the water depth, w s is the sediment settling velocity, k is a constant coefficient considering the combined effects of group sedimentation and density flow, λ is the porosity of the sediment on the bottom bed, ρ s is the density of sediment particles, dt is the calculation time step, x 0 ,y 0 is the coordinate position of the mud dumping point.

[0066] The fast Fourier transform calculation method is used for convolution calculation, which greatly improves the calculation efficiency. The expression is:

[0067]

[0068] Among them, i is a complex number symbol, M s (x, y) is the mass distribution of dredged soil at point (x, y), G(x, y) is the Gaussian kernel function, C s' (x,y) is the calculated transition concentration after the diffusion process and before the sedimentation process at point (x,y), C s' The two-dimensional discrete Fourier transform form of (x,y), Ms The two-dimensional discrete Fourier transform form of (x,y), (m,l) is the frequency domain matrix element after the Fourier transform of point (x,y), and X and Y are the sizes of the frequency domain matrix in two dimensions respectively.

[0069] Step S2.2, grid division and terrain interpolation: Grid division mainly considers the scope of the project area and the points of interest, which is generally about tens of meters. The calculation time step is generally less than the sediment deposition time under the minimum water depth conditions in the area, and is taken as tens of seconds. Terrain interpolation is performed through biharmonic spline interpolation of the divided grids.

[0070] Step S2.3, source term processing: control the source term per unit time by the total amount of mud dumping / mud dumping duration, so that each step in the dumping time has a uniform source term effect to ensure the conservation of mud dumping mass. The expression is:

[0071] dM=M total / t in

[0072] C input (x 0 ,y 0 )=dM*P / (dx*dy*H(x 0 ,y 0 ))

[0073] Reconstruct the global source variable C input (x,y), except for the actual mud dumping point (x 0 ,y 0 ) has a value, there is no other placement point C input The value of (x,y) is 0.

[0074] C s (x,y) 当前时刻 =C s (x,y) 上一时刻 +C input (x,y)

[0075] Among them, M total is the total mass of the dumped mud, t in is the mud throwing time, dM is the mass thrown in each step, P is the calculated mass percentage of each particle size group, C input (x 0 ,y 0 ) is the mud throwing point during mud throwing (x 0 ,y 0 ) concentration, C s (x,y) 当前时刻 is the concentration at the current time point (x, y), C s (x,y) 上一时刻 is the concentration at the previous time point (x, y), Cinput (x, y) is the source variable, that is, the concentration change at any point (x, y) caused by the mud dumping process. dx and dy are the length and width of the unit grid, respectively. 0 ,y 0 ) is the mud throwing point (x 0 ,y 0 ) at the depth of water.

[0076] Step S2.4, parameter selection, including cloud following coefficient η, sediment settling velocity w s , lateral diffusion coefficient K L and the longitudinal diffusion coefficient K T choice.

[0077] Among them, the cloud following coefficient η considered in the diffusion process is:

[0078]

[0079] Among them, ω=2πf is the circular frequency, f is the turbulent pulsation frequency, ρ is the water density, d is the median particle size, μ is the dynamic viscosity, a, b, c are all transition quantities in the calculation process, u s is the moving speed of the sediment cloud, u w is the water flow speed.

[0080] Considering the sediment settling velocity w in the sediment attenuation process s for:

[0081]

[0082] Where s = ρ s / ρ is the dimensionless specific density of sediment particles, ρ is the water density, g is the acceleration of gravity, ν is the kinematic viscosity, and d is the median particle size of each particle size group.

[0083] Transverse diffusion coefficient K L and the longitudinal diffusion coefficient K T Calculate using Elder's formula. The expression is:

[0084]

[0085] Among them, C z is the Xie Cai coefficient, α and β are both constant coefficients.

[0086] Step S2.5, parameter selection, particle size classification: In order to reflect the differences in the suspended diffusion and sedimentation process of sediments with different particle size gradations in the mud dumping, the different particle sizes are graded, and the median particle size components of each particle size grade are calculated separately. Finally, the influence is weighted according to the mass proportion, so as to correspond to the actual situation and improve the calculation accuracy of the mud dumping process. The expression is:

[0087] d=[d 1 ,d 2 ,…,d n ]

[0088] P=[p 1 ,p 2 ,…,p n ]

[0089] p 1 +p 2 +…+p n =1

[0090] Among them, d n is the median size of the particle size group, d is the median size of each particle size group, p n is the mass percentage of the particle size group, P is the calculated mass percentage of each particle size group, and n is the total number of particle size groups obtained based on the particle grading data.

[0091] like Figure 2 As shown in FIG. 1 , the mud dumping diffusion and deposition impact rapid calculation model constructed in step S2 is used to calculate the mud dumping diffusion and deposition impact of a certain mud dumping point. The calculation result of mud dumping diffusion is shown in FIG. Figures 2 to 4 The comparison results of the actual sediment content process and the calculated sediment content process at different sampling points are shown in Figures 5 to 7 The settlement distribution calculation results are shown in Figure 8 shown.

[0092] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have the same meaning as in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined similarly here.

[0093] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A rapid calculation method for the impact of mud dumping diffusion and deposition based on an analytical model, characterized by: The following operations are included: Collect data from the mud dumping project area and pre-process it to obtain water depth data; Construct a fast calculation model of mud diffusion and sedimentation impact based on two-dimensional point source diffusion and sediment deposition equations, including model establishment, grid division, terrain interpolation, source term processing, parameter selection and particle size classification; By constructing a rapid calculation model for the diffusion and deposition of mud dumping, the diffusion process of sand content in the project area over time and the sedimentation process of the bottom bed in the project area can be quickly calculated under the conditions of given mud dumping volume and mud dumping duration, and the sand content change process and bottom bed sedimentation morphology of the focus points can be obtained.

2. A rapid calculation method for the impact of mud dumping diffusion and deposition based on an analytical model according to claim 1, characterized in that: The collected data include: measured underwater terrain elevation data of the mud dumping project area, measured water level, flow velocity, flow direction hydrological test data of the mud dumping project area, porosity of mud dumping dredged soil, sediment particle density and particle grading data.

3. A rapid calculation method for the impact of mud dumping diffusion and deposition based on an analytical model according to claim 2, characterized in that: The preprocessing operation includes: unifying the measured underwater terrain elevation data and the measured water level data of the mud dumping engineering area to the same base surface, and the water depth data is the measured water level data minus the measured underwater terrain elevation data.

4. The method for rapid calculation of mud dumping diffusion and deposition effects based on an analytical model according to claim 1 is characterized by: The expression of the particle size classification is: d=[d1,d2,...,d n ] P=[p1,p2,...,p n ] p1+p2+…+p n =1 Among them, d n is the median size of the particle size group, d is the median size of each particle size group, p n is the mass percentage of the particle size group, P is the calculated mass percentage of each particle size group, and n is the total number of particle size groups obtained based on the particle grading data.

5. The method for rapid calculation of mud dumping diffusion and deposition effects based on an analytical model according to claim 1 is characterized by: The expression of the source term processing is: dM=M total / t in C input (x0,y0)=dM*P / (dx*dy*H(x0,y0)) C s (x,y) 当前时刻 =C s (x,y) 上一时刻 +C input (x,y) Among them, M total is the total mass of the dumped mud, t in is the mud throwing time, dM is the mass thrown in each step, P is the calculated mass percentage of each particle size group, C input (x0, y0) is the concentration of the mud dumping point (x0, y0) during the mud dumping process, C s (x,y) 当前时刻 is the concentration at the current time point (x, y), C s (x,y) 上一时刻 is the concentration at the previous time point (x, y), C input (x, y) is the concentration change at any point (x, y) caused by the mud dumping process, dx and dy are the length and width of the unit grid, respectively, and H(x0, y0) is the water depth at the mud dumping point (x0, y0).

6. The method for rapid calculation of mud dumping diffusion and deposition effects based on an analytical model according to claim 1 is characterized by: The expression reflecting the sediment diffusion process and deposition process obtained by the model is: M s (x,y)=C s (x,y)*(dx*dy*H(x,y)) C s (x,y)=C s' (x,y)exp(K d dt) Among them, C s (x,y) is the concentration at point (x,y), C s' (x, y) is the calculated transition concentration after the diffusion process and before the sedimentation process at point (x, y), M s (x,y) is the mass distribution of dredged soil at point (x,y), dx and dy are the length and width of the unit grid, G(x,y) is the Gaussian kernel function, ΔD(x,y) is the thickness of the bottom bed after settlement at point (x,y), is the convolution operator symbol, H(x,y) is the water depth at point (x,y), K L and K T are the lateral diffusion coefficient and the longitudinal diffusion coefficient, respectively, U and V are the lateral and longitudinal average velocity, respectively, η is the cloud following coefficient, K d =kw s / H is the sedimentation coefficient, H is the water depth, w s is the sediment settling velocity, k is a constant coefficient considering the combined effects of group sedimentation and density flow, λ is the porosity of the sediment on the bottom bed, ρ s is the density of sediment particles, dt is the calculation time step, x0 and y0 are the coordinates of the mud dumping point; Sediment settling velocity w during sedimentation attenuation s for: Where s = ρ s / ρ is the dimensionless specific density of sediment particles, ρ is the water density, g is the acceleration of gravity, ν is the kinematic viscosity, and d is the median particle size of each particle size group.

7. A rapid calculation method for the impact of mud dumping, diffusion and deposition based on an analytical model according to claim 6, characterized in that: The expression of cloud following coefficient η in the process of sediment diffusion with different particle sizes is: Among them, ω=2πf is the circular frequency, f is the turbulent pulsation frequency, ρ is the water density, d is the median particle size, μ is the dynamic viscosity, a, b, c are all transition quantities in the calculation process, u s is the moving speed of the sediment cloud, u w is the water flow speed.

8. A rapid calculation method for the impact of mud dumping, diffusion and deposition based on an analytical model according to claim 6, characterized in that: The lateral diffusion coefficient K in the expression of the reaction sediment diffusion process and the deposition process is L and the longitudinal diffusion coefficient K T Calculated by Elder formula, the expression is: Among them, C z is the Xie Cai coefficient, α and β are both constant coefficients.

9. A rapid calculation method for the impact of mud dumping diffusion and deposition based on an analytical model according to claim 6, characterized in that: The rapid calculation model of mud dumping diffusion and deposition effect adopts fast Fourier transform calculation method to perform convolution calculation, and the calculation expression is: Among them, i is a complex number symbol, M s (x, y) is the mass distribution of dredged soil at point (x, y), G(x, y) is the Gaussian kernel function, C s' (x,y) is the calculated transition concentration after the diffusion process and before the sedimentation process at point (x,y), C s' The two-dimensional discrete Fourier transform form of (x,y), M s The two-dimensional discrete Fourier transform form of (x,y), (m,l) is the frequency domain matrix element after the Fourier transform of point (x,y), and X and Y are the sizes of the frequency domain matrix in two dimensions respectively.

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