Multi-branch estuary port branch water flow control structures and their hydraulic design methods

Abstract

The present invention discloses a multi-branch estuary port branch water flow control structure and its hydraulic design method. The structure includes dry-laid stone revetments arranged on both banks of the river, a permeable submerged dam horizontally placed in the middle of the river, a flow isolation dike T-shaped connected to the permeable submerged dam, and a ship and fish passage. One end of the permeable submerged dam is connected to the dry-laid stone revetment on one side, and the other end of the permeable submerged dam is connected to a flow isolation dike. A ship and fish passage is formed between the flow isolation dike and the dry-laid stone revetment on the other side. The steps of the hydraulic design method are as follows: 1. Establish a two-dimensional hydrodynamic mathematical model of the branched river where the water flow control structure is located; 2. Conduct calibration and verification of the mathematical model; 3. Determine the annual average high tide level and annual average low tide level at the location of the water flow control structure; 4. Draw up a selection scheme for the elevation of the top of the permeable submerged dam, and determine the elevation of the top of the permeable submerged dam through numerical simulation and calculation analysis; 5. Use the hydrodynamic mathematical model to analyze and determine the bottom width and bottom elevation of the ship and fish passage.

Description

Technical Field

[0001] The present invention relates to the technical field of water conservancy, and particularly to a multi-branch estuary port branch water flow control structure and its hydraulic design method. Background Technique

[0002] The movement of water flow and sediment and human activities will change the river morphology and cause river channel evolution. For a braided river channel, the changes in the distribution of water flow and sediment often cause different prosperity and decline changes in each branch channel. Some branch channels may gradually erode and expand due to increased water flow, while other branch channels may gradually shrink due to decreased water flow, and its evolution form is particularly complex. When this ebb and flow evolution form of the port branch does not adapt to the national economic development, it is often necessary to implement port branch control projects. To improve the evolution relationship of the branch channels, the commonly used methods are to build spur dikes or longitudinal dikes to adjust the water flow, or to implement dredging projects on the silted and declining port branches. The common spur dike and longitudinal dike regulation structures usually need to be maintained regularly. In addition, due to the very complex evolution of water and sediment in braided rivers, the spur dike and longitudinal dike control schemes often cannot well adapt to the changes in the river channel boundary conditions and are prone to cause local hydraulic scouring problems; while dredging or blasting measures often have large engineering quantities, high investment, and there are problems of siltation back. In addition, for multi-branch rivers with connecting ports between adjacent port branches, in order to control and regulate the water volume and hydrodynamic force between each port branch, facilities such as barrage gates, dams, and rubber dams are usually also set in the port branch connecting ports. The barrage gates and dams often have high costs and are relatively complex in operation management and maintenance. In addition, they will block the connectivity of the natural river channel, affect the upstream migration of aquatic organisms, and have a greater negative impact on the ecological environment. The rubber dam is also relatively complex in operation management and maintenance and is not very suitable for large river channels with relatively complex water flow conditions.

[0003] Based on this, the present invention designs a multi-branch estuary port branch water flow control structure and its hydraulic design method to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a multi-branch estuary port branch water flow control structure and its hydraulic design method to solve the problems raised in the above background technique.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A multi-branch estuary port branch water flow control structure includes dry rubble masonry slopes provided on both sides of the river bank, a permeable submerged dam transversely arranged in the middle of the river, a flow isolation dike T-shaped connected to the permeable submerged dam, and a ship and fish passage. One end of the permeable submerged dam is connected to the dry rubble masonry slope on one side, the other end of the permeable submerged dam is connected to a flow isolation dike, and a ship and fish passage is formed between the flow isolation dike and the dry rubble masonry slope on the other side;

[0006] The flow isolation dike includes a first layer of rockfill, and a first gabion revetment layer is arranged at the top of the first layer of rockfill and connected to the permeable submerged dam part. A layer of trimmed stones is arranged above the first layer of rockfill at the bottom of the ship and fish passage. A first dry-laid stone slope layer is arranged on the side of the ship and fish passage between the first gabion revetment layer and the layer of trimmed stones. A first crushed stone cushion layer is arranged between the first dry-laid stone slope layer and the first layer of rockfill.

[0007] Preferably, the dry-laid stone revetment includes a second layer of rockfill, and a second crushed stone cushion layer and a second dry-laid stone slope layer are sequentially arranged above the second layer of rockfill.

[0008] Preferably, anti-collision tires are evenly arranged on the slopes on both sides of the ship and fish passage, and navigation marks for guiding ships to pass are arranged at intervals on both the flow isolation dike and the dry-laid stone revetment.

[0009] Preferably, the permeable submerged dam includes a third layer of rockfill with a composite trapezoidal cross-section, alloy wire mesh gabion revetment layers are arranged on the outer sides of the two inclined planes of the third layer of rockfill, and a second gabion revetment layer is arranged on the top surface of the third layer of rockfill.

[0010] Preferably, both ends of the flow isolation dike expand arc-shaped into the river, so that the inlet and outlet sections of the ship and fish passage are both flared.

[0011] Hydraulic design method for flow control structures in multi-branch estuary ports:

[0012] It includes the following steps:

[0013] (1) Establish a two-dimensional hydrodynamic mathematical model of the multi-branch river where the flow control structure is located:

[0014] Collect data such as the river topography, geology, hydrology, riverbed sediment, shoreline, survey and design results of the flow control structure, important river-related structures, operation and management of major water projects, and relevant research results, and establish a two-dimensional hydrodynamic mathematical model of the multi-branch river in the plane.

[0015] (2) Conduct calibration and verification of the mathematical model:

[0016] Use the measured hydrological data to verify the model. The verification content mainly includes the flow and diversion ratio, water level, flow velocity, and flow direction of each branch; mainly by adjusting the grid file, model roughness, and initial water level field boundary, the difference between the calculated value and the measured value at each hydrological station meets the error requirements; the error between the model calculated value and the measured value should meet the relevant requirements of the "Technical Specification for Water Transport Engineering Simulation Test" (JTS-T 231-2021).

[0017] (3) Determine the mean high water level and mean low water level at the location of the water flow control structure over the years:

[0018] The mean high water level and mean low water level over the years can be determined through the statistical values of the measured hydrological data of the adjacent hydrological station. When there is no hydrological station nearby or the hydrological station data is incomplete, it can be obtained by calculating using a hydrodynamic mathematical model; during the calculation, the upper boundary of the model adopts the ecological flow or mean annual flow of the river, and the lower boundary adopts the corresponding tidal level process lines of the mean high water level and mean low water level of the lower boundary water level station of the model.

[0019] (4) Draw up a selection scheme for the elevation of the permeable submerged dam top, and determine the elevation of the permeable submerged dam top through numerical simulation calculation and analysis:

[0020] The elevation of the permeable submerged dam top will affect the water flow regulation effect. The permeable submerged dam should be as high as possible to achieve a better water flow regulation effect; at the same time, the permeable submerged dam should not be set too high to avoid the submerged dam affecting the flood discharge safety of the river channel and blocking the river connectivity during the flood period; therefore, the elevation of the permeable submerged dam to be drawn up should be between the mean tide level of the dam site and the mean high water level over the years It is possible to select several elevation values between the mean tide level over the years and the mean high water level over the years and record them as Z1, Z2,... Zn respectively as the selection scheme for the elevation of the submerged dam top, and use the hydrodynamic mathematical model to carry out hydrodynamic numerical simulation calculation and analysis of different elevation schemes of the permeable submerged dam to determine the recommended value of the elevation of the permeable submerged dam top;

[0021] (5) Use the hydrodynamic mathematical model to carry out hydrodynamic numerical simulation of different bottom widths and bottom elevations of the ship and fish passage, calculate and analyze the ship flow conditions of different schemes, and based on the premise of ship safety, introduce the velocity and water depth limit conditions of the ship and fish passage, so as to analyze and determine different bottom widths and bottom elevation schemes of the ship and fish passage:

[0022] To meet the requirements for the safe passage of fishing boats, the bottom width of the ship and fish passage should be greater than the width of the fishing boat and there should also be a certain surplus width. At the same time, it should be ensured that the ship and fish passage can maintain a certain water depth for most of the time and the flow velocity in the passage should not be too large. In addition, the ship and fish passage should not be set too wide and too deep to avoid excessive water volume loss affecting the water flow regulation effect; considering two schemes of single-ship passage and double-ship passage, therefore, the selection scheme for the bottom width of the ship and fish passage to be drawn up is B + △B and 2B + 2△B, where B is the width of the designed passing ship of the ship and fish passage, and △B is the safety surplus; the bottom elevation of the ship and fish passage should be close to the mean low water level at the passage to ensure that the ship and fish passage has enough water depth for most of the time to ensure the smooth passage of passing ships and aquatic organisms. Therefore, the value of the bottom elevation of the ship passage should be between the mean low water level -1~ Between +1, when comparing the schemes, it can be within -1 to Select several elevation values between +1, denoted as z1, z2, ……, zn respectively, as the comparison schemes for the bottom elevation of the ship and fish passage, and use the hydrodynamic mathematical model to simulate and calculate different bottom width and bottom elevation schemes. By comparing the flow velocity and water depth conditions of the ship and fish passage, the bottom width and bottom elevation schemes are determined.

[0023] In step (1), the hydrodynamic mathematical model uses Mike21 software, which is based on the incompressible Navier-Stokes equation with a uniform Reynolds value and obeys the Boussinesq assumption and the hydrostatic pressure assumption;

[0024] The two-dimensional unsteady shallow water equations are:

[0025] (Equation 1)

[0026] (Equation 2)

[0027] (Equation 3)

[0028] In the formula: is time; is the coordinate in the Cartesian coordinate system; is the water level; is the still water depth; is the total water depth; are respectively the velocity components in the , are respectively the flow velocities averaged based on the water depth in the x and y directions; Pa is the local atmospheric pressure; is the density of water at standard temperature and pressure; , are respectively the shear stresses along the , are respectively the bottom shear stresses along the is the Coriolis force coefficient, , is the angular velocity of the earth's rotation, is the local latitude; is the acceleration due to gravity; is the density of water; are respectively the radiation stress components; is the horizontal viscous stress term, is the source-sink term, is the flow velocity of the source-sink term water flow in the

[0029] In step (1), the scope of the hydrodynamic mathematical model is from the cross-sections of the controlled hydrological stations of the main and tributary rivers or the downstream of the dam of the river-blocking sluice to the cross-section of the hydrological station or the tidal level station downstream of the confluence section of the river branches.

[0030] The hydrodynamic mathematical model adopts unstructured triangular meshes. The mesh size is comprehensively determined according to the accuracy of the topographic map for modeling, the degree of topographic undulation, the dimensions of important river-related structures, etc. The mesh size should be appropriate to the interval of elevation measurement points of the topographic map for modeling. For areas with severe topographic undulation and local areas of important river-related structures, the local meshes should be encrypted, and the encrypted mesh scale should be appropriate to the scale of the river-related structures.

[0031] The roughness coefficient of the hydrodynamic mathematical model can be determined based on experience, initially given in combination with the river type, riverbed morphology, riverbed composition, distribution of river-related structures, etc., and finally determined through model verification and adjustment.

[0032] The upper boundary of the hydrodynamic mathematical model is set at the starting cross-sections of the main and tributary rivers, and the upper boundary adopts the flow rate. The lower boundary of the model is set at the cross-section of the hydrological station or the tidal level station downstream of the confluence section of the river branches, and the lower boundary adopts the water level.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: The multi-branch river water flow control structure proposed by the present invention is mainly applicable to multi-branch rivers with interconnected connecting ports between the river branches. The prominent feature of the structure lies in the organic combination of the permeable submerged dam and the ship and fish passage. Its main technical feature is to set a permeable submerged dam and a ship and fish passage with the functions of passing ships and fish on the connecting port between the river branches. On the one hand, it can realize the regulation of medium and small water levels, enhance the water power of the weak branch, alleviate and reduce the siltation of the weak branch. On the other hand, it can ensure the water flow connectivity of the connecting port, take into account the needs of passing ships and fish, and in addition, it can avoid having an adverse impact on the flood discharge safety during the period of large floods.

[0034] Of course, it is not necessary for any product implementing the present invention to achieve all the above-mentioned advantages simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0036] Figure 1 It is a schematic structural diagram of the multi-branch estuary river branch water flow control structure of the present invention;

[0037] Figure 2 It is a schematic diagram of the flow isolation dike and the structure of the present invention;

[0038] Figure 3 Schematic diagram of the cross-section of the permeable submerged dam and the dry rubble slope protection structure of the present invention;

[0039] Figure 4 Schematic diagram of the location of the flow control structure for a multi-branched river and its connected ports in the present invention;

[0040] Figure 5 Calculation and analysis diagram of the mathematical model for the selection of the top elevation of the permeable submerged dam of the present invention. Detailed implementation manners

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0042] Please refer to Figures 1-3 , the present invention provides a technical solution for a flow control structure for multi-branched estuary ports and its hydraulic design method: A flow control structure for multi-branched estuary ports and its hydraulic design method. To achieve the above object, the present invention provides the following technical solutions: A flow control structure for multi-branched estuary ports includes dry rubble slope protection (1) provided on both sides of the river bank, a permeable submerged dam (2) horizontally placed in the middle of the river, a flow isolation dike (3) T-shaped connected to the permeable submerged dam, and a ship and fish passage (4). One end of the permeable submerged dam 2 is connected to the dry rubble slope protection 1 on one side, and the other end of the permeable submerged dam 2 is connected to a flow isolation dike 3. A ship and fish passage 4 is formed between the flow isolation dike 3 and the dry rubble slope protection 1 on the other side; the top width of the permeable submerged dam 2 is 3-5 m, and the top elevation of the dam should not be higher than the average high tide level of the dam site over the years to avoid affecting the river connectivity and flood discharge and tidal inflow. The specific top elevation of the dam is determined by research, analysis, and comparison of a hydrodynamic mathematical model. The average high tide level of the dam site of the permeable submerged dam can be obtained by statistical analysis of the measured data of the adjacent hydrological station or determined by calculation and analysis of a hydrodynamic mathematical model. The height difference between the top of the permeable submerged dam and the slope platform should be controlled at about 3 m. The upstream and downstream slope ratios are both 1:1.5. The width of the slope platform can be set to 5-10 m, and the slope ratio from the slope platform to the dam toe can be 1:1.5-1:2.

[0043] The flow isolation dike 3 includes a first rockfill layer 31. At the top of the first rockfill layer 31, a first gabion mattress facing layer 32 is arranged at the connection part of the permeable submerged dam 2. At the bottom of the ship and fish passage 4, a rock masonry layer 33 is arranged above the first rockfill layer 31. On the side of the ship and fish passage 4, a first dry rubble slope layer 34 is arranged between the first gabion mattress facing layer 32 and the rock masonry layer 33. A first gravel cushion layer 35 is arranged between the first dry rubble slope layer 34 and the first rockfill layer 31. The top width of the flow isolation dike 3 is 3 m, and the top elevation is the same as that of the permeable submerged dam. The flow isolation dike adopts a trapezoidal cross-section, and the side slope ratios on both sides are both 1:1.5.

[0044] Preferably, the dry rubble slope protection 1 includes a second rockfill layer 11. Above the second rockfill layer 11, a second gravel cushion layer 12 and a second dry rubble slope layer 13 are arranged in sequence.

[0045] Preferably, anti-collision tires 5 are evenly arranged on the side slopes on both sides of the ship and fish passage 4. Navigation marks 6 for guiding ships to pass are arranged at intervals on both the flow isolation dike 3 and the dry rubble slope protection 1.

[0046] Preferably, the permeable submerged dam 2 includes a third rockfill layer 21 with a composite trapezoidal cross-section. Alloy mesh gabion facing layers 22 are arranged on the outer sides of the two inclined planes of the third rockfill layer 21. A second gabion mattress facing layer 23 is arranged on the top surface of the third rockfill layer 21.

[0047] Preferably, both ends of the flow isolation dike 3 expand arc-shaped into the river, so that the inlet and outlet sections of the ship and fish passage 4 are both in a flared shape.

[0048] Hydraulic design method for flow control structures in multi-branch estuary ports:

[0049] It includes the following steps:

[0050] (1) Establish a two-dimensional hydrodynamic mathematical model of the multi-branch river where the flow control structure is located:

[0051] Collect data such as the river topography, geology, hydrology, riverbed sediment, shoreline, survey and design results of the flow control structure, important river-related structures, operation management of major water projects, and relevant research results, and establish a two-dimensional hydrodynamic mathematical model of the multi-branch river plane.

[0052] (2) Conduct calibration and verification of the mathematical model:

[0053] The model is verified using the measured hydrological data. The verification content mainly includes the flow and diversion ratio of each branch, water level, flow velocity, and flow direction. The differences between the calculated values and the measured values at each hydrological station are made to meet the error requirements mainly by adjusting the grid file, model roughness, and the boundary of the initial water level field. The errors between the model calculated values and the measured values should meet the relevant requirements of the "Technical Specification for Simulation Tests in Water Transport Engineering" (JTS-T 231-2021).

[0054] (3)Determine the mean high water level and mean low water level over the years at the location of the flow control structure:

[0055] The mean high water level and mean low water level over the years can be determined by the statistical values of the measured hydrological data of the adjacent hydrological station. When there is no nearby hydrological station or the hydrological station data is incomplete, it can be obtained by calculating using the hydrodynamic mathematical model. When calculating, the upper boundary of the model adopts the ecological flow or mean annual flow of the river, and the lower boundary adopts the corresponding tidal level process lines of the mean high water level and mean low water level of the water level station at the lower boundary of the model.

[0056] (4)Formulate a selection scheme for the elevation of the permeable submerged dam top, and determine the elevation of the permeable submerged dam top through numerical simulation calculation and analysis:

[0057] The elevation of the permeable submerged dam top will affect the flow regulation effect. The permeable submerged dam should be as high as possible to achieve a better flow regulation effect. At the same time, the permeable submerged dam should not be set too high to avoid affecting the flood discharge safety of the river channel and blocking the river connectivity during the large flood period. Therefore, the elevation of the permeable submerged dam proposed should be between the mean tidal level at the dam site and the mean high water level over the years . Several elevation values can be selected between the mean tidal level and the mean high water level over the years , which are respectively denoted as Z1, Z2, …… Zn as the selection scheme for the elevation of the submerged dam top, and the hydrodynamic numerical simulation calculation and analysis of different elevation schemes of the permeable submerged dam are carried out using the hydrodynamic mathematical model to determine the recommended value of the elevation of the permeable submerged dam top;

[0058] (5)Using the hydrodynamic mathematical model, carry out the hydrodynamic numerical simulation of different bottom widths and bottom elevations of the ship and fish passage, calculate and analyze the ship flow conditions of different schemes, and based on the premise of ship safety, introduce the flow velocity and water depth limit conditions of the ship and fish passage, so as to analyze and determine different bottom widths and bottom elevation schemes of the ship and fish passage:

[0059] To meet the requirements for the safe passage of fishing boats, the bottom width of the boat and fish passage should be greater than the width of the fishing boat and should also have a certain surplus width. At the same time, it should be ensured that the boat and fish passage can maintain a certain water depth for most of the time, and the flow velocity in the passage should not be too large. In addition, the boat and fish passage should not be set too wide and too deep to avoid excessive water loss and affect the water flow regulation effect. Considering the two schemes of single-boat passage and double-boat passage, therefore, the selected bottom width comparison schemes for the boat and fish passage are B + △B and 2B + 2△B, where B is the width of the designed passage boat for the boat and fish passage, and △B is the safety surplus. The bottom elevation of the boat and fish passage should preferably be close to the average low tide level at the passage to ensure that there is sufficient water depth in the boat and fish passage for most of the time, so as to ensure the smooth passage of passing boats and aquatic organisms. Therefore, the bottom elevation of the boat passage should be between the average low tide level -1~ +1. When comparing the schemes, several elevation values can be selected between -1~ +1, which are respectively denoted as z1, z2, ……, zn, as the comparison schemes for the bottom elevation of the boat and fish passage, and the hydrodynamic mathematical model is used to simulate and calculate different bottom width and bottom elevation schemes. By comparing the flow velocity and water depth conditions of the boat and fish passage, the bottom width and bottom elevation schemes can be determined.

[0060] In step (1), the hydrodynamic mathematical model uses Mike21 software, which is based on the incompressible Navier-Stokes equation with a uniform Reynolds value and obeys the Boussinesq assumption and the hydrostatic pressure assumption.

[0061] The two-dimensional unsteady shallow water equations are:

[0062] (Equation 1)

[0063] (Equation 2)

[0064] (Equation 3)

[0065] In the formula: is time; is the Cartesian coordinate system coordinate; is the water level; is the still water depth; is the total water depth; are respectively the velocity components in the , are respectively the flow velocities averaged based on the water depth in the x and y directions; Pa is the local atmospheric pressure; is the density of water at standard temperature and pressure; , are respectively along Shearing stress in the and are respectively the undercut stresses along the direction; is the Coriolis force coefficient, , is the angular velocity of the Earth's rotation, is the local latitude; is the acceleration due to gravity; is the density of water; are respectively the radiation stress components; is the horizontal viscous stress term, is the source-sink term, is the flow velocity of the source-sink term water flow in the direction.

[0066] In step (1), the scope of the hydrodynamic mathematical model is from the cross-sections of the controlled hydrological stations of the main and tributary rivers or downstream of the dam of the river-blocking sluice to the cross-section where the hydrological station or the tidal level station is located downstream of the confluence section of the river branches.

[0067] The hydrodynamic mathematical model uses unstructured triangular meshes. The mesh size is comprehensively determined according to the accuracy of the topographic map for modeling, the degree of terrain undulation, the dimensions of important river-related structures, etc. The mesh size should be appropriate to the interval of the elevation measurement points of the topographic map for modeling. The local meshes in areas with severe terrain undulation and important river-related structures should be encrypted, and the encrypted mesh scale should be appropriate to the scale of the river-related structures.

[0068] The roughness coefficient of the hydrodynamic mathematical model can be determined based on experience, initially given in combination with the river type, riverbed morphology, riverbed composition, distribution of river-related structures, etc., and finally determined through model verification and adjustment.

[0069] The upper boundary of the hydrodynamic mathematical model is set at the starting cross-sections of the main and tributary rivers, and the flow rate is used at the upper boundary. The lower boundary of the model is set at the cross-section where the hydrological station or the tidal level station is located downstream of the confluence section of the river branches, and the water level is used at the lower boundary.

[0070] Figure 4This is a schematic diagram of the delta area of ​​a multi-branched river estuary. After the mainstream river 1 and tributary river 2 of the river merge at the estuary, they are separated by many islands, forming three waterways, namely, Harbor 1, Harbor 2, and Harbor 3. Harbor 1, Harbor 2, and Harbor 3 are connected by connecting ports. Harbor 3 has always been the main channel for flood and tide. In history, the river has experienced a major flood of about 50 years. During this major flood, the diversion ratios of Harbor 3, Harbor 2, and Harbor 1 were about 50%, 26%, and 24%, respectively. In recent years, under the combined influence of natural hydrodynamics and human activities, the evolution of the river's estuary branches has become unbalanced, the river flow has become unstable, and the diversion ratio has become imbalanced. Branch 3 has deepened significantly as a whole, and the diversion ratio has continued to increase, increasing the burden of flood control. Branches 1 and 2 have become silted up as a whole, the river channels have shrunk, and the water volume has decreased, especially Branch 2, which has been severely silted up, resulting in poor flood discharge. Analysis and research have shown that the diversion ratio of Branch 2 in a 50-year flood is less than 8%, and it is almost dry during the dry season. From the flow path of the runoff flood in the river branches, it can be seen that the water from the upstream mainstream River 1 is diverted at the head of Island 1 and then discharged from the North Gate of the Weir and the South Gate of the Weir respectively. When the runoff flood from the North Gate of the Weir is discharged to the head of Island 2, it is divided into two branches. One branch is discharged along Branch 1, and the other branch is divided into two branches when it flows along the right side of Island 2 to the head of Branch 3. One branch enters Branch 2 and the other branch is injected into Branch 3 through the connecting port between Branch 2 and Branch 3; the runoff flood from the South Gate of the Weir merges with the water from the tributary River 2 and is all injected into Branch 3. Since the riverbed of Harbor 3 has been cut down significantly as a whole, the main river channel and water level are obviously lower than those of Harbor 1 and Harbor 2. Therefore, the upstream water can only be injected into Harbor 3 through the connecting port, and cannot flow from Harbor 3 into Harbor 2, which has aggravated the problem of insufficient water volume and hydrodynamics in Harbor 1 and Harbor 2 to a certain extent.

[0071] In order to better solve the problem that the limited amount of water released through the north gate of the river dam during the low water season is also partially injected into the harbor 3 through the connecting port, further aggravating the problem of insufficient water power in the harbor 1 and the harbor 2 (especially the harbor 2), the present invention proposes to build a water flow control and guidance structure in the connecting port between the harbor 2 and the harbor 3, such as Figure 4 The plan and section designs of the water flow control and guidance structure are as follows: Figures 1-3 As shown;

[0072] Combination Figure 4The following describes the comparison and selection of the elevation schemes of the permeable submerged dam, which is a water flow control structure at the connecting ports of the river branches 2 and 3 in the shown multi-branched river. The mean high tide level over the years at the location of the permeable submerged dam of the water flow control structure at the connecting port is 2.78 m, the mean low tide level over the years is -0.69 m, the mean tide level over the years is 1.05 m, and the riverbed elevation is -1 to -5 m. In order to enable as much upstream water as possible to enter the under-powered river branch 2 during the middle and low water periods, while avoiding the submerged dam affecting the flood discharge safety of the river channel during the large flood period and blocking the river connectivity. A total of 6 different elevation schemes of the dam crest elevation, namely 1.5 m, 1.8 m, 2.0 m, 2.2 m, 2.5 m, and 2.7 m, are set to conduct numerical simulation calculations under different flood and tidal current conditions, analyze and compare the effects of increasing the diversion ratio of river branch 2, and compare and demonstrate the elevation of the permeable submerged dam crest. The flood conditions consider the once-in-50-year large flood condition and the once-in-2-year common flood condition, and the low water tidal current condition adopts the condition of matching the mean annual flow with the corresponding tidal levels of the mean high and low tides over the years. After the implementation of different elevation schemes of the permeable submerged dam crest under each condition, the change in the diversion ratio of river branch 2 is as shown in Figure 5 shown. It can be seen from the calculation results that each scheme has little influence on the diversion ratio during the large flood period and can meet the requirement of not affecting the flood discharge safety; under the once-in-2-year common small flood condition and the tidal current condition, as the elevation of the permeable submerged dam crest increases, the diversion ratio of river branch 2 gradually increases. When the elevation of the dam crest increases to 2.5 m, the diversion ratio of river branch 2 tends to be stable, and continuing to increase the elevation of the permeable submerged dam crest has little significance for increasing the water power of river branch 2. Therefore, it is recommended that the elevation of the permeable submerged dam crest be 2.5 m.

[0073] Combined with Figure 4 The following describes the comparison and selection of the bottom width and bottom elevation schemes of the ship and fish passage, which is a water flow control structure at the connecting ports of the river branches 2 and 3 in the shown multi-branched river. Field investigations found that the ships passing through the connecting port of the river are fishing boats with a width of about 3 m and a weight of about 20 t. The mean low tide level over the years at the location of the ship and fish passage obtained by hydrodynamic mathematical model calculation is -0.69 m. The safety margin △B of the width of the ship and fish passage is taken as 2 m. Then, when a single ship passes through, the bottom width of the ship and fish passage is 5 m, and when two ships pass through, the bottom width of the ship and fish passage is 10 m. Therefore, in the comparison and selection scheme, the bottom width of the ship and fish passage is considered as 5 m and 10 m, and the bottom elevation is considered to be close to the mean low tide level of -0.69 m over the years. A total of 3 comparison and selection schemes are set. Scheme 1: The bottom width of the ship and fish passage is 10 m and the bottom elevation is 0 m; Scheme 2: The bottom width of the ship and fish passage is 5 m and the bottom elevation is 0 m; Scheme 3: The bottom width of the ship and fish passage is 5 m and the bottom elevation is -1 m.

[0074] From a safety perspective, the flow velocity of the ship and fish passage is selected not to exceed 2.5 m / s, and the water depth of the passage should not be less than 1 m as the limiting conditions for the flow velocity and water depth of the ship passage for comparison. Analyze the flow conditions of the ship and fish passage under the low-water spring tide condition and the annual average water inflow condition of each scheme, and count the duration of inappropriateness for ship passage within 24 hours of a day, as shown in Table 1. By comparison, it can be seen that for the scheme with a bottom width of 5 m and a bottom elevation of -1 m for the ship and fish passage, the water depth is greater than 1 m and the flow velocity is less than 2.5 m / s throughout 24 hours of a day under the annual average water inflow condition, and the duration of inappropriateness for ship passage under the low-water spring tide condition is about 9.75 hours, which is the best among the three schemes. Therefore, it can be determined that the recommended scheme for the ship and fish passage is a bottom width of 5 m and a bottom elevation of -1 m.

[0075] Table 1 Comparison of different ship and fish passage schemes

[0076]

[0077] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0078] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not elaborate on all the details, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the relevant technical field can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A multi-branch estuary water flow control and guidance structure, characterized by: The invention comprises a dry block stone slope protection (1) arranged on both sides of the river bank, a permeable submerged dam (2) arranged horizontally in the middle of the river, a flow-blocking dike (3) connected to the permeable submerged dam in a T-shape, and a passage for passing ships and fish (4), wherein one end of the permeable submerged dam (2) is connected to the dry block stone slope protection (1) on one side, the other end of the permeable submerged dam (2) is connected to the flow-blocking dike (3), and a passage for passing ships and fish (4) is formed between the flow-blocking dike (3) and the dry block stone slope protection (1) on the other side; The flow-isolating dike (3) comprises a first stone-casting layer (31), a first gabion stone cage protective layer (32) is arranged at the top of the first stone-casting layer (31) connected to the permeable submerged dam (2), a block stone masonry layer (33) located on the upper layer of the first stone-casting layer (31) is arranged at the bottom of the ship-passing and fish-passing passage (4), a first dry block stone slope layer (34) located between the first gabion stone cage protective layer (32) and the block stone masonry layer (33) is arranged on the side of the ship-passing and fish-passing passage (4), and a first crushed stone cushion layer (35) is arranged between the first dry block stone slope layer (34) and the first stone-casting layer (31); both ends of the flow-isolating dike (3) expand toward the river in an arc shape, so that the inlet and outlet sections of the ship-passing and fish-passing passage (4) are both open in a trumpet-shaped manner.

2. The multi-branched estuary and harbor water flow control and guidance structure according to claim 1, characterized in that: The dry block stone slope protection (1) comprises a second stone dumping layer (11), and a second crushed stone cushion layer (12) and a second dry block stone slope layer (13) are sequentially arranged above the second stone dumping layer (11).

3. The multi-branched estuary and harbor water flow control and guidance structure according to claim 1, characterized in that: Anti-collision tires (5) are evenly arranged on the slopes on both sides of the ship and fish passage (4), and navigation marks (6) for guiding ships to pass are arranged at intervals on the flow-isolating dike (3) and the dry-block stone slope protection (1).

4. The multi-branched estuary and harbor flow control and guidance structure according to claim 1, characterized in that: The permeable submerged dam (2) comprises a third stone dumping layer (21) with a composite trapezoidal cross-section, the outer sides of the inclined surfaces on both sides of the third stone dumping layer (21) are provided with alloy mesh bag stone cage protective layer (22), and the top surface of the third stone dumping layer (21) is provided with a second gabion stone cage protective layer (23).

5. The hydraulic design method for the multi-branch estuary and harbor flow control and guidance structure according to any one of claims 1 to 4, characterized in that: The steps include: (1) Establish a two-dimensional hydrodynamic mathematical model of the bifurcated river where the flow control and guidance structure is located: Collect data on river topography, geology, hydrology, riverbed, shoreline, survey and design results of flow control structures, important river-related structures, operation and management of major water projects, and related research results, and establish a two-dimensional hydrodynamic mathematical model for bifurcated rivers; (2) Conduct calibration and verification of mathematical models: The model is verified using measured hydrological data, and the verification content mainly includes the flow and diversion ratio of each port, water level, flow velocity, and flow direction; the difference between the calculated value and the measured value of each hydrological station meets the error requirements mainly by adjusting the grid file, model roughness, and initial water level field boundary; the error between the model calculated value and the measured value should meet the relevant requirements of the Technical Specifications for Simulation Tests of Water Transport Engineering (JTS-T 231-2021); (3) Determine the multi-year average high tide level and multi-year average low tide level at the location of the water flow control and diversion structure: The multi-year average high tide level and multi-year average low tide level can be determined by the statistical values ​​of the measured hydrological data of the nearby hydrological stations. When there is no hydrological station nearby or the data of the hydrological station is incomplete, it can be obtained by calculation using the hydrodynamic mathematical model. When calculating, the upper boundary of the model uses the river ecological flow or the multi-year average flow, and the lower boundary uses the tidal process lines corresponding to the multi-year average high tide level and the multi-year average low tide level of the water level station at the lower boundary of the model. (4) Formulate a comparison scheme for the elevation of the permeable submerged dam crest and determine the elevation of the permeable submerged dam crest through numerical simulation analysis: The elevation of the permeable submerged dam top will affect the water flow regulation effect. The higher the permeable submerged dam top is, the better the water flow regulation effect will be. At the same time, the permeable submerged dam should not be set too high to avoid the submerged dam affecting the safety of river flow and blocking river connectivity during major floods. For this reason, the proposed permeable submerged dam top elevation should be between the multi-year average tidal level of the dam site. and the average high tide level over the years Between the multi-year average tide level and the average high tide level over the years A number of elevation values ​​are selected, recorded as Z1, Z2, ... Zn, as the submerged dam top elevation comparison schemes, and the hydrodynamic mathematical model is used to carry out the hydrodynamic numerical simulation calculation and analysis of different submerged dam top elevation schemes to determine the recommended value of the submerged dam top elevation; (5) Using the hydrodynamic mathematical model, we carried out numerical simulation of the hydrodynamics of different bottom widths and bottom elevations of the ship and fish passages, calculated and analyzed the flow conditions of different ship and fish passages, and introduced the flow velocity and water depth restrictions of the ship and fish passages based on the premise of ship safety, so as to analyze and determine the different bottom widths and bottom elevations of the ship and fish passages: In order to meet the requirements for safe passage of fishing vessels, the bottom width of the ship and fish passage should be greater than the width of the fishing boat and should also have a certain surplus width. At the same time, it should be ensured that the ship and fish passage can maintain a certain water depth most of the time, and the flow velocity in the channel should not be too large. In addition, the ship and fish passage should not be set too wide or too deep to avoid excessive water loss affecting the water flow regulation effect; considering the two options of single-ship passage and double-ship passage, the proposed ship and fish passage bottom width ratio ratio is B+△B and 2B+2△B, B is the width of the ship and fish passage designed to pass the ship and fish passage, and △B is a safety surplus; the bottom elevation of the ship and fish passage should be close to the multi-year average low tide level of the channel to ensure that the ship and fish passage has sufficient water depth most of the time to ensure that passing ships and aquatic organisms can pass smoothly. Therefore, the bottom elevation of the ship and fish passage should be between the multi-year average low tide level and the multi-year average low tide level. -1~ +1, when comparing the options, -1~ +1, and denoted as z1, z2, ..., zn, as the comparison scheme of the bottom elevation of the ship and fish passage. The hydrodynamic mathematical model is used to simulate and calculate different bottom widths and bottom elevation schemes. The bottom width and bottom elevation scheme is determined by comparing the flow velocity and water depth conditions of the ship and fish passage.

6. The hydraulic design method for multi-branch estuary and harbor flow control and guidance structures according to claim 5, characterized in that: The hydrodynamic mathematical model in step (1) uses Mike21 software, based on the Navier-Stokes equations with incompressibility and uniform distribution of Reynolds values, and is subject to the Boussinesq assumption and the assumption of hydrostatic pressure; The two-dimensional non-steady shallow water equations are: (Formula 1); (Formula 2); (Formula 3); Where: For time; is the Cartesian coordinate system coordinate; is the water level; is the still water depth; is the total water depth; They are The velocity component in the direction; , are the average flow velocities in the x and y directions based on the water depth; Pa is the local atmospheric pressure; is the density of water at standard temperature and pressure; , Along Shear stress in the direction; , Along Bottom shear stress in direction; is the Coriolis force coefficient, , is the Earth's rotation angular velocity, is the local latitude; is the acceleration due to gravity; is the density of water; are the radiation stress components respectively; is the horizontal viscous stress term, is the source-sink term, The source-sink flow is Flow velocity in direction.

7. The hydraulic design method for multi-branch estuary and harbor flow control and guidance structures according to claim 6, characterized in that: In step (1) The scope of the hydrodynamic mathematical model is from the section of the main and tributary controlling hydrological station or the section below the dam to the section where the hydrological station or tidal station is located downstream of the branch confluence section; The hydrodynamic mathematical model adopts unstructured triangular grids. The grid size is determined comprehensively based on the accuracy of the modeled topographic map, the degree of terrain undulation, and the size of important river-related structures. The grid size should be equivalent to the interval between the elevation measurement points of the modeled topographic map. The local grids in areas with drastic terrain undulations and important river-related structures should be encrypted, and the scale of the encrypted grid should be equivalent to the scale of the river-related structures. The roughness of the hydrodynamic mathematical model is determined based on experience, and is initially given in combination with the river channel type, riverbed morphology, riverbed composition, and distribution of river-related structures, and is finally determined through model verification and adjustment; The upper boundary of the hydrodynamic mathematical model is set at the starting section of the main and tributary rivers, and the upper boundary adopts the flow rate. The lower boundary of the model is set at the section where the hydrological station or tidal station is located downstream of the confluence section of the harbor, and the lower boundary adopts the water level.

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