Multi-branch estuary port branch flow control and guide structure and hydraulic design method thereof

Abstract

The invention discloses a multi-branch estuary port branch flow control and guide structure and a hydraulic design method thereof. The structure comprises dry rubble protection slopes arranged on river banks on the two sides of a river, a permeable submerged dam transversely arranged in the middle of the river, a flow separation embankment in T-shaped connection with the permeable submerged dam and a ship and fish passing channel. One end of the permeable submerged dam is connected with the dry rubble revetment on one side, the other end of the permeable submerged dam is connected with a flow separation embankment, and a ship and fish passing channel is formed between the flow separation embankment and the dry rubble revetment on the other side; the hydraulic design method comprises the following steps that 1, a bifurcated river two-dimensional hydrodynamic mathematical model where the water flow control and guide structure is located is established; 2, carrying out mathematical model calibration verification; 3, the multi-year average high tide level and the multi-year average low tide level of the position where the water flow control and guide structure is located are determined; 4, a permeable submerged dam crest elevation comparison and selection scheme is prepared, and the permeable submerged dam crest elevation is determined through numerical simulation calculation and analysis; and 5, analyzing and determining the bottom width and the bottom elevation of the ship-passing and fish-passing channel by using a hydrodynamic mathematical model.

Description

Technical Field

[0001] The invention relates to the technical field of water conservancy, and in particular to a multi-branched estuary branch water flow control and guidance structure and a hydraulic design method thereof. Background Art

[0002] Water flow, sediment movement and human activities will change the river morphology and cause river channel evolution. For bifurcated rivers, changes in the distribution of water flow and sediment often cause different rise and fall changes in each branch. Some branches may gradually erode and expand due to increased water flow, while other branches may gradually shrink due to reduced water flow. The evolution of the branch is particularly complex. When this kind of branch evolution is not suitable for the development of the national economy, it is often necessary to implement branch management projects. In order to improve the evolution relationship of the branch, the common method is to build a spur dam or a spur dam to adjust the water flow, or to implement dredging projects for the silted and declining branches. Common spur dams usually require regular maintenance. In addition, due to the complex evolution of water and sediment in bifurcated rivers, the spur dam management plan often cannot adapt well to the changes in river boundary conditions and is prone to local hydraulic scouring problems; while dredging or blasting measures often require large engineering workloads, high investment, and siltation problems. In addition, for multi-branched rivers with connecting ports between adjacent branches, in order to control and regulate the water volume and hydrodynamics between the branches, facilities such as sluice gates, dams and rubber dams are usually set up in the connecting ports of the branches. Sluice gates and dams are often expensive and complicated to operate, manage and maintain. In addition, they will block the connectivity of natural river channels, affect the upstream migration of aquatic organisms, and have a large negative impact on the ecological environment. Rubber dams are also complicated to operate, manage and maintain, and are not very suitable for large rivers with complex water flow conditions.

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

[0004] The object of the present invention is to provide a multi-branched estuary and harbor water flow control and guidance structure and a hydraulic design method thereof to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a multi-branch estuary and branch water flow control and guidance structure, comprising dry block stone slope protection arranged on both sides of the river bank, a permeable submerged dam placed horizontally in the middle of the river, a flow separation dam connected to the permeable submerged dam in a T-shape, and a passage for passing ships and fish, wherein one end of the permeable submerged dam is connected to the dry block stone slope protection on one side, the other end of the permeable submerged dam is connected to the flow separation dam, and a passage for passing ships and fish is formed between the flow separation dam and the dry block stone slope protection on the other side; The flow-isolating dike comprises a first stone dumping layer, a first gabion stone cage protective layer is arranged at the top of the first stone dumping layer connected to the permeable submerged dam position, a block stone masonry layer located on the upper layer of the first stone dumping layer is arranged at the bottom of the ship and fish passage, a first dry block stone slope layer is arranged on the side of the ship and fish passage between the first gabion stone cage protective layer and the block stone masonry layer, and a first crushed stone cushion layer is arranged between the first dry block stone slope layer and the first stone dumping layer.

[0006] Preferably, the dry block stone slope protection comprises a second stone dumping layer, and a second crushed stone cushion layer and a second dry block stone slope layer are sequentially arranged above the second stone dumping layer.

[0007] 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 the flow-isolating dike and the dry block stone slope protection.

[0008] Preferably, the permeable submerged dam includes a third stone filling layer with a composite trapezoidal section, the outside of the inclined surfaces on both sides of the third stone filling layer are provided with alloy mesh gabion protective layers, and the top surface of the third stone filling layer is provided with a second gabion stone cage protective layer.

[0009] Preferably, both ends of the flow-isolating dike expand toward the river in an arc shape, so that the inlet and outlet sections of the passage for passing ships and fish are both opened like trumpets.

[0010] Hydraulic design method for flow control and guidance structures in multi-branch estuaries and harbors: The steps include: (1) Establish a two-dimensional hydrodynamic mathematical model of the bifurcated river where the water flow control and guidance structure is located: Collect data on the river topography, geology, hydrology, riverbed, shoreline, survey and design results of the water flow control and guidance structures, important river-related structures, operation and management of major water projects and related research results, and establish a two-dimensional hydrodynamic mathematical model of the bifurcated river; (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 hydrological station data 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 corresponding tidal process lines of the multi-year average high tide level and 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 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 safety of river flood discharge 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 The average tide level over many years 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.

[0011] 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.

[0012] The scope of the hydrodynamic mathematical model in step (1) 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 of elevation measurement points in 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 can be determined based on experience, and can be initially given in combination with the river channel type, riverbed morphology, riverbed composition, and distribution of river-related structures, and can be 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.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: the multi-branch river water flow control and guidance structure proposed by the present invention is mainly suitable for multi-branch rivers with connecting ports between branches, and the outstanding feature of the structure is that the permeable submerged dam and the ship and fish passage are organically combined. Its main technical feature is that by setting a permeable submerged dam and a ship and fish passage with the function of passing ships and fish on the connecting ports between branches, on the one hand, it can achieve the regulation of small and medium water, enhance the water power of weak branches, and alleviate and reduce the siltation of weak branches. On the other hand, it can ensure the connectivity of the connecting port water flow, take into account the needs of passing ships and fish, and in addition, it can avoid adverse effects on flood discharge safety during major floods.

[0014] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0016] Figure 1 The schematic diagram of the structure of the multi-branch estuary water flow control and guidance structure of the present invention; Figure 2 It is a schematic diagram of the flow barrier and structure of the present invention; Figure 3 It is a schematic diagram of the cross section of the permeable submerged dam and the dry-built block stone slope protection structure of the present invention; Figure 4 It is a schematic diagram of the location of a water flow control and guidance structure for a multi-branched river and a branch-connected harbor of the present invention; Figure 5 This is a calculation and analysis diagram of the mathematical model for comparing the elevation of the permeable submerged dam crest of the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] See also Figure 1-3 The present invention provides a multi-branch estuary branch water flow control and guidance structure and a hydraulic design method thereof. To achieve the above-mentioned purpose, the present invention provides the following technical solution: a multi-branch estuary branch water flow control and guidance structure, comprising a dry block stone slope protection (1) arranged on both sides of the river bank, a permeable submerged dam (2) placed horizontally in the middle of the river, a flow separation dike (3) connected to the permeable submerged dam in a T-shape, and a ship passing through the water flow control and guidance structure. Fish passage (4), one end of the permeable submerged dam 2 is connected to the dry block stone slope protection 1 on one side, and the other end of the permeable submerged dam 2 is connected to the flow separation dike 3, and a boat and fish passage 4 is formed between the flow separation dike 3 and the dry block stone slope protection 1 on the other side; the dam crest width of the permeable submerged dam 2 is 3~5m, and the dam crest elevation should not be higher than the multi-year average high tide level of the dam site to avoid affecting the river connectivity and flood discharge and tide intake. The specific dam crest elevation is determined by the analysis and comparison of the hydrodynamic mathematical model. The multi-year average high tide level of the permeable submerged dam site can be obtained by statistics based on the measured data of the nearby hydrological station or determined by calculation and analysis of the hydrodynamic mathematical model. The height difference between the dam crest of the permeable submerged dam and the slope platform should be controlled at about 3m, and the upstream and downstream slope ratios are both 1:1.5. The width of the slope platform can be set to 5~10m, and the slope ratio from the slope platform to the dam foot can be 1:1.5~1:2.

[0019] The flow-isolating dike 3 includes a first stone filling layer 31, a first gabion stone cage protective layer 32 is arranged at the top of the first stone filling layer 31 connected to the permeable submerged dam 2, a block stone masonry layer 33 located on the upper layer of the first stone filling layer 31 is arranged at the bottom of the ship and fish 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 and fish 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 filling layer 31; the top width of the flow-isolating dike 3 is 3m, and the top elevation is consistent with the permeable submerged dam. The flow-isolating dike adopts a trapezoidal section, and the slope ratio on both sides is 1:1.5.

[0020] Preferably, 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 .

[0021] Preferably, 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.

[0022] Preferably, the permeable submerged dam 2 includes a third stone filling layer 21 with a composite trapezoidal section, the outside of the inclined surfaces on both sides of the third stone filling layer 21 are provided with alloy mesh stone cage protective layer 22, and the top surface of the third stone filling layer 21 is provided with a second gabion stone cage protective layer 23.

[0023] Preferably, 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 and fish passage 4 are both opened in a trumpet-shaped manner.

[0024] Hydraulic design method for flow control and guidance structures in multi-branch estuaries and harbors: The steps include: (1) Establish a two-dimensional hydrodynamic mathematical model of the bifurcated river where the water flow control and guidance structure is located: Collect data on the river topography, geology, hydrology, riverbed, shoreline, survey and design results of the water flow control and guidance structures, important river-related structures, operation and management of major water projects and related research results, and establish a two-dimensional hydrodynamic mathematical model of the bifurcated river; (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 hydrological station data 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 corresponding tidal process lines of the multi-year average high tide level and 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 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 safety of river flood discharge 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 The average tide level over many years 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.

[0025] 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.

[0026] The scope of the hydrodynamic mathematical model in step (1) 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 of elevation measurement points in 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 can be determined based on experience, and can be initially given in combination with the river channel type, riverbed morphology, riverbed composition, and distribution of river-related structures, and can be 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.

[0027] 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.

[0028] 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: Figure 1~Figure 3 As shown; Combination Figure 4The multi-branched river and the water flow control and guidance structure permeable submerged dam crest elevation schemes set in the connecting port of branch 2 and branch 3 of the river are compared and explained. The multi-year average high tide level at the permeable submerged dam of the connecting port water flow control and guidance structure is 2.78m, the multi-year average low tide level is -0.69m, the multi-year average tide level is 1.05m, and the riverbed elevation is -1~-5m. In order to make as much upstream water as possible enter the branch 2 with insufficient hydrodynamics during the mid-dry season, and at the same time avoid the submerged dam affecting the flood safety of the river channel during the flood season and blocking the connectivity of the river. A total of 6 different dam crest elevation schemes of 1.5m, 1.8m, 2.0m, 2.2m, 2.5m, and 2.7m are set to carry out numerical simulation calculations of different flood and tidal conditions, analyze and compare the effect of increasing the diversion ratio of branch 2, and compare and demonstrate the permeable submerged dam crest elevation. The flood conditions take into account the 50-year flood condition and the 2-year flood condition. The low-water tidal condition adopts the multi-year average flow to match the multi-year average high and low tide corresponding tidal process conditions. Under each condition, the change of the diversion ratio of the branch 2 after the implementation of different permeable submerged dam top elevation schemes is as follows: Figure 5 As shown in the figure, it can be seen from the calculation results that each scheme has little effect on the diversion ratio during the major flood period, and all can meet the requirement of not affecting the safety of flood discharge; under the conditions of small floods and tidal currents that occur once in two years, with the increase of the dam crest elevation, the diversion ratio of Harbor 2 gradually increases. When the dam crest elevation increases to 2.5m, the diversion ratio of Harbor 2 tends to be stable. Continuing to increase the permeable submerged dam crest elevation has little significance for increasing the water dynamics of Harbor 2. Therefore, it is recommended that the permeable submerged dam crest elevation be 2.5m.

[0029] Combination Figure 4 The following is a comparison of the bottom width and bottom elevation of the water flow control and guidance structures for the multi-branched river and the connecting port between the branch 2 and branch 3 of the river. The on-site investigation found that the ships passing through the river connecting port are fishing boats with a width of about 3m and a capacity of 20t. The hydrodynamic mathematical model calculated that the long-term average low tide level at the ship and fish passage is -0.69m. The safe margin △B of the width of the ship and fish passage is 2m. When a single ship passes, the bottom width of the ship and fish passage is 5m, and when two ships pass, the bottom width of the ship and fish passage is 10m. Therefore, in the setting of the comparison scheme, the bottom width of the ship and fish passage is considered to be 5m and 10m, and the bottom elevation is considered to be close to the long-term average low tide level of -0.69m. A total of three comparison plans are set up, Plan 1: The bottom width of the ship and fish passage is 10m and the bottom elevation is 0m; Plan 2: The bottom width of the ship and fish passage is 5m and the bottom elevation is 0m; Plan 3: The bottom width of the ship and fish passage is 5m and the bottom elevation is -1m.

[0030] From the perspective of safety, the flow velocity of the ship and fish passage is no more than 2.5m / s, and the channel water depth should not be less than 1m as the ship flow velocity and water depth restriction conditions for comparison, and the water flow conditions of the ship and fish passage under the low water and high tide conditions and the multi-year average water inflow conditions of each scheme are analyzed, and the duration of the ship not suitable for passing in 24 hours a day is counted, as shown in Table 1. By comparison, it can be seen that: for the ship and fish passage bottom width 5m, bottom elevation -1m scheme, the multi-year average water inflow conditions meet the water depth > 1m and the flow velocity is less than 2.5m / s for 24 hours a day, and the duration of the ship not suitable for passing in the low water and high tide conditions is about 9.75 hours, which is the best among the three schemes. Therefore, it can be determined that the ship and fish passage bottom width 5m and bottom elevation -1m is the recommended scheme for the ship and fish passage.

[0031] Table 1 Comparison of different ship and fish passage schemes

[0032] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0033] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only 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 dam (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 above the first stone-casting layer (31) is arranged at the bottom of the ship and fish 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 and fish 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).

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 multi-branched estuary and harbor water flow control and guidance structure according to claim 1, characterized in that: 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 and fish passage (4) are both open in a trumpet-shaped manner.

6. The hydraulic design method for the multi-branch estuary and harbor flow control and guidance structure according to any one of claims 1 to 5, 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 the river topography, geology, hydrology, riverbed, shoreline, survey and design results of the water flow control and guidance structures, important river-related structures, operation and management of major water projects and related research results, and establish a two-dimensional hydrodynamic mathematical model of the bifurcated river; (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 hydrological station data 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 corresponding tidal process lines of the multi-year average high tide level and 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 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 safety of river flood discharge 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 The average tide level over many years 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.

7. The hydraulic design method for multi-branch estuary and harbor flow control and guidance structures according to claim 6, 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 the 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.

8. The hydraulic design method for multi-branch estuary and harbor flow control and guidance structures according to claim 7, 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 of elevation measurement points in 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 can be determined based on experience, and can be initially given in combination with the river channel type, riverbed morphology, riverbed composition, and distribution of river-related structures, and can be 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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