Physical model-based method for testing scouring depth of tidal reach at downstream of Yangtze River
By establishing a physical model of the movable bed in the lower reaches of the Yangtze River, simulating the erosion test under multiple sets of hydrological conditions, the problem of difficult to predict the erosion depth of the tidal river section in the existing technology is solved, and the erosion under complex water flow conditions is achieved Accurate simulation of silt changes provides safer and more reliable technical support for tidal estuary areas.
Patent Information
- Application Number
- CN202411152729.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-21
- Publication Date
- 2024-12-20
AI Technical Summary
The prior art is difficult to accurately predict the erosion depth of tidal-sensitive river sections, especially under complex water flow conditions under the combined action of runoff and tide, which makes it difficult to reflect the real erosion and silt changes.
Using the erosion depth test method of the lower reaches of the Yangtze River based on physical models, the riverbed terrain and water flow movement under different hydrological conditions is simulated, including adjusting the roughness and particle size of the model test sand, combined with tidal control System and data collection system, conduct erosion tests under multiple sets of hydrological conditions.
It realizes accurate simulation of the effects of the combination conditions of astronomical tides and typhoons under one flood and small flow conditions, continuous long-term erosion and typical flood combination conditions, and provides safer and more reliable erosion depth prediction under actual conditions, which is applicable Tide and sediment model test in tidal estuary area.
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Figure CN119164600A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the research field of electric power engineering technology, and in particular to a scour depth test method for a tidal river section in the lower reaches of the Yangtze River based on a physical model. Background Art
[0002] When crossing a river in a new long-distance power transmission and transformation project, a river crossing channel needs to be built. The pre-buried depth of the tunnel top is an important parameter in the design of the underwater channel. The choice of line position and burial depth directly affects the project cost. Under the premise of ensuring the safety of the project, shortening the length of the shield section and reducing the burial depth as much as possible are of great significance to reducing the cost. Therefore, accurately predicting the maximum scouring depth of a river section under long-term scouring by water flow is an important measure to ensure the long-term safe operation of the project. The scouring depth is generally obtained through prototype observation, physical model, and mathematical model. Among them, the physical model proposes a model scale based on similarity theory, and the experimental phenomenon can be directly observed, so it is widely used.
[0003] At present, the physical model scour test in power engineering is generally carried out based on a typical flood process. However, when the project is located in a tidal river section, it is obviously affected by the combined effects of runoff and tides. It is difficult to reflect the actual scour and deposition changes by considering it as a single flood scour.
[0004] Therefore, this field urgently needs to develop a scour depth test method for the tidal river section of the lower reaches of the Yangtze River based on a physical model. This method can consider the impact of a single flood, the impact of the combination of astronomical tides and typhoons under small flow conditions on the project, and the impact of the combination of continuous long-term scour and typical floods. Summary of the invention
[0005] The purpose of this application is to provide a scour depth test method for the tidal river section of the lower reaches of the Yangtze River based on a physical model. This method can take into account the impact of a single flood, the impact of the combination of astronomical high tides and typhoons under small flow conditions on the project, and the impact of the combination of continuous long-term scour and typical floods.
[0006] This application provides a method for testing the scour depth of the tidal river section in the lower reaches of the Yangtze River based on a physical model, including:
[0007] Step S1: Obtain an underwater topographic map, which includes riverbed topography, bank slope topography, and levee topography:
[0008] Step S2: determining the geometric scale, water flow scale and sediment movement scale of a suitable model for establishing a moving bed physical model of the tidal river section of the lower reaches of the Yangtze River, as well as the model test sand and comprehensive roughness of the moving bed physical model according to the obtained riverbed topography, bank slope topography, levee topography and similar principles;
[0009] Step S3: establishing the moving bed physical model according to the determined geometric scale, water flow scale, sediment movement scale, model test sand, and comprehensive roughness, wherein the moving bed physical model comprises: a physical model riverbed molded by concrete for simulating the riverbed topography, the model test sand for simulating the bed sand of the tidal river section, plum blossom-shaped pebbles, plastic grass or plastic straws laid on the model test sand for simulating the comprehensive roughness, and a model measurement and control system;
[0010] Step S4: comparing the measured values of the main parameters of the tidal river section in the lower reaches of the Yangtze River with the measured values of the main parameters measured by the moving bed physical model test simulation, thereby verifying the moving bed physical model, and adjusting the roughness by adjusting the spacing between plum blossom pebbles or plastic grass during the verification process; the main parameters include the tide level, flow velocity, branch channel diversion ratio and terrain scouring and silting change of the tidal river section in the lower reaches of the Yangtze River;
[0011] Step S5: Selecting hydrological conditions, and then performing scour tests using the moving bed physical model under each selected hydrological condition to obtain scour depth, wherein the hydrological conditions are composed of three typical hydrological years and one series of years, either individually or in combination.
[0012] In another preferred embodiment, the model test sand is plastic sand.
[0013] In another preferred embodiment, the simulation range of the moving bed physical model is the tidal river section in the lower reaches of the Yangtze River.
[0014] In another preferred example, the moving bed physical model also includes a mainstream section, a tributary section, a twisted waterway, a canal, a mainstream tailgate, a tributary tailgate, a water pump, a sedimentation tank, a tailgate pool and a circulating water pool, a pump, and a water pipe.
[0015] In another preferred example, the moving bed physical model includes a twisted waterway and a water inlet flower wall arranged at the upstream inlet of the physical model, and a tail gate arranged at the downstream outlet of the physical model. A sedimentation tank, a tail gate pool, and a circulating water pool are arranged downstream of the tail gate, and the circulating water pool is connected to the twisted waterway by a pump, a water pipe, and a canal.
[0016] In another preferred example, the median particle size and gradation of the model test sand of the moving bed model are calculated and determined based on the measured prototype bed sand characteristics and median particle size of the river section, so as to select suitable model test sand; and / or the value of the comprehensive roughness of the tidal river section is determined based on the measured natural river channel roughness coefficient combined with the previous mathematical model calculation results of the engineering river section.
[0017] In another preferred example, the model measurement and control system includes a tidal control system, a model inlet flow, sand volume and tailgate water level control system, and a data acquisition system.
[0018] In another preferred embodiment, the tidal control system adopts a water pump tailgate tidal system, in which water is pumped into the physical model from the outside of the tailgate of the moving bed physical model by a water pump, and the tailgate controls the water level change of the model to simulate the tidal flow process.
[0019] In another preferred example, the model inlet flow, sand content and tailgate water level control system is used to control the inlet flow, sand content and tailgate water level of the moving bed physical model, wherein the tailgate water level refers to the water level at the outlet of the downstream section of the model.
[0020] In another preferred embodiment, the data acquisition system is used to measure water level, flow velocity, flow direction and terrain erosion and deposition changes.
[0021] In another preferred embodiment, the three typical hydrological years are 1) a hydrological year with a return period of 100 years, 2) a hydrological year with a return period of 300 years, and 3) a hydrological year with low water flow and high tide, and the hydrological year with low water flow and high tide refers to the storm surge in 2006 and the storm surge in 1997;
[0022] In step S5, a scouring test is performed in each typical hydrological year.
[0023] In another preferred example, the series of years is the series of hydrological years from 2009 to 2013 determined by analysis of measured data in the lower reaches of the Yangtze River, and the various hydrological conditions include a combination of the series of hydrological years from 2009 to 2013 and a hydrological year that occurs once in a hundred years, and a combination of the series of hydrological years from 2009 to 2013 and a hydrological year that occurs once in three hundred years.
[0024] In another preferred embodiment, step S5 also includes determining the flow rate, water level and sediment content required for the scouring test through the moving bed physical model based on the selected hydrological conditions in S5.
[0025] In another preferred embodiment, an observation section is set every 1.5m-2.0m on the moving bed physical model to observe the actual moving bed topography; and / or an observation section is set every 0.5m on the moving bed physical model near the proposed project.
[0026] In another preferred embodiment, the scour test measures the cross-sectional scour depth, starting point distance and deepest point plane swing amplitude of the observation section, and the starting point distance refers to the distance between the observation section and the north bank embankment.
[0027] In another preferred embodiment, the plane swing amplitude of the deepest point refers to the horizontal movement distance of the deepest point of the cross-section measurement point relative to the starting terrain.
[0028] In another preferred embodiment, the scour test of the moving bed physical model shows that the maximum scour depth exists under the hydrological conditions of a series of years and a hydrological year once in three hundred years.
[0029] In another preferred embodiment, the geometric scale includes a plane scale and a vertical scale.
[0030] In another preferred example, the water flow motion scale includes a flow velocity scale, a flow rate scale, and a roughness scale.
[0031] In another preferred embodiment, the sediment movement scale includes starting velocity, sedimentation similarity, bed sand particle size scale, suspended sand similarity, suspended load particle size scale, starting similarity, sediment content scale and scouring and silting time.
[0032] It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (such as embodiments) can be combined with each other to form a new or preferred technical solution. Due to space limitations, they will not be described one by one here. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. It should be understood that the drawings described below are only some implementation examples of the present invention, and ordinary technicians in this field can also obtain other implementation examples based on these drawings without paying creative work.
[0034] Figure 1 It is a schematic flow chart of a scour depth test method for a tidal river section in the lower reaches of the Yangtze River based on a physical model according to the first embodiment of the present application;
[0035] Figure 2 is a schematic diagram of the plan layout of a movable bed model according to the first embodiment of the present application;
[0036] Figure 3 is a schematic diagram of a water pump tailgate type tide generating system according to a first embodiment of the present application;
[0037] Figure 4 It is a physical model modeling site diagram according to the first embodiment of the present application;
[0038] Figure 5 It is a plane scouring and silting change diagram verified by the physical model of the first embodiment of the present application;
[0039] Figure 6 It is the test terrain after the physical model of the first embodiment of the present application has been washed by the hydrological conditions of a typical year of low water and high tide;
[0040] Figure 7 It is a test terrain after the physical model of the first embodiment of the present application is washed by the hydrological conditions of a typical year of once in a hundred years;
[0041] Figure 8 It is a test terrain after the physical model of the first embodiment of the present application has been washed by the hydrological conditions of a typical year that occurs once every three hundred years. DETAILED DESCRIPTION
[0042] Through extensive and in-depth research, the inventors have developed for the first time a scour depth test method for the tidal river section of the lower reaches of the Yangtze River based on a physical model. This method establishes a tidal sediment moving bed model (moving bed physical model), uses measured data to verify the tide level, flow velocity, and terrain scour and siltation, selects three typical hydrological years and a series of five hydrological years, a total of five groups of hydrological conditions, determines the flow, water level and sediment content, and then tests to obtain the scour depth. This test method can take into account the impact of a flood, the impact of the combination of astronomical high tides and typhoons under small flow conditions on the project, and also considers the combination of continuous long-term scour and typical floods, which is more in line with the actual situation and can cover various unfavorable situations. It can provide safer and more reliable technical support for tidal and sediment model tests in tidal estuary areas.
[0043] the term
[0044] As used herein, the term "shield segment" refers to a section or portion excavated by a shield machine (i.e., a shield excavator) during the construction of an underground tunnel;
[0045] As used herein, the term “roughness”, also known as roughness coefficient, represents the physical parameter of the roughness of the interior of a river channel or a canal;
[0046] As used herein, the term "branch flow ratio" refers to a term used to describe the flow distribution of a river or channel at a branch point. Specifically, this ratio indicates the flow ratio between the mainstream and the branch.
[0047] As used herein, the term “starting point distance” refers to the distance between the observation section and the north bank embankment;
[0048] As used herein, the term "north bank levee" refers to a long levee or dam structure on the north bank (i.e., the north side of a river or lake) of a water body such as a river or lake. Such a structure is usually built for flood control, water regulation, shoreline protection, or other water conservancy engineering purposes.
[0049] As used herein, the term "median particle size" refers to a statistic in the particle size distribution, specifically indicating that in the particle diameter sorting, 50% of the particles by mass have a particle size smaller than this value, and the other 50% of the particles by mass have a diameter greater than or equal to the D50 value. In other words, the median particle size is the particle diameter in the middle position after the particles are sorted by size.
[0050] As used herein, the term "gradation" refers to the distribution of particles of different sizes in a granular material, and describes the proportion and distribution characteristics of particles of different sizes in the material.
[0051] As used herein, the term "pipeline gallery tunnel", which is also called a pipeline gallery or pipe gallery, is an underground tunnel or structure used to centrally arrange and maintain various underground pipelines (such as electricity, communications, water pipes, HVAC, etc.).
[0052] As used herein, "water inlet wall" generally refers to a wall or structure that is arranged to make the velocity distribution of the model inlet water flow substantially similar to that of the prototype water flow.
[0053] It should be noted that in the application documents of this patent, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one" do not exclude the existence of other identical elements in the process, method, article or device including the elements. In the application documents of this patent, if it is mentioned that an action is performed according to an element, it means that the action is performed at least according to the element, which includes two situations: performing the action only according to the element, and performing the action according to the element and other elements. Expressions such as multiple, multiple, and multiple include 2, 2 times, 2 kinds, and more than 2, more than 2 times, and more than 2 kinds.
[0054] In the present invention, all directional indications (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.
[0055] This application has at least one of the following advantages:
[0056] (a) The test method of the present application establishes a physical model of the moving bed of the tidal river section in the lower reaches of the Yangtze River by simulation, thereby obtaining an accurate scour depth;
[0057] (b) The test method of the present application can consider the impact of a single flood, the impact of the combination of astronomical high tide and typhoon under small flow conditions on the project, and the impact of the combination of continuous long-term scouring and typical floods on the project. It is more in line with the actual situation and can cover various adverse conditions. Continuous long-term scouring refers to continuous water discharge, and the superposition of flow and sediment content is considered when releasing water;
[0058] (c) The test method of the present application includes tests for simulating tides and sediments, which can more accurately simulate scouring and silting conditions, and provide safer and more reliable technical support for tidal and sediment model tests in tidal estuary areas, so as to provide a reference for subsequent scouring depth simulation calculations in similar estuary areas and pipeline tunnels.
[0059] In the following description, many technical details are provided to help readers better understand the present application. However, those skilled in the art can understand that the technical solution claimed in the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.
[0060] A scour depth test method for the tidal river section of the lower Yangtze River based on a physical model
[0061] See also Figure 1 The present application provides a method for testing the scour depth of a tidal river section in the lower reaches of the Yangtze River based on a physical model, the method comprising:
[0062] Obtain underwater topographic maps, including riverbed topography, bank slope topography, levee topography, and the latest measured topography at a scale of 1:10,000 or above;
[0063] According to the similarity principle, the geometric scale, water flow scale and sediment movement scale of the appropriate model for establishing the moving bed physical model of the tidal river section of the lower reaches of the Yangtze River are determined;
[0064] The designed median particle size and gradation of the test sand are determined based on the measured prototype bed sand characteristics and median particle size calculations in the river section. Plastic sand is generally used for the test sand.
[0065] The comprehensive roughness value of the test river section is determined based on the measured roughness coefficient of the natural river channel combined with the previous mathematical model calculation results of the engineering river section. Generally, plum blossom-shaped pebbles, plastic grass or plastic straws are used to simulate the roughness.
[0066] According to the determined geometric scale, water flow scale, sediment movement scale, sand content scale, scouring and silting time, model sand, and roughness, the moving bed physical model is established, and the moving bed physical model includes: a riverbed molded with concrete to simulate the measured riverbed topography; plastic sand to simulate the bed sand of the engineering river section; plum blossom-shaped pebbles, plastic grass or plastic straws are laid on the bed sand to simulate the roughness; a model measurement and control system composed of a tidal control system, a model inlet flow, a sand volume and a tailgate water level control system, a data acquisition system, and the like;
[0067] Compare the measured values of the main parameters of the tidal river section in the lower reaches of the Yangtze River with the measured values of the main parameters measured by the moving bed physical model test simulation, so as to verify the moving bed physical model, i.e., model verification and calibration, and adjust the spacing between pebbles and plastic grass to adjust the roughness during the verification process; the main parameters include the tide level, flow velocity, branch channel diversion ratio and terrain scouring and silting change of the tidal river section in the lower reaches of the Yangtze River;
[0068] Hydrological conditions are selected, and then scour tests are carried out through the moving bed physical model under each selected hydrological condition, thereby obtaining the scour depth. The hydrological conditions are composed of three typical hydrological years and one series of years, either individually or in combination.
[0069] Preferably, in order to measure the required siltation section, an observation section is set every 1.5m-2.0m on the moving bed physical model to observe the moving bed topography; and / or intensive measurements are made near the proposed project, and an observation section is set every 0.5m on the moving bed physical model.
[0070] Model for scour depth test in the tidal section of the lower Yangtze River
[0071] The moving bed physical model comprises: a physical model riverbed made of concrete for simulating the riverbed topography, the model test sand for simulating the bed sand of the tidal river section, plum blossom-shaped pebbles, plastic grass or plastic straws laid on the model test sand for simulating the comprehensive roughness, and a model measurement and control system;
[0072] See also Figure 2 The moving bed physical model also includes a mainstream section, a tributary section, a twisted waterway, a canal, a mainstream tailgate, a tributary tailgate, a water pump, a sedimentation tank, a tailgate pool, a circulating water pool, a pump, and a water pipe.
[0073] In another preferred example, the moving bed physical model includes a twisted waterway and a water inlet wall arranged at the upstream inlet of the physical model, and a tailgate arranged at the downstream outlet of the physical model. A sedimentation tank, a tailgate pool, and a circulating water pool are arranged downstream of the tailgate, and the circulating water pool is connected to the twisted waterway by a pump, a water pipe, and a water channel. Preferably, the sedimentation tank is located downstream of the mainstream section and the direct flow section, and is used to receive the effluent from the mainstream section and the direct flow section, and the effluent includes water and sand. The sedimentation tank is in fluid communication with the circulating water pool, and the water in the circulating water pool is pumped back to the mainstream section and the direct flow section of the riverbed model through the water pipe, the water channel, and the twisted waterway by the pump. The twisted waterway is located at the upstream inlet of the riverbed model.
[0074] Preferably, the model measurement and control system includes a tidal control system, a model inlet flow, sand volume and tailgate water level control system, and a data acquisition system.
[0075] Preferably, see Figure 3 The tidal control system is used to simulate the tidal process, wherein the control of the rising and falling tides adopts a variable overflow tidal system, which is also called a water pump tailgate type. The water pump tailgate type tidal system uses a water pump to pump water from the outside of the model tailgate into the moving bed physical model. The tailgate controls the water level change of the moving bed physical model to simulate the tidal water flow process. The upstream of the moving bed physical model uses a twisted water channel to connect the water measuring weir and the model test section. The upstream adopts a large-through flow control, and the downstream south and north branches are controlled by a rectangular flat plate flip tailgate tidal device (or system) controlled by the water level to generate the tidal process.
[0076] Preferably, the model inlet flow, sand content and tailgate water level control system is used to control the inlet flow, sand content and tailgate water level of the moving bed physical model, wherein the tailgate water level refers to the water level at the outlet of the downstream section of the model.
[0077] In another preferred embodiment, the data acquisition system is used to measure water level, flow velocity, flow direction and terrain erosion and deposition changes.
[0078] In order to make the purpose, technical solution and advantages of the present invention clearer, the embodiments of the present invention are further described in detail below. It should be understood that these are only some examples that the present invention may take for the reader, but are not intended to limit the scope of the present invention.
[0079] The present application provides a method for testing the scouring depth of the tidal river section in the lower reaches of the Yangtze River based on a physical model. The method establishes a tidal sediment moving bed model (moving bed physical model), uses measured data to verify the tide level, flow velocity, and terrain scouring and silting, selects three typical hydrological years and a series of five hydrological years, a total of five groups of hydrological conditions, determines the flow, water level and sediment content, and then obtains the scouring depth through experiments. The three typical hydrological years are: (1) a hydrological year with a return period of 100 years; (2) a hydrological year with a return period of 300 years; (3) a hydrological year with low water and high tide (2006 + 1997 storm surge). The series of years selects unfavorable test conditions of high water and low sand. Specifically, according to the analysis of measured data in the lower reaches of the Yangtze River, it is determined as follows: (4) a series of hydrological years from 2009 to 2013 (a total of 5 years) + a hydrological year with a return period of 100 years; (5) a series of hydrological years from 2009 to 2013 (a total of 5 years) + a hydrological year with a return period of 300 years. The scouring depth was obtained by testing under the five water and sand conditions selected above.
[0080] As shown in Table 1, a river section in the lower reaches of the Yangtze River was selected, and the scale was determined based on geometric similarity, water flow similarity, sediment movement similarity, verification tests, etc., and a moving bed model was established. Among them, the scale of sediment content and scouring and silting time were determined based on the verification test. The simulation range of the moving bed model starts from Rengang and extends to Baimaoshawei in the south branch of the Yangtze River estuary and Niupinggang in the north branch. The total length of the main stream is about 57km. The terrain adopts the latest measured underwater topographic map. The model plane scale is 1:800, the vertical scale is 1:100, and the model is about 120m long. The model covers a large area, and the boundary conditions such as riverbed topography, suspended sediment and bed sand in the river section, and roughness are fully calibrated.
[0081] See also Figure 2-Figure 4 , Figure 2 A schematic diagram of the planar layout of a moving bed physical model according to an embodiment of the present application is shown; Figure 3 A schematic diagram of a water pump tailgate type tide generating system is shown; Figure 4 A scene diagram of a moving bed physical model according to an embodiment of the present application is shown; Figure 5 A plane scouring and silting change diagram of a moving bed physical model verification according to the first embodiment of the present application is shown;
[0082] See also Figure 2 The moving bed physical model also includes a mainstream section, a tributary section, a twisted waterway, a water channel, a mainstream tailgate, a tributary tailgate, a water pump, a sand settling tank, a tailgate pool, a circulating water pool, a pump, and a water pipe. The twisted waterway and the water inlet flower wall are arranged at the upstream inlet of the moving bed physical model, the tailgate is arranged at the downstream outlet of the moving bed physical model, and the sand settling tank, the tailgate pool, and the circulating water pool are arranged downstream of the tailgate. The circulating water pool and the twisted waterway are connected by a pump, a water pipe, and a water channel.
[0083] Table 1 Main scales of the moving bed model test
[0084]
[0085] Then, the tide level, flow velocity, and topographic scouring and silting were verified using natural measured data, and the verification results are shown in Table 2. The verification results show that the verification results are good and meet the accuracy requirements of relevant specifications.
[0086] Table 2 Comparison of tidal level characteristic values between the moving bed physical model and the prototype (unit: m)
[0087]
[0088] Table 3 Divide ratio verification in September 2014
[0089]
[0090] Table 4 Comparison between physical model verification results and actual measurements (2011.11-2014.9)
[0091]
[0092] Three typical hydrological years were selected: 1) hydrological year with a return period of 100 years; 2) hydrological year with a return period of 300 years; 3) hydrological year with small water and large tide (2006 + 1997 storm surge). The series of years selected unfavorable test conditions of large water and small sand. Specifically, according to the analysis of measured data in the lower reaches of the Yangtze River, it was determined as follows: 4) hydrological year series from 2009 to 2013 (a total of 5 years) + hydrological year with a return period of 100 years; 5) hydrological year series from 2009 to 2013 (a total of 5 years) + hydrological year with a return period of 300 years. That is, 5 hydrological conditions (or working conditions) were selected and the scouring depths of line position 1 and line position 2 (pipeline corridor section) were obtained under the selected water and sand (hydrological) conditions, as shown in Table 5. Line position 1 and line position 2 are sections where pipeline corridors may be set up. Pipeline corridors refer to underground tunnels or structures used to centrally arrange and maintain various underground pipelines (such as electricity, communications, water pipes, HVAC, etc.).
[0093] Figure 6-Figure 8 The typical end-of-year test terrain under different working conditions is shown. Figure 6 The typical year-end test terrain with low water and high tide is shown in the figure. Figure 7 The typical end-of-year test terrain that occurs once every 100 years is shown. Figure 8 The figure shows the typical end-of-year test topography with a return period of once in 300 years, where "end" refers to the test topography after scouring under specific hydrological conditions.
[0094] Table 5 The deepest point of the engineering line section, unit is m
[0095]
[0096] In addition, this project also uses a mathematical model (hereinafter referred to as the digital model) to calculate the scouring depth of the corridor section (i.e., line position 1 and line position 2). The following table records the comparison results between the physical model results and the mathematical model results.
[0097] Table 6 Comparison of physical model results and mathematical model results, unit: m
[0098] Section Name Maximum flushing range Minimum scouring elevation Deepest point plane swing Line 1 (physical model) 8.3 -63.8 170 Line 2 (digital analog) 8.51 -63.97 138 Line 1 (physical model) 9.2 -51.3 184 Line 2 (digital analog) 8.39 -50.46 210
[0099] From the comparison of the results of the physical model and the digital model, the sections of line 1 and line 2 are generally scour, and the scour and siltation properties and scour and siltation amplitudes of the physical model and the digital model are basically the same. Line 1: The maximum scour amplitude of the section under various working conditions of the physical model is about 8.3m, the lowest scour elevation is -63.8m, and the maximum plane swing amplitude at the deepest point is about 170m; the maximum scour amplitude of the section under various working conditions of the digital model is about 8.51m, the lowest scour elevation is -63.97m, and the maximum plane swing amplitude at the deepest point is about 138m.
[0100] Line 2: The maximum scour amplitude of the section under all working conditions of the physical model is about 9.2m, the minimum scour elevation is -51.3m, and the maximum plane swing amplitude at the deepest point is about 184m; the maximum scour amplitude of the section under all working conditions of the digital model is about 8.39m, the minimum scour elevation is -50.46m, and the maximum plane swing amplitude at the deepest point is about 210m.
[0101] From the comparative analysis of model verification, both the physical model and the digital model used measured data to verify the tide level, flow velocity, terrain scouring and siltation, and the results met the accuracy requirements of relevant specifications.
[0102] It can be seen that at line position 1, the lowest scour elevation (63.8m) obtained by the physical moving bed model is lower than the lowest scour elevation (63.97m) obtained by the digital model, while at line position 2, the lowest scour elevation (51.3m) obtained by the physical moving bed model is higher than the lowest scour elevation (50.46m) obtained by the digital model; at line positions 1 and 2, the plane swing amplitude of the deepest point obtained by the physical moving bed model is quite different from that obtained by the digital model.
[0103] Since the maximum scour amplitude and the maximum scour elevation are the same parameter (just a difference in expression), the plane swing amplitude affects the design of the pipeline corridor depth in the swing area. Therefore, the applicant believes that the minimum scour elevation and the plane swing amplitude at the deepest point obtained through physical modeling are more accurate and safer. In this way, accuracy and safety can be guaranteed when the power pipeline is buried, which reduces the burial depth cost and ensures safety.
[0104] The applicant also wants to emphasize that the scouring test of power engineering is generally based on a typical flood process. This project is located in a tidal river section, which is obviously affected by the combined effects of runoff and tide. It is difficult to reflect the actual changes in scouring and silting by considering a single flood scouring. According to the river channel characteristics of the river where this project is located and the flow characteristics and river conditions of the specific location of the project, the engineering design and safe operation of the facilities are comprehensively considered. The scouring test comprehensively considers the upstream water and sand conditions and the scouring and silting effects on the riverbed under the action of tides. For the first time, it is proposed to conduct an experimental study of two groups of hydrological conditions, three typical hydrological years and a series of five hydrological years. The test method of this application can not only consider the impact of a single flood, the impact of the combination of astronomical tides and typhoons under small flow conditions on the project, but also consider the impact of the combination of continuous long-term scouring and typical floods on the project. It is more in line with the actual situation and can cover various unfavorable situations. Compared with the traditional calculation method, the applicant believes that the minimum scouring elevation obtained by the physical model is more accurate and safer, so that when the power pipeline is buried deep, the design and construction safety can be guaranteed. This test method can provide a safe and reliable technical route for tidal current and sediment model tests in tidal estuary areas.
[0105] A large number of technical features are recorded in the specification of this application, which are distributed in various technical solutions. If all possible combinations of technical features of this application (i.e., technical solutions) are to be listed, the specification will be too long. In order to avoid this problem, the various technical features disclosed in the above-mentioned invention content of this application, the various technical features disclosed in the various embodiments and examples below, and the various technical features disclosed in the accompanying drawings can be freely combined with each other to form various new technical solutions (these technical solutions are all deemed to have been recorded in this specification), unless the combination of such technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed, and features C and D are equivalent technical means that play the same role. Technically, only one can be used, and it is impossible to use them at the same time. Feature E can be combined with feature C technically. Then, the solution of A+B+C+D should not be deemed to have been recorded because it is technically infeasible, and the solution of A+B+C+E should be deemed to have been recorded.
[0106] All documents mentioned in this application are considered to be included in the disclosure of this application as a whole, so that they can be used as the basis for modification when necessary. In addition, it should be understood that after reading the above disclosure of this application, those skilled in the art can make various changes or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.
Claims
1. A scour depth test method for the tidal river section of the lower reaches of the Yangtze River based on a physical model, characterized in that: include: Step S1: Obtain an underwater topographic map, which includes riverbed topography, bank slope topography, and levee topography: Step S2: determining the geometric scale, water flow scale and sediment movement scale of a suitable model for establishing a moving bed physical model of the tidal river section of the lower reaches of the Yangtze River, as well as the model test sand and comprehensive roughness of the moving bed physical model according to the obtained riverbed topography, bank slope topography, levee topography and similar principles; Step S3: establishing the moving bed physical model according to the determined geometric scale, water flow scale, sediment movement scale, model test sand, and comprehensive roughness, wherein the moving bed physical model comprises: a physical model riverbed molded by concrete for simulating the riverbed topography, the model test sand for simulating the bed sand of the tidal river section, plum blossom-shaped pebbles, plastic grass or plastic straws laid on the model test sand for simulating the comprehensive roughness, and a model measurement and control system; Step S4: comparing the measured values of the main parameters of the tidal river section in the lower reaches of the Yangtze River with the measured values of the main parameters measured by the moving bed physical model test simulation, thereby verifying the moving bed physical model, and adjusting the roughness by adjusting the spacing between plum blossom pebbles or plastic grass during the verification process; the main parameters include the tide level, flow velocity, branch channel diversion ratio and terrain scouring and silting change of the tidal river section in the lower reaches of the Yangtze River; Step S5: Selecting hydrological conditions, and then performing scour tests using the moving bed physical model under each selected hydrological condition to obtain scour depth, wherein the hydrological conditions are composed of three typical hydrological years and one series of years, either individually or in combination.
2. The scour depth test method according to claim 1, characterized in that: The median particle size and gradation of the model test sand of the moving bed model are calculated and determined based on the measured prototype bed sand characteristics and median particle size of the river section, so as to select suitable model test sand; and / or the value of the comprehensive roughness of the tidal river section is determined based on the measured natural river channel roughness coefficient combined with the previous mathematical model calculation results of the engineering river section.
3. The scour depth test method according to claim 2, characterized in that: The model measurement and control system includes a tidal control system, a model inlet flow, a sand volume and a tailgate water level control system, and a data acquisition system.
4. The scour depth test method according to claim 3, characterized in that: The three typical hydrological years are 1) a hydrological year with a return period of 100 years, 2) a hydrological year with a return period of 300 years, and 3) a hydrological year with low water flow and high tides. The hydrological year with low water flow and high tides refers to the storm surge in 2006 and the storm surge in 1997. In step S5, a scouring test is performed in each typical hydrological year.
5. The scour depth test method according to claim 4, characterized in that: The series of years are the series of hydrological years from 2009 to 2013 determined by analysis of measured data in the lower reaches of the Yangtze River. The various hydrological conditions include a combination of the series of hydrological years from 2009 to 2013 and a hydrological year that returns once in a hundred years, and a combination of the series of hydrological years from 2009 to 2013 and a hydrological year that returns once in three hundred years.
6. The scour depth test method according to claim 5, characterized in that: The step S5 also includes determining the flow rate, water level and sediment content required for the scouring test through the moving bed physical model based on the selected hydrological conditions in S5.
7. The scour depth test method according to claim 6, characterized in that: An observation section is set every 1.5m-2.0m on the moving bed physical model to observe the real moving bed topography; and / or an observation section is set every 0.5m on the moving bed physical model near the proposed project.
8. The scour depth test method according to claim 7, characterized in that: The scour test measures the cross-sectional scour depth, starting point distance and deepest point plane swing amplitude of the observation section, wherein the starting point distance refers to the distance between the observation section and the north bank embankment.
9. The scour depth test method according to any one of claims 1 to 8, characterized in that: The scouring test of the moving bed physical model shows that the maximum scouring depth exists under the hydrological conditions of a series of years and a hydrological year of once in three hundred years.
10. The scour depth test method according to any one of claims 1 to 8, characterized in that: The sediment movement scale includes starting flow velocity, sedimentation similarity, bed sand particle size scale, suspended sediment similarity, suspended load particle size scale, starting similarity, sediment content scale and scouring and silting time.