Silt dam erosion simulation test equipment and test method

Abstract

The invention discloses a silt dam erosion simulation test device and a test method. Relates to the technical field of silt dam test equipment. The device is characterized by comprising a cylinder assembly, a rack assembly, a soil sample placing assembly, a measuring assembly and a control display system. During a test, the method comprises the following steps: S1, preparing a soil sample; s2, placing a to-be-tested soil sample in the soil sample placing assembly; s3, adjusting the length of an axial electric pressing rod assembly until the height of the soil sample placing assembly reaches a preset height; s4, fluid is added, specifically, a water valve communicates with a water source, water is injected into the cylinder, and the fluid smoothly enters the cylinder; after the fluid is added, the water valve is closed, and the water valve is disconnected from the water source; s5, starting the test; s6, after flushing is finished, a water valve is opened, and fluid in the cylinder is discharged; and S7, after the test is completed, taking out the residual soil sample, and drying to obtain the average erosion rate.

Description

Technical Field

[0001] The present invention relates to the technical field of check dam test equipment, and more specifically, to a check dam erosion simulation test equipment and test method. Background Art

[0002] Erosion is one of the main factors for the failure and instability of check dams, and quantitatively analyzing the soil erosion process is also one of the most important challenges.

[0003] When the soil is scoured in water, as the shear force of the water flow on the soil gradually increases, the soil will be damaged. Conducting erosion tests on different types of soils to measure the shear stress, erosion-resistant flow velocity, erosion rate, etc. of the soil, and real-time recording and displaying the rotational speed, torque of the cylinder, and the change status of the soil sample surface can provide accurate erosion model parameters for the calculation of flood during dam break.

[0004] Reference 1: CN114324038A discloses an erosion measurement system and its detection method. This erosion measurement system and its detection method can measure erosion parameters such as the surface erosion area and volume of the tool material specimen after the erosion test, and evaluate the erosion situation of the tool; through the method of conducting erosion test detection and evaluation in the laboratory, the erosion situation of the tool under various working conditions can be conveniently and accurately evaluated.

[0005] Reference 2: CN112945595A discloses an experimental equipment and test method for the process of check dam break. It is mainly used to study the break law of check dams and analyze the influence of flume slope, incoming water flow, dam type, material, and water content on the break process.

[0006] In summary, there is still a lack of equipment for measuring shear stress and erosion rate during the dam break process in the existing research. Summary of the Invention

[0007] The purpose of this application is to provide a check dam erosion simulation test equipment for the deficiencies of the above-mentioned existing technologies.

[0008] Another purpose of this application is to provide a test method.

[0009] The technical solution of this application is as follows:

[0010] A check dam erosion simulation test equipment, comprising: a cylinder assembly, a frame assembly, and a soil sample placement assembly.

[0011] Among them, the cylinder assembly includes: a cylinder, a servo rotating table, and a water valve; the cylinder is fixed to the servo rotating table, the servo rotating table can drive the transparent cylinder to rotate, and a water valve is arranged on the outer shell of the cylinder;

[0012] Among them, the frame assembly includes: a cross beam, two support columns, and a base; the support columns are fixed on the upper surface of the base, and the cross beam is arranged above the base and its two ends are respectively fixed to the two support columns;

[0013] Among them, the soil sample placement assembly includes: an axial electric pressure rod assembly, a soil sample tray, an outer shielding cover, an inner shielding cover, a vertical rod, and a pull-twist sensor; the fixed end of the axial electric pressure rod assembly is fixedly connected to the cross beam, and its movable end is connected to the pull-twist sensor; the vertical rod is fixed to the middle of the soil sample tray, and a pull-twist sensor is arranged on the upper part of the vertical rod, and the pull-twist sensor is connected to the movable end of the axial electric pressure rod assembly through a manual knob;

[0014] The pull-twist sensor is used to measure the torque received by the soil sample during the scouring test and the tension of the axial electric pressure rod assembly on the vertical rod;

[0015] The soil sample tray is used to place the soil sample to be tested;

[0016] The outer shielding cover is vertically arranged and arranged on the outer circumference of the soil sample tray;

[0017] The inner shielding cover is horizontally arranged and fixed on the vertical rod; the upper surface of the inner shielding cover is flush with the upper surface of the soil sample to be tested.

[0018] Furthermore, the cylinder is made of a transparent material.

[0019] Furthermore, the frame assembly further includes: a load beam; the load beam is arranged above the cylinder and below the cross beam; the two ends of the load beam are respectively fixed to the two support columns.

[0020] Furthermore, the bottom of the inner shielding cover is connected to the upper surface of the soil sample tray, so that the soil sample to be tested is integrally in a cylindrical shape.

[0021] Furthermore, the erosion simulation test equipment for the warping dam further includes: a measurement component and a control display system; among them, the measurement component includes: an image monitoring module and a differential pressure type flow velocity measuring instrument;

[0022] The image monitoring module is used to monitor the test process in real time;

[0023] The differential pressure type flow velocity measuring instrument is used to measure the water flow velocity;

[0024] The pull-twist sensor, the image monitoring module, and the differential pressure type flow velocity measuring instrument are all electrically connected to the control display system.

[0025] A test method, which uses the aforementioned erosion simulation test equipment for the warping dam to obtain the average shear stress and the average erosion rate of the soil sample during the test process, is characterized in that it includes the following steps:

[0026] S1. Prepare a soil sample and obtain the water content w, density ρ, and mass m of the soil sample.

[0027] S2. Place the soil sample to be tested on the soil sample placement component.

[0028] S3. Adjust the length of the axial electric pressure rod component until the height of the soil sample placement component reaches a predetermined height.

[0029] S4. Add fluid: Connect the water valve to the water source, inject water into the cylinder, and make the fluid smoothly enter the cylinder. After adding the fluid, close the water valve and disconnect the water valve from the water source.

[0030] S5. Start the test: The cylinder drives the water to rotate, and the water scours the upper surface of the soil sample to be tested; the pull-twist sensor monitors the torque in real time.

[0031] S6. After the scouring is completed, open the water valve to drain the fluid in the cylinder.

[0032] S7. After the test is completed, take out the remaining soil sample and dry it to obtain the average erosion rate.

[0033] Further, step S5 further includes: Outputting the average shear stress between the soil sample and the water in real time, and the average shear stress is calculated by the following formula:

[0034]

[0035] where T represents the torque monitored in real time by the pull-twist sensor;

[0036] where R1 represents the outer radius of the soil sample;

[0037] where R0 represents the radius of the inner shielding cover.

[0038] Further, the average erosion rate E in step S7 is obtained by the following formula:

[0039]

[0040] In the formula: Δt is the test time, ρ is the density of the soil sample before the test, R1 represents the outer radius of the soil sample, R0 represents the radius of the inner shielding cover; m1 is the mass obtained after drying the remaining soil sample.

[0041] Further, in step S4, before the test starts, the height h of the top surface of the added fluid and the top surface of the inner shielding cover should satisfy:

[0042]

[0043] where ω represents the angular velocity of the cylinder, r0 is the radius of the cylinder, and g is the acceleration due to gravity.

[0044] The beneficial effects of this application are as follows:

[0045] First, the basic concept of this application is that the core components of the erosion simulation test equipment for check dams in this application include: a frame assembly, a cylinder assembly, and a soil sample placement assembly.

[0046] 1.1, The cylinder assembly is used to give the water flow an initial velocity. It is placed on the servo rotating table 16, and the servo rotating table 16 is rotatably arranged on the base 13.

[0047] 1.2, The soil sample placement assembly is used to place the soil sample to be tested. It is suspended on the cross beam by the axial electric pressure rod assembly.

[0048] 1.3, During operation, the erosion simulation test equipment for check dams in this application drives the water flow through the rotating transparent cylinder 12 to generate a shear stress acting on the cylindrical specimen to measure the anti-erosion flow velocity and torque of the material, and uses the outer shield 23 and the inner shield 21 to remove the frictional force between the soil sample and the water bodies in other directions.

[0049] Second, in this application, the fixed end of the axial electric pressure rod assembly is fixedly connected to the cross beam, and its movable end is connected to the pull-twist sensor; by the elongation and shortening of the movable end, the erosion situation of the soil sample to be tested at different water depths can be simulated.

[0050] Third, the purpose of this application is to measure the shear stress and erosion rate.

[0051] 3.1, For the shear stress, a rotating cylinder is used to drive the water flow to generate a shear stress acting on the cylindrical specimen to measure the anti-erosion flow velocity and torque of the material. When measuring the torque, the torque between the soil sample and the water flow is transmitted to the soil sample tray 22 and then from the soil sample tray to the pull-twist sensor 20, so as to measure the true shear stress of water flow erosion:

[0052]

[0053] 3.2, For the average erosion rate E,

[0054]

[0055] In the formula: Δt is the test time, ρ is the density of the soil sample before the test, R represents the outer radius of the soil sample, r represents the radius of the inner shield; m1 is the mass of the remaining soil sample after drying, m is the mass of the soil sample before the start of the test, and w is the water content before the start of the test.

[0056] Fourth, this application also proposes the necessary conditions for the fluid height during the test:

[0057]

[0058] Among them, ω represents the angular velocity of the cylinder, r0 is the radius of the cylinder, and g is the acceleration due to gravity. Description of the Drawings

[0059] The present invention will be further described in detail below with reference to the embodiments in the drawings, but it does not constitute any limitation to the present invention.

[0060] Figure 1 It is a three-dimensional structure schematic diagram of the erosion simulation test equipment for the warping dam in the first embodiment.

[0061] Figure 2 It is a three-dimensional structure schematic diagram of the erosion simulation test equipment for the warping dam in the first embodiment from another angle.

[0062] Figure 3 It is a three-dimensional structure schematic diagram of the erosion simulation test equipment for the warping dam in the first embodiment from yet another angle.

[0063] Figure 4 It is a three-dimensional structure schematic diagram of the soil sample placement component in the first embodiment.

[0064] Figure 5 : 5a is the internal structure diagram of the soil sample placement component in the first embodiment when no soil sample is placed; 5b is the internal structure diagram of the soil sample placement component in the first embodiment when a soil sample is placed.

[0065] Figure 6 It is the detail drawing of the differential pressure type flow velocity measuring instrument in the first embodiment.

[0066] Figure 7 It is the flow chart of the test method in the second embodiment.

[0067] Figure 8 It is the mechanical schematic diagram when the water in the cylinder is flowing.

[0068] Figure 9 It is the actual picture of the erosion simulation test equipment for the warping dam of the present application.

[0069] Figure 10 It is the actual picture of the soil sample placement component of the present application.

[0070] Description of the reference numerals is as follows:

[0071] 1. Control and display system;

[0072] 5. Data interface of the pull-twist sensor; 6. Transmission line for flow velocity and monitoring data;

[0073] 7. Axial electric pressure rod assembly; 8. Cross beam; 9. Support column; 10. Load beam; 11. Slide rail; 12. Transparent cylinder; 13. Base;

[0074] 14. Manual knob; 15. Telescopic arm; 16. Servo rotating table; 17. Base plate;

[0075] 18. Image monitoring module; 19. Differential pressure type flow velocity measuring instrument;

[0076] 20. Pull-torsion sensor; 21. Inner shielding cover; 22. Soil sample tray; 23. Outer shielding cover; 24. Soil sample to be tested;

[0077] 28. Total pressure contact of differential pressure sensor; 29. Differential pressure sensor; 30. Static pressure hole; 31. Pitot tube; 32. Fixed support rod; 33. Hall current sensor; 34. Magneto-sensitive angle sensor; 35. Signal wire; 36. Static pressure chamber;

[0078] 37. Water valve. Specific implementation mode

[0079] Next, the technical solution of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. It should be understood that the implementation cases described below are only part of the present invention, rather than all implementation cases. All other implementation cases obtained without creative labor based on the implementation cases in the present invention belong to the scope protected by the present invention.

[0080] <Example 1: A simulation test device for gully erosion>

[0081] A simulation test device for gully erosion includes: a frame assembly, a cylinder assembly, a soil sample placement assembly, a measurement assembly, and a control and display system 1.

[0082] As Figure 1 shown: The frame assembly includes: a cross beam 8, 2 support columns 9, a load beam 10, and a base 13; the support columns 9 are fixed on the upper surface of the base 13, and the load beam 10 and the cross beam 8 are sequentially arranged above the base 13 and both ends of them are fixed to the support columns 9.

[0083] As Figure 2 shown, the cylinder assembly includes: a transparent cylinder 12, a servo rotating table 16, a base plate 17, and a water valve 37; the transparent cylinder 12 is fixed to the servo rotating table 16, that is, when the servo rotating table 16 rotates, it drives the transparent cylinder 12 to rotate; the bottom of the servo rotating table 16 is rotatably arranged on the base plate 17, and the base plate 17 is fixed to the upper surface of the base 13 by hexagon bolts 3; the water valve 37 is arranged below the transparent cylinder 12.

[0084] As Figure 3 、 Figure 4 、 Figure 5As shown in the figure, the soil sample placement component includes: an axial electric press rod component 7, a manual knob 14, a soil sample tray 22, an outer shielding cover 23, an inner shielding cover 21, a vertical rod, and a pull-torsion sensor 20. The fixed end of the axial electric press rod component 7 is fixedly connected to the crossbeam, and its movable end is connected to the pull-torsion sensor 20; the vertical rod is fixed to the middle of the soil sample tray 22, and a pull-torsion sensor 20 is arranged at the upper part of the vertical rod. The pull-torsion sensor 20 is connected to the movable end of the axial electric press rod component 7 through the manual knob 14; the height of the soil sample to be tested in the transparent cylinder is adjusted by the axial electric press rod component 7 (since the soil samples at different heights in the transparent cylinder have different speeds, the axial electric press rod component 7 can be used to simulate the erosion test under different water flow speeds). The outer shielding cover 23 is vertically arranged and is arranged on the outer circumference of the soil sample tray 22 for limiting the soil sample and restricting the water flow. The inner shielding cover 21 is horizontally arranged and is fixed on the vertical rod. The upper surface of the inner shielding cover 21 is flush with the upper surface of the soil sample, and it is used to restrict the water flow. The soil sample placement component is placed inside the transparent cylinder 12, and the soil sample placement component does not contact the transparent cylinder 12.

[0085] The pull-torsion sensor 20 is used to measure the torque suffered by the soil sample during the erosion test. The water flow rotates and erodes at a fixed angular velocity driven by the rotation of the cylinder. The erosion flow velocities of the water flows at different radii show a linear distribution along the radius from the inside to the outside (the vertical center line of the soil sample tray 22 coincides with the vertical center line of the transparent cylinder 12). Therefore, the erosion shear stress received by the upper surface of the soil sample 24 of the ring is uneven. Thus, the data collected by the torque sensor is actually the average shear stress received by the upper surface of the ring soil sample.

[0086] In addition, the pull-torsion sensor 20 can also be used to measure the tensile force, and the measurement result can reflect the loss state of the soil sample during erosion. When the soil sample is eroded, the soil particles are subjected to the shear erosion action of the water flow and break away from the soil sample surface, reducing the weight of the soil sample directly connected to the pull-torsion sensor. At this time, the tensile stress data detected by the tensile stress sensor in real time will gradually decrease as the erosion degree increases. During the erosion test, the erosion degree of the soil sample is judged through the tensile stress change curve. When the tensile stress curve no longer decreases, it can be considered that the soil sample reaches the maximum erosion state, and the erosion should be stopped.

[0087] Such as Figure 2 、 Figure 6As shown in the figure, the measurement component includes an image monitoring module 18 and a differential pressure type flow velocity measuring instrument 19. The image monitoring module 18 (e.g., a camera) is fixed to the frame component and is used to monitor the test process in real time. The differential pressure type flow velocity measuring instrument 19 is used to measure the water flow velocity. During the test, by adjusting the position of the flow velocity instrument, the water flow velocities at different elevations are measured. The differential pressure type flow velocity measuring instrument 19 includes a pitot tube 31 and a fixed support rod 32. A differential pressure sensor 29 and a static pressure chamber 36 are sequentially arranged in the pitot tube. The fixed support rod is hollow and internally provided with a signal wire 6. The lower end of the fixed support rod is connected to the pitot tube through a rolling bearing, and a Hall current sensor 33 and a magnetic sensitive angle sensor 34 are installed at the connection. The flow velocity is measured by using the differential pressure sensor, and the flow velocity current signal is non - contactly converted and output through the Hall current sensor 33. The flow direction is measured by using the magnetic sensitive angle sensor 34.

[0088] The pull - torsion sensor 20, the image monitoring module 18, and the differential pressure type flow velocity measuring instrument 19 are all electrically connected to the control and display system 1.

[0089] The core components of the erosion simulation test device for check dams in this application include a frame component, a cylinder component, and a soil sample placement component. Among them, the cylinder component is used to give the water flow an initial velocity and is placed on the servo rotating table 16, and the servo rotating table 16 is rotatably arranged on the base 13. Among them, the soil sample placement component is used to place the soil sample to be tested and is suspended on the cross - beam through the axial electric pressure rod component.

[0090] During operation, the erosion simulation test device for check dams in this application drives the water flow through the rotation of the transparent cylinder 12 to generate shear stress acting on the cylindrical specimen to measure the erosion - resistant flow velocity and torque of the material, and uses the outer shielding cover 23 and the inner shielding cover 21 to remove the frictional force between the soil sample and the water body in other directions.

[0091] < Example 2: A test method >

[0092] < 2.1, Determination of test steps >

[0093] As Figure 7 shown, the present invention also provides a test method, which uses the erosion simulation test device for check dams in Embodiment 1 and includes the following test steps:

[0094] Step 1, pre - determine the compaction degree and water content of the soil sample, and calculate the required soil mass.

[0095] Pre - prepare a circular soil sample with a compaction degree of p. The compaction degree is defined as the ratio of the dry density of the soil body to its density. Therefore, the calculation method of the soil body compaction degree should be as shown in formula (1), and the compaction degree p is a dimensionless parameter.

[0096]

[0097] Among them, ρ d —dry density of soil sample; ρ dm —maximum dry density of soil sample.

[0098] The soil mass consists of three parts: soil particles, water in the soil, and pores in the soil. Therefore, according to the three-phase relationship of the soil mass, the dry density of the soil sample can be expressed using the water content of the soil mass:

[0099]

[0100] Among them, ρ is the density of the soil sample; w is the water content of the soil sample.

[0101] There is also the density formula:

[0102]

[0103] Among them, m is the mass of the required soil sample, and V is the volume of the soil sample. Substituting formula (2) and formula (3) into formula (1), the required mass of the soil mass can be obtained as:

[0104] m = pρ dm (1 + w)V

[0105] When preparing the sample, according to the specifications of the ring mold selected as required, the height of the soil sample is known. If the height of the soil sample is h, the volume V of the soil sample can be expressed as:

[0106]

[0107] Among them, D is the outer edge diameter of the soil sample; d is the inner edge diameter of the soil sample.

[0108] Substituting formula (5) into formula (4), it can be obtained that when using the soil sample tray to prepare the sample, if the water content of the soil mass, the height of the soil sample, and the prefabricated compaction degree are known, the mass of the soil sample to be used is:

[0109]

[0110] When preparing the sample, the soil sample tray and the mold should be assembled and fixed first, the compaction degree of the soil sample should be determined in advance, the water content of the soil mass should be measured through experiments, and the required mass of the soil mass should be calculated through formula (6).

[0111] Step 2, the soil sample placement component is used to place the soil sample to be tested.

[0112] Step 3, adjust the length of the axial electric pressing rod component 7 until the height of the soil sample placement component reaches the predetermined height.

[0113] Step 4, Fluid addition. Since a large amount of liquid is used to scour the soil in the test, the damage to the soil sample caused by the addition of the fluid should be avoided. When adding the fluid, the water valve 37 should be used to inject water so that the fluid smoothly enters the cylinder.

[0114] Step 5, Start the test. Turn on the control and display system 1, and input the loading speed and the final loading value. Open the data acquisition software, input the interval time, select the signal name, then set the save path of the data file, and then confirm; turn on the oscilloscope, click the start button after the command signal value is stable, and then quickly turn on the data acquisition software and run the function generator.

[0115] Step 6, Scouring ends. Click the "Stop" button in the function generator window, and at the same time stop the data acquisition software, turn off the hydraulic source control, and the test ends.

[0116] Step 7, Open the water valve 37 to drain the fluid in the cylinder.

[0117] Step 8, After the measurement, take out the remaining soil sample and dry it, calculate its remaining mass after scouring, and obtain the actual scouring mass and erosion rate through conversion. After the test is completed, turn off the power, turn off the microcomputer control system, unplug the power plug of the equipment, disassemble the structural system and clean it, properly place the components, screws, etc., clean the test site, and wait for the next test. Ensure that the water and electricity are cut off when leaving.

[0118] < 2.2, Determination of average shear stress >

[0119] By rotating the transparent cylinder to drive the water flow to generate a shear stress acting on the cylindrical specimen to measure the anti-scouring flow velocity and torque of the material. During the measurement process, the soil sample needs to be fixed, and the torque is obtained through the contact between the rotating cylinder and the soil sample, and then converted into shear stress. The amount of water used in this test device is limited, making the physical and chemical parameters of the fluid controllable. Undisturbed soil or remolded soil can be used, and it can also be fine-grained soil or coarse-grained soil. The outer shield and inner shield remove the frictional force between the soil sample and the water in other directions.

[0120] During the measurement process, the soil sample needs to be fixed in a ring shape on the soil sample tray. When measuring the torque, the torque between the soil sample and the water flow is transmitted to the tray and then from the soil sample tray to the pull-twist sensor, so as to measure the true shear stress of the water flow erosion.

[0121] The main purpose of the test is to measure the erosion rate of the soil, and the specific principle is as follows:

[0122] When the water flow scours the soil through rotation and contact, the torque between the soil sample and the water flow is transmitted to the tray and then from the soil sample tray to the pull-twist sensor, so as to measure the true torque of the friction between the soil sample and the water body. Finally, the torque is further converted into shear stress, and its calculation method is as follows (without considering the shear stress between the inner shield and the water):

[0123] T=τπ(R1 2 -R0 2 )

[0124] Where: R1 is the outer radius of the soil sample (inner radius of the outer shield); R0 is the radius of the inner shield; T is the torque; τ is the average shear stress acting on the surface of the soil sample.

[0125] Therefore, the shear stress corresponding to the torque and specimen size is:

[0126]

[0127] < 2.3, Determination of average erosion rate E >

[0128] The mass m1 of the sample after erosion is obtained by evaporating the water in the sample in the test box after the test and weighing it. It can be seen that the change in the mass of the sample before and after erosion is:

[0129] Δm=m-m1(1+w)

[0130] The mass of the above erosion is all lost within the height of the inner shield (in a preferred design, the bottom of the inner shield is connected to the upper surface of the soil sample tray 22, so that the soil sample to be tested is a cylindrical sample as a whole):

[0131] The average erosion rate E is:

[0132]

[0133] Where: E is the erosion rate; Δt is the test time; ρ is the soil sample density obtained before the test.

[0134] < 2.4, Initial fluid addition conditions during the test >

[0135] During the test, the cylinder drives the water flow to rotate and flush the soil sample. If the cylinder is set to rotate around its central vertical axis at a constant angular velocity, the liquid near the inner wall of the barrel will be driven to rotate first due to the viscosity of the liquid, and gradually develop toward the center. When it is finally stable, it can be considered that the cylinder and the water flow unit at any position in the cylinder rotate at the same angular velocity, and the liquid surface will appear funnel-shaped, with the middle part sunken and the surrounding parts raised. Therefore, a certain submergence depth needs to be maintained during the test to prevent the soil sample from being exposed to the air due to too little water during the test, so its submergence depth needs to be estimated.

[0136] In addition, it should be noted that: Figure 8As shown in the figure, take the lowest point of the rotated liquid surface as the coordinate origin O, with the z-axis vertically upward. According to D'Alembert's principle, consider the rotation problem of the liquid particle as an equilibrium problem. Therefore, an inertial force is added to the original acting force of the liquid particle to make it reach the equilibrium state. The magnitude of the inertial force is the product of the mass of the particle and the acceleration of the particle, and its direction is opposite to the direction of the acceleration. The actual acceleration of the liquid particle A(x, y, z) moving in uniform circular motion in the cylinder is v 2 / r, then the inertial force F is:

[0137]

[0138] In the formula, m is the mass of the liquid particle; ω is the angular velocity of the cylinder, r is the distance of the liquid particle from the z-axis. According to the Pythagorean theorem, its calculation method is

[0139] Then, for the inertial force per unit mass, the projections in the three directions of x, y, and z can be expressed as:

[0140]

[0141] Since D'Alembert's principle is used for dynamic consideration, it is considered that the liquid is in an equilibrium state at this time, so the liquid equilibrium equation should be satisfied:

[0142] dp = ρ(Xdx + Ydy + Zdz)

[0143] Substitute formula (12) into (13) to obtain the static equilibrium equation of the liquid in the cylinder:

[0144] dp = ρ(ω 2 xdx + ω 2 ydy - gdz)

[0145] Integrate both sides simultaneously, and we can get:

[0146]

[0147] Because So the above formula can be transformed into:

[0148]

[0149] According to Figure 7 As shown, the liquid pressure at the coordinate origin, that is, at (0, 0, 0), is the atmospheric pressure p a , so the integration constant C in formula (16) can be solved as C = p a .

[0150] Therefore, rewrite the formula by using the specific weight γ of the liquid (where γ = ρg), and the following formula can be obtained:

[0151]

[0152] If it is expressed using relative pressure, the above formula is further simplified as:

[0153]

[0154] If p is set as a constant, then the equation of the isobaric surface in the liquid surface can be expressed by z, that is:

[0155]

[0156] At the free liquid surface, the relative pressure is 0. Then, when the entire cylinder rotates, the equation of the formed free liquid surface is:

[0157]

[0158] Formula (20) shows that when the cylinder rotates at an angular velocity ω, the formed free liquid surface is a rotating paraboloid, and the maximum height of this paraboloid is z max = ω 2 r0 2 / 2g (r0 is the radius of the cylinder). And the volume V of the liquid above the coordinate origin should be the volume V0 of the cylinder with the height of the maximum liquid surface height minus the volume V1 of the rotating paraboloid:

[0159]

[0160] This part of the volume, if it is not rotated, is exactly the volume of a cylindrical liquid, and its height is 1 / 2 of the height of the rotating paraboloid. Therefore, when the cylinder rotates, the height of the added liquid submerging and scouring the soil sample should be at least more than half of the height of the rotating paraboloid. During the experiment, its calculation should be carried out in advance to ensure that the soil sample can be fully eroded by the water flow.

[0161] The above-mentioned embodiments are the preferred embodiments of the present invention, which are only used to conveniently illustrate the present invention and do not impose any form of limitation on the present invention. Any person with ordinary knowledge in the technical field concerned, if without departing from the technical features of the present invention, makes local modifications or equivalent embodiments by using the technical content disclosed in the present invention, and without departing from the technical feature content of the present invention, still belongs to the scope of the technical features of the present invention.

Claims

1. An erosion simulation test device for a check dam, characterized in that, Comprising: A cylinder assembly, a frame assembly, and a soil sample placement assembly; Among them, the cylinder assembly includes: a cylinder, a servo rotating table, and a water valve; the cylinder is fixed to the servo rotating table, the servo rotating table can drive the transparent cylinder to rotate, and a water valve is provided on the outer shell of the cylinder; Among them, the frame assembly includes: a cross beam, two support columns, and a base; the support columns are fixed on the upper surface of the base, the cross beam is arranged above the base and its two ends are respectively fixed to the two support columns; Among them, the soil sample placement assembly includes: an axial electric pressing rod assembly, a soil sample tray, an outer shielding cover, an inner shielding cover, a vertical rod, and a pull-torsion sensor; the fixed end of the axial electric pressing rod assembly is fixedly connected to the cross beam, and its movable end is connected to the pull-torsion sensor; the vertical rod is fixed to the middle of the soil sample tray, a pull-torsion sensor is provided on the upper part of the vertical rod, and the pull-torsion sensor is connected to the movable end of the axial electric pressing rod assembly through a manual knob; The pull-torsion sensor is used to measure the torque received by the soil sample during the scouring test and the pulling force of the axial electric pressing rod assembly on the vertical rod; The soil sample tray is used to place the soil sample to be tested; The outer shielding cover is vertically arranged and is arranged on the outer circumference of the soil sample tray; The inner shielding cover includes a horizontal plate, which is fixed to the vertical rod; the upper surface of the inner shielding cover is flush with the upper surface of the soil sample to be tested.

2. The erosion simulation test equipment for a warping dam according to claim 1, characterized in that, The cylinder is made of a transparent material.

3. An erosion simulation test device for a check dam according to claim 3, characterized in that, The frame assembly further includes: a load beam; the load beam is arranged above the cylinder and below the cross beam; the two ends of the load beam are respectively fixed to the two support columns.

4. The erosion simulation test equipment for a check dam according to claim 1, characterized in that, The bottom of the inner shielding cover is connected to the upper surface of the soil sample tray, so that the soil sample to be tested is in a cylindrical shape as a whole.

5. The warping dam erosion simulation test device according to any one of claims 1 to 4, characterized in that The erosion simulation test equipment for the warping dam also includes: a measurement component and a control display system; among them, the measurement component includes: an image monitoring module and a differential pressure type flow velocity measuring instrument; The image monitoring module is used to monitor the test process in real time; The differential pressure type flow velocity measuring instrument is used to measure the water flow velocity; The pull-torsion sensor, the image monitoring module, and the differential pressure type flow velocity measuring instrument are all electrically connected to the control display system.

6. A test method, which uses the warping dam erosion simulation test equipment described in claim 1 to obtain the average shear stress during the test process and the average erosion rate of the soil sample, is characterized in that Including the following steps: S1, Prepare the soil sample, obtain the water content w, density ρ, and soil sample mass m of the soil sample; S2, Place the soil sample to be tested in the soil sample placement assembly; S3, Adjust the length of the axial electric pressing rod assembly until the height of the soil sample placement assembly reaches the predetermined height; S4, Add fluid: Connect the water valve to the water source, inject water into the cylinder, and make the fluid smoothly enter the cylinder; after adding the fluid, close the water valve and disconnect the water valve from the water source; S5, Start the test: The cylinder drives the water to rotate, and the water scours the upper surface of the soil sample to be tested; the pull-torsion sensor monitors the torque in real time; S6, After the scouring is completed, open the water valve to drain the fluid in the cylinder; S7, After the test is completed, take out the remaining soil sample and dry it to obtain the average erosion rate.

7. The test method according to claim 6, characterized in that: Step S5 further includes: Outputting the average shear stress between the soil sample and the water in real time, and the average shear stress is calculated by the following formula: Among them, T represents the torque monitored in real time by the pull-torsion sensor; Among them, R1 represents the outer radius of the soil sample; Among them, R0 represents the radius of the inner shielding cover.

8. The test method according to claim 6, wherein: The average erosion rate E in step S7 is obtained by the following formula: In the formula: Δt is the test time, ρ is the density of the soil sample before the test, R1 represents the outer radius of the soil sample, R0 represents the radius of the inner shielding cover; m1 is the mass obtained after drying the remaining soil sample.

9. The test method according to claim 6, characterized in that: In step S4, before the test starts, the height h between the top surface of the added fluid and the top surface of the inner shielding cover should satisfy: Among them, ω represents the angular velocity of the cylinder, r0 is the radius of the cylinder, and g is the acceleration due to gravity.

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