A simulated river or lake bottom sand environment water tank test device and a preparation method thereof

Abstract

The application discloses a kind of simulation river or lake bottom sand environment water tank test device and preparation method, comprising: test water tank 1 and its inside from bottom to top sequentially arranged four layers structure of test bottom sand layer 2, geotextile layer 3, coarse sand layer 4, vacuum sealing membrane layer 6, and vacuum tube 5 of the coarse sand layer 4 layer being set in the gas extraction, the air pipe 7 in the upper portion of the vacuum sealing membrane layer 6 with the gas extraction vacuum tube being communicated, the air pipe is sequentially connected water gas separator 12, vacuum air pump 16;The gas extraction vacuum tube 5 is evenly opened multiple through holes (51) on pipe wall, and it is wrapped geotextile filtration on pipe wall.The application is estimated thickness by calculation, using vacuum preloading mode, to test soil body to apply vacuum pressure, increase the principal stress difference, so that it reaches the basic mechanical properties such as test requirement's pore ratio, yield stress, increases test variable, facilitate subsequent test simulation.

Description

Technical Field

[0001] This invention belongs to the technical field of sediment deposition test model design, and relates to the initial substrate environment simulation and shaping technology for silty viscous sediment flume tests. Specifically, it provides a flume test device and preparation method for simulating the sediment environment of river or lake bottoms. Background Technology

[0002] In experiments studying the evolution of river (lake) bed morphology, sediment transport patterns, and sediment deposition characteristics in urban river (lake) basins, the sediment bed surface is required as the initial condition. Unlike non-cohesive sediment beds, which only require a flat initial state, cohesive sediment experiments also need to consider factors such as sand porosity, water content, density, degree of consolidation, and yield stress as experimental variables. Furthermore, the transportation and laying processes during soil sampling from the target watershed disturb the soil to varying degrees, leading to a decrease in its mechanical properties. This makes it difficult to simulate the actual river (lake) sediment environment in flume experiments.

[0003] Therefore, this invention applies vacuum pressure to the test soil through vacuum preloading, which consolidates and drains the soil, increases the principal stress on the soil, and increases the yield strength during the test, so as to achieve the basic mechanical properties required by the test and more accurately simulate the bottom sand environment of the flume test. Summary of the Invention

[0004] This invention provides a flume test apparatus and preparation method for simulating the sediment environment of rivers or lakes. Its purpose is to create a sediment environment that can simulate the cross-sectional characteristics of riverbeds and lake bottoms and provide the same physical and mechanical properties as real riverbeds and lake bottoms before simulating the sedimentation characteristics of rivers and lakes, thereby more accurately simulating the sediment environment of flume tests.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A flume test device simulating the environment of river or lake bottom sand is characterized by comprising: a test flume 1 and a four-layer structure arranged from bottom to top within it, consisting of a test bottom sand layer 2, a geotextile layer 3, a coarse sand layer 4, and a vacuum sealing membrane layer 6; an air extraction vacuum pipe 5 disposed in the coarse sand layer 4; and a ventilation pipe 7 on the upper part of the vacuum sealing membrane layer 6 that communicates with the air extraction vacuum pipe; the ventilation pipe is sequentially connected to a water-air separator 12 and a vacuum pump 16; the air extraction vacuum pipe 5 has multiple permeable small holes 51 evenly opened on its pipe wall, and the pipe wall is wrapped with geotextile for filtration.

[0007] The simulated river or lake bottom sand environment flume test device is described above, wherein a plurality of the small holes 51 are arranged in a quincunx pattern with a spacing of 20-30 mm and a hole diameter of 1-5 mm.

[0008] The aforementioned simulated river or lake bottom sediment environment water tank test device, wherein the test water tank 1 is an ordinary tempered glass water tank, including an external steel frame 101 and an internal tempered glass 102, the tempered glass thickness is 10-15mm; the overall water tank length is 8-20m, width is 0.6-1.2m, and height is 0.5-1.0m.

[0009] The aforementioned flume test apparatus for simulating river or lake bottom sediment environments comprises a test bottom sand layer 2 entirely covered with test bottom sand, which is sediment obtained from soil samples taken from the river area of ​​the target river or lake to be simulated; and a geotextile layer 3, which is a geotextile fabric laid on top of the test bottom sand layer, wherein the geotextile is a plastic flat yarn woven geotextile with a density of 100-300 g / m³. 2 The coarse sand layer 4 is made of ordinary manufactured sand laid on the geotextile layer 3, with a particle diameter of 1mm to 0.5mm; the vacuum sealing membrane layer 6 is made of purchased ordinary PVC vacuum pre-compression membrane that is heat-synthesized and spliced, and is laid on the coarse sand layer 4, with a membrane thickness of 0.12 to 0.16cm; the ventilation pipe 7 is laid on top of the vacuum sealing membrane layer.

[0010] The simulated river or lake bottom sediment environment flume test device includes a vacuum tube 5 laid along the length of the test flume and multiple parallel tubes laid side-by-side along the width of the test flume. The ventilation pipe 7 includes a horizontal ventilation pipe 71 and a ventilation conduit 72. Multiple short ventilation pipes are connected in series along the width of the test flume to form a single horizontal ventilation pipe 71, which is then connected to each of the vacuum tubes 5 via a tee 9 or elbow 8 installed on it. The horizontal ventilation pipe is connected to the ventilation conduit 72 via a tee. The ventilation conduit is connected to the water outlet of the flume. The water-air separator 12 is connected to the water-air separator at its end. The water-air separator is provided with a water outlet 13, a water-air inlet 14, and an air outlet 15. The end of the air outlet 12 is inserted into the liquid inside the water-air separator from the water-air inlet 14. The air outlet 15 is provided with an air outlet 73 connected to a vacuum pump 16. The vacuum pipe 5, the air outlet 72, and the air outlet 73 are all ordinary PE pipes with a diameter of φ30mm. A vacuum pressure gauge 10 is provided on the air outlet 72, and an air valve 11 is provided on the air outlet 73.

[0011] The simulated river or lake bottom sediment environment flume test device includes a vacuum pressure gauge 10, which is a common YZ-40 vacuum pressure gauge with a measurement range of -0.1 to 0.15 MPa and an accuracy class of 1.5 to 2.5; an air valve 11 made of 304 stainless steel with the same diameter as the air vent pipe; and a water-air separator 12 with a height of 1 m and a diameter of 800 mm, which is a sealed cylinder made of 10 mm thick acrylic sheet.

[0012] A method for preparing a flume test apparatus simulating river or lake bottom sediment environment, comprising the apparatus, characterized in that it includes the preliminary calculation of the test bottom sediment thickness, comprising the following steps:

[0013] Step 1: By studying the properties of the bottom sediment of the target river (lake), determine the required water content w0, density ρ0, and particle density ρ of the target soil for the experimental bottom sediment environment. s And calculate the target soil void ratio e0:

[0014]

[0015] Step 2: Sample the target river and test the soil density ρ after sampling. i Moisture content w i and soil particle density ρ si The initial void ratio e for constructing soil in a bottom sand environment was obtained. i :

[0016]

[0017] Step 3: The soil in Step 2 needs to undergo a compression consolidation process to achieve the target soil void ratio in Step 1 through consolidation and drainage.

[0018] Assuming that the soil is compressed under lateral confinement, the degree of compression consolidation can be determined by only considering the change in soil height.

[0019] Therefore, assuming a bottom sand layer height of D is required for the test, an initial soil sample of height d needs to be laid:

[0020]

[0021] The method for preparing a flume test device simulating river or lake bottom sediment environment includes the following construction steps:

[0022] Step 1: After taking the bottom sand of the simulated target river or lake, spread it evenly in the test water tank. The spreading height d is the calculated height, which constitutes the test bottom sand layer 2.

[0023] Step 2: Lay a layer of geotextile on top of the prepared test sand layer 2. The function of the geotextile layer is to filter the mud and sand and drain the water.

[0024] Step 3: First, lay a 1-5cm thick layer of coarse sand on the geotextile layer, and then set up the vacuum pipes. The center-to-center distance between each vacuum pipe 5 is 30cm-50cm, and the minimum distance between the vacuum pipe and the water tank wall is 5cm to ensure the influence range and extraction efficiency of the vacuum pipes. After the vacuum pipes are set up, cover them with coarse sand evenly until the coarse sand is 3-5cm above the top of the vacuum pipes, forming the coarse sand layer 4. The vacuum pipes are connected to the ventilation pipes using tees and elbows, and the ventilation pipes are connected to the outside of the water tank and connected to the water-air separator.

[0025] Step 4: Lay the vacuum sealing membrane layer 6 and vacuum air pressure pipeline on the coarse sand layer 4. The vacuum extraction pipe 5 passes through the air vent pipe and extends out of the vacuum sealing membrane, and is glued to ensure a tight connection with the vacuum sealing membrane to prevent air leakage. When connecting the vacuum sealing membrane to the water tank, the vacuum sealing membrane needs to be buried in the silty and sticky mud and sand layer. At the same time, the upper part of the vacuum sealing membrane at the junction with the water tank is also covered with sticky mud and sand to achieve a sealing effect.

[0026] Step 5: Connect the ventilation line to the vacuum pressure gauge and the water-air separator. Connect the ventilation line to the air valve and the vacuum pump to ensure that the water in the water tank is discharged into the water-air separator and does not enter the vacuum pump during the pumping process.

[0027] Step Six: Open the air valve and vacuum pump, and continue pumping air until the vacuum pressure stabilizes at -85kPa to -200kPa. Observe the liquid level in the water-air separator and drain the water in time. When the water flow is small and the pressure stabilizes for a long time, you can close the air valve and vacuum pump, observe the vacuum pressure gauge, and maintain the internal vacuum. When the vacuum drops, you can open the air valve and vacuum pump again to restore the original vacuum.

[0028] Step 7: Measure the height of the bottom sand layer after compression until the required test height D is reached. If the required test height cannot be reached, continue with Step 6 above.

[0029] Step 8: Take soil samples from the bottom sand layer of the test section to determine its density, water content, and yield stress, and verify whether the bottom sand environment meets the test requirements, that is, whether it meets the target soil water content w0, density ρ0, and soil particle density ρ s If the requirements are met, continue with the subsequent steps of the flume test. If the requirements are not met, repeat steps four to seven until the soil sample in the test section meets the requirements of the flume test.

[0030] The beneficial effects of this invention are:

[0031] This invention simulates river and lake sedimentation, creating a sediment environment that not only mimics the cross-sectional characteristics of riverbeds and lake bottoms but also provides the same physical and mechanical properties as real riverbeds and lakebeds, thus more accurately simulating the sediment environment in flume experiments. Unlike traditional sedimentation experiments where the initial state of the sediment environment only requires flatness, this invention considers factors such as sediment porosity, water content, density, degree of consolidation, and yield stress, increasing the variables and methods in the experimental research process, and more accurately and realistically simulating the bed characteristics and sediment properties of urban river basins such as rivers and lakes. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0033] Figure 2 This is a partial top view of the water tank of the present invention;

[0034] Figure 3 This is a schematic diagram of the vacuum tube structure.

[0035] Figure 4 This is a schematic diagram of a water-air separator.

[0036] Explanation of the attached drawing numbers:

[0037] 1. Test water tank, 101. External steel frame, 102. Internal tempered glass, 2. Test bottom sand layer, 21. Cohesive mud and sand, 3. Geotextile layer, 4. Coarse sand layer, 5. Vacuum pipe, 51. Small hole, 6. Vacuum sealing membrane layer, 7. Ventilation pipe, 71. Horizontal ventilation pipe, 72. Ventilation pipeline, 73. Ventilation pipeline I, 8. Elbow, 9. Tee, 10. Vacuum pressure gauge, 11. Air valve, 12. Water-air separator, 13. Water outlet, 14. Water-air inlet, 15. Air outlet, 16. Vacuum pump; Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be explained and described below with reference to the accompanying drawings. However, the following embodiments are only preferred embodiments of the present invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments in the implementation methods without creative effort are all within the protection scope of the present invention.

[0039] See Figure 1-4As shown, the present invention provides a simulated river or lake bottom sand environment flume test device, comprising: a test flume 1 and a four-layer structure arranged from bottom to top within it: a test bottom sand layer 2, a geotextile layer 3, a coarse sand layer 4, and a vacuum sealing membrane layer 6; an air extraction vacuum pipe 5 disposed in the coarse sand layer 4; and a ventilation pipe 7 on the upper part of the vacuum sealing membrane layer 6 that communicates with the air extraction vacuum pipe. The ventilation pipe is sequentially connected to a water-air separator 12 and a vacuum pump 16. The air extraction vacuum pipe 5 has multiple permeable small holes 51 evenly opened on its pipe wall, and geotextile is wrapped around the pipe wall for filtration, so as to achieve the effect of air extraction, filtration, and drainage.

[0040] See Figure 3 As shown, in the simulated river or lake bottom sand environment flume test device, a plurality of small holes 51 are arranged in a quincunx pattern, preferably with a spacing of 20-30 mm and a hole diameter of 1-5 mm.

[0041] See Figure 1 As shown, the simulated river or lake bottom sediment environment water tank test device, wherein the test water tank 1 is an ordinary tempered glass water tank, including an external steel frame 101 and an internal tempered glass 102. The steel frame structure plays a supporting role for the glass, and the tempered glass thickness is preferably 10-15mm; the overall water tank length is 8-20m, width is 0.6-1.2m, and height is 0.5-1.0m.

[0042] The aforementioned flume test apparatus for simulating river or lake bottom sediment environments comprises a test bottom sand layer 2 entirely covered with test bottom sand, which is sediment obtained from soil samples taken from the river area of ​​the target river or lake to be simulated; and a geotextile layer 3, which is a geotextile fabric laid on top of the test bottom sand layer, wherein the geotextile is a plastic flat yarn woven geotextile with a density of 100-300 g / m³. 2 The coarse sand layer 4 is made of ordinary manufactured sand laid on the geotextile layer 3, with a particle diameter of 1mm to 0.5mm. The vacuum sealing membrane layer 6 is made of purchased ordinary PVC vacuum pre-compression membrane that is heat-synthesized and spliced ​​together, and is laid on the coarse sand layer 4. The membrane thickness is 0.12 to 0.16cm, and it has good ductility and impermeability. The ventilation pipe 7 is laid on top of the vacuum sealing membrane layer.

[0043] See Figure 1 , 2As shown, a simulated river or lake bottom sediment environment flume test device is described, wherein the vacuum tube 5 is laid along the length of the test flume and multiple tubes are laid parallel to each other along the width of the test flume; the venting pipe 7 includes a horizontal venting pipe 71 and a venting pipeline 72, multiple sections of the short venting pipes are connected in series along the width of the test flume to form a single horizontal venting pipe 71, and each of the vacuum tubes 5 is connected to it via a tee 9 or an elbow 8 installed on it; the horizontal venting pipe is connected to the venting pipeline 72 via a tee, and water exits from the venting pipeline. The tank is connected to the water-air separator 12, and the end of the vent pipe is connected to the water-air separator. The water-air separator is provided with a water outlet 13, a water-air inlet 14, and an air outlet 15. The end of the vent pipe is inserted into the liquid inside the water-air separator from the water-air inlet 14. The air outlet 15 is provided with a vent pipe 73 connected to a vacuum pump 16. The vacuum pipe 5, the vent pipe 7, and the vent pipe 73 are all ordinary PE pipes with a diameter of φ30mm. A vacuum pressure gauge 10 is provided on the vent pipe 72, and an air valve 11 is provided on the vent pipe 73.

[0044] The simulated river or lake bottom sediment environment flume test device includes the following: the vacuum pressure gauge 10 is a standard YZ-40 vacuum pressure gauge with a measurement range of -0.1 to 0.15 MPa and an accuracy class of 1.5 to 2.5; the air valve 11 is made of 304 stainless steel, with the same diameter as the vent pipe, and can control the gas inlet and outlet; the water-air separator 12 is 1 m high and 800 mm in diameter, and is a sealed cylinder made of 10 mm thick acrylic sheet to ensure visibility inside the separator; the water outlet 13 is equipped with a switch, which is opened to release water when the liquid level in the water-air separator 12 is close to the air outlet 15; the vacuum pump 16 is a standard piston vacuum pump with a flow rate of 30 to 60 L / min and an ultimate vacuum degree of -85 to -200 kPa.

[0045] The present invention discloses a method for preparing a flume test device for simulating river or lake sediment environments, comprising the aforementioned flume test device for simulating river or lake sediment environments, wherein the method includes the preliminary calculation of the test sediment thickness, comprising the following steps:

[0046] Step 1: By studying the properties of the bottom sediment of the target river (lake), determine the required water content w0, density ρ0, and particle density ρ of the target soil for the experimental bottom sediment environment. s And calculate the target soil void ratio e0:

[0047]

[0048] Step 2: Sample the target river and test the soil density ρ after sampling. i Moisture content wi and soil particle density ρ si The initial void ratio e for constructing soil in a bottom sand environment was obtained. i :

[0049]

[0050] Step 3: The soil in Step 2 needs to undergo a compression consolidation process to achieve the target soil void ratio in Step 1 through consolidation and drainage.

[0051] Assuming that the soil is compressed under lateral confinement, the degree of compression consolidation can be determined by only considering the change in soil height.

[0052] Therefore, assuming a bottom sand layer height of D is required for the test, an initial soil sample of height d needs to be laid:

[0053]

[0054] The method for preparing a flume test device simulating river or lake bottom sediment environment includes the following construction steps:

[0055] Step 1: After taking the bottom sand of the simulated target river or lake, spread it evenly in the test water tank. The spreading height d is the calculated height, which constitutes the test bottom sand layer 2.

[0056] Step 2: Lay a layer of geotextile on top of the prepared test sand layer 2. The function of the geotextile layer is to filter the mud and sand and drain the water.

[0057] Step 3: First, lay a 1-5cm thick layer of coarse sand on the geotextile layer, and then set up the vacuum pipes. The center-to-center distance between each vacuum pipe 5 is 30cm-50cm, and the minimum distance between the vacuum pipe and the wall of the water tank is 5cm to ensure the influence range and extraction efficiency of the vacuum pipes. After the vacuum pipes are set up, cover them with coarse sand evenly until the coarse sand is 3-5cm above the top of the vacuum pipes, forming the coarse sand layer 4. The vacuum pipes are connected to the ventilation pipes using tees and elbows, and the ventilation pipes are connected to the outside of the water tank and connected to the water-air separator.

[0058] Step 4: Lay vacuum compressed air pipes and a vacuum sealing membrane layer 6 on the coarse sand layer 4. The vacuum extraction pipe 5 passes through the vent pipe and extends out of the vacuum sealing membrane, and is glued to ensure a tight connection with the vacuum sealing membrane to prevent air leakage. When connecting the vacuum sealing membrane to the water tank, it needs to be buried in a layer of silty, sticky mud and sand. Simultaneously, the upper part of the vacuum sealing membrane at the junction with the water tank is also covered with sticky mud and sand 21 to achieve a sealing effect. In simpler terms, first bury the sealing membrane in the mud and sand, and then, to ensure a seal, cover it with a layer of mud.

[0059] Step 5: Connect the ventilation line to the vacuum pressure gauge and the water-air separator. Connect the ventilation line to the air valve and the vacuum pump to ensure that the water in the water tank is discharged into the water-air separator and does not enter the vacuum pump during the pumping process.

[0060] Step Six: Open the air valve and vacuum pump, and continue pumping air until the vacuum pressure stabilizes at -85kPa to -200kPa. Observe the liquid level in the water-air separator and drain the water in time. When the water flow is small and the pressure stabilizes for a long time, you can close the air valve and vacuum pump, observe the vacuum pressure gauge, and maintain the internal vacuum. When the vacuum drops, you can open the air valve and vacuum pump again to restore the original vacuum.

[0061] Step 7: Measure the height of the bottom sand layer after compression until the required test height D is reached. If the required test height cannot be reached, continue with Step 6 above.

[0062] Step 8: Take soil samples from the bottom sand layer of the test section to determine its density, water content, and yield stress, and verify whether the bottom sand environment meets the test requirements, that is, whether it meets the target soil water content w0, density ρ0, and soil particle density ρ s If the requirements are met, continue with the subsequent steps of the flume test. If the requirements are not met, repeat steps four to seven until the soil sample in the test section meets the requirements of the flume test.

[0063] The present invention will be further described in summary as follows:

[0064] The test water tank 1 in the device is a long glass water tank. The glass is ordinary tempered glass with a thickness of 10-15mm. The length of the water tank is 8-20m, the width is 0.6-1.2m, and the height is 0.5-1.0m. This material is used for siltation model tests. The test bottom sand layer 2 can be silt obtained from soil samples taken from inland river basins such as simulated target rivers and lakes. The geotextile layer 3 is a permeable geosynthetic material made of synthetic fibers through needle punching or weaving, with a width of 1-3 meters and a length of 12-17 meters. After the test bottom sand layer 2 is laid, it is placed on top of the bottom sand. If the length and width are insufficient, they can be sewn together to serve as a filter for water and to prevent siltation. The coarse sand layer 4 is ordinary manufactured sand with a particle diameter of 1-0.5 mm. The vacuum extraction pipe 5 is modified from a φ30 ordinary PE pipe. Small holes with a diameter of 1-5 mm are evenly opened on the wall of the PE pipe in a staggered pattern with a spacing of 20-30 mm. The geotextile layer is then wrapped around the pipe to achieve the effect of air extraction, filtration, and drainage. The vacuum sealing membrane layer 6 is an ordinary PVC vacuum pre-compression membrane that can be thermally synthesized and spliced. It has a thickness of 0.12-0.16 cm and good ductility and impermeability. The vent pipe 7 is a φ30 PE pipe, one end of which connects to the vacuum pipe 5 via an elbow 8 and a tee 9; the other end is connected to a vacuum pressure gauge 10, a gas valve 11, a water-gas separator 12, and a vacuum pump 16. The vacuum pressure gauge 10 is a standard YZ-40 vacuum pressure gauge with a measuring range of -0.1 to 0.15 MPa and an accuracy class of 1.5 to 2.5. The gas valve 11 is made of 304 stainless steel, with the same diameter as the vent pipe, and controls the gas flow. See also... Figure 4 As shown, the water-air separator 12 is 1m high and 800mm in diameter, and is a sealed cylinder made of 10mm thick acrylic sheet to ensure visibility inside the separator. The water-air separator 12 has three interfaces: a water outlet 13, a water-air inlet 14, and an air outlet 15. The water-air inlet 14 is connected to a vacuum pipe via a vent pipe, and the air outlet 15 is connected to a valve 11 and a vacuum pump 16 via a vent pipe. The water outlet 13 is equipped with a switch; when the water level inside the water-air separator 12 approaches the air outlet 15, the switch is opened to release water. The vacuum pump 16 is a standard piston vacuum pump with a flow rate of 30-60L / min and an ultimate vacuum of -85 to -200kPa.

[0065] Example 1

[0066] See Figures 1-2 To address the need for a suitable bottom sand environment in flume experiments to simulate the characteristics of sediment lifting and settling, and to simultaneously mimic the characteristics of bottom sand at different sedimentation times, this invention provides a method for constructing a bottom sand environment using a vacuum plastic film consolidation and drainage system within the flume. The method includes the following steps:

[0067] 1. Calculation

[0068] The moisture content of the target bottom sand was determined to be w0 = 65.3%, density ρ0 = 1.479 g / cm3, and soil particle density ρ. s =2.675 / cm3, and calculate the void ratio e0 of the target soil:

[0069]

[0070] After collecting soil samples from the target river, the soil density ρ was measured. i =1.389 g / cm3, moisture content w i =65.3%, soil particle density ρ si =2.675 / cm3, the void ratio e of the disturbed soil is obtained. i :

[0071]

[0072] Soil requires a compression consolidation process to achieve the target void ratio through consolidation and drainage. Assuming the soil is under laterally confined compression, only the change in soil height needs to be considered to determine the degree of compression consolidation. Therefore, assuming a bottom sand environment with a required test height of 30cm, a soil sample of height d needs to be laid out, then:

[0073]

[0074]

[0075] 2. Preparation of the water tank:

[0076] Step 1: After taking the bottom sand of the simulated target river, spread it evenly in the test water tank. The dimensions of the test water tank are 12m long × 1m wide × 1m high, and the bottom sand is laid at a height of d = 32cm.

[0077] Step 2: Lay a layer of geotextile on top of the laid cohesive mud and sand. The function of the geotextile layer is to filter the mud and sand and drain water.

[0078] Step 3: As Figure 1 , 2 As shown, a 1cm thick layer of coarse sand is laid, and eight pipes are installed to form four vacuum extraction pipes. Each vacuum pipe is 5.5m long and 30mm in diameter. Two sections of the vacuum pipe can be connected via a tee to form a total pipe length of 11.9m. The minimum distance between each end of the vacuum pipe and the ends of the water tank is 5cm. The center-to-center distance between adjacent vacuum pipes is 30cm, and the distance between the vacuum pipe and the water tank wall is 5cm to ensure the effective range and efficiency of the vacuum extraction. After the vacuum pipes are installed, they are evenly covered with coarse sand until the sand covers the top of the vacuum pipes by 5cm. The vacuum pipes are connected to a vent pipe via a tee and elbow, and the vent pipe extends outside the water tank and connects to the water-air separator.

[0079] Step 4: Lay the vacuum air pressure pipeline and vacuum membrane (i.e., vacuum sealing membrane layer 6). The vacuum pipe passes through the vent pipe and finally exits the vacuum membrane, and is glued to ensure a tight connection with the vacuum membrane to prevent air leakage. When connecting the vacuum membrane to the water tank, it needs to be buried in a layer of silty, sticky mud and sand. Additionally, the upper part of the vacuum membrane at the junction with the water tank can also be covered with sticky mud and sand 21 to achieve a sealing effect.

[0080] Step 5: Connect the air pipe to the vacuum pressure gauge, air valve, water-air separator, and vacuum pump to ensure that the water in the water tank is discharged into the water-air separator and does not enter the vacuum pump during vacuuming.

[0081] Step Six: Open the air valve and vacuum pump, and continue pumping air until the vacuum pressure stabilizes at -100 kPa (the actual vacuum pressure can be adjusted appropriately according to the test water tank's capacity and the rate of water flow). Observe the liquid level in the water-air separator and drain the water promptly. If the water flow is minimal and the pressure stabilizes for a long time, close the air valve and vacuum pump, and observe the vacuum pressure gauge to maintain the internal vacuum level. If the vacuum level drops, reopen the air valve and vacuum pump to restore the original vacuum level.

[0082] Step 7: Measure the height of the soil after compression until the required test height D = 30cm is reached in the bottom sand environment. If the required test height cannot be reached, continue with Step 6 above.

[0083] Step 8: Take soil samples from the test section to determine its density, moisture content, and yield stress, and verify whether the bottom sand environment meets the test requirements (i.e., target bottom sand moisture content w0 = 65.3%, density ρ0 = 1.479 g / cm³). 3 Soil particle density ρ s =2.675 / cm 3 If the requirements are met, proceed to the next steps of the flume test. If the requirements are not met, repeat steps four through seven until the soil sample in the test section meets the requirements of the flume test.

[0084] The test water tank in this embodiment is a long glass water tank used for conventional siltation tests, and its manufacturing and working principle are familiar to those skilled in the art.

[0085] The diameter of the vacuum pressure pipe, ventilation pipe, and connecting elbows and tees involved in this embodiment can be freely configured according to the thickness of the test soil sample and the application scenario. At the same time, the vacuum pressure gauge 10 and vacuum pump 16 involved in this embodiment can be freely configured according to the actual application scenario, and the operation adopts the methods commonly used in the prior art.

[0086] 3. Specific applications of the present invention

[0087] Application 1: Experimental uplift characteristics of bottom sand under different flow velocities

[0088] Step 1: After preparing the water tank as described above, remove the geotextile, coarse sand layer, and vacuum tubes covering the silt. Pour water into the tank (the water inlet is located at the head of the tank) to ensure full contact between the bottom sand and the water. Simultaneously, seal the water inlet with a sponge and keep it as close to the tank as possible to prevent excessive water flow from eroding the bottom sand. The water level should be 80cm.

[0089] Step 2: After water injection is completed, determine the test section for bottom sand lifting 1m away from the water inlet of the water tank, and install flow velocity test and sediment concentration vertical distribution test instruments (the test of water flow velocity and sediment concentration vertical distribution adopts conventional methods in this field).

[0090] Step 3: Start the water pump and open the water tank outlet to form a stable unidirectional water flow in the water tank. Record the water flow velocity and the vertical distribution of sand content in the test section.

[0091] Step 4: During a stable flow period of 1 hour, test and record the vertical distribution of sediment concentration at the lifting section every 5 minutes. For the following 24 hours, record the vertical distribution every 30 minutes. For the following 48 hours, record the vertical distribution every 2 hours. For the following 7 days, record the vertical distribution every 6 hours. Once the vertical distribution of sediment concentration stabilizes (with an interval of 6 hours and a distribution error ≤2%), the current vertical distribution characteristic can be considered the lifting characteristic under the current flow velocity and current sediment consolidation compressibility.

[0092] Furthermore, the experimental process of this device and method can be expanded by changing the internal structure of the water tank, including artificially setting up sand-blocking dam models, silt-reducing ditch models, etc., to increase experimental variables, all of which fall within the scope of this invention.

[0093] Application 2: Experimental sediment deposition characteristics under different flow velocities of bottom sand

[0094] Step 1: After preparing the water tank as described above, remove the geotextile, coarse sand layer, and vacuum tubes covering the silt. Pour water into the tank (the water inlet is located at the head of the tank) to ensure full contact between the bottom sand and the water. Simultaneously, seal the water inlet with a sponge and keep it as close to the tank as possible to prevent excessive water flow from eroding the bottom sand. The water level should be 80cm.

[0095] Step 2: After water injection is completed, determine the sedimentation test sections in the downstream section of the water tank, namely 1m, 2m, 3m, 5m, and 10m away from the bottom sand initiation test sections (if the water tank is long enough, subsequent measurement sections will be taken at 5m intervals). Install flow velocity testing and sediment concentration vertical distribution testing instruments (the tests of water flow velocity and sediment concentration vertical distribution adopt conventional methods in this field).

[0096] Step 3: Start the water pump and open the water tank outlet to form a stable unidirectional water flow in the water tank. Record the initial water flow velocity and the vertical distribution of sand content in the test section.

[0097] Step 3: During a stable water flow period of 1 hour, test and record the vertical distribution of sediment concentration at the siltation cross-section every 5 minutes. For the next 24 hours, record the vertical distribution of sediment concentration at the siltation cross-section every 30 minutes. For the next 48 hours, record the vertical distribution of sediment concentration at the siltation cross-section every 2 hours. For the next 7 days, record the vertical distribution of sediment concentration at the siltation cross-section every 6 hours. Once the vertical distribution of sediment concentration stabilizes (with a 6-hour interval and a cross-sectional sediment concentration distribution error ≤2%), the current vertical distribution characteristics can be considered the siltation characteristics under the current flow velocity and current bottom sediment consolidation compressibility.

[0098] Furthermore, the experimental process of this device and method can be expanded by changing the internal structure of the water tank, including artificially setting up sand-blocking dam models, silt-reducing ditch models, etc., to increase experimental variables, all of which fall within the scope of this invention.

[0099] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments above. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A flume test device simulating a river or lake bottom sediment environment, characterized by, It includes: The test tank (1) and its inside from bottom to top in turn set up four layers structure of test bottom sand layer (2), geotextile layer (3), coarse sand layer (4), vacuum sealing membrane layer (6), and the vacuum pipe (5) of the coarse sand layer (4) layer, the air pipe (7) of the vacuum sealing membrane layer (6) upper portion and the vacuum pipe communication, the air pipe is connected water gas separator (12), vacuum air pump (16) in turn;The vacuum pipe (5) is evenly provided with a plurality of small holes (51) on the pipe wall, and is wrapped with geotextile filter on the pipe wall; The air extraction vacuum pipe (5) is laid along the length direction of the test water tank and multiple pipes are laid in parallel along the width direction of the test water tank; the air pipe (7) comprises a horizontal air pipe (71) and an air pipe line (72), multiple air pipe sections are connected in series by a tee joint along the width direction of the test water tank to form a horizontal air pipe (71), and each air extraction vacuum pipe (5) is connected by a tee joint (9) or an elbow (8) installed thereon, the horizontal air pipe is connected to the air pipe line (72) by a tee joint, the air pipe line is connected to the water-air separator (12) after leaving the water tank, the air pipe line is connected to the water-air separator at the end, the water-air separator is provided with a water outlet (13), a water-air inlet (14) and an air outlet (15); the end of the air pipe line is inserted into the liquid in the water-air separator from the water-air inlet (14); the air outlet (15) is provided with an air pipe line I (73) connected to a vacuum air extraction pump (16); the air extraction vacuum pipe (5), the horizontal air pipe (71), the air pipe line (72) and the air pipe line I (73) all have a diameter of a common PE pipe; a vacuum pressure gauge (10) is arranged on the air pipe line (72), and an air valve (11) is arranged on the air pipe line I (73).

2. A simulated river or lake bed sediment environment flume test apparatus as claimed in claim 1 wherein, A plurality of the small holes (51) are arranged in the shape of plum blossom.

3. A simulated river or lake bed sediment environment flume test apparatus as claimed in claim 1 wherein, The test tank (1) is a common tempered glass tank, including external steel frame (101) and built-in tempered glass (102).

4. A simulated river or lake bed sediment environment flume test apparatus as claimed in claim 1 wherein, The test bottom sand layer (2) is entirely paved with test bottom sand, which is obtained by digging the river area in the target river or lake to be simulated; the geotextile layer (3) is the geotextile paved on the test bottom sand layer, the geotextile is plastic flat wire woven geotextile, the density is 100-300 g / m 2 ; the coarse sand layer (4) is the ordinary machine-made sand paved on the geotextile layer (3), the coarse sand particle diameter is 1 mm-0.5 mm; the vacuum sealing film layer (6) is the ordinary PVC vacuum preloading film purchased and composed by heat synthesis splicing, paved on the coarse sand layer (4), the film thickness is 0.12-0.16 cm; the air pipe (7) is paved above the vacuum sealing film layer.

5. A simulated river or lake bed sediment environment flume test apparatus as claimed in claim 4 wherein, The vacuum pressure gauge (10) is a common YZ-40 vacuum pressure gauge, the measurement range is-0.1~0.15MPa, the accuracy grade is 1.5~2.5;The air valve (11) is made of 304 stainless steel, the diameter is the same as that of the air pipe line one;The water gas separator (12) is 1m high and 800mm in diameter, which is a sealed cylinder made of 10mm thick acrylic plate.

6. A method for preparing a flume test device simulating a river or lake bottom sediment environment, comprising the device according to any one of claims 1 to 5, characterized in that, The test bottom sand thickness estimation includes the following steps: Step one: through the study of the target river, lake bottom sand properties, determine the test bottom sand layer environment required target soil moisture content w0, density p0, soil particle density p s And calculate the target soil porosity e0: Step two: By sampling the target river, test the density of the sampled soil body ρ i , the water content w i , and the soil particle density ρ si , to obtain the initial void ratio e i of the soil body for the bottom sediment environment Step three: the soil in step two needs to go through compression consolidation process to reach the target soil porosity ratio in step one; Assuming that the soil is compressed under lateral restraint, only the change of soil height needs to be considered to determine the degree of compression consolidation; Therefore, assuming that the required test bottom sand layer height is D, the initial soil sample with a height of d needs to be laid:

7. The method of claim 6, wherein the method further comprises the step of: The construction steps include: ​ Step one: after taking the test simulation target river or lake bottom sand, evenly lay it in the test tank, the laying height d is the calculated height, which constitutes the test bottom sand layer (2); Step two: lay a layer of geotextile layer on the top of the laid test bottom sand layer (2), the role of the geotextile layer is to filter the sand and discharge water; Step three: lay 1-5cm thick coarse sand on the geotextile layer, erect the vacuum air pipe, the center distance of each vacuum air pipe (5) is 30cm-50cm, and the minimum distance between the air pipe and the tank wall is 5cm, which ensures the influence range and air efficiency of the air pipe;After the air pipe is erected, evenly cover the coarse sand, until the coarse sand is 3-5cm higher than the top height of the vacuum air pipe, which constitutes the coarse sand layer (4), the air pipe is connected with the air pipe by three-way and elbow, and the air pipe is connected with the water gas separator outside the tank; Step four: lay the vacuum sealing membrane layer (6) and the vacuum air pipe line on the coarse sand layer (4), the vacuum air pipe (5) is connected with the air pipe through the air pipe, and is bonded by glue, which ensures the tight connection between the vacuum sealing membrane and the vacuum sealing membrane, and prevents air leakage;The vacuum sealing membrane is embedded in the muddy clayey silt layer, and the upper part of the vacuum sealing membrane is also covered with adhesive clay, which plays a sealing role. Step five: the vent line is connected with a vacuum pressure gauge and a water vapor separator, the vent line is connected with a gas valve and a vacuum air pump, to ensure that the water in the water tank is discharged into the water vapor separator and not into the vacuum air pump when air is pumped; Step six: open the gas valve and the vacuum air pump, continue to pump air until the vacuum pressure is stable at-85kPa to-200kPa, observe the liquid level in the water vapor separator and discharge the water in time; when the water flow is small and the pressure is stable for a long time, the gas valve and the vacuum air pump can be closed, the vacuum pressure gauge is observed, and the internal vacuum degree is maintained; when the vacuum degree decreases, the gas valve and the vacuum air pump can be opened again to pump air and restore the original vacuum degree; Step seven: measure the height of the compressed soil layer of the test bottom sand, until the bottom sand environment with the required height D of the test is reached, if the required test height cannot be reached, continue step six. Step eight: take soil samples of the test bottom sand layer in the test section to measure its density, water content and yield stress, and check whether the bottom sand environment meets the test requirements, i.e. meets the target soil water content w0, density p0, soil particle density p s ; if it meets the requirements, continue with the subsequent steps of the flume test, if it fails to meet the requirements, repeat steps four to seven until the soil sample in the test section meets the requirements of the flume test.

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