Variable-head dynamic-load pile-supported embankment seepage erosion test device and method

Abstract

The invention discloses a variable-head dynamic-load pile-supported embankment seepage erosion test device and method, and the device comprises an embankment model seepage unit which is used for simulating an actual pile-supported embankment; the solid-liquid material unit is used for simulating actual interaction between soil and water; the oil supply circulating unit is used for providing oil body pressure of a variable water head for the solid-liquid material unit in the soil filling chamber; the loading unit is used for providing a dynamic load; and the visual observation unit is used for realizing a planar laser-induced fluorescence technology. According to the device and the method, the formation of a soil arch effect in an actual pile-supported embankment is simulated in the test process, lossless visual observation of the pile-supported embankment in the seepage erosion process is realized, and most simulation test problems of seepage erosion of the pile-supported embankment under variable water head dynamic load can be researched more scientifically and accurately.

Description

Technical Field

[0001] The invention relates to the technical field of traffic geotechnical engineering, and in particular to a variable water head dynamic load pile-supported embankment seepage erosion test device and method. Background Art

[0002] Soil seepage erosion is a multi-stage development process, which is mainly affected by factors such as soil properties, stress state and hydraulic load. In pile-supported embankments, due to the difference in stiffness between the pile body and the soil between the piles, a "soil arch effect" is formed in the overlying fill, resulting in stress redistribution, that is, the stress at the top of the pile body increases, while the stress at the top of the soil between the piles decreases, thereby exerting the bearing efficiency of the pile body and reducing the uneven settlement and overall settlement of the embankment surface. When the existence of the "soil arch effect" inside the pile-supported embankment causes uneven stress distribution, the initiation and development behavior of its seepage erosion will become more complicated, and the "soil arch effect" will often significantly reduce the anti-seepage performance of the embankment; on the other hand, with the development of seepage erosion, the "soil arch effect" will also deteriorate significantly, mainly manifested in a significant decrease in the stress at the top of the pile body and a significant increase in the stress at the top of the soil between the piles, causing a significant development of the embankment surface settlement, affecting the long-term service stability of the embankment.

[0003] At present, most seepage erosion tests are usually carried out in instruments such as cylindrical seepage meters for unit specimens. It is impossible to conduct in-depth research on the seepage erosion process under the coupling of complex conditions at the model scale, and it is impossible to derive the seepage erosion law close to the actual engineering. When conducting indoor tests at the model scale, in order to obtain the changes in soil parameters, the current mainstream method is to use embedded sensors for measurement, but the parameter measurement values ​​obtained by this method are spatially discrete and cannot reflect the overall changes in the soil model. In order to overcome this shortcoming, a test method combining a transparent boundary model box with image velocimetry technology has been developed, but this method can only obtain the parameter changes of the soil at the boundary, and is easily affected by the boundary effect on the measurement results. Summary of the invention

[0004] The present invention provides a variable head dynamic load pile-supported embankment seepage erosion test device and method with novel technology, simple structure, easy operation, and the ability to visually explore the seepage erosion process of the pile-supported embankment under traffic load, which can solve at least one of the above-mentioned technical problems.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The variable head dynamic load pile-supported embankment seepage erosion test device includes:

[0007] The embankment model seepage unit is used to simulate the actual pile-supported embankment, and includes a model test box, which is sequentially provided with an oil inlet chamber, a soil filling chamber and an oil outlet chamber which are connected from bottom to top, and a trap door is installed in the soil filling chamber to form a "soil arch effect";

[0008] A solid-liquid material unit, including a soil sample mixed with various materials filled into the soil filling chamber, for simulating actual soil-water interaction;

[0009] An oil supply circulation unit, used for providing the solid-liquid material unit in the filling chamber with oil pressure of variable head, comprising an oil pressure control box and an oil collecting tank, wherein the oil pressure control box is connected to the oil inlet chamber via an oil supply pipe, and the oil collecting tank is connected to the oil outlet chamber via an oil outlet pipe;

[0010] A loading unit, used to provide a dynamic load, including a loading plate and a sensor, wherein the loading plate can be raised and lowered to act on the solid-liquid material unit in the soil filling chamber to simulate the dynamic load imposed on the soil sample by the traffic load, and the sensor is arranged on the loading plate to measure the size of the dynamic load and the displacement of the loading plate;

[0011] A visualization observation unit is used to implement planar laser induced fluorescence technology, including a planar laser emitter and an industrial high-speed camera. The planar laser emitter points to the solid-liquid material unit in the filling chamber and is used to provide planar laser to the soil sample. The industrial high-speed camera is used to collect optical images of the soil sample.

[0012] Furthermore, the solid-liquid material unit at least includes fused quartz particles for simulating actual soil, white oil mixture for simulating actual water, and Nile red fluorescent dye for exciting fluorescence, and the fused quartz particles and the white oil mixture meet the refractive index matching requirement.

[0013] Furthermore, the embankment model seepage unit also includes a hand-cranked transmission part, which is installed on the front side of the model test box and is connected to the trap door for controlling the trap door to move downward away from the soil sample so that the solid-liquid material unit forms a "soil arch effect". The trap door is a porous plate structure, which separates the oil inlet chamber from the fill chamber, and the soil sample or coarse particles of the soil sample in the fill chamber cannot pass through the plate holes.

[0014] Furthermore, the embankment model seepage unit also includes a non-buried sensor, and there are multiple non-buried sensors, which are used to monitor changes in soil sample parameters respectively. The front and sides of the model test box are made of transparent acrylic plates, and multiple piezometer measuring points are reserved on the back, and the non-buried sensors are arranged in the piezometer measuring points.

[0015] Furthermore, the oil supply circulation unit also includes an oil supply tank, an oil replenishment tank and an oil return pipe. The oil supply tank is connected to the oil pressure control box via the oil replenishment tank, and is used to inject white oil mixed oil into the oil pressure control box. The oil pressure control box is connected to the oil inlet valve of the oil inlet chamber via the oil supply pipe, and is used to provide a continuous, stable and controllable head oil pressure to the filling chamber. The oil supply tank is connected to the oil collecting tank via the oil return pipe, and the oil supply tank is connected to the oil outlet of the oil outlet chamber via the oil outlet pipe, and is used to collect the outflowing oil, and recover the collected oil to the oil supply tank through the oil return pipe, so as to realize the circulation recovery of the oil.

[0016] Furthermore, the oil pressure control box includes a pressure-stabilizing valve and a pressure measuring tube. The pressure measuring tube is vertically inserted in the oil pressure control box for real-time measurement of the oil pressure in the box. The pressure-stabilizing valve is installed on the oil pressure control box for forming an oil return passage and returning the oil that exceeds its own liquid level to the oil supply tank in time, thereby realizing control of the water head in the oil pressure control box.

[0017] Furthermore, a filter tank is installed at the inner opening of the oil collecting tank, the oil return pipe does not pass through the filter tank but directly extends into the oil collecting tank, the oil outlet pipe extends into the filter tank, and the filter tank is used to filter and collect eroded fused quartz particles.

[0018] Further, the loading unit also includes a loading frame and a servo hydraulic control module;

[0019] The loading frame is built outside the model test box, and the loading plate can be lifted and hoisted under the loading frame and extended into the soil filling chamber. The loading plate is a porous plate structure, which separates the soil filling chamber from the oil outlet chamber. The soil sample or coarse particles of the soil sample in the soil filling chamber cannot pass through the plate holes.

[0020] The servo hydraulic control module includes an electro-hydraulic servo fatigue test component, a servo controller and an industrial computer. The electro-hydraulic servo fatigue test component is installed on the loading frame. The sensor passes through the electro-hydraulic servo fatigue test component and the servo controller in sequence and is electrically connected to the industrial computer for transmitting monitoring signals and control signals.

[0021] Furthermore, the visualization observation unit further includes a temperature controller and a light shield, wherein the light shield is arranged outside the variable head dynamic load pile-supported embankment seepage erosion test device to ensure the collection efficiency of image data, and the temperature controller is used to adjust the test environment temperature to ensure that the solid-liquid material unit achieves refractive index matching;

[0022] The planar laser emitter is equipped with a Powell lens for providing planar laser light that meets the intensity requirement to the solid-liquid material unit and inducing the Nile red fluorescent dye to emit fluorescence;

[0023] The industrial high-speed camera is equipped with a long-pass filter for visually separating the solid-liquid material unit while the industrial high-speed camera is collecting optical images.

[0024] The variable water head dynamic load pile-supported embankment seepage erosion test method is implemented by using the variable water head dynamic load pile-supported embankment seepage erosion test device, and comprises the following steps:

[0025] S1: Mix the fused silica particles with the white oil mixture, add Nile red fluorescent dye, and let it stand for 24 hours to remove bubbles in the mixture;

[0026] S2: Slowly and evenly fill the solid-liquid material unit formed after mixing into the filling chamber of the model test box, and always keep the white oil mixed oil level higher than the fused quartz particles, so that the soil sample is saturated and there are no bubbles inside;

[0027] S3: Setting the temperature controller and the light shield to provide suitable test environment conditions, and placing the non-embedded sensor to the piezometer measuring point on the back of the model test box, the Powell lens to the planar laser emitter, and the long-pass filter to the industrial high-speed camera, and starting data and image acquisition;

[0028] S4: placing a loading plate flat on the top of the soil sample of the solid-liquid material unit, and using a servo hydraulic control module to control the loading plate to apply a dynamic load to the soil sample to compact the soil sample;

[0029] S5: controlling the trap door to move downward by a hand-cranked transmission member to form a "soil arch effect" inside the soil sample of the solid-liquid material unit;

[0030] S6: Open the oil inlet valve to allow the white oil in the oil pressure control box to flow into the oil inlet cavity of the model test box through the oil supply pipe, forming a uniform and stable seepage flow in the soil filling chamber;

[0031] S7: Record and organize various data during the simulation test.

[0032] The beneficial effects of the present invention are embodied in:

[0033] 1. The test device of the present invention has a simple structure and is easy to operate. The material combination is supported by experimental similarity theory, the service life is long, the test volume is small, and the functions are complete. During the test, the formation of the "soil arch effect" in the actual pile-supported embankment can be simulated. Stable and controllable variable water head and cyclic dynamic load can be applied as needed, and non-destructive visual observation of the pile-supported embankment during seepage erosion can be achieved. The scope of application is wider, which helps to provide more scientific and reliable research ideas and means for most of the simulation test problems of seepage erosion of pile-supported embankments under variable water head dynamic loads.

[0034] 2. The present invention overcomes the limitation that traditional test methods can only examine the seepage erosion behavior of unit soil samples or observe model samples from the boundary. It creatively combines the planar laser induced fluorescence technology with the research on the seepage erosion problem of pile-supported embankments, simulates the actual structural form of pile-supported embankments, and at the same time can change the oil pressure and cyclic dynamic load conditions of the soil samples, so as to explore the seepage erosion problem of pile-supported embankments that is closer to the actual engineering situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0036] Figure 1 It is a schematic diagram summarizing the overall structure of the test device of an embodiment of the present invention.

[0037] Figure 2 It is a detailed schematic diagram of the overall structure of the test device according to an embodiment of the present invention.

[0038] Figure 3 It is a schematic diagram of the front structure of the model test box according to an embodiment of the present invention.

[0039] Figure 4 It is a schematic diagram of the back structure of the model test box according to an embodiment of the present invention.

[0040] Figure 5 It is a schematic diagram of the test method flow of an embodiment of the present invention.

[0041] Figure 6 It is a curve chart of the change of soil arch rate during the formation stage of "soil arch effect".

[0042] Figure 7 It is a discrete graph of the variation of the average seepage velocity with the average hydraulic force obtained by the experiment of the embodiment of the present invention.

[0043] Figure 8 It is a schematic diagram of particle changes at different times measured in an experiment of an embodiment of the present invention.

[0044] Fig. 9 The present invention is a graph showing the change of soil arching rate during seepage erosion under different conditions as a function of test time obtained by testing an embodiment of the present invention.

[0045] The markings of the components in the accompanying drawings are:

[0046] 1. Seepage unit of embankment model; 2. Solid-liquid material unit; 3. Oil supply circulation unit; 4. Loading unit; 5. Visual observation unit; 6. Model test box; 7. Oil inlet chamber; 701. Oil inlet valve; 8. Filling chamber; 9. Oil outlet chamber; 901. Oil outlet; 10. Hand-cranked transmission parts; 11. Trap door; 12. Piezometer measuring point; 13. Oil supply tank; 14. Oil replenishment tank; 15. Oil pressure control box; 1501. Pressure stabilizer Valve; 1502, pressure measuring tube; 16, oil return pipe; 17, oil supply pipe; 18, oil outlet pipe; 19, filter tank; 20, oil collecting tank; 21, loading frame; 22, loading plate; 23, sensor; 24, electro-hydraulic servo fatigue test assembly; 25, servo controller; 26, industrial computer; 27, planar laser transmitter; 28, temperature controller; 29, sunshade; 30, industrial high-speed camera; 3001, long-pass filter. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0048] It should be noted that if there are directional indications (such as up, down, left, right, front, back, etc.) involved in the embodiments of the present invention, the directional indications are only used to explain the relative position relationship and movement of the components under a certain specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly. In addition, "multiple" means more than two.

[0049] It should also be noted that those of ordinary skill in the art can understand that all or part of the steps implemented in the embodiments of the present invention can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When hardware is used, it can be implemented in whole or in part in the form of purchased standard parts or modified parts. When software is used for implementation, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiments of the present application is generated in whole or in part.

[0050] See also Figure 1-Figure 2 The embodiment of the present invention provides a variable head dynamic load pile-supported embankment seepage erosion test device, comprising:

[0051] The embankment model seepage unit 1 is used to simulate an actual pile-supported embankment, and includes a model test box 6, wherein the model test box 6 is sequentially provided with an oil inlet chamber 7, a soil filling chamber 8 and an oil outlet chamber 9 which are connected from bottom to top, and a trap door 11 is installed in the soil filling chamber 8 to form a "soil arch effect";

[0052] The solid-liquid material unit 2 includes a soil sample mixed with various materials filled into the soil filling chamber 8, which is used to simulate the actual interaction between soil and water;

[0053] The oil supply circulation unit 3 is used to provide the solid-liquid material unit 2 in the filling chamber 8 with a variable head of oil pressure, and includes an oil pressure control box 15 and an oil collecting tank 20. The oil pressure control box 15 is connected to the oil inlet chamber 7 via an oil supply pipe 17, and the oil collecting tank 20 is connected to the oil outlet chamber 9 via an oil outlet pipe 18.

[0054] The loading unit 4 is used to provide a dynamic load, and includes a loading plate 22 and a sensor 23. The loading plate 22 can be lifted and lowered to act on the solid-liquid material unit 2 in the soil filling chamber 8 to simulate the dynamic load imposed on the soil sample by the traffic load. The sensor 23 is arranged on the loading plate 22 to measure the size of the dynamic load and the displacement of the loading plate 22.

[0055] The visualization observation unit 5 is used to implement the planar laser induced fluorescence technology, including a planar laser emitter 27 and an industrial high-speed camera 30. The planar laser emitter 27 points to the solid-liquid material unit 2 in the filling chamber 8 and is used to provide planar laser to the soil sample. The industrial high-speed camera 30 is used to collect optical images of the soil sample.

[0056] The present invention provides a test device with novel technology, simple structure, convenient operation and the ability to visualize the process of seepage erosion of a pile-supported embankment under traffic load. The test device can not only form a stable and controllable "soil arch effect", provide a stable and controllable water head, apply a stable and controllable cyclic load and truly simulate the seepage erosion process of the pile-supported embankment, but also realize non-destructive visualization observation of soil changes at any cross section of the embankment model, obtain the initiation and development process of seepage erosion in the pile-supported embankment, and the actual influence of seepage erosion on the "soil arch effect", the test means are more scientific and reliable, and the test results are more accurate and effective.

[0057] See also Figure 1 In this embodiment, the solid-liquid material unit 2 at least includes fused quartz particles for simulating actual soil, white oil mixture for simulating actual water, and Nile red fluorescent dye for exciting fluorescence, and the fused quartz particles and the white oil mixture meet the refractive index matching requirements.

[0058] In the present application, by preparing fused quartz particles with larger particle size, the fused quartz particles, the white oil mixture and the actual soil and water satisfy the similar relationship between permeability coefficient and acceleration, thereby simulating the interaction between real soil and water while satisfying the refractive index matching.

[0059] In order to meet the visualization requirements of planar laser induced fluorescence technology, the solid-liquid material unit 2 needs to use transparent materials with matching refractive indices and meet certain similarity theories to ensure that the actual soil-water interaction can be simulated. According to scholars' research, the interaction between fluid and solid is mainly related to the permeability coefficient k:

[0060]

[0061] Where g is the acceleration due to gravity, η is the liquid kinematic viscosity, e is the solid void ratio, and D eff is the effective diameter of the solid material, C K-C is the empirical coefficient, and SF is the solid particle shape coefficient.

[0062] Under the same gravity acceleration, solid porosity, shape coefficient and empirical coefficient, the same permeability coefficient between solid-liquid material and actual water-soil material must be met, that is,:

[0063]

[0064] The diameter of the fused silica particles needs to be scaled to the ratio of the kinematic viscosity of the white oil mixture to water;

[0065] At the same time, according to the mechanical control equation of solid-liquid materials under dynamic conditions:

[0066]

[0067] Among them, σ is the solid stress, L is the gradient operator, ρ s is the solid density, u is the solid displacement, ρ f is the liquid density and ω is the liquid displacement.

[0068] From the above, we can get the similarity relationship of each parameter:

[0069]

[0070] Then we can get:

[0071]

[0072] For the former, it can be judged that under the action of constant gravity, the movement of fused quartz particles is completely similar to that of actual soil particles; for the latter, it can be judged that the density of fused quartz particles is 2.19 g / cm 3, the density of white oil mixed oil is 0.83g / cm 3 , the ratio is 2.64, which is the same as the density ratio between actual water and soil, indicating that the movement of the white oil mixture is completely similar to the movement of actual water.

[0073] Furthermore, in order to achieve refractive index matching, refractive index matching tests were conducted on different white oil mixed oil ratios at different ambient temperatures, and it was determined that when the ambient temperature was 25 degrees Celsius, a mixture of 45% volume fraction of No. 3 white oil and 55% volume fraction of No. 15 white oil could achieve refractive index matching with the fused quartz particles.

[0074] See also Figure 1-Figure 4 and Figure 6 In this embodiment, the embankment model seepage unit 1 also includes a hand-cranked transmission member 10, which is installed on the front of the model test box 6 and is transmission-connected to the trap door 11, and is used to control the trap door 11 to move downward away from the soil sample, so that the solid-liquid material unit 2 forms a "soil arch effect". The movement of the trap door 11 drives the soil sample located above it to follow and synchronously move downward, thereby forming a "soil arch effect" inside the fill. The trap door 11 is a porous plate-like structure, which separates the oil inlet cavity 7 from the fill chamber 8, and the soil sample or coarse particles of the soil sample in the fill chamber 8 cannot pass through the plate holes.

[0075] In this application, the soil arching ratio is defined as the ratio of the vertical stress at the top of the trap door 11 to the overall vertical stress of the soil sample. Figure 6 As shown, it can be seen that as the hand-cranked transmission part 10 controls the trap door 11 to gradually move downward, the soil arch rate gradually decreases, indicating that the vertical stress at the top of the trap door 11 gradually decreases, and the vertical stress at the top of the piles on both sides gradually increases, which means that the test device of the present invention can form a "soil arch effect" in the solid-liquid material unit 2, and can simulate the pile-supported embankment under actual conditions.

[0076] See also Figure 3-Figure 4 In this embodiment, the embankment model seepage unit 1 also includes a non-buried sensor, and the non-buried sensor has multiple sensors, which are used to monitor changes in soil sample parameters. The front and sides of the model test box 6 are made of transparent acrylic plates, and a plurality of piezometer measuring points 12 are reserved on the back, and the non-buried sensors are arranged in the piezometer measuring points 12.

[0077] In the present application, the changes of the solid-liquid material unit 2 inside the fill chamber 8 can be visually observed through the front and sides of the model test box 6. By collecting and analyzing the monitoring data of multiple non-embedded sensors located on the back of the model test box 6, the parameter changes of the soil during the seepage erosion test can be accurately obtained.

[0078] See also Figure 1-Figure 4 In this embodiment, the oil supply circulation unit 3 also includes an oil supply tank 13, an oil replenishment tank 14 and an oil return pipe 16. The oil supply tank 13 is connected to the oil pressure control box 15 via the oil replenishment tank 14, and is used to inject white oil mixed oil into the oil pressure control box 15. The oil pressure control box 15 is connected to the oil inlet valve 701 of the oil inlet chamber 7 via the oil supply pipe 17, and is used to provide a continuous, stable and controllable head oil pressure to the filling chamber 8. The oil supply tank 13 is connected to the oil collecting tank 20 via the oil return pipe 16. The oil supply tank 13 is connected to the oil outlet 901 of the oil outlet chamber 9 via the oil outlet pipe 18, and is used to collect the outflowing oil, and recover the collected oil to the oil supply tank 13 through the oil return pipe 16, so as to realize the circulation recovery of the oil.

[0079] In the present application, between the oil supply circulation unit 3 and the model test box 6, an oil body circulation is formed, namely, the oil supply tank 13 → the oil replenishing tank 14 → the oil pressure control box 15 → the oil supply pipe 17 → the oil inlet chamber 7 → the filling chamber 8 → the oil outlet chamber 9 → the oil collecting tank 20 → the oil return pipe 16 → the oil supply tank 13, so as to realize energy-saving recovery and save test costs.

[0080] See also Figure 2 and Figure 7 In this embodiment, the oil pressure control box 15 includes a pressure regulating valve 1501 and a pressure measuring tube 1502. The pressure measuring tube 1502 is vertically inserted in the oil pressure control box 15 for real-time measurement of the oil pressure in the box. The pressure regulating valve 1501 is installed on the oil pressure control box 15 for forming an oil return passage and returning the oil that exceeds its own liquid level to the oil supply tank 13 in time, so as to control the water head in the oil pressure control box 15.

[0081] In this application, the variation trend of the average seepage velocity with the average hydraulic head was measured, such as Figure 7 As shown in the figure, the results of two sets of repeatability tests are shown. It can be seen that the simulation test results of the device of the present invention have good reproducibility, and there is a good linear relationship between the average seepage flow rate and the average water head, which complies with Darcy's law.

[0082] See also Figure 1-Figure 2 In this embodiment, a filter tank 19 is installed at the inner opening of the oil collecting tank 20, the return oil pipe 16 does not pass through the filter tank 19 but directly extends into the oil collecting tank 20, and the oil outlet pipe 18 extends into the filter tank 19. The filter tank 19 is used to filter and collect eroded molten quartz particles.

[0083] In the present application, the filter tank 19 is installed at the mouth of the oil collecting box 20, so that the eroded fine particles in the white oil mixed oil can be filtered and collected to obtain the quality of the eroded fine particles. Specifically, the oil body carrying the above-mentioned eroded fine particles can pass through the trap door 11 or the plate holes of the loading plate 22 and flow into the filter tank 19 through the pipeline for centralized separation and collection.

[0084] See also Figure 1 , Figure 2 and Fig. 9 , in this embodiment, the loading unit 4 further includes a loading frame 21 and a servo hydraulic control module;

[0085] The loading frame 21 is built outside the model test box 6, and the loading plate 22 can be lifted and hoisted under the loading frame 21 and extended into the filling chamber 8. The loading plate 22 is a porous plate structure, which separates the filling chamber 8 from the oil outlet chamber 9. The soil sample or coarse particles of the soil sample in the filling chamber 8 cannot pass through the plate holes.

[0086] The servo hydraulic control module includes an electro-hydraulic servo fatigue test component 24, a servo controller 25 and an industrial computer 26. The electro-hydraulic servo fatigue test component 24 is installed on the loading frame 21. The sensor 23 passes through the electro-hydraulic servo fatigue test component 24 and the servo controller 25 in sequence and is electrically connected to the industrial computer 26 for transmitting monitoring signals and control signals.

[0087] In the present application, by constructing the loading unit 4 arranged outside the model test box 6, the servo hydraulic control module is used to control the loading plate 22 to act on the solid-liquid material unit 2 in the model test box 6, and the dynamic load applied to the model test box 6 is accurately controlled. The dynamic load applied to the soil sample by the actual traffic load is truly simulated, and the sensor 23 is used to measure the size of the dynamic load and the displacement of the loading plate 22 in real time, so that the degree of automation is higher and the test controllability is better.

[0088] During the test, as the seepage erosion progressed, the "soil arch effect" also developed and changed, such as Fig. 9 As shown in the figure, the curve of soil arching rate changing with test time under different conditions measured by the test device during the test is presented. It can be seen that the "soil arching effect" has undergone significant deterioration, which is mainly manifested in the increase of soil arching rate, indicating that the stress on the top of the soil between piles has increased and the bearing efficiency of the pile body has decreased, which will cause a significant development of surface settlement of the pile-supported embankment.

[0089] See also Figure 1 , Figure 2 and Figure 8In this embodiment, the visualization observation unit 5 further includes a temperature controller 28 and a light shield 29. The light shield 29 is provided outside the variable head dynamic load pile-supported embankment seepage erosion test device to ensure the collection efficiency of image data. The temperature controller 28 is used to adjust the test environment temperature to ensure that the solid-liquid material unit 2 achieves refractive index matching;

[0090] The planar laser emitter 27 is equipped with a Powell lens, which is used to provide planar laser light that meets the intensity requirement to the solid-liquid material unit 2 and induce the Nile red fluorescent dye to emit fluorescence;

[0091] The industrial high-speed camera 30 is provided with a long-pass filter 3001 for visually separating the solid-liquid material unit 2 while the industrial high-speed camera 30 is collecting optical images.

[0092] In the present application, the temperature controller 28 and the shade 29 are used to provide suitable environmental conditions for the experiment. Under normal circumstances, the temperature controller 28 maintains a temperature of 25 degrees Celsius, and the planar laser emitter 27 emits a 532-nanometer laser to the soil sample, inducing the Nile red fluorescent dye to emit a laser with a wavelength greater than 550 nanometers. Under the action of the 550-nanometer long-pass filter 3001, the solid in the solid-liquid material unit 2 will appear dark, and the liquid will appear light, so that there is a clear distinction.

[0093] The industrial high-speed camera 30 can capture the particle changes at a certain cross section inside the model test box 6, thereby obtaining the overall continuous displacement field, velocity field and acceleration field distribution. This test device measures the changes of fused quartz particles at different times. Figure 8 As shown, it can be seen that the optical image acquisition of the device can clearly record information such as the migration of fine particles, changes in the coarse particle skeleton, changes in the pores of the soil sample, etc.

[0094] See also Figure 1 , Figure 2 and Figure 5 The embodiment of the present invention further provides a variable head dynamic load pile-supported embankment seepage erosion test method, which is implemented using the variable head dynamic load pile-supported embankment seepage erosion test device, and includes the following steps:

[0095] S1: Mix the fused silica particles with the white oil mixture, add Nile red fluorescent dye, and let it stand for 24 hours to remove bubbles in the mixture;

[0096] S2: slowly and evenly filling the solid-liquid material unit 2 formed after mixing into the soil filling chamber 8 of the model test box 6, always keeping the white oil mixed oil level higher than the fused quartz particles, so that the soil sample is saturated and there are no bubbles inside;

[0097] S3: Setting the temperature controller 28 and the light shield 29 to provide suitable test environment conditions, and respectively placing the non-embedded sensor to the piezometer measuring point 12 on the back of the model test box 6, the Powell lens to the planar laser emitter 27, and the long-pass filter 3001 to the industrial high-speed camera 30, and starting data and image acquisition;

[0098] S4: placing the loading plate 22 flat on the top of the soil sample of the solid-liquid material unit 2, and using the servo hydraulic control module to control the loading plate 22 to apply a dynamic load to the soil sample to compact the soil sample;

[0099] S5: Controlling the trap door 11 to move downward by the hand-cranked transmission member 10 to form a "soil arch effect" inside the soil sample of the solid-liquid material unit 2;

[0100] S6: Open the oil inlet valve 701 to allow the white oil in the oil pressure control box 15 to flow into the oil inlet chamber 7 of the model test box 6 through the oil supply pipe 17, forming a uniform and stable seepage flow in the soil filling chamber 8;

[0101] S7: Record and organize various data during the simulation test.

[0102] During the S4 test, in the servo-hydraulic control module, the industrial computer 26 and the servo controller 25 are used to control the electro-hydraulic servo fatigue test assembly 24, so as to accurately control the dynamic load of the loading plate 22 on the soil sample, thereby exploring the initiation and development of seepage erosion of the pile-supported embankment under different dynamic loads;

[0103] During the S6 test, the oil level in the oil pressure control box 15 is monitored and controlled by using the pressure measuring tube 1502 and the pressure regulating valve 1501, so as to apply a variable oil pressure to the soil sample. At the same time, the oil is circulated between the oil supply circulation unit 3 and the model test box 6 to ensure stable and uniform seepage inside the soil sample.

[0104] During the above-mentioned seepage erosion simulation test, the following data were closely recorded: local water head, seepage velocity, mass of eroded fine particles, surface settlement, soil pressure above the trapdoor, optical images, etc., and finally the initiation and development mechanism of seepage erosion of pile-supported embankments and the law of service performance degradation were established.

[0105] From the above experiments, it can be seen that through the simulation test device and the simulation test method of the present invention, the seepage erosion problem of pile-supported embankments can be explored more deeply and directly, and the initiation and development mechanism of seepage erosion of pile-supported embankments and the degradation law of service characteristics of pile-supported embankments close to the actual engineering are obtained, which provides effective technical support for the prediction and prevention of seepage erosion of pile-supported embankments in actual engineering.

[0106] It should be understood that the examples and implementation modes described herein are for illustrative purposes only and are not intended to limit the present invention. Those skilled in the art may make various modifications or changes based on the examples and implementation modes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Variable head dynamic load pile-supported embankment seepage erosion test device, characterized in that: include: The embankment model seepage unit (1) is used to simulate an actual pile-supported embankment, and comprises a model test box (6), wherein the model test box (6) is sequentially arranged from bottom to top as an oil inlet chamber (7), a soil filling chamber (8) and an oil outlet chamber (9) which are interconnected, and a trap door (11) is installed in the soil filling chamber (8) to form a "soil arch effect"; The solid-liquid material unit (2) includes a soil sample mixed with multiple materials filled into the soil filling chamber (8) to simulate the actual interaction between soil and water; An oil supply circulation unit (3) is used to provide the solid-liquid material unit (2) in the filling chamber (8) with an oil pressure of a variable water head, and comprises an oil pressure control box (15) and an oil collecting tank (20), wherein the oil pressure control box (15) is connected to the oil inlet chamber (7) via an oil supply pipe (17), and the oil collecting tank (20) is connected to the oil outlet chamber (9) via an oil outlet pipe (18); A loading unit (4) is used to provide a dynamic load, and comprises a loading plate (22) and a sensor (23). The loading plate (22) can be raised and lowered to act on the solid-liquid material unit (2) in the filling chamber (8) to simulate the dynamic load applied to the soil sample by the traffic load. The sensor (23) is arranged on the loading plate (22) to measure the size of the dynamic load and the displacement of the loading plate (22). A visualization observation unit (5) is used to implement planar laser induced fluorescence technology, comprising a planar laser emitter (27) and an industrial high-speed camera (30), wherein the planar laser emitter (27) points to the solid-liquid material unit (2) in the soil filling chamber (8) and is used to provide planar laser to the soil sample, and the industrial high-speed camera (30) is used to collect optical images of the soil sample.

2. The variable head dynamic load pile-supported embankment seepage erosion test device according to claim 1, characterized in that: The solid-liquid material unit (2) at least comprises fused silica particles for simulating actual soil, white oil mixed oil for simulating actual water, and Nile red fluorescent dye for exciting fluorescence, and the fused silica particles and the white oil mixed oil meet the requirements of refractive index matching.

3. The variable water head dynamic load pile-supported embankment seepage erosion test device according to claim 1, characterized in that: The embankment model seepage unit (1) further comprises a hand-cranked transmission member (10), which is mounted on the front of the model test box (6) and is in driving connection with the trap door (11) and is used to control the trap door (11) to move downward away from the soil sample so that the solid-liquid material unit (2) forms a "soil arch effect". The trap door (11) is in a porous plate-like structure, separating the oil inlet cavity (7) from the soil filling chamber (8), and the soil sample or coarse particles of the soil sample in the soil filling chamber (8) cannot pass through the plate holes.

4. The variable water head dynamic load pile-supported embankment seepage erosion test device according to claim 1, characterized in that: The embankment model seepage unit (1) also includes a non-buried sensor, and the non-buried sensors are provided in plurality and are respectively used to monitor changes in soil sample parameters. The front and side surfaces of the model test box (6) are both made of transparent acrylic plates, and a plurality of piezometer measuring points (12) are reserved on the back, and the non-buried sensors are arranged in the piezometer measuring points (12).

5. The variable head dynamic load pile-supported embankment seepage erosion test device according to claim 2, characterized in that: The oil supply circulation unit (3) further comprises an oil supply tank (13), an oil replenishment tank (14) and an oil return pipe (16). The oil supply tank (13) is connected to the oil pressure control box (15) via the oil replenishment tank (14) for injecting white oil mixed oil into the oil pressure control box (15). The oil pressure control box (15) is connected to the oil inlet valve (701) of the oil inlet chamber (7) via the oil supply pipe (17) for providing a continuous, stable and controllable head oil pressure to the filling chamber (8). The oil supply tank (13) is connected to the oil collecting tank (20) via the oil return pipe (16). The oil supply tank (13) is connected to the oil outlet (901) of the oil outlet chamber (9) via the oil outlet pipe (18) for collecting the outflowing oil and recovering the collected oil to the oil supply tank (13) via the oil return pipe (16) to realize the circulation recovery of the oil.

6. The variable water head dynamic load pile-supported embankment seepage erosion test device according to claim 1, characterized in that: The oil pressure control box (15) comprises a pressure stabilizing valve (1501) and a pressure measuring tube (1502). The pressure measuring tube (1502) is vertically inserted in the oil pressure control box (15) and is used to measure the oil pressure in the box in real time. The pressure stabilizing valve (1501) is installed on the oil pressure control box (15) and is used to form an oil return passage and return the oil exceeding its own liquid level to the oil supply tank (13) in time, so as to control the water head in the oil pressure control box (15).

7. The variable water head dynamic load pile-supported embankment seepage erosion test device according to claim 5, characterized in that: A filter tank (19) is installed at the inner opening of the oil collecting tank (20), the oil return pipe (16) does not pass through the filter tank (19) but directly extends into the oil collecting tank (20), the oil outlet pipe (18) extends into the filter tank (19), and the filter tank (19) is used to filter and collect eroded fused quartz particles.

8. The variable water head dynamic load pile-supported embankment seepage erosion test device according to claim 1, characterized in that: The loading unit (4) further comprises a loading frame (21) and a servo hydraulic control module; The loading frame (21) is built outside the model test box (6); the loading plate (22) can be lifted and hoisted under the loading frame (21) and extended into the soil filling chamber (8); the loading plate (22) is a porous plate structure, separating the soil filling chamber (8) and the oil outlet chamber (9); the soil sample or coarse soil sample particles in the soil filling chamber (8) cannot pass through the plate holes; The servo hydraulic control module comprises an electro-hydraulic servo fatigue test component (24), a servo controller (25) and an industrial computer (26); the electro-hydraulic servo fatigue test component (24) is mounted on the loading frame (21); the sensor (23) passes through the electro-hydraulic servo fatigue test component (24) and the servo controller (25) in sequence, and is electrically connected to the industrial computer (26) for transmitting monitoring signals and control signals.

9. The variable water head dynamic load pile-supported embankment seepage erosion test device according to claim 2, characterized in that: The visualization observation unit (5) further comprises a temperature controller (28) and a light shield (29), wherein the light shield (29) is arranged outside the variable head dynamic load pile-supported embankment seepage erosion test device to ensure the collection efficiency of image data, and the temperature controller (28) is used to control the test environment temperature to ensure that the solid-liquid material unit (2) achieves refractive index matching; The planar laser emitter (27) is equipped with a Powell lens for providing planar laser light that meets the intensity requirement to the solid-liquid material unit (2) and inducing the Nile red fluorescent dye to emit fluorescence; The industrial high-speed camera (30) is provided with a long-pass filter (3001) for visually separating the solid-liquid material unit (2) while the industrial high-speed camera (30) is collecting optical images.

10. A variable head dynamic load pile-supported embankment seepage erosion test method, implemented by using a variable head dynamic load pile-supported embankment seepage erosion test device as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: S1: Mix the fused silica particles with the white oil mixture, add Nile red fluorescent dye, and let it stand for 24 hours to remove bubbles in the mixture; S2: slowly and evenly filling the solid-liquid material unit (2) formed after mixing into the soil filling chamber (8) of the model test box (6), always keeping the white oil mixed oil level higher than the fused quartz particles, so that the soil sample is saturated and there are no bubbles inside; S3: Setting the temperature controller (28) and the light shield (29) to provide suitable test environment conditions, and respectively placing the non-embedded sensor to the piezometer measuring point (12) on the back of the model test box (6), the Powell lens to the planar laser emitter (27), and the long-pass filter (3001) to the industrial high-speed camera (30), and starting data and image acquisition; S4: placing a loading plate (22) flat on the top of the soil sample of the solid-liquid material unit (2), and using a servo hydraulic control module to control the loading plate (22) to apply a dynamic load to the soil sample to compact the soil sample; S5: controlling the trap door (11) to move downwards by means of a hand-operated transmission member (10), thereby forming a "soil arch effect" inside the soil sample of the solid-liquid material unit (2); S6: Open the oil inlet valve (701) to allow the white oil in the oil pressure control box (15) to flow into the oil inlet chamber (7) of the model test box (6) through the oil supply pipe (17), thereby forming a uniform and stable seepage flow in the soil filling chamber (8); S7: Record and organize various data during the simulation test.

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