Three-dimensional visible unsaturated soil moisture migration model device

Abstract

The invention relates to the technical field of soil body characteristic research, and particularly discloses a three-dimensional visible unsaturated soil moisture migration model device which comprises a transparent experimental container, a water head control system, an imaging system, a laser sheet generation system and a matrix suction monitoring device, the transparent experimental container is filled with a porous medium; the water head control system is used for conveying fluid with tracer particles into the transparent experimental container; the matrix suction monitoring device is arranged on the transparent experimental container and is used for monitoring the suction change of the porous medium in real time; the laser sheet generation system is used for generating a laser sheet; the imaging system is used for recording the distribution and flow track of the tracer particles; the three-dimensional visible unsaturated soil moisture migration model device can effectively simulate the dynamic process of moisture migration, can clearly display the migration path and behavior, and provides key support for deep research of mechanical properties of unsaturated soil.

Description

Technical Field

[0001] The invention relates to the technical field of soil property research, and in particular to a three-dimensional visual unsaturated soil moisture migration model device. Background Art

[0002] Existing experimental devices lack the ability to visualize the overall water migration process in real time. The flow path of water in porous media is difficult to visualize using the above techniques, especially under complex dry-wet cycle conditions, the dynamic behavior of water migration is even more difficult to accurately restore. This limitation significantly hinders the comprehensive understanding of water movement and related physical processes in unsaturated soils. Therefore, it is particularly important to develop an experimental device that can achieve real-time visualization of water migration. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a three-dimensional visual unsaturated soil moisture migration model device, which can effectively simulate the dynamic process of moisture migration and clearly display the migration path and behavior, providing key support for in-depth research on the mechanical properties of unsaturated soil.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] A three-dimensional visual unsaturated soil water migration model device comprises: a transparent experimental container, a water head control system, an imaging system, a laser sheet generation system and a matrix suction monitoring device.

[0006] The transparent experimental container is filled with porous media.

[0007] The water head control system is used to transport the fluid with tracer particles into the transparent experimental container.

[0008] The matrix suction monitoring device is arranged on the transparent experimental container, and the matrix suction monitoring device is used to monitor the suction change of the porous medium in real time.

[0009] The laser sheet generating system is located at one side of the transparent experimental container, and the laser sheet generating system is used to generate a laser sheet.

[0010] The imaging system is located on one side of the transparent experimental container, and is used to record the distribution and flow trajectory of the tracer particles.

[0011] In the three-dimensional visual unsaturated soil moisture migration model device provided by at least one embodiment of the present disclosure, the porous medium is a porous medium formed by stacking spherical PMMA particles.

[0012] The three-dimensional visual unsaturated soil moisture migration model device provided by at least one embodiment of the present disclosure further includes: a flexible container.

[0013] A liquid outlet is arranged at the bottom of the transparent experimental container, and the transparent experimental container and the flexible container are communicated with each other through the liquid outlet.

[0014] In the three-dimensional visual unsaturated soil moisture migration model device provided by at least one embodiment of the present disclosure, a filter screen is provided at the liquid outlet, and the filter screen is used to filter the porous medium to prevent the porous medium from entering the flexible container.

[0015] In the three-dimensional visual unsaturated soil water migration model device provided by at least one embodiment of the present disclosure, the water head control system includes: a horizontal glass tube, a movable plate, a burette and a bracket.

[0016] The movable plate is horizontally arranged on the bracket.

[0017] The horizontal glass tube is fixedly arranged on the movable plate, the horizontal glass tube is communicated with the burette, and the horizontal glass tube is perpendicular to the burette.

[0018] One end of the horizontal glass tube is connected with a liquid outlet pipe, and the liquid outlet pipe is communicated with the bottom of the transparent experimental container.

[0019] In the three-dimensional visual unsaturated soil moisture migration model device provided by at least one embodiment of the present disclosure, a first valve is provided on the burette.

[0020] The horizontal glass tube is provided with a second valve, and the second valve and the liquid outlet pipe are distributed in sequence along the flow direction of the fluid.

[0021] In the three-dimensional visual unsaturated soil moisture migration model device provided by at least one embodiment of the present disclosure, the bracket is a liftable bracket.

[0022] The heights of the horizontal glass tube and the movable plate are adjusted by the liftable bracket.

[0023] In the three-dimensional visual unsaturated soil moisture migration model device provided by at least one embodiment of the present disclosure, a scale is provided on one side of the bracket, and the horizontal glass tube and the movable plate are both perpendicular to the scale.

[0024] The beneficial effects of the present invention are: it can effectively simulate the dynamic process of water migration, and can also clearly display the migration path and behavior, providing key support for in-depth research on the mechanical properties of unsaturated soil. It has important theoretical significance and practical value for scientific exploration and practical application in geotechnical engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 The present invention is a schematic structural diagram of a three-dimensional visual unsaturated soil moisture migration model device.

[0027] Figure 2 This is a schematic diagram of the structure of the water head control system.

[0028] Figure 3 This is a cross-sectional view of the matrix suction monitoring device.

[0029] In the figure:

[0030] 10. Transparent experimental container;

[0031] 21. Horizontal glass tube; 22. Movable plate; 23. Burette; 24. Bracket; 25. Liquid outlet tube; 26. First valve; 27. Second valve; 28. Scale;

[0032] 30. Imaging system;

[0033] 40. Laser sheet generation system;

[0034] 50. Matrix suction monitoring device; 51. Sensor; 52. Aluminum alloy housing; 53. Clay plate; 54. Rubber sealing material;

[0035] 60. Flexible container. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments will be described clearly and completely below in conjunction with the drawings in the embodiments. Obviously, the described embodiments are only a part of the embodiments, rather than all the embodiments.

[0037] Example

[0038] like Figure 1 and 2 As shown, this embodiment provides a three-dimensional visual unsaturated soil water migration model device, including a transparent experimental container 10, a water head control system, an imaging system 30, a laser sheet generation system 40, a matrix suction monitoring device 50 and a flexible container 60.

[0039] Specifically, the transparent experimental container 10 is filled with a porous medium (not shown). The water head control system is used to transport the fluid with tracer particles into the transparent experimental container 10 .

[0040] Specifically, the matrix suction monitoring device 50 is disposed on the transparent experimental container 10, and the matrix suction monitoring device 50 is used to monitor the suction change of the porous medium in real time. The laser sheet generation system 40 is located on one side of the transparent experimental container 10, and the laser sheet generation system 40 is used to generate a laser sheet.

[0041] Specifically, the imaging system 30 is located at one side of the transparent experimental container 10 , and the imaging system 30 is used to record the distribution and flow trajectory of the tracer particles.

[0042] In this embodiment, the porous medium is a porous medium formed by stacking spherical PMMA particles.

[0043] In this embodiment, a liquid outlet (not shown) is provided at the bottom of the transparent experimental container 10 , and the transparent experimental container 10 and the flexible container 60 are connected through the liquid outlet.

[0044] In this embodiment, a filter screen (not shown) is provided at the liquid outlet, and the filter screen is used to filter the porous medium to prevent the porous medium from entering the flexible container 60 .

[0045] In this embodiment, the water head control system includes a horizontal glass tube 21 , a movable plate 22 , a burette 23 and a bracket 24 .

[0046] Specifically, the movable plate 22 is horizontally disposed on the bracket 24. The horizontal glass tube 21 is fixedly disposed on the movable plate 22, the horizontal glass tube 21 is communicated with the burette 23, and the horizontal glass tube 21 is perpendicular to the burette 23.

[0047] Specifically, one end of the horizontal glass tube 21 is connected to a liquid outlet pipe 25 , and the liquid outlet pipe 25 is connected to the bottom of the transparent experimental container 10 .

[0048] In this embodiment, a first valve 26 is provided on the burette 23. A second valve 27 is provided on the horizontal glass tube 21, and the second valve 27 and the liquid outlet pipe 25 are sequentially distributed along the flow direction of the fluid.

[0049] In this embodiment, the support 24 is a liftable support 24. The heights of the horizontal glass tube 21 and the movable plate 22 are adjusted by the liftable support 24.

[0050] Specifically, a scale 28 is disposed on one side of the support 24 , and the horizontal glass tube 21 and the movable plate 22 are both perpendicular to the scale 28 .

[0051] The transparent experimental container 10 will be further described below.

[0052] The transparent experimental container 10 is made of colorless and transparent PVC material with a size of 10 cm×10 cm×10 cm. The fluid passes through the porous medium from the top of the transparent experimental container 10 under the control of the water head control system, and then is collected by the flexible container 60 at the bottom of the transparent experimental container 10. PMMA particles are specially selected for their smooth surface, good transparency and monodispersity. The diameter of the particles can be selected according to the gradation required by the experiment. The fluid used is Triton X-100, which is a Newtonian fluid with a high viscosity of η=0.270 Pa·s. The typical average fluid velocity is hUi~100mm·s-1. The resulting Reynolds number ρhUid / η~10-3 ensures that the inertial effect can be ignored. At room temperature, the refractive index of the fluid (about 1.492) is close to the refractive index of PMMA particles (about 1.491), making the porous medium almost transparent. Flow visualization and dispersion experiments are carried out by sowing small fluorescent particles (PMMA B-particles, from MF-Rhodamine) in the fluid.

[0053] The water head control system will be further described below.

[0054] Horizontal glass tube 21: Triton X-100 solution is contained in the horizontal glass tube 21. By adjusting the height of the water level in the horizontal glass tube 21, the amount of fluid entering the porous medium is controlled, thereby adjusting the water head and controlling the suction force.

[0055] Movable plate 22: The height of the movable plate 22 is adjusted by a lifting bracket 24, and can be moved up and down to adjust the height of the water head. The precise adjustment of the movable plate 22 enables the accuracy of suction control to reach 0.005 kPa.

[0056] The head can be adjusted from positive to negative head (maximum suction of 10 kPa), allowing fine dynamic control and measurement of fluids in porous media.

[0057] The imaging system and the laser sheet generating system will be further described below.

[0058] The solid structure and fluid velocity within the porous medium are imaged using a two-dimensional (2-D) plane consisting of a flat perpendicular laser beam that moves through the porous medium to reconstruct the 3D field.

[0059] Laser sheet generation system 40: A laser source (wavelength 532nm, power 2W) generates a uniform laser sheet through a rotating mirror (about 104 revolutions per minute) and an optical lens system. The rotating mirror quickly scans the laser beam to form a thin and uniform laser sheet, while the optical lens focuses the laser beam into light of appropriate thickness.

[0060] Imaging system 30: Imaging is performed using a high-resolution camera (ORCA-Flash4.0, 2048×1048 pixels, 16 bits). The camera’s high signal-to-noise ratio and linear response ensure the clarity and accuracy of the imaging. Finally, a high-pass filter (590 nm) installed in front of the lens is used to filter out scattered light, ensuring that only the light emitted by the fluorescent tracer particles is received by the camera.

[0061] The use of two-dimensional planar imaging and three-dimensional reconstruction technology can accurately record the distribution and flow trajectory of tracer particles and reveal the dynamic changes of fluids in porous media.

[0062] The matrix suction monitoring device will be further described below.

[0063] The matrix suction monitoring device 50 is used to monitor the matrix suction changes of the sample in real time and to perform correlation analysis with the fluid distribution and flow characteristics.

[0064] Selection of ceramic head material: Since the viscosity of mineral oil is greater than that of water, a larger porosity (5 microns) is required to allow the mineral oil fluid to pass freely.

[0065] Increase system sealing: Mineral oil has a certain volatility. In order to prevent oil volatilization and leakage, a 1mm thick silicone rubber film is installed on both sides of the clay plate.

[0066] like Figure 3 As shown, the matrix suction monitoring device 50 includes a sensor 51 , an aluminum alloy housing 52 , a clay plate 53 and a rubber sealing material 54 .

[0067] The aluminum alloy housing 52 has a first assembly port (not shown) and a second assembly port (not shown), the first assembly port and the second assembly port are connected, the sensor 51 is inserted into the first assembly port, the clay plate 53 is inserted into the second assembly port, and an oil cavity is formed between the sensor 51 and the clay plate 53.

[0068] The rubber sealing material 54 is disposed in the second assembly opening, and the rubber sealing material 54 is located between the aluminum alloy housing 52 and the clay plate 53 .

[0069] An experimental example of the three-dimensional visual unsaturated soil moisture migration model device in the embodiment will be disclosed below.

[0070] Test materials

[0071] Solid particles: The material is polymethyl methacrylate (PMMA), which is a polymer formed by the addition polymerization of methyl methacrylate (MMA).

[0072] Liquid material: The fluid used is Triton X-100, which is a Newtonian fluid with a high viscosity of η = 0.270 Pa·s. At room temperature, the refractive index of the fluid (about 1.492) is close to the refractive index of PMMA particles (about 1.491), making the porous medium almost transparent.

[0073] Tracer particles: Flow visualization and dispersion experiments are performed by seeding small fluorescent PMMA B-particles in the fluid. PMMA B-particles are particles made of polymethyl methacrylate (PMMA) material. These particles have a diameter of 3.23 μm, which is much smaller than the size of the pores, allowing the particles to accurately follow the fluid flow without interfering with the flow path.

[0074] Experimental steps:

[0075] Sample loading: According to the test requirements, PMMA particles of appropriate particle size are selected and uniformly arranged according to the preset mass and gradation. These particles are three-dimensionally randomly stacked rigid spherical particles, and they are uniformly filled into a transparent experimental container. PMMA B-particles are added to the fluid Triton X-100 as tracer particles. Then, by injecting Triton X-100 fluid into the sample, ensure that the fluid is evenly distributed among the particles. After injection, let it stand for 24 hours to ensure that the porous medium is fully saturated.

[0076] Controlling matrix suction: The matrix suction involved in this device is very small <10kPa, so a water head control system is used to control the matrix suction. Triton X-100 solution is loaded into the horizontal glass tube. In the experiment, the height of the water head is consistent with the water level of the horizontal glass tube, and the water level is always maintained at the height of the horizontal glass tube. By adjusting the movable plate, the movable plate is raised or lowered, thereby changing the water head in the porous medium. The adjustment range of the water head can be from positive water head to negative water head (the maximum suction is 10kPa, that is, the water head can be adjusted to -1000mm). The adjustment accuracy of the water head is 0.5mm, and the corresponding suction control accuracy is 0.005kPa. Driven by the matrix suction, the Triton X-100 solution in the medium begins to migrate and redistribute. By measuring the amount of solution flowing in or out, the change in the amount of liquid in the porous medium can be calculated. The change in the matrix suction of the sample is read through the installed matrix suction monitoring device. When the water head rises, the Triton X-100 solution begins to penetrate into the porous medium, and the pores are gradually replenished. When the water head decreases, the Triton X-100 solution in the pores begins to flow outward and the matrix suction increases.

[0077] Imaging principle:

[0078] The fluid flow field is imaged by reflective seed tracer particles dispersed in the liquid phase. These tracer particles move with the fluid and can accurately track the flow behavior of the fluid. Through high-resolution imaging technology, the displacement and velocity field of the tracer particles are recorded to further reveal the flow characteristics in the porous medium.

[0079] The distribution of PMMA particles and pore fluid in the porous medium is acquired by two-dimensional imaging, which is illuminated by a flat vertical laser beam to provide sufficient brightness and contrast to ensure clear visibility of the tracer particles.

[0080] Three-dimensional field reconstruction: The laser beam moves layer by layer in the porous medium, capturing imaging data of different planes by step-by-step scanning. Each scan generates a series of high-resolution two-dimensional images that record the distribution and flow state of the pore fluid in a specific plane. Since there are gaps between the scanned planes, the gaps in the three-dimensional data need to be filled by an interpolation algorithm to generate continuous three-dimensional field data. This method can restore the three-dimensional pore fluid distribution and its migration path in the porous medium with high precision, while obtaining accurate velocity field distribution information.

[0081] Liquid distribution:

[0082] In porous media composed of spherical PMMA particles, the distribution of pore liquid presents two main forms: free state and capillary state. Free state liquid mainly exists between larger pores, and due to the good connectivity between pores, the liquid can flow freely. The distribution of free state liquid is affected by external factors such as pressure, gravity and environmental humidity. In an alternating dry and wet environment, the liquid is easy to flow and may be discharged. Capillary state liquid is liquid that is attracted by the tension between the pore wall and the air and the surface effect to form a water film or fill the small gaps inside the pore or between solid particles. Due to the small size of the pores, the liquid is bound in these areas and cannot flow freely.

[0083] The laser scanning system accurately monitors the motion trajectory of tracer particles (such as PMMA B-particles). Based on the displacement of particles in a certain period of time and the structural information of the porous medium, the velocity field of the fluid can be calculated. The velocity field represents the velocity distribution of the fluid at different positions, so that the dynamic changes of the fluid in the porous medium can be derived. Specifically, the change of the velocity field can reveal the difference in the flow velocity of the fluid in different pore areas, reflecting the flow resistance, porosity, pore connectivity and other characteristics of the medium.

[0084] Although the embodiments of the present application have been shown and described above, the scope of protection of the present invention is not limited thereto, and any changes or substitutions that are not conceivable through creative work should be included in the scope of protection of the present invention; unless explicitly stated, any elements, actions or instructions used in this document should not be interpreted as critical or necessary.

Claims

1. A three-dimensional visual unsaturated soil water migration model device, characterized in that: include: Transparent experimental container, water head control system, imaging system, laser sheet generation system and matrix suction monitoring device; The transparent experimental container is filled with a porous medium; The water head control system is used to transport the fluid with tracer particles into the transparent experimental container; The matrix suction monitoring device is arranged on the transparent experimental container, and the matrix suction monitoring device is used to monitor the suction change of the porous medium in real time; The laser sheet generation system is located at one side of the transparent experimental container, and the laser sheet generation system is used to generate a laser sheet; The imaging system is located on one side of the transparent experimental container, and is used to record the distribution and flow trajectory of the tracer particles.

2. A three-dimensional visual unsaturated soil water migration model device according to claim 1, characterized in that: The porous medium is a porous medium formed by stacking spherical PMMA particles.

3. The three-dimensional visual unsaturated soil water migration model device according to claim 1 is characterized in that: Also includes: Flexible containers; A liquid outlet is arranged at the bottom of the transparent experimental container, and the transparent experimental container and the flexible container are communicated with each other through the liquid outlet.

4. A three-dimensional visual unsaturated soil water migration model device according to claim 3, characterized in that: A filter screen is provided at the liquid outlet, and the filter screen is used to filter the porous medium to prevent the porous medium from entering the flexible container.

5. The three-dimensional visual unsaturated soil water migration model device according to claim 1 is characterized in that: The water head control system comprises: Horizontal glass tube, movable plate, burette and stand; The movable plate is horizontally arranged on the bracket; The horizontal glass tube is fixedly arranged on the movable plate, the horizontal glass tube is connected with the burette, and the horizontal glass tube is perpendicular to the burette; One end of the horizontal glass tube is connected with a liquid outlet pipe, and the liquid outlet pipe is communicated with the bottom of the transparent experimental container.

6. A three-dimensional visual unsaturated soil water migration model device according to claim 5, characterized in that: The burette is provided with a first valve; The horizontal glass tube is provided with a second valve, and the second valve and the liquid outlet pipe are distributed in sequence along the flow direction of the fluid.

7. The three-dimensional visual unsaturated soil water migration model device according to claim 5, characterized in that: The bracket is a liftable bracket; The heights of the horizontal glass tube and the movable plate are adjusted by the liftable bracket.

8. The three-dimensional visual unsaturated soil water migration model device according to claim 7 is characterized in that: A scale is arranged on one side of the support, and the horizontal glass tube and the movable plate are both perpendicular to the scale.

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