A loess water infiltration observation experimental device and experimental method

Abstract

The present application belongs to the technical field of soil water migration experiment observation, and particularly relates to a loess water infiltration observation experiment device and experiment method, which comprises a loess water infiltration visual sample unit, a packaging and sealing unit, a fluid supply unit and a main control unit; the visual sample unit is provided with an observation channel on the surface of a loess base to simulate a fissure or a preferential flow path; the packaging and sealing unit is surrounded by a transparent cover layer and the loess base to form a closed visual flow cavity, and is provided with a liquid inlet and a liquid outlet; the fluid supply unit supplies test liquid to the cavity; the main control unit synchronously collects water infiltration process images and inlet pressure data to realize real-time analysis of the infiltration dynamics. The present application can continuously observe preferential flow, finger flow and matrix-fissure interface exchange process through the visual cavity and multi-parameter collection, and provides an intuitive and quantitative experimental method for revealing the loess water migration mechanism.

Description

Technical Field

[0001] This invention belongs to the field of soil moisture transport experimental observation technology, specifically relating to an experimental device and method for observing soil moisture infiltration in loess. Background Technology

[0002] Water infiltration and seepage processes in soil are widely observed in civil engineering, environmental engineering, agricultural hydrology, ecological restoration, and pollutant migration control. They are crucial for slope stability assessment, foundation engineering safety, groundwater recharge, pollutant transport in the vadose zone, and analysis of soil disaster mechanisms. Particularly in loess regions, due to the characteristics of loess—developed pore structure, strong heterogeneity, significant collapsibility, and the coexistence of macropores and matrix—the flow path, infiltration rate, and interfacial exchange processes during water infiltration significantly differ from conventional seepage behavior in homogeneous media. Therefore, establishing an experimental method for real-time and intuitive observation of water infiltration processes within loess is of great significance for revealing the complex seepage mechanisms in loess.

[0003] Existing research devices for studying water infiltration processes in soil or loess typically employ non-invasive imaging techniques such as X-ray computed tomography (XCT), neutron imaging, nuclear magnetic resonance imaging (MRI), PET, and SPECT. While these methods can characterize the internal water migration features of soil to some extent, they rely primarily on static imaging or intermittent observations at a specific moment during microscopic soil infiltration experiments, making it difficult to capture the evolution of transient flow behavior in real time. However, the water infiltration process in loess or other structured soils is often highly complex. Under the combined influence of macropores, fissures, and the matrix, phenomena such as fingering, localized stagnation, fine streams, thin film flows, pulsed flows, and lateral exchange at the macropore-matrix interface are prone to occur. These flow phenomena are characterized by significant transient and localized nature, making it difficult to accurately reveal their formation, development, and transformation mechanisms based solely on static results.

[0004] Therefore, there is an urgent need to provide an experimental device that can observe the water infiltration process in loess in real time and intuitively, so as to realize the continuous observation and analysis of complex seepage phenomena inside loess, especially dynamic processes such as dominant flow, macropore-matrix interface exchange, finger flow and local retention. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide an experimental device and method for observing water infiltration in loess, which enables continuous and intuitive observation of transient phenomena such as finger flow, pulse flow, thin film flow, and lateral exchange at the macropore-matrix interface. This eliminates the limitation of static imaging, which can only obtain discrete snapshots, and improves the analytical accuracy and experimental efficiency of the complex seepage mechanism of loess.

[0006] The technical solution of this invention is: An experimental device for observing water infiltration in loess includes: A loess moisture infiltration visualization sample unit includes a loess base, and an observation channel is opened on the surface of the loess base. The observation channel is used to simulate internal fissures or dominant flow paths in loess. The encapsulation and sealing unit includes a transparent covering layer, one side of which is attached to and covers the surface of the loess substrate on which the observation channel is located, together with the loess substrate, enclosing the observation channel to form a closed, visible flow cavity; the covering layer is provided with a liquid supply inlet and a liquid discharge outlet, both of which are connected to the observation channel; A fluid supply unit, the output of which is connected to the liquid supply inlet, is used to deliver test liquid to the observation channel; The main control unit includes a data acquisition module and a processing module. The data acquisition module is used to continuously acquire images of the infiltration process of loess water in the visible flow cavity and the pressure data of the liquid supply inlet. The processing module is used to realize real-time analysis of the loess water infiltration process based on the acquired images and pressure data.

[0007] Preferably, the loess base is a cuboid, the observation channel is a groove opened along the length of the loess base, and the width of the observation channel is in the ratio of 1:50 to the overall width of the loess base, and the depth of the observation channel is the same as the width of the observation channel.

[0008] Preferably, the fluid supply unit includes a constant flow rate liquid supply module, which includes a drive assembly, a syringe, and a connecting conduit. One end of the connecting conduit is connected to the outlet of the syringe, and the other end is connected to the liquid supply inlet on the cover layer. The syringe contains test liquid. The drive assembly has a movable component, which is fixed to the piston rod of the syringe. The drive assembly is used to drive the piston rod through the movable component to move the piston inside the syringe at a constant speed, so as to deliver the test liquid to the liquid supply inlet at a constant speed through the connecting conduit.

[0009] Preferably, the fluid supply unit further includes a constant head liquid supply module. The constant head liquid supply module includes a support frame, a liquid storage container, a vertical liquid supply pipeline, and a control valve. The liquid storage container is vertically fixed on the support frame, and its lower end is provided with a liquid outlet. The liquid outlet is connected to one end of the vertical liquid supply pipeline, and the other end of the vertical liquid supply pipeline is connected to the liquid supply inlet on the cover layer. The control valve is provided on the vertical liquid supply pipeline. The test liquid in the liquid storage container is used to be transported to the liquid supply inlet by gravity after the control valve is opened.

[0010] Preferably, the data acquisition module includes a microscopic observation component and a pressure monitoring component. The microscopic observation component is used to continuously acquire images of water migration in the loess matrix, observation channel, and matrix-fracture interface. The pressure monitoring component is located at the liquid supply inlet and is used to monitor the inlet pressure change of the test liquid in the observation channel during infiltration in real time.

[0011] Preferably, the thickness of the covering layer is the same as the thickness of the loess base, and the light transmittance of the covering layer is ≥90%.

[0012] A method for observing loess water infiltration, implemented using any of the loess water infiltration observation experimental devices described above, includes the following steps: S1. Cut the loess parent body to obtain a loess base of a predetermined size, open an observation channel on the surface of the loess base, cover and attach a transparent material covering layer to the surface of the loess base with the observation channel, and open a liquid supply inlet and a liquid discharge outlet on the covering layer that are connected to the observation channel to form a closed visible flow cavity. S2. Prepare the test liquid according to the preset ratio and deliver the test liquid to the liquid supply inlet; S3. After setting the target flow rate or target head, open the liquid supply inlet to allow the test liquid to enter the observation channel; S4. Continuously acquire images of the infiltration process of loess water in the visible flow cavity and pressure data of the liquid supply inlet, and perform real-time analysis of the loess water infiltration process based on the infiltration process images and pressure data of the liquid supply inlet to obtain the dynamic change characteristics of loess water infiltration, preferential flow formation and matrix-fracture interface.

[0013] Preferably, the test liquid is a tracer solution with added Acid Blue 9 staining agent, and the mass ratio of Acid Blue 9 staining agent to water is 1:250.

[0014] Preferably, the covering layer is formed by mixing and curing polydimethylsiloxane prepolymer and curing agent at a mass ratio of 10:1.

[0015] Compared with the prior art, the experimental device and method for observing water infiltration in loess of the present invention have the following beneficial effects: This invention precisely simulates natural fissures or dominant flow paths by opening observation channels on a loess substrate. Combined with a transparent overburden layer, a closed and visible flow cavity is formed. Under the stable drive of the fluid supply unit, the test liquid flows in a near-in-situ stress environment. The main control unit simultaneously acquires images of water migration and inlet pressure data within the cavity. By using image processing and pressure time series analysis, continuous and intuitive observation of transient phenomena such as finger flow, pulse flow, thin film flow, and lateral exchange at the macropore-matrix interface is achieved. This invention overcomes the limitation of static imaging, which can only obtain discrete snapshots, and significantly improves the analytical accuracy and experimental efficiency of the complex seepage mechanism of loess. Attached Figure Description

[0016] Figure 1 This is a partial structural schematic diagram of an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the loess water infiltration visualization sample unit in an embodiment of the present invention; Figure 3 This is a schematic diagram of the overall structure of the constant flow rate liquid supply module used in an embodiment of the present invention; Figure 4 This is a schematic diagram of the overall structure of the constant head liquid supply module used in an embodiment of the present invention.

[0017] Explanation of reference numerals in the attached figures: 1. Loess base; 2. Overburden layer; 3. Uncured PDMS layer; 4. Connecting conduit; 5. Liquid supply inlet; 6. Observation channel; 7. Drainage outlet; 8. Moving component; 9. Central fixing component; 10. Syringe; 11. Test liquid; 13. Head support component; 14. Drive assembly; 15. Pressure sensor; 16. Electron microscope; 17. Computer; 18. Loess moisture infiltration visualization sample unit; 19. Support frame; 20. Liquid storage container; 21. Vertical liquid supply pipeline. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0020] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0021] See Figures 1 to 4 As shown, in order to achieve continuous and intuitive observation of transient phenomena such as finger flow, pulse flow, thin film flow and lateral exchange at the macropore-matrix interface, and to improve the analytical accuracy and experimental efficiency of the complex seepage mechanism of loess, this embodiment provides an experimental device and method for observing water infiltration in loess.

[0022] Example 1: An experimental device for observing water infiltration in loess. like Figures 1 to 2 As shown, the device includes a loess moisture infiltration visualization sample unit 18, a sealing unit, a fluid supply unit, and a main control unit.

[0023] The loess moisture infiltration visualization sample unit 18 includes a loess base 1, which is loess collected from a typical area of ​​the Loess Plateau. The loess is cut and polished into a rectangular block measuring 4.0cm (length) × 2.6cm (width) × 0.6cm (thickness), with a surface roughness Ra ≤ 3.2μm. It is important to note that the shape and size of the loess base 1 can be prefabricated according to experimental requirements, while ensuring that the carved observation channel 6 can be fully presented under microscope magnification. Furthermore, the size of the loess base 1 should not be too large to avoid damage during the experiment due to the fragility of loess. Preferably, the shape and size of the loess base 1 can be designed within the following range: length 3cm~4cm, width 2cm~3cm, and thickness 0.5cm~1cm.

[0024] The preparation process of the loess block includes: first, cutting the retrieved undisturbed soil with a knife to obtain a loess block whose size and shape are approximately the target value. Then, sanding with 60-grit sandpaper to make the size and shape of the loess block approximately consistent with the target structure. Finally, to make the surface smoother and facilitate the adhesion of the polydimethylsiloxane layer (PDMS), finer-grit 120-grit sandpaper is used for detailed sanding to obtain a cuboid loess block that matches the target requirements.

[0025] An observation channel 6 is created along the length of the upper surface of the loess substrate 1 using a laser etching machine. Specifically, the shape to be etched is first drawn in CAD software, then imported into a Diaotu CZ356 laser etching machine for repeated etching three times to obtain the desired observation channel 6. The cross-sectional shape of the observation channel 6 is semi-elliptical, used to simulate internal fissures or dominant flow paths in the loess, and to directly observe the migration process of water in the loess matrix-fissure system. An etching area of ​​approximately 3.0 cm × 2.0 cm is formed on the smooth loess surface. The rectangular observation channel 6 has a width of approximately 0.05 cm and a depth of 0.05 cm. Preferably, the width of the observation channel 6 is in a 1:50 ratio to the overall width of the loess substrate, and the depth of the observation channel 6 is approximately the same as its width, which is generally set to be identical. The main reasons for this design are: 1. It can be clearly distinguished from the size in the small-pore matrix; 2. It avoids the "open channel flow" being too strong due to the large scale, which will produce turbulence error; 3. It facilitates PDMS microfluidic fabrication and microscopic observation.

[0026] The sealing unit includes a transparent cover layer 2. The thickness of the cover layer 2 can be set to be the same as the thickness of the loess base 1, or it can be set proportionally to the thickness of the loess base 1. Generally, the thickness of the cover layer 2 should not be less than half the thickness of the loess base 1. A thicker cover layer 2 facilitates adhesion to the loess base 1, but it should not be too thick, as this would obstruct the view and cause waste. Its thickness is preferably 0.2cm~0.6cm. Specifically, the cover layer 2 uses a polydimethylsiloxane layer (PDMS) with a light transmittance ≥90%. The preparation method is as follows: the polydimethylsiloxane prepolymer and the curing agent are mixed at a mass ratio of 10:1 and stirred with a glass rod. Stirring is completed when a large number of bubbles are generated in the liquid. After stirring, the mixture is poured into a mold and placed in a vacuum pump to remove air. The air removal is completed when all the bubbles in the liquid disappear. Then, the mold is placed in an oven and cured at 95℃ for 1 hour. A liquid inlet 5 and a liquid outlet 7 with a diameter of 0.2cm are pre-processed on the transparent polydimethylsiloxane layer. During encapsulation, an uncured PDMS layer 3 (i.e., an uncured thin layer of PDMS) with a thickness of approximately 0.1 mm is spin-coated onto the bonding surface of the transparent polydimethylsiloxane layer. It is important to note that spin-coating is performed using a rotary table. 1-2 ml of liquid PDMS is poured onto the dried PDMS coating layer 2 and placed on the rotary table. The rotary table is then started and run at approximately 3000 rpm for 2 minutes before being turned off. Excessive speed can cause the entire PDMS coating layer to fly off, while insufficient speed can result in uneven spin-coating, making it impossible to accurately isolate air during the experiment and leading to experimental failure. After spin-coating, the coating is aligned and bonded to the surface of the loess substrate 1 with the observation channel 6. It is then placed in an 85℃ oven for secondary curing for 1.5 hours to form a closed, visible flow cavity, ensuring no liquid leakage.

[0027] The covering layer 2 can also be bonded to the loess substrate 1 using a transparent glass sheet and edge sealant, but PDMS is generally preferred because it has good optical transparency, is easy to replicate microstructures, has low cost, is easy to process, and is a flowing liquid that can be bonded before drying and has a stable structure after drying.

[0028] like Figure 3 and Figure 4 As shown, the fluid supply unit includes a constant flow rate supply module and a constant head supply module. The constant flow rate supply module and the constant head supply module are selected according to experimental requirements. Specifically, the constant flow rate supply module consists of a drive assembly 14, a syringe 10, and a connecting conduit 4. The syringe 10 has a volume of 10 mL and is connected to the drive assembly 14 via a moving part 8, a central fixing part 9, and a head support part 13, allowing precise control of the flow rate within the range of 0.01 mL / min to 0.1 mL / min. The syringe 10 includes a reservoir, a piston, a piston rod, and a needle. The piston is slidably connected inside the reservoir and fixed to one end of the piston rod. The other end of the piston rod extends out of the reservoir. The needle is fixed to the output end of the reservoir. The moving part 8, as a moving part of the drive assembly, is fixed to the piston rod of the syringe 10. The central fixing part 9 and the head support part 13 are located at both ends of the reservoir to stably position it. One end of the connecting conduit 4 is connected to the needle part of the syringe 10 (the two can be firmly glued together), and the other end is connected to the liquid supply inlet 5 on the cover layer 2. A pressure sensor 15 is installed on the connecting conduit 4. The syringe 10 contains the test liquid 11. The piston rod of the syringe 10 is driven at a constant speed by the moving part of the drive assembly 14, so that the piston rod pushes the piston at a constant speed to deliver the test liquid 11 through the connecting conduit 4 to the liquid supply inlet 5. The pressure sensor 15 monitors the delivery pressure of the test liquid in real time. The drive assembly 14 can be a structure consisting of a controller, a motor, a lead screw, and a lead screw nut. The lead screw nut is mounted on the lead screw as a moving part 8. During the experiment, one end of the lead screw is connected to the output shaft of the motor, and the motor is electrically connected to the controller to control the lead screw to rotate at a constant speed, so that the lead screw nut drives the piston rod to push the piston at a constant speed within the liquid reservoir of the syringe 10, thereby delivering the test liquid 11 through the connecting conduit 4 to the liquid supply inlet 5. Furthermore, the controller has a control panel, which includes a display screen, a stop button, a pause button, a start button, and parameter buttons. These buttons work together to start and stop the experiment and to set and display parameters.

[0029] The constant head liquid supply module consists of a support frame 19, a liquid storage container 20, a vertical liquid supply pipeline 21, and a control valve. The liquid storage container 20 is vertically fixed on the support frame 19, and its lower end is provided with a liquid outlet. The support frame 19 is a telescopic structure, and the height of the liquid storage container 20 is adjustable via the support frame 19. The liquid outlet is connected to one end of the vertical liquid supply pipeline 21, and the other end of the vertical liquid supply pipeline 21 is connected to the liquid supply inlet 5 on the cover layer 2. The control valve is located on the vertical liquid supply pipeline 21. The test liquid 11 in the liquid storage container 20 is used to deliver the liquid to the liquid supply inlet 5 under the action of gravity through the adjustment of the control valve. The head pressure (0 kPa~10 kPa) is adjusted by the height of the support frame 19. The test liquid 11 is a mixed solution of deionized water and Acid Blue 9 staining agent (Acid Blue 9, CAS: 3844-45-9, purity 85%, Bide Pharm, China) at a mass ratio of 1:250 to enhance image contrast.

[0030] The main control unit includes a data acquisition module and a processing module. The data acquisition module is used to continuously acquire images of the infiltration process of loess water within the visible flow cavity and pressure data from the liquid supply inlet 5. Specifically, the data acquisition module includes a microscopic observation component and a pressure monitoring component. The microscopic observation component uses an electron microscope 16 (ZEISS Stemi508) connected to a computer 17 for direct video recording or other optical observation equipment capable of continuously imaging the flow process on the sample surface. It is equipped with a high-speed camera or a CCD camera. The CCD camera's acquisition frequency is set to 5 frames / second, with a resolution of 1920×1080 pixels, for continuously acquiring images of water migration in the loess matrix, observation channel, and matrix-fracture interface. The pressure monitoring component uses a pressure sensor 15, located on one side of the liquid supply inlet 5, to monitor the pressure changes of the test liquid 11 at the inlet of the observation channel 6 during the infiltration process in real time. The processing module is used to perform real-time analysis of the loess water infiltration process based on the acquired images and pressure data. The data processing component is computer 17, which processes the acquired video data using image analysis software (such as ImageJ) to extract parameters such as the location of the wetting front, infiltration rate, and channel filling degree.

[0031] Example 2: An experimental method for observing water infiltration in loess: An experimental setup for observing loess moisture infiltration based on Example 1 was implemented. The experimental method includes the following steps: S1 Sample Preparation: Loess matrix material without obvious natural cracks was selected. After sampling, it was wrapped and sealed for preservation to avoid structural disturbance during transportation. The loess matrix was cut to obtain a loess substrate of predetermined size. The loess substrate was placed in a 100℃ oven to dry for 36 hours. After removal, the observation channel was processed by laser etching. A transparent polydimethylsiloxane layer (dried PDMS) was prepared according to the formula. Liquid PDMS was spin-coated onto the surface of the dried PDMS, and the liquid PDMS side was used to adhere to the loess substrate. After adhesion, it was placed in a 95℃ oven for 1 hour to dry the liquid PDMS, and then sealed and encapsulated to form a visible flow cavity.

[0032] S2 device assembly: Connect one end of the connecting tube or vertical liquid supply line to the liquid supply inlet, and the other end to the syringe or liquid storage container; set the pressure sensor at the liquid supply inlet; place the assembled sample unit on the stage of the microscopic observation component, and adjust the focus to make the observation channel clear.

[0033] S3 Infiltration Test: Activate the drive assembly, set the flow rate to 0.05 mL / min, and inject the staining tracer solution into the visible flow chamber; or set the head pressure to 5 kPa via the constant head supply module and open the control valve to begin infiltration. Maintain an ambient temperature of 25±1℃ and humidity of 50±5% during the test.

[0034] S4 Data Acquisition: Simultaneously activate the microscopic observation component and pressure sensor to record image sequences of the infiltration process and pressure data at the inlet of the observation channel. When the tracer fluid begins to enter the observation channel and begins to infiltrate laterally into the loess matrix, image acquisition of the infiltration process is performed until the wetting front extends to the edge of the loess base or reaches the preset time (e.g., 30 minutes), at which point acquisition stops.

[0035] S5 Data Analysis: The image sequence was binarized using ImageJ software to extract the contours of the wetting front at different times and calculate the infiltration rate; the infiltration pressure-time curve was plotted in conjunction with pressure data to analyze the preferential flow initiation pressure and matrix suction characteristics; and the velocity distribution in the channel and the water exchange flux at the matrix-fracture interface were analyzed using particle image velocimetry (PIV) technology.

[0036] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. An experimental device for observing water infiltration in loess, characterized in that, include: A loess moisture infiltration visualization sample unit includes a loess base, and an observation channel is opened on the surface of the loess base. The observation channel is used to simulate internal fissures or dominant flow paths in loess. The encapsulation and sealing unit includes a transparent covering layer, one side of which is attached to and covers the surface of the loess substrate on which the observation channel is located, together with the loess substrate, enclosing the observation channel to form a closed, visible flow cavity; the covering layer is provided with a liquid supply inlet and a liquid discharge outlet, both of which are connected to the observation channel; A fluid supply unit, the output of which is connected to the liquid supply inlet, is used to deliver test liquid to the observation channel; The main control unit includes a data acquisition module and a processing module. The data acquisition module is used to continuously acquire images of the infiltration process of loess water in the visible flow cavity and the pressure data of the liquid supply inlet. The processing module is used to realize real-time analysis of the loess water infiltration process based on the acquired images and pressure data.

2. The experimental device for observing water infiltration in loess according to claim 1, characterized in that, The loess base is a cuboid, the observation channel is a groove opened along the length of the loess base, and the width of the observation channel is in the ratio of 1:50 to the overall width of the loess base. The depth of the observation channel is the same as the width of the observation channel.

3. The experimental device for observing water infiltration in loess according to claim 1, characterized in that, The fluid supply unit includes a constant flow rate liquid supply module, which includes a drive assembly, a syringe, and a connecting conduit. One end of the connecting conduit is connected to the outlet of the syringe, and the other end is connected to the liquid supply inlet on the cover layer. The syringe contains test liquid. The drive assembly has a movable component, which is fixed to the piston rod of the syringe. The drive assembly is used to drive the piston rod through the movable component to move the piston inside the syringe at a constant speed, so as to deliver the test liquid to the liquid supply inlet at a constant speed through the connecting conduit.

4. The experimental device for observing water infiltration in loess according to claim 1, characterized in that, The fluid supply unit further includes a constant head liquid supply module, which includes a support frame, a liquid storage container, a vertical liquid supply pipeline, and a control valve. The liquid storage container is vertically fixed on the support frame, and its lower end is provided with a liquid outlet. The liquid outlet is connected to one end of the vertical liquid supply pipeline, and the other end of the vertical liquid supply pipeline is connected to the liquid supply inlet on the cover layer. The control valve is located on the vertical liquid supply pipeline. The test liquid in the liquid storage container is used to be transported to the liquid supply inlet by gravity after the control valve is opened.

5. The experimental device for observing water infiltration in loess according to claim 1, characterized in that, The data acquisition module includes a microscopic observation component and a pressure monitoring component. The microscopic observation component is used to continuously acquire images of water migration in the loess matrix, observation channel, and matrix-fracture interface. The pressure monitoring component is located at the liquid supply inlet and is used to monitor the inlet pressure change of the test liquid in the observation channel in real time during the infiltration process.

6. The experimental device for observing water infiltration in loess according to claim 1, characterized in that, The thickness of the covering layer is the same as the thickness of the loess base, and the light transmittance of the covering layer is ≥90%.

7. A method for observing water infiltration in loess, characterized in that, Includes the following steps: S1. Cut the loess parent body to obtain a loess base of a predetermined size, open an observation channel on the surface of the loess base, cover and attach a transparent material covering layer to the surface of the loess base with the observation channel, and open a liquid supply inlet and a liquid discharge outlet on the covering layer that are connected to the observation channel to form a closed visible flow cavity. S2. Prepare the test liquid according to the preset ratio and deliver the test liquid to the liquid supply inlet; S3. After setting the target flow rate or target head, open the liquid supply inlet to allow the test liquid to enter the observation channel; S4. Continuously acquire images of the infiltration process of loess water in the visible flow cavity and pressure data of the liquid supply inlet, and perform real-time analysis of the loess water infiltration process based on the infiltration process images and pressure data of the liquid supply inlet to obtain the dynamic change characteristics of loess water infiltration, preferential flow formation and matrix-fracture interface.

8. The experimental method for observing water infiltration in loess according to claim 7, characterized in that, The test liquid is a tracer solution with added Acid Blue 9 staining agent, and the mass ratio of Acid Blue 9 staining agent to water is 1:

250.

9. The experimental method for observing water infiltration in loess according to claim 7, characterized in that, The covering layer is formed by mixing and curing polydimethylsiloxane prepolymer and curing agent at a mass ratio of 10:1.

Images