A device and method for testing the erosion-disintegration of soil aggregates of a slope

Abstract

This invention discloses a slope soil aggregate erosion and disintegration testing device, belonging to the field of geotechnical engineering testing technology. The device includes: a model box assembly, a rainfall simulation assembly, an optical observation assembly, and a runoff collection assembly. The model box assembly includes a box body and a slope adjustment mechanism. The slope adjustment mechanism uses multiple hinged plates in conjunction with a hydraulic drive device to achieve precise adjustment of the slope angle in segments. The uppermost layer of the filling area inside the box body is divided into several tracer zones, each tracer zone being covered with a soil layer containing different colored fluorescent tracers. The rainfall simulation assembly simulates natural rainfall processes. The optical observation assembly includes a light shield, an ultraviolet light source, a camera, and a filtering system to achieve fluorescence imaging. The runoff collection assembly uses a sampler to collect sediment samples at different time intervals. This invention can accurately track the soil loss path at different slope locations, enabling visualized observation and quantitative analysis of the soil erosion process, providing a systematic experimental method for studying soil disintegration mechanisms.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering testing technology, specifically to a soil aggregate erosion and disintegration testing device and method, which is suitable for studying the soil disintegration process under different slope and soil conditions, as well as for the accurate observation and analysis of soil loss paths and amounts. Background Technology

[0002] Red sandstone has a unique appearance and is widely used in construction, such as for highway slopes. However, red sandstone is easily affected by the external environment; it disintegrates and breaks down upon contact with moisture. Therefore, red sandstone is prone to disintegration and loss under rainfall, which is a significant factor leading to slope instability. Traditional research methods mainly obtain the total loss by simulating rainfall, collecting runoff sediment, and weighing it. However, these methods generally have the following shortcomings: First, it is impossible to accurately track the soil loss path at different locations on the slope. Traditional methods can only measure the total amount of soil loss and cannot distinguish the contribution of soil loss from different areas such as uphill, middle slope, and downhill, making it difficult to reveal the spatial distribution characteristics of soil erosion.

[0003] Second, the observation methods are limited and lack the ability to visualize dynamic monitoring. Traditional experiments mainly rely on manual observation or simple video recording, making it difficult to accurately track and quantitatively analyze the movement trajectory of soil particles.

[0004] Third, the experimental data collection is discontinuous and has low spatiotemporal resolution. Traditional sediment collection methods often use timed sampling, making it difficult to capture the dynamic changes in soil loss during rainfall.

[0005] Fourth, the slope adjustment mechanism is rudimentary and cannot simulate complex slope morphology. Existing devices mostly use fixed slopes or simple overall tilting, which cannot achieve segmented slope adjustment and cannot truly reflect the complex terrain of actual slopes.

[0006] Meanwhile, fluorescence tracing technology has been increasingly applied in soil erosion research in recent years. This technology, by adding fluorescent tracers to the soil and utilizing excitation sources of different wavelengths and specific filtering systems, enables the visual tracking of soil particle movement. However, existing fluorescence tracing research is mostly limited to small-scale laboratory experiments, lacking systematic device design and complete experimental methods, particularly in areas such as zonal tracing, optimization of optical observation systems, and organic integration with traditional sediment collection methods.

[0007] Therefore, it is necessary to develop a comprehensive soil disintegration testing device that integrates functions such as zone tracing, dynamic optical observation, precise rainfall simulation, and continuous sediment collection to meet the needs of in-depth research on soil erosion mechanisms in the field of geotechnical engineering. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a slope soil aggregate erosion and disintegration testing device and method to solve the problems of existing soil disintegration testing devices being unable to track soil loss paths at different slope locations, having limited observation methods, low spatiotemporal resolution of data acquisition, and weak slope morphology adjustment capabilities. This invention is simple to operate, can effectively simulate rainfall erosion, accurately track soil loss paths, and provide high-quality visualized and quantitative experimental data.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: Firstly, this invention provides a slope soil aggregate erosion and disintegration testing device, comprising: a model box assembly, a rainfall simulation assembly, an optical observation assembly, and a runoff collection assembly.

[0010] The model box assembly includes a box body, a base plate, and a slope adjustment mechanism. The box body is a rectangular structure with an open top, preferably made of transparent plexiglass. One end of the base plate is rotatably connected to the bottom of the box body. The slope adjustment mechanism is located at the bottom of the box body, and its drive end is connected to the base plate to adjust the tilt angle of the base plate to simulate different slopes.

[0011] Preferably, to better simulate the slope of an actual slope, the base plate is composed of several continuous plates, with any two adjacent plates hinged together. The slope adjustment mechanism consists of several hydraulic drive devices, each corresponding to one plate, allowing for independent adjustment to simulate a continuous slope with varying slopes in different sections.

[0012] The upper surface of the substrate and the box together form a filling area for filling test soil. The uppermost layer of soil in the filling area is divided into several tracer zones according to different slope sections, including uphill, middle, and downhill zones. A tracer soil layer is laid in each tracer zone, and a fluorescent tracer of a specific color is premixed in the tracer soil layer. The fluorescent tracer is preferably a fluorescent pigment or fluorescent dye, and the addition ratio is 0.1-1.0% of the soil mass. Different fluorescent tracers of different colors are used in different tracer zones.

[0013] The rainfall simulation component includes a support frame and sprinkler heads. The support frame spans across the model box, is height-adjustable, and is made of aluminum alloy profiles to ensure structural stability. The sprinkler heads are mounted on the support frame in a uniform array, and are pressure-type sprinkler heads with adjustable spray angles. The sprinkler heads are connected to a water supply system via pipelines, which includes a water tank, a booster pump, a flow meter, and a pressure regulating valve.

[0014] The optical observation components include a light shield, an ultraviolet light source, a camera system, and a filtering system. The light shield covers the outside of the model box, forming a sealed darkroom environment. It is made of black light-blocking cloth or black plastic sheeting, with an inner wall treated with a matte black coating and a reflectivity of <5%, ensuring that external light sources do not interfere with fluorescence imaging. The light shield should be larger than the model box and include observation windows and operating channels. The ultraviolet light source includes an array of ultraviolet LED lamps or ultraviolet fluorescent lamps, mounted on adjustable-angle brackets on the sides or top of the box.

[0015] The camera system includes a digital camera or an industrial camera, mounted on a camera bracket directly above the model box. The bracket height is adjustable, and the camera lens is vertically downward, aimed at the center of the slope, covering the entire slope. The filtering system is installed in front of the camera lens and includes a long-pass filter and a band-pass filter. The long-pass filter has a cutoff wavelength of 420-450nm and a transmittance of ≥90%, used to block ultraviolet reflected light. The band-pass filter is selected according to the emission wavelength of the fluorescent tracer.

[0016] The runoff collection assembly includes a flow channel and a sample collector. The flow channel is located at the lowest point of the substrate and is made of stainless steel or PVC with a smooth inner wall to ensure smooth flow of the sediment mixture into the sample collector. The sample collector is located at the end of the flow channel and includes a rotary sample bottle rack that can hold multiple sample bottles. A stepper motor drives the rotary rack to rotate, automatically replacing the sample bottles according to a set time interval.

[0017] Preferably, the system also includes a data acquisition and control system, which comprises a central controller, a sensor network, a data recording module, and a human-machine interface. The central controller, using a PLC or industrial computer, coordinates the operation of each component; the sensor network includes slope sensors, flow sensors, pressure sensors, temperature and humidity sensors, etc., to monitor test parameters in real time; the data recording module records all sensor data and image acquisition timestamps in real time, with a data sampling frequency ≥1Hz; the human-machine interface provides parameter setting, test monitoring, and data viewing functions.

[0018] On the other hand, the present invention also provides a testing method based on the above-described apparatus, comprising the following steps: S1. Soil sample preparation, specifically including: The soil samples used in the experiment were air-dried and sieved, and their basic physical properties, such as moisture content, density, and particle size distribution, were measured. Subsequently, according to the experimental design, fluorescent tracers of different colors were thoroughly mixed with the soil samples in proportion to prepare tracer soil samples; the mixing process was carried out by mechanical stirring for ≥10 minutes to ensure uniform dispersion of the tracers.

[0019] S2, Slope adjustment, specifically including: Start the hydraulic drive system, set the tilt angle of each section of the plate according to the test plan, and form the required slope shape; use slope sensors to monitor and record the slope of each section.

[0020] S3. Soil filling, specifically including: Soil samples are filled in layers inside the model box and compacted using a wooden hammer or vibrator. The dry density is controlled within the design range. Filling is stopped when the soil is a certain distance from the box and leveled as the base layer of the slope top surface.

[0021] S4. Tracer zone laying: Specifically, this involves laying soil layers containing different colored fluorescent tracers on the surface of the base soil according to a predetermined zoning plan, while maintaining clear boundaries between each zone during the laying process.

[0022] S5. Rainfall Simulation: Before rainfall begins, the slope is first illuminated by an ultraviolet light source. Camera parameters are adjusted, and an initial fluorescence image is captured as a baseline for comparison. Images of the corresponding fluorescence bands are captured using different bandpass filters. Subsequently, the water supply system is activated, and the water pressure and sprinkler opening are adjusted to bring the rainfall intensity to the set value. The actual rainfall intensity is monitored and recorded using a flow meter.

[0023] S6. Dynamic observation: After the rainfall begins, take fluorescence images at the set time intervals; before each shot, confirm that the ultraviolet light source is working properly and the light shield is sealed well; record the shooting time of each image and the corresponding test duration.

[0024] S7. Runoff Collection and Recording: The sampler is activated simultaneously with the start of rainfall, and the sample bottles are automatically replaced at set time intervals. The start and end times of collection for each sample bottle are recorded and numbered. Rainfall is stopped when the predetermined rainfall duration is reached or soil erosion reaches a stable state. The process of residual water flow receding on the slope is observed and photographed until no significant runoff is generated.

[0025] S8. Data processing and analysis stage, specifically including: The collected sediment mixture from each time period was allowed to settle, the supernatant was poured off, and the precipitate was transferred to an oven to dry to constant weight. The mass of the dried sediment was weighed, and the soil loss and cumulative loss at each time period were calculated.

[0026] The captured fluorescence images were analyzed using image processing software; the distribution areas of different colors of fluorescence were extracted using color separation technology; and the movement trajectories of soil particles were identified by comparing the initial image with images at various times.

[0027] Based on the temporal changes of fluorescence images, the migration paths of soil in different tracer areas are tracked; vector diagrams or flow field diagrams of soil particle movement are drawn; the distribution changes of soil in different tracer areas on the slope are statistically analyzed, and the migration distance, speed and direction of each area are calculated.

[0028] By combining fluorescence intensity calibration curves, the amount of soil loss in different regions was estimated; the image analysis results were compared and verified with sediment collection data; and a quantitative relationship between soil loss and factors such as rainfall intensity, slope, and time was established.

[0029] Compared with the prior art, the present invention has the following beneficial effects: 1. Enable zoned tracking of soil loss. By laying soil layers containing different colored fluorescent tracers at different locations on different slopes, and combining ultraviolet excitation and filter imaging technology, it is possible to clearly distinguish the loss paths and contributions of soil in different areas, revealing the spatial heterogeneity of soil erosion, which is impossible with traditional methods.

[0030] 2. Slope morphology can be precisely controlled. By using a multi-segment hinged plate body in conjunction with a hydraulic drive system, the slope can be precisely adjusted in segments to simulate complex terrains such as convex slopes, concave slopes, and composite slopes, providing a reliable experimental platform for studying the impact of different slope morphologies on soil erosion.

[0031] 3. The optical observation system is comprehensive. By combining a light shield, an ultraviolet light source, a long-pass filter, and a band-pass filter, a professional fluorescence imaging environment is constructed, effectively eliminating ambient light interference and the influence of ultraviolet reflected light, obtaining high-quality, high-contrast fluorescence images, and providing a reliable data foundation for quantitative analysis.

[0032] 4. High temporal resolution. By automatically collecting sediment samples at different time periods using a sampler and combining them with time-series fluorescence imaging, the dynamic changes in the soil erosion process can be accurately captured, with a temporal resolution down to the minute level, significantly improving the temporal accuracy of the data.

[0033] 5. Comprehensive data acquisition. The device integrates multiple functions such as rainfall simulation, fluorescence tracking, image acquisition, and sediment collection, enabling it to simultaneously obtain qualitative visualization data and quantitative quality data, achieving multi-dimensional observation from macro to micro and from qualitative to quantitative.

[0034] 6. Systematic and standardized experimental methods. This invention provides a complete experimental process, from soil sample preparation, tracer preparation, slope filling to rainfall simulation, image acquisition, and data processing. The operation specifications for each step are clearly defined, ensuring the repeatability of the experiment and the reliability of the results.

[0035] 7. Wide applicability. The parameters of the device can be flexibly adjusted, making it suitable for experimental research on different soil types, rainfall conditions, and slope gradients, demonstrating good versatility and expandability. The technical solution of this invention will be further described in detail below through examples. Attached Figure Description

[0036] Figure 1 This is a simplified schematic diagram of the testing device provided by the present invention; Figure 2 This is the curve showing the change in soil loss rate over time in Embodiment 2 of the present invention; Figure 3 This is the curve showing the change of average migration distance of soil particles over time in Example 2 of the present invention; Figure 4 This is the curve showing the change of soil loss contribution rate at different slope positions over time in Embodiment 2 of the present invention; Figure 5 Fluorescence intensity-soil quality calibration curve in Example 2 of this invention.

[0037] Figure label: 1. Chamber; 2. Base plate; 3. Hydraulic drive device; 4. Support frame; 5. Spray head; 6. Light shield; 7. Ultraviolet light source; 8. Camera; 9. Guide channel; 10. Sample collector. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present application, the technical solutions in specific embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by those skilled in the art. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly. If a structure has a central axis or a hollow chamber, then the “inner side” of the structure refers to the side of the structure that is close to the central axis of the structure or is located inside the hollow chamber; the “outer side” of the structure refers to the side of the structure that is away from the central axis of the structure.

[0039] Example 1 like Figure 1 As shown, this embodiment provides a zoned tracing and dynamic observation device for slope soil disintegration testing. The device includes a model box assembly, a rainfall simulation assembly, an optical observation assembly, and a runoff collection assembly.

[0040] The model box assembly includes a box body 1 and a slope adjustment mechanism. Box body 1 is a rectangular structure with an open top, made of transparent acrylic glass, 12mm thick, with a length of 2500mm, a width of 600mm, and a height of 800mm. The bottom of box body 1 has a base plate 2 and a slope adjustment mechanism. The base plate 2 consists of multiple panels connected by hinges, each panel being 600mm long. The slope adjustment mechanism includes multiple hydraulic drive units 3, one of which is installed under each panel. Each hydraulic drive unit 3 includes a hydraulic cylinder, a hydraulic pump station, a solenoid directional valve, and a displacement sensor, enabling independent control of the tilt angle of each panel, with an adjustment range of 0°-45°.

[0041] The interior of box 1 and the upper surface of substrate 2 together form a filling area for filling the test soil to a depth of 500mm. The three plates correspond to different slope sections: the upslope, the middle slope, and the downslope. At the top of the filling area, three tracer zones are defined according to the slope section. Each tracer zone contains a 20mm thick tracer soil layer pre-mixed with different colored fluorescent tracers: the upslope zone uses red fluorescent pigment (Rhodamine B), with an excitation wavelength of 540nm and an emission wavelength of 625nm, added at a ratio of 0.5%; the middle slope zone uses green fluorescent pigment (fluorescein), with an excitation wavelength of 490nm and an emission wavelength of 520nm, added at a ratio of 0.5%; and the downslope zone uses blue fluorescent pigment (Coumarin 6), with an excitation wavelength of 450nm and an emission wavelength of 505nm, added at a ratio of 0.5%.

[0042] The rainfall simulation assembly includes a support frame 4 and sprinkler heads 5. The support frame 4 spans across the model box, is 2.5m high, and is made of 40mm×40mm aluminum alloy square tubing. The sprinkler heads 5 are mounted on the support frame 4 in a uniform array. The sprinkler heads 5 are pressure-type atomizing nozzles with a nozzle diameter of 1.0mm, mounted to the support frame 4 via hinged joints. The spray angle is adjustable. A water tank, centrifugal pump, and electromagnetic flow meter are connected via a water supply pipeline. The water tank has a capacity of 600L, the centrifugal pump has a flow rate of 30L / min, the pressure adjustment range is 0.1-0.4MPa, and the flow meter accuracy is ±1.5%. By adjusting the water pressure and the number of sprinkler heads, the rainfall intensity can be adjusted within the range of 30-120mm / h.

[0043] The optical observation assembly includes a light shield 6, an ultraviolet light source 7, a camera 8, and filters. The light shield 6, made of black light-blocking cloth, covers the exterior of the model box and measures 3000mm × 1000mm × 1200mm. Its inner wall is coated with a matte black coating, resulting in a reflectivity of <3%. The front of the light shield 6 has an openable observation door for easy operation. The ultraviolet light source 7 consists of four sets of ultraviolet LEDs with a wavelength of 365nm and a power of 40W per set. These are mounted on adjustable-angle brackets on both sides of the box 1, allowing the illumination angle to be adjusted within the range of 0°-45° to ensure uniform illumination of the slope.

[0044] Camera 8 is mounted on an aluminum alloy bracket directly above the model box, with a bracket height of 1.5m. Camera 8 has a resolution of ≥20 megapixels, a 24-70mm zoom lens, and an aperture of F2.8-F16. The lens of Camera 8 is vertically downwards, aligned with the center of the slope. Filters are mounted in front of the lens of Camera 8, including one long-pass filter (cutoff wavelength 450nm, visible light transmittance 92%) and three band-pass filters (corresponding to red fluorescence 625nm±15nm, green fluorescence 520nm±10nm, and blue fluorescence 505nm±10nm, respectively, all with peak transmittance >90%). During shooting, different band-pass filters are used as needed to capture the fluorescence signals of the three colors respectively.

[0045] The runoff collection assembly includes a guide channel 9 and a sampler 10. The guide channel 9, a V-shaped groove located at the bottom of the base plate 2, collects runoff and discharges it at the other end, guiding the sediment mixture into the sampler 10. The sampler 10 employs a rotary design, with 20 sample bottles mounted on the turntable. Driven by a stepper motor and controlled by a PLC program, it automatically rotates to a new position every 3 minutes to replace the sample bottles. Each sample bottle is pre-numbered (1-20), and the start and end times of collection are automatically recorded by the data acquisition system.

[0046] The device is also equipped with a data acquisition and control system, using a Siemens S7-1200 PLC as the central controller, connecting various sensors (4 slope sensors, 1 flow sensor, 1 pressure sensor, and 2 temperature and humidity sensors). Sensor data is acquired through analog input modules with a sampling frequency of 2Hz. The PLC communicates with an industrial control computer via Ethernet. The industrial control computer is installed with configuration software, providing a human-machine interface for parameter setting, test monitoring, and data recording.

[0047] Example 2 Based on the apparatus of Example 1, this example provides an experimental method for studying the impact of different rainfall intensities on soil erosion on loess slopes. The specific steps are as follows: S1. Soil sample preparation: Loess was air-dried and passed through a 5mm sieve. Its basic physical properties were determined: natural moisture content 8.5%, dry density 1.45 g / cm³.3 The particle size distribution was 18% clay, 65% silt, and 17% sand. Red, green, and blue fluorescent pigments were mixed with loess at a ratio of 0.5%. The mixture was stirred for 15 minutes using a forced mixer to ensure uniform dispersion of the tracers. After preparation, samples were taken and examined under ultraviolet light to confirm good fluorescence performance.

[0048] S2, Slope Adjustment: The hydraulic system is activated to adjust the four plates to the required angle of 25° to form a continuous slope with a consistent gradient. The slope sensor is used to monitor and confirm that the difference between the slope of each section and the target slope is ±0.2°.

[0049] S3. Soil filling: Five layers of loess were filled into the model box, each 100mm thick. Each layer was compacted with a wooden mallet after filling, controlling the dry density to 1.50g / cm³. 3 After filling to a depth of 500mm, the surface is leveled with a scraper. Then, on the slope, layers of soil containing red, green, and blue fluorescent tracers are laid sequentially from top to bottom, with each area approximately 400cm². 2 The thickness is 20mm. Use a ruler and a marking tool to mark the boundaries of the partitions to ensure that the boundaries are clear.

[0050] Perform a system check before starting the test: check that all systems are working properly.

[0051] S5, Rainfall Simulation: This embodiment designs three rainfall intensities: 40 mm / h, 70 mm / h, and 100 mm / h, with each intensity lasting 60 minutes. The experimental procedure is illustrated using the 70 mm / h intensity as an example.

[0052] Before the rain, close the sunshade 6 and turn on the UV lamp to irradiate the slope for 5 minutes. Adjust the camera parameters 8 to ISO 800, shutter speed 1 / 60s, and aperture F8. First, install the long-pass filter and take a panoramic fluorescence image. Then, replace the red, green, and blue bandpass filters in sequence and take fluorescence images of the three bands respectively as initial comparison benchmarks.

[0053] The water pump was then started, the water pressure was adjusted to 0.25 MPa, and the sprinklers were turned on. The flow rate was monitored and adjusted until the rainfall intensity stabilized at 70 mm / h ± 3 mm / h. The observation door was closed, and timing began.

[0054] S6. Dynamic Observation: After the rainfall begins, a fluorescence image is automatically captured every 30 seconds for 60 minutes, for a total of 120 images. Every 5 minutes, the bandpass filter is changed, and images are captured sequentially in the red, green, and blue bands.

[0055] S7. Runoff Collection and Recording: At the start of rainfall, the sampler turntable 10 is activated simultaneously. It is set to rotate automatically every 3 minutes to replace the sample bottles. A total of 20 sample bottles are collected over a 60-minute test. During the test, the data acquisition system records rainfall intensity, slope outflow, ambient temperature, and humidity every 1 second.

[0056] Observations showed that runoff began on the slope approximately 2 minutes after rainfall started; small erosion gullies appeared on the middle and lower slopes approximately 8 minutes later; these gullies gradually widened and deepened approximately 15 minutes later; and the erosion pattern stabilized approximately 30 minutes later. After 60 minutes, the water pump was turned off, and rainfall ceased. Observations continued for 5 minutes until no significant runoff was observed on the slope. The last sample bottle was collected, and the turntable was turned off.

[0057] S8. Data Processing and Analysis.

[0058] Sediment sample preparation: Twenty sample bottles were allowed to settle for 48 hours, and the supernatant was poured off. The precipitate was transferred to numbered drying trays and dried in a 105℃ oven for 24 hours until constant weight. The samples were then weighed using an electronic balance. Results showed that the first 10 samples lost a total of 1250g of sediment, and the last 10 samples lost a total of 680g of sediment, for a total loss of 1930g. The slope area was 1.5m². 2 The calculated average erosion modulus is 12.87 kg / m³. 2 The temporal distribution of the loss shows that 64.8% of the total loss occurs in the first 30 minutes, and 35.2% in the following 30 minutes, exhibiting a typical erosion pattern of rapid initial loss followed by slower loss. The final results are as follows... Figure 2 As shown in the figure, the horizontal axis represents rainfall time (min), and the vertical axis represents soil loss rate (g / min).

[0059] Fluorescence image processing: MATLAB was used to batch process 120 fluorescence images. Image registration, color separation, and thresholding were performed to obtain the distribution areas of each color of fluorescence. The analysis results showed that the red fluorescence area (soil in the upslope area) was initially concentrated in the upper 1 / 3 of the slope, and after 60 minutes, it was mainly distributed in the middle and lower slopes, with most of the soil being deposited on the slope during migration; the green fluorescence area (soil in the middle slope area) migrated faster, with about 70% entering the runoff after 60 minutes; the blue fluorescence area (soil in the downslope area) had the largest loss rate due to its proximity to the outlet, although the migration distance was short, with about 85% entering the runoff after 60 minutes.

[0060] Loss Path Analysis: Soil particle movement trajectory maps were plotted. The average migration distance and velocity of soil in each tracer zone were calculated: In the upslope zone, the average migration distance was 1.2 m, and the average velocity was 0.33 mm / s; in the middle slope zone, the average migration distance was 0.8 m, and the average velocity was 0.22 mm / s; in the downslope zone, the average migration distance was 0.3 m, and the average velocity was 0.08 mm / s. Although the migration distance of soil in the upslope zone was long, a considerable portion was deposited on the middle and lower slopes, resulting in a lower proportion actually entering the runoff. Although the migration distance of soil in the downslope zone was short, its proximity to the outlet, coupled with the convergence of water flow and strong runoff energy in this area, led to a significantly higher loss rate than other areas. Figure 3 As shown, this curve represents the average migration distance of soil particles over time, with the horizontal axis representing time (min) and the vertical axis representing distance (m). The red curve (uphill area) has the steepest slope and the longest migration distance. Although the proportion of soil ultimately flowing out of the system is lower in the uphill area, its particles exhibit the strongest mobility on the slope and the fastest average migration speed. This is because the uphill area has the highest potential energy and experiences the longest runoff scouring path. The green curve (mid-slope area) has a moderate slope and a moderate migration distance. Its particle migration speed and distance are between those of the uphill and downhill areas. The blue curve (downhill area) has the smallest slope and the shortest migration distance. Although the downhill area has the largest loss, because it is very close to the outlet, the particles only need to travel a short distance to flow out of the system, thus resulting in the shortest average migration distance.

[0061] Quantitative analysis: Fluorescence intensity analysis was performed on some sediment samples. Based on the fluorescence intensity calibration curve, the proportion of soil in runoff in different tracer areas was estimated: about 15% in the upslope area, about 35% in the middle slope area, and about 50% in the downslope area. Theoretical calculations showed that, according to the loss ratio of each tracer area (30% in the upslope area, 70% in the middle slope area, and 85% in the downslope area), the expected total loss was about 2220g, which was about 15% higher than the measured value of 1930g. This deviation was mainly due to: (1) measurement error in the fluorescence intensity calibration process; (2) some lost soil formed deposits on the slope and did not completely enter the runoff collection system; (3) threshold segmentation error in image processing. Considering the combined influence of multiple factors, the 15% deviation was within the allowable range of experimental error. A curve showing the relationship between soil loss rate and time was established. It was found that the loss rate showed a characteristic of rapid growth followed by stabilization, which was consistent with the observed erosion morphology evolution process.

[0062] like Figure 4 As shown, this is a curve showing the change of soil loss contribution rate over time at different slope positions. The horizontal axis represents time (min), and the vertical axis represents the contribution rate (%).

[0063] The blue curve (downhill area) is characterized by an extremely high contribution rate in the initial stage, which then gradually decreases. This is because the soil in the downhill area is closest to the outlet, and the runoff generated in the early stages of rainfall directly carries the soil out of this area with almost no lag. As time goes on, the amount of loose surface material decreases, and sediment from the upstream (middle and upper slopes) begins to be transported to the outlet, resulting in a decrease in its relative contribution rate.

[0064] The green curve (mid-slope area) is characterized by a "rise followed by fall" trend. This is because, in the initial stage of rainfall, the soil in the mid-slope area needs a certain amount of time to migrate to the outlet (lag effect). As runoff erodes, a large amount of sediment from the mid-slope reaches the outlet, significantly increasing its contribution rate. Later, due to the addition of sediment from the upslope and the consumption of its own material, the contribution rate may stabilize or decrease.

[0065] The red curve (uphill area) is characterized by an initial value of 0, a slow increase over time, but consistently the lowest contribution rate throughout the process. This is because the uphill area is furthest from the outlet, requiring soil particles to migrate a long distance before flowing out. The example mentions that most uphill soil is deposited in the lower part of the slope, with only a small portion (approximately 15%) ultimately entering the runoff sampler; therefore, its curve is at the bottom.

[0066] Recommendations regarding fluorescence intensity calibration curves should be provided before the experiment. Soil samples containing red fluorescent tracer should be taken and evenly spread on a 10cm × 10cm black background board according to mass gradients of 5g, 10g, 20g, 30g, 40g, and 50g. Under the same experimental conditions (UV lamp irradiation at 365nm for 5min, irradiation distance 1.5m, irradiation angle 45°), use a camera with ISO 800, shutter speed 1 / 60s, and aperture F8 (8 parameters), along with a red bandpass filter (625nm ± 15nm), to capture calibration images. The average grayscale value of each mass gradient sample should be extracted using the MATLAB image processing toolbox. Specifically, the image should be converted to grayscale, the central region of the sample (8cm × 8cm) should be selected, and the average grayscale value of all pixels within that region should be calculated. The data for the six mass gradients (mass m and grayscale value I) should be linearly fitted to obtain the calibration equation: m = aI + b. The fitting result for this experiment is m = 0.0125I - 2.3 (R²). 2 = 0.98). Using the same method, calibration curves were established for the green and blue fluorescent tracers, and the fitting equations were as follows: Green m = 0.0118I - 1.8 (R 2 = 0.97), blue m = 0.0132I - 2.6 (R 2 = 0.98). For example... Figure 5As shown in the figure, this figure illustrates the linear relationship between the average gray value I of the fluorescence image and the soil mass m, where the horizontal axis represents the average gray value and the vertical axis represents the soil mass. Through these three calibration curves, researchers can convert the brightness of the captured fluorescence image into specific soil loss mass.

[0067] Example 3 This embodiment is used to study the impact of variable slopes on soil erosion. It uses the same apparatus and basic methods as in Embodiment 2, but the slope setting is different.

[0068] Slope setting: The four slabs were set as variable slope surfaces, with angles of 15°, 20°, 25°, and 30° from top to bottom, forming a convex slope. The rainfall intensity was set to 70 mm / h, and the test lasted for 60 minutes.

[0069] The experimental results show that the total soil loss on a convex slope (2380g) is approximately 23% higher than that on a uniform slope (1930g). Fluorescence tracking revealed that after soil erosion begins on a gentler slope, the flow velocity and erosion capacity significantly increase as the slope becomes steeper, leading to a substantial increase in soil loss on the descent. These results reveal the significant impact of slope morphology on soil erosion and provide a reference for slope design in practical slope engineering. It is recommended to strengthen protection at slope inflection points on convex slopes to effectively control soil loss.

[0070] Finally, it should be noted that the described embodiments are merely some, not all, of the embodiments of the present invention. Those skilled in the art will understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents; that is, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A test device for erosion and disintegration of slope soil aggregates, characterized in that, The testing device includes a model box assembly, a rainfall simulation assembly, an optical observation assembly, and a runoff collection assembly. The model box assembly includes a box body, a base plate, and a slope adjustment mechanism. One end of the base plate is rotatably connected to the bottom of the box body. The slope adjustment mechanism is installed inside the box body, and its driving end is connected to the base plate to change the inclination angle of the base plate. Test soil is covered on the base plate to form a slope. The rainfall simulation assembly is mounted above the box body and has several spray heads. The test soil is mixed with fluorescent reagents. The optical observation assembly uses fluorescence tracing technology to observe the soil loss path in real time. The runoff collection assembly is placed at the bottom of the slope to collect sediment samples.

2. The testing apparatus as described in claim 1, characterized in that, The optical observation assembly includes an ultraviolet light source, a camera, and a filtering system. The camera is mounted on the outside of the housing with its lens facing the slope. The filtering system includes a long-pass filter and a band-pass filter installed in front of the lens, which can capture fluorescence signals of different colors according to different wavelengths.

3. The testing apparatus as described in claim 1, characterized in that, The substrate includes several plates, and any two adjacent plates are hinged together. The slope adjustment mechanism includes several hydraulic drive devices corresponding to the plates, and the drive end of each device corresponds to and is connected to one of the plates.

4. The testing apparatus as described in claim 1, characterized in that, The rainfall simulation component includes a support frame and sprinkler heads. The support frame spans across the top of the housing and is height-adjustable. Several sprinkler heads are mounted on the support frame and are evenly distributed in an array. The sprinkler heads are connected to a water supply device through pipelines.

5. The testing apparatus as described in claim 1, characterized in that, The runoff collection assembly includes a sampler connected to the lower end of the substrate, which has several sample bottles for collecting runoff in different time periods.

6. The testing apparatus as described in claim 1, characterized in that, The box is made of transparent acrylic glass.

7. The testing apparatus as described in claim 1, characterized in that, It also includes a data acquisition and control system, with a central controller, sensor network, data recording module and human-machine interface with electrical signal connection, which can monitor experimental parameters and record data in real time.

8. A test method based on the test apparatus according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Soil sample preparation, including soil air drying, sieving, and mixing with tracers; S2. Slope adjustment: Adjust the slope of the model box to simulate different slope shapes; S3. Soil filling: Fill the soil in layers inside the model box and ensure that each layer is compacted evenly. S4. Tracer zone laying: Different colored fluorescent tracers are laid on the surface of the fill soil. S5. Rainfall simulation: Simulates the rainfall process by adjusting the water pressure and opening of the sprinklers; S6. Dynamic observation: capturing fluorescence images through an optical observation system to record soil erosion paths in real time; S7. Runoff collection and recording: Use a sampler to collect sediment samples at different time periods; S8. Data processing and analysis: Analyze fluorescence images and sediment samples to calculate soil loss and its spatial distribution.

9. The test method according to claim 8, characterized in that, Specifically, in S6, the slope is irradiated with an ultraviolet light source and wavelength-selective imaging is performed using a filter to track the movement trajectory of soil particles in real time.

10. The test method according to claim 8, characterized in that, The rainfall simulation step includes controlling the rainfall intensity by adjusting the spray angle and flow rate of the nozzles, with the rainfall intensity range being 30-120 mm / h.

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