Soil body subsurface erosion visual measurement device and subsurface erosion test method

Abstract

The invention relates to the technical field of geotechnical engineering, in particular to a soil body subsurface erosion visual measurement device and a subsurface erosion test method.The soil body subsurface erosion visual measurement device comprises a visual container, an osmotic pressure loading system, a sample loss collection system and a particle image velocity measurement system; the visual container is provided with a first connecting end and a second connecting end; the osmotic pressure loading system is connected with the first connecting end, and the osmotic pressure loading system is configured to provide osmotic fluid for the visual container; the sample loss collecting system comprises a collecting pipeline and a collecting container, and the collecting pipeline is connected with the second connecting end and the collecting container; the particle image velocity measurement system comprises a converter, a solid-state green laser and an image recognition camera; and the converter is arranged on a laser path between the solid-state green laser and the visual container. According to the technical scheme, an advanced test observation technology is further perfected and applied, and mesoscopic behaviors such as migration and deposition of fine particles in the soil sample under the multi-field coupling effect are visually studied.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering, and in particular to a soil erosion visualization measuring device and a erosion testing method. Background Art

[0002] At present, my country has a large number of dams, which have played an important role in flood control, power generation, water supply, irrigation and other aspects, generating significant economic and social benefits. They are important infrastructure for protecting people's lives and property and promoting economic development. However, dams are at risk of collapse due to natural factors. Among them, seepage-subsidence erosion, as a typical form of infiltration damage, occurs in large numbers and has a wide distribution range. When it develops to a certain extent, it is easy to cause local structural damage and overall instability and collapse of seepage geotechnical structures such as earth-rock dams. It is difficult to quickly assess the degree of harm during critical moments during the flood season, and it is very easy to induce major dangerous situations. It is the main reason for safety problems in embankment projects.

[0003] Seepage-underwater erosion is the phenomenon in which fine particles in widely graded sands are lost through the pores between the coarse particles under the action of seeping water. Underwater erosion occurs and develops within dams and dikes, and its behavior is highly hidden and rapid, making it difficult to detect in a short period of time. Real-time observation of the microscopic behaviors of fine particle migration and siltation during underwater erosion is of great theoretical and practical engineering significance for a deeper understanding of the evolution of seepage-underwater erosion and the development of effective prevention and control measures.

[0004] During the research process, the applicant found that in the past research on seepage and erosion of wide-graded soil particles, the interior of the materials used in most seepage and erosion tests was not visible. Conventional tests could only observe surface phenomena through the transparent wall of the instrument, or observe the seepage pressure, seepage water level and leakage volume by deploying sensors, pressure measuring tubes and flow meters to obtain the temporal and spatial distribution characteristics of the seepage deformation of the soil. It was difficult to "directly observe" the internal seepage deformation laws of the soil in a comprehensive and detailed manner, and it was impossible to dynamically display the test results such as particle initiation, migration and loss, and it was impossible to truly realize the qualitative and quantitative analysis of the evolution of the microscopic structure inside the sample. Summary of the Invention

[0005] The main purpose of the present invention is to provide a soil erosion visualization measurement device, which aims to further improve and apply advanced experimental observation technology to visualize the microscopic behavior of fine particle migration and siltation inside soil samples under multi-field coupling.

[0006] To achieve the above purpose, the soil erosion visualization measurement device includes:

[0007] A visualization container having a first connection end and a second connection end, the first connection end and the second connection end being located at two ends of the visualization container in a vertical direction, and the visualization container being configured to accommodate a transparent soil sample;

[0008] an osmotic pressure loading system, the osmotic pressure loading system being connected to the first connection end, the osmotic pressure loading system being configured to provide an osmotic fluid to the visualization container;

[0009] A sample loss collection system, comprising a collection pipe and a collection container, wherein both ends of the collection pipe are connected to the second connection end and the collection container respectively; and

[0010] A particle image velocimetry system includes a converter, a solid-state green laser, and an image recognition camera. The converter is arranged on the laser path between the solid-state green laser and the visualization container. The solid-state green laser is configured to illuminate a transparent soil sample to form a high-brightness speckle field. The image recognition camera is configured to obtain a cross-sectional image of the transparent soil sample under the high-brightness speckle field.

[0011] In one embodiment of the present invention, the soil erosion visualization measurement device also includes a confining pressure system, which includes a pressure driving component and a movable piston group connected to the pressure driving component. The movable piston group includes a first piston and a second piston, and the first piston and the second piston are respectively arranged on both sides of the visualization container.

[0012] In one embodiment of the present invention, the soil erosion visualization measurement device further includes a static penetration test system, the static penetration test system includes a first sensor, a second sensor, and a data processing device, the first sensor and the second sensor are both electrically connected to the data processing device;

[0013] Wherein, the first sensor is arranged on the inner wall of the visualization container, and the second sensor is arranged near the second connection end.

[0014] In one embodiment of the present invention, the osmotic pressure loading system includes an air compressor, an air pressure controller, and a fluid reservoir connected in sequence, and the fluid reservoir pipeline is connected to the first connection end.

[0015] In one embodiment of the present invention, the particle image velocimetry system further includes a slide rail device, and the solid-state green laser is disposed on the slide rail device to obtain the highlight speckle field at different positions of the transparent soil sample.

[0016] In one embodiment of the present invention, the particle image velocimetry system further includes a height adjustment bracket, which connects the slide rail device and the solid-state green laser to obtain the highlight speckle field at different heights of the transparent soil sample.

[0017] In one embodiment of the present invention, the converter is a line prism.

[0018] The present invention also provides a etch test method, which includes:

[0019] Obtaining a transparent soil sample, and filling the transparent soil sample into a visualization container;

[0020] injecting a permeate fluid into the visualization container;

[0021] Acquiring an initial cross-sectional image of the transparent soil sample having a highlight speckle field in an initial state;

[0022] applying osmotic pressure to the transparent soil sample to obtain a loss sample of the transparent soil sample;

[0023] Acquire comparative cross-sectional images of different positions of the transparent soil sample having a highlight speckle field in a permeable state.

[0024] In one embodiment of the present invention, applying osmotic pressure to the transparent soil sample further comprises:

[0025] Obtaining initial strength data of the transparent soil sample in the initial state;

[0026] Acquire strength data of the transparent soil sample under pressure.

[0027] In one embodiment of the present invention, obtaining a transparent soil sample includes:

[0028] Get the refractive index nA and volume fraction φ A The first liquid has a refractive index of nB and a volume fraction of φ B a second liquid, mixing the first liquid and the second fluid to obtain a mixed liquid;

[0029] Mixing fused quartz sand and mixed liquid to obtain an initial sample;

[0030] The initial sample is vacuum-treated to obtain the transparent soil sample.

[0031] In the technical solution of the present invention, the osmotic pressure loading system injects the infiltration fluid into the visualization container to simulate the changes of the transparent soil sample under natural conditions, wherein the sample loss collection system is connected to the second connection end of the visualization container to collect the loss samples of the transparent soil sample under the washing of the infiltration fluid. At the same time, the particle image velocimetry system is used to obtain the internal change image of the transparent soil sample under the washing of the infiltration fluid, thereby realizing the optical quantitative seepage-erosion test under different stress states, different densities, different particle grading states, and different water heads, visualizing the evolution process of the internal structure of the wide-gradation soil sample during the erosion test, and exploring the microscopic mechanisms such as the particle migration behavior inside the soil and the seepage channel formation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 the structures shown in these drawings without paying any creative work.

[0033] Figure 1 This is a schematic structural diagram of an embodiment of a soil erosion visualization measurement device provided by the present invention;

[0034] Figure 2 This is a schematic diagram of the internal structure of the visualization container provided by the present invention.

[0035] Description of Figure Numbers:

[0036] 10. Visualization container; 10a. First connection end; 10b. Second connection end; 11. Transparent soil sample; 20. Osmotic pressure loading system; 21. Air compressor; 22. Air pressure controller; 23. Fluid reservoir; 30. Sample loss collection system; 31. Collection pipeline; 32. Collection container; 40. Particle image velocimetry system; 41. Converter; 42. Solid-state green laser; 43. Image recognition camera; 50. Confining pressure system; 51. Pressure drive element; 52. First piston; 53. Second piston; 60. Static penetration test system; 61. First sensor; 62. Second sensor; 63. Data processing equipment.

[0037] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0040] In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0041] See also Figure 1 The soil erosion visualization measurement device includes:

[0042] A visualization container having a first connection end 10a and a second connection end 10b, wherein the first connection end 10a and the second connection end 10b are respectively located at two ends of the visualization container in a vertical direction, and the visualization container is configured to accommodate a transparent soil sample 11;

[0043] an osmotic pressure loading system 20 , the osmotic pressure loading system 20 being connected to the first connection end 10 a , and the osmotic pressure loading system 20 being configured to provide an osmotic fluid to the visualization container;

[0044] A sample loss collection system 30, comprising a collection pipe 31 and a collection container 32, wherein both ends of the collection pipe 31 are connected to the second connection end 10b and the collection container 32 respectively; and

[0045] A particle image velocimetry system 40 includes a converter 41, a solid-state green laser 42, and an image recognition camera 43. The converter 41 is arranged on the laser path between the solid-state green laser 42 and the visualization container. The solid-state green laser 42 is configured to irradiate a transparent soil sample 11 to form a highlight speckle field. The image recognition camera 43 is configured to obtain a cross-sectional image of the transparent soil sample 11 under the highlight speckle field.

[0046] In the technical solution of the present invention, the osmotic pressure loading system 20 injects the infiltration fluid into the visualization container to simulate the changes of the transparent soil sample 11 under natural conditions, wherein the sample loss collection system 30 is connected to the second connection end 10b of the visualization container to collect the loss sample of the transparent soil sample 11 under the washing of the infiltration fluid. At the same time, with the help of the particle image velocimetry system 40, the internal change image of the transparent soil sample 11 under the washing of the infiltration fluid is obtained, thereby realizing the seepage-erosion optical quantitative test under different stress states, different densities, different particle grading states, and different water heads, visualizing the evolution process of the internal structure of the wide-gradation soil sample during the erosion test, and exploring the microscopic mechanisms such as the particle migration behavior inside the soil and the seepage channel formation process.

[0047] Specifically, at least one side of the visualization container is transparent, and polycarbonate (PC) endurance board, acrylic (PMMA) board, hard PVC transparent board, etc. can be selected as the visualization window according to the degree of stress. The upper and lower ends are respectively provided with a first connection end 10a and a second connection end 10b, and the first connection end 10a and the second connection end 10b are connected to the internal space of the visualization container. The first connection end 10a allows the infiltration fluid to flow into the visualization container, and the second connection end 10b allows the infiltration fluid to flow out of the visualization container from the pore channel of the transparent soil sample 11, thereby simulating the fluid in the natural environment. The flow process in the dam, specifically, an upstream porous cover plate and a sand-permeable pressure plate are respectively provided in the internal space of the visualization container. The upstream porous cover plate is located in the visualization container near the first connection end 10a, and the sand-permeable pressure plate is located in the visualization container near the second connection end 10b. In this way, the upstream porous cover plate and the sand-permeable pressure plate divide the internal space of the visualization container in the vertical direction to form an upstream cavity, a midstream sample cavity and a downstream infiltration cavity. The midstream sample cavity is used to accommodate the transparent soil sample 11, because the upstream porous cover plate and the sand-permeable pressure plate both have multiple spaces for the infiltration fluid to pass through. (pores, channels and other flow structures), so that the infiltration liquid flows in from the first connection end 10a of a single area, and is diverted under the porous effect of the upstream porous cover plate, so that it can flow into the transparent soil sample 11 in multiple areas and evenly, thereby improving the authenticity of the data of subsequent experiments; the permeable sand pressure plate is located between the transparent soil sample 11 and the downstream infiltration cavity, and through its physical structure (such as pores or filter screen), it withstands the lateral and vertical stresses generated by the infiltration pressure of the sample, preventing the soil sample from collapsing due to instability during the infiltration process, while allowing fluids and tiny particles (such as eroded fine particles) to pass through, but blocking larger particles Direct loss simulates the process in nature where fine particles are washed away and the coarse particle skeleton is retained under the action of seepage. For collecting experimental data, the pore size of the sand-permeable pressure plate is designed (for example, the pore size is slightly smaller than the minimum particle diameter of the sample) to allow only the eroded fine particles to enter the downstream infiltration cavity with the fluid, and then be transported to the sample loss collection system 30 through the collection pipe 31. The degree of erosion (such as erosion rate, total loss) can be quantified by collecting data such as the mass and particle size distribution of the lost particles, and compared with the microstructural changes captured by the particle image velocimetry system 40 (PIV) for verification.

[0048] The osmotic pressure loading system 20 is the core module of the soil erosion visualization measurement device that simulates the natural fluid environment. Its function depends on the coordinated operation of multiple components and the refined control of parameters. The osmotic pressure loading system 20 mainly consists of four modules: a pressure pump and a pressure vessel, a flow control valve and a pressure sensor, a pretreatment device, and a buffer circulation system. The pressure pump (such as a plunger pump or a diaphragm pump) provides a power source and is combined with the pressure vessel to store the osmotic fluid (such as groundwater, ion-containing solution, or artificially proportioned simulated fluid). By adjusting the pump output power, the head gradient of different geological units in the natural environment can be accurately reproduced (for example, the range of 0.1-10 MPa corresponds to the seepage conditions from deep aquifers to shallow layers). The flow control valve (such as an electromagnetic proportional valve or a servo valve) is linked to a high-precision pressure sensor to monitor and dynamically adjust the flow rate (0.01-5 mL / min) and pressure fluctuations in real time, so that the fluid dynamic characteristics (laminar flow, turbulent flow state) are highly matched with the target scenario (such as rainfall infiltration, piping damage). The pretreatment device optimizes the physical and chemical properties of the fluid through a multi-stage filtration unit (ultrafiltration membrane, activated carbon adsorption layer) and an ion balance module (pH regulator, salinity controller). For example, it removes suspended impurities to simulate low-turbidity groundwater, or adds specific ions (such as Ca2 + 、Cl -) to reproduce the dissolution-undermining coupling effect under the seawater intrusion environment; the buffer circulation system forms a closed loop through the liquid storage tank and the circulation pump to continuously stabilize the fluid composition (such as preventing ion precipitation or microbial growth) to ensure the chemical uniformity of the infiltration medium during long-term experiments. In this way, by accurately simulating the natural seepage field and dynamically controlling the pressure gradient and flow rate, the hydraulic conditions under real working conditions such as internal piping of dams, slope rainfall infiltration or groundwater level fluctuations can be reproduced. For example, the migration behavior of fine particles in wide-graded soil samples can be stimulated under high head difference, or the cumulative effect of undermining can be studied under periodic pulse pressure; secondly, relying on sensor feedback and automatic control systems (such as PLC or PID algorithm) to maintain steady-state or transient seepage conditions (such as Step pressurization and sinusoidal pressure changes) create a repeatable and comparable experimental basis for quantifying the initiation threshold of erosion (such as critical flow velocity and critical hydraulic gradient) and particle migration patterns (such as fine particle loss rate and coarse particle skeleton stability); further, by switching fluid types (clean water, chemical solutions, tracer-containing fluids) and infiltration modes (unidirectional flow, bidirectional alternating flow, pulsed flow), the effects of composite erosion mechanisms such as mechanical scouring, chemical dissolution, and biological action on soil structure are explored. For example, when simulating seawater intrusion, high-salinity fluids can accelerate the dispersion of clay minerals, while acidic solutions (pH = 3-5) can promote the dissolution of carbonate cements, thereby revealing the intrinsic relationship between porosity evolution and permeability deterioration during erosion. Furthermore, the pressure-flow time series data output by this system can be integrated with the microscopic seepage field (such as velocity vector distribution and particle displacement field) captured by the particle image velocimetry system 40 (PIV) and the particle grading data from the sample loss collection system 30 in a multi-dimensional manner to construct a mapping relationship between macroscopic mechanical response and microstructural evolution. This provides a high-confidence experimental benchmark for validating numerical models (such as discrete element-fluid coupling simulation), ultimately serving engineering practices such as dam safety assessment and geological disaster early warning. Through the integration of these technologies, the osmotic pressure loading system 20 not only achieves a realistic reproduction of the natural fluid environment, but also enhances the scientific depth and engineering guidance value of erosion mechanism research through parameter adjustability and data linkage.

[0049] The sample loss collection system 30 is a key module for quantifying particle loss behavior in the soil erosion visualization measurement device. It is used to capture and analyze the migration process of fine soil particles under the action of infiltration fluid scouring. The sample loss collection system 30 includes a collection pipe 31 and a collection container 32. The collection pipe 31 serves as a transmission channel for fluid and lost particles. It must have pressure resistance and corrosion resistance (such as transparent PVC or borosilicate glass), and integrate a multi-stage filtration unit (such as stainless steel screen, filter membrane) at the end. Through layered interception of different pore sizes (such as 10μm to 2mm), particles are collected according to particle size. For example, the upper screen intercepts coarse particles (simulating the retention of skeleton particles in natural erosion), and the lower filter membrane captures fine particles (characterizing erosion). The collection container 32 is designed as a sealed tank or centrifuge tube array, equipped with an electronic balance or a high-precision mass sensor to monitor the weight change of the collected liquid in real time to calculate the particle loss rate and cumulative amount. At the same time, the turbidity of the fluid can be observed through a transparent window to indirectly judge the intensity of the erosion (for example, the fluid is clear at the beginning of seepage and gradually becomes turbid after the erosion starts). In addition, the system can also be integrated with an online particle counter (such as a laser diffractometer or an image recognition module) to dynamically analyze the particle size distribution and shape parameters of the lost particles. For example, the system can output characteristic particle size curves such as d10, d50, and d90 in real time through a Malvern laser particle size analyzer, or use a high-speed camera to capture the particle motion trajectory to reconstruct the migration mode (rolling, suspension, or jumping).

[0050] The particle image velocimetry system 40 (PIV) is the core optical detection module in the soil erosion visualization measurement device. It consists of three core components: a solid-state green laser 42, a converter 41, and an image recognition camera 43. It uses high-precision optical means to realize the visualization capture of the dynamic evolution of the seepage field and the particle migration trajectory inside the transparent soil sample 11, providing key data support for the study of the microscopic mechanism of erosion. Specifically, the solid-state green laser 42 uses a green light laser source with a wavelength of 532nm. Its short wavelength characteristics (compared to red light or infrared light) can significantly reduce the scattering loss of transparent media and increase the beam penetration depth (up to 200mm), ensuring the formation of a uniform high-brightness speckle field in the transparent soil sample 11. The laser power can be adjusted in the range of 10-500mW, supporting continuous emission and pulse modes (frequency 1-100Hz), adapting to different seepage velocity scenarios (such as slow seepage as low as 0.01mm / s or high-speed scouring of 5mm / s), and the spot size (coverage) can be adjusted by the beam expander. The laser beam can completely cover the observation section of the visualized container and eliminate edge shadow effects. For example, when simulating dam piping failure, the high-power pulse mode (100 Hz) can clearly capture the instantaneous suspension motion of fine particles and avoid image distortion caused by motion blur. The converter 41 consists of a collimating lens group and a beam splitter prism, which is responsible for converting the divergent laser beam into parallel light, eliminating beam distortion, and achieving multi-directional projection of the light path by adjusting the prism angle (such as vertical incidence for planar flow velocity measurement and oblique incidence for three-dimensional tomography). The image recognition camera 43 can be a high-speed CMOS camera or a CCD industrial camera, supporting multi-scale observations from macroscopic specimen deformation (such as overall shear band formation) to microscopic pore flow (such as single particle displacement). It has a built-in cross-correlation analysis algorithm (such as FFT-accelerated window matching technology) to calculate the two-dimensional flow velocity field by the displacement of tracer particles (such as fluorescent microspheres with a diameter of 5-50 μm) in two consecutive frames of images, with a spatial resolution of 0.1 pixel (corresponding to an actual displacement accuracy of ±0.01 mm). Combined with three-dimensional tomographic reconstruction technology (such as multi-plane scanning or holographic PIV), the three-dimensional topological structure of the seepage channel can be reconstructed and the dynamic changes in porosity (such as the increase in porosity from 15% to 25% during the erosion process) can be quantified. For example, when the osmotic pressure loading system 20 applies a gradient head (such as 0.1-10 MPa to simulate soil at different burial depths), the PIV system outputs a seepage velocity distribution map in real time (such as a parabolic velocity profile under laminar flow conditions) to verify the set parameters of the flow control valve (such as the error between the theoretical flow rate of 1.2 mm / s and the actual measured value of 1.18 mm / s is ≤2%). For example, the PIV system tracks the movement mode of tracer particles (such as rolling, suspension, or sliding) and analyzes it in conjunction with the grading data of the sample loss collection system 30 (such as the proportion of 0.1-0.5 mm fine particles retained by the filter membrane is 80%) to establish a mapping relationship between migration mechanism and loss rate.For example, when the proportion of suspended particles increases from 30% to 60%, the loss rate of the mass sensor of the collection container 32 increases from 0.05g / min to 0.15g / min. Through the particle image velocimetry system 40, high-resolution optical imaging and multi-system data fusion are used to elevate the research on soil erosion from the traditional macroscopic mechanical response to the mesoscopic-microscopic multi-scale linkage level, providing an irreplaceable technical means for geological disaster prevention and control (such as landslide warning) and geotechnical engineering safety assessment (such as dam piping prevention and control).

[0051] Furthermore, the soil erosion visualization measurement device also includes a confining pressure system 50, which includes a pressure driving member 51 and a movable piston group connected to the pressure driving member 51. The movable piston group includes a first piston 52 and a second piston 53. The first piston 52 and the second piston 53 are respectively arranged on both sides of the visualization container, wherein the pressure driving member 51 includes a power source and a cylinder. The power source provides driving force for the cylinder, and the movable piston group is connected to the output shaft of the cylinder. In this way, by applying two relative forces to the visualization container, a certain level of confining pressure is applied to the sample. Then, different levels of osmotic oil pressure are applied to the transparent soil sample 11 through the osmotic pressure loading system 20, and the internal seepage of the transparent soil sample 11 is observed until the transparent soil sample 11 undergoes erosion damage. After the seepage-erosion phenomenon occurs, the mass of fine particles is collected at fixed intervals through the sample loss collection system 30, and the fine particle erosion rate is calculated by weighing after drying, thereby driving the symmetrically arranged first piston 52 and second piston 53 to apply uniform lateral confining pressure to both sides of the visualization container to avoid stress unbalanced loading. This system simulates a three-dimensional stress field by synergizing lateral confining pressure (σ3) with vertical seepage pressure (σ1). The system investigates the influence of the principal stress difference (σ1-σ3) on the initiation threshold of soil corrosion and particle migration patterns. For example, when σ3 = 1 MPa and σ1 = 3 MPa, enhanced particle engagement inhibits fine particle loss in soil samples, while low confining pressure (σ3 = 0.5 MPa) can significantly increase the soil corrosion rate. Dynamic confining pressure control utilizes closed-loop feedback from displacement sensors (LVDTs) and pressure sensors (accuracy ±0.2% FS). This system simulates the sinusoidal fluctuations of seismic loads (frequency 0.1-10 Hz, amplitude ±0.2 MPa) to explore the accelerating effects of cyclic stress on soil corrosion. The confining pressure system 50 and the osmotic pressure loading system 20 are integrated and linked through LabVIEW or PLC to reproduce stress-seepage coupling conditions. For example, the osmotic pressure is gradually increased under high confining pressure to determine the change law of the critical hydraulic gradient of erosion. At the same time, the data is integrated with the particle image velocimetry system 40 (PIV) to analyze the correlation between the sudden change of particle displacement vector captured by PIV during confining pressure unloading (such as shear band formation) and the expansion of seepage channels. The particle size distribution data of the sample loss collection system 30 (such as d under high confining pressure) 50The system supports multiple stress paths, including isotropic, conventional triaxial, and true triaxial loading, and is suitable for engineering scenarios such as slopes, tunnels, and reservoirs. By determining the correlation curve between the critical hydraulic gradient for erosion and the critical stress ratio (σ3 / σ1), it provides parameters for engineering safety design.

[0052] Further, see Figure 1 and Figure 2 The soil erosion visualization measurement device also includes a static penetration test system 60, which includes a first sensor 61, a second sensor 62 and a data processing device 63. The first sensor 61 and the second sensor 62 are both electrically connected to the data processing device 63, wherein the first sensor 61 is arranged on the inner wall of the visualization container, and the second sensor 62 is arranged near the second connection end 10b. Specifically, a static penetration hole is provided in the visualization container near the second connection end 10b. The second sensor 62 can be inserted into the static penetration hole and inserted into the transparent soil sample 11. A micro-cone penetration test is performed on the sample before and after, and the cone resistance at the height along the seepage path is continuously measured to evaluate the change in strength caused by internal erosion. During the process of the confining pressure system 50 applying confining pressure to the visualization container, the first sensor 61 records the change in soil strength in real time, and the detection data of the first sensor 61 and the second sensor 62 are transmitted to the data processing device 63 for recording and analysis.

[0053] In one embodiment, the particle image velocimetry system 40 further includes a slide rail device, and the solid-state green laser 42 is disposed on the slide rail device to obtain the highlighted speckle field at different positions of the transparent soil sample 11, thereby achieving all-round and multi-dimensional observation of the particle migration behavior inside the soil. The slide rail device allows the laser to continuously scan along the axial or radial direction of the sample, breaking through the limitations of static irradiation at a single position, expanding the laser coverage range, and capturing the speckle field distribution of the entire sample (including the edge and core areas). This dynamic scanning mechanism enables the system to generate a continuous cross-sectional image sequence with high spatial resolution, and combined with the PIV algorithm, it can accurately track the particle displacement vector field, which is particularly suitable for the refined analysis of non-uniform deformation caused by seepage-erosion in wide-graded soil samples (such as local pore channel expansion and shear band formation). Furthermore, the slide rail device, through multi-angle and multi-faceted data acquisition, can reconstruct the three-dimensional strain field within the soil, revealing the spatial correlation between particle migration paths and the evolution of seepage channels during the erosion process. For example, under the coupling of seepage direction and confining pressure gradient, the slide rail scanning data can quantify the differences in particle loss rates at different depths, verifying the correspondence between stress concentration areas and high-risk areas for erosion. This setup also enhances experimental flexibility, allowing the scanning step size (e.g., 0.1-5mm) to be adjusted according to specimen size or experimental requirements. This adapts to multi-scale studies from microscopic pore scales to macroscopic structural responses, providing high-precision data support for establishing a coupled seepage-erosion-deformation model.

[0054] Furthermore, the particle image velocimetry system 40 further includes a height adjustment bracket, which connects the slide rail device and the solid-state green laser 42 to obtain the highlighted speckle field at different heights of the transparent soil sample 11. In this way, the height adjustment bracket allows the laser to scan layer by layer in the vertical direction, and combines with the horizontal movement of the slide rail to form a grid scanning path, covering the three-dimensional space of the sample. By collecting speckle field image sequences at different height planes, the three-dimensional vector field of particle migration inside the soil can be reconstructed, revealing the vertical expansion law of the seepage channel during the erosion process (such as the curvature and branching structure of the preferential flow path). Secondly, for wide The vertical non-uniform distribution of particle gradation in graded soil samples (such as the sinking of coarse particles under the action of their own weight) can be detected by the height adjustment function, which can obtain high-brightness speckle fields in the surface, middle and bottom layers respectively, and quantify the correlation between the seepage velocity gradient and the fine particle loss rate at different depths. For example, the surface layer is more prone to local scour due to sudden changes in osmotic pressure. At the same time, in the device experiment, the height adjustment bracket can be combined with the slide rail device to realize a "Z-shaped" scanning strategy (horizontal + vertical alternating movement), using high-frequency sampling (such as 10Hz) to capture transient phenomena (such as the layer-by-layer collapse process of the particle skeleton in the critical stage of piping), and combined with cross-frame technology (time interval <100μs) to analyze the vertical particle acceleration distribution.

[0055] In one embodiment, the converter 41 is a line prism, which can generate coplanar concentrated laser rays through the laser through the line prism, and can emit sheet laser with a thickness of 1 mm. Its working power is 2 to 10 W to obtain images of different sections.

[0056] The present invention also provides a etch test method, which includes:

[0057] Step S10: Obtain a transparent soil sample 11, and fill the transparent soil sample 11 into a visualization container;

[0058] Step S20: injecting the permeation fluid into the visualization container;

[0059] Step S30: obtaining an initial cross-sectional image of the transparent soil sample 11 having a highlight speckle field in an initial state;

[0060] Step S40: applying osmotic pressure to the transparent soil sample 11 to obtain a loss sample of the transparent soil sample 11;

[0061] Step S50: obtaining comparative cross-sectional images of different positions of the transparent soil sample 11 having a highlight speckle field in a permeable state.

[0062] In step S10, a transparent soil sample is made of fused quartz sand and a pore fluid with a matching refractive index (such as a mixture of n-dodecane and white oil) to ensure that the optical transmittance and soil mechanical properties (such as porosity and gradation) are equivalent to those of natural soil, providing a basis for PIV non-invasive observation; the container is made of high-strength acrylic or borosilicate glass (pressure resistance ≥10MPa), and an optical window is set on at least one side to ensure that the internal speckle field can still be clearly captured under confining pressure loading. At the same time, a certain amount of fluorescent dye is prepared and mixed with the transparent soil sample 11 and added to the visualization container. The prepared transparent soil sample 11 is filled into the visualization container in layers. During the filling process of each layer, it is continuously stirred gently with a glass plate. After all the soil is filled, the sample is compacted to a predetermined height; after the sample is loaded, a sand-permeable pressure plate on the top of the sample is fixed.

[0063] In step S20, deionized water or glycerol solution is injected through the osmotic pressure loading system 20 driven by the air compressor 21 to simulate groundwater seepage, gradually form a stable seepage field, and trigger fine particle migration and erosion. At the same time, an air pressure controller 22 can be set between the fluid reservoir 23 and the visualization container to dynamically adjust the inlet and outlet pressure difference to achieve a linear change of the hydraulic gradient i = 0.01-10, thereby triggering different erosion modes (for example, contact erosion is dominant when i < 1, and piping occurs when i > 5).

[0064] In step S30, the solid-state green laser 42 is driven by the slide rail device and the height adjustment bracket to scan the sample to generate a global high-brightness speckle field, and the initial image is captured by a CCD camera as a reference for particle displacement analysis.

[0065] In step S40, the migration of fine particles is driven by different osmotic pressure gradients. Combined with the stress field simulated by the confining pressure system 50, the relationship between the erosion rate and the critical hydraulic gradient under different stress ratios is studied. The lost particles are collected by multi-stage filter screens, and the gradation curve offset is measured by a laser particle size analyzer to reveal the pore structure evolution caused by erosion. A safety threshold curve is established through critical state data to provide a basis for engineering anti-seepage design.

[0066] Specifically, in step S40, the following is also included:

[0067] Step S410: obtaining initial strength data of the transparent soil sample 11 in the initial state;

[0068] Step S420: Acquire the strength data of the transparent soil sample 11 under the pressurized state.

[0069] Specifically, a static penetration test is used to determine the initial cone tip resistance, a high-pressure calibration tank is used to simulate the stress state of natural soil, and the large deformation finite element model (ALE method) is used to correct the grid distortion to obtain the initial unconfined compressive strength. Subsequently, the osmotic pressure loading system 20 and the confining pressure system 50 are used to change the strength properties of the transparent soil sample 11. At the same time, a plurality of second sensors 62 are provided in the transparent soil sample 11 to obtain strength data under different pressurized states.

[0070] In one embodiment, obtaining the transparent soil sample 11 includes:

[0071] Obtaining a first liquid having a refractive index nA and a volume fraction φA and a second liquid having a refractive index nB and a volume fraction φB, and mixing the first liquid and the second liquid to obtain a mixed liquid;

[0072] Mixing fused quartz sand and mixed liquid to obtain an initial sample;

[0073] The initial sample is vacuum treated to obtain the transparent soil sample 11.

[0074] Specifically, the first liquid and the second liquid can be 15# white oil and D80 solvent oil respectively. At the same time, the refractive index of the mixed liquid formed by mixing the two is:

[0075] n AB =φ A n A +φ B n B ;

[0076] Different graded fused quartz sands (0.1mm-0.2mm, 0.2-0.5mm, 0.5mm-1.0mm, 1.0mm-2.0mm) were selected and mixed with the mixed liquid to obtain an initial sample. The initial sample was fully stirred and then vacuumed to saturate, and allowed to stand for 12 hours to obtain a transparent soil sample 11.

[0077] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's description and drawings, or direct / indirect applications in other related technical fields, within the scope of the present invention are included in the patent protection scope of the present invention.

Claims

1. A soil erosion visualization measurement device, characterized in that: The soil erosion visualization measurement device comprises: A visualization container (10), the visualization container (10) having a first connection end (10a) and a second connection end (10b), the first connection end (10a) and the second connection end (10b) being located at two ends of the visualization container (10) along a vertical direction, respectively, and the visualization container (10) being configured to accommodate a transparent soil sample (11); an osmotic pressure loading system (20), the osmotic pressure loading system (20) being connected to the first connection end (10a), and the osmotic pressure loading system (20) being configured to provide an osmotic fluid to the visualization container (10); A sample loss collection system (30), comprising a collection pipe (31) and a collection container (32), wherein both ends of the collection pipe (31) are connected to the second connection end (10b) and the collection container (32), respectively; and A particle image velocimetry system (40) includes a converter (41), a solid-state green laser (42), and an image recognition camera (43). The converter (41) is arranged on a laser path between the solid-state green laser (42) and the visualization container (10). The solid-state green laser (42) is configured to irradiate a transparent soil sample (11) to form a high-brightness speckle field. The image recognition camera (43) is configured to obtain a cross-sectional image of the transparent soil sample (11) under the high-brightness speckle field.

2. The soil erosion visualization measuring device according to claim 1, characterized in that: The soil erosion visualization measurement device further includes a confining pressure system (50), the confining pressure system (50) including a pressure driving member (51), a movable piston group connected to the pressure driving member (51), the movable piston group including a first piston (52) and a second piston (53), the first piston (52) and the second piston (53) being respectively arranged on both sides of the visualization container (10).

3. The soil erosion visualization measuring device according to claim 2, characterized in that: The soil erosion visualization measuring device further includes a static penetration test system (60), wherein the static penetration test system (60) includes a first sensor (61), a second sensor (62), and a data processing device (63), wherein the first sensor (61) and the second sensor (62) are both electrically connected to the data processing device (63); The first sensor (61) is arranged near the inner wall of the visualization container (10), and the second sensor (62) is arranged near the second connection end (10b).

4. The soil erosion visualization measuring device according to claim 1, characterized in that: The osmotic pressure loading system (20) includes an air compressor (21), an air pressure controller (22), and a fluid reservoir (23) connected in sequence, and the fluid reservoir (23) is connected to the first connection end (10a) through a pipeline.

5. The soil erosion visualization measuring device according to any one of claims 1 to 4, characterized in that: The particle image velocimetry system (40) further comprises a slide rail device, and the solid-state green laser (42) is arranged on the slide rail device to obtain the highlight speckle field at different positions of the transparent soil sample (11).

6. The soil erosion visualization measuring device according to claim 5, characterized in that: The particle image velocimetry system (40) further comprises a height adjustment bracket, wherein the height adjustment bracket is connected to the slide rail device and the solid-state green laser (42) to obtain the highlight speckle field at different heights of the transparent soil sample (11).

7. The soil erosion visualization measuring device according to claim 1, characterized in that: The converter (41) is a line prism.

8. A etch test method, characterized in that: The etch test method comprises: Obtaining a transparent soil sample, and filling the transparent soil sample into a visualization container; injecting a permeate fluid into the visualization container; Acquiring an initial cross-sectional image of the transparent soil sample having a highlight speckle field in an initial state; applying osmotic pressure to the transparent soil sample to obtain a loss sample of the transparent soil sample; Acquire comparative cross-sectional images of different positions of the transparent soil sample having a highlight speckle field in a permeable state.

9. The etch test method according to claim 8, wherein: The applying of the osmotic pressure to the transparent soil sample further comprises: Obtaining initial strength data of the transparent soil sample in the initial state; The strength data of the transparent soil sample under the pressurized state is obtained.

10. The etch test method according to claim 9, wherein: The method of obtaining a transparent soil sample comprises: Get the refractive index nA and volume fraction φ A The first liquid has a refractive index of nB and a volume fraction of φ B a second liquid, mixing the first liquid and the second fluid to obtain a mixed liquid; Mixing fused quartz sand and mixed liquid to obtain an initial sample; The initial sample is vacuum-treated to obtain the transparent soil sample.

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