Erosion gully microscopic scale model construction method based on soil mechanics theory

Abstract

The invention discloses a soil mechanics theory-based erosion gully microscopic scale model construction method, which comprises the following steps of: firstly, carrying out field exploration on a target erosion gully to obtain geometric and soil mechanics parameters and meteorological data, and determining a scale proportion according to a similarity theory; preparing a similar soil material from quartz sand, clay and the like, and preparing a model substrate from a fiber reinforced composite material; laying materials layer by layer, implanting fibers, setting a vegetation layer simulation environment, setting boundary conditions and a loading and monitoring system; applying a simulated load, comparing model output with a prototype or theoretical result, determining key parameters by sensitivity analysis, and adjusting and optimizing the model. The model constructed by the method is highly similar to the mechanical behavior and erosion process of an actual erosion gully, soil characteristics can be accurately simulated, data are acquired through reliable monitoring, the accuracy is ensured through scientific calibration and optimization, an effective means is provided for erosion gully research, the research cost is reduced, and high universality is achieved.

Description

Technical Field

[0001] This invention relates to the field of constructing a microscale model of an erosion gully based on soil mechanics theory, specifically a method for constructing a microscale model of an erosion gully based on soil mechanics theory. Background Technology

[0002] Gullies are a common and important landform in soil erosion, and their development and evolution have a profound impact on land resources, the ecological environment, and agricultural production. In-depth research into the formation mechanism, development process, and influencing factors of gullies is of paramount importance for soil erosion control, soil and water conservation planning, and ecological environment restoration.

[0003] However, due to the large actual scale of erosion gullies and the limitations imposed by various factors such as natural conditions and geographical environment, direct research on actual erosion gullies often faces numerous difficulties. On the one hand, field observations and experiments require significant human, material, and time resources, and it is difficult to control various variables, thus affecting the accuracy and reliability of the research results. On the other hand, the erosion gully process under natural conditions is complex, influenced by the combined effects of multiple factors, making it difficult to analyze the impact of a single factor on erosion gully development.

[0004] To overcome these difficulties, scaled-down models have become an important tool for studying erosion gullies. By constructing scaled-down models, the formation and development process of erosion gullies can be simulated under laboratory conditions, facilitating the control of experimental conditions and enabling systematic research. However, existing methods for constructing scaled-down erosion gully models have many shortcomings.

[0005] Regarding model similarity, many methods fail to fully consider soil mechanics theory, resulting in significant differences in mechanical behavior between the model and the actual erosion gully, making it impossible to accurately simulate the microscopic processes of erosion gullies. For example, when determining the scale ratio, the similarity in geometry, motion, dynamics, and boundary conditions is not fully considered, causing deviations in the model's simulation of actual conditions.

[0006] In the preparation of similar materials, existing methods struggle to produce materials that are completely similar to actual soil in terms of physical and mechanical properties. This directly affects the model's simulation accuracy of erosion gully soil characteristics. For example, the inability to precisely control key parameters such as particle size distribution, compressibility, and permeability leads to inaccuracies in the model's simulation of soil erosion.

[0007] Existing model building methods also have shortcomings in monitoring systems and model validation. The accuracy and reliability of monitoring systems are insufficient, making it impossible to acquire various parameters of the model during the erosion process in real time and accurately; the model validation process lacks scientific methods and standards, making it difficult to effectively evaluate the accuracy and reliability of the model. Summary of the Invention

[0008] The purpose of this invention is to provide a method for constructing a microscale model of erosion gullies based on soil mechanics theory, so as to solve the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for constructing a microscale model of an erosion gully based on soil mechanics theory, specifically including the following steps: Step 1, Acquisition of basic parameters: Conduct on-site investigation of the target erosion gully using high-precision measuring instruments to comprehensively acquire its geometric parameters, including length, width, depth, slope, and gully wall curvature; at the same time, measure soil mechanical parameters, such as soil particle size distribution, liquid and plastic limits, and shear strength; and collect meteorological data of the area, covering annual average rainfall intensity and rainfall frequency information. Step 2, Determining the scale ratio: Based on dimensional analysis and similarity theory, and taking into account the experimental site, equipment accuracy, and research focus, the scale ratio that satisfies geometric, kinematic, dynamic, and boundary condition similarities is determined. Among them, the geometric similarity ratio is determined based on the size of the target erosion gully and the experimental space; kinematic similarity is guaranteed by dimensionless numbers such as Reynolds number and Froude number; dynamic similarity is achieved by stress and strain similarity relationships; and boundary condition similarity simulates the interaction between actual soil, water, and atmosphere. Step 3, similar material preparation: Quartz sand and clay are used as the main raw materials, and additives are added to adjust the material properties; referring to the particle size distribution curve of the target erosion gully soil, the proportion of sand particles of different sizes is configured by sieving, and the optimal moisture content and maximum dry density are determined by compaction test, so that the prepared material is similar to the prototype soil in terms of compressibility and permeability. Step 4, Model Base Construction: Select high-strength, low-deformation materials to construct the model base, ensuring its shape matches the topography of the target erosion gully; use CNC machining technology to guarantee the dimensional accuracy of the base, and set positioning grooves and markers on the base surface for model material laying and measurement positioning; Step 5, Material layering: Lay similar soil materials in layers according to the preset thickness on the model base. After each layer is laid, use vibration compaction or static compaction to control the compaction deviation within ±2%. During the laying process, implant fibers to simulate root systems according to the actual situation, and lay vegetation cover to simulate the real surface environment. Step 6, Boundary and Loading Settings: Set different boundary conditions (impermeable and permeable) at the model boundary to simulate the water exchange between the erosion gully and the surrounding soil; install a rainfall simulation device that can precisely control the flow rate, pressure, and time, as well as a dynamic loading system that can simulate water erosion. Step 7, Monitoring System Installation: Pre-embed micro displacement, stress, and moisture content sensors in key parts of the model and use distributed fiber optic sensing technology to monitor soil deformation; install flow velocity meters and water level gauges in the water flow channel to collect water flow parameters in real time; and use a data acquisition system to automatically record and store monitoring data. Step 8, Model Calibration and Optimization: Apply simulated loads to the completed model, compare the model output results with the prototype monitoring data or theoretical calculation results, use sensitivity analysis to determine key parameters, and then adjust the similar material ratio and boundary condition parameters until the model can accurately simulate the microscopic process of erosion gullies.

[0010] Furthermore, in the basic parameter acquisition steps, the measurement of soil particle size distribution employs a combination of laser particle size analyzer and sieving method. The laser particle size analyzer can quickly and accurately measure the distribution of small particles in the soil, while the sieving method is used to determine the particle size range of larger particles. This combined method can obtain more comprehensive and accurate soil particle size distribution data. Simultaneously, when acquiring soil shear strength parameters, direct shear tests and triaxial shear tests are used. The direct shear test is simple to operate and can provide a preliminary understanding of the soil's shear characteristics; the triaxial shear test can better simulate the stress state of actual soil, obtaining more accurate shear strength indices and providing a reliable basis for subsequent model construction.

[0011] Furthermore, in the process of determining the scale ratio, in addition to considering the limitations of the target erosion gully size and experimental space, the determination of the geometric similarity ratio also needs to take into account the process accuracy of model making. For some complex erosion gully landform features, such as small gully undulations and irregular gully wall shapes, it is necessary to ensure that they can still be accurately represented by existing model making processes after scaling down. In terms of motion similarity, in addition to relying on the dimensionless numbers Reynolds number, Froude number, and others, it is also necessary to consider the similarity between the turbulence characteristics of the water flow in the model and the prototype. By adjusting the boundary conditions and water flow parameters of the model, the turbulence intensity and vortex structure of the water flow in the model are made similar to the water flow in the actual erosion gully, thereby more realistically simulating the water flow motion during the erosion process.

[0012] Furthermore, in the similar material preparation step, the added additives are polymers and curing agents. The polymers can improve the cohesiveness and flexibility of the similar materials, making them closer to the mechanical behavior of real soil when simulating soil deformation. The curing agents can enhance the early strength and stability of the materials, preventing problems such as loose materials and excessive deformation during model making and experimentation. In the specific addition process, the optimal addition amount of polymers and curing agents is determined through a series of proportioning experiments. At the same time, when preparing similar materials, the durability and anti-aging properties of the materials also need to be considered. By adding antioxidants and preservatives, it is ensured that the performance of the similar materials is stable during long-term experiments, without affecting the accuracy and reliability of the model.

[0013] Furthermore, in the model base fabrication step, high-strength, low-deformation material is used: fiber-reinforced composite material. Fiber-reinforced composite material has the advantages of high strength, low density, good fatigue resistance, and corrosion resistance, which can meet the strength and stability requirements of the model base while reducing the overall weight of the model. During the fabrication process, fiber winding and molding technology are used to accurately shape the model base according to the topography of the target erosion gully. By adding specific filler materials and toughening agents to the fiber-reinforced composite material, the performance of the material is further improved. In addition, the positioning grooves and marking points set on the surface of the model base are made using high-precision laser engraving technology to ensure their positional and dimensional accuracy, providing an accurate benchmark for the subsequent laying and measurement of model materials.

[0014] Furthermore, in the material layering step, the thickness of each layer of similar soil material is determined according to the scale of the model and the layered structure of the actual erosion gully soil. For the bottom layer of material near the model base, the thickness is relatively large to provide stable support; while for the material near the model surface, the thickness gradually decreases to more accurately simulate the characteristics of the surface soil of the erosion gully. During the compaction process, in addition to using vibration compaction or static compaction, ultrasonic vibration technology can also be combined to further improve the compaction effect of the material and reduce the porosity inside the material. At the same time, when implanting fibers to simulate roots, fibers of different lengths, diameters and distribution densities are used according to the distribution characteristics and mechanical effects of different plant roots to more realistically simulate the reinforcement and improvement effect of roots on the soil.

[0015] Furthermore, in the boundary and loading setup steps, the rainfall simulation device employs a combination of rotary nozzles and a pressure control system. The rotary nozzles achieve uniform rainfall distribution, simulating the angle and coverage of natural rainfall. The pressure control system precisely adjusts the rainfall intensity and droplet size to match actual rainfall data. For the dynamic loading system simulating water flow scouring, a circulating water tank and a variable-speed water pump are used. The circulating water tank provides a stable water flow environment, while the variable-speed water pump can flexibly adjust the water flow speed and flow rate according to experimental needs, simulating water flow scouring processes of different intensities. In addition, the waterproof and permeable boundary conditions set at the model boundary are achieved through special waterproof materials and permeable media, ensuring the accuracy and reliability of the boundary conditions.

[0016] Furthermore, in the installation steps of the monitoring system, high-precision fiber optic displacement sensors are used for the miniature displacement sensors. Fiber optic displacement sensors have the advantages of anti-electromagnetic interference, high accuracy, and distributed measurement capabilities, enabling real-time and accurate monitoring of displacement changes of the model soil at different locations. The stress sensors use resistance strain gauge sensors, which, through reasonable point placement and signal processing, can accurately measure the stress distribution inside the soil. For the moisture content sensors, time domain reflectance (TDR) sensors are used, which have high measurement accuracy and fast response speed, enabling real-time monitoring of dynamic changes in soil moisture content. At the same time, wireless data transmission technology is used to transmit the data collected by each sensor to the data acquisition system in real time, realizing remote monitoring and data management, and improving the efficiency and convenience of the experiment.

[0017] Furthermore, in the model calibration and optimization step, a combination of numerical simulation and experimentation is used for model verification. First, professional soil mechanics numerical simulation software, such as ABAQUS and FLAC, is used to numerically simulate the erosion process of the target gully to obtain the theoretical distribution of deformation, stress, and water flow parameters. Then, the experimental results of the model are compared and analyzed with the numerical simulation results to identify the parts with large differences. For these differences, response surface methodology and genetic algorithm optimization algorithms are used to optimize and adjust the key factors of similar material ratios and boundary condition parameters. Through multiple iterative calculations and experimental verifications, the accuracy and reliability of the model are gradually improved, enabling it to more realistically simulate the microscopic process of erosion gullies.

[0018] Furthermore, a quality control system is established throughout the entire model construction process to conduct rigorous quality inspections on the operation process and results of each step. Detailed operating procedures and quality standards are formulated. For example, during the preparation of similar materials, the quality of raw materials, the accuracy of the proportions, and the stability of material properties are regularly tested. During the fabrication of the model substrate, the dimensional accuracy, shape accuracy, and surface flatness of the substrate are strictly checked. During the installation of the monitoring system, the installation position, connection reliability, and measurement accuracy of the sensors are comprehensively tested. By establishing a quality control system, it is ensured that every aspect of the model construction meets the requirements, thereby improving the overall quality and reliability of the model and providing a reliable experimental platform for the study of the microscopic processes of erosion trenches.

[0019] Compared with the prior art, the beneficial effects of the present invention are: Based on soil mechanics theory, this invention comprehensively considers similarity criteria such as geometry, motion, dynamics, and boundary conditions to determine the scaling ratio, so that the constructed microscale model is highly similar to the actual erosion gully in terms of mechanical behavior and erosion process. It can accurately simulate the microscale process of erosion gullies and provide a reliable experimental platform for studying the formation mechanism and development law of erosion gullies.

[0020] By selecting appropriate raw materials and specific formulation processes, model materials that are highly similar to the target gully soil in terms of particle size distribution, physical and mechanical properties, etc., can be prepared. Key parameters such as compressibility, permeability, and shear strength of the material can be precisely controlled, thereby more realistically simulating the mechanical response and erosion characteristics of gully soil under different conditions.

[0021] The model base is made of high-strength, low-deformation material, and CNC machining technology is used to ensure dimensional accuracy, providing stable support for the model material and ensuring the stability and reliability of the model during experiments. Meanwhile, positioning grooves and markers on the base surface facilitate the laying and measurement of model material, improving the accuracy and efficiency of model construction.

[0022] During the layered material laying process, the model simulates the real surface environment by implanting fibers to simulate root systems and laying vegetation cover layers, taking into account the impact of vegetation on soil erosion, making the model closer to reality. In terms of boundary condition setting and loading system design, it can accurately simulate the water exchange between the erosion gully and the surrounding soil, as well as external loads such as rainfall and water scouring, providing the possibility for studying the evolution process of erosion gullies under different environmental conditions.

[0023] Multiple high-precision sensors were pre-embedded in key parts of the model, and distributed fiber optic sensing technology was adopted to monitor changes in parameters such as deformation, stress, and water content of the model in real time and accurately during the erosion process. At the same time, flow meters, water level gauges, and other equipment were arranged in the water flow channel to collect water flow parameters in real time, providing rich data support for studying the erosion mechanism and process of erosion gullies.

[0024] By comparing and analyzing the experimental results of the model with the monitoring data of the prototype or the theoretical calculation results, and using sensitivity analysis to determine key parameters, and adjusting and optimizing the proportion of similar materials and boundary condition parameters, the accuracy and reliability of the model can be continuously improved, ensuring that the model can accurately simulate the microscopic process of erosion gullies. Before model construction, a comprehensive field survey of the target erosion gully is conducted using high-precision measuring instruments to obtain abundant geometric parameters, soil mechanics parameters, and regional meteorological data. This detailed and accurate basic data provides a solid basis for model construction, enabling the model to better reflect the characteristics of actual erosion gullies.

[0025] A comprehensive quality control system has been established, with rigorous quality inspections conducted at every step of model construction, and detailed operating procedures and quality standards formulated. From the quality inspection of raw materials to the precision control of the model-making process, and then to the installation and debugging of the monitoring system, every aspect of model construction is ensured to meet the requirements, thereby improving the overall quality and reliability of the model. The construction method of this invention has strong versatility, not only applicable to the study of specific types of erosion gullies, but also allowing for adjustments to parameters such as scale ratio, similar materials, and boundary conditions according to different research objectives and actual conditions, meeting the needs of various erosion gully research scenarios, and providing an effective method and means for the study of erosion gullies in different regions and of different types. Attached Figure Description

[0026] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Please see Figure 1 The present invention provides a specific implementation method for constructing a microscale model of erosion gullies based on soil mechanics theory: Determine the characteristic parameters of the target erosion gully Before conducting a field survey, the geographical location and extent of the target erosion gully must be clearly defined. By reviewing relevant geological data, satellite imagery, and local land use planning maps, a preliminary understanding of the topography, soil type distribution, and other basic information of the area where the target erosion gully is located should be obtained. A detailed survey plan should be developed, including the survey route, the layout of measurement points, and the necessary instruments and equipment.

[0029] High-precision measuring instruments, such as total stations, GPS receivers, and laser rangefinders, are used to measure the geometric parameters of the target erosion gully, including its length, width, depth, slope, and wall curvature. When measuring length and width, measurement points are set at regular intervals along the gully's direction and transverse direction to ensure that the measurement data accurately reflects the gully's morphological changes. For depth measurement, tools such as levels or sounding rods are used to perform multiple measurements at different locations and average the results.

[0030] Slope measurements are taken using a total station or protractor to obtain slope values ​​at different locations within the erosion gully. Measuring the gully wall curvature is more complex; a 3D laser scanner can be used to scan the gully wall, acquiring 3D point cloud data, which is then used in conjunction with specialized data analysis software to calculate the wall curvature.

[0031] Soil samples were collected from different locations within the erosion gully and brought back to the laboratory. First, the soil samples were air-dried to remove moisture. Then, particle size distribution analysis was performed using a combination of sieving and laser particle size analyzer. For particles larger than 0.075 mm, sieving was used; the soil sample was passed through sieves of different apertures, and the mass of soil particles remaining on each sieve was weighed to calculate the particle content for different size ranges. For particles smaller than 0.075 mm, laser particle size analyzer was used to measure the scattering and diffraction of laser light by the particles, analyzing the particle size distribution of the soil.

[0032] The liquid and plastic limits of soil samples were determined using a combined liquid and plastic limit tester. The prepared soil sample was placed in the sample cup of the combined liquid and plastic limit tester and allowed to sink freely into the sample using a cone penetrator. The relationship between the cone penetration depth and the water content was measured, and the liquid limit and plastic limit were determined according to the specified cone penetration depth (e.g., 17 mm, 10 mm, etc.).

[0033] The shear strength of soil is determined using direct shear tests and triaxial shear tests. In the direct shear test, a soil sample is placed in a shear chamber, a vertical pressure is applied, and then a horizontal shear force is applied to cause shear failure. The shear force and vertical pressure at failure are recorded, and the soil's shear strength index is calculated. The triaxial shear test, on the other hand, applies confining pressure around a cylindrical soil sample and then causes failure through axial pressure, allowing for a more accurate simulation of the soil's shear strength characteristics under actual stress conditions.

[0034] Meteorological data for the target gully area, including annual average rainfall intensity, rainfall frequency, temperature, and wind speed, should be collected. This data can be obtained from local weather stations or queried from meteorological databases or online meteorological service platforms. Simultaneously, the trends and seasonal characteristics of the meteorological data should be analyzed to better simulate the impact of different meteorological conditions on the gully in model building.

[0035] Select scaling ratio Based on dimensional analysis and similarity theory, the similarity relationship between the model and the prototype is determined. Regarding geometric similarity, an appropriate geometric similarity ratio is determined according to the actual size of the target erosion trench and the limitations of the experimental site and equipment. For example, if the experimental site is limited and the target erosion trench is large, a smaller geometric similarity ratio may be necessary to ensure that the model can be built and tested in the laboratory.

[0036] Motion similarity is ensured by dimensionless numbers such as the Reynolds number and Froude number. The Reynolds number reflects the ratio of inertial force to viscous force in a fluid, while the Froude number reflects the ratio of inertial force to gravity. In model design, parameters such as water flow velocity and characteristic length are adjusted to make the Reynolds number and Froude number of the model equal to or close to those of the prototype, thereby ensuring that the motion of the water flow in the model is similar to that of the actual water flow in the erosion gully.

[0037] Dynamic similarity is achieved through stress and strain similarity relationships. By selecting and designing similar materials, it is ensured that the stress and strain distributions of the model and the prototype are similar under the same stress conditions. Boundary condition similarity requires simulating the interaction between actual soil and water bodies and the atmosphere, such as setting appropriate permeable or impermeable conditions at the model boundaries, and simulating atmospheric rainfall, evaporation, and other boundary conditions.

[0038] Taking into account the precision of the experimental equipment, the focus of the research, and the requirements for model similarity, the final scale ratio is determined. For example, if the research focus is on the microstructure of erosion trenches and local flow characteristics, a larger scale ratio may be needed to improve the model's resolution and detail representation. After determining the scale ratio, various parameters of the model are scaled accordingly, including geometric dimensions, material properties, and loading conditions, to ensure that the model and the prototype meet the similarity requirements in all aspects.

[0039] Preparation of similar soil materials The material uses quartz sand and clay as the main raw materials, with additives added to adjust its properties. Quartz sand has good particle stability and permeability; different particle sizes can be selected based on the particle size distribution requirements of the target gully soil. Clay provides the material's cohesiveness and plasticity; by selecting different types of clay, such as kaolin and bentonite, the physical and mechanical properties of similar materials can be adjusted. The selection of additives depends on specific needs; for example, adding polymers can improve the material's cohesiveness and flexibility, while adding curing agents can enhance the material's early strength and stability.

[0040] Referring to the particle size distribution curve of the target gully soil, a sieving method was used to prepare the proportion of sand particles of different sizes. Quartz sand of different sizes was mixed in a certain proportion, and repeated sieving and stirring were performed to ensure that the particle size distribution of the mixed material was uniform. During the preparation process, the proportion of sand particles was continuously adjusted to make the particle size distribution of similar materials as close as possible to that of the target gully soil.

[0041] The optimum moisture content and maximum dry density of similar materials are determined by compaction tests. The prepared similar materials are divided into several portions, each with a different amount of water added to create samples with varying moisture contents. The samples are placed in a compaction cylinder and compacted according to a specified compaction force. The dry density of the compacted samples is then measured. A compaction curve is plotted with moisture content on the x-axis and dry density on the y-axis. The moisture content corresponding to the peak value of the curve is the optimum moisture content, and the corresponding dry density is the maximum dry density.

[0042] Based on the compressibility, permeability, and other performance requirements of the target gully soil, similar materials are further adjusted. For example, if it is necessary to improve the compressibility of the material, the clay content can be appropriately increased or the particle size distribution can be adjusted; if it is necessary to adjust the permeability of the material, this can be achieved by adding a certain amount of coarse particles or changing the pore structure of the material. During the adjustment process, continuous experimental testing is conducted to ensure that the various performance indicators of the similar materials are similar to those of the target gully soil.

[0043] Building model base High-strength, low-deformation fiber-reinforced composite materials are selected for the model base. Fiber-reinforced composite materials have advantages such as high strength, low density, good fatigue resistance, and corrosion resistance, which can meet the strength and stability requirements of the model base while reducing the overall weight of the model. For example, glass fiber reinforced composite materials or carbon fiber reinforced composite materials can be selected based on the specific requirements of the model and the cost budget.

[0044] Using fiber winding and compression molding techniques, the shape of the model base is precisely shaped according to the topography of the target erosion gully. First, a mold for the base is made based on the three-dimensional topographic data of the target erosion gully. Then, fiber material is wound onto the mold in a specific manner, or fiber prepreg is placed into the mold. Through compression molding, the fibers and resin matrix are fully bonded under specific temperature and pressure conditions to form a model base with the required shape and size.

[0045] CNC machining technology is used to ensure the dimensional accuracy of the base. Positioning grooves and markers are set on the base surface for model material placement and measurement positioning. During CNC machining, precise programming and machining parameter settings ensure that the dimensional errors of the base are controlled within allowable limits. The placement of positioning grooves and markers should be based on the model's design requirements and measurement plan to ensure accurate and clear positioning for easy subsequent operations.

[0046] Laying model materials The thickness of each layer of similar soil material is determined based on the model's scale and the layered structure of the actual gully soil. Generally, the bottom layer of material near the model base is relatively thick to provide stable support, while the thickness of the material near the model surface gradually decreases to more accurately simulate the characteristics of the surface soil in the gully. For example, for a model with a scale of 1:100, the thickness of the bottom layer of material can be set to 5-10 cm, while the thickness of the surface layer can be set to 1-2 cm.

[0047] Each layer of similar material is compacted using either vibratory compaction or static compaction, with the compaction deviation controlled within ±2%. Vibratory compaction applies high-frequency vibration to the material using vibrating equipment, causing the material particles to rearrange and increasing the material's density. Static compaction, on the other hand, applies pressure to achieve compaction under static pressure. In practice, the appropriate compaction method can be selected based on the material's characteristics and compaction requirements. Simultaneously, a compaction degree testing instrument is used to monitor the compaction degree in real time to ensure it meets the requirements.

[0048] During the laying process, fibers are implanted to simulate root systems based on actual conditions, and a vegetation cover layer is laid to simulate a real surface environment. The implanted fibers can be natural fibers (such as hemp fibers, coconut fibers, etc.) or synthetic fibers (such as polyester fibers, nylon fibers, etc.), and different lengths, diameters, and distribution densities of fibers are used according to the distribution characteristics and mechanical effects of different plant roots. The vegetation cover layer can be artificially planted turf or materials simulating vegetation, laid according to the vegetation distribution of the target erosion gully to more realistically simulate the impact of vegetation on soil erosion.

[0049] Set boundary conditions and load system Different boundary conditions, such as impermeable and permeable, are set at the model boundary to simulate the water exchange between the erosion gully and the surrounding soil. For locations requiring impermeable boundaries, waterproof membranes or sealants can be used to ensure that water cannot penetrate through the boundary. For permeable boundaries, porous materials or permeable holes can be used to allow water to exchange freely at the boundary. Simultaneously, water level and flow velocity conditions are set at the boundary according to actual conditions to simulate the aquatic environment around the erosion gully.

[0050] Install a rainfall simulation device capable of precisely controlling flow, pressure, and time. This device can combine rotary nozzles and a pressure control system. The rotary nozzles achieve uniform rainfall distribution, simulating the angle and coverage of natural rainfall; the pressure control system precisely adjusts rainfall intensity and droplet size to match actual meteorological data. During installation, the nozzle positions and heights should be strategically arranged to ensure rainfall evenly covers the entire model surface.

[0051] A dynamic loading system simulating water flow scouring is constructed using a circulating water tank and a variable-speed water pump. The circulating water tank provides a stable water flow environment, while the variable-speed water pump allows for flexible adjustment of water velocity and flow rate according to experimental needs, simulating water flow scouring processes of varying intensities. Flow sensors and velocity meters are installed within the water tank to monitor the water flow rate and velocity in real time, ensuring the stability and accuracy of the loading system. Furthermore, based on the characteristics of the model and experimental requirements, the shape and size of the water tank, as well as the inlet and outlet positions of the water flow, are rationally designed to ensure a reasonable flow path within the model.

[0052] Model monitoring system installation Miniature displacement, stress, and moisture content sensors are pre-embedded in key areas of the model, and distributed fiber optic sensing technology is used to monitor soil deformation. High-precision fiber optic displacement sensors can be selected, offering advantages such as electromagnetic interference resistance, high accuracy, and distributed measurement capabilities, enabling real-time and accurate monitoring of soil displacement changes at different locations. The stress sensors employ resistance strain gauges; through appropriate sensor placement and signal processing, they can accurately measure the stress distribution within the soil. The moisture content sensors utilize time-domain reflectometry (TDR) sensors, offering high measurement accuracy and fast response, enabling real-time monitoring of dynamic changes in soil moisture content.

[0053] When deploying sensors, based on the structural characteristics of the model and the research focus, sensors are placed on the walls and bottom of the erosion gully, as well as key areas where deformation and damage may occur. For example, displacement sensors and stress sensors are placed at different heights on the gully walls to monitor the deformation and stress changes of the gully walls under the action of water erosion and soil self-weight; moisture content sensors are placed at the bottom of the gully to monitor changes in soil moisture.

[0054] Flow meters and water level gauges are installed in the water flow channel to collect water flow parameters in real time. The flow meters can be electromagnetic or ultrasonic, selected based on the characteristics of the water flow and the required measurement accuracy. The water level gauges can be pressure gauges or ultrasonic gauges, installed at appropriate locations in the water flow channel to monitor water level changes in real time. These devices allow for the acquisition of parameters such as water velocity, flow rate, and water level, providing crucial data support for studying the water flow movement and erosion process in erosion gullies.

[0055] A data acquisition system is used to automatically record and store monitoring data. This system can employ computer-based automated acquisition equipment, using a data acquisition card to convert analog signals from sensors and monitoring devices into digital signals, which are then transmitted to a computer for storage and processing. Simultaneously, corresponding data processing software is developed to perform real-time analysis and processing of the acquired data, generating visual charts and reports to facilitate researchers' intuitive understanding of the model's changes during the experiment.

[0056] Validation and Adjustment of Model Simulated loads are applied to the completed model, and the model is validated by comparing the model's output results with prototype monitoring data or theoretical calculation results. Different methods can be selected for applying simulated loads, such as rainfall loads, water erosion loads, or soil self-weight loads, depending on the actual situation. During the load application process, the model's response is monitored in real time, and changes in parameters such as deformation, stress, and moisture content are recorded.

[0057] When comparing model experiment results with prototype monitoring data, it is necessary to ensure the accuracy and reliability of the prototype monitoring data. If actual prototype monitoring data is unavailable, theoretical calculation results can be used for comparison. For example, stress and deformation distributions of the model under different load conditions can be calculated using soil mechanics theory and compared with experimental results to analyze the accuracy and reliability of the model.

[0058] Sensitivity analysis was used to identify key parameters that significantly impacted the model results. Sensitivity analysis involves changing the value of a specific parameter while keeping others constant, and observing the changes in the model's output to determine the degree of its influence. For example, among parameters of similar materials, changing parameters such as particle size distribution, moisture content, and shear strength, and observing the changes in deformation, stress, and erosion during the erosion process, can help determine which parameters have the most significant impact on the model results.

[0059] Based on the verification results and sensitivity analysis, adjustments were made to the proportions of similar materials and boundary condition parameters. If significant differences were found between the model's deformation or stress distribution and the actual situation, the proportions of similar materials could be adjusted to alter their physical and mechanical properties, making the model's response closer to reality. Boundary condition parameters, such as rainfall intensity and water flow velocity, could be fine-tuned according to actual conditions to improve the model's simulation accuracy.

[0060] Through multiple iterative calculations and experimental verifications, the model's parameters and structure were continuously optimized, gradually improving its accuracy and reliability to ensure that it could accurately simulate the microscopic processes of erosion gullies. After each adjustment, model verification and sensitivity analysis were performed again until the model met the research requirements.

Claims

1. A method for constructing a microscale model of erosion gullies based on soil mechanics theory, characterized in that, Specifically, the following steps are included: Step 1, Acquisition of basic parameters: Conduct on-site investigation of the target erosion gully using high-precision measuring instruments to comprehensively acquire its geometric parameters, including length, width, depth, slope, and gully wall curvature; at the same time, measure soil mechanical parameters, such as soil particle size distribution, liquid and plastic limits, and shear strength; and collect meteorological data of the area, covering annual average rainfall intensity and rainfall frequency information. Step 2, Determining the scale ratio: Based on dimensional analysis and similarity theory, and taking into account the experimental site, equipment accuracy, and research focus, the scale ratio that satisfies geometric, kinematic, dynamic, and boundary condition similarities is determined. Among them, the geometric similarity ratio is determined based on the size of the target erosion gully and the experimental space; kinematic similarity is guaranteed by dimensionless numbers such as Reynolds number and Froude number; dynamic similarity is achieved by stress and strain similarity relationships; and boundary condition similarity simulates the interaction between actual soil, water, and atmosphere. Step 3, similar material preparation: Quartz sand and clay are used as the main raw materials, and additives are added to adjust the material properties; referring to the particle size distribution curve of the target erosion gully soil, the proportion of sand particles of different sizes is configured by sieving, and the optimal moisture content and maximum dry density are determined by compaction test, so that the prepared material is similar to the prototype soil in terms of compressibility and permeability. Step 4, Model Base Construction: Select high-strength, low-deformation materials to construct the model base, ensuring its shape matches the topography of the target erosion gully; use CNC machining technology to guarantee the dimensional accuracy of the base, and set positioning grooves and markers on the base surface for model material laying and measurement positioning; Step 5, Material layering: Lay similar soil materials in layers according to the preset thickness on the model base. After each layer is laid, use vibration compaction or static compaction to control the compaction deviation within ±2%. During the laying process, implant fibers to simulate root systems according to the actual situation, and lay vegetation cover to simulate the real surface environment. Step 6, Boundary and Loading Settings: Set different boundary conditions (impermeable and permeable) at the model boundary to simulate the water exchange between the erosion gully and the surrounding soil; install a rainfall simulation device that can precisely control the flow rate, pressure, and time, as well as a dynamic loading system that can simulate water erosion. Step 7, Monitoring System Installation: Pre-embed micro displacement, stress, and moisture content sensors in key parts of the model and use distributed fiber optic sensing technology to monitor soil deformation; install flow velocity meters and water level gauges in the water flow channel to collect water flow parameters in real time; and use a data acquisition system to automatically record and store monitoring data. Step 8, Model Calibration and Optimization: Apply simulated loads to the completed model, compare the model output results with the prototype monitoring data or theoretical calculation results, use sensitivity analysis to determine key parameters, and then adjust the similar material ratio and boundary condition parameters until the model can accurately simulate the microscopic process of erosion gullies.

2. The method for constructing a microscale model of an erosion gully based on soil mechanics theory according to claim 1, characterized in that, In the basic parameter acquisition step, the measurement of soil particle size distribution adopts a combination of laser particle size analyzer and sieve analysis. Laser particle size analyzer can quickly and accurately measure the distribution of small particles in the soil, while sieve analysis is used to determine the particle size range of larger particles. Through this combination method, more comprehensive and accurate soil particle size distribution data can be obtained. At the same time, when obtaining soil shear strength parameters, direct shear test and triaxial shear test are used. Direct shear test is simple to operate and can provide a preliminary understanding of the soil's shear characteristics; triaxial shear test can better simulate the stress state of actual soil and obtain more accurate shear strength index, providing a reliable basis for subsequent model construction.

3. The method for constructing a microscale model of an erosion gully based on soil mechanics theory according to claim 1, characterized in that, In the process of determining the scale ratio, the determination of the geometric similarity ratio, in addition to considering the limitations of the target erosion gully size and experimental space, also needs to take into account the process accuracy of model making. For some complex erosion gully landform features, such as small gully undulations and irregular gully wall shapes, it is necessary to ensure that they can still be accurately represented by existing model making processes after scaling down. In terms of motion similarity, in addition to relying on the dimensionless numbers Reynolds number, Froude number, and others, it is also necessary to consider the similarity between the turbulence characteristics of the water flow in the model and the prototype. By adjusting the boundary conditions and water flow parameters of the model, the turbulence intensity and vortex structure of the water flow in the model are made similar to the water flow in the actual erosion gully, thereby more realistically simulating the water flow motion during the erosion process.

4. The method for constructing a microscale model of erosion gullies based on soil mechanics theory according to claim 1, characterized in that, In the preparation of similar materials, the additives are polymers and curing agents. The polymers improve the cohesiveness and flexibility of the similar materials, making them closer to the mechanical behavior of real soil when simulating soil deformation. The curing agents enhance the early strength and stability of the materials, preventing problems such as loosening and excessive deformation during model making and experimentation. In the specific addition process, a series of proportioning experiments are conducted to determine the optimal addition amount of polymers and curing agents. At the same time, when preparing similar materials, the durability and anti-aging properties of the materials must also be considered. By adding antioxidants and preservatives, it is ensured that the performance of the similar materials remains stable during long-term experiments, without affecting the accuracy and reliability of the model.

5. The method for constructing a microscale model of an erosion gully based on soil mechanics theory according to claim 1, characterized in that, In the model base fabrication process, high-strength, low-deformation fiber-reinforced composite materials are used. Fiber-reinforced composite materials have the advantages of high strength, low density, good fatigue resistance, and corrosion resistance, which can meet the strength and stability requirements of the model base while reducing the overall weight of the model. During the fabrication process, fiber winding and molding techniques are used to accurately shape the model base according to the topography of the target erosion gully. By adding specific fillers and toughening agents to the fiber-reinforced composite materials, the performance of the materials is further improved. In addition, the positioning grooves and marking points set on the surface of the model base are made using high-precision laser engraving technology to ensure their positional and dimensional accuracy, providing an accurate benchmark for the subsequent laying and measurement of model materials.

6. The method for constructing a microscale model of an erosion gully based on soil mechanics theory according to claim 1, characterized in that, In the material layering process, the thickness of each layer of similar soil material is determined according to the scale of the model and the layered structure of the actual erosion gully soil. For the bottom layer of material near the model base, the thickness is relatively large to provide stable support; while for the material near the model surface, the thickness gradually decreases to more accurately simulate the characteristics of the surface soil of the erosion gully. During the compaction process, in addition to using vibration compaction or static compaction, ultrasonic vibration technology can also be combined to further improve the compaction effect of the material and reduce the porosity inside the material. At the same time, when implanting fibers to simulate roots, fibers of different lengths, diameters and distribution densities are used according to the distribution characteristics and mechanical effects of different plant roots to more realistically simulate the reinforcement and improvement effect of roots on the soil.

7. The method for constructing a microscale model of erosion gullies based on soil mechanics theory according to claim 1, characterized in that, In the boundary and loading setup steps, the rainfall simulation device combines a rotary nozzle and a pressure control system. The rotary nozzle enables uniform rainfall distribution, simulating the angle and coverage of natural rainfall. The pressure control system precisely adjusts the rainfall intensity and raindrop size to match actual meteorological data. For the dynamic loading system simulating water flow scouring, a circulating water tank and a variable-speed water pump are used. The circulating water tank provides a stable water flow environment, while the variable-speed water pump can flexibly adjust the water flow speed and flow rate according to experimental needs, simulating water flow scouring processes of different intensities. In addition, the waterproof and permeable boundary conditions set at the model boundary are achieved through special waterproof materials and permeable media, ensuring the accuracy and reliability of the boundary conditions.

8. The method for constructing a microscale model of erosion gullies based on soil mechanics theory according to claim 1, characterized in that, In the installation steps of the monitoring system, high-precision fiber optic displacement sensors are used for the miniature displacement sensors. Fiber optic displacement sensors have the advantages of anti-electromagnetic interference, high accuracy, and distributed measurement capabilities. They can monitor the displacement changes of the model soil at different locations in real time and accurately. The stress sensors adopt resistance strain gauge sensors. Through reasonable point placement and signal processing, they can accurately measure the stress distribution inside the soil. For the moisture content sensors, time domain reflectance (TDR) sensors are used. They have high measurement accuracy and fast response speed, and can monitor the dynamic changes of soil moisture content in real time. At the same time, wireless data transmission technology is used to transmit the data collected by each sensor to the data acquisition system in real time, realizing remote monitoring and data management, and improving the efficiency and convenience of the experiment.

9. The method for constructing a microscale model of an erosion gully based on soil mechanics theory according to claim 1, characterized in that, In the model calibration and optimization step, a combination of numerical simulation and experimentation is used for model verification. First, professional soil mechanics numerical simulation software, such as ABAQUS and FLAC, is used to numerically simulate the erosion process of the target gully to obtain the theoretical distribution of deformation, stress, and water flow parameters. Then, the experimental results of the model are compared and analyzed with the numerical simulation results to identify the parts with large differences. For these differences, response surface methodology and genetic algorithm optimization algorithms are used to optimize and adjust the key factors of similar material ratios and boundary condition parameters. Through multiple iterative calculations and experimental verifications, the accuracy and reliability of the model are gradually improved, enabling it to more realistically simulate the microscopic process of erosion gullies.

10. The method for constructing a microscale model of an erosion gully based on soil mechanics theory according to claim 1, characterized in that, Throughout the model construction process, a quality control system was established to rigorously inspect the operation process and results of each step. Detailed operating procedures and quality standards were formulated. For example, during the preparation of similar materials, the quality of raw materials, the accuracy of the proportions, and the stability of material properties were regularly tested. During the fabrication of the model substrate, the dimensional accuracy, shape accuracy, and surface flatness of the substrate were strictly checked. During the installation of the monitoring system, the installation position, connection reliability, and measurement accuracy of the sensors were comprehensively tested. By establishing a quality control system, it was ensured that every aspect of the model construction met the requirements, thereby improving the overall quality and reliability of the model and providing a reliable experimental platform for the study of the microscopic processes of erosion trenches.

Images