Method for testing shear strength of geotextile reinforced soil body

Abstract

The invention provides a method for testing the shear strength of a geotextile reinforced soil body, and belongs to the technical field of physical performance tests.The method comprises the steps that firstly, a standard soil sample is prepared, and geotextile is placed on a shear surface; then installing a sensor array to measure interface stress, and respectively carrying out a static shear test and a dynamic load test; capturing a deformation process by using a high-speed camera system, and quantifying deformation field distribution through a digital image correlation technology; constructing a microscopic contact model by adopting a discrete element method, establishing a macro-scale finite element model, and associating microscopic parameters with macro-performance by adopting a multi-scale coupling method; and finally, comprehensively analyzing the shear strength difference of the geotextile reinforced soil body under the dynamic and static conditions, establishing a geotextile reinforcement mechanism model considering the dynamic effect influence, and solving the technical problem that the interfacial shear characteristics of the geotextile reinforced soil body under the static and dynamic load conditions cannot be effectively evaluated at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of physical property testing, and in particular relates to a method for testing the shear strength of geotextile-reinforced soil. Background Art

[0002] Geotextiles, as an important soil reinforcement material, are widely used in infrastructure such as highways, railways, and water conservancy projects. Their reinforcement effect is primarily reflected in improving soil shear strength. Traditional methods for testing the shear strength of geotextile-reinforced soil primarily rely on static testing methods such as direct shear tests or pullout tests. These methods evaluate the reinforcement effect by measuring the static shear parameters at the geotextile-soil interface. These testing methods have achieved certain results in engineering practice and provide a basis for the selection and design of geotextiles.

[0003] However, traditional testing methods have obvious defects, which are mainly manifested in: First, there are large differences between static test conditions and the dynamic load environment in actual engineering (such as traffic loads, earthquake loads, etc.), making it difficult to truly reflect the reinforcement effect of geotextiles under dynamic conditions; second, existing testing devices are designed for static or dynamic conditions respectively, which makes it difficult to directly compare the test results; third, there is a lack of effective monitoring methods for the micromechanical behavior of the interface during the test, making it difficult to reveal the reinforcement mechanism of geotextiles.

[0004] Due to these shortcomings, the evaluation of geotextile reinforcement under dynamic loads in engineering design primarily relies on empirical formulas or simplified coefficients, lacking a systematic theoretical basis and experimental support. This can easily lead to inappropriate design parameter selection or excessive safety factors. Therefore, accurately evaluating the shear properties of geotextile-reinforced soil interfaces under both static and dynamic conditions has become a pressing technical challenge in this field. Summary of the Invention

[0005] In view of this, the present invention provides a method for testing the shear strength of geotextile-reinforced soil, which can solve the technical problem in the prior art that it is impossible to effectively evaluate the shear properties of the geotextile-reinforced soil interface under static and dynamic load conditions.

[0006] The present invention is implemented as follows: The present invention provides a method for testing the shear strength of geotextile-reinforced soil, which includes the following steps: preparing a soil sample and placing the geotextile on the shear surface of an integrated dynamic and static shear test device; installing a sensor array; applying a vertical load to perform a static shear test; applying a dynamic load to perform a dynamic test; using a high-speed camera system to capture the deformation process; using a discrete element method to construct a microscopic contact model; establishing a macroscopic-scale numerical model based on the finite element method; comprehensively analyzing the differences in the shear strength of geotextile-reinforced soil under dynamic and static conditions, establishing a geotextile reinforcement mechanism model that takes into account the influence of dynamic effects, and outputting the shear strength test results of geotextile-reinforced soil.

[0007] The steps of preparing soil samples and placing geotextiles on the shear surface of the dynamic and static shear test integrated device include: preparing standard soil samples and placing geotextiles on the shear surface, and compacting them layer by layer to the designed density according to the optimal moisture content.

[0008] The step of installing the sensor array includes: installing a piezoelectric sensor array and a displacement sensor, and arranging stress measurement points at key positions of the interface between the geotextile and the soil.

[0009] The step of applying a vertical load to conduct a static shear test includes: applying a constant vertical load, conducting a static shear test after the soil is consolidated and stabilized, and recording a shear force-displacement relationship curve.

[0010] The step of applying a dynamic load to conduct a dynamic test includes: re-preparing the sample, applying a dynamic load, simulating the effects of cyclic loads under different frequency and amplitude conditions, and recording changes in interface stress.

[0011] The step of constructing a microscopic contact model using the discrete element method includes: constructing a microscopic contact model of soil particles and geotextiles using the discrete element method, and applying the geotextile-soil interface dynamics mechanism equations to analyze dynamic response characteristics.

[0012] The step of establishing a macro-scale numerical model based on the finite element method includes: establishing a macro-scale numerical model based on the finite element method, and associating microscopic parameters with macroscopic performance through a multi-scale coupling method.

[0013] Among them, the input parameters of the geotextile-soil interface dynamic mechanism equation group include: normal effective stress, load frequency, soil friction angle, interface roughness coefficient, and soil density; the output parameter of the geotextile-soil interface dynamic mechanism equation group is the interface shear strength under dynamic conditions.

[0014] Among them, the test results of the shear strength of geotextile-reinforced soil include the benchmark shear strength value under static conditions, the shear strength value under different dynamic load conditions, the data table of the change law of the dynamic-static ratio coefficient with frequency and amplitude, and the parameter values ​​of the reinforcement mechanism model considering the dynamic effect.

[0015] The integrated dynamic and static shear test device includes: a base system, a shear box assembly, a vertical loading system, a horizontal drive system, a measurement and control system, and an external connection device; wherein the horizontal drive system generates a periodic shear load in the range of 0.1 to 50 Hz.

[0016] This method systematically evaluates the shear strength of geotextile-reinforced soil under static and dynamic loads by constructing a test device that integrates dynamic and static shear functions, combined with advanced measurement methods such as piezoelectric sensor arrays and digital image correlation technology. This method effectively addresses the shortcomings of traditional testing methods: first, by implementing dynamic and static shear tests in the same test device, the consistency of test conditions and the comparability of results are ensured. Second, through the application of piezoelectric sensor arrays and high-speed camera systems, high-precision real-time monitoring of interfacial stress and deformation fields is achieved, providing experimental evidence at the microscopic level for understanding the geotextile reinforcement mechanism. Finally, by constructing a multi-scale coupled numerical model, a quantitative relationship between microscopic parameters and macroscopic performance is established, forming a geotextile reinforcement mechanism model that considers dynamic effects.

[0017] Through the above-mentioned technical measures, the present invention has achieved for the first time the comparative analysis of the differences in the shear properties of the geotextile-reinforced soil interface under static and dynamic loads under the same conditions, revealing the influence mechanism of dynamic loads on the reinforcement effect of geotextiles, and providing a scientific basis for the rational selection and design of geotextiles in engineering practice, thereby solving the technical problem in the existing technology that it is impossible to effectively evaluate the shear properties of the geotextile-reinforced soil interface under static and dynamic load conditions at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of the method of the present invention.

[0019] Figure 2 Schematic diagram of the overall structure of the integrated dynamic and static shear test device in Example 2.

[0020] Figure 3 Schematic diagram of the shear box assembly structure in Example 2

[0021] Figure 4 Schematic diagram of the vertical loading system structure in Example 2

[0022] Figure 5 Schematic diagram of the horizontal drive system structure in Example 2 DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0024] like Figure 1 FIG. 1 is a flow chart of a method for testing the shear strength of geotextile-reinforced soil provided by the present invention. The method comprises the following steps: S01. Construct an integrated dynamic and static shear test device and use a hydraulic servo control system to simultaneously apply vertical load and horizontal shear force; S02. Prepare standard soil samples and place geotextiles on the shear surface, compacting them layer by layer to the designed density according to the optimal moisture content; S03. Install piezoelectric sensor arrays and displacement sensors, and arrange stress measurement points at key locations on the interface between geotextile and soil; S04. Apply a constant vertical load and conduct a static shear test after the soil is consolidated and stabilized, and record the shear force-displacement relationship curve; S05. Re-prepare the sample, apply dynamic load, simulate cyclic loads under different frequency and amplitude conditions, and record the interface stress changes; S06. Use a high-speed camera system to capture the deformation process of geotextiles and soil, and quantify the deformation field distribution through digital image correlation technology; S07. Use the discrete element method to construct a microscopic contact model between soil particles and geotextiles, and apply the dynamic mechanism equations of the geotextile-soil interface to analyze the dynamic response characteristics; S08. Establish a macro-scale numerical model based on the finite element method, and relate microscopic parameters to macroscopic performance through a multi-scale coupling method; S09. Comprehensively analyze the differences in shear strength of geotextile-reinforced soil under dynamic and static conditions, establish a geotextile reinforcement mechanism model that considers the influence of dynamic effects, and output the geotextile-reinforced soil shear strength test results, including the benchmark shear strength value under static conditions, the shear strength value under different dynamic load conditions, the data table of the variation law of the dynamic-static ratio coefficient with frequency and amplitude, and the parameter values ​​of the reinforcement mechanism model considering dynamic effects.

[0025] Among them, the integrated dynamic and static shear test device refers to a device that can realize static and dynamic shear functions in the same test device, and realize automatic switching between constant load and periodic load through an electro-hydraulic servo control system.

[0026] Among them, the piezoelectric sensor array refers to a grid-like measurement system composed of multiple miniature piezoelectric sensors, which can simultaneously capture multi-point stress changes and has high-frequency response characteristics.

[0027] Among them, digital image correlation technology refers to a non-contact measurement method that calculates the deformation field distribution by comparing the changes in random texture on the sample surface before and after deformation, with an accuracy of up to micron level.

[0028] Among them, the discrete element method refers to a numerical method that regards the soil as a system composed of a large number of discrete particles and studies the macroscopic mechanical properties of the material by simulating the contact force and motion between particles.

[0029] Among them, the multiscale coupling method refers to a computational method that links the mechanical models of the microscale and macroscale, and realizes parameter transfer and interaction between different scales through representative volume units.

[0030] Among them, the geotextile-soil interface dynamic mechanism equation group refers to a mathematical model that describes the law of change of interface shear strength under dynamic load. The input parameters of the geotextile-soil interface dynamic mechanism equation group include: normal effective stress, obtained by converting the vertical load applied in step S04; load frequency, provided by the dynamic load applied in step S05; soil friction angle, measured by the static shear test in step S04; interface roughness coefficient, obtained by measuring the surface morphology of geotextile; soil density, controlled by the sample preparation process in step S02; the output parameter of the geotextile-soil interface dynamic mechanism equation group is the interface shear strength under dynamic conditions, which is used to establish the geotextile reinforcement mechanism model in step S09.

[0031] The integrated dynamic and static shear test device consists of the following main components and their connection relationships: 1. Base system: A stable base made of high-strength alloy steel, with a surface precision-machined to ensure levelness. The base is equipped with a slide guide mechanism to support the relative movement of the upper and lower shear boxes. A shock absorber is installed at the bottom of the base to isolate external vibration interference. 2. Shear box assembly: This assembly includes a fixed lower shear box and a movable upper shear box, forming a horizontal shear plane between them. The inner wall of the shear box is coated with anti-friction material and is designed with a drainage channel system. The upper shear box is connected to a horizontal actuator to achieve horizontal displacement, and the lower shear box is fixed to the base. 3. Vertical loading system: This system consists of a hydraulic cylinder driven by a servo motor. It applies a uniform vertical load to the specimen via a rigid loading plate. The loading plate is designed with a multi-point support structure to ensure uniform force distribution. The hydraulic system is equipped with a high-precision pressure sensor to monitor vertical stress in real time. 4. Horizontal drive system: This system utilizes a combination of bidirectional hydraulic cylinders and a precision servo control system, enabling constant speed displacement control or force control modes. It also features high-frequency response characteristics. The horizontal drive system generates a periodic shear load within the range of 0.1 to 50 Hz. The horizontal drive system is connected to the upper shear box via a rigid connector. 5. Measurement and control system: includes displacement sensor, force sensor, pressure sensor and data acquisition module. The displacement sensor adopts high-frequency response design. The force sensor and pressure sensor signals are transmitted to the data acquisition module after anti-interference processing. The measurement and control system adopts closed-loop PID control algorithm to adjust the hydraulic system output in real time. 6. External connection device: An interface is provided for connecting the high-speed camera system and the piezoelectric sensor array. The high-speed camera system photographs the sample through a transparent observation window, and the piezoelectric sensor array is arranged near the shear surface through a preset threading channel.

[0032] Instructions for use: First, fix the lower shear box on the base, then fill part of the soil sample into the lower shear box according to the test design and tamp it to the designed density; then accurately place the geotextile at the shear surface position; continue to fill the remaining soil sample into the upper shear box and tamp it; install the piezoelectric sensor array and displacement sensor and calibrate them; apply the set vertical load through the measurement and control system and keep it constant; after the soil is consolidated and stabilized, select static mode or dynamic mode according to the test requirements; collect load, displacement and stress distribution data in real time during the test; after the test is completed, process the results through data analysis and output relevant parameters.

[0033] The specific implementation of the above steps is described in detail below.

[0034] The specific implementation of step S01 is to construct an integrated dynamic and static shear test device. This step first determines that the overall size of the device is 400mm×300mm×350mm, which meets the space requirements required for standard geotechnical tests. Then assemble the base system, use 45# high-strength alloy steel to manufacture the base, and control the surface flatness within the range of ±0.05mm. Design a bidirectional slide guide mechanism on the base with a friction coefficient of less than 0.01. Then install the shear box assembly. The inner dimensions of the lower shear box are 100mm×100mm×50mm, and the inner dimensions of the upper shear box are the same. A gap of 2mm±0.2mm is reserved between the two to form a horizontal shear surface. Then connect the vertical loading system, the servo motor has a rated power of 2kW, the hydraulic cylinder has a maximum output pressure of 20MPa, and the loading plate adopts a 16-point support structure to ensure that the pressure uniformity deviation is less than 3%. Then install the horizontal drive system, configure the bidirectional hydraulic cylinder with a maximum thrust of 30kN, a displacement accuracy of ±0.01mm, and a frequency response range of 0.1~50Hz. Finally, the measurement and control system was integrated. The displacement sensor sampling frequency was no less than 1000Hz, and the force sensor sensitivity was better than 0.01kN. All sensor signals were filtered with a 50dB signal-to-noise ratio before being transmitted to the data acquisition module. The goal of this step was to provide a device capable of performing both static and dynamic shear functions within the same test setup. Automatic switching between constant and cyclic loads was achieved through an electro-hydraulic servo control system, providing a stable and reliable test platform for subsequent experiments.

[0035] The specific implementation method of step S02 is to prepare a standard soil sample and place the geotextile on the shear surface. This step first takes a representative soil sample for basic physical and mechanical property testing, including particle analysis, liquid limit determination, density determination, etc. Suitable soil samples are screened in accordance with the "Test Procedures for Geosynthetics for Highway Engineering", where the content of particles with a particle size of less than 2 mm should be greater than 85%, and the plasticity index range is 10 to 20. Then the optimal moisture content is determined, and the standard compaction test method is used to draw a moisture content-dry density curve. The moisture content corresponding to the vertex of the curve is taken as the optimal moisture content, which is usually in the range of 12% to 18%. Then weigh the required soil sample mass and calculate it based on the test volume and target dry density (usually more than 95% of the maximum dry density of the compaction). After that, the moisture content of the soil sample is adjusted to the optimal moisture content value, mixed evenly, and sealed and cured for 24 hours to ensure uniform distribution of moisture content. Subsequently, fill and tamp the soil in three layers in the lower shear box. The thickness of each layer is about 16 mm, and the tamping energy is controlled at 600 kJ / , to ensure good bonding between the layers. After compacting the lower shear box, the pre-cut geotextile (size 120mm×120mm) is accurately placed on the shear surface to ensure it is flat and wrinkle-free. Finally, continue to fill the upper shear box with soil and compact it to the designed density, ensuring that the difference in dry density of the soil in the upper and lower shear boxes is within ±0.02g / The purpose of this step is to prepare standardized and homogeneous samples to ensure the reliability and repeatability of the test results.

[0036] Step S03 involves installing a piezoelectric sensor array and displacement sensors. This step begins with the selection of high-sensitivity piezoelectric sensors with a frequency response range of 0–2000 Hz, a sensitivity of no less than 50 pC / N, and dimensions less than 5 mm × 5 mm × 1 mm. Based on the estimated stress distribution, a 3×3 grid-like piezoelectric sensor array is designed with a grid spacing of 25 mm, covering the entire shear surface. A custom installation tool is then used to precisely embed the piezoelectric sensors at key locations within the geotextile-soil interface, ensuring a close fit and contact pressure within a range of 10–20 kPa. Signal cables are then connected and routed through pre-defined channels. High-impedance coaxial cables are used to minimize signal attenuation, achieving a signal transmission loss of less than 0.5 dB / m. Three-dimensional displacement sensors are then installed to monitor displacement changes in the vertical and two horizontal directions, with a sensitivity better than 0.001 mm. These sensors are rigidly connected to the shear box. Finally, all sensors are calibrated, with a secondary calibration using standard load and displacement inputs to ensure measurement error is less than ±0.5% of full scale. The purpose of this step is to establish a high-precision stress and displacement monitoring system to provide detailed data support for the study of interface stress transfer mechanisms under dynamic and static conditions.

[0037] The specific implementation of step S04 is to apply a constant vertical load to perform a static shear test. This step first sets the test vertical load level, usually selecting four levels of 50kPa, 100kPa, 200kPa and 300kPa to cover the common engineering pressure range. The vertical load is then gradually applied through the servo control system, and the loading rate is controlled to be below 5kPa / min to avoid generating excessive pore water pressure. The vertical displacement change is then monitored. When the vertical displacement change is less than 0.01mm within 30 minutes, the soil consolidation is determined to be stable. The horizontal drive system is then started to perform the shear test, and the shear rate is controlled at 0.2mm / min to ensure that it is carried out under drainage conditions. At the same time, the shear force, vertical displacement and horizontal displacement data are recorded by the data acquisition system, and the sampling frequency is set to 10Hz. The shear strain and shear stress are then calculated, where the shear strain is the ratio of the horizontal displacement to the sample height, and the shear stress is the ratio of the shear force to the shear surface area. Finally, a shear force and displacement relationship curve is generated to determine the peak shear strength and residual shear strength. The purpose of this step is to obtain the basic shear characteristic parameters of geotextile-reinforced soil under static conditions and provide benchmark data for subsequent dynamic characteristic comparison.

[0038] The specific implementation of step S05 is to simulate the effects of cyclic loading under different dynamic load conditions. This step first re-prepare the sample in the same way as step S02 to ensure that the physical properties are consistent with those of the static test sample. Then, a dynamic load test plan is designed, with the frequency range set to 0.5Hz, 1Hz, 2Hz, 5Hz and 10Hz to cover the frequency range of common earthquakes and traffic loads; the amplitude is set to three levels of 10%, 30% and 50% of the static shear strength. Then, a constant vertical load is applied, the same as step S04, and the soil consolidation is stabilized. After that, the dynamic loading control parameters are set, including the waveform (usually a sine wave), frequency and amplitude. Precise control is achieved through a servo control system, and the waveform distortion is less than 3%. The dynamic shear loading system is then started, and each frequency and amplitude combination is loaded for at least 100 cycles, during which the vertical load is kept constant. At the same time, the output signal of the piezoelectric sensor array at the interface is recorded, and the sampling frequency is set to more than 20 times the load frequency to ensure data resolution. Finally, the collected data is filtered using a bandpass filter to remove high-frequency noise and low-frequency drift. Fast Fourier transform (FT) algorithms are used to analyze the spectral characteristics of the signal. This step aims to simulate various dynamic loading conditions that may occur in actual projects and to determine the stress transfer characteristics of the geotextile-soil interface under dynamic loading.

[0039] The specific implementation of step S06 involves capturing and analyzing the deformation process of the geotextile and soil. This step first involves setting up a high-speed camera system with a minimum of 5 million pixels, a frame rate of at least 200 frames per second, and a field of view covering the entire shear surface area. A random texture is then created on the specimen surface. Fine sand with high black and white contrast is evenly sprayed and fixed, ensuring that the texture coverage is within the range of 40% to 60%, and the size of individual feature points is 0.2 to 0.5 mm. A baseline image is then acquired before the test begins, with a resolution of at least 0.05 mm / pixel. A reference coordinate system is also recorded for subsequent deformation calculations. Image sequences are then continuously acquired during the static and dynamic tests, with acquisitions occurring every 0.5 mm of displacement for static tests and at a frequency of 10 times the loading frequency for dynamic tests. The image sequences are then processed using a digital image correlation algorithm, selecting a 30×30 pixel subregion for correlation matching. A biquadratic interpolation algorithm is used to improve subpixel accuracy to 0.01 pixel. Finally, the displacement and strain field distributions are calculated. The displacement field is obtained by tracking the movement of feature points in the image, and the strain field is calculated from the spatial derivative of the displacement field. A high-precision central difference method is used to reduce numerical errors. The purpose of this step is to obtain high-resolution deformation field information, visually demonstrate the spatial distribution characteristics of the geotextile reinforcement mechanism, and provide verification data for subsequent numerical simulations.

[0040] The specific implementation of step S07 involves constructing a microscopic contact model and analyzing its dynamic response characteristics. This step first involves microscopically measuring the geometric characteristics of soil particles, including particle size distribution, shape factor, and surface roughness. The surface roughness Ra value is typically in the range of 5 to 100 μm. Next, geotextile microstructural parameters are measured, including fiber diameter (typically 20 to 50 μm), pore size distribution (pore size range 50 to 500 μm), and surface topography (roughness Ra value 10 to 200 μm). A soil particle model is then constructed using discrete element software, using a multi-sphere or polyhedron combination approach to simulate irregular particle shapes. The number of particles should be no less than 10,000 to ensure statistical representativeness. Next, a geotextile model is constructed, using regularly arranged fiber bundles for woven geotextiles and a randomly distributed fiber network for non-woven geotextiles. A constitutive model for interparticle contact is then defined, using the Hertz-Mindlin contact model to describe elastic contact behavior. The friction coefficient is set based on measured values, typically in the range of 0.2 to 0.6. A contact model between soil particles and geotextiles was also defined, taking into account the nonlinear characteristics of fiber deformation and employing a modified JKR adhesion contact model to describe interfacial bonding behavior. Finally, the dynamic mechanism equations for the geotextile-soil interface were applied, using input parameters including normal effective stress, load frequency, soil friction angle, interface roughness coefficient, and soil density to calculate the interfacial shear strength under dynamic conditions. This step aims to reveal the fundamental mechanism of geotextile-soil reinforcement at the microscale and analyze the force chain network and stress transfer pathways at the particle level.

[0041] The specific implementation of step S08 is to establish a macro-scale numerical model. This step first selects finite element analysis software and uses an explicit dynamics solver to deal with nonlinear large deformation problems. Then, a soil geometric model is established, the size of which is consistent with that of the test device. The mesh is divided into hexahedral elements, and the element size is no more than 10mm to ensure calculation accuracy. Then, a geotextile geometric model is established, and shell elements are used for simulation. The element size is no more than 5mm to ensure that local deformation can be accurately captured. After that, the material constitutive model is defined. The soil adopts the modified Drucker-Prager model, considering strain softening and strain rate effects, and the parameters are calibrated through indoor tests; the geotextile adopts the orthotropic elastic-plastic model, considering the strength and stiffness differences in the fiber direction. Subsequently, the interface contact model is defined, using the surface-to-surface contact algorithm. The friction coefficient is obtained by the static shear test in step S04, while considering the degradation of bond strength with shear displacement. Then, a multi-scale coupling method is applied to establish a representative volume element (RVE) with a size of 50 times the average diameter of the particles. The macro-micro parameter mapping relationship is established by calculating the homogenized stress and strain. Finally, numerical simulations were performed under static and dynamic loading conditions. Static analysis used displacement control, while dynamic analysis used force control. The time step was kept within 80% of the critical time step to ensure computational stability. The goal of this step was to establish a numerical model capable of describing the actual engineering scale, achieving a scale transition from microscopic mechanisms to macroscopic performance.

[0042] The specific implementation of step S09 involves a comprehensive analysis of the differences in shear strength of geotextile-reinforced soil under dynamic and static conditions. This step first compares the interfacial shear strength data obtained under static and dynamic conditions to calculate the dynamic-to-static ratio coefficient (D / S), which is the ratio of the shear strength under dynamic conditions to the shear strength under static conditions, typically ranging from 0.8 to 1.5. The dynamic-to-static ratio coefficient is then analyzed for variations in different frequencies and amplitudes. Generally, it is found that under low frequencies (<1Hz) and high amplitudes (>30%), the dynamic-to-static ratio is less than 1, indicating a decrease in strength; while under high frequencies (>5Hz) and low amplitudes (<20%), the dynamic-to-static ratio is greater than 1, indicating an increase in strength. The physical mechanisms of dynamic effects are then analyzed using a microscopic contact model, including particle rearrangement effects, changes in interfacial friction properties, and the influence of pore water pressure. A geotextile reinforcement mechanism model that accounts for dynamic effects is then established. The core of the model is a modified Mohr-Coulomb strength criterion, which incorporates frequency- and amplitude-dependent coefficients to modify the internal friction angle and cohesion. The specific correction method is to establish the relationship between the cohesion and internal friction angle under dynamic conditions and the corresponding parameters under static conditions, and introduce a dynamic correction function related to frequency and amplitude. Subsequently, the model parameters are determined by regression analysis, and the least squares method is used to fit the test data. The goodness of fit is required to be greater than 0.9. Finally, the model prediction accuracy is verified, and part of the test data is used as a validation set. The relative error between the predicted value and the measured value is required to be less than 15%. The test results of the geotextile-reinforced soil shear strength output in this step include: the baseline shear strength under static conditions, the shear strength under different dynamic load conditions, the variation pattern of the dynamic-static ratio coefficient with frequency and amplitude, and the parameters of the reinforcement mechanism model considering dynamic effects. These results comprehensively reflect the enhancement effect of geotextiles on the shear strength of soil, especially revealing the particularity of the reinforcement mechanism under dynamic load conditions, providing a theoretical basis and calculation method for the reasonable evaluation of the reinforcement effect of geotextiles in engineering practice.

[0043] It should be noted that stress measurement points are placed at key locations on the geotextile-soil interface. These key locations primarily include the center of the shear surface, the edge of the shear surface, the front end of the shear force transmission direction, the area of ​​normal stress concentration, and the tensile deformation area where the geotextile contacts the soil. Furthermore, these locations also include areas with significant shear stress gradient changes at the geotextile-soil interface, weak points where stress concentration may lead to localized failure, areas near geotextile fiber intersections, areas where the geotextile experiences maximum tensile deformation, and the interface between soils of varying densities. The placement of stress measurement points at these key locations comprehensively captures the interfacial stress distribution, providing key data support for accurate analysis of the geotextile reinforcement mechanism.

[0044] Specifically, the principle behind this method is based on the differences in the dynamic and static mechanical behavior of the geotextile-soil interface, as well as on the theoretical basis for testing and evaluation. Under static conditions, geotextile reinforcement of soil primarily improves shear strength through interfacial friction and interlocking. However, under dynamic conditions, cyclic loading causes changes in interfacial stress state, fluctuations in pore water pressure, and nonlinear responses in the material's constitutive relations, resulting in variations in reinforcement effectiveness.

[0045] The technical solution of this invention works as follows: First, the integrated dynamic and static shear test device ensures consistent testing conditions, eliminating systematic errors introduced by different equipment and enabling direct comparability of static and dynamic test results. The device employs an electro-hydraulic servo control system to precisely switch between constant and cyclic loads, ensuring accurate and stable load application.

[0046] Secondly, the application principle of the piezoelectric sensor array is to use the piezoelectric effect to convert interface stress changes into electrical signals, realizing multi-point high-frequency response stress monitoring. Compared with traditional single-point measurement, this method can fully capture the unevenness and dynamic changes of interface stress distribution. At the same time, digital image correlation technology calculates the deformation field distribution by tracking the displacement of random textures on the specimen surface before and after deformation, realizing non-contact, high-precision interface deformation measurement, avoiding the interference of traditional contact measurement on interface behavior.

[0047] Thirdly, this invention combines the microscale discrete element method with the macroscale finite element method to construct a multiscale coupled numerical analysis framework. The discrete element method simulates the contact forces and relative motion between soil particles and geotextile fibers, revealing micromechanical mechanisms; the finite element method analyzes macroscopic stress-strain relationships. By using representative volume elements to transfer parameters between different scales, a mapping relationship between microscopic parameters and macroscopic properties is established.

[0048] Finally, the dynamic mechanism equations of the geotextile-soil interface relate input parameters such as normal effective stress, load frequency, and soil friction angle to the interface shear strength, taking into account factors such as the change in interface stress state under dynamic load and the nonlinear response of the material, and deeply revealing the influence mechanism of dynamic load on the reinforcement effect of geotextiles.

[0049] Through the above principles, the present invention realizes the systematic evaluation and mechanistic analysis of the shear characteristics of the geotextile-reinforced soil interface under static and dynamic conditions, providing a scientific basis for the evaluation of geotextile reinforcement performance considering dynamic effects.

[0050] A specific embodiment 1 of the present invention is provided below. The specific implementation of each step in this embodiment 1 is described in detail as follows.

[0051] The specific implementation of step S01 is to construct an integrated dynamic and static shear test device. This step first determines that the overall size of the device is 400mm×300mm×350mm, which meets the space requirements required for standard geotechnical tests. Then assemble the base system, use 45# high-strength alloy steel to manufacture the base, and control the surface flatness within the range of ±0.05mm. Design a bidirectional slide guide mechanism on the base with a friction coefficient of less than 0.01. Then install the shear box assembly. The inner dimensions of the lower shear box are 100mm×100mm×50mm, and the inner dimensions of the upper shear box are the same. A gap of 2mm±0.2mm is reserved between the two to form a horizontal shear surface. Then connect the vertical loading system, the servo motor has a rated power of 2kW, the hydraulic cylinder has a maximum output pressure of 20MPa, and the loading plate adopts a 16-point support structure to ensure that the pressure uniformity deviation is less than 3%. Then install the horizontal drive system, configure the bidirectional hydraulic cylinder with a maximum thrust of 30kN, a displacement accuracy of ±0.01mm, and a frequency response range of 0.1~50Hz. Finally, the measurement and control system is integrated. The sampling frequency of the displacement sensor is not less than 1000Hz, and the sensitivity of the force sensor is better than 0.01kN. All sensor signals are filtered with a 50dB signal-to-noise ratio and then transmitted to the data acquisition module. This step uses a closed-loop PID control algorithm to achieve precise control of the hydraulic system. Its control equation is: ; in, Indicates the controller output signal, Indicates the error between the target value and the actual value. 、 and are the proportional, integral and differential control parameters respectively, is the time variable, is the integration variable. Typical parameter settings are , , The purpose of this step is to provide a device that can realize static and dynamic shear functions in the same test device, realize automatic switching between constant load and cyclic load through the electro-hydraulic servo control system, and provide a stable and reliable test platform for subsequent tests.

[0052] The specific implementation method of step S02 is to prepare a standard soil sample and place the geotextile on the shear surface. This step first takes a representative soil sample for basic physical and mechanical property testing, including particle analysis, liquid limit determination, density determination, etc. Suitable soil samples are screened in accordance with the "Test Procedures for Geosynthetics for Highway Engineering", where the content of particles with a particle size of less than 2 mm should be greater than 85%, and the plasticity index range is 10 to 20. Then the optimal moisture content is determined, and the standard compaction test method is used to draw a moisture content-dry density curve. The moisture content corresponding to the vertex of the curve is taken as the optimal moisture content, which is usually in the range of 12% to 18%. Then weigh the required soil sample mass and calculate it based on the test volume and target dry density (usually more than 95% of the maximum dry density of the compaction). After that, the moisture content of the soil sample is adjusted to the optimal moisture content value, mixed evenly, and sealed and cured for 24 hours to ensure uniform distribution of moisture content. Subsequently, fill and tamp the soil in three layers in the lower shear box. The thickness of each layer is about 16 mm, and the tamping energy is controlled at 600 kJ / , to ensure good bonding between the layers. After compacting the lower shear box, the pre-cut geotextile (size 120mm×120mm) is accurately placed on the shear surface to ensure it is flat and wrinkle-free. Finally, continue to fill the upper shear box with soil and compact it to the designed density, ensuring that the difference in dry density of the soil in the upper and lower shear boxes is within ±0.02g / The purpose of this step is to prepare standardized and homogeneous samples to ensure the reliability and repeatability of the test results.

[0053] Step S03 involves installing a piezoelectric sensor array and displacement sensors. This step begins with the selection of high-sensitivity piezoelectric sensors with a frequency response range of 0–2000 Hz, a sensitivity of no less than 50 pC / N, and dimensions less than 5 mm × 5 mm × 1 mm. Based on the estimated stress distribution, a 3×3 grid-like piezoelectric sensor array is designed with a grid spacing of 25 mm, covering the entire shear surface. A custom installation tool is then used to precisely embed the piezoelectric sensors at key locations within the geotextile-soil interface, ensuring a close fit and contact pressure within a range of 10–20 kPa. Signal cables are then connected and routed through pre-defined channels. High-impedance coaxial cables are used to minimize signal attenuation, achieving a signal transmission loss of less than 0.5 dB / m. Three-dimensional displacement sensors are then installed to monitor displacement changes in the vertical and two horizontal directions, with a sensitivity better than 0.001 mm. These sensors are rigidly connected to the shear box. Finally, all sensors are calibrated, with a secondary calibration using standard load and displacement inputs to ensure measurement error is less than ±0.5% of full scale. The purpose of this step is to establish a high-precision stress and displacement monitoring system to provide detailed data support for the study of interface stress transfer mechanisms under dynamic and static conditions.

[0054] The specific implementation method of step S04 is to apply a constant vertical load to perform a static shear test. This step first sets the test vertical load level, usually selecting four levels of 50kPa, 100kPa, 200kPa and 300kPa to cover the common engineering pressure range. The vertical load is then applied step by step through the servo control system, and the loading rate is controlled below 5kPa / min to avoid excessive pore water pressure. The vertical displacement change is then monitored. When the vertical displacement change is less than 0.01mm within 30 minutes, the soil consolidation is determined to be stable. The horizontal drive system is then started to perform the shear test, and the shear rate is controlled at 0.2mm / min to ensure that it is carried out under drainage conditions. At the same time, the shear force, vertical displacement and horizontal displacement data are recorded through the data acquisition system, and the sampling frequency is set to 10Hz. The shear strain and shear stress are then calculated, and the shear strain is the ratio of horizontal displacement to specimen height, shear stress is the ratio of shear force to shear surface area, and the calculation formula is: ; ; in, is the horizontal displacement (mm), is the sample height (mm), is the shear force (N), is the shear surface area ( Finally, a shear force versus displacement curve is generated to determine the peak shear strength. and residual shear strength The purpose of this step is to obtain the basic shear characteristic parameters of geotextile-reinforced soil under static conditions and provide benchmark data for subsequent dynamic characteristic comparison.

[0055] The specific implementation of step S05 is to simulate the effects of cyclic loading under different dynamic load conditions. This step first re-prepare the sample in the same way as step S02 to ensure that the physical properties are consistent with those of the static test sample. Then, a dynamic load test plan is designed, with the frequency range set to 0.5Hz, 1Hz, 2Hz, 5Hz and 10Hz to cover the frequency range of common earthquakes and traffic loads; the amplitude is set to three levels of 10%, 30% and 50% of the static shear strength. Then, a constant vertical load is applied, the same as step S04, and the soil consolidation is stabilized. After that, the dynamic loading control parameters are set, including the waveform (usually a sine wave), frequency and amplitude. Precise control is achieved through a servo control system, and the waveform distortion is less than 3%. The dynamic shear loading system is then started, and each frequency and amplitude combination is loaded for at least 100 cycles, during which the vertical load is kept constant. At the same time, the output signal of the piezoelectric sensor array at the interface is recorded, and the sampling frequency is set to more than 20 times the load frequency to ensure data resolution. Finally, the collected data is filtered and a bandpass filter is used to remove high-frequency noise and low-frequency drift. The signal processing uses the fast Fourier transform algorithm to analyze the spectrum characteristics. The dynamic load is represented by the following sine wave function: ; in, is the time-varying shear force (N), is the average shear force (N), is the amplitude (N), is the frequency (Hz), The purpose of this step is to simulate various dynamic load conditions that may occur in actual engineering projects and obtain the stress transfer characteristics of the geotextile-soil interface under dynamic loads.

[0056] The specific implementation of step S06 involves capturing and analyzing the deformation process of the geotextile and soil. This step first involves setting up a high-speed camera system with a minimum of 5 million pixels, a frame rate of at least 200 frames per second, and a field of view covering the entire shear surface area. A random texture is then created on the specimen surface. Fine sand with high black and white contrast is evenly sprayed and fixed, ensuring that the texture coverage is within the range of 40% to 60%, and the size of individual feature points is 0.2 to 0.5 mm. A baseline image is then acquired before the test begins, with a resolution of at least 0.05 mm / pixel. A reference coordinate system is also recorded for subsequent deformation calculations. Image sequences are then continuously acquired during the static and dynamic tests, with acquisitions occurring every 0.5 mm of displacement for static tests and at a frequency of 10 times the loading frequency for dynamic tests. The image sequences are then processed using a digital image correlation algorithm, selecting a 30×30 pixel subregion for correlation matching. A biquadratic interpolation algorithm is used to improve subpixel accuracy to 0.01 pixel. Finally, the displacement field and strain field distribution are calculated. The displacement field is obtained by tracking the movement of image feature points, and the strain field is calculated by the spatial derivative of the displacement field. The high-precision central difference method is used to reduce the numerical error. The core of digital image correlation technology is to maximize the correlation coefficient. To determine the displacement of the subregion: ; in, and are the image grayscale value functions before and after deformation, are the coordinates of the sub-area center, is the displacement vector, and are the average grayscale values ​​of the corresponding sub-regions, is the half width of the sub-area (in this embodiment, ). The strain field is calculated using the following formula: ; in, 、 and They are Direction positive strain, The purpose of this step is to obtain high-resolution deformation field information, intuitively display the spatial distribution characteristics of the geotextile reinforcement mechanism, and provide verification data for subsequent numerical simulations.

[0057] The specific implementation of step S07 involves constructing a microscopic contact model and analyzing its dynamic response characteristics. This step first involves microscopically measuring the geometric characteristics of soil particles, including particle size distribution, shape factor, and surface roughness. The surface roughness Ra value is typically in the range of 5 to 100 μm. Next, geotextile microstructural parameters are measured, including fiber diameter (typically 20 to 50 μm), pore size distribution (pore size range 50 to 500 μm), and surface topography (roughness Ra value 10 to 200 μm). A soil particle model is then constructed using discrete element software, using a multi-sphere or polyhedron combination approach to simulate irregular particle shapes. The number of particles should be no less than 10,000 to ensure statistical representativeness. Next, a geotextile model is constructed, using regularly arranged fiber bundles for woven geotextiles and a randomly distributed fiber network for non-woven geotextiles. A constitutive model for interparticle contact is then defined, using the Hertz-Mindlin contact model to describe elastic contact behavior. The friction coefficient is set based on measured values, typically in the range of 0.2 to 0.6. At the same time, the interface contact model between soil particles and geotextiles is defined, and the nonlinear characteristics of fiber deformation are considered. The improved JKR adhesion contact model is used to describe the interface bonding behavior. Finally, the geotextile-soil interface dynamic mechanism equations are applied. The input parameters include normal effective stress, load frequency, soil friction angle, interface roughness coefficient and soil density. The interface shear strength under dynamic conditions is calculated. The normal force of the Hertz-Mindlin contact model is and tangential force The calculation formula is as follows: ; ; in, is the equivalent elastic modulus, is the equivalent radius, is the equivalent shear modulus, is the normal overlap, is the tangential displacement, is the friction coefficient, 、 、 and ( ) are the elastic modulus, Poisson's ratio, shear modulus and radius of the contact particles respectively. The core of the geotextile-soil interface dynamics equations is to describe the dynamic shear strength Static shear strength Relationship: ; in, is the frequency-dependent function, are amplitude-related functions, respectively expressed as: ; ; in, is the load frequency (Hz), is the load amplitude, is the reference amplitude (usually 10% of the static shear strength), 、 、 、 and To fit the parameters, they are obtained through regression of the test data. The purpose of this step is to reveal the basic mechanism of geotextile reinforcement of soil at the micro scale and to analyze the force chain network and stress transfer path at the particle level.

[0058] The specific implementation of step S08 is to establish a macro-scale numerical model. This step first selects finite element analysis software and uses an explicit dynamics solver to deal with nonlinear large deformation problems. Then, a soil geometric model is established, the size of which is consistent with that of the test device. The mesh is divided into hexahedral elements, and the element size is no more than 10mm to ensure calculation accuracy. Then, a geotextile geometric model is established, and shell elements are used for simulation. The element size is no more than 5mm to ensure that local deformation can be accurately captured. After that, the material constitutive model is defined. The soil adopts the modified Drucker-Prager model, considering strain softening and strain rate effects, and the parameters are calibrated through indoor tests; the geotextile adopts the orthotropic elastic-plastic model, considering the strength and stiffness differences in the fiber direction. Subsequently, the interface contact model is defined, using the surface-to-surface contact algorithm. The friction coefficient is obtained by the static shear test in step S04, while considering the degradation of bond strength with shear displacement. Then, a multi-scale coupling method is applied to establish a representative volume element (RVE) with a size of 50 times the average diameter of the particles. The macro-micro parameter mapping relationship is established by calculating the homogenized stress and strain. Finally, numerical simulations were performed under static and dynamic loading conditions. Static analysis used displacement control, while dynamic analysis used force control. The time step was controlled within 80% of the critical time step to ensure calculation stability. The yield function expression of the modified Drucker-Prager model is: ; in, is the first stress invariant, is the second deviatoric invariant of stress, 、 and The principal stress, and is a material parameter that can be determined by triaxial testing: ; ; in, is the cohesion (kPa), is the internal friction angle (°). Considering the strain rate effect, the dynamic strength enhancement factor is introduced (Dynamic Increase Factor): ; in, is the current strain rate, is the reference strain rate (usually ), is the material parameter (usually in the range of 0.01 to 0.05). Multi-scale coupling uses a homogenization method, and the macro stress and micro stress The relationship is: ; in, The purpose of this step is to establish a numerical model that can describe the actual engineering scale and achieve a scale leap from microscopic mechanism to macroscopic performance.

[0059] The specific implementation of step S09 is to comprehensively analyze the difference in shear strength of geotextile reinforced soil under dynamic and static conditions. This step first calculates the dynamic-static ratio coefficient by comparing the interface shear strength data under static and dynamic conditions obtained by the test. , which is the ratio of the shear strength under dynamic conditions to the shear strength under static conditions, usually ranges from 0.8 to 1.5: ; in, is the shear strength under dynamic conditions, is the shear strength under static conditions. Then analyze different frequencies and amplitude Dynamic-static ratio coefficient under conditions The change pattern of the value is generally found under low frequency (<1Hz) and high amplitude (>30%) conditions. , manifested as reduced intensity; under high frequency (>5Hz) and low amplitude (<20%) conditions , manifested as increased strength. The physical mechanism of the dynamic effect was then analyzed in conjunction with a microscopic contact model, including particle rearrangement effects, changes in interfacial friction characteristics, and the influence of pore water pressure. A geotextile reinforcement mechanism model that considers the dynamic effect was then established. The core of the model is the modified Mohr-Coulomb strength criterion: ; in, is the normal effective stress, and are the cohesion and internal friction angle under dynamic conditions, respectively. They modify the static parameters by introducing frequency correlation coefficient and amplitude correlation coefficient: ; ; in, and are the cohesion and internal friction angle under static conditions, and They are the dynamic correction functions of cohesion and internal friction angle respectively: ; ; in, is the reference amplitude (usually 10% of the static shear strength), 、 、 、 、 and is the fitting parameter. The relationship between dynamic shear strength and static shear strength defined previously can also be used: ; in, is the frequency-dependent function, is the amplitude correlation function, 、 、 、 and is the fitting parameter. Then the model parameters are determined by regression analysis method, and the least squares method is used to fit the test data. The objective function of the least squares method is: ; in, For the The measured dynamic shear strength of each test point is is the corresponding model prediction value, is the total number of experimental data points, goodness of fit The requirement is greater than 0.9. Finally, verify the prediction accuracy of the model, use part of the test data as the verification set, and calculate the relative error between the predicted value and the measured value. : ; Require To ensure the reliability of the model. The geotextile reinforced soil shear strength test results output in this step include: benchmark shear strength under static conditions , different dynamic load conditions Shear strength under , dynamic-static ratio coefficient With frequency and amplitude The changing rules of the enhanced mechanism model considering the dynamic effect ( 、 、 、 、 、 or 、 、 、 、 These results comprehensively reflect the effect of geotextiles on the shear strength of soil, especially revealing the particularity of the reinforcement mechanism under dynamic load conditions, and provide a theoretical basis and calculation method for the rational evaluation of the reinforcement effect of geotextiles in engineering practice.

[0060] The purpose of this step is to establish a geotextile reinforcement mechanism model that considers dynamic effects, providing a theoretical basis and calculation method for rationally evaluating geotextile reinforcement effectiveness in engineering practice. This geotextile reinforcement mechanism model can predict interfacial shear strength under different dynamic load conditions based on actual engineering needs, optimize engineering design solutions, and improve structural safety and economic efficiency. By introducing frequency-correlation coefficients and amplitude-correlation coefficients, the model accurately reflects the impact of dynamic load characteristics on reinforcement effectiveness, and is more consistent with the actual dynamic response characteristics of engineering projects than traditional static analysis methods.

[0061] In order to better understand and implement the present invention, the following provides a specific application scenario of the present invention, Example 2: Researchers tested woven polypropylene (PP) geotextiles and field soil samples used in a high-speed railway roadbed reinforcement project. The geotextile specification is 200g / , tensile strength is 22kN / m, maximum elongation is 12%, effective pore size is 0.15mm. The roadbed filler sampled on site is silty clay with a water content of 16.5% and a dry density of 1.72g / , the liquid limit is 38.2%, the plastic limit is 18.7%, the plasticity index is 19.5, and the particle analysis results are shown in Table 1: Table 1 Analysis results of roadbed filler particles

[0062] According to step S01, an integrated dynamic and static shear test device is constructed. The overall dimensions of the device are 420mm×320mm×360mm. The base is made of 50# high-strength alloy steel with a surface flatness of ±0.032mm. The inner dimensions of the shear box are 100mm×100mm×50mm. The maximum pressure of the vertical loading system is 25MPa, and the frequency response range of the horizontal drive system is 0.1~60Hz. The device composition structure is as follows: Figures 2 to 5 shown.

[0063] Prepare the sample according to step S02, and determine the optimal moisture content to be 15.8% and the maximum dry density to be 1.78g / cm2 through standard compaction test. The test set the target dry density to be 1.70g / (about 95.5% of the maximum dry density). Place a woven PP geotextile with a size of 120mm×120mm on the shear surface, compact the sample layer by layer, and control the difference in soil dry density in the upper and lower shear boxes to ±0.015g / Within.

[0064] According to step S03, a 3×3 grid-shaped piezoelectric sensor array was installed, with a grid spacing of 25 mm, a sensor sensitivity of 68 pC / N, and a frequency response range of 0 to 1800 Hz. A three-dimensional displacement sensor with a sensitivity of 0.0008 mm was also installed, rigidly connected to the shear box.

[0065] Static and dynamic shear tests were conducted according to steps S04-S06. Four vertical load levels of 50 kPa, 100 kPa, 200 kPa, and 300 kPa were used, and the static shear rate was controlled at 0.15 mm / min. Dynamic loading frequencies of 0.5 Hz, 1 Hz, 2 Hz, 5 Hz, and 10 Hz were used, with amplitudes of 10%, 30%, and 50% of the static shear strength. The deformation field was captured using a high-speed camera system (frame rate 250 frames / second) and analyzed using digital image correlation technology. The static shear test results are shown in Table 2:

[0066] Table 2 Geotextile-soil interface shear strength parameters under static conditions

[0067] Based on the static shear test results, the Mohr-Coulomb strength criterion was used to fit the static strength parameters of the geotextile-soil interface: cohesion =5.8kPa, interface friction angle =34.2°, goodness of fit =0.992.

[0068] The dynamic test results show that the interface shear strength is significantly correlated with frequency and amplitude. Tables 3 and 4 show the dynamic shear strength test results under different frequency and amplitude conditions under a vertical load of 100 kPa: Table 3 Dynamic shear strength under different frequency conditions (vertical load 100 kPa, amplitude 30%)

[0069] Table 4 Dynamic shear strength under different amplitude conditions (vertical load 100 kPa, frequency 2 Hz)

[0070] In step S07, the researchers used the discrete element method to establish a microscopic contact model, simulating the interaction between 10,800 soil particles and the geotextile. The soil particles were simulated using a multi-sphere assembly method, with a friction coefficient set to 0.45. The geotextile model took into account the fiber structure and used a modified JKR adhesion contact model to describe the interfacial bonding behavior.

[0071] According to step S08, a macro-scale finite element model is established, and the soil body adopts the modified Drucker-Prager model with parameters =0.285, =10.32, the geotextile adopts the orthotropic elastic-plastic model, the tensile strength in the warp direction is 25kN / m, and the tensile strength in the weft direction is 20kN / m. The strain rate effect is considered in the model, and the dynamic strength enhancement factor parameter =0.032.

[0072] In step S09, a comprehensive analysis of the differences in shear strength of geotextile-reinforced soil under dynamic and static conditions was performed, and a geotextile reinforcement mechanism model considering the dynamic effect was established. The geotextile-reinforced soil shear strength test results were then output. By analyzing the variation in the dynamic-to-static ratio coefficient under different frequency and amplitude conditions, the parameters of the frequency- and amplitude-dependent functions were obtained, as shown in Table 5. Table 5 Dynamic effect affecting model parameters

[0073] Based on the above parameters, the shear strength under dynamic conditions can be expressed as:

[0074] In addition, a modified model of internal friction angle and cohesion under dynamic conditions was established, and its parameters are shown in Table 6: Table 6 Modified model parameters of internal friction angle and cohesion under dynamic conditions

[0075] The model was verified using the validation set data, and the relative error between the predicted value and the measured value is shown in Table 7: Table 7 Model validation results (relative error)

[0076] Traditional geotextile-reinforced soil shear strength testing methods are primarily based on static direct shear tests, which fail to account for dynamic load effects. This leads to biased assessments of geotextile reinforcement effectiveness in actual projects. Traditional methods typically utilize separate static direct shear apparatuses and dynamic triaxial apparatuses for static and dynamic testing, respectively. The separation of these apparatuses makes it difficult to ensure consistent specimen conditions, and the lack of precise observations of interfacial stress and deformation fields complicates microscopic mechanism studies. The simple application of static strength criteria during test result processing ignores the influence of frequency and amplitude on interfacial shear strength, making it impossible to establish a systematic dynamic effect assessment method.

[0077] In contrast, the testing method proposed in this paper offers the following significant advances: First, the integrated dynamic and static shear test device enables static and dynamic testing on the same device, ensuring consistency in test conditions and comparability of data. Second, the combination of piezoelectric sensor arrays and digital image correlation technology enables high-precision monitoring of interfacial stress and deformation fields, providing direct evidence for microscopic mechanism research. Third, the multiscale coupling analysis of the discrete element method and the finite element method establishes a complete theoretical framework from microscopic contact to macroscopic mechanical behavior. Most importantly, this paper establishes a geotextile reinforcement mechanism model that considers the effects of frequency and amplitude, improving the prediction accuracy by approximately 45% compared to traditional methods and reducing the average relative error from 13.2% of traditional methods to 7.3%. These advances enable engineering designers to more accurately predict the reinforcement effect of geotextiles under dynamic loads, improving the rationality and safety of engineering designs.

[0078] It should be noted that the variables involved in the present invention are explained in detail as shown in Tables 8 and 9 below.

[0079] Table 8 Variable Explanation Table (Part I)

[0080] Table 9 Variable Explanation Table (Part II)

[0081] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A method for testing the shear strength of geotextile-reinforced soil, characterized in that: The following steps are involved: Prepare soil samples and place geotextiles on the shear plane of the integrated dynamic and static shear test apparatus; install the sensor array; Static shear test was performed by applying vertical load; Dynamic loads were applied to conduct dynamic tests; deformation processes were captured using a high-speed camera system; a microscopic contact model was constructed using the discrete element method; a macroscopic numerical model was established based on the finite element method; the differences in shear strength of geotextile-reinforced soil under dynamic and static conditions were comprehensively analyzed, a geotextile reinforcement mechanism model considering the influence of dynamic effects was established, and the shear strength test results of geotextile-reinforced soil were output.

2. The method for testing the shear strength of geotextile-reinforced soil according to claim 1, characterized in that: The steps of preparing soil samples and placing geotextiles on the shear surface of the dynamic and static shear test integrated device include: preparing standard soil samples and placing geotextiles on the shear surface, and compacting them layer by layer to the designed density according to the optimal moisture content.

3. The method for testing the shear strength of geotextile-reinforced soil according to claim 2, wherein: The step of installing the sensor array includes: installing a piezoelectric sensor array and a displacement sensor, and arranging stress measurement points at key positions of the interface between the geotextile and the soil.

4. The method for testing the shear strength of geotextile-reinforced soil according to claim 3, wherein: The step of applying a vertical load to perform a static shear test includes: applying a constant vertical load, performing a static shear test after the soil is consolidated and stabilized, and recording a shear force and displacement relationship curve.

5. The method for testing the shear strength of geotextile-reinforced soil according to claim 4, characterized in that: The step of applying a dynamic load to conduct a dynamic test includes: re-preparing a sample, applying a dynamic load, simulating the effects of cyclic loads under different frequency and amplitude conditions, and recording changes in interface stress.

6. The method for testing the shear strength of geotextile-reinforced soil according to claim 5, characterized in that: The step of constructing a micro contact model using the discrete element method includes: constructing a micro contact model of soil particles and geotextiles using the discrete element method, and applying the geotextile-soil interface dynamics mechanism equation group to analyze dynamic response characteristics.

7. The method for testing the shear strength of geotextile-reinforced soil according to claim 6, characterized in that: The step of establishing a macro-scale numerical model based on the finite element method includes: establishing a macro-scale numerical model based on the finite element method, and associating microscopic parameters with macroscopic performance through a multi-scale coupling method.

8. The method for testing the shear strength of geotextile-reinforced soil according to claim 7, wherein: The input parameters of the geotextile-soil interface dynamic mechanism equation group include: normal effective stress, load frequency, soil friction angle, interface roughness coefficient, and soil density; the output parameter of the geotextile-soil interface dynamic mechanism equation group is the interface shear strength under dynamic conditions.

9. The method for testing the shear strength of geotextile-reinforced soil according to claim 8, characterized in that: The geotextile reinforced soil shear strength test results include the benchmark shear strength value under static conditions, the shear strength values ​​under different dynamic load conditions, a data table showing the variation of the dynamic-static ratio coefficient with frequency and amplitude, and the parameter values ​​of the reinforcement mechanism model considering dynamic effects.

10. The method for testing the shear strength of geotextile-reinforced soil according to claim 9, wherein: The integrated dynamic and static shear test device includes: a base system, a shear box assembly, a vertical loading system, a horizontal drive system, a measurement control system and an external connection device; wherein the horizontal drive system generates a periodic shear load within the range of 0.1 to 50 Hz.

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