Dynamic characteristic simulation method and system of granular material under high-frequency vibration

Abstract

The invention discloses a method for simulating dynamic characteristics of a granular material under high-frequency vibration. The method comprises the following steps: S1, constructing a model; s2, calibrating parameters; s3, performing a static shear experiment; s4, vibration loading; s5, carrying out an orthogonal test; and S6, mechanical property analysis. The simulation system comprises a model construction module, a parameter calibration module, an orthogonal test module, a load application module and a dynamic mechanical property analysis module. The triaxial sample model is constructed based on the discrete element method, the physical characteristics of sample particles can be changed at will, the mechanical characteristics of particle materials under complex working conditions can be simulated by applying vibration with different load characteristics to the model, the test cost is reduced, and the mechanical characteristics of the particle materials under complex working conditions can be simulated by performing microscopic parameter calibration. The test precision and the reliability of the test result are improved.

Description

Technical Field

[0001] This invention belongs to the field of numerical simulation technology, and in particular relates to a method and system for simulating the dynamic characteristics of particulate materials under high-frequency vibration. Background Technology

[0002] Railway ballast, as a typical granular material, is widely used in the track beds of heavy-haul and high-speed railways due to its advantages such as low construction cost, short construction period, and good vibration and noise reduction effects. Currently, almost all conventional and heavy-haul railway lines worldwide are paved with ballast track. However, due to the long-term effects of vibration loads, its shear strength attenuation and deformation characteristics have attracted widespread attention. The increased speed of high-speed trains inevitably leads to higher frequency vibrations, which will exacerbate the wear, breakage, and deformation of railway ballast, thereby affecting its load-bearing capacity and threatening the safety of people's lives and property. Therefore, it is necessary to conduct a series of mechanical property studies on railway ballast under high-frequency vibration to provide guidance for the construction and safety of railway engineering lines.

[0003] Current research on the dynamic response characteristics of particulate materials mainly employs physical experiments (modified triaxial experiments and modified direct shear experiments). However, physical experiments are limited by experimental equipment and conditions, and suffer from drawbacks such as difficulty in applying and monitoring high-frequency vibrations, high experimental costs, and the inability to explore the relevant mechanical mechanisms of shear strength attenuation at the microscopic level. Furthermore, the stress state of ballast varies under different particle gradations, loads, shapes, and densities, making it difficult to replicate some complex working conditions in physical experiments. Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for simulating the dynamic characteristics of particulate materials under high-frequency vibration, so as to solve the technical problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for simulating the dynamic properties of particulate materials under high-frequency vibration includes the following steps:

[0007] S1 Model Construction: The Discrete Element Method (DEM) is used. Based on the material physical properties of the granular material itself, the corresponding particle contact model is selected, and the confining pressure is controlled by a servo control mechanism to construct triaxial sample models with different confining pressures.

[0008] S2 parameter calibration: Based on existing physical experiments, the microscopic parameters of the triaxial test model are calibrated;

[0009] S3 Static Shear Test: A static triaxial shear test is conducted on a triaxial test model with calibrated microscopic parameters.

[0010] S4 Vibration loading: Applying vibrations with different load characteristics at different stages of the static shear test;

[0011] S5 Orthogonal Test: Orthogonal tests are conducted on the particle edge angle, confining pressure, vibration application stage, and vibration load characteristic factors of the triaxial test model;

[0012] S6 Mechanical Property Analysis: Macroscopic and microscopic mechanical property analysis is performed on each triaxial specimen model obtained from the orthogonal test.

[0013] Furthermore, in S1, the physical properties of the material include particle shape, gradation distribution, and density; wherein, the particle shape is imported through a particle template; the gradation distribution is imported through the volume fraction of particles in each particle size range; and the density is adjusted by changing the friction coefficient between particles.

[0014] Furthermore, in S1, during the servo control mechanism, when the difference between the target stress and the simulated stress is less than 1e... -5 The target pressure value is reached at that time.

[0015] Furthermore, in S3, during the static triaxial shearing experiment, the longitudinal servo control mechanism is turned off and the upper wall is given a downward velocity to perform monotonic shearing, and the process is maintained as quasi-static shearing during the monotonic shearing process.

[0016] Furthermore, the wall velocity is controlled by the inertia parameter I to maintain quasi-static shear. The definition of the inertia parameter I is:

[0017]

[0018] In the formula, I is the inertial parameter, · is the axial strain rate of the sample, d is the particle size, ρ is the particle density, and p' is the average stress.

[0019] Furthermore, in S4, the static shearing process includes the pre-peak stage and the critical stage.

[0020] Furthermore, the vibration is applied as follows: the sinusoidal vibration is converted into the velocity of the upper wall and superimposed on the original monotonic shear state of the wall, where the function v for converting the sinusoidal vibration into the wall velocity is:

[0021] v = 2πfAsin(2πft)

[0022] In the formula, f is the frequency of vibration, and A is the amplitude.

[0023] Furthermore, in S5, the vibration load characteristics include vibration acceleration and vibration frequency.

[0024] Furthermore, the macroscopic mechanical properties include effective stress ratio and porosity; the microscopic mechanical properties include mechanical coordination number and structural anisotropy.

[0025] A simulation system for the dynamic characteristics of particulate materials under high-frequency vibration includes a model building module, a parameter calibration module, an orthogonal test module, a load application module, and a dynamic mechanical property analysis module.

[0026] The model building module uses the stochastic discrete element method to model particulate materials. Based on the gradation characteristics, density, and shape characteristics of the particulate materials, it selects the corresponding particle contact model to simulate the real physical characteristics of various particulate materials.

[0027] The parameter calibration module is used to calibrate the micromechanical parameters of the generated triaxial model. Based on a large number of simulation calculations, by continuously adjusting the micromechanical parameters in the simulation, the simulation results are calibrated to be consistent with or have the same trend as the existing physical experimental mechanical curves.

[0028] The orthogonal experimental module is used to design the influence of different influencing factors on the mechanical properties of particulate materials under high-frequency vibration by using orthogonal experimental methods;

[0029] The load application module is used to control the wall speed and load the sample under vibration and non-vibration conditions. In the non-vibration state, a downward velocity is applied to the upper wall to complete static shearing. During vibration, the sinusoidal wave is converted into velocity and superimposed on the upper strength velocity.

[0030] The dynamic mechanics analysis module can be used to quickly visualize experimental results, and on this basis, to calibrate microscopic parameters and analyze macroscopic and microscopic experimental results.

[0031] The advantages of this invention compared to the prior art are as follows:

[0032] 1. This invention constructs a triaxial specimen model based on the discrete element method, which can arbitrarily change the physical characteristics of the specimen particles. By applying vibrations with different load characteristics to the model, it can simulate the dynamic mechanical characteristics of granular materials under the combined action of vertical load and vibration load, especially the dynamic mechanical characteristics under high-frequency vibration. This simulates the coupling effect of multiple influencing factors under high-frequency vibration, and can explore the reasons for the attenuation of shear strength of granular materials under vibration from both macroscopic and microscopic perspectives. It solves the problem of difficulty in achieving multi-factor coupling in physical experiments, can simulate the mechanical properties of granular materials under complex working conditions, and reduces experimental costs.

[0033] 2. This invention uses a parameter calibration module to calibrate microscopic parameters, which can quickly achieve parameter calibration with physical experimental results. This allows for a more realistic and accurate reproduction of the dynamic characteristics of various particulate materials, improving experimental accuracy and the reliability of experimental results. Attached Figure Description

[0034] Figure 1 This is a flowchart of the present invention;

[0035] Figure 2 It is a regular-shaped particle template of the present invention;

[0036] Figure 3 This is the natural particle shape template of the present invention;

[0037] Figure 4 This is the triaxial sample preparation process of the present invention;

[0038] Figure 5 This is a schematic diagram of the typical dynamic mechanical response of the particulate material of the present invention under vertical vibration;

[0039] Figure 6 This is a simulation diagram of the dynamic mechanical response of particulate materials under vertical vibration in this invention.

[0040] Figure 7 This is a verification of the stress-force-structure relationship under the critical stage of the present invention;

[0041] Figure 8 This is a diagram showing the dynamic mechanical response of the vibration acceleration of the present invention to the pre-peak stage of the particulate material;

[0042] Figure 9 This is a diagram showing the dynamic mechanical response of the vibration acceleration of the present invention to the granular material in the critical stage;

[0043] Figure 10 This is a diagram showing the dynamic mechanical response of the vibration frequency of the present invention to the pre-peak stage of the particulate material;

[0044] Figure 11 This is a diagram showing the dynamic mechanical response of the vibration frequency of the present invention to the particulate material in the critical stage;

[0045] Figure 12 This is a diagram showing the dynamic mechanical response of the particle edge angle to the pre-peak stage particle material according to the present invention.

[0046] Figure 13 This is a diagram showing the dynamic mechanical response of the particle edge angle to the particle material at the critical stage.

[0047] Figure 14 This is a logarithmic relationship graph between the relative effective stress ratio attenuation and the relative porosity change of the present invention;

[0048] Figure 15This is a schematic diagram illustrating the evolution of the mechanical coordination number with axial strain during the vibration stage of this invention.

[0049] Figure 16 This is a graph showing the relationship between the mechanical coordination number difference of the present invention and various influencing factors;

[0050] Figure 17 This is a schematic diagram illustrating the evolution of the anisotropy of the structure of the present invention with vibration acceleration;

[0051] Figure 18 This is a schematic diagram illustrating the evolution of the anisotropy of the structure of the present invention with vibration frequency;

[0052] Figure 19 This is a schematic diagram illustrating the evolution of the anisotropy of the structure of the present invention with respect to the particle edge angle. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the present invention, and these aspects of the invention can be implemented even without these specific details.

[0054] like Figure 1 As shown, a method for simulating the dynamic characteristics of particulate materials under high-frequency vibration includes the following steps:

[0055] S1 Model Construction: The discrete element method (DEM) is employed. Based on the material physical properties of the particulate material, a corresponding particle contact model is selected. These material physical properties include particle shape, gradation distribution, and density. The particle shape is imported using a particle template; the gradation distribution is imported by the volume fraction of particles across different size ranges; and the density is adjusted by changing the friction coefficient between particles. The confining pressure is controlled via a servo control mechanism. When the difference between the target stress and the simulated stress is less than 1e... -5 The time is when the target pressure value is reached, thus constructing triaxial specimen models with different confining pressures;

[0056] S2 parameter calibration: Based on existing physical experiments, the microscopic parameters of the triaxial test model are calibrated;

[0057] S3 Static Shearing Experiment: The triaxial test model with calibrated micro-parameters is subjected to a static triaxial shearing experiment: the longitudinal servo control mechanism is turned off and the upper wall is given a downward velocity to perform monotonic shearing. The wall velocity is controlled by the inertia parameter I to maintain the quasi-static shearing during the monotonic shearing process.

[0058] The inertial parameter I is defined as follows:

[0059]

[0060] In the formula, I is the inertial parameter, · is the axial strain rate of the sample, d is the particle size, ρ is the particle density, and p' is the average stress.

[0061] S4 Vibration Loading: Vibrations with different accelerations and frequencies are applied during the pre-peak and comprehension phases of the static shear test. The vibration is applied by converting the sinusoidal vibration into the velocity of the upper wall and superimposing it onto the original monotonic shear state wall velocity. The function v for converting the sinusoidal vibration into the wall velocity is:

[0062] v = 2πfAsin(2πft)

[0063] In the formula, f is the frequency of vibration, and A is the amplitude.

[0064] S5 Orthogonal Test: Orthogonal tests are conducted on the particle edge angle, confining pressure, vibration application stage, and vibration load characteristic factors of the triaxial test model;

[0065] S6 Mechanical Property Analysis: Macroscopic and microscopic mechanical property analyses are performed on each triaxial specimen model obtained from the orthogonal test. The macroscopic mechanical properties include effective stress ratio and porosity; the microscopic mechanical properties include mechanical coordination number and structural anisotropy.

[0066] A simulation system for the dynamic characteristics of particulate materials under high-frequency vibration includes a model building module, a parameter calibration module, an orthogonal test module, a load application module, and a dynamic mechanical property analysis module.

[0067] The model building module uses the discrete element method to model particulate materials. Based on the gradation characteristics, density, and shape characteristics of the particulate materials, it imports a particle shape template to construct the shape characteristics of the particles and generates samples with different gradations to simulate the real physical characteristics of various particulate materials. The particles are generated in a cubic sample surrounded by six walls, and an appropriate contact model is selected. A damping coefficient is set to dissipate excess kinetic energy. To eliminate the influence of the gravity gradient, gravity is set to 0. Finally, a servo control mechanism is used to generate samples with different confining pressures.

[0068] The parameter calibration module is used to calibrate the micromechanical parameters of the generated triaxial model. Based on a large number of simulation calculations and according to the evolution law of stress-strain curves obtained from physical experiments, the module continuously adjusts the micromechanical parameters in the simulation, such as elastic modulus, normal / tangential stiffness, and friction coefficient, to calibrate simulation results that are consistent with or have the same trend as the existing physical experimental mechanical curves. This achieves the effect of consistency between the simulation data and the actual physical experimental values ​​or variation laws.

[0069] The orthogonal experimental module is used to design the influence of different influencing factors on the mechanical properties of particulate materials under high-frequency vibration by using orthogonal experimental methods, so as to study the dynamic characteristics of particulate materials under complex conditions;

[0070] The load application module is used to control the wall speed and load the sample under vibration and non-vibration conditions. In the non-vibration state, a downward velocity is applied to the upper wall to complete static shearing. During vibration, the sinusoidal wave is converted into velocity and superimposed on the upper strength velocity.

[0071] The dynamic mechanics analysis module can be used to quickly visualize experimental results, and on this basis, to calibrate microscopic parameters and analyze macroscopic and microscopic experimental results.

[0072] The following description uses more specific examples.

[0073] A method for simulating the dynamic properties of particulate materials under high-frequency vibration includes the following steps:

[0074] S1 Model Construction: Using the model construction module and the discrete element method (DEM), PFC 6.0 software is used to build a three-dimensional numerical model of the granular material within a cube composed of six rigid walls. Based on the material's physical properties, including particle shape, gradation distribution, and density, a suitable particle contact model is selected to simulate the material's true mechanical properties. The particle shape is imported via a particle template, allowing for the import of particles with regularly varying shapes, such as... Figure 2 The particles with different sphericity and angularity shown can also be imported to resemble the shapes of real particles, such as... Figure 3 As shown; the gradation distribution is introduced by the volume fraction of particles in each particle size range; the density is adjusted by changing the friction coefficient between particles, where the friction coefficient u is controlled between 0.0 and 1.0. When the friction coefficient u = 0.0, the densest sample can be generated, and when u = 1.0, a loose sample can be generated. In this embodiment, the friction coefficient u = 0.5 is selected, the contact model is selected as a linear contact model, and the confining pressure is controlled by a servo control mechanism. When the difference between the target stress and the simulated stress is less than 1e... -5 The time is when the target pressure value is reached; each sample generates approximately 5000 particles. In this embodiment, the generation process of one type of triaxial sample with particle shape is as follows: Figure 4 As shown, triaxial specimen models with different confining pressures were finally constructed.

[0075] S2 Parameter Calibration: The microscopic parameters of the triaxial test model are calibrated using the parameter calibration module based on existing physical experiments. In this embodiment, the calibration results of the triaxial sample model are shown in Table 1.

[0076] Table 1. Microscopic parameters after calibration

[0077] parameter numerical values <![CDATA[Particle density (kg / m 3 )]]> 2600 Wall stiffness (N / m) <![CDATA[1×10 8 ]]> <![CDATA[Contact effective modulus E c (Pa)]]> <![CDATA[1×10 8 ]]> Particle-to-particle friction coefficient 0.5 <![CDATA[Ratio k of normal stiffness to tangential stiffness n / k s > 1.0 Wall-particle friction coefficient 0.0 Damping coefficient 0.7

[0078] S3 Static Shear Test: Using the load application module, a static triaxial shear test is conducted on a triaxial test model with calibrated micro-parameters.

[0079] S4 Vibration Loading: Apply vibrations with different load characteristics at different stages of the static shear test; through the load application module, turn off the longitudinal servo control mechanism and give the upper wall a downward velocity to perform monotonic shearing, and control the wall velocity through the inertia parameter I to maintain it as quasi-static shearing during the monotonic shearing process.

[0080] The inertial parameter I is defined as follows:

[0081]

[0082] In the formula, I is the inertial parameter, · is the axial strain rate of the sample, d is the particle size, ρ is the particle density, and p' is the average stress.

[0083] To ensure quasi-static shearing, the I value during shearing should be less than 2.5 × 10⁻⁶. -3 In this embodiment, the velocity of the top wall of the sample is kept constant at 0.001 m / s, and the inertial parameter I during the sample shearing process remains less than 2.9 × 10⁻⁶ m / s. -4 .

[0084] To study the dynamic mechanical characteristics of particulate materials before the peak and in the critical stage, all specimens were loaded to a state with an axial strain of 50% to ensure that a stable critical state could be reached.

[0085] The vibration is superimposed on the original static loading program. When the sample is loaded to the pre-peak stage and critical stage, vibrations with different load characteristics are applied, converting the sinusoidal vibration into the velocity of the upper wall, which is then superimposed on the wall velocity under the original monotonic shear state. The function v that converts the sinusoidal vibration into the wall velocity is:

[0086] =2Asin(2)

[0087] In the formula, f is the frequency of vibration, and A is the amplitude.

[0088] The load characteristics of vibration include vibration acceleration *a* and vibration frequency *f*; the formula for calculating acceleration *a* is:

[0089] =(2π) 2 Acos(2π)

[0090] In the formula, A is the amplitude and f is the vibration frequency.

[0091] like Figure 5 The figure shows a typical dynamic mechanical response of particulate materials under vertical vibration. It can be seen that the application of vibration will cause a decrease in the effective stress ratio q / p′ and the void ratio e.

[0092] like Figure 6 The diagram shown illustrates the dynamic mechanical response of one of the triaxial specimen models in this embodiment. This specimen model is subjected to sinusoidal vibrations when the axial strain reaches 30-31% and 35-36%, respectively, with a confining pressure σ. n =75kPa, vibration accelerations are 0.2g and 0.4g respectively, and vibration frequency f = 60Hz. From Figure 6 As can be seen from the data, under this condition, vibration will cause a decrease in the effective stress ratio q / p′ and the void ratio e, that is, a decrease in strength and a volume compression phenomenon will occur. This is consistent with the typical mechanical response law of particulate materials under vibration, indicating that this method can reasonably and effectively simulate the influence of vibration on the mechanical properties of particulate materials.

[0093] S5 Orthogonal Test: The orthogonal test module is used to conduct orthogonal tests on the particle edge angle, confining pressure, vibration application stage, and vibration load characteristic factors of the triaxial test model, as shown in Table 2.

[0094] Table 2 Orthogonal Experiment Table

[0095]

[0096]

[0097] S6 Mechanical Property Analysis: Through the dynamic mechanical analysis module, macroscopic and microscopic mechanical property analyses are performed on each triaxial specimen model obtained from orthogonal experiments.

[0098] In terms of macroscopic mechanical properties, from Figure 6 As can be seen from (a), the effective stress ratio gradually decreases with the increase of vibration acceleration, but the relationship with the change of vibration acceleration is still unclear. In order to quantify the relationship between the degree of reduction of the effective stress ratio and various influencing factors, the relative effective stress ratio attenuation value Δ(q / p′) / (q / p′) is introduced to quantify the influence of each influencing factor on the effective stress ratio.

[0099] Numerically, Δ(q / p′) = 0.5((q / p′) nom -q / p′) vibmin ), where (q / p′) nom Let (q / p′) be the average effective stress ratio under monotonic shear conditions. vibmin This represents the minimum effective stress ratio under vibration conditions.

[0100] from Figure 6 As can be seen in (b), the porosity first decreases and then increases with the increase of axial strain; when vibration is applied, the porosity gradually accumulates with the continuation of vibration and increases with the increase of vibration acceleration. Similarly, in order to quantify the influence of each influencing factor on the density of particulate materials, the relative porosity loss Δe / e is introduced to quantify the influence of each influencing factor on the porosity.

[0101] Numerically, Δe equals 0.5(e nom -e vibmin ), where e nom e represents the average effective stress ratio under monotonic shear conditions. vibmin This represents the minimum effective stress ratio under vibration conditions.

[0102] The micromechanical properties mentioned include mechanical coordination number and structural anisotropy.

[0103] In terms of micromechanical properties, coordination number is a key indicator for quantifying the internal structural characteristics of a particulate system and is closely related to the mechanical properties of particulate materials. Changes in coordination number can reflect the rearrangement process and compactness of particulate materials under vibration. A decrease in coordination number indicates less contact between particles, making the particulate system looser, while an increase in coordination number indicates a denser particulate system. Existing technologies often use the average coordination number to reflect particle coordination, defined as 2C / N, where C represents the number of contact points and N represents the total number of particles. However, during shearing, a large number of suspended particles exist, which do not play a major role in the strength and stability of the overall system. Therefore, this invention uses the concept of mechanical coordination number to explore the changes in the spatial position of particles during vibration.

[0104] The mechanical coordination number CN excludes the influence of suspended particles and is defined as follows:

[0105]

[0106] In the formula, N0 and N1 represent the number of non-contact particles and the number of particles with only a single contact, respectively.

[0107] Fabric anisotropy can accurately reflect the microstructural changes of a granular system under external loads and can be used to reveal the origin of shear strength in granular materials. Therefore, in order to better understand the effect of vibration on the attenuation of shear strength in granular materials, this invention reveals the microscopic mechanism of shear strength attenuation under vibration from the perspective of fabric anisotropy.

[0108] To link shear strength with anisotropy caused by stress in triaxial tests, the stress ratio of granular materials can be expressed as the sum of anisotropy, and the stress-force-structure relationship is shown below.

[0109]

[0110] In the formula, a c a n a t and a dn These are the anisotropy of the contact normal, normal contact force, tangential contact force, and branch vector, respectively.

[0111] To verify the stress-force-structure relationship given in the formula, the effective stress ratio q / p in the DEM simulation is compared with that obtained from the source of structural anisotropy, such as... Figure 7 As shown, Figure 7 This demonstrates the critical state (σ) of spherical particles. n =75kPa, f=60Hz) The contribution of structural anisotropy within the system to the effective stress ratio q / p. This shows that the formula effectively represents the source of the effective stress ratio q / p throughout the shear and vibration stages. The anisotropy of granular materials plays a crucial role in determining shear strength, and different sources of anisotropy contribute differently. For example, in monotonic shearing, a n Plays a leading role, a c and a t They play a second and third role in shear strength, respectively, while a dn Its effect is minimal. However, during vibration, a n a c and a t The anisotropy of the structure is significantly reduced, while the anisotropy of aden remains essentially unchanged and can be ignored. In general, from the perspective of structural anisotropy, the decrease in the effective stress ratio can be attributed to a... n a c and a t The decrease.

[0112] Results of the influence of vibration from different factors on macroscopic mechanical properties

[0113] 1. Vibration acceleration

[0114] Figure 8 The effects of pre-peak vibration acceleration on the relative effective stress ratio attenuation Δ(q / p′) / (q / p′) and the relative porosity change Δe / e are shown. It can be seen that with increasing vibration acceleration, both the attenuation of the relative effective stress ratio and the change in the relative porosity increase linearly. Meanwhile, under the same vibration acceleration, the lower the confining pressure, the greater the attenuation of the relative effective stress ratio and the change in the porosity of the particle aggregate, especially under confining pressure σ. n = Between 50kPa and 75kPa. This phenomenon can be understood as the confining pressure σ... nThe larger the diameter, the stronger the normal constraint force on the particle system, which can restrain the movement and rearrangement of particles during vibration. As a result, the particle system is less affected by vibration disturbances and exhibits less shear strength reduction.

[0115] Figure 9 The influence of vibration acceleration *a* on the dynamic characteristics of granular materials under critical conditions is demonstrated. Similarly, the changes in relative effective stress ratio attenuation and relative void ratio in the critical stage exhibit the same patterns as in the pre-peak stage. In summary, the results show that the shear strength attenuation and compaction degree of soil under vibration increase with increasing vibration acceleration and decrease with increasing confining pressure. This is because greater vibration acceleration has a stronger disturbance effect on the interparticles, resulting in greater shear strength attenuation and volume change. In practical engineering, the shear strength of soil can be reduced and the compaction degree increased by increasing vibration acceleration, for example, when using vibration for pile driving or foundation compaction.

[0116] 2. Influence of vibration frequency

[0117] Figures 10-11 The evolution trends of the relative effective stress ratio attenuation Δ(q / p′) / (q / p′) and the relative porosity change Δe / e with vibration frequency and confining pressure are shown before the peak and at the critical state. Under a fixed confining pressure, the relative effective stress ratio attenuation Δ(q / p′) / (q / p′) decreases exponentially with vibration frequency. This phenomenon may be because as the vibration frequency increases, the particles cannot completely absorb the energy from the vibration, and the particle structure does not have time to break down, so the shear strength attenuation is smaller. Similarly, before the peak and at the critical state, the relative porosity Δe / e also decreases with increasing vibration frequency, showing a high degree of synchronization with the change law of Δ(q / p′) / (q / p′).

[0118] 3. Influence of particle edge angle

[0119] This study investigates the impact of particle shape changes on the dynamic mechanical properties of particulate materials by altering particle ridge angles. During the simulation, the confining pressure σ is... n Set the Pa to 75 kPa and the vibration frequency to 60 Hz. Figure 12-13 The changes in relative effective stress ratio attenuation and relative porosity ratio of samples with different edge angles under different vibration accelerations are shown for pre-peak and critical states. (Compared to the previous...) Figure 8-9The observed results are similar: with increasing vibration acceleration, the relative effective stress ratio attenuation Δ(q / p′) / (q / p′) and the relative porosity change Δe / e both increase. Furthermore, at the same vibration acceleration, compared to ideal spherical particles (α=0.0), high-angle particles exhibit smaller relative effective stress ratio attenuation and smaller relative porosity change. This is because high-angle particles generate a stronger interlocking force, resulting in a more robust interlocking effect and restricted particle movement. Therefore, under vibration, high-angle particles are less likely to rearrange themselves, leading to a more stable structure and consequently, less shear strength attenuation and volumetric deformation.

[0120] 4. Correlation between effective stress ratio attenuation and porosity change

[0121] The above macroscopic results analysis reveals that, under specific influencing factors such as vibration acceleration, vibration frequency, confining pressure, and effective stress ratio attenuation Δ(q / p′) / (q / p′), there is a correlation between the variation trend of soil and the relative void ratio change Δe / e.

[0122] To study this correlation, the relationship between Δ(q / p′) / (q / p′) and Δe / e was plotted on a logarithmic coordinate axis, as follows: Figure 14 As shown. The results indicate that Δ(q / p′) / (q / p′) and Δe / e have a good linear relationship on the logarithmic scale before the peak and at the critical state, which can be expressed as:

[0123] lg(Δ(q / p′) / (q / p′) nom )=0.71×lg(Δe / e nom )+1.45 (R 2 =0.96)

[0124] lg(Δ(q / p′) / (q / p′) Pre )=0.68×lg(Δe / e Pre )+1.71 (R 2 =0.89)

[0125] Comparing the two formulas, it can be seen that under the same lg(Δe / e), the relative effective stress ratio attenuation is greater in the pre-peak state. This phenomenon can be understood as the density of granular materials in the pre-peak stage being lower than that in the critical stage. Therefore, under the same vibration intensity, it exhibits greater shear strength attenuation. This linear relationship holds true under different confining pressures, accelerations, frequencies, and edge angles, indicating that it can be used in discrete element method (DEM) numerical simulations to predict changes in effective stress ratio attenuation caused by vibration, and has good engineering reference value.

[0126] Results of the influence of vibration from different factors on micromechanical properties

[0127] 1. Mechanical coordination number

[0128] like Figure 15 As shown, the evolution of the mechanical coordination number with axial strain in the critical stage is illustrated. It is worth noting that a similar pattern is observed in the pre-peak stage, but it is not shown here for ease of explanation. It can be clearly observed that the mechanical coordination number of particles in the vibration stage is significantly higher than that in the non-vibration stage; this trend is consistent with… Figure 6 The variation of the porosity e shown is consistent with this phenomenon. This can be understood as the deformation of particles under the combined action of vibration and their own weight, which macroscopically manifests as a decrease in porosity and microscopically as an increase in the mechanical coordination number.

[0129] Figure 16 The evolution of mechanical coordination number with vibrational acceleration, frequency, and particle edge angle is summarized. Figure 16 As shown in (a), ΔCN increases with the increase of vibration acceleration a. This is because high vibration acceleration has a stronger disturbance effect and can cause greater volume compaction deformation. Figure 16 Results (b) and (c) show that ΔCN decreases with increasing vibration frequency and particle edge angle, which is consistent with... Figure 11 (b) and Figure 13 The porosity variation trend shown in (b) is consistent. Furthermore, the change in mechanical coordination number in the pre-peak state is significantly higher than that in the critical state, which may be related to the density of the sample. At the beginning of shearing, the sample is in a relatively loose state, and the compaction effect of vibration is better. As shearing progresses, the sample gradually becomes denser, resulting in a smaller change in ΔCN.

[0130] 2. Structural anisotropy

[0131] 2. Structural anisotropy Macroscopic mechanical properties indicate that the decrease in the effective stress ratio caused by vibration is affected by the vibration acceleration. a Vibration frequency f and particle edge angle α The effect of effective stress ratio attenuation with vibration acceleration. Therefore, in order to study the effect of effective stress ratio attenuation with vibration acceleration. a Vibration frequency f and particle edge angle α The mechanism of anisotropic change was quantitatively studied. Figure 17-19 They explained respectively 0.4Δ a n 0.4Δ a c 0.4Δ a and 0.6Δ at With vibration acceleration a Vibration frequency f and particle edge angle α These occur respectively in the pre-peak and critical stages. Here, 0.4Δ a n 0.4Δ a c 0.4Δ a dn and 0.6Δ a t It is derived from the difference between the values ​​of the non-vibrating sample and the vibrating sample. For example... Figure 17-19 As shown, With 0.4(Δ a n +Δ a c +Δ a dn +1.5Δ a t The values ​​are very close, indicating that the reduction in effective stress-to-strength ratio is mainly attributed to... a n , a c , a t t and a dn The decrease. But here, Δ a dn The changes are very small and can be almost ignored. and 0.4 (Δ a n +Δ a c +Δ a dn +1.5Δ a t )along with a It increases with the increase of [the anisotropic component]. Analysis of the changes in the anisotropic components reveals that... Follow a The increase is mainly due to Δ a n Δ a c and Δ a t The increase is caused by Δ a n The contribution was the largest, followed by Δ a t and Δ a c Similarly, Figure 17-19 The results show that, withf The increase, and 0.4 (Δ a n +Δ a c +Δ a dn +1.5Δ a t The value gradually decreases. This is achieved through research on 0.4Δ. a n 0.4Δ a c 0.4Δadn and 0.6Δ a t As the various influencing factors evolve, it can be observed that... The downward trend is due to Δ a n Δ a c and Δ a t This is caused by the reduction, of which Δ a n The contribution was the largest, followed by Δ a t and Δ a c . The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0132] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for simulating the dynamic characteristics of particulate materials under high-frequency vibration, characterized in that, Includes the following steps: S1 Model Construction: The discrete element method is adopted. Based on the material physical properties of the particulate material itself, the corresponding particle contact model is selected, and the confining pressure is controlled by a servo control mechanism to construct triaxial sample models with different confining pressures. S2 parameter calibration: Based on existing physical experiments, the microscopic parameters of the triaxial test model are calibrated; S3 Static Shear Test: A static triaxial shear test is conducted on a triaxial test model with calibrated microscopic parameters. S4 Vibration loading: Applying vibrations with different load characteristics at different stages of the static shear test; S5 Orthogonal Test: Orthogonal tests are conducted on the particle edge angle, confining pressure, vibration application stage, and vibration load characteristic factors of the triaxial test model; S6 Mechanical Property Analysis: Macroscopic and microscopic mechanical property analysis is performed on each triaxial specimen model obtained from the orthogonal test.

2. The method for simulating the dynamic characteristics of particulate materials under high-frequency vibration according to claim 1, characterized in that: In S1, the physical properties of the material include particle shape, gradation distribution, and density; wherein, the particle shape is imported through a particle template; the gradation distribution is imported through the volume fraction of particles in each particle size range; and the density is adjusted by changing the friction coefficient between particles.

3. The method for simulating the dynamic characteristics of particulate materials under high-frequency vibration according to claim 1, characterized in that: In S1, during the servo control mechanism, when the difference between the target stress and the simulated stress is less than 1e... -5 The target pressure value is reached at that time.

4. The method for simulating the dynamic characteristics of particulate materials under high-frequency vibration according to claim 1, characterized in that: In S3, during the static triaxial shearing experiment, the longitudinal servo control mechanism is turned off and the upper wall is given a downward velocity to perform monotonic shearing, and the process is maintained as quasi-static shearing during the monotonic shearing process.

5. The method for simulating the dynamic characteristics of particulate materials under high-frequency vibration according to claim 4, characterized in that: The wall velocity is controlled by the inertia parameter I to maintain quasi-static shear. The definition of the inertia parameter I is: In the formula, I is the inertial parameter, · is the axial strain rate of the sample, d is the particle size, ρ is the particle density, and p' is the average stress.

6. The method for simulating the dynamic characteristics of particulate materials under high-frequency vibration according to claim 5, characterized in that: In S4, the static shearing process includes the pre-peak stage and the critical stage.

7. The method for simulating the dynamic characteristics of particulate materials under high-frequency vibration according to claim 6, characterized in that: The vibration is applied as follows: the sinusoidal vibration is converted into the velocity of the upper wall and superimposed on the original monotonic shear state of the wall. The function v for converting the sinusoidal vibration into the wall velocity is: v = 2πfAsin(2πft) In the formula, f is the frequency of vibration, and A is the amplitude.

8. The method for simulating the dynamic characteristics of particulate materials under high-frequency vibration according to claim 6, characterized in that: In S5, the vibration load characteristics include vibration acceleration and vibration frequency.

9. The method for simulating the dynamic characteristics of particulate materials under high-frequency vibration according to claim 1, characterized in that: The macroscopic mechanical properties include effective stress ratio and porosity; the microscopic mechanical properties include mechanical coordination number and structural anisotropy.

10. A system for simulating the dynamic characteristics of particulate materials under high-frequency vibration according to any one of claims 1-9, characterized in that: It includes a model building module, a parameter calibration module, an orthogonal test module, a load application module, and a dynamic mechanical property analysis module; The model building module uses the stochastic discrete element method to model particulate materials. Based on the gradation characteristics, density, and shape characteristics of the particulate materials, it selects the corresponding particle contact model to simulate the real physical characteristics of various particulate materials. The parameter calibration module is used to calibrate the micromechanical parameters of the generated triaxial model. Based on a large number of simulation calculations, by continuously adjusting the micromechanical parameters in the simulation, the simulation results are calibrated to be consistent with or have the same trend as the existing physical experimental mechanical curves. The orthogonal experimental module is used to design the influence of different influencing factors on the mechanical properties of particulate materials under high-frequency vibration by using orthogonal experimental methods; The load application module is used to control the wall speed and load the sample under vibration and non-vibration conditions. In the non-vibration state, a downward velocity is applied to the upper wall to complete static shearing. During vibration, the sinusoidal wave is converted into velocity and superimposed on the upper strength velocity. The dynamic mechanics analysis module can be used to quickly visualize experimental results, and on this basis, to calibrate microscopic parameters and analyze macroscopic and microscopic experimental results.

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