Anisotropy testing and analysis device and method for soil fabric of non-homogeneous soil

Abstract

The application discloses a device for testing and analyzing anisotropy of non-homogeneous soil structure, which comprises a multi-dimensional elastic wave testing device, a multi-dimensional image acquisition and analysis system, a wave signal interpretation and processing system and a graded loading model box. The device can be used for measuring the anisotropy degree of non-homogeneous soil structure under different load conditions and different soil characteristics. The multi-dimensional elastic wave testing device is used for measuring the shear wave velocity and compression wave velocity of non-homogeneous soil in different directions. The multi-dimensional image acquisition and analysis system is used for analyzing the structure characteristics of non-homogeneous soil in the microscopic scale on the elastic wave propagation path. The wave signal interpretation and processing system is used for determining the shear wave velocity, compression wave velocity and anisotropy degree of non-homogeneous soil. The graded loading model box comprises a single-face opening transparent model box and a graded weight loading device. The application can realize the multi-scale macroscopic and microscopic observation and characterization of soil structure, and construct the quantitative relationship between the microscopic parameters and the macroscopic characterization parameters of the structure.

Description

Technical Field

[0001] This invention relates to the field of civil engineering, and more particularly to a device and method for testing and analyzing the anisotropy of heterogeneous soil structures. Background Technology

[0002] Clayey silt, clayey sand, silty sand, gravelly soil, and pebble soil are typical forms of natural foundation soil, and heterogeneity is one of the important characteristics of these soils. The composition and structure of soil, often simply called texture, encompasses two main characteristics: the geometric morphology and spatial distribution of soil particles. These characteristics jointly influence the static and dynamic properties of the soil (such as strength, deformation, permeability, dynamic strength, stiffness, modulus, and damping ratio). Taking gravelly soil distributed across 21 provinces in my country as an example, gravelly soil can be generalized as a mixture formed by sand and gravel in a certain proportion and particle size ratio. Therefore, sand and gravel particles exhibit high heterogeneity in spatial arrangement. Furthermore, the particle shapes of sand and gravel particles also differ significantly. Due to the heterogeneity of the soil, the texture exhibits anisotropy (i.e., the texture is different in different directions), and correspondingly, the parameters characterizing the texture also show directionality.

[0003] Existing studies mostly rely on unidirectional fabric indices to evaluate the mechanical properties of soil. This characterization method is often insufficient and imperfect, and may even pose certain safety risks. For example, consider evaluating the liquefaction risk of a site based on in-situ shear wave velocity testing. Assume the site has a liquefaction risk under current industry standards. However, if the soil shear wave velocity obtained during the on-site investigation and design phase only represents the larger shear wave velocity in one direction, without proper correction based on soil fabric anisotropy evaluation methods or without obtaining the smaller shear wave velocity in another direction, industry standards might conclude that the site will not liquefy, thus creating a certain liquefaction safety risk.

[0004] Currently, there are many testing devices and methods for evaluating and analyzing the structural anisotropy of heterogeneous soils. However, these testing devices and methods still have some shortcomings: (1) The testing devices that characterize structural anisotropy only obtain anisotropy test indicators, but cannot be used to reveal the causes of soil structural anisotropy (e.g., CN104897464A); (2) The indicators used to characterize structural anisotropy are relatively simple, such as shear wave velocity (e.g., CN104897464A; CN108344852A), making it difficult to comprehensively evaluate soil structural anisotropy; (3) Existing devices or methods cannot establish the relationship and characterization method between macroscopic test characterization indicators and microscopic parameters of structural anisotropy (e.g., CN108344852A; CN104880366A).

[0005] Therefore, revealing the inducing mechanism of soil texture anisotropy, comprehensively evaluating the texture anisotropy of heterogeneous soil and establishing a texture anisotropy evaluation method, constructing a quantitative characterization relationship between texture micro-parameters and macro-test characterization indicators, and analyzing the influence mechanism of texture anisotropy on the mechanical properties of heterogeneous soil are important research directions in soil mechanics. Establishing a characterization method for the mechanical properties of heterogeneous soil that considers texture anisotropy is a scientific problem that urgently needs to be solved in soil mechanics. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a device and method for testing the anisotropy of heterogeneous soil structures, which is used to simultaneously acquire microscopic parameters and macroscopic test characterization indicators of heterogeneous soil structures. A multi-dimensional evaluation method is used to achieve a comprehensive evaluation of the anisotropy of heterogeneous soil structures, revealing the causes of anisotropy in heterogeneous soil structures, and establishing a quantitative characterization relationship between microscopic parameters and macroscopic test characterization indicators of structural anisotropy, thereby promoting the development of scientific research on the influence of anisotropy of heterogeneous soil structures on mechanical properties.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A heterogeneous soil anisotropy testing device is characterized in that: the heterogeneous soil anisotropy testing device consists of a multidimensional elastic wave testing device, a multidimensional image acquisition and analysis system, a wave signal interpretation and processing system, and a graded loading model box, and can be used to measure the degree of anisotropy of heterogeneous soil structures under different load conditions and different soil properties; the multidimensional elastic wave testing device includes a bending element excitation array and receiving array arranged in multiple directions, a compression element excitation array and receiving array arranged in multiple directions, and an earth pressure cell arranged in multiple directions, used to measure the heterogeneity of heterogeneous soil in different directions under different load conditions and different soil properties. The system includes a multi-dimensional high-definition camera and a PIV particle size distribution analysis system, used to analyze one or more of the gradation characteristics, particle shape characteristics, and porosity characteristics of heterogeneous soil along the elastic wave propagation path; the wave signal interpretation and processing system includes a multi-dimensional shear wave velocity calculation system, a multi-dimensional compression wave velocity calculation system, and a heterogeneous soil fabric anisotropy evaluation system, used to determine one or more of the shear wave velocity, compression wave velocity, and degree of heterogeneous soil fabric anisotropy; the graded loading model box includes a single-sided open transparent model box and a graded weighting device.

[0008] The above technical solution can be further improved through the following technical measures: As a further optimization, the bending element excitation array and receiving array arranged in multiple directions in the multi-dimensional elastic wave testing device include three orthogonal directions (horizontal bidirectional and vertical) to measure the shear wave velocity of heterogeneous soil under different load conditions and different soil properties.

[0009] As a further optimization, the multi-directionally arranged excitation and receiving arrays of the compression elements in the multi-dimensional elastic wave testing device include three orthogonal directions (horizontal bidirectional and vertical), which are used to measure the compression wave velocity of heterogeneous soil under different load conditions and different soil properties.

[0010] As a further optimization, the multi-dimensional elastic wave testing device includes earth pressure cells arranged in three orthogonal directions (horizontal bidirectional and vertical) to measure the vertical and lateral earth pressure values ​​on the elastic wave propagation path under different load conditions.

[0011] As a further optimization, the shooting direction of the multi-dimensional high-definition camera in the multi-dimensional image acquisition and analysis system is perpendicular to the elastic wave propagation path. By orthogonally capturing high-definition images and combining them with the PIV particle size distribution analysis system, the particle size distribution information set, particle shape information set, and pore morphology information set along the elastic wave propagation path are statistically analyzed to analyze the anisotropic parameters of soil structure at the microscale. The particle size distribution information set includes information such as particle size curves, heterogeneous arrangement diagrams of large and small particles, and the distribution of the proportion of large and small particle diameters in the elastic wave propagation path. The particle shape information set includes information such as the aspect ratio and roundness. The pore morphology information set is used to analyze the multi-dimensional pore distribution characteristics of the soil.

[0012] As a further optimization, the multi-dimensional shear wave velocity calculation system includes a shear wave arrival time discrimination module and a shear wave velocity calculation module; the shear wave arrival time discrimination module determines the arrival time using the cross-correlation function method, that is, the arrival time of the shear wave is the point where the cross-correlation coefficient reaches its maximum value; the core calculation method of the shear wave velocity calculation module is shown in the following formula: In the formula: V s Shear wave velocity; L This represents the propagation distance of the shear wave. t The propagation time of the shear wave; V s0 This represents the stress-normalized shear wave velocity. P 0 represents the reference stress (=100 kPa); σ v The vertical earth pressure is measured by earth pressure cells arranged vertically. σ h The horizontal earth pressure is obtained by averaging the values ​​from earth pressure cells arranged in a horizontal bidirectional manner. m This is a stress index related to soil properties.

[0013] As a further optimization, the multi-dimensional compressed wave velocity calculation system includes a compressed wave arrival time discrimination module and a compressed wave velocity calculation module; the compressed wave arrival time discrimination module determines the arrival time using the cross-correlation function method, that is, the arrival time of the compressed wave is the point where the cross-correlation coefficient reaches its maximum value; the core calculation method of the compressed wave velocity calculation module is shown in the following formula: In the formula: L This refers to the distance the compressed wave travels. t To compress the wave propagation time; V p To compress wave speed As a further optimization, the heterogeneous soil anisotropy evaluation system includes a shear wave velocity anisotropy evaluation module and a compression wave velocity anisotropy evaluation module; the shear wave velocity anisotropy evaluation module is used to evaluate the degree of shear wave velocity anisotropy in heterogeneous soil, and the evaluation method is shown in the following formula: In the formula: V s0i The shear wave velocity in a certain direction, i For the X, Y, and Z directions.

[0014] As a further optimization, the compression wave velocity anisotropy evaluation module is used to evaluate the degree of compression wave velocity anisotropy in heterogeneous soil. The evaluation method is shown in the following formula: In the formula: V pi The shear wave velocity in a certain direction, i The X, Y, and Z directions are specified. As a further optimization, the graded loading model box is a transparent plexiglass container with an opening at the top for applying graded weighting devices to create different load conditions; the graded weighting devices are made of lead sand.

[0015] The present invention also provides a testing method for testing the anisotropy of heterogeneous soil structures using the above-mentioned anisotropy testing device for heterogeneous soil structures, wherein the anisotropy testing method for heterogeneous soil structures includes the following testing procedures: (1) Fill the model box with soil of a certain grade. During the filling process, embed the bending element excitation array and receiving array, the compression element excitation array and receiving array, and the earth pressure cell arranged in multiple directions. Arrange multi-dimensional high-definition cameras in orthogonal orientation. (2) Apply lead sand to the upper part of the model box to form different stress states and measure them through earth pressure cells in multiple directions; (3) Conduct multidimensional elastic wave excitation tests and obtain the shear wave velocity and compression wave velocity of heterogeneous soil in different dimensions, as well as the degree of anisotropy of shear wave velocity and compression wave velocity, through the signal interpretation and processing system. (4) Use a multidimensional image acquisition and analysis system to obtain the information set of particle gradation, particle shape and pore morphology of heterogeneous soil along the multidimensional elastic wave propagation path, and analyze and calculate the soil fabric anisotropy parameters at the microscale. (5) Combining the information set of particle gradation, particle shape and pore distribution of heterogeneous soil along the elastic wave propagation path, and the mechanism of structural anisotropy caused by stress state analysis, the characterization relationship between the microscopic parameters of structural anisotropy and the macroscopic test characterization index is established.

[0016] The beneficial effects of this invention are: (1) The present invention can simultaneously acquire and interpret the micro-parameters and macro-characterization parameters of soil structure through a multi-dimensional elastic wave testing device, a multi-dimensional image acquisition and analysis system and a wave signal interpretation and processing system. It is used to analyze the mechanism of structural anisotropy in heterogeneous soil and establish the characterization relationship between the micro-parameters of structural anisotropy and the macro-test characterization index. (2) By embedding an earth pressure cell in a multidimensional elastic wave testing device, the present invention can monitor the lateral earth pressure coefficient of the soil. At the same time, combined with a multidimensional image acquisition and analysis system, the influence of soil gradation characteristics on the lateral earth pressure coefficient of the soil can be analyzed. (3) This invention characterizes the soil structure through a multi-scale and multi-index approach, such as particle size distribution, particle shape and pore distribution at the microscale, and shear wave velocity and compression wave velocity at the macroscale, which deepens researchers’ understanding and knowledge of soil structure anisotropy and promotes the development of scientific research on the influence of heterogeneous soil structure anisotropy on mechanical properties. Attached Figure Description

[0017] Figure 1 This is a three-dimensional schematic diagram of an anisotropy testing and analysis device for heterogeneous soil structures as described in this invention.

[0018] Figure 2 This is a plan view of the anisotropy testing and analysis device for heterogeneous soil structures according to the present invention.

[0019] Figure 3 This is a flowchart of the anisotropy test and analysis process for heterogeneous soil structures as described in this invention.

[0020] In the diagram: 1. Single-sided open transparent model box; 2. Heterogeneous soil; 3. Graded weighting device; 4. Vertical Z-axis high-definition camera; 5. Horizontal X-axis high-definition camera; 6. Horizontal Y-axis high-definition camera; 7. Horizontal X-axis bending element excitation and receiving array; 8. Horizontal Y-axis bending element excitation and receiving array; 9. Vertical Z-axis bending element excitation and receiving array; 10. Horizontal X-axis compression element excitation and receiving array; 11. Horizontal Y-axis compression element excitation and receiving array; 12. Vertical Z-axis compression element excitation and receiving array; 13. Horizontal X-axis earth pressure cell; 14. Horizontal Y-axis earth pressure cell; 15. Vertical Z-axis earth pressure cell. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0022] This invention provides a device for testing and analyzing the anisotropy of heterogeneous soil structures. The device comprises a multidimensional elastic wave testing device, a multidimensional image acquisition and analysis system, a wave signal interpretation and processing system, and a graded loading model box. It can be used to measure the degree of anisotropy of heterogeneous soil structures under different load conditions and soil properties. The multidimensional elastic wave testing device includes a multi-directionally arranged array of bending element excitation and receiving elements, a multi-directionally arranged array of compression element excitation and receiving elements, and a multi-directionally arranged earth pressure cell, used to measure the anisotropy of heterogeneous soil structures under different load conditions and soil properties. The invention describes the shear and compression wave velocities of heterogeneous soil in different directions. The multi-dimensional image acquisition and analysis system includes a multi-dimensional high-definition camera and a PIV particle size distribution analysis system, used to analyze the gradation characteristics, particle shape characteristics, and porosity characteristics of heterogeneous soil along the elastic wave propagation path. The wave signal interpretation and processing system includes a multi-dimensional shear wave velocity calculation system, a multi-dimensional compression wave velocity calculation system, and a heterogeneous soil fabric anisotropy evaluation system, used to determine the shear wave velocity, compression wave velocity, and degree of heterogeneous soil fabric anisotropy. The graded loading model box includes a single-sided open transparent model box and a graded weighting device. Based on this invention, multi-scale macro-micro joint characterization of soil fabric can be achieved, and a quantitative characterization relationship between micro-scale parameters and macro-scale characterization parameters can be constructed, promoting the development of scientific research on the influence of heterogeneous soil fabric anisotropy on mechanical properties. Example

[0023] like Figure 1 and Figure 2As shown, the present invention will be described below using the characterization of anisotropy of gravelly soil structure as an example. The material of the single-sided open transparent model box 1 can be plexiglass, the diameter can be 0.8m, and the height can be 1.2m. By filling the single-sided open transparent model box 1 with four layers of heterogeneous gravelly soil 2 with a certain gradation characteristics, the filling height is set to 0.6m, and sensors are buried at the middle position of the model (at the 0.3m position), including a horizontal X-axis bending element excitation and receiving array 7, a horizontal Y-axis bending element excitation and receiving array 8, a vertical Z-axis bending element excitation and receiving array 9, a horizontal X-axis compression element excitation and receiving array 10, a horizontal Y-axis compression element excitation and receiving array 11, a vertical Z-axis compression element excitation and receiving array 12, a horizontal X-axis earth pressure cell 13, a horizontal Y-axis earth pressure cell 14, and a vertical Z-axis earth pressure cell 15. After the model is filled to 0.3m and the sensors are installed, high-definition photos are first taken using the vertical Z-axis high-definition camera 4. After the model is filled, a 0.4m thick layer of lead sand is poured to apply specific external load conditions to the heterogeneous gravelly soil, and high-definition photos are taken using the horizontal X-axis high-definition camera 5 and the horizontal Y-axis high-definition camera 6. It should be noted that the horizontal X-axis bending element excitation and receiving array 7 and the horizontal Y-axis bending element excitation and receiving array 8 are arranged in orthogonal directions, the horizontal X-axis compression element excitation and receiving array 10 and the horizontal Y-axis compression element excitation and receiving array 11 are arranged in orthogonal directions, the horizontal X-axis earth pressure cell 13 and the horizontal Y-axis earth pressure cell 14 are arranged in orthogonal directions, the horizontal X-axis high-definition camera 5 and the horizontal Y-axis high-definition camera 6 are in orthogonal directions, and the vertical Z-axis high-definition camera 4, the vertical Z-axis bending element excitation and receiving array 9, the vertical Z-axis compression element excitation and receiving array 12 and the vertical Z-axis earth pressure cell 15 are arranged vertically.

[0024] Earth pressure is measured in different directions, including horizontal X-axis earth pressure cell 13 measuring X-axis earth pressure, horizontal Y-axis earth pressure cell 14 measuring Y-axis earth pressure, and vertical Z-axis earth pressure cell 15 measuring Z-axis earth pressure.

[0025] A horizontal X-axis bending element excitation array, a horizontal Y-axis bending element excitation array, and a vertical Z-axis bending element excitation array are excited at different excitation frequencies. The signals received by these arrays are then input into the shear wave arrival time discrimination module and the shear wave velocity calculation module of the multi-dimensional shear wave velocity calculation system for processing and analysis. The shear wave arrival time discrimination module determines the arrival time using a cross-correlation function method; that is, the arrival time is determined by the maximum value of the cross-correlation coefficient. The core calculation method of the shear wave velocity calculation module is shown in the following formula: In the formula: V s Shear wave velocity; LThis represents the propagation distance of the shear wave. t The propagation time of the shear wave; V s0 This represents the stress-normalized shear wave velocity. P 0 represents the reference stress (=100 kPa); σ v The vertical earth pressure is measured by a vertical Z-axis earth pressure cell. σ h The horizontal earth pressure is obtained by averaging the horizontal X-axis earth pressure cell and the horizontal Y-axis earth pressure cell. m The stress index, which is related to soil properties, is set to 0.25.

[0026] The horizontal X-axis compressive element excitation array, the horizontal Y-axis compressive element excitation array, and the vertical Z-axis compressive element excitation array are excited at different excitation frequencies. The signals received by these arrays are then input into the compressive wave arrival time discrimination module and the compressive wave velocity calculation module of the multi-dimensional compressive wave velocity calculation system for processing and analysis. The compressive wave arrival time discrimination module determines the arrival time using the cross-correlation function method; that is, the arrival time is determined by the maximum value of the cross-correlation coefficient. The core calculation method of the compressive wave velocity calculation module is shown in the following formula: In the formula: L This refers to the distance the compressed wave travels. t To compress the wave propagation time; V p To compress the wave velocity.

[0027] The calculated shear wave velocities in the three directions are input into the shear wave velocity anisotropy evaluation module of the heterogeneous soil fabric anisotropy evaluation system. The macroscopic characterization index of sand and gravel fabric anisotropy based on the shear wave velocity index can be obtained according to the following formula: In the formula: V s0i The shear wave velocity in a certain direction, i For the X, Y, and Z directions.

[0028] The calculated compression wave velocities in the three directions are input into the compression wave velocity anisotropy evaluation module of the heterogeneous soil fabric anisotropy evaluation system. The macroscopic characterization index of sand and gravel fabric anisotropy based on the compression wave velocity index can be obtained according to the following formula: In the formula: V pi The shear wave velocity in a certain direction, i For the X, Y, and Z directions.

[0029] By combining images captured by a multi-dimensional high-definition camera in a multi-dimensional image acquisition and analysis system with a PIV particle size distribution analysis system, we can analyze the particle size distribution information set, particle shape information set, and pore morphology information set along the elastic wave propagation path. The particle size distribution information set includes particle size curves, heterogeneous arrangement diagrams of large and small particles, and the distribution of the proportion of large and small particle diameters along the elastic wave propagation path. The particle shape information set includes information such as the aspect ratio and roundness. The pore morphology information set is used to analyze the multi-dimensional pore distribution characteristics of the soil. Obtaining these parameters allows us to establish a method for characterizing the anisotropy of gravelly soil texture at the mesoscale.

[0030] The methods used in the above embodiments can be summarized as follows: Figure 3 The flowchart shown is illustrated. As a further exploration in scientific research, the information sets of particle gradation, particle shape, and pore distribution in gravelly soil along the elastic wave propagation path, along with the mechanism of stress state analysis inducing textural anisotropy in gravelly soil, can be combined to comprehensively evaluate the textural anisotropy of gravelly soil and establish a textural anisotropy evaluation method. Furthermore, the characterization relationship between the microscopic parameters of textural anisotropy and the macroscopic test characterization indicators can be established, thus promoting the development of scientific research on the impact of textural anisotropy on the mechanical properties of heterogeneous soils.

Claims

1. A device for testing and analyzing the fabric anisotropy of a non-homogeneous soil, characterized in that it comprises: The heterogeneous soil structure anisotropy testing device consists of a multidimensional elastic wave testing device, a multidimensional image acquisition and analysis system, a wave signal interpretation and processing system, and a graded loading model box. It can be used to measure the degree of anisotropy of heterogeneous soil structures under different load conditions and different soil properties. The multidimensional elastic wave testing device includes a bending element excitation array and receiving array arranged in multiple directions, a compression element excitation array and receiving array arranged in multiple directions, and an earth pressure cell arranged in multiple directions, used to measure the shear wave velocity and compression wave velocity of heterogeneous soil in different directions under different load conditions and different soil properties. The multidimensional image acquisition and analysis system includes a multidimensional high-definition camera and a PIV particle size distribution analysis system, which are used to analyze the gradation characteristics, particle shape characteristics and porosity characteristics of heterogeneous soil along the elastic wave propagation path; the shooting direction of the multidimensional high-definition camera is perpendicular to the elastic wave wave path. The wave signal interpretation and processing system includes a multi-dimensional shear wave velocity calculation system, a multi-dimensional compression wave velocity calculation system, and an anisotropy evaluation system for heterogeneous soil structure, used to determine the shear wave velocity, compression wave velocity, and degree of anisotropy of heterogeneous soil structure. The graded loading model box includes a single-sided open transparent model box and a graded weighting device.

2. The apparatus for testing the fabric anisotropy of a non-homogeneous soil according to claim 1, characterized in that: The multi-dimensional elastic wave testing device contains a bending element excitation array and a receiving array arranged in three orthogonal directions, namely horizontal bidirectional and vertical, which are used to measure the shear wave velocity of heterogeneous soil under different load conditions and different soil properties.

3. The apparatus for testing the anisotropy of the fabric of anisotropic soils according to claim 1, characterized in that: The multi-dimensional elastic wave testing device includes a multi-directional array of excitation and receiving elements, comprising three orthogonal directions: horizontal (bidirectional) and vertical, used to measure the compressive wave velocity of heterogeneous soil under different load conditions and soil properties.

4. The anisotropy testing device for heterogeneous soil structures according to claim 1, characterized in that: The multi-dimensional elastic wave testing device includes earth pressure cells arranged in three orthogonal directions: horizontal (bidirectional) and vertical. These cells are used to measure the vertical and lateral earth pressure values ​​along the propagation path of elastic waves under different load conditions.

5. The apparatus of claim 1, wherein: The multi-dimensional high-definition camera captures high-definition images orthogonally and combines them with the PIV particle size distribution analysis system to statistically analyze the particle size distribution information set, particle shape information set, and pore morphology information set along the elastic wave propagation path. This information is used to analyze the anisotropic parameters of soil structure at the microscale. The particle size distribution information set includes particle size curves, heterogeneous arrangement diagrams of large and small particles, and the distribution information of the proportion of large and small particle diameters in the elastic wave propagation path. The particle shape information set includes the aspect ratio and roundness information. The pore morphology information set is used to analyze the multi-dimensional pore distribution characteristics of the soil.

6. The apparatus of claim 1, wherein: The multi-dimensional shear wave velocity calculation system includes a shear wave arrival time discrimination module and a shear wave velocity calculation module. The shear wave arrival time discrimination module determines the arrival time using a cross-correlation function method, where the maximum value of the cross-correlation coefficient is taken as the shear wave arrival time. The core calculation method of the shear wave velocity calculation module is shown in the following formula: In the formula: L This represents the propagation distance of the shear wave. t The propagation time of the shear wave; V s0 This represents the stress-normalized shear wave velocity. P 0 is the reference stress (=100kPa); σ v The vertical earth pressure is measured by earth pressure cells arranged vertically. σ h The horizontal earth pressure is obtained by averaging the values ​​from earth pressure cells arranged in a horizontal bidirectional manner. m This is a stress index related to soil properties.

7. The apparatus of claim 1, wherein: The multi-dimensional compressed wave velocity calculation system includes a compressed wave arrival time discrimination module and a compressed wave velocity calculation module. The compressed wave arrival time discrimination module determines the arrival time using a cross-correlation function method, where the maximum value of the cross-correlation coefficient is taken as the compressed wave arrival time. The core calculation method of the compressed wave velocity calculation module is shown in the following formula: wherein: L is the compressed wave propagation distance; t is the compressed wave propagation time; V p is the compressed wave velocity.

8. The apparatus of claim 1, wherein: The heterogeneous soil anisotropy evaluation system includes a shear wave velocity anisotropy evaluation module and a compression wave velocity anisotropy evaluation module; the shear wave velocity anisotropy evaluation module is used to evaluate the degree of shear wave velocity anisotropy in heterogeneous soil, and the evaluation method is shown in the following formula: wherein: V s0i is the shear wave velocity in a certain direction, i X, Y, and Z directions; The compression wave velocity anisotropy evaluation module is used to evaluate the degree of compression wave velocity anisotropy in heterogeneous soil. The evaluation method is shown in the following formula: wherein: V pi is the shear wave velocity in a certain direction, i X, Y, and Z directions.

9. The apparatus of claim 1, wherein: The graded loading model box is a transparent plexiglass container with an opening at the top for applying graded weights to create different load conditions; the graded weights are made of lead sand.

10. A testing method for testing anisotropy of a non-homogeneous soil fabric by using the anisotropy testing device for non-homogeneous soil fabric according to any one of claims 1 to 9, characterized in that: The following testing process is included: (1) Fill the model box with soil of a certain grade. During the filling process, embed the bending element excitation array and receiving array, the compression element excitation array and receiving array, and the earth pressure cell arranged in multiple directions. Arrange multi-dimensional high-definition cameras in orthogonal orientation. (2) Apply lead sand to the upper part of the model box to form different stress states and measure them through earth pressure cells in multiple directions; (3) Conduct multidimensional elastic wave excitation tests and obtain the shear wave velocity and compression wave velocity of heterogeneous soil in different dimensions, as well as the degree of anisotropy of shear wave velocity and compression wave velocity, through the signal interpretation and processing system. (4) Use a multidimensional image acquisition and analysis system to obtain the information set of particle gradation, particle shape and pore morphology of heterogeneous soil along the multidimensional elastic wave propagation path, and analyze and calculate the soil fabric anisotropy parameters at the microscale. (5) Combining the information set of particle gradation, particle shape and pore distribution of heterogeneous soil along the elastic wave propagation path, and the mechanism of structural anisotropy caused by stress state analysis, the characterization relationship between the microscopic parameters of structural anisotropy and the macroscopic test characterization index is established.

Images