Method for detecting thickness of shear band of granular material

Abstract

The invention discloses a granular material shear band thickness detection method, and relates to the field of geotechnical engineering, and the method comprises the following steps: carrying out a ring shear test on a granular material, carrying out three-dimensional sampling to obtain a sample, dipping and curing the sample to obtain a cured sample, and constructing a three-dimensional granular structure model; the solid-phase fraction of each layer is calculated layer by layer in the height direction of the three-dimensional particle structure model, the relative deviation threshold value of the solid-phase fractions is set, the relative deviation is calculated, the positions where the relative deviation exceeds the relative deviation threshold value of the solid-phase fractions for the first time and the last time are the boundaries of the two sides of the shear band, and the distance between the boundaries of the two sides is calculated to obtain the thickness of the shear band. According to the method, the boundary of the shear band is determined according to the fluctuation condition of the solid-phase fraction, so that the thickness of the shear band is calculated, the thickness of the shear band is directly associated with the micromechanical response in a physical quantization mode, subjective errors caused by judging the boundary of the shear band according to experience are reduced, and the precision of shear band thickness detection is improved.

Description

Technical Field

[0001] This application relates to the field of geotechnical engineering, and particularly to a method for detecting the thickness of a shear band in granular materials. Background Art

[0002] The analysis of the shear behavior of granular materials (such as sand, gravel, industrial particles and other medium systems) is a key basis for evaluating slope stability, landslide movement mechanism and fault activity in the fields of geotechnical engineering and geological disaster research. As a key test method that can reproduce the large deformation and long-distance shear process, the ring shear test is the core method for studying the mechanical response and localized deformation mechanism of granular materials. In the ring shear test, the formation and evolution process of the shear band directly determines the shear strength attenuation law, energy dissipation characteristics and failure mode of the material. The accurate determination of its thickness, morphology and evolution law is crucial for establishing constitutive models, optimizing engineering designs and disaster warning.

[0003] Currently, the ring shear test often uses a ring shear apparatus. Granular materials are filled into the annular shear box to simulate the large deformation shear process. Sawteeth are arranged at intervals along the circumferential direction on the inner bottom surface of the annular shear box to reduce the boundary slip effect of the granular materials. After the ring shear test is completed, the whole granular materials are taken out from the annular shear box, solidified after two-dimensional slicing perpendicular to the predetermined shear plane along the radial direction, observed with an optical microscope, the boundary of the shear band is judged by experience, and the thickness range of the shear band is calculated.

[0004] However, due to instrument disturbance and the disturbance of the granular materials after each ring shear test during slicing, the distinguishability between the real shear band and the disturbed area is reduced, which will interfere with the judgment of the shear band boundary. Moreover, the shear band thickness of a single slice or the average thickness of the shear bands of multiple slices replacing the shear band thickness of the whole granular materials depends on the empirical assumption of uniform deformation, which is disconnected from the actual non-uniform deformation mechanism, weakening the correlation between the local deformation mechanism and the overall response, resulting in a reduction in the accuracy of the shear band thickness detection. Summary of the Invention

[0005] In view of the above deficiencies of the related technologies, this application provides a method for detecting the thickness of a shear band in granular materials. This application solidifies the granular materials that have undergone the ring shear test after three-dimensional sampling, then constructs a three-dimensional granular structure model, calculates the solid phase fraction layer by layer based on the data of the three-dimensional granular structure model, determines the boundary of the shear band according to the fluctuation of the solid phase fraction, so as to calculate the shear band thickness. Through a physical quantification method, the shear band thickness is directly related to the micro-mechanical response, reducing the subjective error of judging the shear band boundary according to experience and improving the accuracy of the shear band thickness detection.

[0006] A method for detecting the thickness of a shear band in granular materials provided by this application adopts the following technical solutions: A method for detecting the shear band thickness of a granular material comprises the following steps: performing a ring shear test on the granular material and then performing three-dimensional sampling to obtain a sample; performing impregnation and curing on the sample to obtain a cured sample; and constructing a three-dimensional granular structure model; The three-dimensional granular structure model is smoothed at the subvoxel level. The solid phase fraction of each layer is calculated layer by layer along the height direction of the three-dimensional granular structure model. The relative deviation threshold of the solid phase fraction is set, and the relative deviation of the solid phase fraction of each layer compared with the average solid phase fraction of all previous layers is calculated. The positions where the relative deviation exceeds the relative deviation threshold of the solid phase fraction for the first and last time are the two side boundaries of the shear band. The distance between the two side boundaries is calculated to obtain the shear band thickness.

[0007] Preferably, the construction of the three-dimensional particle structure model includes the following steps: performing tomographic scanning on the solidified sample to generate multi-layer two-dimensional grayscale slices, cropping, contrast adjustment and noise reduction pre-processing of the two-dimensional grayscale slices and then segmenting the components, and finally three-dimensional reconstruction modeling to obtain a three-dimensional particle structure model.

[0008] Preferably, the tomography includes CT scanning, and the scanning parameters are: scanning voltage 100-140 kV, current 110-130 μA, and resolution 10-30 μm.

[0009] Preferably, the tomography includes CT scanning, and the scanning parameters are: scanning voltage 130 kV, current 120 μA, and resolution 26 μm.

[0010] Preferably, the number of layers of the two-dimensional grayscale slices is 1000-1500.

[0011] Preferably, the number of layers of the two-dimensional grayscale slices is 1200.

[0012] Preferably, the calculation of the solid phase fraction includes the following steps: stratifying the three-dimensional particle structure model along the sample height direction, counting the particle phase voxel number and the overall voxel number of each layer, and calculating the ratio of the particle phase voxel number to the overall voxel number to obtain the solid phase fraction.

[0013] Preferably, the three-dimensional sampling includes the following steps: after the granular material undergoes a ring shear test in an annular shear box, a cylindrical sampling knife is inserted from the top of the granular material until it abuts against the inner bottom surface of the annular shear box. The block granular material separated by the cylindrical sampling knife in the annular shear box is the sample.

[0014] Preferably, the cylindrical sampling knife is composed of an inner arc plate, an outer arc plate and two rectangular plates, the inner arc plate and the outer arc plate are coaxially arranged, and one end of the inner arc plate, the outer arc plate and the two rectangular plates are all blade-shaped and are arranged to form the cutting edge of the cylindrical sampling knife.

[0015] Preferably, the inner arc surface of the inner arc plate is flush with the outer wall of the inner ring of the annular shear box, the outer arc surface of the outer arc plate is flush with the inner wall of the outer ring of the annular shear box, and the mutually facing surfaces of the two rectangular plates are located between two adjacent saw teeth on the inner bottom surface of the annular shear box.

[0016] Preferably, the step of impregnating and curing the sample to obtain a cured sample includes the following steps: injecting epoxy resin along the inner wall edge of the cylindrical sampling knife into the cylindrical sampling knife until the sample is submerged by the epoxy resin, standing still until the epoxy resin starts to set, and then lifting the cylindrical sampling knife to further cure under constant temperature conditions until the epoxy resin finally sets. What the cylindrical sampling knife contains is the cured sample.

[0017] Preferably, the injection rate of the injection is 0.5 - 3 mL / min.

[0018] Preferably, the injection rate of the injection is 2 mL / min.

[0019] Preferably, the relative deviation threshold of the solid phase fraction is 3% - 8%.

[0020] Preferably, the relative deviation threshold of the solid phase fraction is 5%.

[0021] In summary, the present application includes at least one of the following beneficial technical effects: 1. In the present application, after three-dimensional sampling and curing of the granular material subjected to the ring shear test, a three-dimensional granular structure model is constructed, and the solid phase fraction is calculated layer by layer based on the data of the three-dimensional granular structure model. The boundary of the shear band is determined by the fluctuation of the solid phase fraction, so as to calculate the shear band thickness. Through a physical quantification method, the shear band thickness is directly correlated with the micro-mechanical response, reducing the subjective error of judging the shear band boundary according to experience and improving the accuracy of shear band thickness detection.

[0022] 2. In the present application, the calculation of the solid phase fraction is based on the voxel data of the constructed three-dimensional granular structure model, and its value reflects the volume ratio of solid particles in a local area. The formation of the shear band is accompanied by particle breakage, rearrangement, and local densification, and these processes are directly reflected as changes in the solid phase fraction. Using the solid phase fraction as a quantification standard excludes the interference of influencing factors such as particle morphology and arrangement randomness; 3. The detection method for the shear band thickness of the granular material in the present application uses the solid phase fraction as a quantification standard. When performing ring shear tests with different displacement amounts, by unifying the quantification standard, the continuous evolution of the shear band thickness with displacement is quantified, and dynamic evolution data of the shear band thickness are obtained, breaking through the limitation that the traditional method can only provide an estimate of the static shear band thickness range. Description of the Drawings

[0023] Figure 1 is the overall structural schematic diagram of the cylindrical sampling knife in the present application.

[0024] Figure 2 is the solid fraction - sample height curve obtained by using the detection method of Example 1; Figure 3 is the solid fraction - sample height curve obtained by using the detection method of Example 2; Figure 4 is the solid fraction - sample height curve obtained by using the detection method of Example 3; Figure 5 is the dynamic evolution diagram of the shear band thickness obtained by using the detection methods of Examples 1 - 3; Figure 6 is the optical microscope image of the two - dimensional slice obtained by using the detection method of Comparative Example 1; Figure 7 is the optical microscope image of the two - dimensional slice obtained by using the detection method of Comparative Example 2; Figure 8 is the optical microscope image of the two - dimensional slice obtained by using the detection method of Comparative Example 3.

[0025] Reference numerals: 1, inner arc plate; 2, outer arc plate; 3, rectangular plate; 4, cutting edge. Detailed implementation manners

[0026] The following further elaborates on the present application in conjunction with examples. The following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those conditions not specified in the following examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For the detection methods used, if not otherwise specified, they are all conventional detection methods well - known in the art. For the consumables and reagents used, if not otherwise specified, they are all commercially available. Unless otherwise stated, the professional and scientific terms used herein have the same meaning as those familiar to skilled personnel in the art. In addition, any detection method or material similar or equivalent to the described content can also be applied to the present invention.

[0027] The raw materials used in the examples and comparative examples are all commercially available.

[0028] Example 1 Example 1 of this application provides a method for detecting the thickness of the shear band of granular materials, including the following steps: Using dry, crushable, and uniformly sized (1-2 mm) quartz sand as the granular material, with a specific gravity of 2.66, a silica (SiO2) content exceeding 99.6%, a compressive strength of 250 MPa, and a Mohs hardness of 7.5. According to the "Standard for Geotechnical Test Methods" (GB / T 50123-2019), after the quartz sand is cleaned and dried, it is filled into the shear box of the ICL-2 type undrained high-speed dynamic ring shear apparatus in layers, with a total filling height of 4.2 mm and the initial solid phase fraction controlled at 0.54. During the ring shear test, a normal stress of 200 kPa and a shear speed of 10 mm / s are set, and a ring shear test with a shear displacement of 1 m is carried out.

[0029] After the test is terminated, remove the upper shear disc and other device components of the sample, and retain the in-situ structure of the granular material that has undergone the ring shear test. Use the cylindrical sampling knife shown in Figure 1 to complete in-situ sampling in cooperation with the laser positioning scale. The cylindrical sampling knife is in the shape of an inner arc plate 1, an outer arc plate 2, and two rectangular plates 3 enclosing each other, integrally formed with a transparent material. The inner arc plate 1 and the outer arc plate 2 are coaxially arranged. One end of the inner arc plate 1, the outer arc plate 2, and the two rectangular plates 3 are all in the shape of a blade, and enclose to form the cutting edge 4 of the cylindrical sampling knife. The size of the cylindrical sampling knife is adaptively designed according to the size of the annular shear box of common ring shear apparatuses on the market (in this application, it is the ICL-2 type undrained high-speed dynamic ring shear apparatus), so that when the cylindrical sampling knife is in use, the inner arc surface of the inner arc plate is flush with the outer wall of the inner ring of the annular shear box, the outer arc surface of the outer arc plate is flush with the inner wall of the outer ring of the annular shear box, and the mutually distant plate surfaces of the two rectangular plates are located between two adjacent sawteeth on the inner bottom surface of the annular shear box. During the acquisition process, monitor the insertion depth and horizontal offset, and manually fine-tune the alignment to ensure that the pressing direction is perpendicular.

[0030] Use LOCTITE EA 9483 type low-viscosity and high-thermal-conductivity epoxy resin, weigh according to the standard mass ratio of the A / B components of the epoxy resin, and use a planetary mixer (rotation speed 200 rpm, time 5 minutes) to fully mix until there are no streaks of non-uniformity. Inject the resin along the inner wall edge of the cylindrical sampling knife through a syringe, with an injection rate of 2 mL / min, to avoid flow shear disturbing the particle structure. Observe the resin penetration through the plexiglass transparent box body, and adopt a "Z"-shaped moving path to ensure that the shear band area is fully impregnated. After the resin starts to set (about 30 minutes), vertically lift the cylindrical sampling knife and the internal sample by 5-10 mm, and insert the lower surface annular cover plate at the bottom for fixation. Take out the sample and place it in a constant temperature oven (25 ± 1 °C) for further curing until the epoxy resin finally sets, with a total curing period ≤ 12 hours. Impregnate and cure the sample in the cylindrical sampling knife to obtain a cured sample, ensuring the non-destructive retention of the three-dimensional shear band structure in the sample.

[0031] The solidified sample was detected by a GE Phoenix Nanotom S-type CT scanner. According to the material properties of the sample, the scanning voltage was set to 130 kV, the current to 120 μA, and the resolution to 26 μm, and 1200 two-dimensional grayscale slices were obtained. In the Avizo commercial software, the two-dimensional grayscale slices were preprocessed by removing the boundary of the shear box and the external loose particle region, enhancing the contrast between the particles and the resin matrix by combining limited contrast adaptive histogram equalization (CLAHE), suppressing noise using non-local means filtering, and retaining the details of the particle edges. The Otsu adaptive threshold algorithm was applied to distinguish the particle phase (bright region) from the matrix phase (dark region) to generate a binary image. The watershed algorithm was used to generate a marker image based on distance transform to segment the contacting or overlapping particles. Finally, the multi-layer two-dimensional grayscale slices were modeled by the Avizo 3D reconstruction software to generate a three-dimensional particle structure model, and sub-voxel level smoothing (Laplacian smoothing coefficient 0.6) was performed on it to eliminate the stepped artifacts.

[0032] The three-dimensional particle structure model was stratified along the height direction. The number of voxel of the particle phase and the total number of voxels of each layer were obtained from the software, and the ratio of the number of voxel of the particle phase to the total number of voxels of each layer was calculated to obtain the solid phase fraction η of each layer i , ( , N voxel-p is the number of voxel of the particle phase of this layer, N voxel-t is the total number of voxels of this layer), and the solid phase fraction - sample height curve was obtained, as shown in Figure 2 ; The relative deviation threshold of the solid phase fraction was set to 5%, and the relative deviation Δη of the solid phase fraction of each layer compared to the average solid phase fraction β of all the previous layers was calculated k ( ). When calculating the relative deviation of the i + 1-th layer, k = i, and the calculation formula is . The positions where the relative deviation first and last exceeded the relative deviation threshold of the solid phase fraction were the two boundaries of the shear band. It can be calculated from Figure 2 that the upper boundary of the shear band was at a sample height of 37.12 mm, and the lower boundary of the shear band was at a sample height of 0.2 mm. The thickness of the shear band was calculated by obtaining the distance between the two boundaries, which was 36.92 mm.

[0033] Example 2 Example 2 of this application provides a method for detecting the thickness of the shear band of particulate materials. The difference between Example 2 and Example 1 is that: in Example 2, the shear displacement in the ring shear test was 10 m. The solid phase fraction - sample height curve obtained in Example 2 is shown in Figure 3 , as shown by Figure 3It can be calculated that the upper boundary of the shear band is at a sample height of 28.55 mm, and the lower boundary of the shear band is at a sample height of 3.72 mm. By calculating the distance between the two boundaries, the shear band thickness is obtained as 24.83 mm.

[0034] Example 3 Example 3 of the present application provides a method for detecting the shear band thickness of granular materials. The difference between Example 3 and Example 2 is that: in Example 3, the shear displacement in the ring shear test is 100 m. The solid fraction - sample height curve obtained in Example 3 is as Figure 4 shown, and by Figure 4 calculation, it can be known that the upper boundary of the shear band is at a sample height of 24.15 mm, and the lower boundary of the shear band is at a sample height of 2.80 mm. By calculating the distance between the two boundaries, the shear band thickness is obtained as 21.35 mm.

[0035] Based on the results of the above Examples 1 - 3, analyzing the relationship between the shear band thickness detected by the method for detecting the shear band thickness of granular materials in Examples 1 - 3 and the shear displacement, the dynamic evolution diagram of the shear band thickness is as Figure 5 shown.

[0036] Comparative Example 1 Comparative Example 1 provides a method for detecting the shear band thickness of granular materials. The difference between Comparative Example 1 and Example 1 is that: the cured sample is cut using a slicing technique to prepare a two - dimensional slice, and an optical microscope is used for two - dimensional finite section observation. The shear band boundary is manually delimited according to an empirical method, and the basis for delimitation is a significant change in particle density. The optical microscope image of the two - dimensional slice is as Figure 6 shown. Through optical microscope observation, it is empirically judged that the sample height range where the upper boundary of the shear band is located is approximately 34 - 39 mm, the sample height range where the lower boundary of the shear band is located is approximately 0 - 1 mm, and the empirical range of the shear band thickness is approximately 33 - 39 mm (average 36 mm).

[0037] Comparative Example 2 Comparative Example 2 provides a method for detecting the shear band thickness of granular materials. The difference between Comparative Example 2 and Comparative Example 1 is that: in Comparative Example 2, the shear displacement in the ring shear test is 10 m. The optical microscope image of the two - dimensional slice is as Figure 7 shown. Through optical microscope observation, it is empirically judged that the sample height range where the upper boundary of the shear band is located is approximately 25 - 34 mm, the sample height range where the lower boundary of the shear band is located is approximately 0 - 3 mm, and the empirical range of the shear band thickness is approximately 22 - 34 mm (average 28 mm).

[0038] Comparative Example 3 Comparative Example 3 provides a method for detecting the thickness of the shear band of granular materials. The difference between Comparative Example 3 and Comparative Example 1 is that: the shear displacement in the ring shear test in Comparative Example 3 is 100 m. The optical microscope image of the two-dimensional slice is as Figure 8 shown. Through optical microscope observation, it is empirically judged that the sample height range where the upper boundary of the shear band is located is about 20 - 31 mm, the sample height range where the lower boundary of the shear band is located is about 0 - 4 mm, and the empirical range of the shear band thickness is about 16 - 31 mm (average 23 mm).

[0039] Result Analysis The present application will be described in detail below in combination with the above experimental data.

[0040] Referring to Figures 2-4 and Figures 6-8 , the shear band thickness values calculated by using the detection method of the shear band thickness of the granular materials in Examples 1 - 3 are within the shear band thickness ranges detected under the same shear displacement conditions by using the detection methods of the shear band thickness of the granular materials in Comparative Examples 1 - 3, verifying the effectiveness of the detection method of the shear band thickness of the granular materials in Examples 1 - 3 of the present application. The sample height of the shear band boundary detected by using the detection method of the shear band thickness of the granular materials in Examples 1 - 3 is an accurate value, and the calculated shear band thickness is also an accurate value. However, the sample height of the shear band boundary judged by using the detection methods of the shear band thickness of the granular materials in Comparative Examples 1 - 3 is a range value, and the detected shear band thickness is also a range value. This shows that it is difficult to obtain an accurate value of the shear band thickness by manual empirical interpretation for the detection methods of the shear band thickness of the granular materials in Comparative Examples 1 - 3. Moreover, the methods in Comparative Examples 1 - 3 only support static observation of local cross-sections and low-precision requirements, and can neither reflect the true shape of the shear band in three-dimensional space (such as non-uniform deformation characteristics such as bending and bifurcation), nor track the dynamic evolution process of the shear band with the shear displacement. It shows that the detection method of the shear band thickness of the granular materials in Examples 1 - 3 of the present application is significantly superior to the traditional experience for judging the shear band thickness in the detection methods of the shear band thickness of the granular materials in Comparative Examples 1 - 3 under the shear band thickness detection at three shear displacements. The error is reduced from ±15% - 20% of the traditional method to ±1%, eliminating the subjective deviation of manual empirical interpretation (such as the arbitrary division of the boundary fuzzy area), which is beneficial to improving the accuracy of the shear band thickness detection. In addition, if the cylindrical sampling knife of the present application is not used for three-dimensional sampling, but the method of chiseling or cutting is adopted to obtain the sample containing the shear band, this process will inevitably physically damage the original structure of the shear band, resulting in structural collapse problems such as particle shedding and boundary collapse.

[0041] Referring to Figure 5It can be seen that the detection method for the shear band thickness in Embodiments 1-3 of the present application can obtain the dynamic evolution process of the shear band thickness with shear, capture the non-linear growth trend of the shear band thickness with shear displacement, and through a unified quantification standard, achieve the quantification of the continuous evolution of the shear band thickness with displacement, obtain the dynamic evolution data of the shear band thickness, breaking through the limitation that the traditional method can only provide an estimate of the static shear band thickness range.

[0042] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A method for detecting the thickness of a shear band in granular materials, characterized in that: It includes the following steps: After performing a ring shear test on granular materials, three-dimensional sampling is carried out to obtain a sample. The sample is impregnated and cured to obtain a cured sample, and a three-dimensional granular structure model is constructed. Perform sub-voxel level smoothing on the three-dimensional granular structure model. Calculate the solid phase fraction of each layer layer by layer along the height direction of the three-dimensional granular structure model. Set the relative deviation threshold of the solid phase fraction. Calculate the relative deviation of the solid phase fraction of each layer compared to the average solid phase fraction of all previous layers. The positions where the relative deviation first and last exceeds the relative deviation threshold of the solid phase fraction are the two side boundaries of the shear band. Calculate the distance between the two side boundaries to obtain the shear band thickness.

2. The detection method for the thickness of the shear band of granular materials according to claim 1, wherein: The construction of the three-dimensional granular structure model includes the following steps: Perform tomographic scanning on the cured sample to generate multiple layers of two-dimensional grayscale slices. After preprocessing the two-dimensional grayscale slices, such as cropping, contrast adjustment, and noise reduction, segment the components, and finally perform three-dimensional reconstruction and modeling to obtain the three-dimensional granular structure model.

3. The detection method of the shear band thickness of a granular material according to claim 2, characterized in that: The tomographic scanning includes CT scanning, and the scanning parameters are: scanning voltage 100 - 140 kV, current 110 - 130 μA, resolution 10 - 30 μm.

4. The detection method of the shear band thickness of a granular material according to claim 2, characterized in that: The number of layers of the two-dimensional grayscale slices is 1000 - 1500.

5. The detection method of the shear band thickness of a granular material according to claim 1, characterized in that: The calculation of the solid phase fraction includes the following steps: Layer the three-dimensional granular structure model along the height direction of the sample. Count the number of voxel of the granular phase and the total number of voxels in each layer. Calculate the ratio of the number of voxel of the granular phase to the total number of voxels to obtain the solid phase fraction.

6. The detection method for the thickness of the shear band of granular materials according to claim 1, wherein: The three-dimensional sampling includes the following steps: When the granular material undergoes a ring shear test in the ring shear box, a cylindrical sampling knife is inserted from the top of the granular material until it abuts against the inner bottom surface of the ring shear box. The block of granular material separated by the cylindrical sampling knife in the ring shear box is the sample.

7. A method for detecting the thickness of the shear band of granular materials according to claim 6, characterized in that: The cylindrical sampling knife is formed by enclosing an inner arc plate, an outer arc plate, and two rectangular plates. The inner arc plate and the outer arc plate are coaxially arranged. One end of the inner arc plate, the outer arc plate, and the two rectangular plates are all in a blade shape, and they enclose to form the blade edge of the cylindrical sampling knife.

8. A method for detecting the thickness of a shear band of granular materials according to claim 7, characterized in that: The inner arc surface of the inner arc plate is flush with the outer wall of the inner ring of the ring shear box. The outer arc surface of the outer arc plate is flush with the inner wall of the outer ring of the ring shear box. And the mutually remote plate surfaces of the two rectangular plates are located between two adjacent sawteeth on the inner bottom surface of the ring shear box.

9. The detection method of the shear band thickness of a granular material according to claim 1, wherein: The impregnation and curing of the sample to obtain a cured sample includes the following steps: Inject epoxy resin along the inner wall edge of the cylindrical sampling knife into the cylindrical sampling knife until the sample is submerged by the epoxy resin. Let it stand still. After the epoxy resin starts to solidify, lift the cylindrical sampling knife and further cure it under constant temperature conditions until the epoxy resin finally solidifies. What the cylindrical sampling knife contains is the cured sample.

10. A method for detecting the thickness of a shear band of granular materials according to claim 9, characterized in that: The injection rate of the injection is 0.5 - 3 mL / min.

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