Test device for failure characteristics of polymer grouting material and test method thereof

Abstract

The present invention discloses a test device for the failure characteristics of a polymer grouting material and a test method thereof. The test device includes a testing machine, a fixture, and a CT machine for scanning and obtaining images of the failure characteristics of the polymer grouting material. During the test, first, the specimen is fixed on the fixture, the testing machine applies different values of vertically downward pressure to the specimen in the fixture multiple times, and the CT machine obtains the internal structure images of the specimen under different pressure actions. By using ImageJ software to segment the grayscale image inside the specimen, the position and size changes of the cracks are obtained, making the obtained failure characteristics of the polymer grouting material more accurate, and solving the problem that the existing failure characteristic characterization method is unreasonable and one-sided in research results because the failure characteristics of the specimen are studied through the surface failure phenomenon of the specimen.

Description

Technical Field

[0001] The present invention relates to the technical field of testing high-polymer grouting materials, and particularly relates to a test device for the failure characteristics of high-polymer grouting materials and a test method thereof. Background Art

[0002] High-polymer grouting materials are widely used in various trenchless repair projects. Compared with traditional excavation and backfill repair, high-polymer grouting repair not only saves engineering costs but also greatly saves time. High-polymer grouting materials have excellent characteristics such as high expansion rate, low density, rapid setting, environmental protection, and water impermeability. These characteristics provide the possibility for wide application in trenchless repair of infrastructure. At present, polyurethane grouting materials have been used for the lifting of pipelines, ballastless tracks, and road surface settlements; the leakage plugging of tunnels, subways, and dams; and the consolidation and reinforcement of foundation and embankment soils.

[0003] When high-polymer grouting materials are used to repair infrastructure, they are often buried underground and mainly bear the upper load. Under the action of the upper load, the internal structure of the material continuously fails, realizing stress redistribution. Therefore, it is necessary to characterize the failure characteristics of the material through a method to provide a theoretical basis for evaluating the engineering effect after repair. At present, researchers mainly study the failure characteristics of specimens by observing the surface failure phenomena of specimens during the compression process, but the failure of specimens first occurs inside the specimens. The surface failure phenomenon is only the result of the cracks formed by the internal failure of the specimens extending outward, which is one-sided and unreasonable.

[0004] Computed Tomography (CT) technology is a widely used non-destructive testing technology at present. Its greatest advantage is that it can reflect the internal spatial structure of the sample in-situ without introducing new artificial defects, and can display the internal structural form of the material layer by layer as a gray-scale image without damage. In the field of grouting technology, CT scanning has been widely used to analyze the internal structures of grouting materials such as rocks, concrete, and foams. It can be considered to characterize the failure characteristics by scanning the internal structure changes of high-polymer grouting material specimens during the compression process.

[0005] When using CT scanning to characterize the failure characteristics of high-polymer grouting materials, there are mainly two problems. One is that for grouting materials, during the process of moving the specimen from the universal testing machine to the CT machine, the specimen will inevitably rebound due to its own elastic properties, interfering with the subsequent CT scanning results. Therefore, it is necessary to solve the problem of specimen rebound after compression through a self-made fixture. The other is that the size of the microcracks inside the compressed specimen is too small, and the position and size changes cannot be directly seen from the gray-scale pictures obtained by CT scanning. Therefore, a segmentation method is needed to identify and segment the position and size changes of the cracks in the CT images. Summary of the Invention

[0006] In view of the above problems in the prior art, the present invention provides a test device and a test method for the failure characteristics of polymer grouting materials, which solve the problem that the existing failure characteristic characterization methods are unreasonable and one-sided in research results because the failure characteristics of specimens are studied through the surface failure phenomena of specimens.

[0007] In order to achieve the above invention purpose, the technical scheme adopted by the present invention is as follows:

[0008] A test device for the failure characteristics of polymer grouting materials is provided, which includes a testing machine, a fixture, and a CT machine for scanning and obtaining images of the failure characteristics of polymer grouting materials; the fixture includes a lower clamping plate, and a plurality of screw rods are arranged on the lower clamping plate, and a threaded section is arranged at the top of each screw rod; a clamping nut is threadedly connected to the top of each screw rod, a pressure sensor is arranged on the upper end surface of the lower clamping plate, the pressure sensor is electrically connected to an electronic pressure gauge, a stress plate is arranged on the upper end surface of the pressure sensor, and an upper clamping plate with a plurality of mounting through holes is arranged on the top of the stress plate, and the upper clamping plate is slidably matched with the tops of the plurality of screw rods through the plurality of mounting through holes; a plurality of clamping nuts are all located on the top of the upper clamping plate; a polymer grouting material specimen is arranged between the lower clamping plate and the upper clamping plate;

[0009] The testing machine includes a test bench for carrying the fixture and a testing machine indenter for applying a vertically downward pressure to the upper clamping plate.

[0010] Furthermore, both the lower clamping plate and the upper clamping plate are of rectangular structures, the number of the plurality of screw rods is 4, and the 4 screw rods are respectively arranged at the four corners of the lower clamping plate;

[0011] The number of the plurality of mounting through holes is 4, the 4 mounting through holes are respectively arranged at the four corners of the upper clamping plate, and the positions of the 4 mounting through holes match the positions of the 4 screw rods.

[0012] The present invention also provides a test method for the test device of the failure characteristics of polymer grouting materials, which includes:

[0013] Step 1, fix the polymer grouting material specimen, remove the upper clamping plate of the fixture, place the specimen on the stress plate, then install the upper clamping plate, and fix the polymer grouting material specimen on the fixture by tightening the clamping nuts;

[0014] Step 2, obtain the original internal structure image of the polymer grouting material specimen, move the fixture with the polymer grouting material specimen fixed in Step 1 to the CT machine for scanning, and obtain the original internal structure image of the polymer grouting material specimen;

[0015] Step 3: Define three stress stages for the failure characteristics of the polymer grouting material specimens. According to the stress-strain curve of the polymer grouting material, define three different stress stages, namely the initial compression stage, the linear elastic stage, and the stress drop stage;

[0016] Step 4: Obtain the internal structure images of the polymer grouting material specimens in the initial compression stage, the linear elastic stage, and the stress drop stage respectively;

[0017] Step 5: Perform image processing on the original internal structure image of the polymer grouting material specimen in Step 2 and the internal structure images of the polymer grouting material specimen in different stress stages in Step 4, and respectively obtain the cracks, pores, and solid matrices in each image.

[0018] Furthermore, in Step 1, in order to avoid damaging the polymer grouting material specimen during the fixing process and affecting the experimental results, when tightening the clamping nut, the value on the electronic pressure gauge does not exceed 1% of the yield strength of the polymer grouting material specimen.

[0019] Furthermore, in Step 2, the original structure inside the specimen is obtained by CT scanning. Before the test, wipe the surface of the specimen with a towel to avoid affecting the scanning results. In order to comprehensively and integrally observe the crack development mode and process of the specimen during the uniaxial compression process, select the entire specimen as the scanning area.

[0020] Furthermore, in Step 4, the steps for respectively obtaining the internal structure images of the polymer grouting material specimens in the initial compression stage, the linear elastic stage, and the stress drop stage are as follows:

[0021] Step 4.1, Start the testing machine. The indenter of the testing machine moves vertically downward, applying a vertically downward pressure to the upper clamping plate until the value on the electronic pressure gauge is the same as the stress value corresponding to the initial compression stage. Then, the indenter of the testing machine stops moving vertically downward. Rotate 4 clamping nuts respectively until the lower end faces of the 4 clamping nuts are in tight contact with the upper end face of the upper clamping plate and then stop. The indenter of the testing machine moves vertically upward, take out the fixture fixed with the polymer grouting material specimen from the testing machine, and move the fixture to the CT scanner for scanning to obtain the internal structure image of the polymer grouting material specimen in the initial compression stage;

[0022] Step 4.2, Take out the fixture fixed with the polymer grouting material specimen from the CT scanner and transfer the fixture to the test bench. The indenter of the testing machine applies a vertically downward pressure to the polymer grouting material specimen through the upper clamping plate until the value on the electronic pressure gauge is the same as the stress value corresponding to the linear elastic stage. Then, the indenter of the testing machine stops. Rotate 4 clamping nuts to clamp the polymer grouting material specimen with the upper clamping plate, take out the fixture and transfer it to the CT scanner for scanning to obtain the internal structure image of the polymer grouting material specimen in the initial compression stage;

[0023] Step 4.3: Remove the fixture with the high-polymer grouting material specimen from the CT scanner, transfer the fixture to the test bench, and apply a vertically downward pressure to the high-polymer grouting material specimen by the press head of the testing machine through the upper clamping plate until the value on the electronic pressure gauge is the same as the stress value corresponding to the stress drop section. Then, stop the press head of the testing machine, turn 4 clamping nuts to clamp the high-polymer grouting material specimen with the upper clamping plate, remove the fixture and transfer it to the CT scanner for scanning to obtain the internal structure image of the high-polymer grouting material specimen in the stress drop section.

[0024] Furthermore, in Step 5, the method for obtaining cracks, pores, and solid matrix in the image includes the following steps:

[0025] Step 5.1: Arbitrarily select a picture from the images in Step 4, and use the cropping function of ImageJ software to crop the edge part of the selected picture.

[0026] Step 5.2: Add the pores, matrix, and cracks in the selected picture to different collections.

[0027] Step 5.3: Training learning scheme. With the help of the Trainable Weka Segmentation plug-in, extract image features from the input image, represent a set of pixel samples as feature vectors to obtain grayscale value data, and train the learning scheme on a set of pixel samples through the random forest algorithm.

[0028] Step 5.4: Classify the remaining image data in the picture through the trained learning scheme to obtain the segmentation result of the picture.

[0029] Step 5.5: Use threshold segmentation for the segmented picture to obtain a binary image, and obtain the position and size change of the internal cracks of the high-polymer grouting material specimen according to the binary image.

[0030] The beneficial effects of the present invention are as follows:

[0031] Obtain the grayscale image of the internal structure of the high-polymer grouting material specimen during the compression process through CT, solve the problem of specimen compression rebound through a self-made fixture, and obtain the position and size change of the cracks by segmenting the internal grayscale image of the specimen using ImageJ software, making the obtained failure characteristics of the high-polymer grouting material more accurate, and solving the problem that the existing failure characteristic characterization method is unreasonable and one-sided due to studying the failure characteristics of the specimen through the surface failure phenomenon of the specimen. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of the test device for the failure characteristics of the high-polymer grouting material.

[0033] Figure 2Schematic diagram of the structure of the fixture in the test device for the failure characteristics of polymer grouting materials.

[0034] Figure 3 It is the stress-strain curve of the polymer grouting material.

[0035] Figure 4 It is a schematic diagram of the automatic segmentation principle of ImageJ based on machine learning.

[0036] Figures 5 to 7 Comparison chart of the CT scan images and the segmented binary images of the internal structure of the polymer grouting material specimen in different regions.

[0037] Among them, 1. Testing machine; 2. Fixture; 3. Lower clamping plate; 4. Screw; 5. Threaded section; 6. Clamping nut; 7. Pressure sensor; 8. Electronic pressure gauge; 9. Force-bearing plate; 10. Upper clamping plate; 11. Polymer grouting material specimen; 12. Test bench; 13. Pressing head of the testing machine. Specific implementation mode

[0038] The following describes the specific implementation mode of the present invention to facilitate those skilled in the art of this technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation mode. For those of ordinary skill in the art of this technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0039] As Figures 1 to 2 shown, the present invention provides a test device for the failure characteristics of polymer grouting materials, including a testing machine 1, a fixture 2, and a CT machine for scanning and obtaining the failure characteristic images of the polymer grouting materials; the fixture 2 includes a lower clamping plate 3, and a plurality of screws 4 are arranged on the lower clamping plate 3, and a threaded section 5 is arranged at the top of each screw 4; a clamping nut 6 is threadedly connected to the top of each screw 4, a pressure sensor 7 is arranged on the upper end surface of the lower clamping plate 3, the pressure sensor 7 is electrically connected to an electronic pressure gauge 8, a force-bearing plate 9 is arranged on the upper end surface of the pressure sensor 7, an upper clamping plate 10 with a plurality of mounting through holes is arranged on the top of the force-bearing plate 9, and the upper clamping plate 10 is slidably matched with the tops of the plurality of screws 4 through the plurality of mounting through holes; a plurality of clamping nuts 6 are all located on the top of the upper clamping plate 10; the polymer grouting material specimen 11 is arranged between the lower clamping plate 3 and the upper clamping plate 10; As Figure 3As shown, the stress-strain curve of the polymer grouting material specimen 11 in this embodiment includes three stages: the initial compression stage, the linear elastic stage, and the stress drop stage. Specifically, the original strain of 0 corresponds to point o, the strain of 0.02 in the initial compression stage corresponds to point a, the strain of 0.03 in the linear elastic stage corresponds to point b, and the strain of 0.08 in the stress drop stage corresponds to point c. The polymer grouting material specimen 11 is prepared according to the standard, with a size of 70.7×70.7×70.7 mm and a density of 0.4 g / cm3.

[0040] The testing machine 1 includes a test bench 12 for carrying the fixture 2 and a testing machine indenter 13 for applying a vertically downward pressure to the upper clamping plate 10. The testing machine 1 can be a WAW-300 electro-hydraulic servo universal testing machine 1, and the specimen strain rate is taken as 10-4 / s, corresponding to a loading rate of 0.42 mm / s.

[0041] The CT machine can be an industrial CT machine of the Novo Voxel 4000 type, with a scanning voltage of 180 kV, a current of 450 A, a resolution of 35.91 m, a single exposure time of 0.3 s, and a total test time of 0.5 h.

[0042] Specifically, both the lower clamping plate 3 and the upper clamping plate 10 are of rectangular structures. The number of the plurality of screw rods 4 is 4, and the 4 screw rods 4 are respectively arranged at the four corners of the lower clamping plate 3; the number of the plurality of mounting through holes is 4, and the 4 mounting through holes are respectively arranged at the four corners of the upper clamping plate 10, and the positions of the 4 mounting through holes match the positions of the 4 screw rods 4.

[0043] The test method of the test device for the failure characteristics of the polymer grouting material is as follows:

[0044] Step 1: Fix the polymer grouting material specimen 11. Remove the upper clamping plate 10 of the fixture 2, place the specimen on the force-bearing plate 9, and then install the upper clamping plate 10. Fix the polymer grouting material specimen 11 on the fixture 2 by tightening the clamping nut 6. Specifically, in Step 1, in order to avoid damaging the polymer grouting material specimen 11 during the fixing process and affecting the experimental results, when tightening the clamping nut 6, the value on the electronic pressure gauge 8 does not exceed 1% of the yield strength of the polymer grouting material specimen 11.

[0045] Step 2: Obtain the original internal structure image of the polymer grouting material specimen 11. Move the fixture 2 with the polymer grouting material specimen 11 fixed in Step 1 to the CT machine for scanning to obtain the original internal structure image of the polymer grouting material specimen 11. Specifically, in Step 2, the original structure inside the specimen is obtained by CT scanning. Before the test, wipe the surface of the specimen with a towel to avoid affecting the scanning results. In order to comprehensively and integrally observe the crack development mode and process of the specimen during the uniaxial compression process, the entire specimen is selected as the scanning area.

[0046] Step 3: As Figure 3 shown, define three stress stages for the failure characteristics of the polymer grouting material specimen 11. According to the stress-strain curve of the polymer grouting material, define three different stress stages, namely the initial compression stage, the linear elastic stage, and the stress drop stage;

[0047] Step 4: Obtain the internal structure images of the polymer grouting material specimen 11 in the initial compression stage, the linear elastic stage, and the stress drop stage respectively;

[0048] Specifically, in Step 4.1, start the testing machine 1. The testing machine indenter 13 moves vertically downward to apply a vertically downward pressure on the upper clamping plate 10 until the value on the electronic pressure gauge 8 is the same as the stress value corresponding to the initial compression stage. Then, the testing machine indenter 13 stops moving vertically downward. Rotate 4 clamping nuts 6 respectively until the lower end surfaces of the 4 clamping nuts 6 are in tight contact with the upper end surface of the upper clamping plate 10 and then stop. After the testing machine indenter 13 maintains for a period of time, release the pressure. The testing machine indenter 13 moves vertically upward. Take out the fixture 2 fixed with the polymer grouting material specimen 11 from the testing machine 1 and move the fixture 2 to the CT scanner for scanning to obtain the internal structure image of the polymer grouting material specimen 11 in the initial compression stage;

[0049] Step 4.2, take out the fixture 2 fixed with the polymer grouting material specimen 11 from the CT scanner and transfer the fixture 2 to the test bench 12. The testing machine indenter 13 applies a vertically downward pressure on the polymer grouting material specimen 11 through the upper clamping plate 10 until the value on the electronic pressure gauge 8 is the same as the stress value corresponding to the linear elastic stage. Then, the testing machine indenter 13 stops. Rotate 4 clamping nuts 6 to clamp the polymer grouting material specimen 11 with the upper clamping plate 10. After the testing machine indenter 13 maintains for a period of time, release the pressure. The testing machine indenter 13 moves vertically upward. Take out the fixture 2 and transfer it to the CT scanner for scanning to obtain the internal structure image of the polymer grouting material specimen 11 in the initial compression stage.

[0050] Step 4.3, take out the fixture 2 fixed with the polymer grouting material specimen 11 from the CT scanner and transfer the fixture 2 to the test bench 12. The testing machine indenter 13 applies a vertically downward pressure on the polymer grouting material specimen 11 through the upper clamping plate 10 until the value on the electronic pressure gauge 8 is the same as the stress value corresponding to the stress drop stage. Then, the testing machine indenter 13 stops. Rotate 4 clamping nuts 6 to clamp the polymer grouting material specimen 11 with the upper clamping plate 10. After the testing machine indenter 13 maintains for a period of time, release the pressure. The testing machine indenter 13 moves vertically upward. Take out the fixture 2 and transfer it to the CT scanner for scanning to obtain the internal structure image of the polymer grouting material specimen 11 in the stress drop stage.

[0051] Step 5: Perform image processing on the original internal structure image of the polymer grouting material sample 11 in Step 2 and the internal structure images of the polymer grouting material sample 11 at different stress stages in Step 4, and respectively obtain the cracks, pores, and solid matrix in each image.

[0052] Specifically, as Figure 4 shown, in Step 5.1, arbitrarily select a picture from the images in Step 4, and use the cropping function of ImageJ software to crop the edge part of the selected picture;

[0053] Step 5.2, add the pores, matrix, and cracks of the selected picture to different collections;

[0054] Step 5.3, training learning scheme, use the Trainable Weka Segmentation plugin to extract image features from the input image, represent a set of pixel samples as feature vectors to obtain grayscale value data, and train the learning scheme on a set of pixel samples through the random forest algorithm;

[0055] Specifically, in Steps 5.1 to 5.3, randomly and manually select the pixels of three different phases of pores, matrix, and cracks on the picture, extract their grayscale values, and mark the pixels as different types of collections according to the grayscale value range; the number of phases such as pores, matrix, and cracks selected on each picture is not less than 20; use the pixel samples, combined with the random forest algorithm to construct a learning scheme, and the finally formed learning scheme is: pixels with a grayscale value greater than or equal to 110 are the matrix, pixels with a grayscale value greater than 60 and less than 110 are pores, and pixels with a grayscale value less than 60 are cracks.

[0056] Step 5.4, classify the remaining image data in the picture through the trained learning scheme to obtain the segmentation result of the picture;

[0057] Step 5.5, perform threshold segmentation on the segmented picture to obtain a binary image, and obtain the position and size change of the internal cracks of the polymer grouting material sample according to the binary image.

[0058] Figures 5 to 7 are the CT scan images and the segmented binary images of the internal structure of the polymer grouting material sample 11 at three different stress stages. Figures 5 to 7 The upper part of the figure in is the CT scan image, and the lower part is the segmented binary image. Before compression, that is, at point o, there is an obvious pore structure inside the polymer grouting material sample 11. As the number of compression increases, the black area inside the polymer grouting material sample 11 gradually increases, and cracks first appear in some areas. When compressed to point c, the cracks are basically connected.

[0059] The gray-scale image of the internal structure of the polymer grouting material specimen 11 during the compression process is obtained by CT. The problem of specimen compression and rebound is solved by the self-made fixture 2. The position and size changes of the cracks are obtained by using the ImageJ software to segment the gray-scale image inside the specimen, making the obtained failure characteristics of the polymer grouting material more accurate, and solving the problem that the existing failure characteristic characterization method is unreasonable and one-sided due to studying the failure characteristics of the specimen through the surface failure phenomenon of the specimen.

Claims

1. A test method for a test device of the failure characteristics of a polymer grouting material, characterized in that, The test device for the failure characteristics of polymer grouting materials includes a testing machine, a fixture, and a CT scanner for scanning and obtaining images of the failure characteristics of polymer grouting materials. The fixture includes a lower clamping plate, on which multiple screw rods are provided, and each screw rod has a threaded section at the top. A clamping nut is threadedly connected to the top of each screw rod. A pressure sensor is provided on the upper end surface of the lower clamping plate, and the pressure sensor is electrically connected to an electronic pressure gauge. A force-bearing plate is provided on the upper end surface of the pressure sensor, and an upper clamping plate with multiple mounting through holes is provided on the top of the force-bearing plate. The upper clamping plate is slidably matched with the tops of the multiple screw rods through the multiple mounting through holes. All the clamping nuts are located on the top of the upper clamping plate. The polymer grouting material specimen is arranged between the lower clamping plate and the upper clamping plate. The testing machine includes a test bench for carrying the fixture and a testing machine indenter for applying a vertically downward pressure to the upper clamping plate. Both the lower clamping plate and the upper clamping plate are rectangular structures. The number of the multiple screw rods is 4, and the 4 screw rods are respectively arranged at the four corners of the lower clamping plate. The number of the multiple mounting through holes is 4, and the 4 mounting through holes are respectively arranged at the four corners of the upper clamping plate, and the positions of the 4 mounting through holes match the positions of the 4 screw rods. The test method includes the following steps: Step 1: Fix the polymer grouting material specimen. Remove the upper clamping plate of the fixture, place the specimen on the force-bearing plate, then install the upper clamping plate, and fix the polymer grouting material specimen on the fixture by tightening the clamping nuts. Step 2: Obtain the original internal structure image of the polymer grouting material specimen. Move the fixture with the polymer grouting material specimen fixed in Step 1 to the CT scanner for scanning to obtain the original internal structure image of the polymer grouting material specimen. Step 3: Define three stress stages of the failure characteristics of the polymer grouting material specimen. Define three different stress stages according to the stress-strain curve of the polymer grouting material. The three different stages are the initial compression stage, the linear elastic stage, and the stress drop stage. Step 4: Respectively obtain the internal structure images of the polymer grouting material specimen in the initial compression stage, the linear elastic stage, and the stress drop stage. Step 5: Perform image processing on the original internal structure image of the polymer grouting material specimen in Step 2 and the internal structure images of the polymer grouting material specimen in different stress stages in Step 4 to respectively obtain cracks, pores, and solid matrices in each image.

2. The test method of the test device for the failure characteristics of the polymer grouting material according to claim 1, characterized in that In Step 1, when tightening the clamping nuts, the value on the electronic pressure gauge does not exceed 1% of the yield strength of the polymer grouting material specimen.

3. The test method of the test device for the failure characteristics of the polymer grouting material according to claim 1, characterized in that, In Step 2, before the CT scanner scans, wipe the surface of the polymer grouting material specimen clean. The scanning area of the CT scanner is the entire polymer grouting material specimen.

4. The test method of the test device for the failure characteristics of the polymer grouting material according to claim 1, characterized in that, In Step 4, respectively obtaining the internal structure images of the polymer grouting material specimen in the initial compression stage, the linear elastic stage, and the stress drop stage includes the following steps: Step 4.1: Start the testing machine. The indenter of the testing machine moves vertically downward to apply a vertically downward pressure on the upper clamping plate until the value on the electronic pressure gauge is the same as the stress value corresponding to the initial compression section. Then, the indenter of the testing machine stops moving vertically downward. Rotate the 4 clamping nuts respectively until the lower end faces of the 4 clamping nuts are in tight contact with the upper end face of the upper clamping plate and then stop. The indenter of the testing machine moves vertically upward. Take out the fixture fixed with the polymer grouting material sample from the testing machine and move the fixture to the CT scanner to obtain the internal structure image of the polymer grouting material sample in the initial compression section. Step 4.2: Take out the fixture fixed with the polymer grouting material sample from the CT scanner and transfer the fixture to the test bench. The indenter of the testing machine applies a vertically downward pressure on the polymer grouting material sample through the upper clamping plate until the value on the electronic pressure gauge is the same as the stress value corresponding to the linear elastic section. Then, the indenter of the testing machine stops. Rotate the 4 clamping nuts to clamp the polymer grouting material sample with the upper clamping plate. Take out the fixture and transfer it to the CT scanner to obtain the internal structure image of the polymer grouting material sample in the initial compression section. Step 4.3: Take out the fixture fixed with the polymer grouting material sample from the CT scanner and transfer the fixture to the test bench. The indenter of the testing machine applies a vertically downward pressure on the polymer grouting material sample through the upper clamping plate until the value on the electronic pressure gauge is the same as the stress value corresponding to the stress drop section. Then, the indenter of the testing machine stops. Rotate the 4 clamping nuts to clamp the polymer grouting material sample with the upper clamping plate. Take out the fixture and transfer it to the CT scanner to obtain the internal structure image of the polymer grouting material sample in the stress drop section.

5. The test method of the test device for the failure characteristics of the polymer grouting material according to claim 1, characterized in that, In Step 5, the methods for obtaining cracks, pores, and solid matrices in the images include the following steps: Step 5.1: Arbitrarily select one of the images in Step 4 and cut off the edge part of the selected image. Step 5.2: Add the pores, matrices, and cracks in the selected image to different collections. Step 5.3: Train the learning scheme. With the help of the Trainable Weka Segmentation plugin, extract image features from the input image, represent a set of pixel samples as feature vectors to obtain gray value data, and train the learning scheme on a set of pixel samples through the random forest algorithm. Step 5.4: Classify the remaining image data in the picture through the trained learning scheme to obtain the segmentation result of the picture. Step 5.5: Use threshold segmentation on the segmented picture to obtain a binary image, and obtain the position and size changes of the internal cracks of the polymer grouting material sample according to the binary image.

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