Method for monitoring expansion path of internal crack of rock under freezing and thawing action

Abstract

The invention discloses a method for monitoring a crack propagation path in a rock under freezing and thawing effects, and relates to the technical field of rock detection, and the method comprises the following steps: obtaining a rock sample from geotechnical engineering in a cold region; performing rock sample preparation on the rock sample to obtain a rock sample to be detected; the method comprises the following steps: scanning a rock sample to be detected by using a microscopic CT scanner to obtain the scale and spatial distribution of natural cracks in the rock sample; placing the rock sample to be detected into a vacuum water saturation instrument for water saturation to obtain a saturated rock sample; putting the saturated rock sample into a freeze-thaw cycle testing machine for a freeze-thaw cycle test, scanning the saturated rock sample after the freeze-thaw cycle by adopting a micro-CT scanner after each freeze-thaw cycle is completed to obtain crack change characteristics, repeating the freeze-thaw cycle test until the saturated rock sample after the freeze-thaw cycle generates macrocracks, and ending the freeze-thaw cycle test; and analyzing multiple microscopic CT scanning results to obtain rock sample structure change characteristics, and determining a rock sample internal crack path extension rule. According to the invention, the observation precision and accuracy can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of rock detection, and particularly to a method for monitoring the propagation path of internal cracks in rocks under freeze-thaw action. Background Art

[0002] Rock is a heterogeneous multiphase composite structural material, containing a large number of joints, fissures (i.e., cracks), microcracks, micropores and other defects inside, and they are randomly distributed. When rocks are subjected to external loads such as load, temperature, and chemistry, the fine defects dispersed inside the rocks continuously evolve, gradually developing from disordered distribution to ordered distribution, thus forming macroscopic cracks. Eventually, the macroscopic cracks converge along a certain azimuth to form large cracks, leading to overall instability and causing rock disasters. During the freeze-thaw cycle of rocks, the phase change of water and ice causes damage to the rock structure, resulting in the initiation, propagation, and penetration of internal cracks in the rocks, and finally leading to rock failure.

[0003] During the repeated freeze-thaw cycles in nature, the cracks inside the rocks will expand, develop, and increase, and finally lead to the destruction of the rock mass structure, thus triggering freeze-thaw disasters such as erosion, landsliding, and even landslides of rock slopes, frost heaving cracking and instability of tunnel rock masses, frost heaving uplift and thaw settlement of roadbeds and building foundations, etc., causing large-scale damage or abnormal operation of cold region projects, resulting in huge economic losses. The freeze-thaw action has become one of the important factors affecting the construction and operation of geotechnical engineering in cold regions. Therefore, it is of great significance to study the changes in the mesoscopic structure of rocks under freeze-thaw action.

[0004] At present, most of the monitoring methods for the propagation path of internal cracks in rocks under freeze-thaw action use industrial CT to scan rock samples after different freeze-thaw cycles, and then obtain the propagation law of macroscopic fissures inside the rock samples. However, during the freeze-thaw process of the rock samples, in addition to macroscopic fissures, a certain number of microscopic fissures are also generated, and traditional industrial CT usually cannot accurately determine the scale and accurate position of the microscopic fissures. Therefore, the current monitoring methods for the propagation path of internal cracks in rocks under freeze-thaw action have problems of low observation accuracy and accuracy. Summary of the Invention

[0005] The purpose of the present application is to provide a method for monitoring the propagation path of internal cracks in rocks under freeze-thaw action, which can improve the observation accuracy and accuracy.

[0006] To achieve the above purpose, the present application provides the following solutions:

[0007] The present application provides a method for monitoring the propagation path of internal cracks in rocks under freeze-thaw action, and the method for monitoring the propagation path of internal cracks in rocks under freeze-thaw action includes:

[0008] Obtain a rock sample from a geotechnical engineering project in a cold region; the rock sample is a rock that needs to be detected and is affected by freeze-thaw;

[0009] Performing rock sample preparation on the rock sample to obtain a rock sample to be tested;

[0010] Scanning the rock sample to be tested by a micro-CT scanner to obtain the scale and spatial distribution of natural cracks inside the rock sample;

[0011] The rock sample to be tested is placed in a vacuum water saturation instrument to be saturated with water to obtain a water-saturated rock sample;

[0012] The saturated rock sample is placed in a freeze-thaw cycle test machine for a freeze-thaw cycle test. After each freeze-thaw cycle, the saturated rock sample after the freeze-thaw cycle is scanned by a micro CT scanner to obtain crack change characteristics. The freeze-thaw cycle test is repeated until macro cracks are generated in the saturated rock sample after the freeze-thaw cycle, and the freeze-thaw cycle test is terminated;

[0013] Analyze multiple micro-CT scanning results to obtain the structural change characteristics of the rock sample and determine the expansion law of the crack path inside the rock sample; the multiple micro-CT scanning results include micro-CT scanning results obtained by using a micro-CT scanner to scan the saturated rock sample after each freeze-thaw cycle.

[0014] Optionally, performing rock sample preparation on the rock sample to obtain a rock sample to be tested specifically includes:

[0015] The rock samples are processed into cubic rock samples with a side length of 100 mm or cylindrical rock samples with a diameter of 50 mm and a height of 100 mm. After the processing is completed, rock samples with obvious defects are removed, and more than or equal to 5 rock samples with basically the same appearance are retained as rock samples to be tested.

[0016] Optionally, the method of scanning the rock sample to be tested with a micro CT scanner to obtain the scale and spatial distribution of natural cracks inside the rock sample specifically includes:

[0017] Scanning the rock sample to be tested by a micro-CT scanner, reconstructing the three-dimensional CT image by using the image automatic acquisition and processing software provided by the micro-CT scanner, and obtaining the result of the micro-CT three-dimensional image reconstruction;

[0018] Based on the results of micro-CT three-dimensional image reconstruction, the scale and spatial distribution of natural cracks inside the rock sample were obtained.

[0019] Optionally, when a micro-CT scanner is used to scan the rock sample to be tested, the scanning interval is less than or equal to 1 mm.

[0020] Optionally, the resolution of the micro CT scanner is less than or equal to 5 μm.

[0021] Optionally, placing the rock sample to be tested in a vacuum water saturation instrument to saturate the rock sample with water to obtain a water-saturated rock sample specifically includes:

[0022] After the rock sample to be tested is placed in the vacuum water saturation instrument, pure water is injected into the vacuum water saturation instrument until the water surface covers the upper surface of the rock sample to be tested by more than or equal to 3 cm. After the water injection is completed, the top cover of the vacuum water saturation instrument is fixed;

[0023] Start the vacuum water saturation instrument. When the vacuum water saturation instrument adopts the vacuum method to saturate the rock sample to be tested with water, the water level in the water saturation container of the vacuum water saturation instrument is higher than the rock sample to be tested. The reading of the vacuum pressure gauge of the vacuum water saturation instrument is the air pressure value of the location of the vacuum water saturation instrument until no bubbles are generated, but the air pumping time is greater than or equal to 4 hours. After the air pumping is completed, the top cover of the vacuum water saturation instrument is loosened, and the rock sample to be tested that has been vacuum-evacuated is still placed in the water saturation container and left to stand for 4 hours under atmospheric pressure.

[0024] Optionally, scanning the saturated rock sample after freeze-thaw cycles using a micro-CT scanner specifically includes:

[0025] A micro-CT scanner is used to scan the saturated rock sample after freeze-thaw cycles, and the three-dimensional CT image is reconstructed using the automatic image acquisition and processing software provided by the micro-CT scanner to obtain the micro-CT scanning result; the micro-CT scanning result is used to obtain the crack change characteristics.

[0026] Optionally, when the freeze-thaw cycle tester is used to perform a freeze-thaw cycle test, the freezing and thawing temperatures are -20°C and 20°C, respectively, and the freezing and thawing times are 8 hours, respectively.

[0027] Optionally, the macro crack is a crack with a length exceeding 5 mm.

[0028] According to the specific embodiments provided in this application, this application has the following technical effects:

[0029] The present application provides a method for monitoring the propagation path of internal cracks in rocks under freeze-thaw action. Rock samples suitable for micro-CT scanning are prepared. The rock samples are scanned using a micro-CT scanner to obtain the scale and spatial distribution of natural cracks inside the rock samples. A water-saturated rock sample suitable for freeze-thaw cycle tests is obtained using a vacuum water saturation instrument. The water-saturated rock sample is subjected to freeze-thaw cycle tests using a freeze-thaw cycle test machine. After each freeze-thaw cycle is completed, the water-saturated rock sample after the freeze-thaw cycle is scanned using a micro-CT scanner to obtain the crack change characteristics. The freeze-thaw cycle test is repeated until macroscopic cracks occur in the water-saturated rock sample after the freeze-thaw cycle, at which point the freeze-thaw cycle test ends. By analyzing the results of multiple micro-CT scans, the structural change characteristics of the rock sample are obtained, and the propagation law of the internal crack path of the rock sample is determined, thereby realizing the monitoring of the propagation path of internal cracks in rocks under freeze-thaw action. Since the accuracy of micro-CT is much higher than that of traditional industrial CT, observing the internal and external cracks of the rock sample before and after freeze-thaw using micro-CT can improve the observation accuracy and accuracy. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 It is a schematic flow chart of a method for monitoring the propagation path of internal cracks in rocks under freeze-thaw action provided by an embodiment of the present application;

[0032] Figure 2 It is a flow chart of a method for monitoring the propagation of internal cracks in rocks under freeze-thaw action provided by the present application. Detailed Embodiments

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0034] The purpose of the present application is to provide a method for monitoring the propagation path of internal cracks in rocks under freeze-thaw action, which can improve the observation accuracy and accuracy.

[0035] In order to make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below in conjunction with the drawings and specific embodiments.

[0036] like Figure 1 As shown, the present application provides a method for monitoring the crack propagation path inside a rock under freeze-thaw action, comprising:

[0037] Step 101: Obtain rock samples from geotechnical engineering in cold regions; the rock samples are rocks that are affected by freeze-thaw and need to be tested.

[0038] Step 102: Prepare the rock sample to obtain a rock sample to be tested.

[0039] The step 102 specifically includes:

[0040] The rock samples were processed into cubic rock samples with a side length of 100 mm or cylindrical rock samples with a diameter of 50 mm and a height of 100 mm. After processing, the rock samples with obvious defects were removed, and more than or equal to 5 rock samples with basically the same appearance were retained as the rock samples to be tested.

[0041] Step 103: Scan the rock sample to be tested using a micro-CT scanner to obtain the scale and spatial distribution of natural cracks inside the rock sample.

[0042] The step 103 specifically includes:

[0043] A micro-CT scanner is used to scan the rock sample to be tested, and the three-dimensional CT image is reconstructed using the image automatic acquisition and processing software provided by the micro-CT scanner to obtain the result of micro-CT three-dimensional image reconstruction.

[0044] Based on the results of micro-CT three-dimensional image reconstruction, the scale and spatial distribution of natural cracks inside the rock sample were obtained.

[0045] Wherein, when a micro-CT scanner is used to scan the rock sample to be tested, the scanning interval is less than or equal to 1 mm.

[0046] The resolution of the micro-CT scanner is less than or equal to 5 μm.

[0047] Step 104: Place the rock sample to be tested into a vacuum water saturation instrument to saturate it with water, thereby obtaining a saturated rock sample.

[0048] The step 104 specifically includes:

[0049] After placing the rock sample to be tested into the vacuum water saturation instrument, pure water is injected into the vacuum water saturation instrument until the water surface covers the upper surface of the rock sample to be tested by more than or equal to 3 cm. After the water injection is completed, the top cover of the vacuum water saturation instrument is fixed.

[0050] Start the vacuum water saturation instrument. When the vacuum water saturation instrument uses the vacuum method to saturate the rock sample with water, the water level in the water saturation container of the vacuum water saturation instrument is higher than the rock sample to be tested. The reading of the vacuum pressure gauge of the vacuum water saturation instrument is the air pressure value where the vacuum water saturation instrument is located, until no bubbles are generated, but the air extraction time is greater than or equal to 4 hours. After the air extraction is completed, loosen the top cover of the vacuum water saturation instrument, and the rock sample to be tested that has been vacuum-extracted is still placed in the water saturation container and left to stand for 4 hours under atmospheric pressure.

[0051] Step 105: Place the saturated rock sample in a freeze-thaw cycle test machine for a freeze-thaw cycle test. After each freeze-thaw cycle, use a micro CT scanner to scan the saturated rock sample after the freeze-thaw cycle to obtain crack change characteristics. Repeat the freeze-thaw cycle test until macro cracks appear in the saturated rock sample after the freeze-thaw cycle, and the freeze-thaw cycle test is terminated.

[0052] Among them, macro cracks are cracks with a length exceeding 5 mm.

[0053] In step 105, a micro-CT scanner is used to scan the saturated rock sample after the freeze-thaw cycle, which specifically includes:

[0054] A micro-CT scanner is used to scan the saturated rock samples after freeze-thaw cycles, and the three-dimensional CT image is reconstructed using the automatic image acquisition and processing software provided by the micro-CT scanner to obtain the micro-CT scanning results; the micro-CT scanning results are used to obtain the crack change characteristics.

[0055] In step 105, when a freeze-thaw cycle test is performed using a freeze-thaw cycle tester, the freezing and thawing temperatures are respectively -20°C and 20°C, and the freezing and thawing times are respectively 8 hours.

[0056] Step 106: Analyze multiple micro-CT scanning results to obtain the structural change characteristics of the rock sample and determine the expansion law of the crack path inside the rock sample; the multiple micro-CT scanning results include micro-CT scanning results obtained by scanning the saturated rock sample after each freeze-thaw cycle using a micro-CT scanner.

[0057] The technical solution of this application is described below with a specific embodiment:

[0058] like Figure 2 As shown, the present application provides a method for monitoring the expansion of cracks inside rocks under freeze-thaw action, that is, a method for monitoring the expansion path of cracks inside rocks under freeze-thaw action, which can realize the monitoring and precise positioning of the expansion of cracks inside rocks under freeze-thaw action. The method has a simple principle and strong operability. The method for monitoring the expansion of cracks inside rocks under freeze-thaw action provided by the present application includes the following steps:

[0059] S1: rock sample preparation and micro-CT scanning. The three-dimensional CT image is reconstructed using the image automatic acquisition and processing software of the micro-CT scanner to obtain the scale and spatial distribution of natural cracks inside the rock sample.

[0060] The rock sample is a rock that needs to be tested and is affected by freeze-thaw, and the rock sample does not disintegrate, swell, muddy, or melt when it comes into contact with water. The rock sample is taken from geotechnical engineering in cold regions (i.e., geotechnical engineering in cold regions). Geotechnical engineering in cold regions is in a freeze-thaw cycle under the influence of seasonal changes and day and night alternations, so the method of the present application can truly reflect the natural environment of the rock and soil in cold regions.

[0061] First, the rock to be tested is processed into a cubic rock block with a side length of 100 mm or a cylindrical rock sample with a diameter of 50 mm and a height of 100 mm. After processing, the rock samples with obvious defects are removed, and no less than 5 rock samples with basically the same appearance are retained as test rock samples.

[0062] Secondly, the rock sample prepared above is scanned by micro-CT (i.e. micro-CT scanner), with a scanning interval of no more than 1 mm and a resolution of no more than 5 μm, to obtain the scale and spatial distribution of the original cracks inside the rock sample (i.e. the scale and spatial distribution of the natural cracks inside the rock sample).

[0063] The rock samples prepared above are scanned by micro-CT, and the scanning interval is no more than 1 mm.

[0064] This step S1 is to prepare the rock sample and perform micro-CT scanning on the rock sample that meets the test requirements, and use the image automatic acquisition and processing software of the micro-CT scanner to reconstruct the three-dimensional CT image to determine the scale and spatial distribution of the original cracks inside the rock (that is, the scale and spatial distribution of the natural cracks inside the rock sample). Wherein, when the rock sample is scanned by micro-CT, the slice thickness is not greater than 1mm (that is, when scanning by micro-CT, the scanning interval is not greater than 1mm), and the resolution of CT is not greater than 5μm; according to the result of the micro-CT three-dimensional image reconstruction, the scale and spatial distribution characteristics of the cracks inside the rock sample (that is, the scale and spatial distribution of the natural cracks inside the rock sample) can be obtained; the main function of obtaining the scale and spatial distribution of the original cracks inside the rock is to show where the cracks inside the rock sample start to expand after freezing and thawing, and how large the expansion scale is.

[0065] S2: Put the rock sample (i.e. the rock sample that meets the test requirements) into a vacuum water saturation instrument to saturate it with water, and obtain a saturated rock sample.

[0066] Among them, the rock samples that meet the test requirements are cylinders with no obvious defects, a diameter of 50mm and a height of 100mm. When the rock samples are saturated with water by vacuum method, the water level in the saturated container should be higher than the rock sample, and the reading of the vacuum pressure gauge should be the local air pressure value until no bubbles are generated, but the vacuum pumping time should not be less than 4h. The vacuum pumped rock samples should be placed in the original container and left to stand for 4h under atmospheric pressure (i.e., loosen the top cover of the vacuum saturation instrument and soak the rock samples in the saturated container for another 4h).

[0067] In this embodiment, step S2 specifically includes:

[0068] First, place the rock sample to be tested into the vacuum water saturation instrument, and inject pure water into the water saturation instrument. The water surface should be at least 3 cm above the upper surface of the rock. After the water injection is completed, fix the top cover of the water saturation instrument as required.

[0069] Secondly, start the vacuum water saturation instrument, set the vacuum gauge pressure to 0.1MPa, and the pumping time to 4h. After the pumping is completed, loosen the top cover of the vacuum water saturation instrument to allow the rock sample to continue to be immersed in the water saturation instrument for 4h.

[0070] S3: Place the saturated rock sample in a freeze-thaw cycle test machine for a freeze-thaw cycle test. After each freeze-thaw cycle, perform a micro-CT scan on the rock sample. Use the automatic image acquisition and processing software of the micro-CT scanner to reconstruct the three-dimensional CT image and obtain the crack change characteristics (i.e., crack space change characteristics). Repeat the above freeze-thaw cycle test until macroscopic cracks visible to the naked eye appear in the rock sample, and the monitoring ends (i.e., the freeze-thaw cycle test ends).

[0071] Among them, macro cracks are cracks longer than 5mm. When the rock sample has cracks longer than 5mm, the test is stopped. During the freeze-thaw cycle test of the rock sample, the freezing and melting temperatures are -20℃ and 20℃ respectively, and the freezing and melting time are 8h respectively. The sign of the end of the freeze-thaw cycle test of the rock sample is the appearance of macro cracks visible to the naked eye.

[0072] Crack change characteristics are also called crack change characteristics, which include the size of the crack, the spatial expansion direction, the starting position of the new crack, etc.

[0073] S4: Analyze the multiple micro-CT scanning results (i.e., micro-CT scanning data) obtained in step S3 to obtain the structural change characteristics of the rock sample and determine the propagation law of the crack path inside the rock sample (i.e., the real-time crack propagation law).

[0074] Among them, the change characteristics (i.e., rock sample structure change characteristics) include the size of the crack, the spatial expansion direction, the starting position of the new crack, etc.

[0075] The expansion law of internal crack paths in rock samples includes the size of fissures, the spatial expansion direction, the starting position of new fissures, the number of newly added fissures, etc.

[0076] This step S4 analyzes the micro-CT scan data, that is, analyzes data such as the number, size, and expansion direction of internal cracks in the rock sample after different freeze-thaw cycles, so as to obtain the characteristics of the structural changes of the rock sample, determine the expansion law of internal cracks in the rock sample, and provide theoretical guidance for the calculation of rock mass mechanical parameters and slope safety protection of open-pit mine slopes. The micro-CT data can accurately determine the spatial distribution of the crack expansion scale and position after each freeze-thaw cycle. Among them, the relationship between the spatial distribution of the crack expansion scale and position after each freeze-thaw cycle and the expansion law of internal crack paths in the rock sample is: according to the change characteristics of internal fissures in the rock sample after each freeze-thaw cycle, analyze the overall change of the fissure path before and after the test, and then obtain the expansion law of the fissure path.

[0077] In this article, specific examples are used to elaborate on the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and its core idea of this application; at the same time, for those of ordinary skill in the art, based on the idea of this application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be construed as a limitation to this application.

Claims

1. A method for monitoring the crack propagation path inside rock under freeze-thaw action, characterized in that: The method for monitoring the crack propagation path inside the rock under the freeze-thaw action includes: Obtain rock samples from geotechnical engineering projects in cold regions; the rock samples are rocks that are affected by freeze-thaw and need to be tested; Performing rock sample preparation on the rock sample to obtain a rock sample to be tested; Scanning the rock sample to be tested by a micro-CT scanner to obtain the scale and spatial distribution of natural cracks inside the rock sample; The rock sample to be tested is placed in a vacuum water saturation instrument to be saturated with water to obtain a water-saturated rock sample; The saturated rock sample is placed in a freeze-thaw cycle test machine for a freeze-thaw cycle test. After each freeze-thaw cycle, the saturated rock sample after the freeze-thaw cycle is scanned by a micro CT scanner to obtain crack change characteristics. The freeze-thaw cycle test is repeated until macro cracks are generated in the saturated rock sample after the freeze-thaw cycle, and the freeze-thaw cycle test is terminated; Analyze multiple micro-CT scanning results to obtain the structural change characteristics of the rock sample and determine the expansion law of the crack path inside the rock sample; the multiple micro-CT scanning results include micro-CT scanning results obtained by using a micro-CT scanner to scan the saturated rock sample after each freeze-thaw cycle.

2. The method for monitoring the crack propagation path of rock under freeze-thaw conditions according to claim 1, characterized in that: The rock sample is prepared to obtain a rock sample to be tested, specifically comprising: The rock samples are processed into cubic rock samples with a side length of 100 mm or cylindrical rock samples with a diameter of 50 mm and a height of 100 mm. After the processing is completed, rock samples with obvious defects are removed, and more than or equal to 5 rock samples with basically the same appearance are retained as rock samples to be tested.

3. The method for monitoring the crack propagation path of rock under freeze-thaw conditions according to claim 1, characterized in that: The method of scanning the rock sample to be tested by a micro-CT scanner to obtain the scale and spatial distribution of natural cracks inside the rock sample specifically includes: Scanning the rock sample to be tested by a micro-CT scanner, reconstructing the three-dimensional CT image by using the image automatic acquisition and processing software provided by the micro-CT scanner, and obtaining the result of the micro-CT three-dimensional image reconstruction; Based on the results of micro-CT three-dimensional image reconstruction, the scale and spatial distribution of natural cracks inside the rock sample were obtained.

4. The method for monitoring the crack propagation path of rock under freeze-thaw conditions according to claim 1, characterized in that: When the rock sample to be tested is scanned by a micro-CT scanner, the scanning interval is less than or equal to 1 mm.

5. The method for monitoring the crack propagation path of rock under freeze-thaw conditions according to claim 1, characterized in that: The resolution of the micro CT scanner is less than or equal to 5 μm.

6. The method for monitoring the crack propagation path of rock under freeze-thaw conditions according to claim 1, characterized in that: The rock sample to be tested is placed in a vacuum water saturation instrument to be saturated with water to obtain a saturated rock sample, specifically comprising: After the rock sample to be tested is placed in the vacuum water saturation instrument, pure water is injected into the vacuum water saturation instrument until the water surface covers the upper surface of the rock sample to be tested by more than or equal to 3 cm. After the water injection is completed, the top cover of the vacuum water saturation instrument is fixed; Start the vacuum water saturation instrument. When the vacuum water saturation instrument adopts the vacuum method to saturate the rock sample to be tested with water, the water level in the water saturation container of the vacuum water saturation instrument is higher than the rock sample to be tested. The reading of the vacuum pressure gauge of the vacuum water saturation instrument is the air pressure value of the location of the vacuum water saturation instrument until no bubbles are generated, but the air pumping time is greater than or equal to 4 hours. After the air pumping is completed, the top cover of the vacuum water saturation instrument is loosened, and the rock sample to be tested that has been vacuum-evacuated is still placed in the water saturation container and left to stand for 4 hours under atmospheric pressure.

7. The method for monitoring the crack propagation path of rock under freeze-thaw conditions according to claim 1, characterized in that: The scanning of the saturated rock sample after the freeze-thaw cycle by using a micro CT scanner specifically includes: A micro-CT scanner is used to scan the saturated rock sample after freeze-thaw cycles, and the three-dimensional CT image is reconstructed using the automatic image acquisition and processing software provided by the micro-CT scanner to obtain the micro-CT scanning result; the micro-CT scanning result is used to obtain the crack change characteristics.

8. The method for monitoring the crack propagation path of rock under freeze-thaw conditions according to claim 1, characterized in that: When the freeze-thaw cycle tester is used to perform the freeze-thaw cycle test, the freezing and thawing temperatures are -20°C and 20°C, respectively, and the freezing and thawing times are 8 hours, respectively.

9. The method for monitoring the crack propagation path inside rock under freeze-thaw conditions according to claim 1, characterized in that: The macro cracks are cracks with a length exceeding 5 mm.

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