Deep rock fracture toughness testing system and method

Abstract

The deep rock fracture toughness test system and method provided by the embodiment of the present application, wherein the system comprises a test sample, a vacuum pressure chamber and a host computer; the vacuum pressure chamber is provided with a confining pressure loading device, an axial pressure loading device, an electric resistance testing device and a camera device; the host computer is used to control the confining pressure loading device and the axial pressure loading device to load pressure on the test sample, so that the initial crack on the test sample is expanded; the host computer is also used to acquire the electric resistance change of the test sample and the expansion image of the initial crack when the initial crack on the test sample is expanded, and determine the fracture toughness of the test sample according to the electric resistance change of the test sample and the expansion image of the initial crack. The small change of the crack of the test sample is detected by monitoring the electric resistance change of the test sample, and the accurate crack change data is obtained by combining the image in the crack expansion process, so that the detection accuracy of the crack is improved, and the calculation accuracy of the rock fracture toughness is ensured.

Description

Technical Field

[0001] This invention belongs to the field of rock physical property testing technology, and particularly relates to a deep rock fracture toughness testing system and method. Background Technology

[0002] Fracture toughness is an important parameter for evaluating the mechanical properties of rocks (including crack initiation, propagation, and fracture mechanisms). Therefore, corresponding rock specimens are usually prepared, and the fracture toughness of the rock is calculated by detecting the changes in cracks on the rock specimens during the loading process under pressure.

[0003] In existing technologies, crack detection on specimens typically employs ultrasonic testing and image detection methods. Ultrasonic testing primarily calculates fracture toughness by detecting and analyzing waveform changes caused by pressure loading. However, the waveform analysis process is complex and easily affected by mechanical waves generated by the device itself, resulting in low detection accuracy. Image detection, limited by the performance of the imaging equipment, has low sensitivity to minute changes in cracks, leading to lower detection accuracy. Summary of the Invention

[0004] In view of this, the present invention provides a deep rock fracture toughness testing system and method, which aims to solve the problem of low accuracy in crack detection of specimens in existing testing systems.

[0005] A first aspect of the present invention provides a deep rock fracture toughness testing system, comprising:

[0006] Test specimens, vacuum pressure chamber, and host computer;

[0007] The test specimen has an initial crack; the test specimen is placed at a predetermined position in the vacuum pressure chamber; the vacuum pressure chamber is equipped with a confining pressure loading device, an axial pressure loading device, a resistance testing device, and a camera device;

[0008] The confining pressure loading device, axial pressure loading device, resistance testing device, and camera device are all connected to the host computer; the resistance testing device is used to measure the resistance of the test specimen; the camera device is used to capture images of the initial crack expansion of the test specimen.

[0009] The host computer is used to control the confining pressure loading device and the axial pressure loading device to apply pressure to the test specimen, so that the initial cracks on the test specimen will expand.

[0010] The host computer is also used to acquire the resistance change and the expansion image of the initial crack on the test specimen when the initial crack on the test specimen expands, and to determine the fracture toughness of the test specimen based on the resistance change and the expansion image of the initial crack.

[0011] In some possible implementations, the host computer is specifically used for:

[0012] Based on the change in resistance of the test specimen, the propagation process of the initial crack is divided into multiple propagation stages;

[0013] Based on the expansion images at the beginning and end of each expansion stage, the displacement field distribution data of the test specimen within each expansion stage are determined.

[0014] The fracture toughness of the test specimen was determined based on the displacement field distribution data of each expansion stage.

[0015] In some possible implementations, the host computer is specifically used for:

[0016] Based on the loading pressure of the confining pressure loading device and the axial pressure loading device, the propagation process of the initial crack is divided into multiple loading stages;

[0017] Based on the extended images at the beginning and end of each loading stage, the displacement field distribution data of the test specimen within each extended stage are determined.

[0018] Based on the extended images at the start and end times of each loading phase

[0019] The correction vector is determined based on the resistance change of the test specimen in each expansion stage;

[0020] The fracture toughness of the test specimen was determined based on the correction vector and displacement field distribution data.

[0021] In some possible implementations, the device also includes: an environmental control device;

[0022] The environmental control device is connected to the host computer; the host computer is used to adjust the environment of the test specimen in the vacuum pressure chamber according to the environmental control device.

[0023] In some possible implementations, the environmental control device includes: a temperature sensor, a pressure sensor, and a heating device;

[0024] Temperature sensors, pressure sensors, and heating devices are all connected to the host computer.

[0025] In some possible implementations, the host computer is also used for:

[0026] Acquire temperature data collected by the temperature sensor and pressure data collected by the pressure sensor;

[0027] The resistance influence factor is determined based on the temperature data collected by the temperature sensor and the pressure data collected by the pressure sensor.

[0028] The resistance variation of the test specimen is corrected based on the resistance influence factor.

[0029] In some possible implementations, the axial pressure loading device includes a static pressure loading device and a dynamic pressure loading device.

[0030] In some possible implementations, the device also includes: a specimen replacement chamber;

[0031] The volume of the specimen replacement chamber is equal to the volume of the test specimen; the specimen replacement chamber is located on one side of the vacuum pressure chamber; the specimen replacement chamber is equipped with a sealable external window and an internal window; the specimen replacement chamber is equipped with a preheating device; the vacuum pressure chamber is also equipped with a replacement robot arm.

[0032] A first aspect of the present invention provides a method for testing the fracture toughness of deep rocks, comprising:

[0033] The test specimen is placed at a predetermined position in the vacuum pressure chamber;

[0034] Control the pressure applied to the test specimen by the confining pressure loading device and the axial pressure loading device;

[0035] Obtain images of the resistance change and initial crack expansion of the test specimen;

[0036] The fracture toughness of the test specimen is determined based on the resistance change and the propagation image of the initial crack.

[0037] In some possible implementations, the method also includes:

[0038] Open the external window of the specimen replacement chamber and place the first specimen into the specimen replacement chamber;

[0039] Seal the external window and heat the first specimen in the specimen replacement chamber according to the preheating device so that the temperature of the first specimen is the same as that of the test specimen in the vacuum pressure chamber;

[0040] Open the inner window of the specimen replacement chamber, and replace the first specimen with the test specimen using the replacement robot arm according to the vacuum pressure chamber.

[0041] The internal window of the sealed test specimen replacement chamber.

[0042] This invention provides a deep rock fracture toughness testing system and method. The system includes a test specimen, a vacuum pressure chamber, and a host computer. The test specimen has an initial crack. The test specimen is positioned at a predetermined location within the vacuum pressure chamber. The vacuum pressure chamber is equipped with a confining pressure loading device, an axial pressure loading device, a resistance testing device, and a camera. The host computer controls the confining pressure loading device and the axial pressure loading device to apply pressure to the test specimen, causing the initial crack on the test specimen to expand. The host computer also acquires images of the resistance change and the expansion of the initial crack on the test specimen when the initial crack expands, and determines the fracture toughness of the test specimen based on these images. By monitoring the resistance change of the specimen to detect minute changes in the crack, and combining this with images of the crack expansion process, accurate crack change data is obtained, thereby improving the crack detection accuracy and ensuring the accuracy of rock fracture toughness calculation. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the deep rock fracture toughness testing system provided in an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of the structure of a deep rock fracture toughness testing system provided in another embodiment of the present invention;

[0046] Figure 3 This is a flowchart illustrating the implementation of the deep rock fracture toughness test method provided in this embodiment of the invention. Detailed Implementation

[0047] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0048] Figure 1 This is a schematic diagram of the deep rock fracture toughness testing system provided in an embodiment of the present invention. Figure 1As shown, in this embodiment, the deep rock fracture toughness testing system includes: a test specimen 11, a vacuum pressure chamber 12, and a host computer 13;

[0049] The test specimen 11 has an initial crack; the test specimen 11 is set at a predetermined position in the vacuum pressure chamber 12; the vacuum pressure chamber 12 is equipped with a confining pressure loading device, an axial pressure loading device, a resistance testing device, and a camera device;

[0050] The confining pressure loading device, axial pressure loading device, resistance testing device, and camera device are all connected to the host computer 13; the resistance testing device is used to measure the resistance of the test specimen 11; the camera device is used to capture images of the initial crack expansion of the test specimen 11.

[0051] The host computer 13 is used to control the confining pressure loading device and the axial pressure loading device to apply pressure to the test specimen 11, so that the initial crack on the test specimen 11 will expand.

[0052] The host computer 13 is also used to acquire the resistance change and the image of the initial crack expansion of the test specimen 11 when the initial crack on the test specimen 11 expands, and to determine the fracture toughness of the test specimen 11 based on the resistance change and the image of the initial crack expansion of the test specimen 11.

[0053] In this embodiment of the invention, the test specimen 11 can be a semi-circular specimen, a cuboid specimen, etc., and is not limited thereto. The confining pressure loading device applies confining pressure to the test specimen 11 in the vacuum pressure chamber 12 by filling the vacuum pressure chamber 12 with inert gas. The loading direction of the axial pressure loading device is on the same straight line as the initial fracture. The confining pressure loading device and the axial pressure loading device can be controlled according to the needs of the experiment to apply different confining pressures and axial pressures to the test specimen 11 respectively, thereby completing the test process of the rock specimen.

[0054] In this embodiment of the invention, the camera device is positioned to capture the initial crack of the test specimen 11 in order to capture the expansion process of the initial crack.

[0055] In this embodiment of the invention, the resistance testing device can be specifically set on the side of the rock specimen where the initial fracture exists, and the test electrodes are set on both sides of the initial fracture to test the surface resistance of the surface where the initial fracture is located. For example, the resistance testing device can use the four-probe method to measure the resistance of the test specimen, that is, with the center point of the initial fracture as the center, two probe electrodes are set on each side of the initial fracture, for a total of four probes. Among them, the two probes closer to the initial fracture measure the potential difference on both sides of the fracture, and the two probes farther away from the initial fracture measure the current. The resistance can be calculated based on the measured potential difference and current.

[0056] As the initial crack expands, the resistance of the specimen will also increase as the crack expands. The higher the resistance detection accuracy of the resistance testing device, the more sensitive it is to changes in the crack.

[0057] By capturing images of the initial crack propagation, the location of microscopic crack propagation in rocks can be identified. However, limited by factors such as the pixel count and resolution of the imaging device, and the recognition error of the crack identification model, image recognition has poor sensitivity and cannot accurately determine the extent of crack propagation. While resistance testing is simple in structure and highly accurate, it can only determine the extent of crack propagation and cannot reveal specific information such as the location of deformation. Therefore, this invention detects minute changes in cracks by monitoring changes in the resistance of the specimen, and combines this with images of the crack propagation process to obtain accurate crack change data, thereby improving the accuracy of crack detection and ensuring the accuracy of rock fracture toughness calculation.

[0058] In some embodiments, the host computer 13 is specifically used to: divide the propagation process of the initial crack into multiple propagation stages based on the resistance change of the test specimen 11; determine the displacement field distribution data of the test specimen 11 in each propagation stage based on the propagation image at the start time and the propagation image at the end time of each propagation stage; and determine the fracture toughness of the test specimen 11 based on the displacement field distribution data of each propagation stage.

[0059] In this embodiment of the invention, since image recognition is less sensitive to expansion, the degree of expansion can be used as a division method. Images of corresponding frames are extracted from the captured video, and then the expansion images of the crack are obtained by comparing the images before and after the expansion stage. This ensures that whenever the crack of the specimen changes to a certain extent, the change can be accurately captured, thus ensuring the accuracy of the fracture toughness calculation.

[0060] In some embodiments, the host computer 13 is specifically used to: divide the initial crack propagation process into multiple loading stages according to the loading pressure of the confining pressure loading device and the axial pressure loading device; determine the displacement field distribution data of the test specimen 11 in each propagation stage according to the propagation images at the beginning and end of each loading stage; determine the correction vector according to the propagation images at the beginning and end of each loading stage; determine the fracture toughness of the test specimen 11 according to the resistance change of the test specimen 11 in each propagation stage; and determine the fracture toughness of the test specimen 11 according to the correction vector and the displacement field distribution data.

[0061] In this embodiment of the invention, for each loading stage, the extended image at the beginning time and the extended image at the end time of each loading stage are compared to obtain a comparison image. Then, the comparison image is divided into multiple regions, and the deformation generated in each region is quantized into a deformation vector through a corresponding recognition model. The deformation vectors of each region together constitute the displacement field distribution shown by the specimen.

[0062] In this embodiment of the invention, after obtaining the displacement field distribution, in order to remove the recognition error of image recognition, a correction vector can be constructed based on the resistance change to correct the deformation vector, thereby improving the accuracy of fracture toughness calculation. For example, if the deformation characteristic value of the displacement field distribution obtained by image recognition at a certain loading stage is 'a', that is, the identified specimen deformation is small, while the deformation characteristic value obtained by resistivity calculation is 'b', that is, the measured deformation characteristic value is large, then a correction factor (ba) / a can be calculated, and each deformation vector can be corrected according to the correction factor.

[0063] In some embodiments, the apparatus further includes: an environmental control device; the environmental control device is connected to a host computer 13; the host computer 13 is used to adjust the environment of the test specimen 11 in the vacuum pressure chamber 12 according to the environmental control device.

[0064] In this embodiment of the invention, the environment of deep rocks is usually different from that of shallow rocks. In order to avoid the influence of environmental factors on fracture toughness testing, an environmental control device can be set in the vacuum pressure chamber 12 to adjust the environment in the vacuum pressure chamber 12 to be the same as the actual deep underground environment.

[0065] In some embodiments, the environmental control device includes a temperature sensor, a pressure sensor, and a heating device; the temperature sensor, pressure sensor, and heating device are all connected to the host computer 13.

[0066] In this embodiment of the invention, the heating device can specifically be a resistance heater, uniformly arranged on the inner wall of the vacuum pressure chamber 12. The environmental control device controls the heating device to heat the vacuum pressure chamber 12 to a preset temperature based on the real-time temperature measured by the temperature sensor. Simultaneously, the environmental control device controls the entry and exit of inert gas based on the real-time pressure measured by the pressure sensor, i.e., adjusts the confining pressure applied by the confining pressure loading device, thereby making the environment of the specimen approximate a deep underground environment.

[0067] In some embodiments, the host computer 13 is further configured to: acquire temperature data collected by the temperature sensor and pressure data collected by the pressure sensor; determine the resistance influence factor based on the temperature data collected by the temperature sensor and the pressure data collected by the pressure sensor; and correct the resistance change of the test specimen 11 based on the resistance influence factor.

[0068] In this embodiment of the invention, the resistance testing device is usually susceptible to the effects of temperature and pressure. Therefore, before applying axial pressure to the crack, the resistance testing device needs to be calibrated according to the temperature and pressure to avoid inaccurate measurements caused by temperature and pressure changes.

[0069] In some embodiments, the axial pressure loading device includes a static pressure loading device and a dynamic pressure loading device.

[0070] In this embodiment of the invention, the static pressure loading device may be a pressure jack, a pressure steel support device, etc., and is not limited thereto. The axial pressure applied by the static pressure loading device increases slowly and continuously. The dynamic pressure loading device may include a spring impactor, a bullet, a track, etc. The bullet is accelerated by the spring impactor and impacts the corresponding position of the specimen along the track, completing the impact loading process of the pressure.

[0071] Figure 2 This is a schematic diagram of a deep rock fracture toughness testing system provided in another embodiment of the present invention. Figure 2 As shown, in some embodiments, the device further includes: a specimen replacement chamber 21; the volume of the specimen replacement chamber 21 is equal to the volume of the test specimen 11; the specimen replacement chamber 21 is disposed on one side of the vacuum pressure chamber 12; the specimen replacement chamber is provided with a sealable external window 22 and an internal window 23; a preheating device is provided in the specimen replacement chamber 21; and a replacement robot is also provided in the vacuum pressure chamber 12.

[0072] The opening and closing of the external window 22 and the internal window 23, as well as the driving of the robotic arm replacement, can all be achieved through a drive motor and a controller. Specifically, a controller can be set up within the deep rock fracture toughness testing system. The controller has a corresponding control program. When the user clicks the open / close / replace button on the controller, the controller drives the external window 22, the internal window 23, or the robotic arm replacement according to the corresponding control program instructions.

[0073] Figure 3 This is a flowchart illustrating the implementation of the deep rock fracture toughness testing method provided in this embodiment of the invention. Figure 3 As shown, in some embodiments, the deep rock fracture toughness testing method is applied to the aforementioned deep rock fracture toughness testing system, and the method includes:

[0074] S310, the test specimen 11 is placed at the predetermined position in the vacuum pressure chamber 12;

[0075] S320, controls the confining pressure loading device and the axial pressure loading device to apply pressure to the test specimen 11;

[0076] S330, acquire images of the resistance change and initial crack expansion of test specimen 11;

[0077] S340. Based on the resistance change and the initial crack propagation image of the test specimen 11, determine the fracture toughness of the test specimen 11.

[0078] In some embodiments, the method further includes:

[0079] Open the external window 22 of the specimen replacement chamber 21 and place the first specimen into the specimen replacement chamber 21;

[0080] The external window 22 is sealed, and the first specimen in the specimen replacement chamber 21 is heated by the preheating device so that the temperature of the first specimen is the same as that of the test specimen 11 in the vacuum pressure chamber 12.

[0081] Open the inner window 23 of the specimen replacement chamber 21, and replace the first specimen with the test specimen 11 according to the replacement robot of the vacuum pressure chamber 12;

[0082] The inner window 23 of the sealed test specimen replacement chamber.

[0083] Testing the fracture toughness of rocks usually requires multiple tests, each with different pressure loading methods. This necessitates constantly replacing the specimens, and each time a new specimen is replaced, the vacuum reaction chamber needs to be repressurized and heated. This process is cumbersome and inefficient.

[0084] In this embodiment of the invention, by setting up a specimen replacement chamber 21, the specimens required for the next test are heated to the corresponding temperature in advance in the specimen replacement chamber 21. After the previous test is completed, the inner window is opened, and the two specimens can be replaced by the set robotic arm. There is no need to repressurize and reheat, which effectively improves the testing efficiency.

[0085] It should be noted that, Figure 1 and Figure 2 The structure of the deep rock fracture toughness test system shown is only an example of the present invention. For different types and shapes of specimens, those skilled in the art can make adaptive adjustments to the system structure (for example, adjust the structure of the specimen replacement chamber or the support structure of the test specimen 11). These adaptive adjustments should all be included within the protection scope of the present invention.

[0086] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0087] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A deep rock fracture toughness testing system, characterized in that, include: Test specimens, vacuum pressure chamber, and host computer; The test specimen has an initial crack; the test specimen is placed at a predetermined position in the vacuum pressure chamber; the vacuum pressure chamber is equipped with a confining pressure loading device, an axial pressure loading device, a resistance testing device, and a camera device; The confining pressure loading device, the axial pressure loading device, the resistance testing device, and the camera device are all connected to the host computer; the resistance testing device is used to measure the resistance of the test specimen; the camera device is used to capture images of the initial crack expansion of the test specimen. The host computer is used to control the confining pressure loading device and the axial pressure loading device to apply pressure to the test specimen, so that the initial cracks on the test specimen will expand. The host computer is also used to acquire the resistance change of the test specimen and the expansion image of the initial crack when the initial crack on the test specimen expands; to divide the expansion process of the initial crack into multiple expansion stages based on the resistance change of the test specimen; to determine the displacement field distribution data of the test specimen in each expansion stage based on the expansion image at the beginning and end of each expansion stage; and to determine the fracture toughness of the test specimen based on the displacement field distribution data of each expansion stage. Alternatively, the host computer may also be used to: divide the propagation process of the initial crack into multiple loading stages based on the loading pressure of the confining pressure loading device and the axial pressure loading device; determine the displacement field distribution data of the test specimen in each propagation stage based on the propagation images at the beginning and end of each loading stage; determine a correction vector based on the resistance change of the test specimen in each propagation stage; and determine the fracture toughness of the test specimen based on the correction vector and the displacement field distribution data.

2. The deep rock fracture toughness testing system according to claim 1, characterized in that, The system also includes: an environmental control device; The environmental control device is connected to the host computer; the host computer is used to adjust the environment of the test specimen in the vacuum pressure chamber according to the environmental control device.

3. The deep rock fracture toughness testing system according to claim 2, characterized in that, The environmental control device includes: a temperature sensor, a pressure sensor, and a heating device; The temperature sensor, the pressure sensor, the heating device, and the pressure control device are all connected to the host computer.

4. The deep rock fracture toughness testing system according to claim 3, characterized in that, The host computer is also used for: Acquire temperature data collected by the temperature sensor and pressure data collected by the pressure sensor; The resistance influence factor is determined based on the temperature data collected by the temperature sensor and the pressure data collected by the pressure sensor. The resistance variation of the test specimen is corrected according to the resistance influence factor.

5. The deep rock fracture toughness testing system according to claim 1, characterized in that, The axial pressure loading device includes a static pressure loading device and a dynamic pressure loading device.

6. The deep rock fracture toughness testing system according to any one of claims 1-5, characterized in that, The system also includes: a specimen replacement chamber; The volume of the specimen replacement chamber is equal to the volume of the test specimen; the specimen replacement chamber is located on one side of the vacuum pressure chamber; the specimen replacement chamber is equipped with a sealable external window and an internal window; the specimen replacement chamber is equipped with a preheating device; and the vacuum pressure chamber is also equipped with a replacement robot arm.

7. A method for testing the fracture toughness of deep rocks using the deep rock fracture toughness testing system described in any one of claims 1-6, characterized in that, The method includes: The test specimen is placed at a predetermined position in the vacuum pressure chamber; The confining pressure loading device and the axial pressure loading device are controlled to apply pressure to the test specimen; Obtain images of the resistance change and initial crack expansion of the test specimen; The fracture toughness of the test specimen is determined based on the resistance change and the initial crack propagation image.

8. The method for testing the fracture toughness of deep rocks according to claim 7, characterized in that, The method further includes: Open the external window of the specimen replacement chamber and place the first specimen into the specimen replacement chamber; The external window is sealed, and the first specimen in the specimen replacement chamber is heated by the preheating device so that the temperature of the first specimen is the same as that of the test specimen in the vacuum pressure chamber. Open the inner window of the specimen replacement chamber, and replace the first specimen with the test specimen according to the replacement robot in the vacuum pressure chamber; Seal the internal window of the specimen replacement chamber.

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