Method and device for determining strain field of coal and rock specimens under load

Abstract

The present invention provides a method and device for determining the strain field of a loaded coal and rock specimen. The method includes: obtaining a first scanned image of the coal and rock specimen in an unloaded state, as well as a plurality of second scanned images and stress-strain curves of the coal and rock specimen in a continuous loading state, thereby determining the relative elastic modulus of each voxel in the plurality of second scanned images according to the plurality of second scanned images and stress-strain curves, and determining the strain of each voxel in the plurality of second scanned images according to the first scanned image and the plurality of second scanned images. Furthermore, according to the relative elastic modulus and strain of each voxel in the plurality of second scanned images, the strain energy density of each voxel in the plurality of second scanned images is determined, so as to determine the spatial continuous strain field of the coal and rock specimen based on the plurality of second scanned images and the strain energy density of each voxel in the plurality of second scanned images. Thus, the spatial continuous quantification of the strain field of the loaded coal and rock specimen can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal and rock, and in particular to a method and device for determining the strain field of a loaded coal and rock specimen. Background Art

[0002] Rock burst is a dynamic phenomenon of sudden and severe damage caused by the instantaneous release of elastic deformation energy accumulated in the coal (rock) around the coal mine roadway or working face. As a complex organic rock, coal and rock belong to natural heterogeneous materials. Affected by the complex geological evolution background of coal formation period, sedimentary system and tectonic movement, the parting and fractures are randomly distributed in the coal matrix. In the prevention and control of rock burst disasters, for coal and rock with strong burst proneness, this non-uniform characteristic and internal interaction will lead to an extremely complex energy distribution state inside the coal and rock under mining stress. The energy distribution state inside the coal and rock plays a key role in evaluating or predicting the mechanical behavior of coal and rock. Especially for coal and rock with strong burst proneness under complex stress states, it is the basis for understanding the dynamic failure mechanism of coal and rock. Therefore, continuously quantifying the internal energy distribution of the loaded coal and rock in space is crucial for analyzing the damage evolution process of coal and rock and preventing coal and rock dynamic disasters.

[0003] At present, the methods for obtaining the energy field of specimens mainly include theoretical calculation and experimental testing. However, the theoretical calculation method requires that the complexity of the specimen cannot be too high, otherwise the analysis of the specimen energy field cannot be obtained, and the applicable range is limited. Moreover, due to the simplification of the specimen, the obtained energy field distribution is quite different from the actual situation. In the experimental testing method, the uniaxial compression test method is only applicable to standard specimens, and the obtained strain energy density is the average density of the entire specimen, which cannot characterize the distribution state of the strain energy inside the specimen. The energy field measurement method based on acoustic emission monitoring is more applicable to homogeneous specimens, but has poor applicability to heterogeneous materials such as coal and rock, and the obtained energy field distribution is discontinuous. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems in the related technologies to some extent. For this purpose, the first object of the present invention is to propose a method for determining the strain field of a loaded coal and rock specimen, so as to realize the combination of CT (Computed Tomography) technology and DVC (Digital Volume Correlation) technology to quantitatively characterize the spatial continuous distribution of the internal strain field of coal and rock, especially coal and rock with strong burst proneness, during the entire loading process.

[0005] The second object of the present invention is to propose a device for determining the strain field of a loaded coal and rock specimen. The third object of the present invention is to propose an electronic device.

[0006] The fourth object of the present invention is to provide a computer-readable storage medium.

[0007] The fifth object of the present invention is to provide a computer program product.

[0008] To achieve the above object, an embodiment of the first aspect of the present invention provides a method for determining the strain field of a loaded coal and rock specimen, including:

[0009] Obtaining a first scanned image of the coal and rock specimen and the coal and rock specimen in an unloaded state, as well as a plurality of second scanned images and stress-strain curves of the coal and rock specimen in a continuous loading state; determining the relative elastic modulus of each voxel in the plurality of second scanned images according to the plurality of second scanned images and the stress-strain curves, and determining the strain of each voxel in the plurality of second scanned images according to the first scanned image and the plurality of second scanned images;

[0010] Determining the strain energy density of each voxel in the plurality of second scanned images according to the relative elastic modulus and strain of each voxel in the plurality of second scanned images, and determining the spatial continuous strain field of the coal and rock specimen based on the plurality of second scanned images and the strain energy density of each voxel in the plurality of second scanned images.

[0011] To achieve the above object, an embodiment of the second aspect of the present invention provides a device for determining the strain field of a loaded coal and rock specimen, including:

[0012] An acquisition module, configured to acquire a first scanned image of the coal and rock specimen and the coal and rock specimen in an unloaded state, as well as a plurality of second scanned images and stress-strain curves of the coal and rock specimen in a continuous loading state;

[0013] A determination module, configured to determine the relative elastic modulus of each voxel in the plurality of second scanned images according to the plurality of second scanned images and the stress-strain curves, and determine the strain of each voxel in the plurality of second scanned images according to the first scanned image and the plurality of second scanned images;

[0014] A first processing module, configured to determine the strain energy density of each voxel in the plurality of second scanned images according to the relative elastic modulus and strain of each voxel in the plurality of second scanned images, and determine the spatial continuous strain field of the coal and rock specimen based on the plurality of second scanned images and the strain energy density of each voxel in the plurality of second scanned images.

[0015] To achieve the above object, an embodiment of the third aspect of the present invention provides an electronic device, which includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein, the memory stores instructions executable by the at least one processor, and when the instructions are executed by the at least one processor, the at least one processor is enabled to execute the method for determining the strain field of a loaded coal and rock specimen in the foregoing first aspect.

[0016] To achieve the above object, an embodiment of the fourth aspect of the present invention provides a computer-readable storage medium storing computer instructions, and the computer instructions are used to cause the computer to execute the method for determining the strain field of a loaded coal and rock specimen in the foregoing first aspect.

[0017] To achieve the above object, an embodiment of the fifth aspect of the present invention provides a computer program product, including a computer program, and when the computer program is executed by a processor, the method for determining the strain field of a loaded coal and rock specimen in the foregoing first aspect is implemented.

[0018] The technical solutions provided by the embodiments of the present invention have the following beneficial effects:

[0019] By acquiring a coal and rock specimen and a first scanned image of the coal and rock specimen in an unloaded state, as well as a plurality of second scanned images and stress-strain curves of the coal and rock specimen in a continuous loading state, thereby determining the relative elastic modulus of each voxel in the plurality of second scanned images according to the plurality of second scanned images and stress-strain curves, and determining the strain of each voxel in the plurality of second scanned images according to the first scanned image and the plurality of second scanned images, and further determining the strain energy density of each voxel in the plurality of second scanned images according to the relative elastic modulus and strain of each voxel in the plurality of second scanned images, so as to determine the spatial continuous strain field of the coal and rock specimen based on the plurality of second scanned images and the strain energy density of each voxel in the plurality of second scanned images. Thus, it is possible to combine CT technology and DVC technology to spatially continuously quantify the relative energy distribution inside the coal and rock, which is crucial for analyzing coal and rock, especially for evaluating or predicting the mechanical behavior of strongly impact-prone coal and rock, and also has important significance for analyzing the damage evolution process of coal and rock and preventing coal and rock dynamic disasters.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Description of the Drawings

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of the embodiments in conjunction with the drawings, wherein:

[0022] Figure 1Schematic flowchart of a method for determining the strain field of a loaded coal and rock specimen provided by an embodiment of the present invention;

[0023] Figure 2 Schematic flowchart of a method for determining the strain field of a loaded coal and rock specimen in a scenario provided by an embodiment of the present invention;

[0024] Figure 3 Schematic result diagram of a device for determining the strain field of a loaded coal and rock specimen provided by an embodiment of the present invention;

[0025] Figure 4 Schematic structural diagram of an electronic device provided by an embodiment of the present invention. Detailed implementation manners

[0026] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as a limitation of the present invention.

[0027] Currently, the methods for obtaining the energy field of specimens mainly include theoretical calculation and experimental testing. In theoretical calculation, it is usually necessary to simplify the actual specimen to convert it into a planar theoretical model and simple three-dimensional theoretical models such as thin plates, cylinders, and disks, and then solve it by solid mechanics methods (CN107194038B). The theoretical calculation method requires that the complexity of the specimen cannot be very high, otherwise the analytical solution of the energy field of the specimen cannot be obtained, and the applicable range is limited. Moreover, due to the simplification of the specimen, the obtained energy field distribution is quite different from the actual situation.

[0028] In the experimental testing method, one type is to conduct a uniaxial compression test on the specimen to be detected, obtain the axial stress value - axial strain curve corresponding to the specimen, and calculate the area enclosed by the curve and the strain axis to obtain the strain energy density of the specimen to be detected (CN115326565A). This type of method is only applicable to standard specimens, and the obtained strain energy density is the average density of the entire specimen, and cannot characterize the distribution state of the strain energy inside the specimen. The other type is to monitor the acoustic emission during the compression process of the specimen, and monitor the dissipation state of the strain energy inside the specimen through the distribution of acoustic emission events and the change trend of the number of events, and calculate the energy field distribution in the specimen based on this (CN103969121B). The test accuracy of this type of method depends on the positioning accuracy of acoustic emission events. Since it is assumed that the propagation speed of stress waves is constant in the acoustic emission positioning algorithm, this type of method is more applicable to homogeneous specimens and less applicable to heterogeneous materials such as coal and rock. Moreover, the energy field distribution obtained by this type of method is based on discrete acoustic emission events, so the obtained energy field distribution is discontinuous.

[0029] In addition, in the past few decades, X-ray computed tomography technology has been successfully applied to the research of coal and rock materials, and the internal material properties can be observed non-destructively in three dimensions. However, these methods focus on visualizing the distribution of primary fractures inside coal and rock by using their scanning imaging principle and three-dimensional reconstruction technology at the microscopic and mesoscopic scales, and do not involve the continuous spatial distribution of the internal energy field during the whole loading process of coal and rock.

[0030] The DVC technology can quantitatively compare the CT image volumes of any sample before and after induced changes. At present, the DVC technology has been successfully applied to the detection of strain fields in artificial composite materials such as concrete and layered rocks, but it is less applied in exploring the continuous spatial quantification of the three-dimensional energy field of coal and rock, especially strongly impact-prone coal and rock, under loading. In view of the above problems, the embodiments of the present invention provide a method for determining the strain field of a loaded coal and rock specimen, so as to realize the combination of CT technology and DVC technology, and quantitatively characterize the continuous spatial distribution of the internal strain field of coal and rock, especially strongly impact-prone coal and rock, during the whole loading process, and overcome the disadvantages that the theoretical calculation method requires that the complexity of the specimen cannot be very high, otherwise the analytical solution of the energy field of the specimen cannot be obtained, the applicable range is limited, and because the specimen is simplified, the obtained energy field distribution is quite different from the actual situation, the single-axis compression test method is only applicable to standard specimens, and the obtained strain energy density is the average density of the whole specimen and cannot characterize the distribution state of the strain energy inside the specimen, and the energy field measurement method based on acoustic emission monitoring has poor applicability to inhomogeneous materials such as coal and rock, and the obtained energy field distribution is discontinuous.

[0031] The following describes the method and device for determining the strain field of a loaded coal and rock specimen according to the embodiments of the present invention with reference to the drawings.

[0032] Figure 1 It is a schematic flow chart of a method for determining the strain field of a loaded coal and rock specimen provided by the embodiments of the present invention.

[0033] As Figure 1 shown, the method for determining the strain field of the loaded coal and rock specimen includes the following steps: Step 101, obtain a coal and rock specimen, a first scanning image of the coal and rock specimen in an unloaded state, and a plurality of second scanning images and stress-strain curves of the coal and rock specimen in a continuous loading state. Among them, the coal and rock specimen can be a coal and rock specimen in any coal and rock area to be studied, and the specifications of the coal and rock specimen are not limited in this embodiment and can be any set specifications. For example, the φ50mm×100mm specification, where φ represents the diameter of a circle, × represents multiplication, connecting the two values of the diameter and the thickness, and the φ50mm×100mm specification represents a cylindrical object with a diameter of 50 millimeters and a thickness of 100 millimeters, and so on.

[0034] Optionally, the coal-rock specimen and the first scanned image of the coal-rock specimen in the unloaded state, as well as multiple second scanned images and stress-strain curves of the coal-rock specimen in the continuous load state, can be obtained through the following steps:

[0035] Step 1011: Obtain a sampling sample in the area to be studied using a preset sampling method, and process the sampling sample according to the preset specimen specifications to obtain a coal-rock specimen.

[0036] Among them, the area to be studied can be any coal-rock area to be studied, and this embodiment does not limit this.

[0037] Among them, the preset sampling method can be any sampling method, that is, this embodiment does not limit the setting of the preset sampling method. Optionally, the preset sampling method can be set according to manual experience. For example, the preset sampling method can be set as the sampling method of drilling cores or the sampling method of test blocks. Or, the preset sampling method can also be dynamically adjusted according to actual application requirements, and this embodiment does not limit this.

[0038] As a possible implementation, a sampling sample can be obtained in the area to be studied using the sampling method of drilling cores or the sampling method of test blocks. Among them, the diameter of the drilled core meets the preset threshold condition, and the specifications of the test block meet the preset specification condition.

[0039] Among them, the preset threshold condition and the preset specification condition can be any conditions, that is, this embodiment does not limit the setting of the preset threshold condition and the preset specification condition. Optionally, the preset threshold condition and the preset specification condition can be set according to manual experience. For example, the preset threshold condition can be set to be greater than 70 mm. At this time, the diameter of the drilled core meeting the preset threshold condition means that the diameter of the drilled core is greater than 70 mm. The preset specification condition can be set to be greater than 250 mm × 250 mm × 250 mm. At this time, the specifications of the test block meeting the preset specification condition means that the specifications of the test block are greater than 250 mm × 250 mm × 250 mm. Or, the preset threshold condition and the preset specification condition can also be dynamically adjusted according to actual application requirements, and this embodiment does not limit this.

[0040] Among them, the preset specimen specifications can be of any specifications, that is, there is no limitation in this embodiment for the setting of the preset specimen specifications. Optionally, the preset specimen specifications can be set according to manual experience. For example, the preset specimen specifications can be set to the above-mentioned φ50mm×100mm specifications, or the preset specimen specifications can also be dynamically adjusted according to actual application requirements, and this is not limited in this embodiment. As an example, sample collection can be carried out first: in the area to be studied, sampling samples are collected by the sampling method of drilling coal cores or the sampling method of test blocks. Among them, the diameter of the drilled coal core should be greater than 70mm, and the size of the test block should be greater than 250mm×250mm×250mm. If there are other research needs, samples of other specifications can also be collected. At the same time, the collected sampling samples should meet the requirement that their height direction is perpendicular to the bedding plane and there should be no obvious cracks. Then, specimen preparation is carried out based on the sampling samples: the collected sampling samples are processed into cylindrical specimens. For the convenience of comparison, it is advisable to use the φ50mm×100mm specifications. If there are other requirements, specimens of other specifications can also be processed, and the shape of the specimens is not limited.

[0041] Step 1012, perform the first CT scan on the coal and rock specimen in the unloaded state to obtain the first scan image.

[0042] Performing the first CT scan on the coal and rock specimen in the unloaded state means that after obtaining the coal and rock specimen, the first CT scan is performed on the coal and rock specimen without applying any load, that is, after obtaining the coal and rock specimen, the obtained coal and rock specimen is directly subjected to the first CT scan. Optionally, the first scan image obtained by performing the first CT scan on the coal and rock specimen in the unloaded state can be used as a reference for the loaded state of the coal and rock specimen.

[0043] As an example, after specimen preparation is completed, the first CT scan can be carried out: the prepared coal and rock specimen is placed flat on the CT scanning device for scanning in the unloaded state (the first CT scan) to obtain the first scan image.

[0044] Step 1013: Apply a continuous load to the coal-rock specimen, and conduct a second CT scan on the coal-rock specimen while it is under the continuous load to obtain multiple second scan images and a stress-strain curve. Among them, the scanning parameters of the second CT scan are the same as those of the first CT scan. It should be noted that both the multiple second scan images and the stress-strain curve are of the coal-rock specimen under the continuous load state, that is, the multiple second scan images are the scan images of the coal-rock specimen under the continuous load state, and the stress-strain curve is the stress-strain curve of the coal-rock specimen under the continuous load state. Optionally, the lowest load in the continuous load can be applied to the coal-rock specimen first, and a second CT scan is conducted on the coal-rock specimen while it is under this lowest load state to obtain a second scan image, and then the load is increased sequentially and the second CT scan is conducted to obtain at least one second scan image. Thus, after applying the above continuous load to the coal-rock specimen and completing the second CT scan, multiple second scan images and a stress-strain curve of the coal-rock specimen under the above continuous load state can be obtained. As an example, after the first CT scan is completed, the load can be applied: apply the first-stage uniaxial or triaxial load (load state 1) to the prepared coal-rock specimen and keep it. The load application device can adopt a universal testing machine or other self-made equipment. The load application stage is selected according to the research purpose, and it is recommended to be not less than 30% of the uniaxial compressive strength (UCS) of the coal-rock specimen. Then conduct the second CT scan: conduct a second CT scan on the coal-rock specimen that maintains the load state to obtain the second scan image of load state 1. Among them, the scanning parameters of the second CT scan must be the same as those of the first CT scan. Thus, by repeating the load application and the second CT scan, the second scan images of all required load states and the stress-strain curve during the loading process of the coal-rock specimen can be obtained.

[0045] In addition, in some embodiments, the coal-rock specimen and the first scan image of the coal-rock specimen in the unloaded state, as well as multiple second scan images and a stress-strain curve of the coal-rock specimen in the continuous load state, can also be obtained through various other public, legal, and compliant methods. For example, the coal-rock specimen and the first scan image of the coal-rock specimen in the unloaded state, as well as multiple second scan images and a stress-strain curve of the coal-rock specimen in the continuous load state, can be obtained from other devices storing them through network transmission or physical copy, etc. This embodiment does not limit this.

[0046] In some embodiments, after obtaining the first scanned image of the coal-rock specimen in the unloaded state and multiple second scanned images of the coal-rock specimen in the continuous loading state, the first scanned image and the multiple second scanned images can be respectively imported into 3D reconstruction software for 3D reconstruction, and noise in the first scanned image and the multiple second scanned images can be eliminated through fast Fourier filtering and / or Gaussian filtering to enhance the image quality.

[0047] Step 102: Determine the relative elastic modulus of each voxel in the multiple second scanned images according to the multiple second scanned images and the stress-strain curve, and determine the strain of each voxel in the multiple second scanned images according to the first scanned image and the multiple second scanned images.

[0048] In some embodiments, the relative elastic modulus can be calculated based on the CT gray value, thereby realizing the determination of the relative elastic modulus of each voxel in the multiple second scanned images according to the multiple second scanned images and the stress-strain curve. Among them, the relative elastic modulus of each voxel in any second scanned image can be understood as the relative elastic modulus of each point of the coal-rock specimen under the load state corresponding to the second scanned image. Optionally, the process of calculating the relative elastic modulus based on the CT gray value and realizing the determination of the relative elastic modulus of each voxel in the multiple second scanned images according to the multiple second scanned images and the stress-strain curve is as follows:

[0049] Step 1021: Import the multiple second scanned images into 3D reconstruction software respectively to obtain the gray value and spatial position of each voxel in the multiple second scanned images, and the gray distribution of the multiple second scanned images.

[0050] Among them, the 3D reconstruction software can be any 3D reconstruction software, such as VisualSFM, Meshroom, etc., and there is no limitation in this embodiment.

[0051] Optionally, for any one of the multiple second scanned images, the gray value and spatial position of each voxel in the second scanned image and the gray distribution of the second scanned image can be obtained by importing the second scanned image into 3D reconstruction software. Thus, the gray value and spatial position of each voxel in the multiple second scanned images, and the gray distribution of the multiple second scanned images can be obtained.

[0052] Step 1022: Determine the elastic modulus of the coal-rock specimen according to the stress-strain curve. Since the stress and strain of the material are in a proportional relationship (i.e., conform to Hooke's law) in the elastic deformation stage, and the proportional coefficient is called the elastic modulus, the elastic modulus of the coal-rock specimen can be determined according to the stress-strain curve obtained in the above steps.

[0053] Step 1023: Determine the relative elastic modulus of each voxel in the multiple second scan images based on the gray value and spatial position of each voxel in the multiple second scan images, the gray distribution of the multiple second scan images, and the elastic modulus of the coal and rock specimen.

[0054] Optionally, for any one of the second scan images, the average gray value of the second scan image can be determined based on the gray value and spatial position of each voxel in the second scan image and the gray distribution of the second scan image. Thus, the relative elastic modulus coefficient of the second scan image can be determined based on the average gray value of the second scan image and the elastic modulus of the coal and rock specimen. Furthermore, the relative elastic modulus of each voxel in the second scan image can be determined based on the relative elastic modulus coefficient of the second scan image and the gray value and spatial position of each voxel in the second scan image.

[0055] Among them, for any one of the second scan images, determining the average gray value of the second scan image based on the gray value and spatial position of each voxel in the second scan image and the gray distribution of the second scan image includes:

[0056] For any one of the second scan images, obtain the frequency of at least one level of gray value corresponding to the second scan image according to the gray distribution of the second scan image;

[0057] Determine the average gray value of the second scan image based on the gray value and spatial position of each voxel in the second scan image and the frequency of at least one level of gray value corresponding to the second scan image. As an example, for any one of the second scan images, assume that the gray value and spatial position of each voxel in the second scan image are represented by Gr i (x i , y i , z i ) and the frequency of at least one level of gray value corresponding to the second scan image is represented by m i , then the average gray value of the second scan image can be calculated by the following formula:

[0058]

[0059] Assume that the elastic modulus of the coal and rock specimen determined according to the stress-strain curve is represented by E. Then, the relative elastic modulus coefficient k of the coal and rock specimen under the load state corresponding to the second scan image can be calculated by the following formula:

[0060] kGr = E

[0061] Furthermore, the relative elastic modulus E′ of each voxel in the second scan image can be calculated by the following formula i :

[0062] E′ i= kGr i

[0063] In some embodiments, in the process of determining the strain of each voxel in a plurality of second scanned images according to the first scanned image and the plurality of second scanned images, for any one of the second scanned images, the exact displacement of each voxel in the second scanned image can be determined according to the second scanned image and the first scanned image, so that the strain of each voxel in the second scanned image can be determined according to the exact displacement of each voxel in the second scanned image and the position of each voxel in the second scanned image in the first scanned image.

[0064] Among them, the exact displacement of each voxel in any one of the second scanned images can be understood as the exact displacement of each point of the coal and rock specimen under the load state corresponding to this second scanned image. Similarly, the strain of each voxel in any one of the second scanned images can be understood as the strain of each point of the coal and rock specimen under the load state corresponding to this second scanned image.

[0065] It should be noted that the exact displacement of each voxel in any one of the second scanned images includes multiple exact displacements in multiple directions, such as the x-axis direction, the y-axis direction, and the z-axis direction. The strain of each voxel in any one of the second scanned images includes multiple strains in multiple directions, such as the strains in the xx, yy, zz, xy, xz, yz directions, as well as the maximum principal strain, the intermediate principal strain, the minimum principal strain, and so on.

[0066] Optionally, in the process of determining the exact displacement of each voxel in any one of the second scanned images according to the second scanned image and the first scanned image, for any one of the second scanned images, the second scanned image and the first scanned image can be divided into image subsets of the same size to determine the rough displacement of each voxel in the second scanned image based on the image subsets, so that with the rough displacement of each voxel in the second scanned image as the boundary condition, based on the second scanned image and the first scanned image, the exact displacement of each voxel in the second scanned image can be determined by using the FEM (Finite Element Method).

[0067] Step 103, determine the strain energy density of each voxel in a plurality of second scanned images according to the relative elastic modulus and strain of each voxel in the plurality of second scanned images, so as to determine the spatial continuous strain field of the coal and rock specimen based on the plurality of second scanned images and the strain energy density of each voxel in the plurality of second scanned images.

[0068] In some embodiments, after obtaining the relative elastic modulus and strain of each voxel in a plurality of second scan images, the calculation of strain energy density can be performed. Optionally, for any second scan image, according to the relative elastic modulus and strain of each voxel in the second scan image, the strain energy density of each voxel in the second scan image can be determined using the following formula:

[0069]

[0070] where v εi represents the strain energy density of the i-th voxel in the target direction in the second scan image, E′ i represents the relative elastic modulus of the i-th voxel in the second scan image, εi represents the strain of the i-th voxel in the second scan image in the target direction, and the target directions include xx, yy, zz, xy, xz, and yz directions.

[0071] Among them, the strain energy density of each voxel in any second scan image can be understood as the strain energy density of each point of the coal and rock specimen under the load state corresponding to the second scan image.

[0072] It should be noted that since the strain of each voxel in any second scan image includes multiple strains in multiple directions, correspondingly, the strain energy density of each voxel in the second scan image determined according to the relative elastic modulus and strain of each voxel in the second scan image also includes multiple strain energy densities in multiple directions.

[0073] In some embodiments, after obtaining the strain energy density of each voxel in a plurality of second scan images, based on the plurality of second scan images and the strain energy density of each voxel in the plurality of second scan images, spatial continuous strain field quantitative visualization can be performed to obtain the spatial continuous strain field of the coal and rock specimen. Optionally, the spatial continuous strain field of the coal and rock specimen can be determined by the following steps based on the plurality of second scan images and the strain energy density of each voxel in the plurality of second scan images:

[0074] Step 1031, based on the plurality of second scan images, obtain the binary three-dimensional image of the coal and rock matrix and fractures of the coal and rock specimen.

[0075] Optionally, import the plurality of second scan images into 3D reconstruction software to determine the fracture threshold through the 3D image gray distribution curve, and obtain the binary three-dimensional image of the coal and rock matrix and fractures of the coal and rock specimen based on the fracture threshold through the interactive threshold segmentation tool.

[0076] As an example, the three-dimensional scanned images of each load state can be imported into three-dimensional reconstruction software. The fracture threshold is determined through the gray distribution curve of the three-dimensional scanned image (during the determination process, the size of the threshold needs to be continuously adjusted, and the fractures measured under the adjusted threshold are compared with the actual fractures until the error between the measured fracture distance and the actual distance is less than 1%, and then the size of the threshold is determined). Based on the fracture threshold, the binary three-dimensional images of the coal-rock matrix and fractures of the coal-rock specimen are obtained through an interactive threshold segmentation tool.

[0077] Step 1032: According to the strain energy density of each voxel in multiple second scanned images, perform three-dimensional rendering on the binary three-dimensional images of the coal-rock matrix and fractures of the coal-rock specimen to obtain the spatial continuous strain field of the coal-rock specimen.

[0078] As an example, the strain energy density of each voxel in multiple second scanned images can be imported into three-dimensional visualization software to perform three-dimensional rendering on the binary three-dimensional images of the coal-rock matrix and fractures of the coal-rock specimen, so as to quantitatively visualize the spatial continuous strain field of the coal-rock specimen and obtain the spatial continuous strain field of the coal-rock specimen.

[0079] The method for determining the strain field of a loaded coal-rock specimen provided in this embodiment obtains the first scanned image of the coal-rock specimen and the coal-rock specimen in the unloaded state, as well as multiple second scanned images and stress-strain curves of the coal-rock specimen in the continuous load state. Then, according to the multiple second scanned images and stress-strain curves, the relative elastic modulus of each voxel in the multiple second scanned images is determined, and according to the first scanned image and the multiple second scanned images, the strain of each voxel in the multiple second scanned images is determined. Furthermore, according to the relative elastic modulus and strain of each voxel in the multiple second scanned images, the strain energy density of each voxel in the multiple second scanned images is determined, so as to determine the spatial continuous strain field of the coal-rock specimen based on the multiple second scanned images and the strain energy density of each voxel in the multiple second scanned images. Thus, it is possible to combine CT technology and DVC technology to continuously and quantitatively visualize the relative energy distribution inside the coal-rock, which is crucial for analyzing coal-rock, especially for evaluating or predicting the mechanical behavior of strongly impact-prone coal-rock, and also has important significance for analyzing the coal-rock damage evolution process and preventing coal-rock dynamic disasters. To clearly illustrate the above embodiments, examples are given below for illustration.

[0080] Figure 2 It is a schematic flowchart of a method for determining the strain field of a loaded coal-rock specimen provided in an embodiment of the present invention.

[0081] As Figure 2 shown, the method for determining the strain field of the loaded coal-rock specimen includes the following steps:

[0082] 1. Sample collection: Samples are collected in the area to be studied using the method of drilling coal cores or taking specimens. The diameter of the drilled coal cores should be greater than 70 mm, and the size of the specimens should be greater than 250 mm×250 mm×250 mm. If there are other research requirements, samples of other specifications can also be collected. At the same time, the collected samples should meet the requirement that their height direction is perpendicular to the bedding plane and there should be no obvious cracks.

[0083] 2. Preparation of coal-rock specimens: The collected samples are processed into cylindrical coal-rock specimens. For convenience of comparison, the specification of φ50mm×100mm is preferably used. If there are other requirements, specimens of other specifications can also be processed, and the shape of the specimens is not restricted.

[0084] 3. Conduct the first CT scan: Place the prepared coal-rock specimens flat on the CT scanning equipment for scanning in the unloaded state to obtain the initial state scanning image (the first scanning image), which is used as a reference for the loaded state.

[0085] 4. Apply load: Apply the first-stage uniaxial or triaxial load to the above-prepared coal-rock specimens and maintain it. The load application device can use a universal testing machine or other self-made equipment. The load application stage is selected according to the research purpose, and it is recommended not to be less than 30% of the uniaxial compressive strength (UCS) of the coal-rock specimens.

[0086] 5. Conduct the second CT scan: Conduct a CT scan on the coal-rock specimens in the load-maintaining state to obtain the scanning image of load state 1 (a second scanning image). The CT scan parameters must be consistent with those of the first CT scan.

[0087] 6. Repeat steps 4 - 5 until all the required scanning images of load states (multiple second scanning images) and the stress-strain curve during the loading process of the coal-rock specimens are obtained.

[0088] 7. Image enhancement: Import the scanning images obtained in the above steps into 3D reconstruction software for 3D reconstruction, and eliminate image noise for the scanning images through two filtering algorithms, namely fast Fourier filtering and Gaussian filtering, to enhance the image quality.

[0089] 8. Rough displacement calculation based on image subsets:

[0090] Based on the 3D scanning images of the initial state and load state 1 of the enhanced coal-rock specimens, obtain the rough displacement of the coal-rock specimens from the initial state to load state 1 based on image subsets.

[0091] 9. Repeat step 8 to obtain the displacement vectors from the initial state to all load states, thereby obtaining the rough displacement field inside the loaded coal-rock specimens based on image subsets.

[0092] 10. Accurate displacement and strain calculation based on the finite element method (FEM):

[0093] Based on the three-dimensional scanned images of the coal and rock specimen in the initial state and the load state 1 after enhancement, the accurate displacement of the coal and rock specimen from the initial state to the load state 1 based on the finite element method (FEM) is obtained.

[0094] 11. Repeat step 8 to obtain the accurate displacements from the initial state to all load states, so as to obtain the accurate displacement field inside the loaded coal and rock specimen based on the finite element method (FEM).

[0095] 12. Based on the accurate displacements from the initial state to all load states and the scanned image of the initial state, obtain the strain of the coal and rock specimen from the initial state to all load states.

[0096] 13. Calculate based on the relative elastic modulus (E′ i ) of the CT gray value:

[0097] 13.1 Import any second scanned image obtained from the second CT scan into the three-dimensional reconstruction software, and obtain the gray value and its spatial position of each voxel in this second scanned image, denoted as Gr i (x i ,y i ,z i ), and at the same time obtain the gray distribution of this second scanned image.

[0098] 13.2 Use Equation (1) to calculate the average gray value Gr of this second scanned image:

[0099]

[0100] In the formula, m i is the frequency of different levels of gray values, obtained from the gray distribution of the image.

[0101] 13.3 Calculate the elastic modulus E of the coal and rock specimen from the stress-strain curve of the specimen obtained in step 6. 13.4 Calculate the relative elastic modulus coefficient k of this second scanned image and the relative elastic modulus E′ of each voxel in this second scanned image respectively using Equation (2) and Equation (3) i

[0102] kGr = E (2)

[0103] E′ i = kGr i (3)

[0104] 14. Repeat step 13 to obtain the relative elastic modulus based on the CT gray value from the initial state to all load states.

[0105] 15. Calculate the strain energy density of the image voxel:

[0106] 15.1 Save the strain tensor format calculated in step 12. Use mathematical software tools to extract the strain values in the xx, yy, zz, xy, xz, and yz directions, as well as the maximum principal strain, intermediate principal strain, and minimum principal strain for each voxel in the image strain tensor, and uniformly represent them as εi.

[0107] 15.2 Calculate the strain energy density v of each voxel in the CT scan image of the coal and rock specimen using equation (4) εi :

[0108]

[0109] 16. Repeat step 15 to obtain the strain energy density of each voxel in the CT scan image of the coal and rock specimen from the initial state to all load states.

[0110] 17. Quantitative visualization of the spatial continuous strain field:

[0111] 17.1 Import the three-dimensional scan images of each load state into three-dimensional reconstruction software. Determine the fracture threshold through the gray distribution curve of the three-dimensional scan image (during the determination process, it is necessary to continuously adjust the size of the threshold and compare the fractures measured under the adjusted threshold with the actual fractures until the error between the measured fracture distance and the actual distance is less than 1%), and obtain the binary three-dimensional image of the coal and rock matrix and fractures of the coal and rock specimen based on the fracture threshold through the interactive threshold segmentation tool.

[0112] 17.2 Import the strain energy density v of each voxel obtained in step 16 εi into three-dimensional visualization software, perform three-dimensional rendering on the binary three-dimensional image, and color it with the strain energy density v εi data to quantitatively visualize the spatial continuous strain field of the coal and rock specimen.

[0113] In summary, the present invention provides a method for spatially continuous quantification of the relative energy field of a loaded coal and rock specimen, which can continuously quantify the internal spatial energy field of the coal and rock, overcoming the limitations of theoretical calculation methods that require the specimen to not be overly complex, otherwise an analytical solution of the specimen's energy field cannot be obtained, and the applicable range is limited. Moreover, due to the simplification of the specimen, there are significant differences between the obtained energy field distribution and the actual situation; it overcomes the shortcomings of the uniaxial compression test method that is only applicable to standard specimens, and the obtained strain energy density is the average density of the entire specimen, which cannot characterize the distribution state of the strain energy inside the specimen; it overcomes the shortcomings of the energy field measurement method based on acoustic emission monitoring, which has poor applicability to heterogeneous materials such as coal and rock, and the obtained energy field distribution is discontinuous.

[0114] The present invention can continuously quantify the relative energy distribution space inside coal and rock, which is crucial for analyzing coal and rock, especially for evaluating or predicting the mechanical behavior of coal and rock with strong impact tendency, and is of great significance for analyzing the damage evolution process of coal and rock and preventing coal and rock dynamic disasters.

[0115] To achieve the above embodiments, the present invention also proposes a device for determining the strain field of a loaded coal and rock specimen.

[0116] Figure 3 It is a schematic structural diagram of a device for determining the strain field of a loaded coal and rock specimen provided by an embodiment of the present invention.

[0117] As Figure 3 shown, the device for determining the strain field of a loaded coal and rock specimen includes: an acquisition module 31, a determination module 32, and a first processing module 33.

[0118] The acquisition module 31 is used to acquire a first scanned image of the coal and rock specimen and the coal and rock specimen in an unloaded state, as well as a plurality of second scanned images and stress-strain curves of the coal and rock specimen in a continuous load state;

[0119] The determination module 32 is used to determine the relative elastic modulus of each voxel in the plurality of second scanned images according to the plurality of second scanned images and the stress-strain curves, and to determine the strain of each voxel in the plurality of second scanned images according to the first scanned image and the plurality of second scanned images;

[0120] The first processing module 33 is used to determine the strain energy density of each voxel in the plurality of second scanned images according to the relative elastic modulus and strain of each voxel in the plurality of second scanned images, so as to determine the spatial continuous strain field of the coal and rock specimen based on the plurality of second scanned images and the strain energy density of each voxel in the plurality of second scanned images.

[0121] Further, in a possible implementation manner of the embodiment of the present invention, the determination module 32 includes:

[0122] The first processing unit is used to respectively import the plurality of second scanned images into three-dimensional reconstruction software to obtain the gray value and spatial position of each voxel in the plurality of second scanned images, and the gray distribution of the plurality of second scanned images;

[0123] The first determination unit is used to determine the elastic modulus of the coal and rock specimen according to the stress-strain curve;

[0124] A second determination unit, configured to determine a relative elastic modulus of each voxel in the plurality of second scan images according to the gray value and spatial position of each voxel in the plurality of second scan images, the gray distribution of the plurality of second scan images, and the elastic modulus of the coal and rock specimen.

[0125] Further, in a possible implementation manner of the embodiment of the present invention, the second determination unit is specifically configured to:

[0126] For any one of the second scan images, determine an average gray value of the second scan image according to the gray value and spatial position of each voxel in the second scan image and the gray distribution of the second scan image;

[0127] Determine a relative elastic modulus coefficient of the second scan image according to the average gray value of the second scan image and the elastic modulus of the coal and rock specimen;

[0128] Determine a relative elastic modulus of each voxel in the second scan image according to the relative elastic modulus coefficient of the second scan image and the gray value and spatial position of each voxel in the second scan image.

[0129] Further, in a possible implementation manner of the embodiment of the present invention, the second determination unit is specifically configured to:

[0130] For any one of the second scan images, obtain the frequency of at least one level gray value corresponding to the second scan image according to the gray distribution of the second scan image;

[0131] Determine an average gray value of the second scan image according to the gray value and spatial position of each voxel in the second scan image and the frequency of at least one level gray value corresponding to the second scan image.

[0132] Further, in a possible implementation manner of the embodiment of the present invention, the first processing module 33 includes:

[0133] A third determination unit, configured to, for any one of the second scan images, determine the strain energy density of each voxel in the second scan image by using the following formula according to the relative elastic modulus and strain of each voxel in the second scan image:

[0134]

[0135] where v εi represents the strain energy density of the i-th voxel in the second scan image in the target direction, E' irepresents the relative elastic modulus of the i-th voxel in the second scanned image, and εi represents the strain of the i-th voxel in the second scanned image in the target direction, where the target direction includes xx, yy, zz, xy, xz, and yz directions.

[0136] Further, in a possible implementation manner of the embodiment of the present invention, the first processing module 33 further includes:

[0137] A second processing unit, configured to obtain a binary three-dimensional image of the coal-rock matrix and fractures of the coal-rock specimen according to the plurality of second scanned images;

[0138] A rendering unit, configured to perform three-dimensional rendering on the binary three-dimensional image of the coal-rock matrix and fractures of the coal-rock specimen according to the strain energy density of each voxel in the plurality of second scanned images, so as to obtain a spatially continuous strain field of the coal-rock specimen.

[0139] Further, in a possible implementation manner of the embodiment of the present invention, the second processing unit is specifically configured to:

[0140] Import the plurality of second scanned images into three-dimensional reconstruction software to determine a fracture threshold through a three-dimensional image gray distribution curve, and obtain a binary three-dimensional image of the coal-rock matrix and fractures of the coal-rock specimen based on the fracture threshold through an interactive threshold segmentation tool.

[0141] Further, in a possible implementation manner of the embodiment of the present invention, the determination module 32 is configured to:

[0142] For any one of the second scanned images, divide the second scanned image and the first scanned image into image subsets of the same size, so as to determine the rough displacement of each voxel in the second scanned image based on the image subsets;

[0143] Taking the rough displacement of each voxel in the second scanned image as a boundary condition, based on the second scanned image and the first scanned image, use the finite element method FEM to determine the exact displacement of each voxel in the second scanned image;

[0144] According to the exact displacement of each voxel in the second scanned image and the position of each voxel in the second scanned image in the first scanned image, determine the strain of each voxel in the second scanned image.

[0145] Further, in a possible implementation manner of the embodiment of the present invention, the acquisition module 31 includes:

[0146] A third processing unit, configured to obtain sampling samples in a region to be studied by using a preset sampling method, and process the sampling samples according to a preset specimen specification to obtain the coal and rock specimens; a scanning unit, configured to perform a first computed tomography (CT) scan on the coal and rock specimens in a state where the specimens are not loaded, so as to obtain the first scan image;

[0147] A fourth processing unit, configured to apply a continuous load to the coal and rock specimens, and perform a second CT scan on the coal and rock specimens in a state where the specimens are under the continuous load, so as to obtain the plurality of second scan images and the stress-strain curve, wherein the scan parameters of the second CT scan are the same as those of the first CT scan.

[0148] Further, in a possible implementation manner of the embodiment of the present invention, the above device further includes: a second processing module, configured to respectively import the first scan image and the plurality of second scan images into three-dimensional reconstruction software for three-dimensional reconstruction, and eliminate noise points in the first scan image and the plurality of second scan images by fast Fourier filtering and / or Gaussian filtering.

[0149] It should be noted that the foregoing explanation of the embodiment of the method for determining the strain field of a loaded coal and rock specimen also applies to the device for determining the strain field of a loaded coal and rock specimen in this embodiment, and will not be repeated here. The device for determining the strain field of a loaded coal and rock specimen provided in this embodiment obtains the first scan image of the coal and rock specimen in an unloaded state, and the plurality of second scan images and the stress-strain curve of the coal and rock specimen in a continuous load state, so as to determine the relative elastic modulus of each voxel in the plurality of second scan images according to the plurality of second scan images and the stress-strain curve, and determine the strain of each voxel in the plurality of second scan images according to the first scan image and the plurality of second scan images, and further determine the strain energy density of each voxel in the plurality of second scan images according to the relative elastic modulus and the strain of each voxel in the plurality of second scan images, so as to determine the spatial continuous strain field of the coal and rock specimen based on the plurality of second scan images and the strain energy density of each voxel in the plurality of second scan images. Thus, it is possible to combine CT technology with DVC technology to continuously and quantitatively analyze the relative energy distribution inside coal and rock, which is crucial for analyzing coal and rock, especially for evaluating or predicting the mechanical behavior of coal and rock with strong impact tendency, and is also of great significance for analyzing the damage evolution process of coal and rock and preventing coal and rock dynamic disasters.

[0150] To implement the above embodiments, the present invention further provides an electronic device, which includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein, the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the method for determining the strain field of a loaded coal and rock specimen proposed in any of the above embodiments of the present invention.

[0151] To implement the above embodiments, the present invention further provides a computer-readable storage medium storing computer instructions, wherein the computer instructions are used to cause a computer to execute the method for determining the strain field of a loaded coal and rock specimen proposed in any of the above embodiments of the present invention.

[0152] To implement the above embodiments, the present invention further provides a computer program product, including a computer program which, when executed by a processor, implements the method for determining the strain field of a loaded coal and rock specimen proposed in any of the above embodiments of the present invention.

[0153] Figure 4 FIG. [X] is a schematic structural diagram of an electronic device provided by an embodiment of the present invention. It should be noted that Figure 4 The electronic device shown is only an example and should not impose any limitations on the functions and usage scope of the embodiments of the present invention.

[0154] As Figure 4 shown, the electronic device includes:

[0155] a memory 41, a processor 42, and a computer program stored on the memory 41 and executable on the processor 42.

[0156] When the processor 42 executes the program, it implements the method for determining the strain field of a loaded coal and rock specimen provided in any of the above embodiments.

[0157] Further, the electronic device further includes:

[0158] a communication interface 43 for communication between the memory 41 and the processor 42.

[0159] The memory 41 is used to store a computer program executable on the processor 42. The memory 41 may include a high-speed RAM memory and may also include non-volatile memory, such as at least one disk memory.

[0160] The processor 42 is used to implement the method for determining the strain field of a loaded coal and rock specimen described in any of the above embodiments when executing the program.

[0161] If the memory 41, the processor 42, and the communication interface 43 are implemented independently, the communication interface 43, the memory 41, and the processor 42 can be interconnected through a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For the sake of convenience of representation, Figure 4 only a thick line is used to represent it in Figure 4 , but it does not mean that there is only one bus or one type of bus.

[0162] Optionally, in a specific implementation, if the memory 41, the processor 42, and the communication interface 43 are integrated on a single chip, the memory 41, the processor 42, and the communication interface 43 can communicate with each other through an internal interface.

[0163] The processor 42 may be a Central Processing Unit (CPU), or an Application Specific Integrated Circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention.

[0164] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0165] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined. Any process or method description represented in a flowchart or otherwise described herein can be understood to represent a module, segment, or portion of code including one or more executable instructions for implementing a customized logical function or process. The scope of the preferred embodiments of the present invention includes additional implementations, where the functions may be executed in a substantially simultaneous manner or in a reverse order according to the involved functions, rather than in the order shown or discussed, which should be understood by those skilled in the art to which the embodiments of the present invention pertain.

[0166] Logic and / or steps represented in a flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. More specific examples (non-exhaustive list) of the computer-readable medium include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer diskette (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpretation, or other appropriate processing as necessary, and then stored in a computer memory.

[0167] It should be understood that various parts of the present invention can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), and the like.

[0168] Those of ordinary skill in the art can understand that all or part of the steps carried by the method of the above embodiments can be completed by instructing relevant hardware through a program. The said program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiments.

[0169] In addition, each functional unit in various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically alone, or two or more units can be integrated into one module. The above integrated module can be implemented in the form of hardware or in the form of a software functional module. When the above integrated module is implemented in the form of a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0170] The above-mentioned storage medium can be a read-only memory, a magnetic disk, an optical disk, etc. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for determining the strain field of a loaded coal-rock specimen, characterized in that: include: Acquire a coal-rock specimen and a first scanning image of the coal-rock specimen in an unloaded state, and a plurality of second scanning images and stress-strain curves of the coal-rock specimen in a continuous load state; Determining a relative elastic modulus of each voxel in the plurality of second scanned images according to the plurality of second scanned images and the stress-strain curve, and determining a strain amount of each voxel in the plurality of second scanned images according to the first scanned image and the plurality of second scanned images; Determine the strain energy density of each voxel in the plurality of second scanned images according to the relative elastic modulus and strain amount of each voxel in the plurality of second scanned images, so as to determine the spatial continuous strain field of the coal-rock specimen based on the plurality of second scanned images and the strain energy density of each voxel in the plurality of second scanned images; Wherein, determining the relative elastic modulus of each voxel in the plurality of second scanned images according to the plurality of second scanned images and the stress-strain curve comprises: For any second scanned image, determining an average grayscale value of the second scanned image according to the grayscale value and spatial position of each voxel in the second scanned image and the grayscale distribution of the second scanned image; Determining the elastic modulus of the coal rock specimen according to the stress-strain curve; Determining a relative elastic modulus coefficient of the second scanned image according to an average grayscale value of the second scanned image and an elastic modulus of the coal-rock specimen; The relative elastic modulus of each voxel in the second scanned image is determined according to the relative elastic modulus coefficient of the second scanned image, and the grayscale value and spatial position of each voxel in the second scanned image.

2. The method according to claim 1, characterized in that The grayscale value and spatial position of each voxel in the second scanned image and the grayscale distribution of the second scanned image are determined, including: The multiple second scan images are respectively imported into three-dimensional reconstruction software to obtain the grayscale value and spatial position of each voxel in the multiple second scan images, and the grayscale distribution of the multiple second scan images.

3. The method according to claim 1, characterized in that The step of determining, for any second scanned image, an average grayscale value of the second scanned image according to the grayscale value and spatial position of each voxel in the second scanned image and the grayscale distribution of the second scanned image comprises: For any second scanned image, obtaining the frequency of at least one grayscale value corresponding to the second scanned image according to the grayscale distribution of the second scanned image; The average grayscale value of the second scanned image is determined according to the grayscale value and spatial position of each voxel in the second scanned image and the frequency of at least one level of grayscale value corresponding to the second scanned image.

4. The method according to claim 1, characterized in that: Determining the strain energy density of each voxel in the plurality of second scanned images according to the relative elastic modulus and strain amount of each voxel in the plurality of second scanned images comprises: For any second scan image, according to the relative elastic modulus and strain amount of each voxel in the second scan image, the strain energy density of each voxel in the second scan image is determined by using the following formula: Among them, v εi represents the strain energy density of the i-th voxel in the target direction in the second scanned image, E i ′ represents the relative elastic modulus of the i-th voxel in the second scanned image, εi represents the strain of the i-th voxel in the second scanned image in the target direction, and the target direction includes xx, yy, zz, xy, xz, and yz directions.

5. The method according to claim 1, characterized in that The step of determining the spatial continuous strain field of the coal-rock specimen based on the plurality of second scanned images and the strain energy density of each voxel in the plurality of second scanned images comprises: Acquire a binary three-dimensional image of the coal rock matrix and cracks of the coal rock specimen according to the plurality of second scanning images; According to the strain energy density of each voxel in the plurality of second scanning images, the binary three-dimensional image of the coal rock matrix and the cracks of the coal rock specimen is three-dimensionally rendered to obtain a spatial continuous strain field of the coal rock specimen.

6. The method according to claim 5, characterized in that The step of obtaining a binary three-dimensional image of a coal rock matrix and cracks of the coal rock specimen according to the plurality of second scanning images comprises: The multiple second scan images are imported into three-dimensional reconstruction software to determine the crack threshold through the three-dimensional image grayscale distribution curve, and based on the crack threshold, a binary three-dimensional image of the coal rock matrix and cracks of the coal rock specimen is obtained through an interactive threshold segmentation tool.

7. The method according to claim 1, characterized in that The step of determining the strain amount of each voxel in the plurality of second scanned images according to the first scanned image and the plurality of second scanned images comprises: For any second scanned image, segment the second scanned image and the first scanned image into image subsets of the same size, so as to determine a rough displacement of each voxel in the second scanned image based on the image subsets; Taking the rough displacement of each voxel in the second scanned image as a boundary condition, based on the second scanned image and the first scanned image, using a finite element method (FEM) to determine the precise displacement of each voxel in the second scanned image; The strain amount of each voxel in the second scanned image is determined according to the precise displacement of each voxel in the second scanned image and the position of each voxel in the second scanned image in the first scanned image.

8. The method according to claim 1, characterized in that: The obtaining of the coal-rock specimen and a first scanning image of the coal-rock specimen in an unloaded state, and a plurality of second scanning images and stress-strain curves of the coal-rock specimen in a continuous load state includes: Acquire sampling samples in the area to be studied by using a preset sampling method, and process the sampling samples according to preset specimen specifications to obtain the coal and rock specimens; Performing a first computer tomography (CT) scan on the coal-rock specimen when the coal-rock specimen is not loaded, so as to obtain the first scan image; A continuous load is applied to the coal-rock specimen, and a second CT scan is performed on the coal-rock specimen while the coal-rock specimen is under the continuous load state to obtain the multiple second scanning images and the stress-strain curve, wherein the scanning parameters of the second CT scan are consistent with the scanning parameters of the first electronic computer tomography CT scan.

9. The method according to any one of claims 1 to 8, characterized in that After acquiring the first scanning image of the coal-rock specimen in an unloaded state and a plurality of second scanning images of the coal-rock specimen in a continuous load state, the method further includes: The first scanned image and the plurality of second scanned images are respectively imported into three-dimensional reconstruction software for three-dimensional reconstruction, and noise points in the first scanned image and the plurality of second scanned images are eliminated by fast Fourier filtering and / or Gaussian filtering.

Images