Method and device for evolution of permeability of composite coal rock mass

Abstract

This disclosure proposes a method and apparatus for estimating the permeability of composite coal-rock masses, relating to the field of rock engineering technology. The method includes: determining the triaxial stress of the coal and rock masses based on their initial effective stresses and material mechanical parameters; determining the matrix strain based on the gas pressure at the gas inlet, the ultimate volumetric strain, and the adsorption deformation pressure of the coal matrix; determining the coal fracture compressibility coefficient based on the coal triaxial stress, the initial effective stress of the coal, the initial fracture compressibility coefficient of the coal, and its rate of decrease with strain; and calculating the permeability by comprehensively considering the coal triaxial stress, the rock triaxial stress, the initial permeability of the coal, the initial effective stress of the rock, the initial effective stress of the coal, the initial effective stress of the rock, the porosity, and the coal fracture compressibility coefficient. This disclosure significantly improves the accuracy of permeability prediction for composite coal-rock masses by comprehensively considering coal-rock interactions and the influence of multiple factors, providing a reliable theoretical basis for efficient coalbed methane extraction.

Description

Technical Field

[0001] This disclosure relates to the field of rock engineering technology, and in particular to a method and apparatus for the evolution of permeability of composite coal-rock mass. Background Technology

[0002] As society becomes increasingly reliant on resources, coalbed methane, as a high-quality clean energy source, is playing an increasingly important role in the energy sector due to its outstanding advantages such as high combustion efficiency and low pollution emissions. Permeability, as a crucial parameter for measuring the migration capacity of coalbed methane, plays a central role in the coalbed methane extraction process. It directly determines the ease with which coalbed methane flows through the pores and fractures of the coal seam, thus profoundly impacting well production, extraction efficiency, and economic benefits.

[0003] In related technologies, most methods for permeability evolution focus on single coal seams or rock strata. However, actual underground geological environments are complex and varied; coal seams and rock strata are often not isolated but intertwined, forming a composite structure. Therefore, current permeability evolution methods cannot be directly applied to composite coal-rock masses, resulting in low accuracy of permeability measurements for such masses. Summary of the Invention

[0004] This disclosure aims to at least partially address one of the technical problems in the related art.

[0005] Therefore, the first aspect of this disclosure proposes a method for the evolution of permeability in composite coal-rock masses, comprising:

[0006] Obtain coal and rock mass parameters of the composite coal and rock mass; wherein, the coal and rock mass parameters include external stress, material mechanical parameters, gas pressure at the gas inlet, initial permeability of coal, initial permeability of rock mass and porosity, and the material mechanical parameters include elastic modulus of coal, elastic modulus of rock mass, Poisson's ratio of coal, Poisson's ratio of rock mass, ultimate volumetric strain of composite coal and rock mass, adsorption deformation pressure of coal matrix, initial fracture compressibility coefficient of coal mass and the rate of decrease of the initial fracture compressibility coefficient of coal mass with strain; The initial effective stress of the coal body and the initial effective stress of the rock mass are obtained from the external stress. The triaxial stress of the coal body is determined based on the initial effective stress of the coal body, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body, and the Poisson's ratio of the rock mass. The triaxial stress of the rock mass is determined based on the initial effective stress of the rock mass, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body, and the Poisson's ratio of the rock mass. The matrix strain is determined based on the gas pressure at the inlet end, the limiting volume strain, and the coal matrix adsorption deformation pressure. The coal fracture compressibility coefficient is determined based on the triaxial stress of the coal body, the initial effective stress of the coal body, the initial fracture compressibility coefficient of the coal body, and the rate of decrease of the initial fracture compressibility coefficient of the coal body with strain. The permeability of the composite coal-rock mass is determined based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the initial permeability of the coal body, the initial effective stress of the coal body, the initial effective stress of the rock mass, the porosity, and the fracture compressibility coefficient of the coal body.

[0007] A second aspect of this disclosure provides a device for estimating the permeability of a composite coal-rock mass, comprising: The acquisition module is used to acquire coal and rock mass parameters of the composite coal and rock mass; wherein, the coal and rock mass parameters include external stress, material mechanical parameters, gas pressure at the gas inlet end, initial permeability of coal, initial permeability of rock mass and porosity, and the material mechanical parameters include elastic modulus of coal, elastic modulus of rock mass, Poisson's ratio of coal, Poisson's ratio of rock mass, ultimate volumetric strain of composite coal and rock mass, adsorption deformation pressure of coal matrix, initial fracture compressibility coefficient of coal mass and the rate of decrease of the initial fracture compressibility coefficient of coal mass with strain; The first determining module is used to obtain the initial effective stress of the coal body and the initial effective stress of the rock mass from the external stress, determine the triaxial stress of the coal body based on the initial effective stress of the coal body, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body and the Poisson's ratio of the rock mass, and determine the triaxial stress of the rock mass based on the initial effective stress of the rock mass, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body and the Poisson's ratio of the rock mass; The second determining module is used to determine the matrix strain based on the gas pressure at the inlet end, the ultimate volumetric strain, and the coal matrix adsorption deformation pressure. The third determining module is used to determine the coal body fracture compressibility coefficient based on the coal body triaxial stress, the coal body initial effective stress, the coal body initial fracture compressibility coefficient, and the coal body initial fracture compressibility coefficient with strain reduction rate. The fourth determining module is used to determine the permeability of the composite coal-rock mass based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the initial permeability of the coal body, the initial permeability of the rock mass, the initial effective stress of the coal body, the initial effective stress of the rock mass, the porosity, and the fracture compressibility coefficient of the coal body.

[0008] A third aspect of this disclosure provides an electronic device, including: a processor, and a memory communicatively connected to the processor; The memory stores computer-executed instructions; The processor executes computer execution instructions stored in the memory to implement the method described in the first aspect above.

[0009] The method for evolving the permeability of composite coal-rock masses disclosed in this paper lays the foundation for accurate analysis by obtaining comprehensive and crucial parameters of the composite coal-rock mass. Processing parameters such as external stress and material mechanics parameters yields the triaxial stress of the coal body and the triaxial stress of the rock mass, accurately reflecting the actual stress state of the coal-rock mass. Further processing of multiple parameters fully considers the influence of various factors on the permeability of the composite coal-rock mass, including the interaction between coal and rock, the external environment, and the mass's own characteristics. Compared to traditional methods, this method can more comprehensively and deeply analyze the influencing mechanism of permeability in composite coal-rock masses, effectively improving the accuracy of permeability obtained for composite coal-rock masses and providing a more reliable theoretical basis for engineering projects such as coalbed methane extraction.

[0010] Additional aspects and advantages of this disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Attached Figure Description

[0011] The above and / or additional aspects and advantages of this disclosure will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, in which: Figure 1 A flowchart illustrating a method for the evolution of permeability in a composite coal-rock mass, provided in an embodiment of this disclosure; Figure 2 This is a schematic diagram of a device for the evolution of permeability of a composite coal and rock mass, provided as an embodiment of this disclosure. Detailed Implementation

[0012] Embodiments of this disclosure are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this disclosure, and should not be construed as limiting this disclosure.

[0013] Specifically, the following describes a method and apparatus for the evolution of permeability of composite coal-rock mass according to embodiments of the present disclosure, with reference to the accompanying drawings.

[0014] Figure 1 This is a schematic flowchart illustrating a method for the evolution of permeability in a composite coal-rock mass, as provided in an embodiment of this disclosure. Figure 1 As shown, the method for estimating the permeability of this composite coal-rock mass may include the following steps: Step 101: Obtain the coal and rock mass parameters of the composite coal and rock mass; wherein, the coal and rock mass parameters include external stress, material mechanical parameters, gas pressure at the gas inlet end, initial permeability of coal, initial permeability of rock mass and porosity, and material mechanical parameters include elastic modulus of coal, elastic modulus of rock mass, Poisson's ratio of coal, Poisson's ratio of rock mass, ultimate volumetric strain of composite coal and rock mass, adsorption deformation pressure of coal matrix, initial fracture compressibility coefficient of coal mass and the rate of decrease of initial fracture compressibility coefficient of coal mass with strain.

[0015] In some embodiments of this disclosure, the total volume of the composite coal-rock mass can be obtained from the volume parameters of the composite coal-rock mass to be measured. and fracture volume Based on total volume and fracture volume Porosity is determined using the following formula. :

[0016] In some embodiments of this disclosure, after obtaining the coal-rock mass parameters of the composite coal-rock mass, the parameters can be preprocessed based on Chebyshev's inequality. Chebyshev's inequality is a probability theory inequality used to describe the degree to which data values ​​deviate from the mean under any distribution. Chebyshev's inequality is independent of the specific distribution of the data and can be applied to any form of probability distribution. By applying Chebyshev's inequality during preprocessing, the deviation range of the data can be effectively limited, reducing the impact of extreme data on the subsequent permeability evolution model calculation results, thereby improving the stability and reliability of the model calculation results.

[0017] In one possible implementation, preprocessing of various coal and rock mass parameters based on Chebyshev's inequality is performed, specifically including: Calculate the entropy values ​​of various coal and rock mass parameters to quantify the sensitivity of the influence of various coal and rock mass parameters on the permeability of composite coal and rock mass; The specific formula for calculating entropy weights is as follows: ; ; in, This represents the entropy value of the parameters of the j-th type of coal and rock mass. This represents the total number of samples for obtaining coal and rock mass parameters. Represents the natural logarithm. This represents the coal and rock mass parameter value of the j-th type of coal and rock mass in the i-th sample. This represents the mean value of the coal and rock mass parameters of the j-th type of coal and rock mass across all samples. This represents the proportion of the absolute deviation of the parameters of the j-th type of coal and rock mass in the i-th sample to the total absolute deviation of the parameters of that category in all samples; Establish an adaptive anomaly detection boundary based on entropy to determine the dynamic allowable deviation thresholds for various coal and rock mass parameters; The specific formula for calculating the dynamic allowable deviation threshold is as follows: ; ; in, This represents the dynamic allowable deviation threshold for the parameters of the j-th type of coal and rock mass. This represents the standard deviation of the coal and rock mass parameters for the j-th type of coal and rock mass across all samples. Represents the normalized importance weights of the parameters of the j-th type of coal and rock mass with respect to entropy values; in, Inheriting the core terms of Chebyshev's inequality, where standard deviation is a quantitative indicator of data dispersion (the larger the standard deviation, the more dispersed the data), the dynamic allowable deviation threshold also uses standard deviation to measure the dispersion of this parameter. Both use standard deviation as the core statistic for data dispersion. Furthermore, while k in Chebyshev's inequality is an adjustable coefficient used to control the confidence level within a reasonable range, the dynamic allowable deviation threshold calculation also retains this adjustable coefficient. Both methods use adjustable coefficients to adjust the strictness of the reasonable range, maintaining Chebyshev's characteristic of "flexible control of confidence levels." The larger the value, the greater the influence of the j-th type of coal and rock mass parameter on the permeability of the composite coal and rock mass.

[0018] Quantile mapping correction is performed on coal and rock mass parameters that exceed the adaptive anomaly detection boundary to complete the preprocessing of various coal and rock mass parameters.

[0019] The revised formula is as follows: ; in, This represents the corrected coal and rock mass parameter value for the j-th type of coal and rock mass in the i-th sample. Represents a symbolic function. This indicates the preset global sensitivity coefficient. Let k represent the cumulative distribution function of a standard normal distribution. The inverse empirical quantile function of historical deviation data of the j-th type of coal and rock mass parameters.

[0020] It should be noted that those skilled in the art can set a preset global sensitivity coefficient according to actual needs. The size of this value is not limited in this disclosure. Optionally, it can be set to 2.5. In this case, It is approximately equal to 0.994.

[0021] The calculation process for the inverse empirical quantile function is as follows: First, calculate the deviation of all historical samples for the j-th parameter; then, sort the deviations to obtain the empirical quantile function. ,in, This represents the proportion of samples with a deviation less than or equal to d, such as... =3, meaning that 99.4% of the historical deviations do not exceed 3; then take its inverse to obtain the inverse function value of the empirical quantile.

[0022] Specifically, this process quantifies the sensitivity of coal and rock mass parameters to permeability through entropy values ​​and utilizes adaptive anomaly detection based on Chebyshev's inequality to identify and correct biased data. First, the entropy values ​​of the coal and rock mass parameters are calculated to quantify the influence of each parameter and determine its contribution to permeability. Then, the standard deviation is used to measure the dispersion of the data, and a dynamic allowable deviation threshold is set according to Chebyshev's inequality to control the reasonable range of the data. For data exceeding this range, an empirical quantile inverse function is used for correction, adjusting the outlier data to a reasonable interval. This approach effectively reduces the interference of extreme data on permeability calculations, ensuring data accuracy and model reliability. Furthermore, this method does not rely on assumptions about data distribution, exhibiting strong flexibility and effective application in various scenarios.

[0023] Step 102: Obtain the initial effective stress of the coal body and the initial effective stress of the rock mass from the external stress. Determine the triaxial stress of the coal body based on the initial effective stress of the coal body, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body, and the Poisson's ratio of the rock mass. Determine the triaxial stress of the rock mass based on the initial effective stress of the rock mass, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body, and the Poisson's ratio of the rock mass.

[0024] By precisely extracting detailed and categorized data from external stress and material mechanics parameters, and determining the triaxial stress of the coal body and the rock body respectively through a coal-rock single-unit stress model, the influence of different parameters on the stress of the coal-rock body is fully considered. This allows for a more accurate simulation of the actual stress situation of the composite coal-rock body, avoiding errors caused by general parameter processing. This effectively improves the accuracy of the obtained triaxial stress of the coal body and rock body, laying a solid foundation for the subsequent accurate calculation of the permeability of the composite coal-rock body.

[0025] In some embodiments of this disclosure, the triaxial stress of the coal body can be determined in the following ways: S11, obtain the initial effective stress in the first direction, the initial effective stress in the second direction, and the initial effective stress in the third direction of the coal body from the initial effective stress of the coal body; S12, Determine the stress in the first direction of the coal body based on the initial effective stress in the first direction of the coal body; S13. Based on the initial effective stress in the first direction of the coal body, the initial effective stress in the second direction of the coal body, the initial effective stress in the third direction of the coal body, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body, and the Poisson's ratio of the rock mass, determine the stress in the second direction of the coal body and the stress in the third direction of the coal body. S14, the first-direction stress, the second-direction stress, and the third-direction stress of the coal body are defined as the triaxial stress of the coal body.

[0026] As an example, the triaxial stress of the coal body can be determined using the following formula based on the initial effective stress of the coal body, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body, and the Poisson's ratio of the rock mass:

[0027]

[0028] in, , , These represent the first-direction stress, the second-direction stress, and the third-direction stress of the coal body, respectively. , , These represent the effective stresses in the three principal stress directions of the composite coal-rock mass. For coal, Poisson's ratio Poisson's ratio of the rock mass The elastic modulus of the coal. The elastic modulus of the rock mass. This represents the adsorption strain value of the coal body.

[0029] By meticulously breaking down the initial effective stress of the coal body, the initial effective stress in three directions is obtained, providing a foundation for accurate calculation of the stress in each direction. In determining the triaxial stress of the coal body, the first-direction stress is first determined based on the initial effective stress in the first direction, and then the second and third-direction stresses are determined by comprehensively considering multiple parameters. This step-by-step and comprehensive approach fully considers the influence of different parameters in different directions, enabling a more accurate simulation of the stress state of the coal body under actual complex environments. This effectively improves the accuracy of determining the triaxial stress of the coal body, providing reliable data support for subsequent accurate analysis of the characteristics of composite coal-rock masses.

[0030] In some embodiments of this disclosure, the triaxial stress of the rock mass can be determined in the following ways: S21, obtain the initial effective stress in the first direction, the initial effective stress in the second direction, and the initial effective stress in the third direction of the rock mass from the initial effective stress of the rock mass; S22, Determine the stress in the first direction of the rock mass based on the initial effective stress in the first direction of the rock mass; S23. Based on the initial effective stress in the first direction of the rock mass, the initial effective stress in the second direction of the rock mass, the initial effective stress in the third direction of the rock mass, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body, and the Poisson's ratio of the rock mass, determine the stress in the second direction of the rock mass and the stress in the third direction of the rock mass. S24 defines the first-direction stress, the second-direction stress, and the third-direction stress of the rock mass as the triaxial stress of the rock mass.

[0031] As an example, the triaxial stress of the rock mass can be determined using the following formula based on the initial effective stress of the rock mass, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body, and the Poisson's ratio of the rock mass:

[0032]

[0033] in, , , These represent the first-direction stress, the second-direction stress, and the third-direction stress of the rock mass, respectively. , , These represent the effective stresses in the three principal stress directions of the composite coal-rock mass. For coal, Poisson's ratio Poisson's ratio of the rock mass The elastic modulus of the coal. The elastic modulus of the rock mass. This represents the adsorption strain value of the coal body.

[0034] By subdividing the initial effective stress of the rock mass into initial effective stresses in three directions, a solid foundation is laid for subsequent accurate calculations of the stresses in each direction. When determining the triaxial stress of the rock mass, the first-direction stress is first derived based on the initial effective stress in the first direction, and then the second and third-direction stresses are determined by integrating various parameters. This approach comprehensively considers the influence of different parameters on the stresses in each direction of the rock mass, more realistically reflecting the stress conditions of the rock mass under complex environments, effectively improving the accuracy of determining the triaxial stress of the rock mass, and providing a reliable basis for accurately analyzing the mechanical properties of rock masses in composite coal-rock masses.

[0035] Step 103: Determine the matrix strain based on the gas pressure at the inlet end, the ultimate volumetric strain, and the coal matrix adsorption deformation pressure.

[0036] In some embodiments of this disclosure, matrix strain can be determined in the following ways: S31, multiply the gas pressure at the inlet end and the limiting volume strain to obtain the first data; S32, add the gas pressure at the inlet end and the coal matrix adsorption deformation pressure to obtain the second data; S33, the ratio of the first data to the second data is determined as the matrix strain.

[0037] As an example, the matrix strain can be determined using the following formula based on the inlet gas pressure, the limiting volumetric strain, and the coal matrix adsorption deformation pressure:

[0038] in, For matrix strain, For the ultimate volumetric strain, This refers to the gas pressure at the intake end. The stress is the pressure at which the coal matrix is ​​adsorbed and deformed.

[0039] The matrix strain is determined through a concise and reasonable calculation procedure. First, the gas pressure at the inlet end is multiplied by the limiting volumetric strain to obtain the first data. Then, the gas pressure at the inlet end and the coal matrix adsorption deformation pressure are added to obtain the second data. Finally, the matrix strain is determined by the ratio of the two. This calculation method fully considers the influence of the gas pressure at the inlet end, the limiting volumetric strain, and the coal matrix adsorption deformation pressure on the matrix strain. It has clear logic, is easy to operate, and can quickly and accurately obtain the matrix strain, providing crucial and reliable data support for the subsequent accurate calculation of the permeability of composite coal-rock masses.

[0040] Step 104: Determine the coal fracture compressibility coefficient based on the triaxial stress of the coal body, the initial effective stress of the coal body, the initial fracture compressibility coefficient of the coal body, and the rate of decrease of the initial fracture compressibility coefficient of the coal body with strain.

[0041] In some embodiments of this disclosure, the coal fracture compressibility coefficient can be determined in the following ways: S41, Obtain the first direction compressibility coefficient, the second direction compressibility coefficient, and the third direction compressibility coefficient of the initial fractures of the coal body from the initial fracture compressibility coefficient of the coal body; S42, based on the first direction stress of the coal body, the initial first direction effective stress of the coal body, the first direction compressibility coefficient of the initial fracture of the coal body, and the rate of decrease of the first direction compressibility coefficient of the initial fracture of the coal body with strain, the first direction compressibility coefficient of the coal body is determined. S43. Based on the second-direction stress of the coal body, the initial second-direction effective stress of the coal body, the second-direction compressibility coefficient of the initial fracture of the coal body, and the rate of decrease of the second-direction compressibility coefficient of the initial fracture of the coal body with strain, the second-direction compressibility coefficient of the coal body is determined. S44. Based on the third-direction stress of the coal body, the initial third-direction effective stress of the coal body, the third-direction compressibility coefficient of the initial fractures of the coal body, and the rate of decrease of the third-direction compressibility coefficient of the initial fractures of the coal body with strain, the third-direction compressibility coefficient of the coal body is determined. S45, the compressibility coefficient of the coal fracture in the first direction, the compressibility coefficient of the coal fracture in the second direction, and the compressibility coefficient of the coal fracture in the third direction are determined as the coal fracture compressibility coefficient.

[0042] As an example, the coal fracture compressibility coefficient can be determined using the following formula based on the triaxial stress of the coal body, the initial effective stress of the coal body, the initial fracture compressibility coefficient of the coal body, and the rate of decrease of the initial fracture compressibility coefficient of the coal body with strain:

[0043] in, (i=1,2,3) represents the compressibility coefficient of the coal fracture. (i=1,2,3) represents the initial fracture compressibility coefficient of the coal body. β i (i=1,2,3) represents the rate of decrease in the initial fracture compressibility coefficient of the coal body with strain. σ 1. σ 2. σ 3 represents the first-direction stress, the second-direction stress, and the third-direction stress of the composite coal-rock mass. σ 1-0 , σ 2-0 , σ 3-0 These represent the initial stresses in the first, second, and third directions of the composite coal-rock mass, respectively.

[0044] By subdividing the initial fracture compressibility coefficient of coal into three directions, a foundation is provided for accurately calculating the compressibility coefficient in each direction. The compressibility coefficients in the three directions of coal fracture are determined based on the stress, initial effective stress, initial compressibility coefficient, and strain reduction rate in each direction. This directional and multi-factor-integrated calculation method fully considers the stress characteristics and fracture variation patterns of the coal in different directions, more accurately reflecting the actual compressibility of coal fractures, effectively improving the accuracy of determining the coal fracture compressibility coefficient, and providing a reliable basis for subsequent accurate calculation of the permeability of composite coal-rock masses.

[0045] Step 105: Determine the permeability of the composite coal-rock mass based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the initial permeability of the coal body, the initial effective stress of the coal body, the initial effective stress of the rock mass, the porosity, and the compressibility coefficient of the coal fracture.

[0046] In some embodiments of this disclosure, the permeability of a composite coal-rock mass can be determined based on the following formula using a composite coal-rock mass permeability evolution model, based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the initial permeability of the coal body, the initial effective stress of the rock mass, the initial effective stress of the coal body, the porosity, and the fracture compressibility coefficient of the coal body: In some embodiments of this disclosure, the permeability of the composite coal-rock mass can be determined using the following formula based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the initial permeability of the coal body, the initial effective stress of the rock mass, the initial effective stress of the coal body, the porosity, and the fracture compressibility coefficient of the coal body:

[0047] in, The permeability of the composite coal-rock mass, The initial permeability of the coal body. The initial permeability of the rock mass. Let be the fracture compressibility coefficient of the coal body in the i-th direction (i = 1, 2, or 3). Let be the effective stress of the coal body in the i-th direction (i is 1, 2, or 3). Let be the initial effective stress of the coal body in the i-th direction (i = 1, 2, or 3). f The differential index of coal body expansion. The inherent porosity of the coal body. Let i be the matrix strain caused by the adsorption of gas in the coal body along direction i (i is 1, 2, or 3). Let be the initial matrix strain caused by the adsorption of gas in the coal body along direction i (i takes values ​​of 1, 2, or 3). Let i be the effective stress of the rock mass in the i-direction (i is 1, 2, or 3). Let be the initial effective stress of the rock mass in the i direction (i is 1, 2, or 3).

[0048] By implementing the embodiments of this disclosure, comprehensive and crucial parameters of the composite coal-rock mass are obtained, laying the foundation for accurate analysis. Processing parameters such as external stress and material mechanics parameters yields the triaxial stress of the coal body and the triaxial stress of the rock mass, accurately reflecting the actual stress state of the coal-rock mass. Further processing of multiple parameters fully considers the influence of various factors on the permeability of the composite coal-rock mass, including the interaction between coal and rock, the external environment, and its own characteristics. Compared to traditional methods, this method can more comprehensively and deeply analyze the influencing mechanism of permeability in composite coal-rock masses, effectively improving the accuracy of permeability obtained for composite coal-rock masses, and providing a more reliable theoretical basis for engineering projects such as coalbed methane extraction.

[0049] Optionally, in some embodiments of this disclosure, after determining the permeability of the composite coal-rock mass, the surge coefficient, initial equivalent plastic shear strain, and equivalent plastic strain can also be obtained from the material mechanical parameters; based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the external stress, the material mechanical parameters, the initial permeability of the coal body, the initial permeability of the rock mass, the surge coefficient, the initial equivalent plastic shear strain, and the equivalent plastic strain, the plastic stage permeability in the damage and failure of the composite coal-rock mass is determined; based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the external stress, the material mechanical parameters, the gas pressure, the volume parameters, the initial permeability of the coal body, the initial permeability of the rock mass, and the surge coefficient, the post-peak stage permeability in the damage and failure of the composite coal-rock mass is determined.

[0050] The formula for calculating the permeability of the plastic stage in the damage and failure of composite coal and rock masses can be referenced as follows:

[0051] in, This is the initial equivalent plastic shear strain. For equivalent plastic strain, The coefficient for sudden increase. This represents the initial penetration rate.

[0052] The formula for calculating the permeability in the post-peak stage of damage and failure in composite coal and rock masses can be referenced as follows:

[0053] After obtaining key parameters from the material mechanics parameters, the permeability of the plastic stage and post-peak stage in the damage and failure of composite coal-rock masses was determined separately. This approach comprehensively considers the influence of various factors such as triaxial stress of the coal and rock mass and external stress on the permeability at different damage stages. It can more meticulously and accurately characterize the permeability changes of composite coal-rock masses during the damage and failure process, providing strong support for a deeper understanding of the seepage laws of composite coal-rock masses at different damage stages, and helping to more accurately assess their safety and stability in engineering applications.

[0054] Figure 2 This is a schematic diagram of a device for analyzing the evolution of permeability in a composite coal-rock mass, as provided in an embodiment of this disclosure. Figure 2 As shown, the device for determining the permeability of the composite coal-rock mass may include: an acquisition module 201, a first determination module 202, a second determination module 203, a third determination module 204, and a fourth determination module 205.

[0055] The acquisition module 201 is used to acquire the coal and rock mass parameters of the composite coal and rock mass. The coal and rock mass parameters include external stress, material mechanical parameters, gas pressure at the gas inlet, initial permeability of the coal, initial permeability of the rock mass, and porosity. The material mechanical parameters include the elastic modulus of the coal, the elastic modulus of the rock mass, the Poisson's ratio of the coal, the Poisson's ratio of the rock mass, the ultimate volumetric strain of the composite coal and rock mass, the adsorption deformation pressure of the coal matrix, the initial fracture compressibility coefficient of the coal, and the rate of decrease of the initial fracture compressibility coefficient of the coal with strain.

[0056] The first determining module 202 is used to obtain the initial effective stress of the coal body and the initial effective stress of the rock mass from the external stress, determine the triaxial stress of the coal body based on the initial effective stress of the coal body, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body and the Poisson's ratio of the rock mass, and determine the triaxial stress of the rock mass based on the initial effective stress of the rock mass, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body and the Poisson's ratio of the rock mass.

[0057] The second determining module 203 is used to determine the matrix strain based on the gas pressure at the inlet end, the ultimate volumetric strain, and the coal matrix adsorption deformation pressure.

[0058] The third determining module 204 is used to determine the coal fracture compressibility coefficient based on the coal body triaxial stress, the initial effective stress of the coal body, the initial fracture compressibility coefficient of the coal body, and the rate of decrease of the initial fracture compressibility coefficient of the coal body with strain.

[0059] The fourth determining module 205 is used to determine the permeability of the composite coal-rock mass based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the initial permeability of the coal body, the initial effective stress of the rock mass, the initial effective stress of the coal body, the porosity, and the compressibility coefficient of the coal fracture.

[0060] In some embodiments of this disclosure, in such Figure 2 Based on the illustrated embodiment, the device for determining the evolution of permeability in composite coal-rock mass can further include a fifth determining module. This fifth determining module is used to: obtain the surge coefficient, initial equivalent plastic shear strain, and equivalent plastic strain from the material mechanical parameters; determine the plastic stage permeability during the damage and failure of the composite coal-rock mass based on the triaxial stress of the coal body, the triaxial stress of the rock mass, external stress, material mechanical parameters, initial permeability of the coal body, initial permeability of the rock mass, surge coefficient, initial equivalent plastic shear strain, and equivalent plastic strain; and determine the post-peak stage permeability during the damage and failure of the composite coal-rock mass based on the triaxial stress of the coal body, the triaxial stress of the rock mass, external stress, material mechanical parameters, gas pressure, volume parameters, initial permeability of the coal body, initial permeability of the rock mass, and surge coefficient.

[0061] Regarding the apparatus in the above embodiments, the specific manner in which each module performs its operation has been described in detail in the embodiments related to the method, and will not be elaborated upon here.

[0062] To implement the above embodiments, this disclosure also proposes an electronic device, including: a processor and a memory communicatively connected to the processor; the memory stores computer execution instructions; the processor executes the computer execution instructions stored in the memory to implement the method provided in the foregoing embodiments.

[0063] To implement the above embodiments, this disclosure also proposes a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the methods provided in the foregoing embodiments.

[0064] In the foregoing descriptions of the embodiments, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0065] Furthermore, 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 number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0066] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of this disclosure includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of this disclosure pertain.

[0067] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may 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 medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0068] It should be understood that various parts of this disclosure can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0069] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0070] Furthermore, the functional units in the various embodiments of this disclosure can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0071] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A method for evolution of composite coal rock permeability, characterized in that, Includes the following steps: Obtain coal and rock mass parameters of the composite coal and rock mass; wherein, the coal and rock mass parameters include external stress, material mechanical parameters, gas pressure at the gas inlet, initial permeability of coal, initial permeability of rock mass and porosity, and the material mechanical parameters include elastic modulus of coal, elastic modulus of rock mass, Poisson's ratio of coal, Poisson's ratio of rock mass, ultimate volumetric strain of composite coal and rock mass, adsorption deformation pressure of coal matrix, initial fracture compressibility coefficient of coal mass and the rate of decrease of the initial fracture compressibility coefficient of coal mass with strain; The initial effective stress of the coal body and the initial effective stress of the rock mass are obtained from the external stress. The triaxial stress of the coal body is determined based on the initial effective stress of the coal body, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body, and the Poisson's ratio of the rock mass. The triaxial stress of the rock mass is determined based on the initial effective stress of the rock mass, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body, and the Poisson's ratio of the rock mass. The matrix strain is determined based on the gas pressure at the inlet end, the limiting volume strain, and the coal matrix adsorption deformation pressure. The coal fracture compressibility coefficient is determined based on the triaxial stress of the coal body, the initial effective stress of the coal body, the initial fracture compressibility coefficient of the coal body, and the rate of decrease of the initial fracture compressibility coefficient of the coal body with strain. The permeability of the composite coal-rock mass is determined based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the initial permeability of the coal body, the initial effective stress of the coal body, the initial effective stress of the rock mass, the porosity, and the fracture compressibility coefficient of the coal body.

2. The method of claim 1, wherein, Based on the initial effective stress of the coal body, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body, and the Poisson's ratio of the rock mass, the triaxial stress of the coal body is determined by the following formula: in, , , These refer to the first-direction stress, second-direction stress, and third-direction stress of the coal body, respectively. , , These represent the effective stresses of the composite coal-rock mass in the three principal stress directions. The Poisson's ratio of the coal body is given. The Poisson's ratio of the rock mass is given. The elastic modulus of the coal body. The elastic modulus of the rock mass is given. This represents the adsorption strain value of the coal body.

3. The method of claim 1, wherein, Based on the initial effective stress of the rock mass, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body, and the Poisson's ratio of the rock mass, the triaxial stress of the rock mass is determined by the following formula: in, , , These refer to the first-direction stress, the second-direction stress, and the third-direction stress of the rock mass, respectively. , , These represent the effective stresses of the composite coal-rock mass in the three principal stress directions. The Poisson's ratio of the coal body is given. The Poisson's ratio of the rock mass is given. The elastic modulus of the coal body. The elastic modulus of the rock mass is given. This represents the adsorption strain value of the coal body.

4. The method of claim 1, wherein, Based on the inlet gas pressure, the limiting volumetric strain, and the coal matrix adsorption deformation pressure, the matrix strain is determined using the following formula: in, For the matrix strain, The limiting volume strain is... The gas pressure at the inlet end is... The adsorption deformation pressure of the coal matrix is ​​denoted as .

5. The method of claim 1, wherein, Based on the triaxial stress of the coal body, the initial effective stress of the coal body, the initial fracture compressibility coefficient of the coal body, and the rate of decrease in the initial fracture compressibility coefficient of the coal body with strain, the fracture compressibility coefficient of the coal body is determined by the following formula: in, (i=1,2,3) represents the compressibility coefficient of the fractured coal body. (i=1,2,3) represents the initial fracture compressibility coefficient of the coal body. β i (i=1,2,3) represents the rate of decrease in the initial fracture compressibility coefficient of the coal body with strain. σ 1. σ 2. σ 3 represents the first-direction stress, the second-direction stress, and the third-direction stress of the composite coal-rock mass, respectively. σ 1-0 , σ 2-0 , σ 3-0 These are the initial stresses in the first direction, the second direction, and the third direction of the composite coal-rock mass, respectively.

6. The method of claim 1, wherein, Based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the initial permeability of the coal body, the initial effective stress of the rock mass, the initial effective stress of the coal body, the porosity, and the fracture compressibility coefficient of the coal body, the permeability of the composite coal-rock mass is determined by the following formula: in, The permeability of the composite coal-rock mass is given. The initial permeability of the coal body. The initial permeability of the rock mass is given. Let be the fracture compressibility coefficient of the coal body in the i-th direction (i = 1, 2, or 3). Let be the effective stress of the coal body in the i-th direction (i is 1, 2, or 3). Let be the initial effective stress of the coal body in the i-th direction (i = 1, 2, or 3). f The differential index of coal body expansion. The inherent porosity of the coal body. Let i be the matrix strain caused by the adsorption of gas in the coal body along direction i (i is 1, 2, or 3). Let be the initial matrix strain caused by the adsorption of gas in the coal body along direction i (i takes values ​​of 1, 2, or 3). Let i be the effective stress of the rock mass in the i-direction (i is 1, 2, or 3). Let be the initial effective stress of the rock mass in the i direction (i is 1, 2, or 3).

7. The method according to any one of claims 1-6, characterized in that, After obtaining the coal and rock mass parameters of the composite coal and rock mass, the process further includes: The parameters of the coal and rock mass are preprocessed based on Chebyshev's inequality.

8. The method according to any one of claims 1-6, characterized in that, Also includes: The sudden increase coefficient, initial equivalent plastic shear strain, and equivalent plastic strain are obtained from the material's mechanical parameters. Based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the external stress, the material mechanical parameters, the initial permeability of the coal body, the initial permeability of the rock mass, the sudden increase coefficient, the initial equivalent plastic shear strain, and the equivalent plastic strain, the permeability of the plastic stage in the damage and failure of the composite coal-rock mass is determined. Based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the external stress, the material mechanical parameters, the gas pressure, the volume parameters, the initial permeability of the coal body, the initial permeability of the rock mass, and the sudden increase coefficient, the post-peak permeability in the damage and failure of the composite coal-rock mass is determined.

9. A device for estimating the permeability of a composite coal-rock mass, characterized in that, include: The acquisition module is used to acquire coal and rock mass parameters of the composite coal and rock mass; wherein, the coal and rock mass parameters include external stress, material mechanical parameters, gas pressure at the gas inlet end, initial permeability of coal, initial permeability of rock mass and porosity, and the material mechanical parameters include elastic modulus of coal, elastic modulus of rock mass, Poisson's ratio of coal, Poisson's ratio of rock mass, ultimate volumetric strain of composite coal and rock mass, adsorption deformation pressure of coal matrix, initial fracture compressibility coefficient of coal mass and the rate of decrease of the initial fracture compressibility coefficient of coal mass with strain; The first determining module is used to obtain the initial effective stress of the coal body and the initial effective stress of the rock mass from the external stress, determine the triaxial stress of the coal body based on the initial effective stress of the coal body, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body and the Poisson's ratio of the rock mass, and determine the triaxial stress of the rock mass based on the initial effective stress of the rock mass, the elastic modulus of the coal body, the elastic modulus of the rock mass, the Poisson's ratio of the coal body and the Poisson's ratio of the rock mass; The second determining module is used to determine the matrix strain based on the gas pressure at the inlet end, the ultimate volumetric strain, and the coal matrix adsorption deformation pressure. The third determining module is used to determine the coal body fracture compressibility coefficient based on the coal body triaxial stress, the coal body initial effective stress, the coal body initial fracture compressibility coefficient, and the coal body initial fracture compressibility coefficient with strain reduction rate. The fourth determining module is used to determine the permeability of the composite coal-rock mass based on the triaxial stress of the coal body, the triaxial stress of the rock mass, the initial permeability of the coal body, the initial permeability of the rock mass, the initial effective stress of the coal body, the initial effective stress of the rock mass, the porosity, and the fracture compressibility coefficient of the coal body.

10. An electronic device, characterized in that, include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executed instructions; The processor executes computer execution instructions stored in the memory to implement the method as described in any one of claims 1-8.

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