An analytical method for stress wave propagation in coal and rock media

Abstract

The present invention discloses an analysis method applicable to the propagation law of stress waves in coal rock media, and belongs to the field of coal mining technology. An analysis method applicable to the propagation law of stress waves in coal rock media, comprising the following steps: determining the physical and mechanical properties and parameters of coal rock, establishing a stress wave propagation theoretical model that includes the internal structure and stress distribution characteristics of coal rock, solving the model using the finite element method and the discrete element method, and changing the model parameters by comparing with actual seismic data or industrial test data and based on the verification results. The present invention solves the problem that existing analysis methods often find it difficult to fully consider the influence of the complex internal structure and non-uniform stress distribution of coal rock on wave propagation, and also have limitations when dealing with the interference effect of multiple types of stress waves and complex boundary conditions. The present invention more accurately predicts the propagation law of stress waves in coal rock by fully considering the complex internal structure of coal rock and considering the situation of non-uniform stress distribution.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mining, and in particular to an analysis method suitable for the propagation law of stress waves in coal and rock media. Background Art

[0002] In coal mining and geological engineering, understanding the propagation characteristics of stress waves in coal and rock media is crucial for ensuring operational safety and optimizing mining techniques. The propagation patterns of stress waves directly influence the failure mode, energy dissipation, and potential geological disaster risks of coal and rock. However, traditional analytical methods often struggle to fully consider the impact of the complex internal structure and non-uniform stress distribution of coal and rock on wave propagation. These methods are often based on simplified assumptions and idealized models, neglecting the influence of factors such as natural fractures, bedding, porosity, and mineral composition. Furthermore, traditional methods have limitations in dealing with the interference effects of multiple stress waves and complex boundary conditions, which restricts their application in practical engineering.

[0003] Therefore, developing a stress wave propagation analysis method that can fully consider the complex internal structure and non-uniform stress distribution of coal rock is of great practical significance for improving the safety of coal mining and optimizing mining technology. Summary of the Invention

[0004] The purpose of the present invention is to provide an analysis method suitable for the propagation law of stress waves in coal rock media, comprehensively considering the complex internal structure of coal rock and the situation of non-uniform stress distribution, solving the model by means of numerical simulation to obtain more accurate information such as stress wave attenuation characteristics, velocity attenuation characteristics and energy dissipation characteristics. At the same time, the effectiveness of the model is verified by comparing with actual seismic data, thereby improving the prediction accuracy, better assessing potential safety risks, and solving the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] An analysis method for stress wave propagation in coal and rock media includes the following steps:

[0007] S1. Determine the physical and mechanical properties and parameters of coal rock, including elastic modulus, Poisson's ratio, density, compressive strength, and tensile strength. Identify natural fractures and bedding in coal rock, and assess the impact of these characteristics on overall failure and damage of coal rock.

[0008] S2. Establish a theoretical model of stress wave propagation that incorporates the internal structure and stress distribution characteristics of coal and rock. Model each type of stress wave generated during the impact coal breaking process, and set the model's boundary conditions, initial conditions, impact load, and initial stress state of the coal and rock.

[0009] S3. Use the finite element method (FEM) and discrete element method (DEM) to solve the model, record the propagation process of stress waves in coal and rock, including the propagation speed, attenuation characteristics and energy dissipation of stress waves, output the calculation results, and describe the interference effects of various types of stress waves;

[0010] S4. Verify the reliability of the proposed model in predicting stress wave propagation characteristics by comparing it with actual earthquake data or industrial test data;

[0011] S5. Based on the verification results, change the model parameters, re-perform the numerical simulation, observe the changes in the model output, evaluate the impact of different parameter changes on the model output, and find out the key parameters and their sensitivity.

[0012] Preferably, the establishment of the stress wave propagation theoretical model includes the following steps:

[0013] Based on the actual geological data of coal rock, a three-dimensional geometric model is established, which includes the geometric shape, cracks, bedding and internal structure of the coal rock;

[0014] Mesh the 3D geometric model to generate finite element or discrete element mesh.

[0015] Preferably, meshing the three-dimensional geometric model to generate a finite element or discrete element mesh includes:

[0016] Extracting first geological data of the actual coal rock, wherein the first geological data includes the number of coal rock layers, the thickness of each layer, and the dip angle of the formation;

[0017] Comparing the number of coal and rock layers with a preset coal and rock layer number threshold;

[0018] comparing the overall thickness of the coal rock with a preset overall thickness threshold;

[0019] When the number of coal rock layers exceeds a preset coal rock layer number threshold and the overall thickness of the coal rock does not exceed a preset overall thickness threshold, a geological evaluation coefficient is obtained using the first geological data; otherwise, a finite element or discrete element mesh is generated by meshing the three-dimensional geometric model according to a preset initial mesh density;

[0020] The geological evaluation coefficient is obtained by the following formula:

[0021]

[0022] Where G represents the geological evaluation coefficient; D represents the overall thickness of the coal rock; n represents the number of coal rock layers; H i represents the thickness of the i-th coal layer; A represents the dip angle of the formation; H c Indicates the preset reference value of the thickness of each coal layer; D yIndicates the preset overall thickness threshold; n y Indicates the preset coal layer number threshold; H p It represents the average thickness of the n-layer coal rock;

[0023] Comparing the geological evaluation coefficient with a preset evaluation coefficient threshold;

[0024] When the geological evaluation coefficient is lower than a preset evaluation coefficient threshold, the three-dimensional geometric model is meshed according to a preset initial mesh density to generate a finite element or discrete element mesh;

[0025] When the geological evaluation coefficient is not lower than a preset evaluation coefficient threshold, the grid density is set, and the three-dimensional geometric model is meshed according to the set grid density to generate a finite element or discrete element grid.

[0026] Preferably, when the geological evaluation coefficient is not lower than a preset evaluation coefficient threshold, the grid density is set, including:

[0027] Extracting first geological data of the actual coal rock, wherein the first geological data includes the number of coal rock layers, the thickness of each layer, and the dip angle of the formation;

[0028] Extracting second geological data of the actual coal rock, wherein the second geological data includes the number and width of cracks in each layer of coal rock;

[0029] Setting a grid density using the first geological data and the second geological data in combination with a preset initial grid density;

[0030] The grid density is obtained by the following formula:

[0031]

[0032] Where P represents the grid density; P c represents the critical pressure; P0 represents the preset initial grid density; n represents the number of coal layers; H i represents the thickness of the i-th coal layer; A represents the dip angle of the formation; H c represents the preset reference value of the thickness of each coal rock layer; m represents the number of cracks in the i-th coal rock layer; L j represents the crack width corresponding to the jth crack in the i-th coal rock layer; L b represents the standard deviation of the overall crack width corresponding to the n-layer coal rock; L max Indicates the maximum crack width corresponding to the n-layer coal rock; L bmax Indicates the standard deviation of the crack width of the coal rock layer corresponding to the maximum crack width; L min Indicates the minimum crack width corresponding to the n-layer coal rock; L bminIt represents the standard deviation of the crack width of the coal rock layer corresponding to the minimum crack width.

[0033] Preferably, the establishment of the stress wave propagation theoretical model further comprises the following steps:

[0034] Select one of the linear elastic constitutive relation, elastoplastic constitutive relation and elastic-brittle constitutive relation to describe the mechanical behavior of coal rock, and input the physical and mechanical parameters of coal rock;

[0035] Set the boundary conditions of the model, including at least fixed boundaries, free boundaries and stress boundaries;

[0036] Set the initial stress state of the coal rock and obtain the initial stress distribution through in-situ stress test data;

[0037] The parameters are set according to the actual impact coal breaking process, including at least the size, direction and time history of the impact load, the impact force and the impact speed.

[0038] Preferably, the finite element method (FEM) and discrete element method (DEM) are used to solve the model, output the stress distribution inside the model, including compressive stress and tensile stress; output the strain distribution inside the model to analyze the deformation; output the displacement distribution inside the model to analyze the overall deformation of the structure; output the energy loss analysis results of the stress wave during propagation, including friction dissipation and heat energy conversion; output the dynamic response analysis results under the action of impact load, including the propagation speed and attenuation characteristics of the stress wave; output the propagation data of the stress wave at different time points.

[0039] Preferably, the interference effects describing various types of stress waves are specifically:

[0040] Calculate the propagation and reflection of cylindrical compression waves in coal and rock, calculate the propagation and reflection of plane isochoric waves in coal and rock, calculate the propagation and attenuation of Rayleigh surface waves near the free surface, and calculate the propagation and reflection of Stoney waves on discontinuities; in each time step, add up the contributions of all stress waves to obtain the total stress field distribution;

[0041] Analyze the superposition effect of different stress waves at the same location to determine whether constructive interference or destructive interference occurs.

[0042] Preferably, the validity and reliability of the proposed model are verified by comparing it with actual earthquake data or industrial test data, specifically:

[0043] Compare the stress wave waveforms obtained from numerical simulations with those from actual seismic data to check the similarity of the waveforms;

[0044] Compare the stress wave amplitudes from numerical simulations and actual data to evaluate the model's ability to predict the amplitudes;

[0045] Compare the frequency components in the numerical simulation and the actual data to check whether the model can accurately predict the spectral characteristics of the stress wave;

[0046] Compare the stress wave propagation velocities in numerical simulations and actual data to evaluate the accuracy of the model's predictions of wave velocities;

[0047] Compare the stress wave attenuation characteristics in numerical simulations and actual data to check whether the model can accurately describe the wave attenuation process;

[0048] Compare the energy dissipation in numerical simulations and actual data to evaluate the model's ability to predict energy dissipation;

[0049] The coal and rock failure patterns in numerical simulations and actual data are compared to evaluate the model's ability to predict the failure mechanism.

[0050] Preferably, the verification of the validity and reliability of the proposed model by comparing it with actual earthquake data or industrial test data further includes:

[0051] Calculate the mean and variance of numerical simulation results and actual data;

[0052] The correlation coefficient was used to evaluate the correlation between the numerical simulation results and the actual data;

[0053] Calculate absolute error, relative error, and root mean square error to quantify the prediction accuracy of the model;

[0054] Draw time series graphs, waveform graphs, and spectrum graphs of numerical simulation results and actual data to intuitively display the comparison results.

[0055] Preferably, the step of changing the model parameters based on the verification results and re-performing the numerical simulation specifically includes the following steps:

[0056] Run the benchmark model once and record its output for reference;

[0057] Set a reasonable range of variation for each selected parameter;

[0058] By combining single-factor analysis with multi-factor analysis, the change in model output before and after each parameter change is calculated;

[0059] Record the impact of each parameter change on the model output;

[0060] Calculate the sensitivity index and rank the parameters according to the sensitivity index;

[0061] Explain the reasons for the deviation of model output caused by parameter changes and improve the model again based on the results of sensitivity analysis.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] 1. This invention establishes a three-dimensional geometric model that encompasses the internal structure and stress distribution characteristics of coal rock and performs meshing. The model details microstructures such as fractures, bedding, and pores, more accurately reflecting the true nature of coal rock and predicting the propagation path and attenuation characteristics of stress waves within the rock. This improves the model's prediction accuracy, optimizes mining plans, reduces unnecessary damage, and enhances engineering efficiency.

[0064] 2. The present invention obtains the initial stress distribution of coal rock by setting reasonable boundary conditions and initial stress state, and fully considers the influence of non-uniform stress distribution, accurately simulating the non-uniform stress distribution in coal rock, which can better assess potential safety risks, thereby improving operational safety and enhancing the reliability and practicality of the model.

[0065] 3. The present invention calculates the interference effects of different types of stress waves, analyzes their superposition effects at the same location, and determines whether constructive interference or destructive interference occurs, so as to more accurately predict the propagation behavior of stress waves in coal rocks and improve the prediction accuracy of the model.

[0066] 4. The present invention combines the advantages of the finite element method and the discrete element method, which are used to deal with continuous media and discontinuous media respectively, and comprehensively solves the stress wave propagation problem. It can handle situations involving a large number of discontinuous surfaces and a large range of continuous media, thereby enhancing the applicability and flexibility of the model. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 is a flow chart of the analysis method of the present invention;

[0068] Figure 2 A flow chart is established for the stress wave propagation theoretical model of the present invention. DETAILED DESCRIPTION

[0069] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0070] To address the problem that existing analysis methods often have difficulty in fully considering the impact of the complex internal structure of coal and rock and the non-uniform stress distribution on wave propagation, and also have limitations in dealing with the interference effect of multiple types of stress waves and complex boundary conditions, please refer to Figure 1-2 , this embodiment provides the following technical solutions:

[0071] An analysis method for stress wave propagation in coal and rock media includes the following steps:

[0072] S1. Determine the physical and mechanical properties and parameters of coal rock, including elastic modulus, Poisson's ratio, density, compressive strength, and tensile strength. Identify natural fractures and bedding in coal rock, and assess the impact of these characteristics on overall failure and damage of coal rock.

[0073] The elastic modulus, Poisson's ratio, density, compressive strength and tensile strength of coal rock are measured through uniaxial compression test, triaxial compression test, Brazilian splitting test and other methods, and the natural cracks and bedding information in coal rock are identified and obtained through microscope and CT scanning technology.

[0074] S2. Establish a theoretical model of stress wave propagation that incorporates the internal structure and stress distribution characteristics of coal and rock. Model each type of stress wave generated during the impact coal breaking process, and set the model's boundary conditions, initial conditions, impact load, and initial stress state of the coal and rock.

[0075] S3. Use the finite element method (FEM) and discrete element method (DEM) to solve the model, record the propagation process of stress waves in coal and rock, including the propagation speed, attenuation characteristics and energy dissipation of stress waves, output the calculation results, and describe the interference effects of various types of stress waves;

[0076] S4. Verify the reliability of the proposed model in predicting stress wave propagation characteristics by comparing it with actual earthquake data or industrial test data;

[0077] S5. Based on the verification results, change the model parameters, re-perform the numerical simulation, observe the changes in the model output, evaluate the impact of different parameter changes on the model output, and find out the key parameters and their sensitivity.

[0078] Establishing the stress wave propagation theoretical model includes the following steps:

[0079] According to the actual geological data of coal rock, Petre l software is used to establish a three-dimensional geometric model, including the geometric shape, cracks, bedding and internal structure of coal rock;

[0080] Mesh the three-dimensional geometric model to generate finite element or discrete element mesh. For complex coal and rock structures, use unstructured mesh.

[0081] Specifically, the 3D geometric model is meshed to generate a finite element or discrete element mesh, including:

[0082] Extracting first geological data of the actual coal rock, wherein the first geological data includes the number of coal rock layers, the thickness of each layer, and the dip angle of the formation;

[0083] Comparing the number of coal and rock layers with a preset coal and rock layer number threshold;

[0084] comparing the overall thickness of the coal rock with a preset overall thickness threshold;

[0085] When the number of coal rock layers exceeds a preset coal rock layer number threshold and the overall thickness of the coal rock does not exceed a preset overall thickness threshold, a geological evaluation coefficient is obtained using the first geological data; otherwise, a finite element or discrete element mesh is generated by meshing the three-dimensional geometric model according to a preset initial mesh density;

[0086] The geological evaluation coefficient is obtained by the following formula:

[0087]

[0088] Where G represents the geological evaluation coefficient; D represents the overall thickness of the coal rock; n represents the number of coal rock layers; H i represents the thickness of the i-th coal layer; A represents the dip angle of the formation; H c Indicates the preset reference value of the thickness of each coal layer; D y Indicates the preset overall thickness threshold; n y Indicates the preset coal layer number threshold; H p It represents the average thickness of the n-layer coal rock;

[0089] Comparing the geological evaluation coefficient with a preset evaluation coefficient threshold;

[0090] When the geological evaluation coefficient is lower than a preset evaluation coefficient threshold, the three-dimensional geometric model is meshed according to a preset initial mesh density to generate a finite element or discrete element mesh;

[0091] When the geological evaluation coefficient is not lower than a preset evaluation coefficient threshold, the grid density is set, and the three-dimensional geometric model is meshed according to the set grid density to generate a finite element or discrete element grid.

[0092] The technical effect of the above-mentioned technical solution is that it can adaptively adjust the mesh density based on the geological characteristics of the coal rock (such as the number of coal rock layers, thickness of each layer, overall thickness, and formation dip). This adaptability ensures that the meshing can be optimized for specific geological conditions, thereby improving simulation accuracy and efficiency. By introducing a geological evaluation coefficient, the solution can more accurately assess the geological complexity of the coal rock. When the geological conditions of the coal rock are more complex (such as a large number of layers, large thickness variations, and large formation dips), the geological evaluation coefficient is correspondingly increased, triggering a finer meshing to improve simulation accuracy. Conversely, for coal rock with relatively simple geological conditions, a coarser meshing is used to save computing resources. The solution effectively controls the meshing density by pre-setting thresholds for the number of coal rock layers, overall thickness, and evaluation coefficient. This control method enables dynamic allocation of computing resources based on the geological complexity of the coal rock, avoiding unnecessary resource waste while ensuring simulation accuracy in key areas. This technical solution is not only applicable to coal rock simulation analysis but can also be extended to the simulation of other geological bodies with complex geological structures. By adjusting preset thresholds and parameters, this solution can flexibly adapt to different geological conditions and simulation requirements. In fields such as coal mining and underground engineering, this technical solution can provide engineers with more accurate geological simulation results, helping them make more informed decisions. For example, in coal mining, by simulating the mechanical behavior of coal and rock, potential risks can be predicted and preventive measures can be taken.

[0093] In summary, this technical solution achieves accurate simulation of coal and rock geological characteristics and optimal allocation of computing resources through the introduction of adaptive grid division and geological evaluation coefficients, providing strong support for research and engineering practice in related fields.

[0094] Specifically, when the geological evaluation coefficient is not lower than a preset evaluation coefficient threshold, the grid density is set, including:

[0095] Extracting first geological data of the actual coal rock, wherein the first geological data includes the number of coal rock layers, the thickness of each layer, and the dip angle of the formation;

[0096] Extracting second geological data of the actual coal rock, wherein the second geological data includes the number and width of cracks in each layer of coal rock;

[0097] Setting a grid density using the first geological data and the second geological data in combination with a preset initial grid density;

[0098] The grid density is obtained by the following formula:

[0099]

[0100] Where P represents the grid density; P c represents the critical pressure; P0 represents the preset initial grid density; n represents the number of coal layers; H i represents the thickness of the i-th coal layer; A represents the dip angle of the formation; H c represents the preset reference value of the thickness of each coal rock layer; m represents the number of cracks in the i-th coal rock layer; L j represents the crack width corresponding to the jth crack in the i-th coal rock layer; L b represents the standard deviation of the overall crack width corresponding to the n-layer coal rock; L max Indicates the maximum crack width corresponding to the n-layer coal rock; L bmax Indicates the standard deviation of the crack width of the coal rock layer corresponding to the maximum crack width; L min Indicates the minimum crack width corresponding to the n-layer coal rock; L bmin It represents the standard deviation of the crack width of the coal rock layer corresponding to the minimum crack width.

[0101] The technical effect of the above-mentioned technical solution is that it not only considers basic geological data of the coal rock (such as the number of coal rock layers, thickness of each layer, and formation dip), but also incorporates more detailed geological data such as the number and width of fractures. This comprehensive consideration allows the grid density setting to be more closely aligned with actual geological conditions, improving the accuracy and realism of the simulation. By combining the first and second geological data, the solution can more accurately assess the geological complexity of the coal rock. Assuming the geological evaluation coefficient is not lower than a preset threshold, the grid density set based on this comprehensive data can more meticulously reflect the internal structure and mechanical properties of the coal rock, thereby improving the accuracy and reliability of the simulation. The grid density setting in this technical solution is a dynamic process, adjusted in real time based on the actual geological data of the coal rock. This dynamic adjustment mechanism ensures that the grid division can respond promptly to the complexity and variability of the coal rock, improving the flexibility and adaptability of the simulation. Although the solution considers more geological factors in the grid density setting, it does not increase unnecessary computational burden. On the contrary, by rationally setting the grid density, the solution can optimize the allocation of computing resources and improve computational efficiency while ensuring simulation accuracy. Because this solution comprehensively considers multiple geological factors of coal and rock, and dynamically adjusts the grid density based on these factors, the simulation results are closer to the actual geological conditions. This reliability is crucial for decision-making in fields such as coal and rock mining and underground engineering, mitigating potential risks and improving project safety. This technical solution is not only applicable to the simulation analysis of coal and rock, but can also be extended to the simulation of other geological bodies with similar geological structures and characteristics. By adjusting the preset initial grid density and related parameters, the solution can flexibly adapt to different geological conditions and simulation requirements.

[0102] In summary, this technical solution achieves accurate simulation of coal and rock geological characteristics and optimizes the allocation of computing resources by comprehensively considering multiple geological factors of coal and rock and dynamically adjusting grid density. This technical solution not only improves the accuracy and reliability of the simulation but also enhances its scalability and applicability, providing strong support for research and engineering practice in related fields.

[0103] Select one of the linear elastic constitutive relation, elastoplastic constitutive relation, and elastoplastic-brittle constitutive relation to describe the mechanical behavior of coal rock, and input the physical and mechanical parameters of coal rock, such as elastic modulus, Poisson's ratio, density, compressive strength, and tensile strength;

[0104] Setting the boundary conditions of the model, including at least fixed boundary, free boundary and stress boundary, wherein the fixed boundary can simulate the tunnel wall and the free boundary can simulate the free surface;

[0105] Set the initial stress state of the coal rock, obtain the initial stress distribution through in-situ stress test data, and input it into the model;

[0106] The parameters are set according to the actual impact coal breaking process, including at least the size, direction and time history of the impact load, the impact force and the impact speed.

[0107] The finite element method (FEM) and discrete element method (DEM) are used to solve the model. The three-dimensional geometric model and mesh are imported, the material properties, boundary conditions and initial conditions are set, the impact load is applied, the numerical simulation is run, and the propagation process of the stress wave in the coal rock is recorded.

[0108] The stress wave propagation of continuous media and discontinuous media is analyzed respectively, and the stress distribution inside the model is output, including compressive stress and tensile stress; the strain distribution inside the model is output to analyze the deformation; the displacement distribution inside the model is output to analyze the overall deformation of the structure; the energy loss analysis results of the stress wave during propagation are output, including friction dissipation and heat energy conversion; the dynamic response analysis results under impact load are output, including the propagation speed and attenuation characteristics of the stress wave; and the propagation data of the stress wave at different time points are output.

[0109] Describe the interference effects of various types of stress waves, specifically:

[0110] Calculate the propagation and reflection of cylindrical compression waves in coal and rock, calculate the propagation and reflection of plane isochoric waves in coal and rock, calculate the propagation and attenuation of Rayleigh surface waves near the free surface, and calculate the propagation and reflection of Stoney waves on discontinuities; in each time step, add up the contributions of all stress waves to obtain the total stress field distribution;

[0111] Analyze the superposition effect of different stress waves at the same location to determine whether constructive interference or destructive interference occurs.

[0112] The effectiveness and reliability of the proposed model are verified by comparing it with actual earthquake data or industrial test data. Specifically:

[0113] Compare the stress wave waveforms obtained from numerical simulations with those from actual seismic data to check the similarity of the waveforms;

[0114] Compare the stress wave amplitudes in numerical simulations and actual data to evaluate the model's ability to predict the amplitude; compare the frequency components in numerical simulations and actual data to check whether the model can accurately predict the spectral characteristics of stress waves; compare the stress wave propagation velocities in numerical simulations and actual data to evaluate the model's accuracy in predicting wave velocity; compare the stress wave attenuation characteristics in numerical simulations and actual data to check whether the model can accurately describe the wave attenuation process; compare the energy dissipation in numerical simulations and actual data to evaluate the model's ability to predict energy dissipation; compare the coal and rock failure modes in numerical simulations and actual data to evaluate the model's ability to predict failure mechanisms.

[0115] The effectiveness and reliability of the proposed model are verified by comparing it with actual earthquake data or industrial test data.

[0116] Calculate the mean and variance of numerical simulation results and actual data;

[0117] The correlation coefficient was used to evaluate the correlation between the numerical simulation results and the actual data;

[0118] Calculate absolute error, relative error, and root mean square error to quantify the prediction accuracy of the model;

[0119] Draw time series graphs, waveform graphs, and spectrum graphs of numerical simulation results and actual data to intuitively display the comparison results.

[0120] Based on the verification results, the model parameters are changed and the numerical simulation is repeated, which specifically includes the following steps:

[0121] Run the benchmark model once and record its output for reference;

[0122] Set a reasonable range of variation for each selected parameter, elastic modulus range 5GPa to 20GPa, Poisson's ratio range 0.15 to 0.40, density range 1800kg / m 3 Up to 2600kg / m 3, compressive strength range 10MPa to 50MPa, tensile strength range 0.5MPa to 5MPa, crack density range 0.01 to 0.2, impact load range 50kN to 200kN, impact velocity range 1m / s to 10m / s, impact time history range 0.01s to 0.1s, friction coefficient range 0.2 to 0.6, thermal conductivity range 0.5W / (m·K) to 2.0W / (m·K);

[0123] By combining single-factor analysis with multi-factor analysis, the change in model output before and after each parameter change is calculated;

[0124] Record the impact of each parameter change on the model output;

[0125] Calculate the sensitivity index and rank the parameters according to the sensitivity index;

[0126] Explain the reasons for the deviation of model output caused by parameter changes and improve the model again based on the results of sensitivity analysis.

[0127] Working Principle: First, the physical and mechanical properties and parameters of the coal rock are determined, natural fractures and bedding within the coal rock are identified, and the impact of these characteristics on the overall failure and damage of the coal rock is evaluated. Next, a three-dimensional geometric model is established that incorporates the internal structure and stress distribution characteristics of the coal rock. Meshing is performed, and appropriate constitutive relations are selected to describe the mechanical behavior of the coal rock. Boundary conditions, initial stress states, and impact loads are set.

[0128] The model is solved using the finite element method and discrete element method, recording the propagation of stress waves in coal and rock, including propagation velocity, attenuation characteristics, and energy dissipation. The results, including stress distribution, strain distribution, and displacement distribution, are then output. By calculating the interference effects of different types of stress waves and analyzing their superposition at the same location, it is determined whether constructive or destructive interference occurs.

[0129] Finally, the numerical simulation results are compared with actual earthquake data or industrial test data to verify the effectiveness and reliability of the model. Based on the verification results, the model parameters are changed, the numerical simulation is repeated, the changes in the model output are observed, the impact of different parameter changes on the model output is evaluated, the key parameters and their sensitivity are identified, and the model is optimized.

[0130] It should be noted that, in this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. The terms "include," "comprises," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0131] While the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions, and alterations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for analyzing the propagation law of stress waves in coal and rock media, characterized in that: The following steps are involved: S1. Determine the physical and mechanical properties and parameters of coal rock, including elastic modulus, Poisson's ratio, density, compressive strength, and tensile strength. Identify natural fractures and bedding in coal rock, and assess their impact on overall failure and damage. S2. Establish a theoretical model of stress wave propagation that incorporates the internal structure and stress distribution characteristics of coal and rock. Model each type of stress wave generated during the impact coal breaking process, and set the model's boundary conditions, initial conditions, impact load, and initial stress state of the coal and rock. Establishing a theoretical model for stress wave propagation includes the following steps: establishing a three-dimensional geometric model based on actual coal rock geological data, which includes the coal rock's geometric shape, cracks, bedding, and internal structure; meshing the three-dimensional geometric model to generate a finite element or discrete element mesh, including: Extracting first geological data of the actual coal rock, wherein the first geological data includes the number of coal rock layers, the thickness of each layer, and the dip angle of the formation; Comparing the number of coal and rock layers with a preset coal and rock layer number threshold; comparing the overall thickness of the coal rock with a preset overall thickness threshold; When the number of coal rock layers exceeds a preset coal rock layer number threshold and the overall thickness of the coal rock does not exceed a preset overall thickness threshold, a geological evaluation coefficient is obtained using the first geological data; otherwise, a finite element or discrete element mesh is generated by meshing the three-dimensional geometric model according to a preset initial mesh density; The geological evaluation coefficient is obtained by the following formula: Where G represents the geological evaluation coefficient; D represents the overall thickness of the coal rock; n represents the number of coal rock layers; H i represents the thickness of the i-th coal layer; A represents the dip angle of the formation; H c Indicates the preset reference value of the thickness of each coal layer; D y Indicates the preset overall thickness threshold; n y Indicates the preset coal layer number threshold; H p It represents the average thickness of the n-layer coal rock; Comparing the geological evaluation coefficient with a preset evaluation coefficient threshold; When the geological evaluation coefficient is lower than a preset evaluation coefficient threshold, the three-dimensional geometric model is meshed according to a preset initial mesh density to generate a finite element or discrete element mesh; When the geological evaluation coefficient is not lower than a preset evaluation coefficient threshold, a grid density is set, and the three-dimensional geometric model is meshed according to the set grid density to generate a finite element or discrete element grid; S3. Use the finite element method and discrete element method to solve the model, record the propagation process of stress waves in coal and rock, including the propagation speed, attenuation characteristics and energy dissipation of stress waves, output the calculation results, and describe the interference effects of various types of stress waves; S4. Verify the reliability of the proposed model in predicting stress wave propagation characteristics by comparing it with actual earthquake data or industrial test data; S5. Based on the verification results, change the model parameters, re-perform the numerical simulation, observe the changes in the model output, evaluate the impact of different parameter changes on the model output, and find out the key parameters and sensitivities.

2. The method for analyzing the propagation law of stress waves in coal and rock media according to claim 1, characterized in that: When the geological evaluation coefficient is not lower than the preset evaluation coefficient threshold, the grid density is set, including: Extracting first geological data of the actual coal rock, wherein the first geological data includes the number of coal rock layers, the thickness of each layer, and the dip angle of the formation; Extracting second geological data of the actual coal rock, wherein the second geological data includes the number and width of cracks in each layer of coal rock; Setting a grid density using the first geological data and the second geological data in combination with a preset initial grid density; The grid density is obtained by the following formula: Where P represents the grid density; P c represents the critical pressure; P0 represents the preset initial grid density; n represents the number of coal layers; H i represents the thickness of the i-th coal layer; A represents the dip angle of the formation; H c represents the preset reference value of the thickness of each coal rock layer; m represents the number of cracks in the i-th coal rock layer; L j represents the crack width corresponding to the jth crack in the i-th coal rock layer; L b represents the standard deviation of the overall crack width corresponding to the n-layer coal rock; L max Indicates the maximum crack width corresponding to the n-layer coal rock; L bmax Indicates the standard deviation of the crack width of the coal rock layer corresponding to the maximum crack width; L min Indicates the minimum value of the crack width corresponding to the n-layer coal rock; L bmin It represents the standard deviation of the crack width of the coal rock layer corresponding to the minimum crack width.

3. The method for analyzing the propagation law of stress waves in coal and rock media according to claim 2, characterized in that: The establishment of the stress wave propagation theoretical model further comprises the following steps: Select one of the linear elastic constitutive relation, elastoplastic constitutive relation and elastic-brittle constitutive relation to describe the mechanical behavior of coal rock, and input the physical and mechanical parameters of coal rock; Set the boundary conditions of the model, including at least fixed boundaries, free boundaries and stress boundaries; Set the initial stress state of the coal rock and obtain the initial stress distribution through in-situ stress test data; The parameters are set according to the actual impact coal breaking process, including at least the size, direction and time history of the impact load, the impact force and the impact speed.

4. The method for analyzing the propagation law of stress waves in coal and rock media according to claim 3, characterized in that: The finite element method and discrete element method are used to solve the model, output the stress distribution inside the model, including compressive stress and tensile stress; output the strain distribution inside the model to analyze the deformation; output the displacement distribution inside the model to analyze the overall deformation of the structure; Output the energy loss analysis results of stress waves during propagation, including friction dissipation and heat energy conversion; output the dynamic response analysis results under impact loads, including the propagation speed and attenuation characteristics of stress waves; Output stress wave propagation data at different time points.

5. The method for analyzing the propagation law of stress waves in coal and rock media according to claim 4, characterized in that: The interference effects of various types of stress waves are described as follows: Calculate the propagation and reflection of cylindrical compression waves in coal and rock, calculate the propagation and reflection of plane isochoric waves in coal and rock, calculate the propagation and attenuation of Rayleigh surface waves near the free surface, and calculate the propagation and reflection of Stoney waves on discontinuities; in each time step, add up the contributions of all stress waves to obtain the total stress field distribution; Analyze the superposition effect of different stress waves at the same location to determine whether constructive interference or destructive interference occurs.

6. The method for analyzing the propagation law of stress waves in coal and rock media according to claim 5, characterized in that: The effectiveness and reliability of the proposed model are verified by comparing it with actual earthquake data or industrial test data. Specifically: Compare the stress wave waveforms obtained from numerical simulations with those from actual seismic data to check the similarity of the waveforms; Compare the stress wave amplitudes from numerical simulations and actual data to evaluate the model's ability to predict the amplitudes; Compare the frequency components in the numerical simulation and the actual data to check whether the model can accurately predict the spectral characteristics of the stress wave; Compare the stress wave propagation velocities in numerical simulations and actual data to evaluate the accuracy of the model's predictions of wave velocities; Compare the stress wave attenuation characteristics in numerical simulations and actual data to check whether the model can accurately describe the wave attenuation process; Compare the energy dissipation in numerical simulations and actual data to evaluate the model's ability to predict energy dissipation; The coal and rock failure patterns in numerical simulations and actual data are compared to evaluate the model's ability to predict the failure mechanism.

7. The method for analyzing the propagation law of stress waves in coal and rock media according to claim 6, characterized in that: The effectiveness and reliability of the proposed model are verified by comparing it with actual earthquake data or industrial test data. Calculate the mean and variance of numerical simulation results and actual data; The correlation coefficient was used to evaluate the correlation between the numerical simulation results and the actual data; Calculate absolute error, relative error, and root mean square error to quantify the prediction accuracy of the model; Draw time series graphs, waveform graphs, and spectrum graphs of numerical simulation results and actual data to intuitively display the comparison results.

8. The method for analyzing the propagation law of stress waves in coal and rock media according to claim 7, characterized in that: Based on the verification results, the model parameters are changed and the numerical simulation is repeated, which specifically includes the following steps: Run the benchmark model once and record the output for reference; Set a reasonable range of variation for each selected parameter; By combining single-factor analysis with multi-factor analysis, the change in model output before and after each parameter change is calculated; Record the impact of each parameter change on the model output; Calculate the sensitivity index and rank the parameters according to the sensitivity index; Explain the reasons for the deviation of model output caused by parameter changes and improve the model again based on the results of sensitivity analysis.

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