A numerical simulation method for evaluating and preventing and controlling rock burst danger of fault

Abstract

The application discloses a fault rock burst danger evaluation and pressure relief prevention and control numerical simulation method, and belongs to the technical field of coal mine safety mining.The application constructs a dynamic and static superposition numerical simulation model, accurately quantifies three induced stresses of tectonic stress, mining stress and dynamic load stress, realizes impact danger grading evaluation, optimizes pressure relief parameters based on the evaluation result, improves the pertinence and effectiveness of fault rock burst prevention and control, effectively overcomes the defects of inaccurate fault rock burst danger evaluation and unscientific pressure relief parameter design in the prior art, realizes accurate grading evaluation of fault rock burst danger, and provides a scientific basis for rock burst prediction and prediction.Furthermore, the method flow of the embodiment is clear and has strong operability, combines field actual data and numerical simulation technology, takes into account the theory and practicability, and can be flexibly applied to coal mines containing faults.

Description

Technical Field

[0001] This invention belongs to the field of coal mine safety mining technology, and more specifically, it relates to a numerical simulation method for assessing the risk of fault rockburst and controlling pressure relief. Background Technology

[0002] As coal mining depths continue to increase, geological conditions become increasingly complex, and fault-slip rockbursts occur frequently. These disasters are characterized by their suddenness, wide impact range, and intense impact, seriously threatening the lives of mine personnel and the safety of equipment.

[0003] The core inducing factors of fault-slip rockbursts are the superposition of tectonic stress, mining stress, and fault-slip moving load stress. However, current technologies lack effective methods to accurately quantify these three stresses and achieve dynamic and static superposition simulation, leading to inaccurate assessments of fault rockburst hazard. Furthermore, decompression mining, as a primary means of rockburst prevention, relies heavily on field experience for decompression parameter design, lacking scientific optimization based on numerical simulation. This makes it difficult to guarantee decompression effectiveness and effectively avoid rockburst risks in high-risk areas. Therefore, a systematic and precise numerical simulation method is urgently needed to achieve accurate assessment of fault rockburst hazards and scientific optimization of decompression parameters. Summary of the Invention

[0004] This invention addresses the technical problems of inaccurate fault impact hazard assessment and unscientific decompression parameter design in existing technologies by providing a numerical simulation method for fault impact ground pressure hazard assessment and decompression control.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A numerical simulation method for assessing fault rockburst hazard and controlling pressure relief includes the following steps: S1. Establish the numerical calculation model and set the basic parameters. A numerical calculation model was constructed based on information from the mine and underground mining operations. The physical and mechanical parameters and constitutive model of the coal and rock strata in the model were defined. Then, boundary conditions were set, fixing the front, back, left, right, and bottom boundaries of the model. A load σ on the upper part of the model, representing unsimulated rock strata, was applied. p ; The self-weight stress of the model is set, and the self-weight stress in the vertical direction and the self-weight stress in the horizontal direction are calculated to obtain the self-weight stress field equilibrium results. S2. The fault formation process is modeled in the forward direction to obtain the tectonic stress distribution. Based on actual fault parameters from the field, the formation processes of normal and reverse faults were modeled by changing the model boundary conditions. Through fault forward modeling, the tectonic stress σ in the fault region was obtained. t Distribution characteristics; S3. Simulate the mining process and obtain the distribution of mining-induced stress. Simulates tunnel excavation and working face excavation, calculates model equilibrium after each excavation, and analyzes the advance support pressure data of the working face. The advance support pressure is determined by the structural stress σ. t With mining stress σ m The superimposed structure was used to obtain the stress distribution of mining operations as the working face advanced to different positions. S4. Simulate fault slippage load to obtain dynamic stress distribution. Monitor fault slip. When the fault slip distance exceeds a set value, activate the numerical simulation dynamic analysis module and change the model's fixed boundary to a static boundary. Simulate fault slip dynamic load by dividing the slipped fault plane into several regions, calculating the seismic moment for each region, and applying it as a concentrated force in a rectangular pattern to the surrounding rock near the fault to complete the fault slip dynamic response simulation. Arrange stress measuring points in the surrounding rock near the working face to obtain the dynamic stress σ. d ; S5. Fault Impact Hazard Classification Assessment The obtained structural stress σ t Mining stress σ m Dynamic stress σ d Superimposed with the uniaxial compressive strength σ of the coal body c The ratio of these values ​​is used as the impact hazard assessment index I. c According to I c Numerical classification of impact hazard levels, combined with on-site uniaxial compressive strength test results of coal seams, completes the fault impact hazard assessment during the working face mining process, and identifies areas with severe impact hazard.

[0006] Preferred options also include: S6. Determine the blasting decompression method and calculate the blasting parameters. For areas identified as having severe impact hazards, blasting for pressure relief is employed. The primary roof above the coal seam or the hard roof strata near the coal seam are identified as the target strata for pressure relief. A combined deep and shallow borehole layout is used, with the horizontal projection of the boreholes perpendicular to the roadway axis. Vertically, deep and shallow boreholes are arranged in combination, with the borehole surface reaching the upper boundary of the hard roof, and horizontally covering the entire working face. Based on the equivalent medium method, the blasting pressure relief effect is simulated by weakening the rock mass parameters in the blasting damage zone. S7. Optimize depressurization parameters and verify depressurization effect. To maintain the balance of the self-weight stress field and the fault forward modeling results, the physical and mechanical parameters of the rock mass in the blasting fracture zone were weakened in the area of ​​severe impact hazard to simulate the blasting decompression process. Numerical simulations of different borehole horizontal spacing R were carried out. After each simulation was completed, S3-S6 were repeated to obtain the impact hazard evaluation results after decompression. The optimal decompression parameters were selected to ensure safe mining of the working face.

[0007] Preferably, in S1, the physical and mechanical parameters set include bulk modulus, shear modulus, tensile strength, internal friction angle, and cohesion, and the model is fixed using the Fix command; Vertical self-weight stress σ zz Based on coal and rock strata density, gravitational acceleration, and load σ p Automatic calculation of horizontal self-weight stress σ xz σ yz The calculation is based on the following formula;

[0008] In the formula, σ xz σ is the horizontal self-weight stress in the X direction, MPa; yz γ is the horizontal self-weight stress in the Y direction, MPa; H is the burial depth of the working face, m; v is the Poisson's ratio of the rock; γ is the unit weight of the rock, N / m³. 3 λ is the ratio of horizontal stress to vertical stress. When the Poisson's ratio of the rock is 0.26, the ratio of horizontal stress to vertical stress is λ = 0.35.

[0009] Preferably, in S2, the fault parameters include fault type, dip angle, and displacement; The specific process of forward modeling a normal fault is as follows: apply velocity at the bottom of the model, apply a downward velocity to the hanging wall of the fault with the same dip angle as the fault, and apply an upward velocity to the footwall of the fault with the same dip angle as the fault, so that the two sides of the fault will shift. When the fault displacement reaches the actual engineering value, stop applying velocity, restore the bottom boundary of the model to a fixed boundary, and the forward modeling is completed.

[0010] Preferably, in S2, the specific process of forward modeling of the inverse fault is as follows: apply velocity at the bottom of the model, apply an upward velocity to the hanging wall of the fault with the same dip angle as the fault, and apply a downward velocity to the footwall of the fault with the same dip angle as the fault, so that the two sides of the fault move. When the fault displacement reaches the actual engineering value, stop applying velocity and complete the forward modeling.

[0011] Preferably, in S4, when the fault slip distance is greater than 0.02m, the numerical simulation dynamic analysis module is activated; The fault slip load is simulated by applying a seismic moment, and the fault slip seismic moment M0 is calculated based on the following formula: M0=GAD In the formula, G is the fault stiffness (GPa); A is the fault area where shear slip occurs (m²). 2 D represents the fault shear slip, in meters. Dynamic stress σ d This is the difference between the peak stress under dynamic load and the static stress.

[0012] Preferably, in S4, when the fault slip distance is detected to be greater than 0.02m, the dynamic analysis module of the numerical simulation is started by using the set dyn on command statement to calculate the fault slip force. During the calculation, the boundary conditions of the model are changed again, and the fixed boundary is changed to the static boundary to avoid the refraction and reflection of the fault slip load stress wave at the model boundary. The fault plane where slip occurred is divided into several regions, and each region is assigned a number. A 1. A 2. A 3…. A n The fault slip seismic moments for each region are calculated as follows: M 01 , M 02 , M 03 … M 0n .

[0013] Preferably, in S5, the impact hazard assessment index I c The calculation method is as follows:

[0014] In the formula, σ c The uniaxial compressive strength of the coal body is expressed in MPa. The standard for classifying impact hazard levels is: I c <1.5 indicates no impact risk; 1.5≤I c <2.0 indicates a minor impact hazard; 2.0≤I c <2.5 indicates a moderate impact risk, I c ≥2.5 indicates a severe impact hazard.

[0015] Preferably, in S6, the borehole layout angle is 20°-75°, the cohesion of the weakened rock mass is 1 / 2-1 / 10 of the initial value, and the tensile strength is reduced to 0; Explosive fragmentation zone radius R p Calculated based on the following formula:

[0016] In the formula, α is the stress wave attenuation value. v is Poisson's ratio; P is the extreme value of blasting stress, MPa. D is the detonation velocity of the explosive, m / s; ρ0 is the density of the explosive, kg / m³. 3 ;r c Where is the radius of the medicine pack, in mm; n is the stress amplification factor; r b S represents the borehole radius, in mm; t denoted as the tensile strength of the rock mass, in MPa.

[0017] Preferably, the weakening criteria for rock mass parameters in the blast damage zone are: cohesion reduced to 1 / 5 of the initial value and tensile strength reduced to 0.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a numerical simulation method for assessing the hazard of fault-induced rockbursts and for stress relief and control. By constructing a dynamic-static superimposed numerical simulation model, it accurately quantifies three induced stresses: tectonic stress, mining-induced stress, and dynamic load stress, achieving a graded assessment of rockburst hazard. Based on the assessment results, it optimizes stress relief parameters, improving the targeting and effectiveness of fault-induced rockburst control. This effectively overcomes the shortcomings of existing technologies, such as inaccurate assessment of fault-induced rockburst hazard and unscientific design of stress relief parameters. It achieves a precise graded assessment of fault-induced rockburst hazard, providing a scientific basis for rockburst prediction and forecasting. Moreover, the method described in this embodiment has a clear process, is highly operable, and combines actual field data with numerical simulation technology, balancing theoretical rigor with practical application. It can be flexibly applied to coal mines containing faults. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the method flow proposed in one embodiment of the present invention; Figure 2 This is a schematic diagram of the model boundary conditions and self-weight stress according to one embodiment of the present invention; Figure 3 This is a schematic diagram of the boundary conditions during forward modeling of a normal fault, according to one embodiment of the present invention. Figure 4 This is a schematic diagram of the boundary conditions during forward modeling of a reverse fault, according to one embodiment of the present invention. Figure 5 This is a stratigraphic columnar section of the L coal mine in one embodiment of the present invention; Figure 6 This is a plan view of the mining engineering of a coal mine working face according to one embodiment of the present invention; Figure 7 This is a schematic diagram of the numerical calculation model of the working surface according to one embodiment of the present invention; Figure 8 This is a displacement contour map of the working face after forward modeling the fault, according to one embodiment of the present invention. Figure 9 This is a vertical stress cloud diagram of the working face after forward modeling the fault, according to one embodiment of the present invention. Figure 10 This is a vertical stress cloud diagram of direct fault stress assignment according to one embodiment of the present invention; Figure 11 This is a comparison curve of forward-modeled fault and directly assigned vertical stress in fault stress according to one embodiment of the present invention; Figure 12 This is a cloud map showing the stress distribution during mining in one embodiment of the present invention. Figure 13 This is a diagram showing the stress distribution curves when the working face is advanced to different positions according to one embodiment of the present invention. Figure 14 This is a simulation diagram of the fault slip volume when the working face advances to the fault location according to one embodiment of the present invention; Figure 15 This is a schematic diagram of the boundary conditions during dynamic calculation of the working face in one embodiment of the present invention; Figure 16 This is a schematic diagram illustrating the application of fault slip seismic moment according to one embodiment of the present invention; Figure 17 This is a velocity cloud map of a mining area under fault slippage load according to one embodiment of the present invention. Figure 18 This is a schematic diagram of the simulation results of fault slip-induced load stress in one embodiment of the present invention; Figure 19 This is a dynamic response curve of surrounding rock stress when the working face is advanced to different positions according to one embodiment of the present invention; Figure 20 This is a schematic cross-sectional view of the blasting borehole arrangement according to one embodiment of the present invention; Figure 21 This is a schematic plan view of the blasting borehole arrangement according to one embodiment of the present invention; Figure 22 This is a cloud map showing the vertical stress distribution in the mining area after blasting and decompression in one embodiment of the present invention without cutting the roof; Figure 23 This is a cloud map showing the vertical stress distribution in the mining area after blasting and decompression, according to one embodiment of the present invention, when the borehole spacing is 12m. Figure 24 This is a cloud map showing the vertical stress distribution in the mining area after blasting and decompression, when the borehole spacing is 10m, according to one embodiment of the present invention. Figure 25 This is a cloud map showing the vertical stress distribution in the mining area after blasting and decompression, when the borehole spacing is 8m, according to one embodiment of the present invention. Figure 26 This is a graph showing the stress-dynamic response curves of the mining area after blasting at different borehole spacings when the working face advances to the fault position, according to one embodiment of the present invention. Detailed Implementation

[0021] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0022] Example 1 Please see Figure 1 This invention provides a numerical simulation method for assessing the hazard of fault rockburst and controlling pressure relief, which includes the following steps: S1. Establish the numerical calculation model and set the basic parameters. A numerical calculation model was constructed based on information from the mine and underground mining operations. The physical and mechanical parameters and constitutive model of the coal and rock strata in the model were defined. Then, boundary conditions were set, fixing the front, back, left, right, and bottom boundaries of the model. A load σ on the upper part of the model, representing unsimulated rock strata, was applied. p ; The self-weight stress of the model is set, and the self-weight stress in the vertical direction and the self-weight stress in the horizontal direction are calculated to obtain the self-weight stress field equilibrium results. S2. The fault formation process is modeled in the forward direction to obtain the tectonic stress distribution. Based on actual fault parameters from the field, the formation processes of normal and reverse faults were modeled by changing the model boundary conditions. Through fault forward modeling, the tectonic stress σ in the fault region was obtained. t Distribution characteristics; S3. Simulate the mining process and obtain the distribution of mining-induced stress. Simulates tunnel excavation and working face excavation, calculates model equilibrium after each excavation, and analyzes the advance support pressure data of the working face. The advance support pressure is determined by the structural stress σ. t With mining stress σ m The superimposed structure was used to obtain the stress distribution of mining operations as the working face advanced to different positions. S4. Simulate fault slippage load to obtain dynamic stress distribution. Monitor fault slip. When the fault slip distance exceeds a set value, activate the numerical simulation dynamic analysis module and change the model's fixed boundary to a static boundary. Simulate fault slip dynamic load by dividing the slipped fault plane into several regions, calculating the seismic moment for each region, and applying it as a concentrated force in a rectangular pattern to the surrounding rock near the fault to complete the fault slip dynamic response simulation. Arrange stress measuring points in the surrounding rock near the working face to obtain the dynamic stress σ. d ; S5. Fault Impact Hazard Classification Assessment The obtained structural stress σ t Mining stress σ m Dynamic stress σ d Superimposed with the uniaxial compressive strength σ of the coal body cThe ratio of these values ​​is used as the impact hazard assessment index I. c According to I c Numerical classification of impact hazard levels, combined with on-site uniaxial compressive strength test results of coal seams, completes the fault impact hazard assessment during the working face mining process, and identifies areas with severe impact hazard.

[0023] This invention, through the construction of a dynamic-static superposition numerical simulation model, accurately quantifies three induced stresses: tectonic stress, mining-induced stress, and dynamic load stress, achieving a graded evaluation of rockburst hazard. Based on the evaluation results, it optimizes stress relief parameters, improving the targeting and effectiveness of fault rockburst prevention and control. This effectively overcomes the shortcomings of existing technologies, such as inaccurate fault rockburst hazard evaluation and unscientific stress relief parameter design, achieving a precise graded evaluation of fault rockburst hazard and providing a scientific basis for rockburst prediction and forecasting. Furthermore, the method described in this embodiment is clear, highly operable, and combines actual field data with numerical simulation technology, balancing theoretical rigor with practical application, making it flexibly applicable to coal mines containing faults.

[0024] Example 2 Based on Example 1, this embodiment of the invention provides a numerical simulation method for assessing the hazard of fault rockburst and controlling pressure relief, comprising the following steps: S1. Establish the numerical calculation model and set the basic parameters. Based on field data such as mine stratigraphic columnar section, mining engineering plan, and test results of coal and rock mass mechanical parameters, a numerical calculation model was constructed. The physical and mechanical parameters and constitutive model of the coal and rock strata in the model were defined, including bulk modulus, shear modulus, tensile strength, internal friction angle, and cohesion. Boundary conditions were set for the model; the front, back, left, right, and bottom of the model were fixed using the Fix command, and a load σ on the upper part of the model was applied to the unsimulated rock strata. p Then, set the self-weight stress of the model, with the vertical self-weight stress σ. zz Based on coal and rock strata density, gravitational acceleration, and load σ p Automatic calculation of horizontal self-weight stress σ xz σ yz The calculation is based on the following formula, where the horizontal stress σ is... xz With σ yz The values ​​are equal in magnitude and are taken as 0.35 times the vertical stress, i.e., λ = 0.35. The boundary conditions and self-weight stress of the model are as follows: Figure 2 As shown.

[0025] After setting the model parameters, boundary conditions, and self-weight stress field, the model is calculated to obtain the self-weight stress field equilibrium results.

[0026] (Equation 1) In the formula, σ xzσ is the horizontal self-weight stress in the X direction, MPa; yz γ is the horizontal self-weight stress in the Y direction, MPa; H is the burial depth of the working face, m; v is the Poisson's ratio of the rock; γ is the unit weight of the rock, N / m³. 3 λ is the ratio of horizontal stress to vertical stress, λ=0.35.

[0027] S2. The fault formation process is modeled in the forward direction to obtain the tectonic stress distribution. Based on the actual fault parameters on site, including fault type (normal fault, reverse fault), dip angle, and displacement, each fault parameter can be adjusted and determined based on the actual site conditions.

[0028] By changing the model boundary conditions, the formation processes of normal and reverse faults were modeled in forward mode, and the tectonic stress σ in the fault region was obtained through fault forward modeling. t Distribution characteristics.

[0029] Furthermore, such as Figure 3 As shown, the specific process of forward modeling a normal fault is as follows: When modeling a normal fault, a velocity is applied to the bottom of the model, a downward velocity with the same dip angle is applied to the hanging wall of the fault, and an upward velocity with the same dip angle is applied to the footwall of the fault, so that the two sides of the fault move. When the fault displacement reaches the actual engineering value, the velocity is stopped, the bottom boundary of the model is restored to a fixed boundary, and the forward modeling is completed.

[0030] like Figure 4 As shown, the specific process of forward modeling of a reverse fault is as follows: When modeling a reverse fault, a velocity is applied to the bottom of the model, an upward velocity of the same dip angle is applied to the hanging wall of the fault, and a downward velocity of the same dip angle is applied to the footwall of the fault, so that the two sides of the fault move. When the fault displacement reaches the actual engineering value, the velocity application is stopped, and the forward modeling is completed.

[0031] S3. Simulate the mining process and obtain the distribution of mining-induced stress. Based on the actual production of tunnel excavation and working face excavation, the tunnel excavation and working face excavation are simulated. Both tunnel excavation and working face excavation adopt a distributed excavation mode. The length of each excavation can be set according to the site conditions (usually 10m-20m, and can be set to 10m, 20m, etc.).

[0032] After each excavation, the model is balanced, and the data on the advance support pressure at the working face are analyzed. The numerical simulation results of the advance support pressure are derived from the structural stress σ. t With mining stress σ m The superimposed structure is used to obtain the stress distribution of mining operations as the working face advances to different positions.

[0033] S4. Simulate fault slippage load to obtain dynamic stress distribution. During mining operations, faults are prone to slippage and activation due to the mining process, releasing a large amount of energy and generating dynamic stress on the surrounding rock. Therefore, it is necessary to monitor fault slippage. When the slippage distance exceeds a set value, the dynamic analysis module of the numerical simulation is activated using the `set dyn on` command. During calculation, the model's boundary conditions are changed again, replacing the fixed boundary with a static boundary to prevent refraction and reflection of the fault slip stress waves at the model boundaries.

[0034] The fault slip load is simulated by applying a seismic moment to the fault slip region. The fault slip seismic moment M0 is calculated based on the following formula: M0 = GAD (Equation 2) In the formula, G is the fault stiffness (GPa); A is the fault area where shear slip occurs (m²). 2 D represents the fault shear slip, in meters (m).

[0035] Furthermore, the fault plane where slippage occurred was divided into several regions, and the seismic moment of each region was calculated and applied to the surrounding rock near the fault in a concentrated force rectangular manner to complete the simulation of the fault slippage dynamic response; stress measuring points were arranged in the surrounding rock near the working face to obtain the dynamic stress σ. d Dynamic stress σ d This is the difference between the peak stress under dynamic load and the static stress.

[0036] In this embodiment, the numerical simulation dynamic analysis module is activated when the fault slip distance is greater than 0.02m.

[0037] Furthermore, the fault plane where slippage occurred is divided into several regions, and each region is assigned a number. A 1. A 2. A 3…. A n The fault slip seismic moments for each region are calculated as follows: M 01 , M 02 , M 03 … M 0n The seismic moment of each region is applied as a concentrated moment to the surrounding rock near the corresponding fault, thereby realizing the numerical simulation calculation of the fault sliding dynamic response. The dynamic response law of the surrounding rock in the mining area under fault sliding load disturbance is obtained through fault dynamic analysis. Stress measuring points are arranged in the surrounding rock near the working face to obtain the magnitude of the dynamic load stress in the surrounding rock of the mining area.

[0038] S5. Fault Impact Hazard Classification Assessment The structural stress σ obtained from the above stepst Mining stress σ m Dynamic stress σ d Superimposed with the uniaxial compressive strength σ of the coal body c The ratio of these values ​​is used as the impact hazard assessment index I. c Impact Risk Assessment Index I c The calculation method is as follows: (Equation 3) In the formula, σ c denoted as uniaxial compressive strength of coal, in MPa.

[0039] The standard for classifying impact hazard levels is: I c <1.5 indicates no impact risk; 1.5≤I c <2.0 indicates a minor impact hazard; 2.0≤I c <2.5 indicates a moderate impact risk, I c ≥2.5 indicates a severe impact hazard.

[0040] Meanwhile, in practical applications, I c The classification threshold can also be calculated back based on historical rockburst cases in the field, and the size of the classification threshold can be optimized and adjusted.

[0041] According to I c Numerical classification of impact hazard levels, combined with on-site uniaxial compressive strength test results of coal seams, completes the fault impact hazard assessment during the working face mining process, and identifies areas with severe impact hazard.

[0042] S6. Determine the blasting decompression method and calculate the blasting parameters. For the severely impact-hazardous areas identified in step S5, if the evaluation results indicate the existence of highly impact-hazardous areas that affect the safe production of the mine, blasting is required to relieve pressure in these highly impact-hazardous areas. This aims to reduce tectonic stress in the fault-affected zone and mining-induced stress during the working face mining process. Blasting is used for pressure relief. Since tectonic stress and elastic energy are concentrated in the hard roof strata, the primary target strata for pressure relief are first identified as the basic roof above the coal seam or the hard roof strata near the coal seam. Then, a borehole layout scheme is determined, employing a combination of deep and shallow boreholes to ensure timely fracturing of the basic roof or hard, thick roof strata after blasting. The horizontal projection of the boreholes is perpendicular to the roadway axis, with a combined deep and shallow borehole arrangement in the vertical direction. The borehole surface reaches the upper boundary of the hard roof, with a borehole angle of 20°-75°. Horizontal boreholes cover the entire working face area. Based on the equivalent medium method, the blasting pressure relief effect is simulated by weakening the rock mass parameters in the blasting damage zone. After weakening, the cohesion of the rock mass is 1 / 2 to 1 / 10 of the initial value, and the tensile strength is reduced to 0. Explosive fragmentation zone radius R p Calculated based on the following formula: (Equation 4) In the formula, α is the stress wave attenuation value. v is Poisson's ratio; P is the extreme value of blasting stress, MPa. D is the detonation velocity of the explosive, m / s; ρ0 is the density of the explosive, kg / m³. 3 ;r c Where is the radius of the medicine pack, in mm; n is the stress amplification factor; r b S represents the borehole radius, in mm; t denoted as the tensile strength of the rock mass, in MPa.

[0043] S7. Optimize depressurization parameters and verify depressurization effect. Keeping the self-weight stress field balance in step S1 and the fault forward modeling results in step S2 unchanged, the physical and mechanical parameters of the rock mass in the blasting fracture zone are weakened in the area of ​​severe impact hazard to simulate the blasting decompression process; multiple sets of numerical simulations with different horizontal spacing R of blast holes are carried out. After each set of simulations is completed, steps S3-S6 are repeated to obtain the impact hazard evaluation results after decompression; the maximum blast hole spacing that can effectively eliminate the area of ​​severe impact hazard is selected as the optimal decompression parameter to ensure safe mining of the working face.

[0044] In this embodiment, the weakening standard for rock mass parameters in the blast damage zone is: the cohesion is reduced to 1 / 5 of the initial value, and the tensile strength is reduced to 0.

[0045] Example 3 This embodiment takes the 3301 working face and FD71 normal fault of a certain L coal mine in China as an example to further verify the numerical simulation method for fault rockburst risk assessment and pressure relief control provided by the present invention with detailed example data.

[0046] During the mining of the 3301 working face in L coal mine, it is necessary to traverse the FD71 normal fault. This fault has a vertical drop of 3 meters and a dip angle of approximately 60°. The mining direction of the working face is from the hanging wall to the footwall of the fault. The uniaxial compressive strength σ of the coal seam was measured in the laboratory. c =17MPa, and the physical and mechanical parameters of the coal and rock mass are shown in Table 1.

[0047] Table 1 Physical and mechanical parameters of coal and rock mass

[0048] The specific implementation steps are as follows.

[0049] S1. Establish the numerical calculation model and set the basic parameters. Based on the test results of relevant data such as the mine's stratigraphic column, mining engineering plan, and coal and rock mass mechanical parameters, a numerical calculation model with a length of 1100m, a width of 270m, and a height of 150m was constructed. The mine's stratigraphic column is shown below. Figure 5 As shown.

[0050] The working face mining engineering plan is as follows Figure 6 As shown, the numerical calculation model is as follows Figure 7 As shown in Table 1, the physical and mechanical parameters and constitutive model of the coal and rock strata are set.

[0051] Secondly, set the boundary conditions for the model, and apply an unsimulated rock layer load σ to the upper part. p Vertical self-weight stress σ zz Automatic calculation of horizontal self-weight stress σ xz σ yz Based on Equation 1, the equilibrium result of the self-weight stress field is obtained.

[0052] S2. The fault formation process is modeled in the forward direction to obtain the tectonic stress distribution. Based on the actual parameters of the FD71 normal fault (fault displacement 3m, dip angle approximately 60°), the normal fault formation was modeled using forward modeling. A velocity of 1×10⁻⁶ was applied to the bottom of the model. -6 m / hour step, with the direction making a 60° angle with the horizontal, controls the downward movement of the hanging wall and the upward movement of the footwall. When the elevation difference between the hanging wall and footwall reaches 3m, the movement of the two sides of the fault ceases, the applied velocity is stopped, the bottom boundary of the model is restored, and the forward modeling is completed. Through simulation, the tectonic stress σ in the FD71 normal fault region is obtained. t Distribution characteristics.

[0053] The displacement contour maps and vertical stress contour maps after forward modeling of the fault are as follows: Figure 8 , Figure 9 As shown, the vertical stress contour diagram of the fault stress is directly assigned as follows: Figure 10 As shown in the figure, the comparison curves between forward-modeled faults and directly assigned vertical stresses are as follows: Figure 11 As shown.

[0054] S3. Simulate the mining process and obtain the distribution of mining-induced stress. A step-by-step excavation mode was adopted, with each excavation length set at 10m. This simulated tunnel excavation and the excavation of the 3301 working face. After each excavation, the model was balanced, and the advance support pressure data of the working face was analyzed. The advance support pressure (including σ) was obtained when the working face advanced to different positions (80m-160m from the fault). t With σ m ).

[0055] Table 2 shows the peak values ​​of the advance support pressure when the working face advances to different positions, and the cloud map of the dynamic stress distribution during mining is shown in the figure. Figure 12 As shown in the figure, the stress distribution curves during mining operations at different positions are as follows: Figure 13 As shown.

[0056] Table 2 Peak values ​​of advance support pressure when the working face advances to different positions

[0057] S4. Simulate fault slippage load to obtain dynamic stress distribution. When the working face was detected to have advanced to the vicinity of the fault, the fault slip distance was greater than 0.02m. The dynamic analysis module was activated, and the fault slip amount when the working face reached the fault location was as follows: Figure 14 As shown. When calculating the fault slip dynamic force, the boundary conditions of the model are changed again, replacing the fixed boundary with a static boundary to prevent refraction and reflection of the fault slip stress waves at the model boundary. The boundary conditions for the dynamic calculation are as follows: Figure 15 As shown.

[0058] Based on Equation 2, the fault slip seismic moment M0 was calculated. The slip surface of the FD71 normal fault was divided into several regions, and corresponding concentrated moments were applied to complete the dynamic response simulation. Stress measuring points were arranged in the surrounding rock near the working face to obtain the dynamic stress σ. d The results are shown in Table 3.

[0059] The effect of applying fault slip seismic moment is as follows: Figure 16 As shown, the velocity contour map of the surrounding rock in the mining area under the disturbance effect of fault slip movement is as follows. Figure 17 As shown in the diagram, the simulation results of fault slip load stress are as follows: Figure 18 As shown, the magnitude of the dynamic stress is the peak stress under dynamic load minus the static stress. The dynamic response curves of the surrounding rock stress at different positions of the working face are shown in the figure. Figure 19 As shown.

[0060] S5. Fault Impact Hazard Classification Assessment The impact hazard assessment index I is calculated based on Equation 3. c Combined with the uniaxial compressive strength σ of the coal body measured in the laboratory c =17MPa, the impact hazard level was classified, and the results are shown in Table 3. As can be seen from Table 3, the working face at 0m, -20m, -40m, and -60m from the fault is a severe impact hazard zone, and the remaining locations are moderate impact hazard zones.

[0061] Table 3 Impact Hazards at Different Positions of the Working Face

[0062] S6. Determine the blasting and depressurization scheme and calculate the blasting parameters. The hard roof above the coal seam was identified as the target stratum for stress relief. A combined deep and shallow borehole layout scheme was adopted, and the borehole layout profile is shown in the figure below. Figure 20As shown, the horizontal projection of the boreholes is perpendicular to the roadway axis. Boreholes are drilled from the two roadways ahead of the working face towards the center of the goaf. To fully pre-split the hard roof, a combination of deep and shallow boreholes is used. The borehole surface reaches the upper boundary of the hard roof. The borehole angle is generally 20°-75°, covering the entire working face area. The borehole layout plan is shown in the figure. Figure 21 As shown.

[0063] The horizontal spacing R of the blast holes was optimized using numerical simulation. Blasting parameters were calculated based on Formula 4: Poisson's ratio was used. v =0.26, stress wave attenuation value α =1.65, explosive detonation velocity D =4000m / s, explosive density ρ 0 = 1300 kg / m³, radius of the medicine pack r c =31.5mm, borehole radius r b =37.5mm, tensile strength of rock mass S t =5MPa, pressure increase factor n =8, the extreme value of blasting stress is calculated. P =7.31GPa, radius of the blasting fragmentation zone R p =1.69m; Set the rock mass parameters for the blasting fracture zone: reduce cohesion to 1 / 5 of the initial value and reduce tensile strength to 0.

[0064] S7. Optimize depressurization parameters and verify depressurization effect. Keeping the model state unchanged in steps 1 and 2, simulate blasting and decompression in a high-impact hazard area, and conduct multiple sets of numerical simulations with different borehole spacings (8m, 10m, 12m). Repeat steps 3-6 after each set of simulations to obtain the impact hazard assessment results after decompression.

[0065] In this embodiment, the vertical stress distribution cloud map of the mining area after blasting and decompression at different borehole spacings is shown below. Figures 22-25 As shown in the figure; the stress-dynamic response curves of the mining area after blasting at different borehole spacings when the working face advances to the fault position are shown in the figure. Figure 26 As shown.

[0066] The results showed that when the borehole spacing was 10m, the severe impact hazard zone was completely eliminated, and all locations were at moderate impact hazard, with the pressure relief effect being optimal. The evaluation results after pressure relief are shown in Table 4, and the optimal borehole spacing was determined to be 10m.

[0067] Table 4 Impact Hazards of the Working Face After Blasting and Pressure Relief

[0068] In summary, the method provided in this embodiment of the invention was used to evaluate and depressurize the rockburst of the FD71 normal fault in the 3301 working face of L coal mine. The severe rockburst hazard area was identified through accurate evaluation, and the optimal borehole spacing of 10m was obtained through optimization. After depressurization, the severe rockburst hazard was completely eliminated, and the working face was safely mined. This verifies the superiority, scientific nature and practicality of the method of this invention.

[0069] This invention provides a numerical simulation method for assessing fault rockburst hazard and controlling pressure relief. By constructing a dynamic-static superimposed numerical simulation model, it accurately quantifies three induced stresses: tectonic stress, mining-induced stress, and dynamic load stress, achieving a graded assessment of rockburst hazard. Based on the assessment results, it optimizes pressure relief parameters, improving the targeting and effectiveness of fault rockburst control. This effectively overcomes the shortcomings of existing technologies, such as inaccurate assessment of fault rockburst hazard and unscientific design of pressure relief parameters, achieving a precise graded assessment of fault rockburst hazard and providing a scientific basis for rockburst prediction and forecasting. Furthermore, this invention proposes a numerical simulation-based method for optimizing blasting pressure relief parameters. Targeting areas with severe rockburst hazard, it determines the optimal borehole spacing through simulation comparison of multiple sets of parameters, overcoming the limitation of relying on experience in pressure relief parameter design, improving the targeting and effectiveness of pressure relief control, effectively eliminating severe rockburst hazards, and ensuring safe mine production.

[0070] The entire process of this invention is clear and easy to operate. Combining actual field data with numerical simulation technology, it balances theory and practicality and can be widely and flexibly applied to various deep coal mines with faults. It has good promotion and application value.

[0071] In the description of this invention, it should be understood that terms such as “length”, “width”, “upper”, “lower”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, and “outer” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0072] Furthermore, in the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0073] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A numerical simulation method for assessing the hazard of fault rockburst and controlling pressure relief, characterized in that, Includes the following steps: S1. Establish the numerical calculation model and set the basic parameters. Based on the mine and underground mining information to build a numerical calculation model, set the physical and mechanical parameters of the coal and rock layer in the model and the constitutive model, then set the model boundary conditions, fix the front, back, left and right and bottom boundaries of the model, and apply the load σ of the non-simulated rock layer to the upper part of the model p ; The self-weight stress of the model is set, and the self-weight stress in the vertical direction and the self-weight stress in the horizontal direction are calculated to obtain the self-weight stress field equilibrium results. S2. The fault formation process is modeled in the forward direction to obtain the tectonic stress distribution. Based on the actual fault parameters, by changing the boundary conditions of the model, respectively, normal fault, reverse fault formation process, through the fault forward simulation, the tectonic stressσ t distribution characteristics; S3. Simulate the mining process and obtain the distribution of mining-induced stress. The simulation of roadway excavation and working face excavation is carried out, the model balance is calculated after each excavation, the advanced abutment pressure data are analyzed, and the advanced abutment pressure is composed of tectonic stress σ t and mining stress σ m superposition, the mining stress distribution when the working face advances to different positions is obtained; S4. Simulate fault slippage load to obtain dynamic stress distribution. Monitor fault slip. When the fault slip distance exceeds a set value, activate the numerical simulation dynamic analysis module and change the model's fixed boundary to a static boundary. Simulate fault slip dynamic load by dividing the slipped fault plane into several regions, calculating the seismic moment for each region, and applying it as a concentrated force in a rectangular pattern to the surrounding rock near the fault to complete the fault slip dynamic response simulation. Arrange stress measuring points in the surrounding rock near the working face to obtain the dynamic stress σ. d ; S5. Fault Impact Hazard Classification Assessment The obtained structural stress σ t Mining stress σ m Dynamic stress σ d Superimposed with the uniaxial compressive strength σ of the coal body c The ratio of these values ​​is used as the impact hazard assessment index I. c According to I c Numerical classification of impact hazard levels, combined with on-site uniaxial compressive strength test results of coal seams, completes the fault impact hazard assessment during the working face mining process, and identifies areas with severe impact hazard.

2. The numerical simulation method for fault rockburst hazard assessment and pressure relief control according to claim 1, characterized in that, Also includes: S6. Determine the blasting decompression method and calculate the blasting parameters. For areas identified as having severe impact hazards, blasting for pressure relief is employed. The primary roof above the coal seam or the hard roof strata near the coal seam are identified as the target strata for pressure relief. A combined deep and shallow borehole layout is used, with the horizontal projection of the boreholes perpendicular to the roadway axis. Vertically, deep and shallow boreholes are arranged in combination, with the borehole surface reaching the upper boundary of the hard roof, and horizontally covering the entire working face. Based on the equivalent medium method, the blasting pressure relief effect is simulated by weakening the rock mass parameters in the blasting damage zone. S7. Optimize depressurization parameters and verify depressurization effect. To maintain the balance of the self-weight stress field and the fault forward modeling results, the physical and mechanical parameters of the rock mass in the blasting fracture zone were weakened in the area of ​​severe impact hazard to simulate the blasting decompression process. Numerical simulations of different borehole horizontal spacing R were carried out. After each simulation was completed, S3-S6 were repeated to obtain the impact hazard evaluation results after decompression. The optimal decompression parameters were selected to ensure safe mining of the working face.

3. The numerical simulation method for fault rockburst hazard assessment and pressure relief control according to claim 1, characterized in that, In S1, the physical and mechanical parameters set include bulk modulus, shear modulus, tensile strength, internal friction angle, and cohesion. The model is fixed using the Fix command. Vertical self-weight stress σ zz Based on coal and rock strata density, gravitational acceleration, and load σ p Automatic calculation of horizontal self-weight stress σ xz σ yz The calculation is based on the following formula; In the formula, σ xz σ is the horizontal self-weight stress in the X direction, MPa; yz γ is the horizontal self-weight stress in the Y direction, MPa; H is the burial depth of the working face, m; v is the Poisson's ratio of the rock; γ is the unit weight of the rock, N / m³. 3 λ is the ratio of horizontal stress to vertical stress. When the Poisson's ratio of the rock is 0.26, the ratio of horizontal stress to vertical stress is λ = 0.

35.

4. The numerical simulation method for fault rockburst hazard assessment and pressure relief control according to claim 1, characterized in that, In S2, fault parameters include fault type, dip angle, and displacement; The specific process of forward modeling a normal fault is as follows: apply velocity at the bottom of the model, apply a downward velocity to the hanging wall of the fault with the same dip angle as the fault, and apply an upward velocity to the footwall of the fault with the same dip angle as the fault, so that the two sides of the fault will shift. When the fault displacement reaches the actual engineering value, stop applying velocity, restore the bottom boundary of the model to a fixed boundary, and the forward modeling is completed.

5. The numerical simulation method for fault rockburst hazard assessment and pressure relief control according to claim 4, characterized in that, In S2, the specific process of forward modeling of inverse faults is as follows: apply velocity at the bottom of the model, apply an upward velocity to the hanging wall of the fault with the same dip angle as the fault, and apply a downward velocity to the footwall of the fault with the same dip angle as the fault, so that the two sides of the fault move. When the fault displacement reaches the actual engineering value, stop applying velocity and the forward modeling is completed.

6. The numerical simulation method for fault rockburst hazard assessment and pressure relief control according to claim 1, characterized in that, In S4, when the fault slip distance is greater than 0.02m, the numerical simulation dynamic analysis module is activated; The fault slip load is simulated by applying a seismic moment, and the fault slip seismic moment M0 is calculated based on the following formula: M0=GAD In the formula, G is the fault stiffness (GPa); A is the fault area where shear slip occurs (m²). 2 D represents the fault shear slip, in meters. Dynamic stress σ d This is the difference between the peak stress under dynamic load and the static stress.

7. A numerical simulation method for assessing fault rockburst hazard and controlling pressure relief as described in claim 1 or 6, characterized in that, In S4, when the fault slip distance is detected to be greater than 0.02m, the dynamic analysis module of the numerical simulation is started by using the set dyn on command statement to calculate the fault slip kinetic force. During the calculation, the boundary conditions of the model are changed again, and the fixed boundary is changed to the static boundary to avoid the refraction and reflection of the fault slip kinetic stress wave at the model boundary. The fault plane where slip occurred is divided into several regions, and each region is assigned a number. A 1. A 2. A 3…. A n The fault slip seismic moments for each region are calculated as follows: M 01 , M 02 , M 03 … M 0n .

8. The numerical simulation method for fault rockburst hazard assessment and pressure relief control according to claim 1, characterized in that, In S5, the impact hazard assessment index I c The calculation method is as follows: In the formula, σ c The uniaxial compressive strength of the coal body is expressed in MPa. The standard for classifying impact hazard levels is: I c <1.5 indicates no impact risk; 1.5≤I c <2.0 indicates a minor impact hazard; 2.0≤I c <2.5 indicates a moderate impact risk, I c ≥2.5 indicates a severe impact hazard.

9. The numerical simulation method for fault rockburst hazard assessment and pressure relief control according to claim 2, characterized in that, In S6, the borehole layout angle is 20°-75°, the cohesion of the weakened rock mass is 1 / 2-1 / 10 of the initial value, and the tensile strength is reduced to 0. Explosive fragmentation zone radius R p Calculated based on the following formula: In the formula, α is the stress wave attenuation value. v is Poisson's ratio; P is the extreme value of blasting stress, MPa. D is the detonation velocity of the explosive, m / s; ρ0 is the density of the explosive, kg / m³. 3 ;r c Where is the radius of the medicine pack, in mm; n is the stress amplification factor; r b S represents the borehole radius, in mm; t denoted as the tensile strength of the rock mass, in MPa.

10. The numerical simulation method for fault rockburst hazard assessment and pressure relief control according to claim 9, characterized in that, The weakening criteria for the rock mass parameters in the blast damage zone are: cohesion reduced to 1 / 5 of the initial value and tensile strength reduced to 0.

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