Method for determining blasting loosening range of rock burst coal seam

Abstract

The invention relates to the crossing field of coal mine safety and blasting engineering, and particularly discloses a method for determining the blasting loosening range of a rock burst coal seam, which comprises the following steps: S1, based on rock burst coal seam parameters actually measured on site, substituting the parameters into a dynamic correction formula to calculate an initial blasting loosening radius; s2, a strain softening-dynamic instability coupling constitutive model matched with the rock burst coal seam is adopted, blasting parameters consistent with theoretical calculation are simulated through LS-DYNA software, and an irregular loosening range boundary and a simulated loosening radius and a fracture extension form under a non-uniform medium are output; s3, testing is carried out in stages after blasting, and data are obtained by combining multi-directional test hole arrangement; and S4, correcting theoretical calculation and numerical simulation results based on field test data to obtain a final blasting loosening range. According to the method, the defects of poor adaptability, simulation distortion, inaccurate test and no closed loop of the existing method are overcome, the accurate quantification of the loosening range is realized, and the method adapts to multiple working conditions and impact grades.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal mine safety and blasting engineering, in particular to a method for determining the blasting loosening range of a coal seam with rock burst. BACKGROUND

[0002] Rock burst is a typical dynamic disaster in coal mines. Its essence is the sudden and violent release of elastic strain energy accumulated in coal and rock mass, which causes dynamic ejection of coal mass on the two sides of the roadway and the roof and floor, and instantaneous destruction of the roadway, seriously threatening the safety of underground workers and normal production of the mine. With the continuous increase in the depth of coal resource mining, the ground stress level of coal seams has significantly increased. Coupled with factors such as coal burst tendency (excessive indicators such as elastic energy index WET and impact energy index KE), complex geological structure, etc., the frequency and intensity of rock burst have been increasing year by year, which has become a core bottleneck restricting the safe mining of deep high-risk coal seams.

[0003] To prevent and control rock burst risks, the industry widely uses blasting pressure relief as a core measure to resolve the danger. The principle is that stress waves and high-pressure gas produced by explosive explosion make the coal form a crushing ring, a fissure zone and a vibration zone. The fissure zone is the key area to realize the softening, strength reduction and elastic energy release of the coal, and can form an effective protection zone around the roadway, shifting the high stress zone to the deep part of the coal, thereby eliminating or reducing the impact risk. The accurate determination of the blasting loosening range, especially the boundary and morphology of the effective fissure zone, is the core prerequisite for optimizing the drilling arrangement parameters (hole spacing, row spacing), ensuring the pressure relief effect and avoiding resource waste, and directly determines the effectiveness and economy of rock burst prevention and control.

[0004] Currently, the methods for determining the blasting loosening range of a rock burst coal seam mainly include theoretical calculation, numerical simulation, field test and combined method, but they still have many defects that are difficult to overcome in engineering application: Poor adaptability of theoretical calculation: existing methods mostly use traditional empirical formulas (such as simplified formulas based on coal density and uniaxial compressive strength), without considering core characteristic parameters of rock burst coal seams (such as elastic energy index WET and impact energy index KE), and ignoring the influence of ground stress size and direction, and coal heterogeneity (joints, soft layers). Since rock burst coal seams are in a dynamic environment of "high stress + energy accumulation", high ground stress can reduce the loosening range by 20%~40%, and directional crack propagation can change the range morphology. The single parameter calculation mode of traditional static formula cannot reflect the multi-factor coupling effect, resulting in a deviation of 25%~40% between the initial calculation result and the actual value, which can only be used as a qualitative reference.

[0005] Numerical simulation methods suffer from insufficient scenario coverage and model accuracy: Existing numerical simulations often employ approximate stress wave simulations using software such as FLAC and RFPA, or, while using dynamic software like LS-DYNA, are limited to single-hole and double-hole blasting scenarios, failing to address commonly used engineering techniques such as fan-shaped hole layout, multi-stage micro-delay blasting, and multi-hole superposition effects. Furthermore, simulation models often assume the coal seam is a homogeneous isotropic medium, neglecting to incorporate geological structures such as faults and folds, as well as coal seam joint networks. They also fail to employ strain softening-dynamic instability coupled constitutive models adapted for rockburst-prone coal seams. Consequently, the simulation results cannot accurately reflect the fracture propagation patterns under complex geological and construction conditions, resulting in high distortion.

[0006] The on-site testing plan is not rigorous and the judgment criteria are vague: the existing on-site testing mainly relies on single ultrasonic testing, which has obvious limitations: First, the testing sequence is unreasonable. Testing is carried out shortly after blasting without considering the time-dependent expansion characteristics of coal seam fractures caused by rockburst (stabilization occurs 24-72 hours after blasting, with the range expanding by 10%-20%), and the measured instantaneous range lacks representativeness; Second, the testing layout is simplistic, with test holes only arranged perpendicular to the blasting borehole, without adjusting for the direction of ground stress, which easily leads to the omission of the largest loosened area with directional expansion; Third, coupling and anti-collapse measures are lacking, as boreholes in rockburst-prone coal seams are prone to collapse and water leakage, resulting in distorted wave velocity data; Fourth, there is a lack of quantitative judgment criteria, relying only on qualitative judgment based on "wave velocity reduction," without clarifying the critical threshold of the effective loosened area, depending on human experience, and resulting in significant errors.

[0007] The combined approach lacks closed-loop and coordinated design: Some existing technologies propose a combined scheme of "theoretical calculation + numerical simulation + field test", but the three are simply superimposed without establishing an iterative closed loop of "calculation-simulation-test-parameter calibration". Field test data cannot feed back into the optimization of theoretical formulas and simulation models. At the same time, focusing only on the determination of "physical loosening range" without linking it to the core objectives of rockburst prevention (elastic energy release and stress relief) may result in "loosening without energy release", which cannot guarantee the effectiveness of disaster relief.

[0008] Existing methods have a narrow scope of application and insufficient practicality: the parameter adaptability of existing technologies is limited to small aperture (≤70mm), shallow aperture (≤15m) and single explosive type, and does not cover the working conditions of large aperture (75~120mm), deep aperture (10~50m) and high-power explosives such as emulsion explosives and water gel explosives commonly used in coal seams prone to rockbursts; in addition, there is a lack of dedicated data processing tools and safety control measures, the test data has large dispersion and the operation is complicated, making it difficult to meet the precise prevention and control needs of mines with different rockburst hazard levels (weak, medium and strong).

[0009] In summary, existing methods for determining the loosening range of coal seams subjected to rockburst have core defects such as poor theoretical adaptability, limited simulation scenarios, imprecise testing schemes, lack of closed-loop design, and narrow applicability. These defects result in insufficient accuracy in determining the loosening range and fail to provide reliable support for the precise prevention and control of rockburst. There is an urgent need to develop a precise determination method that can fully adapt to the characteristics of coal seams subjected to rockburst, cover complex engineering scenarios, and achieve multi-technology coupling and closed-loop optimization. Summary of the Invention

[0010] In view of the above-mentioned problems in the prior art, the present invention provides a method for determining the loosening range of coal seam blasting in the event of rockburst, which solves the problems of poor adaptability, inaccurate distortion and lack of closed loop in the existing methods, and improves the accuracy of loosening range determination and engineering adaptability.

[0011] To achieve the above objectives, this invention proposes a method for determining the loosening range of a coal seam subjected to rockburst blasting, comprising: S1. Theoretical Calculation: Based on the measured parameters of the coal seam subject to rockburst in the field, the initial blasting loosening radius is calculated by substituting them into the dynamic correction formula. The dynamic correction formula is as follows: ; In the formula, K is the coal and rock property coefficient calibrated by field data, with a value range of 0.2 to 0.6; Q is the charge amount per hole, in kg; The maximum principal stress of the coal seam is MPa; WET is the elastic energy index of the coal body, kJ / m. 3 ; The density of the coal mass is t / m³. 3 ; The uniaxial compressive strength of the coal body is expressed in MPa. The coupling function is expressed as: ; In the formula, The minimum principal stress of the coal seam is given in MPa. S2. Numerical Simulation: A strain-softening-dynamic instability coupled constitutive model adapted to rockburst coal seams is adopted. The blasting parameters simulated using LS-DYNA software are consistent with theoretical calculations, covering fan-shaped borehole layout, matrix borehole layout, and multi-stage micro-delay blasting scenarios. Simultaneously, fault location, fold morphology, and coal joint network distribution are imported into the model to simulate the guiding effect of geological weak surfaces on the propagation of blasting fractures. The model outputs the boundary of the irregular loosening range and the simulated loosening radius under non-homogeneous media. , Crack propagation morphology; S3. Multi-source field testing: Tests are conducted in stages after blasting, and data is obtained by combining the layout of multi-directional test holes. S4. Quantitative Correction and Closed-Loop Optimization: Based on the field test data, the theoretical calculation and numerical simulation results are corrected to obtain the final blasting loosening range R.

[0012] Preferably, in S1, the field-measured parameters of the coal seam subjected to rockburst include the coal body elastic energy index (WET), the impact energy index (KE), the dynamic failure time, and the maximum principal stress of the coal seam. Minimum principal stress Coal body density Uniaxial compressive strength of coal Joint development density and lithological parameters of the top and bottom plates.

[0013] Preferably, in S1, the theoretical calculation further includes establishing a formula library for different working conditions: for the range WET < 5.0 kJ / m 3 The weak impact hazard ranges from 5.0 kJ / m. 3 ≤WET<10.0kJ / m 3 The moderate impact hazard ranges from WET ≥ 10.0 kJ / m 3 The strong impact risk, as well as the geostress ranges including <20MPa, 20~30MPa, and >30MPa, are used to set corresponding coal and rock property coefficient K values, forming 6 sets of detailed correction formulas.

[0014] Preferably, in S2, the numerical simulation specifically includes: setting the detonation sequence of multi-stage micro-delay blasting to be adjustable from 0 to 50 ms, simulating the crack interference effect of multi-hole superimposed blasting with 3 or more holes, and outputting the superposition coefficient of loosening range under different detonation intervals, wherein the superposition coefficient is the ratio of the combined loosening range of multiple holes to the loosening range of a single hole.

[0015] Preferably, in S3, the specific scheme for the multi-source field test is as follows: S31. Test sequence: Three tests were conducted at 24h, 48h and 72h after the blasting to capture the crack aging propagation characteristics. S32. Test hole arrangement: Test holes are arranged along the direction of maximum principal stress, the direction of minimum principal stress and the direction perpendicular to the blasting borehole to form a three-dimensional test network. The depth of the test holes is 5~8m deeper than that of the blasting borehole. S33. Anti-collapse hole and coupling measures: The test hole is supported by a casing, and a high-viscosity coupling agent is injected to achieve ultrasonic wave propagation coupling. The viscosity of the coupling agent is high-viscosity.

[0016] Preferably, in S3, the multi-source field test includes ultrasonic testing, panoramic borehole inspection testing, and fiber optic grating monitoring. The ultrasonic testing acquires the wave velocity distribution of the coal body, the panoramic borehole inspection testing statistically analyzes the fracture density, and the fiber optic grating monitoring tracks the fracture propagation rate in real time. The data from the three tests are cross-validated.

[0017] Preferably, in S4, the criterion for quantification correction is a dual-index threshold: S41, Relative wave velocity reduction rate ≥ 35%, Relative wave velocity reduction rate = (Original coal wave velocity before blasting - Coal wave velocity after blasting) / Original coal wave velocity before blasting × 100%; S42, The reduction rate of coal body elasticity index is ≥40%, and the reduction rate of elasticity index is = (coal body elasticity index before blasting - coal body elasticity index after blasting) / coal body elasticity index before blasting × 100%; S43. Areas that simultaneously meet the above two indicators are determined as effective loosening zones. The final loosening range R is obtained by combining the crack morphology boundary from numerical simulation.

[0018] Preferably, in S4, the closed-loop optimization specifically includes: feeding back the wave velocity data, fracture density data, and stress monitoring data from the field test to the dynamic correction formula in S1, recalibrating the parameters of the coal and rock property coefficient K and the coupling function, forming an iterative optimization process of "theoretical calculation - numerical simulation - field test - parameter calibration", with the number of iterations not less than 2.

[0019] Preferably, the blasting parameters suitable for the method are: borehole diameter 42~120mm, borehole depth 10~50m, and explosive types including ammonium nitrate explosives, emulsion explosives and water gel explosives. For different borehole diameters, the distance between the test hole and the blasting borehole is 50~80 times the borehole diameter. A dedicated data processing software is developed to automatically complete wave velocity analysis, fracture density statistics and visualization of loosening range, and output a quantitative report including the boundary coordinates of the loosening range and the effective pressure relief area.

[0020] Preferably, in S3, the safe distance of the test hole is ≥300m, and the safe distance is ≥500m when the coal seam thickness is ≥5m; the test data reliability verification rule is: the dispersion of wave velocity data at the same test depth and the accuracy of fracture identification by panoramic borehole observation meet the preset requirements, and data exceeding the dispersion threshold are removed before correction calculation; for fault-affected areas, the density of test holes is increased, and the distance between adjacent test holes is ≤2m.

[0021] Therefore, this invention proposes a method for determining the loosening range of coal seams subjected to rockburst blasting, which has the following beneficial effects: (1) It integrates theoretical calculation, numerical simulation and multi-source field test, incorporates core parameters such as impact tendency and geostress, embeds geological structure and heterogeneous model, and uses dual indicators to quantitatively determine the effective loosening area, which greatly improves the accuracy and reliability of range determination.

[0022] (2) Construct a closed-loop optimization process that is compatible with multiple apertures, multiple explosive types and full impact levels. It is easy to operate and the data processing is automated. It not only ensures the energy unloading and disaster relief effect, but also avoids excessive blasting and reduces prevention and control costs.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 This is an overall flowchart of a method for determining the loosening range of a coal seam subjected to rockburst blasting according to the present invention; Figure 2 This is a schematic diagram of a numerical simulation model of a method for determining the loosening range of coal seam blasting in rockburst according to the present invention; Figure 3 This is a schematic diagram of the three-dimensional arrangement of multi-directional test holes and the coupling protection of anti-collapse holes in a method for determining the loosening range of coal seam blasting under rockburst according to the present invention. Figure 4 This is a visual diagram of the quantitative boundary of the blasting loosening range and the effective pressure relief zone of a method for determining the blasting loosening range of a coal seam under rockburst according to the present invention; Figure 5 This is a curve comparing the theoretical calculations and field test data corrections for a method of determining the loosening range of coal seams in rockburst according to the present invention. Detailed Implementation

[0025] To make the technical solutions, advantages, and objectives of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the protection scope of this application.

[0026] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0027] like Figures 1-5 As shown, the present invention provides a method for determining the loosening range of a coal seam subjected to rockburst blasting, comprising: S1. Theoretical Calculation: Based on the measured parameters of the coal seam subject to rockburst in the field, the initial blasting loosening radius is calculated by substituting them into the dynamic correction formula. ; The dynamic correction formula is: ; In the formula, K is the coal and rock property coefficient calibrated by field data, with a value range of 0.2 to 0.6; Q is the charge amount per hole, in kg; The maximum principal stress of the coal seam is MPa; WET is the elastic energy index of the coal body, kJ / m. 3 ; The density of the coal mass is t / m³. 3 ; The uniaxial compressive strength of the coal body is expressed in MPa. The coupling function is expressed as: ; In the formula, The minimum principal stress of the coal seam is given in MPa. The parameters of the coal seam subjected to rockburst measured in the field include the coal body elastic energy index (WET), the impact energy index (KE), the dynamic failure time, and the maximum principal stress of the coal seam. Minimum principal stress Coal body density Uniaxial compressive strength of coal Joint development density and lithological parameters of the top and bottom plates.

[0028] Theoretical calculations also include establishing a formula library for different working conditions: for the range WET < 5.0 kJ / m 3 The weak impact hazard ranges from 5.0 kJ / m. 3 ≤WET<10.0kJ / m 3 The moderate impact hazard ranges from WET ≥ 10.0 kJ / m 3 The strong impact risk, as well as the geostress ranges including <20MPa, 20~30MPa, and >30MPa, are used to set corresponding coal and rock property coefficient K values, forming 6 sets of detailed correction formulas.

[0029] S2. Numerical Simulation: A strain-softening-dynamic instability coupled constitutive model adapted to rockburst coal seams is adopted. The blasting parameters simulated using LS-DYNA software are consistent with theoretical calculations, covering fan-shaped borehole layout, matrix borehole layout, and multi-stage micro-delay blasting scenarios. Simultaneously, fault location, fold morphology, and coal joint network distribution are imported into the model to simulate the guiding effect of geological weak surfaces on the propagation of blasting fractures. The model outputs the boundary of the irregular loosening range and the simulated loosening radius under non-homogeneous media. , Crack propagation morphology; The numerical simulation specifically includes: setting the initiation timing of multi-stage micro-delay blasting to be adjustable from 0 to 50 ms, simulating the crack interference effect of multi-hole superimposed blasting with 3 or more holes, and outputting the superposition coefficient of loosening range under different initiation intervals. The superposition coefficient is the ratio of the combined loosening range of multiple holes to the loosening range of a single hole.

[0030] S3. Multi-source field testing: Tests are conducted in stages after blasting, and data is obtained by combining the layout of multi-directional test holes. The specific plan for multi-source field testing is as follows: S31. Test sequence: Three tests were conducted at 24h, 48h and 72h after the blasting to capture the crack aging propagation characteristics. S32. Test hole arrangement: Test holes are arranged along the direction of maximum principal stress, the direction of minimum principal stress and the direction perpendicular to the blasting borehole to form a three-dimensional test network. The depth of the test holes is 5~8m deeper than that of the blasting borehole. S33. Anti-collapse hole and coupling measures: The test hole is supported by a casing, and a high-viscosity coupling agent is injected to achieve ultrasonic wave propagation coupling. The viscosity of the coupling agent is high-viscosity.

[0031] Multi-source field testing includes ultrasonic testing, panoramic borehole inspection testing, and fiber optic grating monitoring. Ultrasonic testing obtains the wave velocity distribution of the coal body, panoramic borehole inspection testing statistically analyzes the fracture density, and fiber optic grating monitoring tracks the fracture propagation rate in real time. The data from the three sources are cross-validated.

[0032] The safe distance for test holes is ≥300m, and the safe distance is ≥500m when the coal seam thickness is ≥5m. The reliability verification rule for test data is: the dispersion of wave velocity data at the same test depth and the accuracy of fracture identification by panoramic borehole observation meet the preset requirements. Data exceeding the dispersion threshold are removed before correction calculation. For fault-affected areas, the density of test holes is increased, and the distance between adjacent test holes is ≤2m.

[0033] S4. Quantitative Correction and Closed-Loop Optimization: Based on the field test data, the theoretical calculation and numerical simulation results are corrected to obtain the final blasting loosening range R.

[0034] The criterion for quantitative correction is a dual-indicator threshold: S41, Relative wave velocity reduction rate ≥ 35%, Relative wave velocity reduction rate = (Original coal wave velocity before blasting - Coal wave velocity after blasting) / Original coal wave velocity before blasting × 100%; S42, The reduction rate of coal body elasticity index is ≥40%, and the reduction rate of elasticity index is = (coal body elasticity index before blasting - coal body elasticity index after blasting) / coal body elasticity index before blasting × 100%; S43. Areas that simultaneously meet the above two indicators are determined as effective loosening zones. The final loosening range R is obtained by combining the crack morphology boundary from numerical simulation.

[0035] The closed-loop optimization specifically includes feeding back the wave velocity data, fracture density data and stress monitoring data from the field test to the dynamic correction formula of S1, recalibrating the parameters of the coal and rock property coefficient K and the coupling function, forming an iterative optimization process of "theoretical calculation - numerical simulation - field test - parameter calibration", with no less than 2 iterations.

[0036] This invention provides a method for determining the loosening range of coal seams subjected to rockburst blasting. The applicable blasting parameters are: borehole diameter 42~120mm, borehole depth 10~50m, and explosive types including ammonium nitrate explosives, emulsion explosives, and water gel explosives. For different borehole diameters, the distance between the test hole and the blasting borehole is 50~80 times the borehole diameter. A dedicated data processing software is developed to automatically complete wave velocity analysis, fracture density statistics, and visualization of the loosening range, outputting a quantitative report including the boundary coordinates of the loosening range and the effective pressure relief area.

[0037] Example This embodiment uses a high-impact coal seam in a deep mine as the application example. The elastic energy index (WET) of the coal seam is 12.5 kJ / m. 3 With a ground stress level of 35 MPa, a deep-hole blasting pressure relief scheme was adopted to verify the effectiveness of the method of the present invention. The specific implementation process is as follows: I. Preliminary Preparations: Field measured parameters were collected: Through laboratory tests and in-situ underground tests, the core parameters of this coal seam were obtained: coal density 1.35 t / m³. 3 Uniaxial compressive strength 28MPa, maximum principal stress 35MPa, minimum principal stress 18MPa, joint development density 3 joints / m, top and bottom lithology is fine sandstone, impact energy index KE=6.8, dynamic failure time 52ms.

[0038] Blasting parameters were determined as follows: the borehole diameter was 90mm, the borehole depth was 30m, the charge per hole was 8kg, and the explosive type was emulsion explosive; the blasting hole layout was a fan-shaped layout with a total of 5 blasting holes; the multi-stage micro-delay blasting initiation sequence was set to three adjustable levels: 10ms, 25ms, and 40ms.

[0039] II. Theoretical Calculations: Operating conditions: WET = 12.5 kJ / m³ 3 (Severe impact hazard), ground stress > 30MPa, corresponding to the coal and rock property coefficient K=0.45 preset in the formula library for the sub-condition.

[0040] Initial loosening radius calculation: Substitute the measured parameters into the dynamic correction formula and coupling function, where the coupling function is calculated as follows, and finally obtain the theoretical value of the initial blasting loosening radius as 8.2m.

[0041] III. Numerical Simulation: Model Construction: A strain softening-dynamic instability coupled constitutive model was established using LS-DYNA software. The measured fault location (15m from the blasting area), fold morphology, and coal joint network distribution data of the region were imported to simulate the fan-shaped hole layout and multi-stage micro-delay blasting scenario.

[0042] Simulation calculation: The detonation timing was set to 10ms, 25ms, and 40ms to simulate the crack interference effect of 5-hole superimposed blasting. The superposition coefficient of loosening range under different detonation intervals was output (1.85 for 10ms interval, 2.12 for 25ms interval, and 1.98 for 40ms interval).

[0043] Results output: The boundary of the irregular loosening range under non-uniform medium is obtained, the simulated loosening radius is 7.9~8.5m, and the crack propagation shows a directional extension characteristic along the direction of the maximum principal stress.

[0044] IV. Multi-source field testing: Test scheme design: The safe distance between test holes is set at 500m (the coal seam thickness is 6m≥5m). A three-dimensional test network is arranged along the direction of the maximum principal stress, the direction of the minimum principal stress, and the direction perpendicular to the blasting borehole. The test hole depth is 38m (8m deeper than the blasting borehole). Casing support is used, and high-viscosity coupling agent is injected to ensure ultrasonic wave propagation and coupling. For the fault-affected area, the spacing between adjacent test holes is set at 1.8m.

[0045] Test Implementation: Three tests were conducted at 24h, 48h, and 72h after blasting. Ultrasonic testing was used to obtain the wave velocity distribution of the coal body, panoramic borehole inspection was used to count the fracture density, and fiber optic grating was used to monitor and track the fracture propagation rate. The data from the three methods were cross-validated. After the reliability of the test data was verified, two sets of wave velocity data that exceeded the dispersion threshold were removed.

[0046] V. Quantitative Correction and Closed-Loop Optimization: Quantitative judgment: Based on the test data, the relative wave velocity of the coal body decreased by 42% (≥35%) and the elastic energy index of the coal body decreased by 48% (≥40%) after blasting. Since both indicators meet the threshold, the effective loosening zone range is determined.

[0047] Result Correction: Combining the fracture morphology boundary from numerical simulation, the theoretical calculation and numerical simulation results were corrected, and the final blasting loosening range R=8.3m was obtained.

[0048] Closed-loop optimization: The wave velocity data, fracture density data and stress monitoring data from the field test are fed back into the dynamic correction formula for theoretical calculation, and the coal and rock property coefficient K=0.47 and coupling function parameters are recalibrated to complete the first iteration; the data are substituted into the formula again and compared with the field data to carry out the second iteration optimization, and finally a stable correction parameter system is formed.

[0049] Report output: Through dedicated data processing software, wave velocity analysis, fracture density statistics and loosening range visualization are automatically completed, and a quantitative report including the boundary coordinates of the loosening range and the effective pressure relief area is output.

[0050] VI. Implementation Results: The method of this invention determines the loosening range by blasting with an error of ≤5% compared with the actual field verification results. This effectively guides the optimization of borehole layout for rockburst prevention in the mine, avoids resource waste caused by excessive blasting, and ensures that the elastic energy of the coal body is fully released. The risk level of rockburst is reduced from strong rockburst to weak rockburst, thus ensuring the safety of underground operations.

[0051] Therefore, this invention provides a method for determining the loosening range of coal seams subjected to rockburst blasting. It specifically addresses the core shortcomings of existing technologies, such as poor theoretical adaptability, limited simulation scenarios, imprecise testing schemes, lack of closed-loop design, and narrow applicability. It can comprehensively cover all rockburst hazard levels, from weak to strong, and is adaptable to various working conditions. It ensures the effectiveness of rockburst relief by accurately defining the effective loosening zone, while avoiding resource waste caused by excessive blasting. At the same time, it automates test analysis and result visualization using dedicated data processing software, greatly improving the convenience and economy of engineering applications, and providing reliable technical support for the safe mining of deep, high-risk coal seams.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for determining the loosening range of a coal seam subjected to rockburst blasting, characterized in that, include: S1. Theoretical Calculation: Based on the measured parameters of the coal seam subject to rockburst in the field, the initial blasting loosening radius is calculated by substituting them into the dynamic correction formula. The dynamic correction formula is as follows: ； In the formula, K is the coal and rock property coefficient calibrated by field data, with a value range of 0.2 to 0.6; Q is the charge amount per hole, in kg; The maximum principal stress of the coal seam is expressed in MPa. WET is the elastic energy index of coal, in kJ / m³. 3 ; The density of the coal mass is t / m³. 3 ; The uniaxial compressive strength of the coal body is expressed in MPa. The coupling function is expressed as: ； In the formula, The minimum principal stress of the coal seam is given in MPa. S2. Numerical Simulation: A strain-softening-dynamic instability coupled constitutive model adapted to rockburst coal seams is adopted. The blasting parameters simulated using LS-DYNA software are consistent with theoretical calculations, covering fan-shaped borehole layout, matrix borehole layout, and multi-stage micro-delay blasting scenarios. Simultaneously, fault location, fold morphology, and coal joint network distribution are imported into the model to simulate the guiding effect of geological weak surfaces on the propagation of blasting fractures. The model outputs the boundary of the irregular loosening range and the simulated loosening radius under non-homogeneous media. , Crack propagation morphology; S3. Multi-source field testing: Tests are conducted in stages after blasting, and data is obtained by combining the layout of multi-directional test holes. S4. Quantitative Correction and Closed-Loop Optimization: Based on the field test data, the theoretical calculation and numerical simulation results are corrected to obtain the final blasting loosening range R.

2. The method according to claim 1, characterized in that, In S1, the field-measured parameters of the coal seam subjected to rockburst include the coal body elastic energy index WET, the impact energy index KE, the dynamic failure time, and the maximum principal stress of the coal seam. Minimum principal stress Coal density Uniaxial compressive strength of coal Joint development density and lithological parameters of the top and bottom plates.

3. The method according to claim 1, characterized in that, In S1, the theoretical calculation also includes establishing a formula library for different working conditions: for the range WET < 5.0 kJ / m 3 The weak impact hazard ranges from 5.0 kJ / m. 3 ≤WET<10.0kJ / m 3 The moderate impact hazard ranges from WET ≥ 10.0 kJ / m 3 The strong impact risk, as well as the geostress ranges including <20MPa, 20~30MPa, and >30MPa, are used to set corresponding coal and rock property coefficient K values, forming 6 sets of detailed correction formulas.

4. The method according to claim 1, characterized in that, In S2, the numerical simulation specifically includes: setting the detonation sequence of multi-stage micro-delay blasting to be adjustable from 0 to 50 ms, simulating the crack interference effect of multi-hole superimposed blasting with 3 or more holes, and outputting the superposition coefficient of loosening range under different detonation intervals. The superposition coefficient is the ratio of the combined loosening range of multiple holes to the loosening range of a single hole.

5. The method according to claim 1, characterized in that, In S3, the specific scheme for the multi-source field test is as follows: S31. Test sequence: Three tests were conducted at 24h, 48h and 72h after the blasting to capture the crack aging propagation characteristics. S32. Test hole arrangement: Test holes are arranged along the direction of maximum principal stress, the direction of minimum principal stress and the direction perpendicular to the blasting borehole to form a three-dimensional test network. The depth of the test holes is 5~8m deeper than that of the blasting borehole. S33. Anti-collapse hole and coupling measures: The test hole is supported by a casing, and a high-viscosity coupling agent is injected to achieve ultrasonic wave propagation coupling. The viscosity of the coupling agent is high-viscosity.

6. The method according to claim 1, characterized in that, In S3, the multi-source field test includes ultrasonic testing, panoramic borehole inspection testing, and fiber optic grating monitoring. The ultrasonic testing obtains the wave velocity distribution of the coal body, the panoramic borehole inspection test counts the fracture density, and the fiber optic grating monitoring tracks the fracture propagation rate in real time. The data from the three tests are cross-validated.

7. The method according to claim 1, characterized in that, In S4, the criterion for quantification correction is a dual-index threshold: S41, Relative wave velocity reduction rate ≥ 35%, Relative wave velocity reduction rate = (Original coal wave velocity before blasting - Coal wave velocity after blasting) / Original coal wave velocity before blasting × 100%; S42, The reduction rate of coal body elasticity index is ≥40%, and the reduction rate of elasticity index is = (coal body elasticity index before blasting - coal body elasticity index after blasting) / coal body elasticity index before blasting × 100%; S43. Areas that simultaneously meet the above two indicators are determined as effective loosening zones. The final loosening range R is obtained by combining the crack morphology boundary from numerical simulation.

8. The method according to claim 1, characterized in that, In S4, the closed-loop optimization specifically includes: feeding back the wave velocity data, fracture density data and stress monitoring data from the field test to the dynamic correction formula in S1, recalibrating the parameters of the coal and rock property coefficient K and the coupling function, forming an iterative optimization process of "theoretical calculation - numerical simulation - field test - parameter calibration", with no less than 2 iterations.

9. The method according to claim 1, characterized in that, The method is compatible with the following blasting parameters: borehole diameter 42~120mm, borehole depth 10~50m, and explosive types including ammonium nitrate explosives, emulsion explosives and water gel explosives. For different borehole diameters, the distance between the test hole and the blasting borehole is 50~80 times the borehole diameter. A dedicated data processing software is developed to automatically complete wave velocity analysis, fracture density statistics and visualization of loosening range, and output a quantitative report including the boundary coordinates of the loosening range and the effective pressure relief area.

10. The method according to claim 1, characterized in that, In S3, the safe distance of the test hole is ≥300m, and the safe distance is ≥500m when the coal seam thickness is ≥5m; The reliability verification rules for test data are as follows: if the dispersion of wave velocity data at the same test depth and the accuracy of fracture identification by panoramic borehole inspection meet the preset requirements, data exceeding the dispersion threshold will be removed before correction calculation; for fault-affected areas, the density of test holes will be increased and the spacing between adjacent test holes will be ≤2m.

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