A Spectral Acoustic Prediction Method for Hazardous Dynamic Phenomena in Coal Mines

Abstract

This application discloses a spectral acoustic prediction method for the hazard of coal mine dynamic phenomena, relating to the field of mining technology, which can effectively improve the reliability of prediction. The method includes: determining a first sub-spectrum, a second sub-spectrum, and a reference amplitude based on the acoustic signal spectrum of the roof strata during coal mine working face operations, wherein the frequency of each spectral component in the first sub-spectrum is lower than the frequency of each spectral component in the second sub-spectrum; determining a first amplitude based on the first sub-spectrum; determining a second amplitude based on the second sub-spectrum; determining a reference frequency based on the reference amplitude; and predicting the hazard of coal mine dynamic phenomena based on the first amplitude, the second amplitude, the reference frequency, and critical values ​​for the first amplitude, the second amplitude, and the reference frequency. This invention is applicable to scenarios involving the prediction of the hazard of mine dynamic phenomena.

Description

Technical Field

[0001] This application relates to the field of mining technology, specifically to a spectral acoustic prediction method for the hazards of dynamic phenomena in coal mines. Background Technology

[0002] As coal mining depth increases, coal seam stress rises, and coal seam gas pressure and content increase, significantly increasing the risk of dynamic phenomena such as coal and gas outbursts and rock bursts during coal mining. Due to the suddenness, rapid pace, and destructive consequences of these dynamic phenomena, they pose a serious threat to safe and efficient coal mine production and the lives of miners. Therefore, predicting and forecasting the hazards of dynamic phenomena has always been an important research task in the field of coal mine safety.

[0003] Based on years of research by scientists and engineers in major coal-producing countries worldwide, a series of methods for predicting the hazards of coal mine dynamic phenomena have been developed and applied in actual coal mine production. Currently, these methods can be divided into two main categories: contact-based discrete prediction methods and non-contact continuous prediction methods.

[0004] The contact-based discrete prediction method involves drilling a predictive borehole of a certain diameter and depth along the coal seam of the working face when the working face is shut down. During the drilling process, indicators characterizing the dynamic hazards of the working face are measured, such as the initial velocity of gas emission from the borehole, the amount of drill cuttings, and the desorption index of drill cuttings gas. The maximum value of these indicators is compared with the critical value. If the maximum value of these indicators is equal to or greater than the critical value, or if signs of dynamic hazards appear during the drilling process, the working face is determined to have dynamic hazards. The main disadvantages of this type of prediction method are: (1) The drilling and prediction process is greatly affected by the subjective factors of the prediction personnel; (2) The working face needs to be shut down when the prediction method is implemented, which interferes with the normal production process of the working face; (3) The dynamic hazards change under the action of mining technology, and the dynamic hazards of the working face are greatest during the mining process. However, this type of prediction method is carried out when the working face is shut down and cannot reflect the real-time dynamics of the dynamic hazards of the working face during the mining process.

[0005] Non-contact continuous prediction methods involve pre-installing sensors with specific functions near the working face. Whether the working face is shut down or in production, these sensors continuously monitor acoustic and electrical signals emitted by micro-fractures in the coal seam or surrounding rock, such as micro-vibration indicators, acoustic emission indicators, and electromagnetic radiation indicators. The maximum values ​​of these measured indicators are compared with their critical values. If the maximum value is equal to or greater than the critical value, the working face is determined to have a dynamic phenomenon hazard. This type of prediction method enables automated, continuous, online monitoring and early warning of dynamic phenomenon hazards, representing the future direction of dynamic phenomenon hazard monitoring and early warning in mines. The predictive mechanism of dynamic phenomena risk using microseismic index, acoustic emission index, and electromagnetic radiation index is as follows: (1) Precursors of micro-fractures are a common feature of dynamic phenomena in mines. Before the occurrence of dynamic phenomena, there are always precursors of micro-fractures (microseismic activity); (2) Increased stress in the rock mass leads to an increase in micro-fractures, and increases in acoustic emission, microseismic, and electromagnetic radiation indices; decreased stress in the rock mass leads to a decrease in micro-fractures, and decreases in acoustic emission, microseismic, and electromagnetic radiation indices; (3) Using acoustic emission, microseismic, and electromagnetic radiation indices can reflect micro-fracture events and stress change trends in the rock mass and predict the risk of dynamic phenomena. The prediction mechanism of acoustic emission, microseismic, and electromagnetic radiation indicators is derived from the correlation between the increase of acoustic emission, microseismic, and electromagnetic radiation indicators with increasing stress when rock blocks are loaded and stressed in the laboratory. This is very different from the actual coal and rock occurrence conditions in the field, and the reliability of the prediction is greatly affected: (1) Coal mine monitoring practice on acoustic emission, microseismic, and electromagnetic radiation indicators shows that before the occurrence of dynamic phenomena, the elastic energy of the coal and rock mass is in a state of accumulation and increase. At this time, the acoustic emission, microseismic, and electromagnetic radiation indicators of the coal and rock mass are low, and the working face is in a calm period; (2) Acoustic emission, microseismic, and electromagnetic radiation The indicators are greatly affected by the strength of the coal and rock mass. When the strength of the coal and rock mass is low, the acoustic emission, micro-vibration, and electromagnetic radiation indicators increase, the coal and rock mass is depressurized, elastic energy cannot be accumulated, and the dynamic phenomenon risk decreases. When the strength of the coal and rock mass is high, the acoustic emission, micro-vibration, and electromagnetic radiation indicators decrease, the coal and rock mass is pressurized, elastic energy accumulates in large quantities, and the dynamic phenomenon risk increases. (3) During the construction of pressure relief drilling at the working face, the transfer of stress to the deep part of the working face, and the depressurization of the coal and rock mass near the working face, the acoustic emission, micro-vibration, and electromagnetic radiation indicators increase, and the actual dynamic phenomenon risk at the working face decreases. In summary, the acoustic emission, micro-vibration, and electromagnetic radiation indicators only represent micro-fracture events in the coal and rock mass. There is no single-value correspondence between them and the stress-strain state and dynamic phenomenon risk in the coal and rock mass. The reliability of dynamic phenomenon risk prediction is low. Summary of the Invention

[0006] To address the low reliability of existing prediction methods, this application provides a spectral acoustic prediction method for the hazards of dynamic phenomena in coal mines.

[0007] In a first aspect, embodiments of the present invention provide a method for predicting the hazard spectrum of coal mine dynamic phenomena using acoustic spectral analysis, comprising:

[0008] Based on the acoustic signal spectrum of the roof strata during coal mine working face operations, the first sub-spectrum, the second sub-spectrum, and the reference amplitude are determined. The frequency of each spectral component in the first sub-spectrum is less than the frequency of each spectral component in the second sub-spectrum.

[0009] Based on the first spectrum, determine the first amplitude; based on the second spectrum, determine the second amplitude; based on the reference amplitude, determine the reference frequency.

[0010] Based on the first amplitude, the second amplitude, the reference frequency, and the critical values ​​of the first amplitude, the second amplitude, and the reference frequency, the risk of coal mine dynamic phenomena is predicted.

[0011] In one specific implementation, the method further includes:

[0012] Based on the acoustic signal spectrum of the roof strata in the working face of a coal mine section with no dynamic phenomenon hazard, determine the first spectrum, second spectrum, and reference amplitude of the safe state;

[0013] Based on the first spectrum, the second spectrum, and the reference amplitude of the safe state, determine the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value.

[0014] In one specific implementation, determining the first amplitude based on the first spectrum and determining the second amplitude based on the second spectrum includes:

[0015] The first amplitude is obtained by summing the amplitudes of each spectral component in the first sub-spectrum;

[0016] The second amplitude is obtained by summing the amplitudes of each spectral component in the second sub-spectrum.

[0017] In one specific implementation, determining the reference frequency based on the reference amplitude includes:

[0018] Based on the maximum amplitude A of the acoustic signal spectrum max , with λA max The reference amplitude is λ, where λ is a multiplier factor, 0 < λ < 1;

[0019] Based on the reference amplitude, the smallest frequency is selected as the reference frequency from the spectral components of the acoustic signal spectrum that are not less than the reference amplitude.

[0020] In one specific implementation, the reference amplitude includes at least a first reference amplitude and a second reference amplitude; the reference frequency includes at least a first reference frequency corresponding to the first reference amplitude and a second reference frequency corresponding to the second reference amplitude.

[0021] In one specific implementation, predicting the hazard of coal mine dynamic phenomena based on the first amplitude, the second amplitude, the reference frequency, and the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value includes:

[0022] If the first amplitude is not greater than the first amplitude critical value, the second amplitude is not less than the second amplitude critical value, and the reference frequency is not less than the reference frequency critical value, the coal mine working face is predicted to have a dynamic phenomenon hazard.

[0023] In one specific implementation, the method further includes: determining a relative stress coefficient based on the first amplitude and the second amplitude; and predicting the hazard of coal mine dynamic phenomena based on the relative stress coefficient, wherein the relative stress coefficient K = A. B / A H A H For the first amplitude, A B This is the second amplitude.

[0024] In one specific implementation, the method further includes calibrating the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value according to the mining progress of the coal mine working face.

[0025] In one specific implementation, before determining the first sub-spectrum, the second sub-spectrum, and the reference amplitude based on the acoustic signal spectrum of the roof strata during coal mine working face operations, the method includes: installing a first seismic detector at the coal mine tunneling face and installing a second seismic detector at the coal mining face.

[0026] In one specific implementation, determining the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value based on the first spectrum, the second spectrum, and the reference amplitude of the safe state includes:

[0027] Based on the first sub-spectrum, second sub-spectrum, and reference amplitude of each of the multiple mining cycles under the safe state, determine the first amplitude critical value, second amplitude critical value, and reference frequency critical value of each of the multiple mining cycles;

[0028] The first amplitude critical value, the second amplitude critical value, and the reference frequency critical value are determined based on the average value of the first amplitude critical value, the average value of the second amplitude critical value, and the average value of the reference frequency critical value of the multiple mining cycles.

[0029] The spectral acoustic prediction method for coal mine dynamic phenomena hazards provided by embodiments of the present invention determines a first sub-spectrum, a second sub-spectrum, and a reference amplitude based on the acoustic signal spectrum of the roof strata during coal mine operations. The frequency of each spectral component in the first sub-spectrum is lower than the frequency of each spectral component in the second sub-spectrum. Then, a first amplitude is determined based on the first sub-spectrum; a second amplitude is determined based on the second sub-spectrum; and a reference frequency is determined based on the reference amplitude. Finally, the hazard of coal mine dynamic phenomena is predicted based on the first amplitude, the second amplitude, the reference frequency, and critical values ​​for the first amplitude, the second amplitude, and the reference frequency. This method, based on the analysis and processing of the acoustic signal spectrum characteristics of the roof strata under external force excitation, effectively improves the reliability of non-contact continuous prediction of coal mine dynamic phenomena hazards. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a flowchart of a spectral acoustic prediction method for the hazards of dynamic phenomena in coal mines, as described in this application.

[0032] Figure 2 A schematic diagram illustrating the reciprocating movement of the maximum value of the support pressure in front of the coal mine working face, provided in an embodiment of this application.

[0033] Figure 3 A schematic diagram of elastic resonance generated in the roof strata of a coal mine working face, provided in an embodiment of this application.

[0034] Figure 4 A schematic diagram of the calculated spectrum of the relative stress coefficient provided in this application;

[0035] Figure 5 A schematic diagram of the artificial acoustic signal spectrum when the working face is dangerous, as provided in this application;

[0036] Figure 6 A schematic diagram of the artificial acoustic signal spectrum when the working surface is safe, as provided in this application;

[0037] Figure 7 A schematic diagram of the mine dynamic phenomenon spectral acoustic monitoring and early warning system provided in this application;

[0038] Figure 8 This is a schematic diagram of the installation of the first seismic detector provided in this application;

[0039] Figure 9 A schematic diagram of the installation of the second seismic detector provided in this application.

[0040] Explanation of key figure labels:

[0041] 11-Metal rod; 12-Nut; 13-First seismic detector; 14-First seismic detector bracket; 15-Bolt; 16-Tunnel sidewall backplate metal mesh; 17-Second seismic detector. Detailed Implementation

[0042] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0043] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0044] Firstly, such as Figure 1 As shown, an embodiment of the present invention provides a spectral acoustic prediction method for the hazards of dynamic phenomena in coal mines, the method including:

[0045] S11. Based on the acoustic signal spectrum of the roof strata during coal mine working face operations, determine the first sub-spectrum, the second sub-spectrum, and the reference amplitude of the working state. The frequency of each spectral component in the first sub-spectrum is less than the frequency of each spectral component in the second sub-spectrum.

[0046] Field observation data indicates that prior to coal and gas outbursts, rock bursts, and other dynamic phenomena, the roof strata of the coal mine face undergo delayed deformation, leading to stress concentration and potential energy accumulation within the coal and rock mass. This is the energy source for the occurrence of coal mine dynamic phenomena. Therefore, this method assesses the stress-strain dynamics of the coal and rock strata at the working face and predicts the hazard of dynamic phenomena by monitoring the degree of deformation delay in the roof strata.

[0047] Specifically, after coal seam excavation, the roof strata of the working face undergo delamination and weakening deformation, forming a series of delamination weakening surfaces within the roof strata. These surfaces vary in degree of weakening and distance from the coal seam, resulting in the release of accumulated stress and energy within the coal and rock mass to varying degrees. Underground seismic spectrum exploration in coal mines indicates that the roof strata near the working face can be considered an oscillating system composed of a series of delamination weakening surfaces. Under external force excitation, the artificial acoustic signal generated within the roof strata consists of a series of resonant harmonics. The resonant frequency is inversely proportional to the distance (stratum thickness) from the delamination weakening surface to the coal seam, while the amplitude depends on the degree of weakening of the roof delamination weakening surfaces. Therefore, based on the spectral characteristics of the acoustic signals excited in the coal and rock mass when cutting mechanisms such as coal mining machines and tunneling machines drop coal, the deformation delay of the roof strata can be monitored, the stress-strain dynamics of the coal and rock strata at the working face can be assessed, and the dynamic phenomenon hazards can be predicted. Therefore, this application obtains the acoustic signal spectrum of the roof strata during coal mine working face operations and performs feature analysis on the acoustic signal spectrum to predict the dynamic phenomenon hazards in coal mines.

[0048] Furthermore, based on artificial acoustic analysis of coal mine working faces, the attenuation coefficient of sound waves decreases with increasing spatial stress near the working face, and this decrease is more pronounced at high frequencies than at low frequencies. (See [link to relevant documentation]). Figure 5 , Figure 6 As shown, where Figure 5 The right-middle figure shows the acoustic signal spectrum obtained from the acoustic signals collected in the left figure when the working face was in danger. Figure 6 The right-middle figure shows the acoustic signal spectrum obtained from the acoustic signals collected in the left figure when the working face was safe. Figure 5 , Figure 6 In this diagram, the horizontal axis represents frequency, and the vertical axis represents amplitude. Therefore, based on the acoustic signal spectrum of the roof strata during coal mine working face operations, this application further determines the first spectrum, the second spectrum, and the reference amplitude for the working state. Specifically, the frequency of each spectral component in the first spectrum is lower than the frequency of each spectral component in the second spectrum. The first spectrum can be the low-frequency portion of the acoustic signal spectrum, the second spectrum can be the high-frequency portion of the acoustic signal spectrum, and the reference amplitude can be specifically determined based on the amplitude characteristics of the spectral components in the acoustic signal spectrum.

[0049] S12. Determine the first amplitude based on the first spectrum; determine the second amplitude based on the second spectrum; determine the reference frequency based on the reference amplitude.

[0050] In this step, after determining the first and second sub-spectrums and the reference amplitude of the working state from the acoustic signal spectrum, based on the aforementioned acoustic wave propagation characteristic that the attenuation coefficient of the sound wave decreases with the increase of spatial stress near the working face, and that this decrease is more pronounced at high frequencies than at low frequencies, this method determines the first amplitude based on the low-frequency portion of the first sub-spectrum, i.e., the acoustic signal spectrum; and determines the second amplitude based on the high-frequency portion of the second sub-spectrum. Specifically, the corresponding first and second amplitudes can be obtained based on the spectral components in the first and second sub-spectrums, respectively, according to the amplitude calculation rules. Similarly, for the reference amplitude, a reference frequency associated with the reference amplitude can be determined based on the acoustic signal spectrum characteristics, and the safety measure based on the reference amplitude is represented by frequency. In this way, based on the safety analysis of amplitude in the acoustic signal spectrum, a safety analysis of frequency in the acoustic signal spectrum is further added, thereby improving the reliability of predicting the hazards of coal mine dynamic phenomena.

[0051] S13. Based on the first amplitude, the second amplitude, the reference frequency, and the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value, predict the danger of coal mine dynamic phenomena.

[0052] In this step, after determining the first amplitude, the second amplitude, and the reference frequency, they can be compared with predetermined first amplitude critical values, second amplitude critical values, and reference frequency critical values, respectively. The risk of coal mine dynamic phenomena is predicted based on the comparison results. The first amplitude critical value, the second amplitude critical value, and the reference frequency critical value can be determined based on empirical values ​​or on-site measurements in the coal mine operating area to further improve the accuracy of the prediction results.

[0053] The spectral acoustic prediction method for coal mine dynamic phenomena hazards provided by embodiments of the present invention determines a first sub-spectrum, a second sub-spectrum, and a reference amplitude based on the acoustic signal spectrum of the roof strata during coal mine operations. The frequency of each spectral component in the first sub-spectrum is lower than the frequency of each spectral component in the second sub-spectrum. Then, a first amplitude is determined based on the first sub-spectrum; a second amplitude is determined based on the second sub-spectrum; and a reference frequency is determined based on the reference amplitude. Finally, the hazards of coal mine dynamic phenomena are predicted based on the first amplitude, the second amplitude, the reference frequency, and critical values ​​for the first amplitude, the second amplitude, and the reference frequency. Therefore, this method, based on the analysis and processing of the acoustic signal spectrum characteristics of the roof strata under external force excitation, effectively improves the reliability of non-contact continuous prediction of coal mine dynamic phenomena hazards.

[0054] Optionally, in one embodiment of the present invention, the method further includes:

[0055] Based on the acoustic signal spectrum of the roof strata in the working face of a coal mine section with no dynamic phenomenon hazard, determine the first spectrum, second spectrum, and reference amplitude of the safe state;

[0056] Based on the first spectrum, the second spectrum, and the reference amplitude of the safe state, determine the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value.

[0057] Optionally, in one embodiment of the present invention, determining the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value based on the first spectrum, the second spectrum, and the reference amplitude of the safe state includes:

[0058] Based on the first sub-spectrum, second sub-spectrum, and reference amplitude of each of the multiple mining cycles under the safe state, determine the first amplitude critical value, second amplitude critical value, and reference frequency critical value of each of the multiple mining cycles;

[0059] The first amplitude critical value, the second amplitude critical value, and the reference frequency critical value are determined based on the average value of the first amplitude critical value, the average value of the second amplitude critical value, and the average value of the reference frequency critical value of the multiple mining cycles.

[0060] In this example, to improve the real-time performance and accuracy of the prediction results, the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value are determined based on on-site measurements in the coal mine operating area. Specifically, through monitoring of the coal mine roadways, in sections confirmed to be at risk of no dynamic phenomena, multiple mining cycles are continuously advanced at the working face, for example, no less than 30 mining cycles. The first spectrum, the second spectrum, and the reference amplitude of each mining cycle under safe conditions in that coal mine section are calculated, and the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value of each mining cycle are determined. The average value of the first amplitude critical value, the average value of the second amplitude critical value, and the average value of the reference frequency critical value of the multiple mining cycles are used as the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value, respectively. This method makes the determined first amplitude critical value, second amplitude critical value, and reference frequency critical value more targeted and real-time, thereby further improving the reliability of the prediction.

[0061] Optionally, in one embodiment of the present invention, the method further includes: calibrating the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value according to the mining progress of the coal mine working face.

[0062] Because the geological characteristics of different areas of a coal mine vary, the accuracy of predictions can be further improved by calibrating the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value.

[0063] Optionally, in one embodiment of the present invention, determining the first amplitude based on the first spectrum and determining the second amplitude based on the second spectrum includes:

[0064] The first amplitude is obtained by summing the amplitudes of each spectral component in the first sub-spectrum;

[0065] The second amplitude is obtained by summing the amplitudes of each spectral component in the second sub-spectrum.

[0066] In this example, determining the first amplitude from the first spectrum specifically involves using the sum of the amplitudes of each spectral component of the first spectrum as the first amplitude, which is used to characterize the low-frequency amplitude characteristics of the acoustic signal spectrum. Determining the second amplitude from the second spectrum specifically involves using the sum of the amplitudes of each spectral component of the second spectrum as the second amplitude, which is used to characterize the high-frequency amplitude characteristics of the acoustic signal spectrum. This further establishes a basis for judging the hazard of coal mine dynamic phenomena based on acoustic amplitude.

[0067] Optionally, in one embodiment of the present invention, determining the reference frequency based on the reference amplitude includes:

[0068] Based on the maximum amplitude A of the acoustic signal spectrum max , with λA max The reference amplitude is λ, where λ is a multiplier factor, 0 < λ < 1;

[0069] Based on the reference amplitude, the smallest frequency is selected as the reference frequency from the spectral components of the acoustic signal spectrum that are not less than the reference amplitude.

[0070] Based on mine testing in coal mines, a delay in surrounding rock deformation inevitably precedes dynamic phenomena. This deformation delay leads to roof overhang, increased formation stress, and the accumulation of potential energy, which is the energy source of the dynamic phenomena. Therefore, monitoring the development of deformation processes in the coal seam roof strata can ensure the prediction of potentially hazardous sections of the dynamic phenomena. Please refer to [link to relevant documentation]. Figure 2 , Figure 3The dynamic deformation of the roof strata and the movement of the maximum bearing pressure exhibit cyclical and reciprocating changes. The reciprocating movement of the maximum bearing pressure is determined by the dynamic deformation of the roof strata. When there is no danger of dynamic phenomena in the surrounding rock near the coal face, the maximum bearing pressure in front of the working face moves back and forth regularly during coal cutting. When the deformation of the roof strata near the working face stagnates or is delayed, the maximum bearing pressure in front of the working face stops moving back and forth, the stress in the surrounding rock increases, and potential energy accumulates. Under certain conditions, the potential energy is converted into kinetic energy, and dynamic phenomena occur at the working face. Therefore, the roof strata of a coal mine roadway can be regarded as an oscillating system separated by a series of weakened interlayer contact surfaces. When the coal mining machine and tunneling machine are operating, the seismic detector mainly records the resonance results generated in the stratification of the roof strata separated by the weakened interlayer contact surfaces during coal cutting. This signal represents the superposition of inherent resonant oscillations generated in stratification with different rock layer thicknesses h and strengths A, which depends on the degree of weakening of the weakened interlayer contact surfaces. In the artificial acoustic signal spectrum, the location of the weakened interlayer contact surfaces is determined based on the resonant frequency, the deformation strength of the weakened interlayer contact surfaces is evaluated based on their amplitude, and their dynamics are monitored during the working face advancement. This allows for the study of the rock layering structure of the roof strata, evaluation of interlayer deformation strength, and relative stress coefficients. The functional relationship between the thickness of the rock layers separated by the weakened interlayer contact surfaces and the resonant frequency of the artificial acoustic signal is: f p =V / h, where f p denoted as the natural resonant frequency, V as the phase velocity of the transverse wave, and h as the thickness of the rock layer where resonance occurs.

[0071] Based on the above analysis, to further improve the reliability of predicting the hazards of coal mine dynamic phenomena, a safety analysis of frequencies in the acoustic signal spectrum is added. The reference frequency is determined based on the reference amplitude; specifically, in this example, the reference amplitude is λA. max Where λ is a multiplicative factor, 0 < λ < 1, A max The maximum amplitude of the acoustic signal spectrum is determined. After determining the reference amplitude, spectral components not less than the reference amplitude are selected from the acoustic signal spectrum. Then, the frequencies of each selected spectral component are compared, and the minimum frequency, i.e. the lower sideband, is selected as the reference frequency. This further constructs a basis for judging the danger of coal mine dynamic phenomena based on acoustic frequency.

[0072] Optionally, in one embodiment of the present invention, the reference amplitude includes at least a first reference amplitude and a second reference amplitude; the reference frequency includes at least a first reference frequency corresponding to the first reference amplitude and a second reference frequency corresponding to the second reference amplitude.

[0073] In this example, based on the two acoustic amplitude-based indices, the first amplitude and the second amplitude, two more acoustic frequency-based indices are introduced to improve the predictive reliability of this method. Specifically, according to the aforementioned method, the first reference amplitude λ1A... max The corresponding first reference frequency F1 is determined by the second reference amplitude λ2A. max The corresponding second reference frequency F2 is determined. For example, values ​​λ1 = 0.5 and λ2 = 0.75 can be taken, thus obtaining the lower sideband of the artificial acoustic signal spectrum at 0.5 times the maximum amplitude as the first reference frequency, and the lower sideband of the artificial acoustic signal spectrum at 0.75 times the maximum amplitude as the second reference frequency. Correspondingly, when determining the corresponding reference frequency critical values, the reference amplitude of the safe state determined by the acoustic signal spectrum of the roof strata of the working face in coal mine sections without dynamic phenomena hazards can take the same values ​​of λ1 and λ2 to determine the corresponding first reference frequency critical value F. 1CV Second reference frequency threshold F 2CV .

[0074] Optionally, in one embodiment of the present invention, predicting the hazard of coal mine dynamic phenomena based on the first amplitude, the second amplitude, the reference frequency, and the first amplitude critical value, the second amplitude critical value, and the reference frequency critical value includes:

[0075] If the first amplitude is not greater than the first amplitude critical value, the second amplitude is not less than the second amplitude critical value, and the reference frequency is not less than the reference frequency critical value, the coal mine working face is predicted to have a dynamic phenomenon hazard.

[0076] For example, in this case, in addition to the first amplitude and second amplitude, which are based on acoustic amplitude, two more indicators based on acoustic frequency, the first reference frequency and second reference frequency, are introduced to improve the reliability of the prediction. Therefore, when A H ≤A HCV A B ≥A BCV And F1≥F 1CV F2≥F 2CV When it is predicted that the coal mine working face has a dynamic phenomenon hazard, corresponding safety countermeasures need to be taken, including: A H For the first amplitude, A HCV A is the first amplitude critical value. B For the second amplitude, A BCV F1 is the second amplitude critical value, F2 is the first reference frequency, and F2 is the second reference frequency. 1CV F is the first reference frequency threshold. 2CV This is the second reference frequency critical value.

[0077] Optionally, in one embodiment of the present invention, the method further includes: determining a relative stress coefficient based on the first amplitude and the second amplitude; and predicting the hazard of coal mine dynamic phenomena based on the relative stress coefficient, wherein the relative stress coefficient K = A. B / A H A H For the first amplitude, A B This is the second amplitude.

[0078] As the spatial stress near the working surface increases, the attenuation coefficient of sound waves decreases, and this decrease is more pronounced at high frequencies than at low frequencies. Therefore, the ratio of harmonic amplitudes of the acoustic signal measured at high and low frequencies increases with increasing stress. Please refer to [link to relevant documentation]. Figure 4 In this diagram, the horizontal axis represents frequency, and the vertical axis represents amplitude. During coal mining and tunneling operations, to assess the relative stress dynamics of the rock mass near the working face, one-third of the spectrum of the artificial acoustic signal can be calculated. Based on this, the low-frequency and high-frequency components of the spectrum corresponding to the sum of the amplitudes of the low-frequency and high-frequency portions of the acoustic signal spectrum can be determined. This allows for the calculation of the relative stress coefficient K, which is equal to the ratio of the sum of the amplitudes of the high-frequency portions of the spectrum to the sum of the amplitudes of the low-frequency portions of the spectrum. In this example, K = A. B / A H A H For the first amplitude, A B The second amplitude is given. It can be seen that an increase in coefficient K corresponds to increased stress, accumulation of potential energy, and increased risk of dynamic phenomena in the surrounding rock of the roadway. Therefore, by further introducing a relative stress coefficient and analyzing and judging the relative stress coefficient, the risk of dynamic phenomena in coal mines can be predicted, thereby further improving the reliability of this prediction method.

[0079] Optionally, in one embodiment of the present invention, before determining the first sub-spectrum, the second sub-spectrum, and the reference amplitude of the working state based on the acoustic signal spectrum of the roof strata during coal mine working face operation, the method includes: installing a first seismic detector at the coal mine tunneling face and installing a second seismic detector at the coal mining face.

[0080] In this plan, a mine monitoring and early warning system can be established, such as... Figure 7 As shown, a first seismic detector 13 is installed at the tunneling face. The distance between the first seismic detector 13 and the end of the tunneling face can be maintained at 20-40m. It is periodically installed as the tunneling face advances. For specific installation instructions for the first seismic detector 13, please refer to [link to relevant documentation]. Figure 8 You can follow these steps:

[0081] (1) Select the fixed location of the first seismic detector 13, remove the metal mesh 16 on the back plate of the roadway sidewall at the location of the first seismic detector 13, and clean up the loose coal at the installation location.

[0082] (2) Use nut 12 to fix the first seismic detector bracket 14 to the protruding part of the anchor metal rod 11;

[0083] (3) Place the first seismic detector 13 into the cylinder against the coal body, bend the bracket of the first seismic detector 13 so that the sensitive part of the first seismic detector 13 will produce an elastic effect when pressed, tighten the bolt 15, and fix the first seismic detector 13.

[0084] (4) The fastening element of the first seismic detector 13 shall not be pressed on the coal body and shall be covered with sound insulation material;

[0085] (5) During operation, the compaction of the coal body by the first seismic detector 13 shall be checked at least once a day;

[0086] (6) When installing the first seismic detector 13 in the new location, ensure that it is securely fastened.

[0087] Please see Figure 9 Two second seismic detectors 17 are installed at the coal face, and these detectors move with the fully mechanized mining support. When installing the second seismic detectors 17 on the supports of the fully mechanized mining support with a hydraulic mechanism, the second seismic detectors 17 should be kept away from high-pressure connecting hoses transmitting vibrations from the pump station, away from other vibrating components, and away from power cables. The connecting cables must also have a certain degree of elasticity to prevent them from breaking under stress when the fully mechanized mining support moves. During the advance of the coal face, ensure that the second seismic detectors 17 are securely installed to prevent them from loosening or falling due to vibration. Installing the second seismic detectors 17 on the supports of the fully mechanized mining support, due to their stable position and lack of vibration, allows for higher quality sound signals and less interference signals received.

[0088] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0089] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0090] In particular, the device embodiment is basically similar to the method embodiment, so the description is relatively simple. For relevant details, please refer to the description of the method embodiment.

[0091] For ease of description, the above apparatus is described by dividing it into various functional units / modules. Of course, in implementing this invention, the functions of each unit / module can be implemented in one or more software and / or hardware.

[0092] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method of acoustic prediction of the danger spectrum of dynamic phenomena in coal mines, characterized in that, The method comprises: determining a first spectrum, a second spectrum, and a reference amplitude of a working state according to a spectrum of an acoustic signal of a roof stratum of a working face during operation of the working face, the spectrum components in the first spectrum having a smaller frequency than the spectrum components in the second spectrum; determining a first amplitude according to the first spectrum; determining a second amplitude according to the second spectrum; determining a reference frequency according to the reference amplitude; predicting a danger of a dynamic phenomenon of the coal mine according to the first amplitude, the second amplitude, the reference frequency, and a first amplitude threshold value, a second amplitude threshold value, and a reference frequency threshold value; determining the first amplitude according to the first spectrum; determining the second amplitude according to the second spectrum comprises: obtaining the first amplitude according to a sum of amplitudes of the spectrum components in the first spectrum; and obtaining the second amplitude according to a sum of amplitudes of the spectrum components in the second spectrum; determining a reference frequency according to the reference amplitude, including: selecting a minimum frequency from spectral components of the acoustic signal spectrum which are not less than the reference amplitude as the reference frequency; and with a reference amplitude, wherein is a multiplication factor, ; determining a reference frequency according to the reference amplitude, including: selecting a minimum frequency from spectral components of the acoustic signal spectrum which are not less than the reference amplitude as the reference frequency; and the method further comprises: determining a first spectrum, a second spectrum, and a reference amplitude of a safe state according to a spectrum of an acoustic signal of a roof stratum of a working face in a section of the coal mine without a danger of a dynamic phenomenon; and determining the first amplitude threshold value, the second amplitude threshold value, and the reference frequency threshold value according to the first spectrum, the second spectrum, and the reference amplitude of the safe state; determining the first amplitude threshold value, the second amplitude threshold value, and the reference frequency threshold value according to the first spectrum, the second spectrum, and the reference amplitude of the safe state comprises: determining a first amplitude threshold value, a second amplitude threshold value, and a reference frequency threshold value of each of a plurality of mining cycles according to a first spectrum, a second spectrum, and a reference amplitude of each of the plurality of mining cycles in the safe state; and determining the first amplitude threshold value, the second amplitude threshold value, and the reference frequency threshold value according to an average of the first amplitude threshold values, an average of the second amplitude threshold values, and an average of the reference frequency threshold values of the plurality of mining cycles; the prediction of the danger of the dynamic phenomenon of the coal mine according to the first amplitude, the second amplitude, the reference frequency, and the first amplitude threshold value, the second amplitude threshold value, and the reference frequency threshold value comprises: predicting that the working face of the coal mine has the danger of the dynamic phenomenon if the first amplitude is not greater than the first amplitude threshold value, the second amplitude is not less than the second amplitude threshold value, and the reference frequency is not less than the reference frequency threshold value.

2. The coal mine dynamic phenomena danger spectrum acoustic prediction method of claim 1, wherein, the reference amplitude comprises at least a first reference amplitude and a second reference amplitude; the reference frequency comprises at least a first reference frequency corresponding to the first reference amplitude and a second reference frequency corresponding to the second reference amplitude.

3. The coal mine power phenomena danger spectrum acoustic prediction method of claim 1, wherein, The method further comprises: determining a corresponding stress coefficient according to the first amplitude and the second amplitude, and predicting a danger of a coal mine dynamic phenomenon according to the corresponding stress coefficient wherein is the first amplitude, is the second amplitude.

4. The coal mine power phenomena danger spectrum acoustic prediction method of claim 3, wherein, The method further comprises: calibrating the first amplitude threshold value, the second amplitude threshold value, and the reference frequency threshold value according to a mining advance of the working face of the coal mine.

5. The coal mine power phenomena danger spectrum acoustic prediction method of claim 1, wherein, Before the determination of the first spectrum, the second spectrum, and the reference amplitude of the working state according to the spectrum of the acoustic signal of the roof stratum of the working face during operation of the working face, the method comprises: installing a first seismic detector at a mining working face of the coal mine and installing a second seismic detector at a coal mining working face.

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