Coal and gas outburst early warning method and system based on stress monitoring in tunneling working face

Abstract

The application relates to the mining technical field and provides a coal and gas outburst early warning method and system based on stress monitoring. In the method, distributed strain optical fibers are laid in coal bodies in front of a tunneling working face through staggered drill fields, continuous and real-time monitoring of the coal body ground stress is realized by means of the Brillouin scattering effect of the optical fibers, and a series of problems such as the locality, large error, discontinuity, large amount of engineering, occupation of operation time and space and the like of stress monitoring of the tunneling working face are made up; noise is removed through ensemble empirical mode decomposition, the coal body ground stress data quality is improved, the coal body ground stress concentration area range is quickly determined, the stress peak value size and stress change rate in the stress concentration area are tracked, and comparison with a critical value is carried out, coal and gas outburst early warning is comprehensively carried out in combination with gas geological information and gas concentration characteristics of the tunneling working face, and the coal and gas outburst prevention and control is suitable for coal and gas outburst mine tunneling working faces.

Description

Technical Field

[0001] This application relates to the field of mining technology, and in particular to a method and system for early warning of coal and gas outbursts in tunneling faces based on stress monitoring. Background Technology

[0002] Coal and gas outburst (referred to as "outburst") is a large-scale dynamic disaster that mainly occurs in the tunneling face of coal mines. When an outburst occurs, it throws a large amount of coal and gas into the working space. The huge impact force can pose a great threat to the lives of underground workers, making it a top priority in coal mine gas prevention and control.

[0003] Coal and gas outbursts are the result of the combined effects of ground stress, gas, and the physical and mechanical properties of coal. However, with increasing mining depth and intensity, ground stress increases, and the outburst situation becomes more complex. Stress-driven outbursts pose a significant challenge to deep coal mining. Monitoring and early warning are the foundation and prerequisite for preventing and controlling outbursts, making stress monitoring crucial for early warning. Currently, coal mines commonly monitor stress by drilling several boreholes and implanting stress sensors. This "point-to-surface" stress monitoring method suffers from a series of drawbacks, including localization, large errors, discontinuity, large workload, and the time and space required for operation.

[0004] Therefore, there is an urgent need to provide a technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0005] The purpose of this application is to provide a method and system for early warning of coal and gas outbursts in tunneling faces based on stress monitoring, so as to solve or alleviate the problems existing in the prior art.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] This application provides a method for early warning of coal and gas outbursts in tunneling faces based on stress monitoring, including: step S101, laying distributed strain optical fiber in the coal body in front of the tunneling face through a staggered drilling site, and determining the original stress data σ0 of the coal body ground stress based on the Brillouin offset of the center wavelength of the distributed strain optical fiber.

[0008] Step S102: Based on ensemble empirical mode decomposition, the original stress data σ0 is denoised and reconstructed to obtain the reconstructed stress data σ of the coal body in-situ stress. z ; and based on the reconstructed stress data σ of multiple coal body geostresses at different locations at the same time. z The peak stress σ in max And according to the formula:

[0009]

[0010] Delineate the stress concentration region J(d) of the coal body x ,d y In the formula, The stress concentration region J(d) x ,d y The peak stress σ in the coal seam max The corresponding position is the distance from the face of the tunneling face; d x d y The stress concentration regions J(d) are respectively x ,d y The shortest and farthest distances from the face of the tunneling face;

[0011] Step S103: Establish the stress concentration region J(d) x ,d y The peak stress σ of the internal coal body max Stress change rate With the stress concentration region J(d) x ,d y The critical value of peak stress σ at the tunneling face described in the text. 临 Critical value of stress change Δσ 临 The relationship is used to provide step-by-step early warning of coal and gas outbursts at the tunneling face.

[0012] Preferably, in step S101, staggered drilling sites are opened on the upper and lower walls outside the face protection distance of the tunneling face, and the distributed strain optical fiber is laid; wherein, on the side of the coal wall facing the tunneling direction, the staggered drilling site on the upper wall is opened at the middle position 3 meters away from the roadway coal wall, 200 meters in front of the tunneling face and parallel to the roadway coal wall drill head protection distance; on the side of the coal wall facing the tunneling direction, the staggered drilling site on the lower wall is opened at the middle position 3 meters away from the roadway coal wall, 250 meters in front of the tunneling face and parallel to the roadway coal wall drill head protection distance.

[0013] Preferably, in step S101, according to the formula:

[0014]

[0015] Determine the original stress data σ0 of the coal seam's in-situ stress; where B (ε) B is the Brillouin shift of the center wavelength of the distributed strain optical fiber when subjected to the geostress of the coal body; (0) ε is the Brillouin offset of the center wavelength of the distributed strain fiber when it is not subjected to external load; ε is the strain of the coal body when the distributed strain fiber is subjected to the in-situ stress of the coal body; E is the elastic modulus of the coal body.

[0016] Preferably, in step S102, according to the formula:

[0017] σ i =σ0+ε i ω

[0018] Gaussian white noise is added to the original stress data σ0 to obtain the stress data σ after adding Gaussian white noise. i In the formula, ε i Let ω be the amplitude of the white noise added for the i-th time;

[0019] Based on ensemble empirical mode decomposition, the stress data σ i Perform cyclic adaptive mode decomposition, and follow the formula:

[0020]

[0021] Calculate the stress data σ i The residual C obtained by performing cyclic adaptive mode decomposition is the (i+1)th residual. i+1 In the formula, IMF i+1 The stress data σ i The (i+1)th mode component obtained by cyclic adaptive mode decomposition, C i The stress data σ i The i-th residual obtained by performing cyclic adaptive mode decomposition, ε i The amplitude of the white noise in the i-th added white noise sequence; n is the number of the original stress data collected;

[0022] In response to the stress data σ i The first residual C I For monotonic decomposition, the validity of the l modal components is judged according to the formula:

[0023]

[0024] All valid modal components are combined to obtain the reconstructed stress data σ of the coal body in-situ stress. z In the formula, IMF l For the l-th effective modal component obtained from the decomposition, C l For the l-th effective modal component IMF l The corresponding residuals; i, l, L≤I; l∈L, where L is the number of effective modal components in the I modal components obtained by decomposition, and I is a positive integer.

[0025] Preferably, the validity determination of the I modal components obtained by decomposition includes: responding to the stress data σ i The IMF of the j-th mode component obtained by adaptive mode decomposition jSatisfies the preset monotonic function:

[0026] σ j =σ i -IMF j

[0027] Calculate the IMF of the j-th modal component. j The Pearson correlation coefficient R with the original stress data σ0; where σ j The stress data σ i The residual after adaptive mode decomposition; j∈I;

[0028] In response to the j-th modal component IMF j If the Pearson correlation coefficient R with the original stress data σ0 satisfies a preset condition, then the IMF of the j-th modal component is... j These are effective modal components.

[0029] Preferably, in response to |R|∈[0.7,1], the j-th modal component IMF j For a valid modal component; in response to |R|∈[0,0.7), the j-th modal component IMF is discarded. j .

[0030] Preferably, in step S103, according to the formula:

[0031]

[0032] Determine the stress concentration region J(d) x ,d y Stress variation rate of the internal coal body

[0033] In the formula, d x d y The stress concentration regions J(d) are respectively x ,d y The shortest and farthest distances from the tunneling face to the working face; t i t i+1 For two adjacent moments, The stress concentration region J(d) x ,d y )inner t i+1 The stress value at each monitoring point at any given time; The stress concentration region J(d) x ,d y )inner t i The stress value at each monitoring point at any given time.

[0034] Preferably, in response to ε max <ε临 and There was no early warning for the coal and gas outburst at the tunneling face.

[0035] Response to σ max ≥ε 临 or Then, a Level I warning for coal and gas outburst at the aforementioned tunneling face will be issued;

[0036] Response to ε max ≥σ 临 or And P ≥ 0.74 MPa or W ≥ 8 m 3 If / t, a level II early warning for coal and gas outburst at the tunneling face is issued; where P is the gas pressure for drilling tests in front of the tunneling face, and W is the gas content for drilling tests in front of the tunneling face.

[0037] Preferably, in response to the issuance of a Level II warning for coal and gas outburst at the tunneling face, gas concentration data at the face of the tunneling face is acquired at a frequency of 30 seconds, and the number N of gas concentration exceeding the limit (greater than 0.8%) within 5 minutes is counted; in response to N≥5, a Level III warning for coal and gas outburst at the tunneling face is issued.

[0038] This application also provides a stress monitoring-based early warning system for coal and gas outbursts in tunneling faces, including:

[0039] The raw data unit is configured to lay distributed strain optical fiber in the coal body in front of the tunneling face through a staggered drilling site, and determine the raw stress data σ0 of the coal body ground stress based on the Brillouin offset of the center wavelength of the distributed strain optical fiber.

[0040] The stress reconstruction and region division unit is configured to perform noise reduction and reconstruction on the original stress data σ0 based on ensemble empirical mode decomposition to obtain the reconstructed stress data σ of the coal body geostress. z And based on the reconstructed stress data σ of the geostress of multiple coal bodies at different locations at the same time, z The peak stress σ in max And according to the formula:

[0041]

[0042] Delineate the stress concentration region J(d) of the coal body x ,d y In the formula, The stress concentration region J(d) x ,d y The peak stress σ in the coal seam maxThe corresponding position is the distance from the face of the tunneling face; d x d y The stress concentration regions J(d) are respectively x ,d y The shortest and farthest distances from the face of the tunneling face;

[0043] The early warning unit is configured to establish the stress concentration region J(d) x ,d y The peak stress σ of the internal coal body max Stress change rate With the stress concentration region J(d) x ,d y The critical value of peak stress σ at the tunneling face described in the text. 临 Critical value of stress change Δσ 临 The relationship is used to provide step-by-step early warning of coal and gas outbursts at the tunneling face.

[0044] Beneficial effects:

[0045] In the stress monitoring-based early warning method for coal and gas outbursts in tunneling faces provided in this application embodiment, distributed strain optical fibers are laid in the coal body in front of the tunneling face through a staggered drilling site. The original stress data σ0 of the coal body's in-situ stress is determined based on the Brillouin offset of the center wavelength of the distributed strain optical fibers. Then, the original stress data σ0 is denoised and reconstructed based on ensemble empirical mode decomposition to obtain the reconstructed stress data σ of the coal body's in-situ stress. z Next, the reconstructed stress data σ of the geostress at different locations of multiple coal bodies at the same time were determined. z The peak stress σ in max And according to the preset stress region division model, the stress concentration region J(d) of the coal body is defined. x ,d y Finally, the stress concentration region J(d) is established. x ,d y The peak stress σ of the internal coal body max Stress change rate With the stress concentration region J(d) x ,d y The critical value of peak stress σ at the tunneling face described in the text. 临 Critical value of stress change Δσ 临 The relationship is used to provide step-by-step early warning of coal and gas outbursts at the tunneling face.

[0046] This method utilizes distributed strain optical fibers laid in the coal seam ahead of the tunneling face through staggered drilling sites. By leveraging the Brillouin scattering effect of the optical fiber, continuous and real-time monitoring of coal seam stress is achieved, overcoming a series of problems associated with stress monitoring at the tunneling face, such as locality, large errors, discontinuity, large workload, and time and space constraints. Noise is eliminated through ensemble empirical mode decomposition, improving the quality of coal seam stress data. This allows for the rapid determination of the stress concentration area, tracking the stress peak value and stress change rate within the stress concentration area, and comparing them with critical values. Simultaneously, it integrates gas geological information and gas concentration characteristics of the tunneling face for comprehensive early warning of coal and gas outbursts. This method is particularly suitable for the prevention and control of coal and gas outbursts in tunneling faces of coal and gas outburst mines, especially for the prevention and control of coal and gas outbursts in deep, high-stress, and high-gas mines. Attached Figure Description

[0047] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0048] in:

[0049] Figure 1 This is a flowchart illustrating a method for early warning of coal and gas outbursts in a tunneling face based on stress monitoring, according to some embodiments of this application.

[0050] Figure 2 This is a schematic diagram of the planar arrangement of distributed strain optical fibers at a tunneling face according to some embodiments of this application;

[0051] Figure 3 This is a schematic diagram of the arrangement of distributed strain optical fibers in a borehole according to some embodiments of this application;

[0052] Figure 4 This is a logical diagram illustrating a step-by-step early warning system for coal and gas outbursts, provided according to some embodiments of this application.

[0053] Figure 5 This is a structural schematic diagram of a stress monitoring-based early warning system for coal and gas outbursts in a tunneling face, according to some embodiments of this application. Detailed Implementation

[0054] The present application will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will understand that modifications and variations can be made to the present application without departing from the scope or spirit of the present application. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention should fall within the scope of protection of the embodiments of the present invention.

[0055] Currently, coal mines commonly monitor stress by drilling several holes and implanting stress sensors. This "point-to-surface" approach to stress monitoring suffers from several drawbacks, including localization, large errors, discontinuity, large workload, and significant time and space commitment. Distributed strain fiber optic cables, however, offer an effective method for stress monitoring. Successful applications have been demonstrated in monitoring structures such as bridges, tunnels, and slopes, and are now being used in monitoring roof movement in coal mines. Their anti-interference capabilities, high sensitivity, wide monitoring range, and continuous monitoring capabilities have garnered widespread attention.

[0056] However, in the field of stress monitoring at coal mine tunneling faces, the deployment of distributed strain optical fibers remains limited, and there is a lack of methods for early warning of coal and gas outbursts at tunneling faces based on stress monitoring. Therefore, this application proposes an early warning method for coal and gas outbursts at tunneling faces based on stress monitoring, to address the problems of existing coal and gas outburst monitoring and early warning technologies at tunneling faces, such as poor longitude of ground stress monitoring, unstable monitoring, small monitoring range, discontinuous monitoring, and inability to provide early warning based on ground stress.

[0057] This stress-monitoring-based early warning method for coal and gas outbursts in tunneling faces involves laying distributed strain optical fibers in the coal body ahead of the tunneling face through a staggered drilling site. By utilizing the Brillouin scattering effect of the optical fiber, continuous and real-time stress monitoring is achieved. The results, including gas geological information and gas concentration characteristics, are used to provide early warning for coal and gas outbursts. This method is suitable for the prevention and control of coal and gas outbursts in tunneling faces of mines without gas outbursts, and is especially suitable for the prevention and control of coal and gas outbursts in deep mines with high ground stress and high gas content.

[0058] like Figures 1 to 4 As shown, this stress-monitoring-based early warning method for coal and gas outbursts in tunneling faces includes:

[0059] Step S101: The distributed strain optical fiber is laid in the coal body in front of the tunneling face through the staggered drilling site, and the original stress data σ0 of the coal body ground stress is determined according to the Brillouin offset of the center wavelength of the distributed strain optical fiber.

[0060] Tunneling faces can easily stretch for hundreds or even thousands of meters, operating in harsh environments and involving complex construction. Therefore, this application employs single-ended, metal-based, steel-stranded optical fibers with meter-level spatial resolution, coupled with self-contained Leybold optical time-domain reflectometry (PTZ) technology. Simultaneously, the face protection distance is obtained through the tunneling face operation procedures, and the elastic modulus of the coal seam is obtained through the geological conditions of the tunneling face.

[0061] When laying optical fibers, staggered drilling sites are established on the upper and lower coal face, outside the face protection distance of the tunneling face, and distributed strain optical fibers are laid there. By establishing these drilling sites, pressure is relieved. When the drilling sites on the upper and lower coal faces are located at the same layer, superimposed stress concentration is likely to occur, inducing coal and rock failure. By staggering the drilling sites on the upper and lower coal faces, superimposed stress concentration at the same layer is effectively avoided.

[0062] The drilling site dimensions are 6 meters × 6 meters × 3 meters, with a spacing of 50 meters between drilling sites. Specifically, on the coal wall facing the direction of excavation, a staggered drilling site for the upper side is established 200 meters ahead of the working face, parallel to the coal wall and at a distance of 3 meters from the middle of the roadway coal wall, with a borehole diameter of 60 millimeters. On the coal wall facing the direction of excavation, a staggered drilling site for the lower side is established 250 meters ahead of the working face, parallel to the coal wall and at a distance of 3 meters from the middle of the working face, with a borehole diameter of 60 millimeters.

[0063] Due to the complex environment of the tunneling face caused by ground stress and water inrush, the strain gauge fiber was tightly wrapped with steel wire and then laid inside the borehole. Finally, cement mortar with an elastic modulus similar to that of the coal was filled in as support. After the cement mortar had been filled for 7 days and its strength had been tested to obtain the physical and mechanical properties of the coal, the strain gauge fiber was connected in sequence to the junction box, single-ended fiber optic demodulator, and monitoring host.

[0064] The single-ended fiber optic demodulator connects to the underground coal mine substation, transmitting data via an underground ring network to a monitoring host deployed on the ground (e.g., a data workstation). The monitoring host then analyzes and displays the data. After the fiber optic cable is laid, the overlying coal and rock strata exert a certain load (i.e., mechanical force) on the fiber optic cable, which affects light reflection within the cable (i.e., Brillouin shift). The light waves propagating in the fiber interact with the sound waves; the backscattered light has a lower frequency than the incident light, and the frequency shift of the Brillouin scattered light is linearly related to the strain and temperature along the fiber optic axis.

[0065] Therefore, by analyzing the Brillouin offset of the fiber center wavelength using a single-ended fiber optic demodulator, the strain ε of the coal body, i.e., the monitored strain at the tunneling face, is obtained. Then, combined with the elastic modulus of the coal body, the in-situ stress of the coal body is obtained. Specifically, according to the formula:

[0066]

[0067] Determine the original stress data σ0 of the coal seam's in-situ stress. Where, B (ε) B represents the Brillouin shift of the center wavelength of a distributed strain optical fiber subjected to coal seam stress; (0) ε is the Brillouin shift of the center wavelength of the distributed strain fiber when it is not subjected to external load; ε is the strain of the coal body when the distributed strain fiber is subjected to in-situ stress; dB (ε) / dε is a constant with a value of 490MHz; E is the elastic modulus of the coal.

[0068] Step S102: Based on ensemble empirical mode decomposition, the original stress data σ0 is denoised and reconstructed to obtain the reconstructed stress data σ of the coal body. z ; and based on the reconstructed stress data σ of multiple coal seams at different locations at the same time. z The peak stress σ in max And according to the formula:

[0069]

[0070] Delineate the stress concentration region J(d) of the coal body x ,d y ).

[0071] Because coal seam stress is influenced by mining, local geological structures, and the physical and mechanical properties of the coal, it exhibits complex variations and is highly susceptible to noise. In this application, the original stress data σ0 is denoised and reconstructed using ensemble empirical mode decomposition to obtain reconstructed stress data σ of the coal seam. z Specifically, according to the formula:

[0072] σ i =σ0+ε i ω

[0073] Adding Gaussian white noise to the original stress data σ0 yields the stress data σ after adding Gaussian white noise. i In the formula, ε i Let ω be the amplitude of the white noise added for the i-th time.

[0074] Then, based on ensemble empirical mode decomposition, the stress data σ i Perform cyclic adaptive mode decomposition, and follow the formula:

[0075]

[0076] Calculate stress data σ i The residual C obtained by performing cyclic adaptive mode decomposition is the (i+1)th residual. i+1 In the formula, IMFi+1 For stress data σ i The (i+1)th mode component obtained by cyclic adaptive mode decomposition, C i For stress data σ i The i-th residual obtained by performing cyclic adaptive mode decomposition, ε i The amplitude of the white noise in the i-th added white noise sequence; n is the number of original stress data collected.

[0077] In a specific example, the stress data σ after adding Gaussian white noise i Perform the first empirical mode decomposition and obtain the first mode f. i The first modal component, IMF1, is obtained by averaging. Specifically, according to the formula:

[0078]

[0079] In the formula, n is the number of samples. Then, by subtracting the first modal component IMF1 from the original stress data σ0, the first residual C1 is obtained, i.e., according to the formula:

[0080] C1=σ0-IMF1

[0081] Calculate the first residual C1.

[0082] Next, Gaussian white noise ε1ω is added to the first residual C1, and a second empirical mode decomposition is performed to obtain the second modal component IMF2. Specifically, according to the formula:

[0083]

[0084] And according to the formula:

[0085] C2 = C1 - IMF2

[0086] Calculate the second residual C2. Repeat this process until the stress data σ is obtained. i The first residual C I Monotonic, stress data σ i The cyclic adaptive mode decomposition process ends. Where i ≤ I; I is a positive integer.

[0087] Then, the validity of the I modal components obtained from the decomposition is judged. Specifically, when the stress data σ i The IMF of the j-th mode component obtained by adaptive mode decomposition j Satisfies the preset monotonic function:

[0088] σ j =v i -IMF j

[0089] Calculate the IMF of the j-th modal component. j The Pearson correlation coefficient R with the original stress data σ0; where σ j For stress data σ i The remainder after adaptive mode decomposition; j∈J.

[0090] Specifically, according to the formula:

[0091]

[0092] Calculate the IMF of the j-th modal component. j The Pearson correlation coefficient R with the original stress data σ0. Where, V σ0 This represents the average value of multiple raw stress data σ0 obtained from different locations at the same time using distributed strain optical fiber; V IMFj Let be the average value of the j modal components obtained from j adaptive mode decompositions.

[0093] According to the IMF of the j-th modal component j The relationship between the Pearson correlation coefficient R and the original stress data σ0 is used to determine the IMF of the j-th modal component. j Is it a valid modal component? Specifically, when |R|∈[0.7,1], then the j-th modal component IMF... j For valid modal components; when |R|∈[0,0.7), then the j-th modal component IMF is removed. j That is, the j-th modal component IMF j This is an invalid mode component.

[0094] Finally, all effective modal components are combined to obtain the reconstructed stress data σ of the coal seam in-situ stress. z Specifically, according to the formula:

[0095]

[0096] By merging all valid modal components, the reconstructed stress data σ of the coal seam's in-situ stress is obtained. z In the formula, IMF l For the l-th effective modal component obtained from the decomposition, C l For the l-th effective modal component IMF l The corresponding residuals; l, L≤I; l∈L, where L is the number of effective modal components in the I modal components obtained by decomposition, and I is a positive integer.

[0097] Finally, based on the reconstructed stress data σ of multiple coal seams at different locations at the same time, z The peak stress σ in max The model is divided according to the preset stress region:

[0098]

[0099] Delineate the stress concentration region J(d) of the coal body x ,d y ).

[0100] In the formula, For stress concentration region J(d) x ,d y The peak stress σ in the coal seam max The corresponding location is the distance from the tunneling face; d x d y These are stress concentration regions J(d) x ,d y The shortest and farthest distances from the tunnel face to the working face.

[0101] Step S103: Establish the stress concentration region J(d) x ,d y The peak stress σ in the internal coal seam max Stress change rate With stress concentration region J(d) x ,d y The critical value of peak stress σ at the tunneling face 临 Critical value of stress change Δσ 临 The relationship is used to provide step-by-step early warning of coal and gas outbursts at the tunneling face.

[0102] Specifically, according to the formula:

[0103]

[0104] Determine the stress concentration region J(d) x ,d y Stress variation rate of the internal coal body In the formula, d x d y These are stress concentration regions J(d) x ,d y The shortest and farthest distances from the tunnel face to the working face; t i t i+1 For two adjacent moments, For stress concentration region J(d) x ,d y )inner t i+1 The stress value at each monitoring point at any given time (one monitoring point is placed every 1 meter in the optical fiber); For stress concentration region J(d) x ,d y )inner t iThe stress value at each monitoring point at any given time.

[0105] Simultaneously, numerical simulations were conducted on coal and gas outbursts at the tunneling face. Based on the simulation results and historical data on coal and gas outbursts at the tunneling face, the critical value σ of the peak stress at the tunneling face within the stress concentration area was determined. 临 Critical value of stress change Δσ 临 .

[0106] Then, based on the stress concentration region J(d) x ,d y Stress change rate of fiber optic monitoring data and stress concentration region J(d) x ,d y The critical value of peak stress σ at the tunneling face 临 Critical value of stress change Δσ 临 A tiered early warning mechanism for coal and gas outbursts is constructed, and the peak stress, rate of change of stress, and their corresponding critical values ​​are compared in real time within the stress concentration area. If σ max <σ 临 and If there is no risk of coal and gas outburst at the tunneling face, no outburst warning will be issued; if σ max ≥σ 临 or A Level I warning for coal and gas outburst at the tunneling face will be issued.

[0107] In this application, the stress concentration region J(d) of the tunneling face is obtained. x ,d y The parameters of gas occurrence in each layer, the geological structure distribution parameters, and the drilling test parameters of the tunneling face are used to determine the parameters based on σ. max σ 临 , △σ 临 Based on coal seam gas occurrence parameters, geological structure distribution parameters, and drilling test parameters, a tiered early warning system is established for coal and gas outbursts at the tunneling face. This is achieved firstly through σ... max σ 临 , △σ 临 Early warning of coal and gas outbursts at the tunneling face is issued; then, based on the coal seam gas occurrence parameters and geological structure distribution parameters, early warning of coal and gas outbursts at the tunneling face is issued; finally, early warning of coal and gas outbursts at the tunneling face is issued based on drilling test parameters.

[0108] In other words, if σ max ≥σ 临 or And the stress concentration region J(d) x ,d yThe gas pressure P ≥ 0.74 MPa or the gas content W ≥ 8 m³ / s when drilling a borehole ahead of the tunnel face is required for testing. 3 / t, issued a Level II early warning for coal and gas outburst at the tunneling face. That is to say, if σ max ≥σ 临 And the stress concentration region J(d) x ,d y The gas pressure P ≥ 0.74 MPa, or σ, is used for drilling tests in front of the tunnel face. max ≥σ 临 Furthermore, the methane content W ≥ 8m³ was measured during drilling tests ahead of the tunnel face. 3 / t, or, And the stress concentration region J(d) x ,d y The gas pressure P for drilling tests in front of the tunnel face is ≥0.74 MPa, or... Furthermore, the methane content W ≥ 8m³ was measured during drilling tests ahead of the tunnel face. 3 If / t, a Level II warning for coal and gas outburst at the tunneling face will be issued.

[0109] Based on the secondary early warning for coal and gas outbursts at the tunneling face, gas concentration data at the tunneling face is acquired every 30 seconds, and the number of gas concentration exceedance points (N) exceeding the limit (greater than 0.8%) within 5 minutes is counted. When N ≥ 5, a tertiary early warning for coal and gas outbursts at the tunneling face is issued. This collaborative early warning system, combining static and dynamic data related to coal mine outbursts, improves the timeliness and reliability of early warnings for coal and gas outbursts at the tunneling face. Finally, the name of the tunneling face and the outburst risk level of the coal and gas outburst warning are broadcast to all underground personnel and sent to relevant management personnel via satellite, SMS, etc., initiating the outburst prevention and control process.

[0110] In this application, distributed strain optical fibers are laid in the coal body in front of the tunneling face through a staggered drilling site. The Brillouin scattering effect of the optical fiber enables continuous and real-time monitoring of coal body stress, overcoming a series of problems associated with stress monitoring at the tunneling face, such as locality, large errors, discontinuity, large workload, and time and space constraints. Noise is eliminated through ensemble empirical mode decomposition, improving the quality of coal body stress data and enabling rapid determination of the stress concentration area. The stress peak value and stress change rate within the stress concentration area are tracked and compared with critical values. Simultaneously, gas geological information and gas concentration characteristics of the tunneling face are integrated to provide early warning of coal and gas outbursts. This method is particularly suitable for the prevention and control of coal and gas outbursts in tunneling faces of coal and gas outburst mines, especially in deep mines with high ground stress and high gas content.

[0111] This application also provides an embodiment of a coal and gas outburst early warning system for tunneling faces based on stress monitoring, such as... Figure 5 As shown, the early warning system includes:

[0112] The original data unit 501 is configured to lay the distributed strain fiber in the coal body in front of the tunneling face through the staggered drilling field, and determine the original stress data σ0 of the coal body ground stress based on the Brillouin offset of the center wavelength of the distributed strain fiber.

[0113] The stress reconstruction and region division unit 502 is configured to denoise and reconstruct the original stress data σ0 based on ensemble empirical mode decomposition to obtain the reconstructed stress data σ of the coal body in-situ stress. z And based on the reconstructed stress data σ of multiple coal bodies at different locations at the same time, z The peak stress σ in max And according to the formula:

[0114]

[0115] Delineate the stress concentration region j(d) of the coal body x ,d y In the formula, For stress concentration region J(d) x ,d y The peak stress σ in the coal seam max The corresponding location is the distance from the tunneling face; d x d y These are stress concentration regions J(d) x ,d y The shortest and farthest distances from the tunnel face;

[0116] Early warning unit 503 is configured to establish stress concentration region J(d) x ,d y The peak stress σ in the internal coal seam max Stress change rate With stress concentration region J(d) x ,d y The critical value of peak stress σ at the tunneling face 临 Critical value of stress change Δσ 临 The relationship is used to provide step-by-step early warning of coal and gas outbursts at the tunneling face.

[0117] The stress-monitoring-based early warning system for coal and gas outbursts in tunneling faces provided in this application embodiment can realize the steps and processes of the stress-monitoring-based early warning method for coal and gas outbursts in tunneling faces in any of the above embodiments, and achieve the same technical effect, which will not be repeated here.

[0118] In the description of this invention, it should be understood that the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0119] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for early warning of coal and gas outbursts in tunneling faces based on stress monitoring, characterized in that, include: Step S101: The distributed strain optical fiber is laid in the coal body in front of the tunneling face through a staggered drilling site, and according to the Brillouin offset of the center wavelength of the distributed strain optical fiber, the following formula is used: Determine the original stress data of the coal body's geostress. In the formula, The Brillouin offset of the center wavelength of the distributed strain optical fiber when subjected to the geostress of the coal body; The Brillouin offset of the center wavelength of the distributed strain fiber when it is not subjected to external load; The strain of the coal body when the distributed strain optical fiber is subjected to the in-situ stress of the coal body; The elastic modulus of the coal body; Specifically, staggered drilling sites are opened on the upper and lower sides of the tunneling face, outside the face protection distance, and the distributed strain optical fiber is laid; on the side of the coal wall facing the tunneling direction, the staggered drilling site is opened on the upper side 200 meters in front of the tunneling face, parallel to the tunneling face protection distance of the tunneling face, at the middle position 3 meters away from the roadway coal wall. On the side of the coal wall facing the direction of excavation, at a position 3 meters away from the middle of the roadway coal wall, 250 meters ahead of the drilling head protection distance of the drilling head parallel to the roadway coal wall in front of the excavation working face, the misaligned drilling site is opened. Step S102: Based on ensemble empirical mode decomposition, analyze the original stress data. Noise reduction and reconstruction are performed to obtain the reconstructed stress data of the coal seam's in-situ stress. ;in, According to the formula: To the original stress data Gaussian white noise was added to obtain the stress data after adding Gaussian white noise. In the formula, For the first The added white noise sequence The amplitude of white noise; Based on ensemble empirical mode decomposition, the stress data Perform cyclic adaptive mode decomposition, and follow the formula: Calculate the stress data The first obtained by performing cyclic adaptive mode decomposition residual In the formula, For the stress data The first obtained by performing cyclic adaptive mode decomposition One modal component, For the stress data The first obtained by performing cyclic adaptive mode decomposition residual For the first The added white noise sequence The amplitude of white noise; The number of the original stress data collected; In response to the stress data The residual Monotonic, for the decomposition obtained The validity of each modal component is determined according to the formula: All valid modal components are combined to obtain the reconstructed stress data of the coal seam in-situ stress. In the formula, The first decomposition obtained One effective modal component, For the first One effective modal component The corresponding residuals; ; , For decomposition The number of effective modal components in each modal component. It is a positive integer; Based on the reconstructed stress data of the geostress of multiple coal bodies at different locations at the same time. Peak stress in And according to the formula: Delineate the stress concentration areas of the coal body In the formula, The stress concentration region Peak stress in medium coal seam The corresponding location is the distance from the face of the tunneling face; These are the stress concentration regions. The shortest and farthest distances from the face of the tunneling working face; Step S103: Establish the stress concentration region The stress peak value of the inner coal body Stress change rate With the stress concentration region The critical value of peak stress at the tunneling face described above. Critical value of stress change The relationship is used to provide step-by-step early warning of coal and gas outbursts at the tunneling face.

2. The method for early warning of coal and gas outbursts in tunneling faces based on stress monitoring according to claim 1, characterized in that, The decomposition obtained The validity of each modal component is determined, including: In response to the stress data The first obtained by adaptive mode decomposition Modal components Satisfies the preset monotonic function: Calculate the first The modal components Compared with the original stress data Pearson correlation coefficient In the formula, For the stress data The remaining margin after adaptive mode decomposition; ; In response to the The modal components Compared with the original stress data Pearson correlation coefficient If the preset conditions are met, then the first The modal components These are effective modal components.

3. The method for early warning of coal and gas outbursts in tunneling faces based on stress monitoring according to claim 2, characterized in that, In response to Then the first The modal components Effective modal components; In response to Then remove the first one. The modal components .

4. The method for early warning of coal and gas outbursts in tunneling faces based on stress monitoring according to claim 1, characterized in that, In step S103, according to the formula: Determine the stress concentration region Stress variation rate of internal coal body ; In the formula, These are the stress concentration regions. The shortest and farthest distances from the face of the tunneling working face; For two adjacent moments, The stress concentration region Inside The stress value at each monitoring point at any given time; The stress concentration region Inside The stress value at each monitoring point at any given time.

5. The method for early warning of coal and gas outbursts in tunneling faces based on stress monitoring according to claim 1, characterized in that, In response to and In this case, there is no early warning for coal and gas outburst at the tunneling face; In response to or If so, a Level I warning for coal and gas outburst at the tunneling face is issued; In response to or ,and or If so, a Level II warning for coal and gas outburst at the aforementioned tunneling face will be issued; among which, The gas pressure is used to test drilling ahead of the tunneling face. The gas content is measured by drilling a hole in front of the tunneling face.

6. The method for early warning of coal and gas outbursts in tunneling faces based on stress monitoring according to claim 5, characterized in that, In response to the issuance of a Level II warning for coal and gas outburst at the tunneling face, gas concentration data at the tunneling face is acquired every 30 seconds, and the number of gas concentration exceeding the limit (greater than 0.8%) within 5 minutes is counted. ; In response to If the above occurs, a Level III warning for coal and gas outburst at the tunneling face will be issued.

7. A coal and gas outburst early warning system for tunneling faces based on stress monitoring, characterized in that, The method for early warning of coal and gas outbursts in tunneling faces based on stress monitoring, as described in any one of claims 1-6, is used to provide step-by-step early warning for coal and gas outbursts in the tunneling face. The system comprises: The raw data unit is configured to lay distributed strain optical fibers in the coal body in front of the tunneling face through a staggered drilling field, and to determine the raw stress data of the coal body's in-situ stress based on the Brillouin offset of the center wavelength of the distributed strain optical fibers. ; The stress reconstruction and region partitioning unit is configured to perform stress reconstruction and region partitioning based on ensemble empirical mode decomposition on the original stress data. Noise reduction and reconstruction are performed to obtain the reconstructed stress data of the coal seam's in-situ stress. And based on the reconstructed stress data of the geostress of multiple coal bodies at different locations at the same time. Peak stress in And according to the formula: Delineate the stress concentration areas of the coal body In the formula, The stress concentration region Peak stress in medium coal seam The corresponding location is the distance from the face of the tunneling face; These are the stress concentration regions. The shortest and farthest distances from the face of the tunneling working face; The early warning unit is configured to establish the stress concentration region. The stress peak value of the inner coal body Stress change rate With the stress concentration region The critical value of peak stress at the tunneling face described above. Critical value of stress change The relationship is used to provide step-by-step early warning of coal and gas outbursts at the tunneling face.

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