Early warning method and system for coal and gas outburst of driving face based on stress monitoring

Abstract

The invention relates to the technical field of mining, and provides an early warning method and system for coal and gas outburst of a driving face based on stress monitoring. According to the method, distributed strain optical fibers are laid in a coal body in front of a tunneling working face through a staggered drilling field, continuous and real-time monitoring of the ground stress of the coal body is achieved by means of the Brillouin scattering effect of the optical fibers, and a series of problems of locality, large errors, discontinuity, large work amount, occupied operation time and space and the like of stress monitoring of the tunneling working face are solved; noise elimination is carried out through ensemble empirical mode decomposition, the quality of coal body crustal stress data is improved, the range of a coal body crustal stress concentration area is rapidly determined, and the internal stress peak value and the stress change rate of the stress concentration area are tracked and compared with critical values. The coal and gas outburst early warning method is suitable for coal and gas outburst prevention and control of the driving face of the coal and gas outburst mine.

Description

Technical Field

[0001] The present 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 an excavation working face based on stress monitoring. Background Art

[0002] Coal and gas outburst (abbreviated as "outburst") is a large-scale dynamic disaster that mainly occurs in the coal mine excavation working face. At the moment of occurrence, a large amount of coal and gas will be thrown into the working space. The huge impact force can pose a huge threat to the lives of underground workers. It is the top priority of coal mine gas prevention and control.

[0003] Coal and gas outbursts are the result of the combined effects of geostress, gas, and the physical and mechanical properties of coal. However, with the increase in mining depth and mining intensity, geostress becomes greater and greater, and the outburst situation becomes more and more complicated. Stress-dominated outbursts will become a problem in deep mining of coal mines. Monitoring and early warning are the basis and prerequisite for preventing and controlling outbursts, and how to monitor stress becomes the key to early warning of outbursts. At present, coal mines generally monitor stress by drilling several holes and implanting stress sensors. This "point-to-surface" stress monitoring method has a series of disadvantages such as locality, large errors, discontinuity, large engineering workload, and occupying operation time and space.

[0004] Therefore, there is an urgent need to provide a technical solution to the above-mentioned deficiencies in the prior art. Summary of the invention

[0005] The purpose of this application is to provide a method and system for early warning of coal and gas outburst in an excavation working face based on stress monitoring, so as to solve or alleviate the problems existing in the above-mentioned prior art.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] The present application provides a method for early warning of coal and gas outburst in a tunneling working face based on stress monitoring, comprising: step S101, laying a distributed strain optical fiber in the coal body in front of the tunneling working face through a dislocated drilling site, and determining the original stress data σ0 of the coal body ground stress of the coal body according to the Brillouin shift of the central wavelength of the distributed strain optical fiber;

[0008] Step S102: De-noise and reconstruct the original stress data σ0 based on the 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 the coal body ground stress at different positions at the same time z The peak stress σ max , and according to the formula:

[0009]

[0010] Determine the stress concentration area J(d x ,d y );where, is the stress concentration area J(d x ,d y ) The peak stress value of coal body σ max The distance between the corresponding position and the front of the excavation working face; d x ,d y They are the stress concentration areas J(d x ,d y ) the shortest distance and the longest distance from the head of the excavation working face;

[0011] Step S103: Establish the stress concentration area J(d x ,d y ) The stress peak value σ of the coal body max , stress change rate The stress concentration area J(d x ,d y ) is the critical value of the peak stress of the excavation working face σ 临 , critical value of stress change △σ 临 The relationship between them can be used to provide step-by-step early warning for coal and gas outbursts in the excavation working face.

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

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

[0014]

[0015] Determine the original stress data σ0 of the coal body ground stress; where B (ε) B is the Brillouin shift of the central wavelength of the distributed strain optical fiber when it is subjected to the coal body ground stress; (0) is the Brillouin shift of the central wavelength of the distributed strain optical fiber when it is not subjected to external load; ε is the strain of the coal body when the distributed strain optical fiber is subjected to the in-situ stress of the coal body; and 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] Add Gaussian white noise to the original stress data σ0 to obtain the stress data σ after adding Gaussian white noise. i ; In the formula, ε i is the white noise amplitude of the white noise sequence ω added for the i-th time;

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

[0020]

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

[0022] In response to the stress data σ i The Ith residual C I Monotonic, the effectiveness of the l modal components obtained by decomposition is judged according to the formula:

[0023]

[0024] All the effective modal components are combined to obtain the reconstructed stress data σ of the coal body ground stress z ; In the formula, IMF l is the lth effective modal component obtained by decomposition, C l is the lth effective modal component IMF l Corresponding residual; i, l, L≤I; l∈L, 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 judgment of the I modal components obtained by decomposition includes: responding to the stress data σ i The jth modal component IMF obtained by adaptive modal decomposition jSatisfies the preset monotonic function:

[0026] σ j =σ i -IMF j

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

[0028] In response to the jth modal component IMF j If the Pearson correlation coefficient R with the original stress data σ0 meets the preset condition, then the jth modal component IMF j is the effective modal component.

[0029] Preferably, in response to |R|∈[0.7,1], the jth modal component IMF j is the effective modal component; in response to |R|∈[0,0.7), the jth modal component IMF is eliminated j .

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

[0031]

[0032] Determine the stress concentration area J(d x ,d y ) Stress change rate of coal body

[0033] Where, d x ,d y They are the stress concentration areas J(d x ,d y ) the shortest distance and the longest distance from the front of the excavation working face; t i ,t i+1 For two adjacent moments, is the stress concentration area J(d x ,d y ) i+1 The stress value of each monitoring point at each moment; is the stress concentration area J(d x ,d y ) i The stress value of each monitoring point at each moment.

[0034] Preferably, in response to ε max <ε临 and Then there is no early warning of coal and gas outburst at the excavation working face;

[0035] In response to σ max ≥ε 临 or A first-level warning of coal and gas outburst at the excavation working face is issued;

[0036] Responding to ε max ≥σ 临 or And P ≥ 0.74MPa or W ≥ 8m 3 / t, a second-level warning of coal and gas outburst in the excavation working face is issued; wherein P is the gas pressure of the drilling test in front of the excavation working face, and W is the gas content of the drilling test in front of the excavation working face.

[0037] Preferably, in response to issuing a second-level warning of coal and gas outburst at the tunneling working face, gas concentration data at the head of the tunneling working face is obtained at a frequency of 30 seconds, and the number of gas concentration exceeding limit points N within 5 minutes where the gas concentration is greater than 0.8% is counted; in response to N≥5, a third-level warning of coal and gas outburst at the tunneling working face is issued.

[0038] The embodiment of the present application also provides a coal and gas outburst early warning system for a tunneling working face based on stress monitoring, comprising:

[0039] A raw data unit is configured to lay a distributed strain optical fiber in the coal body in front of the excavation working face through a dislocated drilling site, and determine the raw stress data σ0 of the coal body ground stress of the coal body according to the Brillouin shift of the central wavelength of the distributed strain optical fiber;

[0040] The stress reconstruction and regional division unit is configured to reduce noise and reconstruct the original stress data σ0 based on the ensemble empirical mode decomposition to obtain the reconstructed stress data σ of the coal body ground stress. z , and based on the reconstructed stress data σ of the coal body ground stress at different positions at the same time z The peak stress σ max , and according to the formula:

[0041]

[0042] Determine the stress concentration area J(d x ,d y );where, is the stress concentration area J(d x ,d y ) The peak stress value of coal body σ maxThe distance between the corresponding position and the front of the excavation working face; d x ,d y They are the stress concentration areas J(d x ,d y ) the shortest distance and the longest distance from the head of the excavation working face;

[0043] The early warning unit is configured to establish the stress concentration area J(d x ,d y ) The stress peak value σ of the coal body max , stress change rate The stress concentration area J(d x ,d y ) is the critical value of the peak stress of the excavation working face σ 临 , critical value of stress change △σ 临 The relationship between them can be used to provide step-by-step early warning for coal and gas outbursts in the excavation working face.

[0044] Beneficial effects:

[0045] In the method for early warning of coal and gas outburst in a tunneling working face based on stress monitoring provided in an embodiment of the present application, a distributed strain optical fiber is laid in the coal body in front of the tunneling working face through a dislocated drilling site, and the original stress data σ0 of the coal body ground stress of the coal body is determined according to the Brillouin shift of the central wavelength of the distributed strain optical fiber; then, the original stress data σ0 is denoised and reconstructed based on the ensemble empirical mode decomposition to obtain the reconstructed stress data σ of the coal body ground stress. z ; Then, determine the reconstructed stress data σ of multiple coal body in-situ stresses at different locations at the same time z The peak stress σ max , and the stress concentration area J(d x ,d y ); Finally, establish the stress concentration area J(d x ,d y ) The stress peak value σ of the coal body max , stress change rate The stress concentration area J(d x ,d y ) is the critical value of the peak stress of the excavation working face σ 临 , critical value of stress change △σ 临 The relationship between them can be used to provide step-by-step early warning for coal and gas outbursts in the excavation working face.

[0046] Therefore, the distributed strain optical fiber is laid in the coal body in front of the excavation working face through the offset drilling site, and the Brillouin scattering effect of the optical fiber is used to realize continuous and real-time monitoring of the coal body ground stress, which makes up for a series of problems in the excavation working face stress monitoring, such as locality, large error, discontinuity, large engineering workload, and occupation of operation time and space; the noise is eliminated by ensemble empirical mode decomposition to improve the quality of coal body ground stress data, so as to quickly determine the range of the coal body ground stress concentration area, track the stress peak value and stress change rate in the stress concentration area, and compare them with the critical value, and simultaneously combine the gas geological information and gas concentration characteristics of the excavation working face to comprehensively carry out coal and gas outburst early warning, which is particularly suitable for the prevention and control of coal and gas outburst in the excavation working face of coal and gas outburst mines, and especially suitable for the prevention and control of coal and gas outburst in the excavation working face of deep high ground stress and high gas mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0048] in:

[0049] Figure 1 A schematic diagram of a process flow of a method for early warning of coal and gas outburst in a tunneling working face based on stress monitoring according to some embodiments of the present application;

[0050] Figure 2 A schematic diagram of a planar layout of distributed strain optical fibers on a tunneling working face provided according to some embodiments of the present application;

[0051] Figure 3 A schematic diagram of the arrangement of a distributed strain optical fiber in a borehole according to some embodiments of the present application;

[0052] Figure 4 A logical schematic diagram of a step-by-step early warning of coal and gas outburst provided according to some embodiments of the present application;

[0053] Figure 5 A schematic structural diagram of a coal and gas outburst early warning system for an excavation face based on stress monitoring is provided according to some embodiments of the present application. DETAILED DESCRIPTION

[0054] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application and does not limit the present application. In fact, it will be clear to those skilled in the art that modifications and variations may be made in the present application without departing from the scope or spirit of the present application. For example, a feature shown or described as a part of an embodiment may be used in another embodiment to produce yet another embodiment. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the embodiments of the present invention should belong to the scope of protection of the embodiments of the present invention.

[0055] At present, coal mines generally monitor stress by drilling several holes and implanting stress sensors. This "point-to-surface" stress monitoring method has a series of disadvantages, such as locality, large errors, discontinuity, large engineering workload, and occupation of operation time and space. Distributed strain optical fiber is an effective means of monitoring stress. It has been successfully used in monitoring structures such as bridges, tunnels, and slopes. It is currently used in coal mine roof movement monitoring. Its anti-interference, high sensitivity, wide monitoring range, and continuous monitoring characteristics have attracted widespread attention.

[0056] However, in terms of stress monitoring of coal mine excavation working faces, the monitoring arrangement of distributed strain optical fibers is still lacking, and there is a lack of early warning methods for coal and gas outbursts in excavation working faces based on stress monitoring. Based on this, this application proposes an early warning method for coal and gas outbursts in excavation working faces based on stress monitoring to solve the problems of poor monitoring longitude, unstable monitoring, small monitoring range, discontinuity, and inability to provide early warnings based on ground stress in existing early warning technologies for coal and gas outbursts in excavation working faces.

[0057] The coal and gas outburst early warning method for the tunneling working face based on stress monitoring, lays the distributed strain optical fiber in the coal body in front of the tunneling working face through the offset drilling site, realizes continuous and real-time monitoring of stress by means of the Brillouin scattering effect of the optical fiber, and comprehensively uses the gas geological information and gas concentration characteristics to carry out coal and gas outburst early warning. It is suitable for the prevention and control of coal and gas outburst in the tunneling working face of mines without gas outburst, and is especially suitable for the prevention and control of coal and gas outburst in the tunneling working face of deep high-ground stress and high-gas mines.

[0058] like Figures 1 to 4 As shown, the coal and gas outburst early warning method based on stress monitoring in the tunneling working face includes:

[0059] Step S101: laying a distributed strain optical fiber in the coal body in front of the excavation working face through a dislocated drilling site, and determining the original stress data σ0 of the coal body ground stress according to the Brillouin shift of the central wavelength of the distributed strain optical fiber.

[0060] The excavation face is often hundreds or thousands of meters long, with a harsh environment and complicated construction. Therefore, in this application, a single-ended, metal-based, steel stranded fiber with a meter-level spatial resolution is used, and the spontaneous Brilliant Optical Time Domain Reflectometry technology is used in conjunction. At the same time, the head-on protection distance of the excavation face is obtained through the operating procedures of the excavation face, and the elastic modulus of the coal body of the excavation face is obtained through the mining geological conditions of the excavation face.

[0061] When laying optical fiber, staggered drilling sites are opened at the upper and lower walls outside the head protection distance of the excavation working face, and distributed strain optical fiber is laid. Pressure is relieved by opening drilling sites. When the drilling sites of the upper and lower coal walls are located at the same layer, the drilling sites are prone to superimposed stress concentration, inducing coal and rock damage. After the drilling sites of the upper and lower coal walls are staggered, superimposed stress concentration is effectively avoided in the same layer.

[0062] The drilling site size is 6m×6m×3m, and the drilling sites are spaced 50m apart. Specifically, on the coal wall facing the excavation direction, the upper wall is opened at the middle position 3m away from the tunnel coal wall, parallel to the tunnel coal wall, and the drill head protection distance is 200m in front of the excavation working face. The diameter of the drill hole is 60mm; on the coal wall facing the excavation direction, the lower wall is opened at the middle position 3m away from the tunnel coal wall, parallel to the tunnel coal wall, and the drill head protection distance is 250m in front of the tunnel working face. The diameter of the drill hole is 60mm.

[0063] Since the excavation working face is affected by ground stress and water inflow, and the environment is complex, the strain optical fiber is tightly wrapped with steel wire, then laid inside the borehole, and finally filled with cement mortar with a similar elastic modulus to the coal body as support. After the cement mortar has been filled for 7 days and the strength of the cement mortar has been tested to obtain the physical and mechanical properties of the coal body, the strain optical fiber is connected to the junction box, single-ended optical fiber demodulator, and monitoring host in sequence.

[0064] Among them, the single-ended fiber demodulator is connected to the underground substation of the coal mine, and transmits data to the monitoring host deployed on the ground (such as a data workstation, etc.) through the underground ring network, and the monitoring host analyzes and displays the data. After the optical fiber is laid, the upper coal rock layer will produce a certain load (i.e., mechanical effect) on the optical fiber, and this mechanical effect will cause an impact on the light reflection in the optical fiber (i.e., Brillouin shift). The light waves propagating in the optical fiber interact with the sound waves, among which the backscattered light is cheaper than the incident light, and the frequency shift of the Brillouin scattered light is linearly related to the strain and temperature of the optical fiber axis.

[0065] Therefore, the Brillouin shift of the optical fiber center wavelength is analyzed by a single-ended optical fiber demodulator to obtain the strain ε of the coal body, that is, the monitoring strain of the excavation working face, and then the coal body ground stress is obtained in combination with the elastic modulus of the coal body. Specifically, according to the formula:

[0066]

[0067] Determine the original stress data σ0 of coal body ground stress. In the formula, B (ε) B is the Brillouin shift of the central wavelength of the distributed strain optical fiber when it is subjected to coal body ground stress; (0) is the Brillouin shift of the central wavelength of the distributed strain optical fiber when it is not subjected to external load; ε is the strain of the coal body when the distributed strain optical fiber is subjected to coal body ground stress; dB (ε) / dε is a constant, with a value of 490MHz; E is the elastic modulus of the coal body.

[0068] Step S102: De-noise and reconstruct the original stress data σ0 based on the ensemble empirical mode decomposition to obtain the reconstructed stress data σ of the coal body ground stress. z ; and based on the reconstructed stress data σ of multiple coal body in-situ stresses at different locations at the same time z The peak stress σ max , and according to the formula:

[0069]

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

[0071] Since the in-situ stress of coal is affected by mining, local geological structure, and the physical and mechanical properties of coal, it presents complex changes and is prone to noise. In this application, the collected original stress data σ0 is de-noised and reconstructed by ensemble empirical mode decomposition to obtain the reconstructed stress data σ of the in-situ stress of coal. z Specifically, according to the formula:

[0072] σ i =σ0+ε i ω

[0073] Add Gaussian white noise to the original stress data σ0 to obtain the stress data σ after adding Gaussian white noise i In the formula, ε i is the white noise amplitude of the white noise sequence ω added for the i-th time.

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

[0075]

[0076] Calculate stress data σ i The i+1th residual C obtained by cyclic adaptive modal decomposition i+1 In the formula, IMFi+1 is the stress data σ i The i+1th modal component obtained by cyclic adaptive modal decomposition, C i is the stress data σ i The i-th residual obtained by performing cyclic adaptive modal decomposition, ε i is the white noise amplitude of the white noise sequence added for the ith time; n is the number of the 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] Where n is the number of samples. Then, the first residual C1 is obtained by subtracting the first modal component IMF1 from the original stress data σ0, that is, according to the formula:

[0080] C1=σ0-IMF1

[0081] Calculate the first residual C1.

[0082] Next, add Gaussian white noise ε1ω to the first residual C1, and perform the second empirical mode decomposition 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 until the stress data σ i The Ith residual C I Monotonic, stress data σ i The cyclic adaptive modal decomposition is completed. Wherein, i≤I; I is a positive integer.

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

[0088] σ j =v i -IMF j

[0089] Calculate the jth modal component IMF j The Pearson correlation coefficient R with the original stress data σ0; where σ j is the stress data σ i Residual after adaptive modal decomposition; j∈J.

[0090] Specifically, according to the formula:

[0091]

[0092] Calculate the jth modal component IMF j The Pearson correlation coefficient R with the original stress data σ0. In the formula, V σ0 is the average value of multiple original stress data σ0 of coal body ground stress at different positions at the same time obtained based on distributed strain optical fiber; V IMFj is the average value of j modal components obtained by j times adaptive modal decomposition.

[0093] According to the jth modal component IMF j The relationship between the Pearson correlation coefficient R of the original stress data σ0 is used to determine the jth modal component IMF. j Is it a valid modal component? Specifically, when |R|∈[0.7,1], the jth modal component IMF j is the effective modal component; when |R|∈[0,0.7), the jth modal component IMF is eliminated j , that is, the jth modal component IMF j is an invalid modal component.

[0094] Finally, all effective modal components are combined to obtain the reconstructed stress data σ of coal body ground stress: z Specifically, according to the formula:

[0095]

[0096] All effective modal components are combined to obtain the reconstructed stress data σ of coal body ground stress z ; In the formula, IMF l is the lth effective modal component obtained by decomposition, C l is the lth effective modal component IMF l Corresponding residual; l, L≤I; l∈L, L is the number of effective modal components in the I modal components obtained by decomposition, and I is a positive integer.

[0097] Finally, according to the reconstructed stress data σ of multiple coal body in-situ stresses at different locations at the same time z The peak stress σ max , and divide the model according to the preset stress area:

[0098]

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

[0100] In the formula, is the stress concentration area J(d x ,d y ) The peak stress value of coal body σ max The distance between the corresponding position and the front of the excavation working face; d x d y They are stress concentration areas J(d x ,d y )The shortest and longest distances from the front of the excavation working face.

[0101] Step S103: Establish stress concentration area J(d x ,d y ) The peak stress of the coal body σ max , stress change rate and stress concentration area J(d x ,d y ) The critical value of the stress peak value σ of the excavation working face 临 , critical value of stress change △σ 临 The relationship between the two is to provide step-by-step early warning for coal and gas outbursts in the excavation working face.

[0102] Specifically, according to the formula:

[0103]

[0104] Determine the stress concentration area J(d x ,d y ) Stress change rate of coal body Where, d x d y They are stress concentration areas J(d x ,d y ) the shortest and longest distances from the front of the excavation face; t i ,t i+1 For two adjacent moments, is the stress concentration area J(d x ,d y ) i+1 The stress value at each monitoring point at any given moment (a monitoring point is set every 1 meter in the optical fiber); is the stress concentration area J(d x ,d y ) iThe stress value of each monitoring point at each moment.

[0105] At the same time, numerical simulation of coal and gas outburst in the tunneling working face was carried out. According to the numerical simulation results and the historical data of coal and gas outburst in the tunneling working face, the critical value of the stress peak σ of the tunneling working face in the stress concentration area was determined. 临 , critical value of stress change △σ 临 .

[0106] Then, according to the stress concentration area J(d x ,d y ) The stress change rate of the optical fiber monitoring data And the stress concentration area J(d x ,d y ) The critical value of the stress peak value σ of the excavation working face 临 , critical value of stress change △σ 临 , build a step-by-step early warning mechanism for coal and gas outbursts, and make real-time comparisons between the stress peak value, stress change rate and their corresponding critical value in the stress concentration area. max <σ 临 and There is no risk of coal and gas outburst in the excavation working face, and no outburst warning is issued; if σ max ≥σ 临 or A Level 1 warning for coal and gas outburst at the excavation face will be issued.

[0107] In this application, the stress concentration area J(d x ,d y ) gas storage parameters of each layer, address structure distribution parameters, and drilling test parameters of the excavation working face, according to σ max , σ 临 , △σ 临 And coal seam gas storage parameters, geological structure distribution parameters, drilling test parameters, to carry out step-by-step early warning of coal and gas outbursts in the excavation working face. max , σ 临 , △σ 临 Early warning of coal and gas outbursts at the excavation working face; then, combined with coal seam gas occurrence parameters and geological structure distribution parameters, early warning of coal and gas outbursts at the excavation working face; finally, combined with drilling test parameters, early warning of coal and gas outbursts at the excavation working face.

[0108] That is, if σ max ≥σ 临 or And the stress concentration area J(d x ,d y) The gas pressure P of the drilling test in front of the excavation face is ≥ 0.74MPa or the gas content W of the drilling test in front of the excavation face is ≥ 8m 3 / t, a second-level warning of coal and gas outburst at the excavation working face is issued. In other words, if σ max ≥σ 临 And the stress concentration area J(d x ,d y ) The gas pressure P of the drilling test in front of the excavation face is ≥ 0.74MPa, or, σ max ≥σ 临 The gas content W of the drilling test in front of the excavation face is ≥8m 3 / t, or And the stress concentration area J(d x ,d y ) The gas pressure P of the drilling test in front of the excavation face is ≥ 0.74MPa, or, The gas content W of the drilling test in front of the excavation face is ≥8m 3 / t, a Level 2 warning for coal and gas outburst at the excavation face will be issued.

[0109] On the basis of the secondary early warning of coal and gas outburst at the excavation working face, the gas concentration data at the head of the excavation working face is obtained at a frequency of 30 seconds, and the number of gas concentration exceeding the limit points N with gas concentration greater than 0.8% within 5 minutes is counted; when N ≥ 5, the third-level early warning of coal and gas outburst at the excavation working face is issued. In this way, the static and dynamic data related to coal mine outburst are coordinated for early warning, which improves the timeliness and reliability of the early warning of coal and gas outburst at the excavation working face. Finally, the name of the excavation working face and the risk level of coal and gas outburst early warning are broadcast to all underground personnel, and sent to relevant managers through satellites, text messages, etc., to start the outburst prevention and control process.

[0110] In this application, distributed strain optical fiber is laid in the coal body in front of the excavation working face through an offset drilling site, and the Brillouin scattering effect of the optical fiber is used to realize continuous and real-time monitoring of the ground stress of the coal body, which makes up for a series of problems in the stress monitoring of the excavation working face, such as locality, large error, discontinuity, large engineering workload, and occupation of operation time and space; noise is removed by ensemble empirical mode decomposition to improve the quality of coal body ground stress data, so as to quickly determine the range of the coal body ground stress concentration area, track the stress peak value and stress change rate in the stress concentration area, and compare them with the critical value, and simultaneously combine the gas geological information and gas concentration characteristics of the excavation working face to comprehensively carry out coal and gas outburst early warning, which is particularly suitable for the prevention and control of coal and gas outburst in the excavation working face of coal and gas outburst mines, and is particularly suitable for the prevention and control of coal and gas outburst in the excavation working face of deep high ground stress and high gas mines.

[0111] The present application also provides a coal and gas outburst early warning system for a tunneling working face 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 optical fiber in the coal body in front of the excavation working face through the offset drilling site, and determine the original stress data σ0 of the coal body ground stress of the coal body according to the Brillouin shift of the central wavelength of the distributed strain optical fiber;

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

[0114]

[0115] Delineate the stress concentration area of ​​the coal body x ,d y );where, is the stress concentration area J(d x ,d y ) The peak stress value of coal body σ max The distance between the corresponding position and the front of the excavation working face; d x d y They are stress concentration areas J(d x ,d y ) the shortest and longest distances from the head of the excavation face;

[0116] The early warning unit 503 is configured to establish a stress concentration area J(d x ,d y ) The peak stress of the coal body σ max , stress change rate and stress concentration area J(d x ,d y ) The critical value of the stress peak value σ of the excavation working face 临 , critical value of stress change △σ 临 The relationship between the two is to provide step-by-step early warning for coal and gas outbursts in the excavation working face.

[0117] The coal and gas outburst warning system for the tunneling working face based on stress monitoring provided in the embodiment of the present application can implement the steps and processes of the coal and gas outburst warning method for the tunneling working face based on stress monitoring in any of the above-mentioned embodiments, and achieve the same technical effects, which will not be repeated here one by one.

[0118] In the description of the present invention, it is to be understood that the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations 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 one or more embodiments or examples in a suitable manner.

[0119] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for early warning of coal and gas outburst in a tunneling working face based on stress monitoring, characterized in that: include: Step S101, laying a distributed strain optical fiber in the coal body in front of the excavation working face through a dislocated drilling site, and determining original stress data σ0 of the coal body ground stress of the coal body according to the Brillouin shift of the central wavelength of the distributed strain optical fiber; Step S102: De-noise and reconstruct the original stress data σ0 based on the 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 the coal body ground stress at different positions at the same time z The peak stress σ max , and according to the formula: Determine the stress concentration area J(d x , d y );where, is the stress concentration area J(d x , d y ) The peak stress value of coal body σ max The distance between the corresponding position and the front of the excavation working face; d x ,d y They are the stress concentration areas J(d x , d y ) the shortest distance and the longest distance from the head of the excavation working face; Step S103: Establish the stress concentration area J(d x , d y ) The stress peak value σ of the coal body max , stress change rate The stress concentration area J(d x , d y ) is the critical value of the peak stress of the excavation working face σ 临 , critical value of stress change Δσ 临 The relationship between them can be used to provide step-by-step early warning for coal and gas outbursts in the excavation working face.

2. The method for early warning of coal and gas outburst in a tunneling working face based on stress monitoring according to claim 1 is characterized in that: In step S101, Displaced drilling sites are opened on the upper and lower walls outside the head protection distance of the tunneling working face and the distributed strain optical fiber is laid; wherein, the displaced drilling site of the upper wall is opened in the middle of the coal wall of the tunnel facing the tunneling direction, 3 meters away from the middle of the tunnel coal wall, and 200 meters in front of the tunneling working face and parallel to the tunnel coal wall drilling head protection distance; On one side of the coal wall facing the excavation direction, in the middle position 3 meters away from the tunnel coal wall, the drilling head is parallel to the tunnel coal wall and protects the staggered drilling site that opens up the lower wall 250 meters ahead in front of the excavation working face.

3. The method for early warning of coal and gas outburst in a tunneling working face based on stress monitoring according to claim 1 is characterized in that: In step S101, according to the formula: Determine the original stress data σ0 of the coal body ground stress; In the formula, B (ε) B is the Brillouin shift of the central wavelength of the distributed strain optical fiber when it is subjected to the coal body ground stress; (0) is the Brillouin shift of the central wavelength of the distributed strain optical fiber when it is not subjected to external load; ε is the strain of the coal body when the distributed strain optical fiber is subjected to the in-situ stress of the coal body; and E is the elastic modulus of the coal body.

4. The method for early warning of coal and gas outburst in a tunneling working face based on stress monitoring according to claim 1 is characterized in that: In step S102, According to the formula: s i =σ0+ε i oh Add Gaussian white noise to the original stress data σ0 to obtain the stress data σ after adding Gaussian white noise. i ; In the formula, ε i is the white noise amplitude of the white noise sequence ω added for the i-th time; Based on the ensemble empirical mode decomposition, the stress data σ i Perform cyclic adaptive modal decomposition and follow the formula: Calculate the stress data σ i The i+1th residual C obtained by cyclic adaptive modal decomposition i+1 ; In the formula, IMF i+1 is the stress data σ i The i+1th modal component obtained by cyclic adaptive modal decomposition, C i is the stress data σ i The i-th residual obtained by performing cyclic adaptive modal decomposition, ε i is the white noise amplitude of the white noise sequence ω added for the ith time; n is the number of the original stress data collected; In response to the stress data σ i The Ith residual C I Monotonic, the effectiveness of the I modal components obtained by decomposition is judged according to the formula: All the effective modal components are combined to obtain the reconstructed stress data σ of the coal body ground stress z ; In the formula, IMF l is the lth effective modal component obtained by decomposition, C l is the lth effective modal component IMF l The corresponding residual; i, l, L≤I; l∈L, L is the number of effective modal components in the I modal components obtained by decomposition, and I is a positive integer.

5. The method for early warning of coal and gas outburst in a tunneling working face based on stress monitoring according to claim 4 is characterized in that: The validity judgment of the I modal components obtained by decomposition includes: In response to the stress data σ i The jth modal component IMF obtained by adaptive modal decomposition j Satisfies the preset monotonic function: s j =s i -IMF j Calculate the jth modal component IMF j The Pearson correlation coefficient R with the original stress data σ0; where σ j is the stress data σ i The residual after adaptive modal decomposition; j∈I; In response to the jth modal component IMF j If the Pearson correlation coefficient R with the original stress data σ0 meets the preset condition, then the jth modal component IMF j is the effective modal component.

6. The method for early warning of coal and gas outburst in a tunneling working face based on stress monitoring according to claim 5 is characterized in that: In response to |R|∈[0.7, 1], the jth modal component IMF j is the effective modal component; In response to |R|∈[0,0.7), the jth modal component IMF is eliminated j .

7. The method for early warning of coal and gas outburst in a tunneling working face based on stress monitoring according to claim 1 is characterized in that: In step S103, according to the formula: Determine the stress concentration area J(d x , d y ) Stress change rate of coal body Where, d x ,d y They are the stress concentration areas J(d x , d y ) the shortest distance and the longest distance from the front of the excavation working face; t i ,t i+1 For two adjacent moments, is the stress concentration area J(d x , d y ) i+1 The stress value of each monitoring point at each moment; is the stress concentration area J(d x , d y ) i The stress value of each monitoring point at each moment.

8. The method for early warning of coal and gas outburst in a tunneling working face based on stress monitoring according to claim 1 is characterized in that: In response to σ max <σ 临 and Then there is no early warning of coal and gas outburst at the excavation working face; In response to σ max ≥σ 临 or A first-level warning of coal and gas outburst at the excavation working face is issued; In response to σ max ≥σ 临 or And P ≥ 0.74MPa or W ≥ 8m 3 / t, a second-level warning of coal and gas outburst in the excavation working face is issued; wherein P is the gas pressure of the drilling test in front of the excavation working face, and W is the gas content of the drilling test in front of the excavation working face.

9. The method for early warning of coal and gas outburst in a tunneling working face based on stress monitoring according to claim 8, characterized in that: In response to issuing a second-level warning of coal and gas outburst at the excavation working face, gas concentration data at the head of the excavation working face is obtained at a frequency of 30 seconds, and the number of gas concentration exceeding limit points N where the gas concentration is greater than 0.8% within 5 minutes is counted; In response to N≥5, a third-level warning of coal and gas outburst at the excavation working face is issued.

10. A coal and gas outburst early warning system for tunneling working face based on stress monitoring, characterized in that: include: A raw data unit is configured to lay a distributed strain optical fiber in the coal body in front of the excavation working face through a dislocated drilling site, and determine the raw stress data σ0 of the coal body ground stress of the coal body according to the Brillouin shift of the central wavelength of the distributed strain optical fiber; The stress reconstruction and regional division unit is configured to reduce noise and reconstruct the original stress data σ0 based on the ensemble empirical mode decomposition to obtain the reconstructed stress data σ of the coal body ground stress. z , and based on the reconstructed stress data σ of the coal body ground stress at different positions at the same time z The peak stress σ max , and according to the formula: Determine the stress concentration area J(d x , d y );where, is the stress concentration area J(d x , d y ) The peak stress value of coal body σ max The distance between the corresponding position and the front of the excavation working face; d x ,d y They are the stress concentration areas J(d x , d y ) the shortest distance and the longest distance from the head of the excavation working face; The early warning unit is configured to establish the stress concentration area J(d x , d y ) The stress peak value σ of the coal body max , stress change rate The stress concentration area J(d x , d y ) is the critical value of the peak stress of the excavation working face σ 临 , critical value of stress change Δσ 临 The relationship between them can be used to provide step-by-step early warning for coal and gas outbursts in the excavation working face.

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