A gas disaster early warning method based on borehole optical fiber sensing monitoring

Abstract

The present application relates to the technical field of gas disaster prediction, in particular to a kind of gas disaster early warning method of borehole optical fiber sensing monitoring, the method comprises: the layer drilling extraction borehole through the region of coal roadway to be excavated is screened and numbered as monitoring borehole;Composite optical fiber sensing cable integrated with temperature and pressure sensing function is installed in monitoring borehole;Gas desorption and outburst risk is early warned by identifying temperature continuous decline, first rise and then fall and other abnormal change modes, and drilling collapse is early warned by identifying pressure fluctuation, sudden drop and other modes.In the process of excavation, the composite optical fiber sensing cable rolled forward by the rear excavation is moved to the front new borehole, realizing the continuous monitoring of gas extraction information.The present application directly senses the physical process inside coal seam, and the early warning is significantly ahead of traditional roadway gas monitoring, and the accuracy is improved through pattern recognition, and the dual early warning of gas disaster and drilling stability is realized, with low cost and high reliability.

Description

Technical Field

[0001] This invention relates to the field of gas disaster prediction technology, and in particular to a gas disaster early warning method based on borehole fiber optic sensing monitoring. Background Technology

[0002] Coal and gas outbursts are a major disaster in underground coal mining, ejecting large amounts of coal, rock, and gas into the production area in a short period, causing mass casualties. Early warning systems for coal and gas outbursts are of great significance for safe coal production. Existing early warning methods for coal and gas outbursts can be divided into two categories based on their principles:

[0003] ① Monitoring signals generated during the fracturing of coal and rock mass, such as micro-vibration and electromagnetic radiation, has the disadvantage of lacking gas information. Although gas desorption induced by coal and rock fracturing is a necessary process for coal and gas outbursts, outbursts will not occur under gas-free conditions due to coal and rock fracturing.

[0004] ② Monitoring of airflow and gas information in roadways. Accident experience shows that before a coal and gas outburst, airflow and gas will exhibit a fluctuating pattern, but this pattern is still unclear. The false alarm rate of airflow and gas early warning is high, and long-term false alarms have reduced the reliability of this indicator, making it unusable in the field.

[0005] To address the problems in existing technologies, this invention provides a method for early warning of gas disasters using borehole fiber optic sensing. Summary of the Invention

[0006] The purpose of this invention is to provide a method for early warning of gas disasters using borehole fiber optic sensing monitoring, in order to solve the technical problems of delayed early warning and high false alarm rate in existing technologies for coal and gas outbursts.

[0007] The technical solution of this invention is: a method for early warning of gas disasters using borehole fiber optic sensing monitoring, comprising:

[0008] In the roadway, drilling holes for gas extraction through layers are constructed. All drilling holes that pass through the coal roadway to be excavated are selected as monitoring holes. Composite fiber optic sensing cables are installed in the monitoring holes to continuously monitor gas extraction information.

[0009] Analyze and determine whether there are abnormal temperature and borehole pressure phenomena in the gas extraction information;

[0010] Based on the characteristics of the observed anomalies, the corresponding warning level is matched, and the corresponding post-processing is executed.

[0011] Preferably, the cross-layer extraction boreholes are constructed in groups, with each group having the same drilling location, the same horizontal azimuth, and different inclination angles, ensuring that each group of cross-layer extraction boreholes has a monitoring borehole that passes through the area to be excavated in the roadway.

[0012] Preferably, the composite optical fiber sensing cable is transported to the monitoring borehole through the gas extraction flower tube, and is fixed in the monitoring borehole through the bag seal.

[0013] The composite optical fiber sensing cable comprises a temperature sensor optical fiber and a pressure sensor optical fiber; the gas extraction information collected by the composite optical fiber sensing cable is demodulated by an optical fiber demodulator to obtain the temperature and pressure information in the monitoring borehole.

[0014] Preferably, the spacing of the through-layer extraction boreholes is not more than the range of the roadway pressure relief zone, and is not less than 2 meters per drill field.

[0015] Preferably, the number of the composite optical fiber sensing cables in one roadway is not less than 10.

[0016] Preferably, in the installation layout of the composite optical fiber sensing cables in one roadway, when the excavation passes through X composite optical fiber sensing cables, M composite optical fiber sensing cables are moved, N composite optical fiber sensing cables are retained, and the installation is rolled forward.

[0017] The time for moving and assembling the M composite optical fiber sensing cables is not more than the time for assembling N composite optical fiber sensing cables in the roadway excavation, so as to avoid the gap period of the early warning, and M≤X.

[0018] Preferably, the data recording form of the composite optical fiber sensing cable is that: under normal working condition, one data is saved every 1 minute; when the monitoring data appears abnormal, 30 seconds of data before and after the abnormal point are retained, and one data is saved every second.

[0019] Preferably, based on the temperature abnormality phenomenon, the corresponding early warning information and early warning level include:

[0020] The early warning information corresponding to the first-level temperature early warning is coal rock rupture; the early warning information corresponding to the second-level temperature early warning is gas desorption; and the early warning information corresponding to the third-level temperature early warning is gas outburst high risk.

[0021] Based on the pressure abnormality phenomenon, the corresponding early warning information and early warning level include:

[0022] The early warning information corresponding to the first-level pressure early warning is borehole instability, the early warning information corresponding to the second-level pressure early warning is borehole fracture penetration, and the early warning information corresponding to the third-level pressure early warning is borehole collapse emergency.

[0023] Preferably, based on the abnormality phenomenon, the characteristic phenomena for determining the early warning level respectively include:

[0024] If the temperature of the borehole section shows a sustained rising trend, the temperature rise amplitude is 1℃-3℃, and the duration is ≥15min, it is determined that the first-level temperature early warning occurs.

[0025] When the temperature of the drilling section is monitored to show a temperature drop, and the temperature drop range is 2-4 DEG C and the duration is greater than or equal to 10 min, the secondary temperature early warning is determined.

[0026] The monitoring feature is that the temperature of the drilling section is monitored to show a temperature rise first, the temperature rise range is 2-4 DEG C, the duration is 5-10 min, then the temperature rapidly drops, the temperature drop range is 3-5 DEG C, and the duration is greater than or equal to 8 min, and the tertiary temperature early warning is determined.

[0027] Preferably, based on the abnormal phenomenon, the tertiary pressure early warning includes:

[0028] When the pressure of the drilling section is monitored to show a large amplitude fluctuation, the pressure of the easy-to-collapse hole fluctuates more than 3 times in 1 hour, the single fluctuation range is 0.03-0.08 MPa, and the fluctuation has no obvious rule, the primary pressure early warning is determined.

[0029] When the pressure of the drilling section is monitored to show a sudden drop, the pressure of the easy-to-collapse hole suddenly drops by 0.08-0.15 MPa in 5-10 min, and the pressure is stable at the low limit after the drop, the secondary pressure early warning is determined.

[0030] When the pressure of the drilling section is monitored to show a sudden drop and a low limit, the pressure of the easy-to-collapse hole suddenly drops by more than 0.15 MPa in 1-3 min, and has no rising trend for 1 hour, the tertiary pressure early warning is determined.

[0031] Compared with the prior art, the present application has the following advantages:

[0032] The present application can monitor the gas extraction information in the through-hole drilling by arranging the composite optical fiber sensing cable in the through-hole drilling, analyze the internal changes of the coal seam in front of the working face and after the excavation based on the obtained temperature and pressure information in the through-hole drilling, directly reflect the energy conversion and gas state change in the coal seam by monitoring the temperature anomaly in the extraction drilling, evaluate the drilling stability and the stress state of the surrounding rock by monitoring the pressure change, and realize the double early warning of the coal and gas outburst and the drilling collapse. Since the temperature information and the pressure information in the internal through-hole drilling in the coal seam are monitored, the present application is prior to the existing roadway gas prediction mode, and is more comprehensive than the simple monitoring of the coal and rock fracture signal, and the monitoring and early warning reliability is improved.

[0033] The present application can monitor the temperature and pressure in the through-hole drilling based on the composite optical fiber sensing cable, effectively utilize the original through-hole gas extraction drilling, realize the one-hole multi-use of the extraction and early warning, have low cost, promote the drilling informatization development, and the optical fiber sensing has the advantages of anti-electromagnetic interference, corrosion resistance and long service life, and is suitable for the harsh environment in the mine. BRIEF DESCRIPTION OF DRAWINGS

[0034] The present application will be further described below in combination with the drawings and embodiments:

[0035] Figure 1 This is a roadmap for the gas disaster early warning technology at the tunneling face of the present invention;

[0036] Figure 2 This is a cross-sectional view of a single-layer drilling site and a schematic diagram of the sensor arrangement boreholes according to the present invention.

[0037] Figure 3 This is a schematic diagram of the installation of the composite optical fiber sensing cable of the present invention inside a borehole;

[0038] Figure 4 A schematic diagram of the composite optical fiber sensing cable layout for the section of the tunnel not yet excavated to the monitoring borehole, provided by the present invention.

[0039] Figure 5 This is a schematic diagram of the composite optical fiber sensing cable layout from tunnel excavation to the monitoring borehole provided by the present invention.

[0040] Among them: 1. Bottom rock roadway; 2. Coal roadway; 3. Coal seam; 4. Cross-layer extraction borehole; 5. Monitoring borehole; 6. Bag sealing device; 7. Rock layer; 8. Gas extraction pipe; 9. Fiber optic demodulator; 10. Composite fiber optic sensing cable. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to specific embodiments:

[0042] Coal roadway excavation faces are high-risk areas for coal and gas outbursts; statistics show that 90% of outburst accidents occur at the excavation face. Before excavation operations in coal roadways with outburst risks, it is essential to first implement strip outburst mitigation, which involves creating a new roadway in the rock strata near the roadway to be excavated, and drilling through-strata boreholes from this new roadway into the strip area of ​​the coal roadway to pre-drain gas. Based on this, this invention proposes a gas disaster early warning method using borehole fiber optic sensing monitoring. By analyzing the temperature, pressure, and other monitoring information from existing cross-strata boreholes in the coal mine, the method identifies patterns of anomalies, thereby achieving early warning of gas exceeding limits / outburst risks and borehole collapses at coal roadway excavation faces.

[0043] This invention provides a method for early warning of gas disasters using borehole fiber optic sensing monitoring. The overall process includes borehole selection, system installation, real-time monitoring and pattern recognition, dynamic system relocation, and iterative optimization. The principle and route are detailed in the appendix. Figure 1 As shown, the specific implementation steps are as follows:

[0044] Step 1: Drill through layers and install the layout.

[0045] Before the coal roadway 2 is excavated, the through-seam extraction borehole 4 is drilled in the floor rock roadway 1 to the coal roadway 2 to-be-excavated area in the coal seam 3. The boreholes are drilled in groups, and each group of boreholes has the same drilling site, the same horizontal azimuth angle and different inclination angles, so that each group of boreholes has the through-seam extraction borehole 4 passing through the roadway to-be-excavated area. See the sectional view of a single group of boreholes in FIG. 1. Figure 2

[0046] From all the through-seam extraction boreholes 4 in the roadway strip area, the monitoring boreholes 5 passing through the coal roadway 2 to-be-excavated area are selected, and are sequentially numbered according to the distance from the initial point of the coal roadway 2 to be excavated, from near to far, as 1-n. See the sectional view of a single through-seam drilling field and the schematic diagram of the sensor arrangement borehole in FIG. 2. Figure 2

[0047] The spacing of the through-seam extraction borehole 4 is not more than the range of the roadway pressure relief area. If the spacing of the through-seam extraction borehole 4 is too large, the early warning information may be lost. The spacing of the through-seam extraction borehole 4 is not less than 2 meters per drilling field, for example, every other or every two drilling fields are numbered.

[0048] Step two, assemble the composite optical fiber sensing cable for monitoring the gas extraction information.

[0049] The floor rock roadway 1 is provided with an optical fiber demodulator 9 and a plurality of composite optical fiber sensing cables 10. The composite optical fiber sensing cable 10 includes a temperature sensing optical fiber and a pressure sensing optical fiber, which can detect the temperature and pressure of the monitoring borehole 5 in real time, and the number is A. The boreholes that do not pass through the coal roadway 2 to-be-excavated area do not need to be installed with the composite optical fiber sensing cable 10.

[0050] FIG. 3 shows the specific installation schematic diagram of the composite optical fiber sensing cable 10 in the borehole. Figure 3

[0051] The monitoring borehole 5 extends through the rock layer 7 to the coal seam 3. When installing, the composite optical fiber sensing cable 10 is bound to the outside of the prefabricated gas extraction flower pipe 8, and is transported into the preset depth of the monitoring borehole 5 together. The capsule packer 6 is used for hole sealing, and the capsule packer 6 presses the composite optical fiber sensing cable 10 against the hole wall of the monitoring borehole 5, so that the composite optical fiber sensing cable 10 is in good contact with the stratum and can reflect the true stratum conditions. The tail end of the composite optical fiber sensing cable 10 is led out to the borehole opening and connected to the explosion-proof junction box, and finally connected to the optical fiber demodulator 9 through the main cable.

[0052] Before the coal roadway 2 starts to be excavated, the optical fiber sensing equipment is inspected and calibrated.

[0053] Step three, during the excavation of the coal roadway 2, the gas extraction information is continuously monitored.

[0054] ​​​After the coal roadway 2 starts to excavate, whether there is an abnormal phenomenon in temperature and whether there is an abnormal phenomenon in drilling pressure in the extraction information of the monitoring drill hole 5 is observed.

[0055] The data record form of the composite optical fiber sensing cable 10 is that when the monitoring data appears abnormal, 30 seconds of data before and after the abnormal point are reserved (one data is saved every second), and one data is saved every 1 minute in the remaining time period. The data is transmitted to the ground server through the underground ring network for fine mode recognition by the ground system.

[0056] Wherein, a large amount of adsorbed gas in the coal seam rapidly changes into free gas, heat absorption leads to temperature drop, or stress concentration of the coal and rock mass leads to deformation heat generation, resulting in an abnormal phenomenon in temperature. Sudden pressure rise may indicate stress concentration of the surrounding rock, with the risk of collapse, or sudden pressure drop may indicate that cracks appear around the drill hole, leading to gas leakage and pressure drop, but it may also be a precursor to collapse, resulting in an abnormal phenomenon in pressure.

[0057] Step four, issuing a warning information based on the abnormal phenomenon.

[0058] When the abnormal phenomenon occurs, timely warning information is issued for the underground coal roadway excavation construction; the warning information is the corresponding warning level.

[0059] In detail, the mine management personnel determine the warning level corresponding to different abnormal degrees of extraction information change based on the relationship between the warning information and the gas dynamic phenomenon and the stability of the drill hole according to the characteristics of the coal mine.

[0060] The warning levels of the temperature mode include: first-level temperature warning, second-level temperature warning and third-level temperature warning.

[0061] The abnormal characteristic phenomenon corresponding to the first-level temperature warning is that the monitoring drill hole section appears persistent temperature rise, the temperature rise amplitude is 1-3℃, and the duration is ≥15min. The phenomenon corresponding to the first-level temperature warning indicates that the coal and rock mass is broken due to excavation disturbance, but the coal seam in the region corresponding to the drill hole is marked as "low gas but high risk of breakage" because the gas content in the region is low and gas desorption is not triggered, although there is no gas outburst risk at present, but the same temperature rise phenomenon may be accompanied by gas desorption in other regions with high gas content, which needs to be warned in advance.

[0062] The abnormal characteristic phenomenon corresponding to the second-level temperature warning is that the monitoring drill hole section appears temperature drop phenomenon, the temperature drop amplitude is 2-4℃, and the duration is ≥10min. The phenomenon corresponding to the second-level temperature warning is caused by the effect of excavation pressure relief, which leads to the conversion of adsorbed gas in the coal seam to free state, and the heat absorption in the desorption process makes the temperature drop. Although the coal and rock structure is complete, a large amount of gas desorption may lead to local gas concentration exceeding the limit, and if the desorption amount continues to increase, it is easy to cause subsequent abnormal gas flow.

[0063] The abnormal characteristic phenomenon corresponding to the third temperature early warning is that the temperature of the monitored borehole section first increases by 2-4°C, and the duration is 5-10 min, and then the temperature rapidly decreases by 3-5°C, and the duration is ≥8 min. The phenomenon corresponding to the third temperature early warning is a direct manifestation of the synergistic effect of coal and rock rupture and gas desorption. The heat generated by the early coal and rock rupture leads to temperature rise, and the cracks generated by the rupture provide a channel for gas desorption, and then the heat absorption of a large amount of gas desorption causes a sharp drop in temperature, which is the core precursor of coal and gas outburst, and has the highest risk level.

[0064] For borehole pressure early warning, first, borehole collapse / closure identification is performed, including:

[0065] The corresponding identification characteristic phenomenon is that the borehole pressure slowly increases continuously for 7 days before tunneling to the initial stage of tunneling, and the pressure increase amplitude is 0.05-0.2 MPa, and the duration is ≥24 h. This characteristic phenomenon indicates that the coal seam where the borehole is located is soft and high-stress coal body. Under the action of high ground stress, the soft coal body is easily extruded into the borehole, leading to the gradual closure of the borehole and the continuous pressure on the optical fiber. The easy-collapsing borehole needs to be screened out and distinguished from the stable borehole, and the easy-collapsing borehole is monitored in the follow-up.

[0066] For easy-collapsing borehole pressure anomaly early warning, the early warning levels include first pressure early warning, second pressure early warning and third pressure early warning.

[0067] The abnormal characteristic phenomenon corresponding to the first pressure early warning is that the pressure fluctuates continuously and greatly, the easy-collapsing borehole pressure fluctuates ≥3 times within 1 h, the single fluctuation amplitude is 0.03-0.08 MPa, and the fluctuation has no obvious rule. The pressure fluctuation of this characteristic phenomenon is caused by the plastic deformation of soft coal body. The coal body slowly flows under the action of stress, leading to repeated contraction and slight expansion of the borehole space. Although the coal body structure is not immediately collapsed, it is in an unstable state and easy to cause subsequent sudden collapse.

[0068] The abnormal characteristic phenomenon corresponding to the second pressure early warning is that the pressure suddenly decreases, the easy-collapsing borehole pressure suddenly decreases by 0.08-0.15 MPa within 5-10 min, and the pressure stabilizes at a lower level after the decrease. The sudden decrease in pressure of this characteristic phenomenon indicates that the coal body around the borehole has appeared local structure instability, which may be caused by the plastic deformation of the coal body leading to crack penetration, or the new gas / stress release channel formed by the local collapse of the borehole. If not handled in time, it is easy to develop into full-hole collapse.

[0069] The abnormal characteristic phenomenon corresponding to the third level pressure warning is: pressure drops suddenly and remains low, the drilling pressure drops by more than 0.15 MPa within 1-3 min and remains low for 1 h without recovery trend. This characteristic phenomenon is an emergency signal of the drilling hole on the verge of collapse, the coal structure has been destabilized in a large range, and serious collapse occurs in the drilling hole, resulting in complete pressure release. If the operation continues, it may cause the collapse of the roadway side or abnormal gas outburst.

[0070] According to the warning data and verification results in the tunneling process, the warning threshold is continuously adjusted and updated.

[0071] The ground personnel analyzes the warning reasons and formulates corresponding underground warning construction schemes according to the warning level based on the warning information sent from the underground. The warning information includes the following:

[0072] The first level temperature warning is coal and rock fracture warning, and the first level pressure warning is drilling instability warning. The warning measures are: marking the corresponding coal and rock fracture area and prompting "stress concentration, pay attention to observation".

[0073] The second level temperature warning is gas desorption warning, and the second level pressure warning is drilling fracture penetration warning. The warning measures are: prompting "coal seam gas is active, with over-limit risk".

[0074] The third level temperature warning is high risk warning of outburst, and the third level pressure warning is emergency warning of drilling collapse. The warning measures are: issuing a third level emergency warning information, and linking sound and light alarm to prompt "suspected outburst precursor, evacuate immediately".

[0075] Step five, dynamic forward movement of the composite optical fiber sensing cable.

[0076] During the tunneling process, when the tunneling passes through X composite optical fiber sensing cables 10, the composite optical fiber sensing cables 10 are dynamically moved in the mode of moving M and leaving N (M+N=A). Increasing the number of M can reduce the moving frequency of the equipment, but it should be ensured that the number of N is not too low to avoid the problem that the time used for moving M composite optical fiber sensing cables 10 is greater than the time used for tunneling N composite optical fiber sensing cables 10, resulting in discontinuous warning. Therefore, it should be satisfied that M≤X.

[0077] For ease of illustration, the tunneling process schematic diagrams provided in the accompanying Figure 4 and the accompanying Figure 5 are taken as examples, in which A=3.

[0078] Figure 4 A schematic diagram of the coal roadway 2 not drilled to the monitoring drilling hole 5 is shown; Figure 5A schematic diagram of the coal roadway 2 excavation to the monitoring borehole 5 is shown. When the roadway excavation reaches (and has passed) the A / 2 composite optical fiber sensing cable 10, the 1-A / 2 composite optical fiber sensing cable 10 is removed and installed at (A+1)-(A+A / 2), and the borehole is observed to change from 1-A to (A / 2+1)-(A+A / 2). Continuous monitoring and early warning of the coal roadway excavation area is achieved, and full monitoring of the long-distance roadway is achieved with limited equipment, taking into account cost and effect.

[0079] In theory, the more the number of composite optical fiber sensing cables 10 A is, the better, but the increase in the number will significantly increase the equipment cost, and the decrease in the number will increase the moving frequency, and increase the labor and time cost. Therefore, considering the cost, labor and time budget, the number of composite optical fiber sensing cables 10 is set, and in this embodiment, the number of composite optical fiber sensing cables 10 A is not less than 10, to ensure continuous monitoring.

[0080] Steps three and four are repeated, and when the roadway excavation exceeds the position of half of the number of composite optical fiber sensing cables arranged, the half of the composite optical fiber sensing cable excavated is moved in sequence to the excavation direction, and step five is referred to.

[0081] Step six, roadway updating and threshold optimization.

[0082] After the roadway excavation is completed, the early warning data and verification results in the excavation process are analyzed, the early warning threshold in step five is improved, all composite optical fiber sensing cables are removed, and are installed in the next roadway to be excavated.

[0083] An embodiment of gas disaster early warning by the present application during the coal roadway 2 excavation process is provided below.

[0084] An industrial test was conducted on a high-gas and outburst-dangerous excavation face in a certain mine. The basic environmental parameters include: the thickness of coal seam 3 is 4.0 m, and the original gas content is 14 m³ / t. The implementation process is as follows:

[0085] Sixty layer-penetrating boreholes 60 (i.e., monitoring boreholes 5) that meet the conditions are selected.

[0086] Ten sets (A=10) of composite optical fiber sensing cables 10 are installed in monitoring boreholes 5 numbered 1-10. On the 12th day of excavation, the No. 7 monitoring borehole 5 located 18 m in front of the working face monitored the abnormal characteristic phenomenon corresponding to the third-level temperature early warning: the temperature rose from 31.5°C to 34.0°C within 7 minutes, and then sharply dropped to 29.8°C within 9 minutes. The ground early warning analysis software immediately triggered a "third-level temperature early warning", and automatically cut off the power supply of the excavation working face, and the on-site construction personnel were urgently evacuated. Subsequent investigation found that the drill cuttings gas desorption indicators Dh2 and K1 values in this area were seriously over-standard, verifying the accuracy of the early warning. Due to timely disposal, no dynamic phenomenon occurred.

[0087] In the whole 500m roadway excavation, the system issued 4 effective secondary temperature warnings and tertiary temperature warnings, averagely leading the roadway gas sensor alarm by 65 minutes. At the same time, the traditional gas concentration monitoring system produced more than 20 false alarms due to blasting, process changes, etc., while the system only misreported twice (eliminated after the optimization of the early warning threshold). At the same time, 2 drilling collapse risks (secondary pressure warning) were warned, and timely hole supplement measures were taken to ensure gas extraction safety.

[0088] Compared with the commonly used coal roadway excavation gas disaster warning method, the warning method in the application is aimed at gas temperature signals and coal and rock fracture signals, and is more sensitive to disasters.

[0089] Abnormal emission of gas in the roadway is an external manifestation of the disaster, and the external characteristics usually lag behind the internal changes of the coal seam. Since the abnormal changes of the coal seam are monitored, the abnormal changes of the roadway air flow are ahead of time, so the application is more advanced in prediction.

[0090] Each coal roadway excavation working face strip area is arranged with a large number of through-layer boreholes, ranging from thousands to tens of thousands. At present, the purpose of these through-layer boreholes is only to extract gas. The through-layer boreholes of the embodiment are not only used for gas extraction, but also for monitoring gas extraction information, without the need to construct new pressure measuring boreholes, with low cost.

[0091] The application is suitable for coal and gas outburst mines and high-gas mines, and is a new method for ensuring coal mine safety production and promoting the construction of intelligent mines.

[0092] The above embodiments are only for illustrating the technical concept and characteristics of the application, and the purpose is to enable those skilled in the art to understand the content of the application and implement it, and cannot limit the protection scope of the application. For those skilled in the art, it is obvious that the application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the application, therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the application is defined by the appended claims rather than the above description, therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the application.

Claims

1. A gas disaster early warning method for borehole optical fiber sensing monitoring, characterized in that, The method comprises the following steps: Drilling cross-layer extraction boreholes in the roadway, screening all cross-layer extraction boreholes passing through the roadway to be excavated, setting the cross-layer extraction boreholes as monitoring boreholes, installing a composite optical fiber sensing cable in the monitoring boreholes, and continuously monitoring gas extraction information; Analyzing and judging whether temperature abnormality and borehole pressure abnormality appear in the gas extraction information; According to the characteristics of the abnormality, matching the corresponding warning level, and executing the post-processing of the corresponding warning level; Based on the temperature abnormality, the corresponding warning information and warning level include: The warning information corresponding to the first temperature warning is coal rock rupture; the warning information corresponding to the second temperature warning is gas desorption; and the warning information corresponding to the third temperature warning is gas outburst high risk; Based on the pressure abnormality, the corresponding warning information and warning level include: The warning information corresponding to the first pressure warning is borehole instability, the warning information corresponding to the second pressure warning is borehole fracture penetration, and the warning information corresponding to the third pressure warning is borehole collapse emergency; Based on the abnormality, the characteristic phenomenon of the warning level is determined to be: If the temperature of the borehole section shows a continuous rising trend, the temperature rising amplitude is 1-3℃, and the duration is greater than or equal to 15 minutes, the first temperature warning is determined; If the monitoring borehole section shows temperature reduction, the temperature reduction amplitude is 2-4℃, and the duration is greater than or equal to 10 minutes, the second temperature warning is determined; The monitoring characteristics are: the monitoring borehole section first shows temperature rise, the amplitude is 2-4℃, and lasts for 5-10 minutes, then the temperature rapidly decreases, the amplitude is 3-5℃, and the duration is greater than or equal to 8 minutes, the third temperature warning is determined.

2. The gas disaster early warning method of drilling optical fiber sensing monitoring according to claim 1, characterized in that, The cross-layer extraction boreholes are drilled in groups, the drilling sites of each group of cross-layer extraction boreholes are the same, the horizontal azimuth angles are the same, and the inclination angles are different, so that there is a monitoring borehole passing through the roadway to be excavated in each group of cross-layer extraction boreholes.

3. The gas disaster early warning method of drilling optical fiber sensing monitoring according to claim 2, characterized in that, The composite optical fiber sensing cable is transported into the monitoring borehole through the gas extraction flower pipe, and is fixed in the monitoring borehole through the capsule bag seal. The composite optical fiber sensing cable includes a temperature sensor optical fiber and a pressure sensor optical fiber; and the gas extraction information collected by the composite optical fiber sensing cable is demodulated by an optical fiber demodulator to obtain the temperature and pressure information in the monitoring borehole.

4. The gas disaster early warning method of borehole optical fiber sensing monitoring according to claim 2, characterized in that, The spacing of the cross-layer extraction boreholes is not more than the range of the roadway pressure relief area, and is not less than 2 meters per drilling site.

5. The gas disaster early warning method of borehole optical fiber sensing monitoring according to claim 1, characterized in that, The number of the composite optical fiber sensing cables in one roadway is not less than 10.

6. The gas disaster early warning method of drilling optical fiber sensing monitoring according to claim 1, characterized in that, In the installation and layout of the composite optical fiber sensing cables in one roadway, when the excavation passes through X composite optical fiber sensing cables, M composite optical fiber sensing cables are moved, N composite optical fiber sensing cables are retained, and the installation is rolled forward; The time for moving and assembling the M composite optical fiber sensing cables is not more than the time for excavating N composite optical fiber sensing cables in the roadway, so as to avoid the existence of a gap period in the warning, and M≤X.

7. The gas disaster early warning method of drilling optical fiber sensing monitoring according to claim 1, characterized in that, The data recording form of the composite optical fiber sensing cable is: under normal working condition, one data is saved every 1 minute; when the monitoring data shows abnormality, 30 seconds of data before and after the abnormal point are retained, and one data is saved every second.

8. The gas disaster early warning method of drilling optical fiber sensing monitoring according to claim 1, characterized in that, Based on the abnormality, the third pressure warning includes: Pressure persistence fluctuation, the pressure of easy collapse hole appears ≥3 times fluctuation in 1 hour, single fluctuation amplitude is 0.03MPa-0.08MPa, and the fluctuation has no obvious rule, is determined as first grade pressure early warning; Pressure mutation reduces, the pressure of easy collapse hole mutation reduces 0.08MPa-0.15MPa in 5-10min, and the pressure is stable at low value lower limit level after reducing, is determined as second grade pressure early warning; Pressure sudden drop and continuous low value lower limit level, the pressure of easy collapse hole mutation reduces 0.15MPa above in 1-3min, and has no rising trend for 1 hour, is determined as third grade pressure early warning.

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