A method for accurately determining a coal column coal spontaneous combustion risk position

Abstract

The application discloses a kind of precision determination methods of coal column coal spontaneous combustion position, it is related to coal mine safety technical field.The method is first to the surface deformation of coal column, broken state monitoring, determine possible risk section of air leakage fracture or coal spontaneous combustion;Then using section air leakage detection mode, determine whether the risk section of coal column has formed air leakage fracture and determine corresponding air leakage fracture position and air leakage speed;Finally in the section that it is judged to exist air leakage fracture, the temperature measuring point is arranged to measure temperature and gas concentration monitoring mode measures the high temperature risk position of coal spontaneous combustion that exists in coal column and its migration trend with roadway excavation or stoping.The present application combines a variety of detection techniques to predict and determine the air leakage fracture and high temperature risk position of coal spontaneous combustion of coal column during excavation and working face stoping from multiple different dimensions, which can further improve the safety of excavation and production under the arrangement mode of coal column gob-side entry driving, and plays an important role for mines using the arrangement mode of coal column gob-side entry driving.

Description

Technical Field

[0001] This invention relates to the field of coal mine safety technology, specifically to a method for accurately determining the location of coal pillar spontaneous combustion risk. Background Technology

[0002] Coal pillar excavation along the goaf offers advantages such as high recovery rates and low support costs, not only increasing the economic benefits of coal mines but also improving the stress environment of the surrounding rock and reducing the occurrence of mine pressure accidents. However, because the coal pillar itself is a porous coal-rock mass, it is prone to cracking or crushing under stress disturbances during roadway excavation and mining. This can easily create air leakage channels leading to spontaneous combustion of residual coal in the goaf, and under certain conditions, the coal pillar itself can also be affected by air leakage, generating oxidation heating points or spontaneous combustion, posing a significant threat to underground production safety.

[0003] For monitoring the deformation and displacement of coal pillars during mining, existing coal pillar monitoring technologies mostly use fiber optic displacement monitoring. This technology cannot accurately determine whether cracks and air leakage channels have formed after the coal pillar has been crushed. As for air leakage in coal pillars, the existing technology mainly uses the tracer gas method. This method can qualitatively determine the air leakage status of the coal pillar, but it cannot determine the specific location of air leakage channels and oxidation and heating hazard areas in coal pillars that have been crushed or have cracks. Summary of the Invention

[0004] To address the shortcomings of existing technologies in monitoring coal pillar air leakage and hazardous areas, this invention proposes a method that combines coal pillar deformation monitoring, section air leakage detection, and key area temperature monitoring to predict and determine hazardous areas and risk sections of the coal pillar during tunneling and face mining from multiple different dimensions.

[0005] A method for accurately determining the location of spontaneous combustion risk in coal pillars, proposed according to the present invention, includes the following steps:

[0006] Step 1: Monitor the deformation of the coal pillar and regularly inspect the surface of the coal pillar for breakage. Based on the monitoring and inspection results, identify potential air leakage cracks and risk zones for spontaneous combustion of coal.

[0007] Step 2: For the potential air leakage cracks and coal spontaneous combustion risk areas identified in Step 1, use the section air leakage detection method to determine whether there are air leakage cracks in the coal pillar, as well as the location and leakage rate of the air leakage cracks.

[0008] Step 3: Install temperature sensors in the coal pillar sections with air leakage cracks identified in Step 2. Measure the locations of high-temperature risk areas for spontaneous combustion of coal within the coal pillar and their migration trends through the arrangement of measuring points and real-time monitoring.

[0009] Preferably, after determining the risk location, gas concentration monitoring is conducted on the coal pillar tunnel every two to three days during coal pillar tunneling or mining. The dangerous section is further determined based on the changes in oxygen concentration and index gas concentration between two adjacent measuring points. If there is a decrease in oxygen concentration and an increase in index gas concentration at two adjacent measuring points, it indicates that the section between the two measuring points is a dangerous section where there may be air leakage cracks or high temperature risk of spontaneous combustion of coal in the coal pillar.

[0010] Preferably, gas concentration monitoring is carried out in sections within the tunneling roadway, with each section being 100m to 150m long. The monitored gases include coal spontaneous combustion indicator gases, such as oxygen, carbon monoxide, and alkane gases.

[0011] Preferably, gas concentration monitoring uses a handheld gas concentration detector combined with a gas sample collection bulb. The gas sample collected by the bulb is analyzed by a ground-based gas chromatograph. The analysis results and the data detected by the handheld gas concentration detector are recorded on a table simultaneously to ensure the accuracy of the detection results.

[0012] Preferably, in step one, the method for identifying potential air leakage cracks and coal spontaneous combustion risk zones based on deformation monitoring and regular inspections includes the following steps:

[0013] S1: Displacement sensors and stress gauges are installed on the surface of the coal pillar to monitor the displacement and stress state of the coal pillar surface in real time. The changes in the data from the displacement sensors and stress gauges reflect the pressure conditions on the coal pillar surface and the coal body.

[0014] S2: When the displacement sensor and stress gauge data reach or exceed the critical value ε t and σ t If the situation is critical, record the corresponding displacement and stress data, and record the corresponding location data. The corresponding location is the risk point.

[0015] S3: Record the measured risk points, inspect the sections with a high density of risk points, check the development of surface cracks in the corresponding sections and record them. Record the sections with a high density of risk points and obvious surface cracks found during the inspection as potential air leakage cracks and coal spontaneous combustion risk sections.

[0016] Preferably, in step two, the section air leakage detection is carried out by tracer gas concentration detection. The tracer gas concentration detection uses a handheld gas concentration detector combined with a gas sample collection bulb. The gas sample collected by the bulb is analyzed by a ground-based gas chromatograph. The analysis results and the data detected by the handheld gas concentration detector are recorded on a table to ensure the accuracy of the detection results.

[0017] Preferably, in step three, the arrangement of the measuring points is based on the location of the air leakage fissures and the corresponding risk sections determined in step two. A temperature measuring borehole is set up every 3 to 5 meters in the coal pillar and coal body of the risk section. The depth of each temperature measuring borehole is 1 to 2 meters, and a set of temperature sensors is buried at the bottom of the borehole. After the measuring points are arranged, the temperature data of each measuring point is detected and collected daily or every two days. The temperature data of each measuring point is then uniformly sorted and summarized to make a temperature data statistical table, plot the location temperature trend image and the temperature change trend graph with time as the axis, summarize the temperature change law in the coal pillar section, and finally determine the high temperature risk location of spontaneous combustion of coal inside the coal pillar.

[0018] Compared with existing technologies, the advantages of the method for accurately determining the location of spontaneous combustion risk in coal pillars disclosed in this invention are:

[0019] (1) This invention combines various detection and monitoring technologies such as coal pillar deformation monitoring, section air leakage detection, key area temperature monitoring and gas concentration monitoring to predict and determine the air leakage cracks and high temperature risk locations of coal pillars during tunneling and face mining from multiple dimensions. This can further improve the safety of tunneling and production in the coal pillar along-goal tunneling layout mode, and plays an important role for mines that adopt the coal pillar along-goal tunneling layout mode.

[0020] (2) The steps in the method disclosed in this invention are interconnected, can be used as a basis for each other, and can also verify each other, which greatly improves the credibility and reliability of the on-site test results. At the same time, the detection and monitoring methods for each step are practical and feasible, and have strong operability on site.

[0021] (3) The present invention uses temperature monitoring technology to monitor the temperature inside the broken coal body of the coal pillar, thereby enabling the prediction and prevention of underground fires that may be caused by oxidation of the broken coal body of the coal pillar. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a technical roadmap for a method for accurately determining the location of spontaneous combustion risk in coal pillars, as disclosed in this invention.

[0024] Figure 2 A schematic diagram showing the selection of temperature measurement sections and the layout of temperature measurement points for a coal pillar.

[0025] Figure 3 This is a schematic diagram showing the location of the high-temperature risk of spontaneous combustion of coal due to air leakage inside the coal pillar.

[0026] In the diagram: 1-coal pillar and coal body; 2-temperature measuring borehole; 3-temperature sensor; 4-air leakage fissure; 5-high temperature risk location for spontaneous combustion of coal in the coal pillar; 6-air leakage airflow; 7-coal pillar. Detailed Implementation

[0027] The specific embodiments of the present invention will be briefly described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] Figures 1-3 A preferred embodiment of the present invention is shown and analyzed in detail.

[0029] The 21404 return air roadway is 3342.8m long and is excavated from the drainage roadway of the fourth panel to the auxiliary haulage roadway of the fourth panel. The roadway is adjacent to the return air roadway of the 21405 working face (21405 goaf), with a 6m wide coal pillar 7 in between.

[0030] like Figure 1 The method for accurately determining the location of spontaneous combustion risk in a coal pillar, as shown, includes the following steps:

[0031] Step 1: Monitor the deformation of coal pillar 7 during tunnel excavation and mining, and regularly inspect the surface fracture condition of coal pillar 7. Based on the monitoring and inspection results, identify potential air leakage fissures 4 and risk zones for spontaneous combustion of coal. This includes the following steps:

[0032] S1: Displacement sensors and stress gauges are installed on the surface of coal pillar 7 to monitor the displacement and stress state of the surface of coal pillar 7 in real time. The changes in data from the displacement sensors and stress gauges reflect the pressure conditions on the surface of coal pillar 7 and the coal body 1 of the coal pillar.

[0033] S2: When the displacement sensor and stress gauge data reach or exceed the critical value ε t and σ t If the corresponding displacement and stress data are recorded, the corresponding location data will be recorded, and the corresponding location will be the risk point.

[0034] S3: Record the measured risk points, inspect the sections with a high density of risk points, check the development of surface cracks in the corresponding sections and record them. Record the sections with a high density of risk points and obvious surface cracks found during the inspection as potential coal pillar coal spontaneous combustion risk sections, each section being 100m to 150m long.

[0035] Step Two: For the potential air leakage fissure 4 and the risk zone of spontaneous combustion of coal identified in Step One, a sectional air leakage detection method is used to determine whether air leakage fissure 4 exists in coal pillar 7, and to ascertain the location, leakage volume, and leakage velocity of air leakage fissure 4. This specifically includes the following steps:

[0036] S1: First, based on the location relationship between the coal pillar 7 to be tested and the adjacent goaf, pressure difference tests are conducted at each sealed point in the goaf to be tested to determine the high-pressure and low-pressure points in the area, estimate the corresponding air leakage channels and leakage methods, set the high-pressure points as tracer gas release points, and set the low-pressure points as sampling points. If the sampling points are set in the roadway, the interval between adjacent sampling points is 100m to 150m.

[0037] S2: Inject nitrogen gas into the goaf to be tested at the release point and monitor the flow rate and pressure of the nitrogen injection pipe. Once the flow rate and pressure of the nitrogen injection pipe stabilize, release SF6 gas into the goaf to be tested from the release point and record the release time t. S .

[0038] S3: Use a portable SF6 detector to monitor the gas in the reserved observation hole in the sealed area in real time at each sampling point. When SF6 gas is detected, collect a preset number of gas samples at each sampling point using a negative pressure pump according to the preset interval, put them into the air bag and seal it, and record the concentration of SF6 gas measured by the portable SF6 detector and the sampling time at each collection.

[0039] S4: Detect the SF6 concentration in the gas samples of each gas bag using a gas chromatograph to determine the SF6 gas concentration collected at each sampling point and at each sampling time. Compare the SF6 concentration in the gas samples collected at each sampling point and at each sampling time with the SF6 gas concentration measured by the portable SF6 detector to determine the SF6 gas concentration at each sampling point and at each sampling time, the sampling time when SF6 gas was first detected at each sampling point, and the sampling time when the maximum concentration of SF6 gas was detected at each sampling point.

[0040] S5: Based on the shortest leakage distance between the release point and each sampling point, the release time, the SF6 gas concentration at each sampling point at each sampling time, the sampling time of the first detection of SF6 gas at each sampling point, and the sampling time of the maximum concentration of SF6 gas detected at each sampling point, the leakage situation of the goaf to be tested is obtained, thereby determining the approximate area where leakage fissure 4 is located and initially determining the location of the danger zone. If a certain concentration of SF6 gas is detected at a certain sampling point, multiple sampling tests are conducted at that sampling point. If the concentration of SF6 gas is greater than 2 ppm in multiple tests, it indicates that there is a danger zone with a leakage channel within 100-200m of that sampling point.

[0041] Step 3: Monitoring the temperature and gas concentration of coal pillar 7:

[0042] like Figure 2 , 3 As shown, the 21404 return air roadway is 3342.8m long, excavated from the drainage roadway of the fourth panel to the auxiliary haulage roadway of the fourth panel. The roadway is adjacent to the return air roadway of the 21405 working face (21405 goaf), with a 6m wide coal pillar 7 in between. Due to the brittle and hard nature of the coal itself, the coal pillar 1 is highly susceptible to stress disturbance during tunneling and subsequent mining, leading to the development of air leakage fissures 4 and even roof falls and spalling. This not only easily forms air leakage channels but also causes the coal pillar 1 itself to form a fragmented accumulation state. Under the influence of weak air leakage 6, the coal inside the pillar 7 can oxidize and generate heat, creating a risk of spontaneous combustion. Therefore, the coal pillar 1 should be monitored during tunneling and mining, including not only gas concentration monitoring but also temperature monitoring.

[0043] Within the multiple hazardous sections identified in Step 2, a representative hazardous area of ​​150m coal pillar 1 with the most significant gas concentration changes is selected. A temperature-measuring borehole 2 is installed every 5m, with a set of temperature sensors 3 embedded inside each borehole 2. The borehole 2 is positioned slightly above the middle of the coal pillar 1. Since the coal pillar 7 itself is 6m wide, the construction of the temperature-measuring borehole 2 should not exceed 2m; typically, drilling to 1m is sufficient. After embedding the temperature sensors 3 and cables, cement grout is injected to seal the borehole 2. After the cement dries completely, an organic material is sprayed onto the surface, and a connector for the temperature sensors 3 is left outside the borehole 2 for subsequent temperature monitoring. After the monitoring points are arranged, temperature data from each point is monitored and collected daily or every two days to promptly identify locations with temperature changes. Problems are addressed by grouting and injecting colloid. The temperature data from each measuring point were collected, summarized, and compiled into a temperature data statistical table. Location temperature trend images and time-based temperature change trend graphs were also plotted. The temperature variation patterns within section 7 of the coal pillar were summarized, ultimately identifying location 5 within coal pillar 7 that presents a high-temperature risk of spontaneous combustion. During monitoring, any locations exhibiting abnormal data should be repeatedly tested. After ruling out human error, timely sealing and fire prevention measures should be implemented at the corresponding locations.

[0044] After identifying the hazardous area, gas concentration monitoring is conducted every two to three days during the excavation or mining of coal pillar 7. The monitored gases include coal spontaneous combustion indicator gases such as oxygen, carbon monoxide, and alkane gases. Gas concentration monitoring is conducted in sections within the excavation roadway, each section being 100m to 150m long. Gas concentration monitoring uses a handheld gas concentration detector combined with bulb gas sampling. The gas samples collected by the bulb are analyzed by a surface gas chromatograph. The analysis results and the data detected by the handheld gas concentration detector are recorded simultaneously in a table to ensure the accuracy of the test results. The determination of the hazardous section is based on the changes in oxygen concentration and indicator gas concentration at two adjacent measuring points. If both adjacent measuring points show a decrease in oxygen concentration and an increase in indicator gas concentration, it indicates that the section between the two measuring points is a hazardous section where there may be air leakage fissure 4 or the high-temperature risk location 5 for coal spontaneous combustion in the coal pillar. Based on the monitoring results, the location of the hazardous area is further determined, specifically including the following steps:

[0045] S1: Key Sampling and Monitoring Area

[0046] ① Gas sampling was conducted using two fireproof, airtight observation holes at the cut-out point of the 21405 goaf. Gas samples were collected using bladders or PVC bags, and their airtightness was checked before sampling. The samples were only used when no leaks were confirmed. Gas chromatograph analysis was performed daily to analyze the recent trends in CO levels and O2 content in the goaf, while also monitoring for the presence of C2H4 and C2H2 in the gas samples.

[0047] ② The bundled pipe system laid in the 21405 intake and return airway was used to conduct gas extraction analysis and temperature monitoring in the deep goaf. Four monitoring points were set up in the 21405 longwall face: one at the entrance of the return airway, two in the goaf monitoring zone of the return airway, and two in the goaf monitoring zone of the intake airway. When the O2 concentration in the monitoring area was found to be between 8% and 18% and CO showed a stable upward trend, the sampling cycle was shortened and the monitoring intensity was increased. At the same time, attention was paid to the temperature change trend inside the goaf. When the temperature increased sharply in a short period or exceeded a specific temperature, nitrogen inerting was promptly carried out in the area to prevent spontaneous combustion of residual coal.

[0048] ③ Conduct daily laboratory analysis of carbon monoxide, carbon dioxide, methane, and oxygen concentrations in the upper corner of the working face and the return airflow. If a significant temperature rise, presence of hydrocarbons, or CO concentration exceeding 24 ppm or increasing rapidly is detected, take targeted and effective measures to reduce the temperature and CO concentration to ensure safe production at the 21405 working face.

[0049] S2: Forecasting and prediction methods:

[0050] If CO is detected in the return air corner with a slow increase in concentration, not exceeding 24 ppm, and CH4 has not yet appeared, continuous, fixed-point, and timed observations should be conducted. When the detected CO gas concentration shows a stable increasing trend and CH4 appears, it can be determined that a high-temperature point or spontaneous combustion source has occurred in the goaf. Once ethylene gas is detected in the return air flow, it can be determined that a high-temperature point or spontaneous combustion source has occurred on the upwind side, and the heat source temperature reaches or exceeds 105.6℃. Once acetylene gas is detected in the return air flow, it can be determined that an open flame or a high-temperature point close to an open flame exists on the upwind side.

[0051] When the CO concentration at the monitoring site rises sharply, it indicates that the oxidation rate of residual coal in the goaf is accelerating, and measures such as nitrogen inerting should be taken, and monitoring should be strengthened. When C2H4 appears in the goaf, it indicates that the spontaneous combustion of coal is relatively serious, and the temperature of some residual coal has been oxidized to above 100℃. At this time, fire prevention and extinguishing measures must be taken quickly to cool down the high-temperature area.

[0052] The above description of the disclosed embodiments enables those skilled in the art to make and use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit and scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for accurately determining the location of spontaneous combustion risk in coal pillars, characterized in that, Includes the following steps: S1. Monitor the deformation of the coal pillar (7) and regularly inspect the surface of the coal pillar (7). Based on the monitoring and inspection results, determine the potential air leakage cracks (4) and the risk zones for spontaneous combustion of coal, including the following steps: S11. Displacement sensors and stress gauges are installed on the surface of the coal pillar (7) to monitor the displacement and stress state of the coal pillar (7) in real time. The data changes of the displacement sensors and stress gauges reflect the pressure on the surface of the coal pillar (7) and the coal body (1) of the coal pillar. S12. When the data from the displacement sensor and stress gauge reach or exceed the critical value ε t and σ t If the situation is critical, record the corresponding displacement and stress data, and record the corresponding location data. The corresponding location is the risk point. S13. Record the measured risk points, inspect the sections with relatively dense risk points, check the surface crack development of the corresponding sections and record it. Record the sections with relatively dense risk points and obvious surface cracks found during the inspection as potential air leakage cracks (4) and coal spontaneous combustion risk sections. S2. For the potential air leakage cracks (4) and the risk zone of spontaneous combustion of coal identified in step one, the section air leakage detection method is used to determine whether there are air leakage cracks (4) in the coal pillar (7) and the location and air leakage speed of the air leakage cracks (4); S3. In step two, temperature sensors are installed in the coal pillar (7) section with air leakage cracks (4). The high temperature risk location (5) of coal spontaneous combustion inside the coal pillar (7) and the migration trend of the high temperature risk location (5) of coal spontaneous combustion inside the coal pillar (7) are measured by the arrangement of measuring points and real-time monitoring.

2. The method for accurately determining the location of spontaneous combustion risk in a coal pillar according to claim 1, characterized in that, After determining the risk location, gas concentration monitoring is carried out on the coal pillar (7) tunneling roadway every two to three days during the coal pillar (7) tunneling or mining period. The dangerous section is further determined based on the changes in oxygen concentration and index gas concentration between two adjacent measuring points. If there is a phenomenon of decreased oxygen concentration and increased index gas concentration at two adjacent measuring points, it indicates that the section between the two measuring points is a dangerous section that may have air leakage cracks (4) or coal pillar spontaneous combustion high temperature risk location (5).

3. The method for accurately determining the location of spontaneous combustion risk in a coal pillar according to claim 2, characterized in that, Gas concentration monitoring was conducted in sections within the tunnel, each section being 100 m to 150 m long. The gases monitored included coal spontaneous combustion indicator gases such as oxygen, carbon monoxide, and alkane gases.

4. The method for accurately determining the location of spontaneous combustion risk in a coal pillar according to claim 2, characterized in that, Gas concentration monitoring employs a handheld gas concentration detector combined with a gas sample collection bulb. The gas sample collected by the bulb is analyzed by a ground-based gas chromatograph. The analysis results and the data detected by the handheld gas concentration detector are recorded simultaneously on a table to ensure the accuracy of the test results.

5. The method for accurately determining the location of spontaneous combustion risk in a coal pillar according to claim 1, characterized in that, In step two, the section air leakage detection is carried out by tracer gas concentration detection. The tracer gas concentration detection is carried out by a handheld gas concentration detector combined with a gas sample collection bulb. The gas sample collected by the bulb is analyzed by a ground-based gas chromatograph. The analysis results and the data detected by the handheld gas concentration detector are recorded on a table to ensure the accuracy of the detection results.

6. The method for accurately determining the location of spontaneous combustion risk in a coal pillar according to claim 1, characterized in that, In step three, the arrangement of the measuring points is based on the location of the air leakage crack (4) and the corresponding risk section determined in step two. A temperature measuring borehole (2) is set up every 3 to 5 m in the coal pillar (1) of the risk section. The depth of each temperature measuring borehole (2) is 1 to 2 m, and a set of temperature sensors (3) is buried at the bottom of the borehole. After the measuring points are arranged, the temperature data of each measuring point is detected and collected daily or every two days. The temperature data of each measuring point is sorted and summarized in a unified manner, and a temperature data statistics table is made. A location temperature trend image and a temperature change trend graph with time as the axis are drawn to summarize the temperature change law in the coal pillar (7) section. Finally, the location (5) of the coal pillar (7) with high temperature risk of spontaneous combustion of coal is determined.

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