Method for dividing goaf coal spontaneous combustion danger zone based on kernel density

Abstract

The application discloses a goaf coal spontaneous combustion danger area division method based on kernel density, which comprises the following steps: continuously collecting CO and O2 concentrations in different areas of a working face, then obtaining kernel density distribution of the CO and O2 concentrations, and obtaining goaf length and corresponding gas concentration corresponding to area division according to kernel density distribution characteristic analysis; the gas concentration nephogram is divided into four areas, the four areas are judged in danger in combination with CO concentration kernel density and O2 concentration kernel density, and the danger degree of each area is given. The method is convenient to operate, can determine the division critical value of the goaf coal spontaneous combustion danger area, avoids the poor adaptability problem of using a single index to divide the goaf coal spontaneous combustion danger area under different mining conditions, weakens the influence of data mutation on the division result, and is higher in accuracy of the danger area division critical value, and avoids the poor adaptability problem caused by the given critical value.

Description

Technical Field

[0001] This invention relates to the field of prevention and early warning of spontaneous combustion of coal in goaf areas, specifically to a method for classifying hazardous areas for spontaneous combustion of coal in goaf areas based on kernel density. Background Technology

[0002] In underground coal mines, spontaneous combustion of coal is one of the hazards affecting the safe mining of the working face. Among them, the goaf is a frequent area of ​​spontaneous combustion, which may lead to major accidents and mine production interruptions. How to effectively prevent spontaneous combustion of coal in the goaf is a key issue in preventing and controlling this disaster.

[0003] Current prevention and control methods for coal spontaneous combustion require the division of coal goaf into three hazardous zones. Oxygen concentration is a key factor in this division, specifically into the heat dissipation zone, oxidation zone, and asphyxiation zone. The oxidation zone is the most common area for coal spontaneous combustion. According to existing fire prevention and extinguishing regulations, the three hazardous zones in the goaf are divided using O2 concentrations of 18% and 5% as critical values ​​to control potential spontaneous combustion hazards.

[0004] However, some problems exist in practical applications. Due to differences in internal geological conditions, ventilation system design, mining methods, and other factors, there is currently no uniform critical value for classifying the three zones of spontaneous combustion in all coal mine working faces. Specific problems are as follows:

[0005] 1) Differences: Different coal mine working faces have unique geological and mining conditions, which means that a prevention and control method that is suitable for some mines may not be suitable for other mines;

[0006] 2) Lack of accuracy: The fixed oxygen concentration threshold used in the current fire prevention and extinguishing guidelines cannot accurately reflect the special conditions of actual coal mine working faces, which affects the accuracy of coal spontaneous combustion prevention strategies.

[0007] Currently, research in the field of coal spontaneous combustion prevention includes studies on processing gas data based on kernel density. Compared to existing technologies, this method provides a more accurate and faster delineation of hazardous areas for coal spontaneous combustion in goaf areas. For example, patent CN 113916615A attempts to obtain the distribution range of different gases during mining based on kernel density cloud maps, dividing the goaf into "heat dissipation zone," "first oxidation zone," "second oxidation zone," and "asphyxiation zone." In practice, this method requires adding profile lines to the kernel density distribution cloud map (as per the patent appendix). Figure 2 (See below), and then plot a curve with the length of the goaf as the abscissa and the kernel density on the corresponding profile line as the ordinate (as shown in the appendix of this patent). Figure 2 (Above), the peak value of the nuclear density distribution and the location of the goaf corresponding to the peak value are obtained.

[0008] However, the existing kernel density-based determination methods have some problems in engineering practice. First, in the practice of coal spontaneous combustion prevention, it was found that the selection range of the profile line of the gas kernel density cloud map is too large, which ultimately leads to a large error in the kernel density distribution curve on the drawn profile line, making it impossible to obtain a more accurate critical value for the division of dangerous areas. At the same time, as can be seen from the curves provided in the attached figure of the patent, the peaks are not obvious and are difficult to distinguish. The division results are easily affected by sudden changes in data, and the corresponding goaf location is not easy to find and there is a possibility of misidentification.

[0009] Clearly, the method based on kernel density is a promising research direction, but existing solutions are still immature and face difficulties in engineering practice. Therefore, there is an urgent need for a faster and more accurate method to determine the risk zone of spontaneous combustion of coal in goaf areas. Summary of the Invention

[0010] The purpose of this invention is to provide a method for classifying coal spontaneous combustion hazard zones in goafs based on kernel density. This method, for different mines and working faces, determines the critical value for classifying coal spontaneous combustion hazard zones in goafs by summarizing the distribution characteristics of a large amount of data, thereby reducing the impact of data mutations on the classification results. At the same time, the accuracy of the critical value for classifying hazard zones is higher, avoiding the problem of poor adaptability caused by a given critical value.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] The method for delineating coal spontaneous combustion hazard zones in goafs based on kernel density includes the following steps:

[0013] S1: Lay several sets of bundled tube sampling devices along the back of the working face support, and collect and detect CO and O2 gas concentrations;

[0014] S2: Plot a 2D kernel density distribution cloud map of CO gas concentration with the length of the goaf as the x-axis and the gas concentration as the y-axis.

[0015] S3: Based on the kernel density cloud map of CO gas concentration drawn in step S2, analyze the inflection point or significant change point of kernel density distribution, and give the coordinates of the point, which is recorded as the characteristic point corresponding to CO; where the vertical axis of the CO characteristic point is the CO critical value, and the horizontal axis is the length of the corresponding goaf.

[0016] S4: Using the feature points in step S3, draw straight lines parallel to the horizontal and vertical axes respectively to divide the gas concentration cloud map into four regions. Determine the hazard level of each of the four regions and give the hazard level of each region.

[0017] S5: Draw a 2D nuclear density distribution cloud map of O2 gas concentration according to the method in step S2 above, analyze the inflection points or significant change points of nuclear density distribution, and determine the characteristic points corresponding to O2; divide the dangerous areas based on CO concentration nuclear density according to the method in step S4 above.

[0018] S6: Compare the lengths of the goaf corresponding to the CO and O2 feature points, make error judgments, and monitor the division results.

[0019] More preferably, in steps S3 and S5, the inflection point or significant change point can be a concentration range, not limited to a single point.

[0020] More preferably, in step S4, the danger of the above four areas is determined, and the danger level of each area is given, including safe area, dangerous area, and potentially dangerous area.

[0021] More preferably, a safe zone is defined as a goaf length shorter than the corresponding goaf length and a CO concentration less than the critical value, or a goaf length longer than the corresponding goaf length and a CO concentration greater than the critical value. A dangerous zone is defined as a goaf length shorter than the corresponding goaf length and a CO concentration greater than the critical value. A potentially dangerous zone is defined as a goaf length longer than the corresponding goaf length and a CO concentration less than the critical value.

[0022] More preferably, in step S6, the length of the goaf corresponding to the CO feature point and the length of the goaf corresponding to the O2 feature point are compared. If the error between the two is ±5m, either of the two division methods is used to divide the dangerous area; otherwise, feedback is given to re-collect and detect the CO and O2 gas concentrations until the error meets the requirements.

[0023] Compared with the prior art, the beneficial effects of this application are as follows:

[0024] 1. By summarizing the distribution characteristics of a large amount of data, the critical value for the division of coal spontaneous combustion hazard zones in goaf areas is determined, which weakens the impact of data mutation on the division results. At the same time, the accuracy of the critical value for the division of hazard zones is higher, avoiding the problem of poor adaptability caused by a given critical value.

[0025] 2. This application is easy to operate. The critical value of the coal spontaneous combustion hazard zone can be determined by judging the distribution characteristics of CO and O2 in the working face. The three-zone division is omitted and no further drawing is required. The location of inflection points or significant change points in the figure is clear. No further data processing is required. The safe area, dangerous area and potential dangerous area are directly divided from the kernel density cloud map. This method is more adaptable and improves the division efficiency.

[0026] 3. This application combines the nuclear density cloud maps of CO concentration and O2 concentration for comprehensive judgment and classification, avoiding the problem of poor adaptability in classifying coal spontaneous combustion hazard areas in goaf under different mining conditions using a single indicator, reducing judgment and classification errors, providing feedback on calculation errors, and improving the accuracy of the final results. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the bundled tube arrangement in the goaf of the working face in Example 1;

[0028] Figure 2 This is a kernel density distribution cloud map of CO concentration in Example 1;

[0029] Figure 3 The hazardous area was delineated based on CO concentration and nuclear density in Example 1;

[0030] Figure 4 This is a nuclear density distribution cloud map of the O2 concentration in Example 1;

[0031] Figure 5 The danger zone was defined based on O2 concentration and nuclear density in Example 1;

[0032] Figure 6 This is a kernel density distribution cloud map of CO concentration in Example 2;

[0033] Figure 7 In Example 2, the hazardous area was delineated based on CO concentration and nuclear density.

[0034] Figure 8 This is a nuclear density distribution cloud map of the O2 concentration in Example 2;

[0035] Figure 9 The danger zone was defined in Example 2 based on O2 concentration and nuclear density. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0037] Example 1

[0038] This invention presents a quantitative method for classifying the critical value of coal spontaneous combustion hazard zones in goafs based on kernel density, using Mengcun Coal Mine as an example for detailed description. Specifically, the CO and O2 concentrations behind support #45 in the 401101 working face are analyzed in detail.

[0039] Step 1: Lay several sets of bundled tube sampling devices (such as...) behind the working face support. Figure 1 (As shown), and collect and detect CO and O2 gas concentrations;

[0040] Step 2: Plot a 2D kernel density distribution cloud map of CO gas concentration with the length of the goaf as the x-axis and the gas concentration as the y-axis. Figure 2 This is a kernel density cloud map of CO concentration;

[0041] Step 3: Based on the kernel density cloud map of CO gas concentration drawn in Step 2, analyze the inflection points or significant change points in the kernel density distribution, and give the coordinates of these points, denoted as characteristic points. Then, obtain the goaf length and corresponding gas concentration corresponding to the regional division, denoted as characteristic values. These characteristic values ​​are the critical values ​​for classifying the goaf coal spontaneous combustion hazard zone. From... Figure 2 From the data, we can directly see that the coordinates of the feature point corresponding to CO are (30, 90).

[0042] Step 4: Using the feature points from Step 3, draw straight lines parallel to the horizontal and vertical axes, respectively. These two lines are perpendicular, dividing the gas concentration cloud map into four regions. Assess the hazard level of each of these four regions and assign a hazard rating. For example... Figure 3 As shown, the hazardous areas are initially delineated based on CO concentration and nuclear density, including safe areas, hazardous areas, and potentially hazardous areas; the goaf length is less than 30m, and the CO concentration is less than 90×10⁻⁶. -6 Or the length of the goaf is greater than 30m and the CO concentration is greater than 90×10⁻⁶. -6 All are safe zones; the length of the goaf is less than 30m and the CO concentration is greater than 90×10⁻⁶. -6 This area is considered hazardous; the goaf is longer than 30m and the CO concentration is less than 90×10⁻⁶. -6 This is a potentially hazardous area;

[0043] Step 5: Draw a 2D nuclear density distribution cloud map of O2 gas concentration using the method described in Step 2 above. Figure 4 This is a nuclear density cloud map of O2 concentration; following the method in step three, analyze the inflection points or significant change points in the nuclear density distribution to determine characteristic points. The coordinates of the characteristic point corresponding to O2 are (30, 15); Figure 5 As shown, dangerous areas are divided according to O2 concentration: a goaf with a length of less than 30m and an O2 concentration greater than 15% or a goaf with a length of more than 30m and an O2 concentration less than 15% are considered safe areas; a goaf with a length of less than 30m and an O2 concentration less than 15% is considered a dangerous area; and a goaf with a length of more than 30m and an O2 concentration greater than 15% is considered a potentially dangerous area.

[0044] Step 6: Compare the lengths of the goaf corresponding to the two feature points in Step 4 and Step 5. If the error between the two is within ±5m, either of the two division methods can be used to divide the dangerous area; otherwise, report a monitoring fault, re-collect and detect the CO and O2 gas concentrations until the error meets the requirements.

[0045] To further subdivide the region, subsequent steps are continued while meeting the error requirements;

[0046] Step 7: Based on the combined judgment of the hazardous area delineation using CO concentration and nuclear density from Step 4 and Step 5 using O2 concentration and nuclear density, when the goaf is less than 30m, the O2 concentration is greater than 15% and the CO concentration is less than 90 × 10⁻⁶. -6 The designated area is a safe zone; the rest is a hazardous zone. In goaf areas greater than 30m, the O2 concentration is less than 15% and the CO concentration is greater than 90 × 10⁻⁶. -6 This area is designated as a safe zone; the rest are considered dangerous zones.

[0047] Example 2

[0048] The following explanation uses gas monitoring data from the goaf of support #75 in a working face of the Hujiahe Mine as an example:

[0049] Step 1: Lay several sets of bundled tube sampling devices behind the working face support, and collect and detect the concentrations of CO and O2 gases;

[0050] Step 2: Plot a 2D kernel density distribution cloud map of CO gas concentration with the length of the goaf as the x-axis and the gas concentration as the y-axis. Figure 6 This is a kernel density cloud map of CO concentration;

[0051] Step 3: Based on the kernel density cloud map of CO gas concentration drawn in Step 2, analyze the inflection points or significant change points in the kernel density distribution, and give the coordinates of these points, denoted as characteristic points. Then, obtain the goaf length and corresponding gas concentration corresponding to the regional division, denoted as characteristic values. These characteristic values ​​are the critical values ​​for classifying the goaf coal spontaneous combustion hazard zone. From... Figure 6 From the data, we can directly see that the coordinates of the feature point corresponding to CO are (35, 100).

[0052] Step 4: Using the feature points from Step 3, draw straight lines parallel to the horizontal and vertical axes, respectively. These two lines are perpendicular, dividing the gas concentration cloud map into four regions. Assess the hazard level of each of these four regions and assign a hazard rating. For example... Figure 7 As shown, the hazardous areas are initially delineated based on CO concentration and nuclear density, including safe areas, hazardous areas, and potentially hazardous areas; the goaf length is less than 35m, and the CO concentration is less than 100×10⁻⁶. -6 Or the length of the goaf is greater than 35m and the CO concentration is greater than 100×10⁻⁶ m. -6 All are safe zones; the length of the goaf is less than 35m and the CO concentration is greater than 100×10⁻⁶. -6 This area is considered hazardous; the goaf is longer than 35m and the CO concentration is less than 100×10⁻⁶ m. -6 This is a potentially hazardous area;

[0053] Step 5: Draw a 2D nuclear density distribution cloud map of O2 gas concentration using the method described in Step 2 above. Figure 8 The O2 concentration kernel density cloud map is generated. Following the method in step three, the inflection points or significant change points of the kernel density distribution are analyzed to determine characteristic points. The coordinates of the characteristic point corresponding to O2 are (30, 15). A goaf length less than 30m and an O2 concentration greater than 15% are considered safe areas, or a goaf length greater than 30m and an O2 concentration less than 15%. A goaf length less than 30m and an O2 concentration less than 15% are considered dangerous areas. A goaf length greater than 30m and an O2 concentration greater than 15% are considered potentially dangerous areas.

[0054] Step 6: Compare the lengths of the goaf corresponding to the two feature points in Step 4 and Step 5. If the error between the two is within ±5m, either of the two division methods can be used to divide the dangerous area; otherwise, report a monitoring fault, re-collect and detect the CO and O2 gas concentrations until the error meets the requirements.

[0055] In Examples 1 and 2 above, steps three and five all use a single point as the inflection point or point of significant change. However, sometimes it can also be a concentration range, not just a single point.

[0056] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for delineating coal spontaneous combustion hazard zones in goafs based on kernel density, characterized in that, Includes the following steps: S1: Lay several sets of bundled tube sampling devices along the back of the working face support to collect and detect CO and O2 gas concentrations; S2: Plot a 2D kernel density distribution cloud map of CO gas concentration with the length of the goaf as the x-axis and the gas concentration as the y-axis; S3: Based on the kernel density cloud map of CO gas concentration drawn in step S2, analyze the inflection point or significant change point of kernel density distribution, and give the coordinates of the point, which is denoted as the characteristic point corresponding to CO; where the vertical axis of the CO characteristic point is the CO critical value, and the horizontal axis is the length of the corresponding goaf. S4: Using the feature points from step S3, draw straight lines parallel to the horizontal and vertical axes to divide the gas concentration cloud map into four regions. Determine the hazard level of each of these four regions, classifying them as safe, hazardous, or potentially hazardous. Specifically, a safe region is defined as one where the goaf length is less than the corresponding goaf length and the CO concentration is less than the critical value, or vice versa. A hazardous region is defined as one where the goaf length is less than the corresponding goaf length and the CO concentration is greater than the critical value. A potentially hazardous region is defined as one where the goaf length is greater than the corresponding goaf length and the CO concentration is less than the critical value. S5: Draw a 2D nuclear density distribution cloud map of O2 gas concentration using the method described in step S2 above, analyze the inflection points or significant change points of the nuclear density distribution, and determine the characteristic points corresponding to O2; delineate hazardous areas based on CO concentration nuclear density using the method described in step S4 above. S6: Compare the lengths of the goaf corresponding to the CO and O2 characteristic points, make error judgments, and monitor the division results.

2. The method for delineating coal spontaneous combustion hazard zones in goafs based on kernel density according to claim 1, characterized in that, In steps S3 and S5, the inflection point or significant change point can be a concentration range, not limited to a single point.

3. The method for delineating coal spontaneous combustion hazard zones in goafs based on kernel density according to claim 1, characterized in that, In step S6, the length of the goaf corresponding to the CO feature point is compared with the length of the goaf corresponding to the O2 feature point. If the error between the two is within ±5 m, either of the two methods is used to divide the dangerous area; otherwise, the CO and O2 gas concentrations are re-collected and detected until the error meets the requirements.

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