A prediction method for outburst in the driving face of underground coal mines

Abstract

The present invention provides a method for predicting outbursts at the driving face in a coal mine, including: S1, uniformly arranging outburst prediction boreholes on the driving face; S2, setting the lateral spacing and longitudinal spacing of the outburst prediction boreholes; S3, setting the opening distance of the outburst prediction boreholes on the driving face; S4, calculating the number of outburst prediction boreholes to be set; S5, calculating the volume of the coal body with the tendency of outburst danger; S6, calculating the relative outburst intensity of the outburst simulation test; S7, predicting the average mass of the outburst coal body when a coal and gas outburst occurs at the roadway driving face; when the mass of the outburst coal body is less than the mass of the coal cut by one blast, outburst prediction boreholes are constructed on the driving face to measure the outburst prediction indexes. The method described in the present invention ensures the comprehensiveness and accuracy of the prediction by uniformly arranging outburst prediction boreholes; by reasonably setting the opening distance, after the driving face continues to advance after a new round of outburst prediction, it can enter the effective prediction zone formed by the new round of prediction.

Description

Technical Field

[0001] The present invention relates to the field of outburst prediction and prevention in underground coal mines, and particularly to a method for predicting outbursts in the driving face of underground coal mines. Background Art

[0002] As a basic energy source in China, coal has long been a dominant position that cannot be ignored. At present, more than 90% of coal mining mines in China are underground mining, and dynamic disasters such as coal and gas outbursts triggered during the mining process occur from time to time, which significantly restricts the safe and efficient production of mines with long-term, complex and repetitive multi-situations.

[0003] A large number of observational studies at home and abroad have shown that in the coal seams at the gas outburst sites, there are soft coal layers with soft coal quality, disordered bedding, severely damaged primary structures, and distributed in layers or lenticular shapes. Conventionally, this kind of coal is called soft-seam coal, and the softening of coal quality is an omen of gas outburst. The destruction of coal body structure is the product of the strong extrusion and shear failure of the coal seam by tectonic forces. Due to the non-uniformity of the force magnitude, action range and stress state, natural layers of different ranges and thicknesses in the coal seam are deformed, losing their original homogeneous and clearly bedded banded structure, and forming broken granular or powdery tectonically damaged coal, which is called tectonic coal.

[0004] With the normalization of deep mining, the number of outburst-prone mines increases year by year, and the work of outburst disaster prevention and outburst prediction becomes more severe. At present, the layout mode of outburst prediction boreholes in the driving face is generally to construct at least 2 - 3 prediction boreholes with a depth of 8 - 10 m in coal seams with different dips, and the prediction boreholes are preferably arranged in the soft coal layer. One borehole is located in the middle of the roadway section and parallel to the driving direction of the roadway. The end points of other boreholes should be located 2 - 4 m outside the two side contour lines of the roadway section.

[0005] However, outburst accidents still inevitably occur when using prediction indicators to predict outburst risks on site. When the active range of tectonic movement is relatively small, such as the development of faults with small throws, it will not produce obvious soft coal layers in the coal seam, but the tectonic soft coal produced exists in the coal seam in the form of local "coal pockets". This situation can be called the mode of "local tectonic coal may exist in hard coal seams". If the driving of the working face does not expose this part of the coal body, it is very difficult to ensure that the prediction borehole will drill into the coal body in this area during the construction of the outburst prediction borehole, resulting in the fact that the measured prediction indicator value cannot truly reflect the outburst risk level existing in the coal body of the working face. In many cases, it is because the borehole does not drill into the coal body with outburst risk, and the measured prediction indicator value is lower than the reference critical value, resulting in "low-index outburst accidents". Therefore, there is an urgent need for an outburst prediction method to determine the layout mode of outburst prediction boreholes and improve the accuracy of outburst prediction in the underground driving face. Summary of the Invention

[0006] To solve the problems existing in the above-mentioned prior art, the present invention provides a prediction method for outburst in the driving face of a coal mine underground, which specifically includes the following technical solutions:

[0007] A prediction method for outburst in the driving face of a coal mine underground includes the following steps:

[0008] S1. Uniformly arrange outburst prediction boreholes on the driving face.

[0009] S2. Collect the width data of the outburst holes in the outburst accidents of the roadway driving face, and set the lateral spacing of the outburst prediction boreholes; determine the longitudinal spacing of the outburst prediction boreholes according to the minimum structural zone height exposed by the coal body.

[0010] S3. Set the opening distance of the outburst prediction boreholes in the driving face to be ≤ 0.5 m.

[0011] S4. Based on the actual area of the roadway driving face, calculate the number of outburst prediction boreholes to be set by comparing the layout spacing and the opening distance of the outburst prediction boreholes obtained in steps S1 - S3.

[0012] S5. Calculate the volume of the coal body with outburst risk tendency through the following formula, and obtain the maximum range of the coal body with outburst risk tendency in the driving face:

[0013]

[0014] In the formula,

[0015] V ′ is the volume of the coal body with outburst risk tendency, m 3 ; h is the predicted driving depth, m; S1 is the cross-sectional area close to the working face; S2 is the cross-sectional area close to the bottom of the prediction borehole, m 2 ;

[0016] S6. Calculate the relative outburst intensity of the outburst simulation test according to the outburst simulation test results. The relative outburst intensity refers to the ratio of the amount of coal thrown out in the outburst simulation test to the total amount of coal.

[0017] S7. Predict the average outburst coal mass when coal and gas outburst occurs in the roadway driving face through the following formula:

[0018] m′ = ψm

[0019] In the formula,

[0020] m = ρV′

[0021] m′ is the predicted outburst coal mass of the working face, kg; ψ is the relative outburst intensity of the coal body, %.

[0022] m is the mass of the coal body with the tendency of outburst danger, in kg; ρ is the apparent density of the coal body, in kg / m 3 ; V′ is the volume of the coal body with the tendency of outburst danger, in m 3 ;

[0023] When the mass of the outburst coal body is less than the mass of the coal cut by one shot, according to the "Regulations on the Prevention and Control of Coal and Gas Outburst" and the number of outburst prediction boreholes determined in step S4, outburst prediction boreholes are constructed on the roadway driving face to measure the outburst prediction indexes.

[0024] Furthermore, the uniform distribution of the outburst prediction boreholes includes: the outburst prediction boreholes are arranged in the soft coal seam area with signs of coal and gas outburst on the driving face, and in the non-outburst index area of the driving face.

[0025] Furthermore, the number of outburst accident samples collected from the roadway driving face ≥ 100 pieces, and includes outburst accidents in domestic and foreign coal mine roadway driving faces; according to the collected samples, a column chart of the outburst hole width of the outburst accident is made to obtain the outburst hole width distribution data.

[0026] Furthermore, the lateral spacing of the outburst prediction boreholes is set to 4 - 6m.

[0027] Furthermore, under the upper limit of the opening distance of ≤ 0.5m, the opening distance of the outburst prediction boreholes is accurately calculated by the following formula:

[0028]

[0029] In the formula,

[0030] l is the opening distance, in m; x is the predicted advance distance, in m; b is the control range of the roadway side, in m; h is the predicted depth, in m.

[0031] Furthermore, the opening angle of the outburst prediction boreholes is determined according to the coal seam dip angle and the driving direction.

[0032] Furthermore, according to the critical value of the initial released gas expansion energy, the outburst intensity of coal and gas outburst is divided into weak outburst level and strong outburst level; the outburst intensity of the weak outburst level is 42.98 mJ / g - 103.8 mJ / g, and the outburst intensity of the strong outburst level is ≥ 103.8 mJ / g.

[0033] Furthermore, the average values of different relative outburst intensities under the strong outburst level and the weak outburst level are used to characterize the relative outburst intensities under different outburst levels.

[0034] Furthermore, the average relative outburst intensity of the weak outburst is set to 22.79%, and the average relative outburst intensity of the strong outburst is set to 63.28%.

[0035] Based on the above technical solution, the present invention has the following beneficial effects:

[0036] 1. For the prominent prediction method described in the present invention, by uniformly arranging the prominent prediction boreholes at the driving face in the coal mine underground, it avoids the situation that only the possible positions of outbursts are considered when arranging the prediction boreholes in the past, while ignoring the fact that obvious soft coal layers cannot be seen in all parts of the driving face, ensuring the comprehensiveness and uniformity of the prediction, and improving the accuracy and coverage of the prediction.

[0037] 2. For the prominent prediction method described in the present invention, by selecting a reasonable opening distance of the prominent prediction boreholes, it ensures that under different prediction conditions, when the working face continues to advance after a new round of prominent prediction and the advancing distance reaches the prediction leading distance left by the previous round of prediction, it can enter the effective prediction zone formed by the new round of prediction.

[0038] 3. For the prominent prediction method described in the present invention, by calculating the average outburst coal volume that may occur at the driving face under different outburst intensities and comparing it with the coal volume cut by one shot, it can more accurately evaluate the outburst risk of the driving face. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 : Schematic flow chart of the prediction method described in the present invention;

[0040] Figure 2 : Front view schematic diagram of the uniform arrangement of the prominent prediction boreholes at the driving face;

[0041] Figure 3 : Top view schematic diagram of the uniform arrangement of the prominent prediction boreholes at the driving face;

[0042] Figure 4 : Schematic diagram of a columnar chart recording the width of the outburst holes in foreign outburst accidents;

[0043] Figure 5 : Schematic diagram of a columnar chart recording the width of the outburst holes in domestic outburst accidents. DETAILED DESCRIPTION OF THE INVENTION

[0044] It should be noted that:

[0045] 1. In the description of the specification and the claims, certain terms are used to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. The specification and the claims do not use the difference in nouns as a way to distinguish components, but use the difference in functions of components as the criterion for distinction.

[0046] 2. Unless otherwise defined, the technical terms or scientific terms used in this disclosure shall have the ordinary meanings as understood by those of ordinary skill in the art to which this disclosure pertains.

[0047] The following will describe the present invention in detail by way of embodiments in conjunction with the attached Figure 1 to the attached Figure 5 drawings.

[0048] A method for predicting outburst in a coal mine roadway driving face includes the following steps:

[0049] S1. Arrange outburst prediction boreholes on the driving face, and the outburst prediction boreholes are evenly distributed on the driving face.

[0050] The even distribution of the outburst prediction boreholes means that: except at the soft coal seams with outburst signs of coal and gas, outburst prediction boreholes are also arranged in the non-outburst index areas of the roadway.

[0051] Evenly arranging outburst prediction boreholes on the coal mine roadway driving face can ensure the comprehensiveness and uniformity of the outburst prediction of coal and gas, and improve the accuracy and coverage of the prediction.

[0052] S2. Set the lateral spacing and longitudinal spacing of the outburst prediction boreholes.

[0053] Among them,

[0054] The lateral spacing refers to the interval distance between adjacent prediction boreholes on the horizontal plane, that is, along the coal seam strike direction;

[0055] The longitudinal spacing refers to the interval distance between adjacent prediction boreholes in the direction perpendicular to the coal seam strike.

[0056] The lateral spacing of the outburst prediction boreholes is determined through the following steps:

[0057] S201. Collect data on outburst accidents that occurred in roadway driving faces at home and abroad. The data includes at least the width data of the outburst holes after the outburst accidents.

[0058] To obtain a more accurate data distribution law, the sample quantity of outburst accidents should be ≥ 100 cases;

[0059] Moreover, based on the technological differences in fully mechanized coal mining operations at home and abroad, set the collected foreign sample data ≥ 50 cases and the domestic sample data ≥ 50 cases, so as to obtain a more scientific and rigorous statistical result.

[0060] In this embodiment, 367 outburst accidents are selected, including 274 times abroad and 93 times in China.

[0061] After a outburst accident occurs, taking each meter as the statistical unit, calculate the proportion of different outburst hole widths in the sample data to obtain the distribution law of outburst hole widths.

[0062] Appendix Figure 4 shows the bar chart of the outburst hole width records of foreign outburst accidents;

[0063] Appendix Figure 5 shows the bar chart of the outburst hole width records of domestic outburst accidents.

[0064] Analysis of the statistical data in step S202 shows that:

[0065] Among the outburst holes formed by 274 outbursts that occurred abroad, the proportion of outbursts with an outburst hole width less than 6m is 89.05%, and the proportion of outbursts with an outburst hole width less than 4m is 76.64%;

[0066] Among the outburst holes formed by 93 outbursts that occurred in China, the proportion of outbursts with an outburst hole width less than 6m is 98.93%, and the proportion of outbursts with an outburst hole width less than 4m is 90.33%.

[0067] Therefore, in this embodiment, the lateral spacing of the outburst prediction boreholes is set to 4 - 6m. The setting of this lateral spacing can predict the outburst - dangerous coal bodies of the vast majority. The longitudinal spacing is determined according to the minimum structural zone height previously exposed in the coal body.

[0068] S3. As a powerful barrier for pressure relief and blocking the sudden exposure of potential outburst coal bodies in front, when the working face advances to the end of the prediction lead distance formed by the previous prediction cycle, the working face should be within the effective prediction zone formed by the new prediction cycle, that is, the safety effect of the prediction lead distance is delayed. Based on the safety effect of the prediction lead distance being delayed, the opening distance of the outburst prediction boreholes in the driving working face is set to ≤0.5m.

[0069] Under the upper limit restriction of the opening distance of ≤0.5m, the opening distance of the outburst prediction boreholes is accurately calculated through the following formula:

[0070]

[0071] In the formula,

[0072] l is the opening distance, m; x is the prediction lead distance, m; b is the roadway side control range, m; h is the prediction depth, m.

[0073] Through the accurate calculation of the opening distance of the outburst prediction boreholes by the above formula, it can be ensured that under different prediction conditions, after the driving working face undergoes a new round of outburst prediction and continues to advance, when the advancing distance reaches the prediction lead distance left by the previous prediction, it can enter the effective prediction zone formed by the new prediction.

[0074] The opening angle of the outburst prediction borehole is determined according to the coal seam dip angle and the driving direction, that is: the principle of borehole layout is to ensure that the borehole is arranged in the coal seam, and the borehole dip angle is parallel to the roadway floor or inclined upward or downward according to the thickness of the coal seam.

[0075] S4. According to the actual area of the roadway driving face, based on the outburst prediction borehole layout spacing and the opening distance obtained in step S1, compare the two to calculate the number of outburst prediction boreholes that need to be set.

[0076] S5. Calculate the volume of the coal body with outburst danger tendency through the following formula to evaluate the maximum range of the coal body with outburst danger tendency in the driving face:

[0077]

[0078] In the formula,

[0079] V ′ is the volume of the coal body with outburst danger tendency, m 3 ; h is the predicted driving depth, m; S1 is the cross-sectional area close to the working face; S2 is the cross-sectional area close to the bottom of the prediction borehole, m 2 .

[0080] Calculate the mass of the coal body with outburst danger tendency through the following formula:

[0081] m = ρV'

[0082] In the formula,

[0083] m is the mass of the coal body with outburst danger tendency, kg; ρ is the apparent density of the coal body, kg / m 3 ; V' is the volume of the coal body with outburst danger tendency, m 3 .

[0084] S6. According to the critical value of the initial released gas expansion energy, divide the coal and gas outburst intensity into weak outburst level and strong outburst level. Specifically, the outburst intensity of the weak outburst level is 42.98 mJ / g to 103.8 mJ / g; the outburst intensity of the strong outburst level is ≥103.8 mJ / g.

[0085] S601, Jiang Chenglin, Yu Qixiang, etc. "The Spherical Shell Instability Mechanism and Prevention Technology of Coal and Gas Outburst" [M]. China University of Mining and Technology Press, 1998. In the experimental research on the "spherical shell instability" hypothesis in Chapter 5, a detailed description of the outburst simulation test is recorded, including the outburst simulation device and simulation materials, the preparation and sampling of outburst coal seams, the outburst simulation test, and the classification of outburst simulation results. Through the results of 46 outburst simulation tests recorded in the literature, a quantitative analysis of the in-situ outburst intensity is carried out to obtain the relative outburst intensity of 46 outburst tests. The relative outburst intensity refers to the ratio of the amount of coal thrown out in the outburst simulation test to the total amount of coal.

[0086] For a single category of weak outburst or strong outburst, the difference in their relative outburst intensities is relatively small. Therefore, the average values of different relative outburst intensities at the strong outburst level and the weak outburst level are selected to represent the relative outburst intensities at different outburst levels.

[0087] It is calculated that:

[0088] The average relative outburst intensity of weak outburst is 22.79%;

[0089] The average relative outburst intensity of strong outburst is 63.28%

[0090] S602. The relative outburst intensities at different outburst levels obtained in step S601 can accurately quantify the actual outburst intensity at the production site. Therefore, according to the average relative outburst intensity of the strong / weak outburst level and the mass of the outburst-dangerous coal body obtained in step S5, the average outburst coal mass when coal and gas outburst may occur in the roadway driving face at the strong / weak outburst level is calculated by the following formula:

[0091] m′ = ψm

[0092] In the formula,

[0093] m′ is the predicted outburst coal mass of the working face, kg; ψ is the relative outburst intensity of the coal body, %; m is the coal mass of the coal body with outburst-dangerous tendency, kg.

[0094] S7. Based on the average outburst coal mass when coal and gas outburst may occur in the roadway driving face at the strong / weak outburst level calculated in step S601, when this coal mass is less than the mass of coal cut by one blast, according to the "Regulations on the Prevention and Control of Coal and Gas Outburst" and the number of outburst prediction boreholes determined in step S4, outburst prediction boreholes are constructed in the roadway driving face to measure outburst prediction indicators.

[0095] By calculating the average outburst coal mass that may occur in the driving face under different outburst intensities and comparing it with the coal cut by one blast, the outburst danger of the driving face can be evaluated more accurately.

[0096] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention as claimed.

Claims

1. A prediction method for outburst in a coal mine heading face, characterized in that, It includes the following steps: S1. Uniformly arrange outburst prediction boreholes on the driving working face; S2. Collect the outburst hole width data of outburst accidents on the roadway driving working face, and set the lateral spacing of the outburst prediction boreholes; determine the longitudinal spacing of the outburst prediction boreholes according to the minimum structural zone height exposed by the coal body; S3. Set the opening distance of the outburst prediction boreholes on the driving working face to be ≤ 0.5 m; S4. According to the actual area of the roadway driving working face, based on the outburst prediction borehole layout spacing and opening distance obtained in steps S1 - S3, calculate the number of outburst prediction boreholes to be set by comparing the two; S5. Calculate the volume of the coal body with outburst risk tendency through the following formula, and obtain the maximum range of the coal body with outburst risk tendency on the driving working face: In the formula, V ′ is the volume of the coal mass with a prominent risk tendency, m 3 ; h is the predicted driving depth, m; S1 is the cross-sectional area near the working face; S2 is the cross-sectional area near the bottom of the prediction borehole, m 2 ; S6. Calculate the relative outburst intensity of the outburst simulation test according to the outburst simulation test results, and the relative outburst intensity refers to the ratio of the amount of coal thrown out in the outburst simulation test to the total amount of coal; S7. Predict the average outburst coal mass when coal and gas outburst occurs on the roadway driving working face through the following formula: m' = ψm In the formula, m = ρV′ m′ is the predicted outburst coal mass of the working face, kg; ψ is the relative outburst intensity of the coal body, %; m is the mass of the coal body with outburst danger tendency, kg; ρ is the apparent density of the coal body, kg / m 3 ; V′ is the volume of the coal body with a tendency of outburst danger, m 3 ; When the outburst coal mass is less than the mass of coal cut by one blasting, according to the "Regulations on the Prevention and Control of Coal and Gas Outburst" and the number of outburst prediction boreholes determined in step S4, construct outburst prediction boreholes on the roadway driving working face to measure the outburst prediction index.

2. A method for predicting outburst on a coal mine underground driving working face according to claim 1, characterized in that The uniform distribution of the outburst prediction boreholes includes: the outburst prediction boreholes are arranged in the soft coal seam area with coal and gas outburst indication on the driving working face, and in the non-outburst index area of the driving working face.

3. A method for predicting outburst on a coal mine underground driving working face according to claim 1, characterized in that The number of outburst accident samples collected from the roadway driving working face is ≥ 100, and includes outburst accidents on coal mine roadways at home and abroad; make a bar chart of the outburst hole width of the outburst accidents according to the collected samples, and obtain the outburst hole width distribution data.

4. A method for predicting outburst on a coal mine underground driving working face according to claim 3, characterized in that The lateral spacing of the outburst prediction boreholes is set to 4 - 6 m.

5. A method for predicting outburst on a coal mine underground driving working face according to claim 1, characterized in that Under the upper limit of the opening distance of ≤ 0.5 m, accurately calculate the opening distance of the outburst prediction boreholes through the following formula: In the formula, l is the opening distance, m; x is the predicted advance distance, m; b is the roadway rib control range, m; h is the predicted depth, m.

6. A method for predicting outburst on a coal mine underground driving working face according to claim 5, characterized in that The opening angle of the outburst prediction boreholes is determined according to the coal seam dip angle and the driving direction.

7. A method for predicting outburst on a coal mine underground driving working face according to claim 1, characterized in that According to the critical value of the initial released gas expansion energy, the outburst intensity of coal and gas is divided into a weak outburst level and a strong outburst level; the outburst intensity of the weak outburst level is 42.98 mJ / g to 103.8 mJ / g, and the outburst intensity of the strong outburst level is ≥103.8 mJ / g.

8. A prediction method for outburst in a coal mine underground heading face according to claim 7, characterized in that The average value of different relative outburst intensities under the strong outburst level and the weak outburst level is used to characterize the relative outburst intensity under different outburst levels.

9. A prediction method for outburst in a coal mine underground heading face according to claim 8, characterized in that The average relative outburst intensity of the weak outburst is set to 22.79%, and the average relative outburst intensity of the strong outburst is set to 63.28%.

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