Gas control method for local abnormal gas area of high-outburst mine thick coal seam mining face

Abstract

The application discloses a gas control method for a local abnormal gas area of a mining face of a super-thick coal seam of a high-outburst mine, wherein a plurality of front exploration drill holes are constructed at a mining face to detect coal seam occurrence conditions and geological structure conditions of a front coal body; drilling and grouting are performed on the grouting drill holes constructed at the mining face for the thickening area or the broken area of the coal seam; the thickening area or the broken area of the coal seam is intensively extracted through the inclined drill holes constructed at the mining face; and the prediction drill holes are constructed between the inclined drill holes, and the extraction is stopped after the local outburst danger prediction index of the prediction drill holes is lower than a critical index. The application adopts grouting plugging to prevent gas from permeating into a lower mining space, intensively reinforces the broken coal body, avoids large-area roof falling or collapse of the coal body caused by mining influence, predicts the local outburst danger of the abnormal area through the prediction drill holes, ensures that the coal body of the abnormal area eliminates the outburst danger of the coal seam, greatly reduces the gas content in the coal body, and ensures safe production of the mining face.

Description

Technical Field

[0001] This invention relates to the field of coal mine gas control technology, and in particular to a method for controlling gas anomalies in localized gas areas at the mining face of extra-thick coal seams in high-outburst mines. Background Technology

[0002] Before coal mining in high-risk coal seams, underground or surface coalbed methane extraction is necessary to remove gas from the coal seam and eliminate its outburst risk. This method is effective for thin, thick, and medium-thick coal seams in actual production. However, for extra-thick coal seams exceeding 8.0m in thickness, especially those with sudden thickenings due to geological structures, conventional gas extraction methods are insufficient to eliminate the outburst risk. Furthermore, in extra-thick coal seams, localized fractured coal seams affected by geological structures are prone to collapse, leading to gas outburst risks that conventional extraction methods cannot eliminate. Therefore, gas control in areas with sudden increases in thickness or in locally fractured coal seams affected by geological structures is a pressing practical problem that needs to be addressed. Summary of the Invention

[0003] This invention addresses the problem that conventional gas extraction methods are insufficient to eliminate the gas outburst risk in the face of a localized gas anomaly in an extra-thick coal seam, where locally fractured coal seams are prone to collapse due to geological structures in extra-thick coal seams. The invention provides a gas control method for localized gas anomaly areas in the mining face of extra-thick coal seams in high-outburst mines.

[0004] To achieve the above objectives, the present invention adopts the following technical solution.

[0005] A method for controlling localized gas anomalies in the mining face of an extra-thick coal seam in a high-risk coal mine includes the following steps:

[0006] (1) Before production operations, several exploration boreholes are drilled at the face of the mining face to detect the coal seam occurrence and geological structure of the coal body in front.

[0007] (2) Grouting is carried out in the grouting boreholes at the working face for the thickened or broken areas of the coal seam.

[0008] (3) After the grouting fluid solidifies, inclined boreholes are drilled at the working face to enhance the extraction of the thickened area or the broken area of ​​the coal seam.

[0009] (4) Predictive boreholes are constructed between the inclined boreholes, and extraction is stopped after the predicted local outburst risk index of the predictive boreholes is lower than the critical index.

[0010] Furthermore, the probing boreholes include first probing boreholes located on both sides of the working face and at least three second probing boreholes located in the middle of the working face.

[0011] Furthermore, the projected length of the second pre-drilled hole in the direction perpendicular to the mining face is not less than 60m.

[0012] Furthermore, the coal seam occurrence includes variations in coal seam thickness, degree of metamorphism, geological structure, and dip angle.

[0013] Furthermore, the grouting borehole crosses the thickened area of ​​the coal seam or the fractured area of ​​the coal seam.

[0014] Furthermore, the grouting borehole is perpendicular to the mining face and is drilled using a three-hole drilling method.

[0015] Furthermore, after the grouting is completed, cement with a hardness higher than that of the grouting material is used to seal the grouting borehole.

[0016] Furthermore, the inclined borehole fully covers the thickened area of ​​the coal seam or the fractured area of ​​the coal seam, and after the inclined borehole is constructed, it is sealed and enhanced extraction is carried out.

[0017] Furthermore, the final hole spacing of the inclined boreholes is 0.5-1m, and the number of inclined boreholes is determined according to the width of the working face roadway.

[0018] Furthermore, the construction process for the predicted borehole is the same as that for the inclined borehole.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention, while proactively detecting areas of thickened coal seams or fractured coal seams due to geological structures, promptly employs grouting to prevent gas from seeping into the lower mining space, thereby strengthening and reinforcing the fractured coal body. This avoids large-scale roof falls or collapses caused by mining activities. After grouting and reinforcement, inclined boreholes are used for directional enhanced extraction at the working face. After a certain extraction period, predictive boreholes are used to predict the local outburst risk in abnormal areas, ensuring that the coal seam outburst risk in abnormal areas is eliminated. This significantly reduces the gas content in the coal body, ensuring safe production at the working face. Attached Figure Description

[0021] Figure 1 This is a plan view of the borehole before the working face of the present invention;

[0022] Figure 2 This is a cross-sectional view of the borehole before the working face of the present invention;

[0023] Figure 3This is a cross-sectional view of the grouting boreholes and inclined boreholes at the working face of the present invention;

[0024] Figure 4 This is a plan view of the grouting drilling face of the present invention;

[0025] Figure 5 This is a schematic diagram of another embodiment of the grouting drilling arrangement method of the present invention.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1 is the left-side forward exploration borehole, 2 is the upper forward exploration borehole, 3 is the front forward exploration borehole, 4 is the lower forward exploration borehole, 5 is the right-side forward exploration borehole, 6 is the coal body of the working face, 7 is the grouting pump, 8 is the grouting pipe, 9 is the working space of the working face, 10 is the working face head, 11 is the inclined borehole, 12 is the grouting borehole, 13 is the coal body in front of the working face, 14 is the drilling site, 15 is the crawler drilling rig, and 16 is the gentle slope of the drilling site. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] The following is a reference to the appendix. Figure 1 To be continued Figure 5 This invention describes a method for controlling localized gas anomalies in the mining face of extra-thick coal seams in high-risk coal mines, as proposed in an embodiment of the present invention.

[0030] The present invention provides a method for controlling gas anomalies in localized gas-prone areas of extra-thick coal seams in high-risk coal mines, comprising the following steps:

[0031] (1) Before production operations, several exploration boreholes are drilled at the face of the mining face to detect the coal seam occurrence and geological structure of the coal body in front.

[0032] (2) Grouting is carried out in the grouting borehole 12 at the working face 10 for the thickened or broken coal seam area;

[0033] (3) After the grouting fluid solidifies, an inclined borehole 11 is drilled at the working face 10 to strengthen the extraction of the thickened or broken coal seam area.

[0034] (4) Predictive drilling is carried out between inclined boreholes 11. Drainage is stopped after the predicted local outburst risk index of the predicted borehole is lower than the critical index.

[0035] In step (1), the occurrence of coal seams includes the changes in coal seam thickness, degree of coal seam metamorphism, geological structure and coal seam dip angle. The coal seam dip angle is the angle between the coal seam bedding plane and the horizontal plane, and the degree of coal seam metamorphism is the degree of change in the physical and chemical properties of coal under temperature, pressure, time and their interaction.

[0036] The advance drilling includes a first advance drilling hole located on both sides of the working face and at least three second advance drilling holes located in the middle of the working face.

[0037] Specifically, the exploratory boreholes include a first exploratory borehole and a second exploratory borehole. The first exploratory borehole is located on the left and right sides of the working face. When constructing the first exploratory borehole in the coal seam facing the working face, a certain borehole spacing is maintained to ensure that there is one borehole on each side of the working face. The second exploratory borehole is located in the middle of the working face. When constructing the second exploratory borehole in the coal seam facing the working face, a certain borehole spacing is maintained to ensure that there are at least three boreholes in the middle of the working face. One borehole is drilled inclined upwards, one borehole is drilled inclined downwards, and the third borehole is drilled perpendicular to the mining face. The first and second exploratory boreholes are used to probe the coal seam conditions and geological structure of the surrounding coal seam and the coal body in front of the working face.

[0038] The projected length of the second exploratory borehole in the direction perpendicular to the mining face shall not be less than 60m. Specifically, the second exploratory borehole is located in the middle of the coal seam. During construction, the drilling direction of the second exploratory borehole is either perpendicular to the mining face or forms a certain angle with the direction perpendicular to the mining face. When the drilling direction of the second exploratory borehole forms a certain angle with the direction perpendicular to the mining face, the projected length of the second exploratory borehole in the direction perpendicular to the mining face shall not be less than 60m to ensure the accuracy and reliability of the detection of the coal seam occurrence ahead.

[0039] In some embodiments, during the exploratory drilling before construction, a crawler drilling rig 15 with a rated torque of 4300 N.m or more and a rated speed of 60 r / min or more is used, which can drill coal seam boreholes with a length of 200 m or more.

[0040] In some embodiments, such as Figure 1 and Figure 2As shown, taking the tunneling face as an example, a total of five exploration boreholes are arranged on the coal body 6 of the working face. The boreholes are opened in the middle of the roadway, not less than 1.0m away from the roadway floor. The exploration boreholes include two first exploration boreholes set on both sides of the working face and three second exploration boreholes set in the middle of the working face. The first exploration boreholes include the left exploration borehole 1 set on the left side of the working face and the right exploration borehole 5 set on the right side of the working face. The first exploration boreholes are controlled to be 15m away from the roadway outline, with a borehole inclination angle of less than 3.2° and a borehole length of not less than 65m. The second exploration boreholes include the upper exploration borehole 2 set at the upper part of the working face and drilled upwards at an angle, the front exploration borehole 3 set at the front of the working face and drilled forward perpendicular to the mining working face, and the lower exploration borehole 4 set at the lower part of the working face and drilled downwards at an angle. The projected length of the upper exploration borehole 2 and the lower exploration borehole 4 in the direction perpendicular to the tunneling working face is not less than 60m. During the preliminary drilling operation, close attention should be paid to the backflow and discharge of slag in the borehole, and the coal seam occurrence and coal quality should be recorded in a timely manner during each meter of drilling.

[0041] When an extra-thick, soft coal seam with a thickness of 8.0m or more is detected, or when a coal sluice with a sudden thickening is detected in the coal seam ahead of the working face, or when there are faults or other geological structures in the coal body ahead that cause the coal to be soft and broken, drilling and grouting measures are taken in the thickened area of ​​the coal seam or the broken area of ​​the coal seam caused by the geological structure. That is, drilling and grouting are carried out in the grouting borehole 12 at the working face 10 in the thickened area of ​​the coal seam or the broken area of ​​the coal seam to improve the strength of the coal seam and avoid the sudden roof fall or collapse of the coal sluice due to mining.

[0042] Grouting borehole 12 is constructed at the working face 10. Grouting borehole 12 crosses the coal seam thickening area or the coal seam fracture area. That is, the length of grouting borehole 12 needs to cross the coal seam thickening area or the coal seam fracture area. When the area is large and difficult to cover at one time, it needs to be constructed in stages. The length of grouting borehole 12 in each stage is not less than 60m.

[0043] like Figure 4 and Figure 5 As shown, in some embodiments, the grouting boreholes 12 are distributed in the coal body 13 in front of the working face. The grouting boreholes 12 are perpendicular to the working face and are constructed in two rows, upper and lower. The distance L1 between the upper and lower rows of grouting boreholes 12 is 0.5m, and the distance L2 between each row of grouting boreholes 12 is 1m. The boreholes are drilled using a three-hole drilling method.

[0044] In some embodiments, after grouting is completed, cement with a hardness higher than that of the grouting material is used to seal the grouting borehole 12.

[0045] Specifically, such as Figure 3As shown, the grouting borehole 12 is constructed using a crawler drilling rig 15. After construction, a grouting nozzle is inserted into the grouting borehole 12. The grouting nozzle is connected to the grouting pump 7 and the grouting pipe 8, ensuring that the grouting pipe 8 is leak-proof. During grouting, the grouting pressure is maintained above 2.0 MPa, and the grouting flow rate is uniform and moderate. Fluctuations in flow rate should be avoided. When the borehole is nearly full, the flow rate should be appropriately reduced. After grouting, cement with a higher hardness than the grouting material is used for sealing; the cement strength should not be lower than C40.

[0046] After the grout has solidified, inclined boreholes 11 are drilled at the working face 10 to enhance extraction in the thickened or fractured areas of the coal seam. This invention first reinforces the thickened or fractured areas of the coal seam through grouting before drilling inclined boreholes 11 for extraction, preventing coal collapse in the thickened or fractured areas due to disturbance during the drilling of inclined boreholes 11.

[0047] like Figure 3 As shown, after the slurry has set for at least 12 hours, inclined boreholes 11 are drilled at the face 10 towards the coal seam fractured or thickened area to enhance extraction in the thickened or geologically fractured area. The inclined boreholes 11 fully cover the thickened or fractured coal seam area to ensure full-area gas outburst elimination in this abnormal region. The length of the inclined boreholes 11 is based on the volume of the abnormal coal seam area ahead. Due to limitations in existing detection technology, to ensure full-area gas outburst elimination, a drilling site 14 is constructed on one side of the roadway in front of the working space 9. The drilling site 14 is located on one side of the roadway, 15-20m from the face 10, and below the working face floor. This allows the crawler drilling rig 15 to drill longer inclined boreholes 11 at a greater elevation angle to eliminate gas outbursts in the abnormal area. (Refer to...) Figure 3 The working face floor and drilling site 14 are connected by a gentle slope 16. A crawler drilling rig 15 is positioned within drilling site 14, and inclined boreholes 11 are drilled into the coal seam using the crawler drilling rig 15. The final spacing of the inclined boreholes 11 is 0.5-1m. The number of inclined boreholes 11 is limited by the width of the working face roadway, and the length of the inclined boreholes 11 is determined by the length of the borehole reaching the roof strata above the coal seam. After the inclined boreholes 11 are completed, a two-plug-one-injection sealing process is used to seal the boreholes. After sealing, they are promptly connected to the mine's high-negative-pressure extraction system for continuous extraction.

[0048] After continuous extraction from inclined borehole 11 for more than 30 days, predictive drilling is conducted in areas of thickened coal seams or fractured geological structures to determine the local outburst risk index. Extraction is stopped once the local outburst risk index from the predictive borehole is below the critical value specified in the "Detailed Rules for the Prevention and Control of Coal and Gas Outbursts," after which production operations can commence at the working face. If the outburst risk index exceeds the standard, intensive extraction is continued. The predictive boreholes mentioned in this invention should be evenly distributed in areas of thickened coal seams or fractured geological structures, avoiding areas with concentrated extraction borehole distribution to prevent distorted measurement results.

[0049] Predictive boreholes are set between the inclined boreholes 11. In some embodiments, the predictive boreholes are arranged in relatively sparse areas between the inclined boreholes 11 to ensure the accuracy of the measurement results.

[0050] In some embodiments, 3-5 predictive boreholes are constructed in the coal seam thickening area or the geological structure coal seam fracture area, and the predictive boreholes adopt the same construction process as the inclined borehole 11.

[0051] In response to the problem that large-scale coal seam collapses or sudden, abnormal gas outbursts can easily occur in areas of localized thickened coal seams or fractured coal seams in high-risk coal mines, this invention, while proactively detecting areas of thickened coal seams or fractured coal seams, promptly employs grouting to prevent gas from seeping into the lower mining space. This strengthens and reinforces the fractured coal body, preventing large-scale roof collapses or breakdowns due to mining activities. After grouting and reinforcement, directional enhanced extraction is carried out using inclined boreholes at the working face. After a certain extraction period, predictive boreholes are used to predict the local outburst risk in the abnormal areas, ensuring that the coal seam outburst risk in the abnormal areas is eliminated. This significantly reduces the gas content in the coal body, ensuring safe production at the working face.

[0052] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0053] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0054] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for controlling gas anomalies in localized areas of extra-thick coal seams at the mining face of high-risk coal mines, characterized in that: Includes the following steps: Before production operations, several exploratory boreholes are drilled at the face of the mining face to detect the occurrence of coal seams and geological structure of the coal body ahead. Grouting is carried out in the coal seam thickening area or coal seam fracture area at the working face construction grouting borehole, and the grouting borehole crosses the coal seam thickening area or coal seam fracture area. After the grouting fluid solidifies, inclined boreholes are drilled at the working face to enhance the extraction of the thickened or fractured coal seam areas. To ensure full-range gas outburst elimination in the area, a drilling site is constructed on one side of the roadway in front of the working face, 15-20m away from the working face. The drilling site is located below the working face floor, which facilitates the crawler drilling rig to drill longer inclined boreholes at a larger elevation angle to eliminate gas outbursts in abnormal areas. Predictive boreholes are drilled between the inclined boreholes, and extraction is stopped once the predicted local outburst risk index of the predicted boreholes falls below the critical index.

2. The method for controlling gas anomalies in localized gas areas of extra-thick coal seams in high-risk coal mines as described in claim 1, characterized in that, The advance drilling holes include first advance drilling holes located on both sides of the working face and at least three second advance drilling holes located in the middle of the working face.

3. The method for controlling gas anomalies in localized gas areas of extra-thick coal seams in high-risk coal mines as described in claim 2, characterized in that, The projected length of the second exploratory borehole in the direction perpendicular to the mining face shall not be less than 60m.

4. The method for controlling gas anomalies in localized gas areas of extra-thick coal seams in high-risk coal mines as described in claim 1, characterized in that, The grouting borehole is perpendicular to the mining face and is drilled using a three-hole drilling method.

5. The method for controlling gas anomalies in localized gas areas of extra-thick coal seams in high-risk coal mines as described in claim 1, characterized in that, After the grouting is completed, the grouting borehole is sealed with cement that has a hardness higher than that of the grouting material.

6. The method for controlling gas anomalies in localized gas areas of extra-thick coal seams in high-risk coal mines as described in claim 1, characterized in that, The inclined borehole fully covers the thickened area of ​​the coal seam or the fractured area of ​​the coal seam. After the inclined borehole is constructed, it is sealed and enhanced extraction is carried out.

7. The method for controlling gas anomalies in localized gas areas of extra-thick coal seams in high-risk coal mines as described in claim 1, characterized in that, The final hole spacing of the inclined boreholes is 0.5-1m, and the number of inclined boreholes is determined according to the width of the working face roadway.

8. The method for controlling gas anomalies in localized gas areas of extra-thick coal seams in high-risk coal mines as described in claim 1, characterized in that, The construction process for the predicted borehole is the same as that for the inclined borehole.

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