Anti-impact safe mining method for quarrying and caving coal in rock burst coal seam

Abstract

The invention relates to the technical field of coal seam safe mining, in particular to a rock burst coal seam quarrying and coal drawing anti-impact safe mining method which comprises the following steps that S1, a rock stratum working face stoping roadway is arranged in a coal seam and a rock stratum, the face length of the rock stratum working face is not smaller than 100 m, and the rock stratum comprises a direct bottom rock stratum and an old bottom rock stratum; s2, the rock stratum is mined, and the mining height is not larger than 3 m; s3, the mined rocks are conveyed to an underground gangue chamber or a gangue filling working face; and S4, adopting a top coal caving process for the coal seam above the rock stratum, automatically collapsing under the action of mine ground pressure, and conveying the collapsed coal to the position above the ground. A mining roadway is arranged in a rock stratum, a working face is arranged in the rock stratum, a traditional coal mining working face is converted into a quarrying working face, a coal seam serves as a rock stratum working face top plate, coal is mined after self collapse, and therefore intrinsic safety mining of the rock burst coal seam is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of safe mining of coal seams, and in particular to a method for safe mining in rock bursting coal seams with rock bursting and coal release to prevent impact. Background Art

[0002] Rock burst refers to the sudden and violent destruction of coal bodies around coal mines or working faces due to the instantaneous release of elastic deformation energy. It is one of the main factors restricting the safe mining of deep coal resources in my country. Statistics show that more than 90% of the impact manifestations in rock burst coal seam mining projects occur in the return tunnels of the working face. my country's coal seam mining mainly uses the longwall retreat mining method, that is, two return tunnels are arranged in the coal seam, and coal mining is carried out by cutting or blasting by coal mining machines. With the deterioration of geological conditions in coal mines and the intensification of stress concentration, the risks faced by mining in some rock burst coal seams have intensified. Even if comprehensive decompression and danger relief measures such as coal seams, roofs, and floors are adopted, the tunnels and working faces arranged in rock burst coal seams are always in danger of impact, and it is impossible to achieve the true "source control" and "disaster source elimination".

[0003] The safe mining of rock burst coal seams mainly adopts the anti-rock burst technology of "regional first" and "local follow-up". "Regional first" means mining the release layer, reasonably arranging the coal seam tunnels, selecting appropriate coal mining methods, and reducing mining disturbances. "Local follow-up" means unloading and resolving dangers of the mined coal seams in the mining space, such as coal seam drilling unloading, coal seam unloading blasting, coal seam water injection, roof deep hole pre-splitting blasting, roof hydraulic fracturing, floor drilling unloading and blasting, etc. In the above methods, whether it is full-height mining, top coal caving or layered mining, the working space is in the coal seam, that is, the working face is arranged in the coal seam, and the mining tunnels directly serving the working face are also arranged in the coal seam. Limited by the current coal seam mining layout, the staff always work in the rock burst coal seam and face the risk of rock burst. Summary of the invention

[0004] In order to improve the safety of the mining process of rock burst coal seams, the present application provides a rock burst coal seam quarrying and coal release anti-bumping safety mining method.

[0005] The present application provides a method for safe mining in rock burst coal seam quarrying and coal placing to prevent impact, which adopts the following technical solutions: A method for preventing rock burst and coal caving in a rock burst coal seam by safe mining comprises the following steps: S1. Arrange the mining tunnel of the rock layer working face in the coal seam and rock layer. The length of the rock layer working face shall not be less than 100m. The rock layer includes the direct bottom rock layer and the old bottom rock layer. S2. Mining the rock layer with a mining height of no more than 3m; S3, transporting the mined rock to the underground gangue chamber or gangue filling working face; S4. The coal seam above the rock layer adopts the top coal caving technology, which collapses automatically under the action of mine pressure, and the collapsed coal is transported to the ground.

[0006] Optionally, in step S1, the following steps are further included: When the coal seam has a weak impact hazard, half of the mining tunnel of the rock face is arranged in the coal seam, and the other half is arranged in the rock layer below the coal seam; When the coal seam has a medium impact hazard, the rock face mining tunnel is arranged in the rock layer below the coal seam, and the tunnel roof is the coal seam; When the coal seam has a strong impact hazard, the mining tunnel of the rock working face is arranged in the old bottom rock layer, and the distance between the tunnel roof and the coal seam is not less than 2m; When the coal seam has the danger of impact and the danger of coal and gas outburst, the mining tunnel of the rock working face shall be arranged in the old bottom rock layer, and the distance between the tunnel roof and the coal seam shall not be less than 5m.

[0007] Optionally, in step S2, it further includes: According to the thickness of coal seam, determine the mining height during the mining process; When the thickness of the coal seam is not more than 3.5m, the mining height shall not exceed 2m; When the coal seam thickness is greater than 3.5m, the mining height is 2-3m.

[0008] Optionally, in step S2, it further includes: According to the uniaxial compressive strength of the rock formation working face, determine the auxiliary rock breaking method of the rock formation working face; When the uniaxial compressive strength of the rock stratum at the working face is not greater than 30MPa, mechanized mining is carried out by direct cutting with a coal mining machine; When the uniaxial compressive strength of the rock stratum at the working face is greater than 30MPa and not greater than 6MPa, blasting is used to assist in rock breaking; When the uniaxial compressive strength of the rock formation at the working face is greater than 60MPa, directional slit orthogonal hydraulic fracturing is used to assist in rock breaking.

[0009] Optionally, in the process of using blasting to assist rock breaking, the following step is further included: Several blasting holes are arranged in the middle of the mined rock stratum in a straight line. The charging depth is the sum of twice the daily mining footage and the sealing length, and the sealing length is not less than one third of the total length of the borehole. The borehole diameter is not greater than 42mm, the distance between adjacent boreholes is 5-10m, and the charging amount of a single hole is not more than 10kg.

[0010] Optionally, in the process of using directional slotted orthogonal hydraulic fracturing to assist in rock breaking, the process further includes: In the horizontal tunnels below the rock working face and in the rock working face, a drilling rig is used to construct perpendicular holes into the mined rock layer, and then a directional pre-crack is formed in the drill hole through a cutting device. Finally, the space close to the pre-crack is sealed by a sealer and high-pressure water injection is performed to expand the pre-crack.

[0011] Optionally, construction is carried out at the middle position of the mining height in the mining rock working face and the middle position of the two lanes of the rock working face; the borehole diameter is 45-65mm; the borehole depth is greater than 100m; the borehole spacing is 10-50m; the pre-crack cutting groove is greater than 2 times the borehole diameter; the pre-crack spacing at different positions in the same borehole is 5-10m; the length of the sealer depends on the pre-crack spacing and is set to 1-2m; the borehole is parallel to the rock layer surface; the hydraulic fracturing pressure range: 10-40Mpa; Among them, the estimated starting pressure required for hydraulic fracturing is: ; (1) In formula (1), p is the estimated starting pressure required for hydraulic fracturing, in MPa, b is the short semi-axis length of the pre-crack, in m, a is the long semi-axis length of the pre-crack, in m, is the maximum principal stress in the fracture working surface area, is the minimum principal stress in the fracture working surface area, It is the tensile strength of rock formation at the fracture point, in MPa.

[0012] Optionally, in step S3, it also includes: The mined rock is transported to the underground gangue chamber or gangue filling working face through the front scraper conveyor, transfer machine and belt conveyor in sequence.

[0013] Optionally, in step S4, it further includes: The collapsed coal is transported to the crusher through the rear scraper conveyor and the transfer machine for crushing, then transported to the coal bunker through the belt conveyor, and then lifted to the ground through the main shaft.

[0014] In summary, the present application includes at least one of the following beneficial technical effects: 1. The mining tunnel is arranged in the rock stratum, and the working face is arranged in the rock stratum, so as to transform the traditional "coal mining" working face into a "stone quarrying" working face, and the coal seam is used as the "roof" of the rock stratum working face. The coal is mined after it collapses by itself through mining pressure or artificial fracturing, thereby realizing the inherently safe mining of the rock pressure coal seam. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1The invention discloses a flow chart of a method for safe mining in rock bursting coal seam for preventing rock bursting and coal caving.

[0016] Figure 2 It is a schematic diagram for showing the rock formation working surface in the embodiment of the present application.

[0017] Figure 3 yes Figure 2 Schematic diagram of the AA section.

[0018] Figure 4 yes Figure 2 Schematic diagram of the BB section.

[0019] Figure 5 It is used to show the layout of the mining tunnels at the rock working face when the coal seam has a weak impact hazard in the embodiment of the present application.

[0020] Figure 6 It is used to show the layout of the mining tunnels at the rock working face when the coal seam has a medium impact hazard in the embodiment of the present application.

[0021] Figure 7 It is used to show the layout of the mining tunnels at the rock working face when the coal seam has a strong impact hazard in the embodiment of the present application.

[0022] Figure 8 It is used to show the layout of the mining tunnels at the rock working face when the coal seam has the danger of impact and the danger of coal and gas outburst in the embodiment of the present application.

[0023] Fig. 9 It is a schematic diagram for showing the directional slit orthogonal hydraulic fracturing assisted rock breaking work in the embodiment of the present application.

[0024] Explanation of the accompanying reference numerals: 1. Coal mining machine; 2. Hydraulic support; 3. Front scraper conveyor; 4. Rear scraper conveyor; 5. End support; 6. Transfer machine; 7. Crusher; 8. Belt conveyor. DETAILED DESCRIPTION

[0025] The present application is further described in detail below in conjunction with all the accompanying drawings.

[0026] Reference Figure 1-Figure 9 The embodiment of the present application discloses a method for safe mining in rock bursting coal seam with rock bursting and coal release to prevent impact.

[0027] A method for preventing rock burst and coal caving in a rock burst coal seam by safe mining comprises the following steps: S1. Arrange the mining tunnel of the rock layer working face in the coal seam and rock layer. The length of the rock layer working face shall not be less than 100m. The rock layer includes the direct bottom rock layer and the old bottom rock layer. S2. Mining the rock layer with a mining height of no more than 3m; S3, transporting the mined rock to the underground gangue chamber or gangue filling working face; S4. The coal seam above the rock layer adopts the top coal caving technology, which collapses automatically under the action of mine pressure, and the collapsed coal is transported to the ground.

[0028] Among them, in step S1, the rock stratum working face mining tunnel is arranged in the coal seam and the rock stratum, and the rock stratum working face mining tunnel is supported by the hydraulic support 2 and the end support 5.

[0029] Further, in step S1, the rock working face mining roadway is arranged in the coal seam and the rock seam. According to the different coal seam impact hazard assessment results, the rock working face mining roadway arrangement layer Li (i=1, 2, 3, 4) is determined. The height of the rock working face mining roadway is H, in meters, and the coal seam thickness is , unit is m.

[0030] When the coal seam has a weak impact hazard, half of the mining tunnel of the rock working face is arranged in the coal seam, and the other half is arranged in the rock layer below the coal seam, and the roof of the tunnel is the coal seam, that is: , if the coal seam thickness h is less than When L1= ; When the coal seam has a medium impact hazard, the rock face mining tunnel is arranged in the rock layer below the coal seam, and the tunnel roof is the coal seam, that is: L2=0; When the coal seam has a strong impact hazard, the mining tunnel of the rock working face is arranged in the old bottom rock layer, and the distance between the tunnel roof and the coal seam is not less than 2m, that is: m; When the coal seam has the danger of impact and the coal seam has the danger of coal and gas outburst, the mining tunnel of the rock layer working face is arranged in the younger rock layer, and the distance between the tunnel roof and the coal seam is not less than 5m, that is: m.

[0031] The coal seam impact hazard level is based on the impact hazard comprehensive index Determine and calculate the comprehensive impact risk index : , (i=1,2,3,4...8,9).

[0032] Specifically, the comprehensive impact risk index parameters include: : The number of rock burst occurrences in history N; : Mining depth H; :Coal seam thickness ; : Elastic energy index of coal ; : Impact tendency of coal; : The thickness relationship between the hard thick rock layer and the coal seam (M, d); :Roof rock thickness characteristic parameters ; : Complexity of geological structure; The evaluation index corresponding to each impact risk comprehensive index parameter can be obtained through analysis and calculation, as shown in Table 1:

[0033] calculate , through the impact risk composite index Determine the coal seam impact hazard level; Shock risk index When it is not greater than 0.25, the impact hazard level is none; Shock risk index When it is greater than 0.25 and not greater than 0.5, the impact hazard level is weak impact; Shock risk index When it is greater than 0.5 and not less than 0.75, the impact hazard level is medium impact; Shock risk index When it is greater than 0.75, the impact hazard level is strong impact.

[0034] Shock Hazard Composite Index The method of determining the coal seam impact hazard and the evaluation index corresponding to all impact hazard comprehensive index parameters are existing technologies and can be obtained through the "Interim Measures for the Identification of Impact Ground Pressure Mines", and will not be described in detail in this application.

[0035] Among them, in step S2, i.e. mining the rock layer, it also includes , determine the mining height during the mining process .

[0036] When the coal seam thickness is not more than 3.5m, m, the mining height is not more than 2m, that is: m; When the coal seam thickness is greater than 3.5m, m, the mining height is 2-3m, that is: .

[0037] Furthermore, in step S2, the fracturing auxiliary rock breaking method of the rock formation working face is determined according to the uniaxial compressive strength R of the rock formation working face.

[0038] When the uniaxial compressive strength of the rock stratum at the working face is not greater than 30MPa, Mpa, mechanized mining is carried out by direct cutting with coal mining machines.

[0039] When the uniaxial compressive strength of the rock formation at the working face is greater than 30MPa and not greater than 60MPa, MPa, blasting is used to assist in rock breaking.

[0040] Specifically, several blasting boreholes are arranged in the middle of the mining rock layer. The blasting boreholes are arranged in a straight line, with the charging depth being the sum of twice the daily mining footage and the sealing length, and the sealing length being not less than one third of the total borehole length. The borehole diameter is not greater than 42mm, the spacing between adjacent boreholes is 5-10m, and the charging amount of a single hole is not more than 10kg.

[0041] When the uniaxial compressive strength of the rock stratum at the working face is greater than 60MPa, MPa, using directional slit orthogonal hydraulic fracturing to assist rock breaking.

[0042] Specifically, perpendicular boreholes are constructed in the horizontal tunnels below the rock working face and in the rock working face by means of a drilling rig, and then directional pre-cracks are formed in the boreholes by means of a cutting device. Finally, the space close to the pre-cracks is sealed by a sealer and high-pressure water injection is performed to expand the pre-cracks.

[0043] Among them, construction is carried out in the middle of the mining height within the mining rock working face and in the middle of the two tunnels of the rock working face; the borehole diameter is 45-65mm; the borehole depth is greater than 100m; the borehole spacing is 10-50m; the pre-crack cutting groove is greater than 2 times the borehole diameter; the pre-crack spacing at different positions in the same borehole is 5-10m; the length of the sealer depends on the pre-crack spacing and is set to 1-2m; the borehole is parallel to the rock layer surface; the hydraulic fracturing pressure range is: 10-40MPa.

[0044] Calculate the estimated starting pressure required for fracturing: ; (1) In formula (1): —Estimated starting pressure required for hydraulic fracturing, MPa; —semi-minor axis of the pre-crack, m; —semi-major axis of the pre-crack, m; —The maximum principal stress in the fracture-causing working surface area; —Minimum principal stress in the fracture-causing working surface area; —Tensile strength of rock formation at the fracture point, MPa.

[0045] Among them, the main operation process of directional slotting orthogonal hydraulic fracturing assisted rock breaking includes drilling, slotting, sealing and water injection fracturing, etc. Drilling is mainly to keep the borehole diameter at 45-65mm as required. In this process, an error of 2mm is allowed due to the characteristics of the rock formation. When the drill pipe drills to a certain depth, the drill pipe is withdrawn and the drill bit is replaced with a slotting tool, and then the slotting tool is sent to the bottom of the borehole. After starting the drilling rig, directional slotting is carried out. First, the drill tool is drilled in vain to flush out the rock powder. After the rock powder in the borehole is flushed clean, the drill pipe is slowly pushed to rotate so that the drill pipe moves forward axially. Under the action of the spring, the blade continues to extend, thereby cutting directional cracks in the borehole. As the drill pipe rotates, the slotting tool will form a pre-crack perpendicular to the axis of the borehole in the borehole, and its cross section is an approximate ellipse. Repeat this process and continue to move forward to form multiple pre-cracks perpendicular to the axis of the borehole. After all directional cracks are cut, fracturing work is carried out. The borehole is sealed at the outer end with a sealer, which is placed 5 to 10 meters away from the first directional crack. Then, high-pressure water injection is carried out into the sealed borehole, where the water injection operation requires a water injection pressure of 10-40Mpa to expand all directional cracks in the borehole. After the fracturing work is completed in the tunnel, it is also necessary to drill and cut the rock formation along the advancing direction of the working face at the mining face. The specific operation method is consistent with the above process. The fracture zone formed by the construction in the working face is orthogonal to the fracture zone formed by fracturing in the tunnel. After multiple rounds of operation, mutually interpenetrating and mutually orthogonal fracture zones are formed in the rock formation, achieving the purpose of regional rock mass fracturing.

[0046] Furthermore, in step S3, the mined rock is transported to an underground gangue chamber or a gangue filling working face, and it also includes constructing mutually perpendicular boreholes to the mined rock formation in the horizontal tunnel below the rock formation working face and the rock formation working face by a drilling rig, and then forming directional pre-cracks in the boreholes by a cutting device, and finally sealing the space close to the pre-cracks by a sealer and performing high-pressure water injection operations to achieve the expansion of the pre-cracks. The water injection operation requires a water injection pressure of 10-40Mpa.

[0047] Furthermore, in step S4, the coal seam above the rock layer adopts the top coal caving process, and collapses automatically under the action of mine pressure, and the collapsed coal is transported to the ground. The collapsed coal is also transported to the crusher 7 through the rear scraper conveyor 4 and the transfer machine 6 for crushing, and then transported to the coal bunker through the belt conveyor 8, and then lifted to the ground through the main shaft.

[0048] The implementation principle of a method for safe mining in rock burst coal seam quarrying and coal release to prevent impact in the embodiment of the present application is: the mining tunnel is arranged in the rock layer, the working face is arranged in the rock layer, the traditional "coal mining" working face is transformed into a "rock burst" working face, the coal seam is used as the "top plate" of the rock layer working face, and the coal is mined after it collapses by itself through mining pressure or artificial fracturing, thereby realizing the inherently safe mining of rock burst coal seam. The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, all equivalent changes made according to the structure, shape, and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for safe mining in rock burst coal seam quarrying and coal placing to prevent impact, characterized in that: The steps include: S1. Arrange the mining tunnel of the rock layer working face in the coal seam and rock layer. The length of the rock layer working face shall not be less than 100m. The rock layer includes the direct bottom rock layer and the old bottom rock layer. S2. Mining the rock layer with a mining height of no more than 3m; S3, transporting the mined rock to the underground gangue chamber or gangue filling working face; S4. The coal seam above the rock layer adopts the top coal caving technology, which collapses automatically under the action of mine pressure, and the collapsed coal is transported to the ground.

2. The method for safe mining in rock burst coal seam quarrying and coal caving to prevent rock burst according to claim 1, characterized in that: In step S1, it also includes: When the coal seam has a weak impact hazard, half of the mining tunnel of the rock face is arranged in the coal seam, and the other half is arranged in the rock layer below the coal seam; When the coal seam has a medium impact hazard, the rock face mining tunnel is arranged in the rock layer below the coal seam, and the tunnel roof is the coal seam; When the coal seam has a strong impact hazard, the mining tunnel of the rock working face is arranged in the old bottom rock layer, and the distance between the tunnel roof and the coal seam is not less than 2m; When the coal seam has the danger of impact and the danger of coal and gas outburst, the mining tunnel of the rock working face shall be arranged in the old bottom rock layer, and the distance between the tunnel roof and the coal seam shall not be less than 5m.

3. The method for safe mining in rock burst coal seam quarrying and coal caving to prevent rock burst according to claim 1, characterized in that: In step S2, it also includes: According to the thickness of coal seam, determine the mining height during the mining process; When the thickness of the coal seam is not more than 3.5m, the mining height shall not exceed 2m; When the coal seam thickness is greater than 3.5m, the mining height is 2-3m.

4. The method for safe mining in rock burst coal seam quarrying and coal caving to prevent rock burst according to claim 1, characterized in that: In step S2, it also includes: According to the uniaxial compressive strength of the rock formation working face, determine the auxiliary rock breaking method of the rock formation working face; When the uniaxial compressive strength of the rock stratum at the working face is not greater than 30 MPa, mechanized mining is carried out by using a coal mining machine (1) to directly cut the rock stratum; When the uniaxial compressive strength of the rock stratum at the working face is greater than 30MPa and not greater than 6MPa, blasting is used to assist in rock breaking; When the uniaxial compressive strength of the rock formation at the working face is greater than 60MPa, directional slit orthogonal hydraulic fracturing is used to assist in rock breaking.

5. A rock burst coal seam quarrying and coal caving anti-bumping safety mining method according to claim 4, characterized in that: The process of using blasting to assist rock breaking also includes: Several blasting holes are arranged in the middle of the mined rock stratum in a straight line. The charging depth is the sum of twice the daily mining footage and the sealing length, and the sealing length is not less than one third of the total length of the borehole. The borehole diameter is not greater than 42mm, the distance between adjacent boreholes is 5-10m, and the charging amount of a single hole is not more than 10kg.

6. A rock burst coal seam quarrying and coal caving anti-rock burst safety mining method according to claim 4, characterized in that: The process of using directional slotted orthogonal hydraulic fracturing to assist in rock breaking also includes: In the horizontal tunnels below the rock working face and in the rock working face, a drilling rig is used to construct perpendicular holes into the mined rock layer, and then a directional pre-crack is formed in the drill hole through a cutting device. Finally, the space close to the pre-crack is sealed by a sealer and high-pressure water injection is performed to expand the pre-crack.

7. A method for safe mining in rock burst coal seam quarrying and coal caving to prevent rock burst according to claim 6, characterized in that: The construction is carried out in the middle of the mining height within the mining rock working face and in the middle of the two lanes of the rock working face; the borehole diameter is 45-65mm; the borehole depth is greater than 100m; the borehole spacing is 10-50m; the pre-crack cutting groove is greater than 2 times the borehole diameter; the pre-crack spacing at different positions in the same borehole is 5-10m; the length of the sealer depends on the pre-crack spacing and is set to 1-2m; the borehole is parallel to the rock layer surface; the hydraulic fracturing pressure range: 10-40Mpa; Among them, the estimated starting pressure required for hydraulic fracturing is: ； Where p is the estimated starting pressure required for hydraulic fracturing, in MPa, b is the short semi-axis length of the pre-crack, in m, a is the long semi-axis length of the pre-crack, in m, is the maximum principal stress in the fracture working surface area, is the minimum principal stress in the fracture working surface area, It is the tensile strength of rock formation at the fracture point, in MPa.

8. The method for safe mining in rock burst coal seam quarrying and coal caving to prevent rock burst according to claim 1, characterized in that: In step S3, it also includes: The mined rock is transported to an underground gangue chamber or a gangue filling working face via a front scraper conveyor (3), a transfer machine (6) and a belt conveyor in sequence.

9. The method for safe mining in rock burst coal seam quarrying and coal caving to prevent rock burst according to claim 1, characterized in that: In step S4, it also includes: The collapsed coal is transported to the crusher (7) through the rear scraper conveyor (4) and the transfer machine (6) for crushing, and then transported to the coal bunker through the belt conveyor (8) and lifted to the ground through the main shaft.

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