Mining method for high-gas coal seams using hydraulic fracturing pressure relief and high-extraction tunneling

Abstract

The present invention belongs to the field of rock burst and gas prevention in coal mines, and relates to a method for mining high-gas coal seams that utilizes hydraulic fracturing to relieve pressure and high-pressure extraction tunnels. The method comprises constructing a high-pressure extraction tunnel, constructing hydraulic fracturing holes and fracturing in a return air chute; constructing through-layer holes from the high-pressure extraction tunnel to the return air chute; excavating the return air chute and ventilating the coal; constructing hydraulic fracturing holes and fracturing in a cut-hole; constructing through-layer holes from the end of the high-pressure extraction tunnel to the cut-hole; excavating the cut-hole and ventilating the coal; connecting the return air chute with the return air tunnel; constructing through-layer holes and fracturing in the return air chute; constructing hydraulic fracturing holes and fracturing in a transport chute; excavating the transport chute and ventilating the coal, and then recovering the coal from the working face. The present invention relieves pressure before tunnel excavation, forms a smooth airflow path for gas extraction before and during tunnel excavation, and can quickly extract newly generated gas from the face. Gas extraction can continue during mining, ensuring the safety of the entire production process.

Description

Technical Field

[0001] The present invention belongs to the field of coal mine rock burst and gas prevention and control, and particularly relates to a high-gas coal seam mining method that cooperates with hydraulic fracturing pressure relief and high-extraction tunneling. Background Art

[0002] Gas is easily attached to underground coal seams. Gas is a toxic gas that is flammable and explosive, making it detrimental to coal production. In coal seams with rock bursts, the gas problem is even more prominent. In existing technologies, there are various means of controlling rock bursts and gas. During tunnel excavation, long boreholes can be constructed to decompress the tunnel and pre-extract gas. Alternatively, through-layer boreholes can be constructed in the bottom rock tunnel to pre-extract gas before tunnel excavation. After tunnel excavation is completed and before coal seam mining, along-layer boreholes can be constructed in the tunnel to fractur e the coal seam to decompress it and extract gas. The coal seam can then be mined using the longwall collapse method. When the gas content is very high, high-extraction tunnels constructed in the top rock layer can also be used during coal seam mining to extract the gas generated by decompression during coal seam mining. These means have greatly improved the effectiveness of rock bursts and gas control, and have essentially resolved the hazards of rock bursts and gas to coal mining. For high-gas coal seams, especially those with rock bursts, a combination of measures is typically used, but this results in low coal production efficiency. Therefore, how to integrate existing rock burst and gas control methods to achieve a more-than-two-plus effect and improve tunneling speed and working face production efficiency has become a research hotspot. Summary of the Invention

[0003] In view of the above-mentioned deficiencies of the prior art, the present invention proposes a method for mining high-gas coal seams by combining hydraulic fracturing pressure relief with high-pressure extraction, which includes the following steps:

[0004] S1: Construction towards the high-extraction roadway; hydraulic fracturing drilling is carried out along the axial direction of the return air chute from the main transport roadway to hydraulically fracture and decompress the return air chute and the nearby coal and rock masses; through-layer drilling is carried out from the high-extraction roadway towards the return air chute;

[0005] S2: Excavate the return air chute and ventilate. The air flows from the transport tunnel to the return air chute, and then through the through-layer drilling to the high-extraction tunnel;

[0006] S3: Hydraulic fracturing drilling is carried out along the axial direction of the cut hole from the return air chute to decompress the cut hole and the coal and rock mass nearby by hydraulic fracturing; through-layer drilling is carried out from the end of the high-extraction roadway to the cut hole;

[0007] S4: Excavate and cut the eye and ventilate. The air flows from the transport tunnel to the return air chute and then to the cut eye, and then through the through-layer drilling to the high-extraction tunnel;

[0008] S5: Disconnect the return air chute from the main transport tunnel, excavate the return air chute in the reverse direction to connect it with the return air tunnel; drill holes along the bedding from the return air chute toward the transport tunnel, and perform hydraulic fracturing to relieve pressure; drill hydraulic fracturing holes along the axial direction of the transport tunnel from the main transport tunnel to perform hydraulic fracturing to relieve pressure on the transport tunnel and the nearby coal and rock masses;

[0009] S6: Excavation of transport tunnel, the air flows from the transport tunnel to the transport tunnel, partly through the bedding drill holes and their hydraulic fractures to the return air tunnel, and partly through the entire transport tunnel through the cut hole, and finally to the return air tunnel;

[0010] S7: After the tunnel excavation is completed, the high-extraction tunnel and the seam drill holes are retained; before mining, the gas in the coal seam in the working face mining area is extracted by using the seam drill holes; then the working face mining area is mined, and during the mining process, the gas in the coal seam in the working face mining area is extracted by using the high-extraction tunnel and the seam drill holes.

[0011] Preferably, in step S1, the through-layer drill holes are arranged at intervals along the strike.

[0012] Preferably, in step S2, ventilation is performed before excavation.

[0013] Preferably, in step S2, the excavated return air chute is closed and supported at a certain distance behind the tunnel face, and the through-layer drill holes in the closed support area are no longer connected to the return air chute.

[0014] Preferably, in step S3, the bottom sections of the through-layer drill holes are arranged at intervals along the length direction of the cut hole.

[0015] Preferably, in step S4, ventilation is performed before excavation.

[0016] Preferably, in step S4, the tunneling cutout is closed and supported at a certain distance behind the tunnel face, and the through-layer drill holes in the closed support area are no longer connected to the cutout.

[0017] Preferably, in step S5, the bedding drill holes are arranged at intervals along the strike direction, and the bedding drill holes are constructed to within the range of the transport drift.

[0018] Preferably, in step S5, the hydraulic fractures of the bedding boreholes are connected to each other and the hydraulic fractures of the bedding boreholes are connected to the hydraulic fractures of the hydraulic fractures of the hydraulic fractures of the hydraulic fractures in the transport chute.

[0019] Preferably, in step S6, ventilation is performed before excavation.

[0020] The beneficial technical effects of the present invention are: 1. The mining method of the present invention utilizes high-extraction tunnel construction to drill through layers, and cooperates with the hydraulic fracturing drill holes and fracturing cracks in the return air chute and the cut eye to form a smooth path for extracting gas, which can relieve the pressure on the tunnel and can quickly extract the newly generated gas at the face, avoiding the impact of impact ground pressure and gas on the excavation of the return air chute and the cut eye.

[0021] 2. The mining method of the present invention first constructs a return air chute, and constructs a layer drill hole in the return air chute to connect with the hydraulic fracturing drill hole and the fracturing crack in the transport chute, thereby unloading the coal seam in the transport chute and the mining area, and forming a smooth path for extracting gas. It can also quickly extract the newly generated gas at the face, avoiding the impact of impact ground pressure and gas on the excavation of the transport chute.

[0022] 3. The present invention can relieve pressure and extract gas from the entire working face during the excavation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic plan view of the arrangement of drilling holes during excavation of the return air chute according to the present invention;

[0024] Figure 2 This is a cross-sectional diagram of the arrangement of drilling holes during excavation of the return air chute according to the present invention;

[0025] Figure 3 This is a schematic plan view of the arrangement of drilling holes during eye cutting and excavation according to the present invention;

[0026] Figure 4 This is a cross-sectional diagram of the arrangement of drilling holes during eye cutting and excavation according to the present invention;

[0027] Figure 5 This is a schematic plan view of the arrangement of drilling holes during excavation of the transport trench according to the present invention;

[0028] Figure 6 This is a schematic plan view of the present invention after the tunnel excavation is completed and the working face is mined;

[0029] In the figure, 1-return air main tunnel or return air uphill, 2-transport main tunnel or transport uphill, 3-return air chute, 4-stretch high-extraction tunnel, 5-transport chute, 6-through-layer drilling, 7-hydraulic fracturing drilling, 8-cutting eye, 9-bed drilling. DETAILED DESCRIPTION

[0030] The specific embodiments of the present invention are described below with reference to the accompanying drawings.

[0031] like Figures 1-6 As shown, the present invention proposes a method for mining high-gas coal seams by combining hydraulic fracturing pressure relief with high-pressure extraction, which includes the following steps:

[0032] S1: If Figure 1-Figure 2As shown, a strike high extraction tunnel 4 is constructed along the strike direction on the roof inside the return air chute 3. The common construction location and function of the strike high extraction tunnel 4 (extraction of gas generated during mining at the working face) are well known in the art and will not be described in detail here. The strike high extraction tunnel 4 is constructed in the rock stratum and is not affected by gas disasters and coal seam impact.

[0033] A hydraulic fracturing borehole 7 is constructed in the axial center of the return air chute 3 from the main transport tunnel 2 to hydraulically fracture and depressurize the return air chute 3 and the coal and rock mass in the vicinity thereof; the hydraulic fracturing borehole 7 is preferably a borehole with a larger diameter; preferably, proppant is injected into the fracture after hydraulic fracturing to support the fracture;

[0034] Constructing through-layer drill holes 6 from the high-extraction lane 4 to the hydraulic fracturing range of the return air chute 3, wherein the through-layer drill holes 6 are connected to the hydraulic fracturing drill holes 7 and their fracturing fissures; the through-layer drill holes 6 are arranged in rows and spaced apart along the strike direction;

[0035] S2: If Figure 1-Figure 2 As shown, negative pressure ventilation is carried out in the strike high extraction lane 4. The air flow direction is: from the transport lane 2, into the hydraulic fracturing borehole 7 and its fracturing fissures at the return air chute 3, carrying gas in the coal seam, and then through the through-layer borehole 6 to the strike high extraction lane 4;

[0036] Under the above ventilation path, the return air chute 3 is excavated from the transport tunnel 2. Before excavation, the hydraulic fracturing of the hydraulic fracturing boreholes 7 has relieved the pressure of the coal seam in the return air chute 3, and pre-extraction of gas has been carried out, which can provide a relatively safe environment for the excavation of the return air chute 3; the excavated return air chute 3 is closed and supported at a certain distance behind the tunnel face, and the through-layer drill holes 6 in the closed support area are no longer connected to the return air chute 3; during the excavation of the return air chute 3, part of the newly generated gas at the tunnel face flows out to the high-extraction tunnel 4 through the through-layer drill holes 6 exposed near the tunnel face, and part of the gas enters the through-layer drill holes 6 from the hydraulic fracturing boreholes 7 and their fracturing cracks in the unexcavated return air chute 3 and then flows out to the high-extraction tunnel 4; the coal dust and gas generated by excavation at the tunnel face flow through the same path;

[0037] S3: If Figure 3-Figure 4 As shown, a hydraulic fracturing borehole 7 is constructed in the axial center of the cut hole 8 from the return air chute 3 to hydraulically fracture and decompress the cut hole 8 and the coal and rock mass nearby; the hydraulic fracturing borehole 7 is preferably a borehole with a larger diameter; preferably, after hydraulic fracturing, a proppant is injected into the fracture to support the fracture;

[0038] Constructing through-layer drill holes 6 from the end of the high-extraction lane 4 to the hydraulic fracturing range of the cut-hole 8, wherein the through-layer drill holes 6 are connected to the hydraulic fracturing drill holes 7 and the fracturing fissures; the bottom sections of the through-layer drill holes 6 are arranged at intervals along the length direction of the cut-hole 8;

[0039] S4: As Figure 3-Figure 4As shown, negative pressure ventilation is carried out in the strike high extraction lane 4. The air flow direction is: from the transport lane 2 into the return air chute 3, then into the hydraulic fracturing borehole 7 at the cut eye 8 and its fracturing fissures, after carrying gas in the coal seam, through the through-layer borehole 6 to the strike high extraction lane 4;

[0040] Under the above ventilation path, the cut eye 8 is excavated from the return air chute 3. Before excavation, the coal seam in the cut eye 8 has been depressurized by hydraulic fracturing of the hydraulic fracturing borehole 7, and gas has been pre-extracted, which can provide a relatively safe environment for the excavation of the cut eye 8. The cut eye 8 that has been excavated is closed and supported at a certain distance behind the tunnel face, and the through-layer boreholes 6 in the closed support area are no longer connected to the cut eye 8. During the excavation of the cut eye 8, part of the newly generated gas at the tunnel face flows out to the high-extraction lane 4 through the through-layer boreholes 6 exposed near the tunnel face, and part enters the through-layer boreholes 6 from the hydraulic fracturing boreholes 7 and their fracturing cracks in the unexcavated cut eye 8 and then flows out to the high-extraction lane 4. The coal dust and gas generated during excavation at the tunnel face flow through the same path.

[0041] S5: If Figure 5 As shown, disconnect the return air chute 3 from the transport tunnel 2, and reversely excavate the return air chute 3 to connect it with the return air tunnel 1;

[0042] Constructing a hydraulic fracturing borehole 7 from the main transport tunnel 2 at the axial center of the transport chute 5 to hydraulically fracture and depressurize the transport chute 5 and the coal and rock mass nearby; the hydraulic fracturing borehole 7 is preferably a borehole with a larger diameter; preferably, after hydraulic fracturing, proppant is injected into the fracture to support the fracture;

[0043] Constructing bedding boreholes 9 from the return air chute 3 toward the transport chute 5, the bedding boreholes 9 being arranged at intervals along the strike direction and being constructed within the range of the transport chute 5; hydraulic fracturing and decompression of the coal seam is performed through the bedding boreholes 9, the fracturing fissures of the bedding boreholes 9 being interconnected, and the fracturing fissures of the bedding boreholes 9 being connected to the fracturing fissures of the hydraulic fracturing boreholes 7 in the transport chute 5; preferably, after hydraulic fracturing, proppant is injected into the fracturing fissures to support the fracturing fissures;

[0044] S6: As Figure 5 As shown, negative pressure ventilation is carried out using the return air chute 3. The air flows from the main transport tunnel 2 into the hydraulic fracturing borehole 7 and its fracturing fissures in the transport chute 5. Part of the air flows through the bed borehole 9 and its fracturing fissures to the return air chute 3. Part of the air flows through the hydraulic fracturing borehole 7 and its fracturing fissures in the entire transport chute 5 and then flows to the cut hole 8 and then to the return air chute 3. In this process, the air will carry away the gas overflowing from the coal seam.

[0045] Under the above ventilation path, the transport chute 5 is excavated from the transport tunnel 2. Before excavation, the hydraulic fracturing of the hydraulic fracturing boreholes 7 has relieved the pressure of the coal seam in the transport chute 5, and gas extraction has been carried out, which can provide a relatively safe environment for the excavation of the transport chute 5. The excavated transport chute 5 is supported at a certain distance behind the tunnel face, and the bed drill holes 9 are not closed during the support. During the excavation of the transport chute 5, part of the newly generated gas at the tunnel face flows out to the return air chute 3 through the bed drill holes 9 near the tunnel face and their fracturing cracks, and part flows out to the cut eye 8 through the hydraulic fracturing boreholes 7 and their fracturing cracks in the unexcavated transport chute 5, and then flows out to the return air chute 3. The coal dust and gas generated by excavation at the tunnel face flow through the same path.

[0046] S7: As Figure 6 As shown, after the excavation of the tunnel is completed, the strike high-extraction tunnel 4 and the layer drill holes 9 are retained, and the layer drill holes 9 are used to continue to extract the gas in the coal seam in the working face mining area; the working face mining area is mined by a coal mining machine in conjunction with a hydraulic support. During the mining process, the strike high-extraction tunnel 4 and the layer drill holes 9 are continuously used to extract the gas in the coal seam in the working face mining area; at this time, the through-layer drill holes 6 can also improve the connectivity between the goaf and the strike high-extraction tunnel 4, and improve the extraction effect of the strike high-extraction tunnel 4 on the goaf gas.

[0047] The above-mentioned transport main tunnel 2 can also be transport uphill 2, and the corresponding return air main tunnel 1 is return air uphill 1.

[0048] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of methods under the inspiration of the present invention. However, any technical solution that is the same or similar to that of the present application falls within the scope of protection of the present invention.

Claims

1. A method for mining high-gas coal seams by combining hydraulic fracturing pressure relief with high-pressure extraction, characterized in that: The steps include: S1: Construction towards the high-extraction roadway; hydraulic fracturing drilling is carried out along the axial direction of the return air chute from the main transport roadway to hydraulically fracture and decompress the return air chute and the nearby coal and rock masses; through-layer drilling is carried out from the high-extraction roadway towards the return air chute; S2: Excavate the return air chute and ventilate. The air flows from the transport tunnel to the return air chute, and then through the through-layer drilling to the high-extraction tunnel; S3: Hydraulic fracturing drilling is carried out along the axial direction of the cut hole from the return air chute to decompress the cut hole and the coal and rock mass nearby by hydraulic fracturing; through-layer drilling is carried out from the end of the high-extraction roadway to the cut hole; S4: Excavate and cut the eye and ventilate. The air flows from the transport tunnel to the return air chute and then to the cut eye, and then through the through-layer drilling to the high-extraction tunnel; S5: Disconnect the return air chute from the main transport tunnel, excavate the return air chute in the reverse direction to connect it with the return air tunnel; drill holes along the bedding from the return air chute toward the transport tunnel, and perform hydraulic fracturing to relieve pressure; drill hydraulic fracturing holes along the axial direction of the transport tunnel from the main transport tunnel to perform hydraulic fracturing to relieve pressure on the transport tunnel and the nearby coal and rock masses; S6: Excavation of transport tunnel, air flow from the transport tunnel to the transport tunnel, part of the air flow is drilled along the layer to the return air tunnel, and part of the air flow is drilled through the entire transport tunnel and then to the return air tunnel; S7: After the tunnel excavation is completed, the high-extraction tunnel and the seam drill holes are retained; before mining, the gas in the coal seam in the working face mining area is extracted by using the seam drill holes; then the working face mining area is mined, and during the mining process, the gas in the coal seam in the working face mining area is extracted by using the high-extraction tunnel and the seam drill holes.

2. The method for mining high-gas coal seams by combining hydraulic fracturing pressure relief with high-pressure extraction tunneling according to claim 1, characterized in that: In step S1, the through-layer drill holes are arranged at intervals along the strike.

3. The method for mining high-gas coal seams by combining hydraulic fracturing pressure relief with high-pressure extraction according to claim 1, characterized in that: In step S2, ventilation is performed before excavation.

4. The method for mining gassy coal seams by combining hydraulic fracturing pressure relief with high-pressure extraction tunneling according to any one of claims 1 to 3, characterized in that: In step S2, the lagging face performs closed support on the return air chute excavated, and the through-layer drill holes in the closed support area are no longer connected to the return air chute.

5. The method for mining high-gas coal seams by combining hydraulic fracturing pressure relief with high-pressure extraction tunneling according to claim 1, characterized in that: In step S3, the bottom sections of the through-layer drill holes are arranged at intervals along the length direction of the cut hole.

6. The method for mining high-gas coal seams by combining hydraulic fracturing pressure relief with high-pressure extraction tunneling according to claim 1, characterized in that: In step S4, ventilation is performed before excavation.

7. The method for mining high-gas coal seams by combining hydraulic fracturing pressure relief with high-pressure extraction tunneling according to claim 1, 5 or 6, characterized in that: In step S4, the lagging face performs closed support on the cut hole excavated, and the through-layer drill holes in the closed support area are no longer connected to the cut hole.

8. The method for mining high-gas coal seams by combining hydraulic fracturing pressure relief with high-pressure extraction tunneling according to claim 1, characterized in that: In step S5, the bedding drill holes are arranged at intervals along the strike direction, and the bedding drill holes are constructed to within the range of the transport drift.

9. The method for mining high-gas coal seams by combining hydraulic fracturing pressure relief with high-pressure extraction tunneling according to claim 8, characterized in that: In step S5, the hydraulic fractures of the bedding boreholes are connected to each other and the hydraulic fractures of the bedding boreholes are connected to the hydraulic fractures of the hydraulic fracture boreholes in the transport chute.

10. The method for mining high-gas coal seams with hydraulic fracturing pressure relief and high-pressure extraction coordinated with claim 9, characterized in that: In step S6, ventilation is performed before excavation.

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