Gas extraction method based on floor rock excavation and hole expansion

Abstract

The present application belongs to the field of coal mine gas control, and particularly relates to a floor gas extraction control method based on floor rock excavation and hole expansion. The present application forms a U-shaped large-diameter floor extraction hole system connected with the upward transportation roadway and the upward air return roadway in the soft rock floor on the basis of the existing U-shaped single-lane arrangement system, wherein the air return floor extraction hole is located in the floor mining fissure zone directly below the O-shaped ring of the stoping working face, thereby being connected with the goaf after the working face is mined. The U-shaped large-diameter floor extraction hole system constitutes a second air intake and return system, which is independent of the air intake and return system of the U-shaped single-lane arrangement system, the air volume can be freely adjusted, the interference with the air intake and return system of the U-shaped single-lane arrangement system can be reduced, the gas control effect is improved, and the emergency treatment capacity can be increased. By setting the U-shaped large-diameter floor extraction hole system, the existing floor extraction roadway or roof extraction roadway can be replaced, thereby greatly reducing the construction workload of the floor extraction system.

Description

Technical Field

[0001] This invention belongs to the field of coal mine gas control, specifically relating to a bottom gas extraction method based on bottom rock excavation and hole enlargement. Background Technology

[0002] High-gas coal seams refer to coal seams that adsorb a large amount of methane. When tunneling and mining in high-gas coal seams, it is necessary to pre-extract the methane to prevent gas-related accidents during tunneling and coal seam recovery. Furthermore, methane drainage is required during coal seam recovery. In existing technologies, the roadway is typically divided into several sections along its axial direction. Before tunneling each section, in-seam boreholes are drilled along the roadway axis for pre-extraction of methane, and then that section is tunneled. This process is repeated until the entire roadway is excavated. However, if the in-seam boreholes are long, the pre-extraction effect is poor; if the in-seam boreholes are short, there are many sections, resulting in low tunneling efficiency. During the longwall mining process, i.e. when mining the coal seam, top or bottom drainage roadways are generally used to assist the return airway in removing gas overflowing from the coal seam. However, top or bottom drainage roadways are constructed in rock strata with high hardness, resulting in slow construction progress and affecting the overall production progress. Furthermore, the air allocated to the top or bottom drainage roadways comes from the transport roadway of the working face. Since the return airway of the working face also needs to ensure air volume, it is difficult to increase the gas emission rate when the gas volume increases abnormally, resulting in poor emergency response.

[0003] Therefore, improving the tunneling efficiency of high-gas coal seams and enhancing gas emission during coal mining have become urgent problems to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a bottom-drainage gas control method based on bottom-plate rock excavation and borehole enlargement, comprising the following steps: S1: Coal is extracted axially along the first transport level roadway, and simultaneously axially along the first return air level roadway; S2: Excavate the first transport level tunnel from the transport uphill direction, and simultaneously excavate the first return air level tunnel from the return air uphill direction; At the same time, the following bottom extraction hole construction is carried out: the first return air bottom extraction hole is constructed in the bottom plate crack area directly below the O-ring of the first working face from the return air uphill, and the first air inlet bottom extraction hole is constructed in the bottom plate crack area directly below the O-ring of the second working face from the transport uphill, and the two are connected by the first connecting section. S3: Extract coal along the axial direction of the first cut, and advance the first cut; S4: The first working face of the longwall mining. During the longwall mining process, air is introduced from the first transport roadway and discharged through the first return air roadway after passing through the coal mining area. At the same time, air is introduced from the first bottom air intake hole, discharged through the first connecting section and then through the first bottom air exhaust hole. S5: Coal is extracted along the axial direction of the second transport level roadway; at the same time, the second return air level roadway is prepared, and coal is extracted along the axial direction of the second cut-out. S6: Excavate the second transport level tunnel from the transport uphill, and simultaneously excavate the second cut-out; At the same time, the following bottom extraction hole construction is carried out: the first air intake bottom extraction hole is connected to the return air uphill hole as the second return air bottom extraction hole; at the same time, the second air intake bottom extraction hole is constructed in the bottom plate crack area directly below the O-ring of the third working face from the transport uphill hole, and the second return air bottom extraction hole is connected through the first connecting section. S7: The second working face is being mined. During the mining process, air is introduced from the second transport roadway and discharged through the second return air roadway after passing through the coal mining area. At the same time, air is introduced from the second bottom air intake hole, discharged through the second connecting section, and discharged through the second bottom air intake hole. S8: Repeat steps S5-S7 to carry out subsequent roadway excavation and coal seam mining.

[0005] Preferably, the coal extraction and excavation method for the first haulage level, the first return air level, the first cut-off, the second haulage level, and the second cut-off is as follows: a. At one end of the haulage roadway, a pilot hole is drilled along the axial direction of the haulage roadway from the upper right side, and a hydraulic fracturing borehole is drilled along the axial direction of the haulage roadway from the lower left side; b. Mechanical coal extraction is performed along the axial direction of the pilot hole to form a mechanical coal extraction hole; c. Hydraulic jet coal extraction is performed along the axial direction of the mechanical coal extraction hole to form a hydraulic coal extraction hole, and a loosening ring is formed outside the hydraulic coal extraction hole; d. Hydraulic fracturing is performed on the haulage roadway from far to near along the axial direction of the hydraulic fracturing borehole, and at least some of the fracturing fractures connect to the hydraulic coal extraction hole; e. High-pressure water is injected from the hydraulic fracturing borehole, and the injected water enters the hydraulic coal extraction hole from the fracturing fracture and returns; then the haulage roadway is excavated.

[0006] Preferably, before the excavation of the mining roadway, the process further includes step f: high-pressure compressed air from the hydraulic fracturing borehole, with the compressed air entering the hydraulic coal extraction hole from the fracturing fracture and returning.

[0007] Preferably, in step S2, a first hydraulic fracturing directional borehole is drilled and enlarged on the bottom rock stratum from the return air uphill section, forming a first return air bottom extraction hole in the straight section. Simultaneously, a second hydraulic fracturing directional borehole is drilled and enlarged on the bottom rock stratum from the transport uphill section, forming a first air intake bottom extraction hole in the straight section. The inclined sections of the first and second hydraulic fracturing directional boreholes are enlarged to form a first connecting section that connects the first air intake bottom extraction hole and the first return air bottom extraction hole. In step S6, a third hydraulic fracturing directional borehole is drilled and enlarged on the bottom rock stratum from the transport uphill section, forming a second air intake bottom extraction hole in the straight section and a second connecting section that connects to the second return air bottom extraction hole in the inclined section.

[0008] Preferably, the enlargement steps for the first hydraulic fracturing directional drilling, the second hydraulic fracturing directional drilling, and the third hydraulic fracturing directional drilling are: mechanical rock removal and hydraulic jet rock removal.

[0009] Preferably, in step S2, before mechanically removing rock from the first and second hydraulic fracturing directional boreholes, the method further includes: performing hydraulic fracturing based on the straight section of the first hydraulic fracturing directional borehole, and connecting the resulting bottom plate fracturing fracture to the first working face; simultaneously, performing hydraulic fracturing based on the straight section of the second hydraulic fracturing directional borehole, and connecting the resulting bottom plate fracturing fracture to the second working face; in step S6, performing hydraulic fracturing based on the straight section of the third hydraulic fracturing directional borehole, and connecting the resulting bottom plate fracturing fracture to the third working face.

[0010] Preferably, the first connecting segment is located outside the first incision; the second connecting segment is located outside the second incision.

[0011] Preferably, the first hydraulic fracturing directional borehole and the first return air bottom extraction borehole formed therefrom are located entirely in soft rock and are connected by a connecting tunnel near the return air uphill section; the second hydraulic fracturing directional borehole and the first intake air bottom extraction borehole formed therefrom are located entirely in soft rock and are connected by a connecting tunnel near the transport uphill section; the third hydraulic fracturing directional borehole and the second intake air bottom extraction borehole formed therefrom are located entirely in soft rock and are connected by a connecting tunnel near the transport uphill section.

[0012] Preferably, in step S6, before connecting the first air inlet bottom extraction hole with the return air uphill hole, the method further includes filling the first connecting section with filling material.

[0013] Preferably, in step S4, the first transport level roadway is left along the goaf; in step S5, the goaf-leaving roadway based on the first transport level roadway is connected with the return air uphill roadway to form the second return air level roadway.

[0014] Preferably, in step S7, the second transport level roadway is left along the goaf.

[0015] Key technical means and beneficial technical effects: 1. Based on the existing U-shaped single-lane layout system, this invention forms a U-shaped large-diameter bottom extraction system in the soft rock of the floor by excavating and enlarging holes, connecting the transport uphill and return air uphill systems. The return air bottom extraction hole is located in the floor mining fracture zone directly below the O-ring of the working face, thus connecting the goaf after the working face is mined. The U-shaped large-diameter bottom extraction system constitutes a second intake and return air system, independent of the intake and return air system of the U-shaped single-lane layout system. The air volume can be freely adjusted, which can reduce interference with the intake and return air system of the U-shaped single-lane layout system, improve the gas control effect, and increase emergency response capabilities (in cases of large gas emission concentration and emission volume).

[0016] 2. This invention, by setting up a U-shaped large-diameter bottom extraction system, can replace existing bottom or top extraction roadways. Because the U-shaped large-diameter bottom extraction system has a large aperture and strong connectivity with the goaf (located in the floor mining fracture zone directly below the O-ring of the longwall face, and with existing floor fracturing fractures), and because the air volume can be freely adjusted without interfering with the intake and return air systems of the U-shaped single-roadway system, the extraction effect is guaranteed. This significantly reduces the amount of roadway excavation work, significantly reduces the construction workload of the bottom extraction system, and can be carried out in parallel with the longwall roadway excavation work, greatly reducing the preparation time for longwall face mining. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the first working surface and its bottom extraction hole of the present invention; Figure 2 This is a schematic cross-sectional view of the first working surface and its bottom extraction hole of the present invention; Figure 3 This is a schematic diagram of the cross-sectional view of the bottom extraction hole and the bottom plate crack during the mining of the first working face of the present invention; Figure 4 This is a schematic diagram of the second working surface and its bottom extraction hole of the present invention; Figure 5 This is a schematic cross-sectional view of the second working surface and its bottom extraction hole of the present invention; Figure 6 This is a schematic diagram of the cross-sectional view of the bottom extraction hole and the bottom plate crack during the mining of the second working face of the present invention; Figure 7 This is a schematic cross-sectional view of the construction of the coal extraction guide hole in the mining roadway of the present invention. Figure 8 This is a schematic diagram of the construction cross-section of the coal extraction hole of the coal extraction machine in the mining roadway of the present invention; Figure 9 This is a schematic diagram of the construction cross-section of the hydraulic coal extraction hole in the coal extraction roadway of the present invention. Figure 10 This is a schematic cross-sectional view of the hydraulic fracturing construction of the coal extraction roadway in this invention. Figures 1-6 In the middle: 11-First haulage level roadway; 12-First cut-in; 13-First return air level roadway; 14-First intake bottom extraction hole; 15-First connecting section; 16-First return air bottom extraction hole; 21-Second haulage level roadway; 22-Second cut-in; 23-Second return air level roadway; 24-Second intake bottom extraction hole; 25-Second connecting section; 26-Second return air bottom extraction hole; 31-Return air incline; 32-Hailage incline; 33-Stop mining line; 34-Coal seam; 35-Goaf; 36-Sealing wall; 37-Sealing material; 38-Floor fracturing fissure; 39-Floor mining fissure zone.

[0018] Figures 7-10In the middle: 01-Return roadway; 02-Diagonal line; 03-Pilot hole; 04-Hydraulic fracturing borehole; 05-Mechanical coal extraction hole; 06-Hydraulic coal extraction hole; 07-Loosening ring; 08-Fracturing fissure. Detailed Implementation

[0019] The invention will now be further described with reference to the accompanying drawings.

[0020] The embodiments of the present invention are based on the geological conditions of a panel of the No. 15 coal seam in Sijiazhuang Coal Mine of Lu'an Chemical Group. The No. 15 coal seam is a high-gas outburst coal seam. The average burial depth of the No. 15 coal seam in this panel is 550m, the dip angle is 5°, and the height is 5.5m. The original working face was designed with top drainage roadways and bottom drainage roadways for gas control. The roadway excavation task was heavy, and the overall production efficiency needed to be improved.

[0021] Example 1

[0022] like Figure 1-6 As shown, the bottom gas extraction method based on bottom slab rock excavation and borehole enlargement of the present invention includes the following steps: S1: As Figures 1-3 As shown; coal is removed from the first transport level 11 along the axial direction of the transport uphill 32 to achieve pressure relief and gas control in the first transport level 11; at the same time, coal is removed from the first return air level 13 along the axial direction of the first return air level 13 to achieve pressure relief and gas control in the first return air level 13.

[0023] S2: As Figures 1-3 As shown; the first haulage level roadway 11 is being excavated from the haulage uphill 32 along the direction of coal seam 34, and the first return air level roadway 13 is being excavated from the return air uphill 31 along the direction of coal seam 34; at the same time, the following bottom extraction hole construction work is being carried out: From the return air incline 31, a first hydraulic fracturing directional borehole is constructed in the same layer of soft rock at the bottom of the first working face. The straight section of the first hydraulic fracturing directional borehole is located on the side of and parallel to the first return air tunnel 13, and the inclined section is located outside the first cut-in 12. Simultaneously, from the transport incline 32, a second hydraulic fracturing directional borehole is constructed in the same layer of soft rock at the bottom of the second working face. The straight section of the second hydraulic fracturing directional borehole is located on the side of and parallel to the first transport tunnel 11, and the inclined section is located outside the first cut-in 12 and connected to the inclined section of the first hydraulic fracturing directional borehole. The diameters of the first and second hydraulic fracturing directional boreholes are 113 mm. Then, hydraulic fracturing is performed based on the straight section of the first hydraulic fracturing directional borehole, so that the resulting bottom fracturing fracture 38 connects to the first working face. Simultaneously, hydraulic fracturing is performed based on the straight section of the second hydraulic fracturing directional borehole. Hydraulic fracturing is performed, and the resulting fracturing fracture 38 in the bottom plate connects to the second working face. Then, mechanical rock removal is carried out on the first hydraulic fracturing directional borehole and the second hydraulic fracturing directional borehole, increasing their diameter to 300 mm. Finally, hydraulic jet rock removal is performed on the first hydraulic fracturing directional borehole, forming the first return air bottom extraction hole 16 in the straight section and the first connecting section 15 in the inclined section. At the same time, hydraulic jet rock removal is performed on the second hydraulic fracturing directional borehole, forming the first air intake bottom extraction hole 14 in the straight section and the first connecting section 15 in the inclined section. At this point, the diameters of the first and second hydraulic fracturing directional boreholes are increased to 600 mm. The above-mentioned process of hydraulic fracturing directional borehole, mechanical rock removal, and hydraulic jet rock removal in soft rock corresponds one-to-one with the existing coal mining drilling, mechanical coal mining, and hydraulic jet coal mining processes, except that the object of construction is changed from coal to soft rock.

[0024] The first return air bottom extraction hole 16 and the first air intake bottom extraction hole 14 are located in the bottom plate mining fracture zone 39 directly below the O-ring formed after the mining of the first working face and the second working face, respectively. The first return air bottom extraction hole 16 and the first air intake bottom extraction hole 14 extend beyond the working face in terms of orientation, that is, the first connecting section 15 is located outside the first cut 12, so as to avoid damaging the first connecting section 15 after the mining of the first working face.

[0025] The first hydraulic fracturing directional borehole and the first return air bottom extraction hole 16 formed therefrom can be located entirely in soft rock and connected by a connecting roadway near the return air incline 31; or the straight section of the first hydraulic fracturing directional borehole and the first return air bottom extraction hole 16 formed therefrom is entirely parallel to the first return air level roadway 13, but a portion near the return air incline 31 gradually slopes downward from the return air incline 31 to achieve the construction of the first hydraulic fracturing directional borehole and the first return air bottom extraction hole 16 in the soft rock floor below the coal seam 34. In the middle; the second hydraulic fracturing directional borehole and the first air intake bottom extraction hole 14 formed therefrom can be located entirely in soft rock and connected by a connecting roadway near the transport incline 32; or the straight section of the second hydraulic fracturing directional borehole and the first air intake bottom extraction hole 14 formed therefrom is generally parallel to the first transport level roadway 11, but a part near the transport incline 32 gradually slopes downward from the transport incline 32 to realize that the second hydraulic fracturing directional borehole and the first air intake bottom extraction hole 14 formed therefrom are constructed in the soft rock of the floor below the coal seam 34.

[0026] S3: As Figures 1-3 As shown; coal is removed from the first transport level 11 along the first cut 12 axial direction to achieve pressure relief and gas control in the first cut 12; the first cut 12 is tunneled from the first transport level 11 along the coal seam 34 to the first return air level 13.

[0027] S4: As Figures 1-3 As shown; coal seam 34 in the first working face is mined from the first cut-off point 12 toward the stop line 33, and the first transport roadway 11 is left along the goaf; during the mining process, air is introduced from the first transport roadway 11, and then the gas overflowing from the mining of coal seam 34 is discharged from the first working face through the first return air roadway 13; after the mining of the first working face, a floor mining fracture zone 39 is generated in the lower part of the goaf 35, and the floor mining fracture zone 39 and the floor pressure fracture 38 are connected to the first return air bottom extraction hole 16 and the O-ring of the first working face; therefore, air is introduced from the first intake air bottom extraction hole 14, passes through the first connecting section 15 and reaches the first return air bottom extraction hole 16, and the gas overflowing from the mining of coal seam 34 can be extracted through the first return air bottom extraction hole 16; the air entering the first transport roadway 11 and the first intake air bottom extraction hole 14 both originate from the transport uphill 32, and the air discharged from the first return air roadway 13 and the first return air bottom extraction hole 16 is discharged through the return air uphill 31.

[0028] The first transport level 11, the coal mining area of ​​the coal mining machine, and the first return air level 13 form an intake and return air system. Due to limitations imposed by workers and equipment, the air volume of this system should not be too large or too small. The first intake bottom extraction hole 14, the first connecting section 15, and the first return air bottom extraction hole 16 form another intake and return air system, solely for gas extraction. Since there are no equipment or workers inside, the intake and return air volumes can be freely controlled. When the gas emission concentration and volume are high, the air volume of this system can be increased to improve gas emission efficiency. Furthermore, because there are no equipment or workers inside, the cross-sectional size can be reduced to increase the air velocity and ensure sufficient gas extraction volume. Therefore, only a 600mm diameter enlarged borehole is needed for gas extraction, eliminating the need for excavating a large-diameter bottom extraction roadway.

[0029] like Figure 4 As shown, after the first working face is mined out, the first return airway 13 is sealed with a sealing wall 36, and the first return airway bottom extraction hole 16 is sealed with sealing material 37.

[0030] S5: As Figures 4-6 As shown; coal is removed from the second transport level 21 along the axis of the transport uphill 32 to achieve pressure relief and gas control in the second transport level 21; at the same time, the goaf retention roadway based on the first transport level 11 is connected to the return air uphill 31 as the second return air level 23, and coal is removed from the second return air level 23 along the axis of the second cut-out 22 to achieve pressure relief and gas control in the second cut-out 22.

[0031] S6: As Figures 4-6 As shown; the second haulage level 21 is excavated from the haulage uphill 32 along the strike of coal seam 34, and simultaneously the second cut-in 22 is excavated from the second return air level 23 along the dip of coal seam 34 to the second haulage level 21; at the same time, the following bottom extraction hole construction work is carried out: The first connecting section 15 is filled with filling material, and the first intake bottom extraction hole 14 is connected to the return air incline 31 as the second return air bottom extraction hole 26. This connection can be achieved by drilling or by connecting small-section roadways. Simultaneously, the third hydraulic fracturing directional borehole is constructed in the soft rock of the floor slab and below the third working face from the transport incline 32. The straight section of the third hydraulic fracturing directional borehole is located on the side of the second transport level 21, parallel to the second transport level 21, and the inclined section is located outside the second cut-out 22 and connected to the second return air bottom extraction hole 26. The diameter of the third hydraulic fracturing directional borehole is 113 mm. Then, based on the straight section of the third hydraulic fracturing directional borehole... Hydraulic fracturing is performed on the line segment, and the resulting bottom plate fracturing fracture 38 connects to the third working face; then, mechanical rock removal is performed on the third hydraulic fracturing directional borehole to enlarge the diameter to 300mm; finally, hydraulic jet rock removal is performed on the third hydraulic fracturing directional borehole to enlarge the diameter to 600mm, forming the second air intake bottom extraction hole 24 on the straight section and the second connecting section 25 on the inclined section; the above-mentioned process of hydraulic fracturing directional drilling, mechanical rock removal, and hydraulic jet rock removal in soft rock corresponds one-to-one with the existing coal mining drilling, mechanical coal mining, and hydraulic jet coal mining processes, except that the object of construction is changed from coal to soft rock.

[0032] The second return air bottom extraction hole 26 and the second intake air bottom extraction hole 24 are located in the bottom plate mining fracture zone 39 directly below the O-ring formed after the mining of the second working face and the third working face, respectively. The second return air bottom extraction hole 26 and the second intake air bottom extraction hole 24 extend beyond the working face in terms of orientation, that is, the second connecting section 25 is located outside the second cut 22, so as to avoid damaging the second connecting section 25 after the mining of the second working face.

[0033] The third hydraulic fracturing directional borehole and the second air intake bottom extraction hole 24 formed therefrom can be located entirely in soft rock and connected by a connecting roadway near the transport incline 32; or the straight section of the third hydraulic fracturing directional borehole and the second air intake bottom extraction hole 24 formed therefrom is parallel to the second transport level roadway 21, but a portion near the transport incline 32 gradually slopes downward from the transport incline 32 to realize that the third hydraulic fracturing directional borehole and the second air intake bottom extraction hole 24 formed therefrom are constructed in the soft rock floor below the coal seam 34.

[0034] S7: As Figures 4-6As shown; coal seam 34 in the second working face is mined from the second cut-in 22 toward the stop line 33, and the second transport roadway 21 is left along the goaf; during the mining process, air is introduced from the second transport roadway 21, and then the gas overflowing from the mining of coal seam 34 is discharged from the second working face through the second return air roadway 23; after the mining of the second working face, a floor mining fracture zone 39 is generated in the lower part of the goaf 35, and the floor mining fracture zone 39 and the floor pressure fracture 38 are connected to the second return air bottom extraction hole 26 and the O-ring of the second working face; therefore, air is introduced from the second air intake bottom extraction hole 24 at the same time, and reaches the second return air bottom extraction hole 26 after passing through the second connecting section 25, and the gas overflowing from the mining of coal seam 34 can be extracted through the second return air bottom extraction hole 26; the air entering the second transport roadway 21 and the second air intake bottom extraction hole 24 both originate from the transport uphill 32, and the air discharged from the second return air roadway 23 and the second return air bottom extraction hole 26 is discharged through the return air uphill 31.

[0035] The second transport level 21, the coal mining area of ​​the coal mining machine, and the second return air level 23 form an intake and return air system. Due to limitations imposed by workers and equipment, the air volume of this system should not be too large or too small. The second intake bottom extraction hole 24, the second connecting section 25, and the second return air bottom extraction hole 26 form another intake and return air system, solely for gas extraction. Since there are no equipment or workers inside, the intake and return air volumes can be freely controlled. When the gas emission concentration and volume are high, the air volume of this system can be increased to improve gas emission efficiency. Furthermore, because there are no equipment or workers inside, the cross-sectional size can be reduced to increase the air velocity and ensure sufficient gas extraction volume. Therefore, only a 600mm diameter enlarged borehole is needed for gas extraction, eliminating the need for excavating a large-diameter bottom extraction roadway.

[0036] After the second working face is completed, the second return airway 23 is sealed with a sealing wall 36, and the second return airway bottom extraction hole 26 is sealed with sealing material 37.

[0037] S8: Repeat steps S5-S7 to carry out roadway excavation and coal seam 34 mining for the third working face and subsequent working faces.

[0038] Example 2

[0039] like Figure 7-10 As shown, the present invention also proposes a method for coal extraction and tunneling in a mining roadway, comprising the following steps: a. such as Figure 7As shown, at one end of the mining roadway 01, a pilot hole 03 is drilled along the axial direction of the mining roadway 01 from the upper right side, and a hydraulic fracturing borehole 04 is drilled along the axial direction of the mining roadway 01 from the lower left side. The diameter of the pilot hole 03 and the hydraulic fracturing borehole 04 is 113 mm. When the mining roadway 01 has a rectangular cross-section, the pilot hole 03 and the hydraulic fracturing borehole 04 are constructed on the diagonal 02. When the other end of the mining roadway 01 is solid coal, the length of the pilot hole 03 and the hydraulic fracturing borehole 04 is the same as the length of the mining roadway 01. When the other end of the mining roadway 01 is the free space formed after the coal seam 34 is excavated, the length of the pilot hole 03 and the hydraulic fracturing borehole 04 should be less than the length of the mining roadway 01, and the bottom of the pilot hole 03 and the hydraulic fracturing borehole 04 should be at least 5-10 m away from the free space.

[0040] b. Figure 8 As shown, mechanical coal removal is performed along the axial direction of the guide hole 03 to form a mechanical coal removal hole 05; the diameter of the mechanical coal removal hole 05 is 300mm.

[0041] c. For example Figure 9 As shown, hydraulic jetting is applied along the axial direction of the mechanical coal extraction hole 05 to form a hydraulic coal extraction hole 06. The diameter of the hydraulic coal extraction hole 06 is not less than 600 mm. A loosening ring 07 is formed outside the hydraulic coal extraction hole 06. The loosening ring 07 refers to the pressure relief zone formed on the outer periphery of the hydraulic coal extraction hole 06, and the diameter of the loosening ring 07 is generally about twice that of the hydraulic coal extraction hole 06.

[0042] d. such as Figure 10 As shown, hydraulic fracturing is performed on the mining roadway 01 from far to near along the axial direction of the hydraulic fracturing borehole 04. The fracturing fractures 08 point to the upper right side, upper middle side, and middle right side of the mining roadway 01, and at least some of the fracturing fractures 08 connect to the hydraulic coal extraction hole 06.

[0043] e. High-pressure water is injected from hydraulic fracturing borehole 04. The injected water enters the hydraulic coal removal hole 06 through the fracturing fracture 08 and returns, which can remove coal dust from the fracturing fracture 08, expand the fracturing fracture 08, expand the range of the hydraulic coal removal hole 06 and its loosened zone 07, and further improve the depressurization effect and gas removal effect of the mining roadway 01. When the mining roadway 01 is long, a perforated pipe can be installed in the hydraulic fracturing borehole 04 for water injection.

[0044] f. High-pressure compressed air from hydraulic fracturing borehole 04 is injected and returns through the fracturing fissure 08 into the hydraulic coal extraction hole 06, which can further improve the gas removal effect of the mining roadway 01. When the mining roadway 01 is long, a perforated pipe can be installed in hydraulic fracturing borehole 04 for compressed air.

[0045] g. A tunneling machine is used to efficiently excavate the mining roadway 01, without the need for depressurization and gas control during the excavation process.

[0046] The coal extraction method for the mining roadway 01 in this second embodiment further defines the coal extraction method for the mining roadway 01 in the first embodiment. Specifically, the mining roadway 01 in the first embodiment can be constructed using the coal extraction method for the mining roadway 01 in this second embodiment. The mining roadway 01 in the first embodiment includes a first haulage level 11, a first cut-out 12, a first return air level 13, a second haulage level 21, a second cut-out 22, and haulage level, cut-out, and return air level that need to be excavated in subsequent working faces. Of course, the coal extraction method for the mining roadway 01 in this second embodiment can also be used independently of the first embodiment.

[0047] The coal extraction method of the present invention for the mining roadway 01 involves extracting coal along the entire axial length of the mining roadway 01, and combining this with hydraulic fracturing borehole 04 for fracturing and permeability enhancement. This greatly improves the depressurization and gas removal effect and efficiency of the mining roadway 01, reduces the amount of gas drilling and shortens the gas extraction cycle. No depressurization and gas control are required during the excavation of the mining roadway 01.

[0048] This invention is not limited to the preferred embodiments described above. Anyone can derive other methods in various forms under the guidance of this invention. Any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A bottom-extraction gas control method based on bottom-plate rock excavation and borehole enlargement, characterized in that, Includes the following steps: S1: Coal is extracted axially along the first transport level roadway, and simultaneously axially along the first return air level roadway; S2: Excavate the first transport level tunnel from the transport uphill direction, and simultaneously excavate the first return air level tunnel from the return air uphill direction; At the same time, the following bottom extraction hole construction is carried out: the first return air bottom extraction hole is constructed in the bottom plate crack area directly below the O-ring of the first working face from the return air uphill, and the first air inlet bottom extraction hole is constructed in the bottom plate crack area directly below the O-ring of the second working face from the transport uphill, and the two are connected by the first connecting section. S3: Extract coal along the axial direction of the first cut, and advance the first cut; S4: The first working face of the longwall mining. During the longwall mining process, air is introduced from the first transport roadway and discharged through the first return air roadway after passing through the coal mining area. At the same time, air is introduced from the first bottom air intake hole, discharged through the first connecting section and then through the first bottom air exhaust hole. S5: Coal is extracted along the axial direction of the second transport level roadway; at the same time, the second return air level roadway is prepared, and coal is extracted along the axial direction of the second cut-out. S6: Excavate the second transport level tunnel from the transport uphill, and simultaneously excavate the second cut-out; At the same time, the following bottom extraction hole construction is carried out: the first air intake bottom extraction hole is connected to the return air uphill hole as the second return air bottom extraction hole; at the same time, the second air intake bottom extraction hole is constructed in the bottom plate crack area directly below the O-ring of the third working face from the transport uphill hole, and the second return air bottom extraction hole is connected through the first connecting section. S7: The second working face is being mined. During the mining process, air is introduced from the second transport roadway and discharged through the second return air roadway after passing through the coal mining area. At the same time, air is introduced from the second bottom air intake hole, discharged through the second connecting section, and discharged through the second bottom air intake hole. S8: Repeat steps S5-S7 to carry out subsequent roadway excavation and coal seam mining.

2. The bottom-extraction gas control method based on bottom plate rock excavation and borehole enlargement according to claim 1, characterized in that, The coal extraction and excavation methods for the first haulage level, first return air level, first cut-off, second haulage level, and second cut-off are as follows: a. At one end of the haulage roadway, a pilot hole is drilled along the axial direction of the haulage roadway from the upper right side, and a hydraulic fracturing borehole is drilled along the axial direction of the haulage roadway from the lower left side; b. Mechanical coal extraction is performed along the axial direction of the pilot hole to form a mechanical coal extraction hole; c. Hydraulic jet coal extraction is performed along the axial direction of the mechanical coal extraction hole to form a hydraulic coal extraction hole, and a loosening ring is formed outside the hydraulic coal extraction hole; d. Hydraulic fracturing is performed on the haulage roadway from far to near along the axial direction of the hydraulic fracturing borehole, and at least some of the fracturing fractures connect to the hydraulic coal extraction hole; e. High-pressure water is injected from the hydraulic fracturing borehole, and the injected water enters the hydraulic coal extraction hole from the fracturing fracture and returns; then the haulage roadway is excavated.

3. The bottom-extraction gas control method based on bottom plate rock excavation and borehole enlargement according to claim 2, characterized in that, Before the excavation of the mining roadway, step f is also included. High-pressure compressed air is injected from the hydraulic fracturing borehole, and the injected air enters the hydraulic coal extraction hole from the fracturing fracture and returns.

4. The bottom-extraction gas control method based on bottom plate rock excavation and borehole enlargement according to claim 1 or 2, characterized in that, In step S2, a first hydraulic fracturing directional borehole is drilled and enlarged on the bottom rock stratum from the return air uphill section, forming the first return air bottom extraction hole in the straight section. Simultaneously, a second hydraulic fracturing directional borehole is drilled and enlarged on the bottom rock stratum from the transport uphill section, forming the first air intake bottom extraction hole in the straight section. The inclined sections of the first and second hydraulic fracturing directional boreholes are enlarged to form the first connecting section connecting the first air intake bottom extraction hole and the first return air bottom extraction hole. In step S6, a third hydraulic fracturing directional borehole is drilled and enlarged on the bottom rock stratum from the transport uphill section, forming the second air intake bottom extraction hole in the straight section and the second connecting section in the inclined section, which is connected to the second return air bottom extraction hole.

5. The bottom-extraction gas control method based on bottom plate rock excavation and borehole enlargement according to claim 4, characterized in that, The enlargement steps for the first, second, and third hydraulic fracturing directional boreholes are: mechanical rock removal and hydraulic jet rock removal.

6. The bottom-extraction gas control method based on bottom plate rock excavation and borehole enlargement according to claim 5, characterized in that, In step S2, before mechanically removing rock from the first and second hydraulic fracturing directional boreholes, the process further includes: performing hydraulic fracturing based on the straight section of the first hydraulic fracturing directional borehole, and connecting the resulting bottom plate fracturing fracture to the first working face; simultaneously, performing hydraulic fracturing based on the straight section of the second hydraulic fracturing directional borehole, and connecting the resulting bottom plate fracturing fracture to the second working face; in step S6, performing hydraulic fracturing based on the straight section of the third hydraulic fracturing directional borehole, and connecting the resulting bottom plate fracturing fracture to the third working face.

7. The bottom-extraction gas control method based on bottom plate rock excavation and borehole enlargement according to claim 6, characterized in that, The first connecting segment is located outside the first cut eye; the second connecting segment is located outside the second cut eye.

8. The bottom-extraction gas control method based on bottom plate rock excavation and borehole enlargement according to claim 7, characterized in that, The first hydraulic fracturing directional borehole and the first return air bottom extraction borehole formed therefrom are located entirely in soft rock and are connected by a connecting tunnel near the return air uphill section; the second hydraulic fracturing directional borehole and the first intake air bottom extraction borehole formed therefrom are located entirely in soft rock and are connected by a connecting tunnel near the transport uphill section; the third hydraulic fracturing directional borehole and the second intake air bottom extraction borehole formed therefrom are located entirely in soft rock and are connected by a connecting tunnel near the transport uphill section.

9. The bottom-extraction gas control method based on bottom plate rock excavation and borehole enlargement according to claim 1 or 2, characterized in that, In step S6, before connecting the first air inlet bottom extraction hole with the return air uphill hole, the process also includes filling the first connecting section with filling material.

10. The bottom-extraction gas control method based on bottom plate rock excavation and borehole enlargement according to claim 1 or 2, characterized in that, In step S4, the first transport level roadway is left along the goaf; in step S5, the goaf-leaving roadway based on the first transport level roadway is connected with the return air uphill roadway to form the second return air level roadway; in step S7, the second transport level roadway is left along the goaf.

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