Multi-source gas prevention and control method for island working face with multiple remaining coal pillars

Abstract

The invention discloses a multi-remaining coal pillar island working face gas multi-source prevention and control method which comprises the steps that the section 150 m before stoping of a mining face is divided into a high-risk area, a buffer area and a safe area, four hydraulic fracturing drill holes are formed in a transportation roadway drill site to cover the dangerous area, the buffer area pressurizes the drill holes through a fracturing pump to enable a 11 # coal seam roof to be broken, and a 11 # coal seam roof is formed in the safe area; fractured gas is extracted through fracturing drill holes, and mechanical cave-building pressure-relief anti-reflection drill holes are constructed in a stress concentration danger area and a buffer area; pressure relief gas continuous extraction is achieved in a working face island stress concentration area; the advanced support of the upper lane and the lower lane of the island stress concentration section adopts advanced combined support of'anchor net cables, T-shaped steel belts, single columns, I-shaped steel and U-shaped sheds'. According to the method, the main pipe of the roof and floor drainage roadway crossing hole is stabilized to be 25% or above, and the extraction pure amount is 6 m / min; the minimum K1 value is 0.07 mL / g.min < 1 / 2 > and the maximum K1 value is 0.19 mL / g.min < 1 / 2 > according to regional verification, except for the initial mining period, the return air flow does not exceed 0.36%, and the upper corner gas does not exceed 0.38%.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas prevention and control, and relates to a multi-source gas prevention and control method for an isolated island working face with multiple remaining coal pillars. Background Art

[0002] The 50-60m section of the 121103 mining face is located below the goaf of the 110302 and 120301 working faces, 57m horizontally from the 110306 return airway. This section is an isolated stress concentration zone. During tunneling of the 121103 return airway, transport tunnel, and cut-hole tunneling, this section experienced high tunnel pressure, severe roof fracture, and frequent K1 stop-stop overshoots. During drilling, blowouts and top drilling were frequent. This is to prevent the indirect effects of high stress concentration during mining, which can trigger gas and roof collapse hazards. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a multi-source gas prevention and control method for an isolated island working face with multiple residual coal pillars, so as to solve the technical problems existing in the prior art.

[0004] The solution implemented by the present invention is:

[0005] The multi-source gas prevention and control method for the isolated island working face with multiple legacy coal pillars is as follows: the 150m section before the mining face is divided into a high-risk area, a buffer zone and a safe area. In this section, a four-dimensional coordinated prevention and control system of "pressure relief - permeability enhancement - extraction - support" is adopted, that is, a prevention and control method of hydraulic fracturing + mechanical cavitation + pressure relief extraction of the adjacent layers of the roof and floor + advanced joint support is adopted. Among them, four hydraulic fracturing boreholes are arranged in the transport tunnel drilling site to cover the dangerous area. The buffer zone uses a fracturing pump to pressurize the borehole to break the roof of the 11# coal seam, thereby increasing the stress. The gas diffusion channel in the stress area relieves the stress and gas in the danger zone and buffer zone, and the fissure gas is extracted through fracturing drilling. Mechanical hole-making and pressure-relief and permeability-enhancing drilling are constructed in the stress concentration danger zone and buffer zone. A hole-making hole is constructed every 3m in the danger zone and every 6m in the buffer zone. Continuous extraction of pressure-relief gas is achieved in the isolated island stress concentration zone of the working face. The advanced support of the upper and lower tunnels in the isolated island stress concentration section adopts the advanced combined support of "anchor net cable + T-shaped steel belt + single column + I-beam + U-shaped shed".

[0006] Furthermore, during the drilling process, The drilling rod is used to make holes and increase permeability, and the clean water pump station is used for pressurized hole making. The drilling opening is 10m long. Drill bit construction (convenient for subsequent hole sealing and continuous extraction), used throughout the entire process The hole-making drill rod is used to relieve pressure and increase permeability.

[0007] Furthermore, the above-mentioned return air extraction tunnel is constructed to pre-extract the extraction drilling holes of the upper adjacent layers 9#, 6# and 5# coal seams, and the 121103 transport extraction tunnel is constructed to pre-extract the extraction drilling holes of the lower adjacent layers 12#, 13# and 15# coal seams. Each group of 20m covers the entire isolated island stress concentration area, and the unmined coal seams on the top and bottom plates are continuously unloaded and extracted at a 20m interval.

[0008] Furthermore, during the above-mentioned advanced combined support, I-beams are used in conjunction with single hydraulic props to support the scaffolding. The spacing is no more than 1m, and the advanced support length is no less than 20m. Two rows of T-shaped steel belts are used in conjunction with anchor cables for support. They are located at the left and right arch shoulders of the roadway, 1.1m away from the center line of the anchor cables. The steel belt stubble is installed on the anchor cables. The anchor cable specifications are as follows:

[0009] The effects of the present invention are as follows: the present invention induces the expansion of cracks in the stress concentration area through hydraulic fracturing, weakens the roof, reduces the area of ​​the hanging roof, reduces the risk of gas accumulation in the upper corner, and reduces the stress concentration of the coal seam; after the regional anti-burst measures are drilled in the coal seam and the effect is verified to be effective, a mechanical hole-making drill with a diameter of 500mm and a hole depth of 110m is constructed to expand the coal body pressure relief range, increase the permeability of the coal seam, release local stress and increase the gas extraction efficiency, and alleviate stress concentration; the return air top extraction lane is constructed by drilling holes through the roof layer to extract the gas from the adjacent layers of the coal seam to relieve pressure; the transport bottom extraction lane is constructed by drilling holes through the bottom layer to extract the gas from the adjacent layers of the coal seam to relieve pressure, and the unmined coal seams on the top and bottom plates are continuously depressurized and extracted to block the gas migration path and reduce the gas influx into the working face; during the normal mining period of the working face, the cross-layer drilling main pipe of the top and bottom plate extraction lanes is stable at more than 25%, and the pure amount of extraction is within 6m 3 / min; the minimum K1 value for regional verification is 0.07mL / g·min 1 / 2 , maximum 0.19mL / g·min 1 / 2 , except during the initial mining period, the return air flow did not exceed 0.36% and the upper corner gas did not exceed 0.38%. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is the plan layout and adjacent relationship diagram of the 121103 working face;

[0011] Figure 2 This is the 121103 working face dip section layout and adjacent relationship diagram;

[0012] Figure 3 This is the strike profile layout and adjacent relationship diagram of the 121103 working face;

[0013] Figure 4 This is the curve of the drill cuttings desorption index K1 exceeded during the excavation of the 121103 working face;

[0014] Figure 5This is a plan diagram of the zoning prevention and control plan for the 121103 working face;

[0015] Figure 6 This is a schematic diagram of the pressure relief gas extraction arrangement in the adjacent layers of the 121103 working face. DETAILED DESCRIPTION

[0016] The present invention will be further described below with reference to specific embodiments.

[0017] Working face overview: The 121103 working face is located below the goaf of the 110302 and 120301 working faces, 57 meters horizontally from the 110306 return air lane. Unmined coal seams exist on the roof and floor, forming an isolated stress concentration zone. Due to the influence of the F119-6 fault, a 230-meter section of the 110302 working face remains unmined, and 120301 is not continuously mined. Portions of the two lanes and cuts of the 121103 working face are located within the disturbance and pressure zone of the coal pillars left behind in the 110302 working face. See [the original text] for details. Figure 1-3 .

[0018] Abnormal analysis of drill cuttings desorption index K1 value

[0019] 1) Effect of stress on coal permeability and gas occurrence

[0020] (1) High stress areas will lead to reduced permeability of coal seams, reduced free gas, and increased proportion of adsorbed gas, which will indirectly affect the measurement results of the K1 value.

[0021] (2) Tectonic stress can cause coal to break or squeeze, changing the dynamic characteristics of gas desorption. The significant fluctuation of K1 value near the fault is related to the change of gas pressure caused by local stress concentration.

[0022] 2) Synergistic effect of stress and gas pressure

[0023] (1) The K1 value is exponentially related to the gas pressure, which is controlled by the ground stress. When the ground stress increases, the coal matrix is ​​compressed, the gas pressure increases, and the K1 value is directly increased.

[0024] (2) Mining stress will change the original gas pressure distribution of the coal seam. Stress redistribution may cause a sudden increase in local gas pressure, thereby causing abnormal K1 value. The measured drilling cuttings desorption index K1 exceeded the standard during the excavation of the 121103 working face. Figure 4 .

[0025] To address the above issues, the present invention proposes a multi-source gas prevention and control method for an isolated working face with multiple residual coal pillars in Example 1. The prevention and control method utilizes an online stress monitoring system to monitor stress distribution and identify abnormal coupled signals of stress and gas.

[0026] Example 1: A multi-source gas prevention and control method for an isolated island working face with multiple legacy coal pillars. The method is as follows: the 150m section before the mining of the 121103 mining face is divided into a high-risk area, a buffer zone, and a safe zone. In this section, a four-dimensional coordinated prevention and control system of "pressure relief - permeability enhancement - extraction - support" is adopted. That is, hydraulic fracturing + mechanical cavitation + pressure relief extraction of the adjacent layers of the roof and floor + advanced joint support are adopted to solve the bottleneck technology of disaster prevention and control in the isolated island working area with high stress concentration under the disturbance of multiple legacy coal pillars. Among them, four hydraulic fracturing boreholes are arranged in the transport tunnel drilling site to cover the dangerous area, and the buffer zone is drilled by the BYW78 / 400 fracturing pump. The hole is pressurized to break the roof of the 11# coal seam, thereby increasing the gas diffusion channel in the stress area to relieve the stress and gas in the danger zone and buffer zone, and the fissure gas is extracted through fracturing drilling. Mechanical hole-making and pressure-relief and permeability-enhancing drilling holes are constructed in the stress-concentrated danger zone and buffer zone. A hole-making hole is constructed every 3m in the danger zone and every 6m in the buffer zone; continuous gas extraction is achieved in the isolated island stress concentration zone of the working face; the advanced support of the upper and lower tunnels in the isolated island stress concentration section of the 121103 working face adopts the advanced combined support of "anchor mesh cable + T-shaped steel belt + single column + I-beam + U-shaped shed".

[0027] Furthermore, during the drilling process, The drilling rod is used to make holes and increase permeability, and the BQWL315 / 16-XQ315 / 12 clean water pump station is used for pressurized hole making. The drilling opening is 10m long. Drill bit construction (convenient for subsequent hole sealing and continuous extraction), used throughout the entire process The hole-making drill rod is used to relieve pressure and increase permeability.

[0028] Furthermore, the above-mentioned 121103 return air extraction tunnel is constructed to pre-extract the extraction drilling holes of the upper adjacent layers 9#, 6# and 5# coal seams, and the 121103 transport extraction tunnel is constructed to pre-extract the extraction drilling holes of the lower adjacent layers 12#, 13# and 15# coal seams. A group of 20m covers the entire isolated island stress concentration area, and the top and bottom unmined coal seams are continuously depressurized and extracted at a 20m interval to block the gas migration path and reduce the gas influx into the working face.

[0029] Furthermore, during the above-mentioned advanced combined support, I-beams are used in conjunction with single hydraulic props to support the scaffolding. The spacing is no more than 1m, and the advanced support length is no less than 20m. Two rows of T-shaped steel belts are used in conjunction with anchor cables for support. They are located at the left and right arch shoulders of the roadway, 1.1m away from the center line of the anchor cables. The steel belt stubble is installed on the anchor cables. The anchor cable specifications are as follows:

[0030] According to the regional verification results during excavation, the working face is divided into "high-risk area-buffer zone-safe zone", and regional control is carried out for different areas. For the high-risk area, ordinary drilling (drilling hole spacing 6m), hydraulic fracturing, mechanical cavitation pressure relief and permeability drilling (drilling hole spacing 3m), and advanced combined support measures are adopted; the buffer zone adopts ordinary drilling (drilling hole spacing 6m), mechanical cavitation pressure relief and permeability drilling (drilling hole spacing 6m); the safe zone adopts ordinary extraction drilling (drilling hole spacing 6m), the plan is detailed in Figure 5-6 .

[0031] The present invention has the following advantages:

[0032] 1) Roof weakening: Through hydraulic fracturing, cracks in the stress concentration area are induced to expand, the roof is weakened, the hanging roof area is reduced, the risk of gas accumulation in the upper corner is reduced, and the stress concentration of the coal seam is reduced.

[0033] 2) Coal seam pressure relief: After the coal seam construction area anti-blowout measures drilling is completed and the effect is verified to be effective, a mechanical hole drilling with a diameter of 500mm and a hole depth of 110m is constructed to expand the coal body pressure relief range, increase the permeability of the coal seam, release local stress, increase gas extraction efficiency, and relieve stress concentration.

[0034] 3) Gas extraction for pressure relief in adjacent layers: Drill holes through the roof in the 121103 return air top extraction tunnel to extract pressure relief gas in the adjacent layers of the No. 9, 6, and 5 coal seams; drill holes through the floor in the 121103 transport bottom extraction tunnel to extract pressure relief gas in the adjacent layers of the No. 12, 13, and 15 coal seams. Continuous pressure relief extraction is carried out on the unmined coal seams on the top and bottom plates to block the gas migration path and reduce the influx of gas into the working face.

[0035] Based on regional verification during excavation, the working face was divided into "high-risk area-buffer zone-safety zone," and regional control measures were implemented for different areas. Conventional drilling (6m spacing between boreholes), hydraulic fracturing, mechanical cavitation, pressure-relief and permeability-enhancing drilling (3m spacing between boreholes), and advanced combined support measures were used in the high-risk area; conventional drilling (6m spacing between boreholes) and mechanical cavitation, pressure-relief and permeability-enhancing drilling (6m spacing between boreholes) were used in the buffer zone; and conventional extraction drilling (6m spacing between boreholes) was used in the safety zone.

[0036] After implementing the present invention, the following better indicators are achieved:

[0037] index Before governance After governance Maximum K1 value <![CDATA[1.02mL / g·min 1 / 2 ]]> <![CDATA[0.17mL / g·min 1 / 2 ]]> Return air flow gas 0.5-0.6% during the initial mining period Stable ≤0.36% Upper corner gas Peak 0.8% ≤0.38% (continuous monitoring) Ergonomics Average excavation speed: 1.3m / d The overall advancement speed of the mining face has increased by 3 times

[0038] During the normal mining period of 121103 working face, the drilling main of the top and bottom plate drainage tunnel was stable at more than 25%, and the pure extraction volume was 6m 3 / min; the minimum K1 value for regional verification is 0.07mL / g·min 1 / 2 , maximum 0.19mL / g·min 1 / 2, except during the initial mining period, the return air flow did not exceed 0.36% and the upper corner gas did not exceed 0.38%.

[0039] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A multi-source gas prevention and control method for working faces with multiple legacy coal pillars and isolated islands, characterized by: The method is as follows: the 150m section before mining is divided into a high-risk area, a buffer zone and a safe area, and a four-dimensional coordinated prevention and control system of "pressure relief - permeability enhancement - extraction - support" is adopted in this section, that is, a prevention and control method of hydraulic fracturing + mechanical cavitation + pressure relief extraction of adjacent layers of the roof and floor plates + advanced joint support is adopted. Among them, four hydraulic fracturing boreholes are arranged in the transportation tunnel drilling site to cover the dangerous area. The buffer zone uses a fracturing pump to pressurize the borehole to break the roof of the 11# coal seam, and the fissure gas is extracted through the fracturing boreholes. Mechanical cavitation, pressure relief and permeability enhancement boreholes are constructed in the stress concentration dangerous area and the buffer zone. A cavitation borehole is constructed every 3m in the dangerous area and every 6m in the buffer zone. Continuous pressure relief gas extraction is achieved in the isolated island stress concentration area of ​​the working face. The advanced support of the upper and lower tunnels in the isolated island stress concentration section adopts the advanced combined support of "anchor net cable + T-shaped steel belt + single column + I-beam + U-shaped shed".

2. The multi-source gas prevention and control method for multi-remaining coal pillars and isolated island working faces according to claim 1 is characterized in that: During drilling, a φ500mm hole-making drill rod was used to create holes and increase permeability, and a clean water pump station was used to pressurize the holes. A φ133mm drill bit was used for the 10m section of the borehole opening, and a φ500mm hole-making drill rod was used throughout the inner section to relieve pressure and increase permeability.

3. The multi-source gas prevention and control method for isolated island working faces with multiple remaining coal pillars according to claim 1 is characterized in that: The return air extraction tunnel is constructed to pre-extract the upper adjacent layers of the 9#, 6#, and 5# coal seams by drilling holes. The 121103 transport extraction tunnel is constructed to pre-extract the lower adjacent layers of the 12#, 13#, and 15# coal seams by drilling holes. Each group of 20 meters covers the entire isolated island stress concentration area, and the unmined coal seams on the top and bottom plates are continuously unloaded and extracted at 20 meters intervals.

4. The multi-source gas prevention and control method for isolated island working faces with multiple remaining coal pillars according to claim 1 is characterized in that: During the advance combined support, I-beams are used in conjunction with single hydraulic pillars to support the strike support shed, with a spacing of no more than 1m and an advance support length of no less than 20m. Two rows of T-shaped steel belts are used in conjunction with anchor cables for support, located at the left and right arch shoulders of the tunnel, 1.1m away from the center line of the anchor cables. The steel belt stubble is installed on the anchor cables, with anchor cable specifications of φ21.6×5300mm.

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