An automatic drainage method and system for fixed-length boreholes in downward gas drainage

Abstract

The present application provides an automatic drainage method and system for fixed-length downward gas drainage boreholes. In this method, the upper main borehole is arranged in the rock formation, which is convenient for hole formation, not prone to hole collapse, and has a long extraction cycle. After the upper mining layer is mined, the lower coal and rock mass expands, generating a large number of fissures, which can effectively intercept the pressure-relieved gas extracted from the adjacent lower layer. Moreover, the initial flat-return position of the upper main borehole gradually constructs upward at a small angle, and the accumulated water can flow into the lower branch borehole along the borehole. When there is less accumulated water in the lower branch borehole, it can pre-drain the gas from the adjacent lower layer. When there is more accumulated water, it is used as the accumulated water borehole for the upper main borehole. Also, affected by the advanced stress of the upper mining layer's working face, the coal boreholes in the adjacent lower layer within the range of the advanced stress are damaged, and a large number of fissures are generated due to the pressure relief of the coal mass around the borehole. While the gas gushes out, it also provides a channel for the discharge of the accumulated water in the borehole. The accumulated water in the branch borehole will automatically flow into the coal mass along the coal mass fissures as the upper working face advances, effectively protecting the interception and extraction effects of the main borehole.

Description

Technical Field

[0001] The present application relates to the technical field of coal mining, and particularly relates to an automatic drainage method and system for downward gas drainage fixed-length boreholes. Background Art

[0002] For high-gas or outburst mines with close coal seam groups in mining, when the upper coal seam or protective layer is mined, the lower adjacent layer or the protected layer is depressurized, and a large amount of coal seam gas gushes out and floods into the mining layer through the goaf, which adds a huge burden to the gas prevention and control of the mining layer.

[0003] Directional boreholes have the advantages of long effective section length, wide coverage range, and controllable trajectory. Therefore, when there are no excavation roadways constructed in the lower adjacent layer or the conditions for bottom drainage roadways are not available, it has a good effect to extract the gas from the adjacent layer by constructing downward intercepting boreholes in the mining layer. However, due to the problem of accumulated water in the borehole, the gas drainage rate of downward boreholes is less than 50% of that of upward boreholes under the same conditions, which severely restricts the popularization and application of downward boreholes.

[0004] Therefore, there is an urgent need to provide a technical solution to address the deficiencies of the above-mentioned existing technologies. Summary of the Invention

[0005] The purpose of the present application is to provide an automatic drainage method and system for downward gas drainage fixed-length boreholes to solve or alleviate the problems existing in the above-mentioned existing technologies.

[0006] To achieve the above purpose, the present application provides the following technical solutions:

[0007] The present application provides an automatic drainage method for downward gas drainage fixed-length boreholes, including: arranging drill sites in the intake airway and return airway of the mining layer, constructing a number of gas drainage intercepting boreholes in the drill sites to evenly cover the dip of the working face and form a layered intercepting section; each intercepting borehole is divided into an upper main hole and a lower branch hole, the upper main hole is arranged in the stable rock between the mining layer and the adjacent layer, and the initial flat-return position of the upper main hole is located at the bottom of the rock formation, and it is gradually constructed upward at a small angle; the lower branch hole is gradually constructed downward at a small angle from the initial flat-return position of the upper main hole to the adjacent layer, and the initial flat-return position of the lower branch hole is located at the top of the adjacent layer.

[0008] Preferably, arranging drill sites in the intake airway and return airway of the mining layer and constructing a number of intercepting boreholes in the drill sites includes: constructing downward boreholes in the coal and rock walls of the mining layer and performing hole sealing operations on the boreholes; after the hole sealing of the boreholes is completed, constructing the upper main hole upward in the boreholes; the junction of the hole sealing section of the borehole and the upper main hole is the initial flat-return position of the upper main hole.

[0009] Preferably, the operation of sealing the hole section of the borehole includes: sealing one end of the sealing pipe with gypsum, inserting the other end into the borehole, and laying a grouting pipe along the axial direction on the outer side of the sealing pipe; sealing between the end of the sealing pipe and the borehole with gypsum; wherein, the end of the grouting pipe extending into the borehole to prevent blowout of the borehole extends out of the sealing gypsum between the end of the sealing pipe and the borehole for blowout prevention of the borehole; grouting into the pores between the coal wall and the sealing pipe through the grouting pipe until the slurry seeps into the coal wall, water seeps out of the coal body or slurry seeps out of the sealing pipe, and then stop grouting.

[0010] Preferably, it further includes: installing a guiding four-way at the orifice of the sealing pipe, connecting the upper end of the guiding four-way to the gas drainage pipeline, connecting the lower end in series with a water slag sedimentation tank, and after installing a hole sealer at the front end, the drill rod passes through the hole sealer to drill an intercepting borehole.

[0011] Preferably, it further includes: in response to the completion of the construction of the intercepting borehole, withdrawing the drill rod, disassembling the guiding four-way, and connecting the sealing pipe and the gas drainage pipeline in series through a water drainer, and a flow valve is provided between the water drainer and the sealing pipe, and an orifice flowmeter is installed between the water drainer and the gas drainage pipeline.

[0012] Preferably, when drilling the intercepting borehole, measure the borehole once every 3 meters or 6 meters, and compare the measurement results with the preset trajectory to adjust the elbow direction according to the comparison results.

[0013] Preferably, when drilling the intercepting borehole, in response to the gas concentration in the drill site reaching 0.8%, stop drilling, and take measures such as exhausting the gas in the drill site through a ventilation duct or extracting the gas through an inserted pipe.

[0014] The embodiment of the present application also provides a downward gas drainage fixed-length borehole automatic drainage system, including: a borehole unit and a drainage unit; the borehole unit is configured to arrange drill sites in the intake airway and return airway of the mining layer, drill a number of intercepting boreholes in the drill sites, evenly cover the dip of the coal mining face, and form a layered intercepting section; each intercepting borehole is divided into an upper main hole and a lower branch hole, the upper main hole is arranged in the stable rock between the mining layer and the adjacent layer, and the initial return-to-horizontal position of the upper main hole is located at the bottom of the rock layer, and it is gradually constructed upward at a small angle; the lower branch hole is gradually constructed downward at a small angle from the initial return-to-horizontal position of the upper main hole to the adjacent layer, and the initial return-to-horizontal position of the lower branch hole is located at the top of the adjacent layer; the drainage unit includes: a water drainer, an orifice flowmeter, a gas drainage pipeline and a flow valve, the inlet of the water drainer is connected to the orifice of the sealing pipe inserted into the borehole for blowout prevention of the coal wall through a pipeline, and the outlet of the water drainer is connected to the gas drainage pipeline; wherein, a flow valve is provided on the connecting pipeline between the inlet of the water drainer and the sealing pipe, and an orifice flowmeter is provided between the outlet of the water drainer and the drainage pipeline.

[0015] Beneficial effects:

[0016] The automatic drainage method for downward gas drainage fixed-length boreholes provided by the embodiments of the present application arranges drill sites in the intake airway and return airway of the mining layer, constructs several gas drainage interception boreholes in the drill sites, evenly covers the dip of the coal mining face, forms a layered interception section, so as to effectively intercept the pressure-relieved gas in the lower adjacent layer; each interception borehole is divided into an upper main hole and a lower branch hole. The upper main hole is arranged in the stable rock between the mining layer and the adjacent layer, and the initial flat-return position of the upper main hole is located at the bottom of the rock layer, and it is gradually constructed upward at a small angle; the lower branch hole is gradually constructed downward at a small angle from the initial flat-return position of the upper main hole to the adjacent layer, and the initial flat-return position of the lower branch hole is located at the top of the adjacent layer.

[0017] Therefore, the upper main hole is arranged in the rock layer, the borehole is easy to form and not prone to caving, and the drainage period is long. After the upper mining layer is mined, the coal and rock mass expands, generating a large number of fissures, which can effectively intercept a large amount of pressure-relieved gas in the lower adjacent layer. Moreover, the initial flat-return position of the upper main hole is gradually constructed upward at a small angle, and the accumulated water can flow into the lower branch hole along the borehole; the lower branch hole can pre-drain the gas in the lower adjacent layer when there is less accumulated water in the borehole, and is used as the accumulated water hole of the upper main hole when there is more accumulated water in the borehole. And affected by the advanced stress of the coal mining face in the upper mining layer, the coal holes in the lower adjacent layer within the range of the advanced stress are damaged, and a large number of fissures are generated due to the pressure relief of the coal mass around the borehole. While the gas gushes out, it also provides a channel for the discharge of the accumulated water in the borehole. The accumulated water in the lower branch hole will automatically flow into the coal body along the coal mass fissures with the advancement of the upper working face, effectively protecting the interception and drainage effects of the main hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The specification drawings forming a part of the present application are used to provide a further understanding of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. Among them:

[0019] Figure 1 FIG. is a schematic diagram of the principle of an automatic drainage method for downward gas drainage fixed-length boreholes provided by some embodiments of the present application;

[0020] Figure 2 is Figure 1 a cross-sectional schematic diagram of the illustrated embodiment;

[0021] Figure 3 FIG. is a layout schematic diagram of a directional borehole anti-blowout device provided by some embodiments of the present application;

[0022] Figure 4 FIG. is a layout schematic diagram of a drainage unit provided by some embodiments of the present application;

[0023] Figure 5 FIG. is a structural schematic diagram of an automatic drainage system for downward gas drainage fixed-length boreholes provided by some embodiments of the present application. Detailed implementation manners

[0024] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application rather than a limitation of the present application. In fact, those skilled in the art will appreciate that modifications and variations can be made to the present application without departing from the scope or spirit thereof. For example, features shown or described as part of one embodiment can be used in another embodiment to yield yet another embodiment. Accordingly, it is desirable that the present application cover such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0025] The applicant's research found that downward drilling can be carried out in the roadway of the existing mine system, which can effectively avoid the problems of slow driving speed of the bottom gas drainage roadway, high construction cost, and tight mining and excavation replacement. However, due to the problem of water accumulation in the hole, the gas drainage rate of downward drilling is less than 50% of that of upward drilling under the same conditions, which severely restricts the application of downward drilling.

[0026] Based on this, the applicant proposed an automatic drainage method for downward gas drainage fixed-length drilling. After the upper main hole returns to the bottom, small-angle upward construction is maintained. During the drainage process, the water accumulated in the upper main hole can automatically flow to the bottom of the hole, ensuring a smooth gas flow channel in the upper main hole; the lower branch holes are constructed at a small angle downward to ensure that the accumulated water can flow into the branch holes, that is, one of the functions of the lower branch holes is to store water; when the influence of the upper working face mining pressure relief reaches the lower coal seam, the coal seam at the bottom area of the lower branch holes is pressure-relieved, generating a large number of fractures, and a large amount of coal seam gas gushes out. While the upper main hole is draining gas, the accumulated water in the lower branch holes automatically drains into the coal seam fractures, that is, the second function of the lower branch holes is to automatically drain water; finally, gas pre-drainage can also be carried out through the lower branch holes.

[0027] As Figure 1 、 Figure 2 shown, drill sites are arranged in the intake airway and return airway of the mining seam. A number of gas drainage interception holes are constructed in the drill sites, evenly covering the dip of the working face to form a layered interception section to effectively intercept the pressure-relieved gas from the lower adjacent seam; each interception hole is divided into an upper main hole and a lower branch hole. The upper main hole is arranged in the stable rock between the mining seam and the adjacent seam, and the initial flat-return position of the upper main hole is at the bottom of the rock layer, and gradually constructs upward at a small angle; the lower branch hole is constructed downward at a small angle from the initial flat-return position of the upper main hole to the adjacent seam, and the initial flat-return position of the lower branch hole is at the top of the adjacent seam.

[0028] In the present application, a directional drilling rig is used for directional drilling. During directional drilling, a measurement-while-drilling device is used to observe the drilling trajectory of the hole, monitor the hole inclination, azimuth, etc., so as to adjust the drilling trajectory in real time and realize the construction of directional holes.

[0029] Among them, drill sites are arranged in the intake airway and return airway of the mining seam. When constructing several gas drainage interception boreholes in the drill site, the laying position of the directional drill is within the range of 1.5 meters to 3 meters from the coal wall opening position. Downward boreholes are constructed on the coal wall and rock wall of the mining seam, and the downward boreholes are sealed. Specifically, first, one end of the sealing pipe is sealed with gypsum, and the other end is inserted into the borehole. Along the axial direction of the outside of the sealing pipe, a grouting pipe is laid. That is, the grouting pipe is wound around the sealing pipe with adhesive tape according to the set winding spacing (50 cm), and then the sealing pipe with one end sealed with gypsum is lowered into the borehole, and the outer end of the sealing pipe extends 20 cm beyond the coal wall (rock wall); then the grouting pipe and the exhaust pipe are inserted. Among them, the outer side is the grouting pipe, and the inner side of the sealing pipe is the exhaust pipe.

[0030] Then, the space between the sealing pipe and the borehole is sealed with gypsum; among them, the end of the grouting pipe extending into the borehole to prevent blowout of the borehole extends beyond the end of the sealing pipe and the sealing gypsum between the air blowout holes of the borehole. Specifically, gypsum powder is mixed with clean water to form a paste to seal the hole opening, and the sealing depth is not less than 40 cm; the coal wall within 60 cm around the hole opening is washed clean with clean water and then covered with gypsum. After the empty space is sealed, it is left still for more than 45 minutes. Grouting operation can only be carried out after the gypsum has solidified.

[0031] Finally, grouting is carried out into the pores between the coal wall and the sealing pipe through the grouting pipe until the slurry seeps into the coal wall, the coal body seeps water or the slurry oozes out of the sealing pipe, and then the grouting stops. Specifically, the grouting pipe is connected to the sealing pump, and the cement slurry is stirred in the mixing drum. Among them, the ratio of cement to water is 50 kg of cement to 15 liters of water. After the cement slurry is stirred evenly, it is grouted through the grouting pipe.

[0032] After it is filled, tie the exhaust pipe with iron wire, etc., and continue grouting to make the cement slurry seep into the coal wall. When water seeps out and bubbles appear from the coal wall, stop grouting; tie the grouting pipe with iron wire and saw off the grouting pipe with a handsaw. After the grouting is completed, the sealing pump needs to be cleaned. During the grouting process, follow the principle of "small flow rate, long time" to gradually increase the pressure in the hole, so that the cement slurry can seep more into the coal wall to ensure the airtightness of the sealing; and after the sealing is completed, it is left still for 24 hours to allow the mortar to solidify before drilling.

[0033] After the downward borehole is sealed, an upper main hole is constructed upward in the borehole; among them, the junction of the sealed section of the borehole and the upper main hole is the initial return flat position of the upper main hole. Specifically, the upper main hole is arranged in the stable rock between the mining seam and the adjacent seam, and the initial return flat position of the upper main hole is at the bottom of the target layer, gradually at a small angle, and constructed upward to facilitate the backflow of accumulated water in the hole. After the upper main hole is constructed, a lower branch hole is constructed in the coal seam. The initial return flat position of the lower branch hole is at the top of the coal seam and gradually at a small angle, and constructed downward.

[0034] Accordingly, each intercept borehole is divided into two layers. The first-layer main borehole is arranged in the stable rock between the mining layer and the adjacent layer, and the initial flat-return position of the main borehole is at the bottommost part of the target layer, gradually rising upward at a small angle to facilitate the backflow of accumulated water in the borehole. The second-layer branch borehole is arranged in the coal seam, and the initial flat-return position of the branch borehole is at the top of the coal seam, gradually descending downward at a small angle.

[0035] In this application, after hole sealing and before drilling the upper-layer main borehole, a guiding four-way joint is installed at the orifice of the hole-sealing pipe. The upper end of the guiding four-way joint is connected to the gas drainage pipeline, the lower end is connected in series with a water slag sedimentation tank, and a hole-sealing device is installed at the front end. Then, the drill pipe passes through the hole-sealing device to drill the intercept borehole. That is, the layout of the directional borehole anti-blowout device is completed. Specifically, a guiding four-way joint is installed at the outer end of the hole-sealing pipe at the orifice. A control valve is provided between the upper end of the guiding four-way joint and the gas drainage pipe. Then, after the gas drainage pipe is connected in series with a water drainer, it is connected to the gas drainage pipeline. During the borehole construction process, the size of the on-site gas is detected by a methane detector, and the control valve is adjusted to achieve simultaneous drilling and drainage, as Figure 3 shown.

[0036] When drilling the intercept borehole, first, correct the direction of the elbow. Place the downhole motor into the borehole and connect the drill pipe of the downhole tool. Retract the drill pipe so that the elbow direction mark is exposed outside the borehole, and set the elbow direction to 360 degrees. Conduct a monitoring measurement once to confirm that the elbow direction is 360 degrees, and then add drill pipes until the downhole motor, downhole tool, and drill pipes all enter the borehole. Then, send the downhole motor to the bottom of the already enlarged borehole, start the water pump. After water returns from the borehole and it is confirmed that the returned slag is normal, drill with the downhole motor to 15 meters, press the reset button for inspection and measurement, record the reading of the borehole azimuth angle, and conduct a measurement every 3 meters or 6 meters subsequently, and compare the measurement results with the preset trajectory to adjust the elbow direction according to the comparison results. Among them, when drilling the upper-layer main borehole, at the branch point (the bottom of the downward borehole) of the upper-layer borehole and the lower-layer branch borehole, there is at least a 0.5-degree climb.

[0037] During the drilling process, in case of abnormal phenomena such as cross-borehole, sticking of the drill, or sudden increase in water pressure, drilling should be stopped immediately; when the methane detector detects that the gas concentration in the drill site reaches 0.8%, stop drilling immediately, and take measures such as exhausting the gas in the drill site through a ventilation duct or inserting a pipe for drainage to reduce the gas concentration in the drill site.

[0038] When the construction of the intercept borehole is completed, withdraw the drill pipe, disassemble the guiding four-way joint, and connect the hole-sealing pipe and the gas drainage pipeline in series through a water drainer. A flow valve is provided between the water drainer and the hole-sealing pipe, and an orifice flowmeter is installed between the water drainer and the gas drainage pipeline. Specifically, after the construction of the intercept borehole is completed, withdraw all the drill pipes, remove the downhole motor at the bottom of the hole, disconnect the connection between the ground anchor and the drill rig. After withdrawing the drill pipe, install an orifice flowmeter and a flow valve, and connect them to the gas drainage pipeline through a water drainer to complete the layout of the gas extraction unit, as Figure 4 shown.

[0039] The embodiment of the present application also provides an automatic drainage system for downward gas drainage with fixed-length boreholes, as Figure 5 shown. The automatic drainage system includes: a borehole unit 501 and a drainage unit 502. The borehole unit 501 is configured to arrange drill sites in the intake airway and return airway of the mining layer, construct a number of intercepting boreholes in the drill sites, evenly cover the dip of the coal mining face, and form a layered intercepting cross-section. Each intercepting borehole is divided into an upper main hole and a lower branch hole. The upper main hole is arranged in the stable rock between the mining layer and the adjacent layer, and the initial flat-return position of the upper main hole is located at the bottom of the rock stratum, and it is gradually constructed upward at a small angle. The lower branch hole is gradually constructed downward at a small angle from the initial flat-return position of the upper main hole to the adjacent layer, and the initial flat-return position of the lower branch hole is located at the top of the adjacent layer. The drainage unit 502 includes: a water drainer, an orifice flowmeter, a gas drainage pipeline, and a flow valve. The inlet of the water drainer is connected to the orifice of the sealing pipe inserted into the borehole blowout prevention hole of the coal wall through a pipeline, and the outlet of the water drainer is connected to the gas drainage pipeline. Among them, a flow valve is provided on the connecting pipeline between the inlet of the water drainer and the sealing pipe, and an orifice flowmeter is provided between the outlet of the water drainer and the drainage pipeline.

[0040] In the embodiment of the automatic drainage of downward gas drainage with fixed-length boreholes of the present application, since the upper main hole is arranged in the rock stratum, the borehole is easy to form and not prone to collapse, and the drainage period is long. After the upper mining layer is mined, the coal and rock mass expands, generating a large number of fissures, which can effectively intercept a large amount of depressurized gas drained from the adjacent lower layer. Moreover, the upper main hole is constructed upward, and the accumulated water can flow into the lower branch hole along the borehole. When the water in the lower branch hole is less, it does not affect the pre-drainage of the adjacent layer gas. When the water in the lower branch hole is more, it is used as the water accumulation hole for the upper-level borehole. And affected by the advanced stress of the coal mining face in the upper mining layer, the coal holes in the adjacent lower layer within the range of the advanced stress are damaged, the coal mass around the borehole is depressurized, generating a large number of fissures. While the gas gushes out, it also provides a channel for the drainage of the accumulated water in the borehole. The accumulated water in the lower borehole will automatically flow into the coal body as the upper working face advances, effectively protecting the interception and drainage effects of the upper main hole.

[0041] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An automatic drainage method for downward gas drainage fixed-length boreholes, characterized in that, it includes: Drilling sites are arranged in the intake airway and return airway of the mining layer. Gas drainage interception boreholes are constructed in the drilling sites, evenly covering the dip of the working face to form a layered interception section; each interception borehole is divided into an upper main hole and a lower branch hole. The upper main hole is arranged in the stable rock between the mining layer and the adjacent layer, and the initial flat-return position of the upper main hole is located at the bottom of the rock formation, and it is gradually constructed upward at a small angle; among them, downward boreholes are constructed in the coal and rock walls of the mining layer, and the downward boreholes are sealed. After the sealing is completed, the upper main hole is constructed upward in the borehole, and the intersection of the borehole sealing section and the upper main hole is the initial flat-return position of the upper main hole; after the construction of the upper main hole is completed, the lower branch hole is constructed in the coal seam; and after sealing and before constructing the upper main hole, a guiding four-way is installed at the orifice of the sealing pipe, and the interception borehole is constructed through the guiding four-way to complete the layout of the directional borehole anti-blowout device. Subsequently, the guiding four-way is disassembled to complete the layout of the gas drainage unit; The lower branch hole is gradually constructed downward at a small angle from the initial flat-return position of the upper main hole to the adjacent layer, and the initial flat-return position of the lower branch hole is located at the top of the adjacent layer.

2. The automatic drainage method for downward gas drainage fixed-length boreholes according to claim 1, characterized in that, the operation of sealing the downward borehole includes: One end of the sealing pipe is sealed with gypsum, the other end is inserted into the borehole, and a grouting pipe is axially laid along the outside of the sealing pipe; Seal with gypsum between the end of the sealing pipe and the borehole; Grout into the pores between the coal wall and the sealing pipe through the grouting pipe until the slurry penetrates into the coal wall, the coal body seeps water or the slurry oozes out of the sealing pipe, and then stop grouting.

3. The automatic drainage method for downward gas drainage fixed-length boreholes according to claim 2, characterized in that, it further includes: The upper end of the guiding four-way is connected to the gas drainage pipeline, the lower end is connected in series with a water slag sedimentation tank, and after a hole blocker is installed at the front end, the drill pipe passes through the hole blocker to construct the interception borehole.

4. The automatic drainage method for downward gas drainage fixed-length boreholes according to claim 3, characterized in that, it further includes: In response to the completion of the construction of the interception borehole, the drill pipe is withdrawn, the guiding four-way is disassembled, and the sealing pipe is connected in series with the gas drainage pipeline through a water drainer. A flow valve is provided between the water drainer and the sealing pipe, and an orifice flowmeter is installed between the water drainer and the gas drainage pipeline.

5. The automatic drainage method for downward gas drainage fixed-length boreholes according to claim 1, characterized in that, When constructing the interception borehole, the borehole is measured once every 3 meters or 6 meters, and the measurement result is compared with the preset trajectory to adjust the elbow direction according to the comparison result.

6. The automatic drainage method for downward gas drainage fixed-length boreholes according to claim 1, characterized in that, When constructing the interception borehole, in response to the gas concentration in the drilling site reaching 0.8%, stop drilling, and take measures such as exhausting the gas in the drilling site through a ventilation duct or extracting the gas by inserting a pipe.

7. A downward gas drainage fixed-length borehole automatic drainage system, characterized in that, it includes: a borehole unit and a drainage unit; The drilling unit is configured to arrange drill sites in the intake airway and return airway of the mining seam, construct intercepting boreholes in the drill sites, evenly cover the dip of the coal face, and form a layered interception section; each intercepting borehole is divided into an upper main hole and a lower branch hole. The upper main hole is arranged in the stable rock between the mining seam and the adjacent seam, and the initial flat-return position of the upper main hole is located at the bottom of the rock formation, and it is gradually constructed upward at a small angle; the lower branch hole is gradually constructed downward at a small angle from the initial flat-return position of the upper main hole to the adjacent seam, and the initial flat-return position of the lower branch hole is located at the top of the adjacent seam; among them, downward boreholes are constructed in the coal and rock walls of the mining seam, and the downward boreholes are sealed. After the sealing is completed, the upper main hole is constructed upward in the borehole, and the junction of the sealed section of the borehole and the upper main hole is the initial flat-return position of the upper main hole; after the upper main hole is constructed, the lower branch hole is constructed in the coal seam; and after sealing and before constructing the upper main hole, a guiding four-way is installed at the orifice of the sealing pipe, and the intercepting borehole is constructed through the guiding four-way to complete the layout of the directional borehole anti-blowout device. Subsequently, the guiding four-way is disassembled to complete the layout of the gas drainage unit; The drainage unit includes: a water drainer, an orifice flowmeter, a gas drainage pipeline, and a flow valve. The inlet of the water drainer is connected to the orifice of the sealing pipe inserted into the anti-blowout borehole in the coal wall through a pipeline, and the outlet of the water drainer is connected to the gas drainage pipeline; among them, a flow valve is provided on the connecting pipeline between the inlet of the water drainer and the sealing pipe, and an orifice flowmeter is provided between the outlet of the water drainer and the drainage pipeline.

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