A grouting pipe for preventing and treating spontaneous combustion of goaf and two-lane residual coal and a use method thereof

Abstract

The application discloses a grouting pipe for preventing and treating gob area and two-lane residual coal spontaneous combustion and a use method thereof. Slurry in the grouting pipe is divided into multiple parts, one part of the slurry is transported to the grouting pipe head through the inside of the square pipe, and the slurry is directly injected into the deep part of the gob area. When the slurry around the pipe flows to the first horn-shaped flow divider, under the action of the arc-shaped flow divider, a part of the slurry changes the flowing direction along the arc of the arc-shaped flow divider, the slurry changing the direction is sprayed out through the outer pipe perforations to inject the slurry into the residual coal in the gob area around the perforations. The remaining part of the slurry flows to the next horn-shaped flow divider through the perforations on the arc-shaped flow divider and the gap between the arc-shaped flow dividers and the outer pipe, and the above-mentioned multiple times of flow dividing and turning process of the slurry are repeated. Therefore, the flowing time of the slurry in the grouting pipe is increased, the grouting pressure is increased, the amount of the slurry entering the gob area through the perforations arranged in the grouting pipe is increased, and the prevention and treatment effect of the residual coal spontaneous combustion in the area is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of grouting pipe for preventing and treating goaf and two lane residual coal spontaneous combustion and its use method, belong to working face goaf residual coal spontaneous combustion prevention technical field. BACKGROUND

[0002] In recent years, fully mechanized top coal mining technology is widely used in China, resulting in more residual coal in goaf, serious air leakage, and frequent spontaneous combustion fire. Especially in the two lanes of the coal mining face (i.e. the transport crossheading and the track crossheading), there is more residual coal. Since the residual coal in the two lanes cannot be recovered during mining, if no measures are taken, the residual coal in the goaf will have the risk of coal spontaneous combustion, affecting the normal recovery of the underground working face.

[0003] At present, the more common method for preventing and treating coal spontaneous combustion in China is grouting for fire prevention and extinguishment, and good results have been achieved in practice, becoming one of the main measures for controlling internal fire in the mine. For example, Chinese Patent Application No. CN201810169869.7, entitled "Method for preventing and treating residual coal spontaneous combustion in goaf during fully mechanized top coal mining face withdrawal", grouts into the goaf and determines whether to conduct secondary grouting by judging the grouting effect through the construction of a measure hole. Another example is Chinese Patent Application No. CN202110633051.8, entitled "Mine intermittent grouting fire prevention and extinguishment device and method", which uses a double grouting pipe network to achieve the purpose of plugging the cracks in the goaf by means of intermittent and alternate grouting. However, the above-mentioned grouting for fire prevention and extinguishment technology has the following problems when applied: ① The existing grouting pipe has a structure that only a flower hole is opened on the wall of the transport pipe as a grouting pipe. Since the grout flows in the axial direction of the grouting pipe, the flower hole opening on the side wall is actually perpendicular to the flow direction, and the flow rate of the grout flowing out of the flower hole is low when the grout flows through the grouting pipe, resulting in a short spraying distance of the grout flowing out of the flower hole. Therefore, the grout cannot be quickly and effectively pumped to the upper part of the two lanes and cover the coal body during grouting, and only long-term continuous grouting can achieve this purpose. ② Due to the structure of the above-mentioned existing grouting pipe, most of the grout passing through the grouting pipe is transported from one end to the other end, and only a small part is discharged into the cracks in the goaf around the grouting pipe through the flower hole, resulting in a small amount of grouting in the area near the flower hole, and the residual coal still has the risk of coal spontaneous combustion for a period of time.

[0004] In summary, the existing grouting pipe cannot meet the requirements of preventing and treating residual coal spontaneous combustion in the goaf and the two lanes of the working face. Therefore, how to provide a new grouting pipe and its use method, so that it has a high grouting amount around the coal body during grouting, and the grout sprayed from the flower hole has a long spraying distance, can cover the coal body in the upper part of the two lanes, and reduce the possibility of residual coal spontaneous combustion in the goaf and the two lanes, is one of the research directions in the industry. SUMMARY

[0005] In view of the problems of the prior art, the present application provides a grouting pipe for preventing and treating spontaneous combustion of goaf and residual coal in two roadways and a use method thereof, so that the grouting pipe can have a high grouting amount for surrounding coal bodies when grouting, and the grouting liquid sprayed from the borehole has a long spraying distance, so as to cover the coal bodies in the upper part of the two roadways and reduce the possibility of spontaneous combustion of the goaf and residual coal in the two roadways.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a grouting pipe for preventing and treating spontaneous combustion of goaf and residual coal in two roadways, comprising an outer pipe, a flow dividing device and a grouting pipe head, the grouting pipe head is installed at one end of the outer pipe, and a threaded interface is arranged at the other end of the outer pipe;

[0007] Four fixed grooves are formed in the inner wall of the outer pipe, and the four fixed grooves are uniformly distributed on the inner wall of the outer pipe and are parallel to the axis of the outer pipe;

[0008] The flow dividing device comprises a square pipe and a plurality of horn-shaped flow dividers, the plurality of horn-shaped flow dividers are arranged at equal intervals on the outer surface of the square pipe, and are used to change the flow direction of the grouting liquid in the outer pipe, the horn-shaped flow divider comprises four arc-shaped flow dividing pieces, the four arc-shaped flow dividing pieces are fixedly connected with each other to form a horn-shaped flow divider, two ports of the horn-shaped flow divider are a small square horn mouth and a large square horn mouth respectively, the horn-shaped flow divider is sleeved on the outer surface of the square pipe, and the small square horn mouth of the horn-shaped flow divider is fixedly connected with the square pipe, a plurality of boreholes are formed in each arc-shaped flow dividing piece, the outer pipe wall and the grouting pipe head;

[0009] The flow dividing device is placed in the outer pipe, the small square horn mouth of each horn-shaped flow divider faces the threaded interface, and the four top corners of the large square horn mouth of each horn-shaped flow divider are placed in the four fixed grooves, so that the flow dividing device can move along the axis of the outer pipe in the outer pipe, and is prevented from moving radially along the outer pipe, and a gap is left between each edge of the large square horn mouth of each horn-shaped flow divider and the inner wall of the outer pipe.

[0010] Further, the number of the horn-shaped flow dividers is 6-10, and 9-12 boreholes are arranged on each arc-shaped flow dividing piece. This number setting can further ensure the grouting effect of the grouting pipe.

[0011] Further, the number of the boreholes arranged on the side close to the working face and the upper side of the outer pipe after installation is more than that of the boreholes arranged on the other sides. This setting can make more grouting liquid be sprayed on the side close to the working face and the upper side, and improve the fire prevention and extinguishing effect of the residual coal at the above two positions.

[0012] Further, the radian of each arc-shaped flow dividing piece is 55°-65°. This radian setting can improve the speed and distance of the grouting liquid sprayed from the boreholes of the outer pipe after the direction of the grouting liquid is changed, and further improve the grouting effect on the surrounding coal bodies.

[0013] The grouting fire prevention and extinguishing method of the grouting pipe for preventing and treating goaf and two-lane residual coal spontaneous combustion has the following specific steps:

[0014] A. According to the field measurement and geological data, the range of each of the three zones of coal spontaneous combustion in the goaf is determined, and the three zones of coal spontaneous combustion are heat dissipation zone, oxidation zone and suffocation zone;

[0015] B. Two grouting pipes are preset in the upper lane of the working face along the lane direction, which are 1# grouting pipe and 2# grouting pipe, and the working face excavation direction is the front. The end of the 2# grouting pipe is arranged 15-20 m in front of the end of the 1# grouting pipe, and the ends of the two grouting pipes are both connected with a grouting pipe for preventing and treating goaf and two-lane residual coal spontaneous combustion through thread connection;

[0016] C. After the 1# grouting pipe is connected with the grouting pipe and buried in the oxidation zone of the goaf, the slurry is transported to the goaf through the 1# grouting pipe. After the slurry enters the outer pipe of the grouting pipe, the flow divider is impacted. Part of the slurry enters the square pipe and is transported to the position of the grouting pipe head, and finally is discharged from the perforation of the grouting pipe head to the surrounding coal body. Some of the slurry changes the flow direction after the curvature of the arc-shaped flow divider, and is sprayed from the perforation of the outer pipe wall to the surrounding coal body. Some of the slurry flows to the second flow divider through the perforation of the first flow divider and the gap between the first flow divider and the outer pipe, and impacts the second flow divider. At this time, the processing process of the second flow divider is the same as that of the first flow divider. Then the slurry flows to the subsequent flow dividers in turn. The 1# grouting pipe continuously injects the slurry to realize the grouting fire prevention and extinguishing work of the current oxidation zone of the goaf. At this time, the 2# grouting pipe is in a disconnected state;

[0017] D. With the advancement of the working face, after the 2# grouting pipe and the grouting pipe enter the oxidation zone of the goaf, the 1# grouting pipe is closed, the 2# grouting pipe is connected and the slurry is injected into the goaf. The grouting process of the grouting pipe on the 2# grouting pipe is the same as that of the grouting pipe on the 1# grouting pipe in step C. At the same time, the 1# grouting pipe and the grouting pipe for preventing and treating goaf and two-lane residual coal spontaneous combustion are disassembled and the length of the 1# grouting pipe is removed, so that the end of the 1# grouting pipe is located 15-20 m in front of the end of the 2# grouting pipe. Then the grouting pipe for preventing and treating goaf and two-lane residual coal spontaneous combustion is reconnected at the end of the current 1# grouting pipe. The 2# grouting pipe continuously injects the slurry to realize the grouting fire prevention and extinguishing work of the current oxidation zone of the goaf;

[0018] E, with the advancing of the working face, the 1# grouting pipe to be reset and its grouting pipe enter the range of the goaf oxidation zone, at this time, the 1# grouting pipe is grouted, the 2# grouting pipe repeats the processing procedure of the 1# grouting pipe in step D, the grouting to the goaf and the two roadways of the coal mining face is continued, the cycle is repeated, the 1# grouting pipe and the 2# grouting pipe alternately perform the grouting operation, until the mining of the whole working face is completed.

[0019] Compared with the prior art, the present application divides the slurry in the grouting pipe into multiple parts by installing a flow dividing device inside the conventional grouting pipe, one part of the slurry is transported to the grouting pipe head through the inside of the square pipe to make the slurry directly injected into the deep part of the goaf, the slurry flowing around the pipe is changed in flow direction by the arc-shaped flow dividing piece when flowing to the first horn-shaped flow divider, a plurality of holes are arranged on the outer pipe wall on the extension line of the changed flow direction, the changed direction slurry is sprayed out through the outer pipe holes to grout the residual coal in the goaf around the holes, the remaining part of the slurry flows to the next horn-shaped flow divider through the holes on the arc-shaped flow dividing piece and the gap between the arc-shaped flow dividing piece and the outer pipe, and the slurry is repeatedly divided and changed in direction, that is, the slurry is divided and changed in direction for multiple times after passing through each horn-shaped flow divider. The existence of the arc-shaped flow dividing piece increases the time of the slurry flowing in the grouting pipe, increases the grouting pressure, and increases the amount of the slurry entering the goaf through the holes arranged in the grouting pipe, greatly improving the prevention and control effect of the residual coal spontaneous combustion in the area. Meanwhile, the arc-shaped flow dividing piece can change the flow direction of a part of the slurry, the flow speed of the slurry after the flow direction is changed is increased, the spraying distance of the slurry after being sprayed out is farther, and the slurry is more efficiently transported to the deep part of the residual coal in the four directions of up, down, left and right of the grouting pipe, solving the problem of coal spontaneous combustion in the goaf. In addition, the arc-shaped flow dividing piece is arc-shaped and has holes processed thereon, reducing the energy loss when the slurry changes the flow direction. Therefore, the grouting pipe of the present application can divide the slurry for multiple times after the slurry enters the outer pipe, the divided slurries are transported respectively, and a high grouting amount of the coal body around the grouting pipe can be obtained during grouting, and the slurry sprayed out from the holes has a far spraying distance, which can cover the coal body above the two roadways, reducing the possibility of residual coal spontaneous combustion in the goaf and the two roadways. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the internal structure diagram of the grouting pipe of the present application;

[0021] Figure 2 is the side view of the grouting pipe of the present application;

[0022] Figure 3 is the structure diagram of the flow dividing piece in the present application;

[0023] Figure 4is a schematic diagram of slurry flow in the outer tube in the present application;

[0024] Figure 5 is a schematic diagram of the distribution of the flower hole on the side and the lower side of the outer tube away from the working face in the present application;

[0025] Figure 6 is a schematic diagram of the distribution of the flower hole on the side and the upper side of the outer tube close to the working face in the present application;

[0026] Figure 7 is a CO concentration diagram of the return air corner of the working face after grouting and fire prevention by using ordinary grouting pipe and existing grouting method;

[0027] Figure 8 is a CO concentration diagram of the return air corner of the working face after grouting and fire prevention by using the grouting pipe and the working method of the present application;

[0028] Figure 9 is a schematic diagram of the layout during the grouting process of the present application.

[0029] In the figure: 1-outer tube, 2-horn-shaped flow divider, 3-grouting pipe head, 4-threaded interface, 5-fixing groove, 6-square tube, 7-flower hole, 8-slurry flow direction, 9-arc-shaped flow piece. DETAILED DESCRIPTION

[0030] The present application will be further described below.

[0031] As shown in Figure 1 and 2 , a grouting pipe for preventing and treating the spontaneous combustion of goaf and residual coal in two roadways, comprising an outer tube 1, a flow dividing device and a grouting pipe head 3, the grouting pipe head 3 is installed at one end of the outer tube 1, and the other end of the outer tube 1 is provided with a threaded interface 4;

[0032] Four fixing grooves 5 are formed on the inner wall of the outer tube 1, and the four fixing grooves 5 are uniformly distributed on the inner wall of the outer tube 1 and are parallel to the axis of the outer tube 1;

[0033] The flow dividing device comprises a square tube 6 and a plurality of horn-shaped flow dividers 2, the plurality of horn-shaped flow dividers 2 are arranged at equal intervals on the outer surface of the square tube 6, and are used to change the flow direction of the slurry in the outer tube 1, the horn-shaped flow divider 2 comprises four arc-shaped flow pieces 9, the four arc-shaped flow pieces 9 are fixedly connected to each other to form the horn-shaped flow divider 2, two ports of the horn-shaped flow divider 2 are small square horn mouths and large square horn mouths respectively, the horn-shaped flow divider 2 is sleeved on the outer surface of the square tube 6, and the small square horn mouth thereof is fixedly connected with the square tube 6, a plurality of flower holes 7 are formed on each arc-shaped flow piece 9, the outer tube 1 and the grouting pipe head 3; the number of the horn-shaped flow dividers 2 is 6-10, and 9-12 flower holes 7 are arranged on each arc-shaped flow piece 9. The number of the horn-shaped flow dividers 2 is arranged to further ensure the grouting effect of the grouting pipe.

[0034] The shunt device is placed in the outer pipe 1, and the small square horn mouth of each horn-shaped shunt 2 faces the threaded interface 4, and the four top corners of the large square horn mouth of each horn-shaped shunt 2 are placed in the four fixed grooves 5 respectively, so that the shunt device can move axially in the outer pipe 1 and is prevented from moving radially in the outer pipe 1, thus ensuring that it does not rotate in the outer pipe 1 when shunting the slurry and affecting the shunting effect, and a gap is left between the four edges of the large square horn mouth of each horn-shaped shunt 2 and the inner wall of the outer pipe 1.

[0035] As an improvement of the present application, as shown in Figure 5 and 6 , the number of the boreholes 7 arranged on the side close to the working face and the upper side of the outer pipe 1 after installation is more than that of the boreholes 7 arranged on the other sides. This arrangement can make more slurry be sprayed on the side close to the working face and the upper side, and improve the fire prevention and extinguishing effect of the residual coal at the above two positions.

[0036] As another improvement of the present application, as shown in Figure 3 , the curvature of each arc-shaped shunt piece 9 is 55°-65°. With this curvature, the speed and distance of the slurry sprayed from the boreholes of the outer pipe 1 after the slurry changes direction can be improved, and the grouting effect on the surrounding coal body can be further improved.

[0037] The grouting fire prevention and extinguishing method of the grouting pipe for preventing and treating the spontaneous combustion of residual coal in the goaf and the two roadways is as follows:

[0038] A. First, according to the field measurement and geological data, the ranges of the three zones of coal spontaneous combustion, i.e., the heat dissipation zone, the oxidation zone and the suffocation zone, are determined.

[0039] B. As shown in Figure 9 , two grouting pipes are arranged along the roadway strike in the upper roadway of the working face, which are 1# grouting pipe and 2# grouting pipe respectively. With the heading direction of the working face as the front, the end of the 2# grouting pipe is arranged at 15-20 m in front of the end of the 1# grouting pipe, and the ends of the two grouting pipes are both connected with a grouting pipe for preventing and treating the spontaneous combustion of residual coal in the goaf and the two roadways through a threaded connection.

[0040] C. After the 1# grouting pipe is connected with the grouting pipe and is buried in the oxidation zone of the goaf, the slurry is transported to the goaf through the 1# grouting pipe, and the slurry impacts the shunt device after entering the outer pipe 1 of the grouting pipe, as shown in Figure 4As shown, a portion of the slurry enters the square pipe 6 and is transported to the grouting pipe head 3. Finally, it is discharged from the hole 7 of the grouting pipe head 3 to the surrounding coal body. When the other portion of the slurry impacts the first distributor, some of the slurry changes its flow direction with the curvature of the arc-shaped distributor plate 9 and is sprayed out from the hole 7 of the outer pipe 1 to the surrounding coal body. Some of the slurry flows through the hole 7 of the first distributor and the gap between the first distributor and the outer pipe during the impact to the second distributor and impacts the second distributor. At this time, the processing process of the second distributor is the same as that of the first distributor. Then the slurry flows to the subsequent distributors in sequence. The 1# grouting pipe continues to inject slurry to realize the grouting and fire prevention work of the oxidation zone in the current goaf. At this time, the 2# grouting pipe is in the disconnected state.

[0041] D. As the working face advances, once grouting pipe #2 and its injection pipe enter the oxidation zone of the goaf, grouting pipe #1 is closed, grouting pipe #2 is connected, and grout is injected into the goaf. The grouting process of the injection pipe on grouting pipe #2 is the same as the grouting process of the injection pipe on grouting pipe #1 in step C. At the same time, grouting pipe #1 is separated from the injection pipe for preventing spontaneous combustion of coal residue in the goaf and the two roadways, and part of the length of grouting pipe #1 is disassembled, so that the end of grouting pipe #1 is 15-20m in front of the end of grouting pipe #2. Then, the injection pipe for preventing spontaneous combustion of coal residue in the goaf and the two roadways is reconnected at the current end of grouting pipe #1. Grouting pipe #2 continues to inject grout to achieve grouting and fire prevention work in the oxidation zone of the current goaf.

[0042] E. As the working face advances, after the newly installed No. 1 grouting pipe and its injection pipe enter the oxidation zone of the goaf, grouting is performed on No. 1 grouting pipe. The No. 2 grouting pipe repeats the treatment process of No. 1 grouting pipe in step D, continuously injecting grout into the goaf of the coal mining face and the two roadways. This cycle continues, with No. 1 grouting pipe and No. 2 grouting pipe alternating grouting operations until the mining of the entire working face is completed.

[0043] On-site verification:

[0044] During the longwall mining of the 3171 working face at the Hongqi Coal Mine in Shandong Province, CO levels frequently exceeded the limit (greater than 24 ppm) in the upper corner of the working face. The Hongqi Coal Mine adopted grouting fire prevention and extinguishing technology, injecting yellow mud slurry into the working face roadway using conventional grouting pipes and existing grouting processes. Grouting was continuously carried out in the goaf area of ​​the working face from February 18th to February 28th, 2022 (a total of 11 days). Figure 7 As shown, the CO concentration at the return air corner of the working face remained consistently above 24 ppm, indicating that grouting was ineffective in preventing spontaneous combustion of residual coal. From March 23 to March 31, 2022 (9 days in total), yellow mud slurry was injected into the roadway of the working face using the grouting pipe and grouting method of this invention. Figure 8As shown, the CO concentration in the return corner of the working face is maintained below 24 ppm at all times.

[0045] The above merely describes the preferred embodiments of the present application, and it should be pointed out that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A grouting pipe for preventing spontaneous combustion of goaf and two-lane residual coal, characterized in that, The injection pipe head is arranged at one end of the outer pipe, and the other end of the outer pipe is provided with a threaded interface; Four fixed grooves are formed in the inner wall of the outer pipe, and the four fixed grooves are uniformly distributed on the inner wall of the outer pipe and are parallel to the axis of the outer pipe; The shunt device comprises a square pipe and a plurality of horn-shaped shunt devices, the plurality of horn-shaped shunt devices are arranged at equal intervals on the outer surface of the square pipe, and are used for changing the flow direction of the slurry in the outer pipe; the horn-shaped shunt device comprises four arc-shaped shunt plates, the four arc-shaped shunt plates are fixedly connected with each other to form the horn-shaped shunt device, two ports of the horn-shaped shunt device are a small square horn mouth and a large square horn mouth respectively, the horn-shaped shunt device is sleeved on the outer surface of the square pipe, and the small square horn mouth is fixedly connected with the square pipe; a plurality of flower holes are formed in each arc-shaped shunt plate, the outer pipe wall and the injection pipe head; The shunt device is arranged in the outer pipe, the small square horn mouth of each horn-shaped shunt device faces the threaded interface, the large square horn mouth of each horn-shaped shunt device is arranged in the four fixed grooves respectively, so that the shunt device can move along the axis of the outer pipe in the outer pipe, and movement of the shunt device along the radial direction of the outer pipe is prevented, and a gap is formed between each edge of the large square horn mouth of each horn-shaped shunt device and the inner wall of the outer pipe.

2. The grouting pipe for preventing coal spontaneous combustion in goaf and two-road residual coal of claim 1, wherein, The number of the horn-shaped shunt devices is 6-10, and 9-12 flower holes are formed in each arc-shaped shunt plate.

3. The grouting pipe for preventing coal spontaneous combustion in goaf and two-road residual coal of claim 1, wherein, The number of the flower holes arranged on the side close to the working face and the upper side of the outer pipe after installation is greater than the number of the flower holes arranged on the other sides.

4. The grouting pipe for preventing coal spontaneous combustion in goaf and two-road residual coal of claim 1, wherein, The arc of each arc-shaped shunt plate is 55-65°.

5. The method according to any one of claims 1 to 4, wherein the method is a grouting fire prevention and extinguishing method for preventing and treating gob and two-road residual coal spontaneous combustion by using the grouting pipe. The specific steps are as follows: A. First, according to the field measurement and geological data, the ranges of the three zones of coal spontaneous combustion in the goaf are determined, and the three zones of coal spontaneous combustion are heat dissipation zone, oxidation zone and suffocation zone; B. Two grouting pipes are arranged along the tunnel direction in the upper roadway of the working face, and are 1# grouting pipe and 2# grouting pipe respectively, the working face excavation direction is the front, the end of the 2# grouting pipe is arranged at a position 15-20 m in front of the end of the 1# grouting pipe, and the end of the two grouting pipes is connected with an injection pipe for preventing and treating the spontaneous combustion of the goaf and the residual coal in the two roadways through a threaded connection; C. After the 1# grouting pipe is connected with the injection pipe and is buried in the oxidation zone of the goaf, the slurry is injected into the goaf through the 1# grouting pipe, the slurry is impacted on the shunt device after entering the outer pipe of the injection pipe, part of the slurry enters the square pipe and is transported to the position of the injection pipe head, and finally is discharged from the flower holes of the injection pipe head to the surrounding coal body, the other part of the slurry changes the flow direction after being impacted on the first shunt device, some of the slurry is sprayed from the flower holes of the outer pipe wall to the surrounding coal body, and the other part of the slurry flows to the second shunt device through the flower holes of the first shunt device and the gap between the first shunt device and the outer pipe, and impacts the second shunt device, at this time, the processing process of the second shunt device is the same as that of the first shunt device, then the slurry flows to the subsequent shunt devices in turn, the 1# grouting pipe continuously injects the slurry, and the grouting and fire prevention work in the oxidation zone of the current goaf is realized, at this time, the 2# grouting pipe is in a disconnected state. D. With the advancing of the working face, when the 2# grouting pipe and its grouting pipe enter the range of the goaf oxidation zone, the 1# grouting pipe is closed, the 2# grouting pipe is connected and grout is injected into the goaf, the grouting process of the grouting pipe on the 2# grouting pipe is the same as that of the grouting pipe on the 1# grouting pipe in step C, at the same time, the 1# grouting pipe is split and the length of the 1# grouting pipe is removed, so that the end of the 1# grouting pipe is located 15-20m in front of the end of the 2# grouting pipe, then the grouting pipe for preventing and treating the spontaneous combustion of the goaf and the two roadways is reconnected at the end of the 1# grouting pipe; the 2# grouting pipe continuously injects grout, and the grouting and fire prevention work for the current goaf oxidation zone is realized; E. With the advancing of the working face, when the 1# grouting pipe and its grouting pipe enter the range of the goaf oxidation zone, the 1# grouting pipe is grouted, the 2# grouting pipe repeats the process of the 1# grouting pipe in step D, and continuously grouts into the goaf and the two roadways of the coal mining face, so that the 1# grouting pipe and the 2# grouting pipe alternately grout until the mining of the whole working face is completed.

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