Variable coal pillar type mining method

Abstract

The invention provides a variable coal pillar type mining method, relates to the technical field of coal mining, and aims to solve the problem of low coal recovery rate. The variable coal pillar type mining method comprises the steps that after a first roadway is deflected in the direction deviating from a goaf during tunneling, tunneling continues to be conducted in the length direction parallel to a preset coal pillar, and a protruding coal pillar is formed; and after the protruding coal pillar is formed, a second roadway with the two ends communicating with the first roadway is excavated from the root of the protruding coal pillar in the direction parallel to the preset coal pillar. The coal recovery rate can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, and in particular to a variable coal pillar type mining method. Background Art

[0002] At present, underground coal mining usually adopts a longwall mining mode in which two tunnels 34 enclose a working face 31, and a section coal pillar 33 is left between adjacent working faces 31. Figure 1 and Figure 2 Usually, the size of the adjacent section coal pillars 33 of a working face 31 will not change once it is determined. The adjacent section coal pillars 33 usually have two sizes, namely, large coal pillars of 20m-50m and small coal pillars of 4m-10m.

[0003] However, in some cases, such coal pillars are difficult to meet the needs of the site: although large coal pillars play an effective supporting role and can isolate harmful gases or mine water from adjacent goafs 32, they will waste coal resources and have a low recovery rate in the mining area; small coal pillars have a high recovery rate and a high coal mining rate, but often the tunnels 34 and coal pillars have certain deformations, which can easily lead to the leakage of harmful gases and mine water from adjacent goafs 32, affecting the safety of the current working face 31 and adjacent goafs 32. In the mining of small coal pillars, once the above situation occurs, reinforcement measures such as coal wall grouting and spraying need to be taken. Although they can solve the on-site problems to a certain extent, they will still affect the progress of excavation or bring greater safety hazards, such as oxygen leakage to goafs 32 will lead to natural gas in goafs 32, gas leakage to tunnels 34 will lead to gas explosions, and water leakage from goafs 32 to tunnels 34 will lead to water accumulation in tunnels 34. Summary of the invention

[0004] The first aspect of the present invention aims to provide a variable coal pillar mining method to solve the technical problem of low existing coal recovery rate.

[0005] The first aspect of the present invention provides a variable coal pillar mining method, comprising: when excavating a first tunnel, after deviating in the direction away from the goaf, and then continuing to excavate in a length direction parallel to a preset coal pillar to form a protruding coal pillar; after the protruding coal pillar is formed, excavating a second tunnel connected to the first tunnel at both ends from the root of the protruding coal pillar in a direction parallel to the preset coal pillar.

[0006] The beneficial effects brought by the coal pillar mining method of the present invention are: Since the drainage and ventilation equipment are mostly imperfect and the exhaust and drainage capacity is weak when the first tunnel is excavated, if the excavation is carried out completely along the edge of the preset coal pillar, if the preset coal pillar leaks, the drainage and ventilation capacity will be far behind the speed of gas leakage or water inflow in the tunnel, which is very likely to cause danger. Therefore, when designing the first tunnel, or when excavating the first tunnel, if it is found that the preset tunnel does not meet the requirements, the excavation direction of the first tunnel can be adjusted to increase the thickness of the coal pillar between the first tunnel and the goaf to form a protruding coal pillar. The increase in the thickness of the coal pillar can not only effectively isolate the gas and water in the goaf and prevent them from leaking into the first tunnel, but also reduce the leakage of oxygen in the first tunnel into the goaf, causing spontaneous combustion in the goaf. Moreover, since the first tunnel is partially deflected in the direction away from the goaf, the deflection method can improve the coal recovery rate compared to directly using a large coal pillar, which is conducive to green mining.

[0007] In an optional technical solution, after continuing to excavate in a direction parallel to the length of the preset coal pillar, the first tunnel is also excavated obliquely in a direction toward the goaf.

[0008] In an optional technical solution, after the first tunnel is excavated obliquely in a direction toward the goaf, the first tunnel is continued to be excavated in a direction parallel to the length of the preset coal pillar.

[0009] Among the optional technical solutions, the variable coal pillar mining method also includes: In an optional technical solution, after excavating the second tunnel, the first tunnel is partially filled corresponding to the protruding coal pillar.

[0010] In an optional technical solution, when excavating the second tunnel, forward excavation, reverse excavation or multi-head excavation is adopted.

[0011] In an optional technical solution, the multi-head excavation also continues to excavate the first tunnel.

[0012] In an optional technical solution, during the multi-head excavation, a connecting tunnel is excavated at the lowest point of the protruding coal pillar, and then excavated upward to both sides in a direction parallel to the preset coal pillar.

[0013] In an optional technical solution, the deflection is in the direction away from the goaf, and the deflection angle is 10°~15°.

[0014] In an optional technical solution, the direction toward the goaf is tilted, and the angle of the tilt is 10°~15°.

[0015] In an optional technical solution, the maximum width of the protruding coal pillar is 20m~50m. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the background technology, the drawings required for use in the embodiments or the background technology description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0017] Figure 1 It is a top view schematic diagram of the mining method in the background technology.

[0018] Figure 2 It is a side view of the mining method in the background technology.

[0019] Figure 3 A schematic diagram of a tunnel to be excavated in the variable coal pillar mining method provided in an embodiment of the present invention.

[0020] Figure 4 A schematic diagram of a tunnel to be excavated in the variable coal pillar mining method provided in an embodiment of the present invention in which there is a region where the coal pillar width needs to be changed.

[0021] Figure 5 A schematic diagram of setting a region for changing the width of a coal pillar in the variable coal pillar mining method provided in an embodiment of the present invention.

[0022] Figure 6 A schematic diagram of digging a second tunnel in the variable coal pillar mining method provided in an embodiment of the present invention.

[0023] Figure 7 A schematic diagram of reverse excavation of a second tunnel in the variable coal pillar mining method provided in an embodiment of the present invention.

[0024] Figure 8 A schematic diagram of multi-head excavation of the second tunnel in the variable coal pillar mining method provided in an embodiment of the present invention.

[0025] Fig. 9 A schematic diagram of continuing to excavate the first tunnel while multiple heads excavate the second tunnel in the variable coal pillar mining method provided in an embodiment of the present invention.

[0026] Fig.10 A schematic diagram of setting a protruding coal pillar in a specific implementation of the variable coal pillar mining method provided in an embodiment of the present invention.

[0027] Fig.11 A side view of a second tunnel being excavated by multiple heads in a specific implementation of the variable coal pillar mining method provided in an embodiment of the present invention.

[0028] Description of reference numerals: 11-first lane; 12-second lane; 13-filling area; 21-preset coal pillar; 22-protruding coal pillar; 23-connecting tunnel; 31-working face; 32-goaf; 33-section coal pillar; 34-tunnel. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] Embodiment 1: Figure 3 A schematic diagram of a tunnel to be excavated in the variable coal pillar mining method provided in an embodiment of the present invention. Figure 4 A schematic diagram of a tunnel to be excavated in the variable coal pillar mining method provided in an embodiment of the present invention in which there is a region where the coal pillar width needs to be changed. Figure 5 A schematic diagram of setting a region for changing the width of a coal pillar in the variable coal pillar mining method provided in an embodiment of the present invention. Figure 6 A schematic diagram of the second tunnel excavation in the variable coal pillar mining method provided in an embodiment of the present invention. Figure 7 A schematic diagram of reverse excavation of a second tunnel in the variable coal pillar mining method provided in an embodiment of the present invention. Figure 8 A schematic diagram of multi-head excavation of the second tunnel in the variable coal pillar mining method provided in an embodiment of the present invention, wherein Figure 8 The state shown in the figure is the state after the connecting lane is filled. Figure 3-Figure 8 As shown, the variable coal pillar mining method provided in the first embodiment of the present invention includes: when excavating the first tunnel 11, after deviating in the direction away from the goaf 32, and then continuing to excavate along the length direction parallel to the preset coal pillar 21 to form a protruding coal pillar 22; after the protruding coal pillar 22 is formed, excavating a second tunnel 12 connected to the first tunnel 11 at both ends from the root of the protruding coal pillar 22 along the direction parallel to the preset coal pillar 21.

[0031] Since the drainage and ventilation equipment are mostly imperfect and the exhaust and drainage capabilities are weak when the first tunnel 11 is excavated, if the excavation is carried out completely along the edge of the preset coal pillar 21, if the preset coal pillar 21 leaks, the drainage and ventilation capabilities will be far behind the speed of gas leakage or water inflow into the tunnel 34, which is very likely to cause danger. Therefore, when designing the first tunnel 11, or when excavating the first tunnel 11, if it is found that the preset tunnel does not meet the requirements, the excavation direction of the first tunnel 11 can be adjusted to increase the thickness of the coal pillar between the first tunnel 11 and the goaf 32 to form a protruding coal pillar 22. The increase in the thickness of the coal pillar can not only effectively isolate the gas and water in the goaf 32 to prevent them from leaking into the first tunnel 11, but also reduce the leakage of oxygen in the first tunnel 11 into the goaf 32, which may cause spontaneous combustion in the goaf 32. Moreover, since the first tunnel 11 is partially deflected away from the goaf 32, the deflection method can improve the coal recovery rate compared to directly using a large coal pillar, which is conducive to green mining. By excavating the second tunnel 12 in the protruding coal pillar 22 to connect with the first tunnel 11, the second tunnel 12 in the protruding coal pillar 22 and the first tunnel 11 outside the protruding coal pillar 22 can be used to form an integral tunnel, which is convenient for arranging coal mining equipment to recover along the working face 31. Moreover, the coal in the protruding coal pillar 22 can also be mined, thereby improving the recovery rate.

[0032] Among them, since the drainage and exhaust facilities are not complete when the protruding coal pillar 22 is excavated, the drainage and exhaust capabilities are weak, so the ability to deal with gas leakage or water seepage accidents is poor. However, after the protruding coal pillar 22 is formed, the equipment in the first tunnel 11 is laid in place, and it has strong drainage and ventilation capabilities. Therefore, excavating the protruding coal pillar 22 at this time can also dilute the leaked gas or discharge the leaked water in time, and there will be no danger, so the excavation of the second tunnel 12 can be carried out.

[0033] Specifically, whether the overall tunnel of the preset tunnel meets the requirements depends on the geological data obtained before designing the first tunnel 11. If the information displayed by the geological data shows that the coal seam gas content is high or the goaf is waterlogged, such as Figure 3 As shown, a protruding coal pillar 22 can be designed in the first tunnel 11 during design. Figure 4 and Figure 5 As shown, when excavating, the tunnel deviates in the direction away from the goaf 32 at the corresponding position. Alternatively, when geological data is insufficient, excavation can be carried out according to the preset coal pillar 21. When it is found that the gas exceeds the standard or the water inflow is too large during the excavation process, the first tunnel 11 can be excavated at an angle. The specific situation of gas exceeding the standard may be that the gas concentration exceeds 1% or the carbon dioxide concentration exceeds 1.5%. And the water inflow is too large, for example, due to water accumulation or water inflow at the excavation head, the excavation speed is reduced by more than 30%. Figure 4 and Figure 5 The area enclosed by the dotted rectangle on the left side of the center is the area with high gas content or high water content as shown by geological data.

[0034] Among them, in the present application, excavation parallel to the length direction of the preset coal pillar 21 does not limit the angle between the excavation direction and the length direction of the preset coal pillar 21 to be exactly the same, and does not mean that there can be no angle of 0.01°. In the present application, parallel to the length direction of the preset coal pillar 21 can cover the situation where the angle between the excavation direction and the length direction of the preset coal pillar 21 is less than 5°.

[0035] like Figure 5 As shown, optionally, it is tilted away from the goaf 32, and the tilt angle is 10° to 15°.

[0036] By tilting in the direction away from the goaf 32 at the above angle, the width of the coal pillar can be increased to the required width within the appropriate overall length of the tunnel. Moreover, by using the above range of deflection angles, the speed of the angle conversion of the first tunnel 11 can be controlled appropriately to reduce the difficulty of changing the excavation angle.

[0037] like Figure 5 As shown, optionally, it is tilted toward the goaf 32, and the tilt angle is 10°~15°.

[0038] By tilting the coal pillar toward the goaf 32 at the above angle, the width of the coal pillar can be reduced to the required width within the appropriate overall length of the tunnel. Moreover, by using the above range of deflection angles, the speed of the angle conversion of the first tunnel 11 can be controlled appropriately to reduce the difficulty of changing the excavation angle.

[0039] like Figure 5 As shown, optionally, after continuing to excavate in a length direction parallel to the preset coal pillar 21 , the first tunnel 11 is also excavated obliquely in a direction toward the goaf 32 .

[0040] By deviating in the direction toward the goaf 32, the excavation position can be restored to the preset coal pillar 21 after bypassing the higher-risk position in the preset coal pillar 21, thereby reducing the width of the coal pillar in the local area, thereby reducing coal pillar waste and improving coal recovery rate.

[0041] Of course, in another implementation, if the area where the coal pillar needs to be thickened is the end of the first tunnel 11 , it is not necessary to dig the first tunnel 11 obliquely toward the goaf 32 .

[0042] Optionally, the maximum width of the protruding coal pillar 22 is 20m-50m.

[0043] When the width of the protruding coal pillar 22 is selected to be the above value, it can be equivalent to the width of the large coal pillar, which is sufficient to effectively support the coal seam above and form a sufficient barrier between the goaf 32 and the first tunnel 11 to prevent water seepage in the goaf 32, gas leakage, or oxygen in the first tunnel 11 from entering the goaf 32 and causing danger.

[0044] like Figure 5 As shown, optionally, after the first tunnel 11 is excavated obliquely in the direction toward the goaf 32 , the first tunnel 11 is continued to be excavated in a length direction parallel to the preset coal pillar 21 .

[0045] After excavating the protruding coal pillar 22 and excavating obliquely in the direction of the goaf 32, the first tunnel 11 is continued to be excavated in a direction parallel to the preset coal pillar 21. This can not only reduce the waste of coal seams, but also be coaxially arranged with the first tunnel 11 before excavating the protruding coal pillar 22. If the protruding coal pillar 22 is excavated through, they can form an integral tunnel together.

[0046] Of course, in another implementation method, if the area where the coal pillar needs to be thickened is close to the first tunnel 11, and the process of excavating the first tunnel 11 obliquely toward the goaf 32 is completed and the width of the preset coal pillar 21 is reached at the same time, the end of the first tunnel 11 is also reached, then there is no need to excavate the first tunnel 11 in a direction parallel to the preset coal pillar 21.

[0047] like Figure 6-Figure 8 As shown, optionally, after the second tunnel 12 is excavated, a portion of the first tunnel 11 corresponding to the protruding coal pillar 22 is filled.

[0048] After the second tunnel 12 is excavated, the second tunnel 12 in the protruding coal pillar 22 and the first tunnel 11 outside the protruding coal pillar 22 together form an integral tunnel. When the integral tunnel is ventilated, since the portion of the first tunnel 11 corresponding to the protruding coal pillar 22 is in a broken line shape, the ventilation airflow mainly passes through the second tunnel 12 rather than the portion of the first tunnel 11 located outside the protruding coal pillar 22, so the gas concentration of the first tunnel 11 in this portion may increase. Therefore, after the ventilation capacity of the integral tunnel is formed, even if the portion of the first tunnel 11 corresponding to the protruding coal pillar 22 is filled to form a filling area 13, it can prevent the gas concentration in this portion from being too high and causing danger. Since the space in this portion is occupied by the filling material, even if there is a gas leak in the coal seam near this portion, the leaked gas also exists in the integral tunnel and is taken away in the ventilation of the integral tunnel.

[0049] like Figure 6-Figure 8 As shown, optionally, when excavating the second tunnel 12, forward excavation, reverse excavation or multi-head excavation is adopted.

[0050] By adopting multiple methods to excavate the second tunnel 12, it can be adapted to the specific situation of the protruding coal pillar 22. That is, if the tail end of the protruding coal pillar 22 is high, the method of digging the second tunnel 12 in the forward direction can be adopted, because when digging the second tunnel 12, it can be used to dig upside down, and the water in the coal body flows to the head of the first tunnel 11, which will not interfere with the excavation working face 31. If the head end of the protruding coal pillar 22 is high, the method of digging the second tunnel 12 in the reverse direction can be adopted, so that the water in the coal body can flow to the tail of the first tunnel 11, which will not interfere with the excavation working face 31. By adopting the multi-head excavation method, the connecting tunnel 23 can be excavated from the approximate middle position of the protruding coal pillar 22 toward the goaf 32, and the excavation can be carried out from the inner end of the connecting tunnel 23 toward the head and tail of the first tunnel 11, respectively, so that the excavation speed of the second tunnel 12 can be increased, which is conducive to forming the working face 31 earlier.

[0051] Fig. 9 A schematic diagram of a method for mining coal with variable coal pillars provided in an embodiment of the present invention in which multiple heads excavate a second tunnel while continuing to excavate a first tunnel, wherein Fig. 9 The state shown in the figure is the state after the connecting lane is filled. Fig. 9 As shown, optionally, the first tunnel 11 is continued to be excavated during multi-head excavation.

[0052] When excavating the second tunnel 12, it is not necessary to complete the excavation of the first tunnel 11. In particular, when the protruding coal pillar 22 is far away from the tail of the first tunnel 11, the excavation of the first tunnel 11 to its tail and the multi-head excavation of the second tunnel 12 can be carried out simultaneously to increase the speed of forming the working face 31.

[0053] Fig.11 A side view of a second tunnel being excavated by multiple heads in a specific implementation of the variable coal pillar mining method provided in an embodiment of the present invention. Fig.11 As shown, optionally, during multi-head excavation, a connecting tunnel 23 is excavated at the lowest point of the protruding coal pillar 22, and then excavated upward to both sides in a direction parallel to the preset coal pillar 21.

[0054] The connecting tunnel 23 is set at the lowest point of the protruding coal pillar 22. After the excavation of the connecting tunnel 23 is completed, excavation is carried out from the inner end of the connecting tunnel 23 to both sides. No matter which side is excavated, the end of the connecting tunnel 23 is the lowest position of the entire tunnel being excavated. That is, no matter which side is excavated, it is an overhead excavation. If there is a protruding coal pillar 22, Fig.11 In the water accumulation area shown in the middle blue area, the water during the excavation process will flow to the end of the connecting tunnel 23. Since the first tunnel 11 outside the protruding coal pillar 22 has been laid with relevant drainage facilities when the connecting tunnel 23 is excavated, the water flowing to the connecting tunnel 23 can be quickly pumped away, and when the second tunnel 12 is excavated, the excavation work will not be disturbed by the accumulation of flowing water on the excavation working face 31.

[0055] The following embodiments are listed to specifically illustrate this method: like Figure 3 As shown, first, for a certain working face 31, the first tunnel 11 near the goaf 32 is excavated according to a small coal pillar of 8m. Fig.10 A schematic diagram of setting a protruding coal pillar in a specific implementation of the variable coal pillar mining method provided in an embodiment of the present invention. Fig.10 and Fig.11 As shown, when excavating at a certain position, it is found that water is gushing into the first tunnel 11 on one side of the goaf 32. At this time, the tunnel as a whole is excavating downward, and it is easy to accumulate water when excavating head-on, making it difficult to drain water, which seriously affects the excavation speed; so that the excavation direction is deviated by 10°~15° away from the goaf 32. When the width of the protruding coal pillar 22 is 30m, the deviated excavation is stopped, and the excavation is changed to the direction parallel to the length of the preset coal pillar 21. After the water leakage phenomenon is eliminated, it is deviated by 10°~15° in the direction toward the goaf 32. When it reaches the width position of the preset coal pillar 218m, the excavation is changed to the direction parallel to the length of the preset coal pillar 21.

[0056] After the excavation is completed, the working face 31 is connected, and after the mining begins, the second tunnel 12 is excavated in the area of ​​the protruding coal pillar 22. The coal recovery rate of the working face 31 can be improved by using the second tunnel 12 for mining. Specifically, the connecting tunnel 23 is first excavated from the lowest point of the water accumulation area of ​​the protruding coal pillar 22. After the connecting tunnel 23 is excavated in place, it is excavated upward from the inner end of the connecting tunnel 23, that is, the lowest point, to both sides. On the one hand, it can increase the excavation speed. On the other hand, it is not easy to encounter water accumulation in the upward excavation. The gushing water will flow to the inner end of the connecting tunnel 23 and be discharged by the drainage equipment that has been laid in the first tunnel 11, which is conducive to the excavation work.

[0057] After the excavation of the second tunnel 12 is completed, the first tunnel 11 outside the protruding coal pillar 22 is filled to avoid air leakage and fire, and the second tunnel 12 in the protruding coal pillar 22 and the first tunnel 11 except the protruding coal pillar 22 form an integral tunnel, and one side wall of the integral tunnel is the side wall of the preset coal pillar 21, and the leading side wall of the integral tunnel can be the mining face 31. Mining through the integral tunnel can improve the recovery rate. Moreover, compared with the large coal pillar, the preset coal pillar 21 with a smaller width in this embodiment is more conducive to maintenance, and the stress inside it is also smaller, and it is not easy to have the risk of sudden stress release.

[0058] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

[0059] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0060] In the above embodiments, the descriptions of directions such as “upper” and “lower” are all based on the drawings.

[0061] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0062] Thus, the present invention will not be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A coal pillar mining method, characterized in that: include: When excavating the first tunnel (11), the tunnel deviates in a direction away from the goaf (32), and then continues to excavate in a length direction parallel to the preset coal pillar (21) to form a protruding coal pillar (22); after the protruding coal pillar (22) is formed, a second tunnel (12) is excavated from the root of the protruding coal pillar (22) in a direction parallel to the preset coal pillar (21) to connect the first tunnel (11) at both ends.

2. The coal pillar mining method according to claim 1, characterized in that: After continuing to excavate in a length direction parallel to the preset coal pillar (21), the first tunnel (11) is also excavated obliquely in a direction toward the goaf (32).

3. The coal pillar mining method according to claim 3, characterized in that: After the first tunnel (11) is excavated obliquely in a direction toward the goaf (32), the first tunnel (11) is continued to be excavated in a length direction parallel to the preset coal pillar (21).

4. The coal pillar mining method according to claim 1, characterized in that: After the second tunnel (12) is excavated, a portion of the first tunnel (11) corresponding to the protruding coal pillar (22) is filled.

5. The coal pillar mining method according to claim 1, characterized in that: When excavating the second tunnel (12), forward excavation, reverse excavation or multi-head excavation is adopted.

6. The coal pillar mining method according to claim 5, characterized in that: During the multi-head excavation, the first tunnel (11) continues to be excavated.

7. The coal pillar mining method according to claim 5, characterized in that: During the multi-head excavation, a connecting tunnel (23) is excavated at the lowest point of the protruding coal pillar (22), and then excavated upwards to both sides in a direction parallel to the preset coal pillar (21).

8. The coal pillar mining method according to any one of claims 1 to 7, characterized in that: The deflection is in the direction away from the goaf (32), and the deflection angle is 10° to 15°.

9. The coal pillar mining method according to claim 2, characterized in that: The direction is deflected away from the goaf (32), and the deflection angle is 10° to 15°.

10. The coal pillar mining method according to any one of claims 1 to 7, characterized in that: The maximum width of the protruding coal pillar (22) is 20m to 50m.

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