A retreat tunnel layout method for pre-cracking and decompression in the working face of hard roof in medium-thick coal seams

Abstract

The present invention discloses a retreat tunnel arrangement method for pre-splitting and decompressing a working face of a hard roof in a medium-thick coal seam at the end of mining. During the advancement of the working face, main and auxiliary retreat tunnels and a pressure relief tunnel are excavated outside the influence range of the advance support pressure. At the same time, the construction, charging and blasting of pre-splitting blasting drilling, vertical loosening blasting drilling and fan-shaped loosening blasting drilling are completed in the pressure relief tunnel. First, the roof between the main retreat tunnel and the rear goaf is cut off by pre-splitting blasting. Then, the hard roof of the working face of the end-mining section is weakened by loosening blasting. When the working face is mined to the main retreat tunnel, the roof of the goaf behind the hydraulic support of the working face collapses and relieves pressure in time. At this time, the suspended top distance of the working face is reduced, and the supporting performance of the hydraulic support is utilized to the maximum extent, thereby optimizing the stress distribution of the mining field at the end of mining, effectively controlling the deformation of the surrounding rock, reducing the support cost of the retreat tunnel, improving the safe production environment of the end-mining section, and shortening the moving and reversing time of the working face.

Description

Technical Field

[0001] The present invention relates to a coal mining technology, in particular to a retreat tunnel arrangement method for pre-cracking and decompression of a hard roof working face in a medium-thick coal seam, and is particularly related to retreat tunnel maintenance during the final mining period and shortening of the moving and reversing time. Background Art

[0002] During coal mining, the hard working face roof (especially the hard basic roof) is difficult to collapse and cannot be promptly repaired, resulting in significant pressure on the working face and the withdrawal tunnel. When the working face enters the final mining stage, the working face advances slowly, and mining must be stopped to withdraw the working face equipment. At this time, the pressure and deformation of the working face and the tunnel surrounding rock continue to accumulate, posing a significant challenge to the withdrawal tunnel maintenance.

[0003] A common method for final mining at the working face is to pre-excavate a withdrawal tunnel. When the working face reaches the main withdrawal channel, mining is stopped. Hydraulic supports and other equipment are then withdrawn from the auxiliary withdrawal tunnel via a connecting tunnel between the main and auxiliary withdrawal tunnels. Pre-excavating a withdrawal tunnel avoids interference between tunneling and mining, but it cannot control the working face's advanced support pressure and the basic roof cyclic pressure. Therefore, it is often necessary to stop mining or reduce the speed to maintain constant pressure before reaching the stop-mining line to prevent the withdrawal tunnel from ending up within the pressure peak zone.

[0004] The pressure adjustment speed of the end-of-mining isobaric mining technology is slow and mostly relies on experience for judgment. Dense unit / stack-type supports often need to be arranged in the withdrawal tunnel, and the support cost is high. In essence, this is because the current end-of-mining withdrawal tunnel layout plan cannot change the working face roof structure in the end-of-mining stage. Passive support and pressure adjustment measures are inefficient, costly, and ineffective.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a retreat tunnel arrangement method for the end-of-mining pre-splitting and decompression of a hard roof working face in a medium-thick coal seam.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The method for arranging retreat tunnels in a medium-thick coal seam hard roof working face of the present invention comprises the following steps:

[0009] A. Design the air inlet and return tunnels and cutting holes for the hard roof working face of medium and thick coal seams to form a complete tunnel system for the working face.

[0010] B. The working face is mined and continuously advanced. After advancing a certain distance, the main and auxiliary retreat tunnels and pressure relief tunnels are excavated at the stop-mining line. The surrounding rock of the two retreat tunnels is supported by anchor bolts and high-preload, large-deformation anchor cables.

[0011] C. After the retreat tunnel is excavated and the support is completed, when it is not affected by the advanced support pressure of the working face, pre-splitting drill holes are constructed along the roof on the side of the pressure relief tunnel close to the stop mining line;

[0012] D. Install shaped charge blasting tubes, explosives and detonators in the pre-split boreholes, and after blasting, cut through the tunnel roof rock along the set plane;

[0013] E. Along the center line of the roof of the pressure relief tunnel, drill holes for loosening blasting vertically toward the roof;

[0014] F. On the side of the pressure relief tunnel close to the working face, construct fan-shaped loosening blasting drill holes along the tunnel direction. Each group of fan-shaped loosening blasting drill holes includes two drill holes with different angles and the same height;

[0015] G. After the loosening blasting drilling construction in the pressure relief tunnel is completed, starting from one side of the tunnel, explosives are installed and blasted section by section to destroy the integrity of the roof rock layer of the working face of the last mining section and reduce the strength of the roof rock layer;

[0016] H. When the working face advances to the pressure relief tunnel, install an air curtain device on the main retreat tunnel side of the connecting tunnel between the pressure relief tunnel and the main retreat tunnel to prevent polluted air from the working face from flowing into the main retreat tunnel through the connecting tunnel during mining, which also increases the difficulty of managing the ventilation system.

[0017] I. After the coal mining machine on the working face completes the mining of the coal pillar between the pressure relief tunnel and the main withdrawal tunnel, the working face stops advancing and the coal mining machine, scraper conveyor, hydraulic support and other mechanical equipment on the working face begin to withdraw.

[0018] It can be seen from the above technical scheme that compared with the currently commonly used double-retrieval channel end-of-mining technology, the withdrawal tunnel layout method for pre-cracking and decompression of the hard roof working face of medium and thick coal seams at the end of mining of the present invention proposes to add a pressure relief tunnel in the end-of-mining stage, and use the pressure relief tunnel to weaken the hard roof of the working face by loosening blasting. At the same time, the pre-cracking and concentrated energy blasting technology is used to cut off the rock stratum connection between the main withdrawal tunnel and the rear goaf. The roof above the withdrawal tunnel when mining is stopped is actively adjusted to a cantilever beam structure to avoid periodic fracture of the roof above the withdrawal tunnel, reduce the pressure and deformation of the surrounding rock of the withdrawal tunnel, reduce the support and maintenance cost of the withdrawal tunnel, and finally improve the safe production environment at the end of mining and shorten the time for moving and reversing the working face. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A top view of the arrangement structure of the retreat tunnel for pre-splitting and decompression in the working face of a hard roof of a medium-thick coal seam provided by an embodiment of the present invention;

[0020] Figure 2 This is a cross-sectional view of the structure taken along the working face at the end of the mining section of the working face according to an embodiment of the present invention;

[0021] Figure 3 This is a cross-sectional view of the structure BB along the working face at the end of the mining section of the working face according to an embodiment of the present invention.

[0022] Figure 4 This is a structural cross-sectional view along the working face after the working face is advanced to the stop mining line position according to an embodiment of the present invention.

[0023] In the picture:

[0024] 1-working face air intake lane, 2-working face return air lane, 3-auxiliary retreat lane; 4-connecting lane; 5-retreat lane coal pillar; 6-temporary air curtain; 7-main retreat lane; 8-auxiliary coal pillar, 9-pressure relief lane, 10-fan-shaped loosening blasting drilling hole, 11-vertical loosening blasting drilling hole, 12-pre-splitting blasting drilling hole, 13-working face hydraulic support. DETAILED DESCRIPTION

[0025] The following is a clear and complete description of the technical solutions in the embodiments of the present invention, in conjunction with the accompanying drawings. It is obvious that the described embodiments are only some of the embodiments of the present invention, not all of them, and do not constitute a limitation of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] First, the following terms may be used in this article:

[0027] The term “and / or” means that either or both of them can be realized at the same time. For example, X and / or Y includes both “X” or “Y” and “X and Y”.

[0028] The terms "include," "comprises," "contains," "has," or other similar expressions should be interpreted as non-exclusive. For example, "including certain technical features (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products, or manufactured articles, etc.) should be interpreted as including not only the technical features explicitly listed, but also other technical features known in the art that are not explicitly listed.

[0029] The term "consisting of" excludes any technical features not explicitly listed. If used in a claim, this term renders the claim closed, excluding any technical features other than those explicitly listed, except for conventional impurities associated with them. If this term appears only in a clause of a claim, it limits only the elements explicitly listed in that clause; elements listed in other clauses are not excluded from the claim as a whole.

[0030] Unless otherwise specified or limited, the terms "mounted," "connected," "connect," and "fixed" should be interpreted broadly. For example, they can refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this document based on specific circumstances.

[0031] The terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings and are only for the convenience and simplification of description, and do not explicitly or implicitly indicate that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as a limitation to this document.

[0032] The contents not described in detail in the examples of the present invention belong to the prior art known to those skilled in the art. If specific conditions are not specified in the examples of the present invention, the methods are carried out according to conventional conditions in the art or the conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments used in the examples of the present invention are not specified, they are all conventional products that can be purchased commercially.

[0033] The method for arranging a roadway in a top coal caving working face of an extra-thick coal seam according to the present invention comprises the following steps:

[0034] A. Design the air intake and return tunnels and cutting holes for the hard roof working face of medium and thick coal seams to form a complete tunnel system for the working face.

[0035] B. The working face is mined and continuously advanced. After advancing a certain distance, the main and auxiliary retreat tunnels and pressure relief tunnels are excavated at the stop-mining line. The surrounding rock of the two retreat tunnels is supported by anchor bolts and high-preload, large-deformation anchor cables.

[0036] C. After the retreat tunnel is excavated and the support is completed, when it is not affected by the advance support pressure of the working face, pre-splitting blasting drilling is carried out along the roof on the side of the pressure relief tunnel close to the stop mining line;

[0037] D. Install shaped charge blasting tubes, explosives and detonators in the pre-split boreholes, and after blasting, cut through the tunnel roof rock along the set plane;

[0038] E. Along the center line of the roof of the pressure relief tunnel, drill holes for loosening blasting vertically toward the roof;

[0039] F. On the side of the pressure relief tunnel close to the working face, construct fan-shaped loosening blasting drill holes along the tunnel direction. Each group of fan-shaped loosening blasting drill holes includes two drill holes with different angles and the same height;

[0040] G. After the loosening blasting drilling construction in the pressure relief tunnel is completed, starting from one side of the tunnel, explosives are installed and blasted section by section to destroy the integrity of the roof rock layer of the working face of the last mining section and reduce the strength of the roof rock layer;

[0041] H. When the working face advances to the pressure relief tunnel, install an air curtain device on the main withdrawal tunnel side of the connecting tunnel between the pressure relief tunnel and the main withdrawal tunnel to prevent polluted air from the working face from flowing into the main withdrawal tunnel through the connecting tunnel during mining, thereby avoiding increasing the difficulty of ventilation system management;

[0042] I. After the coal mining machine on the working face completes the mining of the coal pillar between the pressure relief tunnel and the main withdrawal tunnel, the working face stops advancing and the coal mining machine, scraper conveyor, hydraulic support and other mechanical equipment on the working face begin to withdraw.

[0043] In step B, the width of the coal pillar between the main retreat tunnel and the pressure relief tunnel is the length of the top beam of the hydraulic support of the working face.

[0044] In step C, the pre-splitting blasting drilling is biased towards the stop-mining line, the distance between adjacent pre-splitting blasting drilling holes is 0.8-1.5m, and the drilling depth L Y for:

[0045]

[0046] Where θ is the angle between the pre-splitting blasting borehole and the plumb bob direction, which is generally 10°; H Z H is the thickness of the direct top of the working surface; J It is the thickness of the basic top of the working surface.

[0047] In step D, the shaped charge blasting tube is charged in an axially non-coupled manner, and the charge structure and charge amount are determined based on on-site blasting tests to ensure that the rock between two adjacent boreholes is penetrated by cracks after blasting.

[0048] In the step E, the depth of the loosening blasting drill hole constructed vertically along the center line of the roof is the thickness H of the direct roof. Z and basic top thickness H J The sum of the boreholes is 2-5m, and the distance between adjacent boreholes along the tunnel direction is 2-5m.

[0049] In step F, the fan-shaped loosening blasting drilling at each position of the roadway includes two holes in total, the angles between the holes and the horizontal plane are 30° and 45° respectively, and the hole depths are:

[0050]

[0051]

[0052] In step G, in order to avoid roof collapse when the working face approaches the pressure relief tunnel, when installing explosives in the loose blasting drill holes on the center line of the tunnel roof and the side of the tunnel roof close to the working face, no explosives are installed within the direct roof thickness range, and only taphole mud needs to be filled; explosives are installed within the basic top range of the roof for blasting to increase penetration.

[0053] In step I, after the working face stops mining, the top beam of the working face hydraulic support should just support the cantilever roof formed by the pressure relief tunnel after pre-splitting blasting, and maximize its supporting effect on the overlying roof during the relocation and reversal period.

[0054] In summary, it can be seen that the retreat tunnel layout method for pre-cracking and decompression of the hard working face of medium and thick coal seams in the embodiment of the present invention can adopt the layout scheme of double retreat tunnels + pressure relief tunnels at the end of working face mining, actively adjust the structure of the hard roof of the working face during the end of mining through top cutting and loosening blasting, control the large deformation of the retreat tunnel in the end of mining stage caused by the hanging top or periodic breaking of the hard roof, and other strong mine pressure manifestations, optimize the stress distribution of the surrounding rock at the end of mining, reduce the support cost of the retreat tunnel, and speed up the moving and reversing speed.

[0055] In order to more clearly demonstrate the technical solutions and technical effects provided by the present invention, the embodiments of the present invention are described in detail below with reference to specific embodiments.

[0056] Example 1

[0057] like Figure 1 、 Figure 2 、 Figure 3 and Figure 4 The specific steps are as follows:

[0058] A. First, excavate the working face air inlet tunnel 1 and the working face return air tunnel 2 along the coal seam bottom plate in the hard roof working face of the medium-thick coal seam. After the excavation of the working face is completed, arrange the working face and start the mining of the working face.

[0059] B. After the working face is mined for a certain distance, and the distance between the working face and the stop mining line is greater than the width of the advance support pressure influence zone, the main withdrawal tunnel 7, the auxiliary withdrawal tunnel 3 and the pressure relief tunnel 9 are excavated at the stop mining line position, and the anchor rods and high preload and large deformation anchor cable supports of the main withdrawal tunnel 7 and the auxiliary withdrawal tunnel 3 are completed.

[0060] C. After the excavation of the main retreat tunnel 7, the auxiliary retreat tunnel 3, and the pressure relief tunnel 9 is completed, on the side of the pressure relief tunnel 9 close to the stop mining line, a pre-splitting blasting drill hole 12 is constructed along the roof obliquely toward the stop mining line, provided that it is not affected by the advance support pressure;

[0061] The depth L of the pre-splitting blasting borehole 12 isY for::

[0062]

[0063] Wherein, θ is the angle between the pre-splitting blasting borehole 12 and the plumb bob direction, which is generally 10°; H Z H is the thickness of the direct top of the working surface; J It is the thickness of the basic top of the working surface.

[0064] D. Installing shaped charge blasting tubes, explosives and detonators in the pre-splitting blasting borehole 12, and cutting the roadway roof rock layer along the set plane after blasting;

[0065] E. Along the center line of the roof of the pressure relief tunnel 9, construct vertical loosening blasting drilling holes 11 toward the roof;

[0066] F. On the side of the pressure relief tunnel 9 close to the working face, construct fan-shaped loosening blasting drill holes 10 along the tunnel direction. Each group of fan-shaped loosening blasting drill holes 10 includes two drill holes with different angles and the same height;

[0067] The calculation formulas for the depth of the above-mentioned fan-shaped loosening blasting holes are:

[0068]

[0069]

[0070] The angle between the fan-shaped loosening blasting drill hole 10 of the lower roof and the horizontal plane is 30°, and the angle between the fan-shaped loosening blasting drill hole 10 of the upper roof and the horizontal plane is 45°.

[0071] G. After the fan-shaped loosening blasting drilling holes 10 in the pressure relief tunnel 9 are completed, explosives are installed and blasted section by section starting from one side of the tunnel to destroy the integrity of the roof rock layer of the working face of the last mining section and reduce the strength of the roof rock layer;

[0072] H. When the working face advances to the pressure relief tunnel 9, a temporary air curtain 6 device is installed on the main withdrawal tunnel 7 side of the connecting tunnel 4 between the pressure relief tunnel 9 and the main withdrawal tunnel 7 to prevent the polluted air from the working face from flowing into the main withdrawal tunnel 7 through the connecting tunnel 4 during mining, and to avoid increasing the difficulty of ventilation system management;

[0073] I. After the working face coal mining machine completes the mining of the auxiliary coal pillar 8 between the pressure relief tunnel 9 and the main withdrawal tunnel 7, the working face stops advancing and the working face coal mining machine, scraper conveyor, hydraulic support and other mechanical equipment begin to withdraw.

[0074] In step B, the width of the auxiliary coal pillar 8 between the main retreat tunnel 7 and the pressure relief tunnel 9 is equal to the length of the top beam of the hydraulic support 13 of the working face.

[0075] In step C, the distance between adjacent pre-splitting blasting boreholes 12 is 0.8-1.5 m, and the specific value needs to be determined based on the results of on-site pre-splitting blasting tests.

[0076] In step D, the shaped charge blasting tube is charged in an axially non-coupled manner, and the charge structure and charge amount are determined based on on-site blasting tests to ensure that the rock between two adjacent boreholes is penetrated by cracks after blasting.

[0077] In the step E, the vertical loosening blasting drilling hole 11 constructed along the center line of the roof is as deep as the thickness H of the direct roof. Z and basic top thickness H J The sum of the boreholes is 2-5m, and the distance between adjacent boreholes along the tunnel direction is 2-5m.

[0078] In step G, in order to avoid roof collapse when the working face approaches the pressure relief tunnel, when installing explosives in the vertical loosening blasting drill holes 11 on the center line of the tunnel roof and the fan-shaped loosening blasting drill holes 10 on the tunnel roof side close to the working face, no explosives are installed within the direct roof thickness range, and only taphole mud needs to be filled; explosives are installed within the basic top range of the roof for blasting to increase penetration.

[0079] In step I, after the working face stops mining, the top beam of the working face hydraulic support 13 should just support the cantilever roof formed by the pressure relief tunnel 9 after pre-splitting blasting, and during the relocation and reversal period, it should maximize its supporting role on the overlying roof.

[0080] Compared with the traditional pre-excavated double-retreat tunnel layout method, the present invention provides construction space for the hard roof breaking and loosening blasting near the stop mining line by adding a pressure relief tunnel. Therefore, by actively adjusting the layout of the end-mining tunnel, the roof of the working face of the end-mining section can be pre-treated, the roof structure of the working face in the end-mining stage can be changed, the stress distribution of the surrounding rock of the working face in the end-mining stage can be optimized, and the severe deformation of the retreat tunnel in the end-mining stage can be effectively controlled, thereby reducing the end-mining process and construction difficulty, reducing the support and maintenance cost of the working face retreat tunnel, and achieving the purpose of shortening the working face relocation and reversal time. The new retreat tunnel layout method has obvious safety and economic advantages.

[0081] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art.

Claims

1. A method for arranging retreat tunnels for pre-splitting and decompression in a medium-thick coal seam with a hard roof working face, characterized in that: Including steps: A. Design the air intake and return tunnels and cut holes for the hard roof working face of medium-thick coal seams to form a complete tunnel system for the working face; B. The working face is mined and continuously advanced. After advancing a certain distance, the main and auxiliary retreat tunnels and pressure relief tunnels are excavated at the stop-mining line. The surrounding rock of the two retreat tunnels is supported by anchor bolts and high-preload, large-deformation anchor cables. C. After the retreat tunnel is excavated and the support is completed, when it is not affected by the advanced support pressure of the working face, pre-splitting blasting drilling is carried out along the roof on the side of the pressure relief tunnel close to the stop mining line; D. Install shaped charge blasting tubes, explosives and detonators in the pre-split boreholes, and after blasting, cut through the tunnel roof rock along the set plane; E. Along the center line of the roof of the pressure relief tunnel, drill holes for loosening blasting vertically toward the roof; F. On the side of the pressure relief tunnel close to the working face, construct fan-shaped loosening blasting drill holes along the tunnel direction. Each group of fan-shaped loosening blasting drill holes includes two drill holes with different angles and the same height; G. After the loosening blasting drilling construction in the pressure relief tunnel is completed, starting from one side of the tunnel, explosives are installed and blasted section by section to destroy the integrity of the roof rock layer of the working face of the last mining section and reduce the strength of the roof rock layer; H. When the working face advances to the pressure relief tunnel, install an air curtain device on the main withdrawal tunnel side of the connecting tunnel between the pressure relief tunnel and the main withdrawal tunnel to prevent polluted air from the working face from flowing into the main withdrawal tunnel through the connecting tunnel during mining, thereby avoiding increasing the difficulty of ventilation system management; I. After the working face coal mining machine completes the mining of the coal pillar between the pressure relief tunnel and the main withdrawal tunnel, the working face stops advancing and the working face coal mining machine, scraper conveyor and hydraulic support begin to withdraw.

2. The method for arranging retreat tunnels for pre-splitting and decompression in a medium-thick coal seam hard roof working face at the end of mining according to claim 1 is characterized in that: In step B, the width of the coal pillar between the main retreat tunnel and the pressure relief tunnel is the length of the top beam of the hydraulic support of the working face.

3. The method for arranging retreat tunnels for pre-splitting and decompression in a medium-thick coal seam hard roof working face according to claim 2 is characterized in that: In step C, the pre-splitting blasting drilling is biased towards the stop-mining line, the distance between adjacent pre-splitting blasting drilling holes is 0.8-1.5m, and the drilling depth L Y for: Where θ is the angle between the pre-splitting blasting borehole and the plumb bob direction, which is generally 10°; H Z H is the thickness of the direct top of the working surface; J It is the thickness of the basic top of the working surface.

4. The method for arranging retreat tunnels for pre-splitting and decompression in a medium-thick coal seam hard roof working face at the end of mining according to claim 3 is characterized in that: In step D, the shaped charge blasting tube is charged in an axially non-coupled manner, and the charge structure and charge amount are determined based on on-site blasting tests to ensure that the rock between two adjacent boreholes is penetrated by cracks after blasting.

5. The method for arranging retreat tunnels for pre-splitting and decompression in a medium-thick coal seam hard roof working face at the end of mining according to claim 4 is characterized in that: In the step E, the depth of the loosening blasting drill hole constructed vertically along the center line of the roof is the thickness H of the direct roof. Z and basic top thickness H J The sum of the boreholes is 2-5m, and the distance between adjacent boreholes along the tunnel direction is 2-5m.

6. The method for arranging retreat tunnels for pre-splitting and decompression in a medium-thick coal seam hard roof working face at the end of mining according to claim 5 is characterized in that: In step F, the fan-shaped loosening blasting drilling at each position of the roadway includes two holes in total, the angles between the holes and the horizontal plane are 30° and 45° respectively, and the hole depths are:

7. The method for arranging retreat tunnels for pre-splitting and decompression in a medium-thick coal seam hard roof working face according to claim 6 is characterized in that: In step G, in order to avoid roof collapse when the working face approaches the pressure relief tunnel, when installing explosives in the loose blasting drill holes on the center line of the tunnel roof and the side of the tunnel roof close to the working face, no explosives are installed within the direct roof thickness range, and only taphole mud needs to be filled; explosives are installed within the basic top range of the roof for blasting to increase penetration.

8. The method for arranging retreat tunnels for pre-splitting and decompression in a medium-thick coal seam hard roof working face at the end of mining according to claim 7 is characterized in that: In step I, after the working face stops mining, the top beam of the working face hydraulic support should just support the cantilever roof formed by the pressure relief tunnel after pre-splitting blasting, and maximize its supporting effect on the overlying roof during the relocation and reversal period.

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