A coal pillar-free mining method suitable for fully-mechanized caving face of thick and hard coal seam

Abstract

The present application relates to the technical field of coal seam mining, in particular to a coal pillar-free mining method suitable for thick and hard coal seam fully-mechanized caving face, comprising: first reinforcing the upper section track roadway; constructing a top breaking hole and a directional long borehole in the upper section track roadway; performing hydraulic fracturing through the directional long borehole; performing blasting top breaking through the top breaking hole; performing mining on the upper section working face and second reinforcing the upper section track roadway. The present application cuts off the stress transmission path of the goaf and the roadway roof rock stratum by directional blasting top breaking, improves the stress environment of the end of the working face surrounding rock; the thick and hard top coal is weakened by directional borehole hydraulic fracturing technology, which improves the top coal caving property and the coal recovery rate of the working face; in addition, the directional blasting top breaking and directional borehole hydraulic fracturing are performed before the mining of the working face, which does not increase the construction process during the mining of the working face.

Description

Technical Field

[0001] This invention relates to the field of coal seam mining technology, and more specifically, to a pillarless mining method suitable for fully mechanized longwall mining faces in thick and hard coal seams. Background Technology

[0002] Thick, hard coal seams are the main coal seams for achieving high-yield and efficient mining in my country, and have resource reserves advantages. However, due to their large thickness and high hardness, existing mining methods will lead to waste of coal resources and safety hazards.

[0003] The following technical problems exist: (1) The stress environment at the end of the working face cannot be improved, which leads to the stress in the goaf being transmitted to the roof strata of the roadway; (2) The top coal cannot be fully mined; (3) The coal pillars of the working face are retained, which reduces the coal resource recovery rate. At the same time, due to the stress concentration at the location of the coal pillars, there is a risk of safety accidents caused by stress concentration; (4) There is a problem of tight mine process continuity. Summary of the Invention

[0004] The purpose of this invention is to provide a pillarless mining method suitable for fully mechanized longwall mining faces in thick and hard coal seams, so as to solve at least one existing problem in the mining process of thick and hard coal seams.

[0005] This invention provides a pillarless mining method suitable for fully mechanized longwall mining faces in thick, hard coal seams. The method includes the following steps: first reinforcement of the upper section track roadway; construction of roof-breaking holes and directional long boreholes in the upper section track roadway; the roof-breaking holes include open-cut roof-breaking holes and upper section track roadway roof-breaking holes for mining the sidewalls and roofs, the open-cut roof-breaking holes being set at an angle to the vertical direction and biased towards the working face side, and the upper section track roadway roof-breaking holes being set at an angle to the vertical direction and biased towards the upper section pre-mining area side; hydraulic fracturing through the directional long boreholes; directional blasting roof breaking through the roof-breaking holes; mining the upper section working face; and second reinforcement of the upper section track roadway.

[0006] Optionally, the first reinforcement of the upper section of the track tunnel includes: arranging anchor cables, anchor bolts, and high-strength anchor cables in the upper section of the track tunnel.

[0007] Optionally, the high-strength anchor cable is located at a first preset distance from the side roadway of the upper section of the track roadway in the upper section; the value of the first preset distance is in the range of 0.4-0.6m.

[0008] Optionally, the length of the high-strength anchor cable exceeds a preset value for the depth of the top hole; the preset value ranges from 2 to 2.2 m.

[0009] Optionally, the construction of roof-breaking holes and directional long boreholes in the upper section track roadway includes: constructing the roof-breaking hole at the corner of the working face within a preset range of the opening hole near the upper section track roadway; constructing the roof-breaking hole for mining the upper section track roadway at the corner of the side roadway of the upper section pre-recovery area in the upper section track roadway; constructing a drilling site in the middle of the upper section track roadway and at the stop line; and constructing two or more directional long boreholes in the drilling site, wherein the number of directional long boreholes is determined by the working face width and the fracturing radius of the directional long boreholes.

[0010] Optionally, the top-breaking holes are arranged sequentially at a preset interval along the working face of the upper section, and the preset interval ranges from 0.4 to 0.6 m; the top-breaking holes for mining the sidewalls and roofs of the upper section track roadway are arranged sequentially at the preset interval along the track roadway of the upper section; the distance between the edge directional long boreholes and the roadway side is half the distance between the directional long boreholes.

[0011] Optionally, the formula for calculating the height of the cut-off hole is as follows:

[0012] ,

[0013] in, The height of the broken top hole, To extract high, This represents the amount of roof subsidence. For the bottom drum volume, is the coefficient of fragmentation of the top strata.

[0014] Optionally, the second reinforcement of the upper section track roadway includes: installing I-beams and steel mesh in the upper section track roadway behind the upper section working face frame on the side of the upper section goaf, and arranging unit frames behind the upper section working face frame near the side of the upper section goaf.

[0015] Optionally, the top end of the I-beam is inserted into the roof rock layer, and the bottom end of the I-beam is inserted into the bottom plate; the unit frame is located at a second preset distance from the side roadway of the upper section goaf in the upper section of the track roadway; the value of the second preset distance is 0.8-1.2m.

[0016] Optionally, the second reinforcement of the upper section track roadway further includes: moving the unit frame located at a third preset distance behind the upper section working face to the rear of the upper section working face frame; the value of the third preset distance is in the range of 200-300m.

[0017] Compared with the prior art, the beneficial effects of the pillarless mining method for fully mechanized longwall mining faces in thick and hard coal seams provided by the present invention are as follows:

[0018] This invention provides a pillarless mining method suitable for fully mechanized longwall mining faces in thick, hard coal seams. The method involves first reinforcing the upper section of the track roadway to ensure safety during subsequent construction; drilling roof-breaking holes and directional long boreholes in the upper section of the track roadway; the roof-breaking holes include open-cut roof-breaking holes and upper section track roadway roof-breaking holes for mining the sidewalls and roof. The open-cut roof-breaking holes are angled to the vertical direction and biased towards the working face side, while the upper section track roadway roof-breaking holes are angled to the vertical direction and biased towards the upper section pre-recovery mining area side; hydraulic fracturing is performed through the directional long boreholes; and the thick, hard top coal is weakened through directional drilling hydraulic fracturing technology, improving... Raising the roof coal release capability improves the coal recovery rate of the working face; directional blasting to break the roof through the aforementioned roof breaking holes cuts off the stress transmission path of the roof strata in the goaf and roadway, forcing stress to transfer to the depth of the solid coal, thus improving the stress environment of the surrounding rock at the working face end; in addition, directional blasting to break the roof and hydraulic fracturing of directional holes before the working face is mined does not increase the construction procedures during the working face mining process, solving the problem of tight schedules; mining the upper section of the working face does not require the retention of the working face protection coal pillar, improving the coal resource recovery rate, and the aforementioned upper section track roadway is reinforced a second time, allowing the upper section track roadway to be completely preserved for use as the lower section belt conveyor roadway. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 A schematic flowchart illustrating a pillarless mining method suitable for fully mechanized longwall mining faces in thick, hard coal seams, provided as an embodiment of the present invention;

[0021] Figure 2 This is a top view of the working face and tunnel layout in an embodiment of the present invention;

[0022] Figure 3 This is a cross-sectional view of the upper section track roadway working face before mining in an embodiment of the present invention;

[0023] Figure 4 This is a side view of the upper section of the track roadway in an embodiment of the present invention;

[0024] Figure 5 This is a cross-sectional view of the upper section of the track roadway working face after mining in an embodiment of the present invention;

[0025] Figure 6 This is a side view of the roadway after the upper section of the track roadway working face has been mined in an embodiment of the present invention.

[0026] Explanation of reference numerals in the attached diagram: 1—Upper section belt conveyor roadway; 2—Upper section working face;

[0027] 3—Opening cut-off hole for roof breaking; 4—Roof breaking hole for mining the upper section of the track roadway; 5—Drilling site;

[0028] 6—Directional long borehole; 7—Upper section track roadway; 8—Lower section working face;

[0029] 9—Lower section track roadway; 10—Anchor bolt; 11—Anchor cable; 12—Reinforcing anchor cable; 13—Top coal;

[0030] 14—Coal seam overlying strata one; 15—Coal seam overlying strata two;

[0031] 16—I-beams and reinforcing mesh; 17—Unit frame. Detailed Implementation

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0033] This invention provides a pillarless mining method suitable for fully mechanized longwall mining faces in thick, hard coal seams. See [link to relevant documentation]. Figure 1 The diagram shown is a schematic flow chart of a pillarless mining method suitable for fully mechanized longwall mining faces in thick and hard coal seams. The method includes the following steps:

[0034] S110, the first reinforcement of the upper section of the track tunnel.

[0035] Optionally, step S110 includes: arranging anchor cables, anchor bolts, and high-strength anchor cables in the upper section of the track roadway.

[0036] Optionally, the high-strength anchor cable is located at a first preset distance from the sidewall of the pre-mining area in the upper section of the track roadway; the value of the first preset distance ranges from 0.4 to 0.6 meters. Thus, because the stress on both sides of the upper section track roadway differs after mining, exhibiting asymmetrical subsidence deformation characteristics, and with greater stress on the mining side, constructing high-strength anchor cables close to the mining side can mitigate the subsidence of the roadway roof on the mining side, ensuring the stability of the upper section mining roadway.

[0037] Optionally, the length of the high-strength anchor cable exceeds a preset value for the depth of the roof break hole; the preset value ranges from 1.9 to 2.2 meters. This avoids cracks in the roof after blasting, preventing a reduction in the roadway support effect of the high-strength anchor cable. By setting the correct length of the high-strength anchor cable, the roadway support effect of the high-strength anchor cable is guaranteed.

[0038] S120 involves constructing jacking holes and directional long boreholes in the aforementioned upper section of the track tunnel.

[0039] The aforementioned roof-breaking holes include open-cut roof-breaking holes and upper section track roadway roof-breaking holes. The open-cut roof-breaking holes are set at an angle to the vertical direction and biased towards the working face side; the upper section track roadway roof-breaking holes are set at an angle to the vertical direction and biased towards the upper section pre-mining area side. Thus, all the roof-breaking holes are biased towards the goaf, making it easier for the goaf roof to collapse after the working face is mined.

[0040] Optionally, step S120 includes: constructing the aforementioned cut-out roof-breaking hole at the top corner of the working face within a predetermined range near the upper section track roadway; constructing the aforementioned upper section track roadway roof-breaking hole at the sidewall corner of the upper section pre-recovery mining area in the upper section track roadway; constructing a drilling site in the middle of the aforementioned upper section track roadway and at the stop-mining line; and constructing two or more directional long boreholes within the aforementioned drilling sites, the number of which is determined by the working face width and the fracturing radius of the directional long borehole. Thus, by constructing the cut-out roof-breaking hole, the upper section track roadway roof-breaking hole, and the directional long borehole using the above method, the subsequent blasting roof-breaking and hydraulic fracturing effects are improved.

[0041] Optionally, the aforementioned incision holes for roof fracturing are arranged sequentially along the working face of the upper section at preset intervals, the preset intervals ranging from 0.4 to 0.6 m; the aforementioned roof fracturing holes for mining the sidewalls and roof of the upper section track roadway are arranged sequentially along the upper section track roadway at the aforementioned preset intervals; the distance between the aforementioned directional long boreholes at the edge and the roadway sidewall is half the distance between the aforementioned directional long boreholes. Thus, through the specific arrangement of the aforementioned incision holes for roof fracturing, the roof fracturing holes for mining the sidewalls and roof of the upper section track roadway, and the directional long boreholes, the subsequent blasting roof fracturing and hydraulic fracturing effects are further improved.

[0042] Optionally, the formula for calculating the height of the above-mentioned jacking hole is as follows:

[0043] ,

[0044] in, The height of the aforementioned top hole. To extract high, This represents the amount of roof subsidence. For the bottom drum volume, is the coefficient of fragmentation of the top strata.

[0045] S130, hydraulic fracturing is performed through the aforementioned directional long borehole.

[0046] S140, directional blasting is performed to break the roof through the aforementioned roof-breaking hole.

[0047] S150 involves back mining of the upper section working face and secondary reinforcement of the aforementioned upper section track roadway.

[0048] Optionally, step S150 includes: installing I-beams and steel mesh in the upper section track roadway behind the upper section working face frame on the upper section goaf side, and arranging unit frames behind the upper section working face frame near the upper section goaf side. In this way, the bearing capacity of the artificial roadway sidewalls behind the working face is improved by arranging unit frames, thereby enhancing the stability of the roadway during the working face mining process.

[0049] Optionally, the top of the aforementioned I-beam is inserted into the roof stratum, and the bottom of the aforementioned I-beam is inserted into the floor stratum; the aforementioned unit frame is located at a second preset distance from the side wall of the upper section goaf in the upper section of the track roadway; the value of the aforementioned second preset distance ranges from 0.8 to 1.2 m. In this way, by fixing the top and bottom of the I-beam, the tilting of the I-beam is prevented, ensuring the support effect of the I-beam; in addition, by selecting a suitable location to arrange the unit frame, damage to the high-strength anchor cable locking device is avoided, ensuring the support effect of the high-strength anchor cable.

[0050] Optionally, step S150 further includes: moving the unit frame located at a third preset distance behind the upper section working face to the rear of the upper section working face frame; the third preset distance is in the range of 200-300m. In this way, the unit frame is recycled by cyclically moving forward.

[0051] This invention provides a pillarless mining method suitable for fully mechanized longwall mining faces in thick, hard coal seams. Before the longwall face is mined, roof-breaking holes are arranged behind the headstock and in the roof strata on the side of the roadway for blasting and roof-breaking. After the longwall face is mined, this facilitates the timely collapse of the roof strata in the goaf, reduces the overhang area, and improves the stress environment of the surrounding rock in the roadway section. A drilling site is set up in the roadway section, and directional long boreholes are arranged in the boreholes. Hydraulic fracturing is performed before the longwall face is mined to destroy the integrity of the top coal and improve the roof coal venting capability. To prevent excessive subsidence of the roof strata on the side of the goaf after the longwall face is mined, unit frames are arranged in the roadway section. When the surrounding rock in the roadway section tends to stabilize, the unit frames can be gradually removed or moved forward. The construction parameters of the roof-breaking holes behind the frame, the roof-breaking holes in the roadway roof strata, and the directional long boreholes can be adjusted according to the site geological conditions and the level of construction equipment.

[0052] See Figure 2 The top view of the working face and roadway layout shown includes the upper section belt conveyor roadway 1, the upper section working face 2, the opening cut roof breaking hole 3, the upper section track roadway roof breaking hole 4, the drilling site 5, the directional long borehole 6, the upper section track roadway 7, the lower section working face 8, and the lower section track roadway 9.

[0053] See Figure 3 The cross-sectional view of the upper section track roadway working face before mining is shown, including the upper section track roadway mining side and roof break hole 4, upper section track roadway 7, anchor bolt 10, anchor cable 11 and high-strength anchor cable 12.

[0054] See Figure 4 The side view of the upper section track roadway shown includes the upper section track roadway mining side roof break hole 4, drilling site 5, directional long borehole 6, upper section track roadway 7, top coal 13, coal seam overlying roof strata one 14, and coal seam overlying roof strata two 15.

[0055] See Figure 5 The cross-sectional view of the upper section track roadway working face after mining is shown, including the upper section track roadway mining side and roof break hole 4, upper section track roadway 7, anchor bolt 10, anchor cable 11, high-strength anchor cable 12, I-beam and steel mesh 16 and unit frame 17.

[0056] See Figure 6 The diagram shown is a side view of the upper section track roadway after mining, including I-beams and steel mesh 16 and unit frame 17.

[0057] This invention provides a pillarless mining method suitable for fully mechanized longwall mining faces in thick, hard coal seams, with the following specific steps:

[0058] Step (1): After the upper section working face 2 is mined, the non-mining side of the upper section mining roadway 7 (the roadway along the goaf) is solid coal, and the mining side is artificial roadway side. In view of the asymmetric subsidence and deformation characteristics of its roof, before the upper section working face 2 is mined, a row of high-strength anchor cables 12 is arranged at a position 0.5m away from the edge of the goaf in the upper section track roadway 7.

[0059] Step (2): When constructing the high-strength anchor cable 12, the top-cutting hole 3, the top-cutting hole 4 of the upper section track roadway mining sidewall and top-cutting hole 4, and the drilling site 5 can be constructed simultaneously. After the drilling site 5 is completed, the directional long borehole 6 can be constructed in the drilling site 5.

[0060] Step (3): After the reinforcement support is completed, hydraulic fracturing is performed on the hard top coal 13 through directional long borehole 6. While destroying the integrity of the top coal 13, it can also achieve the effect of water injection and softening, thereby improving the top coal 13 venting and achieving the purpose of improving the recovery rate of the top coal 13 in the working face.

[0061] Step (4): After hydraulic fracturing of top coal 13, blasting is carried out on the top cutting hole 3 and the top cutting hole 4 of the upper section track roadway to ensure that after the upper section working face 2 is mined, the overlying roof rock layer 14 (top cutting side roof rock layer) and the overlying roof rock layer 25 (roof rock layer) can collapse and fill the goaf in time.

[0062] Step (5): After the upper section working face 2 is mined, an artificial roadway sidewall with I-beams and steel mesh 16 is installed at the edge of the goaf in the left roadway section. In order to prevent the roof rock strata of the upper section track roadway 7 from becoming unstable during the pressure period, a row of unit frames 17 is arranged at a position 1.0m away from the edge of the goaf in the upper section track roadway 7.

[0063] Step (6): As the upper section working face 2 continues to advance, when it lags behind the upper section working face by 300m (according to past engineering experience, when it lags behind the working face by 300m, the surrounding rock of the roadway section will tend to be stable. In actual operation, the distance of the forward-moving unit frame 17 from the working face can be flexibly adjusted according to the on-site mine pressure monitoring data), and the surrounding rock of the upper section track roadway 7 tends to be stable, the unit frame 17 can be moved forward, and only the artificial roadway side of the I-beam and steel mesh 16 is retained to block the rock.

[0064] Step (7): Repeat steps (5) and (6) until all the upper section track roadways 7 are retained. The upper section track roadways 7 can be used as the lower section belt conveyor roadway to serve the mining of the lower section working face 8. That is, the lower section working face 8 only needs to excavate one track roadway 9.

[0065] In one specific embodiment, this embodiment provides a pillarless mining method applicable to fully mechanized longwall mining faces in thick and hard coal seams, and the specific implementation method is as follows:

[0066] There exists a mine with a main coal seam of average thickness of 6.7m, including a mining height of 3.0m and a coal release height of 3.7m, meaning the roadway height is 3.0m and the coal seam thickness is 3.7m. The roof strata consist of alternating layers of sandy mudstone and mudstone (i.e., roof strata 14 over the coal seam) of 5.3m and alternating layers of fine sandstone and mudstone (i.e., roof strata 25 over the coal seam) of 4.6m. Due to the high hardness of the thick and hard roof strata 13, the recovery rate of roof 13 is not ideal, and the retention of protective coal pillars in sections wastes a large amount of coal resources. Therefore, this embodiment of the invention improves the venting capability of roof 13 through hydraulic fracturing using directional long boreholes 6, and improves the mechanical environment of the surrounding rock in the roadway by cutting the headframe and the roof of the track roadway. Artificial roadway walls made of I-beams and steel mesh are used to achieve roadway retention along the goaf, eliminating the need for section coal pillars, thereby improving the working face recovery rate.

[0067] Before the second working face of the upper section is mined, a row of high-strength anchor cables 12 is arranged 0.5m away from the side roadway of the pre-mining area of ​​the upper section in the upper section track roadway 7, with a spacing of 1m and a length of 16m. To ensure the reinforcement and support effect of the high-strength anchor cables 12, the length of the high-strength anchor cables 12 must be at least 2m longer than the depth of the roof break hole. If the length of the high-strength anchor cables 12 is insufficient, it will not be able to effectively constrain the roof strata of the upper section track roadway 7. When the roof strata of the goaf collapse, it is easy to cause excessive subsidence of the roof strata of the upper section track roadway 7, thus affecting the secondary reuse of the roadway along the goaf. At the same time as reinforcement, the roof break hole 3 of the opening is constructed at the corner of the working face within about 30m of the opening of the upper section track roadway 7, and the roof break hole 4 of the upper section track roadway mining side roadway is constructed at the corner of the side roadway of the pre-mining area of ​​the upper section in the upper section track roadway 7. Based on the formula for calculating the height of the cut-off borehole, the height is 14.5m, and the angle between the cut-off borehole and the vertical direction is 15°. This translates to a borehole depth of 14m and a borehole spacing of 0.5m. A reasonable cut-off height ensures that after mining, the roof strata within the cut-off area can promptly collapse and fill the mining area. This severs the direct connection between the roadway and the roof strata in the goaf, cutting off the stress transmission path and shifting the stress peak to the deeper coal seam, thus improving the mechanical environment of the surrounding rock in the roadway. Furthermore, the roof strata, after collapsing and filling the goaf, effectively support the overlying strata, ensuring their timely stabilization and reducing the dynamic pressure impact of the overlying strata on the surrounding rock in the roadway. The upper section working face 2 has a length of 1100m along the mineable strike. One drilling site 5 is constructed in the middle of the upper section track roadway 7 and at the stop-mining line. After the reinforcement and strengthening construction is completed, three directional long boreholes 6 are drilled in each drilling site 5. The total length of the directional long boreholes 6 is approximately 550m, and the width of the upper section working face 2 is 180m. The hydraulic fracturing radius of the directional long boreholes 6 is approximately 30m in the horizontal direction and approximately 3m in the vertical direction. The arrangement of three directional long boreholes 6 can basically weaken all the top coal 13 of the working face, which is conducive to improving the recovery rate of the top coal 13 of the fully mechanized longwall face. Hydraulic fracturing of the directional long boreholes 6 begins. First, hydraulic fracturing is carried out on the directional long boreholes 6 in the middle of the upper section track roadway 7. After the fracturing is completed, hydraulic fracturing is carried out on the directional long boreholes 6 at the stop line position. The main purpose of the directional long boreholes 6 is to weaken the thick and hard top coal 13 overlying on the fully mechanized longwall face through the hydraulic fracturing technology of the directional long boreholes 6, improve the venting of the top coal 13, and thus improve the recovery rate of the top coal 13. After hydraulic fracturing is completed, blasting is used to cut the roof of the opening borehole 3 and the upper section track roadway roof of the upper section. All of the above procedures are completed before the working face is mined.

[0068] After the upper section working face 2 began mining, an artificial roadway sidewall consisting of I-beams and a steel mesh 16 was installed on the side of the goaf behind the support frame. The I-beams were 4.0m long. To prevent the I-beams from overturning, the top of the I-beams was inserted 0.2m into the roof strata and the bottom was inserted 0.3m into the floor strata. The steel mesh dimensions were 3.5m x 1.2m (height x width). During the mining of the upper section working face 2, the upper section track roadway 7 was affected by the disturbance and mine pressure from the mining of the upper section working face 2. The surrounding rock of the roadway was unstable within a range of approximately 300m behind the upper section working face 2. Unit frames 17 are required to prevent instability of the roof strata in the retained roadway section. The spacing of unit frames 17 is 0.5m. After 300m behind the working face, the surrounding rock of the retained roadway section tends to be stable, and unit frames 17 can be removed, leaving only the artificial roadway side composed of I-beams and steel mesh 16. That is, the unit frames 17 located 300m behind the upper section working face 2 are moved forward to the hydraulic support of the upper section working face 2, and the unit frames 17 are moved forward in a cycle to ensure that there are always unit frames 17 supporting the roof of the goaf side within the 300m area behind the upper section working face 2. High-strength anchor cables 12 are arranged at a distance of 0.5m from the side roadway of the upper section mining area. To prevent unit frames 17 from damaging the high-strength anchor cable locks, unit frames 17 are arranged at a distance of 1.0m from the side roadway of the upper section mining area. Due to the large mining height of the fully mechanized longwall face, the solid coal roadway side of the retained roadway has strong bearing capacity while the artificial roadway side has weak bearing capacity, so the roof will exhibit obvious asymmetrical deformation characteristics. To prevent roadway retention failure due to large deformation of the roof on the goaf side during the process, high-strength anchor cables 12 were installed on the goaf side, along with unit frames 17. This improved the bearing capacity of the artificial roadway sidewalls and prevented roof instability and collapse on the goaf side. The entire upper section track roadway 7 was retained, and it can now serve as a belt conveyor roadway for the lower section working face 8 during mining. In other words, the lower section working face 8 only needs to excavate one lower section track roadway 9.

[0069] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

[0070] Finally, it should be noted that in this document, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0071] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A pillarless mining method suitable for fully mechanized longwall mining faces in thick, hard coal seams, characterized in that, The method includes the following steps: The upper section track roadway is reinforced for the first time. The upper section track roadway is located between the upper section and the lower section. The upper section is located between the upper section belt conveyor roadway and the upper section track roadway. In the upper section of the track roadway, roof-breaking holes and directional long boreholes are constructed. The roof-breaking holes include open-cut roof-breaking holes and upper section track roadway sidewall and roof-breaking holes. The open-cut roof-breaking holes are constructed at the corner of the working face within a predetermined range near the open-cut area of ​​the upper section track roadway. These open-cut roof-breaking holes are angled to the vertical direction and biased towards the working face. The upper section track roadway sidewall and roof-breaking holes are constructed at the corner of the upper section pre-recovery mining area side roadway. These upper section track roadway sidewall and roof-breaking holes are angled to the vertical direction and biased towards the upper section pre-recovery mining area side. The upper section track roadway sidewall and roof-breaking holes are arranged sequentially along the upper section track roadway at predetermined intervals, with the predetermined interval ranging from 0.4 to 0.6 meters. The directional long boreholes extend into the top coal of the upper section. Hydraulic fracturing is performed through the aforementioned directional long borehole; After hydraulic fracturing of the top coal, directional blasting is performed through the aforementioned roof-breaking hole to break the roof. The upper section working face was back-mined, and the upper section track roadway was reinforced a second time.

2. The method according to claim 1, characterized in that, The first reinforcement of the upper section of the track tunnel includes: Anchor cables, anchor bolts, and high-strength anchor cables are arranged in the upper section of the track roadway.

3. The method according to claim 2, characterized in that, The high-strength anchor cable is located at a first preset distance from the side roadway of the upper section of the track roadway in the upper section of the pre-recovery mining area; the value of the first preset distance is in the range of 0.4-0.6m.

4. The method according to claim 2, characterized in that, The length of the high-strength anchor cable exceeds the preset depth of the top hole; the preset value ranges from 2 to 2.2 m.

5. The method according to claim 1, characterized in that, The construction of directional long boreholes in the upper section of the track tunnel includes: A drilling site was constructed in the middle of the upper section of the track roadway and at the stop line location; Two or more directional long boreholes are constructed within the drilling site, the number of which is determined by the working face width and the fracturing radius of the directional long borehole.

6. The method according to claim 1, characterized in that, The cutting holes are arranged sequentially at a preset interval along the working surface of the upper section. The distance between the directional long borehole at the edge and the roadway side is half the distance between the directional long boreholes.

7. The method according to claim 1, characterized in that, The formula for calculating the height of the cut-off hole is as follows: ， in, The height of the broken top hole, To extract high, This represents the amount of roof subsidence. For the bottom drum volume, is the coefficient of fragmentation of the top strata.

8. The method according to claim 1, characterized in that, The second reinforcement of the upper section of the track tunnel includes: I-beams and steel mesh are installed in the upper section track roadway behind the upper section working face frame on the side of the upper section goaf, and unit frames are arranged behind the upper section working face frame near the side of the upper section goaf.

9. The method according to claim 8, characterized in that, The top of the I-beam is inserted into the roof rock layer, and the bottom of the I-beam is inserted into the bottom plate; the unit frame is located at a second preset distance from the side roadway of the upper section goaf in the upper section of the track roadway; the value of the second preset distance is 0.8-1.2m.

10. The method according to claim 8, characterized in that, The second reinforcement of the upper section of the track tunnel also includes: The unit frame located at a third preset distance behind the upper section working surface is moved forward to the rear of the upper section working surface frame; the value of the third preset distance is in the range of 200-300m.

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