Non-pillar mining method suitable for thick and hard coal seam fully mechanized caving face

Abstract

The invention relates to the technical field of coal seam mining, in particular to a coal-pillar-free mining method suitable for a thick and hard coal seam fully mechanized caving face, which comprises the following steps: carrying out first reinforcement on an upper section track roadway; a broken top hole and a directional long drill hole are constructed in the upper section track roadway; hydrofracture is carried out through the directional long drill hole; performing blasting roof breaking through the roof breaking hole; and the working face of the upper section is stoped, and the track roadway of the upper section is reinforced for the second time. The stress environment of surrounding rock at the end of the working face is improved through directional blasting roof breaking and cutting of a goaf and roadway roof rock stratum stress transfer path; through a directional drilling hydraulic fracturing technology, the thick and hard top coal is weakened, the top coal caving property is improved, and the coal recovery rate of a working face is increased; in addition, directional blasting roof breaking and directional hole hydraulic fracturing are carried out before working face stoping, and the construction procedure in the working face stoping process is not added.

Description

Technical Field

[0001] The invention relates to the technical field of coal seam mining, and in particular to a coal pillar-free mining method suitable for a fully mechanized caving working face in a thick and hard coal seam. Background Art

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

[0003] The following technical problems exist at present: (1) It is impossible to improve the stress environment in the end area of ​​the working face, resulting in the stress in the goaf being transferred to the rock layer on the roof of the tunnel; (2) It is impossible to fully mine the top coal; (3) The working face protective coal pillar is retained, which reduces the coal resource recovery rate. At the same time, due to the stress concentration at the position of the coal pillar, there is a risk of safety accidents caused by stress concentration; (4) There is a problem of tight continuity of mine processes. Summary of the invention

[0004] The object of the present invention is to provide a pillar-free mining method suitable for a fully mechanized caving working face in a thick hard coal seam, so as to solve at least one existing problem in the mining process of the thick hard coal seam.

[0005] An embodiment of the present invention provides a pillar-free mining method suitable for a fully mechanized caving working face in a thick hard coal seam, the method comprising the following steps: reinforcing the upper section track tunnel for the first time; constructing a top-breaking hole and a directional long drill hole in the upper section track tunnel; the top-breaking hole comprises an opening eye top-breaking hole and an upper section track tunnel mining side roof top-breaking hole, the opening eye top-breaking hole is arranged at an angle to the vertical direction and is biased towards the working face side, the upper section track tunnel mining side roof top-breaking hole is arranged at an angle to the vertical direction and is biased towards the upper section pre-mining area side; hydraulic fracturing is performed through the directional long drill hole; directional blasting top-breaking is performed through the top-breaking hole; mining the upper section working face, and reinforcing the upper section track tunnel for the second time.

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

[0007] Optionally, the high-strength anchor cable is located at a first preset distance from the side wall of the pre-mining area in the upper section of the upper section rail tunnel; the value range of the first preset distance is 0.4-0.6m.

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

[0009] Optionally, the construction of a top-breaking hole and a directional long borehole in the upper section rail tunnel comprises: constructing the top-breaking hole for the cutting eye at a top angle position of the working face within a preset range of the cutting eye close to the upper section rail tunnel; constructing the top-breaking hole for the mining side slab of the upper section rail tunnel at a top angle position of the side tunnel in the upper section pre-mining area of ​​the upper section rail tunnel; constructing a drilling site in the middle of the upper section rail tunnel and at the stop-mining line respectively; constructing more than two of the directional long boreholes in the drilling site, and the number of the directional long boreholes is determined by the width of the working face and the fracturing radius of the directional long borehole.

[0010] Optionally, the opening and cutting top holes are arranged in sequence at a preset spacing along the direction of the upper section working face, and the preset spacing ranges from 0.4 to 0.6 m; the upper section rail tunnel mining side top plate broken top holes are arranged in sequence at the preset spacing along the direction of the upper section rail tunnel; the spacing between the edge of the directional long drill holes and the tunnel side is half of the spacing between the directional long drill holes.

[0011] Optionally, the height calculation formula of the broken top hole is as follows: , in, is the height of the broken top hole, To collect height, is the top plate subsidence, is the kick drum volume, is the coefficient of expansion of the roof rock.

[0012] Optionally, the second reinforcement of the upper section track tunnel includes: installing I-beams and steel mesh in the upper section track tunnel on the upper section goaf side behind the upper section working face frame, and arranging unit frames behind the upper section working face frame and close to the upper section goaf side.

[0013] 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 wall of the upper section goaf in the upper section rail tunnel; the second preset distance has a value range of 0.8-1.2m.

[0014] Optionally, the second reinforcement of the upper section track lane also includes: moving the unit frame located at a third preset distance behind the upper section working surface forward to behind the upper section working surface frame; the value range of the third preset distance is 200-300m.

[0015] Compared with the prior art, the pillar-free mining method for fully mechanized caving working face in thick hard coal seams provided by the present invention has the following beneficial effects: The embodiment of the present invention provides a pillar-free mining method suitable for a fully mechanized caving working face in a thick hard coal seam. The method ensures the safety of subsequent construction by reinforcing the upper section track tunnel for the first time; constructs a top-breaking hole and a directional long drill hole in the upper section track tunnel; the top-breaking hole includes an opening eye top-breaking hole and an upper section track tunnel mining top plate top-breaking hole. The opening eye top-breaking hole is set at an angle to the vertical direction and is biased toward the working face side. The upper section track tunnel mining top plate top-breaking hole is set at an angle to the vertical direction and is biased toward the upper section pre-mining area side. Hydraulic fracturing is performed through the directional long drill hole. The thick hard top coal is weakened by the directional drilling hydraulic fracturing technology to provide a method for mining. The top coal is released to improve the coal recovery rate of the working face; the top is cut by directional blasting through the above-mentioned top-breaking holes, and the stress transfer path of the rock strata in the goaf and the roof of the roadway is cut off, forcing the stress to transfer to the deep of the solid coal, thereby improving the stress environment of the surrounding rock at the end of the working face; in addition, directional blasting and directional hole hydraulic fracturing are carried out before the working face is mined, and the construction process in the working face mining process is not increased, which solves the problem of tight process; the upper section working face is mined, and there is no need to retain the working face protection coal pillar, which improves the coal resource recovery rate, and the above-mentioned upper section track lane is reinforced for the second time, so that the upper section track lane is completely retained for use as the lower section belt lane. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below 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 A schematic flow chart of a pillar-free mining method applicable to a fully mechanized caving working face in a thick hard coal seam provided in an embodiment of the present invention; Figure 2 A top view of the working surface and tunnel arrangement in an embodiment of the present invention; Figure 3 This is a front cross-sectional view of the upper section track lane working face in the embodiment of the present invention; Figure 4 It is a side view of the upper section track lane in an embodiment of the present invention; Figure 5 It is a cross-sectional view of the working face of the upper section track lane after mining in an embodiment of the present invention; Figure 6 It is a side view of the rear tunnel wall after mining of the upper section rail tunnel working face in an embodiment of the present invention.

[0018] Description of reference numerals: 1—belt lane of upper section; 2—working surface of upper section; 3—opening and cutting hole; 4—top hole for mining the roof of the upper section track tunnel; 5—drilling site; 6—directional long drilling hole; 7—upper section track lane; 8—lower section working surface; 9—lower section track tunnel; 10—anchor rod; 11—anchor cable; 12—reinforcement anchor cable; 13—top coal; 14—1st layer of roof rock overlying the coal seam; 15—2nd layer of roof rock overlying the coal seam; 16—I-beam and steel mesh; 17—unit frame. DETAILED DESCRIPTION

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0020] The embodiment of the present invention provides a pillar-free mining method applicable to a fully mechanized caving working face in a thick hard coal seam. Figure 1 The schematic flow chart of a pillar-free mining method applicable to a fully mechanized caving working face in a thick hard coal seam is shown, and the method comprises the following steps: S110, the first reinforcement of the upper section track tunnel was carried out.

[0021] Optionally, the above step S110 includes: arranging anchor cables, anchor rods and high-strength anchor cables in the above upper section track tunnel.

[0022] Optionally, the high-strength anchor cable is located at a first preset distance from the side roadway wall of the upper section pre-mining area in the upper section track roadway; the value range of the first preset distance is 0.4-0.6m. In this way, since the stresses on both sides of the upper section track roadway are different after mining, they show asymmetric sinking deformation characteristics and the stress on the mining side is relatively large. By constructing high-strength anchor cables close to the mining side, the sinking of the roadway roof on the mining side can be slowed down, ensuring the stability of the upper section mining roadway.

[0023] Optionally, the length of the high-strength anchor cable exceeds the preset depth of the broken top drilling hole; the preset value ranges from 1.9 to 2.2 m. In this way, cracks in the roof after blasting and breaking the top are avoided, which reduces the tunnel support function of the high-strength anchor cable. By setting the correct length of the high-strength anchor cable, the tunnel support function of the high-strength anchor cable is guaranteed.

[0024] S120, construct top-breaking holes and directional long boreholes in the above-mentioned upper section track tunnel.

[0025] The above-mentioned top-breaking holes include the top-breaking holes for the opening eye and the top-breaking holes for the mining side of the upper section rail roadway; the top-breaking holes for the opening eye are set at an angle with the vertical direction and are biased towards the working face; the top-breaking holes for the mining side of the upper section rail roadway are set at an angle with the vertical direction and are biased towards the upper section pre-mining area. In this way, the top-breaking holes are all biased towards the goaf, which makes it easy for the top of the goaf to collapse after the working face is mined.

[0026] Optionally, the above step S120 includes: constructing the above-mentioned cut-eye broken top hole at the top angle position of the working face within the preset range of the cut-eye near the upper section rail roadway; constructing the above-mentioned upper section rail roadway mining side roof broken top hole at the top angle position of the side roadway in the upper section pre-mining area in the upper section rail roadway; constructing a drilling site in the middle of the above-mentioned upper section rail roadway and the stop mining line respectively; constructing more than two directional long boreholes in the above-mentioned drilling site, and the number of the above-mentioned directional long boreholes is determined by the width of the working face and the fracturing radius of the directional long borehole. In this way, the cut-eye broken top hole, the upper section rail roadway mining side roof broken top hole and the directional long borehole are constructed by the above method to improve the subsequent blasting broken top and hydraulic fracturing effects.

[0027] Optionally, the above-mentioned cut-eye broken top holes are arranged in sequence at a preset spacing along the direction of the upper section working face, and the value range of the above-mentioned preset spacing is 0.4-0.6m; the above-mentioned upper section rail roadway mining side roof broken top holes are arranged in sequence at the above-mentioned preset spacing along the direction of the upper section rail roadway; the spacing between the above-mentioned directional long drill holes at the edge and the roadway side is half of the spacing between the above-mentioned directional long drill holes. In this way, through the specific arrangement of the above-mentioned cut-eye broken top holes, the upper section rail roadway mining side roof broken top holes and the directional long drill holes, the subsequent blasting broken top and hydraulic fracturing effects are further improved.

[0028] Optionally, the height calculation formula of the above-mentioned broken top hole is as follows: , in, is the height of the above-mentioned broken top hole, To collect height, is the top plate subsidence, is the kick drum volume, is the coefficient of expansion of the roof rock.

[0029] S130, hydraulic fracturing is performed through the above-mentioned directional long drilling hole.

[0030] S140, directional blasting is performed through the above-mentioned top-breaking hole.

[0031] S150, mining is carried out on the upper section working face, and the upper section track tunnel is reinforced for the second time.

[0032] Optionally, the above step S150 includes: installing I-beams and steel mesh in the upper section track lane on the upper section goaf side behind the upper section working face frame, and arranging unit frames behind the upper section working face frame close to the upper section goaf side. In this way, the bearing capacity of the artificial lane wall behind the working face is improved by arranging the unit frames, thereby improving the stability of the lane during the working face mining process.

[0033] Optionally, 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 wall of the goaf in the upper section of the upper section track tunnel; the value range of the second preset distance is 0.8-1.2m. In this way, by fixing the top and bottom of the I-beam, the I-beam is prevented from tipping over, and the support effect of the I-beam is guaranteed; in addition, by selecting a suitable position to arrange the unit frame, the unit frame is prevented from damaging the high-strength anchor cable lock, and the support effect of the high-strength anchor cable is guaranteed.

[0034] Optionally, the step S150 further includes: moving the unit frame located at a third preset distance behind the upper section working surface to behind the upper section working surface frame; the third preset distance has a value range of 200-300m. In this way, the unit frame is cyclically moved forward to achieve the recycling of the unit frame.

[0035] The embodiment of the present invention provides a pillar-free mining method suitable for a fully mechanized caving working face in a thick hard coal seam. Before the working face is mined, broken top holes are arranged behind the opening eye frame and in the roof rock layer on the side of the roadway for mining, and blasting and cutting the top are carried out. After the working face is mined, it is beneficial for the roof rock layer in the goaf to collapse in time, reduce the hanging roof area, and improve the stress environment of the surrounding rock in the remaining road section. A drilling site is arranged in the remaining road section, and directional long boreholes are arranged in the boreholes. Hydraulic fracturing is carried out before the working face is mined to destroy the integrity of the top coal and improve the venting of the top coal. In order to prevent the side roof of the goaf from sinking too much after the working face is mined, a unit frame is arranged in the remaining road section. When the surrounding rock in the remaining road section tends to be stable, the unit frame can be gradually removed or moved forward. The construction parameters of the broken top holes behind the frame, the broken top holes in the roadway roof rock layer, and the directional long boreholes can be adjusted according to the on-site geological conditions and the level of construction equipment.

[0036] See also Figure 2 The top view of the working face and tunnel layout shown includes the upper section belt tunnel 1, the upper section working face 2, the cut eye broken top hole 3, the upper section rail tunnel mining top plate broken top hole 4, the drilling site 5, the directional long drill hole 6, the upper section rail tunnel 7, the lower section working face 8, and the lower section rail tunnel 9.

[0037] See also Figure 3 The front cross-sectional view of the upper section rail tunnel working face after mining is shown, including the upper section rail tunnel mining side roof broken top hole 4, the upper section rail tunnel 7, anchor rods 10, anchor cables 11 and high-strength anchor cables 12.

[0038] See also Figure 4 The side view of the upper section track tunnel shown includes the upper section track tunnel mining side roof broken top hole 4, the drilling site 5, the directional long drill hole 6, the upper section track tunnel 7, the top coal 13, the roof rock layer 1 overlying the coal seam 14, and the roof rock layer 2 overlying the coal seam 15.

[0039] See also Figure 5 The cross-sectional view of the upper section track tunnel working face after mining is shown, including the upper section track tunnel mining side roof broken top hole 4, the upper section track tunnel 7, anchor rods 10, anchor cables 11, high-strength anchor cables 12, I-beams and steel mesh 16 and unit frames 17.

[0040] See also Figure 6 The side view of the rear tunnel wall of the upper section rail tunnel working face after mining is shown, including I-beams and steel mesh 16 and unit frames 17.

[0041] The present invention provides a specific coal pillar-free mining method applicable to a fully mechanized caving working face of a thick hard coal seam, and the specific steps are as follows: Step (1): After the upper section working face 2 is mined, the non-mining wall of the upper section mining roadway 7 (the roadway retained along the goaf) is solid coal, and the mining wall is an artificial roadway wall. In view of the asymmetric sinking deformation characteristics of its roof, before the upper section working face 2 is mined, a row of high-strength anchor cables 12 is arranged in the upper section track roadway 7 at a position 0.5m away from the edge of the goaf.

[0042] Step (2): When constructing the high-strength anchor cable 12, the eye-cutting broken top hole 3, the upper section track tunnel mining side top plate broken top hole 4 and the drilling site 5 can be constructed simultaneously. When the drilling site 5 is completed, the directional long drill hole 6 can be constructed in the drilling site 5.

[0043] Step (3): After the reinforcement support is completed, the hard top coal 13 is hydraulically fractured through the directional long drill hole 6, which not only destroys the integrity of the top coal 13, but also has the effect of softening it by water injection, thereby improving the venting property of the top coal 13 and achieving the purpose of improving the recovery rate of the top coal 13 on the working face.

[0044] Step (4): After the hydraulic fracturing of the top coal 13 is completed, the top cut hole 3 and the top cut hole 4 of the upper section track tunnel mining side are blasted and cut to ensure that after the upper section working face 2 is mined, the overlying roof rock layer 14 (the roof rock layer on the cutting side) and the overlying roof rock layer 2 15 (the roof rock layer) on the coal seam can collapse and fill the goaf in time.

[0045] Step (5): After the upper section working face 2 is mined, an artificial roadway wall composed of I-beams and steel mesh 16 is installed at the edge of the goaf of the remaining roadway section. To prevent the rock strata on the roof of the upper section track roadway 7 from becoming unstable during pressure, a row of unit frames 17 is arranged at a position 1.0 m away from the edge of the goaf of the upper section track roadway 7.

[0046] Step (6): As the upper section working face 2 continues to advance forward, when it lags behind the upper section working face by 300 m (based on previous engineering experience, when the lag working face is 300 m, the surrounding rock of the retained tunnel section will tend to be stable. In actual operation, the distance between the forward unit frame 17 and the lagging working face can be flexibly adjusted according to the on-site mine pressure monitoring data), after the surrounding rock of the upper section track tunnel 7 tends to be stable, the unit frame 17 can be moved forward, leaving only the artificial tunnel wall of the I-beam and the steel mesh 16 to block the gangue.

[0047] Step (7): Repeat the above steps (5) and (6) until all the upper section track tunnel 7 is preserved. The upper section track tunnel 7 can be used as the lower section belt tunnel to serve the lower section working face 8. That is, the lower section working face 8 only needs to excavate one track tunnel 9.

[0048] In a specific embodiment, this embodiment provides a specific coal pillar-free mining method applicable to a fully mechanized caving working face in a thick hard coal seam, and the specific implementation method is as follows: There is a mine, the average thickness of the main coal seam is 6.7m, of which the mining height is 3.0m and the coal discharge height is 3.7m, that is, the thickness of the coal seam at the tunnel height is 3.0m, and the thickness of the top coal 13 is 3.7m. The sandy mudstone and mudstone interlayers of the roof rock layer (i.e., the roof rock layer 14 overlying the coal seam) are 5.3m, and the fine sandstone and mudstone interlayers of the roof rock layer (i.e., the roof rock layer 2 15 overlying the coal seam) are 4.6m. Due to the high hardness of the top coal 13 of the thick and hard coal seam, the recovery rate of the top coal 13 is not ideal, and a large amount of coal resources are wasted due to the section protection coal pillar. Therefore, the embodiment of the present invention improves the discharge of the top coal 13 by the method of directional long drilling 6 hydraulic fracturing, and improves the mechanical environment of the tunnel surrounding rock by breaking the top after the opening of the eye frame and the roof of the track tunnel, adopts the artificial roadway wall of I-beam and steel mesh, realizes the roadway along the goaf, cancels the section coal pillar, and thus improves the recovery rate of the working face.

[0049] Before mining the upper section working face 2, a row of high-strength anchor cables 12 are arranged at a position 0.5m away from the side roadway wall of the upper section pre-mining area 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 broken top drilling hole; if the length of the high-strength anchor cables 12 is insufficient, it will not be able to effectively constrain the roadway roof rock layer of the upper section track roadway 7. When the top rock layer of the goaf area collapses, it is easy to cause the roadway roof rock layer of the upper section track roadway 7 to sink too much, thereby affecting the secondary reuse of the goaf-retained roadway. While reinforcing and strengthening, an eye-cutting broken top hole 3 is constructed at the top angle of the working face within about 30m of the opening eye of the upper section track roadway 7, and an upper section track roadway mining wall top plate broken top hole 4 is constructed at the top angle of the side roadway wall of the upper section pre-mining area in the upper section track roadway 7. According to the calculation formula of the top-break hole height, the top-break hole height is 14.5m, and the angle with the vertical direction is 15°. The top-break hole depth is 14m, and the hole spacing is 0.5m. The reasonable top-break height can ensure that after the working face is mined, the top rock layer in the cutting range collapses in time to fill the mining area; in this way, on the one hand, the direct connection between the roadway and the top rock layer in the goaf area is cut off, the stress transfer path is cut off, and the stress peak is transferred to the deep coal body, which improves the mechanical environment of the surrounding rock of the remaining roadway; on the other hand, after the top rock layer collapses and fills the goaf area, it plays an effective supporting role for the overburden stratum, ensuring that the overburden stratum tends to stabilize in time, and reducing the dynamic pressure effect of the overburden stratum on the surrounding rock of the remaining roadway. The length of the upper section working face 2 along the mining strike is 1100m, and a drilling site 5 is constructed in the middle of the upper section track roadway 7 and the stop mining line. After the reinforcement construction is completed, three directional long boreholes 6 are constructed in each drilling site 5. The total length of the directional long boreholes 6 is about 550m. The width of the upper section working face 2 is 180m. The hydraulic fracturing radius of the directional long boreholes 6 in the horizontal direction is about 30m, and the hydraulic fracturing radius in the vertical direction is about 3m. 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 caving working face. The directional long borehole 6 hydraulic fracturing is started. The directional long borehole 6 in the middle of the upper section track lane 7 is hydraulically fractured first. After the fracturing is completed, the directional long borehole 6 at the stop line position is hydraulically fractured. The directional long borehole 6 mainly weakens the thick hard top coal 13 on the fully mechanized caving working face through the directional long borehole 6 hydraulic fracturing technology, improves the venting property of the top coal 13, and improves the recovery rate of the top coal 13. After the hydraulic fracturing is completed, the top of the opening cut hole 3 and the top of the upper section track roadway mining side roof top hole 4 are blasted and cut. All the above processes are completed before the working face is mined.

[0050] After the mining of the upper section working face 2 began, an artificial roadway wall consisting of an I-beam and a steel mesh 16 was installed on the side of the goaf behind the frame. The length of the I-beam was 4.0m. To prevent the I-beam from overturning, the top of the I-beam was inserted into the roof rock layer 0.2m, and the bottom was inserted into the bottom plate 0.3m. The size of the steel mesh was height × width = 3.5m × 1.2m. During the mining of the upper section working face 2, the upper section track roadway 7 was affected by the mining disturbance of the upper section working face 2 and the mine pressure. The surrounding rock of the roadway within about 300m of the lagging upper section working face 2 was not stable. It is necessary to arrange unit frames 17 to prevent the top rock layer of the retained roadway section from becoming unstable. The spacing of unit frames 17 is 0.5m. After 300m of the lagging working face, the surrounding rock of the retained roadway section tends to be stable, and the unit frames 17 can be removed to only retain the artificial roadway wall composed of I-beams and steel mesh 16. That is, the unit frame 17 at the position 300m behind the upper section working face 2 is moved forward to the hydraulic support of the upper section working face 2, and the unit frame 17 is moved forward cyclically to ensure that there is always a unit frame 17 in the area 300m behind the upper section working face 2 to support the side roof of the goaf area. The high-strength anchor cable 12 is arranged at a position 0.5m away from the side roadway wall of the upper section mining area. In order to prevent the unit frame 17 from damaging the high-strength anchor cable lock, the unit frame 17 is arranged at a position 1.0m away from the side roadway wall of the upper section mining area. Due to the large mining height of the fully mechanized caving working face, the bearing capacity of the solid coal roadway wall of the retained roadway along the goaf is strong, while the bearing capacity of the artificial roadway wall is weak, so the roof will show obvious asymmetric deformation characteristics. In order to prevent the failure of the tunnel retaining process due to the large deformation of the roof on the side of the goaf, high-strength anchor cables 12 are arranged on the side of the goaf, and unit frames 17 are also arranged to improve the bearing capacity of the artificial tunnel wall and avoid the instability and collapse of the roof on the side of the goaf. The upper section track tunnel 7 is completely retained and ended. The upper section track tunnel 7 can be used as the lower section belt tunnel to serve the lower section working face 8, that is, the lower section working face 8 only needs to excavate a lower section track tunnel 9.

[0051] 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.

[0052] Finally, it should be noted that in this article, the term "comprise" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0053] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A pillar-free mining method suitable for fully mechanized caving working face in thick hard coal seam, characterized in that: The method comprises the following steps: Carry out the first reinforcement of the track lane in the upper section; Constructing top-breaking holes and directional long boreholes in the upper section track tunnel; the top-breaking holes include cutting eye top-breaking holes and upper section track tunnel mining top-breaking holes, the cutting eye top-breaking holes are arranged at an angle with the vertical direction and are biased toward the working face side, and the upper section track tunnel mining top-breaking holes are arranged at an angle with the vertical direction and are biased toward the upper section pre-mining area side; Performing hydraulic fracturing through the directional long borehole; Directional blasting of the top is carried out through the top-breaking hole; The upper section working face is mined and the upper section track tunnel is reinforced for the second time.

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

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 wall of the pre-mining area in the upper section of the upper section track tunnel; the value range of the first preset distance is 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 value of the broken top drilling hole; the preset value ranges from 2 to 2.2 m.

5. The method according to claim 1, characterized in that The construction of the top-breaking hole and the directional long drilling hole in the upper section track lane includes: Constructing the cut-off top hole at the top angle position of the working face within the preset range of the cut-off near the upper section track lane; Constructing the upper section track lane mining side roof slab breaking top hole at the upper section pre-mining area side lane top corner position in the upper section track lane; A drilling site is constructed in the middle of the track tunnel in the upper section and at the stop-mining line respectively; More than two directional long boreholes are constructed in the drilling site, and the number of the directional long boreholes is determined by the width of the working surface and the fracturing radius of the directional long boreholes.

6. The method according to claim 1, characterized in that The cut-eye broken top holes are arranged in sequence at a preset interval along the working surface of the upper section, and the preset interval ranges from 0.4 to 0.6 m; The upper section track tunnel mining side roof broken top holes are arranged in sequence at the preset intervals along the direction of the upper section track tunnel; The distance between the edge of the directional long drilled hole and the lane side is half of the distance between the directional long drilled holes.

7. The method according to claim 1, characterized in that The height calculation formula of the broken top hole is as follows: ， in, is the height of the broken top hole, To collect height, is the top plate subsidence, is the kick drum volume, is the coefficient of expansion of the roof rock.

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

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

Images