Basic roof partial slot blasting along empty roadway method

Abstract

The present application belongs to the field of coal mine roadway construction, and particularly relates to a method for gob-side entry retaining by partial cutting blasting of basic roof. The method comprises the following steps: drilling a field in the front part of a working face and close to a right side of a mining roadway; setting a cutting blasting area in the basic roof, with the upper part of the basic roof as a buffer block; drilling anchor cable holes and cutting blasting holes along the strike in the field and close to the coal seam on the right side of the field, and installing anchor cables; cutting the basic roof and the immediate roof at a negative angle by cutting holes at the back of the working face, blasting and fracturing the cutting blasting area by blasting holes, constructing a roadway-side gangue retaining structure, anchoring the anchor cables on the roadway-side gangue retaining structure, and monitoring the deformation of the steel mesh at the anchor cable and adjusting the deformation by nuts. The present application can realize the stability and safety of gob-side entry retaining under the condition that the thickness of the immediate roof is small and the thickness of the basic roof is large.

Description

Technical Field

[0001] This invention belongs to the field of coal mine roadway construction, specifically involving a method for leaving roadways along the goaf through partial blasting of the basic roof. Background Technology

[0002] Goaf retention is a pillarless roadway construction technique that preserves the mining roadway (transport roadway or return airway) of the previous working face during mining, using roadway-side support methods to continue serving the next working face. It can reduce roadway excavation work, alleviate the tension between mining and excavation succession in the mine, and improve coal recovery rate. Among them, the roof-cutting self-forming roadway goaf retention method has the advantages of fast construction speed and low cost due to its simple roadway-side support methods. The roof-cutting self-forming roadway goaf retention method involves drilling a positive-angle roof-cutting hole along the goaf boundary towards the goaf in the roof of the mining roadway to cut off the roof and reduce the cantilever length of the roof, thereby reducing the stress on the goaf retention roadway; then, a simple roadway-side retaining structure is formed by using single hydraulic props in conjunction with steel mesh.

[0003] However, using a straight-angle roof cutting method can easily lead to collapsed rock entering the mining roadway. Furthermore, when the immediate roof thickness is small and the main roof thickness is large, the amount of collapsed rock generated after coal seam mining is small and cannot compensate for the goaf created by coal seam mining. Conversely, a large main roof thickness results in large collapsed blocks and a large downward displacement, easily impacting the collapsed rock and causing it to burst into the mining roadway or impact the roadway's retaining structure. The shock wave from the collapse of the main roof is also detrimental to the stability of the roadway's retaining structure. Therefore, improving the stability and safety of the roof cutting and self-forming roadway retention process under conditions of small immediate roof thickness and large main roof thickness has become an urgent problem to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for localized blasting and goaf retention along the main roof, applicable to situations where the immediate roof thickness is small and the main roof thickness is large. The method includes the following steps: S1: At the front of the first working face, the drilling site is always ahead of the mining area near the right side of the return roadway; the first working face is located on the right side of the return roadway, and the left side of the return roadway is the next working face; S2: A slotting blasting zone is set up within the basic roof. The basic roof above the slotting blasting zone is not blasted and is retained as a buffer block. The height of the slotting blasting zone meets the following requirements: the amount of rock fragmentation generated by the collapse of the slotting blasting zone and the immediate roof is slightly less than the mining height of the coal seam. On the right side of the drilling site, near the coal seam, anchor cable boreholes and slotting blasting boreholes are constructed alternately along the strike. The anchor cable borehole is constructed to the middle of the basic roof on the right side of the slotting blasting zone. The slotting blasting boreholes are distributed in a fan shape on the dip profile, including one roof-cutting borehole and multiple blasting boreholes. The roof-cutting borehole is constructed to the left to the middle of the basic roof, cutting out the left boundary of the slotting blasting zone. Multiple blasting boreholes are constructed to the right into the slotting blasting zone. Anchor cables are installed in the anchor cable boreholes. S3: In the mining area, the coal seam is continuously mined forward. When the anchor cable and the cutting blasting borehole are exposed behind the mining area, the main roof and the immediate roof are cut at a negative angle through the roof cutting borehole. The cutting blasting zone is blasted and fractured through the blasting borehole. The roadway retaining structure is constructed by using steel mesh in conjunction with single hydraulic props, and the anchor cable is anchored to the roadway retaining structure. S4: Monitor the deformation of the reinforcing mesh at the grouting anchor cable. When the reinforcing mesh protrudes towards the mining roadway, tighten the nut to move the reinforcing mesh towards the goaf. When the reinforcing mesh moves towards the goaf due to the tension of the anchor cable, loosen the nut to move the reinforcing mesh towards the mining roadway. S5: Repeat steps S1-S4 until the first working face is mined and the goaf retention work of the return roadway is completed.

[0005] Preferably, in step S1, hydraulic supports are arranged in the mining area; the drilling area is rectangular in plan view, and the right boundary of the drilling area is located in the gap between the first hydraulic support and the second hydraulic support starting from the mining roadway; individual hydraulic supports are intermittently installed on the left side of the drilling area along the strike.

[0006] Preferably, in step S2, the amount of fragmentation generated by the blasting zone and the gangue formed by the direct roof collapse can reach 85%-95% of the coal seam mining height in height; the average width of the blasting zone is 5-8m.

[0007] Preferably, in step S2, the angle between the anchor cable borehole and the vertical direction is 65°-75°; the angle between the top-cut borehole and the vertical direction is 5°-8°.

[0008] Preferably, in step S2, resin cartridges are installed in the anchor cable borehole located in the base top, and then anchor cables are installed in the anchor cable borehole. The length of the anchor cable is greater than the drilling depth of the anchor cable borehole. After installation, the outer end of the anchor cable is not anchored. Explosives are installed in the slot blasting borehole.

[0009] Preferably, in step S2, the anchor cable consists of an anchoring section, a conventional section, and a threaded section from the inside out. The threaded section is provided with a tray and a nut, and the conventional section has rings fixed at intervals along the length of the anchor cable on its outer periphery.

[0010] Preferably, in step S3, the coal seam is continuously mined forward in the mining area, and the individual hydraulic props located near the mining area in the drilling area are recovered.

[0011] Preferably, in step S3, the collapsed gangue carries the anchor cable into the goaf and presses the anchor cable into the collapsed gangue, and the anchor cable anchoring section is anchored in the main roof.

[0012] Preferably, in step S3, the steel mesh is located between the single hydraulic support and the collapsed gangue, covering the entire height of the mining roadway; the gangue retaining structure is set at the original right boundary of the mining roadway and is located on the left side of the entire cut-off section of the basic roof above the mining roadway.

[0013] Preferably, in step S3, anchor bolts are installed at intervals along the direction of the gangue to reinforce the support.

[0014] The inventive points and beneficial technical effects of this invention are as follows: 1. For working conditions where the immediate roof thickness is relatively small and the main roof thickness is relatively large, this invention proposes to set a slotting blasting zone of a certain width and thickness in the main roof near the mining roadway. The upper part of the slotting blasting zone is retained as a buffer block, so that the amount of fragmentation caused by the collapse of the gangue formed by the slotting blasting zone and the immediate roof is slightly less than the mining height of the coal seam, thereby forming a sufficiently high buffer layer to support the overlying strata and reducing the supporting force of the roof directly above the mining roadway on the overlying strata; at the same time, it can also ensure that the buffer block breaks. The immediate roof thickness on the right side of the slotting blasting zone is small and the amount of fragmentation is very small, while the main roof thickness is large. The overall collapse is large, but due to the support of the buffer block, the impact generated by its downward movement is reduced, mitigating the impact on the mining roadway. In addition, the thick gangue at the bottom of the buffer block can also isolate the impact.

[0015] 2. This invention provides an advanced mining site construction drilling area where cutting and blasting boreholes and anchor cable boreholes are drilled. Compared to drilling these boreholes in the goaf behind the mining area, this significantly improves construction efficiency and ensures safety. Furthermore, by strategically positioning the cutting and blasting boreholes and anchor cable boreholes, the exposed anchor cables can smoothly pass through the hydraulic supports.

[0016] 3. This invention allows the construction of a drilling site to shift the location of the roof-cutting borehole towards the goaf, thus facilitating the construction of negative-angle roof-cutting boreholes. However, when constructing negative-angle roof-cutting boreholes, it is difficult to install roadway retaining structures at the borehole opening, as this could easily damage the roof. Therefore, when using negative-angle roof-cutting boreholes, the roadway retaining structures need to be shifted towards the mining roadway. If negative-angle roof-cutting is performed directly in the mining roadway without a drilling site, the final roadway retaining structure will be located within the mining roadway, reducing the width of the goaf-retaining roadway and hindering service to the next working face. This invention, by constructing a drilling site a certain width in advance, ensures that the construction location of the roadway retaining structure does not affect the width of the goaf-retaining roadway while maintaining the integrity of the roof. Furthermore, because negative-angle roof-cutting boreholes can cut a section that deviates towards the goaf, the collapsed rock moves towards the goaf and does not move significantly into the mining roadway, ensuring construction safety within the mining roadway. At the same time, the collapsed gangue will move towards the mining roadway under the influence of its self-flowing characteristics and the force of the overlying strata, occupying the exposed roof space outside the gangue retaining structure beside the roadway. In other words, this space is a buffer space for the movement of gangue, avoiding occupying the width of the mining roadway.

[0017] 4. This invention creatively proposes an advanced construction anchor cable, anchoring the anchoring end of the cable to the basic roof on the right side of the cut-and-blast zone. When the immediate roof and the cut-and-blast zone collapse into gangue, part of the anchor cable is wrapped around it. The outer end is then anchored after the gangue has stabilized, thus completing the anchor cable construction, improving support strength, and solving the problem of not being able to install anchor cables into the gangue in the goaf. Gangue near the return roadway in the goaf is prone to move towards the return roadway under the pressure of the overlying strata; however, because the anchor cable penetrates deep into the thick basic roof far from the return roadway, the gangue under the thick basic roof will continuously compress under the force of the overlying strata, reducing the amount of fragmentation. This will generate a tensile force on the grouting anchor cable towards the goaf, thereby holding back the gangue moving towards the return roadway and improving the stability of the gangue retaining structure beside the roadway. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the basic top local cutting blasting method for leaving a roadway along the goaf in this invention; Figure 2 This is a schematic diagram of the dip section at the drilling site for the basic top local cutting blasting and goaf retention method of the present invention; Figure 3 This is a schematic diagram of the dip section behind the stope of the basic top local cutting blasting method for leaving a roadway along the goaf, as described in this invention. Figure 4 This is a schematic diagram of the anchor cable structure used in the basic top local cutting blasting method for leaving a roadway along the goaf in this invention; In the diagram, 1-first working face; 11-coal seam; 12-drilling area; 13-gangue; 2-recovery roadway; 3-second working face; 4-single hydraulic prop; 5-mining area; 51-hydraulic support; 61-anchor cable borehole; 62-grooving blasting borehole; 621-roof cutting borehole; 622-blasting borehole; 71-steel mesh; 72-anchor bolt; 81-direct roof; 82-basic roof; 821-buffer block; 822-grooving blasting zone; 9-anchor cable; 91-threaded section; 92-pallet; 93-nut; 94-conventional section; 95-ring; 96-anchoring section. Detailed Implementation

[0019] The invention will now be further described with reference to the accompanying drawings.

[0020] like Figures 1-4 As shown, the dip angle of coal seam 11 in Hecaogou Coal Mine is 1°-3°, with a designed mining height of 2.1m. The mining roadway 2 is 2.5m high and 4.2m wide. Mining roadway 2 is constructed along the floor of coal seam 11 and partially excavates the direct roof 81 to meet the height requirements of mining roadway 2. The direct roof 81 is thin, only 2.7m, mainly composed of mudstone with a compressive strength of approximately 20MPa. The basic roof 82 is 11.18m thick, composed of oil shale with a compressive strength of 37MPa. The goaf retention technique is used in mining roadway 2 to continue serving the next working face. In response, this invention proposes a method of localized blasting and goaf retention along the basic roof, suitable for conditions where the direct roof 81 is thin and the basic roof 82 is thick. The specific steps include: S1: As Figures 1-2As shown, in the front part of the mining area 5 of the first working face 1, near the right side of the retreat roadway 2, the advanced mining area 5 tunneling drilling site 12 is located. The mining area 5 is equipped with hydraulic supports 51, a coal mining machine, and a scraper conveyor, among other coal mining equipment, for mining the coal seam 11. The retreat roadway 2 is supported by a comprehensive anchoring support method using anchor bolts 72, anchor cables 9, and steel mesh 71. Individual hydraulic props 4 are arranged at intervals along the strike in the middle of the retreat roadway 2 to reinforce the support. The first working face 1 is located on the right side of the retreat roadway 2, and the left side of the retreat roadway 2 is the second working face 3. The second working face 3 is a continuing working face, where the retreat roadway 2 is left behind after goaf entry to continue serving the second working face 3. In this application, the strike... The drilling site 12 is aligned with the forward and backward direction and the diagonal direction. The diagonal width of the drilling site 12 is greater than the width of a single hydraulic support 51 but does not exceed the sum of the width of a single hydraulic support 51 and the diagonal spacing of the hydraulic supports 51. That is, the right boundary of the drilling site 12 is located in the gap between the first hydraulic support 51 and the second hydraulic support 51 starting from the mining roadway 2. The length of the drilling site 12 along the strike is about 10m, that is, a drilling site 12 with a length of about 10m is always constructed ahead of the mining site 5. The drilling site 12 is excavated using a small tunneling machine or drilling rig. The drilling site 12 is rectangular in plan view. In order to maintain the stability of the drilling site 12, single hydraulic supports 4 are installed at intervals along the strike on the left side of the drilling site 12.

[0021] S2: As Figures 1-2 As shown, due to the thinness of the immediate roof 81, the amount of rock fragmentation 13 generated by the collapse of the immediate roof 81 after the mining of coal seam 11 is small and cannot compensate for the goaf space formed by the mining of coal seam 11. Therefore, it is proposed to perform slotting blasting on part of the basic roof 82. The basic roof 82 that needs to be slotted is defined as the slotting blasting zone 822. The basic roof 82 above the slotting blasting zone 822 is not blasted and is retained as a buffer block 821. The height of the slotting blasting zone 822 satisfies the following condition: the height of the slotting blasting zone 822 and the immediate roof 81 collapses... The amount of fragmentation generated by the gangue 13 formed by the collapse is slightly less than the mining height of the coal seam 11 in height. That is, the height of the gangue 13 formed by the collapse of the cutting blasting zone 822 and the immediate roof 81 is slightly less than the sum of the mining height of the coal seam 11, the thickness of the immediate roof 81, and the thickness of the cutting blasting zone 822. In this embodiment, the amount of fragmentation generated by the gangue 13 formed by the collapse of the cutting blasting zone 822 and the immediate roof 81 can reach 85%-95% of the mining height of the coal seam 11 in height. The average width of the cutting blasting zone 822 is 5-8m.

[0022] Near the coal seam 11 on the right side of drilling site 12, anchor cable boreholes 61 and slotting blasting boreholes 62 are constructed alternately along the strike, with adjacent anchor cable boreholes 61 and slotting blasting boreholes 62 spaced 1.5m apart. The anchor cable boreholes 61 are constructed to the basic top 82 on the right side of the slotting blasting zone 822, and are constructed towards the first working face 1 on the right, with a positive construction angle and an angle of 65°-75° with the vertical direction. In this invention, the drilling angle towards the first working face 1 on the right is positive, and the drilling angle towards the second working face 3 on the left is negative. The slotting blasting boreholes 62 are distributed in a fan shape on the dip profile, including one top-cutting borehole 621 and multiple... A blasting borehole 622; the top-cutting borehole 621 is constructed to the basic top 82, and then constructed towards the second working face 3 on the left, with a negative construction angle and an angle of 5°-8° with the vertical direction, to cut out the left boundary of the blasting zone 822; multiple blasting boreholes 622 are constructed towards the first working face 1 on the right, with a positive construction angle, and are distributed as evenly as possible in the blasting zone 822; explosives are installed in the blasting boreholes 62; resin cartridges are installed in the anchor cable boreholes 61 located in the basic top 82, and then anchor cables 9 are installed in the anchor cable boreholes 61, the length of which is greater than the construction depth of the anchor cable boreholes 61, with an excess length of about 2m.

[0023] like Figure 4 The anchor cable 9 consists of an anchoring section 96, a conventional section 94, and a threaded section 91 from the inside out. The threaded section 91 is approximately 1.5m long. The anchoring section 96 has a barb structure on its outer periphery and is approximately 3.5m long. The conventional section 94 is approximately 7m long. The conventional section 94 is the ordinary anchor cable section, which does not have barbs compared to the anchoring section 96 and does not need to be threaded compared to the threaded section 91. The threaded section 91 is equipped with a tray 92 and a nut 93 for anchoring the grouting anchor cable 9. The conventional section 94 has rings 95 fixed at intervals along the length of the anchor cable 9 on its outer periphery. The rings 95 increase the sliding resistance in the broken gangue 13. The anchor cable 9 is fixed in the basic top 82 by the anchoring section 96 of the anchor cable 9 in conjunction with the resin cartridge. The threaded section 91 is not anchored immediately after the anchor cable 9 is installed.

[0024] S3: As Figures 1-3As shown, in the mining area 5, the coal seam 11 of the first working face 1 is continuously mined forward, and the single hydraulic prop 4 located near the mining area 5 in the drilling area 12 is recovered; as the mining area 5 moves forward, the anchor cable 9 and the slotting blasting borehole 62 for installing explosives are exposed behind the mining area 5. At this time, the basic roof 82 and the immediate roof 81 are cut at a negative angle through the roof cutting borehole 621, and the slotting blasting zone 822 is blasted and fractured through the blasting borehole 622. The amount of fragmentation generated by the gangue 13 formed by the collapse of the slot blasting zone 822 and the immediate roof 81 is only slightly less than the mining height of the coal seam 11 in height, thus forming a sufficiently high buffer layer to support the overlying strata and reduce the supporting force of the roof directly above the mining roadway 2 on the overlying strata; at the same time, the amount of fragmentation generated by the gangue 13 formed by the collapse of the slot blasting zone 822 and the immediate roof 81 is only slightly less than the mining height of the coal seam 11 in height, which can also ensure that the buffer block 821 breaks. The basic roof 82 on the right side of the blasting zone 822 is thick and collapses entirely, pressing down on the gangue 13 formed by the collapse of the basic roof 82 below it. Because the basic roof 82 is thin here and the amount of fragmentation is small, the collapse height of the basic roof 82 is large. However, due to the support of the buffer block 821, the impact generated by its downward movement is reduced, mitigating the impact on the mining roadway 2. In addition, the thick gangue 13 below the buffer block 821 can also isolate the impact. However, if the entire basic roof 82 is blasted in a blasting manner (the height of the blasting zone 822 is equal to that of the basic roof 82), the buffer block 821 cannot buffer the impact of the thick basic roof 82 on the right side, and the amount of fragmented gangue 13 will be large, which can easily enter the mining roadway 2, creating a safety hazard. However, if the entire basic roof 82 is simply cut off in height without blasting and fracturing, on the one hand, it will generate a large impact into the mining roadway 2. On the other hand, since the fracturing amount of the direct roof 81 is small, the total height of the overlying strata fracture increases, and the possibility of impact from the overlying strata fracture increases, which is not conducive to the stability and safety of the mining roadway 2.

[0025] Since the anchor cable borehole 61 in step S2 is located in the gap between the first hydraulic support 51 and the second hydraulic support 51, the portion of the anchor cable 9 that extends beyond the anchor cable borehole 61 can pass smoothly between the two hydraulic supports 51. Furthermore, due to the negative angle used for roof cutting, the gangue 13 formed by the collapse of the cutting blast zone 822 and the immediate roof 81 will slide to the right along the roof cutting section, away from the mining roadway 2, thus preventing the gangue 13 from directly falling into the mining roadway 2; at the same time, the collapsed gangue 13 carries the anchor cable 9 into the goaf, pressing the anchor cable 9 into the collapsed gangue 13, but the anchoring section 96 of the anchor cable 9 is still anchored in the basic roof 82; due to the self-flowing characteristics of the gangue 13 that collapses from the cutting blast zone 822, it will move towards the mining roadway 2, occupying a certain width below the exposed roof. At this time, a gangue retaining structure is constructed by using steel mesh 71 in conjunction with single hydraulic props 4 to block the gangue 13 from continuing to move towards the mining roadway 2 under the pressure of the overlying strata and the impact of the thicker basic roof 82 on the right side, while also protecting the exposed roof. The steel mesh 71 is located between the single hydraulic prop 4 and the collapsed gangue 13, and its height covers the entire height of the mining roadway 2. The exposed length of the grouting anchor cable 9 is about 2m, which can accommodate the problem of it shrinking into the goaf due to compression by the gangue 13. The roadway retaining structure, namely the steel mesh 71 and the single hydraulic prop 4 that cooperates with it, is set at the original right boundary of the mining roadway 2, and is located on the left side of the entire cut-off section of the basic roof 82 above the mining roadway 2. That is, a vertical line is drawn downward from the leftmost cut-off position of the basic roof 82 above the mining roadway 2, and this vertical line is located on the right side of the roadway retaining structure. This can ensure that the roadway retaining structure supports the roof and avoids damage to the roof. Anchor rods 72 are installed at intervals along the strike towards the gangue 13 to strengthen the support. Since the anchor rods 72 are rigid and short in length, they are easy to construct.

[0026] S4: Monitor the deformation of the reinforcing mesh 71 at anchor cable 9. When the reinforcing mesh 71 protrudes towards the mining roadway 2, tighten nut 93 to move the reinforcing mesh 71 towards the goaf. When the reinforcing mesh 71 moves towards the goaf under the tension of anchor cable 9, loosen nut 93 to move the reinforcing mesh 71 towards the mining roadway 2.

[0027] S5: Repeat steps S1-S4 until the first working face 1 is mined out and the goaf retention work of the return roadway 2 is completed for use in the second working face 3.

[0028] This invention is not limited to the preferred embodiments described above. Anyone can derive other methods in various forms under the guidance of this invention. Any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method for localized blasting and gob-side entry in the basic roof, used in situations where the immediate roof thickness is small and the basic roof thickness is large, characterized in that... Includes the following steps: S1: At the front of the first working face, the drilling site is always ahead of the mining area near the right side of the return roadway; the first working face is located on the right side of the return roadway, and the left side of the return roadway is the next working face; S2: A slotting blasting zone is set up within the basic roof. The basic roof above the slotting blasting zone is not blasted and is retained as a buffer block. The height of the slotting blasting zone meets the following requirements: the amount of rock fragmentation generated by the collapse of the slotting blasting zone and the immediate roof is slightly less than the mining height of the coal seam. On the right side of the drilling site, near the coal seam, anchor cable boreholes and slotting blasting boreholes are constructed alternately along the strike. The anchor cable borehole is constructed to the middle of the basic roof on the right side of the slotting blasting zone. The slotting blasting boreholes are distributed in a fan shape on the dip profile, including one roof-cutting borehole and multiple blasting boreholes. The roof-cutting borehole is constructed to the left to the middle of the basic roof, cutting out the left boundary of the slotting blasting zone. Multiple blasting boreholes are constructed to the right into the slotting blasting zone. Anchor cables are installed in the anchor cable boreholes. S3: In the mining area, the coal seam is continuously mined forward. When the anchor cable and the cutting blasting borehole are exposed behind the mining area, the main roof and the immediate roof are cut at a negative angle through the roof cutting borehole. The cutting blasting zone is blasted and fractured through the blasting borehole. The roadway retaining structure is constructed by using steel mesh in conjunction with single hydraulic props, and the anchor cable is anchored to the roadway retaining structure. S4: Monitor the deformation of the reinforcing mesh at the grouting anchor cable. When the reinforcing mesh protrudes towards the mining roadway, tighten the nut to move the reinforcing mesh towards the goaf. When the reinforcing mesh moves towards the goaf due to the tension of the anchor cable, loosen the nut to move the reinforcing mesh towards the mining roadway. S5: Repeat steps S1-S4 until the first working face is mined and the goaf retention work of the return roadway is completed.

2. The basic top local blasting and gob-side roadway retention method according to claim 1, characterized in that, In step S1, hydraulic supports are arranged in the mining area; the drilling site is rectangular in plan view, and the right boundary of the drilling site is located in the gap between the first hydraulic support and the second hydraulic support starting from the mining roadway; individual hydraulic props are set at intervals along the strike on the left side of the drilling site.

3. The basic top local blasting and gob-side roadway retention method according to claim 2, characterized in that, In step S2, the amount of fragmentation generated by the gangue formed by the cutting blasting zone and the direct roof collapse can reach 85%-95% of the coal seam mining height in height; the average width of the cutting blasting zone is 5-8m.

4. The basic top local blasting and gob-side roadway retention method according to claim 3, characterized in that, In step S2, the angle between the anchor cable borehole and the vertical direction is 65°-75°; the angle between the top-cut borehole and the vertical direction is 5°-8°.

5. The basic top local blasting and gob-side roadway retention method according to claim 4, characterized in that, In step S2, resin cartridges are installed in the anchor cable borehole located in the top of the base, and then anchor cables are installed in the anchor cable borehole. The length of the anchor cable is greater than the drilling depth of the anchor cable borehole. After installation, the outer end of the anchor cable is not anchored. Explosives are installed in the slot blasting borehole.

6. The basic top local blasting and gob-side roadway retention method according to claim 5, characterized in that, In step S2, the anchor cable consists of an anchoring section, a conventional section, and a threaded section from the inside out. The threaded section is equipped with a tray and a nut, and the conventional section has rings fixed at intervals along the length of the anchor cable on its outer periphery.

7. The basic top local blasting and gob-side roadway retention method according to claim 1, characterized in that, In step S3, the coal seam is continuously mined forward in the mining area, and the individual hydraulic props located near the mining area in the drilling area are recovered.

8. The basic top local blasting and gob-side roadway retention method according to claim 6, characterized in that, In step S3, the collapsed gangue carries the anchor cable into the goaf and presses the anchor cable into the collapsed gangue, while the anchor section of the anchor cable is anchored in the main roof.

9. The basic top local blasting and gob-side roadway retention method according to claim 8, characterized in that, In step S3, the steel mesh is located between the single hydraulic support and the collapsed gangue, covering the entire height of the mining roadway; the gangue retaining structure is set at the original right boundary of the mining roadway and is located on the left side of the entire cut-off section of the basic roof above the mining roadway.

10. The basic top local blasting and gob-side roadway retention method according to claim 9, characterized in that, In step S3, anchor bolts are installed at intervals along the direction of the gangue to reinforce the support.

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