Roof-cutting pressure-relief coal mining method under deep-buried sandstone group stratum condition

Abstract

The invention belongs to the field of rock burst prevention and control coal mining methods, and particularly relates to a roof-cutting pressure-relief coal mining method under the stratum condition of a deeply-buried sandstone group. Comprising the following steps: respectively constructing detection drill holes inside and outside a first mining working face, and checking an interface in a stratum in a hydraulic pressure test mode so as to accurately determine a key layer. On the basis, on the basis of gob-side entry retaining, roof cutting drill holes are creatively constructed in a roof cutting special roadway and a transportation roadway correspondingly, so that roof cutting work is conducted on key layers in a bent sinking zone rock stratum, a water flowing fissure zone and a caving zone rock stratum in a roof; therefore, the suspended roof length of a part of the water flowing fractured zone rock stratum and the caving zone rock stratum is reduced but still reserved, the supporting force needing to be borne by the gob-side entry retaining is reduced, and a sheltering space is provided for the gob-side entry retaining. The bent sinking zone rock stratum is subjected to vertical drilling top cutting, and a top cutting transition area is reserved, so that superposition of fracture of the bent sinking zone rock stratum and fracture of the water flowing fissure zone rock stratum can be reduced, and the stratum pressure needing to be borne by gob-side entry retaining is reduced to the maximum extent.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of rock burst prevention and coal mining method, in particular to a method for cutting roof and pressure relief mining under the condition of deep buried sandstone group stratum. BACKGROUND

[0002] Rock burst is a common geological problem in coal mining, which is mainly caused by high ground stress and thick and hard rock stratum in the bedrock. In the prior art, the key stratum in the rock stratum is first determined, and then the key stratum is cut off in advance during coal mining to prevent the key stratum from breaking in a large range and releasing a large amount of energy. The key stratum refers to a rock stratum with relatively large thickness and high hardness that controls the movement of the rock stratum. Therefore, it is of great significance to determine the key stratum in the stratum for guiding rock burst prevention.

[0003] When determining the key stratum, the occurrence of the stratum needs to be obtained first, that is, the borehole columnar graph needs to be obtained. However, the borehole columnar graph is usually obtained by logging, which generally divides the stratum according to different lithology. This division method is relatively accurate when dividing strata with large differences in lithology (such as adjacent mudstone and sandstone), but it is not accurate when determining strata with similar lithology (such as adjacent fine-grained sandstone and medium-grained sandstone), because there may be no real boundary between strata with similar lithology, and they are actually one stratum with different lithology. In addition, logging technology is difficult to observe the bonding force between rock strata. If the bonding force between two strata is large, they can be regarded as one stratum, and if the bonding force between two strata with the same lithology is small, they should be regarded as two strata.

[0004] The main coal seam in Shiwulasi coal mine is buried at a depth of more than 650m, and the thickness of the rock stratum is more than 580m. The rock stratum mainly consists of sandstone stratum, including siltstone, fine-grained sandstone, medium-grained sandstone and coarse-grained sandstone. It is a typical rock burst mine, and the method for preventing rock burst is to cut off the key stratum in the stratum. However, there are too many similar sandstone strata in the stratum, and it is difficult to accurately determine the position of the key stratum without clear boundaries between the strata, which makes it difficult to make targeted roof cutting work. If a key stratum is missed, the roof cutting may not be complete, and rock burst may still occur. If too many key strata are determined, the roof cutting workload will increase. Therefore, accurately determining the position of the key stratum is of great significance for guiding coal mining and pressure relief work.

[0005] Furthermore, existing methods of roof cutting and pressure relief often involve drilling roof-cutting holes into the working face's mining roadways, setting appropriate cutting angles for these holes. However, the entire cutting angle is uniform, meaning all critical strata are cut along a straight line. This can potentially lead to a chain reaction of instability in the critical strata. That is, if the lower critical stratum fails, the upper critical stratum may also fail following suit, potentially causing rockbursts. Therefore, selecting appropriate roof-cutting locations in strata with many thick, hard rock layers (such as deeply buried sandstone strata) is crucial for optimizing roof cutting operations and preventing chain reactions of roof instability.

[0006] Furthermore, in order to improve the coal recovery rate, coal mines such as Shiwulasu often adopt the technique of leaving roadways along the goaf. How to coordinate the work of leaving roadways along the goaf with roof cutting and pressure relief is also a problem that needs to be solved. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a method for roof-cutting and pressure-relief coal mining under deep-buried sandstone strata conditions, comprising the following steps:

[0008] S1: Select the first mining face;

[0009] S2: After mining, drill exploratory borehole B outside the first mining face and within the dip range of the water-conducting fracture zone; drill exploratory borehole A3 inside the first mining face; obtain logging data including all strata above the coal seam and the thickness of each stratum;

[0010] S3: Test the rock layer interfaces obtained from well logging with water in sequence, and verify the authenticity of the interfaces based on whether water can be injected.

[0011] S4: Based on the accurate location of the strata and their boundaries, as well as the thickness of each stratum, the key strata are identified according to the key strata identification method;

[0012] S5: Prepare the return airway for the next working face by excavating along the goaf. Conduct roof cutting boreholes in the goaf excavation to cut the roof of all key layers in the rock strata.

[0013] S6: Excavate the next working face transport roadway, and excavate the roof cutting special roadway in the working face at a certain width interval from the transport roadway. From the roof cutting special roadway, construct the roof cutting borehole B to the water-seeping fracture zone rock strata and the collapse zone rock strata. From the transport roadway, construct the roof cutting borehole to the curved and subsided zone rock strata.

[0014] S7: Mining; leave roadways along the goaf in the transport roadway; as the working face advances, cut off the key layers in the water-conducting fracture zone and the caving zone behind the hydraulic support through the top-cutting borehole B to reduce the overhang length; then cut off the key layers in the upper part of the curved subsidence zone through the top-cutting borehole A, and retain 1 to 2 key layers in the lower part.

[0015] Preferably, in step S1, the first mining face is not affected by mining, and the width of the first mining face is greater than 1.2 times the height of the water flowing fractured zone.

[0016] Preferably, in step S2, the detection borehole B is constructed to the coal seam, and logging is performed based on the detection borehole B; and the detection borehole A at least completely penetrates the curved subsidence zone rock stratum.

[0017] Preferably, in step S3, water can be pressed into the rock stratum interface under a set pressure, which indicates that the rock stratum interface actually exists; if water cannot be pressed in, it indicates that the rock stratum interface does not exist, and the rock stratum interface is cancelled and the two rock strata above and below the rock stratum interface are combined into one.

[0018] Preferably, in step S3, it further includes segmentally testing water in height for the stratum with greater thickness obtained by logging, to check whether the stratum with greater thickness has a boundary that has not been detected.

[0019] Preferably, in step S3, the detection borehole A is used to detect the curved subsidence zone rock stratum, and the detection borehole B is used to detect the water flowing fractured zone rock stratum and the caving zone rock stratum.

[0020] Preferably, in step S6, in terms of inclination, the top cutting borehole B is inclined to the inside of the working face, and the top cutting borehole A is a vertical borehole.

[0021] Preferably, in step S7, the coal mining machine always moves from the return airway to the transportation roadway in terms of inclination.

[0022] Preferably, in step S7, the top cutting borehole B is used for top cutting work after the top cutting borehole A.

[0023] Preferably, it further includes step S8: using the gob-side entry retained by the previous working face as the return airway of the next working face, and referring to step S6 to excavate the transportation roadway, the top cutting special roadway and the top cutting borehole of the next working face; and referring to step S7 to perform mining, top cutting and gob-side entry work of the next working face.

[0024] Then, the roadway excavation, the top cutting borehole construction, the mining, the top cutting and the gob-side entry work of the subsequent working face are repeatedly performed.

[0025] In view of the problem that the key layer is not accurately determined due to inaccurate rock stratum boundary, the application further provides a method for accurately determining the key layer under the condition of deep buried sandstone group stratum, which includes the following steps:

[0026] S1: selecting a first mining face;

[0027] S2: drilling a detection borehole B outside the first mining face after mining and within the range of the water flowing fractured zone; drilling a detection borehole A3 inside the first mining face; obtaining logging data of all strata above the coal seam and thicknesses of the strata;

[0028] S3: sequentially performing water pressure test on the stratum interfaces obtained by logging, and checking the authenticity of the interfaces according to whether water can be injected into the interfaces;

[0029] S4: judging the key layer according to the key layer judgment method based on the accurate stratum positions and thicknesses of the strata.

[0030] Preferably, in step S1, the first mining face is not affected by mining, and the width of the first mining face is greater than 1.2 times the height of the water flowing fractured zone.

[0031] Preferably, in step S2, the detection borehole B is drilled to the coal seam, and logging is performed based on the detection borehole B; the detection borehole A at least completely penetrates the curved subsidence zone strata.

[0032] Preferably, in step S3, water can be injected into the stratum interface under a set pressure, indicating that the stratum interface actually exists; if water cannot be injected, it indicates that the stratum interface does not exist, and the two strata above and below the stratum interface are combined into one stratum.

[0033] Preferably, in step S3, the strata with large thicknesses obtained by logging are further segmented in height for water pressure test to check whether the strata with large thicknesses have interfaces that have not been detected.

[0034] Preferably, in step S3, the detection borehole A is used to detect the curved subsidence zone strata, and the detection borehole B is used to detect the water flowing fractured zone strata and the caving zone strata.

[0035] The key technical means and beneficial technical effects of the present application are as follows:

[0036] 1. To solve the problem of inaccurate key layer judgment caused by inaccurate stratum interface, the present application constructs two detection boreholes inside and outside the working face, respectively checks the stratum interfaces in the curved subsidence zone strata, the water flowing fractured zone strata and the caving zone strata by hydraulic pressure test, and checks whether the thick and hard strata have sub-layers; the external detection borehole can be drilled to the coal seam to perform logging on the entire strata above the coal seam, and then the logging data can be used for checking. The checked strata and their corresponding thicknesses can accurately determine the position of the key layer, and then the top cutting work can be performed in a targeted manner, and the top cutting work is accurate and efficient.

[0037] 2. For the problem of rock burst in deep buried sandstone group stratum, for the second working face connected with the first working face for exploration in non-sufficient mining, the application creatively proposes a top cutting and pressure releasing work based on the roadway driving along the goaf, the top cutting can reduce the overhanging distance of the upper roof stratum of the roadway driving along the goaf and cut off the key layer of the bending subsidence zone; this can reduce the stratum range supported by the roadway driving along the goaf and reduce the width of the coal pillar; on the other hand, it can reduce the impact of thick and hard rock stratum on the second working face mining, which is beneficial to the cantilever beam breaking mode of the roof of the subsequent second working face and reduces the rock burst.

[0038] 3. Further, the application adopts the roadway driving along the goaf for the subsequent working face, and no coal pillar is left between the adjacent working faces, which greatly improves the coal recovery rate. On this basis, the application creatively proposes to construct top cutting boreholes in the top cutting special roadway and the transportation roadway respectively to cut the key layer in the bending subsidence zone, the water flowing fractured zone and the caving zone of the roof. The key layer in the water flowing fractured zone and the caving zone is inclined to the middle of the working face, which on the one hand reduces the overhanging length of the water flowing fractured zone and the caving zone and reduces the support force required by the roadway driving along the goaf, and on the other hand, the construction of the top cutting special roadway can retain a certain overhanging length to provide a shelter space for the roadway driving along the goaf. When cutting the key layer in the bending subsidence zone, the vertical borehole is used for cutting, and the inclination cutting position is located directly above the roadway driving along the goaf, and the depth cutting retains a top cutting transition zone, which on the one hand can reduce the superposition of the breaking of the bending subsidence zone and the water flowing fractured zone (the top cutting transition zone plays a role of isolation and buffering), and on the other hand can maximize the cutting of the bending subsidence zone in the inclination, thereby maximizing the reduction of the stratum pressure required by the roadway driving along the goaf.

[0039] 4. Further, based on the above-mentioned top cutting method, the mining machine always moves from the return air roadway to the transportation roadway in the inclination (the width direction of the working face); this design is because the roof stratum on the side of the return air roadway has been cut off by the top cutting borehole, and when mining from the return air roadway to the transportation roadway, the roof always breaks based on the cantilever beam structure, the breaking step distance is small, and the possibility of rock burst is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is the plan view schematic diagram of the 1201 working face and the exploration borehole arrangement in the embodiment of the application;

[0041] Figure 2 is the sectional view schematic diagram of the 1201 working face and the exploration borehole arrangement in the embodiment of the application;

[0042] Figure 3 is the plan view schematic diagram of the 1202 working face and the top cutting borehole arrangement in the embodiment of the application;

[0043] Figure 4 This is a schematic cross-sectional view of the 1202 working face and the arrangement of the top-cutting boreholes in an embodiment of the present invention;

[0044] Figure 5 This is a schematic diagram of the working face 1203 and the arrangement of the top-cutting boreholes in an embodiment of the present invention;

[0045] Figure 6 This is a schematic cross-sectional view of the 1203 working face and the arrangement of the top-cutting boreholes in an embodiment of the present invention;

[0046] In the diagram: 1021 return airway-1; 1021 transport airway-2; exploratory borehole A-3; exploratory borehole B-4; strata in the bent subsidence zone-5; strata in the water-conducting fracture zone-6; water-conducting fracture zone-61; strata in the caving zone-7; caving zone range-71; coal seam-8; 1201 goaf-9; small coal pillar-10; 1202 goaf-11; 1202 return airway-12; roof cutting special roadway-13; intermittent coal pillar-14; 1202 transport airway-15; roadway along the goaf-16; filling wall-17; roof cutting borehole A-18; roof cutting borehole B-19; 1203 return airway-20; roof cutting borehole C-21; roof cutting transition zone-22; fracture line-23; 1203 goaf-24; 1203 transport airway-25. Detailed Implementation

[0047] The following is in conjunction with the appendix Figures 1-6 Specific embodiments of the present invention will be described in detail below.

[0048] Example 1

[0049] Taking the Shilawusu coal mine as an example, this invention proposes a method for accurately identifying key layers under deep-buried sandstone strata conditions, including the following steps:

[0050] S1: As Figures 1-2 As shown, the main strata and their thickness affected by the water-conducting fracture zone 61 after the mining of coal seam 8 are determined. The affected strata are mainly the caving zone strata 7 and the water-conducting fracture zone strata 6 (caving zone 71 is entirely generated by caving zone strata 7, but not all caving zone strata 7 will generate caving zones, such as...). Figure 2 As shown in the figure (as is known in the art); in this embodiment, the mining height of coal seam 8 is 8m, and 25 times the mining height is taken as the height of the water-conducting fracture zone 61 (in this invention, the height of the water-conducting fracture zone 61 is mainly taken as the height of the middle part, although the height of the two sides is large, the water-conducting capacity is small), so after the coal seam 8 is mined, the total thickness of the strata (collapsing zone rock strata 7 and water-conducting fracture zone rock strata 6) mainly affected by the water-conducting fracture zone 61 is 200m.

[0051] Select a first mining face which is not mined in four weeks (at least the coal body on both sides of the working face inclination is not mined), and the selected first mining face in this embodiment is 1201 working face; take 1.2 times of the height of the water flowing fractured zone 240m as the minimum working face width to ensure that the water flowing fractured zone 61 is fully generated; combine the mine design production capacity and the production capacity demand to select the appropriate working face inclination width, and according to the production capacity demand and the production capacity, the working face width of Shilawusu coal mine is recommended to be 300m. Since 240m<300m, the width of the first mining face is selected to be 300m. The working face inclination width of the subsequent working face is determined to be 300m according to the production capacity demand and the production capacity.

[0052] S2: Excavate 1201 return air lane 1 and 1201 transportation lane 2 for 1201 working face, arrange the mining equipment in the open-off cut, and perform mining on 1201 working face; after the mining is completed, drill a detection borehole B4 outside 1201 working face and within the inclination range of the water flowing fractured zone 61, drill the detection borehole B4 to the coal seam 8, and after the detection borehole B4 is drilled, perform logging to obtain a borehole column chart, which contains all strata above the coal seam 8 and the thickness of each stratum; drill a detection borehole A3 near the center of 1201 working face, and the detection borehole A3 at least completely penetrates the curved subsidence zone stratum 5;

[0053] S3: Perform water pressure test on the stratum interfaces obtained by logging under the set pressure, if water can be pressed into the stratum interface under the set pressure, it indicates that the stratum interface exists, if it cannot be pressed, it indicates that the stratum interface does not exist, the stratum interface is cancelled and the two strata above and below the stratum interface are combined into one stratum; at the same time, segmentally perform water pressure test on the strata with large thickness (the possibility of becoming key layer is large, and the logging is single lithology) in height to check whether the strata with large thickness exist interfaces which are not detected; when performing water pressure test, a drill rod with two ends blocked and middle water outlet is used, which is well known to those skilled in the art and will not be described here. Among them, the curved subsidence zone stratum 5 is detected by the detection borehole A3, and the water flowing fractured zone stratum 6 and the caving zone stratum 5 are detected by the detection borehole B4.

[0054] The reason for setting up two exploratory boreholes is that after the mining of the 1201 working face, the rock strata in the caving zone 5 are broken and disordered, and the rock strata in the water-conducting fracture zone 6 have longitudinal and transverse fractures, making it impossible to conduct hydraulic pressure testing to detect the interface between these two areas. The rock strata in the flexural subsidence zone 5 have the clearest boundary at the center of the working face. Therefore, exploratory borehole A3 was drilled near the center of the 1201 working face to detect the interface of the flexural subsidence zone 5. To detect the rock strata in the water-conducting fracture zone 6 and the caving zone 7, exploratory boreholes were drilled outside the 1201 working face... Exploratory borehole B4 was drilled within the dip range of the water-conducting fracture zone 61. Due to its proximity to the 1201 working face, the rock strata at this location will be affected by the mining operations at the 1201 working face, and the interfaces within the rock strata will be somewhat disrupted. This facilitates the detection of the rock strata interface between the water-conducting fracture zone strata 6 and the collapse zone strata 7. At the same time, based on the exploratory borehole B4 drilled at this location, well logging can also be performed to obtain the formation data for hydraulic pressure testing (determining the exact location for detection, i.e., first obtaining well logging data, and then calibrating and correcting it through hydraulic pressure testing).

[0055] S4: Based on step S3, the actual rock strata interfaces can be obtained. This allows for the correction of the formations and corresponding thicknesses obtained from well logging, resulting in accurate locations of the formations and their interfaces, as well as the thicknesses of each stratum. Then, based on these accurate locations and thicknesses, key layers are identified using a key layer identification method, selecting the key layers that control the movement of the rock strata. The key layer identification method is well-known in the field and will not be elaborated upon here.

[0056] Example 2

[0057] Taking the Shilawusu coal mine as an example, this invention also proposes a method for roof-cutting and pressure-relief mining under deep-buried sandstone strata conditions. Based on Example 1, this method includes, in addition to all the steps in Example 1, the following steps:

[0058] S5: As Figures 3-4 As shown, a goaf excavation is carried out along the original 1201 transport roadway 2 to excavate the 1202 return airway 12. A small coal pillar 10 is left between the 1202 return airway 12 and the goaf 9 generated after the mining of the 1201 working face. Several top-cutting boreholes C21 are drilled at intervals along the strike in the 1202 return airway 12. The top-cutting boreholes C21 are inclined towards the 1201 working face. The top-cutting boreholes C21 cut the top of all key layers in the rock strata, thereby reducing the overhang length of the water-conducting fracture zone rock strata 6 and the caving zone rock strata 7 above the 1202 return airway 12, and cutting off the connection between the curved and subsided rock strata 5. This reduces the range of the upper curved and subsided rock strata 5 that the 1202 return airway 12 needs to support, thereby reducing the overall formation pressure that the 1202 return airway 12 needs to bear.

[0059] S6: excavate the 1202 haulage roadway 15, and excavate the small cross-section top cutting special roadway 13 in the 1202 working face after leaving a coal pillar 14 between the 1202 haulage roadway 15 and the 1202 working face, and excavate the top cutting borehole B19 from the top cutting special roadway 13 to the water flowing fractured zone rock stratum 6 and the caving zone rock stratum 7, and excavate the top cutting borehole A18 from the 1202 haulage roadway 15 to the curved subsidence zone rock stratum 5; in the inclination direction, the top cutting borehole B19 is inclined to the inside of the 1202 working face, and the top cutting borehole A18 is a vertical borehole, and the inclination angles in the inclination direction and the strike direction are both 90°.

[0060] S7: stoping the 1202 working face, and the coal winning machine is always in the direction from the 1202 return air roadway 12 to the 1202 haulage roadway 15 in the inclination direction (the working face width direction); this design is because the roof rock stratum on one side of the 1202 return air roadway 12 has been cut off by the top cutting borehole C21, and when mining from the 1202 return air roadway 12 to the 1202 haulage roadway 15 side, the roof is always broken based on a cantilever beam structure, the broken step distance is small, and the possibility of rock burst is reduced;

[0061] The 1202 haulage roadway 15 is gob-side entry retained, and the filling wall 17 is constructed near the side of the 1202 goaf 11 of the gob-side entry retained roadway 16, and because the gob-side entry retained roadway belongs to the technology well known in the art, the specific construction details are not described here; with the advance of the 1202 working face, the key layers in the water flowing fractured zone rock stratum 6 and the caving zone rock stratum 7 are cut off by the top cutting borehole B19 behind the hydraulic support (there is only one basic roof in the caving zone rock stratum 7, that is, the key layer closest to the coal seam 8), so as to reduce the length of the suspended roof of the water flowing fractured zone rock stratum 6 and the caving zone rock stratum 7; then the top cutting work of the top cutting borehole B19 lags behind to cut off the key layers in the upper part of the curved subsidence zone rock stratum 5 by the top cutting borehole A18, and 1-2 key layers in the lower part are retained, and the area of the lower part of the curved subsidence zone rock stratum 5 where the key layers are not cut off is defined as the top cutting transition zone 22; of course, if the ground has the construction condition of the top cutting borehole A18, the top cutting borehole A18 can also be constructed from the ground in step S6, so as to reduce the construction difficulty of the top cutting borehole A18 (the top cutting borehole A18 only needs to be constructed from the ground to the top surface of the top cutting transition zone 22).

[0062] The application creatively proposes two kinds of roof cutting boreholes, namely roof cutting borehole A 18 and roof cutting borehole B 19, at the gob-side entry retaining 16 to respectively perform roof cutting work on the key layers in the curved subsidence zone 5, the water flowing fractured zone 6 and the caving zone 7 in the roof. The roof cutting is inclined to the middle part of the working face for the water flowing fractured zone 6 and the caving zone 7, which on the one hand reduces the length of the roof hanging of the water flowing fractured zone 6 and the caving zone 7 and reduces the support force required to be borne by the gob-side entry retaining 16, and on the other hand enables a certain length of the roof hanging to be retained through the construction of the roof cutting special roadway 13 to provide a shelter space for the gob-side entry retaining 16. However, when the roof cutting is performed on the key layers in the curved subsidence zone 5, the vertical drilling is adopted, and the inclined position of the roof cutting is located directly above the gob-side entry retaining 16, and the roof cutting transition zone 22 is retained in the depth, which on the one hand can reduce the superposition of the breakage of the curved subsidence zone 5 and the breakage of the water flowing fractured zone 6 (the roof cutting transition zone 22 plays a role of isolation and buffering), and on the other hand can maximally perform the roof cutting on the curved subsidence zone 5 in the inclination, thereby maximally reducing the stratum pressure required to be borne by the gob-side entry retaining 16.

[0063] S8: as shown in Figures 5-6 1202 working face construction of the gob-side entry retaining 16 as the 1203 working face return airway 20, reference step S6 for 1203 working face haulage roadway 25, roof cutting special roadway 13 and roof cutting borehole construction; specific, 1203 haulage roadway 25 is excavated, and after the interval coal pillar 14 is arranged between 1203 working face and 1203 haulage roadway 25, the small section roof cutting special roadway 13 is excavated, the roof cutting borehole B 19 is constructed from the roof cutting special roadway 13 to the water flowing fractured zone 6 and the caving zone 7, and the roof cutting borehole A 18 is constructed from the 1203 haulage roadway 25 to the curved subsidence zone 5; in the inclination, the roof cutting borehole B 19 is inclined to the inside of the 1203 working face, and the roof cutting borehole A 18 is a vertical borehole, and the inclination angles in the inclination and the strike are both 90 DEG.

[0064] Reference step S7 for 1203 working face mining, roof cutting and gob-side entry retaining work;

[0065] S9: repeat step S8, and perform the roadway excavation, roof cutting borehole construction of the subsequent working face, working face mining, roof cutting and gob-side entry retaining work.

[0066] Of course, the above description is only for the preferred embodiments of the present application, and the present application is not limited to the above-mentioned embodiments. It should be noted that any skilled person in the art can make all equivalent replacements and obvious modifications under the guidance of the present application, which all fall within the scope of the present application, and should be protected by the present application.

Claims

1. A method for roof-cutting and pressure-relief coal mining under deep-buried sandstone strata conditions, characterized in that, Includes the following steps: S1: Select the first mining face; S2: After mining, drill exploratory borehole B outside the first mining face and within the dip range of the water-conducting fracture zone; drill exploratory borehole A3 inside the first mining face; obtain logging data including all strata above the coal seam and the thickness of each stratum; S3: Test the rock layer interfaces obtained from well logging with water in sequence, and verify the authenticity of the interfaces based on whether water can be injected. S4: Based on the accurate location of the strata and their boundaries, as well as the thickness of each stratum, the key strata are identified according to the key strata identification method; S5: Prepare the return airway for the next working face by excavating along the goaf. Conduct roof cutting boreholes in the goaf excavation to cut the roof of all key layers in the rock strata. S6: Excavate the next working face transport roadway, and excavate the roof cutting special roadway in the working face at a certain width interval from the transport roadway. From the roof cutting special roadway, construct the roof cutting borehole B to the water-seeping fracture zone rock strata and the collapse zone rock strata. From the transport roadway, construct the roof cutting borehole to the curved and subsided zone rock strata. S7: Mining; leave roadways along the goaf in the transport roadway; as the working face advances, cut off the key layers in the water-conducting fracture zone and the caving zone behind the hydraulic support through the top-cutting borehole B to reduce the overhang length; then cut off the key layers in the upper part of the curved subsidence zone through the top-cutting borehole A, and retain 1 to 2 key layers in the lower part.

2. The method for roof-cutting and pressure-relief coal mining under deep-buried sandstone strata conditions according to claim 1, characterized in that, In step S1, the first mining face is not affected by mining activity, and the width of the first mining face is greater than 1.2 times the height of the water-conducting fracture zone.

3. The method for roof-cutting and pressure-relief coal mining under deep-buried sandstone strata conditions according to claim 1, characterized in that, In step S2, the exploratory borehole B is drilled to the coal seam, and logging is performed based on the exploratory borehole B; the exploratory borehole A at least completely traverses the bent subsidence zone strata.

4. The method for roof-cutting and pressure-relief coal mining under deep-buried sandstone strata conditions according to claim 3, characterized in that, In step S3, if water can be injected into the rock strata interface under the set pressure, it indicates that the rock strata interface truly exists; if water cannot be injected, it indicates that the rock strata interface does not exist, and the rock strata interface is canceled and the two rock strata above and below the rock strata interface are combined into one layer.

5. The method for roof-cutting and pressure-relief coal mining under deep-buried sandstone strata conditions according to claim 3 or 4, characterized in that, Step S3 also includes performing segmented water pressure tests on the thick strata obtained from well logging in order to verify whether there are interfaces in the thick strata that have not been detected.

6. The method for roof-cutting and pressure-relieving coal mining under deep-buried sandstone strata conditions according to claim 5, characterized in that, In step S3, probe borehole A is used to probe the rock strata in the bent subsidence zone, and probe borehole B is used to probe the rock strata in the water-conducting fracture zone and the collapse zone.

7. The method for roof-cutting and pressure-relief coal mining under deep-buried sandstone strata conditions according to claim 1, characterized in that, In step S6, the top-cutting borehole B is inclined inward toward the working face, while the top-cutting borehole A is a vertical borehole.

8. The method for roof-cutting and pressure-relief coal mining under deep-buried sandstone strata conditions according to claim 1, characterized in that, In step S7, the coal mining machine always mines coal from the return airway towards the transport roadway in an inclined direction.

9. The method for roof-cutting and pressure-relief coal mining under deep-buried sandstone strata conditions according to claim 7, characterized in that, In step S7, top cutting is performed after top cutting hole A is drilled and top cutting hole B is drilled.

10. The method for top-cutting and pressure-relieving coal mining under deep-buried sandstone strata conditions according to any one of claims 7-9, characterized in that, It also includes step S8: using the gob-side retention roadway constructed in the previous working face as the return airway of the next working face, and referring to step S6 to carry out the excavation of the transport roadway and the roof-cutting special roadway of the next working face, as well as the construction of the roof-cutting borehole; referring to step S7 to carry out the mining, roof-cutting and gob-side retention work of the next working face. Then, this process is repeated continuously, including subsequent roadway excavation, roof cutting drilling, working face mining, roof cutting, and goaf retention.

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