Coal face wall spalling prevention method

Abstract

The coal wall spalling prevention and treatment method of the coal mining face comprises the following steps: S1, arranging a drilling machine and a pump set in a drilling field; S2, using the drilling machine to drill a first borehole in a roof rock layer above a coal seam; S3, using the pump set to inject water into the first borehole so as to perform hydraulic fracturing on the roof rock layer; S4, using the drilling machine to drill a second borehole in the coal seam; and S5, using the pump set to inject a reinforcing slurry into the second borehole so that the reinforcing slurry can reinforce the coal seam after diffusing in the coal seam. Therefore, the coal wall spalling prevention and treatment method of the coal mining face has the advantages of improving the coal mining efficiency and safety.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, specifically to a method for preventing coal face spalling in coal mining faces. Background Technology

[0002] High-extraction, full-thickness mining is a major technology for efficient mining of thick coal seams in my country. However, as the mining height increases, the disturbance space also increases significantly. The high-level roof cannot break and collapse in time to fill the goaf, leading to more severe mine pressure in high-extraction faces. In high-extraction faces, the exposed coal face area is large, and the horizontal stress decreases rapidly. Hydraulic supports provide vertical support to withstand the mining pressure and horizontal support to the coal face, passively resisting the strong mine pressure generated by roof collapse and displacement. Under the support pressure caused by mining, the coal body is prone to numerous fractures, resulting in a higher frequency and intensity of coal face spalling, increased end-face distance, and a significant risk of roof fall in front of the supports. These spalling and roof fall problems seriously affect the safe and efficient mining of high-extraction faces. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a method for preventing coal face spalling in coal mining faces.

[0004] The method for preventing coal face spalling in coal mining faces according to an embodiment of the present invention includes the following steps:

[0005] S1. Arrange drilling rigs and pump sets within the drilling site;

[0006] S2. Using the drilling rig, a first borehole is drilled in the roof strata above the coal seam;

[0007] S3. Use the pump set to inject water into the first borehole in order to perform hydraulic fracturing on the top rock layer.

[0008] S4. Use the drilling rig to drill a second borehole in the coal seam;

[0009] S5. The pump set is used to inject reinforcing slurry into the second borehole so that the reinforcing slurry can reinforce the coal seam after it diffuses in the coal seam.

[0010] Therefore, the coal face spalling prevention method according to the embodiments of the present invention has the advantages of improving coal mining efficiency and safety.

[0011] In some embodiments, in step S2

[0012] Within the roof strata, a target fracturing layer with its thickness direction in the vertical direction is selected, and the target fracturing layer is divided into multiple target fracturing zones along the strike of the coal seam working face;

[0013] Multiple first boreholes are drilled within each of the fracturing target zones;

[0014] Each of the first boreholes includes a first horizontal section that extends along the strike of the coal seam working face;

[0015] Multiple first horizontal segments of each fracturing target zone are spaced apart along the dip of the coal seam working face.

[0016] In some embodiments, in step S2

[0017] There are multiple fracturing target layers, which are spaced apart in the vertical direction, and hydraulic fracturing is performed on the multiple fracturing target layers.

[0018] The drilling site is set up between two adjacent fracturing target zones so that the drilling rig in one of the drilling sites can open the first borehole in two adjacent fracturing target zones;

[0019] Each of the first horizontal segments has a dimension of 300 meters or more and 500 meters or less along the direction of the coal seam working face.

[0020] In some embodiments, in step S3

[0021] The first horizontal section is divided into multiple fracturing sections along the direction of the coal seam working face, and hydraulic fracturing is performed on the multiple fracturing sections sequentially along the direction away from the bottom of the first borehole in the direction of the coal seam working face.

[0022] Hydraulic fracturing is performed on the fracturing section using a fracturing packer and the pump set, wherein after hydraulic fracturing of one fracturing section, the fracturing packer is moved away from the bottom of the first borehole to the next adjacent fracturing section.

[0023] In some embodiments, in step S4

[0024] A first grouting target layer with the thickness direction in the vertical direction is selected at the top of the coal seam, so that the distance between the first grouting target layer and the roof rock layer in the vertical direction is less than or equal to a first preset value;

[0025] The drilling rig is used to drill multiple second boreholes within the first grouting target layer.

[0026] In some embodiments, in step S4, the position of the second borehole in the first grouting target layer in the vertical direction is determined based on the borehole columnar diagram of the coal seam and the diffusion radius of the reinforcing grout, so that the reinforcing grout in the second borehole in the first grouting target layer can reach the interface between the coal seam and the roof strata after diffusion.

[0027] In some embodiments, in step S4

[0028] The distance between the second borehole within the first grouting target layer and the top rock layer is less than or equal to the diffusion radius of the reinforcing grout;

[0029] A second grouting target layer with a thickness direction of vertically is selected within the coal seam, and the second grouting target layer is located below the first grouting target layer;

[0030] The drilling rig is used to drill multiple second boreholes within the second grouting target layer.

[0031] In some embodiments, in step S4

[0032] The first grouting target layer is divided into multiple grouting target areas along the coal seam working face, and the second grouting target layer is divided into multiple grouting target areas along the coal seam working face.

[0033] Multiple second boreholes are drilled within each of the grouting target areas;

[0034] Each of the second boreholes includes a second horizontal section that extends along the strike of the coal seam working face;

[0035] Multiple second horizontal segments of each grouting target area are spaced apart along the dip of the coal seam working face.

[0036] In some embodiments, in step S4

[0037] There are multiple second grouting target layers, which are spaced apart in the vertical direction;

[0038] The drilling site is set up between two adjacent grouting target areas so that the drilling rig in one drilling site can open the second borehole in two adjacent grouting target areas;

[0039] Each of the second horizontal segments has a dimension of 300 meters or more and 500 meters or less along the direction of the coal seam working face.

[0040] In some embodiments, in step S5

[0041] The second horizontal section is divided into multiple grouting sections along the direction of the coal seam working face, and the reinforcing grout is injected into the multiple grouting sections sequentially along the direction away from the bottom of the second borehole.

[0042] The reinforcing grout is injected into the grouting section using a grouting sealing device and the pump set, wherein after grouting one of the grouting sections, the grouting sealing device is moved away from the bottom of the second borehole to the next adjacent grouting section. Attached Figure Description

[0043] Figure 1 This is a top view of hydraulic fracturing of the top rock strata according to an embodiment of the present invention.

[0044] Figure 2 This is a top view of injecting reinforcing slurry into a coal seam according to an embodiment of the present invention.

[0045] Figure 3 This is a schematic diagram of the movement of the grouting sealing device according to an embodiment of the present invention.

[0046] Figure label:

[0047] 1. Top strata; 11. First borehole; 12. First horizontal section; 13. Hydraulic fracturing fracture.

[0048] 2. Coal seam; 21. Second borehole; 22. Second horizontal section; 23. Reinforced slurry diffusion area;

[0049] 3. Drilling site;

[0050] 4. Grout inlet pipe; 41. Grouting sealing device. Detailed Implementation

[0051] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0052] The following describes a method for preventing coal face spalling in a coal mining face according to an embodiment of the present invention, with reference to the accompanying drawings. Figures 1 to 3 As shown, the coal face spalling prevention method according to an embodiment of the present invention includes the following steps:

[0053] S1. Arrange the drilling rig and pump set in drilling site 3.

[0054] S2. Using a drilling rig, the first borehole 11 is drilled in the roof rock layer 1 above the coal seam 2.

[0055] S3. Use a pump set to inject water into the first borehole 11 in order to perform hydraulic fracturing on the top rock layer 1.

[0056] S4. Use a drilling rig to open a second borehole 21 in coal seam 2.

[0057] S5. Use a pump set to inject reinforcing slurry into the second borehole 21 so that the reinforcing slurry can be diffused in the coal seam 2 to reinforce the coal seam 2.

[0058] The coal face fracturing method according to an embodiment of the present invention involves drilling a first borehole 11 in the roof stratum 1 above the coal seam 2. The first borehole 11 may extend horizontally. Then, hydraulic fracturing is performed on the roof stratum 1 using the first borehole 11 and a pump unit. This fracturing of at least a portion of the roof stratum 1 causes the rock mass to collapse during mining, eliminating large-area overhang and prompting the roof stratum 1 to fracture and collapse in time to fill the goaf, reducing the supporting pressure on the coal seam. This achieves active pressure relief, thereby reducing the pressure of the roof stratum 1 on the coal seam 2, weakening dynamic load disturbance, optimizing the stress environment of the coal face, and reducing the probability of coal seam fracturing due to high pressure.

[0059] The coal face fracturing prevention method according to an embodiment of the present invention involves drilling a second borehole 21 in the coal seam 2, which can extend horizontally. Then, a reinforcing grout is injected into the second borehole 21 using a pump unit. The reinforcing grout, diffusing within the coal seam 2, fills coal joints and fissures, improving the strength and integrity of the coal body and enhancing the support capacity of the goaf, hydraulic supports, and coal face support system. Furthermore, grouting reinforcement of the coal seam 2 can be performed simultaneously with hydraulic fracturing of the roof strata 1.

[0060] In other words, the coal face spalling prevention method according to embodiments of the present invention achieves pressure relief by fracturing the roof strata 1 and grouting the coal seam 2 to improve the strength of the coal body, thereby achieving a synergistic effect of pressure relief of the roof strata 1 and coal body reinforcement. This allows the roof strata 1 to collapse and fill the goaf in a timely manner during mining, effectively preventing coal face spalling, ensuring safe and efficient production at the working face, and thus improving the efficiency and safety of coal mining.

[0061] Therefore, the coal face spalling prevention method according to the embodiments of the present invention has the advantages of improving coal mining efficiency and safety.

[0062] In some embodiments, in step S1, the drilling site 3 is selected within the mined roadway. Specifically, after the roadway is mined, the drilling site 3 is arranged within the existing mined roadway, and there can be multiple drilling sites 3. Each drilling site 3 is equipped with drilling rigs and pump sets, etc. For example, the drilling site 3 is arranged within the mined transport roadway and return air roadway, with the drilling rig being a directional drilling rig and the pump set being a high-pressure pump set.

[0063] In some embodiments, in step S2, a target fracturing layer with its thickness direction in the vertical direction is selected within the roof rock layer 1. Specifically, the position of the target fracturing layer in the vertical direction is determined based on the structure, geostress parameters, and strength parameters of the roof rock layer 1. This facilitates the timely fracture and collapse of the roof rock layer 1 to fill the goaf after hydraulic fracturing of the target layer.

[0064] like Figure 1 As shown, in step S2, the target fracturing layer is divided into multiple target fracturing zones along the strike of the coal seam 2 working face. Dividing the target fracturing layer into multiple target fracturing zones facilitates drilling into multiple areas of the target fracturing layer separately. Both the strike and dip of the working face are horizontal; the strike can be left-right, and the dip can be front-back. The left-right and front-back directions are shown by arrows in the figure. For example, the target fracturing layer is divided into multiple target fracturing zones along the left-right direction of coal seam 2.

[0065] like Figure 1 As shown, in step S2, multiple first boreholes 11 are drilled in each fracturing target area. Each first borehole 11 includes a first horizontal section 12, which extends along the working face of the coal seam 2. The multiple first horizontal sections 12 in each fracturing target area are spaced apart along the dip of the working face of the coal seam 2. Specifically, the drilling site 3 is located on the side of the fracturing target area along the dip of the working face. The directional drilling rig in the drilling site 3 extends into the fracturing target area in a horizontal direction (arc direction) and then drills along the working face to form the first horizontal section 12. Multiple first boreholes 11 can be drilled in the fracturing target area, and the multiple first horizontal sections 12 are spaced apart along the dip of the working face of the coal seam 2, which facilitates more uniform crushing when hydraulically fracturing the target layer. The multiple first boreholes 21 are sequentially fracturing in the direction adjacent to the drilling site 3 along the dip of the working face. For example, the multiple first boreholes 21 are sequentially fracturing from back to front.

[0066] In some embodiments, in step S2, there are multiple target fracturing layers, which are spaced apart in the vertical direction, and hydraulic fracturing is performed on multiple target fracturing layers. That is, hydraulic fracturing is performed on multiple top rock layers 1 in the vertical direction. This increases the range of hydraulic fracturing on the top rock layer 1. For example, hydraulic fracturing is performed on multiple target fracturing layers from bottom to top.

[0067] like Figure 1 As shown, in some embodiments, in step S2, a drilling field 3 is set between two adjacent fracturing target zones (in the horizontal direction) so that a drilling rig in a drilling field 3 can drill a first borehole 11 in the two adjacent fracturing target zones. For example, a drilling rig in a drilling field 3 can drill to the left to drill a first borehole 11 in the fracturing target zone on its left, and a drilling rig in the drilling field 3 can drill to the right to drill a first borehole 11 in the fracturing target zone on its right.

[0068] In some embodiments, the dimension of each first horizontal segment 12 in the direction of the working face of the coal seam 2 is greater than or equal to 300 meters and less than or equal to 500 meters. For example, the dimension of each first horizontal segment 12 in the direction of the working face of the coal seam 2 is 400 meters.

[0069] In some embodiments, the dimension of each first horizontal segment 12 along the working face of the coal seam 2 is less than 300 meters. The first horizontal segment 12 can be opened in the roof strata 1 and its length determined according to the actual situation.

[0070] like Figure 1 As shown, in some embodiments, in step S3, the first horizontal segment 12 is divided into multiple fracturing sections (fracturing locations) along the working face of the coal seam 2. Hydraulic fracturing is then performed sequentially on these multiple fracturing sections along the working face of the coal seam 2 in a direction away from the bottom of the first borehole 11, in order to form multiple hydraulic fracturing fractures 1. That is, hydraulic fracturing is performed sequentially on multiple fracturing sections from the bottom of the first borehole 11 to the inlet of the first borehole 11.

[0071] Hydraulic fracturing of the fracturing section is performed using a fracturing packer and a pump unit. Specifically, the fracturing packer is a packer that is inserted into the fracturing section adjacent to the bottom of the first borehole 11. The two packer members define a packing cavity with the wall of the first borehole 11 (first horizontal section 12). The inlet pipe of the high-pressure pump unit is inserted into the packing cavity, and then high-pressure water is introduced into the packing cavity through the inlet pipe to utilize the water pressure to fracture part of the fracturing section of the top rock stratum 1. After hydraulic fracturing of one fracturing section, the fracturing packer is moved away from the bottom of the first borehole 11 to the next adjacent fracturing section for hydraulic fracturing. That is, a staged retreat fracturing process is used to hydraulically fracture the top rock stratum 1. After the fracturing operation is completed, the fracturing packer is removed.

[0072] In some embodiments, in step S4, a first grouting target layer with its thickness direction in the vertical direction is selected at the top of the coal seam 2, such that the distance between the first grouting target layer and the roof rock layer 1 in the vertical direction is less than or equal to a first preset value. Multiple second boreholes 21 are drilled within the first grouting target layer using a drilling rig. Grouting is performed on the coal seam 2 that is closer to the roof rock layer 1 as the first grouting target layer, thereby improving the structural strength of the top of the coal seam 2, thus increasing the bearing capacity of the coal body and improving the safety of mining.

[0073] In some embodiments, in step S4, the position of the second borehole 21 in the first grouting target layer in the vertical direction is determined based on the borehole columnar diagram of the coal seam 2 and the diffusion radius of the reinforcing grout, so that the reinforcing grout in the second borehole 21 in the first grouting target layer can reach the interface between the coal seam 2 and the roof rock layer 1 after diffusion.

[0074] Specifically, borehole columnar sections are engineering geological maps compiled to describe the strata, thickness, lithology, structure, and contact relationships of the rock strata through which the borehole passes, as well as groundwater sampling and testing, borehole structure, and drilling progress. They are an important basis for analyzing engineering geological conditions and drawing geological cross-sections. As a fundamental tool for visualizing underground exploration information, borehole columnar sections play a crucial role in the analysis and decision-making of various projects.

[0075] The reinforcing grout diffuses into the coal seam 2 via fracturing through the grouting and sealing device 41, and then fills the fracture structure of the coal seam 2 to reinforce it. The diffusion radius of the reinforcing grout (the diffusion area 23 of the reinforcing grout) is related to the injection pressure of the reinforcing grout, the total volume (total amount) of the reinforcing grout injected into the grouting and sealing device 41, and the fracture structure of the coal seam 2.

[0076] Based on the borehole columnar section of coal seam 2 and the diffusion radius of the reinforcing grout, the vertical diffusion range of the reinforcing grout within the first grouting target layer of coal seam 2 can be derived. This allows for the determination of the vertical position of the second borehole 21 within the first grouting target layer, ensuring that the reinforcing grout can reach the interface (contact surface) between coal seam 2 and roof stratum 1 after diffusion through the second borehole 21. Specifically, the distance between the second borehole 21 within the first grouting target layer and roof stratum 1 is less than or equal to the diffusion radius of the reinforcing grout, thereby ensuring that all locations of coal seam 2 adjacent to roof stratum 1 can be reinforced by the reinforcing grout.

[0077] In some embodiments, in step S4, a second grouting target layer with its thickness direction in the vertical direction is selected within the coal seam 2, and the second grouting target layer is located below the first grouting target layer; a plurality of second boreholes 21 are drilled within the second grouting target layer using a drilling rig. That is, grouting can be performed below the first grouting target layer, thereby strengthening the structural strength of the coal seam 2 below the first grouting target layer.

[0078] In some embodiments, in step S4, the first grouting target layer is divided into multiple grouting target areas along the working face of the coal seam 2, and the second grouting target layer is also divided into multiple grouting target areas along the working face of the coal seam 2. Dividing the first and second grouting target layers into multiple grouting target areas facilitates drilling and grouting of multiple areas of the first and second grouting target layers respectively. For example, the first grouting target layer can be divided into multiple grouting target areas in the left-right direction, and the second grouting target layer can also be divided into multiple grouting target areas in the left-right direction.

[0079] like Figure 2 As shown, multiple second boreholes 21 are drilled within each grouting target area. Each second borehole 21 includes a second horizontal section 22 extending along the strike of the coal seam 2 working face. The multiple second horizontal sections 22 in each grouting target area are spaced apart along the dip of the coal seam 2 working face. Grouting is performed sequentially on the multiple second boreholes 21 in the direction adjacent to the drilling site 3 along the dip of the working face. For example, grouting is performed sequentially on the multiple second boreholes 21 from back to front.

[0080] Specifically, drilling site 3 is located on the side of the first and second grouting target layers along the working face dip. The directional drilling rig in drilling site 3 extends horizontally (arcally) into the grouting target area and then drills along the working face to form the second horizontal section 22. Multiple second boreholes 21 can be opened in the grouting target area, and the multiple second horizontal sections 22 are spaced apart along the working face dip of the coal seam 2, thereby facilitating more uniform grouting of the second boreholes 21.

[0081] In some embodiments, in step S4, there are multiple second grouting target layers, which are spaced apart in the vertical direction. This means that more coal seams 2 are reinforced by grouting in the vertical direction. Therefore, the reinforcement range of the coal seam 2 can be increased.

[0082] like Figure 2 As shown, a drilling site 3 is set between two adjacent grouting target areas so that a drilling rig in one drilling site 3 can open a second borehole 21 in the two adjacent grouting target areas. For example, a drilling rig in one drilling site 3 can drill to the left to open a second borehole 21 in the grouting target area on its left, and a drilling rig in the same drilling site 3 can drill to the right to open a second borehole 21 in the grouting target area on its right.

[0083] The dimension of each second horizontal segment 22 in the direction of the working face of the coal seam 2 is greater than or equal to 300 meters and less than or equal to 500 meters. In some embodiments, the dimension of each second horizontal segment 22 in the direction of the working face of the coal seam 2 is 400 meters.

[0084] In some embodiments, the dimension of each second horizontal segment 22 along the working face of the coal seam 2 is less than 300 meters. The second horizontal segment 22 can be opened in the coal seam 2 and its length determined according to actual conditions.

[0085] like Figure 3 As shown, in some embodiments, in step S5, the second horizontal section 22 is divided into multiple grouting sections (grouting locations) along the working face of the coal seam 2. Reinforcing grout is then injected sequentially into these multiple grouting sections along the working face of the coal seam 2 in a direction away from the bottom of the second borehole 21. That is, grouting is performed sequentially into multiple grouting sections from the bottom of the second borehole 21 to its inlet, so that the reinforcing grout can diffuse sequentially from the bottom of the second borehole 21 to its inlet.

[0086] A reinforcing grout is injected into the grouting section using a grouting packer 41 and a pump set. Specifically, the grouting packer 41 is a packer that extends into the fracturing section adjacent to the bottom of the second borehole 21. The two packer elements of the packer define a packing cavity with the wall of the second borehole 21 (second horizontal section 22). The inlet pipe of the high-pressure pump set enters the packing cavity, and then the high-pressure pump set injects high-pressure reinforcing grout into the packing cavity through the inlet pipe to facilitate diffusion of the reinforcing grout in the coal seam 2. After grouting one section, the grouting packer 41 is moved away from the bottom of the second borehole 21 to the next adjacent grouting section. That is, a segmented retreating grouting process is used to grout the coal seam 2. After the grouting operation is completed, the grouting packer 41 is withdrawn. For example, the reinforcing grout includes polyurethane reinforcing material.

[0087] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0088] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0089] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0090] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0091] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0092] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for preventing coal face spalling in a coal mining face, characterized in that, Includes the following steps: S1. Arrange drilling rigs and pump sets within the drilling site; S2. Using the drilling rig, a first borehole is drilled in the roof strata above the coal seam; S3. Use the pump set to inject water into the first borehole in order to perform hydraulic fracturing on the top rock layer. S4. Use the drilling rig to drill a second borehole in the coal seam; S5. The pump set is used to inject reinforcing slurry into the second borehole so that the reinforcing slurry can reinforce the coal seam after it diffuses in the coal seam. In step S2 Within the roof strata, a target fracturing layer with its thickness direction in the vertical direction is selected, and the target fracturing layer is divided into multiple target fracturing zones along the strike of the coal seam working face; Multiple first boreholes are drilled within each of the fracturing target zones; Each of the first boreholes includes a first horizontal section that extends along the strike of the coal seam working face; Multiple first horizontal segments of each fracturing target zone are spaced apart along the dip of the coal seam working face; There are multiple fracturing target layers, which are spaced apart in the vertical direction, and hydraulic fracturing is performed on the multiple fracturing target layers. The drilling site is set up between two adjacent fracturing target zones so that the drilling rig in one of the drilling sites can open the first borehole in two adjacent fracturing target zones; The dimension of each first horizontal segment along the direction of the coal seam working face is greater than or equal to 300 meters and less than or equal to 500 meters; In step S4 A first grouting target layer with the thickness direction in the vertical direction is selected at the top of the coal seam, so that the distance between the first grouting target layer and the roof rock layer in the vertical direction is less than or equal to a first preset value; The drilling rig is used to drill multiple second boreholes within the first grouting target layer; The position of the second borehole in the first grouting target layer in the vertical direction is determined based on the borehole columnar diagram of the coal seam and the diffusion radius of the reinforcing grout, so that the reinforcing grout in the second borehole in the first grouting target layer can reach the interface between the coal seam and the roof rock layer after diffusion; The distance between the second borehole within the first grouting target layer and the top rock layer is less than or equal to the diffusion radius of the reinforcing grout; A second grouting target layer with a thickness direction of vertically is selected within the coal seam, and the second grouting target layer is located below the first grouting target layer; The drilling rig is used to drill multiple second boreholes within the second grouting target layer; The first grouting target layer is divided into multiple grouting target areas along the coal seam working face, and the second grouting target layer is divided into multiple grouting target areas along the coal seam working face. Multiple second boreholes are drilled within each of the grouting target areas; Each of the second boreholes includes a second horizontal section that extends along the strike of the coal seam working face; Multiple second horizontal segments of each grouting target area are spaced apart along the dip of the coal seam working face.

2. The method for preventing coal face spalling in coal mining faces according to claim 1, characterized in that, In step S3 The first horizontal section is divided into multiple fracturing sections along the direction of the coal seam working face, and hydraulic fracturing is performed on the multiple fracturing sections sequentially along the direction away from the bottom of the first borehole in the direction of the coal seam working face. Hydraulic fracturing is performed on the fracturing section using a fracturing packer and the pump set, wherein after hydraulic fracturing of one fracturing section, the fracturing packer is moved away from the bottom of the first borehole to the next adjacent fracturing section.

3. The method for preventing coal face spalling in coal mining faces according to claim 1, characterized in that, In step S4 There are multiple second grouting target layers, which are spaced apart in the vertical direction; The drilling site is set up between two adjacent grouting target areas so that the drilling rig in one of the drilling sites can open the second borehole in two adjacent grouting target areas; Each of the second horizontal segments has a dimension of 300 meters or more and 500 meters or less along the direction of the coal seam working face.

4. The method for preventing coal face spalling in coal mining faces according to claim 1, characterized in that, In step S5 The second horizontal section is divided into multiple grouting sections along the direction of the coal seam working face, and the reinforcing grout is injected into the multiple grouting sections sequentially along the direction away from the bottom of the second borehole. The reinforcing grout is injected into the grouting section using a grouting sealing device and the pump set, wherein after grouting one of the grouting sections, the grouting sealing device is moved away from the bottom of the second borehole to the next adjacent grouting section.

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