Coal mine underground working face coal wall spalling control method

Abstract

The present application belongs to the technical field of coal seam mining, and particularly relates to a coal mine underground working face coal wall spalling control method, which comprises a pre-mining control process and a mining control process. The pre-mining control process comprises, before mining of the working face, surveying the roof strata of the working face to determine the horizon of a target fracturing strata in the roof strata; fracturing the target fracturing strata to cause a fracture network in the target fracturing strata; obtaining fracture distribution data in the working face coal seam; and injecting liquid into the working face coal seam. The mining control process comprises, during mining of the working face, spraying a surface protection slurry on the coal wall, and allowing the surface protection slurry to solidify and adhere to the surface of the coal wall; and using hydraulic supports to support the coal wall. The present application can effectively reduce the stress of the strata, improve the structural strength of the coal seam, effectively reinforce and support the coal wall, control the risk of coal wall spalling, and improve the safety and sustainability of mining with an ultra-large mining height.

Description

Technical Field

[0001] This invention belongs to the field of coal seam mining technology, specifically relating to a method for controlling coal wall spalling in underground coal mine working faces. Background Technology

[0002] In recent years, my country's mining technology and equipment development level has been greatly improved. With the continuous increase in mining intensity, scale and capacity of large coal bases, as well as the rapid development of modern, automated and integrated mechanized mining technologies, the coal output of high-seam mining faces has been rising continuously, making it the main mining method for thick and extra-thick coal seams in my country.

[0003] In related technologies, high-extraction mining faces the challenge of controlling coal wall spalling. During the mining process of ultra-high coal face working faces, coal blasting and flying coal blocks can injure people and damage equipment. Regional or large-scale coal wall spalling can cause roof collapse in front of the frame, and large amounts of giant coal and rock masses can be thrown out and fall into the working face, causing phased shutdowns of the working face and resulting in significant losses and even casualties. This seriously restricts the safe, efficient and sustainable development of coal mines. The control of coal wall stability in ultra-high mining faces determines the success or failure of ultra-high mining. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention propose a method for controlling coal wall spalling in underground coal mine working faces, which can effectively reduce rock stress, improve the structural strength of coal seams, effectively reinforce and support coal walls, control the risk of coal wall spalling, and improve the safety and sustainability of ultra-high mining.

[0006] The coal face spalling control method of the present invention includes a pre-mining control process and a mining control process. The pre-mining control process includes the following steps:

[0007] Before mining the working face, the roof strata of the working face are investigated to determine the stratigraphic position of the target fractured rock layer in the roof strata.

[0008] The target fractured rock layer is fractured to create a fracture network, which is used to relieve pressure on the target fractured rock layer.

[0009] Obtain fracture distribution data in the coal seam of the working face;

[0010] Injecting liquid into the coal seam at the working face allows the reinforcing grout to fill the cracks in the coal seam and solidify, thus reinforcing the coal seam at the working face.

[0011] The sampling control process includes the following steps:

[0012] During the longwall mining process, a protective slurry is sprayed onto the coal face, and the protective slurry is then cured and adhered to the surface of the coal face.

[0013] Hydraulic supports are used to provide top support for the coal face.

[0014] The coal face spalling control method of the coal mine underground working face according to the present invention can effectively reduce rock stress, improve the structural strength of coal seam, effectively reinforce and support the coal face, control the risk of coal face spalling, and improve the safety and sustainability of ultra-high mining.

[0015] In some embodiments, the exploration of the roof strata of the working face to determine the stratigraphic position of the target fracturing strata within the roof strata includes the following steps:

[0016] The exploration scope of the roof strata is determined, and the vertical dimension of the exploration scope is not less than 10M, where M is the coal seam thickness;

[0017] The rock strata within the exploration area are surveyed to obtain the performance parameters of different rock strata;

[0018] If the stress in the corresponding rock layer is greater than the first threshold and the elastic modulus in the corresponding rock layer is greater than the second threshold, then the corresponding rock layer is the initial target rock layer.

[0019] Based on the fracture development and calcareous cemented lithology of the preliminary target rock layers, determine whether the corresponding preliminary target rock layers need to be hydraulically fractured and depressurized.

[0020] If so, the corresponding initially selected target rock layer is selected as the target fracturing rock layer, and the stratigraphic position of the target fracturing rock layer is determined.

[0021] In some embodiments, fracturing the target fractured rock layer to create a fracture network in the target fractured rock layer includes the following steps:

[0022] Horizontal directional holes are arranged in the target fractured rock layer, and the horizontal directional holes extend to a depth of 500m to 800m in the coal seam excavation direction;

[0023] Deploy fracturing equipment;

[0024] The target fracturing strata are subjected to segmented fracturing and depressurization using a retreating segmented fracturing process. The interval between two adjacent fracturing zones is not less than 50m, and the duration of a single fracturing operation is not less than 120min.

[0025] In some embodiments, the acquisition of fracture distribution data in the coal seam of the working face is carried out by at least one of the following methods: seismic wave method, borehole detection method, and numerical simulation method, to obtain the fracture orientation, fracture width, and fracture depth in the coal seam of the working face.

[0026] In some embodiments, the injection of liquid into the coal seam at the working face to fill and solidify the reinforcing slurry into the fractures of the coal seam includes the following steps:

[0027] Based on the fracture distribution data in the coal seam of the working face, the drilling path is determined;

[0028] Directional holes and branch holes are arranged in the coal seam of the working face;

[0029] Arrange grouting equipment and determine grouting parameters based on the crack width and depth, crack area, and rheological properties of the grout in the corresponding area;

[0030] Start the grouting equipment to fill the cracks in the coal seam of the working face with the reinforcing grout and solidify it.

[0031] In some embodiments, the process of spraying a protective slurry onto the coal face and allowing the slurry to solidify and adhere to the coal face surface involves a spraying device positioned behind the drum of the coal mining machine, through which the protective slurry is sprayed onto the coal face.

[0032] In some embodiments, the protective coating slurry includes a two-component reactive polyurethane, a urea spraying material, a two-component silicate-modified polyurethane spraying material, a two-component polyacrylate spraying material, or a single-component organic-inorganic composite spraying material.

[0033] In some embodiments, the hydraulic support has a side protection level of 3 or higher; and / or

[0034] The hydraulic support has a double-layer sidewall protection mechanism for protecting the coal wall and roof respectively; and / or

[0035] The protective surface area of ​​the hydraulic support shall not be less than 13m². 2 .

[0036] In some embodiments, the vertical support height of the hydraulic support is greater than or equal to 1 / 2H, where H is the coal seam mining height of the working face.

[0037] In some embodiments, the coal face spalling control method in underground coal mines further includes a fracturing evaluation process, which includes:

[0038] Before and after fracturing the target fracturing rock stratum, the advance support pressure and coal stress were measured, and the first measurement data before fracturing and the second measurement data after fracturing were obtained.

[0039] By comparing the first and second measurement data, the difference between the peak value of the advance support pressure before and after fracturing, and the difference between the peak value of the coal stress, are obtained to evaluate the fracturing effect.

[0040] Data on any one or more of the following parameters can be obtained to perform a secondary evaluation of the fracturing effect: periodic pressure step distance, pressure duration distance, support dynamic load coefficient, and safety valve opening rate.

[0041] Based on the primary and secondary evaluation results, a comprehensive evaluation is conducted on the fracturing and pressure relief effect of the target fracturing rock layer. Attached Figure Description

[0042] Figure 1 This is a flowchart of a coal mine underground working face coal wall spalling control method according to an embodiment of the present invention.

[0043] Figure 2 This is a flowchart illustrating the determination of the stratigraphic position of the target fractured rock layer in the top strata according to an embodiment of the present invention.

[0044] Figure 3 This is a schematic diagram of fracturing grouting according to an embodiment of the present invention.

[0045] Figure 4 This is a comparison diagram of the advanced support pressure before and after fracturing according to an embodiment of the present invention.

[0046] Figure 5 This is a stress curve diagram before fracturing according to an embodiment of the present invention.

[0047] Figure 6 This is a stress curve diagram after fracturing according to an embodiment of the present invention. Detailed Implementation

[0048] 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.

[0049] The following is in conjunction with the appendix Figures 1-6 The coal face spalling control method of the present invention is described in detail below. The coal face spalling control method of the coal face includes pre-mining control technology and in-mining control technology. The pre-mining control technology includes the following steps:

[0050] S101. Before mining the working face, the roof strata should be explored to determine the location of the target fracturing strata. It should be understood that fracturing is performed in the high-stress critical strata area of ​​the coal seam roof to form fractures, reduce strata stress, and thus reduce the risk of coal wall spalling. The width and depth of the fracturing fractures should be designed based on the strata strength, stress field conditions, and the height of the ultra-large coal seam mining height.

[0051] S102. Fracturing the target fractured rock layer to create a fracture network, which is used to relieve pressure on the target fractured rock layer.

[0052] In other words, before mining ultra-high coal face, regional fracturing is carried out on the high-stress, thick and hard strata of the coal seam roof to weaken the integrity of the hard rock strata in advance and release a large amount of elastic energy contained in the rock strata. During the mining process, the rock strata in the roof collapse zone and fracture zone can collapse in time and fill the goaf, avoiding the formation of a large area of ​​overhang in the goaf and generating ultra-high support pressure. By fracturing and depressurizing the thick and hard key rock strata, the force generated by the coal seam roof and its movement on the coal face is reduced, thereby effectively preventing coal face instability, collapse, or ejection.

[0053] S103. Obtain fracture distribution data in the coal seam of the working face.

[0054] S104. Inject liquid into the coal seam of the working face so that the reinforcing grout fills the cracks in the coal seam and solidifies, for use in grouting and reinforcing the coal seam of the working face.

[0055] It should be understood that before the working face is mined, directional drilling and branch holes are drilled into the coal seam through the two roadway spaces. High pressure and large displacement of coal-friendly nano-scale ultrafine reinforcing slurry are injected into the coal seam through the drilling. The slurry should be able to enter the micro-fractures and pores of the coal seam, and its hardened strength should be comparable to the strength of the coal seam. The slurry should also have the characteristics of not affecting the coal quality and not polluting the environment.

[0056] The process control during mining includes the following steps:

[0057] S105. During the longwall mining, a protective slurry is sprayed onto the coal face and the protective slurry is cured and adhered to the coal face surface.

[0058] S106. Utilize hydraulic supports for roof support of the coal face. It should be understood that during the mining process, the hydraulic support's sidewall mechanism promptly adheres to the coal face, providing maximum active surface support force, creating confining pressure on the coal face surface, improving coal face stability, and preventing or reducing the severity of coal face spalling.

[0059] The coal face spalling control method of the coal mine underground working face according to the present invention can effectively reduce rock stress, improve the structural strength of coal seam, effectively reinforce and support the coal face, control the risk of coal face spalling, and improve the safety and sustainability of ultra-high mining.

[0060] like Figure 2 As shown, in some embodiments, the exploration of the roof strata of the working face to determine the stratigraphic position of the target fracturing strata within the roof strata includes the following steps:

[0061] S201. Determine the exploration scope of the roof strata. The vertical dimension of the exploration scope shall not be less than 10 meters, where M is the coal seam thickness. It should be understood that pre-fracturing testing is used to determine the fracturing strata: A comprehensive test of the roof strata is conducted to determine the target fracturing strata. The vertical testing range of the roof strata should be greater than 10 times the coal seam thickness. For example, the vertical dimension of the exploration scope can be 10 meters, 12 meters, 15 meters, 15.5 meters, or 16 meters. Taking a mining height of 8.8 meters as an example, the vertical dimension of the exploration scope should be at least 88 meters. It can also be 100 meters, 120 meters, 135 meters, or 144 meters, etc.

[0062] S202. Conduct surveys on the rock strata within the exploration area to obtain performance parameters of different rock strata. The survey content includes: geostress field, surrounding rock strength, rock core sampling, rock well logging, rock structure, laboratory physical and mechanical parameters, etc., and evaluate the characteristics of the rock strata from multiple dimensions by using as many survey methods as possible.

[0063] S203. Determine whether the in-situ stress in the corresponding rock layer is greater than the first threshold, and determine whether the elastic modulus of the corresponding rock layer is greater than the second threshold.

[0064] S204. If at least one of the two is true, then the corresponding rock stratum is the preliminary target rock stratum. For example, when the values ​​of the in-situ stress and elastic modulus of the rock stratum are determined, if the in-situ stress exceeds the first threshold by too much, or the elastic modulus exceeds the second threshold by too much, then the in-situ stress and elastic modulus can be used as separate evaluation criteria, or the in-situ stress and elastic modulus can be evaluated together to determine whether it is the preliminary target rock stratum.

[0065] S205. Based on the fracture development and calcareous cemented lithology of the initially selected target rock strata, determine whether the corresponding initially selected target rock strata need to be fracturing and depressurized. When the fracture development is not ideal or the calcareous cemented lithology does not meet the requirements, the rock strata are further evaluated to determine the target rock strata for fracturing, so as to achieve fracturing and depressurization of the rock strata with the lowest possible construction cost.

[0066] S206. If so, select the corresponding initial target rock layer as the target fracturing rock layer and determine the stratigraphic position of the target fracturing rock layer.

[0067] like Figure 3 As shown, in some embodiments, fracturing the target fractured rock layer to create a fracture network includes the following steps:

[0068] S301. Arrange horizontal directional holes in the target fractured rock layer, with the horizontal directional holes extending to a depth of 500m to 800m in the direction of coal seam excavation.

[0069] S302. Arrange fracturing equipment.

[0070] S303. The target fracturing strata are subjected to segmented fracturing and depressurization using a retreating segmented fracturing process. The interval between two adjacent fracturing zones shall not be less than 50m, and the duration of a single fracturing operation shall not be less than 120min.

[0071] Specifically, during rock fracturing, directional borehole fracturing technology is adopted, in which horizontal directional boreholes are arranged within the target fracturing rock layer. The borehole depth is generally 500-800m to fully ensure the control effect on coal face spalling in the mining area. For example, the borehole depth is 500m, 530m, 560m, 594m, 654m, 666m, 750m, 761m or 800m. When the borehole depth is less than 500m, the formation stress in the fracturing area is likely to affect the mining area, and problems such as coal face spalling may occur. When the borehole depth is greater than 800m, the construction difficulty and construction cost will increase, and the formation stress in other areas beyond 800m has a relatively small impact on the current mining area. Reasonable planning of the operating depth can improve construction efficiency, reduce construction costs and optimize the process of spalling control.

[0072] The embodiments of this invention employ a back-retreating segmented fracturing process with an open-hole aperture, a fracturing interval of not less than 50m, and a fracturing time of not less than 120min. The hydraulic fracture distribution is closely related to the characteristics of the rock strata. Through practice, it has been found that, based on the above fracturing operation, the fracture network distribution in dense and intact sandstone strata is generally as follows: fracture length not less than 100m, fracture width not less than 60m, and fracture height not less than 10m, which can meet the effect of rock strata fracturing and pressure relief.

[0073] In some embodiments, the fracture distribution data in the working face coal seam is obtained by using at least one of the following methods: seismic wave method, borehole detection method, and numerical simulation method to obtain the fracture orientation, fracture width, and fracture depth in the working face coal seam.

[0074] Among them, the seismic wave method uses the propagation characteristics of seismic waves to predict coal seam fractures.

[0075] Borehole inspection method: Drilling holes in the coal seam and inspecting the borehole walls to determine the direction, width, and depth of coal seam fractures.

[0076] Numerical simulation method: Based on the stress field of the coal seam, a computer is used to perform numerical simulation to predict the direction, width and depth of coal seam fractures.

[0077] By comprehensively judging the data from these three sources, we can obtain relatively clear data on the orientation, depth, and width of coal seam fractures, thereby providing a basis for designing grouting parameters for the reinforcement grout and ensuring the effectiveness of grouting reinforcement of the coal seam.

[0078] In some embodiments, injecting liquid into the coal seam at the working face to fill and solidify the reinforcing grout includes the following steps:

[0079] S401. Determine the borehole path based on the fracture distribution data in the coal seam of the working face.

[0080] S402. Arrange directional holes and branch holes in the coal seam of the working face.

[0081] S403. Arrange the grouting equipment and determine the grouting parameters based on the crack width and depth, crack area, and rheological properties of the grout in the corresponding area.

[0082] S404. Start the grouting equipment to fill the cracks in the coal seam of the working face with the reinforcing grout and solidify it.

[0083] Specifically, the grouting pressure is designed based on the width and depth of the crack, the grouting speed is designed based on the rheological properties of the nano-ultrafine grout, and the grouting volume is designed based on the area of ​​the crack. The curing time of the nano-ultrafine grout is related to factors such as the grout's composition, proportions, and temperature. Generally, the curing time of the nano-ultrafine grout is 1-2 days. Grouting equipment can use a grouting machine or an injection pump to inject the nano-ultrafine grout into the crack.

[0084] Furthermore, the reinforcing grout in this embodiment of the invention is a nano-ultrafine grout. The nano-ultrafine grout mainly comprises nano-ultrafine materials, cement, and other additives. The nano-ultrafine materials are the main component of the nano-ultrafine grout and possess excellent permeability and adhesion. Cement acts as a curing agent for the nano-ultrafine grout. Other additives can improve the performance of the nano-ultrafine grout.

[0085] The formulation of nano-ultrafine slurry is mainly determined based on the content of nano-ultrafine materials, cement, and other additives. For example, the content of nano-ultrafine materials is 10-30%, the content of cement is 60-70%, and the content of other additives is 10-20%.

[0086] The pre-injection of nano-ultrafine slurry into coal seam fractures in this embodiment of the invention improves the strength and impact resistance of the coal face, preventing coal face spalling accidents. It also reduces coal face deformation, improves the stability of the working face roadway, and extends the service life of the working face roadway.

[0087] In some embodiments, a protective slurry is sprayed onto the coal face, and the slurry is allowed to solidify and adhere to the coal face surface. A spraying device is installed behind the drum of the coal mining machine, and the protective slurry is sprayed onto the coal face through the spraying device. The slurry, rich in fibers and coal-affinity, is sprayed onto the coal face. After contacting the coal face, the slurry begins to solidify and adhere to the coal face surface. The resulting sprayed surface has a certain surface tension, which generates a protective force on the coal face.

[0088] Furthermore, the protective coating slurry includes two-component reactive polyurethane, urea spraying material, or two-component silicate-modified polyurethane spraying material, or two-component polyacrylate spraying material, or single-component organic-inorganic composite spraying material.

[0089] In other words, during the longwall mining process, a spraying device is installed behind the coal mining machine drum. This device sprays a fast-reacting, high-strength, and highly adhesive coating material onto the coal face. The material can be a two-component reactive polyurethane or urea coating, a two-component silicate-modified polyurethane coating, a two-component polyacrylate coating, or a single-component organic-inorganic composite coating, etc. After passing through the spraying equipment, the coating components are mixed at a volume ratio of 1:1 or other required ratios and then sprayed onto the coal face. Upon contact with the coal face, the coating begins to solidify and adhere to the coal face surface, forming a coating layer with a certain degree of adhesion and strength, thus providing a protective force against the coal face.

[0090] The protective grout, when solidified and bonded to the coal face, primarily functions in two ways: First, it prevents coal body detachment, prevents further crack propagation leading to coal face instability, and maintains the coal face's self-stabilizing properties. Second, the surface adhesion force generated by the sprayed material bonds the coal face surface into a whole, and its tensile and shear strength maintains the integrity of the coal face surface, providing semi-active support, improving the stress state of the coal face, and enhancing its stability.

[0091] In some embodiments, the hydraulic support has a side protection level of 3 or higher; and / or the hydraulic support has a double-layer side protection plate mechanism for protecting the coal wall and roof respectively; and / or the surface area of ​​the hydraulic support is not less than 13m². 2 .

[0092] Furthermore, the vertical support height of the hydraulic support is greater than or equal to 1 / 2H, where H is the coal seam mining height of the working face.

[0093] Specifically, the hydraulic support in this embodiment of the invention employs a double telescopic beam + a 3-level ultra-large area side protection plate, extending the support length of the telescopic beam and the side protection plate to support the ultra-high coal face at the working face. During the mining process, the hydraulic support side protection plate mechanism promptly adheres to the coal face, providing maximum active surface protection force to the coal face, providing confining pressure to the coal face surface, improving coal face stability, and preventing or reducing the severity of coal face spalling.

[0094] The larger the surface area of ​​the sidewall support structure, the better it can prevent coal wall spalling and the better the support effect. The sidewall support structure of this embodiment is mainly as follows: ≥3 levels of support, double-layered: one layer has 3 or more levels for coal wall support, and the other layer has a single level for roof support. The surface area of ​​the sidewall support structure should not be less than 13m². 2 For example, the surface area of ​​the side panel mechanism is 13m². 2 14m 215.5m 2 17.2m 2 18m 2 wait.

[0095] The higher the rigidity and the larger the surface area of ​​the protective plate mechanism, the better the support effect on the coal wall.

[0096] Specifically, the stiffness of the sidewall support mechanism is determined based on the coal wall thickness and stress field conditions. While ensuring structural stiffness, the surface area of ​​the sidewall support mechanism increases the support effect on the coal wall by increasing the surface area. The surface area also needs to be determined based on the coal wall thickness and stress field conditions. The vertical surface height of the hydraulic support should be ≥1 / 2H, for example, 1 / 2H, 2 / 3H, or 3 / 4H. When the surface height is less than 1 / 2H, it easily leads to more exposed coal wall, poor coal wall support effect, increased risk of spalling, and is detrimental to ensuring construction safety and controlling spalling.

[0097] In some embodiments, the coal wall spalling control method for underground coal mine working faces further includes a fracturing evaluation process, which includes:

[0098] S501. Before and after fracturing the target fracturing rock layer, measure the advance support pressure and coal stress respectively, and obtain the first measurement data before fracturing and the second measurement data after fracturing.

[0099] S502. Compare the first and second measurement data to obtain the difference between the peak value of the advance support pressure before and after fracturing, and the difference between the peak value of the coal body stress, in order to evaluate the fracturing effect. Specifically, as follows... Figures 4-6 As shown, Figure 4 A comparison chart showing the peak values ​​of the advance support pressure before and after fracturing is presented. Figure 5 A schematic diagram of the stress in the coal seam before fracturing is shown. Figure 6 A schematic diagram of the stress in the coal seam after fracturing is shown.

[0100] S503. Obtain data on any one or more of the following: cycle pressure step distance, pressure duration distance, support dynamic load coefficient, and safety valve opening rate, in order to conduct a secondary evaluation of the fracturing effect.

[0101] S504. Based on the results of the first and second evaluations, a comprehensive evaluation is conducted on the fracturing and pressure relief effect of the target fracturing rock layer.

[0102] This invention evaluates the effects of fracturing using a multi-parameter comprehensive evaluation method. These parameters include: working face height, periodic pressure step distance, pressure duration distance, support dynamic load coefficient, safety valve opening rate, coal stress and advance support pressure, and coal wall spalling. By comparing the changes in these parameters before and after fracturing, the fracturing effect is comprehensively evaluated.

[0103] On the one hand, it can better guide the shortcomings in the process of controlling rock spalling and optimize the process steps. On the other hand, it can promptly identify weak areas and further strengthen the area by means of hydraulic support, rock fracturing, grouting of reinforcing grout, and spraying of surface grout to prevent rock spalling.

[0104] In this embodiment of the invention, the pre-mining control process and the in-mining control process can solve the problem of coal face spalling through different operating methods. The entire control process can be carried out before and during the long working face mining, and can play a complementary role. On the one hand, it can prevent spalling in advance, and on the other hand, it can provide timely support measures when there is a risk of spalling. The pre-mining control process can eliminate the predicted potential risks and avoid safety accidents during mining. The in-mining control process can prevent unpredictable risks in the pre-mining control process and ensure safe operation during mining.

[0105] 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 are not intended to 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for controlling coal wall spalling in underground coal mine working faces, characterized in that, This includes pre-mining control technology and in-mining control technology. The pre-mining control technology includes the following steps: Before mining the working face, the roof strata of the working face are investigated to determine the stratigraphic position of the target fractured rock layer in the roof strata. The target fractured rock layer is fractured to create a fracture network, which is used to relieve pressure on the target fractured rock layer. Obtain fracture distribution data in the coal seam of the working face; Injecting liquid into the coal seam at the working face allows the reinforcing grout to fill the cracks in the coal seam and solidify, thus reinforcing the coal seam at the working face. The sampling control process includes the following steps: During the longwall mining process, a protective slurry is sprayed onto the coal face, and the protective slurry is then cured and adhered to the surface of the coal face. Hydraulic supports are used to provide top support for the coal face; The exploration of the roof strata of the working face to determine the stratigraphic position of the target fracturing strata within the roof strata includes the following steps: The exploration scope of the roof strata is determined, and the vertical dimension of the exploration scope is not less than 10M, where M is the coal seam thickness; The rock strata within the exploration area are surveyed to obtain the performance parameters of different rock strata; If the stress in the corresponding rock layer is greater than the first threshold and the elastic modulus in the corresponding rock layer is greater than the second threshold, then the corresponding rock layer is the initial target rock layer. Based on the fracture development and calcareous cemented lithology of the preliminary target rock layers, determine whether the corresponding preliminary target rock layers need to be hydraulically fractured and depressurized. If so, the corresponding initially selected target rock layer is selected as the target fracturing rock layer, and the stratigraphic position of the target fracturing rock layer is determined; In obtaining the fracture distribution data in the coal seam of the working face, the fracture orientation, fracture width, and fracture depth in the coal seam of the working face are obtained by at least one of the following methods: seismic wave method, borehole detection method, and numerical simulation method. The process of injecting liquid into the coal seam at the working face to fill and solidify the reinforcing slurry includes the following steps: Based on the fracture distribution data in the coal seam of the working face, the drilling path is determined; Directional holes and branch holes are arranged in the coal seam of the working face; Arrange grouting equipment and determine grouting parameters based on the crack width and depth, crack area, and rheological properties of the grout in the corresponding area; Start the grouting equipment to fill the cracks in the coal seam of the working face with the reinforcing grout and solidify it; The method for controlling coal wall spalling in underground coal mine working faces also includes a fracturing evaluation process, which includes: Before and after fracturing the target fracturing rock stratum, the advance support pressure and coal stress were measured, and the first measurement data before fracturing and the second measurement data after fracturing were obtained. By comparing the first and second measurement data, the difference between the peak value of the advance support pressure before and after fracturing, and the difference between the peak value of the coal stress, are obtained to evaluate the fracturing effect. Data on any one or more of the following parameters can be obtained to perform a secondary evaluation of the fracturing effect: periodic pressure step distance, pressure duration distance, support dynamic load coefficient, and safety valve opening rate. Based on the primary and secondary evaluation results, a comprehensive evaluation is conducted on the fracturing and pressure relief effect of the target fracturing rock layer.

2. The method for controlling coal wall spalling in underground coal mine working faces according to claim 1, characterized in that, The process of fracturing the target fractured rock layer to create a fracture network includes the following steps: Horizontal directional holes are arranged in the target fractured rock layer, and the horizontal directional holes extend to a depth of 500m to 800m in the coal seam excavation direction; Deploy fracturing equipment; The target fracturing strata are subjected to segmented fracturing and depressurization using a retreating segmented fracturing process. The interval between two adjacent fracturing zones is not less than 50m, and the duration of a single fracturing operation is not less than 120min.

3. The method for controlling coal wall spalling in underground coal mine working faces according to claim 1, characterized in that, The process involves spraying a protective slurry onto the coal face, allowing the slurry to solidify and adhere to the coal face surface. A spraying device is installed behind the drum of the coal mining machine to spray the protective slurry onto the coal face.

4. The method for controlling coal wall spalling in underground coal mine working faces according to claim 3, characterized in that, The protective coating slurry includes two-component reactive polyurethane, urea spraying material, or two-component silicate-modified polyurethane spraying material, or two-component polyacrylate spraying material, or single-component organic-inorganic composite spraying material.

5. The method for controlling coal wall spalling in underground coal mine working faces according to claim 1, characterized in that, The hydraulic support has a side protection level of 3 or higher; and / or The hydraulic support has a double-layer side protection plate mechanism, which is used to protect the coal wall and the roof respectively; and / or The protective surface area of ​​the hydraulic support shall not be less than 13m². 2 .

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