A method for strengthening the strength of coal in advance in a working face of a stone gate uncovering soft and protruding coal seam

Abstract

This application discloses a method for pre-strengthening the coal body strength in a rock-gate coal uncovering face of a soft, outburst-prone coal seam, relating to the field of coal seam reinforcement and outburst prevention technology in coal mining. The method includes: determining the coal body area requiring pre-strengthening based on the design location of the rock-gate coal uncovering face, coal seam geological conditions, and gas parameters; forming a strengthening borehole network within the coal body area and acquiring borehole feedback parameters in real time, adjusting the strengthening borehole parameters in real time based on these parameters; injecting strengthening material into the strengthening boreholes and adjusting the injection parameters of the strengthening material in real time based on the borehole feedback parameters to form a three-dimensional continuous strengthened and consolidated body; determining the strength of the strengthened and consolidated body in real time; and completing the pre-strengthening of the coal body strength once the strength of the strengthened and consolidated body reaches the set strength. This application can fundamentally improve the mechanical properties of soft coal, thereby comprehensively enhancing the integrity and stability of the coal body from macroscopic to microscopic levels.

Description

Technical Field

[0001] This application relates to the field of coal seam reinforcement and outburst prevention technology in coal mining, and in particular to a method for pre-strengthening the coal body strength in a rock-gate coal uncovering face of a soft outburst coal seam. Background Technology

[0002] Rock-gate coal seam exposure is a crucial step in coal mine development and tunneling, referring to the process of traversing a coal seam through a rock tunnel. Soft, outburst-prone coal seams are characterized by low strength (compressive strength typically less than 10 MPa), well-developed fractures, poor permeability (less than 0.1 mD), and high gas pressure. During rock-gate coal seam exposure, the coupled effects of mining stress and gas pressure make coal and gas outburst accidents highly likely, seriously threatening construction safety and mining efficiency.

[0003] Outburst prevention measures in Shimen coal seam exposure mainly include regional and localized measures. These measures are tailored to the coal seam's firmness coefficient. f For soft coal seams with a strength less than 0.5, regional outburst prevention measures must be implemented before the coal face is advanced to a minimum normal distance of more than 7 meters from the coal seam. Once regional verification or the effectiveness test of regional outburst prevention measures confirms a face without outburst risk, the outburst-prone coal seam can be exposed. However, if, after implementing regional outburst prevention measures, regional verification or the effectiveness test confirms a face still as having outburst risk, local outburst prevention measures must be implemented. Common regional outburst prevention measures include pre-drilling for gas extraction, pre-drilling for gas discharge, metal reinforcement, coal grouting and solidification, and hydraulic flushing. Coal grouting and solidification refers to grouting (such as cement grout or chemical grout) into broken coal seams to increase coal strength and reduce dynamic phenomena during coal exposure.

[0004] Existing grouting reinforcement technologies mostly use cement-based grout or ordinary organic grout. Cement-based grout has a shrinkage rate of more than 15%, and after curing, it is easy to generate new cracks, which become channels for gas accumulation. Ordinary organic grout (such as polyurethane, malathion, etc.) has insufficient shear strength, poor flame retardancy, and limited permeability, and can only reinforce shallow coal bodies (depth less than 0.5m), and cannot form an effective advanced reinforcement zone. Rigid support technologies, such as anchor bolt and cable support, are prone to local crushing of the coal body due to stress concentration at the anchoring end, and are extremely prone to corrosion in high gas and high water content coal seams, thus affecting the support effect. Moreover, the process is complicated and takes up 50-60% of the total tunneling time.

[0005] In summary, existing conventional methods mainly focus on macroscopic support and gas drainage, lacking reinforcement materials that can actively penetrate into the micro-fractures of the coal seam and form a high-strength, high-toughness bond with the coal body. Therefore, they cannot fundamentally improve the mechanical properties of soft coal seams. Thus, there is an urgent need for an advanced strengthening technology for coal seam exposure in rock face mining that can actively intervene, coordinate multiple technologies, and comprehensively improve the integrity and stability of the coal body from macroscopic to microscopic levels. Summary of the Invention

[0006] The purpose of this application is to provide a method for pre-strengthening the strength of coal in a rock-gate coal uncovering face of a soft, outburst-protruding coal seam, which can fundamentally improve the mechanical properties of soft coal and thus comprehensively enhance the integrity and stability of the coal body from macroscopic to microscopic levels.

[0007] To achieve the above objectives, this application provides the following solution: This application provides a method for pre-strengthening the coal body strength in a rock-gate coal uncovering face of a soft, outburst-prone coal seam, including: Based on the design location of the rock-gate coal uncovering face in a soft, outburst-prone coal seam, the geological conditions of the coal seam, and the gas parameters, the coal body areas that require advanced reinforcement are determined. In the coal seam area requiring advanced reinforcement, multiple rows of reinforcement boreholes are drilled from the Shimen roadway into the coal seam to form a reinforcement borehole network. During the construction process, borehole feedback parameters are acquired in real time, and the reinforcement coal seam borehole parameters are adjusted in real time based on the borehole feedback parameters. A reinforcing material is injected into a reinforced borehole, and the injection parameters of the reinforcing material are adjusted in real time according to the borehole feedback parameters to form a three-dimensional continuous reinforced solidified body; the reinforcing material is composed of AB two-component liquid materials in a set ratio; The strength of the reinforced and consolidated body is determined in real time. When the strength of the reinforced and consolidated body reaches the set strength, the pre-strengthening of the coal body strength is completed.

[0008] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a method for pre-strengthening the coal body strength in a rock-gate coal uncovering face in a soft, outburst-prone coal seam. By drilling reinforcement boreholes within the coal body area requiring pre-strengthening, determined based on the design location of the face, coal seam geological conditions, and gas parameters, and injecting a reinforcement material composed of two-component liquid materials in a predetermined ratio, a high-strength, high-toughness, three-dimensional continuous reinforced and consolidated body (i.e., a three-dimensional network reinforcement layer) can be constructed in the coal body ahead of the face. This achieves pre-penetration consolidation and overall reinforcement of the coal body, significantly improving its resistance to mining stress and gas pressure. It fundamentally improves the mechanical properties of the soft coal body and comprehensively enhances its integrity and stability from macroscopic to microscopic levels, thereby ensuring safe and efficient rock-gate coal uncovering. Attached Figure Description

[0009] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 A flowchart illustrating a method for pre-strengthening the coal body strength in a rock-gate coal uncovering face of a soft, outburst-prone coal seam, provided as an embodiment of this application; Figure 2 A schematic diagram of the pre-delineation of the three-dimensional prevention and control zone and the borehole layout provided in an embodiment of this application; Figure 3 A schematic diagram of the logic flow of a dynamic testing and strengthening consolidation process provided in an embodiment of this application; Figure 4 A schematic diagram illustrating the working principle of the liquid injection device provided in an embodiment of this application for connecting to the working face of a coal seam in a Shimen coal uncovering roadway and for "root-like" reinforcement of coal seam fractures. Detailed Implementation

[0011] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0012] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0013] In one exemplary embodiment, this application provides a method for pre-strengthening the coal body strength in a rock-gate coal uncovering face of a soft, outburst-prone coal seam, such as... Figure 1 As shown, the method includes: Step 100: Based on the design location of the coal seam face revealing operation in a soft, outburst-prone coal seam, the geological conditions of the coal seam, and the gas parameters, determine the coal body area requiring pre-enhancing. The main purpose of this step is to determine the enhancement area. For example, the enhancement area is located in front of the coal seam face, and its range covers at least 5-8m above, 3-5m below, and 3-5m on each side of the planned coal seam face outline, with a depth of 8-15m along the tunneling direction.

[0014] Step 101: In the coal seam area that requires advanced reinforcement, construct multiple rows of reinforcement boreholes from the Shimen roadway into the coal seam to form a reinforcement borehole network. During the construction process, obtain borehole feedback parameters in real time and adjust the reinforcement coal seam borehole parameters in real time based on the borehole feedback parameters.

[0015] Step 102: Inject reinforcing material into the reinforced borehole, and adjust the injection parameters of the reinforcing material in real time according to the borehole feedback parameters to form a three-dimensional continuous reinforced solidified body. The reinforcing material is composed of two-component liquid materials (AB) in a set ratio. Under pressure and capillary action, the reinforcing material penetrates into the coal seam fracture network, undergoes a chemical reaction and gel solidification within the network, thereby actively constructing a three-dimensional continuous reinforced solidified body.

[0016] Step 103: Determine the strength of the reinforced solidified body in real time. Once the strength of the reinforced solidified body reaches the set strength, the advanced reinforcement of the coal body strength is completed.

[0017] By implementing steps 100-103 above, this application can solve the problems of insufficient reinforcement depth, poor adaptability, and limited anti-outburst effect of existing advanced anti-outburst technology for coal seam exposure in soft outburst-prone coal seams. It has the characteristics of simple operation and high safety, and can be applied to advanced coal body strengthening and anti-outburst in coal seam exposure working faces in soft outburst-prone coal seams.

[0018] In an exemplary embodiment of this application, in step 100 above, based on geological exploration and gas geological data, a three-dimensional advanced prevention zone completely enclosing the defined coal seam disturbance range can be delineated within the coal seam ahead of the planned coal seam exposure face as the coal seam area requiring advanced reinforcement. The criteria for delineating the three-dimensional advanced prevention zone can be: extending 10-15 meters forward (i.e., into the deeper part of the coal seam) from the planned coal seam along the tunneling direction. On a plane perpendicular to the tunneling direction, its boundary extends beyond the coal seam outline, extending 5-12 meters upwards into the coal seam, 3-10 meters downwards into the coal seam, and 3-8 meters to each side of the roadway.

[0019] In an exemplary embodiment of this application, two types of borehole networks with different functions can be constructed within the advanced prevention and control zone. Based on this, the enhanced borehole network in step 101 above can include enhanced borehole groups for injecting reinforcing materials and information verification borehole groups for real-time acquisition of coal mechanics and gas state information. The enhanced borehole groups are arranged non-uniformly and hierarchically: in the shallow part of the prevention and control zone near the roadway, in the geological structure zone, or in the abnormally fractured coal zone determined by the information verification boreholes, boreholes are arranged with a first density (e.g., borehole spacing of 0.8-1.2m). In the deep part of the prevention and control zone and in the relatively intact coal zone, boreholes are arranged with a second density (e.g., borehole spacing of 1.5-2.0m).

[0020] For example, reinforced boreholes are arranged in a fan-shaped or rectangular grid pattern. The diameter of the reinforced boreholes is 75-113 mm. The spacing between reinforced boreholes is 0.8-1.5 m. The depth of the reinforced boreholes penetrates the reinforced area. The borehole orientation is optimized according to the coal seam occurrence and the main fracture development direction to maximize the material penetration range.

[0021] Furthermore, in the outer boundary of the advanced prevention and control zone or in the internal stress concentration zone, pressure relief guide boreholes are also constructed, which involve drilling without injecting materials, to induce the gradual release of ground stress and gas pressure in a designated direction.

[0022] In an exemplary embodiment of this application, in order to verify the coal body parameters fed back in real time during the construction of the borehole group based on information, dynamically assess the outburst hazard level and injectability of the local coal body, and adjust the spatial layout parameters and / or grouting process parameters of the subsequent reinforced borehole group to be constructed in real time accordingly. In this embodiment, the borehole feedback parameters obtained in real time in step 102 above may include: drill cuttings volume S value, borehole gas emission initial velocity q value, drill cuttings gas desorption index K1 value, and images of peri-hole fracture development obtained using a borehole inspection instrument. The reinforced coal body borehole parameters adjusted in real time include the spacing, row spacing, borehole depth, and azimuth angle of the reinforced boreholes. Based on this, the implementation process of step 102 above can be described as follows: 1. During the information verification drilling process, the following core parameters should be collected simultaneously to ensure data timeliness: (1) Mechanical parameters: S value of cuttings (mass of cuttings per meter of borehole).

[0023] (2) Gas parameters: initial gas emission velocity q value (initial gas emission velocity after drilling construction), and gas desorption index K1 value of drill cuttings (gas desorption velocity of drill cuttings within a specified time).

[0024] (3) Geological parameters: The development of fractures around the borehole was photographed by a borehole inspection instrument, and the fracture density, connectivity, development direction and degree of coal body fragmentation were recorded.

[0025] 2. Dynamically assess the risk level.

[0026] Referring to the safety regulations for preventing coal mine outbursts, the critical thresholds (such as the critical values ​​of K1, q, and S, which need to be calibrated in conjunction with the specific geological conditions of the mine) should be clearly defined.

[0027] Parameter comparison: The real-time collected K1 value, q value, and S value are compared with the critical threshold.

[0028] Classification: 1) No outburst risk: All three parameters are below the critical threshold, and the fracture development is gentle with no obvious coal body breakage. 2) Weak outburst risk: One or two parameters are close to the critical threshold, or there are dense local fractures but they have not formed a connected network. 3) Strong outburst risk: At least one parameter exceeds the critical threshold, or there are dynamic phenomena such as blowouts or stuck drills, and the fractures are connected in a network.

[0029] 3. Dynamically assess the injectability of the coal seam.

[0030] Based on crack image analysis: High injectability: fracture density ≥3 fractures / m, good connectivity, no large-area collapse, and moderate coal porosity.

[0031] Medium groutability: Crack density 1-3 cracks / m, locally connected, with a small number of hole collapses but not affecting the grouting channel.

[0032] Low injectability: fracture density < 1 fracture / m, poor connectivity, or severe hole collapse or hole blockage.

[0033] Auxiliary judgment: Combine drilling construction smoothness (whether the drill gets stuck or the hole collapses frequently) and drill cuttings moisture content to eliminate factors that affect the grouting effect, such as water damage.

[0034] 4. Real-time verification and secondary adjustment.

[0035] After each set of information verification borehole assessments and parameter adjustments are completed, grouting feedback (such as changes in borehole pressure and fluid return) is monitored synchronously during subsequent enhanced borehole construction. If abnormalities such as a sudden increase in grouting pressure or no fluid return occur, additional information verification boreholes are immediately added, the local coal seam condition is reassessed, and parameters are fine-tuned a second time to ensure that the enhancement measures are adapted to the actual coal seam conditions.

[0036] Based on the above description, the advanced construction of the reinforced borehole group in this application is to build a dedicated channel for the subsequent high-pressure injection of reinforcing materials (such as two-component flexible chain reinforcing materials). By scientifically arranging the boreholes, the material can be accurately penetrated, reinforced to the whole area, and stress can be optimized in a coordinated manner, laying the foundation for the construction of a three-dimensional continuous reinforced solidified body, and ultimately achieving the goal of coal solidification and gas blocking to prevent outbursts.

[0037] In one exemplary embodiment of this application, the implementation process of step 102 described above may include: Step 1: Preset the volume mixing ratio of material A and material B, as well as the target grouting pressure range. For example, connect a two-component grouting device, start the stirring device in the storage tanks of materials A and B to homogenize them, and preset the volume mixing ratio of materials A and B and the target grouting pressure range in the control system.

[0038] Step 2: Using compressed air from the mine shaft as power, material A and material B are uniformly mixed according to the volume mixing ratio to obtain the reinforced material. For example, using compressed air from the mine shaft as power, material A and material B are synchronously and at the same pressure transported to the static mixer in a preset ratio through an independently closed-loop controlled conveying pipeline, achieving uniform mixing of the two-component materials within a short time within the specified ratio range.

[0039] Step 3: Inject the reinforcing material into the reinforcing borehole at the target grouting pressure range (e.g., not less than 2 MPa), so that it sequentially undergoes the following in the coal seam fractures: (1) Pressure-driven macroscopic fracture filling based on injection pressure. (2) Capillary micro-fracture penetration based on the surface modification effect of nanoparticles in the material. Monitor and compare the instantaneous flow rates of material A and material B in real time, and maintain a constant mixing ratio through feedback adjustment to form a three-dimensional continuous reinforced solidified body. Among them, the material injection volume in a single hole is terminated when the designed injection volume is reached or when ungelled mixture is returned from adjacent observation holes / fractures.

[0040] Based on the above description, in practical applications, the volume mixing ratio of component A to component B is 1:0.8 to 1:1.2. Component A, by mass percentage, consists of 65% to 70% epoxy-modified polyurea semi-prepolymer, 15% to 18% nano-silica with a particle size of 50-100 nm, 13% to 17% of a first flame retardant suspension, and 2% to 3% of an amine catalyst. Component B, by mass percentage, consists of 45% to 75% polyamine curing agent, 15% to 30% polyurethane resin, and 10% to 25% of a second flame retardant suspension. Both the first and second flame retardant suspensions are composite aqueous suspensions containing sodium silicate, nano-aluminum hydroxide, and a silane coupling agent. The nano-aluminum hydroxide has a particle size of 45 nm to 55 nm.

[0041] In practical applications, the injected mixture (i.e., the reinforcing material) fills most of the borehole space under compressed air, and most of it diffuses and permeates outwards along the internal fissures, bedding, and pore networks of the coal body under pressure. Material A and Material B react within the coal body, forming a gel within 10 minutes of surface drying. After 40 minutes, the tensile strength is ≥2MPa, and it eventually solidifies into a flexible chain network with high bonding strength and high toughness. The reinforcing material formed after the reaction between Material A and Material B stops and after final solidification has a tensile strength ≥18MPa, an elongation at break ≥400%, a tear strength ≥80kN / m, and an adhesion force ≥10MPa. This network binds loose coal particles and lumps into a whole and tightly fills fissures at all levels, forming a dense, reinforced barrier layer.

[0042] In one exemplary embodiment of this application, the reinforcing material injection device can be a dedicated grouting device. This grouting device includes: a visual control system, two independent material A conveying units and a material B conveying unit (each unit includes a storage tank, an in-tank stirring and dispersion monitoring device, a flow rate monitoring meter, and a delivery pump driven by compressed air), and a static mixer connected to the outlets of the material A and material B conveying units. The visual control system is communicatively connected to the flow rate monitoring meters and the delivery pump control terminals of the material A and material B conveying units, forming a closed-loop control circuit for real-time adjustment and maintaining a constant mixing ratio of materials A and B. Check valves and quick-connect plugs are installed on the outlet pipes of both material A and material B conveying units. The outlet of the static mixer is connected to a mixture injection pipe via a high-pressure pipeline.

[0043] Furthermore, a flexible polymer sealing device is installed at the borehole opening of each reinforced borehole to ensure a secure seal. The injection port of the sealing device is then connected to the mixture injection pipe of the grouting equipment via a pipeline.

[0044] In one exemplary embodiment of this application, the reinforcing material injection device may include a visualization controller, an A / B material feeding system, an A / B material compressed air system, an A / B material conveying system, and a mixing silo and a mixing material injection pipe. The visualization controller is used to monitor and control the flow rate, velocity, and material dispersion in the storage tank of materials A and B in real time.

[0045] In one exemplary embodiment of this application, the strength of the reinforced solidified body is considered to have reached a predetermined strength when all of the following conditions are met: (1) The material curing time is ≥12 hours, and the short-term strength and final setting strength indicators at 40 min are both met.

[0046] (2) In the point inspection, the increase in uniaxial compressive strength of the coal body and the material adhesion force met the standards, the gas emission attenuation rate was ≥60%, and the K1 value, q value, and S value were all lower than the critical value. In the surface inspection, the geophysical scan showed that the overall coal body was strengthened and there were no areas that were not properly reinforced.

[0047] (3) On-site practical verification: During the construction of the inspection hole, there were no dynamic phenomena such as blowouts, stuck drills, or spalling, and the borehole wall was stable. Furthermore, to determine whether to initiate safe coal seam uncovering operations, after step 103 above, various methods can be used to verify the overall strengthening and sealing effect of the advanced prevention and control zone. For example, only after confirming a significant increase in coal body strength and the disappearance of abnormal gas emission can the coal seam uncovering operation be carried out according to safety regulations. This is based on quantitative verification results. For instance, in practical applications, the effectiveness of the consolidated body can be verified using a comprehensive point-surface testing method. Point verification: Through construction effect inspection holes, the uniaxial compressive strength increment of the reinforced coal body and the borehole gas emission attenuation rate are directly measured. Surface verification: The advanced prevention and control zone is scanned using the mine transient electromagnetic method or seismic wave CT fluoroscopy method. By comparing the wave velocity field or resistivity field distribution images before and after reinforcement, the range and uniformity of the overall strengthening of the coal body are qualitatively and quantitatively assessed. If the comprehensive inspection combining point and surface measurements fails to meet the standards (i.e., insufficient coal strength, excessive gas parameters, or the existence of reinforcement blind spots), safe coal uncovering operations will not be initiated. Instead, adjustments must be made according to the closed-loop logic of identifying the problem, targeted rectification, and secondary inspection. The specific process is as follows: 1. Review and verify the test data to accurately pinpoint the root cause of the problem.

[0048] First, combine the results of point inspection and area inspection to identify the core reasons for non-compliance. Common problem types and judgment criteria are as follows: (1) The coal body strength does not meet the standard, with uniaxial compressive strength increment <50% and material adhesion <10MPa. 40min tensile strength <2MPa or final set tensile strength <18MPa. Possible causes of this problem include: ① Insufficient material injection pressure (<2MPa), resulting in insufficient material penetration. ② Excessive borehole spacing, leading to non-overlapping material diffusion. ③ Material ratio deviation, resulting in insufficient reaction.

[0049] (2) Poor gas sealing effect, gas emission attenuation rate <60%, K1 value (q value or S value) exceeds the critical threshold. Possible reasons: ① Micro-cracks were not completely filled, and gas channels were not blocked. ② Insufficient material injection in local areas, resulting in sealing blind spots. ③ Micro-cracks were generated after the material solidified.

[0050] (3) There are blind spots in the reinforced area. Geophysical scanning shows local low wave velocity, i.e. (no continuous consolidation body is formed). The possible reasons are as follows: ① The borehole layout does not cover the fracture development zone or stress concentration zone. ② The borehole azimuth is not adapted to the coal seam occurrence, and the material penetration range is limited.

[0051] (4) The solidified body has poor uniformity; some test holes meet the strength standard while others do not. Geophysical images show the following reasons for the fragmentation of the solidified body: ① Fluctuations in the mixing ratio of A / B materials during grouting. ② Excessive moisture content in local coal seams, affecting material solidification. ③ Failure to construct pressure relief boreholes, leading to stress concentration and damage to the solidified body. 2. Targeted adjustment measures.

[0052] (1) Adjusting grouting parameters: Increase the grouting pressure to 2.5-3 MPa (not exceeding the equipment's pressure resistance limit) to enhance the "pressure-driven macroscopic fracture filling" effect. Fine-tune the material ratio: If the coal body has a high moisture content, adjust the volume ratio of A / B materials to 1:1.1~1.2 (increase the proportion of polyamine curing agent in B material to accelerate solidification). If penetration is insufficient, increase the nano-silica content of A material to 17-18% (enhance capillary penetration capacity).

[0053] Supplementary grouting: For existing reinforced boreholes in substandard areas, perform secondary grouting at 50-80% of the designed grouting volume. The termination condition is "return grouting occurs in adjacent observation holes" or "grouting pressure stabilizes above 2.5 MPa for 30 minutes". If the existing borehole spacing is too large (e.g., a spacing of 1.5-2.0m in the intact area results in material non-overlap), additional reinforced boreholes should be drilled in the substandard areas, with spacing arranged according to the first density (0.8-1.2m), and the hole depth should penetrate the reinforced area.

[0054] (2) Locate the blind zone. Based on the seismic wave CT / transient electromagnetic scanning images, pinpoint the coordinates of the low-velocity / low-resistivity blind zone (such as uncovered areas on both sides of the roadway or insufficient extension of the coal seam roof and floor). For supplementary drilling, if the blind zone is a fractured area / geological structure zone, drill in a fan-shaped grid pattern with a borehole diameter of 75-113mm and an azimuth angle adapted to the main development direction of the fractures to ensure material coverage of the blind zone. If the blind zone is located deep within the prevention and control area, the supplementary drilling depth needs to be 2-3m deeper than the original reinforcement borehole, penetrating the stress concentration area. Simultaneously, supplement 1-2 pressure-relief guide boreholes around the blind zone to induce a gradual release of stress and prevent damage to the consolidated body under pressure after secondary grouting.

[0055] (3) Calibrate the grouting equipment, check the closed-loop control accuracy of the visual control system and the A / B material conveying unit, replace faulty flow rate monitoring meters or check valves, and ensure that the A / B material mixing ratio is stable at 1:0.8~1.2. Improve the solidification environment: If the coal body moisture content is too high, first drain some of the accumulated water through the pressure relief borehole, and then adopt "staged grouting" (first clear the blockage at low pressure of 0.5MPa, and then fill at high pressure of 2.5MPa). Extend the curing time. After the second grouting, the static curing time is ≥12 hours (4-6 hours longer than the first curing) to ensure that the material fully reacts and solidifies, and avoid a second inspection before the strength is reached.

[0056] (4) If the test finds that the material solidification speed is too slow (not surface dry in 10 minutes) or the flame retardancy is not up to standard, the content of amine catalyst in material A needs to be checked (2-3%). If it is insufficient, the catalyst should be added. Check the amount of first / second flame retardant suspension added (13-17% for material A, 10-25% for material B) to ensure that the median particle size of nano aluminum hydroxide is 45-55nm. If it does not meet the standard, replace it with qualified material and re-grout.

[0057] 3. Secondary maintenance and secondary inspection until the standards are met.

[0058] After rectification, allow the material to stand according to the original curing standards: 40 minutes for short-term strength testing and ≥12 hours for final setting strength testing. Repeat the "point-to-surface" testing process: if the second test still fails to meet the standards, repeat the "problem identification → rectification" process until all indicators meet the design requirements before coking operations can begin. If the standards are still not met after three rectifications, the scope of the advanced prevention zone needs to be reassessed (e.g., expanding the extension length) or core parameters (e.g., material ratio, borehole density) needs to be adjusted.

[0059] Furthermore, the pre-drilling function of this application also includes: (1) As the dedicated transport and diffusion carrier for grouting (high-pressure grouting) in step 103 above, the reinforced borehole is the only channel for injecting the two-component reinforced material into the coal body. Its diameter (75-113mm) and depth (penetration into the advanced prevention zone) are designed to meet the high-pressure grouting requirements of not less than 2MPa: (2) High-density drilling (0.8-1.2m spacing) is used in shallow, fractured, and geologically structural zones to ensure sufficient material injection into the fractured coal body and avoid localized weak reinforcement. Low-density drilling (1.5-2.0m spacing) is used in deep and intact zones to control construction costs and efficiency while ensuring reinforcement effect.

[0060] (3) It can adapt to the dynamic adjustment of parameters in steps 101 and 102, ensuring that the reinforcement parameters are accurately implemented. Although the drilling group is constructed in advance, the spacing, row spacing, depth, azimuth and other parameters of the boreholes will be dynamically adjusted according to the feedback of the information verification borehole in S3. Its "adjustability" provides support for subsequent accurate reinforcement: if the information verification borehole detects a high level of local protrusion danger and good injectability, it can be supplemented by densification on the basis of the constructed boreholes to ensure that the dangerous area is reinforced in place. If a change in the development direction of local fractures is detected, the azimuth of the unconstructed boreholes can be adjusted to make the material fit the fracture distribution better and improve the penetration efficiency.

[0061] (4) Supporting the point-surface combination effect verification of this application, verifying the effectiveness of reinforcement. The layout range and density of the reinforced boreholes directly determine the formation quality of the three-dimensional solidified body, providing a core verification object for effect verification: In point inspection, the effect inspection holes can be constructed along the layout trajectory of the reinforced boreholes to directly measure the strength increase of the reinforced coal body and the gas emission attenuation rate, accurately reflecting the reinforcement effect after the material is injected through the boreholes. In surface inspection, the area scanned by the mine transient electromagnetic method or seismic wave CT is precisely the advanced prevention zone covered by the reinforced boreholes. The solidified body formed by the injected material will demonstrate the overall reinforcement effect through changes in the wave velocity field and resistivity field.

[0062] (5) In conjunction with the pressure relief directional boreholes, the stress and gas distribution of the enhanced borehole group are optimized. The enhanced borehole group and the pressure relief directional boreholes constructed in step 101 form a enhanced-pressure relief synergistic system: the solidified body formed after the material is injected into the enhanced boreholes provides rigid support and flexible buffer to resist ground stress. The stress induced by the pressure relief directional boreholes is released gradually, and the two work together to reduce the stress concentration in the coal body and further improve the safety of coal outburst prevention. This synergistic effect requires the advance arrangement of the enhanced boreholes as a prerequisite.

[0063] In one exemplary embodiment of this application, the prerequisite for verifying the overall reinforcement and sealing effect of the advanced prevention and control zone using multiple methods is that the material curing time meets the standard. First, the solidification time of the reinforcing material is verified, and the material is left to cure statically for ≥2 hours after injection. During this period, there is no external disturbance (such as drilling or tunnel excavation) to ensure the material fully reacts and solidifies. Based on this, the verification method can be described as follows: 1. Point inspection.

[0064] Representative locations were selected within the advanced prevention and control zone (one inspection hole corresponding to every 5-8 reinforced boreholes) to verify the construction effect, and four core indicators were tested and confirmed: (1) Test of the amount of drill cuttings S: Use standard drilling tools to construct inspection holes, collect drill cuttings every 1 meter of drilling, weigh and record them.

[0065] Confirmation criteria: S value ≤ mine outburst prevention critical value (e.g. ≤ 6 kg / m, subject to calibration based on mine geological conditions), and there is no abnormal phenomenon of "sudden increase in drill cuttings".

[0066] (2) Test of the gas desorption index K1 value of drill cuttings: Collect drill cuttings with a special desorption instrument and measure the gas desorption rate within a specified time (e.g., 5 minutes).

[0067] Confirmation criterion: K1 value < mine critical threshold (e.g., <0.5 mL / g·min) 1 / 2 Furthermore, the attenuation rate is ≥60% compared to before reinforcement.

[0068] Uniaxial compressive strength test of coal body: Coal core samples (including solidified reinforced material) are taken through inspection holes, and the compressive strength is tested in situ in the laboratory or underground.

[0069] Confirmation criteria: The uniaxial compressive strength of the coal body after reinforcement is increased by ≥50% compared with that before reinforcement, and the adhesion between the material and the coal body is ≥10MPa (meeting the final setting design index).

[0070] Borehole gas emission attenuation rate test: The gas emission rate after the test hole is constructed is continuously monitored using a gas emission velocity meter.

[0071] Confirmation criteria: Gas emission attenuation rate ≥60%, stable for 30 minutes without rebound, and no abnormal gas overflow.

[0072] 2. Surface verification – Full-domain verification of integrity (no blind spot coverage).

[0073] Geophysical exploration techniques were used to scan the entire advanced prevention and control area to confirm that there were no blind spots for reinforcement. The mine transient electromagnetic method or seismic wave CT imaging method (either one or a combination) was then used. The scan was conducted in a grid pattern to cover the entire three-dimensional advanced prevention and control area (extending beyond the cross-sectional outline 10-15m in the tunneling direction), generating wave velocity / resistivity field distribution images before and after reinforcement.

[0074] Confirmation criteria: The wave velocity or resistivity of the coal body after reinforcement is significantly increased compared with that before reinforcement (wave velocity increase ≥30%, resistivity increase ≥50%), the wave velocity field or resistivity field is uniformly distributed, and there are no obvious low wave velocity / low resistivity areas, indicating that the three-dimensional solidified body is continuous and complete, and there are no blind areas where reinforcement is not in place.

[0075] 3. On-site verification.

[0076] During the construction of the inspection hole and geophysical scanning, the on-site working conditions were observed simultaneously. During the construction of the inspection hole: (1) there were no dynamic phenomena such as blowouts, stuck drills, spalling, or hole collapse. (2) the hole wall was stable, with no obvious falling blocks, and the reinforced material was tightly bonded to the coal body without peeling or falling off. (3) the gas concentration in the working area was always lower than the limit of the coal mine safety regulations (e.g., ≤0.8%), and there was no gas over-limit alarm.

[0077] 4. Prepare to start coal uncovering.

[0078] The four indicators from the point inspection, the geophysical results from the face inspection, and the on-site records are compiled to ensure that all data meet the above confirmation standards. The construction team, technical department, and safety supervision department jointly review the inspection data and records and sign off on the confirmation. The inspection report and coal uncovering application are submitted to the mine management department. After approval, a coal uncovering operation plan is formulated in accordance with the coal mine safety regulations (such as controlling the tunneling speed and strengthening real-time gas monitoring). Only after all approval processes are completed and on-site safety protection measures (such as gas monitors and anti-outburst ventilation doors) are in place can the coal uncovering operation in the stone gate be started.

[0079] In summary, this application essentially provides a comprehensive prevention and control method applicable to rock-gate coal uncovering operations in soft, fractured, and high-gas-outburst-risk coal seams. This method integrates advanced detection borehole layout, coal seam reinforcement borehole layout, dynamic adjustment of material injection parameters, and flexible chain reinforcement of soft coal seams. The method includes: (1) delineating a three-dimensional advanced prevention and control zone based on coal seam geological data; (2) constructing advanced detection boreholes within the prevention and control zone to obtain information such as coal seam strength and gas pressure, while these advanced detection boreholes can also be used for later coal seam parameter feedback; (3) designing and adjusting the reinforcement coal body borehole and reinforcement material injection parameters based on the feedback parameters from the detection boreholes; and (4) the reinforcement material is composed of AB dual-component liquid materials, which, after being mixed in a specific ratio, possess high toughness, high strength, high permeability, and excellent flame retardancy. A dedicated injection equipment enables precise material proportioning, visual monitoring, and high-pressure injection. Through the material's own fluidity and weak expansion properties, it penetrates into the fracture network of the soft coal seam, forming "tree root-like" flexible chains that are rooted in the weak coal seam. (5) Multiple flexible chains work together on the coal face, bonding with deep fissures and pores to form a flexible chain reinforcement zone, significantly improving the coal seam's compressive and shear strength and cohesion, while also blocking gas channels to a certain extent. Based on this, this application uses a specially made flexible chain reinforcement material and a dedicated injection device to construct a high-strength, high-toughness three-dimensional network "reinforcement layer" in the coal body ahead of the coal seam, achieving advanced penetration consolidation and overall reinforcement of the coal body, thereby significantly improving the coal body's ability to resist mining stress and gas pressure, ensuring safe and efficient coal seam uncovering.

[0080] Furthermore, the method provided in this application, compared to the prior art, mainly achieves the following objectives: (1) A flexible chain reinforcement zone is formed with the axial direction of the reinforced borehole in the advanced reinforcement area as the main trunk and the penetration into the coal seam fissures as the secondary root system, covering the outburst danger area.

[0081] (2) Improve the compressive and shear strength and cohesiveness of the coal body and block the gas passage.

[0082] (3) The material has high permeability and can penetrate into deep micro-cracks.

[0083] (4) The materials are flame-retardant and environmentally friendly, and meet the safety standards of coal mines.

[0084] (5) Simple operation and high construction efficiency.

[0085] In one exemplary embodiment of this application, such as Figure 2As shown, the scenario implemented in this application is the end of a stone gate roadway preparing to expose a soft, outburst-protruding coal seam. First, based on geological data and the coal seam exposure plan, the location of the coal seam to be exposed is determined, and a three-dimensional area of ​​the coal body to be reinforced is demarcated outwards (i.e., in the opposite direction of the stone gate excavation). This area forms a reinforced shell enclosing the future coal exposure section. In this embodiment, the length and width can be 10-15m, and the distance from the bottom of the stone gate roadway to the lower reinforcement zone is no less than 6m. Within this reinforcement zone, a certain number of information detection / verification holes and a large number of reinforcement drills are constructed from the face and both sides of the stone gate roadway according to the designed spacing. The drilling depth must penetrate the entire reinforcement zone. The drilling angle can be adjusted according to the coal seam dip angle to ensure that the drilling trajectory is evenly distributed within the coal body.

[0086] After drilling is completed, a flexible sealing device is first made using a rapid-solidifying material of the same origin as the flexible chain reinforcement material (i.e., the reinforcement material) to tightly seal the borehole opening. The reinforcement hole injection pipes are then connected to a mobile flexible chain reinforcement material injection device.

[0087] After the injection equipment is started, component A (containing epoxy-modified polyurea semi-prepolymer, nano-silica, flame retardant, and catalyst) and component B (containing polyamine curing agent, polyurethane resin, and flame retardant) are precisely metered and mixed, and then conveyed to the borehole via compressed air. The mixture is injected into the coal seam under pressure. In the initial stage, the material preferentially fills larger boreholes and fractures. As the pressure continues, the material, guided by the nanoparticles and its own weak expansibility, further penetrates into the micro-fractures.

[0088] The injection process is monitored by a visual controller to ensure a constant ratio of materials A and B and a stable flow rate. When backflow is observed in adjacent boreholes or monitoring holes, it can be determined that the area has been sufficiently injected, and the process switches to the next set of boreholes. After all boreholes have been injected, they are left to cure. The material initially solidifies into a gel within 10 minutes, reaches its maximum strength within 2 hours while maintaining its flexibility, and finally solidifies into a "flexible chain" network with high bonding strength and high toughness. The reinforced material formed after the reaction between materials A and B has stopped and after final solidification has a tensile strength ≥18MPa, an elongation at break ≥400%, a tear strength ≥80kN / m, and an adhesion force ≥10MPa. This network binds loose coal particles and lumps into a whole and tightly fills fractures at all levels, forming a dense and reinforced barrier layer.

[0089] After the curing is completed, the gas desorption index K1 of drill cuttings is measured through construction inspection boreholes. Comparing the data before and after the strengthening process, if the K1 value decreases significantly and falls below the critical value, and there are no dynamic phenomena such as blowouts or stuck drills during construction, it indicates that the strengthening effect is good. At the same time, geophysical exploration methods can be used to scan the strengthened area to visually show that the integrity of the coal body has been improved. After acceptance, the coal seam uncovering operation can be carried out in accordance with safety technical measures. Since the coal body in front has been strengthened into a relatively complete, high-strength, low-permeability solidified body, the risks of roof falls, gas overflows, and other hazards during the uncovering process are greatly reduced.

[0090] In one exemplary embodiment of this application, reference is made to Figure 4 The application scenario shown involves reinforcing areas of soft, outburst-prone coal seams that require strengthening. The working conditions for these soft, outburst-prone coal seams include: coal seam firmness coefficient. f <0.3, brittle texture, powdery or flaky, cohesive strength less than 0.5 MPa, gas pressure P ≥ 0.74 MPa, extremely prone to coal and gas outburst accidents. Specific steps are as follows: (1) Connect the underground substation to the visualization controller to ensure that the visualization controller displays the remaining amount and dispersion information of raw materials in the A material storage tank and the B material storage tank. If there is insufficient raw material or abnormal dispersion, open the A material feed valve and the B material feed valve in time to replenish the raw materials. Start the A material dispersion monitoring and stirring device and the B material dispersion monitoring and stirring device through the visualization controller to ensure that the concentration of raw materials is consistent in all places.

[0091] (2) Connect the first multi-functional air pump to the underground compressed air inlet pipeline, and adjust the air speed through the compressed air pipeline valve, air velocity meter and A material flow rate monitoring table to control the A material intake (the operation of B material is the same).

[0092] (3) Connect the output end of the first multi-functional air pump to the ball valve of the A material conveying pipe, the one-way valve of the A material conveying pipe, the quick connector of the A material conveying pipe, the mixing injection pipe, and the mixing chamber in sequence (the operation of B material is the same).

[0093] (4) Start the first multi-functional air pump, adjust the compressed air pipeline valve and the ball valve of the A material conveying pipe (the operation of B material is the same) to ensure that A material and B material are mixed in the mixing chamber at a volume ratio of 1:1 and sprayed out from the mixing injection pipe.

[0094] (5) Based on the parameters such as the number of boreholes, borehole diameter and azimuth angle of the coal wall, and the specific conditions on site, generate a flexible polymer material sealing device in the shape of a hollow cylinder along the borehole wall (the material used is the same as the flexible chain reinforcement material). After the flexible polymer material sealing device solidifies, connect the borehole injection pipe and the mixture injection pipe, and inject the mixture of material A and material B through the mixture injection pipe until the liquid returns through the return pipe, and stop the injection.

[0095] (6) Turn off the first multi-functional air pump and the second multi-functional air pump, disconnect the mixture injection pipe, and repeat steps (4) and (5) of this embodiment in the next borehole until the mixture of material A and material B is injected into all boreholes. Then, obtain information such as the amount of coal seam cuttings and the amount of gas desorption from the cuttings after reinforcement from the information verification hole to determine whether the reinforcement is effective. Otherwise, based on... Figure 3 The logical flow shown is to improve the drilling parameters and injection pressure, repeat the above steps until the information verifies that the drilling parameters meet the standards, then remove the equipment and clean the pipeline.

[0096] Figure 2 and Figure 4 In the diagram, 1 is the stone gate roadway, 2 is the information detection / verification borehole, 3 is the coal seam reinforcement borehole, 4 is the coal seam to be exposed, 5 is the advanced prevention zone (i.e., the coal body area requiring advanced reinforcement), 6 is the fracture, 7 is the flexible chain reinforcement material (i.e., the reinforcement material), 8 is the sealing device, 9 is the backflow pressure gauge, 10 is the orifice injection pipe, 11 is the return pipe, 12 is the return pipe valve, 13 is the underground transformer box, 14 is the visual controller, 15 is the cable, 16 is the A material feed valve, 17 is the A material feed pipeline, 18 is the A material storage tank, 19 is the A material dispersion monitoring and stirring device, 20 is the A material flow rate and velocity monitoring meter, and 21 is the A material suction pipe. 2 is the underground compressed air inlet pipe, 23 is the compressed air pipe valve, 24 is the air velocity and flow meter, 25 is the first multi-functional air pump, 26 is the A material conveying pipe, 27 is the A material conveying pipe ball valve, 28 is the A material conveying pipe check valve, 29 is the A material conveying pipe quick connector, 30 is the mixed material injection pipe, 31 is the mixing chamber, 32 is the B material conveying pipe quick connector, 33 is the B material conveying pipe check valve, 34 is the B material conveying pipe ball valve, 35 is the B material conveying pipe, 36 is the B material suction pipe, 37 is the B material flow rate and velocity monitoring meter, 38 is the B material dispersion monitoring and stirring device, 39 is the B material storage tank, 40 is the B material feed valve, and 41 is the B material feed pipe.

[0097] In summary, compared with the prior art, this application has at least the following advantages: (1) By verifying the information through boreholes, we can achieve simultaneous exploration and treatment, dynamically adjust the prevention and control parameters, make the strengthening measures more in line with the actual situation of the coal body, and improve the accuracy and reliability of prevention and control.

[0098] (2) By material penetration and three-dimensional consolidation, the mechanical strength (compression, shear and tension) and integrity of the coal body are fundamentally improved, and the cracks are effectively sealed. The solid content of the material after solidification is high, which can tightly fill and seal the cracks of various sizes in the coal body, significantly reduce the permeability of the coal body, block the gas flow channel, and achieve the dual effect of solidifying coal and blocking gas.

[0099] (3) The constructed three-dimensional solidified zone (i.e., the coal body area that requires advanced strengthening, including three-dimensional continuous reinforced solidified body) has high strength and safety factor. Even if new stress disturbances are generated during the coal uncovering process, this area can improve the pressure collapse generated by the previous rigid solidified body due to the tensile fracture strength and reliable adhesion of the flexible chain cable, and provide a reliable buffer zone and safety barrier, significantly reducing the possibility and intensity of disasters.

[0100] (4) The material itself has excellent flame retardant properties and rapid solidification characteristics, which greatly improves the shortcomings of traditional cement slurry-reinforced coal body curing time and low overall construction efficiency. Moreover, there is no high-temperature open flame during the construction process, and the solidified material does not support combustion, which fully meets the inherent safety requirements of underground coal mines. Using underground compressed air as power and with the help of special liquid injection equipment, large flow rate, long distance transportation and precise proportion mixing can be achieved, resulting in high construction efficiency and low labor intensity.

[0101] (5) Before coal exposure, large-scale and deep chemical reinforcement of the coal body in front is carried out. Multiple flexible chain reinforcement materials can penetrate into micro-cracks and form a three-dimensional interwoven flexible chain network after solidification. Like a steel mesh, it wraps and cements the coal body, greatly improving its integrity and toughness. It can effectively resist stress concentration and vibration during coal exposure and reduce the amount and distance of coal slag leakage when a coal outburst occurs.

[0102] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0103] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (RRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).

[0104] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0105] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0106] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for pre-strengthening the coal body strength in a rock-gate coal uncovering face of a soft, outburst-prone coal seam, characterized in that, include: Based on the design location of the rock-gate coal uncovering face in a soft, outburst-prone coal seam, the geological conditions of the coal seam, and the gas parameters, the coal body areas that require advanced reinforcement are determined. In the coal seam area requiring advanced reinforcement, multiple rows of reinforcement boreholes are drilled from the Shimen roadway into the coal seam to form a reinforcement borehole network. During the construction process, borehole feedback parameters are acquired in real time, and the reinforcement coal seam borehole parameters are adjusted in real time based on the borehole feedback parameters. A reinforcing material is injected into a reinforced borehole, and the injection parameters of the reinforcing material are adjusted in real time according to the borehole feedback parameters to form a three-dimensional continuous reinforced solidified body; the reinforcing material is composed of AB two-component liquid materials in a set ratio; The strength of the reinforced and consolidated body is determined in real time. When the strength of the reinforced and consolidated body reaches the set strength, the pre-strengthening of the coal body strength is completed.

2. The method for enhancing the strength of coal body in advance at the rock-gate coal uncovering face of soft outburst coal seam according to claim 1, wherein the coal body area that needs to be enhanced in advance is a three-dimensional advanced prevention and control zone that surrounds the set coal uncovering disturbance range; The criteria for defining the three-dimensional advanced prevention and control zone are as follows: along the tunneling direction, it extends 10-15 meters into the depth of the coal body from the planned coal uncovering face; on the plane perpendicular to the tunneling direction, its boundary extends beyond the outline of the coal uncovering section, extending 5-12 meters into the upper coal body, 3-10 meters into the lower coal body, and 3-8 meters into both sides of the roadway.

3. The method for pre-strengthening coal body strength in a rock-gate coal face of a soft, outburst-prone coal seam according to claim 2, characterized in that, The enhanced borehole network includes enhanced borehole groups for injecting reinforcing materials and information verification borehole groups for real-time acquisition of coal mechanics and gas state information. The arrangement of the enhanced borehole group is as follows: in the shallow part of the prevention and control zone, the geological structure zone, or the abnormally fractured coal body zone determined by the borehole group based on the information verification, the enhanced boreholes are arranged with a first density; in the deep part of the prevention and control zone and the relatively intact coal body zone, the enhanced boreholes are arranged with a second density; the deep part of the prevention and control zone refers to the area at a set distance from the starting position of the three-dimensional advanced prevention and control zone.

4. The method for pre-strengthening coal body strength in a rock-gate coal face of a soft, outburst-prone coal seam according to claim 3, characterized in that, The first density is a borehole spacing of 0.8-1.2m; the second density is a borehole spacing of 1.5-2.0m.

5. The method for pre-strengthening coal body strength in a rock-gate coal face of a soft, outburst-prone coal seam according to claim 1, characterized in that, The reinforced boreholes are arranged in a fan-shaped or rectangular grid pattern; the diameter of the reinforced boreholes is 75-113 mm; the spacing between the reinforced boreholes is 0.8-1.5 m; and the depth of the reinforced boreholes penetrates the coal seam area.

6. The method for pre-strengthening coal body strength in a rock-gate coal face of a soft, outburst-prone coal seam according to claim 1, characterized in that, The real-time borehole feedback parameters include: drill cuttings volume S value, borehole gas emission initial velocity q value, drill cuttings gas desorption index K1 value, and borehole perimeter fracture development images obtained using a borehole inspection instrument. The real-time adjusted parameters for enhanced coal seam drilling include the spacing, row spacing, drilling depth, and azimuth of the enhanced boreholes.

7. The method for pre-strengthening coal body strength in a rock-gate coal face of a soft, outburst-prone coal seam according to claim 1, characterized in that, The injection parameters of the reinforcing material include the injection pressure and ratio of the reinforcing material.

8. The method for pre-strengthening coal body strength in a rock-gate coal face of a soft, outburst-prone coal seam according to claim 1, characterized in that, Injecting reinforcing material into a reinforced borehole, and adjusting the injection parameters of the reinforcing material in real time based on the borehole feedback parameters to form a three-dimensional continuous reinforced solidified body, including: The preset volume mixing ratio of material A and material B and the target grouting pressure range are set. Using compressed air from underground wells as power, material A and material B are uniformly mixed according to the volume mixing ratio to obtain the reinforced material; The reinforcing material is injected into the reinforcing borehole according to the target grouting pressure range, and the instantaneous flow rates of material A and material B are monitored and compared in real time. The mixing ratio is maintained constant through feedback adjustment to form a three-dimensional continuous reinforced solid body.

9. The method for pre-strengthening coal body strength in a rock-gate coal face of a soft, outburst-prone coal seam according to claim 8, characterized in that, The volume mixing ratio of component A to component B is 1:0.8 to 1:1.

2. Component A is composed of 65% to 70% epoxy-modified polyurea semi-prepolymer, 15% to 18% nano-silica with a particle size of 50-100nm, 13% to 17% first flame retardant suspension, and 2% to 3% amine catalyst by mass percentage. Component B is composed of 45% to 75% polyamine curing agent, 15% to 30% polyurethane resin, and 10% to 25% second flame retardant suspension by mass percentage.

10. The method for pre-strengthening coal body strength in a rock-gate coal face of a soft, outburst-prone coal seam according to claim 9, characterized in that, Both the first flame retardant suspension and the second flame retardant suspension are composite aqueous suspensions containing sodium silicate, nano-aluminum hydroxide and silane coupling agent; the nano-aluminum hydroxide has a particle size of 45nm-55nm.

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