Method for grouting reinforcement and re-mining recovery of residual coal resources in damaged area of small coal kiln

Abstract

The invention discloses a grouting reinforcement and re-mining recovery method for residual coal resources in a damaged area of a small coal kiln. The grouting reinforcement and re-mining recovery method comprises the steps that a stope face is arranged; grouting drill holes are formed in the peripheral areas of the contour lines of the air return crossheading roadway and the transportation crossheading roadway through underground directional drilling, and a medium-strength filling material is adopted for grouting reinforcement; horizontal drill holes along the coal seam are constructed in the direction from the air return crossheading to the transportation crossheading, and grouting reinforcement is conducted on the open-off cut position through a high-strength filling material; the reinforced crossheading serves as a drill site, and the interior of the working face is subjected to grouting reinforcement through a low-strength filling material through the horizontal directional long drill holes; and working face stoping is carried out. According to the method, a differential graded grouting system is adopted, and a system scheme of combining ground centralized pulping, vertical drilling material conveying and underground directional drilling grouting technologies is adopted, so that the problem that safety and efficiency are difficult to consider in the re-mining process of the damaged area of the small coal kiln is solved. Practice verifies that the method can enable the resource recovery rate to reach more than 85%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coal mining, and particularly relates to a method for grouting reinforcement and recovery of residual coal resources in a small coal mine damage area. BACKGROUND

[0002] There are a large number of mining areas left by small coal mines due to disordered mining in China, the geological conditions of which are seriously damaged, forming goaf, caving area and stress anomaly area. Although there is considerable residual coal resources, the surrounding rock is broken, the stress is concentrated, and the hydrogeological conditions are complex. Conventional recovery is prone to cause roof collapse, roadway deformation, gas outburst and other safety accidents, so the recovery risk is high and the cost is large.

[0003] The existing recovery and mining technology for coal resources in the small coal mine damage area has the following defects: (1) The strength of the filling body lacks systematicness, and the reinforcement matching of the whole process from "roadway excavation" to "working face recovery" is not considered. Overuse of high-strength materials leads to difficult recovery cutting or insufficient strength to ensure excavation safety.

[0004] (2) The process is extensive, the grouting process is single, and the internal mechanical requirements of the roadway formation and working face are not differentiated. The economy and effectiveness are poor.

[0005] (3) The whole underground drilling grouting reinforcement occupies the underground space in the mode of underground station building, which makes material transportation difficult and restricts the grouting scale and construction efficiency.

[0006] (4) The whole ground drilling grouting reinforcement causes damage to the surface ecological environment.

[0007] Therefore, there is an urgent need for a safe, economical and efficient integrated method for recovery and mining of residual coal resources in the special geological conditions of the small coal mine damage area. SUMMARY

[0008] The purpose of the present application is to overcome the defects of the prior art and provide a method for grouting reinforcement and recovery of residual coal resources in a small coal mine damage area. Through the core idea of "first solidification and then excavation, internal and external grading, underground drilling, and ground centralized grouting", precise reinforcement and efficient and safe recovery of the small coal mine damage area are realized.

[0009] The technical solution adopted by the present application is: A method for grouting reinforcement and recovery of residual coal resources in a small coal mine damage area, specifically comprising: Step 1, arranging a recovery working face according to the mining plan; Step 2, arranging grouting boreholes in the peripheral area of the return air chute and the transportation chute roadway profile line by using underground directional drilling, and using middle-strength filling material with a compressive strength of 8-12 MPa for grouting reinforcement; Step 3, the horizontal drilling of the coal seam is constructed from the return air chute to the transportation chute, and high-strength filling material with a compressive strength of 10-15 MPa is used to grout and reinforce the open-off cut position; Step 4, the reinforced chute is used as a drilling site, and low-strength filling material with a compressive strength of 2-4 MPa is used to grout and reinforce the inside of the working face through horizontal directional long drilling; Step 5, the working face is mined.

[0010] The application also has the following characteristics: In step 2, the reinforcement range is 10-15 m outside the return air chute and the transportation chute, the drilling spacing is 5-10 m, and the grouting hole filling pressure is 2.5-3.5 MPa.

[0011] In step 3, the drilling spacing of the horizontal drilling is 5-10 m, the grouting and reinforcement are performed on the open-off cut starting point and the through point, and the grouting hole filling pressure is 2.5-3.5 MPa.

[0012] In step 4, the grouting drilling is arranged inside the working face through horizontal directional drilling technology, the drilling spacing is 15-30 m, the drilling direction is consistent with the coal seam trend, and the grouting hole filling pressure is 3.5-5.0 MPa.

[0013] In steps 2-4, after the grouting and reinforcement are completed, the reinforcement quality is detected by drilling peeping, acoustic detection, core strength test, and grouting pressure-flow rate curve analysis.

[0014] In steps 2-4, the filling material is prepared by a ground central grouting station, after the slurry is prepared, it is transported to the underground roadway slurry pipeline through the vertical material conveying drilling, and then distributed to each grouting drilling; the slurry slump is 200-260 mm, the bleeding rate is ≤3%, and the solidified body bulk density is ≥1.7 t / m 3 .

[0015] In steps 2-4, the components and contents of each filling material are as follows: The amount of high-strength filling material per square meter is: water 380-410 kg, cement 340-380 kg, fly ash 300-355 kg, coal gangue 700-900 kg, and composite admixture 5-10 kg; The amount of medium-strength filling material per square meter is: water 390-410 kg, cement 245-270 kg, fly ash 300-355 kg, coal gangue 830-1020 kg, and composite admixture 5-10 kg; The amount of low-strength filling material per square meter is: water 390-420 kg, cement 115-130 kg, fly ash 300-355 kg, coal gangue 950-1150 kg, and composite admixture 5-10 kg; The composite additive comprises a water reducing agent, an early strength agent and a retarder.

[0016] In the recovery process of step 5, a microseismic monitoring system is used to monitor the reinforced area in real time, and the system is composed of a microseismic sensor, a data collector and analysis software, wherein the microseismic sensor is arranged at an interval of less than or equal to 10 m; A stress online monitoring system is arranged at the key position of the reinforced area and the surrounding rock to monitor the stress change of the surrounding rock in real time, and the system is composed of a stress sensor, a data collector and analysis software, and the measurement range is 0-30 MPa; According to the data fed back by the microseismic monitoring system and the stress online monitoring system, the grouting parameters, the recovery speed and the supporting parameters are dynamically adjusted in combination with the geological conditions and the recovery progress.

[0017] The beneficial effects of the present application are: (1) Solve the core contradiction of "safety and recovery": innovatively introduce the concept of "graded grouting", and match the strength of different grouting materials according to the different mechanical requirements of roadway forming (medium strength 8-12 MPa), key position of cut eye (high strength 10-15 MPa) and internal working face (low strength 2-4 MPa), which not only ensures the safety of excavation and support, but also avoids the difficulty of cutting by the coal mining machine caused by the high strength of the material, and realizes "reinforcement for mining".

[0018] (2) Innovative and efficient grouting construction mode: integrate ground centralized grouting, vertical drilling material conveying and underground directional drilling grouting technology, and ground station is equipped with an automatic batching system, the quality of the slurry is stable, the vertical drilling and the underground slurry conveying pipe network are linked to convey materials, which greatly reduces the operation links, site occupation and material transportation difficulty, and improves the grouting scale and construction efficiency.

[0019] (3) Precise control and risk avoidance: remote precise grouting is realized by using underground directional drilling technology to avoid high risk of direct excavation in broken areas; through the "monitoring-analysis-adjustment" closed-loop control mechanism (microseismic monitoring, stress online monitoring), the grouting parameters, recovery speed and supporting parameters are dynamically optimized, the surrounding rock state is real-time controlled, and the safety hidden dangers such as roof collapse and gas outburst are avoided.

[0020] (4) Reduce cost and improve resource recovery rate: the graded grouting system reasonably matches the material strength, reduces the overuse of high-strength materials, and reduces the material cost; the ground centralized station and vertical material conveying drilling design reduce the underground equipment investment and material transportation cost, and the comprehensive construction cost is significantly reduced. In addition, through systematic reinforcement and precise construction, the recovery rate of residual coal resources is improved to more than 85%, which successfully liberates hundreds of millions of residual coal resources, and the economic benefit is remarkable.

[0021] (5) Easy to promote, green and environmental protection: the method steps are clear, the technical requirements are clear, and the existing directional drilling machine, grouting equipment and fully mechanized mining equipment can be perfectly matched without large-scale modification of the existing facilities, which is easy to implement on site in the coal mine. The ground centralized station reduces the environmental disturbance of underground construction; the grouting wastewater treatment, noise and dust control are strengthened to realize the standard discharge of wastewater, improve the underground operation environment, reduce the damage to the surface ecology, and have social benefits and environmental protection value.

[0022] (6) The method of the application discards the inherent thinking set of "overall reinforcement" or "adventurous weak support" when the existing technology faces the problem of small coal mine re-mining, and through the process path of "channel first, region second, high strength first, low strength second" and the circular progressive idea of "using the reinforced roadway as the subsequent reinforcement construction base", the recovery rate and recovery efficiency of residual resources are greatly improved under the premise of ensuring absolute safety, and the comprehensive cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a flow chart of the method of the application; Figure 2 is a working face layout and grouting staged reinforcement schematic diagram in the method of the application; Figure 3 is a working face roadway reinforcement schematic diagram in the method of the application; Figure 4 is a schematic diagram of the underground directional drilling and grouting process profile in the method of the application; Figure 5 is a material vertical conveying drilling structure diagram in the method of the application.

[0024] In the figure, 1. Panel roadway, 2. Return air crossheading, 3. Transportation crossheading, 4. Working face open-off cut, 5. Working face crossheading roadway medium strength reinforcement area, 6. Working face open-off cut high strength reinforcement area, 7. Working face internal low strength reinforcement area. DETAILED DESCRIPTION

[0025] The application will be described in detail below in combination with the drawings and specific embodiments.

[0026] A kind of small coal mine destruction area residual coal resource grouting reinforcement and re-mining recovery method of the application, as shown in Figure 1 and Figure 2 , is specifically implemented according to the following steps: Step 1, working face planning and layout According to the long-term mining plan in the mine, combined with the geological exploration report, the distribution range, reserves and mining conditions of the residual coal resources in the small coal mine destruction area are determined, a detailed mining and excavation replacement plan is made, and the position, size and mining sequence of the working face are determined.

[0027] On the basis of mining replacement plan, the mining face is arranged. The length of the face is determined according to the coal seam occurrence condition and equipment capacity, and is usually 100-220 m. The advancing direction of the face is consistent with the coal seam trend, so as to ensure the coal cutting efficiency of the coal winning machine.

[0028] Step 2, crossheading reinforcement and roadway excavation As shown in Figure 3 , Figure 4 , the grouting boreholes are arranged in the area 10-15 m away from the crossheading profile line by using the underground directional drilling technology. The drilling spacing is determined according to the broken degree of the surrounding rock and the diffusion radius of the grouting material, and is usually 5-10 m. Then, the pre-grouting reinforcement is carried out by using the medium strength filling material (8-12 MPa of compressive strength) to form a stable roadway excavation environment. After the grouting reinforcement is completed, the reinforcement quality is detected, and the roadway excavation is carried out after the detection is qualified.

[0029] Step 3, reinforcement and construction of the key position of the open-off cut At the position of the open-off cut of the face, the horizontal boreholes are constructed from the excavated crossheading to the direction of the transportation crossheading, and the high strength filling material (10-15 MPa) is used to reinforce the key stress concentration areas such as the starting slope point and the through point of the open-off cut. After the reinforcement quality is detected to meet the requirements, the formal construction of the open-off cut of the face is carried out.

[0030] Among them, the arrangement and construction technology of the grouting boreholes are the same as those of the crossheading reinforcement. The open-off cut construction is carried out by using the fully mechanized excavator, and the deformation of the roof and the surrounding rock of the side part is monitored in real time during the excavation process to ensure the construction safety.

[0031] Step 4, internal grouting reinforcement of the face The grouting boreholes are arranged in the face by using the horizontal directional drilling technology with the reinforced crossheading as the drilling site. The drilling spacing is 15-30 m, and the drilling direction is consistent with the coal seam trend to ensure that the slurry can fully penetrate into the coal and rock body fissures. Then, the low strength filling material (2-4 MPa) is used to implement the large area grouting reinforcement of the coal and rock body in the face. The strength of the filled material after solidification is determined according to the requirements of the cutting of the fully mechanized equipment and the roof management, which can ensure the integrity of the face during the mining and avoid the damage of the coal winning machine cutting pick due to the high strength.

[0032] After the grouting reinforcement is completed, the reinforcement quality is detected, and the preparation work before the mining of the face is carried out after the detection is qualified.

[0033] Step 5, resource recovery The coal mining of the working face is carried out by using the fully mechanized mining process. In the mining process, a microseismic monitoring system is used to monitor the reinforced area in real time. The system is composed of a microseismic sensor, a data collector and analysis software. The microseismic sensor is arranged at an interval of less than or equal to 10 m, can capture the microseismic signals generated by the surrounding rock rupture in real time, analyze the rupture position, energy and development trend, and feed back the surrounding rock state and reinforcement effect in real time.

[0034] In addition, a stress online monitoring system is arranged at the key position of the reinforced area and the surrounding rock to monitor the stress change of the surrounding rock in real time. The system is composed of a stress sensor, a data collector and analysis software, and the measurement range is 0-30 MPa. The system can feed back the stress state of the surrounding rock in real time and provide a basis for mining decision.

[0035] According to the data fed back by the microseismic monitoring system and the stress online monitoring system, combined with the geological conditions and the mining progress, the grouting parameters, the mining speed and the supporting parameters are dynamically adjusted to form a closed-loop control mechanism of "monitoring-analysis-adjustment", so as to ensure the safe and efficient mining.

[0036] In the grouting reinforcement and mining process, the coal mine safety regulations are strictly implemented, the ventilation management is strengthened to prevent gas accumulation, the roof and side support is strengthened to prevent roof and side falling, and the equipment maintenance is strengthened to ensure the safe operation of the equipment.

[0037] The method adopts a differentiated hierarchical grouting strength system, that is, a differentiated hierarchical grouting principle of "high strength around the roadway and low strength inside the working face". The strength of the filling body is determined according to the integrity of the surrounding rock of the roadway, the support requirement of the working face cut hole end and the advance support pressure during the mining of the working face. According to the Mohr-Coulomb criterion, combined with the buried depth of the treatment area, the size of the coal pillar and the range of the filling stone body, the strength of the filling body is calculated according to the following formula:

[0038] In the formula: σ 3 - horizontal principal stress; μ - Poisson's ratio of the coal wall complex; γ - average unit weight of overburden; H - buried depth of the small coal mine goaf; φ - internal friction angle of the coal wall combination; σ c - uniaxial compressive strength of the coal wall combination, which is determined by the coal pillar and the filling stone body according to the area weighted average.

[0039] Through calculation, the compressive strength of the reinforcing material of the return air channel and the transportation channel is preferably 8-12 MPa, so as to ensure the safety of the roadway excavation and long-term maintenance; the compressive strength of the reinforcing material of the cut position is 10-15 MPa, so as to provide strong support for the key position; and the compressive strength of the reinforcing material of the internal working face is preferably 2-4 MPa, so as to meet the support requirement of the fully-mechanized mining equipment and realize the goal of "reinforcement for mining".

[0040] The filling raw material of the present application is selected from water, cement, fly ash, coal gangue crushed material and additive.

[0041] The quantity of the high-strength filling material slurry per square meter is: water 380-410 kg, cement 340-380 kg, fly ash 300-355 kg, coal gangue 700-900 kg, and composite additive 5-10 kg. The composite additive includes water reducing agent, early strength agent and setting retarder, and is used for improving the fluidity, early strength and setting time of the slurry.

[0042] The quantity of the medium-strength filling material slurry per square meter is: water 390-410 kg, cement 245-270 kg, fly ash 300-355 kg, coal gangue 830-1020 kg, and composite additive 5-10 kg. The composite additive has the same formula as the high-strength filling material slurry.

[0043] The quantity of the low-strength filling material slurry per square meter is: water 390-420 kg, cement 115-130 kg, fly ash 300-355 kg, coal gangue 950-1150 kg, and composite additive 5-10 kg. The composite additive has the same formula as the high-strength filling material slurry.

[0044] In addition, the method of the present application adopts a ground centralized grouting station and vertical material feeding drilling technology, and the high-strength, medium-strength and low-strength filling materials are all prepared by the ground centralized grouting station. After the preparation of the slurry, the quality is controlled by an automatic batching system, so as to ensure that the slump of the slurry is controlled within 200-260 mm, the bleeding rate is less than or equal to 3%, and the solidified body bulk density is greater than or equal to 1.7 t / m 3The prepared grout is transported to the underground roadway grouting pipeline through a vertical conveying borehole, and then distributed to each grouting borehole. The filling pressure at the borehole opening of the return airway, transport roadway, and cut-in location is 2.5–3.5 MPa, while the filling pressure at the borehole opening of the grouting borehole inside the working face is 3.5–5.0 MPa. This invention uses different grouting pressures to control the grout diffusion radius for different treatment areas. For the return airway, transport roadway, and key locations of the cut-in location, a low pressure of 2.5–3.5 MPa is used to control the diffusion radius, thus reinforcing key areas while preventing excessive grout diffusion (achieving a borehole spacing of 5–10 m) and preventing increased treatment costs. For the inside of the working face, a higher grouting pressure of 3.5–5.0 MPa is used to achieve effective grout diffusion, increasing the diffusion range (borehole spacing of 15–30 m), reducing drilling work, and lowering project costs. The grouting volume is determined based on the borehole depth and the degree of fracture development in the surrounding rock. During the grouting process, the grouting pressure and flow rate are monitored in real time to ensure that the grout is evenly diffused into the surrounding rock fissures and coal and rock mass fissures.

[0045] In addition, the diameter of the wear-resistant conveying pipeline with a borehole lining for vertical material conveying is calculated according to the pipeline conveying capacity and the slurry flow velocity inside the pipe using the following formula:

[0046] In the formula: D —Pipe inner diameter; Q —Pipeline transport capacity, m 3 / h; V — Slurry flow velocity inside the pipe, m / s.

[0047] To prevent particle sedimentation in the slurry, the slurry flow rate inside the pipe is... V The critical settlement velocity calculated using the Durand formula must be satisfied. V L : V > V L =4.99× D 0.5 .

[0048] The pipe thickness is determined according to the pressure resistance calculation formula:

[0049] In the formula: — Pipe thickness calculation, mm; P —The maximum pressure that the pipeline can withstand is 16 MPa; D 0 — Pipe outer diameter, mm; — Allowable stress of material at design temperature, MPa; E J — Welding coefficient; Y — Temperature correction coefficient.

[0050] In addition, in steps 2-4, after the grouting reinforcement is completed, the reinforcement quality is detected by drilling peeping, acoustic wave detection, core strength test, and grouting pressure-flow curve analysis. The drilling peeping method observes the surrounding rock crack filling condition through a drilling peeping instrument; the acoustic wave detection method detects the change of wave speed of the surrounding rock to evaluate the reinforcement effect; the core strength test method tests the compressive strength by drilling a core to ensure that the compressive strength of the solidified body of each filling material reaches the target value.

[0051] Example 1: Taking the recovery of residual coal resources in a typical small coal mine destruction area as an example.

[0052] First, the 101 secondary mining working face is planned. A ZDY-12000 type directional drilling machine is used to drill a directional hole from the production roadway to the area 10-15 m outside the contour line of the designed working face return air crossheading and transportation crossheading, and cement gangue slurry with a compressive strength of 9 MPa is injected at a grouting pressure of 2.5-3.5 MPa. Through drilling peeping, acoustic wave detection, core strength test, and grouting pressure-flow curve analysis, it is confirmed that the broken rock mass is effectively filled and cemented, and then a fully mechanized excavation machine is used to safely and efficiently excavate the two crossheadings.

[0053] After the crossheading excavation is completed, a horizontal coal seam drilling hole is drilled from the return air crossheading to the transportation crossheading at a position 10 m away from the roadway around the open-off cut, and cement gangue slurry with a compressive strength of 12 MPa is used for grouting reinforcement at a grouting pressure of 2.5-3.5 MPa. After passing the detection, the open-off cut is excavated.

[0054] Subsequently, hundreds of meters long horizontal directional drilling holes are drilled into the working face from the two stable crossheadings, and a fan-shaped hole arrangement is used to cover the entire working face area. Cement gangue slurry with a compressive strength of 2 MPa is injected to fill the goaf and coal and rock cracks.

[0055] As shown in Figure 5 , the material vertical conveying drilling hole of the present embodiment has a first opening diameter of Ф311 mm, enters the stable bedrock for 5 m, and a Ф244.5x6 mm casing is lowered and cemented for the whole section; a second opening diameter is Ф215.9 mm, and a Ø168x10 mm filling pipe is lowered and cemented for the whole section.

[0056] The whole process of the core reinforcement operation in this embodiment adopts downhole directional drilling technology. In the directional drilling, the first opening has a diameter of Ф177.8 mm, and a Ф152 mm orifice pipe is lowered for 15 m after drilling for 15 m; the second opening has a diameter of Ф120 mm, and grouting is performed once every 25 m of drilling, and grouting is increased when drilling exposes a goaf; when detecting the same roadway, a 30 m advanced safety distance is reserved for excavation to provide protection for the next stage of detection.

[0057] Finally, the microseismic monitoring system is used to scan the reinforced working face, and after confirming that there is no large-scale stress anomaly, the fully mechanized mining equipment is put into use for recovery. During the recovery process, the roof of the working face is complete, the coal cutting machine cuts smoothly, and the resource recovery rate reaches more than 85%.

[0058] Embodiment 2 The grouting reinforcement and recovery method for residual coal resources in a small coal mine damage area in this embodiment is implemented according to the following steps: Step 1, arrange a recovery working face according to the mining plan; Step 2, use downhole directional drilling to arrange grouting drill holes in the peripheral area of the return air crossheading and the transportation crossheading profile line, and use a medium-strength filling material with a compressive strength of 8-12 MPa for grouting reinforcement; Step 3, construct a horizontal drill hole along the coal seam from the return air crossheading to the transportation crossheading, and use a high-strength filling material with a compressive strength of 10-15 MPa to grout and reinforce the open-off cut position; Step 4, use the reinforced crossheading as a drilling site, and use a low-strength filling material with a compressive strength of 2-4 MPa to grout and reinforce the inside of the working face through horizontal directional long drill holes; Step 5, perform recovery of the working face.

[0059] Embodiment 3 On the basis of Embodiment 2, in Step 2, the reinforcement range is 10-15 m in the peripheral area of the return air crossheading and the transportation crossheading profile line, the drill hole spacing is 5-10 m, and the grouting drill hole orifice filling pressure is 2.5-3.5 MPa.

[0060] Embodiment 4 On the basis of Embodiment 3, in Step 3, the horizontal drill hole spacing is 5-10 m, the open-off cut starting point and the breakthrough point position are grouted and reinforced, and the grouting drill hole orifice filling pressure is 2.5-3.5 MPa.

[0061] Embodiment 5 On the basis of Embodiment 4, in Step 4, grouting drill holes are arranged in the inside of the working face through horizontal directional drilling technology, the drill hole spacing is 15-30 m, the drill hole direction is consistent with the coal seam trend, and the grouting drill hole orifice filling pressure is 3.5-5.0 MPa.

[0062] Example 6 On the basis of Example 5, after the completion of the grouting reinforcement in steps 2-4, the reinforcement quality is detected by using borehole peeping, acoustic wave detection, core strength test and grouting pressure-flow curve analysis.

Claims

1. A method for grouting reinforcement and remining of residual coal resources in a damaged area of ​​a small coal mine, characterized in that, Specifically: Step 1: Arrange the longwall mining face according to the mining plan; Step 2: Use downhole directional drilling to arrange grouting boreholes in the outer area of ​​the return air roadway and transport roadway outline, and use medium-strength filling material with a compressive strength of 8-12MPa for grouting reinforcement. Step 3: Drill horizontal boreholes along the coal seam from the return air roadway to the transport roadway, and reinforce the cut-in locations with high-strength filling material with a compressive strength of 10-15 MPa by grouting. Step 4: Using the reinforced roadway as the drilling site, grout the interior of the working face with low-strength filling material with a compressive strength of 2-4 MPa through horizontal directional long boreholes. Step 5: Conduct face mining.

2. The method for grouting reinforcement and remining of residual coal resources in a small coal mine damaged area according to claim 1, characterized in that, In step 2, the reinforcement area is a 10-15m area outside the outline of the return air roadway and the transport roadway. The borehole spacing is 5-10m, and the filling pressure at the grouting borehole opening is 2.5-3.5MPa.

3. The method for grouting reinforcement and remining of residual coal resources in a small coal mine damaged area according to claim 1, characterized in that, In step 3, the drilling spacing of the horizontal boreholes is 5 to 10 m, and grouting is performed to reinforce the starting point and the penetration point of the cut. The filling pressure of the grouting borehole opening is 2.5 to 3.5 MPa.

4. The method for grouting reinforcement and remining of residual coal resources in a small coal mine damaged area according to claim 1, characterized in that, In step 4, grouting boreholes are arranged inside the working face using horizontal directional drilling technology. The borehole spacing is 15-30m, and the drilling direction is consistent with the coal seam strike. The filling pressure at the borehole opening is 3.5-5.0MPa.

5. The method for grouting reinforcement and remining of residual coal resources in a small coal mine damaged area according to claim 1, characterized in that, In steps 2-4, after the grouting reinforcement is completed, the reinforcement quality is tested by borehole inspection, sonic detection, core strength test, and grouting pressure-flow curve analysis.

6. The method for grouting reinforcement and remining of residual coal resources in a small coal mine damaged area according to claim 1, characterized in that, In steps 2-4, the filling material is prepared by a centralized grouting station on the ground. After the grout is prepared, it is transported to the underground roadway grouting pipeline through a vertical conveying borehole, and then distributed to each grouting borehole. The slump of the grout is 200-260 mm, the bleeding rate is ≤3%, and the solidified bulk density is ≥1.7 t / m³. 3 .

7. The method for grouting reinforcement and remining of residual coal resources in a small coal mine damaged area according to claim 1, characterized in that, In steps 2-4, the components and content of each component of the filling material are as follows: The amount of high-strength filling material used per cubic meter is: 380-410 kg of water, 340-380 kg of cement, 300-355 kg of fly ash, 700-900 kg of coal gangue, and 5-10 kg of composite admixture; The amount of medium-strength filling material used per cubic meter is: 390-410 kg of water, 245-270 kg of cement, 300-355 kg of fly ash, 830-1020 kg of coal gangue, and 5-10 kg of composite admixture; The amount of low-strength filling material used per cubic meter is: 390-420 kg of water, 115-130 kg of cement, 300-355 kg of fly ash, 950-1150 kg of coal gangue, and 5-10 kg of composite admixture; Among them, composite admixtures include water-reducing agents, early-strength agents, and retarders.

8. The method for grouting reinforcement and remining of residual coal resources in a small coal mine damaged area according to claim 1, characterized in that, During the mining process in step 5, a microseismic monitoring system is used to monitor the reinforced area in real time. The system consists of microseismic sensors, a data acquisition unit, and analysis software, with the spacing between the microseismic sensors ≤ 10m. An online stress monitoring system was deployed in the reinforced area and at key locations of the surrounding rock to monitor the stress changes in the surrounding rock in real time. The system consists of stress sensors, data acquisition devices and analysis software, and the measurement range is 0 to 30 MPa. Based on the data fed back from the microseismic monitoring system and the online stress monitoring system, and in combination with geological conditions and mining progress, the grouting parameters, mining speed and support parameters are dynamically adjusted.

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