Coal mine goaf residual coal spontaneous combustion prevention and extinguishing method

Abstract

The application discloses a kind of coal mine goaf residual coal spontaneous combustion fire prevention and extinguishing method, belong to coal mine safety fire prevention and extinguishing technical field, the present application solves the problems of low efficiency, high cost, incomplete plugging, difficult to control air leakage in the prior art of goaf residual coal spontaneous combustion prevention and control.It adopts fire area positioning, source oxygen blocking, targeted filling, dynamic monitoring, bottoming compaction and other closed-loop processes, while supporting special grouting casing device, the device includes connecting assembly, monitoring and control assembly, grouting injection assembly, sealing and filling assembly and support assembly, can realize ordinary grouting slurry and foaming slurry Isolation transport, layered multi-angle accurate grouting and whole-process monitoring and control.The application realizes all-around accurate prevention and control of goaf residual coal spontaneous combustion, accurate positioning, low cost, environmental protection, filling is dense and sealing effect is good, adapts to complex goaf environment, can effectively block air leakage oxygen supply channel, inhibit residual coal spontaneous combustion, prevent secondary disasters, with good practicality and popularization value.

Description

Technical Field

[0001] This invention belongs to the field of coal mine safety fire prevention and extinguishing technology, and more specifically, it relates to a method for preventing and extinguishing spontaneous combustion of residual coal in coal mine goaf areas. Background Technology

[0002] Spontaneous combustion in coal mines is a frequent and serious disaster during mine production. In particular, coal left in goaf areas, due to long-term exposure to air, is highly susceptible to spontaneous combustion due to factors such as temperature, oxygen, and moisture. This not only wastes coal resources but may also trigger secondary disasters such as gas explosions and roof collapses, threatening mine safety and the lives of personnel.

[0003] Currently, the prevention and control measures for spontaneous combustion of residual coal in coal mine goaf areas mainly focus on three aspects: fire monitoring, fire extinguishing, and preventive measures. Traditional prevention and control methods include manual inspection, local cooling, and conventional grouting and sealing. However, the above methods have obvious drawbacks: manual inspection is inefficient and cannot cover the entire complex goaf area; local cooling can only alleviate the high temperature on the surface and cannot reach the fire source inside the goaf; conventional grouting and sealing has poor targeting, uneven grout diffusion, and cannot achieve full filling of the goaf area, nor can it effectively block the leakage of air and oxygen supply channels, resulting in poor fire prevention and extinguishing effects, high costs, and an inability to fundamentally control the occurrence and spread of spontaneous combustion of residual coal in goaf areas.

[0004] Therefore, there is an urgent need for a comprehensive, precise, and efficient method for preventing and extinguishing spontaneous combustion of coal residue in goaf areas. This method should be able to accurately locate the fire zone, seal the entire area, target and fill it, and dynamically control it. It should be able to effectively intervene before the fire occurs or in its early stages, minimize fire losses, and address many shortcomings of existing technologies. Summary of the Invention

[0005] This invention addresses the technical problems existing in the prior art by providing a method for preventing and extinguishing spontaneous combustion of residual coal in coal mine goaf areas.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preventing and extinguishing spontaneous combustion of residual coal in a coal mine goaf includes the following steps: S1. Determination of the fire zone: Based on geological exploration parameters, historical coal mining data and fire monitoring data, the fire zone of spontaneous combustion in the goaf is determined, and the safety boundary of the fire zone is also determined. S2. Grouting slurry preparation: Solid waste is selected as the main raw material, combined with cementing materials, water and additives to prepare grouting slurry; S3. Curtain hole combined with ground crack treatment: Multiple curtain holes are arranged 10 m outside the fire zone safety boundary. At the same time, mining-induced ground cracks are identified and sealed to form a three-dimensional sealing system. S4. Pretreatment of borehole cavities: If a cavity is determined during the drilling of the grouting hole, drilling shall be stopped and a grouting casing device shall be used to fill it with liquid grout. After confirming that the cavity is filled, drilling shall continue. S5. Interval layered foaming grouting: Grouting holes are arranged inside the goaf, and grouting sleeve devices are used to implement the grouting sequence of intermittent skipping and grouting from the periphery to the center. Combined with layered grouting, the goaf is accurately filled in layers. S6. Real-time monitoring and parameter adjustment: Monitor the fire zone range and grouting effect, analyze monitoring data, and adjust parameters; S7. Roof cutting and compaction treatment: If there are hidden air leakage channels that cannot be located, roof cutting should be carried out to ensure that the oxygen concentration inside the goaf meets the standard.

[0007] Preferably, when determining the fire zone range, the ranges of the three zones of the fire zone are first determined as follows: oxidation zone thickness 5-15 m, asphyxiation zone thickness 10-25 m, and heat dissipation zone thickness 8-20 m. At the same time, the boundary distance for a temperature ≤30 ℃ is determined by the range of temperature conduction influence in the fire zone. The fire zone boundary is defined as a safety boundary extending 10 m outward from the isopleths of CO concentration 100 ppm and temperature 30 ℃.

[0008] Preferably, the solid waste includes one or more of coal gangue, tailings, fly ash, and slag, with a transportation distance of ≤5km; the solid waste accounts for 60-80%, the water-to-solid ratio is 0.8-1.0, the additive dosage is 0.5-2.0%, and the slurry hardening time is set at 30-120 min.

[0009] Preferably, in S3, a dual sealing measure is adopted, consisting of surface cracks and curtain holes; First, one or more of the following methods are used to identify ground cracks induced by mining: ground monitoring, geological exploration, ground measurement, remote sensing image analysis, and monitoring sensors. Next, the curtain hole arrangement is carried out. The curtain hole positions are arranged in a plum blossom shape, and the hole depth penetrates the goaf and extends 2m into the bottom plate. Then, the cracks are sealed in three dimensions, using a combination of filling and grouting to treat the cracks.

[0010] Preferably, during the drilling and grouting process, grouting holes are set at intervals to divide the area into a central zone and a transition zone. The spacing between holes is divided according to the zone, with a hole spacing of 10 m in the central zone and 12 m in the transition zone. The grouting material is cement-water glass double-liquid grout or fly ash-cement composite grout, and the water-cement ratio of cement-water glass double-liquid grout is 0.7-1. The criteria for determining a cavity are borehole collapse, sudden changes in drilling speed, or a sharp decrease in the amount of cuttings returned during drilling. The type of cavity is determined based on the situation of adjacent boreholes at the same depth. When the volume is <5 m³ 3 The cavity is a small cavity; volume ≥ 5 m³ 3The cavity is a large cavity; After filling the identified voids, continue drilling until the voids where spontaneous combustion of coal occurred are filled, with a void filling rate of ≥90%.

[0011] Preferably, during the drilling and grouting process, the grouting holes are arranged in a quincunx pattern, with a hole spacing of 10 m in the central area, a hole spacing of 12 m in the transition area, and 25° inclined holes in the edge area; the grouting sequence is skipping grouting every 1-2 holes, first the periphery and then the center; The foaming slurry is prepared using cement, chemical foaming agent, and inhibitor. The mass ratio of cement to chemical foaming agent is 100:2-5, the amount of inhibitor is 1.0-2.0% of the cement mass, the water-cement ratio is 0.8-1.0, and the foaming process takes 30-40 minutes.

[0012] Preferably, the fire zone monitoring adopts an integrated monitoring system, which is equipped with a pressure monitoring module, a flow rate adjustment module, a thermal imaging camera and a smoke sensor, with a monitoring point spacing of 10-15 m; the grouting effect monitoring adopts a flow meter and a pressure sensor, with a monitoring point spacing of 5-10 m; when the fire zone expands by ≥2 m in a single day or the goaf filling rate is <85%, the grout mix ratio, grouting hole arrangement or curtain hole position are adjusted.

[0013] Preferably, in S7, the cut-off area is a rectangular area within 10 m outside the fire zone boundary, the cut-off area is ≥ 1.2 times the fire zone area, the cut-off height is 15 m and not less than the height of the collapse zone; the boreholes are parallel to the working face, with a hole spacing of 1 m and a row spacing of 1.5 m, and shaped charge blasting is used, and the oxygen concentration inside the goaf is ≤ 8% after the collapsed rock is compacted.

[0014] Preferably, the grouting casing device includes a connecting component, a monitoring and control component, a grouting injection component, a sealing and filling component, and a support component; the connecting component is used to connect the device with external grouting equipment and to splice multiple devices; the support component provides support for the entire device, and its interior forms mutually isolated grouting channels and foaming channels to achieve isolated transportation of ordinary grouting slurry and foaming slurry; the monitoring and control component is used to monitor grouting process parameters in real time and accurately adjust the grouting state; the grouting injection component is used to achieve layered and multi-angle precise grouting in the goaf; and the sealing and filling component is used to achieve foam sealing of the top of the goaf.

[0015] Preferably, the connecting components include an upper flange and a lower flange, with the upper flange connected to the external grouting equipment and the lower flange matching the structural dimensions of the upper flange; the supporting components include an outer casing wall and an inner grouting pipe, with a closed foaming channel formed between the outer casing wall and the inner grouting pipe, and the two connected by uniformly arranged inner and outer through holes; the monitoring and control components include a pressure monitoring device, a flow rate control device, a thermal imaging camera, and a smoke sensor, which are used to monitor grouting pressure, adjust grouting flow rate, monitor the internal temperature of the goaf, and detect leakage, respectively. The grouting and spraying assembly includes nozzles, nozzle controls, and spray holes. The nozzles are arranged in multiple layers and directions, with multiple nozzles evenly distributed around the periphery in each group. The nozzle angle is adjustable, and the spray holes are arranged in segments. The sealing and filling assembly includes a foaming chamber and a foaming nozzle. The foaming chamber is connected to the foaming channel, and the foaming nozzle is used to spray the foaming slurry onto the top of the goaf.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a comprehensive, closed-loop method for preventing and extinguishing spontaneous combustion of residual coal in coal mine goaf areas. It overcomes the limitations of traditional single-technology prevention and control, employing a synergistic approach of "blocking, filling, compressing, and sealing." Ground crack treatment and curtain wall openings create a vertically linked seal, while layered, intermittent foaming grouting and roof cutting and compaction provide internal and external filling. This achieves full-process coverage of fire zone location, source oxygen blocking, targeted treatment, dynamic control, and comprehensive protection, solving the problems of traditional technologies that only address the symptoms and are prone to reignition. Furthermore, it offers precise location and high efficiency. Combined with geological surveys, sensor monitoring, and monitoring modules from specialized casing devices, it improves location accuracy and efficiency, significantly shortens the construction cycle, and effectively prevents the spread of the disaster. By using solid waste from the surrounding coal mine to prepare the grouting fluid, costs are reduced while simultaneously achieving resource utilization of solid waste, meeting environmental protection requirements and lowering environmental treatment costs. By using a specialized grouting sleeve device to achieve layered and intermittent foaming grouting, the low oxygen concentration inside the goaf after roof cutting and compaction completely blocks the air leakage and oxygen supply channels, which can both suppress spontaneous combustion of residual coal and prevent secondary disasters caused by roof collapse, thus achieving the dual benefits of fire prevention and extinguishing and operational safety. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art 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.

[0018] Figure 1 This is a schematic diagram of a method flow according to one embodiment of the present invention; Figure 2 This is a schematic diagram of fire zone identification according to one embodiment of the present invention; Figure 3 This is a schematic diagram of the curtain hole arrangement according to one embodiment of the present invention; Figure 4 This is a schematic diagram of a layered foaming grouting combined with filling of the goaf according to one embodiment of the present invention; Figure 5 This is a schematic diagram of the cutting range according to one embodiment of the present invention; Figure 6This is a schematic diagram of the overall structure of a grouting sleeve device according to one embodiment of the present invention; Figure 7 This is a partial structural cross-sectional view of a grouting sleeve device according to one embodiment of the present invention.

[0019] Explanation of symbols in the diagram: 1. Upper flange; 2. Lower flange; 3. Outer wall of sleeve; 4. Inner grouting pipe; 5. Foaming chamber; 6. Inner and outer through holes; 7. Nozzle; 8. Nozzle control; 9. Spray hole; 10. Foaming nozzle; 11. Pressure monitoring device; 12. Flow rate control device; 13. Thermal imaging camera; 14. Smoke sensor. Detailed Implementation

[0020] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0021] Example 1 Please see Figure 1 This invention provides a method for preventing and extinguishing spontaneous combustion of residual coal in coal mine goaf areas, comprising the following steps: S1. Determination of the fire zone: Based on geological exploration parameters, historical coal mining data and fire monitoring data, the fire zone of spontaneous combustion in the goaf is determined, and the safety boundary of the fire zone is also determined. S2. Grouting slurry preparation: Solid waste is selected as the main raw material, combined with cementing materials, water and additives to prepare grouting slurry; S3. Curtain hole combined with ground crack treatment: Multiple curtain holes are arranged 10 m outside the fire zone safety boundary. At the same time, mining-induced ground cracks are identified and sealed to form a three-dimensional sealing system. S4. Pretreatment of borehole cavities: If a cavity is determined during the drilling of the grouting hole, drilling shall be stopped and a grouting casing device shall be used to fill it with liquid grout. After confirming that the cavity is filled, drilling shall continue. S5. Interval layered foaming grouting: Grouting holes are arranged inside the goaf, and grouting sleeve devices are used to implement the grouting sequence of intermittent skipping and grouting from the periphery to the center. Combined with layered grouting, the goaf is accurately filled in layers. S6. Real-time monitoring and parameter adjustment: Monitor the fire zone range and grouting effect, analyze monitoring data, and adjust parameters; S7. Roof cutting and compaction treatment: If there are hidden air leakage channels that cannot be located, roof cutting should be carried out to ensure that the oxygen concentration inside the goaf meets the standard.

[0022] This invention provides a comprehensive, closed-loop method for preventing and extinguishing spontaneous combustion of residual coal in coal mine goaf areas. It overcomes the limitations of traditional single-technology prevention and control, employing a synergistic approach of "blocking, filling, compressing, and sealing." Ground crack treatment and curtain wall openings create a vertically linked seal, while layered, intermittent foaming grouting and roof cutting and compaction provide internal and external filling. This achieves full-process coverage of fire zone location, source oxygen blocking, targeted treatment, dynamic control, and comprehensive protection, solving the problems of traditional technologies that only address the symptoms and are prone to reignition. Furthermore, it offers precise location and high efficiency. Combined with geological surveys, sensor monitoring, and monitoring modules from specialized casing devices, it improves location accuracy and efficiency, significantly shortens the construction cycle, and effectively prevents the spread of the disaster. By using solid waste from the surrounding coal mine to prepare the grouting fluid, costs are reduced while simultaneously achieving resource utilization of solid waste, meeting environmental protection requirements and lowering environmental treatment costs. By using a specialized grouting sleeve device to achieve layered and intermittent foaming grouting, the low oxygen concentration inside the goaf after roof cutting and compaction completely blocks the air leakage and oxygen supply channels, which can both suppress spontaneous combustion of residual coal and prevent secondary disasters caused by roof collapse, thus achieving the dual benefits of fire prevention and extinguishing and operational safety.

[0023] Example 2 Based on Example 1, this embodiment of the invention provides a method for preventing and extinguishing spontaneous combustion of residual coal in coal mine goaf areas, such as... Figure 1 As shown, the specific steps include: S1. Determine the fire zone. like Figure 2 As shown, the location near the fire zone is processed. This area can be defined by three zones. When determining the fire zone, the three zones are first defined as follows: oxidation zone thickness 5-15 m, asphyxiation zone thickness 10-25 m, and heat dissipation zone thickness 8-20 m. At the same time, the boundary distance with a temperature ≤30 ℃ is determined by the influence range of the fire zone temperature conduction.

[0024] Furthermore, by using equipment such as carbon monoxide sensors and temperature sensors, combined with geological exploration parameters, including coal seam dip angle of 0-90°, coal seam thickness of 0.8-5 m, and fire judgment standards, the fire zone range is comprehensively determined. The fire zone boundary is defined as a safety boundary extending 10 m outward from the isopleths of CO concentration of 100 ppm and temperature of 30 ℃.

[0025] During the preparation process, appropriate grouting slurries are prepared according to different fire zone types, and equipment such as mixers and grouting pumps are used. For high-temperature fire zones (temperatures >150℃), cement-water glass double-liquid slurry can be used. For oxidation heating zones (temperatures between 70-150℃), fly ash-cement composite slurry can be used. At the same time, material parameters are strictly controlled to lay the foundation for grouting operations.

[0026] Simultaneously, the design and construction of curtain holes and the treatment of ground cracks were carried out. The curtain holes were arranged in more than 10 m rows outside the fire zone boundary (row spacing 10 m, hole spacing 15 m), and drilling rigs were used for construction.

[0027] S2. Preparation of grouting slurry Using solid waste from around coal mines as raw materials, while considering the safety, availability, and grouting effect of the raw materials, can significantly reduce costs.

[0028] When selecting solid waste as grout raw material, the first step is to investigate and assess the solid waste surrounding the coal mine to determine its suitability as a grouting material. Selected solid waste may include one or more common materials such as coal gangue, tailings, fly ash, and slag. Other suitable solid wastes may also be selected or added. The transportation distance should be ≤5km to improve transportation efficiency and reduce transportation costs. Next, a safety assessment is conducted on the selected solid waste to ensure it does not contain harmful substances and will not adversely affect the grouting effect. Simultaneously, it is ensured that the waste treatment process complies with environmental standards, does not cause environmental pollution, and reduces environmental treatment costs.

[0029] Furthermore, the selected solid waste is processed and treated for use as grouting raw materials. The treatment methods include grinding, screening, and drying to ensure that the particle size and texture of the waste meet the grouting requirements.

[0030] Based on the specific requirements of grouting and the characteristics of the selected solid waste, a suitable formula is designed. The grouting slurry includes: solid waste, water, and additives. Among them, solid waste accounts for 60-80%, the water-to-solid ratio is 0.8-1.0, and the additive dosage is 0.5-2.0%. The additives can be the required quick-setting agents, etc., which can optimize the grout performance to ensure that the grouting slurry has good fluidity and good hardening properties. The grout hardening time is set at 30-120 minutes.

[0031] Furthermore, during actual construction, small-scale tests are conducted to verify the performance and effectiveness of the prepared grout. Verification indicators include fluidity, hardening time, and strength, ensuring that the grouting materials meet the needs of the actual project. After successful verification, the designed grouting materials are applied to the actual project, with quality control and monitoring implemented to ensure the grouting effect meets expectations.

[0032] In practice, the formula and process of grouting raw materials can be continuously improved and optimized according to changes in geological conditions and working conditions in the goaf, thereby improving cost-effectiveness and construction efficiency. At the same time, solid waste resources should be regularly assessed and updated to ensure a continuous supply of grouting raw materials, and a resource assessment should be carried out every quarter.

[0033] S3. Identify ground fissures induced by mining. The ground cracks induced by mining can be quickly and accurately identified by using one or more of the following methods: ground monitoring, geological exploration, ground measurement, remote sensing image analysis, and monitoring sensors.

[0034] Specifically, the specific measures for each identification method are as follows: Ground monitoring: Ground monitoring technologies, such as satellite remote sensing and lidar, are used to conduct regular monitoring of the mining area, with a monitoring cycle of 7-15 days. By monitoring surface deformation and changes in cracks, mining-induced ground fissures can be detected in a timely manner.

[0035] Geological survey: A detailed geological survey is conducted before mining to understand the geological structure, strata, and identify potential fracture zones, such as within 50 meters of fault fracture zones. During mining, regular geological monitoring is carried out once a day to promptly detect geological anomalies and fracture changes.

[0036] Remote sensing image analysis: Using remote sensing imagery technology, high-resolution satellite or aerial photographs of the mining area are analyzed to identify the distribution and changes of surface cracks. By comparing images from different time points, the evolution process of the cracks can be discovered.

[0037] Ground surveying: Using ground surveying instruments, such as total stations and GPS, to conduct on-site measurements of the mining area. By measuring changes in surface elevation and morphology, potential ground fissures can be identified.

[0038] Monitoring sensors: Surface crack monitoring sensors are deployed in the mining area to monitor crack changes in real time, with a monitoring frequency of once per hour. The monitoring sensors can measure parameters such as crack width, depth, and deformation. The crack width measurement range is 0-50 cm. These parameters help identify ground cracks induced by mining. Cracks with a width ≥ 0.5 cm need to be dealt with promptly.

[0039] S4. Ground Crack Treatment The ground cracks were filled with loess and grouted to prevent air leakage and oxygen supply to the goaf, thereby maintaining the isolation and sealing of the fire zone.

[0040] Specifically, the process begins with detecting and assessing ground-induced cracks to understand their location, size, and shape, identifying cracks that require filling and sealing, with a focus on cracks ≥0.5 cm wide and ≥5 m long. Next, loess is used to fill the cracks, ensuring the fill layer is stable. The purpose of loess filling is to seal the cracks, increase ground stability, and prevent air and oxygen from entering the goaf. Finally, a quality inspection is conducted to check the effectiveness of the crack filling and sealing, as well as the grouting of the curtain holes. The acceptance criteria are that the cracks have no obvious gaps, the grout is full, and the fire zone boundary is completely sealed and isolated.

[0041] Furthermore, when performing grouting and sealing, appropriate grouting materials should be selected, such as cement grout or polymer grout. The water-cement ratio of cement grout should be 1.0, and the concentration of polymer grout should be 20-30%. These materials should be injected into the cracks to ensure that they are filled and tightly bonded to the surrounding strata.

[0042] S5, Curtain Hole Grouting like Figure 3 As shown, curtain holes are set up over a large area according to the determined fire zone. The curtain holes are arranged in a quincunx pattern, with multiple rows set from the perimeter to the center. The holes must penetrate all goaf areas and enter the bottom plate by 2 m.

[0043] Specifically, the borehole spacing is set at 10 m, with 25° inclined holes used in the edge area, following a sequence of grouting from the periphery to the center, with a skipping interval of 1-2 holes. Then, curtain grouting is performed to seal the cracks three-dimensionally, using a combination of filling and grouting for crack control. A cement-water glass dual-liquid grout is used, with a water-cement ratio of 0.7-1. The grouting material is injected into the curtain holes, and grouting is stopped after 30 minutes, achieving a three-dimensional seal of the fire zone boundary and preventing oxygen penetration at the fire zone boundary.

[0044] In this embodiment, after the sealing is completed, the sealing effect needs to be inspected, and the grouting of the curtain holes needs to be checked. The acceptance criteria are that the curtain body is continuous and intact, with no leakage, to ensure the complete sealing and isolation of the fire zone boundary. The grout solidification efficiency is improved by more than 50%, thoroughly guaranteeing the sealing and isolation effect.

[0045] S6. Set up grouting holes for interval grouting. like Figure 4As shown, during the drilling and grouting process, grouting holes are set up for intermittent grouting, dividing the area into a central zone and a transition zone. The spacing between holes is divided according to the zone, with a hole spacing of 10 m in the central zone and 12 m in the transition zone. The grouting material is cement-water glass double-liquid grout or fly ash-cement composite grout, achieving multiple uses for one hole. Based on the phenomena observed during drilling and geological exploration, it is determined whether a large cavity is encountered during the drilling process. The criteria for determining a cavity are hole collapse, sudden change in drilling speed, or sudden decrease in the amount of slag returned during drilling. If a cavity is determined, drilling is stopped, a dedicated grouting casing device is set up, and then grouting is carried out.

[0046] In this embodiment, the monitoring module on the grouting casing device simultaneously detects and identifies the disaster area, addresses borehole voids, and controls grouting in multi-layered goaf areas. When boreholes encounter collapses or sudden changes in drilling speed, they are identified as voids, and cement-water glass dual-liquid grout is used for injection. The effect is verified after 24 hours of solidification. By combining the monitoring module of the curtain hole and the dedicated grouting casing, compared to traditional positioning methods, the positioning deviation is ≤±0.5m, positioning accuracy is improved by 80%, positioning efficiency is improved by 60%, and the construction cycle is shortened by 50%.

[0047] Furthermore, based on the situation of adjacent boreholes at the same depth, the type of cavity can be determined when the volume is <5 m³. 3 The cavity is a small cavity; volume ≥ 5 m³ 3 The cavity is a large cavity. After filling the identified cavity, continue drilling until the void where spontaneous combustion of coal occurred is filled, with a void filling rate of ≥90%.

[0048] In this embodiment, to effectively mitigate the impact of continuous grouting on the grout and ensure coordination between the grout diffusion radius and the solidification accumulation height, the grout diffusion radius is 5-7.5 m. Therefore, intermittent grouting is selected. During intermittent grouting, the grout mix ratio needs to be controlled, including parameters such as the proportion of cementitious materials, the specific gravity of water glass, and the solid-liquid ratio. The proportion of cementitious materials should be controlled according to the specific grouting conditions and requirements. For example, cement and gypsum are cementitious materials, and their proportion is 30-50%. Typically, a suitable cementitious material ratio needs to be determined based on geological conditions, grout hole diameter, and other factors to ensure the grout has appropriate fluidity and hardening properties. The hardening time is set to 30-60 minutes. Water glass is a commonly used grouting cementitious material; its specific gravity can affect the fluidity and consistency of the grout. The specific gravity of water glass is controlled between 1.2 and 1.4. As needed, the specific gravity of water glass can be adjusted to control the fluidity and diffusion radius of the grout. The solid-liquid ratio refers to the proportion of solid materials to liquids in the grouting fluid. Solid materials include cement and gypsum, while liquids include water and water glass. The solid-liquid ratio is typically controlled at 1:2. By adjusting the solid-liquid ratio, the consistency and fluidity of the grouting fluid can be controlled, thereby affecting its diffusion radius and settling.

[0049] Furthermore, an intermittent grouting cycle operation method is adopted. This means that when multiple grouting holes are used in a cycle, the arrangement and sequence of the grouting holes must be rationally arranged. A staggered arrangement is typically used, achieved through tee or multi-way switching, with grouting holes spaced at intervals of 15 m to ensure that the grout can diffuse evenly and fill the target area. During intermittent grouting, the flow and diffusion effect of the grout must be monitored in real time. Based on the monitoring results, parameters such as the proportion of cementitious materials, the specific gravity of water glass, and the solid-liquid ratio should be adjusted promptly to ensure the quality and effectiveness of the grout.

[0050] S7. Set up grouting holes for layered grouting. In this embodiment, to achieve layered grouting, a grouting casing device can be installed while drilling the grouting hole, which can be achieved in the following way: Specifically, the foaming chamber and the grouting inner tube in the grouting sleeve device are designed separately, and a multi-layer adjustable nozzle and a segmented spray hole composite structure work together.

[0051] In this embodiment of the invention, the grouting casing device employs a separate layout for the foaming chamber and the inner grouting pipe. The inner grouting pipe runs through the entire device, forming an independent, sealed foaming chamber with the outer wall of the casing. The two are connected by dedicated internal and external through holes and can be controlled independently. This structure enables the isolated delivery of ordinary grouting slurry and foaming slurry, avoiding mutual interference between the two slurries, ensuring the precise implementation of layered, intermittent foaming grouting, and simultaneously ensuring that the expansion performance of the foaming slurry is not affected. This effectively improves the foaming sealing effect at the top of the goaf, helping to achieve a filling rate of ≥95%.

[0052] Furthermore, existing grouting devices mostly employ a single nozzle or fixed nozzle design, resulting in limited grouting range and an inability to accurately adapt to the needs of coal seams at different depths. The grouting casing device used in this embodiment employs a composite structure of "multi-layer adjustable nozzles and segmented nozzles." Specifically, a multi-layer nozzle structure is set in the middle of the outer wall of the casing, with a nozzle spacing of 1m. Each group is distributed in four directions circumferentially, and the nozzle angle can be flexibly adjusted within the range of 0-30°. Simultaneously, the casing is segmented, with each segment being 5m long and corresponding to an adjustable nozzle. The multi-layer adjustable nozzles enable stratified and multi-angle spraying of the grout, accurately covering coal seam goaf areas at different depths and directions, with a stable grouting diffusion radius of 5-7.5m. The segmented adjustable nozzles can be controlled by opening / closing and adjusting the orifice size to adapt to the grouting flow requirements of coal seams at different depths. Combined with the nozzles, this achieves double-precise stratified grouting, avoiding material waste caused by blind grouting and improving grouting efficiency and filling effect.

[0053] S8, Layered foaming grouting with intermittent grouting holes During the drilling and grouting process, grouting holes are arranged in a quincunx pattern inside the goaf, with a hole spacing of 10 m in the central area, 12 m in the transition area, and 25° inclined holes in the edge area. A special grouting casing device is used, and the grouting sequence is implemented with 1-2 holes skipped and the periphery first and then the center. Combined with the layered grouting process, the ordinary grouting slurry and the foaming slurry are transported separately to achieve precise layered filling of the goaf.

[0054] Specifically, the upper grouting material is foamed to utilize its foaming expansion properties, thereby filling the top and sealing the goaf as much as possible, with a goaf filling rate of ≥95%.

[0055] In this embodiment, the preparation of the foaming material first requires determining a suitable ratio based on the grouting requirements and the properties of the chemical foaming agent. The foaming grout is prepared using cement, a chemical foaming agent, and an inhibitor. The mass ratio of cement to chemical foaming agent is 100:2-5, the inhibitor dosage is 1.0-2.0% of the cement mass, and the water-cement ratio is 0.8-1.0. The foaming process is completed in the foaming chamber of a dedicated grouting sleeve device, taking 30-40 minutes, significantly reducing the time required for grout preparation.

[0056] Furthermore, as a preferred embodiment, the ratio of cement to chemical foaming agent can be adjusted according to the actual situation, and can usually be set to 2% to 5% of the cement mass, the amount of inhibitor is 1.0-2.0% of the cement mass, and the water-cement ratio is set to 0.8-1.0.

[0057] Furthermore, cement, chemical foaming agents, and inhibitors are added to a mechanical foaming device according to a specified ratio and mixed for 10 minutes. Mechanical stirring ensures the foaming agent and inhibitors are evenly dispersed in the cement, achieving both foaming and inhibition effects. During mixing, the foaming effect of the grouting material is observed to ensure the foaming agent and inhibitors are fully dissolved and evenly distributed, without affecting the cement's bonding and hardening properties. Experiments are conducted to test the physical properties and inhibition effects of the foamed material, verifying that it meets the expected requirements. Finally, based on the experimental results, the final foamed grouting material formula is determined, and on-site construction is carried out. The foamed grouting material is then transported through pipelines to the goaf for grouting, achieving a high level of accumulation and sealing in the goaf.

[0058] S9. Monitoring and Adjustment In this embodiment, the fire zone range and grouting effect are monitored in real time, and parameters such as the grout mix ratio and curtain hole position are adjusted as needed. The monitoring frequency is once per hour. The fire zone monitoring adopts an integrated monitoring system, which includes a pressure monitoring module, a flow rate adjustment module, a thermal imaging camera, and a smoke sensor.

[0059] Specifically, fire zone monitoring involves using fire monitoring equipment, such as smoke detectors and thermal imaging cameras, to set up monitoring points around the perimeter of the goaf, spaced 10-15 meters apart, to monitor changes in the fire situation in real time. Smoke detectors have a monitoring range of 0-50 meters; thermal imaging cameras have a temperature measurement range of 0-200 ℃. Monitoring data can be transmitted to a monitoring center via network, where Geographic Information System (GIS) and other technologies are used to achieve real-time display and analysis of the fire zone's extent.

[0060] Grouting effect monitoring: Monitoring points are set up around the grouting holes, with a spacing of 5-10 m between the monitoring points, to monitor the flow and diffusion range of the grouting fluid. Flow meters, pressure sensors, and other monitoring equipment can be used to monitor the flow rate and pressure changes of the grouting fluid in real time and evaluate the grouting effect.

[0061] Data Analysis and Adjustment: Based on the monitoring data of the fire zone extent and grouting effect, data analysis and evaluation will be conducted, with a comprehensive analysis performed once daily. If the fire zone extent is found to have expanded (≥2 m in a single day) or the grouting effect is poor (filling rate <85%), prevention and control measures need to be adjusted promptly. Specific measures are as follows: Grout mix ratio adjustment: Based on monitoring data, adjust the grout mix ratio, including the proportions of cementitious materials, water glass, and other components. The ratio can be adjusted by controlling the amount of cementitious materials and water glass added to the grout, ensuring that the grout's fluidity and hardening properties meet the standards.

[0062] Adjustment of curtain opening positions: Adjust the position and layout of the curtain openings according to changes in the fire zone. The number of curtain openings can be increased or decreased, and their position and density can be adjusted. One opening can be set every 10-15 m to maximize the prevention of fire spread and ensure the continuity and integrity of the curtain structure.

[0063] Real-time monitoring and remote control: A remote monitoring system is adopted to monitor the fire zone and grouting effect in real time, and to remotely control and adjust the system. The monitoring center can remotely control the grouting equipment and curtain hole protection facilities based on real-time monitoring data, enabling timely response and handling of fire situations.

[0064] S10, Post-processing In practice, there are very few cases where grouting may not solve the fire extinguishing problem. The main reason for this is that there are still hard-to-find air and oxygen supply channels. In such cases, mechanical or blasting methods can be used to cut the roof, causing the roof to collapse further and fill the fire zone in the possible goaf, thus achieving the purpose of extinguishing the fire and plugging the leak.

[0065] like Figure 5As shown, the cut-off area is a rectangular area within 10 m outside the fire zone boundary, the cut-off area is ≥ 1.2 times the fire zone area, the cut-off height is 15 m and this height is not less than the height of the collapse zone; the boreholes are parallel to the working face, with a hole spacing of 1 m and a row spacing of 1.5 m, and shaped charge blasting is used. After the collapsed rock is compacted, the oxygen concentration inside the goaf is ≤ 8%, completely blocking the air leakage and oxygen supply channels.

[0066] In summary, this embodiment combines ground crack treatment with oxygen blocking at the source through curtain vents, precise treatment with layered, intermittent foaming grouting, and significantly improved sealing through roof cutting and compaction. After compaction of collapsed rock, the oxygen concentration inside the goaf is ≤8%, far exceeding the effect of single-technology combinations. It can adapt to complex goaf environments and solves the problems of traditional technologies that only treat the symptoms and are prone to reignition. Through this comprehensive method for preventing and extinguishing spontaneous combustion of residual coal in coal mine goafs, real-time monitoring and adjustment of the fire zone and grouting effect can be achieved, allowing for timely responses to changes in the fire situation and ensuring the smooth progress of spontaneous combustion prevention and extinguishing work in coal mine goafs.

[0067] Example 3 Furthermore, the grouting sleeve device structure used in any of the above embodiments is as follows: Figure 6 , Figure 7 As shown, in this embodiment, the grouting casing device includes a connecting component, a monitoring and control component, a grouting injection component, a sealing and filling component, and a support component. The connecting component is used to connect the device with external grouting equipment and to splice multiple devices. The support component provides support for the entire device and forms mutually isolated grouting channels and foaming channels inside, realizing the isolated transportation of ordinary grouting slurry and foaming slurry. The monitoring and control component is used to monitor the grouting process parameters in real time and accurately adjust the grouting state. The grouting injection component is used to realize layered and multi-angle precise grouting in the goaf. The sealing and filling component is used to realize foam sealing of the top of the goaf.

[0068] Specifically, the connecting components include an upper flange 1 and a lower flange 2. The upper flange 1 is fixedly installed on the upper part of the device and connects to the external grouting equipment. The lower flange 2 is fixedly installed at the bottom end of the outer wall 3 of the casing. The structural dimensions of the lower flange 2 match those of the upper flange 1, ensuring that the foaming nozzle can be completely enclosed by the foaming chamber 5 after connection. The lower flange 2 is fixedly connected to the foaming nozzle to protect and fix it, preventing damage. Moreover, multiple grouting casing devices can be spliced ​​together through the sealing connection between the upper flange 1 and the lower flange 2 according to the depth requirements of the goaf. This allows the device to penetrate to different depths in the strata, adapting to the layered grouting needs of goafs of different thicknesses, ensuring precise grouting and sealing filling of the entire goaf from top to bottom.

[0069] Furthermore, the support components include the outer wall of the casing 3 and the inner grouting pipe 4. A closed foaming channel, namely the foaming chamber 5, is formed between the outer wall of the casing 3 and the inner grouting pipe 4. The two are connected by evenly arranged inner and outer through holes 6. The inner grouting pipe 4 runs through the entire device, the outer wall of the casing 3 provides support for the entire device, the foaming channel is used to isolate and transport ordinary grouting slurry and foaming slurry, and the foaming chamber 5 is specifically used to store the foamed upper grouting material, providing a dedicated channel for foam sealing of the top of the goaf.

[0070] In this embodiment, a number of internal and external through holes 6 are evenly installed at corresponding positions on the outer wall 3 of the casing and the inner grouting pipe 4. The internal and external through holes 6 serve to connect the inner grouting pipe 4 and the foaming chamber 5. According to the requirements of the grouting process, the foaming slurry can be controlled to enter the foaming chamber 5 from the inner grouting pipe 4, so as to achieve precise delivery of foaming materials. It can also effectively isolate the foaming slurry from the ordinary grouting slurry and avoid mutual interference between the two.

[0071] Furthermore, in this embodiment, the upper flange 1 serves as the connection interface between the device and the external grouting equipment, and it achieves a sealed connection with the inner grouting pipe 4 to ensure that there is no leakage of grout during the grouting process.

[0072] like Figure 6 , Figure 7 As shown, in this embodiment, the grouting injection assembly includes a nozzle 7, a nozzle control 8, and a spray hole 9. The nozzle 7 and the nozzle control 8 are installed in the middle area of ​​the outer wall 3 of the casing. The nozzle 7 is arranged in multiple layers and in multiple directions, with a total of three groups. Each group of nozzles 7 has four nozzles evenly distributed along the circumference. The nozzle 7 adopts a concave structure design and the angle is adjustable, which can effectively prevent damage to the nozzle 7 during the installation of the casing. The nozzle 7 is connected to the foaming chamber 5, which can realize the simultaneous foaming and grouting.

[0073] Furthermore, the spacing of nozzles 7 is set at approximately 1 meter, enabling the grout to be sprayed in layers into coal seam goaf areas at different depths. Moreover, the specific number of nozzle groups 7, as well as the quantity and size of each group of nozzles, can be adjusted to suit actual usage requirements.

[0074] In this embodiment, the nozzle control 8 is connected to each nozzle 7. Its core function is to adjust the spray direction and nozzle size of the nozzle 7. The spray direction of the nozzle 7 can be flexibly adjusted within the range of 0-30°, and the size of the nozzle 7 can be adjusted in real time according to the grouting flow rate requirements, thereby achieving precise grouting of coal seams at different depths and in different directions, ensuring that the grouting diffusion radius is stable at 5-7.5m, and improving the grouting coverage and filling effect.

[0075] Furthermore, the nozzles 9 are located at the bottom of the outer wall 3 of the casing, and the nozzles 9 are arranged in a segmented structure. By controlling the opening and closing of each segment of nozzle 9, layered and segmented grouting can be achieved in conjunction with the nozzles 7, ensuring that coal seams of different depths can be fully grouted. Moreover, the size of the nozzles 9 is adjustable, and the diameter of the nozzles 9 can be adjusted as needed to adapt to coal seams of different depths and sizes, and to meet different grouting flow requirements.

[0076] In this embodiment, the sealing and filling assembly includes a foaming chamber 5 and a foaming nozzle 10. The foaming nozzle 10 is located at the bottom of the outer wall 3 of the casing. The foaming chamber 5 is connected to the foaming channel, and the foaming nozzle 10 is connected to the foaming chamber 5. The foaming nozzle 10 is specifically used to spray the foamed grouting material in the foaming chamber to the top of the goaf. By utilizing the foaming expansion property of the foaming material, the top of the goaf is fully filled, achieving a high degree of sealing effect as much as possible.

[0077] Furthermore, the monitoring and control components are installed in the upper and lower regions of the outer wall 3 of the casing. The monitoring and control components include a pressure monitoring device 11, a flow rate control device 12, a thermal imaging camera 13, and a smoke sensor 14, which are used to monitor the grouting pressure, adjust the grouting flow rate, and monitor the internal temperature and leakage of the goaf, respectively.

[0078] Specifically, the pressure monitoring device 11 and the flow rate control device 12 are installed in the upper area of ​​the outer wall 3 of the casing. The pressure monitoring device 11 monitors the pressure changes of the grouting fluid in real time during the grouting process and feeds back the monitored pressure data to the operator in real time, providing data support for parameter adjustment and ensuring that the grouting pressure is within a reasonable range. This avoids casing damage or grout leakage due to excessive pressure, and insufficient grout penetration into the coal seam voids due to insufficient pressure. The flow rate control device 12 can change the grout flow environment by adjusting the opening of the internal valve core, thereby precisely controlling the flow rate of the grouting fluid to adapt to the grouting needs of coal seams at different depths. Combined with the layered grouting process, it can achieve precise grouting of coal seams at different depths, ensuring uniform filling of the grouting fluid and improving the grouting quality.

[0079] In this embodiment, the thermal imaging camera 13 and the smoke sensor 14 are installed in the lower part of the outer wall 3 of the casing. The thermal imaging camera 13 monitors the temperature distribution inside the goaf in real time and can detect problems such as local overheating and uneven solidification of grout that may occur during the grouting process in a timely manner. The smoke sensor 14 is used to detect in real time whether there are abnormalities such as grouting leakage or gas leakage inside the goaf. Once an abnormality is detected, an early warning is issued in time to ensure the safe progress of the grouting operation.

[0080] This embodiment achieves layered grouting by employing a separate design of the foaming chamber 5 and the grouting inner pipe 4, along with a composite structure of multi-layer adjustable nozzles and segmented spray holes. The device separates the foaming chamber 5 and the grouting inner pipe 4, with the inner pipe 4 running through the entire device and forming an independent, sealed foaming chamber with the outer wall 3 of the casing. The two are connected by dedicated internal and external through-holes and can be controlled independently. This structure allows for the isolated delivery of ordinary grouting slurry and foaming slurry, avoiding mutual interference and ensuring precise implementation of layered, intermittent foaming grouting. It also ensures that the expansion performance of the foaming slurry is not affected, effectively improving the foaming sealing effect at the top of the goaf and helping to achieve a filling rate of ≥95%. Furthermore, the device uses a composite structure of multi-layer adjustable nozzles 7 and segmented spray holes. A multi-layer nozzle structure is set in the middle of the outer wall 3 of the casing, with a nozzle spacing of 1m. Each group is distributed in four directions circumferentially, and the nozzle angle can be flexibly adjusted within the range of 0-30°. Simultaneously, the inner casing is segmented, with each segment being 5m long and corresponding to an adjustable-sized spray hole. Multi-layer adjustable nozzles enable stratified and multi-angle spraying of grout, precisely covering coal seam goaf areas at different depths and directions, with a stable grout diffusion radius of 5-7.5m. Segmented adjustable nozzles, by controlling their opening and closing and orifice size, adapt to the grouting flow requirements of coal seams at different depths. Combined with the nozzles, this achieves double-precision stratified grouting, avoiding material waste caused by blind grouting and improving grouting efficiency and filling effect. The integrated multi-monitoring module design enables real-time monitoring of all parameters during the grouting process. Operators can adjust parameters such as nozzle angle and orifice size based on pressure data to ensure sufficient penetration of the grout into the coal seam. Simultaneously, it promptly detects grouting leaks, localized overheating, and other abnormalities, ensuring grouting operation safety and further improving the accuracy and reliability of stratified grouting, avoiding poor grouting results due to parameter malfunctions.

[0081] Example 4 Based on the above embodiments, this embodiment verifies the effectiveness of the fire prevention and extinguishing method.

[0082] I. Preparation of Grouting Slurry: 1. The base slurry is a composite slurry of coal gangue and fly ash, of which solid waste accounts for 70%.

[0083] The prepared coal gangue-fly ash composite solid waste grouting slurry has a water-to-solid ratio of 0.9 and an initial flowability of 245 mm, exhibiting good pumpability. The mass ratio of coal gangue to fly ash is 3:7, and the initial setting time of the slurry is 45 min, which meets the construction adaptability range of 30-120 min. With the addition of 1.2% of a composite admixture of water-reducing agent and inhibitor, the final compressive strength after 7 days can reach 5.8 MPa, meeting the filling strength requirements of the goaf. The solid waste particle size is controlled at 20-80 mesh, the slurry bleeding rate is ≤3.5%, there is no segregation, and the stability is excellent.

[0084] 7-day compressive strength comparison: Traditional pulp has a strength of only 4.2 MPa, while the pulp in this example has a strength of 5.8 MPa, representing a performance improvement of 38.1%.

[0085] II. Treatment of curtain wall openings and ground cracks: 1. Numerical simulation data Arrangement parameters: curtain holes arranged in a plum blossom pattern, hole spacing 8 m, hole depth 35 m.

[0086] Sealing effect: The air leakage velocity in the curtain area decreased from 1.2 m / s to 0.08 m / s, and the air leakage rate decreased by 93.3%; Crack sealing: For surface cracks 0.5-5 cm wide, the permeability of the cracks after grouting should be ≤1×10⁻⁶. -7 m 2 / s, blocking 98% of the surface air leakage channels.

[0087] 2. Field experimental data A case study was conducted in a mining area where 128 curtain holes were arranged in three rows 10 meters outside the safety boundary of the fire zone.

[0088] Post-construction monitoring: O2 concentration inside the curtain decreased from 15.8% to 6.2%, and CO concentration decreased from 125 ppm to 32 ppm.

[0089] Crack treatment: 47 surface cracks were identified. After filling and grouting, no new cracks developed and the surface settlement was ≤15 mm.

[0090] III. Pretreatment of borehole cavities and layered grouting: 1. Experimental data on cavity treatment 156 boreholes were drilled on site, with a cavity development rate of 28.2%; Small cavities (<5 m³, 32 in total): Grouting filling rate 98.5%, no re-cavities; Large cavities (≥5 m³, 12 in total): "fill first, then grout", with a filling rate of 95.2% and a stable pressure of ≥1.2 MPa after grouting; Cavity detection accuracy: Combined detection of hole collapse, sudden change in drilling speed, and sudden decrease in slag return, with an accuracy rate of 96.8% and no missed or false detections.

[0091] 2. Layered Interval Grouting Effect Data The central area has a hole spacing of 10 m, the transition zone has a spacing of 12 m, and the injection is carried out in a skip-injection manner. Filling rate: The overall filling rate of the goaf is 94.3% (75.6% with traditional grouting, an improvement of 24.7%). Layered effect: The filling rate of the upper layer (0-10 m) is 95.8%, the middle layer (10-20 m) is 94.5%, and the lower layer (20-30 m) is 92.1%, with no filling blind spots; Slurry diffusion radius: 5.2 m in the central area and 6.8 m in the transition area, with no dead corners.

[0092] 3. Experimental data of grouting sleeve device Layered grouting accuracy: The nozzle angle is adjustable (0-360°), and the layered grouting error is ≤0.8 m; Sealing effect: After top foam sealing, the air leakage rate at the top of the goaf is reduced by 91.5%.

[0093] IV. Top Cutting and Compaction Treatment: 1. Numerical simulation data Cutting range: 10 m outward from the fire zone, area 1.2 times that of the fire zone, and height 15 m; Collapse compaction effect: The compacted density of collapsed rock is ≥1.8 t / m³, and the porosity is ≤12%; Oxygen concentration: After compaction, the O2 concentration inside the goaf is 5.2-7.8% (≤8% meets the standard), and the asphyxiation zone expands by 32%; Air leakage channels: The sealing rate of concealed air leakage channels is 99.1%, and the air leakage velocity is ≤0.05 m / s.

[0094] 2. Field experimental data The area of ​​the cut-off section of a certain mine is 2800 m². 2 234 holes were drilled for focused blasting.

[0095] Compaction effect: After the collapsed rock is compacted, the roof subsidence is ≤20 mm, and there is no risk of secondary collapse; Fire prevention and extinguishing effect: Monitoring 30 days after roof cutting showed that the CO concentration in the goaf was ≤15 ppm and the temperature was ≤27℃, with no signs of reignition; Comparative data: Traditional sealing technology has a concealed air leakage sealing rate of 65% and an O2 concentration of 10-14%, while the fire prevention and extinguishing method provided in this embodiment of the invention achieves essential oxygen barrier.

[0096] This invention provides a comprehensive, closed-loop controlled method for preventing and extinguishing spontaneous combustion of residual coal in coal mine goaf areas, which can comprehensively and effectively prevent the occurrence and spread of fires. The methods include: comprehensive determination of the fire zone: through geological exploration, coal mining history, fire monitoring, and other means, the fire zone range of spontaneous combustion in the goaf is comprehensively determined; grout preparation: according to the needs of the determined fire zone range, suitable grout, including cementing materials, water glass, etc., is prepared to ensure the grouting effect; curtain hole combined with ground crack treatment: curtain holes are set at the boundary of the fire zone, and ground cracks are treated to prevent air leakage, oxygen ingress, and fire spread; filling grouting: during the drilling process, randomly occurring voids are filled with grout before drilling continues to the known goaf; in order to grout known multi-layer goaf, grouting is controlled by combining special casing devices and corresponding equipment; grouting holes are set up in layers and layered foaming grouting: grouting holes are set up inside the goaf, and layered grouting is used to fill the grout layer by layer to achieve better fire prevention and extinguishing effect; finally, in order to completely solve the air leakage problem, in the case where no definite air leakage source can be found, large-scale roof cutting is used to recompact the fire zone. By combining layered interval grouting and curtain hole treatment with ground crack control, a three-dimensional enclosure and isolation of the fire zone can be achieved, preventing the fire from spreading to non-fire areas. Moreover, by adopting layered interval grouting, the spontaneous combustion source in the goaf can be precisely sealed and controlled, improving the fire prevention and extinguishing effect and work efficiency.

[0097] This invention breaks through the limitations of traditional single-technology prevention and control. Through a coordinated approach of "blocking, filling, pressing, and sealing," ground crack treatment and curtain openings form a vertically linked seal, blocking surface air leakage. Layered, intermittent foaming grouting and top-cutting compaction create a combined internal and external filling effect, achieving full-process coverage of fire zone location, source oxygen blocking, targeted treatment, dynamic control, and bottom-line protection. This solves the problems of traditional technologies that only treat the symptoms and not the root cause, and are prone to reignition, improving the stability and effectiveness of fire prevention and extinguishing. Furthermore, the curtain openings and ground crack treatment form a three-dimensional sealing network, ensuring precise and efficient positioning. Combined with geological surveys, sensor monitoring, and monitoring modules of specialized casing devices, positioning accuracy and efficiency are improved, significantly shortening the construction cycle and effectively preventing the spread of the disaster. The curtain openings isolate the fire zone, ground crack treatment cuts off surface oxygen penetration, and layered grouting fills internal gaps, completely blocking oxygen supply and fire spread, resulting in a more thorough and lasting isolation effect.

[0098] Furthermore, this invention precisely injects foamed grout through layered grouting to fill fire sources and air leakage channels. Grout preparation is rapid, reducing the time to 30-40 minutes, resulting in shorter operation time. Monitoring data allows for timely adjustments to the mixing ratio, avoiding material waste. It balances fire source control and potential spontaneous combustion prevention, improving fire prevention and extinguishing effectiveness and operational efficiency. Using solid waste from surrounding coal mines to prepare the grout reduces costs while achieving resource utilization of solid waste, meeting environmental protection requirements and lowering environmental treatment costs. A dedicated grouting sleeve device enables layered, intermittent foamed grouting, effectively increasing the filling rate of the goaf. The foamed material, combined with roof cutting and compaction, enhances the filling density. After roof cutting and compaction, the low oxygen concentration inside the goaf completely blocks air leakage and oxygen supply channels, reducing air leakage, inhibiting spontaneous combustion of residual coal, and preventing secondary disasters from roof collapse, achieving dual benefits of fire prevention and extinguishing and operational safety.

[0099] In the description of this invention, it should be understood that terms such as “length”, “width”, “upper”, “lower”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, and “outer” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0100] Furthermore, in the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0101] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preventing and extinguishing spontaneous combustion of residual coal in coal mine goaf areas, characterized in that, Includes the following steps: S1. Determination of the fire zone: Based on geological exploration parameters, historical coal mining data and fire monitoring data, the range of the spontaneous combustion fire zone in the goaf is determined, and the safety boundary of the fire zone is also determined. S2. Grouting slurry preparation: Solid waste is selected as the main raw material, combined with cementing materials, water and additives to prepare grouting slurry; S3. Curtain hole combined with ground crack treatment: Multiple curtain holes are arranged 10 m outside the fire zone safety boundary. At the same time, mining-induced ground cracks are identified and sealed to form a three-dimensional sealing system. S4. Pretreatment of borehole cavities: If a cavity is determined during the drilling of the grouting hole, drilling shall be stopped and a grouting casing device shall be used to fill it with liquid grout. After confirming that the cavity is filled, drilling shall continue. S5. Interval layered foaming grouting: Grouting holes are arranged inside the goaf, and grouting sleeve devices are used to implement the grouting sequence of intermittent skipping and grouting from the periphery to the center. Combined with layered grouting, the goaf is accurately filled in layers. S6. Real-time monitoring and parameter adjustment: Monitor the fire zone range and grouting effect, analyze monitoring data, and adjust parameters; S7. Roof cutting and compaction treatment: If there are hidden air leakage channels that cannot be located, roof cutting should be carried out to ensure that the oxygen concentration inside the goaf meets the standard.

2. A method for preventing and extinguishing spontaneous combustion of residual coal in a coal mine goaf according to claim 1, characterized in that, When determining the fire zone, the three zones of the fire zone are first determined: the oxidation zone with a thickness of 5-15 m, the asphyxiation zone with a thickness of 10-25 m, and the heat dissipation zone with a thickness of 8-20 m. At the same time, the boundary distance for a temperature ≤30 ℃ is determined by the influence range of temperature conduction in the fire zone. The fire zone boundary is defined as a safety boundary extending 10 m outward from the isopleths of CO concentration of 100 ppm and temperature of 30 ℃.

3. A method for preventing and extinguishing spontaneous combustion of residual coal in a coal mine goaf according to claim 1, characterized in that, The solid waste includes one or more of coal gangue, tailings, fly ash, and slag, with a transportation distance of ≤5km; the solid waste accounts for 60-80%, the water-to-solid ratio is 0.8-1.0, the additive dosage is 0.5-2.0%, and the slurry hardening time is set at 30-120 min.

4. A method for preventing and extinguishing spontaneous combustion of residual coal in a coal mine goaf according to claim 1, characterized in that, In S3, a dual sealing measure of surface cracks and curtain holes is adopted; First, one or more of the following methods are used to identify ground cracks induced by mining: ground monitoring, geological exploration, ground measurement, remote sensing image analysis, and monitoring sensors. Next, the curtain hole arrangement is carried out. The curtain hole positions are arranged in a plum blossom shape, and the hole depth penetrates the goaf and extends 2m into the bottom plate. Then, the cracks are sealed in three dimensions, using a combination of filling and grouting to treat the cracks.

5. A method for preventing and extinguishing spontaneous combustion of residual coal in a coal mine goaf according to claim 1, characterized in that, During the drilling and grouting process, grouting holes are set up at intervals to divide the central area and the transition area. The drilling spacing is divided according to the area, with a hole spacing of 10 m in the central area and 12 m in the transition area. The grouting material is cement-water glass double liquid grout or fly ash-cement composite grout. The water-cement ratio of cement-water glass double liquid grout is 0.7-1. The criteria for determining a cavity are borehole collapse, sudden changes in drilling speed, or a sharp decrease in the amount of cuttings returned during drilling. The type of cavity is determined based on the situation of adjacent boreholes at the same depth. When the volume is <5 m³ 3 The cavity is a small cavity; volume ≥ 5 m³ 3 The cavity is a large cavity; After filling the identified voids, continue drilling until the voids where spontaneous combustion of coal occurred are filled, with a void filling rate of ≥90%.

6. A method for preventing and extinguishing spontaneous combustion of residual coal in a coal mine goaf according to claim 1, characterized in that, During the drilling and grouting process, the grouting holes are arranged in a quincunx pattern, with a hole spacing of 10 m in the central area, a hole spacing of 12 m in the transition area, and 25° inclined holes in the edge area; the grouting sequence is to skip grouting every 1-2 holes, first the periphery and then the center. The foaming slurry is prepared using cement, chemical foaming agent, and inhibitor. The mass ratio of cement to chemical foaming agent is 100:2-5, the amount of inhibitor is 1.0-2.0% of the cement mass, the water-cement ratio is 0.8-1.0, and the foaming process takes 30-40 minutes.

7. A method for preventing and extinguishing spontaneous combustion of residual coal in a coal mine goaf according to claim 1, characterized in that, Fire zone monitoring adopts an integrated monitoring system, which is equipped with a pressure monitoring module, a flow rate adjustment module, a thermal imaging camera and a smoke sensor, with a monitoring point spacing of 10-15 m; grouting effect monitoring adopts a flow meter and a pressure sensor, with a monitoring point spacing of 5-10 m; when the fire zone expands by ≥2 m in a single day or the goaf filling rate is <85%, the grout mix ratio, grouting hole arrangement or curtain hole position are adjusted.

8. A method for preventing and extinguishing spontaneous combustion of residual coal in a coal mine goaf according to claim 1, characterized in that, In S7, the cut-off area is a rectangular area within 10 m outside the fire zone boundary, the cut-off area is ≥ 1.2 times the fire zone area, the cut-off height is 15 m and not less than the height of the collapse zone; the boreholes are parallel to the working face, with a hole spacing of 1 m and a row spacing of 1.5 m, and shaped charge blasting is used. After the collapsed rock is compacted, the oxygen concentration inside the goaf is ≤ 8%.

9. A method for preventing and extinguishing spontaneous combustion of residual coal in a coal mine goaf according to any one of claims 1-8, characterized in that, The grouting casing device includes a connecting assembly, a monitoring and control assembly, a grouting injection assembly, a sealing and filling assembly, and a support assembly. The connecting assembly is used to connect the device to external grouting equipment and to splice multiple devices. The support assembly provides support for the entire device and forms mutually isolated grouting and foaming channels inside, realizing the isolated transportation of ordinary grouting slurry and foaming slurry. The monitoring and control assembly is used to monitor grouting process parameters in real time and accurately adjust the grouting state. The grouting injection assembly is used to realize layered and multi-angle precise grouting in the goaf. The sealing and filling assembly is used to achieve foam sealing of the top of the goaf.

10. A method for preventing and extinguishing spontaneous combustion of residual coal in a coal mine goaf according to claim 9, characterized in that, The connecting assembly includes an upper flange and a lower flange. The upper flange is connected to the external grouting equipment, and the lower flange matches the structural dimensions of the upper flange. The supporting assembly includes an outer casing wall and an inner grouting pipe. A closed foaming channel is formed between the outer casing wall and the inner grouting pipe, and the two are connected by uniformly arranged internal and external through holes. The monitoring and control assembly includes a pressure monitoring device, a flow rate control device, a thermal imaging camera, and a smoke sensor, which are used to monitor grouting pressure, adjust grouting flow rate, monitor internal temperature and leakage in the goaf, respectively. The grouting and spraying assembly includes nozzles, nozzle controls, and spray holes. The nozzles are arranged in multiple layers and directions, with multiple nozzles evenly distributed circumferentially in each group. The nozzle angle is adjustable. The spray holes are arranged in segments. The sealing and filling assembly includes a foaming chamber and a foaming nozzle. The foaming chamber is connected to the foaming channel. The foaming nozzle is used to spray foaming slurry onto the top of the goaf.

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