Methods for preventing and extinguishing fires in open-pit coal seams

Abstract

This invention relates to the field of fire prevention and extinguishing technology, specifically to a method for preventing and extinguishing coal seams in open-pit mines. The method includes: selecting different extinguishing methods based on pre-obtained combustion parameters of the fire zone at the location of the open-pit mine, coal seam occurrence parameters, and geological parameters; wherein the extinguishing methods include at least one of grouting extinguishing, backfilling isolation, and stripping; determining the slope cutting angle based on the slope stability of the fire zone; determining the coal spontaneous combustion depth based on coal spontaneous combustion exploration parameters; determining the fire zone range based on the slope cutting angle and coal spontaneous combustion depth; and extinguishing the fire in the fire zone using the selected extinguishing method. Embodiments of this invention provide a method for preventing and extinguishing coal seams in open-pit mines that can improve fire extinguishing effectiveness.

Description

Technical Field

[0001] This invention relates to the field of fire prevention and extinguishing technology, specifically to a method for preventing and extinguishing fires in open-pit coal seams. Background Technology

[0002] During the mining process of open-pit coal mines, exposed coal seams are prone to spontaneous combustion. Moreover, due to the disturbance caused by excavation, a large amount of air enters the interior of the residual coal. As the air continuously enters, it provides oxygen to the residual coal, which can easily ignite new spontaneous combustion points and fire zones. The fire prevention and extinguishing methods used in related technologies for open-pit mines are mainly water-based methods and isolation methods. However, water-based methods and isolation methods are not very effective in extinguishing spontaneous combustion of residual coal in deep areas. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a method for preventing and extinguishing fires in open-pit coal seams, which can improve fire extinguishing effectiveness.

[0004] The open-pit coal seam fire prevention and extinguishing method of this invention includes:

[0005] Different fire extinguishing methods are selected based on the combustion parameters of the fire zone, the occurrence parameters of the coal seam, and the geological parameters of the open-pit mine location obtained in advance. The fire extinguishing methods include at least one of the following: grouting fire extinguishing method, backfilling isolation method, and stripping method.

[0006] The slope cutting angle is determined based on the slope stability of the fire zone.

[0007] Determine the depth of spontaneous combustion of coal based on coal spontaneous combustion exploration parameters;

[0008] The ignition zone range is determined based on the slope angle and the coal spontaneous combustion depth.

[0009] The selected fire extinguishing method will be used to extinguish the fire in the affected area.

[0010] In some embodiments, determining the depth of spontaneous combustion of coal based on coal spontaneous combustion exploration parameters includes:

[0011] Geophysical exploration was used to determine the temperature anomaly zone;

[0012] Pilot drilling is used to determine the temperature anomaly zone;

[0013] If the temperature inside the hole is greater than 400℃, it is determined to be the ignition point;

[0014] The depth of spontaneous combustion of coal is determined based on the ignition depth of the ignition point.

[0015] In some embodiments, the grouting fire extinguishing method includes:

[0016] The spacing of the grouting boreholes is determined based on geological parameters;

[0017] The depth of the grouting borehole is determined based on the spontaneous combustion depth of the coal.

[0018] The number of grouting boreholes is determined based on the temperature parameters of the ignition point;

[0019] Grouting holes are drilled in sequence at intervals according to their spacing, depth, and number, and grout is injected into the ignition point.

[0020] In some embodiments, the grouting borehole includes a first grouting borehole, a second grouting borehole, and a third grouting borehole, wherein the interval sequence is a three-stage interval construction and the third grouting borehole is used as an inspection borehole.

[0021] In some embodiments, the grouting fire extinguishing method further includes: inspecting the fire extinguishing status of the grouting borehole.

[0022] In some embodiments, inspecting the fire extinguishing status of the grouting borehole includes:

[0023] Set up inspection boreholes to detect the temperature at the ignition point;

[0024] If the temperature of the entire borehole is less than 100℃, the fire is considered extinguished.

[0025] In some embodiments, the slurry includes fly ash slurry, clay slurry, and fly ash clay slurry, wherein the water-cement ratio of the fly ash slurry is 5:1-1:1.3, the fly ash concentration is ≥15%, the water-cement ratio of the clay slurry is 3:1-1:2, and the water-solid ratio of the fly ash clay slurry is 5:1-1:1.3.

[0026] In some embodiments, the grout injection volume is: Q 浆 = K×H×S×n×η / a, where Q 浆 Grouting volume / m 3 K is the grouting backup coefficient, with a value ranging from 1.05 to 1.20; H is the coal spontaneous combustion depth (m); S is the plane area of ​​abnormal coal seam temperature within the fire zone (m²). 2 n is the porosity of the coal and rock mass in the fire zone, with a value of 0.15-0.30; η is the slurry filling coefficient, with a value of 0.85-0.95; and a is the slurry stone-forming rate.

[0027] In some embodiments, the slope is cut by gradually leveling the slope from the top to the bottom.

[0028] In some embodiments, the backfill isolation method includes:

[0029] For the exposed coal seam resulting from stripping, excavate 10-30 meters inward into the slope in a direction perpendicular to the slope.

[0030] The excavated area is backfilled with loess or grout is injected to form a protective isolation zone. Attached Figure Description

[0031] Figure 1 This is a schematic flowchart of an open-pit coal seam fire prevention and extinguishing method according to an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the process for determining the spontaneous combustion depth of coal according to an embodiment of the present invention. Detailed Implementation

[0033] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0034] like Figure 1 As shown, the open-pit coal seam fire prevention and extinguishing method of this invention includes: selecting different fire extinguishing methods based on the combustion parameters of the fire zone, the occurrence parameters of the coal seam, and the geological parameters of the fire zone at the location of the open-pit mine, wherein the fire extinguishing methods include at least one of grouting fire extinguishing method, backfilling isolation method, and stripping method; determining the slope cutting angle based on the slope stability of the fire zone; determining the coal spontaneous combustion depth based on the coal spontaneous combustion exploration parameters; determining the fire zone range based on the slope cutting angle and the coal spontaneous combustion depth; and extinguishing the fire in the fire zone range using the selected fire extinguishing method.

[0035] Specifically, geological parameters refer to the natural geographical environment parameters of the fire zone at the location of the open-pit mine. Different fire extinguishing methods are selected based on the combustion parameters, coal seam occurrence parameters, and natural geographical environment parameters of the fire zone at different locations of open-pit mines.

[0036] It should be noted that the stripping method involves removing spontaneously combusting coal by stripping it away based on the surveyed fire zone's extent. The grouting method involves drilling and injecting grout to lower the fire zone temperature below the coal's spontaneous combustion critical temperature. Grouting seals fault fissures, goafs, and roadways, reducing air leakage within the coal seam. This method is suitable for fire zones with excessively high temperatures during stripping or for remaining unstripped fire zones, disrupting the heat storage environment to achieve fire prevention and extinguishing. The backfilling isolation method involves further excavating to a certain depth in newly exposed goafs or solid coal seams after slope stripping, then backfilling with loess or injecting high-concentration fly ash slurry to isolate residual coal from air, effectively blocking oxygen supply channels to achieve fire prevention and extinguishing.

[0037] In this embodiment of the invention, after determining the slope cutting angle based on the slope stability of the fire zone, the fire zone of the slope is stripped. After stripping and excavation, the fire zone is divided into a burning zone and an unburned zone. The burning zone is extinguished using the grouting method, while the newly exposed coal seams, goafs and roadways in the unburned zone are protected using the grouting method and backfilling isolation method to prevent spontaneous combustion of coal in the unburned zone later.

[0038] In determining the spontaneous combustion depth of coal, this invention first determines the spontaneous combustion temperature distribution characteristics based on coal spontaneous combustion exploration parameters, then determines the spontaneous combustion depth, and subsequently determines the vertical fire prevention and extinguishing depth. For example, for planar coal gangue, spontaneous combustion generally occurs on the slope, with a spontaneous combustion depth of about 2.5m. The coal seam surface cannot store heat, and further depths will not burn due to lack of air. Based on experience, the vertical treatment range for shallow fire zones is determined to be 30-50m. For underground coal seams, due to faults or roadways forming oxygen supply channels, deep fire zones are easily formed. The spontaneous combustion depth is determined based on the location of the goaf and the actual fire depth. This invention employs different extinguishing methods for the fire zone and the unfired zone to ensure rapid fire extinguishing in the fire zone, keeping the fire temperature below the critical spontaneous combustion temperature. Meanwhile, the newly exposed coal seam, goaf, roadway, and fault structure stripped from the slope form a protective isolation layer of a certain width, effectively blocking the oxygen supply channels to improve the fire extinguishing effect.

[0039] For example, when the fire zone is only on the surface of the coal seam, the stripping method is chosen to remove the spontaneous combustion source for fire extinguishing. For the newly exposed unburned coal seams, goafs, and roadways after stripping, grouting and backfilling methods are used to prevent fire extinguishing. Compared with the problem of potential reignition of surface ash after stripping in related technologies, the embodiments of this invention use a combination of stripping and backfilling methods for fire extinguishing, that is, backfilling loess on the stripped surface ash, which makes the fire extinguishing effect more thorough and thus improves the fire extinguishing effect.

[0040] Before carrying out fire prevention and extinguishing work, the surface temperature of the fire area is lowered by a combination of ground water spraying, water injection, or grouting. This can quickly displace the heat in the accessible surface area, eliminate the high temperature in the lower part in advance, and facilitate subsequent fire prevention and extinguishing operations. Then, the fire can be extinguished in the fire area according to the selected fire extinguishing method.

[0041] In some embodiments, such as Figure 2 As shown, determining the spontaneous combustion depth of coal based on coal spontaneous combustion exploration parameters includes: using geophysical exploration to identify temperature anomaly zones; using pilot drilling in the temperature anomaly zones for judgment; if the temperature inside the borehole is greater than 400℃, it is determined to be the ignition point; and determining the spontaneous combustion depth of coal based on the ignition depth of the ignition point.

[0042] Specifically, based on the geophysical exploration results, the temperature anomaly zone is determined, and then the location of the pilot borehole is determined. The probe is inserted into the ground through the pilot borehole to detect the underground temperature, so as to determine whether the temperature anomaly zone is the ignition point. By combining geophysical exploration and pilot borehole methods to determine the ignition point, the accuracy of the ignition point location is improved. Moreover, the pilot borehole can also determine the depth of the ignition point, thereby determining the depth of coal spontaneous combustion.

[0043] For example, geophysical exploration can use drones to fly over the surface of an open-pit mine to identify areas of temperature anomalies.

[0044] In some embodiments, the grouting fire extinguishing method includes: determining the spacing of grouting boreholes according to geological parameters; determining the depth of grouting boreholes according to the spontaneous combustion depth of coal; determining the number of grouting boreholes according to the temperature parameters of the ignition point; drilling boreholes in a staggered sequence according to the spacing, depth, and number of grouting boreholes, and injecting grout into the ignition point.

[0045] Specifically, the parameters of the grouting borehole are determined based on geological parameters, coal spontaneous combustion depth, and temperature parameters of the ignition point. Then, the borehole is drilled and grout is injected according to the determined parameters. By destroying the heat storage environment, the fire prevention and extinguishing effect on the ignition point area is achieved.

[0046] It should be noted that if grouting is not performed in a timely manner after large-scale stripping and excavation of the slope, the disturbance caused by the excavation will result in a large amount of air entering the residual coal, which can easily trigger new spontaneous combustion points and fire zones, greatly increasing the risk of spontaneous combustion and the number of ignition points. This embodiment of the invention uses a combined stripping and excavation method and a grouting method for fire suppression. Specifically, during the slope stripping process, grouting operations are carried out in parallel. The location of the grouting boreholes is determined according to the location of the fire point, and fly ash slurry or loess slurry is injected into the fire area to achieve the purpose of extinguishing the fire and filling voids and fissures. After the fire source in the grouting area is eliminated and the fissures are sealed, the next stage of flat-plate fire suppression work is carried out.

[0047] In this embodiment of the invention, the grouting material is finely granulated and then mixed with water and additives to prepare a slurry. This slurry is then hydraulically transported to the fire prevention and extinguishing area. This process can seal air leakage channels, encapsulate coal and rock to prevent oxidation, and cool the temperature of the coal and rock, thereby achieving the effect of fire prevention and extinguishing.

[0048] In some embodiments, the grouting borehole includes a first grouting borehole, a second grouting borehole, and a third grouting borehole, with the three grouting boreholes being constructed at intervals and the third grouting borehole serving as an inspection borehole.

[0049] Specifically, in this embodiment of the invention, grouting drilling is carried out using a three-stage interval construction method. That is, after the first grouting borehole is completed, the second grouting borehole is constructed, and after the second grouting borehole is completed, the third grouting borehole is constructed. The second grouting borehole is adjusted based on the grout absorption and diffusion of the grout in the formation of the first grouting borehole, and the third grouting borehole is adjusted based on the grout absorption and diffusion of the grout in the formation of the second grouting borehole, thereby improving the fire extinguishing effect of the grouting fire extinguishing method.

[0050] In some embodiments, the grouting fire extinguishing method further includes: inspecting the fire extinguishing status of the grouting borehole.

[0051] Specifically, by inspecting the fire extinguishing performance of the grouting boreholes, the effectiveness of the grouting fire extinguishing method can be determined, thereby improving its reliability.

[0052] In some embodiments, inspecting the fire extinguishing status of the grouting borehole includes: setting up an inspection borehole to detect the temperature of the ignition point; if the overall borehole temperature of the inspection borehole is less than 100°C, the fire is determined to be extinguished.

[0053] Specifically, when inspecting the extinguishing effect of the grouting method, the temperature of the ignition point can be detected by setting up inspection boreholes. Inspection boreholes can be set up individually, or some third grouting boreholes can be used as inspection boreholes to inspect the grouting extinguishing effect. By detecting the temperature of the entire inspection borehole, if the highest temperature of the entire borehole is less than 100℃, and the highest temperature of more than 90% of the inspection boreholes is stable below 70℃, then the grouting method is determined to have extinguished the fire.

[0054] Optionally, when inspecting a surface fire zone, the disappearance of surface fire symptoms and the absence of pungent smoke can be used as the inspection standard to determine whether the surface fire zone has achieved the desired fire extinguishing effect.

[0055] In some embodiments, the slurry includes fly ash slurry, clay slurry, and fly ash clay slurry, wherein the water-cement ratio of the fly ash slurry is 5:1-1:1.3 and the fly ash concentration is ≥15%, the water-cement ratio of the clay slurry is 3:1-1:2, and the water-solid ratio of the fly ash clay slurry is 5:1-1:1.3.

[0056] Specifically, the fly ash slurry is a stable slurry with suitable concentration and good fluidity formed by stirring water, fly ash, and additives. It is mainly used for grouting residual coal fissures in the ignition zone, and can also be used for grouting and filling roadways or goaf areas. The water-ash ratio of the slurry is designed to be 5:1-1:1.3, and the fly ash slurry concentration is greater than 15%, that is, it should not be lower than 15%. For example, a water-ash ratio of 1:0.6. This embodiment of the invention does not impose specific limitations on the water-ash ratio and concentration of the fly ash slurry; the actual implementation shall prevail.

[0057] Clay slurry is a stable slurry with suitable concentration and good fluidity, formed by stirring water, clay, and additives. The critical stabilization time of the slurry is 20-60 minutes. Clay slurry has good permeability and is easy to transport. It is mainly used for filling tunnels and goaf cavities, with a water-cement ratio ranging from 3:1 to 1:2. For example, when using clay slurry to fill the fissures of residual coal in a fire zone, an appropriate amount of lime can be added. When using mud slurry for fire extinguishing, the water-soil ratio is 8:1-3:1.

[0058] Fly ash clay slurry is a stable slurry with suitable concentration and good fluidity formed by mixing water, fly ash, clay and additives. It is used to fill the fissures of residual coal in the ignition zone and the voids in the roadway. The clay material needs to be pre-crushed before entering the mixing tank to mix with fly ash. The water-solid ratio of the slurry is in the range of 5:1-1:1.3. The mass ratio of clay to fly ash is determined according to the actual implementation.

[0059] It should be noted that the types of grouting target layers are quite extensive, including fire zones, goaf zones, partial goaf zones, roadways, mining-induced fractures, and fault fractures. The spatial dimensions and fracture sizes of the grouting target layers vary, resulting in significant differences in injectability. Therefore, various types of grouts with different properties are required. For example, for areas with large-scale fires, fly ash-lime grout can be appropriately injected. Low-concentration grouts are generally prepared inert filling materials, which, in addition to lowering the temperature, can also seal formation fractures. For goaf zones and roadway voids, a certain amount of high-concentration grout needs to be injected. This invention does not specifically limit the type of grout for the grouting target layers; the actual implementation shall prevail.

[0060] For example, since fly ash slurry is alkaline, which is beneficial for extinguishing spontaneous combustion of residual coal, when using fly ash slurry or fly ash clay slurry in the residual coal ignition zone, lime can be added. The amount of lime added should not exceed half the weight of the clay or fly ash, for example, the amount of lime added is 10-50%. The extinguishing slurry is a low-concentration slurry, and the water-cement ratio of the slurry is designed to be 5:1-1:1. The grouting extinguishing effect can be improved by adding lime to the slurry.

[0061] For example, when filling and grouting tunnels and goaf cavities, fly ash slurry, clay slurry, or fly ash clay composite slurry can be selected. In specific implementation, high-concentration slurry can be selected, and pumping agents can be added to the slurry to increase its fluidity. The water-ash ratio of the slurry is designed to be 2:1-1:2.

[0062] In this embodiment of the invention, grouting is performed inside the grouting borehole to basically fill the fissures in the fire zone. Grouting is stopped after the fire zone is in a closed state, that is, when the temperature of coal, rock and gas in the fire zone drops below 100°C and there is no upward trend within 48 hours, grouting is stopped.

[0063] In some embodiments, the grout injection volume is: Q 浆= K×H×S×n×η / a, where Q 浆 Grouting volume / m 3 K is the grouting backup coefficient, with a value ranging from 1.05 to 1.20; H is the coal spontaneous combustion depth (m); S is the plane area of ​​abnormal coal seam temperature within the fire zone (m²). 2 n is the porosity of the coal and rock mass in the fire zone, with a value of 0.15-0.30; η is the slurry filling coefficient, with a value of 0.85-0.95; and a is the slurry stone-forming rate.

[0064] In this embodiment of the invention, the void volume of the ignition zone can be calculated by analyzing the porosity of the residual coal ignition zone, the spontaneous combustion depth of the coal, and the range of the ignition zone. Combined with the filling performance of fly ash slurry, the grouting volume can be calculated.

[0065] For example, the slurry stone formation rate is obtained through actual laboratory measurements.

[0066] It should be noted that due to the different slope angles of the stripping method, the newly exposed goaf and coal seam areas will vary, resulting in different grouting volumes. When grouting, a centralized or zoned approach can be adopted. During the grouting process, grouting parameters can be dynamically adjusted based on grouting construction data to improve the grouting effect, thereby enhancing the fire extinguishing effect of the grouting fire extinguishing method.

[0067] In some embodiments, the slope is cut by gradually leveling the slope from the top to the bottom.

[0068] Specifically, when using the stripping method to cut slopes in fire zones, the slope is cut from top to bottom, leveling each section one by one. For cases of spontaneous combustion in the shallow part of the slope, the ignition source is eliminated by directly excavating the slope, thus eliminating the spontaneous combustion source. For fire zones with excessively high temperatures, water or grout can be injected to cool them down before stripping operations.

[0069] According to the fire zone location, this invention employs a stripping and excavation method to completely remove the fire source when the fire depth is near the slope cut line, only drilling and grouting are performed on newly exposed coal seams or goaf areas. After stripping and excavation, the slope is leveled. For areas where the fire zone is located at a significant depth below the slope cut line, the total excavation workload is substantial. Therefore, during the first-stage slope cutting and leveling operation, grouting is performed on the fire zone after drilling conditions are met. After fire extinguishing, the next stage of slope cutting and leveling and fire extinguishing operations are carried out step by step. This invention improves the fire extinguishing effect by combining the stripping and excavation method with the grouting method.

[0070] For example, the slope cutting angle is 36°, 33°, or 25°. The slope cutting angle refers to the angle between the slope surface and the horizontal line. The slope cutting angle is determined based on the slope stability. The smaller the slope, the more stable it is. This embodiment of the invention does not specifically limit the slope cutting angle. The actual slope cutting angle is determined by the slope stability during specific implementation.

[0071] In some embodiments, the backfill isolation method includes: excavating the exposed coal seam generated by stripping 10-30 meters into the slope in a direction perpendicular to the slope; and backfilling the stripped area with loess or injecting grout to seal it and form a protective isolation zone.

[0072] Specifically, in the embodiments of the present invention, in the unburned area of ​​the slope stripping operation, the newly exposed goaf or roadway generated by the stripping is grouted and sealed. The new coal seam generated by the stripping is excavated along the coal seam dip for 10-30m, and then backfilled with loess or injected with high-concentration slurry to seal it, forming a protective isolation zone. The new exposed coal seam or goaf generated by the slope stripping is sealed and isolated by the backfilling isolation method, thereby improving the fire extinguishing effect.

[0073] The open-pit coal seam fire prevention and extinguishing method of this invention is applied in an open-pit mine where there are multiple spontaneous combustion points. The fire areas in some areas have expanded and merged into one large fire area. Based on the terrain conditions of the open-pit mine, the situation of the spontaneous combustion zone of residual coal, and the construction environment inside and outside the site, the fire area is divided into 18 fire areas and treated in different areas.

[0074] Example 1

[0075] The eastern fire zone of the open-pit mine covers an area of ​​approximately 334,300 square meters and consists of four fire zones. Fire Zone 1 is located near E2750 and N870, covering approximately 81,300 square meters; Fire Zone 2 is located near E2400 and N760, covering approximately 120,900 square meters; Fire Zone 3 is located near E2380 and N620, covering approximately 63,000 square meters; and Fire Zone 4 is located near E2400 and SN0, covering approximately 69,200 square meters.

[0076] The fire in the eastern part of the open-pit mine is severe, involving the main coal mines in the vicinity, including the Laowuqi Mine, the Eastern Mine, and the former Gaode Coal Mine. The upper part of the fire is caused by air leakage in the goaf and roadways of the Laowuqi Mine, leading to spontaneous combustion of the intermediate coal seam. The lower part is caused by air leakage in the goaf and roadways of the Eastern Mine and the former Gaode Mine, leading to spontaneous combustion of the Taiping coal seam. Furthermore, the gangue discharged from the open-pit mine adheres to the upper part of the pit bottom. Due to insufficient separation of the gangue and raw coal, the gangue has a high calorific value, approximately 800 to 1500 calories, which spontaneously combusts under sufficient oxidation. Based on the causes of spontaneous combustion in the eastern part of the open-pit mine, and considering the coal seam's occurrence and geological parameters, a combination of stripping, grouting, and backfilling methods is used for fire suppression. Specifically, surface cooling and leveling are applied by spraying water, while deeper areas are treated with cooling water, excavation and replacement, and partial grouting for sealing.

[0077] Example 2

[0078] The central fire zone in the open-pit mine covers an area of ​​approximately 154,600 square meters, comprising four fire zones. Specifically, Fire Zone 5, located near E2100 and N550, covers approximately 72,300 square meters; Fire Zone 9, located near E1050 and N280, covers approximately 52,300 square meters; Fire Zone 10, located near E1230 and N100, covers approximately 23,800 square meters; and Fire Zone 12, located near E460 and N100, covers approximately 6,100 square meters.

[0079] The ignition of the coal seams in Fire Zone No. 5 mainly consisted of the Taiping seam and the internal gangue. There were two factors that triggered the fire. First, the residual coal in the goaf and roadways formed by mining in the eastern mine and Gaohai Coal Mine had sufficient oxidation conditions and continuous air leakage, providing sufficient continuous oxygen supply. The heat generated by oxidation could not be dissipated, thus causing spontaneous combustion. Second, the internal gangue in the open-pit mine was attached to the upper part of the pit bottom. Due to insufficient separation of gangue and raw coal, the internal gangue had a high calorific value, about 800 to 1500 calories, which caused spontaneous combustion during sufficient oxidation. Based on the causes of spontaneous combustion in fire zone No. 5, combined with the occurrence parameters and geological parameters of the coal seam, a combination of stripping, grouting, and backfilling methods was adopted for fire extinguishing. For the surface, water spraying for cooling and excavation for leveling were recommended. For the deeper parts, water spraying for cooling, excavation and replacement, and partial grouting for sealing were adopted. At the same time, sorting and screening of coal gangue with calorific value were carried out to make full use of it, prevent reignition, and improve the fire prevention and extinguishing effect.

[0080] The spontaneous combustion of fire zone 9 was caused by gangue from the open-pit mine adhering to the north slope and pit bottom. Insufficient separation of gangue and raw coal resulted in a high calorific value of gangue, approximately 800 to 1500 calories. Spontaneous combustion occurred during full oxidation. For fire zone 9, a combination of excavation and backfilling isolation methods was used for fire extinguishing. Specifically, excavation and replacement were carried out, and the calorific value portion was fully utilized to prevent reignition.

[0081] Fire zones 10 and 12 were formed by the spontaneous combustion of exposed coal at the bottom of the pit after full oxidation. The calorific value of the exposed coal is about 2000 to 2500 calories. In this embodiment of the invention, the fire is extinguished by a combination of stripping and backfilling isolation methods. After cooling by water spraying, the coal is excavated, sorted and utilized, and the area is covered with graded rock and soil.

[0082] Example 3

[0083] The northern fire zone of the open-pit mine covers an area of ​​approximately 56,900 square meters and consists of four fire zones. Fire zone 8 is located near E920 and N650, with an area of ​​approximately 6,800 square meters; fire zone 7 is located near E980 and N820, with an area of ​​approximately 32,100 square meters; fire zone 6 is located near E1000 and N1100, with an area of ​​approximately 5,700 square meters; and fire zone 11 is located near E200 and N1120, with an area of ​​approximately 11,800 square meters.

[0084] The spontaneous combustion in the northern fire zone of the open-pit mine is caused by the adhering of gangue from the mine's internal dumping area to the northern slope. Insufficient separation of gangue and raw coal results in a high calorific value (approximately 800 to 1500 calories) in the gangue, leading to spontaneous combustion during full oxidation. To address this spontaneous combustion phenomenon in the northern fire zone, this invention employs a combination of excavation and backfilling for fire suppression. Measures include water spraying for cooling, excavation and replacement, and slope leveling. Furthermore, sorting and screening are carried out to fully utilize the calorific value of the coal gangue, preventing reignition.

[0085] Example 4

[0086] The western fire zone of the open-pit mine covers an area of ​​approximately 76,200 square meters, comprising five fire zones. Fire zone 13 is located near W360 and N1200, covering an area of ​​approximately 26,300 square meters; fire zone 14 is located near W540 and N930, covering an area of ​​approximately 9,900 square meters; fire zone 15 is located near W600 and N830, covering an area of ​​approximately 2,300 square meters; fire zone 16 is located near W660 and N1050, covering an area of ​​approximately 5,600 square meters; and fire zone 17 is located near W700 and N900, covering an area of ​​approximately 32,000 square meters.

[0087] The spontaneous combustion in Fire Zone 13 was caused by gangue from the open-pit mine adhering to the north slope. Insufficient separation of gangue and raw coal resulted in a high calorific value (approximately 800-1500 calories) in the gangue, leading to spontaneous combustion during thorough oxidation. To address this spontaneous combustion phenomenon, this embodiment of the invention employs a stripping and excavation method for fire extinguishing. This involves leveling the slope, removing the source of spontaneous combustion, and then separating and screening the calorific value portion for full utilization to prevent reignition.

[0088] Fire zones 14, 16, and 17 were severely burned. The burning coal seams were mainly the deep Sunben and Taiping seams. The ignition factor was the residual coal in the goaf and roadways formed by the Xinghai West Coal Mine and Taiping Fifth Pit mining. Due to sufficient oxidation conditions and continuous air leakage, sufficient oxygen supply was provided. The heat generated by oxidation could not be dissipated, leading to spontaneous combustion. To address the cause of spontaneous combustion, a combination of excavation and grouting methods was used for fire suppression. Surface treatment included water spraying for cooling and slope leveling, while deeper areas were treated with water spraying for cooling and grouting for sealing.

[0089] Fire Zone No. 15 was caused by the spontaneous combustion of exposed coal on the northwest slope after full oxidation. The calorific value of the exposed coal was approximately 2000 to 2500 calories. This embodiment of the invention employs a combination of excavation and backfilling methods for fire extinguishing. Specifically, water is sprayed to cool the area before excavation, and the excavated material is sorted and reused. The area is then covered with graded soil and rock to prevent reignition.

[0090] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0091] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0092] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0093] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that they are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0094] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0095] It is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preventing and extinguishing fire in a coal seam of an open-pit mine, characterized in that, The method comprises the following steps: selecting different fire extinguishing methods according to the combustion parameters of the fire area at the location of the open-pit mine, the occurrence parameters and the geological parameters of the coal seam, wherein the fire extinguishing methods include grouting fire extinguishing method, backfilling isolation method and stripping method; determining the slope cutting angle according to the slope stability of the fire area; determining the coal spontaneous combustion depth according to the coal spontaneous combustion exploration parameters, which comprises the following steps: adopting geophysical prospecting to determine the temperature anomaly area; adopting pilot drilling to determine the temperature anomaly area; if the temperature in the hole is greater than 400 DEG C, it is determined that it is an ignition point; determining the coal spontaneous combustion depth according to the ignition depth of the ignition point; determining the ignition area range according to the slope cutting angle and the coal spontaneous combustion depth; extinguishing the ignition area range by the selected fire extinguishing method; after determining the slope cutting angle according to the slope stability of the fire area, stripping the slope fire area, and after stripping and excavating, the fire area is divided into an ignition area and an unignited area, wherein the ignition area adopts the grouting fire extinguishing method for fire prevention and extinguishing, the newly exposed coal seam, goaf and roadway in the unignited area adopt the grouting fire extinguishing method and backfilling isolation method for prevention and control measures to prevent the coal in the unignited area from spontaneous combustion in the later period; the grouting fire extinguishing method comprises the following steps: determining the spacing of the grouting drill hole according to the geological parameters; determining the depth of the grouting drill hole according to the coal spontaneous combustion depth; determining the number of the grouting drill hole according to the temperature parameters of the ignition point; drilling the drill hole at intervals according to the spacing, depth and number of the grouting drill hole, and pouring grout into the ignition point; the grout comprises fly ash grout, clay grout and fly ash clay grout, wherein the water-cement ratio of the fly ash grout is 5:1-1:1.3, the fly ash concentration is greater than or equal to 15%, the water-cement ratio of the clay grout is 3:1-1:2, and the water-solid ratio of the fly ash clay grout is 5:1-1:1.3; The grouting amount of the slurry is: wherein, is the grouting amount / m 3 , is the grouting standby coefficient, is 1.05-1.20; is the coal spontaneous combustion depth / m; is the coal seam temperature anomaly plane area in the fire area / m 2 ; is the porosity of the coal rock mass in the fire area, is 0.15-0.30, is the slurry filling coefficient, is 0.85-0.95, is the slurry stone rate; the slope cutting of the slope is performed from the top of the slope to the bottom of the slope in a way of cutting the slope by a flat disc.

2. The method for preventing and extinguishing fire in a coal seam in an open-pit mine according to claim 1, characterized in that, The grouting drill hole comprises a first grouting drill hole, a second grouting drill hole and a third grouting drill hole, and the interval drilling is performed in three sequences, and the third grouting drill hole is used as a test drill hole.

3. The method for preventing and extinguishing fire in a coal seam in an open-pit mine according to claim 1, characterized in that, The grouting fire extinguishing method further comprises testing the fire extinguishing situation of the grouting drill hole.

4. The method for preventing and extinguishing fire in a coal seam in an open-pit mine according to claim 3, characterized in that, The testing of the fire extinguishing situation of the grouting drill hole comprises the following steps: setting a test drill hole to detect the temperature of the ignition point; if the whole hole temperature of the test drill hole is less than 100 DEG C, it is determined that the fire has been extinguished.

5. The method for preventing and extinguishing fire in a coal seam in an open-pit mine according to claim 1, characterized in that, The backfilling isolation method comprises the following steps: stripping the exposed coal seam produced by stripping in the slope in a direction perpendicular to the slope by 10-30 meters; backfilling loess or pouring grout to form a protective isolation belt in the stripped area.

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