A method for cooling and extinguishing fires in small kiln fire zones on overlying slopes of shallow-buried deep coal seams

Abstract

This invention discloses a method for cooling and extinguishing fires in small kiln fire zones on overlying slopes of shallow-buried deep coal seams. The method involves using a spray gun to spray and cover severely smoky areas of the slope surface with inorganic solidified foam for oxygen isolation and cooling; cleaning and maintaining the slope surface; fabricating a mesh and installing anchor bolts on the slope surface; spraying concrete onto the slope surface to seal cracks and prevent air leakage; the spraying operation is carried out in sections, with the spraying sequence within the same section from bottom to top, each spray thickness not less than 40mm, and the final thickness of the sprayed concrete not less than 100mm; to ensure sealing quality, the thickness is increased in concave areas of the slope surface according to site conditions; secondary spraying concrete is applied to areas with large fires; cement mortar is injected into boreholes during slope platform construction, and cement grout is injected first to dissipate heat from high-temperature cracks encountered during grouting, followed by cement mortar until full; the grouting boreholes are arranged in a staggered pattern; monitoring holes are evenly distributed on the slope platform; temperature and gas levels are monitored every two months.

Description

Technical Field

[0001] This invention belongs to the field of coal mine fire zone cooling and extinguishing technology, specifically relating to a method for cooling and extinguishing fires in small kiln fire zones on the overlying slope of shallow-buried deep coal seams. Background Technology

[0002] Safe mining of coal seams beneath small-scale fire zones is a significant technical challenge for coal mines. Currently, common management measures include stripping and backfilling of the fire zone, underground construction isolation, grouting, nitrogen injection, and pressure equalization ventilation. Stripping and backfilling are effective for smaller fire zones, but when the fire zone is large, incomplete stripping or untimely backfilling can easily lead to the creation of new fire zones, resulting in substantial construction work and high costs. While construction isolation zones can control the spread of fire even with adequate construction quality, they cannot directly extinguish the fire or completely prevent it from threatening mine safety. Pressure equalization ventilation can prevent the intrusion of harmful gases such as CO within the fire zone to some extent, but it increases the required mining speed of the lower coal seams. This increases the spontaneous combustion risk in the lower goaf, with the overlying goaf oxidation zone exceeding the width of the lower goaf oxidation zone, making the overlying coal more prone to spontaneous combustion and increasing the risk of spontaneous combustion at the working face. Meanwhile, pressure equalization cannot completely prevent CO and CO2 gases from invading the overlying goaf from the fire zone. Furthermore, surface and underground grouting and nitrogen injection for fire prevention and extinguishing measures must be carried out only after the fractures are completely sealed; otherwise, it will not only waste resources but also fail to achieve the expected fire prevention and extinguishing effects.

[0003] Therefore, given the above problems, it is necessary to propose a targeted treatment method to comprehensively and efficiently cool and extinguish small kiln fire zones on the overlying slopes of shallow-buried coal seams, and prevent these small kiln fire zones from threatening the safe production of coal mines. Summary of the Invention

[0004] This invention addresses the aforementioned problems and overcomes the shortcomings of existing technologies by providing a method for cooling and extinguishing fires in small kiln fire zones on overlying slopes of shallow-buried deep coal seams.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] This invention provides a method for cooling and extinguishing fires in small kiln fire zones on overlying slopes of shallow-buried deep coal seams, comprising the following steps:

[0007] Step 1: First, use a spray gun to spray and cover the severely smoking areas on the slope surface with inorganic curing foam to isolate oxygen and cool down;

[0008] Step 2: Clean and maintain the slope surface;

[0009] Step 3: Install the hanging netting and anchor bolts on the slope surface;

[0010] Step 4: Shotcrete is applied to the slope surface to seal cracks and prevent air leakage. The shotcrete operation is carried out in sections, with the spraying sequence within the same section from bottom to top. Each spraying thickness is not less than 40mm, and the final thickness of the shotcrete is not less than 100mm. To ensure the sealing quality, the thickness of the shotcrete is increased in the recessed areas of the slope surface according to the site conditions. Areas with large fires are sprayed with two or more times.

[0011] Step 5: Grouting and drilling of the slope platform for cement mortar injection. During the grouting process, if high-temperature cracks are encountered, cement slurry is injected first to dissipate heat, and then cement mortar is injected until the cracks are full. The grouting holes are arranged in a five-hole pattern, and the grouting pressure is 0.2-1.0 MPa. First, a test hole is constructed for grouting. After grouting is completed, the grout diffusion radius is measured by excavation to determine the spacing of the grouting holes. Temperature is measured simultaneously during the construction of the grouting holes, and the hole with a temperature below 60℃ is taken as the final hole position.

[0012] Step 6: Evenly distribute monitoring holes on the slope platform. The monitoring radius of the monitoring holes is 25-50m. The entire length of the monitoring holes is covered by a casing. The casing is 0.1-0.6m above the ground surface. The casing opening is equipped with a detachable cap so that the opening can be sealed tightly when not measuring temperature.

[0013] Step 7: Monitor the temperature and gas at the monitoring well every two months. If the temperature exceeds 70°C or CO is detected, repeat step 4.

[0014] Furthermore, in step one, the area covered by the inorganic curing foam is centered on the fire point in the area of ​​severe smoke on the slope surface, and the thickness of the inorganic curing foam is 5 to 20 cm.

[0015] Furthermore, in step one, the inorganic cured foam is a completely inorganic material, which has absolute flame retardant and antistatic effects, and conforms to the national standard "Q / FSRNAN.002~2019 Foamed Materials for Filling and Sealing in Coal Mines".

[0016] Furthermore, the specific steps for cleaning and maintaining the slope surface in step two include: while maintaining the original terrain slope, manually removing weathered, loose, and broken rocks from the slope surface, with a cleaning thickness of 5 to 30 cm, and the cleaning process is carried out from top to bottom.

[0017] Furthermore, the specific steps for fabricating the hanging net and installing anchor bolts on the slope surface in step three include: the hanging net is made of multiple galvanized wire mesh sheets, and the connection between the multiple wire mesh sheets is achieved by binding with wire; anchor bolts are installed at the same time as the hanging net is fabricated, with the anchor bolts being 1000-1800mm in length, the wire mesh sheets being used to fix the concrete, the anchor bolt installation is pressured by a diesel-powered mobile screw air compressor, holes are drilled and anchor bolts are driven in using a pneumatic rock drill, and anchoring is achieved using anchoring agent, and then the tray and nuts are installed.

[0018] Furthermore, the anchor rods in step three are made of fiberglass, and the spacing between the fiberglass anchor rods is 500mm×500mm~2000mm×2000mm.

[0019] Furthermore, in step four, the strength grade of the sprayed concrete is not lower than C25.

[0020] Furthermore, in step five, the mix proportion of the cement mortar for injection is calculated according to the ratio of cement:sand:water:accelerator 2.6:4.1:1:0.13 (mass ratio), and the mix proportion of the cement slurry for injection is calculated according to the ratio of cement:water:accelerator 1:1:0.05 (mass ratio).

[0021] Furthermore, in step six, the temperature is measured using a thermistor thermometer or a digital thermometer, and the gas concentration is analyzed using a gas chromatograph.

[0022] Compared with existing technologies, the beneficial effects of this invention are as follows: The cooling and fire extinguishing method of this invention not only prevents toxic and harmful gases from polluting the atmosphere on the surface of the small kiln fire zone on the slope, but also cuts off air leakage channels by sealing cracks. Through measures such as hanging netting, spraying concrete, and drilling and grouting on the slope surface and inside the small kiln fire zone, the spread of fire in the small kiln fire zone on the slope is prevented, and continuous cooling and fire extinguishing are achieved. This invention avoids the problem that traditional fire zone management methods are not applicable to small kiln fire zones on slopes or neglect the control of atmospheric pollution on the slope surface. It prevents the problem of fire reignition caused by large air leakage areas and incomplete sealing of cracks, thereby contributing to atmospheric environmental protection and safe production at the working face of the small kiln fire zone on the overlying slope. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating a method for cooling and extinguishing a small kiln fire zone on an overlying slope of a shallow-buried deep coal seam, according to the present invention.

[0024] Figure 2 This is a schematic diagram showing the arrangement of grouting boreholes on the slope platform and the mesh and anchor bolts on the slope surface.

[0025] Figure 3 This is a top view of the grouting boreholes arranged on the slope platform.

[0026] The markings in the diagram are: 1. Slope platform; 2. Grouting borehole; 3. Wire mesh; 4. Fiberglass anchor; 5. Slope surface; 6. Monitoring hole; 7. Casing. Detailed Implementation

[0027] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0028] Example 1

[0029] Reference Figure 1 and Figure 2 As shown, a method for cooling and extinguishing a small kiln fire zone on an overlying slope of a shallow-buried coal seam includes the following steps:

[0030] Step 1: First, use a spray gun to spray and cover the five severely smoking areas on the slope surface with inorganic cured foam that conforms to the national standard "Q / FSRNAN.002-2019 Foaming Material for Coal Mine Filling and Sealing". The coverage area should be centered on the five smoking points on the slope surface and extend outwards. The thickness of the inorganic cured foam should be 5-20cm, preferably 10cm, to avoid air pollution. The inorganic cured foam is a completely inorganic material with absolute flame retardant and antistatic properties.

[0031] Step 2: Clean and maintain the slope surface 5. While maintaining the original terrain slope, manually remove the weathered, loose and broken rocks on the slope surface 5. The thickness of the cleaned rocks should be 5-30cm, preferably 10cm. The cleaned rocks should be removed from top to bottom.

[0032] Step 3: Hang wire mesh 3 on the slope surface 5 and install fiberglass anchors 4 to fix the wire mesh 3. The wire mesh 3 is only used to fix the concrete. The fiberglass anchors 4 are installed with pressure provided by a diesel-powered mobile screw air compressor. The anchor length is 1000-1800mm, and the preferred anchor length is 1200mm. Use a pneumatic rock drill to drill holes and install the fiberglass anchors 4. The fiberglass anchors 4 are arranged at 90° to the slope surface 5. The spacing between the fiberglass anchors is 500mm×500mm to 2000mm×2000mm, and the preferred spacing between the fiberglass anchors 4 is 1200mm×1200mm. Anchoring agent is used for anchoring. Install the tray and nuts.

[0033] Step 4: Apply C25 grade concrete to seal the air leaks in the five cracks on the slope surface (the sprayed concrete is only used to seal the air leaks in the five cracks on the slope surface and is not used for slope protection). The spraying operation is carried out in sections, and the spraying sequence within the same section should be from bottom to top. The thickness of each spray is 40mm, and the final thickness of the sprayed concrete is 100mm. To ensure the sealing quality, the thickness of the five recessed areas on the slope surface should be appropriately increased according to the site conditions. In some areas with large fire intensity, sprayed concrete should be applied two or more times (with a thickness of not less than 100mm).

[0034] Step 5: Refer to Figure 3 As shown, cement mortar was injected into grouting boreholes 2 on the slope platform 1. During the grouting process, cement slurry was injected first to dissipate heat when encountering high-temperature cracks, and then cement mortar was injected until the cracks were full. The cement mortar mix ratio was calculated as cement:sand:water:accelerator ratio 2.6:4.1:1:0.13 (mass ratio), and the cement slurry mix ratio was calculated as cement:water:accelerator ratio 1:1:0.05 (mass ratio). The grouting pressure was 0.5MPa. First, a test hole was constructed for grouting. After grouting was completed, the slurry diffusion radius was measured by excavation to determine the spacing of grouting boreholes 2. Temperature was measured simultaneously during the construction of grouting boreholes 2, and the position where the temperature of grouting borehole 2 was less than 60℃ was taken as the final hole position.

[0035] Step 6: The monitoring holes 6 are evenly distributed on the slope platform 1. The monitoring radius of the monitoring holes 6 is 30m. The monitoring holes 6 (φ108mm) are all covered with sleeves 7. The sleeves 7 are made of steel pipes. The final height of the sleeves 7 above the slope platform 1 is 0.5m. The pipe opening of the sleeves 7 is equipped with a detachable pipe cap, which can seal the pipe opening when not measuring temperature.

[0036] Step 7: Monitor the temperature and gas in well 6 every two months using a thermistor thermometer and a gas chromatograph. If the temperature exceeds 70°C or CO is detected, repeat step 4.

[0037] Example 2

[0038] The difference from Example 1 is that a digital thermometer is used in step seven to monitor the temperature of monitoring hole 6.

[0039] The cooling and extinguishing method of the present invention can effectively eliminate the threat of small kiln fire zones on the overlying slope of shallow and deep coal seams by cooling and extinguishing fires through measures such as eliminating air leakage on the slope surface 5 and grouting drilling 2 during the construction of the slope platform 1, thereby ensuring the safe production of coal mines.

[0040] It is understood that the above specific description of the present invention is only for illustrating the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effect; as long as the use needs are met, they are all within the protection scope of the present invention.

Claims

1. A method for cooling and extinguishing fires in small kiln fire zones on overlying slopes of shallow-buried deep coal seams, characterized in that: Includes the following steps: Step 1: First, use a spray gun to spray and cover the severely smoking areas on the slope surface with inorganic curing foam to isolate oxygen and cool down; the area covered with inorganic curing foam is centered on the fire point in the severely smoking area on the slope surface and extends outwards, with a thickness of 5-20cm. Step 2: Clean and maintain the slope surface; while maintaining the original topographic slope, manually remove weathered, loose and broken rocks from the slope surface, with a thickness of 5-30cm. The removal process should be carried out from top to bottom. Step 3: Construct a wire mesh and install anchor bolts on the slope surface; the wire mesh is made of multiple galvanized wire mesh sheets, which are connected by wire binding; anchor bolts are installed at the same time as the wire mesh is constructed. The anchor bolts are 1000-1800mm long. The wire mesh sheets are used to fix the concrete. The anchor bolts are installed using a diesel-powered mobile screw air compressor to provide pressure. A pneumatic rock drill is used to drill holes and insert the anchor bolts. Anchoring agent is used to anchor them. The trays and nuts are then installed. Step 4: Shotcrete is applied to the slope surface to seal cracks and prevent air leakage. The shotcrete operation is carried out in sections, with the spraying sequence within the same section from bottom to top. Each spraying thickness is not less than 40mm, and the final thickness of the shotcrete is not less than 100mm. To ensure the sealing quality, the thickness of the shotcrete is increased in the recessed areas of the slope surface according to the site conditions. Areas with large fires are sprayed with two or more times. Step 5: Grouting and injection of cement mortar into the slope platform. During grouting, if high-temperature cracks are encountered, cement slurry is injected first to dissipate heat, followed by cement mortar until full. The grouting holes are arranged in a five-hole pattern, with an injection pressure of 0.2–1.0 MPa. First, a test hole is constructed for grouting. After grouting, the slurry diffusion radius is measured by excavation to determine the spacing between grouting holes. Temperature is measured simultaneously during grouting hole construction, and the hole with a temperature below 60℃ is designated as the final hole location. The cement mortar mix ratio is calculated based on a cement:sand:water:accelerator mass ratio of 2.6:4.1:1:0.13, and the cement slurry mix ratio is calculated based on a cement:water:accelerator mass ratio of 1:1:0.

05. Step 6: Evenly distribute monitoring holes on the slope platform. The monitoring radius of the monitoring holes is 25-50m. The entire length of the monitoring holes is covered by a casing. The casing is 0.1-0.6m above the ground surface. The casing opening is equipped with a detachable cap so that the opening can be sealed tightly when not measuring temperature. Step 7: Monitor the temperature and gas at the monitoring well every two months. If the temperature exceeds 70°C or CO is detected, repeat step 4.

2. The method for cooling and extinguishing fires in small kiln fire zones on overlying slopes of shallow-buried deep coal seams according to claim 1, characterized in that: The anchor rods used in step three are fiberglass anchor rods, and the spacing between the fiberglass anchor rods is 500mm×500mm~2000mm×2000mm.

3. The method for cooling and extinguishing fires in small kiln fire zones on overlying slopes of shallow-buried deep coal seams according to claim 1, characterized in that: In step four, the strength grade of the sprayed concrete shall not be lower than C25.

4. The method for cooling and extinguishing fires in small kiln fire zones on overlying slopes of shallow-buried deep coal seams according to claim 1, characterized in that: In step six, a thermistor thermometer or digital thermometer is used to measure the temperature, and a gas chromatograph is used to analyze the gas concentration.

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