System and method for preventing and controlling rock burst in coal mine

Abstract

The application discloses a system for preventing and treating rock burst in a coal mine in a three-dimensional manner, comprising a plurality of ground microseismic monitoring devices arranged on the ground and a plurality of underground microseismic monitoring devices, ground sound monitoring devices, stress monitoring devices and mine pressure monitoring devices arranged on a mining working face, wherein the devices are connected with a comprehensive early warning platform arranged on the ground. The application also discloses a method for preventing and treating rock burst in a coal mine in a three-dimensional manner, wherein a L-shaped horizontal well is constructed in a rock stratum, a roof directional long borehole hydraulic fracturing and roof pre-splitting blasting are used to achieve regional three-dimensional weakening of low, medium and high hard roofs; and a large-diameter pressure relief and coal seam blasting are used to achieve the purpose of coordinated pressure relief in the coal mine. The system and method disclosed by the application can realize advanced, regional and source treatment of rock burst on the basis of improving the monitoring precision of rock burst, and greatly improve the pressure relief effect.

Description

Technical Field

[0001] This invention belongs to the field of deep coal mining technology, specifically relating to a three-dimensional system for preventing rockbursts in coal mines, and also to a method for three-dimensional prevention of rockbursts in coal mines. Background Technology

[0002] Rockbursts are one of the major hazards faced in deep coal mining, causing incalculable losses to mines and personnel. However, the management of deep rockburst mines is often very difficult, and the conventional measures such as large-diameter pressure relief and coal seam blasting are no longer effective in reducing the rockburst risk in deep mines. Furthermore, the existing rockburst monitoring devices underground are difficult to monitor the activity of high-level rock strata. Summary of the Invention

[0003] The purpose of this invention is to provide a system for three-dimensional prevention and control of rockbursts in coal mines. Another purpose of this invention is to provide a method for three-dimensional prevention and control of rockbursts in coal mines. Using this system and method, it is possible to achieve proactive, regional and source control of rockbursts, and significantly improve the prevention and control effect of rockbursts.

[0004] The technical solution adopted in this invention is a three-dimensional system for preventing and controlling rockbursts in coal mines, including several ground microseismic monitoring devices arranged on the ground and several underground microseismic monitoring devices, ground sound monitoring devices, stress monitoring devices and mine pressure monitoring devices arranged in the underground mining face. The ground microseismic monitoring devices, underground microseismic monitoring devices, ground sound monitoring devices, stress monitoring devices and mine pressure monitoring devices are all connected to a comprehensive early warning platform set on the ground.

[0005] The invention is further characterized by:

[0006] The spacing between the microseismic probes of two adjacent downhole microseismic monitoring devices is 500m to 1000m, the spacing between the ground sound probes of two adjacent ground sound monitoring devices is no more than 100m, and the spacing between the stress sensors of two adjacent stress monitoring devices is no more than 30m.

[0007] Another technical solution adopted in this invention is:

[0008] The method for three-dimensional prevention of rockburst in coal mines involves using the system of this invention to monitor the effects of various construction measures in real time during construction and adjusting construction process parameters based on the monitoring results. The specific steps include:

[0009] Step 1: Conduct surface hydraulic fracturing in an L-shaped horizontal well on the surface, and use surface microseismic monitoring devices, downhole microseismic monitoring devices, and ground sound monitoring devices to detect the development of coal and rock fractures during fracturing;

[0010] Step 2: In the middle of the hard roof of the coal mining face, hydraulic fracturing measures are taken by directional long borehole drilling. During this process, ground sound monitoring devices and stress monitoring devices are used to monitor the activity of micro-cracks in the coal body and the changes in coal body stress during fracturing. Underground micro-vibration monitoring devices are used to monitor the roof fracture during roof fracturing.

[0011] Step 3: Take pre-splitting blasting measures for the low-lying hard roof. Use a ground micro-seismic monitoring device to monitor the roof fracture during the blasting process.

[0012] Step 4: Take large-diameter depressurization and local depressurization measures such as coal seam blasting in the underground coal seam. During the depressurization process, use underground micro-seismic monitoring devices and ground sound monitoring devices to monitor the changes in micro-seismic and ground sound events before and after the depressurization of the coal and rock mass. Use stress monitoring devices to monitor the stress changes in the depressurized coal body.

[0013] Another feature of the technical solution of the present invention is that:

[0014] Step 1 is as follows:

[0015] Step 1.1: Determine the fracturing strata based on the mine's comprehensive geological columnar section, the location of the microseismic event source, the observation of the three zones of adjacent mining faces, and the key layer theory;

[0016] Step 1.2: In advance, set up more than three ground microseismic monitoring devices within a range of 2km to 3km in the surface fracturing roadway. Set up two microseismic probes and two ground sound probes in each of the two roadways of the underground coal mining face corresponding to the surface drilling site to detect the development of coal and rock strata fractures during the fracturing of the surface horizontal well.

[0017] Step 1.3: Construct an L-shaped horizontal well on the surface. First, construct the first well. After completion, install a casing and reinforce the wellhead. Then, construct the second well. Stop drilling when the well reaches 30m to 100m above the fracturing layer and begin directional drilling.

[0018] Step 1.4: Use a directional drilling device to drill horizontally in the fracturing layer. After drilling to the target position, withdraw the drill rod, install the perforation projectile, and carry out the projectile firing operation to create 4 to 6 clusters of perforations in the rock layer.

[0019] Step 1.5: Lower packers or bridge plugs into the horizontal well and inject high-pressure water into the two-stage packers or bridge plugs to perform retreat fracturing.

[0020] During the fracturing process in step 1.5, the distance between fracturing segments shall not exceed 50m, and the fracturing flow rate shall not be less than 10m³. 3 / min, fracture proppant must be continuously injected during the fracturing process.

[0021] In step 2, before hydraulic fracturing the roof through a long directional borehole, two ground acoustic probes need to be installed within the fracturing influence range of the construction roadway, and coal stress gauges need to be installed at intervals of 20m to 30m to monitor the activity of micro-cracks and changes in coal stress during fracturing. Four or more underground microseismic probes need to be installed within a 1000m diameter range of the construction borehole to monitor the roof fracture during roof fracturing.

[0022] The specific construction process for step 2 is as follows:

[0023] Step 2.1: Based on the comprehensive geological columnar section of the mine and the stratigraphic position of microseismic events, determine the target rock layer for fracturing through calculation;

[0024] Step 2.2: Move the directional drilling rig and coordinate with the directional drilling device to construct a long directional borehole in the roof slab;

[0025] Step 2.3: Perform backward fracturing in the directional long borehole in the top plate.

[0026] The specific construction process of the long directional drilling of the top plate in step 2.2 is as follows: a Ф96mm drill bit is used to open the hole. After reaching 5m of the top plate rock, the drill rod is withdrawn. The hole is enlarged with a Ф153mm drill bit. A Ф108mm casing is installed to reinforce the hole wall. After the hole is solidified, a Ф96mm drill bit, a Ф73mm screw motor, a drilling measurement device, and a Ф73mm drill rod are used to directionally drill to the specified depth.

[0027] Step 3 is as follows: First, deploy ground microseismic probes on the ground corresponding to the underground working face. Specifically, deploy four or more ground microseismic probes within a 1000m diameter range of the construction area to monitor the roof fracture. Then, construct deep-hole directional blasting holes for the roof with a diameter of 75mm and a depth equal to the distance from the bottom of the vertical fracture generated by the hydraulic fracturing of the roof directional long borehole in Step 2 to the roadway roof. Use Φ60mm packed explosives, with the amount of explosives determined by the roof lithology and hole depth. The sealing length should not be less than 1 / 3 of the hole depth.

[0028] In step 4, before the large-diameter decompression and coal seam blasting, four or more underground microseismic probes are arranged within a radius of 1000m in the construction area, and two or more ground sound probes are arranged within a radius of 200m in the construction area to monitor the changes in microseismic and ground sound events before and after the decompression of the coal and rock mass; coal stress gauges are arranged at intervals of 20m to 30m within a radius of 100m in the construction area to monitor the stress changes in the decompressed coal body.

[0029] The beneficial effects of this invention are:

[0030] (1) The three-dimensional rockburst prevention system of the present invention for coal mines uses a combination of ground microseismic monitoring devices and underground microseismic, ground sound, stress and mine pressure monitoring devices to effectively reduce the vertical error of microseismic events and improve the positioning accuracy.

[0031] (2) The method for preventing and controlling rockburst in coal mines in three dimensions by means of the above-ground horizontal well segmented fracturing and underground roof directional long borehole hydraulic fracturing, roof pre-fracturing blasting, coal seam blasting and large-diameter boreholes can achieve advanced, regional and source control of rockburst and greatly improve the pressure relief effect. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the arrangement of the ground microseismic monitoring device in the system of the present invention;

[0033] Figure 2 This is a schematic diagram of the arrangement of various downhole rockburst monitoring devices in the system of this invention;

[0034] Figure 3 This is a schematic diagram of the arrangement of various rockburst monitoring devices in the system of the present invention;

[0035] Figure 4 This is a schematic diagram of the measures taken in the method of the present invention for different hard top plates.

[0036] In the figure, 1. Surface microseismic monitoring device, 2. Stress monitoring device, 3. Downhole microseismic monitoring device, 4. Ground sound monitoring device, 5. L-shaped horizontal well, 6. Roof directional long borehole, 7. Roof deep hole directional blasting hole, 8. Coal seam large-diameter pressure relief hole or coal seam blasting hole, 9. Mine pressure monitoring device, 10. Surface, 11. High-level hard roof, 12. Mid-level hard roof, 13. Low-level hard roof, 14. Coal seam. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0038] The coal mine three-dimensional rockburst prevention system of the present invention is a combined surface and underground monitoring system, including several surface microseismic monitoring devices 1 arranged on the surface and several underground microseismic monitoring devices 3, ground sound monitoring devices 4, stress monitoring devices 2, and mine pressure monitoring devices 9 arranged in the underground mining face. The arrangement of various monitoring devices is as follows: Figures 1-3 As shown.

[0039] The ground microseismic monitoring device 1 is specifically deployed according to the mining plan of the mine panel, requiring the ground network to record microseismic events of 100J or higher in the production activity area. The deployment method of the ground microseismic monitoring device 1 in this invention is as follows: Figure 1 As shown.

[0040] Among the various monitoring devices underground, the underground microseismic monitoring device 3 is compatible with the surface microseismic monitoring device 1, and the underground microseismic monitoring device 3 must cover the entire mine. The ground sound monitoring device 4, stress monitoring device 2, and mine pressure monitoring device 9 are deployed according to the current mining situation and the industry standard "Methods for Measurement, Monitoring and Prevention of Rockburst" (GB / T 25217). In this invention, the underground microseismic monitoring device 3 mainly monitors energy events with an energy greater than 100J and a frequency of 0.1Hz to 150Hz, requiring a spacing of 500m to 1000m between microseismic probes; the ground sound monitoring device 4 mainly monitors energy events with an energy less than 100J and a frequency greater than 150Hz, requiring a spacing of no more than 100m between ground sound probes; the stress monitoring device 2 mainly monitors the stress in the coal and rock mass of the mining face, requiring a spacing of no more than 30m between adjacent stress sensors, and is used to monitor the dynamic and static loads required for the initiation of rockburst for far-field dynamic load, near-field dynamic load, and static load, respectively.

[0041] The ground microseismic monitoring device 1 and the underground microseismic monitoring device 3, ground sound monitoring device 4, stress monitoring device 2 and mine pressure monitoring device 9 are all connected to the integrated early warning platform set on the ground. Data from various monitoring devices are sent to this platform. The platform uses visualization technology to intuitively display stress cloud maps, microseismic time microseismic data, frequency changes, etc., to achieve in-depth development and integration of multi-parameter and multi-scale early warning information such as microseismic data, ground sound data, stress data and mine pressure data, so as to accurately evaluate the pressure relief effect.

[0042] This invention relates to a method for three-dimensional prevention and control of rockbursts in coal mines, such as... Figure 4 As shown, specifically, horizontal well fracturing is implemented at the surface in the high-level hard roof 11; directional long borehole hydraulic fracturing is implemented at the mid-level hard roof 12; pre-fracturing blasting is implemented at the low-level hard roof 13; and large-diameter borehole depressurization and coal seam blasting depressurization are implemented at the coal seam 14. This achieves a coordinated pressure relief and anti-shocking system covering the high, mid, and low-level hard rock strata and coal seams. The specific steps are as follows:

[0043] Step 1: Weakening the high-level hard roof 11 before working face excavation. This is achieved by hydraulic fracturing the surface through an L-shaped horizontal well 5 (constructed at the surface 10) to weaken the high-level hard roof 11 above 60m in the coal seam. During the process, a surface microseismic monitoring device 1, an underground microseismic monitoring device 3, and a ground acoustic monitoring device 4 are used to monitor the development of fractures in the coal and rock strata during fracturing. The specific procedure is as follows:

[0044] Step 1.1: Determine the fracturing strata based on the mine's comprehensive geological columnar section, the location of the microseismic event source, the observation of the three zones of adjacent mining faces, and the key layer theory;

[0045] Step 1.2: In advance, set up more than three ground microseismic monitoring devices 1 within a range of 2km to 3km in the ground fracturing roadway. Set up two microseismic probes and two ground sound probes in each of the two roadways of the underground coal mining face corresponding to the ground drilling site to detect the development of coal and rock strata fractures during the fracturing of the ground horizontal well.

[0046] Step 1.3: Construct L-shaped horizontal well 5 on the surface. First, construct the first well. After completion, install the casing and reinforce the wellhead. Then, construct the second well. Stop drilling when the well reaches 30m to 100m above the fracturing layer and start the directional drilling.

[0047] Step 1.4: Use a directional drilling device to drill horizontally in the fracturing layer. After drilling to the target position, withdraw the drill rod, install perforation projectiles, and carry out projectile firing. Pre-fire 4 to 6 clusters of perforations in the rock layer at a certain angle. This allows for pre-control of the direction and depth of the fractures in the rock layer and also eliminates the energy consumed when breaking the rock with high-pressure water. Fracturing can be carried out only in the perforation holes, which further enhances the fracturing effect.

[0048] Step 1.5: Lower packers or bridge plugs into the horizontal well, and inject high-pressure water into the two-stage packers or bridge plugs for fracturing. The fracturing stage distance should not exceed 50m, and the fracturing flow rate should not be less than 10m³ / h. 3 At a rate of / min, fracturing fluid and fracture proppant such as fine sand are continuously injected during the fracturing process to ensure the effectiveness of the fracturing. The entire fracturing operation is carried out using a retreating method.

[0049] Step 2: Weakening the hard roof 12 in the middle section before mining. This is achieved by drilling a long directional borehole 6 into the underground roadway and performing hydraulic fracturing to weaken the hard roof 12 in the middle section of the coal seam above 40m. Before hydraulic fracturing the long directional borehole, two ground acoustic probes need to be installed within the fracturing influence area of ​​the construction roadway, and coal stress gauges should be installed at intervals of 20m to 30m to monitor the activity of micro-fractures and stress changes in the coal seam during fracturing. Four or more underground microseismic probes should be installed within a 1000m diameter range of the borehole to monitor roof fracture during fracturing. The specific construction process is as follows:

[0050] Step 2.1: Determine the fracturing strata. Based on the mine's comprehensive geological columnar section and microseismic event strata, the target fracturing strata are determined through calculation.

[0051] Step 2.2: Construct 6 directional long boreholes in the top slab. Move the directional drilling rig and coordinate with the directional drilling device to construct the directional long borehole. Specifically, use a Ф96mm drill bit to open the hole, and after reaching 5m of top slab rock, withdraw the drill rod. Use a Ф153mm drill bit to enlarge the hole, and then run a Ф108mm casing to reinforce the borehole wall. After stabilizing the hole, use a Ф96mm drill bit + Ф73mm screw motor + drilling while measuring device + Ф73mm drill rod to directionally drill to the specified depth.

[0052] Step 2.3: Perform retreating fracturing in the directional long borehole 6 in the top plate, with a segment spacing of about 30m. Use clean water as the fracturing fluid, without adding any activators or flame retardants.

[0053] Step 3: Weakening the low-lying hard roof 13 during the working face mining. This is achieved by pre-fracture blasting of the roof in the underground roadway to weaken the low-lying hard roof 13 within a 10m-40m range of the coal seam. Before the roof pre-fracture blasting, ground microseismic probes must be deployed on the ground corresponding to the underground mining face. Specifically, four or more ground microseismic probes should be deployed within a 1000m diameter range of the construction area to monitor the roof fracture. A deep-hole directional blasting hole 7 is designed for the roof, with a diameter of 75mm and a depth equal to the distance from the bottom of the vertical fracture generated by the hydraulic fracturing of the long directional borehole in Step 2 to the roadway roof. Φ60mm packed explosives are used. In this example, the explosive specifications are: 350mm in length and 1.1kg / roll. The amount of explosive depends on the roof lithology and hole depth, and the sealing length must not be less than 1 / 3 of the hole depth.

[0054] Step 4: In underground coal seam 14, implement localized pressure relief measures such as large-diameter pressure relief and coal seam blasting. Construct large-diameter pressure relief holes or coal seam blasting holes 8 to transfer high stress to deeper parts of the roadway and reduce the impact risk at the mining face. Before constructing large-diameter pressure relief and coal seam blasting, four or more underground microseismic probes must be deployed within a 1000m radius of the construction area, and two or more ground acoustic probes must be deployed within a 200m radius of the construction area to monitor changes in microseismic and ground acoustic events before and after pressure relief of the coal and rock mass. Coal stress gauges should be deployed at intervals of 20m to 30m within a 100m radius of the construction area to monitor changes in stress in the pressure-relieved coal body. During the construction of large-diameter pressure relief and coal seam blasting, the spacing of large-diameter pressure relief holes and coal seam blasting holes should be adjusted according to the roadway impact risk level, and different hole spacings should be constructed in different areas.

[0055] Before implementing any type of pressure relief project, it is essential to complete the installation and construction of various rockburst monitoring devices, including those for microseismic, ground sound, stress, and mine pressure monitoring, forming a rockburst monitoring network that combines regional and local monitoring and covers both dynamic and static loads. During the construction process of steps 1 to 4 above, the system for three-dimensional rockburst prevention and control in coal mines according to this invention collects data on microseismic, ground sound, and coal stress changes during the pressure relief project construction process. The system monitors the effects of various construction measures in real time to accurately evaluate the pressure relief effect, adjusts construction process parameters based on monitoring results, and uses this system and method to conduct real-time rockburst monitoring and rockburst prevention effect verification in the mine.

Claims

1. A method for three-dimensional prevention and control of rockbursts in coal mines, characterized in that, During construction, a three-dimensional system for preventing rockbursts in coal mines is used to monitor the effects of various construction measures in real time, and construction process parameters are adjusted based on the monitoring results. The coal mine three-dimensional rockburst prevention system includes several ground microseismic monitoring devices (1) arranged on the ground and several underground microseismic monitoring devices (3), ground sound monitoring devices (4), stress monitoring devices (2) and mine pressure monitoring devices (9) arranged in the underground mining face. The ground microseismic monitoring devices (1), underground microseismic monitoring devices (3), ground sound monitoring devices (4), stress monitoring devices (2) and mine pressure monitoring devices (9) are all connected to the comprehensive early warning platform set on the ground. The distance between the microseismic probes of two adjacent downhole microseismic monitoring devices (3) is 500m~1000m, the distance between the ground sound probes of two adjacent ground sound monitoring devices (4) is no more than 100m, and the distance between the stress sensors of two adjacent stress monitoring devices (2) is no more than 30m. The method for preventing rockbursts in coal mines, both above and below ground, specifically includes the following steps: Step 1: Construct an L-shaped horizontal well (5) on the ground (10) to carry out surface hydraulic fracturing, and use a surface microseismic monitoring device (1), a downhole microseismic monitoring device (3) and a ground sound monitoring device (4) to detect the development of coal and rock fractures during fracturing; Step 2: In the middle hard roof (12) of the coal mining face, take the measures of directional long borehole hydraulic fracturing. During this process, use the ground sound monitoring device (4) and stress monitoring device (2) to monitor the activity of micro-cracks in the coal body and the change of coal body stress during fracturing. Use the underground micro-vibration monitoring device (3) to monitor the roof fracture during roof fracturing. Step 3: Take pre-splitting blasting measures on the low-lying hard roof (13), and use a ground micro-seismic monitoring device (1) to monitor the roof fracture during the blasting process; Step 4: Take large-diameter depressurization and local depressurization measures by coal seam blasting in the underground coal seam (14). During the depressurization process, use the underground micro-vibration monitoring device (3) and the ground sound monitoring device (4) to monitor the changes in micro-vibration and ground sound events before and after the depressurization of the coal and rock mass. Use the stress monitoring device (2) to monitor the stress changes of the depressurized coal body. Step 1 is as follows: Step 1.1: Determine the fracturing strata based on the mine's comprehensive geological columnar section, the location of the microseismic event source, the observation of the three zones of adjacent mining faces, and the key layer theory; Step 1.2: In advance, three or more ground microseismic monitoring devices (1) are set up within a range of 2km to 3km in the ground fracturing roadway. Two microseismic probes and two ground sound probes are set up in each of the two roadways of the underground coal mining face corresponding to the ground drilling site to detect the development of coal and rock strata fractures during the fracturing of the ground horizontal well. Step 1.3: Construct an L-shaped horizontal well (5) on the ground. First, construct the first well. After completion, install the casing and reinforce the wellhead. Then, construct the second well. Stop drilling when the well is 30m to 100m above the fracturing layer and start the directional drilling. Step 1.4: Use a directional drilling device to drill horizontally in the fracturing layer. After drilling to the target position, withdraw the drill rod, install the perforation projectile, and carry out the projectile firing operation to create 4 to 6 clusters of perforations in the rock layer. Step 1.5: Lower packers or bridge plugs into the horizontal well, and inject high-pressure water into the two-stage packers or bridge plugs to perform retreat fracturing; In step 2, before hydraulic fracturing the roof through a long directional borehole, two ground acoustic probes need to be installed within the fracturing influence range of the construction roadway, and coal stress gauges need to be installed at intervals of 20m to 30m to monitor the activity of micro-cracks in the coal body and the changes in coal stress during fracturing. Four or more underground micro-vibration probes need to be installed within a 1000m diameter range of the construction borehole to monitor the roof fracture during roof fracturing. The specific construction process for step 2 is as follows: Step 2.1: Based on the comprehensive geological columnar section of the mine and the stratigraphic position of microseismic events, determine the target rock layer for fracturing through calculation; Step 2.2: Move the directional drilling rig and coordinate with the directional drilling device to construct a long directional borehole in the top plate (6); Step 2.3: Perform backward fracturing in the directional long borehole (6) in the top plate; Step 3 is as follows: First, place ground microseismic probes on the ground corresponding to the underground mining face. Specifically, place four or more ground microseismic probes within a 1000m diameter range of the construction area to monitor the roof fracture. Then, construct a deep-hole directional blasting hole (7) for the roof. The hole diameter is 75mm, and the hole depth is the distance from the bottom of the vertical fracture generated by the hydraulic fracturing of the roof directional long borehole in Step 2 to the roof of the roadway. Use Φ60mm shell explosives. The amount of explosives depends on the roof lithology and hole depth. The sealing length is not less than 1 / 3 of the hole depth.

2. The method for three-dimensional prevention of rockburst in coal mines according to claim 1, characterized in that, During the fracturing process in step 1.5, the distance between fracturing segments shall not exceed 50m, and the fracturing flow rate shall not be less than 10m³. 3 / min, fracture proppant must be continuously injected during the fracturing process.

3. The method for three-dimensional prevention and control of rockbursts in coal mines according to claim 1, characterized in that, The specific construction process of the top plate directional long borehole (6) in step 2.2 is as follows: use a Ф96mm drill bit to open the hole, and after seeing the top plate rock for 5m, withdraw the drill rod, use a Ф153mm drill bit to enlarge the hole, and run a Ф108mm casing to reinforce the wall of the fracturing hole. After solidifying the hole, use a Ф96mm drill bit, a Ф73mm screw motor, a drilling measurement device and a Ф73mm drill rod to directionally drill to the specified depth.

4. The method for three-dimensional prevention and control of rockburst in coal mines according to claim 1, characterized in that, In step 4, before the large-diameter decompression and coal seam blasting, four or more underground microseismic probes are arranged within a radius of 1000m in the construction area, and two or more ground sound probes are arranged within a radius of 200m in the construction area to monitor the changes in microseismic and ground sound events before and after the decompression of the coal and rock mass; coal stress gauges are arranged at intervals of 20m to 30m within a radius of 100m in the construction area to monitor the stress changes in the decompressed coal body.

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