A method for preventing and controlling rock burst by releasing pressure in double release layers of coal seams with a buried depth of more than one kilometer

Abstract

The application provides a method for preventing and treating rock burst by releasing pressure of double release layers of coal seams with super-thousand-meter buried depth, which comprises the following steps: S1, determining a working face arrangement and a drilling columnar diagram; S2, determining a number of fracturing target layer groups according to the working face arrangement and the drilling columnar diagram, wherein the fracturing target layer groups comprise a coal seam upper roof fracturing target layer and a coal seam lower floor fracturing target layer; S3, fracturing the target layer regions of the coal seam roof and floor; and S4, excavating and mining a roadway in the coal seam within the fracturing coverage range to safely mine. The method for preventing and treating rock burst by releasing pressure of double release layers of coal seams with super-thousand-meter buried depth can effectively reduce vertical stress and horizontal stress, and ensure the safety of coal seam mining.

Description

Technical Field

[0001] This invention relates to the field of coal mine safety mining technology, specifically to a method for preventing rockbursts in coal seams with a depth of over 1,000 meters using a double-layer decompression system. Background Technology

[0002] After coal mines enter the deepest burial depth of over 1,000 meters, the surrounding rock environment undergoes significant changes, with geological conditions characterized by high ground stress and increased rock mass failure strength. Under high vertical and horizontal stress conditions, if the accumulated energy is released slowly, it can cause the tunnel floor to heave gradually, leading to insufficient ventilation and transportation capacity. If the accumulated energy is released instantaneously, it can trigger dynamic disasters, causing the tunnel floor to heave instantly, resulting in casualties and equipment damage.

[0003] Because the mining depth exceeds 1000 meters, the vertical and horizontal stresses of the coal and rock mass increase by 3-5 times compared to shallow mining. The risk of rockburst accidents during tunneling and mining increases exponentially. Since there is no effective solution, Chinese regulations have suspended the mining of coal seams exceeding 1000 meters in depth. This invention provides a double release layer for coal seams exceeding 1000 meters in depth, transforming the high-stress environment at depth into a low-stress environment at depth, thereby ensuring the safe mining of coal seams exceeding 1000 meters in depth. Summary of the Invention

[0004] 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 double-layer decompression method for preventing rockbursts in coal seams buried at depths exceeding one kilometer. This method can effectively reduce vertical and horizontal stresses, ensuring the safety of coal seam mining.

[0005] The method for preventing rockbursts in coal seams buried at depths exceeding 1,000 meters using a double-layer decompression system includes the following steps:

[0006] S1. Determine the layout of the working face and the borehole columnar section;

[0007] S2. Based on the working face layout and borehole columnar section, determine the number of target fracturing layers. The target fracturing layers include the roof fracturing target layers above the coal seam and the floor fracturing target layers below the coal seam.

[0008] S3. Perform hydraulic fracturing on the target stratum area determined in the roof and floor of the coal seam.

[0009] S4. Excavate mining roadways within the fracturing coverage area of ​​the coal seam to ensure safe mining operations.

[0010] The method for preventing rockburst in coal seams with a depth of over 1,000 meters using a double-liberation layer addresses high vertical stress by performing surface fracturing on the roof above the coal seam and high horizontal stress by performing surface fracturing on the floor below the coal seam, thus creating an artificial double-liberation layer. This reduces both the high vertical and horizontal stresses in the coal seam, keeping it in a protected state and proactively reducing the stress levels of the original rock and tectonic structures in the working face tunneling and mining areas, thereby preventing rockburst at its source.

[0011] In some embodiments, in step S1, determining the working face layout includes determining the dip length L1 of the working face and calculating the number N1 of the fracturing target layer groups in the dip direction of the working face, i.e., N1 = L1 / 200, and N1 is an integer.

[0012] In some embodiments, in step S1, determining the working face layout further includes determining the strike length L2 of the longwall face and calculating the number N2 of the target fracturing formations in the strike direction of the working face, i.e., N2 = L2 / 1000, where N2 is an integer.

[0013] In some embodiments, the total number N of target fracturing layers in the roof above the coal seam and the floor below the coal seam is determined. 总 =2*N1*N2.

[0014] In some embodiments, in step S1, determining the borehole column includes: determining the location of sandstone layers above and below the coal seam.

[0015] In some embodiments, a sandstone layer with a thickness greater than 10 meters is selected as the target layer for fracturing.

[0016] In some embodiments, in step S2, a sandstone layer located 50 to 100 meters above the coal seam is selected as the target layer for fracturing the roof above the coal seam. In some embodiments, a sandstone layer located 30 to 50 meters below the coal seam is selected as the target layer for fracturing the floor below the coal seam. In some embodiments, the vertical fracturing height of both the target layer for fracturing the roof above the coal seam and the target layer for fracturing the floor below the coal seam is greater than or equal to 20 meters and less than or equal to 40 meters.

[0017] In some embodiments, in step S3, the fracturing range of the region is monitored in real time to determine that the fracturing range of the region can cover the working face mining area.

[0018] In some embodiments, in step S3, hydraulic fracturing is used to fracturing the target stratum region.

[0019] In some embodiments, the method for preventing rockburst in a coal seam with double-layer decompression and pressure relief in a depth of over 1,000 meters according to the present invention further includes the following steps: before step S4, stress monitoring equipment is used to detect the stress of the original rock in the tunnel to be excavated area and the mining area in real time. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural diagram illustrating the implementation process of the method for preventing rockbursts in coal seams buried at depths exceeding 1,000 meters using a double-release layer pressure relief technique.

[0021] Figure 2 This is a schematic diagram illustrating the implementation process of the double-layer decompression method for preventing rockbursts in coal seams buried at depths exceeding 1,000 meters, according to an embodiment of the invention.

[0022] Figure 3 This is a longitudinal cross-sectional schematic diagram of the implementation process of the method for preventing rockbursts in coal seams buried at depths of over 1,000 meters using a double-release layer pressure relief technique.

[0023] Figure label:

[0024] 100. Shaft; 200. Development roadway; 300. Preparation roadway; 400. Coal seam.

[0025] 1. Longwall face,

[0026] 2. Target stratum for top plate fracturing.

[0027] 3. Target layer for base plate fracturing.

[0028] 4. Shaft,

[0029] 5. Fracturing horizontal wells in the top plate area.

[0030] 6. Fracturing horizontal wells in the bottom plate area.

[0031] 7. Fracturing zone. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below, with examples of the embodiments 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.

[0033] like Figures 1-3 As shown in the figure, the method for preventing rockbursts in coal seams with double-layer decompression and pressure relief in depths exceeding 1,000 meters according to an embodiment of the present invention includes the following steps:

[0034] S1. Determine the working face layout and borehole columnar section. Understandably, before fracturing, it is necessary to fully consider the in-situ stress, surrounding rock stability, and potential stress concentration areas in coal seam 400 at depths exceeding 1000 meters. The borehole columnar section needs to detail the geological structure of the roof above and the floor below coal seam 400, as well as the distribution of brittle rock strata, to provide basic data for subsequent fracturing design.

[0035] Specifically, such as Figures 1-3 As shown, shaft 100 is a crucial passage connecting the surface and the mine interior. It is used for transporting materials, equipment, and miners, and is also a key passage for ventilation and drainage. The development roadway 200 penetrates the ore body and connects to the preparation roadway 300 and shaft 100, forming a link between the mine interior and the surface, providing the main transportation and ventilation channels within the mine. The roof fracturing target layer 2 and the floor fracturing target layer 3 are located above and below the longwall face 1, respectively.

[0036] In some embodiments, determining the borehole column includes identifying the locations of sandstone layers above and below the coal seam. That is, considering the physical and geological properties of the sandstone layers, as well as the flow characteristics of coalbed methane, fracturing in sandstone layers makes it easier to ensure the effectiveness and safety of fracturing.

[0037] S2. Based on the working face layout and borehole columnar section, determine the number of target fracturing layers. The target fracturing layers include target layer 2 for the roof above coal seam 400 and target layer 3 for the floor below coal seam 400. It is understandable that when determining the number of target fracturing layers, it is necessary to distinguish the characteristics of the roof and floor of coal seam 400 according to the actual situation, consider the changes in surrounding rock stability under high vertical and horizontal stress environments, and ensure that an appropriate number of target fracturing layers is selected to improve the stability of the surrounding rock.

[0038] S3. Perform hydraulic fracturing on the target strata area of ​​the roof and floor of coal seam 400. Understandably, during the fracturing process, the fracturing parameters are precisely controlled based on factors such as the fracture distribution and rock strength of coal seam 400 to ensure good fracturing results while avoiding unnecessary disaster risks.

[0039] Specifically, such as Figures 1-3 As shown, to perform fracturing on the target stratum, it is necessary to drill a vertical shaft 4 from the ground and a horizontal shaft in the target stratum (i.e., the target rock stratum on the roof of coal seam 400 and the target rock stratum on the floor of coal seam 400). The horizontal shafts include a fracturing horizontal shaft 5 in the roof area and a fracturing horizontal shaft 6 in the floor area. Finally, the horizontal shafts are used to gradually fracture from far to near, forming a fracturing area 7.

[0040] Optionally, hydraulic fracturing can be used to fracture the target stratum. It should be noted that hydraulic fracturing involves injecting high-pressure water into the rock strata, creating immense pressure that breaks the rock and alters its structure, increasing its stability. More specifically, this involves drilling a borehole at the identified target stratum, then injecting high-pressure fluid into the hole. The fluid expands within the borehole, generating immense pressure that causes the rock to fracture or shift. This fracturing method can reinforce tunnels and improve the stability of the surrounding rock, particularly in coal mines with depths exceeding 1,000 meters, effectively improving geological conditions and enhancing tunnel stability and safety.

[0041] Preferably, the fracturing range is monitored in real time to ensure that it covers the working face's mining area. It is understood that during fracturing, the fracturing pressure and flow rate are controlled to manage the extent of fracture propagation, thereby ensuring that the fracturing range covers the working face's mining area and avoiding pre-fracture blind spots.

[0042] S4. When excavating and mining roadways within the fracturing coverage area of ​​the coal seam, safe mining operations must be conducted. During roadway excavation, it is crucial to monitor roadway deformation and implement timely support measures to ensure safe mining operations. In practice, the mining plan should be flexibly adjusted based on on-site monitoring data and real-time early warning systems to minimize safety hazards.

[0043] In some embodiments, the method for preventing rockburst in a coal seam with double-layer decompression and pressure relief in depths exceeding 1,000 meters according to the present invention further includes the following step: using stress monitoring equipment to detect the stress of the original rock in the tunnel to be excavated area and the mining area in real time.

[0044] Understandably, using stress monitoring equipment to monitor the stress of the original rock in the tunnel to be excavated area and the mining area in real time is a key step. It helps to ensure that the stress state can be understood and controlled in a timely manner when tunneling operations are carried out in the fracturing tunnel area, and to prevent potential safety risks.

[0045] It should be noted that stress monitoring equipment includes stress gauges, stress relief instruments, borehole deformation meters, acoustic emission monitoring systems, hydraulic fracturing equipment, electromagnetic stress detectors, and other instruments or equipment that can be used to continuously monitor the stress borne by rock masses. Of course, when selecting specific equipment, factors such as the monitoring objective, geological conditions, environmental factors, and cost need to be considered. In practical applications, multiple devices can be used in combination for monitoring as needed to improve the accuracy and reliability of the monitoring results.

[0046] Therefore, the double-liberation layer stress relief method for preventing rockburst in coal seams with a burial depth of over 1,000 meters in this embodiment of the invention targets high vertical stress by carrying out surface fracturing in the roof above coal seam 400; and targets high horizontal stress by carrying out surface fracturing in the floor below coal seam 400, thus creating an artificial double-liberation layer. This reduces both the high vertical and horizontal stresses in coal seam 400, keeping it in a protected state and proactively reducing the stress levels of the original rock and tectonic structures in the working face tunneling and mining areas, thereby achieving source prevention of rockburst.

[0047] In some embodiments, such as Figure 1 As shown, in step S1, determining the working face layout includes determining the dip length L1 of the working face 1 and calculating the number N1 of the fracturing target layer groups in the dip direction of the working face, i.e., N1 = L1 / 200, and N1 is an integer.

[0048] Understandably, in step S1, determining the working face layout includes determining the dip length L1 of the longwall face 1 and calculating the number N1 of the target fracturing strata. This process is crucial. In coal mines with a burial depth exceeding 1,000 meters, geological conditions are characterized by high ground stress and increased rock mass failure strength, which will affect the layout of the longwall face 1 and the number of target fracturing strata.

[0049] Specifically, based on the determined dip length L1 of the longwall face 1, the number of target strata groups N1 that need to be fractured can be calculated. Assuming the dip length of the roadway is L1, the number of target strata groups N1 determined in S2 can be calculated using the following formula: N1 = L1 / 200. This value is an approximation and needs to be rounded to the nearest integer.

[0050] In addition, in actual operation, this value can be adjusted appropriately according to the actual situation of the roadway and changes in geological conditions to ensure that the fracturing effect can meet the needs of coal mining.

[0051] In some embodiments, in step S1, determining the working face layout further includes determining the strike length L2 of the working face 1 and calculating the number N2 of the target fracturing layers in the strike direction of the working face, i.e., N2 = L2 / 1000, and N2 is an integer.

[0052] Understandably, when calculating the number of target fracturing formations, it is necessary to consider not only the dip length L1 of the working face 1, but also the strike length L2 of the working face 1, and to calculate the values ​​of N1 and N2 based on N1 = L1 / 200 and N2 = L2 / 1000.

[0053] In some embodiments, the total number N of target fracturing layers in the roof above the coal seam and the floor below the coal seam is determined. 总= 2 * N1 * N2. That is, a fracturing target layer group includes two fracturing target layers: the fracturing target layer above the coal seam and the fracturing target layer below the coal seam. Therefore, based on the dip length L1 and strike length L2 of the longwall face 1, the number of fracturing target layer groups in the dip and strike directions of the longwall face 1 can be calculated, i.e., N1 * N2, and the total number of fracturing target layers N... 总 It is twice the number of target formations for fracturing.

[0054] Preferably, in step S2, a sandstone layer located 50 to 100 meters above the coal seam is selected as the target layer for fracturing the roof above coal seam 400.

[0055] It should be noted that in coal mines with a burial depth of over 1,000 meters, selecting the target fracturing depth for the roof above 400 meters and the floor below 400 meters of the coal seam is crucial, as the stability of these layers directly affects the stability and safety of the roadway.

[0056] Therefore, considering the high vertical stress in coal mines with depths exceeding 1,000 meters, the sandstone layer within 50 to 100 meters above coal seam 400 was selected as the target layer for fracturing. This sandstone layer is typically a key rock layer for inducing impact, possesses favorable mechanical properties, and is prone to fracture, thus facilitating fracturing operations. Fracturing this sandstone layer at this depth significantly reduces stress transmission to coal seam 400. Simultaneously, the sandstone layer at this depth, located above coal seam 400, prevents its destruction due to the propagation of hydraulic fracturing fractures in the roof.

[0057] Preferably, selecting a sandstone layer located 30 to 50 meters below the coal seam as the target layer for fracturing the floor below coal seam 400 is understandable. In response to the high-level stress in coal mines with a burial depth of over 1,000 meters, surface fracturing is carried out on the floor below coal seam 400, with the target layer located 30 to 50 meters below coal seam 400. This significantly reduces the high-level stress in coal seam 400. Together with the target fracturing layers of the roof above coal seam 400 and the floor below coal seam 400, coal seam 400 is kept in a protected state, thus proactively reducing the original rock stress and tectonic stress levels in the working face tunneling and mining areas.

[0058] Preferably, the target fracturing layer 2 above the coal seam 400 and the target fracturing layer 3 below the coal seam 400 are both located in sandstone layers with a thickness greater than 10 meters. It is understood that selecting sandstone layers with a thickness greater than 10 meters as target fracturing layers is usually because they are key rock layers that induce impact, and in order to ensure that the fracturing operation can generate fractures in a large area, thereby ensuring the fracturing effect.

[0059] Preferably, the vertical height of the fracturing target layer 2 above the coal seam 400 and the vertical height of the fracturing target layer 3 below the coal seam 400 are both greater than or equal to 20 meters and less than or equal to 30 meters.

[0060] Understandably, the requirement that the vertical height of the fracturing operation be greater than or equal to 20 meters and less than or equal to 30 meters is to ensure that the fracturing operation can generate enough fractures in the sandstone layer, while avoiding the fractures being too long and affecting adjacent rock layers.

[0061] Therefore, the double-liberation layer stress relief method for preventing rockbursts in coal seams with a burial depth of over 1,000 meters, as described in this invention, solves the problems of severe rockburst disasters in deep coal mines (coal mines mined at depths exceeding 1,000 meters) and the ineffectiveness of single roof fracturing measures in eliminating rockburst disasters. Specifically, for high vertical stress, surface fracturing is carried out on the roof above the 400-meter coal seam; for high horizontal stress, surface fracturing is carried out on the floor below the 400-meter coal seam. By carrying out regional fracturing on the roof above the 400-meter coal seam and the floor below the 400-meter coal seam in the area to be excavated and mined, an artificial double-liberation layer is formed, reducing the high vertical and horizontal stresses of the 400-meter coal seam. This multi-level, full-structure, proactive, and advanced reduction of the original rock stress and tectonic stress levels in the area to be excavated and mined in the working face enables safe tunnel excavation and safe mining of the working face in low-stress areas, achieving source prevention of rockbursts.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature 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 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 that the first feature is at a lower horizontal level than the second feature.

[0066] 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.

[0067] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for preventing rockbursts in coal seams buried at depths exceeding 1,000 meters using a double-layer decompression system, characterized in that... Includes the following steps: S1. Determine the layout of the working face and the borehole columnar section. Determining the layout of the working face includes determining the dip length L1 and the strike length L2 of the longwall face. S2. Based on the working face layout and borehole columnar section, determine the number of target fracturing layers. These target layers include the roof fracturing target layers above the coal seam and the floor fracturing target layers below the coal seam. Sandstone layers located 50-100 meters above the coal seam are selected as the roof fracturing target layers, and sandstone layers located 30-50 meters below the coal seam are selected as the floor fracturing target layers. The number of target fracturing layers N1 along the dip direction of the working face is calculated as N1 = L1 / 200, where N1 is an integer. The number of target fracturing layers N2 along the strike direction of the working face is calculated as N2 = L2 / 1000, where N2 is an integer. The total number N of the roof fracturing target layers above the coal seam and the floor fracturing target layers below the coal seam is then determined. 总 =2 N1 N2; S3. Perform hydraulic fracturing on the target stratum area determined by the roof and floor of the coal seam. The vertical height of the hydraulic fracturing target stratum on the roof above the coal seam and the vertical height of the hydraulic fracturing target stratum on the floor below the coal seam are both greater than or equal to 20 meters and less than or equal to 40 meters. S4. Excavate mining roadways within the fracturing coverage area of ​​the coal seam to ensure safe mining operations.

2. The method for preventing rockbursts in coal seams with double-layer decompression and pressure relief at depths exceeding 1,000 meters as described in claim 1, is characterized in that... In step S1, determining the borehole columnar section includes: determining the location of sandstone layers above and below the coal seam.

3. The method for preventing rockbursts in coal seams with double-layer decompression and pressure relief at depths exceeding 1,000 meters as described in claim 2, is characterized in that... Sandstone layers with a thickness greater than 10 meters were selected as the target layers for fracturing.

4. The method for preventing rockbursts in coal seams with double-layer decompression and pressure relief as described in claim 1, characterized in that, In step S3, the fracturing range of the region is monitored in real time to determine whether the fracturing range covers the working face mining area.

5. The method for preventing rockbursts in coal seams with double-layer decompression and pressure relief as described in claim 1, characterized in that, In step S3, hydraulic fracturing is used to fracturing the target stratum region.

6. The method for preventing rockbursts in coal seams with double-layer decompression and pressure relief according to any one of claims 1-5, characterized in that, It also includes the following steps: Before step S4, stress monitoring equipment is used to detect the stress of the original rock in the tunnel to be excavated area and the mining area in real time.

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