Roof fracturing and blasting roof cutting composite pressure relief method

Abstract

The invention relates to the technical field of mine coal mining, in particular to a roof fracturing and blasting roof cutting composite pressure relief method which comprises the following steps: determining the position of a surrounding rock impact ground pressure master control or mine earthquake master control rock stratum above a coal seam in a mining area; detecting and ensuring that the gas concentration of the underground area is within a preset range, performing combination of one of ground vertical well fracturing, ground horizontal well fracturing and underground long drill hole segmented hydraulic fracturing on rock burst main control or mine earthquake main control rock strata of surrounding rock above a coal seam and underground deep hole presplitting blasting, and performing reinforced support on a working surface of a mining area. According to the roof fracturing and blasting roof cutting composite pressure relief method, hydraulic fracturing and deep hole blasting are combined to relieve pressure of rock burst master control and mine earthquake master control rock stratums in an overlying roof so as to improve the pressure relief effect.

Description

Technical Field

[0001] The present application relates to the technical field of coal mining in mines, and in particular to a combined pressure relief method of roof fracturing and blasting. Background Art

[0002] During coal mining, the integrity and stress state of the rock strata that are the main controllers of rock burst or mine tremors above the target coal seam potentially restrict the safe production of the mine, especially when there are multiple thick layers of hard roof above the mined coal seam, which greatly increases the risk of rock burst or mine tremors. The idea of ​​treating thick hard roofs is to modify the thick hard roofs by increasing the cracks in the hard roofs and weakening the overall rock structure. The existing hydraulic fracturing technology was first used in the oil and gas field field. It uses volume fracturing to form artificial cracks in a large area of ​​dense rock formations. It is a commonly used fracturing production enhancement technology. When faced with multiple layers of thick and hard roofs, a single hydraulic fracturing technology cannot accurately treat multiple target rock formations at the same time, resulting in unsatisfactory pressure relief effects, which in turn leads to low efficiency and multiple pressure relief situations. Summary of the Invention

[0003] The present application provides a combined pressure relief method of roof fracturing and blasting roof cutting, which uses a combination of regional hydraulic fracturing and local deep hole blasting to relieve pressure on rock formations that are mainly controlled by rock burst or mine earthquakes, so as to improve the pressure relief effect.

[0004] The present application provides a combined pressure relief method for roof fracturing and blasting roof cutting, comprising:

[0005] Determine the location of the main rock strata controlling rock burst pressure or mine earthquake above the coal seam in the mining area;

[0006] Detect and ensure that the gas concentration in the underground area is within the preset range;

[0007] For the surrounding rock strata above the coal seam that are mainly controlled by rock burst pressure or mine earthquake, any of the following methods can be used: surface vertical well fracturing, surface horizontal well fracturing, underground long-hole staged hydraulic fracturing, and local deep-hole pre-splitting blasting;

[0008] Strengthen support for the working face in the mining area.

[0009] The present application provides a combined pressure relief method of roof fracturing and blasting roof cutting, which uses a combination of regional hydraulic fracturing and local deep hole blasting to relieve pressure on rock formations that are mainly controlled by rock burst or mine earthquakes, so as to improve the pressure relief effect.

[0010] In some embodiments, the surrounding rock above the coal seam in the mining area is divided into a low roof, a middle-high roof and a high roof; the high roof is fractured by ground vertical wells or horizontal wells, the middle-high roof is fractured by ground vertical wells, ground horizontal wells or underground long-borehole segmented hydraulic fracturing, and the low roof is fractured by deep-hole pre-splitting blasting.

[0011] In some embodiments, when deep hole pre-splitting blasting is performed to relieve pressure on the low roof, a hole of preset depth and preset diameter is drilled in the roof, blasting agents are loaded at the pre-splitting position, the blasting connection device is checked, and a safe construction distance is set.

[0012] In some embodiments, when deep hole pre-splitting blasting is performed on the low roof, the spacing of the drill holes used for blasting in the mining direction of the working face is 5m to 10m.

[0013] In some embodiments, the blasting effect is checked and the construction parameters are optimized.

[0014] In some embodiments, the checking of pre-splitting effect and optimization of blasting parameters include the following steps:

[0015] After drilling and blasting, an inspection hole is constructed between the two drill holes on the drill hole connection line. The angle of the inspection hole is consistent with the angle of the blasting hole.

[0016] Clean the inspection hole and use a borehole peep instrument to check the pre-cracking effect of the top plate of the inspection hole. If the expected effect is achieved, adopt the construction parameters. If not, adjust the construction parameters until the expected effect is achieved.

[0017] In some embodiments, monitoring the pressure relief effect of the pressure relief area includes the following steps:

[0018] The working face is monitored by online drilling stress monitoring, microseismic monitoring and hydraulic support pressure monitoring;

[0019] If any monitoring data of drilling stress, microseismicity, or hydraulic support pressure exceeds the preset value, deep hole pre-splitting blasting will be carried out in the alarm area to supplement pressure relief so that the monitoring index is lower than the warning value.

[0020] In some embodiments, before depressurizing the lower roof, the gas concentration of the working face is detected to determine whether it exceeds a preset gas concentration, and a gas circulation and exhaust device is set to keep the gas concentration within a preset range.

[0021] In some embodiments, during drilling stress monitoring, drilling is performed on both sides of the working face and drilling stress monitoring is performed, and the spacing between multiple boreholes in the mining direction of the working face is no more than 30m.

[0022] In some embodiments, four microseismic sensors are set on the working face for microseismic monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 This is one of the schematic diagrams of a combined roof fracturing and blasting roof cutting method for roof pressure relief in an embodiment of the present application;

[0025] Figure 2 This is a second schematic diagram of a combined roof fracturing and blasting roof-cutting pressure relief method for roof pressure relief in an embodiment of the present application;

[0026] Figure 3 This is a schematic diagram of the embodiment of the present application using long-drilled staged hydraulic fracturing to relieve pressure on the middle and high roof;

[0027] Figure 4 This is a schematic diagram of using surface vertical wells for fracturing high roof and mid-high roof in an embodiment of the present application;

[0028] Figure 5 This is a schematic diagram of hydraulic fracturing to relieve pressure on the mid-high roof in an embodiment of the present application.

[0029] The above drawings include the following reference numerals:

[0030] Overlying roof 1, low roof 11, middle and high roof 12, high roof 13,

[0031] Coal seam 2,

[0032] Ground 3, ground vertical well fracturing 4, ground horizontal well fracturing 5, underground long borehole staged hydraulic fracturing 6, deep hole pre-splitting blasting 7. DETAILED DESCRIPTION

[0033] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0034] It should be noted that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating positions or positional relationships, are based on the positions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present application and simplifying the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present application. The terms "mounted", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be internal communication between two elements. The terms "parallel", "perpendicular", and "equal" include the situations described and situations similar to the situations described, and the range of the similar situations is within an acceptable deviation range, where the acceptable deviation range is determined by a person of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system). For example, "parallel" includes both absolute parallelism and approximate parallelism, where the acceptable deviation range for approximate parallelism may be, for example, within 5°; "perpendicular" includes both absolute perpendicularity and approximate perpendicularity, where the acceptable deviation range for approximate perpendicularity may also be, for example, within 5°. "Equal" includes both absolute equality and approximate equality, where the acceptable deviation range for approximate equality may be, for example, that the difference between the two is less than or equal to 5% of either. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0035] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0036] The present application provides a combined pressure relief method for roof fracturing and blasting roof cutting, comprising:

[0037] Determine the location of the main rock layer controlling rock burst pressure or mine earthquake above the coal seam 2 in the mining area,

[0038] Detect and ensure that the gas concentration in the underground area is within the preset range,

[0039] The surrounding rock pressure control layer above the coal seam 2 or the rock layer controlled by mine earthquake is decompressed by any of the following methods: surface vertical well fracturing 4, surface horizontal well fracturing 5, underground long borehole staged hydraulic fracturing 6, combined with local deep hole pre-splitting blasting 7.

[0040] Strengthen the support of the working face in the mining area. It is understandable that when there are multiple rock layers in the overburden of the mining area, the rock layer that controls the movement of the rock mass in whole or in part is called the key layer. The movement of the key rock layer will have a significant impact on the mine pressure, rock movement and surface subsidence of the entire mining area.

[0041] Specifically, if Figures 1 to 5 As shown, the position of the main rock burst control layer or the main rock burst control layer of the surrounding rock above the mining area is determined, the surrounding rock above the target coal seam 2 is divided into a low roof 11, a middle-high roof 12 and a high roof 13, the position of the main rock burst control layer or the main rock burst control layer of the surrounding rock above the target coal seam 2 is determined in the surrounding rock above the target coal seam 2, the main rock burst control layer or the main rock burst control layer of the surrounding rock above the target coal seam 2 is decompressed, and the main rock burst control layer or the main rock burst control layer of the surrounding rock above the coal seam 2 is decompressed by any one of the following methods: surface vertical well fracturing 4, surface horizontal well fracturing 5, underground long borehole staged hydraulic fracturing 6, and local deep hole pre-splitting blasting 7.

[0042] There are multiple key layers in the low roof 11, the middle and high roof 12 and the high roof 13. The positions of the multiple key layers on different roofs are determined, and then it is judged which key layers are the main controlling rock layers of rock burst or mine earthquake.

[0043] Different pressure relief methods are used according to the rock formations that are mainly controlled by impact ground pressure or mine earthquake at different levels. For example, deep hole pre-splitting blasting 7 is used for the low-level roof 11, ground vertical well fracturing 4, ground horizontal well fracturing 5 or downhole long borehole segmented hydraulic fracturing 6 is used for the middle and high-level roof 12, and ground vertical well fracturing 4 or ground horizontal well fracturing 5 is used for the high-level roof 13.

[0044] The low roof 11 is depressurized by deep hole pre-splitting blasting 7. The drilling depth is shallow and the drilling construction is relatively easy, which effectively reduces the stress concentration of the roof and reduces the risk of roof collapse.

[0045] The pressure relief of the middle and high roof 12 is achieved by using surface vertical well fracturing 4, surface horizontal well fracturing 5 or downhole long-bore staged hydraulic fracturing 6. Surface vertical well fracturing 4 and surface horizontal well fracturing 5 require drilling horizontal wells from the surface 3. Hydraulic fracturing can form a crack network over a large area, effectively reducing the stress concentration of the roof. Regional fracturing can form a crack network in multiple key layers, effectively reducing the stress concentration of the roof, effectively controlling the collapse of the roof, and reducing the deformation of the roadway and the support pressure.

[0046] The high roof 13 is depressurized by ground vertical well fracturing 4 or ground horizontal well fracturing 5. Ground vertical well fracturing 4 or ground horizontal well fracturing 5 requires drilling a vertical well from the ground 3. Regional fracturing can form a crack network in multiple key layers, effectively reduce roof stress concentration, effectively control roof collapse, and reduce tunnel deformation and support pressure.

[0047] Before depressurization, the gas concentration in the underground area must be tested and ensured to be within the preset safety range. Through testing, ventilation, and extraction measures, as well as real-time monitoring and adjustment, gas concentrations can be effectively reduced to ensure safe production in the mine.

[0048] Conduct comprehensive inspections using portable gas detectors and fixed gas sensors. Reduce gas concentrations through ventilation and extraction. Before pressure relief operations, such as deep-hole pre-splitting blasting, continuously monitor gas concentrations and dynamically adjust measures to ensure gas concentrations remain within safe ranges.

[0049] Determination of the main controlling rock strata for rock burst and mine tremors: First, use the borehole histogram and key layer calculation to calculate all the key layers above the coal seam, and then use microseismic monitoring to determine the key layers that play a dominant role in the occurrence of rock burst or mine tremors, that is, the main controlling key layers, also called the main controlling rock strata for rock burst and mine tremors.

[0050] This application provides a combined roof fracturing and blasting decompression method, which uses a combination of regional hydraulic fracturing and deep-hole blasting to decompress rock formations primarily responsible for rock bursts or mine tremors, thereby enhancing the decompression effect. The parameters of the fracturing and abrasive jet axial decompression can also be adjusted according to the specific conditions of different coal mines, making it suitable for coal mining under various geological conditions, thereby improving the applicability of this decompression method.

[0051] In some embodiments, the rock strata mainly controlled by rock burst or mine earthquake above the coal seam 2 in the mining area are divided into a low roof 11, a middle-high roof 12 and a high roof 13; the high roof 13 adopts ground vertical well fracturing 4 or ground horizontal well fracturing 5, the middle-high roof 12 adopts ground vertical well fracturing 4, ground horizontal well fracturing 5 or underground long borehole segmented hydraulic fracturing 6, and the low roof 11 adopts deep hole pre-splitting blasting.

[0052] Specifically, if Figures 1 to 5 As shown, during surface vertical well fracturing 4 or surface horizontal well fracturing 5, decompression is achieved. ① Drilling: Key technologies such as rotary steering and drill trajectory control are used to sequentially construct wellbores of varying diameters at specific target locations. After drilling reaches a certain depth, casing is installed and cement is poured into the annular space between the casing and the wellbore wall to reinforce the exposed rock formation.

[0053] ② Perforating: Use oil pipe or cable to lower the perforator into the fracturing layer. The pressure difference causes the perforating bullet to explode and penetrate the casing and cement ring, so that the crack reaches a certain depth in the formation, connecting the fracturing rock formation and the wellbore, and providing a smooth channel for the fracturing fluid to enter the formation.

[0054] ③ Fracturing: After perforating, flush the wellbore. Connect the coiled tubing to the jetting tool, penetrate the wellbore, seal the packer, and inject fracturing fluid into the target rock formation through the coiled tubing at a specific flow rate and pressure. Once the current section is fracturing complete, pull the tubing backward to repeat the fracturing of the remaining sections.

[0055] In other words, surface vertical well fracturing 4 involves drilling a vertical well on the surface 3 to reach the rock layer above the target coal seam 2, which is primarily responsible for rock bursts or mine seismic activity. High-pressure fluid is then injected, creating cracks in the rock of the key controlling layer, thereby reducing stress in the key layer and achieving pressure relief. This method is convenient to operate and can simultaneously treat multiple critical roof layers, achieving excellent pressure relief, effectively reducing stress in the key layers and minimizing gas influx. It is suitable for a wide range of geological conditions, particularly in areas with deep coal seams 2.

[0056] Surface horizontal well fracturing 5: A horizontal well is drilled on the surface 3, with the horizontal well section penetrating the critical formation, followed by fracturing. The horizontal well increases the contact area with the critical formation, improving the fracturing effect. This large contact area allows the horizontal well section to more effectively cover the critical formation, enhancing fracturing effectiveness. The wide pressure relief range allows for decompression of a large area of ​​the critical formation, reducing gas influx. This method is suitable for areas with thick critical formations or high gas content.

[0057] During downhole long-hole hydraulic fracturing and pressure relief, ① Drilling: Key technologies such as rotary steering and real-time drilling trajectory control are used to complete wellbore construction at a specific target point. During drilling, visual inspection is used to determine the rock formation position, lithology, and fragmentation status based on drilling speed, drilling pressure, and drilling debris.

[0058] ② Fracturing: The fracturing tool string is pushed down to the bottom of the well via the fracturing drill pipe. The pressure differential seals the packer, and the fracturing fluid is pumped into the target rock formation at a specific flow rate and pressure. After the fracturing of the current section is completed, the drill pipe is pulled back to repeat the fracturing of the remaining sections.

[0059] Deep hole pre-splitting blasting for pressure relief: ① Drilling: Drill holes in the coal mine working face or at the location where pre-splitting is required in the ore body according to the design requirements. The depth, diameter, and spacing of the holes should be determined based on the ore body conditions, pre-splitting requirements, and blasting design.

[0060] ②Charging: Use an appropriate blasting agent and evenly load it into the drill hole. Ensure uniform distribution of the charge during charging to ensure effective blasting. Install the blasting equipment, including electric detonators, fuses, and blasting networks. The blasting system must be securely connected to ensure synchronization and safety of the blasting.

[0061] ③ Detonation: Before blasting, a detailed inspection is required, including the charge level in the hole, equipment installation, and safety measures to ensure that the blasting can proceed smoothly and without safety issues. An appropriate safety distance is set to ensure the safety of workers and equipment. The surrounding area must be cordoned off before blasting. Detonation is carried out according to the designed plan, typically using electric detonators or other electronic equipment for controlled blasting.

[0062] The composite pressure relief method of roof fracturing and blasting top cutting in the embodiment of the present application adopts regional fracturing for the low-level roof 11, the middle-high-level roof 12, and the high-level roof 13 above the coal seam 2 according to the main controlling rock formations of rock burst and mine earthquake at different levels, and adopts a composite pressure relief method of local deep hole pre-splitting blasting 7 for the low-level roof 11 to increase the pressure relief range and thereby improve the pressure relief effect.

[0063] Furthermore, when the low-position roof 11 is depressurized by deep hole pre-splitting blasting 7, a hole of a preset depth and diameter is drilled into the roof, blasting agents are loaded into the pre-splitting position, the blasting connection device is checked, and a safe construction distance is set.

[0064] Drill holes according to preset parameters at the coal mine working face or in areas of the ore body requiring pre-splitting. Use blasting agents and evenly load them into the drilled holes. Ensure uniform distribution of the charge during loading to ensure effective blasting. Install the blasting equipment, including electric detonators, fuses, and blasting networks. Ensure the blasting system is securely connected to ensure synchronization and safety of the blasting.

[0065] Before blasting, a detailed inspection is required, including the charge level in the hole, equipment installation, and safety measures to ensure that the blasting can proceed smoothly and without safety issues. An appropriate safety distance should be set to ensure the safety of workers and equipment. The surrounding area should be cordoned off before blasting. Detonation should be carried out according to the design plan.

[0066] The combined pressure relief method of roof fracturing and blasting top cutting in the embodiment of the present application can effectively alleviate stress concentration in the roof area, prevent the occurrence of rock burst and mine tremors, improve the stability and efficiency of coal mining, and reduce the impact of rock burst and mine tremors on production through the combined fracturing technology of regional fracturing and blasting. The parameters of fracturing and blasting can also be adjusted according to the specific conditions of different coal mines, making the process suitable for coal mining under various geological conditions.

[0067] In some embodiments, when deep-hole pre-splitting blasting 7 is performed on the low roof 11, the boreholes used for blasting are spaced 5 to 10 meters apart in the mining direction of the working face. This facilitates the use of different drilling and blasting spacings for different roof types. When performing deep-hole pre-splitting blasting 7 on the low roof 11, properly selecting the borehole spacing can effectively reduce stress concentration in the roof, minimizing the risk of roof collapse while optimizing construction costs and efficiency. Selecting the appropriate borehole spacing based on specific geological conditions and blasting design requirements can ensure effective pressure relief.

[0068] Furthermore, the blasting effect of the low roof 11 is checked and the construction parameters are optimized.

[0069] Furthermore, the checking of the pre-splitting effect and the optimization of the blasting parameters include the following steps:

[0070] After drilling and blasting, an inspection hole is constructed between the two drill holes on the drill hole connection line. The angle of the inspection hole is consistent with the angle of the blasting hole.

[0071] Clean the inspection hole and use a borehole peep to check the pre-cracking effect of the roof of the inspection hole. If the expected effect is achieved, adopt the construction parameters. If not, adjust the construction parameters until the expected effect is achieved. On the drilling line of multiple boreholes, splitting cracks are formed on both sides of each borehole at the blasting position. Multiple splitting cracks deep in the rock layer form a regular structural weak surface on the drilling line. Under the action of mine pressure, the roof rock layer is cut and falls along the structural weak surface. Then, the subsidence of the surrounding rock tunnel roof, the bulge of the tunnel bottom, the stress of the roof anchor cable, and the pressure of the tunnel side support can be monitored to compare the changes before and after decompression to determine whether the analysis effect meets the expectations.

[0072] In some embodiments, monitoring the pressure relief effect of the pressure relief area includes the following steps:

[0073] The working face is monitored by online drilling stress monitoring, microseismic monitoring and hydraulic support pressure monitoring;

[0074] If any of the monitored data for borehole stress, microseismicity, or hydraulic support pressure exceeds a preset value, deep-hole pre-splitting blasting (7) is performed in the alarm area to supplement pressure relief, reducing the monitored indicators below the warning value. Borehole stress monitoring involves drilling holes in the sidewalls and roof of the working face to monitor stress changes in the roof and coal seam in real time and evaluate the effectiveness of pressure relief. Borehole stress sensors are installed in pre-set boreholes. Ensure the sensor is accurately positioned to effectively monitor stress changes in the target area. Stress data is collected in real time and transmitted to a monitoring center via a data transmission system. The collected stress data is analyzed and monitored in real time to determine whether the stress exceeds the preset value.

[0075] Microseismic monitoring monitors microseismic activity in the roof and coal seams to assess crack propagation and stress release. Microseismic sensors are installed at pre-set locations on the working face. These sensors are arranged to ensure coverage of the monitored area. Microseismic data is collected in real time and transmitted to a monitoring center via a data transmission system. This data is analyzed in real time to determine if there are any abnormalities in the microseismic activity.

[0076] Set preset values ​​for online monitoring of drilling stress, microseismic monitoring and hydraulic support pressure monitoring respectively. When any monitoring data exceeds the preset value, the system automatically issues a warning signal. The monitoring system should have a real-time feedback function to promptly feed back abnormal data to the operator so that corresponding measures can be taken.

[0077] If any monitoring data of drilling stress, microseismicity, or hydraulic support pressure exceeds a preset value, deep hole pre-splitting blasting 7 is performed on the alarm area to supplement pressure relief and reduce stress.

[0078] After the supplementary pressure relief operation is completed, continue to monitor the borehole stress, microseismicity and hydraulic support pressure to ensure that the monitoring indicators are lower than the warning value within the preset time.

[0079] Furthermore, before depressurizing the low roof 11, the gas concentration of the working face is detected to determine whether it exceeds the preset gas concentration, and a gas circulation and exhaust device is set to keep the gas concentration within the preset range, thereby improving the safety and stability of the construction.

[0080] In some embodiments, during borehole stress monitoring, boreholes are drilled on both sides of the working face and borehole stress monitoring is performed. The spacing between multiple boreholes in the mining direction of the working face is no more than 30m. Four microseismic sensors are set on the working face for microseismic monitoring. Through borehole stress monitoring and microseismic monitoring, the stress state and microseismic events of the roof can be monitored comprehensively and in real time, potential unstable factors can be discovered in a timely manner, and effective preventive measures can be taken to ensure safe production in the mine. Reasonable borehole spacing and microseismic sensor arrangement can improve the accuracy and efficiency of monitoring, optimize construction parameters, and reduce construction risks and costs.

[0081] The above is a detailed introduction to the method provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core ideas of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A roof fracturing and blasting combined pressure relief method, characterized in that: include: Determine the location of the main rock strata controlling rock burst pressure or mine earthquake above the coal seam in the mining area; Detect and ensure that the gas concentration in the underground area is within the preset range; For the main rock burst control layer or mine earthquake control layer of the surrounding rock above the coal seam, one of the following methods is used: surface vertical well fracturing, surface horizontal well fracturing, underground long borehole staged hydraulic fracturing, and combined with underground deep hole pre-splitting blasting to relieve pressure; Strengthen support for the working face in the mining area.

2. The combined pressure relief method of roof fracturing and blasting roof cutting according to claim 1 is characterized in that: The surrounding rock above the coal seam in the mining area is divided into low-level roof, medium-high-level roof and high-level roof; the high-level roof is fractured by ground horizontal wells or vertical wells, the medium-high-level roof is fractured by ground fracturing or underground long-borehole segmented hydraulic fracturing, and the low-level roof is fractured by deep-hole pre-splitting blasting.

3. The roof fracturing and blasting roof cutting combined pressure relief method according to claim 2, characterized in that: When performing deep hole pre-splitting blasting to relieve pressure on the low roof, drill holes of preset depth and diameter on the roof, load blasting agents at the pre-splitting position, check the blasting connection device, and set a safe construction distance.

4. The roof fracturing and blasting roof cutting combined pressure relief method according to claim 3, characterized in that: When deep hole pre-splitting blasting is carried out on the low roof, the spacing of the drill holes used for blasting in the mining direction of the working face is 5m to 10m.

5. The roof fracturing and blasting roof cutting combined pressure relief method according to claim 3, characterized in that: Check the blasting effect and optimize the construction parameters.

6. The roof fracturing and blasting roof cutting combined pressure relief method according to claim 5, characterized in that: The method of checking the pre-splitting effect and optimizing the blasting parameters comprises the following steps: After drilling and blasting, an inspection hole is constructed between the two drill holes on the drill hole connection line. The angle of the inspection hole is consistent with the angle of the blasting hole. Clean the inspection hole and use a borehole peep instrument to check the pre-cracking effect of the top plate of the inspection hole. If the expected effect is achieved, adopt the construction parameters. If not, adjust the construction parameters until the expected effect is achieved.

7. The roof fracturing and blasting roof cutting combined pressure relief method according to claim 6, characterized in that: When monitoring the pressure relief effect of the pressure relief area, the following steps are included; The working face is monitored by online drilling stress monitoring, microseismic monitoring and hydraulic support pressure monitoring; If any monitoring data of drilling stress, microseismicity, or hydraulic support pressure exceeds the preset value, deep hole pre-splitting blasting will be carried out in the alarm area to supplement pressure relief so that the monitoring index is lower than the warning value.

8. The roof fracturing and blasting roof cutting combined pressure relief method according to claim 6, characterized in that: Before depressurizing the low roof, the gas concentration at the working face is tested to determine whether it exceeds the preset gas concentration, and a gas circulation and exhaust device is set up to keep the gas concentration within the preset range.

9. The roof fracturing and blasting roof cutting combined pressure relief method according to claim 6, characterized in that: During drilling stress monitoring, holes are drilled on both sides of the working face and drilling stress monitoring is performed. The spacing between multiple boreholes in the mining direction of the working face is no more than 30m.

10. The roof fracturing and blasting roof cutting combined pressure relief method according to claim 7, characterized in that: Four microseismic sensors are set up on the working face for microseismic monitoring.

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