Three-dimensional integrated anti-shocking method for hard coal and rock strata using directional and pulse fracturing

Abstract

This invention discloses a three-dimensional integrated anti-shocking method combining directional and pulse fracturing in hard coal and rock strata. First, boreholes of different heights are drilled into the rock and coal seams within the transport roadway, return airway, and opening cut. Then, a three-dimensional integrated anti-shocking measure combining directional and pulse fracturing is employed to control the overhang of the goaf and prevent the energy released from the goaf roof fracture and the dynamic pressure from mining from being transmitted to the working face roadway and adjacent working face roadways. This invention can reduce peak stress and dynamic load disturbance, thereby reducing the large deformation and impact risk in the working face roadway and adjacent working face roadways.

Description

Technical Field

[0001] This invention relates to the field of coal mine safety technology, specifically to a three-dimensional integrated anti-rock erosion method using directional and pulse fracturing in hard coal and rock strata. Background Technology

[0002] Rockbursts are a typical dynamic disaster in coal mines, characterized by their suddenness, rapidity, and intensity. They often cause severe damage to mine shafts and tunnels, resulting in significant casualties and even surface damage and localized earthquakes. When the roof of the working face is a hard, dense, intact, and thick rock stratum, the energy released by large-scale overhanging roof fractures and slippage in the goaf can easily induce rockbursts, also known as hard-roof type rockbursts.

[0003] Currently, a preliminary rockburst prevention and control technology system combining regional prevention and local mitigation has been established. Regional prevention methods utilize techniques such as protective layer mining, staggered layout of thick coal seams, and optimized mining layout and sequence to preemptively reduce (unload) pressure over a large area or avoid the formation of stress superposition zones during the mine planning and design phase. Local mitigation primarily involves reducing stress peaks or dynamic load disturbances through pressure-relief blasting, large-diameter drilling in coal seams, and other pressure-relief methods, directly altering the properties of the pressure-bearing medium. Among these methods, pressure relief blasting involves drilling and blasting near high-stress areas (or areas where stress concentration is expected) to actively disrupt the coal and rock mass, causing it to lose its bearing capacity and thus achieving pressure relief. However, due to its poor safety, the "Coal Mine Safety Regulations" have prohibited the use of explosives in mining-affected zones. Furthermore, explosive blasting presents challenges such as complex management of explosives, large drilling workload, and difficulties in deep-hole loading. Large-diameter drilling for pressure relief in coal seams involves constructing large-diameter boreholes within the coal seam to prevent rockbursts. Its purpose is to provide space for coal deformation, achieving a "low-density" effect in rockburst prevention. While large-diameter drilling is simple, convenient, and versatile, it involves a large workload, a relatively small pressure relief range, and high costs. Therefore, it is necessary to find a reliable local mitigation technology to complement regional prevention measures for jointly preventing rockbursts caused by hard roofs. Summary of the Invention

[0004] The purpose of this invention is to provide a three-dimensional integrated method for preventing rockbursts in hard coal and rock strata using directional and pulse fracturing, in order to overcome the shortcomings of local pressure relief methods such as blasting and large-diameter drilling in coal seams in preventing rockbursts caused by hard roofs.

[0005] To achieve the above objectives, the present invention provides a three-dimensional integrated anti-rock erosion method combining directional and pulsed fracturing in hard coal and rock strata, comprising the following steps:

[0006] Step S1: Using a drilling rig, drill one row of Class I and Class II high-level roof boreholes along the direction of the cut-out. Drill one row each of Class III, Class IV, coal seam in-seam boreholes, and low-level roof boreholes along the direction of the transport roadway and return air roadway.

[0007] The opening position of the first type of high-level roof drilling is close to the roof of the front coal wall inside the cut-out, and the high-level roof drilling is carried out obliquely towards the front coal wall;

[0008] The second type of high-level roof drilling is located in the cut-out hole near the roof of the rear coal wall, and the high-level roof drilling is carried out obliquely towards the rear coal wall.

[0009] The opening position of the third type of high-level roof drilling is at the center line of the roof in the transport roadway and return air roadway, and the high-level roof drilling is carried out obliquely towards the side roadway of the working face.

[0010] The final positions of the first type of high-level roof borehole, the second type of high-level roof borehole, and the third type of high-level roof borehole are all located in the middle and upper part of the high-level hard rock strata, so as to cut off the old roof above the coal seam, thereby shortening the initial pressure and periodic pressure step distance, and cutting off the transmission path of the mining dynamic pressure to the transport roadway and return air roadway of this working face.

[0011] The fourth type of high-level roof drilling is located on the roof near the coal pillar sidewall in the transport roadway and return air roadway. The drilling orientation is perpendicular to the roadway direction at the drilling site. The drilling is inclined towards the coal pillar sidewall. The drilling end point is in the middle and upper part of the high-level hard rock layer above the coal pillar, so as to cut off the transmission path of dynamic pressure generated by the fracture of the old roof above the goaf to the adjacent working face roadway.

[0012] The opening position of the coal seam in-seam borehole is at the working face side roadway in the transport roadway and return air roadway. The borehole orientation is perpendicular to the roadway direction at the borehole construction site. The borehole is divided into a non-fracturing section and a fracturing section along its length. The non-fracturing section is close to the roadway at the borehole construction site to ensure the stability of the roadway surrounding rock and support structure.

[0013] The opening position of the low-level roof borehole is at the center line of the roof at the end of the transport roadway and the return air roadway. The low-level roof borehole is drilled vertically, and the final position of the borehole is in the middle and upper part of the low-level hard rock layer above the coal seam, so that the low-level roof can collapse in time and fill the goaf.

[0014] Step S2: Use a hydraulic fracturing high-pressure pump to inject high-pressure water into the first type of roof high-level borehole through the pipeline for fracturing. Use the method of simultaneous fracturing of multiple boreholes to induce the cracks to expand along the direction of the borehole connection line in order to directionally cut off the roof.

[0015] Step S3: Use a hydraulic fracturing high-pressure pump to inject high-pressure water into the high-level borehole of the second type of roof through the pipeline for fracturing. Use the method of simultaneous fracturing of multiple boreholes to induce the cracks to expand along the direction of the borehole connection line in order to directionally cut off the roof.

[0016] Step S4: Use a hydraulic fracturing high-pressure pump to inject high-pressure water into the high-level borehole of the third type of roof through the pipeline for fracturing. Use the method of simultaneous fracturing of multiple boreholes to induce the cracks to expand along the direction of the borehole connection line in order to directionally cut off the roof.

[0017] Step S5: Use a hydraulic fracturing high-pressure pump to inject high-pressure water into the high-level borehole of the fourth type of roof through the pipeline for fracturing. Use the method of simultaneous fracturing of multiple boreholes to induce the cracks to expand along the direction of the borehole connection line in order to directionally cut off the roof.

[0018] Step S6: Use a hydraulic fracturing pulse pump to inject pulsed water into the coal seam through pipeline to perform fracturing, thereby fully breaking the coal seam;

[0019] Step S7: Use a hydraulic fracturing high-pressure pump to inject high-pressure water into the low-level borehole of the top plate through the pipeline for fracturing. Use the method of simultaneous fracturing of multiple boreholes to induce the cracks to expand along the direction of the borehole connection, so as to directionally cut off the top plate.

[0020] Furthermore, the length of the coal seam in-seam borehole is 40–100 m, wherein the non-fracturing section is 20 m, and the borehole spacing is 20–30 m.

[0021] Furthermore, the spacing between the holes drilled in the low-level top plate is 6 to 15 meters.

[0022] Furthermore, the spacing between the first type of high-level drilling holes in the top plate, the second type of high-level drilling holes in the top plate, the third type of high-level drilling holes in the top plate, and the fourth type of high-level drilling holes in the top plate is 10 to 20 m.

[0023] The beneficial effects of this invention are as follows: This invention adopts a three-dimensional hydraulic fracturing and anti-scour measure of "coal seam - low-level hard rock strata - high-level hard rock strata". Drilling boreholes along the coal seam can form a complex and uniform hydraulic fracture network within the coal body, fully cutting the coal body, weakening its strength, and thus reducing the impact risk of the coal seam. Drilling low-level roof boreholes can prevent the formation of large-area overhangs at the end of the working face, preventing the stress in the goaf at the end of the working face from being transmitted to the mining roadway of this working face and the mining roadway of adjacent working faces, and eliminating the impact dynamic load caused by the sudden collapse of large-area overhangs at the end of the working face. Drilling Class I, II, III, and IV high-level roof boreholes can reduce the initial pressure step distance and the periodic pressure step distance of the working face, reducing the limit area of ​​the overhang in the goaf during the initial and periodic pressure periods, thereby reducing the stress peak and the dynamic pressure intensity caused by the collapse of the overhang, and reducing the overall impact risk of the surrounding rock in the advance support section of the transport roadway and return air roadway of this working face. In addition, drilling the third type of high-level roof boreholes can prevent the dynamic pressure from the working face from being transmitted to the transport roadway and return airway of this working face, further reducing the impact risk of the overall surrounding rock in the advanced support section of the transport roadway and return airway of this working face; drilling the fourth type of high-level roof boreholes can prevent the dynamic pressure from the working face from being transmitted to the transport roadway and return airway of adjacent working faces, further reducing the impact tendency of the advanced support section of the transport roadway and return airway of adjacent working faces. Compared with traditional explosive blasting, hydraulic fracturing has a large single-hole effective range for controlling hard top coal roof, is less affected by the stress environment, and is convenient and efficient in sealing the borehole, enabling long-distance fracturing and overcoming the charging and sealing difficulties of deep-hole blasting. The hydraulic fracturing process is spark-free and impact-free, with higher safety, improving the safety of the anti-impact technology itself. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the application scenario of the three-dimensional integrated anti-rock erosion method of directional and pulsed fracturing in hard coal and rock strata according to the present invention;

[0025] Figure 2 yes Figure 1 The AA-direction cross-section shows the locations of the first type of high-level drill holes and the second type of high-level drill holes in the top plate.

[0026] Figure 3 yes Figure 1 The BB-direction cross-section shows the locations of the third type of high-level roof boreholes, the fourth type of high-level roof boreholes, the low-level roof boreholes, and the coal seam in-seam boreholes.

[0027] Figure 4 This is a schematic diagram of a hydraulic fracturing device;

[0028] In the diagram, 1-high-level hard rock strata, 2-soft roof rock strata, 3-low-level hard rock strata, 4-coal seam, 5-direct floor, 6-old floor, 7-cut hole, 8-transport roadway, 9-return airway, 10-adjacent working face roadway, 11-coal pillar, 12-first-class high-level roof borehole, 13-second-class high-level roof borehole, 14-third-class high-level roof borehole, 15-fourth-class high-level roof borehole, 16-low-level roof borehole. 17-Coal seam in-seam drilling, 18-Dynamic pressure, 19-Radial and tangential stress, 20-Hydraulic fracturing pulse pump, 21-Hydraulic fracturing high-pressure pump, 22-Stop valve, 23-Tee, 24-Drain valve, 25-Sensor, 26-Adaptor connector, 27-Water injection steel pipe, 28-High-pressure automatic sealing device, 29-Dual packer, 30-High-pressure hose, 31-Hand pump, 32-Hydraulic fracturing control instrument, 33-High-pressure hose. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] When the roof of the working face is a hard, dense, intact, and thick rock stratum, the energy released by the large-scale overhanging fracture and slippage in the goaf can easily induce rockbursts in the roadway of the working face or adjacent working faces. To reduce the occurrence of such rockbursts caused by hard roofs, this invention discloses a three-dimensional integrated rockburst prevention method combining directional and pulse fracturing in hard coal and rock strata, starting from reducing the energy source and cutting off the energy transmission path. The specific approach is as follows: First, the overhanging length of the goaf roof should be effectively reduced, including reducing the overhanging length at the ends of the two roadways of the working face, reducing the initial pressure step distance of the working face, and reducing the periodic pressure step distance, thereby reducing the energy released by the fracture of the goaf roof; Second, the transmission path of the energy released by the fracture of the goaf roof and the dynamic pressure of mining to the roadway of the working face and adjacent working faces should be cut off, preventing the energy released by the fracture of the goaf roof and the dynamic pressure of mining to be transmitted to the roadway of the working face and adjacent working faces. In summary, the goal is to reduce the peak stress of the surrounding rock in the dynamic pressure roadway and reduce dynamic load disturbance, thereby reducing the risk of large deformation and impact in the roadway of this working face and adjacent working faces.

[0031] The specific steps of the three-dimensional integrated anti-rock erosion method combining directional and pulse fracturing in hard coal and rock strata disclosed in this invention are as follows:

[0032] Step S1: Using a drilling rig, drill the following six types of boreholes at the opening 7, transport roadway 8, and return air roadway 9: Type I high-level roof borehole 12, Type II high-level roof borehole 13, Type III high-level roof borehole 14, Type IV high-level roof borehole 15, low-level roof borehole 16, and coal seam in-seam borehole 17. Please refer to... Figure 2Above coal seam 4 are low-lying hard rock strata 3, soft roof rock strata 2, and high-lying hard rock strata 1. Below coal seam 4 are the immediate floor 5 and the old floor 6. The first type of high-level roof borehole 12 is opened within the cut-out 7 near the front coal wall roof, and is drilled obliquely towards the front coal wall, with the final borehole located in the upper-middle part of the high-lying hard rock strata 1. The second type of high-lying roof borehole 13 is opened within the cut-out near the rear coal wall roof, and is drilled obliquely towards the rear coal wall, with the final borehole located in the upper-middle part of the high-lying hard rock strata 1. (The text repeats itself here.) Figure 3 As shown, the third type of high-level roof borehole 14 is located at the centerline of the roof within the transport roadway 8 and return air roadway 9, and is constructed obliquely towards the side roadway of the working face. The final borehole is located in the upper-middle part of the high-level hard rock stratum 1. The fourth type of high-level roof borehole 15 is located at the centerline of the roof within the transport roadway and return air roadway, and is constructed obliquely towards the side roadway of the coal pillar. The final borehole is located in the upper-middle part of the high-level hard rock stratum 1 above the coal pillar. The low-level roof borehole 16 is located at the centerline of the roof at the end of the transport roadway and return air roadway, and is constructed vertically. The final borehole is located in the upper-middle part of the low-level hard rock stratum 3 above the coal seam 4, so that the low-level roof can collapse in time and fill the goaf. The opening position of the coal seam in-seam borehole 17 is 1 to 1.5m away from the bottom plate on the side wall of the working face in the transport roadway and return air roadway. The coal seam borehole is drilled vertically into the working face, with a borehole length of 40m. Among them, a 20m range is designated as a non-fracturing section to ensure the stability of the surrounding rock and support structure in the weak structure internal roadway.

[0033] Step S2: Using a hydraulic fracturing high-pressure pump 21, high-pressure water is injected into the first type of roof high-level drill hole 12 through the pipeline for fracturing. The method of simultaneous fracturing of multiple holes is used to induce the cracks to expand along the direction of the drill hole connection, so as to directionally cut off the roof.

[0034] Step S3: Using a hydraulic fracturing high-pressure pump 21, high-pressure water is injected into the second type of roof high-level drill hole 13 through the pipeline for fracturing. The method of simultaneous fracturing of multiple holes is used to induce the cracks to expand along the direction of the drill hole connection, so as to directionally cut off the roof.

[0035] Step S4: Using a water-pressure fracturing high-pressure pump 21, high-pressure water is injected into the third type of roof high-level drill hole 14 through the pipeline for fracturing. The method of simultaneous fracturing of multiple holes is used to induce the cracks to expand along the direction of the drill hole connection, so as to directionally cut off the roof.

[0036] Step S5: Using a hydraulic fracturing high-pressure pump 21, high-pressure water is injected into the high-level borehole 15 of the fourth type of roof through the pipeline for fracturing. The method of simultaneous fracturing of multiple boreholes is used to induce the cracks to expand along the direction of the borehole connection, so as to directionally cut off the roof.

[0037] like Figure 1As shown, during the initial roof caving after the working face is mined, the roof is fixedly supported at all four ends. During the initial roof caving, the roof forms an "OX" fracture (the middle of the roof fractures into an X-shape, and the outside fractures into an O-shape), resulting in initial pressure. Subsequently, as the working face is mined back, the roof is in a state of fixed support at three ends. The roof periodically hangs over a certain distance and then periodically collapses, resulting in periodic pressure. Within the cut-off hole 7, first-class high-level roof boreholes 12 and second-class high-level roof boreholes 13 are constructed obliquely towards the coal face. Within the transport roadway 8 and return air roadway 9, third-class high-level roof boreholes 14 and fourth-class high-level roof boreholes 15 are constructed obliquely towards the working face. All boreholes are constructed using a multi-hole simultaneous fracturing method to induce cracks to initiate and propagate along the borehole connection line, cutting off the hard roof above the cut-off hole 7, transport roadway 8, and return air roadway 9, making the roof in a state of one-end fixed support. This reduces the initial and periodic pressure step distance of the working face, reduces the limit area of ​​the suspended roof in the goaf during the initial and periodic pressure, thereby reducing the stress peak and the dynamic pressure intensity caused by the roof collapse. At the same time, it cuts off the transmission path of the dynamic pressure 18 generated by the fracture of the old roof above the goaf to the transport roadway 8 and return air roadway 9 of the working face, reducing the impact risk of the overall surrounding rock of the advanced support section of the transport roadway 8 and return air roadway 9 of this working face. Simultaneously, fourth-class high-level roof boreholes were drilled on the coal pillar side of transport roadway 8 and return air roadway 9. A multi-hole simultaneous fracturing method was used to induce cracks to initiate and propagate along the borehole connection line, cutting off the overlying roof of the coal pillar. This prevented the dynamic pressure 18 generated by the fracture of the old roof above the goaf from being transmitted to the coal pillar 11 and the adjacent working face roadway 10, reducing the impact risk of the advanced support section of the goaf roadway.

[0038] Step S6: Using a hydraulic fracturing pulse pump 20, pulsed water is injected into the coal seam through pipelines into the in-seam borehole 17 for fracturing. Generally, compared to rock strata, coal seams have lower strength and more developed internal joints and fractures. Compared to the top and bottom rock strata of the transport roadway and return airway, the coal seams on the sides of the transport roadway and return airway are more likely to be impacted. Therefore, the coal seams on the sides of the roadways should be weakened. During pulsed hydraulic fracturing, the pulsed water pressure propagates in a sinusoidal manner. When the pulsed pressure wave reaches the interface between the water and the coal fracture tip, it generates pulsed incident waves and pulsed reflected waves. The reflection, superposition, and reciprocation of the pulsed pressure wave cause phenomena such as the expansion of the pulsed pressure wave amplitude and the increase in pressure. Furthermore, due to the effect of frictional resistance, an increased pressure phenomenon also occurs at the fracture tip. In addition, the continuous impact of high-frequency pulsed water pressure on the coal and rock mass causes fatigue damage to the coal, making the coal no longer controlled by the three-dimensional stress field and generating a large number of cracks along multiple directions. This not only increases the number of cracks but also breaks through the constraints of joints, bedding, and stress fields on uniform fracturing, ultimately forming a complex network of uniform hydraulic fractures in the coal, which fully breaks the coal. After drilling a row of coal seam in-seam boreholes 17 along the direction of the transport roadway 8 and return air roadway 9, and implementing pulse fracturing measures, the surrounding rock of the roadway can be considered as the innermost small structure (strong structure) composed of roadway supports; outside the small structure is the weak structure after loosening and destabilization; outside the weak structure is the undisturbed original rock structure (strong structure). That is, the surrounding rock of the roadway has a "strong-weak-strong" structural characteristic from the inside out. In the absence of impact vibration, the stress in the coal seams on both sides of the roadway is redistributed due to the presence of the weak structure. Both radial and tangential stresses 19 are transferred to the deeper parts of the surrounding rock, placing the small structure of the coal seam supports on both sides of the roadway in a stress-reduced zone, which is beneficial for the maintenance and stability of the roadway. Due to the presence of weak structures, strong impact stresses transmitted from the shock source (generally in the original rock structure far from the roadway) undergo reflection and transmission at the surface of the strong and weak structures. Some stress is reflected back into the strong structure, significantly reducing the amplitude of stress transmitted into the weak structure. Within the weak structure, the stress is further weakened through scattering and absorption, greatly reducing the stress transmitted to the small support structures of the coal seam on both sides of the roadway. Therefore, the "strong-weak-strong" structure has a weakening and absorption effect on impact stress waves. Furthermore, in the absence of impact vibrations, it transfers high stress within the coal seam on both sides of the roadway to deeper layers, keeping the coal seam on both sides of the roadway in a lower stress state and reducing the impact risk to the working face.

[0039] Step S7: Using a hydraulic fracturing high-pressure pump 21, high-pressure water is injected into the low-level borehole 16 in the roof through pipelines for fracturing. A multi-hole simultaneous fracturing method is used to induce the cracks to expand along the borehole connection line, thereby directionally cutting off the roof. Vertically upward drilling and fracturing are performed on the low-level borehole 16 in the transport roadway 8 and return air roadway 9 to directionally cut off the lateral support of the coal pillar 11 to the end-face overhang, ensuring the end-face overhang collapses promptly with the working face's retreat, preventing the formation of a large-area overhang in the end-face area, preventing the stress in the goaf from being transmitted to the transport roadway 8 and return air roadway 9 of this working face and the adjacent working face roadway 10, and eliminating the impact dynamic load caused by the sudden collapse of a large-area end-face overhang.

[0040] In summary, the present invention, through the above-mentioned three-dimensional fracturing and anti-impact measures of "coal seam - low-level hard rock strata - high-level hard rock strata", reduces the peak stress and dynamic load disturbance at the same time. The synergistic effect of the two can significantly reduce the impact risk of the working face.

[0041] In addition, if either directional fracturing of hard rock strata or pulse fracturing of hard coal seams can guarantee the anti-rock erosion effect, only one measure needs to be taken.

[0042] like Figure 4 The image shows the hydraulic fracturing equipment used in this method. This equipment includes a hydraulic fracturing pulse pump 20, a hydraulic fracturing high-pressure pump 21, a shut-off valve 22, a tee 23, a drain valve 24, a sensor 25, a conversion connector 26, a water injection steel pipe 27, a high-pressure automatic wellbore sealer 28, a dual-path packer 29, a high-pressure hose 30, a hand pump 31, a hydraulic fracturing monitoring and control instrument 32, and a high-pressure hose 33. The hydraulic fracturing high-pressure pump and the hydraulic fracturing pulse pump 21 are connected via the tee 23 and the high-pressure hose 33. Shut-off valves 22 are installed on the high-pressure hoses 33 between the tee 23 and the hydraulic fracturing pulse pump 20, and between the tee 23 and the hydraulic fracturing high-pressure pump 22. The purpose of these valves is to allow switching between pulse fracturing and direct high-pressure water fracturing water supply methods to accommodate different drilling fracturing requirements. A sensor 25 is installed on the high-pressure hose 33 at the outlet end of the tee 23. The sensor 25 is connected to the hydraulic fracturing control instrument to monitor water pressure changes. A drain valve 24 is installed on the high-pressure hose 33 at the outlet end of the tee 23. After fracturing, the residual pressure in the fracturing system can be discharged through the drain valve 24.

[0043] (1) When drilling high-level holes 12, 13, 14, 15, and 16 in the first, second, third, and fourth categories of the roof, respectively, high-pressure water is directly supplied by the hydraulic fracturing high-pressure pump 21 to fracture the holes. At this time, the shut-off valve 22 connected to the hydraulic fracturing pulse pump 20 is turned off. The end of the high-pressure hose 33 at the outlet of the tee 23 is connected to the water injection steel pipe 27. The water injection steel pipe 27 is connected to the main pressure automatic sealing device 28 and then enters the holes. A conversion joint 26 is provided at the inlet end of the water injection steel pipe 27.

[0044] (2) When performing hydraulic fracturing on the coal seam in-seam borehole 17, a pulse fracturing method is required. In this case, the hydraulic fracturing pulse pump 20 operates, while the hydraulic fracturing high-pressure pump 21 does not operate. At this time, the shut-off valve 22 connected to the hydraulic fracturing high-pressure pump 21 is closed. The end of the high-pressure hose 33 at the outlet of the tee 23 is connected to... Figure 4 The horizontally placed water injection steel pipe 27 is connected and passes through the dual-path packer 29 before entering the borehole for pulsed high-pressure water fracturing. Additionally, before fracturing, a hand pump 31 is connected to the dual-path packer 29 via a high-pressure hose 30 for auxiliary borehole sealing.

[0045] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes that can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention are all within the protection scope of the claims of the present invention.

Claims

1. A method for comprehensive anti-washing of hard coal rock strata directional and pulse fracturing, characterized in that, It comprises the following steps: Step S1, using a drilling rig to drill a row of first type roof high drilling holes and second type roof high drilling holes along the opening cut eye trend, and a row of third type roof high drilling holes, fourth type roof high drilling holes, coal seam bedding drilling holes and roof low drilling holes along the transportation crossheading and air return crossheading trend; wherein, The first type roof high drilling hole is opened at the position close to the front coal wall roof in the opening cut eye, and the high roof drilling hole is constructed obliquely to the front coal wall; The second type roof high drilling hole is opened at the position close to the rear coal wall roof in the opening cut eye, and the high roof drilling hole is constructed obliquely to the rear coal wall; The third type roof high drilling hole is opened at the position of the roof middle line in the transportation crossheading and air return crossheading, and the high roof drilling hole is constructed obliquely to the working face side roadway; The first type roof high drilling hole, the second type roof high drilling hole, the third type roof high drilling hole and the fourth type roof high drilling hole are all located in the middle and upper part of the high hard rock stratum, so as to cut off the old roof above the coal seam, thereby shortening the initial pressure and periodic pressure step distance, and cutting off the transmission path of the dynamic pressure generated by the old roof fracture above the goaf to the transportation crossheading and air return crossheading of the working face; The fourth type roof high drilling hole is opened at the position close to the coal pillar side roadway on the roof in the transportation crossheading and air return crossheading, the drilling hole direction is perpendicular to the roadway trend at the drilling hole construction site, the drilling hole is inclined to the coal pillar side roadway, and the drilling hole end position is in the middle and upper part of the high hard rock stratum above the coal pillar, so as to cut off the transmission path of the dynamic pressure generated by the old roof fracture above the goaf to the crossheading of the adjacent working face; The coal seam bedding drilling hole is opened at the position of the working face side roadway in the transportation crossheading and air return crossheading, the drilling hole direction is perpendicular to the roadway trend at the drilling hole construction site, the drilling hole is divided into a non-fracturing section and a fracturing section along the length direction, and the non-fracturing section is close to the roadway at the drilling hole construction site, which is used to ensure the stability of the roadway surrounding rock and supporting body; The roof low drilling hole is opened at the position of the roof middle line at the end of the transportation crossheading and air return crossheading, and the low roof drilling hole is vertically drilled, and the drilling hole end position is in the middle and upper part of the low hard rock stratum above the coal seam, so as to make the low roof collapse in time and fill the goaf; Step S2, using a water pressure fracturing high pressure pump to inject high pressure water into the first type roof high drilling hole for fracturing, using the method of multiple hole simultaneous fracturing to induce the cracks to expand along the direction of the drilling hole connecting line, so as to cut off the roof in a directional manner; Step S3, using a water pressure fracturing high pressure pump to inject high pressure water into the second type roof high drilling hole for fracturing, using the method of multiple hole simultaneous fracturing to induce the cracks to expand along the direction of the drilling hole connecting line, so as to cut off the roof in a directional manner; Step S4, using a water pressure fracturing high pressure pump to inject high pressure water into the third type roof high drilling hole for fracturing, using the method of multiple hole simultaneous fracturing to induce the cracks to expand along the direction of the drilling hole connecting line, so as to cut off the roof in a directional manner; Step S5, using a water pressure fracturing high pressure pump to inject high pressure water into the fourth type roof high drilling hole for fracturing, using the method of multiple hole simultaneous fracturing to induce the cracks to expand along the direction of the drilling hole connecting line, so as to cut off the roof in a directional manner; Step S6, a hydraulic fracturing pulse pump is used to inject pulse water into the coal seam bedding borehole through a pipeline to perform fracturing, so as to fully crush the coal seam; Step S7, a hydraulic fracturing high-pressure pump is used to inject high-pressure water into the roof low-position borehole through a pipeline to perform fracturing, and a multi-hole simultaneous fracturing method is used to induce the cracks to expand along the direction of the borehole connecting line to cut off the roof in a directional manner.

2. The method according to claim 1, wherein, The coal seam bedding borehole has a length of 40-100 m, wherein the non-fracturing section is 20 m, and the borehole spacing is 20-30 m.

3. The method according to claim 1, wherein, The spacing of the low-position roof borehole is 6-15 m.

4. The method according to claim 1, wherein the method is characterized in that, The spacing of the first-type roof high-position borehole, the second-type roof high-position borehole, the third-type roof high-position borehole and the fourth-type roof high-position borehole is 10-20 m.

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