A Precise Pressure Relief Method for Hydraulic Slot Cutting in Wide Coal Pillar Sections under High Stress Conditions

Abstract

This invention discloses a precise pressure relief method for hydraulic slotting in wide coal pillars under high stress conditions to prevent drill bit seizure. The specific steps are: dividing the roadway into rockburst hazard zones, determining the borehole layout, implementing small-diameter pressure relief boreholes, implementing single ultra-high pressure hydraulic slotting boreholes, and sequentially implementing multiple sets of ultra-high pressure hydraulic slotting boreholes. This method draws on the principle of protective layer mining. Under high ground stress, a pressure relief zone is formed by implementing two rows of densely packed small-diameter pressure relief boreholes along the bedding plane in wide coal pillars. Implementing ultra-high pressure hydraulic slotting boreholes in this zone can effectively prevent borehole collapse and drill bit seizure. By dividing the wide coal pillar into "three zones," efficient and precise pressure relief through hydraulic slotting operations can be achieved, while preserving the bearing capacity of the coal pillar. This can effectively prevent rockburst disasters, reduce roadway deformation, and improve the safety and economic benefits of the mine.

Description

Technical fields:

[0001] This invention relates to the field of pressure relief and roadway protection technology, specifically to a precise pressure relief method for hydraulic slotting in wide coal pillar sections under high stress conditions to prevent drill seizure. Background technology:

[0002] Leaving wide coal pillars is an effective method for roadway protection. This method involves leaving a coal pillar of a certain width (30-40m) between the upper haulage roadway and the lower return airway. After the upper working face is mined, the pillar effectively supports the collapsed roof, allowing the lower return airway to avoid the peak stress area caused by roof collapse. However, the size of the coal pillar is mainly based on experience from other mines, lacking a mature theoretical framework. Excessive pillar width results in 10%-30% resource waste, while insufficient width makes it highly susceptible to rockburst disasters due to secondary mining disturbances, goaf roof deformation, and geological structures, leading to significant roadway deformation, a surge in maintenance workload, and a major safety threat to personnel and equipment. Therefore, to ensure maximum resource recovery and safe mining, it is necessary to decompress the wide coal pillars.

[0003] In recent years, ultra-high pressure hydraulic slotting technology has emerged as a highly efficient coal seam decompression technology. Ultra-high pressure water jets can form annular or rectangular slots within the coal seam, providing space for decompression. By rationally arranging slotting borehole groups, a network of slots can be formed within the slotted control area, achieving uniform decompression throughout the area. This allows concentrated static loads from the roof to be transferred to the coal pillar or deeper into the working face, while also blocking and weakening the transmission of dynamic load disturbance waves caused by mining. This effectively prevents rockburst disasters and ensures the safety of working face roadways, personnel, and equipment. This technology has been widely applied in various mining areas across my country. However, when ultra-high pressure hydraulic slotting boreholes are implemented in wide coal pillar sections, they are affected by concentrated static and dynamic load disturbances, leading to frequent borehole collapses and drill bit jamming, severely impacting operational efficiency and drastically increasing drill rod consumption. Summary of the Invention:

[0004] In view of this, the purpose of this invention is to provide a precise pressure relief method for hydraulic slotting in wide coal pillars under high stress conditions, to solve the problem of frequent hole collapse and drill bit seizure when hydraulic slotting is carried out in wide coal pillars due to concentrated static load. Drawing on the principle of protective layer mining, a row of small-diameter pressure relief boreholes is implemented above and below the hydraulic slotting borehole group. The spacing of the small-diameter boreholes is adjusted according to the impact hazard zone to regulate the pressure relief effect. The amount of drill cuttings from the small-diameter boreholes is counted, the coal pillar is divided into three zones, and the number of slotting cutters is rationally planned. This method relieves pressure on the coal pillar while preserving its bearing capacity, simultaneously preventing hole collapse and drill bit seizure, and improving the efficiency of slotting operations.

[0005] This invention is implemented by the following technical solution: a precise pressure relief method for hydraulic slotting in wide coal pillar sections under high stress conditions to prevent drill seizure, specifically including the following steps:

[0006] S1. Classification of roadway impact hazard zones: weak impact hazard zone, medium impact hazard zone, and strong impact hazard zone;

[0007] S2. Determine the borehole layout orientation; based on the zoning of the roadway's impact hazard zones, plan the layout parameters for ultra-high pressure hydraulic slotting boreholes and small-diameter pressure relief boreholes; specifically:

[0008] When the height H of the wide coal pillar in the section is greater than or equal to 2.2m, at least two rows of small-diameter pressure relief boreholes shall be arranged above and below the ultra-high pressure hydraulic cutting borehole; when the height H of the wide coal pillar in the section is less than 2.2m, one to two rows of small-diameter pressure relief boreholes shall be arranged above the ultra-high pressure hydraulic cutting borehole.

[0009] Ultra-high pressure hydraulic slotting and small-diameter pressure relief drilling are carried out perpendicular to the strike of the wide coal pillar in the section, along its dip.

[0010] H1∈[0.8,1.5]m, where H1 is the distance between the line connecting the ultra-high pressure hydraulic slotted borehole and the line connecting the small-diameter pressure relief borehole.

[0011] H2∈[0.2,0.3]m, where H2 is the distance between the lines connecting multiple rows of small-diameter pressure relief boreholes on the same side of the ultra-high pressure hydraulic slotting borehole;

[0012] H3∈[0.8,1.8]m, where H3 is the distance from the line connecting the ultra-high pressure hydraulic slotted borehole to the top or bottom of the coal pillar;

[0013] H4∈[0.2,0.3]m, where H4 is the distance between the line connecting the small-diameter pressure relief boreholes closest to the top or bottom of the coal pillar and the top or bottom of the coal pillar;

[0014] High-impact hazard zone: L1∈[3,4]m, L2∈[0.2,0.3]m;

[0015] Medium impact hazard zone: L1∈[4,5]m, L2∈[0.3,0.5]m;

[0016] Weak impact hazard zone: L1∈[6,7]m, L2∈[0.5,0.8]m;

[0017] Where L1 is the distance between adjacent ultra-high pressure hydraulic slotted boreholes; L2 is the distance between adjacent small-diameter pressure relief boreholes;

[0018] S3. Implement small-diameter pressure relief drilling; utilize a small-diameter drilling system to perform drilling operations;

[0019] S4. Implement a single ultra-high pressure hydraulic slotting borehole; use an ultra-high pressure hydraulic slotting system to perform ultra-high pressure hydraulic slotting boreholes to form a flat annular slot in the coal seam;

[0020] S5. Multiple sets of ultra-high pressure hydraulic slotting boreholes are carried out in sequence; multiple sets of in-seam hydraulic slotting boreholes are carried out along the wide coal pillar side of the roadway section and the slotting operation is completed. Step S4 is repeated in each slotting borehole to form an annular slotted network in the coal pillar, so as to realize the overall transfer of the concentrated static load borne by the coal and rock mass around the roadway to the elastic area of ​​the coal pillar, and to block or weaken the impact of dynamic load disturbance waves on the roadway.

[0021] Preferably, in step S2, according to GB / T 25217 "Methods for Measurement, Monitoring and Prevention of Rockburst", one or more of the following methods are used to assess the rockburst risk of the mining roadway: comprehensive index method, probability index method, microseismic, ground sound, electromagnetic radiation, drill cuttings volume, and mining stress monitoring method. By comprehensively assessing the burial depth of the evaluation area, the mechanical parameters of the coal and rock mass, the degree of concentrated static load support of the coal and rock mass, geological structure, development layout, and surrounding dynamic load disturbance factors, the rockburst risk level of the evaluation area is accurately determined.

[0022] Preferably, in step S3, field practice has shown that small-diameter boreholes are less prone to collapse and drill bit jamming under high ground stress. Therefore, a Φ50mm drill bit and a Φ42mm drill rod are selected to carry out small-diameter pressure relief drilling, forming a pressure relief zone in the hydraulic cutting area of ​​the wide coal pillar section, to prevent borehole collapse and drill bit jamming during hydraulic cutting operations.

[0023] Preferably, in step S4, the ultra-high pressure hydraulic slit cutting system includes a hydraulic slit cutting drill bit, a high-low pressure conversion slit cutter, a shallow spiral high-pressure drill rod, a hydraulic slit cutting rig, a high-pressure water tail, multiple steel wire wound high-pressure hoses, and an ultra-high pressure clean water pump connected in sequence. When drilling, the ultra-high pressure clean water pump provides low-pressure water to the system to facilitate slag removal. After the high-pressure conversion slit cutter reaches the stress concentration zone, the ultra-high pressure clean water pump gradually increases the water pressure, the front end of the high-low pressure conversion slit cutter is closed, and high-pressure water is sprayed out from the side slit nozzle to cut the coal body. At the same time, the hydraulic slit cutting rig drives the high-low pressure conversion slit cutter to rotate slowly in place, forming a flat annular slit groove in the coal body.

[0024] Preferably, in step S3, the small-diameter drilling system includes a small-diameter drill bit, a small-diameter drill rod, and a drilling rig connected in sequence.

[0025] Preferably, the small-diameter drilling system also includes a cuttings collection and weighing device installed at the borehole opening. The collected cuttings are weighed and recorded after each drill rod is drilled. Based on the cuttings weighing data during the drilling process, a curve is formed to divide the wide coal pillar into three zones: the coal pillar pressure relief zone, the stress concentration zone, and the original stress zone.

[0026] The coal body in the coal pillar stress relief zone is relatively fragmented and has weak pressure-bearing capacity, resulting in a slow increase in drill cuttings during drilling. The coal body in the stress concentration zone is in an elastoplastic failure state and is the main support area for concentrated stress; borehole collapse and drill bit seizure accidents mainly occur in this area, where drill cuttings increase rapidly and then slowly decrease. The coal body in the original stress zone has good integrity, and the amount of drill cuttings remains relatively stable within a reasonable range.

[0027] In step S4, the hydraulic slotting operation is adjusted according to the division of the "three zones" of the wide coal pillar in the section. No slotting is performed in the coal pillar pressure relief zone to ensure the integrity of the roadway sidewalls. The slotting spacing L3 in the stress concentration zone is [1,3]m. During slotting, the pressure is slowly increased by 5~10MPa each time. After the water and slag return is normal, the pressure is increased again, with the pressure reaching a maximum of 100MPa. Then the pressure is slowly decreased by 10~20MPa each time. The water and slag return is observed. After it is normal, the pressure is continued to decrease until it drops to 0MPa. If abnormal water and slag return occurs, the pressure is quickly reduced to 0MPa and the drill rod is moved back and forth. After it is normal, the operation continues. The optimal slag discharge is 0.5~0.8t. The slotting spacing L3 in the original stress zone is [3,5]m. Slotting operation is carried out normally.

[0028] Preferably, in step S5, after the ultra-high pressure hydraulic slotting drilling operation and the small-diameter pressure relief drilling construction are completed, the borehole is sealed to prevent gas from gushing out at the borehole opening and causing excessive gas levels in the roadway.

[0029] Advantages of this invention:

[0030] 1. Based on the principle of protective layer mining, this invention arranges a row of small-diameter boreholes above and below the ultra-high pressure hydraulic slit borehole parallel to the top and bottom plates of the roadway to form a pressure relief zone. According to field experience, small-diameter boreholes are implemented in high-pressure coal bodies, resulting in better hole formation and less likelihood of borehole collapse or drill bit seizure accidents.

[0031] 2. Implementing ultra-high pressure hydraulic slotting in the coal seam decompression area can effectively avoid hole collapse and drill bit jamming. By statistically analyzing the amount of drill cuttings from small-diameter boreholes, the "three zones" (coal pillar decompression zone, stress concentration zone, and original stress zone) of the wide coal pillar section can be accurately divided. The technical parameters of ultra-high pressure hydraulic slotting can be adjusted according to the different mechanical properties of the "three zones" of the wide coal pillar section, so as to achieve efficient and precise decompression of hydraulic slotting operation, while preserving the coal pillar bearing capacity. This can effectively prevent rockburst disasters, ensure the efficient implementation of ultra-high pressure hydraulic slotting operation, and ensure safe and rapid mining of the mining face. Attached image description:

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the construction design for ultra-high pressure hydraulic slotting drilling and small-diameter pressure relief drilling provided in Example 1;

[0034] Figure 2 This is a schematic diagram illustrating the division of rock hazard zones in the working face mining roadway, provided in an embodiment of the present invention.

[0035] Figure 3 A schematic diagram (AA section view) of the construction of ultra-high pressure hydraulic slotting drilling and small-diameter pressure relief drilling in wide coal pillar sections provided for embodiments of the present invention.

[0036] Figure 4 This is a schematic diagram of the construction of annular slotted mesh for ultra-high pressure hydraulic slotting boreholes in wide coal pillar sections, provided in an embodiment of the present invention.

[0037] Figure 5 A schematic diagram illustrating the division of a wide coal pillar small-diameter pressure relief borehole into three zones based on the amount of drill cuttings, provided for an embodiment of the present invention;

[0038] Figure 6 This is a schematic diagram of the drilling construction design for Example 1 (BB ​​section view);

[0039] Figure 7 This is a schematic diagram of the construction design for ultra-high pressure hydraulic slotting drilling and small-diameter pressure relief drilling provided in Example 2;

[0040] Figure 8 This is a schematic diagram of the drilling construction design for Example 2 (BB cross-sectional view).

[0041] Explanation of reference numerals in the attached figures:

[0042] 1-Wide coal pillar section; 2-Small diameter pressure relief borehole; 2.1-Lower row of small diameter pressure relief boreholes; 2.2-Upper row of small diameter pressure relief boreholes; 3-Ultra-high pressure hydraulic slotting borehole; 3.1-Ultra-high pressure hydraulic slotting annular groove; 4-Strong impact hazard zone; 5-Medium impact hazard zone; 6-Weak impact hazard zone; 7-Annular hydraulic slotting groove; 8-Ultra-high pressure hydraulic slotting system; 8.1-Ultra-high pressure clean water pump; 8.2-Hydraulic slotting drill rig; 8.3-Multiple steel wire wound high-pressure hose; 8.4-High pressure water tail; 8.5-Shallow spiral high-pressure drill rod; 8.6-High-low pressure conversion slotting device; 8.7-Hydraulic slotting drill bit; 9-Small diameter drilling system; 9.1-Ordinary drilling rig; 9.2-Small diameter drill rod; 9.3-Drill cuttings collection and weighing device; 9.4-Small diameter drill bit. Detailed implementation method:

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The following examples were all conducted in the return air roadway of the 21105 working face of the Hulusu Coal Mine of Zhongtian Hechuang Energy Co., Ltd.: The average thickness of the coal seam mined in the 21105 working face is about 2.79 meters, the working face length is 1500 meters, and the coal seam dip angle is 1 to 3°. The adjacent working face on the side of the return air roadway is a goaf area, and a 30m wide coal pillar is left to protect the return air roadway of the working face. Due to the impact of mine pressure on the coal pillar caused by the collapse of the roof of the mining area, the risk of impact increases sharply.

[0045] Example 1:

[0046] like Figures 1 to 6 As shown, a precise pressure relief method for hydraulic slotting in wide coal pillar sections under high stress conditions to prevent drill seizure is described, and the main steps are as follows:

[0047] S1. The rockburst risk of mining roadways is assessed using both the comprehensive index method and the probability index method. The likelihood of regional rockbursts is diagnosed based on factors such as mine geology, mining technology, regional stress field distribution, and regional coal and rock mass rockburst tendency. The regional rockburst risk levels are then classified as: weak rockburst risk zone 6, medium rockburst risk zone 5, and strong rockburst risk zone 4. Figure 2 As shown;

[0048] S2. Based on the impact hazard level of the mining roadway area, rationally plan the layout parameters of ultra-high pressure hydraulic slotting borehole 3 and small-diameter pressure relief borehole 2. The ultra-high pressure hydraulic slotting borehole 3 and small-diameter pressure relief borehole 2 are perpendicular to the coal pillar and have an inclination angle of 0°.

[0049] The height of the wide coal pillar 1 in section H=2.4m, which is greater than 2.2m. Therefore, a row of small-diameter pressure relief boreholes 2.2 is arranged above the ultra-high pressure hydraulic slotting borehole 3, and a row of small-diameter pressure relief boreholes 2.1 is arranged below it, with H1=1m and H3=1.2m. Strong impact hazard zone 4: L1=3m and L2=0.2m; Medium impact hazard zone 5: L1=4m and L2=0.3m; Weak impact hazard zone 6: L1=6m and L2=0.5m.

[0050] S3. Connect the small-diameter drill bit 9.4, small-diameter drill rod 9.2, and ordinary drilling rig 9.1 sequentially to the small-diameter drilling system 9. Install a drill cuttings collection and weighing device 9.3 at the borehole opening, and begin drilling operations. Weigh and record the collected drill cuttings after each drill rod is drilled. Drill to the edge of the coal pillar L5=2m, then withdraw the drill and seal the hole. Based on the weighing data of the drill cuttings during drilling, form a curve to divide the wide coal pillar section into three zones: the coal pillar pressure relief zone, the stress concentration zone, and the original stress zone. Figure 5 As shown, when the amount of drill cuttings in the borehole increases abnormally, the borehole moves from the coal pillar stress relief zone into the stress concentration zone. Subsequently, the amount of drill cuttings gradually decreases and stabilizes within a certain range. This stable area is the original rock stress zone of the coal pillar.

[0051] S4. Connect the hydraulic slotting drill bit 8.7, high / low pressure conversion slotting device 8.6, shallow spiral high-pressure drill rod 8.5, hydraulic slotting drill rig 8.2, high-pressure water tail 8.4, multiple wire-wound high-pressure hose 8.3, and ultra-high pressure clean water pump 8.1 in sequence to form an ultra-high pressure hydraulic slotting system 8. First, start the ultra-high pressure clean water pump 8.1 to provide low-pressure water to the system during drilling to facilitate slag removal. After the high-pressure conversion slotting device 8.6 reaches the stress concentration zone, perform slotting by retracting the drill. Gradually increase the water pressure of the ultra-high pressure clean water pump 8.1, switching between high and low pressure. The front end of the conversion slit cutter 8.6 is closed, and high-pressure water is sprayed from the side slit nozzle to cut the coal body. At the same time, the hydraulic slit drill 8.2 drives the high-low pressure conversion slit cutter 8.6 to slowly rotate in place to cut a slit, forming a flat annular hydraulic slit groove 7 in the coal body. The single-cut slit time is 5~10 minutes and the slag output is 0.5~0.8t. After completing one slit cut operation, the shallow spiral high-pressure drill rod 8.5 is 1m long. According to the slit spacing, the corresponding number of drill rods are retracted to the next slit cut position to continue the slit cut operation. After the slit cut operation is completed, the hole is sealed.

[0052] S5. Along the wide coal pillar 1 side of the roadway section, implement multiple sets of in-seam hydraulic slotting boreholes 3 and complete the slotting operation. Repeat steps S3 and S4 in each slotting borehole. The ultra-high pressure hydraulic slotting operation will generate a large amount of water and coal slag on site. In order to ensure safe and civilized construction and prevent coal slag from accumulating and blocking the roadway and causing large-scale water accumulation on site, it is necessary to set up sedimentation ponds and drainage ditches in the mining roadway and deal with the coal slag in a timely manner.

[0053] Example 2:

[0054] like Figure 7 and Figure 8 As shown, a precise pressure relief method for hydraulic slotting in wide coal pillar sections under high stress conditions to prevent drill seizure is described, and the main steps are as follows:

[0055] S1. The rockburst risk of mining roadways is assessed using both the comprehensive index method and the probability index method. The likelihood of regional rockbursts is diagnosed based on factors such as mine geology, mining technology, regional stress field distribution, and regional coal and rock mass rockburst tendency. The regional rockburst risk levels are then classified as: weak rockburst risk zone 6, medium rockburst risk zone 5, and strong rockburst risk zone 4. Figure 2 As shown;

[0056] S2. Based on the impact hazard level of the mining roadway area, rationally plan the layout parameters of ultra-high pressure hydraulic slotting borehole 3 and small-diameter pressure relief borehole 2. The azimuth of ultra-high pressure hydraulic slotting borehole 3 and small-diameter pressure relief borehole 2 is at an angle of 270° with the working face, and the dip angle is consistent with the dip angle of the wide coal pillar 1 in the section.

[0057] like Figure 8 As shown, in this embodiment, the height of the wide coal pillar 1 in section H=2.1m is less than 2.2m. Therefore, two rows of small-diameter pressure relief boreholes 2.1 and 2.2 are arranged above the ultra-high pressure hydraulic slit borehole 3, with H1=0.9m, H2=0.2m, H3=0.8m, and H4=0.2m. The strong impact hazard zone 4 has L1=3m and L2=0.2m, the medium impact hazard zone 5 has L1=4m and L2=0.3m, and the weak impact hazard zone 6 has L1=6m and L2=0.5m.

[0058] S3. Connect the small-diameter drill bit 9.4, the small-diameter drill rod 9.2, and the ordinary drilling rig 9.1 in sequence. Set up a drill cuttings collection and weighing device 9.3 at the borehole opening and start drilling. Weigh and record the collected drill cuttings after each drill rod is drilled. Drill to the edge of the coal pillar L5=2m and then retract the drill to seal the hole. Based on the weighing data of the amount of drill cuttings during the drilling process, form a curve to divide the wide coal pillar section into three zones: the coal pillar pressure relief zone, the stress concentration zone, and the original stress zone.

[0059] S4. Connect the hydraulic slotting drill bit 8.7, high / low pressure conversion slotting device 8.6, shallow spiral high-pressure drill rod 8.5, hydraulic slotting drill rig 8.2, high-pressure water tail 8.4, multiple wire-wound high-pressure hose 8.3, and ultra-high pressure clean water pump 8.1 in sequence to form an ultra-high pressure hydraulic slotting system 8. First, start the ultra-high pressure clean water pump 8.1 to provide low-pressure water to the system during drilling to facilitate slag removal. After the high-pressure conversion slotting device 8.6 reaches the stress concentration zone, perform slotting by retracting the drill. Gradually increase the water pressure of the ultra-high pressure clean water pump 8.1, switching between high and low pressure. The front end of the conversion slit cutter 8.6 is closed, and high-pressure water is sprayed from the side slit nozzle to cut the coal body. At the same time, the hydraulic slit drill 8.2 drives the high-low pressure conversion slit cutter 8.6 to slowly rotate in place to cut a slit, forming a flat annular hydraulic slit groove 7 in the coal body. The single-cut slit time is 5~10 minutes and the slag output is 0.5~0.8t. After completing one slit cut operation, the shallow spiral high-pressure drill rod 8.5 is 1m long. According to the slit spacing, the corresponding number of drill rods are retracted to the next slit cut position to continue the slit cut operation. After the slit cut operation is completed, the hole is sealed.

[0060] S5. Along the wide coal pillar 1 side of the roadway section, implement multiple sets of in-seam hydraulic slotting boreholes 3 and complete the slotting operation. Repeat steps S3 and S4 in each slotting borehole. The ultra-high pressure hydraulic slotting operation will generate a large amount of water and coal slag on site. In order to ensure safe and civilized construction and prevent coal slag from accumulating and blocking the roadway and causing large-scale water accumulation on site, it is necessary to set up sedimentation ponds and drainage ditches in the mining roadway and deal with the coal slag in a timely manner.

[0061] The aforementioned precise pressure relief method for hydraulic slotting in wide coal pillars under high stress conditions solves the serious problems of hole collapse and drill bit seizing during ultra-high pressure hydraulic slotting drilling in wide coal pillars, reducing the hole collapse and drill bit seizing rate by more than 90%. The ground sound deviation values ​​in the test area are all in a stable and low state, indicating that the pressure relief method described in this patent can effectively improve the stress of the coal pillar, reducing it by 20% to 35%. The slotting weakens the elasticity of the coal pillar, reducing its impact risk, and the roadway shrinkage deformation is reduced by more than 45%, promoting the further development of ultra-high pressure hydraulic slotting in the prevention and control of rockbursts.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high stress state under the section wide coal pillar anti-drill hydraulic slotting precision pressure relief method, characterized in that, Specifically comprising the following steps: S1, roadway impact dangerous area division; weak impact dangerous area, medium impact dangerous area (5), strong impact dangerous area; S2, determine the drilling arrangement direction; according to the roadway impact dangerous area division, plan the arrangement parameters of the ultrahigh pressure hydraulic slotting drill hole and the small aperture pressure relief drill hole; specifically: When the section wide coal pillar height H is greater than or equal to 2.2m, at least two rows of small aperture pressure relief drill holes are arranged above and below the ultrahigh pressure hydraulic slotting drill hole; when the section wide coal pillar height H is less than 2.2m, 1-2 rows of small aperture pressure relief drill holes are arranged above the ultrahigh pressure hydraulic slotting drill hole; The ultrahigh pressure hydraulic slotting drill hole and the small aperture pressure relief drill hole are perpendicular to the section wide coal pillar trend, and drilling operation is implemented along the inclination thereof, H1∈[0.8,1.5]m, H1 is the distance between the connecting line of the ultrahigh pressure hydraulic slotting drill hole and the connecting line of the small aperture pressure relief drill hole; H2∈[0.2,0.3]m, H2 is the distance between the connecting lines of the multiple rows of small aperture pressure relief drill holes on the same side of the ultrahigh pressure hydraulic slotting drill hole (3); H3∈[0.8,1.8]m, H3 is the distance from the connecting line of the ultrahigh pressure hydraulic slotting drill hole to the top or bottom of the coal pillar; H4∈[0.2,0.3]m, H4 is the distance between the connecting line of the small aperture pressure relief drill hole closest to the top or bottom of the coal pillar and the top or bottom of the coal pillar; Strong impact dangerous area: L1∈[3,4]m, L2∈[0.2,0.3]m; Medium impact dangerous area: L1∈[4,5]m, L2∈[0.3,0.5]m; Weak impact dangerous area: L1∈[6,7]m, L2∈[0.5,0.8]m; Wherein, L1 is the distance between adjacent ultrahigh pressure hydraulic slotting drill holes; L2 is the distance between adjacent small aperture pressure relief drill holes; S3, implement small aperture pressure relief drill hole; drilling operation is implemented by using a small aperture drill hole system; S4, implement a single ultrahigh pressure hydraulic slotting drill hole; ultrahigh pressure hydraulic slotting drill hole is implemented by using an ultrahigh pressure hydraulic slotting system, and a flat annular slot is formed in the coal body; S5, sequentially implement multiple groups of ultrahigh pressure hydraulic slotting drill holes; multiple groups of in-seam hydraulic slotting drill holes are implemented along the section wide coal pillar side of the roadway and slotting operation is completed, and step S4 is repeated in each slotting drill hole, so that an annular slot network is formed in the coal pillar, the overall static load borne by the coal and rock body around the roadway is transferred to the elastic area of the coal pillar, and the influence of dynamic load disturbance wave on the roadway is blocked or weakened.

2. The method according to claim 1, wherein the method is characterized in that, In step S2, according to GB / T 25217 "Method for determination, monitoring and prevention of rock burst", one or more of the following methods is used to evaluate the rock burst danger of the mining roadway: comprehensive index method, possible index method, microseism, ground sound, electromagnetic radiation, drill cuttings amount, and mining stress monitoring method. Through comprehensive evaluation of the evaluation area depth, coal and rock body mechanical parameters, coal and rock body concentrated static load support degree, geological structure, development arrangement and surrounding dynamic load disturbance factors, the impact danger grade of the evaluation area is accurately determined.

3. The method according to claim 1, wherein the method is characterized in that, In step S3, a Φ50mm drill bit and a Φ42mm drill rod are selected to implement the small aperture pressure relief drill hole, and a pressure relief area is formed in the section wide coal pillar hydraulic slotting area to prevent hole collapse and drill sticking during hydraulic slotting operation.

4. The method according to claim 1, characterized in that, In step S4, the ultra-high pressure hydraulic slotting system comprises, in sequence, a hydraulic slotting drill bit, a high-low pressure conversion slotter, a shallow spiral high-pressure drill rod, a hydraulic slotting drilling machine, a high-pressure water tail, a multiple steel wire wound high-pressure rubber pipe, and an ultra-high pressure clean water pump. After the high-low pressure conversion slotter reaches the stress concentration zone, the ultra-high pressure clean water pump gradually increases the water pressure. The front end of the high-low pressure conversion slotter is closed, and high-pressure water is sprayed from the side slotting nozzles to cut the coal body. At the same time, the hydraulic slotting drilling machine drives the high-low pressure conversion slotter to slowly rotate in place, forming a flat annular slot in the coal body.

5. The method according to claim 4, wherein the method is characterized in that, In step S3, the small-diameter drilling system comprises, in sequence, a small-diameter drill bit, a small-diameter drill rod, and a drilling machine.

6. The method according to claim 5, wherein the method is characterized in that, In step S3, the small-diameter drilling system further comprises a drill cuttings collection and weighing device arranged at the borehole. The collected drill cuttings are weighed and recorded after drilling in each drill rod. According to the drill cuttings weight data during drilling, a curve is formed to divide the section wide coal pillar "three zones": coal pillar pressure relief zone, stress concentration zone, and original stress zone. In step S4, the hydraulic slotting operation is adjusted according to the division of the section wide coal pillar "three zones". The coal pillar pressure relief zone is not slotted to ensure the integrity of the roadway side. The stress concentration zone has a slotting interval L3∈[1,3]m, and the pressure is slowly increased during slotting. Each time the pressure is increased by 5~10MPa. After the return water and return slag are normal, the pressure is increased again, and the highest pressure is increased to 100MPa. Then the pressure is slowly decreased, and each time the pressure is decreased by 10~20MPa. The return water and return slag are observed. After normal, continue to decrease the pressure until it is 0MPa. If the return water and return slag are abnormal, the pressure is quickly decreased to 0MPa, and the drill rod is moved forward and backward. After normal, continue the operation. The original stress zone has a slotting interval L3∈[3,5]m, and the slotting operation is normally performed.

7. A method for precision pressure relief of a high stress state section wide coal pillar by hydraulic slotting and drill holding prevention according to claim 1, characterized in that, In step S5, after the ultra-high pressure hydraulic slotting drilling slotting operation and small-diameter pressure relief drilling construction are completed, the borehole is plugged to prevent gas from flowing out of the borehole and causing the roadway gas to exceed the standard.

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