A method for km horizontal drilling, fracturing, roof cutting, pressure releasing, and protecting roadway and reducing coal pillar width

Abstract

The application discloses a method for km horizontal drilling, pressure fracturing, roof cutting, pressure relief, and roadway protection and reduction of coal pillar width, and belongs to the field of coal mining. The technical points of the method are as follows: the size and direction of the maximum principal stress and the minimum principal stress are determined, the horizon and thickness of the hard rock layer which plays a key role in the pressure on the working face are determined, and the design km horizontal drilling parameters and the water pressure fracturing parameters are determined in combination with the ground stress test results, the uniaxial compressive strength, the thickness and the like of the hard rock layer. After the method is used, the load on the coal pillar is reduced, the coal recovery rate of the working face is improved, and the convergence amount and the maintenance amount of the roadway are reduced. Compared with the traditional vertical roadway roof drilling roof cutting, the method can reduce the labor intensity and operation cost of personnel, and improve the safety after the km horizontal drilling, pressure fracturing, roof cutting, and accurate determination of the horizon.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coal mining, in particular, relates to a method for drilling and fracturing roof pressure relief and protecting roadway at kilometer level. BACKGROUND

[0002] With the substantial increase in production of coal mining face and the emergence of a large number of high gas mines, the problems of coal mine transportation, ventilation and gas are increasingly prominent. For this reason, many mine working faces adopt double-lane, multi-lane layout. The most prominent problem of this layout is that a lane may serve both the current working face and the next working face. Therefore, the lane (i.e. the remaining lane) is not only affected by the advanced and lateral support pressure of the current working face, but also by the advanced support pressure of the next working face, and the stability of the surrounding rock cannot be guaranteed.

[0003] Meanwhile, the main scientific problem of deformation and failure of the remaining lane in double-lane (multi-lane) layout under the influence of adjacent working face mining is the dynamic change of lateral abutment pressure in the goaf, that is, the remaining lane needs to go through the process of goaf lateral roof fracture-rotation-stability, resulting in the lateral abutment pressure in dynamic adjustment, so that the remaining lane needs to go through the dynamic pressure action of three stages of adjacent working face advanced support pressure transmission, goaf lateral abutment pressure dynamic evolution, and current working face advanced support pressure in the whole mining process, resulting in the load borne by the surrounding rock of the lane in constant change.

[0004] Firstly, in order to solve the above problems, one idea is to reduce the influence of mining by increasing the width of the protective lane coal pillar. However, field research shows that under the conditions of hard roof strata, large mining height working face, large burial depth, etc., increasing the width of the protective lane coal pillar has little effect on reducing the influence of mining, and the remaining lane is prone to a series of problems such as large convergence of surrounding rock and even serious damage, damage of supporting members, etc. If the width of the protective lane coal pillar is further increased, it will lead to a large loss of coal resources.

[0005] Secondly, in order to solve the above problems, one idea is to use strong support or grouting reinforcement method. However, the above method has many limitations and timeliness in controlling the stability of the lane, and cannot effectively guarantee the safe and effective use of the lane in the whole life cycle of the adjacent working face mining and the current working face mining.

[0006] In summary, the basic way to control the stability of the surrounding rock of the lane is: 1) reducing the stress of the surrounding rock of the lane; 2) selecting a reasonable support method. At present, double-lane layout mainly controls the large deformation of the surrounding rock by strong support measures combined with a wider coal pillar.

[0007] The document with the application number 201310167156.4 and the title "A small coal pillar along the empty lane surrounding rock control method" proposes that, when mining in the upper section working face, the integrity of the basic roof is destroyed by deep hole pre-splitting blasting, and the basic roof is broken at the predetermined position by the roof pressure after the working face is mined, the roof stress transmission path is cut off, the roadway roof pressure is weakened, and thus the coal pillar load is reduced. However, the method has the disadvantages of large engineering quantity and explosive quantity, relatively poor safety, high cost, pollution of underground air, and the like, especially the current coal mine explosive control is more and more strict, and the use of explosive is gradually limited.

[0008] In addition, as shown in Figure 1 The existing deep hole blasting and water pressure cracking roof cutting pressure are drilled upward from the vertical roadway roof in the roadway, and the hole spacing is about 0.6-5.0 m. On the one hand, the drilling engineering quantity is large, the roof cutting position is not accurate due to the arrangement in the soft and hard rock, and the work efficiency is low. On the other hand, the drilling operation is affected by the equipment, belt or track in the roadway.

[0009] Therefore, it is a technical problem to be solved to study a roof cutting pressure surrounding rock control method with less work and high work efficiency. SUMMARY

[0010] The application provides a method for drilling and fracturing a kilometer horizontal hole to cut the roof, release the pressure, protect the roadway and reduce the width of the coal pillar, and aims to solve the problems in the prior art.

[0011] A method for drilling and fracturing a kilometer horizontal hole to cut the roof, release the pressure, protect the roadway and reduce the width of the coal pillar, which comprises the following steps:

[0012] A method for drilling and fracturing a kilometer horizontal hole to cut the roof, release the pressure, protect the roadway and reduce the width of the coal pillar, which comprises the following steps:

[0013] Firstly, the maximum and minimum principal stress size and direction are measured by the water pressure cracking method;

[0014] Secondly, the layer position and thickness of the hard rock layer which plays a key role in the working face pressure are determined according to the mine drilling columnar chart, the pressure step distance of the previous working face, the coal seam mining height and the goaf crushing coefficient; then the hole spacing and water pressure strength are determined in combination with the lithology and thickness of the hard roof;

[0015] Thirdly, a horizontal hole is drilled by using a kilometer drilling machine, and when the drilling in a drilling field is completed, the key layer position for controlling the pressure is cut off by the horizontal hole and water pressure cracking in the drilling field, so that the working face goaf roof collapses in time, and the width of the roadway protection coal pillar is reduced.

[0016] A method for fracturing roof pressure relief and protecting roadway and reducing coal pillar width by kilometer horizontal drilling, comprising the following steps:

[0017] S1, obtaining the geomechanical information of the surrounding rock of the roadway to be protected;

[0018] S2, determining the layer and thickness of the hard rock layer that plays a key role in the working face pressure;

[0019] S3, determining the kilometer horizontal drilling parameters and hydraulic fracturing parameters;

[0020] The kilometer horizontal drilling parameters include: drilling layer, relative position to coal pillar, horizontal and vertical distance between drilling holes, drilling length;

[0021] The hydraulic fracturing parameters include: water pressure, fracturing direction, and fracturing section (the method for determining the hydraulic fracturing parameters is a prior art and is not described again);

[0022] S4, constructing kilometer horizontal drilling on site;

[0023] S5, carrying out hydraulic fracturing on site.

[0024] Further, the following steps are further included:

[0025] S6, reducing the width of the coal pillar.

[0026] Further, in step S6, after the entire working face is mined, the near-field hard roof above the working face goaf is basically fully caved under the action of kilometer directional horizontal drilling hydraulic fracturing, the adjacent roadway is weakened by the mining influence, and the width of the coal pillar of the next working face can be reduced to 3-10 m based thereon. Strong support means are provided to reduce the width of the coal pillar of the next working face to 3-10 m.

[0027] Further, the step S1 includes: on-site investigation of mine engineering geology and test analysis of the geomechanical information of the surrounding rock of the roadway to be protected; rock structure and thickness, physical and mechanical properties of surrounding rock, hydrogeological conditions, structure, mining influence, and ground stress information of the roadway measured by hydraulic fracturing method.

[0028] Further, the ground stress information of the roadway measured by the hydraulic fracturing method includes: the size and direction of the maximum principal stress and the minimum principal stress.

[0029] Further, the step S2 includes: according to the mine drilling columnar chart, the previous mining working face pressure step distance and the coal seam mining height, and the goaf swelling coefficient, the layer and thickness of the hard rock layer that plays a key role in the working face pressure are determined.

[0030] Further, the kilometer horizontal drilling parameters need to be determined in combination with the ground stress test results, the caving angle of the hard roof, and the lithology and thickness of the hard roof.

[0031] Further, the water pressure fracturing parameters need to be determined in combination with the stress test results of hard rock strata, uniaxial compressive strength, and thickness.

[0032] Further, the step S4 includes: setting the first drilling field from the advanced open-off cut 300-500 m, setting the next drilling field every 280-480 m, and until the last drilling field exceeds the stop line by 20-40 m;

[0033] A kilometer directional drilling machine is installed in the drilling field, and then drilling is started from the first drilling field, the vertical distance between adjacent two drill holes is 1-4 m, and the horizontal distance between adjacent two drill holes is 0-6 m;

[0034] The trajectory of the drill hole is curved at the initial part and is approximately horizontal straight line at the main part.

[0035] Further, the relationship between the number of drill holes drilled in each drilling field in the step S4 and the thickness of the cut hard roof is:

[0036] One drill hole is drilled when the thickness of the cut hard roof is less than 5 m;

[0037] Two drill holes are drilled when the thickness of the cut hard roof is 5-10 m.

[0038] When cutting the roof, the cutting effect and the protection of the recovery roadway are considered: drilling is performed near the solid coal side of the recovery roadway, the horizontal distance between the drill hole and the coal pillar is x (x is generally in the range of 9-17 m), which is obtained by using the following formula:

[0039] x = h / tan θ

[0040] Wherein, h is the height of the hard roof layer, and θ is the caving angle, wherein: the caving angle of the medium stable roof is 60°, and the caving angle of the stable roof is 45°.

[0041] Further, the relationship between the vertical distance between drill holes in the same drilling field and the uniaxial compressive strength of hard roof rock (the uniaxial compressive strength of the cut hard roof rock is 60-100 MPa) and the water pressure is:

[0042] When the uniaxial compressive strength of the rock is 80-100 MPa and the water pressure is 15-20 MPa, the hole distance is 1-2 m;

[0043] When the uniaxial compressive strength of the rock is 60-80 MPa and the water pressure is 10-15 MPa, the hole distance is 3-4 m.

[0044] Further, the relationship between the horizontal distance between drill holes in the same drilling field and the direction and size of the maximum principal stress is:

[0045] When the maximum principal stress is the vertical stress, the horizontal distance between drill holes is 0 m;

[0046] When the maximum principal stress is horizontal stress:

[0047] If the horizontal stress difference is 1-5 MPa, the horizontal spacing of the borehole is 0-2 m;

[0048] If the horizontal stress difference is 5-10 MPa, the horizontal spacing of the borehole is 2-4 m;

[0049] If the horizontal stress difference is 10-15 MPa, the horizontal spacing of the borehole is 4-6 m.

[0050] Further, step S5 comprises:

[0051] First, a high-pressure water injection pump is arranged in the drilling field, and hydraulic fracturing is started in the drilling field after drilling in the drilling field is completed; the borehole is arranged in a hard rock layer, and a retreating type multiple fracturing is used for each borehole, the hard rock layer in the borehole is fractured every 10-30 m, each fracturing time is not less than 30 min, the water head direction must be perpendicular to the roadway roof during fracturing, and the fracturing of the segment is stopped when the water pressure suddenly decreases greatly, and the hard rock layer in the horizontal borehole is fractured until the hard rock layer is fractured.

[0052] Then, the working face is started to be mined, and when the working face is mined to about 50 m before the next horizontal borehole, the next horizontal borehole is started to be fractured in segments, and the cycle is repeated until the working face is mined.

[0053] Further, the horizontal drilling length that can be reached by each borehole is 300-500 m.

[0054] The application has the beneficial effects that:

[0055] First, the basic idea of the application is that the application breaks through the conventional surrounding rock control means mainly based on strong support, is based on the principle of roof cutting and pressure releasing, considers the problem that the traditional construction vertical roof cutting borehole is affected by many operations in the roadway and has large engineering quantity, and proposes that a kilometer directional horizontal borehole is constructed in advance in the crossheading drilling field of the mining working face, and hydraulic fracturing is performed in the borehole, the stress transmission path of the roof is cut off, the roof pressure of the adjacent roadway and the load on the coal pillar are reduced, the surrounding rock stability of the roadway is improved, and the coal pillar width is reduced and the coal resource recovery rate is improved.

[0056] Second, the second inventive idea of the application is that the conventional borehole is arranged vertically on the roof of the roadway at a uniform interval, and the patent is arranged in the drilling field of the roadway. The kilometer horizontal borehole is arranged in the hard rock layer of the roof.

[0057] Third, the difficulty of the application is how to realize kilometer horizontal drilling. This problem has not been studied before the application.

[0058] The core solution is:

[0059] 3.1 The first drilling site is set up from the advanced open-off cut 300-500 m, and the next drilling site is set up every 280-480 m until the last drilling site is 20-40 m beyond the stop line.

[0060] 3.2 A kilometer directional drilling machine is installed in the drilling site, and then a hole is drilled from the first drilling site, 1-2 holes are drilled in each drilling site, the vertical distance between adjacent two holes is 1-4 m, and the horizontal distance between adjacent two holes is 0-4 m. The trajectory of the hole is curved at the initial part and is approximately horizontal straight line at the main part.

[0061] 3.3 The number of holes is related to the thickness of the hard roof to be cut, and when the thickness of the hard roof to be cut is less than 5 m, one hole is drilled; when the thickness of the hard roof to be cut is 5-10 m, two holes are drilled.

[0062] 3.4 When cutting the roof, the hole is drilled near the solid coal side close to the recovery roadway, and the horizontal distance between the hole and the coal pillar is x, which is obtained according to the following formula:

[0063] x = h / tan θ

[0064] h is the height of the hard roof layer;

[0065] θ is the caving angle, wherein the caving angle of the medium stable roof is 60°, and the caving angle of the stable roof is 45°.

[0066] 3.5 The vertical distance between the holes in the same drilling site is mainly related to the uniaxial compressive strength of the hard roof rock and the water pressure, and when the uniaxial compressive strength of the rock is 80-100 MPa and the water pressure is 15-20 MPa, the hole distance is 1-2 m; when the uniaxial compressive strength of the rock is 60-80 MPa and the water pressure is 10-15 MPa, the hole distance is 3-4 m. The horizontal distance between the holes in the same drilling site is related to the direction and size of the maximum principal stress. When the maximum principal stress is the vertical stress, the horizontal distance between the holes is 0 m; when the maximum principal stress is the horizontal stress, the horizontal stress difference is 1-5 MPa, the horizontal distance between the holes is 0-2 m, the horizontal stress difference is 5-10 MPa, the horizontal distance between the holes is 2-4 m, and the horizontal stress difference is 10-15 MPa, the horizontal distance between the holes is 4-6 m. BRIEF DESCRIPTION OF DRAWINGS

[0067] Figure 1 is the actual diagram of the existing vertical roadway roof upward drilling.

[0068] Figure 2 is a single kilometer horizontal hole plane schematic diagram of Example 1.

[0069] Figure 3 is a single kilometer horizontal borehole profile schematic of Example 1.

[0070] Figure 4 is a two kilometer horizontal borehole plan schematic of Example 2.

[0071] Figure 5 is a two kilometer horizontal borehole profile schematic of Example 2.

[0072] Figure 6 is a practical map of the method of the present application.

[0073] Figures 1-4 The figure descriptions in are as follows:

[0074] 1 : Open-off cut;

[0075] 2: Working face;

[0076] 3: Stope line;

[0077] 4: Return air crossheading;

[0078] 5: Transportation crossheading;

[0079] 6: Next working face transportation crossheading;

[0080] 7: Coal pillar;

[0081] 8: Drilling field;

[0082] 9: Kilometer horizontal borehole;

[0083] 10: Initial borehole trajectory;

[0084] 11 : Two-drilling field borehole overlap position;

[0085] 12: Borehole hydraulic fracturing fracture;

[0086] 13: Second kilometer horizontal borehole;

[0087] 14: Horizontal distance of borehole from coal pillar;

[0088] 15: Vertical distance between boreholes;

[0089] 16: Horizontal distance between boreholes. DETAILED DESCRIPTION

[0090] The specific embodiments of the present application are further illustrated by the following specific examples in conjunction with the accompanying drawings.

[0091] Example One: Mine One

[0092] The application discloses a method for cutting roof and relieving pressure and protecting a roadway by using a kilometer directional horizontal drilling water pressure fracturing in a coal mine, and reducing a coal pillar width.

[0093] Step I: field investigation of mine engineering geology profile, and testing and analyzing geological mechanics features of surrounding rock of a roadway to be protected, such as rock stratum structure and thickness, physical and mechanical properties of surrounding rock, hydrogeological conditions, structure conditions, mining influence conditions and the like, especially measuring the ground stress of the roadway by using the water pressure fracturing method, and learning that the maximum principal stress is a horizontal stress with a size of 20.8 MPa, and the minimum principal stress is a horizontal stress with a size of 11.8 MPa, and the two stresses are perpendicular and parallel to the roadway axial direction respectively.

[0094] Step II: according to a mine drilling columnar graph, a first weighting step distance of 29.4 m of a previous mining working face, a coal thickness of 6.5 m (adopting fully-mechanized caving mining, a mining height of 3.2 m, and a caving height of 3.3 m), and a goaf crushing coefficient of 1.2, the hard limestone with a stratum thickness of 4.8 m, which is 17.2 m away from the roadway roof, is determined as a hard stratum playing a key role in weighting of the working face.

[0095] Step III: kilometer horizontal drilling parameters and water pressure fracturing parameters are designed, and specifically, the kilometer horizontal drilling parameters are designed as follows: the drilling is located in the hard limestone which is 17.2 m away from the roadway roof, and a horizontal distance between the drilling and the coal pillar is x, and the distance is obtained according to the following formula:

[0096] x = h / tan θ

[0097] h is a key layer height;

[0098] θ is a caving angle, wherein the caving angle of a medium stable roof is 60°, and the caving angle of a stable roof is 45°. In the example, the caving angle is 60°, the horizontal distance between the drilling and the coal pillar is 9.9 m in the example according to the formula, and the length of a single drilling is 477 m; and the water pressure fracturing parameters are designed as follows: the water pressure is 20 MPa, and a fracturing section needs to ensure that a crack penetrates the hard stratum.

[0099] Step IV: after the height of the cutting roof layer and the horizontal distance between the drilling and the coal pillar are determined, a first drilling field is arranged at a position of 477 m from the starting cutting hole, a next drilling field is arranged at every interval of 477 m, and the last drilling field is arranged at a position of 30 m beyond the stop mining line. A kilometer directional drilling machine is installed in the drilling field, then drilling is started from the first drilling field, and one drilling is drilled in each drilling field. A starting part of a drilling track is a curve, and a main part of the drilling track is an approximately horizontal straight line. When the roof is cut, the drilling is performed close to a solid coal side of the mining roadway in consideration of a cutting roof effect and a protection condition of the mining roadway.

[0100] Step V, on-site water pressure fracturing, i.e. arranging high-pressure water injection pump in the drilling field, and starting water pressure fracturing in the drilling field after drilling in the drilling field is completed. The drilling is arranged in hard rock stratum, and each drilling adopts retreating type multiple fracturing, fracturing is performed every 20 m in the hole, each fracturing time is not less than 30 min, and the water head direction must be perpendicular to the roadway roof during fracturing. The fracturing of the segment is stopped when the water pressure suddenly decreases greatly, and the cycle is repeated until the hard rock stratum in the horizontal drilling is fractured completely. Then, the working face is mined, and when the working face is mined to about 50 m before the next horizontal drilling, the next horizontal drilling is fractured in segments, and the cycle is repeated until the working face is mined completely.

[0101] Step VI, after the entire working face is mined and the hard roof above the working face goaf is fully caved under the action of the kilometer directional horizontal drilling water pressure fracturing, the influence of mining on the adjacent roadway is weakened. The coal pillar width of the next working face double roadway is reduced from 20 m to 8 m, and the anchor cable reinforcement is performed on the coal pillar side of the dynamic pressure roadway.

[0102] Example Two: Mine Two

[0103] A method for cutting roof and relieving pressure and protecting roadway by kilometer directional horizontal drilling water pressure fracturing in a coal mine underground, which is performed according to the following steps:

[0104] Step I, on-site investigation of mine engineering geological profile, and test analysis of the geological mechanics characteristics of the surrounding rock of the roadway to be protected, such as rock stratum structure and thickness, physical and mechanical properties of surrounding rock, hydrogeological conditions, structure, mining influence, etc. Especially, the ground stress of the roadway is measured by using water pressure fracturing method, and it is understood that the maximum principal stress is horizontal stress, which is 21.5 MPa, and is perpendicular to the axis of the roadway, and the minimum principal stress is horizontal stress, which is 17.3 MPa, and is parallel to the axis of the roadway.

[0105] Step II, according to the mine drilling columnar chart, the previous working face pressure step distance 28.6 m, the coal seam mining height 2.65 m, and the goaf expansion coefficient 1.3, it is determined that the hard rock stratum which plays a key role in the working face pressure is the limestone which is 18.7 m away from the roadway roof, and the rock stratum thickness is 9.95 m.

[0106] Step III, design of kilometer horizontal drilling parameters and water pressure fracturing parameters. Specifically, the kilometer horizontal drilling parameters include: the drilling is located in the limestone which is 18.7 m away from the roadway roof, and the horizontal distance between the drilling and the coal pillar is x, which is obtained according to the following formula:

[0107] x = h / tan θ

[0108] Wherein, h is the key layer height; θ is the caving angle, wherein: the medium stable roof caving angle is 60°, and the stable roof caving angle is 45°. In the example, the caving angle is 60°, the horizontal distance between the drill hole and the coal pillar is 10.8m, the vertical spacing of the drill holes in the same drill field is mainly related to the uniaxial compressive strength (Prouse coefficient) of the hard roof rock and the water pressure, the uniaxial compressive strength of the rock in the example is 100MPa, the water pressure is 15MPa, the hole spacing is 3m, the horizontal spacing of the drill holes is related to the direction and size of the maximum principal stress, the maximum principal stress in the example is the horizontal stress, the horizontal stress difference is 4MPa, the horizontal spacing of the drill holes is 1.5m, and the length of a single drill hole is 493m; the water pressure fracturing parameters include: the water pressure is 15MPa, and the fracturing section needs to ensure that the cracks penetrate the hard rock layer.

[0109] Step IV, after determining the height of the top cutting layer and the horizontal distance 14 between the drill hole and the coal pillar 7, the first drill field is set from the open-off cut 1, and every 493m, the next drill field is set until the last drill field exceeds the stop line (3) by 30m. A kilometer directional drilling machine is installed in the drill field, and then the hole is drilled from the first drill field, and two drill holes 9 are drilled in each drill field. The vertical spacing 15 between the two adjacent drill holes is 3m, and the horizontal spacing 16 between the two adjacent drill holes is 1.5m. The trajectory of the drill hole is a curve 10 at the beginning and a nearly horizontal straight line in the main part. When cutting the roof, the effect of cutting the roof and the protection of the recovery roadway are considered, and the drill hole is drilled near the solid coal side of the recovery roadway.

[0110] Step V, the water pressure fracturing is carried out on site, that is, a high-pressure water injection pump is arranged in the drill field, and the water pressure fracturing is started in the drill field after the drilling of the drill hole in the drill field is completed. The drill hole is arranged in the hard rock layer, and each drill hole adopts a retreating type multiple fracturing. The fracturing is carried out every 20m in the hole, and the fracturing time is not less than 30min each time. When fracturing, the water head direction must be perpendicular to the roof of the roadway. When the water pressure suddenly decreases greatly, stop fracturing this section, and repeat the process until the hard rock layer in the horizontal drill hole is completely fractured. Then, the working face is recovered, and when the working face is recovered to about 50m in front of the next horizontal drill hole, the next horizontal drill hole is started for segmented fracturing, and the cycle is repeated until the working face is recovered.

[0111] Step VI, after the water pressure fracturing of the kilometer directional horizontal drill hole, the hard roof above the working face goaf is basically fully caved, the adjacent roadway is weakened by the mining influence, the coal pillar width of the double roadway drivage of the next working face is reduced from 15m to 6m, and the anchor cable reinforcement is carried out on the dynamic pressure roadway coal pillar side.

[0112] The above-mentioned embodiments are the preferred embodiments of the present application, which are only used for facilitating the description of the present application, and do not limit the present application in any form. Any person skilled in the art, if making partial changes or modifications to the equivalent embodiments within the scope of the technical features of the present application, without departing from the technical features of the present application, and without departing from the technical features of the present application, all still belong to the scope of the technical features of the present application.

Claims

1. A method for km horizontal drilling, fracturing, roof cutting, pressure releasing, and protecting roadway, and reducing coal pillar width, characterized in that, The method comprises the following steps: S1, obtaining the geomechanical information of the surrounding rock of the roadway to be protected; the step S1 comprises: field investigation of the mine engineering geological profile and test analysis of the geomechanical information of the surrounding rock of the roadway to be protected; rock structure and thickness, physical and mechanical properties of the surrounding rock, hydrogeological conditions, tectonic conditions, mining influence, and ground stress information of the roadway measured by using the water pressure cracking method; the ground stress information of the roadway measured by using the water pressure cracking method comprises: the maximum principal stress, the minimum principal stress, and the direction of the minimum principal stress; S2, determining the layer and thickness of the hard rock layer that plays a key role in the pressure of the working face; the step S2 comprises: determining the layer and thickness of the hard rock layer that plays a key role in the pressure of the working face according to the mine drilling columnar chart, the pressure step distance of the previous mining working face, the coal seam mining height, and the goaf crushing coefficient; S3, determining the parameters of the kilometer horizontal drilling and the water pressure cracking parameters; The parameters of the kilometer horizontal drilling comprise: the drilling layer, the relative position of the coal pillar, the horizontal distance and the vertical distance between the drillings, and the drilling length; The water pressure cracking parameters comprise: the water pressure, the cracking direction, and the fracturing section; S4, field construction of the kilometer horizontal drilling; the step S4 comprises: setting the first drilling field from the super-long open-off cut of 300-500 m, setting the next drilling field every 280-480 m, and stopping at the last drilling field beyond the stop line by 20-40 m; installing the kilometer directional drilling machine in the drilling field, then starting drilling from the first drilling field, the vertical distance between the adjacent two drillings is 1-4 m, and the horizontal distance between the adjacent two drillings is 0-6 m; the trajectory of the drilling starts as a curve, and the main part is an approximately horizontal straight line; The relationship between the number of drillings in each drilling field in the step S4 and the thickness of the hard roof to be cut is: one drilling is drilled when the thickness of the hard roof to be cut is less than 5 m; two drillings are drilled when the thickness of the hard roof to be cut is 5-10 m; When cutting the roof, the drilling is performed close to the solid coal side of the mining roadway, the horizontal distance between the drilling and the coal pillar is x, and the following formula is used to obtain x: x = h / tanθ wherein, h is the height of the hard roof layer, and θ is the caving angle, wherein: the caving angle of the medium stable roof is 60°, and the caving angle of the stable roof is 45°; S5, field development of water pressure cracking; S6, reducing the width of the coal pillar; in the step S6, after the entire working face is mined and the hard roof above the working face goaf is fully collapsed under the action of the kilometer horizontal drilling water pressure cracking, the influence on the adjacent roadway is weakened, the width of the coal pillar is reduced, and strong support means is provided to reduce the width of the coal pillar of the next working face to 3-10 m.

2. The method according to claim 1, wherein: the relationship between the vertical distance between the drillings in the same drilling field and the uniaxial compressive strength of the hard roof rock and the water pressure is: when the uniaxial compressive strength of the rock is 80-100 MPa and the water pressure is 15-20 MPa, the distance between the drillings is 1-2 m; when the uniaxial compressive strength of the rock is 60-80 MPa and the water pressure is 10-15 MPa, the distance between the drillings is 3-4 m. ​ The relationship between the horizontal distance of the boreholes in the same drilling field and the direction and size of the maximum principal stress is as follows: when the maximum principal stress is the vertical stress, the horizontal distance of the boreholes is 0 m; when the maximum principal stress is the horizontal stress: if the horizontal stress difference is 1-5 MPa, the horizontal distance of the boreholes is 0-2 m; if the horizontal stress difference is 5-10 MPa, the horizontal distance of the boreholes is 2-4 m; if the horizontal stress difference is 10-15 MPa, the horizontal distance of the boreholes is 4-6 m.

3. The method of claim 1, wherein: Step S5 comprises: First, a high-pressure water injection pump is arranged in the drilling field, and hydraulic fracturing is started in the drilling field after the drilling of one drilling field is completed; the boreholes are arranged in hard rock strata, and a retreating type multiple fracturing is used for each borehole, the hard rock strata in the borehole are fractured every 10-30 m, the fracturing time is not less than 30 min each time, the water head direction must be perpendicular to the roof of the roadway during fracturing, the fracturing of the segment is stopped when the water pressure suddenly decreases greatly, and the hard rock strata in the borehole are fractured completely through the above-mentioned repeated process; Then, the working face is started to be mined, and the next borehole is started to be fractured in segments when the working face is mined to about 50 m in front of the next borehole, and the cycle is repeated until the working face is mined completely.

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