Method for constructing a floor aquifuge in a coal mine under pressure

Abstract

The application discloses a method for constructing a floor water-resisting layer in coal mining under pressure, and the method comprises the following steps: taking a ground with a coal seam, a floor, multiple rock layers and an aquifer from top to bottom as a construction area, and selecting a construction site in the construction area according to the distribution of buildings; calculating the critical elevation of a target layer and selecting the target layer according to the value of the critical elevation; drilling a hole from the edge of the construction area to the target layer and drilling branch holes in the horizontal direction until the branch holes cover the target layer, and each branch hole is segmented; perforating two sides of each segment to form multiple horizontal fractures; inputting water-swelling particles into each horizontal fracture; injecting high-pressure water into the target layer to connect the horizontal fractures into a through fracture; injecting cement slurry into the through fracture to block a concealed collapse column developed to the target layer after setting; and cyclically operating until the perforating, particle-throwing, fracturing and grouting of all segments and branch holes are completed. The application can slow down the influence of hole collapse on grouting, the slurry diffuses in an orderly manner during the grouting process, and the potential threat of the concealed collapse column is eliminated.

Description

Technical Field

[0001] This invention belongs to the technical field of bottom plate water-resistant layer construction methods, and relates to a method for constructing a bottom plate water-resistant layer in a pressurized coal mine. Background Technology

[0002] In North my country's coalfields, coal seam mining commonly faces the threat of water hazards from the underlying limestone aquifer. Regional grouting is a common method for preventing and controlling these hazards. However, traditional grouting methods rely on boreholes as grout transport channels, which are limited by surface grouting pressure, resulting in a small grout diffusion radius and low treatment efficiency. Previous hydraulic fracturing grouting relied on surface hydraulic fracturing to create formation fractures, but the directionality of these fractures is difficult to control. These fractures tend to diffuse randomly along weak surfaces in the formation structure, leading to disordered grout diffusion during the grouting process and making it difficult to construct a stable aquitard. Furthermore, due to the small borehole diameter, there is a lack of support after drilling, making borehole collapse easy and limiting the grout diffusion range. In addition, the difficulty in controlling the direction of fractures generated by surface hydraulic fracturing leads to poor connectivity of formation fractures, making it difficult to connect them to hidden collapse columns. This can leave safety hazards after treatment, posing potential risks to coal mine safety. Summary of the Invention

[0003] The purpose of this invention is to provide a method for constructing a waterproof layer in a pressurized coal mine, which solves the problem of disordered grout diffusion during grouting and difficulty in constructing a stable waterproof layer in the prior art.

[0004] The technical solution adopted in this invention is a method for constructing a water-resistant layer on the bottom plate in a coal mine under pressure, specifically including the following steps:

[0005] Step 1: Define the area where the ground contains coal seams, floor, multiple rock strata, and aquifers in descending order as the construction zone, and select the construction site within the construction zone based on the distribution of buildings; calculate the critical elevation of the target layer and select the target layer based on its value;

[0006] Step 2: Drill holes from the edge of the construction area to the target layer and branch holes horizontally until the branches cover the target layer, and divide each branch into segments;

[0007] Step 3: Create multiple horizontal fractures by perforating both sides of a segment; introduce water-swellable particles into each horizontal fracture; inject high-pressure water into the target layer to connect the horizontal fractures into a through fracture; inject cement grout into the through fracture, and after solidification, seal the hidden collapse column that has developed into the target layer.

[0008] Step 4: Repeat step 3 until all segments and branches have completed the perforation, granulation, fracturing, and grouting work.

[0009] The method for constructing a waterproof layer in a pressurized coal mine according to the present invention is further characterized by:

[0010] Step 1 is implemented as follows:

[0011] Step 1.1: The planned mining area of ​​the mine consists of coal seam, floor, multiple rock strata and aquifer from the ground down. Based on the mining plan and the water hazard threat from the aquifer, the boundary of the planned mining area is extended by 30m-50m to form the area of ​​the floor aquifer that needs to be constructed. The ground surface where the floor aquifer is located is designated as the construction area.

[0012] Step 1.2: Select a flat, open, and easily accessible area within the construction zone as the construction site; drill water level observation holes extending from the ground to the aquifer on the construction site; install water level observation gauges outside the water level observation holes;

[0013] Step 1.3: Based on the elevation of the bottom plate measured by the exploration boreholes constructed during the mine construction, check the water level elevation of the observation boreholes from the water level observation table, and calculate the water pressure value P and the critical elevation H4 of the target layer:

[0014]

[0015]

[0016] Where H2 is the water level elevation of the water level observation well; H1 is the elevation of the bottom plate; 1 MPa of water pressure corresponds to a water level of 100 m; T is the coal seam mining water inrush coefficient value, which is 0.1;

[0017] Step 1.4: Select a sandstone or limestone layer with a critical elevation lower than the target layer from among the multiple rock layers between the base plate and the aquifer as the target layer;

[0018] Step 1.5: Deploy the transport vehicle, the perforation fracturing vehicle equipped with perforation fracturing equipment and control switches, the material mixing and grouting station, the drilling rig with drill rods inside, the drilling rig control room, and the grouting pump equipped with pressure gauges at the construction site; connect the transport vehicle to the material mixing and grouting station, the material mixing and grouting station to the grouting pump, the perforation fracturing vehicle to the grouting pump, and the grouting pump to the drilling rig through delivery pipes.

[0019] In step 1.5, the drilling rig is a long-distance directional drilling rig; the perforation fracturing equipment includes a guide head, one end of which is fixedly connected to one end of a mechanical locator, the other end of which is fixedly connected to one end of a hydraulic perforator, the other end of which is fixedly connected to one end of a centralizer, the other end of which is fixedly connected to a connector, and the outer wall of the hydraulic perforator is provided with several nozzles located on the same horizontal line.

[0020] Step 2 is implemented as follows:

[0021] Step 2.1: Design the vertical drilling trajectory from the edge of the construction area to the target layer, and the horizontal drilling trajectory from the endpoint of the vertical drilling trajectory into the inner side of the target layer, reaching another edge line opposite to the endpoint of the vertical drilling trajectory. The horizontal drilling trajectory is divided into several intermittent branch drilling trajectories, and each branch drilling trajectory is further divided into several connected segments. The interval between two adjacent branch drilling trajectories on the horizontal drilling trajectory is 40m-60m, and the segment length on each branch drilling trajectory is 400m-600m. The calculation methods for the number of segments m and the number of branch drilling trajectories n are as follows:

[0022]

[0023]

[0024] Where d1 is the length of the horizontal borehole trajectory. d1 is the average length of the segment; d2 is the length of the edge line of the construction zone perpendicular to the horizontal borehole trajectory. The average spacing between all adjacent branch borehole trajectories;

[0025] Step 2.2: Move the drilling rig to the starting position of the vertical drilling trajectory, drill the drill rod along the vertical drilling trajectory to its ending position, and then drill along a branch of the horizontal drilling trajectory to its ending position to form a borehole.

[0026] Step 2.3: Retract the drill rod to the outside of the borehole opening, install and open the gate valve at the borehole opening, install the perforation fracturing equipment on the head of the drill rod, and advance the perforation fracturing equipment to the end position of the vertical drilling trajectory through the guide head.

[0027] Step 2.4: Based on the three-dimensional coordinates of the borehole displayed in real time in the drilling rig control room, the perforation fracturing equipment is advanced to the end position of the drilled branch borehole trajectory using a mechanical positioner.

[0028] Step 2.5: By advancing, retreating, and rotating the guide head, and fixing the hydraulic perforator with a stabilizer, the nozzles on the hydraulic perforator are aligned with the dip of the formation, ensuring that the perforation spreads along the bedding planes of the formation.

[0029] Step 3 is implemented as follows:

[0030] Step 3.1: Take the segment closest to the end point of the branch drilling trajectory as the first segment, turn on the control switch, and use the perforation fracturing equipment to perform the first perforation operation on the first segment;

[0031] Step 3.2: After the first perforation operation is completed, move the perforation fracturing equipment back 100m-120m and adjust the perforation fracturing equipment again to the end position of the next perforation operation using the guide head. Then, use the stabilizer to fix the hydraulic perforator so that the nozzle of the hydraulic perforator is consistent with the formation dip.

[0032] Step 3.3, repeat steps 3.1 and 3.2 until all perforation work in the first segment is completed, turn off the control switch, and then remove the drill rod and perforation fracturing equipment from the borehole. During the construction process, it is necessary to record and analyze the pressure value of each perforation segment.

[0033] Step 3.4: Use a transport vehicle to transport the water-swellable particles and oil-based lubricating materials to the material mixing and grouting station through the conveying pipe;

[0034] Step 3.5: Mix water-swellable particles with oil-based lubricating material at a volume ratio of 1:4-6 and then transport the mixture to the grouting pump through the delivery pipe. The grouting pump injects the mixture into all horizontal fissures through the delivery pipe. During the construction process, it is necessary to record and analyze the amount of water-swellable particles injected in each section. The particle injection work of the first section is completed.

[0035] Step 3.6: High-pressure water is delivered to the grouting pump through the delivery pipe using a perforation fracturing truck. The grouting pump injects high-pressure water into the target layer through the delivery pipe. Water-swellable particles expand upon contact with water, thus supporting the horizontal fractures. The high-pressure water splits the horizontal fractures and forms a through fracture. The high-pressure water drives the water-swellable particles to move within the through fracture. The borehole opening is closed by a gate valve, allowing the water-swellable particles to expand under the immersion of water and support the through fracture.

[0036] Step 3.7: After the water-swellable particles expand and become stuck in the fissures between the rock strata, open the borehole opening through the gate valve and release the high-pressure water at a rate of 0.4MPa / h-0.6MPa / h until the borehole opening pressure drops to 0MPa. During the construction process, it is necessary to record and analyze the pressure value and the amount of high-pressure water injected for each fracturing segment. The fracturing work of the first segment is completed.

[0037] Step 3.8: After the high-pressure water is released, use a grouting pump to inject cement grout into the through-cracks in the target layer to fill and seal the cracks between the rock layers. After the cement grout solidifies, it forms a bottom waterproof layer and seals the hidden collapse column that is connected to the target layer through the through-cracks.

[0038] Step 3.9: Use the pressure gauge on the grouting pump to check the grouting pressure. When the grouting pressure reaches 1.6 to 2.4 times the water pressure value P calculated based on the water level elevation H2 of the water level observation hole and the bottom plate elevation H1, stop grouting, close the borehole opening, and wait for the cement grout between the fractures to solidify and form a cement stone body. During the construction process, it is necessary to record and analyze the pressure value and the amount of cement grout injected for each grouting segment. The grouting work of the first segment is completed.

[0039] Step 4: During the drilling process, it is necessary to perform cuttings logging analysis to observe whether the returned cuttings contain cement-bonded stones. If cement-bonded stones are visible in the returned cuttings throughout the entire drilling process, the branch borehole treatment is deemed qualified. If more than 30m of the returned cuttings do not contain cement-bonded stones, the section without cement-bonded stones is identified as an abnormal section. Analyze the abnormal sections during the construction process and perform supplementary cyclical operations on the abnormal sections until the entire construction area is fully covered.

[0040] The beneficial effects of this invention are:

[0041] Compared with existing technologies, the method for constructing a bottom aquitard in pressurized coal mining of this invention involves perforating the target layer, followed by granulation and fracturing. This allows for easier control of the directionality of the formation fractures. Injecting cement grout then results in orderly diffusion of the grout, significantly expanding the diffusion range. This allows for increased spacing between horizontal branch boreholes, reducing the number of boreholes required and simplifying the coordination of various equipment. The introduction of water-swellable granules into the horizontal fractures effectively supports them upon contact with water, mitigating the impact of borehole collapse on grouting and ensuring the grout diffusion radius meets design requirements. Fracturing connects horizontal fractures into continuous fractures. The cement grout fully fills these continuous fractures and any potential hidden collapse columns, forming a well-cemented bottom aquitard between rock strata. This effectively eliminates the potential threat of hidden collapse columns and avoids creating blind spots in the treatment process. The bottom aquitard is primarily composed of cement-cemented aggregates, exhibiting good integrity and strong water-tightening performance. It effectively blocks the movement of aquifers between working faces, ensuring safe mine recovery. Attached Figure Description

[0042] Figure 1 This is a diagram showing the geological space structure and equipment layout in the method for constructing a bottom waterproof layer in a pressurized coal mine according to the present invention.

[0043] Figure 2 This is a structural diagram of the perforation fracturing equipment used in the method for constructing a water-tight layer in a coal mine under pressure mining according to the present invention.

[0044] Figure 3 This is a three-dimensional diagram of the vertical and horizontal drilling trajectories in the method for constructing a water-resistant layer in a pressurized coal mine according to the present invention.

[0045] Figure 4This is a perforation cross-section diagram in the method for constructing a water-resistant layer in a pressurized coal mine according to the present invention;

[0046] Figure 5 This is a cross-sectional view of the granulation and fracturing process in the method for constructing a water-resistant layer in a coal mine under pressure mining according to the present invention.

[0047] Figure 6 This is a magnified view of a portion of the method for constructing a waterproof layer in a coal mine under pressure, as described in this invention, involving the introduction of water-swellable particles into horizontal fissures.

[0048] Figure 7 This is a cross-sectional view of grouting in the method for constructing a waterproof layer in a pressurized coal mine according to the present invention.

[0049] In the diagram, 1. Transport vehicle, 2. Perforation and fracturing vehicle, 3. Material mixing and grouting station, 4. Drilling rig, 5. Borehole, 6. Coal seam, 7. Target layer, 8. Water level observation hole, 9. Aquifer, 10. Perforation and fracturing equipment, 11. Mechanical locator, 12. Hydraulic perforator, 13. Centralizer, 14. Guide head, 15. Hidden collapse column, 16. Water-swellable particles, 17. Horizontal fracture, 18. Cement-aggregate body, 19. Drilling rig control room, 20. Grouting pump, 21. Pressure gauge, 22. Gate valve, 23. Drill rod, 24. Water level observation gauge, 25. Base plate, 26. Control switch, 27. Delivery pipe, 28. Through fracture, 29. Connector, 30. Nozzle. Detailed Implementation

[0050] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0051] A method for constructing a waterproof layer in a pressurized coal mine includes the following steps:

[0052] Step 1: Refer to Figure 1 The planned mining area of ​​the mine, from the surface downwards, includes coal seam 6, floor 25, multiple rock strata, and aquifer 9. Based on the mine's mining plan and the water hazard threat posed by aquifer 9, the planned mining area boundary is extended outwards by 30m-50m to define the area requiring the construction of a floor aquitard. The ground surface within this aquitard area is designated as the construction zone. A flat, open, and easily accessible area is selected within the construction zone based on the distribution of surface buildings. Water level observation wells 8 are drilled extending from the surface to aquifer 9 on the construction site. A water level gauge 24 is installed outside the water level observation wells 8. The elevation of floor 25 is measured using exploratory boreholes drilled during mine construction. The water level elevation of the water level observation wells 8 is checked from the water level gauge 24, and the water pressure value P and the critical elevation H4 of the target layer 7 are calculated.

[0053]

[0054]

[0055] Where H2 is the water level elevation of the water level observation well 8; H1 is the elevation of the bottom plate 25; 1 MPa water pressure corresponds to a water level of 100 m; T is the coal seam mining water inrush coefficient value, taken as 0.1; among the multiple rock layers between the bottom plate 25 and the aquifer 9, a sandstone layer or limestone layer with a critical elevation lower than the target layer 7 is selected as the target layer 7; the transport vehicle 1, the perforation fracturing vehicle 2 equipped with the perforation fracturing equipment 10 and control switch 26, the material mixing and grouting station 3, the drilling rig 4 with drill rod 23 inside, the drilling rig control room 19, and the grouting pump 20 equipped with pressure gauge 21 are arranged at the construction site; the transport vehicle 1 is connected to the material mixing and grouting station 3, the material mixing and grouting station 3 is connected to the grouting pump 20, the perforation fracturing vehicle 2 is connected to the grouting pump 20, and the grouting pump 20 is connected to the drilling rig 4 through the delivery pipe 27; the drilling rig 4 is a long-distance directional drilling rig; refer to Figure 2 The perforation fracturing equipment 10 includes a guide head 14, one end of which is fixedly connected to one end of a mechanical positioner 11, the other end of which is fixedly connected to one end of a hydraulic perforator 12, the other end of which is fixedly connected to one end of a centralizer 13, the other end of which is fixedly connected to a connector 29, and the outer wall of the hydraulic perforator 12 is provided with a plurality of nozzles 30 located on the same horizontal line.

[0056] Step 2: Refer to Figure 3 The design includes a vertical drilling trajectory from the edge of the construction area to the target layer 7, and a horizontal drilling trajectory starting from the endpoint of the vertical drilling trajectory and drilling inwards towards the inner edge of the target layer 7, reaching another edge line opposite to the endpoint of the vertical drilling trajectory. The horizontal drilling trajectory is divided into several intermittent branch drilling trajectories, and each branch drilling trajectory is further divided into several connected segments. The interval between two adjacent branch drilling trajectories on the horizontal drilling trajectory is 40m-60m, and the segment length on each branch drilling trajectory is 400m-600m. The calculation methods for the number of segments m and the number of branch drilling trajectories n are as follows:

[0057]

[0058]

[0059] Where d1 is the length of the horizontal borehole trajectory. d1 is the average length of the segment; d2 is the length of the edge line of the construction zone perpendicular to the horizontal borehole trajectory. The average spacing of all adjacent branch borehole tracks is defined. The drilling rig 4 is moved to the starting position of the vertical borehole track, and the drill rod 23 is drilled along the vertical borehole track to its ending position and along a branch borehole track of the horizontal borehole track to its ending position, forming borehole 5. The drill rod 23 is retracted to the outside of the borehole 5, and a gate valve 22 is installed at the borehole 5 and opened. The perforation fracturing equipment 10 is installed at the head of the drill rod 23, and the perforation fracturing equipment 10 is advanced to the ending position of the vertical borehole track through the guide head 14. According to the three-dimensional coordinates of the borehole displayed in real time in the drilling rig control room 19, the perforation fracturing equipment 10 is advanced to the ending position of the drilled branch borehole track through the mechanical positioner 11. By advancing, retreating and rotating the guide head 14, and fixing the hydraulic perforator 12 with the centralizer 13, the nozzle on the hydraulic perforator 12 is aligned with the formation dip to ensure that the perforation spreads along the formation bedding.

[0060] Step 3: Designate the segment closest to the end point of the branch borehole trajectory as the first segment. Turn on control switch 26 and use the perforation fracturing equipment 10 to perform the first perforation operation on the first segment. After the first perforation operation is completed, retract the perforation fracturing equipment 10 by 100-120 meters. Adjust the perforation fracturing equipment 10 again using the guide head 14 to the end point of the next perforation operation, and use the centralizer 13 to fix the hydraulic perforator 12, ensuring that the nozzle of the hydraulic perforator 12 is aligned with the formation dip. Repeat this process until all perforations in the first segment are completed, referring to... Figure 4 Multiple horizontal fractures 17 are formed in the target layer 7. The control switch 26 is turned off, and then the drill rod 23 and the perforation fracturing equipment 10 are withdrawn from the borehole 5. During the construction process, the pressure value of each perforation segment needs to be recorded and analyzed. The water-swellable particles 16 and oil-based lubricating material are transported to the material mixing and grouting station 3 through the delivery pipe 27 using the transport vehicle 1. The water-swellable particles 16 and oil-based lubricating material are mixed at a volume ratio of 1:4-6 and then transported to the grouting pump 20 through the delivery pipe 27. The grouting pump 20 injects the mixture into all the horizontal fractures 17 through the delivery pipe 27. During the construction process, the amount of water-swellable particles 16 injected into each segment needs to be recorded and analyzed. The particle injection work of the first segment is completed. The perforation fracturing vehicle 2 delivers high-pressure water to the grouting pump 20 through the delivery pipe 27. The grouting pump 20 injects high-pressure water into the target layer 7 through the delivery pipe 27. The water-swellable particles 16 expand upon contact with water, thereby supporting the horizontal fractures 17. The high-pressure water splits the horizontal fractures 17 and forms a through fracture 28. Figure 5 High-pressure water drives the water-swellable particles 16 to move within the through-crack 28. A gate valve 22 closes the borehole 5, causing the water-swellable particles 16 to expand under water immersion and support the through-crack 28. (Refer to...) Figure 6After the water-swellable particles 16 expand and become lodged in the fissures between rock strata, the borehole 5 is opened through gate valve 22, and high-pressure water is released at a rate decreasing from 0.4 MPa / h to 0.6 MPa / h until the borehole 5 pressure drops to 0 MPa. During the construction process, the pressure value and the volume of high-pressure water injected for each fracturing segment need to be recorded and analyzed. The fracturing work of the first segment is then completed. (Refer to...) Figure 7 After the high-pressure water is released, cement grout is injected into the through-cracks 28 in the target layer 7 using grouting pump 20 to fill and seal the cracks between rock layers. After the cement grout solidifies, a bottom water-proof layer is formed and the hidden collapse column 15 that is connected to the target layer 7 is sealed through the through-cracks 28. The grouting pressure is checked using pressure gauge 21 on grouting pump 20. When the grouting pressure reaches 1.6 to 2.4 times the water pressure value P calculated based on the water level elevation H2 of water level observation hole 8 and the elevation H1 of bottom plate 25, grouting is stopped, the borehole 5 is closed, and the cement grout between the through-cracks 28 is allowed to solidify and form cement stone body 18. During the construction process, the pressure value and the amount of cement grout injected for each grouting segment need to be recorded and analyzed. The grouting work of the first segment is completed.

[0061] Step 4: Repeat Step 3 until all sections and branches have completed perforation, granulation, fracturing, and grouting. During the drilling process of drill pipe 23, perform cuttings logging analysis to observe whether the returned cuttings contain cement-bonded stone bodies 18. If cement-bonded stone bodies 18 are visible in the returned cuttings throughout the entire drilling process, the branch borehole treatment is deemed qualified. If more than 30m of the returned cuttings throughout the entire drilling process do not contain cement-bonded stone bodies 18, the construction section without cement-bonded stone bodies 18 is identified as an abnormal construction section. Analyze the abnormal construction sections during the construction process and supplement the abnormal construction sections with cyclical operations until the entire construction area is fully covered.

[0062] The working principle of this invention is:

[0063] Using the perforation fracturing equipment 10, segmented perforation is performed within the target layer 7, which facilitates control over the directionality of formation fractures and forms horizontal fractures 17. Segmented particle injection within the horizontal fractures 17 effectively supports them. Segmented fracturing within the horizontal fractures 17 connects them to form a through fracture 28. After segmented injection of cement grout into the through fracture 28, it fully fills the through fracture 28 and any potential hidden collapse columns 15, effectively eliminating the potential threat of vertical water-guiding channels such as hidden collapse columns 15. During the drilling process of the drill pipe 23, cuttings logging analysis is performed to determine whether the treatment of each branch borehole is qualified. For abnormal construction sections, additional cyclic operations are carried out until the entire construction area is fully covered.

[0064] Example 1:

[0065] A method for constructing a waterproof layer in a pressurized coal mine includes the following steps:

[0066] Step 1: The planned mining area of ​​the mine, from the surface downwards, includes coal seam 6, floor 25, multiple rock strata, and aquifer 9. Based on the mine's mining plan and the water hazard threat posed by aquifer 9, the boundary of the planned mining area is extended by 30m to define the area of ​​the floor aquitard to be constructed. The ground surface within the floor aquitard area is designated as the construction zone. A flat, open, and easily accessible area is selected within the construction zone based on the distribution of surface buildings. A water level observation well 8 is drilled extending from the surface to aquifer 9 on the construction site. A water level gauge 24 is installed outside the water level observation well 8. The elevation of floor 25 is measured based on the exploration boreholes drilled during mine construction. The water level elevation of the water level observation well 8 is checked from the water level gauge 24, and the water pressure value P and the critical elevation H4 of the target layer 7 are calculated.

[0067]

[0068]

[0069] Where H2 is the water level elevation of the water level observation well 8; H1 is the elevation of the bottom plate 25; 1 MPa water pressure corresponds to a water level of 100 m; T is the coal seam mining water inrush coefficient value, taken as 0.1; among the multiple rock layers between the bottom plate 25 and the aquifer 9, a sandstone layer or limestone layer with a critical elevation lower than the target layer 7 is selected as the target layer 7; the transport vehicle 1, the perforation fracturing vehicle 2 equipped with the perforation fracturing equipment 10 and the control switch 26, the material mixing and grouting station 3, the drilling rig 4 with the drill rod 23 inside, the drilling rig control room 19, and the grouting pump 20 equipped with the pressure gauge 21 are arranged at the construction site; through the delivery pipe 2 7. Connect the transport vehicle 1 to the material mixing and grouting station 3, the material mixing and grouting station 3 to the grouting pump 20, the perforation and fracturing vehicle 2 to the grouting pump 20, and the grouting pump 20 to the drilling rig 4; the drilling rig 4 is a long-distance directional drilling rig; the perforation and fracturing equipment 10 includes a guide head 14, one end of the guide head 14 is fixedly connected to one end of the mechanical positioner 11, the other end of the mechanical positioner 11 is fixedly connected to one end of the hydraulic perforator 12, the other end of the hydraulic perforator 12 is fixedly connected to one end of the centralizer 13, the other end of the centralizer 13 is fixedly connected to a connector 29, and the outer wall of the hydraulic perforator 12 is provided with three nozzles 30 located on the same horizontal line.

[0070] Step 2: Design the vertical drilling trajectory from the edge of the construction area to the target layer 7, and the horizontal drilling trajectory from the end of the vertical drilling trajectory into the inner side of the target layer 7, reaching the opposite edge line to the edge line where the end of the vertical drilling trajectory is located. The horizontal drilling trajectory is divided into several intermittent branch drilling trajectories, and each branch drilling trajectory is divided into several connected segments. The interval between two adjacent branch drilling trajectories on the horizontal drilling trajectory is 40m, and the segment length on each branch drilling trajectory is 400m. The calculation methods for the number of segments m and the number of branch drilling trajectories n are as follows:

[0071]

[0072]

[0073] Where d1 is the length of the horizontal borehole trajectory. d1 is the average length of the segment; d2 is the length of the edge line of the construction zone perpendicular to the horizontal borehole trajectory. The average spacing of all adjacent branch borehole tracks is defined. The drilling rig 4 is moved to the starting position of the vertical borehole track, and the drill rod 23 is drilled along the vertical borehole track to its ending position and along a branch borehole track of the horizontal borehole track to its ending position, forming borehole 5. The drill rod 23 is retracted to the outside of the borehole 5, and a gate valve 22 is installed at the borehole 5 and opened. The perforation fracturing equipment 10 is installed at the head of the drill rod 23, and the perforation fracturing equipment 10 is advanced to the ending position of the vertical borehole track through the guide head 14. According to the three-dimensional coordinates of the borehole displayed in real time in the drilling rig control room 19, the perforation fracturing equipment 10 is advanced to the ending position of the drilled branch borehole track through the mechanical positioner 11. By advancing, retreating and rotating the guide head 14, and fixing the hydraulic perforator 12 with the centralizer 13, the nozzle on the hydraulic perforator 12 is aligned with the formation dip to ensure that the perforation spreads along the formation bedding.

[0074] Step 3: Designate the segment closest to the end point of the branch borehole trajectory as the first segment. Turn on control switch 26 and use the perforation fracturing equipment 10 to perform the first perforation operation on the first segment. After the first perforation operation is completed, move the perforation fracturing equipment 10 back 100m. Then, adjust the perforation fracturing equipment 10 again using the guide head 14 to the end point of the next perforation operation. Use the centralizer 13 to fix the hydraulic perforator 12, ensuring the nozzle of the hydraulic perforator 12 is aligned with the formation dip. Repeat this process until all perforations in the first segment are completed. Turn off control switch 26, and then remove the drill rod 23 and the perforation fracturing equipment 10 from the borehole opening of borehole 5. Records and analyses of each step during the construction process are necessary. The pressure values ​​of the perforation in each segment; using transport vehicle 1, water-swellable particles 16 and oil-based lubricating material are transported to the material mixing and grouting station 3 through the delivery pipe 27; the water-swellable particles 16 and oil-based lubricating material are mixed at a volume ratio of 1:4 and then transported to the grouting pump 20 through the delivery pipe 27. The grouting pump 20 injects it into all horizontal fractures 17 through the delivery pipe 27. During the construction process, the amount of water-swellable particles 16 injected in each segment needs to be recorded and analyzed. The particle injection work of the first segment is completed; using perforation fracturing vehicle 2, high-pressure water is transported to the grouting pump 20 through the delivery pipe 27. The grouting pump 20 injects high-pressure water into the target layer 7 through the delivery pipe 27. The water-swellable particles 16 expand upon contact with water. This supports the horizontal fracture 17. High-pressure water splits the horizontal fracture 17 and forms a through fracture 28. The high-pressure water drives the water-swellable particles 16 to move within the through fracture 28. The borehole 5 is closed by the gate valve 22, allowing the water-swellable particles 16 to expand under water immersion and support the through fracture 28. After the water-swellable particles 16 expand and become stuck in the fracture between rock strata, the borehole 5 is opened by the gate valve 22, and the high-pressure water is released at a rate of 0.4 MPa / h until the borehole pressure drops to 0 MPa. During the construction process, the pressure value and the amount of high-pressure water injected for each fracturing segment need to be recorded and analyzed. The fracturing work of the first segment is completed. After the high-pressure water is released, a grouting pump is used. Cement grout is injected into the through-fracture 28 in the target layer 7 to fill and seal the inter-layer fractures. After the cement grout solidifies, it forms a bottom water-proof layer and seals the hidden collapse column 15 that is connected to the target layer 7 through the through-fracture 28. The pressure gauge 21 on the grouting pump 20 is used to check the grouting pressure. When the grouting pressure reaches 1.6 times the water pressure value P calculated based on the water level elevation H2 of the water level observation hole 8 and the elevation H1 of the bottom plate 25, the grouting is stopped, the borehole 5 is closed, and the cement grout between the through-fracture 28 is allowed to solidify and form a cement-stone body 18. During the construction process, the pressure value and the amount of cement grout injected for each grouting segment need to be recorded and analyzed. The grouting work of the first segment is completed.

[0075] Step 4: Repeat Step 3 until all sections and branches have completed perforation, granulation, fracturing, and grouting. During the drilling process of drill pipe 23, perform cuttings logging analysis to observe whether the returned cuttings contain cement-bonded stone bodies 18. If cement-bonded stone bodies 18 are visible in the returned cuttings throughout the entire drilling process, the branch borehole treatment is deemed qualified. If more than 30m of the returned cuttings throughout the entire drilling process do not contain cement-bonded stone bodies 18, the construction section without cement-bonded stone bodies 18 is identified as an abnormal construction section. Analyze the abnormal construction sections during the construction process and supplement the abnormal construction sections with cyclical operations until the entire construction area is fully covered.

[0076] Example 2:

[0077] A method for constructing a waterproof layer in a pressurized coal mine includes the following steps:

[0078] Step 1: The planned mining area of ​​the mine, from the surface downwards, includes coal seam 6, floor 25, multiple rock strata, and aquifer 9. Based on the mine's mining plan and the water hazard threat posed by aquifer 9, the boundary of the planned mining area is extended by 40m to define the area of ​​the floor aquitard to be constructed. The ground surface within the floor aquitard area is designated as the construction zone. A flat, open, and easily accessible area is selected within the construction zone based on the distribution of surface buildings. Water level observation wells 8 are drilled extending from the surface to aquifer 9 on the construction site. A water level gauge 24 is installed outside the water level observation well 8. The elevation of floor 25 is measured based on the exploration boreholes drilled during mine construction. The water level elevation of the water level observation well 8 is checked from the water level gauge 24, and the water pressure value P and the critical elevation H4 of the target layer 7 are calculated.

[0079]

[0080]

[0081] Where H2 is the water level elevation of the water level observation well 8; H1 is the elevation of the bottom plate 25; 1 MPa water pressure corresponds to a water level of 100 m; T is the coal seam mining water inrush coefficient value, taken as 0.1; among the multiple rock layers between the bottom plate 25 and the aquifer 9, a sandstone layer or limestone layer with a critical elevation lower than the target layer 7 is selected as the target layer 7; the transport vehicle 1, the perforation fracturing vehicle 2 equipped with the perforation fracturing equipment 10 and the control switch 26, the material mixing and grouting station 3, the drilling rig 4 with the drill rod 23 inside, the drilling rig control room 19, and the grouting pump 20 equipped with the pressure gauge 21 are arranged at the construction site; through the delivery pipe 2 7. Connect the transport vehicle 1 to the material mixing and grouting station 3, the material mixing and grouting station 3 to the grouting pump 20, the perforation and fracturing vehicle 2 to the grouting pump 20, and the grouting pump 20 to the drilling rig 4; the drilling rig 4 is a long-distance directional drilling rig; the perforation and fracturing equipment 10 includes a guide head 14, one end of the guide head 14 is fixedly connected to one end of the mechanical positioner 11, the other end of the mechanical positioner 11 is fixedly connected to one end of the hydraulic perforator 12, the other end of the hydraulic perforator 12 is fixedly connected to one end of the centralizer 13, the other end of the centralizer 13 is fixedly connected to a connector 29, and the outer wall of the hydraulic perforator 12 is provided with four nozzles 30 located on the same horizontal line.

[0082] Step 2: Design the vertical drilling trajectory from the edge of the construction area to the target layer 7, and the horizontal drilling trajectory from the end of the vertical drilling trajectory into the inner side of the target layer 7, reaching the opposite edge line to the edge line where the end of the vertical drilling trajectory is located. The horizontal drilling trajectory is divided into several intermittent branch drilling trajectories, and each branch drilling trajectory is divided into several connected segments. The interval between two adjacent branch drilling trajectories on the horizontal drilling trajectory is 50m, and the segment length on each branch drilling trajectory is 500m. The calculation methods for the number of segments m and the number of branch drilling trajectories n are as follows:

[0083]

[0084]

[0085] Where d1 is the length of the horizontal borehole trajectory. d1 is the average length of the segment; d2 is the length of the edge line of the construction zone perpendicular to the horizontal borehole trajectory. The average spacing of all adjacent branch borehole tracks is defined. The drilling rig 4 is moved to the starting position of the vertical borehole track, and the drill rod 23 is drilled along the vertical borehole track to its ending position and along a branch borehole track of the horizontal borehole track to its ending position, forming borehole 5. The drill rod 23 is retracted to the outside of the borehole 5, and a gate valve 22 is installed at the borehole 5 and opened. The perforation fracturing equipment 10 is installed at the head of the drill rod 23, and the perforation fracturing equipment 10 is advanced to the ending position of the vertical borehole track through the guide head 14. According to the three-dimensional coordinates of the borehole displayed in real time in the drilling rig control room 19, the perforation fracturing equipment 10 is advanced to the ending position of the drilled branch borehole track through the mechanical positioner 11. By advancing, retreating and rotating the guide head 14, and fixing the hydraulic perforator 12 with the centralizer 13, the nozzle on the hydraulic perforator 12 is aligned with the formation dip to ensure that the perforation spreads along the formation bedding.

[0086] Step 3: Designate the segment closest to the end point of the branch borehole trajectory as the first segment. Turn on control switch 26 and use the perforation fracturing equipment 10 to perform the first perforation operation on the first segment. After the first perforation operation is completed, move the perforation fracturing equipment 10 back 110m. Adjust the perforation fracturing equipment 10 again using the guide head 14 to the end point of the next perforation operation, and use the centralizer 13 to fix the hydraulic perforator 12, ensuring the nozzle of the hydraulic perforator 12 is aligned with the formation dip. Repeat this process until all perforations in the first segment are completed. Turn off control switch 26, and then remove the drill rod 23 and the perforation fracturing equipment 10 from the borehole opening of borehole 5. Records and analyses of each step during the construction process are necessary. The pressure values ​​of the perforation in each segment; using transport vehicle 1, water-swellable particles 16 and oil-based lubricating material are transported to the material mixing and grouting station 3 through the delivery pipe 27; the water-swellable particles 16 and oil-based lubricating material are mixed at a volume ratio of 1:5 and then transported to the grouting pump 20 through the delivery pipe 27. The grouting pump 20 injects it into all horizontal fractures 17 through the delivery pipe 27. During the construction process, the amount of water-swellable particles 16 injected in each segment needs to be recorded and analyzed. The particle injection work of the first segment is completed; using perforation fracturing vehicle 2, high-pressure water is transported to the grouting pump 20 through the delivery pipe 27. The grouting pump 20 injects high-pressure water into the target layer 7 through the delivery pipe 27. The water-swellable particles 16 expand upon contact with water. The high-pressure water expands to support the horizontal fracture 17, splitting the horizontal fracture 17 and forming a through fracture 28. The high-pressure water drives the water-swellable particles 16 to move within the through fracture 28. The borehole 5 is closed by the gate valve 22, allowing the water-swellable particles 16 to expand under water immersion and support the through fracture 28. After the water-swellable particles 16 expand and become stuck in the inter-layer fracture, the borehole 5 is opened by the gate valve 22, and the high-pressure water is released at a rate of 0.5 MPa / h until the borehole 5 pressure drops to 0 MPa. During the construction process, the pressure value and the amount of high-pressure water injected for each fracturing segment need to be recorded and analyzed. The fracturing work of the first segment is completed. After the high-pressure water is released, the injection... The grout pump 20 injects cement grout into the through-crack 28 in the target layer 7, filling and sealing the cracks between the rock layers. After the cement grout solidifies, it forms a bottom water-proof layer and seals the hidden collapse column 15 that is connected to the target layer 7 through the through-crack 28. The pressure gauge 21 on the grout pump 20 is used to check the grouting pressure. When the grouting pressure reaches twice the water pressure value P calculated based on the water level elevation H2 of the water level observation hole 8 and the elevation H1 of the bottom plate 25, the grouting is stopped, the borehole 5 is closed, and the cement grout between the through-crack 28 is allowed to solidify and form a cement-stone body 18. During the construction process, it is necessary to record and analyze the pressure value and the amount of cement grout injected for each grouting segment. The grouting work of the first segment is completed.

[0087] Step 4: Repeat Step 3 until all sections and branches have completed perforation, granulation, fracturing, and grouting. During the drilling process of drill pipe 23, perform cuttings logging analysis to observe whether the returned cuttings contain cement-bonded stone bodies 18. If cement-bonded stone bodies 18 are visible in the returned cuttings throughout the entire drilling process, the branch borehole treatment is deemed qualified. If more than 30m of the returned cuttings throughout the entire drilling process do not contain cement-bonded stone bodies 18, the construction section without cement-bonded stone bodies 18 is identified as an abnormal construction section. Analyze the abnormal construction sections during the construction process and supplement the abnormal construction sections with cyclical operations until the entire construction area is fully covered.

[0088] Example 3:

[0089] A method for constructing a waterproof layer in a pressurized coal mine includes the following steps:

[0090] Step 1: The planned mining area of ​​the mine, from the surface downwards, includes coal seam 6, floor 25, multiple rock strata, and aquifer 9. Based on the mine's mining plan and the water hazard threat posed by aquifer 9, the boundary of the planned mining area is extended by 50m to define the area of ​​the floor aquitard to be constructed. The ground surface within the floor aquitard area is designated as the construction zone. A flat, open, and easily accessible area is selected within the construction zone based on the distribution of surface buildings. Water level observation wells 8 are drilled extending from the surface to aquifer 9 on the construction site. A water level gauge 24 is installed outside the water level observation well 8. The elevation of floor 25 is measured based on the exploration boreholes drilled during mine construction. The water level elevation of the water level observation well 8 is checked from the water level gauge 24, and the water pressure value P and the critical elevation H4 of the target layer 7 are calculated.

[0091]

[0092]

[0093] Where H2 is the water level elevation of the water level observation well 8; H1 is the elevation of the bottom plate 25; 1 MPa water pressure corresponds to a water level of 100 m; T is the coal seam mining water inrush coefficient value, taken as 0.1; among the multiple rock layers between the bottom plate 25 and the aquifer 9, a sandstone layer or limestone layer with a critical elevation lower than the target layer 7 is selected as the target layer 7; the transport vehicle 1, the perforation fracturing vehicle 2 equipped with the perforation fracturing equipment 10 and the control switch 26, the material mixing and grouting station 3, the drilling rig 4 with the drill rod 23 inside, the drilling rig control room 19, and the grouting pump 20 equipped with the pressure gauge 21 are arranged at the construction site; through the delivery pipe 2 7. Connect the transport vehicle 1 to the material mixing and grouting station 3, the material mixing and grouting station 3 to the grouting pump 20, the perforation and fracturing vehicle 2 to the grouting pump 20, and the grouting pump 20 to the drilling rig 4; the drilling rig 4 is a long-distance directional drilling rig; the perforation and fracturing equipment 10 includes a guide head 14, one end of the guide head 14 is fixedly connected to one end of the mechanical positioner 11, the other end of the mechanical positioner 11 is fixedly connected to one end of the hydraulic perforator 12, the other end of the hydraulic perforator 12 is fixedly connected to one end of the centralizer 13, the other end of the centralizer 13 is fixedly connected to a connector 29, and the outer wall of the hydraulic perforator 12 is provided with five nozzles 30 located on the same horizontal line.

[0094] Step 2: Design the vertical drilling trajectory from the edge of the construction area to the target layer 7, and the horizontal drilling trajectory starting from the end of the vertical drilling trajectory and drilling inwards towards the inner side of the target layer 7, reaching the opposite edge line to the edge line where the end of the vertical drilling trajectory is located. The horizontal drilling trajectory is divided into several intermittent branch drilling trajectories, and each branch drilling trajectory is divided into several connected segments. The interval between two adjacent branch drilling trajectories on the horizontal drilling trajectory is 60m, and the segment length on each branch drilling trajectory is 600m. The calculation method for the number of segments and the number of branch drilling trajectories is as follows:

[0095]

[0096]

[0097] Where d1 is the length of the horizontal borehole trajectory. d1 is the average length of the segment; d2 is the length of the edge line of the construction zone perpendicular to the horizontal borehole trajectory. The average spacing of all adjacent branch borehole tracks is defined. The drilling rig 4 is moved to the starting position of the vertical borehole track, and the drill rod 23 is drilled along the vertical borehole track to its ending position and along a branch borehole track of the horizontal borehole track to its ending position, forming borehole 5. The drill rod 23 is retracted to the outside of the borehole 5, and a gate valve 22 is installed at the borehole 5 and opened. The perforation fracturing equipment 10 is installed at the head of the drill rod 23, and the perforation fracturing equipment 10 is advanced to the ending position of the vertical borehole track through the guide head 14. According to the three-dimensional coordinates of the borehole displayed in real time in the drilling rig control room 19, the perforation fracturing equipment 10 is advanced to the ending position of the drilled branch borehole track through the mechanical positioner 11. By advancing, retreating and rotating the guide head 14, and fixing the hydraulic perforator 12 with the centralizer 13, the nozzle on the hydraulic perforator 12 is aligned with the formation dip to ensure that the perforation spreads along the formation bedding.

[0098] Step 3: Designate the segment closest to the end point of the branch borehole trajectory as the first segment. Turn on control switch 26 and use the perforation fracturing equipment 10 to perform the first perforation operation on the first segment. After the first perforation operation is completed, move the perforation fracturing equipment 10 back 120m. Adjust the perforation fracturing equipment 10 again using the guide head 14 to the end point of the next perforation operation, and use the centralizer 13 to fix the hydraulic perforator 12, ensuring the nozzle of the hydraulic perforator 12 is aligned with the formation dip. Repeat this process until all perforations in the first segment are completed. Turn off control switch 26, and then remove the drill rod 23 and the perforation fracturing equipment 10 from the borehole opening of borehole 5. Records and analyses of each step during the construction process are necessary. The pressure values ​​of the perforation in each segment; using transport vehicle 1, water-swellable particles 16 and oil-based lubricating material are transported to the material mixing and grouting station 3 through delivery pipe 27; the water-swellable particles 16 and oil-based lubricating material are mixed at a volume ratio of 1:6 and then transported to the grouting pump 20 through delivery pipe 27. The grouting pump 20 injects it into all horizontal fractures 17 through delivery pipe 27. During the construction process, the amount of water-swellable particles 16 injected in each segment needs to be recorded and analyzed. The particle injection work of the first segment is completed; using perforation fracturing vehicle 2, high-pressure water is transported to the grouting pump 20 through delivery pipe 27. The grouting pump 20 injects high-pressure water into the target layer 7 through delivery pipe 27. The water-swellable particles 16 expand upon contact with water. This supports the horizontal fracture 17. High-pressure water splits the horizontal fracture 17 and forms a through fracture 28. The high-pressure water drives the water-swellable particles 16 to move within the through fracture 28. The borehole 5 is closed by the gate valve 22, allowing the water-swellable particles 16 to expand under water immersion and support the through fracture 28. After the water-swellable particles 16 expand and become stuck in the fracture between rock strata, the borehole 5 is opened by the gate valve 22, and the high-pressure water is released at a rate of 0.6 MPa / h until the borehole pressure drops to 0 MPa. During the construction process, the pressure value and the amount of high-pressure water injected for each fracturing segment need to be recorded and analyzed. The fracturing work of the first segment is completed. After the high-pressure water is released, a grouting pump is used. Cement grout is injected into the through-fracture 28 in the target layer 7 to fill and seal the inter-layer fractures. After the cement grout solidifies, it forms a bottom water-proof layer and seals the hidden collapse column 15 that is connected to the target layer 7 through the through-fracture 28. The pressure gauge 21 on the grouting pump 20 is used to check the grouting pressure. When the grouting pressure reaches 2.4 times the water pressure value P calculated based on the water level elevation H2 of the water level observation hole 8 and the elevation H1 of the bottom plate 25, the grouting is stopped, the borehole 5 is closed, and the cement grout between the through-fracture 28 is allowed to solidify and form a cement-stone body 18. During the construction process, the pressure value and the amount of cement grout injected for each grouting segment need to be recorded and analyzed. The grouting work of the first segment is completed.

[0099] Step 4: Repeat Step 3 until all sections and branches have completed perforation, granulation, fracturing, and grouting. During the drilling process of drill pipe 23, perform cuttings logging analysis to observe whether the returned cuttings contain cement-bonded stone bodies 18. If cement-bonded stone bodies 18 are visible in the returned cuttings throughout the entire drilling process, the branch borehole treatment is deemed qualified. If more than 30m of the returned cuttings throughout the entire drilling process do not contain cement-bonded stone bodies 18, the construction section without cement-bonded stone bodies 18 is identified as an abnormal construction section. Analyze the abnormal construction sections during the construction process and supplement the abnormal construction sections with cyclical operations until the entire construction area is fully covered.

Claims

1. A method for constructing a waterproof layer in a pressurized coal mine, characterized in that, Specifically, the following steps are included: Step 1: The ground surface with coal seam (6), floor (25), multiple rock layers and aquifer (9) in sequence is designated as the construction area, and the construction site is selected within the construction area according to the distribution of buildings; the critical elevation of the target layer (7) is calculated and the target layer (7) is selected according to its value; Step 2: Design the vertical drilling trajectory from the edge of the construction area to the target layer (7) and the horizontal drilling trajectory from the end of the vertical drilling trajectory to the inner side of the target layer (7) and to the opposite edge line to the edge line where the end of the vertical drilling trajectory is located; the horizontal drilling trajectory is divided into several branch drilling trajectories at intervals, and each branch drilling trajectory is divided into several connected segments; the interval between two adjacent branch drilling trajectories on the horizontal drilling trajectory is 40m-60m, and the segment length on each branch drilling trajectory is 400m-600m; the calculation methods for the number of segments m and the number of branch drilling trajectories n are as follows: （3） （4） Where d1 is the length of the horizontal borehole trajectory. d1 is the average length of the segment; d2 is the length of the edge line of the construction zone perpendicular to the horizontal borehole trajectory. The average spacing of all adjacent branch borehole trajectories; the drill rig (4) is moved to the starting position of the vertical borehole trajectory, the drill rod (23) is drilled along the vertical borehole trajectory to its ending position and along a branch borehole trajectory of the horizontal borehole trajectory to its ending position, forming a borehole (5); the drill rod (23) is withdrawn to the outside of the borehole (5), a gate valve (22) is installed at the borehole (5) and the gate valve (22) is opened, the perforation fracturing equipment (10) is installed on the head of the drill rod (23), and through The guide head (14) advances the perforation fracturing equipment (10) to the end position of the vertical drilling trajectory; according to the three-dimensional coordinates of the drilling rig displayed in real time in the drilling rig control room (19), the perforation fracturing equipment (10) is advanced to the end position of the drilled branch drilling trajectory through the mechanical positioner (11); by advancing, retreating and rotating the guide head (14), and fixing the hydraulic perforator (12) with the stabilizer (13), the nozzle on the hydraulic perforator (12) is aligned with the formation dip, ensuring that the perforation spreads along the formation bedding. Step 3: Take the segment closest to the end point of the branch borehole trajectory as the first segment, turn on the control switch (26), and use the perforation fracturing equipment (10) to perform the first perforation operation on the first segment. After the first perforation operation is completed, move the perforation fracturing equipment (10) back 100m-120m, and adjust the perforation fracturing equipment (10) again to the end point of the next perforation operation through the guide head (14). Fix the hydraulic perforator (12) with the centralizer (13) so that the nozzle of the hydraulic perforator (12) is consistent with the formation dip. Repeat the operation until all perforation work of the first segment is completed. Turn off the control switch (26), and then remove the drill rod (23) and the perforation fracturing equipment (10) from the borehole. 5) Outside the orifice, during construction, it is necessary to record and analyze the pressure value of each perforation segment. Using a transport vehicle (1), water-swellable particles (16) and oil-based lubricating materials are transported to the material mixing and grouting station (3) through the delivery pipe (27). The water-swellable particles (16) and oil-based lubricating materials are mixed at a volume ratio of 1:4-6 and then transported to the grouting pump (20) through the delivery pipe (27). The grouting pump (20) injects it into all horizontal fractures (17) through the delivery pipe (27). During construction, it is necessary to record and analyze the amount of water-swellable particles (16) put into each segment. After the particle feeding work of the first segment is completed, the perforation fracturing vehicle (2) is used to transport high-pressure water to the grouting pump (27) through the delivery pipe (27). 20), the grouting pump (20) injects high-pressure water into the target layer (7) through the delivery pipe (27). The water-swellable particles (16) expand upon contact with water, thereby supporting the horizontal fracture (17). The high-pressure water splits the horizontal fracture (17) and forms a through fracture (28). The high-pressure water drives the water-swellable particles (16) to move within the through fracture (28). The borehole (5) is closed by the gate valve (22), allowing the water-swellable particles (16) to expand under the immersion of water and support the through fracture (28). After the water-swellable particles (16) expand and become stuck in the fracture between the rock layers, the borehole (5) is opened by the gate valve (22), and the high-pressure water is released at a rate of 0.4 MPa / h-0.6 MPa / h until the borehole is fully saturated. The pressure at the orifice of hole (5) drops to 0 MPa. During the construction process, it is necessary to record and analyze the pressure value and the amount of high-pressure water injected for each segment of fracturing. After the fracturing work of the first segment is completed, after the high-pressure water is released, cement grout is injected into the through fracture (28) in the target layer (7) using the grouting pump (20) to fill and seal the fracture between rock layers. After the cement grout solidifies, a bottom plate water-proof layer is formed and the hidden collapse column (15) that is connected to the target layer (7) is sealed through the through fracture (28). The pressure gauge (21) on the grouting pump (20) is used to check the grouting pressure. When the grouting pressure reaches 1.6 times - 2 times the water pressure value P calculated based on the water level elevation H2 of the water level observation hole (8) and the elevation H1 of the bottom plate (25), the grouting pressure is determined.When the grouting reaches 4 times the density, stop grouting, close the borehole (5), and wait for the cement grout between the through-cracks (28) to solidify and form a cement-aggregate body (18). The grouting work of the first section is completed. Step 4: Repeat Step 3 until all sections and branches have completed perforation, granulation, fracturing, and grouting. During the drilling process of the drill rod (23), it is necessary to perform cuttings logging analysis and observe whether the returned cuttings contain cement-bonded stone bodies (18). If cement-bonded stone bodies (18) are visible in the returned cuttings throughout the drilling process, the branch borehole treatment is deemed qualified. If cement-bonded stone bodies (18) are not seen for more than 30m of the returned cuttings throughout the drilling process, the construction section without cement-bonded stone bodies (18) is judged as an abnormal construction section. Analyze the abnormal construction sections during the construction process and supplement the abnormal construction sections with cyclical operations until the construction area is fully covered.

2. The method for constructing a waterproof layer in a pressurized coal mine according to claim 1, characterized in that, Step 1 is implemented in the following steps: Step 1.1 The planned mining area of ​​the mine includes coal seam (6), floor (25), multiple rock strata and aquifer (9) from the ground down. Based on the mining plan and the water hazard threat of the aquifer (9), the boundary of the planned mining area of ​​the mine is extended by 30m-50m to form the area of ​​the floor aquifer that needs to be constructed. The ground where the floor aquifer is located is the construction area. Step 1.2: Select a flat, open, and easily accessible area within the construction zone as the construction site; open a water level observation hole (8) extending from the ground to the aquifer (9) on the construction site; install a water level observation meter (24) outside the water level observation hole (8); Step 1.3: Based on the elevation of the bottom plate (25) measured by the exploration boreholes constructed during the mine construction, check the water level elevation of the water level observation hole (8) from the water level observation table (24), and calculate the water pressure value P and the critical elevation H4 of the target layer (7): （1） （2） Where H2 is the water level elevation of the water level observation hole (8); H1 is the elevation of the bottom plate (25); 1 MPa water pressure corresponds to a water level of 100 m; T is the coal seam mining water inrush coefficient value, which is 0.1; Step 1.4: Select a sandstone or limestone layer with a critical elevation lower than the target layer (7) from among the multiple rock layers between the base plate (25) and the aquifer (9) as the target layer (7). Step 1.5: The transport vehicle (1), the perforation fracturing vehicle (2) equipped with the perforation fracturing equipment (10) and control switch (26), the material mixing and grouting station (3), the drilling rig (4) with drill rod (23) inside, the drilling rig control room (19), and the grouting pump (20) equipped with pressure gauge (21) are arranged at the construction site; the transport vehicle (1) is connected to the material mixing and grouting station (3), the material mixing and grouting station (3) is connected to the grouting pump (20), the perforation fracturing vehicle (2) is connected to the grouting pump (20), and the grouting pump (20) is connected to the drilling rig (4) through the delivery pipe (27).

3. The method for constructing a waterproof layer in a pressurized coal mine according to claim 2, characterized in that, In step 1.5, the drilling rig (4) is a long-distance directional drilling rig; the perforation fracturing equipment (10) includes a guide head (14), one end of the guide head (14) is fixedly connected to one end of a mechanical locator (11), the other end of the mechanical locator (11) is fixedly connected to one end of a hydraulic perforator (12), the other end of the hydraulic perforator (12) is fixedly connected to one end of a centralizer (13), the other end of the centralizer (13) is fixedly connected to a connector (29), and the outer wall of the hydraulic perforator (12) is provided with several nozzles (30) located on the same horizontal line.

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