Method for constructing water-resisting curtain wall by grouting in coal mine roof sandstone aquifer

Abstract

The application discloses a method for constructing a water-resisting curtain wall by grouting in a coal mine roof sandstone aquifer, and specifically comprises the following steps: determining the planar position and height of the water-resisting curtain wall; constructing a directional long drill hole in the target sandstone aquifer; performing a back-throw type segmented vertical perforating blasting in the directional long drill hole to form a vertical perforation; performing hydraulic fracturing in the vertical perforation to form perforation and fracture gaps which are perpendicular to the target sandstone aquifer and are interconnected; and injecting porous ceramic and superfine cement slurry into the directional long drill hole and the perforation and fracture gaps, so as to form the water-resisting curtain wall. The application forms a surrounding ring by constructing the curtain water-resisting wall by long-distance directional drilling and grouting outside the influence range of coal seam mining, cuts off the interlayer supply channels in the planned mining range from external water sources, and realizes the target of intercepting and draining and eliminating the sandstone water disaster of the roof.

Description

Technical Field

[0001] This invention belongs to the field of coal mine water hazard control technology, and relates to a method for constructing a water-resistant curtain wall by grouting within the sandstone aquifer on the roof of a coal mine. Background Technology

[0002] Water hazards are one of the major threats to safe coal mine production. Some mines in my country face the threat of water hazards from thick, highly water-rich sandstone aquifers in the roof. Previously, the primary approach to addressing water hazards from these roof sandstone aquifers was preemptive drainage. However, due to the large thickness, high water content, and smooth flow between sandstone layers in some mines, coupled with favorable recharge conditions, the volume of water that can be drained from the roof is enormous. Prolonged drainage is insufficient to completely dry the aquifers, impacting underground mining operations and placing significant pressure on mine drainage and surface water treatment. Furthermore, long-term drainage may cause surface ecological problems.

[0003] The water in the sandstone aquifer at its top mainly consists of two parts: static water, which is stored in the pores and fissures within the sandstone mass, and dynamic water, which is replenished by external water flow. For water hazards in sandstone aquifers at their top, an effective control method is to first cut off the water supply channels to eliminate dynamic water, and then drain the static water, thereby completely eliminating the threat of water hazards. In the past, when controlling water hazards in sandstone aquifers at their top, only the drainage of water was emphasized, while the sealing of the aquifer's replenishment channels was neglected, resulting in long-term drainage effects failing to meet expectations. Furthermore, under conditions of deep aquifer burial, traditional curtain grouting often employs the technique of constructing underground continuous walls on the ground, which is extremely costly, difficult to control in terms of construction quality, and unreliable in ensuring treatment effectiveness. Therefore, it is necessary to explore and research new methods for constructing curtain aquifer water-blocking walls in sandstone aquifers. Summary of the Invention

[0004] The purpose of this invention is to provide a method for constructing a water-resistant curtain wall by grouting within the sandstone aquifer on the roof of a coal mine, thereby solving the problems of high engineering costs, difficulty in controlling construction quality, and difficulty in guaranteeing treatment effects in existing curtain grouting methods.

[0005] The technical solution adopted in this invention is a method for constructing a water-resistant curtain wall by grouting within the sandstone aquifer of a coal mine roof, comprising the following steps:

[0006] Step 1: Within the target sandstone aquifer, determine the planar location for constructing the water-resistant curtain wall by extending 30m outward from the boundary of the coal seam mining influence area;

[0007] Step 2: Determine the construction height of the water-resistant curtain wall based on the thickness of the target sandstone aquifer and the structure of the top and bottom strata;

[0008] Step 3: Determine the location and number of directional long boreholes based on the thickness and spatial structure of the target sandstone aquifer; use a long-distance directional drilling rig to drill four directional long boreholes in the same layer of the target sandstone aquifer, with the trajectories of the four directional long boreholes forming a rectangular area;

[0009] Step 4: Perform push-type segmented vertical perforation blasting within the directional long borehole. Set the segment distance for perforation blasting according to the length of the directional long borehole. After lowering the perforator from the borehole opening to the final position, adjust the position of the perforator so that the perforation direction is perpendicular to the planar distribution direction of the target sandstone aquifer. Detonate the shaped charge perforating shell inside the perforator to form a vertical blasting perforation. Retract the perforator to the designated position according to the segment distance. Repeat the steps of adjusting the position of the perforator and detonating the shaped charge perforating shell to obtain several vertical blasting perforations.

[0010] Step 5: Use a high-pressure hydraulic fracturing truck to perform hydraulic fracturing in the vertical blasting perforations to form perforated fractures that are perpendicular to the target sandstone aquifer and interconnected.

[0011] Step 6: Use a high-pressure hydraulic fracturing truck to inject porous ceramic particles into the fractures of the directional long borehole and perforation;

[0012] Step 7: Inject ultrafine cement grout into the directional long boreholes and perforated cracks using a grouting pump;

[0013] Step 8: Repeat steps 4-7 until all sections of the directional long boreholes are filled with ultrafine cement grout to form a waterproof curtain wall.

[0014] The invention is further characterized by:

[0015] The method for constructing a water-tight curtain wall by grouting in the sandstone aquifer of the coal mine roof, the specific steps for determining the target sandstone aquifer in step 1 are as follows: Based on the mining rights boundary and mining planning design of the mine, determine the planned mining range of the coal seam; based on the development height of the water-conducting fracture zone formed after coal seam mining and the rock strata movement and failure angle, determine the range of influence of coal seam mining, and take the main water-bearing aquifer within the range of influence of coal seam mining as the target sandstone aquifer.

[0016] The method for constructing a water-resistant curtain wall by grouting within the sandstone aquifer in the roof of a coal mine, specifically step 2 for determining the construction height of the water-resistant curtain wall, is as follows: the bottom of the water-resistant curtain wall rests within the first mudstone aquifer, and the top of the water-resistant curtain wall extends into the second mudstone aquifer.

[0017] The method for constructing a water-resistant curtain wall by grouting in the sandstone aquifer of the coal mine roof, wherein the segmented distance of the perforation blasting in step 4 is 100m to 200m.

[0018] The method for constructing a water-resistant curtain wall by grouting in the sandstone aquifer of the coal mine roof, step 6, involves pressing porous ceramsite into the porous ceramsite, the diameter of which is 5-10 mm.

[0019] The method for constructing a water-resistant curtain wall by grouting within the sandstone aquifer in the roof of a coal mine, step 7 involves injecting ultrafine cement grout with a fineness of 350–600 μm. 2 / kg; High-strength fibers are added to the ultrafine cement slurry, including one or more of polyester fibers, polypropylene fibers and nylon fibers.

[0020] The beneficial effects of this invention are:

[0021] 1. Constructing a water-resistant curtain wall within the main water-bearing aquifer blocks the interlayer runoff recharge channels of the aquifer, which can significantly reduce the amount of underground water drainage work, alleviate the mine drainage pressure and the pressure on surface water treatment after the mine water is discharged;

[0022] 2. By constructing a water-resistant curtain wall, water extraction can be reduced, avoiding ecological and environmental problems caused by excessive rainwater drainage;

[0023] 3. The curtain water-tight wall is constructed by long-distance directional drilling and blasting and hydraulic fracturing. The amount of work, construction period and cost will be significantly less than traditional processes such as ground continuous wall and ground conventional drilling and grouting curtain wall.

[0024] 4. Long-distance directional drilling requires less site area, causes less disturbance to the surface ecological environment, and reduces the workload of ground construction site coordination;

[0025] 5. By blocking the dynamic water supply and draining the static water in the aquifer within the curtain wall, the threat of water damage from the sandstone aquifer on the roof can be better eliminated. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the geological space structure and surface drilling site layout of the present invention;

[0027] Figure 2 This is a plan view showing the relationship between the directional long borehole and the mining area of ​​this invention;

[0028] Figure 3 This is a schematic diagram of the waterproof curtain wall structure of the present invention;

[0029] Figure 4 This is a schematic diagram of the perforation and crack filling of porous ceramic particles according to the present invention;

[0030] Figure 5 This is a schematic diagram of the perforation fracturing method of the present invention;

[0031] Figure 6 This is a schematic diagram of the porous ceramic aggregate input in this invention;

[0032] Figure 7 This is a schematic diagram illustrating the injection of ultrafine cement slurry and its water-blocking effect according to the present invention.

[0033] In the figure: 1. Directional long borehole; 2. Water-tight curtain wall; 3. Water flow direction between sandstone layers; 4. Vertical blasting perforation; 5. Target sandstone aquifer; 6. First mudstone aquifer; 7. Coal seam; 8. Second mudstone aquifer; 9. Perforation fracture. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0035] The method for constructing a water-resistant curtain wall by grouting within a sandstone aquifer in the roof of a coal mine, provided by this invention, specifically includes the following steps:

[0036] Step 1: Within the target sandstone aquifer 5, define the planar location for constructing the water-resistant curtain wall 2 by extending 30m outward from the boundary of the coal seam mining influence zone, ensuring that the location of the water-resistant curtain wall 2 will not be damaged by mining disturbance. The specific steps for determining the target sandstone aquifer 5 are as follows:

[0037] like Figure 1 As shown, based on the mining rights boundary and mining planning design, the planned mining area of ​​the coal seam is determined; based on the development height of the water-conducting fracture zone formed after the mining of coal seam 7 and the rock strata movement and failure angle, the mining impact range of the coal seam is determined, as follows. Figure 2 and Figure 1 As shown, the main water-bearing aquifer within the range of coal seam mining influence is taken as the target sandstone aquifer 5.

[0038] Step 2: Based on the thickness of the target sandstone aquifer 5 and the structure of the top and bottom strata, determine the construction height of the water-resistant curtain wall 2, specifically as follows:

[0039] like Figure 1 As shown, the bottom of the waterproof curtain wall 2 rests within the first mudstone waterproof layer 6, and the top of the waterproof curtain wall 2 extends into the second mudstone waterproof layer 8.

[0040] Step 3: As Figure 1 As shown, based on the thickness and spatial structure of the target sandstone aquifer 5, the location and number of directional long boreholes 1 are determined, and a long-distance directional drilling rig and a high-pressure hydraulic fracturing truck are installed at appropriate locations on the ground. Using the long-distance directional drilling rig, four directional long boreholes 1 are drilled at the same stratum of the target sandstone aquifer 5. The trajectories of the four directional long boreholes 1 form a rectangular area, as shown... Figure 2 and Figure 3 As shown.

[0041] When the target sandstone aquifer 5 is thick, and the perforation cracks 9 formed by a single layer of vertical blasting perforations 4 are insufficient to cut off the entire target sandstone aquifer 5, multiple layers of directional long boreholes 1 are arranged in the target sandstone aquifer 5 according to the thickness of the target sandstone aquifer 5 and the cutting depth of the perforation cracks 9. The same sequence and process are followed to construct a complete and continuous water-tight curtain wall 2, so as to completely cut off the target sandstone aquifer 5.

[0042] Step 4: Perform backward-pushing segmented vertical perforation blasting within the directional long borehole 1. Based on the length of the directional long borehole 1, set the segmented blasting distance to 100m-200m. Lower the perforator from the borehole opening of the directional long borehole 1 to the final position, then adjust the position of the perforator so that the perforation direction is perpendicular to the planar distribution direction of the target sandstone aquifer 5. Detonate the shaped charge perforating projectile inside the perforator to form vertical blasting perforations 4. Retract the perforator to the designated position according to the segmented distance, repeating the steps of adjusting the perforator position and detonating the shaped charge perforating projectile, blasting perforations segment by segment to obtain several vertical blasting perforations 4, such as... Figure 1 As shown.

[0043] Step 5: Within the completed section of the blasting perforations, a ground-based high-pressure hydraulic fracturing truck performs hydraulic fracturing within the vertical blasting perforations 4, forming interconnected perforated fracturing fractures 9 perpendicular to the target sandstone aquifer 5. Figure 3 and Figure 5 As shown, several perforations and fissures 9 form a fracture surface perpendicular to the target sandstone aquifer 5, thereby cutting off the target sandstone aquifer 5.

[0044] Step 6: After the perforation fracture 9 is formed, porous ceramic particles with a diameter of 5-10 mm are injected into the directional long borehole 1 and the perforation fracture 9 using a ground high-pressure hydraulic fracturing truck. Figure 4 and Figure 6 As shown, the perforation pressure crack 9 is opened to prevent it from closing automatically, which facilitates the injection of ultrafine cement slurry later.

[0045] Step 7: Inject ultrafine cement grout into the directional long borehole 1 and the perforated crack 9 using a grouting pump. The fineness of the ultrafine cement grout is 350-600 μm. 2 / kg; Under high pressure, ultrafine cement grout fills the interconnected perforated fractures 9. The ultrafine cement grout moves up and down within the perforated fractures 9, thus forming a water-resistant curtain wall 2 within the target sandstone aquifer 5, such as Figure 3 As shown, this alters the direction of water flow between sandstone layers, as 3. Figure 7As shown, the recharge source of the target sandstone aquifer 5 within the planned mining area of ​​the blocked coal seam is blocked. High-strength fibers are added to the ultrafine cement slurry to improve the integrity of the water-resistant curtain wall 2. The high-strength fibers include one or more of polyester fibers, polypropylene fibers, and nylon fibers.

[0046] Step 8: Repeat steps 4-7 until all sections of the directional long boreholes 1 are filled with ultrafine cement grout, thereby forming a complete and continuous waterproof curtain wall 2.

[0047] After the water-resistant curtain wall 2 is formed, according to the mining plan, advanced drainage boreholes will be constructed before the underground working face is mined to drain the static water of the target sandstone aquifer 5 within the range of the working face mining, so as to achieve the goal of interception and drainage and eliminate water hazards to the roof sandstone.

[0048] Example 1

[0049] This invention provides a method for constructing a water-resistant curtain wall by grouting within a sandstone aquifer in the roof of a coal mine. The specific steps are as follows:

[0050] Step 1: Determine the planned mining area of ​​the coal seam based on the mining rights boundary and mining planning design; determine the impact range of coal seam mining based on the development height of the water-conducting fracture zone formed after coal seam 7 mining and the rock strata movement and failure angle, such as... Figure 2 and Figure 1 As shown, the main water-bearing aquifer within the coal seam mining influence range is designated as the target sandstone aquifer 5. Within the target sandstone aquifer 5, the planar location for constructing the water-resistant curtain wall 2 is determined by extending 30m outward from the boundary of the coal seam mining influence range, ensuring that the location of the water-resistant curtain wall 2 will not be damaged by mining disturbances.

[0051] Step 2: Based on the thickness of the target sandstone aquifer 5 and the structure of the top and bottom strata, determine the construction height of the water-resistant curtain wall 2 as follows: the bottom of the water-resistant curtain wall 2 falls within the first mudstone aquifer 6, and the top of the water-resistant curtain wall 2 extends into the second mudstone aquifer 8.

[0052] Step 3: As Figure 1 As shown, based on the thickness and spatial structure of the target sandstone aquifer 5, the location and number of directional long boreholes 1 are determined, and a long-distance directional drilling rig and a high-pressure hydraulic fracturing truck are installed at appropriate locations on the ground. Using the long-distance directional drilling rig, four directional long boreholes 1 are drilled at the same stratum of the target sandstone aquifer 5. The trajectories of the four directional long boreholes 1 form a rectangular area, as shown... Figure 2 and Figure 3 As shown.

[0053] When the target sandstone aquifer 5 is thick, and the perforation cracks 9 formed by a single layer of vertical blasting perforations 4 are insufficient to cut off the entire target sandstone aquifer 5, multiple layers of directional long boreholes 1 are arranged in the target sandstone aquifer 5 according to the thickness of the target sandstone aquifer 5 and the cutting depth of the perforation cracks 9. The same sequence and process are followed to construct a complete and continuous water-tight curtain wall 2, so as to completely cut off the target sandstone aquifer 5.

[0054] Step 4: Perform backward-pushing segmented vertical perforation blasting within the directional borehole 1. Based on the length of the directional borehole 1, set the segmented blasting distance to 100m. Lower the perforator from the borehole opening to the final position, then adjust the perforator's position so that the perforation direction is perpendicular to the planar distribution direction of the target sandstone aquifer 5. Detonate the shaped charge perforating projectile inside the perforator to form vertical blasting perforations 4. Retract the perforator to the designated position according to the segmented distance, repeating the steps of adjusting the perforator position and detonating the shaped charge perforating projectile, blasting perforations segment by segment to obtain several vertical blasting perforations 4, such as... Figure 1 As shown.

[0055] Step 5: Within the completed section of the blasting perforations, a ground-based high-pressure hydraulic fracturing truck performs hydraulic fracturing within the vertical blasting perforations 4, forming interconnected perforated fracturing fractures 9 perpendicular to the target sandstone aquifer 5. Figure 3 and Figure 5 As shown, several perforations and fissures 9 form a fracture surface perpendicular to the target sandstone aquifer 5, thereby cutting off the target sandstone aquifer 5.

[0056] Step 6: After the perforation fracture 9 is formed, porous ceramic particles with a diameter of 5mm are injected into the directional long borehole 1 and the perforation fracture 9 using a ground high-pressure hydraulic fracturing truck. Figure 4 and Figure 6 As shown, the perforation pressure crack 9 is opened to prevent it from closing automatically, which facilitates the injection of ultrafine cement slurry later.

[0057] Step 7: Inject ultrafine cement grout into the directional long borehole 1 and the perforated pressure fracture 9 using a grouting pump. The ultrafine cement grout has a fineness of 350 μm. 2 / kg; Under high pressure, ultrafine cement grout fills the interconnected perforated fractures 9. The ultrafine cement grout moves up and down within the perforated fractures 9, thus forming a water-resistant curtain wall 2 within the target sandstone aquifer 5, such as Figure 3 As shown, this alters the direction of water flow between sandstone layers, as 3. Figure 7 As shown, the recharge source of the target sandstone aquifer 5 within the planned coal seam mining area is blocked. Polyester and polypropylene fibers are added to the ultrafine cement slurry to improve the integrity of the water-resistant curtain wall 2.

[0058] Step 8: Repeat steps 4-7 until all sections of the directional long boreholes 1 are filled with ultrafine cement grout, thereby forming a complete and continuous waterproof curtain wall 2.

[0059] Example 2

[0060] This invention provides a method for constructing a water-resistant curtain wall by grouting within a sandstone aquifer in the roof of a coal mine. The specific steps are as follows:

[0061] Step 1: Determine the planned mining area of ​​the coal seam based on the mining rights boundary and mining planning design; determine the impact range of coal seam mining based on the development height of the water-conducting fracture zone formed after coal seam 7 mining and the rock strata movement and failure angle, such as... Figure 2 and Figure 1 As shown, the main water-bearing aquifer within the coal seam mining influence range is designated as the target sandstone aquifer 5. Within the target sandstone aquifer 5, the planar location for constructing the water-resistant curtain wall 2 is determined by extending 30m outward from the boundary of the coal seam mining influence range, ensuring that the location of the water-resistant curtain wall 2 will not be damaged by mining disturbances.

[0062] Step 2: Based on the thickness of the target sandstone aquifer 5 and the structure of the top and bottom strata, determine the construction height of the water-resistant curtain wall 2 as follows: the bottom of the water-resistant curtain wall 2 falls within the first mudstone aquifer 6, and the top of the water-resistant curtain wall 2 extends into the second mudstone aquifer 8.

[0063] Step 3: As Figure 1 As shown, based on the thickness and spatial structure of the target sandstone aquifer 5, the location and number of directional long boreholes 1 are determined, and a long-distance directional drilling rig and a high-pressure hydraulic fracturing truck are installed at appropriate locations on the ground. Using the long-distance directional drilling rig, four directional long boreholes 1 are drilled at the same stratum of the target sandstone aquifer 5. The trajectories of the four directional long boreholes 1 form a rectangular area, as shown... Figure 2 and Figure 3 As shown.

[0064] When the target sandstone aquifer 5 is thick, and the perforation cracks 9 formed by a single layer of vertical blasting perforations 4 are insufficient to cut off the entire target sandstone aquifer 5, multiple layers of directional long boreholes 1 are arranged in the target sandstone aquifer 5 according to the thickness of the target sandstone aquifer 5 and the cutting depth of the perforation cracks 9. The same sequence and process are followed to construct a complete and continuous water-tight curtain wall 2, so as to completely cut off the target sandstone aquifer 5.

[0065] Step 4: Perform segmented vertical perforation blasting within the directional borehole 1. Based on the length of the directional borehole 1, set the segmented blasting distance to 150m. Lower the perforator from the borehole opening to the final position, then adjust the perforator's position so that the perforation direction is perpendicular to the planar distribution direction of the target sandstone aquifer 5. Detonate the shaped charge perforating projectile inside the perforator to form vertical blasting perforations 4. Retract the perforator to the designated position according to the segmented distance, repeating the steps of adjusting the perforator position and detonating the shaped charge perforating projectile, blasting perforations segment by segment to obtain several vertical blasting perforations 4, such as... Figure 1 As shown.

[0066] Step 5: Within the completed section of the blasting perforations, a ground-based high-pressure hydraulic fracturing truck performs hydraulic fracturing within the vertical blasting perforations 4, forming interconnected perforated fracturing fractures 9 perpendicular to the target sandstone aquifer 5. Figure 3 and Figure 5 As shown, several perforations and fissures 9 form a fracture surface perpendicular to the target sandstone aquifer 5, thereby cutting off the target sandstone aquifer 5.

[0067] Step 6: After the perforation fracture 9 is formed, porous ceramic particles with a diameter of 7mm are injected into the directional long borehole 1 and the perforation fracture 9 using a ground high-pressure hydraulic fracturing truck. Figure 4 and Figure 6 As shown, the perforation pressure crack 9 is opened to prevent it from closing automatically, which facilitates the injection of ultrafine cement slurry later.

[0068] Step 7: Inject ultrafine cement grout into the directional long borehole 1 and the perforated pressure fracture 9 using a grouting pump. The ultrafine cement grout has a fineness of 470 μm. 2 / kg; Under high pressure, ultrafine cement grout fills the interconnected perforated fractures 9. The ultrafine cement grout moves up and down within the perforated fractures 9, thus forming a water-resistant curtain wall 2 within the target sandstone aquifer 5, such as Figure 3 As shown, this alters the direction of water flow between sandstone layers, as 3. Figure 7 As shown, the recharge source of the target sandstone aquifer 5 within the planned coal seam mining area is blocked. Polypropylene fibers and nylon fibers are added to the ultrafine cement slurry to improve the integrity of the water-resistant curtain wall 2.

[0069] Step 8: Repeat steps 4-7 until all sections of the directional long boreholes 1 are filled with ultrafine cement grout, thereby forming a complete and continuous waterproof curtain wall 2.

[0070] Example 3

[0071] This invention provides a method for constructing a water-resistant curtain wall by grouting within a sandstone aquifer in the roof of a coal mine. The specific steps are as follows:

[0072] Step 1: Determine the planned mining area of ​​the coal seam based on the mining rights boundary and mining planning design; determine the impact range of coal seam mining based on the development height of the water-conducting fracture zone formed after coal seam 7 mining and the rock strata movement and failure angle, such as... Figure 2 and Figure 1 As shown, the main water-bearing aquifer within the coal seam mining influence range is designated as the target sandstone aquifer 5. Within the target sandstone aquifer 5, the planar location for constructing the water-resistant curtain wall 2 is determined by extending 30m outward from the boundary of the coal seam mining influence range, ensuring that the location of the water-resistant curtain wall 2 will not be damaged by mining disturbances.

[0073] Step 2: Based on the thickness of the target sandstone aquifer 5 and the structure of the top and bottom strata, determine the construction height of the water-resistant curtain wall 2 as follows: the bottom of the water-resistant curtain wall 2 falls within the first mudstone aquifer 6, and the top of the water-resistant curtain wall 2 extends into the second mudstone aquifer 8.

[0074] Step 3: As Figure 1 As shown, based on the thickness and spatial structure of the target sandstone aquifer 5, the location and number of directional long boreholes 1 are determined, and a long-distance directional drilling rig and a high-pressure hydraulic fracturing truck are installed at appropriate locations on the ground. Using the long-distance directional drilling rig, four directional long boreholes 1 are drilled at the same stratum of the target sandstone aquifer 5. The trajectories of the four directional long boreholes 1 form a rectangular area, as shown... Figure 2 and Figure 3 As shown.

[0075] When the target sandstone aquifer 5 is thick, and the perforation cracks 9 formed by a single layer of vertical blasting perforations 4 are insufficient to cut off the entire target sandstone aquifer 5, multiple layers of directional long boreholes 1 are arranged in the target sandstone aquifer 5 according to the thickness of the target sandstone aquifer 5 and the cutting depth of the perforation cracks 9. The same sequence and process are followed to construct a complete and continuous water-tight curtain wall 2, so as to completely cut off the target sandstone aquifer 5.

[0076] Step 4: Perform backward-pushing segmented vertical perforation blasting within the directional borehole 1. Based on the length of the directional borehole 1, set the segmented blasting distance to 200m. Lower the perforator from the borehole opening to the final position, then adjust the perforator's position so that the perforation direction is perpendicular to the planar distribution direction of the target sandstone aquifer 5. Detonate the shaped charge perforating projectile inside the perforator to form vertical blasting perforations 4. Retract the perforator to the designated position according to the segmented distance, repeating the steps of adjusting the perforator position and detonating the shaped charge perforating projectile, blasting perforations segment by segment to obtain several vertical blasting perforations 4, such as... Figure 1 As shown.

[0077] Step 5: Within the completed section of the blasting perforations, a ground-based high-pressure hydraulic fracturing truck performs hydraulic fracturing within the vertical blasting perforations 4, forming interconnected perforated fracturing fractures 9 perpendicular to the target sandstone aquifer 5. Figure 3 and Figure 5 As shown, several perforations and fissures 9 form a fracture surface perpendicular to the target sandstone aquifer 5, thereby cutting off the target sandstone aquifer 5.

[0078] Step 6: After the perforation fracture 9 is formed, porous ceramic particles with a diameter of 10mm are injected into the directional long borehole 1 and the perforation fracture 9 using a ground high-pressure hydraulic fracturing truck. Figure 4 and Figure 6 As shown, the perforation pressure crack 9 is opened to prevent it from closing automatically, which facilitates the injection of ultrafine cement slurry later.

[0079] Step 7: Inject ultrafine cement grout into the directional long borehole 1 and the perforated pressure fracture 9 using a grouting pump. The ultrafine cement grout has a fineness of 600 μm. 2 / kg; Under high pressure, ultrafine cement grout fills the interconnected perforated fractures 9. The ultrafine cement grout moves up and down within the perforated fractures 9, thus forming a water-resistant curtain wall 2 within the target sandstone aquifer 5, such as Figure 3 As shown, this alters the direction of water flow between sandstone layers, as 3. Figure 7 As shown, the recharge source of the target sandstone aquifer 5 within the planned coal seam mining area is blocked. Polypropylene fibers are added to the ultrafine cement slurry to improve the integrity of the water-resistant curtain wall 2.

[0080] Step 8: Repeat steps 4-7 until all sections of the directional long boreholes 1 are filled with ultrafine cement grout, thereby forming a complete and continuous waterproof curtain wall 2.

Claims

1. A method for constructing a water-resistant curtain wall by grouting within a sandstone aquifer in the roof of a coal mine, characterized in that, Includes the following steps: Step 1: Within the target sandstone aquifer (5), the boundary of the coal seam mining influence range is extended by 30m to determine the planar location for constructing the water-tight curtain wall (2); Step 2: Determine the construction height of the water-resistant curtain wall (2) based on the thickness of the target sandstone aquifer (5) and the structure of the top and bottom strata; Step 3: Determine the location and number of directional long boreholes (1) based on the thickness and spatial structure of the target sandstone aquifer (5); use a long-distance directional drilling rig to drill 4 directional long boreholes (1) in the same layer of the target sandstone aquifer (5), and the trajectories of the 4 directional long boreholes (1) form a rectangular area; Step 4: Perform push-type segmented vertical perforation blasting in the directional long borehole (1). Set the segment distance of the perforation blasting according to the length of the directional long borehole (1). After the perforator is lowered from the opening of the directional long borehole (1) to the end position, adjust the position of the perforator so that the perforation direction is perpendicular to the plane distribution direction of the target sandstone aquifer (5). Detonate the shaped charge perforating shell in the perforator to form a vertical blasting perforation (4). Move the perforator back to the designated position according to the segment distance. Repeat the steps of adjusting the position of the perforator and detonating the shaped charge perforating shell to obtain several vertical blasting perforations (4). Step 5: Use a high-pressure hydraulic fracturing truck to perform hydraulic fracturing in the vertical blasting perforation (4) to form perforation fracturing fissures (9) that are perpendicular to the target sandstone aquifer (5) and interconnected. Step 6: Use a high-pressure hydraulic fracturing truck to inject porous ceramic particles into the directional long borehole (1) and the perforated fracturing fissure (9); Step 7: Inject ultrafine cement grout into the directional long borehole (1) and the perforated crack (9) using a grouting pump; Step 8: Repeat steps 4-7 until all sections of the directional long boreholes (1) are filled with ultrafine cement grout to form a water-resistant curtain wall (2).

2. The method for constructing a water-resistant curtain wall by grouting within a sandstone aquifer in the roof of a coal mine according to claim 1, characterized in that, The specific steps for determining the target sandstone aquifer (5) in step 1 are as follows: Based on the mining rights boundary and mining planning design, the planned mining range of the coal seam is determined; based on the development height of the water-conducting fracture zone formed after mining of the coal seam (7) and the rock strata movement and failure angle, the range of influence of coal seam mining is determined, and the main water-bearing aquifer within the range of influence of coal seam mining is taken as the target sandstone aquifer (5).

3. The method for constructing a water-resistant curtain wall by grouting within a sandstone aquifer in the roof of a coal mine according to claim 2, characterized in that, The specific steps for determining the construction height of the waterproof curtain wall (2) in step 2 are as follows: The bottom of the waterproof curtain wall (2) falls within the first mudstone waterproof layer (6), and the top of the waterproof curtain wall (2) extends into the second mudstone waterproof layer (8).

4. The method for constructing a water-resistant curtain wall by grouting within a sandstone aquifer in the roof of a coal mine according to claim 3, characterized in that, In step 4, the segmented distance of the perforation blasting is 100m to 200m.

5. The method for constructing a water-resistant curtain wall by grouting within a sandstone aquifer in the roof of a coal mine according to claim 4, characterized in that, The diameter of the porous ceramic particles pressed into the porous ceramic particles in step 6 is 5-10 mm.

6. The method for constructing a water-resistant curtain wall by grouting within a sandstone aquifer in the roof of a coal mine according to claim 5, characterized in that, The ultrafine cement slurry injected in step 7 has a fineness of 350–600 μm. 2 / kg; High-strength fibers are added to the ultrafine cement slurry, and the high-strength fibers include one or more of polyester fibers, polypropylene fibers and nylon fibers.

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