Double-layer pipe hole sealing structure for directional long drill hole in thick coal seam mining pressure relief zone

Abstract

A thick coal seam mining pressure relief zone directional long drill hole double-layer pipe hole sealing structure comprises an outer orifice pipe and an inner orifice pipe, the length of the inner orifice pipe is larger than that of the outer orifice pipe, the inner orifice pipe is coaxially arranged in the outer orifice pipe, and the outer orifice pipe is coaxially arranged in a large-diameter mounting hole constructed firstly. A first polyurethane hole sealing section and a first cement mortar hole sealing section are sequentially arranged in a first annular cavity between the outer circle of the outer orifice pipe and the inner circle of the large-diameter mounting hole from the orifice to the hole bottom; a second annular cavity formed between the outer circle of the inner orifice pipe and the inner circle of the outer orifice pipe is sequentially provided with a second polyurethane hole sealing section and a second cement mortar hole sealing section from the orifice to the hole bottom. The supporting strength and the supporting length are greatly improved, severe deformation of a coal rock layer formed by mining pressure relief of an adjacent working face and fracture development caused by deformation can be completely supported, the directional long drill hole can meet the sealing effect needed by long-term high negative pressure extraction, and the purpose of high-concentration, high-purity and long-distance long-term extraction is achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of gas extraction hole sealing, and in particular relates to a double-layer pipe hole sealing structure for a directional long borehole in a thick coal seam mining pressure relief zone. Background Art

[0002] At present, for coal mines with thick coal seams, the mining operation causes a large range of coal seam pressure relief, resulting in a large amount of gas outflow from the return air flow of the mining face. The high gas concentration in the upper corner is the main factor that troubles the safe production of the mining face. In order to study safe and efficient mining face gas extraction technology, coal mine researchers have developed a high-level gas extraction technology in the fracture zone at the top of the coal seam, which has alleviated the gas problem in the mining face to a certain extent. The high-level extraction technology in the fracture zone at the top of the coal seam is based on the existence of "three vertical zones and three horizontal zones" in the roof of the coal seam at the mining face. It is believed that the pore and fracture structures of different scales in the curved sinking zone and the fracture zone are the goaf of the working face, providing a path and space for gas migration, flow and storage. The high diffusivity and low viscosity of gas purify the gas in the goaf in the curved sinking zone and the fracture zone, and the gas concentration in the fracture zone is significantly higher than that in the lower caving zone. If drilling is arranged in the fracture zone, high-concentration and high-purity gas will be extracted, effectively reducing the gas outflow of the return air flow of the working face and the gas concentration in the upper corner. However, due to the influence of traditional drilling technology, the effective length of the borehole is short and the trajectory cannot be controlled. The high-position gas extraction technology in the fracture zone at the top of the coal seam has the problems of short single-hole efficient extraction distance, low extraction gas concentration, unstable extraction effect, high cost, and large drilling construction workload, which seriously affects the gas extraction effect.

[0003] In recent years, my country's directional long drilling construction technology and equipment have made great progress. The advantages of directional long drilling are as follows: ① Using the measurement while drilling system, the drilling trajectory can fluctuate and always be in the appropriate roof fracture zone to ensure effective and stable drilling extraction; ② Greatly improve the construction depth of a single hole, reduce the overlap length of the borehole, and the unreasonable layer positions at the start and end of the borehole, thereby increasing the gas extraction range of a single hole; ③ The drilling rig is moved less times, the drilling efficiency is high, and the control distance of a single cycle is long, which effectively shortens the construction period and alleviates the contradiction between mining and excavation succession. Therefore, the technology of extracting gas by long directional drilling holes in fractures has received much attention. That is, by using underground directional drilling technology and equipment in coal mines, long-distance and large-diameter directional drilling holes are constructed in the fracture zone of the coal seam roof. The fractures in the roof are used as gas flow channels to extract gas from the overlying rock strata, coal seams and corners of the working face, change the gas flow distribution in the goaf, and effectively reduce the flow of gas from the goaf and adjacent layers to the working face. This fundamentally solves the problem of excessive gas in the corners of the working face and the return air lane caused by large-scale gas outflow from the goaf or adjacent layers, ensures safe operation of the coal mining face, and improves the production capacity of the mining face.

[0004] Analyzing the key technologies of gas extraction technology for directional long boreholes in fracture zones, in addition to the design of the layer, slope, and plane position of the directional long borehole to complete the construction, the quality of the sealing hole in the pressure relief zone of the mining adjacent to the working face of the thick coal seam is another key technology related to the extraction effect. If the sealing hole structure is not sufficient to support the severe deformation of the coal and rock layer formed by the mining pressure relief of the adjacent working face, and the development of fractures caused by the deformation, the directional long borehole cannot meet the sealing effect required for long-term high negative pressure extraction, and the directional long borehole is difficult to achieve the goal of high concentration, high purity, long distance and long-term extraction. Utility Model Content

[0005] In order to solve the deficiencies in the prior art, the utility model provides a double-layer pipe sealing structure for directional long drilling holes in thick coal seam mining pressure relief zones, which is safe and reliable and ensures that the directional long drilling holes are not deformed and has good sealing effect.

[0006] In order to solve the above technical problems, the utility model adopts the following technical scheme: a double-layer pipe sealing structure for directional long drilling in a thick coal seam mining pressure relief zone, comprising an outer orifice pipe and an inner orifice pipe, the inner orifice pipe is longer than the outer orifice pipe, the inner orifice pipe is coaxially arranged inside the outer orifice pipe, and the outer orifice pipe is coaxially arranged in a large-diameter installation hole constructed first, the large-diameter installation hole is inclined with a low orifice and a high hole bottom, the first annular cavity between the outer circle of the outer orifice pipe and the inner circle of the large-diameter installation hole is composed of a first polyurethane sealing section and a first cement mortar sealing section from the orifice to the bottom of the hole; the second annular cavity formed between the outer circle of the inner orifice pipe and the inner circle of the outer orifice pipe is composed of a second polyurethane sealing section and a second cement mortar sealing section from the orifice to the bottom of the hole.

[0007] The port of the outer orifice tube located outside the orifice is provided with an annular overflow baffle which is sleeved on the outer circle of the inner orifice tube. The inner circle of the annular overflow baffle is provided with a first sealing ring which is sealed with the outer circle of the inner orifice tube. The annular overflow baffle is connected to the end face of the outer orifice tube by a plurality of first screws arranged circumferentially.

[0008] A disc-shaped baffle is provided at the port of the inner orifice tube located outside the orifice, and the disc-shaped baffle is connected to the end face of the inner orifice tube by a plurality of second screws arranged circumferentially, and a second sealing ring is provided between the disc-shaped baffle and the end face of the inner orifice tube; a tube penetration hole is provided on the disc-shaped baffle, and a pressure measuring tube is connected to the disc-shaped baffle and passes through the tube penetration hole and extends into the inner orifice tube, and a valve and a pressure gauge are installed on the pressure measuring tube.

[0009] The outer circle of the outer hole mouth tube is provided with external stirring thorns for hanging and stirring the polyurethane AB material packaging bag, and a plurality of external stirring thorns are evenly arranged on the outer circle of the outer hole mouth tube.

[0010] The outer circle of the inner hole mouth tube is provided with inner stirring thorns for hanging and stirring the polyurethane AB material packaging bag, and a plurality of inner stirring thorns are evenly arranged on the outer circle of the inner hole mouth tube.

[0011] Using the above technical solution, the specific construction steps of the utility model are as follows:

[0012] (1) Prepare the external orifice pipe and installation materials, including polyurethane AB material, cement mortar, flange, grouting pump, grouting pipe and exhaust return grouting pipe. The length of the grouting pipe and exhaust return grouting pipe is longer than that of the external orifice pipe. The flange is provided with two through holes for passing the grouting pipe and exhaust return grouting pipe respectively.

[0013] (2) Use a drilling rig to quickly push several sections of external orifice tubes connected in series into the large-diameter installation hole, and hang a suitable amount of polyurethane AB material on the external stirring spikes on the circumference of the last section of the external orifice tube. When the drilling rig drives the external orifice tube to rotate into the large-diameter installation hole, the polyurethane AB material packaging bag is scratched by friction with the inner wall of the large-diameter installation hole, and the external stirring spikes stir and evenly mix the A material oxidant and the B material reductant, and the polyurethane AB material reacts and expands quickly, preliminarily fixing the outer circumference of the external orifice tube into the large-diameter installation hole;

[0014] (3) Install the flange to seal the lower port of the outer hole pipe, insert the plastic grouting pipe and exhaust return grouting pipe into the two through holes on the flange respectively, and let the upper ends of the grouting pipe and exhaust return grouting pipe extend to the bottom of the large diameter installation hole; complete the grouting preparation work;

[0015] (4) Connect the grouting pipe and the grouting pump, mix and stir the cement mortar evenly, start the grouting pump, and inject the cement mortar into the large-diameter installation hole. The cement mortar is filled into the inside of the outer orifice pipe and the first annular cavity between the outer circle of the outer orifice pipe and the inner circle of the large-diameter installation hole. Stop grouting until the lower port of the exhaust return grouting pipe discharges a large amount of cement mortar. Allow the cement mortar to settle, solidify and harden, so as to properly deal with the severely deformed pressure relief zone. Since the grouting pipe is short, the height difference between the grouting pump and the grouting pipe outlet is small, generally 7 to 8 meters, so the concentration of cement mortar should be appropriately increased;

[0016] (5) After the cement mortar solidifies and hardens to the required hardness, the flange is removed to complete the installation and fixation of the outer orifice pipe. Then, the cement mortar block solidified inside the outer orifice pipe is drilled along the center line of the outer orifice pipe. The drilling is stopped after reaching a certain length to form an inner pipe installation hole with a diameter equivalent to the inner diameter of the outer orifice pipe and a length greater than the large-diameter installation hole.

[0017] (6) Use a multi-stage plug-in grouting sealing method and process. The required materials and equipment include a grouting pump, a hook-type grouting pipe, cement mortar, polyurethane AB material and an annular overflow baffle. The annular overflow baffle is installed at the lower end of the outer orifice pipe by means of a flange connection to seal the annular gap between the inner circle of the outer orifice pipe and the inner circle of the inner orifice pipe; cement mortar is used as a sealing material, and its fluidity, high strength and controllable dosage are utilized to inject grout until the annular gap between the outer circle of the inner orifice pipe and the inner circle of the outer orifice pipe, the annular gap between the outer circle of the inner orifice pipe and the coal rock around the inner pipe installation hole are filled, the cracks in the severely deformed pressure relief zone that are not sufficiently sealed when the outer orifice pipe is installed, and the cracks in the surrounding rock of the borehole formed by the construction drilling are filled; The annular anti-overflow baffle and the disc-shaped baffle block the outer orifice pipe and the inner orifice pipe. After the second annular cavity formed between the outer circle of the inner orifice pipe and the inner circle of the outer orifice pipe, the annular gap between the outer circle of the inner orifice pipe and the inner circle of the inner pipe installation hole, and the closed space formed inside the inner orifice pipe are filled with cement mortar, the dead weight of the slurry will generate a certain pressure, which provides power for the cement mortar to settle and compact and penetrate into the surrounding rock cracks, effectively ensuring the sealing quality; the grouting pipe is connected by several sections, and the upper end is designed to be hook-type, which is convenient for hanging on the upper end of the inner orifice pipe during grouting;

[0018] (7) Use a drilling rig to quickly push several sections of inner orifice tubes connected in series into the large-diameter installation hole, and hang a suitable amount of polyurethane AB material on the internal stirring spikes on the circumference of the last section of the inner orifice tube. During the process of the drilling rig driving the inner orifice tube to rotate and enter the large-diameter installation hole, the polyurethane AB material packaging bag is scratched by friction with the inner wall of the large-diameter installation hole, and the internal stirring spikes stir and evenly mix the A material oxidant and the B material reductant. The polyurethane AB material reacts and expands quickly, and the inner circle of the inner orifice tube is initially fixed to the lower port of the outer orifice tube; then, the annular anti-overflow baffle is put on the inner orifice tube and fixedly connected to the lower port of the outer orifice tube to ensure that the polyurethane AB material does not overflow downward;

[0019] (8) Insert the grouting pipe from the inner orifice pipe, with a length that is basically equal to the length of the inner orifice pipe, so that the hook of the hook-type grouting pipe can be easily hung on the upper edge of the inner orifice pipe, temporarily fix the hook-type grouting pipe, and extend the outlet end of the hook-type grouting pipe into the annular gap between the outer circle of the inner orifice pipe and the coal rock around the inner pipe installation hole. Connect the lower end of the hook-type grouting pipe to the grouting pump to meet the grouting conditions; at this time, the inner orifice pipe serves as a return water pipe;

[0020] (9) Stir the cement mortar evenly, start the grouting pump to start grouting, and inject the slurry into the annular closed space outside the inner orifice pipe through the outlet of the hook-type grouting pipe. When the closed space outside the inner orifice pipe is filled with cement mortar, continue for a period of time until the cement sand particles sink to the middle and lower part of the annular closed space after preliminary sedimentation, and the muddy water with lower concentration flows downward through the upper port of the inner orifice pipe until the mud and sand concentration in the slurry returned from the lower port of the inner orifice pipe is high. Then stop grouting and allow the cement mortar that has been injected into the annular closed space outside the inner orifice pipe to settle for a long time to complete the first grouting;

[0021] (10) After the injected cement mortar has fully settled, eight hours or one day later, continue to use the existing grouting pump and hook-type grouting pipe to start the second grouting; because the density of the cement mortar injected last time is relatively large and has settled, the newly injected cement mortar first squeezes out and fills the slurry water remaining in the upper part after the previous grouting sedimentation and stratification, and then the muddy water with lower concentration flows out through the inner orifice pipe after preliminary sedimentation; when the returned mortar has a high concentration, stop grouting and complete the second grouting; it is not difficult to understand that after the cement mortar injected this time has fully settled, the length of the slurry water section remaining in the upper part after the grouting sedimentation and stratification will be much shorter than the length of the slurry water section remaining in the upper part after the first grouting sedimentation and stratification; repeat the grouting operation 3 to 4 times, and the annular closed space outside the inner orifice pipe is basically filled with solid and well-condensed mud and sand, so as to achieve a better sealing effect.

[0022] After the double-layer pipe sealing structure is completed, the sealing effect is tested by using the directional long borehole vertical water column pressure observation method. The specific process of the test is as follows:

[0023] (1) A disc-shaped baffle is connected to the flange at the lower end of the inner orifice pipe, a pressure measuring tube is connected to the disc-shaped baffle, and a valve and a pressure gauge with a minimum scale of 1~2KPa are installed on the pressure measuring tube;

[0024] (2) The pressure gauge is connected to the water supply pipe in the underground tunnel. The water pressure in the water supply pipe in the underground tunnel can reach hundreds of KPa. After the valve is opened, the water pressure will quickly flow into the inner orifice pipe through the pressure gauge under the action of positive pressure, and continue to flow upward into the inner pipe installation hole and the directional long borehole. Since the volume of water is nearly incompressible, the water pressure will not suddenly increase after initially flowing into the borehole. As the height of the water column continues to increase, the pressure gauge reading gradually increases. When the pressure gauge reading reaches 80 KPa, close the valve and observe the changes in the pressure gauge;

[0025] (3) Since the tested area is the smallest, the water seepage path in the directional long borehole is single. If the sealing quality is qualified, the pressure gauge reading will stabilize quickly. After 24 hours of observation, if the pressure gauge reading stabilizes quickly, it indicates that the sealing is qualified and the pressure test has passed.

[0026] (4) Remove the disc-shaped baffle of the flange at the lower end of the inner orifice pipe, release the water injected into the directional long borehole for testing, connect the lower end of the inner orifice pipe to the tunnel extraction system, and enter the gas extraction stage.

[0027] To sum up, the utility model greatly improves the supporting strength and length (depth) by setting a double-layer sealing structure of an outer orifice tube and an inner orifice tube, which can fully support the severe deformation of coal and rock layers caused by mining and unloading of adjacent working faces, and the development of cracks caused by deformation, so that the directional long borehole can meet the sealing effect required for long-term high-negative pressure extraction, so as to achieve the goal of high-concentration, high-purity, long-distance and long-term extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the installation and reinforcement of the outer hole pipe of the directional long drilling hole in the medium-thick coal seam of the present invention;

[0029] Figure 2 It is a schematic diagram of sealing the inner hole of the multi-stage internal insertion grouting pipe in the present invention;

[0030] Figure 3 It is a schematic diagram of testing the sealing effect of the vertical water column pressure observation method of the directional long borehole in the medium-thick coal seam according to the present invention. DETAILED DESCRIPTION

[0031] The utility model discloses a double-layer pipe sealing structure for directional long drilling in a thick coal seam mining pressure relief zone, comprising an outer orifice pipe 4 and an inner orifice pipe 7. The inner orifice pipe 7 is longer than the outer orifice pipe 4, the inner orifice pipe 7 is coaxially arranged inside the outer orifice pipe 4, the outer orifice pipe 4 is coaxially arranged inside a large-diameter mounting hole 5 constructed earlier, the large-diameter mounting hole 5 is inclined with a low orifice and a high hole bottom, a first annular cavity between the outer circle of the outer orifice pipe 4 and the inner circle of the large-diameter mounting hole 5 is composed of a first polyurethane sealing section 11 and a first cement mortar sealing section 12 from the orifice to the hole bottom; a second annular cavity formed between the outer circle of the inner orifice pipe 7 and the inner circle of the outer orifice pipe 4 is composed of a second polyurethane sealing section 13 and a second cement mortar sealing section 14 from the orifice to the hole bottom.

[0032] The port of the outer orifice tube 4 located outside the orifice is provided with an annular overflow baffle 10 which is sleeved on the outer circle of the inner orifice tube 7. The inner circle of the annular overflow baffle 10 is provided with a first sealing ring which is sealed with the outer circle of the inner orifice tube 7. The annular overflow baffle 10 is connected to the end face of the outer orifice tube 4 by a plurality of first screws arranged circumferentially.

[0033] A disc-shaped baffle 15 is provided at the port of the inner orifice tube 7 located outside the orifice, and the disc-shaped baffle 15 is connected to the end face of the inner orifice tube 7 by a plurality of second screws arranged circumferentially, and a second sealing ring is provided between the disc-shaped baffle 15 and the end face of the inner orifice tube 7; a tube penetration hole is provided on the disc-shaped baffle 15, and a pressure measuring tube 16 is connected to the disc-shaped baffle 15 and extends into the inner orifice tube 7 through the tube penetration hole, and a valve 17 and a pressure gauge 18 are installed on the pressure measuring tube 16.

[0034] The outer circumference of the outer orifice tube 4 is provided with external stirring thorns for hanging and stirring the polyurethane AB material packaging bag, and a plurality of external stirring thorns are evenly arranged on the outer circumference of the outer orifice tube 4.

[0035] The outer circumference of the inner hole mouth tube 7 is provided with inner stirring thorns for hanging and stirring the polyurethane AB material packaging bag, and a plurality of inner stirring thorns are evenly arranged on the outer circumference of the inner hole mouth tube 7.

[0036] like Figure 1 and Figure 2 As shown, the specific construction steps of the utility model are as follows:

[0037] (1) Prepare the outer orifice pipe 4 and the materials used for installation, including polyurethane AB material, cement mortar, flange 1, grouting pump, grouting pipe 2 and exhaust return grouting pipe 3. The length of grouting pipe 2 and exhaust return grouting pipe 3 is longer than that of the outer orifice pipe 4. The flange 1 is provided with two through holes for passing the grouting pipe 2 and the exhaust return grouting pipe 3 respectively.

[0038] (2) Use a drilling rig to quickly push several sections of external orifice tubes 4 connected in series into the large-diameter installation hole 5, and hang a suitable amount of polyurethane AB material on the external stirring spikes on the circumference of the last section of the external orifice tube 4. When the drilling rig drives the external orifice tube 4 to rotate and enter the large-diameter installation hole 5, the polyurethane AB material packaging bag is scratched by friction with the inner wall of the large-diameter installation hole 5, and the external stirring spikes stir and evenly mix the oxidant of material A and the reductant of material B, and the polyurethane AB material reacts and expands quickly, preliminarily fixing the outer circumference of the external orifice tube 4 to the large-diameter installation hole 5;

[0039] (3) Install the flange 1 to seal the lower end of the outer orifice pipe 4, insert the plastic grouting pipe 2 and the exhaust return grouting pipe 3 into the two through holes on the flange 1 respectively, and let the upper ends of the grouting pipe 2 and the exhaust return grouting pipe 3 extend into the bottom of the large diameter installation hole 5; complete the grouting preparation work;

[0040] (4) Connect the grouting pipe 2 and the grouting pump, mix and stir the cement mortar evenly, start the grouting pump, and inject the cement mortar into the large-diameter installation hole 5. The cement mortar is filled into the outer orifice pipe 4 and the first annular cavity between the outer circle of the outer orifice pipe 4 and the inner circle of the large-diameter installation hole 5. Stop grouting until the lower port of the exhaust return grouting pipe 3 discharges a large amount of cement mortar. Allow the cement mortar to settle, solidify and harden, so as to properly deal with the severely deformed pressure relief zone. Since the grouting pipe 2 is short, the height difference between the grouting pump and the grouting outlet of the grouting pipe 2 is small, generally 7 to 8 m, so the concentration of the cement mortar is appropriately increased;

[0041] (5) After the cement mortar solidifies and hardens to a hardness that meets the requirements, the flange 1 is removed to complete the installation and fixation of the outer orifice pipe 4. Then, the cement mortar block solidified inside the outer orifice pipe 4 is drilled along the center line direction of the outer orifice pipe 4; the drilling is stopped after reaching a certain length, forming an inner pipe installation hole 6 with a diameter equivalent to the inner diameter of the outer orifice pipe 4 and a length greater than the large-diameter installation hole 5;

[0042] (6) A multi-stage plug-in grouting sealing method and process is used, and the required materials and equipment include a grouting pump, a hook-type grouting pipe 9, cement mortar, polyurethane AB material and an annular overflow baffle 10. The annular overflow baffle 10 is installed at the lower end of the outer orifice pipe 4 by means of a flange connection to seal the annular gap between the inner circle of the outer orifice pipe 4 and the inner circle of the inner orifice pipe 7; cement mortar is used as a sealing material, and its fluidity, high strength and controllable dosage are utilized to inject grout until the annular gap between the outer circle of the inner orifice pipe 7 and the inner circle of the outer orifice pipe 4, the annular gap between the outer circle of the inner orifice pipe 7 and the coal rock around the inner pipe installation hole 6, the cracks in the severely deformed pressure relief zone that are not sufficiently sealed when the outer orifice pipe 4 is installed, and the cracks in the surrounding rock of the borehole formed during the construction of the borehole; due to The annular overflow prevention baffle 10 and the disc-shaped baffle 15 block the outer orifice pipe 4 and the inner orifice pipe 7. After the second annular cavity formed between the outer circle of the inner orifice pipe 7 and the inner circle of the outer orifice pipe 4, the annular gap between the outer circle of the inner orifice pipe 7 and the inner circle of the inner pipe mounting hole 6, and the closed space formed inside the inner orifice pipe 7 are filled with cement mortar, the dead weight of the slurry will generate a certain pressure, which provides power for the cement mortar to settle and compact and penetrate into the surrounding rock cracks, effectively ensuring the sealing quality; the grouting pipe 2 is connected by several sections, and the upper end is designed to be hook-type, which is convenient for hanging on the upper end of the inner orifice pipe 7 during grouting;

[0043] (7) Use a drilling rig to quickly push several sections of inner orifice tubes 7 connected in series into the large-diameter mounting hole 5, and hang a suitable amount of polyurethane AB material on the inner stirring spikes on the circumference of the last section of the inner orifice tube 7. During the process of the drilling rig driving the inner orifice tube 7 to rotate and enter the large-diameter mounting hole 5, the polyurethane AB material packaging bag is scratched by friction with the inner wall of the large-diameter mounting hole 5, and the inner stirring spikes stir and evenly mix the A material oxidant and the B material reductant, and the polyurethane AB material reacts and expands quickly, preliminarily fixing the inner circle of the inner orifice tube 7 to the lower end of the outer orifice tube 4; then, put the annular anti-overflow baffle 10 on the inner orifice tube 7 and fix it to the lower end of the outer orifice tube 4 to ensure that the polyurethane AB material does not overflow downward;

[0044] (8) Insert the grouting pipe 2 from the inner orifice pipe 7, with a length substantially equal to that of the inner orifice pipe 7, so that the hook of the hook-type grouting pipe 9 can be conveniently hooked to the upper edge of the inner orifice pipe 7, and temporarily fix the hook-type grouting pipe 9. The outlet end of the hook-type grouting pipe 9 extends into the annular gap between the outer circle of the inner orifice pipe 7 and the coal rock around the inner pipe mounting hole 6, and the lower end of the hook-type grouting pipe 9 is connected to the grouting pump to meet the grouting conditions; at this time, the inner orifice pipe 7 serves as a return water pipe;

[0045] (9) Stir the cement mortar evenly, start the grouting pump to start grouting, and inject the slurry into the annular closed space outside the inner orifice pipe 7 through the outlet of the hook-type grouting pipe 9. When the closed space outside the inner orifice pipe 7 is filled with cement mortar, continue for a period of time until the cement sand particles sink to the middle and lower part of the annular closed space after preliminary sedimentation, and the muddy water with lower concentration flows downward through the upper port of the inner orifice pipe 7. When the mud and sand concentration in the slurry returned from the lower port of the inner orifice pipe 7 is high, stop grouting and allow the cement mortar that has been injected into the annular closed space outside the inner orifice pipe 7 to settle for a long time to complete the first grouting;

[0046] (10) After the injected cement mortar has fully settled, eight hours or one day later, the existing grouting pump and hook-type grouting pipe 9 are used to start the second grouting. Since the density of the cement mortar injected last time is relatively large and has already settled, the newly injected cement mortar is first squeezed out to fill the slurry water remaining in the upper part after the previous grouting sedimentation and stratification, and then the muddy water with lower concentration flows out through the inner orifice pipe 7 after preliminary sedimentation. When the returned mortar has a high concentration, the grouting is stopped and the second grouting is completed. It is not difficult to understand that after the injected cement mortar has fully settled, the length of the slurry water section remaining in the upper part after the grouting sedimentation and stratification will be much shorter than the length of the slurry water section remaining in the upper part after the first grouting sedimentation and stratification. The grouting operation is repeated 3 to 4 times, and the annular closed space outside the inner orifice pipe 7 is basically filled with solid and well-condensed mud and sand, thus achieving a better sealing effect.

[0047] like Figure 3As shown in the figure, after the double-layer pipe sealing structure is completed, the sealing effect is tested by using the directional long borehole vertical water column pressure observation method. The specific process of the test is as follows:

[0048] (1) A disc-shaped baffle 15 is connected to the flange at the lower end of the inner orifice pipe 7, a pressure measuring tube 16 is connected to the disc-shaped baffle 15, and a valve 17 and a pressure gauge 18 with a minimum scale of 1~2KPa are installed on the pressure measuring tube 16;

[0049] (2) The pressure measuring tube 16 is connected to the water supply pipe in the underground tunnel. The water pressure in the water supply pipe in the underground tunnel can reach hundreds of KPa. After the valve 17 is opened, the water pressure will flow rapidly into the inner orifice pipe 7 through the pressure measuring tube 16 under the action of positive pressure, and continue to flow upward into the inner pipe installation hole 6 and the directional long borehole 8. Since the volume of water has a nearly incompressible characteristic, the water pressure will not suddenly increase after initially flowing into the borehole. As the height of the water column continues to increase, the reading of the pressure gauge 18 gradually increases. When the reading of the pressure gauge 18 reaches 80 KPa, close the valve 17 and observe the changes in the pressure gauge 18;

[0050] (3) Since the detected area is the smallest, the water seepage path in the directional long borehole 8 is single. If the sealing quality is qualified, the reading of the pressure gauge 18 will stabilize quickly. After observing for 24 hours, if the reading of the pressure gauge 18 stabilizes quickly, it indicates that the sealing is qualified and the pressure test has passed;

[0051] (4) Remove the disc-shaped baffle 15 of the flange at the lower end of the inner orifice pipe 7, release the water injected into the directional long borehole 8 for testing, connect the lower end of the inner orifice pipe 7 to the tunnel extraction system, and enter the gas extraction stage.

[0052] Figure 1-Figure 3 Other reference numerals in the figure are: 20 - drilling site roof, 21 - drilling site side wall, 22 - coal seam roof, 23 - coal seam.

[0053] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A double-layer pipe sealing structure for directional long drilling in a thick coal seam mining pressure relief zone, characterized by: It comprises an outer orifice tube and an inner orifice tube, the inner orifice tube is longer than the outer orifice tube, the inner orifice tube is coaxially arranged inside the outer orifice tube, the outer orifice tube is coaxially arranged inside the large-diameter installation hole constructed first, the large-diameter installation hole is inclined with a low orifice and a high hole bottom, the first annular cavity between the outer circle of the outer orifice tube and the inner circle of the large-diameter installation hole is composed of a first polyurethane sealing section and a first cement mortar sealing section from the orifice to the hole bottom; the second annular cavity formed between the outer circle of the inner orifice tube and the inner circle of the outer orifice tube is composed of a second polyurethane sealing section and a second cement mortar sealing section from the orifice to the hole bottom.

2. The double-layer pipe sealing structure for directional long drilling of thick coal seam mining pressure relief zone according to claim 1 is characterized by: The port of the outer orifice tube located outside the orifice is provided with an annular overflow baffle which is sleeved on the outer circle of the inner orifice tube. The inner circle of the annular overflow baffle is provided with a first sealing ring which is sealed with the outer circle of the inner orifice tube. The annular overflow baffle is connected to the end face of the outer orifice tube by a plurality of first screws arranged circumferentially.

3. The double-layer pipe sealing structure for directional long drilling of thick coal seam mining pressure relief zone according to claim 2 is characterized in that: A disc-shaped baffle is provided at the port of the inner orifice tube located outside the orifice, and the disc-shaped baffle is connected to the end face of the inner orifice tube by a plurality of second screws arranged circumferentially, and a second sealing ring is provided between the disc-shaped baffle and the end face of the inner orifice tube; a tube penetration hole is provided on the disc-shaped baffle, and a pressure measuring tube is connected to the disc-shaped baffle and passes through the tube penetration hole and extends into the inner orifice tube, and a valve and a pressure gauge are installed on the pressure measuring tube.

4. The double-layer pipe sealing structure for directional long drilling of thick coal seam mining pressure relief zone according to any one of claims 1 to 3, characterized in that: The outer circle of the outer hole mouth tube is provided with external stirring thorns for hanging and stirring the polyurethane AB material packaging bag, and a plurality of external stirring thorns are evenly arranged on the outer circle of the outer hole mouth tube.

5. The double-layer pipe sealing structure for directional long drilling of thick coal seam mining pressure relief zone according to any one of claims 1 to 3, characterized in that: The outer circle of the inner hole mouth tube is provided with inner stirring thorns for hanging and stirring the polyurethane AB material packaging bag, and a plurality of inner stirring thorns are evenly arranged on the outer circle of the inner hole mouth tube.

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