Multiphase substance filling method for scrapped roadway of coal face of spontaneous combustion coal seam

Abstract

The invention discloses a multiphase substance filling method for a discarded roadway of a coal face of a spontaneous combustion coal seam. The method comprises the following steps: S1, determining a closed position of the discarded roadway; s2, drilling holes beside the scrapped roadway and laying gas production pipes; s3, an inner side sealing wall is built in the scrapped roadway, and an air injection pipe is arranged; and S4, CO2 gas is injected into the scrapped roadway on the inner side of the inner side sealing wall through a gas injection pipe, and leakproofness detection and other steps are carried out. According to the discarded roadway, sealing and gravel filling are only conducted on the portion, 30 m away from the coal face side, of the discarded roadway through the two sealing walls, CO2 gas is injected into the discarded roadway, after rocks on a top plate of the goaf continuously collapse, the goaf is continuously compacted again, then liquid CO2 is injected into the discarded roadway, and permanent sealing and storage of the goaf can be achieved. And drilling holes are constructed in the periphery of the scrapped roadway, gas in the drilling holes is sampled through the gas production pipe, the diffusion range of CO2 gas in the scrapped roadway is detected, and it is guaranteed that liquid CO2 in the scrapped roadway does not leak.

Description

Technical Field

[0001] The invention relates to the technical field of treatment of abandoned tunnels in underground coal mines, and in particular to a method for filling abandoned tunnels with multiphase materials in a spontaneous combustion coal seam coal mining working face. Background Art

[0002] Most coal mines in my country are underground mines, which mainly mine underground coal seams. Affected by geological conditions, the occurrence conditions of most coal seams are relatively complex, and there may be geological structures such as faults and folds, which brings huge challenges to the excavation of underground tunnels and the layout of coal mining faces. A complete coal mining face is generally composed of an intake tunnel, a return air tunnel and a working face. Among them, the working face is the core area of ​​coal mining operations. It was originally a tunnel excavated along the coal seam and connected to the intake tunnel and the return air tunnel. It is also called an open cut, which can form an independent ventilation system with the intake tunnel and the return air tunnel. Under normal circumstances, the open cut is perpendicular to the return air tunnel and the intake tunnel, that is, the intake tunnel is parallel to the return air tunnel and the end positions of the two tunnels deep into the coal seam are collinear. However, due to factors such as geological conditions and mining plans, after one tunnel (the first tunnel) of the coal mining face is excavated, the other tunnel (the second tunnel) may encounter geological structures, abnormal gas outburst areas, etc. during the excavation process, making it impossible to continue excavating the tunnel. At this time, the excavation of the tunnel is generally stopped, and the tunnel is excavated directly from one end of the tunnel to the other tunnel (the first tunnel) until it is connected with the other and forms an independent ventilation system. This causes the inner section of the first tunnel to become a useless tunnel, that is, a scrapped tunnel. Figure 1 As shown. According to Article 129 of the Coal Mine Safety Regulations (2016 Edition): Abandoned tunnels must be closed, so the tunnel needs to be closed.

[0003] At present, the treatment of abandoned tunnels in coal mines is generally to build closed walls in the tunnels, or to fill the entire abandoned tunnels with materials such as loess. Under the disturbance of mining stress, the former is very prone to damage and air leakage; the latter requires the transportation of relevant materials from the ground to the underground, which increases the workload of underground scheduling. If the length of the abandoned tunnel is large, the engineering volume will be very large, which will seriously affect the mining plan of the coal mining face. In addition, if the tunnel is not filled in full section, that is, there is a non-filled section in the abandoned tunnel, when the coal seam is in danger of spontaneous combustion and meets certain conditions, the coal wall or coal residue in the non-filled section of the tunnel may spontaneously combust, which will pose a huge threat to the safe production of the coal mining face. At this time, if there is still gas accumulation in the non-filled section of the tunnel, in the presence of high-temperature heat sources, gas explosion accidents are very likely to occur, which may cause huge casualties and economic losses to the mine. Based on this, it can be seen that the existing treatment methods for abandoned tunnels in coal mines can no longer meet the safety treatment of such abandoned tunnels. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a method for filling abandoned tunnels with multi-phase materials in a spontaneous combustion coal seam mining working face.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a method for filling a multi-phase material in an abandoned roadway of a spontaneous combustion coal seam mining working face, which specifically comprises the following steps:

[0006] S1. Determination of the closed position of the scrapped tunnel:

[0007] Two closed walls are built in the scrapped tunnel, namely an inner closed wall and an outer closed wall. The outer closed wall is built at the connection between the scrapped tunnel and the cut eye, and the inner closed wall is built on the inner side of the scrapped tunnel at a distance L from the outer closed wall.

[0008] S2. Drill holes next to the abandoned tunnel to lay out the gas production pipe:

[0009] On the sidewall of the abandoned tunnel adjacent to the inner closed wall and far from the cutting eye, several boreholes are constructed in the coal seam outside the abandoned tunnel far from the cutting eye, a gas production pipe is placed in each borehole, and each borehole is blocked with a plugging material, the gas production pipe is fixed, and the outer end of the plugging material is flush with the borehole opening, and a gap is left between the inner end of the plugging material and the bottom of the borehole as a gas production chamber, the head end of the gas production pipe is placed in the gas production chamber, and an L-shaped elbow pipe is provided at the opening of each borehole, and the tail end of the gas production pipe passes through the L-shaped elbow pipe;

[0010] S3. Build an inner closed wall in the scrapped tunnel and arrange a gas injection pipe;

[0011] S4. Inject CO2 gas into the scrapped tunnel on the inner side of the inner closed wall through the gas injection pipe and perform a tightness test;

[0012] S5. Fill gravel along the outer side of the inner sealed wall from inside to outside. During the filling process of gravel, connect the extended gas injection pipe and gas production pipe in sequence, and lay the grouting pipe;

[0013] S6. Build the outer closed wall and arrange the gas injection pipe and grouting pipe;

[0014] S7, injecting grouting material into the scrapped tunnel filled with crushed stone and hardening it;

[0015] S8, coal working face recovery, connect the extended gas injection pipe and gas production pipe in sequence, and observe the CO2 gas pressure in the scrapped tunnel. If the pressure drops, add CO2 gas;

[0016] S9, Liquid CO2 filling: When the goaf roof continues to collapse and compacts the goaf, connect the tail end of the gas injection pipe to the external gas injection hose. Before injection, all the pipe openings of the gas production pipes must be blocked first, and then liquid CO2 is injected into the scrapped tunnel inside the inner closed wall, and the tail end of the gas injection pipe is connected to the 1-inch pipeline through a reducer;

[0017] S10. Detection of CO2 gas diffusion range: As the coal mining face continues to advance, the 1-inch pipeline and the gas production pipe inside it are continuously connected, and the gas in each borehole is sampled through the gas production pipe to detect the CO2 gas concentration, thereby realizing the detection of the CO2 gas diffusion range. When the CO2 gas concentration in the gas sample in a certain borehole is detected to be more than 50% for three consecutive days, it is considered that CO2 gas has diffused to the borehole, and the gas production pipe in the borehole is blocked. In the future, CO2 gas detection and gas production pipe extension will no longer be performed on the borehole, and this cycle will be repeated until the coal mining face is recovered.

[0018] Furthermore, the inner closed wall includes a first inner wall, a first filler and a first outer wall, and an air injection pipe is inserted through the first inner wall, the first filler and the first outer wall; the outer closed wall includes a second inner wall, a second filler and a second outer wall, and an air injection pipe and a grouting pipe are inserted through the second inner wall, the second filler and the second outer wall; L=30m;

[0019] The total thickness of the inner closed wall is 3.0m, the thickness of the first inner wall and the first outer wall are both 0.37m, and the thickness of the first filler is 2.26m; the total thickness of the outer closed wall is 2.0m, the thickness of the second inner wall and the second outer wall are both 0.37m, and the thickness of the second filler is 1.26m.

[0020] Furthermore, in step S2, the specific steps of constructing a plurality of boreholes on the sidewall of the abandoned roadway adjacent to the inner closed wall and in the outer coal seam of the abandoned roadway away from the cutting eye are as follows:

[0021] Construct multiple holes on the side of the abandoned roadway adjacent to the inner closed wall and far from the side of the cut-out, with the horizontal distance between each hole along the direction of the roadway being 0.5m, and then construct a drilling hole in the outer coal seam of the abandoned roadway far from the side of the cut-out at each hole; the diameter of the drilling hole is 75mm, and the horizontal distance between the line connecting the position of the end hole of each drilling hole and the inner wall of the inner closed wall is 10m, the spacing between the positions of the end holes of each drilling hole is 2m, the drilling hole closest to the side of the abandoned roadway is 4m away from the side of the abandoned roadway; the straight-line distance k between the drilling hole closest to the abandoned roadway wall and the outer edge of the inner and outer walls of the inner closed wall is not less than 1m;

[0022] Height of drilling hole: If the coal seam thickness is less than the roadway height, the final hole position is half of the coal seam thickness; if the coal seam thickness is higher than the roadway height, the final hole position is half of the roadway height.

[0023] Furthermore, in step S2, the total length d of the plugging material in the borehole is not less than 15m, and the length l of the gas production chamber is 20cm-50cm; the gas production pipe is a stainless steel capillary tube, and the outer diameter of the stainless steel capillary tube is 2mm-3mm.

[0024] Furthermore, in step S3, the specific steps of building the inner closed wall and arranging the gas injection pipe are:

[0025] Grooving: Grooving is performed around the abandoned roadway at a distance of 30m from the opening of the coal mining face. First, the axial groove width of the two sides of the abandoned roadway is 1.0m, and the groove depth is 50cm; then the axial groove width of the bottom plate is 1.0m, and the groove depth is 50cm when the bottom plate is a coal seam, and the groove depth is 30cm when the bottom plate is a rock layer; finally, the axial groove width of the top plate is 1.0m, and the groove depth is 50cm when the top plate is a coal seam, and the groove depth is 30cm when the top plate is a rock layer;

[0026] Building the first inner wall: after the trenching is completed, the first inner wall is built with bricks or stones. When building the first inner wall, the gas injection pipe is inserted horizontally. The front end of the gas injection pipe passes through the first inner wall and penetrates 2.0m into the scrapped tunnel. The tail end of the gas injection pipe passes through the first filling material and the first outer wall in turn. After the first inner wall is built, the scrapped tunnel is further trenched in the above trenching sequence. The trenching width is 2.0m and the trenching depth remains unchanged.

[0027] Filling the first filling material and building the first exterior wall: when loess is the first filling material, bricks or stones are used to build the first exterior wall at the position of the first exterior wall, and loess is filled between the first exterior wall and the first interior wall as the first exterior wall is built; when fluid concrete is used as the first filling material, after the first interior wall is built, the scrapped tunnel is continued to be trenched in the above-mentioned trenching sequence, the trenching depth remains unchanged, and the trenching width is 2.0m. Then, bricks or stones are used to build the first exterior wall at the position of the first exterior wall. During the construction, a grouting pipe is additionally reserved on the first exterior wall. After the first exterior wall is built, fluid concrete is injected between the first interior wall and the first exterior wall through the grouting pipe. After the fluid concrete hardens, the grouting pipe is removed and the installation position of the grouting pipe is sealed.

[0028] Furthermore, in step S4, the specific steps of injecting CO2 gas into the scrapped tunnel on the inner side of the inner closed wall through the gas injection pipe and performing a tightness test are:

[0029] The tail end of the gas injection pipe on the outside of the first outer wall is connected to the external gas injection hose in the scrapped tunnel. In order to prevent the gas from entering the stainless steel capillary, it is necessary to seal the pipe openings of each gas production pipe before gas injection, and inject CO2 gas into the scrapped tunnel inside the inner closed wall through the external gas injection hose and the gas injection pipe until the gas pressure in the scrapped tunnel exceeds 20% of the coal seam gas pressure and remains unchanged for 24 hours. At this time, the sealing of the inner closed wall meets the requirements; after the sealing test is completed, the external gas injection hose is removed from the gas injection pipe.

[0030] Furthermore, the specific steps of step S5 are:

[0031] The crushed stone produced by the excavation of the rock tunnel is directly transported to the scrapped tunnel, and the crushed stone is filled from the inside to the outside along the outside of the inner closed wall. During the filling process of the crushed stone, multiple gas injection pipes are connected in sequence at the tail end of the gas injection pipe. When the gas injection pipe is laid to the vicinity of the openings of the four adjacent boreholes, four tees are installed on the gas injection pipe in sequence, and are respectively connected to the L-shaped elbow pipes on the four boreholes, so that the gas production pipe enters the gas injection pipe through the tees, and the gas injection pipe is installed on the outermost tee to continue filling the crushed stone. The gas injection pipe and all the gas production pipes are continuously connected and extended outward with the crushed stone filling; when the crushed stone filling is 15m away from the first inner wall, the grouting pipe is laid with the crushed stone filling, and the gas injection pipe, grouting pipe and all the gas production pipes are continuously connected and extended until the crushed stone filling is completed.

[0032] Furthermore, in step S6, the specific steps of building the outer closed wall and arranging the gas injection pipe and the grouting pipe are:

[0033] Grooving: Build the outer closed wall from the inside to the outside at a distance of 28m from the first inner wall. When building the outer closed wall, firstly, groove the surroundings of the abandoned tunnel. First, the axial groove width of the two sides of the abandoned tunnel is 1.0m, and the groove depth is 50cm; then the axial groove width of the bottom plate is 1.0m, and the groove depth is 50cm when the bottom plate is a coal seam, and the groove depth is 30cm when the bottom plate is a rock layer; finally, the axial groove width of the top plate is 1.0m, and the groove depth is 50cm when the top plate is a coal seam, and the groove depth is 30cm when the top plate is a rock layer;

[0034] Building the second inner wall: After the trenching is completed, the second inner wall is built with bricks or stones. When building the second inner wall, the air injection pipe and the grouting pipe are inserted horizontally. The front ends of the air injection pipe and the grouting pipe are respectively connected to the air injection pipe and the grouting pipe laid during the crushed stone filling. The tail ends of the air injection pipe and the grouting pipe must be exposed from the second outer wall. After the second inner wall is built, the scrapped tunnel is further trenched in accordance with the above trenching sequence. The trenching width is 1.0m and the trenching depth remains unchanged.

[0035] Filling the second filling material and building the second outer wall: when loess is used as the second filling material, bricks or stones are used to build the second outer wall at the position of the second outer wall, and loess is filled between the second outer wall and the second inner wall as the second outer wall is built; when fluid concrete is used as the second filling material, after the second inner wall is built, the scrapped tunnel is continued to be grooved in accordance with the above-mentioned groove excavation sequence, and the groove depth and width remain unchanged, and then bricks or stones are used to build the first outer wall at the position of the second outer wall. During the construction, a grouting pipe is additionally reserved on the first outer wall. After the first outer wall is built, fluid concrete is injected between the first inner wall and the first outer wall through the grouting pipe. After the fluid concrete hardens, the grouting pipe is removed and the installation position of the grouting pipe is sealed.

[0036] Furthermore, the specific steps of step S7 are:

[0037] The tail end of the grouting pipe on the outer closed wall is connected to the feed pipe in the scrapped tunnel for inputting grouting materials. The feed pipe is connected to the grouting pump. The grouting pump is used to inject the grouting material into the scrapped tunnel filled with gravel through the feed pipe and the grouting pipe, and fill it up. After the grouting is completed, wait for it to harden.

[0038] Furthermore, the specific steps of step S8 are:

[0039] As the coal mining face is continuously mined, the roof of the goaf will collapse periodically. While the coal mining face is being mined, the gas injection pipe outside the outer closed wall and the gas production pipe inside it are continuously connected;

[0040] Each time the gas injection pipe is connected, it is necessary to connect the gas injection pipe to the external gas injection hose on one side of the coal mining working face. The external gas injection hose is provided with a pressure gauge and a valve. The pressure gauge value must be checked each time a connection is made. When it is observed that the CO2 gas pressure in the scrapped tunnel is 10% lower than the pressure in step S2, it is necessary to replenish CO2 gas through the gas injection pipe to restore its pressure to 120% of the gas pressure in the coal seam.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The present invention builds two closed walls in the abandoned tunnel and fills the space between the two closed walls with crushed stones. The closed walls are simple to construct and have strong adaptability. Each closed wall is composed of two walls and a filling material. It has a stable structure and strong pressure bearing capacity, and can effectively prevent the penetration of moisture and gas, thereby maintaining the stability of the internal environment of the abandoned tunnel.

[0043] (2) The scrapped tunnel of the present invention is sealed and filled with only two closed walls within 30m of the coal mining face, and the filling section of the tunnel is filled with only crushed stones excavated from the rock tunnel, which effectively reduces the scheduling workload of the entire mine, and the overall construction difficulty is low and the construction steps are simple.

[0044] (3) The present invention first injects CO2 gas into the abandoned tunnel, which can effectively reduce the oxygen content of the air inside it, inhibit the spontaneous combustion of coal, and ensure the construction safety during the sealing of the abandoned tunnel; the inert gas has good stability, is environmentally friendly and pollution-free, and has low economic cost; and it can be used to detect the sealing of the closed wall.

[0045] (4) According to the present invention, after the roof rock of the goaf continues to collapse, the goaf is continuously re-compacted. At this time, liquid CO2 is injected into the abandoned tunnel to achieve permanent sealing, thereby helping to reduce greenhouse gas emissions and achieve the reuse of abandoned tunnels.

[0046] (5) The present invention constructs holes around abandoned tunnels, samples the gas in the holes through gas sampling pipes, and detects the diffusion range of CO2 gas in the abandoned tunnels. This can provide a reference for the reasonable coal pillar between the abandoned coal mining face and the adjacent coal mining face, and at the same time provide a reference for the support measures in the tunnels of the adjacent working faces, thereby effectively ensuring that the liquid CO2 in the abandoned tunnels will not leak. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of the location of the abandoned underground tunnel of the present invention.

[0048] Figure 2 It is a schematic diagram of the inner closed wall, the outer closed wall and the drilling arrangement in the scrapped tunnel of the present invention.

[0049] Figure 3 It is a schematic diagram of the installation structure of the gas production pipe and the L-shaped elbow in the borehole of the present invention.

[0050] Figure 4 It is a schematic diagram of the structure of the inner closed wall of the present invention built in the abandoned tunnel.

[0051] Figure 5 It is a schematic diagram of the structure of the outer closed wall of the present invention built in the scrapped tunnel.

[0052] Figure 6 It is a structural schematic diagram of the present invention after completing steps S1-S7 in a scrapped tunnel before mining at a coal mining face.

[0053] Figure 7 It is a construction schematic diagram of injecting liquid CO2 into the abandoned tunnel during the recovery process of the coal mining working face of the present invention.

[0054] Figure 8 The figure is a schematic diagram of the installation of the gas injection pipe, the tee, the L-shaped elbow pipe and the gas production pipe of the present invention.

[0055] Description of reference numerals:

[0056] 1. Abandoned tunnel; 2. Inner closed wall; 21. First inner wall; 22. First filling material; 23. First outer wall; 3. Outer closed wall; 31. Second inner wall; 32. Second filling material; 33. Second outer wall; 4. Cutting hole; 5. Gas injection pipe; 6. Grouting pipe; 7. Drilling hole; 8. Gas production pipe; 9. Blocking material; 10. Gas production chamber; 11. L-shaped elbow pipe; 12. CO2 gas; 13. Gravel; 14. Tee; 15. Liquid CO2; 16. Goaf;

[0057] 100, return air tunnel; 200, air intake tunnel; 300, auxiliary transport tunnel in mining area; 400, belt tunnel in mining area; 500, return air tunnel in mining area. DETAILED DESCRIPTION

[0058] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0059] Example

[0060] Reference Figure 1-Figure 8 A method for filling abandoned tunnels with multiphase materials in a self-igniting coal seam mining working face, wherein the abandoned tunnel 1 has a length greater than 30m and the layout of the abandoned tunnels in the mine is as follows: Figure 1 As shown, the cut hole 4 is perpendicular to the return air lane 100 and the air inlet lane 200. A mining area auxiliary transport lane 300, a mining area belt lane 400 and a mining area return air lane 500 are also arranged underground. The scrap lane 1 is located on the inner side of the cut hole 4. The specific steps include:

[0061] S1. Determination of the closed position of scrapped tunnel 1:

[0062] Reference Figure 2 , build two closed walls in the abandoned tunnel 1, namely the inner closed wall 2 and the outer closed wall 3, wherein the outer closed wall 3 is built at the connection between the abandoned tunnel 1 and the cut eye 4, and the inner closed wall 2 is built in the abandoned tunnel 1 at a distance of L from the outer closed wall 3, L = 30m;

[0063] The inner closed wall 2 includes a first inner wall 21, a first filler 22 and a first outer wall 23, and a gas injection pipe 5 is inserted through the first inner wall 21, the first filler 22 and the first outer wall 23; the outer closed wall 3 includes a second inner wall 31, a second filler 32 and a second outer wall 33, and a gas injection pipe 5 and a grouting pipe 6 are inserted through the second inner wall 31, the second filler 32 and the second outer wall 33;

[0064] The total thickness of the inner closed wall 2 is 3.0m, the thickness of the first inner wall 21 and the first outer wall 23 are both 0.37m, and the thickness of the first filler 22 is 2.26m; the total thickness of the outer closed wall 3 is 2.0m, the thickness of the second inner wall 31 and the second outer wall 33 are both 0.37m, and the thickness of the second filler 32 is 1.26m;

[0065] S2. Drill a hole 7 next to the abandoned tunnel 1 and lay out a gas extraction pipe 8:

[0066] On the sidewall of the abandoned tunnel 1 adjacent to the inner closed wall 2 and away from the cutting eye, several boreholes 7 are constructed in the outer coal seam of the abandoned tunnel 1 away from the cutting eye 4. The specific steps are: construct multiple holes on the sidewall of the abandoned tunnel 1 adjacent to the inner closed wall 2 and away from the cutting eye 4, and the horizontal distance between each hole along the tunnel direction is 0.5m, and then construct a borehole 7 in the outer coal seam of the abandoned tunnel 1 away from the cutting eye 4 at each hole; the diameter of the borehole 7 is 75mm, and the horizontal distance between the line where the end hole of each borehole 7 is located and the inner wall of the inner closed wall 2 is 10m, and the spacing between the end hole positions of each borehole 7 is 2m, and the borehole 7 closest to the sidewall of the abandoned tunnel 1 is 4m away from the sidewall of the abandoned tunnel 1; the straight-line distance k between the borehole 7 closest to the wall of the abandoned tunnel 1 and the outer edge of the outer wall of the inner closed wall 2 is not less than 1m;

[0067] The height of the borehole 7 is: if the coal seam thickness is less than the tunnel height, the final hole position is located at half the coal seam thickness; if the coal seam thickness is greater than the tunnel height, the final hole position is located at half the tunnel height;

[0068] In this embodiment, the number of boreholes 7 is 4, the horizontal distance between the final position of the four boreholes 7 and the inner wall of the inner closed wall 2 is 10m, and the distance between the final position of each borehole 7 and the sidewall of the abandoned tunnel 1 is 4m, 6m, 8m and 10m respectively;

[0069] Reference Figure 3, a gas collection pipe 8 is placed in each borehole 7, and each borehole 7 is blocked with a plugging material 9, the gas collection pipe 8 is fixed, and the outer end of the plugging material 9 is flush with the borehole 7, and a gap is left between the inner end of the plugging material 9 and the bottom of the borehole 7, as a gas collection chamber 10, the head end of the gas collection pipe 8 is placed in the gas collection chamber 10, and an L-shaped elbow pipe 11 is provided at the mouth of each borehole 7 for connecting with a tee 14, and the tail end of the gas collection pipe 8 passes through the L-shaped elbow pipe 11;

[0070] Preferably, the total length d of the plugging material 9 in the borehole 7 is not less than 15 m, and the length l of the gas extraction chamber 10 is 20 cm-50 cm;

[0071] The gas sampling pipe 8 is a stainless steel capillary tube, and the outer diameter of the stainless steel capillary tube is 2mm-3mm;

[0072] S3. Build an inner closed wall 2 in the scrapped tunnel 1 and arrange the gas injection pipe 5. The gas injection pipes 5 in this embodiment are all 2-inch pipes, and the length of a single gas injection pipe 5 is 1m-1.5m. When extending, the gas injection pipes 5 are connected to each other;

[0073] Reference Figure 4 The specific implementation steps of the inner closed wall 2 are as follows:

[0074] Grooving: At a distance of 30m from the opening eye 4 of the coal mining working face, grooves are cut around the abandoned tunnel 1. First, the groove width along the axial direction of the two sides of the abandoned tunnel 1 is 1.0m, and the groove depth is 50cm; then the groove width along the axial direction of the bottom plate is 1.0m, and the groove depth is 50cm when the bottom plate is a coal seam, and the groove depth is 30cm when the bottom plate is a rock layer; finally, the groove width along the axial direction of the top plate is 1.0m, and the groove depth is 50cm when the top plate is a coal seam, and the groove depth is 30cm when the top plate is a rock layer;

[0075] Building the first inner wall 21: after the trenching is completed, the first inner wall 21 is built with bricks or stones. When building the first inner wall 21, the gas injection pipe 5 is inserted in the horizontal direction. The front end of the gas injection pipe 5 passes through the first inner wall 21 and penetrates 2.0m into the scrapped tunnel 1. The tail end of the gas injection pipe 5 passes through the first filler 22 and the first outer wall 23 in turn. After the first inner wall 21 is built, the scrapped tunnel 1 is further trenched in accordance with the above trenching sequence. The trenching width is 2.0m and the trenching depth remains unchanged.

[0076] Filling the first filling material 22 and building the first outer wall 23: When loess is used as the first filling material 22, bricks or stones are used to build the first outer wall 23 at the position of the first outer wall 23, and loess is filled between the first outer wall 23 and the first inner wall 21 as the first outer wall 23 is built; when fluid concrete is used as the first filling material 22, after the first inner wall 21 is built, the scrapped tunnel 1 is continuously cut in accordance with the above-mentioned cutting sequence, the cutting depth remains unchanged, and the cutting width is 2.0 m, and then bricks or stones are used to build the first outer wall 23 at the position of the first outer wall 23. During the construction, a grouting pipe 6 (not shown in the figure) is additionally reserved on the first outer wall 23. After the first outer wall 23 is built, fluid concrete is injected between the first inner wall 21 and the first outer wall 23 through the grouting pipe 6. After the fluid concrete hardens, the grouting pipe 6 is removed, and the installation position of the grouting pipe 6 is blocked;

[0077] S4, injecting CO2 gas 12 into the scrapped tunnel 1 on the inner side of the inner closed wall 2 through the gas injection pipe 5, and performing a tightness test, the specific steps are:

[0078] Reference Figure 6 , connect the tail end of the gas injection pipe 5 outside the first outer wall 23 to the external gas injection hose in the scrapped tunnel 1, and inject CO2 gas 12 into the scrapped tunnel 1 inside the inner closed wall 2 (to prevent the gas from entering the stainless steel capillary, it is necessary to seal the openings of each stainless steel capillary before gas injection), until the gas pressure in the scrapped tunnel 1 exceeds 20% of the coal seam gas pressure (if the coal seam gas pressure is 0.5MPa, the gas pressure after the CO2 gas 12 is injected into the tunnel should not be less than 0.6MPa), and keep it unchanged for 24 hours. At this time, the sealing of the inner closed wall 2 meets the requirements; after the sealing test is completed, remove the external gas injection hose from the gas injection pipe 5;

[0079] S5, filling gravel 13 from inside to outside along the outer side of the inner closed wall 2, in the process of filling the gravel 13, connecting the extended gas injection pipe 5 and the gas production pipe 8 in sequence, and laying the grouting pipe 6, the specific implementation steps are:

[0080] Reference Figure 6 and Figure 8The crushed stones 13 generated by the excavation of the rock tunnel are directly transported to the abandoned tunnel 1, and the crushed stones 13 are filled from the inside to the outside along the outer side of the first outer wall 23 of the inner closed wall 2. During the filling process of the crushed stones 13, the crushed stones 13 with smaller blocks are placed on the upper part of the abandoned tunnel 1. During the filling process of the crushed stones 13, multiple gas injection pipes 5 are connected in sequence at the tail end of the gas injection pipe 5. When the gas injection pipe 5 is laid to the vicinity of the openings of the adjacent four boreholes 7, four tees 14 are installed in sequence on the gas injection pipe 5, which are connected to the four boreholes 7 respectively. The L-shaped elbow pipe 11 on the hole 7 is connected, and the gas injection pipe 5 is installed on the outermost tee 14, so that the stainless steel capillary enters the gas injection pipe 5 through the tee 14, and the gravel 13 is continuously filled. The gas injection pipe 5 and all the gas collection pipes 8 are continuously connected and extended outward with the gravel 13 filling; when the gravel 13 is filled to a distance of 15m from the first inner wall 21, the grouting pipe 6 is laid with the gravel 13 filling, and the gas injection pipe 5, the grouting pipe 6 and all the gas collection pipes 8 are continuously connected and extended until the gravel 13 is filled;

[0081] S6, build the outer closed wall 3 and arrange the gas injection pipe 5 and the grouting pipe 6, the specific steps are:

[0082] Reference Figure 5 , Grooving: Build the outer closed wall 3 from the inside to the outside at a distance of 28m from the first inner wall 21. When building the outer closed wall 3, firstly, grooves are cut around the abandoned tunnel 1. First, the axial groove width of the two sides of the abandoned tunnel 1 is 1.0m, and the groove depth is 50cm; then, the axial groove width of the bottom plate is 1.0m, and the groove depth is 50cm when the bottom plate is a coal seam, and the groove depth is 30cm when the bottom plate is a rock layer; finally, the axial groove width of the top plate is 1.0m, and the groove depth is 50cm when the top plate is a coal seam, and the groove depth is 30cm when the top plate is a rock layer;

[0083] Building the second inner wall 31: After the trenching is completed, the second inner wall 31 is built with bricks or stones. When building the second inner wall 31, the gas injection pipe 5 and the grouting pipe 6 are inserted in the horizontal direction. The front ends of the gas injection pipe 5 and the grouting pipe 6 are respectively connected to the gas injection pipe 5 and the grouting pipe 6 laid when the crushed stone 13 is filled. The tail ends of the gas injection pipe 5 and the grouting pipe 6 need to be exposed from the second outer wall 33. After the second inner wall 31 is built, the scrapped tunnel 1 is further trenched according to the above trenching sequence. The trenching width is 1.0m and the trenching depth remains unchanged.

[0084] Filling the second filling material 32 and building the second outer wall 33: When loess is used as the second filling material 32, bricks or stones are used to build the second outer wall 33 at the position of the second outer wall 33, and loess is filled between the second outer wall 33 and the second inner wall 31 as the second outer wall 33 is built; When fluid concrete is used as the second filling material 32, after the second inner wall 31 is built, the scrapped lane 1 is continuously cut in accordance with the above-mentioned cutting sequence, and the cutting depth and width remain unchanged, and then bricks or stones are used to build the first outer wall 23 at the position of the second outer wall 33. During the construction, a grouting pipe 6 (not shown in the figure) is additionally provided on the first outer wall 23. After the first outer wall 23 is built, fluid concrete is injected into the space between the first inner wall 21 and the first outer wall 23 through the grouting pipe 6. After the fluid concrete hardens, the grouting pipe 6 is removed, and the installation position of the grouting pipe 6 is blocked;

[0085] S7, injecting grouting material into the abandoned tunnel 1 filled with crushed stone 13 and hardening it:

[0086] The tail end of the grouting pipe 6 on the outer closed wall 3 is connected to the feed pipe for inputting grouting material in the scrapped tunnel 1, and the feed pipe is connected to the grouting pump. The grouting pump is used to inject the grouting material into the scrapped tunnel 1 filled with crushed stone 13 through the feed pipe and the grouting pipe 6, and fill it up. After the grouting is completed, wait for it to harden;

[0087] S8, coal working face recovery, connect the extended gas injection pipe 5 and the gas production pipe 8 in sequence, and observe the pressure of CO2 gas 12 in the scrapped tunnel 1. If the pressure drops, replenish CO2 gas 12. The specific steps include:

[0088] As the coal mining face is continuously mined, the roof of the goaf 16 will collapse periodically. While the coal mining face is being mined, the gas injection pipe 5 outside the outer closed wall 3 and the gas production pipe 8 inside it are continuously connected;

[0089] Each time the gas injection pipe 5 is connected, it is necessary to connect the gas injection pipe 5 to the external gas injection hose on one side of the coal mining face. The external gas injection hose is provided with a pressure gauge and a valve. The pressure gauge value must be checked each time the connection is made. When it is observed that the pressure of the CO2 gas 12 in the scrapped tunnel 1 drops by 10% compared with the pressure in step S2, it is necessary to replenish the CO2 gas 12 through the gas injection pipe 5 to restore its pressure to 120% of the gas pressure in the coal seam.

[0090] S9, Liquid CO215 filling:

[0091] Reference Figure 7, when the top plate of the goaf 16 is continuously collapsed to compact the goaf 16 (in this embodiment, the top plate of the goaf 16 is collapsed 5 times), the tail end of the gas injection pipe 5 is connected to the external gas injection hose. Before injection, all the pipe openings of the gas production pipes 8 must be blocked first, and then liquid CO215 is injected into the scrapped tunnel 1 on the inner side of the inner closed wall 2 until the pressure of the liquid CO215 in the scrapped tunnel 1 reaches 12MPa. At this time, the valve on the external gas injection hose is closed and the pressure gauge is removed, and the external gas injection hose is disassembled from the gas injection pipe 5; since it is no longer necessary to inject CO2 gas 12 into the scrapped tunnel 1 at this time, the tail end of the gas injection pipe 5 is connected to the 1-inch pipeline through a reducer. On the one hand, the 1-inch pipeline can be used to protect the gas production pipe 8, and on the other hand, the construction cost can be reduced;

[0092] S10, CO2 gas 12 diffusion range detection:

[0093] As the coal mining face continues to advance, the 1-inch pipeline and the gas production pipe 8 inside it are continuously connected, and the gas in each borehole 7 is sampled through the gas production pipe 8 at least once a day to observe the diffusion radius of the CO2 gas 12 around the scrapped tunnel 1. When the CO2 gas 12 concentration in the gas sample in a certain borehole 7 is detected to be more than 50% for three consecutive days, it is considered that the CO2 gas 12 has diffused to that place and the gas production pipe 8 in the borehole 7 is blocked, and it will no longer be tested or extended in the future; this cycle is repeated until the coal mining face is recovered.

[0094] The above contents are only preferred embodiments of the present invention. For ordinary technicians in this field, many changes can be made in the specific implementation methods and application scopes based on the ideas of the present invention. As long as these changes do not deviate from the concept of the present invention, they all belong to the protection scope of the present invention.

Claims

1. A method for filling abandoned tunnels with multiphase materials in a self-igniting coal seam mining working face, characterized in that: The specific steps include: S1. Determination of the closed position of the scrapped tunnel: Two closed walls are built in the scrapped tunnel, namely an inner closed wall and an outer closed wall. The outer closed wall is built at the connection between the scrapped tunnel and the cut eye, and the inner closed wall is built on the inner side of the scrapped tunnel at a distance L from the outer closed wall. S2. Drill holes next to the abandoned tunnel to lay out the gas production pipe: On the sidewall of the abandoned tunnel adjacent to the inner closed wall, several boreholes are constructed in the outer coal seam of the abandoned tunnel away from the cutting eye, a gas production pipe is placed in each borehole, and each borehole is sealed with a plugging material, the gas production pipe is fixed, and the outer end of the plugging material is flush with the borehole opening, and a gap is left between the inner end of the plugging material and the bottom of the borehole as a gas production chamber, the head end of the gas production pipe is placed in the gas production chamber, and an L-shaped elbow pipe is provided at the opening of each borehole, and the tail end of the gas production pipe passes through the L-shaped elbow pipe; S3. Build an inner closed wall in the scrapped tunnel and arrange a gas injection pipe; S4. Inject CO2 gas into the scrapped tunnel on the inner side of the inner closed wall through the gas injection pipe and perform a tightness test; S5. Fill gravel along the outer side of the inner sealed wall from inside to outside. During the filling process of gravel, connect the extended gas injection pipe and gas production pipe in sequence, and lay the grouting pipe; S6. Build the outer closed wall and arrange the gas injection pipe and grouting pipe; S7, injecting grouting material into the scrapped tunnel filled with crushed stone and hardening it; S8, coal working face recovery, connect the extended gas injection pipe and gas production pipe in sequence, and observe the CO2 gas pressure in the scrapped tunnel. If the pressure drops, add CO2 gas; S9, Liquid CO2 filling: When the goaf roof continues to collapse and compacts the goaf, connect the tail end of the gas injection pipe to the external gas injection hose. Before injection, all the pipe openings of the gas production pipes must be blocked first, and then liquid CO2 is injected into the scrapped tunnel inside the inner closed wall, and the tail end of the gas injection pipe is connected to the 1-inch pipeline through a reducer; S10. Detection of CO2 gas diffusion range: As the coal mining face continues to advance, the 1-inch pipeline and the gas production pipe inside it are continuously connected, and the gas in each borehole is sampled through the gas production pipe to detect the CO2 gas concentration, thereby realizing the detection of the CO2 gas diffusion range. When the CO2 gas concentration in the gas sample in a certain borehole is detected to be more than 50% for three consecutive days, it is considered that CO2 gas has diffused to the borehole, and the gas production pipe in the borehole is blocked. In the future, CO2 gas detection and gas production pipe extension will no longer be performed on the borehole, and this cycle will be repeated until the coal mining face is recovered.

2. A method for filling abandoned tunnels with multiphase materials in a self-igniting coal seam mining working face as claimed in claim 1, characterized in that: The inner closed wall includes a first inner wall, a first filler and a first outer wall, and an air injection pipe is inserted through the first inner wall, the first filler and the first outer wall; the outer closed wall includes a second inner wall, a second filler and a second outer wall, and an air injection pipe and a grouting pipe are inserted through the second inner wall, the second filler and the second outer wall; L=30m; The total thickness of the inner closed wall is 3.0m, the thickness of the first inner wall and the first outer wall are both 0.37m, and the thickness of the first filler is 2.26m; the total thickness of the outer closed wall is 2.0m, the thickness of the second inner wall and the second outer wall are both 0.37m, and the thickness of the second filler is 1.26m.

3. A method for filling abandoned tunnels with multiphase materials in a self-igniting coal seam mining working face as claimed in claim 1, characterized in that: In step S2, the specific steps of constructing a plurality of boreholes on the sidewall of the abandoned roadway adjacent to the inner closed wall and far from the cutting hole, and in the outer coal seam of the abandoned roadway far from the cutting hole are as follows: Construct multiple holes on the side of the abandoned roadway adjacent to the inner closed wall, with the horizontal distance between each hole along the direction of the roadway being 0.5m, and then construct a drilling hole in the outer coal seam of the abandoned roadway away from the side of the cutting eye at each hole; the diameter of the drilling hole is 75mm, and the horizontal distance between the line connecting the positions of the end holes of each drilling hole and the inner wall of the inner closed wall is 10m, the spacing between the positions of the end holes of each drilling hole is 2m, the drilling hole closest to the side of the abandoned roadway is 4m away from the side of the abandoned roadway; the straight-line distance k between the drilling hole closest to the abandoned roadway wall and the outer edge of the inner outer wall of the inner closed wall is not less than 1m; Height of drilling hole: If the coal seam thickness is less than the roadway height, the final hole position is half of the coal seam thickness; if the coal seam thickness is higher than the roadway height, the final hole position is half of the roadway height.

4. A method for filling abandoned tunnels with multiphase materials in a self-igniting coal seam mining working face as claimed in claim 1, characterized in that: In step S2, the total length d of the plugging material in the borehole is not less than 15m, and the length l of the gas collection chamber is 20cm-50cm; the gas collection pipe is a stainless steel capillary tube, and the outer diameter of the stainless steel capillary tube is 2mm-3mm.

5. A method for filling abandoned tunnels with multiphase materials in a spontaneous combustion coal seam mining working face as claimed in claim 1, characterized in that: In step S3, the specific steps of building the inner closed wall and arranging the gas injection pipe are: Grooving: Grooving is performed around the abandoned roadway at a distance of 30m from the opening of the coal mining face. First, the axial groove width of the two sides of the abandoned roadway is 1.0m, and the groove depth is 50cm; then the axial groove width of the bottom plate is 1.0m, and the groove depth is 50cm when the bottom plate is a coal seam, and the groove depth is 30cm when the bottom plate is a rock layer; finally, the axial groove width of the top plate is 1.0m, and the groove depth is 50cm when the top plate is a coal seam, and the groove depth is 30cm when the top plate is a rock layer; Building the first inner wall: after the trenching is completed, the first inner wall is built with bricks or stones. When building the first inner wall, the gas injection pipe is inserted horizontally. The front end of the gas injection pipe passes through the first inner wall and penetrates 2.0m into the scrapped tunnel. The tail end of the gas injection pipe passes through the first filling material and the first outer wall in turn. After the first inner wall is built, the scrapped tunnel is further trenched in the above trenching sequence. The trenching width is 2.0m and the trenching depth remains unchanged. Filling the first filling material and building the first exterior wall: when loess is the first filling material, bricks or stones are used to build the first exterior wall at the position of the first exterior wall, and loess is filled between the first exterior wall and the first interior wall as the first exterior wall is built; when fluid concrete is used as the first filling material, after the first interior wall is built, the scrapped tunnel is continued to be trenched in the above-mentioned trenching sequence, the trenching depth remains unchanged, and the trenching width is 2.0m. Then, bricks or stones are used to build the first exterior wall at the position of the first exterior wall. During the construction, a grouting pipe is additionally reserved on the first exterior wall. After the first exterior wall is built, fluid concrete is injected between the first interior wall and the first exterior wall through the grouting pipe. After the fluid concrete hardens, the grouting pipe is removed and the installation position of the grouting pipe is sealed.

6. A method for filling abandoned tunnels with multiphase materials in a self-igniting coal seam mining working face as claimed in claim 1, characterized in that: In step S4, the specific steps of injecting CO2 gas into the scrapped tunnel on the inner side of the inner closed wall through the gas injection pipe and performing airtightness detection are: The tail end of the gas injection pipe on the outside of the first outer wall is connected to the external gas injection hose in the scrapped tunnel. In order to prevent the gas from entering the stainless steel capillary, it is necessary to seal the pipe openings of each gas production pipe before gas injection, and inject CO2 gas into the scrapped tunnel inside the inner closed wall through the external gas injection hose and the gas injection pipe until the gas pressure in the scrapped tunnel exceeds 20% of the coal seam gas pressure and remains unchanged for 24 hours. At this time, the sealing of the inner closed wall meets the requirements; after the sealing test is completed, the external gas injection hose is removed from the gas injection pipe.

7. A method for filling abandoned tunnels with multiphase materials in a spontaneous combustion coal seam mining working face as claimed in claim 1, characterized in that: The specific steps of step S5 are: The crushed stone produced by the excavation of the rock tunnel is directly transported to the scrapped tunnel, and the crushed stone is filled from the inside to the outside along the outer side of the inner closed wall. During the filling process of the crushed stone, multiple gas injection pipes are connected in sequence at the tail end of the gas injection pipe. When the gas injection pipe is laid to the vicinity of the openings of the four adjacent boreholes, four tees are installed on the gas injection pipe in sequence, and are respectively connected to the L-shaped elbow pipes on the four boreholes, so that the gas production pipe enters the gas injection pipe through the tees. The gas injection pipe is installed on the outermost tee to continue filling with crushed stone. The gas injection pipe and all gas production pipes are continuously connected and extended outward with the crushed stone filling; when the crushed stone filling is 15m away from the first inner wall, the grouting pipe is laid with the crushed stone filling, and the gas injection pipe, grouting pipe and all gas production pipes are continuously connected and extended until the crushed stone filling is completed.

8. A method for filling abandoned tunnels with multiphase materials in a self-igniting coal seam mining working face as claimed in claim 1, characterized in that: In step S6, the specific steps of building the outer closed wall and arranging the gas injection pipe and the grouting pipe are as follows: Grooving: Build the outer closed wall from the inside to the outside at a distance of 28m from the first inner wall. When building the outer closed wall, firstly, groove the surroundings of the abandoned tunnel. First, the axial groove width of the two sides of the abandoned tunnel is 1.0m, and the groove depth is 50cm; then the axial groove width of the bottom plate is 1.0m, and the groove depth is 50cm when the bottom plate is a coal seam, and the groove depth is 30cm when the bottom plate is a rock layer; finally, the axial groove width of the top plate is 1.0m, and the groove depth is 50cm when the top plate is a coal seam, and the groove depth is 30cm when the top plate is a rock layer; Building the second inner wall: After the trenching is completed, the second inner wall is built with bricks or stones. When building the second inner wall, the air injection pipe and the grouting pipe are inserted horizontally. The front ends of the air injection pipe and the grouting pipe are respectively connected to the air injection pipe and the grouting pipe laid during the crushed stone filling. The tail ends of the air injection pipe and the grouting pipe must be exposed from the second outer wall. After the second inner wall is built, the scrapped tunnel is further trenched in accordance with the above trenching sequence. The trenching width is 1.0m and the trenching depth remains unchanged. Filling the second filling material and building the second outer wall: when loess is used as the second filling material, bricks or stones are used to build the second outer wall at the position of the second outer wall, and loess is filled between the second outer wall and the second inner wall as the second outer wall is built; when fluid concrete is used as the second filling material, after the second inner wall is built, the scrapped tunnel is continued to be grooved in accordance with the above-mentioned groove excavation sequence, and the groove depth and width remain unchanged, and then bricks or stones are used to build the first outer wall at the position of the second outer wall. During the construction, a grouting pipe is additionally reserved on the first outer wall. After the first outer wall is built, fluid concrete is injected between the first inner wall and the first outer wall through the grouting pipe. After the fluid concrete hardens, the grouting pipe is removed and the installation position of the grouting pipe is sealed.

9. A method for filling abandoned tunnels with multiphase materials in a spontaneous combustion coal seam mining working face as claimed in claim 1, characterized in that: The specific steps of step S7 are: The tail end of the grouting pipe on the outer closed wall is connected to the feed pipe in the scrapped tunnel for inputting grouting materials. The feed pipe is connected to the grouting pump. The grouting pump is used to inject the grouting material into the scrapped tunnel filled with gravel through the feed pipe and the grouting pipe, and fill it up. After the grouting is completed, wait for it to harden.

10. A method for filling abandoned tunnels with multiphase materials in a self-igniting coal seam mining working face as claimed in claim 1, characterized in that: The specific steps of step S8 are: As the coal mining face is continuously mined, the roof of the goaf will collapse periodically. While the coal mining face is being mined, the gas injection pipe outside the outer closed wall and the gas production pipe inside it are continuously connected; Each time the gas injection pipe is connected, it is necessary to connect the gas injection pipe to the external gas injection hose on one side of the coal mining working face. The external gas injection hose is provided with a pressure gauge and a valve. The pressure gauge value must be checked each time a connection is made. When it is observed that the CO2 gas pressure in the scrapped tunnel is 10% lower than the pressure in step S2, it is necessary to replenish CO2 gas through the gas injection pipe to restore its pressure to 120% of the gas pressure in the coal seam.

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