Method for preventing and treating coal rock dynamic disasters on driving face through advanced water injection

Abstract

The invention relates to a method for preventing and treating coal rock dynamic disasters on a driving face through advanced water injection. The method comprises the following steps that 1, the advanced water injection width is determined; 2, the number of advanced water injection drill holes is determined; 3, determining the length of the advanced water injection drill hole; 4, advanced water injection construction time is determined; 5, an advanced water injection construction process; and step 6, tunneling. The method can solve the problems of large work amount, long time and the like of gas mining control of high-gas and outburst coal seams, and the problem that the tunneling speed is influenced by cross operation of tunneling and drilling during rock burst coal seam mining, and can continuously inject water into roadway surrounding rocks in the roadway tunneling process, continuously weaken a coal body and reduce the gas release speed, thereby improving the mining efficiency of the roadway. And gas outburst and rock burst risks are reduced.

Description

Technical Field

[0001] The invention relates to a method for preventing and controlling coal-rock dynamic disasters in a tunneling working face by advanced water injection, and belongs to the technical field of coal-rock dynamic disaster prevention and control and coal mining. Background Art

[0002] As the main body of my country's energy structure, the stable supply of coal is vital to national energy security. However, with the increasing depletion of shallow coal resources, deep mining has become a strategic choice to ensure my country's energy security. As the mining depth continues to increase, the coal seam environment has changed significantly, showing complex characteristics such as high ground stress, strong gas adsorption and low permeability, resulting in frequent coal-rock dynamic disasters, which seriously restricts the efficient and safe production of coal mines. This situation poses a severe challenge to the safe and efficient development of deep coal resources, and it is urgent to solve the key scientific problems in deep mining through technological innovation and theoretical breakthroughs.

[0003] In the mining process of high-gas or coal seams with outbursts, the traditional method usually adopts high-level tunnels or bottom extraction tunnels to arrange through-layer drilling holes for gas extraction and water injection prevention and control. However, this method has problems such as large engineering workload, long time consumption, and poor through-layer pre-extraction effect. It is easy to form a blank zone for prevention and control, which significantly increases the risk of coal and gas outbursts. For coal seams with rock burst, the existing technology mostly adopts the method of cross-operation of tunneling and drilling pressure relief or water injection pressure relief, which seriously restricts the efficiency of tunnel excavation. In addition, after the tunnel pressure relief drilling hole fails, it is difficult to implement secondary pressure relief prevention and control in time, which further increases the impact risk behind the excavation working face. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for pre-water injection to prevent and control coal rock dynamic disasters in the tunneling working face. The method can solve the problems of large amount of gas control engineering and long time in the mining of high-gas and protruding coal seams, as well as the problem of cross-operation of tunneling and drilling affecting the tunneling speed during the mining of rock burst coal seams. At the same time, water can be continuously injected into the surrounding rock of the tunnel during the tunnel excavation process to continuously weaken the coal body and reduce the gas release rate, thereby reducing the risk of gas burst and rock burst.

[0005] To solve the above problems, the specific technical solution of the present invention is as follows: A method for preventing and controlling coal-rock dynamic disasters in a tunneling working face by advanced water injection comprises the following steps: Step 1: Determine the advance water injection width: Collect the design parameters of the tunnel to be excavated and the coal seam thickness data in the excavation area, and determine the advance water injection width N through the following formula: N=S+2c (1) Where S is the width of the lane; c is the width of the disaster prevention area on one side of the lane; Step 2: Determine the number of advance water injection boreholes: According to the actual conditions of the mine, the high-pressure water injection fracturing radius R is determined by combining on-site measurements or numerical simulations. The spacing between the advance water injection holes is 2R, and the number of holes K in a single tunnel is calculated and determined by the following formula: (2) in It is a rounding operation, that is, taking the integer part of the calculation result; Step 3: Determine the length of the advance water injection drilling hole: The water injection drilling holes are arranged in the middle of the coal seam and constructed along the direction of the roadway by directional drilling. The length is determined by the designed direction length L of the roadway and the width c of the disaster prevention area on one side of the roadway. The length of the water injection drilling holes in the two chute of the working face is L+c, and the cut eye is Lc. Step 4: Determine the advance water injection construction time: Reasonably arrange the start time of advanced water injection drilling construction according to the planned excavation time of the tunnel to be excavated, the gas extraction time, and the high-pressure water injection fracturing time to ensure that the advanced water injection measures have been completed when each tunnel to be excavated starts excavation; Step 5: Advance water injection construction process: After the construction of advanced water injection drilling begins, the first directional drilling hole is first arranged in the center of the tunnel to be excavated, and then other drilling holes are arranged in sequence with a spacing of 2R on both sides of the center hole, and the number of holes on one side is (K-1) / 2; after the drilling construction is completed, high-pressure water injection fracturing is carried out in sections from the inside to the outside along each drilling hole until the remaining outer section of the drilling hole is 20 to 30 meters without fracturing; after fracturing, the outer section of each drilling hole is sealed, and the sealing length is determined according to the coal seam conditions; after the sealing is completed, if the coal seam is high-gas or protruding coal seam, all drilling holes are first subjected to gas extraction, and after the gas extraction is completed, static pressure water injection is immediately carried out until the designed water injection volume is reached or a large amount of water is discharged from the coal wall; Step 6: Digging After the water injection is completed, the water injection device in the tunnel to be excavated is removed, and the water injection device outside the 10m range outside the tunnel outline is retained; in the process of excavation, the water injection device outside the 10m range outside the tunnel outline is opened every 100m of excavation, and static pressure water injection is continued until water is discharged from the wall of the excavated tunnel, so as to maintain the moisture content of the tunnel surrounding rock and coal body and reduce the risk of increased dynamic disasters in the tunnel due to water loss.

[0006] In step 1, the width c of the single-side disaster prevention and control area of ​​the tunnel is determined according to the thickness of the coal seam in the excavation area. When the thickness of the coal seam is less than 3.5 meters, c is not less than 15 meters; when the thickness of the coal seam is 3.5 to 8 meters, c is not less than 20 meters; when the thickness of the coal seam is greater than 8 meters, c is not less than 25 meters.

[0007] The method for preventing and controlling coal-rock dynamic disasters in the tunneling working face by pre-injection water injection in this application adopts the above technical solution, which has the following beneficial effects: 1. The method provided by the present invention arranges water injection drilling holes before excavating the roadway to be excavated, injects high-pressure water for fracturing, forms a large number of cracks in the coal body of the roadway to be excavated and the surrounding rock area, increases the permeability of the coal body, reduces the stress concentration of the coal body, and improves the gas extraction efficiency. At the same time, water injection can continue during the excavation process to continuously weaken the roadway excavation area and the surrounding rock and reduce the gas release rate, thereby greatly reducing the risk of gas outburst. Compared with arranging through-layer drilling holes in high-position rock lanes or bottom-pumping rock lanes before coal seam roadway excavation for gas extraction and water injection, the present invention has the advantages of reducing engineering workload, shortening engineering time, and improving prevention and control effects; 2. In the method provided by the present invention, while not affecting the excavation construction, the integrity of the excavation area and the surrounding rock is destroyed by high-pressure water fracturing, the impact tendency of the coal body is reduced, and water is continuously injected to weaken the coal body during the excavation process, thereby reducing stress concentration and improving the anti-impact effect. Compared with the traditional cross-operation of excavation and drilling pressure relief or water injection pressure relief, the present invention can improve the anti-impact effect without affecting the excavation speed, and has the advantage of improving the excavation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a top view of the working surface of an embodiment of the present invention.

[0009] Figure 2 For along Figure 1 Vertical section of the tunnel.

[0010] In the figure: 1 - excavated tunnel; 2 - transport tunnel to be excavated; 3 - cutting tunnel to be excavated; 4 - return air tunnel to be excavated; 5 - coal body; 6 - working face; 7 - water injection drilling hole; 8 - tunnel to be excavated. DETAILED DESCRIPTION

[0011] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0012] The coal seam mining thickness of a certain working face in a certain mine is 4.5 meters. Figure 1 As shown in the figure, the tunnel construction plan is: the length of the transport tunnel is 200 meters and the width is 5 meters; the length of the return air tunnel is 200 meters and the width is 5 meters; the length of the cut-eye tunnel is 100 meters and the width is 5 meters. The transport tunnel is the first tunnel to be excavated, and the return air tunnel is the last tunnel to be excavated. According to the field experiment, the radius of high-pressure water injection fracturing is 3.5 meters. The gas content of this coal seam is high, and gas prevention and control is required.

[0013] For the above-mentioned coal seams, the method of pre-injection water to prevent and control coal-rock dynamic disasters in the excavation working face includes the following steps: Step 1: Determine the advance water injection width.

[0014] The coal seam thickness in the excavation area is 4.5 meters. The width c of the disaster prevention area on one side of the tunnel is 23 meters. The width S of the three tunnels is 5 meters. According to formula (1), the advance water injection width N of the three tunnels is 51 meters.

[0015] Step 2: Determine the number of advance water injection boreholes.

[0016] The radius of high-pressure water injection fracturing measured on site is 3.5 meters. According to formula (2), the number of advance water injection drilling holes K in the three tunnels is 9.

[0017] Step 3: Determine the length of the advance water injection drilling hole.

[0018] The designed strike length of the first and second tunnels is 200 meters, c is 23 meters, the length of the water injection drilling holes in the transport tunnel and return air tunnel is 223, and the length of the cut-eye water injection drilling holes is 77 meters.

[0019] Step 4: Determine the construction time of advance water injection.

[0020] The start time of the advance water injection drilling construction is determined based on the planned excavation time of the tunnel to be excavated, the gas extraction time, and the high-pressure water injection fracturing time to ensure that the advance water injection measures are completed when each tunnel to be excavated begins excavation.

[0021] According to the actual situation of the on-site project, it is estimated that it will take 269 days to complete the excavation construction of the first tunnel and 257 days to complete the construction of the second tunnel. According to the actual measurement on site, it is estimated that it will take 40 days to complete the advance water injection construction of the second tunnel and 30 days to complete the advance water injection construction of the cut-eye tunnel. Therefore, the advance water injection construction of the second tunnel will be started before the 229th day of the construction of the first tunnel; and the advance water injection construction of the cut-eye tunnel will be started before the 227th day of the construction of the second tunnel.

[0022] Step 5: Advance water injection construction process.

[0023] After the construction of the advanced water injection drilling begins, Figure 2 First, arrange the first directional borehole in the center of the tunnel to be excavated, and then arrange other boreholes on both sides of the center hole with a spacing of 7 meters. The number of holes on a single side is 4. After the drilling construction is completed, high-pressure water injection and fracturing are carried out in sections from the inside to the outside along each borehole until the remaining 20 to 30 meters of the outer section of the borehole are not fractured. After fracturing, the outer section of each borehole is sealed, and the sealing length is determined according to the coal seam conditions. After the sealing is completed, all boreholes are first subjected to gas extraction. After the gas extraction is completed, static pressure water injection is immediately carried out until the designed water injection volume is reached or a large amount of water is discharged from the coal wall.

[0024] Step 6: Digging.

[0025] After the water injection is completed, the water injection device in the tunnel to be excavated is removed, and the water injection device outside the 10m range outside the tunnel outline is retained; in the process of excavation, the water injection device outside the 10m range outside the tunnel outline is opened every 100m of excavation, and static pressure water injection is continued until water is discharged from the wall of the excavated tunnel, so as to maintain the moisture content of the tunnel surrounding rock and coal body and reduce the risk of increased dynamic disasters in the tunnel due to water loss.

[0026] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which are all within the protection of the present invention.

Claims

1. A method for preventing and controlling coal-rock dynamic disasters at a tunneling working face by pre-injection water injection, characterized in that The steps include: Step 1: Determine the advance water injection width: Collect the design parameters of the tunnel to be excavated and the coal seam thickness data in the excavation area, and determine the advance water injection width N through the following formula: N = S + 2 × c (1) Where S is the width of the lane; c is the width of the disaster prevention area on one side of the lane; Step 2: Determine the number of advance water injection boreholes: According to the actual conditions of the mine, the high-pressure water injection fracturing radius R is determined by combining on-site measurements or numerical simulations. The spacing between the advance water injection holes is 2R, and the number of holes K in a single tunnel is calculated and determined by the following formula: （2） in It is a rounding operation, that is, taking the integer part of the calculation result; Step 3: Determine the length of the advance water injection drilling hole: The water injection drilling holes are arranged in the middle of the coal seam and constructed along the direction of the roadway by directional drilling. The length is determined by the designed direction length L of the roadway and the width c of the disaster prevention area on one side of the roadway. The length of the water injection drilling holes in the two chute of the working face is L+c, and the cut eye is Lc. Step 4: Determine the advance water injection construction time: Reasonably arrange the start time of advanced water injection drilling construction according to the planned excavation time of the tunnel to be excavated, the gas extraction time, and the high-pressure water injection fracturing time to ensure that the advanced water injection measures have been completed when each tunnel to be excavated starts excavation; Step 5: Advance water injection construction process: After the construction of advanced water injection drilling begins, the first directional drilling hole is first arranged in the center of the tunnel to be excavated, and then other drilling holes are arranged in sequence with a spacing of 2R on both sides of the center hole, and the number of holes on one side is (K-1) / 2; after the drilling construction is completed, high-pressure water injection fracturing is carried out in sections from the inside to the outside along each drilling hole until the remaining outer section of the drilling hole is 20 to 30 meters without fracturing; after fracturing, the outer section of each drilling hole is sealed, and the sealing length is determined according to the coal seam conditions; after the sealing is completed, if the coal seam is high-gas or protruding coal seam, all drilling holes are first subjected to gas extraction, and after the gas extraction is completed, static pressure water injection is immediately carried out until the designed water injection volume is reached or a large amount of water is discharged from the coal wall; Step 6: Digging After the water injection is completed, the water injection device in the tunnel to be excavated is removed, and the water injection device outside the 10m range outside the tunnel outline is retained; in the process of excavation, the water injection device outside the 10m range outside the tunnel outline is opened every 100m of excavation, and static pressure water injection is continued until water is discharged from the wall of the excavated tunnel, so as to maintain the moisture content of the tunnel surrounding rock and coal body and reduce the risk of increased dynamic disasters in the tunnel due to water loss.

2. The method for preventing and controlling coal-rock dynamic disasters in a tunneling working face by advanced water injection according to claim 1 is characterized in that: In step 1, the width c of the single-side disaster prevention and control area of ​​the tunnel is determined according to the thickness of the coal seam in the excavation area. When the thickness of the coal seam is less than 3.5 meters, c is not less than 15 meters; when the thickness of the coal seam is 3.5 to 8 meters, c is not less than 20 meters; when the thickness of the coal seam is greater than 8 meters, c is not less than 25 meters.

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