Drainage and consolidation combined outburst elimination method for pulverized coal seam

Abstract

The invention discloses a coal seam drainage and solid combination outburst elimination method, and relates to the technical field of high outburst gas tunnel coal seam gas control. The method comprises the following steps: step 1, drilling a coal seam on the outer side of a tunnel main hole; secondly, hydraulic punching is conducted on the drill hole corresponding to the isolation structure to be formed, coal around the end hole of the drill hole and in front of the end hole of the drill hole are discharged, and a cavity is formed; thirdly, the drilled hole subjected to hydraulic punching is blocked, and gas of the drilled hole subjected to hydraulic punching is pumped and drained; step 4, filling the cavity to form an isolation structure; fifthly, the first step to the third step are repeated, so that the multiple isolation structures form an isolation belt surrounding the tunnel main hole on the outer side of the tunnel main hole; step 6, reinforcing the isolation belt; and seventhly, gas drainage is conducted on all the drill holes which are not subjected to hydraulic punching. The anti-reflection effect of the powder coal seam of the high outburst gas tunnel is improved, the gas drainage efficiency is improved, the outburst elimination effect is enhanced, and the purpose of coal uncovering conditions is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of coal seam gas control in high-outburst gas tunnels, and in particular to a method for eliminating outbursts in a pulverized coal seam by combining solid removal. Background Art

[0002] The technology to eliminate the outburst of pulverized coal gas in tunnels with extremely deep burial depth (kilometer level), high ground stress environment (44.42MPa), large deformation (≥1m), multi-layer (9 layers), and extremely poor permeability is a world-class problem that has not been solved yet. The coal seam is powdery, the coal seam permeability coefficient is much less than the critical value of the difficult extraction, and the borehole gas attenuation coefficient is much greater than the critical value of the difficult extraction, indicating that the coal seam gas is extremely difficult to extract, and has the characteristics of high gas adsorption capacity, low fluidity, and extremely fast attenuation. Regarding the research on permeability enhancement of low permeability coal seams, the main methods of permeability enhancement of coal seams at home and abroad can be summarized into two categories: pressure relief and external physical field. Among them, the pressure relief method includes dense drilling method, hydraulic method (hydraulic punching, hydraulic fracturing), blasting fracturing method, CO2 phase change gas explosion fracturing method, construction of multi-branch horizontal wells, etc.; the external physical field mainly includes water injection / gas displacement, heat injection, external electric field, ultrasonic vibration, electric pulse and electrochemistry, etc. Practice has proved that these methods have played a certain positive role in strengthening coal seam gas extraction. However, when the burial depth of the coal seam increases (kilometer level), due to the high ground stress-pulverized coal coupling characteristics such as ultra-deep burial, high ground stress, soft coal seam, large coal seam thickness and small spacing, the existing technology has poor permeability enhancement effect and low gas extraction efficiency, and the conditions for eliminating coal bursts and uncovering cannot be achieved in a short time. Summary of the invention

[0003] The purpose of the present invention is to provide a method for combining solid removal and outburst elimination in pulverized coal seams, which improves the permeability enhancement effect of pulverized coal seams in high outburst gas tunnels, increases gas extraction efficiency, enhances outburst elimination effects, and achieves the purpose of coal uncovering conditions.

[0004] To achieve the above object, the present invention provides the following solutions: The present invention provides a method for removing solids from a pulverized coal seam and eliminating outbursts, comprising the following steps: Step 1: Drilling the coal seam outside the tunnel main hole; Step 2: After the drilling is completed, hydraulic punching is performed on the borehole corresponding to the isolation structure to discharge the coal body around and in front of the end hole of the drilling to form a cavity; Step 3, plugging the drilled holes that have been hydraulically punched, and draining the gas from the drilled holes that have been hydraulically punched; Step 4: After the coal seam gas extraction is completed, cement slurry is injected into the cavity to fill the cavity and form an isolation structure; Step 5, repeating steps 1 to 3, so that a plurality of isolation structures form an isolation zone around the tunnel main hole outside the tunnel main hole; Step 6: Reinforce the isolation belt; Step seven, extract gas from the boreholes that have not been hydraulically flushed.

[0005] Preferably, in step one, the coal seam gas extraction range is a range set outside the excavation contour lines on both sides of the tunnel main tunnel in the direction of the coal seam and a certain distance above and below the excavation contour lines. The drill holes penetrate all coal seams to be extracted and enter the coal seam floor.

[0006] Preferably, in step one, after drilling a certain distance, a casing is lowered to close the hole and a gas-slag separation device is installed to drain the drilling gas and drill cuttings.

[0007] Preferably, in the step 2, a flushing structure is used to prepare for hydraulic punching and permeability enhancement, the flushing structure includes a water supply pipeline, a water tank and a water pump arranged in sequence, one end of the water supply pipeline extends into the borehole, and the slag flushed out by the flushing structure enters the sedimentation tank through the drainage ditch; the drill rod used for drilling is replaced with a hydraulic punching drill rod compatible with the high-low pressure conversion puncher, and the high-low pressure conversion puncher is used to perform water impact on the coal body near the gas tunnel burst elimination range to flush out the coal powder and form a cavity.

[0008] Preferably, in step three, before sealing the borehole, the borehole is cleaned, an extraction tube is placed in the hole, and the borehole and the extraction tube are sealed. One end of the extraction tube is connected to the cavity, and the other end of the extraction tube is connected to the extraction structure.

[0009] Preferably, in step three, the extraction structure includes an extraction main pipeline, a branch pipeline, a discharge pipeline and a gas extraction pump station, the extraction main pipeline is connected to the branch pipeline, the gas extraction pump station and the extraction pipe respectively, the branch pipeline is connected to several of the discharge pipelines, and each of the discharge pipelines is provided with a valve.

[0010] Preferably, in step four, a grouting pipe is installed in the extraction pipe, the space between the grouting pipe and the extraction pipe is sealed, and cement slurry is injected into the cavity through the grouting pipe. When the grouting pressure reaches the designed final pressure, the pressure is maintained and the grouting is terminated to form an isolation structure after hardening.

[0011] Preferably, in step six, the gas extraction holes are blocked, and a number of pillars are arranged between the tunnel main hole and the isolation zone to reinforce the isolation zone.

[0012] Preferably, in the step seven, before sealing the boreholes that have not been hydraulically punched, the boreholes that have not been hydraulically punched are cleaned, an extraction tube is placed in the hole, and the boreholes that have not been hydraulically punched and the extraction tube are sealed. One end of the extraction tube is connected to the cavity, and the other end of the extraction tube is connected to the extraction structure, and gas is extracted from each borehole that has not been hydraulically punched.

[0013] Compared with the prior art, the present invention has achieved the following technical effects: The method for combining solidification and drainage of pulverized coal seams of the present invention is characterized in that "drainage" refers to gas extraction on the one hand and coal slag extraction on the other hand, both of which increase the permeability and relieve pressure on the coal rock layer; "solidification" refers to cement grouting of the coal seam after hydraulic punching to form coal body solidification. Drainage: After drilling, hydraulic punching is performed to discharge the coal body around and in front of the end hole of the drilling hole to form a cavity, and then the coal seam gas is extracted to achieve the effect of pressure relief and permeability increase of the soft coal seam. After the permeability increase effect of hydraulic punching decays, high-pressure grouting is immediately used. Solidification: After gas extraction for a period of time, grouting of the coal rock body is performed through the extraction holes to fill the cavity formed by hydraulic punching, forming a hard concrete block in the coal body. Grouting is performed using the extraction holes around the tunnel, so that the concrete blocks form a solidified isolation zone outside the anti-burst range of the tunnel, thereby achieving the effect of solidifying the soft coal body. Under the action of additional high-pressure grouting pressure, the coal seam gas can further increase the effect of coal seam gas extraction and permeability increase. Combined drainage and solidification gas control: The combined drainage and solidification method of coal bursting and coal uncovering is carried out multiple times by using the drainage holes set around the gas tunnel, so that after the cement slurry solidifies and hardens, an isolation zone is formed outside the tunnel excavation contour, isolating the main body of the coal seam from the coal body outside the tunnel bursting prevention range, and reinforcing the isolation zone to reduce the high-pressure ground stress of the coal seam roof and floor plates on the coal seam, avoid the extrusion and displacement of the coal body under the high-pressure ground stress of the roof and floor plates, increase the retention time of the subsequent hydraulic punching cavity, and achieve a better bursting elimination effect. The present invention improves the permeability enhancement effect of the pulverized coal seam in the high-burst gas tunnel, improves the gas extraction efficiency, enhances the bursting elimination effect, and achieves the purpose of coal uncovering conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 It is a schematic diagram of the pulverized coal seam solid removal and outburst elimination method of the present invention; Figure 2 It is a schematic diagram of step 1 of the method for solid removal and outburst elimination of pulverized coal seams of the present invention; Figure 3 Schematic diagram of step 2 of the method for removing solids from pulverized coal seams combined with eliminating outbursts according to the present invention Figure 1 ; Figure 4 Schematic diagram of step 2 of the method for removing solids from pulverized coal seams combined with eliminating outbursts according to the present invention Figure 2 ; Figure 5 Schematic diagram of step 3 of the method for removing solids from pulverized coal seams combined with eliminating outbursts according to the present invention Figure 1 ; Figure 6 Schematic diagram of step 3 of the method for removing solids from pulverized coal seams combined with eliminating outbursts according to the present invention Figure 2 ; Figure 7 Schematic diagram of step 4 of the method for removing solids from pulverized coal seams combined with eliminating outbursts of the present invention Figure 1 ; Figure 8 Schematic diagram of step 4 of the method for removing solids from pulverized coal seams combined with eliminating outbursts of the present invention Figure 2 ; Fig. 9 Schematic diagram of step 4 of the method for removing solids from pulverized coal seams combined with eliminating outbursts of the present invention Figure 3 ; Fig.10 This is a schematic diagram of step 5 of the pulverized coal seam solid removal and outburst elimination method of the present invention; Fig.11 It is a schematic diagram of step 6 of the method for solid removal and outburst elimination of pulverized coal seams of the present invention; In the figure: 1-tunnel main hole, 2-coal seam, 3-drill rod, 4-gas-slag separation device, 5-hose, 6-water supply pipeline, 7-water tank, 8-water pump, 9-drainage ditch, 10-sedimentation tank, 11-hydraulic punching drill rod, 12-high and low pressure conversion puncher, 13-water braid, 14-cavity, 15-extraction pipe, 16-sealing pump, 17-gas extraction pump station, 18-extraction main pipeline, 19-branch pipeline, 20-valve, 21-discharge pipeline, 22-grouting pipe, 23-isolation structure, 24-isolation belt, 25-pillar. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The purpose of the present invention is to provide a method for combining solid removal and outburst elimination in pulverized coal seams, which improves the permeability enhancement effect of pulverized coal seams in high outburst gas tunnels, increases gas extraction efficiency, enhances outburst elimination effects, and achieves the purpose of coal uncovering conditions.

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] like Figures 1 to 11As shown, this embodiment provides a method for removing solids from a pulverized coal seam and eliminating outbursts, which is proposed for the characteristics of excavation of pulverized coal seams in high-outburst gas tunnels, and is combined with hydraulic punching and grouting reinforcement, including the following steps: Step 1: Drill a hole in the coal seam 2 outside the tunnel main hole 1.

[0020] Specifically, in step one, the drilling setting is as follows: the coal seam gas extraction range is 15m long along the direction of the coal seam 2 outside the excavation contour line on both sides of the tunnel main tunnel 1 and 10m above and below the excavation contour line. The effective extraction radius of the through-layer drilling pre-extraction of coal seam gas is determined to be 2m. The holes are evenly distributed according to the final hole spacing of 4m in the coal seam 2. The drilling hole spacing is not less than 0.3m. The borehole penetrates all coal seams 2 to be extracted and enters the coal seam floor 0.5m.

[0021] In this embodiment, in step 1, drilling preparation: select ZDY-4000 mining tunnel drilling rig according to the drilling depth, the opening diameter is Φ86mm, the final hole diameter is Φ75mm, and the drill rod 3 diameter is Φ63mm.

[0022] In this embodiment, in step one, the drilling process: implement extraction drilling construction, lower the casing to close the hole opening and install the gas-slag separation device 4 after the hole is opened for 5m, drain the gas and drill cuttings in the hole to ensure the safety of the drilling construction, the hole diameter is φ86mm, and after the hole is opened for 10m, the hole diameter is changed to φ75m.

[0023] Step 2: After the drilling is completed, hydraulic punching is performed on the borehole corresponding to the isolation structure 23 to be formed, and the coal body around and in front of the end of the drilling hole is discharged to form a cavity 14.

[0024] In this embodiment, in step 2, hydraulic punching and permeability enhancement preparation: a flushing structure is used for hydraulic punching and permeability enhancement preparation, and a hydraulic punching technology is selected to enhance the permeability of the coal seam 2 according to the measured coal seam permeability coefficient and the borehole gas flow attenuation coefficient. The flushing structure includes a water supply pipeline 6, a hose 5, a water tank 7 and a water pump 8 arranged in sequence. The diameter of the hose 5 is 25 mm, and the water pump 8 is an ultra-high pressure clean water pump. One end of the water supply pipeline 6 extends into the borehole, and the slag flushed out by the flushing structure enters the sedimentation tank 10 through the drainage ditch 9. The water flow provided by the water supply pipeline 6 needs to be full. The water flow rate required by the water pump 8 during the punching operation is sufficient, and continuous water supply is guaranteed during the punching operation; high-pressure water is discharged from the hole to flush and discharge slag; the water pump 8 can be connected to a 1140V or 660V circuit, and the motor power is 220KW; when drilling and punching, the extraction pipe 15 and the extraction monitoring and metering device must be installed in advance, and the accessories, materials, pipelines, cables, fire-fighting equipment, sealing and extraction materials, measuring instruments, etc. required for sealing and extraction must be prepared, and they must be neatly stacked in a safe place near the construction site, so that the hole can be sealed in time after punching and the extraction can be connected.

[0025] Hydraulic punching and permeability enhancement process: After the drilling construction is completed, the drill rod 3 is withdrawn after the through-layer gas extraction drilling construction reaches the coal seam 2, and the drill rod 3 used for drilling is replaced with a hydraulic punching drill rod compatible with the high-low pressure conversion punch 12. The high-low pressure conversion punch 12 is connected to one end of the hydraulic punching drill rod, and the water braid 13 is connected to the other end of the hydraulic punching drill rod. The water braid 13 is preferably a high-pressure sealed water braid. The high-low pressure conversion punch 12, the hydraulic punching drill rod and the water braid 13 are withdrawn from the bottom plate position for hydraulic punching. The high-low pressure conversion punch 12 is used to perform high-pressure water impact on the coal body near the gas tunnel burst elimination range (10m), and the coal powder (accompanied by a small amount of gas discharge) is flushed out to form a 2-5m cavity 14, thereby increasing the permeability and relieving the pressure of the coal seam 2.

[0026] Step three, seal the drilled holes that have been hydraulically punched and drain the gas from the drilled holes that have been hydraulically punched.

[0027] In this embodiment, in step three, the sealing process: before sealing the borehole, use water or compressed air to clean the remaining coal and rock chips in the borehole that has been hydraulically punched, put the extraction tube 15 into the hole, the casing diameter is DN32mm, the sealing length is the coal seam section and the rock layer section, and use the sealing pump 16 to send mortar into the borehole sealing section until the borehole is sealed, and the borehole and the extraction tube 15 are sealed. The mortar can be selected from cement mortar, which is made by mixing silicate cement above M20, sand and water. The mass ratio of cement to sand is 1:2.4, and the sand particle diameter is 0.5mm.

[0028] Gas extraction process: After the hydraulic punching is completed and the drilling and sealing are completed, the coal seam gas is extracted, one end of the extraction pipe 15 is connected to the cavity 14, and the other end of the extraction pipe 15 is connected to the extraction structure.

[0029] In this embodiment, in step three, the extraction structure includes an extraction main pipeline 18, a branch pipeline 19, a discharge pipeline 21 and a gas extraction pump station 17. The extraction main pipeline 18 is connected with the branch pipeline 19, the gas extraction pump station 17 and the extraction pipe 15 respectively. The extraction main pipeline 18 uses a seamless steel pipe of φ133mm×4. The extraction main pipeline 18 and the extraction pipe 15 are connected with a hose of DN40mm in diameter. The branch pipeline 19 is connected with several discharge pipelines 21, and each discharge pipeline 21 is provided with a valve 20.

[0030] Gas extraction mainly relieves the pressure of coal seams and reduces the risk of gas outburst during grouting. The gas extraction time cannot be too long, as it will cause the cavity 14 formed by hydraulic punching to close. The longer the gas extraction time, the smaller the cavity 14 retained. Therefore, the extraction time should be controlled within 2d~4d according to the degree and speed of coal rock deformation.

[0031] Step 4: After the coal seam gas extraction is completed, cement slurry is injected into the cavity 14 to fill the cavity 14 and form an isolation structure 23.

[0032] In this embodiment, in step 4, the grouting curing process: after 2d~4d of gas extraction, 0.7:1 cement slurry is injected through the extraction hole to fill the cavity 14 formed by hydraulic punching, and the slurry strength grade is required to be not less than M10; the single-hole grouting end standard is adopted: the grouting pressure is gradually increased, and when the designed final pressure is reached and the pressure is maintained; when grouting the extraction hole is adopted, the pressure record of each borehole is made; the grouting pipe 22 is pushed into the extraction pipe 15 by the drilling rig, and the grouting pipe 22 is preferably a steel pipe, and the steel pipe segments are connected with threads; The radial error of the work is not more than 15cm, and the adjacent circumferential distance is not more than 5cm. After the grouting pipe 22 is pushed into place, the gap between the grouting pipe 22 and the extraction pipe 15 is tightly blocked with quick-setting cement or other materials to prevent the slurry from escaping. In order to prevent slurry from coming out during the grouting process, after each hole is drained and the gas is extracted, the grouting pipe 22 of the hole is immediately installed and grouting is carried out, and then the construction of the next hole is carried out. The unclosed cavity 14 generated by hydraulic punching in step 2 is filled with cement slurry, and an isolation structure 23 is formed after hardening.

[0033] Step 5, the construction process of the isolation zone 24: repeat steps 1 to 3, and through the drainage-solidification combination technology coordinated with hydraulic punching and grouting reinforcement, finally make several isolation structures 23 form an isolation zone 24 with a thickness of 2 to 5 meters around the tunnel main hole 1 outside the gas tunnel burst elimination range (10m), isolating the main body of the coal seam 2 from the coal body in the gas tunnel burst elimination range, and achieving a better burst elimination effect.

[0034] Step six, reinforcing the isolation belt 24.

[0035] In this embodiment, in step six, the isolation belt 24 reinforcement process: after the solidified isolation belt 24 is formed, the gas extraction holes that have not been hydraulically punched are retained, and the gas extraction holes that have been hydraulically punched are grouting-sealed, and the isolation belt 24 is connected to the surrounding lining of the tunnel main hole 1 with pillars 25. The pillars 25 are made of concrete and play a supporting and reinforcing role for the isolation belt 24; a strip-type skeleton is formed in the range of the elimination of the outburst, so as to reduce the high-pressure ground stress of the coal seam roof and floor on the coal seam 2, avoid the coal body from being squeezed and displaced under the high-pressure ground stress of the roof and floor, increase the retention time of the subsequent hydraulic punching cavity 14, and improve the hydraulic punching permeability enhancement and drainage effect.

[0036] Step seven, extract gas from the boreholes that have not been hydraulically flushed.

[0037] In this embodiment, in step seven, the final outburst elimination process: before plugging the boreholes that have not been hydraulically punched, clean the boreholes that have not been hydraulically punched, put the extraction pipe 15 in the hole, plug the boreholes that have not been hydraulically punched and the extraction pipe 15, one end of the extraction pipe 15 is connected to the cavity 14, and the other end of the extraction pipe 15 is connected to the extraction structure, and the gas is extracted from the boreholes that have not been hydraulically punched. This step extracts gas from the coal body within the anti-outburst range of the gas tunnel coal seam 2, that is, the isolation zone 24, to eliminate the risk of gas outburst.

[0038] This embodiment provides a method for solid removal and outburst elimination in a pulverized coal seam, so as to solve the problem that when the coal seam is soft, the gas extraction is slow, the outburst elimination effect is poor, and the coal uncovering conditions cannot be met due to the high adsorption capacity, low fluidity, and extremely fast attenuation of gas.

[0039] This embodiment improves the permeability enhancement effect of the pulverized coal seam in a high-outburst gas tunnel, increases the gas extraction efficiency, enhances the outburst elimination effect, and achieves the purpose of coal uncovering conditions.

[0040] The pulverized coal seam solidification and outburst elimination method of this embodiment, wherein "discharge" refers to gas extraction on the one hand, and coal slag discharge on the other hand, both of which increase the permeability and relieve pressure on the coal rock layer; "solidification" refers to cement grouting of the coal seam 2 after hydraulic punching to form coal body solidification.

[0041] Drainage: After drilling, hydraulic punching is performed to drain the coal around and in front of the end of the drilling hole to form a cavity 14, and then the coal seam gas is drained to achieve the effect of decompression and permeability enhancement of the soft coal seam 2. After the hydraulic punching permeability enhancement effect decays, high-pressure grouting is immediately used.

[0042] Solidification: After a period of gas extraction, grouting is performed through the extraction holes to fill the cavity 14 formed by hydraulic punching, forming a hard concrete block in the coal body. Grouting is performed through the extraction holes around the tunnel, so that the concrete blocks form a solidified isolation zone 24 outside the tunnel burst prevention range, thereby achieving the effect of solidifying the soft coal body. Under the action of additional high-pressure grouting pressure, the coal seam gas extraction and permeability enhancement effect can be further increased.

[0043] Drainage-solid combination gas control: Utilize the drainage holes set around the gas tunnel to carry out the drainage-solid combination method of eliminating sudden coal bursts and uncovering coal multiple times, so that after the cement slurry solidifies and hardens, a 2-5 meter thick isolation zone 24 is formed 10 meters outside the tunnel excavation outline (anti-sudden burst range), isolating the main body of the coal seam from the coal body outside the anti-sudden burst range of the tunnel, and forming a strip-type skeleton in the anti-sudden burst range, reducing the high-pressure ground stress of the coal seam roof and floor plates on the coal seam 2, avoiding the extrusion and displacement of the coal body under the high-pressure ground stress of the roof and floor plates, and increasing the retention time of the subsequent hydraulic punching cavity 14, so as to achieve better anti-sudden burst effect.

[0044] Different from the previous coal uncovering methods in gas tunnels which are only applicable to coal seams with small burial depths, the outburst elimination method combining hydraulic punching and grouting reinforcement proposed in this embodiment is targeted at coal seams with ultra-deep burrowing and high ground stress.

[0045] Different from the previous gas tunnel grouting reinforcement method which only reinforces the roof and floor of the coal seam, the method of eliminating outbursts by combining hydraulic punching and grouting reinforcement proposed in this embodiment adopts a combination of drainage and solidification to inject cement slurry through the gas extraction holes into the cavity 14 formed in the main body of the coal seam after hydraulic punching, so as to solidify the coal body.

[0046] Different from the previous gas tunnel grouting reinforcement range which was limited to the tunnel contour, the method of eliminating sudden outbursts by combining hydraulic punching and grouting reinforcement proposed in this embodiment can expand the solidification range to the coal seam outside the gas tunnel sudden outburst prevention range by utilizing the gas extraction holes, and leave a solidified skeleton between the tunnel and the isolation zone 24.

[0047] Different from the previous coal uncovering methods in gas tunnels which only increase the exposed area of ​​the coal seam by using hydraulic cutting and hydraulic fracturing methods, the method of eliminating coal bursts by combining hydraulic punching and grouting reinforcement proposed in this embodiment adopts hydraulic punching technology to punch out the coal body near the anti-burst range of the gas tunnel to form a cavity 14, which not only increases the permeability of the coal seam 2 but also leaves a huge space for grouting reinforcement, which is beneficial to both gas extraction and coal seam 2 solidification.

[0048] Different from the previous grouting reinforcement of gas tunnels, which requires the additional application of steel pipes for grouting, the combined hydraulic punching and grouting reinforcement method proposed in this embodiment utilizes gas extraction holes for grouting to leave a solidified skeleton between the tunnel and the isolation zone 24, which is more convenient and efficient.

[0049] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for solid removal and outburst elimination in a pulverized coal seam, characterized in that: The following steps are involved: Step 1: Drilling the coal seam outside the tunnel main hole; Step 2: After the drilling is completed, hydraulic punching is performed on the borehole corresponding to the isolation structure to discharge the coal body around and in front of the end hole of the drilling to form a cavity; Step 3, plugging the drilled holes that have been hydraulically punched, and draining the gas from the drilled holes that have been hydraulically punched; Step 4: After the coal seam gas extraction is completed, cement slurry is injected into the cavity to fill the cavity and form an isolation structure; Step 5, repeating steps 1 to 3, so that a plurality of isolation structures form an isolation zone around the tunnel main hole outside the tunnel main hole; Step 6: Reinforce the isolation belt; Step seven, extract gas from the boreholes that have not been hydraulically flushed.

2. The method for removing solids and eliminating outbursts in a pulverized coal seam according to claim 1 is characterized in that: In the step 1, the coal seam gas extraction range is a range set outside the excavation contour lines on both sides of the tunnel main tunnel in the direction of the coal seam and a certain distance above and below the excavation contour lines. The drilling penetrates all the coal seams to be extracted and enters the coal seam floor.

3. The method for removing solids and eliminating outbursts in a pulverized coal seam according to claim 1, characterized in that: In the step 1, after drilling a certain distance, the casing is lowered to close the hole and a gas-slag separation device is installed to drain the drilling gas and drilling cuttings.

4. The method for removing solids and eliminating outbursts in a pulverized coal seam according to claim 1, characterized in that: In the step 2, a flushing structure is used to prepare for hydraulic punching and permeability enhancement. The flushing structure includes a water supply pipeline, a water tank and a water pump arranged in sequence. One end of the water supply pipeline extends into the borehole. The slag flushed out by the flushing structure enters the sedimentation tank through the drainage ditch. The drill rod used for drilling is replaced with a hydraulic punching drill rod compatible with the high-low pressure conversion puncher. The high-low pressure conversion puncher is used to perform water impact on the coal body near the gas tunnel burst elimination range to flush out the coal powder and form a cavity.

5. The method for removing solids and eliminating outbursts in a pulverized coal seam according to claim 1 is characterized in that: In the step three, before sealing the borehole, the borehole is cleaned, an extraction tube is placed in the hole, and the borehole and the extraction tube are sealed. One end of the extraction tube is connected to the cavity, and the other end of the extraction tube is connected to the extraction structure.

6. The method for solid removal and outburst elimination of pulverized coal seams according to claim 5 is characterized in that: In step three, the extraction structure includes an extraction main pipeline, branch pipelines, a discharge pipeline and a gas extraction pump station. The extraction main pipeline is connected to the branch pipelines, the gas extraction pump station and the extraction pipe respectively. The branch pipeline is connected to several of the discharge pipelines, and each of the discharge pipelines is provided with a valve.

7. The method for removing solids and eliminating outbursts in a pulverized coal seam according to claim 5, characterized in that: In the step 4, a grouting pipe is installed in the extraction pipe, the space between the grouting pipe and the extraction pipe is sealed, and cement slurry is injected into the cavity through the grouting pipe. When the grouting pressure reaches the designed final pressure, the pressure is maintained and the grouting is terminated. After hardening, an isolation structure is formed.

8. The method for removing solids and eliminating outbursts in a pulverized coal seam according to claim 1, characterized in that: In the step six, the gas extraction holes are blocked, and a number of pillars are set between the tunnel main hole and the isolation zone to reinforce the isolation zone.

9. The method for removing solids and eliminating outbursts in a pulverized coal seam according to claim 1, characterized in that: In the step seven, before sealing the boreholes that have not been hydraulically punched, the boreholes that have not been hydraulically punched are cleaned, and an extraction tube is placed in the hole. The boreholes that have not been hydraulically punched and the extraction tube are sealed. One end of the extraction tube is connected to the cavity, and the other end of the extraction tube is connected to the extraction structure. Gas is extracted from each borehole that has not been hydraulically punched.

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