Gob-side entry retaining wall spraying type gas extraction plugging method

Abstract

The invention provides a gob-side entry retaining wall spraying type gas extraction plugging method, and belongs to the technical field of gas extraction plugging. The method comprises the steps that through gas multi-point flow measurement and three-dimensional ground penetrating radar scanning, a gas main enrichment area and a seepage channel are accurately positioned in combination with a gas seepage formula, a main extraction pipe, an auxiliary extraction pipe and a branch-shaped diversion trench are arranged to form an extraction network, and pressure relief holes are formed to balance gas pressure; the edge weak zone is anchored and reinforced, and a surrounding rock-wall integrated reinforcing zone is formed; a layered spraying process is adopted, and pressure gradient regulation and control are combined to directionally displace gas to an extraction network; and after the spraying layer reaches the standard, the extraction pipe is plugged through flexible and rigid combined reverse grouting, the diversion trench is filled and compacted, and overall plugging is completed. According to the method, through full-process connection of extraction, displacement, plugging and reinforcement, the gas extraction efficiency and the plugging durability are improved, the safety risk is avoided, the wall stability is enhanced, the treatment cost is reduced, and reliable technical support is provided for safe and efficient mining of gob-side entry retaining.

Description

Technical Field

[0001] This invention belongs to the field of gas extraction and sealing technology, specifically a gas extraction and sealing method using spray coating on the wall of a goaf-retaining roadway. Background Technology

[0002] Goaf retention, a key technology for efficient coal mining, can effectively improve coal resource recovery, reduce roadway excavation, and lower mining costs, and is widely used in underground coal mining. However, the walls of goaf retention are mostly constructed by pouring backfill material along the roadway. The contact interface between the wall and the roof, floor, and surrounding coal wall is prone to cracks, and the wall itself is easily broken and deformed under mining pressure. This allows gas to easily seep and leak through these cracks and pores, creating a potential gas accumulation hazard.

[0003] Currently, existing gas drainage and sealing methods mostly employ a single drainage or single sealing mode. During the drainage phase, it's difficult to accurately locate the main gas-rich areas and seepage channels, and the drainage network layout is often unreasonable, resulting in blind spots and low drainage efficiency. During the sealing phase, methods often involve overall spraying or simple grouting, without specific reinforcement of vulnerable areas such as weak edges. Furthermore, the sealing materials and construction techniques are not well-matched, leading to cracking and detachment of the sealing layer and recurring gas leaks. Simultaneously, existing processes fail to achieve integrated integration of drainage, displacement, sealing, and reinforcement. Inaccurate gas pressure control during construction can easily trigger safety accidents such as blowouts and excessive gas levels, failing to meet the requirements for long-term safe and stable operation of goaf-side roadways. Therefore, developing a precise, efficient, safe, and reliable gas drainage and sealing method for goaf-side roadway walls has become an urgent need to solve the current challenges of coal mine gas management. Summary of the Invention

[0004] This invention provides a gas extraction and sealing method using spray coating on the wall of a goaf-retention tunnel, in order to overcome the defects existing in the prior art.

[0005] This invention provides a method for gas extraction and sealing by spraying onto the wall of a goaf-retention tunnel, comprising: S1. Conduct gas seepage and rock mass characteristic tests on the wall to be constructed along the goaf, locate the main gas enrichment area and seepage channel, pre-embed the main extraction pipe on the wall surface, and arrange the branched diversion channel along the seepage direction with the main extraction pipe as the center and connect it with the auxiliary extraction hole as the auxiliary extraction pipe to form a gas directional extraction network.

[0006] S2. Anchoring spray holes are opened at the weak edge of the contact zone between the tunnel wall and the surrounding rock, and anchoring polymer cementitious material is injected to form an integrated reinforcement zone of surrounding rock and wall. During construction, the gas extraction state of the extraction network is maintained.

[0007] S3. A layered spraying process is adopted between the reinforcement strip and the core area of ​​the wall. The spraying is gradually advanced from the outside to the core area. By adjusting the spraying pressure and material diffusion parameters, the gas is directed to the extraction network for centralized extraction.

[0008] S4. After the sprayed coating reaches the design strength, reverse grouting is performed to seal the main and auxiliary extraction pipes. At the same time, foamed sealing material is used to fill and compact the diversion channel to complete the gas extraction and overall sealing of the goaf wall.

[0009] According to the present invention, a gas extraction and sealing method for spraying along the wall of a goaf-retention tunnel is provided. In step S1, a multi-point gas flow measurement combined with three-dimensional ground-penetrating radar scanning is used, and the gas seepage determination formula is applied. Identify the main gas-rich areas, among which For gas seepage velocity, To measure the gas emission rate at the measurement point, To detect the effective area of ​​the cross-section, The effective porosity of the rock mass is used as the reference point. The main gas seepage channel is located using an inversion algorithm, and the main extraction pipe is installed at that location.

[0010] According to the present invention, a gas extraction and sealing method for spraying along the wall of a goaf-retention tunnel is provided. In step S1, there are 48 branched diversion channels. The diversion channels are fully connected with the main extraction pipe and auxiliary extraction holes. The width of the diversion channels is 80 to 120 mm and the depth is 50 to 80 mm. The distance between adjacent diversion channels is 0.8 to 1.5 m. The auxiliary extraction holes are arranged symmetrically in two rows on both sides of a single diversion channel. The distance between adjacent auxiliary extraction holes on the same side is 0.8 to 1.5 m. The auxiliary extraction holes on both sides are arranged in an equilateral triangle staggered arrangement. That is, the center point of a single auxiliary extraction hole on one side of the diversion channel is opposite to the center point of two adjacent auxiliary extraction holes on the opposite side, and the line connecting the centers of the three forms an equilateral triangle.

[0011] According to the present invention, a gas extraction and sealing method for spraying along the wall of a goaf-retention tunnel is provided. In step S2, the effective thickness of the reinforcement strip in the direction perpendicular to the wall surface is 1.0 to 2.5 m, the initial setting time of the anchoring polymer cementitious material is ≤1 h, and the bond shear strength with the surrounding rock after curing is ≥2.0 MPa. During construction, the gas concentration in the weak zone is controlled below 0.5% through the extraction network.

[0012] According to the present invention, a method for gas extraction and sealing by spraying on the wall of a goaf-retention tunnel is provided. In step S1, multiple pressure relief holes are opened on the surface of the wall to balance the gas pressure. In step S3, the pressure relief holes are used as auxiliary spraying holes, and spraying branch pipes with atomizing nozzles are installed. The diameter of the spraying branch pipes is 30 to 60 mm smaller than that of the pressure relief holes, and the atomization angle of the nozzles is 60 to 90°.

[0013] According to the present invention, a gas extraction and sealing method for spraying along the wall of a goaf-retention tunnel is provided. In step S3, the gas is driven in a directional manner by optimizing the spraying pressure gradient, and the pressure gradient is calculated according to the formula... Regulation, among which For spraying pressure difference, The gas permeability coefficient of the wall rock mass. For gas dynamic viscosity, For spraying displacement distance, The equivalent diameter of the seepage channel. The gas seepage velocity.

[0014] According to the present invention, a method for gas extraction and sealing by spraying onto a goaf-side retaining wall is provided. In steps S2 and S3, the spacing between adjacent anchor spray holes and auxiliary spray holes is 0.6 to 1.2 m. The construction adopts the staggered spraying method, and the time interval between adjacent holes is more than 12 hours. Backflow detection holes are set at predetermined locations on the wall, spaced 20 to 40 cm apart from the spray holes. Gas concentration and pressure sensors are installed in the holes. The ratio of spray holes to backflow detection holes is 3:1. Spraying parameters are adjusted in real time based on the detection data.

[0015] According to the present invention, a gas extraction and sealing method using spray coating on the wall of a goaf-side retaining tunnel is provided. In step S2, an anchoring polymer cementitious material is injected to form an integrated reinforcement zone between the surrounding rock and the wall. In step S3, spraying is gradually advanced from the periphery to the core area. In step S4, reverse grouting is performed to seal the main and auxiliary extraction pipes. In each step, a gas-expanding polymer sealing material is first injected to form a temporary sealing layer, followed by the injection of an inorganic cementitious reinforcement material to form a permanent reinforcement layer. The expansion ratio of the expandable polymer material is 150 to 250 times, and the 28-day compressive strength of the inorganic cementitious material is ≥30 MPa.

[0016] According to the present invention, a gas extraction and sealing method for spraying along the wall of a goaf-retention tunnel is provided. In step S4, after injecting a gas-expanding polymer sealing material, when the total gas extraction volume of the extraction network is reduced by more than 70% compared with that before construction and the gas concentration does not rise significantly within 4 hours, the diffusion range of the material is detected. After 6 to 10 hours, an inorganic cementitious reinforcement material is used for grouting to ensure the sealing performance and structural strength of the sealing layer.

[0017] According to the present invention, a gas extraction and sealing method for a goaf-retention wall spraying method is provided. In step S4, a grouting core pipe is installed inside the main extraction pipe. While the extraction pipe continuously extracts gas, grout is injected in reverse through the core pipe into the gap between the extraction pipe and the borehole wall, according to the grouting saturation formula. Controlling the grouting quality, among which To ensure grout filling saturation, This represents the actual grouting volume. This is the theoretical volume of the gap between the extraction pipe and the borehole wall, until... Then, the guide channel is filled with foamed sealing material in layers and compacted.

[0018] This invention provides a gas extraction and sealing method using spray coating on the wall of a goaf-retention tunnel. By combining multi-point gas flow measurement with three-dimensional ground-penetrating radar scanning and a gas seepage determination formula, it can accurately locate the main gas enrichment area and seepage channel, providing a scientific basis for the layout of the extraction network, avoiding extraction blind spots, significantly improving gas extraction efficiency, and ensuring thorough gas extraction.

[0019] By employing a fully interconnected gas extraction network combining branched diversion channels with main and auxiliary extraction pipes, and using pressure relief holes to balance gas pressure in real time, safety risks such as blowouts and gas surges during construction are effectively avoided, ensuring operational safety. A specialized anchoring reinforcement process for weak edge zones involves injecting anchoring polymer cementitious materials to form an integrated reinforcement zone, enhancing the integrity of the wall and surrounding rock, reducing crack formation and gas leakage, and improving the structural stability of the wall.

[0020] By combining layered spraying with pressure gradient control, directional gas displacement and sealing are carried out simultaneously, preventing gas turbulence and crossflow, and ensuring a more durable sealing effect. The reverse grouting sealing process, combining flexibility and rigidity, balances sealing performance with structural durability, ensuring long-term leak-free operation. Through the seamless integration of extraction, displacement, sealing, and reinforcement, the safety, efficiency, and long-term effectiveness of gas control are improved, reducing coal mine gas control costs and providing reliable technical support for safe and efficient mining along goaf-side roadways. Attached Figure Description

[0021] The invention will now be further described with reference to the accompanying drawings.

[0022] Figure 1 This is a schematic diagram of the process of a gas extraction and sealing method using spray coating on the wall of a goaf-retaining roadway in this invention. Figure 2 This is a schematic diagram of the gas extraction network deployment process in this invention; Figure 3 This is a flowchart of the anchoring and reinforcement of the weak edge zone in this invention; Figure 4 This is a schematic diagram of the final sealing process of the extraction pipe and the guide channel in this invention. Detailed Implementation

[0023] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0024] like Figures 1 to 4 As shown in the figure, an embodiment of the present invention provides a method for gas extraction and sealing by spraying a gas extraction coating onto a goaf-retention wall, comprising: S1. Conduct gas seepage and rock mass characteristic tests on the wall to be constructed along the goaf, locate the main gas enrichment area and seepage channel, pre-embed the main extraction pipe on the wall surface, and arrange the branched diversion channel along the seepage direction with the main extraction pipe as the center and connect it with the auxiliary extraction hole as the auxiliary extraction pipe to form a gas directional extraction network.

[0025] The method employs multi-point gas flow measurement combined with three-dimensional ground-penetrating radar scanning, and uses the gas seepage determination formula. Identify the main gas-rich areas, among which For gas seepage velocity, To measure the gas emission rate at the measurement point, To detect the effective area of ​​the cross-section, The effective porosity of the rock mass in the wall is denoted as .

[0026] The main gas seepage channel was located using an inversion algorithm, and the main extraction pipe was installed at this location. Before detection, the surface of the wall was cleaned of loose coal, broken gangue, and debris to ensure a flat and unobstructed detection surface. During 3D ground-penetrating radar scanning, a survey line was set every 0.5m along the wall direction, and the lines were evenly distributed vertically from the bottom to the top of the wall, with the antenna in close contact with the wall surface. After scanning, the data was filtered, inverted, and imaged to identify fractured rock areas, densely fractured zones, and areas with developed pores. Multi-point gas flow measurement was performed using a portable gas flow meter, with boreholes arranged at three heights (top, middle, and bottom) on the wall, at depths of 0.5m, 1.0m, and 1.5m, for continuous monitoring. Stable data is obtained after 48 hours of measurement. The coordinates of the measuring point, the gas emission rate, the cross-sectional area, and the porosity are substituted into the formula for calculation. When the gas seepage velocity is greater than 0.01m / s and remains stable, it is determined to be the main gas enrichment zone. Then, the path with the best connectivity and the largest flow rate is determined as the main seepage channel through the fracture inversion algorithm. The main extraction pipe is a DN50 seamless steel pipe, which is pre-embedded vertically or inclined along the main seepage channel. Water and air filter slits with a width of 1 to 2mm are opened on the outer wall of the pipe. The bottom of the pipe extends into the main enrichment zone by more than 0.5m, and the pipe opening extends 150mm out of the wall surface to facilitate connection to the extraction pipeline.

[0027] There are 48 branched guide channels. The guide channels are fully connected with the main extraction pipe and auxiliary extraction holes. The guide channels are 80 to 120 mm wide and 50 to 80 mm deep. The distance between adjacent guide channels is 0.8 to 1.5 m. The auxiliary extraction holes are arranged symmetrically in two rows on both sides of a single guide channel. The distance between adjacent auxiliary extraction holes on the same side is 0.8 to 1.5 m. The auxiliary extraction holes on both sides are arranged in an equilateral triangle staggered arrangement. That is, the center point of a single auxiliary extraction hole on one side of the guide channel is opposite to the center point of two adjacent auxiliary extraction holes on the opposite side, and the line connecting the centers of the three forms an equilateral triangle.

[0028] The branched diversion channels are arranged radially and in a grid pattern around the main extraction pipe. First, a grooving machine is used to cut the channels along the preset seepage direction. Before cutting, the channels are marked and positioned to ensure that the channels are straight and of uniform depth. After cutting, high-pressure air is used to clean the rock powder and debris in the channels to ensure that the channels are rough and free of smooth surfaces, which is conducive to material adhesion. The auxiliary extraction holes are constructed using a rock bolt drilling machine with a hole diameter of 32mm and a hole depth of 1.0m. After drilling, the holes are cleaned and DN25 extraction branch pipes are installed. The branch pipes are sealed to the diversion channels using a T-joint. When arranged in a staggered pattern, the horizontal and vertical spacing is 1.0m, so that gas from any position in the diversion channels can enter the extraction holes within 3 seconds, forming a fully covered and highly unobstructed extraction network.

[0029] Multiple pressure relief holes are drilled on the wall surface to balance the gas pressure. These holes are constructed using a pneumatic drilling machine, with a diameter of 50mm and a depth of 1.0m. They are arranged horizontally at 1.5m intervals and vertically at 1.0m intervals along the wall. After drilling, perforated pressure relief pipes are installed, and the pipes are wrapped with dustproof and anti-clogging filters. The pressure relief holes remain open throughout the testing and pipe laying stages, automatically releasing the gas pressure inside the wall and stabilizing the internal pressure between 0.1 and 0.2MPa to prevent excessive pressure from causing blowouts, cracking, or gas surges.

[0030] S2. Anchoring spray holes are opened at the weak edge of the contact zone between the tunnel wall and the surrounding rock, and anchoring polymer cementitious material is injected to form an integrated reinforcement zone of surrounding rock and wall. During construction, the gas extraction state of the extraction network is maintained.

[0031] The weak edge zone is a ring-shaped area where the wall, roof and floor, and coal face meet, with a width of 1.0m. The fissure opening in this area is greater than 0.5mm and the rock mass integrity is poor. Fissure observation and gas concentration detection are carried out in this area. Air leakage points and deformation-sensitive points are marked. Anchor spraying holes are arranged at intervals of 0.6m. The drilling direction is perpendicular to the contact interface and inclined at 5 to 10 degrees towards the inside of the surrounding rock to ensure that the borehole penetrates the interface and enters the stable surrounding rock. After drilling, the hole is thoroughly cleaned with compressed air to remove rock powder, water accumulation, and debris.

[0032] The effective thickness of the reinforcement strip in the direction perpendicular to the wall surface is 1.0 to 2.5 m. The initial setting time of the anchoring polymer cementitious material is ≤1 h. After curing, the bond shear strength with the surrounding rock is ≥2.0 MPa. During construction, the gas concentration in the weak zone is controlled below 0.5% through the extraction network.

[0033] The anchoring polymer cementitious material is a two-component grouting material. Components A and B are mixed in a 1:1 volume ratio and delivered using a dual-liquid grouting pump. The grouting pressure is gradually increased from 0.5MPa to 1.5MPa, with slow, low-pressure grouting to ensure full material penetration. Grouting is stopped when the grout concentration at the borehole opening matches the grout concentration at the inlet, and the borehole opening is sealed promptly. The material completes initial setting within 1 hour, reaches initial strength in 3 hours, and is fully cured in 24 hours. After curing, it forms an integral structure with the surrounding rock and wall. During construction, the extraction system maintains a negative pressure of 15 to 20 kPa and operates continuously to extract and desorb methane in real time. A dedicated person checks the methane concentration every 10 minutes, and if it exceeds 0.5%, the extraction negative pressure is immediately increased to ensure operational safety.

[0034] S3. A layered spraying process is adopted between the reinforcement strip and the core area of ​​the wall. The spraying is gradually advanced from the outside to the core area. By adjusting the spraying pressure and material diffusion parameters, the gas is directed to the extraction network for centralized extraction.

[0035] The spraying construction follows the principle of starting from the periphery and then moving to the core, starting from the low and then moving to the high, and proceeding in stages. The periphery transition zone is 1.2m wide. First, the base coat is sprayed in this area, and then it extends to the central core area. The core area is the area with the largest central area of ​​the wall. The spraying sequence proceeds from the far end of the extraction pipeline to the near end of the extraction pipeline. The spraying pressure is used to gradually drive the gas towards the extraction point.

[0036] The pressure relief hole is used as an auxiliary spraying hole. Spraying branch pipes with atomizing nozzles are installed, with a diameter 30-60mm smaller than the pressure relief hole. The atomization angle of the nozzles is 60-90°. A retractable spraying branch pipe is installed inside the auxiliary spraying hole, with a universal atomizing nozzle installed at the front end. The nozzle is kept 300-500mm away from the wall surface. During spraying, a test spray is performed to adjust the pressure and angle, ensuring the atomized fan evenly covers the wall surface. The spraying material is a mixture of inorganic sealing coating and polymer adhesive, stirred for at least 5 minutes until thoroughly mixed without lumps or sediment. During spraying, the sprayer moves back and forth horizontally, overlapping each row by 1 / 3 of its width to ensure a continuous, uniform, and seamless coating. The gas is directionally driven away by optimizing the spraying pressure gradient, which is calculated using the formula... Regulation, among which For spraying pressure difference, The gas permeability coefficient of the wall rock mass. For gas dynamic viscosity, For spraying displacement distance, The equivalent diameter of the seepage channel. The gas seepage velocity.

[0037] Before construction, parameters such as wall permeability coefficient, gas viscosity, and seepage velocity are measured and substituted into the formula to calculate the target spraying pressure difference. On-site, a variable frequency spraying machine is used to achieve precise pressure adjustment: 0.8 MPa for the outer perimeter, 1.2 MPa for the transition zone, and 1.8 MPa for the core zone, forming a pressure gradient that increases from the outside to the inside. The pressure gradient changes by no more than 0.3 MPa per meter, so that the gas flows stably along the guide channel to the extraction pipeline under pressure, without turbulence, crossflow, or local accumulation.

[0038] The spacing between adjacent anchoring spray holes and auxiliary spray holes is 0.6 to 1.2 meters. The construction adopts an alternating-hole skip-spraying method, with an interval of more than 12 hours between adjacent holes. Backflow detection holes are installed at designated locations on the wall, spaced 20 to 40 centimeters apart from the spray holes. Gas concentration and pressure sensors are installed inside these holes. The ratio of spray holes to backflow detection holes is 3:1. Spraying parameters are adjusted in real time based on the detection data. Alternating-hole skip-spraying means that holes 1, 3, and 5 are sprayed first, and holes 2, 4, and 6 are sprayed after 12 hours of curing. This avoids stress superposition and material disturbance caused by simultaneous construction at adjacent holes. The backflow detection holes have integrated sensors that collect gas concentration, pressure, and flow data in real time and transmit them wirelessly to the monitoring platform. When abnormalities such as increased gas concentration or decreased pressure are detected, the system automatically reduces the spraying speed, increases the extraction negative pressure, and extends the pressure holding time, dynamically matching the displacement and sealing rhythm.

[0039] S4. After the sprayed coating reaches the design strength, reverse grouting is performed to seal the main and auxiliary extraction pipes. At the same time, foamed sealing material is used to fill and compact the diversion channel to complete the gas extraction and overall sealing of the goaf wall.

[0040] The spray coating is applied in three coats: the first coat is for sealing, the second coat is for leveling, and the third coat is for sealing. The total thickness is not less than 15mm. After spraying, allow it to cure naturally for 48 hours. During the curing period, avoid collisions, watering, and disturbance. After curing, use a rebound hammer to test the strength to ensure that the compressive strength is not less than 20MPa. At the same time, check that the surface is free of cracks, hollow areas, and missed areas. Only after the strength is qualified can the sealing process begin.

[0041] In step S2, anchoring polymer cementitious material is injected to form an integrated rock-wall reinforcement strip. In step S3, spraying is gradually advanced from the periphery to the core area. In step S4, reverse grouting is performed to seal the main and auxiliary extraction pipes. All these steps employ a combination of flexible sealing and rigid reinforcement: injecting gas-expanding polymer sealing material to form a temporary sealing layer, and injecting inorganic cementitious reinforcement material to form a permanent reinforcement layer. The expansion ratio of the expandable polymer material is 150 to 250 times, and the 28-day compressive strength of the inorganic cementitious material is ≥30 MPa.

[0042] The flexible sealing material is a single-component gas-expanding material, which is injected at low pressure using a grouting pump. After contacting the gas, the material rapidly foams and expands, filling pipe gaps and micro-cracks to form a sealed cushion layer. After the expansion stabilizes for 4 hours, a high-grade inorganic cementitious material is injected, and the grouting pressure is gradually increased to 2.5 MPa to ensure that the material is densely filled and consolidated as a whole. The flexible layer prevents leakage, while the rigid layer bears the load, resulting in a dual structure that is stable and reliable in the long term.

[0043] After injecting gas-expanding polymer sealing material, when the total gas extraction volume of the extraction network is reduced by more than 70% compared with that before construction and the gas concentration does not rise significantly within 4 hours, the diffusion range of the material is tested. After 6 to 10 hours, inorganic cementitious reinforcement material is used for grouting to ensure the sealing performance and structural strength of the sealing layer.

[0044] An online flow monitoring device is installed in the extraction pipeline to record the total extraction volume and instantaneous flow rate in real time. When the flow rate drops to the standard and the concentration is stable below 0.3%, the filling status of the sealing material is checked with an in-hole camera. After confirming that it is full and without gaps, rigid grouting is carried out at 8-hour intervals. During the grouting process, the return of grout at the orifice is observed. If grout returns, the process is stopped to ensure that the sealing is tight and leak-free.

[0045] A grouting core pipe is installed inside the main extraction pipe. While the extraction pipe continuously extracts gas, grout is injected in reverse through the core pipe into the gap between the extraction pipe and the borehole wall, according to the grouting saturation formula. Controlling the grouting quality, among which To ensure grout filling saturation, This represents the actual grouting volume. This is the theoretical volume of the gap between the extraction pipe and the borehole wall, until... Then, the guide channel is filled with foamed sealing material in layers and compacted.

[0046] The outer diameter of the grouting core pipe is 25mm smaller than the inner diameter of the extraction pipe. A one-way valve is installed at the bottom of the pipe. During reverse grouting, the extraction machine does not stop. The negative pressure state is maintained so that the grout can fully fill the gap under the action of pressure difference. The grouting metering system automatically records the theoretical volume and the actual injection volume, calculates the saturation in real time, and stops grouting when it reaches more than 95%. The pipe opening is sealed for curing. The guide channel is filled with high-elastic foamed sealing material, which is filled in 50mm thin layers in sections. Each layer is compacted with a tamping tool to ensure that there are no air holes or gaps and that the surface is flush with the wall. Finally, a sealing surface layer is sprayed on the whole to complete the entire sealing process.

[0047] In summary, this embodiment provides a gas extraction and sealing method using spray coating on the wall of a goaf-retention tunnel. By combining multi-point gas flow measurement with three-dimensional ground-penetrating radar scanning and using a gas seepage determination formula, it can accurately locate the main gas enrichment area and seepage channel, providing a scientific basis for the layout of the extraction network, avoiding extraction blind spots, significantly improving gas extraction efficiency, and ensuring thorough gas extraction.

[0048] By employing a fully interconnected gas extraction network combining branched diversion channels with main and auxiliary extraction pipes, and using pressure relief holes to balance gas pressure in real time, safety risks such as blowouts and gas surges during construction are effectively avoided, ensuring operational safety. A specialized anchoring reinforcement process for weak edge zones involves injecting anchoring polymer cementitious materials to form an integrated reinforcement zone, enhancing the integrity of the wall and surrounding rock, reducing crack formation and gas leakage, and improving the structural stability of the wall.

[0049] By combining layered spraying with pressure gradient control, directional gas displacement and sealing are carried out simultaneously, preventing gas turbulence and crossflow, and ensuring a more durable sealing effect. The reverse grouting sealing process, combining flexibility and rigidity, balances sealing performance with structural durability, ensuring long-term leak-free operation. Through the seamless integration of extraction, displacement, sealing, and reinforcement, the safety, efficiency, and long-term effectiveness of gas control are improved, reducing coal mine gas control costs and providing reliable technical support for safe and efficient mining along goaf-side roadways.

[0050] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for gas extraction and sealing by spraying gas onto the wall of a goaf-retention tunnel, characterized in that, include: S1. Conduct gas seepage and rock mass characteristic detection on the wall to be constructed along the goaf, locate the main gas enrichment area and seepage channel, pre-embed the main extraction pipe on the wall surface, and arrange the branched diversion channel along the seepage direction with the main extraction pipe as the center and connect it with the auxiliary extraction hole as the auxiliary extraction pipe to form a gas directional extraction network. S2. Anchoring spray holes are opened in the weak zone where the wall of the tunnel contacts the surrounding rock, and anchoring polymer cementitious material is injected to form an integrated reinforcement zone of surrounding rock and wall. During construction, the gas extraction state of the extraction network is maintained. S3. A layered spraying process is adopted between the reinforcement strip and the core area of ​​the wall. The spraying is gradually advanced from the periphery to the core area. By adjusting the spraying pressure and material diffusion parameters, the gas is directed to the extraction network for centralized extraction. S4. After the sprayed coating reaches the design strength, reverse grouting is performed to seal the main and auxiliary extraction pipes. At the same time, foamed sealing material is used to fill and compact the diversion channel to complete the gas extraction and overall sealing of the goaf wall.

2. The method for gas extraction and sealing by spraying along the wall of a goaf-retention tunnel according to claim 1, characterized in that, In step S1, a method combining multi-point gas flow measurement and three-dimensional ground-penetrating radar scanning is used, and the gas seepage determination formula is applied. Identify the main gas-rich areas, among which For gas seepage velocity, To measure the gas emission rate at the measurement point, To detect the effective area of ​​the cross-section, The effective porosity of the rock mass is determined; the main gas seepage channel is located using an inversion algorithm, and the main extraction pipe is installed at that location.

3. The method for gas extraction and sealing by spraying along the wall of a goaf-retention tunnel according to claim 1, characterized in that, In step S1, there are 48 branched guide channels. The guide channels are fully connected to the main extraction pipe and auxiliary extraction holes. The width of the guide channels is 80 to 120 mm and the depth is 50 to 80 mm. The distance between adjacent guide channels is 0.8 to 1.5 m. The auxiliary extraction holes are arranged symmetrically in two rows on both sides of a single guide channel. The distance between adjacent auxiliary extraction holes on the same side is 0.8 to 1.5 m. The auxiliary extraction holes on both sides are arranged in an equilateral triangle staggered arrangement. That is, the center point of a single auxiliary extraction hole on one side of the guide channel is opposite to the center point of two adjacent auxiliary extraction holes on the opposite side, and the line connecting the centers of the three forms an equilateral triangle.

4. The method for gas extraction and sealing by spraying along the wall of a goaf-retention tunnel according to claim 1, characterized in that, In step S2, the effective thickness of the reinforcement strip in the direction perpendicular to the wall surface is 1.0 to 2.5 m, the initial setting time of the anchoring polymer cementitious material is ≤1 h, the bond shear strength with the surrounding rock after curing is ≥2.0 MPa, and the gas concentration in the weak zone is controlled below 0.5% through the extraction network during construction.

5. The method for gas extraction and sealing by spraying along the wall of a goaf-retention tunnel according to claim 1, characterized in that, In step S1, multiple pressure relief holes are opened on the wall surface to balance the gas pressure; in step S3, the pressure relief holes are used as auxiliary spraying holes, and spraying branch pipes with atomizing nozzles are installed. The diameter of the spraying branch pipes is 30 to 60 mm smaller than that of the pressure relief holes, and the atomization angle of the nozzles is 60 to 90°.

6. The method for gas extraction and sealing by spraying along the wall of a goaf-retention tunnel according to claim 1, characterized in that, In step S3, the directional expulsion of gas is achieved by optimizing the spraying pressure gradient, and the pressure gradient is calculated according to the formula... Regulation, among which For spraying pressure difference, The gas permeability coefficient of the wall rock mass. For gas dynamic viscosity, For spraying displacement distance, The equivalent diameter of the seepage channel. The gas seepage velocity.

7. The method for gas extraction and sealing by spraying along the wall of a goaf-retention tunnel according to claim 1, characterized in that, In steps S2 and S3, the spacing between adjacent anchor spray holes and auxiliary spray holes is 0.6 to 1.2 m. The construction adopts the staggered spraying method, and the time interval between adjacent holes is more than 12 hours. Backflow detection holes are set at designated positions on the wall, 20 to 40 cm apart from the spray holes. Gas concentration and pressure sensors are installed in the holes. The ratio of spray holes to backflow detection holes is 3:

1. The spraying parameters are adjusted in real time based on the detection data.

8. The method for gas extraction and sealing by spraying along the wall of a goaf-retention tunnel according to claim 1, characterized in that, In step S2, anchoring polymer cementitious material is injected to form an integrated reinforcement strip of surrounding rock and wall. In step S3, spraying is gradually advanced from the periphery to the core area. In step S4, reverse grouting is performed to seal the main and auxiliary extraction pipes. In all these steps, gas-expanding polymer sealing material is first injected to form a temporary sealing layer, and then inorganic cementitious reinforcement material is injected to form a permanent reinforcement layer. The expansion ratio of the expansion polymer material is 150 to 250 times, and the 28-day compressive strength of the inorganic cementitious material is ≥30MPa.

9. A method for gas extraction and sealing by spraying along the wall of a goaf-retention tunnel according to claim 8, characterized in that, After injecting the gas-expanding polymer sealing material, when the total gas extraction volume of the extraction network is reduced by more than 70% compared with that before construction and the gas concentration does not rise significantly within 4 hours, the diffusion range of the material is detected. After 6 to 10 hours, inorganic cementitious reinforcement material is used for grouting to ensure the sealing performance and structural strength of the sealing layer.

10. The method for gas extraction and sealing by spraying along the wall of a goaf-retention tunnel according to claim 1, characterized in that, In step S4, a grouting core tube is installed inside the main extraction pipe. While the extraction pipe continuously extracts gas, grout is injected in reverse through the core tube into the gap between the extraction pipe and the borehole wall, according to the grouting saturation formula. Controlling the grouting quality, among which To ensure grout filling saturation, This represents the actual grouting volume. This is the theoretical volume of the gap between the extraction pipe and the borehole wall, until... Then, the guide channel is filled with foamed sealing material in layers and compacted.

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