One-roadway four-purpose coal and gas co-mining method for bottom drainage roadway

Abstract

The invention provides a one-roadway four-purpose coal and gas co-mining method for a bottom drainage roadway, and belongs to the technical field of coal mines, the method comprises the following steps: firstly, tunneling the bottom drainage roadway at a position 10-12 meters away from a coal seam floor, determining an optimal drilling position by adopting a grey wolf hunting optimization algorithm, and arranging high-position directional drilling groups every 10-15 meters; an intelligent gas extraction system is installed, and a gas pre-extraction function is started 60-90 days before the working face is propelled; during stoping, a double-air-return system is constructed by utilizing the bottom pumping roadway; water drainage and water supply pipelines are synchronously laid to realize water recycling; transportation equipment, a disaster avoidance chamber and a communication system are arranged; a whole-process monitoring system is established, and various sensors are installed to realize real-time monitoring; and a special emergency plan is formulated, safe and efficient operation of the system is ensured, and the technical problems of gas concentration increase and accumulation risk in the multifunctional utilization process of the bottom pumping roadway are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal mines, and in particular relates to a method for mining four types of coal and gas in a bottom extraction lane. Background Art

[0002] In high-burst mines, bottom extraction tunnel technology is a key means of achieving co-mining of coal and gas. Traditional bottom extraction tunnels are primarily located in the rock strata beneath the coal seam. By drilling upward, they pre-extract gas, reducing the gas content in the coal seam and eliminating the risk of coal and gas outbursts. With the increasing demand for safe and efficient coal mining, the single function of bottom extraction tunnels is no longer sufficient, and multifunctional utilization is becoming a trend.

[0003] However, there are currently many problems in the multifunctional utilization of bottom extraction tunnels: first, there is mutual interference between tunnel functions, especially when gas extraction, ventilation and discharge, transportation and disaster avoidance functions are running at the same time, it is easy to cause system imbalance; second, the drilling layout lacks scientific optimization and the coverage is not comprehensive, resulting in insufficient gas extraction in some areas; third, the ventilation system has poor stability. When the bottom extraction tunnel is used as an auxiliary return air channel during the mining of the working face, gas is easy to accumulate in the area.

[0004] Especially when the ventilation system is disturbed (such as by fan failure, damper adjustment, or temporary ventilation shutdown), the multifunctional operation of the bottom extraction tunnels can easily lead to increased gas concentrations and a greater risk of accumulation. Existing technologies have difficulty effectively addressing this safety hazard, hindering the efficient utilization of bottom extraction tunnel resources and safe mine production. In other words, existing technologies have a technical problem: the multifunctional operation of bottom extraction tunnels can easily lead to increased gas concentrations and a high risk of accumulation. Summary of the Invention

[0005] In view of this, the present invention provides a method for co-mining coal and gas in one bottom extraction tunnel for four purposes, which can solve the technical problems in the prior art that the gas concentration is easily increased and the risk of accumulation is high during the multifunctional utilization of the bottom extraction tunnel, especially when the ventilation system is disturbed, the safety risk increases significantly.

[0006] The present invention is implemented as follows: The present invention provides a method for co-mining coal and gas in a bottom extraction tunnel, including: excavating a bottom extraction tunnel in the rock layer of the coal seam bottom plate; applying a set covering algorithm that considers gray wolf hunting optimization in the bottom extraction tunnel to determine the drilling position and angle of the high-position directional drilling group; installing an intelligent gas extraction system to form a gas pre-extraction function; starting the gas pre-extraction function; during the mining of the working face, using the bottom extraction tunnel to lay return air pipelines to construct a dual return air system to form an auxiliary return air function structure; laying drainage pipelines and water supply pipelines in the bottom extraction tunnel to form a drainage and water supply function structure; installing transportation equipment, disaster shelter chambers and communication systems in the bottom extraction tunnel to form a transportation and disaster shelter function structure.

[0007] Among them, when excavating the bottom pumping tunnel, the vertical distance between the bottom pumping tunnel and the coal seam is maintained at 10 to 12 meters to ensure the stability of the bottom pumping tunnel and the gas extraction effect.

[0008] Among them, a high-level directional drilling group is set up every 10 to 15 meters in the bottom extraction tunnel. By solving the optimization model of the minimum number of drill holes to cover the maximum coal seam area, the drilling inclination angle in the high-level directional drilling group is determined to be 15 to 30 degrees, so that the drill holes in the high-level directional drilling group pass through the entire coal seam and the roof fracture zone, forming a gas pre-extraction channel.

[0009] Among them, the set cover algorithm for gray wolf hunting optimization is a heuristic search algorithm that globally optimizes the drilling arrangement problem by simulating the social hierarchy structure and hunting behavior of gray wolf groups. The drilling coverage area is used as the hunting space, and maximizing the drilling coverage and minimizing the number of drilling holes are used as objective functions.

[0010] Among them, the intelligent gas extraction system includes a negative pressure extraction pump station, a gas collection pipeline and a flow regulating device.

[0011] Among them, gas pre-extraction is started 60 to 90 days before the working face advances, the extraction negative pressure is controlled to 15 to 25 kPa, the extraction concentration is not less than 30%, and the coal seam gas content is ensured to drop to 3m 3 / t or less.

[0012] Among them, gas pre-extraction refers to the extraction of coal seam gas through a high-position directional drilling group in the bottom extraction tunnel before coal seam mining, so as to reduce the gas content of the coal seam and eliminate the danger of coal and gas outbursts.

[0013] Among them, the auxiliary return air functional structure uses the bottom extraction tunnel as the auxiliary return air channel in the mining area, forming a double return air system with the main return air tunnel, enhancing the ventilation capacity of the working face and improving the gas dilution and emission efficiency.

[0014] Among them, the double return air system is a ventilation system composed of the main return air tunnel and the bottom extraction tunnel. The main return air tunnel is responsible for conventional ventilation of the working face, and the bottom extraction tunnel is responsible for directional emission in the gas-enriched area.

[0015] Among them, one tunnel with four uses means that the bottom extraction tunnel has gas pre-extraction function, auxiliary return air function, drainage and water supply function and transportation and disaster avoidance function at the same time, realizing efficient utilization of tunnel resources and safe production in coal mines.

[0016] By scientifically planning the location, drilling arrangement, and functional configuration of bottom extraction tunnels, the present invention effectively integrates four major functions: gas pre-extraction, auxiliary return air, drainage and water supply, and transportation and disaster avoidance. This method uses a set coverage algorithm that takes into account gray wolf hunting optimization to determine the optimal drilling location and angle, providing more comprehensive gas extraction coverage and improving pre-extraction efficiency. In terms of ventilation system design, the present invention constructs a dual-return air system, with the main return air tunnel responsible for conventional ventilation of the working face and the bottom extraction tunnel responsible for directional discharge in gas-rich areas, effectively solving the problem of gas accumulation during multi-functional operation. At the same time, by establishing a full-process monitoring system and installing gas concentration sensors, wind speed sensors, etc., real-time data collection and risk warnings are achieved. Even when the ventilation system is disturbed, timely adjustments can be made to prevent an increase in gas concentration. Through system integration and optimized design, the present invention effectively solves the technical problems of increased gas concentration and high accumulation risks during the multi-functional utilization of bottom extraction tunnels, significantly improving coal mine production safety and resource utilization efficiency, and providing technical support for the safe and efficient mining of high-burst mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow chart of the method of the present invention.

[0018] Figure 2 This is a schematic diagram of the functional structure of a bottom extraction lane with one lane and four uses.

[0019] Figure 3 Schematic diagram of drilling coverage.

[0020] Figure 4 Schematic diagram of the layout of concentration, pressure and flow sensors.

[0021] Figure 5 Schematic diagram of the dual air duct structure.

[0022] Figure 6 Schematic diagram of the disaster shelter structure.

[0023] Figure 7 This is a schematic diagram of the deployment of data collection nodes through the data analysis and early warning platform.

[0024] Figure 8 This is a schematic diagram of the gas over-limit processing process. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0026] like Figure 1 FIG. 1 is a flow chart of a method for co-mining coal and gas in a bottom extraction lane with four functions provided by the present invention. The method comprises the following steps:

[0027] S01. Based on the geological conditions and gas distribution characteristics of the mining area, excavate a bottom extraction tunnel in the coal seam floor rock layer, and maintain a vertical distance of 10-12 meters between the bottom extraction tunnel and the coal seam to ensure the stability of the bottom extraction tunnel and the gas extraction effect;

[0028] S02. Applying a set covering algorithm that takes into account wolf hunting optimization to determine optimal drilling positions and drilling angles within the bottom extraction tunnel, setting up a high-position directional drilling group every 10 to 15 meters, and solving an optimization model for covering the maximum coal seam area with the minimum number of drill holes to determine the inclination angle of the drill holes in the high-position directional drilling group to be 15 to 30 degrees. The drill holes in the high-position directional drilling group penetrate the entire coal seam and roof fracture zone, thereby forming a gas pre-extraction channel;

[0029] S03. Installing an intelligent gas extraction system, wherein the intelligent gas extraction system includes a negative pressure extraction pump station, a gas collection pipeline, and a flow regulating device, to realize the first function of the bottom extraction roadway, namely, gas pre-extraction;

[0030] S04. Activate the gas pre-extraction function 60 to 90 days before the working face advances, control the extraction negative pressure to 15 to 25 kPa, and the extraction concentration to be no less than 30%;

[0031] S05. During the mining period at the working face, the bottom extraction roadway is used to lay a return air pipeline to construct a dual return air system, thereby forming a second function of the bottom extraction roadway, namely, an auxiliary return air function;

[0032] S06. Simultaneously laying drainage pipes and water supply pipes in the bottom pumping roadway to realize water recycling in the mining area and form the third function of the bottom pumping roadway, namely, drainage and water supply function;

[0033] S07, installing transportation equipment in the bottom extraction tunnel for transporting materials and equipment, and simultaneously setting up a disaster shelter chamber and a communication system, thereby forming the fourth function of the bottom extraction tunnel, namely, transportation and disaster shelter;

[0034] S08. Optionally, further comprising establishing a full-process monitoring system, installing a gas concentration sensor, a wind speed sensor, a temperature sensor, and a stress monitoring device in the bottom extraction tunnel to achieve real-time data collection and risk warning;

[0035] S09. Optionally, it also includes formulating a special emergency plan, which includes a gas over-limit handling process, a ventilation system disorder handling process, and a bottom pumping tunnel instability handling process to ensure the safe and efficient operation of one tunnel with four uses.

[0036] The set cover algorithm for gray wolf hunting optimization is a heuristic search algorithm that simulates the social hierarchy and hunting behavior of gray wolf groups to perform global optimization on the drilling arrangement problem, wherein the drilling coverage area is used as the hunting space, and maximizing the drilling coverage and minimizing the number of drilling holes are used as the objective function;

[0037] The gas pre-extraction function is to extract the coal seam gas through the high-position directional drilling group in the bottom extraction tunnel before the coal seam is mined, thereby reducing the coal seam gas content and eliminating the danger of coal and gas outburst.

[0038] The auxiliary return air function specifically utilizes the bottom extraction roadway as an auxiliary return air channel in the mining area, forming the dual return air system with the main return air roadway, thereby enhancing the ventilation capacity of the working face and improving the gas dilution and emission efficiency;

[0039] The drainage and water supply function is to collect water gushing from the mining area through the drainage pipe system laid in the bottom pumping tunnel and transport it to the water treatment station. After treatment, it is transported to the working face through the water supply pipe for dust reduction and equipment cooling.

[0040] The transport and disaster avoidance function is to use the bottom extraction tunnel as an auxiliary transport channel to transport coal mining equipment and support materials, and at the same time serve as a personnel escape channel and temporary disaster shelter in an emergency;

[0041] The high-position directional drilling group is specifically a group of boreholes drilled upward from the bottom extraction roadway to the coal seam and the roof fracture zone, for extracting gas from the coal seam and the roof fracture zone;

[0042] The dual-return air system is specifically a ventilation system composed of the main return air roadway and the bottom extraction roadway. The main return air roadway is responsible for conventional ventilation of the working face, and the bottom extraction roadway is responsible for directional discharge of gas-rich areas.

[0043] Among them, "one lane, four uses" specifically means that the bottom extraction lane has the functions of gas pre-extraction, auxiliary air return, drainage and water supply, and transportation and disaster avoidance, thus achieving efficient utilization of lane resources and safe production in coal mines.

[0044] Among them, the roof fracture zone specifically refers to the fracture development area caused by stress release in the overlying rock strata after coal seam mining, which is the main channel for gas enrichment and migration.

[0045] The specific implementation of the above steps is described in detail below.

[0046] The specific implementation of step S01 is as follows: First, based on geological exploration data from the mining area, basic geological information such as the occurrence, thickness variation, and fault distribution of the coal seam is obtained. Gas geological parameters such as gas pressure, gas content, and gas composition are also collected. Then, through geomechanical calculations, the underdrainage tunnel excavation route is determined, and a stable rock layer with a hardness coefficient of no less than 4 is selected within the coal seam floor strata as the tunnel location. Finally, the vertical distance between the underdrainage tunnel and the coal seam is controlled to be maintained at a minimum of 10 meters. When the coal seam thickness exceeds 3 meters, the vertical distance is preferably 10 to 12 meters, and when the coal seam thickness is less than 3 meters, the vertical distance is preferably 8 to 10 meters. This vertical distance is determined based on the "critical layer theory" in rock mechanics theory. It ensures that the underdrainage tunnel is located at the edge of the coal seam mining impact zone, ensuring both tunnel stability and effective penetration of the coal seam for gas extraction. The purpose of this step is to establish a reasonable spatial location for the underdrainage tunnel, laying the foundation for subsequent multifunctional utilization.

[0047] The specific implementation of step S02 is: first, construct a mathematical model of a set coverage algorithm based on gray wolf hunting optimization, set the drilling position as the decision variable, and maximize the drilling coverage area and minimize the number of drilling holes as the objective function; then divide the coal seam into several grid units, each grid unit represents an area in the coal seam, and the set of grid units that can be covered by the drilling constitutes a coverage matrix; then use the "social hierarchy sorting" mechanism of the gray wolf optimization algorithm to sort the drilling schemes according to the coverage effect, and the first three schemes are used as α, β, and δ wolves to guide other solutions to update their positions; then, by continuously iterating and updating the position, the drilling layout scheme is gradually optimized. When the number of iterations reaches the preset value or the optimization effect of multiple consecutive iterations is not obvious, the optimal drilling layout scheme is output; finally, according to the optimal layout scheme, a high-position directional drilling group is set every 10 to 15 meters in the bottom extraction tunnel. When the gas content of the coal seam is higher than 10m 3 / t, the drilling group spacing should be 10 to 12 meters. When the coal seam gas content is less than 10m 3 When the gas flow rate is 1 / t, the spacing between drill hole groups should be 13 to 15 meters. Within each drill hole group, the inclination angle is set between 15 and 30 degrees. By solving the three-dimensional spatial geometric relationship, the drill holes are ensured to penetrate the entire coal seam and the roof fracture zone, forming an effective gas pre-extraction channel. The purpose of this step is to use the set coverage algorithm optimized by gray wolf hunting to solve the optimal drill hole arrangement problem, achieving maximum coverage of the coal seam area with the fewest drill holes, thereby improving pre-extraction efficiency.

[0048] The specific implementation of step S03 is: first configure the negative pressure extraction pump station, calculate the gas extraction volume, and select the appropriate pump station specifications. Usually, the coal seam gas content is 10m 3 / tThe extraction capacity must be no less than 80m 3 / min pumping station; then, a gas collection pipeline system is designed, with a main pipeline diameter of no less than 150 mm and branch pipelines no less than 100 mm. All pipeline joints are flanged to ensure airtightness, meeting the requirement of a leakage rate of less than 5%. Next, an intelligent flow control device is installed, including an electric regulating valve, a digital pressure gauge, and a flow meter. An automatic control unit is also set up to stabilize extraction parameters through negative feedback regulation. Finally, a data acquisition and remote monitoring system is constructed, with explosion-proof sensors installed to collect gas concentration, pressure, flow, and other parameters, which are transmitted to the control center via industrial Ethernet. This intelligent gas extraction system fulfills the primary function of the bottom extraction tunnel, namely, gas pre-extraction. By extracting coal seam gas through high-level directional drilling groups in the bottom extraction tunnel, it reduces the gas content in the coal seam and eliminates the risk of coal and gas outbursts. The goal of this step is to establish a comprehensive gas extraction system and create conditions for efficient gas pre-extraction.

[0049] The specific implementation method of step S04 is: first calculate the gas pre-extraction start-up time, and according to the working face advancement speed and the coal seam gas precipitation law, determine to start the gas pre-extraction function 60 to 90 days before the working face advancement, 80 to 90 days for high-gas mines and 60 to 70 days for low-gas mines; then set the extraction negative pressure parameter, control the extraction negative pressure to 15 to 25 kPa, when the gas outburst volume is large in the initial drilling, the negative pressure should be controlled at 15 to 18 kPa, and as the gas outburst volume decreases, gradually increase the negative pressure to 20 to 25 kPa; then monitor the extraction concentration, and ensure that the extraction concentration is not less than 30% by adjusting the negative pressure and flow rate, keep it outside the explosion limit, and increase the extraction purity; finally, regularly measure the coal seam gas content, and use direct or indirect measurement methods to ensure that the coal seam gas content is reduced to 3m 3 / t or less. This step, based on the theory of gas desorption kinetics, promotes the desorption of adsorbed gas from the coal seam through the action of continuous negative pressure, converting it into free gas that is captured by the extraction system. The goal of this step is to effectively pre-extract coal seam gas, reducing its content to a safe level and creating safe conditions for subsequent coal mining operations.

[0050] The specific implementation of step S05 is as follows: first, optimize the design of the working face ventilation system and establish a three-dimensional ventilation network model of the working face based on the principles of computational fluid dynamics; then, lay the return air duct in the bottom extraction tunnel. The duct diameter is determined based on the return air volume, usually not less than 1000 mm. The pipe is made of flame-retardant and antistatic materials, and the pipe joints are flanged to ensure airtightness; then, install auxiliary local ventilators in the piping system. Based on the ventilation resistance calculation, the appropriate fan model is selected, usually with a pressure of not less than 800 Pa and an air volume of not less than 30% of the total air volume of the working face; finally, adjust the air volume distribution between the bottom extraction tunnel and the main return air tunnel through dampers and air bridges, forming a dual return air system. This system uses the main return air tunnel for conventional ventilation of the working face, while the bottom extraction tunnel is responsible for directional exhaust of gas-rich areas, realizing the secondary function of the bottom extraction tunnel, namely, auxiliary return air. The purpose of this step is to use the bottom extraction tunnel to construct a dual return air system, improve the ventilation capacity of the working face, and improve gas emission conditions.

[0051] The specific implementation of step S06 is as follows: first, based on the hydrogeological conditions of the mining area, the amount of water inflow from the working face is predicted and the capacity of the drainage pipe system is designed. Generally, the diameter of the drainage pipe is not less than 150 mm, and the pipe material is corrosion-resistant and pressure-resistant material; then, a drainage pipe is laid along the side wall of the bottom pumping tunnel, with a pipe slope of not less than 3‰, and a collection pit and water pump are set every 50 meters, using a multi-stage relay drainage method; then, a water supply pipe is laid on the other side wall of the bottom pumping tunnel, with a pipe diameter of not less than 100 mm and a working pressure of not less than 2 MPa, and valves and branch interfaces are set every 100 meters; finally, a water treatment system is established, including a sedimentation tank, a filtration device, and water quality testing equipment, to ensure that the treated water quality meets the coal mine water quality standards. The system collects the water inflow from the mining area through the drainage pipe in the bottom pumping tunnel and transports it to the water treatment station. After treatment, it is then transported to the working face through the water supply pipe for dust reduction and equipment cooling, realizing the third function of the bottom pumping tunnel, namely drainage and water supply. The purpose of this step is to use bottom pumping tunnels to solve the drainage and water supply problems in the mining area and realize the recycling of water resources.

[0052] The specific implementation of step S07 is as follows: First, design a bottom-extraction tunnel transportation system. Based on the equipment and material transportation requirements, the transportation method is determined, typically using a monorail crane or belt conveyor. Then, appropriate transportation equipment is installed within the bottom-extraction tunnel. The monorail crane track must be suspended at least 2.2 meters high, the track load capacity must be no less than 5 tons, and the belt conveyor must be no less than 800 mm wide. Then, disaster shelters are set up every 300 meters within the bottom-extraction tunnel. The chambers are at least 15 square meters in size and can accommodate at least 10 people at a time. They are equipped with compressed oxygen self-rescuers, medical first aid kits, and communication devices. Finally, a communication system is installed along the entire length of the bottom-extraction tunnel, including wired telephones, wireless communication base stations, and surveillance cameras to ensure 100% signal coverage. This system uses the bottom-extraction tunnel as an auxiliary transportation channel for transporting coal mining equipment and support materials. It also serves as a personnel escape route and temporary shelter in emergencies, fulfilling the fourth function of the bottom-extraction tunnel: transportation and disaster relief. The purpose of this step is to fully utilize the space in the bottom-extraction tunnel to address transportation and safe disaster relief issues within the mining area.

[0053] Step S08 is optional and is specifically implemented as follows: First, a sensor network topology is constructed, using a tree-like network architecture. Data acquisition nodes are set up every 50 meters within the underdrainage tunnel. Multiple sensors are then installed, including a gas concentration sensor, a wind speed sensor, a temperature sensor, and a stress monitoring device. The gas sensor has a measurement range of 0 to 100% with an accuracy of no less than ±2%, a wind speed sensor has a measurement range of 0 to 20 m / s with an accuracy of no less than ±0.1 m / s, a temperature sensor has a measurement range of -10 to 60 degrees Celsius with an accuracy of no less than ±0.5 degrees Celsius, and a stress monitoring device uses fiber Bragg grating technology with a measurement range of 0 to 20 MPa. Next, a data transmission system is deployed, combining industrial Ethernet and fiber optic communications to ensure reliable and real-time data transmission. Finally, a data analysis and early warning platform is established, utilizing big data analysis and machine learning algorithms to construct a risk prediction model. When monitoring parameters exceed thresholds or show abnormal trends, the system automatically issues an alarm. This full-process monitoring system achieves comprehensive monitoring of the underdrainage tunnel's operating status through real-time data acquisition, transmission, and analysis. The purpose of this step is to establish a complete monitoring system to ensure the multifunctional and safe operation of the bottom pumping tunnel.

[0054] Step S09 is optional and is implemented as follows: First, a process for handling excessive gas levels is established. When the gas concentration exceeds 1%, a level 1 warning is activated, increasing ventilation volume; when the gas concentration exceeds 1.5%, a level 2 warning is activated, adjusting extraction parameters; and when the gas concentration exceeds 2%, a level 3 warning is activated, halting operations and evacuating personnel. Next, a process for handling ventilation system disturbances is established. When wind flow reversal occurs, the relevant dampers are immediately closed and main fan parameters are adjusted. When wind speed drops below 0.25 m / s, the auxiliary fans are activated to increase air volume; and when wind temperature exceeds 26°C, cooling measures are initiated. Finally, a process for handling instability in the underdrainage tunnel is established. When stress monitoring data indicates increased surrounding rock pressure, support strength is increased; when deformation in the underdrainage tunnel exceeds the allowable value, underdrainage tunnel repairs are carried out; and when signs of water inrush appear, the drainage system is immediately activated and personnel are evacuated. This special emergency plan ensures the safe and efficient operation of the underdrainage tunnel, which serves four functions, by clarifying the procedures for handling various abnormal situations. The purpose of this step is to establish a sound emergency plan system, improve the ability to respond to emergencies, and ensure the stable functioning of the bottom pumping tunnels.

[0055] The implementation of this bottom-extraction laneway, four-way, four-purpose coal and gas co-mining method enables a single laneway to simultaneously perform gas pre-extraction, auxiliary return air, drainage and water supply, and transportation and disaster avoidance functions, maximizing the efficient utilization of laneway resources. The optimal drilling location is determined using a set-covering algorithm optimized for gray wolf hunting, significantly improving gas extraction efficiency. The construction of a dual-return air system significantly improves working face ventilation conditions. Water recycling reduces mine drainage costs. The provision of transportation and disaster avoidance channels enhances mining area safety. Overall, this method achieves safe and efficient co-mining of coal and gas, embodying the advanced concept of comprehensive utilization of mining resources.

[0056] Specifically, the principles of this invention are as follows: The technical principles of this invention are based on the laws of gas migration, rock fracture mechanisms, and systems engineering principles. First, the bottom extraction tunnel is located 8-12 meters below the coal seam floor, ensuring tunnel stability while being within the effective gas extraction zone. This location is consistent with the mechanical properties of the rock formation, avoiding the main stress concentration areas in the mining-affected zone, while allowing effective access to the coal seam and roof fracture zone through high-level directional drilling.

[0057] The drilling arrangement utilizes a set-covering algorithm optimized for gray wolf hunting. By treating the drill hole coverage area as the hunting space and maximizing drill hole coverage and minimizing the number of drill holes as objective functions, this method addresses the incomplete coverage and redundant number issues inherent in traditional drilling arrangements. The 15-30 degree inclination design of the high-level directional drilling group, based on the formation mechanism of fracture zones and gas migration pathways, ensures that the drill holes penetrate the entire coal seam and roof fracture zones, creating efficient gas extraction channels.

[0058] The dual-return air system design, inspired by ventilation network theory, creates differentiated ventilation paths through the main return air roadway and the bottom extraction roadway, enabling zonal gas management. The main return air roadway provides routine ventilation for the working face, while the bottom extraction roadway provides targeted exhaust in gas-rich areas. This collaborative approach eliminates the risk of gas accumulation in a single channel. A controlled extraction negative pressure of 15-25 kPa and a minimum extraction concentration of 30%, based on the principles of gas desorption kinetics, effectively reduces coal seam gas content to a safe level.

[0059] The design of the full-process monitoring system and specialized emergency response plans, based on the principles of safety systems engineering, establishes a three-dimensional safety management system focused on prevention, monitoring and early warning, and emergency response. Multiple sensors work together to form a closed information loop. Even if the ventilation system is disturbed, real-time data analysis enables timely adjustment of operating parameters to prevent elevated gas concentrations and ensure safe and stable system operation.

[0060] A specific embodiment 1 of the present invention is provided below. The specific implementation of each step in this embodiment 1 is described in detail as follows.

[0061] The specific implementation method of step S01 is: first, based on the geological exploration data of the mining area, obtain basic geological information such as the occurrence state, thickness change and fault distribution of the coal seam, and at the same time collect gas geological parameters such as gas pressure, gas content and gas composition; then, through geomechanical calculations, determine the excavation route of the bottom pumping tunnel, and select a stable rock layer with a hardness coefficient of not less than 4 in the coal seam bottom rock layer as the tunnel position; finally, control the vertical distance between the bottom pumping tunnel and the coal seam to maintain it within the range of 8 to 12 meters, wherein when the coal seam thickness exceeds 3 meters, the vertical distance should be 10 to 12 meters, and when the coal seam thickness is less than 3 meters, the vertical distance should be 8 to 10 meters. The setting of this vertical distance is based on the critical layer theory to ensure that the bottom pumping tunnel is located at the edge of the coal seam mining impact area, which can not only ensure the stability of the tunnel, but also ensure that the drill hole can effectively penetrate the coal seam for gas extraction. The vertical distance D between the bottom pumping tunnel and the coal seam can be determined by the following formula:

[0062] D=max(8,min(12,K h ·h c +5)),

[0063] Where D is the vertical distance between the bottom extraction tunnel and the coal seam, in meters; K h h is the influence coefficient of coal seam thickness, ranging from 1.5 to 2.0, and the greater the coal seam strength, the smaller the value; c The purpose of this step is to establish a reasonable spatial location for the bottom extraction roadway and lay the foundation for subsequent multifunctional utilization.

[0064] The specific implementation of step S02 is: first, construct a mathematical model of the set coverage algorithm based on gray wolf hunting optimization, set the drilling position as the decision variable, and maximize the drilling coverage area and minimize the number of drilling holes as the objective function; then divide the coal seam into several grid units, each grid unit represents an area in the coal seam, and the set of grid units that can be covered by the drilling constitutes a coverage matrix; then use the social hierarchy sorting mechanism of the gray wolf optimization algorithm to sort the drilling schemes according to the coverage effect, and the first three schemes are used as α, β, and δ wolves to guide other solutions to update their positions; then, by continuously iterating and updating the position, gradually optimize the drilling layout scheme, and when the number of iterations reaches the preset value or the optimization effect of multiple consecutive iterations is not obvious, output the optimal drilling layout scheme; finally, according to the optimal layout scheme, set a high-position directional drilling group every 10 to 15 meters in the bottom pumping tunnel. The set coverage problem can be expressed as:

[0065]

[0066] x j ∈{0,1}, j=1,2,...,n,

[0067] Where n is the number of candidate drilling locations; m is the number of coal seam grid cells that need to be covered; x j is the decision variable, when the drilling is set at the jth position x j =1, otherwise x j =0;N i is the set of drilling positions that can cover the i-th grid cell. In the Grey Wolf Algorithm, the position update equation is:

[0068]

[0069] in, is the position vector of the current solution; is the prey position vector (optimal solution); is the distance vector from the current solution to the optimal solution; and is the coefficient vector, is a vector that decreases linearly with the number of iterations, from 2 to 0; and is a random vector in the interval [0, 1]. In the drilling group, the drilling inclination angle is set to 15 to 30 degrees. The inclination angle θ can be determined by the following formula:

[0070]

[0071] Where θ is the drilling inclination, in degrees; h t is the height of the roof fracture zone, in meters; h c is the thickness of the coal seam, in meters; Ld is the horizontal projection length of the borehole, in meters. The purpose of this step is to use the set-covering algorithm optimized by the gray wolf hunting algorithm to solve the optimal borehole arrangement problem, achieving the goal of covering the maximum coal seam area with the fewest boreholes and improving pre-extraction efficiency.

[0072] The specific implementation of step S03 is: first configure the negative pressure extraction pump station, calculate the gas extraction volume, and select the appropriate pump station specifications. Usually, the coal seam gas content is 10m 3 / tThe extraction capacity must be no less than 80m 3 / min pumping station; then design the gas collection pipeline system, the main pipeline diameter is not less than 150 mm, the branch pipeline diameter is not less than 100 mm, and all pipeline joints are flanged to ensure that the air tightness meets the requirement of air leakage rate less than 5%; then install the intelligent flow regulation device, including electric regulating valve, digital pressure gauge and flow meter, and set up an automatic control unit to achieve the stability of extraction parameters through negative feedback regulation; finally, build a data acquisition and remote monitoring system, install explosion-proof sensors to collect gas concentration, pressure, flow and other parameters, and transmit them to the control center via industrial Ethernet. The calculation formula of the pumping station extraction capacity Q is:

[0073]

[0074] Where Q is the extraction capacity of the pumping station, in m 3 / min; C g is the coal seam gas content, unit is m 3 / t; M is the thickness of the coal seam at the working face, in meters; V is the advancement speed of the working face, in meters / day; ρ is the density of the coal seam, in t / m 3 ;K e is the gas extraction efficiency coefficient, ranging from 0.3 to 0.6; T is the pre-extraction time, in days; K s is a safety factor, ranging from 1.2 to 1.5. This intelligent gas extraction system provides the primary function of the bottom extraction roadway, namely, gas pre-extraction. By extracting coal seam gas through high-level directional drilling holes in the bottom extraction roadway, it reduces the gas content in the coal seam and eliminates the risk of coal and gas outbursts. This step aims to establish a comprehensive gas extraction system and create conditions for efficient gas pre-extraction.

[0075] The specific implementation method of step S04 is: first calculate the gas pre-extraction start-up time, and according to the working face advancement speed and the coal seam gas precipitation law, determine to start the gas pre-extraction function 60 to 90 days before the working face advancement, 80 to 90 days for high-gas mines and 60 to 70 days for low-gas mines; then set the extraction negative pressure parameter, control the extraction negative pressure to 15 to 25 kPa, when the gas outburst volume is large in the initial drilling, the negative pressure should be controlled at 15 to 18 kPa, and as the gas outburst volume decreases, gradually increase the negative pressure to 20 to 25 kPa; then monitor the extraction concentration, and ensure that the extraction concentration is not less than 30% by adjusting the negative pressure and flow rate, keep it outside the explosion limit, and increase the extraction purity; finally, regularly measure the coal seam gas content, and use direct or indirect measurement methods to ensure that the coal seam gas content is reduced to 3m 3 / t or less. The calculation formula for the pre-pumping time T is:

[0076]

[0077] Wherein, T is the pre-extraction time, in days; C g is the initial coal seam gas content, in m 3 / t;C f is the target coal seam gas content, in m 3 / t; q is the gas extraction rate per unit time and unit coal volume, unit is m 3 / (t·d);K e is the gas extraction efficiency coefficient; K t is the time influence coefficient, which takes into account the reduced efficiency caused by prolonged extraction time and has a value range of 0.8 to 0.95. The relationship between gas extraction concentration and negative pressure can be calculated using the Langmuir isotherm adsorption equation:

[0078]

[0079] Where C is the gas extraction concentration, expressed as a percentage; a and b are the Langmuir isotherm adsorption constants, which are dependent on the coal type and temperature; and P is the extraction negative pressure, expressed in kilopascals. This step, based on the theory of gas desorption kinetics, promotes the desorption of adsorbed gas from the coal seam into free gas through the continuous negative pressure, which is then captured by the extraction system. The goal of this step is to effectively pre-extract coal seam gas, reducing its content to a safe level and creating safe conditions for subsequent coal mining operations.

[0080] The specific implementation method of step S05 is as follows: first, optimize the design of the working face ventilation system and establish a three-dimensional ventilation network model of the working face based on the principles of computational fluid dynamics; then, lay the return air duct in the bottom extraction tunnel. The diameter of the duct is determined according to the return air volume, usually not less than 1000 mm. The pipe material is flame-retardant and antistatic material, and the pipe joints are flange-connected to ensure air tightness; then, set up an auxiliary local ventilator in the pipeline system, and select the appropriate fan model based on the ventilation resistance calculation. Usually, the wind pressure is not less than 800 Pa, and the air volume is not less than 30% of the total air volume of the working face; finally, adjust the air volume distribution between the bottom extraction tunnel and the main return air tunnel through the damper and the wind bridge to form a dual return air system. The calculation formula for the return air duct diameter D is:

[0081]

[0082] Where D is the diameter of the return air duct, in meters; Q is the designed return air volume, in m 3 / s; v is the design wind speed, in m / s, generally 8 to 12 m / s. In a double-return air system, the proportion of air volume R borne by the bottom extraction roadway can be calculated using the following formula:

[0083]

[0084] Among them, R is the proportion of air volume borne by the bottom extraction tunnel; Q b The return air volume of the bottom extraction tunnel is m 3 / min;Q m Return air volume of the main return air channel, unit is m 3 / min;Q t is the total return air volume of the working surface, in m 3 / min. Based on the gas outflow rate at the working face, R ranges from 0.3 to 0.5, with greater gas outflow indicating a higher R value. This system utilizes the main return airway for conventional ventilation of the working face, while the bottom extraction roadway provides targeted exhaust in gas-rich areas, thus fulfilling the bottom extraction roadway's secondary function: auxiliary return air. This step aims to utilize the bottom extraction roadway to establish a dual return air system, improving working face ventilation capacity and enhancing gas emission conditions.

[0085] The specific implementation of step S06 is as follows: first, based on the hydrogeological conditions of the mining area, predict the water inflow from the working face and design the capacity of the drainage pipe system. Usually, the diameter of the drainage pipe is not less than 150 mm, and the pipe material is corrosion-resistant and pressure-resistant material; then, a drainage pipe is laid along the side wall of the bottom pumping tunnel, with a pipe slope of not less than 3‰, and a collection pit and water pump are set every 50 meters, using a multi-stage relay drainage method; then, a water supply pipe is laid on the other side wall of the bottom pumping tunnel, with a pipe diameter of not less than 100 mm, a working pressure of not less than 2 MPa, and valves and branch interfaces are set every 100 meters; finally, a water treatment system is established, including a sedimentation tank, a filtration device and water quality testing equipment, to ensure that the treated water quality meets the coal mine water use standards. Drainage pipe diameter D w The calculation formula is:

[0086]

[0087] Among them, D w is the diameter of the drainage pipe, in meters; Q w is the design displacement, in m 3 / s;v w The design water flow velocity is expressed in m / s, generally ranging from 1.2 to 1.8 m / s. The water recycling efficiency η can be calculated using the following formula:

[0088]

[0089] Wherein, η is the water recycling rate, expressed in percentage; Q rec is the recycled water volume, in m 3 / d;Q tot is the total water consumption, in m 3 / d. This system uses drainage pipes installed within the underdrainage roadway to collect water gushing from the mining area and transport it to a water treatment station. After treatment, it is then transported to the working face via water supply pipes for dust suppression and equipment cooling, fulfilling the underdrainage roadway's third function: drainage and water supply. This step aims to utilize the underdrainage roadway to address both drainage and water supply issues within the mining area, achieving water recycling.

[0090] The specific implementation of step S07 is as follows: first, design the bottom pumping tunnel transportation system, determine the transportation method based on the equipment and material transportation requirements, usually using a monorail crane or a belt conveyor; then install the corresponding transportation equipment in the bottom pumping tunnel, with the monorail crane track hanging height not less than 2.2 meters, the track load capacity not less than 5 tons, and the belt conveyor width not less than 800 mm; then set up disaster shelter chambers every 300 meters in the bottom pumping tunnel, with an area of not less than 15 square meters, capable of accommodating more than 10 people at a time, and equipped with compressed oxygen self-rescue devices, medical first aid kits and communication devices; finally, install a communication system along the entire length of the bottom pumping tunnel, including wired telephones, wireless communication base stations and surveillance cameras, to ensure that the signal coverage rate reaches 100%. Monorail crane transportation capacity C t The calculation formula is:

[0091]

[0092] Among them, C t is the monorail crane's transport capacity, in t / d; G is the monorail crane's rated load, in tons; V is the monorail crane's operating speed, in m / min; K u is the equipment utilization coefficient, ranging from 0.75 to 0.85; L is the transportation distance, in meters; K l is the loading factor, ranging from 0.8 to 0.9. This system utilizes the underdrainage roadway as an auxiliary transport channel for transporting coal mining equipment and support materials. It also serves as a refuge for personnel and a temporary shelter in emergencies, fulfilling the underdrainage roadway's fourth function: transport and disaster relief. This step aims to fully utilize the underdrainage roadway space to address transportation and disaster relief issues within the mining area.

[0093] The specific implementation method of step S08 is: first, construct a sensor network topology, adopt a tree network architecture, and set a data acquisition node every 50 meters in the bottom pumping tunnel; then install a variety of sensors, including gas concentration sensors, wind speed sensors, temperature sensors and stress monitoring devices, where the gas sensor has a measurement range of 0 to 100% and an accuracy of not less than ±2%, the wind speed sensor has a measurement range of 0 to 20 meters per second and an accuracy of not less than ±0.1 meters per second, the temperature sensor has a measurement range of -10 to 60 degrees Celsius and an accuracy of not less than ±0.5 degrees Celsius, and the stress monitoring device uses fiber grating technology with a measurement range of 0 to 20 MPa; then deploy a data transmission system, using a combination of industrial Ethernet and fiber optic communication to ensure data transmission reliability and real-time performance; finally, establish a data analysis and early warning platform, use big data analysis and machine learning algorithms to build a risk prediction model, and when the monitoring parameters exceed the threshold or show an abnormal change trend, the system automatically issues an alarm. The calculation formula for the sensor data acquisition frequency f is:

[0094]

[0095] Where f is the data acquisition frequency, in Hz; τ min The minimum characteristic time scale is in seconds and is determined based on the rate of change of the monitoring parameters. The risk warning model is established based on the Bayesian network, and the calculation formula for the gas over-limit risk probability P(R) is:

[0096]

[0097] Among them, p(R) is the probability of gas exceeding the limit risk; p(R|E i ) is in evidence E i The probability of risk under the conditions; P(E i ) is evidence E i The probability of a failure is 0; n is the number of pieces of evidence. This full-process monitoring system achieves comprehensive monitoring of the operating status of the underfloor pumping tunnels through real-time data collection, transmission, and analysis. The goal of this step is to establish a comprehensive monitoring system to ensure the multifunctional and safe operation of the underfloor pumping tunnels.

[0098] The specific implementation of step S09 is as follows: first, formulate a gas over-limit handling process. When the gas concentration exceeds 1%, activate the first-level warning and increase the ventilation volume; when the gas concentration exceeds 1.5%, activate the second-level warning and adjust the extraction parameters; when the gas concentration exceeds 2%, activate the third-level warning, stop the operation and evacuate personnel; then formulate a ventilation system disorder handling process. When the wind reversal occurs, immediately close the relevant dampers and adjust the main fan parameters; when the wind speed is lower than 0.25 m / s, turn on the auxiliary fan to increase the air volume; when the wind temperature exceeds 26 degrees Celsius, initiate cooling measures; finally, formulate a bottom pumping tunnel instability handling process. When the stress monitoring data shows that the surrounding rock pressure increases, increase the support strength; when the bottom pumping tunnel deformation exceeds the allowable value, repair the bottom pumping tunnel; when there are signs of water inrush, immediately start the drainage system and evacuate personnel. Emergency response time T r The calculation formula is:

[0099] T r =T d +T p +T e ,

[0100] Among them, T r is the total emergency response time, in minutes; T d T is the abnormality detection time in minutes; p is the decision processing time, in minutes; T e The time it takes to implement the disposal measures is in minutes. The formula for calculating the safe evacuation time is:

[0101]

[0102] Among them, T s is the safe evacuation time in minutes; L is the evacuation distance in meters; V e T is the personnel evacuation speed, in m / min, generally 40-60 m / min; p This represents the personnel preparation time, expressed in minutes, typically 2-3 minutes. This special emergency plan ensures the safe and efficient operation of the four-purpose underdrain tunnel by clarifying the procedures for handling various abnormal situations. The goal of this step is to establish a robust emergency plan system, enhance the ability to respond to emergencies, and ensure the stable functioning of the underdrain tunnel.

[0103] The set covering algorithm for gray wolf hunting optimization in the bottom extraction lane, one lane and four coal and gas co-mining method is a hybrid optimization algorithm that combines the gray wolf algorithm and the set covering problem. The gray wolf algorithm simulates the social hierarchy structure and hunting behavior of the gray wolf group, and guides the position update of other wolves through the three levels of α, β, and δ to achieve a balance between global search and local search. The set covering problem is a classic combinatorial optimization problem, and the goal is to cover the entire set with the least subset. In the drilling layout problem, the drilling layout position is regarded as a subset, and the coal seam area to be covered is regarded as an element. The gray wolf algorithm is used to search for the optimal drilling layout scheme, and the largest coal seam area is covered with the least number of boreholes. The position update mechanism of the gray wolf algorithm includes four stages: surrounding prey, hunting, attacking prey, and searching prey. The coefficient vector and Controls the algorithm's search behavior. When , the gray wolf moves toward the prey (development); when When , the wolf moves away from the current prey to find a better solution (exploration). The coefficient vector Increasing the randomness of the search improves the algorithm's global search capabilities. The algorithm's relevance to the drilling layout problem lies in the fact that drilling layout requires considering the maximum coal seam coverage while minimizing the number of holes to reduce costs. The gray wolf algorithm's social hierarchy and adaptive search capabilities can effectively handle high-dimensional nonlinear optimization problems such as drilling layout. By using the drilling coverage area as the hunting space and maximizing drilling coverage and minimizing the number of holes as the objective function, global optimization of drilling layout is achieved.

[0104] The implementation of this four-in-one bottom extraction tunnel method for coal and gas co-mining enables a single tunnel to simultaneously perform gas pre-extraction, auxiliary return air, drainage and water supply, and transportation and disaster avoidance functions, maximizing the efficient utilization of tunnel resources. The optimal drill hole location is determined using a set-covering algorithm optimized by gray wolf hunting, significantly improving gas extraction efficiency. The construction of a dual return air system significantly improves working face ventilation conditions. Water recycling reduces mine drainage costs. The provision of transportation and disaster avoidance channels enhances mining area safety. Overall, this method achieves safe and efficient co-mining of coal and gas, embodying the advanced concept of comprehensive utilization of mine resources. The core value of the four-in-one bottom extraction tunnel lies in resource integration and functional integration. By achieving four functions, gas control, ventilation optimization, water resource utilization, and safety assurance, a single tunnel not only saves tunnel excavation investment but also improves coal mining efficiency and safety, providing reliable technical support for the safe and efficient mining of high-gas mines.

[0105] In this embodiment, an optimization method combining the Gray Wolf Algorithm with the Set Cover Problem demonstrates significant advantages in the co-mining of coal and gas in a single, four-way bottom extraction tunnel. Traditional drilling layout methods typically rely on expert experience or simple geometric rules, making them difficult to adapt to complex and changing geological conditions, resulting in redundant boreholes or insufficient coverage. The Gray Wolf Optimization Algorithm, which simulates the social hierarchy and hunting behavior of gray wolves, possesses powerful global search and local optimization capabilities, making it particularly well-suited for solving high-dimensional nonlinear problems. The Set Cover Problem precisely defines the mathematical model for drilling layout, enabling quantitative evaluation of layout plans.

[0106] The hybrid optimization algorithm formed by combining the two approaches uses a mathematical model to divide the coal seam space into grid cells, transforming the drill hole layout problem into a problem of how to cover the largest number of coal seam grids with the fewest drill holes. The Grey Wolf Algorithm uses three levels of α, β, and δ to guide the exploration of the solution space, achieving rapid convergence to the global optimal solution. The dynamic adjustment mechanism of the coefficient vector adaptively balances global exploration and local development during the search process, enhancing the algorithm's adaptability to diverse geological conditions.

[0107] In practical application, this method can reduce the number of drill holes by 20% to 30%, while increasing the coverage area by 15% to 25%, significantly saving drilling construction costs. Compared with traditional methods, computational efficiency is increased by approximately 40%, enabling rapid generation of an optimal layout. More importantly, the optimized drilling layout improves gas pre-extraction efficiency, increasing gas extraction concentration by an average of 10 percentage points and shortening pre-extraction time by approximately 20%, creating favorable conditions for safe and efficient mining at the working face. This method can also dynamically adjust the drilling layout based on real-time geological changes, demonstrating its high practicality and technological advancement.

[0108] The following is an example 2 of a practical application scenario of the present invention: The average thickness of the coal seam in a certain coal mine is 3.5 meters, the inclination is 5 degrees, the coal seam is buried at a depth of 450-650 meters, and the coal seam gas content is 12.5m 3 / t, with a gas pressure of 2.1 MPa, making it a mine prone to coal and gas outbursts. The mining area is characterized by well-developed faults, and the surrounding rock of the coal seams is primarily sandstone and mudstone, with a hardness coefficient of 4.5-5.8. The planned working face length is 210 meters, with an advance length of 1,500 meters and a daily coal production of 5,000 tons. Based on these geological conditions, researchers designed and implemented a four-lane, coal and gas mining method using a bottom extraction tunnel. The specific implementation process is as follows.

[0109] First, the research team determined the optimal location of the bottom extraction tunnel by analyzing the geological exploration data of the mining area. After rock mechanics calculations, a sandstone layer with a hardness coefficient of 5.2 was selected as the excavation rock layer for the bottom extraction tunnel. Based on the characteristic of the coal seam thickness of 3.5 meters, the vertical distance between the bottom extraction tunnel and the coal seam is controlled to be 10-12 meters. The tunnel cross-section is rectangular, 4.5 meters wide, 3.8 meters high, and 1,650 meters long, covering the entire mining area working face and the protective coal pillars on both sides. Figure 2 As shown, the schematic diagram of the four-purpose functional structure of the bottom extraction lane clearly demonstrates the multifunctional configuration of the lane.

[0110] For the arrangement of drilling holes, the researchers applied the gray wolf hunting optimized set coverage algorithm to determine the optimal drilling position and angle. First, the working surface was divided into 105 grid units of 20 meters × 20 meters, and then the effective coverage radius of the drilling was set to 25 meters to construct a coverage matrix. After 350 iterative calculations, it was determined that a high-position directional drilling group would be set up every 12 meters in the bottom pumping tunnel. Each group contained 5 boreholes, which were drilled upward at inclinations of 18 degrees, 22 degrees, 25 degrees, 27 degrees and 29 degrees respectively. The borehole diameter was 94 mm and the maximum drilling length was 145 meters. Figure 3 The drilling coverage diagram shows the optimized drilling arrangement plan. According to this plan, a total of 138 drilling groups, a total of 690 boreholes, and a total drilling length of 85,560 meters are required. The drilling coverage effect data is shown in Table 1:

[0111] Table 1 Drilling coverage effect data table

[0112]

[0113] To achieve the gas pre-extraction function, researchers installed an intelligent gas extraction system. The system is equipped with a total extraction capacity of 1000m 3 / min negative pressure extraction pump station, including 10 single units with extraction capacity of 100m 3 / min water ring vacuum pump. The gas collection pipeline system has a main pipeline diameter of 200 mm and a branch pipeline diameter of 120 mm. The pipeline is made of high-strength steel pipe and the pipe joints are flange-connected. The air leakage rate in the air tightness test is only 3.2%. Electric regulating valves, digital pressure gauges and flow meters are installed in each drilling group to form an intelligent flow control device, which realizes automatic adjustment through the PLC control unit. Figure 4 As shown in the figure, the concentration, pressure and flow sensor layout diagram shows in detail the installation location and connection method of various sensors in the system. The main parameters of the system are shown in Table 2:

[0114] Table 2 Gas extraction system parameters

[0115] Parameter name Parameter value Control method Allowable error range Negative pressure 15-25kPa Automatic adjustment ±0.5kPa Drilling flow <![CDATA[0.5-3.8m 3 / min]]> Automatic adjustment <![CDATA[±0.2m 3 / min]]> Gas concentration 30-85％ Monitoring alarm ±2％ Pipeline network temperature 15-22℃ Monitoring alarm ±1℃ Pipeline network pressure drop <1.8kPa / 100m Monitoring alarm ±0.2kPa

[0116] Gas pre-extraction work was started 85 days before the working face was advanced. The initial extraction negative pressure was controlled at 16kPa. As the gas outflow decreased, it was gradually increased to 23kPa. During the extraction process, the gas concentration was maintained between 42-68%, and the pure extraction volume reached 7.8m 3 / min. After 80 days of continuous extraction, the coal seam gas content decreased from the initial 12.5m 3 / t reduced to 2.6m 3 / t, a decrease of 79.2%, effectively eliminating the danger of coal and gas outburst. The extraction data during the gas pre-extraction period are shown in Table 3:

[0117] Table 3 Gas pre-extraction stage extraction data

[0118]

[0119] In order to realize the auxiliary return air function, the researchers laid the return air pipeline in the bottom extraction tunnel. The pipeline diameter is 1200 mm and it is made of flame retardant and antistatic materials. Three auxiliary local ventilators are set in the pipeline system, with a single unit air pressure of 850Pa and an air volume of 15m 3 / s. By adjusting the damper and the air bridge, the air volume distribution ratio between the bottom extraction tunnel and the main return air tunnel is 3:7, forming a double return air system. Figure 5 The dual-duct structure diagram shows the layout of the ventilation system consisting of the main return air duct and the bottom extraction duct. This system effectively improves the gas emission capacity of the working face, controlling the gas concentration below 0.4%, which is significantly better than the national safety standard of 0.8%. The main parameters of the ventilation system are shown in Table 4:

[0120] Table 4 Double return air system operating parameters

[0121]

[0122]

[0123] In order to realize the drainage and water supply function, the researchers laid a drainage pipeline along one side of the bottom pumping tunnel. The pipeline diameter is 180 mm, the pipe material is corrosion-resistant high-strength composite material, and the pipeline slope is 3.5‰. A collection pit and a water pump are set up every 45 meters, and a multi-stage relay drainage method is adopted. A water supply pipeline is laid on the other side of the bottom pumping tunnel. The pipeline diameter is 120 mm and the working pressure is 2.5 MPa. The established water treatment system includes 550m 3 The system realizes the recycling of mine water and processes 4200m3 of water per day. 3 , saving 3600m3 of fresh water 3 , the water recycling rate reached 85.7%. The mine water treatment and utilization situation is shown in Table 5:

[0124] Table 5 Mine water treatment and utilization data

[0125] Water quality parameters Before treatment After processing National Standards Compliance pH 6.4 7.2 6-9 meet the standards Suspended solids (mg / L) 286 12 ≤20 meet the standards Chemical oxygen demand (mg / L) 48 15 ≤50 meet the standards Sulfide (mg / L) 0.82 0.08 ≤0.5 meet the standards Total hardness (German scale) 15.8 8.4 ≤12 meet the standards Iron ion (mg / L) 2.5 0.12 ≤0.3 meet the standards

[0126] In order to realize the function of transport and disaster avoidance, researchers installed a monorail crane transportation system in the bottom pumping tunnel. The track suspension height is 2.3 meters and the track load capacity is 8 tons. The equipment is equipped with 4 monorail cranes, each with a traction capacity of 3 tons and a maximum operating speed of 120m / min. Disaster shelter chambers are set up every 280 meters in the bottom pumping tunnel. The chamber area is 18 square meters and can accommodate 15 people at the same time. It is equipped with 30 compressed oxygen self-rescuers, 3 medical first aid kits, 2 sets of communication devices, and drinking water and food reserves for 15 people for 72 hours. Figure 6 As shown in the figure, the disaster shelter structure diagram shows the layout and equipment configuration of the disaster shelter chamber in detail. The equipment configuration of the disaster shelter chamber is shown in Table 6:

[0127] Table 6 Disaster Shelter Chamber Equipment Configuration

[0128] Device Name quantity Specifications Validity period Compressed oxygen self-rescuer 30 units ZYX-60 5 years First aid kit 3 YJX-III 2 years Telephone 1 set KTH-15 8 years Wireless communication devices 1 set KXT-3 8 years drinking water 180 bottles 550mL / bottle 1 year Compressed biscuits 60 packs 125g / pack 2 years Emergency lighting 6 lamps ZM-12 10 years Gas detectors 2 units JCB-50 3 years

[0129] In terms of the full-process monitoring system, researchers built a sensor network with a tree-like network architecture, setting up a data acquisition node every 48 meters in the bottom pumping tunnel, for a total of 35 nodes. 42 gas concentration sensors, 28 wind speed sensors, 42 temperature sensors, and 18 stress monitoring devices were installed. Sensor data is transmitted to the data analysis and early warning platform in real time through a combination of industrial Ethernet and fiber optic communication. Figure 7 The diagram below shows the deployment of data collection nodes through the data analysis and early warning platform, demonstrating the network structure and data flow of the entire monitoring system. This system uses big data analysis and machine learning algorithms to build a risk prediction model, achieving an early warning accuracy rate of 95.4% and an average lead time of 12.5 minutes. The main sensor parameters of the monitoring system are shown in Table 7:

[0130] Table 7 Monitoring system sensor parameters

[0131]

[0132] Researchers have developed special emergency plans and clarified the procedures for handling various abnormal situations. Figure 8 The gas over-limit handling process diagram detailed the emergency response steps for different gas concentration thresholds. When the gas concentration exceeds 1%, a Level 1 alert is activated, increasing ventilation by 20%. When the gas concentration exceeds 1.5%, a Level 2 alert is activated, increasing the extraction pressure by 30%. When the gas concentration exceeds 2%, a Level 3 alert is activated, halting operations and evacuating personnel. Through repeated drills, this plan ensures an emergency response time of less than 3 minutes, effectively improving the ability to respond to emergencies.

[0133] The combined coal and gas mining method, using four methods in one bottom-drained lane and one lane, has achieved remarkable results. This method achieved a coal seam gas extraction rate of 82.5%, increased the face recovery rate by 5.8 percentage points to 89.4%, improved coal mining efficiency by 18.2% to 6,250 tons per day, extended the safe production cycle by 22.4% to 48 days, increased lane resource utilization by 300%, and boosted overall economic benefits by 26.8%.

[0134] Traditional coal mining typically utilizes single-function tunnels, requiring separate excavation for gas extraction, return air, drainage, and haulage tunnels. This results in extensive tunnel construction and significant resource waste. Traditional gas extraction methods often rely on empirical methods to determine borehole layout, resulting in incomplete coverage and redundant drilling, leading to low extraction efficiency. Traditional ventilation systems often utilize a single return air duct, which can easily create gas accumulation areas and pose safety risks.

[0135] This invention achieves the integration of tunnel functions through the innovative design of a bottom extraction tunnel with four functions, integrating the functions of four tunnels into one tunnel, significantly reducing tunnel engineering workload and saving construction costs. The drilling layout is determined by the set coverage algorithm optimized by gray wolf hunting. Compared with the traditional empirical method, the number of drill holes is reduced by 15.6%, the coverage rate is increased by 12.3%, and the extraction efficiency is increased by 28.5%. The dual return air system design increases the gas emission capacity by 62.4% and reduces the average gas concentration at the working face by 45.8%. The water recycling system design increases the mine water utilization rate from the traditional 50% to 85.7%, significantly reducing the risk of environmental pollution.

[0136] It should be noted that the variables involved in the present invention are explained in detail as shown in Table 8 below.

[0137] Table 8 Variable explanation table

[0138]

[0139]

[0140] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A method for mining coal and gas in a bottom extraction lane with four uses, characterized in that: include: Excavating bottom extraction tunnels in the coal seam floor rock layer; In the bottom extraction tunnel, a set covering algorithm that takes into account wolf hunting optimization is applied to determine the drilling positions and angles of the high-level directional drilling group; an intelligent gas extraction system is installed to provide a gas pre-extraction function; Start the gas pre-extraction function; during the mining period of the working face, use the bottom extraction tunnel to lay the return air pipeline to build a double return air system to form an auxiliary return air functional structure; lay drainage pipelines and water supply pipelines in the bottom extraction tunnel to form a drainage and water supply functional structure; install transportation equipment, disaster shelter chambers and communication systems in the bottom extraction tunnel to form a transportation and disaster shelter functional structure.

2. The method for mining coal and gas in a bottom extraction lane with four functions according to claim 1 is characterized in that: When excavating the bottom pumping tunnel, keep the vertical distance between the bottom pumping tunnel and the coal seam at 10-12 meters to ensure the stability of the bottom pumping tunnel and the gas extraction effect.

3. The method for mining coal and gas in a bottom extraction lane with four functions according to claim 2 is characterized in that: A high-position directional drilling group is set up every 10 to 15 meters in the bottom extraction tunnel. By solving the optimization model of covering the maximum coal seam area with the minimum number of drill holes, the inclination angle of the drill holes in the high-position directional drilling group is determined to be 15 to 30 degrees, so that the drill holes in the high-position directional drilling group pass through the entire coal seam and the roof fracture zone, forming a gas pre-extraction channel.

4. The method for mining coal and gas in a bottom extraction lane with four functions according to claim 3 is characterized in that: The set cover algorithm for gray wolf hunting optimization is a heuristic search algorithm that simulates the social hierarchy structure and hunting behavior of gray wolf groups to globally optimize the drilling arrangement problem. The drilling coverage area is used as the hunting space, and maximizing the drilling coverage and minimizing the number of drilling holes are used as the objective functions.

5. The method for mining coal and gas in a bottom extraction lane with four functions according to claim 4 is characterized in that: The intelligent gas extraction system includes a negative pressure extraction pump station, a gas collection pipeline and a flow regulating device.

6. The method for co-mining coal and gas in a bottom extraction lane and a fourth lane according to claim 5 is characterized in that: Start gas pre-extraction 60 to 90 days before the working face advances, control the extraction negative pressure to 15 to 25 kPa, and the extraction concentration to be no less than 30%, ensuring that the coal seam gas content is reduced to 3m 3 / t or less.

7. The method for mining coal and gas in a bottom extraction lane and a fourth lane according to claim 6 is characterized in that: Gas pre-extraction refers to the extraction of coal seam gas through a high-position directional drilling group in the bottom extraction tunnel before coal seam mining, thereby reducing the gas content in the coal seam and eliminating the danger of coal and gas outbursts.

8. The method for mining coal and gas in a bottom extraction lane with four functions according to claim 7, characterized in that: The auxiliary return air functional structure uses the bottom extraction tunnel as the auxiliary return air channel in the mining area, forming a double return air system with the main return air tunnel, enhancing the ventilation capacity of the working face and improving the gas dilution and emission efficiency.

9. The method for mining coal and gas in a bottom extraction lane with four functions according to claim 8, characterized in that: The double-return air system is a ventilation system composed of the main return air roadway and the bottom extraction roadway. The main return air roadway is responsible for conventional ventilation of the working face, and the bottom extraction roadway is responsible for directional discharge of gas-enriched areas.

10. The method for mining coal and gas in a bottom extraction lane with four functions according to claim 9, characterized in that: One tunnel with four uses means that the bottom extraction tunnel has the functions of gas pre-extraction, auxiliary return air, drainage and water supply, and transportation and disaster avoidance, thus realizing efficient utilization of tunnel resources and safe production in coal mines.

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