Gas extraction method across goaf of working face and double-source sensing and dynamic joint debugging system

Abstract

This invention belongs to the field of coal mine gas drainage technology. The purpose is to provide a method for gas drainage across the goaf of a working face and a dual-source sensing and dynamic control system, applicable to small coal pillar and pillarless mining processes, achieving the goal of pre-treatment and full-cycle coverage of gas in the goaf of two working faces using a single borehole. The technical solution is as follows: S1, Before the start of mining in the first working face, plan at least one directional long borehole penetrating the mining-affected area of ​​both working faces from the solid coal roadway of the subsequent working face; S2, Complete the construction of the directional long borehole according to the designed trajectory, and implement graded targeted borehole protection for high-risk sections within the directional long borehole; S3, Connect all directional long boreholes to the gas drainage system, draining gas from the first working face during its mining period, and draining gas from both working faces during the mining period of the subsequent working face. This invention is used for gas drainage in small coal pillar and pillarless mining processes in coal mines.

Description

Technical Field

[0001] This invention relates to a method for gas extraction across working faces and a dual-source sensing and dynamic control system for goaf extraction, belonging to the field of coal mine gas extraction technology. Background Technology

[0002] To improve coal resource recovery rates, techniques such as small coal pillar roadway excavation along the goaf and pillarless self-contained roadways (such as the "110 method") are widely used. However, these techniques reduce or eliminate traditional isolation coal pillars between working faces, with pillar widths ranging from 0-8m. This leads to the connection of roof fractures in adjacent goaf areas, causing complex gas migration and mutual influence between the two working faces under mining pressure, resulting in the unprecedented challenge of "regional gas collaborative management." Specifically, this manifests as follows: (1) Governance blind spots: Existing technologies mostly adopt an isolated governance model of "one face, one policy", that is, to construct high-level roof boreholes or high-level drainage roadways separately for each mining face. This method can only extract gas from the goaf of a single working face and cannot effectively intercept gas outbursts from adjacent goafs. There are governance blind spots in the working face connection area, and the risk of gas exceeding the limit in the upper corner is high.

[0003] (2) Repetitive and inefficient engineering: Each working face needs to carry out independent extraction engineering, resulting in superimposed engineering volume and high cost. In addition, frequent gas control engineering occupies roadway space and construction time, exacerbating the tight situation of mining succession.

[0004] (3) Traditional high-level boreholes have limited length and short service cycles, and are prone to collapse and failure, especially under the influence of mining. Moreover, the borehole design parameters are fixed and cannot be optimized according to different coal pillar conditions (no coal pillar and small coal pillar), and the reliability and effectiveness are unstable under different geological conditions.

[0005] (4) Insufficient technical adaptability: The control of the existing gas extraction system mainly relies on manual experience. The valves are manually adjusted based on limited monitoring point data (such as the upper corner). The response is lagging, and it is impossible to accurately identify and balance gas outbursts from different sources. The control process is crude, and the safety level is greatly affected by human factors.

[0006] Therefore, there is an urgent need for an innovative approach that can systematically solve the above problems from the perspective of overall safety and economic benefits of dual working faces. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for gas extraction across goaf areas in working faces and a dual-source sensing and dynamic adjustment system, applicable to small coal pillar and no coal pillar (coal pillar width of 0-8m) mining processes, achieving the goal of pre-treatment of gas in goaf areas of two working faces with a single borehole and full-cycle coverage.

[0008] In this invention, "dual sources" refers to the gas in the goaf of the first mining face and the gas in the face of the subsequent mining face.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a method for gas extraction across the goaf of a working face, comprising the following steps: S1. Before the first mining face begins to be mined, at least one directional long borehole is planned from the solid coal roadway of the subsequent mining face to penetrate the mining-affected area of ​​both mining faces. The directional long borehole should cover the mining-affected fracture area that will be formed during the future mining of the subsequent mining face, and its end point should be located within the effective extraction range of the goaf of the first mining face. S2. Complete the construction of the directional long borehole according to the design trajectory, and implement graded targeted borehole protection for high-risk sections within the directional long borehole; S3. Connect all directional long boreholes to the gas extraction system and extract the gas from the first working face during the mining period. In the subsequent working face mining period, extract the gas from both working faces.

[0010] Preferably, in S1, when planning directional long boreholes, there are two trajectory types, which are selected according to the width W of the coal pillar between the first mining face and the subsequent mining face. The high-level rapid crossing trajectory is suitable for situations where W<3m, i.e., there is no coal pillar or extremely narrow coal pillar. It requires the directional long borehole to be constructed towards the roof at a set elevation angle of 15° to 25°, so that the directional long borehole can quickly enter and stabilize in the relatively stable rock strata in the upper part of the fracture zone of the roof of the goaf, and extend horizontally along this stratum for a long distance. The stress edge crossing trajectory is suitable for situations where the coal seam is 3m≤W≤8m, i.e., small coal pillars. It requires directional long boreholes to be constructed towards the roof at a set elevation angle of 10° to 18°. The horizontal projection path needs to be designed to cross the roof rock layer directly above the small coal pillar in a curved form, and the vertical distance h of the crossing, i.e., the vertical distance from the coal seam roof, should be controlled within the range of 2 to 6 times the mining height.

[0011] Preferably, in S2, when W < 3m, the long horizontal section of the directional long borehole is fully protected; when 3m ≤ W ≤ 8m, the directional long borehole is locally reinforced and protected in the stress disturbance zone of the coal pillar.

[0012] Preferably, when W < 3m, high-strength screen pipes are installed along the entire length of the horizontal section of the directional long borehole for borehole protection. When 3m ≤ W ≤ 8m, high-strength shear-resistant screen pipes are installed along the stress disturbance zone of the coal pillar through the directional long borehole, and a composite method of targeted reinforcement and grouting is used for borehole protection.

[0013] Preferably, in S2, the opening section of the directional long borehole is a conventional risk zone, and a standard casing consolidation process is used to protect the borehole.

[0014] Preferably, in S3, the gas extraction system is equipped with a dual-source sensing and dynamic coordination system, which includes: a physical sensing layer, a data transmission layer, an analysis and decision-making layer, and a collaborative execution layer. The physical sensing layer includes a multi-parameter sensor network positioned at the depth, shallowness, orifice, and upper corner of the dual working surfaces of the directional long borehole, collecting the following data in real time: The physical sensing layer includes a multi-parameter sensor network positioned at the depth, shallowness, orifice, and upper corner of the dual working surfaces of the directional long borehole, collecting the following data in real time: a. Gas parameters of the old coal seam at the first mining face: Sensors installed deep in directional long boreholes, located in the corresponding section of the goaf roadway or above the coal pillar near the first mining face at the junction of the first mining face and the subsequent mining face, collect the actual gas concentration at their location in real time. and negative pressure ; b. Gas parameters of the working face: Gas concentration at the location of the sensor installed in the shallow part of the directional long borehole, in the section corresponding to the future goaf of the working face, is collected in real time. ; c. Comprehensive parameters at the borehole opening: The gas concentration at the borehole opening is collected in real time by a comprehensive monitoring unit installed at the borehole opening of the directional long borehole. Orifice gas flow and orifice negative pressure ; d. Safety monitoring parameters: The gas concentration at the upper corner of the first mining face and the upper corner of the subsequent mining face is collected in real time by sensors installed at the upper corner of the upper corner. and ; The data collected by the aforementioned physical sensing layer is uploaded to the analysis and decision-making layer in real time through the data transmission layer; The analysis and decision-making layer receives data transmitted from the physical perception layer through the data transmission layer. Through the built-in gas emission source analysis model, it dynamically calculates the gas contribution rate of the dual working faces in the corresponding directional long borehole. Based on the changes in the contribution rate and safety objectives, it generates two-level collaborative control instructions. The collaborative execution layer includes two levels of actuators: one is the frequency conversion control system of the ground extraction pump station, which adjusts the total negative pressure of the extraction system according to the collaborative control instructions; the other is the intelligent regulating valve installed at the orifice of each directional long borehole, which adjusts the resistance and flow distribution of its respective branch according to the collaborative control instructions.

[0015] Preferably, the gas emission source analysis model in the analysis and decision-making layer is constructed based on the two-end concentration-flow balance method, and dynamically calculates the gas contribution rate of the two working faces through real-time monitoring data. Its core algorithm is as follows: The dynamic calculation formula for gas contribution rate is as follows: In the formula: —Gas contribution rate of the goaf area in the first mining face (1), % —Gas contribution rate of the goaf area of ​​the continuing working face (2), % —Gas concentration measured by deep sensor in directional long borehole (4), % —Gas flow rate in the deep section of the directional long borehole (4), m³ / min; —Measured methane concentration at the borehole opening of directional long borehole (4), % —Measured gas flow rate at the orifice of the directional long borehole (4), m³ / min; in, Without measured data, it is necessary to perform inverse calculations using the mass balance equations, and solve the following system of equations simultaneously: In the formula: —Gas concentration measured by shallow sensor in directional long borehole (4), % —Gas flow rate in the shallow section of the directional long borehole (4), m³ / min.

[0016] Preferably, the analysis and decision-making layer incorporates a hierarchical control strategy, based on the real-time calculated contribution rate of the old goaf area in the first mining face. Execute the following coordinated control instructions: a. Strong Draining of Old Pool Mode: When When the gas content is ≥70%, the main source of gas in the goaf of the first mining face is determined to be gas. The control objective is to increase the negative pressure of the drainage system on the old mining side. The instructions are executed simultaneously: ① Increase the frequency of the frequency converter of the surface drainage pump station to increase the total negative pressure of the drainage system; ② Increase the opening of the intelligent regulating valve at the orifice of the corresponding directional long borehole to reduce the resistance of this branch. The negative pressure on the old mining side is monitored in real time. The upward trend is used to verify the effectiveness of instruction execution; b. Dynamic Balance Mode: When 70% > When the concentration is >30%, it is determined to be the period of dual-source gas mixing equilibrium. The control objective is to match the extraction capacity of the directional long borehole with the proportion of dual-source gas emission. The instructions are executed synchronously: ① Dynamically optimize the total negative pressure of the extraction system based on the mixing ratio; ② Based on the current calculated... / The ratio is the target value. The opening of the intelligent regulating valve at the orifice of the corresponding directional long borehole is finely adjusted, and the gas concentration at the orifice is monitored. and orifice gas flow The stability of the balance is used to evaluate its effectiveness. c. Current-maintaining and voltage-controlled mode: When When the gas concentration is ≤30%, the gas source of the working face is determined to be the working face itself. The control objective is to ensure the gas extraction flow rate of the working face while preventing air leakage in the goaf due to excessive negative pressure. The instructions are executed simultaneously: ① Maintain or slightly reduce the total negative pressure of the extraction system to the economic operating range; ② Finely adjust the opening of the intelligent regulating valve at the orifice of the corresponding directional long borehole to reduce the negative pressure at the orifice of the directional long borehole. Controlling the gas flow rate within the optimal extraction window by monitoring the orifice gas flow rate. and the gas concentration in the upper corner of the working face To determine the effectiveness of the control.

[0017] A dual-source sensing and dynamic coordination system for implementing the above-mentioned cross-working face goaf gas extraction method, comprising a physical sensing layer, a data transmission layer, an analysis and decision-making layer, and a collaborative execution layer.

[0018] Compared with the prior art, the present invention has the following beneficial effects.

[0019] 1. This invention pioneered the "one hole protects two sides throughout the entire cycle" model, eliminating blind spots in gas control in both space and time, and realizing regionalized control.

[0020] 2. In this invention, two directional long borehole trajectories are set for different situations, and a graded targeted borehole protection process is adopted to ensure the long-term effectiveness of directional long boreholes under different coal pillar conditions.

[0021] 3. In this invention, the dual-source sensing and dynamic coordination system enables accurate sensing, source and flow analysis, and automatic coordinated control of complex gas outbursts, thus elevating gas management to a new level of intelligence.

[0022] 4. The technology of this invention has significant economic benefits, reducing the amount of special engineering work for roof gas control by about 50%, greatly reducing the cost per ton of coal, and effectively alleviating the contradiction between mining and excavation. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly introduced below.

[0024] Figure 1 This is a schematic diagram of the overall process layout of the present invention.

[0025] Figure 2This is a cross-sectional schematic diagram of the directional long borehole in this invention when it follows a high-level, rapid-crossing trajectory.

[0026] Figure 3 This is a cross-sectional schematic diagram of the directional long borehole in this invention when it follows a stress edge crossing trajectory.

[0027] Figure 4 This is a cross-sectional schematic diagram of the graded targeted hole protection process in the present invention when the directional long borehole has a high-position rapid crossing trajectory.

[0028] Figure 5 This is a cross-sectional schematic diagram of the graded targeted hole protection process in this invention when the directional long borehole has a stress edge crossing trajectory.

[0029] Figure 6 This is a schematic diagram of the dual-source sensing and dynamic coordination system architecture and working principle in this invention.

[0030] In the diagram: 1 is the first mining face, 2 is the subsequent mining face, 3 is the solid coal roadway, 4 is the directional long borehole, and 5 is the coal pillar. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The present invention provides the following embodiments.

[0033] like Figure 1 As shown, the gas extraction method for cross-working face goaf of the present invention includes the following steps: S1. Before the first mining face 1 begins to be mined, at least one directional long borehole 4 is planned from the solid coal roadway 3 of the subsequent mining face 2 to penetrate the mining-affected area of ​​the two mining faces. The directional long borehole 4 should cover the mining-affected fracture area that will be formed when the subsequent mining face 2 is mined in the future, and its end point is located within the effective extraction range of the goaf of the first mining face 1. S2. Complete the construction of directional long borehole 4 according to the design trajectory, and implement graded targeted borehole protection for high-risk sections within directional long borehole 4; S3. Connect all directional long boreholes 4 to the gas extraction system, extract the gas from the first working face 1 during its mining period, and extract the gas from both working faces during the mining period of the subsequent working face 2.

[0034] like Figure 2 , Figure 3As shown, in S1, when planning the directional long borehole 4, there are two types of trajectory, which are selected according to the width W of the coal pillar 5 between the first mining face 1 and the subsequent mining face 2. The high-level rapid crossing trajectory is suitable for situations where W<3m, i.e., there is no coal pillar or extremely narrow coal pillar. It requires the directional long borehole 4 to be constructed towards the roof at a set elevation angle of 15° to 25°, so that the directional long borehole 4 can quickly enter and stabilize in the relatively stable rock strata in the upper part of the fracture zone of the roof of the goaf, and extend horizontally along this stratum for a long distance. The stress edge crossing trajectory is suitable for situations where the coal seam is 3m≤W≤8m, i.e., small coal pillars. It requires the directional long borehole 4 to be constructed towards the roof at a set elevation angle of 10° to 18°. Its horizontal projection path needs to be designed to cross the roof rock layer directly above the small coal pillar in a curved form, and the vertical distance h of the crossing, i.e., the vertical distance from the coal seam roof, should be controlled within the range of 2 to 6 times the mining height.

[0035] Parameter Description: The range of the vertical distance h is determined based on the following: it is necessary to ensure that the trajectory of the directional long borehole 4 is located above the coal pillar 5 within the fracture development zone formed by mining, and effectively avoids the high-stress core area directly below the coal pillar 5. Based on theoretical analysis and engineering practice, this vertical distance h should be 2 to 6 times the mining height. When h is less than 2 times the mining height, the directional long borehole 4 is easily unstable due to the concentrated stress of the coal pillar 5 and the direct roof collapse. When h is greater than 6 times the mining height, the directional long borehole 4 may exceed the effective fracture connectivity zone, resulting in a significant reduction in extraction efficiency. In particular, when h is within the range of 2.5 to 4.5 times the mining height, an optimal balance can be achieved between borehole stability and gas extraction efficiency.

[0036] In S2, when W < 3m, the long horizontal section of the directional long borehole 4 is fully protected, and when 3m ≤ W ≤ 8m, the directional long borehole 4 is locally reinforced to protect the stress disturbance zone of the coal pillar.

[0037] like Figure 4 , Figure 5 As shown, specifically, when W < 3m, high-strength screen pipes are installed along the entire length of the horizontal section of the directional long borehole 4 for borehole protection. When 3m ≤ W ≤ 8m, high-strength shear-resistant screen pipes are installed along the stress disturbance zone of the coal pillar through the directional long borehole 4, and a composite method of targeted reinforcement is used to strengthen the borehole protection by combining grouting reinforcement.

[0038] In S2, the opening section of the directional long borehole 4 is a conventional risk zone, and the standard casing consolidation process is used to protect the borehole.

[0039] In S3, the gas extraction system is equipped with a dual-source sensing and dynamic coordination system, which includes: a physical sensing layer, a data transmission layer, an analysis and decision-making layer, and a collaborative execution layer. like Figure 6As shown, the physical sensing layer includes a multi-parameter sensor network installed at the deep and shallow parts, the borehole opening, and the upper corner of the dual working surfaces of the directional long borehole 4, which collects the following data in real time: a. Gas parameters of the first mining face 1: The actual gas concentration at the location of the sensor installed deep in the directional long borehole 4, at the junction of the first mining face 1 and the subsequent mining face 2, in the corresponding section of the goaf roadway or above the coal pillar 5 near the first mining face 1, is collected in real time. and negative pressure ; b. Gas parameters of the working face 2: Gas concentration at the location of the sensor installed in the shallow part of the directional long borehole 4, in the corresponding section of the future goaf of the working face 2, is collected in real time. ; The sensor is installed in the shallow section of the directional long borehole 4, which is located in the main section of the directional long borehole 4 where gas is flowing into the face. The concentration value is between and Between these values, the changes can sensitively reflect the changes in the intensity of gas outburst at the surface; c. Comprehensive parameters at the borehole opening: The gas concentration at the borehole opening is collected in real time by a comprehensive monitoring unit installed at the opening of the 4th borehole in the directional long borehole. Orifice gas flow and orifice negative pressure It is used to monitor the overall drilling extraction effect and provide quality balance constraints for the dual-source contribution rate calculation. d. Safety monitoring parameters: The gas concentration at the upper corner of the first working face 1 and the upper corner of the subsequent working face 2 is collected in real time. and This serves as the final criterion for determining safety threshold control. The data collected by the aforementioned physical sensing layer is uploaded to the analysis and decision-making layer in real time through the data transmission layer; The analysis and decision-making layer receives data from the physical perception layer through the data transmission layer. Using the built-in gas emission source analysis model, it dynamically calculates the gas contribution rate of the two working faces in the corresponding directional long borehole 4. Based on the changes in the contribution rate and the safety target, it generates two-level collaborative control instructions. The collaborative execution layer includes two levels of execution mechanisms: one is the frequency conversion control system of the ground extraction pump station, which adjusts the total negative pressure of the extraction system according to the collaborative control instructions; the other is the intelligent regulating valve installed at the four orifices of each directional long borehole, which adjusts the resistance and flow distribution of their respective branches according to the collaborative control instructions.

[0040] The gas emission source analysis model in the analysis and decision-making layer is constructed based on the two-end concentration-flow balance method. It dynamically calculates the gas contribution rate of the two working faces by real-time monitoring data. Its core algorithm is as follows: The dynamic calculation formula for gas contribution rate is as follows: In the formula: —Gas contribution rate of the goaf area in the first mining face 1, % —Gas contribution rate of the goaf area of ​​the second working face, % —Measured methane concentration using a deep sensor in a directional long borehole, % —Gas flow rate in the corresponding section of the deep part of directional long borehole 4, m³ / min; —Measured methane concentration at the four borehole openings of the directional long borehole, % —Measured gas flow rate at the four borehole openings of a directional long borehole, m³ / min; in, Without measured data, it is necessary to perform inverse calculations using the mass balance equations, and solve the following system of equations simultaneously: In the formula: —Gas concentration measured by shallow sensor in directional long borehole (4), % —Gas flow rate in the shallow section of the directional long borehole (4), m³ / min.

[0041] Adaptive correction: The gas emission source analysis model automatically corrects the calculation parameters every 24 hours based on the mass balance relationship between the measured gas concentration in the upper corner and the total amount extracted, thus eliminating systematic errors.

[0042] The analysis and decision-making layer incorporates a hierarchical control strategy, which is based on the real-time calculated contribution rate of the goaf area of ​​the first mining face. Execute the following coordinated control instructions: a. Strong Draining of Old Pool Mode: When When the gas concentration is ≥70%, the main source of gas in the goaf of the first mining face is determined to be methane. The control objective is to increase the negative pressure of the drainage system on the old mine side. The instructions are executed simultaneously: ① Increase the frequency of the frequency converter of the surface drainage pump station to increase the total negative pressure of the drainage system; ② Increase the opening of the intelligent regulating valve at the opening of the corresponding directional long borehole 4 to reduce the resistance of this branch. The negative pressure on the old mine side is monitored in real time. The upward trend is used to verify the effectiveness of instruction execution; b. Dynamic Balance Mode: When 70% > When the concentration is >30%, it is determined to be the period of dual-source gas mixing equilibrium. The control objective is to match the extraction capacity of the directional long borehole 4 with the gas emission ratio of the dual sources. The instructions are executed synchronously: ① Dynamically optimize the total negative pressure of the extraction system based on the mixing ratio; ② Based on the current calculation... / The ratio is the target value. The opening of the intelligent regulating valve at the four orifices of the corresponding directional long borehole is finely adjusted, and the gas concentration at the orifice is monitored. and orifice gas flow The stability of the balance is used to evaluate its effectiveness. In dynamic equilibrium mode, the goal is to match the extraction capacity of the extraction system with the current actual gas emission ratio. In other words, the opening of the intelligent regulating valve at the orifice should allow the gas flowing in from the two sources to be extracted smoothly without accumulation. Therefore, the goal of regulation is to maintain stable extraction under the current ratio. c. Current-maintaining and voltage-controlled mode: When When the gas concentration is ≤30%, the gas source of the working face (2) is determined to be the main source. The control objective is to ensure the gas extraction flow rate of the working face while preventing air leakage in the goaf due to excessive negative pressure. The instructions are executed simultaneously: ① Maintain or slightly reduce the total negative pressure of the extraction system to the economic operating range; ② Finely adjust the opening of the intelligent regulating valve at the orifice of the corresponding directional long borehole (4) to reduce the negative pressure at the orifice of the directional long borehole. Controlling the gas flow rate within the optimal extraction window by monitoring the orifice gas flow rate. and the gas concentration in the upper corner of the working face The effectiveness of the control is determined by this method. The optimal sampling window is determined from historical data or experiments.

[0043] The above-mentioned tiered control strategy includes the following: Two thresholds.

[0044] 70% threshold: When the contribution rate of the old working face exceeds 70%, it indicates that the gas outburst from the second working face is relatively small, and the system resources can be concentrated on pumping out the old working face to prevent it from flowing into the working face through the coal pillar fissures.

[0045] 30% threshold: When the contribution rate of the old pond is less than 30%, it indicates that the gas in the old pond is about to be depleted or the channel is blocked. The system should switch to gas extraction from the service face to ensure the safety of the extraction.

[0046] Intermediate section: Continuous adjustment rather than on / off control is used to ensure a smooth transition during the extraction process.

[0047] The present invention provides a dual-source sensing and dynamic coordination system for implementing the above-mentioned cross-working face goaf gas extraction method, comprising: a physical sensing layer, a data transmission layer, an analysis and decision-making layer, and a collaborative execution layer.

[0048] This invention has been practically applied to coal mine gas extraction, and the results have been very good. Two examples are listed below.

[0049] I. No coal pillar condition (W≈0).

[0050] Working conditions: A mine in Qinyuan, Changzhi, Shanxi Province adopts the "110 method", which is a coal pillar-free mining method, that is, the width of the coal pillar W≈0m. The first mining face 1 and the subsequent mining face 2 are arranged in sequence.

[0051] 1. Advanced planning and design: Time: Before the start of mining at the first mining face 1.

[0052] Location: Opening from the solid coal roadway 3 of the subsequent working face 2.

[0053] Trajectory: Since W≈0m, a high-level rapid crossing trajectory is adopted. Directional long borehole 4 enters the roof at a 22° elevation angle, rapidly ascends and stabilizes in stable rock strata approximately 28m above the coal seam roof, about 8 times the mining height, and extends horizontally to a depth of 30m in the designed goaf of the first mining face 1. The total designed length is 650m, and this trajectory simultaneously covers the future mining-induced fracture zones of both working faces.

[0054] 2. Construction and Hole Protection: The drilling was completed in one go. Given the large range of roof movement, high-strength spiral screen pipes were installed along the entire length of the approximately 500m long horizontal section of the directional long borehole 4 above the goaf for preventative borehole protection.

[0055] 3. Dynamic joint debugging and full-cycle operation: Directional borehole 4 was connected to a gas extraction system with dual-source sensing and dynamic adjustment capabilities. During the mining of the first working face 1, directional borehole 4 efficiently extracted gas, with the concentration in the upper corner remaining stable below 0.5%. During the mining of the subsequent working face 2, the system automatically identified the dual-source mixing (gas from the old pond in the first working face 1 and gas from the current face in the subsequent working face 2). Through coordinated commands, the borehole valves were opened wider and the total negative pressure of the surface pumping station was increased, achieving balanced extraction. Throughout the entire service cycle, the gas in the upper corners of both working faces was effectively controlled.

[0056] II. Small coal pillar conditions (W=6m).

[0057] Operating conditions: A 6m coal pillar is left between the first mining face 1 and the subsequent mining face 2 in a mine in Gaoping, Jincheng, Shanxi. The solid coal roadway of the subsequent mining face 2 has been formed.

[0058] 1. Advanced planning and design: Time: Before the start of mining at the first mining face 1.

[0059] Location: Opening from the solid coal roadway 3 of the subsequent working face 2.

[0060] Trajectory: Due to W=6m, a stress edge crossing trajectory is adopted. The directional long borehole 4 enters the roof at a 14° elevation angle. The horizontal projection of the trajectory crosses directly above the 6m coal pillar in a curve. The vertical distance h is controlled within the fracture development zone of approximately 4.4 times the mining height (14m). The final borehole is located at a depth of 40m in the goaf of the first mining face 1. The total designed length is 720m.

[0061] 2. Construction and Hole Protection: The drilling was completed in one go, and the approximately 80m section that traverses the stress disturbance zone of the coal pillar was identified as the core risk area. High-strength screen pipes were installed in this section and grouting was used for reinforcement, implementing targeted reinforcement of the borehole.

[0062] 3. Dynamic joint debugging and full-cycle operation: The directional long borehole 4 was connected to a gas extraction system with dual-source sensing and dynamic adjustment capabilities. During the initial mining phase, the extraction concentration reached 55%. During subsequent mining phases, the system dynamically identified changes in the primary and secondary gas levels and dynamically balanced the total negative pressure of the ground pump station by fine-tuning the valve opening angle, ensuring the safety of both working faces. This borehole successfully replaced traditional double-face drilling projects.

[0063] This invention pioneers a "one-hole-for-two-faces-full-cycle" model, eliminating blind spots in gas control both spatially and temporally, and achieving regionalized control. It also establishes two directional long borehole trajectories for different situations and employs a graded targeted borehole protection process to ensure the long-term effectiveness of directional long boreholes under various coal pillar conditions. Furthermore, this invention incorporates a dual-source sensing and dynamic coordination system, enabling precise sensing, source and flow analysis, and automatic collaborative control of complex gas outbursts, elevating gas management to a new level of intelligence. Practical application has yielded significant economic benefits, reducing the amount of dedicated roof gas control engineering by approximately 50%, substantially lowering the cost per ton of coal, and effectively alleviating the conflict between mining and tunneling operations.

[0064] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for gas extraction across a working face goaf, characterized in that Includes the following steps: S1. Before the first mining face (1) begins mining, at least one directional long borehole (4) is planned from the solid coal roadway (3) of the subsequent mining face (2) to penetrate the mining-affected area of ​​the two mining faces. The directional long borehole (4) should cover the mining-affected fracture area that will be formed when the subsequent mining face (2) is mined in the future, and its end point is located within the effective extraction range of the goaf of the first mining face (1). S2. Complete the construction of the directional long borehole (4) according to the design trajectory, and implement graded targeted protection for the high-risk sections within the directional long borehole (4); S3. Connect all directional long boreholes (4) to the gas extraction system, extract the gas during the first mining face (1) mining period, and extract the gas from both mining faces during the subsequent mining face (2) mining period.

2. The method of claim 1, wherein: In S1, when planning a directional long borehole (4), there are two types of trajectory, which are selected according to the width W of the coal pillar (5) between the first mining face (1) and the subsequent mining face (2). High-level rapid crossing trajectory: applicable to W<3m, i.e. no coal pillar or extremely narrow coal pillar, requiring the directional long borehole (4) to be constructed towards the roof at a set elevation angle of 15° to 25°, so that the directional long borehole (4) can quickly enter and stabilize in the relatively stable rock layer in the upper part of the fracture zone of the roof of the goaf, and extend horizontally along this layer for a long distance. Stress edge crossing trajectory: Applicable to the case of 3m≤W≤8m, i.e. small coal pillars. It requires directional long borehole (4) to be constructed towards the roof at a set elevation angle of 10°~18°. Its horizontal projection path needs to be designed to cross the roof rock layer directly above the small coal pillar in a curved form, and the vertical distance h of the crossing, i.e. the vertical distance from the top of the coal seam, should be controlled within the range of 2~6 times the mining height.

3. The method of claim 1, wherein: In S2, when W < 3m, the long horizontal section of the directional long borehole (4) is protected throughout. When 3m ≤ W ≤ 8m, the directional long borehole (4) is locally reinforced to protect the stress disturbance zone of the coal pillar.

4. The method of claim 3, wherein: When W < 3m, high-strength screen pipes are installed along the entire length of the horizontal section of the directional long borehole (4) for hole protection. When 3m ≤ W ≤ 8m, high-strength anti-shear screen pipes are installed along the section of the directional long borehole (4) that passes through the stress disturbance zone of the coal pillar, and the hole is protected by a composite method of targeted reinforcement through grouting.

5. The method of gas extraction across the goaf of the working face according to claim 1 or 3 or 4, characterized in that: In S2, the opening section of the directional long borehole (4) is a conventional risk zone, and the standard casing consolidation process is used to protect the borehole.

6. The method of claim 1 or 2, wherein: In S3, the gas extraction system is equipped with a dual-source sensing and dynamic coordination system, which includes: a physical sensing layer, a data transmission layer, an analysis and decision-making layer, and a collaborative execution layer. The physical sensing layer includes a multi-parameter sensor network located at the deep and shallow parts, the orifice, and the upper corner of the dual working surfaces of the directional long borehole (4), which collects the following data in real time: a、First mining face (1) old pond gas parameters: through the sensor installed in the deep directional long borehole (4) at the junction of the first mining face (1) and the successive working face (2) along the empty roadway or coal pillar (5) above the first mining face (1) on the side close to the first mining face (1) in the corresponding section, real-time collection of the actual gas concentration at its location and negative pressure ; b. Gas parameters of the working face (2): The gas concentration at the location of the sensor installed in the shallow part of the directional long borehole (4) and in the corresponding section of the future goaf of the working face (2) is collected in real time. ; c. Comprehensive parameters at the borehole opening: The gas concentration at the borehole opening is collected in real time by a comprehensive monitoring unit installed at the opening of the directional long borehole (4). Orifice gas flow and orifice negative pressure ; d. Safety monitoring parameters: The gas concentration at the upper corner of the first mining face (1) and the upper corner of the subsequent mining face (2) is collected in real time by sensors installed at the upper corner of the upper corner of the first mining face (1) and the subsequent mining face (2). and ; The data collected by the aforementioned physical sensing layer is uploaded to the analysis and decision-making layer in real time through the data transmission layer; The analysis and decision layer receives data transmitted from the physical perception layer through the data transmission layer. Through the built-in gas emission source analysis model, it dynamically calculates the gas contribution rate of the two working faces in the corresponding directional long borehole (4). Based on the change in contribution rate and safety objectives, it generates two-level collaborative control instructions. The collaborative execution layer includes two levels of execution mechanisms: one is the frequency conversion control system of the ground extraction pump station, which adjusts the total negative pressure of the extraction system according to the collaborative control instructions; the other is the intelligent regulating valve installed at the orifice of each directional long borehole (4), which adjusts the resistance and flow distribution of its respective branch according to the collaborative control instructions.

7. The gas extraction method across the goaf of a working face according to claim 6, characterized in that: The gas emission source analysis model in the analysis and decision-making layer is constructed based on the two-end concentration-flow balance method. It dynamically calculates the gas contribution rate of the two working faces by real-time monitoring data. Its core algorithm is as follows: The dynamic calculation formula for gas contribution rate is as follows: In the formula: —Gas contribution rate of the goaf area in the first mining face (1), % —Gas contribution rate of the goaf area of ​​the continuing working face (2), % —Gas concentration measured by deep sensor in directional long borehole (4), % —Gas flow rate in the deep section of the directional long borehole (4), m³ / min; —Measured methane concentration at the borehole opening of directional long borehole (4), % —Measured gas flow rate at the orifice of directional long borehole (4), m³ / min; in, Without measured data, it is necessary to perform inverse calculations using the mass balance equations, and solve the following system of equations simultaneously: In the formula: —Measured gas concentration by shallow sensor in directional long borehole (4), % —Gas flow rate in the shallow section of the directional long borehole (4), m³ / min.

8. The gas extraction method for cross-working face goaf area according to claim 7, characterized in that: The analysis and decision-making layer incorporates a hierarchical control strategy, which is based on the real-time calculated contribution rate of the goaf area of ​​the first mining face. Execute the following coordinated control instructions: a. Strong Draining of Old Pool Mode: When When the gas content is ≥70%, the gas in the goaf of the first mining face (1) is determined to be the main source. The control objective is to increase the negative pressure of the old pond side extraction. The instructions are executed synchronously: ① Increase the frequency of the frequency converter of the ground extraction pump station to increase the total negative pressure of the extraction system; ② Open the opening of the intelligent regulating valve at the orifice of the corresponding directional long borehole (4) to reduce the resistance of this branch. The negative pressure of the old pond side is monitored in real time. The upward trend is used to verify the effect of instruction execution; b. Dynamic Balance Mode: When 70% > When the gas concentration is >30%, it is determined to be in the dual-source gas mixing equilibrium period. The control objective is to match the extraction capacity of the directional long borehole (4) with the gas emission ratio of the dual sources. The instructions are executed synchronously: ① Dynamically optimize the total negative pressure of the extraction system according to the mixing ratio; ② Based on the current calculated... / The ratio is the target, and the opening of the intelligent regulating valve at the orifice of the corresponding directional long borehole (4) is finely adjusted by monitoring the gas concentration at the orifice. and orifice gas flow The stability of the balance is used to evaluate its effectiveness. c. Current-maintaining and voltage-controlled mode: When When the gas concentration is ≤30%, the gas source of the working face (2) is determined to be the main source. The control objective is to ensure the gas extraction flow rate of the working face while preventing air leakage in the goaf due to excessive negative pressure. The instructions are executed simultaneously: ① Maintain or slightly reduce the total negative pressure of the extraction system to the economic operating range; ② Finely adjust the opening of the intelligent regulating valve at the orifice of the corresponding directional long borehole (4) to reduce the negative pressure at the orifice of the directional long borehole. Controlling the gas flow rate within the optimal extraction window by monitoring the orifice gas flow rate. and the gas concentration in the upper corner of the working face To determine the effectiveness of the control.

9. A dual-source sensing and dynamic coordination system for implementing the method of claim 6, 7, or 8, characterized in that... include: The physical perception layer, data transmission layer, analysis and decision-making layer, and collaborative execution layer are described.

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