Method for preventing transient abnormal emission of gas in goaf by intelligent roof control and cut-off

Abstract

This invention discloses a method for intelligent roof control and diversion to prevent sudden and abnormal gas outbursts in goaf areas. This method involves determining the initial and cyclical pressure step distance, optimizing the design and construction of roof control and diversion borehole parameters, introducing a controllable, slow-release static fracturing agent into key strata, installing stainless steel screens and sealing and continuously pumping out the gas, intelligently controlling the coupling of roof fracturing and diversion / extraction parameters, evaluating and optimizing the effects, and cyclically executing the method as the working face advances. This forms a collaborative prevention and control system of "active weakening - intelligent control." This invention shifts the disaster management operation space from the longwall mining face to the floor drainage roadway, and the roof weakening method shifts from traditional blasting to a safe, environmentally friendly, and controllable static fracturing agent pre-fracture method. The management approach shifts from single-hazard management to multi-hazard collaborative management, achieving intelligent roof control and diversion to prevent sudden and abnormal gas outbursts in goaf areas. This fundamentally eliminates the adverse effects of strong mine pressure manifestations and abnormal gas outbursts in goaf areas on safe production, curbing risks at the source.

Description

Technical Field

[0001] This invention belongs to the field of collaborative prevention and control of multiple disasters in coal mine safety, and specifically relates to a method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas. Background Technology

[0002] During coal mining, due to the complexity of the geological conditions of the coal seam roof, about one-third of coal mines nationwide face problems such as hard roofs, large overhanging areas, long overhanging distances, and difficulty in timely collapse. These hard roofs exhibit significant characteristics during mining, including long periodic pressure steps, high intensity of mine pressure manifestation, turbulent airflow in the goaf, and rapid and unpredictable abnormal gas outbursts, making them one of the major hazards facing coal mine safety production.

[0003] With the improvement of mechanization and intelligent equipment in coal mines, high-intensity and rapid mining has become the mainstream trend in mine development. However, this mining method further exacerbates the problems of strong mine pressure manifestation and abnormal gas outbursts in goaf areas. The mining face is equipped with a large number of large pieces of equipment such as hydraulic supports, scraper conveyors, and coal mining machines, resulting in very limited working space. This makes it difficult to effectively implement traditional measures for weakening key roof layers and goaf gas control technologies, while also severely affecting the continuous operation efficiency of the mining face. Traditional roof weakening relies heavily on blasting, but in high-gas environments, blasting operations pose high safety risks, have low control precision, and poor environmental performance. Goaf gas control is often limited to single-hazard prevention and lacks deep synergy with mine pressure control. Drainage boreholes are easily compacted and blocked by the collapse of rock masses in the goaf, especially conventional PVC screens, which cannot withstand the pressure, leading to the failure of drainage channels. The adjustment of extraction parameters mainly relies on manual experience, which cannot respond in real time to the mine pressure and gas changes caused by roof collapse, resulting in problems such as insufficient extraction (excessive gas accumulation) or excessive air leakage (causing spontaneous combustion of residual coal oxidation).

[0004] High coal seam pressure can trigger coal face spalling, roof collapse, support collapse, and even mine tremors. Roof fracture simultaneously disrupts the gas migration patterns in the goaf, leading to sudden and abnormal gas outbursts. This causes a sharp increase in gas concentration at the working face, especially in the upper corner, easily triggering a chain reaction of disasters such as gas exceeding limits, personnel asphyxiation, and even gas explosions. These coupled risks of multiple hazards seriously threaten safe coal mine production and hinder the continued advancement of high-intensity mining. Therefore, the weakening of key coal seam roof fractures and the control of abnormal gas outbursts in the goaf have become core technical challenges urgently needing to be addressed for safe and efficient mine mining. Existing technologies struggle to simultaneously control high coal seam pressure and sudden gas outbursts at the source, resulting in problems such as limited working space, simplistic control methods, and outdated regulatory mechanisms. There is an urgent need for a comprehensive management method that can transform the working space, adopt safe and environmentally friendly weakening methods, and achieve intelligent collaboration of multi-source information to fundamentally contain the risks at their source. Summary of the Invention

[0005] In view of this, the present invention addresses the problems of severe manifestation of strong mine pressure in hard roofs and difficulty in controlling sudden and abnormal gas outbursts in goaf areas in the existing technology. It provides a method for intelligent roof control and diversion to prevent sudden and abnormal gas outbursts in goaf areas. By determining the appropriate pressure step distance, designing and constructing parameters for large-diameter roof control and diversion boreholes, introducing static fracturing agents into key strata, installing stainless steel screen pipes for sealing and continuous extraction, and intelligent regulation based on multi-source information, a collaborative prevention and control system of "active weakening-intelligent diversion and extraction" is constructed to achieve precise source control of strong mine pressure and multiple gas disasters.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas includes the following steps: S1. Determination of reasonable initial and periodic pressure step distances: Research and analysis are conducted on coal seam mining conditions, periodic pressure step distances, and mine pressure intensity manifestations to determine the key layers for roof failure. Combined with coal seam gas parameters and ventilation methods, the gas emission rate and return air gas concentration are predicted to identify the risk sources of transient gas emission risks. In order to control roof mine pressure manifestations and transient gas emission, a reasonable target pressure step distance is determined by analyzing the initial and periodic pressure loads of previous working faces and their gas emission patterns. S2. Optimization design of parameters for large-diameter roof control and interception boreholes: Design the spacing of large-diameter roof control and strong drainage boreholes based on the determined target and step distance; Design the borehole parameters based on the positional relationship between the bottom gas drainage roadway and the working face. S3. Construction of large-diameter roof control and cutoff boreholes: The drilling site is set up according to the drilling design parameters. A high-power drilling rig with trajectory measurement is installed in the drilling site to carry out drilling construction. During the drilling construction, the drilling passes through the bottom plate of the coal seam goaf, the collapsed and broken rock mass of the goaf, and the intact roof of the goaf, as well as its lithology, to ensure that the drilling depth passes through the top surface of the key layer. S4. Static fracturing agent is introduced into the key drilling layer: After the drilling is completed, the drill rod tail braid is removed. The pre-made static fracturing agent cartridge is sent to the key drilling layer through the hollow annular space of the drill rod and compacted. The drill is slowly withdrawn until the key layer is filled with the pre-made static fracturing agent cartridge and compacted, so as to achieve non-explosive and controllable weakening of the hard top plate. S5. Installation and Sealing of Stainless Steel Screen Pipes: After the pre-made static fracturing agent cartridges are delivered to the key layer of each borehole, the drill rod is withdrawn. The stainless steel screen pipe is then driven by the drilling rig to rotate and advance along the borehole until it reaches the lower interface of the key layer. The diameter of the stainless steel screen pipe is 42-108mm. After the stainless steel screen pipe is installed, the borehole is sealed using a two-plug-one-injection sealing process. It is then connected to the extraction branch pipeline through the extraction hose, ball valve, and guide short section. S6. Intelligent Control of Roof Fracture-Interception and Drainage Parameters: Based on the changes in support load, working face gas volume fraction, and gas drainage parameters of the control borehole before and after the key layer fractures under the action of pre-made static fracturing agent cartridges, a borehole valve opening criterion is designed. A closed-loop intelligent control system based on support load, gas concentration, and drainage parameters is established and embedded with a PLC control module. When the support load or working face gas volume fraction decreases to the set critical value after the initial or periodic pressure, the PLC control module outputs a command to control the ball valve opening to carry out goaf interception and drainage. S7. Evaluation of Results and Optimization; S8. As the working face continues to advance, steps S3 to S6 are executed cyclically to carry out the design and construction of the top control and interception borehole, the introduction of static fracturing agent, the installation of screen pipes and sealing and continuous pumping, and the intelligent control of pumping parameters to form a continuous treatment capability.

[0007] Furthermore, the specific method for determining the key layer of roof failure in step S1 is to analyze the coal seam thickness, mining height, dip angle, roof and floor lithology, and mining intensity, and to study the periodic pressure step distance and mine pressure intensity manifestation. The roof pressure of the working face increases sharply and instantaneously, and then shows a step-like decrease or a slow decrease, with a clear peak inflection point.

[0008] Furthermore, the specific method for determining the risk source of transient gas outburst risk in step S1 is to predict the gas outburst volume and return air gas concentration by combining coal seam gas parameters and ventilation methods, provided that the overhanging roof area of ​​the goaf exceeds 8m². 2 Or the roof pressure at the working face exceeds 80% of the safety threshold for strong mine pressure manifestation disasters in the mine's history.

[0009] Furthermore, in step S1, an analysis is conducted based on the mining intensity and the load of the support during the initial and periodic pressure of the previous working face, as well as the gas emission pattern in the goaf. The relationship between safety and cost of measures is considered to determine a reasonable pressure step distance. Among them, the relationship between the pressure step distance and potential losses is that the larger the step distance L, the greater the elastic energy E accumulated in the roof, and the types of disasters caused include support damage, roadway damage, and abnormal gas outbursts, gas exceeding limits, or even explosions. The expected repair losses for support damage and roadway damage, including direct and indirect costs, are C. d The direct and indirect costs of gas over-limit shutdowns and explosions are C. g ; The probability of an accident, P(L), increases exponentially with the step size L. Therefore, the relationship between the pressure step size and the probability of a potential disaster is expressed as:

[0010] Where k is the risk coefficient, which is determined based on geological conditions; The formula for calculating the safety risk cost R(L) is:

[0011] The cost of retrofit measures is inversely proportional to the cycle length. The formula for calculating the cost of retrofit measures, M(L), is as follows:

[0012] In the formula: A is a coefficient related to modification measures such as borehole density; The total cost T(L) is obtained as follows:

[0013] Considering both the overall safety risk cost and the cost of modification measures, the step distance L that minimizes the total cost T(L) is selected as the pressure step distance.

[0014] Furthermore, in step S6, the drilling valve opening criterion is designed based on the changes in support load before and after the key layer breaks under the action of the pre-made static fracturing agent cartridge, the changes in gas volume fraction at the working face, and the gas extraction parameters of the control and interception borehole. The ball valve is closed when the support load or gas volume fraction at the working face decreases to the set critical value after the initial or periodic pressure is applied, to avoid the problem of natural oxidation of residual coal caused by long-term air leakage during extraction in the goaf. After the initial grouting, curing, sealing, and continuous extraction, the valve is kept open. After the peak pressure inflection point of the working face roof passes, and the gas purity or gas concentration reaches the peak value for 1 hour, the valve opening is gradually adjusted, and the valve is closed when the concentration decreases to 5%.

[0015] Furthermore, in step S7, based on the change in gas volume fraction at the working face during the pressure period from the roof, the drilling design parameters, static fracturing agent usage, and valve opening criteria are optimized.

[0016] Furthermore, the reasonable pressure step distance in step S1 refers to the step distance that can be effectively controlled within the rated working resistance range of the hydraulic support of the working face, without causing serious coal wall spalling or collapse.

[0017] Furthermore, in step S2, based on the determined reasonable pressure step distance, the spacing of the large-diameter control top strong extraction drilling holes is designed to be 10-20m, ensuring that the drilling depth penetrates 0.5m through the top surface of the key layer, the drilling diameter is 94-159mm, and the spacing is 15-20m.

[0018] Further, in step S3, the large-diameter roof control and interception borehole is constructed from the bottom gas drainage roadway, passing through the goaf floor, collapsed and fractured rock mass, to the key layer of the overlying intact roof, with a depth of 0.5m through the top surface of the key layer; a metal stainless steel screen pipe is installed from the lower interface of the key layer to the coal seam floor, and extends to the borehole opening through a threaded connection with the stainless steel pipe, forming a continuous drainage channel; the stainless steel screen pipe and the stainless steel pipe are connected to the drainage branch pipe through drainage hoses, ball valves, and guide short sections; the working face roof pressure acquisition end is set on the hydraulic support, the working face gas acquisition end is set at the upper corner, and the borehole drainage parameter acquisition device is set on each borehole drainage pipeline. The working face roof pressure acquisition end, the working face gas acquisition end, and the borehole drainage parameter acquisition device are respectively connected to the PLC control end. The PLC control end outputs commands to control the ball valve opening according to the preset borehole valve opening criteria, realizing closed-loop flow control.

[0019] Furthermore, in step S3, the drill rod used for drilling is a large-diameter drill rod, and the drill bit is an openable / closable drill bit.

[0020] Furthermore, the static breaker agent mentioned in step S4 is a controlled-release static breaker agent.

[0021] Furthermore, the static rupture agent cartridge is made by encapsulating a CaO / Al2O3 composite matrix and an organic slow-release catalyst in a 3:1 ratio within a temperature-sensitive capsule.

[0022] Furthermore, in step S5, after the stainless steel screen pipe is installed in place, a two-plug-one-grout sealing process is adopted; the stainless steel screen pipe is installed to the bottom plate of the coal seam, and the section from the bottom plate of the coal seam to the orifice is made of stainless steel pipe. Threaded connections are used between stainless steel screen pipes, between stainless steel pipes, and between the two. The length of the stainless steel screen pipe and the stainless steel pipe is no more than 1000mm; the orifice is sealed with Marl powder and grout is used for sealing.

[0023] The beneficial effects of this invention are as follows: This invention weakens the key roof structure and alters the gas flow field movement pattern in the goaf by rationally determining the pressure step distance in the longwall face, designing and constructing large-diameter roof control and cutoff borehole parameters, installing metal stainless steel screens and sealing and continuously pumping gas, and intelligently controlling the cutoff and extraction parameters. It deeply couples "active roof weakening" with "intelligent gas extraction" to construct a collaborative prevention and control system of "active weakening-intelligent control". Through a closed-loop control system that integrates multi-source information fusion, it achieves integrated and precise management of strong mine pressure manifestation and transient abnormal gas outbursts caused by roof failure.

[0024] Specifically, step S1 determines a reasonable pressure step distance by analyzing coal seam mining conditions, combining historical data, and a cost function model, ensuring controllability within the rated resistance range of the hydraulic support and avoiding severe coal wall spalling and collapse, thus controlling mine pressure intensity from the source. Steps S2 and S3 optimize and construct large-diameter roof control and interception boreholes, extending from the floor gas drainage roadway to the key layer. This changes the traditional situation where it is difficult to operate under limited working face space. The borehole depth accurately penetrates the top surface of the key layer by 0.5m and records the conditions of each rock layer, providing a reliable channel for subsequent weakening and extraction. Step S4 precisely delivers pre-made static fracturing agent cartridges to the key layer through the hollow space of the drill pipe and compacts them, achieving non-explosive, controllable roof weakening. This offers significant safety and environmental advantages over traditional blasting, reducing the risk of blasting in high-gas environments.

[0025] Step S5 involves rotating and installing a stainless steel screen pipe to the lower interface of the critical layer, along with threaded stainless steel pipes and two plugs and one injection sealant, to completely solve the problem of conventional PVC screen pipes being blocked by pressure in the goaf, ensuring long-term unobstructed drainage channels. Step S6 involves constructing a multi-source information closed-loop intelligent control system based on support load, gas volume fraction at the upper corner of the working face, and borehole drainage parameters. The PLC control module adjusts the electric or pneumatic ball valves in real time according to the embedded valve opening criteria, achieving coupled control of roof fracture and interception drainage parameters: during pressure inrush, the valves are opened appropriately for interception drainage to alleviate the strong mine pressure manifestation caused by roof fracture and the sudden gas surge caused by gas outburst at the working face; after pressure inrush, when the gas or load drops to the critical value, the ball valves are automatically closed to prevent long-term air leakage from causing spontaneous combustion of residual coal oxidation, thereby accurately avoiding chain disasters such as mine shock, gas over-limit, asphyxiation, and explosion.

[0026] Step S7 optimizes drilling parameters, fracturing agent dosage, and control model based on actual gas changes. Step S8 involves cyclical construction as the working face advances, forming a continuous dynamic governance capability.

[0027] Overall, this invention realizes the transformation of the governance operation space from longwall mining to floor drainage roadways, the transformation of roof weakening from traditional blasting to safe, environmentally friendly and controllable static fracturing agent pre-fracture, and the transformation of governance approach from single-hazard governance to multi-hazard collaborative governance. It provides a complete technical chain from roof source weakening to gas outburst path control and then to dynamic intelligent risk response.

[0028] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the longitudinal section of the control-top flow-cutting borehole in this embodiment.

[0030] Figure 2 This is a schematic diagram of the transverse cross-section of the control-top flow-cutting borehole in this embodiment.

[0031] Figure 3 This is a schematic diagram of the top plate fracture extraction borehole structure in this embodiment.

[0032] Figure 4 This is a schematic diagram of the intelligent control principle for top-controlled flow interception drilling in this embodiment.

[0033] Attached reference numerals: 1. Key layer; 2. Indirect roof; 3. Direct roof; 4. Coal seam; 5. Direct floor; 6. Indirect floor; 7. Floor drainage roadway; 8. Transport roadway; 9. Return airway; 10. Longwall face; 11. Roof control and cutoff borehole; 12. Static fracturing agent cartridge; 13. Stainless steel screen pipe; 14. Cement slurry; 15. Mary powder; 16. Stainless steel pipe; 17. Gas acquisition end of working face; 18. Pressure acquisition end of working face roof; 19. Borehole drainage parameter acquisition device; 20. PLC control end; 21. Electric (pneumatic) ball valve; 22. Borehole drainage pipe; 23. Drainage branch pipe. Detailed Implementation

[0034] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0035] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0036] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0037] Example 1 Please refer to Figures 1-4 A method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas includes the following steps: S1. Determination of reasonable initial and periodic pressure step distances: Research and analysis are conducted on coal seam mining conditions, periodic pressure step distances, and mine pressure intensity manifestations to determine the key layer 1 for roof failure. Combined with coal seam gas parameters and ventilation methods, the gas emission rate and return air gas concentration are predicted to identify the risk sources of transient gas emission risks. In order to control roof mine pressure manifestations and transient gas emission, combined with the analysis of the initial and periodic pressure loads of previous working faces and their gas emission patterns, a reasonable target pressure step distance is determined. Among them, the reasonable pressure step distance refers to the step distance that can be effectively controlled within the rated working resistance range of the hydraulic support of the longwall face 10, without causing serious coal wall spalling or collapse. The specific method for determining the key layer 1 for roof failure is to analyze the thickness, mining height, dip angle, roof and floor lithology, and longwall mining intensity of coal seam 4, and to study the periodic pressure step distance and mine pressure intensity manifestation. The roof pressure of the working face rises sharply and instantaneously, followed by a step-like or slow decline, with a clear peak inflection point. The specific method for determining the risk source of transient gas outburst risk is to predict the gas outburst volume and return air gas concentration by combining the gas parameters of coal seam 4 and the ventilation mode. The suspended roof area of ​​the goaf exceeds 8m². 2 Or the roof pressure at the longwall face exceeds 80% of the safety threshold for strong mine pressure manifestation disasters in the mine's history; Based on the analysis of the mining intensity and the load on the supports during the initial and periodic pressure surges in previous mining faces, as well as the gas emission patterns in the goaf, a reasonable pressure surge distance was determined by considering the relationship between safety and cost. Specifically, the relationship between the pressure surge distance and potential losses is that the larger the distance L, the greater the elastic energy E accumulated in the roof, leading to disasters including support damage, roadway damage, and abnormal gas emission (gas exceeding limits or even explosions). The estimated direct and indirect costs of repair losses for support damage and roadway damage are C. d The direct and indirect costs of gas over-limit shutdowns and explosions are C.g ; The probability of an accident, P(L), increases exponentially with the step size L. Therefore, the relationship between the pressure step size and the probability of a potential disaster is expressed as:

[0038] Where k is the risk coefficient, which is determined based on geological conditions; The formula for calculating the safety risk cost R(L) is:

[0039] The cost of retrofit measures is inversely proportional to the cycle length. The formula for calculating the cost of retrofit measures, M(L), is as follows:

[0040] In the formula: A is a coefficient related to modification measures such as borehole density; The total cost T(L) is obtained as follows:

[0041] Considering both the overall safety risk cost and the cost of modification measures, the step distance L that minimizes the total cost T(L) is selected as the pressure step distance.

[0042] S2. Optimization design of large-diameter roof control and diversion borehole parameters: Design the row spacing of large-diameter roof control and strong drainage boreholes based on the determined target and step distance; design the borehole parameters based on the positional relationship between the bottom drainage roadway 7 and the longwall face 10; design the row spacing of large-diameter roof control and strong drainage boreholes to be 10-20m based on the determined reasonable step distance, ensuring that the borehole depth penetrates the top surface of the key layer 1 by 0.5m, the borehole diameter is 94-159mm, and the spacing is 15-20m. S3. Construction of large-diameter roof control and cutoff boreholes: The drilling site is set up according to the borehole design parameters. A high-power drilling rig with trajectory measurement is installed in the drilling site to carry out drilling construction. During the drilling construction, the drilling passes through the bottom plate of the coal seam 4 goaf, the collapsed and fractured rock mass of the goaf, and the intact roof of the goaf, as well as the lithology, to ensure that the drilling depth penetrates the top surface of the key layer 1. The large-diameter roof control and cutoff borehole 11 is constructed from the bottom plate drainage roadway 7, passing through the direct bottom 5, indirect bottom 6, goaf bottom plate, collapsed and fractured rock mass, to the key layer 1 with the intact roof, with a depth of 0.5m penetrating the top surface of the key layer 1. The drill rods used in the drilling construction are large-diameter drill rods, and the drill bits are openable and closable drill bits. The transport roadway 8 and return airway 9 serve as auxiliary channels to ensure construction safety. S4. Static fracturing agent is introduced into the key drilling layer: After the drilling is completed, the drill rod tail brace is removed, and the pre-made static fracturing agent cartridge 12 is delivered to the key layer 1 of the control and cutoff borehole 11 through the hollow annular space of the drill rod using a push rod and compacted. The drill is slowly withdrawn until the borehole at the key layer 1 is filled with the pre-made static fracturing agent cartridge 12 and compacted, so as to achieve non-explosive and controllable weakening of the hard roof. The direct roof 3 and indirect roof 2 are affected during the weakening of the key layer 1. The static fracturing agent is a controllable slow-release static fracturing agent. The static fracturing agent cartridge 12 is made by encapsulating CaO / Al2O3 composite matrix and organic slow-release catalyst in a 3:1 ratio in a temperature-sensitive capsule. S5. Installation and Sealing of Stainless Steel Screen Pipes: After the pre-fabricated static fracturing agent cartridge 12 is delivered to the critical layer 1 position of each control-roof-cutoff borehole 11, the drill rod is withdrawn. The stainless steel screen pipe 13 is then driven by the drilling rig to rotate and advance along the control-roof-cutoff borehole 11 until it reaches the lower interface of the critical layer 1. The diameter of the stainless steel screen pipe 13 is 42-108mm. After the stainless steel screen pipe 13 is installed, a two-plug-one-injection sealing process is used for sealing. It is connected to the extraction branch pipe 23 via the extraction hose, electric (pneumatic) ball valve 21, and guide short section. The stainless steel screen pipe 13 is installed to the bottom plate of coal seam 4. The section from the bottom plate of coal seam 4 to the borehole opening uses stainless steel pipe 16. The 13th and 16th stainless steel pipes are all connected by threads. The length of the stainless steel screen pipe 13 and stainless steel pipe 16 is no more than 1000mm. The orifice is sealed with 15 molasses and grout is injected with cement slurry 14 to seal the orifice. The metal stainless steel screen pipe 13 is installed from the lower interface of the key layer 1 to the bottom plate of the coal seam 4, and extends to the orifice through the threaded connection with the stainless steel pipe 16 to form a continuous extraction channel. The stainless steel screen pipe 13 and stainless steel pipe 16 are connected to the extraction branch pipe 23 through the extraction hose, electric (pneumatic) ball valve 21, and guide short section. The drilled extraction pipe 22 connects the stainless steel pipe 16 and the electric (pneumatic) ball valve 21 to ensure smooth extraction. S6. Intelligent Control of Roof Fracture-Interception and Extraction Parameters: Based on the collected data on the changes in support load, working face gas volume fraction, and gas extraction parameters of the control borehole 11 before and after the fracture of the key layer 1 under the action of the pre-made static fracturing agent cartridge 12, a borehole valve opening criterion is designed. A closed-loop intelligent control system based on support load, gas concentration, and extraction parameters is established and embedded in the PLC control terminal 20. When the support load or working face gas volume fraction decreases to the set critical value after the initial or periodic pressure injection, the PLC control terminal 20 outputs a command to control the electrical... The opening of the pneumatic ball valve 21 is adjusted to perform goaf interception and drainage. The working face roof pressure acquisition end 18 is set on the hydraulic support, the working face gas acquisition end 17 is set at the upper corner, and the borehole drainage parameter acquisition device 19 is set on the drainage pipeline of each roof control interception borehole 11. The working face roof pressure acquisition end 18, the working face gas acquisition end 17, and the borehole drainage parameter acquisition device 19 are respectively connected to the PLC control end 20. The PLC control end 20 outputs commands to control the opening of the electric (pneumatic) ball valve 21 according to the preset borehole valve opening criteria to realize closed-loop flow regulation. The borehole valve opening criteria are designed based on the changes in support load before and after the key layer 1 is broken under the action of the pre-made static fracturing agent cartridge 12, the changes in gas volume fraction at the working face, and the gas extraction parameters of the roof control and interception borehole 11. When the support load or gas volume fraction at the working face decreases to the set critical value after the initial or periodic pressure, the electric (pneumatic) ball valve 21 is closed to avoid the problem of natural oxidation of residual coal caused by long-term air leakage during extraction in the goaf. After the initial grouting, solidification, and sealing of the borehole, the valve is kept open. After the peak pressure inflection point of the working face roof passes, the gas purity or gas concentration reaches the peak value for 1 hour, and the valve opening is gradually adjusted until the concentration decreases to 5% and then the valve is closed. S7. Effect evaluation and optimization: Based on the change of gas volume fraction in the longwall face during the roof pressure period, optimize the borehole design parameters, static fracturing agent usage and valve opening criteria. S8. As the longwall face 10 advances, steps S3 to S6 are executed cyclically to design and construct the roof control and flow interception borehole, push in the static fracturing agent, install the screen pipe and seal the hole for continuous extraction, and intelligently control the extraction parameters to form a continuous governance capability.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas, characterized in that, Includes the following steps: S1. Determination of reasonable initial and periodic pressure step distances: Research and analysis are conducted on coal seam mining conditions, periodic pressure step distances, and mine pressure intensity manifestations to determine the key layers for roof failure. Combined with coal seam gas parameters and ventilation methods, the gas emission rate and return air gas concentration are predicted to identify the risk sources of transient gas emission risks. In order to control roof mine pressure manifestations and transient gas emission, a reasonable target pressure step distance is determined by analyzing the initial and periodic pressure loads of previous working faces and their gas emission patterns. S2. Optimization design of parameters for large-diameter roof control and interception boreholes: Design the spacing of large-diameter roof control and strong drainage boreholes based on the determined target and step distance; Design the borehole parameters based on the positional relationship between the bottom gas drainage roadway and the working face. S3. Construction of large-diameter roof control and cutoff boreholes: The drilling site is set up according to the drilling design parameters. A high-power drilling rig with trajectory measurement is installed in the drilling site to carry out drilling construction. During the drilling construction, the drilling passes through the bottom plate of the coal seam goaf, the collapsed and broken rock mass of the goaf, and the intact roof of the goaf, as well as its lithology, to ensure that the drilling depth passes through the top surface of the key layer. S4. Static fracturing agent is introduced into the key drilling layer: After the drilling is completed, the drill rod tail braid is removed. The pre-made static fracturing agent cartridge is sent to the key drilling layer through the hollow annular space of the drill rod and compacted. The drill is slowly withdrawn until the key layer is filled with the pre-made static fracturing agent cartridge and compacted, so as to achieve non-explosive and controllable weakening of the hard top plate. S5. Installation and Sealing of Stainless Steel Screen Pipes: After the pre-made static fracturing agent cartridges are delivered to the key layer of each borehole, the drill rod is withdrawn. The stainless steel screen pipe is then driven by the drilling rig to rotate and advance along the borehole until it reaches the lower interface of the key layer. The diameter of the stainless steel screen pipe is 42-108mm. After the stainless steel screen pipe is installed, the borehole is sealed using a two-plug-one-injection sealing process. It is then connected to the extraction branch pipeline through the extraction hose, ball valve, and guide short section. S6. Intelligent Control of Roof Fracture-Interception and Drainage Parameters: Based on the changes in support load, working face gas volume fraction, and gas drainage parameters of the control borehole before and after the key layer fractures under the action of pre-made static fracturing agent cartridges, a borehole valve opening criterion is designed. A closed-loop intelligent control system based on support load, gas concentration, and drainage parameters is established and embedded with a PLC control module. When the support load or working face gas volume fraction decreases to the set critical value after the initial or periodic pressure, the PLC control module outputs a command to control the ball valve opening to carry out goaf interception and drainage. S7. Evaluation of Results and Optimization; S8. As the working face continues to advance, steps S3 to S6 are executed cyclically to carry out the design and construction of the top control and interception borehole, the introduction of static fracturing agent, the installation of screen pipes and sealing and continuous pumping, and the intelligent control of pumping parameters to form a continuous treatment capability.

2. The method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas according to claim 1, characterized in that, The specific method for determining the key layer of roof failure in step S1 is to analyze the coal seam thickness, mining height, dip angle, roof and floor lithology, and mining intensity, and to study the periodic pressure step distance and mine pressure intensity manifestation. The roof pressure of the working face increases sharply and instantaneously, and then shows a step-like decrease or a slow decrease, with a clear peak inflection point.

3. The method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas according to claim 2, characterized in that, The specific method for determining the risk source of transient gas outburst risk in step S1 is to predict the gas outburst volume and return air gas concentration by combining coal seam gas parameters and ventilation methods, provided that the overhanging roof area of ​​the goaf exceeds 8m². 2 Or the roof pressure at the working face exceeds 80% of the safety threshold for strong mine pressure manifestation disasters in the mine's history.

4. The method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas according to claim 3, characterized in that, In step S1, the analysis is conducted based on the mining intensity and the load of the support during the initial and periodic pressure of the previous working face, as well as the gas emission pattern in the goaf. The relationship between safety and cost of measures is considered to determine a reasonable pressure step distance. Among them, the relationship between the pressure step distance and potential losses is that the larger the step distance L, the greater the elastic energy E accumulated in the roof, and the types of disasters caused include support damage, roadway damage, and abnormal gas outbursts, gas exceeding limits, or even explosions. The expected repair losses for support damage and roadway damage, including direct and indirect costs, are C. d The direct and indirect costs of gas over-limit shutdowns and explosions are C. g ; The probability of an accident, P(L), increases exponentially with the step size L. Therefore, the relationship between the pressure step size and the probability of a potential disaster is expressed as: Where k is the risk coefficient, which is determined based on geological conditions; The formula for calculating the safety risk cost R(L) is: The cost of retrofit measures is inversely proportional to the cycle length. The formula for calculating the cost of retrofit measures, M(L), is as follows: In the formula: A is a coefficient related to modification measures such as borehole density; The total cost T(L) is obtained as follows: Considering both the overall safety risk cost and the cost of modification measures, the step distance L that minimizes the total cost T(L) is selected as the pressure step distance.

5. The method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas according to claim 1, characterized in that, In step S6, the drilling valve opening criterion is designed based on the changes in support load before and after the key layer breaks under the action of the pre-made static fracturing agent cartridge, the changes in gas volume fraction at the working face, and the gas extraction parameters of the control and interception borehole. The ball valve is closed when the support load or gas volume fraction at the working face decreases to the set critical value after the initial or periodic pressure is applied, to avoid the problem of natural oxidation of residual coal caused by long-term air leakage during extraction in the goaf. After the initial grouting, curing, sealing, and continuous extraction, the valve is kept open. After the peak pressure inflection point of the working face roof passes, and the gas purity or gas concentration reaches the peak value for 1 hour, the valve opening is gradually adjusted, and the valve is closed when the concentration decreases to 5%.

6. The method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas according to claim 5, characterized in that, In step S7, based on the change in gas volume fraction at the working face during the pressure period from the top plate, the drilling design parameters, static fracturing agent usage, and valve opening criteria are optimized.

7. The method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas according to claim 1, characterized in that, In step S1, the reasonable pressure step distance refers to the step distance that can be effectively controlled within the rated working resistance range of the hydraulic support of the working face, without causing serious coal wall spalling or collapse.

8. The method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas according to claim 7, characterized in that, In step S2, based on the determined reasonable pressure step distance, the spacing of the large-diameter control top strong extraction drilling holes is designed to be 10-20m, ensuring that the drilling depth penetrates 0.5m through the top surface of the key layer, the drilling diameter is 94-159mm, and the spacing is 15-20m.

9. The method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas according to claim 8, characterized in that, In step S3, the large-diameter roof control and cutoff borehole is constructed from the bottom gas drainage roadway, passing through the goaf floor, collapsed and fractured rock mass, and reaching the key layer of the overlying intact roof, with a depth of 0.5m through the top surface of the key layer. A metal stainless steel screen pipe is installed from the lower interface of the key layer to the coal seam floor, and extends to the borehole opening through a threaded connection with the stainless steel pipe, forming a continuous drainage channel. The stainless steel screen pipe and the stainless steel pipe are connected to the drainage branch pipe through drainage hoses, ball valves, and guide short sections. The working face roof pressure acquisition end is set on the hydraulic support, the working face gas acquisition end is set at the upper corner, and the borehole drainage parameter acquisition device is set on each borehole drainage pipeline. The working face roof pressure acquisition end, the working face gas acquisition end, and the borehole drainage parameter acquisition device are respectively connected to the PLC control end. The PLC control end outputs commands to control the ball valve opening according to the preset borehole valve opening criteria, realizing closed-loop flow control.

10. The method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas according to claim 1, characterized in that, In step S3, the drill rod used for drilling is a large-diameter drill rod, and the drill bit is an openable / closable drill bit.

11. The method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas according to claim 1, characterized in that, The static breaker agent mentioned in step S4 is a controlled-release static breaker agent.

12. The method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas according to claim 11, characterized in that, The static catalytic agent cartridge is made by encapsulating a CaO / Al2O3 composite matrix and an organic slow-release catalyst in a 3:1 ratio within a temperature-sensitive capsule.

13. The method for intelligent roof control and flow interception to prevent transient and abnormal gas outbursts in goaf areas according to claim 1, characterized in that, In step S5, after the stainless steel screen pipe is installed in place, a two-plug-one-grout sealing process is adopted; the stainless steel screen pipe is installed to the bottom plate of the coal seam, and the section from the bottom plate of the coal seam to the orifice is made of stainless steel pipe. Threaded connections are used between stainless steel screen pipes, between stainless steel pipes, and between the two. The length of the stainless steel screen pipe and the stainless steel pipe is no more than 1000mm; the orifice is sealed with Marl powder and grout is used for sealing.

Images