A method for gas control based on cascade progressive detection

Abstract

This invention discloses a gas control method based on tiered, progressive detection, relating to the fields of coal mining and gas control technology. The method utilizes both long-range geophysical exploration and short-range control measures for gas control. Long-range geophysical exploration includes using geophysical surveys, drilling, and probing to detect karst gas in advance, and implementing drilling and release measures in abnormal areas. Simultaneously, it requires comprehensive analysis of geophysical data and geological conditions to formulate safety technical measures. Furthermore, it involves the design and construction of dedicated gas extraction roadways, and drilling in specific areas to determine the distance between the roadway and the coal seam. Short-range control includes drilling, probing, gas extraction, gas venting, gas blocking, and detour. This invention, through its two major steps of long-range geophysical exploration and short-range control, ensures that all aspects from detection to control are covered, solving the problems of poor systemicity and low safety in existing karst fissure gas control management mechanisms.

Description

Technical Field

[0001] This invention relates to the field of coal mining and gas control technology, and in particular to a gas control method based on cascade progressive detection. Background Technology

[0002] In Southwest China, numerous coal mines are prone to outbursts. One of the core and crucial measures for preventing coal and gas outbursts is pre-drainage of coal seams through boreholes. However, before conducting pre-drainage, dedicated gas extraction roadways need to be pre-installed in the underlying or overlying strata. During the excavation of rock roadways in coal mines, predicting and assessing the engineering geological conditions of the area traversed is essential. Early on, insufficient attention was paid to this issue, leading to several situations where unclear geological conditions severely hampered excavation. With the increasing number of rock roadway excavations, especially in deep horizontal coal mines, the application of advanced geological prediction technology has become more widespread and sophisticated. However, complex geological issues, such as weak geological zones, karst, and gas conditions, pose significant challenges in advanced geological prediction, particularly when several geological problems occur simultaneously or when groundwater content is high, which can easily reduce prediction accuracy. Secondly, the limited space in coal mine rock tunnels and the significant interference with the placement of construction equipment make it difficult to set up some instruments, leading to inaccurate forecasts. Furthermore, the analysis of advanced geological forecast results requires a high level of technical expertise from the staff. Reflecting specific geological conditions through graphics or data requires extensive knowledge and experience, which is also a challenge in advanced geological forecasting technology.

[0003] Because coal mine rock roadway excavation often traverses areas with frequent geological activity, resulting in highly complex geological conditions and a wide variety of geological problems, and because each advanced geological prediction method has its own advantages and disadvantages, choosing only one method is unlikely to achieve the desired results and the prediction results may not be accurate enough. Therefore, for most coal mine rock roadway excavations, the comprehensive application of various advanced geological prediction methods is a relatively correct choice. However, the guidance, operation, and understanding of the comprehensive advanced geological prediction system for coal mine rock roadway excavation may vary depending on the specific mining area and mine.

[0004] Furthermore, geological structures such as fault zones, fracture zones, and collapse columns disrupt the continuity of the aquitard, easily becoming outburst channels for karst fissure gas and water, and are the triggering factors for karst fissure gas and water outbursts. Mining projects cause a redistribution of ground stress, which to some extent damages the aquitard, exacerbating the possibility of karst fissure gas and water outbursts, and are the inducing factors for karst fissure gas and water outbursts.

[0005] As mines become deeper, abnormal outbursts of karst water or karst fissure gas are becoming more frequent, and in some areas, they have even caused injuries. Southwest China has high-pressure, water-rich karst aquifers and karst fissure gas. Therefore, during the excavation of dedicated gas-draining roadways or other rock roadways, an improved gas detection and control method is needed. This is of great significance for improving the efficiency of rock roadway excavation, ensuring the effectiveness of gas control, and ensuring safe mine excavation. Summary of the Invention

[0006] The purpose of this invention is to provide a gas control method based on tiered progressive detection, which can solve the problems of poor systemicity and low safety of existing karst fissure gas control management mechanisms.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] A gas control method based on tiered progressive detection utilizes a long-range geophysical exploration component and a short-range control component for gas control;

[0009] The long-range geophysical exploration includes the following steps:

[0010] S1. During tunnel excavation, karst gas must be detected and released in advance; the methods for advance detection and release include geophysical exploration, drilling, and probing.

[0011] S2. If an abnormal area is still found after the review, drilling and exploration measures must be taken within 10 meters of the abnormal area.

[0012] S3. If no geophysical anomaly zone is found after verification, no drilling or blasting measures will be taken, but the construction of probe holes and blasting requirements will still be carried out in accordance with the original geophysical anomaly zone requirements.

[0013] S4. After drilling, combine geophysical data and geological conditions of adjacent areas to draw drilling results, and formulate safety technical measures based on the drilling results notification.

[0014] S5. Set the vertical distance between the top of the dedicated gas extraction roadway and the coal seam to be 8-15m, except for the design of uphill sections and stone gates that cross coal-bearing strata.

[0015] S6. When tunneling, if there is no measured or geological borehole stratigraphic control data within 150-200m around the head of the normal area, at least one borehole shall be drilled to determine the distance between the tunnel and the coal seam and the thickness of the aluminous mudstone. In areas where the strike or dip of faults or coal seams changes significantly, geological boreholes must be densified. Both sides of the fault must be controlled by geological boreholes at the same time, and a stratigraphic control borehole log shall be established.

[0016] The methods for close-range prevention and control include: drilling, probing, air extraction, air venting, air blocking, and bypassing.

[0017] The drilling was conducted as follows: When there was a certain deviation in the measurement of the abnormal range of karst fissures using the transient electromagnetic method or a mine geological detector, the drilling method was used to verify the accuracy of the transient electromagnetic method.

[0018] The probing method is as follows: after the drilling method was used for verification in the first test, since the traditional drilling method is a point contact method and the number of boreholes is small, the control range is limited. Therefore, a larger number of probing methods are used for final verification.

[0019] The gas extraction method involves using the well-established main extraction system in the study area to directly seal and extract the gas from the karst fissures, thereby releasing harmful gases.

[0020] The exhaust is as follows: when the amount of gas enriched in karst fissures is low, local ventilation measures are used to safely discharge harmful gases to the mine's main return air system;

[0021] The gas blocking refers to the shielding measures taken when the outflow of karst gas and water is large, and there is a continuous supply of gas and water, which is insufficient to reduce the safety threat to an acceptable level in a short period of time.

[0022] The avoidance method refers to avoiding fissures and structures that could significantly impact safe production. For complex karst fissures and structures that have been identified, proactive avoidance methods are adopted to reduce construction complexity and potential safety risks.

[0023] Optionally, in the long-distance geophysical exploration, if karst gas, water, bauxite, or coal seams are detected during step S6 when drilling probing holes or blast holes in the Maokou limestone tunnel, the operation must be stopped.

[0024] Optionally, the anomalous area includes a geophysical anomalous area and a drilling anomalous area; wherein, the geophysical anomalous area is the range of the anomalous area delineated based on a comprehensive analysis of geophysical data and the geological information at hand; the drilling anomalous area is the anomalous area actually exposed by the borehole and the area within 5m before and after that area.

[0025] Optionally, the requirements for the safety technical measures include: when geophysical exploration is abnormal but drilling is normal, the procedures for drilling and blasting in the geophysical exploration abnormality area shall be followed; when both geophysical exploration and drilling are abnormal, specific measures shall be formulated separately according to the drilling abnormality.

[0026] Optionally, in the area where there are no geophysical anomalies, at least three probe holes shall be constructed in each cycle, with two holes ending 1.0m outside the roadway and one hole inside the roadway outline. The opening and ending positions of the probe holes in each cycle shall be staggered and alternated with those in the previous cycle.

[0027] Optionally, during the gas extraction process, the gas extraction pipeline needs to be constructed simultaneously with the gas extraction roadway excavation. The distance between the end of the pipeline and the working face should not exceed 200m to facilitate timely extraction of karst and fissure gas. The diameter of the extraction pipeline is calculated according to the following formula:

[0028]

[0029] In the formula, D is the pipe diameter (m); Q is the flow rate (m³). 3 / s; V is the economic flow velocity, taken as 10-15m / s; In addition, the water supply and air supply pipelines are temporarily converted into karst fissure gas extraction pipelines to quickly and effectively reduce the threat of karst gas. Furthermore, in cases of small outflow, low concentration, and no pressure, temporary plugging of exploratory holes is used for extraction.

[0030] Optionally, during the full-rock tunnel excavation process, if various exploratory boreholes detect hidden karst gas risk factors, and if the amount of water accumulated in the karst is small, the gas emission characteristics are gentle, and the safety threat to the workers at the mining face is relatively small, and the risk level is low, then drilling rigs or rock drills can be used to drill boreholes at a certain distance from the karst for advance control and emission of gas, water, and other harmful substances; the required ventilation volume at the tunneling face is calculated using the following formula:

[0031] Q j =100×q j ×K j

[0032] In the formula, Q j The actual required air volume (m) at the tunneling face 3 / min; q j The absolute gas emission rate (m³) at the tunneling face 3 / min;K j The absolute gas outburst imbalance coefficient at the tunneling face is taken as 1.3 to 1.5.

[0033] Optionally, the gas plugging is divided into three categories based on the location of the karst plugging: the first category mainly acts on the interior of the karst; the second category is to plug the exterior of the karst; and the third category is to plug the exposed part of the karst.

[0034] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0035] This invention discloses a gas control method based on tiered, progressive detection. The method includes both long-range geophysical exploration and short-range control measures. Long-range geophysical exploration involves using geophysical surveys, drilling, and probing to detect karst gas in advance, and implementing drilling and gas release measures in abnormal areas. Simultaneously, it requires comprehensive analysis of geophysical data and geological conditions to formulate safety technical measures. Furthermore, it involves the design and construction of dedicated gas extraction roadways, and drilling in specific areas to determine the distance between the roadway and the coal seam. Short-range control measures include drilling, probing, gas extraction, gas venting, gas blocking, and detours. This invention first establishes a systematic gas prevention and control process through two major steps: long-distance geophysical exploration and short-distance prevention and control, ensuring that all aspects from detection to prevention are covered. Secondly, it uses geophysical exploration, drilling, and probing to detect karst gas in advance, enabling prevention before gas disasters occur and reducing the risk of accidents. Finally, it provides a variety of prevention and control methods, such as drilling, probing, gas extraction, gas exhaust, gas blocking, and detour, allowing for flexible selection of the most suitable prevention and control method based on actual conditions. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the probe hole arrangement in this embodiment;

[0038] Figure 2 This is a longitudinal sectional view of the probe hole arrangement in this embodiment;

[0039] Figure 3 This is a schematic cross-sectional view of the probe hole arrangement in this embodiment.

[0040] Reference numerals in the attached drawings: 1. First probe hole; 2. Second probe hole; 3. Third probe hole; 4. Fourth probe hole; 5. Fifth probe hole. Detailed Implementation

[0041] The technical solutions of the embodiments 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 embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The purpose of this invention is to provide a gas control method based on tiered progressive detection, which can solve the problems of poor systemicity and low safety of existing karst fissure gas control management mechanisms.

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] like Figures 1-3 As shown, this invention provides a gas control method based on tiered progressive detection, including gas control using a long-range geophysical exploration section and a short-range control section. The figure shows the location arrangement of each probe hole, specifically including a first probe hole 1, a second probe hole 2, a third probe hole 3, a fourth probe hole 4, and a fifth probe hole 5.

[0045] Long-range geophysical exploration includes the following steps:

[0046] S1. During tunnel excavation, geophysical exploration, drilling, and probing must be used to detect and release karst gas in advance. The advance distance for geophysical exploration is 10m, for drilling it is 5m, and for probing it is 1.5m. Geophysical verification should be carried out again 10m before the tunnel enters each geophysical anomaly zone.

[0047] S2. For any abnormal areas that still exist after verification, drilling and exploration measures must be taken within 10 meters of the abnormal area. Mine geological technicians shall comprehensively determine the drilling parameters (the borehole diameter shall not exceed 65mm) based on the scope of the geophysical abnormal area in this roadway, the excavated area, and the occurrence and structural development of karst gas exposed in the mining area or level.

[0048] S3. If no geophysical anomaly zone is found after verification, drilling and blasting measures will no longer be taken. However, the construction of probe holes and blasting requirements will still be implemented according to the original geophysical anomaly zone. If probe holes or blast holes are made in the Maokou limestone roadway during long-distance geophysical exploration, and karst gas, water, bauxite, or coal seam are detected, the operation must be stopped.

[0049] The anomaly zones are divided into geophysical anomaly zones and drilling anomaly zones, and the scope of the anomaly zones is defined as follows: Geophysical anomaly zone: the scope of the anomaly zone delineated based on comprehensive analysis of geophysical data and geological information; Drilling anomaly zone: the anomaly area actually revealed by the borehole and the area within 5m before and after this area are all considered drilling anomaly zones. The safety technical measures are as follows: When geophysical anomaly occurs but drilling is normal, the procedures for probing and blasting shall be followed as for geophysical anomaly zones; when both geophysical and drilling anomalies exist, specific measures shall be formulated separately based on the drilling anomaly situation.

[0050] S4. After drilling, the drilling results are obtained by combining geophysical data and geological conditions of adjacent areas. Safety technical measures are formulated based on the drilling results notification. In non-geophysical anomaly areas, at least 3 probe holes are drilled per cycle. Two of the holes end at 1.0m outside the roadway, and one hole is located inside the roadway outline. The opening and closing positions of the probe holes in each cycle should be staggered and alternated with those in the previous cycle.

[0051] S5. The vertical distance between the top of the gas drainage roadway and the coal seam is 8 to 15 meters (except for the uphill sections and stone gates designed to pass through coal-bearing strata). If it exceeds this range, the roadway strata should be adjusted in a timely manner or special measures should be developed.

[0052] S6. When tunneling, if there is no measured (or geological borehole) stratigraphic control data within 150-200m around the head of the normal area, at least one borehole should be drilled to determine the distance of the tunnel from the coal seam and the thickness of the aluminous mudstone. In areas with significant changes in the strike or dip of faults or coal seams, geological boreholes must be increased. Both sides of the fault must be controlled by geological boreholes simultaneously, and a stratigraphic control borehole log should be established.

[0053] Close-range prevention includes the following methods:

[0054] Method 1: Drilling. Using transient electromagnetic methods or mine geological detectors to determine the area of ​​karst fissure anomalies may result in some deviation. To verify the accuracy of the transient electromagnetic method, this experiment uses drilling as the verification method. The drilling rig used is a ZYG-150 fully hydraulic drilling rig, mainly used for drilling gas drainage holes, grouting and fire extinguishing holes, coal seam water injection holes, geological exploration holes, and related engineering holes in coal mines. This drilling rig is suitable for various coal and rock formations with a rock strength coefficient f≤8. It is suitable for roadway cross-sections S≥4.5m. 2 .

[0055] Method 2: Probing. The transient electromagnetic method may have some deviation in determining the range of karst fissure anomalies. To verify the accuracy of the transient electromagnetic method, the first test used drilling. However, drilling is a point contact method with a small number of boreholes, which limits the control range and may still have some deviation. Therefore, it is proposed to use a larger number of probing holes for final verification.

[0056] Method 3: Gas extraction. Utilizing the existing well-established main gas extraction system in the study area, the gas extraction pipeline is directly sealed off from the karst fissures to release harmful gases. When implementing gas extraction for prevention and control, the gas extraction pipeline should be excavated simultaneously with the gas extraction roadway. The distance between the end of the pipeline and the working face should preferably not exceed 200m to facilitate timely extraction of karst and fissure gas. The diameter of the extraction pipe can be calculated using the following formula:

[0057]

[0058] In the formula: D is the pipe diameter (m), Q is the flow rate (m³ / h). 3 / s), where V is the economic flow velocity, generally taken as 10-15m / s. In addition, water supply and air supply pipelines can be temporarily converted into karst fissure gas extraction pipelines, which can quickly and effectively reduce the threat of karst gas. Furthermore, in cases of small outflow, low concentration, and no pressure, temporary plugging of exploratory holes can be used for extraction.

[0059] Method 4: Venting. When the amount of gas accumulated in karst fissures is low, make full use of local ventilation measures to safely discharge harmful gases to the mine's main return air system. During the full-rock tunnel excavation process, if various exploratory boreholes reveal hidden karst gas risk factors, and if the amount of water accumulated in the karst is small, the gas emission characteristics are gentle, and the safety threat to workers at the mining face is relatively low, then drilling rigs or rock drills can be used to pre-control and discharge harmful substances such as gas and water at a certain distance from the karst. The required ventilation volume at the tunneling face is calculated using the following formula:

[0060] Q j =100×q j ×K j

[0061] In the formula, Q j The actual required air volume (m) at the tunneling face 3 / min; q j The absolute gas emission rate (m³) at the tunneling face 3 / min;K j The absolute gas outburst imbalance coefficient at the tunneling face is taken as 1.3 to 1.5.

[0062] Method 5: Gas Blocking. When the outflow of karst gas and water is large, with a continuous supply of gas and water, and the safety threat cannot be reduced to an acceptable level in a short time, shielding measures are taken. Gas blocking can be divided into three categories based on the location of the karst sealing: The first category mainly acts on the interior of the karst, such as grouting to seal karst fissures. This type of engineering measure should be the first choice when encountering karst in railway, bridge and tunnel projects, and main development tunnels of mines. The purpose is to ensure the stability of the surrounding rock and prevent the further expansion of karst cavities, thereby endangering the safety of the project; the second category is sealing on the outside of the karst, such as for mines... For secondary shaft engineering used for gas extraction, the first option is to implement bypass measures, seal the exposed karst at a relatively safe location, and take drainage measures in the sealed area. If necessary, the sealing facilities can be reopened. A typical approach is to construct a sealed wall at a certain position after the tunneling face and reserve extraction boreholes for drainage. The third type is to seal the exposed karst. For karst with a small impact range, in order to ensure support safety, measures such as anchor bolts, anchor mesh, shotcrete, and erection of I-beam supports are used to seal and reinforce the karst. The purpose is to ensure support safety and prevent gas accumulation in karst cavities.

[0063] Method 6: Avoidance. In order to avoid the significant impact of fissures and structures on safe production, for karst fissures and structures that have been explored to be relatively complex, the main active method of avoidance is to reduce the complexity of construction and potential safety risks.

[0064] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0065] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A gas control method based on cascaded progressive detection, characterized in that, Gas control is carried out using both long-range geophysical exploration and short-range prevention components. The long-range geophysical exploration includes the following steps: S1. During tunnel excavation, karst gas must be detected and released in advance; the methods for advance detection and release include geophysical exploration, drilling, and probing. S2. If an abnormal area is still found after the review, drilling and exploration measures must be taken within 10 meters of the abnormal area. S3. If no geophysical anomaly zone is found after verification, no drilling or blasting measures will be taken, but the construction of probe holes and blasting requirements will still be carried out in accordance with the original geophysical anomaly zone requirements. S4. After drilling, combine geophysical data and geological conditions of adjacent areas to draw drilling results, and formulate safety technical measures based on the drilling results notification. S5. Set the vertical distance between the top of the dedicated gas extraction roadway and the coal seam to be 8-15m, except for the design of uphill sections and stone gates that cross coal-bearing strata. S6. When tunneling, if there is no measured or geological borehole stratigraphic control data within 150-200m around the head of the normal area, at least one borehole shall be drilled to determine the distance between the tunnel and the coal seam and the thickness of the aluminous mudstone. In areas where the strike or dip of faults or coal seams changes significantly, geological boreholes must be densified. Both sides of the fault must be controlled by geological boreholes at the same time, and a stratigraphic control borehole log shall be established. The methods for close-range prevention and control include: drilling, probing, air extraction, air venting, air blocking, and bypassing. The drilling was conducted as follows: When there was a certain deviation in the measurement of the abnormal range of karst fissures using the transient electromagnetic method or a mine geological detector, the drilling method was used to verify the accuracy of the transient electromagnetic method. The probing method is used for final verification after the drilling method was used in the first test. Since the traditional drilling method is a point contact method and the number of holes is small, the control range is limited. The gas extraction method involves using the well-established main extraction system in the study area to directly seal and extract the gas from the karst fissures, thereby releasing harmful gases. The exhaust is as follows: when the amount of gas enriched in karst fissures is low, local ventilation measures are used to safely discharge harmful gases to the mine's main return air system; The gas blocking refers to the shielding measures taken when the outflow of karst gas and water is large and there is a continuous supply of gas and water, and it is not enough to reduce the safety threat to an acceptable level in a short period of time. The avoidance method refers to avoiding the impact of fissures and structures on safe production. For karst fissures and structures that have been identified as relatively complex, an active avoidance method is adopted to reduce the complexity of construction and potential safety risks.

2. The gas control method based on cascaded progressive detection according to claim 1, characterized in that, In the aforementioned long-distance geophysical exploration, if karst gas, water, bauxite, or coal seams are detected during step S6 of the Maokou limestone tunnel excavation, the operation must be stopped.

3. The gas control method based on cascaded progressive detection according to claim 1, characterized in that, The anomaly zone includes a geophysical anomaly zone and a drilling anomaly zone; wherein, the geophysical anomaly zone is the range of the anomaly zone delineated based on a comprehensive analysis of geophysical data and the geological information at hand; the drilling anomaly zone is the anomaly area actually exposed by the borehole and the area within 5m before and after that area.

4. The gas control method based on cascade progressive detection according to claim 1, characterized in that, The requirements for the aforementioned safety technical measures include: when geophysical exploration is abnormal but drilling is normal, the procedures for drilling and blasting in the geophysical exploration abnormality area shall be followed; when both geophysical exploration and drilling are abnormal, specific measures shall be formulated separately based on the drilling abnormality.

5. The gas control method based on cascaded progressive detection according to claim 1, characterized in that, In the area where there are no geophysical anomalies, at least three probe holes shall be constructed in each cycle, with two holes ending 1.0m outside the roadway and one hole inside the roadway outline. The opening and closing positions of the probe holes in each cycle shall be staggered and alternated with those in the previous cycle.

6. The gas control method based on cascaded progressive detection according to claim 1, characterized in that, When implementing the gas extraction, the gas extraction pipeline needs to be excavated simultaneously with the gas extraction roadway. The distance between the end of the pipeline and the working face should not exceed 200m to facilitate timely extraction of karst and fissure gas. The diameter of the extraction pipeline is calculated according to the following formula: ， In the formula, D Pipe diameter, in meters (m); Q For flow rate, m 3 / s; V For economical flow velocity, a value of 10-15 m / s is adopted. In addition, the water and air supply pipelines are temporarily converted into karst fissure gas extraction pipelines to quickly and effectively reduce the threat of karst gas. Furthermore, in cases where the outflow is small, the concentration is low, and there is no pressure, temporary plugging of the exploratory hole extraction method is adopted for treatment.

7. The gas control method based on cascaded progressive detection according to claim 1, characterized in that, When the aforementioned ventilation is implemented during the full-rock tunnel excavation process, if various exploratory boreholes detect hidden karst gas risk factors, and if the amount of water accumulated in the karst is small, the gas emission characteristics are gentle, and the safety threat to the workers at the mining face is low, and the risk level is low, then drilling rigs or rock drills are used to drill boreholes at a certain distance from the karst for advance control and discharge of gas and water. The required ventilation volume at the tunneling face is calculated using the following formula: ， In the formula, The actual required air volume (m) at the tunneling face 3 / min; The absolute gas emission rate (m³) at the tunneling face 3 / min; The absolute gas outburst imbalance coefficient at the tunneling face is taken as 1.3 to 1.

5.

8. The gas control method based on cascaded progressive detection according to claim 1, characterized in that, When implementing the gas plugging, it is divided into three categories according to the location of the karst plugging: the first category is to act on the inside of the karst; the second category is to plug on the outside of the karst; and the third category is to plug at the exposed part of the karst.

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