Deep outburst coal seam cross-cut coal uncovering grading outburst prevention method

Abstract

The deep outburst coal seam cross-cut coal uncovering grading outburst prevention method comprises the steps that outburst risk grades are divided according to gas pressure of different areas, and the outburst risk grades include the low risk grade, the medium risk grade and the high risk grade; if the current coal uncovering coal seam area is low in risk, outburst elimination is conducted through a drilling method; if the risk is medium, a roadway method is adopted for outburst elimination, and if the risk is high, a well-ground combined comprehensive method is adopted for outburst elimination; through grading precise prevention and control, the method adapts to the complex geological conditions of three highs and one disturbance of the deep part, and the problem that in the prior art, adaptability to coal seams with different outburst risks is poor is solved; in addition, a well-ground combined comprehensive method is adopted, a pressure relief-energy dissipation-reinforcement synergistic process system is constructed, finally, a modified coal seam protection structure of a caving breaking energy absorption area-a gas extraction energy dissipation area-a grouting reinforcement area is formed in front of a coal uncovering roadway, passive support is changed into active prevention and control, the safety and operation efficiency of deep cross-cut coal uncovering are greatly improved, and the safety of deep cross-cut coal uncovering is improved. And reliable technical support is provided for safe mining of the deep high-risk coal seam.

Description

Technical Field

[0001] This invention relates to a graded method for preventing coal and gas outbursts by opening coal seams through rock passages in deep outburst-prone coal seams, belonging to the field of coal and gas outburst prevention and control technology. Background Technology

[0002] Deep coal seams, subjected to the unique mining conditions of "high ground stress, high ground temperature, high gas pressure, and strong disturbance" ("three highs and one disturbance"), are highly susceptible to coal and gas outbursts and gas explosions during seam exposure operations. Therefore, the safe and efficient mining of deep coal resources is one of the key research directions in the coal mining industry today. Seam exposure, as a transitional link between development preparation and coal seam recovery, has one of its core tasks being to solve the problem of "gas control and outburst prevention," and is essential for achieving the aforementioned safe mining practices.

[0003] Outbursts during coal seam exposure are primarily the result of the combined effects of factors such as ground stress, coal seam gas pressure, and coal-rock dynamics. Currently, methods for exposing outburst-prone coal seams mainly focus on two aspects: pressure relief and seam reinforcement. Pressure relief and permeability enhancement methods include hydraulic perforation, hydraulic fracturing, and hydraulic slotting. Seam reinforcement primarily involves grouting and metal reinforcement. While these methods have achieved good results in preventing outbursts, the complexity of the outburst mechanism during exposure and the effects of strong impact loads and high gas pressure at depth reveal limitations to single-method outburst prevention. These limitations include the inability to consistently achieve outburst prevention during exposure, and the potential for pressure relief to decrease coal seam stability, impacting the safety of subsequent coal seam exposure operations.

[0004] In summary, the research direction of this invention is to provide a new method for preventing coal seam outbursts that can be adapted to different gas pressure zones in the coal seam, and can improve coal stability and ensure safe coal uncovering operations while eliminating outbursts through pressure relief duration. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a graded anti-outburst method for coal seam rock gate exposure in deep outburst coal seams. This method can be adapted to different gas pressure zones in the coal seam, and while eliminating outbursts through pressure relief duration, it can also improve coal body stability and ensure safe subsequent coal seam exposure.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for graded coal seam uncovering and outburst prevention in deep outburst coal seams, comprising the following steps: Step 1: Based on geological exploration data, determine the extent and geological complexity of the coal seam to be exposed, and then arrange for the measurement of gas pressure and gas content in different areas of the coal seam. Based on the gas pressure in different areas, classify the outburst risk level as low risk, medium risk, and high risk.

[0007] Step 2: Determine the spatial location of the coal seam to be exposed and the pre-exposed coal seam exposure roadway. The tunneling head of the pre-exposed coal seam exposure roadway continues to advance towards the coal seam to be exposed. When the distance between the tunneling head and the coal seam to be exposed is equal to the set value, the tunneling stops. According to the risk level classified in Step 1, if the current coal seam area to be exposed is low risk, proceed to Step 3; if it is medium risk, proceed to Step 4; if it is high risk, proceed to Step 5.

[0008] Step 3: At the excavation head of the Shimen coal uncovering roadway, use an underground directional drilling rig to construct a cross-layer extraction borehole in the direction of excavation. After completion, connect the borehole of the cross-layer extraction borehole to the underground gas extraction pipeline for gas extraction and pressure relief. Then continue to excavate the Shimen coal uncovering roadway until it passes through the coal seam and enters the roof of the coal seam, completing the Shimen coal uncovering operation in this coal seam area.

[0009] Step 4: In the coal seam uncovering roadway, the depressurization roadway is arranged in sections using the roadway method to extract gas and depressurize the coal seam. Then, the coal seam uncovering roadway is continued to be excavated until it passes through the coal seam and enters the roof of the coal seam, thus completing the coal seam uncovering operation in this coal seam area.

[0010] Step 5: The coal seam to be exposed is treated using a comprehensive anti-outburst measure that includes surface well drilling for pressure relief, surface and underground gas extraction and energy dissipation, and grouting reinforcement. Then, the stone gate coal exposure roadway is continued to be excavated until it passes through the exposed coal seam and enters the roof of the coal seam, thus completing the stone gate coal exposure operation in this coal seam area.

[0011] Furthermore, in step one, the risk levels are divided as follows: if the gas pressure in a certain area is less than 1 MPa, it is determined to be low risk; if the gas pressure in a certain area is between 1 MPa and 2 MPa, it is determined to be medium risk; if the gas pressure in a certain area is greater than 2 MPa, it is determined to be high risk.

[0012] Furthermore, the setting value for step two is 10m.

[0013] Furthermore, in step four, the depressurization roadway is arranged in sections using the tunnel method to extract gas from the exposed coal seam. Specifically, the depressurization roadway is excavated in sections according to the sequence of "outer first, then inner; top first, then bottom," with each section being supported immediately after excavation of 10-15m. After the roadway reaches the designed length, extraction pipelines are laid simultaneously, extraction holes are constructed and sealed for gas extraction. During the extraction process, equipment parameters are dynamically adjusted according to the gas concentration and extraction volume in each section. Monitoring is carried out throughout the process to promptly handle any abnormalities and ensure uniform and stable depressurization and extraction. This process is an existing method that can achieve the required depressurization and gas extraction effects.

[0014] Furthermore, the comprehensive anti-surprise measures in step five are specifically as follows: Ⅰ. Surface Well Caving and Pressure Relief: At the pre-designated well location on the surface, a vertical well is constructed using a kilometer-long drilling rig, drilling to the target cavitation area of ​​the exposed coal seam. Then, high-pressure water jet cavitation technology is used to radially enlarge the surrounding coal body to create cavitation, thereby forming a cavitation and energy absorption zone in the target cavitation area to absorb impact kinetic energy. After the cavitation is completed, a casing is installed and cemented. The bottom of the casing extends to a fixed position above the cavitation, and the outer side of the casing is sealed with cement. At the same time, a connection interface for docking with the downhole extraction system is reserved on the casing, completing the surface well cavitation construction.

[0015] II. Coordinated Surface and Underground Gas Drainage and Energy Dissipation: At the excavation head of the coal seam uncovering roadway in the Shimen area, an underground directional drilling rig is used to construct a cross-layer drainage borehole in the direction of excavation. After completion, the borehole opening of the cross-layer drainage borehole is connected to the underground gas drainage pipeline. At the same time, the casing from step I is connected to the surface gas drainage system through the reserved interface of the surface well casing, forming a coordinated surface well-underground borehole drainage system. Coordinated gas drainage is carried out simultaneously until the gas concentration is reduced to within the safe control range, thereby achieving energy dissipation of the coal seam in this area.

[0016] III. Grouting Reinforcement: After step II is completed, the cross-layer extraction borehole is temporarily sealed. Grouting boreholes are constructed at the excavation head and both sides of the roadway of the coal seam in the Shimen coal uncovering roadway to the surrounding coal body. Then, cement mortar is used to grout the coal seam through the grouting boreholes to improve the coal body structure and fully fill the fracture network in the coal seam with cement mortar. During the grouting reinforcement process, the grouting volume is monitored in real time until the required grouting volume is reached. The grouting operation is then stopped. After the grout has completely solidified, a grouting reinforcement zone is formed around the Shimen coal uncovering roadway.

[0017] IV. Modified Coal Seam Structure: After the construction in steps I to III, a modified coal seam structure is formed in the coal seam to be exposed in front of the Shimen coal uncovering roadway, consisting of a cavity-forming and crushing energy absorption zone, a gas extraction and energy dissipation zone, and a grouting reinforcement zone, thus completing the comprehensive anti-outburst measures.

[0018] Furthermore, the preset pressure range of the high-pressure water used in the high-pressure water jet cavity-creating technology in step I is 18~22MPa.

[0019] Furthermore, in step IV, the grouting reinforcement zone encloses the pre-excavation area of ​​the coal seam's rock-gate coal exposure roadway, the cavity-forming and crushing energy absorption zone encloses the grouting reinforcement zone, and the gas extraction and energy dissipation zone covers both the grouting reinforcement zone and the cavity-forming and crushing energy absorption zone.

[0020] Furthermore, the thickness of the grouting reinforcement zone on the cross-section of the coal seam in the rock-gate uncovering roadway ranges from 2 to 5 meters; the thickness of the cavity-forming and crushing energy-absorbing zone on the cross-section of the coal seam in the rock-gate uncovering roadway ranges from 5 to 10 meters. The specific values ​​of the two zones are determined based on the actual distribution range and thickness of the coal seam to be uncovered, as well as the design protection range of the coal seam uncovering operation in the rock-gate.

[0021] Compared with the prior art, the present invention has the following advantages: 1. This invention provides differentiated solutions for areas with different gas pressure levels. For low-risk areas, drilling is used; for medium-risk areas, tunneling is used; and for high-risk areas, a combined well-ground approach is used. This approach is adapted to the complex geological conditions of deep areas with high gas pressure, high humidity, high temperature, high risk, and high risk of disturbance. It solves the problem of poor adaptability of existing technologies to coal seams with different outburst risks, thereby achieving graded and precise prevention and control, and breaking through the limitations of traditional single outburst prevention methods.

[0022] 2. This invention employs a combined well-ground approach for high-risk applications, constructing a synergistic "pressure relief-energy dissipation-reinforcement" process system. First, pressure relief, energy absorption, and fracturing zones and permeability enhancement channels are pre-constructed through surface well drilling, laying the foundation for subsequent gas extraction. Then, gas energy dissipation is enhanced through an underground extraction system. Finally, grouting reinforcement is performed after extraction reaches the required standards to prevent grout from blocking gas seepage channels. This solves the problem of poor synergy between pressure relief, extraction, and reinforcement in existing technologies, thus forming an active prevention and control structure and improving disaster resistance. Ultimately, a modified coal seam protection structure is formed in front of the coal seam exposure roadway, consisting of a drilling fracturing and energy absorption zone, a gas extraction and energy dissipation zone, and a grouting reinforcement zone. This transforms passive support into active prevention and control, effectively addressing the insufficient ability of existing technologies to prevent combined rockburst and gas outburst disasters. It significantly improves the safety and operational efficiency of deep coal seam exposure, providing reliable technical support for the safe mining of deep, high-risk coal seams. Attached Figure Description

[0023] Figure 1 This is the conflict resolution method adopted for different levels of prominent risk in this invention.

[0024] Figure 2 This is a schematic diagram of the layout during high-risk construction in this invention.

[0025] Figure 3 yes Figure 2 A schematic diagram of the cross-section of the coal seam through which the Shimen coal seam is exposed after construction.

[0026] In the diagram: 1-coal seam, 2-coal uncovering roadway, 3-tunneling head, 4-safe rock pillar, 5-cavitation and energy absorption zone, 6-grouting reinforcement zone, 7-cross-layer extraction borehole. Detailed Implementation

[0027] The present invention will be further described below.

[0028] As shown in the figure, the present invention includes the following steps: Step 1: Based on geological exploration data, determine the extent and geological complexity of the coal seam to be exposed. Then, arrange for the measurement of gas pressure and gas content in different areas of the coal seam. Based on the gas pressure in different areas, classify the outburst risk level as follows: if the gas pressure in a certain area is less than 1 MPa, it is determined to be low risk; if the gas pressure in a certain area is between 1 MPa and 2 MPa, it is determined to be medium risk; if the gas pressure in a certain area is greater than 2 MPa, it is determined to be high risk.

[0029] Step Two: Determine the spatial location of the coal seam to be exposed and the pre-exposed coal seam exposure roadway. The tunneling head of the pre-exposed coal seam exposure roadway continues to advance towards the coal seam to be exposed. Tunneling stops when the distance between the tunneling head and the coal seam to be exposed is equal to 10m. This reserves safe working space for subsequent surface well drilling and underground gas extraction, ensuring smooth construction. Based on the outburst risk level determined in Step One, if the current coal seam area is low-risk, proceed to Step Three using the borehole method for pressure relief; if it is medium-risk, proceed to Step Four using the roadway method for pressure relief; if it is high-risk, proceed to Step Five using a combined well-surface method for pressure relief. Figure 1 As shown.

[0030] Step 3: At the excavation head of the Shimen coal uncovering roadway, use an underground directional drilling rig to construct a cross-layer extraction borehole in the direction of excavation. After completion, connect the borehole of the cross-layer extraction borehole to the underground gas extraction pipeline for gas extraction and pressure relief. Then continue to excavate the Shimen coal uncovering roadway until it passes through the coal seam and enters the roof of the coal seam, completing the Shimen coal uncovering operation in this coal seam area.

[0031] Step 4: Within the coal seam uncovering roadway, the depressurization roadway is arranged in sections using the roadway method to extract gas from the uncovered coal seam. Specifically, the depressurization roadway is excavated in sections according to the sequence of "outer first, then inner; top first, then bottom," with each section being supported immediately after excavation of 10-15m. After the roadway reaches the designed length, extraction pipelines are laid simultaneously, extraction holes are constructed and sealed for gas extraction. During the extraction process, equipment parameters are dynamically adjusted based on the gas concentration and extraction volume in each section. Monitoring is conducted throughout the process to promptly address any abnormalities and ensure uniform and stable depressurization and extraction. This process is an existing method that can achieve the required depressurization and gas extraction effects. Subsequently, the coal seam uncovering roadway continues to be excavated until it passes through the uncovered coal seam and enters the roof of the coal seam, completing the coal seam uncovering operation in this coal seam area.

[0032] Step 5: A comprehensive anti-outburst measure is adopted to treat the exposed coal seam, including surface well drilling for pressure relief, coordinated surface and underground gas extraction and energy dissipation, and grouting reinforcement. Subsequently, the rock-gate coal uncovering roadway continues to be excavated until it passes through the exposed coal seam and enters the roof, completing the rock-gate coal uncovering operation in this coal seam area. Figure 2 As shown, specifically: I. Surface Well Caving and Pressure Relief: At the pre-designated well location on the surface, a vertical well is constructed using a kilometer-long drilling rig, reaching the target cavitation area of ​​the coal seam to be exposed. Then, high-pressure water jet cavitation technology is used to radially enlarge the surrounding coal seam, creating cavitation zones. The pre-designed pressure range for the high-pressure water is 18-22 MPa, thus forming a cavitation and energy-absorbing zone in the target cavitation area to absorb impact kinetic energy. The thickness of this cavitation and energy-absorbing zone on the cross-section of the coal seam to be exposed ranges from 5 to 10 meters; the specific value is determined based on the actual distribution range and thickness of the coal seam to be exposed, as well as the design protection range for the coal seam exposure operation. After cavitation is completed, a casing is installed and cemented. The bottom of the casing extends to a fixed position above the cavitation area, and the outer side of the casing is sealed with cement. A connection interface for the underground extraction system is pre-installed on the casing, completing the surface well cavitation construction.

[0033] II. Coordinated Surface and Underground Gas Drainage and Energy Dissipation: At the excavation head of the coal seam uncovering roadway in the Shimen area, an underground directional drilling rig is used to construct a cross-layer drainage borehole in the direction of excavation. After completion, the borehole opening of the cross-layer drainage borehole is connected to the underground gas drainage pipeline. At the same time, the casing from step I is connected to the surface gas drainage system through the reserved interface of the surface well casing, forming a coordinated surface well-underground borehole drainage system. Coordinated gas drainage is carried out simultaneously until the gas concentration is reduced to within the safe control range, thereby achieving energy dissipation of the coal seam in this area.

[0034] III. Grouting Reinforcement: After step II is completed, the cross-seam extraction boreholes are temporarily sealed. Grouting boreholes are drilled at the excavation head and on both sides of the coal seam in the Shimen coal uncovering roadway, and then cement mortar is injected into the coal seam through the grouting boreholes to improve the coal structure and fully fill the fracture network within the coal seam. During the grouting reinforcement process, the grouting volume is monitored in real time until the required grouting volume is reached, at which point the grouting operation is stopped. After the grout has completely solidified, a grouting reinforcement zone is formed around the Shimen coal uncovering roadway. The thickness of the grouting reinforcement zone on the cross-section of the Shimen coal uncovering roadway ranges from 2 to 5 meters. The specific value is determined based on the actual distribution range and thickness of the coal seam to be uncovered, as well as the design protection range of the Shimen coal uncovering operation.

[0035] IV. Modified Coal Seam Structure: After construction steps I to III, a modified coal seam structure is formed in the coal seam to be exposed in front of the Shimen coal uncovering roadway, consisting of a cavity-forming and crushing energy absorption zone, a gas drainage and energy dissipation zone, and a grouting reinforcement zone, as shown below. Figure 3As shown, the grouting reinforcement zone encloses the pre-excavation area of ​​the coal seam's rock-gate coal exposure roadway, the cavity-making and crushing energy absorption zone encloses the grouting reinforcement zone, and the gas drainage and energy dissipation zone covers both the grouting reinforcement zone and the cavity-making and crushing energy absorption zone, ensuring the gas drainage effect in both areas and thus completing the comprehensive gas outburst prevention measures.

[0036] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for graded coal seam outburst prevention through rock passage exposure in deep outburst-prone coal seams, characterized in that, Includes the following steps: Step 1: Based on geological exploration data, determine the extent and geological complexity of the coal seam to be exposed, and then arrange for the measurement of gas pressure and gas content in different areas of the coal seam. Based on the gas pressure in different areas, classify the outburst risk level as low risk, medium risk and high risk. Step 2: Determine the spatial location of the coal seam to be exposed and the pre-exposed coal seam exposure roadway. The tunneling head of the pre-exposed coal seam exposure roadway continues to advance towards the coal seam to be exposed. When the distance between the tunneling head and the coal seam to be exposed is equal to the set value, the tunneling stops. According to the risk level classified in Step 1, if the current coal seam area to be exposed is low risk, proceed to Step 3; if it is medium risk, proceed to Step 4; if it is high risk, proceed to Step 5. Step 3: At the excavation head of the Shimen coal uncovering roadway, use an underground directional drilling rig to construct a cross-layer extraction borehole in the direction of excavation. After completion, connect the borehole of the cross-layer extraction borehole to the underground gas extraction pipeline for gas extraction and pressure relief. Then continue to excavate the Shimen coal uncovering roadway until it passes through the coal seam and enters the roof of the coal seam, completing the Shimen coal uncovering operation in this coal seam area. Step 4: In the coal seam uncovering roadway, the depressurization roadway is arranged in sections using the roadway method to extract gas and depressurize the coal seam. Then, the coal seam uncovering roadway is continued to be excavated until it passes through the coal seam and enters the roof of the coal seam, thus completing the coal seam uncovering operation in this coal seam area. Step 5: The coal seam to be exposed is treated using a comprehensive anti-outburst measure that includes surface well drilling for pressure relief, surface and underground gas extraction and energy dissipation, and grouting reinforcement. Then, the stone gate coal exposure roadway is continued to be excavated until it passes through the exposed coal seam and enters the roof of the coal seam, thus completing the stone gate coal exposure operation in this coal seam area.

2. The method for graded coal seam outburst prevention and control in deep outburst coal seams according to claim 1, characterized in that, In step one, the risk levels are classified as follows: if the gas pressure in a certain area is less than 1 MPa, it is determined to be low risk; if the gas pressure in a certain area is between 1 MPa and 2 MPa, it is determined to be medium risk; if the gas pressure in a certain area is greater than 2 MPa, it is determined to be high risk.

3. The method for graded coal seam outburst prevention and control in deep outburst coal seams according to claim 1, characterized in that, The setting value for step two is 10m.

4. The method for graded coal seam outburst prevention and control in deep outburst coal seams according to claim 1, characterized in that, In step four, the depressurization roadway is arranged in sections using the roadway method to extract gas from the exposed coal seam. Specifically, the depressurization roadway is excavated in sections according to a set sequence, and each section is supported immediately after being excavated for 10-15m. After the roadway is constructed to the designed length, the extraction pipeline is laid simultaneously, the extraction holes are constructed and sealed to begin gas extraction. During the extraction process, the equipment parameters are dynamically adjusted according to the gas concentration and extraction volume of each section to ensure uniform and stable depressurization extraction.

5. The method for graded coal seam outburst prevention and control in deep outburst coal seams according to claim 1, characterized in that, The comprehensive anti-surprise measures in step five are as follows: Ⅰ. Surface well cavity creation and pressure relief: Construct a vertical surface well at the pre-designated well location, drilling to the target cavity creation area of ​​the exposed coal seam. Then, use high-pressure water jet cavity creation technology to radially enlarge the surrounding coal body to create cavities, thereby forming a cavity creation and energy absorption zone in the target cavity creation area to absorb impact kinetic energy. After the cavity creation is completed, run the casing and cement the well to complete the surface well cavity creation construction. II. Coordinated surface and underground gas extraction and energy dissipation: At the excavation head of the coal seam uncovering roadway in the Shimen, an underground directional drilling rig is used to construct a cross-layer extraction borehole in the direction of excavation. After completion, the borehole opening of the cross-layer extraction borehole is connected to the underground gas extraction pipeline. At the same time, the casing from step I is connected to the surface gas extraction system to form a coordinated surface well-underground borehole extraction system. Coordinated gas extraction is carried out until the gas extraction concentration is reduced to a safe control range, thereby achieving energy dissipation of the coal seam in this area. III. Grouting Reinforcement: After step II is completed, the cross-layer extraction borehole is temporarily sealed. Grouting boreholes are constructed at the excavation head and both sides of the roadway of the Shimen coal uncovering roadway to the surrounding coal body. Then, cement mortar is used to grout the coal seam through the grouting boreholes to improve the coal body structure and make the cement mortar fully fill the fracture network in the coal seam. During the grouting reinforcement process, the grouting volume is monitored in real time until the required grouting volume is reached. The grouting operation is stopped and the grout is completely solidified to form a grouting reinforcement zone around the Shimen coal uncovering roadway. IV. Modified Coal Seam Structure: After the construction in steps I to III, a modified coal seam structure is formed in the coal seam to be exposed in front of the Shimen coal uncovering roadway, consisting of a cavity-forming and crushing energy absorption zone, a gas extraction and energy dissipation zone, and a grouting reinforcement zone, thus completing the comprehensive anti-outburst measures.

6. The method for graded coal seam outburst prevention and control in deep outburst coal seams according to claim 5, characterized in that, The preset pressure range of the high-pressure water used in the high-pressure water jet cavity-creating technology in step I is 18~22MPa.

7. The method for graded coal seam outburst prevention and control in deep outburst coal seams according to claim 5, characterized in that, In step IV, the grouting reinforcement zone encloses the pre-excavation area of ​​the coal seam's rock-gate coal exposure roadway, the cavity-forming and crushing energy absorption zone encloses the grouting reinforcement zone, and the gas extraction and energy dissipation zone covers both the grouting reinforcement zone and the cavity-forming and crushing energy absorption zone.

8. The method for graded coal seam outburst prevention and control in deep outburst coal seams according to claim 7, characterized in that, The thickness of the grouting reinforcement zone on the cross-section of the coal seam uncovering roadway ranges from 2 to 5 m; the thickness of the cavity-forming and crushing energy-absorbing zone on the cross-section of the coal seam uncovering roadway ranges from 5 to 10 m.

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