A method for measuring gas emission time limit of coal wall in tunneling roadway
By measuring gas flow rate by covering the coal face with a sealed gas collection hood, and using exponential function fitting and mathematical modeling to calculate the limit time of gas emission from the coal face, the problem of large prediction error of gas emission in existing technologies has been solved, and more accurate gas emission time measurement has been achieved, guiding safe production in coal mines.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA COAL TECH & ENG GRP SHENYANG ENG CO
- Filing Date
- 2026-03-20
- Publication Date
- 2026-06-05
AI Technical Summary
Existing technologies have significant errors in predicting the amount of gas emitted from coal walls in tunneling roadways, which affects coal mine safety and production costs. In particular, conventional statistical methods are distorted in high-risk mines, leading to inaccurate predictions of gas emission.
By covering the coal face with a wall-type sealed gas collection hood, the flow rate of gas emanating from the coal face is measured using a gas flow meter. The gas emission attenuation coefficient and initial flow rate of the coal face are obtained by fitting an exponential function. The limit time of gas emission from the coal face is predicted by combining a mathematical model, and the final limit time is determined by verifying the formula.
It enables accurate determination of the limit time of coal wall gas outburst under actual field conditions, reduces errors caused by differences in tunneling speed, guides safe production and gas control, conforms to actual field conditions, and is easy to operate.
Smart Images
Figure CN122148388A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of coal mine safety, specifically relating to a method for determining the ultimate gas outburst time in the coal wall of a tunneling roadway. Background Technology
[0002] Gas emission prediction is the work of pre-calculating the gas emission during a certain production period in a mining face, mining area, level, and mine based on production methods, production allocation conditions, coal and rock characteristics, gas occurrence, and other conditions. It provides basic data for ventilation design, gas extraction design, and gas prevention and control in mines, mining areas, and working faces. The accuracy of its prediction results largely determines the reliability of mine production safety and also directly affects the investment cost of mine production.
[0003] The absolute gas emission rate of the coal wall in a tunneling face is a crucial component. The gas emission rate from a fixed coal wall decreases rapidly with increasing exposure time. When the exposure time exceeds the emission limit time, gas emission ceases. Therefore, a maximum gas emission rate exists in long-distance tunneling coal seams. Standards and specifications used in Chinese coal mines, such as the "Specification for Predicting Mine Gas Emissions" (AQ1018-2006) and the "Method for Predicting Gas Emissions in Fully Mechanized Top Coal Caving Faces" (NB / T10364-2019), all utilize the ultimate gas emission equilibrium length of the tunneling face coal wall, and preferentially recommend using actual mine measurement data. It is an industry consensus that the ultimate gas emission equilibrium length of the tunneling face coal wall is directly related to the coal wall exposure time when factors such as coal seam gas pressure, gas content, ground stress, burial depth, and coal seam permeability remain constant. With the advancement of coal mine intensification, the speed of roadway excavation varies greatly. In particular, in high-outburst mines, the need to pre-extract coal seam gas to meet standards during roadway excavation leads to distortion in the calculation of coal wall gas emission from conventional roadway gas emission data. This results in significant errors in technical activities such as gas emission prediction and coal seam gas extraction, directly affecting coal mine safety and social stability.
[0004] Therefore, there is an urgent need for a method to determine the ultimate gas emission time in the coal wall of a tunneling roadway, which can determine the equilibrium length of the ultimate gas emission in the coal wall of a tunneling roadway through actual measurement and give a scientific and reasonable ultimate time. Summary of the Invention
[0005] This invention addresses the aforementioned problems and overcomes the shortcomings of existing technologies by providing a method for determining the ultimate gas emission time in the coal face of a tunnel, comprising the following steps: ① Dig a flat coal surface on the coal face to a depth of not less than 0.2m into the coal seam; ② Cover the flat coal surface with a wall-mounted sealed gas collection hood, and fix the wall-mounted sealed gas collection hood to the coal wall using sealing material; ③ The gas flow rate emanating from the coal wall was measured using a gas flow meter under different coal wall exposure times, and the measured gas flow rate values were no less than 8 sets. ④ Based on the coal wall exposure time and the coal wall gas emission flow rate, the coal wall gas emission attenuation coefficient and the initial gas emission flow rate of the exposed coal wall are obtained by fitting an exponential function. The exponential function is: ; q t The coal face exposure time is t Coal wall gas flow rate at that time; q 0 The initial gas flow rate of the coal face; α The attenuation coefficient of coal wall gas emission; t The coal face exposure time; ⑤ Based on the mathematical model, the estimated limit time for gas outburst from the coal face is derived; The mathematical model is as follows: ; To estimate the maximum time for gas to emerge from the coal face; ⑥ Actual measurement of the gas flow rate corresponding to the predicted limit time of gas outburst from the coal wall, and determination of the final limit time of gas outburst from the coal wall by verifying the formula. The verification formula is: .
[0006] in, For the maximum time for coal wall gas to emerge, To actually determine and estimate the coal face gas flow rate corresponding to the limit time of coal face gas emission, This refers to the exposure time when the actual measured gas emission from the coal face is less than 5% of the initial gas emission intensity q0.
[0007] Preferably, step ③, which involves measuring the gas flow rate emanating from the coal wall using a gas flow meter under different coal wall exposure times, specifically involves: completing the first set of coal wall gas flow rate measurements within 1 hour after sealing; measuring at least 2 sets of coal wall gas flow rate measurements within 1 hour to 8 hours; measuring at least 2 sets of coal wall gas flow rate measurements at even time intervals within 8 hours to 24 hours; and continuing to measure 3 sets of measurements after the gas flow rate reaches 50% of the first set of coal wall gas flow rate.
[0008] Preferably, the sealing material is sealing clay.
[0009] Preferably, the gas flow meter is a volumetric flow meter or an intelligent gas flow meter with correction function.
[0010] Preferably, the measurement of the coal wall exposure time is based on the initial exposure time of the coal wall, and the measurement time unit is days.
[0011] Preferably, the wall-mounted sealed gas collection hood is disc-shaped or polygonal.
[0012] Beneficial effects of this invention: The measurement method of this invention can continuously collect coal face gas emission flow rate in situ, obtain the coal face gas emission attenuation coefficient and the initial gas emission flow rate of the exposed coal face, and then calculate the coal face gas emission limit time. Simultaneously, it is verified using actual measured coal face gas emission rates. Compared with the conventional statistical method of calculating the coal face gas emission limit time using roadway gas emission rates, this method avoids the emission rate error caused by inconsistent roadway excavation speeds. Furthermore, the actual measurement verification can better guide safe production. This method, measured under the original field conditions of coal seam gas pressure, gas content, ground stress, burial depth, and coal permeability, is more realistic and can better guide on-site gas disaster management in coal mines. It has the advantages of being consistent with actual field conditions, simple in method, and easy to operate. Attached Figure Description
[0013] Figure 1 This is a schematic diagram of a coal wall gas outburst flow measurement system for tunneling roadways; Figure 2 This is a flowchart for determining the ultimate gas outburst time in the coal face of a tunnel. Figure 3 This is a schematic diagram of the fitting of the gas flow rate attenuation in the coal face.
[0014] 1 is the coal seam, 2 is the sealing material, 3 is the wall-mounted sealed gas collection hood, and 4 is the gas flow meter. Detailed Implementation
[0015] 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.
[0016] The main coal seams mined in a certain coal mine are No. 3 and No. 9. No. 3 is a high-gas coal seam, and No. 9 is an outburst coal seam. Both coals are anthracite and belong to inclined and near-inclined coal seams.
[0017] The designed length of the No. 3 coal seam tunneling face is 2000m, and the designed length of the No. 9 coal seam tunneling face is 1800m. Before mining the No. 1 coal seam, it is necessary to predict the gas emission volume. If the gas emission volume prediction of the tunneling face is calculated according to the designed length, the predicted gas emission volume will be significantly overestimated, which will affect the gas control method and control cost of the tunneling face. It is necessary to actually measure the limit time of gas emission in the coal wall and then obtain the limit length of gas emission in the coal wall.
[0018] Example 1
[0019] Determine the ultimate gas emission time of the No. 3 coal seam wall, such as Figure 2 As shown, it includes the following steps: a) To facilitate flow testing, the maintenance team excavated a flat coal surface to a depth of 0.4m on the freshly exposed coal face towards the solid coal seam. b) such as Figure 1 As shown, a circular wall-mounted air-collecting hood 3 with a diameter of 1.5m is covered on the flat coal surface and fixed to the coal wall with sealing material 2. The sealing material 2 used is sealing yellow mud. c) Use gas flow meter 4 to measure the gas flow rate emanating from the coal wall. The gas flow meter 4 should be an intelligent gas flow meter with correction function. Specifically, the initial exposure time of the coal wall is taken as t0, and the measurement time of each group is converted into days (d). The first group of coal wall gas flow rate measurements should be completed within 1 hour after sealing. The coal wall gas flow rate should be measured for no less than 2 groups within 1 hour to 8 hours. The coal wall gas flow rate should be measured for no less than 2 groups at even time intervals within 8 hours to 24 hours. After the gas flow rate reaches 50% of the first group of coal wall gas flow rate, continue to measure for 3 more groups to finish. See Table 1 for specific data.
[0020] Table 1. Statistics on gas flow rate and exposure time of coal face .
[0021] d) Determine the corresponding array of coal face outburst gas flow rates under different coal face exposure times ( t i , q t ), and plotted scatter plots of the coal wall outburst gas flow measurement array under different coal wall exposure times using an exponential function fit, such as Figure 3 As shown, the exponential function regression fitting yielded a coal face gas emission attenuation coefficient α of 0.038 and an initial gas emission flow rate q0 of 300.10 L / min for the exposed coal face; e) Determine the estimated limit time for gas outburst from the coal face. The time is 3 ÷ 0.038 = 78.95 days. f) Actual measured flow rate of gas emanating from the coal face after 79 days of coal face exposure. It is 13.53 L / min; g) Determine the limit time for gas outburst from the coal face using the verification formula: .
[0022] ( =13.53L / min) < ( =14.71 L / min), which is the limit time for gas to emerge from the coal face. for The value is 78.95 days.
[0023] Example 2
[0024] Determine the ultimate gas emission time of the No. 9 coal seam wall, such as... Figure 2 As shown, it includes the following steps: a) To facilitate flow testing, the maintenance team excavated a flat coal surface to a depth of 0.4m on the freshly exposed coal face towards the solid coal seam. b) Cover the flat coal surface with a circular wall-mounted airtight gas collection hood with a diameter of 1.5m and fix it to the coal wall with sealing yellow mud; c) Use a smart gas flow meter with correction function to measure the gas flow rate emanating from the coal wall. Specifically, the initial exposure time of the coal wall is taken as t0, and the measurement time of each group is converted into days (d). The first group of coal wall gas flow rate measurements should be completed within 1 hour after sealing. The coal wall gas flow rate measurements should be no less than 2 groups within 1 hour to 8 hours. The coal wall gas flow rate measurements should be no less than 2 groups within 8 hours to 24 hours at even time intervals. After the gas flow rate reaches 50% of the first group of coal wall gas flow rate, continue to measure 3 groups to end. d) Determine the corresponding array of coal face outburst gas flow rates under different coal face exposure times ( t i , q t The data of coal wall gas emission at different coal wall exposure times were plotted as scatter points using exponential function fitting. The gas emission attenuation coefficient α was found to be 0.025 and the initial gas emission flow rate q0 of the exposed coal wall was 287.56 L / min. e) Determine the estimated limit time for gas outburst from the coal face. The total is 3 ÷ 0.025 = 120 days; f) Actual measured flow rate of gas emanating from the coal face after 120 days of coal face exposure. It is 16.50 L / min; g) Substitute the above data into the verification formula to determine: .
[0025] ( =16.50L / min) > ( =14.38 L / min).
[0026] Therefore, the actual measurement of coal wall gas outburst flow rate continued until day 135, when the measured coal wall gas outburst rate was less than 14.38 L / min, thus determining the coal wall gas outburst limit time. It takes 135 days.
[0027] It is understood that the above specific description of the present invention is only for illustrating the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effect; as long as the use needs are met, they are all within the protection scope of the present invention.
Claims
1. A method for determining the ultimate gas emission time in the coal face of a tunnel, characterized in that, Includes the following steps: ① Dig a flat coal surface on the coal face to a depth of not less than 0.2m into the coal seam; ② Cover the flat coal surface with a wall-mounted sealed gas collection hood, and fix the wall-mounted sealed gas collection hood to the coal wall using sealing material; ③ The gas flow rate emanating from the coal wall was measured using a gas flow meter under different coal wall exposure times, and the measured gas flow rate values were no less than 8 sets. ④ Based on the coal wall exposure time and the coal wall gas emission flow rate, the coal wall gas emission attenuation coefficient and the initial gas emission flow rate of the exposed coal wall are obtained by fitting an exponential function. The exponential function is: ; q t The coal face exposure time is t Coal wall gas flow rate at that time; q 0 The initial gas flow rate of the coal face; α The attenuation coefficient of coal wall gas emission; t The coal face exposure time; ⑤ Based on the mathematical model, the estimated limit time for gas outburst from the coal face is derived; The mathematical model is as follows: ; To estimate the maximum time for gas to emerge from the coal face; ⑥ Actual measurement of the gas flow rate corresponding to the predicted limit time of gas outburst from the coal wall, and determination of the final limit time of gas outburst from the coal wall by verifying the formula. The verification formula is: in, For the maximum time for coal wall gas to emerge, To actually determine and estimate the coal face gas flow rate corresponding to the limit time of coal face gas emission, This refers to the exposure time when the actual measured gas emission from the coal face is less than 5% of the initial gas emission intensity q0.
2. The method for determining the ultimate gas emission time in the coal face of a tunnel as described in claim 1, characterized in that, Step ③ describes the use of a gas flow meter to measure the gas flow rate emanating from the coal wall under different coal wall exposure times. Specifically, the first set of coal wall gas flow rate measurements is completed within 1 hour after sealing. Within 1 hour to 8 hours, at least 2 sets of coal wall gas flow rate measurements are performed. Within 8 hours to 24 hours, at least 2 sets of coal wall gas flow rate measurements are performed at even time intervals. After the gas flow rate reaches 50% of the first set of coal wall gas flow rate measurements, 3 more sets of measurements are performed to conclude the process.
3. The method for determining the ultimate gas emission time in the coal face of a tunnel as described in claim 1, characterized in that, The sealing material is sealing yellow mud.
4. The method for determining the ultimate gas emission time in the coal face of a tunnel as described in claim 1, characterized in that, The gas flow meter is a volumetric flow meter or an intelligent gas flow meter with correction function.
5. The method for determining the ultimate gas emission time in the coal face of a tunneling roadway according to claim 1, characterized in that, The measurement of coal wall exposure time is based on the initial exposure time of the coal wall, and the measurement unit is days.
6. The method for determining the ultimate gas emission time in the coal face of a tunnel as described in claim 1, characterized in that, The wall-mounted sealed gas collection hood is disc-shaped or polygonal.