A method for predicting the absolute gas emission volume during coal mining at tunnel face

Abstract

The present invention discloses a method for predicting the absolute gas emission of coal mining in a tunnel face, by obtaining tunnel parameters, coal seam occurrence parameters and coal seam gas parameters; according to the tunnel parameters and coal seam occurrence parameters, the calculation formula of the coal volume per cycle of tunnel construction, the area of ​​newly exposed coal seam at the face and the area of ​​newly exposed coal seam on the tunnel wall is derived; the coal seam gas parameters are substituted into the calculation formula of the coal volume per cycle of tunnel construction, the area of ​​newly exposed coal seam at the face and the area of ​​newly exposed coal seam on the tunnel wall, and the absolute gas emission of coal mining per cycle of the tunnel, the absolute gas emission of newly exposed coal seam at the face and the absolute gas emission of newly exposed coal seam on the wall are obtained by calculation; according to the absolute gas emission of coal mining per cycle of the tunnel, the absolute gas emission of newly exposed coal seam at the face and the absolute gas emission of newly exposed coal seam on the wall, the absolute gas emission of coal mining per cycle of the tunnel is calculated. The present invention ensures construction safety and improves construction efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of gas tunnel construction safety, and in particular discloses a method for predicting the absolute gas emission amount of coal uncovering at a tunnel face. Background Art

[0002] Tunnels pass through coal-bearing strata. When coal is uncovered, gas will gush out of the tunnel. When the gas concentration exceeds a certain limit, a series of dangers will occur, causing casualties and property losses. When coal is uncovered, the prediction of the absolute gas gush volume is of great significance to ensure the safety of the construction process. The absolute gas gush volume is the main indicator for assessing the grade of the gas work area. At the same time, the gas concentration also affects the ventilation volume of the face.

[0003] The absolute gas emission volume is determined by measuring the ventilation volume near the excavation working face and the maximum gas concentration in the air volume return flow in the gas work area. However, it is difficult to measure the absolute gas emission volume generated during the coal mining process before construction, which brings certain difficulties to the reasonable arrangement of the construction plan and the accurate assessment of safety risks. Regarding the prediction of coal mining gas emission volume, the existing methods have certain limitations. There is no unified formula for estimating the volume of coal falling in the tunnel and the area of ​​the newly exposed coal seam, and it is difficult to accurately predict the absolute gas emission volume of coal mining. Therefore, a prediction method is needed that can more accurately predict the absolute gas emission volume to reduce the safety hazards of the coal mining process and ensure the smooth progress of construction. Summary of the invention

[0004] The present invention provides a method for predicting the absolute gas emission amount of coal mining at a tunnel face, aiming to solve at least one defect existing in the above-mentioned existing method for predicting the absolute gas emission amount of coal mining.

[0005] The present invention relates to a method for predicting the absolute gas emission amount of coal mining at a tunnel face, comprising the following steps:

[0006] Obtain tunnel parameters, coal seam occurrence parameters and coal seam gas parameters;

[0007] According to the tunnel parameters and coal seam occurrence parameters, a three-dimensional spatial model of the tunnel crossing the coal seam is constructed, and combined with the tunnel construction parameters, the calculation formulas for the coal falling volume per cycle of tunnel construction, the area of ​​newly exposed coal seams on the face, and the area of ​​newly exposed coal seams on the tunnel wall are derived;

[0008] Substitute coal seam gas parameters into the calculation formula of coal falling volume, newly exposed coal seam area at tunnel face and newly exposed coal seam area at tunnel wall in each cycle of tunnel construction, and obtain the absolute gas emission volume of coal falling, newly exposed coal seam at tunnel face and newly exposed coal seam at tunnel wall in each cycle of tunnel construction.

[0009] Based on the absolute gas emission of coal falling in each cycle of the tunnel, the absolute gas emission of newly exposed coal seams at the face and the absolute gas emission of newly exposed coal seams on the wall, the absolute gas emission of coal uncovering in each cycle of the tunnel is calculated.

[0010] Furthermore, the steps of obtaining tunnel parameters, coal seam occurrence parameters and coal seam gas parameters include:

[0011] Collect tunnel design data and obtain tunnel parameters, including tunnel net width and tunnel direction;

[0012] Conduct advance drilling at a set vertical distance between the tunnel face and the coal seam to obtain coal seam occurrence parameters, including coal seam thickness, inclination and azimuth;

[0013] Coal cores are drilled at a set vertical distance from the coal seam to measure coal seam gas parameters, which include coal density and gas content per ton of coal.

[0014] Furthermore, according to the tunnel parameters and coal seam occurrence parameters, a three-dimensional spatial model of the tunnel passing through the coal seam is constructed, and combined with the tunnel construction parameters, the calculation formulas for the coal falling volume per cycle of tunnel construction, the area of ​​newly exposed coal seams on the face, and the area of ​​newly exposed coal seams on the tunnel wall are derived. The coal falling volume per cycle of tunnel construction is:

[0015]

[0016] in, is the total volume of coal dropped in each cycle of coal uncovering, is the coal seam inclination, is the excavation distance per cycle, is the average thickness of the coal seam.

[0017] Furthermore, according to the tunnel parameters and coal seam occurrence parameters, a three-dimensional spatial model of the tunnel passing through the coal seam is constructed, and combined with the tunnel construction parameters, the calculation formulas for the coal falling volume per cycle of tunnel construction, the area of ​​the newly exposed coal seam at the tunnel face, and the area of ​​the newly exposed coal seam on the tunnel wall are derived. The area of ​​the newly exposed coal seam at the tunnel face is:

[0018]

[0019] in, is the area of ​​newly exposed coal seam at the face. is half of the tunnel's net width k. is the coal seam inclination, is the excavation distance per cycle, is the average thickness of the coal seam.

[0020] Furthermore, according to the tunnel parameters and coal seam occurrence parameters, a three-dimensional spatial model of the tunnel passing through the coal seam is constructed, and combined with the tunnel construction parameters, the calculation formulas for the coal falling volume per cycle of tunnel construction, the area of ​​the newly exposed coal seam on the face, and the area of ​​the newly exposed coal seam on the tunnel wall are derived. The area of ​​the newly exposed coal seam on the tunnel wall is:

[0021]

[0022] in, is the area of ​​newly exposed coal seam on the wall, is the coal seam inclination, is the excavation distance per cycle, is the average thickness of the coal seam.

[0023] Furthermore, the coal seam gas parameters are substituted into the calculation formula of the coal falling volume per cycle of tunnel construction, the newly exposed coal seam area at the tunnel face, and the newly exposed coal seam area on the tunnel wall. By calculating the absolute gas emission of coal falling per cycle of the tunnel, the absolute gas emission of newly exposed coal seam at the tunnel face, and the absolute gas emission of newly exposed coal seam on the tunnel wall, the absolute gas emission of coal falling per cycle of the tunnel is:

[0024]

[0025] in, is the absolute gas emission of coal falling in each cycle of the tunnel, is the total volume of coal dropped in each cycle of coal uncovering, is the density of coal, It is the gas content per ton of coal.

[0026] Furthermore, the coal seam gas parameters are substituted into the calculation formula of the coal falling volume per cycle of tunnel construction, the newly exposed coal seam area at the tunnel face, and the newly exposed coal seam area on the tunnel wall. By calculating the absolute gas emission volume of coal falling per cycle of the tunnel, the absolute gas emission volume of the newly exposed coal seam at the tunnel face, and the absolute gas emission volume of the newly exposed coal seam on the tunnel wall, the absolute gas emission volume of the newly exposed coal seam at the tunnel face is:

[0027]

[0028] in, is the absolute gas emission volume of the newly exposed coal seam at the face, is the area of ​​newly exposed coal seam at the face. is the initial intensity of gas overflow per unit coal wall area per unit time, is the time attenuation coefficient, is the coal seam inclination, is the excavation distance per cycle, is the average thickness of the coal seam, It is half of the net width k of the tunnel.

[0029] Furthermore, the coal seam gas parameters are substituted into the calculation formula of the coal falling volume per cycle of tunnel construction, the newly exposed coal seam area at the tunnel face, and the newly exposed coal seam area on the tunnel wall. In the step of obtaining the absolute gas emission of coal falling per cycle of the tunnel, the absolute gas emission of the newly exposed coal seam at the tunnel face, and the absolute gas emission of the newly exposed coal seam on the tunnel wall, the time attenuation coefficient is:

[0030]

[0031] in, is the time attenuation coefficient, is the attenuation coefficient, Calculate the time for coal wall exposure.

[0032] Furthermore, the coal seam gas parameters are substituted into the calculation formula of the coal falling volume per cycle of tunnel construction, the newly exposed coal seam area at the tunnel face, and the newly exposed coal seam area on the tunnel wall. By calculating the absolute gas outburst volume per cycle of tunnel falling, the absolute gas outburst volume of the newly exposed coal seam at the tunnel face, and the absolute gas outburst volume of the newly exposed coal seam on the tunnel wall, the initial intensity of gas overflow per unit coal wall area per unit time is:

[0033]

[0034] in, is the initial intensity of gas overflow per unit coal wall area per unit time, is the gas content per ton of coal, Volatile matter of coal seams.

[0035] Furthermore, the coal seam gas parameters are substituted into the calculation formula of the coal falling volume per cycle of tunnel construction, the newly exposed coal seam area at the tunnel face, and the newly exposed coal seam area on the tunnel wall. By calculating the absolute gas emission volume of coal falling per cycle of the tunnel, the absolute gas emission volume of the newly exposed coal seam at the tunnel face, and the absolute gas emission volume of the newly exposed coal seam on the wall, the absolute gas emission volume of the newly exposed coal seam on the wall is:

[0036]

[0037] in, is the absolute gas outburst volume of the newly exposed coal seam on the wall, is the area of ​​newly exposed coal seam on the wall, is the initial intensity of gas overflow per unit coal wall area per unit time, is the time attenuation coefficient, is the coal seam inclination, is the excavation distance per cycle, is the average thickness of the coal seam.

[0038] Furthermore, according to the absolute gas emission of coal falling in each cycle of the tunnel, the absolute gas emission of newly exposed coal seams at the tunnel face, and the absolute gas emission of newly exposed coal seams at the wall, in the step of calculating the absolute gas emission of coal uncovering in each cycle of the final tunnel, the absolute gas emission of coal uncovering in each cycle of the final tunnel is:

[0039]

[0040] in, is the absolute gas emission of each coal mining cycle in the final tunnel, is the absolute gas emission of coal falling in each cycle of the tunnel, is the absolute gas emission volume of the newly exposed coal seam at the face, is the absolute gas outburst volume of the newly exposed coal seam on the wall, is the correction factor.

[0041] The beneficial effects achieved by the present invention are:

[0042] The present invention provides a method for predicting the absolute gas emission of coal mining at a tunnel face, by acquiring tunnel parameters, coal seam occurrence parameters and coal seam gas parameters; constructing a three-dimensional spatial model of a tunnel crossing a coal seam according to the tunnel parameters and the coal seam occurrence parameters, and deducing a calculation formula for the volume of coal falling in each cycle of tunnel construction, the area of ​​newly exposed coal seams at the face and the area of ​​newly exposed coal seams on the tunnel wall in combination with tunnel construction parameters; substituting the coal seam gas parameters into the calculation formula for the volume of coal falling in each cycle of tunnel construction, the area of ​​newly exposed coal seams at the face and the area of ​​newly exposed coal seams on the tunnel wall, and obtaining the absolute gas emission of coal falling in each cycle of the tunnel, the absolute gas emission of newly exposed coal seams at the face and the absolute gas emission of newly exposed coal seams on the wall by calculation; and calculating the absolute gas emission of coal mining in each cycle of the tunnel according to the absolute gas emission of coal falling in each cycle of the tunnel, the absolute gas emission of newly exposed coal seams at the face and the absolute gas emission of newly exposed coal seams on the wall. The method for predicting the absolute gas emission volume of coal uncovering at a tunnel face provided by the present invention solves the problem that the existing methods cannot accurately predict the gas emission volume generated by the volume of coal dropped during tunneling, and can more accurately predict the absolute gas emission volume generated during the coal uncovering process, thereby ensuring construction safety and improving construction efficiency. When calculating the absolute gas emission volume of each cycle of coal dropping, the regular shape of the volume of the overlapping part of the tunnel and the coal seam in each cycle is taken into account for the specific coal seam structure, and the gas emission volume of the newly exposed coal seam is calculated. Compared with the existing method, the absolute gas emission volume of coal uncovering can be predicted more accurately, with better reliability and accuracy, thereby providing a strong guarantee for the safe construction of tunnels crossing coal seams. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a flow chart of an embodiment of a method for predicting the absolute gas emission volume of coal mining at a tunnel face according to the present invention;

[0044] Figure 2 This is an overall schematic diagram of the tunnel passing through the coal seam in the present invention;

[0045] Figure 3 A local cross-sectional perspective view of a tunnel passing through a coal seam in the present invention;

[0046] Figure 4 It is a local cross-sectional view of the tunnel passing through the coal seam in the present invention;

[0047] Figure 5 This is a schematic diagram of the overall exposed coal portion of the tunnel in the present invention;

[0048] Figure 6 A schematic diagram of exposed coal on the tunnel wall and tunnel bottom in the present invention;

[0049] Figure 7 It is a schematic diagram of exposed coal at different faces of the tunnel in the present invention.

[0050] Description of Figure Numbers:

[0051] 1. Coal seam inclination; 2. Average thickness of coal seam; 3. Coal seam; 4. Coal uncovering point; 5. Working face; 6. Net width of tunnel; 7. Coal seam exposed at the bottom of tunnel; 8. Excavation distance per cycle; 9. Tunnel entrance; 10. Newly exposed coal seam at the working face; 11. Newly exposed coal seam on the tunnel wall. DETAILED DESCRIPTION

[0052] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0053] like Figure 1 and Figure 2 As shown, the first embodiment of the present invention provides a method for predicting the absolute gas emission volume of coal mining at a tunnel face, comprising the following steps:

[0054] Step S100, obtaining tunnel parameters, coal seam occurrence parameters and coal seam gas parameters.

[0055] Tunnel parameters are collected based on tunnel design data, mainly including the net width of the tunnel and the direction of the tunnel; then, advance drilling is carried out at a vertical distance of 20m from the coal seam to obtain coal seam occurrence parameters, including coal seam thickness, inclination and azimuth; thirdly, coal cores are drilled at the same position to carry out coal seam gas parameter measurement, including coal density and gas content per ton of coal.

[0056] Step S200: construct a three-dimensional spatial model of the tunnel passing through the coal seam based on the tunnel parameters and the coal seam occurrence parameters, and derive the calculation formulas for the coal falling volume, the newly exposed coal seam area at the tunnel face and the newly exposed coal seam area on the tunnel wall in each cycle of tunnel construction in combination with the tunnel construction parameters.

[0057] According to the occurrence parameters of the tunnel and coal seam, a three-dimensional spatial model of the tunnel crossing the coal seam is constructed. Combined with the tunnel construction parameters, the calculation formulas for the volume of coal falling in each cycle of tunnel construction, the area of ​​newly exposed coal seam on the heading face, and the area of ​​newly exposed coal seam on the tunnel wall are derived.

[0058] Step S300, substitute the coal seam gas parameters into the calculation formula of the coal falling volume in each cycle of tunnel construction, the newly exposed coal seam area at the tunnel face and the newly exposed coal seam area on the tunnel wall, and obtain the absolute gas emission volume of coal falling in each cycle of the tunnel, the absolute gas emission volume of the newly exposed coal seam at the tunnel face and the absolute gas emission volume of the newly exposed coal seam on the wall through calculation.

[0059] Substituting the coal seam gas parameters into the above formula, the absolute gas emission of coal falling in each tunnel cycle, the absolute gas emission of newly exposed coal seams at the tunnel face and the absolute gas emission of newly exposed coal seams on the wall are calculated.

[0060] Step S400, calculating the absolute gas emission of each coal uncovering cycle in the final tunnel according to the absolute gas emission of coal falling in each cycle of the tunnel, the absolute gas emission of newly exposed coal seams at the tunnel face and the absolute gas emission of newly exposed coal seams at the wall.

[0061] The correction coefficient is determined based on the overall size of the falling coal, and the absolute gas emission per coal uncovering cycle in the final tunnel is calculated.

[0062] Further, see Figures 1 to 7 The method for predicting the absolute gas emission volume of coal mining at a tunnel face provided in this embodiment includes step S100:

[0063] Step S110: Collect tunnel design data and obtain tunnel parameters, where the tunnel parameters include the clear width of the tunnel and the direction of the tunnel.

[0064] Tunnel parameters are collected based on tunnel design data. Tunnel parameters mainly include tunnel net width and tunnel direction.

[0065] Step S120, advance drilling is performed at a set vertical distance between the tunnel face and the coal seam to obtain coal seam occurrence parameters, which include coal seam thickness, inclination and azimuth.

[0066] Advance drilling is carried out at a vertical distance of 20m between the face and the coal seam to obtain coal seam occurrence parameters, which include coal seam thickness, inclination and azimuth.

[0067] Step S130, drilling a coal core at a set vertical distance between the tunnel face and the coal seam, and measuring coal seam gas parameters, where the coal seam gas parameters include coal density and gas content per ton of coal.

[0068] Coal cores are drilled at the same location to measure coal seam gas parameters, including coal density and gas content per ton of coal.

[0069] Preferably, see Figures 1 to 7 In the method for predicting the absolute gas emission volume of coal excavation at a tunnel face provided in this embodiment, in step S200, the coal falling volume of each cycle of tunnel construction is the overlapping part of the tunnel and the coal seam within the excavation distance of each cycle, and the coal falling volume of each cycle of tunnel construction is:

[0070] (1)

[0071] In formula (1), The total volume of coal dropped in each cycle of coal uncovering, in m 3 ; is the coal seam inclination, in degrees; is the excavation distance per cycle, in m; is the average thickness of the coal seam, in meters.

[0072] The area of ​​newly exposed coal seams at the tunnel face is:

[0073] (2)

[0074] In formula (2), The newly exposed coal seam area at the face, in m 2 ; It is half of the net width k of the tunnel, in m; is the coal seam inclination, in degrees; is the excavation distance per cycle, in m; is the average thickness of the coal seam, in meters.

[0075] During the coal mining process, the newly exposed coal seam area on the tunnel wall consists of two parts: one is the newly exposed coal seam area on both sides of the tunnel, and the other is the newly exposed coal seam area on the tunnel bottom. Due to the angle between the coal seam and the tunnel, the newly exposed coal seam on the tunnel bottom only appears in the first cycle. The newly exposed coal seam area on the tunnel wall is:

[0076] (3)

[0077] In formula (3), is the area of ​​newly exposed coal seam on the wall, in m 2 ; is the coal seam inclination, in degrees; is the excavation distance per cycle, in m; is the average thickness of the coal seam, in meters.

[0078] In this embodiment, if it is the first cycle, the area of ​​the newly exposed coal seam on the tunnel wall is:

[0079] (4)

[0080] In formula (4), is the area of ​​newly exposed coal seam on the wall, in m 2 ; is the coal seam inclination, in degrees; is the excavation distance per cycle, in m; is the average thickness of the coal seam, in meters.

[0081] Further, see Figures 1 to 7 In the method for predicting the absolute gas emission of coal mining in a tunnel face provided in this embodiment, in step S300, the absolute gas emission of coal mining in each cycle of the tunnel is:

[0082] (5)

[0083] In formula (5), The absolute gas emission of coal falling in each cycle of the tunnel, in m 3 / min; The total volume of coal dropped in each cycle of coal uncovering, in m 3 ; is the density of coal, in t / m 3 ; is the gas content per ton of coal, in m 3 / t.

[0084] The absolute gas emission of the newly exposed coal seam at the face is:

[0085] (6)

[0086] In formula (6), is the absolute gas emission of the newly exposed coal seam at the face, in m 3 / min; The newly exposed coal seam area at the face, in m 2 ; The initial intensity of gas overflow per unit coal wall area per unit time, in m 3 / (m 2 •min); is the time attenuation coefficient, is the coal seam inclination, in degrees; is the excavation distance per cycle, in m; is the average thickness of the coal seam, in m; It is half of the net width k of the tunnel, in meters.

[0087] The absolute gas outburst volume of newly exposed coal seam on the wall is:

[0088] (7)

[0089] In formula (7), is the absolute gas outburst volume of the newly exposed coal seam on the wall, in m 3 / min; is the area of ​​newly exposed coal seam on the wall, in m 2 ; The initial intensity of gas overflow per unit coal wall area per unit time, in m 3 / (m 2 •min); is the time attenuation coefficient, is the coal seam inclination, in degrees; is the excavation distance per cycle, in m; is the average thickness of the coal seam, in meters.

[0090] The time decay coefficient is:

[0091] (8)

[0092] In formula (8), is the time attenuation coefficient, is the attenuation coefficient, in m 3 / min; The calculation time of coal wall exposure. The gas attenuation is uniform, and the time attenuation function in the calculation of gas emission of newly exposed coal seams in tunnels, the calculation time of coal seam exposure is half of the coal seam exposure time.

[0093] The initial intensity of gas overflow per unit coal wall area per unit time is:

[0094] (9)

[0095] In formula (9), is the initial intensity of gas overflow per unit coal wall area per unit time, is the gas content per ton of coal, Volatile matter of coal seams.

[0096] Further, see Figures 1 to 7 In the method for predicting the absolute gas emission of coal mining in a tunnel face provided in this embodiment, in step S100, the absolute gas emission of each cycle of coal mining in the tunnel is:

[0097] (10)

[0098] In formula (10), The absolute gas emission volume of each cycle of coal mining in the final tunnel, in m 3 / min; is the correction coefficient, ranging from 0 to 1; The absolute gas emission of coal falling in each cycle of the tunnel, in m3 / min; is the absolute gas emission of the newly exposed coal seam at the face, in m 3 / min; is the absolute gas outburst volume of the newly exposed coal seam on the wall, in m 3 / min.

[0099] like Figures 1 to 7 As shown, the following is a specific example to illustrate the method for predicting the absolute gas emission volume of coal mining at a tunnel face provided by the present application:

[0100] A method for predicting the absolute gas emission volume of coal mining at a tunnel face, such as Figure 1 As shown in the figure, firstly, tunnel parameters are collected according to tunnel design data, mainly including the net width of the tunnel 6 and the direction of the tunnel; then, advance drilling is carried out at a vertical distance of 20m from the coal seam 3 to obtain coal seam occurrence parameters, including coal seam thickness 2, coal seam inclination 1 and azimuth; then, coal cores are drilled at the same position to carry out coal seam gas parameter determination, including coal density and gas content per ton of coal; further, according to tunnel and coal seam parameters, a three-dimensional spatial model of the tunnel crossing the coal seam is constructed, and combined with tunnel construction parameters, the calculation formulas for the volume of coal falling per cycle of tunnel construction, the area of ​​newly exposed coal seam at the tunnel face and the area of ​​newly exposed coal seam on the tunnel wall are derived; secondly, the coal seam gas parameters are substituted into the above formulas to calculate the absolute gas emission of coal falling per cycle of the tunnel, the absolute gas emission of newly exposed coal seam 10 at the tunnel face and the absolute gas emission of newly exposed coal seam 11 on the tunnel wall; finally, the correction coefficient is taken according to the overall size of the coal falling block, and the absolute gas emission of coal uncovering per cycle of the final tunnel is calculated.

[0101] A gas tunnel on a highway, as shown in the schematic diagram Figure 3 As shown, the coal excavation point is 4, the construction speed is 2 m per day, the tunnel net width is 6, k=11 m, the average thickness of the coal seam is 2, d=1.0 m, the coal seam inclination is 1, θ=53°, and the gas content per ton of coal is W=10m 3 / t, volatile matter V r =17%, gas escape attenuation coefficient a=0.06, coal seam density ρ=1.2t / m 3 .

[0102] ① Absolute gas emission during each cycle of tunnel construction

[0103] Each time excavation is carried out, the volume of the overlapping part of the coal seam and the tunnel is approximately calculated as the volume of a cuboid. The side length of the cuboid is obtained by the relationship between the excavation distance 8 and the coal seam inclination 1 in the right triangle. The total volume of coal blocks dropped in each cycle is:

[0104]

[0105] Absolute gas emission from coal falling:

[0106]

[0107] ② Absolute gas emission from newly exposed coal seams at the face

[0108] The area of ​​newly exposed coal seam 10 on tunnel wall surface per cycle:

[0109]

[0110] Initial intensity of gas leakage from cave wall per square meter per minute:

[0111]

[0112] Time decay coefficient:

[0113]

[0114] Gas emission from newly exposed coal seams at the face:

[0115]

[0116] ③Absolute gas outburst volume of newly exposed coal seam on the wall

[0117] Except for the first time, the area of ​​newly exposed coal seam on the tunnel wall in each cycle is:

[0118]

[0119] Absolute gas emission of newly exposed coal seam on the wall per cycle:

[0120]

[0121] The area of ​​newly exposed coal seams on the first cycle wall (11 exposed coal seams on the tunnel wall and 7 exposed coal seams on the tunnel bottom):

[0122]

[0123] Absolute gas outburst volume of newly exposed coal seam on the wall during the first cycle:

[0124]

[0125] ④ Absolute gas outflow

[0126] It is judged that the coal pieces are generally small and crushed, so the correction coefficient is α1=0.78 based on experience.

[0127] Non-first cycle:

[0128]

[0129] First cycle:

[0130]

[0131] The absolute gas emission during the first cycle of coal mining is 1.241m 3 / min, and the absolute gas outflow per cycle is 1.154m 3 / min.

[0132] Compared with the prior art, the method for predicting the absolute gas emission of coal mining at the tunnel face provided in the present embodiment obtains tunnel parameters, coal seam occurrence parameters and coal seam gas parameters; constructs a three-dimensional spatial model of the tunnel crossing the coal seam according to the tunnel parameters and the coal seam occurrence parameters, and derives the calculation formulas for the volume of coal falling in each cycle of tunnel construction, the area of ​​newly exposed coal seam at the tunnel face and the area of ​​newly exposed coal seam on the tunnel wall in combination with the tunnel construction parameters; substitutes the coal seam gas parameters into the calculation formulas for the volume of coal falling in each cycle of tunnel construction, the area of ​​newly exposed coal seam at the tunnel face and the area of ​​newly exposed coal seam on the tunnel wall, and obtains the absolute gas emission of coal falling in each cycle of the tunnel, the absolute gas emission of newly exposed coal seam at the tunnel face and the absolute gas emission of newly exposed coal seam on the wall by calculation; and calculates the absolute gas emission of coal mining in each cycle of the tunnel according to the absolute gas emission of coal falling in each cycle of the tunnel, the absolute gas emission of newly exposed coal seam at the tunnel face and the absolute gas emission of newly exposed coal seam on the wall. The method for predicting the absolute gas emission volume of coal uncovering at the tunnel face provided in this embodiment solves the problem that the existing methods cannot accurately predict the gas emission volume generated by the volume of coal dropped during tunneling, and can more accurately predict the absolute gas emission volume generated during the coal uncovering process, thereby ensuring construction safety and improving construction efficiency. When calculating the absolute gas emission volume of each cycle of coal dropping, the regular shape of the overlapping volume of the tunnel and the coal seam in each cycle is taken into account for the specific coal seam structure, and the gas emission volume of the newly exposed coal seam is calculated. Compared with the existing methods, the absolute gas emission volume of coal uncovering can be predicted more accurately, with better reliability and accuracy, providing a strong guarantee for the safe construction of tunnels crossing coal seams.

[0133] Although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for predicting the absolute gas emission volume of coal mining at a tunnel face, characterized in that: The following steps are involved: Obtain tunnel parameters, coal seam occurrence parameters and coal seam gas parameters; According to the tunnel parameters and the coal seam occurrence parameters, a three-dimensional spatial model of the tunnel passing through the coal seam is constructed, and combined with the tunnel construction parameters, the calculation formulas for the coal falling volume per cycle of tunnel construction, the area of ​​newly exposed coal seams on the face, and the area of ​​newly exposed coal seams on the tunnel wall are derived; Substituting the coal seam gas parameters into the calculation formula of the coal falling volume, the newly exposed coal seam area at the tunnel face and the newly exposed coal seam area at the tunnel wall in each cycle of the tunnel construction, the absolute gas emission volume of the coal falling, the absolute gas emission volume of the newly exposed coal seam at the tunnel face and the absolute gas emission volume of the newly exposed coal seam at the tunnel wall in each cycle of the tunnel construction are obtained by calculation; According to the absolute gas emission of coal falling in each cycle of the tunnel, the absolute gas emission of the newly exposed coal seam at the tunnel face and the absolute gas emission of the newly exposed coal seam on the wall, the absolute gas emission of the coal uncovering in each cycle of the final tunnel is calculated; According to the tunnel parameters and the coal seam occurrence parameters, a three-dimensional spatial model of the tunnel passing through the coal seam is constructed, and in combination with the tunnel construction parameters, the calculation formulas for the coal falling volume per cycle of tunnel construction, the area of ​​the newly exposed coal seam at the tunnel face, and the area of ​​the newly exposed coal seam on the tunnel wall are derived. The coal falling volume per cycle of tunnel construction is: in, is the total volume of coal dropped in each cycle of coal uncovering, is the coal seam inclination, is the excavation distance per cycle, is the average thickness of the coal seam; The area of ​​newly exposed coal seam at the face is: in, is the area of ​​newly exposed coal seam at the face. It is half of the tunnel's net width length k; The area of ​​newly exposed coal seam on the tunnel wall is: in, It is the area of ​​newly exposed coal seam on the wall.

2. The method for predicting the absolute gas emission volume of coal mining at a tunnel face according to claim 1, characterized in that: The step of obtaining tunnel parameters, coal seam occurrence parameters and coal seam gas parameters comprises: Collect tunnel design data and obtain tunnel parameters, wherein the tunnel parameters include the clear width of the tunnel and the direction of the tunnel; Perform advance drilling at a set vertical distance between the tunnel face and the coal seam to obtain coal seam occurrence parameters, including coal seam thickness, inclination and azimuth; A coal core is drilled at a set vertical distance from the coal seam to measure coal seam gas parameters, including coal density and gas content per ton of coal.

3. The method for predicting the absolute gas emission amount of coal mining in a tunnel face according to claim 1, characterized in that: Substituting the coal seam gas parameters into the calculation formula of the coal falling volume, the newly exposed coal seam area at the tunnel face and the newly exposed coal seam area at the tunnel wall in each cycle of the tunnel construction, and obtaining the absolute gas emission of coal falling, the absolute gas emission of the newly exposed coal seam at the tunnel face and the absolute gas emission of the newly exposed coal seam at the tunnel wall in each cycle of the tunnel construction, the absolute gas emission of coal falling in each cycle of the tunnel is: in, is the absolute gas emission of coal falling in each cycle of the tunnel, is the total volume of coal dropped in each cycle of coal uncovering, is the density of coal, It is the gas content per ton of coal.

4. The method for predicting the absolute gas emission amount of coal mining in a tunnel face according to claim 1, characterized in that: Substituting the coal seam gas parameters into the calculation formula of the coal falling volume per cycle of the tunnel construction, the newly exposed coal seam area at the tunnel face, and the newly exposed coal seam area on the tunnel wall, the absolute gas emission of the coal falling per cycle of the tunnel, the absolute gas emission of the newly exposed coal seam at the tunnel face, and the absolute gas emission of the newly exposed coal seam on the tunnel wall are obtained by calculation. The absolute gas emission of the newly exposed coal seam at the tunnel face is: in, is the absolute gas emission volume of the newly exposed coal seam at the face, is the initial intensity of gas overflow per unit coal wall area per unit time, is the time decay coefficient.

5. The method for predicting the absolute gas emission amount of coal mining at a tunnel face as claimed in claim 4, characterized in that: Substituting the coal seam gas parameters into the calculation formula of the coal falling volume, the newly exposed coal seam area at the tunnel face and the newly exposed coal seam area at the tunnel wall in each cycle of the tunnel construction, in the step of obtaining the absolute gas emission of coal falling, the absolute gas emission of the newly exposed coal seam at the tunnel face and the absolute gas emission of the newly exposed coal seam at the wall in each cycle of the tunnel construction, the time attenuation coefficient is: in, is the time attenuation coefficient, is the attenuation coefficient, Calculate time for coal wall exposure; The initial intensity of gas overflow per unit coal wall area per unit time is: in, is the initial intensity of gas overflow per unit coal wall area per unit time, is the gas content per ton of coal, Volatile matter of coal seams.

6. The method for predicting the absolute gas emission amount of coal mining in a tunnel face according to claim 1, characterized in that: Substituting the coal seam gas parameters into the calculation formula of the coal falling volume per cycle of the tunnel construction, the newly exposed coal seam area at the tunnel face, and the newly exposed coal seam area on the tunnel wall, the absolute gas emission of the coal falling per cycle of the tunnel, the absolute gas emission of the newly exposed coal seam at the tunnel face, and the absolute gas emission of the newly exposed coal seam on the wall are obtained by calculation. The absolute gas emission of the newly exposed coal seam on the wall is: in, is the absolute gas outburst volume of the newly exposed coal seam on the wall, is the initial intensity of gas overflow per unit coal wall area per unit time, is the time decay coefficient.

7. The method for predicting the absolute gas emission volume of coal mining at a tunnel face according to claim 1, characterized in that: According to the absolute gas emission of coal falling in each cycle of the tunnel, the absolute gas emission of the newly exposed coal seam at the tunnel face and the absolute gas emission of the newly exposed coal seam on the wall, in the step of calculating the absolute gas emission of coal uncovering in each cycle of the final tunnel, the absolute gas emission of coal uncovering in each cycle of the final tunnel is: in, is the absolute gas emission of each coal mining cycle in the final tunnel, is the absolute gas emission of coal falling in each cycle of the tunnel, is the absolute gas emission volume of the newly exposed coal seam at the face, is the absolute gas outburst volume of the newly exposed coal seam on the wall, is the correction factor.

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