Method for calculating gas release amount of direct roof oil shale gob-side entry retaining working face

Abstract

The invention belongs to the technical field of coal mining gob-side entry retaining, and discloses an immediate roof oil shale gob-side entry retaining working face gas release amount calculation method in order to solve the problem that in the prior art, gas calculation is not accurate enough, and the immediate roof oil shale gob-side entry retaining working face gas release amount calculation method comprises the following steps that 1, mine geological data is collected, and a working face is drilled for sampling; sending to a laboratory to measure coal seam and roof gas parameters; 2, measuring the absolute gas emission amount of the mining layer of the working face; 3, calculating the total amount of gas desorbed during caving of the immediate roof of the goaf; 4, calculating the absolute emission amount of newly added gas of the working face; and 5, calculating the total average absolute emission amount of the working face gas. According to the method, the gas calculation accuracy is improved, accurate data support can be provided for ventilation and gas prevention and control schemes of follow-up mine gob-side entry retaining, the problem of gas overrun of the working face is better avoided, and the safety of the gob-side entry retaining technology is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of gob-side entry retaining in coal mines, and particularly relates to a calculation method for the gas emission amount of a gob-side entry retaining working face with direct top oil shale. Background Technique

[0002] In most current calculation methods of coal mine gas, it is considered that the mined coal and the coal wall are the main sources of gas generation in the working face. During the mining and excavation process, the mine pressure causes cracks in the intact coal wall and a large area of the mined coal to be exposed, enabling the gas attached to the coal body to seep out from the cracks. However, in mines where the direct top is oil shale, as the working face advances, the direct top in the gob collapses, and a part of the gas is also released with the collapse of the rock to form a free state. In addition, the huge pressure acting directly on the remaining coal in the gob during the instant collapse of the direct top causes the gas in the gob to be released and flow towards the working face. This part of the gas is most likely to be ignored, resulting in the problem of gas overrun in the upper corner, which in turn affects the mining speed of the working face. Therefore, it is necessary to formulate ventilation and gas control plans in advance based on theoretical calculations. The core problem lies in how to calculate the total average absolute gas emission amount of the gob-side entry retaining working face with direct top oil shale.

[0003] To ensure the ventilation safety of the mine under the condition that the direct top is oil shale, it is necessary to accurately calculate the total average absolute gas emission amount of the gob-side entry retaining working face with direct top oil shale. Summary of the Invention

[0004] In order to ensure that gas overrun problems do not occur during the mining process of a high-gas roof mine and solve the problem that the gas content in the working face is significantly different from the theoretical calculation in actual engineering, resulting in insufficient ventilation volume, the invention optimizes the gas calculation method for the working face. On the basis of the original calculation of the gas content in the working face, the gas emission amount of the collapsed direct top rock is considered, and a more accurate calculation method for the gas emission amount of the gob-side entry retaining working face with a high-gas direct top is provided.

[0005] To solve the above technical problems, the technical solution adopted by the invention is as follows: A calculation method for the gas emission amount of a gob-side entry retaining working face with direct top oil shale, comprising the following steps:

[0006] Step 1: Collect the geological data of the mine, take drill samples at the working face, and send them to the laboratory to measure the gas parameters of the coal seam and the roof;

[0007] Step 2: Measure the absolute gas emission amount q of the mining layer in the working face 1 ;

[0008] Step 3: Calculate the total amount of desorbed gas q when the direct top in the gob collapses. The calculation formula is:

[0009]

[0010] Among them, t represents the time taken for one cut in the working face, w represents the analytical amount of the immediate roof rock per unit weight, and V 1 represents the volume of caving of the oil shale in the immediate roof of the working face, and ρ represents the density of the immediate roof rock;

[0011] Step 4: Calculate the absolute gas emission q newly increased in the working face 新增 , and the calculation formula is:

[0012]

[0013] Among them, t 1 represents the time for the remaining desorbed gas to gradually enter the return air current;

[0014] Step 5: Calculate the total average absolute gas emission of the working face according to the absolute gas emission q 1 of the coal seam being mined in the working face and the absolute gas emission q 新增 newly increased in the working face.

[0015] In the said Step 1, the collected mine geological data includes the working face length, coal cutting speed, driving depth, and immediate roof lithology.

[0016] In the said Step 1, boreholes are drilled and sampled along the coal seam and roof on both sides of the working face gateway.

[0017] In the said Step 1, the determined parameters to be measured include the density ρ of the immediate roof rock and the analytical amount of the immediate roof rock per unit weight.

[0018] In the said Step 1, the analytical amount w of the immediate roof rock per unit weight can be obtained by conducting laboratory experiments on immediate roof block specimens.

[0019] The calculation formula for the total average absolute gas emission q 总 of the working face is:

[0020] q 总 = q 1 + q 新增 .

[0021] The present invention has the following beneficial effects compared with the prior art:

[0022] (1) Compared with the traditional working face gas calculation method, the present invention takes into account the gas volume released by the caving of the immediate roof, greatly improving the accuracy of the theoretical calculation of the working face gas.

[0023] (2) By accurately calculating the total average absolute gas emission of the working face, the present invention provides relatively accurate data support for the ventilation and gas prevention and control schemes of gob-side entry retaining in subsequent oil shale roof mines, better avoiding the problem of gas overrun in the working face and improving the safety of the gob-side entry retaining technology. Description of the Drawings

[0024] Figure 1 It is a schematic diagram of the gas concentration behind the gob area of the gob-side entry retaining with high gas roof

[0025] Figure 2 It is a schematic diagram of the key research area behind the gob area of the gob-side entry retaining with high gas roof Detailed Implementation Modes

[0026] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention

[0027] The embodiments of the present invention provide a calculation method for the gas emission amount of the gob-side entry retaining with direct roof oil shale Figure 1 In the schematic diagram of the gas concentration behind the gob area given in, it is found that the gas concentration near the working face is relatively low, indicating that the gas in the area has not been completely desorbed after the direct roof collapses. Therefore, this area is taken as the key research area for calculation, that is Figure 2 The blue area in. The method includes the following steps

[0028] Step 1: Collect mine geological data, drill and take samples on the working face, and send them to the laboratory to measure the gas parameters of the coal seam and roof

[0029] Specifically, in step 1, the collected mine geological data includes the working face length, coal cutting speed, driving depth, and direct roof lithology

[0030] Specifically, in step 1, drill and take samples along the coal seam and roof on both sides of the working face gateway

[0031] Specifically, in step 1, the determined parameters to be measured include the density ρ of the direct roof rock and the desorption amount w of the unit weight of the direct roof rock

[0032] The desorption amount w of the unit weight of the direct roof rock can be obtained by conducting laboratory experiments on direct roof block specimens

[0033] Step 2: Measure the absolute gas emission amount q of the coal seam being mined in the working face 1 . The absolute gas emission amount q of the coal seam being mined in the working face 1 can be measured by existing technical means

[0034] Step 3: Calculate the total amount of gas desorbed when the direct roof in the gob area collapses, and the calculation formula is

[0035]

[0036] Among them, \(t\) represents the time taken for one cut of the working face, \(w\) represents the analytical quantity of the immediate roof rock per unit weight, \(V\) 1 represents the volume of the caving of the immediate roof oil shale in the working face, and \(\rho\) represents the density of the immediate roof rock.

[0037] Specifically, the theoretical gas content \(Q\) of the immediate roof rock 理论 can be expressed as:

[0038] \(Q\) 理论 = \(V\times\rho\times n\); (2)

[0039] In the formula: \(Q\) 理论 represents the theoretical gas content of the immediate roof rock, \(m\) 3 ; \(V\) represents the volume of the immediate roof rock, \(m\) 3 ; \(\rho\) represents the density of the immediate roof rock, \(t / m\) 3 ; \(n\) represents the gas content in the immediate roof rock, \(m\) 3 / t.

[0040] The gas desorption amount \(Q\) of the immediate roof oil shale 解吸 can be expressed as:

[0041] \(Q\) 解吸 = \(V\times\rho\times w\); (3)

[0042] In the formula: \(Q\) 解吸 represents the total gas desorption amount of the immediate roof oil shale, \(m\) 3 ; \(V\) represents the volume of the immediate roof rock mass, \(m\) 3 ; \(\rho\) represents the density of the immediate roof rock, \(t / m\) 3 ; \(w\) represents the gas desorption amount per unit weight of the immediate roof rock, \(mL / (g\cdot min)\).

[0043] Then the gas desorption rate \(N\) of the immediate roof oil shale can be expressed as:

[0044]

[0045] The total amount of gas \(q\) desorbed from the caving of the immediate roof in the goaf can be expressed as:

[0046] \(q = N\times Q\div t\); (5)

[0047] Among them, \(q\) represents the total amount of gas desorbed when the immediate roof in the goaf caves, \(m\) 3 / min; \(N\) represents the gas desorption rate of the immediate roof rock; \(Q\) represents the theoretical gas content of the immediate roof oil shale in the working face, \(m\) 3 ; \(t\) represents the time taken for one cut of the working face, min. Among them, the theoretical gas content of the immediate roof oil shale in the working face can be expressed as:

[0048] Q = V 1 ×ρ×n; (6)

[0049] In the formula: Q represents the theoretical gas content of the immediate roof oil shale in the working face, m 3 ; V 1 represents the caving volume of the immediate roof oil shale in the working face, m 3 ; ρ represents the density of the immediate roof oil shale, t / m 3 ; n represents the gas content in the immediate roof rock, m 3 / t.

[0050] Therefore, by combining and simplifying equations (2) to (6), the above equation (1) can be obtained. Through the above equation (1), the total amount of desorbed gas q when the immediate roof in the goaf caves can be directly calculated.

[0051] Step 4: Calculate the new absolute gas emission rate q of the working face 新增 , and the calculation formula is:[[]]

[0052]

[0053] Among them, t 1 represents the time for the remaining desorbed gas to gradually enter the return air current.

[0054] Specifically, the average absolute gas emission rate q 1 of the gas in the return airway of the coal mining working face, and the proportion m of the desorbed gas volume entering the return air current at one time is:[[]]

[0055]

[0056] The total desorbed gas volume of the immediate roof oil shale in the working face can be expressed as:[[]]

[0057] Q 1 = V 1 ×ρ×w = qt; (9)

[0058] In the formula: Q 1 represents the total desorbed gas volume of the immediate roof oil shale in the working face, m 3 ; V 1 represents the caving volume of the immediate roof oil shale in the working face, m 3 ; ρ represents the density of the immediate roof oil shale, t / m 3 ; w represents the desorbed gas volume per unit weight of the immediate roof oil shale, mL / g.

[0059] The new absolute gas emission rate of the working face can be expressed as:[[]]

[0060]

[0061] In the formula: q 新增Indicates the absolute gas emission increase on the working face, m 3 / min; b represents the proportion of the gas desorption amount that enters the return air flow at one time; Q 1 Indicates the total gas desorption amount of the immediate roof oil shale on the working face, m 3 ; t 1 Indicates the time for the remaining desorbed gas to gradually enter the return air flow, min.

[0062] Therefore, substituting Equations (8) and (9) into Equation (10), the above Equation (7) can be obtained. According to the above Equation (7), the absolute gas emission increase q on the working face can be directly calculated 新增 .

[0063] Step 5: Calculate the average absolute total gas emission q on the working face 总 .

[0064] The average absolute total gas emission on the working face is the sum of the average absolute gas emission q 1 in the return air flow of the return airway of the coal mining face and the absolute gas emission increase, that is:

[0065] q 总 = q 1 + q 新增 ; (11)

[0066] Therefore, in this embodiment, the calculation formula for the average absolute total gas emission q 总 on the working face is:

[0067]

[0068] where t 1 Indicates the time for the remaining desorbed gas to gradually enter the return air flow. According to the above Equation (12), the average absolute total gas emission q on the working face can be calculated 总 .

[0069] In summary, the present invention provides a method for calculating the gas emission amount of an immediate roof oil shale gob-side entry retaining working face. By measuring the absolute gas emission amount of the working face of the mining seam, sampling and measuring the desorption amount per unit weight of the immediate roof rock, the expression of the absolute gas emission increase on the working face is derived using the gas desorption rate of the immediate roof rock, and finally the average absolute total gas emission amount of the gob-side entry retaining working face with rich gas roof is calculated, improving the accuracy of the average absolute total gas emission amount of the gob-side entry retaining working face of the immediate roof oil shale.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the gas release amount of a gob-side entry retaining working face in direct top oil shale, characterized in that: The following steps are involved: Step 1: Collect mine geological data, drill holes at the working face to take samples, and send them to the laboratory to measure coal seam and roof gas parameters; Step 2: Measure the absolute gas emission q1 of the mining layer at the working face; Step 3: Calculate the total amount of gas desorbed when the direct roof of the goaf collapses. The calculation formula is: Among them, t represents the time taken for one cut of the working face, w represents the analytical volume of the unit weight of the direct top rock, V1 represents the volume of the oil shale collapse on the direct top of the working face, and ρ represents the density of the direct top rock; Step 4: Calculate the absolute additional gas outflow volume q at the working face 新增 , the calculation formula is: Among them, t1 represents the time when the remaining desorbed gas gradually enters the return air flow; Step 5: According to the absolute gas outflow volume q1 of the mining layer of the working face and the absolute additional gas outflow volume q 新增 , calculate the average absolute total amount of gas outburst at the working face.

2. The method for calculating gas release in a gob-side entry retaining working face of direct top oil shale according to claim 1 is characterized in that: In step 1, the collected mine geological data include working face length, coal cutting speed, footage depth, and direct top lithology.

3. The method for calculating gas release in a gob-side entry retaining working face of direct top oil shale according to claim 1 is characterized in that: In the step 1, holes are drilled and samples are taken from the coal seams and the roof on both sides of the working face.

4. The method for calculating gas release in a gob-side entry retaining working face of direct top oil shale according to claim 1 is characterized in that: In the step 1, the parameters determined include the density ρ of the direct top rock and the analytical volume per unit weight of the direct top rock.

5. The method for calculating gas release amount in a gob-side entry retaining working face of direct top oil shale according to claim 4 is characterized in that: In step 1, the analytical amount w of the unit weight of the direct top rock can be obtained by conducting laboratory experiments on direct top block specimens.

6. The method for calculating gas release in a gob-side entry retaining working face of direct top oil shale according to claim 1 is characterized in that: Average absolute total amount of gas outflow from the working face q 总 The calculation formula is: q 总 =q1+q 新增 。

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