CN116006243A - Large-area full-time empty high-efficiency gas control method for soft outburst coal seam - Google Patents

Abstract

The invention relates to a full-time empty high-efficiency gas control method for a large area of a soft outburst coal seam, and belongs to the field of coal mine gas control. S1, arranging high-position directional branch long drilling holes of a coal seam roof; s2, arranging long drill holes of low-position directional branches of the coal seam roof, S3, and connecting the long drill holes with a drainage pipeline to conduct gas drainage. The method adopts the high-position and low-position directional branch long drilling holes of the coal seam roof to realize the efficient treatment of gas in coal lanes, fracture zones, upper corners, stoping working faces, adjacent layers and goafs in the extraction process of the soft coal seam, solves the technical problems of large construction difficulty, easy hole collapse, poor extraction effect, small gas treatment area, incapability of large-area advanced gas treatment, low efficiency and the like of the soft protruding coal seam, and has important significance in reducing the gas treatment engineering quantity and cost, the gas treatment effect and the full-time empty efficient gas treatment.

Description

Full-time and space-time high-efficiency gas control method for large area of soft outburst coal seam

technical field

The invention belongs to the field of coal mine gas control, and in particular relates to a full-time and space-time high-efficiency gas control method in a large area of soft and outburst coal seams.

Background technique

Gas disasters have seriously affected the safe production of coal mines. In order to realize the safe recovery of the mining face of the outburst coal seam, it is necessary to realize the standard of mining drainage and the control of gas emission in essence. The soft coal seam has low hardness and poor air permeability, and there are problems such as difficult construction, easy collapse of the hole, and poor drainage effect when drilling along the bedding; with the development of technology, although there are large-scale directional drilling rigs, there are still directional long holes that cannot be drilled deep. And other problems have seriously affected the mining succession and are not conducive to safety management. In addition, the existing gas control method has a small gas control area, and there are problems that large-scale advanced gas control cannot be realized, and the efficiency is low, which seriously restricts the safe and efficient production of coal mines.

Contents of the invention

In view of this, the object of the present invention is to provide a large-area, full-time and space-time efficient gas control method for soft and outburst coal seams, so as to solve the problems existing in the existing gas control process.

To achieve the above object, the present invention provides the following technical solutions:

A full-time and space-time high-efficiency gas control method for large areas of soft and outburst coal seams, comprising the following steps: S1, arranging high-level directional branch long drilling holes on the coal seam roof; S2, arranging low-level directional branch long drilling holes on the coal seam roof; S3, connecting to the drainage pipeline carry out gas extraction;

In step S1, the high-position directional branch long holes on the roof of the coal seam include the high-position main hole and the high-position branch hole; wherein the reasonable spatial construction position of the high-position main hole includes the construction range in the coal seam inclination direction and the construction layer in the vertical direction;

The construction range of the high-level main hole in the direction of coal seam inclination is: W+Y _p ≤ Y ₃ ≤ L/3;

In the formula: W is the width of the return airway of the mining face, in m; Y _p is the width of the gas discharge belt of the return airway of the mining face, in m; L is the length of the cut hole in the mining face, in m ;

The method for determining the construction level of the high-level main hole in the vertical direction is as follows: firstly determine the construction row number N of the high-level main hole, and then determine the construction level of the high-level main hole according to the arithmetic sequence according to the number of construction rows, so that each high-level The layer height of the main hole gradually increases from the return airway of the mining face to the middle of the mining face;

The number of construction rows N is determined according to the construction range _Y3 and the coal seam extraction radius r:

N＝[L/3－(W+Y _p )]÷2r+1;

In the formula: L is the length of the cut hole in the mining face, the unit is m; _Yp is the width of the gas discharge belt of the return airway of the mining face, the unit is m; r is the extraction radius of the coal seam, the unit is m;

Assuming that the construction layer h ranges from a to b, then the tolerance of the arithmetic sequence is (b-a)/N, then the layer heights of the i, j, and k high-level main holes are a+i×( b－a)/N, a+j×(b－a)/N, a+k×(b－a)/N, and so on, the construction level of each high-level main hole can be determined;

In step S2, the low-level directional branch long borehole on the coal seam roof includes a low-level main hole and a low-level branch hole; the low-level main hole is arranged at a distance of 1 to 5 m from the coal seam roof in the vertical direction.

Further, in step S1, in the direction of coal seam inclination, the design spacing between adjacent high-level main holes and adjacent high-level branch holes is Y ₁ , and Y ₁ is twice the extraction radius r; in the direction of coal seam direction, the high-level The drilling design length of the main hole is greater than the length X of the mining face and exceeds 20m.

Further, in step S1, after the reasonable spatial construction position of the high-level main hole is determined, the high-level branch holes are designed in _the direction of coal seam inclination and the direction of coal seam strike; Spacing arrangement.

Furthermore, the construction length of each high-level branch hole is controlled by the end-hole point, and the distance between the end-hole points of two adjacent high-level branch holes is less than or equal to twice the drainage radius r.

Further, in step S1, the high-level main hole is constructed first, and when the high-level main hole is constructed to a predetermined depth, the high-level branch holes are sequentially constructed at intervals of X ₁ from the bottom of the high-level main hole to the hole opening.

Further, in step S1, high-level main holes of different heights are arranged at the roof of the coal seam within a certain range on the left and right sides of the return airway of the mining face in the roof fissure zone, so as to realize simultaneous full coverage of the mining face and adjacent layers pouring into the cracks Bring gas.

Further, in step S2, in the direction of coal seam inclination, the design spacing of adjacent low-level main holes is Y ₁ , and Y ₁ is twice the extraction radius r; in the direction of coal seam direction, the designed length of the low-level main holes The length of the mining face is X and exceeds 20m.

Further, in step S2, in the direction of coal seam strike, adjacent low-level branch holes are arranged equidistantly at a distance of _X1 .

Further, X ₁ is 100 to 300 m.

Furthermore, during the coal roadway excavation process, a tee is installed in the coal roadway strip branch hole exposed in the coal roadway, and a pipeline is led out to simultaneously extract coal seam and goaf gas.

The beneficial effects of the present invention are:

This control method adopts high-level and low-level directional branch long holes on the roof of the coal seam to realize the efficient control of gas in coal roadways, fissure zones, upper corners, mining working faces, adjacent layers, and goafs during the mining process of soft coal seams. Soft and outburst coal seams have technical problems such as difficult construction, easy hole collapse, poor drainage effect, small gas control area, inability to advance large-scale gas control, and low efficiency. All-time and space-time efficient gas control is of great significance.

Other advantages, objects and features of the present invention will be set forth in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the investigation and research below, or can be obtained from Taught in the practice of the present invention. The objects and other advantages of the invention may be realized and attained by the following specification.

Description of drawings

In order to make the purpose of the present invention, technical solutions and advantages clearer, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

Figure 1 is a schematic diagram of the full-time and space-time high-efficiency gas control plan layout in a large area of soft outburst coal seam.

Figure 2 is a schematic diagram of the cross-sectional layout of the high and low directional branch long boreholes on the coal seam roof in the direction of the coal seam dip;

Fig. 3 is a schematic diagram of the cross-sectional layout of the low-level main hole and the low-level branch hole of the low-level directional branch long borehole on the coal seam roof in the coal seam direction;

Figure 4 is a schematic diagram of the cross-sectional layout of the first high-level main hole and high-level branch holes in the direction of coal seam strike;

Fig. 5 is a schematic diagram of the cross-sectional layout of the i-th high-level main hole and high-level branch holes in the coal seam direction;

Fig. 6 is a schematic diagram of the cross-sectional layout of the jth high-level main hole and high-level branch holes in the direction of coal seam strike;

Fig. 7 is a schematic diagram of the cross-sectional layout of the kth high-level main hole and high-level branch holes in the direction of coal seam strike.

Reference signs:

1- Open up and down the mountain lanes;

2- The transport lane of the mining face;

3- Air return lane of mining face;

4-cut eye in mining face;

5-The low-level main hole of the low-level directional branch long drill hole on the roof of the coal seam;

6- The kth high-level main hole in the high-level directional branch long drill hole on the roof of the coal seam;

7- The jth high-level main hole in the high-level directional branch long drill hole on the roof of the coal seam;

8- The i-th high-level main hole in the high-level directional branch long drill hole on the roof of the coal seam;

9- The first high-level main hole in the high-level directional branch long drill hole on the roof of the coal seam;

10-The high-level branch hole connected with the high-level main hole in the high-level directional branch long drill hole on the roof of the coal seam;

11 - coal seam;

12 - Drainage pipeline;

13-The low-level branch hole connected with the low-level main hole in the low-level directional branch long borehole of the coal seam roof;

X - the length of the mining face;

X ₁ - the design spacing between adjacent branch holes in the direction of coal seam strike;

L - the length of the cut eye in the mining face;

W - the width of the air return lane of the mining face;

N- the number of construction rows of high-level main holes in the high-level directional branch long drill holes on the roof of the coal seam;

h - the construction layers of each high-level main hole in the high-level directional branch long borehole of the coal seam roof;

h _g1 - the construction level of the first high-level main hole;

h _gi - the construction level of the i-th high main hole;

h _gj - the construction level of the jth high main hole;

h _gk - the construction level of the kth high main hole;

h _d - the distance between the lower main hole and the coal seam roof in the vertical direction;

r - the extraction radius of the coal seam,

Y ₁ - the design spacing between adjacent main holes and branch holes in the direction of coal seam inclination;

Y ₂ - Bounded by the lower coal wall of the return airway of the mining face, in the direction of coal seam inclination, the construction range of the high-level main hole on the left side of the return airway of the mining face;

Y ₃ - Bounded by the lower coal wall of the return airway of the mining face, in the direction of coal seam inclination, the construction range of the high-level main hole on the right side of the return airway of the mining face;

Y _p - the width of the gas discharge zone of the return airway of the mining face.

Detailed ways

Embodiments of the present invention are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes, and various modifications or changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following embodiments are only schematically illustrating the basic concept of the present invention, and the following embodiments and the features in the embodiments can be combined with each other in the case of no conflict.

Wherein, the accompanying drawings are for illustrative purposes only, and represent only schematic diagrams, rather than physical drawings, and should not be construed as limiting the present invention; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, Enlargement or reduction does not represent the size of the actual product; for those skilled in the art, it is understandable that certain known structures and their descriptions in the drawings may be omitted.

In the drawings of the embodiments of the present invention, the same or similar symbols correspond to the same or similar components; , "front", "rear" and other indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred devices or elements must It has a specific orientation, is constructed and operated in a specific orientation, so the terms describing the positional relationship in the drawings are for illustrative purposes only, and should not be construed as limiting the present invention. For those of ordinary skill in the art, the understanding of the specific meaning of the above terms.

Please refer to Fig. 1, the present invention provides a large-area full-time and space-time gas efficient control method for soft and outburst coal seams, which specifically includes the following steps:

Step 1: Design and construct high-level directional branch long boreholes on the roof of the coal seam.

The high-position directional branch long boreholes on the roof of the coal seam include high-position main holes and high-position branch holes. First determine the reasonable spatial position of the high-level main hole, and then design and construct the high-level main hole and high-level branch holes. The specific implementation methods are detailed as follows:

(1) Determine the reasonable spatial construction position of the high main hole

The reasonable spatial construction position of the high-level main hole mainly includes the construction scope in the coal seam inclination direction and the construction layer in the vertical direction. The determination method is as follows:

1) The scope of construction in the direction of coal seam inclination

Referring to Figure 1 and Figure 2, according to the gas control requirements, the high-level main hole should cover a certain range on the left and right sides of the return airway 3 of the mining face in the direction of coal seam inclination, with the lower coal wall of the return airway 3 of the mining face as the boundary According to the advancing direction of the mining face, the high-level main hole in the high-level directional branch long borehole on the roof of the coal seam is divided into left and right sides.

Let the construction scope on the left be Y ₂ , and the construction scope on the right be Y ₃ .

The construction scope on the right should cover the return air lane 3 of the mining face and the gas discharge zone of the air return lane of the mining face, so the calculation formula is: Y ₃ ≥ W+Y _p ; where W is the air return of the mining face The width of the lane, the unit is m; Y _p is the width of the gas discharge belt of the return air lane of the mining face, the unit is m.

The construction scope on the left should avoid the re-compaction area of the goaf. According to the empirical formula, the re-compaction area of the goaf is generally not greater than 1/3 of the length L of the cutting hole of the working face, which is recorded as Y ₃ ≤ L/3.

To sum up, the construction range of the high-level main hole in the dip direction of the coal seam (in the high-level directional branch long drilling of the roof of the coal seam) is W+Y _p ≤ Y ₃ ≤ L/3.

2) Construction layers in the vertical direction

Referring to Figure 2, collect the comprehensive column diagram of the mine, mine geological exploration drilling and drilled holes, analyze the lithology and mechanical parameters of the coal seam roof strata, and according to the roof "three zones" theory, the layout of the high-level directional branch long drilling holes in the coal seam roof In the roof fissure zone, in the vertical direction, the construction layer h of the high-level main hole is generally 2 to 5 times the thickness M of the coal seam.

Due to the difference in the amount of gas emission at different heights of the roof, the high-level directional branch long boreholes on the roof of the coal seam with different layers (heights) are arranged on the roof of the coal seam, which can fully cover the extraction and recovery working face and the gas flowing into the fracture zone from adjacent layers. For gas, the determination method for the construction level of each high-level main hole is as follows:

Referring to Fig. 2, first determine the construction row number N of the high-level main hole (in the high-level directional branch long drilling hole of the coal seam roof), and then follow the arithmetic sequence according to the construction row number N, from the return airway of the mining face along the advancing direction of the mining face The initial design layer height h on the right is the high-level main hole that becomes larger in turn.

① Construction rows of high-level main holes

(In the high-level directional branch long drilling holes on the roof of the coal seam) the construction row number N of the high-level main holes can be determined according to the construction range _Y3 of the high-level main holes in the coal seam inclination direction and the extraction radius r of the coal seam. The calculation formula is as follows:

N＝[L/3－(W+Y _p )]÷2r+1;

In the formula: L is the length of the cut hole of the mining face, in m; Y _p is the width of the gas discharge belt of the return airway of the mining face, in m; r is the extraction radius of the coal seam, in m.

②Construction layer of high main hole

Assuming (in the high-level directional branch long drilling hole on the roof of the coal seam) that the construction layer h of the high-level main hole is in the range of a to b, then the tolerance of the arithmetic sequence is (b-a)/N, then the i, j, and kth The heights of the elevated main holes are a+i×(b-a)/N, a+j×(b-a)/N, a+k×(b-a)/N in sequence. By analogy, the construction layers of each high-level main hole can be determined.

(2) Design and construction of high-level main holes and high-level branch holes

1) Design high-level main holes and high-level branch holes

Referring to Figures 3 to 6, after the reasonable spatial position of the high-level main hole is determined, the high-level main hole and high-level branch holes are designed in the direction of coal seam dip and strike direction.

In the direction of coal seam inclination, the design spacing between adjacent high-level main holes and adjacent high-level branch holes is Y ₁ , and Y ₁ is generally twice the extraction radius r. In the direction of the coal seam, the design length of the high-level main hole is generally greater than the length X of the mining face, and exceeds 20m.

In the direction of coal seam strike, the adjacent high-level branch holes are designed at an equal interval of X ₁ , and X ₁ is generally 100-300m, which can be determined according to the occurrence of coal seams. The construction length of the high-level branch holes is controlled by the end-hole point, and the distance between the end-hole points of two adjacent high-level branch holes is less than or equal to twice the extraction radius r.

The construction design of the branch hole can be realized by inputting the above parameters into the construction parameter design software of the intelligent drilling rig, the same below.

2) Construction of high-level main holes and high-level branch holes

After the design of the construction parameters of the high-level main hole and the high-level branch hole is completed, the construction shall be carried out according to the design parameters. The high-level main hole is constructed first, and when the high-level main hole is constructed to the predetermined depth, the high-level branch holes are constructed sequentially from the bottom of the high-level main hole to the hole at an interval of X ₁ .

Step 2: Design and construction of long boreholes with directional branches at low positions on the roof of the coal seam

(1) Design the low main hole and the low branch hole

Referring to Fig. 1 and Fig. 2, the construction range of the low-level directional branch long drilling on the coal seam roof is outside the area of the high-level directional branch long drilling on the coal seam roof. Referring to Figure 7, the low-level directional branch long boreholes on the coal seam roof are divided into low-position main holes and low-position branch holes. The low-position main holes of the low-position directional branch long boreholes on the coal seam roof are generally arranged at a distance of 1 to 5 m from the coal seam roof in the vertical direction.

Referring to Fig. 1 and Fig. 2, the design parameters of the low-position main hole and the low-position branch hole of the low-position directional branch long borehole on the coal seam roof are the same as those of the high-position main hole and the high-position branch hole. That is, in the direction of coal seam inclination, the design spacing between adjacent low-level main holes and adjacent low-level branch holes is Y ₁ , and Y ₁ is twice the extraction radius r; The design length is greater than the length X of the mining face and exceeds 20m.

In the direction of coal seam strike, the adjacent low-level branch holes are arranged at equal intervals of X ₁ , and X ₁ is generally 100-300m, which is determined according to the occurrence of coal seams. The construction length of the low-level branch holes is controlled by the end-hole point, and the distance between the end-hole points of two adjacent low-level branch holes is less than or equal to twice the extraction radius r.

(2) Construction of low main hole and low branch hole

See Figures 1-2, the construction method is the same as that of the high-position main hole and the high-position branch hole, that is, the low-position main hole is constructed first, and when the low-position main hole is constructed to a predetermined depth, every interval X ₁ is retreated from the bottom of the low-position main hole to the orifice. Construct the lower branch holes sequentially.

Step 3: Connect the drainage pipeline for gas drainage.

Referring to Figure 1, according to the outburst prevention requirements, the low-level and high-level directional branch long boreholes of each mining face are separately divided into a drainage unit, and the drainage pipelines are separately connected to the gas drainage volume measure. Then, according to the amount of gas drainage, the evaluation of gas drainage compliance is carried out. When the gas drainage in the coal roadway strip area reaches the standard, the coal roadway excavation operation can be carried out; after the gas drainage in the mining area reaches the standard, the mining operation can be carried out.

After the evaluation of gas drainage standards, the coal roadway excavation is carried out. During the coal roadway excavation process, the branch holes of the coal roadway strips exposed in the coal roadway are installed with tees, and the leading pipeline is connected with the goaf pipeline, which is the working face. Prepare for gob gas drainage during mining, and the original branch holes continue to drain gas in fractured areas and upper corners, so as to realize efficient gas control in a large area of soft coal seams in all time and space, so as to realize the mining process of soft coal seams Gas in middle coal roadway, fissure zone, upper corner, mining face, adjacent layers and goaf. This process description only takes one mining face as an example, and the other adjacent working faces can be deduced according to the excavation succession.

Finally, it is noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements, without departing from the spirit and scope of the technical solution, should be included in the scope of the claims of the present invention.

Claims (10)

1. A full-time empty high-efficiency gas treatment method for a large area of a soft outburst coal seam is characterized by comprising the following steps of: s1, arranging high-position directional branch long drill holes of a coal seam roof; s2, arranging long drill holes of low-position directional branches of a coal seam roof; s3, accessing a gas extraction pipeline to carry out gas extraction;

in the step S1, a high-position directional branch long drilling hole of a coal seam roof comprises a high-position main hole and a high-position branch hole; the reasonable space construction position of the high-level main hole comprises a construction range of the coal seam inclination direction and a construction horizon of the vertical direction;

the construction range of the high-level main hole in the coal seam inclination direction is as follows: W+Y _p ≤Y ₃ ≤L/3；

Wherein: w is the width of a return airway of the stope face, and the unit is m; y is Y _p The width of the gas discharge zone of the return airway of the stope face is m; l is the length of a cutting hole of the stope face, and the unit is m;

the construction horizon determination method of the high-level main hole in the vertical direction comprises the following steps: firstly determining the construction row number N of the high-level main holes, and then determining the construction layer positions of the high-level main holes according to the construction row number and the arithmetic series, so that the layer height of each high-level main hole sequentially increases from the return airway of the stope face to the middle of the stope face;

wherein the construction row number N is according to the construction range Y ₃ And determining the extraction radius r of the coal seam:

N＝[L/3－(W+Y _p )]÷2r+1；

wherein: l is the length of a cutting hole of the stope face, and the unit is m; y is Y _p Band width of gas exhaust band for return airway of stope faceThe unit is m; r is the extraction radius of the coal seam, and the unit is m;

assuming that the range of the construction horizon h is a-b, the tolerance of the arithmetic series is (b-a)/N, and the horizon heights of the ith, j and k high-order main holes are a+i× (b-a)/N, a +j× (b-a)/N, a +k× (b-a)/N in sequence, and the like, so as to determine the construction horizon of each high-order main hole;

in the step S2, the low-level directional branch long drilling hole of the coal seam roof comprises a low-level main hole and a low-level branch hole; the low-level main hole is arranged at a position 1-5 m away from the coal seam roof in the vertical direction.

2. The method for high-efficiency gas treatment in large-area full-time space of soft outburst coal seams according to claim 1, which is characterized in that: in step S1, in the coal seam inclination direction, the design intervals between adjacent high-level main holes and between adjacent high-level branch holes are all Y ₁ ，Y ₁ 2 times of the extraction radius r; in the direction of the coal seam trend, the drilling design length of the high-level main hole is greater than the length X of the stope face and exceeds more than 20 m.

3. The method for high-efficiency gas treatment in large-area full-time space of soft outburst coal seams according to claim 1, which is characterized in that: in the step S1, after the reasonable space construction position of the high-level main hole is determined, designing high-level branch holes in the coal seam trend direction and the coal seam trend direction respectively; in the direction of the coal seam trend, adjacent high-level branch holes are divided into X-shaped branch holes ₁ Are arranged at equal intervals, X ₁ 100-300 m.

4. A method for high efficiency gas abatement in large areas of a soft protruding coal seam in full time space according to claim 3, wherein: the construction length of each high-level branch hole is controlled by a final hole point, and the final hole point distance of two adjacent high-level branch holes is less than or equal to 2 times of the extraction radius r.

5. The method for high-efficiency gas treatment in large-area full-time space of soft outburst coal seams according to claim 1, which is characterized in that: in the step S1, a high-level main hole is firstly constructed,when the high-order main hole is constructed to a preset depth, each interval X ₁ And sequentially constructing the high branch holes from the bottom of the high main hole to the hole opening in a retreating way.

6. The method for high-efficiency gas treatment in large-area full-time space of soft outburst coal seams according to claim 1, which is characterized in that: in the step S1, high-position main holes with different heights are arranged at the coal seam roof in a certain range at the left side and the right side of the return airway of the stope face in the roof fracture zone so as to realize the purpose of simultaneously and fully covering gas which flows into the fracture zone from the stope face and the adjacent layers.

7. The method for high-efficiency gas treatment in large-area full-time space of soft outburst coal seams according to claim 1, which is characterized in that: in the step S2, in the coal seam inclination direction, the design intervals of adjacent low-level main holes are all Y ₁ ，Y ₁ 2 times of the extraction radius r; in the direction of the coal seam trend, the drilling design length of the low-level main hole is greater than the length X of the stope face and exceeds more than 20 m.

8. The method for high-efficiency gas treatment in large-area full-time space of soft outburst coal seams according to claim 1, which is characterized in that: in step S2, in the coal seam trend direction, adjacent low-level branch holes are divided by X ₁ Are arranged at equal intervals.

9. The method for high-efficiency gas treatment in large-area full-time space of soft outburst coal seams according to claim 1, which is characterized in that: in step S2, the low-level main holes are firstly constructed, and when the low-level main holes are constructed to a preset depth, each interval X ₁ And sequentially constructing the low-level branch holes in a way that the distance is retreated from the hole bottom of the main hole to the hole opening.

10. The method for high-efficiency gas treatment in large-area full-time space of soft outburst coal seams according to claim 1, which is characterized in that: in the coal roadway tunneling process, tee joints are arranged on branch holes of coal roadway strips exposed in the coal roadway, and a pipeline is led out to simultaneously extract coal seam and goaf gas.

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