Mining method of extremely close coal seam

Abstract

The invention discloses a mining method for an extremely close coal seam, and belongs to the technical field of coal mining. The method aims at a third type of working faces which cannot be safely mined and are used for an extremely close coal seam with the interlayer spacing smaller than 2m; the upper coal seam is not provided with a coal face, the coal face is arranged on the lower coal seam, a roadway is tunneled along a bottom plate of the lower coal seam, and normal mining can be achieved during mining in an anchor net cable active supporting mode; the mudstone in the roof between the coal seams is broken by adopting a shallow hole blasting, deep hole blasting or water injection method, and the recovery rate of the upper coal seam is improved. The method has the advantages that the resource recovery rate is increased, the roadway tunneling rate is reduced, and hidden dangers such as goaf roof, water accumulation, gas accumulation and gas accumulation are eliminated; the problems of arrangement, passive support and the like of an upper coal seam working face roadway are avoided; and the method can be widely applied to extremely close coal seams with interlayer spacing less than 2m.

Description

Technical Field

[0001] The invention relates to a mining method for an extremely close-distance coal seam, and in particular to a method for simultaneously mining an upper coal seam and a lower coal seam in an extremely close-distance coal seam with an interlayer spacing of less than 2m; and belongs to the technical field of coal mining. Background Art

[0002] The mining methods of close-range or very close-range coal seams are to first mine the upper coal seam and then the lower coal seam. The main technical content of the research is the structure and movement law of the rock layer of the upper coal seam roof, the stress and displacement change law of the upper coal seam floor, that is, the lower coal seam roof, the failure characteristics and the seepage characteristics after the failure. The support theory mainly includes masonry beam, transfer rock beam, cantilever beam and three-zone theory under the floor. Since the mining of very close-range coal seams is the stratified mining of the upper and lower coal seams, its core is the movement law of the overburden structure of the mining area and the surrounding rock control technology. Whether the surrounding rock of the mining area can be successfully controlled is the prerequisite for the normal production of the lower coal seam working face. As the distance between coal seams decreases, the mutual influence between the mining of upper and lower coal seams will gradually increase, especially when the distance between coal seams is very close. The integrity of the roof before the mining of the lower coal seam has been affected by the disturbance of the mining of the upper coal seam. Above it is the gangue that falls directly from the top during the mining of the upper coal seam. In addition, the concentrated pressure formed on the bottom plate by the coal pillars in the section after the mining of the upper coal seam leads to changes in the roof structure and stress environment of the lower coal seam mining area, resulting in many new mining pressure phenomena in the mining of extremely close coal seams.

[0003] In the process of coal seam mining at very close distance, the stability of the mining area roof during mining of the lower coal seam mainly depends on factors such as the rock strength of the roof between coal seams, the layered composition, and the load (dynamic load) of the collapsed gangue after mining of the upper coal seam. When the support effect is considered, the coal seam spacing, that is, the safe thickness of the interlayer roof is generally about 4 to 6 meters; when the support effect is not considered, the safe thickness of the interlayer roof is generally about 3 to 4 meters. Therefore, for coal seams with a very close distance of more than 4 meters between coal seams, it is called the first type of working face that can be mined safely. When this type of working face is excavated, anchor nets are often used for active support, and short anchors are used for anchors; during mining, normal mining can be achieved. For coal seams with a very close distance of 2 to 4 meters between coal seams, it is called the second type of working face that can basically guarantee safe mining. When excavating this type of working face, composite support is often used. On the basis of active support of anchor nets, shed-type passive support is used as a reinforcement support method; during mining, the upper coal seam adopts the roof net laying measure, which is similar to layered mining, and normal mining can be achieved. When the distance between coal seams is less than 2m, it is called the third type of working face that cannot be mined safely. When this type of working face is excavated, a shed-type passive support method is adopted. During mining, the safe control of the mining area roof of the lower coal seam working face cannot be guaranteed, and normal mining cannot be achieved. A series of problems will be encountered, such as the reasonable layout and reliable support of the tunnels of the lower coal seam working face, the safety and stability of the lower roof of the goaf area of ​​the lower coal seam working face and the leakage of the machine road roof, the influence of water accumulation in the goaf area of ​​the upper coal seam working face, and the prevention and control of gas outbursts in the upper coal seam working area.

[0004] For the third type of working face that cannot be mined safely, it is necessary to design a mining method for extremely close coal seams. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a method for mining extremely close coal seams. For working faces of extremely close coal seams with an interlayer spacing of less than 2m that cannot be safely mined under existing technical conditions, a method for simultaneously mining upper and lower coal seams is proposed.

[0006] The present invention is based on the existing mining method for extremely close-distance coal seams, and for extremely close-distance coal seams with interlayer spacing less than 2m, and third-type working faces that cannot be mined safely, a mining method for extremely close-distance coal seams is proposed. The principle is as follows: for extremely close-distance coal seams with interlayer spacing less than 2m, no coal mining working face is arranged in the upper coal seam, and the coal mining working face is arranged in the lower coal seam, and the tunnel is excavated along the bottom plate of the lower coal seam; relative to the upper and lower coal seam stratified mining process, this method can design the third-type working face that cannot be mined safely into a first-type working face that can be mined safely. During excavation, the shed-type passive support is cancelled, and the anchor net cable active support method is adopted. Normal mining can be achieved during mining, and there is no safety and stability of the roof under the goaf and leakage of the machine road roof. , water accumulation in goaf, accumulated gas outburst and other safety hazards; the geological strata of the coal seam are sedimentary rocks. When the interlayer spacing of the coal seams in the closest distance is less than 2m, the lithology and stratification composition are mostly mudstone, carbonaceous mudstone or sandy mudstone. The lithology of the roof between coal seams is mudstone, that is, the coal seams with a thickness of less than 2m are interbedded with gangue. The gangue is the bottom plate of the upper coal seam and also the roof plate of the lower coal seam. It is an important factor affecting the recovery rate of the upper coal seam. Shallow hole blasting, deep hole blasting or water injection methods can be used to break up the interlayer mudstone and improve the recovery rate of the upper coal seam.

[0007] The present invention provides a mining method for extremely close coal seams. No coal mining working face is arranged in the upper coal seam, but the coal mining working face is arranged in the lower coal seam. The tunnel is excavated along the bottom plate of the lower coal seam. The support method adopts active support of anchor net cables. Normal mining can be achieved during mining, and the safety and stability of the lower roof of the goaf and the potential safety hazards such as leakage of the machine road roof, water accumulation in the goaf, and gas outburst can be effectively solved. Shallow hole blasting, deep hole blasting or water injection methods are used to break the mudstone in the roof between coal seams to improve the recovery rate of the upper coal seam.

[0008] The present invention is aimed at the third type of working face that cannot be mined safely, which is required to be a very close distance coal seam with a layer spacing of less than 2m. The very close distance coal seam refers to: the upper coal seam is a thin and medium thick coal seam with a thickness of less than 1.6m, and the lower coal seam is a thick coal seam.

[0009] The specific steps of the above mining method are: (1) Arrangement of coal mining face: No coal mining face is arranged in the upper coal seam, but the coal mining face is arranged in the lower coal seam, and the coal mining face tunnel is excavated along the bottom plate of the lower coal seam; (2) Support: anchor net cable support; (3) Mining: First, shallow hole blasting is used in the coal mining face to blast the upper coal seam floor, with a blasthole length of 2m, a hole spacing of 0.5m, a charging length of 0.5~1.0m, and a charging amount of 1.2~2.4kg; then, deep hole blasting is used in the coal mining face tunnel to blast the upper coal seam floor, with a horizontal projection length of the blasthole greater than 1 / 2 of the length of the coal mining face, a hole spacing of 0.5m, and charging of the blasthole section in the upper coal seam floor, with a charging length of no more than 8m and a charging amount of no more than 9.6kg; then, water injection is used to soften the upper coal seam floor in the coal mining face tunnel, with a horizontal projection length of the borehole greater than 1 / 2 of the length of the coal mining face, a hole spacing of 5~10m, a water injection pressure of 6~10MPa, and a water injection time of 1~3 months.

[0010] In the above mining method, shallow hole blasting is implemented at the coal mining face, and deep hole blasting and water injection softening are carried out in the coal mining face tunnel. Specifically, deep hole blasting holes and water injection holes are set at the same time in the coal mining face tunnel. When the upper coal seam floor and the mining pressure in the mining field can be safely controlled, deep hole blasting is only implemented on the advanced coal mining face; when the upper coal seam floor and the mining pressure in the mining field cannot be safely controlled, deep hole blasting is first implemented on the advanced coal mining face, and then water injection softening construction is carried out on the coal mining face.

[0011] Beneficial effects of the present invention: (1) For the third type of working face that cannot be mined safely, during the excavation process, problems such as the layout and passive support of the upper coal seam working face tunnel were avoided; (2) During the mining process of the lower coal seam working face, the stability of the lower roof of the goaf area of ​​the lower coal seam working face and the leakage of the machine way roof were eliminated, and the safety hazards such as the impact of water accumulation in the goaf area of ​​the upper coal seam working face and the prevention and control of accumulated gas outburst were avoided; (3) The present invention has the advantages of improving resource recovery rate, reducing tunnel excavation rate, and eliminating hidden dangers such as roof, water accumulation, gas accumulation and gas accumulation in goaf areas; (4) The method of the present invention can be widely applied to extremely close coal seams with interlayer spacing less than 2 m, especially to extremely close coal seams with upper coal seams being thin or medium-thick coal seams with a thickness of less than 1.6 m and lower coal seams being thick coal seams. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of a method for mining coal seams at extremely close distances according to the present invention.

[0013] Figure 2 for Figure 1 Top view of the .

[0014] In the figure: 1-upper coal seam; 2-lower coal seam; 3-upper coal seam floor; 4-coal mining face; 5-coal mining face tunnel; 6-shallow hole blasting blasting hole; 7-deep hole blasting blasting hole; 8-blasting hole section in the upper coal seam floor; 9-water injection drilling hole. DETAILED DESCRIPTION

[0015] The present invention is further illustrated by the following examples, but is not limited to the following examples. Example 1

[0016] The coal seam inclination angle of the fourth mining area of ​​the 11# coal seam in a certain mine is 2 to 8°, with an average of 4°. The average thickness of the 11# upper coal seam is 1.66m, and the average thickness of the 11# lower coal seam is 4.46m. The maximum interlayer distance between the 11# upper coal seam and the 11# lower coal seam is 2.46m, the minimum interlayer distance is 1.01m, and the average interlayer distance is 1.74m. The working faces of the 11# lower coal seam are all third-class working faces that cannot be mined safely. A method for mining extremely close-distance coal seams of the present invention is implemented in the fourth mining area of ​​the 11# coal seam, and its characteristic steps are: In the extremely close distance coal seam with an average interlayer spacing of 1.74m (interlayer spacing less than 2m), the 11# upper coal seam 1 is not arranged with a coal mining face, the coal mining face 4 is arranged in the 11# lower coal seam 2, the coal mining face tunnel 5 is excavated along the 11# lower coal seam floor, and the 11# upper and lower coal seams are mined simultaneously; the upper coal seam floor is blasted by shallow hole blasting at the coal mining face 4, the length of the shallow hole blasting blast hole 6 is 2m, the hole spacing is 0.5m, the charge length is 1.0m, and the charge amount is 2.4kg; in the coal mining face tunnel 5, The upper coal seam floor was deep-hole blasted. The horizontal projection length of deep-hole blasting blast hole 7 (all holes) was greater than 1 / 2 of the length of the coal mining face, which was 130m. The hole spacing was 0.5m. The blast hole section in the upper coal seam floor was charged with explosives. The length of the charge was 8m and the charge was 9.6kg. Water injection was used to soften the upper coal seam floor in the coal mining face tunnel 5. The horizontal projection length of water injection drilling hole 9 was greater than 1 / 2 of the length of the coal mining face, which was 130m. The hole spacing was 10m. The water injection pressure was 6MPa and the water injection time was 3 months. The implementation effect was good: the roof of the coal mining face in the fourth mining area of ​​the 11# coal seam could be safely controlled, and the leading pressure of the coal mining face was basically not apparent.

[0017] from Figure 2 In the middle, the shallow hole blasting blast holes 6 are evenly distributed and arranged in a non-parallel manner, and are provided with an inclination angle of 4-6°; The deep hole blasting blast hole 7 is provided with an inclination angle of 4-6°; The water injection borehole 9 is provided with an inclination angle of 4-6°.

[0018] There are two types of drilling holes in underground mines, one is dry drilling and the other is water drilling; in this embodiment, water drilling is used for drilling. Example 2

[0019] The 15204 coal mining face in the second mining area of ​​the 15# coal seam of a certain mine is buried at a depth of about 320m, the coal seam thickness is 4m, the coal seam interlayer is 1.4m, it is a low-gas mine, the return air chute is 4.2m wide and 3.5m high. A method for mining a very close coal seam of the present invention is implemented in the tunnel. The 15204 coal mining face tunnel is excavated along the bottom plate of the 15# coal seam. Shallow hole blasting is used in the coal mining face to blast the coal seam with gangue. The length of the blasthole is 2m, the hole spacing is 0.5m, the charging length is 0.5m, and the charging amount is 1.2kg. Deep hole blasting is used in the coal mining face tunnel to blast the coal seam with gangue. The horizontal projection length of the blasthole is greater than 1 / 2 of the length of the coal mining face, which is 110m. The hole spacing is 0.5m. The blasthole section in the bottom plate of the upper coal seam is charged with charges. The charging length is 5.5m, and the charging amount is 6.0kg (not greater than 6.6kg). Water injection is used to soften the coal seam with gangue in the coal mining face tunnel. The horizontal projection length of the drill hole is greater than 1 / 2 of the length of the coal mining face, which is 110m. The hole spacing is 10m, the water injection pressure is 6MPa, and the water injection time is 1 month. The implementation effect is good: the roof of the 15204 coal mining face can be safely controlled, and the end hanging roof area is less than 10m 2 , the leading pressure of the coal mining face is basically not apparent. Others are the same as implementation mode 1.

Claims

1. A method for mining coal seams at very close distances, characterized in that: There is no coal mining face in the upper coal seam. The coal mining face is arranged in the lower coal seam. The tunnel is excavated along the bottom plate of the lower coal seam. The support method adopts active support of anchor mesh cables. Shallow hole blasting, deep hole blasting or water injection methods are used to break up the mudstone in the roof between coal seams to improve the recovery rate of the upper coal seam.

2. The method for mining extremely close distance coal seams according to claim 1, characterized in that: The mining method is aimed at the third type of working face that cannot be mined safely, which is an extremely close distance coal seam with an interlayer spacing of less than 2m.

3. The method for mining extremely close distance coal seams according to claim 2, characterized in that: The extremely close distance coal seams refer to: the upper coal seam is a thin or medium thick coal seam with a thickness of less than 1.6m, and the lower coal seam is a thick coal seam.

4. The method for mining a very close distance coal seam according to any one of claims 1 to 3, characterized in that The specific steps are: (1) Arrangement of coal mining face: No coal mining face is arranged in the upper coal seam, but the coal mining face is arranged in the lower coal seam, and the coal mining face tunnel is excavated along the bottom plate of the lower coal seam; (2) Support: anchor net cable support; (3) Mining: First use shallow hole blasting, then use deep hole blasting, and then inject water to soften; First, shallow hole blasting is used in the coal mining face to blast the upper coal seam floor, with a blasthole length of 2m, a hole spacing of 0.5m, a charge length of 0.5~1.0m, and a charge amount of 1.2~2.4kg; then, deep hole blasting is used in the coal mining face tunnel to blast the upper coal seam floor, with a horizontal projection length of the blasthole greater than 1 / 2 of the length of the coal mining face, a hole spacing of 0.5m, and charge loading in the blasthole section of the upper coal seam floor, with a charge length of no more than 8m and a charge amount of no more than 9.6kg; then, water injection is used to soften the upper coal seam floor in the coal mining face tunnel, with a horizontal projection length of the borehole greater than 1 / 2 of the length of the coal mining face, a hole spacing of 5~10m, a water injection pressure of 6~10MPa, and a water injection time of 1~3 months.

5. The method for mining extremely close distance coal seams according to claim 4, characterized in that: Deep hole blasting holes and water injection holes are set up in the coal mining face tunnels at the same time. When the upper coal seam floor and the mining pressure in the mining area can be safely controlled, deep hole blasting is only implemented in the advance coal mining face. When the upper coal seam floor and the mining pressure in the mining area cannot be safely controlled, deep hole blasting is first implemented in the advance coal mining face, and then water injection softening construction is carried out on the coal mining face.

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