Steeply-inclined short-distance coal group horizontal subsection combined coal and gangue mining separate collection and separate control technology

Abstract

The invention provides a separate collection and separate control technology for horizontal subsection combined mining of coal and gangue in a steeply inclined short-distance coal group. Comprising the following steps: step 1, determining a section height H and a mining and releasing ratio n: 8.25 m < = H < = 15m, and 1: 5 < = n < = 1: 2.3; step 2, top coal separate caving control under the side wall effect: (1) increasing the inclination angle of a working face, and (2) optimizing a coal caving mode; and step 3, controlling collapse of the dirt band layer under the action of asymmetric dynamic constraint: (1) presplitting the dirt band layer and top coal, and (2) designing a coal caving sequence. According to the steeply-inclined short-distance coal group horizontal section combined mining coal gangue separate collection and separate control technology provided by the invention, through the three steps from the working face dimension and the trend dimension, the roadway tunneling rate of the working face is reduced, the moving times of the working face are reduced, the top coal caving side wall effect is inhibited, the resource mining rate is increased, and the working efficiency is improved. Invalid transportation and lifting of a large amount of gangues are reduced, and green, safe and efficient mining can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of special coal seam mining, and in particular to a technology for coal gangue separation and control by horizontal segmented combined mining of steeply inclined and closely spaced coal groups. Background Art

[0002] Steeply inclined coal seams are internationally recognized as difficult to mine. They are widely distributed in western my country, and most of them are scarce coal species such as high-quality anthracite and coking coal. Due to the large inclination angle, complex occurrence conditions and coal-forming environment, mining is difficult, and the mining output accounts for less than 5% of the total coal output in the country.

[0003] In recent years, with the increase in mining intensity, many coal mines are faced with the mining of steeply inclined coal seams, and the comprehensive mechanized mining of steeply inclined coal seams under specific conditions has been initially realized. Different development methods are adopted for coal seams with large inclination angles and different thicknesses: (1) For steeply inclined thin and medium-thick coal seams with an inclination angle of less than 60°, the longwall comprehensive mechanized mining method is successfully used. This method effectively improves the efficiency and safety of coal mining through advanced mechanized equipment and technology, and has become the main means of mining such coal seams. (2) For steeply inclined coal seams with a thickness of between 5 and 20 m and an inclination angle of less than 60°, the comprehensive mechanized top coal caving mining method has been successfully applied. This method combines the advantages of mechanized equipment to achieve efficient and precise control of the top coal caving process, further improving the efficiency and safety of coal mining. (3) For steeply inclined coal seams with a thickness of more than 20 m, the horizontal segmented comprehensive mechanized top coal caving mining method has become an effective mining method. This method achieves stable and efficient mining of thick coal seams through horizontal segmentation and combined with comprehensive mechanization technology. (4) The short-wall fully mechanized caving method for steeply inclined thick coal seams with a thickness of 4 to 10 m is still in the experimental stage and requires further research and practical verification.

[0004] For steeply inclined and close-range coal groups, the horizontal segmented comprehensive mining method is explored and practiced. Although it realizes the simultaneous mining and caving of coal seams and interlayer gangue layers, reduces the labor intensity of workers, and improves production efficiency and resource recovery rate; however, this method also causes a large amount of interlayer gangue to mix with top coal, which reduces the resource grade, increases the ineffective lifting and transportation volume of the mine, and increases the cost of coal gangue sorting and solid waste treatment, which in turn leads to an increase in the cost per ton of coal, which is not conducive to achieving green mining.

[0005] In summary, at present, in the mining process of steeply inclined and close-range coal groups, it is not possible to achieve separate collection and control of top coal and interlayer gangue and no lifting of gangue to the surface. Therefore, it is urgent to innovate the technology of coordinated control of top coal recovery and interlayer gangue collapse. Summary of the invention

[0006] The purpose of the present invention is to provide a technology for the separate collection and control of coal gangue in horizontal segmented combined mining of steeply inclined and closely spaced coal groups.

[0007] The present invention is achieved through the following technical solutions:

[0008] The present invention relates to a technology for coal gangue separation and control in horizontal segmented combined mining of steeply inclined and closely spaced coal groups, comprising the following steps:

[0009] Step 1, determination of segment height H and mining ratio n: 8.25m≤H≤15m, 1:5≤n≤1:2.3;

[0010] Among them, the segment height H is the sum of the mining height h1 of the coal mining machine and the top coal caving height h2; the mining and caving ratio n is the ratio of the mining height h1 of the coal mining machine to the top coal caving height h2;

[0011] In the horizontal segmented top coal caving combined mining of steeply inclined and close-range coal groups, it is crucial to reasonably determine the segment height H and the mining-caving ratio n for the top coal release rate and the safety of the roof and floor plates. The segment height H is the sum of the mining height h1 of the coal mining machine and the top coal caving height h2; the mining-caving ratio n is the ratio of the mining height h1 of the coal mining machine to the top coal caving height h2. The two need to be adjusted according to factors such as the thickness, inclination, hardness, degree of joint development, thickness of the interlayer and the advancement speed of the working face. The ideal segment height H and mining-caving ratio n should ensure that the height of the top coal after it is fully crushed and loosened is equal to the mining height h1 of the coal mining machine, so as to avoid insufficient crushing of the top coal due to the excessive top coal caving height h2, accumulation on the inclined floor, difficulty in caving and recovery, or irregular falling of the top coal, serious mixing of gangue and risk of roof caving due to excessive mining height h1 of the coal mining machine;

[0012] The machine mining height h1 is usually related to the support stability and the size of the ventilation section, and the mining height of the heavy support top coal caving working face is mostly set at about 2.5m. Although the adjustment range of the machine mining height h1 is limited, the coal mine safety regulations have clear provisions for the horizontal segmented top coal caving ratio n of steeply inclined thick coal seams, that is, the mining ratio n cannot be less than 1:8, which limits the segment height H, that is, the segment height H≤9h1. The top coal caving height h2 directly affects the cycle caving time. Excessive caving time not only increases the operation time, but also may affect the advancement speed and mine pressure control of the working face, and even increase the risk of spontaneous combustion of the coal seam. Therefore, when controlling the top coal caving height h2, it is necessary to weigh various factors to avoid the disturbance of the interlayer and the problem of difficulty in control caused by excessive height.

[0013] The segment height and the mining ratio are determined by the following three steps:

[0014] ① Engineering analogy method The engineering analogy method can be based on the actual working conditions and the geological characteristics of similar mines or working faces to more reasonably determine the corresponding segment height range under the geological characteristics of the working face.

[0015] The geological characteristic parameters of each coal mine are analyzed based on a large amount of relevant data, and the scope is further narrowed by comparing them with the geological characteristics of the designed mining area.

[0016] ② Numerical calculation uses finite difference numerical simulation software such as FLAC3D and 3DEC to compare the top coal discharge rate and the safety of the roof and floor under three to five segmented height conditions in the range of step ① to determine an optimal value.

[0017] ③Production verification and safety verification

[0018] Based on the specific parameters of the working face, calculate the lowest segment height when reaching full production and compare it with the optimal value determined in step ②. If this optimal value is greater than the lowest segment height when reaching full production and complies with the coal mine safety regulations, it is determined as the final value.

[0019] Step 2: Top coal caving control under side wall effect:

[0020] In the field of mining engineering, the sidewall effect is generally understood as a top coal flow characteristic in the top coal caving process, that is, when the top coal is broken under the pressure of the mine and is ready to be caved, its flow characteristics are affected by the inclined sidewall. For example, the top coal flows along the inclined coal wall or rock wall, forming a certain pattern of accumulation near the coal wall or rock wall. This change in flow characteristics can be regarded as a manifestation of the sidewall effect.

[0021] In order to reduce the influence of the side wall effect on the top coal during the discharge process and avoid the accumulation of the top coal on the coal wall, the present invention increases the inclination of the working face and optimizes the coal discharge method in the working face dimension to improve the top coal discharge rate.

[0022] ①Increase the inclination angle of the working surface

[0023] According to the ore-laying ellipsoid theory, the horizontal segmented top coal caving method is used for steeply inclined and close-range coal groups, and when the working face is arranged horizontally, there is a large amount of triangular coal in the roof that is difficult to release. Assuming that the inclination angle of a coal seam in a certain working face is α, and the beneficial thickness of the coal group is m, in order to reduce the triangular coal area, the inclination angle of the working face θ can be appropriately increased to increase the length of the working face, and the number of top coal caving supports arranged accordingly is increased, so that the boundary of the caving ellipsoid moves to the triangular coal area, achieving the purpose of increasing the top coal release rate η, and at the same time, it is also helpful for gas to be discharged along the top of the tunnel, improving the safety of underground operations, as shown in the following formula:

[0024] The following formula is summarized and concluded from a large number of engineering examples and simulation experiments:

[0025] η=f1(θ,α,m)

[0026] Taking the working face inclination angle θ as the dependent variable, the formula can be obtained:

[0027] θ=f2(η,α,m)

[0028] Where: θ----the inclination angle of the working face. To avoid the inclination angle being too large and affecting the production of the working face, the value range is 0 to 18°;

[0029] η----Top coal discharge rate, according to safety production requirements, needs to be controlled at 75% to 87%;

[0030] α----coal seam inclination, 45~90°;

[0031] m----beneficial thickness of coal group, 10~24m;

[0032] In a certain working face, the coal seam inclination α and the beneficial thickness m of the coal group are regarded as constants. Based on the above functional relationship, the most reasonable working face inclination θ when the top coal release rate η is as large as possible is calculated.

[0033] ②Optimize coal placing method

[0034] The order, number, number of coal discharge ports opened at the same time and the amount of coal discharged in each cycle of the top coal discharge working face are called the coal discharge method. The present invention mainly reduces the influence of the side wall effect by optimizing the order and number of coal discharge, thereby improving the top coal discharge rate.

[0035] For steeply inclined and close-range coal groups, intermittent coal placement can effectively prevent gangue from entering the coal placement opening, thereby reducing mixed gangue and increasing the top coal release rate. By intermittent coal placement, multiple coal placements can be achieved, which can speed up the coal placement speed, thereby increasing the output of the working face and helping to achieve high-yield and high-efficiency production goals.

[0036] When the top coal is caving in horizontal sections, the top coal is thicker, and multi-round caving is particularly suitable for working faces with thicker coal seams. For such coal seams with a thickness greater than 10m, the use of multi-round caving can effectively reduce the mixed gangue rate and improve coal mining efficiency. At the same time, combined with the specific method of the present invention, multi-round caving can gradually loosen the upper top coal, which is beneficial to the subsequent caving operation, and by finely controlling the amount of caving in each round, the risk of large pieces of coal and gangue blocking the caving port can be reduced, the caving port can be kept unobstructed, and the continuity and stability of caving can be improved.

[0037] For steeply inclined and close-range coal groups, the optimized coal caving method is as follows: after cutting the coal seams and interlayers within the mining height range, the lower coal seam adopts multiple rounds of interval caving from the bottom plate to the top plate, and the upper coal seam adopts multiple rounds of interval caving from the top plate to the bottom plate, and the hydraulic support caving port under the interlayer is always closed. Ensure that both coal seams complete the final caving near the interlayer, that is, the upper coal seam first caving in the order of odd-numbered 1, 3, 5, 7... supports, and then caving in the order of even-numbered 2, 4, 6, 8... supports; the lower coal seam first caving in the order of 2n-1, 2n-3, 2n-5, 2n-7... supports, and then caving in the order of 2n, 2n-2, 2n-4, 2n-6... supports. Repeated caving to avoid caving out interlayer rocks during caving. The amount of coal caving each time should not be too large, and the amount of coal caving in each round should be controlled at about 1 / 2 or 1 / 3 of the top coal.

[0038] Step 3: Control of interlayer collapse under asymmetric dynamic constraints

[0039] The interlayer under asymmetric dynamic constraint is effectively controlled mainly in the strike dimension by pre-splitting the interlayer and top coal and designing the coal caving sequence. The following are the technical requirements for the two.

[0040] ① Pre-splitting of interlayer and top coal

[0041] After the working face is formed, hydraulic fracturing with different pre-cracking degrees is carried out on the top coal and interlayer of gangue within 25m in front of the working face in the mining tunnel.

[0042] Specifically, a series of drill faces are arranged in the transport tunnel and the return air tunnel, including a top coal pre-splitting drill face formed by a number of top coal pre-splitting drill holes 21 and a gangue pre-splitting drill face formed by a number of gangue pre-splitting drill holes 22; the top coal pre-splitting drill face, the pre-splitting layer position is obliquely upward from the two tunnels to the middle of the two top coal layers; the gangue pre-splitting drill face, the pre-splitting layer position is obliquely upward from the two tunnels to the middle of the gangue layer 3.

[0043] During hydraulic fracturing, the pre-splitting degree of the top coal meets the coal discharge requirements, and the pre-splitting degree of the interlayer meets the requirements of periodic breaking and collapse, so the pre-splitting degree of the top coal is greater than that of the interlayer. The pre-splitting degree is controlled by the drill face spacing. The pre-splitting drill face spacing of the top coal is designed to be d1, and the pre-splitting drill face spacing of the interlayer is designed to be d2, then d1<d2.

[0044] In addition, according to the empirical formula of coal placement step distance:

[0045] L=(0.15~0.21)[(TM)-h]

[0046] Where: L----coal caving step distance, m;

[0047] T---coal seam thickness, m;

[0048] M---coal cutting height of the shearer, m;

[0049] h----vertical height from the coal opening to the coal seam floor, m;

[0050] It is concluded that the suitable coal discharge step distance for the working face involved in the present invention is two mining and one discharge or three mining and one discharge, in which the cutting depth of the drum coal mining machine is 0.6m. Therefore, in the process of cutting coal to moving the frame, in order to reduce floating coal and prevent roof collapse in front of the frame, the pre-splitting drill surface spacing d1 of the top coal needs to ensure that the top coal within the coal discharge step distance in front of the hydraulic support is in a relatively stable state during this time period. Similarly, the pre-splitting drill surface spacing d2 of the interlayer gangue layer needs to ensure that the interlayer gangue layer within the range of the roof periodic pressure step distance is in a relatively stable state during this time period.

[0051] ② Design coal placing sequence

[0052] In the process of top coal discharge, the traditional coal discharge method often cannot effectively control the interlayer rock, resulting in coal-gangue mixing, affecting coal quality and production efficiency. To overcome this problem, the present invention proposes an optimized coal discharge sequence, which can effectively control the interlayer rock by accurately controlling the coal discharge process and finally fall into the goaf.

[0053] Specifically, in the process of caving coal, the present invention first caves out 60% of the top coal away from both sides of the interlayer, and then caving out the top coal close to both sides of the interlayer.

[0054] A key to this step is to avoid prematurely touching the interlayer, and to avoid disturbance of the interlayer rock and structural instability to the greatest extent, so as to ensure the integrity and stability of the interlayer, effectively prevent coal-gangue mixing, and provide an important guarantee for the interlayer to be stably retained before the rack is moved. Another key to this step is to gradually release most of the top coal away from both sides of the interlayer from far to near, so as to gradually reduce the pressure of the top coal around the interlayer, prevent the top coal from piling up above the coal discharge port, and create favorable conditions for subsequent coal discharge; the interlayer 3 is within the discharge ellipsoid 8, but affected by the pre-cracking degree, coal discharge method and coal discharge sequence, the interlayer rock will not be released.

[0055] It should be added that when the working face is mined, the coal mining machine 13 can pass through the broken interlayer 3, and the coal seam within the machine mining height falls into the front scraper conveyor 11, and the broken top coal and rock are released from the coal discharge port of the hydraulic support 7, fall into the rear scraper conveyor 12, and then are transferred to the belt conveyor 15 by the transfer machine 14, and thus transported out of the working face.

[0056] In addition, an advance support group 17 is used for advance support within the mining tunnel range 20m in front of the working face. Fresh air flows in from the transport level tunnel and blows into the working face. The polluted air flow 18 flows from the working face to the return air level tunnel 6 and finally flows out from the return air level tunnel 6.

[0057] The present invention has the following advantages:

[0058] (1) The technology of coal gangue separation and control in horizontal segmented joint mining of steeply inclined close-range coal groups involved in the present invention is based on the technology of coal gangue separation and control in horizontal segmented joint mining of top coal. In the working face dimension, the top coal separation and control are determined by segment height, mining and caving ratio, and side wall effect. In the strike dimension, the collapse of the interlayer gangue is controlled by asymmetric dynamic constraints, so as to achieve the purpose of green, safe and efficient mining of steeply inclined close-range coal groups with a thickness of 20 to 30 meters (single layer thickness is 5 to 12 meters, and the thickness of the interlayer gangue is less than 9 meters).

[0059] (2) The present invention reduces the tunneling rate of the steeply inclined and close-range coal group mining working face by determining a reasonable segment height and mining-release ratio in the working face dimension, reduces the number of working face moves, improves mining efficiency, and is beneficial to safe and efficient production in the mine.

[0060] (3) The present invention achieves effective top coal release and improves resource recovery rate by suppressing the side wall effect of top coal release in the working face dimension. At the same time, the method of appropriately increasing the working face inclination angle also helps gas to be discharged along the top of the tunnel, which is beneficial to ensure ventilation safety and improve the safety of underground workers.

[0061] (4) The present invention controls the collapse of the interlayer gangue under the action of asymmetric dynamic constraints in the strike dimension, so that the interlayer gangue collapses periodically in the goaf after the top coal is released, thereby reducing the ineffective lifting and transportation volume of the mine, reducing energy consumption and operating costs, and increasing the actual production capacity of the mine. At the same time, it avoids the waste of land resources caused by large-scale open-air stacking of coal gangue, reduces the spontaneous combustion of gangue mountains and the emission of harmful gases, and helps to achieve green mining and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a plan view of the layout of the steeply inclined and close-distance coal group fully mechanized caving combined mining working face involved in the present invention;

[0063] Figure 2 It is a schematic diagram of the arrangement of pre-splitting drilling holes for the fully mechanized caving combined mining of steeply inclined and close-range coal groups involved in the present invention;

[0064] Figure 3 A triangular coal distribution diagram of a steeply inclined close-range coal group fully mechanized caving combined mining working face with an inclination angle of 0° involved in the present invention;

[0065] Figure 4 A triangular coal distribution diagram of a steeply inclined close-range coal group fully mechanized caving combined mining working face with an inclination angle of 10° involved in the present invention;

[0066] The attached drawings are marked as follows: 1 is the upper coal seam; 2 is the lower coal seam; 3 is the interlayer of gangue; 4 is the goaf of the previous section; 5 is the transport lane; 6 is the return air lane; 7 is the hydraulic support; 8 is the releasing ellipsoid; 9 is the triangular coal area of ​​the horizontal working face; 10 is the triangular coal area of ​​the working face with an inclination of 10°; 11 is the front scraper conveyor; 12 is the rear scraper conveyor; 13 is the coal mining machine; 14 is the transfer machine; 15 is the belt conveyor; 16 is the goaf of this section; 17 is the advance support group; 18 is the dirty air flow; 19 is the fresh air flow; 20 is the coal transportation line; 21 is the top coal pre-splitting drill hole; 22 is the interlayer of gangue pre-splitting drill hole. DETAILED DESCRIPTION

[0067] The present invention is described in detail below in conjunction with specific embodiments. It should be noted that the following embodiments are only further descriptions of the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0068] Example

[0069] This embodiment relates to a technology for combined mining of top coal by horizontal segmented caving of steeply inclined and close-range coal groups, which is applicable to steeply inclined thick coal seams with a coal seam inclination angle greater than 45°, a coal seam thickness of 4 to 12 m, and a gangue layer thickness of less than 9 m. Referring to the schematic diagram, the following steps are specifically included: Figure 1 , Figure 2 As shown, 4 is the goaf of the previous section; 11 is the front scraper conveyor; 12 is the rear scraper conveyor; 13 is the coal mining machine; 14 is the transfer machine; 15 is the belt conveyor; 16 is the goaf of this section; 17 is the advanced support group; 18 is the polluted air flow; 19 is the fresh air flow; 20 is the coal transportation line; 21 is the top coal pre-splitting drill hole; 22 is the interlayer pre-splitting drill hole.

[0070] 1. Determination of segment height and mining ratio

[0071] A mine has an annual output of 400,000 tons. It is known that the annual production time is 330 days, the daily cycle number is 9, the coal mining machine cutting depth is 0.8m, and the mining height is 2.5m. Under the goaf 4 of the previous section, the upper coal seam 1 is 6.2m thick, the interlayer 3 is siltstone 6.8m thick, the lower coal seam 2 is 7.8m thick, the coal seam inclination α is 57°, and the apparent density of coal is 1.38g / cm 3 The recovery rate is 80%, which belongs to the steeply inclined close-distance thick coal seam group. Taking into account multiple factors, the mining and release ratio is stipulated as follows: 1:5≤n≤1:2.3.

[0072] Determining the specific values ​​of the segment height and the mining-releasing ratio includes the following steps:

[0073] ① As shown in Table 1, the basic situation of each coal mine adopting small-section high-level segmented mining according to different geological characteristics is intended to provide a reference for engineering analogy.

[0074] Table 1

[0075]

[0076] From the data in Table 1, it can be seen that the determination of segment height is related to multiple parameters such as coal seam inclination, coal seam thickness, and roof and floor hardness coefficients.

[0077] The engineering analogy is based on a large number of coal mines that use small-section high-level segmented top coal mining method in coal seam mining. The geological characteristic parameters of the above coal mines are analyzed and compared with the geological characteristics of the mining area in the embodiment, and it is roughly determined that the segment height is between 9.5 and 12 meters.

[0078] ② Finite difference numerical simulation software such as FLAC3D and 3DEC were used to compare the top coal release rate and the safety of the roof and floor plates under different segment heights between 9.5 and 12 m. It was found that when the segment height was 11 m, the release rate was the highest and the safety of the roof and floor plates could be guaranteed.

[0079] ③Based on the above geological characteristics and working conditions, it is calculated that the segment height is at least 10.9m when reaching full production. That is, the optimal segment height of step ②, 11m, has been verified by production.

[0080] In summary, it is determined that the segment height in this embodiment is 11m and the mining-to-release ratio is 1:3.4, which complies with the safety regulations of coal mines.

[0081] In this specific embodiment, the heights of adjacent segments are H1=H2=...=H n =11m.

[0082] 2. Control of top coal discharge due to side wall effect

[0083] ①Increase the inclination angle of the working surface

[0084] The following formula is summarized and concluded from a large number of engineering examples and simulation experiments:

[0085] θ=f2(η,α,m)

[0086] Where: θ----the inclination angle of the working face. To avoid the inclination angle being too large and affecting the production of the working face, the value range is 0 to 18°;

[0087] η----Top coal discharge rate, according to safety production requirements, needs to be controlled at 75% to 87%;

[0088] α----coal seam inclination, 57°;

[0089] m----Beneficial thickness of coal group, 14m.

[0090] In the working face of this embodiment, the coal seam inclination α and the coal group useful thickness m remain unchanged. According to the above functional relationship, when the top coal discharge rate η is 87%, the working face inclination θ is 10°. Therefore, the working face inclination is designed to be 10°. The triangular coal area 10 of the working face with an inclination of 10° is shown in FIG. Figure 4 When θ is 0°, it is the triangular coal area 9 of the horizontal working face. Figure 3 shown.

[0091] ②Optimize coal placing method

[0092] For the coal group of this embodiment, the optimized coal discharge method is as follows: after cutting the upper coal seam 1, lower coal seam 2 and interlayer 3 within the mining height range, the lower coal seam 2 adopts multiple rounds of interval discharge from the bottom plate to the top plate, and the upper coal seam 1 adopts multiple rounds of interval discharge from the top plate to the bottom plate, and the coal discharge port of the hydraulic support 7 under the interlayer 3 is always closed. Ensure that both coal seams complete the final coal discharge near the interlayer 3, that is, the upper coal seam 1 first discharges coal in the order of 1, 3, 5, 7..., and then in the order of 2, 4, 6, 8...; the lower coal seam 2 first discharges coal in the order of 2n-1, 2n-3, 2n-5, 2n-7..., and then in the order of 2n, 2n-2, 2n-4, 2n-6... Repeatedly release coal to avoid releasing the interlayer 3 during the coal release process. The amount of coal released each time should not be too large. The amount of coal released in each round should be controlled at about 1 / 3 of the top coal.

[0093] 3. Control of interlayer under asymmetric dynamic constraint

[0094] ① Pre-splitting of interlayer and top coal

[0095] After the working face is formed, hydraulic fracturing with different pre-cracking degrees is performed on the top coal and interlayer 3 within 25m in front of the working face in the mining tunnel.

[0096] Specifically, a series of drill faces are arranged in the transport tunnel 5 and the return air tunnel 6, including a top coal pre-splitting drill face formed by a number of top coal pre-splitting drill holes 21 and an interlayer pre-splitting drill face formed by a number of interlayer pre-splitting drill holes 22; a top coal pre-splitting drill face, in which the pre-splitting layer position is obliquely upward from the two tunnels to the middle of the two top coal layers; a pre-splitting drill face for the interlayer 3, in which the pre-splitting layer position is obliquely upward from the two tunnels to the middle of the interlayer 3.

[0097] During the hydraulic fracturing process, the pre-cracking degree of the top coal meets the coal discharge requirements, and the pre-cracking degree of the interlayer 3 meets the requirements of periodic breaking and collapse into the goaf 16 of this section. The pre-cracking degree is controlled by the drill face spacing. The pre-cracking drill face spacing of the top coal is designed to be d1, and the pre-cracking drill face spacing of the interlayer 3 is designed to be d2, then d1<d2.

[0098] According to the empirical formula of coal caving step distance:

[0099] L=(0.15~0.21)[(TM)-h]

[0100] Where: L----coal caving step distance, m;

[0101] T---coal seam thickness, take 11m;

[0102] M---coal cutting height of shearer 16, take 2.5m;

[0103] h----The vertical height from the coal opening to the coal seam floor is 1.5m.

[0104] It is calculated that the suitable coal caving step distance for the coal caving working face of this embodiment is two mining and one caving. Therefore, during the process of coal cutting to frame moving, the pre-splitting drill face spacing d1 of the top coal needs to ensure that the 1.6m in front of the hydraulic support 7 and the top coal are in a relatively stable state during this time period. Similarly, the pre-splitting drill face spacing d2 of the interlayer gangue layer needs to ensure that the interlayer gangue layer 3 within the range of the roof periodic pressure step distance is in a relatively stable state during this time period.

[0105] ② Design coal placing sequence

[0106] During the top coal caving process, 60% of the top coal away from both sides of the interlayer 3 is caved out first, and then the top coal close to both sides of the interlayer 3 is caved out.

[0107] like Figure 3 As shown, the interlayer 3 is within the discharge ellipsoid 8, but affected by the pre-splitting degree, coal discharge method and coal discharge sequence, the interlayer 3 rock will not be discharged.

[0108] It should be added that when the working face is mined, the coal mining machine 13 can pass through the broken interlayer 3, and the coal seam within the machine mining height falls into the front scraper conveyor 11, and the broken top coal and rock are discharged from the coal discharge port of the hydraulic support 7 and fall into the rear curved scraper conveyor 12, and then are transferred to the belt conveyor 15 by the transfer machine 14, so as to be transported out of the working face, that is, Figure 1 Coal transportation route 20 is shown.

[0109] In addition, an advance support group 17 is used for advance support within the mining tunnel range 20m in front of the working face. Fresh air flow 19 flows in from the transport level tunnel 5 and blows into the working face. The polluted air flow 18 flows from the working face to the return air level tunnel 6 and finally flows out from the return air level tunnel 6.

[0110] In summary, the pre-splitting degree of the interlayer 3 and top coal and the coal placing sequence must meet the following requirements in the overall coal mining process:

[0111] a. After the working face is formed, hydraulic pre-cracking is carried out by arranging appropriate pre-cracking drill faces so that the pre-cracking degree of the top coal meets the requirements for coal release, and the pre-cracking degree of the interlayer 3 meets the requirements for periodic breaking and collapse into the goaf 16 of this section.

[0112] b. During the process from coal cutting to frame moving, it is necessary to ensure that the interlayer 3 and top coal 1.6m in front of the hydraulic support 7 are in a relatively stable state during this period of time.

[0113] c. During the coal caving process, the hydraulic support 7 and the top coal work together to ensure that the interlayer 3 does not fall off on a large scale.

[0114] d. During the coal discharge process, the top coal away from both sides of the interlayer 3 is first discharged. After about 60% of the top coal is discharged, the top coal near the interlayer 3 is discharged.

[0115] In summary, the present invention reduces the tunneling rate of the steeply inclined and close-distance coal group mining working face by determining a reasonable segment height and mining ratio, reduces the number of working face moves, improves mining efficiency, and is conducive to safe and efficient production of the mine; the present invention achieves effective top coal release and improves resource recovery rate by suppressing the side wall effect of top coal release in the working face dimension. At the same time, the method of appropriately increasing the inclination of the working face also helps to discharge gas along the top of the tunnel, which is conducive to ensuring ventilation safety and improving the safety of underground workers; in the strike dimension, the present invention controls the collapse of the interlayer under the action of asymmetric dynamic constraints, so that the interlayer collapses periodically in the goaf after the top coal is released, reducing the ineffective lifting and transportation volume of the mine, reducing energy consumption and operating costs, and increasing the actual production capacity of the mine. At the same time, it avoids the waste of land resources caused by large-scale open-air stacking of coal gangue, reduces the spontaneous combustion of gangue mountains and the emission of harmful gases, and helps to achieve green mining and environmental protection.

[0116] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which will not affect the essence of the present invention.

Claims

1. A technology for combined mining of coal gangue and separate collection and control in horizontal segmentation of steeply inclined and closely spaced coal groups, characterized in that: The following steps are involved: Step 1, determination of segment height H and mining ratio n: 8.25m≤H≤15m, 1:5≤n≤1:2.3; Among them, the segment height H is the sum of the mining height h1 of the coal mining machine and the top coal caving height h2; the mining and caving ratio n is the ratio of the mining height h1 of the coal mining machine to the top coal caving height h2; Step 2: Top coal caving control under side wall effect: ①Increase the inclination angle of the working surface Assuming that the coal seam inclination of a certain working face is α, the useful thickness of the coal group is m, the formula for the top coal release rate η is as follows: η=f1(θ,α,m) Taking the working face inclination angle θ as the dependent variable, the formula can be obtained: θ=f2(η,Δ,m) Where: θ----the inclination angle of the working surface, θ is 0~18°; η----top coal discharge rate, η is 75% to 87%; α----coal seam inclination, α is 45~90°; m----beneficial thickness of coal group, m is 10~24m; In a certain working face, the coal seam inclination angle α and the coal group beneficial thickness m are regarded as constant values. According to the above functional relationship, the most reasonable working face inclination angle θ when the top coal discharge rate η is as large as possible is calculated; ②Optimize coal placing method After the coal seams and interlayers (3) within the mining height range are cut, the lower coal seam (2) is discharged in multiple rounds from the bottom plate to the top plate, and the upper coal seam (1) is discharged in multiple rounds from the top plate to the bottom plate. The coal discharge port of the hydraulic support under the interlayer is always closed. The upper coal seam (1) first discharges coal in the order of odd-numbered supports, and then discharges coal in the order of even-numbered supports; the lower coal seam (2) first discharges coal in the order of 2n-1, 2n-3, 2n-5, 2n-7, etc., and then discharges coal in the order of 2n, 2n-2, 2n-4, 2n-6, etc., and discharges coal repeatedly, with the amount of coal discharged in each round being 1 / 2 to 1 / 3 of the top coal; Step 3: Control of interlayer collapse under asymmetric dynamic constraints: ① Pre-splitting of interlayer and top coal After the working face is formed, hydraulic fracturing with different pre-cracking degrees is carried out on the top coal and interlayer of gangue within 25m in front of the working face in the mining tunnel, specifically: A series of drill faces are arranged in the transport lane and the return air lane, including a top coal pre-splitting drill face formed by a plurality of top coal pre-splitting drill holes (21) and a gangue layer pre-splitting drill face formed by a plurality of gangue layer pre-splitting drill holes (22), the top coal pre-splitting drill face, the pre-splitting layer position is from the two lanes obliquely upward to the middle of the two top coal layers; the gangue layer pre-splitting drill face, the pre-splitting layer position is from the two lanes obliquely upward to the middle of the gangue layer (3); During hydraulic fracturing, the pre-cracking degree of the top coal is greater than that of the interlayer. The pre-cracking degree is controlled by the drill face spacing. The drill face spacing of the top coal pre-cracking is designed to be d1, and the drill face spacing of the interlayer is designed to be d2, then d1<d2; Empirical formula for coal caving step distance: L=(0.15~0.21)[(TM)-h] Where: L----coal caving step distance, m; T---coal seam thickness, m; M---coal cutting height of the shearer, m; h----vertical height from the coal opening to the coal seam floor, m; The coal caving step distance of the working face is two mining and one caving or three mining and one caving; among which, the cutting depth of the drum coal mining machine is 0.6m; ② Design coal placing sequence First, release 60% of the top coal away from both sides of the interlayer, and then release the two sides of the top coal close to the interlayer (3).

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