Double-strip mixed mining method for hard and thin coal seam in strip mine

Abstract

The invention discloses a double-strip mixed mining method for a hard and thin coal seam in a strip mine. The method comprises the steps of strip division, digging of a communicated roadway, digging of a cut hole and arrangement of equipment, strip mixed transverse mining, strip continuing and stripping follow-up, mining circulation and the like. A transverse mining mode is adopted, so that frequent lateral movement of the wheel bucket excavator is avoided; horizontal drilling is adopted, the blasting mode is implemented step by step, reasonable blasting is achieved, and coal and rock mixing is avoided; reverse throwing blasting can throw and gather the thin coal seam from an original tiled state to form a coal pile, rapid concentration of the thin coal seam is achieved, and the economical and reasonable height needed by wheel bucket excavation is met. Different transportation modes are adopted at different positions, so that the transportation efficiency is effectively improved, and the system stability is ensured; the strip-type mining avoids concentrated and massive advanced stripping, so that the stripping pressure is relieved, and spontaneous combustion of the coal seam is effectively avoided. And by adopting a following stripping mode, each step pressed by the thin coal seam is timely and gradually released, and normal propulsion of the strip mine is ensured.

Description

Technical Field

[0001] The invention relates to an open-pit mixed mining method, in particular to a double-strip mixed mining method for a hard and thin coal seam in an open-pit mine. Background Art

[0002] Thin coal seams are an important part of the coal reserves in open-pit mines, especially for large and extra-large open-pit mines, where the reserves of thin coal seams are considerable and the mining benefits are obvious. At present, the commonly used methods for mining thin coal seams in open-pit mines mainly include: small hydraulic excavators or high-horsepower front loaders directly mining thin coal seams, bulldozers equipped with loosening plows and front loaders jointly mining thin coal seams, and open-pit miners or coal plows directly mining thin coal seams. The above methods each have their own advantages, but overall, there are the following disadvantages: First, the above schemes are poorly adaptable to medium-hard coal seams. Second, the schemes are all intermittent processes with low mining efficiency, which affects the overall advancement speed of open-pit mines. Third, the schemes are all similar to the "layered peeling" method. For thin coal seams with larger thickness, repeated mining is required, which affects the mining capacity and increases the mining cost. At the same time, multiple mining will aggravate environmental pollution such as dust. Fourth, during blasting, due to the low thickness of the coal seam, the short blasting borehole, the poor charging and blasting effects, and the low coal pile after blasting, it is impossible to meet the economically reasonable height required for mining equipment excavation.

[0003] Bucket wheel excavator + conveyor has the characteristics of continuous operation, large excavation height and low cost. If it can overcome the adverse effects of coal seam hardness and thickness, it will play an important role in open-pit thin coal seam mining. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a double-strip mixed mining method for hard thin coal seams in open-pit mines, which avoids coal-rock mixing, achieves rapid concentration of thin coal seams, ensures normal advancement of open-pit mines, and improves mining efficiency.

[0005] To achieve the above object, the present invention provides the following technical solution: a double-strip mixed mining method for hard and thin coal seams in open-pit mines, comprising the following steps: Strip division: along the open-pit mine advancement direction, the thin coal seams to be mined within the annual advancement range are divided into several parallel mining strips; Excavation of connecting tunnels: on the roof of the thin coal seam near one side of the open-pit mine, a connecting tunnel is excavated along the direction of the open-pit mine; each stripping step above the connecting tunnel is stripped in advance to expose the top of the thin coal seam, and the thin coal seam in the connecting tunnel is blasted and mined by horizontal blasting until the end of the connecting tunnel; excavation of cutting eyes and equipment layout: starting from the connecting tunnel, the stripping step above the thin coal seam in the first mining strip is stripped in advance and then the first cutting eye groove is excavated on the first mining strip by horizontal blasting. After the construction of the first cutting eye groove is completed, the thin coal seam in the cutting eye groove is blasted by horizontal blasting, and a bucket wheel excavator is arranged in the cutting eye groove, and a single bucket truck is used to transport coal; in the connecting tunnel, a telescopic centralized conveyor is arranged from the second mining strip to the end of the connecting tunnel, and at the end of the connecting tunnel, a lifting conveyor connected to the centralized conveyor is arranged across the end wall; Mixed strip horizontal mining: when lagging behind the first mining strip X, the second cutting slot is excavated in the same way as the first cutting slot, and then a bucket wheel excavator and a transfer conveyor connected to a centralized conveyor are arranged in the second cutting slot; the thin coal seam in the second mining strip is blasted by reverse throwing blasting; the first mining strip and the second mining strip are combined to carry out double-strip mixed mining of the thin coal seam; Strip connection and stripping follow-up: When there is D1 time left before the first mining strip is mined to the boundary, start to dismantle the transfer conveyor, and dig the third cut groove in the same way as the first cut groove. Then, a bucket wheel excavator and a transfer conveyor connected to the centralized conveyor are arranged in the third cut groove. The thin coal seam in the third mining strip is blasted by reverse throwing blasting. The centralized conveyor in the connecting tunnel is telescopic, and the telescopic head is located on the side of the second mining strip. Mining cycle: When there is still time D1 left before the second mining strip is mined to its limit, the fourth cutting slot and the thin coal seam mining in the fourth mining strip will be started in the same way as above, and so on, to realize the continuous cycle of mining strips.

[0006] Furthermore, the plurality of parallel mining strips are numbered sequentially along the open-pit mine advancement direction, the width of the first mining strip along the open-pit mine advancement direction is not less than K, and the width of subsequent mining strips is not less than 1.5K, where K is a reasonable mining width of a bucket wheel excavator.

[0007] Furthermore, the horizontal blasting method is: drilling horizontal separation boreholes along the coal-rock boundary, and drilling horizontal blasting boreholes inside the thin coal seam; the above two types of drilling depths are ultra-deep bucket wheel excavators with a reasonable mining width of 1-2m; the separation boreholes are filled with a small amount of explosives and detonated before the blasting boreholes. The main purpose is to separate the thin coal seam from the rock to avoid blasting the rock under the thin coal seam during blasting, resulting in coal-rock mixing; the blasting boreholes are coupled with explosives and blasted, and the drilling density and charge amount are adjusted with the goal of achieving reasonable crushing of the thin coal seam.

[0008] Furthermore, the stripping width of the advanced transverse stripping exceeds the width of the mining strip in which it is located by a distance of a safety step.

[0009] Furthermore, the reverse throwing blasting method is: Along the direction of open-pit mine advancement, the mining strip is divided into three areas, namely, the throwing area, the throwing loose transition area and the loose area, at equal intervals from outside to inside; multiple rows of throwing drill holes are arranged at intervals in the throwing area, and the throwing drill holes are inclined inward, and the inclination angle increases row by row, the inclination angle of the outermost row of throwing drill holes is 30°, and the inclination angle of the innermost row of throwing drill holes is 45°; the depth of the ultra-deep thin coal seam of the throwing drill hole is 1-2m; the throwing drill hole is coupled with charging and blasting, the purpose of which is to reversely throw the coal to the side of the stripping step after charging and blasting, and the design of the drilling angle The main purpose is to maximize the throwing effect and ensure that the outer thin coal seam can be fully thrown to the side of the stripping step; multiple rows of mixed drill holes are arranged at intervals in the loose transition zone of throwing, and the mixed drill holes are inclined inward, and the inclination angle increases row by row. The inclination angle of the outermost row of throwing drill holes is 45°, and the inclination angle of the innermost row of throwing drill holes is 90°; the depth of the ultra-deep thin coal seam of the mixed drill hole is 1-2m; the mixed drill hole is coupled with charging and blasting. The purpose is to take into account blasting and throwing. After charging and blasting, the coal is blasted and thrown in reverse to the side of the stripping step. Because this area is close to the stripping step, the effect of blasting is to loosen and throw the coal at the same time. The closer the coal is to the stripping step, the less it needs to be thrown. It only needs to be loosened by blasting in situ to facilitate subsequent excavation. Multiple rows of loose drill holes are arranged at intervals in the loose area, and the loose drill holes are set vertically. The depth of the mixed drill hole for ultra-deep thin coal seams is 1-2m. The coupled charging and blasting in the borehole is for the purpose of loosening by blasting. After the charging and blasting, the coal is loosened in situ to facilitate subsequent excavation.

[0010] Furthermore, during the mining process of the first mining strip, the stripping steps below the platform where the thin coal seam is located are advanced accordingly, and during the mining process, the spoil dump is advanced accordingly; the advancement degree is the same as the width of the first mining strip or slightly smaller than the strip width, with the aim of timely and gradually releasing the steps pressed down by the thin coal seam to ensure the normal advancement of the open-pit mine.

[0011] Furthermore, the length of the connecting tunnel in the advancement direction of the open-pit mine is not less than the annual advancement rate of the open-pit mine, and is preferably equal to or slightly greater than the annual advancement rate of the open-pit mine; the width of the connecting tunnel in the strip extension direction is not less than B, B=Bw+2Harctanβ+By+A, wherein Bw is the width required for the operation of small excavation equipment, H is the coal seam height, β is the coal seam slope angle, By is the width of the conveyor, and A is the safety distance between equipment.

[0012] Furthermore, when the first mining strip X is delayed in the strip mixed horizontal mining step, X=Bw+A+Lb2+A1, wherein Bw is the width required for the operation of the small excavation equipment, A is the safety distance between the equipment, Lb2 is the length of each blasting of the second mining strip in the extension direction of the strip, and A1 is the safety distance between the blasting position of each second mining strip and the mining and transportation equipment of the first mining strip.

[0013] Furthermore, the first eye-cutting groove is as wide as the first mining strip, and the length of the first eye-cutting groove along the extension direction of the strip is not less than L, L=Bw+Bd+A, wherein Bw is the width required for the operation of small excavation equipment, Bd is the width required for the rotation of a single-bucket truck, and A is a safe distance between equipment; the second eye-cutting groove is as wide as the second mining strip, and the length of the second eye-cutting groove along the extension direction of the strip is not less than L, L=Bw+A, wherein Bw is the width required for the operation of small excavation equipment, A is the safety distance between equipment, and L is not less than the minimum layout length of the converted belt conveyor.

[0014] Compared with the prior art, the present invention adopts a horizontal mining method to avoid frequent lateral movement of the bucket wheel excavator; adopts horizontal drilling and implements blasting in steps, which not only achieves reasonable blasting but also avoids coal-rock mixing. Reverse throwing blasting can throw and gather thin coal seams from the original flat state to form a coal pile, realize the rapid concentration of thin coal seams, and meet the economic and reasonable height required by bucket wheel excavation. Different transportation methods are used in different positions to effectively improve transportation efficiency and ensure system stability. Strip mining avoids a large amount of concentrated advanced stripping, which not only relieves the stripping pressure, but also effectively avoids spontaneous combustion of coal seams. The follow-up stripping method timely and gradually releases the various steps pressed down by the thin coal seam to ensure the normal advancement of the open-pit mine. The use of interconnected tunnels provides sufficient and effective space for the implementation of the scheme and avoids excessive occupation of step platforms. The design of the lifting conveyor across the steps will not affect the transportation of the mine end wall. The entire thin coal seam can be mined at one time, avoiding environmental pollution and improving mining efficiency. The implementation process of the present invention is simple, and no additional technicians and construction equipment are required, which avoids cost increase. The dual-strip simultaneous mining improves the mining efficiency of thin coal seams and avoids the impact on mine advancement. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of a top view of the strip mixed horizontal mining and its preceding steps of the present invention; Figure 2 It is a schematic diagram of the horizontal blasting method of the present invention; Figure 3 It is a schematic diagram of the reverse throwing blasting method of the present invention; Figure 4 This is a schematic diagram of a coal pile after reverse throwing blasting according to the present invention; Figure 5It is a top view schematic diagram of the strip connection and stripping follow-up and the preceding steps of the present invention; In the figure: 1-open pit mine advancement direction; 2-thin coal seam; 3-mining strip; 3.1-first strip; 3.2-second strip; 3.3 third strip; 4-end wall; 5-connecting tunnel; 6-strip extension direction; 7-peeling step; 8-step where thin coal seam is located; 9-coal-rock boundary; 10-separation borehole; 11-blasting borehole; 12-rock; 13-wheel bucket excavator; 14-single bucket truck; 15-central conveyor; 16-telescopic head; 17-lifting conveyor; 18-second cutting eye trough; 19-converting conveyor; 20-throwing area; 21-throwing loose transition area; 22-loose area; 23-coal pile; 24-third cutting eye trough; 25-dumping yard. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with the accompanying drawings.

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] The present invention provides a double-strip mixed mining method for hard and thin coal seams in open-pit mines, comprising the steps of strip division, excavation of connecting tunnels, excavation of cutting holes and equipment layout, strip mixed horizontal mining, strip connection and stripping follow-up, mining cycle and the like.

[0019] Strip division: Figure 1 As shown, along the open-pit mine advancement direction 1, the thin coal seam 2 that needs to be mined within the annual advancement range is divided into several parallel mining strips 3; they are numbered sequentially along the open-pit mine advancement direction 1, namely the first strip 3.1, the second strip 3.2, the third strip 3.3, until the last Nth strip, the width of the first mining strip 3, i.e. the first strip 3.1, along the open-pit mine advancement direction 1 is not less than K, and the widths of the subsequent mining strips 3, i.e. from the second strip 3.2 to the Nth strip, are not less than 1.5K, wherein K is the reasonable mining width of the bucket wheel excavator 13, which is generally 20-30m.

[0020] Excavation of connecting tunnels: on the roof of the thin coal seam 2 near one side end wall 4 of the open-pit mine, preferably near the end wall 4 on the side of the industrial square, along the advancement direction 1 of the open-pit mine, excavate connecting tunnels 5; the length of the connecting tunnels 5 in the advancement direction 1 of the open-pit mine is not less than the annual advancement rate of the open-pit mine, and is preferably equal to or slightly greater than the annual advancement rate of the open-pit mine; the width of the connecting tunnels 5 in the strip extension direction 6, that is, from the end wall 4 on one side to the end wall 4 on the other side, is not less than B, B=Bw+2Harctanβ+By+A, wherein: Bw is the width required for the operation of small excavation equipment, H is the coal seam height, β is the coal seam slope angle, By is the width of the belt conveyor, and A is the safety distance between equipment.

[0021] Each stripping step 7 above the connecting tunnel 5 is stripped in advance by a combination + segmentation method. By increasing or decreasing the height of 1-2 stripping steps above and below the thin coal seam 2, the parameters of the stripping step 7 are adjusted to expose the top of the thin coal seam 2 and to be at the top of the step where it is located, ensuring that the height of the step 8 where the thin coal seam is located does not exceed the maximum drilling height of the horizontal drilling rig; the thin coal seam 2 in the connecting tunnel 5 is blasted by horizontal blasting, and along the direction of advancement of the open-pit mine, small excavation equipment such as excavators are used to mine the thin coal seam 2 in the connecting tunnel 5 until mining reaches the end of the connecting tunnel 5, at which time the construction of the connecting tunnel 5 is completed.

[0022] like Figure 2 As shown, the horizontal blasting method is: drilling a horizontal separation borehole 10 along the coal-rock boundary 9, and drilling a horizontal blasting borehole 11 inside the thin coal seam 2; the above two types of drilling depths are ultra-deep bucket wheel excavators with a reasonable mining width of 1-2m; the separation borehole 10 is filled with a small amount of explosives and is detonated before the blasting borehole 11. The main purpose is to separate the thin coal seam 2 from the rock 12 to avoid blasting the rock 12 under the thin coal seam 2 during blasting, resulting in coal-rock mixing; the blasting borehole 11 is coupled with explosives and blasted, and the drilling density and charge amount are adjusted to achieve reasonable crushing of the thin coal seam 2.

[0023] Excavation and equipment layout: starting from the connecting tunnel 5 and based on the adjusted stripping step 7 parameters, the stripping step 7 above the thin coal seam 2 in the first strip 3.1 is stripped in advance and transversely, that is, the stripping direction is the same as the strip extension direction 6, so that the thin coal seam 2 is gradually exposed. The stripping width of the advanced transverse stripping is wider than the width of the first strip 3.1 by a safety step, generally about 10m, in order to prevent the falling rocks from above from affecting the operation of the equipment; the first cutting groove is excavated on the first strip 3.1 by horizontal blasting. The first cutting groove is the same width as the first strip 3.1, and the length of the first cutting groove along the strip extension direction 6 is not less than L, L=Bw+Bd+A, where Bw is the length of the small excavation equipment. The width required for the operation of the equipment is Bd, the width required for the rotation of the single-bucket truck is A, and the safety distance between the equipment is; after the construction of the first cutting groove is completed, the stripping step 7 above the thin coal seam 2 in the first strip 3.1 continues to advance the horizontal stripping, and following the horizontal stripping, the thin coal seam 2 in the first strip 3.1 is blasted in a continuous horizontal blasting manner along the strip extension direction 6 to reduce the hardness of the coal seam, and a bucket wheel excavator 13 is arranged in the cutting groove, and a single-bucket truck 14 is matched to carry out horizontal mining of the thin coal seam 2 in the first strip 3.1, and the mining speed lags behind the upper stripping step 7 by a safety step to prevent falling rocks from above from affecting the safety of the equipment; the coal mined by the bucket wheel excavator 13 is transported to the surface by the single-bucket truck 14.

[0024] In the connecting tunnel 5, a telescopic centralized conveyor 15 is arranged from the second belt 3.2 to the end of the connecting tunnel 5. The centralized conveyor 15 is a telescopic belt conveyor. The telescopic head 16 of the centralized conveyor 15 is located on the side of the second belt 3.2. The transportation capacity of the centralized conveyor 15 is preferably 1.2 times that of a thin coal seam in one belt. At the end of the connecting tunnel 5, a lifting conveyor 17 connected to the centralized conveyor 15 is arranged across the end wall 4. The lifting conveyor 17 is responsible for lifting the coal to the surface of the open-pit mine. When the lifting conveyor 17 crosses the end wall steps, it is elevated to avoid affecting the transportation of the end wall 4.

[0025] Strip mixed horizontal mining: when lagging behind the first strip 3.1X, X=Bw+A+Lb2+A1, where Bw is the required width for small excavation equipment, A is the safe distance between equipment, Lb2 is the length of each blasting of the second mining strip 3 in the strip extension direction 6, and A1 is the safe distance between each blasting position of the second mining strip 3 and the mining and transportation equipment of the first mining strip 3; starting from the connecting tunnel 5, the second strip 3.2 inner thin coal seam 2 above the stripping step 7 advances horizontally Stripping, the stripping width of the advanced horizontal stripping exceeds the width of the second strip 3.2 by the distance of a safety step; after the thin coal seam 2 is exposed, the second eye-cutting groove 18 is excavated in the same way as the first eye-cutting groove. The second eye-cutting groove 18 is the same width as the second mining strip 3, and the length of the second eye-cutting groove 18 along the strip extension direction 6 is not less than L, L=Bw+A, wherein Bw is the width required for the operation of small excavation equipment, A is the safety distance between equipment, and L is not less than the minimum layout length of the conversion conveyor 19.

[0026] After the second eye-cutting groove 18 is completed, a bucket wheel excavator 13 is arranged in the second eye-cutting groove 18, and a transfer conveyor 19 connected to the centralized conveyor 15 is arranged near the side of the third belt 3.3 to transport the coal. The conveyor is responsible for receiving the coal excavated by the bucket wheel in the second belt 3.2 and transporting it to the surface; the thin coal seam 2 in the second belt 3.2 is blasted by reverse throwing blasting.

[0027] like Figure 3 As shown, the reverse throwing blasting method is: Along the open-pit mine advancement direction 1, the mining strip 3 is divided into three areas, namely, a throwing area 20, a throwing loose transition area 21 and a loose area 22, in order from outside to inside at equal intervals; Multiple rows of throwing drill holes are arranged at intervals in the throwing area 20. The throwing drill holes are tilted inwards, and the tilt angle increases row by row. The tilt angle of the outermost row of throwing drill holes is 30°, and the tilt angle of the innermost row of throwing drill holes is 45°. The depth of the ultra-deep thin coal seam 2 of the throwing drill hole is 1-2m. The throwing drill hole is coupled with charging and blasting. The purpose is to reversely throw the coal blasting to the side of the stripping step 7 after charging and blasting. The design of the drilling angle is mainly to maximize the throwing effect and ensure that the outer thin coal seam 2 can be fully thrown to the side of the stripping step 7. Multiple rows of mixed boreholes are arranged at intervals in the throw loose transition zone 21, and the mixed boreholes are tilted inwardly, and the tilt angle increases row by row, the tilt angle of the outermost row of throw boreholes is 45°, and the tilt angle of the innermost row of throw boreholes is 90°; the depth of the ultra-deep thin coal seam 2 of the mixed borehole is 1-2m; the mixed borehole is coupled with charging and blasting, and the purpose is to take into account blasting and throwing, and after charging and blasting, the coal is blasted and thrown in the reverse direction to the side of the stripping step 7; because this area is close to the stripping step 7, the effect of blasting is to take into account the loosening and throwing of coal, and the closer the coal is to the stripping step, the less it needs to be thrown, and it only needs to be loosened by in-situ blasting to facilitate subsequent excavation; Multiple rows of loose boreholes are arranged at intervals in the loose area 22, and the loose boreholes are set vertically; the depth of the mixed borehole ultra-deep thin coal seam 2 is 1-2m; coupled charging and blasting are carried out in the borehole, the purpose of which is to loosen the coal by blasting. After charging and blasting, the coal is loosened in situ to facilitate subsequent excavation.

[0028] like Figure 4 As shown, the effect achieved by the reverse throwing blasting method is that the thin coal seam 2 is thrown from the original flat state to the side of the step 8 where the thin coal seam is located near the stripping step 7, and a coal pile 23 with a height exceeding the thickness of the original thin coal seam 2 and running through the entire step 8 where the thin coal seam is located is formed. The width of the coal pile 23 in the open-pit mine advancement direction 1 is less than the width of the second strip 3.2. The present invention is designed as a reasonable mining width of the bucket wheel excavator 13 to improve the excavation efficiency of the equipment. The bucket wheel excavator 13 in the second strip 3.2 actually excavates the coal pile 23 formed after the reverse throwing blasting. The coal pile 23 is continuous, high in height and suitable in width, so it can greatly improve the efficiency of the bucket wheel excavator 13. The second strip 3.2 is transported by a conveyor, which greatly reduces the transportation cost and improves the mining efficiency of the thin coal seam 2. The above-mentioned first strip 3.1 and second strip 3.2 are combined to perform double-strip mixed mining on the thin coal seam 2. When the conveyor of any link fails, the single bucket truck 14 continues the transportation to achieve non-stop mining.

[0029] Strip splicing and stripping follow-up: Figure 5As shown, when there is still time D1 left before the first strip 3.1 is mined to the limit, D1 is the time for dismantling the transfer conveyor 19, and the transfer conveyor 19 used in the second strip 3.2 begins to be dismantled. Thereafter, the coal transportation of the second strip 3.2 is changed to transportation by a single-bucket truck 14. During the dismantling of the transfer conveyor 19, starting from the connecting tunnel 5, the stripping step 7 above the thin coal seam 2 in the third strip 3.3 is advanced and transversely stripped. The stripping width of the advanced transverse stripping exceeds the width of the third strip 3.3 by a distance of a safety step. After the thin coal seam 2 is exposed, the third eye-cutting groove 24 is excavated in the same way as the first eye-cutting groove. The third eye-cutting groove 24 is the same width as the third strip 3.3, and the length along the strip extension direction 6 is not less than L, L=Bw+A, wherein Bw is the required width for the operation of small excavation equipment, A is the safety distance between equipment, and L is not less than the minimum layout length of the transfer conveyor 19.

[0030] After the excavation of the third eye-cutting groove 24 is completed, a bucket wheel excavator 13 is arranged in the third eye-cutting groove 24, and a transfer conveyor 19 connected to the centralized conveyor 15 is arranged near the side of the fourth belt to transport the coal. The transfer conveyor 19 is the transfer conveyor 19 removed in the above steps. The thin coal seam 2 in the third belt 3.3 is blasted by reverse throwing blasting. The coal excavated by the bucket wheel is transported to the surface for storage by the transfer conveyor 19 and the centralized conveyor 15. The centralized conveyor 15 in the connecting tunnel 5 is telescopic, and the telescopic head 16 is located on one side of the third belt 3.3.

[0031] During the mining process of the first strip 3.1, each stripping step 7 below the step 8 where the thin coal seam is located follows the advancement, and the advancement degree is the same as the width of the first strip 3.1 or slightly less than the strip width. The purpose is to timely and gradually release the various steps pressed down by the thin coal seam 2 to ensure the normal advancement of the open-pit mine; during the mining process, the spoil dump 25 follows the advancement.

[0032] Mining cycle, the mining cycle is divided into internal cycle and external cycle.

[0033] Internal cycle: within one year of advancement, the mining cycle between each mining strip 3. When there is time D1 left before the second strip 3.2 is mined to the limit, the fourth cutting slot and the thin coal seam 2 in the fourth mining strip 3 are mined in the same way as above, and so on, to achieve the continuous cycle of mining strip 3.

[0034] External circulation: refers to the circulation between the interconnected tunnels 5 between different years; when the remaining time D2 from the completion of all mining strips 3 within the first annual advancement range, the subsequent thin coal seam 2 is mined in accordance with the above-mentioned strip division, excavation of interconnected tunnels, excavation of cuttings and equipment layout, strip mixed horizontal mining, strip continuation and stripping follow-up and internal circulation method; wherein D2 is the time required for strip division, excavation of interconnected tunnels, excavation of cuttings and equipment layout.

[0035] In the prior art, when a wheel bucket is used to mine the main coal seam, the mining direction is generally along the advancement direction of the open-pit mine. However, when mining thin coal seams, if this method is continued, the wheel bucket needs to be frequently moved sideways, which is not conducive to equipment operation and increases equipment idling time. The present invention adopts a horizontal mining method, which can achieve continuous mining of thin coal seams, and correspondingly readjusts the stripping method to avoid excessive advanced stripping; the blasting pile formed by reverse throwing blasting can further improve the excavation efficiency.

[0036] In the prior art, vertical drilling is used to blast coal seams. However, due to the low thickness of thin coal seams, it is impossible to reasonably load explosives and implement blasting when the vertical drilling is shallow. The present invention adopts horizontal drilling, reverse casting blasting and other methods, and implements the blasting method in steps, which can achieve reasonable blasting and avoid coal-rock mixing.

[0037] In the prior art, bucket wheel excavators are mostly used with conveyors or single bucket trucks. The present invention combines the two modes of transportation and continuously converts them into each other. Using different modes of transportation at different locations can effectively improve the transportation efficiency and ensure the stability of the system.

[0038] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any slight modification, equivalent substitution and improvement made to the above embodiment based on the technical essence of the present invention should be included in the protection scope of the technical solution of the present invention.

Claims

1. A double-strip mixed mining method for hard and thin coal seams in an open-pit mine, comprising the following steps: Strip division: Along the open pit advance direction (1), the thin coal seams to be mined within the annual advance range (2) are divided into several parallel mining strips (3); Excavating a connecting tunnel: excavating a connecting tunnel (5) along the open-pit mine advancement direction (1) on the top plate of a thin coal seam (2) near one side end wall (4) of the open-pit mine; each stripping step (7) above the connecting tunnel (5) is stripped in advance so that the top of the thin coal seam (2) is exposed, and the thin coal seam (2) in the connecting tunnel (5) is blasted and mined by horizontal blasting until the end of the connecting tunnel (5); Excavation and equipment layout: starting from the connecting tunnel (5), the stripping step (7) above the thin coal seam (2) in the first mining strip (3) is stripped in advance and then the first cutting groove is excavated on the first mining strip (3) by horizontal blasting. After the first cutting groove is constructed, the thin coal seam (2) in the cutting groove is blasted by horizontal blasting, and a bucket wheel excavator (13) is arranged in the cutting groove, and a single bucket truck (14) is used to transport coal; In the connecting tunnel (5), a telescopic centralized conveyor (15) is arranged from the position of the second mining strip (3) to the end position of the connecting tunnel (5); at the end of the connecting tunnel (5), a lifting conveyor (17) connected to the centralized conveyor (15) is arranged across the end wall (4); Strip mixed horizontal mining: when lagging behind the first mining strip (3) by X, the second cutting groove (18) is excavated in the same way as the first cutting groove, and then a bucket wheel excavator (13) and a transfer conveyor (19) connected to a centralized conveyor (15) are arranged in the second cutting groove (18); the thin coal seam (2) in the second mining strip (3) is blasted by reverse throwing blasting; the first mining strip (3) and the second mining strip (3) are combined to carry out double strip mixed mining of the thin coal seam (2); Strip connection and stripping follow-up: When there is time D1 left before the first mining strip (3) is mined to the limit, the transfer conveyor (19) is dismantled and the third cutting groove (24) is excavated in the same way as the first cutting groove. Then, a bucket wheel excavator (13) and a transfer conveyor (19) connected to the centralized conveyor (15) are arranged in the third cutting groove (24). The thin coal seam (2) in the third mining strip (3) is blasted by reverse throwing blasting. The centralized conveyor (15) in the connecting tunnel (5) is extended and retracted, and the retractable machine head (16) is located on one side of the second mining strip (3); Mining cycle: When there is time D1 left before the second mining strip (3) is mined to its limit, the fourth cutting slot and the thin coal seam (2) in the fourth mining strip (3) are mined in the same manner as above, and so on, to achieve a continuous cycle of the mining strip (3).

2. The double-strip mixed mining method for hard and thin coal seams in open-pit mines according to claim 1 is characterized in that: The plurality of parallel mining strips (3) are numbered sequentially along the open-pit mine advancement direction (1), the width of the first mining strip (3) along the open-pit mine advancement direction (1) is not less than K, and the width of subsequent mining strips (3) is not less than 1.5K, wherein K is the mining width of the bucket wheel excavator (13).

3. The double-strip mixed mining method for hard and thin coal seams in open-pit mines according to claim 1 is characterized in that: The horizontal blasting method is as follows: a horizontal separation borehole (10) is drilled along the coal-rock boundary (9), and a horizontal blasting borehole (11) is drilled inside the thin coal seam (2); the depths of the separation borehole (10) and the blasting borehole (11) are both 1-2 m deeper than the mining width of a bucket wheel excavator (13); the separation borehole (10) is detonated before the blasting borehole (11), and the blasting borehole (11) is coupled with explosives and blasted.

4. The double-strip mixed mining method for hard and thin coal seams in open-pit mines according to claim 1 is characterized in that: The stripping width of the advanced transverse stripping exceeds the width of the mining strip (3) where it is located by a distance of a safety step.

5. The double-strip mixed mining method for medium-hard thin coal seams in an open-pit mine according to claim 1, characterized in that: The reverse throwing blasting method is: Along the open-pit mine advancement direction (1), the mining strip (3) is divided into three areas, namely, a throwing area (20), a throwing loose transition area (21), and a loose area (22), in order of equal distance from the outside to the inside; Multiple rows of throwing drill holes are arranged at intervals in the throwing area (20), the throwing drill holes are inclined inwardly, and the inclination angle increases row by row, the inclination angle of the throwing drill holes in the outermost row is 30°, and the inclination angle of the throwing drill holes in the innermost row is 45°; the depth of the throwing drill holes in the ultra-deep thin coal seam (2) is 1-2m; Multiple rows of mixed boreholes are arranged at intervals in the thrown loose transition zone (21), the mixed boreholes are inclined inwardly, and the inclination angle increases row by row, the inclination angle of the outermost row of thrown boreholes is 45°, and the inclination angle of the innermost row of thrown boreholes is 90°; the depth of the mixed boreholes in the ultra-deep thin coal seam 2 is 1-2m; Multiple rows of loose boreholes are arranged at intervals in the loose area (22), and the loose boreholes are arranged vertically; the depth of the mixed borehole ultra-deep thin coal seam 2 is 1-2m.

6. The double-strip mixed mining method for medium-hard thin coal seams in an open-pit mine according to claim 1, characterized in that: During the mining process of the first mining strip (3), each stripping step (7) below the step (8) where the thin coal seam is located is advanced accordingly, and during the mining process, the spoil dump (25) is advanced accordingly.

7. The double-strip mixed mining method for medium-hard thin coal seams in an open-pit mine according to claim 1, characterized in that: The length of the connecting tunnel (5) in the open-pit mine advancement direction (1) is not less than the annual advancement rate of the open-pit mine, and the width of the connecting tunnel (5) in the strip extension direction (6) is not less than B, B=Bw+2Harctanβ+By+A, wherein Bw is the width required for the operation of the excavation equipment, H is the coal seam height, β is the coal seam slope angle, By is the width of the conveyor area, and A is the safety distance between equipment.

8. The double-strip mixed mining method for hard and thin coal seams in open-pit mines according to claim 1 is characterized in that: When the first mining strip (3) is delayed by X in the strip mixed horizontal mining step, X=Bw+A+Lb2+A1, wherein Bw is the width required for the operation of the excavation equipment, A is the safety distance between the equipment, Lb2 is the length of each blasting of the second mining strip (3) in the strip extension direction (6), and A1 is the safety distance between each blasting position of the second mining strip (3) and the mining and transportation equipment of the first mining strip (3).

9. The double-strip mixed mining method for medium-hard thin coal seams in an open-pit mine according to claim 1, characterized in that: The first cutting groove is equal in width to the first mining strip (3), and the length of the first cutting groove along the strip extension direction (6) is not less than L, L=Bw+Bd+A, wherein Bw is the width required for the operation of the excavation equipment, Bd is the width required for the rotation of the single bucket truck, and A is the safety distance between the equipment; the second cutting groove (18) is equal in width to the second mining strip (3), and the length of the second cutting groove (18) along the strip extension direction (6) is not less than L, L=Bw+A, wherein Bw is the width required for the operation of the excavation equipment, A is the safety distance between the equipment, and L is not less than the minimum layout length of the converted belt conveyor (19).

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