A double-strip mixed mining method for hard and thin coal seams in open-pit mines

Abstract

The present invention discloses a double-strip mixed mining method for hard thin coal seams in open-pit mines, including 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, etc. The present invention adopts a horizontal mining method to avoid frequent lateral movement of the bucket wheel excavator; adopts horizontal drilling and implements blasting methods 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 their original flat state to form a coal pile, achieve rapid concentration of thin coal seams, and meet the economic and reasonable height required for bucket wheel excavation; adopts different transportation methods at different locations to effectively improve transportation efficiency and ensure system stability; strip mining avoids the concentration of a large amount of 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 under the pressure of the thin coal seam to ensure the normal advancement of the open-pit mine.

Description

Technical Field

[0001] The invention relates to a mixed mining method for an open-pit mine, 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 a significant component of open-pit coal reserves, particularly in large and extra-large open-pit mines, where reserves are substantial and mining is highly profitable. Currently, common methods for mining thin coal seams in open-pit mines include: direct mining with small hydraulic excavators or high-horsepower front-loaders; bulldozers equipped with loosening plows and front-loaders for thin seam extraction; and direct mining with open-pit miners or plows. Each of these methods has its advantages, but overall, they suffer from several drawbacks. First, these methods are poorly adapted for medium-hard and higher-hardness coal seams. Second, they are all intermittent processes, resulting in low mining efficiency and impacting the overall speed of open-pit mine advancement. Third, these methods, similar to the "scaling" method, require repeated mining for thick, thin seams, impacting mining capacity and increasing costs. Furthermore, repeated mining increases dust and other environmental pollution. Fourth, during blasting, due to the thin seam thickness, the blasting borehole is short, resulting in poor charging and blasting effectiveness. Furthermore, the resulting coal pile is low, failing to meet the economically reasonable height required for mining equipment.

[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 the mining of thin coal seams in open-pit mines. Summary of the Invention

[0004] In response to the problems existing in the above-mentioned prior art, the present invention provides a double-strip mixed mining method for hard and 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:

[0006] Strip division: along the direction of open pit mine advancement, the thin coal seams to be mined within the annual advancement range are divided into several parallel mining strips;

[0007] 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 advancement; the stripping steps above the connecting tunnel are 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 steps above the thin coal seam in the first mining strip are 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 the coal; in the connecting tunnel, a telescopic centralized conveyor is arranged from the second mining strip position to the end position 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;

[0008] Strip mixed 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 the centralized conveyor are deployed in the second cutting slot; the thin coal seam in the second mining strip is blasted using the reverse throw blasting method; the first mining strip and the second mining strip are combined to carry out double-strip mixed mining of the thin coal seam;

[0009] Strip connection and stripping follow-up: When there is D1 left before the first mining strip reaches its limit, the transfer conveyor is dismantled and the third cut is excavated in the same way as the first cut. Then, a bucket wheel excavator and a transfer conveyor connected to the centralized conveyor are deployed in the third cut. The thin coal seam in the third mining strip is blasted using reverse throw blasting. The centralized conveyor in the connecting roadway is extended and retracted, with the retractable conveyor head located on the side of the second mining strip.

[0010] Mining cycle: When there is 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 are started according to the same method as above, and so on, to realize the continuous cycle of mining strips.

[0011] Furthermore, the 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 the reasonable mining width of the bucket wheel excavator.

[0012] Furthermore, the horizontal blasting method is as follows: 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, and the reasonable mining width of the bucket wheel excavator is 1-2m; the separation borehole is filled with a small dose of explosives and is detonated before the blasting borehole. The main purpose is to separate the thin coal seam from the rock, so as to avoid blasting the rock under the thin coal seam together during blasting, causing coal and rock mixing; the blasting borehole is coupled with charging and blasting, and the drilling density and charging amount are adjusted with the goal of achieving reasonable crushing of the thin coal seam.

[0013] 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.

[0014] Furthermore, the reverse throwing blasting method is:

[0015] 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 the outside to the inside. Multiple rows of throwing drill holes are arranged at intervals in the throwing area. 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 and thin coal seam of the throwing drill holes is 1-2m. The throwing drill holes are coupled with charging and blasting. The purpose is to reversely throw the coal to the side of the stripping step after charging and blasting. The design of the drilling angle , mainly 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 tilted 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, with the purpose of taking into account blasting and throwing. After charging and blasting, the coal is blasted and thrown in the reverse direction to the side of the stripping step. Because the area is close to the stripping step, the effect of blasting is to take into account both loosening and throwing of the coal. 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 holes for ultra-deep and thin coal seams is 1-2m. The coupled charging and blasting in the boreholes are carried out. The purpose is to loosen the coal by blasting. After the charging and blasting, the coal is loosened in situ to facilitate subsequent excavation.

[0016] Furthermore, during the mining process of the first mining strip, the various 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 or slightly smaller than the width of the first mining strip, with the purpose of timely and gradual release of the various steps under pressure from the thin coal seam to ensure the normal advancement of the open-pit mine.

[0017] Furthermore, the length of the connecting tunnel in the direction of advancement 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 height of the coal seam, β is the slope angle of the coal seam, By is the width of the conveyor, and A is the safety distance between equipment.

[0018] 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 direction of strip extension, and A1 is the safety distance between each blasting position of the second mining strip and the mining and transportation equipment of the first mining strip.

[0019] 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 the safety 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.

[0020] Compared to existing technologies, this invention utilizes a horizontal mining method, eliminating frequent lateral movement of the bucket wheel excavator. It also employs horizontal drilling and staged blasting, achieving both efficient blasting and preventing coal-rock mixing. Reverse blasting can throw thin coal seams from their original flat state into a coal pile, rapidly concentrating them and achieving the economically reasonable height required for bucket wheel excavation. Using different transportation methods for different locations effectively improves transportation efficiency and ensures system stability. Strip mining avoids large amounts of concentrated, advanced stripping, alleviating stripping pressure and effectively preventing spontaneous combustion of the coal seam. A follow-up stripping method promptly and gradually releases the pressure from the individual steps of the thin coal seam, ensuring smooth progress in the open-pit mine. The use of interconnected tunnels provides ample and efficient space for implementation, avoiding excessive use of step platforms. The cross-step design of the hoist conveyor eliminates interference with transport from the mine's end walls. The entire thin coal seam can be mined in one go, minimizing environmental pollution and improving mining efficiency. The invention offers a simple implementation process, requiring no additional technicians or equipment, and thus avoiding increased costs. The simultaneous mining of two strips improves the mining efficiency of thin coal seams and avoids the impact on mine advancement. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1Schematic diagram of the strip mixing and horizontal mining process and its preceding steps from above;

[0022] Figure 2 This is a schematic diagram of the horizontal blasting method of the present invention;

[0023] Figure 3 This is a schematic diagram of the reverse throwing blasting method of the present invention;

[0024] Figure 4 This is a schematic diagram of a coal pile after reverse throwing blasting according to the present invention;

[0025] Figure 5 A schematic top view of the strip splicing and stripping process and its preceding steps of the present invention;

[0026] 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-stripping step; 8-step where the thin coal seam is located; 9-coal-rock interface; 10-separation drill hole; 11-blasting drill hole; 12-rock; 13-bucket wheel excavator; 14-single bucket truck; 15-central conveyor; 16-telescopic head; 17-lifting conveyor; 18-second cut-eye trough; 19-converted conveyor; 20-throwing area; 21-throwing loose transition area; 22-loose area; 23-coal pile; 24-third cut-eye trough; 25-dumping yard. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings.

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0029] 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, and mining cycle.

[0030] Strip division: Figure 1As 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 to the last Nth strip, and 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 width of the subsequent mining strips 3, i.e. from the second strip 3.2 to the Nth strip, is not less than 1.5K, where K is the reasonable mining width of the bucket wheel excavator 13, which is generally 20-30m.

[0031] 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 on the side end wall 4 near the industrial square, along the open-pit mine advancement direction 1, a connecting tunnel 5 is excavated; 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 is preferably equal to or slightly greater than the annual advancement rate of the open-pit mine; the width of the connecting tunnel 5 in the strip extension direction 6, that is, from one side end wall 4 to the other side end wall 4, 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 occupied by the belt conveyor, and A is the safety distance between equipment.

[0032] The various stripping steps 7 above the connecting tunnel 5 are advanced stripped 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 so that the top of the thin coal seam 2 is exposed and 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 small excavation equipment such as excavators are used along the advancement direction of the open-pit mine to mine the thin coal seam 2 in the connecting tunnel 5 until the mining reaches the end of the connecting tunnel 5 and stops. At this time, the construction of the connecting tunnel 5 is completed.

[0033] 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, and the reasonable mining width of a bucket wheel excavator is 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, so as to avoid blasting the rock 12 below 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.

[0034] 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 advanced horizontal stripping, that is, the stripping direction is the same as the strip extension direction 6, so that the thin coal seam 2 is gradually exposed, and the stripping width of the advanced horizontal stripping exceeds the width of the first strip 3.1 by the distance of a safety step, generally about 10m, in order to avoid the impact of falling rocks from above on equipment operation; 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 equipment to operate is Bd, the width required for the single-bucket truck to rotate is Bd, and A is the safety distance between the equipment; 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. 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.

[0035] In the connecting tunnel 5, a telescopic centralized conveyor 15 is arranged from the second belt 3.2 position to the end position 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 a strip; 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; it 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 adopts an elevated method to avoid affecting the transportation of the end wall 4.

[0036] 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 stripping step 7 above the thin coal seam 2 in the second strip 3.2 is advanced 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 cutting groove 18 is excavated in the same way as the first cutting groove. The second cutting groove 18 is the same width as 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, where 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.

[0037] After the second eye-cutting groove 18 is completed, a bucket wheel excavator 13 is placed in the second eye-cutting groove 18, and a transfer conveyor 19 connected to the centralized conveyor 15 is placed near the side of the third belt 3.3 to transport the coal. It is responsible for taking over 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.

[0038] like Figure 3 As shown, the reverse throwing blasting method is:

[0039] 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, from the outside to the inside along the open-pit mine advancing direction 1;

[0040] Multiple rows of throwing drill holes are arranged at intervals in the throwing area 20. The throwing drill holes are tilted inward, and the tilt angle increases row by row. The tilt angle of the outermost row of throwing drill holes is 30 degrees, and the tilt angle of the innermost row of throwing drill holes is 45 degrees. The depth of the ultra-deep thin coal seam 2 of the throwing drill holes is 1-2 meters. The throwing drill holes are coupled with charging and blasting. The purpose is to reversely throw the coal 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.

[0041] Multiple rows of mixed drill holes are arranged at intervals in the throw loose transition zone 21. The mixed drill holes are tilted inward, and the tilt angle increases row by row. The tilt angle of the outermost row of throw drill holes is 45 degrees, and the tilt angle of the innermost row of throw drill holes is 90 degrees. The depth of the ultra-deep and thin coal seam 2 of the mixed drill holes is 1-2 meters. The mixed drill holes are 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 the opposite direction to the side of the stripping step 7. Because this area is close to the stripping step 7, the blasting effect is to take into account both coal loosening and throwing. The closer the coal is to the stripping step, the less it needs to be thrown. It only needs to be loosened by in-situ blasting to facilitate subsequent excavation.

[0042] 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.

[0043] like Figure 4 As shown, the reverse-throw blasting method achieves the effect of throwing the thin coal seam 2 from its original flat state onto the side of the step 8 where the thin coal seam is located, near the stripping step 7. This creates a coal pile 23 that exceeds the original thickness of the thin coal seam 2 and extends throughout the entire step 8 where the thin coal seam is located. The width of the coal pile 23 in the open-pit mine's advancement direction 1 is less than the width of the second strip 3.2. This design optimizes the mining width of the bucket wheel excavator 13 to improve the equipment's excavation efficiency. The bucket wheel excavator 13 in the second strip 3.2 actually excavates the coal pile 23 formed by the reverse-throw blasting. The continuous, high, and appropriately wide coal pile 23 significantly improves the efficiency of the bucket wheel excavator 13. The second strip 3.2 is transported by conveyor, significantly reducing transportation costs and improving the mining efficiency of the thin coal seam 2. The combination of the first strip 3.1 and the second strip 3.2 enables dual-strip mixed mining of the thin coal seam 2. If the conveyor fails in any link, a single-bucket truck 14 takes over, ensuring uninterrupted mining.

[0044] Strip splicing and stripping follow-up: Figure 5As shown, when there is 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. After that, the coal transportation of the second strip 3.2 is changed to transportation by single-bucket trucks 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 horizontally stripped. The stripping width of the advanced horizontal stripping exceeds the width of the third strip 3.3 by a safety step. After the thin coal seam 2 is exposed, the third cutting groove 24 is excavated in the same way as the first cutting groove. The third 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, where 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 transfer conveyor 19.

[0045] After excavation of the third eye 24 is complete, a bucket wheel excavator 13 is deployed within the third eye 24. A transfer conveyor 19 connected to the centralized conveyor 15 is deployed near the fourth strip to transport the coal. This transfer conveyor 19 is the same transfer conveyor 19 removed in the previous step. The thin coal seam 2 within the third strip 3.3 is blasted using reverse throw blasting. The coal excavated by the bucket wheel is transported to the surface for storage via the transfer conveyor 19 and the centralized conveyor 15. The centralized conveyor 15 within the connecting roadway 5 is retracted, with the retractable conveyor head 16 located on one side of the third strip 3.3.

[0046] During the mining process of the first strip 3.1, the stripping steps 7 below the step 8 where the thin coal seam is located follow the advancement, and the advancement speed is the same as or slightly less than the width of the first strip 3.1. The purpose is to timely and gradually release the various steps under the pressure of 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.

[0047] Mining cycle, the mining cycle is divided into internal cycle and external cycle.

[0048] Internal cycle: Within a year's advancement, the mining cycle continues between each mining zone 3. When there is time D1 left until the second zone 3.2 is mined to its limit, the fourth cut slot and the thin coal seam 2 within the fourth mining zone 3 are mined using the same method as above. This cycle continues in this manner, completing the mining cycle of each mining zone 3.

[0049] External circulation: refers to the circulation between the various connecting 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 connecting tunnels, excavation of cuttings and equipment layout, strip mixed horizontal mining, strip connection and stripping follow-up and internal circulation method; D2 is the time required for strip division, excavation of connecting tunnels, excavation of cuttings and equipment layout.

[0050] In the prior art, when a wheel bucket is used to mine the main coal seam, the mining direction is generally along the direction of advancement of the open-pit mine. However, when mining thin coal seams, if this method is continued, the wheel bucket needs to be moved sideways frequently, 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 blast pile formed by reverse throwing blasting can further improve mining efficiency.

[0051] In the existing technology, vertical drilling is used to blast coal seams. However, due to the low thickness of thin coal seams, it is impossible to reasonably charge and implement blasting when the vertical drilling holes are shallow. The present invention adopts horizontal drilling, reverse throwing blasting and other methods, and implements the blasting method in steps, which can achieve reasonable blasting and avoid coal-rock mixing.

[0052] In the existing technology, bucket wheel excavators are mostly equipped with conveyors or single-bucket trucks. The present invention combines the two modes of transportation and continuously converts them into each other. Using different transportation modes at different locations can not only effectively improve transportation efficiency but also ensure system stability.

[0053] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent replacements, and improvements made to the above embodiments based on the technical essence of the present invention shall be included in the scope of protection of the technical solution of the present invention.

Claims

1. A double-strip mixed mining method for hard and thin coal seams in open-pit mines, comprising the following steps: Strip division: Along the direction of open pit advance (1), the thin coal seams to be mined within the annual advance range (2) are divided into several parallel mining strips (3); Excavation of a connecting tunnel: on the top plate of the thin coal seam (2) near one side end wall (4) of the open-pit mine, a connecting tunnel (5) is excavated along the open-pit mine advancement direction (1); 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 thin coal seam (2) in the first mining strip is stripped in advance by the stripping step (7) above, and then the first cutting groove is excavated on the first mining strip by horizontal blasting. After the construction of the first cutting groove is completed, 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 the coal; In the connecting tunnel (5), a telescopic centralized conveyor (15) is arranged from the second mining strip position to the end position of the connecting tunnel (5), and 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); Mixed strip horizontal mining: when lagging behind the first mining strip X, X=Bw+A+Lb2+A1, where Bw is the required width of the excavation equipment, A is the safety distance between the equipment, Lb2 is the length of each blasting of the second mining strip in the strip extension direction (6), and A1 is the safety distance between each blasting position of the second mining strip and the mining and transportation equipment of the first mining strip; 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 the centralized conveyor (15) are arranged in the second cutting groove (18); the thin coal seam (2) 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 (2); Strip connection and stripping follow-up: When there is time D1 left from the first mining strip to the boundary, D1 is the time for dismantling the transfer conveyor (19), and the transfer conveyor (19) begins to be dismantled. At the same time, the third cut groove (24) is excavated in the same way as the first cut groove. Then, a bucket wheel excavator (13) and a transfer conveyor (19) connected to the centralized conveyor (15) are arranged in the third cut groove (24). The thin coal seam (2) in the third mining strip 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 the side of the second mining strip. Mining cycle: When there is time D1 left before the second mining strip reaches its limit, the fourth cutting slot and the thin coal seam (2) in the fourth mining strip are mined according to the same method as above, and so on, to achieve the 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, characterized in that: The plurality of parallel mining strips (3) are numbered sequentially along the open-pit mine advancing direction (1), the width of the first mining strip along the open-pit mine advancing direction (1) is not less than K, and the width of the subsequent mining strips (3) is not less than 1.5K, where 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, 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 and charged and blasted.

4. The double-strip mixed mining method for hard and thin coal seams in open-pit mines according to claim 1, 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 hard and thin coal seams in open-pit mines according to claim 1, characterized in that: The reverse throwing blasting method is: Along the open-pit mine advancing direction (1), the mining strip (3) is divided into three areas with equal intervals from outside to inside, namely, the throwing area (20), the throwing loose transition area (21) and the loose area (22); Multiple rows of throw drill holes are arranged at intervals in the throw area (20), the throw drill holes are tilted inwards, and the tilt angle increases row by row, the tilt angle of the outermost row of throw drill holes is 30 degrees, and the tilt angle of the innermost row of throw drill holes is 45 degrees; the depth of the throw drill holes in the ultra-deep thin coal seam (2) is 1-2 meters; Multiple rows of mixed boreholes are arranged at intervals in the thrown loose transition zone (21), the mixed boreholes are tilted inwards, and the tilt angle increases row by row, the tilt angle of the outermost row of thrown boreholes is 45 degrees, and the tilt angle of the innermost row of thrown boreholes is 90 degrees; the depth of the mixed boreholes in the ultra-deep thin coal seam (2) is 1-2 meters; 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 boreholes in the ultra-deep thin coal seam (2) is 1-2m.

6. The double-strip mixed mining method for hard and thin coal seams in open-pit mines according to claim 1, characterized in that: During the mining process of the first mining strip, 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 hard and thin coal seams in open-pit mines 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, characterized in that: The first eyelet groove is equal in width to the first mining strip, and the length of the first eyelet 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 eyelet groove (18) is equal in width to the second mining strip, and the length of the second eyelet 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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