Safe mining method for water-rich gently inclined coal seam

Abstract

The application discloses a safe mining method for water-rich gently-inclined coal seams, which comprises the steps of cut strip preparation, local drainage system construction, cut strip mining, original coal horizontal mining, continuous drainage system construction, earth dam construction, internal drainage following and mining circulation, etc.; the application uses coal bodies and roller compacted earth dams to alternately support internal earth dumping sites, so that the stability of the internal earth dumping site slope is ensured; long-term three-side water drainage of the coal bodies, especially the bedding water drainage in the advancing direction, is beneficial to the quality improvement of the original coal through water drainage; the coal seams are mined in the central-to-side-to-central direction, so that the mining distance of the stripped materials along the internal drainage of the two side end slopes is shortened, and the internal drainage bridge which is rapidly extended shortens the internal drainage distance of the stripped materials in the middle part; the application does not change the overall advancing direction and step division of the open-pit mine, the construction process is simple, all the used devices are the original mine devices, and the cost is controllable.

Description

TECHNICAL FIELD

[0001] The present application relates to a coal mining method, in particular to a safe mining method of water-rich low-inclined coal seam. BACKGROUND

[0002] ‌When open-pit mining is adopted, the low-inclined coal seam refers to the coal seam with a floor inclination of 5°~15°. During the mining process, the following problems are faced. First, the inclination angle is relatively large, although there is a certain internal discharge condition, but the dump still has a tendency to slide along the floor, which seriously affects the safety and effective capacity of the internal dump slope. Second, the water from the end slope and the internal dump will gather in the mining working face and soak the mining working face for a long time. For the open-pit mine with a large water inflow, not only the safety of the equipment operation in the mining link is affected, but also the water content of the mined coal is increased, which affects the calorific value of the raw coal. SUMMARY

[0003] In view of the problems existing in the prior art, the present application provides a safe mining method of water-rich low-inclined coal seam, which ensures the safety of the internal dump slope and reduces the water content of the raw coal.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a safe mining method of water-rich low-inclined coal seam, comprising the following steps:

[0005] Preparation of cut eye strip: on the working slope coal seam, symmetrical positions on both sides of the coal seam central axis are divided into cut eye strips along the advancing direction of the open-pit mine, the width of the cut eye strip in the advancing direction of the open-pit mine is less than the annual advancing degree; the cut eye strip coal seam is advanced in advance above the stripping bench, and the coal seam in the cut eye strip is completely exposed;

[0006] Construction of local drainage system: at the junction of the coal seam in the cut eye strip and the upper stripping bench, a groove with super-deep coal seam floor is excavated as a precipitation ditch; the precipitation ditch takes the coal seam central axis as a midpoint, and is arranged obliquely to the two side slopes along the coal seam floor, forming a 0.5%~1% water flow slope, and the positions close to the two side slopes are low points, and a water collecting pit connected with the precipitation ditch is excavated at the low point position; a groove with super-deep coal seam floor is excavated as a water guide ditch along the advancing direction of the open-pit mine at the coal seam central axis, and the water guide ditch is connected with the precipitation ditch to form a “T” shaped drainage structure;

[0007] Mining of cut eye strip: the coal seam in the cut eye strip is divided into small bench mining along the advancing direction of the open-pit mine; after the coal seam is mined, the floor is exposed, and the width of the exposed range along the coal seam strike is more than four times the thickness of the coal seam, then rubble is laid in the area of the super-deep coal seam floor of the precipitation ditch and the water guide ditch, and a straw curtain or gauze net is overlaid, to form a precipitation blind ditch and a water guide blind ditch;

[0008] Original coal horizontal mining: after the completion of the cut strip, the steps on both sides of the cut strip in the direction of the strip advancement are widened to form two horizontal mining faces, which respectively advance towards the end slope direction to mine the coal seam in the working slope, and the stripping steps above the coal seam advance ahead of the horizontal mining face;

[0009] Building a continuous drainage system: as the horizontal mining face continuously advances towards the two sides of the end slope direction, the coal seam floor is continuously exposed, the dewatering blind ditch also extends to both sides synchronously, and the catchment pit also changes its construction position synchronously, but always locates at the end point position of the dewatering blind ditch near the end slope; a phase guide blind ditch parallel to the dewatering blind ditch is built on the coal seam floor every 100-200 m, and is connected with the dewatering blind ditch;

[0010] Building a retaining dam: during the original coal horizontal mining, the stripping material of the open pit is layered and removed along the edge of the dewatering ditch near the internal dump site and is rolled to form a retaining dam in the goaf after the coal seam in the cut strip is mined; at the same time, the material that can permeate water is backfilled as a permeable layer between the working slope coal seam and the retaining dam;

[0011] Internal dump following: after the retaining dam reaches the designed height and extends to both sides of the end slope direction beyond the width of the two open pit tracks, a dump bridge connecting the internal dump site and the working slope coal seam is built above the retaining dam, and the internal dump site follows the dump bridge to the end slope and the open pit advancement direction, respectively;

[0012] Mining cycle: when the original coal horizontal mining reaches both sides of the end slope and the internal dump site follows to the end slope, the current mining is completed, at which time the permeable layer is recovered, and then the next cut strip is demarcated, and the next round of mining is carried out according to the above steps, and so on, to realize the cyclic mining.

[0013] Further, the length of the cut strip in the direction perpendicular to the advancement direction of the open pit is not less than L , L =2 B min + H arctan β , wherein: B min is the minimum pit bottom width, H is the coal seam height, β is the coal seam slope angle, and the vertical depth is less than a step height.

[0014] Further, the dewatering ditch is more than 2 m deep to the coal seam floor.

[0015] Further, the guide ditch is more than 2 m deep to the coal seam floor.

[0016] Further, the small bench in the cut eye strip mining step is divided into horizontal layers from the working slope to the direction of the internal dump, and each bench height is not more than 3m.

[0017] Further, the retaining dam takes the coal seam centerline as the starting point, keeps the distance from the minimum pit bottom width of the transverse mining working face to follow the advance, and the total height of the retaining dam is equal to the open pit one-time depth, and the layer height is 1-2m.

[0018] Further, in the internal dump following step, with the internal dump advancing to the direction of the two side end slopes, a second layer dump bridge connecting the internal dump and the upper bench of the coal seam of the working slope is constructed near the coal seam centerline.

[0019] Compared with the prior art, the coal body and the rolled retaining dam of the application alternately support the internal dump, guarantee the stability of the internal dump slope; the long-term three-side dewatering of the coal body, especially the bedding dewatering in the advancing direction, is beneficial to the coal quality improvement by dewatering; the coal seam is mined in the direction of the two sides to the middle, which shortens the stripping material transport distance along the two side end slopes, and the fast-extended dump bridge shortens the internal dump transport distance of the middle part of the stripping material; the application does not change the overall advancing direction of the open pit, the construction technology is simple, the equipment used is the original mine equipment, and the cost is controllable. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a cut eye strip preparation and local drainage system schematic diagram of the application;

[0021] Figure 2 It is a local drainage system and cut eye strip mining schematic diagram of the application;

[0022] Figure 3 It is an original coal transverse mining and construction of continuous drainage system schematic diagram of the application;

[0023] Figure 4 It is a retaining dam construction schematic diagram of the application;

[0024] Figure 5 It is an internal dump following schematic diagram of the application;

[0025] In the figure: 1-working slope coal seam; 2-open pit advancing direction; 3-cut eye strip; 4-coal seam centerline; 5-stripping bench; 6-dewatering ditch; 7-end slope; 8-catchment pit; 9-water diversion ditch; 10-dewatering blind ditch; 11-water diversion blind ditch; 12-transverse mining working face; 13-stage water diversion blind ditch; 14-internal dump; 15-retaining dam; 16-permeable layer; 17-dump bridge. DETAILED DESCRIPTION

[0026] The application will be further described below in combination with the drawings.

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0028] As Figures 1 to 5 shown, the present application provides a technical solution, including steps of cutting eye strip preparation, construction of partial drainage system, cutting eye strip mining, raw coal horizontal mining, construction of continuous drainage system, construction of retaining dam, internal drainage follow-up, and mining cycle.

[0029] Cutting eye strip preparation:

[0030] According to the bench height and horizontal advancing strength of the open-pit mine, a cutting eye strip 3 is divided on both sides of a coal seam center line 4 on a working bank coal seam 1 along an open-pit advancing direction 2, a width of the cutting eye strip 3 on the open-pit advancing direction 2 is less than an annual advancing degree, and a length of the cutting eye strip 3 on a direction perpendicular to the open-pit advancing direction 2 is not less than L , L =2 B min + H arctan β , wherein: B min is a minimum pit bottom width, generally not less than 50 m, H is a coal seam height, β is a coal bank slope angle; a vertical depth is less than a bench height, and the vertical depth is a height difference between the cutting eye strip 3 start and end points corresponding to the coal seam.

[0031] The cutting eye strip 3 is advanced in advance by stripping a bench 5 above a coal seam roof to completely expose the coal seam in the cutting eye strip 3; the bench above the coal seam roof adopts a combined bench + steep working bank mining mode to reduce the advance stripping engineering quantity.

[0032] Construction of partial drainage system:

[0033] At a position where the coal seam in the cutting eye strip 3 and the upper stripping bench 5 are connected, a long-arm excavator is used to dig a groove above 2 m of the coal seam floor as a precipitation ditch 6; the precipitation ditch 6 is pseudo-obliquely arranged along the coal seam floor to both side end banks 7 with the coal seam center line 4 as a midpoint to form a 0.5%~1% water flow slope, and the precipitation ditch 6 has a structure of high in the middle and low at both ends, and low points of the precipitation ditch 6 are positions close to the both side end banks 7, and water collection pits 8 connected with the precipitation ditch 6 are dug at the low points.

[0034] At the position of the coal seam axis 4, a trench more than 2m deep is excavated along the open-pit advancing direction 2 as a water guide ditch 9, which is connected with the water drainage ditch 6 to form a "T" shaped drainage structure, so as to collect the pit bottom water into the water collecting pits 8 at both ends of the water drainage ditch 6 and discharge the water.

[0035] Cutting strip mining:

[0036] The coal seam in the cutting strip 3 is divided into small bench mining along the open-pit advancing direction 2, and a hydraulic backhoe is used for excavating and loading a car, and the small bench division principle is to horizontally layer from the working slope to the direction of the internal dump 14, and the height of each bench is not more than 3m, so as to adapt to the change of the coal seam inclination to the greatest extent.

[0037] After the coal seam is mined, the floor is exposed, and the width of the exposed range along the coal seam trend is more than four times the thickness of the coal seam, and then the rubble is laid in the area of the water drainage ditch 6 and the water guide ditch 9 of the overdeep coal seam floor, and a straw curtain or gauze net is overlaid, to form a water drainage blind ditch 10 and a water guide blind ditch 11, which can continuously play a role in dewatering and water reduction of the coal seam.

[0038] Original coal horizontal mining:

[0039] After the completion of the cutting strip 3, the bench on both sides of the advancing direction of the cutting strip 3 is widened to form two horizontal mining working faces 12, which respectively advance towards the end slope 7, and the coal seam 1 in the working slope is mined, and the stripping bench 5 in the upper part of the coal seam advances ahead of the horizontal mining working face 12 to speed up the recovery of the original coal.

[0040] Construction of continuous drainage system:

[0041] With the continuous advancement of the horizontal mining working face 12 to the two sides of the end slope 7, the coal seam floor is continuously exposed, the water drainage blind ditch 10 is also synchronously extended to the two sides, and the water collecting pit 8 also changes the construction position synchronously, but always locates at the endpoint position of the water drainage blind ditch 10 close to the end slope 7; and a phase water guide blind ditch 13 parallel to the water drainage blind ditch 10 is constructed every 100~200m on the coal seam floor, and is connected with the water drainage blind ditch 10, so as to guide the water in the internal dump 14 to the water drainage blind ditch 10 and collect it into the water collecting pit 8.

[0042] Construction of retaining dam:

[0043] During the horizontal mining of the original coal, the stripping material of the open-pit is layered and discarded along the edge of the water drainage ditch 6 close to the internal dump 14 in the goaf after the coal seam in the cutting strip 3 is mined, and is rolled to form a retaining dam 15 supporting the internal dump 14, the retaining dam 15 takes the coal seam axis 4 as the starting point, keeps a minimum distance from the minimum pit bottom width of the horizontal mining working face 12 and advances, and the total height of the retaining dam 15 is equal to the one-time depth of the open-pit, and the layered height is 1~2m, and the specific height is determined according to the effective compaction depth of the rolling equipment.

[0044] Meanwhile, the permeable material such as sandstone is backfilled between the working slope coal seam 1 and the retaining dam 15 as the permeable layer 16, which can support the retaining dam 15 and ensure the normal water seepage of the working slope coal seam 1 to the blind drainage ditch 10.

[0045] Inner row follow-up:

[0046] After the retaining dam 15 reaches the designed height and extends to the two side end slopes 7 beyond the width of two open-pit mine tracks, the dump bridge 17 connecting the inner dump 14 and the working slope coal seam 1 is constructed above the retaining dam 15 with the coal seam center line 4 as the starting point, and the inner dump 14 follows up the dumping in two directions of the two side end slopes 7 and the open-pit mine advancing direction 2 with the dump bridge 17 as the starting point.

[0047] In order to accelerate the inner row follow-up, the second layer dump bridge 17 connecting the inner dump 14 and the upper step of the working slope coal seam 1 is constructed near the coal seam center line 4 as the inner dump 14 advances to the two side end slopes 7.

[0048] Mining cycle:

[0049] When the raw coal horizontal mining reaches the two side end slopes 7 and the inner dump 14 synchronously follows up to the end slopes 7, the current mining is ended, at this time, the permeable layer 16 is recovered, then the next round of cut strip 3 is demarcated, and the next round of mining is carried out according to the above steps, and so on, the mining is cycled.

[0050] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, but can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference signs in the claims should not be construed as limiting the claims to the figures in which the reference signs are used.

[0051] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application, any slight modification, equivalent replacement and improvement made according to the technical essence of the present application to the above embodiment should be included in the protection scope of the technical scheme of the present application.

Claims

1. A safe mining method of water-rich gently inclined coal seam, characterized in that, The method comprises the following steps: Cutting strip preparation: Divide a cutting strip (3) on the working coal seam (1) on both sides of the coal seam central axis (4) in the open-pit advancing direction (2), the width of the cutting strip (3) in the open-pit advancing direction (2) is less than the annual advancing degree; the cutting strip (3) is advanced in the superposition step (5) above the coal seam roof, and the coal seam in the cutting strip (3) is completely exposed; Building a local drainage system: Dig a super-deep coal seam floor trench as a precipitation ditch (6) at the junction of the coal seam and the superposition step (5) in the cutting strip (3); the precipitation ditch (6) is pseudo-obliquely arranged along the coal seam floor to both side end walls (7) with the coal seam central axis (4) as the midpoint, forming a 0.5%-1% water flow gradient, and the position close to the both side end walls (7) is the low point, and a water collecting pit (8) is dug at the low point and connected with the precipitation ditch (6); a super-deep coal seam floor trench is dug as a water guide ditch (9) along the open-pit advancing direction (2) at the coal seam central axis (4), and the water guide ditch (9) is connected with the precipitation ditch (6) to form a "T" shaped drainage structure; Cutting strip mining: Divide the coal seam in the cutting strip (3) into small steps for mining in the open-pit advancing direction (2); after the coal seam is mined, the floor is exposed, the exposure range along the coal seam strike is greater than four times the coal seam thickness, then in the area of the super-deep coal seam floor of the precipitation ditch (6) and the water guide ditch (9), rubble is laid, and a straw curtain or gauze net is overlaid to form a precipitation blind ditch (10) and a water guide blind ditch (11); Original coal horizontal mining: After the cutting strip (3) is completed, the steps on both sides of the cutting strip (3) advancing direction are widened to form two horizontal mining working faces (12), the horizontal mining working faces (12) respectively advance towards the end walls (7) to mine the working coal seam (1), and the superposition step (5) above the coal seam advances in front of the horizontal mining working face (12); Building a continuous drainage system: With the continuous advancing of the horizontal mining working face (12) towards the both side end walls (7), the coal seam floor is continuously exposed, the precipitation blind ditch (10) is also synchronously extended to both sides, and the water collecting pit (8) is also synchronously changed in the construction position, but always located at the endpoint position of the precipitation blind ditch (10) close to the end wall (7); a stage water guide blind ditch (13) parallel to the water guide blind ditch (11) is built every 100-200m on the coal seam floor; Building a retaining dam: In the process of the original coal horizontal mining, the superposition step (5) after the coal seam in the cutting strip (3) is mined, layered open-pit stripping materials are discarded and rolled along the edge of the precipitation ditch (6) close to the internal dumping site (14) to form a retaining dam (15); meanwhile, water permeable materials are backfilled as a permeable layer (16) between the working coal seam (1) and the retaining dam (15); Internal dumping follow-up: When the retaining dam (15) reaches the designed height and extends to the two side end walls (7) beyond the width of two open-pit tracks, a dump bridge (17) is built on the retaining dam (15) above the coal seam central axis (4) to connect the internal dump (14) and the working slope coal seam (1), and the internal dump (14) follows the dump bridge (17) to the two side end walls (7) and the open-pit advancing direction (2). Mining cycle: When the original coal horizontal mining reaches the two side end walls (7) and the internal dump (14) synchronously follows to the end walls (7), the current mining is finished, at this time, the permeable layer (16) is recovered, then the next round of cut-and-fill strip (3) is demarcated, and the next round of mining is carried out according to the above steps, and so on, the mining is circular.

2. The method according to claim 1, characterized in that, The length of the strip (3) in the direction perpendicular to the advancing direction (2) of the open pit is not less than L , L =2 B min + H arctan β , wherein: B min is the minimum pit bottom width, H is the coal seam height, β is the coal seam slope angle, and the vertical depth is less than one step height.

3. The method for safe mining of water-rich gently inclined coal seams according to claim 1, characterized in that, The precipitation ditch (6) is more than 2m above the bottom of the super-deep coal seam.

4. The method for safe mining of water-rich gently inclined coal seams according to claim 1, characterized in that, The water diversion ditch (9) is more than 2m above the bottom of the super-deep coal seam.

5. The method for safe mining of water-rich gently inclined coal seams according to claim 1, characterized in that, In the cut-and-fill strip mining step, the small steps are divided into horizontal layers from the working slope to the internal dump (14) direction, and the height of each step is not more than 3m.

6. The method for safe mining of water-rich gently inclined coal seams according to claim 1, characterized in that, The retaining dam (15) takes the coal seam central axis (4) as the starting point, keeps the minimum pit bottom width distance from the horizontal mining working face (12) and follows the advancing, the total height of the retaining dam (15) is equal to the open-pit one-time depth reduction, and the layer height is 1-2m.

7. The method for safe mining of water-rich gently inclined coal seams according to claim 1, characterized in that, In the internal dump following step, as the internal dump (14) advances to the two side end walls (7), a second layer of dump bridge (17) is built near the coal seam central axis (4) to connect the internal dump (14) and the upper step of the working slope coal seam (1).

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