Coal mining method with grouting and filling in overburden strata under large mining width

Abstract

The present application belongs to the field of coal mine filling mining, and particularly relates to a method for overburden grouting and filling mining under the condition of large mining width, which comprises the following steps: selecting an overburden grouting layer; leaving a section coal pillar between a working face to be mined and an adjacent working face that has been mined, wherein the width of the section coal pillar can meet the requirement of keeping stable before the basic roof collapses after the working face to be mined is mined, and the section coal pillar loses stability after the basic roof collapses; constructing a plurality of grouting drill holes along the advancing direction of the two working faces at intervals; mining the working face to be mined, and performing grouting and filling from the grouting drill holes. The width of the section coal pillar is specially designed, the section coal pillar keeps stable in the area where the basic roof has not collapsed, which is beneficial to normal mining and grouting and filling; with the continuous advancing of the working face, the basic roof breaks, the section coal pillar gradually loses stability, and the goaf gradually transfers to the separation position, which is beneficial to the grouting and filling work and the disposal of gangue.

Description

Technical Field

[0001] This invention belongs to the field of coal mine backfilling mining, specifically a method for coal mining with overburden grouting and backfilling under wide mining conditions. Background Technology

[0002] The Hulusu Coal Mine is located in the Hujierte Mining Area of ​​the Dongsheng Coalfield, within Ordos City, Inner Mongolia Autonomous Region. The Hulusu Coal Mine's coal preparation plant currently uses a "heavy medium shallow trough" separation process. After mine expansion, the total annual gangue production is approximately 2.56 million tons. Currently, the mine has a fully mechanized longwall face gangue solid backfilling system, with dedicated backfilling faces for backfilling mining to dispose of the gangue. However, the designed gangue backfilling capacity of the fully mechanized longwall face gangue solid backfilling system is only 1 million tons per year. Furthermore, a portion of the gangue consists of coarse tailings and flotation tailings from fine coal washing. Due to their high moisture content (22% and 29% respectively) and high viscosity, they cannot be solidified using the fully mechanized longwall face gangue solid backfilling system. If roadside disposal is used, the spillage would pollute the road surface, failing to meet environmental protection requirements and incurring disposal costs.

[0003] In response to the aforementioned challenges in handling gangue, especially high-moisture gangue, our company, China Coal Tianjin Design & Engineering Co., Ltd., collaborated with China University of Mining and Technology to initiate a research project. The project proposed the construction of an overburden delamination gangue filling system, employing overburden delamination grouting filling technology to dispose of the remaining gangue.

[0004] The Hulusu Coal Mine is currently mining the 2-1 coal seam, with a depth of 617-640m, including a loose stratum thickness of approximately 25m. The designed production panels are Panel 1, Panel 2, and Panel 4, with the mining sequence of the working faces in Panel 4 being 21405, 21406, 21404, and 21407. At the time of the project initiation study, working faces 21405 and 21406 were already being mined. Working face 21404 is adjacent to working face 21405, and working face 21407 is adjacent to working face 21406. Working face 21404 is designed with a mining width of 300m, a designed longwall length of 3080m, and a mining height of 4.3m. After the mining of working faces 21405 and 21406, the strata did not fully collapse, and a large amount of space in the goaf was not transferred upwards. However, when mining the adjacent working faces 21404 and 21407, the total mining width was comparable to the thickness of the overburden, and the strata faced the problem of full mining. At this time, the mining space of the already mined working faces 21405 and 21406 would be transferred upwards along with the mining of working faces 21404 and 21407. At this time, the amount of goaf space transferred was large and the speed of transfer was fast. If this opportunity could not be captured in time, the goaf space would be transferred to the surface, resulting in a small space for grouting. This is not conducive to the grouting and filling of the overburden and to the disposal of gangue.

[0005] Therefore, when adjacent working faces have already been mined, how to carry out overburden grouting and backfilling work during the mining of this working face in order to dispose of a sufficient amount of gangue is an urgent technical problem that needs to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a method for coal mining with overburden grouting and backfilling under conditions of wide mining width, comprising the following steps: S1: Select the overburden grouting layer; S2: A section coal pillar is left between the working face to be mined and the adjacent working face that has been mined. The width of the section coal pillar can meet the following requirements: as the working face to be mined continues to mine the basic roof periodically, for each collapse of the basic roof, the section coal pillar corresponding to the collapse step distance remains stable before a certain basic roof collapses, and loses stability after the basic roof collapses. S3: Construct several grouting boreholes at intervals along the advancing direction of the two working faces respectively; S4: When the working face is prepared for mining, when it advances to the point where it is aligned with a grouting borehole in the width direction, grouting is performed from that grouting borehole.

[0007] Preferably, in step S1, an isolation layer of a certain thickness is set upward on the water-conducting fracture zone, and the rock strata within a certain height range above the isolation layer are used as the overburden grouting layer.

[0008] Preferably, in step S2, maintaining the stability of the coal column section means maintaining a certain amount of elastic zone in the center of the width.

[0009] Preferably, in step S2, the loss of stability of the coal column section refers to the transformation of the elastic zone at the center of the width into the plastic zone.

[0010] Preferably, in step S3, for each working face, the distance from the first grouting borehole to the cut is less than or equal to the grout diffusion radius, the distance from the last grouting borehole to the finishing line is less than or equal to the grout diffusion radius, and the spacing between grouting boreholes is less than or equal to twice the grout diffusion radius.

[0011] Preferably, in step S3, except for the first and last grouting boreholes, the grouting boreholes of the two working faces are arranged in a staggered quincunx pattern along the working face advancement direction, and the number of grouting boreholes in the working face to be mined is greater than that in the working face that has already been mined.

[0012] Preferably, in step S3, the grouting boreholes in both working faces are biased towards the location of the coal pillar section.

[0013] Preferably, in step S4, grouting of a grouting borehole is stopped when the grouting pressure of a certain grouting borehole reaches the design pressure and grout cannot be injected further.

[0014] Preferably, in step S4, the grouting and filling system used for grouting and filling includes a buffer chamber, a ball mill system, and a mixing system. The inlet of the ball mill system is connected to the buffer chamber and mine water. The buffer chamber is used to store the final gangue and coarse tailings. After the ball mill system grinds the gangue slurry with a suitable particle size, it is transported to the mixing system. The mixing system is also connected to the coal slime underflow conveying system. The mixed slurry after being mixed by the mixing system is connected to a secondary pumping station through a filling pump and a filling body pipeline. The secondary pumping station is connected to the grouting borehole through the filling pipeline for injecting the mixed slurry into the separation space.

[0015] Beneficial effects: 1. This invention addresses the mining conditions of a wide-sided goaf face. It proposes to arrange grouting boreholes in both the already mined face and the face to be mined, in accordance with normal working face conditions. Since the already mined face has not been fully mined in the width direction, after the face to be mined is mined, the sum of the widths of the two faces is basically equivalent to the overburden thickness, and the width is basically fully mined. At this time, the goaf space generated by coal seam mining in the two faces will be rapidly and extensively transferred to the delamination area. Therefore, it is necessary to arrange grouting boreholes in both faces to increase the grouting filling volume and prevent the rapid and extensive subsidence of the strata from resulting in a small delamination space that can be grouted, which is not conducive to the disposal of gangue.

[0016] 2. This invention features a special design for the width of the coal pillar section. In areas where the main roof has not collapsed, the coal pillar section remains stable, and both working faces are in a state of incomplete mining. At this time, the disturbance of the overlying strata to the coal seam is small, the separation space is small, which is conducive to the normal mining of the working face and the grouting and filling of the overlying strata (the grouting and filling capacity can match the separation rate). As the working face continues to advance, the main roof breaks, and the overlying strata gradually collapse. The gravity of the overlying strata on the coal pillar section increases, and the coal pillar section gradually loses stability. Because this process is gradual, the impact generated when the main roof collapses is small, which is conducive to the normal mining of the working face. Furthermore, because the instability of the coal pillar section is a gradual process, the achievement of full mining in width for both working faces is also a gradual process, and the transfer of the goaf to the separation position is also a gradual process, which is conducive to grouting and filling and the disposal of gangue.

[0017] 3. Furthermore, in the above-mentioned section coal pillar design scheme of the present invention, the section coal pillar will become unstable in the later stage, and the delamination space between the two working faces will be connected. The connected delamination space will be basin-shaped in width. Therefore, setting the grouting boreholes of the two working faces to be biased towards the section coal pillar in width can ensure that the grouting boreholes are located at the deepest part of the basin, which is conducive to the diffusion of grout and to improving the grouting filling speed. In the direction of working face advancement, the grouting boreholes of adjacent working faces are arranged in a quincunx pattern, which is conducive to the diffusion of grout and reduces the mutual influence of grout from adjacent grouting boreholes grouting at close range at the same time. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a portion of the working face and the arrangement of boreholes in the fourth panel area of ​​the Hulusu Coal Mine, according to an embodiment of the present invention. Figure 2 These are schematic cross-sectional views of the working surfaces of embodiments 21404 and 21405 of the present invention (before the top plate of 21404 collapses). Figure 3 These are schematic cross-sectional views of the working surfaces of embodiments 21404 and 21405 of the present invention (after the top plate of 21404 collapsed). Figure 4 This is a schematic diagram of the overburden grouting and filling system according to an embodiment of the present invention; In the diagram: 1. Working face; 2. Section coal pillar; 3. Goaf; 4. Permanent coal pillar; 5. Grouting borehole; 6. Recovery roadway. Detailed Implementation

[0019] The technical solution of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiments of the present invention.

[0020] The Hulusu Coal Mine is currently mining the 2-1 coal seam, with a burial depth of 617-640m, including a loose layer thickness of approximately 25m. The designed production panels are Panel 1, Panel 2, and Panel 4. Figure 1 As shown, the mining sequence of the four working faces in the four-panel area is 21405, 21406, 21404, and 21407. At the time of the project initiation study, working faces 21405 and 21406 had already been mined, working face 21404 was adjacent to working face 21405, and working face 21407 was adjacent to working face 21406. The designed mining width of each longwall face 1 is 300m, the designed longwall length is basically the same at approximately 3080m, and the mining height is 4.3m.

[0021] like Figure 2 As shown, after the mining of working faces 21405 and 21406, the strata did not fully collapse, and there was still a large amount of space in goaf 3 that had not been transferred upwards. However, when mining the adjacent working faces 21404 and 21407, the total mining width (600m) was comparable to the thickness of the overburden (592-615m), and the strata faced the problem of full mining. At this time, the goaf space of the already mined working faces 21405 and 21406 would be transferred upwards along with the mining of working faces 21404 and 21407, respectively. At this time, the amount of goaf space transferred was large and the speed of transfer was fast. If this opportunity could not be captured in time, the space in goaf 3 would be transferred to the surface, resulting in a small space for grouting. This is not conducive to the grouting and filling of the overburden and is not conducive to the disposal of gangue.

[0022] To address the aforementioned technical issues, our company, China Coal Tianjin Design & Engineering Co., Ltd., collaborated with China University of Mining and Technology to initiate a research project and propose two solutions. For example...Figure 1 As shown, there is a permanent, unminable coal pillar 4 between the 20405 and 21406 working faces. Therefore, the working conditions for the 21404 and 21407 working faces are basically the same (the wide-width side is mined out). Thus, it is proposed to apply two technical solutions to the 21404 and 21407 working faces respectively. This invention takes the 21404 working face as an example, and mainly requests protection for one of the technical solutions, as follows: The method for grouting and backfilling coal mining under conditions of wide mining width and one-sided goaf includes the following steps: S1: Based on the already mined 21405 working face, determine the height of the water-conducting fracture zone. On the basis of the water-conducting fracture zone, set up an isolation layer of a certain thickness upwards, and use the rock strata within a certain height range above the isolation layer as the overburden grouting layer. S2: A section coal pillar 2 is left between the 21404 working face to be mined and the 21405 working face that has already been mined. The width of the section coal pillar 2 is sufficient to meet the following requirements: as the basic roof of the 21404 working face collapses periodically during mining, for each collapse of the basic roof, such as... Figure 2 As shown, before a certain basic roof collapse, the coal pillar 2 corresponding to this collapse step distance remains stable (for example, in terms of width, the center of coal pillar 2 maintains a certain amount of elasticity). Figure 3 As shown, after the collapse of the basic roof, the section coal pillar 2 corresponding to the collapse step distance loses stability (for example, in terms of width, the elastic zone in the center of section coal pillar 2 becomes a plastic zone). Before the collapse of the basic roof, the basic roof and the roof strata above it will transfer some of the overburden gravity on section coal pillar 2 to the coal body to be mined in the 21404 working face. After the collapse of the basic roof, the overburden gravity on section coal pillar 2 directly acts on section coal pillar 2. The coal body to be mined in the 21404 working face no longer shares the overburden gravity for the collapsed basic roof. Section coal pillar 2 loses its elasticity and undergoes plastic deformation and failure. S3: Based on the grout diffusion radius of the grouting borehole 5, construct several grouting boreholes 5 at intervals along the advancing direction of the 21404 working face and the 21405 working face respectively; for the 21404 working face and the 21405 working face, the distance of the first grouting borehole 5 from the cut hole is less than or equal to the grout diffusion radius, the distance of the last grouting borehole 5 from the finishing line is less than or equal to the grout diffusion radius, and the spacing between the grouting boreholes 5 is less than or equal to twice the grout diffusion radius; Preferably, except for the first and last grouting boreholes 5, the grouting boreholes 5 of the two working faces are arranged in a staggered quincunx pattern along the working face advancement direction, and the number of grouting boreholes 5 in working face 21404 is greater than that in working face 21405. Preferably, the grouting boreholes 5 in the 21404 working face and the grouting boreholes 5 in the 21405 working face are both located towards the section coal pillar 5.

[0023] S4: During the retreat mining of the 21404 working face, when the working face advances to a point where it is aligned with a grouting borehole 5 in the width direction of the working face (perpendicular to the direction of working face advancement), grouting is performed through that grouting borehole 5; For example... Figure 1 As shown, the grouting sequence of grouting borehole 5 is as follows: the first grouting borehole of working face 21404 and the first grouting borehole of working face 21405 → the second grouting borehole of working face 21404 → the second grouting borehole of working face 21405 → the third grouting borehole of working face 21404 → the third grouting borehole of working face 21405... the last grouting borehole of working face 21404 and the last grouting borehole of working face 21405; When the grouting pressure of a certain grouting borehole 5 reaches the design pressure and grout cannot be injected further, grouting of that grouting borehole shall be stopped.

[0024] like Figure 4 As shown, the overburden grouting and backfilling system includes a buffer chamber, a ball mill system, and a mixing system. The ball mill system is connected to the buffer chamber and mine water at its inlet. The buffer chamber is used to store the final gangue and coarse tailings. After the ball mill system grinds the gangue slurry to a suitable particle size, it is transported to the mixing system. The mixing system is also connected to the coal slime underflow conveying system. The mixed slurry after being mixed by the mixing system is connected to a secondary pumping station via a backfilling pump and a backfilling pipeline. The secondary pumping station is connected to the grouting borehole via a backfilling pipeline for injecting the mixed slurry into the separation space.

[0025] This invention addresses the mining conditions of a goaf face with a large mining width. It proposes that grouting boreholes 5 be arranged in both the already mined 21405 working face and the 21404 working face to be mined, as if they were normal working faces. Since the already mined 21404 working face has not been fully mined in the width direction, after the 21405 working face is mined, the sum of the widths of the two working faces is basically equivalent to the overburden thickness, and the width is basically fully mined. At this time, the goaf space generated by coal seam mining in the two working faces will be rapidly and massively transferred to the separation area. Therefore, it is necessary to arrange grouting boreholes 5 in both working faces to increase the grouting filling volume and prevent the rapid and massive subsidence of the strata from resulting in a small separation space available for grouting, which is not conducive to the disposal of gangue.

[0026] Furthermore, the present invention has made special designs on the width of the coal pillar 2 in the section, such as... Figure 2 As shown, in the area where the basic roof has not collapsed, section coal pillar 2 remains stable (with an elastic zone in width, not unstable). Both working faces are in a state of incomplete mining. At this time, the disturbance of the coal seam to the overlying strata is small, the separation space is small, which is conducive to the normal mining operation of the 21404 working face and to the grouting and filling of the overlying strata (the grouting and filling capacity can match the separation rate). Figure 3As shown, with the continuous advancement of the working face, the basic roof periodically breaks, and the overlying strata gradually collapse. The gravity of the overlying strata on section coal pillar 2 increases, and section coal pillar 2 gradually loses stability (the elastic zone gradually becomes the plastic zone in width, and it becomes unstable). Since the instability of section coal pillar 2 is a gradual process, the impact generated when the basic roof collapses is small, which is conducive to the normal mining work of the 21404 working face. Moreover, since the instability of section coal pillar 2 is a gradual process, the full mining of the two working faces in width is also a gradual process, and the transfer of the goaf to the separation position is also a gradual process, which is conducive to grouting and filling work and the disposal of gangue.

[0027] Furthermore, in the above-mentioned section coal pillar 2 design scheme of the present invention, the section coal pillar 2 will become unstable in the later stage, and the delamination space between the two working faces will be connected. The connected delamination space will be basin-shaped in width. Therefore, setting the grouting boreholes 5 of the two working faces to be biased towards the section coal pillar 2 in width can ensure that the grouting boreholes 5 are located at the deepest part of the basin, which is conducive to the diffusion of grout and to improving the grouting filling speed. In the direction of working face advancement, the grouting boreholes 5 of adjacent working faces are arranged in a quincunx pattern, which is conducive to the diffusion of grout and reduces the mutual influence of grout from adjacent grouting boreholes 5 being grouted at close range at the same time.

[0028] In addition, it should be noted that the collapse of the basic roof is a periodic failure along the working face advance direction. Therefore, the instability of section coal pillar 2 is also a periodic failure along the length direction, that is, the working face advance direction. The length of the periodic instability is consistent with the periodic failure step of the basic roof.

[0029] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for coal mining with overburden grouting and backfilling under wide mining conditions, characterized in that, include: S1: Select the grouting layer for overburden separation; S2: A section coal pillar is left between the working face to be mined and the adjacent working face that has been mined. The width of the section coal pillar can meet the following requirements: as the working face to be mined continues to mine the basic roof periodically, for each collapse of the basic roof, the section coal pillar corresponding to the collapse step distance remains stable before a certain basic roof collapses, and loses stability after the basic roof collapses. S3: Construct several grouting boreholes at intervals along the advancing direction of the two working faces; S4: When the working face is prepared for mining, when it advances to the point where it is flush with a grouting borehole in the width direction, grouting is performed from that grouting borehole.

2. The overburden grouting and backfilling coal mining method according to claim 1, characterized in that, In step S1, an isolation layer of a certain thickness is set upward on the water-conducting fracture zone, and the rock strata within a certain height range above the isolation layer are used as the overburden separation grouting layer.

3. The overburden grouting and backfilling coal mining method according to claim 1, characterized in that, In step S2, maintaining the stability of the coal pillar section means maintaining a certain amount of elasticity in the center of the width.

4. The overburden grouting and backfilling coal mining method according to claim 1, characterized in that, In step S2, the loss of stability of the coal column section means that the elastic zone in the center of the width becomes the plastic zone.

5. The overburden grouting and backfilling coal mining method according to any one of claims 1-4, characterized in that, In step S3, for each working face, the distance between the first grouting borehole and the cut is less than or equal to the grout diffusion radius, the distance between the last grouting borehole and the finishing line is less than or equal to the grout diffusion radius, and the spacing between grouting boreholes is less than or equal to twice the grout diffusion radius.

6. The overburden grouting and backfilling coal mining method according to claim 5, characterized in that, In step S3, except for the first and last grouting boreholes, the grouting boreholes of the two working faces are arranged in a staggered quincunx pattern along the working face advancement direction, and the number of grouting boreholes in the working face to be mined is greater than that in the working face that has already been mined.

7. The overburden grouting and backfilling coal mining method according to any one of claims 5, characterized in that, In step S3, the grouting boreholes in both working faces are all biased towards the location of the coal pillar in the section.

8. The overburden grouting and backfilling coal mining method according to any one of claims 1-4, characterized in that, In step S4, grouting of a grouting borehole is stopped when the grouting pressure reaches the design pressure and grout cannot be injected further.

9. The overburden grouting and backfilling coal mining method according to any one of claims 1-4, characterized in that, In step S4, the grouting and filling system used for grouting and filling includes a buffer chamber, a ball mill system, and a mixing system. The ball mill system is connected to the buffer chamber and mine water at its inlet. The buffer chamber is used to store the final gangue and coarse tailings. After the ball mill system grinds the gangue slurry with a suitable particle size, it is transported to the mixing system. The mixing system is also connected to the coal slime underflow conveying system. The mixed slurry after being mixed by the mixing system is connected to the secondary pumping station through the filling pump and the filling body pipeline. The secondary pumping station is connected to the grouting borehole through the filling pipeline for injecting the mixed slurry into the separation space.

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