Grouting and filling green coal mining method for overlying strata in one-side goaf

Abstract

The invention belongs to the field of coal mine filling mining, and particularly relates to a one-side goaf overlying strata grouting filling green coal mining method which comprises the steps that a plurality of goaf grouting drill holes close to a coal wall supporting area are constructed in a mined working face; constructing a grouting filling system; injecting gangue mixed slurry into the goaf; gob-side entry driving is carried out on the reserved section coal pillar, and the width of the section coal pillar can meet the requirement that under auxiliary supporting of a goaf filling body, the section coal pillar is kept stable after working face stoping and before basic roof caving, and the section coal pillar is unstable after basic roof caving; the goaf grouting drilling holes are changed into separation layer grouting drilling holes; a plurality of separation layer grouting drill holes are constructed in the working face to be stoped; a grouting filling system is connected with the separation layer grouting drill hole; and the working face to be stoped is stoped, and grouting filling is conducted on the self-grouting drill holes. According to the method, the stress of the section coal pillar can be reduced, so that the reserved width of the section coal pillar is reduced, the coal loss is reduced, the grouting filling amount of the separation layer can be ensured, and the gangue absorption amount is ensured.

Description

Technical Field

[0001] This invention belongs to the field of coal mine backfilling mining, specifically a green coal mining method for backfilling with grouting in the overlying rock of one side of the mine. Background Technology

[0002] The Hulusu Coal Mine uses a "heavy medium shallow trough" coal preparation process. After the mine expansion, the annual amount of gangue produced is about 2.56 million tons. The existing fully mechanized mining face gangue solid filling system consumes about 1 million tons of gangue annually, leaving 1.56 million tons of gangue that needs to be processed. Some of these gangues are coarse tailings and flotation tailings produced by fine coal washing. Therefore, it is proposed to use overburden separation grouting filling technology for processing.

[0003] The mining sequence of the working faces in the fourth panel area of ​​Hulusu Coal Mine is 21405, 21406, 21404, and 21407, with a designed mining width of 300m. Working faces 21405 and 21406 have already been mined. Working face 21404 is adjacent to working face 21405, and working face 21407 is adjacent to working face 21406. 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.

[0004] 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 absorb a sufficient amount of gangue has become a technical problem that needs to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a green coal mining method involving grouting and backfilling of overburden in one-sided mining areas, comprising the following steps: S1: Within the already mined working face, several goaf grouting boreholes are constructed at intervals along the length of the working face. On the width of the working face, the goaf grouting boreholes are close to the coal wall support area. S2: Construct a grouting and filling system and connect it to the grouting boreholes in the goaf; S3: Inject gangue mixed slurry into the goaf from the grouting borehole; S4: Leave a section coal pillar for goaf excavation. 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 collapse, and loses stability after the basic roof collapses. S5: Select the overburden grouting layer; Seal the portion of the goaf grouting borehole below the grouting layer and change the goaf grouting borehole to a separation grouting borehole; Preferably, in step S5, an isolation layer of a certain thickness is set upwards 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.

[0006] S6: Within the working face to be mined, construct several separation grouting boreholes at intervals along the length of the working face; connect the grouting filling system to the separation grouting boreholes through filling pipelines; S7: 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.

[0007] Preferably, in step S4, maintaining the stability of the coal column section means maintaining a certain amount of elastic zone in the center of the width.

[0008] Preferably, in step S4, 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.

[0009] Preferably, the grouting and filling system 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.

[0010] Beneficial effects: This invention addresses the mining conditions of wide-sided goaf faces by proposing to first construct grouting boreholes in the goaf area of ​​the already mined face, near the prepared mining face, to grout the goaf. This improves the support of the coal wall support area in the goaf area of ​​the already mined face near the prepared mining face, reduces the stress on the coal pillars in the section, and thus reduces the width of the coal pillars and coal loss. Later, the goaf grouting boreholes are replaced with separation grouting boreholes, which, together with the separation grouting boreholes arranged in the prepared mining face, are used to grout the overburden separation layer. This allows for timely detection of the overburden separation grouting opportunity, ensuring the amount of grout filling to the separation layer and the amount of gangue disposal. Attached Figure Description

[0011] 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 This is a schematic diagram of the cross-sections of working faces 21406 and 21407 before mining in embodiment 21407 of the present invention; Figure 3 This is a schematic diagram of the cross-section of the grouting and gangue disposal area in the working face of Embodiment 21406 of the present invention; Figure 4 This is a schematic cross-sectional view of working surfaces 21406 and 21407 after the basic collapse of working surface 21407 in embodiment 2 of the present invention; Figure 5 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; 51. Goaf grouting borehole; 52. Separation grouting borehole; 53. Roof strata roadway along the goaf; 7. Goaf filling body. Detailed Implementation

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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 coal pillar 4 between the 20405 and 21406 working faces that cannot be mined. Therefore, the working conditions for the 21404 and 21407 working faces are basically the same (one side of the wide mining width is mined out). Therefore, it is proposed to use two technical solutions for the 21404 and 21407 working faces respectively. The first technical solution can start the mining of the working face as soon as possible and is suitable for the 21404 working face that is about to be put into production. The second technical solution requires the goaf area on one side to be filled first and then the working face can be mined. That is, the working face cannot be mined immediately and is suitable for the 21407 working face that follows the 21404 working face.

[0016] Taking the 21407 working face as an example, this invention requests protection for one of its technical solutions, as follows: The green coal mining method of grouting and backfilling the overlying rock of mined-out coal gangue includes the following steps: S1: As Figure 1-3 As shown, within the already mined 21406 working face, several goaf grouting boreholes 51 are constructed at intervals along the length of the working face. The spacing of the goaf grouting boreholes 51 is determined based on the diffusion radius of the grout in the goaf. The distance between the first goaf grouting borehole 51 and the cut-off point is less than or equal to the diffusion radius of the grout in the goaf. The distance between the last goaf grouting borehole 51 and the finishing line is less than or equal to the diffusion radius of the grout in the goaf. The spacing between the goaf grouting boreholes 51 is less than or equal to twice the diffusion radius of the grout in the goaf. In terms of working face width, the goaf grouting borehole 51 is close to the coal wall support area, for example, the goaf grouting borehole 51 passes through the broken rock block (block B in the masonry beam mechanical model) close to the coal wall support area. S2: As Figure 5 As shown, a grouting and filling system is constructed, including 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. The ball mill system grinds gangue slurry of suitable particle size and then transports it 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 filling pump and a filling body pipeline. The secondary pumping station is connected to the grouting borehole 51 in the goaf via the filling pipeline. S3: As Figure 3 As shown, gangue mixed slurry is injected into the goaf 3 of the 21406 working face from the grouting borehole 51. The solid particles in the gangue mixed slurry remain on the side of the goaf 3 near 21407 and continue to accumulate. Water flows away from the 21407 working face and infiltrates into the bottom rock layer of the goaf 3. S4: Along the boundary of the goaf 3 of the 21406 working face, a horizontal roadway 6 (goaf-side roadway) is used for the excavation and recovery of the 21407 working face. A section coal pillar 2 is left between the horizontal roadway 6 and the goaf 3 of the 21406 working face. The width of the section coal pillar 2 is sufficient to ensure that, as the basic roof of the 21407 working face collapses periodically during mining, for each collapse of the basic roof, such as... Figure 3 As shown, before each basic roof collapse, the coal pillar 2 corresponding to this collapse step distance remains stable (for example, in terms of width, the center of the coal pillar 2 maintains a certain amount of elasticity). Figure 4 As shown, after the collapse of the basic roof, the section coal pillar 2 corresponding to this collapse step 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 21407 working face. After the collapse of the basic roof, the overburden gravity on section coal pillar 2 acts directly on section coal pillar 2. The coal body to be mined in the 21407 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. In addition, due to the auxiliary support of the goaf filling body 7, the width of section coal pillar 2 can be reduced, thereby reducing coal loss. At the same time, injecting gangue mixed slurry into the goaf 3 can increase the amount of gangue that can be disposed of. S5: Determine the height of the water-conducting fracture zone. Based on the water-conducting fracture zone, set an isolation layer of a certain thickness upwards. Use the rock strata within a certain height range at the top of the isolation layer as the overburden grouting layer. Seal the part below the grouting layer of the goaf grouting borehole 51 and change the goaf grouting borehole 51 to the separation grouting borehole 52. S6: Within the 21407 working face to be prepared for mining, a number of separation grouting boreholes 52 are constructed at intervals along the length of the working face; the spacing of the separation grouting boreholes 52 is determined based on the diffusion radius of the grout in the separation layer. The distance between the first separation grouting borehole 52 and the cut-off point is less than or equal to the diffusion radius of the grout in the separation layer, and the distance between the last separation grouting borehole 52 and the finishing line is less than or equal to the diffusion radius of the grout in the separation layer. The spacing between the separation grouting boreholes 52 is less than or equal to twice the diffusion radius in the separation layer. In the width of the working face, the separation grouting boreholes 52 are constructed close to the coal pillar 2 of the section. S7: Connect the secondary pump station to the grouting borehole 52 via a filling pipeline; during the mining of the 21407 working face, when the working face advances to the point where it is aligned with a certain grouting borehole in the width direction of the working face (perpendicular to the direction of working face advancement), grouting and filling are performed from that grouting borehole; if... Figure 1As shown, the grouting sequence of the delamination grouting boreholes is as follows: the first delamination grouting borehole on the 21406 working face → the first delamination grouting borehole on the 21407 working face → the second delamination grouting borehole on the 21406 working face → the third delamination grouting borehole on the 21406 working face → the second delamination grouting borehole on the 21407 working face… the last delamination grouting borehole on the 21407 working face → the last delamination grouting borehole on the 21406 working face; grouting of a certain delamination grouting borehole is stopped when the grouting pressure of a certain delamination grouting borehole reaches the design pressure and grout cannot be injected further. During the longwall mining process at the 21407 working face, such as Figure 3 As shown, the width of the section coal pillar 2 is sufficient to ensure that, with the auxiliary support of the goaf filling body 7 to the roof strata, the section coal pillar 2 remains stable after the main roof collapses following the mining of the 21407 working face (for example, in terms of width, the center of the section coal pillar 2 maintains a certain amount of elasticity). Figure 4 As shown, after the basic roof collapses, the section coal pillar 2 loses stability (for example, in terms of width, the elastic zone in the center of section coal pillar 2 becomes a plastic zone). Under the combined action of overburden pressure and separation grouting pressure, section coal pillar 2 undergoes plastic deformation, its height decreases, and it deforms under pressure to both sides. Under the combined action of overburden pressure and separation grouting pressure, the goaf filling body 7 also undergoes compression deformation in the direction away from the 21407 working face. Here, the compression space of goaf 3 is transferred to the separation zone, increasing the space of the separation zone. Grouting is carried out to fill the separation zone through separation grouting borehole 52, increasing the amount of grout filling and absorbing more gangue. Due to the auxiliary support effect of goaf filling body 7, the width of section coal pillar 2 can be reduced, thereby reducing coal loss. At the same time, injecting gangue mixed slurry into goaf 3 can increase the amount of gangue absorbed. Since the collapse of the basic roof is a periodic failure along the working face advance direction, 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 of the section coal pillar is consistent with the periodic failure step of the basic roof.

[0017] This invention addresses the mining conditions of a wide-span goaf face. First, grouting boreholes are drilled on the side of the already mined 21406 working face near the 21407 working face to be mined, and grout is injected into the goaf area. This improves the support of the coal wall support zone on the side of the 21406 working face near the 21407 working face, reduces the stress on the coal pillars in the section, and thus reduces the width of the coal pillars and coal loss.

[0018] Then, the goaf grouting boreholes in the 21406 working face were changed to delamination grouting boreholes, and delamination grouting boreholes were constructed in the 21407 working face, which was to be mined. Since the 21406 working face, which had already been mined, had not been fully mined in the width direction, after the 21407 working face was mined, the sum of the widths of the two working faces was basically equivalent to the thickness of the overburden, and the width was basically fully mined. In the later stage, the coal pillar in the section would become unstable, compressed and deformed, and its height would decrease. The goaf filling body would also be compressed and deformed, and its height would decrease. The resulting goaf space would be transferred to the delamination position. The resulting delamination space was large and fast (relative to a working face that was not mined on one side and was not fully mined in width), and the delamination space between the two working faces would be connected. Therefore, it was necessary to arrange delamination grouting boreholes in both working faces to increase the amount of grouting and filling, and to prevent the rapid and large-scale subsidence of the strata from resulting in a small delamination space that could be grouted, which would be not conducive to the disposal of gangue.

[0019] Regarding the width of the coal pillar section, in areas where the main roof has not collapsed, the coal pillar section remains stable (for example, in terms of width, coal pillar section 2 has an elastic zone in width and has not become 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 21407 working face and to the grouting and filling of the overlying strata separation (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, increasing the gravity of the overlying strata on coal pillar section 2. As the coal pillar 2 gradually loses stability (for example, in terms of width, the elastic zone of coal pillar 2 gradually becomes the plastic zone, resulting in instability), the instability of coal pillar 2 is a gradual process. Therefore, the impact generated when the main roof collapses is small, which is conducive to the normal mining operation of the 21407 working face. Furthermore, since the instability of coal pillar 2 is a gradual process, the full mining of the two working faces in terms of width is also a gradual process. The transfer of the goaf to the separation position is also a gradual process, which is conducive to the grouting and filling of the overburden separation and the disposal of gangue.

[0020] 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 green coal mining method involving grouting and backfilling of overlying rock in a side-side goaf, characterized in that, include: S1: Within the already mined working face, several goaf grouting boreholes are constructed at intervals along the length of the working face. On the width of the working face, the goaf grouting boreholes are close to the coal wall support area. S2: Construct a grouting and filling system and connect it to the grouting boreholes in the goaf; S3: Inject gangue mixed slurry into the goaf from the grouting borehole; S4: Leave a section coal pillar for goaf excavation. 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 collapse, and loses stability after the basic roof collapses. S5: Select the overburden grouting layer; Seal the portion of the goaf grouting borehole below the grouting layer and change the goaf grouting borehole to a separation grouting borehole; S6: Within the working face to be mined, construct several separation grouting boreholes at intervals along the length of the working face; connect the grouting filling system to the separation grouting boreholes through filling pipelines; S7: 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 green coal mining method for grouting and filling overburden in one-sided mining as described in claim 1, characterized in that, In step S4, maintaining the stability of the coal pillar section means maintaining a certain amount of elastic zone in the center of the width.

3. The green coal mining method for grouting and backfilling overburden in one-sided mining as described in claim 1, characterized in that, In step S4, the loss of stability of the coal column section means that the elastic zone in the center of the width becomes the plastic zone.

4. The green coal mining method for grouting and filling overburden in one-sided mining as described in claim 1, characterized in that, In step S5, an isolation layer of a certain thickness is set upwards 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.

5. The green coal mining method for grouting and backfilling overburden in one-sided mining as described in any one of claims 1-4, characterized in that, The grouting and filling 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 filling pump and a filling body pipeline. The secondary pumping station is connected to the grouting borehole via the filling pipeline.

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