A method for treating coal mining subsidence areas

Abstract

The present invention relates to the field of coal mining reclamation, and in particular to a method for treating coal mining subsidence areas. The present invention first blocks the water supply from the aquifer outside the subsidence area to the subsidence area, and then drains all the accumulated water in the subsidence area; then injects fly ash material into the caving zone to fill it densely, and then injects water-blocking material into the water-conducting fracture zone to cut off the water-conducting channel between the bedrock layer and the loose layer; then injects water-blocking material into the stratum staggered surface at the loose layer to separate the loose layer in the staggered area from the loose layer outside it; finally, the surface soil in the staggered area is stripped to the same level as the bottom boundary of the uppermost water-blocking layer in the non-staggered areas on both sides, and the same stratum structure as the non-staggered areas on both sides is laid from bottom to top to complete the reclamation. The subsidence area reclaimed by the present invention can be used as fertile farmland, and at the same time, the danger of water inrush in the coal mine can be prevented.

Description

Technical Field

[0001] The present invention relates to the field of coal mining and reclamation, and in particular to a method for treating coal mining subsidence areas. Background Art

[0002] The environmental damage caused by coal mining is receiving increasing attention. In recent years, technologies such as backfill mining and post-mining reclamation have developed rapidly. The main reasons hindering the application of backfill mining are its high cost and the mismatch between backfilling efficiency and coal mining efficiency, resulting in low backfilling efficiency. Therefore, backfill mining is mostly used in areas with existing villages and other structures on the surface. Where the surface is fertile farmland, a mining-first, then reclamation approach is often adopted, where traditional coal mining techniques are used to mine the coal seam, followed by post-mining reclamation.

[0003] Since the coal mining cycle is very long, the mining period of a mining area is generally around 5-10 years, so the timing of reclamation is relatively delayed. For working conditions where the coal seam is relatively shallow or the cumulative mining thickness of the coal seam is large, the cracks generated after mining can penetrate the surface and cause the aquifer in the loose layer to be dislocated. In addition, the rainy season water accumulates in the surface subsidence basin, and eventually the surface water in the post-mining collapse area directly penetrates into the goaf. On the one hand, this will lead to the risk of water inrush in the coal mine. On the other hand, the water in the goaf is connected with the water in the loose layer, which can easily pollute the water in the loose layer. Of course, this is also not conducive to post-mining reclamation work.

[0004] Existing post-mining reclamation methods are mostly applicable to unconnected goafs and unconnected aquifers on the surface. These reclamation methods often involve first filling waste rock materials and then covering with soil. However, this approach only addresses the symptoms, not the root cause. Reclaimed land can be used for construction but cannot be used as fertile farmland. To be used as fertile farmland, an aquifer beneath the topsoil must be present to supply water. Summary of the Invention

[0005] To address the problem that existing reclamation technologies are unable to restore "subsidence areas connected to goaf, surface water, and loose layer aquifers" into fertile farmland, and that there is a risk of underground water inrush, the present invention provides a solution, specifically a method for treating coal mining subsidence areas, comprising the following steps:

[0006] a. Isolate the aquifer within the loose layer of the subsidence basin from the aquifer outside it, preventing the aquifer outside from supplying water to the subsidence area;

[0007] b. Drain the water in the collapsed area;

[0008] c. Estimate the grouting filling volume of the caving zone;

[0009] d. In the staggered area, construct grouting and filling boreholes from the surface to the goaf. First, inject fly ash slurry into the caving zone to the designed amount through the grouting and filling boreholes. Then, inject water-blocking materials into the fissures in the water-conducting fissure zone through the grouting and filling boreholes.

[0010] e. Inject water-blocking materials into the fault plane of the loose layer;

[0011] f. Strip the surface soil directly above the staggered area until it is flush with the bottom boundary of the uppermost aquiclude in the non-staggered areas on both sides, and then lay the same stratum as that in the non-staggered areas on both sides from bottom to top;

[0012] g. The uppermost aquiclude, the uppermost aquifer and the upper soil layer in the subsidence area are repaired and reclaimed as fertile farmland.

[0013] Preferably, in step a, a freezing borehole is constructed at the boundary of the sinking basin to the top surface of the bedrock, and the aquifer is frozen by a freezing method to block the external aquifer from supplying water to the collapsed area; and in step g, the freezing is cancelled.

[0014] Preferably, in step b, the water accumulated in the caving zone is discharged by its own weight in the coal mine, and the water in the water-conducting fracture zone, the water in the aquifer in the loose layer and the surface water are discharged simultaneously through the conductive fractures.

[0015] Preferably, in step b, a high-power water pump is used on the surface to discharge the surface water.

[0016] Preferably, in step c, the current void content of the caving zone is obtained by subtracting the volume of the caving zone before the collapse of the rock formation from the current volume of the caving zone after the collapse, which is the grouting filling amount required for the caving zone.

[0017] Preferably, in step d, a casing is installed in the grouting filling borehole, and the casing comprises two sections, the upper section is a non-porous casing located in the loose layer, and the lower section is a flower pipe located in the water-conducting fracture zone and the caving zone, the slurry holes of the flower pipe are distributed in layers along the axial direction of the casing, and a grouting pipe with a bottom circumferential band seal is inserted into the casing; the grouting pipe and the seal are moved from bottom to top to expose the slurry holes on the flower pipe layer by layer, and the caving zone is grouted layer by layer using the exposed slurry holes, so that the volume of the fly ash entity injected in each layer is equal to the void volume in the caving zone of that layer; the grouting pipe and the seal are moved upward to expose the slurry holes on the flower pipe layer by layer, and facilitate the exposed slurry holes to inject polymer double slurry into the fractures in the water-conducting fracture zone.

[0018] Preferably, in step d, the outer diameter of the sealing plug is equal to the inner diameter of the casing, and the inner diameter of the sealing plug 54 is equal to the outer diameter of the grouting pipe 53 .

[0019] Preferably, in step d, the slurry injected into the caving zone is fly ash slurry, and during grouting, water in the goaf is continuously discharged underground in the coal mine, so that the fly ash remains in the gaps of the caving zone and the water is discharged from the caving zone.

[0020] Preferably, in step d, the polymer double slurry is a polymer double liquid grouting material poly-pressed grease, and the polymer double liquid grouting material poly-pressed grease contains a resin and a catalyst in a volume ratio of 1:1.

[0021] Preferably, in step e, the water-blocking material is asphalt or polymer double slurry, the polymer double slurry is polymer double liquid grouting material poly-pressed grease, and the polymer double liquid grouting material poly-pressed grease contains resin and catalyst in a volume ratio of 1:1.

[0022] Preferably, in step f, first lay an aquiclude and connect it to the uppermost aquiclude in the non-staggered area, then lay an aquifer and connect it to the uppermost aquifer in the non-staggered area, and finally cover with soil to the elevation before collapse.

[0023] The inventive points and beneficial effects of the present invention are as follows: 1. The present invention first blocks the water-bearing layer outside the subsidence area from supplying water to the subsidence area, and then drains all the accumulated water in the subsidence area; then, fly ash material is injected into the caving zone to fill it densely, and then water-blocking material is injected into the water-conducting fracture zone to cut off the water-conducting channel between the bedrock layer and the loose layer; then, water-blocking material is injected into the stratigraphic fault surface at the loose layer to separate the loose layer in the fault zone from the loose layer outside it; finally, the surface soil in the fault zone is stripped to the same level as the bottom boundary of the uppermost water-blocking layer in the non-faulted areas on both sides, and the same stratigraphic structure as the non-faulted areas on both sides is laid from bottom to top to complete the reclamation. The subsidence area reclaimed by the present invention can be used as fertile farmland, and at the same time, the danger of water inrush in the coal mine can be prevented.

[0024] 2. The grouting drilling structure proposed in this invention can significantly increase the grouting volume in the caving zone, ensuring its compactness and providing a foundation for the subsequent injection of water-blocking materials into the water-conducting fracture zone, which would otherwise drain into the caving zone. Furthermore, the simultaneous grouting and drainage technology also helps increase the grouting volume in the caving zone, ensuring its compactness. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 —Schematic diagram of a stratum cross section before coal seam mining according to an embodiment of the present invention;

[0026] Figure 2 —Schematic diagram of a stratum cross section after coal seam mining according to an embodiment of the present invention;

[0027] Figure 3 —Schematic cross-section diagram of the treatment of coal mining subsidence area according to an embodiment of the present invention;

[0028] Figure 4 —Schematic diagram of the grouting filling drilling structure according to an embodiment of the present invention;

[0029] Figure 5 —Schematic cross-sectional view of a coal mining subsidence area after treatment according to an embodiment of the present invention;

[0030] Description of the drawings: loose layer 1, ground surface 10, first aquifer 11, first aquiclude 12, second aquifer 13, second aquiclude 14, third aquifer 15, third aquiclude 16, through-going fissure 17, sinking basin 18, sinking basin boundary 19; bedrock layer 2, bedrock top surface 20, water-conducting fissure zone 21, caving zone 22; coal seam 3, coal pillar 31; frozen borehole 4; grouting borehole 5, casing 51, flower pipe 52, grouting pipe 53, first sealing plug 54, first water-proof filling body 55, second water-proof filling body 56; surface water 6; staggered layer area 7, stratum staggered layer surface 71; repaired aquifer 11′, repaired aquiclude 12′. DETAILED DESCRIPTION

[0031] In the detailed implementation section, Figure 1-5 The technical solution of the present invention is elaborated in detail.

[0032] like Figure 1-2 As shown, a coal seam 3 in a certain mining area is located under fertile farmland. Between the coal seam 3 and the ground surface 10, there are a bedrock layer 2 and a loose layer 1. The loose layer 1 contains three aquifers from top to bottom, namely the first aquifer 11, the second aquifer 13, and the third aquifer 15. The lower parts of these three aquifers are the first aquiclude 12, the second aquiclude 14, and the third aquiclude 16. Since the coal seam mining height 3 is relatively large and the bedrock layer 2 is thin, the cracks generated in the stratum after the coal seam 3 is mined directly reach the ground surface 10, and a sinking basin is formed on the ground surface 10. The ground 18 (the surface manifestation of the collapsed area) also produces a caving zone 22 and a water-conducting fracture zone 21 above it in the bedrock layer 2. The water-conducting fracture zone 21 penetrates to the top surface 20 of the bedrock. A longitudinal through-fracture 17 is also produced in the loose layer 1. At the same time, the strata within the loose layer 1 (including the aquifer and the aquiclude) and the strata within the bedrock layer 2 (the dislocations within the bedrock layer are mainly the rock layers within the water-conducting fracture zone, and the rock layers in the caving zone collapse to form broken, unlayered rock blocks) also produce dislocations, forming a dislocation zone 7 within the stratum dislocation plane 71. Due to the dislocations between the aquifer and the aquiclude within the loose layer 1, water in the aquifer in the loose layer and surface water 6 flow downward from the stratum dislocation plane 71 and the through-fracture 17 to the water-conducting fracture zone 21 and the caving zone 22 in the bedrock layer. If the water in the first aquifer 11 has a certain water pressure, the water in the first aquifer 11 will flow into the surface sinking basin 18 , and together with the accumulated water during the rainy season, will eventually form surface water 6 in the sinking basin 18 .

[0033] When reclaiming land for the above working conditions and reducing the possibility of water inrush in the mine, the problem of interconnectedness of the goaf (mainly the caving zone 22), the aquifer in the loose layer, and the surface water 6 is faced. At the same time, the repair of the aquifer when reclaiming land for fertile fields is also difficult. In this regard, the present invention proposes a method for treating coal mining subsidence areas, such as Figure 2-5As shown, first, the freezing method is used to isolate the loose layer in the surface subsidence basin 18 from the loose layer outside it, and all the accumulated water in the collapsed area is drained; then, fly ash material is injected into the caving zone 22 to fill it densely, and then waterproof material is injected into the water-conducting fracture zone 21 to isolate the water-conducting channel between the bedrock layer and the loose layer; then, waterproof material is injected into the stratigraphic fault surface 71 at the loose layer to separate the loose layer in the fault zone 7 from the loose layer outside it; the surface soil in the fault zone 7 is stripped until it is flush with the bottom boundary of the first waterproof layer 12 in the non-faulted areas on both sides, and the same stratigraphic structure as the non-faulted areas on both sides is laid from bottom to top to complete the reclamation.

[0034] The specific steps include:

[0035] a. Construct a freezing borehole 4 at the boundary 19 of the subsidence basin to the top surface 20 of the bedrock. Use the freezing method to freeze the first aquifer 11, the second aquifer 13, and the third aquifer 15, isolating the loose layer within the surface subsidence basin 18 from the loose layer outside it, and blocking the external first aquifer 11, the second aquifer 13, and the third aquifer 15 from supplying water to the subsidence area.

[0036] b. Use a high-powered water pump on the surface to drain the surface water 6. Simultaneously, use the water's own weight to drain the water in the caving zone 22 into the underground water tank in the coal mine until all the water in the subsidence area is drained. The water in the subsidence area includes the surface water 6, the water in the first aquifer 11, the second aquifer 13, the third aquifer 15 in the subsidence area, and the water in the water-conducting fracture zone 21 and the caving zone 22. Since the surface water 6 in the subsidence area, the water in the first aquifer 11, the second aquifer 13, the third aquifer 15, and the water in the water-conducting fracture zone 21 and the caving zone 22 are interconnected, all the water in the subsidence area can be drained from the lower part of the goaf. Using a high-powered water pump on the surface can drain the surface water; draining water from both top and bottom simultaneously can improve the overall drainage efficiency.

[0037] c. Estimated grouting volume of the caving zone 22. The current void content of the caving zone 22 is determined based on the volume of the caving zone 22 before the rock formation collapsed and the current volume of the caving zone 22 after the collapse. Specifically, the current void content of the caving zone is obtained by subtracting the volume of the caving zone before the rock formation collapsed from the current volume of the caving zone after the collapse. This is the required grouting volume (volume) of the caving zone.

[0038] d. Stripping the surface silt in the subsidence basin 18, constructing a grouting borehole 5 from the ground surface 10 to the goaf directly above the staggered zone 7, and installing a casing in the grouting borehole 5. The casing comprises two sections: an upper section, a non-porous casing 51, located in the loose layer 1; and a lower section, a floral pipe 52, located in the water-conducting fracture zone 21 and the caving zone 22. The slurry outlet holes of the floral pipe 52 are layered along the axial direction of the casing. A grouting pipe 53 with a circumferential sealing plug 54 at the bottom is inserted into the casing. The outer diameter of the sealing plug 54 is equal to the inner diameter of the casing, and the inner diameter of the sealing plug 54 is equal to the outer diameter of the grouting pipe 53. The sealing plug can be a rubber plug.

[0039] The grouting pipe 53 and the sealing plug 54 are moved from bottom to top, and the slurry holes on the flower pipe 52 are exposed layer by layer, and the caving zone 22 is grouted layer by layer using the exposed slurry holes. The injected slurry is fly ash slurry. When the grouting filling amount of each layer reaches the design requirement, grouting is performed from the slurry hole of the upper layer, and this process is repeated until the grouting amount of the entire caving zone 22 reaches the designed grouting filling amount. Since the injected slurry is fly ash slurry, it is necessary to remove water from the slurry so that the volume of the injected fly ash entity is equal to the volume of the voids in the caving zone 22. During the grouting filling process of the caving zone, water in the goaf is continuously discharged in the coal mine, so that the fly ash remains in the voids of the caving zone and the water is discharged from the caving zone.

[0040] Continue to move the grouting pipe 53 and the sealing plug 54 from bottom to top, gradually exposing the slurry holes on the flower tube 52, and injecting polymer double slurry into the cracks in the water-conducting fracture zone 21 through the exposed slurry holes, and do this until all the cracks in the water-conducting fracture zone 21 are injected, forming a first water-proof filling body 55 in the cracks, wherein the polymer double slurry is a polymer double-liquid grouting material poly-compressed grease, and the polymer double-liquid grouting material poly-compressed grease contains a resin and a catalyst in a volume ratio of 1:1.

[0041] The construction in step d can isolate the water-conducting channel between the bedrock layer 2 and the loose layer 1 .

[0042] e. Inject water-proof material into the fault plane surface 71 of the loose layer. The water-proof material can be asphalt or polymer double slurry. The polymer double slurry is a polymer double liquid grouting material poly-pressed grease. The polymer double liquid grouting material poly-pressed grease contains a resin and a catalyst in a volume ratio of 1:1.

[0043] The construction in step e can separate the loose layer in the staggered area 7 from the loose layer outside it, thereby preventing water in the outer loose layer from flowing into the staggered area 7 .

[0044] f. Strip the surface soil directly above the staggered area 7 to the level with the bottom boundary of the first aquiclude 12 in the non-staggered areas on both sides. Then, lay the same stratum as that in the non-staggered areas on both sides from bottom to top. That is, first lay the aquiclude to form a repair aquiclude 12', then lay the aquifer to form a repair aquiclude 11'. The repair aquiclude 12' and the repair aquiclude 11' are connected to the first aquiclude 12 and the first aquiclude 11, respectively. Cover the first aquiclude 11 with soil to the elevation before the collapse. Seal and grout the borehole 5.

[0045] g. The freezing is cancelled, and the first aquifer 11, the first aquifer 12 and the upper soil layer in the collapsed area are repaired and reclaimed as fertile farmland. The second aquifer 56 can avoid being affected by the first, second and third aquifers 13 and 15 outside the staggered area. The first aquifer 55 and the first aquifer 12 can block the water in the first aquifer 11 from seeping downward.

Claims

1. A method for treating coal mining subsidence areas, suitable for working conditions where cracks in coal seams reach the surface directly after mining, and only caving zones and water-conducting fracture zones are generated in the bedrock layer, characterized in that: The steps include: a. Isolate the aquifer within the loose layer of the subsidence basin from the aquifer outside it to prevent the aquifer from supplying water to the subsidence area. The loose layer contains multiple aquifers, each of which is directly below an aquiclude. The aquifer and aquiclude are completely disconnected in the staggered area from the non-staggered area, with no vertical connection. b. Drain the water in the collapsed area; c. Estimate the grouting filling volume of the caving zone; d. In the staggered area, construct grouting and filling boreholes from the surface to the goaf. First, inject fly ash slurry into the caving zone to the designed amount through the grouting and filling boreholes. Then, inject water-blocking materials into the fissures in the water-conducting fissure zone through the grouting and filling boreholes. A casing is installed in the grouting and filling borehole, wherein the casing comprises two sections, an upper section being a non-porous casing located in the loose layer, and a lower section being a flower pipe located in the water-conducting fracture zone and the caving zone, wherein the slurry outlet holes of the flower pipe are distributed in layers along the axial direction of the casing, and a grouting pipe with a bottom circumferential band seal plug is inserted into the casing; the grouting pipe and the seal plug are moved from bottom to top to expose the slurry outlet holes on the flower pipe layer by layer, and the caving zone is grouted layer by layer using the exposed slurry outlet holes, so that the volume of the fly ash entity injected in each layer is equal to the void volume in the caving zone of that layer; the grouting pipe and the seal plug are moved upward to expose the slurry outlet holes on the flower pipe layer by layer, and facilitate the exposed slurry outlet holes to inject polymer double slurry into the fractures in the water-conducting fracture zone; e. Inject water-blocking materials into the fault plane of the loose layer; f. Strip the surface soil directly above the staggered area until it is flush with the bottom boundary of the uppermost aquiclude in the non-staggered areas on both sides, and then lay the same stratum as that in the non-staggered areas on both sides from bottom to top; g. The uppermost aquiclude, the uppermost aquifer and the upper soil layer in the subsidence area are repaired and reclaimed as fertile farmland.

2. The method for treating coal mining subsidence area according to claim 1, characterized in that: In step a, a freezing borehole is constructed at the boundary of the sinking basin to the top surface of the bedrock, and the aquifer is frozen using a freezing method to block the external aquifer from supplying water to the collapsed area; in step g, the freezing is canceled.

3. The method for treating coal mining subsidence area according to claim 1, characterized in that: In step b, the water in the caving zone is discharged by its own weight in the coal mine, and the water in the water-conducting fracture zone, the water in the aquifer in the loose layer and the surface water are discharged simultaneously through the conductive fractures.

4. The method for treating coal mining subsidence area according to claim 3, characterized in that: In step b, a high-power water pump is used on the surface to discharge the surface water.

5. The method for treating coal mining subsidence area according to claim 1, characterized in that: In step c, the current void content of the caving zone is obtained by subtracting the volume of the caving zone before the collapse of the rock formation from the current volume of the caving zone after the collapse, which is the grouting filling amount required for the caving zone.

6. The method for treating coal mining subsidence area according to claim 1, characterized in that: In step d, the outer diameter of the sealing plug is equal to the inner diameter of the casing, and the inner diameter of the sealing plug is equal to the outer diameter of the grouting pipe.

7. The method for treating coal mining subsidence area according to claim 1 or 6, characterized in that: In step d, the slurry injected into the caving zone is fly ash slurry. During grouting, water in the goaf is continuously discharged underground in the coal mine, so that the fly ash remains in the gaps of the caving zone and the water is discharged from the caving zone.

8. The method for treating coal mining subsidence area according to claim 1 or 6, characterized in that: In step d, the polymer double slurry is a polymer double liquid grouting material poly-pressed grease, and the polymer double liquid grouting material poly-pressed grease contains a resin and a catalyst in a volume ratio of 1:

1.

9. The method for treating coal mining subsidence area according to claim 1, characterized in that: In step e, the water-proof material is asphalt or polymer double slurry, the polymer double slurry is polymer double liquid grouting material poly-pressed grease, and the polymer double liquid grouting material poly-pressed grease contains resin and catalyst in a volume ratio of 1:

1.

10. The method for treating coal mining subsidence area according to claim 1, characterized in that: In step f, first lay an aquiclude to connect with the uppermost aquiclude in the non-staggered area, then lay an aquifer to connect with the uppermost aquifer in the non-staggered area, and finally cover with soil to the elevation before collapse.

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