Goaf floor grouting filling water conservation coal mining method

Abstract

The present application relates to the field of coal mine water-preserved mining and filling mining, in particular to a goaf floor grouting filling water-preserved coal mining method; it is especially suitable for the working condition that there are multiple pressure-bearing water-rich strata in the coal seam roof, and the water inflow of the top water mining is large, comprising arranging the mining face in the mining area, determining the range of the floor failure zone below the coal seam, selecting a certain thickness of strata below the floor failure zone as the floor grouting pressure-bearing layer; constructing the directional grouting borehole from the ground outside the working face cut, the horizontal section of the directional grouting borehole is constructed close to the bottom interface of the floor pressure-bearing protective layer, and is constructed at least to a certain range inside the working face; after the working face pushes through the open cut by a certain distance, high-pressure grouting filling is carried out through the directional grouting borehole; the grout injected into the floor and the floor crushing and swelling caused by grouting together offset part of the space generated by the coal seam mining, reduce the equivalent mining height of the coal seam, and further reduce the height of the water-conducting fractured zone, so as to realize water-preserved coal mining.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coal mine water-preserved mining and backfill mining, in particular to a goaf floor grouting and filling water-preserved mining method. BACKGROUND

[0002] When there are multiple layers of pressure-bearing water-bearing rock layers above the coal seam roof, especially when the water-bearing rock layers are located in the water-conducting fractured zone or close to the water-conducting fractured zone, the water-preserved mining technology is particularly important and becomes a core element in the green coal mining strategy. Mining activities reveal that even if the water-conducting fractured zone caused by mining is separated from the water-bearing rock layer by a certain distance, water can still seep into the mining area through the developed rock fissures. This enhanced permeability caused by mining and the absence of an aquiclude make water resources face the risk of loss. Without effective water-preserved measures, long-term and intensified mining will lead to the gradual depletion of water resources in the water-bearing layer, seriously threatening the regional ecological environment. Therefore, the water-preserved mining technology plays a crucial role in protecting water resources and ecological balance in the mining area. SUMMARY

[0003] To solve the above technical problems, the present application provides a goaf floor grouting and filling water-preserved mining method, which comprises the following steps:

[0004] S1: arranging a mining working face in the mining area, and arranging coal pillars on both sides of the mining working face;

[0005] S2: determining the range of the floor failure zone below the coal seam based on the lithology and thickness of the floor rock layer, and the floor failure zone can form a water-conducting channel; selecting a certain thickness of rock layer below the floor failure zone as a floor grouting pressure-bearing layer, and the floor grouting pressure-bearing layer arches under the grouting pressure, but does not generate cracks that connect to the cracks in the floor failure zone above, or the generated cracks do not communicate with the cracks in the floor failure zone;

[0006] S3: constructing a directional grouting borehole from the ground outside the open-off cut of the working face, and the horizontal section of the directional grouting borehole is constructed close to the bottom interface of the floor pressure-bearing protection layer and at least constructed to a certain range within the working face;

[0007] S4: after the working face is pushed through the open-off cut by a certain distance, high-pressure grouting and filling are performed through the directional grouting borehole;

[0008] S5: the working face is continuously mined forward, and grouting is continuously performed from the directional grouting borehole, and the grouting is stopped when the slurry cannot be injected after the working face mining is completed.

[0009] Preferably, the method is particularly suitable for the working condition that there are multiple layers of pressure-bearing water-rich rock layers above the coal seam roof and the water inflow of the top water mining is large.

[0010] The application point and beneficial effect of the present application: the present application is aimed at the working condition of multi-layer pressure-bearing water-rich rock stratum existing in the coal seam roof and large water inflow in the coal mining with water on top, and creatively proposes a goaf floor grouting and filling water conservation coal mining method, the slurry injected into the floor and the grouting cause the floor to crush and swell, which together offset part of the space generated by the coal seam mining, thereby reducing the equivalent mining height of the coal seam (actual mining height minus the mining height offset by filling and crushing and swelling), and further reducing the height of the caving zone, fractured zone and water-conducting fractured zone, so that the water-conducting fractured zone does not communicate with the upper aquifer, thereby realizing water conservation coal mining. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a schematic diagram of water loss of water-bearing rock stratum in the prior art when the conventional caving method is used for mining;

[0012] Figure 2 is a schematic diagram of the principle of the goaf floor grouting and filling water conservation coal mining method in the present application;

[0013] In the figure: floor pressure-bearing layer-1, loose layer-2, floor uniform fracture zone-3, floor crushing and swelling zone-4, coal pillar-5, caving zone-6, fractured zone-7, bedrock aquifer-8, directional grouting borehole-9, grouting slurry-10, water-conducting fractured zone-11. DETAILED DESCRIPTION

[0014] In order to better understand the technical content of the present application, specific embodiments are described below with reference to the accompanying drawings. In the present application, aspects of the present application are described with reference to the accompanying drawings, which show many illustrative embodiments. The embodiments of the present application are not limited to the drawings described. It should be understood that the present application is realized by any one of the above-mentioned various concepts and embodiments, and the concepts and embodiments described in detail below, because the concepts and embodiments disclosed in the present application are not limited to any embodiment. In addition, some aspects disclosed in the present application can be used alone, or in any suitable combination with other aspects disclosed in the present application.

[0015] As Figure 1 shown, when the coal seam is mined using the prior art (such as the caving method), the water-conducting fractured zone 11 can develop to the bedrock aquifer 8 or the water-bearing layer in the loose layer 2; causing the water in the bedrock aquifer 8 or the water in the loose layer 2 to seep into the working face through the water-conducting fractured zone 11 (including the caving zone 6 and the fractured zone 7), thereby causing the water resources to face a serious risk of loss and threatening the stability of the regional ecological environment.

[0016] As Figure 2 described, to solve the above problems, the present application proposes a goaf floor grouting and filling water conservation coal mining method, which is particularly suitable for the working condition of multi-layer pressure-bearing water-rich rock stratum and large water inflow in the coal mining with water on top, and the water conservation coal mining method specifically includes the following steps:

[0017] S1: arranging a mining face in the mining area, and coal pillars 5 on both sides of the mining face;

[0018] S2: determining the range of the floor failure zone below the coal seam based on the lithology and thickness of the floor strata, the floor failure zone including a floor broken and swelling zone 4 and a floor uniform broken zone 3, the floor broken and swelling zone 4 having the floor strata broken into irregular net shapes with relatively small broken blocks, and having certain swelling characteristics due to the gaps between the broken blocks; the floor uniform broken zone 3 having the floor strata broken into regular vertical and horizontal cracks with regular relatively large broken blocks, the floor failure zone being able to form a water conducting channel; selecting a certain thickness of strata (usually including multiple layers of strata) below the floor failure zone as a floor pressure bearing protective layer 1, the floor pressure bearing protective layer 1 arching under the grouting pressure, but not generating cracks that conduct to the upper floor failure zone, or the generated cracks not being communicated with the cracks of the floor failure zone;

[0019] S3: constructing a directional grouting borehole 9 from the ground outside the open-off cut of the working face, the horizontal section of the directional grouting borehole 9 being constructed close to the bottom interface of the floor pressure bearing protective layer 1 and being constructed at least to a certain range within the working face;

[0020] S4: after the working face is pushed through the open-off cut by a certain distance, high pressure grouting and filling is performed through the directional grouting borehole 9, the injected high pressure slurry 10 gradually lifting the floor pressure bearing protective layer 1 and the floor uniform broken zone 3 and the floor broken and swelling zone 4 thereon; the floor uniform broken zone 3 and the floor broken and swelling zone 4 will increase the damage range (compared with the prior art without floor grouting, as shown in Figure 1 ), and the loose degree of the irregular rock blocks in the floor broken and swelling zone 4, i.e. the broken and swelling degree, will also increase, further filling the goaf space together with the injected slurry 10 to offset part of the space formed by the coal seam mining, so as to reduce the equivalent mining height of the coal seam, and the height of the caving zone 6, the fractured zone 7 and the water conducting fractured zone 11 will also be reduced (compared with the prior art without floor grouting, as shown in Figure 1 ), not forming a channel for downward leakage of the aquifer, avoiding the leakage of water in the bedrock aquifer 8 and the loose layer 2, and finally achieving the effect of water conservation;

[0021] S5: continuously mining forward with the working face, continuously grouting from the directional grouting borehole 9, and stopping grouting when the slurry 10 cannot be injected after the mining of the working face is completed.

[0022] The present application is not limited to the above best mode of implementation, and anyone can derive other various forms of methods under the inspiration of the present application, as long as the technical solutions are the same or similar to the present application, they fall within the protection scope of the present application.

Claims

1. A method for grouting and filling the bottom plate of a goaf for water-retaining coal mining, used in situations where there are multiple pressure-bearing, water-rich rock strata in the roof of the coal seam and a large water inflow during top-water mining, characterized in that... Includes the following steps: S1: A longwall face is set up within the mining area, with coal pillars on both sides of the longwall face; S2: Based on the lithology and thickness of the floor strata, determine the extent of the floor failure zone below the coal seam. The floor failure zone can form a water-conducting channel. Select a certain thickness of strata below the floor failure zone as the floor grouting bearing layer. The floor grouting bearing layer arches upward under grouting pressure, but does not generate fissures that connect to the upper floor failure zone, or the generated fissures are not connected to the fissures in the floor failure zone. S3: Construct directional grouting boreholes from the ground outside the working face cut-out. The horizontal section of the directional grouting borehole is constructed close to the bottom interface of the pressure-bearing protective layer of the bottom plate, and is constructed to at least a certain range within the working face. S4: After the working face has been pushed a certain distance past the cut-out, high-pressure grouting is carried out through directional grouting boreholes. The injected high-pressure grout gradually lifts the pressure-bearing protective layer of the bottom plate and the uniform fracture zone and fracture expansion zone of the bottom plate above it. Under the action of grouting, the uniform fracture zone and fracture expansion zone of the bottom plate will increase the damage range, and the looseness of the irregular rock blocks in the fracture expansion zone of the bottom plate will also increase, which further fills the goaf space. Together with the injected grout, it offsets part of the space formed by coal seam mining, thereby reducing the equivalent mining height of the coal seam. The height of the caving zone, fracture zone and water-conducting fracture zone will also be reduced, and the channel for the aquifer to seep downward will not be formed. This avoids the loss of water in the bedrock aquifer and loose layer, and finally achieves the effect of water retention. S5: The working face continues to advance and back mining, and grouting is continuously injected into the self-directional grouting borehole. Grouting stops when grout can no longer be injected after the working face has finished mining.

Images