Method for active pumping and recycling of water separated from grouting slurry in overburden rock isolation grouting and filling

Abstract

This invention relates to the field of coal mine backfilling mining, specifically to a method for actively pumping out and recycling water from grouting slurry used in overburden isolation backfilling. This invention involves pre-constructing grouting boreholes for the next working face, and during grouting and backfilling of the previous working face, utilizing these boreholes to drain water seeping into the rock strata from the previous working face. By fracturing the fractures in a plane, the pumping efficiency of the seeping water can be greatly improved. This not only eliminates the potential risk of water inrush to the working face from the seeping water, but also allows the pumped-out water to be reused as grouting water, reducing the total amount of water used for grouting. This has significant engineering implications for alleviating the water shortage situation in water-scarce mines. This invention controls the amount of seeping water by calculating the water content in the grout injected from the previous working face and controlling the amount of water pumped out. This further controls the amount of water remaining in the overburden of the previous working face, thereby facilitating an increase in the amount of solid filler injected into the overburden fractures and improving the subsidence control effect.

Description

Technical Field

[0001] This invention relates to the field of coal mine backfilling mining, specifically to a method for actively pumping out and recycling the slurry precipitated from the backfilling grout. Background Technology

[0002] Overburden isolation grouting and backfilling is a green mining technology that liberates coal resources under the "three underground" (underground, underground, and underground) and effectively protects surface buildings and structures. It is of great significance for ensuring efficient coal resource recovery and alleviating the tension in mine succession. Simultaneously, overburden isolation grouting and backfilling technology has a positive impact on the treatment of fly ash solid waste and the prevention of gangue discharge. Grouting water, as the fluid medium carrying fly ash and gangue powder, is an indispensable raw material in the preparation of grouting slurry. Because the backfilling slurry needs a certain degree of fluidity, the water-to-solid material ratio in the prepared slurry must be maintained at a certain mass ratio (e.g., 1.0~1.4). When the water-cement ratio is low, the fluidity is poor, making effective transportation difficult and resulting in poor grouting effect. Only when the water-cement ratio reaches a certain value does the fluidity improve, but this requires a larger water consumption.

[0003] A high water-ash ratio brings numerous engineering problems. In regions where coal and water resources are characterized by "rich coal and poor water," meaning coal-producing areas face water scarcity, this becomes a limiting factor for the large-scale application of grouting technology. The water used in grouting, after being injected into the fissures of the formation by a pressurized pump, is subjected to formation pressure. Part of it seeps out of the grout, permeating and diffusing into the pores and fissures of the rock strata as free water. The remainder is stored in the fly ash and gangue compacted within the overlying strata. This seeping and diffusing water from the grout, influenced by various factors such as geological structure, has the potential to migrate to the underground coal face, causing water inrush and posing a potential risk to safe production.

[0004] One way to reduce water consumption is to add water-reducing agents. However, existing water-reducing agent products are limited by economic costs, making large-scale application difficult. Therefore, how to improve the utilization rate of water in overburden isolation grouting, avoid water resources becoming a constraint on the application of grouting technology, and improve the safety of grouting production have become urgent problems to be solved.

[0005] It should be noted that the information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of this invention, and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] To address the shortcomings of the existing technology, this invention proposes a method for draining and recycling the precipitated water from the grouting filling for overburden isolation, comprising the following steps: S1: Several adjacent working faces are arranged within the coal seam, and the mining sequence is sequential mining; S2: Select the key grouting layer. The key grouting layer refers to the grouting layer or main grouting layer below the key layer. That is, the bottom surface of the rock layer of the key grouting layer and the top surface of the rock layer below it form a mining-induced fracture for grouting filling. S3: Construct several vertical grouting boreholes on the surface above the first mining face, and continue drilling the grouting boreholes until the mining begins below the key grouting layer. S4: Determine the water-tight rock layer closest to the grouting key layer in the vertical direction; construct several vertical grouting boreholes on the ground surface above the second working face; construct the grouting boreholes in the second working face to the point where they are close to the water-tight rock layer closest to the grouting key layer and located below the grouting key layer. S5: The first mining face is mined and grout is injected into the grouting boreholes within it; water is actively pumped out from the grouting boreholes in the second mining face. Following step S4, grouting drilling is carried out in the third working face; following step S5, the mining and grouting work of the first working face is carried out in the second working face; this process is repeated until the mining and grouting work of all working faces is completed.

[0007] Preferably, in step S2, the key grouting layer is located above the water-conducting fracture zone and is separated from the water-conducting fracture zone by a rock layer as an isolation layer.

[0008] Preferably, in step S3, the grouting boreholes are arranged at intervals along the working face advancing direction in the first mining face; in step S4, the grouting boreholes are arranged at intervals along the working face advancing direction in the second mining face.

[0009] Preferably, in step S4, the self-grouting borehole constructs planar fracturing fractures in the rock strata between the key grouting layer and the upper water-resistant rock strata closest to the key grouting layer, and constructs planar fracturing fractures in the rock strata between the key grouting layer and the lower water-resistant rock strata closest to the key grouting layer, with the planar fracturing fractures having the same dip angle as the rock strata.

[0010] Preferably, in step S4, the planar fracturing fracture is located between adjacent rock layers.

[0011] Preferably, in step S4, the planar fracturing cracks on the working face width cannot reach the grout diffusion range during the grouting process of the first working face.

[0012] Preferably, in step S5, during the mining process, fly ash slurry and / or gangue powder slurry are injected into the mining fractures below the key grouting layer from the grouting borehole of the first mining face. The fly ash slurry is a slurry made by mixing fly ash and water, and the gangue powder slurry is a slurry made by mixing gangue powder and water.

[0013] Preferably, in step S5, water is actively pumped from the grouting borehole in the second working face to create a pressure difference between the grout precipitated water in the rock strata and the corresponding section in the grouting borehole. This guides the grout precipitated water in the rock strata to flow towards the grouting borehole in the second working face and is then pumped out from the grouting borehole to the ground for recycling as a water source for grout production.

[0014] Preferably, by calculating the water content in the grout injected into the first mining face, the amount of water extracted from the grouting borehole in the second mining face is controlled, thereby controlling the amount of water remaining in the mining-induced fractures of the first mining face and increasing the amount of ash body injected into the mining-induced fractures.

[0015] Preferably, after the first mining face is completed and grouting is completed, the planar fracturing fractures in the second working face are sealed with reinforcement materials, and the bottom part of the grouting boreholes in the second working face is sealed with reinforcement materials, so that the grouting boreholes in the second working face end at the selected mining-induced fracture position below the key grouting layer.

[0016] The inventive points and beneficial effects of this invention are as follows: 1. This invention pre-constructs grouting boreholes for the next working face, and during grouting and filling of the previous working face, the grouting boreholes of the next working face are used to drain the water that seeps into the rock strata during grouting and filling of the previous working face. The efficiency of draining the seeping water can be greatly improved by fracturing the fractures in the plane. This invention not only eliminates the potential risk of water seepage from the grout to the working face, but also allows the drained seeping water to be reused as grouting water, reducing the total amount of grouting water used. This has important engineering significance for alleviating the shortage of filling water in water-scarce mines.

[0017] 2. The technical solution of the present invention controls the amount of water released by calculating the amount of water contained in the grout injected in the previous working face and controlling the amount of water extracted. This can further control the amount of water remaining in the overburden of the previous working face, thereby facilitating the increase of the amount of solids filled in the fissures of the injected overburden and improving the settlement control effect. Attached Figure Description

[0018] Figure 1 This is a plan view of the borehole layout during the first mining operation of this invention, involving grouting and filling of the overlying rock isolation face.

[0019] Figure 2 This is a cross-sectional view of the borehole layout during the first mining operation of this invention, involving grouting and filling of the overlying rock isolation face.

[0020] Figure 3 This is a plan view of the borehole layout during the overburden isolation grouting and backfilling mining of the second working face of the present invention.

[0021] Figure 4 This is a cross-sectional view of the borehole layout during the overburden isolation grouting and backfilling mining of the second working face of this invention.

[0022] In the diagram: Coal seam-1, rock strata-2, water-resistant rock strata-3, grouting key layer-4, working face-5, coal pillar-6, grouting borehole-7, hydraulic fracturing fracture-8, mining-induced fracture-9, filling body-10, reinforcement material-11; goaf-12. Detailed Implementation

[0023] 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.

[0024] This invention proposes a method for pumping out and recycling the water released from the grout during rock overburden isolation grouting, such as... Figures 1-4 As shown, it includes the following steps: S1: Several adjacent working faces 5 are arranged in the coal seam 1. Coal pillars 6 are set between the working faces 5 according to production needs, or coal pillars 6 may not be set. The design is to carry out mining and overburden isolation grouting backfilling of the working faces 5 from left to right. That is, the leftmost one in the figure is the first mining working face, followed by the second and third working faces in sequence. According to geological conditions, the fourth working face, the fifth working face, etc. can be set up later.

[0025] S2: Determine the location of the key layer in rock stratum 2 and select the key grouting layer 4. The key grouting layer 4 refers to the grouting layer or main grouting layer below the key layer. That is, the bottom surface of the rock stratum of the key grouting layer 4 and the top surface of the rock stratum below it form a mining-induced fracture 9 for grouting filling. The key grouting layer 4 is located above the water-conducting fracture zone and is separated from the water-conducting fracture zone by rock stratum 2 as an isolation layer.

[0026] S3: Along the advancing direction of working face 5 in the first mining face ( Figure 1 (In the front and rear direction) Several vertical grouting boreholes 7 are constructed at intervals on the ground surface above the first mining face. The grouting boreholes 7 are finally constructed to the selected mining-induced fracture 9 position below the key grouting layer 4.

[0027] S4: Determine the water-resistant rock layer 3 closest to the grouting key layer 4 in the vertical direction. The water-resistant rock layer 3 is generally a rock layer with low porosity, such as mudstone or shale, which is basically not permeable by water. In the second working face adjacent to the first mining working face, construct several vertical grouting boreholes 7 at intervals on the ground surface above the second working face along the advancement direction of the second working face. The grouting boreholes 7 in the second working face are constructed to the point where they are close to the water-resistant rock layer 3 closest to the grouting key layer 4 and located below the grouting key layer 4. That is, the final hole of the grouting borehole 7 in the second working face is close to the water-resistant rock layer 3 located below the grouting key layer 4, but is not constructed to the point where it is located below the grouting key layer 4. The self-grouting borehole 7 constructs planar fracturing fractures 8 in the rock strata between the key grouting layer 4 and the nearest upper water-resistant rock stratum 3, towards the first mining face. The self-grouting borehole 7 also constructs planar fracturing fractures 8 in the rock strata between the key grouting layer 4 and the nearest lower water-resistant rock stratum 3, towards the first mining face. The planar fracturing fractures 8 are at the same dip angle as the rock strata. The planar fracturing fractures 8 are preferably located between adjacent rock strata 2. The planar fracturing fractures 8 should not reach the slurry diffusion range during the grouting process of the first working face in terms of the working face width. Preferably, the distance from the coal pillar 6 between the second working face and the first mining face is 20-40m.

[0028] S5: The first mining face is then mined. During the mining process, fly ash slurry and / or gangue powder slurry are injected into the mining-induced fracture 9 below the key grouting layer 4 from the grouting borehole 7 of the first mining face. The fly ash slurry is made by mixing fly ash with water, and the gangue powder slurry is made by mixing gangue powder with water. Under the grouting filling pressure and formation pressure, the slurry injected into the mining-induced fracture 9 is compressed into filling ash body 10 by the seepage water. A small amount of water exists in the mining-induced fracture 9, and the remaining water will seep into the surrounding sandstone and other highly permeable rock layers 2. Water is actively pumped from the grouting borehole 7 in the second working face to remove the slurry seeping into the rock layer 2. The pressure difference between the precipitated water and the corresponding layer in the grouting borehole 7 guides the grout precipitated water from the rock stratum 2 to flow towards the grouting borehole 7 of the second working face, and is then extracted from the grouting borehole 7 of the second working face to the ground surface, where it is recycled as a water raw material for making grout. By pumping water out of the grouting process of the first mining face through the grouting borehole 7 of the second working face, it is possible to avoid the water precipitated in the rock stratum 2 from flowing into the goaf 12, thus avoiding the potential risk of water inrush at the working face (the isolation layer and the water-resistant rock stratum 3 may develop micro-cracks due to mining, resulting in a certain seepage capacity). At the same time, it is also possible to recycle the water, reduce the overall water consumption, and save water.

[0029] In addition, by calculating the amount of water contained in the grout injected into the first mining face and controlling the amount of water extracted from the grouting borehole of the second mining face (i.e., controlling the amount of water exuded from the mining-induced fracture 9 of the first mining face), the amount of water remaining in the mining-induced fracture 9 of the first mining face can be controlled, thereby increasing the amount of ash body 10 injected into the mining-induced fracture 9 and improving the subsidence control effect.

[0030] S6: After the first mining face is completed and grouting is completed, the plane pressure fracture 8 in the second working face is sealed with reinforcement material 11, and the bottom part of the grouting borehole 7 in the second working face is sealed with reinforcement material 11, so that the grouting borehole 7 in the second working face ends at the selected mining fracture 9 position below the grouting key layer 4.

[0031] S7: Referring to step S4, grouting drilling is carried out in the third working face. Specifically, in the third working face adjacent to the second working face, several vertical grouting holes 7 are drilled at intervals on the ground surface above the third working face along the advancing direction of the third working face. The grouting holes 7 in the third working face are drilled to a position close to the water-resistant rock layer 3 located below the grouting key layer 4. That is, the final hole of the grouting hole 7 in the third working face is close to the water-resistant rock layer 3 located below the grouting key layer 4, but is not drilled to the water-resistant rock layer 3 located below the grouting key layer 4. Planar fracturing fractures 8 are constructed in the rock strata between the nearest upper water-resistant rock stratum 3 to the grouting key layer 4, and in the rock strata between the grouting key layer 4 and the nearest lower water-resistant rock stratum 3 to the grouting key layer 4, and in the direction of the second working face. The planar fracturing fractures 8 are at the same dip angle as the rock strata. The planar fracturing fractures 8 are preferably located between adjacent rock strata 2. The planar fracturing fractures 8 should not reach the grout diffusion range during the grouting process of the second working face in the working face width. The distance from the coal pillar 6 between the third working face and the first mining face is preferably 20-40m.

[0032] S8: Referring to the mining and grouting work of the first mining face in step S5, the second mining face is also mined and grouted. Specifically, during the mining process of the second mining face, fly ash slurry and / or gangue powder slurry are injected into the mining fracture 9 below the grouting key layer 4 from the grouting borehole 7 of the second mining face. The fly ash slurry is a slurry made by mixing fly ash and water, and the gangue powder slurry is a slurry made by mixing gangue powder and water, so that the grouting borehole 7 can serve multiple purposes. The grout injected into the mining-induced fracture 9 is compressed into filling ash body 10 by the seepage of water under the action of formation pressure and grouting filling pressure. There is a small amount of water in the mining-induced fracture 9, and the rest of the water will seep into the surrounding sandstone and other rock layers with strong permeability 2. Negative pressure pumping is carried out from the grouting borehole 7 of the third working face to guide the water seeping into the rock layer 2 to flow towards the grouting borehole 7 in the third working face, and then pumped out from the grouting borehole 7 to the ground surface, where it is recycled as water raw material for making grout.

[0033] In addition, by calculating the amount of water contained in the grout injected into the second working face and controlling the amount of water extracted from the grouting borehole of the third working face (i.e., controlling the amount of water exuded from the mining-induced fracture 9 of the second working face), the amount of water remaining in the mining-induced fracture 9 of the second working face can be controlled, thereby facilitating an increase in the amount of ash body 10 injected into the mining-induced fracture 9 and improving the settlement control effect.

[0034] S9: Repeat this process until all working faces have completed the backfilling and grouting work.

[0035] 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 draining and recycling water from grouting fluid used in grouting for rock overburden isolation, characterized in that: Includes the following steps: S1: Several adjacent working faces are arranged within the coal seam, and the mining sequence is sequential mining; S2: Select the key grouting layer. The key grouting layer refers to the grouting layer or main grouting layer below the key layer. That is, the bottom surface of the rock layer of the key grouting layer and the top surface of the rock layer below it form a mining-induced fracture for grouting filling. S3: Construct several vertical grouting boreholes on the surface above the first mining face, and continue drilling the grouting boreholes until the mining begins below the key grouting layer. S4: Determine the water-tight rock layer closest to the grouting key layer in the vertical direction; construct several vertical grouting boreholes on the ground surface above the second working face; construct the grouting boreholes in the second working face to the point where they are close to the water-tight rock layer closest to the grouting key layer and located below the grouting key layer. S5: The first mining face is mined and grout is injected into the grouting boreholes within it; water is actively pumped out from the grouting boreholes in the second mining face. Following step S4, grouting drilling is carried out in the third working face; following step S5, the mining and grouting work of the first working face is carried out in the second working face; this process is repeated until the mining and grouting work of all working faces is completed.

2. The method for draining and recycling the precipitated water from the grouting filling for overburden isolation according to claim 1, characterized in that, In step S2, the key grouting layer is located above the water-conducting fracture zone and is separated from the water-conducting fracture zone by a rock layer as an isolation layer.

3. The method for draining and recycling the grout effluent from the overburden isolation grouting filling as described in claim 1, characterized in that, In step S3, grouting boreholes are arranged at intervals along the working face advancing direction in the first mining face; in step S4, grouting boreholes are arranged at intervals along the working face advancing direction in the second mining face.

4. The method for draining and recycling the precipitated water from the grouting filling for overburden isolation according to claim 1, characterized in that, In step S4, the self-grouting borehole constructs planar fracturing fractures in the rock strata between the key grouting layer and the upper water-resistant rock strata closest to the key grouting layer, and constructs planar fracturing fractures in the rock strata between the key grouting layer and the lower water-resistant rock strata closest to the key grouting layer, with the planar fracturing fractures having the same dip angle as the rock strata.

5. The method for draining and recycling the grout effluent from the overburden isolation grouting filling as described in claim 4, characterized in that... In step S4, the planar hydraulic fracturing fracture is located between adjacent rock layers.

6. The method for draining and recycling the precipitated water from the grouting filling for overburden isolation according to claim 5, characterized in that, In step S4, the planar fracturing cracks on the working face width cannot reach the grout diffusion range during the grouting process of the first working face.

7. The method for draining and recycling the precipitated water from the grouting filling for overburden isolation according to any one of claims 1-6, characterized in that, In step S5, during the mining process, fly ash slurry and / or gangue powder slurry are injected into the mining fractures below the key grouting layer from the grouting borehole of the first mining face. The fly ash slurry is a slurry made by mixing fly ash and water, and the gangue powder slurry is a slurry made by mixing gangue powder and water.

8. The method for draining and recycling the precipitated water from the grouting filling for overburden isolation according to any one of claims 1-6, characterized in that, In step S5, water is actively pumped from the grouting borehole in the second working face to create a pressure difference between the grout precipitated water in the rock strata and the corresponding section in the grouting borehole. This guides the grout precipitated water in the rock strata to flow towards the grouting borehole in the second working face and is then pumped out from the grouting borehole to the ground for recycling as a water source for grout production.

9. The method for draining and recycling the precipitated water from the grouting filling for overburden isolation according to any one of claims 1-6, characterized in that, By calculating the water content in the grout injected into the first mining face, the amount of water extracted from the grouting borehole in the second mining face is controlled, thereby controlling the amount of water remaining in the mining-induced fractures of the first mining face and increasing the amount of ash body injected into the mining-induced fractures.

10. The method for draining and recycling the precipitated water from the grouting filling for overburden isolation according to any one of claims 4-6, characterized in that... After the first mining face is completed and grouting is completed, the planar fracturing fractures in the second working face are sealed with reinforcement materials, and the bottom part of the grouting boreholes in the second working face is sealed with reinforcement materials, so that the grouting boreholes in the second working face reach the selected mining-induced fracture position below the key grouting layer.

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