Coal mining ecological diving protection method adopting nanobubbles

Abstract

The invention discloses a coal mining ecological diving protection method adopting nanobubbles, which comprises the following steps of: 1, predicting the development height H of a water flowing fractured zone by utilizing a water flowing fractured zone prediction method; 2, calculating the development depth h of the earth surface ground fissures; 3, judging the influence types of coal mining on diving, wherein the influence types comprise a diving rising type, a diving falling type and a diving disappearing type; 4, according to the judgment result in the step 3, corresponding nano bubble technologies are adopted for different influence types; and 5, after coal mining is conducted on the adjacent working faces, the first step to the fourth step are repeated till the phreatic aquifer is artificially or naturally restored, the above steps are stopped, and coal mining ecological environment protection is achieved. The method is wider in application range, atmospheric precipitation can be fully utilized, manual irrigation is reduced, the environment is relatively friendly, and meanwhile the extra labor intensity of underground special mining operation can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical fields of environmental engineering and mining engineering, and particularly relates to a method for protecting ecological phreatic water in coal mining using nano-bubbles. Background Art

[0002] The main areas of coal mining in China are concentrated in ecologically fragile areas. The shallow ecology in ecologically fragile areas is controlled by ecological phreatic water. Therefore, the protection of ecological phreatic water in coal mining areas is of great significance. Existing ecological water protection technologies mainly include means such as reducing coal mining height, filling mining, water storage and irrigation in goafs, artificial irrigation, and leaving protective coal pillars, but there are the following problems:

[0003] 1) Methods such as reducing coal mining height damage coal resources and cause resource waste;

[0004] 2) The mining cost of filling mining increases significantly, and it seriously affects the speed of coal mining, increasing the labor intensity underground;

[0005] 3) Water storage and irrigation in goafs pose a potential threat of water damage to underground coal mining and are not safe enough;

[0006] 4) Artificial irrigation is a waste of water resources in the coal mining fracture zone and is not environmentally friendly enough;

[0007] 5) Magnetization control of the capillary water rise height is applicable to cohesive soils such as loess with capillary rise effect, and the application range is relatively limited. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for protecting ecological phreatic water in coal mining using nano-bubbles, which has a wider application range, can make full use of atmospheric precipitation, reduce artificial irrigation, is relatively environmentally friendly, and can also reduce the additional labor intensity of special mining operations underground.

[0009] To achieve the above purpose, the present invention provides a method for protecting ecological phreatic water in coal mining using nano-bubbles, including the following steps:

[0010] Step 1: Use the prediction method of water-conducting fissure zone to predict the development height H of the water-conducting fissure zone;

[0011] Step 2: Calculate the development depth h of surface ground fissures;

[0012] Step 3: Judge the influence type of coal mining on phreatic water, including phreatic water rising type, phreatic water falling type, and phreatic water disappearing type;

[0013] Step 4: According to the judgment result of Step 3, adopt corresponding nano-bubble technologies for different influence types;

[0014] Step 5: After adjacent coal mining faces, repeat Steps 1 to 4 until the artificial or natural restoration of the phreatic aquifer stops the above steps, achieving the ecological environment protection of coal mining.

[0015] As a further solution of the present invention: In Step 1: In the formula, m is the coal seam mining thickness, obtained through the borehole columnar section; n is the number of coal mining layers, obtained through the coal mining design.

[0016] As a further solution of the present invention: In Step 2: In the formula, c is the cohesion of the surface soil, obtained through soil mechanics experiments; is the internal friction angle of the surface soil, obtained through soil mechanics experiments; γ is the unit weight of the surface soil, obtained through soil mechanics experiments.

[0017] As a further solution of the present invention: In Step 3, the influence type is determined by combining the distance D between the phreatic aquifer underlying aquitard and the mined coal seam, and the relationship between the aquitard thickness M and H, specifically as follows:

[0018] 1) When H ≤ D, it is determined as the phreatic water rising type, and the rising height W = m×α, where m is the coal seam mining thickness and α is the subsidence coefficient;

[0019] 2) When D < H < D + M, it is determined as the phreatic water falling type, and the phreatic water falling height A = N×(H - D) / M, where N is the height of the phreatic water surface from the phreatic aquifer floor before coal mining;

[0020] 3) When H ≥ D + M, it is determined as the phreatic water disappearing type.

[0021] As a further solution of the present invention: In Step 4, corresponding nano - bubble technologies are adopted for different influence types, specifically as follows:

[0022] 1) Phreatic water rising type:

[0023] Drill holes from the ground to the underground, with the drill hole depth greater than h. Install nano - bubble generating devices in the drill holes. Carry out nano - oxygen aeration in the nano - bubble generating devices. The increased oxygen content X2 = W / N×X1, where X1 is the oxygen content of the phreatic water before coal mining, obtained through sampling and testing; the spacing between adjacent drill holes is K×I×T, where K is the permeability coefficient after phreatic water coal mining, obtained through pumping tests; I is the hydraulic gradient after coal mining, obtained through observation and calculation of adjacent drill holes; T is the nano - bubble stability time, taking 12 - 36 hours; the operating time interval of the nano - generating device is a×T, and a is the bubble stability coefficient, taking 0.6 - 0.9;

[0024] 2) Phreatic water falling type:

[0025] If B - (N - A) ≤ 3 meters, the nano - bubble technology is implemented according to the diving - rising type. If B - (N - A) > 3 meters, the following method is adopted: Drill holes from the ground to the underground, with the drilling depth greater than h. Install a nano - bubble generating device in the drill holes. Conduct nano - hydrogen aeration in the nano - bubble generating device until the depth of the phreatic surface from the ground is 1.5 - 3 meters after coal mining. The time interval for the operation of the nano - bubble generating device starts after the phreatic surface drops to 3 meters, and the spacing between adjacent drill holes is the same as that of the rising type. Here, N is the height of the phreatic surface from the phreatic floor before coal mining, obtained from the drill - hole columnar diagram; A is the height of the phreatic surface drop, obtained from step three; B is the height of the phreatic floor from the ground before coal mining, obtained from the drill - hole columnar diagram.

[0026] 3) Diving - disappearance type:

[0027] Drill holes from the ground into the underground at the coal - mining fissures on the ground, with the drilling depth being 1.5 - 3 meters. Inject a clay suspension into the drill holes. The mass ratio of clay to water in the suspension is 1:10 - 20. The injection interval of the suspension is b×T, where b is the stable coefficient of the suspension bubbles, taking 0.9 - 1.0. The injection end criterion is that the injection pressure is greater than 0.1 MPa, and the spacing between adjacent drill holes is 0.8 - 1.2 times of E, where E is the weighting interval of the coal face, obtained from the observation of the coal - mine pressure.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1) It does not require a large number of changes in mining engineering and is simple and easy to implement;

[0030] 2) It is not only applicable to cohesive soils such as loess but also to sandy soils, with a wider application range;

[0031] 3) It makes full use of atmospheric precipitation, reduces artificial irrigation, and is relatively environmentally friendly;

[0032] 4) It does not cause large - scale accumulation of underground water bodies, with better safety;

[0033] 5) It does not affect normal coal - mining engineering and reduces the extra labor intensity of special underground mining operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of the method for protecting ecological phreatic water in coal mining using nano - bubbles of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The present invention will be further described below through embodiments.

[0036] As Figure 1 shown, a method for protecting ecological phreatic water in coal mining using nano - bubbles includes the following steps:

[0037] Step 1: Use the prediction method of water-conducting fissure zone to predict the development height H of the water-conducting fissure zone;

[0038] Specifically, in Step 1: In the formula, m is the coal seam mining thickness, obtained from the borehole columnar section; n is the number of coal mining slices, obtained from the coal mining design;

[0039] Step 2: Calculate the development depth h of surface ground fissures;

[0040] Specifically, in Step 2: In the formula, c is the cohesion of the surface soil mass, obtained from soil mechanics experiments; is the internal friction angle of the surface soil mass, obtained from soil mechanics experiments; γ is the unit weight of the surface soil mass, obtained from soil mechanics experiments;

[0041] Step 3: Judge the influence type of coal mining on the phreatic water, including the phreatic water rising type, the phreatic water falling type, and the phreatic water disappearing type;

[0042] Specifically, in Step 3, the influence type is determined by combining the spacing D between the underlying aquitard of the phreatic water and the coal seam being mined, and the relationship between the thickness M of the aquitard and H, as follows:

[0043] 1) When H ≤ D, it is determined as the phreatic water rising type, and the rising height W = m × α, where m is the coal seam mining thickness and α is the subsidence coefficient;

[0044] 2) When D < H < D + M, it is determined as the phreatic water falling type, and the phreatic water falling height A = N × (H - D) / M, where N is the height of the phreatic water surface above the phreatic water floor before coal mining;

[0045] 3) When H ≥ D + M, it is determined as the phreatic water disappearing type;

[0046] Step 4: According to the judgment result of Step 3, adopt the corresponding nano-bubble technology for different influence types;

[0047] Specifically, in Step 4, for different influence types, adopt the corresponding nano-bubble technology, as follows:

[0048] 1) Phreatic water rising type:

[0049] Implement boreholes from the ground to the underground, with the borehole depth greater than h. Install a nano-bubble generating device in the borehole, and conduct nano-oxygen aeration in the nano-bubble generating device. The increased oxygen content X2 due to aeration is X2 = W / N × X1, where X1 is the oxygen content in the phreatic water before coal mining, obtained through sampling and testing; the spacing between adjacent boreholes is K × I × T, where K is the permeability coefficient after phreatic coal mining, obtained through a pumping test; I is the hydraulic gradient after coal mining, obtained through observation and calculation between adjacent boreholes; T is the nano-bubble stabilization time, taking 12 - 36 hours; the time interval for the operation of the nano-generating device is a × T, and a is the bubble stability coefficient, taking 0.6 - 0.9;

[0050] 2) Phreatic water decline type:

[0051] If B - (N - A) ≤ 3 meters, implement the nano-bubble technology according to the phreatic water rise type. If B - (N - A) > 3 meters, then adopt the following method: Implement boreholes from the ground to the underground, with the borehole depth greater than h. Install a nano-bubble generating device in the borehole, and conduct nano-hydrogen aeration in the nano-bubble generating device until the phreatic water surface after coal mining is at a burial depth of 1.5 - 3 meters from the ground. The time interval for the operation of the nano-bubble generating device starts after the phreatic water surface drops to 3 meters, and the spacing between adjacent boreholes is the same as that of the rise type; where N is the height of the phreatic water surface from the phreatic floor before coal mining, obtained through a borehole columnar diagram; A is the phreatic water decline height, obtained from Step 3; B is the height of the phreatic floor from the ground before coal mining, obtained through a borehole columnar diagram;

[0052] 3) Phreatic water disappearance type:

[0053] Implement boreholes from the ground into the underground at the coal mining fissures on the ground, with the borehole depth being 1.5 - 3 meters. Inject a clay suspension into the borehole. The mass ratio of clay to water in the suspension is 1:10 - 20. The injection interval of the suspension is b × T, and b is the suspension bubble stability coefficient, taking 0.9 - 1.0. The injection end criterion is that the injection pressure is greater than 0.1 MPa. The spacing between adjacent boreholes is 0.8 - 1.2 times E, and E is the weighting interval of coal mining, obtained through the observation of coal mining strata pressure;

[0054] Step Five: After adjacent coal mining working faces, repeat Step One to Step Four until the artificial or natural restoration of the phreatic aquifer stops the above steps, achieving the ecological environmental protection of coal mining.

[0055] The implementation principle of the present invention: Nano-bubbles have 3 main characteristics, corresponding to 3 types of working conditions for ecological phreatic water protection:

[0056] First, nano - bubbles have good stability and adsorption. Compared with millimeter - sized and micron - sized bubbles, the stability of nano - bubbles is improved by more than 4 orders of magnitude. Therefore, during their migration, the bubble stability is always maintained. Combining with the capillary rise and adsorption of clay, they can be stored in the coal - mining fracture soil for a long time. After the bubbles burst, they can continuously provide water resources for vegetation, and it is not easy to cause large - scale loss, improving the utilization rate of water resources. Therefore, it is especially suitable for the type of disappearing phreatic water.

[0057] Second, after adding light gases such as hydrogen, nano - bubbles can significantly reduce the density of the water - gas mixture, thereby effectively raising the water level. The raised water level can effectively offset the problem of the decline in the phreatic water level caused by coal mining. Aiming at protecting the ecological optimal water - level burial depth of 1.5 - 3 meters, it is especially suitable for the situation where the buried depth in the phreatic - water decline type is greater than the ecological suitable phreatic - water level.

[0058] Third, when nano - bubbles burst, they can release a large amount of hydroxyl free radicals and oxygen, which can provide oxygen for the vegetation submerged in water and kill harmful bacteria. It is especially suitable for the phreatic - water rising type.

[0059] During specific implementation:

[0060] The ecological environment of a certain coal mine is fragile. After coal mining, the phreatic water level has dropped, affecting the local ecological environment. In the past, the method of reducing the coal - mining height was used, resulting in a large waste of coal resources. Therefore, on the basis of using this technology to mine coal resources as much as possible, the phreatic water is protected as follows:

[0061] Step 1: Use the prediction method of the water - conducting fissure zone to predict the development height H of the water - conducting fissure zone;

[0062] In the formula, m = 4m, n = 1, and at this time, H = 61.44m;

[0063] Step 2: Calculate the development depth h of the surface ground fissures;

[0064] In the formula, c = 69kPa, which is the cohesion of the surface soil and is obtained through soil mechanics experiments; is the internal friction angle of the surface soil and is obtained through soil mechanics experiments; γ = 17.0kN / m3, which is the unit weight of the surface soil and is obtained through soil mechanics experiments. At this time, h = 14.32m;

[0065] Step 3: Determine the type of influence of coal mining on the phreatic water;

[0066] Combining the distance D = 44.69m between the underlying aquitard of the phreatic water and the coal - mining seam and the thickness M = 40.66m of the aquitard, and the relationship with H, it is determined as the phreatic - water decline type:

[0067] When D = 44.69 < H = 61.44 < D + M = 85.35, it is determined as the type of phreatic water decline. The phreatic water decline height A = N×(H - D) / M = 16×16.75 / 40.66 = 6.59 m, where N = 16 m, which is the height of the phreatic water surface from the phreatic floor before coal mining;

[0068] Step 4: According to the judgment result in Step 3, adopt corresponding nano-bubble water accumulation;

[0069] Since B - (N - A) = 18 - 9.41 = 8.59 > 3 m, the following method is adopted: Drill holes from the ground to the underground with a depth of 15 m. Install nano-bubble generating devices in the holes and conduct nano-hydrogen aeration in the devices until the phreatic water surface after coal mining is 2 m deep from the ground. The operation time interval of the nano-generating device starts after the phreatic water surface drops to 3 m, and the spacing between adjacent drill holes is the same as that in the rising type; where N = 16 m, which is the height of the phreatic water surface from the phreatic floor before coal mining, obtained from the drill hole columnar diagram; A = 6.59 m, which is the phreatic water decline height, obtained from Step 3; B = 18 m, which is the height of the phreatic floor from the ground before coal mining, obtained from the drill hole columnar diagram;

[0070] Step 5: After adjacent coal mining working faces, repeat Steps 1 - 4 until the artificial restoration of the phreatic aquifer stops the above steps, realizing the ecological environment protection during coal mining.

[0071] Since there is no need to reduce coal mining, each working face mines about 0.4 million tons more coal resources, while protecting the local ecological environment and effectively solving the contradiction between coal mining and ecological environment protection.

Claims

1. A method for protecting ecological submergence of coal mining by using nanobubbles, characterized in that: The following steps are involved: Step 1: Use the water-conducting fracture zone prediction method to predict the development height H of the water-conducting fracture zone; Step 2: Calculate the depth h of the ground fissures on the surface; Step 3: Determine the impact type of coal mining on diving, including diving ascent type, diving descent type, and diving disappearance type; Step 4: Based on the results of step 3, adopt corresponding nanobubble technology for different impact types; Step 5: Repeat steps 1 to 4 after the adjacent working face of coal mining until the phreatic aquifer is artificially or naturally restored. Stop the above steps to achieve ecological and environmental protection of coal mining.

2. A method for protecting coal mining ecology and submergence using nanobubbles according to claim 1, characterized in that: In step one: In the formula, m is the mining thickness of the coal seam, which is obtained through the drilling column chart; n is the number of coal mining layers, which is obtained through coal mining design.

3. The method for protecting ecological submergence of coal mining by using nanobubbles according to claim 1, characterized in that: In step 2: In the formula, c is the cohesion of the surface soil, which is obtained through soil mechanics experiments; is the internal friction angle of the surface soil, which is obtained through soil mechanics experiments; γ is the bulk density of the surface soil, which is obtained through soil mechanics experiments.

4. A method for protecting ecological submergence of coal mining using nanobubbles according to any one of claims 1 to 3, characterized in that: The impact type in step 3 is determined by combining the distance D between the underlying impermeable layer and the mined coal seam, and the relationship between the thickness of the impermeable layer M and H, as follows: 1) When H≤D, it is determined to be a diving ascent type, and the ascent height W=m×α, where m is the mining thickness of the coal seam and α is the sinking coefficient; 2) When D<H<D+M, it is determined to be a diving descent type, and the diving descent height A=N×(HD) / M, where N is the height of the diving surface from the diving bottom plate before coal mining; 3) When H≥D+M, it is determined to be a diving disappearance type.

5. A method for protecting ecological submergence of coal mining using nanobubbles according to claim 4, characterized in that: In step 4, corresponding nanobubble technology is adopted for different impact types, as follows: 1) Diving ascent type: Drilling is carried out underground from the ground, the drilling depth is greater than h, a nano bubble generator is buried in the borehole, nano oxygen explosion is carried out in the nano bubble generator, and the oxygen content increased by explosion is X2=W / N×X1, wherein X1 is the diving oxygen content before coal mining, obtained by sampling test; the spacing between adjacent boreholes is K×I×T, wherein K is the permeability coefficient after diving coal mining, obtained by pumping experiment; I is the hydraulic gradient after coal mining, obtained by observation and calculation of adjacent boreholes; T is the nano bubble stabilization time, which is 12 to 36 hours; the time interval of the nano generator operation is a×T, and a is the bubble stability coefficient, which is 0.6 to 0.9; 2) Diving descent type: If B-(NA)≤3 meters, the nanobubble technology is implemented according to the diving ascent type. If B-(NA)>3 meters, the following method is adopted: drilling is carried out underground through the ground, the drilling depth is greater than h, a nanobubble generating device is buried in the borehole, and nano hydrogen aeration is carried out in the nanobubble generating device until the diving surface after coal mining is at a depth of 1.5 to 3 meters from the ground. The time interval of the operation of the nanobubble generating device is carried out after the diving surface drops to 3 meters, and the spacing between adjacent boreholes is consistent with the ascent type; wherein N is the height of the diving surface from the diving bottom plate before coal mining, obtained by the drilling column chart; A is the diving descent height, obtained by step three; B is the height of the diving bottom plate from the ground before coal mining, obtained by the drilling column chart; 3) Types of diving disappearance: Drilling is carried out underground at the coal mining cracks on the ground. The drilling depth is 1.5 to 3 meters. Clay suspension is injected into the borehole. The mass ratio of clay and water in the suspension is 1:10 to 20. The interval of suspension injection is b×T, b is the suspension bubble stability coefficient, which is 0.9 to 1.

0. The injection end standard is that the injection pressure is greater than 0.1MPa. The spacing between adjacent boreholes is 0.8 to 1.2 times of E, where E is the coal mining pressure step distance, which is obtained through coal mining mine pressure observation.

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