Green mining method for bauxite under coal

Abstract

The invention relates to the technical field of bauxite mining, in particular to a green mining method for bauxite under coal, and mainly solves the technical problems that pollutants in a goaf of an upper coal seam easily enter an aluminum layer, the recovery rate is low, an overlying rock layer easily collapses and a large amount of solid waste polluting the environment is generated in existing mining of bauxite under coal. The method comprises the following steps: S1, selecting a target rock stratum; s2, permeability transformation is conducted on the target rock stratum; s3, in-situ presplitting of bauxite; and S4, pillar-free comprehensive mechanical bag type filling mining is carried out. According to the method, old kiln water and poisonous and harmful gas in a coal seam goaf can be prevented from entering an aluminum mining working face during aluminum layer recovery, and the safety of aluminum layer recovery operation is greatly improved; ore body strength weakening can be achieved, fully-mechanized coal mining equipment loss is reduced, and fully-mechanized coal mining efficiency is improved; the recovery rate of bauxite can also be improved, and an overlying rock layer is prevented from collapsing; the coal gangue and the red mud can be treated and utilized in a large-scale and green manner, and the influence of industrial solid waste of the coal gangue and the red mud on the ecological environment is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of bauxite mining, and in particular to a green mining method for bauxite under coal. Background Art

[0002] my country has extremely rich reserves of bauxite resources, of which Shanxi Province accounts for about 40% of the country's bauxite reserves, ranking first in the country. Most of the bauxite in Shanxi Province is found in the Benxi Formation of the Middle Carboniferous System, closely associated with the Permian coal seams, and underlying the coal-bearing strata.

[0003] The existing mining of bauxite under coal has the following technical problems: First, in the actual production process, considering factors such as investment and production efficiency, the mining sequence of coal and aluminum resources is generally downward mining, that is, mining coal first and then mining aluminum. In the process of downward mining, a large amount of pollutants such as mine wastewater and toxic and harmful gases may accumulate in the goaf of the upper coal seam, and coal mining will cause the development of cracks in the bottom rock layer; if the cracks in the top rock layer are connected with the cracks in the bottom rock layer of the coal seam during aluminum mining, pollutants will enter the aluminum mining site, which will not only affect the safety and efficiency of the mining operation, but also may cause pollution to the underground environment.

[0004] Secondly, due to the high hardness of bauxite ore, the cutting capacity of general comprehensive excavation equipment cannot meet the normal mining needs, and the equipment wears out seriously. Therefore, bauxite mining currently mainly adopts caving mining by blasting. After mining, a large number of pillars are retained to support the roof, resulting in a low bauxite recovery rate of only about 50%. At the same time, under the action of long-term load, the bearing capacity of the pillars will gradually weaken. If the pillars become unstable and cause the overlying rock strata to collapse, the upper water system may be destroyed and the surface may sink, causing ecological environmental damage and geological disasters.

[0005] Third, a large amount of coal gangue and red mud industrial solid waste is generated in the process of coal and bauxite production and washing. If it is not effectively disposed of, it will seriously affect the ecological environment.

[0006] Based on this, it is urgent to explore a green mining method suitable for bauxite under coal. Summary of the invention

[0007] In order to overcome the technical defects of existing bauxite mining under coal, such as pollutants in the goaf of the upper coal seam easily entering the aluminum layer, low recovery rate, easy collapse of the overlying rock layer, and generation of a large amount of solid waste that pollutes the environment, the present invention provides a green mining method for bauxite under coal.

[0008] The green mining method of bauxite under coal provided by the present invention comprises the following steps: S1. Select target rock formation: Explore the distribution of rock layers between coal seams and aluminum layers, and select rock layers with relatively large porosity as target rock layers; S2. Improve the permeability of the target rock formation: Adopting multi-branch horizontal directional drilling grouting technology to inject gangue-based slurry into the target rock formation to improve the impermeability of the target rock formation; S3. In-situ pre-cracking of bauxite: Using horizontal directional drilling grouting technology, fracturing fluid is injected into the aluminum layer to create cracks in the bauxite in the aluminum layer; S4. Pillarless comprehensive mechanized bag filling mining: The aluminum layer is divided into several blocks of preset lengths along the mining direction; as the comprehensive mining equipment moves forward, filling bags are hung on the top plate of each mined block in turn, and red mud-based slurry is pumped into the filling bags to support the blocks after solidification.

[0009] Optionally, step S2 includes the following sub-steps: S21. Expand 15m to 60m outward from the boundary of the aluminum mining working face below as the construction area of ​​the target rock layer; S22. The wellhead is arranged on the left side of the construction area, and a first vertical main well is drilled vertically downward to the target rock formation using a single-bend screw drill bit on the ground, and casing and pipe fixing operations are performed simultaneously; S23. Continue to drill horizontally to the right to the first horizontal main well at the right boundary of the construction area, and simultaneously perform casing and pipe fixing operations; S24. Drilling horizontal branch wells on both sides of the first horizontal main well by means of backward sidetracking; S25. Installing oil pipes in the first vertical main well and the first horizontal main well, pumping the gangue-based slurry to the horizontal branch well through the oil pipes, and injecting the gangue-based slurry into the target rock formation through the shotcrete pipe; S26. Carry out grouting operation of the next horizontal branch well in a backward manner until the construction of the entire construction area is completed.

[0010] Optionally, the horizontal branch wells located on both sides of the first horizontal main well are distributed in a feather shape.

[0011] Optionally, the gangue-based slurry is a mixture of gangue fine aggregate, ultrafine cement and water.

[0012] Optionally, step S3 includes the following sub-steps: S31. Use a single-bend screw drill to extend into the first vertical main well and drill a second vertical main well vertically downward at the turning point of the first vertical main well to reach the aluminum layer, and simultaneously perform casing and pipe fixing operations; S32. Continue to drill horizontally to the right to the second horizontal main well at the right boundary of the aluminum mining working face, and simultaneously perform casing lowering and pipe fixing operations; S32. Install a fracturing pipe in the second vertical main well and the second horizontal main well, and install a fracturing device at the front end of the fracturing pipe; S33. Pumping the fracturing fluid into the fracturing device, the fracturing device injects the fracturing fluid into the aluminum layer, causing cracks in the bauxite in the aluminum layer; S34. Complete the fracturing of the bauxite in the entire aluminum mining face by retreating.

[0013] Optionally, the fracturing fluid is a mixture of water, sand and additives.

[0014] Optionally, the red mud-based slurry is a mixture of red mud fine aggregate, cement and water.

[0015] The technical solution provided by the present invention has the following advantages compared with the prior art: 1) The green mining method of bauxite under coal provided by the present invention adopts multi-branch horizontal directional drilling and grouting technology to transform the permeability of the target rock layer with relatively large porosity between the coal seam and the aluminum layer, which can prevent the old kiln water and toxic and harmful gases in the coal seam goaf from entering the aluminum mining working face when the aluminum layer is mined, greatly improving the safety of the aluminum layer mining operation; 2) The green mining method for bauxite under coal provided by the present invention uses a large-scale ground ore body fracturing technology to pre-crack the ore body before the aluminum layer recovery operation, which can weaken the ore body strength, reduce the loss of comprehensive mining equipment, and improve the comprehensive mining efficiency; 3) The green mining method of bauxite under coal provided by the present invention adopts comprehensive mechanized mining combined with bag filling of goaf to recover the ore body, which can greatly improve the recovery rate of bauxite and extend the service life of the mine; and can prevent the collapse of the overlying rock layer and effectively protect the upper water system; 4) The green mining method of bauxite under coal provided by the present invention uses a gangue-based slurry with gangue waste as the main component to transform the permeability of the target rock formation, and uses a red mud-based slurry with red mud waste as the main component to fill the goaf. It can process and utilize gangue and red mud in a large-scale and green manner, avoid the impact of industrial solid waste of gangue and red mud on the ecological environment, and achieve green, low-carbon and high-quality development of mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 A schematic diagram showing the structure of the stratum targeted in the embodiment of the present invention; Figure 2 A flow chart showing a green mining method for bauxite under coal in an embodiment of the present invention; Figure 3 A schematic cross-sectional view showing the operation of step S2 in an embodiment of the present invention; Figure 4 A schematic top view showing the operation of step S2 in an embodiment of the present invention; Figure 5 A schematic diagram showing the installation structure of a grouting pipe in an embodiment of the present invention; Figure 6 A schematic cross-sectional view showing the operation of step S3 in an embodiment of the present invention; Figure 7 A schematic top view showing the operation of step S3 in an embodiment of the present invention; Figure 8 A schematic diagram showing the installation structure of a fracturing device according to an embodiment of the present invention; Fig. 9 A schematic cross-sectional view of the operation of step S4 in an embodiment of the present invention is shown.

[0019] In the figure: 100, aquifer; 200, coal seam; 300, aluminum layer; 400, mudstone layer; 500, sandstone layer; 600, coal pillar; 700, goaf; 1. Ore block; 2. Comprehensive mining equipment; 3. Filling bag; 4. Red mud-based slurry; 5. Aluminum mining face; 6. Construction area; 7. First vertical main shaft; 8. First horizontal main shaft; 9. Horizontal branch shaft; 10. Oil pipe; 11. Grouting pipe; 12. Second vertical main shaft; 13. Second horizontal main shaft; 14. Fracturing pipe; 15. Fracturing machine; 16. First packer; 17. Connecting rod; 18. Second packer. DETAILED DESCRIPTION

[0020] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0021] In the description, it should be noted that the terms “first” and “second” are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0022] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0023] Combine the following Figures 1 to 9 The specific embodiments of the present invention are described in detail.

[0024] Reference Figure 1 The present embodiment is directed to the strata of the second mining area of ​​a certain coal-bauxite mine in Shanxi Province, which has the Quaternary, Neogene, Permian and Carboniferous systems from top to bottom; the Quaternary and Permian systems are rich in groundwater, each with an aquifer 100; the Carboniferous system has a coal seam 200 and an aluminum layer 300, the coal seam 200 has an average burial depth of 182m and an average thickness of 4.6m, the aluminum layer 300 has an average burial depth of 210m and an average thickness of 3.8m, the aluminum mining face 5 is about 500m long and 150m wide, and between the coal seam 200 and the aluminum layer 300 are a mudstone layer 400, a sandstone layer 500 and a mudstone layer 400, which are distributed from top to bottom; the mudstone layer 400 is a mud structure, mainly composed of clay minerals, and has a porosity of about 9%; the sandstone layer 500 is a silty structure, mainly composed of quartz, and has a porosity of about 25%. Due to the limitations of early mining technology, a large number of coal pillars 600 are retained in the residual mining area of ​​coal seam 200 to support the overlying rock strata; due to the impact of mining on the ultra-high development of water-conducting fracture zones, a large amount of old kiln water and toxic and harmful gases are accumulated in the goaf 700 of coal seam 200.

[0025] Reference Figures 2 to 9 This embodiment provides a green mining method for bauxite under coal, including steps S1 to S4.

[0026] S1. Selecting a target rock layer: exploring the distribution of rock layers between the coal layer 200 and the aluminum layer 300, and selecting a rock layer with relatively large porosity as a target rock layer.

[0027] It should be noted that the so-called relatively large means that the porosity of the rock layers between the coal seam 200 and the aluminum layer 300 is the largest. For example, in this embodiment, there are two mudstone layers 400 and one sandstone layer 500 between the coal seam 200 and the aluminum layer 300, and the porosity of the sandstone layer 500 is greater than that of the mudstone layer 400, so the sandstone layer 500 is selected as the target rock layer.

[0028] S2. Transform the permeability of the target rock formation: Use multi-branch horizontal directional drilling grouting technology to inject gangue-based slurry into the target rock formation to improve the impermeability of the target rock formation.

[0029] Specifically, the gangue-based slurry of this embodiment is a mixture of gangue fine aggregate, ultrafine cement and water, and the particle size of the gangue fine aggregate is 0 mm to 5 mm.

[0030] More specifically, the mass ratio of the components of the gangue-based slurry in this embodiment is: gangue fine aggregate: ultrafine cement: water = 1:0.3:1.3. In specific implementation, the mass ratio of the components of the gangue-based slurry can be adjusted in time according to the grouting situation so that the permeability coefficient of the target rock layer after grouting is less than 0.01m / d.

[0031] Specifically, step S2 of this embodiment includes the following sub-steps: S21. Expand 15m to 60m outward from the boundary of the aluminum mining working face 5 below as the construction area 6 of the target rock formation; S22. Arrange the wellhead on the left side of the construction area 6, and use a single-bend screw drill to drill a first vertical main well 7 directly to the target rock formation on the ground vertically downward, and simultaneously perform casing and pipe fixing operations; S23. Continue to drill rightward in the horizontal direction to the first horizontal main well 8 at the right boundary of the construction area 6, and simultaneously Perform casing lowering and pipe fixing operations; S24. Use the backward side drilling method to drill horizontal branch wells 9 on both sides of the first horizontal main well 8; S25. Install oil pipes 10 in the first vertical main well 7 and the first horizontal main well 8, pump the gangue-based slurry into the horizontal branch well 9 through the oil pipes 10, and inject the gangue-based slurry into the target rock formation through the grouting pipe 11; S26. Use the backward method to perform grouting operations in the next horizontal branch well 9 until the construction of the entire construction area 6 is completed.

[0032] More specifically, when the grouting pipe 11 of this embodiment works in the horizontal branch well 9, first packers 16 are provided at both ends, and the gangue-based slurry is injected into the sandstone layer 500 through the grouting pipe 11 under the sealing effect of the two first packers 16; after each grouting of a certain distance, the grouting pipe 11 is pushed forward by the connecting rod 17 to carry out the next grouting until the grouting in the horizontal branch well 9 is completed. In detail, under the pressurized effect of the grouting pump, the grouting diffusion range of the grouting pipe 11 of this embodiment in the sandstone layer 500 can reach up to 30m.

[0033] It should be noted that the single-bend screw drill bit is a mature equipment in the existing technology. It can change the well inclination and azimuth to achieve precise control of the wellbore trajectory. For example, as shown in the "Discussion on the Causes and Prevention Measures of Well Inclination in Oil Drilling Construction" published by Yu Hui in the 23rd issue of "China Petroleum and Chemical Standards and Quality" in 2023, the structure of the single-bend screw drill bit will not be repeated.

[0034] More specifically, in this embodiment, the horizontal branch wells 9 on both sides of the first horizontal main well 8 are distributed in a feather shape, which can solve the problem of wellbore instability caused by concentrated side drilling at a side drilling point. In detail, the horizontal branch wells 9 on the same side are spaced 60 meters apart, and the horizontal branch wells 9 on the opposite side are spaced 30 meters apart.

[0035] S3. In-situ pre-cracking of bauxite: Using horizontal directional drilling grouting technology, a fracturing fluid is injected into the aluminum layer 300 to create cracks in the bauxite in the aluminum layer 300.

[0036] Specifically, the fracturing fluid is a mixture of water, sand and additives.

[0037] Specifically, step S3 of this embodiment includes the following sub-steps: S31. Use a single-bend screw drill to extend into the first vertical main well 7 and drill vertically downward at the turning point of the first vertical main well 7 to reach the second vertical main well 12 of the aluminum layer 300, and simultaneously perform casing lowering and pipe fixing operations; S32. Continue to drill rightward in the horizontal direction to the second horizontal main well 13 at the right boundary of the aluminum mining working face 5, and simultaneously perform casing lowering and pipe fixing operations; S32. Install a fracturing pipe 14 in the second vertical main well 12 and the second horizontal main well 13, and install a fracturing device 15 at the front end of the fracturing pipe 14; S33. Pump the fracturing fluid into the fracturing device 15, and the fracturing device 15 injects the fracturing fluid into the aluminum layer 300, so that cracks are generated in the bauxite of the aluminum layer 300; S34. Use a backward method to complete the fracturing of the bauxite of the entire aluminum mining working face 5.

[0038] It should be noted that the second vertical main shaft 12 is formed by continuing to drill downward to the aluminum layer 300 on the basis of the first vertical main shaft 7, so the second vertical main shaft 12 includes the first vertical shaft.

[0039] More specifically, when the fracturing device 15 of this embodiment works in the second horizontal main well 13, second packers 18 are provided at both ends, and the fracturing fluid is injected into the aluminum layer 300 in the horizontal direction through the fracturing device 15 under the sealing effect of the two second packers 18. Specifically, under the pressurization of the high-pressure pump, the diffusion range of the cracks formed after the aluminum layer 300 of this embodiment is fractured can reach up to 80m.

[0040] S4. Pillar-free comprehensive mechanized bag-filling mining: the aluminum layer 300 is divided into several blocks 1 of preset length along the mining direction; as the comprehensive mining equipment 2 advances forward, filling bags 3 are hung on the top plate of each mined block 1 in turn, and red mud-based slurry 4 is pumped into the filling bags 3 to support the blocks 1 after solidification.

[0041] It is easy to understand that the preset length of block 1 is smaller than the basic roof cycle pressure step distance to prevent the roof from collapsing during the mining process.

[0042] It should be noted that before the red mud-based slurry 4 is pumped into the filling bag 3 , air may be firstly pumped into the filling bag 3 to expand it.

[0043] Specifically, the red mud-based slurry 4 of this embodiment is a mixture of red mud fine aggregate, cement and water, and the particle size of the red mud-based fine aggregate is 0 mm to 5 mm.

[0044] More specifically, the mass ratio of the components of the red mud-based slurry 4 of this embodiment is: red mud fine aggregate: cement: water = 1:0.2:0.7. The compressive strength of the filling body of the red mud-based slurry 4 after solidification can reach 20 MPa.

[0045] The above is only a specific implementation of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions are given with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A green mining method for bauxite under coal, characterized in that: The steps include: S1. Select target rock formation: Exploring the distribution of rock layers between the coal layer (200) and the aluminum layer (300), and selecting a rock layer with relatively large porosity as a target rock layer; S2. Improve the permeability of the target rock formation: Adopting multi-branch horizontal directional drilling grouting technology to inject gangue-based slurry into the target rock formation to improve the impermeability of the target rock formation; S3. In-situ pre-cracking of bauxite: Using horizontal directional drilling grouting technology, a fracturing fluid is injected into the aluminum layer (300) to generate cracks in the bauxite in the aluminum layer (300); S4. Pillarless comprehensive mechanized bag filling mining: The aluminum layer (300) is divided into a plurality of ore blocks (1) of preset lengths along the mining direction; as the fully mechanized mining equipment (2) advances forward, a filling bag (3) is hung on the top plate of each mined ore block (1) in turn, and red mud-based slurry (4) is pumped into the filling bag (3) to support the ore block (1) after solidification.

2. The green mining method of bauxite under coal according to claim 1, characterized in that: The step S2 comprises the following sub-steps: S21. Expand the boundary of the aluminum mining working face (5) below by 15m to 60m to form the construction area (6) of the target rock layer; S22. The wellhead is arranged on the left side of the construction area (6), and a single-bend screw drill is used to drill a first vertical main well (7) vertically downward to the target rock formation on the ground, and casing and pipe fixing operations are performed simultaneously; S23. Continue to drill horizontally to the right to the first horizontal main well (8) at the right boundary of the construction area (6), and simultaneously perform casing and pipe fixing operations; S24. Drilling horizontal branch wells (9) on both sides of the first horizontal main well (8) by means of backward sidetracking; S25. Installing oil pipes (10) in the first vertical main well (7) and the first horizontal main well (8), pumping the gangue-based slurry through the oil pipes (10) to the horizontal branch well (9), and injecting the gangue-based slurry into the target rock formation through the shotcrete pipe (11); S26. The grouting operation of the next horizontal branch well (9) is carried out in a backward manner until the construction of the entire construction area (6) is completed.

3. The green mining method of bauxite under coal according to claim 2, characterized in that: The horizontal branch wells (9) located on both sides of the first horizontal main well (8) are distributed in a feather-like manner.

4. The green mining method for bauxite under coal according to any one of claims 1 to 3, characterized in that: The gangue-based slurry is a mixture of gangue fine aggregate, ultrafine cement and water.

5. The green mining method of bauxite under coal according to claim 1, characterized in that: The step S3 comprises the following sub-steps: S31. Use a single-bend screw drill to extend into the first vertical main well (7) and drill vertically downward at the turning point of the first vertical main well (7) to reach the aluminum layer (300) to form a second vertical main well (12), and simultaneously perform casing and pipe fixing operations; S32. Continue to drill horizontally to the right to the second horizontal main well (13) at the right boundary of the aluminum mining working face (5), and simultaneously perform casing and pipe fixing operations; S32. Installing a fracturing pipe (14) in the second vertical main well (12) and the second horizontal main well (13), and installing a fracturing device (15) at the front end of the fracturing pipe (14); S33. Pumping the fracturing fluid into the fracturing device (15), the fracturing device (15) injects the fracturing fluid into the aluminum layer (300), so that cracks are generated in the bauxite of the aluminum layer (300); S34. The bauxite fracturing of the entire aluminum mining face (5) is completed by retreating.

6. The green mining method for bauxite under coal according to claim 1 or 5, characterized in that: The fracturing fluid is a mixture of water, sand and additives.

7. The green mining method of bauxite under coal according to claim 1, characterized in that: The red mud-based slurry (4) is a mixture of red mud fine aggregate, cement and water.

Images