Coal gangue ditch filling and land building method and system

Abstract

The application discloses a coal gangue ditch-filling land creation method and system, relates to the field of coal gangue treatment, and comprises the following steps: pretreating coal gangue; dividing a target ditch into units according to a coal mining step distance; reinforcing the base of the divided units; performing shotcrete treatment on the ground of the ditch; calculating a ditch-filling waiting time, and after coal mining is completed and reaches the ditch-filling waiting time, layering coal gangue mixture and isolation mixture in the target ditch after the shotcrete treatment; after the layering is completed, embedding a nano bubble generator into a groundwater aquifer, and continuously feeding nano bubbles through the nano bubble generator; and covering the backfilled target ditch with greenery. The application can guarantee site stability, fundamentally solidify heavy metals and continuously purify groundwater, and does not need to consume a large amount of clay resources.

Description

Technical Field

[0001] This application relates to the field of coal gangue treatment, and in particular to a method and system for filling ditches and creating land from coal gangue. Background Technology

[0002] With the continuous advancement of coal mine construction, coal gangue, as the main solid waste generated during mining, has become a pressing environmental and engineering challenge for proper treatment and resource utilization. Currently, the main methods for treating coal gangue include underground backfilling, manufacturing engineering building materials, and surface trenching for land reclamation. However, underground backfilling suffers from drawbacks such as high costs, complex processes, and reduced mining efficiency; while manufacturing engineering building materials is limited by transportation radius, resulting in relatively small quantities being utilized. Therefore, coal gangue trenching for land reclamation has become an important approach to achieving large-scale coal gangue disposal and land reclamation.

[0003] However, existing coal gangue filling and land reclamation technologies still face many technical bottlenecks in practical applications, mainly in the following aspects: (1) Poor site stability and potential safety hazards. The areas where coal gangue filling and land reclamation are located are mostly coal mining areas or goaf areas, and the surface stability is strictly controlled by coal mining activities and the movement of overlying strata. Existing filling and land reclamation methods often fail to fully consider key geological and mining factors such as the stable period of coal mining, the distance of coal mining pressure step, and the development depth of water-conducting fracture zones. As a result, filling and land reclamation projects are highly susceptible to the impact of subsequent coal mining or residual settlement, and there are risks such as foundation instability and uneven settlement.

[0004] (2) High environmental pollution risk and high treatment cost. Coal gangue usually contains heavy metals and sulfides, which are harmful components. Heavy metals are easily released in the natural environment. At the same time, after being leached by rainwater, various pollutants can easily seep into and pollute groundwater. Existing treatment methods mostly rely on physical compaction to mitigate pollution, but this cannot fundamentally block the release and migration of pollutants. Traditional chemical water treatment facilities for polluted groundwater have the disadvantages of huge construction and operation costs and difficulty in large-scale application in vast mining areas. In addition, in the absence of oxygen and the presence of pyrite, coal gangue is prone to continuously producing acidic mine water, which further aggravates the deterioration of the ecological environment.

[0005] (3) The seepage lining layer causes a waste of natural resources. In existing coal gangue landfill projects, clay is usually used as a seepage lining layer to prevent leachate from seeping in. Large-scale trench filling and land reclamation construction requires the consumption of massive clay resources, which not only causes a serious waste of limited natural ecological resources, but also the long-term seepage resistance and barrier effect of a single clay lining under complex geological stress is still limited.

[0006] Therefore, there is an urgent need in this field for a coal gangue filling and land reclamation method that can fully integrate mining geological laws to ensure site stability, fundamentally solidify heavy metals and continuously purify groundwater, and does not require a large consumption of clay resources, in order to solve the problems of poor stability, difficult environmental pollution control and resource waste in the existing technology. Summary of the Invention

[0007] The purpose of this application is to provide a method and system for filling ditches with coal gangue to create land, which can ensure site stability, fundamentally solidify heavy metals and continuously purify groundwater, without consuming large amounts of clay resources.

[0008] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a method for filling ditches and creating land using coal gangue, comprising: Pre-treatment of coal gangue; The target channel is divided into units based on the coal mining pressure step distance; The base of the divided units is reinforced; and the trench surface is sprayed with grout; the raw materials for the grouting treatment include pretreated coal gangue, fly ash and water glass; Calculate the trench filling waiting time, and after the coal mining is completed and the trench filling waiting time is reached, lay coal gangue mixture and isolation mixture in layers in the target trench after shotcreting treatment; the coal gangue mixture includes treated coal gangue and microbial solidification material; After the laying is completed, a nanobubble generator is buried in the groundwater aquifer, and nanobubbles are continuously introduced through the nanobubble generator; the burial range of the nanobubble generator is determined according to the coal mining influence range and the bubble diffusion range; the spacing of the nanobubble generator is determined according to the coal mining pressure step distance. The backfilled ditch was covered with greenery.

[0009] Secondly, this application provides a coal gangue ditch filling and land reclamation system, constructed using the aforementioned coal gangue ditch filling and land reclamation method, comprising: A base reinforcement layer is placed at the bottom of the unit division area of ​​the target trench; A shotcrete impermeable layer is installed on the trench surface above the base reinforcement layer; A layered fill body is provided above the shotcrete seepage prevention layer; the layered fill body is composed of alternating layers of coal gangue mixture and isolation mixture. The nanobubble purification component includes a nanobubble generator buried in an aquifer; the burial range of the nanobubble generator is determined according to the coal mining influence range and the bubble diffusion range; the spacing of the nanobubble generators is determined according to the coal mining pressure step distance. Green cover layer, used to cover the backfilled target trench with greenery.

[0010] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a method and system for land reclamation through coal gangue filling. The method divides the target trench into units based on the coal mining step distance and scientifically calculates the filling waiting time by comprehensively considering key factors such as coal mining depth, height, working face slope, and advance speed. This ensures that the land reclamation project is carried out after the surface stabilization period of coal mining, fully utilizing the law that the step distance determines the stability of the block in the subsidence zone cycle. This effectively avoids foundation instability and uneven settlement caused by subsequent mining activities, significantly improving the long-term safety and stability of the site. Furthermore, by pre-treating the coal gangue at the source, the sulfur content is significantly reduced, fundamentally reducing the continuous production of acidic mine water in oxygen-deficient and pyrite-bearing environments. Simultaneously, microbial solidification materials are introduced into the layered coal gangue mixture. Utilizing the principle of microbial-induced calcite crystallization, heavy metal elements in the coal gangue are continuously solidified, fundamentally preventing their release and diffusion. Furthermore, the *Bacillus megaterium* within the material can decompose nutrients such as phosphorus and potassium from the coal gangue, providing crucial nutrition for subsequent surface vegetation cover, achieving the dual benefits of environmental protection and ecological restoration. This application introduces a nanobubble generation system, continuously introducing nanobubbles into the groundwater aquifer to partially replace traditional, expensive chemical water treatment with physical purification. This is not only economical and reasonable but also effectively improves the living environment of microorganisms in the groundwater, further inhibiting the production of acidic mine water. More importantly, this invention scientifically defines the burial range of the nanobubble generator, precisely matching it with the coal mining impact range and the bubble diffusion range, achieving effective and targeted control of groundwater pollution from coal gangue leachate. This application abandons the traditional practice of using large amounts of clay as an impermeable lining in landfill projects. Instead, it directly utilizes the clay minerals contained in coal gangue and their nano-alkali activation properties, combined with fly ash, to spray grout the trench surface. This application not only forms a reliable impermeable isolation layer but also realizes the large-scale on-site resource utilization of coal gangue materials, greatly saving limited natural clay resources. Furthermore, the construction process is simple and easy to implement, possessing extremely high engineering promotion value. This application systematically solves the core technical problems of existing coal gangue trench filling and land reclamation technologies, such as poor stability, easy heavy metal pollution, high groundwater treatment costs, and waste of clay resources, through the synergistic combination of multiple technologies including scientifically coordinating mining geological laws, microbial solidification technology, and nano-bubble physical purification technology. It has extremely high practical value and economic and environmental benefits. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of a method for filling ditches and creating land with coal gangue in one embodiment of this application; Figure 2 This is a schematic diagram of the overall process of a coal gangue filling and land reclamation method according to one embodiment of this application. Detailed Implementation

[0013] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0014] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] In one exemplary embodiment, this application does not require a large amount of clay material for lining engineering, but directly utilizes clay minerals in coal gangue, making it simple and easy to implement; although water treatment facilities are also equipped, the groundwater is continuously purified through nanobubbles, i.e., partial physical purification replaces chemical purification, thus making it economical and reasonable; considering the impact of coal mining on site stability, the stability is better; using the principle of microbial solidification, heavy metals in coal gangue can be solidified, while Bacillus megaterium can release phosphorus and potassium elements from the coal gangue, making it more environmentally friendly and providing better greening effects. Figure 1 and Figure 2 As shown, a method for land reclamation through coal gangue filling is provided, including the following steps S101 to S106. Wherein: S101, Pretreatment of coal gangue; S101 specifically includes: S11, Grind the coal gangue to bring the particle size of the coal gangue within the set range to the target particle size range; Specifically, more than 60% of the coal gangue is ground to a particle size of 5mm~10mm; S12 is used to desulfurize the ground coal gangue.

[0016] Specifically, sulfur-containing components in coal gangue are screened out, reducing the sulfur content to below 0.5%; S102, the target channel is divided into units according to the coal mining pressure step distance; As a specific implementation, the unit is divided according to 2 to 4 mining pressure steps, continuously divided along the target channel direction. The mining pressure step distance is obtained through on-site measurement at the coal mining site.

[0017] S103, the base of the divided unit is reinforced; and the trench surface is sprayed with grout; the raw materials for the grouting treatment include pretreated coal gangue, fly ash and water glass; S103 specifically includes: S31. When the distance between the coal mining water-conducting fracture zone and the ground surface is greater than the threshold distance, grouting reinforcement is not carried out. S32, when the distance between the coal mining water-conducting fracture zone and the ground surface is less than or equal to the threshold distance, grouting reinforcement shall be carried out on the area below the ground threshold distance.

[0018] The threshold distance is 20m; The water-cement ratio of the grouting material for grouting reinforcement is 0.5~1, and the solid materials are cement and cohesive soil with a mass ratio of 1:1~1:3. As a specific embodiment, the water-cement ratio of the raw material for shotcrete treatment is 0.5~0.7, the alkali equivalent of water glass is: coal gangue: fly ash 5 parts~7 parts: 50 parts~70 parts: 20 parts~30 parts, and the shotcrete temperature shall not be lower than 20℃; S104, calculate the trench filling waiting time, and after the coal mining is completed and the trench filling waiting time is reached, lay coal gangue mixture and isolation mixture in layers in the target trench after shotcreting treatment; the coal gangue mixture includes treated coal gangue and microbial solidification material; The waiting time T for filling the ditch is determined using the formula T = 0.15H + 3h + 1.5L - 10v + C; Where H is the mining depth in meters (m); h is the mining height in meters (m); L is the slope length of the mining face in meters (m); V is the mining advance speed in meters per day (m / d); and C is a correction factor, ranging from 0 to 5.

[0019] As a specific example, the height of the coal gangue mixture and the isolation mixture laid in layers within the target trench is less than a height threshold.

[0020] As a specific example, the microbial solidification material includes organic matter, fly ash, Bacillus megaterium, urea, and calcium chloride.

[0021] Specifically, for every 2m-4m of coal gangue mixture laid, a 0.2m-0.5m layer of isolation mixture is laid, with the final laying height being less than 10m. The water-ash ratio of the coal gangue mixture is 0.2-0.3, with coal gangue, organic matter, fly ash, Bacillus megaterium, urea, and calcium chloride accounting for 70-80 parts, 10-20 parts, 10-20 parts, 3-5 parts, 3-5 parts, and 1-2 parts, respectively. The water-ash mixing ratio of the isolation mixture is 0.5-1, with the alkali equivalent of water glass being 5-7 parts: 50-70 parts: 20-30 parts for coal gangue and fly ash.

[0022] S105, after the laying is completed, a nanobubble generator is buried in the groundwater aquifer, and nanobubbles are continuously introduced through the nanobubble generator; the burial range of the nanobubble generator is determined according to the coal mining influence range and the bubble diffusion range; the spacing of the nanobubble generator is determined according to the coal mining pressure step distance. In addition, the oxygen content in the gas injected by the nanobubble generator should reach more than 21%.

[0023] The groundwater aquifer is the first aquifer extending from the surface to the groundwater; the permeability coefficient of the first aquifer is greater than 0.1 m / d.

[0024] The installation range X of the nanobubble generator is determined using the formula X=H / tanα+u×k×f; Where H is the mining depth in meters (m); α is the mining fracture angle, obtained through field observation in degrees (°); u is the flow velocity of the first aquifer, obtained through field observation in m / d; k is the existence time of nanobubbles under the mixed action of coal gangue leachate, obtained through laboratory experiments. The laboratory experiments involved taking water from the first aquifer and soaking the coal gangue mixture for 10 days, then injecting nanobubbles into the water body, and using dynamic light scattering to observe the time when more than 40% of the nanobubbles disappeared; f is the bubble disappearance safety factor, ranging from 0.4 to 0.8.

[0025] S106, cover the backfilled target ditch with greenery.

[0026] As a specific example, the backfilled target ditch is covered with vegetation, and the vegetation used for covering is the dominant vegetation at that time, with the covered area reaching more than 70% of the channel.

[0027] Through S101-S106, the main principle of this application is as follows: Coal gangue contains certain nano-alkali-activated raw materials, which can therefore be used as shotcrete materials, achieving the goal of large-scale use of coal gangue. The periodic pressure step distance of the subsidence zone formed after coal mining determines the stability of the block, thereby reducing environmental pollution. In addition, coal mining will form downward fractures, and the development depth of downward fractures generally does not exceed 20m, that is, 20m above the water-conducting fracture zone is the key threshold for treatment. After coal mining, land reclamation requires a stabilization period. After the stabilization period, surface changes are significantly reduced. The stabilization time is controlled by various factors. This application uses statistical principles to consider factors such as coal mining depth, height, working face slope length, and advance speed. It also uses the principle of microbial-induced calcite crystallization to continuously solidify coal gangue materials and prevent the diffusion of heavy metals in coal gangue. In addition, Bacillus megaterium can decompose nutrients such as phosphate fertilizer in coal gangue, providing key nutrients for surface vegetation cover. Fifth, nanobubbles can continuously purify groundwater, especially in oxalic environments where coal gangue, when present in pyrite deposits, continuously produces acidic mine water. Physical purification can improve the microbial environment, thereby inhibiting the production of acidic mine water. Furthermore, the installation range of nanobubbles is related to the impact of coal mining and the diffusion range of the bubbles; therefore, the installation range of nanobubbles has been defined to effectively control the pollution of groundwater by coal gangue.

[0028] The following is a specific example illustrating the situation. A coal mine in western China is located in a mountainous area, where there is no suitable area for processing coal gangue. Underground backfilling was implemented to reduce coal gangue production, but the cost was too high. Therefore, a coal gangue backfilling and land reclamation project was implemented, as detailed below: Step 1: Pre-treat the coal gangue by grinding the coal gangue to a particle size of 5mm~10mm, with 72% of the particles having a diameter of 5mm~10mm.

[0029] Step 2: Screen out sulfur-containing components from coal gangue, reducing the sulfur content to 0.3%.

[0030] Step 3: Divide the channel into units, which are determined by two coal mining pressure steps, and continuously divided along the target channel direction. The coal mining pressure step distance is 8m, obtained through on-site measurement at the coal mining site.

[0031] Step 4: Perform foundation grouting reinforcement on each unit divided in Step 3. The grouting reinforcement is carried out in the following ways: When the water-conducting fracture zone in coal mining is less than 10m from the ground surface, grouting is carried out in the area below 20m from the ground surface. The water-cement ratio of the grouting material is 0.6, and the solid materials are cement and cohesive soil with a mass ratio of 1:1.

[0032] Step 5: Spray grout onto the trench surface. The water-cement ratio of the grout is 0.5, and the alkali equivalent of water glass is 5 parts: 60 parts: 30 parts for coal gangue and fly ash. The spraying temperature is 25℃.

[0033] Step Six: The time T between the start of coal gangue filling and the completion of coal mining is calculated using the following formula: T = 0.15H + 3h + 1.5L - 10v + C = 9 + 9 + 225 - 70 + 5 = 178 days; Wherein, H=60m; h=3m; L=180m; V=7m / d; C=5.

[0034] Step 7: Lay the coal gangue mixture. For every 3m of coal gangue mixture laid, lay a 0.5m layer of isolation mixture. The final laying height should be less than 10m. The water-ash ratio of the coal gangue mixture is 0.3, with coal gangue, organic matter, fly ash, Bacillus megaterium, urea, and calcium chloride accounting for 75 parts, 15 parts, 15 parts, 5 parts, 5 parts, and 1 part respectively. The water-ash mixing ratio of the isolation mixture is 0.6, with the alkali equivalent of water glass being 5 parts: 60 parts: 20 parts for coal gangue and fly ash.

[0035] Step 8: After the coal gangue mixture is laid, a nanobubble generator is installed from the surface into the first aquifer. The first aquifer should have a permeability coefficient greater than 0.1 m / d. The installed nanobubble generator continuously injects nanobubbles. The spacing between the generators is the coal mining pressure step distance determined in Step 3, and the installation area extends X beyond the coal gangue laying area in Step 7, where X is calculated using the following formula. The oxygen content of the gas injected by the nanobubble generator should reach 25%.

[0036] X=H / tanα+u×k×f=60 / tan75°+1×81×0.6=16.1+48.6=64.7m; Step 9: Cover the backfilled trench with vegetation, selecting the dominant vegetation at the time, and cover the area to 75% of the trench.

[0037] Based on the same inventive concept, this application also provides a coal gangue ditch filling and land reclamation system constructed based on the above-mentioned coal gangue ditch filling and land reclamation method, the system comprising: A base reinforcement layer is placed at the bottom of the unit division area of ​​the target trench; A shotcrete impermeable layer is installed on the trench surface above the base reinforcement layer; A layered fill body is provided above the shotcrete seepage prevention layer; the layered fill body is composed of alternating layers of coal gangue mixture and isolation mixture. The nanobubble purification component includes a nanobubble generator buried in an aquifer; the burial range of the nanobubble generator is determined according to the coal mining influence range and the bubble diffusion range; the spacing of the nanobubble generators is determined according to the coal mining pressure step distance. Green cover layer, used to cover the backfilled target trench with greenery.

[0038] The sprayed impermeable layer is formed by spraying a mixture of water glass, pretreated coal gangue, and fly ash; the coal gangue mixture layer is formed by laying a mixture of pretreated coal gangue, organic matter, fly ash, Bacillus megaterium, urea, and calcium chloride; and the isolation mixture layer is formed by laying a mixture of water glass, pretreated coal gangue, and fly ash.

[0039] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0040] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for filling ditches and creating land using coal gangue, characterized in that, include: Pre-treatment of coal gangue; The target channel is divided into units based on the coal mining pressure step distance; The base of the divided units is reinforced; The trench surface is then sprayed with grout; the raw materials for the grouting treatment include pretreated coal gangue, fly ash, and water glass. Calculate the trench filling waiting time, and after the coal mining is completed and the trench filling waiting time is reached, lay coal gangue mixture and isolation mixture in layers in the target trench after shotcreting treatment; the coal gangue mixture includes treated coal gangue and microbial solidification material; After the laying is completed, a nanobubble generator is buried in the groundwater aquifer, and nanobubbles are continuously introduced through the nanobubble generator; the burial range of the nanobubble generator is determined according to the coal mining influence range and the bubble diffusion range; the spacing of the nanobubble generator is determined according to the coal mining pressure step distance. The backfilled ditch was covered with greenery.

2. The method for filling ditches and creating land using coal gangue according to claim 1, characterized in that, The pretreatment of coal gangue specifically includes: The coal gangue is ground to bring the particle size of the coal gangue within a set range to the target particle size range; The ground coal gangue is subjected to desulfurization treatment.

3. The method for filling ditches and creating land using coal gangue according to claim 1, characterized in that, The base reinforcement of the divided units specifically includes: When the distance between the water-conducting fracture zone and the ground surface is greater than the threshold distance, grouting reinforcement is not performed. When the distance between the coal mining water-conducting fracture zone and the ground surface is less than or equal to the threshold distance, grouting reinforcement is carried out on the area below the ground threshold distance.

4. The method for filling ditches and creating land using coal gangue according to claim 1, characterized in that, The waiting time T for filling the ditch is determined using the formula T = 0.15H + 3h + 1.5L - 10v + C; Where H is the mining depth, h is the mining height, L is the slope length of the mining face, V is the mining advance speed, and C is the correction coefficient.

5. The method for filling ditches and creating land using coal gangue according to claim 1, characterized in that, The height of the coal gangue mixture and the isolation mixture laid in layers within the target trench is less than the height threshold.

6. The method for filling ditches and creating land using coal gangue according to claim 1, characterized in that, The microbial solidification material includes organic matter, fly ash, Bacillus megaterium, urea, and calcium chloride.

7. The method for filling ditches and creating land using coal gangue according to claim 1, characterized in that, The groundwater aquifer is the first aquifer extending from the surface to the groundwater; the permeability coefficient of the first aquifer is greater than 0.1 m / d.

8. The method for filling ditches and creating land using coal gangue according to claim 7, characterized in that, The installation range X of the nanobubble generator is determined using the formula X=H / tanα+u×k×f; Where H is the mining depth, α is the mining fracture angle, u is the flow velocity of the first aquifer, k is the existence time of nanobubbles under the mixing action of coal gangue leachate, and f is the bubble disappearance safety factor.

9. A coal gangue ditch filling and land reclamation system, characterized in that, The method of filling ditches and creating land using coal gangue as described in any one of claims 1-8 is used for construction, comprising: A base reinforcement layer is placed at the bottom of the unit division area of ​​the target trench; A shotcrete impermeable layer is installed on the trench surface above the base reinforcement layer; A layered fill body is provided above the shotcrete seepage prevention layer; the layered fill body is composed of alternating layers of coal gangue mixture and isolation mixture. The nanobubble purification component includes a nanobubble generator buried in an aquifer; the burial range of the nanobubble generator is determined according to the coal mining influence range and the bubble diffusion range; the spacing of the nanobubble generators is determined according to the coal mining pressure step distance. Green cover layer, used to cover the backfilled target trench with greenery.

10. The coal gangue ditch filling and land reclamation system according to claim 9, characterized in that, The sprayed impermeable layer is formed by spraying a mixture of water glass, pretreated coal gangue and fly ash; the coal gangue mixture layer is formed by laying a mixture of pretreated coal gangue, organic matter, fly ash, Bacillus megaterium, urea and calcium chloride; the isolation mixture layer is formed by laying a mixture of water glass, pretreated coal gangue and fly ash.

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