Methods for landfilling and disposing of coal gangue in goaf areas

Abstract

The present invention provides a method for landfilling coal gangue in goaf areas. The method comprises mixing a first coal gangue, a second coal gangue, a first portion of fly ash, sodium polyacrylate, sodium bentonite, and water to obtain a bottom landfill anti-permeability layer; filling the surface with a fourth coal gangue, mixing aeolian sand, a second portion of fly ash, a third coal gangue, sodium bentonite, and water to obtain a coal gangue gel, which is injected into the voids of the fourth coal gangue to obtain a coal gangue filling layer; covering the coal gangue filling layer with solid waste residue and / or sludge to obtain a compacted layer; alternating the coal gangue filling layer and the compacted layer until the goaf is filled; and finally, placing a soil cover layer. The present invention adopts a multi-layer alternating landfill method, using graded coal gangue as the main material for the anti-permeability layer. No calcination or other treatment is required, and the heavy metal pollution problem can be solved while reducing landfill costs. The coal gangue gel can further adsorb heavy metals while being flame retardant and improving the mechanical strength of the landfill body.

Description

Technical Field

[0001] This invention relates to the field of solid waste utilization technology, and more specifically, to a method for landfilling and treating coal gangue in mining subsidence areas. Background Technology

[0002] Coal gangue is a type of rock that coexists with raw coal and is a solid waste generated during coal mining. Coal gangue is a mixture of various minerals and rocks, mainly including claystone, sandstone, carbonate rocks, and aluminous rocks, with claystone making up a significant proportion. The chemical composition of coal gangue is primarily organic and inorganic. The inorganic components are mainly SiO2 and Al2O3, followed by Fe2O3, CaO, MgO, Na2O, K2O, and some Ti, Ga, Co, Cu, Zn, Mn, and Co, as well as toxic heavy metals such as Pb, Cd, Hg, and Cr. If no measures are taken, the goaf formed by coal mining will subside and form permanent basins, severely disrupting soil properties, adversely affecting nutrient cycling, making the land barren and unproductive, and exacerbating the scarcity of land resources.

[0003] In existing technologies, patents CN113441525A, CN112943356A, CN109718498A, and CN110529119A all disclose technical solutions for solid waste utilization or backfilling of mining subsidence areas using coal gangue. However, direct backfilling of coal gangue has the problem of excessive porosity, which easily allows air to mix in and causes spontaneous combustion; moreover, it contains a high content of heavy metals, and direct backfilling will pollute the surrounding groundwater and surface water sources, causing long-term heavy metal pollution. Generally, the reclamation and backfilling of coal mine subsidence areas using coal gangue needs to be carried out according to specific circumstances. The reclaimed land is mainly used for agricultural production, afforestation, and construction.

[0004] While existing coal gangue backfilling technologies document methods of crushing coal gangue into slurry to fill voids in coal gangue piles, these slurry preparation techniques are often complex, requiring calcination of the coal gangue or the addition of alkaline activators to enhance its heavy metal adsorption properties. However, alkaline substances are easily washed into the soil by natural rainfall, causing secondary pollution. Furthermore, calcination processes are costly and energy-intensive. Therefore, despite some progress in coal gangue backfilling and reclamation, many problems remain, such as heavy metal migration and high operating costs. Summary of the Invention

[0005] The main objective of this invention is to provide a method for landfilling coal gangue in goaf areas, so as to solve the problem that the existing technology cannot simultaneously achieve low heavy metal pollution and low usage cost when filling goaf areas with coal gangue.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for landfilling coal gangue in a goaf is provided. The coal gangue includes a first coal gangue, a second coal gangue, a third coal gangue, and a fourth coal gangue; wherein the average particle size of the first coal gangue is <1 mm, the average particle size of the second coal gangue is 1 mm to 1 cm, the average particle size of the third coal gangue is >1 cm and <2 cm, and the average particle size of the fourth coal gangue is 2 to 30 cm; wherein the method includes the following steps: Step S1, mixing the first coal gangue, the second coal gangue, a first portion of fly ash, sodium polyacrylate, sodium bentonite, and water to obtain coal gangue. Step S1: Inject coal gangue slurry and cover the bottom surface of the goaf to obtain an impermeable layer; Step S2: Mix aeolian sand, second part of fly ash, third coal gangue, sodium bentonite and water to obtain coal gangue gel; Fill the fourth coal gangue into and cover the upper surface of the impermeable layer, and then inject coal gangue gel into the voids of the fourth coal gangue to obtain a coal gangue filling layer; Step S3: Fill and cover the upper surface of the coal gangue filling layer with solid waste and / or sludge to obtain a compacted layer; Step S4: Alternately place the coal gangue filling layer and compacted layer until the goaf is filled; Step S5: Place a soil cover layer on the surface of the goaf.

[0007] Furthermore, the average particle size of the first coal gangue is 0.1–0.5 mm; and / or the average particle size of the second coal gangue is 0.3–0.8 cm; and / or the third coal gangue can be replaced by the first coal gangue and / or the second coal gangue; and / or the average particle size of the fourth coal gangue is 2–10 cm.

[0008] Further, in step S1, the mass ratio of the first coal gangue, the second coal gangue, the first portion of fly ash, sodium polyacrylate, and sodium bentonite is (2-5):(4-10):(1-2):(0.01-0.05):(0.5-1); preferably (3-4):(5-8):(1.2-1.7):(0.02-0.03):(0.7-0.8); preferably, the mass ratio of the first coal gangue and the second coal gangue is 1:(1-2), more preferably 1:(1.3-1.5); more preferably, the number average molecular weight of sodium polyacrylate is 1000-5000, more preferably 2000-3000; more preferably, the solid content of the coal gangue slurry is 50-60 wt%.

[0009] Furthermore, in step S1, before preparing the coal gangue slurry, a step of surface modification of the first coal gangue is included. The surface modification includes: step B1, adding a flotation agent to the first coal gangue for flotation to obtain flotated material; step B2, adding organosiloxane and sodium polyacrylate to the flotated material for dispersion modification to obtain surface-modified first coal gangue; wherein the flotation agent is an aqueous solution of polyol, carboxylic acid or organic amine.

[0010] Further, in step B1, the polyol is one or more of ethylene glycol, propylene glycol, butanediol, isopentyl glycol and glycerol; and / or the carboxylic acid is one or more of acetic acid, propionic acid, oxalic acid, acrylic acid and succinic acid; and / or the organic amine is one or more of ethylenediamine, propylenediamine, diethylenediamine and tetraethylenediamine; preferably, the mass concentration of the flotation agent is 5 to 15 wt%.

[0011] Further, in step B2, the amount of organosiloxane added is 0.1-0.5% of the mass of the first coal gangue, preferably 0.2-0.3%; the amount of sodium polyacrylate added is 1-3% of the mass of the first coal gangue, preferably 1.5-2%; preferably, the dispersion modification temperature is 50-80°C and the time is 0.1-1h; more preferably, the dispersion modification is ultrasonic dispersion or microwave dispersion.

[0012] Further, in step S2, the mass ratio of aeolian sand, second part fly ash, third part coal gangue and sodium bentonite is (3-5):(3-5):(8-18):(1-3); preferably (4-4.5):(4-4.5):(10-15):(1.5-2); preferably, the solid content of the coal gangue gel is 40-60%.

[0013] Further, in step S2, before preparing the coal gangue gel, the step of immersing the third coal gangue in an activator solution for activation treatment is included; preferably, the activator solution is a sodium polyacrylate solution and / or an organic carboxylic acid solution; more preferably, the mass concentration of the activator solution is 0.1-1 wt%; and even more preferably, the immersion time is 1-10 h.

[0014] Further, in step S1, the thickness of the impermeable layer is 30-150 cm, preferably 50-100 cm; and / or in step S2, the thickness of the coal gangue layer is 3-10 m, preferably 4-6 m; and / or in step S3, the thickness of the compacted layer is 30-70 cm, preferably 40-60 cm; and / or in step S4, the coal gangue filling layer and the compacted layer are placed alternately, until 2-5 layers of each are placed; preferably 3-4 layers of each are placed; and / or in step S5, the thickness of the soil cover layer is 50-150 cm, preferably 80-100 cm.

[0015] Furthermore, in step S1, before injecting the coal gangue slurry, the step of laying an organic polymer anti-seepage layer on the bottom surface of the goaf is also included; preferably, the organic polymer anti-seepage layer is an HDPE membrane layer; and / or in step S3, the solid waste is boiler slag, and the sludge is sewer sludge and / or river sludge.

[0016] The technical solution of this invention employs a multi-layered alternating landfill method consisting of an impermeable layer, a coal gangue filling layer, a compacted layer, and a soil cover layer. Each layer is individually designed with specific material considerations for its function, maximizing the utilization of coal gangue. Firstly, the bottom layer uses graded coal gangue with different particle sizes as the main material for the impermeable layer, supplemented by a series of auxiliary materials, effectively reducing permeability. Furthermore, the coal gangue used in this invention does not require calcination or other treatments, improving landfill efficiency and reducing costs while fully considering environmental impact, with a focus on addressing the heavy metal pollution problem that is difficult to overcome in existing technologies. Secondly, a slurry material based on aeolian sand, fly ash, and coal gangue is used as the cementing system to obtain a coal gangue gel with flame-retardant and heavy metal adsorption functions; simultaneously, it increases the bulk density of the coal gangue, significantly improving the mechanical strength of the landfill. In summary, the landfill method of this invention effectively balances low heavy metal pollution with low operating costs. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0018] Figure 1 A schematic diagram of a coal gangue landfill layer according to Embodiment 1 of the present invention is shown.

[0019] The above figures include the following reference numerals:

[0020] 1. Impermeable layer; 2. Coal gangue filling layer; 3. Compacted layer; 4. Soil cover layer. Detailed Implementation

[0021] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0022] As described in the background section of this invention, existing technologies suffer from the problem that coal gangue filling of goaf areas cannot simultaneously achieve both low heavy metal pollution and low usage costs. To address this issue, in a typical embodiment of this invention, a method for landfilling coal gangue in goaf areas is provided. The coal gangue includes first coal gangue, second coal gangue, third coal gangue, and fourth coal gangue; wherein the average particle size of the first coal gangue is <1mm, the average particle size of the second coal gangue is 1mm to 1cm, the average particle size of the third coal gangue is >1cm and <2cm, and the average particle size of the fourth coal gangue is 2 to 30cm; the method includes the following steps: Step S1, mixing the first coal gangue, the second coal gangue, a first portion of fly ash, sodium polyacrylate, sodium bentonite, and water to obtain coal gangue. The process involves several steps: 1) Injecting coal gangue slurry and covering the bottom of the goaf to form an impermeable layer; 2) Mixing aeolian sand, second part fly ash, third part coal gangue, sodium bentonite, and water to form coal gangue gel; filling and covering the upper surface of the impermeable layer with fourth part coal gangue, then injecting coal gangue gel into the voids of the fourth part coal gangue to form a coal gangue filling layer; 3) filling and covering the upper surface of the coal gangue filling layer with solid waste and / or sludge to form a compacted layer; 4) alternately placing the coal gangue filling layer and compacted layer until the goaf is filled; 5) placing a soil cover layer on the surface of the goaf. It should be noted that the first and second parts of fly ash are only used to distinguish their use in different landfill layers, and their specific components do not need to be differentiated.

[0023] The inventors unexpectedly discovered during their research that coal gangue has high density and strong load-bearing capacity. Compared to coal, coal gangue has lower carbon content and lower calorific value, and possesses a certain degree of combustibility. Furthermore, coal gangue exhibits suitable water conductivity, adsorption properties, and leaching behavior. When crushed into smaller stones, coal gangue can be directly used as backfill material with good compaction. When mixed with fly ash, it exhibits excellent compressive strength and density. Therefore, using it as a backfill material for backfilling and reclamation not only reduces the land occupation caused by coal gangue stockpiles and enables on-site disposal of coal gangue, but also mitigates surface subsidence caused by underground coal mining, resulting in significant economic and environmental benefits.

[0024] This invention first separates and crushes coal gangue into different particle sizes to obtain first, second, third, and fourth coal gangue with different particle sizes. Then, the coal gangue is piled up in multiple alternating layers for landfilling. At the bottom of the goaf, i.e., the bottom layer of coal gangue accumulation, graded coal gangue with different particle sizes serves as the main material of the impermeable layer, effectively reducing permeability. Simultaneously, additives such as fly ash, sodium bentonite, and sodium polyacrylate are introduced as auxiliary materials to prepare a novel composite impermeable layer with excellent performance and extremely low permeability, applicable to various engineering construction scenarios. Through reasonable improvements to the design of the bottom sealing layer of coal gangue, and through a series of treatments based on the coal gangue material, a low-permeability material meeting national standards is achieved, with a permeability of less than 1×10⁻⁶. -7 cm / s.

[0025] Secondly, by using aeolian sand-fly ash-coal gangue-based slurry as a cementing system, a dynamic equilibrium system for the solidification of heavy metals and the regulation of material porosity was established, resulting in a coal gangue gel with flame-retardant and heavy metal adsorption functions. This ensures that the landfill material has a certain porosity while also solidifying heavy metals. Simultaneously, injecting the two different slurries into specific locations within the landfill layer effectively prevents spontaneous combustion of coal gangue and heavy metal leaching, thus preventing environmental pollution. After filling the fourth type of coal gangue and covering the upper surface of the impermeable layer, coal gangue gel is injected into the voids of the fourth type of coal gangue to bind the coal gangue blocks. This not only significantly reduces the dissolution of heavy metals and exhibits excellent heavy metal adsorption performance, but also prevents the entry and flow of oxygen, thus reducing the flammability of the coal gangue. Furthermore, it increases the bulk density of the coal gangue, significantly improving the mechanical strength of the layer and resulting in a dense coal gangue filling layer.

[0026] Then, solid waste and / or sludge are filled and covered on the upper surface of the coal gangue filling layer to form a compacted layer, which further provides support for the landfill. Finally, the coal gangue filling layer and the compacted layer are alternately placed until the goaf is filled. After that, a soil covering layer is placed on the surface of the goaf to complete the coal gangue landfill treatment of the goaf.

[0027] This invention employs a multi-layered alternating landfill method, with material design tailored to the function of each layer, maximizing the utilization of coal gangue. In the bottom layer, graded coal gangue with different particle sizes serves as the primary material for the impermeable layer, supplemented by a series of auxiliary materials, effectively reducing permeability. Furthermore, it eliminates the need for calcination or other treatments, improving landfill efficiency and reducing costs while fully considering environmental impact, with a focus on addressing the heavy metal pollution problem that is difficult to overcome in existing technologies. Using aeolian sand-fly ash-coal gangue-based slurry as the cementing system, a coal gangue gel with flame-retardant and heavy metal adsorption functions is obtained; simultaneously, the bulk density of the coal gangue is increased, significantly improving the mechanical strength of the landfill, effectively balancing low heavy metal pollution and low operating costs.

[0028] In a preferred embodiment, the average particle size of the first coal gangue is 0.1–0.5 mm; and / or the average particle size of the second coal gangue is 0.3–0.8 cm; and / or the third coal gangue can be replaced by the first and / or the second coal gangue; and / or the average particle size of the fourth coal gangue is 2–10 cm. This allows for better synergy between different landfill layers, improving seepage prevention, reducing heavy metal pollution, maximizing the utilization of coal gangue of different particle sizes, and reducing landfill costs.

[0029] To further improve the seepage prevention effect of the landfill layer, in a preferred embodiment, in step S1, the mass ratio of the first coal gangue, the second coal gangue, the first part of fly ash, sodium polyacrylate, and sodium bentonite is (2-5):(4-10):(1-2):(0.01-0.05):(0.5-1); preferably (3-4):(5-8):(1.2-1.7):(0.02-0.03):(0.7-0.8); preferably, the mass ratio of the first coal gangue and the second coal gangue is 1:(1-2), more preferably 1:(1.3-1.5), thereby better achieving the gradation of coal gangue; more preferably, the number average molecular weight of sodium polyacrylate is 1000-5000, further preferably 2000-3000; even more preferably, the solid content of the coal gangue slurry is 50-60 wt%, which can maximize the utilization of coal gangue materials.

[0030] In a preferred embodiment, step S1, before preparing the coal gangue slurry, further includes a step of surface modification of the first coal gangue. The surface modification includes: step B1, adding a flotation agent to the first coal gangue to perform flotation and obtain flotated material; step B2, adding organosiloxane and sodium polyacrylate to the flotated material to perform dispersion modification and obtain surface-modified first coal gangue; wherein the flotation agent is an aqueous solution of polyol, carboxylic acid or organic amine.

[0031] In the aforementioned surface modification process, flotation can partially dissolve heavy metals in coal gangue, further reducing heavy metal leaching during landfill disposal. Sodium polyacrylate, with its abundant carboxylate cations, undergoes complex chemical reactions under the action of silane crosslinking agents, exhibiting excellent physical and chemical adsorption and fixation effects, effectively reducing the environmental damage caused by heavy metal spillage. This modification treatment can improve the permeability of the impermeable layer while further reducing heavy metal migration pollution within it.

[0032] In a preferred embodiment, in step B1, the polyol is one or more of ethylene glycol, propylene glycol, butylene glycol, isopentyl glycol, and glycerol; and / or the carboxylic acid is one or more of acetic acid, propionic acid, oxalic acid, acrylic acid, and succinic acid; and / or the organic amine is one or more of ethylenediamine, propylenediamine, diethylenediamine, and tetraethylenediamine; preferably, the mass concentration of the flotation agent is 5–15 wt%. Under the above conditions, environmental pollution caused by heavy metal penetration or migration can be further reduced.

[0033] To further improve the modification effect, in a preferred embodiment, in step B2, the amount of organosiloxane added is 0.1-0.5% of the mass of the first coal gangue, preferably 0.2-0.3%; the amount of sodium polyacrylate added is 1-3% of the mass of the first coal gangue, preferably 1.5-2%; preferably, the dispersion modification temperature is 50-80°C and the time is 0.1-1h; more preferably, the dispersion modification is ultrasonic dispersion or microwave dispersion, preferably ultrasonic dispersion.

[0034] In a preferred embodiment, in step S2, the mass ratio of aeolian sand, the second part of fly ash, the third part of coal gangue, and sodium bentonite is (3-5):(3-5):(8-18):(1-3); preferably (4-4.5):(4-4.5):(10-15):(1.5-2). This can further reduce the dissolution of heavy metals, reduce the combustibility of coal gangue, and improve the mechanical strength of the layer. Preferably, the solid content of the coal gangue gel is 40-60%. More preferably, the coal gangue gel is left to stand for 3-7 days after preparation before use. This allows for optimal mixing of the materials in the coal gangue filling layer, facilitating subsequent landfill construction.

[0035] To further improve the preparation effect, in a preferred embodiment, step S2, before preparing the coal gangue gel, further includes immersing a third coal gangue in an activator solution for activation treatment; preferably, the activator solution is a sodium polyacrylate solution and / or an organic carboxylic acid solution; more preferably, the mass concentration of the activator solution is 0.1-1 wt%; and even more preferably, the immersion time is 1-10 h.

[0036] In a preferred embodiment, in step S1, the thickness of the impermeable layer is 30–150 cm, preferably 50–100 cm; and / or in step S2, the thickness of the coal gangue layer is 3–10 m, preferably 4–6 m; and / or in step S3, the thickness of the compacted layer is 30–70 cm, preferably 40–60 cm; and / or in step S4, the coal gangue filling layer and the compacted layer are alternately placed, up to 2–5 layers of each, preferably 3–4 layers of each; and / or in step S5, the thickness of the soil cover layer is 50–150 cm, preferably 80–100 cm. This allows for better impermeability, reduced heavy metal pollution, and increased mechanical strength of the layers, while also better adapting to actual sites and having a wider range of applications. The thickness of each layer can be adjusted according to site requirements, which is understandable to those skilled in the art and will not be elaborated further here.

[0037] To further improve the seepage prevention effect of the landfill, in a preferred embodiment, step S1 includes laying an organic polymer seepage prevention layer on the bottom surface of the goaf before injecting coal gangue slurry; preferably, the organic polymer seepage prevention layer is an HDPE (high-density polyethylene) membrane layer; and / or in step S3, the solid waste is boiler slag, and the sludge is sewer sludge and / or river sludge, which can further realize waste utilization and reduce landfill costs.

[0038] Typical, but not limiting, the average particle size of the first coal gangue is 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or any two of these values; the average particle size of the second coal gangue is 0.1 cm, 0.2 cm, 0.3 cm, 0.4 cm, 0.5 cm, 0.6 cm, 0.7 cm, 0.8 cm, 0.9 cm, 1 cm, or any two of these values; the average particle size of the third coal gangue... The average particle size is 1.1cm, 1.2cm, 1.3cm, 1.4cm, 1.5cm, 1.6cm, 1.7cm, 1.8cm, 1.9cm or any two of these values; 2-30cm; the average particle size of the fourth coal gangue is 2cm, 4cm, 6cm, 8cm, 10cm, 12cm, 14cm, 16cm, 18cm, 20cm, 22cm, 24cm, 26cm, 28cm, 30cm or any two of these values.

[0039] Typically, but not limitingly, in step S1, the mass ratio of the first coal gangue, the second coal gangue, the first portion of fly ash, sodium polyacrylate, and sodium bentonite is (2-5):(4-10):(1-2):(0.01-0.05):(0.5-1); within the above ratio range, the first coal gangue is 2, 3, 4, 5, or any two of these values; the second coal gangue is 4, 5, 6, 7, 8, 9, 10, or any two of these values; the first portion of fly ash is 1, 1.2, 1.4, 1.6, 1.7, 1.8, 2, or any two of these values; the sodium polyacrylate is 0.01, 0.02, 0.03, 0.04, 0.05, or any two of these values; and the sodium bentonite is 0.5, 0.6, 0.7, 0.8, 0.9, 1, or any two of these values.

[0040] Typically, but not limitingly, in step S1, the mass ratio of the first coal gangue to the second coal gangue is 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, or any two of these ratios within a range.

[0041] Typically, but not limitingly, in step S1, the number average molecular weight of sodium polyacrylate is 1000, 2000, 3000, 4000, 5000, or any two of these values.

[0042] Typically, but not limitingly, in step S1, the solid content of the coal gangue slurry is 50 wt%, 52 wt%, 54 wt%, 56 wt%, 58 wt%, 60 wt%, or any two of these values.

[0043] Typically, but not limitingly, in step S1, the thickness of the impermeable layer is 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm, 100cm, 110cm, 120cm, 130cm, 140cm, 150cm, or any two of these values.

[0044] Typically, but not limitingly, in step S1, when surface-modifying the first coal gangue, the mass concentration of the flotation agent is 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, or any two of these values; the amount of organosiloxane added is 0.1%, 0.2%, 0.3%, 0.4%, 0.5% of the mass of the first coal gangue, or any other value thereof. The range of any two values; the amount of sodium polyacrylate added is 1%, 1.5%, 2%, 2.5%, 3% of the mass of the first coal gangue, or any two values ​​thereof; the dispersion modification temperature is 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, or any two values ​​thereof; the time is 0.1h, 0.2h, 0.4h, 0.6h, 0.8h, 1h, or any two values ​​thereof.

[0045] Typically, but not limitingly, in step S2, the mass ratio of aeolian sand, second part fly ash, third part coal gangue, and sodium-based bentonite is (3-5):(3-5):(8-18):(1-3); within the above ratio range, the aeolian sand is 3, 3.5, 4, 4.5, 5, or any two of these values; the second part fly ash is 3, 3.5, 4, 4.5, 5, or any two of these values; the third part coal gangue is 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or any two of these values; and the sodium-based bentonite is 1, 1.5, 2, 2.5, 3, or any two of these values.

[0046] Typically, but not limitingly, in step S2, the solid content of the coal gangue gel is 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, 50 wt%, 52 wt%, 54 wt%, 56 wt%, 58 wt%, 60 wt%, or a range of any two of these values.

[0047] Typically, but not limitingly, in step S2, the thickness of the coal gangue layer is 3m, 4m, 5m, 6m, 7m, 8m, 9m, 10m or any two of these values.

[0048] Typically, but not limitingly, in step S2, when activating the third coal gangue, the mass concentration of the activator solution is 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, or any two of these values; the impregnation time is 1h, 2h, 4h, 6h, 8h, 10h, or any two of these values.

[0049] Typically, but not limitingly, in step S3, the thickness of the compacted layer is 30cm, 40cm, 50cm, 60cm, 70cm, or any two of these values.

[0050] Typically, but not limitingly, in step S5, the thickness of the soil cover layer is 50cm, 60cm, 70cm, 80cm, 90cm, 100cm, 110cm, 120cm, 130cm, 140cm, 150cm, or any two of these values.

[0051] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0052] Unless otherwise specified, the different grades of coal gangue in the following examples and comparative examples are obtained by the following methods: Coal gangue raw materials are screened or crushed and sieved to obtain first coal gangue with an average particle size <1mm, second coal gangue with an average particle size of 1mm to 1cm, third coal gangue with an average particle size >1cm and <2cm, and fourth coal gangue with an average particle size of 2 to 30cm. The first and second coal gangue can be obtained by: crushing the coal gangue raw materials using a crusher and sieving to obtain particles smaller than 1cm; returning particles larger than 1cm to the crusher for re-crushing; further crushing and sieving the particles smaller than 1cm in a ball mill; particles smaller than 1mm are the first coal gangue, and particles larger than 1mm and smaller than 1cm are the second coal gangue.

[0053] Example 1

[0054] The average particle size of the first coal gangue is 0.3 mm, the average particle size of the second coal gangue is 0.5 mm, the average particle size of the third coal gangue is <2 cm, and the average particle size of the fourth coal gangue is 5 cm. The number average molecular weight of sodium polyacrylate is 2500. A schematic diagram of the coal gangue landfill layer is shown below. Figure 1 .

[0055] Step S1: Mix the first coal gangue, the second coal gangue, fly ash, sodium polyacrylate, and sodium bentonite in a mass ratio of 2:4:2:0.03:0.5. Add water to the coal gangue slurry with a solid content of 50wt% and perform ultrasonic stirring. After standing for 3 days, the coal gangue slurry is obtained. Inject the coal gangue slurry and cover the bottom surface of the goaf. After drying, an impermeable layer with a thickness of 50cm is obtained.

[0056] Step S2: Aeolian sand, fly ash, third coal gangue, and sodium bentonite are mixed in a mass ratio of 3:5:12:1. Water is added to the coal gangue gel with a solid content of 40wt% and stirred. After standing for 3 days, coal gangue gel is obtained. Fourth coal gangue is filled and covered on the upper surface of the impermeable layer. Then, coal gangue gel is injected into the voids of the fourth coal gangue to obtain a coal gangue filling layer with a thickness of 5m.

[0057] Step S3: Fill and cover the upper surface of the coal gangue filling layer with boiler slag to obtain a compacted layer with a thickness of 50cm.

[0058] Step S4: Then, alternately place one layer of coal gangue filling layer and one layer of compacted layer;

[0059] Step S5: Place a 1m thick soil cover layer on top.

[0060] Example 2

[0061] The average particle size of the first coal gangue is 0.3 mm, the average particle size of the second coal gangue is 0.5 mm, the average particle size of the third coal gangue is <2 cm, the average particle size of the fourth coal gangue is 5 cm, and the number average molecular weight of sodium polyacrylate is 2500.

[0062] Step S1: After washing the first coal gangue with water, flotation is performed using an excess of ethylene glycol with a mass concentration of 15wt% to obtain flotation material; after drying the flotation material, 0.2% of organosiloxane and 1.5% of sodium polyacrylate equivalent to the mass of the first coal gangue are added, and the mixture is ultrasonically dispersed at 50℃ for 1 hour to modify it, thereby obtaining surface-modified first coal gangue;

[0063] Surface-modified first coal gangue, second coal gangue, fly ash, sodium polyacrylate, and sodium bentonite were mixed in a mass ratio of 2:4:2:0.03:0.5. Water was added to the coal gangue slurry with a solid content of 50wt%, and the mixture was ultrasonically stirred. After standing for 3 days, the coal gangue slurry was obtained. The coal gangue slurry was injected and covered the bottom surface of the goaf. After drying, a 50cm thick impermeable layer was obtained.

[0064] Step S2: Aeolian sand, fly ash, third coal gangue, and sodium bentonite are mixed in a mass ratio of 3:5:12:1. Water is added to the coal gangue gel with a solid content of 40wt% and stirred. After standing for 3 days, coal gangue gel is obtained. Fourth coal gangue is filled and covered on the upper surface of the impermeable layer. Then, coal gangue gel is injected into the voids of the fourth coal gangue to obtain a coal gangue filling layer with a thickness of 5m.

[0065] Step S3: Fill and cover the upper surface of the coal gangue filling layer with boiler slag to obtain a compacted layer with a thickness of 50cm.

[0066] Step S4: Then, alternately place one layer of coal gangue filling layer and one layer of compacted layer;

[0067] Step S5: Place a 1m thick soil cover layer on top.

[0068] Example 3

[0069] The average particle size of the first coal gangue is 0.3 mm, the average particle size of the second coal gangue is 0.5 mm, the average particle size of the third coal gangue is <2 cm, the average particle size of the fourth coal gangue is 5 cm, and the number average molecular weight of sodium polyacrylate is 2500.

[0070] Step S1: Mix the first coal gangue, the second coal gangue, fly ash, sodium polyacrylate, and sodium bentonite in a mass ratio of 2:4:2:0.03:0.5. Add water to the coal gangue slurry with a solid content of 50wt% and perform ultrasonic stirring. After standing for 3 days, the coal gangue slurry is obtained. Inject the coal gangue slurry and cover the bottom surface of the goaf. After drying, an impermeable layer with a thickness of 80cm is obtained.

[0071] Step S2: The third coal gangue is immersed in a sodium polyacrylate solution with a mass concentration of 1 wt% for 1 hour to carry out activation treatment and obtain activated third coal gangue.

[0072] Aeolian sand, fly ash, activated third coal gangue, and sodium bentonite were mixed in a mass ratio of 3:5:12:1. Water was added to the mixture to obtain a coal gangue gel with a solid content of 40wt%, and the mixture was stirred. After standing for 3 days, the coal gangue gel was obtained. Fourth coal gangue was filled into the mixture and covered the upper surface of the impermeable layer. Then, coal gangue gel was injected into the voids of the fourth coal gangue to obtain a coal gangue filling layer with a thickness of 5m.

[0073] Step S3: Fill and cover the upper surface of the coal gangue filling layer with boiler slag to obtain a compacted layer with a thickness of 50cm.

[0074] Step S4: Then, alternately place one layer of coal gangue filling layer and one layer of compacted layer;

[0075] Step S5: Place a 1m thick soil cover layer on top.

[0076] Example 4

[0077] The average particle size of the first coal gangue is 0.3 mm, the average particle size of the second coal gangue is 0.5 mm, the average particle size of the third coal gangue is <2 cm, the average particle size of the fourth coal gangue is 5 cm, and the number average molecular weight of sodium polyacrylate is 2500.

[0078] Step S1: After washing the first coal gangue with water, flotation is performed using an excess of ethylene glycol with a mass concentration of 10wt% to obtain flotation material; after drying the flotation material, 0.2% of organosiloxane and 1.5% of sodium polyacrylate equivalent to the mass of the first coal gangue are added, and the mixture is ultrasonically dispersed at 50℃ for 1 hour to modify it, thereby obtaining surface-modified first coal gangue;

[0079] Surface-modified first coal gangue, second coal gangue, fly ash, sodium polyacrylate, and sodium bentonite were mixed in a mass ratio of 2:4:2:0.03:0.5. Water was added to the coal gangue slurry with a solid content of 50wt%, and the mixture was ultrasonically stirred. After standing for 3 days, the coal gangue slurry was obtained. The coal gangue slurry was injected and covered the bottom surface of the goaf. After drying, a 100cm thick impermeable layer was obtained.

[0080] Step S2: The third coal gangue is immersed in a sodium polyacrylate solution with a mass concentration of 1 wt% for 1 hour to carry out activation treatment and obtain activated third coal gangue.

[0081] Aeolian sand, fly ash, activated third coal gangue, and sodium bentonite were mixed in a mass ratio of 3:5:12:1. Water was added to the mixture to obtain a coal gangue gel with a solid content of 40wt%, and the mixture was stirred. After standing for 3 days, the coal gangue gel was obtained. Fourth coal gangue was filled into the mixture and covered the upper surface of the impermeable layer. Then, coal gangue gel was injected into the voids of the fourth coal gangue to obtain a coal gangue filling layer with a thickness of 5m.

[0082] Step S3: Fill and cover the upper surface of the coal gangue filling layer with boiler slag to obtain a compacted layer with a thickness of 50cm.

[0083] Step S4: Then, alternately place one layer of coal gangue filling layer and one layer of compacted layer;

[0084] Step S5: Place a 1m thick soil cover layer on top.

[0085] Examples 5 to 8

[0086] The difference between Examples 5 to 8 and Example 4 is that the particle size of the coal gangue is different, as shown in Table 1.

[0087] Table 1

[0088] / First coal gangue mm Second coal gangue cm Third coal gangue cm Fourth coal gangue cm Example 5 0.1 0.1 1.1 2 Example 6 0.1 0.3 1.5 2 Example 7 0.5 0.8 1.5 10 Example 8 0.9 1 1.9 30

[0089] Examples 9 to 16

[0090] The difference between Examples 9 to 16 and Example 4 is that the raw material composition, solid content of coal gangue slurry, and thickness of the anti-permeability layer are different in step S1, as shown in Table 2.

[0091] Table 2

[0092]

[0093] Examples 17 to 20

[0094] The difference between Examples 17 to 20 and Example 4 is that the raw material composition, the solid content of the coal gangue gel, and the thickness of the coal gangue filling layer are different in step S2, as shown in Table 3.

[0095] Table 3

[0096] / Aeolian sandy soil fly ash Third coal gangue Sodium bentonite Solid content (wt%) Thickness m Example 17 3 3 18 1 40 3 Example 18 4 4 15 1.5 50 4 Example 19 4.5 4.5 10 2 50 6 Example 20 5 5 8 3 60 10

[0097] Example 21

[0098] The difference between Example 21 and Example 4 is that in step S1, the first coal gangue is washed with water and then floated with an excess of propylene glycol with a mass concentration of 5wt% to obtain the floated material; after drying the floated material, 0.1% of organosiloxane and 1% of sodium polyacrylate equivalent to the mass of the first coal gangue are added, and the mixture is ultrasonically dispersed at 50°C for 1 hour to modify it, thereby obtaining the surface-modified first coal gangue.

[0099] Example 22

[0100] The difference between Example 22 and Example 4 is that in step S1, the first coal gangue is washed with water and then floated with an excess of acetic acid with a mass concentration of 10wt% to obtain the floated material; after drying the floated material, 0.2% of the mass of the first coal gangue and 1.5% of the mass of the first coal gangue are added, and the mixture is ultrasonically dispersed at 60°C for 1 hour to modify it, thereby obtaining the surface-modified first coal gangue.

[0101] Example 23

[0102] The difference between Example 23 and Example 4 is that in step S1, the first coal gangue is washed with water and then floated with an excess of ethylenediamine with a mass concentration of 10wt% to obtain the floated material; after drying the floated material, 0.3% of organosiloxane and 2% of sodium polyacrylate equivalent to the mass of the first coal gangue are added, and the mixture is ultrasonically dispersed at 60°C for 1 hour to modify it, thereby obtaining the surface-modified first coal gangue.

[0103] Example 24

[0104] The difference between Example 24 and Example 4 is that in step S1, the first coal gangue is washed with water and then floated with an excess of 15wt% glycerol to obtain the floated material; after drying the floated material, 0.5% of the mass of the first coal gangue and 3% of the mass of the first coal gangue are added to the organic siloxane and sodium polyacrylate, respectively, and the mixture is ultrasonically dispersed at 80°C for 0.1h to modify it, thereby obtaining the surface-modified first coal gangue.

[0105] Example 25

[0106] The difference between Example 25 and Example 4 is that in step S2, the third coal gangue is immersed in a sodium polyacrylate solution with a mass concentration of 0.1 wt% for 10 hours to carry out activation treatment and obtain activated third coal gangue.

[0107] Example 26

[0108] The difference between Example 26 and Example 4 is that the number average molecular weight of the sodium polyacrylate used is 1000; the thickness of the compacted layer in step S3 is 30cm; in step S4, four layers of coal gangue filling layer and four layers of compacted layer are alternately placed; and the thickness of the soil cover layer in step S5 is 0.5m.

[0109] Example 27

[0110] The difference between Example 27 and Example 4 is that the number average molecular weight of the sodium polyacrylate used is 2000; the thickness of the compacted layer in step S3 is 40cm; three layers of coal gangue filling layer and three layers of compacted layer are alternately placed in step S4; and the thickness of the soil cover layer in step S5 is 0.8m.

[0111] Example 28

[0112] The difference between Example 28 and Example 4 is that the number average molecular weight of the sodium polyacrylate used is 3000; the thickness of the compacted layer in step S3 is 60cm; three layers of coal gangue filling layer and three layers of compacted layer are alternately placed in step S4; and the thickness of the soil cover layer in step S5 is 1m.

[0113] Example 29

[0114] The difference between Example 29 and Example 4 is that the number average molecular weight of the sodium polyacrylate used is 5000; the thickness of the compacted layer in step S3 is 70cm; two layers of coal gangue filling layer and two layers of compacted layer are alternately placed in step S4; and the thickness of the soil cover layer in step S5 is 1.5m.

[0115] Comparative Example 1

[0116] The average particle size of the second coal gangue is 1 cm, the average particle size of the third coal gangue is <2 cm, the average particle size of the fourth coal gangue is 20 cm, and the number average molecular weight of sodium polyacrylate is 2500.

[0117] Step S1: Mix the second coal gangue, fly ash, sodium polyacrylate, and sodium bentonite in a mass ratio of 6:2:0.03:0.5. Add water to the coal gangue slurry with a solid content of 50% and perform ultrasonic stirring. After standing for 3 days, the coal gangue slurry is obtained. Inject the coal gangue slurry and cover the bottom surface of the goaf. After drying, an impermeable layer with a thickness of 50cm is obtained.

[0118] Step S2: Aeolian sand, fly ash, third coal gangue, and sodium bentonite are mixed in a mass ratio of 3:5:12:1. Water is added to the coal gangue gel with a solid content of 40%, and the mixture is stirred. After standing for 3 days, the coal gangue gel is obtained. Fourth coal gangue is filled into and covers the upper surface of the impermeable layer. Then, coal gangue gel is injected into the voids of the fourth coal gangue to obtain a coal gangue filling layer with a thickness of 5m.

[0119] Step S3: Fill and cover the upper surface of the coal gangue filling layer with boiler slag to obtain a compacted layer with a thickness of 50cm.

[0120] Step S4: Then, alternately place one layer of coal gangue filling layer and one layer of compacted layer;

[0121] Step S5: Place a 1m thick soil cover layer on top.

[0122] Comparative Example 2

[0123] The average particle size of the first coal gangue is <1mm, the average particle size of the third coal gangue is <2cm, the average particle size of the fourth coal gangue is 20cm, and the number average molecular weight of sodium polyacrylate is 2500.

[0124] Step S1: Mix the first coal gangue, fly ash, sodium polyacrylate and sodium bentonite in a mass ratio of 6:2:0.03:0.5. Add water to the coal gangue slurry with a solid content of 50% and perform ultrasonic stirring. After standing for 3 days, the coal gangue slurry is obtained. Inject the coal gangue slurry and cover the bottom surface of the goaf. After drying, an impermeable layer with a thickness of 50cm is obtained.

[0125] Step S2: Aeolian sand, fly ash, third coal gangue, and sodium bentonite are mixed in a mass ratio of 3:5:12:1. Water is added to the coal gangue gel with a solid content of 40%, and the mixture is stirred. After standing for 3 days, the coal gangue gel is obtained. Fourth coal gangue is filled into and covers the upper surface of the impermeable layer. Then, coal gangue gel is injected into the voids of the fourth coal gangue to obtain a coal gangue filling layer with a thickness of 5m.

[0126] Step S3: Fill and cover the upper surface of the coal gangue filling layer with boiler slag to obtain a compacted layer with a thickness of 50cm.

[0127] Step S4: Then, alternately place one layer of coal gangue filling layer and one layer of compacted layer;

[0128] Step S5: Place a 1m thick soil cover layer on top.

[0129] Comparative Example 3

[0130] The average particle size of the third coal gangue is <2cm, the average particle size of the fourth coal gangue is 20cm, and the number average molecular weight of sodium polyacrylate is 2500.

[0131] Step S1: Mix aeolian sand, fly ash, third coal gangue, and sodium bentonite in a mass ratio of 3:5:12:1. Add water to the coal gangue gel with a solid content of 40% and stir. After standing for 3 days, the coal gangue gel is obtained. Inject the coal gangue gel into and cover the bottom surface of the goaf. After drying, an impermeable layer with a thickness of 50cm is obtained.

[0132] Step S2: Fill and cover the upper surface of the impermeable layer with the fourth coal gangue, and then inject coal gangue gel into the voids of the fourth coal gangue to obtain a coal gangue filling layer with a thickness of 5m.

[0133] Step S3: Fill and cover the upper surface of the coal gangue filling layer with boiler slag to obtain a compacted layer with a thickness of 50cm.

[0134] Step S4: Then, alternately place one layer of coal gangue filling layer and one layer of compacted layer;

[0135] Step S5: Place a 1m thick soil cover layer on top.

[0136] The permeability of the impermeable layers formed after drying in the above embodiments and comparative examples was tested. After six months of landfilling, the concentration of heavy metals (Cu, Cr, Pb) in the soil within 100m of the surrounding area was detected. The results are shown in Table 4.

[0137] Table 4

[0138]

[0139]

[0140]

[0141] As can be seen from the above, compared with the comparative examples, the embodiments of the present invention employ a multi-layered alternating landfill method consisting of an impermeable layer, a coal gangue filling layer, a compacted layer, and a soil cover layer. The materials for each layer are designed separately for their function, maximizing the utilization of coal gangue materials. On one hand, using graded coal gangue with different particle sizes as the main material of the impermeable layer in the bottom layer of the landfill, along with a series of auxiliary materials, effectively reduces permeability. Furthermore, the coal gangue used in this invention does not require calcination or other treatments, improving landfill efficiency and reducing landfill costs while fully considering environmental damage and impact, focusing on the heavy metal pollution problem that is difficult to overcome in existing technologies. On the other hand, using aeolian sand-fly ash-coal gangue-based slurry material as the cementing system yields a coal gangue gel with flame-retardant and heavy metal adsorption functions; it also increases the bulk density of the coal gangue, significantly improving the mechanical strength of the landfill. In summary, the landfill method of the present invention can effectively balance low heavy metal pollution and low operating costs.

[0142] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for landfilling and disposing of coal gangue in a goaf, characterized in that, The coal gangue includes first coal gangue, second coal gangue, third coal gangue, and fourth coal gangue; wherein the average particle size of the first coal gangue is <1mm, the average particle size of the second coal gangue is 1mm~1cm, the average particle size of the third coal gangue is >1cm and <2cm, and the average particle size of the fourth coal gangue is 2~30cm; wherein the method includes the following steps: Step S1: Mix the first coal gangue, the second coal gangue, a portion of fly ash, sodium polyacrylate, sodium bentonite, and water to obtain a coal gangue slurry; inject the coal gangue slurry into and cover the bottom surface of the goaf to obtain an impermeable layer; Step S2: Mix aeolian sand, second part of fly ash, third coal gangue, sodium bentonite and water to obtain coal gangue gel; fill and cover the upper surface of the impermeable layer with the fourth coal gangue, and then inject the coal gangue gel into the voids of the fourth coal gangue to obtain a coal gangue filling layer. Step S3: Fill and cover the upper surface of the coal gangue filling layer with solid waste residue and / or sludge to obtain a compacted layer; Step S4: Alternately place the coal gangue filling layer and the compacted layer until the goaf is filled; Step S5: Place a soil cover layer on the surface of the goaf.

2. The method according to claim 1, characterized in that, The average particle size of the first coal gangue is 0.1~0.5mm; and / or the average particle size of the second coal gangue is 0.3~0.8cm; and / or the average particle size of the fourth coal gangue is 2~10cm.

3. The method according to claim 1 or 2, characterized in that, In step S1 The mass ratio of the first coal gangue, the second coal gangue, the first portion of fly ash, the sodium polyacrylate, and the sodium-based bentonite is (2~5):(4~10):(1~2):(0.01~0.05):(0.5~1).

4. The method according to claim 3, characterized in that, The mass ratio of the first coal gangue, the second coal gangue, the first portion of fly ash, the sodium polyacrylate, and the sodium-based bentonite is (3~4):(5~8):(1.2~1.7):(0.02~0.03):(0.7~0.8).

5. The method according to claim 3, characterized in that, The mass ratio of the first coal gangue to the second coal gangue is 1:(1~2).

6. The method according to claim 3, characterized in that, The mass ratio of the first coal gangue to the second coal gangue is 1:(1.3~1.5).

7. The method according to claim 3, characterized in that, The number-average molecular weight of the sodium polyacrylate is 1000~5000.

8. The method according to claim 3, characterized in that, The number average molecular weight of the sodium polyacrylate is 2000-3000.

9. The method according to claim 3, characterized in that, The solid content of the coal gangue slurry is 50-60 wt%.

10. The method according to claim 1 or 2, characterized in that, In step S1, before preparing the coal gangue slurry, a step of surface modification of the first coal gangue is included, wherein the surface modification includes: Step B1: Add flotation agent to the first coal gangue to perform flotation and obtain flotated material; Step B2: Organosiloxane and sodium polyacrylate are added to the flotation material to carry out dispersion modification, thereby obtaining the first coal gangue with surface modification; The flotation agent is an aqueous solution of a polyol, carboxylic acid, or organic amine.

11. The method according to claim 10, characterized in that, In step B1 The polyol is one or more of ethylene glycol, propylene glycol, butylene glycol, isopentylene glycol, and glycerol; and / or The carboxylic acid is one or more of acetic acid, propionic acid, oxalic acid, acrylic acid, and succinic acid; and / or The organic amine is one or more of ethylenediamine, propylenediamine, diethylenediamine, and tetraethylenediamine.

12. The method according to claim 10, characterized in that, The mass concentration of the flotation agent is 5~15wt%.

13. The method according to claim 10, characterized in that, In step B2 The amount of the organosiloxane added is 0.1-0.5% of the mass of the first coal gangue; the amount of the sodium polyacrylate added is 1-3% of the mass of the first coal gangue.

14. The method according to claim 13, characterized in that, The amount of organosiloxane added is 0.2 to 0.3% of the mass of the first coal gangue.

15. The method according to claim 13, characterized in that, The amount of sodium polyacrylate added is 1.5 to 2% of the mass of the first coal gangue.

16. The method according to claim 13, characterized in that, The dispersion modification is performed at a temperature of 50~80℃ for a time of 0.1~1h.

17. The method according to claim 13, characterized in that, The dispersion modification is performed by ultrasonic dispersion or microwave dispersion.

18. The method according to claim 1 or 2, characterized in that, In step S2 The mass ratio of the aeolian sand, the second part of fly ash, the third coal gangue and the sodium bentonite is (3~5):(3~5):(8~18):(1~3).

19. The method according to claim 18, characterized in that, The mass ratio of the aeolian sand, the second part of fly ash, the third part of coal gangue and the sodium bentonite is (4~4.5):(4~4.5):(10~15):(1.5~2).

20. The method according to claim 18, characterized in that, The solid content of the coal gangue gel is 40-60%.

21. The method according to claim 1 or 2, characterized in that, In step S2, before preparing the coal gangue gel, the step further includes immersing the third coal gangue in an activator solution for activation treatment.

22. The method according to claim 21, characterized in that, The activator solution is a sodium polyacrylate solution and / or an organic carboxylic acid solution.

23. The method according to claim 21, characterized in that, The activator solution has a mass concentration of 0.1~1wt%.

24. The method according to claim 21, characterized in that, The soaking time is 1 to 10 hours.

25. The method according to claim 1 or 2, characterized in that, In step S1, the thickness of the impermeable layer is 30~150cm; and / or In step S2, the thickness of the coal gangue filling layer is 3~10m; and / or In step S3, the thickness of the compacted layer is 30~70cm; and / or In step S4, the coal gangue filling layer and the compacted layer are alternately placed until 2 to 5 layers of each are placed; and / or In step S5, the thickness of the soil cover layer is 50~150cm.

26. The method according to claim 25, characterized in that, In step S1, the thickness of the anti-permeability layer is 50~100cm.

27. The method according to claim 25, characterized in that, In step S2, the thickness of the coal gangue filling layer is 4~6m.

28. The method according to claim 25, characterized in that, In step S3, the thickness of the compacted layer is 40~60cm.

29. The method according to claim 25, characterized in that, In step S4, the coal gangue filling layer and the compacted layer are placed alternately until 3 to 4 layers of each are placed.

30. The method according to claim 25, characterized in that, In step S5, the thickness of the soil cover layer is 80~100cm.

31. The method according to claim 1 or 2, characterized in that, In step S1, before injecting the coal gangue slurry, the method further includes laying an organic polymer anti-seepage layer on the bottom surface of the goaf; and / or In step S3, the solid waste residue is boiler slag, and the sludge is sewer sludge and / or river sludge.

32. The method according to claim 31, characterized in that, The organic polymer geomembrane is an HDPE membrane.

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