Waste dump oxygen suppression covering method based on reverse air permeability structure

Abstract

The invention discloses a hillock oxygen suppression covering method based on a reverse air permeability structure, and belongs to the technical field of coal gangue disaster prevention and ecological remediation. The method comprises the steps that discharged gangue is subjected to three-stage screening, and coarse-particle gangue, medium-particle gangue and fine-particle gangue are obtained; according to coarse-particle gangue, medium-particle gangue and fine-particle gangue obtained through screening, layered stacking and compacting are sequentially conducted from bottom to top, and a reverse air permeability structure with the upper average particle size smaller than the lower average particle size is formed; and after paving and compacting of each gangue layer are completed, an oxygen inhibition covering layer matched with the gangue layer in function is synchronously constructed on the surface, and a gradient oxygen inhibition covering system with the gangue layers and the covering layers alternately nested is formed. Through the multi-dimensional synergistic effect of physical barrier, chemical inhibition, structural regulation and dynamic management, the oxygen diffusion path is effectively blocked, the technical problem of spontaneous combustion caused by oxygen permeation of the gangue dump is solved, and ecological restoration and long-term stability are both considered.

Description

Technical Field

[0001] This invention belongs to the field of coal gangue disaster prevention and ecological restoration technology, and particularly relates to an oxygen suppression and covering method for gangue hills based on a reverse permeability structure. Background Technology

[0002] With the continuous development of the coal industry, coal gangue, a large amount of solid waste generated during mining and beneficiation, has become a major hidden danger to ecological restoration and safe production in mining areas due to its stockpiling. Spontaneous combustion of gangue piles originates from the continuous exothermic oxidation reaction of active components such as pyrite under the action of oxygen. This not only releases large amounts of toxic and harmful gases, polluting the atmosphere, but may also induce secondary disasters such as collapses and explosions, seriously hindering the green transformation and sustainable development of mining areas. The core driving force of this spontaneous combustion process lies in the transport and diffusion capacity of oxygen within the gangue pile, and the heterogeneity of the pile structure directly determines the complexity and non-uniformity of the oxygen migration path.

[0003] During natural stockpiling, gangue undergoes crushing, weathering, and gravity sorting, forming a multi-scale particle size distribution system composed of coarse-grained boulders, medium-sized crushed stone, and fine-grained powder. This highly heterogeneous particle size structure results in a significant zoning of the internal pore network: coarse-grained regions form highly interconnected large-pore channels, becoming "high-speed paths" for rapid oxygen infiltration; while fine-grained regions, due to their dense structure and poor permeability, easily form localized heat accumulation centers, hindering the effective dissipation of heat and moisture. Existing oxygen-suppressing covering technologies mostly use single materials such as loess or fly ash for overall sealing, neglecting the spatial differences in the particle size distribution and pore structure of the underlying gangue layer, making it difficult to achieve precise control over oxygen diffusion behavior in different areas.

[0004] Existing technologies generally suffer from three major drawbacks: First, the design of the capping layer lacks compatibility with the particle size structure of the underlying gangue, failing to effectively seal macroscopic pores in areas rich in coarse particles, leading to continuous oxygen infiltration and exacerbating local oxidation. Second, the capping material has a single function; while it can block oxygen in fine-particle areas, it also inhibits internal heat and moisture migration, easily triggering thermal accumulation effects and increasing the risk of methane accumulation and thermal runaway. Third, the remediation models are mostly passive interventions after stockpiling, failing to simultaneously construct an active prevention and control system with gradient oxygen blocking and ecological synergy functions during the disposal and stockpiling process. Although some studies have attempted to introduce the concept of layered capping, a systematic design method based on the particle size-pore size-oxygen flux mapping relationship has not yet been established, especially lacking a source-based oxygen suppression strategy that matches specific functional materials to different particle size layers and achieves integrated structural and functional design.

[0005] Therefore, there is an urgent need for a method that can simultaneously construct a reverse permeable structure during the disposal of gangue and achieve precise adaptation of the covering layer function to suppress oxygen. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a method for oxygen suppression and covering of waste rock piles based on a reverse permeability structure, comprising the following steps: The waste gangue was subjected to three-stage screening to obtain coarse-grained gangue, medium-grained gangue, and fine-grained gangue. Based on the coarse, medium, and fine gangue obtained from screening, the gangue is layered and compacted from bottom to top to form a reverse permeable structure with an average particle size in the upper part smaller than that in the lower part. After each layer of gangue is laid and compacted, an oxygen-suppressing covering layer adapted to its function is simultaneously constructed on the surface, forming a gradient oxygen-suppressing covering system in which gangue layers and covering layers are nested alternately.

[0007] Optionally, the gradient oxygen suppression covering system comprises, from bottom to top, a bottom structural unit, a middle structural unit, and a surface structural unit; the bottom structural unit consists of a compacted coarse-particle gangue layer and a bottom polymer microcapsule sealing layer; the middle structural unit consists of a compacted medium-particle gangue layer and a middle inorganic composite oxygen barrier layer; the surface structural unit consists of a compacted fine-particle gangue layer and a surface ecological breathable covering layer, wherein the surface ecological breathable covering layer is the uppermost functional layer of the entire gradient oxygen suppression covering system.

[0008] Optionally, the process of layering and compacting coarse-grained gangue, medium-grained gangue, and fine-grained gangue obtained from screening, from bottom to top, includes: Only the gangue layer is compacted in layers, and no mechanical compaction is carried out after the overburden layer is constructed. The compaction degree of the gangue layer increases from bottom to top.

[0009] Optionally, after each layer of gangue has been laid and compacted, the process of simultaneously constructing an oxygen-suppressing covering layer adapted to its function on the surface includes: Before constructing the oxygen-suppressing covering layer on the surface of each gangue layer, a polyester filament needle-punched geotextile is first laid on the surface of the gangue layer as an interface buffer layer.

[0010] Optionally, the bottom polymer microcapsule sealing layer is made of biodegradable polymer encapsulating nano-inorganic particles, which cure naturally after spraying to form a flexible film; wherein the biodegradable polymer is at least one of polylactic acid, polyhydroxyalkanoate or polycaprolactone, and the nano-inorganic particles include nano-silica, nano-calcium carbonate or nano-zinc oxide.

[0011] Optionally, the intermediate inorganic composite oxygen barrier layer is composed of a mixture of fly ash, bentonite, cement, and magnesium oxide.

[0012] Optionally, the surface ecological breathable covering layer is composed of improved loess, natural plant fibers, highly absorbent water-retaining resin, slow-release organic matter, and local suitable grass species; wherein, the improved loess is obtained by increasing the organic matter content of loess to a preset threshold.

[0013] Optionally, the process of determining the design thickness of the oxygen-suppressing coating includes: The design thickness of the cover layer is obtained based on the functional relationship between the average particle size and porosity of the underlying gangue layer, empirical coefficients related to the performance of the cover material, ambient oxygen concentration, and target oxygen concentration corresponding to different particle size layers.

[0014] Optionally, it also includes a sensor network pre-embedded in the middle inorganic composite oxygen barrier layer and the surface ecological breathable covering layer to continuously collect oxygen concentration and temperature data, monitor and maintain the gradient oxygen suppression covering system, issue an early warning when the oxygen concentration or temperature data exceeds a preset threshold, and inject a water-based polymer sealing agent into the covering layer above the warning area for local reinforcement.

[0015] Optionally, a three-stage vibrating screening device may be used for the three-stage screening process of the waste gangue.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: This invention integrates three-stage screening, reverse-sequence stockpiling, and simultaneous construction of a functional cover layer during the waste disposal process, transforming the traditional passive sealing and treatment after stockpiling into an active construction process. This method avoids secondary pollution and increased costs caused by secondary excavation, effectively blocks the oxygen intrusion path at its source, and significantly reduces the risk of spontaneous combustion and treatment costs.

[0017] This invention utilizes a bottom-up approach, sequentially layering coarse, medium, and fine-grained gangue to create a reverse permeability structure with decreasing particle size. The highly permeable coarse-grained layer is placed at the bottom, while the low-permeability fine-grained layer is placed at the top. This structure overturns the naturally occurring top-coarse, bottom-fine permeability pattern of stockpiling, eliminating the chimney effect of the coarse-grained area as a pathway for rapid oxygen infiltration. It structurally blocks the vertical diffusion path of oxygen into the deeper parts of the stockpile, thus fundamentally improving oxygen suppression efficiency.

[0018] This invention addresses the differences in pore structure and oxidation risk characteristics of coarse, medium, and fine gangue layers by matching a bottom layer of polymer microcapsules for sealing, a middle layer of inorganic composite oxygen barrier, and a top layer of ecologically permeable covering material, respectively. The bottom layer uses microcapsules to penetrate and seal macroscopic pores; the middle layer forms a dense chemical barrier through inorganic composite materials; and the top layer uses ecological materials to both block oxygen and dissipate heat and moisture. This approach overcomes the limitation of single-material coverings in meeting the differentiated barrier control needs of different particle sizes, achieving a gradient synergistic effect from macroscopic pore sealing to microscopic dense barrier and then to integrated ecological functions.

[0019] This invention establishes a quantitative calculation relationship between the designed thickness of the overburden layer and the average particle size, porosity, material properties, and target oxygen concentration of the underlying gangue layer, transforming the traditional experience-based design method into a precise calculation based on a scientific model. This approach provides a quantifiable design basis for determining the staged compaction parameters and the thickness of the overburden layer, ensuring the reliability and consistency of the engineering implementation effect and improving the engineering applicability and replicability of the technical solution.

[0020] This invention utilizes a pre-embedded gridded sensor network within the middle and surface cover layers to collect real-time oxygen concentration and temperature data. Combined with an early warning platform and a grouting response mechanism, it forms a closed-loop management system of monitoring, evaluation, and control. This method endows the cover structure with dynamic self-maintenance capabilities, enabling proactive intervention when local oxygen suppression effectiveness declines. It overcomes the shortcomings of traditional cover technologies that lack long-term operation and maintenance mechanisms, ensuring the stability of oxygen suppression effects throughout their entire lifecycle.

[0021] This invention utilizes industrial solid wastes such as fly ash and bentonite as the core materials for the middle oxygen barrier layer, employs polymer-encapsulated nano-inorganic particles to construct the bottom layer structure, and utilizes modified loess to construct the surface ecological layer, organically integrating waste resource utilization with ecological restoration functions. This approach achieves efficient oxygen suppression while promoting vegetation restoration on the surface of the mining pile, unifying pollution control, resource recycling, and ecological restoration, aligning with the goals of green mine construction.

[0022] In summary, this invention, through the system integration of structural innovation, functional matching, quantitative design and intelligent operation and maintenance, effectively blocks the oxygen diffusion path by working synergistically from multiple dimensions such as physical barrier, chemical inhibition, structural regulation and dynamic management. It solves the technical problem of spontaneous combustion caused by oxygen infiltration in gangue piles, while taking into account ecological restoration and long-term stability. Attached Figure Description

[0023] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the method flow according to an embodiment of the present invention. Detailed Implementation

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0026] Example 1 like Figure 1 As shown, this embodiment provides a method for oxygen suppression and covering of gangue hills based on a reverse permeability structure, including the following steps: Step S1: Perform online three-stage screening on the waste gangue to separate it into three grades: coarse gangue, medium gangue, and fine gangue. Step S2: The coarse-grained gangue, medium-grained gangue and fine-grained gangue are piled up from bottom to top to form a coarse-grained gangue layer, a medium-grained gangue layer and a fine-grained gangue layer, so that the average particle size of the gangue layer at the top of the pile is smaller than the average particle size of the gangue layer at the bottom, thus forming a reverse permeable structure. Step S3: After the paving and compaction of any gangue layer is completed, an oxygen-suppressing covering layer with the same function is immediately constructed on its surface to form a gradient composite oxygen-suppressing covering system in which gangue layers and covering layers are nested alternately. Furthermore, the design thickness H of each oxygen-suppressing capping layer is determined by a calculation model based on the average particle size d and porosity n of the underlying gangue layer. The expression of this model is as follows: ; In the formula, H is the designed thickness of the cover layer in cm; d is the average particle size of the underlying gangue layer in mm; n is the porosity of the underlying gangue layer; C0 is the ambient oxygen concentration, which is 20.9%; C is the target oxygen concentration below the cover layer; and k is an empirical coefficient related to the performance of the cover material, with a value ranging from 0.8 to 1.5.

[0027] In the calculation model, the target oxygen concentration C ≤ 5% for coarse-grained gangue layers; C ≤ 6% for medium-grained gangue layers; and C ≤ 8% for fine-grained gangue layers. The empirical coefficient k is adjusted according to the type of covering material: the k value for the bottom layer of polymer microcapsule sealing layer is 1.2-1.5, the k value for the middle layer of inorganic composite oxygen barrier layer is 0.9-1.2, and the k value for the surface layer of ecological breathable covering layer is 0.8-1.0.

[0028] The feasible gradient composite oxygen-suppressing cover system comprises, from bottom to top, a bottom structural unit, a middle structural unit, and a surface structural unit. The bottom structural unit consists of a compacted coarse-particle gangue layer and a bottom polymer microcapsule sealing layer; the middle structural unit consists of a compacted medium-particle gangue layer and a middle inorganic composite oxygen-barrier layer; and the surface structural unit consists of a compacted fine-particle gangue layer and a surface ecologically permeable cover layer, with the surface ecologically permeable cover layer being the uppermost functional layer of the entire structure and directly exposed to the atmospheric environment.

[0029] Furthermore, the bottom polymer microcapsule sealing layer is made of biodegradable polymer encapsulating nano-inorganic particles, which cures naturally after spraying to form a flexible film with a thickness of 5-10 cm; the particle size distribution of the microcapsules is 0.1-10 µm; the biodegradable polymer is selected from at least one of polylactic acid, polyhydroxyalkanoate, or polycaprolactone, with a degradation cycle of 3-5 years; the nano-inorganic particles include nano-silica, nano-calcium carbonate, or nano-zinc oxide, with a particle size range of 20-100 nm.

[0030] The intermediate inorganic composite oxygen barrier layer is composed of fly ash, bentonite, cement, and magnesium oxide mixed in a mass ratio of 50:30:15:5, with a paving thickness of 15-25cm; the water-cement ratio of the mixture is 0.35-0.45, and the initial setting time is not less than 2 hours; the material has a 28-day compressive strength greater than 5MPa and a permeability coefficient less than 1×10⁻⁶. -7 cm / s, pH value maintained in the range of 10-12.

[0031] Furthermore, the intermediate inorganic composite oxygen barrier layer is constructed using a layered paving process, with each layer not exceeding 8cm in thickness. A plate vibrator is used for compaction to ensure a tight, seamless bond between layers. After construction, the curing period is no less than 7 days, during which the surface is kept moist.

[0032] The surface ecological breathable covering layer consists of 60%-75% improved loess, 10%-20% natural plant fiber, 3%-8% highly absorbent water-retaining resin, 2%-5% slow-release organic matter, and 0.5%-2% local suitable grass species; the organic matter content of the improved loess is 3%-5%; the length of the plant fiber is 2-5cm; the water absorption ratio of the water-retaining resin is 200-400 times; the local suitable grass species include tall fescue, ryegrass, or bermudagrass, with a seed germination rate of not less than 85% and a sowing density of 30-50g / m². 2 .

[0033] In practice, in step S1, the coarse gangue has a particle size greater than 50 mm, the medium gangue has a particle size of 10-50 mm, and the fine gangue has a particle size less than 10 mm; the screening process uses a three-stage vibrating screening device, with the first-stage screen having a mesh size of 50 mm and the second-stage screen having a mesh size of 10 mm, achieving a screening efficiency of 150 t of gangue material per hour.

[0034] In step S2, only the gangue layer is compacted, and no mechanical compaction is performed after the construction of each overburden layer; the compaction degree of the coarse-grained gangue layer is 80%-85%, the compaction degree of the medium-grained gangue layer is 85%-90%, and the compaction degree of the fine-grained gangue layer is 90%-93%; the paving thickness of each gangue layer is 30-40cm; and the average particle size ratio of adjacent gangue layers is controlled between 1.5 and 2.5.

[0035] Furthermore, in step 2, the construction of the reverse permeability structure requires that the average particle size ratio of adjacent gangue layers be controlled between 1.5 and 2.5. The average particle size of the coarse-grained gangue layer is 60-80 mm, the average particle size of the medium-grained gangue layer is 25-35 mm, and the average particle size of the fine-grained gangue layer is 5-8 mm.

[0036] In step 3, a bottom layer of polymer microcapsule sealing layer is applied to the coarse-grained gangue layer. This sealing layer is made of biodegradable polymer encapsulating nano-inorganic particles, and after spraying, it naturally cures to form a flexible film with a thickness of 5-10 cm. The microcapsule particle size distribution is 0.1-10 µm, and the sealing efficiency reaches over 95%.

[0037] It is feasible to lay a layer with a unit area mass of not less than 300g / m² before constructing the overburden layer on the surface of any gangue layer. 2 Polyester filament needle-punched geotextile is used as an interface buffer layer; the longitudinal tensile strength of the geotextile is greater than 20,000 N / m, the transverse tensile strength is greater than 18,000 N / m, and the elongation is 40%-80%.

[0038] As an optional implementation, this embodiment also proposes a monitoring and maintenance system, which includes a sensor network embedded in the middle inorganic composite oxygen barrier layer and the surface ecological breathable covering layer for continuously collecting oxygen concentration and temperature data; the node spacing of the sensor network is 10-15m, and the data acquisition frequency is once per hour; the sensors adopt a self-powered design, powered by solar panels, with a battery life of more than 30 days; the oxygen concentration measurement error does not exceed ±0.5%, and the temperature measurement error does not exceed ±0.5℃.

[0039] The monitoring and maintenance system also includes a data processing and early warning platform that is connected to the sensor network. This platform is configured to automatically trigger an early warning when the oxygen concentration reading at a certain monitoring point exceeds 120% of the target threshold C of its layer for 24 consecutive hours, and / or the daily temperature rise exceeds 5°C. The early warning signal is sent to the monitoring center via a wireless transmission module.

[0040] The monitoring and maintenance system also includes a response mechanism linked to the early warning platform. It injects water-based polymer sealing agent into the cover layer above the early warning area through a preset grouting pipe for local reinforcement. The grouting pressure is 0.3-0.5MPa and the grouting volume at a single point is 50-200L.

[0041] The sensor network of the monitoring and maintenance system adopts a self-powered design, powered by solar panels, with a battery life of over 30 days. The sensor accuracy requirements are: oxygen concentration measurement error not exceeding ±0.5%, and temperature measurement error not exceeding ±0.5℃.

[0042] This embodiment proposes to achieve precise control of the oxygen diffusion path in the coal gangue pile by constructing a reverse permeable structure and a gradient functional covering layer, effectively blocking the spontaneous combustion reaction chain; the use of synchronous construction technology significantly improves the treatment efficiency and avoids environmental disturbance caused by secondary excavation; the multi-layer composite structure not only ensures the oxygen barrier effect but also maintains the necessary heat and moisture migration channels, preventing the risk of local heat accumulation; the introduction of an intelligent monitoring system enables real-time evaluation and proactive maintenance of the treatment effect, forming a complete closed-loop prevention and control system.

[0043] Example 2 refer to Figure 1 The core of the oxygen-suppressing and covering method for gangue piles based on a reverse permeability structure described in this embodiment lies in simultaneously carrying out the gangue disposal process and the construction process of the oxygen-suppressing and covering structure. Through four major stages—online screening, reverse-sequence stacking, functional layer adaptation, and intelligent monitoring—a gradient composite oxygen-suppressing system with decreasing particle size and progressive functions from bottom to top is constructed. The construction process of this system strictly follows the following steps.

[0044] In the oxygen-suppressing covering method for gangue piles based on a reverse permeability structure in Embodiment 1, step S1 involves online three-stage screening of the gangue to separate it into three grades: coarse, medium, and fine particles. Specifically, step S1 relies on a three-stage vibrating screening device integrated into the gangue disposal and transportation line. The first-stage screen has a mesh size of 50mm to intercept coarse gangue particles larger than 50mm; the second-stage screen has a mesh size of 10mm to intercept medium-sized gangue particles between 10-50mm; and fine gangue particles smaller than 10mm fall through the second-stage screen into the collection device below. The screening process is continuous, achieving a screening efficiency of 150 tons of gangue material per hour, ensuring matching the capacity of subsequent landfill processes. The three types of gangue after screening are transported to their respective landfill areas via independent conveyor belts or chutes, providing a raw material basis for the construction of the reverse permeability structure. The key to this screening process is to ensure that the particle size boundaries of each grade are clear and to avoid mixing, thereby ensuring the controllability of the pore structure of the subsequent packing layer.

[0045] In the oxygen-suppressing covering method for gangue piles based on a reverse permeability structure in Example 1, step S2 involves constructing the reverse permeability structure by sequentially piling coarse-grained gangue layers, medium-grained gangue layers, and fine-grained gangue layers from bottom to top, ensuring that the average particle size of the upper gangue layer is smaller than that of the lower gangue layer. Specifically, step S2 first involves spreading a coarse-grained gangue layer on the base of the gangue pile, with an average particle size controlled within the range of 60-80 mm; then spreading a medium-grained gangue layer on top, with an average particle size controlled within the range of 25-35 mm; and finally spreading a fine-grained gangue layer on top, with an average particle size controlled within the range of 5-8 mm. The average particle size ratio of adjacent gangue layers is strictly controlled between 1.5 and 2.5 to ensure a significant gradient change in the pore structure. The thickness of each gangue layer was controlled between 30-40cm, and only the gangue layer itself was compacted; no mechanical compaction was performed after the construction of each overburden layer. The compaction process used a self-weight roller for layered compaction. The compaction degree of the coarse-grained gangue layer was controlled at 80%-85%, the medium-grained gangue layer at 85%-90%, and the fine-grained gangue layer at 90%-93%. This gradient design of compaction degree aims to balance structural stability and pore connectivity: the lower coarse-grained layer maintains a high porosity to accommodate possible settlement deformation, while the upper fine-grained layer forms an initial physical barrier through high density. The construction of this reverse permeability structure fundamentally reverses the "fine on top, coarse on bottom" permeability pattern formed by natural stockpiling, placing the highly permeable coarse-grained layer at the bottom and the low-permeability fine-grained layer at the top, effectively inhibiting the vertical diffusion of oxygen from the top atmosphere to the deeper parts of the stockpile.

[0046] In the oxygen-suppressing covering method for gangue piles based on a reverse permeability structure described in Example 1, step S3 involves synchronously covering and adapting the functional layer. After each gangue layer is laid and compacted, an oxygen-suppressing covering layer with the same function is immediately and synchronously applied to its surface, forming a composite structure of alternating nested gangue layers and covering layers. Specifically, step S3 includes three sub-operations, each corresponding to the functional requirements of the three gangue layers.

[0047] First, after the coarse-grained gangue layer is laid and compacted, immediately lay a layer on its surface with a unit area mass greater than or equal to 300g / m². 2 Polyester filament needle-punched geotextile is used as an interface buffer layer. This geotextile has a tensile strength greater than 20,000 N / m longitudinally and greater than 18,000 N / m transversely, with an elongation controlled between 40% and 80%. Its function is to isolate the underlying coarse-particle gangue from the overlying cover layer, preventing the loss of the cover layer material during construction or subsequent settlement, and providing a smooth construction base surface. Subsequently, a bottom layer of polymer microcapsule sealing layer is applied on this geotextile. This sealing layer is made of biodegradable polymers encapsulating nano-inorganic particles, uniformly sprayed using high-pressure airless spraying equipment, and then naturally cured at room temperature to form a flexible film with a thickness of 5-10 cm. The biodegradable polymer is selected from at least one of polylactic acid, polyhydroxyalkanoates, or polycaprolactone, with a designed degradation cycle of 3-5 years to match the oxygen suppression requirements during the initial high-risk period of the gangue pile. The nano-inorganic particles, including nano-silica, nano-calcium carbonate, or nano-zinc oxide, with a particle size ranging from 20 to 100 nm, serve to fill the microscopic pores between microcapsules, improving the compactness of the sealing layer. The overall particle size distribution of the microcapsules is 0.1-10 µm, enabling them to effectively penetrate and seal the macroscopic pore network at the top of the coarse-particle gangue layer, achieving a sealing efficiency of over 95%, thereby precisely blocking the dominant pathway for oxygen permeation.

[0048] Secondly, after the medium-particle gangue layer is laid and compacted, a layer of polyester filament needle-punched geotextile of the above specifications is laid as an interface buffer layer. Subsequently, a middle-layer inorganic composite oxygen barrier layer is constructed on this geotextile. This oxygen barrier layer is composed of fly ash, bentonite, cement, and magnesium oxide mixed in a mass ratio of 50:30:15:5. The water-cement ratio of the mixture is strictly controlled within the range of 0.35-0.45 to ensure good workability and final strength, and its initial setting time is no less than 2 hours to allow sufficient time for construction operations. The material is laid to a thickness of 15-25cm using a layered paving process, with each layer not exceeding 8cm in thickness. A plate vibrator is used for compaction to ensure a tight, seamless bond between layers. After construction, curing is required for no less than 7 days, during which the surface is kept moist to ensure sufficient hydration reaction. The material achieves a compressive strength of over 5MPa after 28 days and a permeability coefficient of less than 1×10⁻⁶. -7With a flow rate of cm / s and a pH value maintained within the range of 10-12, it combines high strength, low permeability, and an alkaline environment, effectively inhibiting the oxidation reaction of pyrite.

[0049] Finally, after the fine-particle gangue layer is laid and compacted, a layer of polyester filament needle-punched geotextile is laid as an interface buffer layer. Subsequently, an ecologically permeable surface cover layer is constructed on this geotextile. This cover layer consists of 60%-75% improved loess, 10%-20% natural plant fiber, 3%-8% highly absorbent water-retaining resin, 2%-5% slow-release organic matter, and 0.5%-2% local suitable grass species. The improved loess undergoes organic matter content enhancement treatment, achieving an organic matter content of 3%-5% to improve soil structure and fertility; natural plant fiber length is controlled at 2-5cm, providing reinforcement and water retention; the highly absorbent water-retaining resin has a water absorption ratio of 200-400 times, storing water during the rainy season and slowly releasing it during the dry season to maintain the water needed for vegetation growth; the slow-release organic matter provides long-lasting nutrients for plants; locally suitable grass species include tall fescue, ryegrass, or bermudagrass, with a seed germination rate of over 85% and a sowing density of 30-50g / m². 2 This covering layer ensures a certain degree of breathability to facilitate the dissipation of internal heat and moisture, while further reinforcing the surface through the growth of plant roots, thus achieving ecological restoration.

[0050] The thickness of each overburden layer is not a fixed value, but is precisely determined by a calculation model based on the average particle size and porosity of the underlying gangue layer. The model expression is: Where H is the designed thickness of the cover layer in cm; d is the average particle size of the underlying gangue layer in mm; n is the porosity; C0 is the ambient oxygen concentration, taken as 20.9%; C is the target oxygen concentration below the cover layer; and k is an empirical coefficient related to the performance of the cover material, ranging from 0.8 to 1.5. The target oxygen concentration C is set differently for different layers: for coarse-grained gangue layers, C is less than or equal to 5%; for medium-grained gangue layers, C is less than or equal to 6%; and for fine-grained gangue layers, C is less than or equal to 8%. These target concentration values ​​are determined based on experimental data of pyrite oxidation kinetics to ensure that the oxidation reaction rate is suppressed within a safe threshold. The empirical coefficient k is adjusted according to the specific proportions of the cover material: for the bottom layer of polymer microcapsule sealing, k is taken as 1.2-1.5; for the middle layer of inorganic composite oxygen barrier layer, k is taken as 0.9-1.2; and for the surface layer of ecologically permeable cover layer, k is taken as 0.8-1.0. This model directly links physical parameters with functional objectives, enabling the scientific and precise design of the overlay layer.

[0051] In the oxygen-suppressing covering method for gangue hills based on a reverse permeability structure in Example 1, step S4, structure formation, completes the above three-layer filling and covering, forming an integrated gradient oxygen-suppressing covering system. Specifically, step S4 marks the completion of the physical construction of the entire oxygen-suppressing structure. The final gradient composite oxygen-suppressing covering structure includes a bottom layer structural unit, a middle layer structural unit, and a surface layer structural unit from bottom to top. The bottom layer structural unit consists of a compacted coarse-grained gangue layer and a bottom layer of polymer microcapsules for sealing, and its main function is to seal macroscopic pore channels; the middle layer structural unit consists of a compacted medium-grained gangue layer and a middle layer of inorganic composite oxygen barrier layer, and its main function is to provide a high-strength, low-permeability chemical oxygen barrier; the surface layer structural unit consists of a compacted fine-grained gangue layer and a surface ecological permeable covering layer, and its main function is to achieve ecological restoration and heat and humidity control. Among them, the surface ecological permeable covering layer is the uppermost functional layer of the entire structure, directly exposed to the atmospheric environment, and undertakes the final ecological and landscape functions.

[0052] To enable long-term monitoring and proactive maintenance of the oxygen-suppressing effect, this embodiment also includes a monitoring and maintenance system for the oxygen-suppressing cover structure. This system comprises a sensor network embedded in the middle inorganic composite oxygen-barrier layer and the surface ecological breathable cover layer, used to continuously collect oxygen concentration and temperature data. The sensor network node spacing is set to 10-15m, forming a grid-like monitoring layout, with data acquisition frequency once per hour. The sensor network adopts a self-powered design, powered by solar panels, with a battery life of over 30 days, ensuring long-term stable operation without external power. The sensor accuracy requirements are that the oxygen concentration measurement error does not exceed ±0.5%, and the temperature measurement error does not exceed ±0.5℃, to ensure data reliability.

[0053] The monitoring and maintenance system also includes a data processing and early warning platform connected to the sensor network. This platform is configured to analyze the collected data in real time and automatically trigger an early warning when the oxygen concentration reading at a monitoring point exceeds 120% of the target threshold C for its stratum for 24 consecutive hours, or when the daily temperature rise exceeds 5°C. The early warning signal is transmitted to the monitoring center via a wireless transmission module to notify maintenance personnel.

[0054] The monitoring and maintenance system also includes a response mechanism linked to the early warning platform. For warning areas, a water-based polymeric sealing agent is injected into the overburden layer above the area via a network of grouting pipes pre-installed within the overburden layer for localized reinforcement. The grouting pressure is controlled at 0.3-0.5 MPa, and the grouting volume at a single point is determined according to the warning level, ranging from 50-200 L. This response mechanism achieves closed-loop management from passive monitoring to proactive intervention, effectively addressing the risk of potential localized oxygen suppression failure.

[0055] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for oxygen suppression and covering of gangue hills based on a reverse permeability structure, characterized in that, Includes the following steps: The waste gangue was subjected to three-stage screening to obtain coarse-grained gangue, medium-grained gangue, and fine-grained gangue. Based on the coarse, medium, and fine gangue obtained from screening, the gangue is layered and compacted from bottom to top to form a reverse permeable structure with an average particle size in the upper part smaller than that in the lower part. After each layer of gangue is laid and compacted, an oxygen-suppressing covering layer adapted to its function is simultaneously constructed on the surface, forming a gradient oxygen-suppressing covering system in which gangue layers and covering layers are nested alternately.

2. The method according to claim 1, characterized in that, The gradient oxygen suppression covering system comprises, from bottom to top, a bottom structural unit, a middle structural unit, and a surface structural unit. The bottom structural unit consists of a compacted coarse-particle gangue layer and a bottom polymer microcapsule sealing layer. The middle structural unit consists of a compacted medium-particle gangue layer and a middle inorganic composite oxygen barrier layer. The surface structural unit consists of a compacted fine-particle gangue layer and a surface ecological breathable covering layer, wherein the surface ecological breathable covering layer is the uppermost functional layer of the entire gradient oxygen suppression covering system.

3. The method according to claim 1, characterized in that, The process of layering and compacting coarse, medium, and fine-grained gangue obtained from screening, from bottom to top, includes: Only the gangue layer is compacted in layers, and no mechanical compaction is carried out after the overburden layer is constructed. The compaction degree of the gangue layer increases from bottom to top.

4. The method according to claim 1, characterized in that, After each layer of gangue is laid and compacted, the process of simultaneously constructing an oxygen-suppressing covering layer adapted to its function on the surface includes: Before constructing the oxygen-suppressing covering layer on the surface of each gangue layer, a polyester filament needle-punched geotextile is first laid on the surface of the gangue layer as an interface buffer layer.

5. The method according to claim 2, characterized in that, The bottom polymer microcapsule sealing layer is made of polymer encapsulating nano-inorganic particles, which are naturally cured after spraying to form a flexible film; wherein, the polymer is at least one of polylactic acid, polyhydroxyalkanoate or polycaprolactone, and the nano-inorganic particles include nano-silica, nano-calcium carbonate or nano-zinc oxide.

6. The method according to claim 2, characterized in that, The intermediate inorganic composite oxygen barrier layer is composed of fly ash, bentonite, cement and magnesium oxide.

7. The method according to claim 2, characterized in that, The surface ecological breathable covering layer is composed of improved loess, natural plant fibers, highly absorbent and water-retaining resin, slow-release organic matter, and local suitable grass species; wherein, the improved loess is obtained by increasing the organic matter content of loess to a preset threshold.

8. The method according to claim 1, characterized in that, The process of determining the design thickness of the oxygen-suppressing coating includes: The design thickness of the cover layer is obtained based on the functional relationship between the average particle size and porosity of the underlying gangue layer, empirical coefficients related to the performance of the cover material, ambient oxygen concentration, and target oxygen concentration corresponding to different particle size layers.

9. The method according to claim 1, characterized in that, It also includes a sensor network embedded in the middle inorganic composite oxygen barrier layer and the surface ecological breathable covering layer to continuously collect oxygen concentration and temperature data, monitor and maintain the gradient oxygen suppression covering system, issue an early warning when the oxygen concentration or temperature data exceeds the preset threshold, and inject water-based polymer sealing agent into the covering layer above the warning area for local reinforcement.

10. The method according to claim 1, characterized in that, The process of three-stage screening of waste gangue is carried out using a three-stage vibrating screening device.

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