Barrier drought area non-ferrous metal mine waste rock field surface covering layer and construction method thereof

Abstract

The application belongs to the technical field of pollution treatment and mine ecological restoration, and provides a barrier surface covering layer for non-ferrous metal mine waste rock yard in a drought area and a construction method thereof, which comprises, from bottom to top, a filler layer, a barrier layer, a waterproof layer and an improved soil layer laid on the surface of the non-ferrous metal mine waste rock yard in the drought area; the filler layer comprises matured sludge and rice husk biochar mixed at a preset mass ratio; the barrier layer is beet lime; the waterproof layer comprises a waterproof and breathable membrane made of non-woven fabric, polyethylene / polypropylene and non-woven fabric; and the improved soil layer is the undisturbed soil around the waste rock yard mixed with the matured sludge and the rice husk biochar. The matured sludge, the rice husk biochar and the beet lime are used to restore the ecology of the non-ferrous metal mine in the drought area through multi-layer covering and soil improvement, and the waterproof layer is constructed by laying the waterproof and breathable membrane to inhibit the generation of acid water, so as to realize the ecological restoration and long-term greening of the non-ferrous metal mine waste rock yard.

Description

Technical Field

[0001] This invention belongs to the field of pollution control and mine ecological restoration technology, and in particular relates to a surface covering layer for non-ferrous metal mine waste rock sites in arid areas and its construction method. Background Technology

[0002] Due to rapid industrial development, the demand for and extraction of mineral resources have been increasing year by year. Along with the increase in mining scale, the amount of mine waste rock generated has also increased annually, leading to increasingly serious environmental problems. Waste rock generated from mining stripping operations accounts for a large proportion of the total new waste rock; followed by coal gangue, tailings, and other mine waste rock. According to relevant provisions of the Solid Waste Pollution Prevention and Control Law, stockpiled mine waste rock falls under the category of solid waste. However, when waste rock is stored using current methods, the toxic and harmful substances it contains are continuously released through weathering, rainwater leaching, and other natural processes, causing secondary pollution to the surrounding environment.

[0003] In non-ferrous metal mines in arid regions, the ecological problems caused by waste rock accumulation are even more complex. Waste rock contains easily oxidizable minerals such as sulfides, which will still undergo oxidation reactions when exposed to limited water in arid environments, generating acidic water. This accelerates the leaching and migration of heavy metals such as Cu, Fe, Cd, Zn, and Pb, not only polluting the soil and groundwater, but also leading to severe ecological degradation problems in waste rock sites, including extreme soil acidification, heavy metal enrichment, nutrient depletion, vegetation death, and soil erosion.

[0004] Current remediation technologies for waste rock acidification and heavy metal pollution have significant limitations: conventional measures such as single-material covering or mixing alkaline materials into the improvement materials can partially alleviate acidity or supplement nutrients, but cannot simultaneously achieve heavy metal control and vegetation restoration. Specifically, the addition of lime alone can easily lead to localized strong soil alkalization, inhibiting plant growth; when simply laying topsoil, the underlying waste rock continuously produces acid and releases heavy metals, causing rapid degradation of the upper soil layer and low plant survival rates; in arid climates, single-layer covering is difficult to retain soil moisture for long periods, leading to vegetation restoration failure. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a surface covering layer and its construction method for non-ferrous metal mine waste rock sites in arid regions. It addresses issues such as the tendency for simply laying topsoil to lead to continuous acid production and heavy metal release from the underlying waste rock, the potential for strong local soil alkalization and inhibition of plant growth due to the use of alkaline materials, and the difficulty of maintaining soil moisture in arid regions with a single covering layer. This invention utilizes matured sludge, rice husk biochar, and beet lime to perform ecological restoration of non-ferrous metal mines in arid regions through multi-layer covering and soil amendment. Furthermore, it constructs a waterproof and breathable membrane to inhibit acid water generation, thereby achieving the ecological restoration and long-term revegetation of non-ferrous metal mine waste rock sites.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a surface covering layer for non-ferrous metal mine waste rock sites in arid areas, comprising a filler layer, a barrier layer, a waterproof layer and a soil amendment layer laid sequentially from bottom to top on the surface of non-ferrous metal mine waste rock sites in arid areas. The filler layer comprises matured sludge and rice husk biochar mixed in a preset mass ratio; the barrier layer is beet lime; the waterproof layer comprises a waterproof and breathable membrane made of non-woven fabric, polyethylene / polypropylene, and non-woven fabric; and the improved soil layer is the original soil surrounding the waste rock dump mixed with matured sludge and rice husk biochar.

[0007] Furthermore, the mass ratio of matured sludge to rice husk biochar in the packing layer is 6~8:4~2.

[0008] Furthermore, the thickness of the filler layer is 10cm to 15cm.

[0009] Furthermore, the thickness of the barrier layer is 5cm to 10mm.

[0010] Furthermore, the thickness of the waterproof layer is 5cm to 10mm.

[0011] Furthermore, the waterproof layer is a double-layer non-woven fabric spunbond polyethylene / polypropylene waterproof and breathable membrane with a thickness of 0.5mm to 1mm.

[0012] Furthermore, the waterproof layer is provided with a 1cm to 2cm thick layer of gravel and fine sand mixture on one side near the barrier layer; and a 3cm to 5mm thick layer of fine sand on the other side.

[0013] Furthermore, the improved soil layer consists of the original soil surrounding the waste rock dump, mixed with 5% to 10% matured sludge and 2.5% to 5% rice husk biochar by mass.

[0014] Furthermore, the thickness of the improved soil layer is not less than 20 cm.

[0015] In a second aspect, the present invention provides a method for constructing a surface cover layer for a non-ferrous metal mine waste rock site in arid areas, using the surface cover layer for a non-ferrous metal mine waste rock site in arid areas as described in the first aspect, comprising: laying a filler layer, a barrier layer, a waterproof layer and a soil improvement layer sequentially from bottom to top on the surface of the waste rock site.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The materials used in the covering layer of this invention include matured sludge, rice husk biochar, beet lime, a waterproof and breathable membrane, gravel, and fine sand. Matured sludge can improve acidic conditions using its alkaline substances and organic components. The nitrogen and phosphorus-rich organic matter in the sludge can act as effective adsorbents for anions and cations, while also integrating or complexing some heavy metal ions to alleviate their toxicity. Rice husk biochar, based on its porous structure and organic carbon source, possesses the characteristics of adsorbing heavy metals, improving soil permeability and water retention, and can also provide a new outlet for biochar, a byproduct of biomass power plants. Beet lime is rich in calcium carbonate and calcium hydroxide, as well as a small amount of organic matter. On the one hand, it can neutralize acidic water; on the other hand, the organic matter helps reconstruct the soil environment and promote soil fertility. This invention combines acid suppression, heavy metal fixation, soil condition improvement, and vegetation growth promotion. It is simple to construct, low in cost, and enables long-term ecological restoration of non-ferrous metal mine waste rock sites in arid areas.

[0017] 2. This invention organically combines physical barrier, chemical neutralization, and ecological restoration through a multi-layered structure, effectively preventing acidification and heavy metal leaching and migration from waste rock sites, and significantly improving the vegetation growth environment. The structure is optimized through multi-layered material coverage. On the one hand, the filler layer reduces waste rock porosity, decreases oxygen contact, inhibits acid water generation, and stabilizes and seals heavy metals; on the other hand, soil moisture and nutrient conditions are greatly improved, creating favorable conditions for the ecological restoration of waste rock sites in arid non-ferrous metal mines. This combined process overcomes the shortcomings of traditional single remediation measures, enabling simultaneous pollution barrier and ecological reconstruction in arid mining waste rock sites.

[0018] 3. In arid regions, sulfides in waste rock from non-ferrous metal mines undergo continuous oxidation reactions under the influence of oxygen and water, producing acidic water. This is the main mechanism for the generation of acidic water and the release of heavy metals. The waterproof layer in this invention, by laying a double-layered non-woven polyethylene / polypropylene waterproof and breathable membrane, effectively isolates moisture from the waste rock layer, preventing water seepage. Simultaneously, this waterproof and breathable membrane ensures a certain level of oxygen circulation, preventing plant roots from dying due to oxygen deficiency and affecting vegetation restoration. The barrier layer, by laying beet lime, effectively neutralizes the acidic water. The filler layer, by mixing and compacting matured sludge and rice husk biochar, reduces the porosity of the waste rock, thereby reducing the contact between oxygen and the waste rock and reducing the generation of acidic water at its source. Furthermore, the filler layer itself is composed of alkaline materials, which, combined with the barrier layer on top of the existing waterproof layer, further neutralize the generated acidic water.

[0019] 4. This invention adopts the principle of capillary barrier coverage and blocking. The beet lime in the barrier layer has a small particle size, while the gravel in the waterproof layer has a much larger particle size than the beet lime. When the two particle layers with different particle sizes come into contact, due to the difference in unsaturated hydraulic properties, the vertical water flow between the two layers is often restricted, thereby generating a capillary barrier effect. This allows the waterproof layer to maintain high saturation moisture and prevent oxygen and water from contacting sulfides.

[0020] 5. The waterproof layer of the present invention is composed of a waterproof and breathable membrane made of non-woven fabric + polyethylene / polypropylene + non-woven fabric. When combined with rice husk biochar and matured sludge in the soil improvement layer, it can effectively improve the soil's water retention and fertilizer retention capacity, and promote the ecological restoration and vegetation revegetation of waste rock sites. Attached Figure Description

[0021] The accompanying drawings, which form part of this embodiment, are used to provide a further understanding of this embodiment. The illustrative embodiments and their descriptions are used to explain this embodiment and do not constitute an improper limitation of this embodiment.

[0022] Figure 1 This is a schematic diagram of the surface cover layer structure of the present invention; Figure 2 This is an experimental diagram of the filler layer of the present invention; Figure 3 For the present invention Figure 2 Experimental index graph; Figure 4 These are experimental diagrams of the filler layer and barrier layer of the present invention; Figure 5 For the present invention Figure 4 Experimental index graph; Figure 6 This is a diagram of a planting experiment using the improved soil layer of the present invention; Figure 7 For the present invention Figure 6 Experimental index graph; Figure 8 This is an experimental diagram of the present invention; Figure 9 For the present invention Figure 8 Experimental index graph; The layers are: 1. Filler layer; 2. Barrier layer; 3. Waterproof layer; 4. Soil improvement layer; 5. Waste rock layer. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0025] In non-ferrous metal mines in arid regions, the ecological problems caused by waste rock accumulation are more complex. Waste rock contains easily oxidized minerals such as sulfides, which, even in arid environments with limited moisture, will still undergo oxidation reactions, producing acidic water. Taking pyrite as an example, the main oxidation process is as follows: 2FeS2+7O2+2H2O=2FeSO4+2H2SO4; 4FeSO4+2H2SO4+O2=2Fe2(SO4)3+2H2O; Fe2(SO4)3+6H2O=2Fe(OH)3+3H2SO4; FeS2+7Fe2(SO4)3+8H2O=15FeSO4+8H2SO4; 2S + 3O₂ + 2H₂O = 2H₂SO₄; This acidic environment accelerates the leaching and migration of heavy metals such as Cu, Fe, Cd, Zn, and Pb, which not only pollutes the soil and groundwater but also leads to serious ecological degradation problems in waste rock dumps, such as extreme soil acidification, heavy metal enrichment, nutrient deficiency, vegetation death, and soil erosion.

[0026] As described in the background section, current remediation technologies for waste rock acidification and heavy metal pollution have significant limitations: conventional measures such as covering with a single material or mixing modified materials with alkaline substances can partially alleviate acidity or supplement nutrients, but cannot simultaneously achieve heavy metal control and vegetation restoration.

[0027] To address the acid generation problem from copper and iron sulfide waste rock in arid non-ferrous metal mines, such as... Figure 1 As shown, the present invention provides a surface covering layer for non-ferrous metal mine waste rock sites in arid areas. The covering layer includes a filler layer 1, a barrier layer 2, a waterproof layer 3, and a soil improvement layer 4, which are laid sequentially from bottom to top on the surface of the non-ferrous metal mine waste rock site in arid areas.

[0028] Optionally, the filler layer 1 is obtained by uniformly mixing matured sludge and rice husk biochar at a mass ratio of 6-8:4-2, and the thickness of the filler layer is 10cm-15cm. The barrier layer 2 is beet lime, with a thickness of 5cm-10mm. The waterproof layer 3 is a waterproof and breathable membrane made of non-woven fabric + polyethylene / polypropylene + non-woven fabric, with a thickness of 5cm-10mm. The improved soil layer 4 is the original soil around the waste rock dump, mixed with 5%-10% matured sludge and 2.5%-5% rice husk biochar by mass, with a thickness of ≥20cm. Below the waterproof layer 3, a mixed layer of gravel and fine sand is laid, with a thickness of 1cm-2cm, and above it, a layer of fine sand is laid, with a thickness of 3cm-5mm.

[0029] The materials used in the covering layer of this invention include sludge, rice husk biochar, beet lime, waterproof and breathable membrane, gravel, and fine sand. Resource utilization of solid waste is an important direction for mine waste rock management, not only reducing waste volume but also promoting circular economy development through the concept of "treating waste with waste." In mine environmental management, sludge, rice husk biochar, and beet lime are chosen to reduce waste rock porosity, effectively neutralize acidity, adsorb heavy metals, enhance soil structure, and promote plant growth. Sludge can improve acidic conditions using its alkaline substances and organic components. The nitrogen and phosphorus organic matter in the sludge can act as effective adsorbents for anions and cations, while also integrating or complexing some heavy metal ions to alleviate their toxicity. Rice husk biochar, based on its porous structure and organic carbon source, possesses the characteristics of adsorbing heavy metals, improving soil aeration and water retention capacity, and can also provide a new outlet for biochar, a byproduct of biomass power plants. Beet lime is rich in calcium carbonate and calcium hydroxide, as well as a small amount of organic matter. On the one hand, it can neutralize acidic water, and on the other hand, the organic matter can reconstruct the soil environment and promote soil fertility.

[0030] The present invention also provides a method for constructing a surface covering layer for non-ferrous metal mine waste rock sites in arid areas. The method uses the surface covering layer for non-ferrous metal mine waste rock sites in arid areas as described in the present invention, which includes laying a filler layer 1, a barrier layer 2, a waterproof layer 3, and a soil improvement layer 4 sequentially from bottom to top on the surface of the waste rock site.

[0031] The invention comprises several layers: a filler layer 1 reduces porosity in the waste rock, inhibits its oxidation and acid production, and passivates heavy metals; a barrier layer 2 neutralizes the acidic water generated by the waste rock flowing from bottom to top; a waterproof layer 3 prevents water infiltration from top to bottom, avoiding water entry into the barrier layer and into the waste rock layer, while simultaneously preventing the acidic water and heavy metals carried by the waste rock from entering the improved soil layer from bottom to top; and an improved soil layer 4 improves the aggregate structure of the original soil around the waste rock site, enhancing its fertility and water retention capacity, creating favorable conditions for vegetation growth. This invention targets waste rock from non-ferrous metal mines, effectively reducing and preventing its reaction with water and its contact with oxygen, thereby inhibiting the acid production process at its source. The filler layer and barrier layer further control the acidic water generated by the waste rock at the end, and inhibit the leaching and migration of heavy metals. This multi-layer covering process can create a safe and favorable soil environment for the ecological restoration of non-ferrous metal mine waste rock sites in arid areas, and ensure the normal growth of vegetation and the long-term revegetation of waste rock sites.

[0032] Example 1: To verify the effectiveness of the surface cover layer for non-ferrous metal mine waste rock sites in arid areas, this embodiment conducted an immersion experiment on the filler layer: like Figure 2 As shown, 100g of waste rock was filled into a 250ml beaker to simulate a waste rock site. To determine the effect of the filler layer on inhibiting acid production from the waste rock, different addition ratios of matured sludge and rice husk biochar were set: A1 (2:8), A2 (4:6), A3 (5:5), A4 (6:4), and A5 (8:2). The filler layer was laid on the waste rock and compacted. The matured sludge and rice husk biochar were added at a ratio of 10% of the mass of the waste rock. The weight compensation method was used to keep the filler layer constantly submerged in water. The soaking solution was extracted into centrifuge tubes every three days for testing.

[0033] like Figure 3 As shown in the experimental results of measuring pH and EC in the soaking solution, it was found that as time increased, the waste rock continuously oxidized, producing acid and releasing soluble salts, leading to a gradual decrease in pH and a continuous increase in EC in each group. However, the inhibition effect of group A4 (6:4) was significantly better than that of the other groups. Initially, the pH of each group was close to neutral (7.29~7.73). After 12 days, the pH of group A4 increased by 24% compared to group A1 and by 25% compared to group A2. This indicates that the alkaline substances of the matured sludge in the 6:4 ratio and the adsorption functional groups of rice husk biochar form a synergistic buffer system, continuously neutralizing the H⁺ produced by the oxidation of waste rock.

[0034] The EC content in group A4 was 21% lower than that in group A1 after 12 days, and lower than that in group A2 (7.31±1.09). The 24% reduction indicates that this formulation utilizes the porous structure of rice husk biochar for adsorption. , , , , The presence of heavy metal ions, combined with the alkaline neutralization effect of matured sludge, effectively inhibits the leaching of soluble salts.

[0035] Example 2: To verify the effectiveness of the barrier layer on the surface cover of non-ferrous metal mine waste rock sites in arid areas, this embodiment conducted a barrier layer infiltration experiment: like Figure 4 As shown, 100g of waste rock was filled into a 250ml beaker to simulate a waste rock layer. To determine the inhibitory effect of the barrier layer on the acid production of waste rock, different addition ratios of matured sludge and rice husk biochar were set: A1 (2:8), A2 (4:6), A3 (5:5), A4 (6:4), and A5 (8:2), and compaction was performed. The matured sludge and rice husk biochar were added at a ratio of 10% of the mass of waste rock. A 5-10mm layer of beet lime was laid on top of the packing layer as a barrier layer. The weight compensation method was used to keep the packing layer constantly submerged in water. The leachate was collected in centrifuge tubes every three days for testing.

[0036] like Figure 5 As shown in the figure, the experimental results of measuring pH and EC in the leachate indicate that as time increases, the waste rock continuously oxidizes, producing acid and releasing soluble salts, leading to a gradual decrease in EC, while the pH continuously increases due to the effect of beet lime in the barrier layer. (See attached figure.) Figure 3 It can be seen that the pH of the experimental groups increased by 25.6% to 131% after 12 days. Group A1 increased by 153.2% compared to Example 1; Group A2 increased by 91.6% compared to Example 1 after 12 days; Group A3 increased by 68.8% compared to Example 1; Group A4 increased by 25.8% compared to Example 1; and Group A5 increased by 116.6% compared to Example 1. This comparison fully demonstrates that the addition of the beet lime barrier layer effectively neutralized the acidity, prevented the pH decrease trend in Example 1, improved the acid-base buffering capacity of the system, and created a more favorable acid-base environment for ecological restoration.

[0037] contrast Figure 3 It can be seen that the EC values ​​of the experimental groups decreased by 37.8% to 52.9% at 12 days. Group A1 decreased by 52.9% compared to Example 1; Group A2 decreased by 50.1%; Group A3 decreased by 39.5%; Group A4 decreased by 37.8%; and Group A5 decreased by 44.3%. This comparison shows that the EC values ​​of all experimental groups decreased significantly after the addition of the barrier layer. This indicates that the beet lime barrier layer not only neutralizes acidity but also promotes the precipitation of soluble salts in the solution, reducing ion dissolution. This contrasts sharply with the increasing EC trend in Example 1, effectively reducing conductivity and minimizing salt pollution to the surrounding environment.

[0038] The selection of groups A4 (6:4) and A5 (8:2) was primarily based on pH and EC data. Regarding pH, both groups demonstrated superior acid-base buffering and regulation capabilities compared to the other groups. In terms of EC, both groups showed significant inhibition of ion dissolution and enhanced stability.

[0039] Example 3: To verify the effectiveness of surface cover layers in blocking non-ferrous metal mine waste rock sites in arid regions, this embodiment conducted a planting experiment on the improved soil layer: like Figure 6 The surface microstructure and elemental distribution of the rice husk biochar were characterized and analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). In the planting experiment, *Cephalotaxus fortunei* seeds were selected, ensuring they were similar in size and plumpness. The selected seeds were soaked in a 1% NaClO solution for 5 minutes, then rinsed repeatedly with distilled water 2-3 times, and finally blotted dry with filter paper. 100 seeds were sown in each pot during planting. A waterproof layer was constructed at the bottom of a PVC column, topped with 1.6 kg of soil and matured sludge (10%), with a soil layer of 20 cm, containing 10% activated sludge. On the first day, watering was carried out at 60% of the previously determined field water holding capacity (54.41%). The total weight was measured daily thereafter, and the effect of different rice husk biochar addition ratios (0%, 2.5%, 5%) on soil water retention capacity was determined based on the weight loss. Soil moisture content decreased with different biochar addition ratios, but the addition of biochar slowed the decrease in moisture content. Overall, adding biochar has a positive effect on improving soil water retention capacity, and the effect is relatively better at a 5% addition ratio.

[0040] Example 4: To verify the effectiveness of surface cover layers for non-ferrous metal mine waste rock sites in arid regions, this embodiment conducted an experiment to construct a multi-layer cover combination process: 1 kg of waste rock was added for compaction to reduce oxygen contact with the waste rock, thus reducing oxidation and acid production. Matured sludge and rice husk biochar were added at a ratio of 8:2 (10%), and a 5 mm thick layer of beet lime was added on top to increase the pH and neutralize the acid produced by the waste rock layer. A waterproof layer consisting of gravel, fine sand, and a waterproof and breathable membrane was then laid on top to prevent moisture from contacting the waste rock. A 1.6 kg improved soil layer, a mixture of soil and matured sludge (10%), was placed on top in the 0-20 cm layer. The effect of this multi-layered covering process on preventing acid production from waste rock was studied by setting addition ratios of 0%, 2.5%, and 5% rice husk biochar, as well as experimental groups with and without a waterproof layer (T1, T3, T5) and a control group (T2, T4, T6). Soil solution samplers were inserted at a 45° angle into the soil layer.

[0041] An ecological restoration process was constructed using PVC pipes. On the first day, the soil was irrigated at 60% of the previously determined field capacity (54.41%). Subsequently, the moisture content was kept constant daily using a weight compensation method. A negative pressure environment was created by inserting a soil solution sampler obliquely into the soil layer and using a syringe connected to it to extract soil solution for measuring various indicators. Samples were taken every fifteen days.

[0042] like Figure 9 As shown in the comparison, regardless of whether a waterproof layer was present, the soil pH of each experimental group was >7, and no significant acidification was observed. This indicates that the barrier layer had a good neutralizing effect on the generated acidic water. The EC values ​​of the leachate measured in the experiment showed that after adding the waterproof layer, the EC values ​​of each experimental group were significantly higher than those without a waterproof layer. Specifically, the increase was 104.5% at 15 days, 93.8% at 30 days, 85.9% at 45 days, 101.1% at 60 days, and 75.4% at 75 days. Specifically, the EC values ​​of group T1 were 104.5% higher than those of group T2 (without a waterproof layer) at 15 days, group T3 was 93.8% higher than those of group T4 at 30 days, and group T5 was 101.1% higher than those of group T6 at 60 days. This comparison shows that the EC values ​​of the experimental groups with waterproof layers were significantly higher than those without, indicating that the waterproof layer can effectively block water infiltration and contact with waste rock, prevent the oxidation of waste rock to produce acid, and prevent acidic water from entering the soil layer.

[0043] The above description is merely a preferred embodiment of this practice and is not intended to limit the scope of this practice. Various modifications and variations can be made to this practice by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this practice should be included within the protection scope of this practice.

Claims

1. A surface covering layer for non-ferrous metal mine waste rock disposal sites in arid regions, characterized in that, This includes a filler layer, a barrier layer, a waterproof layer, and a soil amendment layer laid sequentially from bottom to top on the surface of waste rock dumps in non-ferrous metal mines in arid regions. The filler layer comprises matured sludge and rice husk biochar mixed in a preset mass ratio; the barrier layer is beet lime; the waterproof layer comprises a waterproof and breathable membrane made of non-woven fabric, polyethylene / polypropylene, and non-woven fabric; and the improved soil layer is the original soil surrounding the waste rock dump mixed with matured sludge and rice husk biochar.

2. The surface covering layer for blocking waste rock from non-ferrous metal mines in arid areas as described in claim 1, characterized in that, The mass ratio of matured sludge to rice husk biochar in the packing layer is 6~8:4~2.

3. The surface covering layer for blocking waste rock from non-ferrous metal mines in arid areas as described in claim 2, characterized in that, The thickness of the filler layer is 10cm to 15cm.

4. The surface covering layer for blocking waste rock from non-ferrous metal mines in arid areas as described in claim 1, characterized in that, The thickness of the barrier layer is 5cm to 10mm.

5. The surface covering layer for blocking waste rock from non-ferrous metal mines in arid areas as described in claim 1, characterized in that, The thickness of the waterproof layer is 5cm to 10mm.

6. The surface covering layer for blocking waste rock from non-ferrous metal mines in arid areas as described in claim 5, characterized in that, The waterproof layer is a double-layer non-woven spunbond polyethylene / polypropylene waterproof and breathable membrane with a thickness of 0.5mm to 1mm.

7. The surface covering layer for blocking waste rock from non-ferrous metal mines in arid areas as described in claim 6, characterized in that, The waterproof layer is covered with a 1cm to 2cm thick layer of gravel and fine sand on one side near the barrier layer; the other side is covered with a 3cm to 5mm thick layer of fine sand.

8. The surface covering layer for blocking waste rock from non-ferrous metal mines in arid areas as described in claim 1, characterized in that, The improved soil layer consists of the original soil surrounding the waste rock dump, mixed with 5% to 10% matured sludge and 2.5% to 5% rice husk biochar by mass.

9. The surface covering layer for blocking waste rock from non-ferrous metal mines in arid areas as described in claim 6, characterized in that, The thickness of the improved soil layer shall not be less than 20 cm.

10. A method for constructing a surface cover layer to block waste rock from non-ferrous metal mines in arid regions, characterized in that, The surface cover layer for blocking non-ferrous metal mine waste rock sites in arid areas, as described in any one of claims 1-9, includes: laying a filler layer, a barrier layer, a waterproof layer, and a soil improvement layer sequentially from bottom to top on the surface of the waste rock site.

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