Method for backfilling and repairing mine by adopting engineering waste muck and slurry

Abstract

The invention relates to the technical field of abandoned mine ecological restoration, in particular to a method for restoring a mine through engineering abandoned muck and slurry backfilling. The method comprises the following steps: cleaning a mine pit, leveling a terrain, backfilling engineering waste slag, and laying a tailing transition layer to form a graded tailing layer; impurities in the engineering waste muck are screened out, the engineering waste muck is laid on the grading tailing layer, and a compacted muck layer is obtained through compaction; the method comprises the following steps: flocculating and dewatering engineering waste slurry to obtain cement control slurry, adding an exogenous fertilizer for improvement, and then mixing with field waste slag in proportion and backfilling to form a sludge vegetation layer; according to the method, the waste mine is used as a raw material, the residue covering compost layer and the vegetation surface soil layer with certain thickness are sequentially covered on the waste mine, the synergistic ecological effect of soil reconstruction and restoration treatment of the waste mine is formed, green cyclic utilization of waste resources is achieved, the treatment cost of the waste mine is reduced, and the high efficiency and sustainability of mine ecological restoration are improved.

Description

Technical Field

[0001] This invention relates to the field of ecological restoration technology for abandoned mines, and in particular to a method for restoring mines by backfilling with engineering waste slag and mud. Background Technology

[0002] With the acceleration of urbanization and the improvement of industrialization, construction waste such as slag and mud generated by engineering construction activities is increasing. How to efficiently treat and rationally utilize construction slag has become a serious environmental and ecological problem.

[0003] In actual engineering practice, engineering mud and some excavated soil, such as shield tunneling excavated soil, often have problems such as high water content, low strength, slow consolidation and poor bearing capacity. As a result, the existing treatment technologies are often time-consuming, labor-intensive, unstable and expensive. In particular, for dewatered mud, it still has a high water content after dewatering, which makes it difficult to treat.

[0004] The rapid development of the mining industry has led to increasingly serious ecological and environmental problems in mining areas, such as soil erosion, land subsidence, and vegetation destruction. Currently, when engineering waste soil and slurry are disposed of in mines, they are solidified by mixing them with a solidifying agent. However, the slurry has a high water content, and the soil has a clumpy structure, making it difficult, inefficient, and costly to mix evenly with the solidifying agent. While using a layered, pre-embedded vacuum filter network for high-power vacuum filtration to reconstruct the foundation of the mine pit is an option, its construction process is extremely complex and difficult. It is poorly suited for complex mine terrain, cannot be applied rapidly on a large scale, and has a long construction cycle.

[0005] The current ecological restoration of mines faces a severe situation with numerous accumulated problems and heavy restoration tasks. Existing conventional restoration and treatment methods suffer from severe ecological degradation, high restoration costs, unsustainable treatment effects, and poor treatment effects on heavy metals in mine-contaminated soil. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for mine restoration using engineering waste soil and mud backfilling.

[0007] A method for remediating mines using engineering waste slag and mud backfilling includes the following steps: S1. Clean up debris at the bottom of the mine pit, level the terrain at the bottom of the pit, backfill with engineering waste slag, mechanically compact it, and lay a tailings transition layer on top to form a graded tailings layer. S2. Screen out impurities from the engineering waste soil and adjust the moisture content to 18-22%; lay it on the graded tailings layer and compact it to obtain a compacted soil layer. S3. Add flocculant to the engineering mud for flocculation treatment and remove water to obtain controlled mud slurry; S4. Mix the fermentation bacteria and mix them into the sawdust to form mixed sawdust; S5. Mix the mixed sawdust with cement slurry, silica aerogel, slag and water-retaining agent evenly to obtain mud substrate, and then lay the mud substrate on the compacted slag layer to form mud vegetation substrate layer. S6. Crush the straw, add livestock and poultry manure, peat soil and silica aerogel, mix evenly, spread it on the mud and slag vegetation substrate layer, and then inoculate earthworms to form a slag compost layer. S7. Use the original topsoil stripped from the mine to backfill and lay it on the surface of the slag compost layer to form a vegetation topsoil.

[0008] Preferably, in S1, the particle size of the engineering waste slag is 2-50mm; the porosity of the tailings transition layer is 25-30%, and the slag is made from waste stone or slag from the mine site, or at least one of them; The ratio of the backfill thickness of the engineering waste slag to the thickness of the tailings transition layer is 20-50:5-10; The compaction degree of mechanical rolling is ≥90%.

[0009] Preferably, in step S2, impurities with a particle size >10cm in the engineering waste soil are screened out; the compaction degree of the soil layer is ≥93%.

[0010] Preferably, in S2, Φ50mm vent pipes are buried at intervals of 1.5-2.5m in the compacted slag layer, wherein the longitudinal slope of the vent pipe is 2.5-3.5%, and the vent pipe is wrapped with geotextile.

[0011] Preferably, in S3, the flocculant is polyacrylamide; the mass of the engineering mud is... a The water content of the engineering mud is b The mass of the flocculant is c ,but a × b : c ≥80:0.5-1, where b ≥80%; the water content of the controlled cement slurry is 40%-50%.

[0012] Preferably, in S4, the fermentation bacteria are composting agents, and the mass ratio of fermentation bacteria to sawdust is 1-3:800.

[0013] Preferably, in S5, the volume ratio of mud to slag is 1:3-5:1, and the mass ratio of the total weight of slag and mud to the mass of silica aerogel, water-retaining agent and mixed sawdust is 600-900:1-5:0-2:20-80.

[0014] Preferably, in S6, the mass ratio of straw, livestock manure, peat moss, and silica aerogel is 30-60:40-60:20-40:0.1-0.5; the earthworm density is 30-50 earthworms / m³. 2 .

[0015] Preferably, in S7, the thickness ratio of the graded tailings layer, the compacted slag layer, the mud and slag vegetation substrate layer, the slag composting layer, and the vegetation topsoil is 10:20-30:5-15:1-2:2-4.

[0016] Preferably, the specific surface area of ​​the silica aerogel is 800-1200 m². 2 / g.

[0017] Beneficial effects

[0018] This invention fully utilizes existing mine tailings and other resources, while also considering the high water content of engineering waste mud. It directly modifies the mud and mixes it with mine tailings to prepare a vegetation substrate. On-site mixing is convenient and efficient (or the mud's fluidity can be used for pumping and interlayer backfilling to form a mud-slag vegetation substrate layer, making construction even simpler and more efficient). In this method, the tailings aggregate acts as the substrate filling framework, providing structural strength; while the mud effectively binds the substrate, balancing water and fertilizer retention for plant growth with the bearing capacity requirements of the foundation. This invention is low-cost, environmentally friendly, simple in process, and economically efficient.

[0019] The graded tailings layer of this invention mainly utilizes the waste tailings stone material from the mine as the bottom layer of the mine pit for backfilling; the compacted slag layer mainly uses engineering slag and other waste soil for resource utilization, and after backfilling and compaction, it serves as the base layer of the mine pit filling site to meet the bearing capacity requirements for construction land and greening land after mine restoration; the mud and slag vegetation substrate layer, the slag composting layer, and the vegetation topsoil layer mainly serve as the revegetation layer for ecological restoration of the mine area. The mud and slag vegetation substrate layer is mainly improved by adding an appropriate amount of exogenous fertilizer to the engineering mud, and then mixed with tailings aggregate for backfilling to form a vegetation substrate with certain mechanical strength, porosity, and fertility, providing nutrients and support for the growth of surface vegetation. The slag composting layer can be set according to the specific requirements of mine restoration to further improve the organic matter content and fertility level of the surface soil. As for the vegetation topsoil layer, it generally uses the original stripped topsoil from the mine. If there is no stripped topsoil or the topsoil stock is insufficient, mud and slag vegetation substrate can be used as a substitute.

[0020] This invention introduces silica aerogel into engineering mud, which, on the one hand, utilizes its porous structure and superhydrophobicity to significantly improve the water retention and air permeability of the mud, and on the other hand, promotes the colonization and activity of microbial agents, accelerating the decomposition of organic matter and the release of nutrients. Subsequently, the silica aerogel is combined with straw, livestock and poultry manure, and peat soil to provide an ideal microenvironment for earthworm activity, significantly improving earthworm biomass and activity efficiency, and effectively accelerating the composting process of organic compost.

[0021] The application of silica aerogel in mud in this invention provides suitable moisture and oxygen conditions for subsequent earthworm activity, while the earthworm activity further improves the dispersibility and stability of the aerogel, forming a virtuous cycle. This synergistic effect significantly improves the water and fertilizer retention performance of the vegetation substrate layer, while enhancing the bearing capacity of the foundation, providing a stable and nutrient-rich substrate for vegetation growth. Simultaneously, the introduction of silica aerogel effectively reduces the migration of heavy metals. Through its surface adsorption and fixation, it reduces the harm of heavy metals to plants and the environment, achieving high efficiency and sustainability in mine ecological restoration. This invention processes dry sawdust to convert it into an external fertilizer source for subsequent plant production. During the natural fermentation process after the sawdust is landfilled, it provides nutrients to the plants. At the same time, the combination of sawdust and aerogel can further lock in the moisture in the engineering waste sludge, improve the morphology of the engineering waste sludge, reduce its fluidity, improve the stability and strength of the backfill soil layer, and facilitate the growth of the replanted plants. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of each layer in the method of the present invention.

[0023] Figure 2 The graph shows the change in the growth height of tall fescue after backfilling and remediating abandoned mines using the methods of Example 2 and Comparative Examples 1-2.

[0024] Figure 3 This is a comparison chart showing the rate of reduction in heavy metals after backfilling and remediating abandoned mines using the methods of Example 2 and Comparative Examples 1-2. Figure 4 This is a sample image of engineering waste soil and slag with a size of 2-50mm used in this invention; Figure 5 This is a sample image of engineering waste stone slag with a size of 20-50mm used in this invention; Figure 6 This is a sample image of engineering waste stone chips with a size of 2-10mm used in this invention; Figure 7 This is a sample image of the cement slurry with a water content of 40% used in this invention; Figure 8This is a schematic diagram of the field planting experiment model structure in this invention; Figure 9 This is a comparison chart showing the growth of tall fescue planted in experimental group A after 14 days in this invention; Figure 10 This is a comparison chart showing the growth of tall fescue planted in experimental group A after 21 days in this invention. Detailed Implementation

[0025] The present invention will be further explained below with reference to specific embodiments.

[0026] Example 1

[0027] A method for remediating mines using engineering waste slag and mud backfilling includes the following steps: S1. Clean up debris at the bottom of the mine pit, level the terrain at the bottom of the pit, and backfill with engineering waste slag. The slag can be stone chips or slag soil or at least one of these. The particle size of the engineering waste slag is 2-50mm. Mechanically compact it to a compaction degree of 90%. Lay a tailings transition layer (porosity 25%) on top to form a graded tailings layer. The ratio of the backfill thickness of the engineering waste slag to the thickness of the tailings transition layer is 4:1. The tailings can be any one of small-particle-size tailings, soil, or graded tailings from the mine site. S2. Screen out impurities with a particle size >10cm from the engineering waste soil, adjust the moisture content to 18% (spray water if too dry, add tailings aggregate if too wet); lay it on the graded tailings layer, and compact it with vibration to a compaction degree of 93% to obtain a compacted soil layer. Meanwhile, Φ50mm vent pipes are buried at 1.5m intervals in the compacted slag layer, with a longitudinal slope of 2.5% and geotextile wrapped around the vent pipes. S3. Add flocculant to the engineering mud for flocculation treatment, remove water to obtain cement slurry with a water content of 45%; S4. Adjust the sawdust moisture content to 60-65%, and apply it at a rate of approximately 0.5 ml per 500 kg of dry sawdust. 3 Mix 1 kg of fermented bacteria evenly; then dilute 2 kg of urea with water to make urea solution and sprinkle it on the inoculated sawdust to form mixed sawdust.

[0028] S5. Mix cement slurry and slag at a volume ratio of 2:1 to obtain a mud-slag composition. Add silica aerogel, water-retaining agent and mixed sawdust and mix evenly to obtain a mud-slag substrate. Then lay the mud-slag substrate on the compacted slag layer to form a mud-slag vegetation substrate layer. The mass ratio of the mud composition, silica aerogel, water-retaining agent, and mixed sawdust is 800:2:1:40.

[0029] S6. Crush the corn stalks, add chicken manure, peat moss, and silica aerogel, mix well, and spread on the compacted slag layer. Inoculate with earthworms (earthworm density: 30 worms / m²). 2 ) to form a slag-covered compost layer; The mass ratio of straw, livestock and poultry manure, peat moss, and silica aerogel was 30:40:20:0.1, and the specific surface area of ​​the silica aerogel was 1000±200 m². 2 / g; S7. Reuse the original topsoil stripped from the mine and lay it on the surface of the slag compost layer to obtain the vegetation topsoil. The thickness ratio of the above-mentioned graded tailings layer, compacted slag layer, mud and slag vegetation substrate layer, slag composting layer, and vegetation topsoil is 10:20:5:1:2.

[0030] Example 2

[0031] A method for remediating mines using engineering waste slag and mud backfilling includes the following steps: S1. Clean up debris at the bottom of the mine pit, level the terrain at the bottom of the pit, and backfill with engineering waste slag. The slag can be stone chips or slag soil or at least one of them. The particle size of the engineering waste slag is 2-50mm. Mechanically compact it with a compaction degree of 92%. Lay a tailings transition layer (porosity of 26%) on top to form a graded tailings layer. The ratio of the backfill thickness of the engineering waste slag to the thickness of the tailings transition layer is 5:1. S2. Screen out impurities with a particle size >10cm from the engineering waste soil, adjust the moisture content to 22% (spray water if too dry, add tailings aggregate if too wet); lay it on the graded tailings layer, and compact it with vibration to a compaction degree of 94% to obtain a compacted soil layer. Meanwhile, Φ50mm ventilators are buried at 2.5m intervals in the compacted slag layer, with a longitudinal slope of 3.5% and geotextile wrapped around the ventilators. S3. Add flocculant to the engineering mud for flocculation treatment, remove water to obtain cement slurry with a water content of 45%; S4. Adjust the sawdust moisture content to 60-65%, and apply it at a rate of approximately 0.5 ml per 500 kg of dry sawdust. 3 Mix 1.5 kg of fermented bacteria evenly; then dilute 1.5 kg of urea with water to make urea solution and sprinkle it on the inoculated sawdust to form mixed sawdust. S5. Mix cement slurry and slag at a volume ratio of 3:1 to obtain a mud-slag composition. Add silica aerogel, water-retaining agent and mixed sawdust and mix evenly to obtain a mud-slag substrate. Then lay the mud-slag substrate on the compacted slag layer to form a mud-slag vegetation substrate layer. The mass ratio of the mud composition, silica aerogel, water-retaining agent, and mixed sawdust is 800:1.5:0.5:40. S6. Crush the corn stalks, add chicken manure, peat moss, and silica aerogel, mix well, and spread on the compacted slag layer. Inoculate with earthworms (earthworm density: 50 worms / m²). 2 ) to form a slag-covered compost layer; The mass ratio of straw, livestock and poultry manure, peat soil, and silica aerogel is 36:36:24:0.3. S7. Reuse the original topsoil stripped from the mine and lay it on the surface of the slag compost layer to obtain the vegetation topsoil. The thickness ratio of the above-mentioned graded tailings layer, compacted slag layer, mud and slag vegetation substrate layer, slag composting layer, and vegetation topsoil is 10:30:15:2:4.

[0032] Comparative Example 1: A method for remediating mines using engineering waste slag and mud backfilling includes the following steps: S1. Clean up debris at the bottom of the mine pit, level the terrain at the bottom of the pit, backfill with engineering waste slag, the particle size of the engineering waste stone slag is 2-50mm; mechanically compact, the compaction degree of mechanical compaction is 92%; lay a tailings transition layer (porosity 26%) on the top to form a graded tailings layer, the ratio of the backfill thickness of engineering waste slag to the thickness of the tailings transition layer is 5:1. S2. Screen out impurities with a particle size >10cm from the engineering waste soil, adjust the moisture content to 22% (spray water if too dry, add tailings aggregate if too wet); lay it on the graded tailings layer, and compact it with vibration to a compaction degree of 94% to obtain a compacted soil layer. Meanwhile, Φ50mm ventilators are buried at 2.5m intervals in the compacted slag layer, with a longitudinal slope of 3.5% and geotextile wrapped around the ventilators. S3. Add flocculant to the engineering mud for flocculation treatment, remove water to obtain cement slurry with a water content of 45%; S4. Adjust the sawdust moisture content to 60-65%, and apply it at a rate of approximately 0.5 ml per 500 kg of dry sawdust. 3 Add 1.5 kg of fermented bacteria evenly to the mixture; then dilute 1.5 kg of urea with water to make urea solution and sprinkle it on the inoculated sawdust to form mixed sawdust. S5. Mix cement slurry and slag at a volume ratio of 3:1 to obtain a mud-slag composition. Add activated carbon, water-retaining agent and mixed sawdust and mix evenly to obtain a mud-slag substrate. Then lay the mud-slag substrate on the compacted slag layer to form a mud-slag vegetation substrate layer. The mass ratio of the mud composition, activated carbon, water-retaining agent, and mixed sawdust is 800:1.5:0.5:40. S6. Crush the corn stalks, add chicken manure, peat moss, and activated carbon, mix well, and spread the mixture on the compacted slag layer. Inoculate with earthworms (earthworm density: 50 worms / m²).2 ) to form a slag-covered compost layer; The mass ratio of straw, livestock and poultry manure, peat moss, and activated carbon is 36:36:24:0.3. S7. Reuse the original topsoil stripped from the mine and lay it on the surface of the slag compost layer to obtain the vegetation topsoil. The thickness ratio of the above-mentioned graded tailings layer, compacted slag layer, mud and slag vegetation substrate layer, slag composting layer, and vegetation topsoil is 10:30:15:2:4.

[0033] Comparative Example 2: A method for remediating mines using engineering waste slag and mud backfilling includes the following steps: S1. Clean up debris at the bottom of the pit, level the terrain at the bottom of the pit, and backfill with engineering waste slag. The particle size of the engineering waste slag is 2-50mm. Mechanically compact it to a compaction degree of 92%. Lay a tailings transition layer (porosity 26%) on top to form a graded tailings layer. The ratio of the backfill thickness of the engineering waste slag to the thickness of the tailings transition layer is 5:1. S2. Screen out impurities with a particle size >10cm from the engineering waste soil, adjust the moisture content to 22% (spray water if too dry, add tailings aggregate if too wet); lay it on the graded tailings layer, and compact it with vibration to a compaction degree of 94% to obtain a compacted soil layer. Meanwhile, Φ50mm ventilators are buried at 2.5m intervals in the compacted slag layer, with a longitudinal slope of 3.5% and geotextile wrapped around the ventilators. S3. Add flocculant to the engineering mud for flocculation treatment, remove water to obtain cement slurry with a water content of 45%; S4. Adjust the sawdust moisture content to 60-65%, and apply it at a rate of approximately 0.5 ml per 500 kg of dry sawdust. 3 Mix 1.5 kg of fermented bacteria evenly; then dilute 1.5 kg of urea with water to make urea solution and sprinkle it on the inoculated sawdust to form mixed sawdust. S5. Mix cement slurry and slag at a volume ratio of 3:1 to obtain a mud-slag composition. Add water-retaining agent and mix sawdust evenly to obtain a mud-slag substrate. Then lay the mud-slag substrate on the compacted slag layer to form a mud-slag vegetation substrate layer. The mass ratio of the mud composition, water-retaining agent, and mixed sawdust is 800:0.5:40. S6. Crush the corn stalks, mix them evenly with chicken manure and peat moss, spread the mixture on the compacted slag layer, and inoculate with earthworms (earthworm density of 50 worms / m²). 2 ) to form a slag-covered compost layer; The mass ratio of straw, livestock and poultry manure, and peat soil is 36:36:24. S7. Reuse the original topsoil stripped from the mine and lay it on the surface of the slag compost layer to obtain the vegetation topsoil. The thickness ratio of the above-mentioned graded tailings layer, compacted slag layer, mud and slag vegetation substrate layer, slag composting layer, and vegetation topsoil is 10:30:15:2:4.

[0034] Three abandoned mines were selected and backfilled for remediation according to the methods of Example 2, Comparative Example 1, and Comparative Example 2, respectively. After remediation, each group was planted with tall fescue (seeding rate of 20 g / m²). 2 () as the test subject.

[0035] On days 15, 30, and 45 after sowing, tall fescue samples were taken from each group using the same sampling method, and the growth height of each group of tall fescue was measured.

[0036] like Figure 2 As shown, the tall fescue grew to the highest height after backfilling and remediation of the abandoned mine using the method of Example 2, which was significantly better than the comparative example.

[0037] On the 60th day after tall fescue sowing, soil samples were taken from each group to determine the contents of As, Pb, and Cd, and the reduction rate of As, Pb, and Cd in each group was calculated.

[0038] Reduction rate = (Original heavy metal content - Post-remediation heavy metal content) ÷ Original heavy metal content × 100%.

[0039] like Figure 3 As shown, the method in Example 2 resulted in the highest reduction rate of heavy metals after backfilling and remediation of the abandoned mine. Specifically, heavy metal As decreased by 60%, and heavy metal P... b It decreased by 36%, heavy metal C d It decreased by 70%, significantly better than Comparative Example 1 and Comparative Example 2.

[0040] Example 3

[0041] Control group A: Using Example 1 as a baseline, the water content of the mud was adjusted to 40%, such as... Figure 7 As shown, in step S5, the mud and slag are mixed at a ratio of 2:1, and mixed sawdust is added at a mass ratio of 5%; wherein, the slag includes, for example, Figure 4 The waste soil and debris shown at the construction site, such as Figure 5 The 20-50mm waste stone chips shown are from the construction site. Figure 6 The waste stone chips from the construction site, ranging from 2-10mm, are shown. Test group A is divided according to the following proportions, as shown in Table 1. Table 1 shows the composition of control group A:

[0042] On-site planting experiments were conducted using template partitions. Each template partition measured 1m x 1m x 0.7m, and the substrate molding height was approximately 0.5-0.6m. Figure 8 As shown; in, Figure 9 The growth of grass seeds planted in experimental groups 1-1, 1-2, 1-3 and experimental groups 2-1, 2-2 after 14 days; Figure 10 The growth of grass seeds planted in experimental groups 1-1, 1-2, 1-3 and experimental groups 2-1, 2-2 after 28 days; It is evident that at 14 days, the initial germination rate of grass seeds from the modified and mixed slurry and slag substrate was significantly better than that of the pure slurry and pure soil / slag groups. At 28 days, the plant height and vegetation coverage of the grass seeds from the modified and mixed slurry and slag substrate were also significantly better than those of the pure slurry and pure soil / slag groups. This demonstrates that by simply modifying and mixing slurry and slag, a vegetation layer with good pore structure and water and fertilizer retention properties can be formed, resulting in significant economic and social benefits.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for remediating mines by backfilling with engineering waste slag and mud, characterized in that, Includes the following steps: S1. Clean up debris at the bottom of the mine pit, level the terrain at the bottom of the pit, backfill with engineering waste slag, mechanically compact it, and lay a tailings transition layer on top to form a graded tailings layer. S2. Screen out impurities from the engineering waste soil and adjust the moisture content to 18-22%; lay it on the graded tailings layer and compact it to obtain a compacted soil layer. S3. Add flocculant to the engineering mud for flocculation treatment and remove water to obtain controlled mud slurry; S4. Mix the fermentation bacteria into the sawdust to form mixed sawdust; S5. Mix the mixed sawdust with cement slurry, silica aerogel, slag and water-retaining agent evenly to obtain mud substrate, and then lay the mud substrate on the compacted slag layer to form a mud vegetation substrate layer. S6. Crush the straw, add livestock and poultry manure, peat soil and silica aerogel, mix evenly, spread it on the mud and slag vegetation substrate layer, and then inoculate earthworms to form a slag compost layer. S7. The original topsoil from the mine is used for backfilling and laying to the surface of the slag compost layer to form a vegetation topsoil.

2. The method according to claim 1, characterized in that, In S1, the particle size of the engineering waste slag is 2-50mm; the porosity of the tailings transition layer is 25-30%, and the slag is made from waste stone or slag from the mine site or at least one of them; The ratio of the backfill thickness of the engineering waste slag to the thickness of the tailings transition layer is 20-50:5-10; The compaction degree of mechanical rolling is ≥90%.

3. The method according to claim 1, characterized in that, In S2, impurities with a particle size >10cm in the engineering waste soil are screened out; the compaction degree of the soil layer is ≥93%.

4. The method according to claim 1, characterized in that, In S2, Φ50mm vent pipes are buried at intervals of 1.5-2.5m in the compacted slag layer, with a longitudinal slope of 2.5-3.5% for the vent pipes and geotextile wrapped around them.

5. The method according to claim 1, characterized in that, In S3, the flocculant is polyacrylamide; the mass of the engineering mud is... a The water content of the engineering mud is b The mass of the flocculant is c ,but a × b : c ≥80:0.5-1, where b ≥80%; the water content of the controlled cement slurry is 40%-50%.

6. The method according to claim 1, characterized in that, In S4, the fermentation bacteria are composting agents, and the mass ratio of fermentation bacteria to sawdust is 1-3:

800.

7. The method according to claim 1, characterized in that, In S5, the volume ratio of mud to slag is 1:3-5:1, and the mass ratio of the total weight of slag and mud to the mass of silica aerogel, water-retaining agent and mixed sawdust is 600-900:1-5:0-2:20-80.

8. The method according to claim 1, characterized in that, In S6, the mass ratio of straw, livestock and poultry manure, peat moss, and silica aerogel is 30-60:40-60:20-40:0.1-0.5; the earthworm density is 30-50 earthworms / m³. 2 .

9. The method according to claim 1, characterized in that, In S7, the thickness ratio of the graded tailings layer, compacted slag layer, mud and slag vegetation substrate layer, slag composting layer, and vegetation topsoil is 10:20-30:5-15:1-2:2-4.

10. The method according to claim 1, characterized in that, The specific surface area of ​​silica aerogel is 800-1200 m². 2 / g.

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