A method for shield tunneling desiccation soil and coal gangue coordinated ecological backfilling

Abstract

The present invention provides a method for coordinated ecological backfilling of shield-dried soil and coal gangue. First, initial shield-dried soil, initial coal gangue, modified coal gangue, and modified shield-dried soil are obtained respectively to meet backfill requirements. Then, a bottom anti-seepage layer is laid from bottom to top in the area to be backfilled, and N+1 layers of coal gangue backfill layers and N layers of shield-dried soil backfill layers are laid alternately. Each layer of shield-dried soil backfill layer is located between two adjacent layers of coal gangue backfill layers. An ecological anti-seepage layer is laid on top of the N+1 layer of coal gangue backfill layer, thereby obtaining a repaired backfill area. Finally, pits are excavated and shrubs are planted every 0.8-1.2 m in the repaired backfill area. The present invention uses the shield dried soil backfill layer as the interlayer covering soil of the coal gangue backfill layer to play the role of oxygen isolation and flame retardancy; the shield dried soil is modified by coal gangue, coal gasification slag and agricultural, forestry and animal husbandry waste to obtain regenerated shield dried soil, thereby improving the nutritional content and water holding capacity of the repair backfill area.

Description

Technical Field

[0001] The invention belongs to the technical field of ecological restoration and backfilling, and particularly relates to a method for coordinated ecological backfilling of shield-dried soil and coal gangue. Background Art

[0002] Shield soil refers to the waste soil and rock fragments produced by shield machines when excavating underground space. It is usually disposed of by open-air stacking or landfill. However, the surfactants contained in shield soil are difficult to dry, have high fluidity, and large amounts of accumulation are prone to landslides and other safety hazards. Landfilling can cause surfactants to contaminate water bodies. Therefore, there is an urgent need to provide a method for harmlessly treating shield soil.

[0003] my country relies on coal as its primary energy source, producing large quantities of gangue. This accumulation of gangue can lead to a certain degree of resource waste. Gangue is typically utilized through ground backfilling. However, the primary method involves layering gangue and loess, followed by alternating layers of gangue and loess after compaction. Once the specified filling capacity is reached, the backfill site is covered with loess, followed by ecological restoration. Throughout the backfill and restoration process, loess is used as both the isolation material and for vegetation growth in ecological restoration, and the amount used is enormous. However, loess is in short supply in most mining areas, and removing soil from the mountain by cutting into the ground can cause secondary damage.

[0004] Therefore, how to provide a method for coordinated ecological backfilling of shield-dried soil and coal gangue, replace loess with shield-dried soil, and combine it with coal gangue to construct a repair backfill area through the synergistic effect of shield-dried soil and coal gangue, is a technical problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for shield-turbine dried soil and coal gangue coordinated ecological backfilling to solve at least one of the above technical problems.

[0006] To achieve the above-mentioned purpose, the first aspect of the present invention provides a method for the coordinated ecological backfilling of shield drying soil and coal gangue, the method comprising the following steps: obtaining initial shield drying soil, wherein the leaching concentration of the surfactant in the initial shield drying soil is less than 0.3 mg / L; obtaining initial coal gangue, wherein the initial coal gangue is composed of crushed coal gangue with a particle size of 3-5 mm and a mass proportion of 40%, crushed coal gangue with a particle size of 1-3 mm and a mass proportion of 30%, and crushed coal gangue with a particle size of less than 1 mm and a mass proportion of 30%; adding the initial coal gangue into a pelletizing machine, and adding the initial shield drying soil, mixing, and obtaining modified coal gangue; dehydrating the initial shield drying soil by fly ash and carbide slag to obtain modified shield drying gangue. Soil; first lay a bottom anti-seepage layer in the area to be backfilled, the bottom anti-seepage layer is formed by rolling the modified shield-dried soil, and the compaction degree is greater than 90%; on the top of the bottom anti-seepage layer, N+1 layers of coal gangue backfill layer and N layers of shield-dried soil backfill layer are laid in sequence, each layer of shield-dried soil backfill layer is located between two adjacent layers of coal gangue backfill layer, the coal gangue backfill layer is formed by rolling the modified coal gangue, and the compaction degree is 70-80%; the shield-dried soil backfill layer is formed by rolling the modified shield-dried soil, and the compaction degree is 80-90%; lay an ecological anti-seepage layer on the N+1 layer of coal gangue backfill layer to obtain a repaired backfill area; in the repaired backfill area, trenches are excavated every 0.8-1.2m and shrubs are planted; wherein N is a positive integer.

[0007] In the first aspect, the obtaining of initial shield dried soil comprises: adding activated sludge to shield soil, mixing uniformly, and obtaining initial shield dried soil; the amount of activated sludge added is 3-5% of the mass of the shield soil.

[0008] In the first aspect, the dehydration treatment of the initial shield-dried soil by fly ash and carbide slag includes: selecting fly ash and carbide slag with particle sizes of 50-70 μm; adding the fly ash and carbide slag to the initial shield-dried soil by plowing, the amount of fly ash added is 3-8% of the dry weight of the initial shield-dried soil, and the amount of carbide slag added is 3-8% of the dry weight of the initial shield-dried soil; after mixing evenly, dehydration treatment is carried out by plowing and airing until the optimal moisture content is reached to obtain modified shield-dried soil.

[0009] In the first aspect, the bottom anti-seepage layer has a thickness of 0.8-1.5 m.

[0010] In the first aspect, the thickness of the gangue backfill layer is 1.5 m, and the thickness of the shield dried soil backfill layer is 1.5 m.

[0011] In the first aspect, the ecological anti-seepage layer is laid on the N+1 layer of the gangue backfill layer, including: laying a water-proof and oxygen-blocking layer on the N+1 layer of the gangue backfill layer, the water-proof and oxygen-blocking layer is formed by rolling modified shield-dried soil, and the compaction degree is greater than 90%; laying a capillary barrier layer on the water-proof and oxygen-blocking layer, the capillary barrier layer is formed by rolling crushed gangue with a particle size of 1-3mm, and the compaction degree is 60-70%; laying a vegetation layer on the capillary barrier layer; laying shield-dried soil turf on the vegetation layer.

[0012] In the first aspect, the thickness of the water-proof and oxygen-blocking layer is 0.5-0.8 μm; the thickness of the capillary barrier layer is 0.5-0.8 μm.

[0013] In the first aspect, the vegetation layer is formed by rolling regenerated shield-dried soil with a compaction degree of 50-60%; the regenerated shield-dried soil is made by the following method: the initial shield-dried soil, crushed coal gangue with a particle size of less than 3 mm, coal gasification slag with a particle size of 0.075-1 mm and agricultural, forestry and animal husbandry waste are mixed evenly in a mass ratio of (5-6): (2-3): (0.5-1): (0.5-1), and decomposed for 7 days to obtain regenerated shield-dried soil.

[0014] In the first aspect, the agricultural, forestry and animal husbandry waste includes at least one of chicken manure, cow manure, pig manure and straw.

[0015] In the first aspect, the shield dried soil turf is made by the following method: adding pioneer grass seeds to the regenerated shield dried soil, mixing evenly and then rolling it to a compaction degree of 50-60% to obtain a compacted soil body; cutting the compacted soil body into a mud cake with a length of 30 cm, a width of 30 cm, and a thickness of 8-12 cm; watering and cultivating the mud cake, and forming a shield dried soil turf after 7 days.

[0016] Beneficial effects:

[0017] The present invention provides a method for the coordinated ecological backfilling of shield drying soil and coal gangue. First, initial shield drying soil, initial coal gangue, modified coal gangue and modified shield drying soil are obtained respectively. The shield soil is purified by activated sludge so that the leaching concentration of the surfactant in the initial shield drying soil is less than 0.3 mg / L. The initial coal gangue is crushed by graded crushing so that the initial coal gangue contains 40% by mass of crushed coal gangue with a particle size of 3-5 mm and 30% by mass of crushed coal gangue with a particle size of 1-3 mm. The invention relates to a method for preparing a modified coal gangue by mixing crushed coal gangue with a mass ratio of 30% and a particle size of less than 1 mm, thereby reducing the porosity and oxygen content in the initial coal gangue, reducing the risk of spontaneous combustion and making the structure stable after compaction; the modified coal gangue obtained by adhering a layer of initial shield drying soil on the surface of the initial coal gangue can reduce the contact between the coal gangue and oxygen, and reduce the leaching rate of heavy metals in the coal gangue; the modified shield drying soil is obtained by dehydrating and drying the initial shield drying soil with fly ash and carbide slag, and controlling the moisture content of the modified shield drying soil can be achieved. Improve the compaction degree; then, first lay the bottom anti-seepage layer in the area to be backfilled. The bottom anti-seepage layer is made of modified shield-dried soil and has a compaction degree greater than 90%. After compaction, the pores are small, the cation exchange capacity is large, and it has good anti-seepage performance; then, N+1 layers of coal gangue backfill layers and N layers of shield-dried soil backfill layers are laid alternately on the bottom anti-seepage layer. Each layer of shield-dried soil backfill layer is located between two adjacent layers of coal gangue backfill layers. The coal gangue backfill layer is made of modified coal gangue and has a compaction degree of 100%. The shield drying soil backfill layer is made of modified shield drying soil with a compaction degree of 80-90%. The compacted shield drying soil backfill layer has low permeability, which can isolate oxygen from entering the coal gangue backfill layer; finally, an ecological anti-seepage layer is laid on the N+1 layer of coal gangue backfill layer to provide nutrients for plant growth, thereby obtaining a repaired backfill area; in the repaired backfill area, pits are excavated every 0.8-1.2m to improve the utilization rate of rainfall, so as to plant shrubs. The shield drying soil and coal gangue coordinated ecological backfilling method provided by the present invention obtains modified shield drying soil and modified coal gangue by modifying the shield drying soil and coal gangue, and thus sequentially arranges a bottom anti-seepage layer, an alternating coal gangue backfill layer and a shield drying soil layer, and an ecological anti-seepage layer in the area to be backfilled from bottom to top, fully utilizing the synergistic effect of the modified shield drying soil and the modified coal gangue, so that shrubs can be normally planted in the repaired backfill area, thereby improving the utilization efficiency of the soil. At the same time, a large amount of coal gangue and shield soil are consumed, reducing the hazards of their storage and disposal.

[0018] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 The present invention provides a flow chart of a shield tunneling method for coordinated ecological backfilling of dried soil and coal gangue. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific embodiments and examples are for illustrating the present invention, rather than for limiting the present invention.

[0022] Throughout this specification, unless otherwise specified, the terms used herein should be understood as having the same meaning as commonly used in the art. Therefore, unless otherwise defined, 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 invention belongs. In the event of any conflict, the present specification shall take precedence.

[0023] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or obtained through existing methods.

[0024] See also Figure 1The present invention provides a method for the coordinated ecological backfilling of shield dried soil and coal gangue, the method comprising the following steps: obtaining initial shield dried soil, wherein the leaching concentration of the surfactant in the initial shield dried soil is less than 0.3 mg / L; obtaining initial coal gangue, wherein the initial coal gangue is composed of crushed coal gangue with a particle size of 3-5 mm and a mass proportion of 40%, crushed coal gangue with a particle size of 1-3 mm and a mass proportion of 30%, and crushed coal gangue with a particle size of less than 1 mm and a mass proportion of 30%; adding the initial coal gangue into a pelletizing machine, and adding the initial shield dried soil, mixing, and obtaining modified coal gangue; dehydrating the initial shield dried soil with fly ash and carbide slag to obtain modified shield dried soil; and A bottom anti-seepage layer is first laid in the backfill area, and the bottom anti-seepage layer is formed by rolling the modified shield-dried soil, and the compaction degree is greater than 90%; N+1 layers of coal gangue backfill layer and N layers of shield-dried soil backfill layer are laid in sequence on the bottom anti-seepage layer, and each layer of shield-dried soil backfill layer is located between two adjacent layers of coal gangue backfill layer, and the coal gangue backfill layer is formed by rolling the modified coal gangue, and the compaction degree is 70-80%; the shield-dried soil backfill layer is formed by rolling the modified shield-dried soil, and the compaction degree is 80-90%; an ecological anti-seepage layer is laid on the N+1 layer of coal gangue backfill layer to obtain a repair backfill area; in the repair backfill area, pits are excavated every 0.8-1.2m and shrubs are planted; wherein N is a positive integer.

[0025] Specifically, the present invention provides a method for the coordinated ecological backfilling of shield drying soil and coal gangue. First, the initial shield drying soil, initial coal gangue, modified coal gangue and modified shield drying soil are obtained respectively, and the shield soil is purified by activated sludge so that the leaching concentration of the surfactant in the initial shield drying soil is less than 0.3 mg / L; the initial coal gangue is crushed by graded crushing so that the initial coal gangue contains 40% by mass of crushed coal gangue with a particle size of 3-5 mm, 30% by mass of crushed coal gangue with a particle size of 1-3 mm, and 10% by mass of crushed coal gangue with a particle size of 1-3 mm. Crushed gangue and crushed gangue with a mass ratio of 30% less than 1mm can reduce the porosity and oxygen content in the initial gangue, reduce the risk of spontaneous combustion and stabilize the structure after compaction; modified gangue is obtained by adhering a layer of initial shield drying soil on the surface of the initial gangue, which can reduce the contact between gangue and oxygen and reduce the leaching rate of heavy metals in the gangue; the initial shield drying soil is dehydrated and dried by fly ash and carbide slag to obtain modified shield drying soil, and the water content of the modified shield drying soil is controlled. The rate can improve the compaction degree; then, the bottom anti-seepage layer is laid in the area to be backfilled. The bottom anti-seepage layer is made of modified shield-dried soil and has a compaction degree of more than 90%. After compaction, the pores are small, the cation exchange capacity is large, and it has good anti-seepage performance; then, N+1 layers of coal gangue backfill layers and N layers of shield-dried soil backfill layers are laid alternately on the bottom anti-seepage layer. Each layer of shield-dried soil backfill layer is located between two adjacent layers of coal gangue backfill layers. The coal gangue backfill layer is made of modified coal gangue and compacted. The degree of compaction is 70-80%. The shield drying soil backfill layer is made of modified shield drying soil with a compaction degree of 80-90%. The compacted shield drying soil backfill layer has low permeability, which can isolate oxygen from entering the coal gangue backfill layer; finally, an ecological anti-seepage layer is laid on the N+1 layer of coal gangue backfill layer to provide nutrients for plant growth, thereby obtaining a repaired backfill area; in the repaired backfill area, pits are excavated every 0.8-1.2m to improve the utilization rate of rainfall, so as to plant shrubs. The shield drying soil and coal gangue coordinated ecological backfilling method provided by the present invention obtains modified shield drying soil and modified coal gangue by modifying the shield drying soil and coal gangue, and thus sequentially arranges a bottom anti-seepage layer, an alternating coal gangue backfill layer and a shield drying soil layer, and an ecological anti-seepage layer in the area to be backfilled from bottom to top, fully utilizing the synergistic effect of the modified shield drying soil and the modified coal gangue, so that shrubs can be normally planted in the repaired backfill area, thereby improving the utilization efficiency of the soil. At the same time, a large amount of coal gangue and shield soil are consumed, reducing the hazards of their storage and disposal.

[0026] In some possible embodiments, obtaining initial shield dried soil includes: adding activated sludge to shield soil, mixing evenly, and obtaining initial shield dried soil; the amount of activated sludge added is 3-5% of the mass of the shield soil.

[0027] Those skilled in the art will appreciate that activated sludge contains a large number of microorganisms, some of which use the surfactants in shield soil as an organic carbon source, thereby degrading the surfactants. Furthermore, activated sludge can also serve as a nutrient activator for coal gangue and agricultural, forestry, and livestock waste, providing a foundation for subsequent regeneration of shield-dried soil.

[0028] In some possible embodiments, the dehydration treatment of the initial shield-dried soil by fly ash and carbide slag includes: selecting fly ash and carbide slag with a particle size of 50-70 μm; adding the fly ash and carbide slag to the initial shield-dried soil by plowing, the amount of fly ash added is 3-8% of the dry weight of the initial shield-dried soil, and the amount of carbide slag added is 3-8% of the dry weight of the initial shield-dried soil; after mixing evenly, dehydration treatment is carried out by plowing and airing until the optimal moisture content is reached to obtain modified shield-dried soil.

[0029] This is because, by controlling the moisture content of the modified shield drying soil and combining fly ash and carbide slag, the compaction degree of the modified shield drying soil can be improved, making it have better impermeability, so that it can be used as the bottom anti-seepage layer in the backfill area and the interlayer cover soil of the coal gangue backfill layer to isolate oxygen; if fly ash and carbide slag are not used to modify the initial shield drying soil, then during the subsequent rolling process, it is easy to crack or shrink in volume, thereby destroying the structure of the modified shield drying soil and making it lose its anti-seepage and retardation effect. In addition, it is also necessary to control the amount of fly ash and carbide slag added. When the amount of fly ash and carbide slag added exceeds 8% of the dry weight of the initial shield drying soil, the prepared modified shield drying soil will react with the fly ash under the action of carbide slag as an activator, resulting in hydration and agglomeration, making it difficult to roll and compact. Furthermore, due to excessive addition, the alkalinity is enhanced, which is easy to cause secondary pollution to the surrounding environment.

[0030] In some possible embodiments, the bottom anti-seepage layer has a thickness of 0.8-1.5 m.

[0031] In some possible embodiments, the thickness of the gangue backfill layer is 1.5 m, and the thickness of the shield dried soil backfill layer is 1.5 m.

[0032] In some possible embodiments, laying an ecological anti-seepage layer on top of the N+1 layer of the gangue backfill layer includes: laying a water-proof and oxygen-blocking layer on top of the N+1 layer of the gangue backfill layer, the water-proof and oxygen-blocking layer being formed by compacting modified shield-dried soil and having a compaction degree greater than 90%; laying a capillary barrier layer on top of the water-proof and oxygen-blocking layer, the capillary barrier layer being formed by compacting crushed gangue with a particle size of 1-3 mm and having a compaction degree of 60-70%; laying a vegetation layer on top of the capillary barrier layer; and laying shield-dried soil turf on top of the vegetation layer.

[0033] Those skilled in the art will appreciate that an ecological anti-seepage layer is laid on top of the N+1 layer of coal gangue backfill to repair the ecological environment and provide a living environment for the planted trees. The ecological anti-seepage layer includes a water-proof and oxygen-blocking layer, a capillary barrier layer, a vegetation layer and a shield-dried soil turf from bottom to top; the water-proof and oxygen-blocking layer is formed by modified shield drying and rolling, with a compaction degree greater than 90%, and has excellent impermeability, which can isolate the upper air and moisture from entering, and reduce the pollution leaching of the lower coal gangue backfill layer; the capillary barrier layer is formed by rolling crushed coal gangue with a particle size of 1-3mm, with a compaction degree of 60-70%, and its particle size is larger than that of the vegetation layer above. Under the capillary action of unsaturated soil, water is concentrated in areas with smaller particle pores. The setting of a capillary barrier layer can prevent rainwater from the upper vegetation layer from seeping into the backfill area and increasing the water holding capacity of the vegetation layer; further, setting a shield-dried soil turf on the vegetation layer can improve biodiversity, so that the backfill area can quickly enter a benign ecological succession cycle.

[0034] In some possible embodiments, the thickness of the water-proof and oxygen-blocking layer is 0.5-0.8 μm; the thickness of the capillary barrier layer is 0.5-0.8 μm.

[0035] In some possible embodiments, the vegetation layer is formed by rolling regenerated shield-dried soil with a compaction degree of 50-60%; the regenerated shield-dried soil is made by the following method: the initial shield-dried soil, crushed coal gangue with a particle size of less than 3 mm, coal gasification slag with a particle size of 0.075-1 mm and agricultural, forestry and animal husbandry waste are mixed evenly in a mass ratio of (5-6): (2-3): (0.5-1): (0.5-1), and decomposed for 7 days to obtain regenerated shield-dried soil.

[0036] This is because the use of coal gangue, coal gasification slag, and agricultural, forestry, and livestock waste to modify the initial shield-dried soil to obtain regenerated shield-dried soil can improve the nutrient content and water holding capacity of the regenerated shield-dried soil, increase shrub survival rate, and repair the soil environment. The addition of coal gangue can improve the pore channels for water, gas, and heat transfer, reducing the risk of desiccation in the shield-dried soil. It can also provide organic carbon, nitrogen, phosphorus, potassium, silicon, and magnesium, nutrients required for plant growth, providing nutrients through activation. The pore structure of coal gasification slag can help retain water and fertilizer. The decomposition of agricultural, forestry, and livestock waste can reduce pathogens and decompose large molecular organic matter. The regenerated shield-dried soil thus modified not only provides organic carbon and non-nutrient elements such as nitrogen, phosphorus, and potassium required for plant growth, but also contains a large number of microorganisms that can activate coal gangue, which can promote the release of coal gangue nutrients through long-term reproduction and metabolism.

[0037] In some possible embodiments, the agricultural, forestry and animal husbandry waste includes at least one of chicken manure, cow manure, pig manure and straw.

[0038] In some possible embodiments, the shield dried soil turf is made by: adding pioneer grass seeds to the regenerated shield dried soil, mixing evenly and then rolling it to a compaction degree of 50-60% to obtain a compacted soil body; cutting the compacted soil body into mud cakes with a length of 30 cm, a width of 30 cm, and a thickness of 8-12 cm; watering and cultivating the mud cakes, and forming a shield dried soil turf after 7 days.

[0039] Those skilled in the art will appreciate that adding pioneer grass seeds to regenerated shield-dried soil can create growth conditions for subsequently planted shrubs, playing a key role in initiating the restoration and reconstruction of the ecosystem. Furthermore, pioneer grass seeds can survive in adverse environments such as resource scarcity and poor soil conditions, possessing strong reproductive capacity and growth rates. This provides ecological restoration conditions for early shield-dried soil turf, enabling it to quickly enter a benign ecological succession cycle and providing growth conditions for subsequently planted trees.

[0040] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0041] Example

[0042] This embodiment provides a shield drying soil and coal gangue coordinated ecological backfilling method, which specifically includes the following steps:

[0043] (1) Obtaining initial shield drying soil: adding activated sludge to the shield soil, the amount of activated sludge added is 3% of the mass of the shield soil, and mixing evenly to obtain initial shield drying soil, the leaching concentration of the surfactant in the initial shield drying soil is less than 0.3 mg / L; wherein, the shield soil comes from a slag disposal site, the moisture content is 40%, and the activated sludge comes from a sewage treatment plant. After dilution, the activated sludge is sprayed into the crushed shield soil at a mass ratio of 3%, plowed and mixed evenly, and cured at room temperature for 1 day. The detected surfactant concentration is less than 0.3 mg / L; the surfactant concentration detection method: after leaching the initial shield drying soil and water at a solid-liquid ratio of 1:10, the concentration of the surfactant in the leachate is detected;

[0044] (2) Obtaining initial gangue: The gangue was graded and crushed by a jaw crusher to obtain crushed gangue of different particle sizes. Based on the optimal dense packing model, the initial gangue was composed of crushed gangue with a particle size of 3-5 mm and a mass proportion of 40%, crushed gangue with a particle size of 1-3 mm and a mass proportion of 30%, and crushed gangue with a particle size of less than 1 mm and a mass proportion of 30%. After rolling and compaction, the initial gangue had a porosity of 0.08 and an air flow velocity of 0.8×10 -5 m / s;

[0045] (3) Obtaining modified gangue: adding initial gangue with different particle sizes into a rotary / rolling pelletizing machine, and adding initial shield drying soil, and mixing so that a layer of initial shield drying soil adheres to the surface of the initial gangue, thereby obtaining modified gangue;

[0046] (4) Obtaining modified shield drying soil: selecting fly ash and carbide slag with a particle size of 50-70 μm; adding fly ash and carbide slag to the initial shield drying soil by plowing, with the amount of fly ash added being 3% of the dry weight of the initial shield drying soil, and the amount of carbide slag added being 3-8% of the dry weight of the initial shield drying soil; after mixing evenly, dehydrating the soil by plowing and airing until the optimum moisture content reaches 29%, thereby obtaining modified shield drying soil;

[0047] (5) Obtaining regenerated shield drying soil: the initial shield drying soil, crushed coal gangue with a particle size of less than 3 mm, coal gasification slag with a particle size of 0.075-1 mm, and agricultural, forestry, and animal husbandry waste are mixed uniformly in a mass ratio of 5:3:1:1, and decomposed for 7 days to obtain regenerated shield drying soil;

[0048] (6) Obtaining shield-dried soil turf: adding pioneer grass seeds to the regenerated shield-dried soil, mixing evenly and rolling it to a compaction degree of 60% to obtain a compacted soil mass; cutting the compacted soil mass into mud cakes with a length of 30 cm, a width of 30 cm, and a thickness of 10 cm; watering and cultivating the mud cakes to form shield-dried soil turf after 7 days;

[0049] (7) A 1m thick bottom anti-seepage layer is first laid in the area to be backfilled. The bottom anti-seepage layer is made of modified shield-dried soil with a compaction degree of 92% and a permeability coefficient of 1.3×10 -8 m / s;

[0050] (8) N+1 layers of gangue backfill and N layers of shield drying soil backfill are laid in sequence on top of the bottom anti-seepage layer. Each layer of shield drying soil backfill is located between two adjacent layers of gangue backfill. The thickness of the shield drying soil backfill and the gangue backfill are both 1.5m. The gangue backfill is made of modified gangue and has a compaction degree of 70%. The shield drying soil backfill is made of modified shield drying soil and has a compaction degree of 80%.

[0051] (9) An ecological anti-seepage layer is laid on top of the N+1 layer of gangue backfill, including first laying a 0.8m thick water-proof and oxygen-proof layer, which is made of modified shield-dried soil and has a compaction degree of 92%; then laying a 0.5m thick capillary barrier layer, which is made of crushed gangue with a particle size of 1-3mm and a compaction degree of 70%; then laying a 0.8m thick vegetation layer, which is made of recycled shield-dried soil and has a compaction degree of 50%; finally laying shield-dried soil turf, thereby obtaining a repaired backfill area;

[0052] (10) In the repaired backfill area, dig pits every 1m and plant shrubs.

[0053] Comparative Example 1

[0054] In this comparative example, the activated sludge was diluted and sprayed at a mass ratio of 1% on the crushed shield soil, and the soil was evenly plowed and cured at room temperature for 1 day. The concentration of surfactant in the leachate was detected to be 6.7 mg / L. After 10 days of curing, the concentration of surfactant in the leachate was detected to be lower than 0.3 mg / L. This shows that when the added content of activated sludge in the shield soil is low, it takes a longer time to purify the surfactant in the shield soil; if the added amount of activated sludge in the shield soil is high, the risk of pathogens brought by the activated sludge will increase easily.

[0055] Comparative Example 2

[0056] In this comparative example, fly ash and carbide slag were not used to dehydrate the initial shield-dried soil. The maximum compaction degree of the shield-dried soil after rolling was 67.2%, and the permeability coefficient was 2.4×10 -5 m / s, which cannot meet the requirement of more than 90% compaction degree of modified shield drying soil, and thus cannot be used as the bottom anti-seepage layer (permeability coefficient is less than 1.0×10 -7 m / s) and water-proof and oxygen-barrier layers, that is, the target backfill requirements cannot be met.

[0057] Comparative Example 3

[0058] In this comparative example, although the same mass of fly ash and carbide slag as in the example was added to the initial shield-dried soil for dehydration treatment, the moisture content of the modified shield-dried soil obtained after dehydration was 36%, which exceeded the optimal moisture content of 5%, resulting in a maximum compaction degree of 76% and a permeability coefficient of 1.4×10 -6 m / s, and also cannot meet the requirement of more than 90% compaction degree of modified shield drying soil, and cannot be used as the bottom anti-seepage layer (permeability coefficient is less than 1.0×10 -7 m / s) and water-proof and oxygen-barrier layer.

[0059] Comparative Example 4

[0060] In this comparative example, the gangue was obtained directly without using a jaw crusher for graded crushing. After rolling and compaction, the gangue had a porosity of 0.3 and an airflow velocity of 0.08, which could easily cause spontaneous combustion. When the air velocity in a gangue pile is less than 4.4×10⁻⁵ m / s, spontaneous combustion of the gangue pile is avoided.

[0061] Comparative Example 5

[0062] In this comparative example, the initial gangue was not pelletized with the initial shield-dried soil. Instead, the initial gangue was directly subjected to the HJ299 toxicity leaching standard test. The leached concentrations of Pb, As, and Hg increased by 43% compared to those in the example, failing to meet backfill requirements. The results indicate that adhering a layer of initial shield-dried soil to the surface of the initial gangue can reduce its exposure to the environment and lower heavy metal leaching.

[0063] Comparative Example 6

[0064] In this comparative example, the ecological anti-seepage layer was laid without the water- and oxygen-blocking layer formed by rolling the modified shield-dried soil. Testing revealed that the oxygen content in the lower 1 meter of the N+1 layer of gangue backfill increased by 22% compared to the example, increasing the risk of gangue spontaneous combustion.

[0065] Comparative Example 7

[0066] In this comparative example, the capillary barrier layer formed by compacting crushed coal gangue with a particle size of 1-3 mm was not laid during the ecological anti-seepage layer. Dye tracing and simulated rainfall tests revealed that the water-proof and oxygen-blocking layer competes with the vegetation layer for water. The water output of the upper vegetation layer in this comparative example is 38% lower than the water storage capacity of the vegetation layer in the example. The results show that the water in the example is almost entirely stored in the vegetation layer due to the blocking effect of the large-particle capillary barrier layer. This not only provides sufficient water supply for plant growth, but also reduces the risk of surface water infiltration into the landfill area.

[0067] Comparative Example 8

[0068] In this comparative example, no gangue was added to the regenerated shield-dried soil in the vegetation layer. Instead, the regenerated shield-dried soil was obtained by mixing initial shield-dried soil, coal gasification slag with a particle size of 0.075-1 mm, and agricultural, forestry, and livestock waste in a mass ratio of 5:1:1, followed by composting for 7 days. Testing revealed that the aggregates in the vegetation layer in this comparative example were larger than 0.25 mm, a 52% reduction compared to the example. The density of the vegetation layer in this comparative example was 30% higher than that in the example. This resulted in a highly viscous and densely packed vegetation layer, hindering water, air, and heat transfer within the vegetation layer and thus affecting plant growth.

[0069] Comparative Example 9

[0070] In this comparative example, no coal gasification slag was added to the regenerated shield-dried soil in the vegetation layer. Instead, the regenerated shield-dried soil was obtained by mixing initial shield-dried soil, crushed coal gangue with a particle size of less than 3 mm, and agricultural, forestry, and livestock waste in a mass ratio of 5:3:1, followed by decomposition for 7 days. Testing showed that the water retention of the vegetation layer in this comparative example was 10% lower than that of the vegetation layer in the example.

[0071] Comparative Example 10

[0072] In this comparative example, no pits were excavated in the repaired backfill area. A simulated rainfall test found that the interception of rainfall in this comparative example was 42% less than that in the example. The results show that the lack of shrub pits in this comparative example reduced plant diversity and, due to the poor water permeability of the turf, resulted in a low utilization rate of rainfall. In contrast, the shrub pits excavated every 1 m in the example allowed rainfall to converge there and diffuse into the vegetation matrix, increasing the utilization rate of rainfall storage.

[0073] In summary, compared with the prior art, the present invention has the following advantages:

[0074] (1) The present invention dehydrates and dries shield-dried soil using fly ash and carbide slag to obtain modified shield-dried soil with high compaction and good impermeability, and uses the soil as an insulating layer between two adjacent layers of gangue backfill, thereby isolating water and oxygen and reducing the risk of spontaneous combustion of the gangue backfill layer;

[0075] (2) The present invention is based on an optimal tight packing model, graded crushing of coal gangue, and uniform mixing with initial shield drying soil with high adhesion to obtain modified coal gangue, thereby reducing the spontaneous combustion risk and heavy metal leaching rate of coal gangue;

[0076] (3) The present invention modifies the initial shield-dried soil by using coal gangue, coal gasification slag and agricultural, forestry and animal husbandry waste to obtain regenerated shield-dried soil, thereby improving the nutritional content and water holding capacity of the regenerated shield-dried soil, increasing the survival rate of shrubs and repairing the soil environment;

[0077] (4) The present invention constructs an ecological anti-seepage layer on the last layer of coal gangue backfill. The ecological anti-seepage layer consists of a water-proof and oxygen-blocking layer, a capillary barrier layer, a vegetation layer and a shield-dried soil turf, creating living conditions for plant growth, thereby repairing the ecological environment.

[0078] Finally, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0079] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0080] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for shield-drying soil and coal gangue coordinated ecological backfilling, characterized in that: The method comprises the following steps: obtaining initial shield-dried soil, wherein the leaching concentration of the surfactant in the initial shield-dried soil is less than 0.3 mg / L; Obtaining initial coal gangue, wherein the initial coal gangue consists of crushed coal gangue with a particle size of 3-5 mm and a mass proportion of 40%, crushed coal gangue with a particle size of 1-3 mm and a mass proportion of 30%, and crushed coal gangue with a particle size of less than 1 mm and a mass proportion of 30%; Adding the initial gangue into a pelletizing machine, and adding the initial shield-dried soil, and mixing them to obtain modified gangue; Dehydrating the initial shield-dried soil using fly ash and carbide slag to obtain modified shield-dried soil; First, a bottom anti-seepage layer is laid in the area to be backfilled. The bottom anti-seepage layer is formed by rolling the modified shield-dried soil, and the compaction degree is greater than 90%; N+1 layers of gangue backfill and N layers of shield-dried soil backfill are laid in sequence on top of the bottom anti-seepage layer. Each layer of shield-dried soil backfill is located between two adjacent layers of gangue backfill. The gangue backfill is formed by rolling the modified gangue with a compaction degree of 70-80%. The shield-dried soil backfill is formed by rolling the modified shield-dried soil with a compaction degree of 80-90%. Laying an ecological anti-seepage layer on the N+1 layer of coal gangue backfill layer to obtain a repaired backfill area; In the repaired backfill area, trenches are dug every 0.8-1.2 m and shrubs are planted; Wherein, N is a positive integer.

2. The method for shield-dried soil and coal gangue coordinated ecological backfilling according to claim 1, characterized in that: The method of obtaining the initial shield drying soil comprises: adding activated sludge to the shield soil, mixing the activated sludge uniformly, and obtaining the initial shield drying soil; the amount of the activated sludge added is 3-5% of the mass of the shield soil.

3. The method for shield-dried soil and coal gangue coordinated ecological backfilling according to claim 1, characterized in that: The dehydration treatment of the initial shield drying soil by using fly ash and carbide slag includes: Select fly ash and carbide slag with particle sizes of 50-70 μm; Adding the fly ash and the carbide slag to the initial shield-dried soil by plowing, wherein the amount of fly ash added is 3-8% of the dry weight of the initial shield-dried soil, and the amount of carbide slag added is 3-8% of the dry weight of the initial shield-dried soil; After being mixed evenly, the soil is dehydrated by plowing and airing until the optimum moisture content is reached to obtain modified shield-dried soil.

4. The method for shield-dried soil and coal gangue coordinated ecological backfilling according to claim 1, characterized in that: The thickness of the bottom anti-seepage layer is 0.8-1.5m.

5. The method for shield-dried soil and coal gangue coordinated ecological backfilling according to claim 1, characterized in that: The thickness of the gangue backfill layer is 1.5m, and the thickness of the shield dried soil backfill layer is 1.5m.

6. The method for shield-dried soil and coal gangue coordinated ecological backfilling according to claim 1, characterized in that: The step of laying an ecological anti-seepage layer on the N+1 layer of coal gangue backfill layer comprises: A water-proof and oxygen-blocking layer is laid on the N+1 layer of coal gangue backfill, wherein the water-proof and oxygen-blocking layer is formed by rolling modified shield-dried soil, and the compaction degree is greater than 90%; A capillary barrier layer is laid on the water-proof and oxygen-barrier layer, wherein the capillary barrier layer is formed by rolling crushed coal gangue with a particle size of 1-3 mm and a compaction degree of 60-70%; Laying a vegetation layer on the capillary barrier layer; Shield-dried soil turf is laid on the vegetation layer.

7. The method for shield-dried soil and coal gangue coordinated ecological backfilling according to claim 6, characterized in that: The thickness of the water-proof and oxygen-blocking layer is 0.5-0.8 μm; the thickness of the capillary blocking layer is 0.5-0.8 μm.

8. The shield-dried soil and coal gangue coordinated ecological backfilling method according to claim 6, characterized in that: The vegetation layer is formed by rolling regenerated shield-dried soil with a compaction degree of 50-60%. The regenerated shield-dried soil is made by the following method: the initial shield-dried soil, crushed coal gangue with a particle size of less than 3 mm, coal gasification slag with a particle size of 0.075-1 mm, and agricultural, forestry, and animal husbandry waste are evenly mixed in a mass ratio of (5-6): (2-3): (0.5-1): (0.5-1), and decomposed for 7 days to obtain the regenerated shield-dried soil.

9. The shield-dried soil and coal gangue coordinated ecological backfilling method according to claim 8, characterized in that: The agricultural, forestry and animal husbandry waste includes at least one of chicken manure, cow manure, pig manure and straw.

10. The shield-dried soil and coal gangue coordinated ecological backfilling method according to claim 8, characterized in that: The shield-dried soil turf is made by: adding pioneer grass seeds to the regenerated shield-dried soil, mixing evenly and then rolling it to a compaction degree of 50-60% to obtain a compacted soil body; cutting the compacted soil body into mud cakes with a length of 30 cm, a width of 30 cm, and a thickness of 8-12 cm; watering and cultivating the mud cakes, and forming the shield-dried soil turf after 7 days.

Images