A mine wasteland ecological restoration slope structure and a construction method thereof

Abstract

This invention discloses a slope structure and construction method for ecological restoration of abandoned mining areas. The slope body comprises, from bottom to top, the original abandoned land foundation layer, a bottom impermeable layer, a coal-based solid waste modified expansive soil-geotextile composite layer, a lime-soil intermediate impermeable layer, a surface waterproof membrane layer, a composite ecological planting layer, and a vegetation greening layer. The coal-based solid waste modified expansive soil-geotextile composite layer is composed of several layers of modified soil and geotextile alternately superimposed. The modified soil layer comprises 50-60 parts expansive soil, 12-18 parts fly ash, 12-18 parts bottom ash, 8-12 parts gasification slag, and 4-6 parts desulfurized gypsum. This invention achieves multiple objectives, including effective suppression of expansive soil swelling and shrinkage, long-term slope stability, double-layer impermeability and water blocking, and high-value utilization of coal-based solid waste. It completes the ecological restoration of abandoned mining areas and the synergistic utilization of solid waste resources, effectively solving the problems of insufficient utilization of coal-based solid waste resources, improvement of poor expansive soil properties, and weak impermeability systems in existing abandoned mining area slope restoration.

Description

Technical Field

[0001] This invention relates to the field of ecological restoration technology for abandoned mining areas, specifically to a slope structure for ecological restoration of abandoned mining areas and its construction method. Background Technology

[0002] Expansive soils exhibit undesirable properties such as softening upon contact with water and shrinking when wet and swelling when dry, leading to slope cracking, slippage, and collapse. Expansive soil remediation often relies on single materials like lime and fly ash, which are costly and lack environmental benefits. Current ecological restoration of coal-based waste sites often employs only single-layer impermeable structures, resulting in limited effectiveness and insufficient long-term slope stability.

[0003] Existing slope seepage prevention in mining areas mostly adopts single-layer geomembrane or single lime-soil structure, which is prone to settlement damage, micro-cracks and leakage problems. It cannot effectively block the rise of groundwater capillary water and the infiltration of surface rainwater, resulting in softening of the improved soil when exposed to water and a decrease in slope stability.

[0004] Large quantities of solid wastes generated from coal-based mining, such as fly ash, gasification slag, blast furnace slag, and desulfurization gypsum, are stockpiled, occupying land and easily causing environmental pollution. Existing technologies do not synergistically utilize multiple types of coal-based solid wastes for expansive soil improvement and form a composite restoration structure that integrates slope stability, double-layer seepage prevention, and ecological greening. Related technical solutions lack targeted ecological restoration technologies with high resource utilization rates. Summary of the Invention

[0005] The purpose of this invention is to address the problems in existing technologies for slope restoration in abandoned mining areas, such as insufficient utilization of coal-based solid waste resources, poor improvement of expansive soil properties, and weak anti-seepage systems, by providing an ecological restoration slope structure and its construction method for abandoned mining areas.

[0006] The technical solution adopted in this invention is: an ecological restoration slope structure for abandoned mining areas, comprising a slope body, wherein the slope body comprises, from bottom to top, an original abandoned land foundation layer, a bottom impermeable layer, a coal-based solid waste improved expansive soil-geotextile composite layer, a lime-soil intermediate impermeable layer, a surface waterproof membrane layer, a composite ecological planting layer and a vegetation greening layer. The slope surface of the slope body is provided with drainage holes; The coal-based solid waste modified expansive soil-geotextile composite layer is composed of several modified soil layers and geotextile layers stacked alternately; the components of the modified soil layer include, by weight, 50-60 parts of expansive soil, 12-18 parts of fly ash, 12-18 parts of bottom ash, 8-12 parts of gasification slag and 4-6 parts of desulfurization gypsum.

[0007] As a further optimization of the slope structure for ecological restoration of abandoned mining areas according to the present invention, the drainage holes are arranged along the slope surface of the slope body at an outward inclination angle of 5%, with a hole diameter of ≥50mm and a hole depth of not less than 0.5m.

[0008] As a further optimization of the slope structure for ecological restoration of abandoned mining areas according to the present invention, the thickness of the improved soil layer in the coal-based solid waste improved expansive soil-geotextile composite layer is 0.8-1.2m.

[0009] As a further optimization of the slope structure for ecological restoration of abandoned mining areas according to the present invention, the thickness of the intermediate seepage-proof layer of the lime-soil mixture is 5-10cm.

[0010] As a further optimization of the slope structure for ecological restoration of abandoned mining areas according to the present invention, the composite ecological planting layer includes an upper planting soil layer and a lower cultivated soil layer, wherein the cultivated soil layer is 20-30cm thick and the planting soil layer is 15-20cm thick.

[0011] The construction method for the ecological restoration slope structure of the abandoned mining area includes the following steps: S1. Level the original soil of the abandoned mining area and compact it to form the foundation layer of the original abandoned site; S2. Lay the waterproof membrane on top of the original abandoned foundation layer, which is the bottom waterproof layer; S3. Take 50-60 parts by weight of expansive soil, 12-18 parts of fly ash, 12-18 parts of bottom ash, 8-12 parts of gasification slag, and 4-6 parts of desulfurization gypsum, and mix them evenly to make improved soil. Spread and compact the improved soil in layers above the bottom seepage prevention layer. After each 0.8-1.2m layer of coal-based solid waste improved soil is laid, a layer of geotextile is laid on top until the preset height is reached. This is the coal-based solid waste improved expansive soil-geotextile composite layer. S4. Lay the lime-soil mixture on the coal-based solid waste improved expansive soil-geotextile composite layer and compact it to form the lime-soil intermediate seepage prevention layer. S5. Lay a waterproof membrane on the intermediate seepage prevention layer of the lime-soil mixture and seal the joints to form the surface waterproof membrane layer. S6. Lay the topsoil layer and planting soil layer in sequence on the surface waterproof membrane layer to form the composite ecological planting layer. S7. Planting green vegetation in the composite ecological planting layer is called the vegetation greening layer. S8. Drill drainage holes to complete the construction.

[0012] As a further optimization of the construction method of the ecological restoration slope structure of the abandoned mining area of ​​the present invention, the seepage-proof membrane mentioned in S2 is an HDPE geomembrane or an SBS modified bitumen waterproof membrane; and the overlap width is ≥10cm, and the joint is sealed.

[0013] As a further optimization of the construction method of the ecological restoration slope structure of the abandoned mining area of ​​the present invention, the layered paving and compaction in S3 are as follows: the thickness of each layer is 20-30cm, and the layers are compacted in layers with a compaction coefficient ≥0.95; the edge overlap of the geotextile is ≥15cm.

[0014] As a further optimization of the construction method of the ecological restoration slope structure of the abandoned mining area of ​​the present invention, the waterproof membrane mentioned in S5 is an HDPE geomembrane or a 2-3cm thick waterproof mortar layer.

[0015] As a further optimization of the construction method of the ecological restoration slope structure of the abandoned mining area of ​​the present invention, the cultivated soil layer mentioned in S6 is a natural cultivated soil layer, and the planting soil layer is a soil layer prepared by mixing coal-based solid waste improved expansive soil with 5-10% humus and 2-3% compound fertilizer by weight.

[0016] Compared with the prior art, the present invention has the following beneficial effects: I. This invention uses four types of coal-based solid waste to synergistically improve expansive soil. Through physical filling, skeleton support, and cementation, it improves the swelling and shrinkage properties and softening properties when exposed to water, thereby significantly enhancing the overall stability of the slope and preventing landslides and cracking.

[0017] II. This invention constructs a three-layer seepage prevention system consisting of a bottom seepage prevention layer, an intermediate seepage prevention layer of lime-soil mixture, and a surface waterproof membrane layer. This system completely blocks the seepage path of water, solves the problem of water immersion and deterioration of improved soil, and extends the service life of the slope.

[0018] Third, the composite ecological planting layer in this invention takes into account soil fertility, air permeability and root growth needs, improves vegetation survival rate, realizes rapid and long-term ecological restoration of mining slopes, and has excellent soil and water conservation effects.

[0019] Fourth, the present invention can fully utilize various coal-based solid wastes such as fly ash, bottom ash, gasification slag, and desulfurization gypsum, with a high resource utilization rate. It does not require a large amount of traditional cementing materials, reduces construction costs, and reduces solid waste storage pollution, which is in line with the concept of green environmental protection and low-carbon remediation.

[0020] Fifth, the construction process of this invention is standardized, highly operable, and adaptable to complex construction sites in mining areas, combining engineering, ecological, and economic benefits. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall slope structure of the present invention; Figure 2 This is a partial cross-sectional schematic diagram of the composite ecological planting layer in this invention; Figure 3 This is a schematic diagram of the drainage hole structure in this invention; Attached reference numerals: 1. Bottom seepage barrier layer; 2. Coal-based solid waste improved expansive soil-geotextile composite layer; 201. Coal-based solid waste improved expansive soil layer; 202. Geotextile layer; 3. Lime-fly ash soil intermediate seepage barrier layer; 4. Surface waterproof membrane layer; 5. Composite ecological planting layer; 501. Planting soil layer; 502. Topsoil layer; 6. Drainage hole; 601. PVC pipe; 602. Filter layer. Detailed Implementation

[0022] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0023] like Figure 1 As shown, an ecological restoration slope structure for abandoned mining areas includes a slope body, which, from bottom to top, comprises an original abandoned land foundation layer, a bottom impermeable layer, a coal-based solid waste improved expansive soil-geotextile composite layer, a lime-soil intermediate impermeable layer, a surface waterproof membrane layer, a composite ecological planting layer, and a vegetation greening layer; the slope surface of the slope body is provided with drainage holes; the coal-based solid waste improved expansive soil-geotextile composite layer is composed of several layers of improved soil and geotextile alternately superimposed; the components of the improved soil layer, by weight, include: 50-60 parts of expansive soil, 12-18 parts of fly ash, 12-18 parts of furnace bottom slag, 8-12 parts of gasification slag, and 4-6 parts of desulfurized gypsum.

[0024] In order to drain the water trapped in the slope in a timely manner, the drainage holes are arranged along the slope surface of the slope body at an outward angle of 5%, with a hole diameter of ≥50mm and a hole depth of not less than 0.5m.

[0025] In order to make the slope of the present invention have better resistance to expansion and contraction, the thickness of the improved soil layer in the coal-based solid waste improved expansive soil-geotextile composite layer is 0.8-1.2m.

[0026] The thickness of the intermediate seepage-proof layer of the lime-soil mixture is 5-10cm. It is compacted and formed to serve as a secondary seepage-proof and buffer layer, sealing micro-cracks, blocking water infiltration, and balancing the flatness of the slope.

[0027] like Figure 2 As shown, the composite ecological planting layer includes an upper planting soil layer and a lower cultivated soil layer, with the cultivated soil layer having a thickness of 20-30cm and the planting soil layer having a thickness of 15-20cm.

[0028] The construction method for the ecological restoration slope structure of the abandoned mining area includes the following steps: S1. Level the original soil of the abandoned mining area, remove construction waste, weeds and large-diameter stones, and compact it to form the foundation layer of the original abandoned site. S2. Lay the waterproof membrane on top of the original abandoned foundation layer, which is the bottom waterproof layer; S3. Take 50-60 parts by weight of expansive soil, 12-18 parts of fly ash, 12-18 parts of bottom ash, 8-12 parts of gasification slag, and 4-6 parts of desulfurization gypsum, and mix them evenly to make improved soil. Spread and compact the improved soil in layers above the bottom seepage prevention layer. After each 0.8-1.2m layer of coal-based solid waste improved soil is laid, a layer of geotextile is laid on top until the preset height is reached. This is the coal-based solid waste improved expansive soil-geotextile composite layer. S4. Lay the lime-soil mixture on the coal-based solid waste improved expansive soil-geotextile composite layer, compact it into shape, and that is the lime-soil intermediate seepage prevention layer. S5. Lay a waterproof membrane on the intermediate seepage prevention layer of the lime-soil mixture and seal the joints to form the surface waterproof membrane layer. S6. Lay the topsoil layer and planting soil layer in sequence on the surface waterproof membrane layer to form the composite ecological planting layer. S7. Planting green vegetation in the composite ecological planting layer is called the vegetation greening layer. S8. Drill drainage holes to complete the construction.

[0029] The seepage-proof membrane described in S2 is an HDPE geomembrane or an SBS modified bitumen waterproof membrane; the overlap width is ≥10cm, and the joints are sealed. The seepage-proof membrane is fully laid on top of the original abandoned foundation layer, and the joints are sealed with heat welding or special sealant. The overlap width and sealing effect are strictly controlled, leakage detection is completed, and the upward seepage of underground capillary water is completely blocked to prevent the improved expansive soil from softening due to water immersion.

[0030] The layered spreading and compaction described in S3 specifically refer to the following: each layer is 20-30cm thick, compacted in layers, with a compaction coefficient ≥0.95; the edge overlap of the geotextile is ≥15cm. The coal-based solid waste improved expansive soil-geotextile composite layer is composed of multiple layers of improved expansive soil units and geotextiles superimposed on each other. Through the synergistic effect of multiple layers, the physical filling and chemical modification of the expansive soil are achieved, inhibiting its swelling and shrinkage.

[0031] The lime-fly ash-soil mixture mentioned in S4 is an inorganic material composed of lime, fly ash, and soil. The thickness of the lime-fly ash-soil impermeable layer is 5-10cm, and it is compacted until there is no obvious settlement, with a compaction coefficient ≥0.95.

[0032] The waterproof membrane described in S5 is an HDPE geomembrane or a 2-3cm thick waterproof mortar layer. The waterproof membrane is fully laid and sealed to prevent surface rainwater from seeping in, forming a double-layer closed-loop seepage prevention system with the underlying impermeable layer, thus preventing water from intruding into the improved soil body.

[0033] The cultivated soil layer described in S6 is a natural cultivated soil layer. The planting soil layer is a soil layer prepared by mixing coal-based solid waste improved expansive soil with 5-10% humus and 2-3% compound fertilizer by weight. The planting layer is improved by adding fertilizer to enhance soil fertility and water retention and aeration.

[0034] The vegetation greening layer described in S7 uses grass seeds or drought-resistant shrubs suitable for growth in the mining area to form a green vegetation layer on the slope, thereby achieving ecological restoration and soil and water conservation.

[0035] The drainage holes described in S8 are arranged in a quincunx pattern after the slope filling is completed, with a spacing of 2m. They are formed by mechanical drilling. The drainage holes are arranged along the slope surface at a 5% outward angle, and the hole depth is not less than 0.5m into the slope. PVC pipes are installed inside the holes, and a filter layer is installed outside the PVC pipes. Figure 3 As shown, the filter layer is a fine sand layer, or a geotextile wrapped around a PVC pipe, with a gravel layer outside the geotextile. The drainage hole opening is sealed around its perimeter and has an internal filter structure, which ensures smooth drainage of seepage water from the slope while preventing backflow and moisture at the hole location, soil loss, and does not damage the overall waterproof structure of the slope.

[0036] After the slope structure of this invention is constructed, grass seeds are sown or shrubs are planted. When spraying, ensure that the grass seeds are in full contact with the soil. Water regularly for 7-10 days in the early stage to ensure the survival of the vegetation. In the later stage, carry out routine ecological management.

[0037] Example 1:

[0038] A construction method for an ecological restoration slope structure in a mining wasteland includes the following steps: S1. Level the original soil of the abandoned mining area, remove construction waste, weeds and large-diameter stones, and compact it to form the foundation layer of the original abandoned site. S2. Lay the 2.0mm thick HDPE geomembrane on top of the original abandoned foundation layer to form the bottom seepage barrier layer. S3. Take 55 parts by weight of expansive soil, 15 parts of fly ash, 15 parts of furnace bottom ash, 10 parts of gasification slag, and 5 parts of desulfurization gypsum, and mix them evenly to prepare coal-based solid waste modified expansive soil; spread and compact the coal-based solid waste modified expansive soil in layers above the bottom seepage prevention layer, with each layer being 25cm thick and compacted in layers, with a compaction coefficient ≥0.95; after each 1m of coal-based solid waste modified expansive soil is laid, a layer of geotextile is laid on top until the preset height is reached, with the edge overlap of the geotextile ≥15cm, which is the coal-based solid waste modified expansive soil-geotextile composite layer; S4. Lay the lime-soil mixture on the coal-based solid waste improved expansive soil-geotextile composite layer, compact it into shape, and that is the lime-soil intermediate seepage barrier layer; the thickness of the lime-soil intermediate seepage barrier layer is 8cm. S5. Lay a 2-3cm thick waterproof mortar layer on the intermediate seepage prevention layer of the lime-soil mixture, and seal the joints to form the surface waterproof membrane layer. S6. A topsoil layer and a planting soil layer are laid sequentially on the surface waterproof membrane layer to form a composite ecological planting layer. The topsoil layer is a natural topsoil layer, and the planting soil layer is a soil layer prepared by mixing coal-based solid waste improved expansive soil with 8% humus and 2.5% compound fertilizer by weight. S7. Select grass seeds or drought-resistant shrubs suitable for the mining area to plant in the composite ecological planting layer to form a green vegetation layer on the slope, which is the vegetation greening layer. S8. After the slope filling is completed, drainage holes are drilled on the slope surface in a quincunx pattern with a spacing of 2m. The holes are formed by mechanical drilling. The drainage holes are arranged along the slope surface of the slope body at an outward inclination of 5%, with a hole diameter of ≥50mm and a hole depth of not less than 0.5m into the slope. PVC pipes are installed in the holes, and a filter layer of fine sand is set outside the PVC pipes. The construction is then completed.

[0039] Example 2:

[0040] A construction method for an ecological restoration slope structure in a mining wasteland includes the following steps: S1. Level the original soil of the abandoned mining area, remove construction waste, weeds and large-diameter stones, and compact it to form the foundation layer of the original abandoned site. S2. Lay the SBS modified bitumen waterproof membrane on top of the original abandoned foundation layer to form the bottom waterproof layer. S3. Take 50 parts by weight of expansive soil, 18 parts of fly ash, 18 parts of furnace bottom ash, 8 parts of gasification slag, and 6 parts of desulfurization gypsum, and mix them evenly to prepare coal-based solid waste modified expansive soil. Spread and compact the coal-based solid waste modified expansive soil in layers above the bottom seepage prevention layer. The thickness of each layer is 20cm. Compact each layer with a compaction coefficient ≥0.95. After laying 0.8m of coal-based solid waste modified expansive soil, lay a layer of geotextile until the preset height is reached. The edge overlap of the geotextile is ≥15cm, which is the coal-based solid waste modified expansive soil-geotextile composite layer. S4. Lay the lime-soil mixture on the coal-based solid waste improved expansive soil-geotextile composite layer, compact it into shape, and that is the lime-soil intermediate seepage barrier layer; the thickness of the lime-soil intermediate seepage barrier layer is 5cm. S5. Lay a waterproof HDPE geomembrane on the intermediate impermeable layer of lime-soil and seal the joints to form the surface waterproof membrane layer. S6. A topsoil layer and a planting soil layer are laid sequentially on the surface waterproof membrane layer to form a composite ecological planting layer. The topsoil layer is a natural topsoil layer, and the planting soil layer is a soil layer prepared by mixing coal-based solid waste improved expansive soil with 5% humus and 2% compound fertilizer by weight. S7. Select grass seeds or drought-resistant shrubs suitable for the mining area to plant in the composite ecological planting layer to form a green vegetation layer on the slope, which is the vegetation greening layer. S8. After the slope filling is completed, drainage holes are drilled on the slope surface in a quincunx pattern with a spacing of 2m. The holes are formed by mechanical drilling. The drainage holes are arranged along the slope surface at an outward angle of 5%, with a diameter of ≥50mm and a depth of not less than 0.5m into the slope. PVC pipes are installed in the holes, and a filter layer is set outside the PVC pipes. The filter layer is geotextile wrapped around the PVC pipes, and a gravel layer is set outside the geotextile. The construction is then completed.

[0041] Example 3:

[0042] A construction method for an ecological restoration slope structure in a mining wasteland includes the following steps: S1. Level the original soil of the abandoned mining area, remove construction waste, weeds and large-diameter stones, and compact it to form the foundation layer of the original abandoned site. S2. Lay a 1.5mm thick HDPE geomembrane on top of the original abandoned foundation layer to form the bottom seepage barrier layer. S3. Take 60 parts by weight of expansive soil, 12 parts of fly ash, 12 parts of furnace bottom ash, 12 parts of gasification slag, and 4 parts of desulfurization gypsum, and mix them evenly to prepare coal-based solid waste modified expansive soil. Spread and compact the coal-based solid waste modified expansive soil in layers above the bottom seepage prevention layer. Each layer is 30cm thick and compacted in layers with a compaction coefficient ≥0.95. After laying 1.2m of coal-based solid waste modified expansive soil, lay a layer of geotextile until the preset height is reached. The edge overlap of the geotextile is ≥15cm, which is the coal-based solid waste modified expansive soil-geotextile composite layer. S4. Lay the lime-soil mixture on the coal-based solid waste improved expansive soil-geotextile composite layer, compact it into shape, and that is the lime-soil intermediate seepage barrier layer; the thickness of the lime-soil intermediate seepage barrier layer is 10cm. S5. Lay a waterproof HDPE geomembrane on the intermediate impermeable layer of lime-soil and seal the joints to form the surface waterproof membrane layer. S6. A topsoil layer and a planting soil layer are laid sequentially on the surface waterproof membrane layer to form a composite ecological planting layer. The topsoil layer is a natural topsoil layer, and the planting soil layer is a soil layer prepared by mixing coal-based solid waste improved expansive soil with 10% humus and 3% compound fertilizer by weight. S7. Select grass seeds or drought-resistant shrubs suitable for the mining area to plant in the composite ecological planting layer to form a green vegetation layer on the slope, which is the vegetation greening layer. S8. After the slope filling is completed, drainage holes are drilled on the slope surface in a quincunx pattern with a spacing of 2m. The holes are formed by mechanical drilling. The drainage holes are arranged along the slope surface at an outward angle of 5%, with a diameter of ≥50mm and a depth of not less than 0.5m into the slope. PVC pipes are installed in the holes, and a filter layer is set outside the PVC pipes. The filter layer is geotextile wrapped around the PVC pipes, and a gravel layer is set outside the geotextile. The construction is then completed.

[0043] This invention relies on four types of local associated solid wastes from the entire coal industry process—fly ash, bottom ash, gasification slag, and desulfurization gypsum—as the base material for improvement, forming a unique quality ratio improvement system with in-situ expansive soil. By using coal-based solid waste to improve expansive soil, the invention achieves complementary advantages and synergistic modification of multiple solid wastes. Through physical replacement, chemical modification, and hydration-cementation synergistic modification mechanisms, the invention improves the swelling and shrinkage characteristics of expansive soil at the microstructural level.

[0044] The four types of coal-based solid waste used in this invention are all taken from the same large-scale northern power coal industrial park, which integrates raw coal power generation, heating, gasification, and flue gas desulfurization. The solid waste has the same source, low cost, and can be disposed of on-site. The modified soil is applied to the seven-layer structure scheme of the ecological slope of the abandoned mining area, combined with the on-site mixing construction technology, to realize the integrated management of mining solid waste, prevention and control of geological disasters in expansive soil, and ecological restoration of mining slope.

[0045] All coal-based solid waste originates from the same mining area, encompassing the entire industrial chain of raw coal power generation, heating, gasification, and flue gas desulfurization. (1) Fly ash: It is taken from the coal-fired generator set in the mining area. It is the fly ash collected by the electrostatic precipitator after the local raw coal is burned at high temperature. It is a fine particulate solid waste exclusive to the thermal power generation process in the park. It does not use commercial fly ash or fly ash from power plants in other places.

[0046] (2) Bottom ash: Taken from the bottom ash of the coal-fired boiler in the mining area, it is coarse hard ash left after the raw coal is fully burned. It belongs to the original waste residue of the heat supply process in the mining area and does not contain external waste residue from the smelting and building materials industries.

[0047] (3) Gasification slag: Taken from the coal gasification unit in the mining area, it is the molten cooling residue generated during the process of producing syngas from local raw coal through high-temperature gasification. It is a unique by-product solid waste of coal deep processing and coal chemical process, which is different from ordinary coal combustion waste residue and has unique mineral active components.

[0048] (4) Desulfurization gypsum: It is taken from the wet desulfurization system of the coal-fired boiler in the mining area. It is a by-product of calcium sulfate dihydrate generated after removing sulfur dioxide from the flue gas using limestone slurry. It is a special solid waste for the environmental protection treatment of flue gas in the plant area. Natural gypsum or industrially processed gypsum is not used.

[0049] The core mechanism of this invention for improving expansive soil from coal-based solid waste is as follows: It regulates the swelling and shrinkage deformation characteristics of expansive soil and optimizes soil gradation. 1. Physical displacement mechanism Bottom ash and gasification ash are coarse-grained hard skeleton materials. After being crushed and screened, they are mixed into the expansive soil, which reduces the expansibility of the expansive soil from a physical perspective.

[0050] 2. Chemical modification mechanism Expansive soil is rich in hydrophilic montmorillonite and illite clay minerals, which absorb water molecules upon contact with water, causing it to expand in volume. Desulfurized gypsum dissociates into Ca... 2+ The cations exchange with the low-valence cations on the surface of expansive clay particles, weakening the thickness of the water film on the surface of the clay particles; thus significantly reducing the hydrophilicity and swelling properties of the soil.

[0051] 3. Hydration-gelling mechanism Fly ash and gasification slag contain a large amount of active SiO2 and Al2O3 active mineral components. Under the alkaline activation environment of desulfurized gypsum, they undergo volcanic ash hydration reaction to generate cementitious hydration products, which cement soil particles and form a stable spatial network structure, thereby improving the strength, impermeability and erosion resistance of slope soil.

[0052] 4. Mechanism of Coordinated Stabilization of Soil and Water The compounding of multiple solid wastes not only regulates the swelling and shrinkage deformation characteristics of expansive soil but also optimizes soil gradation. This improves the structural mechanical stability of slopes and the soil and water conditions for ecological vegetation growth, achieving both engineering stability and ecological restoration.

[0053] In summary, the ecological restoration slope structure and construction method based on coal-based solid waste-modified expansive soil provided by this invention achieve multiple objectives, including effective suppression of expansive soil swelling and shrinkage, long-term slope stability, double-layer seepage prevention and water blocking, and high-value disposal of coal-based solid waste. It completes the ecological restoration of abandoned mining areas and the synergistic utilization of solid waste resources, effectively solving the problems of insufficient utilization of coal-based solid waste resources, improvement of poor expansive soil properties, and weak seepage prevention system in existing slope restoration of abandoned mining areas.

[0054] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A slope structure for ecological restoration of abandoned mining areas, characterized in that: The slope body includes, from bottom to top, the original abandoned land foundation layer, the bottom seepage-proof layer, the coal-based solid waste improved expansive soil-geotextile composite layer, the lime-soil intermediate seepage-proof layer, the surface waterproof membrane layer, the composite ecological planting layer and the vegetation greening layer. The slope surface of the slope body is provided with drainage holes; The coal-based solid waste modified expansive soil-geotextile composite layer is composed of several modified soil layers and geotextile layers stacked alternately; the components of the modified soil layer include, by weight, 50-60 parts of expansive soil, 12-18 parts of fly ash, 12-18 parts of bottom ash, 8-12 parts of gasification slag and 4-6 parts of desulfurization gypsum.

2. The slope structure for ecological restoration of abandoned mining areas as described in claim 1, characterized in that: The drainage holes are arranged along the slope surface of the slope body at an outward inclination of 5%, with a hole diameter of ≥50mm and a hole depth of not less than 0.5m.

3. The slope structure for ecological restoration of abandoned mining areas as described in claim 1, characterized in that: The thickness of the improved soil layer in the coal-based solid waste improved expansive soil-geotextile composite layer is 0.8-1.2m.

4. The slope structure for ecological restoration of abandoned mining areas as described in claim 1, characterized in that: The thickness of the intermediate seepage-proof layer of the lime-soil mixture is 5-10cm.

5. The slope structure for ecological restoration of abandoned mining areas as described in claim 1, characterized in that: The composite ecological planting layer includes an upper planting soil layer and a lower cultivated soil layer, with the cultivated soil layer being 20-30cm thick and the planting soil layer being 15-20cm thick.

6. The construction method for the ecological restoration slope structure of abandoned mining areas as described in claim 1, characterized in that, Includes the following steps: S1. Level the original soil of the abandoned mining area and compact it to form the foundation layer of the original abandoned site; S2. Lay the waterproof membrane on top of the original abandoned foundation layer, which is the bottom waterproof layer; S3. Take 50-60 parts by weight of expansive soil, 12-18 parts of fly ash, 12-18 parts of bottom ash, 8-12 parts of gasification slag, and 4-6 parts of desulfurization gypsum, and mix them evenly to make improved soil. Spread and compact the improved soil in layers above the bottom seepage prevention layer. After each 0.8-1.2m layer of coal-based solid waste improved soil is laid, a layer of geotextile is laid on top until the preset height is reached. This is the coal-based solid waste improved expansive soil-geotextile composite layer. S4. Lay the lime-soil mixture on the coal-based solid waste improved expansive soil-geotextile composite layer and compact it to form the lime-soil intermediate seepage prevention layer. S5. Lay a waterproof membrane on the intermediate seepage prevention layer of the lime-soil mixture and seal the joints to form the surface waterproof membrane layer. S6. Lay the topsoil layer and planting soil layer in sequence on the surface waterproof membrane layer to form the composite ecological planting layer. S7. Planting green vegetation in the composite ecological planting layer is called the vegetation greening layer. S8. Drill drainage holes to complete the construction.

7. The construction method for the ecological restoration slope structure of abandoned mining areas as described in claim 6, characterized in that: The seepage-proof membrane described in S2 is an HDPE geomembrane or an SBS modified bitumen waterproof membrane; and the overlap width is ≥10cm, with the joints sealed.

8. The construction method for the ecological restoration slope structure of abandoned mining areas as described in claim 6, characterized in that: The layered paving and compaction described in S3 are as follows: each layer is 20-30cm thick, compacted in layers, with a compaction coefficient ≥0.95; the edge overlap of the geotextile is ≥15cm.

9. The construction method for the ecological restoration slope structure of abandoned mining areas as described in claim 6, characterized in that: The waterproof membrane mentioned in S5 is an HDPE geomembrane or a 2-3cm thick waterproof mortar layer.

10. The construction method for the ecological restoration slope structure of abandoned mining areas as described in claim 6, characterized in that: The cultivated soil layer mentioned in S6 is the natural cultivated soil layer, and the planting soil layer is a soil layer prepared by mixing coal-based solid waste improved expansive soil with 5-10% humus and 2-3% compound fertilizer by weight.

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