Ecological reconstruction method for surface soil stripping, ditch filling and land reclamation of open pit coal mine in karst region

Abstract

The invention discloses a karst region open pit coal mine surface soil stripping ditch filling land reclamation ecological reconstruction method, and relates to the technical field of ecological restoration, and the method comprises the following steps: adopting a three-layer backfill structure to carry out soil profile reconstruction, and calculating the addition amount of an acid-base restoration agent for soil with the pH value lower than a threshold value; according to the relationship between the soil bulk density and the ideal soil bulk density, the biochar addition amount for soil remediation is determined; constructing a heavy metal stability evaluation model to calculate a heavy metal stability index, and determining the dosage of a soil heavy metal pollution repairing agent; the slope stability is evaluated, and the slope ecological restoration safety coefficient and the vegetation configuration scheme are calculated in combination with the vegetation configuration diversity index; and constructing an improved moisture characteristic curve model to calculate the soil volume moisture content and formulate an irrigation plan. According to the method, soil improvement and ecological restoration are achieved through the steps of soil backfilling, restoration agent adding, vegetation configuration and precise irrigation, and scientificity and accuracy of the restoration process are ensured by building the model.

Description

Technical Field

[0001] This invention relates to the field of ecological restoration technology, specifically to a method for ecological reconstruction by stripping topsoil and filling ditches in open-pit coal mines in karst areas. Background Technology

[0002] Large-scale open-pit coal mining has driven economic development, but it has also caused serious damage to the ecological environment. The geological conditions and mining environment change significantly after mining, resulting in a series of problems such as mine subsidence, soil erosion, water pollution, and impacts on biodiversity, thus damaging the ecosystem and environment of the mining area. For example, during the entire mining process, uneven subsidence and tilting occur in various forms on the surface. During heavy rains, this triggers soil erosion, affecting vegetation cover and growth, biodiversity, and consequently, the ecosystem. Furthermore, mining requires a large amount of water, but much wastewater and sewage is discharged directly into the ecological environment without any treatment, severely polluting surface water. These problems not only affect the stability and function of the regional ecosystem but also threaten biodiversity, exacerbate environmental degradation, and seriously hinder regional sustainable development. Therefore, restoring the ecosystem function of open-pit coal mining areas has become an important research direction in current ecology and environmental science.

[0003] However, the ecological environment of open-pit coal mines is complex and diverse, and remediation work requires the coordinated restoration of multiple ecological elements such as soil, water, and air. Traditional methods consider the synergistic effects of multiple factors such as soil profile reconstruction, bulk density optimization, and heavy metal stabilization, but lack effective assessment of complex pollution from multiple heavy metals, and vegetation configuration and irrigation schemes rely on experience-based judgment.

[0004] For example, Chinese patent CN114747415A discloses a plant composition method for ecological restoration of coal mining areas based on remote sensing images, relating to the field of ecological restoration technology. Its operational steps are as follows: Step 1: Using remote sensing imagery technology, auxiliary data for different site conditions are used to classify the sites into different types; Step 2: By comparing the auxiliary data for different site conditions and the plant species composition under different vegetation cover change trends, the key plant types needed for vegetation restoration and reconstruction in each site condition and vegetation cover change trend area are identified. This invention is applicable to ecological restoration. By improving the vegetation composition, optimizing the plant restoration ratio for different site conditions, and distributing vegetation, it improves the sustainability and efficiency of mine ecological restoration, generating good ecological benefits. A reasonable vegetation ratio combination exhibits good symbiosis and excellent ecological sustainability, possessing significant promotional value.

[0005] For example, Chinese Patent Publication No. CN116843533A discloses a method for vegetation reconstruction in mining areas based on vegetation classification and site type division. This method utilizes remote sensing technology to acquire remote sensing images, performs image preprocessing, classifies the vegetation in the mining area, and selects site factors that may affect site type division for processing. Site types are obtained with slope and soil fertility as the dominant factors. Based on the evolution trends of the normalized difference vegetation index (NDVI) for different vegetation types and the NDVI for different vegetation types corresponding to different site types, the method analyzes the vegetation growth in the mining area since ecological restoration. Samples are selected from areas with good vegetation growth. The vegetation classification result of the samples is used as the decision attribute, and the site type is used as the condition attribute to obtain a decision tree model based on vegetation classification and site type division for vegetation reconstruction. This invention provides a basis for site-appropriate regional ecological restoration in mining areas and provides guidance for accelerating the ecological restoration of high-altitude open-pit coal mines. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology by providing a method for ecological reconstruction of open-pit coal mines in karst areas by stripping topsoil and filling ditches.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The ecological reconstruction method for stripping topsoil and filling trenches in open-pit coal mines in karst areas includes the following steps:

[0009] Step S1: Soil profile reconstruction is carried out using a three-layer backfill structure, and the amount of acid-base remediation agent added is calculated for soils with pH values ​​below the threshold.

[0010] Step S2: Determine the amount of biochar to be added for soil remediation based on the relationship between soil bulk density and ideal soil bulk density;

[0011] Step S3: Construct a heavy metal stability assessment model, calculate the heavy metal stability index, and determine the dosage of soil heavy metal pollution remediation agent;

[0012] Step S4: Assess slope stability and, in conjunction with the vegetation configuration diversity index, calculate the safety factor and vegetation configuration scheme for slope ecological restoration.

[0013] Step S5: Construct an improved moisture characteristic curve model to calculate soil volumetric water content, and formulate an irrigation plan based on the water content.

[0014] Furthermore, in step S1, the three-layer backfill structure includes: a bottom layer, a middle layer, and a top layer;

[0015] The bottom layer, 0.3-0.5m thick, consists of sand and gravel with a particle size of 5-20mm, and is used to enhance drainage capacity. The middle layer, 0.5-0.8m thick, is a mixture of original soil, acid and alkali remediation agents, biochar, and soil heavy metal pollution remediation agents, and is used to improve the chemical and physical properties of the soil. The top layer, 0.2-0.3m thick, consists of topsoil and is used to provide the nutrients and microbial environment required by plants.

[0016] Furthermore, in step S1, the amount of acid-base remediation agent added takes into account soil buffering capacity, cation exchange capacity, and soil texture, and the specific formula is as follows:

[0017]

[0018] in, This indicates the amount of acid-base repair agent added, specifically the amount of slaked lime added. Indicates the bulk density of the middle soil layer. Indicates the thickness of the middle soil layer. Indicates the target pH value. This indicates the current soil pH value. This indicates soil buffering capacity, which is the soil's ability to resist pH changes. This represents the correction factor for cation exchange capacity. Indicates cation exchange capacity, This indicates the reference cation exchange capacity value. Indicates the texture correction factor. It indicates the clay content, which is the percentage of clay particles in the soil.

[0019] Furthermore, in step S2, the specific formula for the amount of biochar added for soil remediation is as follows:

[0020]

[0021] in, Indicates the amount of biochar added. This represents a correction factor, which depends on the soil type. Indicates the current soil bulk density. Indicates the ideal soil bulk density. Indicates soil volume, The density coefficient represents the density of biochar, which is the ratio of the density of biochar to that of soil. Indicates the influence coefficient of organic carbon. Indicates organic carbon content, This indicates the reference organic carbon content.

[0022] Furthermore, the heavy metal stability index comprehensively considers the heavy metal weight, stable form concentration, total concentration, decay coefficient, and reference concentration;

[0023] The dosage of the soil heavy metal pollution remediation agent includes parameters such as the remediation agent efficiency coefficient, heavy metal stability index, total heavy metal concentration, soil area, soil layer thickness, soil bulk density, and clay content, and the dosage of the remediation agent is adjusted by the clay adsorption coefficient.

[0024] Furthermore, step S4 specifically includes the following steps:

[0025] Step S4.1: Calculate the slope safety factor, and calculate the safety factor increased by the root system considering the reinforcement effect of vegetation roots;

[0026] Step S4.2: Add the slope safety factor and the root system increase safety factor to obtain the safety factor after vegetation reinforcement;

[0027] Step S4.3: Calculate the vegetation configuration diversity index based on the Shannon-Wiener index;

[0028] Step S4.4: Based on the safety factor and vegetation configuration diversity index after vegetation reinforcement, determine the specific vegetation configuration scheme through a predefined vegetation configuration decision map.

[0029] Furthermore, in step S4.4, the vegetation configuration decision map is a two-dimensional decision matrix, with the horizontal axis representing the safety factor after vegetation reinforcement and the vertical axis representing the vegetation configuration diversity index. The slope condition is divided into nine regions, each corresponding to a specific vegetation configuration scheme.

[0030] Furthermore, the improved moisture characteristic curve model is calculated based on the van Genuchten model, wherein the parameters of the van Genuchten model are corrected by introducing organic carbon content and clay content.

[0031] Furthermore, in step S5, the irrigation plan based on water content includes determining the irrigation threshold and the irrigation amount, wherein the irrigation threshold is calculated based on field water holding capacity, irrigation coefficient and reference evapotranspiration, and the irrigation amount is calculated based on the current water content, root layer depth, area and wind speed.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. The three-layer backfill structure of this invention, along with the synergistic calculation of the amount of multiple remediation agents and biochar, simultaneously achieves acidity adjustment, bulk density optimization, and heavy metal stabilization. Compared with traditional single improvement methods, the improvement of soil physicochemical properties is more comprehensive.

[0034] 2. This invention constructs a heavy metal stability index model to quantitatively assess the stability of various heavy metals, accurately calculates the amount of remedial agent based on the HSI value, and introduces the clay adsorption coefficient to improve the utilization rate of the remedial agent.

[0035] 3. This invention establishes a vegetation configuration decision map, which organically combines the safety factor after vegetation reinforcement with the vegetation configuration diversity index to form a two-dimensional decision matrix divided into nine regions, thereby achieving dual optimization of engineering safety and ecological benefits.

[0036] 4. This invention is based on the improved van Genuchten water characteristic curve model. By correcting the model parameters through organic carbon and clay content, it can accurately predict soil moisture dynamics. Furthermore, the irrigation plan comprehensively considers factors such as field water holding capacity, evapotranspiration, and wind speed, effectively addressing drought stress. Attached Figure Description

[0037] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0038] Figure 1 This is a flowchart illustrating an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of a vegetation configuration decision map according to an embodiment of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] like Figure 1 As shown, the ecological reconstruction method for stripping topsoil and filling trenches in open-pit coal mines in karst areas includes the following steps:

[0042] Step S1: Soil profile reconstruction is carried out using a three-layer backfill structure, and the amount of acid-base remediation agent added is calculated for soils with pH values ​​below the threshold.

[0043] Step S2: Determine the amount of biochar to be added for soil remediation based on the relationship between soil bulk density and ideal soil bulk density;

[0044] Step S3: Construct a heavy metal stability assessment model, calculate the heavy metal stability index, and determine the dosage of soil heavy metal pollution remediation agent;

[0045] Step S4: Assess slope stability and, in conjunction with the vegetation configuration diversity index, calculate the safety factor and vegetation configuration scheme for slope ecological restoration.

[0046] Step S5: Construct an improved moisture characteristic curve model to calculate soil volumetric water content, and formulate an irrigation plan based on the water content.

[0047] In step S1, the three-layer backfill structure includes: a bottom layer, a middle layer, and a top layer;

[0048] The bottom layer, 0.3-0.5m thick, consists of sand and gravel with a particle size of 5-20mm, and is used to enhance drainage capacity. The middle layer, 0.5-0.8m thick, is a mixture of original soil, acid and alkali remediation agents, biochar, and soil heavy metal pollution remediation agents, and is used to improve the chemical and physical properties of the soil. The top layer, 0.2-0.3m thick, consists of topsoil and is used to provide the nutrients and microbial environment required by plants.

[0049] For soils with a pH value below 5.5, calculate the amount of slaked lime to add to neutralize the acidity;

[0050] In step S1, the amount of acid-base remediation agent added takes into account soil buffering capacity, cation exchange capacity, and soil texture, and the specific formula is as follows:

[0051]

[0052] in, This indicates the amount of acid-base repair agent added, specifically the amount of slaked lime added. Indicates the bulk density of the middle soil layer. Indicates the thickness of the middle soil layer. Indicates the target pH value. This indicates the current soil pH value. This indicates soil buffering capacity, which is the soil's ability to resist pH changes. This represents the correction factor for cation exchange capacity. Indicates cation exchange capacity, This indicates the reference cation exchange capacity value. Indicates the texture correction factor. It indicates the clay content, which is the percentage of clay particles in the soil.

[0053] in, The unit is kg / m², which represents the mass of quicklime required per unit area; soil bulk density. The unit is kg / m³, representing the dry weight of a unit volume of soil, determined by the ring sampler method; soil buffering capacity. The unit is kg / kg / pH, representing the soil's ability to resist pH changes, determined by laboratory titration; cation exchange capacity correction factor. Dimensionless, typically taken as 0.1-0.3, used to adjust the effect on cation exchange capacity; cation exchange capacity The unit is cmol / kg, representing the soil's ability to retain and exchange cations, determined by the ammonium acetate method; the reference CEC value is usually taken as 10 cmol / kg; texture correction factor. Dimensionless, usually taken as 0.05-0.15, used to account for the influence of clay content;

[0054] In step S2, the specific formula for the amount of biochar added for soil remediation is as follows:

[0055]

[0056] in, Indicates the amount of biochar added. This represents a correction factor, which depends on the soil type. Indicates the current soil bulk density. Indicates the ideal soil bulk density. Indicates soil volume, The density coefficient represents the density of biochar, which is the ratio of the density of biochar to that of soil. Indicates the influence coefficient of organic carbon. Indicates organic carbon content, This indicates the reference organic carbon content.

[0057] Among them, the correction coefficient Dimensionless, depending on soil type, e.g., 0.8 for clay, 1.2 for sandy soil; ideal soil bulk density. Typically, the density coefficient of biochar is 1200-1400 kg / m³. Dimensionless, representing the density ratio of biochar to soil, typically 0.2-0.4; Organic carbon influence coefficient. Dimensionless, typically taken as 0.1-0.3; organic carbon content is determined by combustion method; reference organic carbon content is typically taken as 1%.

[0058] The heavy metal stability index comprehensively considers the heavy metal weight, stable form concentration, total concentration, decay coefficient, and reference concentration.

[0059] The dosage of the soil heavy metal pollution remediation agent includes parameters such as the remediation agent efficiency coefficient, heavy metal stability index, total heavy metal concentration, soil area, soil layer thickness, soil bulk density, and clay content, and the dosage of the remediation agent is adjusted by the clay adsorption coefficient.

[0060] The specific formula for the heavy metal stability index is as follows:

[0061]

[0062] in, This represents the stability index of heavy metals. Indicates an index of heavy metal species. Indicates the quantity of different types of heavy metals. The weight of heavy metal i is represented by a value based on toxicity and mobility. The concentration of heavy metal i in its stable form was determined by a sequential extraction method. The concentration of total heavy metal i is determined by atomic absorption spectrometry. The reference concentration for heavy metal i is usually taken as the local background value or standard limit. This represents the attenuation coefficient of heavy metals, typically ranging from 0.5 to 1.0.

[0063] The specific formula for the dosage of the soil heavy metal pollution remediation agent is as follows:

[0064]

[0065] in, Indicates the dosage of soil heavy metal pollution remediation agent. This represents the efficiency coefficient of the repair agent, expressed in kg of repair agent / mg of heavy metal, typically ranging from 0.00005 to 0.0001. This indicates the total heavy metal concentration. Indicates soil area, The clay adsorption coefficient is dimensionless and is usually taken as 0.2-0.5.

[0066] Step S4 specifically includes the following steps:

[0067] Step S4.1: Calculate the slope safety factor, and calculate the safety factor increased by the root system considering the reinforcement effect of vegetation roots;

[0068] Step S4.2: Add the slope safety factor and the root system increase safety factor to obtain the safety factor after vegetation reinforcement;

[0069] Step S4.3: Calculate the vegetation configuration diversity index based on the Shannon-Wiener index;

[0070] Step S4.4: Based on the safety factor and vegetation configuration diversity index after vegetation reinforcement, determine the specific vegetation configuration scheme through a predefined vegetation configuration decision map.

[0071] The specific formula for the slope safety factor is as follows:

[0072]

[0073] in, This represents the slope safety factor, which is dimensionless. A value greater than 1 indicates stability. This represents effective cohesion, measured in kPa, and is determined through a direct shear test. This represents the effective normal stress, in kPa. This represents the effective internal friction angle, determined through a triaxial test. Shear stress, in kPa;

[0074] The formulas for calculating the effective normal stress and the shear stress are as follows:

[0075]

[0076]

[0077] in, Indicates soil density. Indicates soil depth. Indicates the slope angle;

[0078] The specific formula for the increased safety factor of the root system is as follows:

[0079]

[0080] in, This indicates the safety factor due to the increased root system. This represents the root reinforcement coefficient, which depends on the vegetation type; for example, 0.5 is used for shrubs and 1.0 for trees. This indicates the root area ratio. That is, the ratio of the root system's cross-sectional area to the soil area. Indicates root depth. This represents the root distribution coefficient, which is dimensionless and typically ranges from 0.1 to 0.3. This indicates root density, measured through root sampling. This represents the reference root density, usually taken as 100 kg / m³.

[0081] The specific formula for the vegetation diversity index is as follows:

[0082]

[0083] in, This represents the vegetation diversity index; a higher value indicates better diversity. Indicates the number of species. Represents a species index. The proportion of species i is calculated as the ratio of the area covered by that species to the total area. This represents the diversity enhancement coefficient, which is dimensionless and typically ranges from 0.1 to 0.2.

[0084] In step S4.4, the vegetation configuration decision map is a two-dimensional decision matrix. The horizontal axis is the safety factor after vegetation reinforcement, and the vertical axis is the vegetation configuration diversity index. The slope condition is divided into nine regions, and each region corresponds to a specific vegetation configuration scheme.

[0085] like Figure 2 As shown, the vegetation configuration decision map specifically includes:

[0086] 1. High stability-high diversity areas, meaning the safety factor after vegetation reinforcement is ≥1.5 and the vegetation diversity index is ≥2.5, mainly consisting of ornamental plants such as flowers and landscape shrubs; 8-12 species; and 20-30% deep-rooted plants.

[0087] 2. High stability-medium diversity area, i.e., the safety factor after vegetation reinforcement is ≥1.5 and 1.5≤vegetation configuration diversity index<2.5, mixed configuration of ornamental plants and soil-stabilizing plants, 6-8 species, and deep-rooted plants accounting for 30-40%;

[0088] 3. High stability - low diversity areas, i.e., the safety factor after vegetation reinforcement is ≥1.5 and the vegetation configuration diversity index is <1.5. To increase diversity, introduce a variety of soil-stabilizing plants, with 4-6 species and deep-rooted plants accounting for 40-50%;

[0089] 4. Medium stability to high diversity areas, i.e., 1.2 ≤ safety factor after vegetation reinforcement < 1.5 and vegetation configuration diversity index ≥ 2.5, maintain diversity, increase the proportion of deep-rooted plants, with 7-10 species and 40-50% of deep-rooted plants;

[0090] 5. Medium stability-medium diversity zone, i.e., 1.2 ≤ safety factor after vegetation reinforcement < 1.5 and 1.5 ≤ vegetation configuration diversity index < 2.5, balanced configuration, combination of deep-rooted and shallow-rooted plants, 5-7 species, with deep-rooted plants accounting for 50-60%;

[0091] 6. Medium stability to low diversity areas, i.e., 1.2 ≤ safety factor after vegetation reinforcement < 1.5 and vegetation configuration diversity index < 1.5, focus on increasing deep-rooted plants, moderately improve diversity, with 4-6 species and deep-rooted plants accounting for 60-70%;

[0092] 7. Low stability-high diversity areas, i.e., the safety factor after vegetation reinforcement is <1.2 and the vegetation configuration diversity index is ≥2.5, with deep-rooted soil-stabilizing plants as the main species, maintaining necessary diversity, with 6-8 species and deep-rooted plants accounting for 70-80%;

[0093] 8. Low stability to medium diversity areas, i.e., the safety factor after vegetation reinforcement is <1.2 and 1.5≤vegetation configuration diversity index<2.5, focus on planting plants with strong soil-fixing ability, with 4-6 species and deep-rooted plants accounting for 80-90%;

[0094] 9. Low stability-low diversity areas, i.e., the safety factor after vegetation reinforcement is <1.2 and the vegetation configuration diversity index is <1.5, require emergency reinforcement, configuration of strong deep-rooted plants, 3-5 species, and deep-rooted plant ratio of 90-100%.

[0095] The improved moisture characteristic curve model is calculated based on the van Genuchten model, wherein the parameters of the van Genuchten model are corrected by introducing organic carbon content and clay content.

[0096] The specific formula for the improved moisture characteristic curve model is as follows:

[0097]

[0098] in, This indicates volumetric water content, which is the proportion of water volume in the total volume of the soil. This represents matrix suction, specifically the force with which soil particles attract water. This indicates residual moisture content, which is the minimum amount of water in the soil that cannot be utilized by plant roots. This indicates saturated water content, which is the water content when the soil pores are completely filled with water. , and These are model parameters used to fit the soil moisture characteristic curve;

[0099] Among them, parameters and The formula is as follows: (Corrected by organic carbon content and clay content)

[0100]

[0101]

[0102] in, For parameters The baseline value is set between 0.01 and 0.05. For parameters The baseline value is set between 1.2 and 1.8. and Describe the parameters of organic carbon and clay respectively. Correction factor, and Describe the parameters of organic carbon and clay respectively. Correction factor;

[0103] Among them, for parameters The correction factor is typically between 0.1 and 0.3, because organic carbon and clay have different effects on the environment. The impact on parameters is relatively significant; The correction factor is typically between 0.05 and 0.15, because organic carbon and clay have different effects on the environment. The impact is relatively small.

[0104] In step S5, the irrigation plan based on water content includes determining the irrigation threshold and the irrigation amount. The irrigation threshold is calculated based on field water holding capacity, irrigation coefficient and reference evapotranspiration, and the irrigation amount is calculated based on the current water content, root layer depth, area and wind speed.

[0105] The specific formula for the irrigation threshold is as follows:

[0106]

[0107] in, Indicates the irrigation threshold. The field water holding capacity is indicated by a pressure plate meter. This represents the evapotranspiration effect coefficient, which is dimensionless and ranges from 0.1 to 0.2. This represents the actual reference evapotranspiration calculated from meteorological data using the Penman-Monteith formula. This represents the baseline reference evapotranspiration, typically taken as 5 mm / day, but adjusted according to the local climate.

[0108] The specific formula for the irrigation amount is as follows:

[0109]

[0110] in, Indicates irrigation amount, This indicates the current volumetric moisture content. Indicates the depth of the root layer. Indicates the area to be irrigated. This represents the area-area airflow correction factor, dimensionless, ranging from 0.05 to 0.1. Indicates wind speed. This represents the reference wind speed, which is usually taken as 2 m / s.

[0111] The specific implementation plan for the ecological reconstruction project based on the above calculation results includes:

[0112] Phase 1: Preliminary Preparation and Site Survey (1-2 weeks):

[0113] On-site survey and sampling were conducted, with soil samples collected in a 20×20m grid. Basic parameters were measured, including pH value, bulk density, heavy metal content, and organic matter content. Laboratory analysis and calculations were performed, and the dosage of each additive was calculated according to the formula. A detailed construction ratio table was generated, and a construction plan for each area was developed.

[0114] Phase 2: Soil Profile Reconstruction and Improvement (2-3 weeks):

[0115] Construction is carried out in layers: bottom layer construction, middle layer improvement, and top layer laying. Bottom layer (sand and gravel layer): 0.4m thick sand and gravel is laid with a 2% drainage slope. Middle layer (improvement layer): quicklime, biochar, and heavy metal remediation agent are added according to the calculated amount. Top layer (vegetation layer): 0.25m thick nutrient topsoil is laid.

[0116] Phase 3: Vegetation Configuration and Planting (1-2 weeks):

[0117] The vegetation type of each area was determined according to the decision map, and the initial irrigation plan was implemented by combining mixed sowing and hole planting. Protective nets were set up to prevent soil erosion.

[0118] Phase Four: Monitoring and Maintenance (Long-Term)

[0119] Establish a monitoring system to collect vegetation growth data regularly, dynamically adjust maintenance plans and irrigation schedules, and supplement fertilizer application based on vegetation growth.

[0120] The examples described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. A method for ecological reconstruction by stripping topsoil and filling ditches in open-pit coal mines in karst areas, characterized in that: Includes the following steps: Step S1: Soil profile reconstruction is carried out using a three-layer backfill structure, and the amount of acid-base remediation agent added is calculated for soils with pH values ​​below the threshold. Step S2: Determine the amount of biochar to be added for soil remediation based on the relationship between soil bulk density and ideal soil bulk density; Step S3: Construct a heavy metal stability assessment model, calculate the heavy metal stability index, and determine the dosage of soil heavy metal pollution remediation agent; Step S4: Assess slope stability and, in conjunction with the vegetation configuration diversity index, calculate the safety factor and vegetation configuration scheme for slope ecological restoration. Step S5: Construct an improved moisture characteristic curve model to calculate soil volumetric water content, and formulate an irrigation plan based on the water content.

2. The method according to claim 1, characterized in that, In step S1, the three-layer backfill structure includes: a bottom layer, a middle layer, and a top layer; The bottom layer, 0.3-0.5m thick, consists of sand and gravel with a particle size of 5-20mm, and is used to enhance drainage capacity. The middle layer, 0.5-0.8m thick, is a mixture of original soil, acid and alkali remediation agents, biochar, and soil heavy metal pollution remediation agents, and is used to improve the chemical and physical properties of the soil. The top layer, 0.2-0.3m thick, consists of topsoil and is used to provide the nutrients and microbial environment required by plants.

3. The method according to claim 2, characterized in that, In step S1, the amount of acid-base remediation agent added takes into account soil buffering capacity, cation exchange capacity, and soil texture, and the specific formula is as follows: ； in, This indicates the amount of acid-base repair agent added, specifically the amount of slaked lime added. Indicates the bulk density of the middle soil layer. Indicates the thickness of the middle soil layer. Indicates the target pH value. This indicates the current soil pH value. This indicates soil buffering capacity, which is the soil's ability to resist pH changes. This represents the correction factor for cation exchange capacity. Indicates cation exchange capacity, This indicates the reference cation exchange capacity value. Indicates the texture correction factor. It indicates the clay content, which is the percentage of clay particles in the soil.

4. The method according to claim 3, characterized in that, In step S2, the specific formula for the amount of biochar added for soil remediation is as follows: ； in, Indicates the amount of biochar added. This represents a correction factor, which depends on the soil type. Indicates the current soil bulk density. Indicates the ideal soil bulk density. Indicates soil volume. The density coefficient represents the density of biochar, which is the ratio of the density of biochar to that of soil. This represents the influence coefficient of organic carbon. Indicates organic carbon content, This indicates the reference organic carbon content.

5. The method according to claim 4, characterized in that, The heavy metal stability index comprehensively considers the heavy metal weight, stable form concentration, total concentration, decay coefficient, and reference concentration. The dosage of the soil heavy metal pollution remediation agent includes parameters such as the remediation agent efficiency coefficient, heavy metal stability index, total heavy metal concentration, soil area, soil layer thickness, soil bulk density, and clay content, and the dosage of the remediation agent is adjusted by the clay adsorption coefficient.

6. The method according to claim 5, characterized in that, Step S4 specifically includes the following steps: Step S4.1: Calculate the slope safety factor, and calculate the safety factor increased by the root system considering the reinforcement effect of vegetation roots; Step S4.2: Add the slope safety factor and the root system increase safety factor to obtain the safety factor after vegetation reinforcement; Step S4.3: Calculate the vegetation configuration diversity index based on the Shannon-Wiener index; Step S4.4: Based on the safety factor and vegetation configuration diversity index after vegetation reinforcement, determine the specific vegetation configuration scheme through a predefined vegetation configuration decision map.

7. The method according to claim 6, characterized in that, In step S4.4, the vegetation configuration decision map is a two-dimensional decision matrix. The horizontal axis is the safety factor after vegetation reinforcement, and the vertical axis is the vegetation configuration diversity index. The slope condition is divided into nine regions, and each region corresponds to a specific vegetation configuration scheme.

8. The method according to claim 7, characterized in that, The improved moisture characteristic curve model is calculated based on the van Genuchten model, wherein the parameters of the van Genuchten model are corrected by introducing organic carbon content and clay content.

9. The method according to claim 8, characterized in that, In step S5, the irrigation plan based on water content includes determining the irrigation threshold and the irrigation amount. The irrigation threshold is calculated based on field water holding capacity, irrigation coefficient and reference evapotranspiration, and the irrigation amount is calculated based on the current water content, root layer depth, area and wind speed.

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