Large-volume pyrite slag in-situ curing and final covering structure and repairing method

Abstract

The invention belongs to the technical field of repairing of solid waste treatment and disposal, and particularly relates to a large-volume pyrite slag in-situ curing and final covering structure and a repairing method. The remediation method comprises the following steps: evaluating the waste residue mass in a project area, and evaluating the waste residue pollution stability; an original waste residue point in-situ curing method is adopted, and implementation is carried out by selecting a stabilizer and leaching engineering; an original waste residue point final covering method is adopted, and an anti-seepage layer is formed by laying an anti-seepage geotextile mold; according to the method, an ecological restoration method is adopted, soil stabilization treatment is carried out through a soil covering and backfilling method, and ecological restoration is carried out through nursery stock selection, soil selection and cultivation key points; therefore, a stable and efficient comprehensive treatment method for large-volume pyrite waste residues, which adapts to environmental factors such as local climate, terrain, soil and the like, is established.

Description

Technical Field

[0001] The present invention belongs to the technical field of restoration of solid waste treatment and disposal, and specifically relates to an in-situ solidification and final covering structure for large-volume pyrite slag and a restoration method. Background Art

[0002] A large amount of waste residue is produced during the mining of pyrite, which contains heavy metals such as arsenic, cadmium, and lead, causing serious harm to the surrounding environment and human health. Traditional treatment methods include ex situ landfill and resource utilization, but there are problems such as large land occupation, high cost, and secondary pollution risk. In the process of mineral development, due to the neglect of the protection of the ecological environment of the mine and the natural landscape of geological landforms, serious water pollution, serious vegetation destruction, and exposed rocks have occurred in some local areas. The surface vegetation is exposed to a large extent, and most of the vegetation is thatch, with few shrubs, and serious soil erosion. Therefore, in order to solve the above problems, a method combining centralized safe landfill of sulfide iron ore slag + on-site solidification treatment + final cover structure design + vegetation ecological restoration is adopted. Through these control measures, the pollution of the ecological environment of the surrounding areas caused by the random storage of residual waste slag and tailings can be effectively eliminated, and the desertification and rocky desertification of regional mountains caused by surface exposure can be alleviated. The historical environmental pollution and geological environmental problems can be solved, the regional water environment can be improved, the vegetation coverage of regional mountains can be restored, the water conservation and soil and water conservation functions can be restored, the local water quality and the drinking water safety of the surrounding people can be guaranteed, and the purpose of ecological protection and restoration of mountains, rivers, forests, fields, lakes and grasslands can be achieved.

[0003] To this end, the present invention establishes a large-volume pyrite slag in-situ solidification and final field covering structure and restoration method, adopts a treatment method combining in-situ solidification treatment + final field covering structure design + vegetation ecological restoration, which can remove the pollution caused by historical waste residues and cut off the migration path of pollutants in the waste residues. It is of great significance to improve the local water environment quality and improve the quality of downstream farmland soil, making up for the problems of insufficient resource utilization and secondary pollution risks. It can also solve the problem of heavy metal pollution in the basin, prevent the continuous harm of arsenic and cadmium waste residues to water and soil, effectively improve the local ecological environment, protect the health of the people, and maintain the environmental safety of the surrounding areas. Summary of the invention

[0004] The purpose of the present invention is to focus on solving the problem of heavy metal pollution left over from the history of iron sulfide mines, improve the water quality and environmental conditions in the project area, and prevent the pollution risk of surrounding agricultural land from increasing. By selecting the in-situ solidification method, the harmfulness of pyrite slag can be reduced, so that the slag can meet the requirements for landfill disposal after solidification treatment; by selecting the final covering method, the cost can be reduced and the covering layer material can be selected to ensure that the covering layer can effectively isolate pollutants and promote vegetation growth. It is of great significance to solve the problem of heavy metal pollution in the basin and prevent the continuous harm of arsenic and cadmium waste residues to water and soil.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A large-volume pyrite slag in-situ solidification and final field covering structure and repair method, comprising the following steps:

[0007] 1) Assess the volume of waste slag in the slag area to be repaired and conduct a waste slag pollution stability assessment;

[0008] The step 1) specifically includes the following steps: evaluating the volume of waste slag in the slag area to be repaired and the existence of slag piles and slag platforms, and sampling and testing the heavy metal indicators and pH value of the waste slag.

[0009] 2) Adopt the original waste slag point in-situ solidification method and leaching engineering, select the appropriate stabilizer according to the composition characteristics of the pyrite slag, and evenly add it to the slag, mix and stir, and finally compact it;

[0010] The step 2) specifically comprises the following steps:

[0011] 2.1) Soil leaching is performed using inorganic salt eluting agent ferric chloride;

[0012] 2.2) Use an excavator to dig again. When the digging depth is greater than 1m, use air drying to reduce the moisture content, and use professional crushing, screening and mixing equipment to achieve uniform mixing of waste residue and stabilizer;

[0013] 2.3) Finally, the mixture is compacted using a roller or a vibratory roller.

[0014] Preferably, in step 2.2), the components of the stabilizer include fly ash, calcium aluminoferrite, blast furnace slag, calcium sulfate, an alkaline activator and clay minerals, wherein the weight percentage of the clay minerals is 10-30%; the alkaline activator is one or more of caustic soda, silicates containing alkaline elements, and sulfates.

[0015] 3) Adopt the final covering method of the original waste residue point, and adopt slope repair, sewage diversion interception and drainage engineering, barrier engineering, and rainwater drainage system to achieve final covering;

[0016] The step 3) specifically comprises the following steps:

[0017] 3.1) The slope is trimmed by cutting and pressing the slope to form a drainage slope from high to low, and then HDPE membrane is laid on the trimmed slope. On this basis, a multi-layer structure of the covering layer is adopted, with the bottom layer being clay with poor permeability, the middle layer being nutrient soil or planting soil, and the surface layer being a vegetation layer for final coverage;

[0018] 3.2) Set up a drainage system at the bottom of the cover layer;

[0019] 3.3) Set up retaining wall on the side of drainage ditch.

[0020] Preferably, in step 3.2), the drainage system includes drainage ditches and diversion channels.

[0021] 4) Use soil backfilling and soil stabilization, select plants that are resistant to barrenness and drought, and adopt correct cultivation points to restore vegetation and biodiversity;

[0022] The step 4) specifically comprises the following steps:

[0023] 4.1) Soil stabilization treatment: Add lime binders and additives to the contaminated soil to react with the contaminated soil, change the physical and chemical properties of the soil, and form the soil into a stabilized product with dense structure, strong compression resistance and low permeability;

[0024] 4.2) Selection of seedlings: The plant configuration pattern adopts a combination of trees, shrubs and herbs;

[0025] 4.3) Planting: Take correct cultivation points to ensure the survival rate of trees.

[0026] Preferably, in step 4.1), the additive is one or both of organoclay and bentonite.

[0027] Preferably, in step 4.2), the plant configuration pattern is Robinia pseudoacacia + Amorpha fruticosa + Centipede grass, Robinia pseudoacacia and Amorpha fruticosa are planted in a 1:1 ratio, and the planting row spacing is 2m×2m.

[0028] Preferably, in step 4.3), the key points of cultivation are: when planting bare-root seedlings, first straighten the seedlings and put them in the pit, then fill the pit with fertilizer, and then backfill with soil; after backfilling half of the soil, gently lift the seedlings to stretch the roots to ensure that the roots of the trees are all facing downward; then fill the soil in layers and compact it, so that the trees are level with the original root necks, and the shrubs are 5cm to 10cm deeper than the original roots to ensure that the seedlings are rooted.

[0029] The beneficial effects of the present invention are:

[0030] 1. Save floor space: In-situ solidification and final covering can save a lot of land resources and reduce management costs.

[0031] 2. Reduce the risk of secondary pollution: Anti-seepage geomembrane can effectively prevent leachate leakage and reduce the risk of secondary pollution.

[0032] 3. Improve ecological benefits: Ecological restoration can restore vegetation coverage and improve land utilization. After the project is implemented, the slag and sedimentation ponds left over from the sulfide iron ore will be cleaned up and the ecology restored, which can restore vegetation in the damaged area and reuse the land; at the same time, it can enhance the water conservation capacity of the storage site, alleviate scouring, eliminate the safety hazards of soil erosion, and effectively improve the ecological environment.

[0033] 4. Improve environmental benefits: Through treatment, the waste residues left over from historical mines can be solved, pollution sources can be effectively controlled, and the exposed state of waste residues containing arsenic, cadmium, and lead can be solved. Heavy metals such as arsenic, cadmium, and lead in the waste residues can be prevented from being transferred into the downstream surface water or soil after years of exposure to the sun and rain, thus avoiding the spread of pollution and reducing the risk of heavy metal migration. It can effectively improve the water environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of the repair method of the present invention.

[0035] Figure 2 This is a partial diagram of the treatment area implemented by the repair method of Example 1 of the present invention, wherein 1-treatment area, 201-slag platform I, 202-slag platform II, 203-slag platform III, 301-drainage ditch I, 302-drainage ditch II, 303-drainage ditch III, 4-diversion channel, 5-river channel.

[0036] Figure 3 This is a slope modification diagram of Example 1 of the present invention, wherein 2-slag platform, 6-mountain, 7-slope cutting area, 701-original slope surface, 702-slope surface after slope cutting, and 8-slope pressing area.

[0037] Figure 4 This is a cross-sectional view of drainage ditch I in embodiment 1 of the present invention.

[0038] Figure 5 This is a plan view of the diversion channel of Example 1 of the present invention.

[0039] Figure 6 The present invention is a process flow chart of the soil backfilling method and soil stabilization technology according to Example 1 of the present invention. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0041] Example 1

[0042] Take the restoration of the “historical slag pollution area of ​​a sulfide iron mine in Benxi City” as an example:

[0043] like Figure 1 As shown, a large-volume pyrite slag in-situ solidification and final field covering structure and repair method includes the following steps:

[0044] 1) Waste residue treatment is carried out according to the region. Through the preliminary investigation and experimental data and relevant information collection, on-site measurements are carried out to draw an assessment map for waste residue treatment. There are 3 slag platforms in the project area. The slopes of each slag platform are exposed. Most of the vegetation that was once planted has died (the coverage rate is less than 3%), and there are obvious gullies on the surface. The rapid screening data of waste residue show that the waste residue of the slag platform is severely and extremely severely acidified, and arsenic, lead, copper and zinc exceed the standard, and the excess multiples are 0.5-1.3, 0.1-4.4, 0.8-8.0 and 0.03-0.7 times respectively.

[0045] 2) Adopt the original waste residue point in-situ solidification method and soil leaching technology, first use inorganic salt leaching agent ferric chloride for soil leaching, the leaching technology changes the physical, chemical and toxicological properties of the waste, so that the waste is solidified or stabilized, acid-base neutralization and other treatments to reduce, mitigate or eliminate the harmfulness of the waste itself; then use an excavator to dig, when the excavation depth is greater than 1m, the water content of the waste residue increases, and the water content is reduced by air drying and other methods, and professional crushing, screening and mixing equipment are used to achieve uniform mixing of the waste residue and stabilizer. The stabilizer is mainly composed of fly ash, calcium aluminoferrite, blast furnace slag, calcium sulfate and alkaline activator (caustic alkali, silicate containing alkaline elements, sulfate or one or more), and in order to enhance the adsorption of heavy metal pollutants, 10-30% of clay minerals are added; finally, use equipment such as rollers or vibrating rollers to compact the mixture to improve the density and strength of the solidified body and reduce water penetration and pollutant diffusion.

[0046] 3) Adopt the final covering method of the original waste slag point

[0047] 3.1) The slope is trimmed by cutting and pressing the slope to form a drainage slope from high to low. After the slope is cut, the slope of each slag platform is below 35°, and a step slope needs to be formed. The height of each step is not more than 10m, and the width of the step is 4-6m. After the slope is cut in the treatment area, the earthwork is piled at the bottom of the original slope, and the slope is cut and the foot of the slope is pressed. The earthwork volume is balanced on the spot: the slope surface and the step platform are filled with pit-shaped soil after the slope is cut. Then, HDPE film is laid on the trimmed slope to block rainwater that infiltrates the waste rock pile; on this basis, a multi-layer structure of the covering layer is adopted, with the bottom layer being clay with poor permeability, the middle layer being nutrient soil or planting soil, and the surface layer being a vegetation layer, for final coverage to ensure that the covering layer can effectively isolate pollutants and promote vegetation growth.

[0048] 3.2) Drainage system is set up at the bottom of the covering layer, such as drainage ditch, diversion channel (used to guide water flow to flow smoothly into the downstream river), etc. The drainage ditch is made of mortar masonry, with an expansion joint every 20m, and 20mm asphalt hemp fiber is used in the joint. Figure 4The upper opening size of drainage ditch I is 2.5m, the lower opening size is 1.5m, and the ditch depth is 1.5m, which meets the requirements of water collection and drainage. Figure 5 The slope protection on both sides of the diversion channel is made of mortar-laid rubble stone, and the bottom of the diversion channel is made of dry-laid rubble stone with a thickness of 0.5m.

[0049] 3.3) A 2m high retaining wall is set up on the side of drainage ditch II close to the slag platform.

[0050] 4) Use soil backfilling and soil stabilization

[0051] 4.1) Technical process and key points:

[0052] Technical process flow chart Figure 6 .

[0053] 4.2) Key points for seedling survival

[0054] a. Soil stabilization treatment: Add lime binders and additives (such as organoclay, bentonite, etc.) to the contaminated soil to make them react with the contaminated soil, change the physical and chemical properties of the soil, and form the soil into a stabilized product with dense structure, strong compression resistance and low permeability, thereby reducing the mobility of pollutants in the soil.

[0055] b. Covering with foreign soil: Use hole-shaped foreign soil and cover all the foreign soil in the hole.

[0056] c. Selection of seedlings: The selection of seedlings focuses on diversity. The plant configuration mode adopts a combination of trees, shrubs and herbs. The specific plant configuration mode is Robinia pseudoacacia + Amorpha fruticosa + Centipede grass. Amorpha fruticosa and Robinia pseudoacacia are planted at a ratio of 1:1, and the planting row spacing is 2m×2m. Centipede grass can absorb soil contaminated by arsenic. It generally grows in soil containing 50-4030mg / kg of arsenic, and can even grow normally in slag containing up to 23400mg / kg of arsenic. The enriched arsenic content can reach 1-2%. Centipede grass likes to grow in warm, moist and semi-shady environments, so consider matching it with shrubs and trees for shading.

[0057] d. Key points for planting: When planting bare-root seedlings, first straighten the seedlings and place them in the pit, then fill the pit with an appropriate amount of fertilizer and backfill with soil. After backfilling half of the soil, gently lift the seedlings to stretch the roots, so that the roots of the trees are all facing downward. Then fill the soil in layers and tamp it down. The tree and the original root neck should be level, and the shrubs should be 5cm to 10cm deeper than the original roots to ensure that the seedlings take root. During the planting process, attention should be paid to the uprightness of the seedlings and the compaction process after the soil is cultivated. Unqualified seedlings should be replanted.

[0058] 5) In order to give full play to the long-term effectiveness of vegetation greening measures, the surrounding polluted areas are blocked by backfilling, and a stable and efficient comprehensive treatment method for large-scale pyrite waste slag that is compatible with local climate, topography, soil and other environmental factors is established by combining vegetation greening and engineering measures.

Claims

1. A large volume of pyrite slag in-situ solidification and final field covering structure and repair method, characterized in that: The steps include: 1) Assess the volume of waste slag in the slag area to be repaired and conduct a waste slag pollution stability assessment; 2) Adopt the original waste slag point in-situ solidification method and leaching engineering, select the appropriate stabilizer according to the composition characteristics of the pyrite slag, and evenly add it to the slag, mix and stir, and finally compact it; 3) Adopt the final covering method of the original waste residue point, and adopt slope repair, sewage diversion interception and drainage engineering, barrier engineering, and rainwater drainage system to achieve final covering; 4) Use soil backfilling and soil stabilization, select plants that are resistant to barrenness and drought, and adopt correct cultivation points to restore vegetation and biodiversity.

2. A large-volume pyrite slag in-situ solidification and final covering structure and repair method according to claim 1, characterized in that: The step 1) specifically includes the following steps: evaluating the volume of waste slag in the slag area to be repaired and the existence of slag piles and slag platforms, and sampling and testing the heavy metal indicators and pH value of the waste slag.

3. A large-volume pyrite slag in-situ solidification and final covering structure and repair method according to claim 1, characterized in that: The step 2) specifically comprises the following steps: 2.1) Soil leaching is performed using inorganic salt eluting agent ferric chloride; 2.2) Use an excavator to dig again. When the digging depth is greater than 1m, use air drying to reduce the moisture content, and use professional crushing, screening and mixing equipment to achieve uniform mixing of waste residue and stabilizer; 2.3) Finally, the mixture is compacted using a roller or a vibratory roller.

4. A large-volume pyrite slag in-situ solidification and final covering structure and repair method according to claim 3, characterized in that: In step 2.2), the stabilizer comprises fly ash, calcium aluminoferrite, blast furnace slag, calcium sulfate, alkaline activator and clay mineral, wherein the weight percentage of clay mineral is 10-30%; the alkaline activator is one or more of caustic soda, silicate containing alkaline elements and sulfate.

5. A large volume of pyrite slag in-situ solidification and final covering structure and repair method according to claim 1, characterized in that: The step 3) specifically comprises the following steps: 3.1) The slope is trimmed by cutting and pressing the slope to form a drainage slope from high to low, and then HDPE membrane is laid on the trimmed slope. On this basis, a multi-layer structure of the covering layer is adopted, with the bottom layer being clay with poor permeability, the middle layer being nutrient soil or planting soil, and the surface layer being a vegetation layer for final coverage; 3.2) Set up a drainage system at the bottom of the cover layer; 3.3) Set up retaining wall on the side of drainage ditch.

6. A large-volume pyrite slag in-situ solidification and final covering structure and repair method according to claim 5, characterized in that: In step 3.2), the drainage system includes drainage ditches and diversion channels.

7. A large-volume pyrite slag in-situ solidification and final covering structure and repair method according to claim 1, characterized in that: The step 4) specifically comprises the following steps: 4.1) Soil stabilization treatment: Add lime binders and additives to the contaminated soil to react with the contaminated soil, change the physical and chemical properties of the soil, and form the soil into a stabilized product with dense structure, strong compression resistance and low permeability; 4.2) Selection of seedlings: The plant configuration pattern adopts a combination of trees, shrubs and herbs; 4.3) Planting: Take correct cultivation points to ensure the survival rate of trees.

8. A large volume of pyrite slag in-situ solidification and final covering structure and repair method according to claim 7, characterized in that: In step 4.1), the additive is one or both of organoclay and bentonite.

9. A large volume of pyrite slag in-situ solidification and final covering structure and repair method according to claim 7, characterized in that: In step 4.2), the plant configuration pattern is Robinia pseudoacacia + Amorpha fruticosa + Centipede grass, Robinia pseudoacacia and Amorpha fruticosa are planted in a 1:1 ratio, and the planting row spacing is 2m×2m.

10. A large volume of pyrite slag in-situ solidification and final covering structure and repair method according to claim 7, characterized in that: In step 4.3), the key points of cultivation are: when planting bare-root seedlings, first straighten the seedlings and put them in the pit, then fill the pit with fertilizer, and then backfill with soil; after backfilling half of the soil, gently lift the seedlings to stretch the roots to ensure that the roots of the trees are all facing downward; then fill the soil in layers and compact it, so that the trees are level with the original root necks, and the shrubs are 5cm to 10cm deeper than the original roots to ensure that the seedlings are rooted.

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