Ecological Restoration Structures and Applications of Open-Pit Mines

Abstract

This invention provides an ecological restoration structure and application for open-pit mines, specifically relating to the field of solid waste treatment technology. The ecological restoration structure for open-pit mines includes, from bottom to top, a foundation stratum, an impermeable layer, a backfill area, a barrier layer, and a vegetation restoration layer; wherein the backfill area is filled with flotation tailings from a metal mine. The ecological restoration structure for open-pit mines provided by this invention uses an impermeable layer and a barrier layer to seal the backfill area, preventing rainwater from entering and effectively isolating the flotation tailings. Using flotation tailings as a matrix material to fill the backfill area not only completes the ecological restoration of the abandoned mine pit but also utilizes the resources of this solid waste.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment technology, and in particular to an ecological restoration structure and application for open-pit mines. Background Technology

[0002] Historically, the unregulated open-pit mining has left behind numerous abandoned pits, severely damaging the surrounding landscape and posing significant safety hazards such as landslides and mudslides, necessitating ecological restoration. Backfilling these pits is a common ecological restoration method, requiring large quantities of excavated soil. Directly using surrounding natural rock and soil would inevitably cause further ecological damage. China currently has over 2,000 tailings ponds, holding approximately 6 billion tons of tailings, with about 300 million tons added annually. Tailings storage and disposal require vast amounts of land and pose significant safety risks.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] One of the objectives of this invention is to provide an ecological restoration structure for open-pit mines, which aims to solve the problems of topography and safety near mines in the prior art, as well as the land waste and safety issues caused by tailings ponds.

[0005] The second objective of this invention is to provide the application of the above-mentioned open-pit mine ecological restoration structure in open-pit mine ecological restoration.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides an ecological restoration structure for open-pit mines, the restoration structure comprising, from bottom to top, a foundation stratum, an impermeable layer, a backfill zone, a barrier layer, and a vegetation restoration layer.

[0008] The open-pit mine includes mines formed by open-pit mining of metal mines, building material mines, or chemical mines; the backfill area is filled with metal flotation tailings.

[0009] Furthermore, the metal flotation tailings are general industrial solid waste.

[0010] The average particle size of the metal flotation tailings is 0.02mm-0.5mm, and the mass percentage of particles with a particle size ≤0.074mm is 60-85%.

[0011] Furthermore, the moisture content of the metal flotation tailings is 10%-15%.

[0012] The flotation tailings are filled into the backfill area by layered compaction and backfilling.

[0013] Furthermore, a leachate drainage pipe is provided within the backfill area.

[0014] Furthermore, the impermeable layer is formed by laying a first tailings paste made of metal flotation tailings and a first flocculant, with a thickness of 75cm-85cm.

[0015] The moisture content of the first tailings paste is 25%-35%.

[0016] Furthermore, the barrier layer is used to seal the backfill area and is mainly composed of a second tailings paste made of metal flotation tailings and a second flocculant, with a thickness of 30cm-50cm.

[0017] The second tailings paste has a water content of 25%-35%.

[0018] Furthermore, the first flocculant or the second flocculant is independently selected from at least one of polyacrylamide, aluminum salt polymer and iron salt polymer.

[0019] Furthermore, the vegetation restoration layer is mainly composed of a mixture of metal flotation tailings, organic matter, and water-retaining agents.

[0020] The moisture content of the metal flotation tailings is 15%-20%.

[0021] The organic matter includes at least one of urban riverbed sediment, sewage treatment sediment, and crushed agricultural waste.

[0022] The water-retaining agent includes an acrylamide-acrylate copolymer crosslinker.

[0023] Furthermore, the thickness of the vegetation restoration layer is 20cm-100cm.

[0024] A second aspect of the present invention provides the application of the aforementioned open-pit mine ecological restoration structure in open-pit mine ecological restoration.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] This invention provides an ecological restoration structure for open-pit mines, which uses an impermeable layer and a barrier layer to seal the backfill area, preventing rainwater from entering and effectively blocking metal flotation tailings. By using metal flotation tailings as the matrix material to fill the backfill area, not only is the ecological restoration of the abandoned mine completed, but the resource utilization of this solid waste, tailings, is also achieved.

[0027] The application of the open-pit ecological restoration structure provided by this invention in the ecological restoration of open-pit mines offers a low-cost and effective restoration method, promotes the development of tailings solid waste treatment, solves the concerns of mining, and is suitable for large-scale promotion and use. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 A schematic diagram of the open-pit mining ecological restoration structure provided by the present invention.

[0030] Diagram: 1-Basic strata; 2-Imperible layer; 3-Backfill area; 4-Barrier layer; 5-Vegetation restoration layer. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0032] The first aspect of the present invention provides an ecological restoration structure for open-pit mines, the restoration structure comprising, from bottom to top, a foundation stratum, an impermeable layer, a backfill zone, a barrier layer, and a vegetation restoration layer.

[0033] The open-pit mine includes mines formed by open-pit mining of metal mines, building material mines, or chemical mines; the backfill area is filled with metal flotation tailings.

[0034] Figure 1 The schematic diagram of the open-pit mine ecological restoration structure provided by the present invention includes a foundation stratum 1, an impermeable layer 2, a backfill area 3, a barrier layer 4, and a vegetation restoration layer 5, extending upwards from the bottom of the mine. During the ecological restoration of the open-pit mine, the foundation stratum 1 of the abandoned mine is first cleaned. After cleaning, the foundation stratum 1 is a continuous and stable stratum.

[0035] The impermeable layer 2 is installed on the surface of the foundation stratum 1, completely covering it to prevent liquid from the flotation tailings in the backfill area 3 from seeping downwards into the foundation stratum 1 and contaminating the groundwater. The water-tightening effect of the impermeable layer 2 should be comparable to that of the natural foundation stratum with a saturated permeability coefficient < 1 × 10⁻⁶. -5The density is approximately 1000 cm / s, and the thickness of the foundation stratum is greater than 0.75m. The pit area formed by the impermeable layer 2 forms a backfill area 3, which is used to fill flotation tailings. A barrier layer 4 is set above the backfill area 3 to prevent surface water from entering the backfill area 3 and reduce the amount of leachate generated in the backfill area. The barrier layer 4 is adjacent to the impermeable layer 2 at the top of the pit area formed by the impermeable layer 2. The barrier layer 4 and the impermeable layer 2 enclose a closed space called the backfill area 3, which spatially prevents the flotation tailings in the backfill area 3 from polluting the surface and underground soil.

[0036] In some embodiments of the present invention, the top surface of the barrier layer 4 and the portion bordering the ground surface are provided with intercepting drainage ditches to achieve separation of clean and dirty water.

[0037] In some embodiments of the present invention, a leachate drainage pipe is provided at the bottom of the backfill area 3 to drain the water in the flotation tailings.

[0038] A vegetation restoration layer 5 is provided above the barrier layer 4 for planting vegetation and rebuilding a plant community that is in harmony with the surrounding natural landscape.

[0039] This invention provides an ecological restoration structure for open-pit mines. An impermeable layer 2 and a barrier layer 4 are used to seal the backfill area 3, preventing rainwater from entering and effectively isolating flotation tailings. Using flotation tailings as a matrix material to fill the backfill area 3 not only completes the ecological restoration of the abandoned mine but also utilizes tailings as a solid waste resource.

[0040] Furthermore, the flotation tailings are general industrial solid waste. The general industrial solid waste is tailings of Class I general industrial solid waste. It should be noted that the flotation tailings used in this invention cannot be hazardous waste, and this invention is not applicable to the ecological restoration of mining pits containing hazardous waste.

[0041] The metal flotation tailings have a particle size of 0.02mm-0.5mm, with particles ≤0.074mm accounting for 60-85% of the total mass. Metal flotation tailings within this range represent tailings generated during the flotation process in metal mines. Within this particle size range, an adsorbed water film forms on the surface of the tailings, exhibiting flocculation. Upon reaching a certain concentration, a flocculent network is formed, increasing the viscosity of the slurry. After adding a flocculant, a paste is formed, exhibiting excellent seepage prevention properties and providing good seepage control and barrier effects. Therefore, it serves as a primary material for seepage prevention and barrier layers. In the backfill area, the fine particles of metal flotation tailings result in smaller voids, allowing for denser backfilling and reducing the risk of excessive future ground subsidence. In the vegetation restoration layer, the fine particles of metal flotation tailings are closer to the particle size of natural soil, facilitating vegetation restoration.

[0042] Furthermore, the moisture content of the metal flotation tailings is 10%-15%. When the moisture content of the flotation tailings is greater than 15%, the flotation tailings are filtered down to this moisture content range before backfilling or mixing. The moisture content of the tailings is limited to 10%-15% because a lower moisture content reduces the generation of leachate and prevents significant future settling.

[0043] The metal flotation tailings were filled into the backfill area using a layered compaction backfilling method. This method ensured the compaction degree of the backfill area and improved the strength of the open-pit ecological restoration structure.

[0044] Furthermore, the impermeable layer is formed by laying a first tailings paste made of metal flotation tailings and a first flocculant, with a thickness of 75cm-85cm. In some embodiments of the present invention, the thickness of the impermeable layer is typically, but not limited to, 70cm, 72cm, 74cm, 76cm, 78cm, or 85cm.

[0045] The moisture content of the first tailings paste is 25%-35%, which is similar to that of natural clay. If the moisture content is below 25%, it is sandy soil, and its seepage prevention performance is reduced. If the moisture content is above 35%, it is wet tailings and cannot form a paste. In some embodiments of the present invention, the moisture content of the first tailings paste is typically, but not limited to, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, or 35%.

[0046] Furthermore, the barrier layer is used to seal the backfill area and is mainly composed of a compacted and laid second tailings paste made of metal flotation tailings and a second flocculant, with a thickness of 30cm-50cm. In some embodiments of the present invention, the thickness of the barrier layer is typically, but not limited to, 30cm, 35cm, 40cm, 45cm, or 50cm.

[0047] The second tailings paste has a moisture content of 25%-35%. The second tailings paste is used to form a barrier layer. In some embodiments of the invention, the moisture content of the second tailings paste is typically, but not limited to, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, or 35%.

[0048] The present invention uses the first tailings paste and the second tailings paste as the seepage prevention layer and the barrier layer respectively, mainly by utilizing the seepage prevention performance of the fine metal flotation tailings itself; at the same time, the flocculant added to the tailings paste can further enhance the seepage prevention performance.

[0049] Furthermore, the first flocculant or the second flocculant is independently selected from at least one of polyacrylamide, aluminum salt polymer and iron salt polymer.

[0050] Further, the independent addition amount of the first flocculant or the second flocculant is 10 mg / kg to 30 mg / kg. In some embodiments of the present invention, the independent addition amount of the first flocculant or the second flocculant is typically, but not limited to, 10 mg / kg, 15 mg / kg, 20 mg / kg, 25 mg / kg or 30 mg / kg.

[0051] Furthermore, the vegetation restoration layer is mainly composed of a mixture of metal flotation tailings, organic matter, and a water-retaining agent. In some embodiments of the present invention, the flotation tailings, organic matter, and water-retaining agent are mixed in a mass ratio of 50:30:20.

[0052] The moisture content of the metal flotation tailings is 15%-20%.

[0053] The organic matter includes at least one of urban riverbed sediment, sewage treatment sediment, and crushed agricultural waste.

[0054] The water-retaining agent includes an acrylamide-acrylate copolymer crosslinker.

[0055] Furthermore, the thickness of the vegetation restoration layer is 20cm-100cm, within which it is conducive to the expansion and growth of the vegetation root system. Depending on the local climate, the vegetation restoration layer may use native, suitable species, mixed grass seeds, or trees and shrubs to rebuild a plant community that harmonizes with the surrounding natural landscape.

[0056] A second aspect of the present invention provides the application of the aforementioned open-pit mine ecological restoration structure in open-pit mine ecological restoration.

[0057] The application of the open-pit ecological restoration structure provided by this invention in the ecological restoration of open-pit mines offers a low-cost and effective restoration method, promotes the development of tailings solid waste treatment, solves the concerns of mining, and is suitable for large-scale promotion and use.

[0058] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other. Unless otherwise specified, all raw materials used in the present invention are commercially available.

[0059] Example 1

[0060] This embodiment provides a brick and tile excavation waste pit (40m long × 30m wide × 10m deep) located in Heilongjiang Province. A copper mine is located within 10 kilometers of the waste pit, and its copper tailings are classified as Class I general industrial solid waste. This invention utilizes copper tailings for the ecological remediation of the brick and tile excavation waste pit, including the following steps:

[0061] (1) Cleaning the foundation strata. Cleaning the foundation strata of the mining pit mainly involves cleaning and leveling the abandoned mining pit.

[0062] (2) Laying the seepage barrier layer. Copper tailings mixed with 20 mg / kg flocculant, concentrated to a paste with a water content of 35%, are laid on the foundation stratum as a seepage barrier layer, 0.75 m thick, with a permeability coefficient less than 1 × 10⁻⁶. -5 cm / s.

[0063] (3) Constructing the backfill area. The copper tailings are filtered to a moisture content of approximately 15%, then compacted in layers before backfilling. Approximately 9000 m³ of tailings from a brick and tile excavation pit are being comprehensively utilized. 3 .

[0064] (4) Laying a barrier layer. Mix copper tailings with 20 mg / kg flocculant and thicken to a paste with a water content of 35%. Lay the paste on the foundation stratum as a barrier layer with a thickness of 50 cm. At the same time, construct drainage ditches around the perimeter and on the top surface.

[0065] (5) Laying a vegetation restoration layer. Mix tailings (filtered to a moisture content of 20%), crushed agricultural waste, and water-retaining agent in a ratio of 50:30:20 to form a vegetation restoration layer, with a thickness of 1m. Then plant Masson pine trees.

[0066] Example 2

[0067] This embodiment provides a sand and stone quarrying waste pit (70m long × 50m wide × 9m deep) located in Hulunbuir, Inner Mongolia. A copper-molybdenum mine is located within 20 kilometers of the waste pit, and its copper-molybdenum tailings are classified as Class I general industrial solid waste. This invention utilizes copper-molybdenum tailings for ecological restoration of the sand and stone quarrying waste pit, including the following steps:

[0068] (1) Cleaning the foundation strata. Cleaning the foundation strata of the mining pit mainly involves cleaning and leveling the abandoned mining pit.

[0069] (2) Laying the seepage barrier layer. Copper-molybdenum tailings mixed with 25 mg / kg flocculant, concentrated to a paste with a water content of 35%, are laid on the foundation stratum as a seepage barrier layer, 0.75 m thick, with a permeability coefficient less than 1 × 10⁻⁶. -5 cm / s.

[0070] (3) Constructing the backfill area. The tailings are filtered to a moisture content of approximately 15%, then compacted in layers before backfilling. Approximately 27,000 m³ of tailings from a sand and stone quarry waste pit are being comprehensively utilized. 3 .

[0071] (4) Laying a barrier layer. Mix copper-molybdenum tailings with 25 mg / kg flocculant, thicken to a paste with a water content of 35%, and lay it on the foundation stratum as a barrier layer with a thickness of 30 cm. At the same time, construct drainage ditches around the perimeter and on the top surface.

[0072] (5) Laying a vegetation restoration layer. A vegetation restoration layer is prepared by mixing tailings (filtered to a moisture content of 20%), domestic sewage treatment sediment, and a water-retaining agent in a ratio of 50:30:20, and laid to a thickness of 40 cm. Then, a mixture of *Stipa krousi*, *Leymus chinensis*, and *Leymus chinensis* seeds is sown at a density of 25 kg / hm². 2 .

[0073] Example 3

[0074] This embodiment provides a historical abandoned mining pit (80m long × 70m wide × 0m deep) of an iron ore mine, located in Hefei, Anhui Province. The tailings dump of the iron ore mine is located nearby, and the iron ore flotation tailings generated are classified as Class I general industrial solid waste. This invention utilizes iron ore tailings for ecological restoration of the abandoned mining pit, including the following steps:

[0075] (1) Cleaning the foundation strata. Cleaning the foundation strata of the mining pit mainly involves cleaning and leveling the abandoned mining pit.

[0076] (2) Laying the seepage barrier layer. Iron ore tailings mixed with 25 mg / kg flocculant, concentrated to a paste with a water content of 30%, are laid on the foundation stratum as a seepage barrier layer, 0.75 m thick, with a permeability coefficient less than 1 × 10⁻⁶. -5 cm / s.

[0077] (3) Constructing the backfill area. The tailings were filtered to a moisture content of approximately 15%, then compacted in layers and backfilled. Approximately 89,600 m³ of tailings from the iron ore mine's abandoned pit were utilized for comprehensive utilization. 3 .

[0078] (4) Laying a barrier layer. Mix iron ore tailings with 25 mg / kg flocculant, thicken to a paste with a water content of 30%, and lay it on the base stratum as a barrier layer with a thickness of 30 cm. At the same time, construct drainage ditches around the perimeter and on the top surface.

[0079] (5) Laying a vegetation restoration layer. Mix tailings (filtered to a moisture content of 20%), crushed agricultural waste, and water-retaining agent in a ratio of 50:30:20 to form a vegetation restoration layer, with a thickness of 80cm. Then plant arborescent fir trees.

[0080] Example 4

[0081] This embodiment provides a historical abandoned mining pit (70m long × 50m wide × 15m deep) of a copper mine, located in Yunnan Province. The tailings dump of the copper mine is located nearby, and the copper mine tailings generated are classified as Class I general industrial solid waste. This invention utilizes copper mine tailings for ecological restoration of the abandoned mining pit, including the following steps:

[0082] (1) Cleaning the foundation strata. Cleaning the foundation strata of the mining pit mainly involves cleaning and leveling the abandoned mining pit.

[0083] (2) Laying the seepage barrier layer. Copper mine tailings mixed with 25 mg / kg flocculant, concentrated to a paste with a water content of 25%, are laid on the foundation stratum as a seepage barrier layer, 0.75 m thick, with a permeability coefficient less than 1 × 10⁻⁶. -5 cm / s.

[0084] (3) Constructing the backfill area. The tailings were filtered to a moisture content of approximately 15%, then compacted in layers and backfilled. Approximately 42,000 m³ of tailings from the copper mine's abandoned mining area were utilized for comprehensive utilization. 3 .

[0085] (4) Laying a barrier layer. Mix copper mine tailings with 25 mg / kg flocculant and thicken to a paste with a water content of 25%. Lay the paste on the foundation stratum as a barrier layer with a thickness of 30 cm. At the same time, construct drainage ditches around the perimeter and on the top surface.

[0086] (5) Laying a vegetation restoration layer. Mix tailings (filtered to a moisture content of 20%), domestic sewage treatment sediment, and water-retaining agent in a ratio of 50:30:20 to form a vegetation restoration layer, with a thickness of 60cm. Then plant slash pine trees.

[0087] Example 5

[0088] This embodiment provides a quartzite waste pit (100m long × 40m wide × 25m deep) located in Bayannur, Inner Mongolia. An iron mine is located within 20 kilometers of the waste pit, and its flotation iron tailings are classified as Class I general industrial solid waste. This invention utilizes iron tailings for ecological remediation of the quartzite waste pit, including the following steps:

[0089] (1) Cleaning the foundation strata. Cleaning the foundation strata of the mining pit mainly involves cleaning and leveling the abandoned mining pit.

[0090] (2) Laying the seepage barrier layer. Iron tailings mixed with 25 mg / kg flocculant, concentrated to a paste with a water content of 28%, are laid on the foundation stratum as a seepage barrier layer, 0.75 m thick, with a permeability coefficient less than 1 × 10⁻⁶. -5 cm / s.

[0091] (3) Constructing the backfill area. The copper-molybdenum tailings were filtered to a moisture content of approximately 15%, then compacted and backfilled in layers. Approximately 80,000 m³ of tailings from this quartzite waste pit were utilized for comprehensive utilization. 3 .

[0092] (4) Laying a barrier layer. Mix copper-molybdenum tailings with 25 mg / kg flocculant, thicken to a paste with a water content of 28%, and lay it on the foundation stratum as a barrier layer with a thickness of 30 cm. At the same time, construct drainage ditches around the perimeter and on the top surface.

[0093] (5) Laying a vegetation restoration layer. Mix tailings (filtered to a moisture content of 20%), domestic sewage treatment sediment, and water-retaining agent in a ratio of 50:30:20 to form a vegetation restoration layer, with a thickness of 40cm. Then sow grass seeds such as sheepgrass at a density of 25kg / hm². 2 .

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ecological restoration structure for open-pit mines, characterized in that, The repair structure comprises, from bottom to top, a foundation stratum, an impermeable layer, a backfill zone, a barrier layer, and a vegetation restoration layer; The open-pit mine is a mine formed by open-pit mining of metal mines, building material mines or chemical mines; The backfill area is filled with metal flotation tailings; The impermeable layer is formed by compacting and laying a first tailings paste, which is made of metal flotation tailings and a first flocculant, with a thickness of 75cm-85cm; the moisture content of the first tailings paste is 25%-35%. The barrier layer is used to seal the backfill area. It is mainly composed of metal flotation tailings and a second tailings paste made of a second flocculant, compacted and laid with a thickness of 30cm-50cm. The moisture content of the second tailings paste is 25%-35%.

2. The open-pit mining ecological restoration structure according to claim 1, characterized in that, The metal flotation tailings are general industrial solid waste; The metal flotation tailings have a particle size of 0.02mm-0.5mm, and the mass percentage of the metal flotation tailings with a particle size ≤0.074mm is 60%-85%.

3. The open-pit mining ecological restoration structure according to claim 2, characterized in that, The moisture content of the metal flotation tailings is 10%-15%; The flotation tailings were filled into the backfill area using a layered compaction and backfilling method.

4. The open-pit mining ecological restoration structure according to claim 1, characterized in that, A leachate drainage pipe is installed in the backfill area.

5. The open-pit mining ecological restoration structure according to claim 1, characterized in that, The first flocculant or the second flocculant is independently selected from at least one of polyacrylamide, aluminum salt polymer and iron salt polymer.

6. The open-pit mining ecological restoration structure according to claim 2, characterized in that, The vegetation restoration layer is mainly composed of a mixture of metal flotation tailings, organic matter and water-retaining agent; The moisture content of the metal flotation tailings is 15%-20%; The organic matter includes at least one of urban riverbed sediment, domestic sewage treatment sediment, and crushed agricultural waste. The water-retaining agent includes an acrylamide-acrylate copolymer crosslinker.

7. The open-pit mining ecological restoration structure according to claim 1, characterized in that, The thickness of the vegetation restoration layer is 20cm-100cm.

8. The application of the open-pit mine ecological restoration structure according to any one of claims 1-7 in the ecological restoration of open-pit mines.

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