A dry tailings recovery method

Abstract

The application discloses a dry mining method for a tailing pond, which comprises a mining I area, a mining II area and a mining III area for final mining, and adopts the following technical scheme to mine and discharge the sand: the tailing pond is divided into areas, blocks and strips, and the sand is taken from each area layer by layer and strip by strip. During the mining process, the beach trend of the mining process is strictly controlled, and a water diversion ditch is arranged at the junction of the areas to discharge floodwater, so that the flood discharge pressure is reduced; the sand is mined layer by layer, and the slope ratio of the mining slope is controlled during the mining process, so that the safety and stability of the mining slope are improved; meanwhile, the safety of the artificial mining protection structure in the mining protection area is improved, the transportation efficiency of the tailing pond sand mining and discharge is improved, and the storage site problem of the sand drying is solved.

Description

Technical Field

[0001] This invention relates to the field of tailings dam disposal engineering technology, specifically a dry tailings dam mining method. Background Technology

[0002] Tailings, as a type of artificial secondary resource, are mined differently from primary mineral resources. Generally, tailings are mined in open-pit mines. Because the bearing capacity of accumulated tailings is low and uneven, the bearing capacity of tailings and rainfall must be considered when selecting a mining method. In particular, the safety and stability of the slope and the requirements for flood discharge capacity during the mining process must be considered.

[0003] Tailings recovery mainly involves two methods: water-based and dry-based. Water-based recovery, a more mature method, includes dredger-based recovery and hydraulic flushing, typically requiring additional filter press facilities. Dry-based recovery generally uses excavators and transportation systems. Generally, dredger-based recovery offers relatively better safety and causes less damage to the tailings dam and drainage system, but it requires significant initial investment, necessitates frequent replenishment of water within the dam, and has higher management and operational costs. Hydraulic flushing recovery is relatively simple, but demands higher skill levels from operators. To recover tailings, an artificial swamp area needs to be created at the tailings dam's tail, which poses a greater risk during the rainy season or when rainfall is heavy. Excavator-based recovery with a transportation system is simpler, less labor-intensive, and easier to manage for safety. Truck transport is widely used due to its mobility and ease of movement.

[0004] Studies have shown that, considering that most tailings ponds currently being mined have been out of use or closed for many years, with hardened surfaces and a certain bearing capacity, dry mining is simpler and more flexible than tailings water mining. It eliminates the need for dewatering and filtration, and makes drainage pressure and slope control easier, resulting in a higher safety factor. However, dry mining also presents several challenges: when extracting sand from closed tailings ponds with areas requiring special protection, it faces difficulties such as large-scale, unregulated mining during a single operation, high pressure on drainage within the pond, insufficient stability during the mining process, and a high risk of structural damage to structures within the pond. Summary of the Invention

[0005] The purpose of this invention is to provide a dry tailings dam mining method. This method involves dividing the tailings dam into zones, blocks, and strips, and then extracting sand layer by layer in each zone. During the mining process, the orientation of the tailings surface is strictly controlled, and drainage ditches are installed at the boundary areas to reduce flooding pressure. Layered mining is employed, and the slope ratio of the mining slopes is controlled to increase their safety and stability. Simultaneously, artificial mining protection structures are used to ensure the structural safety of the mining protection zone, thus addressing the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A dry tailings dam mining method includes mining zone I, mining zone II, and the final mining zone III. The mining zones and blocks utilize sand extraction strips, sand extraction access roads, in-dam transport roads, and drainage pits in the sand extraction pits, and employ the following technical solutions for sand extraction and dam disposal; the specific steps are as follows:

[0008] S1: During the tailings dam mining process, the sand extraction strip has a plane width of 20m, a vertical layer thickness of 1.5m, and a slope ratio of 1:4 for sand extraction.

[0009] S2: The top width of the sand extraction access road is 5.0m. The access road is made of crushed stone and compacted soil, and the slope ratio on both sides of the access road is 1:2.

[0010] S3: During the sand extraction process, tailings piles or other materials are strictly prohibited from being formed within 20m in front of the tailings dam and within 10m around the top of the tailings pit.

[0011] S4: Mining Zone I is excavated one layer more than Mining Zone II to create flood control storage capacity;

[0012] S5: The surface of mining area I always slopes towards the reservoir by ≥1%; the surface of mining area II always slopes towards the drainage ditch by ≥3‰, in order to ensure that the surface is dry during the sand extraction process.

[0013] S6: On the plane of mining area I, sand is extracted strip by strip from east to west. On the plane of mining area II, sand is extracted in the order of mining area II block A → mining area II block B → mining area II block C → mining area II block D.

[0014] S7: Before mining, a buffer pool is excavated around the overflow tower. During mining, a drainage pit is excavated to connect the sand mining pit to the buffer pool, so that seepage water and rainwater can be clarified and discharged through the buffer pool. Several geotextiles are installed in sections of the drainage pit for filtration and blocking. A grid is installed around the overflow tower to fix the geotextiles for filtration and blocking. A return water pool is set outside the tailings dam downstream of the flood discharge system.

[0015] S8: Safety warning signs shall be set up along the flood discharge structure during the sand extraction process. The drainage pit, drainage pipe, transfer well and buffer pool of the sand extraction pit shall be protected within a 15m range. The sand extraction operation shall be carried out by manual mining and water gun mining. The slope ratio of the sand extraction side slope around the overflow tower shall be 1:4.

[0016] S9: During the operation of mining zones I and II, protection work shall be carried out for mining zone III. The total slope ratio of the sand extraction slope at the junction of mining zones I and II with mining zone III shall be ≥1:5, and the slope step height shall be determined according to the actual situation. During the mining process, settlement and displacement monitoring shall be carried out on the structures in mining zone III to determine the thickness of the tailings accumulation body under the newly built plant and auxiliary facilities in the reservoir area, the stress diffusion angle of the stratum, and the horizontal transmission distance of the foundation stress in the tailings accumulation body.

[0017] Furthermore, the sand extraction area within the silo is divided into three mining zones: Zone I, Zone II, and Zone III. Zone II is further subdivided into Zone II Block A, Zone II Block B, Zone II Block C, and Zone II Block D. Zone III is the area for the brick factory buildings and auxiliary facilities. After Zones I and II are completed, Zone III will be dry-mined layer by layer, and the factory buildings and auxiliary facilities will be dismantled.

[0018] Furthermore, the specific method in S6 is as follows:

[0019] S601: First, mine two mining layers from mining zone I to the beach in a vertical direction, and then mine the No. 3 mining layer in mining zone I. Maintain the height difference between mining zone I and mining zone II.

[0020] S602: In mining zone II, one layer is mined vertically in the order of blocks A, B, C and D, while mining zone I and mining zone II maintain a mining height difference.

[0021] S603: In the vertical direction, mining zone I will mine another mining layer of one mining height, up to mining layer No. 3 in mining zone I. At this time, mining zone I and mining zone II will maintain a height difference of two mining heights.

[0022] S604: In mining zone II, one layer is mined vertically in the order of blocks A, B, C and D. Mining zone I and mining zone II maintain a height difference in mining depth until mining reaches the original surface of the reservoir bottom.

[0023] Furthermore, the horizontal safety distance between newly built factory buildings and auxiliary facilities in the reservoir area and the sand mining slope shall be ≥40m.

[0024] Furthermore, the sand extraction area generally covers the area enclosed by the initial dam and the reservoir boundary in the horizontal direction, and generally covers the current beach surface to the original surface of the reservoir bottom in the vertical direction.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. The present invention provides a dry tailings dam mining method, which can use excavators, bulldozers and dump trucks to extract and transport tailings from the tailings dam. It has the advantages of being simple and flexible and does not require pressure filtration and dewatering.

[0027] 2. The present invention provides a dry tailings dam mining method, which adopts a zoned mining system, wherein the mining zone 1 is always mined one layer more than the mining zone 2, thus meeting the requirements of the tailings dam for flood control capacity during the mining process.

[0028] 3. The dry tailings dam mining method provided by the present invention maintains the lowest elevation of the overflow zone of the overflow tower throughout the mining process, directs the surface runoff of the dam area down the slope to the area where the overflow tower is located, and achieves the purpose of drainage in the tailings dam by using the existing drainage system in the tailings dam.

[0029] 4. The present invention provides a dry tailings dam mining method, which solves the problem of tailings drying site by drying tailings in the sand mining strip, and at the same time reduces the tailings mining process and solves the cost of tailings dam sand extraction and storage.

[0030] 5. The present invention provides a dry tailings dam mining method, which uses the mined tailings for brick making by constructing new factory buildings and auxiliary facilities in the mining zone III within the tailings dam. This solves the problem of land resource occupation for the site selection of new factory buildings and auxiliary facilities, reduces the transportation distance of tailings from the tailings dam, and lowers the transportation cost of tailings from the dam.

[0031] 6. The dry tailings mining method provided by this invention uses the tailings extracted from the tailings pond for brick making, which not only turns waste into treasure and alleviates resource and environmental pressure, but also has high social and environmental benefits, in line with the overall goal of "green mines and waste-free mines" currently being advocated. Attached Figure Description

[0032] Figure 1 This is a plan view of the tailings dam layout according to the present invention;

[0033] Figure 2 This is a cross-sectional structural diagram of the present invention.

[0034] Figure 3 This is a cross-sectional structural diagram of the BB section of the present invention;

[0035] Figure 4 This is a cross-sectional structural diagram of the sand extraction and transportation access road of the present invention;

[0036] Figure 5 This is a cross-sectional view of the ring-shaped transport road structure of the present invention;

[0037] Figure 6 This is a cross-sectional view of the weak foundation treatment structure for the ring road transportation road of the present invention;

[0038] Figure 7 This is a schematic diagram of the overflow tower flood discharge system of the present invention;

[0039] Figure 8 This is a schematic diagram of the CC section structure of the overflow tower flood discharge system of the present invention;

[0040] Figure 9 This is a schematic diagram of the geogrid-fixed geotextile filter barrier structure of the present invention.

[0041] In the diagram: 1. Sand extraction strip; 2. Sand extraction access road; 3. In-storage transport road; 4. Ring transport road; 5. Drainage pit for sand extraction; 6. Overflow tower; 7. Drainage pipe; 8. Transfer well; 9. Geogrid fixed geotextile filter barrier; 10. Paved bamboo fence and steel plate; 11. Buffer pool; 13. Geotextile. Detailed Implementation

[0042] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In this embodiment of the invention: a dry tailings dam mining method includes mining zone I, mining zone II, and mining zone III, which is the last mining zone. The mining zones and blocks are designed using sand extraction strips 1, sand extraction access roads 2, in-dam transportation roads 3, and drainage pits 5. The design principle is as follows:

[0044] 1) In this embodiment of the invention, the sand extraction area within the tailings dam is divided into three mining zones: Zone I, Zone II, and Zone III. Zone II is further subdivided into Zone II A, Zone II B, Zone II C, and Zone II D. Zone III (protected area) is the area where the brick factory buildings and auxiliary facilities are located. After the mining in Zones I and II is completed, Zone III will be dry-mined layer by layer, and the factory buildings and auxiliary facilities will be dismantled. The overall sand extraction area within the tailings dam covers the area enclosed by the initial dam and the dam edge line, and vertically in the opposite direction, it covers the current beach surface to the original surface of the dam bottom. After the sand extraction is completely completed, the main dam, initial dam, rockfill dam, and flood discharge structures will be dismantled to completely restore the original topography and landform.

[0045] 2) During the mining process, to meet the requirements of flood control capacity, first, two mining layers are mined vertically from Mining Zone I to the beach surface, up to Mining Layer No. 3 in Mining Zone I, maintaining a height difference of two mining heights between Mining Zone I and Mining Zone II; then, one layer is mined vertically in Mining Zone II according to the order of Blocks A, B, C, and D, maintaining a height difference of one mining height between Mining Zone I and Mining Zone II; then, another mining layer of mining height is mined vertically in Mining Zone I, up to Mining Layer No. 3 in Mining Zone I, maintaining a height difference of two mining heights between Mining Zone I and Mining Zone II; then, one layer is mined vertically in Mining Zone II according to the order of Blocks A, B, C, and D, maintaining a height difference of one mining height between Mining Zone I and Mining Zone II, until mining reaches the original surface of the reservoir bottom.

[0046] 3) In this embodiment, during the tailings dam mining process, the sand extraction strip 1 is 20m wide, with a vertical layer thickness of 1.5m, and the slope ratio of the sand extraction strip 1 is 1:4 to prevent slope collapse. The top width of the sand extraction access road 2 is 5.0m, and the access road is constructed with compacted gravel and soil (compaction degree to ensure safe vehicle passage), with a slope ratio of 1:2 on both sides. During the sand extraction process, tailings piles or other materials are strictly prohibited within 20m in front of the tailings dam and within 10m around the top of the tailings extraction pit. To ensure safety during the flood season, mining area I should always be excavated one layer more than mining area II to form the necessary flood control capacity. To ensure surface dryness during the sand extraction process, the surface of mining area I should always slope towards the reservoir at a rate of ≥1%; the surface of mining area II should always slope towards the drainage ditch at a rate of ≥3‰.

[0047] 4) Taking into account the requirements of drainage and orderly operation, sand will be extracted in strips from east to west in the mining area I, and in the mining area II, sand will be extracted in the following order: Block A of mining area II → Block B of mining area II → Block C of mining area II → Block D of mining area II. To prevent tailings leakage and environmental problems, a buffer pool 11 will be excavated around the overflow tower before mining. During mining, a drainage pit 5 will be excavated to connect the sand mining pit to the buffer pool 11, so that seepage water and rainwater can be clarified and discharged through the buffer pool 11. The drainage pit 5 should be divided into sections with several grids fixed to geotextile filter barriers 9 for filtration and blocking. The overflow tower 6 will be equipped with grids fixed to geotextile filter barriers 9 around the tower body. A return water pool will be set up outside the tailings dam downstream of the flood discharge system for further clarification of external drainage. Safety warning signs should always be set up along the flood discharge structure during the sand extraction process, and machinery and transportation equipment are strictly prohibited from crossing it. The area within 15m around the sand extraction pit, drainage pit 5, drainage pipe 7, transfer well 8, and buffer pool 11 should be specially protected. Sand extraction operations should be carried out by manual mining and water gun extraction. The slope ratio of the sand extraction side slope around the overflow tower 6 should be 1:4.

[0048] 5) During the operation of mining zones I and II, protection work should be carried out in mining zone III. The total slope ratio of the sand extraction slope at the junction of mining zones I and II with mining zone III should be ≥1:5, and the slope step height should be determined according to the actual situation. When the slope height of mining zone III is >3m when it is connected to other mining zones, a special safety construction plan must be prepared and approved by experts. Settlement and displacement monitoring of structures in mining zone III is required during the mining process. Based on the preliminary survey, the thickness of the tailings accumulation body under the newly built plant and auxiliary facilities in the reservoir area, the angle of stress diffusion in the strata, and the horizontal transmission distance of foundation stress in the tailings accumulation body should be determined. For safety reasons, the horizontal safety distance between the newly built plant and auxiliary facilities in the reservoir area and the sand extraction slope should be ≥40m.

[0049] Based on the above principles, the specific steps of this embodiment of the invention are as follows:

[0050] S1: During the tailings dam mining process, the sand extraction strip 1 has a plane width of 20m, a vertical layer thickness of 1.5m, and a slope ratio of 1:4 for sand extraction to prevent slope collapse.

[0051] S2: Sand extraction access road 2 has a top width of 5.0m. The access road is constructed with crushed stone and compacted soil (the degree of compaction is based on meeting the requirements for safe vehicle passage). The slope ratio on both sides of the access road is 1:2.

[0052] S3: During the sand extraction process, tailings piles or other materials are strictly prohibited from being formed within 20m in front of the tailings dam and within 10m around the top of the tailings pit.

[0053] S4: To ensure safety during the flood season, mining zone I should always be excavated one layer more than mining zone II to form the necessary flood control capacity;

[0054] S5: To ensure the surface remains dry during the sand extraction process, the surface of mining area I shall always slope inward toward the reservoir by ≥1%; the surface of mining area II shall always slope inward toward the drainage ditch by ≥3‰.

[0055] S6: Taking into account the requirements of drainage and orderly operation, sand is extracted from the east to the west in the plane of mining area I, and sand is extracted in the following order in the plane of mining area II: Block A of mining area II → Block B of mining area II → Block C of mining area II → Block D of mining area II.

[0056] S7: To prevent tailings leakage from causing environmental problems, a buffer pool 11 is excavated around the overflow tower 6 before mining. During the mining process, a drainage pit 5 is excavated to connect with the buffer pool 11, so that seepage water and rainwater can be clarified and discharged through the buffer pool 11. Several geotextiles 13 are installed in sections of the drainage pit 5 for filtration and blocking. A grid is installed around the overflow tower 6 to fix the geotextile filter 9. A return water pool is set outside the tailings dam downstream of the flood discharge system to further clarify the external drainage.

[0057] S8: Safety warning signs shall be set up along the flood discharge structure during the sand extraction process, and mechanical and transportation equipment shall be strictly prohibited from crossing it; the sand extraction pit drainage pit 5, drainage pipe 7, transfer well 8 and buffer pool 11 shall be protected within a 15m range around the perimeter. The sand extraction operation shall be carried out by manual mining and water gun mining. The slope ratio of the sand extraction side slope around the overflow tower 6 shall be 1:4.

[0058] S9: During the operation of mining zones I and II, protection work is carried out on mining zone III. The total slope ratio of the sand extraction slope at the junction of mining zones I and II with mining zone III is ≥1:5, and the slope step height is determined according to the actual situation. During the mining process, settlement and displacement monitoring are carried out on the structures in mining zone III to determine the thickness of the tailings accumulation body under the newly built plant and auxiliary facilities in the reservoir area, the stress diffusion angle of the stratum, and the horizontal transmission distance of the foundation stress in the tailings accumulation body. For safety reasons, in the actual application of this invention in a ferrous metal mine tailings dam, the horizontal safety distance between the newly built plant and auxiliary facilities in the reservoir area and the sand extraction slope is ≥40m.

[0059] The dry tailings mining method provided in this invention was applied to the tailings disposal project of a large-scale ferrous metallurgical mine. This invention uses strip-shaped tailings dry mining to dispose of tailings from a previously closed tailings dam. By drying the tailings in the strip, the problem of excessively high moisture content in some tailings during the mining process was solved. At the same time, by arranging a sand extraction access road 2 along the sand extraction strip 1, the transportation efficiency of tailings from the tailings dam was greatly improved. By constructing a brick-making factory and other auxiliary facilities on the relatively stable tailings surface within the tailings dam, the problem of land occupation for new factory buildings was solved, saving economic costs associated with tailings mining and disposal, and improving the economic benefits of tailings brick making.

[0060] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A dry tailings dam mining method, characterized in that, The mining area includes mining zone I, mining zone II, and mining zone III, which is the last mining zone. The mining zones and blocks are constructed by using sand extraction strips (1), sand extraction access roads (2), in-storage transport roads (3), and drainage pits (5) for sand extraction. The following technical solutions are adopted for sand extraction and storage: S1: During the tailings dam mining process, the sand extraction strip (1) has a plane width of 20m, a vertical layer thickness of 1.5m, and a mining pit slope ratio of 1:4 for sand extraction; S2: Sand extraction access road (2) has a top width of 5.0m. The access road is made of crushed stone and compacted soil. The slope ratio on both sides of the access road is 1:

2. S3: During the sand extraction process, tailings piles or other materials are strictly prohibited from being formed within 20m in front of the tailings dam and within 10m around the top of the tailings pit. S4: Mining Zone I is excavated one layer more than Mining Zone II to create flood control storage capacity; S5: The surface of mining area I always slopes towards the reservoir at a rate of ≥1%; the surface of mining area II always slopes towards the drainage ditch at a rate of ≥3‰, in order to ensure that the surface is dry during the sand extraction process. S6: On the plane of mining zone I, sand is extracted strip by strip from east to west. On the plane of mining zone II, sand is extracted in the order of mining zone II block A → mining zone II block B → mining zone II block C → mining zone II block D. S7: Before mining, a buffer pool (11) is excavated around the overflow tower (6). During the mining process, a sand pit drainage channel (5) is excavated to connect with the buffer pool (11), so that seepage water and rainwater are clarified and discharged through the buffer pool (11). Several geotextiles (13) are set in sections of the sand pit drainage channel (5) for filtering and blocking. A grid is set around the overflow tower (6) to fix the geotextile filter barrier (9). A return water pool is set outside the tailings dam downstream of the flood discharge system. S8: Safety warning signs are set up along the flood discharge structure during the sand extraction process. The sand extraction pit drainage pit (5), drainage pipe (7), transfer well (8) and buffer pool (11) are protected within a 15m range. The sand extraction operation is carried out by manual mining and water gun mining. The slope ratio of the sand extraction side slope around the overflow tower (6) is 1:

4. S9: During the operation of mining zones I and II, protection work shall be carried out for mining zone III. The total slope ratio of the sand extraction slope at the junction of mining zones I and II with mining zone III shall be ≥1:5, and the slope step height shall be determined according to the actual situation. During the mining process, settlement and displacement monitoring shall be carried out on the structures in mining zone III to determine the thickness of the tailings accumulation body under the newly built plant and auxiliary facilities in the reservoir area, the stress diffusion angle of the stratum, and the horizontal transmission distance of the foundation stress in the tailings accumulation body.

2. The dry tailings dam mining method as described in claim 1, characterized in that: The sand extraction area within the silo is divided into three mining zones: Zone I, Zone II, and Zone III. Zone II is further subdivided into Zone II Block A, Zone II Block B, Zone II Block C, and Zone II Block D. Zone III is the area for the brick factory buildings and auxiliary facilities. After Zones I and II are completed, Zone III will be dry-mined layer by layer, and the factory buildings and auxiliary facilities will be dismantled.

3. The dry tailings dam mining method as described in claim 1, characterized in that: The specific method in S6 is as follows: S601: First, mine two mining layers from mining zone I to the beach in a vertical direction, and then mine the No. 3 mining layer in mining zone I. Maintain the height difference between mining zone I and mining zone II. S602: In mining zone II, one layer is mined vertically in the order of blocks A, B, C and D, while mining zone I and mining zone II maintain a mining height difference. S603: In the vertical direction, mining zone I will mine another mining layer of one mining height, up to mining layer No. 3 in mining zone I. At this time, mining zone I and mining zone II will maintain a height difference of two mining heights. S604: In mining zone II, one layer is mined vertically in the order of blocks A, B, C and D. Mining zone I and mining zone II maintain a height difference in mining depth until mining reaches the original surface of the reservoir bottom.

4. The dry tailings dam mining method as described in claim 1, characterized in that: The horizontal safety distance between newly built factory buildings and auxiliary facilities in the reservoir area and the sand mining slope shall be ≥40m.

5. A dry tailings dam mining method as described in claim 2, characterized in that, The sand extraction area generally covers the area enclosed by the initial dam and the reservoir boundary in the horizontal direction, and generally covers the current beach surface to the original surface of the reservoir bottom in the vertical direction.

Images