An ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas and its construction method

Abstract

The present invention relates to the technical field of governance of abandoned pyrite mining areas, and particularly relates to an ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas and a construction method thereof, including a passivation layer formed on the surface layer of the waste rock pile body in the abandoned pyrite mining area, a shotcrete layer with wire mesh arranged on the surface of the passivation layer, lattice beams arranged on the surface of the shotcrete layer with wire mesh, and a soil-covered greening layer arranged in the grid space of the lattice beams; fixing network anchor pipes and slope-fixing anchor pipes are arranged in the waste rock pile, the wire mesh of the shotcrete layer with wire mesh is fixed on the waste rock pile slope through the fixing network anchor pipes and the slope-fixing anchor pipes, and the lattice beams are fixed on the waste rock pile slope through the slope-fixing anchor pipes. The present invention can in-situ seal the waste rock pile body in the abandoned pyrite mining area through the passivation layer, the shotcrete layer with wire mesh, the slope-fixing anchor pipes and the lattice beams, greatly reduce pyrite acid mine drainage at the source, and the overall structure has long-term stability and long-term functionality. At the same time, the use of the soil-covered greening layer can better achieve ecological reconstruction.

Description

Technical Field

[0001] The present invention relates to the technical field of governance of abandoned pyrite mining areas, and particularly relates to an ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas and a construction method thereof. Background Art

[0002] The reserves of sulfur ore in China are very rich, mainly pyrite. During the mining and smelting of pyrite, its chemical pollution has a very serious impact on and damage to the geological environment. Moreover, after it is closed and abandoned, the slag, waste rock, and waste residue left over from mining and smelting are piled up disorderly and exposed in the mining area. These waste rock and soil have the characteristics of being loose and highly permeable. Rainwater infiltration and surface water flow through the pile body. Under the combined action of air and microbial bacteria, a large amount of strongly acidic mine wastewater (AMD) will be formed, seriously polluting the surrounding groundwater and soil environment.

[0003] The slag, waste rock, and soil left over from old abandoned pyrite mining areas for many years are mostly contaminated Class II solid wastes under long-term natural mixed stacking. It is necessary to carry out anti-seepage treatment on their storage and disposal sites. Under the leaching of atmospheric precipitation, the AMD generated by the exposed waste rock piles will cause a certain degree of pollution to the regional water and soil environment. Combining the formation principle and environment of acidic wastewater, greatly reducing the entry of water sources into the pile body and creating an anaerobic or oxygen-isolated and bacteriostatic pile body environment is one of the ideas to solve the core problem; in the process of ecological restoration and governance of waste rock piles in mining areas, there is a close connection between the slope stability of waste rock piles and engineering safety. Therefore, how to effectively reduce AMD, efficiently carry out ecological restoration, and ensure the slope stability of the waste rock pile body is particularly prominent.

[0004] Currently, the most effective method to reduce the entry of water into the slope body is to carry out anti-seepage treatment on the surface layer of the slope. The materials used in the anti-seepage technology for slope surfaces are mainly compacted clay anti-seepage, concrete anti-seepage, high-density polyethylene geomembrane anti-seepage, and sodium bentonite waterproof blanket (GCL) anti-seepage. However, when applied to specific engineering practices, various anti-seepage processes have various problems due to conditions such as site, source materials, and construction. For example, when using the method of spraying concrete for anti-seepage, cracks are likely to occur, resulting in a poor anti-seepage effect; when using membrane materials for anti-seepage, rolling stones sometimes occur on the slope, and the sharp corners of the rolling stones on the slope surface cause damage to the membrane materials, and it is necessary to replace the anti-seepage membrane over a large area again, which is neither economical nor convenient; for the anti-seepage of slopes based on clay materials, a large amount of clay is required, and for abandoned mining areas (mountainous areas) lacking clay, there are huge difficulties in the procurement and transportation of materials.

[0005] In view of the problems existing in the current slope anti-seepage structures or technologies and focusing on the treatment of AMD in pyrite mining areas, it is necessary to design a composite ecological anti-seepage structure suitable for waste rock piles in abandoned pyrite mining areas to achieve source control and reduction, reduce water infiltration, create an anaerobic and antibacterial pile environment, and ensure the slope stability of the waste rock pile. Summary of the Invention

[0006] The purpose of the present invention is to provide an ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas and its construction method, which has strong comprehensiveness, high suitability, and can be engineered on a large scale, can greatly reduce acidic pyrite wastewater from the source, and the overall structure has long-term stability and long-lasting functionality.

[0007] To achieve the above purpose, the technical solution of the present invention is an ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas, including a passivation layer formed on the surface layer of the waste rock pile in the abandoned pyrite mining area, a shotcrete layer with wire mesh arranged on the surface of the passivation layer, lattice beams arranged on the surface of the shotcrete layer with wire mesh, and a soil-covered greening layer arranged in the grid space of the lattice beams; fixing network anchor pipes and slope-fixing anchor pipes are arranged in the waste rock pile, the wire mesh of the shotcrete layer with wire mesh is fixed on the waste rock pile slope through the fixing network anchor pipes and the slope-fixing anchor pipes, and the lattice beams are fixed on the waste rock pile slope through the slope-fixing anchor pipes.

[0008] Furthermore, the passivation layer is formed on the surface layer of the waste rock pile by injecting a repair agent into the waste rock pile through the fixing network anchor pipes and the slope-fixing anchor pipes.

[0009] Even further, both the fixing network anchor pipes and the slope-fixing anchor pipes include anchor pipes and anchor rods arranged in the anchor pipes. The anchor pipes include a tail non-opening section, a densified opening section, a normal opening section, and a head non-opening closed section connected in sequence. The anchor rods are arranged along the central axis of the anchor pipes, and the anchor head end of the anchor rod is fixed to the tip of the head non-opening closed section, and the anchor tail end of the anchor rod is connected to the anchor tail end of the tail non-opening section.

[0010] Furthermore, a three-dimensional geogrid mat one is laid between the passivation layer and the shotcrete layer with wire mesh. The four sides of the three-dimensional geogrid mat one are fixed by nails, and the middle is fixed by the fixing network anchor pipes.

[0011] Furthermore, a root separation layer is arranged between the soil-covered greening layer and the shotcrete layer with wire mesh.

[0012] Furthermore, the soil-covered greening layer includes soil and vegetation planted in the soil, and a three-dimensional geogrid mat two is laid on the surface of the soil.

[0013] Furthermore, a berm is arranged on the waste rock pile slope, and intercepting and drainage ditches are arranged on the berm and at the four boundaries of the waste rock pile and are interconnected.

[0014] Furthermore, a drain pipe is provided in the lattice beam at the bottom of the greening soil layer, and an anti-filter measure is provided at the pipe orifice of the drain pipe.

[0015] Further, the shotcrete layer with wire mesh is made of C25 concrete, and 5 kg of cement-based permeable crystalline waterproof material is incorporated into each cubic meter of concrete.

[0016] The present invention also provides a construction method for an ecological anti-seepage structure of a waste rock pile in an abandoned pyrite mining area, including the following steps:

[0017] 1) Install fixed-network anchor pipes and slope-fixing anchor pipes on the slope of the waste rock pile in the abandoned pyrite mining area;

[0018] 2) First inject a repair agent into the waste rock pile through the fixed-network anchor pipes and slope-fixing anchor pipes to form a passivation layer on the surface of the waste rock pile, and then inject cement mortar and cure it until the design strength is reached;

[0019] 3) Lay a three-dimensional geogrid mat on the surface of the passivation layer. The four sides of the three-dimensional geogrid mat are fixed by nails, and the middle is fixed by the fixed-network anchor pipes;

[0020] 4) Lay a wire mesh on the surface of the three-dimensional geogrid mat and fix it by the fixed-network anchor pipes and slope-fixing anchor pipes, and then spray and cure it until the design strength is reached to form a shotcrete layer with wire mesh;

[0021] 5) Construct lattice beams and horse paths on the surface of the shotcrete layer with wire mesh, fix the lattice beams to the slope-fixing anchor pipes, construct intercepting and draining ditches on the horse paths and at the boundaries around the waste rock pile, and connect the intercepting and draining ditches;

[0022] 6) Cover the lattice space of the lattice beam with soil and plant vegetation to form a soil-covered greening layer.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention forms a water control, passivation, oxygen control, and antibacterial environment on the surface layer of the pyrite waste rock pile through the passivation layer and the shotcrete layer with wire mesh, greatly reducing the amount of acidic wastewater generated by leaching the pyrite waste rock pile from the source, and the overall structure has long-term stability;

[0025] (2) The present invention combines the lattice beam and the slope-fixing anchor pipes to anchor the slope of the waste rock pile. At the same time, the passivation layer formed around the anchor pipes also effectively reduces the possibility of the anchor structure being corroded by acidic substances, ensuring the long-term stability of the waste rock pile;

[0026] (3) The present invention adopts in-situ repair technology, which can solve the problems of large amount of pyrite soil, secondary pollution caused by off-site disposal, and high engineering cost;

[0027] (4) The present invention adopts a source control method to effectively control the waste rock pile, which is one of the sources of pyrite acidic wastewater. Compared with the end treatment method, it has better effects and is more economical.

[0028] (5) The present invention particularly considers the connection structure between the anti-seepage layer and the ecological layer, and better realizes ecological reconstruction. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0030] Figure 1 It is a schematic diagram of the ecological anti-seepage structure of the waste rock pile in the abandoned pyrite mining area provided by the embodiment of the present invention;

[0031] Figure 2 It is a detailed drawing of the drain pipe in the lattice beam at the bottom of the greening soil covering layer;

[0032] Figure 3 It is a schematic diagram of the shotcrete layer with wire mesh;

[0033] Figure 4 It is a schematic diagram of the structure of the anchor pipe rod provided by the embodiment of the present invention;

[0034] Figure 5 For Figure 4 The enlarged schematic diagram at position E in

[0035] Figure 6 For Figure 4 The F-F cross-sectional view of

[0036] In the figure: 1. Waste rock pile body in the abandoned pyrite mining area; 2. Passivation layer; 3. Three-dimensional geogrid mat one; 4. Shotcrete layer with wire mesh; 41. Wire mesh; 42. Concrete; 5. Anchor pipe for fixing the net; 6. Lattice beam; 7. Anchor pipe for slope stabilization; 8. Soil covering and greening layer; 9. Root separation layer; 10. Three-dimensional geogrid mat two; 11. Access road; 12. Intercepting and drainage ditch; 13. Drain pipe; 14. First steel bar for fixing the pipe; 15. Anchor pipe; 16. Anchor rod; 17. Grouting hole; 18. Steel pressing plate; 19. Steel bar for fixing the rod; 20. Slurry; 21. Second steel bar for fixing the pipe; A. Tail non-opening section; B. Dense opening section; C. Normal opening section; D. Head non-opening and closed section. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Embodiment 1

[0038] This embodiment provides an ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas, including a passivation layer 2 formed on the surface layer of the waste rock pile body 1 in the abandoned pyrite mining area, a shotcrete layer with wire mesh 4 arranged on the surface of the passivation layer 2, a lattice beam 6 arranged on the surface of the shotcrete layer with wire mesh 4, and a soil-covered greening layer 8 arranged in the grid space of the lattice beam 6; fixed net anchor pipes 5 and slope-fixing anchor pipes 7 are arranged in the waste rock pile. The wire mesh 41 of the shotcrete layer with wire mesh 4 is fixed to the waste rock pile slope through the fixed net anchor pipes 5 and the slope-fixing anchor pipes 7, and the lattice beam 6 is fixed to the waste rock pile slope through the slope-fixing anchor pipes 7.

[0039] In this embodiment, by forming a passivation layer 2 on the surface layer of the waste rock pile body 1 in the abandoned pyrite mining area, it has the functions of passivation, oxygen control, and antibacterial, which can protect the anchoring structure; the shotcrete layer with wire mesh 4 is used for anti-seepage and slope protection of the surface layer of the waste rock pile, which can greatly reduce the infiltration amount of water bodies, and jointly form an anti-seepage, oxygen-isolating, and antibacterial shell with the inner layer; the slope-fixing anchor pipes 7 and the lattice-type anchoring beam are combined to anchor the waste rock pile body, which can ensure the stability of the waste rock pile body; through the passivation layer 2, the shotcrete layer with wire mesh 4, the fixed net anchor pipes 5, the slope-fixing anchor pipes 7 and the lattice beam, the waste rock pile body 1 in the abandoned pyrite mining area is sealed in-situ, which can greatly reduce pyrite acid mine drainage from the source, and the overall structure has long-term stability and long-term functionality. At the same time, the soil-covered greening layer 8 in the grid space of the lattice beam 6 can better realize ecological reconstruction.

[0040] Considering that the shotcrete shell is rigid and its deformation characteristics are not coordinated with the covered plastic rock and soil mass, the concrete shell formed after shotcrete is prone to cracking. To improve the tensile strength of the shotcrete shell, in this embodiment, a wire mesh 41 is laid on the surface layer of the waste rock pile before shotcrete, and then shotcrete is carried out to form a shotcrete shell with wire mesh for anti-seepage. In addition, a expansion joint can be set every about 10 m to improve the crack resistance of the concrete anti-seepage layer.

[0041] Furthermore, the thickness of the passivation layer 2 is about 1 m. It is formed on the surface of the waste rock heap after the waste rock heap 1 in the abandoned pyrite mining area is shaped and the repair agent is injected into the waste rock heap through the fixed network anchor pipe 5 and the slope-fixing anchor pipe 7. The construction operation of in-situ injection of the repair agent can reduce the disturbance to the natural heap. The specific method of injecting the repair agent is as follows: The repair agent is mixed with water in a certain proportion to form a slurry. Due to the general characteristics of loose and strong water permeability of the pyrite waste rock heap, the repair agent slurry is pressurized and injected into the pyrite waste rock heap through the fixed network anchor pipe 5 and the slope-fixing anchor pipe 7, and an annular passivation area can be formed around the anchor pipe 15. The passivation layer 2 covering the surface of the waste rock heap can be formed through the injection site design of the fixed network anchor pipe 5 and the slope-fixing anchor pipe 7. Among them, the fixed network anchor pipes 5 can be arranged at intervals of 2×2 m.

[0042] Furthermore, both the fixed network anchor pipe 5 and the slope-fixing anchor pipe 7 include an anchor pipe 15 and a bolt 16 arranged in the anchor pipe 15. The anchor pipe 15 includes a tail non-opening section A, a densified opening section B, a normal opening section C, and a head non-opening closed section D connected in sequence. The bolt 16 is arranged along the central axis of the anchor pipe 15, and the anchor head end of the bolt 16 is fixed to the tip of the head non-opening closed section D, and the anchor tail end of the bolt 16 is connected to the anchor tail end of the tail non-opening section A. The structures of the fixed network anchor pipe 5 and the slope-fixing anchor pipe 7 in this embodiment are the same, but the slope-fixing anchor pipe 7 is longer than the fixed network anchor pipe 5. By arranging the bolt 16 in the anchor pipe 15, the advantages of the two anchoring structures of the anchor pipe 15 and the bolt 16 are absorbed. The pipe wall structure of the anchor pipe 15 can be used for adding the repair agent and injecting the cement mortar for slope fixation. Figure 4 The slurry 20 is cement mortar or a repair agent. The bolt 16 has the characteristics of low cost, fast construction speed, good anchoring effect, and wide applicability. The bolt 16 is sleeved into the anchor pipe 15. After the injection and curing of the repair agent and the cement mortar are completed and cured, a complete anchoring structure will be formed together with the anchor pipe. On the one hand, it solves the problems of easy hole collapse and hole shrinkage during the construction process due to the looseness of the waste rock heap. On the other hand, the bolt structure can greatly relieve or replace the anchoring function of the anchor pipe 15. Through this composite anchoring structure, it can be more closely combined with the loose rock and soil mass to form a more complete local anchoring whole, with better anchoring effect, lower construction cost and difficulty. At the same time, the repair agent combined with the densified opening section B at the end of the anchor pipe 15 can form the passivation layer 2 on the surface of the waste rock heap to reduce the generation of acidic wastewater.

[0043] In this embodiment, after prefabricating in sections according to the lengths of the non-opening section A at the tail, the densified opening section B, the normal opening section C, and the non-opening and closed section D at the head of the slope-fixing anchor pipe 7 and the net-fixing anchor pipe 5, the pipe walls are welded together in sequence to form an integral body. Among them, grouting holes 17 are provided on both the densified opening section B and the normal opening section C, and no grouting holes 17 are provided on the non-opening section A at the tail and the non-opening and closed section D at the head.

[0044] In this embodiment, one end of the non-opening and closed section D at the head, which faces away from the normal opening section C, is closed to form a tip, which serves to fix the anchor rod 16.

[0045] In this embodiment, the length of the densified opening section B is 1 - 1.2 m, the axial opening spacing is 45 - 55 mm, preferably 50 mm. The circumferential opening interval angle and the opening size of the pipe wall can be adjusted according to the diameter of the anchor pipe 15, but the circumferential opening interval angle is less than or equal to 90°, that is, there are at least 4 openings in the circumferential direction of the pipe wall. It not only has the normal function of combining the slurry output with the waste rock pile, but also is located at the position of the anchor pipe 15 close to the slope surface and the openings are densified, and a passivation layer 2 with a thickness of about 1 m can be formed within the range of the surface layer of the waste rock pile, which can reduce the generation of acidic wastewater from the acidic waste rock pile to a certain extent.

[0046] In this embodiment, the length of the normal opening section C can be adjusted according to the requirements of slope anchoring design. The axial opening spacing is 90 - 110 mm, preferably 100 mm, and the circumferential opening interval angle is 120°, that is, there are 3 openings in the circumferential direction of the pipe wall.

[0047] In this embodiment, a certain length of the non-opening section A at the tail needs to be exposed during construction to facilitate the fixation of the wire mesh 41 or the lattice beam 6 of the shotcrete layer 4 with wire mesh. Further, a steel pressing plate 18 is fixed on the non-opening section A at the tail. After the anchor pipe 15 and the anchor rod 16 are installed, the steel pressing plate 18 is pressed against the slope surface and welded and fixed to the anchor pipe 15 through a steel bar.

[0048] Optimally, a number of first pipe-fixing steel bars 14 and a number of second pipe-fixing steel bars 21 are also welded to the non-opening section A at the tail. The first pipe-fixing steel bars 14 and the second pipe-fixing steel bars 21 are both located on the side of the steel pressing plate 18 close to the anchor head. Optimally, the first pipe-fixing steel bars 14 are arranged along the slope surface and horizontally and are spot-welded to the anchor pipe 15, and the second pipe-fixing steel bars 21 are arranged along the length direction of the anchor pipe 15 and are welded to the anchor pipe 15.

[0049] Further, a bracket for positioning the installation position of the anchor rod 16 in the anchor pipe 15 is provided at the anchor head end of the anchor rod 16. Through this bracket, the anchor rod 16 can be controlled to be located at the central axis position of the anchor pipe 15, and the anchor head end of the anchor rod 16 abuts against the tip of the anchor pipe 15. As an implementation manner, the bracket includes an inner ring, an outer ring, and steel bars for connecting the inner ring and the outer ring. The inner ring is sleeved on the anchor head end of the anchor rod 16 and welded and fixed. Since the inner ring, the outer ring, and the anchor rod 16 are concentrically arranged, it can be ensured that the anchor rod 16 is at the central axis position of the anchor pipe 15. And when the outer ring contacts the inner wall of the anchor pipe 15, the anchor rod 16 reaches the designated position inside the anchor pipe 15. At this time, the anchor head end of the anchor rod 16 is fixed to the tip of the anchor pipe 15.

[0050] To optimize the above embodiment, a layer of three-dimensional geogrid mat 3 is laid between the passivation layer 2 and the shotcrete layer with wire mesh 4, which can reduce the disturbance to the underlying passivation layer 2 during the construction of the shotcrete layer with wire mesh 4. Specifically, the four sides of the three-dimensional geogrid mat 3 are nailed every 30 cm, and the length of the nails is generally 15 cm. The length of the nails should be increased and the nails should be appropriately densified at relatively loose positions of the slope. When laying on a high slope, the length of the nails used on the upper slope should be longer than that on the lower slope. The middle of the three-dimensional geogrid mat 3 is fixed by the solidifying mesh anchor pipe 5, which can play an obvious role in soil fixation and a good slope protection effect.

[0051] To prevent the root splitting effect of vegetation from damaging the shotcrete layer with wire mesh 4, a root separation layer 9 is provided between the soil covering and greening layer 8 and the shotcrete layer with wire mesh 4 in this embodiment. The thickness of the root separation layer 9 is 1-2 mm, and a polyethylene geomembrane can be used.

[0052] In this embodiment, the soil covering and greening layer 8 includes soil covering and vegetation planted in the soil covering. The thickness of the soil covering is about 300-500 mm. The planted vegetation is preferably selected from dominant native plants with drought resistance, erosion resistance, and acid resistance. Optimally, to reduce the scouring of rainwater and surface runoff on the greening layer and at the same time improve the survival rate of the vegetation, a layer of three-dimensional geogrid mat 10 is laid on the surface of the soil covering, which can effectively prevent soil erosion and increase the greening area.

[0053] Further, a berm 11 is provided on the waste rock pile slope. The berm 11 is an auxiliary structure for shaping and grading the slope of the pyrite waste rock pile, which is beneficial to the long-term integrity of the concrete impervious layer and adapts to the rigid structural characteristics of the concrete layer. Optimally, intercepting and drainage ditches 12 are provided on the berm 11 and at the boundaries of the four sides of the waste rock pile, and the intercepting and drainage ditches 12 on the berm 11 are interconnected with the intercepting and drainage ditches 12 around, so as to intercept the surface runoff formed by atmospheric rainfall and quickly drain it outside the waste rock pile body. At the same time, it also reduces the scouring of water flow on the impervious structure, ensuring that rainwater can be quickly and orderly drained outside the waste rock pile body. The size of the intercepting and drainage ditches 12 can be specifically designed according to the actual project.

[0054] In order to prevent rainwater from being retained in the greening soil layer for a long time and affecting plant growth and slope stability, in this embodiment, a drainage pipe 13 is pre-buried in the lattice beam 6 at the bottom of the greening covering layer, and the drainage pipe 13 is arranged along the slope and a filter measure is provided at the pipe mouth to gradually discharge the retained water in each lattice grid into the intercepting drainage ditch 12 on the horseway 11.

[0055] Furthermore, the thickness of the mesh sprayed concrete layer 4 is about 150 mm, C25 concrete is used, and 5 kg of cement-based permeable crystalline waterproof material is added to each cubic meter of concrete to enhance the concrete's anti-seepage performance. To ensure the integrity of the concrete layer, a 2×2m square steel mesh 41 is first laid on the slope surface, and a fixed mesh anchor pipe 5 with a length of 2m, a diameter of 50mm, a wall thickness of 3mm, an inclination of 30°, and a spacing of 2m is used to fix it on the slope surface, and combined with a slope anchor pipe 7 for reinforcement, the steel mesh 41 grid spacing is 100×100mm, and spraying is carried out on this basis, and the spraying is divided into two layers, the first layer is 70mm thick, and the second layer is 80mm thick. Embodiment 2

[0056] This embodiment provides a construction method for an ecological anti-seepage structure of a waste rock pile in an abandoned pyrite mine area, comprising the following steps:

[0057] 1) Installing a fixed mesh anchor pipe 5 and a fixed slope anchor pipe 7 on the slope of a waste rock pile 1 in an abandoned pyrite mine area;

[0058] 2) Firstly, a repair agent is injected into the waste rock pile through the fixed mesh anchor pipe 5 and the fixed slope anchor pipe 7 to form a passivation layer 2 on the surface of the waste rock pile, and then cement mortar is injected and cured until the designed strength is reached;

[0059] 3) Laying a three-dimensional geonet mat on the surface of the passivation layer 2, the three-dimensional geonet mat is fixed by nails on all sides and fixed in the middle by a fixed mesh anchor pipe 5;

[0060] 4) Lay a steel mesh 41 on the surface of the three-dimensional geonet mat and fix it with a mesh anchor pipe 5 and a slope anchor pipe 7, then spray mix and maintain until the designed strength is reached to form a mesh spray concrete layer 4;

[0061] 5) construct lattice beams 6 and horse paths 11 on the surface of the mesh sprayed concrete layer 4, fix the lattice beams 6 to the slope anchor pipes 7, construct intercepting and draining ditches 12 on the horse paths 11 and around the boundaries of the waste rock pile, and connect the intercepting and draining ditches 12;

[0062] 6) Covering the grid spaces of the lattice beams 6 with soil and planting vegetation to form a soil covering greening layer 8.

[0063] Optimally, a polyethylene geomembrane with a thickness of 1-2 mm is first laid on the surface of the shotcrete layer 4 as a root barrier layer 9, and then soil is covered, and a three-dimensional geogrid mat two 10 is laid on the surface of the covered soil to prevent soil erosion and increase the greening area.

[0064] Before installing the fixed-net anchor pipe 5 and the slope-fixing anchor pipe 7, the injection point positioning, drilling angle positioning, drill positioning, drilling, hole cleaning, and hole position inspection are carried out. During construction, the angle between the drill hole and the horizontal plane is 30° to facilitate the injection of the agent; the method of installing the fixed-net anchor pipe 5 and the slope-fixing anchor pipe 7 after drilling is as follows: the assembled anchor pipe 15 is directly sent into the corresponding drilled hole with a pneumatic drill. After the anchor pipe 15 is fixed, a small amount of clear water is first pumped to lift the residue at the bottom of the hole, and then the assembled anchor rod 16 is inserted into the anchor pipe 15 until the bracket at the head of the anchor rod 16 contacts the inner wall of the anchor pipe 15. At this time, the head of the anchor rod 16 is inserted into the tip of the head of the anchor pipe 15 to form a fixed structure; and after the grouting is completed, the anchor pipe 15 and the tail of the anchor rod 16 are fixed by the fixing rod steel bar 19. The middle of the fixing rod steel bar 19 is spot-welded to the tail of the anchor rod 16, and the two ends of the fixing rod steel bar 19 are respectively welded to the anchor pipe 15.

[0065] As an implementation method, the repair agent of this embodiment includes a neutralization passivator, a biological passivator, and a long-acting neutralizer. The proportion of each component is adjusted according to the requirements of slope repair. Specifically:

[0066] The neutralization passivator can be sodium hydroxide, calcium hydroxide, etc. It can be used for impact addition in deep local acidic wastewater areas to treat the acidic wastewater stored in the saturated water zone in the waste rock pile, and can also be used for passivation of surface acidic waste rock to treat the acidic wastewater in the vadose zone; on the one hand, the neutralization passivator can promote the formation of hydroxide precipitation of trivalent iron and the coprecipitation of various heavy metals. The generated Fe precipitate has a coating effect. At the same time, the alkaline environment caused by the neutralization passivator can inhibit the growth of Thiobacillus ferrooxidans and the catalysis of microorganisms, and form a passivation layer 2 around the anchor pipe 15 rod to protect the integrity of the anchoring structure and function, with multiple functions of passivation and protection;

[0067] The biological passivator can be potassium salt, sodium salt, etc., which is used to increase the alkali metal content of the waste rock pile and promote the conversion of dissolved iron and sulfate ions in the acidic mine wastewater into biological minerals under the action of Thiobacillus in the waste rock pile, further strengthening the passivation effect on the surface of the waste rock;

[0068] The long-acting neutralizer can be calcium carbonate, etc. As a long-acting buffer, it is wrapped in the effective radius area around the anchor pipe 15 to maintain the neutralization effect with acidic waste rock and acidic wastewater for a long time.

[0069] Optimally, when injecting the repair agent, attention should be paid to the order. The dosage of the agent is adopted according to the repair design. The agent should be used immediately after mixing and injected slowly and evenly. The specific injection method is as follows:

[0070] First, inject the neutralizing and passivating agent into the wastewater vadose zone of the acidic waste rock layer on the slope. The injection speed should keep the agent slow and uniform. The flow rate is determined according to the water injection test, and the total injection volume is determined according to the design. A metering pump is used to control the injection flow rate and pressure.

[0071] Next, after completing the injection of the neutralizing and passivating agent, with an interval of 2 h, then inject the biological passivating agent into the wastewater vadose zone of the acidic waste rock layer on the slope. The injection speed should keep the agent slow and uniform. The flow rate is determined according to the water injection test, and the total injection volume is determined according to the design. A metering pump is used to control the injection flow rate and pressure.

[0072] Then, after completing the injection of the biological passivating agent, with an interval of 2 h, then inject the long-acting neutralizing agent into the wastewater vadose zone of the acidic waste rock layer on the slope. The injection speed should keep the agent slow and uniform. The flow rate is determined according to the water injection test, and the total injection volume is determined according to the design. A metering pump is used to control the injection flow rate and pressure.

[0073] The dosage of each passivating agent is adopted according to the repair design. Each passivating agent is injected in two times with an interval of 30 min.

[0074] After completing the injection of the long-acting passivating agent, with an interval of 2 h, finally inject the cement mortar. The cement mortar is used as the final filling gel material of the anchor pipe 15, and is proportioned according to the designed strength. The cement mortar diffuses outside the anchor pipe 15 through the openings on the anchor pipe 15. After final setting, it forms the final composite anchor body corresponding to the effective anchoring area with the anchor pipe 15, provides the anchoring force, and keeps the slope stable in this area. Optimally, the cement mortar is grouted in two times:

[0075] The first grouting is normal-pressure grouting. Inject the prepared cement mortar from the bottom of the anchor pipe 15 from bottom to top, so that the cement mortar flows back from the bottom of the anchor pipe 15. When the flowing slurry is similar to pure cement mortar, stop grouting. If there is slurry shrinkage at the hole opening, make up the slurry, and then seal the hole with cotton yarn and mortar.

[0076] The second grouting is pressure-splitting grouting, which is carried out from the bottom of the hole upwards. First, insert the grouting steel pipe near the bottom end of the anchor pipe 15, install the sealing cover, connect the high-pressure grouting pipe, open the exhaust valve, gradually increase the pressure for grouting, discharge the gas or residual water in the pipe. When pure slurry flows out from the exhaust valve, block the exhaust valve, continue to increase the pressure for grouting, and pay attention to observing and recording the changes of the grouting volume and the pressure of the orifice pressure gauge during the operation process.

[0077] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas, characterized in that: It includes a passivation layer formed on the surface layer of the waste rock heap in the abandoned pyrite mining area, a shotcrete layer with wire mesh laid on the surface of the passivation layer, lattice beams arranged on the surface of the shotcrete layer with wire mesh, and a soil-covered greening layer arranged in the grid space of the lattice beams; solidifying anchor pipes and slope-fixing anchor pipes are arranged in the waste rock heap, the wire mesh of the shotcrete layer with wire mesh is fixed on the waste rock heap slope through the solidifying anchor pipes and the slope-fixing anchor pipes, and the lattice beams are fixed on the waste rock heap slope through the slope-fixing anchor pipes; the passivation layer is formed on the surface layer of the waste rock heap after injecting a repair agent into the waste rock heap through the solidifying anchor pipes and the slope-fixing anchor pipes; both the solidifying anchor pipes and the slope-fixing anchor pipes include anchor pipes and anchor rods arranged in the anchor pipes, the anchor pipes include a tail non-opening section, a densified opening section, a normal opening section and a head non-opening closed section connected in sequence, the anchor rods are arranged along the central axis of the anchor pipes, and the anchor head end of the anchor rod is fixed to the tip of the head non-opening closed section, and the anchor tail end of the anchor rod is connected to the anchor tail end of the tail non-opening section.

2. The ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas according to claim 1, characterized in that: A three-dimensional geogrid mat one is laid between the passivation layer and the shotcrete layer with wire mesh, the four sides of the three-dimensional geogrid mat one are fixed by nails, and the middle is fixed by the solidifying anchor pipes.

3. The ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas according to claim 1, characterized in that: A root separation layer is arranged between the soil-covered greening layer and the shotcrete layer with wire mesh.

4. The ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas according to claim 1, characterized in that: The soil-covered greening layer includes soil and vegetation planted in the soil, and a three-dimensional geogrid mat two is laid on the surface of the soil.

5. The ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas according to claim 1, characterized in that: A berm is arranged on the waste rock heap slope, and intercepting and drainage ditches are arranged on the berm and at the boundaries of the four sides of the waste rock heap and are interconnected.

6. The ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas according to claim 5, characterized in that: A drain pipe is arranged in the lattice beam at the bottom of the greening soil-covered layer, and an anti-filter measure is arranged at the pipe orifice of the drain pipe.

7. The ecological anti-seepage structure for waste rock piles in abandoned pyrite mining areas according to claim 1, characterized in that: The shotcrete layer with wire mesh uses C25 concrete, and 5 kg of cement-based permeable crystalline waterproof material is incorporated into each cubic meter of concrete.

8. A construction method for the ecological anti-seepage structure of waste rock piles in abandoned pyrite mining areas, characterized in that, It includes the following steps: 1) Install solidifying anchor pipes and slope-fixing anchor pipes on the waste rock heap slope in the abandoned pyrite mining area; 2) First inject a repair agent into the waste rock heap through the solidifying anchor pipes and the slope-fixing anchor pipes to form a passivation layer on the surface layer of the waste rock heap, and then inject cement mortar and cure until the design strength is reached; 3) Lay a three-dimensional geogrid mat on the surface of the passivation layer, fix the four sides of the three-dimensional geogrid mat with nails, and fix the middle with the solidifying anchor pipes; 4) Lay a wire mesh on the surface of the three-dimensional geogrid mat, fix it with the solidifying anchor pipes and the slope-fixing anchor pipes, and then spray concrete and cure until the design strength is reached to form a shotcrete layer with wire mesh; 5) Construct lattice beams and berms on the surface of the shotcrete layer with wire mesh, fix the lattice beams with the slope-fixing anchor pipes, construct intercepting and drainage ditches on the berm and at the boundaries of the four sides of the waste rock heap, and connect the intercepting and drainage ditches; 6) Cover the grid space of the lattice beams with soil and plant vegetation to form a soil-covered greening layer.

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