New method for reconstructing flood drainage system in tailings pond in service

Abstract

Disclosed in the present invention is a new method for reconstructing a flood drainage system in a tailings pond in service. The reconstructed flood drainage system is composed of a beveled-edge steel open caisson (1), a stilling well (4), pile foundations (6), an annular pile cap (7), and a new flood drainage well (8); the stilling well (4) is excavated in layers within the beveled-edge steel open caisson (1), and uses reinforced concrete to cast retaining walls to form a net circular cross-section; the pile foundations (6) are annularly arranged on the periphery of the beveled-edge steel open caisson (1); the annular pile cap (7) is cast and supported on the pile foundations (6); and the new flood drainage well (8) is constructed and supported on the annular pile cap (7). According to the present invention, the open caisson is used for transformation of an original drainage culvert, such that the construction period can be effectively shortened, construction costs are reduced, the requirement for normal tailings discharge of a tailings pond can be satisfied, and the requirement for flood drainage in a heavy rainfall season can also be satisfied, thereby achieving good economic benefits.

Description

A new method for reconstructing flood drainage systems in existing tailings ponds Technical Field

[0001] The present invention belongs to the technical field of mine tailings pond drainage system management, and specifically relates to a new method for reconstructing a drainage system in an existing tailings pond. The method is particularly suitable for modifying the drainage culvert after the original drainage system of the tailings pond is damaged to reconstruct the drainage system. Background Art

[0002] The main function of the tailings pond flood discharge system is to control the flood in the reservoir catchment area and discharge it safely and effectively outside the reservoir, preventing dam breach accidents caused by floods, and plays a vital role in the safe operation of the tailings pond.

[0003] At present, most tailings ponds with large catchment areas use a "drainage well + drainage culvert" type of drainage system. Especially for tailings ponds with a long operating life, the safety of the drainage system is very important. Once a safety hazard occurs in the drainage system, such as the tilt of the drainage well body or damage to the drainage culvert structure, the drainage system needs to be managed in a timely manner.

[0004] Chinese patent application No. 201610715699.9 discloses a drainage system suitable for upstream dry tailings ponds. The drainage system comprises a vertical drainage shaft, a flood control and sump, a return water hole, and a filter layer. The specific structure is as follows: a flood control and sump is constructed around the vertical drainage shaft. The shaft utilizes a metal shaft structure and a reinforced concrete base, with a return water hole and a filter layer surrounding the shaft. This drainage system collects floodwater in the flood control and sump, rapidly increasing the depth of the floodwater at the vertical drainage shaft so that the shaft quickly reaches a weir flow state, increasing discharge capacity, reducing drainage time, and draining all floodwater from the tailings pond. This reduces floodwater infiltration into the reservoir area and avoids the formation of weak interlayers or unstable infiltration lines in the saturated tailings caused by deep floodwater infiltration. However, this drainage system is only suitable for use in upstream dry tailings pond drainage systems and is not suitable for the rapid, high-volume discharge required by existing tailings ponds with large catchment areas during heavy rain seasons.

[0005] At present, the most common solution for managing the drainage system of mine tailings ponds is to build a new drainage system. However, the construction period of a new complete drainage system is long and difficult, which makes it difficult to meet the timeliness of emergency management of the drainage system, and also puts a heavy burden on the operating costs of the enterprise.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to address the problems of long construction period and great difficulty in building a new flood drainage system after the flood drainage system of an existing tailings pond is damaged. By modifying the drainage culverts in the original flood drainage system of the tailings pond, a new method for reconstructing the flood drainage system in an existing tailings pond is provided, which is convenient to construct, economical and effective, safe and stable, so as to meet the needs of quickly, efficiently and safely reconstructing the flood drainage system and reduce the construction difficulty during the new construction of the flood drainage system of the tailings pond.

[0008] To achieve the above-mentioned object of the present invention, a new method for reconstructing a flood drainage system in a tailings pond of the present invention is implemented by the following technical solutions:

[0009] The present invention discloses a new method for reconstructing a flood drainage system in an existing tailings pond. The reconstructed flood drainage system is composed of a steel blade angle caisson, a stilling well, a pile foundation, an annular cap, and a new flood drainage well. The stilling well is dug in layers within the steel blade angle caisson, and reinforced concrete is used to cast a retaining wall to form a net circular cross-section. The pile foundation is arranged in a circular ring around the steel blade angle caisson. The annular cap is cast and supported on the pile foundation. The new flood drainage well is constructed and supported on the annular cap, and the method is implemented by the following steps:

[0010] S1 Construction Preparation Work

[0011] First, based on the location of the damaged tailings pond's drainage well and the original drainage culvert's buried location, the location where the drainage system needs to be rebuilt is determined; earthwork operations are then carried out inside the pond to build connecting roads and construction platforms to the location where the drainage system needs to be rebuilt;

[0012] S2 steel blade caisson sinks under its own weight and seals the bottom

[0013] After the filling and surveying of the connecting roads and construction platforms are completed, the steel blade angle caisson is sunk by its own weight to seal the bottom. Angle steel is welded to the blade foot of the steel blade angle caisson. The steel blade angle caisson is sunk to the design elevation. The location of the original drainage culvert is explored by probing at the center and on both sides. After the steel blade angle caisson is sunk to the design elevation and the settlement is stable, the bottom is sealed with concrete. The strength of the bottom sealing concrete is required to be no less than 75% of the design strength before the next construction.

[0014] S3 grouting area drilling grouting

[0015] Grouting holes are arranged in layers along the outer periphery of the steel blade caisson, with inclined grouting adopted from the outside to the inside, forming a grouting area. The grouting holes are sealed with upward-flowing blocking grouting from the bottom up. After the grouting is completed, the permeability coefficient of the grouting body is not less than 1 Lu Rong, and the strength of the grouting body is not less than 2 MPa.

[0016] S4 stilling well construction

[0017] The stilling well is excavated layer by layer from the bottom of the steel blade-angle caisson, and reinforced concrete is poured into the retaining wall to form a circular foundation pit section. The original drainage culvert is cut within the excavation range of the foundation pit, and the concrete at the junction of the original drainage culvert and the stilling well is manually chiseled out, retaining the steel bars. The original drainage culvert is then overlapped with the steel bars at the bottom of the stilling well, and then cast with concrete to seal it.

[0018] S5 pile foundation construction

[0019] Lay out pile foundations in the filled construction platform. The pile foundations are symmetrically arranged around the stilling well and on both sides of the original drainage culvert. The pile foundations must enter the underlying foundation bearing layer.

[0020] S6 ring bearing platform construction

[0021] The annular cap is constructed on a pre-filled construction platform. The annular cap adopts a reinforced concrete structure. Before tying the steel bars, the floating slurry portion of the pile foundation head is first chiseled out, and the pile body and main reinforcement are embedded in the annular cap. The concrete of the annular cap is poured in one step. The concrete is preferably poured in a flat paving method. After the concrete strength after pouring is not less than 70% of the design value, the new upper drainage well is constructed.

[0022] Construction of new flood drainage well S7

[0023] The new drainage well is constructed on the annular foundation. The well body is a reinforced concrete structure. The inner diameter R of the new drainage well is calculated according to the "Design Code for Tailings Facilities" (GB 50863-2013), and the well body structural parameters must meet the flood prevention and drainage requirements.

[0024] Research shows that the steel blade angle caisson is preferably constructed with C35 reinforced concrete. According to the "Design Code for Tailings Facilities" (GB 50863-2013) and other relevant regulations, the relevant dimensional parameters are calculated. The inner diameter of the new drainage well is denoted as R, and the inner diameter of the steel blade angle caisson is 1.5 to 2.0R, the wall thickness δ is 0.35 to 0.5m, and the height is 3.0 to 5.5m. The blade angle welded angle steel of the steel blade angle caisson has a size of ∠(200 to 500) mm*(200 to 500) mm*(9 to 12) mm, that is, the angle steel size ranges from ∠200mm*200mm*9mm to ∠500mm*500mm*12mm, with ∠200mm*200mm*10mm to ∠500mm*500mm*10mm being preferred. Under this structural parameter, it can meet the sinking requirements while also achieving the designed strength and displacement requirements.

[0025] In order to improve the stability of the foundation and meet the reliability requirements of the reconstructed flood drainage system, the radius is the common central axis of the steel blade caisson, the stilling well and the new flood drainage well. The grouting area range is Dr = 4 to 6R, the grouting hole diameter is φ = 90 to 130 mm, and the layers are arranged in layers along the annular plane, with 2 to 3 layers and a layer spacing of φ. d =1.5m~2.5m, grouting depth h=5m~10m, grouting is inclined from outside to inside, and the inclination angle is 55°~65°. Under this technical parameter, the system reliability and construction economy are most reasonable and optimized.

[0026] The energy dissipation well is dug in layers in the steel blade-angle caisson, with a layered excavation height of 0.5m to 1.0m, and adopts C25 reinforced concrete cast-in-place earth retaining wall, with a retaining wall thickness of 0.2m to 0.3m and a height of 0.5m to 1.0m. After the retaining wall is cast, a circular section with a net cross-section diameter of 1.0m to 2.0m is formed.

[0027] In order to improve the stability of the foundation, the pile foundation is a C40 bored cast-in-place pile with a pile body diameter in the range of 500 to 700 mm, preferably 600 mm; the diameter of the pile area is 2R to 4R, and the pile length L is 10 to 20 m. The specific calculation can be determined in accordance with the "Technical Specifications for Building Pile Foundations" (JGJ 94-2008) and other regulations.

[0028] Furthermore, the new drainage well is a C35 reinforced concrete structure with an inner diameter of 1.8 to 2.3 m and a wall thickness of 0.27 to 0.34 m.

[0029] Furthermore, the annular foundation is a C35 reinforced concrete structure, the inner diameter D1 is the same as the diameter of the stilling well, the outer diameter D2 = 3 to 5R, and the height H = 2 to 3m.

[0030] Furthermore, in step S3, the grouting pressure is 0.23-0.28 MPa, preferably 0.25 MPa; the grouting stop pressure is in the range of 0.7-0.8 MPa, preferably 0.75 MPa.

[0031] Furthermore, a C20 concrete cushion layer 5 is poured at the bottom of the stilling well. The thickness of the cushion layer 5 is 45 to 55 cm, generally 50 cm.

[0032] The novel method of the present invention for reconstructing a flood drainage system in a tailings pond adopts the above technical solution, which has the following positive effects:

[0033] (1) The present invention transforms the original drainage culvert through a steel blade-angle caisson, performs grouting construction through grouting holes in the grouting area to improve the stability of the foundation, and further improves the foundation stability through a pile foundation. After the steel blade-angle caisson sinks to the top of the original drainage culvert, the steel blade-angle caisson structure is optimized into a stilling well, and then a ring-shaped pedestal and a new flood drainage well are constructed to achieve the purpose of flood drainage system management, effectively shorten the construction period, and improve economic benefits while ensuring the safety and reliability of the flood drainage system.

[0034] (2) The present invention utilizes the rheological properties of the tailings in the reservoir and sinks the steel blade-angle caisson by its own weight, thereby establishing a construction space for the yard drainage culvert renovation in the steel blade-angle caisson, which has the advantages of strong operability and reliable construction.

[0035] (3) The present invention utilizes caisson renovation on the basis of the original drainage culvert, which can effectively shorten the construction period and reduce the construction cost. It can not only meet the normal tailings discharge requirements of the tailings pond, but also ensure the need for flood discharge during heavy rainfall seasons, and has good economic benefits.

[0036] (4) Compared with the single foundation of the traditional flood drainage well, the present invention has improved foundation stability and is safer and more reliable through structures such as pile foundation and annular foundation.

[0037] (5) Industrial test studies have shown that the method of the present invention can effectively control the safe and rapid discharge of floods in the reservoir catchment area, prevent dam breach accidents caused by floods, and ensure the safe operation of the tailings pond.

[0038] (6) The method of the present invention can reduce the construction cost by 30% to 40% compared with building a new flood drainage system, and the construction efficiency is more than 45% faster, with significant application effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG1 is a cross-sectional view of a novel method for reconstructing a flood drainage system in an existing tailings pond according to the present invention;

[0040] FIG2 is a top view of a novel method for reconstructing a flood drainage system in a tailings pond according to the present invention.

[0041] Figure numerals: 1-steel blade-angle caisson; 2-angle steel; 3-1-grouting area; 3-2-grouting hole; 4-energy dissipation well; 5-cushion; 6-pile foundation; 7-annular cap; 8-new drainage well; 9-original drainage culvert. DETAILED DESCRIPTION

[0042] To further describe the present invention, a new method for reconstructing a flood discharge system in an existing tailings pond according to the present invention is described in further detail below with reference to the accompanying drawings.

[0043] As shown in FIG1 , which is a cross-sectional view of a new method for reconstructing a flood drainage system in an existing tailings pond according to the present invention, and in combination with FIG2 , it can be seen that the flood drainage system reconstructed by the method of the present invention is composed of a steel blade-angle caisson 1, a stilling well 4, a pile foundation 6, an annular pedestal 7, and a new flood drainage well 8, and a cushion layer 5 is also provided at the lower part of the foundation pit of the stilling well 4.

[0044] In the embodiment, monitoring revealed that the drainage well of a tailings pond in use at a certain mineral processing plant was tilted, posing a serious safety hazard. Based on the actual production conditions of the enterprise and the water collection in the tailings pond, the present invention employed a new method for reconstructing a drainage system in an in-use tailings pond to eliminate the hidden dangers of the drainage system. Specifically, the following steps were used:

[0045] Step 1: Steel blade caisson 1 sinks and seals the bottom under its own weight

[0046] First, earthwork operations are performed in the reservoir to fill connecting roads and construction platforms. After the connecting roads and construction platforms are filled and measured and laid out, the steel blade-angle caisson 1 is sunk by its own weight to seal the bottom. In the embodiment, the inner diameter of the steel blade-angle caisson 1 is 3m, and the blade foot of the steel blade-angle caisson 1 is welded with a ∠200mm*200mm*10mm angle steel 2 to increase the sand-breaking ability of the sinking. The self-weight sinking and bottom sealing process can be coordinated with the control of the sinking speed by mechanically excavating sand evenly. The steel blade-angle caisson 1 sinks to within 2m of the top elevation of the original drainage culvert. The original drainage culvert 9 is explored at the center and on both sides by the probing method. After the steel blade-angle caisson 1 sinks to the design elevation and the settlement is stable, C35 concrete is used for bottom sealing. The strength of the bottom sealing concrete is required to be not less than 75% of the design strength before the next construction.

[0047] Step 2: Drilling and grouting in the grouting area

[0048] Grouting construction is carried out in the grouting area 3-1 through the grouting hole 3-2. Regional parameters such as grouting depth and grouting range are determined according to actual conditions. The grouting depth in the embodiment is 5.7m, the outer diameter of the grouting area 3-1 is 10m, and the grouting holes 3-2 are arranged in two layers in the plane circumferential direction within the grouting area 3-1. The grouting holes 3-2 are spaced 1.5m apart in the circumferential direction. Inclined grouting is adopted from the outside to the inside in sequence, with an inclination angle of 60°, a grouting pressure of 0.25MPa, and a stop grouting pressure of 0.75MPa. The orifice is closed and the upward-type hole-blocking grouting is adopted from the bottom up. Grouting should start from low pressure and a large injection volume and end at the final pressure and a small injection volume. The final grouting pressure should not be less than the design pressure. It is required that after the grouting is completed, the permeability coefficient of the grouting body is not less than 1 Lu Rong and the strength of the grouting body is not less than 2MPa.

[0049] Step 3: Construction of energy dissipation well 4

[0050] The stilling well 4 was excavated layer by layer from the bottom of the steel blade-shaped caisson 1 downwards, with a circular cross-section of 3.0m in diameter. The excavation was carried out in layers, with each layer height being 0.5m. During the excavation process, a reinforced concrete retaining wall was poured, with a thickness of 0.25m and a height of 0.5m. After the retaining wall was poured, a circular pit cross-section with a net cross-section diameter of 1.5m was formed. A C20 concrete cushion layer 5 with a thickness of 50cm was poured at the bottom of the stilling well 4. The existing drainage culvert 9 within the excavation range needed to be cut, with the upstream side of the original drainage culvert 9 extending along the pit wall, while the downstream side remained 0.75m inside the pit. The concrete of the original drainage culvert 9 was manually chiseled, retaining the steel reinforcement, which was then overlapped with the steel reinforcement of the stilling well 4.

[0051] Step 4: Pile foundation 6 construction

[0052] The pile foundation 6 is laid out on the filled construction platform and is symmetrically arranged around the stilling well 4 and on both sides of the original drainage culvert 9. The pile foundation 6 uses C40 bored cast-in-place piles with a pile body diameter of 600mm and an outer diameter of the pile area of ​​6.5m. The pile length is L and must enter the bearing layer of the foundation below.

[0053] Step 5: Construction of annular platform 7

[0054] The annular cap 7 is constructed on a pre-filled construction platform using C35 reinforced concrete. Its clear diameter D1 is 1.0m, its outer diameter D2 is 8.6m, and its height is 2.5m. Before reinforcing steel is tied, the floating grout at the pile head of the pile foundation 6 is removed, and the pile body and its main reinforcement are embedded in the annular cap 7. The concrete for the annular cap 7 is poured in a single step, preferably using the flat-lay method. Construction of the new upper drainage shaft 8 begins only after the concrete reaches a strength of at least 70% of the design value.

[0055] Step 6: Construction of new flood drainage well 8

[0056] The new drainage well 8 is constructed on the annular foundation 7. The well body of the new drainage well 8 is a C35 reinforced concrete structure with an inner diameter of 2.0m, a wall thickness of 0.3m, and an outer diameter of 2.6m. The well body structural parameters must meet the flood prevention and drainage requirements.

[0057] The calculation results after the method of the present invention was applied to the tailings pond in use at the ore dressing plant showed that, compared with building a new flood drainage system, the construction cost of rebuilding the flood drainage system by using the method of the present invention was reduced by 38.5%, the construction efficiency was increased by 51.0%, and it was safe and reliable, and withstood the test of the rainy season, achieving unexpected technical results.

[0058] It should be noted that the directions or positional relationships indicated by the terms "up", "down", "left", "right", "inside", "outside", etc. in the present invention are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred parts or elements must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention.

[0059] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A new method for reconstructing a flood drainage system in an existing tailings pond, characterized in that The reconstructed flood drainage system is composed of a steel blade angle caisson (1), a stilling well (4), a pile foundation (6), an annular cap (7), and a new flood drainage well (8); the stilling well (4) is dug down in layers in the steel blade angle caisson (1), and a reinforced concrete retaining wall is cast to form a net circular cross section; the pile foundation (6) is arranged in a circular ring outside the steel blade angle caisson (1); the annular cap (7) is cast and supported on the pile foundation (6); the new flood drainage well (8) is constructed and supported on the annular cap (7), and is implemented by the following steps: S1 Construction Preparation Work First, based on the location of the damaged tailings pond's drainage well and the original drainage culvert's buried location, the location where the drainage system needs to be rebuilt is determined; earthwork operations are then carried out inside the pond to build connecting roads and construction platforms to the location where the drainage system needs to be rebuilt; S2 steel blade caisson sinks under its own weight and seals the bottom After the filling and measurement and layout of the connecting road and the construction platform are completed, the steel blade angle caisson (1) is sunk by its own weight to seal the bottom; the angle steel (2) is welded at the blade foot of the steel blade angle caisson (1), and the steel blade angle caisson (1) is sunk to the range of 2m of the top elevation of the original drainage culvert (9). The location of the original drainage culvert (9) is explored by the method of probing at the center and both sides. After the steel blade angle caisson (1) sinks to the design elevation and the settlement is stable, the bottom is sealed with concrete, and the strength of the bottom sealing concrete is required to be not less than 75% of the design strength before the next construction; S3 grouting area drilling grouting The grouting holes (3-2) are arranged in layers along the outer periphery of the steel blade angle caisson (1), and inclined grouting is sequentially adopted from the outside to the inside to form a grouting area (3-1). The grouting holes (3-2) adopt the hole-opening closure and upward-type hole-blocking grouting from bottom to top. After the grouting is completed, the permeability coefficient of the grouting body is not less than 1 Lu Rong, and the strength of the grouting body is not less than 2 MPa. S4 stilling well construction The energy dissipation well (4) is excavated in layers downward from the bottom of the steel blade angle caisson (1), and reinforced concrete is poured into the retaining wall to form a circular foundation pit section; the original drainage culvert (9) is cut within the excavation range of the foundation pit, and the concrete at the joint between the original drainage culvert (9) and the energy dissipation well (4) is manually chiseled out. Concrete, retain the steel bars, overlap the original drainage culvert (9) and the lower steel bars of the stilling well (4), and then cast concrete to seal it; S5 pile foundation construction Arrange pile foundations (6) in the filled construction platform. The pile foundations (6) are symmetrically arranged around the stilling well (4) and on both sides of the original drainage culvert (9). The pile foundations (6) must enter the underlying foundation bearing layer. S6 ring bearing platform construction The annular cap (7) is constructed on a well-filled construction platform. The annular cap (7) adopts a reinforced concrete structure. Before tying the steel bars, the floating slurry part of the pile head of the pile foundation (6) is chiseled out first, and the pile body and its main reinforcement are buried inside the annular cap (7). The concrete of the annular cap (7) is poured in one time. The concrete is preferably poured into the groove by a flat paving method. After the strength of the concrete is not less than 70% of the design value after pouring, the upper new flood discharge well (8) is constructed. Construction of S7 new flood drainage well The new drainage well (8) is constructed on the annular foundation (7). The well body of the new drainage well (8) is a reinforced concrete structure. The inner diameter R of the new drainage well (8) is calculated according to the "Design Code for Tailings Facilities" (GB 50863-2013). The well body structural parameters must meet the flood prevention and drainage requirements.

2. A new method for reconstructing a flood drainage system in a tailings pond as claimed in claim 1, characterized in that The steel blade angle caisson (1) is a C35 reinforced concrete structure; the inner diameter of the steel blade angle caisson (1) is 1.5-2.0R, the wall thickness δ is 0.35-0.5m, and the height is 3.0-5.5m; the blade angle of the steel blade angle caisson (1) is welded with an angle steel, and the angle steel size is ∠(200-500)mm*(200-500)mm*(9-12)mm.

3. A new method for reconstructing a flood drainage system in a used tailings pond as claimed in claim 1, characterized in that : With the common central axis of the steel blade angle caisson (1), the stilling well (4) and the new flood discharge well (8) as the radius, the grouting area (3-1) ranges from Dr = 4 to 6R, the grouting hole (3-2) has a hole diameter of φ = 90 to 130 mm, and is arranged in layers along the annular plane, with 2 to 3 layers and a layer spacing of φ d =1.5m~2.5m, grouting depth h=5m~10m, grouting is inclined from outside to inside, and the inclination angle is 55°~65°.

4. A new method for reconstructing a flood drainage system in an existing tailings pond as claimed in claim 1, characterized in that The energy dissipation well (4) is dug down in layers in the steel blade angle caisson (1), with a layered digging height of 0.5m to 1.0m, and a C25 reinforced concrete cast earth retaining wall is used, with a retaining wall thickness of 0.2m to 0.3m and a height of 0.5m to 1.0m. After the retaining wall is cast, a circular section with a net cross-section diameter of 1.0m to 2.0m is formed.

5. A new method for reconstructing a flood drainage system in an existing tailings pond as claimed in claim 1, characterized in that The pile foundation (6) is a C40 bored pile with a pile body diameter in the range of 500 to 700 mm, a pile area diameter of 2R to 4R, and a pile length L of 10 to 20 m.

6. A new method for reconstructing a flood drainage system in an existing tailings pond as claimed in claim 1, characterized in that The annular support (7) is a C35 reinforced concrete structure, with an inner diameter D1 being the same as the diameter of the stilling well (4), an outer diameter D2 = 3 to 5R, and a height H = 2 to 3m.

7. A new method for reconstructing a flood drainage system in an existing tailings pond as claimed in claim 1, characterized in that The new flood drainage well (8) is a C35 reinforced concrete structure with an inner diameter of 1.8 to 2.3 m and a wall thickness of 0.27 to 0.34 m.

8. A new method for reconstructing a flood drainage system in an existing tailings pond as claimed in claim 1, characterized in that : In step S3, the grouting pressure is 0.23~0.28MPa, and the stop grouting pressure is 0.7~0.8MPa.

9. A new method for reconstructing a flood drainage system in an existing tailings pond as claimed in claim 1, characterized in that : A C20 concrete cushion layer (5) is poured at the bottom of the stilling well (4), and the cushion layer (5) has a thickness of 45 to 55 cm.

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