Layered and partitioned solid waste backfilling method suitable for abandoned sunken mining pit

Abstract

The invention discloses a layered and partitioned solid waste backfilling method suitable for a waste sunken mining pit, which comprises the following steps of: performing pouring and filling on a surrounding rock mass microfracture (1), and forming a composite impermeable layer at the bottom of the waste sunken mining pit by a mining pit bottom grouting reinforcing layer (7), a curing backfilling layer (6) and an artificial composite impermeable layer (5); the longitudinal trapezoidal permeable dams (12Z) and the transverse trapezoidal permeable dams (12H) jointly form a latticed solid waste subarea backfilling area (4) on the bottommost layer, and leachate collecting pipes (13) for collecting common solid waste leachate are arranged at the bottoms of the transverse trapezoidal permeable dams (12H) on each layer. And the solid waste is backfilled from bottom to top in a layered and partitioned manner to form funnel-shaped solid waste backfilling bodies (3). The geologic structure stability of the backfill area is effectively guaranteed, the danger caused by differential settlement is reduced, a modernized common solid waste disposal mode is provided, and the environmental safety risk management and control level is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of safe and environmentally friendly disposal of general industrial solid waste, and particularly relates to a method for disposing general industrial solid waste by using abandoned concave pit backfilling. BACKGROUND

[0002] The general industrial solid waste storage and disposal site refers to a centralized storage place for non-permanent storage (later resource recycling) and permanent disposal (final landfill of waste without resource value), and the core value thereof lies in: ① economic efficiency: realizing safe, efficient and low-cost temporary storage and disposal of solid waste, and guaranteeing continuous production of enterprises; ② resource recycling: providing a resource transformation hub for recyclable solid waste (such as metal tailings and construction aggregates); and ③ ecological barrier: blocking the migration of pollutants and protecting the surrounding water and soil environment.

[0003] The current storage and disposal method of traditional general industrial solid waste has significant defects: firstly, the disposal facilities cannot adapt to the diversity of the materials, especially for high-moisture solid waste such as tailings and materials with significant discrete properties, and the adaptability of the existing equipment and process is insufficient, resulting in rising processing costs and increasing technical difficulty; secondly, the safety risk in the operation process is prominent, which not only manifests as direct accident hazards such as equipment overturning and damaged transportation vehicles, but also derives from local slope collapse and uneven settlement of rock and soil engineering problems, which further seriously restricts the development and utilization of the later surface space; meanwhile, the disordered stacking mode ignores the classification characteristics and resource demand of the materials, and the mixed stacking of various solid wastes causes difficulty in later separation, greatly increasing the recycling cost; in addition, the secondary pollution risk continues to exist, and the efficiency of the leachate collection system is low, combined with the structural damage of the impermeable layer, which may cause continuous pollution of the surrounding soil and water.

[0004] In order to solve the problem of land occupation of general industrial solid waste stacking, the article "Analysis of Abandoned Quarry as General Industrial Solid Waste Landfill Site" published in Environmental Science and Management in 2008 discusses the use of abandoned quarry as the site of the first type of general industrial solid waste landfill site from the perspective of urban industrial solid waste consumption and abandoned quarry as a landfill site, and illustrates the availability of using abandoned quarry as the site of the first type of general industrial solid waste landfill site through examples in Guangzhou, which has certain reference significance for the comprehensive utilization of abandoned quarry. However, the article does not provide a specific technical scheme.

[0005] The "general industrial solid waste landfill engineering example" published in October 2020 of "Chinese Science and Technology Periodical Database (full text version) Engineering Technology" mainly introduces the design of a general industrial solid waste landfill from site conditions, overall planning, dam engineering, slope treatment, seepage prevention system, flood interception ditch drainage engineering, site closure and ecological restoration. However, the general industrial solid waste landfill is aimed at the case of stable surrounding rock of the mine pit without microcracks. For the case of microcracks in the surrounding rock of the mine pit, the technical scheme provided in the paper cannot be handled.

[0006] It should be particularly pointed out that the above-mentioned solid waste disposal dilemma and the idle space resources of abandoned mine pits form a sharp contradiction: on the one hand, the disposal site is overburdened, and on the other hand, the geological hazards of the mine pit have not been eliminated and the space value has been buried. The existing technical system cannot realize the adaptation of material characteristics and the coordinated control of safety risks, and cannot establish an organic linkage mechanism for solid waste disposal and mine pit repair. Therefore, it is urgent to develop an innovative technology that takes into account disposal safety, resource recycling and space efficiency to solve the resource mismatch problem. SUMMARY

[0007] The purpose of the present application is to solve the technical problems of traditional general industrial solid waste backfilling methods, such as extensive partition management, insufficient environmental risk control, and low space utilization efficiency. The present application provides a method for backfilling solid waste in layers and partitions in abandoned concave mining pits. Through the deep cross of environmental engineering, geotechnical engineering, material science and Internet of Things technology, the solid waste disposal is upgraded from "end filling" to "geological space remodeling-solid waste resource activation" active control mode. Under the premise of ensuring the safety and environmental protection requirements during the backfilling process and after the site closure, the low-cost disposal of general industrial solid waste and the resource utilization of abandoned concave mining pits are realized, which promotes convenient, partitioned, orderly and high-quality storage and disposal, realizes the multiple purposes of general industrial solid waste resource utilization and safe and environmentally friendly disposal, and opens up a new technical path for the synergistic effect of mine pit repair and solid waste disposal.

[0008] To achieve the above-mentioned purpose of the present application, a method for backfilling solid waste in layers and partitions in abandoned concave mining pits is provided. According to the characteristics, yield and stacking plan of the general industrial solid waste to be stored and disposed, the surface of the nearby abandoned concave mining pit is cleaned and disposed, the surrounding rock microcracks caused by the mining process are grouted, and the artificial anti-seepage layer of surrounding rock and basement is laid. The method is implemented by the following steps:

[0009] S1 Surrounding rock and bottom anti-seepage treatment of abandoned concave mining pit

[0010] According to the actual site conditions of the selected abandoned concave pit, the microcracks of the surrounding rock mass of the abandoned concave pit are filled with early strength ultra-fine alkali-activated silicon-aluminum-based solid waste materials, and the original ground at the bottom of the abandoned concave pit is cleaned and leveled, and then an artificial anti-seepage layer is laid on the surrounding rock base of the original ground by using early strength ultra-fine alkali-activated silicon-aluminum-based solid waste materials with initial setting time ≤ 30 min, and then a pit bottom grouting reinforcement layer, a solidification backfill layer and an artificial composite anti-seepage layer are laid on the artificial anti-seepage layer at the bottom of the abandoned concave pit from bottom to top, which further ensures safety through the artificial anti-seepage layer of the surrounding rock and the base, so as to avoid leakage and pollution of the surrounding environment. The pit bottom grouting reinforcement layer, the solidification backfill layer and the artificial composite anti-seepage layer jointly constitute the composite anti-seepage layer at the bottom of the abandoned concave pit. The pit bottom grouting reinforcement layer not only ensures the anti-seepage effect of the bottom, but also ensures the firmness of the bottom stratum base, avoiding the generation of cracks and solution infiltration in the base rock stratum during long-term storage; the solidification backfill layer forms a high-strength backfill layer, which is the most important part of the foundation to ensure the stability of the foundation, effectively ensuring the stability of the foundation during backfilling and avoiding uneven settlement during the backfilling pressure process; the uppermost layer is an artificial composite anti-seepage layer, which is directly in contact with the backfill solid waste and is used to prevent solution infiltration in the backfill material.

[0011] S2 Grid-shaped solid waste partition backfill area construction

[0012] According to the size and strike of the abandoned concave pit, a first layer of longitudinal trapezoidal permeable dam is constructed in the long axis direction of the abandoned concave pit above the composite anti-seepage layer at the bottom of the abandoned concave pit, and a first layer of transverse trapezoidal permeable dam is constructed in the short axis direction of the abandoned concave pit; the longitudinal trapezoidal permeable dam and the transverse trapezoidal permeable dam jointly constitute the bottommost grid-shaped solid waste partition backfill area; the longitudinal trapezoidal permeable dam and the transverse trapezoidal permeable dam are collectively referred to as trapezoidal permeable dams, and the top width of the trapezoidal permeable dam is the width required for the transportation and construction vehicles to travel; a leachate collection pipe for collecting general solid waste leachate is arranged at the bottom of the transverse trapezoidal permeable dam, the outlet of the leachate collection pipe is connected with a leachate diversion pipe, the outlet of the leachate diversion pipe is communicated with a leachate treatment area of the solid waste landfill, and the leachate diversion pipe collects leachate from each layer and discharges it into the leachate treatment area. In order to realize graded and partitioned backfilling, the backfilling material in each grid can be set as different backfilling areas, and the solid waste for backfilling is planned and classified according to physical and chemical properties such as category and water content, and is filled in the grid, which can facilitate the recycling and utilization of non-permanent backfilling solid waste. The trapezoidal permeable dam should ensure vehicle passage to facilitate the construction and transportation vehicles to dump waste into the backfilling area.

[0013] S3 Layered and partitioned backfilling of solid waste

[0014] According to the characteristics of different types of solid waste, the solid waste is classified and backfilled in the bottom layer of the grid-shaped solid waste partitioned backfill area. After the bottom layer of the grid-shaped solid waste partitioned backfill area is filled with solid waste, the surface of the solid waste is compacted and leveled, and a solidified backfill layer is laid on the compacted and leveled surface of the solid waste. Then, the second layer of longitudinal trapezoidal permeable dams is constructed on the first layer of longitudinal trapezoidal permeable dams, and the second layer of transverse trapezoidal permeable dams is constructed on the first layer of transverse trapezoidal permeable dams, thereby forming the second layer of grid-shaped solid waste partitioned backfill area. According to the characteristics of different types of solid waste, the solid waste is classified and backfilled in the second layer of grid-shaped solid waste partitioned backfill area. After the second layer of grid-shaped solid waste partitioned backfill area is filled with solid waste, the surface of the solid waste is compacted and leveled, and a solidified backfill layer is laid on the compacted and leveled surface of the solid waste. In this way, the third layer, the fourth layer, and the nth layer are sequentially constructed, partitioned and backfilled from bottom to top until the designed height is reached, and the uppermost layer of grid-shaped solid waste partitioned backfill area is filled. The thickness of each layer can be set according to the type, physical and chemical characteristics of the stored solid waste, and the filling progress. The bottom of the transverse trapezoidal permeable dams of each layer is provided with a leachate collection pipe for collecting general solid waste leachate. The outlet of the leachate collection pipe is connected to a leachate guide pipe, and the outlet of the leachate guide pipe is connected to a solid waste landfill leachate treatment area.

[0015] It should be noted that during the process of filling solid waste in the bottom layer of the grid-shaped solid waste partitioned backfill area, high-moisture solid waste needs to be left to stand and wait for its leachate to be completely drained through the leachate collection pipe and the leachate guide pipe. After the backfill waste is filled, it is compacted and leveled. During the standing and draining process, the same layer of grid can be alternately filled to effectively ensure the backfill efficiency. After the different grid backfill areas are filled and compacted, a solidified backfill layer with the same strength as the bottom layer of the basement is laid on the compacted and leveled surface of the solid waste, so as to ensure the strength of the backfilled solid waste in the independent area.

[0016] S4 surface treatment

[0017] After the uppermost grid-shaped solid waste partition backfill area is filled with solid waste, the solid waste on the surface of the uppermost grid-shaped solid waste partition backfill area is leveled, after leveling, waste rock is laid to form a waste rock heap preloading layer, and an artificial anti-seepage barrier layer is arranged on the surface of the waste rock heap preloading layer, and a topsoil layer is laid on the artificial anti-seepage barrier layer for agricultural land / construction land / ecological restoration land. The waste rock heap preloading layer is laid to ensure good solidification strength and structural stability, and reduce uneven settlement of the surface layer; the artificial anti-seepage barrier layer is different from the artificial anti-seepage layer laid on the surrounding rock base of the original ground, and the layer is to prevent rainwater on the ground from forming a small part of surface runoff into the solid waste-filled abandoned concave mining pit, and inhibit the oxidation leaching reaction of the generally solid waste which has been drained, compacted and dried. The compaction degree of the waste rock heap preloading layer needs to be more than 90% to ensure the water content and compaction degree of the mixed material.

[0018] Preferably, the early-strength ultra-fine alkali-activated silicon-aluminum-based solid waste material is prepared by mixing slag and fly ash in a certain proportion, adding an alkali activator and water, the mass ratio of slag to fly ash is 3: (0.8-1.2), preferably 3:1; the average particle size of the slag and fly ash is ≤5 μm, the fineness is ≥800 meshes, and the specific surface area is 0.5-0.6 m 2 / g; the alkali activator is NaOH, and the dosage is 4%-8% of the total mass of slag and fly ash. Under the condition of forming a slurry with a water-cement ratio of 1:1, the viscosity is ≤0.1 Pa·s, the grouting flow is 50-60 L / min, and the final grouting pressure is not higher than 6 MPa.

[0019] Preferably, the artificial anti-seepage barrier layer uses a silicon-calcium solid waste-based barrier material, the overall thickness of the artificial anti-seepage barrier layer is not less than 50 cm, the permeability coefficient of the 7-day consolidated body is ≤1×10 -5 cm / s, and the 3-5 day consolidated body has a compressive strength of ≥1 MPa.

[0020] Preferably, the artificial composite anti-seepage layer uses an HDPE composite geomembrane anti-seepage material, and a modified epoxy resin is used as the adhesive material. Different material models are selected according to different backfill solid wastes and geological characteristics.

[0021] Preferably, the solidified backfill layer uses a silicon-calcium solid waste-based cemented tailings backfill material with a cement-sand ratio of (0.8-1.2):6, preferably 1:6, uses local waste rock and tailings as aggregate, and has a thickness of not less than 0.5 m and a 28-day consolidated body with a compressive strength of ≥3.5 MPa.

[0022] Preferably, the raw materials and mass ratio used in the bottom grouting reinforcement layer of the mining pit are as follows: ordinary Portland cement 70% to 80%, quartz sand / tailings sand with a particle size of 0.1-0.5 mm 15% to 25%, superplasticizer 0.5 to 1%, micro-expansion agent 3% to 5%, early strength agent 1% to 1%; initial setting time 30-45 minutes, 7-day compressive strength ≥ 12 MPa, 28-day compressive strength ≥ 25 MPa; slurry flowability ≥ 250 mm during grouting, water-cement ratio 0.5 to 0.6; and the permeability coefficient of the bottom grouting reinforcement layer of the mining pit is ≤ 1 × 10 -8 cm / s when it is stable.

[0023] Preferably, the artificial anti-seepage layer adopts a two-layer structure, the main anti-seepage layer is a HDPE geomembrane with a thickness of 1.5-2.0 mm, and the protective layer is a non-woven geotextile with a weight ≥ 400 g / m 2 Preferably, the permeability coefficient of the artificial anti-seepage layer is ≤ 1 × 10 -11 cm / s, the tensile strength is ≥ 20 kN / m, the elongation at break is ≥ 500%, and the puncture resistance is ≥ 500N. The construction requirements and key points of the artificial anti-seepage layer are as follows: the flatness of the foundation is ≤ 3 cm / 2 m; the overlap width of the membrane material is ≥ 10 cm; the welding temperature is 180-220℃; the welding seam is detected by vacuum pressure to avoid the membrane material being pierced by sharp objects; a proper slackness is reserved during laying, and the protective layer is constructed in a timely manner.

[0024] Preferably, the thickness of the single-layer grid-shaped solid waste partition backfill area is 0.5 m to 2 m, and the area of a single grid should be 60 m × 60 m to 120 m × 120 m. The grid size can be adjusted according to the characteristics and types of solid waste, and the grid distribution can be adjusted according to the geological features of the waste concave mining pit.

[0025] Preferably, the topsoil layer is laid on the artificial anti-seepage barrier layer, and the thickness of the soil layer covering for agricultural land is 0.8-1.0 m, and the thickness of the soil layer covering for ecological restoration land is 0.5-0.7 m.

[0026] Preferably, the material of the leachate collection pipe and the leachate diversion pipe is hard polyvinyl chloride plastic pipe, and the pipe has a compressive strength of ≥ 5 MPa. The diameter of the pipe at the bottom of each trapezoidal permeable dam can be determined according to the water content of the filled solid waste.

[0027] Further, in the S1 step, the injection filling of the micro-fracture of the surrounding rock mass of the waste concave mining pit is implemented by using the coupled rock mass fracture grouting anti-seepage technology, and the drilling spacing is 3 m × 3 m to 5 m × 5 m.

[0028] The artificial anti-seepage barrier layer adopts a silicon-calcium solid waste-based barrier material, mainly using local solid wastes such as fly ash, slag, steel slag, and carbide slag, and can be mixed with tailings and waste rocks and the like. Water is sprayed during the mixing process to ensure that the moisture content of the mixed material is controlled at 15% to 18%. The mixed material is spread in two layers on the surface of the compacted backfill area, and the thickness of each layer is 26 cm to 35 cm, preferably 30 cm. After spreading, the material is compacted by a road roller, and the thickness after rolling is about 23 cm to 27 cm. When the compaction degree is more than 90%, the first layer is considered to be completed. Then, the second layer is spread, and the construction process of the first layer is repeated.

[0029] The method for filling solid waste in a waste concave pit in layers and zones according to the present application has the following positive effects after adopting the above technical solution:

[0030] 1) The method considers the problems of extensive zoning management and low space utilization efficiency in the traditional general industrial solid waste backfilling method. The method adopts "fine zoning, accurate management, risk control, and space optimization". The idle space resources of the waste concave pit are divided into layers and zones by the trapezoidal permeable dam. The backfilling area is classified according to the properties of the solid waste (such as non-permanent storage or permanent disposal), and accurate filling is achieved. The method effectively realizes the use of the waste concave pit for filling solid waste in layers and zones, and can effectively plan and design the sites for non-permanent storage and permanent disposal of solid waste.

[0031] 2) The method considers the problem of lack of effective adaptation of high-moisture solid waste (such as tailings) and materials with significant discrete physical and chemical properties. The trapezoidal permeable dam is used to realize the grid-shaped backfilling area in layers and zones. By controlling the staggered filling of different grid backfilling areas, the drainage time can be effectively shortened, and the backfilling efficiency of high-moisture solid waste can be improved.

[0032] 3) The method considers the safety risks in the backfilling operation. After the single grid backfilling area is filled, the surface compaction and reinforcement can ensure the stability of the site, avoid damage to transport vehicles and collapse of the backfilling edge area, and avoid uneven settlement of the entire backfilling area of the waste concave pit, which can be beneficial to widening the application range of the backfilling area of the waste concave pit.

[0033] 4) The method considers the low leachate collection efficiency and the damage to the anti-seepage layer in the traditional general industrial solid waste backfilling method. The inverted trapezoidal "funnel"-shaped backfilling body formed by the trapezoidal permeable dam can effectively accelerate the drainage process of high-moisture solid waste, effectively reduce the pollution amount of leachate, and collect the leachate. The method effectively reduces the impact of leachate on the basement anti-seepage layer and reduces the persistent threat to the water and soil environment.

[0034] 5) This method takes into account the potential for leakage channels to form in the surrounding rock fissures of abandoned sunken mining pits. By coupling this method with rock mass fissure grouting and anti-seepage technology, it effectively manages the infiltration and diffusion of small amounts of leachate in the fractured rock and soil layers, allowing abandoned sunken mining pits to be used as solid waste backfill storage and disposal sites, thereby increasing the utilization value of the space. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A plan view of a layer of a method for backfilling solid waste in a stratified and partitioned manner in an abandoned sunken mining pit according to the present invention;

[0036] Figure 2 A cross-sectional view of a method for backfilling solid waste in abandoned sunken pits in layers and partitions according to the present invention;

[0037] Figure 3 for Figure 2 A partial enlarged view;

[0038] Figure 4 for Figure 2 B is a partial enlarged view;

[0039] Figure 5 This is a cross-sectional view of a single-grid backfilling area of ​​a method for backfilling solid waste in layers and zones in abandoned sunken mining pits according to the present invention.

[0040] Figure markings: 1-micro cracks in surrounding rock; 2-artificial anti-seepage layer; 3-"funnel" type solid waste backfill body; 4-bottom-layer grid-shaped solid waste partitioned backfill area; 5-artificial composite anti-seepage layer; 6-solidified backfill layer; 7-grouting reinforcement layer at the bottom of the mining pit; 8-top-layer grid-shaped solid waste partitioned backfill area; 9-waste rock pile preloading layer; 10-artificial anti-seepage barrier layer; 11-agricultural land / construction land / ecological restoration land; 12-trapezoidal permeable dam; 12H-horizontal trapezoidal permeable dam; 12Z-longitudinal trapezoidal permeable dam; 13-leachate collection pipe; 14-leachate diversion pipe. DETAILED DESCRIPTION

[0041] To further describe the present invention, a method for backfilling solid waste in abandoned sunken mining pits in layers and zones according to the present invention will be described in further detail below with reference to the accompanying drawings.

[0042] Depend on Figure 1 The present invention is a method for backfilling solid waste in abandoned sunken pits in layers and zones. Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 It can be seen that the method of the present invention, which is applicable to backfilling solid waste in layers and zones in abandoned sunken mining pits, is implemented by the following steps:

[0043] S1 Abandoned sunken pit surrounding rock and bottom anti-seepage treatment

[0044] According to the actual site condition of the selected abandoned concave pit, the micro fissure 1 of the surrounding rock mass of the abandoned concave pit is filled and plugged with early strength type ultra-fine alkali activated silicon-aluminum based solid waste material, the filling and plugging is implemented by using coupling rock mass fissure grouting anti-seepage technology, the drilling spacing is 3 m x 3 m ~ 5 m x 5 m, the grouting flow is 50 ~ 60 L / min, and the final grouting pressure is not higher than 6 MPa. The original surface of the bottom of the abandoned concave pit is cleaned and leveled, and then the early strength type ultra-fine alkali activated silicon-aluminum based solid waste material with initial setting time ≤ 30 min is used to lay an artificial anti-seepage layer 2 on the surrounding rock base of the original surface, and then the bottom grouting reinforcement layer 7, the solidified backfill layer 6 and the artificial composite anti-seepage layer 5 are laid on the artificial anti-seepage layer 2 from bottom to top, and the bottom grouting reinforcement layer 7, the solidified backfill layer 6 and the artificial composite anti-seepage layer 5 jointly constitute the composite anti-seepage layer of the bottom of the abandoned concave pit.

[0045] In the embodiment, the early strength type ultra-fine alkali activated silicon-aluminum based solid waste material is mixed by slag and fly ash in a certain proportion, and an alkali activator and water, the mass ratio of slag to fly ash is 3:1; the average particle size of the slag and fly ash is ≤ 5 μm, the fineness is ≥ 800 meshes, and the specific surface area is 0.5 ~ 0.6 m 2 / g; the alkali activator is NaOH, the dosage is 4% ~ 8% of the total mass of slag and fly ash, and the viscosity under the condition of forming a slurry with a water-cement ratio of 1:1 is ≤ 0.1 Pa·s. The artificial anti-seepage layer 2 adopts a two-layer structure, the main anti-seepage layer is HDPE geomembrane with a thickness of 1.5-2.0 mm, and the protective layer is non-woven geotextile with a weight ≥ 400 g / m 2 The permeability coefficient of the artificial anti-seepage layer 2 is ≤ 1 x 10 -11cm / s, tensile strength ≥ 20 kN / m, elongation at break ≥ 500%, puncture resistance ≥ 500 N. The artificial composite impermeable layer 5 uses HDPE composite geomembrane impermeable material, and modified epoxy resin as the bonding material. The solidified backfill layer 6 uses a silico-calcium solid waste-based cemented tailings backfill material with a sand-to-cement ratio of 1:6, uses local waste rock and tailings as aggregate, and has a thickness of not less than 0.5 m, with a 28-day compressive strength of the solidified body ≥ 3.5 MPa. The grouting reinforcement layer 7 at the bottom of the mining pit uses the following raw materials and mass ratios: ordinary Portland cement 70%-80%, quartz sand / tailings sand with a particle size of 0.1-0.5 mm 15%-25%, high-efficiency water reducing agent 0.5-1%, micro-expansion agent 3%-5%, and early strength agent 1%-2%; initial setting time 30-45 minutes, 7-day compressive strength ≥ 12 MPa, 28-day compressive strength ≥ 25 MPa; slurry flowability ≥ 250 mm when grouting, water-cement ratio 0.5-0.6; the permeability coefficient of the grouting reinforcement layer 7 at the bottom of the mining pit is ≤ 1×10 -8 cm / s.

[0046] S2 Grid-shaped solid waste partitioned backfill area construction

[0047] According to the size and strike of the abandoned concave mining pit, a first layer of longitudinal trapezoidal permeable dam 12Z is constructed in the long axis direction of the abandoned concave mining pit above the composite impermeable layer at the bottom of the abandoned concave mining pit, and a first layer of transverse trapezoidal permeable dam 12H is constructed in the short axis direction of the abandoned concave mining pit; the longitudinal trapezoidal permeable dam 12Z and the transverse trapezoidal permeable dam 12H together constitute the bottommost grid-shaped solid waste partitioned backfill area 4. The longitudinal trapezoidal permeable dam 12Z and the transverse trapezoidal permeable dam 12H are collectively referred to as trapezoidal permeable dam 12, and the upper top width of the trapezoidal permeable dam 12 is the width required for the transportation and construction vehicles to travel; a leachate collection pipe 13 for collecting general solid waste leachate is provided at the bottom of the transverse trapezoidal permeable dam 12H, the outlet of the leachate collection pipe 13 is connected to a leachate diversion pipe 14, and the outlet of the leachate diversion pipe 14 is connected to the leachate treatment area of the solid waste landfill.

[0048] S3 Layered and partitioned backfill of solid waste

[0049] According to the characteristics of different types of solid waste, the solid waste is classified and backfilled in the bottom layer of the grid-shaped solid waste partition backfill area 4. After the bottom layer of the grid-shaped solid waste partition backfill area 4 is filled with solid waste, the surface of the solid waste is compacted and leveled, and then a solidified backfill layer 6 is laid on the compacted and leveled solid waste surface. Then, the second layer of longitudinal trapezoidal permeable dam 12Z is constructed on the first layer of longitudinal trapezoidal permeable dam 12Z, and the second layer of horizontal trapezoidal permeable dam 12H is constructed on the first layer of horizontal trapezoidal permeable dam 12H, thereby forming a second layer of grid-shaped solid waste partition backfill area. According to the characteristics of different types of solid waste, the solid waste is classified and backfilled in the second layer of grid-shaped solid waste partition backfill area. After the second layer of grid-shaped solid waste partition backfill area is filled with solid waste, the surface of the solid waste is compacted and leveled, and then a solidified backfill layer 6 is laid on the compacted and leveled solid waste surface. In this way, the third layer, the fourth layer,..., and the nth layer are sequentially constructed, partitioned and backfilled from bottom to top until the backfilling reaches the designed height, and the uppermost layer of grid-shaped solid waste partition backfill area 8 is filled. The thickness of a single layer of grid-shaped solid waste partition backfill area is 0.5m-2m, which can be adjusted according to the actual topographic features of the waste concave pit, the types of solid waste stored, the physical and chemical characteristics and the filling progress. The area of a single grid should be 60m x 60m-120m x 120m. According to the differences in water content and physical and chemical properties of the backfilled waste, a "funnel" type solid waste backfill body 3 is formed in the grid-shaped solid waste partition backfill area, which is more conducive to the settlement and compaction of high-moisture solid waste. At the bottom of each layer of horizontal trapezoidal permeable dam 12H, there is a leachate collection pipe 13 for collecting general solid waste leachate. The outlet of the leachate collection pipe 13 is connected to a leachate guide pipe 14, and the outlet of the leachate guide pipe 14 is connected to a solid waste landfill leachate treatment area. The materials of the leachate collection pipe 13 and the leachate guide pipe 14 are hard polyvinyl chloride plastic pipes.

[0050] S4 surface treatment

[0051] After the uppermost layer of grid-shaped solid waste partition backfill area 8 is filled with solid waste, the surface of the solid waste in the uppermost layer of grid-shaped solid waste partition backfill area 8 is leveled, and then a waste rock heap preloading layer 9 is laid using waste rock. The compaction degree of the waste rock heap preloading layer 9 is ≥ 90% by using layered compaction + preloading, which can ensure that the settlement amount is less than 5cm in 50 years. An artificial impermeable barrier layer 10 is provided on the surface of the waste rock heap preloading layer 9, and a topsoil layer is laid on the artificial impermeable barrier layer 10 for agricultural land / construction land / ecological restoration land 11. The artificial impermeable barrier layer 10 uses a silicon-calcium solid waste-based barrier material, and the overall thickness of the artificial impermeable barrier layer 10 is not less than 50cm, and the 7-day consolidated body permeability coefficient is ≤ 1x10 -5cm / s, 3-5 days consolidated body compressive strength ≥ 1 MPa. The topsoil layer is laid on the artificial anti-seepage barrier 10, and the soil layer covering thickness for agricultural land is 0.8-1.0 m, and the soil layer covering thickness for ecological restoration land is 0.5-0.7 m.

[0052] In the embodiment, the artificial anti-seepage barrier 10 is divided into two parts (in parts) using a silicon-calcium solid waste-based barrier material. The cementing powder mainly uses steel slag (10 parts), slag (75 parts), desulfurization gypsum (10 parts), and lime powder (5 parts). The cementing powder and tailings can be dry mixed at a ratio of 1:10. Water is sprayed during the mixing process to ensure that the moisture content of the mixed material is controlled at about 17%. The mixed material is spread on the surface of the compacted backfill area in two times, and the thickness of each time is about 30 cm. After spreading, the mixed material is compacted by a road roller, and the thickness after rolling is about 25 cm. When the compaction degree is more than 90, the first layer construction is considered to be completed. Then, the second layer is spread, and the construction process of the first layer is repeated.

[0053] In practical application, the longitudinal trapezoidal water-permeable dam 12Z has a spacing deviation of ≤ 15%, and the grid area change rate is ≤ 20%. The horizontal trapezoidal water-permeable dam 12H of each layer is arranged in the direction of the short axis of the abandoned concave pit in equal intervals, and does not need to be arranged from bottom to top based on the first layer. The actual topographic characteristics of the abandoned concave pit can be adjusted.

[0054] The method of the present application has been applied in a project of filling general industrial solid waste in a closed pit of a certain open-pit iron mine. More than 500,000 tons of different types of general industrial solid waste are treated per year, and the annual benefit is more than 20 million yuan.

[0055] The above description is only a preferred embodiment of the present application, but the protection scope of the present application is not limited thereto. Any skilled person in the art can make equivalent replacements or changes to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for backfilling solid waste in layers and zones in abandoned sunken mining pits, characterized in that Use the following steps to implement: S1 Abandoned sunken pit surrounding rock and bottom anti-seepage treatment According to the actual site conditions of the selected abandoned sunken mining pit, the micro cracks (1) of the surrounding rock mass of the abandoned sunken mining pit are filled with early-strength ultrafine alkali-activated silica-aluminum-based solid waste materials, and the original surface of the bottom of the abandoned sunken mining pit is cleaned and leveled. Then, an artificial anti-seepage layer (2) is laid on the surrounding rock base of the original surface using early-strength ultrafine alkali-activated silica-aluminum-based solid waste materials with an initial setting time of ≤ 30 min. Then, a pit bottom grouting reinforcement layer (7), a solidified backfill layer (6), and an artificial composite anti-seepage layer (5) are laid from bottom to top on the artificial anti-seepage layer (2) at the bottom of the abandoned sunken mining pit. The pit bottom grouting reinforcement layer (7), the solidified backfill layer (6), and the artificial composite anti-seepage layer (5) together constitute the composite anti-seepage layer at the bottom of the abandoned sunken mining pit. S2 Grid-shaped solid waste zoning backfill area construction According to the size and direction of the abandoned pit, a first layer of longitudinal trapezoidal permeable dam (12Z) is constructed on the composite anti-seepage layer at the bottom of the abandoned pit and in the long axis direction of the abandoned pit, and a first layer of transverse trapezoidal permeable dam (12H) is constructed in the short axis direction of the abandoned pit; the longitudinal trapezoidal permeable dam (12Z) and the transverse trapezoidal permeable dam (12H) together constitute the bottom layer of the grid-shaped solid waste partition backfill area (4); the longitudinal trapezoidal permeable dam (12 Z), the transverse trapezoidal permeable dam (12H) is collectively referred to as the trapezoidal permeable dam (12), the upper width of the trapezoidal permeable dam (12) is the width required for the transportation and construction vehicles to travel; a leachate collection pipe (13) for collecting general solid waste leachate is provided at the bottom of the transverse trapezoidal permeable dam (12H), the outlet of the leachate collection pipe (13) is externally connected to a leachate diversion pipe (14), and the outlet of the leachate diversion pipe (14) is connected to the leachate treatment area of ​​the solid waste landfill; S3 Layered and zoned backfill of solid waste According to the characteristics of different types of solid waste, the solid waste is backfilled in the bottom grid-shaped solid waste partition backfill area (4) in a zoned and classified manner. After the bottom grid-shaped solid waste partition backfill area (4) is filled with solid waste, the surface of the solid waste is compacted and leveled, and then a solidified backfill layer (6) is laid on the compacted and leveled surface of the solid waste; then, a second layer of longitudinal trapezoidal permeable dam (12Z) is constructed on top of the first layer of longitudinal trapezoidal permeable dam (12Z), and a second layer of transverse trapezoidal permeable dam (12H) is constructed on top of the first layer of transverse trapezoidal permeable dam (12H), thereby forming a second layer of grid-shaped solid waste partition backfill area; according to the characteristics of different types of solid waste, the solid waste is backfilled in the second layer of grid-shaped solid waste partition backfill area. Backfill the solid waste in different categories. After the second layer of the grid-shaped solid waste partitioned backfill area is filled with solid waste, the surface of the solid waste is compacted and leveled, and then a solidified backfill layer (6) is laid on the compacted and leveled solid waste surface. Similarly, the third, fourth, ... nth layers are constructed and backfilled in layers from bottom to top until the backfill reaches the designed height, and until the topmost grid-shaped solid waste partitioned backfill area (8) is filled. A leachate collection pipe (13) for collecting general solid waste leachate is provided at the bottom of each layer of the transverse trapezoidal permeable dam (12H). The outlet of the leachate collection pipe (13) is externally connected to a leachate diversion pipe (14), and the outlet of the leachate diversion pipe (14) is connected to the leachate treatment area of ​​the solid waste landfill. S4 Surface Treatment After the top grid-shaped solid waste partition backfill area (8) is filled with solid waste, the solid waste on the surface of the top grid-shaped solid waste partition backfill area (8) is leveled, and after leveling, a waste rock preloading layer (9) is laid using waste rock, and an artificial anti-seepage barrier layer (10) is set on the surface of the waste rock preloading layer (9), and a topsoil layer is laid on top of the artificial anti-seepage barrier layer (10) for agricultural land / construction land / ecological restoration land (11).

2. A method for backfilling solid waste in layers and zones in abandoned sunken mining pits as claimed in claim 1, characterized in that: The early-strength ultrafine alkali-activated silicon-aluminum-based solid waste material is prepared by mixing slag and fly ash in proportion, adding an alkali activator and water, and the mass ratio of slag to fly ash is 3: (0.8-1.2); the average particle size of the slag and fly ash is ≤ 5μm, the fineness is ≥ 800 mesh, and the specific surface area is 0.5-0.6 m 2 / g; the alkali activator is NaOH, and the dosage is 4% to 8% of the total mass of slag and fly ash.

3. The method for backfilling solid waste in abandoned sunken mining pits in layers and zones as claimed in claim 1, characterized in that: The artificial anti-seepage barrier layer (10) is made of silicon-calcium solid waste-based barrier material. The overall thickness of the artificial anti-seepage barrier layer (10) is not less than 50 cm, and the 7-day solidified body permeability coefficient is ≤ 1×10 -5 cm / s, and the compressive strength of the consolidated body is ≥ 1 MPa after 3 to 5 days.

4. The method for backfilling solid waste in abandoned sunken mining pits in layers and zones as claimed in claim 1, characterized in that: The artificial composite anti-seepage layer (5) adopts HDPE composite geomembrane anti-seepage material and modified epoxy resin as bonding material.

5. The method for backfilling solid waste in layers and zones in abandoned sunken mining pits according to claim 1, characterized in that: The solidified backfill layer (6) is made of silica-calcium solid waste-based adhesive tailings backfill material with a ash-sand ratio of (0.8-1.2):6, and uses local waste rock and tailings as aggregate. The thickness is not less than 0.5 m, and the 28-day consolidated body compressive strength is ≥ 3.5 MPa.

6. The method for backfilling solid waste in layers and zones in abandoned sunken mining pits according to claim 1, characterized in that: The raw materials and mass ratios used in the pit bottom grouting reinforcement layer (7) are as follows: ordinary Portland cement 70% to 80%, quartz sand / tailings sand with a particle size of 0.1-0.5 mm 15% to 25%, high-efficiency water reducer 0.5% to 1%, micro-expansion agent 3% to 5%, early strength agent 1% to 1%; initial setting time 30 to 45 minutes, 7-day compressive strength ≥ 12 MPa, 28-day compressive strength ≥ 25 MPa; slurry fluidity during grouting ≥ 250 mm, water-cement ratio 0.5 to 0.6; permeability coefficient of the pit bottom grouting reinforcement layer (7) when stable ≤ 1×10 -8 cm / s.

7. The method for backfilling solid waste in layers and zones in abandoned sunken mining pits according to claim 1, characterized in that: The artificial anti-seepage layer (2) adopts a two-layer structure, the main anti-seepage layer is a HDPE geomembrane with a thickness of 1.5-2.0 mm, and the protective layer is a HDPE geomembrane with a weight of ≥ 400 g / m 2 Non-woven geotextile; the permeability coefficient of the artificial anti-seepage layer (2) ≤ 1×10 -11 cm / s, tensile strength ≥ 20 kN / m, elongation at break ≥ 500%, puncture resistance ≥ 500N.

8. A method for backfilling solid waste in layers and zones in abandoned sunken mining pits as claimed in claim 1, 2, 3, 4, 5, 6 or 7, characterized in that: The thickness of a single-layer grid-shaped solid waste partition backfill area is 0.5m to 2m, and the area of ​​a single grid should be 60m × 60m to 120m × 120m.

9. A method for backfilling solid waste in layers and zones in abandoned sunken mining pits as claimed in claim 8, characterized in that: A topsoil layer is laid on the artificial anti-seepage barrier layer (10). The thickness of the topsoil layer for agricultural land is 0.8 to 1.0 m, and the thickness of the topsoil layer for ecological restoration land is 0.5 to 0.7 m.

10. The method for backfilling solid waste in layers and zones in abandoned sunken mining pits according to claim 9, characterized in that: The leachate collecting pipe (13) and the leachate diversion pipe (14) are made of rigid polyvinyl chloride plastic pipes. In step S1, the micro-cracks (1) of the surrounding rock mass of the abandoned sunken pit are grout-filled using a coupled rock mass crack grouting anti-seepage technology, with a drilling spacing of 3 m × 3 m to 5 m × 5 m.

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