Efficient and energy-saving combined drainage method for closed tailings pond

Abstract

The invention relates to the technical field of tailing pond treatment, in particular to a tailing pond closing efficient energy-saving combined drainage method which comprises a drainage area division step and a combined drainage construction step. Wherein for the deep fine silt saturated water area, a passive self-drainage and drainage layer independent of external power is constructed, the self-drainage and drainage layer is composed of a horizontal layered structure, the structure at least comprises an evaporation water guide layer and a capillary conducting layer which are arranged from top to bottom, and the capillary conducting layer is laid on the leveled beach face and used for sucking water in lower fine silt; the evaporation water guide layer is used for guiding the water absorbed by the capillary conduction layer upwards and promoting the evaporation of the water; through regional identification and differentiated treatment strategies, active drainage and passive drainage technologies are combined, a self-drainage and drainage layer structure based on natural force driving is adopted, comprehensive drainage from ground surface water to deep fine silt confining water is achieved in a safe, economical and efficient mode, the beach face bearing capacity is rapidly improved, and the service life of the beach face is prolonged. And conditions are created for subsequent closed reservoir engineering construction.

Description

Technical Field

[0001] This invention relates to the field of tailings dam management technology, and in particular to a high-efficiency and energy-saving combined drainage method for tailings dam closure. Background Technology

[0002] Tailings ponds, as facilities for storing tailings slurry after mineral processing, often have complex sedimentation conditions due to long-term discharge before closure and remediation. The following problems are common: large amounts of surface water accumulate in low-lying areas of the pond, forming ponds; while in the vast beach areas, tailings sand and mud contain a large amount of pore water and bound water in both shallow and deep layers due to sedimentation and sorting, and the overall state is saturated or supersaturated, resulting in extremely low beach bearing capacity.

[0003] Currently, the conventional drainage methods used in the industry to address this type of problem mainly include: For open water, drainage ditches are dug mechanically or manually to divert the flow, but equipment and personnel are prone to getting stuck in the surrounding soft mud, resulting in high safety risks and low efficiency. For shallow water-bearing areas, we tried to excavate grid-shaped drainage ditches, but for fine mud layers with extremely poor permeability, the drainage effect was slow and the ditches were prone to collapse and blockage. For deep water-bearing formations, active pumping technologies such as lightweight wellpoint dewatering are used. However, this method requires a continuous power supply, resulting in high energy consumption. Furthermore, the filter tubes are prone to clogging in fine-particle environments, making maintenance difficult and costly.

[0004] The common problem with existing technologies is that they rely too heavily on active mechanical excavation or power pumping. When dealing with large-scale, low-permeability, saturated fine mud areas, they exhibit high energy consumption, low efficiency, poor safety, and unstable long-term effects. In particular, for capillary water and weakly bound water "trapped" in tailings, traditional gravity drainage or negative pressure suction principles are difficult to effectively drive their migration, becoming a key bottleneck restricting the progress and safety of reservoir closure construction.

[0005] Therefore, existing tailings dam closure and drainage methods rely excessively on active mechanical excavation or power pumping, which leads to problems such as high energy consumption, low efficiency, poor safety, and unstable long-term effects when dealing with large-scale, low-permeability fine mud saturated areas. To address these issues, a highly efficient and energy-saving combined drainage method for tailings dam closure is proposed. Summary of the Invention

[0006] To overcome the problem that existing tailings dam closure and drainage methods rely too heavily on active mechanical excavation or power pumping, which results in high energy consumption, low efficiency, poor safety, and unstable long-term performance when dealing with large-scale, low-permeability, fine mud-saturated areas.

[0007] The technical solution of this invention is: a high-efficiency and energy-saving combined drainage method for tailings dam closure, comprising the following steps: S1: Drainage area division steps: Based on the water surface morphology of the tailings pond beach, the tailings particle size distribution and water depth, the area to be treated is divided into open water area, shallow saturated water area and deep fine mud saturated water area. S2: Combined drainage construction steps: S21: For the open water area, construct a surface flow drainage channel to guide the open water to a preset water collection or drainage structure; S22: For the shallow saturated area, a shallow drainage ditch network system is constructed to collect and drain the shallow stagnant water in the area; S23: For the deep fine mud saturated area, a passive self-draining and dewatering layer that does not rely on external power is constructed. The self-draining and dewatering layer is composed of a horizontal layered structure, which includes at least an evaporation water-conducting layer and a capillary conduction layer arranged from top to bottom. The capillary conduction layer is laid on the leveled beach surface and is used to absorb water from the lower fine mud. The evaporation water-conducting layer is used to guide the water absorbed by the capillary conduction layer upward and promote its evaporation.

[0008] Preferably, in step S1, the open water area is an area with visible surface water; the shallow saturated area is an area with no surface water and an estimated saturation depth within a preset first depth threshold; the deep fine mud saturated area is an area mainly composed of fine-particle tailings, with an estimated saturation depth exceeding the first depth threshold and a permeability coefficient lower than a preset threshold.

[0009] Preferably, in step S21, the method of constructing the surface flow drainage channel is: to form a trench by hydraulic erosion and to control the slope of the trench so that the water can flow by gravity.

[0010] Preferably, in step S22, the shallow drainage network system includes a main drainage ditch and capillary blind ditches. The capillary blind ditches are distributed on both sides of the main drainage ditch and are connected to the main drainage ditch. The capillary blind ditches are filled with permeable aggregate.

[0011] Preferably, the shallow drainage network system is connected to the edge of the self-draining and dewatering layer or via a drainage pipe, for receiving and draining water discharged from the self-draining and dewatering layer.

[0012] Preferably, in step S23, a moisture transport and storage layer is further provided between the capillary conduction layer and the evaporative water-conducting layer. The moisture transport and storage layer is composed of a mixture of highly absorbent resin particles and hydrophobic porous aggregate.

[0013] Preferably, the hydrophobic porous aggregate is an inorganic or organic porous particle that has undergone surface hydrophobic modification.

[0014] Preferably, in step S23, while or after constructing the self-draining and dewatering layer, vertical drainage units are arranged at preset intervals in the deep fine mud saturated area. The lower end of the vertical drainage unit extends into the permeable layer at the bottom of the deep fine mud saturated area or deeper. The vertical drainage unit is filled with water-conducting material, and its upper part is connected to the water transport and storage layer or evaporation water-conducting layer of the self-draining and dewatering layer.

[0015] Preferably, the water-conducting material filled in the vertical drainage unit comprises highly absorbent resin particles.

[0016] Preferably, the evaporative water-conducting layer is a permeable geosynthetic material layer with a dark surface color and a three-dimensional spatial structure.

[0017] The beneficial effects of this invention are: In treating deep, fine, saturated mud zones, this invention constructs a passive, self-draining dewatering layer consisting of a capillary conduction layer, a water transport and storage layer, and an evaporative water-conducting layer. It employs vertical drainage units, utilizing capillary force as the driving force for water rise, solar energy as the driving force for water evaporation, and the moisture regulation capabilities of functional materials (SAP, hydrophobic aggregates). These steps work synergistically to form a continuous, stable, and externally-power-free drainage and solidification system characterized by "downward suction-middle storage / transportation-upward evaporation" or "downward suction-middle storage / transportation-side discharge / downward infiltration." The mechanism overcomes the problem of low drainage efficiency of traditional methods for low-permeability fine mud layers, and achieves effective removal of "trapped water". At the same time, the entire method significantly reduces the operating range and depth of heavy machinery on dangerous soft foundations, improving construction safety. Its passive operation characteristics reduce long-term energy consumption and maintenance costs. The flexibility of the zoning combination enables it to adapt to the complex and variable geological and hydrological conditions within the tailings dam, thereby achieving the effect of efficient, energy-saving, safe and economical comprehensive dewatering of the tailings dam surface and rapid improvement of bearing capacity before closure. Attached Figure Description

[0018] Figure 1 The illustration shows a schematic diagram of the implementation of the tailings dam closure high-efficiency and energy-saving combined drainage method of the present invention for treating the deep fine mud saturated area. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Example 1 Please see Figure 1 This invention provides an embodiment: a high-efficiency and energy-saving combined drainage method for tailings dam closure, comprising the following steps: S1: Drainage Area Delineation Steps: Based on the water morphology of the tailings pond beach, the tailings particle size distribution, and the water depth, the area to be treated is divided into open water area, shallow saturated water area, and deep fine mud saturated water area. This delineation is based on hydrogeological surveys and on-site investigations, such as through exploratory pits, static cone penetration tests, or pore water pressure tests, to determine the boundaries of each area. The preferred delineation criteria are: the open water area is the area with visible surface water; the shallow saturated water area is the area without surface water and whose estimated saturation depth is within a preset first depth threshold (e.g., 3 meters). In this area, the tailings particles are relatively coarse and have a certain degree of permeability; the deep fine mud saturated water area is the area mainly composed of fine-particle tailings (e.g., particles smaller than 0.075 mm accounting for more than 40%), whose estimated saturation depth exceeds the first depth threshold, and whose permeability coefficient is lower than the preset threshold (e.g., on the order of 10^-5 cm / s). This area is the difficult and key point for drainage consolidation. S2: Combined drainage construction steps: S21: For open water areas, construct surface flow drainage channels to guide the open water to pre-designated water collection or drainage structures (such as existing drainage wells or newly constructed pumping stations); in a preferred embodiment, a trench is formed by hydraulic erosion, using high-pressure water jets to cut, suspend, and transport slurry to naturally form a drainage ditch, and the slope of the trench is measured and controlled to ensure that the water can flow by gravity; this method avoids the risks of heavy machinery operating on soft soil. S22: For shallow saturated areas, a shallow drainage network system is constructed to collect and drain shallow stagnant water in the area; in a preferred embodiment, the system includes an excavated main drainage ditch and capillary blind ditches distributed on both sides thereon; the capillary blind ditches are filled with permeable aggregate (such as graded gravel) and covered with geotextile to prevent siltation; the network can effectively intercept and collect shallow groundwater runoff and accelerate the desiccation of the area; S23: For deep, fine mud saturated areas, a passive self-draining and dewatering layer that does not rely on external power is constructed. The self-draining and dewatering layer consists of a horizontal layered structure, which includes at least an evaporative water-conducting layer and a capillary conduction layer arranged from top to bottom. The capillary conduction layer is laid on the leveled mud surface and is usually made of hydrophilic non-woven geotextile with a high capillary rise height. Its working principle is to utilize the micropores formed between fibers to generate strong capillary force, actively and continuously drawing capillary water and weakly bound water from the micropores of the underlying fine mud and causing them to migrate upwards. The evaporative water-conducting layer covers the capillary conduction layer and is preferably a permeable geosynthetic material layer with a dark surface color (such as black) and a three-dimensional spatial structure. Its dark surface enhances solar radiation absorption and increases its own and the temperature of the underlying layer. The three-dimensional structure provides a huge evaporation surface area and air circulation channels, thereby accelerating the vaporization and dissipation process of water migrating from the capillary conduction layer. This passive cycle of "bottom absorption and top evaporation" achieves continuous drainage without the need for external energy input.

[0021] As a further preferred embodiment of the present invention, a moisture transport and storage layer is provided between the capillary conduction layer and the evaporative water-conducting layer; this layer is composed of a mixture of highly absorbent resin particles and hydrophobic porous aggregate; the highly absorbent resin particles can quickly absorb and temporarily store a large amount of moisture from the capillary conduction layer, playing a buffering and water-retaining role and preventing moisture backflow; the hydrophobic porous aggregate is preferably inorganic (such as waste ceramic particles) or organic porous particles that have undergone surface hydrophobic modification, which form a hydrophobic interconnected pore network in the mixture; this network provides a horizontal fast transport channel for liquid water (including water released from SAP), guiding the water flow to the water collection point or edge; on the other hand, its hydrophobic properties ensure that the pores are not completely blocked by water, and always maintain the water-conducting capacity.

[0022] As a further preferred embodiment of the present invention, in step S23, while or after constructing the self-draining dewatering layer, vertical drainage units are arranged at a preset interval (e.g., a 15m × 15m grid) within the deep fine mud saturated zone; the lower end of the vertical drainage unit extends into the bottom of the deep fine mud saturated zone or into the permeable layer at a deeper depth, and its upper part is connected to the water transport and storage layer or the evaporation water-conducting layer of the self-draining dewatering layer; the vertical drainage unit is filled with water-conducting material, and preferably contains highly absorbent resin particles; the vertical unit constitutes a "vertical reinforced capillary column" that works in conjunction with the horizontal dewatering layer; it can not only assist in lifting deeper water to the horizontal layer for treatment through capillary action, but also serve as a gravity drainage channel when the horizontal layer is saturated with water or requires rapid drainage, guiding water into the deeper drainage system, forming a "vertical-horizontal" three-dimensional drainage network.

[0023] In addition, to optimize the overall system efficiency, the shallow drainage network system can be connected to the edge of the self-draining and dewatering layer or through a drainage pipe; in this way, the water that is collected and transported from the self-draining and dewatering layer to the edge can be effectively collected and drained by the shallow drainage network system, avoiding secondary accumulation of water in the edge area.

[0024] Through the above steps, the method of this invention, when treating the saturated area of ​​deep fine mud, constructs a passive self-draining and dewatering layer composed of a capillary conduction layer, a water transport and storage layer, and an evaporative water-conducting layer. It employs vertical drainage units, utilizing capillary force as the driving force for water rise, solar energy as the driving force for water evaporation, and the moisture regulation capabilities of functional materials (SAP, hydrophobic aggregates). This series of steps works synergistically to form a continuous and stable "downward suction-middle storage / transport-upward evaporation" or "downward suction-middle storage / transport-side discharge / downward infiltration" system that requires no external power. The drainage consolidation mechanism overcomes the problem of low drainage efficiency of traditional methods for low-permeability fine mud layers, achieving effective removal of "trapped water." Simultaneously, the entire method significantly reduces the operating range and depth of heavy machinery on hazardous soft foundations, improving construction safety. Its passive operation reduces long-term energy consumption and maintenance costs. The flexibility of its zoned combination allows it to adapt to the complex and varied geological and hydrological conditions within the tailings dam, thus achieving efficient, energy-saving, safe, and economical comprehensive dewatering of the tailings dam surface and rapid improvement of its bearing capacity before closure.

[0025] Example 2 Optionally, this embodiment provides a basic but complete tailings dam closure method with high efficiency and energy saving combined drainage.

[0026] The implementation steps are as follows: Site survey and zoning (S1): A detailed survey of the target tailings dam beach surface was conducted; the tailings sedimentary structure, particle size distribution, and water content profile were obtained through geological drilling, static cone penetration testing (CPT), and surface investigation. Based on the survey data, the reservoir area is divided into three functional zones: Area with visible surface water (Zone I): This refers to an area with visible surface water, typically ranging from 0.3 meters to 2.0 meters in depth; its extent is determined by visual inspection combined with topographic surveying. Shallow saturated zone (Zone II): This refers to a zone where there is no surface water, but the groundwater level is relatively shallow (usually the first depth threshold H1 is set at 3.0 meters). The tailings are mainly medium to fine sand, with a permeability coefficient k > 1×10⁻⁶. -4 The region of cm / s; this region can be preliminarily delineated by the CPT cone tip resistance qc value (usually qc < 2 MPa) and pore pressure dissipation test; Deep fine mud saturated zone (Zone III): refers to the tailings sediment deposition zone dominated by silt and clay particles (particle size <0.075mm content >40%), with a saturated depth exceeding 3.0 meters and a permeability coefficient k < 1×10⁻⁶. -5 The weak region is characterized by a shear strength of cm / s and a vane shear strength Su < 20 kPa; this region is the difficult point for drainage consolidation.

[0027] Drainage construction in open water area (S21): Within Zone I, a high-pressure water pump (pressure ≥ 5 MPa) is used to connect to a water gun, and the operator works in a secured safe area or on a floating raft. Through hydraulic erosion, the surface tailings are cut and liquefied along the designed path (pointing to the reservoir drainage wells or the II zone drainage network) to form drainage channels; the slope i of the channels needs to be precisely controlled to ensure gravity drainage; the slope design can be checked based on the following principle formula: i ≥ (v 2 * n 2 ) / R^(4 / 3) Where i is the longitudinal slope of the ditch bottom; v is the design flow velocity (m / s), which is determined according to the characteristics of the tailings slurry; n is the Manning roughness coefficient of the ditch, which can be taken as 0.02-0.03 for muddy ditches formed by erosion; R is the hydraulic radius (m); by real-time measurement, the erosion depth and direction are controlled to ensure that the slope from the ditch inlet to the outlet is continuous and meets the above gravity flow conditions; The mud generated by erosion can be diverted into a pre-designed reinforced geotextile bag for natural sedimentation and consolidation.

[0028] Drainage construction in shallow saturated areas (S22): In Zone II, a small backhoe excavator (equipped with wide tracks) is used to excavate the main drainage ditch, which is 1.5-2.0 meters deep, 1.0 meter wide at the bottom, and has a slope of 1:1.5. The main drainage ditch extends and connects to the end gully of Zone I or directly connects to the drainage well. Within a range of approximately 10-15 meters on both sides of the main drainage ditch, excavate parallel to the surface or lay capillary blind ditches using a trench opener; the spacing between capillary blind ditches should be 3-5 meters, with a depth of 0.8 meters and a width of 0.3 meters; immediately after excavation, backfill with well-graded coarse sand or gravel with a particle size of 5-10 mm as permeable aggregate, and cover the top with needle-punched nonwoven geotextile (specification 200g / m²). 2 To prevent fine particles from entering and clogging the drainage system, the capillary blind drain should slope towards the main drainage ditch at a gradient of not less than 2%.

[0029] Drainage construction of deep fine mud saturated zone (S23): After there is no obvious water accumulation on the surface of Zone III, use a light bulldozer or manual labor to roughly level it; Laying the capillary conduction layer: using high-strength reinforced hydrophilic non-woven geotextile (unit area mass ≥300g / m²). 2 Vertical permeability coefficient > 1×10 -2 cm / s); the overlap width between geotextile webs is not less than 0.5 meters; this layer generates strong capillary force through the micron-level pores formed between its fibers (the capillary rise height can be determined in the laboratory, usually >1.0 meter), and its working principle is similar to the capillary transport model in porous media. The capillary suction potential ψ_c drives the pore water of the lower tailings to migrate upward. Laying the evaporative drainage layer: A black high-density polyethylene (HDPE) three-dimensional drainage composite mat (hereinafter referred to as "three-dimensional mat") is directly laid on the capillary conduction layer. This three-dimensional mat consists of two layers of black geogrid (mesh size approximately 8mm × 6mm) sandwiched in between a layer of black geotextile, with a total thickness ≥10mm. Its dark surface has a high solar radiation absorptivity (α > 0.9), significantly increasing the surface temperature; the three-dimensional structure increases the contact area with air. According to Dalton's law of evaporation, the evaporation rate is proportional to the surface area and the saturated vapor pressure difference, thereby enhancing water evaporation. System connection: Fix the three-dimensional pad at the edge of Zone III with geotextile ropes or U-shaped nails, and extend its end into the capillary blind ditch in Zone II or connect it to the main drainage ditch through a Φ50mm flexible permeable pipe to ensure that the water discharged from Zone III can be effectively collected by the ditch network in Zone II.

[0030] This embodiment achieves rapid drainage of open water and effective collection of shallow water through zoned treatment, and for the first time treats deep fine muddy water through a passive circulation system of "capillary force-evaporation". This method avoids large-scale mechanical excavation in Zone III, significantly improves construction safety, and greatly reduces continuous energy consumption.

[0031] Example 3 Optionally, this embodiment adds a moisture transport and storage layer based on embodiment 2, thereby optimizing the drainage efficiency and stability of zone III.

[0032] The implementation steps are as follows: In this embodiment, steps S1, S21, and S22 are the same as in embodiment 2; in step S23, the structure of the self-draining and dewatering layer in the deep fine mud saturated zone is optimized by adding the following steps: After laying the capillary conduction layer (hydrophilic geotextile) and before laying the evaporative water-conducting layer (black three-dimensional mat), a water transport and storage layer is added. Preparation and Laying of Moisture Transport and Storage Layer: This layer is made by on-site mixing of superabsorbent polymer (SAP) particles and hydrophobic porous aggregate at a dry volume ratio of 1:4; SAP particles are made of cross-linked sodium polyacrylate with a particle size range of 0.5-1.0 mm and a water absorption ratio (deionized water) ≥300 g / g. Their function is to quickly absorb and lock in the water transported from the capillary conduction layer, forming a local "micro reservoir" to prevent water from accumulating on the top of the capillary conduction layer and causing possible reverse osmosis. The hydrophobic porous aggregate is made from waste ceramic particles (particle size 3-8mm, porosity >40%, contact angle >90°) that have been surface modified with silane coupling agent. Its hydrophobic surface ensures that the pore network formed between the aggregates is not completely filled by liquid water, thereby maintaining good gas connectivity and secondary water transport channels. Spread the mixture evenly on the capillary conduction layer to a thickness of 10 cm; after laying, use a light roller (line load <20 kN / m) to statically compact it once to ensure close contact within the layer but without compaction; Structural integration: Subsequently, the evaporative water-conducting layer (black three-dimensional mat) is laid directly on top of the water transport and storage layer; the lower geotextile layer of the three-dimensional mat is in direct contact with the SAP / aggregate mixture layer. At this point, the water migration path becomes: tailings pore water → capillary conduction layer (driven upward by capillary force) → water transport and storage layer (absorbed and stored by SAP, and diffused horizontally within the mixed layer through hydrophobic pore network and concentration gradient) → evaporation water conduction layer (water is guided by the three-dimensional structure to evaporate on the surface, or transported laterally to the edge drainage point through the hydrophobic pore network). The interconnected pores formed by hydrophobic porous aggregates provide a low-resistance horizontal transport path for water vapor and liquid water released by SAP particles during the moisture absorption-desorption cycle. Its water conductivity can be conceptually described by a modified Darcy's law, in which the permeability coefficient is directly related to the connectivity of the hydrophobic pores.

[0033] In this embodiment, the addition of a moisture transport and storage layer buffers the unevenness of moisture supply and improves the system's adaptability to rainy weather; the hydrophobic aggregate network significantly enhances the lateral collection and drainage capacity of moisture, resulting in a wider drainage range and higher efficiency, especially suitable for Zone III, which has a large area and where moisture in the central area is difficult to drain to the edge.

[0034] Example 4 Optionally, based on Example 3, this embodiment introduces a vertical drainage unit to construct a "horizontal-vertical" three-dimensional drainage system, which is suitable for ultra-soft and fine mud areas with large thickness and difficulty in raising deep water.

[0035] The implementation steps are as follows: In this embodiment, steps S1, S21, and S22 are the same as in embodiment 2, and step S23 adds the construction of a vertical drainage unit based on embodiment 3. After the capillary conduction layer and the moisture transport and storage layer have been laid, but the evaporation water-conducting layer has not yet been covered, the following operations shall be performed: Vertical drainage unit layout (S23 supplement): In Zone III, the holes for vertical drainage units are arranged in a grid pattern of 15 meters × 15 meters; Using a light vibratory plate press or static pressure equipment, the prefabricated composite filter tube is vertically pressed into the design depth; the design depth must penetrate the deep fine mud saturated zone of the target treatment and enter the relatively permeable tailings layer below it by at least 0.5 meters; the filter tube is made of biodegradable pulp tube or highly permeable geotextile hose with a diameter of 150mm. The water transport and storage layer mixture (SAP and hydrophobic aggregate) from Example 3 was used as filler and poured into the composite filter tube until it was full; during the filling process, it was gently vibrated to ensure compaction; The top of the vertical drainage unit should protrude approximately 10cm above the surface of the moisture transport and storage layer to ensure good communication with the horizontal layer; Three-dimensional system integration: Subsequently, the evaporative water-conducting layer (black three-dimensional pad) is laid. During the laying process, holes are made in the three-dimensional pad at the top of the vertical drainage unit or it is directly covered on the top of the unit to ensure that the water vapor of the vertical unit is connected to the horizontal evaporative water-conducting layer. At this point, the system works as follows: Horizontal drainage path: Same as in Example 3; Vertical auxiliary drainage path: Moisture in deep tailings is indirectly extracted through the horizontal expansion effect of the capillary conduction layer. On the other hand, the vertical drainage unit itself forms a "giant capillary column". The SAP filler inside it directly attracts moisture from the surrounding soil through hygroscopic action and transports it upward to the horizontal layer through the hydrophobic pore network inside the filler. At the same time, when the horizontal layer is saturated with moisture or the rainy season arrives, the vertical drainage unit can act as a gravity drainage channel, discharging the collected water through its lower permeable section into a deeper drainage layer (such as a pre-designed blind drainage ditch at the bottom of the reservoir), effectively preventing system blockage. Overall system connectivity: Ultimately, the three-dimensional drainage system at the edge of Zone III will be reliably connected to the shallow drainage network of Zone II, forming a complete drainage link from deep to shallow and from the center to the edge.

[0036] In this embodiment, by introducing vertical drainage units, this method forms a crisscrossing three-dimensional drainage network. The vertical units not only enhance the upward migration ability of deep water, but also provide emergency gravity drainage outlets, thereby enhancing the system's robustness and drainage efficiency in response to different working conditions (such as continuous rainfall). This solution is suitable for extremely soft sites with thick tailings layers that are almost impossible to handle using traditional methods.

[0037] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A highly efficient and energy-saving combined drainage method for tailings dam closure, characterized in that: Includes the following steps: S1: Drainage area division steps: Based on the water surface morphology of the tailings pond beach, the tailings particle size distribution and water depth, the area to be treated is divided into open water area, shallow saturated water area and deep fine mud saturated water area. S2: Combined drainage construction steps: S21: For the open water area, construct a surface flow drainage channel to guide the open water to a preset water collection or drainage structure; S22: For the shallow saturated area, a shallow drainage ditch network system is constructed to collect and drain the shallow stagnant water in the area; S23: For the deep fine mud saturated area, a passive self-draining and dewatering layer that does not rely on external power is constructed. The self-draining and dewatering layer is composed of a horizontal layered structure, which includes at least an evaporation water-conducting layer and a capillary conduction layer arranged from top to bottom. The capillary conduction layer is laid on the leveled beach surface and is used to absorb water from the lower fine mud. The evaporation water-conducting layer is used to guide the water absorbed by the capillary conduction layer upward and promote its evaporation.

2. The tailings dam closure high-efficiency and energy-saving combined drainage method according to claim 1, characterized in that: In step S1, the open water area is an area with visible surface water; the shallow saturated area is an area with no surface water and an estimated saturation depth within a preset first depth threshold; the deep fine mud saturated area is an area mainly composed of fine-particle tailings, with an estimated saturation depth exceeding the first depth threshold and a permeability coefficient lower than a preset threshold.

3. The tailings dam closure high-efficiency and energy-saving combined drainage method according to claim 1, characterized in that: In step S21, the method of constructing the surface flow drainage channel is as follows: a trench is formed by hydraulic erosion, and the slope of the trench is controlled so that the water can flow by gravity.

4. The tailings dam closure high-efficiency and energy-saving combined drainage method according to claim 1, characterized in that: In step S22, the shallow drainage network system includes a main drainage ditch and capillary blind ditches. The capillary blind ditches are distributed on both sides of the main drainage ditch and are connected to the main drainage ditch. The capillary blind ditches are filled with permeable aggregate.

5. A tailings dam closure high-efficiency and energy-saving combined drainage method according to claim 1 or 4, characterized in that: The shallow drainage network system is connected to the edge of the self-draining and dewatering layer or through a drainage pipe, and is used to receive and drain water discharged from the self-draining and dewatering layer.

6. The tailings dam closure high-efficiency and energy-saving combined drainage method according to claim 1, characterized in that: In step S23, a moisture transport and storage layer is further provided between the capillary conduction layer and the evaporative water-conducting layer. The moisture transport and storage layer is composed of a mixture of highly absorbent resin particles and hydrophobic porous aggregate.

7. A tailings dam closure method for efficient and energy-saving combined drainage according to claim 6, characterized in that: The hydrophobic porous aggregate is an inorganic or organic porous particle that has undergone surface hydrophobic modification.

8. The tailings dam closure high-efficiency and energy-saving combined drainage method according to claim 1, characterized in that: In step S23, while or after constructing the self-draining and dewatering layer, vertical drainage units are arranged at preset intervals in the deep fine mud saturated area. The lower end of the vertical drainage unit extends into the bottom of the deep fine mud saturated area or into the permeable layer. The vertical drainage unit is filled with water-conducting material, and its upper part is connected to the water transport and storage layer or evaporation water-conducting layer of the self-draining and dewatering layer.

9. A tailings dam closure method for efficient and energy-saving combined drainage according to claim 8, characterized in that: The water-conducting material filled in the vertical drainage unit contains highly absorbent resin particles.

10. A tailings dam closure method for efficient and energy-saving combined drainage according to claim 1, characterized in that: The evaporative water-conducting layer is a permeable geosynthetic material layer with a dark surface color and a three-dimensional spatial structure.

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