A landfill anti-seepage covering and grading drainage linkage control method

Abstract

The application discloses a landfill anti-seepage covering and grading drainage linkage control method, which is used for solving the problems of large rainwater infiltration, weak anti-seepage and drainage connection and insufficient leachate liquid level control precision of a stage sealing landfill. The method sequentially constructs an anti-seepage covering system, a grading and regional surface water drainage system and a dam front leachate pumping system: HDPE film is laid along water and is welded by a hot melting process, and a sandbag net type ballast structure is matched to strengthen wind resistance; a grading drainage system of a first-stage water collection, a second-stage water convergence and a main drainage channel centralized drainage is built; leachate pumping dynamic regulation and control is realized relying on liquid level monitoring, and a sludge standardized storage, partition construction control and long-term operation and maintenance mechanism are simultaneously matched. The application can realize the synergistic linkage of surface water source head reduction, leachate precise regulation and control and stable operation of the anti-seepage system, effectively reduces leachate production, improves dam operation stability and is suitable for environmental risk control engineering of a stage sealing landfill.

Description

Technical Field

[0001] This invention relates to the field of environmental risk prevention and control technology for solid waste landfills, specifically a method for the linkage between landfill seepage prevention covering and graded drainage control. Background Technology

[0002] Phased closure of municipal solid waste landfills represents a transitional operational scenario in the solid waste landfill disposal process. These sites typically employ temporary impermeable covering layers, surface water drainage systems, and leachate extraction facilities to achieve rainwater containment, surface runoff drainage, and liquid level control within the landfill. This controls the scale of leachate generation, reduces fugitive landfill gas emissions, and ensures the stability of the dam structure and the safety of the site environment. Currently, the industry standard practice is to use HDPE membranes for temporary covering, combined with on-site excavated drainage ditches and independent extraction wells, to meet the basic environmental management requirements during the closure phase.

[0003] Existing conventional technologies still have several shortcomings: First, the sealing and wind resistance of temporary covering systems are insufficient. After the membrane material ages and breaks, it is easy for rainwater to seep in and for landfill gas to escape. Simple ballast anchoring methods are difficult to adapt to the climatic conditions of typhoon-prone areas, and membrane displacement and tearing are likely to occur. Second, the surface water drainage system lacks a graded confluence design. Rainwater flows along the slope and is prone to erosion and wear of the covering membrane and drainage facilities. Moreover, the drainage structure and HDPE covering membrane are mostly simply overlapped, and there are leakage gaps at the joints, which cannot form a complete seepage prevention system. Third, there is no linkage mechanism between leachate drainage and surface water drainage. It is difficult to accurately control the leachate level in front of the dam, which poses a risk of dam leakage and instability. At the same time, most sites lack standardized sludge temporary storage facilities, which can easily cause secondary pollution. Summary of the Invention

[0004] The purpose of this invention is to provide a landfill seepage prevention and control method that combines layered drainage to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A landfill seepage prevention and control method combining layered drainage and sealing includes the following steps: Step 1: Construction of the seepage-proof cover system: HDPE membrane is laid on the surface of the landfill body in the direction of water flow. The overlap of the membrane is hot-melt welded and fixed with sandbag netting to form a complete seepage-proof cover layer. Step 2: Construction of a graded and regional surface water drainage system: Based on the landfill topography and existing facility boundaries, the reservoir area is divided into several landfill areas and drainage zones. In each landfill area, a differentiated drainage structure including drainage platforms, rapid flow channels, drainage ditches and / or trapezoidal membrane ditches is constructed to form a surface water drainage network with decentralized confluence and centralized drainage. Step 3: Construction of the leachate drainage system in front of the dam: Drill drainage wells in the area in front of the dam and connect the drainage wells with the existing drainage blind ditches of the landfill to form a leachate collection and drainage structure of "horizontal blind ditches + vertical wells", and install drainage equipment and liquid level monitoring system. Step 4: Joint Control Operation: The liquid level monitoring system monitors the leachate level in front of the dam in real time. When the level exceeds the preset threshold, the pumping equipment is activated for forced pumping. At the same time, the surface water drainage system is used to quickly drain rainwater runoff from the surface of the landfill to reduce the amount of leachate generated. The seepage prevention covering system blocks rainwater infiltration and disorderly escape of landfill gas, achieving comprehensive control over the environmental risks of the landfill.

[0006] Preferably, in step one, the HDPE membrane is a 1.0mm thick double-sided HDPE membrane, the overlap width of the membrane is controlled at 10±2cm, and the membrane is anchored 1.5m outward; the sandbag mesh ballast uses anti-oxidation nylon rope to connect multiple ballast sandbags into a mesh structure and cover the surface of the HDPE membrane.

[0007] Preferably, in step two, the main drainage channel is constructed with alternating gentle sections and cascading sections along its length; the length of the gentle sections is greater than the length of the cascading sections, and the gentle sections have a longitudinal slope of 0.3%-0.5%, while the cascading sections have a steep slope of 1:2, forming a continuous natural height difference, so as to utilize gravitational potential energy to achieve non-powered drainage and eliminate the kinetic energy of water flow, thereby reducing the scouring and wear of the water flow on the inner wall of the main drainage channel.

[0008] Preferably, in step two, multiple annular drainage branches are circumferentially arranged at equal intervals along the height direction on the slope of each landfill pile as a primary water catchment area, with a vertical spacing of 2-3m between adjacent annular drainage branches; longitudinal second drainage branches are respectively arranged on both sides of the bottom edge of the pile as secondary water catchment areas; multiple first drainage branches are arranged along the slope direction between each annular drainage branch and the corresponding second drainage branch, so that the annular drainage branch, the first drainage branch, and the second drainage branch are connected in sequence; the annular drainage branch, the first drainage branch, and the second drainage branch are all set close to the slope of the pile, and all have a slope difference consistent with the slope of the pile along the water flow direction to ensure that the surface water flows smoothly under the action of gravity.

[0009] Preferably, the second drainage branch pipe is connected to the main drainage channel through the water collection pipe, and the second drainage branch pipe and the water collection pipe are connected by a flange seal to facilitate disassembly and maintenance later.

[0010] Preferably, in step two, anchoring flanges integrally formed with the main drainage channel are provided on both sides of the top. The edges of the HDPE covering film are hot-melt welded to the anchoring flanges to form a complete sealed and seepage-proof structure. Fixing rings are pre-embedded at equal intervals along the length direction on the upper end face of the anchoring flanges. Ballast sandbags are stacked on the anchoring flanges between two adjacent fixing rings. Antioxidant nylon rope nets are covered on top of the ballast sandbags, and the edges and nodes of the nylon rope nets are respectively tied to the corresponding fixing rings to form a triple fixing system of anchoring flanges, ballast sandbags and nylon rope nets to enhance the wind resistance stability of the HDPE covering film and the main drainage channel.

[0011] Preferably, it also includes step five: construction of a standardized sludge storage system, which involves constructing a closed storage pit using the existing slopes and roadside terrain of the landfill area, laying HDPE membranes at the bottom and slopes of the storage pit for full coverage and seepage prevention, and constructing drainage ditches, dams, unloading ports and maintenance ports around the storage pit for the safe storage of sludge in the landfill.

[0012] Preferably, steps one to four adopt a construction mode of "zoning operation and simultaneous rectification and protection", prioritizing construction in high environmental risk areas such as the area in front of the dam.

[0013] Preferably, it also includes construction safety management steps: during the construction process, the methane concentration in the landfill gas is monitored in real time, explosion-proof construction equipment is used, and fire protection facilities are provided.

[0014] Preferably, it also includes long-term maintenance steps: establishing a dynamic operation and maintenance mechanism that includes daily inspections, regular maintenance and post-special weather checks, and periodically testing and closing-loop repairing the integrity and function of the seepage-proof cover layer, surface water drainage system and leachate pumping system.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention, through the coordinated construction of an anti-seepage covering system and a graded and regional surface water drainage system, can reduce the volume of rainwater infiltrating into the landfill, reduce leachate generation and the operating load of the treatment plant, and at the same time optimize the connection and sealing method between the covering membrane and the drainage structure, improve the integrity of the anti-seepage system, and reduce the risk of landfill gas escape and pollutant diffusion.

[0016] This invention, through the coordinated operation of the dam-front leachate pumping system and the liquid level monitoring device, can dynamically adjust the leachate level in front of the dam. Combined with surface water source diversion and reduction measures, it helps to improve the anti-sliding stability of the dam body and reduce safety risks during landfill operation.

[0017] This invention, through the coordinated setup of a zoned construction mode, a construction safety management system, and a long-term operation and maintenance mechanism, can control the site exposure range and safety hazards during the construction phase, ensuring the long-term stable effectiveness of the project. Combined with standardized sludge temporary storage facilities, it can reduce the risk of secondary sludge pollution and the cost of off-site transportation and disposal. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the method flow of the present invention; Figure 2 This is a three-dimensional schematic diagram of the surface water drainage structure of the present invention; Figure 3 This is a cross-sectional schematic diagram of the surface water drainage structure of the present invention; Figure 4 This is a top view of the main drainage channel of the present invention located in a portion of the landfill. In the diagram: 1. Main drainage channel; 101. Gentle slope section; 102. Anchoring wing; 2. Water baffle; 3. Water inlet; 4. Water collection pipe; 5. Drop section; 6. Ballast sandbags; 7. Fixing ring; 8. Landfill; 9. Landfill area; 10. Circular drainage branch pipe; 11. First drainage branch pipe; 12. Second drainage branch pipe. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example: Please see Figures 1 to 4 The present invention provides a technical solution: A landfill seepage prevention and control method combining layered drainage and sealing includes the following steps: Step 1: Construction of the seepage prevention and covering system HDPE membranes were laid on the surface of the eight landfill blocks in the direction of water flow. The overlaps of the membranes were hot-melt welded and fixed with sandbag netting to form a complete impermeable cover layer.

[0021] Specifically, in this embodiment, the area requiring replacement of the HDPE membrane for the temporary closure and covering project of landfill 8 is 93,000 m². The HDPE membrane used is a 1.0 mm thick double-sided HDPE membrane, which balances mechanical strength and ease of construction. The double-sided structure facilitates good contact with the upper and lower layers. During laying, it is laid in the direction of water flow, that is, the long side of the membrane material is consistent with the mainstream direction of the slope of the landfill, to avoid rainwater forming lateral streams on the membrane surface and reduce erosion of the membrane surface. The membrane material overlap is achieved using a hot-melt welding process, with the overlap width standardized and controlled at 10 ± 2 cm to ensure reliable sealing of the welded area. After welding, the weld is tested by air pressure or vacuum, and only after passing the test can the next process be carried out. The membrane material is anchored 1.5 m outward, that is, an anchoring trench is dug at the edge of the landfill, the edge of the membrane material is buried in the trench and backfilled and compacted to prevent the membrane material from being blown away by the wind or rainwater from flowing back in from the edge.

[0022] To enhance the wind resistance of the covering membrane, especially in typhoon-prone areas, this embodiment employs a sandbag net ballast. Specifically, multiple sandbags (6) are connected into a net structure using antioxidant nylon ropes. The sandbags are woven bags filled with fine sand, with the weight of a single bag determined based on site wind conditions, generally controlled between 15-20 kg. The connected sandbags are then placed over the HDPE membrane surface, focusing on areas susceptible to wind loads, such as membrane overlaps, slope transitions, and the edges of anchoring trenches. The antioxidant nylon ropes possess excellent weather resistance and UV resistance, maintaining strength over a long period and ensuring the sandbag net does not loosen or shift under wind and rain conditions.

[0023] The impermeable cover layer constructed in the above manner has complete impermeability and reliable wind resistance stability, which can effectively block rainwater from seeping into the landfill and prevent landfill gas from escaping from the damaged parts of the cover membrane.

[0024] Step 2: Construction of a tiered and regional surface water drainage system Based on the topography of landfill 8 and the boundaries of existing facilities, the reservoir area is divided into several landfill zones 9 and drainage zones. Differentiated drainage structures, including drainage platforms, rapid flow channels, drainage ditches and / or trapezoidal membrane ditches, are constructed in each landfill zone 9 to form a surface water drainage network of "decentralized confluence and centralized drainage".

[0025] In this embodiment, the entire landfill area is divided into four major drainage zones, with the existing roads and dam body of landfill 8 as boundaries. Each zone selects a specific drainage structure based on its topographic features, catchment area, and landfill slope. For example, drainage platforms are installed in gently sloping areas, rapid flow channels are installed in steeper areas to dissipate energy and reduce speed, dedicated drainage ditches are installed on the landfill surface, and trapezoidal membrane trenches are created on the membrane surface using a heat-sealing process to guide surface runoff. These drainage structures are interconnected, forming a network covering the entire landfill area 9.

[0026] Based on this, a main drainage channel 1 is constructed that runs through the landfill 8. The main drainage channel 1 runs through the landfill 8 in a front-to-back direction. Multiple landfill areas 9 are symmetrically distributed on both sides of the main drainage channel 1 along its length. The secondary catchment area corresponding to each landfill area 9 is connected to the main drainage channel 1 to achieve centralized drainage of surface water in the landfill area 9.

[0027] The main drainage channel 1 is a prefabricated concave-section drainage channel made of HDPE material, which has good corrosion resistance and aging resistance. Its interior is composed of alternating gentle slope sections 101 and cascading sections 5 along its length. The length of the gentle slope section 101 is greater than the length of the cascading section 5, and the gentle slope section 101 has a longitudinal slope of 0.3%-0.5%, while the cascading section 5 has a steep slope of 1:2. The gentle slope section 101 and the cascading section 5 form a continuous natural height difference, utilizing gravitational potential energy to achieve non-powered drainage without the need for additional power equipment. The cascading section 5 effectively eliminates the kinetic energy generated during rainwater flow, reducing the scouring and wear of the inner wall of the main drainage channel 1 by high-speed water flow, thereby extending the service life of the drainage channel. The alternating distribution of the gentle slope section 101 and the cascading section 5 also avoids the problem of uncontrolled water flow acceleration caused by long-distance drainage with a single slope.

[0028] like Figure 4 On the slope of each landfill 9, multiple annular drainage branches 10 are installed at equal intervals along the height direction to serve as primary catchment areas. The vertical spacing between two adjacent annular drainage branches 10 is 2-3m, which is determined according to the height of the landfill and the slope ratio. This spacing enables the collection of surface water across the entire height range of the landfill, preventing rainwater from forming long-distance streams on the slope that could erode the cover film. The annular drainage branches 10 are installed circumferentially along the slope of the landfill 9, with inlets at equal intervals on their inner sides. Rainwater flowing down the slope first enters the nearest annular drainage branch 10.

[0029] Longitudinal second drainage branch pipes 12 are installed on both sides of the bottom edge of the pile body as secondary water collection areas. The second drainage branch pipes 12 are perpendicular to the length direction of the main drainage channel 1. Between each annular drainage branch pipe 10 and the corresponding second drainage branch pipe 12 on both sides, multiple first drainage branch pipes 11 are installed along the slope direction. The upper end of the first drainage branch pipe 11 is connected to the annular drainage branch pipe 10, and the lower end is connected to the second drainage branch pipe 12. In this way, the surface water collected by the annular drainage branch pipe 10 is transported to the second drainage branch pipe 12 through the first drainage branch pipe 11, realizing the gradual collection from the high point of the slope to the low point.

[0030] The aforementioned annular drainage branch pipe 10, first drainage branch pipe 11, and second drainage branch pipe 12 are all installed flush with the slope of the landfill 9, and each has a slope difference consistent with the slope of the landfill along the water flow direction. This design ensures that surface water flows smoothly under gravity, without any water accumulation or dead zones. All branch pipes are made of HDPE material, the same material as the covering membrane, which facilitates hot-melt welding to form an integrated seepage prevention system.

[0031] The second drainage branch pipe 12 is connected to the main drainage channel 1 via the collection pipe 4. Collection ports 3 are located on both side walls of the main drainage channel 1 at the positions corresponding to each landfill area 9, and collection pipes 4 are sealed to the collection ports 3. A flange is installed at the end of the second drainage branch pipe 12 closest to the main drainage channel 1, and a matching flange is installed at the end of the collection pipe 4 furthest from the main drainage channel 1. The second drainage branch pipe 12 and the collection pipe 4 are sealed together via flanges. This flange connection method facilitates disassembly and maintenance in case of pipe blockage or damage, allowing for the replacement of partial pipe sections without damaging the pipeline.

[0032] Anchoring flanges 102 and water-blocking plates 2, integrally formed with the main drainage channel 1, are installed on both sides of the top. The anchoring flanges 102 protrude outwards, forming a reliable interface for connection with the cover membrane. The edge of the HDPE cover membrane is hot-melt welded to the anchoring flanges 102, with the weld width controlled at 10±2cm, forming a complete sealed and seepage-proof structure. This structure completely solves the problem of gap leakage caused by the simple overlap between the traditional drainage ditch and the cover membrane.

[0033] Anchoring rings 7 are pre-embedded at equal intervals along the length of the upper end face of the anchoring wing 102. The anchoring rings 7 are made of stainless steel and have corrosion resistance. Ballast sandbags 6 are stacked on the anchoring wing 102 between two adjacent anchoring rings 7. Antioxidant nylon rope netting is placed on top of the ballast sandbags 6, and the edges and nodes of the nylon rope netting are tied to the corresponding anchoring rings 7. This forms a triple fixing system of "anchoring wing 102 + ballast sandbags 6 + nylon rope netting". The anchoring wing 102 provides the basis for welding connection, the ballast sandbags 6 provide vertical pressure, and the nylon rope netting connects the sandbags into a whole and fixes them to the pre-embedded rings. The three work together to significantly enhance the wind resistance stability of the HDPE cover film and the main drainage channel 1, making it particularly suitable for landfills 8 in typhoon-prone areas.

[0034] Step 3: Construction of the seepage drainage system in front of the dam Drainage wells were drilled in the area in front of the dam and connected to the existing drainage blind ditch of landfill 8 to form a leachate collection and drainage structure of "horizontal blind ditch + vertical well". Drainage equipment and liquid level monitoring system were installed.

[0035] In this embodiment, the high level of leachate in front of the dam is the main risk source affecting the stability of the dam. To address this issue, three new drainage wells were added in the area in front of the dam. The specific locations of the drainage wells were determined based on the topography in front of the dam and the distribution of the existing drainage blind ditches, ensuring effective interception of leachate flowing into the dam area. The drainage wells are constructed of reinforced concrete or steel pipe, with perforated walls and a filter layer to prevent fine particles of waste from entering and causing blockages. The bottom of the drainage wells connects to the existing drainage blind ditches, which are typically filled with gravel and have good water conductivity. Through this "horizontal blind ditch + vertical well" structure, the leachate from the eight landfill piles can be collected along the horizontal blind ditches to the drainage wells, and then pumped to the surface treatment facilities by the pumping equipment.

[0036] The pumping equipment installed in conjunction with the system typically uses submersible pumps or self-priming pumps, with the pump selection determined based on the designed pumping flow rate and head. The liquid level monitoring system employs submersible level gauges or ultrasonic level gauges to monitor changes in the liquid level within the pumping well in real time. The liquid level signal can be connected to an automatic control system for on-demand start / stop operation.

[0037] Step 4: Interlocking and Restriction Control Operation The liquid level monitoring system monitors the leachate level in front of the dam in real time. When the level exceeds a preset threshold, the pumping equipment is activated for forced pumping. At the same time, the surface water drainage system is used to quickly drain rainwater runoff from the surface of the landfill, reducing the amount of leachate generated. The seepage prevention covering system blocks rainwater infiltration and disorderly escape of landfill gas, achieving comprehensive control over the environmental risks of the landfill site.

[0038] The four steps described above do not operate independently but form a coordinated control system. Specifically: the surface water drainage system rapidly drains rainwater from landfill 8, reducing the amount of water entering the landfill and thus reducing leachate generation at the source—this is a "source reduction" measure. The seepage prevention covering system blocks the infiltration channels of residual rainwater and external moisture, further reducing the increase in leachate—this is a "path control" measure. The leachate extraction system in front of the dam promptly extracts leachate already generated within the landfill, controlling the liquid level in front of the dam within a safe range—this is a "disposal" measure. These three measures work synergistically to achieve targeted control of the entire environmental risk sources of landfill 8 across the entire chain.

[0039] In addition to the steps described above, the following additional steps may also be included: Construction of a standardized sludge storage system: A closed storage pit was constructed using the existing slopes and roadside topography of the landfill area. This pit relies on the existing terrain, reducing earthwork excavation. HDPE membranes were laid at the bottom and slopes of the pit for full coverage and seepage prevention, preventing pollutants in the sludge from seeping into the ground. Drainage ditches were constructed around the pit to intercept and divert surrounding runoff; a retaining dam was built to enhance the structural stability of the pit; a dedicated unloading port was provided for easy unloading of sludge transport vehicles; and an inspection port was provided for regular checks on the storage status of the sludge and the integrity of the seepage prevention layer. Through these facilities, the safe storage and environmental management of landfill sludge were achieved, reducing the cost of off-site disposal.

[0040] Zoned Construction Mode: Steps one through four above adopt a "zoned operation, simultaneous rectification and protection" construction mode. That is, the entire landfill 8 is divided into several construction zones, with priority given to high-environmental-risk areas such as the area in front of the dam. During the construction of one zone, other zones maintain their original coverage and drainage functions to ensure that the overall environmental risk of landfill 8 is controllable. After the rectification of one zone is completed, the seepage prevention coverage and drainage function of that zone are immediately restored before proceeding to the next zone. This mode avoids the risk of large-scale exposure caused by full-scale excavation and achieves simultaneous implementation of rectification and protective measures.

[0041] Construction safety management steps: During construction, the methane concentration in the landfill gas is monitored in real time. The landfill's No. 8 waste pile produces a large amount of methane under anaerobic conditions, posing an explosion risk when the methane concentration reaches 5%-15%. Therefore, portable methane detectors or online monitoring equipment are used to continuously monitor the work area before and during construction. All construction equipment entering the site is explosion-proof, including welding equipment, lighting fixtures, and transport vehicles, to prevent the generation of electrical sparks. Fire protection facilities are provided on site, including fire extinguishers, fire sand, and fire hoses, and an emergency plan is developed. Especially before open flame operations such as HDPE film hot-melt welding, it must be confirmed that the methane concentration in the work area is below 10% of the lower explosive limit before any open flame work can commence.

[0042] Long-term maintenance procedures: Establish a dynamic operation and maintenance mechanism that includes daily inspections, regular maintenance, and post-inclement-day checks. Daily inspections should be conducted at least weekly, checking for damage or holes in the impermeable cover layer, blockages or cracks in the surface water drainage system, the normal operation of the leachate pumping system, and whether the liquid level monitoring data is within the normal range. Regular maintenance should be conducted monthly or quarterly, including cleaning silt and debris from drainage ditches and pipes, checking for weld detachment or aging of the HDPE membrane, calibrating the liquid level monitoring equipment, and maintaining the pumping equipment. After inclement-day weather, a comprehensive inspection should be organized within 24 hours, focusing on checking for membrane tears, loose anchors, damage to the drainage structure, and abnormal liquid levels in front of the dam. Any problems discovered should be immediately addressed through a closed-loop repair process: "discovery—assessment—repair—review," ensuring the long-term stable operation of the project.

[0043] In summary, this invention constructs a three-in-one targeted control and risk prevention system for environmental risk sources in landfills through the coordinated operation of steps one through four: "seepage prevention cover - graded drainage - leachate extraction". Specifically, the seepage prevention cover system uses a 1.0mm thick double-sided HDPE membrane laid in the direction of water flow, hot-melt welding, and sandbag netting to ensure the cover layer has no leakage blind spots and is suitable for typhoon-prone climates. The graded and regional surface water drainage system, with the main drainage channel 1 as its core, combines a ring-shaped drainage branch pipe 10, a first drainage branch pipe 11, a second drainage branch pipe 12, anchoring wings 102, ballast sandbags 6, nylon rope netting, and other structures to form a highly efficient drainage network of "dispersed confluence - centralized drainage", significantly improving rainwater drainage capacity and reducing infiltration. The leachate extraction system in front of the dam connects to the existing drainage blind ditch through a "horizontal blind ditch + vertical well" type extraction well, equipped with liquid level monitoring and automatic start / stop, effectively controlling the liquid level in front of the dam and ensuring the stability of the dam body. The additional standardized sludge storage, zoned construction, construction safety management, and long-term maintenance steps further enhance the overall safety and sustainability of the project. This invention systematically solves common environmental risks of phased landfill closures, such as aging and damage to temporary cover films, poor surface water drainage, high liquid levels in front of the dam, and a lack of dedicated sludge storage pits. It achieves a significant reduction in leachate production, effective improvement in dam stability, and standardized control of disorderly landfill gas emissions, combining technological advancement, environmental benefits, and engineering practicality. All other parts of this invention not described herein are identical to existing technologies, are publicly known technologies, or can be implemented using existing technologies; therefore, they will not be detailed here.

[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for integrated seepage control and graded drainage in landfills, characterized in that, Includes the following steps: Step 1: Construction of the seepage prevention cover system: HDPE membrane is laid on the surface of the landfill (8) in the direction of water flow. The membrane overlap is hot-melt welded and fixed with sandbag net ballast to form a complete seepage prevention cover layer. Step 2: Construction of a graded and regional surface water drainage system: Based on the topography of the landfill (8) and the boundaries of existing facilities, the reservoir area is divided into several landfill areas (9) and drainage zones. Differentiated drainage structures including drainage platforms, rapid flow channels, drainage ditches and / or trapezoidal membrane ditches are constructed in each landfill area (9) to form a surface water drainage network with decentralized confluence and centralized drainage. Step 3: Construction of the dam front leachate drainage system: Drill drainage wells in the dam front area and connect the drainage wells with the existing drainage blind ditches of the landfill (8) to form a "horizontal blind ditch + vertical well" leachate collection and drainage structure, and install drainage equipment and liquid level monitoring system. Step 4: Joint control operation: The liquid level monitoring system monitors the leachate level in front of the dam in real time. When the liquid level exceeds the preset threshold, the pumping equipment is activated for forced pumping. At the same time, the surface water drainage system is used to quickly drain the rainwater runoff from the surface of the landfill to reduce the amount of leachate generated. The seepage prevention and covering system is used to block rainwater infiltration and disorderly escape of landfill gas, so as to achieve comprehensive control of the environmental risks of the landfill (8).

2. The landfill seepage prevention covering and graded drainage linkage control method according to claim 1, characterized in that, In step one, the HDPE membrane is a 1.0mm thick double-sided HDPE membrane, the overlap width of the membrane is controlled at 10±2cm, and the membrane is anchored 1.5m outward; the sandbag net ballast uses anti-oxidation nylon rope to connect multiple ballast sandbags (6) into a net structure and cover the HDPE membrane surface.

3. The landfill seepage prevention covering and graded drainage linkage control method according to claim 1, characterized in that, In step two, the main drainage channel (1) is constructed with alternating gentle sections (101) and waterfall sections (5) along its length. The length of the gentle section (101) is greater than the length of the waterfall section (5), and the gentle section (101) has a longitudinal slope of 0.3%-0.5%, while the waterfall section (5) has a steep slope of 1:2, forming a continuous natural height difference. This allows for the use of gravitational potential energy to achieve unpowered drainage and eliminate the kinetic energy of the water flow, thereby reducing the scouring and wear of the water flow on the inner wall of the main drainage channel (1).

4. The landfill seepage prevention covering and graded drainage linkage control method according to claim 1, characterized in that, In step two, on the slope of each landfill area (9) pile, multiple annular drainage branches (10) are set at equal intervals along the height direction as primary water catchment areas, and the vertical distance between two adjacent annular drainage branches (10) is 2-3m; on the two sides of the bottom of the pile, longitudinal second drainage branches (12) are set as secondary water catchment areas; between each annular drainage branch (10) and the corresponding second drainage branch (12), multiple first drainage branches (11) are set along the slope direction, so that the annular drainage branch (10), the first drainage branch (11), and the second drainage branch (12) are connected in sequence; the annular drainage branch (10), the first drainage branch (11), and the second drainage branch (12) are all set close to the slope of the pile, and all have a slope difference consistent with the slope of the pile along the water flow direction to ensure that the surface water flows smoothly under the action of gravity.

5. The landfill seepage prevention covering and graded drainage linkage control method according to claim 4, characterized in that, The second drainage branch pipe (12) is connected to the main drainage channel (1) through the water collection pipe (4), and the second drainage branch pipe (12) and the water collection pipe (4) are connected by a flange seal to facilitate disassembly and maintenance later.

6. The landfill seepage prevention covering and graded drainage linkage control method according to claim 3, characterized in that, In step two, anchoring wing edges (102) integrally formed with the main drainage channel (1) are set on the top of both sides of the main drainage channel (1). The edge of the HDPE covering film is hot-melted and welded to the anchoring wing edges (102) to form a complete sealed and seepage-proof structure. Fixing rings (7) are pre-embedded at equal intervals along the length direction on the upper end face of the anchoring wing edges (102). Ballast sandbags (6) are stacked on the anchoring wing edges (102) between two adjacent fixing rings (7). Antioxidant nylon rope net is covered on the top of the ballast sandbags (6), and the corners and nodes of the nylon rope net are tied to the corresponding fixing rings (7) to form a triple fixing system of anchoring wing edges (102), ballast sandbags (6) and nylon rope net to enhance the wind resistance stability of the HDPE covering film and the main drainage channel (1).

7. The landfill seepage prevention covering and graded drainage linkage control method according to claim 1, characterized in that, It also includes step five: construction of a standardized sludge storage system, using the existing slopes and roadside terrain of the landfill area to construct a closed storage pit, laying HDPE membranes at the bottom and slopes of the storage pit for full coverage and seepage prevention, and constructing drainage ditches, dams, unloading ports and maintenance ports around the storage pit for safe storage of sludge in the landfill (8).

8. The landfill seepage prevention covering and graded drainage linkage control method according to claim 1, characterized in that, Steps one through four adopt a construction mode of "zoning operations and simultaneous rectification and protection", prioritizing construction in high environmental risk areas such as the area in front of the dam.

9. The landfill seepage prevention covering and graded drainage linkage control method according to claim 1, characterized in that, It also includes construction safety management steps: during the construction process, the methane concentration in the landfill gas is monitored in real time, explosion-proof construction equipment is used, and fire protection facilities are provided.

10. The landfill seepage prevention covering and graded drainage linkage control method according to claim 1, characterized in that, It also includes long-term maintenance steps: establishing a dynamic operation and maintenance mechanism that includes daily inspections, regular maintenance and post-severity checks, and periodically testing and closing-loop repair of the integrity and function of the seepage prevention cover layer, surface water drainage system and leachate pumping system.

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