A solidified fly ash landfill seepage prevention structure

Abstract

This utility model relates to the field of solid waste treatment technology and discloses a seepage prevention structure for solidified fly ash landfills. The seepage prevention structure includes seepage prevention facilities, which, from top to bottom, consist of a leachate collection and drainage system, a main seepage prevention layer, a leakage detection layer, a secondary seepage prevention layer, a foundation layer, and a groundwater collection and drainage system. The main seepage prevention layer is laid on top of the leakage detection layer. This utility model addresses core issues in the prior art by constructing a multi-layered collaborative structure and settlement adaptation design: the leakage detection layer can monitor and locate leaks in real time, avoiding environmental risks caused by response lag; soil bags and reinforced soil settlement buffer zones are set on the back side of the landfill dam, and geogrids are embedded in the backfill soil to coordinate settlement deformation between the dam and the landfill material; the settlement buffer zone absorbs uneven settlement stress through flexible overlap, preventing cracking of the seepage prevention layer joints, significantly improving overall seepage prevention reliability, and meeting the requirements for safe landfilling of solidified fly ash.

Description

Technical Field

[0001] This utility model relates to the field of solid waste treatment technology, and more specifically, to a seepage-proof structure for solidified fly ash landfills. Background Technology

[0002] Solidified fly ash is a product of solidification treatment of fly ash from municipal solid waste incineration. It still contains toxic and harmful substances such as heavy metals and dioxins, and is classified as hazardous waste. Its leachate is highly corrosive, requiring extremely high chemical corrosion resistance of landfill anti-seepage systems.

[0003] In existing technologies, the impermeable layers of sanitary landfills for municipal solid waste often utilize ordinary HDPE membranes or composite structures of HDPE membranes and compacted soil. However, ordinary HDPE membranes are prone to aging and degradation when exposed to strong acids, heavy metal ions, and other substances in solidified fly ash leachate over long periods, leading to decreased impermeability and insufficient resistance to chemical corrosion, making it difficult to meet the long-term impermeability requirements of solidified fly ash landfills. Therefore, improvements are needed. Utility Model Content

[0004] In order to overcome the shortcomings of the existing technology, this utility model provides a solidified fly ash landfill seepage prevention structure with the advantage of high chemical corrosion resistance.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a solidified fly ash landfill seepage prevention structure, comprising seepage prevention facilities, wherein the seepage prevention facilities, from top to bottom, include a leachate collection and drainage system, a main seepage prevention layer, a leakage detection layer, a secondary seepage prevention layer, a foundation layer, and a groundwater collection and drainage system; the main seepage prevention layer is laid on top of the leakage detection layer, the leakage detection layer is laid on top of the secondary seepage prevention layer, the secondary seepage prevention layer is laid on top of the foundation layer, and the foundation layer is laid on top of the groundwater collection and drainage system; The seepage prevention facilities cover the bottom, slope and garbage dam of the landfill, forming a seepage prevention layer at the bottom and seepage prevention layers at the slope and garbage dam. Soil bags and reinforced soil settlement buffer zones are set on the back side of the garbage dam. Geogrids are buried in the backfill soil to coordinate the settlement deformation between the dam and the landfill. The leachate collection and drainage system includes a drainage layer, a main blind ditch, and branch blind ditches. The drainage layer is laid on top of the main impermeable layer, covering the reservoir bottom and slope areas. The main blind ditch is located in the middle of the drainage layer at the bottom of the reservoir along the length of the site. The branch blind ditches are arranged in a grid pattern, vertically connected to the main blind ditch, and extend to the slope waist. The drainage layer is made of graded granite pebbles with a particle size of 16-32mm, a thickness of 300mm, and a calcium carbonate content of ≤5%. Said main anti-seepage layer comprises a first protective layer, a first 2.0 mm thick double-rough-surface carbon black-added ultraviolet-resistant chemical-corrosion-resistant HDPE membrane and a sodium-based bentonite geosynthetic clay liner; said leakage detection layer comprises a detection diversion layer and a detection pipe, wherein the detection pipe is arranged along the slope bottom and the middle of the reservoir bottom, a detection port is provided every 50 m, and a pH sensor and a heavy metal ion detector are installed inside; said secondary anti-seepage layer comprises a second protective layer, a second 2.0 mm thick double-rough-surface carbon black-added ultraviolet-resistant chemical-corrosion-resistant HDPE membrane and a compacted clay protective layer; said base layer is compacted plain soil, with a degree of compaction of not less than 93% at the reservoir bottom and not less than 90% at the side slope; said groundwater collection and drainage system comprises underground blind ditches and a gravel diversion layer.

[0006] As a preferred technical solution of the present utility model, an HDPE double-walled perforated pipe with a pipe diameter of 200 mm is laid in the main blind ditch, an HDPE double-walled perforated pipe with a pipe diameter of 150 mm is laid in the branch blind ditch, the main blind ditch and the branch blind ditch are connected by hot melt butt joint, and the joint is externally wrapped with 200 g / m² filament non-woven geotextile.

[0007] As a preferred technical solution of the present utility model, the first protective layer is 600 g / m² polyester filament non-woven geotextile, with a breaking strength of not less than 30 kN / m and a CBR bursting strength of not less than 5.5 kN, and is laid along the slope surface in the side slope anti-seepage layer area without horizontal joints.

[0008] As a preferred technical solution of the present utility model, the second protective layer is 600 g / m² polypropylene filament non-woven geotextile, the acid and alkali resistance of which conforms to JC / T1068-2008, and it is overlapped and lapped with the first protective layer in the settlement buffer zone area, with a lap width of not less than 150 mm.

[0009] As a preferred technical solution of the present utility model, the carbon black content of the first HDPE membrane and the second HDPE membrane is 2.0%-3.0%, the stress cracking resistance (notched constant load tensile method) is not less than 300 h, the oxidative induction time at atmospheric pressure is not less than 100 min, and the roughness height is not less than 250 μm.

[0010] As a preferred technical solution of the present utility model, the total mass per unit area of the sodium-based bentonite geosynthetic clay liner is not less than 5000 g / m², wherein the mass of bentonite is not less than 5000 g / m², the permeability coefficient is not more than 5×10⁻¹¹m / s, the volume expansion of bentonite is not less than 24 mL / 2g, and the liner is laid in a "triangular staggered" pattern in the side slope anti-seepage layer area without cross lapping.

[0011] As a preferred technical solution of the present utility model, the detection diversion layer of the leakage detection layer is a geocomposite drainage net, with a longitudinal breaking strength of not less than 45 kN / m, a transverse breaking strength of not less than 30 kN / m, and a water conductivity of not less than 3×10⁻³m³ / s; said detection pipe is an HDPE perforated pipe with a diameter of 150 mm.

[0012] As a preferred embodiment of this utility model, the permeability coefficient of the compacted clay protective layer is ≤5×10⁻ 8 m / s, thickness 300mm, compaction degree ≥95%; underground blind drains of the groundwater collection and drainage system are spaced 10m apart, filled with pebbles with a particle size of 16-32mm, with 350mm diameter HDPE perforated pipes laid inside, and wrapped with 200g / m² geotextile on the outside; the gravel diversion layer is 300mm thick and has a permeability coefficient ≥1×10⁻³m / s.

[0013] Compared with the prior art, the beneficial effects of this utility model are as follows: 1. This utility model addresses the core issues in the background technology by constructing a multi-layered collaborative structure and a settlement adaptation design: the granite pebble diversion layer combined with a chemically resistant HDPE membrane can resist long-term erosion by the highly corrosive leachate of solidified fly ash; the leakage detection layer can monitor and locate leakage in real time, avoiding environmental risks caused by response lag; the settlement buffer zone absorbs uneven settlement stress through flexible overlap, preventing cracking of the anti-seepage layer joints, significantly improving the overall anti-seepage reliability, and meeting the requirements for safe landfilling of solidified fly ash.

[0014] 2. This utility model significantly enhances the anti-UV aging performance of HDPE membranes by adding carbon black and using an anti-UV formula: carbon black can effectively absorb ultraviolet rays, reduce their damage to HDPE molecular chains, and extend the service life of the membrane; at the same time, carbon black works synergistically with other additives to improve the weather resistance of the membrane, prevent the membrane from becoming brittle and cracking under high temperature and strong light conditions, ensure the long-term stable function of the geomembrane, and reduce the later maintenance costs. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a schematic diagram of the seepage prevention facility of this utility model; Figure 3 This is a schematic diagram of the leachate collection and drainage system of this utility model; Figure 4 This is a schematic diagram of the main seepage-proof layer of this utility model; Figure 5 This is a schematic diagram of the secondary seepage-proof layer of this utility model.

[0016] In the diagram: 1. Seepage prevention facilities; 11. Seepage prevention layer at the bottom of the reservoir; 12. Settlement buffer zone; 13. Seepage prevention layer on the slope; 14. Leachate collection and drainage system; 141. Drainage layer; 142. Main blind ditch; 143. Branch blind ditch; 15. Main seepage prevention layer; 151. First protective layer; 152. First HDPE membrane; 153. Sodium bentonite waterproof blanket; 16. Leakage detection layer; 17. Secondary seepage prevention layer; 171. Second protective layer; 172. Second HDPE membrane; 173. Compacted clay protective layer; 18. Foundation layer; 19. Groundwater collection and drainage system. Detailed Implementation

[0017] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0018] like Figures 1 to 5 As shown, this utility model provides a seepage prevention structure for solidified fly ash landfills, including a seepage prevention facility 1. The seepage prevention facility 1 includes, from top to bottom, a leachate collection and drainage system 14, a main seepage prevention layer 15, a leakage detection layer 16, a secondary seepage prevention layer 17, a foundation layer 18, and a groundwater collection and drainage system 19. The main seepage prevention layer 15 is laid on top of the leakage detection layer 16, the leakage detection layer 16 is laid on top of the secondary seepage prevention layer 17, the secondary seepage prevention layer 17 is laid on top of the foundation layer 18, and the foundation layer 18 is laid on top of the groundwater collection and drainage system 19. The seepage prevention facility 1 covers the bottom and slope of the landfill, forming a seepage prevention layer 11 at the bottom and a seepage prevention layer 13 at the slope. A settlement buffer zone 12 is provided between the seepage prevention layer 11 at the bottom and the seepage prevention layer 13 at the slope. The leachate collection and drainage system 14 includes a diversion layer 141, a main blind ditch 142, and branch blind ditches 143. The diversion layer 141 is laid on top of the main impermeable layer 15, covering the reservoir bottom and slope area. The main blind ditch 142 is located in the middle of the diversion layer 141 at the bottom of the reservoir along the length of the site. The branch blind ditches 143 are arranged in a grid pattern and are perpendicularly connected to the main blind ditch 142 and extend to the toe of the slope. The diversion layer 141 is made of graded granite pebbles with a particle size of 16-32mm, a thickness of 300mm, and a calcium carbonate content of ≤5%. The main impermeable layer 15 includes a first protective layer 151, a 2.0mm thick double-textured carbon black UV-resistant and chemically resistant first HDPE membrane 152, and a sodium-based bentonite waterproof blanket 153; the leakage detection layer 16 includes a detection diversion layer and a detection pipe, with the detection pipe arranged along the bottom of the slope and the middle of the reservoir bottom, and a detection port every 50m, containing a pH sensor and a heavy metal ion detector; the secondary impermeable layer 17 includes a second protective layer 171, a 2.0mm thick double-textured carbon black UV-resistant and chemically resistant second HDPE membrane 172, and a compacted clay protective layer 173; the foundation layer 18 is compacted plain soil, with a reservoir bottom compaction degree ≥93% and a slope compaction degree ≥90%; the groundwater collection and drainage system 19 includes an underground blind ditch and a gravel diversion layer.

[0019] The leachate generated after solidified fly ash landfill is first received by the flow guide layer 141 of the leachate collection and drainage system 14. Due to the uniform particle spacing of the granite pebbles in the flow guide layer 141, the leachate can be quickly guided to the grid-distributed main blind drain 142 and branch blind drain 143. The main blind drain 142 serves as the main confluence channel, and the branch blind drain 143 assists in collecting water from both sides. The two are connected by thermal fusion to form a closed drainage channel, which quickly discharges the leachate from the landfill area, avoids the leachate from lingering on the surface of the main impermeable layer 15, and reduces the long-term erosion pressure on the impermeable layer.

[0020] When a small amount of leachate breaks through the guide layer 141 and comes into contact with the main impermeable layer 15, the first HDPE membrane 152 of the main impermeable layer 15 first acts as a physical barrier to prevent the leachate from penetrating downwards. If there is a minor damage to the first HDPE membrane 152, the sodium bentonite waterproof blanket 153 below will expand upon contact with water to form a waterproof colloid, which will automatically heal the damaged area and maintain the integrity of the first impermeable barrier. If the main impermeable layer 15 experiences abnormal leakage, the leachate will enter the leakage detection layer 16, at which point the secondary impermeable layer 17 will immediately activate its backup protection. The second HDPE membrane 172 of the secondary impermeable layer 17 blocks the leachate from continuing to penetrate, and the compacted clay protective layer 173 below further intercepts it through its own low permeability, forming a second barrier of "membrane-soil" synergy to prevent toxic substances from polluting the soil and groundwater.

[0021] The leakage detection layer 16 is located between the main seepage prevention layer 15 and the secondary seepage prevention layer 17. When the leakage liquid enters the flow guiding layer of the leakage detection layer 16, the flow guiding layer, with its high water conductivity, quickly collects the leakage liquid into the detection pipe. The pH sensor and heavy metal ion detector inside the detection pipe capture changes in liquid composition in real time. Once an abnormal pH value or excessive heavy metal ions are detected, an early warning signal is immediately sent to the monitoring center via a wireless module. Staff can quickly locate the leakage point based on the location of the detection pipe, thus gaining time for timely repair.

[0022] During the landfilling process, the bottom impermeable layer 11 will experience some settlement due to the weight of fly ash, while the slope impermeable layer 13 will experience less settlement. Therefore, soil bags and reinforced soil settlement buffer zones 12 are installed on the back side of the landfill dam, and geogrids are embedded in the backfill soil to coordinate the settlement deformation between the dam and the landfill. The HDPE membranes of the main impermeable layer 15 and the secondary impermeable layer 17 of the settlement buffer zone 12 adopt a flexible overlapping design. The overlapping section can adapt to the settlement by stretching, absorbing the settlement stress and preventing the impermeable layer from cracking due to stress concentration. At the same time, the first protective layer 151, the second protective layer 171 and the detection pipe of the settlement buffer zone 12 also adopt a flexible structure to ensure that the entire impermeable facility 1 remains continuous and intact during the settlement process without compromising its protective function.

[0023] The main blind drain 142 is filled with a 200mm diameter HDPE double-wall perforated pipe, and the branch blind drain 143 is filled with a 150mm diameter HDPE double-wall perforated pipe. The main blind drain 142 and the branch blind drain 143 are connected by hot-melt butt welding, and the connection is wrapped with 200g / m² long filament nonwoven geotextile.

[0024] The main blind drain 142 serves as the main trunk to collect leachate, while the branch blind drain 143 assists in diversion, adapting to different flow rates for different pipe diameters; hot-melt butt welding ensures a sealed connection, and geotextile wrapping prevents pebbles from entering the pipe and causing blockage; graded drainage improves efficiency, and the sealed connection and anti-clogging design reduce the risk of leakage, ensuring the long-term smooth operation of the drainage system and reducing maintenance frequency.

[0025] The first protective layer 151 is a 600g / m² polyester filament nonwoven geotextile with a tensile strength ≥30kN / m and a CBR puncture strength ≥5.5kN. It is laid along the slope surface in the slope seepage prevention layer 13 area without horizontal joints.

[0026] High-strength geotextile resists puncture and friction during fly ash landfill, and the seamless design of the slope avoids joint cracking during settlement, protecting the underlying first HDPE membrane 152; it enhances the damage resistance of the main anti-seepage layer 15, and the slope laying method adapts to terrain changes, extending the service life of the anti-seepage facilities.

[0027] The second protective layer 171 is a 600g / m² polypropylene filament nonwoven geotextile with acid and alkali resistance conforming to JC / T1068-2008. It overlaps with the first protective layer 151 in the settlement buffer zone 12 area, with an overlap width ≥150mm.

[0028] The acid and alkali resistance properties prevent the erosion of leachate. The overlapping and jointed settlement buffer zone 12 forms a transition zone to absorb settlement stress and prevent the two protective layers from separating. The durability of the secondary seepage prevention layer 17 is improved, and the overlapping design enhances the structural continuity and prevents the protection from failing due to settlement.

[0029] Wherein, the carbon black content of the first HDPE membrane 152 and the second HDPE membrane 172 is 2.0%-3.0%, the environmental stress cracking resistance (notched constant tensile load method) is ≥300h, the atmospheric pressure oxidation induction time is ≥100min, and the roughness height is ≥250μm.

[0030] Carbon black blocks ultraviolet rays to delay aging, high stress cracking resistance resists landfill pressure, and the rough surface increases friction with the upper and lower layers to prevent displacement; the anti-aging and damage resistance capabilities of the membrane body are improved, the service life of the anti-seepage barrier is prolonged, and the rough surface ensures interlayer stability.

[0031] Wherein, the total mass per unit area of the sodium-based bentonite waterproof blanket 153 is ≥5000g / m², the bentonite mass per unit area is ≥5000g / m², the permeability coefficient is ≤5×10⁻¹¹m / s, the volume expansion degree of bentonite is ≥24mL / 2g, and the waterproof blanket is laid in a "triangular staggered" pattern in the area of the slope anti-seepage layer 13 without cross lap joints.

[0032] High-content bentonite swells in contact with water to form a sealed colloid, and the extremely low permeability coefficient blocks leakage; the "triangular staggered" laying reduces lap gaps and adapts to the curvature of the slope; it can automatically repair tiny damages on the membrane body, enhance the reliability of the main anti-seepage layer 15, and the slope laying method reduces leakage hidden hazards.

[0033] Wherein, the detection and diversion layer of the leakage detection layer 16 is a geotechnical composite drainage network, the longitudinal breaking strength is ≥45kN / m, the transverse breaking strength is ≥30kN / m, the water conductivity is ≥3×10⁻³m³ / s; the detection pipe is a perforated HDPE pipe with a diameter of 150mm.

[0034] The high water conductivity diversion layer quickly collects leakage into the detection pipe, and the high strength resists structural settlement pressure; it can quickly capture leakage signals, improve detection sensitivity, ensure monitoring stability, and facilitate timely repair.

[0035] Wherein, the permeability coefficient of the compacted clay protective layer 173 is ≤5×10⁻ 8 m / s, the thickness is 300mm, and the degree of compaction is ≥95%; the spacing of the underground blind ditches of the groundwater collection and drainage system 19 is 10m, the blind ditches are filled with pebbles with a particle size of 16-32mm, a perforated HDPE pipe with a diameter of 350mm is laid inside, and the pipe is wrapped with geotextile of 200g / m²; the thickness of the gravel diversion layer is 300mm, and the permeability coefficient is ≥1×10⁻³m / s.

[0036] Low-permeability clay blocks leakage, and high-strength compaction ensures stability; the groundwater drainage system quickly discharges groundwater through pebble gaps and perforated pipes, reducing the pressure on the anti-seepage layer; it enhances the barrier capability of the secondary anti-seepage layer 17, and timely drainage of groundwater prevents the anti-seepage layer from being damaged by water pressure, improving the safety of the overall structure.

[0037] The working principle and application procedure of the present utility model are as follows: First, the landfill site is leveled, and sharp debris such as stones and tree roots are removed to ensure that the slope meets the design requirements. Then, the groundwater collection and drainage system 19 is laid. First, a gravel diversion layer is laid for the groundwater collection and drainage system 19. Then, underground blind drains are excavated at intervals. Perforated pipes are installed in the blind drains and wrapped with geotextile to prevent soil particles from clogging the pipes. Finally, pebbles are backfilled to fix the blind drains and form a groundwater drainage network. Next, the subgrade soil is compacted in layers to form the foundation layer 18. The compaction degree of the foundation layer 18 is ensured to meet the standards (≥93% in the bottom area and ≥90% in the slope area), and the surface is flat to provide stable support for the subsequent laying of the impermeable layer.

[0038] First, a secondary impermeable layer 17 is laid on the base layer 18; then, clay is compacted in layers to form a compacted clay protective layer 173, ensuring that the permeability coefficient of the compacted clay protective layer 173 meets the standard; next, a second HDPE membrane 172 of the secondary impermeable layer 17 is laid, and the membrane joints are connected by hot-melt welding to ensure welding strength; finally, a second protective layer 171 of the secondary impermeable layer 17 is laid to cover the surface of the second HDPE membrane 172 to prevent damage. After the secondary impermeable layer 17 is completed, a leakage detection layer 16 is laid; first, a flow guiding layer of the leakage detection layer 16 is laid, then detection pipes are arranged according to the design spacing, the detection pipes are connected to the sensors, and the monitoring system is debugged to ensure normal data transmission. Finally, the main impermeable layer 15 is laid; first, the sodium-based bentonite waterproof blanket 153 of the main impermeable layer 15 is laid to ensure that the overlap width of the blanket meets the standard; then, the first HDPE membrane 152 of the main impermeable layer 15 is laid and sealed by hot-melt welding; finally, the first protective layer 151 of the main impermeable layer 15 is laid to complete the construction of the core layer of the entire impermeable facility 1.

[0039] A drainage layer 141 of the leachate collection and drainage system 14 is laid on top of the main impermeable layer 15. It is laid in layers according to the design thickness and lightly compacted to ensure uniform spacing between pebbles. Then, the trenches of the main blind ditch 142 and the branch blind ditch 143 are excavated. Corresponding perforated pipes are laid in the trenches respectively. The connection between the main blind ditch 142 and the branch blind ditch 143 is made by hot-melt butt welding. After the welding is completed, geotextile is wrapped around the outside, and then pebbles are backfilled to fix the blind ditch. Finally, the leachate discharge pipe is connected and a water flow test is conducted to ensure that the leachate collection and drainage system 14 is free from blockage and leakage and that the water flows smoothly.

[0040] After the leachate collection and drainage system 14 is successfully commissioned, the solidified fly ash is filled in layers, with the thickness of each layer controlled within the design range. After filling, the fly ash is compacted appropriately. During operation, the outflow and water quality of the leachate collection and drainage system 14 are checked daily, and the drainage pipes are cleaned regularly to prevent blockage. At the same time, the data of the leakage detection layer 16 is monitored in real time. If an early warning signal is received, personnel are immediately organized to locate the leakage point and handle it by excavation repair or grouting. After repair, the seepage prevention test is carried out again to ensure that the standard is met before the landfill operation is resumed.

[0041] After landfilling is completed, the anti-seepage facility 1 will be continuously maintained; the sensors of the leakage detection layer 16 will be calibrated quarterly, the integrity of the first HDPE membrane 152 and the second HDPE membrane 172 will be checked, and the damaged parts of the first protective layer 151 and the second protective layer 171 will be repaired; the surrounding groundwater quality will be sampled and tested annually to ensure that it meets environmental protection standards; the pipes of the groundwater collection and drainage system 19 will be cleaned regularly to prevent siltation from affecting the drainage function, and to ensure that the entire anti-seepage facility 1 can maintain its protective effect for a period of time after the landfill is decommissioned, thus avoiding future environmental risks.

[0042] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0043] Although embodiments of the present 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 present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A seepage-proof structure for solidified fly ash landfills, comprising seepage-proof facilities (1), characterized in that: The anti-seepage facility (1) sequentially comprises a leachate collection and drainage system (14), a main anti-seepage layer (15), a leakage detection layer (16), a secondary anti-seepage layer (17), a base layer (18) and a groundwater collection and drainage system (19) from top to bottom, wherein the main anti-seepage layer (15) is laid on the top of the leakage detection layer (16), the leakage detection layer (16) is laid on the top of the secondary anti-seepage layer (17), the secondary anti-seepage layer (17) is laid on the top of the base layer (18), and the base layer (18) is laid on the top of the groundwater collection and drainage system (19); The anti-seepage facility (1) integrally covers the bottom, side slopes of the landfill yard and the garbage dam, correspondingly forming a yard bottom anti-seepage layer (11) and a side slope anti-seepage layer (13), a soil bag and reinforced soil settlement buffer zone (12) is arranged on the back side of the dam body of the garbage dam, a geogrid is embedded in backfill soil to coordinate the settlement deformation between the dam body and landfill garbage; The leachate collection and drainage system (14) comprises a diversion layer (141), a main blind ditch (142) and branch blind ditches (143), the diversion layer (141) is laid on the top of the main anti-seepage layer (15) and covers the yard bottom and side slope areas, the main blind ditch (142) is arranged in the middle of the yard bottom diversion layer (141) along the length direction of the yard, the branch blind ditches (143) are vertically communicated with the main blind ditch (142) in a grid shape and extend to the middle of the side slopes, the diversion layer (141) adopts graded granite pebbles with a particle size of 16-32 mm, has a thickness of 300 mm, and has a calcium carbonate content of ≤ 5%; The main anti-seepage layer (15) comprises a first protective layer (151), a 2.0 mm thick first double-rough-surface carbon-black-added ultraviolet-resistant corrosion-resistant HDPE membrane (152) and a sodium-based bentonite geosynthetic clay liner (153); the leakage detection layer (16) comprises a detection diversion layer and detection pipes, the detection pipes are arranged along the bottom of the side slopes and the middle of the yard bottom, a detection opening is arranged every 50 m, and a pH sensor and a heavy metal ion detector are installed inside the detection opening; the secondary anti-seepage layer (17) comprises a second protective layer (171), a 2 mm thick second double-rough-surface carbon-black-added ultraviolet-resistant corrosion-resistant HDPE membrane (172) and a compacted clay protective layer (173); the base layer (18) is compacted plain soil, with a compactness of ≥ 93% at the yard bottom and ≥ 90% at the side slopes; the groundwater collection and drainage system (19) comprises underground blind ditches and a pebble diversion layer; The sodium-based bentonite geosynthetic clay liner (153) has a total mass per unit area of ≥ 5000 g / m², wherein the mass of bentonite is ≥ 5000 g / m², the permeability coefficient is ≤ 5×10⁻¹¹m / s, the volume expansion degree of bentonite is ≥ 24 mL / 2g, and the sodium-based bentonite geosynthetic clay liner is laid in a delta-shaped arrangement without cross lapping; The detection diversion layer of the leakage detection layer (16) is a geocomposite drainage net, with a longitudinal breaking strength of ≥ 45 kN / m, a transverse breaking strength of ≥ 30 kN / m, and a water conductivity of ≥ 3×10⁻³m³ / s; the detection pipe is a perforated HDPE pipe with a pipe diameter of 150 mm; The compacted clay protective layer (173) has a permeability coefficient of ≤5×10⁻ 8 m / s, thickness 300mm, compaction degree ≥95%; the underground blind drains of the groundwater collection and drainage system (19) are spaced 10m apart, filled with pebbles with a particle size of 16-32mm, with HDPE perforated pipes of 350mm diameter laid inside, and wrapped with 200g / m² geotextile on the outside; the gravel diversion layer is 300mm thick and has a permeability coefficient ≥1×10⁻³m / s.

2. The seepage-proof structure for solidified fly ash landfills according to claim 1, characterized in that: The main blind drain (142) is filled with a 200mm diameter HDPE double-wall perforated pipe, and the branch blind drain (143) is filled with a 150mm diameter HDPE double-wall perforated pipe. The main blind drain (142) and the branch blind drain (143) are connected by hot-melt butt welding, and the connection is wrapped with 200g / m² long filament nonwoven geotextile.

3. The seepage-proof structure for solidified fly ash landfills according to claim 1, characterized in that: The first protective layer (151) is a 600g / m² polyester filament nonwoven geotextile with a tensile strength ≥30kN / m and a CBR puncture strength ≥5.5kN. It is laid along the slope in the area of ​​the slope seepage prevention layer (13) without horizontal joints.

4. The seepage-proof structure for solidified fly ash landfills according to claim 1, characterized in that: The second protective layer (171) is a 600g / m² polypropylene filament nonwoven geotextile with acid and alkali resistance conforming to JC / T1068-2008, and overlaps with the first protective layer (151) in the settlement buffer zone (12) area with an overlap width ≥150mm.

5. The seepage-proof structure for a solidified fly ash landfill according to claim 1, characterized in that: The first HDPE film (152) and the second HDPE film (172) have a carbon black content of 2.0%-3.0%, a tensile stress cracking time of ≥300h, an atmospheric pressure oxidation induction time of ≥100min, and a roughness height of ≥250μm.

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