Method for filling land by using dredged sludge, domestic waste incinerator slag and fly ash

Abstract

This invention discloses a method for land reclamation using dredged sludge, municipal solid waste incineration slag, and fly ash, comprising the following steps: S1: raw material pretreatment; S2: mixing the pretreated dredged sludge, slag, and fly ash with bentonite, soil stabilizer, and water to obtain three pumpable materials, namely material A, material B, and material C; S3: pumping the three materials to a designated reclamation area for underwater casting to obtain a sandwich-type seepage-proof protective structure that is wrapped from the inside out, effectively sealing pollutants inside the structure; S4: curing and inspection. This invention transforms hazardous waste fly ash into part of the land reclamation engineering material. Through the multi-layered low-permeability solidified body and the encapsulation structure, the dual effects of physical isolation and chemical stabilization completely eliminate the risk of leaching of pollutants such as heavy metals and dioxins, solving the problem of their safe disposal.

Description

Technical Field

[0001] This invention relates to the field of land reclamation methods. More specifically, this invention relates to a method for land reclamation using dredged silt, municipal solid waste incineration slag, and fly ash. Background Technology

[0002] With the development of coastal areas and the demands of port construction, land reclamation projects require massive amounts of sand and gravel, leading to a growing shortage and high costs of natural building materials. At the same time, dredging of waterways and ports, as well as waste-to-energy incineration, generate large amounts of solid waste, placing immense pressure on its treatment and disposal.

[0003] Dredged sludge typically has high water content, low strength, and poor load-bearing capacity. Traditional treatment methods often involve stockpiling or ocean dumping, which occupy large amounts of land and pose environmental risks. Direct use in engineering landfill requires complex modification treatment. While municipal solid waste incineration ash is classified as general solid waste, it still contains a certain amount of heavy metals and other pollutants, and improper disposal may cause environmental risks. Currently, its main application is as roadbed material, with limited disposal channels. Municipal solid waste incineration fly ash is classified as hazardous waste (HW18), enriched with high concentrations of heavy metals, dioxins, and other toxic and harmful substances. The current mainstream treatment method is "chemical chelation solidification + secure landfill." This technology has significant drawbacks: extremely high cost: the cost of chelation solidification treatment is about 2,000 yuan per cubic meter, which is a heavy economic burden; failure to achieve resource utilization: the solidified body after treatment still needs to be sealed in a secure landfill, which not only occupies valuable land resources, but also fails to transform it into valuable engineering materials, which is a passive "end-of-life" strategy; long-term risks: the landfill anti-seepage system is at risk of aging and failure, and there is a potential threat of long-term leaching of pollutants and pollution of the surrounding environment.

[0004] Existing technologies, such as the patent with publication number CN102941209A, propose the co-solidification of municipal solid waste incineration slag, dredged sludge, and quicklime. However, the effect of quicklime is limited; it cannot effectively stimulate the natural activity of the dredged sludge and municipal solid waste incineration slag particles, resulting in slow and limited strength growth of the solidified slag. For example, its maximum strength tested is 80 kPa. Simply increasing the amount of quicklime does not significantly increase the strength of the solidified slag, and there is an optimal dosage. Excessive dosage can actually reduce the strength, failing to meet the bearing capacity requirements of building foundations. Furthermore, it does not address municipal solid waste incineration fly ash, thus lacking significant economic advantages and failing to achieve the effect of co-treating hazardous waste. The core contradiction of existing technologies lies in the fact that land reclamation projects urgently need inexpensive and sufficient filler materials, while the treatment of large amounts of solid waste (especially fly ash) requires high costs and land resources. Existing technologies have failed to effectively combine these two needs to achieve "waste treatment with waste, co-utilization, cost reduction and efficiency improvement." Summary of the Invention

[0005] To achieve these and other objectives and advantages according to the present invention, a preferred embodiment of the present invention provides a method for land reclamation using dredged silt, municipal solid waste incineration ash, and fly ash, comprising the following steps: S1: Raw material pretreatment Remove impurities from the dredged silt screen; collect fly ash from municipal solid waste incineration; crush and screen the slag. S2: Material mixing and stirring Pretreated dredged sludge, slag, fly ash, bentonite, soil stabilizer, and water were mixed to obtain three pumpable materials: Material A: sludge stabilized soil, Material B: slag stabilized soil, and Material C: fly ash stabilized soil. S3: Underwater stratified pumping filling and structural construction The three materials are pumped through pipelines to the designated reclamation area for underwater pouring: First, material A is pumped to form the first bottom impermeable protective layer at the bottom of the seabed; Material B is pumped on top of the first bottom impermeable protective layer to form the second bottom impermeable layer. Material C is pumped inside the planned core area, while material B is pumped outside the core area and above the second-level bottom impermeable layer, together forming the third core sealing layer and the outer secondary impermeable layer. At this time, the initial shape of material C being wrapped by material B has been formed. Material B is pumped on top of the third core sealing layer and the outer secondary seepage barrier layer to form the fourth top seepage barrier layer. On the sides of the second-level bottom impermeable layer, the third-level core sealing layer and the outer secondary impermeable layer, and the fourth-level top impermeable layer, material A continues to be pumped to wrap and form an outer peripheral impermeable protective layer. At this time, all the materials together form the initial structure. Finally, material A is pumped onto the top of the entire initial structure to form the fifth top seepage protection layer, at which point the continuously wrapped stable fill structure is cast and formed. S4: Curing and Inspection. After construction, the fill should be left to cure for no less than 28 days. After curing, the bearing capacity, overall stability, and impermeability of the fill should be inspected. Curing refers to the process of allowing the cast fill to naturally solidify and harden in a suitable environment, thereby improving its structural performance.

[0006] Preferably, the weight percentages of material A are as follows: 72% dredged silt, 6% soil stabilizer, and 22% water; The weight percentages of component B are as follows: dredged sludge 35%, municipal solid waste incinerator slag 18%, bentonite 3%, soil stabilizer 8%, and added water 36%; The weight percentages of material C are as follows: dredged sludge 20%, municipal solid waste incineration fly ash 22%, bentonite 6%, soil stabilizer 10%, and added water 42%.

[0007] Preferably, the bentonite is sodium-based bentonite with a particle size of 200 mesh.

[0008] Preferably, the permeability coefficients of the three materials are related as follows: Material A < Material B < Material C, forming a gradient seepage prevention system with increasing permeability from the outside to the inside.

[0009] Preferably, the unconfined compressive strength of material A after 28 days is 494 kPa, and the permeability coefficient is [missing value]. The unconfined compressive strength of material B after 28 days is 972 kPa, and its permeability coefficient is [missing value]. The C material has an unconfined compressive strength of 870 kPa after 28 days and a permeability coefficient of [missing value]. .

[0010] Preferably, the particle size of the slag in S1 after crushing and screening is controlled to be ≤10mm; the dredged sludge is obtained by dredging with a grab bucket boat, and after being transported ashore by barge, large impurities are removed by a screen.

[0011] Preferably, the slump of materials A, B, and C are all maintained within the range of 180-220 mm.

[0012] The present invention has at least the following beneficial effects: (1) Achieve efficient and safe storage and resource utilization of hazardous waste: This invention transforms hazardous waste fly ash into part of the land reclamation engineering materials. Through a multi-layered, low-permeability solidified body and encapsulation structure, it achieves both physical isolation and chemical stabilization, completely eliminating the risk of leaching of pollutants such as heavy metals and dioxins, thus solving the problem of their safe disposal.

[0013] (2) Significant economic benefits: greatly reduces processing costs: Compared to the combined cost of traditional fly ash chelation solidification (approximately 2000 RMB / cubic meter) and secure landfill, this invention primarily utilizes bulk solid waste and conventional cementing materials, reducing costs by over 60%. It saves on filler costs: replacing expensive natural sand and gravel fillers, it provides a cheap and stable material source for land reclamation projects. It saves land resources: eliminating the need to construct or occupy new secure landfills, it achieves "in-situ" engineering utilization of waste.

[0014] (3) Synergistic curing, performance optimization The high moisture content and viscosity of the dredged sludge used in this invention provide excellent workability (flowability) for the mixture and effectively encapsulate ash particles; the aggregate in the slag acts as a skeletal support for the solidified soil, enhancing its overall strength; the active components in the fly ash can undergo hydration, pozzolanic, and ion exchange reactions with the soil stabilizer, forming a dense three-dimensional network structure. These three elements complement each other, producing a synergistic solidification effect of "1+1+1>3".

[0015] (4) Dual benefits of environmental protection and engineering: This invention solves three major problems simultaneously: dredging sludge disposal, municipal solid waste incineration ash disposal, and land reclamation fill material shortage. It realizes a green circular model of "creating land from waste, turning waste into treasure, and achieving high efficiency and economy", which is in line with the sustainable development strategy.

[0016] (5) Convenient construction and controllable quality This invention uses pumpable fluid materials for underwater casting, which is suitable for reclamation projects, has high construction efficiency, and produces a uniform, dense, and well-bonded fill with good structural quality that is easy to guarantee.

[0017] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0018] Figure 1 This is a schematic top view of the solidified composite structure in this invention.

[0019] Figure 2 This is a schematic cross-sectional view of the solidified composite structure in this invention.

[0020] Figure 3 This is a diagram showing the casting sequence of the solidified composite structure in this invention. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0022] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious modifications will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0023] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0024] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0025] like Figure 1-3 As shown, a preferred embodiment of the present invention provides a method for land reclamation using dredged silt, municipal solid waste incineration slag, and fly ash, comprising the following steps: S1: Raw material pretreatment Remove impurities from the dredged silt screen; collect fly ash from municipal solid waste incineration; crush and screen the slag. The slag in S1, after crushing and screening, has a particle size controlled to ≤10mm. The dredged sludge is obtained through dredging using a grab bucket vessel, transported ashore by barge, and then passes through a screen to remove large impurities. The combined use of the grab bucket vessel and barge achieves efficient acquisition and transport of dredged sludge. The screen effectively removes large impurities from the sludge, preventing them from affecting subsequent material mixing and structural forming, thus improving the purity and uniformity of the sludge raw material. After crushing and screening, the slag particle size is strictly controlled to be no greater than ten millimeters. The fine, uniform slag particles can fully integrate with dredged sludge, bentonite, soil stabilizers, and other materials, improving the density and solidification strength of the mixture and preventing problems such as uneven mixing and voids after solidification caused by large slag particles. Simultaneously, controlling the slag particle size improves the material's flowability, facilitating subsequent pipeline pumping construction, preventing pipeline blockage, and improving construction efficiency. The entire pretreatment process is simple and efficient, providing qualified raw materials for subsequent material mixing and pouring construction, ensuring project quality, reducing the incidence of construction failures, and guaranteeing the smooth progress of land reclamation projects. At the same time, it improves the utilization rate of raw materials and reduces waste.

[0026] S2: Material mixing and stirring Pretreated dredged sludge, slag, fly ash, bentonite, soil stabilizer, and water were mixed to obtain three pumpable materials: Material A: sludge stabilized soil, Material B: slag stabilized soil, and Material C: fly ash stabilized soil. Pumpable materials refer to mixtures that have suitable flowability and can be transported through pipelines to a designated area; S3: Underwater stratified pumping filling and structural construction The three materials are pumped through pipelines to the designated reclamation area for underwater pouring: First, material A is pumped to form the first bottom impermeable protective layer at the bottom of the seabed; the impermeable protective layer refers to a structural layer with low permeability that can prevent the penetration and diffusion of water and harmful substances. Material B is pumped on top of the first bottom impermeable protective layer to form the second bottom impermeable layer. Material C is pumped inside the planned core area, while material B is pumped outside the core area and above the bottom seepage barrier layer of the second layer, together forming the third core storage layer and the outer secondary seepage barrier layer. At this time, the initial shape of material C being wrapped by material B has been formed. The core storage layer refers to the core structural layer used to contain fly ash materials and realize the harmless disposal of hazardous waste. Material B is pumped on top of the third core sealing layer and the outer secondary seepage barrier layer to form the fourth top seepage barrier layer. On the sides of the second-level bottom impermeable layer, the third-level core sealing layer and the outer secondary impermeable layer, and the fourth-level top impermeable layer, material A continues to be pumped to wrap and form an outer peripheral impermeable protective layer. At this time, all the materials together form the initial structure. Finally, material A is pumped onto the top of the entire initial structure to form the fifth top seepage protection layer, at which point the continuously wrapped stable fill structure is cast and formed. First, pump material A at a controlled pumping speed of 15 to 20 cubic meters per hour to evenly spread it on the seabed, forming the first bottom impermeable layer. Once material A has initially solidified and there is no obvious flow on the surface, continue pumping material B at the same speed, spreading it on top of the first bottom impermeable layer to form a second bottom impermeable layer with a thickness of 40 to 60 centimeters. Following a pre-defined core area, pump material C within the core area, while simultaneously pumping material B around the core area and on top of the second bottom impermeable layer, forming the third core sealing layer. Material B then surrounds the core area and spreads on top of the bottom impermeable layer, forming the outer secondary impermeable layer. Initially, a structural prototype is formed where material C is wrapped by material B. Material B continues to be pumped on top of the third core sealing layer and the outer secondary seepage barrier layer to form the fourth top seepage barrier layer. Laterally, material A is slowly pumped to the outside of the second bottom seepage barrier layer, the third core sealing layer and the outer secondary seepage barrier layer, and the fourth top seepage barrier layer to wrap the material, with the pumping speed controlled at a slightly low level, such as 10 to 15 cubic meters per hour, so that material A can fully fill the lateral gaps to form an outer peripheral seepage barrier layer. At this point, all materials together constitute the initial structure. Finally, material A is evenly pumped to the top of the entire initial structure to form the fifth top seepage barrier layer, completing the casting and shaping of the continuously wrapped stable fill body.

[0027] S4: Curing and Inspection. After construction, the soil shall be left to cure for no less than 28 days. After curing, the foundation bearing capacity, overall stability and seepage prevention performance of the fill shall be inspected.

[0028] The aforementioned technical solution mixes dredged sludge, municipal solid waste incineration slag, and municipal solid waste incineration fly ash with soil stabilizers, bentonite, and other additives in specific proportions to prepare three pumpable solidified mixtures (component A, component B, and component C) with different properties. Based on their differences in permeability and mechanical properties, a sandwich-type seepage-proof protective structure is constructed in the reclamation area, wrapping the structure from the inside out. This effectively seals pollutants (especially heavy metals and dioxins in fly ash) within the structure, while simultaneously forming a fill body that meets engineering requirements. This achieves the synergistic resource utilization of the three wastes—dredged sludge, municipal solid waste incineration slag, and fly ash—effectively reducing the land resources occupied by waste landfill and lowering the risk of environmental pollution.

[0029] The system comprises three layers: Material A (silt-stabilized soil) is primarily used for the outer perimeter, top, and bottom main barriers; Material B (slag-stabilized soil) is used for the secondary outer and secondary impermeable layers; and Material C (fly ash-stabilized soil) is used for the innermost core containment area. This layered impermeable system provides the fill with excellent impermeability, effectively preventing seawater infiltration and the diffusion of harmful substances in the materials. The fly ash in the core containment layer is encapsulated by multiple layers of Material B and Material A, achieving harmless disposal. After curing, the foundation bearing capacity of the fill meets the basic requirements for land reclamation projects. The overall structure exhibits strong stability, resisting seawater erosion and daily external forces, and its impermeability meets standards, effectively preventing pollution of the surrounding marine environment. Furthermore, the entire process is simple and controllable, allowing for precise underwater pouring of materials via pipeline pumps, resulting in high construction efficiency. This method is suitable for large-scale land reclamation projects, balancing environmental protection and engineering practicality.

[0030] The present invention also provides the following technical solution: the weight percentage of material A is as follows: 72% dredged silt, 6% soil stabilizer, and 22% water; the weight percentage of material B is as follows: 35% dredged silt, 18% municipal solid waste incineration slag, 3% bentonite, 8% soil stabilizer, and 36% added water; the weight percentage of material C is as follows: 20% dredged silt, 22% municipal solid waste incineration fly ash, 6% bentonite, 10% soil stabilizer, and 42% added water.

[0031] The above technical solution, through strict control of the weight ratio of each material, ensures that the prepared materials A, B, and C all possess the required physical and mechanical properties and flowability, meeting the construction requirements for underwater pumping and layered casting. Material A, with dredged silt as its main component, is mixed with an appropriate amount of soil stabilizer and water. After solidification, it possesses good impermeability and a certain strength, and can serve as the core material for each impermeable protective layer. Material B, with the addition of an appropriate amount of slag and bentonite, has superior strength and impermeability after solidification compared to material A, and can effectively serve as an intermediate impermeable layer and wrapping layer to protect the core area. Material C, through a reasonable ratio of fly ash, bentonite, and soil stabilizer, achieves stable sealing of fly ash while ensuring the solidification strength and pumpability of the material, preventing the leakage of harmful substances from the fly ash. The proportioning design of the three materials takes into account the waste utilization rate, material performance and engineering requirements, so that each layer of the structure can perform its corresponding function, improve the stability, impermeability and safety of the entire filling body, and maximize the use of dredged sludge and incineration by-products, achieving a unity of environmental protection and engineering benefits. The proportioning scheme is scientific and reasonable, highly repeatable and suitable for large-scale production.

[0032] This invention also provides a technical solution where the bentonite is sodium-based bentonite with a particle size of 200 mesh. During the mixing process, the sodium-based bentonite is first mixed with a small amount of water until it forms a paste, and then added to other materials. This avoids the formation of agglomerates when added directly, ensuring that the bentonite is uniformly dispersed in the mixture and fully utilizing its water absorption, swelling, and binding properties. Throughout the process, the performance of the sodium-based bentonite is sampled and tested, including indicators such as water absorption swelling rate and bonding strength, to ensure that it meets the standard requirements for sodium-based bentonite and is free of quality defects.

[0033] Using 200-mesh sodium-based bentonite as raw material, its fine particle size allows for thorough mixing with dredged sludge, slag, fly ash, and soil stabilizers, increasing the contact area between materials and improving the cohesiveness and uniformity of the mixture. Sodium-based bentonite's strong water absorption and expansion properties allow it to absorb excess moisture during mixing and curing, while also filling voids between materials after expansion, effectively reducing permeability and enhancing the seepage prevention performance of each layer. Compared to other types of bentonite and coarse-grained bentonite, 200-mesh sodium-based bentonite provides superior curing effects for materials B and C, resulting in more stable strength and seepage prevention performance after curing, preventing delamination, cracking, and leakage, and providing reliable protection for the entire fill structure's seepage prevention system. Furthermore, qualified sodium-based bentonite exhibits stable performance, adapting to underwater curing environments and providing long-term seepage prevention and bonding effects, enhancing the durability of the fill structure and ensuring the long-term stability of the land reclamation project. The selected scheme meets the actual needs of the project, improving the reliability and applicability of the entire method.

[0034] The present invention also provides the following technical solution, wherein the permeability coefficient relationship of the three materials is defined as: material A < material B < material C, forming a gradient anti-seepage system with increasing permeability from the outside to the inside, which can effectively block the outward migration of pollutants. In actual construction, material A, with the lowest permeability coefficient, is used for the outermost and top / bottom impermeable protective layers, forming the first impermeable barrier to prevent seawater and external moisture from penetrating. Material B, with a medium permeability coefficient, is used for the intermediate impermeable layer and the core area's wrapping layer, forming the second impermeable barrier to further block potentially penetrating water and harmful substances within the core area. Moreover, material B (slag-stabilized soil) has the highest strength, and thanks to the aggregate effect of slag, it provides good skeletal support, serving as the main skeletal support for the entire structure. Material C, with the highest permeability coefficient, is used for the core sealing layer. Because it is wrapped by multiple layers of material B and material A, its relatively strong permeability will not affect the overall impermeability effect, while ensuring the structural stability after solidification. The design of the gradient impermeability system conforms to the fluid permeability law, effectively dispersing seepage pressure, avoiding local impermeability failure that leads to a decline in overall impermeability performance, and improving the impermeability reliability of the entire fill body. Meanwhile, the system does not require all materials to be of high impermeability. Under the premise of ensuring the impermeability effect, it can reasonably control the proportion and cost of each material, taking into account both the safety and economy of the project. This allows the land reclamation project to meet environmental protection requirements while controlling construction costs, and has good practical application value.

[0035] The present invention also provides the following technical solution, wherein the 28-day unconfined compressive strength of material A is 494 kPa, and the permeability coefficient is... The unconfined compressive strength of material B after 28 days is 972 kPa, and its permeability coefficient is [missing value]. The C material has an unconfined compressive strength of 870 kPa after 28 days and a permeability coefficient of [missing value]. .

[0036] Material B has the highest 28-day unconfined compressive strength, making it suitable as an intermediate impermeable layer and wrapping layer. It provides reliable structural support for the fill structure, resisting external pressure and seawater erosion. Material C has slightly lower strength than Material B, but still meets the structural requirements of the core containment layer. Furthermore, it has the lowest permeability coefficient, enabling safe containment of fly ash when used in conjunction with the outer protection layer. Material A has relatively lower strength, but its permeability coefficient meets the requirements of the impermeable protective layer, and its lower raw material cost makes it suitable for the outer layer and top and bottom protection, controlling costs while ensuring impermeability. The performance indicators of each material are matched to create a complementary advantage, ensuring that the entire fill structure possesses sufficient foundation bearing capacity and overall stability to meet the subsequent development and utilization needs after land reclamation, while also exhibiting excellent impermeability to prevent pollution of the surrounding marine environment.

[0037] This invention also provides the following technical solution: the slump of materials A, B, and C are all maintained within the range of 180-220 mm. If the slump value is lower than 180 mm, it indicates insufficient material fluidity. Appropriate amounts of water are added to the mixing tank using a water replenishment device, and after thorough mixing, samples are taken again for testing until the slump value enters the preset range. If the slump value is higher than 220 mm, it indicates excessive material fluidity. A small amount of curing agent or drying material can be added to adjust the material consistency, and after thorough mixing, the sample is tested again until the standard is met.

[0038] The aforementioned technical solution strictly controls the slump of the three materials within the range of 180 to 220 millimeters, ensuring good material flowability. This allows the materials to be smoothly pumped through pipelines to designated underwater locations, preventing pipeline blockages due to insufficient flowability and improving construction efficiency. Simultaneously, suitable flowability enables the materials to spread evenly after pouring, forming a flat and dense structural layer, avoiding localized accumulation and voids, and enhancing the overall integrity and stability of each layer. The material flowability is not excessive, allowing it to quickly maintain its structural shape after pouring, preventing excessive diffusion and loss, and ensuring precise thickness and positioning of the layered structure, providing a solid foundation for subsequent structural construction.

[0039] To fully illustrate the technical effects of the present invention, the following embodiments are provided.

[0040] Dredged silt: The silt was taken from a grab dredger in a waterway, with an initial water content of 65%.

[0041] Municipal solid waste incineration fly ash (FA): Taken from the bag filter of a municipal solid waste incineration power plant, classified as hazardous waste (HW18). Main pollutants: Pb (1500 mg / kg), Cd (50 mg / kg), Zn (5000 mg / kg), dioxin toxicity equivalent (TEQ) 3.0 ngTEQ / g.

[0042] Municipal solid waste incinerator ash (BA): Taken from the lower part of the grate in the same plant, after crushing, screening, and separation of valuable metals (magnetic metals, copper, aluminum, gold, silver, etc.), particles with a diameter ≤10mm are selected, with an apparent density of [missing information]. .

[0043] Soil stabilizer: A commercially available soil stabilizer was used, and its quality met the requirements of CJ / T 486-2015 standard.

[0044] Bentonite: Sodium-based bentonite with a particle size of 200 mesh is selected to enhance impermeability.

[0045] Water replenishment: It is taken from municipal tap water and used to adjust the water-solid ratio, thereby controlling the flow and meeting the pumping requirements.

[0046] The implementation and coordination are as follows: Silt-stabilized soil: Silt: Soil stabilizer: Water = 1080kg: 90kg: 320kg.

[0047] Slag-stabilized soil: Silt: Slag: Bentonite: Soil stabilizer: Water added = 495kg: 250kg: 50kg: 115kg: 520kg.

[0048] Fly ash stabilized soil: silt: fly ash: bentonite: soil stabilizer: water added = 278kg: 320kg: 100kg: 147kg: 625kg.

[0049] Table 1 Performance Indicators of Three Types of Solidified Soil The three types of pumpable solidified soil prepared by this invention, with a controlled water-to-solid ratio of 1.0 (the ratio of the total mass of water to the mass of solids in the solidified soil), have similar wet densities in their freshly mixed state, ranging from 1.43 to 1.49 g / cm³, and a slump of 200 ± 20 mm. This characteristic ensures stability at the interface between different materials during continuous pumping construction, preventing segregation or blockage and facilitating the formation of a uniform and dense fill structure. The addition of bentonite further enhances the material's impermeability.

[0050] Leaching toxicity tests were conducted on specimens of raw fly ash, C-material (fly ash solidified soil) after 28 days of curing, and composite structural material according to the "Leaching Toxicity Method for Solid Waste - Sulfuric Acid and Nitric Acid Method" (HJ / T 299) and the "Determination of Dioxins in Solid Waste - Isotope Dilution High-Resolution Gas Chromatography-High-Resolution Mass Spectrometry" (HJ 77.3), and the results were compared with the limits in the "Pollution Control Standard for Municipal Solid Waste Landfills" (GB 16889).

[0051] Table 2 Leaching toxicity test results After treatment by the synergistic solidification process of this invention, hazardous waste fly ash is transformed into environmentally friendly engineering materials. The leaching concentrations of all key pollutants are not only far below the national standard limits, but also reduced by more than two orders of magnitude compared to the original fly ash leaching concentration. In particular, the leaching toxicity equivalent concentration of dioxins decreased from an excessive 150 pg TEQ / L to 0.85 pg TEQ / L, demonstrating that the hydration reaction, pozzolanic reaction, and ion exchange reaction involving soil stabilizers can generate a tight three-dimensional network structure, and that the adsorption of bentonite and the chemical stabilization effect under high pH conditions are extremely effective.

[0052] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for land reclamation using dredged silt, municipal solid waste incineration slag, and fly ash, characterized in that, Includes the following steps: S1: Raw material pretreatment Remove impurities from the dredged silt screen; Collect fly ash from municipal solid waste incineration; crush and screen slag. S2: Material mixing and stirring Pretreated dredged sludge, slag, fly ash, bentonite, soil stabilizer, and water were mixed to obtain three pumpable materials: Material A: sludge stabilized soil, Material B: slag stabilized soil, and Material C: fly ash stabilized soil. S3: Underwater stratified pumping filling and structural construction The three materials are pumped through pipelines to the designated reclamation area for underwater pouring: First, material A is pumped to form the first bottom impermeable protective layer at the bottom of the seabed; Material B is pumped on top of the first bottom impermeable protective layer to form the second bottom impermeable layer. Material C is pumped inside the planned core area, while material B is pumped outside the core area and above the second-level bottom impermeable layer, together forming the third core sealing layer and the outer secondary impermeable layer. At this time, the initial shape of material C being wrapped by material B has been formed. Material B is pumped on top of the third core sealing layer and the outer secondary seepage barrier layer to form the fourth top seepage barrier layer. On the sides of the second-level bottom impermeable layer, the third-level core sealing layer and the outer secondary impermeable layer, and the fourth-level top impermeable layer, material A continues to be pumped to wrap and form an outer peripheral impermeable protective layer. At this time, all the materials together form the initial structure. Finally, material A is pumped onto the top of the entire initial structure to form the fifth top seepage protection layer, at which point the continuously wrapped stable fill structure is cast and formed. S4: Curing and Inspection. After construction, the soil shall be left to cure for no less than 28 days. After curing, the foundation bearing capacity, overall stability and seepage prevention performance of the fill shall be inspected.

2. The method for land reclamation using dredged silt, municipal solid waste incinerator slag, and fly ash as described in claim 1, characterized in that, The weight percentages of material A are as follows: dredged silt 72%, soil stabilizer 6%, and water 22%. The weight percentages of component B are as follows: dredged sludge 35%, municipal solid waste incinerator slag 18%, bentonite 3%, soil stabilizer 8%, and added water 36%; The weight percentages of material C are as follows: dredged sludge 20%, municipal solid waste incineration fly ash 22%, bentonite 6%, soil stabilizer 10%, and added water 42%.

3. The method for land reclamation using dredged silt, municipal solid waste incinerator slag, and fly ash as described in claim 1, characterized in that... The bentonite is sodium-based bentonite with a particle size of 200 mesh.

4. The method for land reclamation using dredged silt, municipal solid waste incinerator slag, and fly ash as described in claim 1, characterized in that, The permeability coefficients of the three materials are related as follows: Material A < Material B < Material C, forming a gradient seepage prevention system with increasing permeability from the outside to the inside.

5. The method for land reclamation using dredged silt, municipal solid waste incineration slag, and fly ash according to claim 1, characterized in that, The unconfined compressive strength of material A after 28 days is 494 kPa, and the permeability coefficient is... The unconfined compressive strength of material B after 28 days is 972 kPa, and its permeability coefficient is [missing value]. The C material has an unconfined compressive strength of 870 kPa after 28 days and a permeability coefficient of [missing value]. .

6. The method for land reclamation using dredged silt, municipal solid waste incinerator slag, and fly ash according to claim 1, characterized in that, The slag in S1 is crushed and screened to a particle size of ≤10mm; the dredged sludge is obtained by dredging with a grab bucket boat, and after being transported ashore by barge, large impurities are removed by a screen.

7. The method for land reclamation using dredged silt, municipal solid waste incinerator slag, and fly ash according to claim 1, characterized in that, The slump of materials A, B, and C are all maintained within the range of 180-220mm.

Images