River dredged sediment instant solidification treatment process

Abstract

This invention discloses an instant solidification process for river dredging sediment, belonging to the technical field of river environmental management and sediment resource utilization. This process includes four core steps: in-situ closed dredging, onboard instant solidification, closed-loop transportation and backfilling reuse, and ecological restoration. An environmentally friendly dredging vessel with a closed suction pipe is used to perform negative pressure suction of the sediment. On the dredging vessel, a dual-shaft continuous mixing device uniformly mixes fresh sediment with a special environmentally friendly compound solidifying agent. The solidified sediment is then directly and sealed-loop transported to the ecological engineering site for backfilling reuse, ultimately leading to the planting of native vegetation. This invention achieves integrated instant treatment of the entire process from dredging to solidification to reuse, with a 100% sediment reuse rate. The solidified sediment achieves an unconfined compressive strength of over 1.5 MPa after 28 days, and its moisture content is reduced to below 30%. It combines environmental friendliness, economy, and ecological compatibility, completely solving the industry pain points of traditional sediment treatment processes, such as long processing times, high risk of secondary pollution, and low resource utilization rates.

Description

Technical Field

[0001] This invention relates to the fields of river environmental management, water body ecological restoration and solid waste resource utilization, and in particular to an instant solidification treatment process for river dredging sediment. Background Technology

[0002] With the deepening of water environment management in my country, river dredging has become one of the core engineering measures for eliminating black and odorous water bodies and improving the flood control capacity of rivers. The river dredging process generates a large amount of dredged sediment, which is usually characterized by high water content, high compressibility, and low mechanical strength. Some of it also contains pollutants such as heavy metals and organic matter. If not properly treated and disposed of, it can easily cause secondary pollution and occupy a large amount of land resources.

[0003] Currently, the mainstream treatment method for dredged sediment in domestic rivers is "dredging-transportation-storage drying-dewatering disposal". This process has many drawbacks: First, dredged sediment needs to be transported over long distances to temporary storage sites, resulting in high transportation costs and the risk of spillage and leakage during transportation, causing soil and water pollution along the way; Second, the natural drying and dewatering cycle of sediment is long, usually requiring 3-6 months, which occupies a large amount of land resources, and a large amount of leachate will be generated during the rainy season, posing a risk of secondary pollution; Third, most of the dewatered sediment is disposed of by landfill, resulting in extremely low resource utilization and serious waste of resources.

[0004] Existing sediment solidification technologies mostly involve ex-situ solidification, requiring the sediment to be transported to fixed solidification sites for treatment. This approach cannot achieve immediate on-site treatment during dredging, resulting in long processes and low efficiency. Some in-situ solidification technologies require the injection and mixing of solidifying agents underwater in the river channel, which can easily cause water disturbance and solidifying agent diffusion, affecting the aquatic ecosystem of the river. Furthermore, the solidification effect is uneven and cannot meet the mechanical performance requirements for subsequent resource recovery and reuse. At the same time, existing solidifying agents are mostly cement and lime, resulting in high alkalinity and poor ecological compatibility of the solidified sediment, making it difficult to use directly in ecological engineering. Moreover, they have a weak ability to adsorb and solidify pollutants in the sediment, posing an environmental risk of pollutant leaching.

[0005] Therefore, developing an instant solidification treatment process for river dredged sediment that can achieve integrated dredging-solidification-reuse, with no secondary pollution, high solidification efficiency, good ecological compatibility, and full resource recovery of sediment has become an urgent technical problem to be solved in this industry. Summary of the Invention

[0006] In order to overcome the above-mentioned defects of the prior art, the purpose of this invention is to provide an on-site solidification treatment process for river dredging sediment, which realizes on-site on-site solidification of dredged sediment, closed and pollution-free process, 100% resource utilization and ecological reuse, and solves the technical pain points of traditional sediment treatment process such as long process, high cost, high risk of secondary pollution, low resource utilization rate and poor ecological compatibility.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a process for immediate solidification of dredged sediment in river channels, comprising the following steps: S1 In-situ closed dredging: using an environmentally friendly dredging vessel to dredge the target river channel sediment in situ. During the dredging process, a closed suction pipe with an anti-diffusion suction port is used for negative pressure suction to prevent the dredged sediment from spreading and causing secondary pollution to the water body; S2 Onboard immediate solidification: a dual-shaft continuous mixing device is installed on the dredging vessel to continuously transport the fresh dredged sediment extracted in step S1 into the mixing device. Simultaneously, an environmentally friendly compound curing agent is added to the mixing device, and the bottom sediment and curing agent are mixed evenly to obtain solidified modified bottom sediment; S3 Closed conveying and backfilling reuse: The solidified modified bottom sediment prepared in step S2 is directly conveyed to the construction area of ​​the river ecological reuse project through a closed conveying pipe, and is used as engineering fill material for layered backfilling. After each layer is filled, it is compacted using compaction equipment; S4 Ecological restoration: Local native herbaceous plants are planted in the area filled in step S3 to complete the full ecological reuse of dredged bottom sediment.

[0008] Furthermore, in step S2, the environmentally friendly compound curing agent is a composite material made of fly ash, biochar, and cement-based curing agent in a mass ratio of 5:3:2. Fly ash is industrial solid waste generated by coal-fired power plants, enabling resource utilization of solid waste while reducing cement usage in the curing system, decreasing carbon emissions, and optimizing the particle size distribution of the cured sediment, thus improving its later strength stability. The biochar is porous biochar prepared by pyrolysis of agricultural and forestry waste, possessing extremely strong adsorption properties. It can efficiently solidify heavy metals and organic pollutants in the sediment, preventing pollutant leaching, while also improving the pore structure of the sediment, providing nutrients for plant growth, and enhancing ecological compatibility. The cement-based curing agent is environmentally friendly sulfoaluminate cement, which provides rapid early strength, enabling rapid curing and shaping of the sediment, shortening the filling waiting time, and ensuring the feasibility of immediate construction.

[0009] Furthermore, in step S2, the amount of environmentally friendly compound curing agent added is 8%-10% of the dry weight of the dredged sediment, preferably 9% of the dry weight of the dredged sediment.

[0010] Furthermore, in step S2, the mixing time of the bottom mud and the curing agent is 15-20 minutes, preferably 18 minutes; the curing agent and the bottom mud are fully and evenly mixed by the forced mixing of the dual-shaft continuous mixing device. After the mixing is completed, the moisture content of the cured and modified bottom mud is reduced to below 30%, which meets the workability and strength requirements of subsequent filling construction.

[0011] Furthermore, in step S3, the solidified modified sediment can be reused as ecological revetment filler in the river channel. The thickness of each layer in the layered filling is 30cm. After filling, a light roller is used for compaction. The unconfined compressive strength of the solidified sediment after compaction reaches more than 1.5MPa, which meets the structural stability requirements of the ecological revetment.

[0012] Furthermore, in step S3, the solidified and modified sediment can also be reused as a substrate for wetland parks. The thickness of a single layer in the layered filling is 25-30cm, and the compaction degree is controlled at 85%-90%. This not only meets the stability requirements for shaping the terrain of wetland parks, but also has good air and water permeability, which is suitable for the growth needs of wetland plants.

[0013] Furthermore, in step S1, the dredging depth is determined based on the thickness of the polluted layer of riverbed sediment. During the dredging process, the negative pressure inside the suction pipe is controlled at 0.02-0.05 MPa to precisely control the dredging range, avoid excessive dredging that could disturb the original riverbed sediment, and protect the original aquatic ecosystem of the river.

[0014] Beneficial effects Compared with the prior art, the present invention has the following significant advantages: 1. The entire process is integrated and processed instantly, achieving a seamless connection between "dredging-solidification-reuse". Fresh dredged sediment does not need to be transported off-site or stored in a yard for drying and dehydration. It can be solidified and modified on the dredging vessel and directly transported to the reuse site for filling construction. This significantly shortens the sediment treatment cycle, reducing the traditional processing cycle of several months to several hours. At the same time, it significantly reduces transportation costs, yard construction costs and land occupation, greatly improving the economic efficiency of the project.

[0015] 2. Fully enclosed construction to completely eliminate secondary pollution. A closed-loop suction pipe is used for negative pressure dredging to prevent the spread of suspended sediment and secondary pollution of the water body; the solidification process is completed in a closed mixing device on board, ensuring no leakage of the solidifying agent; the finished sediment is directly transported to the construction area through a closed conveying pipe, with no spillage, leakage, or leachate generation throughout the entire process, demonstrating excellent environmental performance.

[0016] 3. A specialized environmentally friendly compound curing agent achieves synergistic performance in terms of strength, environmental protection, and ecology. Fly ash, biochar, and cement-based curing agent are compounded in a 5:3:2 ratio to form a synergistic system: cement-based materials provide rapid early strength, ensuring immediate construction feasibility; fly ash enables high-value utilization of industrial solid waste, reduces cement usage and carbon emissions, and optimizes sediment gradation; biochar efficiently adsorbs pollutants in the solidified sediment, eliminating the risk of pollutant leaching, while improving the sediment's pore structure, providing favorable conditions for plant growth, and significantly enhancing the ecological compatibility of the solidified sediment.

[0017] 4. 100% of the bottom sediment is recycled and reused, truly achieving "on-site sourcing and in-situ reuse". The solidified and modified bottom sediment can be directly used as ecological engineering materials such as river ecological revetment filler and wetland park substrate, without additional treatment. This completely solves the problem of difficult disposal of traditional dredged bottom sediment, while reducing the resource consumption and transportation carbon emissions of purchased sand and gravel fillers in ecological engineering, thus achieving both environmental and economic benefits.

[0018] 5. Excellent ecological compatibility, balancing structural stability and ecological restoration. The solidified sediment has an unconfined compressive strength of over 1.5 MPa, meeting the requirements for engineering structural stability. At the same time, its low alkalinity and suitable pore structure allow for the direct planting of local native herbaceous plants, enabling the simultaneous completion of sediment treatment and river ecological restoration, which aligns with the current ecological development direction of comprehensive water environment management.

[0019] 6. High construction flexibility and wide applicability. All core processes of this technology are completed on the dredging vessel, without being limited by the surrounding site conditions of the river channel. It is especially suitable for urban rivers, landscape rivers, and other scenarios where there is no surrounding storage yard. It can be widely used in the treatment and resource recycling of sediment in various river dredging projects. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process of the present invention; Figure 2 This is a schematic diagram of the hull structure in this invention; Figure 3 This is a schematic diagram of the inhalation tube in this invention; Figure 4 This is a schematic diagram of the feeding box in this invention.

[0021] The labels in the diagram represent the following: 1. Hull; 2. Suction pipe; 3. Filter screen; 4. Mixing tank; 5. Feeding tank; 6. Mixing chamber; 7. Motor; 8. Pump body; 9. Discharge pipe. Detailed Implementation

[0022] The technical solutions in 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.

[0023] Example 1 This embodiment provides an immediate solidification process for dredged river sediment, applied to a dredging project for treating black and odorous water bodies in an urban river. The specific steps are as follows: S1 In-situ closed dredging: An environmentally friendly dredging vessel is used to dredge the target river sediment in situ. The average thickness of the polluted sediment layer is 0.8m, and the dredging depth is controlled at 0.8m. A closed suction pipe with an anti-diffusion inlet is used for negative pressure suction, with the negative pressure inside the suction pipe controlled at 0.03MPa. This process prevents sediment diffusion and secondary pollution of the water body, and does not disturb the original riverbed. S2 Onboard immediate solidification: A dual-shaft continuous mixing device is installed on the dredging vessel. The fresh dredged sediment extracted in step S1 is continuously transported to the mixing device, and an environmentally friendly compound solidifying agent is simultaneously added. The solidifying agent consists of fly ash, biochar, and environmentally friendly sulfoaluminate. Cement was compounded in a mass ratio of 5:3:2, and the amount of curing agent added was 9% of the dry weight of the dredged sediment. The mixing time was controlled at 18 minutes. After uniform mixing, solidified modified sediment was obtained. The moisture content of the solidified modified sediment after mixing was tested to be 28.7%. S3 Closed-loop transportation and backfilling reuse: The solidified modified sediment prepared in step S2 was directly transported to the ecological revetment construction area of ​​the river channel through a closed-loop transportation pipe. It was used as revetment fill material for layered backfilling. The thickness of each layer was 30cm. After each layer was filled, it was compacted with a light roller. A total of 5 layers were filled, with a total backfilling height of 1.5m. S4 Ecological restoration: Local native herbaceous plants, including Bermuda grass, Liriope muscari, and Acorus calamus, were planted on the completed ecological revetment to achieve full ecological reuse of the dredged sediment, with a sediment reuse rate of 100%.

[0024] The performance of the solidified and compacted bottom mud in this embodiment was tested, and the results are as follows: the unconfined compressive strength at 7 days was 1.62 MPa, and the unconfined compressive strength at 28 days was 2.15 MPa; the heavy metal leaching concentration met the Class III standard limit of the "Groundwater Quality Standard" (GB / T14848-2017), and there was no risk of pollutant leaching; three months after filling, the survival rate of the revetment vegetation reached more than 95%, the revetment structure was stable, and there was no settlement or cracking.

[0025] Example 2 This embodiment provides a process for immediate solidification of dredged sediment in a river channel, applied to an ecological restoration project of a wetland park attached to a river. The specific steps are as follows: S1 In-situ closed dredging: An environmentally friendly dredging vessel is used to dredge the target riverbed sediment in situ. The average thickness of the polluted sediment layer is 1.2m, and the dredging depth is controlled at 1.2m. A closed suction pipe with an anti-diffusion inlet is used for negative pressure suction, with the negative pressure inside the suction pipe controlled at 0.04MPa, preventing secondary pollution of the water body caused by sediment diffusion throughout the process; S2 Onboard immediate solidification: A dual-shaft continuous mixing device is installed on the dredging vessel to continuously transport the fresh dredged sediment from step S1 into the mixing device. Simultaneously, an environmentally friendly compound solidifying agent is added to the mixing device. The solidifying agent consists of fly ash, biochar, and environmentally friendly sulfoaluminate cement in a specific mass ratio. The mixture was prepared in a 5:3:2 ratio, with the solidifying agent added at 8% of the dry weight of the dredged sediment. The mixing time was controlled at 20 minutes. After thorough mixing, the solidified and modified sediment was obtained. The moisture content of the solidified and modified sediment after mixing was 29.5%. S3 Closed-loop transportation and backfilling reuse: The solidified and modified sediment prepared in step S2 was directly transported to the construction area of ​​the wetland park through a closed-loop transportation pipe. It was used as a substrate for wetland topography shaping and layered backfilling. The thickness of each layer was 25cm. After each layer was filled, it was compacted using a light compaction device with a compaction degree controlled at 88%. The total backfilling height was 2.0m. S4 Ecological restoration: Native wetland plants, including reeds, cattails, and canna lilies, were planted in the backfilled wetland park area to achieve full ecological reuse of the dredged sediment, with a sediment reuse rate of 100%.

[0026] The performance of the solidified and compacted bottom mud in this embodiment was tested, and the results are as follows: the 7-day unconfined compressive strength was 1.58 MPa, and the 28-day unconfined compressive strength was 2.03 MPa; the heavy metal leaching concentration met the Class III standard limit of the "Surface Water Environmental Quality Standard" (GB3838-2002); 6 months after filling, the wetland plants grew well, the matrix structure was stable, and there was no soil erosion.

[0027] Example 3 This embodiment provides an instant solidification treatment process for river dredging sediment. The only difference from Embodiment 1 is that in step S2, the amount of environmentally friendly compound solidifying agent added is 10% of the dry weight of the dredging sediment, the mixing time is 15 minutes, and the moisture content of the solidified and modified sediment after mixing is 27.2%.

[0028] The performance of the solidified and compacted bottom mud in this embodiment was tested, and the results are as follows: the 7-day unconfined compressive strength is 1.75 MPa, and the 28-day unconfined compressive strength is 2.31 MPa; the heavy metal leaching concentration meets the relevant standard requirements, the vegetation survival rate reaches 96%, and the revetment structure is stable.

[0029] Comparative Example 1 This comparative example uses a traditional riverbed sediment treatment process, specifically: ordinary dredging vessels are used to dredge the riverbed sediment, which is then transported by tanker truck to a temporary storage site 30km away for natural drying and dehydration. The drying period is 4 months, and after dehydration, the sediment moisture content drops to about 40%. Cement is then added for solidification, with the cement content being 12% of the dry weight of the sediment. After being mixed evenly, the sediment is transported to the revetment construction site for filling.

[0030] Compared with Example 1, this comparative example has a treatment cycle that is more than 120 times longer, a treatment cost that is 65% higher, occupies 12,000 square meters of land in the storage area, experiences three instances of spillage and leakage during transportation, and generates approximately 800 cubic meters of leachate during the drying process, requiring additional wastewater treatment. The unconfined compressive strength of the solidified sediment is 1.21 MPa at 7 days and 1.53 MPa at 28 days, which is lower than that of the present invention. The leaching concentration of heavy metals is 3.2 times that of Example 1, posing an environmental risk. The vegetation survival rate after filling is only 72%, indicating poor ecological compatibility.

[0031] Comparative Example 2 This comparative example uses the existing underwater in-situ solidification process, specifically: cement curing agent is injected into the bottom sediment layer through drilling in the river channel, and underwater mixing equipment is used for mixing and solidification. The cement content is 15% of the dry weight of the bottom sediment. After solidification, dredging and excavation are carried out for bank protection filling.

[0032] Compared with Example 1, the solidification process in this comparative example caused turbidity in the river water, with COD and suspended solids concentrations increasing by more than 8 times compared to the background values, resulting in secondary pollution of the water body; the solidification effect was uneven, with the coefficient of variation of solidified sediment strength reaching 35%, and the average compressive strength after 7 days being only 0.85 MPa, which could not meet the requirements of the bank protection structure; the amount of solidifying agent used was large, increasing the cost by 42% compared to Example 1, and the alkalinity of the solidified sediment was high, resulting in a vegetation survival rate of only 65%.

[0033] The results of the above embodiments and comparative examples fully demonstrate that the instant solidification treatment process for river dredging sediment of the present invention realizes the rapid, environmentally friendly, and full-scale resource recycling of dredged sediment, with excellent solidification effect, good ecological compatibility, and lower cost. It completely solves many defects of traditional processes and has extremely high promotion and application value.

[0034] Example 4 This embodiment provides a dredging and solidification vessel used in the immediate solidification treatment of riverbed dredging sediment, such as... Figure 2 , Figure 3 and Figure 4 As shown, the vessel includes a hull 1 and a suction pipe 2 that runs through the bottom of the hull 1. A filter screen 3 is detachably installed at the bottom end of the suction pipe 2, and a mixing box 4 is connected to the top end of the suction pipe 2. The bottom of the mixing box is fixedly connected to the top of the hull 1. The suction pipe 2 and the filter screen 3 installed at the end of the suction pipe 2 can suck the silt at the bottom of the river into the hull 1, which facilitates the subsequent mixing and solidification process. At the same time, by installing the filter screen 3 at the bottom of the suction pipe 2, large solid impurities at the bottom of the river can be prevented from being intercepted outside the suction pipe 2 during the suction process. Furthermore, the shape and installation method of filter screen 3 are disclosed: The filter screen 3 is conical in shape. A sealing ring is provided on the side of the filter screen 3 near the end of the suction pipe 2. The sealing ring contacts and presses against the end of the suction pipe 2. A connecting buckle is provided on the outer arc surface of the filter screen 3. The filter screen 3 is detachably connected to the end of the suction pipe 2 through the connecting buckle. The conical filter screen 3 can perform preliminary filtration of silt when sucking in silt from the bottom of the river. At the same time, the conical structure of the filter screen 3 can prevent solid impurities from clogging the surface of the filter screen 3. When solid impurities are adsorbed on the surface of the filter screen 3, the solid impurities slide along the conical inclined surface and then detach from the surface of the filter screen 3.

[0035] The top of the hull 1 also includes a feeding box 5 that is fixedly connected to the top of the mixing box 4. The top of the feeding box 5 is provided with a feeding port, and the bottom of the feeding box 5 is provided with a control valve. The bottom discharge end of the control valve is connected to the top of the mixing box 4. The combination of mixing box 4 and feeding box 5 enables the addition of activated carbon and fly ash powder to sludge, thereby achieving a solidification effect. Furthermore, the mixing chamber 4 is connected to a stirring chamber 6 at the end away from the suction pipe 2. A motor 7 is fixedly installed on the top of the stirring chamber 6, and a stirring component is rotated inside the stirring chamber 6. The stirring chamber 6 is used to stir and mix the sludge with added curing agent, so that the sludge and activated carbon and other substances are fully and evenly mixed. The bottom of the mixing chamber 6 is connected to a pump body 8, and the bottom of the pump body 8 is connected to a discharge pipe 9. The discharge pipe 9 faces the bottom of the river. The pump body 8 can generate negative pressure on the suction pipe 2 and the mixing box 4, so that the sludge can smoothly enter the hull 1. At the same time, the sludge mixture after mixing with the solidifying agent can be discharged back to the bottom of the river through the discharge pipe 9. Since the solidifying agent is added to the sludge, the sludge will not be washed away in the water flow environment, thus achieving the effect of filling and solidifying the bottom of the river.

[0036] This invention integrates five core functions—negative pressure closed dredging, impurity pre-filtration, precise distribution of solidifying agent, dual-shaft continuous mixing and solidification, and closed directional conveying—into a single vessel, forming an integrated "dredging-solidification-transportation" operation platform. This completely breaks away from the traditional model of separating dredging and solidification processes and requiring multiple equipment to work together. It eliminates the need for fixed solidification sites and transfer transportation equipment, perfectly adapting to the entire process requirements of the invention's instant solidification treatment technology. This enables continuous construction that combines dredging, solidification, and reuse, reducing the traditional sediment treatment cycle from several months to several hours and increasing construction efficiency by over 90%.

[0037] From sediment extraction, solidifier addition, mixing and stirring to finished product transportation, the entire process uses a closed cavity and pipeline connection. With the anti-diffusion suction port and sealing ring at the end of the suction pipe, there is no diffusion of suspended sediment during the extraction process, avoiding excessive COD and suspended solids concentration in the river water. There is no leakage during solidifier addition and stirring, and there is no spillage or leachate discharge during finished product transportation. This completely solves the pain points of water pollution caused by traditional underwater in-situ solidification, leachate generation during storage and drying, and secondary pollution caused by spillage and leakage during transportation. It fully meets the construction requirements for river environmental protection management.

[0038] The use of a conical, detachable filter screen not only pre-intercepts debris during the sludge suction process, effectively protecting core components such as the pump body and agitator from damage by hard debris, but also prevents the filter screen from clogging due to the self-cleaning effect of the conical slope, significantly reducing the probability of equipment blockage failure. At the same time, the filter screen can be detached and installed through connecting buckles, and with the sealing design of the sealing ring, it is easy to disassemble, clean, and replace, significantly improving the continuous operation time of the equipment, reducing maintenance downtime, and adapting to the long-term continuous construction needs of river dredging projects.

[0039] The feeding box is equipped with a precisely adjustable control valve, which can dynamically match the amount of curing agent added according to the real-time suction flow of the bottom sediment, strictly ensuring that the curing agent dosage deviation is controlled within ±0.5%, precisely matching the curing agent dosage requirements of the process of this invention; together with the dual-shaft forced stirring structure in the mixing chamber, it achieves full and uniform mixing of bottom sediment and curing agent, avoiding the problems of uneven mixing caused by traditional mixing equipment, such as fluctuations in curing effect and large dispersion of strength, ensuring that the moisture content of bottom sediment after curing is stably reduced to below 30%, and the 28-day unconfined compressive strength is stably above 1.5MPa, fully meeting the performance requirements for subsequent ecological reuse.

[0040] The equipment's discharge pipe can be flexibly connected to sealed conveying pipelines of different lengths, and the conveying distance can be flexibly adjusted according to construction needs. It can directly convey materials to ecological revetments and wetland park construction areas around the river, and can also be adapted to various scenarios such as temporary storage and off-site reuse. It is not limited by the site conditions around the river, and is especially suitable for construction scenarios such as urban rivers and landscape rivers where there is no storage site nearby. At the same time, the entire equipment can be modularly modified based on existing environmentally friendly dredging vessels, without the need to build a new dedicated hull. The modification cost is low, the equipment is highly versatile, and it can be quickly promoted and implemented in the river management industry. Together with the treatment process of this invention, it forms a complete technical system, comprehensively solving the industry pain points of difficult, costly, high-risk pollution, and low resource utilization rate of river dredging sediment.

[0041] The core working principle is as follows: After the pump body 8 is started, a stable negative pressure environment is formed in the closed space of the suction pipe 2, mixing box 4, and mixing chamber 6. The target bottom sediment layer of the river is precisely suctioned through the closed suction pipe 2, realizing in-situ closed dredging. Before the bottom sediment enters the suction pipe 2, it passes through the conical filter screen 3 at the end. Large stones and hard debris in the river are effectively intercepted, preventing them from entering the pipeline and causing blockage or equipment damage. The conical filter screen structure allows the intercepted debris to automatically slide off the conical surface under the flushing of the water flow, preventing the filter screen surface from being blocked. At the same time, the sealing ring at the end of the filter screen can ensure the airtightness of the suction pipeline and stabilize the negative pressure in the pipe at 0.02-0.05MPa. This ensures the suction efficiency while avoiding excessive disturbance to the original bottom sediment of the river and preventing the bottom sediment from spreading and causing secondary pollution to the water body.

[0042] Fresh sediment drawn through suction pipe 2 enters mixing tank 4 directly. Simultaneously, based on the sediment suction flow rate, the dosage of environmentally friendly compound curing agent is precisely controlled through the control valve at the bottom of feeding tank 5. The curing agent dosage is strictly controlled to be 8%-10% of the dry weight of sediment, achieving synchronous feeding and continuous premixing of sediment and curing agent. This solves the problems of uneven mixing and large deviations in curing agent dosage caused by traditional intermittent feeding, laying the foundation for subsequent uniform curing.

[0043] The premixed sediment and curing agent mixture is continuously fed into the mixing chamber 6. The motor 7 drives the twin-shaft agitator in the mixing chamber to perform forced continuous mixing. By controlling the feed flow rate and the volume of the mixing chamber, the mixing residence time of the mixture is precisely controlled to be 15-20 minutes, so that the curing agent and sediment particles can fully contact and mix evenly, triggering hydration and adsorption curing reactions, realizing the immediate modification and curing of the sediment, and rapidly reducing the moisture content of the sediment to below 30%, thus completing the core process of immediate curing on board.

[0044] The solidified and modified sediment, after mixing, is directly and continuously transported to the target reuse construction areas such as river ecological revetment and wetland park through the conveying pressure provided by pump body 8 and closed discharge pipe 9. The entire process is sealed without leakage or spillage, and no transfer transportation is required. It can be directly combined with layered filling construction to realize the integrated continuous operation of the entire process of "dredging-solidification-reuse".

[0045] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for immediate solidification of dredged sediment in river channels, characterized in that, Includes the following steps: S1, In-situ Closed Dredging: Environmentally friendly dredging vessels are used to dredge the bottom sediment of the target river channel in situ. During the dredging process, a closed suction pipe with an anti-diffusion suction port is used for negative pressure suction to prevent the dredged bottom sediment from spreading and causing secondary pollution to the water body. S2, Onboard Instant Solidification: A dual-shaft continuous mixing device is installed on the dredging vessel to continuously transport the fresh dredged sediment pumped in step S1 into the mixing device. At the same time, an environmentally friendly compound solidifying agent is added to the mixing device to mix the sediment and the solidifying agent evenly, thereby obtaining solidified modified sediment. S3, Closed-loop transportation and backfilling reuse: The solidified modified sediment prepared in step S2 is directly transported to the construction area of ​​the river ecological reuse project through a closed-loop transportation pipe, and is used as engineering fill material for layered backfilling. After each layer is filled, it is compacted using compaction equipment. S4, Ecological Restoration: Plant local native herbaceous plants in the areas filled in step S3 to achieve full ecological reuse of dredged sediment.

2. The instant solidification treatment process for river dredging sediment according to claim 1, characterized in that, In step S2, the environmentally friendly compound curing agent is a composite material made by compounding fly ash, biochar, and cement-based curing agent in a mass ratio of 5:3:

2.

3. The instant solidification treatment process for river dredging sediment according to claim 2, characterized in that, In step S2, the amount of environmentally friendly compound curing agent added is 8%-10% of the dry weight of the dredged sediment.

4. The instant solidification treatment process for river dredging sediment according to claim 3, characterized in that, The environmentally friendly compound curing agent is added at a rate of 9% of the dry weight of the dredged sediment.

5. The instant solidification treatment process for river dredging sediment according to claim 1, characterized in that, In step S2, the mixing time between the bottom mud and the curing agent is 15-20 minutes.

6. The instant solidification treatment process for river dredging sediment according to claim 5, characterized in that, The mixing time is 18 minutes. After mixing, the moisture content of the solidified modified sediment drops to below 30%.

7. The instant solidification treatment process for river dredging sediment according to claim 1, characterized in that, In step S3, the solidified modified bottom mud is reused as ecological revetment filler in the river channel. The thickness of each layer is 30cm. After filling, a light roller is used for compaction. The unconfined compressive strength of the solidified bottom mud after compaction is above 1.5MPa.

8. The instant solidification treatment process for river dredging sediment according to claim 1, characterized in that, In step S3, the solidified and modified sediment is reused as a substrate for the wetland park. The thickness of each layer in the layered filling is 25-30cm, and the compaction degree is controlled at 85%-90%.

9. The instant solidification treatment process for river dredging sediment according to claim 2, characterized in that, The cement-based curing agent is environmentally friendly sulfoaluminate cement, the biochar is porous biochar prepared by pyrolysis of agricultural and forestry waste, and the fly ash is Class II or higher grade fly ash from coal-fired power plants.

10. The instant solidification treatment process for river dredging sediment according to claim 1, characterized in that, In step S1, the dredging depth is determined based on the thickness of the polluted layer of riverbed sediment. During the dredging process, the negative pressure inside the suction pipe is controlled at 0.02-0.05 MPa to avoid disturbing the original riverbed sediment.

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