An artificial island reclamation construction method for a shallow sand flow section in an inland river

Abstract

The application discloses a kind of artificial island hydraulic filling construction methods of inland shallow quicksand section, belong to the technical field of water conservancy and port engineering. Including: the quicksand ground magnetic parameter surveying and mapping and foundation bearing capacity distribution modeling of construction area are carried out;Deep pore grouting solidification and landslide prevention treatment of quicksand foundation are implemented;Multi-level composite scouring cofferdam system is constructed, the cofferdam system includes geogrid reinforced layer, long filament woven geotextile bottom protection layer and high-strength filling bag facing envelope layer from inside to outside in sequence;The step-by-step stacking and coordinated air sealing of filling bag cofferdam are implemented;Shallow relay type efficient hydraulic filling transmission system is constructed;Multi-stage chemical flocculation and physical retention coupled hydraulic filling operation is executed;Dynamic drainage and vacuum-assisted consolidation of hydraulic filling area are implemented;Full-cycle digital stability monitoring and feedback regulation mechanism is established. The application realizes stable island building on extremely low bearing capacity stratum, increases quicksand retention rate to more than 85%, effectively avoids liquefaction and instability risk, and has very high engineering popularization and application value.

Description

Technical Field

[0001] This invention belongs to the field of water conservancy and port engineering technology, specifically relating to a method for artificial island reclamation in shallow water and quicksand sections of inland rivers. Background Technology

[0002] With the deepening of inland waterway construction, tidal flat management, and water conservancy projects in my country, artificial islands, as an important component of waterway diversion, ecological restoration, navigation aids, and navigation structures, are finding increasingly widespread application and their importance is becoming more prominent. In modern water conservancy engineering practice, using dredged soil for land reclamation not only enables the resource utilization of abandoned dredged materials and reduces overall project costs, but also plays an irreplaceable role in reconstructing the micro-topography of waterways, optimizing the navigation environment, and improving local aquatic ecosystems.

[0003] Traditional hydraulic reclamation techniques typically rely on large or medium-sized cutter suction dredgers or trailing suction hopper dredgers. The powerful force generated by centrifugal pumps transports the underwater mixture of sediment and water to the designated reclamation area via fully enclosed pipelines. In conventional hydraulic engineering environments, the initial construction involves building a relatively enclosed space with erosion resistance by constructing robust earth-rock cofferdams, sheet pile cofferdams, or large-diameter geotextile-filled bag cofferdams. Once the cofferdam is airtight and reaches its design strength, the land is gradually filled and slack-loaded using the principle of gravity settlement of sediment in still water. This process offers significant advantages in deep-water areas or in existing foundations with good bearing capacity, including mature construction technology, high earthwork transportation efficiency, and rapid land reclamation. Especially during the construction of large cofferdams, the tiered stacking of multiple layers of geosynthetic materials, supplemented by vacuum preloading or slack-load drainage consolidation techniques, can largely ensure the overall stability of the retaining structure, thus providing a reliable physical barrier for subsequent large-scale hydraulic reclamation operations.

[0004] However, when the construction environment shifts to extremely shallow inland waters where the original strata consist primarily of thick quicksand, the existing technical solutions exhibit significant systemic limitations in both practical operation and mechanical principles. Specifically, the shallow inland water environment imposes stringent physical limitations on the draft of construction vessels. Large, efficient reclamation equipment often cannot approach the shore due to insufficient water levels. This not only forces the construction team to add multiple relay pumping stations, leading to a surge in energy consumption, but also severely weakens the continuity and economy of construction. A deeper technical contradiction lies in the intense conflict between the inherent physical and mechanical properties of quicksand geology and the stability requirements of reclamation structures. Quicksand possesses extremely high fluidity, extremely low cohesion, and significant thixotropy. Under the continuous lateral scouring of inland river runoff and the coupling effect of hydrodynamic pressure generated during reclamation operations, it is highly susceptible to liquefaction caused by a surge in pore water pressure. Traditional geotechnical cofferdams often fail to form a stable mechanical support structure on such a soft and sensitive quicksand foundation. Due to the severe lack of bearing capacity of the foundation, the cofferdam is prone to uneven settlement, overall sliding, or even dam failure when bearing the weight of the backfill material and the seepage pressure generated by the difference in water levels inside and outside.

[0005] Based on this, due to the extremely fine and uniform particle size distribution of quicksand, its settling velocity within the reclamation area is extremely slow. In shallow, flowing water environments, conventional natural overflow drainage methods cannot guarantee the effective retention of fine-grained sediment. A large amount of micro-particles will be lost back into the river channel with the overflow water. This not only leads to low reclamation efficiency and a huge waste of earthwork resources, but also causes a rapid increase in the concentration of suspended solids in the surrounding waters, posing a serious risk of aquatic ecological environment pollution. Fundamentally, existing reclamation technologies struggle to simultaneously address the core contradiction between "island formation efficiency" and "structural stability," failing to balance equipment navigation in shallow water environments with a high sand retention rate in quicksand strata. Simply increasing the cross-sectional size of the cofferdam or strengthening the foundation to pursue stability would lead to an exponential increase in project costs and make the construction period difficult to control. If traditional open or simple retaining reclamation methods are used, the dilemma of uncontrollable quicksand loss and difficulty in maintaining the geometric outline of the artificial island will inevitably arise.

[0006] Correspondingly, the complex working conditions resulting from the interplay of shallow water dynamic constraints, extremely low bearing capacity of quicksand foundations, and high loss rate of fine particles present a critical technological bottleneck in the field of water conservancy and waterway engineering. This necessitates efficient and dynamic deployment of construction equipment under extremely low water levels, and the development of a dredging control system that effectively intercepts fine particles while adapting to foundation settlement and deformation. Therefore, developing a dredging construction method for artificial islands that balances construction flexibility in shallow water environments, quicksand foundation stabilization, and efficient retention of dredged materials has become a major challenge and a pressing technical problem for those skilled in the art. Summary of the Invention

[0007] This invention provides a method for constructing artificial islands in shallow water and quicksand sections of inland rivers. It aims to solve the systemic technical problems of large and medium-sized filling equipment being difficult to approach in extremely shallow inland water environments, the extremely low bearing capacity of quicksand foundations leading to easy instability of cofferdams, and the high loss rate of fine-particle quicksand under the scouring of flowing water, resulting in serious environmental pollution.

[0008] To achieve the above-mentioned objectives, this invention provides a method for constructing artificial islands in shallow water and quicksand sections of inland rivers. The method includes the following steps, categorized by time and spatial hierarchy: S1. Conduct geomagnetic parameter mapping of quicksand and foundation bearing capacity distribution modeling in the construction area; specifically including: S11. A multibeam echo sounder and a shallow seismic profiler are used to continuously probe the thickness of the bottom sediment and quicksand layer in the reclamation area, obtaining the horizontal distribution boundary and vertical depth profile of the quicksand layer. The multibeam echo sounder uses high-frequency sound waves with a frequency of 200-400kHz to obtain underwater topographic cloud maps with sub-decimeter accuracy. The shallow seismic profiler uses a low-frequency FM signal of 3-7kHz, penetrating the quicksand layer to a depth of not less than 15 meters, with a stratigraphic resolution of not less than 0.1 meters. The collected raw data is imported into three-dimensional finite element analysis software after surge compensation, sound velocity correction, and coordinate transformation. The three-dimensional finite element analysis software performs nonlinear dynamic response analysis on the quicksand layer based on the Drucker-Prager yield criterion to determine the distribution range of the ultimate plastic zone under reclamation load. S12. Based on the particle size distribution curve of the quicksand obtained from drilling sampling, determine the median particle size d of the quicksand. 50 Coefficient of uniformity C u and curvature coefficient C c ; S13. Based on the above physical parameters, construct a rheological model of the quicksand foundation in a three-dimensional digital twin platform, calculate the pore water pressure response function under different loading rates, and determine the initial bearing capacity critical value of the cofferdam layout axis.

[0009] S2. Implement deep micropore grouting solidification and landslide prevention treatment for quicksand foundations; specifically including: S21. Within a 5-meter radius on both sides of the pre-set axis of the artificial island cofferdam, a multi-head small-diameter deep mixing pile machine is used for pretreatment; the pile machine is equipped with an adaptive draft-adjustable pontoon to ensure normal operation in extremely shallow waters with a depth of less than 0.8 meters; an array-type quincunx pile arrangement is adopted; the center distance L between adjacent pile positions is determined based on the foundation stability calculation results, and its calculation formula is: Where d is the pile diameter, τ cuγ is the ultimate frictional resistance between the pile and the quicksand, H is the saturated unit weight of the quicksand, φ is the proposed filling height, and φ is the internal friction angle of the quicksand. This arrangement forms a continuous anti-slip key at the bottom of the cofferdam, blocking the shear deformation of the quicksand along the sliding surface. S22. The grouting material is a composite grout of water glass and silicate cement. The selected cement strength grade is 42.5, the water-cement ratio is controlled between 0.45 and 0.55, the water glass modulus is controlled between 2.4 and 2.8, and its volumetric admixture ratio is 3%-5% of the cement grout volume. By controlling the grouting pressure between 0.3 and 0.6 MPa, the grout forms an interwoven consolidation network in the pores of the quicksand, improving the shear strength of the cofferdam foundation. The front end of the grouting pipe is equipped with a rotary nozzle with a low-speed, high-torque mixing process. Its rotation speed is controlled between 15 and 25 rpm, and the lifting speed is controlled between 0.2 and 0.3 m / min. Through the low-speed, high-torque mixing process, it is ensured that the grout and quicksand are fully mixed to form a solidified body with a homogeneity coefficient of not less than 0.85. After grouting is completed, the curing strength is checked using a static cone penetration tester, requiring its cone tip resistance q. c The value increases by no less than three times that of the original quicksand.

[0010] For areas where the thickness of quicksand exceeds 10 meters, steel sections are inserted into the grouting and solidification piles during the grouting and solidification process to form cement-soil mixing piles with reinforcement.

[0011] S3. Construct a multi-level composite erosion-resistant cofferdam system, wherein the cofferdam system comprises, from the inside out, a geogrid reinforcement layer, a long-filament woven geotextile backing layer, and a high-strength filling bag backing layer; specifically including: S31. A layer of polypropylene filament woven geotextile with a weight of not less than 600 g / m² and a tensile strength of not less than 100 kN / m is laid on the solidified foundation surface as a flexible embankment to isolate the quicksand layer and the dredged fill layer. The difference in warp and weft tensile strength is controlled within 10%. The edge of the filament woven geotextile embankment is provided with a ballast bag groove for erosion prevention. The opening of the ballast bag is provided with a one-way sleeve valve to prevent mud leakage. It automatically closes when the filling pressure reaches 0.15 MPa. The ballast bag is filled with crushed stone with a particle size of 20 mm to 50 mm and a total weight of not less than 120 kg / m. S32. Longitudinal stiffening ribs are arranged vertically above the packing body in the direction perpendicular to the axis. The stiffening ribs are made of prefabricated high-strength polyethylene rope netting to limit the lateral displacement of the filling bags during the stacking process.

[0012] S4. Implement stepped stacking and coordinated airtightness of filled bag cofferdams; specifically including: S41. A layered filling process is adopted, with the height of a single layer of filling bags controlled at 0.5-0.8 meters. The filling material is coarse sand produced by dredging in this section of the river, which is pumped by a small pump-suction dredger, and its slurry concentration is controlled at 15%-20%. The end of the filling pipe is connected to a five-way manifold with a diversion function. The ball valve on the five-way manifold is used to switch and distribute the material evenly to the five filling points at the same time. Between each layer of filling bags, a 10-centimeter-thick layer of graded gravel is laid as an interlayer drainage layer to accelerate the lateral discharge of mud liquid in the bags. S42. During the filling process, a laser rangefinder is used to monitor the geometric dimensions of the bags in real time to ensure that the overlap length between adjacent bags is not less than 1.5 meters. A cross-interlocking stepped stacking arrangement is adopted. For each layer of cofferdam that rises, its inner slope surface shrinks centripetally by 0.5-1.0 meters relative to the lower layer, forming a step structure with no less than three levels. S43. In the closure section of the cofferdam, a non-circular filling component with pressure relief function is installed. The component, through a built-in check-loop drainage blind pipe, allows water to drain while preventing quicksand from seeping out, thereby reducing the dynamic water pressure difference inside and outside the cofferdam and preventing the closure section from collapsing.

[0013] S5. Construct a shallow-water relay-type high-efficiency dredging and reclamation system; specifically including: S51. To address shallow water limitations, a relay pumping unit consisting of multiple low-draft, modular small cutter suction dredgers is employed. Each small cutter suction dredger has a rated flow rate controlled at 400-600 cubic meters per hour and is equipped with a high-precision GNSS-RTK positioning system with a positioning accuracy of ±2cm. Through an onboard BIM terminal, operators can observe the spatial position of the cutter head relative to the pre-set reclamation floor plan in real time. The cutting depth of the cutter head is dynamically adjusted according to the thickness of the quicksand layer to ensure that the mud concentration at the suction inlet remains stable at 1.2g / cm³. The concentration of sediment is between 3 and 1.5 g / cm³; each small cutter suction dredger is powered by a submersible motor-driven sludge pump. The surface of the submersible motor housing is equipped with a spiral guide plate to prevent sand deposition, and the pump blades are coated with a 0.5 mm thick ultra-hard tungsten carbide coating; the sludge conveying pipeline is made of high-molecular-weight polyethylene flexible pipe, with wear-resistant ceramic plates lined inside the pipe wall to reduce frictional resistance, and flexible compensators with tensile strength are installed at the connection flanges of the sludge conveying pipeline; the pipeline is erected on a specially made lightweight pontoon, and the draft of the pontoon is no more than 0.3 meters; S52. A high-efficiency vortex-type energy dissipation diffuser is installed at the outlet end of the mud conveying pipe. By changing the mud flow direction, the impact kinetic energy is converted into radially divergent advection energy, reducing the direct scouring and damage of the mud to the quicksand foundation. All mechanical connection parts are made of steel with a performance grade of not less than Q355B. The electrical control system meets the IP68 protection level. All sensor modules exchange data through the Modbus-RTU protocol. The construction site is equipped with no less than two sets of backup generator sets, whose total installed power is more than 1.2 times the total power of the dredging, grouting and vacuum systems.

[0014] S6. Perform multi-stage chemical flocculation and physical retention coupled air-filling operations; specifically including: S61. An automatic dosing module is installed at the outlet of the mud conveying pipe to dynamically add high molecular weight polyethyleneimine or polyacrylamide flocculants according to the mud flow rate and solids content. The charge density of the flocculants is between 30% and 50%. The flocculants cause the fine sand particles to undergo adsorption, charge neutralization and bridging effects to form large-diameter flocs. The automatic dosing module includes an electromagnetic flowmeter, an online concentration monitor, and a variable frequency metering pump; the output flow rate Q of the variable frequency metering pump is... a With mud flow rate Q m Mud concentration C m And the preset drug dosage ratio η satisfies a linear compensation relationship: Q a =k·Q m ·C m ·η+b, where k and b are calibration coefficients determined based on field experiments; The flocculant dissolution system employs a three-tank fully automated continuous preparation device. The first tank performs initial mixing of dry powder and water, the second tank performs maturation and stirring, and the third tank serves as a storage tank. The impeller speed of the mixer is set to 30 rpm. A static mixer is installed in the middle section of the sludge conveying pipe, utilizing the turbulence generated by baffles to ensure thorough mixing of the flocculant and sludge, with the mixing intensity controlled at a G value of 200-500 seconds. -1 ; Calculate the settling velocity after flocculation based on the modified Stokes' law: Where D is the equivalent particle size after flocculation, ρ p ρ is the particle density. f Where is the fluid density, μ is the dynamic viscosity, C is the mud concentration, and n is the flow resistance coefficient; S62. By controlling the dredging zones, the residence time of the slurry in the dredging zone is made longer than the theoretical settling time of the flocculated particles, thus achieving efficient interception of quicksand. During the dredging operation, a flexible antifouling screen is pre-installed on the outside of the cofferdam closure section. The antifouling screen consists of a floating pipe, a skirt, and a bottom chain. The skirt is made of synthetic fiber filter cloth with a pore size of 50-80 micrometers. The antifouling screen forms a closed semi-transparent barrier underwater to intercept suspended particles overflowing from the dredging operation and control them within a 10-meter radius around the construction area. S63. In the later stage of the hydraulic reclamation construction, a mobile microwave heating container is used to dehydrate and harden the quicksand within 20 cm of the surface layer of the hydraulic reclamation layer; the microwave frequency is 2450MHz and the output power is controlled at 10-50kW, so that the moisture content can be rapidly reduced to below the plastic limit.

[0015] S7. Implement dynamic drainage and vacuum-assisted consolidation in the reclamation area; specifically including: S71. A three-dimensional drainage network consisting of plastic drainage boards and horizontal filter pipes is pre-embedded inside the reclamation layer; the plastic drainage boards adopt a C-shaped or Ω-shaped structure, and their water flow rate is not less than 30 cubic centimeters / second; the horizontal filter pipes are connected to the main pipe through a T-joint and connected to the water collection tank; the water collection tank is equipped with high and low liquid level sensors, which work with a variable frequency drainage pump to achieve automatic drainage; S72. Utilizing the residual water head pressure in the reclamation area and the micro-vacuum pump set added later, the water in the pores of the quicksand is forcibly discharged, accelerating the dissipation of the superstatic pore water pressure; in the initial stage of vacuum preloading, a step-by-step loading strategy is adopted, with the initial negative pressure controlled at 20 kPa, and then increased at a rate of 10 kPa / day to the design negative pressure, which is maintained above 80 kPa for a duration of no less than 14 days and nights, so as to increase the shear strength of the quicksand layer to above 25 kPa; the vacuum-assisted consolidation system achieves spatial isolation by covering the surface of the reclamation area with two layers of high-density polyethylene sealing film with a thickness of 0.12 mm.

[0016] S8. Establish a full-cycle digital stability monitoring and feedback adjustment mechanism; specifically including: S81. At key nodes of the cofferdam, the grouting and solidification zone, and the center of the reclamation zone, an integrated sensor array based on MEMS technology is pre-embedded, including a pore water pressure gauge, a settlement magnetic ring, and a three-dimensional inclinometer; the sensor data is transmitted to the control center in real time through a wireless sensor network, and the sensor data acquisition frequency is set to 1Hz. S82. When the monitored pore water pressure growth rate exceeds the preset threshold, the flow rate of the dredging pump group is automatically adjusted or the operation is temporarily stopped; the data processing algorithm adopts a trend prediction model based on Kalman filtering; when the monitored foundation settlement rate exceeds 10 mm / day for three consecutive days, or the pore water pressure ratio reaches 0.6, the system automatically triggers an early warning and adjusts the dredging pump group.

[0017] The combination of all the above-mentioned technical features of this invention forms an integrated construction system covering the entire life cycle from foundation investigation, solidification treatment, structural construction, sediment transportation to environmentally friendly discharge. It profoundly solves the core technical contradictions of "unable to stand, unable to be blown in, unable to be retained, and unable to be precisely controlled" in the reclamation of artificial islands in shallow water and quicksand environments of inland rivers, and has extremely high engineering promotion and application value.

[0018] During implementation, all mechanical connection components were constructed using steel of Q355B grade or higher performance level, conforming to national standards. The electrical control system meets IP68 protection standards to adapt to humid underwater operating environments. All sensor modules interact via the Modbus-RTU protocol, ensuring system integration compatibility and reliability. The entire construction process strictly adhered to the safety and quality clauses in the "Code for Construction Organization Design of Water Conservancy and Hydropower Projects" and the "Technical Specification for Underwater Deep Cement Mixing Method for Foundation Reinforcement."

[0019] In practice, the construction site should be equipped with no fewer than two backup generator sets, whose total installed power should cover 1.2 times the total power of the backfilling, grouting, and vacuum systems. All connecting flanges of the mud conveying pipeline should be fitted with flexible compensators with tensile strength to absorb pipeline strain caused by water flow fluctuations. For extremely deep quicksand sections exceeding 10 meters in thickness, this method also recommends inserting steel sections into the grouting and solidification piles to form cement-soil mixing reinforced piles (SMW method) to further enhance stability against lateral earth pressure.

[0020] In summary, the artificial island reclamation method for shallow water and quicksand sections of inland rivers of the present invention achieves precise control and efficient output of artificial island construction under extremely complex working conditions through the integration of multidisciplinary technologies. Attached Figure Description

[0021] Figure 1 This is a flowchart of the construction method of the present invention; Figure 2 This is a flowchart of the underwater exploration and numerical simulation analysis of quicksand geology in this invention; Figure 3 This is a schematic diagram of the deep grouting and solidification system for quicksand foundations of the present invention; Figure 4 This is a schematic diagram of the layered structure of the composite cofferdam on a quicksand foundation according to the present invention; Figure 5 Diagram of equipment system composition for shallow water reclamation construction in quicksand geology; Figure 6 Schematic diagram of an automatic dosing control system for flocculants used in quicksand geological reclamation. Figure 7 Schematic diagram of key parameter monitoring and range configuration for hydraulic reclamation construction. Detailed Implementation

[0022] Example 1

[0023] Before detailing the artificial island reclamation method for shallow-water quicksand sections of inland rivers according to this invention, it is necessary to clarify that the design logic of this scheme is based on a system coupling analysis of complex hydrodynamic environment and extremely soft foundation conditions. This invention achieves integrated construction from micro-particle reinforcement to macro-structural stability through digital dynamic control of the entire construction cycle. Figure 1 As shown, the present invention includes the following steps: S1. Conduct geomagnetic parameter mapping of quicksand in the construction area and model the foundation load distribution.

[0024] This step is not traditional topographic mapping, but rather involves acquiring multiphysics data to provide a high-precision digital foundation for subsequent engineering decisions. The specific implementation steps are as follows: Figure 2 As shown, a multibeam echo sounder and a shallow seismic profiler were used for simultaneous scanning. The multibeam echo sounder employed high-frequency acoustic waves of 200-400 kHz to acquire underwater topographic maps with sub-decimeter accuracy, ensuring precise capture of micro-topographic undulations in shallow water areas. Simultaneously, the shallow seismic profiler emitted low-frequency FM signals of 3-7 kHz, capable of penetrating loose quicksand layers to a depth of at least 15 meters, with a stratigraphic resolution of at least 0.1 meters. The acquired raw acoustic data underwent rigorous surge compensation, sound velocity correction, and coordinate transformation before being imported into three-dimensional finite element analysis software.

[0025] Within the 3D digital twin platform, technicians used the horizontal distribution boundaries and vertical depth profiles of the quicksand layer obtained through detection, combined with the quicksand particle size distribution curves obtained from on-site drilling and sampling, to accurately determine the median particle size d of the quicksand through indoor experiments. 50 Coefficient of uniformity C u and curvature coefficient C c Based on these key physical parameters, a rheological model of the quicksand foundation was constructed. The core of this model lies in simulating the pore water pressure response function under different loading rates, specifically using the Drucker-Prager yield criterion to perform nonlinear dynamic response analysis of the quicksand layer. This process not only calculated the bearing capacity under steady-state conditions but, more importantly, determined the extent of the ultimate plastic zone under dynamic dredging loads, thus providing a critical reference value for the initial bearing capacity of the cofferdam's layout axis.

[0026] S2. Implement deep micropore grouting solidification and landslide prevention treatment for quicksand foundations, using methods such as... Figure 3The grouting and solidification system shown is designed to address the extremely low bearing capacity of shallow, quicksand sections of inland rivers. Multiple small-diameter deep-layer mixing piles are deployed within a 5-meter radius on either side of the pre-set axis of the artificial island cofferdam for pretreatment. These piles are equipped with specially designed adaptive draft-adjusting pontoons. By adjusting the ballast water inside the pontoons, the machinery can maintain a draft of less than 0.3 meters and operate normally and stably in extremely shallow waters (less than 0.8 meters deep). In terms of the grouting process, this invention uses a composite grout of water glass and silicate cement. The cement used is ordinary silicate cement with a strength grade of 42.5, and the water-cement ratio is strictly controlled between 0.45 and 0.55 to ensure the grout's permeability and later strength. The water glass modulus is set between 2.4 and 2.8, and its volumetric admixture ratio is 3%-5% of the cement grout volume. This formulation results in a grout with excellent initial setting time and an extremely high early strength gain rate.

[0027] Regarding the control of specific construction parameters, the rotation speed of the rotary nozzle at the front end of the grouting pipe is maintained at 15-25 rpm, and the lifting speed is controlled at 0.2-0.3 m / min. Through this low-speed, high-torque mixing process, the grout and quicksand undergo a vigorous physicochemical reaction in situ, causing the grout to form an interwoven consolidation network in the pores of the quicksand, ultimately forming a reinforced body with a homogeneity coefficient of not less than 0.85. The grouting pressure is consistently maintained between 0.3 MPa and 0.6 MPa to prevent splitting damage to the foundation due to excessive pressure or insufficient grouting due to insufficient pressure. To ensure the reinforcement effect, an array-type quincunx pile arrangement is used in the grouting and solidification process, and the center distance L between adjacent piles is determined according to the foundation stability calculation formula. Where d is the pile diameter, τ cu Let γ be the ultimate skin friction resistance between the pile and the quicksand, γ be the saturated unit weight of the quicksand, H be the proposed fill height, and φ be the internal friction angle of the quicksand. This layout can form a continuous and stable anti-slip key at the bottom of the cofferdam, effectively blocking the shear deformation of the quicksand along the sliding surface. After grouting, a static cone penetration test (CPT) is used to check the solidification strength to ensure the cone tip resistance q. c The value increases by no less than three times that of the original quicksand.

[0028] S3. Construct a multi-level composite scour-resistant cofferdam system, such as Figure 4As shown in the diagram. This system is designed to adapt to the slight uneven settlement of quicksand foundations through a combination of flexible materials, while resisting erosion by water flow. The cofferdam system consists of a geogrid reinforcement layer, a long-filament woven geotextile base layer, and a high-strength filling bag protective layer from the inside out. First, a layer of polypropylene long-filament woven geotextile with a tensile strength of not less than 100 kN / m is laid on the solidified foundation surface. This geotextile, as a flexible embankment, plays a crucial role in isolation, preventing the backfill material from mixing with the underlying quicksand. The edges of the long-filament woven geotextile are designed with ballast bag grooves to prevent erosion. The inside is filled with crushed stone with a particle size of 20-50 mm and a total weight of not less than 120 kg / m, thereby preventing localized undercutting and scouring caused by inland river runoff at the base of the cofferdam.

[0029] Above the laid flexible packing, longitudinal stiffening ribs made of prefabricated high-strength polyethylene rope mesh are arranged perpendicular to the axis. The main function of these stiffening ribs is to limit the lateral displacement of the filling bags during subsequent stacking, and to transform the force of individual filling bags into the force of the overall frame.

[0030] S4. Stepped stacking and coordinated airtightness of the filling bag cofferdam. The filling bags are made of polypropylene woven fabric with a basis weight of not less than 600 g / m², and the difference in tensile strength between the warp and weft directions is controlled within 10% to ensure uniform stress distribution. The opening of the filling bag is equipped with a one-way sleeve valve to prevent mud leakage. When the filling pressure inside the bag reaches 0.15 MPa, the sleeve valve automatically closes to ensure the compactness of the filling.

[0031] In the specific implementation of the hydraulic reclamation operation, the height of a single layer of filling bags is strictly controlled between 0.5 and 0.8 meters. The filling material comes from coarse sand dredged from this section of the river, which is pumped using a small pump-suction dredger, and the slurry concentration is maintained at 15%-20%. To ensure stacking accuracy, construction personnel use laser rangefinders to monitor the geometric three-dimensional dimensions of the bags in real time, ensuring that the overlap length between adjacent bags is not less than 1.5 meters, and strictly adopting a cross-interlocking I-shaped arrangement. With each layer of cofferdam rising, its inner slope shrinks centripetally by 0.5 to 1.0 meters relative to the lower layer, forming a stepped structure with no less than three levels. This stepped geometry effectively disperses the huge horizontal earth pressure generated by the hydraulic reclamation soil and directs the final resultant force towards the solidified zone deep in the foundation, significantly improving the anti-sliding stability of the cofferdam.

[0032] For the critical closure section in cofferdam construction, this invention incorporates a uniquely shaped filling component with pressure relief capabilities. This component, through its built-in check-loop drainage blind pipe, allows excess water to drain smoothly from the bag during filling and subsequent drainage, while the filter layer of the blind pipe prevents the seepage of quicksand particles. This design significantly reduces the dynamic water pressure difference between the inside and outside of the cofferdam, preventing dam collapse due to excessive flow velocity during the closure stage. Furthermore, a 10-centimeter-thick layer of graded gravel is laid between each layer of filling bags as an interlayer drainage layer, accelerating the lateral discharge of mud and liquid from the bags.

[0033] S5. Construct a shallow water relay-type high-efficiency dredging and reclamation system, such as Figure 5 Considering the limitation that large cutter suction dredgers cannot enter shallow water areas, this invention employs a relay pump unit composed of multiple low-draft, modular small cutter suction dredgers. Each pump unit has a rated flow rate of 400-600 cubic meters per hour, and the power source is a sludge pump driven by a submersible motor. To cope with the wear caused by high sand content, the motor housing surface is equipped with a spiral guide plate to prevent sand deposition, and the pump blade surface is coated with a 0.5 mm thick ultra-hard tungsten carbide coating. The sludge conveying pipeline uses a flexible high-molecular-weight polyethylene pipe, with wear-resistant ceramic plates lined the inner wall. The pipeline is supported on a specially designed lightweight pontoon, with the pontoon's draft strictly limited to within 0.3 meters.

[0034] Each small cutter suction dredger is equipped with a high-precision GNSS-RTK positioning system with a positioning accuracy of ±2cm. Through the onboard BIM terminal, operators can observe the cutter head's position in three-dimensional space in real time. The cutting depth of the cutter head is dynamically adjusted based on real-time data of the quicksand layer thickness, ensuring the mud concentration at the suction inlet remains stable between 1.2-1.5 g / cm³. At the outlet end of the mud conveying pipe, a high-efficiency vortex-type energy dissipation diffuser is installed. This device converts the high-speed linear impact kinetic energy of the mud into radially divergent advection energy through internal guide vanes, thereby greatly reducing the direct scouring and damage of the mud to the quicksand in the reclamation area and protecting the initial geotextile substrate from physical impact.

[0035] S6. Perform a combined multi-stage chemical flocculation and physical retention airfill operation. For example... Figure 6 As shown, an automatic dosing module is installed before the sludge conveying pipe outlet. This module includes an electromagnetic flowmeter, an online concentration monitor, and a variable frequency metering pump. Based on real-time monitoring of the sludge flow rate and solids content, a polyacrylamide flocculant with a charge density between 30% and 50% is dynamically added. The output flow rate Q of the variable frequency metering pump... a With mud flow rate Q m Mud concentration C m And the preset drug dosage ratio η satisfies a linear compensation relationship: Q a =k·Q m ·C m·η+b, where k and b are calibration coefficients determined based on field experiments. The dissolution process of the flocculant is completed in a three-tank fully automated preparation device, with low-speed stirring (30 rpm) protecting the polymer chains from mechanical shearing damage.

[0036] A static mixer installed in the middle section of the mud conveying pipe utilizes turbulence to ensure thorough mixing of the reagents and mud / sand, with the mixing intensity G value controlled between 200 and 500 seconds. -1 Flocculants, through adsorption, charge neutralization, and bridging, cause fine quicksand particles to aggregate into large-diameter flocs. Based on a modified Stokes' law, technicians calculated the settling velocity after flocculation. By precisely controlling the area and flow lines of the reclamation zone, the average residence time of the slurry within the reclamation zone is ensured to be significantly longer than the theoretical settling time of the flocculated particles. To further meet environmental protection requirements, a flexible anti-fouling screen made of synthetic fiber filter cloth is installed outside the cofferdam closure section, with its pore size controlled at 50-80 micrometers. This screen intercepts suspended particles overflowing from the reclamation operation within a 10-meter radius of the construction area, allowing them to settle slowly within the barrier.

[0037] S7. Dynamic Drainage and Vacuum-Assisted Consolidation in the Reclamation Area. To accelerate the formation of the artificial island's landmass, a three-dimensional drainage network is pre-embedded within the reclamation layer. This network consists of C-shaped or Ω-shaped plastic drainage boards and horizontal filter pipes, with a water flow rate of no less than 30 cubic centimeters per second. The horizontal filter pipes are connected to a main pipe via T-joints, leading to a high-efficiency water collection tank. In the later stages of construction, two layers of 0.12 mm thick HDPE sealing membrane are applied to the surface of the reclamation area, and a negative pressure of no less than 80 kPa is generated using a micro-vacuum pump set. Vacuum preloading adopts a stepped loading strategy, with the initial negative pressure controlled at 20 kPa, subsequently increasing gradually at a rate of 10 kPa / day. This method effectively prevents fine quicksand particles from prematurely clogging the drainage board filter membrane, ensuring deep transmission of vacuum pressure. Continuous vacuum preloading for 14 days and nights can increase the shear strength of the quicksand layer to over 25 kPa.

[0038] S8, full-cycle digital stability monitoring and feedback adjustment. For example... Figure 7 As shown, an integrated sensor array based on MEMS technology, including a pore water pressure gauge, a settlement magnetic ring, and a three-dimensional inclinometer, is pre-embedded at key nodes of the cofferdam, the grouting and solidification zone, and the center of the reclamation zone. The sensors collect data at a frequency of 1Hz and transmit it to the control center via a wireless sensor network. The algorithm uses a Kalman filter model to filter out environmental noise. When the pore water pressure growth rate exceeds a preset threshold, the settlement rate exceeds 10mm / day for three consecutive days, or the pore water pressure ratio reaches 0.6, the system automatically triggers an early warning and feeds back to the reclamation pump group, automatically adjusting the flow rate or suspending operations to completely avoid the risk of quicksand thixotropic liquefaction.

[0039] To further improve the surface bearing capacity, this invention also employs a rapid surface hardening treatment based on microwave-assisted drying after the dredging is completed. A mobile microwave heating chamber is used to heat the top 20 cm of quicksand at a frequency of 2450 MHz and a power of 10-50 kW. The coupling oscillation between microwave energy and water molecules rapidly reduces the moisture content below the plastic limit.

[0040] To demonstrate the superiority of the artificial island reclamation method for shallow water and quicksand sections of inland rivers described in this invention, the following provides a comparative analysis of specific embodiments and comparative examples.

[0041] Example 2

[0042] This embodiment uses the complete construction method described in Embodiment 1. The construction site is located in a very shallow water and quicksand section in the middle and lower reaches of an inland river, with an average water depth of 0.6 meters, a quicksand layer thickness of 8.5 meters, and a d50 of 0.08 mm.

[0043] 1. Foundation treatment: The grouting and curing scheme described in this invention is adopted, using cement / water glass composite grout and plum blossom-shaped pile arrangement.

[0044] 2. Cofferdam construction: stepped stacking, with long-fiber geotextile for bottom protection.

[0045] 3. Hydraulic filling process: Shallow water relay pump set combined with automatic chemical dosing for flocculation.

[0046] 4. Post-treatment: Vacuum pre-compression for 14 days combined with microwave-assisted drying.

[0047] The comparison proportion uses the traditional conventional hydraulic filling construction method.

[0048] 1. Foundation treatment: No deep grouting is performed; only a single layer of ordinary geotextile is laid.

[0049] 2. Cofferdam construction: ordinary sand is used to build cofferdams.

[0050] 3. Hydraulic reclamation process: conventional medium-sized dredgers are used for long-distance dumping and reclamation.

[0051] 4. Post-treatment: Natural sedimentation drainage, without vacuum or chemical intervention.

[0052] The experimental comparison data are shown in Table 1 below: Table 1. Comparison of performance indicators between the embodiments of the present invention and the comparative examples.

[0053] A rigorous analysis of the data in Table 1 reveals that the method described in this invention exhibits significant engineering advantages across multiple core technical dimensions. Regarding the retention rate of quicksand, traditional methods, lacking effective coupling between chemical flocculation and physical retention, result in a substantial loss of fine-particle quicksand under the influence of flowing water, with a retention rate of only 42%. In contrast, this invention, through a precise chemical dosing system and a stepped cofferdam structure, increases the retention rate to 91.5%. This means that, with the same amount of work, this invention significantly reduces the required dredging volume. In terms of structural stability, the horizontal displacement of the cofferdam in this invention is only about 14.5% of that in traditional methods, and the shear strength of the foundation is improved by nearly 2.5 times. This fully demonstrates the scientific validity of deep microporous grouting and solidification combined with the stepped structure in dealing with strata with extremely low bearing capacity.

[0054] Furthermore, this invention also excels in environmental protection and efficiency. The dramatic reduction in suspended solids content in the construction area is attributed to the application of multi-level anti-fouling barriers and chemical flocculation technology. Regarding the shortened construction period, the combination of vacuum-assisted consolidation and microwave-assisted drying technologies enabled the reclamation area, which would normally take months to become usable, to meet operational requirements in just 48 hours. This has irreplaceable value in inland river emergency rescue or rapid island construction projects.

[0055] In further implementation of this invention, all mechanical connection components were selected from steel conforming to the Q355B performance grade, ensuring fatigue life under complex stress environments. The entire system's electrical control system achieves IP68 protection level, and sensor data interaction follows the Modbus-RTU standard protocol. The construction process strictly adheres to the "Technical Specification for Underwater Deep Cement Mixing Method for Foundation Reinforcement." For extreme working conditions with quicksand thickness exceeding 10 meters, this invention also incorporates reinforcing steel into the grouting piles, forming SMW method stiffened piles to cope with greater lateral earth pressure.

[0056] In summary, the artificial island reclamation construction method for shallow water and quicksand sections of inland rivers of the present invention systematically solves four major problems in shallow water and quicksand environments: limited construction equipment, insufficient foundation bearing capacity, high quicksand loss rate, and serious environmental pollution, through the close coordination of eight core steps: surveying and modeling, grouting and solidification, composite cofferdam, stepped stacking, relay pumping, chemical flocculation, vacuum drainage, and dynamic monitoring. It provides a highly reliable, efficient, and environmentally friendly integrated solution for inland water conservancy projects.

Claims

1. A method for constructing artificial islands in shallow, shifting sand sections of inland rivers, characterized in that, The method, based on the time dimension and spatial hierarchy, includes the following steps: S1. Conduct geomagnetic parameter mapping of quicksand and foundation bearing capacity distribution modeling in the construction area; specifically including: S11. A multibeam echo sounder and a shallow seismic profiler are used to continuously probe the thickness of the bottom sediment and quicksand layer in the reclamation area, obtaining the horizontal distribution boundary and vertical depth profile of the quicksand layer. The multibeam echo sounder uses high-frequency sound waves with a frequency of 200-400kHz to obtain underwater topographic cloud maps with sub-decimeter accuracy. The shallow seismic profiler uses a low-frequency FM signal of 3-7kHz, penetrating the quicksand layer to a depth of not less than 15 meters, with a stratigraphic resolution of not less than 0.1 meters. The collected raw data is imported into three-dimensional finite element analysis software after surge compensation, sound velocity correction, and coordinate transformation. The three-dimensional finite element analysis software performs nonlinear dynamic response analysis on the quicksand layer based on the Drucker-Prager yield criterion to determine the distribution range of the ultimate plastic zone under reclamation load. S12. Based on the particle size distribution curve of the quicksand obtained from drilling sampling, determine the median particle size d of the quicksand. 50 Coefficient of uniformity C u and curvature coefficient C c ; S13. Based on the above physical parameters, construct a rheological model of the quicksand foundation in a three-dimensional digital twin platform, calculate the pore water pressure response function under different loading rates, and determine the initial bearing capacity critical value of the cofferdam layout axis. S2. Implement deep micropore grouting solidification and landslide prevention treatment for quicksand foundations; specifically including: S21. Within a 5-meter radius on both sides of the pre-set axis of the artificial island cofferdam, a multi-head small-diameter deep mixing pile machine is used for pretreatment; the pile machine is equipped with an adaptive draft-adjustable pontoon to ensure normal operation in extremely shallow waters with a depth of less than 0.8 meters; an array-type quincunx pile arrangement is adopted; the center distance L between adjacent pile positions is determined based on the foundation stability calculation results, and its calculation formula is: Where d is the pile diameter, τ cu γ is the ultimate frictional resistance between the pile and the quicksand, H is the saturated unit weight of the quicksand, φ is the proposed filling height, and φ is the internal friction angle of the quicksand. This arrangement forms a continuous anti-slip key at the bottom of the cofferdam, blocking the shear deformation of the quicksand along the sliding surface. S22. The grouting material is a composite grout of water glass and silicate cement. The selected cement strength grade is 42.5, the water-cement ratio is controlled between 0.45 and 0.55, the water glass modulus is controlled between 2.4 and 2.8, and its volumetric admixture ratio is 3%-5% of the cement grout volume. By controlling the grouting pressure between 0.3 and 0.6 MPa, the grout forms an interwoven consolidation network in the pores of the quicksand, improving the shear strength of the cofferdam foundation. The front end of the grouting pipe is equipped with a rotary nozzle with a low-speed, high-torque mixing process. Its rotation speed is controlled between 15 and 25 rpm, and the lifting speed is controlled between 0.2 and 0.3 m / min. Through the low-speed, high-torque mixing process, it is ensured that the grout and quicksand are fully mixed to form a solidified body with a homogeneity coefficient of not less than 0.

85. After grouting is completed, the curing strength is checked using a static cone penetration tester, requiring its cone tip resistance q. c The value increases by no less than three times the original quicksand value; S3. Construct a multi-level composite anti-scour cofferdam system, wherein the cofferdam system includes, from the inside out, a geogrid reinforcement layer, a long-filament woven geotextile bottom layer, and a high-strength filling bag protective layer. S4. Implement stepped stacking and coordinated airtightness of filled bag cofferdams; S5. Construct a shallow water relay-type high-efficiency dredging and transportation system; S6. Perform a multi-stage chemical flocculation and physical retention coupled air-filling operation; S7. Implement dynamic drainage and vacuum-assisted consolidation in the reclamation area; specifically including: S71. A three-dimensional drainage network consisting of plastic drainage boards and horizontal filter pipes is pre-embedded inside the reclamation layer; the plastic drainage boards adopt a C-shaped or Ω-shaped structure, and their water flow rate is not less than 30 cubic centimeters / second; the horizontal filter pipes are connected to the main pipe through a T-joint and connected to the water collection tank; the water collection tank is equipped with high and low liquid level sensors, which work with a variable frequency drainage pump to achieve automatic drainage; S72. Utilizing the residual water head pressure in the reclamation area and the micro-vacuum pump set added later, water in the pores of the quicksand is forcibly discharged, accelerating the dissipation of excess pore water pressure; in the initial stage of vacuum preloading, a step-by-step loading strategy is adopted, with the initial negative pressure controlled at 20 kPa, and then increased at a rate of 10 kPa / day to the design negative pressure, which is maintained above 80 kPa for a duration of no less than 14 days and nights, so as to increase the shear strength of the quicksand layer to above 25 kPa; the vacuum-assisted consolidation system achieves spatial isolation by covering the surface of the reclamation area with two layers of high-density polyethylene sealing film with a thickness of 0.12 mm; S8. Establish a full-cycle digital stability monitoring and feedback adjustment mechanism; specifically including: S81. At key nodes of the cofferdam, the grouting and solidification zone, and the center of the reclamation zone, an integrated sensor array based on MEMS technology is pre-embedded, including a pore water pressure gauge, a settlement magnetic ring, and a three-dimensional inclinometer; the sensor data is transmitted to the control center in real time through a wireless sensor network, and the sensor data acquisition frequency is set to 1Hz. S82. When the monitored pore water pressure growth rate exceeds the preset threshold, the flow rate of the dredging pump group is automatically adjusted or the operation is temporarily stopped; the data processing algorithm adopts a trend prediction model based on Kalman filtering; when the monitored foundation settlement rate exceeds 10 mm / day for three consecutive days, or the pore water pressure ratio reaches 0.6, the system automatically triggers an early warning and adjusts the dredging pump group.

2. The method for constructing artificial islands in shallow water and quicksand sections of inland rivers according to claim 1, characterized in that: For areas where the thickness of quicksand exceeds 10 meters, steel sections are inserted into the grouting and solidification piles during the grouting and solidification process to form cement-soil mixing piles with reinforcement.

3. The method for constructing artificial islands in shallow water and quicksand sections of inland rivers according to claim 1, characterized in that: S3 specifically includes: S31. A layer of polypropylene filament woven geotextile with a weight of not less than 600 g / m² and a tensile strength of not less than 100 kN / m is laid on the solidified foundation surface as a flexible embankment to isolate the quicksand layer and the dredged fill layer. The difference in warp and weft tensile strength is controlled within 10%. The edge of the filament woven geotextile embankment is provided with a ballast bag groove for erosion prevention. The opening of the ballast bag is provided with a one-way sleeve valve to prevent mud leakage. It automatically closes when the filling pressure reaches 0.15 MPa. The ballast bag is filled with crushed stone with a particle size of 20 mm to 50 mm and a total weight of not less than 120 kg / m. S32. Longitudinal stiffening ribs are arranged vertically above the packing body in the direction perpendicular to the axis. The stiffening ribs are made of prefabricated high-strength polyethylene rope netting to limit the lateral displacement of the filling bags during the stacking process.

4. The method for constructing artificial islands in shallow water and quicksand sections of inland rivers according to claim 1, characterized in that: S4 specifically includes: S41. A layered filling process is adopted, with the height of a single layer of filling bags controlled at 0.5-0.8 meters. The filling material is coarse sand produced by dredging in this section of the river, which is pumped by a small pump-suction dredger, and its slurry concentration is controlled at 15%-20%. The end of the filling pipe is connected to a five-way manifold with a diversion function. The ball valve on the five-way manifold is used to switch and distribute the material evenly to the five filling points at the same time. Between each layer of filling bags, a 10-centimeter-thick layer of graded gravel is laid as an interlayer drainage layer to accelerate the lateral discharge of mud liquid in the bags. S42. During the filling process, a laser rangefinder is used to monitor the geometric dimensions of the bags in real time to ensure that the overlap length between adjacent bags is not less than 1.5 meters. A cross-interlocking stepped stacking arrangement is adopted. For each layer of cofferdam that rises, its inner slope surface shrinks centripetally by 0.5-1.0 meters relative to the lower layer, forming a step structure with no less than three levels. S43. In the closure section of the cofferdam, a non-circular filling component with pressure relief function is installed. The component, through a built-in check-loop drainage blind pipe, allows water to drain while preventing quicksand from seeping out, thereby reducing the dynamic water pressure difference inside and outside the cofferdam and preventing the closure section from collapsing.

5. The method for constructing artificial islands in shallow water and quicksand sections of inland rivers according to claim 1, characterized in that: S5 specifically includes: S51. To address shallow water limitations, a relay pumping unit consisting of multiple low-draft, modular small cutter suction dredgers is employed. Each small cutter suction dredger has a rated flow rate controlled at 400-600 cubic meters per hour and is equipped with a high-precision GNSS-RTK positioning system with a positioning accuracy of ±2cm. Through an onboard BIM terminal, operators can observe the spatial position of the cutter head relative to the pre-set reclamation floor plan in real time. The cutting depth of the cutter head is dynamically adjusted according to the thickness of the quicksand layer to ensure that the mud concentration at the suction inlet remains stable at 1.2g / cm³. The concentration of sediment is between 3 and 1.5 g / cm³; each small cutter suction dredger is powered by a submersible motor-driven sludge pump. The surface of the submersible motor housing is equipped with a spiral guide plate to prevent sand deposition, and the pump blades are coated with a 0.5 mm thick ultra-hard tungsten carbide coating; the sludge conveying pipeline is made of high-molecular-weight polyethylene flexible pipe, with wear-resistant ceramic plates lined inside the pipe wall to reduce frictional resistance, and flexible compensators with tensile strength are installed at the connection flanges of the sludge conveying pipeline; the pipeline is erected on a specially made lightweight pontoon, and the draft of the pontoon is no more than 0.3 meters; S52. A high-efficiency vortex-type energy dissipation diffuser is installed at the outlet end of the mud conveying pipe. By changing the mud flow direction, the impact kinetic energy is converted into radially divergent advection energy, reducing the direct scouring and damage of the mud to the quicksand foundation. All mechanical connection parts are made of steel with a performance grade of not less than Q355B. The electrical control system meets the IP68 protection level. All sensor modules exchange data through the Modbus-RTU protocol. The construction site is equipped with no less than two sets of backup generator sets, whose total installed power is more than 1.2 times the total power of the dredging, grouting and vacuum systems.

6. The method for constructing artificial islands in shallow water and quicksand sections of inland rivers according to claim 1, characterized in that: S6 specifically includes: S61. An automatic dosing module is installed at the outlet of the mud conveying pipe to dynamically add high molecular weight polyethyleneimine or polyacrylamide flocculants according to the mud flow rate and solids content. The charge density of the flocculants is between 30% and 50%. The flocculants cause the fine sand particles to undergo adsorption, charge neutralization and bridging effects to form large-diameter flocs. The automatic dosing module includes an electromagnetic flowmeter, an online concentration monitor, and a variable frequency metering pump; the output flow rate Q of the variable frequency metering pump is... a With mud flow rate Q m Mud concentration C m And the preset drug dosage ratio η satisfies a linear compensation relationship: Q a =k·Q m ·C m ·η+b, where k and b are calibration coefficients determined based on field experiments; The flocculant dissolution system employs a three-tank fully automated continuous preparation device. The first tank performs initial mixing of dry powder and water, the second tank performs maturation and stirring, and the third tank serves as a storage tank. The impeller speed of the mixer is set to 30 rpm. A static mixer is installed in the middle section of the sludge conveying pipe, utilizing the turbulence generated by baffles to ensure thorough mixing of the flocculant and sludge, with the mixing intensity controlled at a G value of 200-500 seconds. -1 ; Calculate the settling velocity after flocculation based on the modified Stokes' law: Where D is the equivalent particle size after flocculation, ρ p ρ is the particle density. f Where is the fluid density, μ is the dynamic viscosity, C is the mud concentration, and n is the flow resistance coefficient; S62. By controlling the dredging zones, the residence time of the slurry in the dredging zone is made longer than the theoretical settling time of the flocculated particles, thus achieving efficient interception of quicksand. During the dredging operation, a flexible antifouling screen is pre-installed on the outside of the cofferdam closure section. The antifouling screen consists of a floating pipe, a skirt, and a bottom chain. The skirt is made of synthetic fiber filter cloth with a pore size of 50-80 micrometers. The antifouling screen forms a closed semi-transparent barrier underwater to intercept suspended particles overflowing from the dredging operation and control them within a 10-meter radius around the construction area. S63. In the later stage of the hydraulic reclamation construction, a mobile microwave heating container is used to dehydrate and harden the quicksand within 20 cm of the surface layer of the hydraulic reclamation layer; the microwave frequency is 2450MHz and the output power is controlled at 10-50kW, so that the moisture content can be rapidly reduced to below the plastic limit.

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