Construction method for preventing siltation in port subgrade

Abstract

This invention discloses a method for preventing siltation in port subgrade construction, comprising: erecting an adjustable silt interception assembly consisting of corrugated grates and hydraulically lifting columns around the subgrade construction area; the corrugated grates are inclined on the hydraulically lifting columns and consist of alternating protrusions and depressions; a flow guiding device consisting of three sets of V-shaped flow guiding units connected in series is installed 20 m in front of the corrugated grates in the upstream direction, with its bottom rotatable base adjusting the flow guiding angle according to the tidal direction; a silt thickness monitoring device is installed on the downstream side of the corrugated grates, and the hydraulically lifting columns are controlled to lift the corrugated grates according to the monitoring data; after the corrugated grates are lifted, a jet-type dredging vessel is used to dredge the silt at fixed points along the downstream side and transport the mud-water mixture to an onshore treatment station. This method is mainly used for preventing siltation in port subgrade construction.

Description

Technical Field

[0001] This invention relates to the field of port engineering construction technology. More specifically, this invention relates to a method for preventing siltation in port subgrade. Background Technology

[0002] During the construction and maintenance of port projects, the problem of siltation in the port subgrade has been a serious concern for engineers, posing a significant threat to the normal operation and structural stability of the port.

[0003] Port foundations are situated in a complex marine environment. The flow of seawater, tidal changes, and the movement of seabed sediment make the foundations highly susceptible to siltation. Once siltation occurs, the silt on the foundation surface accumulates continuously, not only reducing the foundation's load-bearing capacity and affecting the stability of port structures, but also potentially causing the channel to become shallower, hindering normal ship passage, and increasing port dredging costs and maintenance difficulties.

[0004] Conventional anti-siltation measures are not entirely effective in dealing with complex marine environments. For example, early simple interception devices, due to their fixed structure, cannot be adjusted according to changes in tides and water flow, and are therefore ineffective in preventing silt backflow. During different tidal periods, the direction and speed of water flow vary significantly, and fixed interception devices cannot adapt to these dynamic changes, allowing some silt to bypass the interception devices and continue to deposit in the bedrock area.

[0005] Traditional methods for monitoring silt thickness rely on periodic manual inspections, which are not only inefficient but also prone to significant errors, failing to provide accurate real-time information on silt thickness on the substrate surface. This hinders engineers from taking timely and effective dredging measures, leading to a gradual worsening of the silt accumulation problem.

[0006] Furthermore, in the dredging process, previous dredging vessel operations lacked specificity and failed to effectively coordinate with the bed siltation prevention system. During dredging, either the dredging was incomplete, leaving a large amount of silt on the bed surface, or excessive dredging damaged the bed structure and may also lead to secondary pollution, resuspending pollutants originally deposited on the bed in the seawater.

[0007] In addressing the issue of siltation in port subgrades, engineers face numerous technical challenges. On one hand, the complexity and variability of the marine environment make any single anti-siltation technology insufficient to handle all situations. Effective control of water flow and silt movement requires a comprehensive consideration of multiple factors, necessitating the development of an anti-siltation system capable of dynamically adapting to changes in the marine environment. On the other hand, real-time and accurate monitoring of subgrade siltation, and the organic integration of monitoring data with anti-siltation and dredging measures, are also pressing issues. Furthermore, developing dredging technologies that are both highly efficient and avoid negative impacts on the subgrade and the marine environment presents a significant challenge.

[0008] In summary, the problem of siltation in port subgrades is serious, and existing anti-siltation and dredging technologies have many shortcomings. There is an urgent need for a more efficient, intelligent, and environmentally friendly method for preventing siltation in port subgrades to cope with the complex marine environment and ensure the safe operation and sustainable development of ports. Summary of the Invention

[0009] Another objective of this invention is to address the issue that siltation in port subgrade can affect its stability and subsequent use, and existing methods for preventing siltation are insufficient to systematically solve the problems of siltation monitoring, interception, and cleanup. This technology aims to construct a comprehensive construction method encompassing interception, diversion, monitoring, and dredging to effectively prevent siltation in port subgrades.

[0010] If the flow guiding device is poorly designed, it cannot efficiently guide the water flow, reducing its anti-backflow effect. This technology aims to improve the flow guiding ability of the flow guiding device and enhance its overall anti-backflow performance by optimizing the structure and parameters of the flow guiding device.

[0011] If the materials and components of a flow guiding device are of poor quality, they are easily corroded and damaged, shortening their service life and increasing maintenance costs. This technology aims to improve the durability and reliability of the flow guiding device by selecting high-quality materials and optimizing component design.

[0012] If the anti-corrosion coating is ineffective, the flow guiding device is easily corroded. This technology aims to enhance the anti-corrosion performance of the flow guiding device by designing a multi-layer composite anti-corrosion coating and optimizing the construction and curing process.

[0013] If the performance and preparation process of fluorosilicone-modified acrylate hydrophobic layers are not perfect, it will affect the hydrophobic and protective effects of the anti-corrosion coating. This technology aims to optimize its composition and preparation process to improve the hydrophobic properties and protective capabilities of the coating.

[0014] Adjustable sludge interception components, if improperly installed, are unlikely to effectively intercept sludge and may experience problems such as settlement and erosion during construction. This technology aims to standardize the installation process of adjustable sludge interception components and improve their interception effect and stability.

[0015] Without properly converting construction parameters based on terrain data, it is impossible to strategically deploy anti-siltation facilities. This technology aims to optimize the deployment of anti-siltation facilities by constructing a construction parameter conversion method based on three-dimensional terrain data.

[0016] If dredging vessels fail to plan their operation routes according to risk levels, dredging efficiency will be low or dredging will be incomplete. This technology aims to improve dredging efficiency and quality by establishing a risk-level-based method for planning dredging vessel operation routes.

[0017] To achieve these objectives and other advantages according to the present invention, a method for preventing siltation in port subgrade is provided, comprising the following steps:

[0018] S1. An adjustable grid silt interception assembly is erected around the base bed construction area. The adjustable grid silt interception assembly includes a corrugated grid and a hydraulic lifting column. The corrugated grid is composed of alternating protrusions and depressions. The height of the protrusions is 60 cm, the depth of the depressions is 40 cm, and the center-to-center distance between adjacent protrusions is 80 cm. The corrugated grid is inclined on the hydraulic lifting column, and the lower end of the hydraulic lifting column is anchored to the seabed.

[0019] S2. Install a silt thickness monitoring device on the back surface of the corrugated grid. The silt thickness monitoring device includes a laser thickness gauge, an acoustic Doppler current profiler, and a turbidity sensor arranged at intervals. One laser thickness gauge rotates every 15 m. The turbidity sensor is installed 0.8 m above the laser thickness gauge. The turbidity sensor samples twice per minute. The acoustic Doppler current profiler is installed in the recess of the grid to monitor the bottom water flow velocity in real time. When the laser thickness gauge detects that the silt thickness on the substrate surface reaches 25 cm, the bottom water flow velocity is <0.3 m / s and the water turbidity is above 50%. Start the hydraulic lifting column to lift the corrugated grid as a whole by 40 cm. After lifting, the bottom of the corrugated grid and the seabed surface maintain a 20 cm gap for 6 hours.

[0020] S3. After the corrugated grid lifting operation is completed, a jet-type dredging vessel is used to perform fixed-point dredging along the back surface of the corrugated grid. The mud-water mixture discharged by the jet-type dredging vessel is transported to the land-based treatment station through pipelines.

[0021] Preferably, in step S1, the installation of the adjustable grid sludge interception assembly includes the following steps:

[0022] A1. Start seabed topographic scanning 24 hours before construction. Use a multibeam echo sounder to map the area 50 m outside the base bed with a grid accuracy of 0.5 m × 0.5 m, generate three-dimensional topographic scanning data, and mark the high turbulence zone with velocity gradient > 0.3 m / s / m.

[0023] A2. Based on the three-dimensional topographic scanning data, the corrugated grid is deployed on the downstream side of the high turbulence zone. The axis of the corrugated grid forms a dynamic angle β=5°~35° with the direction of the maximum flow velocity. The spacing D between adjacent corrugated grids is calculated according to the formula D=2H2+1.5H1, and the minimum spacing is not less than 4 m, where H2 is the water depth and H1 is the wave crest height of the corrugated grid.

[0024] A3. The hydraulic lifting column is constructed using the vibratory pile driving method. The pile driving rate is controlled at 0.5m / min. The penetration change is monitored in real time. The pile driving is terminated when the penetration ΔS ≤ 2cm after 10 consecutive blows.

[0025] A4. The installation and debugging of the corrugated grid plate is carried out in three stages of loading:

[0026] a1. During the initial installation stage, adjust the inclination angle of the corrugated grid plate to θ1=55°±1°, maintain this angle for 12 hours, and monitor the process using a total station.

[0027] Measure the settlement of the foundation bed;

[0028] a2. During the secondary loading stage, adjust the tilt angle of the corrugated grid plate to θ2 = 60° ± 0.5°, start the laser thickness gauge and turbidity sensor to monitor sedimentation, and simultaneously activate the acoustic Doppler velocity profiler to continuously scan the bottom velocity of the backflow surface.

[0029] a3. During the third loading stage, adjust the tilt angle of the corrugated grid plate to θ3 = 65° ± 0.3°. When the acoustic Doppler velocity profiler detects that the standard deviation of the back flow velocity σ ≤ 0.1 m / s and lasts for 30 minutes, fix the tilt angle of the corrugated grid plate.

[0030] A5. Dynamic control during the construction period includes:

[0031] b1. During the rock-filling operation of the foundation bed, the corrugated grid plate is raised by 20 cm every day during low tide for 2 hours, and the peak of the low tide velocity is used to flush the bottom silt.

[0032] b2. When the multibeam echo sounder detects a scour pit depth > 1m at the leading edge of the corrugated grid, lateral reinforcement of the pile foundation is triggered, with a jet grouting pressure ≥ 2 MPa and a grout diffusion radius ≥ 0.8 m.

[0033] b3. Six hours before the dredging vessel begins operation, the corrugated grid is lowered to 90% of the design elevation to form a 2-meter-wide guide channel. The dredging vessel then travels along the centerline of the channel at a constant speed of 0.8 m / s.

[0034] Preferably, in step S1, a flow guiding device is installed 20 m in front of the corrugated grid in the direction of the flow. The flow guiding device consists of three sets of V-shaped flow guiding units connected in series. Each V-shaped flow guiding unit is formed by welding two arc-shaped flow guiding vanes. The radius of curvature of the flow guiding vanes is the same as the crest radius of the corrugated grid. The opening angle of a single V-shaped flow guiding unit is 120 degrees, and the unit spacing is 1.5 times the length of the flow guiding unit. A rotatable base is provided at the bottom of the flow guiding unit, and the rotatable base adjusts the flow guiding angle according to the tidal direction.

[0035] Preferably, the thickness of the guide vane is 1 / 25 of the crest height H1 of the corrugated grid and not less than 15 mm.

[0036] Preferably, in step A1, after obtaining the three-dimensional terrain data, the three-dimensional terrain data is converted into construction parameters, specifically including the following steps:

[0037] c1. A multibeam echo sounder is used to perform a full-coverage scan of the 50 m perimeter of the bed, generating 3D terrain data with a 0.5 m × 0.5 m grid. The elevation measurement accuracy is ±2 cm, and the data acquisition density is ≥200 points / m².

[0038] c2. Based on 3D terrain data, calculate the velocity gradient field using a fluid dynamics model, mark high-turbulence zones with velocity gradients > 0.3 m / s / m, and classify their risk levels:

[0039] Level I risk zone: The velocity gradient is 0.3-0.5 m / s / m, and the spacing between the guide elements is S=1.2L, where L is the length of the guide element;

[0040] Level II risk zone: The velocity gradient is 0.5-0.8 m / s / m. A flow guiding unit is added, with a spacing of S=0.8L between the flow guiding units.

[0041] Level III risk zone: The velocity gradient is greater than 0.8 m / s / m. Add flow guiding units with a spacing of S=0.6L and pre-embed anti-scour gabions. Fill the anti-scour gabions with riprap to protect the bottom layer.

[0042] c3. Convert the three-dimensional terrain data and velocity gradient field into construction control parameters, using the following method:

[0043] Based on the risk level zones divided by c2, the axial direction of the corrugated grid plate is dynamically adjusted. In the Class I risk zone, the axial direction of the corrugated grid plate forms an angle of 5° to 15° with the direction of water flow. In the Class II risk zone, the angle is increased to 15° to 25°. In the Class III risk zone, the angle is set to 25° to 35°. The projection of the corrugated grid plate covers the area of ​​the pre-buried gabion bottom protection.

[0044] Based on the risk level zones defined by C2, the anchoring depth of the hydraulic lifting bollards is adjusted as follows: In Level I risk zone, the anchoring depth of the hydraulic lifting bollards is 2.5 times the water depth; in Level II risk zone, the anchoring depth of the hydraulic lifting bollards is increased by 10% compared to Level I risk zone; and in Level III risk zone, the anchoring depth of the hydraulic lifting bollards is increased by 20% compared to Level I risk zone.

[0045] Preferably, based on the risk level, the dredging vessel navigation system loads the risk zone level generated by C2 in real time, and adjusts the dredging vessel's operating path according to the risk zone level, specifically as follows:

[0046] Level I risk zone: The dredging vessel will conduct parallel dredging 1.5 m outside the boundary line of the wave-shaped grid backflow surface, with the vessel speed set at 1.0 m / s ± 0.1 m / s;

[0047] Level II Risk Zone: The dredging vessel dredges along the projection line of the concave part of the corrugated grid in a serpentine manner, and the speed of the dredging vessel is reduced to 0.8m / s±0.1m / s;

[0048] Level III Risk Zone: The dredging vessel uses a spiral dredging method with the pre-embedded gabion bottom layer as the center. The speed of the dredging vessel is limited to 0.6m / s±0.1m / s. The suction pipe of the dredging vessel should maintain a safe distance of 0.3m from the surface of the anti-erosion gabion.

[0049] When the laser thickness gauge detects a silt thickness gradient greater than 5 cm / m on the dredging path, it triggers the dredging vessel to automatically densify its operating trajectory, reducing the path spacing to 50% of the original design.

[0050] The present invention has at least the following beneficial effects:

[0051] First, this invention constructs a comprehensive construction method integrating interception, diversion, monitoring, and dredging. The adjustable sludge interception assembly effectively blocks sludge, the diversion device guides water flow to reduce sludge accumulation, and the monitoring device provides real-time feedback on sludge conditions, enabling timely sludge removal and dredging operations. This entire process significantly improves anti-sludge retention efficiency, ensures the stability of the subgrade, extends the service life of port facilities, and reduces subsequent maintenance costs. By optimizing the structure and parameters of the diversion device, it better integrates with the corrugated sludge. The arc-shaped diversion vane and specific diversion groove design more effectively guide water flow. Dynamic compensation based on the PID algorithm can adjust the diversion angle in real time to adapt to tidal and water flow changes, improving the control over water flow and further enhancing the overall anti-sludge retention effect, reducing sludge deposition in the subgrade area.

[0052] Secondly, this invention uses duplex stainless steel to make the guide vanes and optimizes components such as the hydraulic rotating base, improving the durability and reliability of the guide device. It standardizes the installation process of the adjustable grid silt interception assembly, and through seabed topography scanning and reasonable parameter settings, makes the arrangement of the wave-shaped grid and hydraulic lifting columns more scientific. Three-stage loading and commissioning ensures the stability of the grid, and dynamic control during construction can promptly address various construction problems, improving the interception effect and stability of the interception system and ensuring the smooth progress of the construction process.

[0053] Third, this invention converts construction parameters based on three-dimensional terrain data, enabling the rational deployment of anti-siltation facilities according to different risk levels. Dynamically adjusting the axial direction of the corrugated grid plates and the anchoring depth of the hydraulic lifting columns makes the anti-siltation system more targeted, improving the deployment efficiency and effectiveness of anti-siltation facilities while reducing project costs. Planning the dredging vessel's operating path based on risk levels makes dredging operations more targeted. Adjusting the dredging vessel's speed and operating mode according to different risk levels improves dredging efficiency and quality, avoids insufficient or excessive dredging, and ensures the safety of the dredging process, reducing damage to the subgrade and erosion-resistant gabions.

[0054] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0055] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0056] This invention provides a method for preventing siltation in port subgrade. The adjustable sludge interception assembly, consisting of a corrugated slab and a hydraulically lifted column, is used to intercept silt backflow. The flow guiding device, installed on the flow-facing side of the corrugated slab, guides the water flow and reduces silt deposition in the subgrade area. The silt thickness monitoring device, composed of a laser thickness gauge, an acoustic Doppler current profiler, and a turbidity sensor, can monitor the silt thickness on the subgrade surface, the bottom water flow velocity, and the water turbidity in real time.

[0057] S1. When implementing anti-siltation construction for port subgrade, the first step is to erect adjustable silt interception gratings around the subgrade construction area. These adjustable silt interception gratings include corrugated gratings and hydraulically lifted columns. The corrugated gratings consist of alternating protrusions and recesses, with the protrusions extending 60 cm in height and the recesses extending 40 cm in depth, with a center-to-center distance of 80 cm between adjacent protrusions. Hydraulically lifted columns adapted to the marine environment can be selected, with their lower ends anchored below the seabed. The corrugated gratings are then installed at an angle on the hydraulically lifted columns. This design disrupts the water flow and effectively intercepts silt.

[0058] S2. Install a silt thickness monitoring device on the back surface of the corrugated grid. Install a laser thickness gauge every 15 m, and a turbidity sensor 0.8 m above each laser thickness gauge, sampling twice per minute. Install an acoustic Doppler current profiler in the recess of the grid to monitor the bottom water flow velocity in real time. When the laser thickness gauge detects a silt thickness of 25 cm on the substrate surface, and the bottom water flow velocity (obtained by the acoustic Doppler current profiler) is less than 0.3 m / s, and the water turbidity reaches 50% or more, activate the hydraulic lifting column to raise the corrugated grid by 40 cm. After raising, maintain a 20 cm gap between the bottom of the corrugated grid and the seabed surface for 6 hours, allowing some water flow to carry away the silt through the gap.

[0059] S3. After the corrugated grating lifting operation is completed, a jet-type dredging vessel is used to perform targeted dredging along the back surface of the corrugated grating. The jet-type dredging vessel uses high-pressure water jets to impact the sludge, suspending it, and then sucks in the mud-water mixture through a sludge suction device, which is then transported through pipelines to an onshore treatment station for processing.

[0060] The corrugated grid is made of duplex stainless steel, which consists of austenitic and ferritic components, offering excellent strength and corrosion resistance. When water flows through it, the protrusions and depressions alter the direction and speed of the flow, creating turbulence and reducing the water's ability to carry silt, thus intercepting it. Based on hydrodynamic principles, this irregular shape increases water flow resistance, promoting silt settling. During long-term use, the corrugated grid is periodically cleaned using an underwater robot or unmanned submersible equipped with a high-pressure water gun to remove attached organisms.

[0061] The cylinder body of the hydraulic lifting column is made of nickel-based alloy with a nickel content of no less than 62%. Nickel-based alloys have long been widely used in marine engineering due to their excellent corrosion resistance in many corrosive environments. At the same time, the corrugated grid is installed at an angle on the hydraulic lifting column. The two work together to effectively disperse the impact force of seawater when intercepting silt, reduce the direct impact on the lifting column, reduce the risk of structural damage, and ensure stability in seawater. Through the silt thickness monitoring device and dynamic control during construction, the working status of the hydraulic lifting column can be monitored in real time. If any abnormalities are found, such as displacement or corrosion caused by seawater erosion, timely measures can be taken to repair or adjust it, ensuring its continuous and stable operation in seawater.

[0062] The laser thickness gauge emits a laser using pulse-code modulation, giving the laser signal stronger anti-interference capabilities. At the receiving end, digital signal processing technology is used to reduce noise and enhance the reflected light signal. The laser thickness gauge employs a nano-coating, which effectively prevents seawater and microorganisms from contacting the equipment surface, greatly extending the service life of the protective layer. Nano-coatings have been successfully applied to some marine monitoring equipment, significantly reducing the corrosion rate.

[0063] Turbidity sensors are relatively mature technologies, and their working principles mainly include optical scattering and transmission methods. These technologies can accurately measure seawater turbidity. Compared with some high-end marine monitoring equipment, turbidity sensors are less expensive and will not impose excessive economic pressure on projects when deployed on a large scale. This allows turbidity sensors to be widely deployed in different locations in port bed monitoring to obtain more comprehensive seawater turbidity data and improve the accuracy and reliability of monitoring. Turbidity sensors also utilize remote control technology, allowing technicians to calibrate the sensors on shore via wireless communication and adjust calibration parameters in real time.

[0064] Acoustic Doppler current profilers (ADCPs) can accurately measure the velocity and direction of seawater at different depths. In port areas, water flow conditions are complex and variable, influenced by factors such as tides, waves, and ship navigation. ADCPs can acquire these dynamically changing flow data in real time, helping staff understand the three-dimensional structure of the water flow around the port bed. During tidal changes, ADCPs can accurately monitor the changes in water velocity at different depths during high and low tides. Acoustic Doppler current profiler technology is quite mature and has wide applications in marine science research, marine engineering, and hydraulic engineering. Its measurement principle is based on the Doppler effect, calculating water velocity by transmitting and receiving sound waves, offering high accuracy and reliability. For noise and outliers in the raw data, common data processing software (such as MATLAB) provides various filtering algorithms, such as median filtering and mean filtering. Selecting an appropriate filtering method based on the data characteristics can effectively remove noise and outliers. For analyzing flow velocity data at different depths, existing oceanographic research results and methods can be referenced.

[0065] By employing this technical solution, this invention constructs a complete anti-siltation system for port subgrade through a series of construction steps. This system can monitor subgrade siltation in real time, effectively reducing siltation through interception and dredging, ensuring subgrade stability, lowering maintenance costs, extending the service life of port facilities, and ensuring normal port operation. This invention utilizes corrugated grids, hydraulic lifting columns, laser thickness gauges, acoustic Doppler current profilers, and turbidity sensors. The corrugated grids, in conjunction with the hydraulic lifting columns, effectively intercept silt, reducing the amount of siltation in the port subgrade. Real-time monitoring by the laser thickness gauge, acoustic Doppler current profiler, and turbidity sensor accurately grasps the siltation situation, making dredging operations more targeted, avoiding unnecessary dredging work, and reducing dredging frequency and costs. In the long run, this can significantly reduce the manpower, material resources, and financial investment required for port maintenance; reducing siltation in the foundation bed can lower the risk of silt erosion and damage to port structure foundations, enhance the stability of port facilities, extend the service life of wharves, trestle bridges, and other facilities, and reduce the number of facility repairs and reconstructions; precise monitoring and efficient anti-siltation measures ensure smooth navigation, reduce ship waiting time and navigation obstruction, improve port cargo throughput capacity, and increase port operating revenue; unified construction standards and processes can improve construction efficiency and reduce construction time and labor costs in large-scale applications. For example, the installation of corrugated gratings and hydraulic lifting columns can achieve standardized operations on a large scale, reducing construction risks and costs. Although the initial equipment installation and system setup costs are high, in the long run, the reduced maintenance costs and increased operating revenue far outweigh the initial investment.

[0066] In another technical solution, a multibeam echo sounder is a device capable of measuring underwater topography and quickly acquiring water depth data over large areas. Penetration refers to the depth to which a pile penetrates the soil under the impact of a hammer.

[0067] In step S1, the installation of the adjustable grid sludge interception assembly includes the following steps:

[0068] A1. 24 hours before construction, start the multibeam echo sounder and use a grid of 0.5 m × 0.5 m to survey a 50 m area around the base bed, generate three-dimensional terrain scanning data, and mark areas with a velocity gradient greater than 0.3 m / s / m as high turbulence zones.

[0069] A2. Based on the three-dimensional topographic scanning data, the corrugated grids are arranged downstream of the high turbulence zone, with the axis of the corrugated grids forming a dynamic angle of 5° to 35° with the direction of maximum flow velocity. The spacing between adjacent corrugated grids is determined based on the water depth H2 and the wave crest height H1 of the corrugated grids, with a minimum spacing of 4 m.

[0070] A3. The hydraulic lifting column is constructed using the vibratory pile driving method. The pile driving rate is controlled at 0.5 m / min. The penetration change is monitored in real time. When the penetration ΔS ≤ 2cm after 10 consecutive blows, the pile driving is terminated.

[0071] A4. The installation and debugging of the corrugated grid plate is carried out in three stages of loading:

[0072] a1. During the initial installation stage, the inclination angle θ2 of the corrugated grid plate is adjusted to 55°, with an allowable error of 1°. This is maintained for 12 hours, and the settlement of the subgrade is monitored using a total station.

[0073] a2. In the secondary loading stage, the tilt angle θ2 of the corrugated grid is adjusted to 60°, with an allowable error of 0.5°. The laser thickness gauge and turbidity sensor are activated to monitor sedimentation, and the acoustic Doppler velocity profiler is activated to continuously scan the flow velocity of the bottom layer of the back flow surface.

[0074] a3. In the third loading stage, the tilt angle θ2 of the corrugated grid plate is adjusted to 65°, with an allowable error of 0.3°. When the acoustic Doppler velocity profiler detects that the standard deviation of the back flow velocity σ ≤ 0.1 m / s and lasts for 30 min, the tilt angle of the corrugated grid plate is fixed.

[0075] A5. Dynamic control during the construction period includes:

[0076] b1. During the rock-filling operation of the foundation bed, the corrugated grid plate is raised by 20 cm every day during low tide for 2 hours, and the peak of the low tide velocity is used to flush the bottom silt.

[0077] b2. When the multibeam echo sounder detects that the depth of the scour pit at the leading edge of the corrugated grid exceeds 1 m, the lateral reinforcement of the pile foundation is triggered, the injection grouting pressure is not less than 2 MPa, and the grout diffusion radius is not less than 0.8 m.

[0078] b3. Six hours before the dredging vessel begins operation, the corrugated grid is lowered to 90% of the design elevation to form a 2m wide guide channel. The dredging vessel then sails at a constant speed of 0.8 m / s along the centerline of the channel.

[0079] By adopting this technical solution, the present invention improves the stability and interception effect of the adjustable sludge interception component by standardizing the installation process of the adjustable sludge interception component and implementing dynamic control during the construction period, thus ensuring the smooth progress of the construction process and reducing construction risks.

[0080] In another technical solution, the hydraulic rotating base is a device installed at the bottom of the flow guiding unit to realize the angle adjustment of the flow guiding unit. It consists of a double-acting hydraulic cylinder and an angle feedback encoder. The PID control algorithm is a commonly used control algorithm that can dynamically compensate for the flow guiding angle according to the real-time flow velocity value.

[0081] In step S1, a flow guiding device is installed 20 m in front of the corrugated grid in the direction of the current. The flow guiding device consists of three sets of V-shaped flow guiding units connected in series. Each V-shaped flow guiding unit has an opening angle of 120 degrees, and the unit spacing is 1.5 times the length of the flow guiding unit. A rotatable base is installed at the bottom of the flow guiding unit. The base is equipped with a device that can time according to tidal changes, adjusting the flow guiding angle according to the tidal direction (the adjustment interval of the flow guiding angle is determined according to the local tidal cycle characteristics; for example, in a semi-diurnal tidal zone, the flow guiding angle is adjusted every 6 hours; in a diurnal tidal zone, the flow guiding angle is adjusted every 12 hours), thereby guiding the water flow and reducing the amount of silt transported to the bed area.

[0082] The V-shaped flow guiding unit of the flow guiding device is welded together from two arc-shaped flow guiding vanes. The radius of curvature of the flow guiding vanes must be consistent with the crest radius of the corrugated grid plate. This allows the flow guiding device and the corrugated grid plate to work together better, improving the guiding effect on the water flow.

[0083] A hydraulic rotating base is installed at the bottom of the flow guiding unit. A double-acting hydraulic cylinder inside the base drives the flow guiding unit to rotate, thereby adjusting the flow guiding angle. An angle feedback encoder monitors the angle of the flow guiding unit in real time and feeds the information back to the control system. The spacing between the flow guiding units is set to twice the length of the flow guiding unit, and the length L of the flow guiding unit and the peak height H1 of the corrugated grid satisfy the condition that L is three times H1.

[0084] When adjusting the flow guide angle, a dynamic compensation mechanism based on a PID control algorithm is employed. The control system calculates the compensation amount based on the real-time flow velocity value monitored by the acoustic Doppler velocity profiler; the compensation amount is 0.15 times the real-time flow velocity value. By controlling the extension and retraction of the double-acting hydraulic cylinder, precise adjustment of the flow guide angle is achieved, enabling the flow guide device to better adapt to dynamic changes in water flow.

[0085] During implementation, both arc-shaped guide vanes of the V-shaped flow guiding unit are rolled from duplex stainless steel (duplex stainless steel is a type of stainless steel composed of austenitic and ferritic materials, possessing excellent strength and corrosion resistance). The vane thickness is determined by 1 / 25 of the wave crest height H1 of the corrugated grid, and the thickness must not be less than 15 mm. The properties of duplex stainless steel effectively enhance the durability and corrosion resistance of the guide vanes.

[0086] The double-acting hydraulic cylinder of the hydraulic rotating base is equipped with an energy storage compensation module (the energy storage compensation module, installed on the double-acting hydraulic cylinder, can store and replenish hydraulic oil to ensure stable operation of the cylinder), and the accumulator volume is 1.2 times the stroke volume of the hydraulic cylinder. The piston rod surface of the hydraulic cylinder is coated with a nickel-based tungsten carbide coating by laser cladding, which significantly improves the wear resistance of the piston rod. The working pressure of the hydraulic cylinder is set at 12 MPa to ensure its stable actuation of the guide unit to adjust the angle.

[0087] The length L of the guide unit is three times the peak height H1 of the corrugated grid. The unit spacing S is twice L, with an allowable error range of 0.1 times L. On the flow-facing surface of the guide vane, isosceles trapezoidal grooves with a top width of 10 mm, a bottom width of 15 mm, and a depth of 8 mm are formed. The groove spacing is 0.6 times the peak height H1 of the corrugated grid, with an allowable error of 0.01 times H1. The groove axis is deflected 12° relative to the normal of the guide vane, with an allowable error of 0.5°. The water-based anti-corrosion coating within the grooves is composed of a nano-ceramic underlayer and a graphene-modified top layer. The nano-ceramic underlayer enhances the coating adhesion, while the graphene-modified top layer improves the coating's anti-corrosion performance.

[0088] The flow guiding device effectively directs seawater flow, altering its direction and velocity to reduce silt deposition in the port bed area. Together with corrugated grids and silt thickness monitoring devices, it forms a complete anti-siltation system. In conjunction with the corrugated grids, the flow guiding device directs water flow more smoothly through them, enhancing the grids' silt interception effect. When the monitoring device detects anomalies, the flow guiding device adjusts its angle based on feedback, optimizing the water flow and improving the overall anti-siltation performance of the system. In practical applications, this collaborative working mode effectively addresses the complexity of the marine environment, improving the efficiency and reliability of anti-siltation. The design and manufacturing technology of the flow guiding device is relatively mature and has been widely used in marine engineering, hydraulic engineering, and other fields. Its structural design and material selection have a well-established theoretical and practical foundation. For example, in the construction of some large cross-sea bridges, flow guiding devices are used to guide water flow and protect the bridge pier foundations from erosion. Although installing flow diversion devices requires initial investment, the long-term benefits are significant. Effectively reducing siltation lowers port dredging costs and avoids damage and maintenance expenses to port facilities caused by siltation of the silt bed. It also improves port operational efficiency, reduces ship waiting time, and increases cargo throughput. With large-scale application, as production and installation technologies mature, unit costs can be further reduced, improving the cost-effectiveness ratio.

[0089] By adopting this technical solution, the present invention optimizes the structure and parameters of the flow guiding device, thereby enhancing its ability to guide water flow and improving its anti-siltation effect. Based on a dynamic compensation mechanism using a PID algorithm, the flow guiding device can adjust its guiding angle in real time according to changes in water flow, reducing silt deposition in the substrate area and further ensuring the stability of the port substrate. Furthermore, by selecting high-quality materials and optimizing component design and coating structure, the present invention significantly improves the durability and reliability of the flow guiding device, reducing the frequency of equipment maintenance and replacement. It can operate stably even in complex marine environments, continuously playing its role in preventing siltation.

[0090] In another technical approach, the fluid dynamics model is a mathematical model based on the principles of fluid dynamics, used to simulate the motion of water flow. The risk level is determined by classifying the degree of siltation risk in the subgrade area based on the magnitude of the velocity gradient.

[0091] c1. Use a multibeam echo sounder to perform a full-coverage scan of the 50 m perimeter of the base bed, generating 3D terrain data with a 0.5 m × 0.5 m grid. The elevation measurement accuracy is controlled within ±2 cm, and the data acquisition density is not less than 200 points / m².

[0092] c2. Based on three-dimensional terrain data, the velocity gradient field is calculated using a fluid dynamics model. Areas with a velocity gradient greater than 0.3 m / s / m are designated as high-turbulence zones, and risk levels are assigned: In Level I risk zones with a velocity gradient of 0.3 - 0.5 m / s / m, the spacing between guide units is 1.2 times the length of the guide unit; in Level II risk zones with a velocity gradient of 0.5 - 0.8 m / s / m, additional guide units are added, with a spacing of 0.8 times the length of the guide unit; in Level III risk zones with a velocity gradient greater than 0.8 m / s / m, additional guide units are also added, with a spacing of 0.6 times the length of the guide unit. Furthermore, scour-resistant gabions are pre-embedded, and the gabions are filled with riprap to form a protective bottom layer.

[0093] c3. Convert the three-dimensional terrain data and velocity gradient field into construction control parameters, using the following method:

[0094] Based on the risk level zones, the axis direction of the corrugated grate is dynamically adjusted. In Level I risk zone, the axis of the corrugated grate forms an angle of 5° to 15° with the water flow direction. In Level II risk zone, the angle increases to 15° to 25°. In Level III risk zone, the angle is set to 25° to 35°, and the projection of the corrugated grate covers the area of ​​the pre-embedded gabion bottom protection. Simultaneously, the anchoring depth of the hydraulic lifting columns is adjusted: in Level I risk zone, the anchoring depth is 2.5 times the water depth; in Level II risk zone, the anchoring depth increases by 10% compared to Level I; and in Level III risk zone, the anchoring depth increases by 20% compared to Level I.

[0095] By adopting this technical solution, the present invention converts construction parameters based on three-dimensional terrain data, realizes the targeted layout of anti-siltation facilities, improves the adaptability of the anti-siltation system to different risk areas, enhances the anti-siltation effect, and reduces engineering costs.

[0096] In another technical solution, the dredging vessel navigation system provides navigation services to the dredging vessel, guiding it to perform dredging operations along a predetermined path. The silt thickness gradient refers to the change in silt thickness per unit length.

[0097] Based on the risk level, the dredging vessel's navigation system loads the risk zone level generated by C2 in real time and adjusts the dredging vessel's operating path accordingly.

[0098] In the Level I risk zone, the dredging vessel extends 1.5 m outward along the boundary line of the backflow surface of the wave-shaped grid to perform parallel dredging, with the vessel speed set at 1.0 m / s and an allowable error of 0.1 m / s.

[0099] In the Level II risk zone, the dredging vessel will carry out dredging operations along the projection line of the concave part of the wave-shaped grid plate, using a serpentine path (a serpentine path is a path shape similar to the crawling trajectory of a snake, mainly a movement trajectory that moves back and forth left and right (or up and down) in a plane. For example, the dredging vessel will sway left and right along the projection line of the concave part of the wave-shaped grid plate, just like a "zigzag"), with the vessel speed reduced to 0.8 m / s, allowing an error of 0.1 m / s.

[0100] In the Level III risk zone, the dredging vessel will operate using a spiral path (a spiral path is a continuous curve, like the shape of a spring, that rotates around a central point and moves towards or away from the center) centered on the pre-buried gabion base. The vessel speed is limited to 0.6 m / s, with an allowable error of 0.1 m / s. The suction pipe of the dredging vessel will maintain a safe distance of 0.3 m from the surface of the anti-erosion gabion.

[0101] When the laser thickness gauge detects that the silt thickness gradient on the dredging path exceeds 5 cm / m, it triggers the dredging vessel to automatically densify the operation trajectory, reducing the path spacing to 50% of the original design.

[0102] By adopting this technical solution, the present invention adjusts the operation path of the dredging vessel based on the risk level, making the dredging operation more targeted, improving the efficiency and quality of dredging, avoiding the problems of insufficient or excessive dredging, ensuring the safety of the dredging operation, and reducing damage to the bed and erosion-resistant gabions.

[0103] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for preventing siltation in port subgrade, characterized in that, Includes the following steps: S1. An adjustable grid silt interception assembly is erected around the perimeter of the foundation bed construction area. The adjustable grid silt interception assembly includes a corrugated grid and a hydraulic lifting column. The corrugated grid consists of alternating protrusions and depressions. The height of the protrusions is 60 cm, the depth of the depressions is 40 cm, and the center-to-center distance between adjacent protrusions is 80 cm. The corrugated grid is inclined on the hydraulic lifting column, and the lower end of the hydraulic lifting column is anchored to the seabed. S2. Install a silt thickness monitoring device on the back surface of the corrugated grid. The silt thickness monitoring device includes a laser thickness gauge, an acoustic Doppler current profiler, and a turbidity sensor arranged at intervals. One laser thickness gauge rotates every 15 m. The turbidity sensor is installed 0.8 m above the laser thickness gauge. The turbidity sensor samples twice per minute. The acoustic Doppler current profiler is installed in the recess of the grid to monitor the bottom water flow velocity in real time. When the laser thickness gauge detects that the silt thickness on the substrate surface reaches 25 cm, the bottom water flow velocity is <0.3 m / s and the water turbidity is above 50%. Start the hydraulic lifting column to lift the corrugated grid as a whole by 40 cm. After lifting, the bottom of the corrugated grid and the seabed surface maintain a 20 cm gap for 6 hours. S3. After the corrugated grid lifting operation is completed, a jet-type dredging vessel is used to perform fixed-point dredging along the back surface of the corrugated grid. The mud-water mixture discharged by the jet-type dredging vessel is transported to the land-based treatment station through pipelines.

2. The port subgrade anti-siltation construction method as described in claim 1, characterized in that, In step S1, the installation of the adjustable grid sludge interception assembly includes the following steps: A1. Start seabed topographic scanning 24 hours before construction. Use a multibeam echo sounder to map the area 50 m outside the base bed with a grid accuracy of 0.5 m × 0.5 m, generate three-dimensional topographic scanning data, and mark the high turbulence zone with velocity gradient > 0.3 m / s / m. A2. Based on the three-dimensional topographic scanning data, the corrugated grid is deployed on the downstream side of the high turbulence zone. The axis of the corrugated grid forms a dynamic angle β=5°~35° with the direction of the maximum flow velocity. The spacing D between adjacent corrugated grids is calculated according to the formula D=2H2+1.5H1, and the minimum spacing is not less than 4 m, where H2 is the water depth and H1 is the wave crest height of the corrugated grid. A3. The hydraulic lifting column is constructed using the vibratory pile driving method. The pile driving rate is controlled at 0.5m / min. The penetration change is monitored in real time. The pile driving is terminated when the penetration ΔS ≤ 2cm after 10 consecutive blows. A4. The installation and debugging of the corrugated grid plate is carried out in three stages of loading: a1. During the initial installation stage, adjust the inclination angle of the corrugated grid plate to θ1=55°±1°, maintain this angle for 12 hours, and monitor the process using a total station. Measure the settlement of the foundation bed; a2. During the secondary loading stage, adjust the tilt angle of the corrugated grid plate to θ2 = 60° ± 0.5°, start the laser thickness gauge and turbidity sensor to monitor sedimentation, and simultaneously activate the acoustic Doppler velocity profiler to continuously scan the bottom velocity of the backflow surface. a3. During the third loading stage, adjust the tilt angle of the corrugated grid plate to θ3 = 65° ± 0.3°. When the acoustic Doppler velocity profiler detects that the standard deviation of the back flow velocity σ ≤ 0.1 m / s and lasts for 30 minutes, fix the tilt angle of the corrugated grid plate. A5. Dynamic control during the construction period includes: b1. During the rock-filling operation of the foundation bed, the corrugated grid plate is raised by 20 cm every day during low tide for 2 hours, and the peak of the low tide velocity is used to flush the bottom silt. b2. When the multibeam echo sounder detects a scour pit depth > 1m at the leading edge of the corrugated grid, lateral reinforcement of the pile foundation is triggered, with a jet grouting pressure ≥ 2 MPa and a grout diffusion radius ≥ 0.8 m. b3. Six hours before the dredging vessel begins operation, the corrugated grid is lowered to 90% of the design elevation to form a 2-meter-wide guide channel. The dredging vessel then travels along the centerline of the channel at a constant speed of 0.8 m / s.

3. The port subgrade anti-siltation construction method as described in claim 1, characterized in that, In step S1, a flow guiding device is installed 20 m in front of the corrugated grid in the direction of the flow. The flow guiding device consists of three sets of V-shaped flow guiding units connected in series. Each V-shaped flow guiding unit is formed by welding two arc-shaped flow guiding vanes. The radius of curvature of the flow guiding vanes is the same as the radius of the crest of the corrugated grid. The opening angle of a single V-shaped flow guiding unit is 120 degrees. The unit spacing is 1.5 times the length of the flow guiding unit. A rotatable base is provided at the bottom of the flow guiding unit. The rotatable base adjusts the flow guiding angle according to the tidal direction.

4. The port subgrade anti-siltation construction method as described in claim 3, characterized in that, The thickness of the guide vane is 1 / 25 of the crest height H1 of the corrugated grid and not less than 15 mm.

5. The port subgrade anti-siltation construction method as described in claim 4, characterized in that, In step A1, after obtaining the three-dimensional terrain data, the data is converted into construction parameters, which specifically includes the following steps: c1. A multibeam echo sounder is used to perform a full-coverage scan of the 50 m perimeter of the bed, generating 3D terrain data with a 0.5 m × 0.5 m grid. The elevation measurement accuracy is ±2 cm, and the data acquisition density is ≥200 points / m². c2. Based on 3D terrain data, calculate the velocity gradient field using a fluid dynamics model, mark high-turbulence zones with velocity gradients > 0.3 m / s / m, and classify their risk levels: Level I risk zone: The velocity gradient is 0.3-0.5 m / s / m, and the spacing between the guide elements is S=1.2L, where L is the length of the guide element; Level II risk zone: The velocity gradient is 0.5-0.8 m / s / m. A flow guiding unit is added, with a spacing of S=0.8L between the flow guiding units. Level III risk zone: The velocity gradient is greater than 0.8 m / s / m. Add flow guiding units with a spacing of S=0.6L and pre-embed anti-scour gabions. Fill the anti-scour gabions with riprap to protect the bottom layer. c3. Convert the three-dimensional terrain data and velocity gradient field into construction control parameters, using the following method: Based on the risk level zones divided by c2, the axial direction of the corrugated grid plate is dynamically adjusted. In the Class I risk zone, the axial direction of the corrugated grid plate forms an angle of 5° to 15° with the direction of water flow. In the Class II risk zone, the angle is increased to 15° to 25°. In the Class III risk zone, the angle is set to 25° to 35°. The projection of the corrugated grid plate covers the area of ​​the pre-buried gabion bottom protection. Based on the risk level zones defined by C2, the anchoring depth of the hydraulic lifting bollards is adjusted as follows: In Level I risk zone, the anchoring depth of the hydraulic lifting bollards is 2.5 times the water depth; in Level II risk zone, the anchoring depth of the hydraulic lifting bollards is increased by 10% compared to Level I risk zone; and in Level III risk zone, the anchoring depth of the hydraulic lifting bollards is increased by 20% compared to Level I risk zone.

6. The port subgrade anti-siltation construction method as described in claim 5, characterized in that, Based on the risk level, the dredging vessel's navigation system loads the risk zone level generated by C2 in real time and adjusts the dredging vessel's operating path accordingly. Specifically: Level I risk zone: The dredging vessel will conduct parallel dredging 1.5 m outside the boundary line of the wave-shaped grid backflow surface, with the vessel speed set at 1.0 m / s ± 0.1 m / s; Level II Risk Zone: The dredging vessel dredges along the projection line of the concave part of the corrugated grid in a serpentine manner, and the speed of the dredging vessel is reduced to 0.8 m / s ± 0.1 m / s; Level III Risk Zone: The dredging vessel uses a spiral dredging method with the pre-embedded gabion bottom layer as the center. The speed of the dredging vessel is limited to 0.6 m / s ± 0.1 m / s. The suction pipe of the dredging vessel should be kept at a safe distance of 0.3m from the surface of the anti-erosion gabion. When the laser thickness gauge detects a silt thickness gradient greater than 5 cm / m on the dredging path, it triggers the dredging vessel to automatically densify its operating trajectory, reducing the path spacing to 50% of the original design.