Seabed sand excavation pit repair control method and system based on marine dredged mud

Abstract

The invention relates to the technical field of seabed sand excavation pit repair, and discloses a seabed sand excavation pit repair control method and system based on marine dredged mud. The method comprises the steps that surveying and mapping and environment analysis are conducted on a seabed sand excavation pit, three-dimensional topographic data are obtained, and dredged mud is improved; formulating a filling scheme based on data analysis, and establishing a barge and pipeline combined transportation system; filling materials layer by layer, and tamping and grouting; a three-layer protection structure is constructed, and a gabion mesh cage and an energy dissipation device are additionally arranged in a high-risk area; and the restoration effect is evaluated by monitoring the network to form an evaluation database. According to the method, marine dredged mud is used as a main material, and efficient and stable repairing of the seabed sand excavation pit is achieved through scientific improvement treatment and layered filling technologies in combination with multi-layer protection measures and a perfect monitoring and evaluating system.

Description

Technical Field

[0001] This application relates to the technical field of seabed sand mining pit restoration, and particularly to a control method and system for seabed sand mining pit restoration based on marine dredged mud. Background Art

[0002] Seabed sand mining activities are widely carried out due to engineering requirements such as construction and reclamation. However, this behavior has caused a large number of seabed sand mining pits, seriously damaging the marine ecosystem and seabed topography. Traditional seabed sand mining pit restoration methods mainly include natural restoration methods, artificial filling methods, and combined methods, etc. The natural restoration method relies on the natural sedimentation process to slowly fill the sand mining pit, with a long cycle and being uncontrollable; the artificial filling method usually uses materials such as sand and gravel to directly fill the pit, with high costs and large resource consumption; the combined method combines artificial measures and natural processes, but lacks a systematic technical solution. At the same time, with the increase in marine dredging projects, a large amount of dredged mud needs to be disposed of. Traditional methods such as marine dumping and landfilling not only occupy resources but may also cause secondary pollution.

[0003] The main deficiencies in the prior art are as follows: First, there is a lack of a systematic solution for using dredged mud to restore sand mining pits, and the recycling of resources cannot be achieved; second, the stability of the filling material is poor, and it is easily washed away under marine hydrodynamic conditions, resulting in an unsustainable restoration effect; third, the improvement treatment of the filling material during the restoration process is insufficient, which may lead to the release of pollutants; fourth, the protection measures are imperfect and cannot cope with the differential hydrodynamic conditions in different regions; fifth, there is a lack of an effective monitoring and evaluation system, making it difficult to scientifically evaluate and timely maintain the restoration effect. These problems have severely restricted the effect and popularization of seabed sand mining pit restoration work. Summary of the Invention

[0004] This application provides a control method and system for seabed sand mining pit restoration based on marine dredged mud, which is used to use marine dredged mud as the main material, and through scientific improvement treatment and layered filling technology, combined with multi-level protection measures and a perfect monitoring and evaluation system, to achieve the efficient and stable restoration of seabed sand mining pits.

[0005] In a first aspect, the present application provides a method for controlling the repair of a seabed sand mining pit based on marine dredged mud. The method for controlling the repair of a seabed sand mining pit based on marine dredged mud includes: conducting topographic surveying and environmental sample collection and analysis on the seabed sand mining pit to obtain three-dimensional topographic data of the sand mining pit, and performing improvement treatment on the marine dredged mud to obtain repair materials; analyzing a filling plan based on the three-dimensional topographic data and the repair materials to generate a target filling plan, and constructing a transportation system combining barge transportation and pipeline transportation; filling the repair materials into the sand mining pit in layers of bottom layer, middle layer, and surface layer based on the transportation system, and performing vibration compaction and underwater grouting treatment on each layer of filling body to obtain a filling structure; constructing a three-layer protection structure on the surface of the filling structure, and adding gabion cages and energy dissipation structures in high-scour-risk areas to obtain an erosion-resistant surface system; evaluating the repair effect of the erosion-resistant surface system according to a preset monitoring network to obtain a repair effect evaluation database.

[0006] In a second aspect, the present application provides a control system for repairing a seabed sand mining pit based on marine dredged mud. The control system for repairing a seabed sand mining pit based on marine dredged mud includes: a collection module, configured to conduct topographic surveying and environmental sample collection and analysis on the seabed sand mining pit to obtain three-dimensional topographic data of the sand mining pit, and perform improvement treatment on the marine dredged mud to obtain repair materials; an analysis module, configured to analyze a filling plan based on the three-dimensional topographic data and the repair materials to generate a target filling plan, and construct a transportation system combining barge transportation and pipeline transportation; a filling module, configured to fill the repair materials into the sand mining pit in layers of bottom layer, middle layer, and surface layer based on the transportation system, and perform vibration compaction and underwater grouting treatment on each layer of filling body to obtain a filling structure; a construction module, configured to construct a three-layer protection structure on the surface of the filling structure, and add gabion cages and energy dissipation structures in high-scour-risk areas to obtain an erosion-resistant surface system; an evaluation module, configured to evaluate the repair effect of the erosion-resistant surface system according to a preset monitoring network to obtain a repair effect evaluation database.

[0007] In a third aspect, there is provided a control device for repairing a seabed sand mining pit based on marine dredged mud, including: a memory and at least one processor, wherein instructions are stored in the memory; the at least one processor invokes the instructions in the memory so that the control device for repairing a seabed sand mining pit based on marine dredged mud executes the above-mentioned method for controlling the repair of a seabed sand mining pit based on marine dredged mud.

[0008] Fourthly, a computer-readable storage medium is provided, in which instructions are stored. When the instructions run on a computer, the computer is made to execute the above-mentioned control method for repairing a seabed sand mining pit based on marine dredged mud.

[0009] In the technical solution provided by this application, the steps of topographic surveying and environmental sample collection and analysis of the seabed sand mining pit construct a comprehensive and accurate three-dimensional topographic model and environmental assessment system, providing an accurate data basis for subsequent repair. At the same time, targeted improvement treatment is carried out on marine dredged mud, realizing the resource utilization of dredged mud and solving the problem of dredged mud disposal; based on the three-dimensional topographic data and repair materials, the filling scheme is analyzed, and artificial intelligence algorithms are applied to simulate and predict the hydrodynamic conditions and sediment migration laws, generating a target filling scheme for a specific environment, and constructing a precisely positioned transportation system, greatly improving the construction accuracy and efficiency; the layered filling technology is combined with vibration compaction and underwater grouting treatment to form a filling body with stable structure, enhancing the overall bearing capacity and anti-deformation ability; the three-layer protection structure design is combined with gabion cages and energy dissipation structures in high-risk areas, constructing an all-round anti-erosion surface system, significantly improving the anti-scouring ability and long-term stability of the repaired area under extreme hydrodynamic conditions; the pre-set monitoring network is combined with data processing algorithms to realize the scientific evaluation and dynamic management of the repair effect. Through the intelligent processing of a large amount of spatial data, accurate analysis and prediction of complex seabed environments are achieved, improving the pertinence and scientific nature of the scheme. An association model between hydrodynamic parameters and material properties is established in the anti-scouring performance assessment, realizing the precise matching of protection requirements in different regions, and anomaly detection algorithms are applied in the monitoring data processing to improve the data quality and early warning accuracy. Description of the Drawings

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for description in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0011] Figure 1 It is a schematic diagram of an embodiment of the control method for repairing a seabed sand mining pit based on marine dredged mud in an embodiment of this application; Figure 2 It is a schematic diagram of an embodiment of the control system for repairing a seabed sand mining pit based on marine dredged mud in an embodiment of this application; Figure 3 It is a structural schematic block diagram of the control equipment for repairing a seabed sand mining pit based on marine dredged mud in an embodiment of the present invention. Detailed Embodiments

[0012] The embodiments of the present application provide a method and system for controlling the repair of a seabed sand mining pit based on marine dredged mud. The terms "first", "second", "third", "fourth", etc. (if any) in the specification, claims and the above-mentioned drawings of the present application are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the term "including" or "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0013] For ease of understanding, the specific process of the embodiments of the present application will be described below. Please refer to Figure 1 , an embodiment of the method for controlling the repair of a seabed sand mining pit based on marine dredged mud in the embodiments of the present application includes: Step S101, conduct topographic surveying and environmental sample collection and analysis on the seabed sand mining pit to obtain three-dimensional topographic data of the sand mining pit, and perform improvement treatment on the marine dredged mud to obtain repair materials; Step S102, analyze the filling plan based on the three-dimensional topographic data and the repair materials, generate a target filling plan, and construct a transportation system that combines barge transportation and pipeline transportation; Step S103, fill the repair materials into the sand mining pit in layers of bottom, middle and surface based on the transportation system, and perform vibration compaction and underwater grouting treatment on each layer of filling body to obtain a filling structure; Step S104, construct a three-layer protection structure on the surface of the filling structure, and add gabion cages and energy dissipation structures in high-scour-risk areas to obtain an erosion-resistant surface system; Step S105, evaluate the repair effect of the erosion-resistant surface system according to the preset monitoring network to obtain a repair effect evaluation database.

[0014] It can be understood that the execution subject of the present application can be a control system for repairing a seabed sand mining pit based on marine dredged mud, or a terminal or a server. Specifically, it is not limited here. The embodiments of the present application are described by taking the server as the execution subject as an example.

[0015] Specifically, a multi-beam sonar and a side-scan sonar system are used to survey the seabed sand mining pits. The multi-beam sonar measures the water depth data at different positions by emitting multiple acoustic beams and receiving echo signals; the side-scan sonar scans the seabed by emitting a fan-shaped acoustic beam to obtain the bottom sediment reflection intensity information. The navigation speed of the survey vessel is controlled at 3-5 knots to ensure data accuracy. The collected original bathymetric data is processed by marine geographic information system software to remove noise points, supplement missing data and perform coordinate transformation, generating three-dimensional terrain data of the sand mining pit, including key parameters such as pit depth, slope, and area. At the same time, multiple bottom sediment sampling points are set inside and around the sand mining pit, and bottom sediment samples with a depth of up to 30 cm are collected for laboratory analysis to determine environmental quality parameters such as grain size distribution, organic matter content, and heavy metal content. When improving the dredged mud, multiple representative samples are first taken for physical property and chemical composition analysis to determine physical parameters such as moisture content, density, and plasticity index, as well as the content of heavy metals and organic pollutants, and classified and rated to obtain the characteristics data of the dredged mud. Different treatment agents are added according to the type of pollution: a solidifying agent and a stabilizing agent are added to the heavy metal-polluted dredged mud to cause a chelation reaction between the heavy metal ions and the stabilizing agent, reducing their mobility; an oxidizing agent and a catalyst are added to the dredged mud with a high content of organic pollutants to promote the decomposition of organic pollutants. Finally, aggregate and fiber materials are added to enhance the strength, and permeable materials and modifiers are added to adjust the drainage performance to obtain the repair material.

[0016] Based on the three-dimensional terrain data, the hydrodynamic conditions in the sand mining pit area are analyzed to analyze the influence degree of local tidal currents, waves, ocean currents and other factors on the filling materials. Through hydrodynamic calculations, the incipient velocity and transport law of sediments under different water flow conditions are determined, and combined with the physical properties of the repair materials, the stability parameters required for the filling materials in each area are calculated. The sand mining pit is divided into filling units according to the filling area zoning scheme, and the filling thickness, material ratio and construction time sequence of each unit are determined. The filling principle of "first deep then shallow, first inside then outside" is adopted, first filling the deepest part of the pit bottom, gradually expanding towards the pit wall and the edge, and reserving a settlement space of 10-15%. The transportation route and method of the repair materials are designed. When the distance between the storage location of the repair materials and the sand mining pit exceeds 10 kilometers, a combination of barge transportation and pipeline transportation is used. The barge is equipped with a GPS positioning system and an automatic bathymetric system. The pipeline system is made of wear-resistant materials, with a pipe diameter of not less than 300 mm, and an adjustable diffuser is designed at the end to control the release speed and range.

[0017] The repair materials are filled into the sand mining pit in layers through a transportation system. When filling the bottom layer, the repair materials mixed with aggregate are directionally placed into the deepest part of the sand mining pit, with a filling thickness of 1.5 - 2.5 meters. Then, underwater vibration compaction equipment is used for vibration treatment, and the vibration frequency and amplitude are adjusted according to the density of the filling materials to increase the compactness of the filling body. The middle layer is filled with the repair materials mixed with a curing agent, carried out in a sectional and partitioned manner, with a thickness of 0.8 - 1.2 meters, to form a stepped filling structure to enhance the interlayer bonding. Underwater grouting treatment is carried out on the middle layer filling body. The grouting points are arranged in a grid pattern, with a spacing of 2 - 3 meters, and the grouting pressure is controlled at 0.2 - 0.3 MPa to form a grid-shaped reinforcement system. The surface layer is filled with a mixed material of improved dredged mud and fine sand, with a thickness of 0.5 - 0.8 meters. The area in contact with the pit wall is connected by grid anchors, which penetrate into the pit wall by 0.5 - 1 meter to prevent the filling body from separating from the pit wall. A three-layer protection structure is constructed. First, a mixture of fine sand and clay with a fine particle size is prepared as the transition layer material and laid on the surface of the filling structure to form a transition protection layer, with a thickness of 0.2 - 0.3 meters. An anti-scour test is carried out on the transition protection layer, the material loss rate under simulated water flow conditions is measured, and the anti-scour performance index is calculated. Gravel and cementitious materials are mixed and covered on the transition protection layer to form the middle protection layer, with a thickness of 0.3 - 0.5 meters. When the anti-scour performance index is lower than the set threshold, the proportion of the cementitious material is increased for reinforcement treatment. Natural materials similar to the surrounding seabed environment are selected to cover the middle protection layer to form the surface protection layer, with a thickness of 0.3 - 0.4 meters, so that the surface smoothly transitions to the elevation of the surrounding seabed. High-scour risk areas are identified through the analysis of water flow effects. In these areas, gabion cages with a size of 1 m × 1 m × 0.5 m are laid, filled with hard stones with a particle size of 50 - 100 mm. The gabion cages are tightly connected by connecting wires, and the edges are buried more than 0.5 meters into the bottom layer. An energy dissipation device composed of riprap or concrete blocks is set up to divert and dissipate the incoming water flow energy.

[0018] Evaluate the repair effect through a pre - installed monitoring network. Install settlement monitoring points, water flow monitoring devices, and pore pressure sensors at key positions to collect settlement data, water flow parameters, and pore water pressure data. Process the monitoring data, eliminate outliers, and calculate the settlement rate, water flow velocity change, and pressure change trend. For example, the data recorded by the settlement monitoring points show that the settlement rate gradually decreases from the initial 8 mm / day to 3 mm / day within 28 days after filling, and the total settlement is about 120 mm, within the reserved settlement range; the pore water pressure data show that the pressure gradually stabilizes, indicating that the consolidation process is proceeding normally. Measure the surface morphology change through underwater sonar scanning, calculate the erosion depth and range, and evaluate the integrity of the protection structure. According to the stability determination and anti - erosion effect evaluation, grade the repaired area and mark the areas that need to be reinforced or strengthened. Integrate the monitoring data, stability determination results, anti - erosion effect evaluation, and subsequent maintenance area identification to construct a repair effect evaluation database, including time - series data and spatial distribution data, which is convenient for long - term tracking and evaluating the repair effect.

[0019] In the embodiment of the present application, the steps of topographic surveying and environmental sample collection and analysis of the seabed sand - mining pit have constructed a comprehensive and accurate three - dimensional topographic model and environmental assessment system, providing an accurate data basis for subsequent repair. At the same time, targeted improvement treatment of marine dredged mud has realized the resource utilization of dredged mud and solved the problem of dredged mud disposal; based on the three - dimensional topographic data and repair materials for filling plan analysis, applying artificial intelligence algorithms to simulate and predict the hydrodynamic conditions and sediment migration laws, generating a target filling plan for a specific environment, and constructing a precisely positioned transportation system, greatly improving the construction accuracy and efficiency; the layered filling technology combined with vibration compaction and underwater grouting treatment has formed a filling body with stable structure, enhancing the overall bearing capacity and anti - deformation ability; the three - layer protection structure design combined with the application of gabion cages and energy - dissipating structures in high - risk areas has constructed an all - round anti - erosion surface system, significantly improving the anti - scouring ability and long - term stability of the repaired area under extreme hydrodynamic conditions; the pre - installed monitoring network combined with data - processing algorithms has realized the scientific evaluation and dynamic management of the repair effect. Through the intelligent processing of a large amount of spatial data, it has realized the accurate analysis and prediction of complex seabed environments, improved the pertinence and scientific nature of the plan, established a correlation model between hydrodynamic parameters and material properties in the anti - scouring performance evaluation, realized the precise matching of protection requirements in different regions, and applied anomaly detection algorithms in the monitoring data processing to improve the data quality and warning accuracy.

[0020] In a specific embodiment, the process of executing step S101 may specifically include the following steps: Use a multi - beam sonar system and a side - scan sonar system to survey the seabed sand - mining pit, and perform three - dimensional modeling processing on the survey data through marine geographic information system software to obtain three - dimensional topographic data; Set up multiple bottom sediment sample collection points inside and around the sand mining pit, collect bottom sediment samples of a specific depth from each point, conduct laboratory analysis on the samples, and obtain environmental quality parameters; Based on terrain data and environmental quality parameters, a sand pit status assessment index system was constructed to conduct zoning assessments on sand pits and obtain restoration priorities and difficulty levels. Conduct physical property testing and chemical composition analysis on dredged mud samples, classify and rate the dredged mud according to engineering applicability and environmental safety indicators, and obtain dredged mud characteristic data; According to the dredged mud characteristic data, solidifying agent and stabilizer are added to the heavy metal polluted dredged mud for solidification and stabilization treatment, and oxidant and catalyst are added to the organic polluted dredged mud for chemical oxidation treatment to obtain harmless dredged mud; Aggregates and fiber materials are added to the harmless dredged mud to enhance its strength, and permeable materials and modifiers are added to adjust its drainage performance to obtain repair materials.

[0021] Specifically, the multi-beam sonar system is a marine detection device that transmits multiple sound beams through an array transmitter and receives the reflected echo from the seabed. One scan can obtain multiple water depth points on a survey line on the seabed to form a fan-shaped measurement area. The side-scan sonar system transmits fan-shaped sound beams to both sides of the seabed, receives the reflected signals from the seabed at different positions, and obtains information on the seabed topography and bottom type. During surveying, the surveying vessel sails at a stable speed of 3-5 knots, keeping the survey line spacing no more than 3 times the water depth, ensuring that the data coverage rate reaches more than 90%. The collected original surveying data contains information such as water depth, geographic coordinates, and reflection intensity, which needs to be processed by marine geographic information system software, including data cleaning, noise filtering, coordinate conversion, and data interpolation. First, the outliers that are obviously deviated from the surrounding points are eliminated, and then the Kriging interpolation method is used to fill the blank areas of the data. Finally, the three-dimensional terrain model of the sand mining pit is constructed by the triangular irregular network (TIN) method to accurately calculate the area, volume, maximum depth, slope and other parameters of the sand mining pit.

[0022] After completing the topographic survey, multiple bottom sediment sample collection points need to be set inside and around the sand mining pit. The layout of the points follows the principle of representativeness. Usually, several points are set at the bottom of the pit, on the pit wall, and in the surrounding area. The distance between the points is determined according to the area of the sand mining pit, generally 50 - 100 meters. A grab sampler or a gravity corer is used to collect bottom sediment samples with a depth of not less than 30 cm from each point, and the weight of each sample is about 2 kg. The collected samples are sealed and sent to the laboratory for analysis. The analysis items include particle size distribution (measured by a laser particle size analyzer), organic matter content (measured by the potassium dichromate oxidation method), heavy metal content (measured by atomic absorption spectrophotometry or inductively coupled plasma mass spectrometry), etc. The data obtained through analysis are the environmental quality parameters, which are used to evaluate the bottom sediment environmental status of the sand mining pit. Based on the three-dimensional topographic data and environmental quality parameters, a sand mining pit status evaluation index system is constructed to conduct a zonal evaluation of the sand mining pit. The index system includes two major categories: topographic indexes and environmental indexes. Topographic indexes include the depth recovery coefficient (the ratio of the maximum depth of the sand mining pit to the depth of the surrounding natural seabed), the slope stability coefficient (the ratio of the slope of the sand mining pit to the critical stable slope), etc. Environmental indexes include the bottom sediment quality index (the comprehensive evaluation value of the heavy metal pollution degree), the water quality status index (the comprehensive evaluation value of parameters such as dissolved oxygen and turbidity), etc. By assigning weights to each index and calculating the comprehensive score, a zonal evaluation of the sand mining pit is carried out, which is divided into high-priority areas (areas with large depth, steep slope, and serious environmental pollution), medium-priority areas, and low-priority areas. At the same time, the repair difficulty level is determined according to the topographic complexity and bottom sediment conditions.

[0023] Comprehensive quality testing of marine dredged mud samples is the key to ensuring the performance of the repair materials. First, collect no less than 5 representative dredged mud samples, and the weight of each sample is not less than 2 kg. Conduct physical property tests on the samples, including water content (measured by the drying method), particle size distribution (measured by sieving method and hydrometer method), density (measured by pycnometer method), plasticity index and liquidity index (measured by the limit water content method), etc. At the same time, conduct chemical composition analysis to determine the organic matter content, nutrient element content, sulfide content, pH value, etc. Of particular importance is to conduct an environmental risk assessment to detect the heavy metal content (such as copper, lead, zinc, cadmium, mercury, arsenic, etc.) and the concentrations of persistent organic pollutants (such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, etc.) in the dredged mud. Classify and rate the dredged mud according to engineering applicability indexes (such as strength, compressibility, permeability, etc.) and environmental safety indexes (such as pollutant content, biological toxicity, etc.) to obtain the characteristic data of the dredged mud.

[0024] According to the dredged mud characteristic data, differential improvement treatments are adopted for different types of pollution. For the dredged mud with severe heavy metal pollution, solidification / stabilization technology is used for treatment. Solidifying agents (such as cement, lime, fly ash, etc., with an addition ratio of 5 - 10%) and stabilizing agents (such as modified clay, zeolite, etc., with an addition ratio of 3 - 5%) are added to the dredged mud, and they are fully mixed through a special mixing device, and the reaction time is controlled within 24 - 48 hours. The solidification / stabilization process reduces the bioavailability and mobility of pollutants through mechanisms such as physical encapsulation (encapsulating pollutants in the solidified body), chemical fixation (chemical reactions occur between pollutants and stabilizing agents to form poorly soluble compounds), and ion exchange (heavy metal ions are adsorbed by stabilizing agents). For the dredged mud with a high content of organic pollutants, chemical oxidation technology is adopted. Oxidants (such as hydrogen peroxide, persulfate, etc., with an addition ratio of 3 - 5%) and catalysts (such as iron salts, manganese salts, etc., with an addition ratio of 0.5 - 1%) are added to promote the oxidation and decomposition of organic pollutants. At the same time, a pH regulator is added to maintain the reaction system within the optimal pH range (usually neutral or weakly alkaline). The strength of the dredged mud after harmless treatment is enhanced and the drainage performance is adjusted. Aggregates (such as sand, gravel, etc., with an addition ratio of 5 - 15%) and fiber materials (such as polypropylene fiber, glass fiber, etc., with an addition ratio of 3 - 7%) are added to improve the shear strength and stability of the dredged mud through the skeleton effect and fiber reinforcement. At the same time, permeable materials (such as sand, zeolite, etc., with an addition ratio of 5 - 10%) and modifiers (such as cement, lime, etc., with an addition ratio of 2 - 3%) are added to improve the drainage performance of the dredged mud and accelerate the consolidation process. After the above series of treatments, the dredged mud is transformed into an engineering material that meets the requirements for the repair of the seabed sand mining pit, and its shear strength, stability, erosion resistance, and environmental compatibility all reach the design standards.

[0025] In a specific embodiment, the process of executing step S102 may specifically include the following steps: Analyze the hydrodynamic conditions of the sand mining pit area for the three-dimensional terrain data, calculate the influence degree of tidal current, wave, and ocean current on the filling material, and obtain the hydrodynamic influence evaluation result; Calculate the sediment migration law based on the hydrodynamic influence evaluation result, and combine the physical properties of the repair material to determine the stability parameters of the filling material in each area, and obtain the filling area zoning plan; Divide the sand mining pit into multiple filling units according to the filling area zoning plan, determine the specific filling thickness, material ratio, and construction time for each filling unit, and obtain the project implementation plan; Optimize the project implementation plan, calculate the connection method between each filling unit, and obtain the target filling plan with reserved settlement space; Determine the optimal transportation route based on the spatial relationship between the storage location of the repair material and the sand mining pit, design the barge specifications, loading capacity, and positioning system to obtain the offshore transportation plan; Design the conveying pipeline system based on the offshore transportation plan, determine the pipe diameter, flow rate, conveying pressure, and diffuser parameters, and construct a transportation system that combines barge transportation and pipeline transportation.

[0026] Specifically, extract the geometric characteristic parameters of the sand mining pit, including pit depth distribution, slope change, and surface roughness, etc. At the same time, collect the local hydrological and meteorological data to obtain the basic data of tidal current, wave, and ocean current. The tidal current data includes the maximum flow velocity, flow direction, and tidal period; the wave data includes the significant wave height, wave period, and wave direction; the ocean current data includes the flow velocity, flow direction, and vertical distribution characteristics. Combine these hydrological parameters with the three-dimensional terrain data of the sand mining pit, and use hydrodynamic numerical simulation technology to construct a hydrodynamic model of the seabed sand mining pit area. During the simulation calculation, the sand mining pit area is discretized into a large number of grid cells, and the hydrodynamic control equations are applied to each cell, and the flow field and wave field distributions of the entire area are obtained by solving. The calculation results are expressed as parameters such as the flow velocity, flow direction, wave height, and wave direction at each grid point under different filling stages. By comparing the changes in hydrodynamic parameters before and after filling, evaluate the impact degree of filling on the hydrodynamic environment, and form the hydrodynamic impact evaluation result.

[0027] Based on the hydrodynamic impact evaluation result, further calculate and analyze the sediment migration law. First, determine the starting condition of the sediment, that is, when the water flow force exceeds the critical starting force of the sediment, the critical state when the sediment begins to move. For sediments with different particle sizes and densities, their critical starting flow velocities are different. Combine the physical characteristic parameters of the repair material (such as particle size, density, cohesion, etc.) with the hydrodynamic simulation results to calculate the starting probability and transport intensity of the filling material in each area under the action of water flow. For areas with a high starting probability, the filling material is easily scoured by the water flow, and the stability parameters need to be improved; for areas with a large transport intensity, secondary erosion is likely to occur after filling, and protection measures need to be strengthened. By comprehensively considering the hydrodynamic conditions and sediment characteristics, determine the stability parameters of the filling material in each area, including the minimum particle size requirement, minimum density requirement, and structural strength requirement, etc., and form the filling area zoning plan.

[0028] According to the filling area zoning plan, the sand mining pit is divided into multiple filling units. The division principle is based on the similarity of pit bottom depth, slope change and hydrodynamic conditions. The area of each filling unit is controlled within 5000 square meters to ensure the controllability of the filling process. Detailed engineering parameters are formulated for each filling unit, including filling thickness (determined according to the difference between the target restoration elevation and the current elevation), material ratio (adjusting the proportion of aggregate, curing agent and fiber material according to the stability parameter requirements of this area), and construction time (considering the material curing time and the connection sequence of adjacent units). The filling thickness is larger in the pit bottom area and gradually decreases in the pit wall area, forming a smoothly transitional terrain. The material ratio increases the proportion of aggregate and curing agent in the area with strong hydrodynamic action to improve the anti-scouring ability. The construction time arrangement follows the principle of "from deep to shallow, from inside to outside", and considers tidal cycles and seasonal meteorological conditions, avoiding adverse construction periods such as storm surges.

[0029] When optimizing the project implementation plan, key considerations include the connection method between filling units and the settlement reservation problem. The connection between units adopts a stepped filling method, and the height difference between adjacent units is controlled within 0.5 meters, forming a gentle slope transition to avoid local scouring caused by terrain drops. At the same time, consider the consolidation settlement effect under the action of the self-weight of the filling material and seawater immersion. By analyzing the compression index and consolidation coefficient of the filling material, the expected settlement amount is calculated. Generally, the reserved settlement space is 1.1 - 1.2 times the expected final settlement amount, usually 10 - 15% of the total filling thickness. The optimized filling plan also considers the treatment of boundary conditions. A smooth transition section is designed at the junction of the sand mining pit and the surrounding natural seabed, with a slope not exceeding 1:10, to prevent the formation of new terrain fractures.

[0030] According to the spatial relationship between the storage location of the repair material and the sand mining pit, the optimal transportation route is designed. Consideration factors include transportation distance, water depth conditions, waterway conditions and avoiding sensitive areas, etc. When the transportation distance exceeds 10 kilometers, the combined method of barge transportation and pipeline transportation is more economical and efficient. The barge design should consider load capacity, navigation stability and positioning accuracy. The load capacity is determined according to the single filling volume and round-trip time. Generally, a flat-bottom barge with a load capacity of 200 - 500 cubic meters is selected; the navigation stability requires that the hull can withstand certain wind and wave conditions; the positioning accuracy is achieved by equipping with a GPS positioning system and a dynamic positioning system, and the positioning accuracy reaches ±1 meter. After the barge arrives at the designated filling position, it needs to be accurately positioned and moored stably to prevent drifting during the unloading process.

[0031] When designing a conveying pipeline system based on a maritime transportation plan, key parameters need to be determined, including pipe diameter, flow velocity, conveying pressure, and diffuser parameters. The pipe diameter is selected based on the conveying volume and distance, and generally, pipes with a diameter of 300 - 500 mm are used. The flow velocity is controlled at 2 - 3 m / s to avoid pipe wear and prevent sediment blockage at low flow velocities. The conveying pressure is calculated based on the elevation difference, conveying distance, and material properties. Generally, a high-pressure conveying pump needs to be equipped, and the pressure reaches 0.8 - 1.2 MPa. The pipe material is selected as a wear-resistant and corrosion-resistant composite material. The pipeline laying considers the stability under the action of waves and water flow, and regular inspections and maintenance are carried out to prevent leakage. The diffuser design is the key to ensuring the uniform distribution of the filling material. The release speed and diffusion range are controlled through multiple outlets, and the number and diameter of the outlets are determined according to the filling unit area.

[0032] In a specific embodiment, the process of executing step S103 may specifically include the following steps: Use the transportation system to direct the repair material of the mixed aggregate to the deepest part of the sand excavation pit to form the bottom filling material. The filling thickness is controlled according to the depth gradient of the sand excavation pit to obtain the bottom filling body. Use underwater vibration compaction equipment to vibrate the bottom filling body. The vibration frequency and amplitude are adjusted according to the density of the filling material, and the surface after compaction is leveled to obtain a dense bottom foundation. Transport the repair material mixed with the curing agent to above the bottom foundation in sections by the transportation system to form the middle filling body. A specific gradient change is maintained between the middle filling body and the bottom foundation to obtain a stepped filling structure. Perform underwater grouting treatment on the stepped filling structure. The grouting points are arranged in a grid pattern. The grouting pressure and grouting time are determined according to the size of the filling area and the material properties to obtain a middle layer solidified body with a firmly connected interior. Transport the mixed material of the improved dredged mud and fine sand to the surface of the middle layer solidified body, control the surface layer thickness and surface flatness, and perform grille anchoring treatment on the area in contact with the pit wall to obtain a filling structure anchored and connected to the pit wall.

[0033] Specifically, using the transportation system to direct the repair material of the mixed aggregate to the deepest part of the sand mining pit is the first step of bottom filling. The directed placement technology refers to the technology of accurately placing specific materials at the predetermined position by precisely controlling the placement position and placement method. In actual operation, after the barge arrives at the designated filling area, the precise position is determined through the GPS positioning system and the underwater acoustic positioning system. The end of the placement pipeline maintains an appropriate distance from the seabed, generally 3 - 5 meters, to avoid material dispersion caused by being too far away or seabed disturbance caused by being too close. The bottom filling material is a mixture of dredged mud and aggregate. The aggregate is mainly gravel with a particle size of 5 - 20 mm, and the mixing ratio is the mass ratio of dredged mud to aggregate of 7:3. The filling thickness is controlled according to the depth gradient of the sand mining pit. The filling thickness is larger at the deepest part of the pit bottom, generally 1.5 - 2.5 meters, and gradually decreases towards the pit wall, forming a filling body that smoothly transitions with the natural terrain. During the filling process, the filling height is monitored in real time through an echo sounder, and the placement stops when the designed thickness is reached, controlling the filling accuracy within ±10 cm. The underwater vibration compaction equipment is a mechanical device dedicated to compacting loose materials underwater, mainly composed of a vibration source, a ram plate, and a control system. The mechanical vibration generated by the vibration source is transmitted to the filling body through the ram plate, causing the particles of the filling material to rearrange, reducing the porosity, and increasing the density. The vibration frequency and amplitude are two key parameters that need to be adjusted according to the density of the filling material. For filling materials with a relatively large density (such as mixtures with a high proportion of aggregate), the vibration frequency is set relatively low, generally 20 - 30 Hz, and the amplitude is relatively large, 5 - 8 mm; for filling materials with a relatively small density, the vibration frequency is set relatively high, 30 - 40 Hz, and the amplitude is relatively small, 3 - 5 mm. The compaction process is carried out along a grid-like route with a grid spacing of 1.5 - 2 meters to ensure coverage of the entire filling area. The vibration time at each point is 30 - 60 seconds. After compaction, an underwater leveling device is used to level the surface, eliminating local protrusions and depressions, and controlling the surface height difference within ±5 cm to form a uniform and flat bottom foundation.

[0034] Transporting the repair material mixed with the curing agent to above the underlying foundation in sections through the transportation system is the main process of middle layer filling. The middle layer filling material is a mixture of dredged mud and the curing agent. The curing agent is mainly composed of cement, fly ash and active lime, with a mixing ratio of 3:5:2, and the mixing ratio with the dredged mud is dredged mud:curing agent = 9:1 (mass ratio). The middle layer filling is carried out in sections. The entire filling area is divided into several filling units, and the area of each unit is about 500 - 1000 square meters. The purpose of sectional filling is to control the filling volume each time, ensure uniform distribution of the material and have sufficient time for curing. The filling thickness is controlled at 0.8 - 1.2 meters, and the height difference between adjacent filling areas does not exceed 0.5 meters, forming a stepped filling structure. The design purpose of the stepped structure is to increase the interlayer contact area, improve the interlayer bonding strength and prevent interlayer slip. A specific gradient change is maintained between the middle layer filling body and the underlying foundation, that is, the middle layer edge gradually thins, forming a wedge-shaped transition zone with the bottom layer to enhance the overall stability.

[0035] Underwater grouting treatment of the stepped filling structure is an important measure to improve the internal strength of the filling body. Underwater grouting refers to the technology of injecting a specific slurry into the underwater structure through grouting equipment to fill the pores and improve the overall strength and impermeability. The grouting points are arranged in a grid pattern with a grid spacing of 2 - 3 meters, covering the entire middle - layer filling body. The grouting slurry is composed of ultra - fine cement, water glass, and retarder. The particle size of the ultra - fine cement is less than 20 microns, which has good fluidity and permeability; water glass is used as an early - strength agent to accelerate the solidification of the slurry; the retarder controls the setting time to ensure that the slurry can fully penetrate into the filling body. The grouting pressure is controlled at 0.2 - 0.3 MPa. Excessive pressure will cause damage to the filling body, while too low pressure will not allow the slurry to fully penetrate. The grouting time is determined according to the size of the filling area and the material properties, generally 15 - 30 minutes for each grouting point until the slurry overflows from adjacent grouting points, indicating that the area is completely saturated. Through grouting treatment, a grid - shaped reinforcement system is formed, significantly improving the overall strength and erosion resistance of the middle - layer filling body. Transporting the improved dredged mud and fine - sand mixture to the surface of the middle - layer solidified body is the key process of surface filling. The surface - filling material is specially improved dredged mud, adding 10 - 15% fine sand (particle size 0.1 - 2 mm), 5 - 8% shell debris, and 3 - 5% organic matter (such as seaweed residues) to simulate the natural seabed sediment environment. The surface material is transported in a low - pressure and low - disturbance manner to prevent damage to the underlying structure. The surface thickness is controlled at 0.5 - 0.8 meters, and the thickness uniformity is controlled within ±5 cm. After the surface filling is completed, an underwater leveling device is used to finely level the surface to ensure that the surface is flush with or slightly lower than the surrounding natural seabed by 5 - 10 cm, leaving space for subsequent natural sedimentation. For the area in contact with the pit wall, the grille anchoring technology is used for treatment. Grille anchoring refers to the technology of installing stainless - steel grille anchor parts on the pit wall to firmly connect the filling body with the pit wall. The spacing of the anchor parts is 3 - 5 meters, and they penetrate 0.5 - 1 meter into the pit wall, forming an anchoring connection with the filling body to prevent the filling body from separating from the pit wall and enhancing the overall stability.

[0036] In a specific embodiment, the process of executing step S104 may specifically include the following steps: According to the surface characteristics and hydrodynamic conditions of the filling structure, prepare a mixture of fine - sand and clay with a fine particle size as the transition - layer material, and lay the transition - layer material on the surface of the filling structure to obtain a transition protection layer; Judge whether the transition protection layer meets the bottom - layer connection requirements. If it meets, mix gravel and cementing material and cover the transition protection layer to form a middle - layer protection layer, obtaining a stable structure; Judge the anti - erosion performance of the middle - layer protection layer. If the anti - erosion performance index is lower than the set threshold, increase the proportion of the cementing material for reinforcement treatment; if the anti - erosion performance index is higher than the threshold, select natural materials to cover the middle - layer protection layer to obtain a three - layer protection structure; Analyze the water flow effect on the filling structure, calculate the water flow velocity and scouring intensity in each area. When the scouring intensity exceeds the bearing capacity of the protective layer, it is determined as a high scouring risk area, and the distribution map of the protection strengthening area is obtained. Judge the position and scope of the protection strengthening area. When it is located at the pit edge and the water flow concentration area, lay the gabion cage structure, bury the cage edge into the bottom layer, and connect the cages through connecting lines to obtain the anti-scouring structure. Judge the water flow velocity around the anti-scouring structure. When the velocity exceeds the critical value, set up an energy dissipation device composed of riprap or concrete blocks to divert and reduce the energy of the incoming water flow, and obtain the anti-erosion surface system.

[0037] Specifically, when formulating the transition layer material according to the surface characteristics and hydrodynamic conditions of the filling structure, it is first necessary to analyze the physical characteristics of the filling structure surface and the hydrodynamic conditions of the water area. The surface characteristics include particle size composition, surface roughness, and permeability, etc., which are obtained through on-site sampling analysis; the hydrodynamic conditions include wave height, flow velocity, flow direction, and tidal cycle, etc., which are obtained through hydrological observations. According to these data, formulate a suitable transition layer material, which is mainly composed of fine sand with a particle size of 0.1 - 0.5 mm and clay mixed in a mass ratio of 7:3. The fine sand provides a skeleton support function, while the clay fills the particle gaps and provides cohesion. The water content of the prepared mixture is controlled at 25 - 30%, ensuring that the material has appropriate fluidity and plasticity. Lay this mixture evenly on the surface of the filling structure through a conveying pipeline, with a thickness of 0.2 - 0.3 m, ensuring that there are no blank areas on the coverage surface, and the thickness error is controlled within ±2 cm, thus forming a transition protection layer.

[0038] The judgment criteria include three aspects: bonding strength, permeability, and uniformity. Take cylindrical samples with a diameter of 10 cm at different positions by the core sampling method for indoor bonding strength testing to determine the interfacial bonding strength between the transition protection layer and the underlying filling structure; measure the permeability coefficient of the transition protection layer through on-site permeability tests; detect the uniformity of the transition layer thickness distribution through ultrasonic scanning technology. When the bonding strength reaches the design value (generally 30 - 50 kPa), the permeability coefficient is not greater than 1×10^-5 cm / s, and the thickness uniformity is good (the coefficient of variation is less than 15%), it is determined that the transition protection layer meets the bottom connection requirements. After meeting the requirements, formulate the middle protection layer material, mix gravel with a particle size of 5 - 20 mm and a cementing material (such as modified asphalt, epoxy resin, etc.) in a mass ratio of 8:2. The cementing material plays a role in bonding gravel particles and preventing the loss of fine particles. Cover the mixed material evenly on the transition protection layer, with a thickness of 0.3 - 0.5 m, to form the middle protection layer and obtain a preliminary stable structure.

[0039] The anti-scouring performance refers to the ability of the protection structure to resist material loss under the action of water flow, which is expressed by the anti-scouring performance index. The anti-scouring performance index is obtained through a flume scouring test. The specific method is to simulate the on-site water flow conditions (flow velocity, water depth, waves, etc.) in the laboratory flume, scour the sample of the protective layer material at regular intervals, measure the material loss per unit time, calculate the loss rate, and then determine the anti-scouring performance index according to the ratio of the loss rate to the critical loss rate. The critical loss rate refers to the maximum allowable material loss rate during the design service life, which is usually determined according to the engineering design standards. When the anti-scouring performance index is lower than the set threshold (usually 1.2), it indicates that the anti-scouring ability of the protective layer is insufficient, and it is necessary to increase the proportion of the cementitious material for reinforcement treatment. The reinforcement treatment is achieved by increasing the proportion of the cementitious material to 25-30%, or replacing it with a high-strength cementitious material. If the anti-scouring performance index is higher than the threshold, natural materials similar to the surrounding seabed environment (such as sandy, gravelly or shell debris on the local seabed) are selected to cover the middle protective layer with a thickness of 0.3-0.4 meters to form the surface protective layer, so that the repaired area can naturally transition to the surrounding seabed environment and complete the construction of the three-layer protection structure.

[0040] The analysis of the water flow action on the filling structure is the basis for identifying high-scouring risk areas. The data for the water flow action analysis are obtained through two methods: one is on-site observation, using an acoustic Doppler current profiler (ADCP) to measure the water flow field around the filling area under different tidal levels and seasonal conditions to obtain parameters such as flow velocity and flow direction; the other is numerical simulation, based on a three-dimensional computational fluid dynamics (CFD) model, inputting the topographic data after the sand excavation pit is filled and the local hydrological conditions into the model to simulate the water flow distribution under different working conditions. By analyzing and processing these data, the water flow velocity and scouring intensity of each area are calculated. The calculation of the scouring intensity takes into account the comprehensive influence of water flow velocity, bottom shear stress, wave action and topographic factors. When the calculated scouring intensity exceeds the bearing capacity of the protective layer (i.e., the critical incipient motion stress of the material), this area is determined as a high-scouring risk area. All high-scouring risk areas are marked on the plan of the filling area to form a distribution map of the protection strengthening areas, providing spatial guidance for subsequent strengthening protection measures.

[0041] Judging the location and scope of the enhanced protection area is the basis for determining the layout of the gabion cage structure. By analyzing the distribution map of the enhanced protection area and combining with the topographic features and hydrodynamic conditions, the location characteristics of each high-scouring risk area are judged. When the high-scouring risk area is located at the edge of the pit (i.e., the transition zone between the sand mining pit and the natural seabed) or the water flow concentration area (such as the terrain depression, the water flow convergence channel, etc.), the gabion cage structure is used for protection. The gabion cage is a kind of cage woven by high-strength steel wire or synthetic material, filled with stones inside to form an integral structure, which has high scour resistance and flexibility. The size of the gabion cage is usually 1 m × 1 m × 0.5 m, the mesh size is 6 cm × 8 cm, and the filling particle size is 50 - 100 mm of hard stones. When laying, it is arranged according to the shape of the risk area, and the cages are firmly connected by connecting wires to form an overall protection net. At the contact with the bottom layer, the edge of the cage is buried at least 0.5 m deep into the bottom layer to prevent the structure from losing stability due to undercutting by the water flow. After laying, an underwater inspection is carried out to ensure that there is no deformation, disconnection or filler loss in the cage structure, and an effective anti-scour structure is formed.

[0042] Judging the water flow velocity around the anti-scour structure is the basis for determining whether to set up an energy dissipation device. Through the data obtained from the aforementioned water flow action analysis, the water flow velocity distribution information of the area around the anti-scour structure is extracted. According to the design code for hydraulic protection structures, the critical velocity value under the local environment is determined. The critical velocity refers to the minimum velocity at which obvious scouring begins to occur around the anti-scour structure under the action of this velocity, and it is usually determined through engineering experience and test data. When the actual velocity exceeds the critical value, an energy dissipation device needs to be set up for velocity control. The energy dissipation device mainly includes two forms: one is the rockfill structure, which is composed of irregularly shaped stones piled up, and the particle size of the stones is generally 200 - 500 mm, and the stacking height is 0.6 - 1.0 m; the other is the concrete block, which is a standardized concrete component, such as energy dissipation blocks in the shape of hexagons, quadrangular pyramids, etc., and the weight of a single block is 50 - 200 kg. The energy dissipation device is set on the upstream side in the incoming flow direction, and by changing the water flow path, generating eddy currents and frictional losses, the purpose of reducing the water flow energy and lowering the velocity is achieved. The layout of the energy dissipation device should consider the water flow direction, intensity and variation law to form a protection system matching the water flow characteristics. After careful design and fine construction, a complete anti-erosion surface system is finally formed to effectively protect the filling structure from water flow scouring and erosion.

[0043] In a specific embodiment, the process of performing the step of constructing the three-layer protection structure may specifically include the following steps: Sampling the middle protection layer for anti-scour test, measuring the loss amount per unit time of the protection layer material under water flow scouring, calculating the material loss rate, and obtaining the basic anti-scour data; Compare and analyze the anti-erosion basic data with the evaluation results of hydrodynamic effects, calculate the anti-erosion performance index of the middle protective layer in different areas, and obtain the anti-erosion performance distribution map; Determine the anti-erosion performance threshold according to the material mechanical properties and engineering experience values, compare the anti-erosion performance index with the threshold, mark the areas where the index is lower than the threshold, and obtain the distribution of reinforcement areas; Increase the proportion of cementitious materials in the middle protective layer of the reinforcement area, determine the addition amount of cementitious materials according to the difference between the anti-erosion performance index and the threshold in different areas, and supplement and add the cementitious materials to obtain the reinforced middle protective layer; Select natural materials matching the surrounding seabed environment as the surface layer materials, determine the particle size and thickness of the surface layer materials according to water depth, wave conditions and seabed types, form a design scheme for the surface protective layer, and obtain the surface layer formula; Uniformly cover the materials of the surface layer formula on the surface of the middle protective layer, control the covering thickness and flatness, and make the surface smoothly transition with the surrounding seabed elevation to obtain a three-layer protective structure.

[0044] Specifically, sampling the middle protective layer for anti-erosion test is the first step to obtain anti-erosion basic data. The specific operation is to take multiple representative samples from the completed middle protective layer. The sample size is usually 30 cm × 30 cm × the actual thickness of the protective layer. The sampling positions should cover different water depth areas and terrain feature areas to ensure the representativeness of the samples. The taken samples are sent into a special flume erosion test device, which can simulate the hydrodynamic conditions of the actual sea area, including parameters such as flow velocity, waves and water depth. The test conditions are set as the extreme hydrodynamic conditions of the local sea area, such as the maximum flow velocity and wave height once in a hundred years. Under the set conditions, conduct a continuous 72-hour erosion test on the samples, take out the samples to weigh every 6 hours, and record the change of sample weight over time. By calculating the weight loss of the samples per unit time, obtain the material loss rate, with the unit of kg / m² / day. This data directly reflects the anti-erosion ability of the protective layer material under the action of water flow. The lower the loss rate, the stronger the anti-erosion ability.

[0045] Comparing and analyzing the anti-scour foundation data with the results of hydrodynamic impact assessment is a necessary step to evaluate the performance of the protective layer in the actual use environment. The results of hydrodynamic impact assessment include parameters such as water flow velocity, wave height, and wave period at each point in the repair area. By comparing these parameters with the anti-scour test conditions, a relationship function of the material loss rate under different hydrodynamic conditions can be established. The specific operation is to spatially match the location information of the sampling points with the grid points in the hydrodynamic impact assessment to establish a set of hydrodynamic parameters for each sample point, and then obtain the hydrodynamic distribution of the entire repair area through interpolation. Correlation analysis is carried out between the material loss rate of each sample and the hydrodynamic parameters at the corresponding location to establish a functional relationship between the loss rate and the hydrodynamic parameters. Based on this relationship and combined with the hydrodynamic distribution of the entire repair area, the anti-scour performance index of the middle protective layer in different areas is calculated. The anti-scour performance index is defined as the ratio of the critical loss rate of the protective layer material to the predicted loss rate, and the critical loss rate refers to the maximum material loss rate allowed within the design service life. The calculated anti-scour performance index is plotted on the plan of the repair area in the form of contour lines to form an intuitive anti-scour performance distribution map, clearly showing the anti-scour performance status of each area. Determining the anti-scour performance threshold based on the material mechanical properties and engineering experience values is the basis for judging whether the protective layer needs to be strengthened. The anti-scour performance threshold is determined by comprehensively considering multiple factors, including the physical and mechanical properties of the protective material (such as particle size, density, cohesion, etc.), design service life, engineering safety level, and accumulated engineering experience values. For general marine engineering, the anti-scour performance threshold is usually set at 1.2 - 1.5, that is, the predicted loss rate should not be greater than 67% - 83% of the critical loss rate, providing sufficient safety redundancy for the system. Compare the calculated anti-scour performance index of each area with the set threshold. When the index is lower than the threshold, mark it as the area that needs to be strengthened. Mark all the areas that need to be strengthened on the plan of the repair area to form a reinforcement area distribution map for guiding subsequent reinforcement work. This method based on the comparison of the performance index and the threshold can accurately identify weak links and implement targeted reinforcement measures, ensuring both the protection effect and saving engineering costs.

[0046] Increasing the proportion of the cementitious material in the middle protective layer of the reinforced area is an effective means to improve the anti-erosion performance. The cementitious material refers to the material that can bond loose particles into an integral structure, such as epoxy resin, modified asphalt, cement-based materials, etc. The specific operation of increasing the proportion of the cementitious material is to determine the supplementary addition amount of the cementitious material according to the difference between the anti-erosion performance index and the threshold value in different areas. The larger the difference, the higher the proportion of the cementitious material to be added. The calculation formula is: Supplementary addition ratio = Basic addition ratio × (Threshold value / Index - 1) × Adjustment coefficient, where the basic addition ratio is the proportion of the cementitious material in the initial design, generally 15%-20%; the adjustment coefficient is a parameter determined according to the type of cementitious material and environmental conditions, generally 1.1-1.3. After calculating the proportion of the cementitious material to be supplemented in each area, make supplementary additions according to the area division. The supplementary addition adopts the surface perfusion method. First, evenly spray the liquid cementitious material on the surface of the protective layer, and use its own weight and pressure to assist the cementitious material to penetrate into the interior of the protective layer. After the cementitious material solidifies, an integral structure is formed. After reinforcement, conduct sampling inspection on the protective layer to confirm that the anti-erosion performance index has been increased above the threshold value, and form the reinforced middle protective layer. Selecting natural materials that match the surrounding seabed environment as the surface material is an important measure to achieve seamless connection between the repaired area and the natural seabed. The selection of the surface material should be based on a detailed investigation of the surrounding seabed environment, including the type of bottom sediment, particle size composition, mineral composition, etc. Through multi-point sampling and laboratory analysis, obtain the bottom sediment characteristic data of the surrounding seabed. At the same time, consider the influence of water depth, wave conditions and seabed type on the surface material. Water depth affects the light intensity and water pressure, and thus affects the stability of the material; wave conditions determine the anti-erosion ability required by the material; the seabed type determines the physical and chemical properties that the surface material should possess. Considering these factors comprehensively, determine the particle size range and thickness of the surface material. Generally speaking, the particle size should be close to or slightly larger than the particle size of the natural sediment on the surrounding seabed to provide sufficient stability; the thickness is determined according to the wave conditions and water depth, generally 0.3-0.6 meters. According to the above parameters, form a design scheme for the surface protective layer, including material composition, particle size range, thickness distribution, etc., and finally obtain a specific surface formula.

[0047] Before covering, the surface of the middle protective layer is cleaned to remove loose objects and impurities to ensure good adhesion between the surface layer and the middle layer. The covering method adopts the partition and layer laying method, dividing the entire repair area into several construction units, and each unit evenly lays the surface material according to the designed thickness. During the laying process, the thickness is measured in real time to ensure that the covering thickness meets the design requirements and the thickness error is controlled within ±5 cm. After the covering is completed, the surface is finely leveled using underwater leveling equipment to ensure that the surface flatness meets the design requirements. Special attention is paid to the transition area between the repair area and the surrounding natural seabed. A gradual thickness design is adopted to make a smooth transition between the surface of the repair area and the surrounding seabed elevation. The width of the transition zone is generally 5-10 meters, and the slope is not greater than 1:10, to avoid the formation of obvious terrain drop and prevent water disturbance and scouring caused by local terrain changes. Through this series of fine operations, a three-layer protective structure with complete structure and coordinated functions is finally formed, providing long-term and stable protection for the filling body.

[0048] In a specific embodiment, the process of executing step S105 may specifically include the following steps: Install settlement monitoring points, water flow monitoring equipment and pore pressure sensors at key locations of the anti-erosion surface system to collect settlement data, water flow parameters and pore water pressure data to obtain raw monitoring data; Process the raw monitoring data, remove abnormal values, calculate the sedimentation rate, water flow velocity change and pressure change trend, and obtain the processed monitoring data; Compare the processed monitoring data with the design standard value to determine whether the settlement of the filling body exceeds the reserved settlement amount and whether the pore water pressure reaches a stable state, and obtain the stability determination result; Underwater sonar scanning of the anti-erosion surface system measures changes in surface morphology, calculates erosion depth and range, determines the integrity of the protective structure, and obtains an anti-erosion effect evaluation; According to the stability determination results and anti-erosion effect evaluation, the repair area is graded and assessed, and the areas that need to be reinforced or strengthened are marked to obtain subsequent maintenance area identification; The monitoring data, stability determination results, anti-erosion effect evaluation and subsequent maintenance area identification are integrated and stored, and an information system containing time series data and spatial distribution data is established to obtain a restoration effect evaluation database.

[0049] Specifically, installing monitoring equipment at key locations of the anti-erosion surface system is the basis for obtaining engineering status data. The selection of key locations is based on the topographic characteristics and hydrodynamic conditions of the filling area, usually including the center point of the filling area, the edge transition zone, the area with large terrain drop, and the water flow concentration area. The settlement monitoring point is a special device for measuring the vertical displacement of the filling body. It consists of a settlement plate, a measuring pole and a signal transmission device. It is installed at different depths inside the filling body or on the surface. Generally, 1-2 are arranged per 1,000 square meters, and the number is appropriately increased in areas where the filling thickness changes significantly. The water flow monitoring equipment is mainly an acoustic Doppler current profiler (ADCP), which measures the water flow velocity and direction through the ultrasonic Doppler effect. It is installed in areas with strong water flow. The measurement range covers all layers of the water body. The collection frequency is once an hour, and the parameters such as water flow velocity, flow direction and wave height are recorded. The pore pressure sensor is an instrument for measuring the pore water pressure inside the filling body. It is buried at different depths of the filling body. Each settlement monitoring point corresponds to 2-3 pore pressure sensors to form a vertical measurement profile. The collection frequency is once an hour. The data collected by these monitoring devices are transmitted to the data receiving terminal in real time through the underwater communication system, forming an original data set containing time, location, and measurement values. Processing the raw monitoring data is a necessary step in analyzing the performance of the filling body. First, data cleaning is performed to eliminate outliers. The 3σ rule is used to determine outliers, that is, data points that deviate from the mean value ±3 times the standard deviation are considered abnormal and eliminated. For settlement data, the settlement curve of each monitoring point over time is calculated, and the settlement rate is calculated using the difference method in millimeters per day. The settlement rate calculation formula is: settlement rate = (current settlement - previous settlement) / (current time - previous time). For water flow data, the mean, maximum and direction change characteristics of the flow velocity at different water depths of each monitoring point are calculated, and the flow velocity change trend and extreme value occurrence time within the tidal cycle are analyzed. For pore water pressure data, the pressure change trend with time and depth is calculated, and the drainage during the consolidation process is analyzed. By processing these data, key indicator values ​​that can reflect the engineering status of the filling body are obtained to form a processed monitoring data set. Comparing the processed monitoring data with the design standard value is an important part of judging the status of the project. The design standard value is the allowable range of various indicators determined according to theoretical calculations and empirical values ​​during the engineering design stage, including reserved settlement, maximum allowable settlement rate, pore water pressure dissipation rate, etc. The comparison process first checks whether the settlement of the filling body exceeds the reserved settlement. The reserved settlement is usually 10-15% of the total thickness of the filling. Compare the measured maximum settlement with the reserved settlement. When the measured value is less than 80% of the reserved value, it is judged to be in the safe range; when the measured value reaches 80%-100% of the reserved value, it is judged to be in the warning range; when the measured value exceeds the reserved value, it is judged to be in the over-standard range.Secondly, analyze the changing trend of the settlement rate. Under normal circumstances, the settlement rate should gradually decrease over time and tend to be stable. When the settlement rates measured three times in a row are all less than the set threshold (usually 0.5 mm / day), it is determined that the settlement has entered the stable stage. Thirdly, analyze the pore water pressure data and calculate the pressure dissipation rate, which is the ratio of the decrease in pore water pressure to the initial excess hydrostatic pressure. When the pressure dissipation rate reaches over 90% and the pressure value tends to be stable, it is determined that the consolidation process is basically completed. Through these comparison analyses, a comprehensive determination result of the stability of the filling body is obtained.

[0050] Underwater sonar scanning of the anti-erosion surface system is a direct means to evaluate the integrity of the protection structure. Underwater sonar scanning uses a multi-beam sounding system or a side-scan sonar system to conduct full-coverage scanning of the repaired area to obtain high-precision topographic data. The scanning is carried out along equally spaced survey lines, and the line spacing is no greater than twice the water depth to ensure that the data overlap rate reaches over 50% and the scanning resolution reaches 10 cm or higher. Compare the topographic data obtained from the scanning with the reference topographic data at the completion of the repair, calculate the change in surface elevation, and draw an isogram of the change amount to visually display the eroded or silted areas. The erosion depth refers to the vertical distance by which the surface has dropped and is calculated by the difference between the current elevation and the reference elevation; the erosion extent refers to the area where the erosion depth exceeds the set threshold (generally 5 cm). Based on the distribution characteristics of the erosion depth and extent, judge the integrity status of the protection structure. When the maximum erosion depth is less than 20% of the designed protection layer thickness and the erosion extent accounts for no more than 10% of the total area, it is judged to be in a good state; when the maximum erosion depth reaches 20%-50% of the designed protection layer thickness, or the erosion extent accounts for 10%-30% of the total area, it is judged to be in a state that requires attention; when the maximum erosion depth exceeds 50% of the designed protection layer thickness, or the erosion extent accounts for more than 30% of the total area, it is judged to be in a state that requires repair. Through this quantitative evaluation method, objectively evaluate the anti-erosion effect. Based on the stability determination result and the anti-erosion effect evaluation, grading the repaired area is an important step in guiding subsequent maintenance. The grading uses the matrix method to combine the stability determination and anti-erosion evaluation results to form a comprehensive rating matrix. The stability determination result is divided into three levels: stable, basically stable, and unstable; the anti-erosion effect evaluation is divided into three levels: good, requiring attention, and requiring repair. The combination of the two forms nine states, which are further simplified into five grades: excellent, good, average, poor, and very poor. Areas in the excellent grade do not require maintenance measures; areas in the good grade require regular observation; areas in the average grade require increased monitoring frequency and formulation of preventive maintenance plans; areas in the poor grade require timely local reinforcement or strengthening; areas in the very poor grade require immediate implementation of comprehensive repair. On the plan of the repaired area, mark each grade area with different colors to form an intuitive identification map of the subsequent maintenance area to guide the priority order and resource allocation of the maintenance work.

[0051] Integrating and storing monitoring data, stability determination results, anti-erosion effect evaluation, and subsequent maintenance area identification to establish a repair effect evaluation database is the guarantee for realizing long-term scientific management. The database adopts a hierarchical structure design, including four levels: the original data layer, the processed data layer, the evaluation result layer, and the decision support layer. The original data layer stores the original data collected by monitoring devices, including information such as timestamps, device IDs, and measurement values; the processed data layer stores various index values after data processing, such as settlement rates and pressure dissipation rates; the evaluation result layer stores the stability determination results and anti-erosion effect evaluation results; the decision support layer stores the grading evaluation results and maintenance suggestions. The database supports two data organization methods: time series data organization, which stores the parameter change processes of each monitoring point in chronological order for trend analysis; spatial distribution data organization, which stores the state parameters of each area according to spatial positions for spatial analysis. The database provides query, statistics, analysis, and visualization functions, supports multi-dimensional data display and early warning functions, and automatically triggers an early warning and pushes relevant information when the monitoring parameters exceed the preset thresholds. Through this systematic data management, scientific monitoring and management of the entire life cycle of the repair project are realized.

[0052] The above describes the method for controlling the repair of submarine sand mining pits based on marine dredged mud in the embodiments of the present application. Next, the control system for the repair of submarine sand mining pits based on marine dredged mud in the embodiments of the present application will be described. Please refer to Figure 2 , an embodiment of the control system for the repair of submarine sand mining pits based on marine dredged mud in the embodiments of the present application includes: A collection module 201, configured to perform topographic mapping and environmental sample collection and analysis on the submarine sand mining pit to obtain three-dimensional topographic data of the sand mining pit, and perform improvement processing on the marine dredged mud to obtain repair materials; An analysis module 202, configured to analyze the filling plan based on the three-dimensional topographic data and the repair materials, generate a target filling plan, and construct a transportation system combining barge transportation and pipeline transportation; A filling module 203, configured to fill the repair materials into the sand mining pit in layers of bottom, middle, and surface based on the transportation system, perform vibration compaction and underwater grouting treatment on each layer of filling body to obtain a filling structure; A construction module 204, configured to construct a three-layer protection structure on the surface of the filling structure, and add gabion cages and energy dissipation structures in high-scour-risk areas to obtain an anti-erosion surface system; An evaluation module 205, configured to evaluate the repair effect of the anti-erosion surface system according to a preset monitoring network to obtain a repair effect evaluation database.

[0053] Through the collaborative cooperation of the above-mentioned various components, the steps of topographic surveying and mapping of the seabed sand mining pit and collection and analysis of environmental samples have constructed a comprehensive and accurate three-dimensional topographic model and environmental assessment system, providing an accurate data basis for subsequent restoration. At the same time, targeted improvement treatment has been carried out on marine dredged mud, realizing the resource utilization of dredged mud and solving the problem of dredged mud disposal; based on the three-dimensional topographic data and restoration materials, the filling scheme analysis has been carried out, and the artificial intelligence algorithm has been used to simulate and predict the hydrodynamic conditions and sediment migration laws, generating a target filling scheme for the specific environment, and constructing a precisely positioned transportation system, greatly improving the construction accuracy and efficiency; the layered filling technology is combined with vibration compaction and underwater grouting treatment to form a filling body with stable structure, enhancing the overall bearing capacity and anti-deformation ability; the three-layer protection structure design is combined with the application of gabion cages and energy dissipation structures in high-risk areas to construct an all-round anti-erosion surface system, significantly enhancing the anti-scouring ability and long-term stability of the restoration area under extreme hydrodynamic conditions; the combination of the pre-set monitoring network and data processing algorithm has realized the scientific evaluation and dynamic management of the restoration effect. Through the intelligent processing of a large amount of spatial data, the accurate analysis and prediction of the complex seabed environment have been realized, improving the pertinence and scientificity of the scheme. In the anti-scouring performance evaluation, the correlation model between hydrodynamic parameters and material properties has been established, realizing the precise matching of protection requirements in different areas, and the anomaly detection algorithm has been applied in the monitoring data processing to improve the data quality and early warning accuracy.

[0054] Above Figure 2 From the perspective of modular functional entities, the seabed sand mining pit restoration control system based on marine dredged mud in the embodiments of the present invention is described in detail. Next, the seabed sand mining pit restoration control equipment based on marine dredged mud in the embodiments of the present invention is described in detail from the perspective of hardware processing.

[0055] Figure 3FIG. 0 is a schematic structural diagram of a control device for repairing a seabed sand mining pit based on marine dredged mud provided by an embodiment of the present invention. The control device 300 for repairing a seabed sand mining pit based on marine dredged mud may vary greatly due to different configurations or performances, and may include one or more processors (central processing units, CPU) 310 (for example, one or more processors) and a memory 320, and one or more storage media 330 for storing application programs 333 or data 332 (for example, one or more mass storage device terminals). Among them, the memory 320 and the storage media 330 may be transient storage or persistent storage. The program stored in the storage media 330 may include one or more modules (not shown in the figure), and each module may include a series of instruction operations on the control device 300 for repairing a seabed sand mining pit based on marine dredged mud. Further, the processor 310 may be configured to communicate with the storage media 330 and execute a series of instruction operations in the storage media 330 on the control device 300 for repairing a seabed sand mining pit based on marine dredged mud to implement the steps of the above-mentioned control method for repairing a seabed sand mining pit based on marine dredged mud.

[0056] The control device 300 for repairing a seabed sand mining pit based on marine dredged mud may further include one or more power supplies 340, one or more wired or wireless network interfaces 350, one or more input / output interfaces 360, and / or one or more operating systems 331, such as Windows Serve, Mac OS X, Unix, Linux, FreeBSD, etc. Those skilled in the art can understand that Figure 3 The shown structural diagram of the control device for repairing a seabed sand mining pit based on marine dredged mud does not limit the control device for repairing a seabed sand mining pit based on marine dredged mud provided by the present invention, and may include more or fewer components than shown in the figure, or combine some components, or have different component arrangements.

[0057] The present invention also provides a computer-readable storage medium, which may be a non-volatile computer-readable storage medium or a volatile computer-readable storage medium. Instructions are stored in the computer-readable storage medium. When the instructions run on a computer, the computer is made to execute the steps of the control method for repairing a seabed sand mining pit based on marine dredged mud.

[0058] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the above-described systems, systems, and units can refer to the corresponding processes in the foregoing method embodiments and will not be described herein again.

[0059] When the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a seabed sand mining pit repair control device based on marine dredged mud (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical discs that can store program codes.

[0060] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of various embodiments of the present invention.

Claims

1. A method for controlling the repair of a seabed sand pit based on marine dredged mud, characterized in that: The method comprises: Carry out topographic mapping and environmental sample collection and analysis of seabed sand mining pits to obtain three-dimensional topographic data of sand mining pits, and improve and process marine dredged mud to obtain restoration materials; Performing a filling scheme analysis based on the three-dimensional terrain data and the repair material, generating a target filling scheme, and constructing a transportation system combining barge transportation and pipeline transportation; Based on the transportation system, the repair material is filled into the sand mining pit in layers according to the bottom layer, the middle layer and the surface layer, and each layer of the filling body is subjected to vibration compaction and underwater grouting treatment to obtain a filling structure; A three-layer protective structure is constructed on the surface of the filling structure, and gabion cages and energy dissipation structures are added in high scour risk areas to obtain an anti-erosion surface system; The repair effect of the anti-erosion surface system is evaluated according to a preset monitoring network to obtain a repair effect evaluation database.

2. The method for controlling the repair of a seabed sand pit based on marine dredged mud according to claim 1, characterized in that: The above-mentioned three-dimensional topographic data of the sand mining pit is obtained by mapping the seabed sand mining pit and collecting and analyzing environmental samples, and the marine dredged mud is improved and processed to obtain the restoration material, including: Multi-beam sonar system and side-scan sonar system are used to map the seabed sand mining pits, and the surveying data is processed by three-dimensional modeling through marine geographic information system software to obtain three-dimensional terrain data; Set up multiple bottom sediment sample collection points inside and around the sand mining pit, collect bottom sediment samples of a specific depth from each point, conduct laboratory analysis on the samples, and obtain environmental quality parameters; According to the terrain data and the environmental quality parameters, a sand mining pit status assessment index system is constructed, and the sand mining pits are evaluated by zoning to obtain restoration priorities and difficulty levels; Conduct physical property testing and chemical composition analysis on dredged mud samples, classify and rate the dredged mud according to engineering applicability and environmental safety indicators, and obtain dredged mud characteristic data; According to the dredged mud characteristic data, a solidifying agent and a stabilizer are added to the heavy metal polluted dredged mud for solidification and stabilization treatment, and an oxidant and a catalyst are added to the organic polluted dredged mud for chemical oxidation treatment to obtain harmless dredged mud; Aggregates and fiber materials are added to the harmless dredged mud to enhance its strength, and permeable materials and modifiers are added to adjust its drainage performance to obtain a repair material.

3. The method for controlling the repair of a seabed sand pit based on marine dredged mud according to claim 1, characterized in that: The filling scheme analysis is performed based on the three-dimensional terrain data and the repair material, a target filling scheme is generated, and a transportation system combining barge transportation and pipeline transportation is constructed, including: Analyzing the hydrodynamic conditions of the sand pit area on the three-dimensional terrain data, calculating the influence of tides, waves and ocean currents on the filling materials, and obtaining the hydrodynamic impact evaluation results; Based on the hydrodynamic impact assessment results, the sediment migration law is calculated, and combined with the physical properties of the repair material, the stability parameters of the filling materials in each area are determined to obtain a filling area zoning plan; Divide the sand mining pit into multiple filling units according to the filling area zoning plan, determine the specific filling thickness, material ratio and construction time for each filling unit, and obtain a project implementation plan; The project implementation plan is optimized, the connection mode between each filling unit is calculated, and the target filling plan for the reserved settlement space is obtained; According to the spatial relationship between the storage location of the repair material and the sand mining pit, the best transportation route is determined, the barge specifications, loading capacity and positioning system are designed, and the marine transportation plan is obtained; Based on the offshore transport scheme, a transport pipeline system is designed, the pipe diameter, flow rate, transport pressure and diffuser parameters are determined, and a transport system combining barge transport and pipeline transport is constructed.

4. The method for controlling the repair of a seabed sand pit based on marine dredged mud according to claim 1, characterized in that: The method of filling the repair material into the sand mining pit in layers according to the bottom layer, the middle layer and the surface layer based on the transportation system, performing vibration compaction and underwater grouting treatment on each layer of the filling body to obtain a filling structure includes: The mixed aggregate repair material is directed to the deepest part of the sand mining pit by using the transportation system to form a bottom filling material, and the filling thickness is controlled according to the depth gradient of the sand mining pit to obtain a bottom filling body; The bottom filling body is vibrated by underwater vibration compaction equipment, the vibration frequency and amplitude are adjusted according to the density of the filling material, and the compacted surface is leveled to obtain a dense bottom foundation; The repair material mixed with the curing agent is transported to the top of the bottom foundation in sections and sections through the transportation system to form a middle-layer filling body, and a specific gradient change is maintained between the middle-layer filling body and the bottom foundation to obtain a stepped filling structure; Underwater grouting is performed on the stepped filling structure, the grouting points are arranged in a grid shape, the grouting pressure and the grouting time are determined according to the size of the filling area and the material properties, and a middle layer reinforcement body with a firm internal connection is obtained; The improved dredged mud and fine sand mixed material is transported to the surface of the middle layer reinforcement body, the surface thickness and surface flatness are controlled, and the grid anchoring treatment is performed on the area contacting the pit wall to obtain a filling structure anchored to the pit wall.

5. The method for controlling the repair of a seabed sand pit based on marine dredged mud according to claim 1, characterized in that: The three-layer protection structure is constructed on the surface of the filling structure, and gabion cages and energy dissipation structures are added in high scour risk areas to obtain an anti-erosion surface system, including: According to the surface characteristics and hydrodynamic conditions of the filling structure, a mixture of fine sand and clay is prepared as a transition layer material, and the transition layer material is laid on the surface of the filling structure to obtain a transition protective layer; Determine whether the transitional protective layer meets the bottom layer connection requirements. If so, mix gravel with cementing materials, cover the transitional protective layer, form a middle protective layer, and obtain a stable structure. Determine the anti-scour performance of the middle protective layer. If the anti-scour performance index is lower than the set threshold, increase the proportion of cementing materials for reinforcement. If the anti-scour performance index is higher than the threshold, select natural materials to cover the middle protective layer to obtain a three-layer protective structure. Analyze the water flow effect on the filling structure, calculate the water flow velocity and scouring force in each area, and when the scouring force exceeds the bearing capacity of the protective layer, it is determined to be a high scouring risk area, and the distribution map of the protection enhancement area is obtained; Determine the location and scope of the enhanced protection area. When it is located at the edge of the pit and the water flow concentrated area, lay the gabion cage structure, bury the edge of the cage into the bottom layer, and connect the cages with connecting wires to obtain an anti-scour structure; Determine the flow velocity of water around the anti-scour structure. When the flow velocity exceeds the critical value, set up a rockfill or concrete block to form an energy dissipation device to divert and dissipate the energy of the incident water flow to obtain an anti-erosion surface system.

6. The method for controlling the repair of a seabed sand pit based on marine dredged mud according to claim 5, characterized in that: The anti-scour performance of the middle protective layer is judged. If the anti-scour performance index is lower than the set threshold, the proportion of cementing material is increased for reinforcement. If the anti-scour performance index is higher than the threshold, natural materials are selected to cover the middle protective layer to obtain a three-layer protective structure, including: Take samples of the middle protective layer for anti-scouring test, measure the loss of protective layer materials per unit time under water scouring, calculate the material loss rate, and obtain the basic anti-scouring data; Compare and analyze the anti-scour basic data with the hydrodynamic impact assessment results, calculate the anti-scour performance index of the middle protective layer in different areas, and obtain an anti-scour performance distribution map; Determine the anti-scour performance threshold value according to the mechanical properties of the material and the engineering experience value, compare the anti-scour performance index with the threshold value, mark the area with an index lower than the threshold value, and obtain the distribution of the reinforced area; The proportion of cementing material is increased in the middle protective layer of the reinforced area, the amount of cementing material added is determined according to the difference between the anti-scour performance index and the threshold value in different areas, and the cementing material is supplemented to obtain the reinforced middle protective layer; Select natural materials that match the surrounding seabed environment as surface materials, determine the particle size and thickness of the surface materials according to the water depth, wave conditions and seabed type, form a surface protective layer design plan, and obtain the surface formula; The material of the surface layer formula is evenly covered on the surface of the middle protective layer, and the covering thickness and flatness are controlled to make a smooth transition between the surface and the surrounding seabed elevation, thereby obtaining a three-layer protective structure.

7. The method for controlling the repair of a seabed sand pit based on marine dredged mud according to claim 1, characterized in that: The repair effect evaluation of the anti-erosion surface system is performed according to the preset monitoring network to obtain a repair effect evaluation database, including: Install settlement monitoring points, water flow monitoring equipment and pore pressure sensors at key locations of the anti-erosion surface system to collect settlement data, water flow parameters and pore water pressure data to obtain raw monitoring data; Processing the raw monitoring data, removing abnormal values, calculating sedimentation rate, water flow velocity change and pressure change trend, and obtaining processed monitoring data; Comparing the processed monitoring data with the design standard value to determine whether the settlement of the filling body exceeds the reserved settlement amount and whether the pore water pressure reaches a stable state, thereby obtaining a stability determination result; Underwater sonar scanning of the anti-erosion surface system measures changes in surface morphology, calculates erosion depth and range, determines the integrity of the protective structure, and obtains an anti-erosion effect evaluation; According to the stability determination results and anti-erosion effect evaluation, the repair area is graded and assessed, and the area that needs to be reinforced or strengthened is marked to obtain the subsequent maintenance area identification; The monitoring data, stability determination results, anti-erosion effect evaluation and subsequent maintenance area identification are integrated and stored, an information system including time series data and spatial distribution data is established, and a restoration effect evaluation database is obtained.

8. A seabed sand pit repair control system based on marine dredged mud, characterized in that: Used to implement the seabed sand pit repair control method based on marine dredging mud as described in any one of claims 1 to 7, the seabed sand pit repair control system based on marine dredging mud comprises: The collection module is used to conduct topographic mapping and environmental sample collection and analysis of the seabed sand mining pits, obtain the three-dimensional topographic data of the sand mining pits, and improve the marine dredged mud to obtain restoration materials; An analysis module, used to analyze a filling scheme based on the three-dimensional terrain data and the repair material, generate a target filling scheme, and construct a transportation system combining barge transportation and pipeline transportation; A filling module is used to fill the repair material into the sand mining pit in layers according to the bottom layer, middle layer and surface layer based on the transportation system, and perform vibration compaction and underwater grouting treatment on each layer of filling body to obtain a filling structure; A construction module is used to construct a three-layer protection structure on the surface of the filling structure, and add gabion cages and energy dissipation structures in high scour risk areas to obtain an anti-erosion surface system; The evaluation module is used to evaluate the repair effect of the anti-erosion surface system according to a preset monitoring network to obtain a repair effect evaluation database.

9. A seabed sand pit repair control device based on marine dredged mud, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program that can be run on the processor, and the processor implements the seabed sand pit repair control method based on marine dredged mud as described in any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the processor is caused to execute the seabed sand pit repair control method based on marine dredged mud as claimed in any one of claims 1 to 7.

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