Experimental device and test method for re-erosion rate of deep-sea bottom flow in multi-metal nodule area

Abstract

The invention relates to the field of deep-sea mining environment influence simulation and deposition dynamics experimental testing, and particularly provides a multi-metal nodule area deep-sea bottom flow re-erosion rate experimental device and a testing method. The device comprises an annular water tank, a settling tank, an acoustic distance measurement type depth meter, an underwater camera, an acoustic Doppler current meter, a multi-parameter turbidimeter and other data collection modules, the test method comprises the following steps: synchronously acquiring multi-source data such as sedimentary layer thickness, suspended particle concentration, flow velocity and bed surface images through a plurality of sensors, establishing a mass conservation relation and an image thickness inversion model, calculating single-point and regional erosion rates, and introducing a tuberculosis volume fraction and a buried depth to correct critical shear stress. And the erosion rate under the future working condition is predicted by further combining a physical constraint neural network. According to the method, quantitative, spatialized and predictable analysis on the erosion process of the plume redeposition layer under the indoor controllable condition is realized, and the accuracy and engineering applicability of evaluation on the mining environment influence of the deep-sea tuberculosis area are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of deep-sea mining environmental impact simulation and sedimentary dynamics experimental testing technology. Specifically, it relates to an experimental device and testing method for the re-erosion rate of deep-sea submarine currents in polymetallic nodule areas. This indoor experimental device and testing method are used to study the plume redeposition and re-erosion processes caused by deep-sea submarine currents under polymetallic nodule mining conditions. In particular, it is a comprehensive testing and analysis method based on the fusion of multi-source data from acoustic ranging depth gauges, turbidimeters, current meters, and underwater cameras, combined with the distribution characteristics of polymetallic nodules and hydrodynamic parameters, to quantitatively invert and predict sediment layer thickness changes, suspended particle mass flux, and regional erosion rates. This method is suitable for indoor physical simulation and assessment of sediment re-erosion mechanisms and environmental impacts in polymetallic nodule areas under deep-sea mining disturbance conditions. Background Technology

[0002] With the continuous advancement of deep-sea mineral resource development technologies, the commercial mining of deep-sea minerals such as polymetallic nodules has gradually entered the engineering verification and pilot mining stages. Polymetallic nodules are widely distributed in the surface layer of deep-sea plains, and their occurrence environment is characterized by low sedimentation rates, weak hydrodynamics, thin fine-grained sediment cover, and high sensitivity to disturbance. During mining operations, the disturbance of the seabed surface by mining vehicles and the tailwater discharged by the hoisting system will generate a large number of fine-particle plumes. These plumes diffuse, settle, and re-cover the original nodule area and the surrounding seabed under the action of near-bottom hydrodynamics, forming a mining-induced sedimentary layer.

[0003] Existing research indicates that mining plume redeposition layers typically possess high porosity, loose structure, and low shear strength. Under the influence of deep-sea currents, these layers are highly susceptible to re-erosion and resuspension, leading to long-term cyclic diffusion of plume particles. This results in a sustained impact on benthic habitats, nodule regeneration environments, and regional sedimentary patterns. Therefore, quantitatively measuring and predicting the erosion rate, resuspension flux, and spatial distribution characteristics of mining-induced deposits under different flow velocities and nodule distribution conditions is a crucial scientific and technological issue for deep-sea mining environmental impact assessment and engineering scheme optimization.

[0004] Existing research mainly relies on methods such as in-situ turbidity monitoring, acoustic echo detection, or discrete sampling analysis to estimate plume concentration or depositional changes. However, these methods generally have the following shortcomings: First, most can only obtain data from a single point or a single height layer, making it difficult to reflect the spatial non-uniformity of plume redeposition and erosion processes. Second, there is a lack of reliable physical conversion between turbidity and depositional thickness, making it difficult to directly obtain the true depositional quality and erosion flux. Third, existing methods usually ignore the spatial distribution of polymetallic nodules and their modulating effect on bed stability, resulting in significant deviations in the description of the true erosion process in the nodule area. Fourth, existing testing methods are mostly based on post-hoc analysis, making it difficult to predictively assess the erosion process under different flow velocity conditions and nodule coverage conditions.

[0005] Therefore, there is an urgent need for a comprehensive testing device and method that can simultaneously obtain sediment layer thickness, suspended particle mass, hydrodynamic conditions and nodule distribution characteristics under controlled indoor conditions, and can extend single-point measurement results to the regional scale to further realize quantitative inversion and prediction of erosion rate, so as to provide a scientific basis for environmental impact assessment and engineering design of deep-sea polymetallic nodule mining activities. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides an experimental apparatus and testing method for the re-erosion rate of deep-sea submarine currents in polymetallic nodule areas. Addressing the problems in existing studies on the environmental impact of deep-sea polymetallic nodule mining, such as the difficulty in quantitatively characterizing the re-erosion process of mining plume redeposition layers under the influence of deep-sea submarine currents, insufficient spatial representativeness, and the difficulty in incorporating the nodule impact into a unified analytical framework, this invention proposes an experimental apparatus and testing method for the re-erosion rate of polymetallic nodule deep-sea submarine currents. This aims to conduct a systematic, quantitative, and predictable study of the erosion behavior of mining-disturbed sedimentary layers under controlled indoor conditions.

[0007] In existing technologies, the study of erosion processes often relies on single sensors or single-point observation data, making it difficult to simultaneously acquire changes in sediment thickness and suspended particle mass flux. This results in a lack of physical closure in the calculation of erosion rates, leading to limited reliability of the results. This invention establishes a mass conservation relationship between changes in sediment thickness and suspended particle mass by combining acoustic ranging depth gauges and turbidimeters, enabling a physical inversion of the re-erosion rate and thus improving the accuracy and interpretability of erosion rate measurement results.

[0008] Furthermore, traditional methods, which are mostly based on point data, struggle to reflect the spatially non-uniform distribution of redeposition and erosion processes in mining plumes. This invention introduces an underwater camera to continuously observe the sedimentary bed surface, establishing an image-based method for inverting sedimentary coverage and thickness fields. This extends the single-point erosion rate to the regional erosion rate within the field of view, achieving a spatially quantitative description of the erosion process.

[0009] Furthermore, considering the widespread distribution of polymetallic nodules on the deep seabed and their significant impact on sediment stability, this invention incorporates the nodule volume fraction and burial depth into the bed boundary shear stress model. This allows the erosion rate calculation to reflect the modulating effect of nodules on the initiation and re-erosion processes of the sedimentary layer, thereby more realistically simulating the erosion behavior of polymetallic nodule zones.

[0010] Building upon this foundation, the present invention further constructs a physically constrained neural network model using multi-source experimental data to learn the variation patterns of erosion rates under different flow velocities and nodule coverage conditions, thereby enabling the prediction and analysis of re-erosion rates under future operating conditions. Through the aforementioned technical means, the overall objective of this invention is to establish an experimental testing method capable of multi-scale quantitative measurement, mechanism analysis, and trend prediction of the re-erosion process of polymetallic nodule mining plume redeposition layers under indoor conditions, providing a scientific basis for deep-sea mining environmental impact assessment and engineering scheme optimization.

[0011] This invention is achieved through the following technical solution: an experimental device for deep-sea current re-erosion rate in a polymetallic nodule region, comprising an annular water tank, supported by a load-bearing frame fixedly installed at its bottom and a bridge in its middle, a clamp installed on the annular water tank, a metal bracket fixedly installed at the top of the annular water tank, a data collection module fixedly installed on the annular water tank via the clamp and the metal bracket, a data processor fixedly installed on the upper part of the bridge, a settling tank connected to the bottom of the annular water tank installed below the front part of the annular water tank, and a propeller flow generator installed at the rear of the annular water tank; deep-sea sediments are spread flat in the settling tank to be level with the bottom of the annular water tank, and polymetallic nodules are distributed in the deep-sea sediments; the left and right side walls of the settling tank are respectively provided with baffles that can be raised and lowered by a baffle lifter; The data collection module includes an acoustic ranging depth gauge and underwater camera located at the top of the settling tank, an acoustic Doppler current meter located at the left end of the settling tank, and a multi-parameter turbidity meter located at the right end of the settling tank. A flow rate controller is installed inside the annular water tank.

[0012] As a preferred option, an acoustic ranging depth gauge is installed 20cm above the settling tank; an acoustic Doppler current meter is fixed on a metal bracket and its probe is 10cm from the bottom of the annular tank; a multi-parameter turbidity meter is fixed on a metal bracket and its probe is 10cm from the bottom of the annular tank; and an underwater camera is fixed above the settling tank by a clamp.

[0013] As a preferred option, the propeller generator is equipped with blades.

[0014] A testing method for an experimental setup of deep-sea current re-erosion rate in polymetallic nodule regions, specifically including the following steps: Step S1, Test System Inspection and Initialization: Perform benchmark calibration on the acoustic ranging depth gauge to obtain the initial distance H0 from the probe to the bottom plate of the settling tank; perform zero-point and range calibration on the multi-parameter turbidimeter and establish the calibration relationship between turbidity and suspended particle concentration; perform zero-velocity calibration on the acoustic Doppler current meter and confirm that its measurement height position near the bottom is correct. S2. Construction of plume sediment bed: Pre-prepared deep-sea sediment samples and polymetallic nodule simulation samples are laid in the settling trough of the annular flume to form a uniform simulated deep-sea mining area bottom bed at the bottom of the settling trough. S3. Module Deployment and Adjustment: An acoustic ranging depth gauge, an acoustic Doppler current meter, a multi-parameter turbidimeter, and an underwater camera are deployed in the annular water tank to cover the plume deposition zone in the center of the settling tank. Simulated seawater is slowly injected into the annular water tank. When the water level reaches the set height, a baffle is raised to isolate the settling tank from the simulated seawater, thereby constructing a stable local plume redeposition and re-erosion experimental environment. During this process, each measurement module is activated to enter continuous data acquisition mode and obtain initial baseline data. S4. Formation of plume redeposition layer: After assembling all instruments, the plume sediment sample is injected into the settling tank from above the annular flume in a controlled manner, allowing it to settle naturally under still water or different flow rates and form a plume redeposition layer on the bottom surface. The spatial continuity and coverage of the sediment layer within the field of view are confirmed using an underwater camera. S5. Data Acquisition and Erosion Rate Calculation: Lower the baffle and start the annular water tank flow system to make the near-bottom flow velocity change step by step according to the set operating conditions, while simultaneously collecting the calculation data transmitted back from each module.

[0015] As a preferred option, step S5 specifically includes the following steps: S5-1, Calculation of bottom current driving force: The velocity measured by the velocity meter is U(t) near the bottom layer above the sediment layer, and the shear stress on the sediment surface is: in The shear stress Pa acting on the surface of the plume deposit, For water density, U is the seabed drag coefficient, and U is the bottom current velocity. S5-2, Correction for the influence of polymetallic nodules: Let the volume fraction of polymetallic nodules in the depositional region be . The average burial depth of the tuberculosis is D. n Define the tuberculosis enhancement coefficient: In the formula, The tuberculosis enhancement coefficient, D represents the volume fraction of polymetallic nodules. n Let m be the average burial depth of the polymetallic nodules, and α and β be the morphology and quality coefficients of the polymetallic nodules. S5-3, Erosion Status Determination: The effective critical shear stress is: In the formula This represents the equivalent critical shear stress of the sediment in the presence of polymetallic nodules. The critical shear stress of the sediment. These are conversion factors; Define the flow driving factor: In the formula As a factor of erosion degree; S5-4, Resuspension Inversion: Deposition layer geometry thickness and resuspension mass: In the formula This represents the thickness of the plume redeposition layer. The initial water depth, This is the acoustic ranging value. The concentration of suspended particles at height z; S5-5, Erosion Rate Calculation: Single-point erosion rate calculation considering nodules and flow velocity: In the formula To account for the erosion rate of plume sediments after the presence of polymetallic nodules and the influence of ocean currents, Plume sediment particle density, Porosity of the sedimentary layer The rate of change of the sedimentary layer thickness. Let be the rate of change of suspended particulate matter, when If the value is 0, it is determined that no erosion has occurred; Deposition rate under the influence of nodules: S5-6, Image Information Extraction: Extending the erosion rate at a single point across the entire field of view, the physical relationship between image grayscale and deposition thickness is shown in the original image acquired by the underwater camera: In the formula: It is represented as the planar coordinates of pixels in the image, t represents the observation time, and I is the gray value of the image; After plume sediment cover, the reflectivity and light scattering of the substrate change. Therefore, under calibration conditions, there is a functional relationship between grayscale and sediment thickness. The image is then converted into a thickness field. In the formula Represents in pixels ( The thickness of the plume deposit at time t at point ) This is the mapping function between grayscale values ​​and sediments; S5-7, Resedimentation Inversion: The average deposition thickness within the field of view is: In the formula The average sediment thickness within the field of view is denoted as A, and the field of view area acquired by the underwater camera is denoted as A.

[0016] If the area of ​​a single pixel is ΔA, then the plume deposition volume is: Total sediment volume within the field of view: In the formula: Particle density, Porosity; Joint constraints are applied between the image deposition thickness field and the acoustic single-point thickness: In the formula: The effective thickness of the deposited layer after fusion. These are the weighting coefficients; S5-8, Calculation of regional erosion rate: Image coverage weight: In the formula This represents the plume coverage area obtained from image recognition.

[0017] Total erosion rate: S5-9, Erosion Rate and Resuspension Flux Prediction: Constructing historical samples based on multi-source data: For each historical moment t i Constructing feature vectors: The corresponding output erosion rate is: The output conforms to physical constraints, and the following loss function is constructed during training: In the formula: The total erosion rate within the field of view predicted by the neural network. This represents the actual erosion rate within the field of view retrieved by the multi-sensor system. The actual erosion rate calculated from the model.

[0018] To predict the erosion rate under future operating conditions, let the future operating conditions be: The predicted future erosion rate is: Within a unit of time, the mass of sediment eroded from the bed surface will enter the overlying water body and form resuspended particles. Therefore, the resuspended mass flux per unit area within the field of view can be directly expressed by the erosion rate as: In the formula The volumetric flux of sediment resuspension. The particle density of suspended sediments. For sediment porosity, The average deposition rate is denoted as .

[0019] To ensure consistency between the calculated resuspension flux and experimental observations, the resuspension flux must satisfy the mass conservation relationship of suspended particles: In the formula The concentration of suspended sediment at height z. The effective water layer thickness near the bottom, The output flux caused by water flow transport.

[0020] Calculated resuspension volumetric flux Further used for predicting redeposition thickness variations, the relationship is as follows: In the formula The average deposition thickness within the field of view. This represents the deposition rate per unit area.

[0021] As a preferred option, step S6, mine application prediction, is also included: For the target mining area, construct the mining area state input vector: In the formula The near-bottom average current velocity in deep-sea mining areas. This represents the average shear stress at the mine bed surface. A single mining operation affects the area of ​​the mining area. The duration of a single mining operation. The abundance of nodules in polymetallic nodule ore areas. The average burial depth of the tuberculosis, The source strength of sediments released by disturbances during mining operations.

[0022] By substituting the input parameters of the mining area into the erosion rate prediction model trained based on experimental data, the average erosion rate at the mining area scale is obtained: In the formula This represents the erosion rate per unit area within the deep-sea mining area. This is a prediction model trained based on the experimental data of this invention.

[0023] This invention, by employing the above technical solutions, offers the following advantages compared to existing technologies: Compared to existing methods relying on single turbidity measurements, acoustic echoes, or discrete sampling, this invention integrates multiple sources—acoustic ranging depth gauges, turbidity meters, current meters, and underwater cameras—to simultaneously acquire sediment thickness variations, suspended particle mass flux, hydrodynamic conditions, and sediment coverage within the same experimental system. This introduces mass conservation and spatial weight constraints into the erosion rate calculation, resulting in higher physical consistency and stability in the quantification of the re-erosion process. Compared to existing methods that estimate erosion solely based on turbidity or bed elevation changes, this invention considers both sediment migration and bed surface changes during erosion rate inversion, effectively reducing uncertainties caused by single observations.

[0024] Compared to traditional experimental methods that primarily rely on single-point or single-section observations, this invention utilizes underwater cameras to conduct area-wide observations of the sedimentary bed surface. Through image recognition, it obtains plume deposition coverage and thickness fields, extending the single-point erosion rate to the regional erosion rate within the field of view. This enhances the representativeness of the experimental results for actual mining areas on a spatial scale. This point-to-area quantification approach is more applicable than existing technologies in describing the spatial distribution of plume redeposition and re-erosion.

[0025] Compared with sediment erosion models that do not consider the influence of polymetallic nodules, this invention introduces the modulation relationship between nodule volume fraction and burial depth on the bed boundary shear stress in the erosion rate calculation. This allows the experimental results to reflect the changes in sedimentary layer stability under nodule cover conditions, which helps to reduce the bias generated when homogeneous sediment models are directly applied to nodule areas, thereby improving the adaptability to polymetallic nodule mining scenarios.

[0026] Furthermore, compared with experimental methods that can only perform post-hoc analysis, this invention introduces a physically constrained neural network model based on multi-source data inversion, which allows the erosion rate to be obtained not only from current observation data, but also to be predicted under given future flow velocity and nodule coverage conditions. This enables the assessment of re-erosion trends under different operating conditions and improves the application efficiency of the experimental device in engineering scheme comparison and environmental impact analysis.

[0027] In summary, the present invention has more advantageous technical effects than the prior art in terms of the quantitative accuracy of erosion rate, spatial representativeness, and applicability to actual working conditions in polymetallic nodule regions.

[0028] Additional aspects and advantages of the invention will become apparent in the following description or may be learned by practice of the invention. Attached Figure Description

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a front view schematic diagram of the experimental apparatus of the present invention; Figure 2 This is a side view of the experimental apparatus of the present invention. Figure 3 This is a top view of the experimental apparatus of the present invention. Figure 4 This is a flowchart of the testing method of the present invention. in, Figures 1 to 3 The correspondence between the reference numerals and components in the attached drawings is as follows: 1-Acoustic ranging depth gauge, 2-Acoustic Doppler current meter, 3-Multi-parameter turbidity meter, 4-Underwater camera, 5-Clamping device, 6-Metal bracket, 7-Paddle generator, 8-Annular flume, 9-Polymetallic nodule, 10-Deep-sea sediment, 11-Settling trough, 12-Supporting frame, 13-Baffle, 14-Baffle lifter, 15-Bridge, 16-Data processor, 17-Paddle blade, 18-Flow rate controller. Detailed Implementation

[0030] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0031] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0032] The following is combined Figures 1 to 4 The experimental apparatus and testing method for the re-erosion rate of deep-sea currents in the polymetallic nodule region according to embodiments of the present invention are described in detail.

[0033] like Figures 1 to 3 As shown, this invention proposes an experimental device for the re-erosion rate of deep-sea currents in a polymetallic nodule region. The device includes an annular tank 8, supported by a load-bearing frame 12 fixedly installed at its bottom and a bridge 15 in its middle. A clamp 5 is installed on the annular tank 8, and a metal support 6 is fixedly installed at its top. A data collection module is fixedly installed on the annular tank 8 via the clamp 5 and the metal support 6. A data processor 16 is fixedly installed on the upper part of the bridge 15. A settling tank 11, connected to the bottom of the annular tank 8, is installed below the front of the annular tank 8. A propeller flow generator 7 is installed at the rear of the annular tank 8, equipped with propeller blades 17. Deep-sea sediment 10 is laid flat in the settling tank 11 until it is flush with the bottom of the annular tank 8, and polymetallic nodules 9 are distributed in the deep-sea sediment 10. The left and right side walls of the settling tank 11 are respectively equipped with baffles 13 that can be raised and lowered by baffle lifters 14. The data collection module includes an acoustic ranging depth gauge 1 and an underwater camera 4 located on the upper part of the settling tank 11, an acoustic Doppler current meter 2 located at the left end of the settling tank 11, and a multi-parameter turbidity meter 3 located at the right end of the settling tank 11. The acoustic ranging depth gauge 1 is positioned 20cm above the settling tank 11. The acoustic Doppler current meter 2 is fixed on a metal bracket 6 and measures at a distance of 10cm from the bottom of the annular water tank 8. The multi-parameter turbidity meter 3 is fixed on a metal bracket 6, with its probe 10cm from the bottom of the annular water tank 8. The underwater camera 4 is fixed above the settling tank by a clamp 5.

[0034] The annular water tank 8 is equipped with a flow rate controller 18.

[0035] A testing method for an experimental setup of deep-sea current re-erosion rate in polymetallic nodule regions, specifically including the following steps: Step S1, Test System Inspection and Initialization: Perform an integrity check on the data collection modules of the acoustic ranging depth gauge 1, acoustic Doppler current meter 2, multi-parameter turbidimeter 3, and underwater camera 4, confirming that the power supply, signal interface, and time synchronization functions of each module are normal; perform benchmark calibration on the acoustic ranging depth gauge 1 to obtain the initial distance H0 from the probe to the bottom plate of the settling tank; perform zero-point and range calibration on the multi-parameter turbidimeter 3 and establish the calibration relationship between turbidity and suspended particle concentration; perform zero-velocity calibration on the acoustic Doppler current meter 2 and confirm that its measurement height position near the bottom is correct; S2. Construction of plume sediment bed: Pre-prepared deep-sea sediment samples 10 and polymetallic nodules 9 simulated samples are laid in the settling trough 11 of the annular flume 8 to form a uniform simulated deep-sea mining area bottom bed at the bottom of the settling trough 11. S3. Module Deployment and Adjustment: According to the test design drawings, such as... Figures 1 to 3 An acoustic ranging depth gauge 1, an acoustic Doppler current meter 2, a multi-parameter turbidimeter 3, and an underwater camera 4 are deployed in the annular water tank 8 to cover the plume deposition zone in the center of the settling tank 11. Simulated seawater is slowly injected into the annular water tank 8. When the water level reaches a set height, the baffle 13 is raised to isolate the settling tank 11 from the simulated seawater, thereby constructing a stable local plume redeposition and re-erosion experimental environment. During this process, each measurement module is activated to enter a continuous data acquisition state and obtain initial baseline data. S4. Formation of plume redeposition layer: such as Figure 4 The process shown involves assembling all the instruments and then injecting the plume sediment sample into the settling tank 11 from above the annular flume 8 in a controlled manner. The sample settles naturally under still water or different flow rates and forms a plume redeposition layer on the bottom surface. An underwater camera is used to confirm the spatial continuity and coverage of the sediment layer within the field of view. S5. Data acquisition and erosion rate calculation: Lower baffle 13, start the flow system of annular water tank 8, so that the near bottom flow velocity changes step by step according to the set working conditions, and at the same time collect the calculation data transmitted back by each module. Specifically, the following steps are included: S5-1, Calculation of bottom current driving force: The velocity measured by the velocity meter is U(t) near the bottom layer above the sediment layer, and the shear stress on the sediment surface is: in The shear stress Pa acting on the surface of the plume deposit, For water density, U is the seabed drag coefficient, and U is the bottom current velocity. S5-2, Correction for the influence of polymetallic nodules: Let the volume fraction of polymetallic nodules in the depositional region be . The average burial depth of the tuberculosis is D. n Define the tuberculosis enhancement coefficient: In the formula, The tuberculosis enhancement coefficient (dimensionless) D represents the volume fraction of polymetallic nodules. n Let m be the average burial depth of the polymetallic nodules, and α and β be the morphology and quality coefficients of the polymetallic nodules. S5-3, Erosion Status Determination: The effective critical shear stress is: In the formula This represents the equivalent critical shear stress of the sediment in the presence of polymetallic nodules. The critical shear stress of the sediment. These are conversion factors; Define the flow driving factor: In the formula As a factor of erosion degree; S 5-4, Resuspension Inversion: Deposition layer geometry thickness and resuspension mass: In the formula This represents the thickness of the plume redeposition layer. The initial water depth, This is the acoustic ranging value. The concentration of suspended particles at height z; S5-5, Erosion Rate Calculation: Single-point erosion rate calculation considering nodules and flow velocity: In the formula To account for the erosion rate of plume sediments after the presence of polymetallic nodules and the influence of ocean currents, Plume sediment particle density, Porosity of the sedimentary layer The rate of change of the sedimentary layer thickness. Let be the rate of change of suspended particulate matter, when If the value is 0, it is determined that no erosion has occurred; Deposition rate under the influence of nodules: S5-6, Image Information Extraction: Extending the erosion rate at a single point across the entire field of view, the physical relationship between image grayscale and deposition thickness is shown in the original image acquired by the underwater camera: In the formula: It is represented as the planar coordinates of pixels in the image, t represents the observation time, and I is the gray value of the image; After plume sediment cover, the reflectivity and light scattering of the substrate change. Therefore, under calibration conditions, there is a functional relationship between grayscale and sediment thickness. The image is then converted into a thickness field. In the formula Represents in pixels ( The thickness of the plume deposit at time t at point ) This is the mapping function between grayscale values ​​and sediments; S5-7, Resedimentation Inversion: The average deposition thickness within the field of view is: In the formula The average sediment thickness within the field of view is denoted as A, and the field of view area acquired by the underwater camera is denoted as A.

[0036] If the area of ​​a single pixel is ΔA, then the plume deposition volume is: Total sediment volume within the field of view: In the formula: Particle density, Porosity; Joint constraints are applied between the image deposition thickness field and the acoustic single-point thickness: In the formula: The effective thickness of the deposited layer after fusion. These are the weighting coefficients; S5-8, Calculation of regional erosion rate: Image coverage weight: In the formula This represents the plume coverage area obtained from image recognition.

[0037] Total erosion rate: S5-9, Erosion Rate and Resuspension Flux Prediction: Constructing historical samples based on multi-source data: For each historical moment t i Constructing feature vectors: The corresponding output erosion rate is: The output conforms to physical constraints, and the following loss function is constructed during training: In the formula: The total erosion rate within the field of view predicted by the neural network. This represents the actual erosion rate within the field of view retrieved by the multi-sensor system. The actual erosion rate calculated from the model.

[0038] To predict the erosion rate under future operating conditions, let the future operating conditions be: The predicted future erosion rate is: Within a unit of time, the mass of sediment eroded from the bed surface will enter the overlying water body and form resuspended particles. Therefore, the resuspended mass flux per unit area within the field of view can be directly expressed by the erosion rate as: In the formula The volumetric flux of sediment resuspension. The particle density of suspended sediments. For sediment porosity, The average deposition rate is denoted as .

[0039] To ensure consistency between the calculated resuspension flux and experimental observations, the resuspension flux must satisfy the mass conservation relationship of suspended particles: In the formula The concentration of suspended sediment at height z. The effective water layer thickness near the bottom, The output flux caused by water flow transport.

[0040] Calculated resuspension volumetric flux Further used for predicting redeposition thickness variations, the relationship is as follows: In the formula The average deposition thickness within the field of view. This represents the deposition rate per unit area.

[0041] Step S6, Mining Area Application Prediction: Based on the above experimental setup and testing methods, this invention further provides a method for predicting sediment cover and resuspension in actual deep-sea polymetallic nodule mining areas. This method inputs measured or planned data from the mining area into the erosion prediction model established by this invention to quantitatively predict the total amount of sediment cover, resuspension flux, and sediment thickness distribution that may result from a single mining operation. This data is used for deep-sea mining environmental impact assessment and operational scheme optimization.

[0042] For the target mining area, construct the mining area state input vector: In the formula The near-bottom average current velocity in deep-sea mining areas. This represents the average shear stress at the mine bed surface. A single mining operation affects the area of ​​the mining area. The duration of a single mining operation. The abundance of nodules in polymetallic nodule ore areas. The average burial depth of the tuberculosis, The source strength of sediments released by disturbances during mining operations.

[0043] By substituting the input parameters of the mining area into the erosion rate prediction model trained based on experimental data, the average erosion rate at the mining area scale is obtained: In the formula This represents the erosion rate per unit area within the deep-sea mining area. This is a prediction model trained based on experimental data from this invention. By constructing a bottom flow erosion model in an annular flume or deep-water environment simulation device, and simultaneously deploying acoustic ranging depth gauges, turbidity meters, current meters, and underwater cameras, the changes in bed surface, suspended sediment concentration, and resuspension behavior of the plume sedimentary layer are monitored under controllable hydrodynamic conditions, thereby inverting the erosion rate, deposition rate, and resuspension flux of mining plume sediments.

[0044] This method avoids the problems of high cost and poor repeatability of in-situ deep-sea observation, and enables controlled research on plume deposition-erosion mechanisms under different mining disturbance intensities and flow field conditions in indoor environments.

[0045] In the description of this invention, the term "a plurality of" refers to two or more. Unless otherwise explicitly defined, the terms "upper," "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. The terms "connection," "installation," "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0046] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0047] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An experimental apparatus for the re-erosion rate of deep-sea currents in a polymetallic nodule region, comprising an annular water tank (8), characterized in that... The annular water tank (8) is supported by a load-bearing frame (12) fixedly installed at its bottom and a bridge (15) in its middle. A clamp (5) is installed on the annular water tank (8). A metal bracket (6) is fixedly installed on the top of the annular water tank (8). A data collection module is fixedly installed on the annular water tank (8) through the clamp (5) and the metal bracket (6). A data processor (16) is fixedly installed on the upper part of the bridge (15). A settling tank (11) connected to the bottom of the annular water tank (8) is installed below the front part of the annular water tank (8). A propeller flow generator (7) is set in the rear part of the annular water tank (8). Deep-sea sediments (10) are laid flat in the settling tank (11) to be flush with the bottom of the annular water tank (8), and polymetallic nodules (9) are distributed in the deep-sea sediments (10). The left and right side walls of the settling tank (11) are respectively equipped with partitions (13) that can be raised and lowered by partition lifters (14). The data collection module includes an acoustic ranging depth gauge (1) and an underwater camera (4) located at the top of the settling tank (11), an acoustic Doppler current meter (2) located at the left end of the settling tank (11), and a multi-parameter turbidity meter (3) located at the right end of the settling tank (11). The annular water tank (8) is equipped with a flow rate controller (18).

2. The experimental apparatus for the re-erosion rate of deep-sea currents in a polymetallic nodule region according to claim 1, characterized in that... The acoustic ranging depth gauge (1) is installed 20cm above the settling tank (11); the acoustic Doppler current meter (2) is fixed on the metal bracket (6) and its probe is 10cm away from the bottom of the annular water tank (8); the multi-parameter turbidity meter (3) is fixed on the metal bracket (6) and its probe is 10cm away from the bottom of the annular water tank (8); the underwater camera (4) is fixed above the settling tank by a clamp (5).

3. The experimental apparatus for the re-erosion rate of deep-sea currents in a polymetallic nodule region according to claim 1, characterized in that... The propeller flow generator (7) is equipped with blades (17).

4. A test method for an experimental apparatus for the re-erosion rate of deep-sea currents in polymetallic nodule regions, characterized in that... Specifically, it includes the following steps: Step S1, Test System Inspection and Initialization: Perform benchmark calibration on the acoustic ranging depth gauge (1) and obtain the initial distance H0 from the probe to the bottom plate of the settling tank; perform zero-point and range calibration on the multi-parameter turbidimeter (3) and establish the calibration relationship between turbidity and suspended particle concentration; perform zero-velocity calibration on the acoustic Doppler velocimeter (2) and confirm that its measurement height position near the bottom is correct; S2, Construction of plume sediment bed: Pre-prepared deep-sea sediment (10) samples and polymetallic nodule (9) simulation samples are laid in the settling trough (11) of the annular flume (8) to form a uniform simulated deep-sea mining area bottom bed at the bottom of the settling trough (11). S3. Module Deployment and Adjustment: An acoustic ranging depth gauge (1), an acoustic Doppler current meter (2), a multi-parameter turbidity meter (3), and an underwater camera (4) are deployed in the annular water tank (8) to cover the plume deposition area in the center of the settling tank (11). Simulated seawater is slowly injected into the annular water tank (8). When the water level reaches the set height, the baffle (13) is raised to isolate the settling tank (11) from the simulated seawater, thereby constructing a stable local plume redeposition and re-erosion experimental environment. During this process, each measurement module is activated to enter the continuous data acquisition state and obtain the initial baseline data. S4. Formation of plume redeposition layer: After assembling all instruments, the plume sediment sample is injected into the settling tank (11) from above the annular water tank (8) in a controlled manner, so that it settles naturally under still water or different flow rates and forms a plume redeposition layer on the bottom surface. The spatial continuity and coverage of the sediment layer within the field of view are confirmed by an underwater camera. S5. Data acquisition and erosion rate calculation: Lower the baffle (13), start the flow system of the annular water tank (8), so that the near bottom flow velocity changes step by step according to the set working conditions, and at the same time collect the calculation data transmitted back by each module.

5. The testing method for the experimental apparatus for the re-erosion rate of deep-sea currents in a polymetallic nodule region according to claim 4, characterized in that... Step S5 specifically includes the following steps: S5-1, Calculation of bottom current driving force: The velocity measured by the velocity meter is U(t) near the bottom layer above the sediment layer, and the shear stress on the sediment surface is: in The shear stress Pa acting on the surface of the plume deposit, For water density, U is the seabed drag coefficient, and U is the bottom current velocity. S5-2, Correction for the influence of polymetallic nodules: Let the volume fraction of polymetallic nodules in the depositional region be . The average burial depth of the tuberculosis is D. n Define the tuberculosis enhancement coefficient: In the formula, The tuberculosis enhancement coefficient, D represents the volume fraction of polymetallic nodules. n Let m be the average burial depth of the polymetallic nodules, and α and β be the morphology and quality coefficients of the polymetallic nodules. S5-3, Erosion Status Determination: The effective critical shear stress is: In the formula This represents the equivalent critical shear stress of the sediment in the presence of polymetallic nodules. The critical shear stress of the sediment. These are conversion factors; Define the flow driving factor: In the formula This is a factor representing the degree of erosion. S 5-4, Resuspension Inversion: Sediment layer geometry thickness and resuspension mass: In the formula This represents the thickness of the plume redeposition layer. The initial water depth, This is the acoustic ranging value. The concentration of suspended particles at height z; S5-5, Erosion Rate Calculation: Single-point erosion rate calculation considering nodules and flow velocity: In the formula To account for the erosion rate of plume sediments after the presence of polymetallic nodules and the influence of ocean currents, Plume sediment particle density, Porosity of the sedimentary layer The rate of change of the sedimentary layer thickness. Let be the rate of change of suspended particulate mass, when If the value is 0, it is determined that no erosion has occurred; Deposition rate under the influence of nodules: S5-6, Image Information Extraction: Extending the erosion rate at a single point across the entire field of view, the physical relationship between image grayscale and deposition thickness is shown in the original image acquired by the underwater camera: In the formula: It is represented as the planar coordinates of pixels in the image, t represents the observation time, and I is the gray value of the image; After plume sediment cover, the reflectivity and light scattering of the substrate change. Therefore, under calibration conditions, there is a functional relationship between grayscale and sediment thickness. The image is then converted into a thickness field. In the formula Represents in pixels ( The thickness of the plume deposit at time t at point ) This is the mapping function between grayscale values ​​and sediments; S5-7, Resedimentation Inversion: The average deposition thickness within the field of view is: In the formula The average sediment thickness within the field of view is denoted as A, and the field of view area acquired by the underwater camera is denoted as A. If the area of ​​a single pixel is ΔA, then the plume deposition volume is: Total sediment volume within the field of view: In the formula: Particle density, Porosity; Joint constraints are applied between the image deposition thickness field and the acoustic single-point thickness: In the formula: The effective thickness of the deposited layer after fusion. These are the weighting coefficients; S5-8, Calculation of regional erosion rate: Image coverage weight: In the formula This represents the plume coverage area obtained from image recognition. Total erosion rate: S5-9, Erosion Rate and Resuspension Flux Prediction: Constructing historical samples based on multi-source data: For each historical moment t i Constructing feature vectors: The corresponding output erosion rate is: The output conforms to physical constraints, and the following loss function is constructed during training: In the formula: The total erosion rate within the field of view predicted by the neural network. This represents the actual erosion rate within the field of view retrieved by the multi-sensor system. The actual erosion rate calculated from the model. To predict the erosion rate under future operating conditions, let the future operating conditions be: The predicted future erosion rate is: Within a unit of time, the mass of sediment eroded from the bed surface will enter the overlying water body and form resuspended particles. Therefore, the resuspended mass flux per unit area within the field of view can be directly expressed by the erosion rate as: In the formula The volumetric flux of sediment resuspension. The particle density of suspended sediments. For sediment porosity, The average deposition rate is denoted as . To ensure consistency between the calculated resuspension flux and experimental observations, the resuspension flux must satisfy the mass conservation relationship of suspended particles: In the formula The concentration of suspended sediment at height z. The effective water layer thickness near the bottom, The output flux caused by water flow transport. Calculated resuspension volumetric flux Further used for predicting redeposition thickness variations, the relationship is as follows: In the formula The average deposition thickness within the field of view. This represents the deposition rate per unit area.

6. The testing method for the experimental apparatus for the re-erosion rate of deep-sea currents in a polymetallic nodule region according to claim 4, characterized in that... It also includes step S6, mining area application prediction: For the target mining area, construct the mining area state input vector: In the formula The near-bottom average current velocity in deep-sea mining areas. This represents the average shear stress at the mine bed surface. A single mining operation affects the area of ​​the mining area. The duration of a single mining operation. The abundance of nodules in polymetallic nodule ore areas. The average burial depth of the tuberculosis, The source strength of sediments released by disturbances during mining operations. By substituting the input parameters of the mining area into the erosion rate prediction model trained based on experimental data, the average erosion rate at the mining area scale is obtained: In the formula This represents the erosion rate per unit area within the deep-sea mining area. This is a prediction model trained based on the experimental data of this invention.

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