Offshore sand wave environment under the local scour of pile foundation optical fiber sensing monitoring device and method

Abstract

The application provides a kind of offshore sand wave environment under the local scouring of pile foundation optical fiber sensing monitoring device and method, belong to offshore engineering monitoring technical field, device includes optical fiber sensing module, data acquisition unit, data processing unit and early warning module, constitute " perception-acquisition-processing-early warning " automation closed loop system;Method contains system layout, data acquisition, processing analysis, early warning release and regular calibration steps.This scheme borrows mixed optical fiber sensing to obtain seabed scouring form and pile strain, combined with Brillouin / Raman scattering technology, numerical simulation auxiliary and multi-source calibration to improve precision, through trend prediction to realize active early warning, solve the problem of traditional monitoring dispersion, rely on artificial, low precision, suitable for harsh offshore unmanned monitoring, provide reliable support for pile foundation safety.

Description

Technical Field

[0001] This invention relates to the field of nearshore engineering monitoring technology, specifically to a fiber optic sensing monitoring device and method for local scour of pile foundations in nearshore sand wave environments. Background Technology

[0002] Traditional monitoring of localized scour of nearshore pile foundations has significant limitations: First, the monitoring methods are singular and scattered, making it difficult to simultaneously meet the dual requirements of "large-scale seabed morphology coverage" and "high-precision measurement of key points in the pile body"; second, it relies on manual inspections, which are difficult and unsafe to operate in harsh nearshore environments (such as high waves and high salt spray), and cannot guarantee the real-time and continuous nature of monitoring; third, data interpretation lacks support, is easily affected by environmental interference, lacks multi-source data verification and calibration mechanisms, and makes it difficult to establish the correlation between "seabed scour and pile response," resulting in insufficient accuracy and robustness of monitoring results, and failing to provide timely and reliable decision-making basis for pile foundation safety protection. Summary of the Invention

[0003] The present invention aims to solve the problems mentioned in the background art by providing a fiber optic sensing monitoring device and method for local scour of pile foundations in nearshore sand wave environments.

[0004] The specific technical solution is as follows: A fiber optic sensing monitoring device for localized scour of pile foundations in nearshore sand wave environments includes: Fiber optic sensing modules are deployed on the seabed around the pile foundation and on the surface of the pile body to monitor the morphology of scour pits and the strain of the pile body in real time. The data acquisition unit, connected to the fiber optic sensing module, is used to acquire the optical signal output by the fiber optic sensing module and convert it into an electrical signal. The data processing unit, connected to the data acquisition unit, is used to process and analyze electrical signals to extract information on scour depth, scour range, and pile stress distribution. The early warning module, connected to the data processing unit, is used to issue a scour early warning signal based on a preset threshold. The fiber optic sensing module, data acquisition unit, data processing unit, and early warning module are connected in sequence to form a complete monitoring system.

[0005] The aforementioned fiber optic sensing monitoring device for localized scour of pile foundations in nearshore sand wave environments includes a fiber optic sensing module comprising distributed fiber optic sensors and point-type fiber optic grating sensors. The distributed fiber optic sensors are arranged in a mesh pattern along the seabed around the pile, while the point-type fiber optic grating sensors are arranged along the axial and circumferential directions of the pile.

[0006] The aforementioned fiber optic sensing monitoring device for localized scour of pile foundations in nearshore sand wave environments, wherein the distributed fiber optic sensor is implemented using a Brillouin optical time domain reflectometer or a Raman optical time domain reflectometer.

[0007] The aforementioned fiber optic sensing monitoring device for localized scour of pile foundations in nearshore sand wave environments includes a data acquisition unit comprising an optical signal demodulator and a signal amplifier, used to enhance the optical signal and convert it into a digital signal.

[0008] The fiber optic sensing monitoring device for local scour of pile foundations in the aforementioned nearshore sand wave environment includes a data processing unit with a built-in scour depth calculation module, stress analysis module, and trend prediction module, which are used to realize dynamic simulation and prediction of scour evolution.

[0009] The aforementioned fiber optic sensing monitoring device for localized scour of pile foundations in nearshore sand wave environments includes an early warning module comprising an audible and visual alarm and a remote communication unit, which supports sending early warning information to the monitoring center via a wireless network.

[0010] This invention also provides a method for monitoring localized scour of pile foundations in nearshore sand wave environments, employing the aforementioned fiber optic sensing monitoring device for localized scour of pile foundations in nearshore sand wave environments, comprising the following steps: Fiber optic sensing modules were deployed on the seabed around the pile and on the pile itself. The fiber optic sensor signal is acquired in real time through the data acquisition unit; The data processing unit is used to analyze the signals and obtain data on the erosion pit morphology and pile stress. Determine whether to trigger the early warning module based on the analysis results.

[0011] The above-mentioned monitoring method for local scour of pile foundations in nearshore sand wave environment includes a data processing step that involves inverting the scour depth based on numerical simulation results and verifying it in conjunction with physical model experimental data.

[0012] The above-mentioned monitoring method for local scour of pile foundations in nearshore sand wave environment, wherein the early warning triggering condition is that the scour depth exceeds 0.2 times the pile diameter or the pile stress exceeds 80% of the material's allowable stress.

[0013] The aforementioned monitoring method for localized scour of pile foundations in nearshore sand wave environments also includes a step of periodically calibrating the fiber optic sensing module. The calibration method includes comparing data with ADV current meters and topographic scanners.

[0014] The present invention has the following beneficial effects: 1. Enhanced comprehensive perception: Through a hybrid fiber optic sensing strategy of "distributed + point", it achieves comprehensive coverage from "the source of seabed scour" to "the response of the pile structure", which can not only obtain the macroscopic morphological evolution of scour pits, but also capture the stress concentration of key sections of the pile body, thus solving the "fragmented" problem of traditional monitoring.

[0015] 2. Optimization of monitoring efficiency and reliability: Automated closed-loop operation significantly reduces reliance on manual labor, improves the real-time and continuous nature of monitoring, and is adaptable to unmanned monitoring in harsh near-shore environments; at the same time, it enhances the ability to capture weak signals through "low-noise amplification + high-resolution demodulation", and reduces the ambiguity of data inversion by combining "numerical simulation prior knowledge + multi-source calibration", thereby improving the accuracy and long-term stability of monitoring data.

[0016] 3. Upgraded forward-looking safety decision-making: The trend prediction function (machine learning / numerical extrapolation) of the data processing unit drives the system to shift from "passive monitoring" to "proactive predictive maintenance", which can predict future safety conditions; the multi-dimensional safety threshold model (geometry + structure) avoids misjudgment by a single indicator, and the early warning results are directly related to the safety margin of the pile foundation, providing a more scientific and guiding basis for the formulation of protective measures. Attached Figure Description

[0017] Figure 1 A schematic diagram of the architecture of the fiber optic sensing monitoring device for local scour of pile foundations in nearshore sand wave environment provided in an embodiment of the present invention. Figure 2 A graph showing the change in scour depth of a pile foundation over time in a nearshore sand wave environment, provided as an embodiment of the present invention. Figure 3 The stress distribution curve of the pile foundation in a near-shore sand wave environment is provided for the embodiments of the present invention. Figure 4 A comparison chart of early warning thresholds for the fiber optic sensing monitoring device for local scour of pile foundations in nearshore sand wave environment provided in an embodiment of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0019] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this application. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0020] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present 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. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] Example 1 Reference Figure 1-4 ,in: Figure 2 The horizontal axis represents time (0-10 days); the vertical axis represents scour depth (0-0.5 meters); the curves represent the following: the blue curve simulates the scour depth fluctuating sinusoidally and increasing linearly over time; the red dashed line represents the warning threshold of 20% of the pile diameter (0.2 meters). This figure demonstrates the device's real-time monitoring capability for the dynamic evolution of the scour pit. Figure 3 The horizontal axis represents the pile position (0-10 meters, from pile top to pile bottom); the vertical axis represents the stress value (0-50 MPa); the curves represent the following: the green curve simulates the stress distribution along the pile body with exponential decay and periodic fluctuations, and the red dashed line represents the warning threshold of 80% of the material's yield strength (40 MPa). This figure reflects the three-dimensional monitoring accuracy of the device in responding to the pile structure. Figure 4 The horizontal axis represents three monitoring points; the vertical axis represents numerical values ​​(meters / MPa); data comparison: the blue bars represent the measured values ​​of scour depth (0.18 / 0.22 / 0.25 meters for monitoring points 1-3 respectively), the green bars represent the measured values ​​of stress (35 / 42 / 38 MPa), and the red / magenta dashed lines represent the corresponding thresholds. This figure intuitively demonstrates the multi-parameter early warning decision-making logic.

[0023] The fiber optic sensing monitoring device for localized scour of pile foundations in nearshore sand wave environments provided in this embodiment, such as... Figures 1-4As shown, it includes: a fiber optic sensing module, a data acquisition unit, a data processing unit, and an early warning module, wherein: The fiber optic sensing module consists of several sensing fibers, which are densely arranged in a predetermined topology on the surface of the pile foundation and in the surrounding seabed area. They are used to sense changes in seabed morphology and strain of the pile structure caused by scouring, and generate corresponding changes in optical signals. The data acquisition unit is optically connected to the fiber optic sensing module via a waterproof optical cable. This unit has a built-in optical signal demodulator and analog-to-digital converter, which are used to receive, demodulate optical signals and convert them into digital electrical signals in real time. The data processing unit is electrically connected to the data acquisition unit via a data bus. This unit includes a processor and a memory, which stores analysis algorithm programs for interpreting, calculating, and analyzing the received digital electrical signals, thereby quantitatively extracting the depth and planar distribution range of the scour pit, as well as the stress and strain distribution data of the pile structure. The early warning module is connected to the data processing unit via a communication interface. This module has a built-in comparator and communication circuit, which is used to compare the real-time monitoring data output by the data processing unit with the safety threshold preset in the memory. When the data exceeds the threshold range, an early warning signal is automatically generated and issued. The fiber optic sensing module, data acquisition unit, data processing unit, and early warning module are connected in sequence to form an automated closed-loop monitoring system that integrates signal sensing, acquisition, processing, and risk warning.

[0024] This solution achieves integrated monitoring of the entire process of pile foundation scour and multiple parameters (morphology and mechanics) by constructing an automated system that integrates sensing, acquisition, processing and early warning, overcoming the limitations of traditional single and decentralized monitoring methods.

[0025] By utilizing fiber optic sensors deployed on the pile body and seabed, comprehensive perception of scour phenomena from the source (seabed) to the structural response (pile body) was achieved, providing more comprehensive and more correlated monitoring data, laying a solid foundation for accurately judging the structural safety status.

[0026] The closed-loop automated operation of the system significantly reduces reliance on external manual inspections and improves the real-time and continuous nature of monitoring. It is especially suitable for nearshore waters with harsh environments and inaccessible to personnel, achieving unmanned and intelligent monitoring.

[0027] Specifically, in this embodiment, the fiber optic sensing module includes distributed fiber optic sensors and point-type fiber optic grating sensors. The distributed fiber optic sensors are laid in a grid or ring pattern on the surface of the seabed around the pile and in the shallow layer to sense large-scale scour topographic changes. The point-type fiber optic grating sensors are fixedly installed in an array on the surface or inside the pile structure, distributed along the axial and circumferential directions of the pile, to accurately measure the strain and temperature at key locations.

[0028] This scheme employs a hybrid sensing strategy combining "distributed" and "point" sensors, offering the advantages of both wide-area coverage measurement and high-precision measurement of key points. Distributed optical fibers provide information on the overall morphological evolution of scour pits, while point gratings accurately capture stress concentration phenomena at key sections of the pile, achieving complementary macroscopic and microscopic monitoring.

[0029] This arrangement optimizes the performance and cost of the sensor network, ensuring the acquisition of critical data while avoiding the waste of sensor resources.

[0030] Specifically, in this embodiment, the distributed optical fiber sensor is implemented using sensing technology based on Brillouin scattering optical time domain reflectometer or Raman scattering optical time domain reflectometer, which can acquire strain and temperature information continuously distributed along the length of the optical fiber.

[0031] This scheme utilizes distributed sensing technology based on the principles of Brillouin or Raman scattering to achieve truly continuous spatial measurement. It can locate deformation at any position on the edge of the scour pit without the need for preset measurement points, and has high spatial resolution and measurement efficiency. It can simultaneously sense strain and temperature, and eliminate the cross-sensitivity effect of temperature changes on strain measurement through data analysis, thereby improving the accuracy of pure strain measurement caused by scour.

[0032] Specifically, in this embodiment, the data acquisition unit includes a high-resolution optical signal demodulator and a low-noise signal amplifier; the optical signal demodulator is used to identify changes in the optical wavelength or optical power returned by the optical fiber sensing module; the signal amplifier is used to amplify the converted weak electrical signal to improve the signal-to-noise ratio and measurement accuracy.

[0033] This scheme, through the combination of high-resolution demodulation and low-noise amplification, significantly enhances the system's ability to capture weak signals, enabling the device to effectively detect early and slight scour signals, thereby improving monitoring sensitivity and early warning capabilities. The high signal-to-noise ratio ensures the signal quality received by the subsequent data processing unit, providing a prerequisite for accurate and reliable data analysis and reducing the risk of false alarms and missed alarms.

[0034] Specifically, in this embodiment, the algorithm program built into the data processing unit includes: The scour depth calculation module is used to invert seabed elevation changes based on strain changes in distributed optical fibers and calculate scour depth. The stress analysis module is used to calculate the actual stress distribution of the pile structure based on the wavelength drift of the point fiber grating. The trend prediction module uses machine learning or numerical extrapolation algorithms based on historical monitoring data to predict scour development trends and pile safety.

[0035] This solution uses a dedicated software module to deeply process the raw data, transforming it into physical quantities with direct engineering significance (such as scour depth and stress value), greatly improving the intuitiveness and usability of the monitoring results. The introduction of trend prediction function enables the system to move from passive monitoring to proactive prediction, predicting the safety situation in the future and providing forward-looking decision support for taking protective measures, thus realizing predictive maintenance.

[0036] The scour depth calculation module uses the following scour depth inversion model: ; in: D s (t) represents the scouring depth at time t (unit: m). D0 is the initial seabed height (unit: m); ε(x,t) is the strain (unit: μm / m) measured by the distributed fiber optic sensor at position x at time t. ε0(x) is the initial strain reference, obtained after system calibration (unit: μm / m). L is the coverage length of the sensing fiber (unit: m). K sat The saturated strain coefficient of sediment is determined by calibration tests (unitless). β is the time decay coefficient, reflecting the characteristic of erosion rate decaying with time under sand wave environment (unit: day). -1 ); α is a proportionality coefficient, which is related to factors such as sediment type and flow velocity (unitless).

[0037] I. Derivation Process This model is derived based on the following physical assumptions and observational phenomena: 1. Strain changes caused by scouring are positively correlated with scouring depth: The strain changes sensed by the distributed optical fiber sensor mainly originate from the bending or stretching of optical fibers caused by soil loss.

[0038] 2. The scouring rate decays over time in a sand-eroded environment: the initial scouring rate is high, but it gradually approaches saturation as the scouring pit develops, exhibiting an exponential decay term (1-e). -βt Simulate the process.

[0039] 3. Strain response exhibits saturation characteristics: When scouring reaches a certain depth, strain change tends to saturate. Introducing K... sat Make corrections.

[0040] In summary, an integral inversion model is established. By integrating the strain change over the entire length of the optical fiber and combining it with time decay and saturation characteristics, the scour depth is obtained.

[0041] II. Example: Assume that the strain value at each point of a distributed fiber optic sensor deployed on the seabed around a pile is ε(x,t) at a certain time t. The initial strain ε0(x) and parameter K are known. sat =0.05, β=0.1day -1 If α=0.8 and D0=0m, then the current scour depth can be calculated through numerical integration: .

[0042] III. Technical Effects Improve inversion accuracy: combine time decay and saturation characteristics to better reflect the physical process of scouring development under sand wave environment; Enhanced robustness: Local noise is smoothed through integral forms to improve anti-interference capability; Supports dynamic forecasting: The model includes a time term and can be combined with the trend forecasting module to achieve scour development forecasting; Multi-parameter adaptive: coefficients α, β, K sat It can be dynamically updated through machine learning or on-site data to adapt to different environments.

[0043] IV. Working Principle and Flowchart 1. Data sensing: Distributed fiber optic sensors acquire the seabed strain distribution ε(x,t) in real time; 2. Benchmark Comparison: Compare with the initial strain ε0(x) to obtain the strain change; 3. Model Calculation: Substitute the data into the inversion model and calculate the current scour depth D using numerical integration. s (t); 4. Threshold comparison: D s (t) is compared with a preset threshold (e.g., 0.2 times the pile diameter); 5. Warning Trigger: If the limit is exceeded, the warning module will be triggered.

[0044] Specifically, in this embodiment, the early warning module includes an on-site audible and visual alarm and a remote communication unit; the remote communication unit supports 4G / 5G or satellite communication protocols and is used to wirelessly transmit early warning information and key monitoring data to a remote monitoring center or designated terminal.

[0045] The solution provides immediate on-site warnings through on-site audible and visual alarms, facilitating rapid response by on-site staff. Through remote communication, it enables long-distance, wireless transmission of monitoring information, breaking geographical limitations and allowing managers to have a comprehensive view of the status of multiple pile foundations from the rear monitoring center, achieving remote centralized monitoring and efficient management.

[0046] Example 2 Unlike Example 1, this example provides a method for monitoring localized scour of pile foundations in a nearshore sand wave environment. It employs the monitoring device for localized scour of pile foundations in a nearshore sand wave environment described in Example 1, and includes the following steps: S1. System deployment steps: After the pile foundation construction or before maintenance, the fiber optic sensing modules are deployed on the pile body and the surrounding seabed according to the designed topology. S2. Data acquisition steps: Start the data acquisition unit to acquire the optical signals of the fiber optic sensing module in real time or periodically at a predetermined sampling frequency; S3. Data processing and analysis steps: The data processing unit calls the built-in algorithm to process the collected signals and analyze the depth, range, three-dimensional shape map of the scour pit and the stress distribution cloud map of the pile body in real time. S4. Warning Judgment and Issuance Steps: The parsed real-time data is compared with the preset safety threshold model. If the threshold is exceeded, the warning module is triggered to issue a warning.

[0047] This method defines a standardized and streamlined operating procedure, ensuring the orderliness of the monitoring process and the repeatability of the results. Through the complete steps from deployment to early warning, it realizes the whole-process management of pile foundation scour "sensing-diagnosis-early warning", forming an effective solution, rather than just a collection of scattered technologies.

[0048] Specifically, in this embodiment, the data processing and analysis steps include using the simulation results of a pre-established scour hydrodynamic-sediment migration coupling model using numerical simulation software (such as FLUENT) as a prior knowledge base to assist in the inversion interpretation and accuracy correction of the measured data.

[0049] This scheme combines numerical simulation predictions with field measurement data, enabling mutual verification and correction. Utilizing prior knowledge from simulation can reduce the ambiguity of inversion and improve the accuracy and reliability of scour pattern interpretation; it forms a prototype of a "digital twin," enhancing the depth of understanding and knowledge of complex physical phenomena (scour) through the interaction between the virtual model and the physical entity.

[0050] Specifically, in this embodiment, the safety threshold model in the early warning judgment and issuance step includes, but is not limited to: Geometric thresholds: such as the ratio threshold of scour depth to pile diameter; Thresholds based on structural response: such as the threshold for the ratio of stress at key sections of the pile to the material's yield strength.

[0051] This scheme employs a multi-indicator, multi-dimensional threshold judgment model, avoiding potential misjudgments caused by a single indicator. It considers both the "quantity" (depth) of scour and its "effect" (impact on the structure), making the early warning judgment more comprehensive and scientific. The threshold based on structural response is directly linked to the structural safety margin of the pile foundation, achieving an upgrade from "geometric alarm" to "substantive safety alarm," thus enhancing the engineering guidance significance of the early warning.

[0052] Specifically, in this embodiment, a system calibration step is also included: periodically or after a major storm or scour event, the flow field around the pile is measured using an acoustic Doppler current profiler, the actual scour topography is measured using a high-precision underwater 3D scanner, and the measured data is cross-compared and calibrated with the data from the fiber optic monitoring system.

[0053] This scheme introduces a periodic calibration mechanism, utilizing other high-precision instruments as benchmarks to effectively eliminate potential systematic errors and long-term drift in the fiber optic monitoring system, ensuring the long-term accuracy and stability of monitoring data throughout the project lifecycle. Through multi-source data fusion calibration, the robustness and reliability of the entire monitoring system are enhanced, making its output a reliable basis for engineering decisions.

[0054] In summary, this solution takes "hybrid fiber optic sensing + automated closed loop" as its core, constructing a complete logical chain from signal perception to risk warning, as detailed below: 1. Signal Sensing: Through a hybrid topology of “distributed fiber optic sensors (grid / surrounded on the seabed around the pile) + point fiber optic grating sensors (array on the pile body)”, the morphological changes (distributed) caused by seabed scouring and the strain of the pile body structure (point) are simultaneously sensed and converted into changes in optical signals; among them, the distributed sensing is based on the Brillouin / Raman scattering principle, which can realize continuous spatial measurement, and the point sensing can accurately capture the stress of key sections.

[0055] 2. Signal Conversion: The data acquisition unit receives optical signals through a waterproof optical cable. After passing through the built-in optical signal demodulator, analog-to-digital converter, and low-noise amplifier, the signal is processed from "optical signal → demodulation → digital electrical signal → signal amplification" to improve the signal-to-noise ratio of weak signals.

[0056] 3. Data Analysis: The data processing unit receives digital electrical signals through the data bus, calls the built-in algorithms (scour depth calculation, stress analysis, trend prediction), and combines the prior knowledge of the "hydraulic-sediment migration coupling model" of numerical simulation (such as FLUENT) to quantitatively extract the scour pit depth / plane range, pile stress and strain distribution, and realize the prediction of scour development trend.

[0057] 4. Risk Warning: The warning module acquires processed data through the communication interface and compares it with preset "geometric morphology threshold (such as scour depth / pile diameter ratio) + structural response threshold (such as stress / material yield strength ratio)". If the limit is exceeded, an immediate warning is issued through the on-site audible and visual alarm, and the information is transmitted to the remote monitoring center through 4G / 5G / satellite communication, forming an automated closed loop of "sensing-collection-processing-warning".

[0058] How to use Based on the above monitoring device, the monitoring process is standardized and streamlined, and the specific steps are as follows: S1. System deployment steps: After the pile foundation is constructed or before maintenance, according to the designed topology, the distributed optical fiber sensors are laid on the seabed surface and shallow layer around the pile, and the point-type fiber optic grating sensors are fixed on the surface / inside of the pile (distributed along the axial direction and circumferential direction).

[0059] S2. Data acquisition steps: Start the data acquisition unit to acquire the optical signals output by the fiber optic sensing module at a predetermined sampling frequency (real-time / periodic).

[0060] S3. Data Processing and Analysis Steps: The data processing unit calls the algorithm to interpret the digital electrical signal, combines the prior knowledge of numerical simulation to generate a three-dimensional morphological map of the scour pit and a cloud map of the stress distribution of the pile body, and predicts the direction of scour development through the trend prediction module.

[0061] S4. Early Warning Judgment and Issuance Steps: Compare real-time monitoring data with a multi-dimensional safety threshold model. If the data exceeds the limit, trigger the early warning module and simultaneously issue on-site audible and visual early warnings and remote early warning information.

[0062] S5. System calibration steps: Periodically or after large winds, waves, or scour events, use an acoustic Doppler current profiler (to measure the flow field) and a high-precision underwater 3D scanner (to measure the actual scour topography) to cross-compare and calibrate with fiber optic monitoring data to eliminate system errors and long-term drift.

[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A fiber optic sensing monitoring device for localized scour of pile foundations in nearshore sand wave environments, characterized in that, include: Fiber optic sensing modules are deployed on the seabed around the pile foundation and on the surface of the pile body to monitor the morphology of scour pits and the strain of the pile body in real time. The data acquisition unit, connected to the fiber optic sensing module, is used to acquire the optical signal output by the fiber optic sensing module and convert it into an electrical signal. The data processing unit, connected to the data acquisition unit, is used to process and analyze electrical signals to extract information on scour depth, scour range, and pile stress distribution. The early warning module, connected to the data processing unit, is used to issue a scour early warning signal based on a preset threshold. The fiber optic sensing module, data acquisition unit, data processing unit, and early warning module are connected in sequence to form a complete monitoring system. The fiber optic sensing module includes distributed fiber optic sensors and point-type fiber optic grating sensors. The distributed fiber optic sensors are arranged in a mesh pattern along the seabed around the pile, while the point-type fiber optic grating sensors are arranged along the axial and circumferential directions of the pile. The distributed fiber optic sensors are implemented using Brillouin optical time-domain reflectometers or Raman optical time-domain reflectometers. The data processing unit has a built-in scour depth calculation module, stress analysis module, and trend prediction module, used to realize the dynamic simulation and prediction of scour evolution. The scour depth calculation module uses the following model to invert the scour depth: ;in, The scouring depth at time t; This represents the initial seabed height. The strain measured by the distributed fiber optic sensor at location x at time t; The initial strain reference is L; the coverage length of the sensing fiber is L. The saturated strain coefficient of sediment; This is the time decay coefficient; This is the proportionality coefficient.

2. The fiber optic sensing monitoring device for localized scour of pile foundations in nearshore sand wave environments according to claim 1, characterized in that, The data acquisition unit includes an optical signal demodulator and a signal amplifier, which are used to enhance the optical signal and convert it into a digital signal.

3. The fiber optic sensing monitoring device for localized scour of pile foundations in nearshore sand wave environments according to claim 1, characterized in that, The early warning module includes an audible and visual alarm and a remote communication unit, which supports sending early warning information to the monitoring center via a wireless network.

4. The fiber optic sensing monitoring device for localized scour of pile foundations in nearshore sand wave environments according to claim 1, characterized in that, The working principle and process of the scour depth calculation module using the scour depth inversion model are as follows: S1. Data Sensing: Distributed fiber optic sensors acquire real-time seabed strain distribution data. ; S2. Benchmark Comparison: Compared with initial strain By comparison, the change in strain is obtained; S3. Model Calculation: Substitute the data into the inversion model and calculate the current scour depth using numerical integration. ; S4. Threshold Comparison: ... Compare with a preset threshold; S5. Warning Trigger: If the limit is exceeded, the warning module will be triggered.

5. A method for monitoring localized scour of pile foundations in a nearshore sand wave environment, comprising using a fiber optic sensing monitoring device for localized scour of pile foundations in a nearshore sand wave environment according to any one of claims 1 to 4, characterized in that, Includes the following steps: Fiber optic sensing modules were deployed on the seabed around the pile and on the pile itself. The fiber optic sensor signal is acquired in real time through the data acquisition unit; The data processing unit is used to analyze the signals and obtain data on the erosion pit morphology and pile stress. Determine whether to trigger the early warning module based on the analysis results.

6. The monitoring method for local scour of pile foundations in nearshore sand wave environments according to claim 5, characterized in that, The data processing steps include inverting the scour depth based on numerical simulation results and verifying it in conjunction with experimental data from a physical model.

7. The monitoring method for local scour of pile foundations in nearshore sand wave environments according to claim 5, characterized in that, The warning is triggered when the scour depth exceeds 0.2 times the pile diameter or the pile stress exceeds 80% of the material's allowable stress.

8. The monitoring method for local scour of pile foundations in nearshore sand wave environment according to claim 5, characterized in that, It also includes the step of periodically calibrating the fiber optic sensing module, and the calibration method includes comparing data with ADV current meters and terrain scanners.

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