Coastal slope deformation cooperative monitoring method based on dual wavelength and fiber grating network

Abstract

The invention discloses a coast slope deformation cooperative monitoring method based on dual wavelengths and a fiber grating network, and belongs to the technical field of geotechnical engineering safety monitoring, and the method comprises the steps: carrying out the sensor deployment of a top edge layer, a bevel edge layer and a bottom edge layer of a coast slope according to a network topology structure; working wavelengths of a top edge layer sensor and a bevel edge layer sensor are distributed, spectral separation of environmental interference and deformation signals is achieved, then parameters are dynamically calibrated, signals are collected to extract strain, interference of tidal action is removed through hydrostatic pressure compensation and wave filtering, and signal accuracy is ensured; annual scale monitoring accumulated displacement correction and sensor service life prediction are carried out on the top edge layer sensor and the bottom edge layer sensor. According to the invention, the space cooperation of the three-layer network and the fusion of the dual-wavelength signals are realized, the slope deformation is dynamically corrected and accurately monitored through multi-layer cooperation, the high-precision and anti-interference monitoring of the coast slope deformation is finally realized, and the safety of the coast slope is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of geotechnical engineering safety monitoring, and in particular relates to a method for collaboratively monitoring coastal slope deformation based on dual wavelengths and a fiber Bragg grating network. Background Art

[0002] Coastal slope deformation monitoring faces severe environmental challenges. Due to the coupling of multiple factors such as periodic tidal immersion, high-salinity fog erosion, and marine organism attachment, traditional monitoring technologies have significant limitations: (1) Bottlenecks in traditional monitoring technology Electrical sensors (such as resistance strain gauges and electrolytic inclinometers) generally suffer from electrochemical corrosion failure in coastal environments. Salt spray penetration causes the insulation resistance between the electrodes inside the sensor to decrease exponentially; at the same time, the dense adhesion of marine organisms on the sensor surface can cause the mechanical transmission mechanism to jam, resulting in inclinometer measurement errors. Satellite positioning technology (such as GPS) is affected by the multipath effect of sea surface reflection and the loss of satellite signal lock at low tide. Its vertical positioning accuracy is usually greater than 3 cm, and the data loss rate during heavy rain is as high as 40%. Manual inspection methods have the defect of time lag. The response time for slope instability precursors can be less than 2 hours, while the conventional inspection cycle is usually 7 days. In addition, the poor accessibility of the intertidal zone terrain leads to a missed detection rate of trailing edge cracks exceeding 70%.

[0003] (2) Existing fiber Bragg grating (FBG) technology defects Although FBG sensors have the advantage of being immune to electromagnetic interference, they still have three major technical drawbacks in coastal slope applications: 1. Temperature and strain cross-sensitivity problem: wavelength offset of a single FBG sensor Responding to temperature changes and mechanical strain , its physical relationship can be expressed as The large temperature difference between day and night in coastal environments can produce relatively high equivalent strain errors; even at high tide, seawater immersion can cause the sensor surface to cool suddenly, leading to more serious measurement distortion.

[0004] 2. Tidal load induces signal drift: The rise and fall of tide level imposes periodic hydrostatic pressure and wave dynamic load on the slope. The hydrostatic pressure P is transmitted to the sensor through the rock and soil, generating additional strain. (E is the elastic modulus of rock and soil, A is the cross-sectional area of ​​the sensing area), and the high-frequency noise caused by wave loads will cause serious errors in the measurement data.

[0005] 3. Long-term wavelength distortion caused by salt crystal adhesion: Sea salt mist continues to deposit on the surface of the optical fiber, and sodium chloride crystals will change the refractive index n of the optical fiber cladding. According to the Bragg equation (Λ is the grating period), which directly leads to the non-strained shift of wavelength.

[0006] Current improvement proposals all have fundamental limitations: when using a reference FBG to compensate for temperature effects, the compensation sensor is also affected by salt spray corrosion, resulting in residual errors greater than 8με; while a low-pass filter can suppress high-frequency tidal noise, it also filters out the characteristic slope creep signal at the 0.01Hz level; and while salt-repellent coatings can slow corrosion, they reduce strain transfer sensitivity by 42% when the thickness exceeds 200μm. Existing technologies are unable to simultaneously address the three core issues of temperature-strain decoupling, tidal interference suppression, and salt spray drift control in the complex environment of coastal slopes. Innovative monitoring methods are urgently needed to overcome the technical bottleneck of long-term, reliable monitoring. Summary of the Invention

[0007] In response to the shortcomings of the background technology, the purpose of the present invention is to propose a collaborative monitoring method for coastal slope deformation based on dual-wavelength and fiber Bragg grating networks. This method forms a collaborative monitoring architecture by deploying a sensor network topology consisting of a top layer, a hypotenuse layer, and a bottom layer: the top layer captures pure environmental interference signals, the hypotenuse layer captures shear deformation along the principal strain direction, and the bottom layer establishes an absolute displacement benchmark; the environmental and mixed signals are separated by a dual-wavelength division of labor mechanism, and the parameters are dynamically calibrated and corrected to extract strains. Tidal interference is then suppressed by hydrostatic pressure compensation and wave filtering, supplemented by annual accumulated drift correction and sensor life prediction to achieve full-process signal optimization; this method specifically addresses key issues such as environmental interference (temperature, salt spray), tidal and wave effects, sensor drift and life assessment, and through technical means such as layered monitoring, dual-wavelength reference, and dynamic correction, the accuracy and long-term stability of slope deformation monitoring are significantly improved, ensuring that potential slope risks can be effectively identified in complex coastal environments.

[0008] The technical solution adopted by the present invention is: A method for collaboratively monitoring coastal slope deformation based on dual wavelength and fiber Bragg grating network comprises the following steps: S1) Deploy sensors on the top, slope, and bottom layers of the coastal slope based on the network topology. Top layer sensors capture environmental disturbances, slope layer sensors capture shear deformation data, and bottom layer sensors establish absolute displacement reference points, building a spatial topology foundation for collaborative monitoring. S2) Assigning operating wavelengths to top and sloping sensors, and dynamically modifying parameters to ensure accuracy. Strain is extracted from signals, and a tide-wavelength offset mapping table is established to compensate for hydrostatic pressure. Phase difference analysis is used to filter wave interference to suppress tidal interference, enabling monitoring of coastal slope deformation and providing reliable data for slope stability assessment. S3) The annual average drift of the top edge layer and the base drift of the bottom edge layer are extracted through the top edge layer sensor and the bottom edge layer sensor, and the annual corrosion attenuation coefficient is calculated to correct the cumulative displacement of the annual monitoring scale; S4) Calculate the normal operating hours based on the annual corrosion attenuation coefficient and salt spray concentration to predict the sensor service life.

[0009] Preferably, in step S1), deploying a sensor network topology structure on the coastal slope includes: A sensor network topology is deployed on the top, slope and bottom layers of the coastal slope. The top layer sensor array is used to capture pure environmental interference signals; the slope layer sensor array is used to capture shear deformation along the principal strain direction of the slope; and the bottom layer sensor array is used to establish an absolute displacement reference point.

[0010] Preferably, in step S2), the operating wavelengths of the top layer sensor and the slant layer sensor are assigned, the parameters are dynamically corrected to ensure accuracy, the signals are collected to extract strain, a tide level-wavelength offset mapping table is established to compensate for hydrostatic pressure, and phase difference analysis is used to filter wave interference. The specific steps are as follows: a1. Dual wavelength division of labor The spectral spatial allocation of the operating wavelengths of the top layer sensor array and the slant layer sensor array is performed as follows: (1) Limit the operating wavelength of the top layer sensor array to the first band that is only sensitive to environmental physical quantities ; (2) Limiting the operating wavelength of the bevel layer sensor array to the second band that responds synchronously to mechanical strain and environmental interference ; (3) The working wavelength deployment of the bottom layer sensor array covers the first band and the second band middle; The first band and the second band are separated by a certain distance in the spectral domain to avoid wavelength aliasing; a2. Dynamic correction Recalibrate the environmental coupling factor, strain sensitivity coefficient, and corrosion attenuation coefficient dynamically in the following four situations. The specific operations are as follows: (1) When a salt spray mutation event occurs, the environment interferes with the bottom layer sensor and the environmental coupling factor is recalculated; when the bottom layer sensor detects , environmental coupling factor Correction and calculation of environmental coupling factor , the formula is as follows:

[0011] in, is the step change threshold; is the change in the baseline environmental noise, that is, the baseline environmental noise signal; is the reference strain zero point variation under strain and environmental interference, that is, the reference strain zero point signal; is the current benchmark value; is the initial calibration value; is the change of initial environmental noise, that is, the initial environmental noise signal; is the initial strain zero-point quantity, that is, the initial strain zero-point signal; (2) When the deformation detected by the slope layer sensor exceeds the long-term drift threshold When the sensor strain , the strain sensitivity coefficient Make corrections and calculate the strain sensitivity coefficient The steps are as follows: Apply hydraulic load to the bottom layer , hydraulic load Dynamic adjustment based on real-time inversion of geotechnical elastic modulus E to meet hydraulic load >2 times the maximum static pressure of the tide level, collect and record the ambient wavelength offset of the bottom layer sensor and hybrid wavelength shift First, eliminate the environmental interference and obtain the wavelength change caused by deformation. Then, convert it into the deformation caused by force through the rock and soil elastic modulus E, and then use the hydraulic load Calculate the strain sensitivity coefficient , the formula is as follows:

[0012] In the formula For the first band The wavelength shift of ambient noise under environmental interference, For the second band Hybrid wavelength shift due to downstrain and environmental disturbances; (3) When the temperature is in a stable period, the environmental coupling factor is corrected with a cycle of 24 hours; the corrected environmental coupling factor is calculated using the ratio of the total change in environmental interference of the top layer sensor over 24 hours to the total change in environmental interference of the bottom layer sensor. , the formula is as follows:

[0013] in, is the corrected environmental coupling factor; is the environmental coupling factor before correction; The wavelength measured by the top layer sensor over time The amount of change; The wavelength measured by the bottom layer sensor over time The amount of change; (4) The corrosion attenuation coefficient and strain sensitivity coefficient are corrected on an annual basis to maintain the long-term accuracy of the top and bottom layer sensors. The corrosion attenuation coefficient is corrected using the ratio of the corrosion wavelength change rate of the top layer sensor to the reference wavelength change rate of the bottom layer sensor. The corrected corrosion attenuation coefficient and strain sensitivity coefficient are calculated using the following formula:

[0014] in, is the corrected corrosion attenuation coefficient; is the corrosion attenuation coefficient before correction; is the absolute value of the wavelength change rate of the top sensor, is the absolute value of the wavelength change rate of the bottom layer sensor, ; is the strain sensitivity coefficient after correction for one cycle; is the strain sensitivity coefficient before correction for one cycle; is the salt spray concentration; is the duration in salinity environment; a3. Collect signals and extract strain (1) Collect wavelength offset of top layer sensor , which is used as a pure ambient noise reference; (2) Collecting wavelength offset of the bevel layer sensor , which is used as a mixed monitoring signal; (3) From the bevel layer sensor In the equation, the environmental interference is removed and then converted into strain through the strain sensitivity coefficient. The strain without considering the tidal interference is extracted according to the following formula:

[0015] in, is the strain without considering the interference of tidal effect; a4. Eliminate tidal interference (1) Hydrostatic pressure compensation First, a tide-wavelength offset mapping table is built based on the tide height data to calibrate the wavelength offset and equivalent strain corresponding to the tide height data; the tide level is collected in real time and the equivalent strain is obtained by looking up the mapping table. This is then subtracted from the actual measured value of the hypotenuse sensor to obtain the true strain after eliminating tidal interference. ; (2) Wave dynamic filtering Real-time strain monitoring signals and tidal theory simulation signals are collected synchronously and decomposed into different frequencies through frequency domain transformation. Through phase difference discrimination, the frequency bands determined to be wave interference are filtered out, and the real deformation signals of low frequencies <0.1Hz and high frequencies >10Hz are retained.

[0016] More preferably, in step a4, the hydrostatic pressure is compensated by looking up a mapping table by the tide level, and the wave interference is filtered by phase difference analysis. The specific steps are as follows: (1) Hydrostatic pressure compensation Establish a tide-wavelength offset mapping table: Use tide height data to determine the hydraulic gradient of the bottom layer caused by the simulated tide height data, and calibrate the generated wavelength offset and equivalent strain; collect tide height data in real time, and look up the mapping table to generate the equivalent strain , deducted from the actual measured value of the bevel layer sensor, the formula is as follows:

[0017] in, To eliminate the true strain after tidal disturbance; (2) Filtering wave dynamics The bottom layer sensor signal generates two types of interference: pseudo strain noise and spectrum aliasing. Phase difference analysis is used to identify interference. The specific operation is as follows: ①Signal synchronous acquisition: The real-time strain monitoring signal of the slope and the tidal theory simulation signal are collected in parallel; the tidal theory simulation signal is generated through the hydrostatic pressure mapping table, reflecting the ideal strain waveform under the action of pure tidal load; ② Frequency domain transformation processing: Frequency domain analysis is performed on the real-time monitoring signal and the tidal simulation signal respectively, and they are decomposed into spectral components of different frequency components. The frequency domain analysis uses fast spectrum conversion technology with a resolution of not less than 0.01Hz to ensure the distinction between different frequencies. ③Phase consistency judgment: Calculate the phase offset angle of each frequency component: When the phase offset angle between the monitoring signal and the simulation signal in a specific frequency band is less than 30 degrees, the signal in that frequency band is determined to be dominated by wave dynamic interference; when the phase offset angle is greater than 30 degrees, it is retained as a true deformation signal. The phase offset angle is determined by comparing the degree of peak / trough alignment of the same-frequency components of the two signals. ④Interference signal mark: Add filter marks to the frequency bands determined to be wave interference and filter them out; retain the true deformation signals of low-frequency creep signals and high-frequency rupture signals with a phase shift angle greater than 30 degrees.

[0018] Preferably, in step S3), the annual average drift of the top edge layer and the baseline drift of the bottom edge layer are extracted respectively by the top edge layer sensor and the bottom edge layer sensor, and after the annual corrosion attenuation coefficient is calculated, the annual scale monitoring cumulative displacement is corrected. The specific steps are as follows: (1) Extracting the average annual drift of top-edge layer sensors ; (2) Obtaining the baseline drift of the bottom layer sensor ; (3) Calculation of annual corrosion attenuation coefficient The formula is as follows:

[0019] Among them, time For one year, is the salt spray concentration function; (4) The formula for correcting the cumulative displacement of annual monitoring is as follows:

[0020] in, is the corrected cumulative displacement, is the cumulative displacement before correction, is the annual corrosion attenuation coefficient, is the cumulative time, is the dynamic corrosion factor.

[0021] More preferably, the dynamic corrosion factor Obtained by the following steps: For each top edge layer sensor in the top edge layer, the component caused by temperature change is deducted from the wavelength offset output by the sensor to obtain the wavelength offset after temperature compensation; the temperature change component is obtained by multiplying the ambient temperature change at the sensor location by the pre-calibrated temperature sensitivity coefficient; ②Conversion of salt spray deposition: The wavelength offset after temperature compensation is divided by the salt spray sensitivity coefficient of the top edge layer sensor to obtain the salt spray deposition amount at the corresponding moment; the salt spray sensitivity coefficient is obtained in advance through the laboratory salt spray chamber calibration test; ③Calculation of instantaneous rate of change: For each top-edge layer sensor, calculate the difference in salt spray deposition between two adjacent sampling time points; Divide the difference by the corresponding time interval to obtain the instantaneous value of the dynamic corrosion factor of the top edge layer sensor in the current period; ④Spatial fusion processing: The arithmetic average of the instantaneous values ​​of the dynamic corrosion factors of all valid top edge layer sensors at the same moment is taken as the dynamic corrosion factor at that moment; The effective sensor should meet the requirement that the instantaneous value of its dynamic corrosion factor is within the preset reasonable range, and exclude abnormal data caused by biological attachment or mechanical damage; ⑤Abnormal data processing: When the data of a top edge layer sensor is missing, the average value of the three adjacent top edge layer sensors in the area where the top edge layer sensor is located is used as a replacement; When the regional data is missing as a whole, the salt spray concentration change rate data provided by the meteorological station is used as the backup dynamic corrosion factor value.

[0022] Preferably, in step S4), the normal working hours are calculated based on the annual corrosion attenuation coefficient and the salt spray concentration to predict the service life of the sensor. The specific steps are as follows: When the sensitivity of the top edge layer sensor, the bevel layer sensor and the bottom edge layer sensor is attenuated to 80% of the initial value due to salt spray deposition, the annual corrosion attenuation coefficient and salt spray concentration Calculate the normal working time, the formula is as follows:

[0023] in, The normal working time of the sensor.

[0024] Compared with the existing technology, the present invention proposes a method for collaborative monitoring of coastal slope deformation based on dual wavelength and fiber Bragg grating network. The advantages of this method are: The present invention fundamentally solves the coupling problem of tide, salt spray and temperature interference in coastal slope monitoring through the triple technological innovations of trapezoidal network spatial isolation, dual-wavelength dynamic decoupling and drift collaborative suppression: first, the top edge layer captures pure environmental noise, the bottom edge layer anchors the absolute reference, and the oblique edge layer accurately senses strain to achieve physical separation of interference sources; secondly, the temperature drift error is compressed by utilizing the λ1 / λ2 band division of labor and the real-time update of the environmental coupling factor η; further, tidal interference is suppressed through hydrostatic pressure lookup table compensation and wave phase difference filtering; finally, combined with the real-time correction of the corrosion factor δ and the historical backtracking of the attenuation coefficient β, the technical bottleneck of the inability to achieve both millimeter-level resolution and ten-year life in salt spray environment is broken through, providing reliable monitoring guarantee for the entire life cycle of major coastal infrastructure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A deployment diagram of a three-layer topology of a sensor network according to the present invention; Figure 2 This is a flow chart of the dual-wavelength division mechanism and parameter correction processing of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of this application to further clearly and completely describe the technical solutions in the embodiments of this application. It should be noted that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making any creative work shall fall within the scope of protection of this application.

[0027] In order to make the invention objectives, technical solutions and advantages of this application clearer, the embodiments of this application are further described in detail in conjunction with the drawings in the specification: In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the advantages of the present invention will be further illustrated by comparing the embodiments in conjunction with the drawings and specific implementation methods.

[0028] The present invention proposes a method for collaboratively monitoring coastal slope deformation based on dual wavelength and fiber Bragg grating network. The steps of the method are described in detail: S1) Deploy sensors on the top, slope, and bottom layers of the coastal slope based on the network topology. Top layer sensors capture environmental disturbances, slope layer sensors capture shear deformation data, and bottom layer sensors establish absolute displacement reference points, building a spatial topology foundation for collaborative monitoring. Specifically, in step S1), the sensor network topology structure is deployed on the coastal slope, including: The sensor network topology is deployed on the top, slope and bottom layers of the coastal slope. The top layer sensor array is used to capture pure environmental interference signals (temperature fluctuations / salt fog deposition) and provide a dynamic environmental reference benchmark for the entire network; the slope layer sensor array is used to capture shear deformation along the main strain direction of the slope, minimize strain transmission loss, and ensure the sensitivity of sliding surface identification; the bottom layer sensor array is used to establish an absolute displacement reference point, using the stability of the bedrock environment to eliminate long-term drift, and eliminate plane position errors through vertical alignment; the deployment diagram of the three-layer topology of the sensor network is shown in the attached figure. Figure 1 As shown; Top side layer sensor layout: The top layer sensor is packaged on a zero strain ceramic substrate (thermal expansion coefficient ), a rigid substrate is installed above the surface at the rear edge of the slope via a supporting structure, exposing the sensor array directly to the atmosphere. The array extends horizontally parallel to the coastline, covering the full width of the rear edge of the slope. Each sensor is fixed to the substrate surface at equal intervals to ensure physical isolation from the surface soil and a zero-strain state. Bevel layer sensor arrangement: The starting point of the sensor chain in the oblique layer coincides with the vertical projection of the center point of the top layer. From this point, the sensor chain extends obliquely toward the slope foot at the characteristic inclination of the rock and soil shear. The sensor chain is laid out obliquely toward the slope foot at the characteristic inclination of the rock and soil shear. The chain path crosses the potential sliding surface area, and the measuring points are set according to the preset minimum resolution unit spacing. The terminal extends to the seabed plane corresponding to the slope foot. Bottom layer sensor layout: The bottom layer sensor is a bedrock anchored dual-wavelength FBG, which is a dual-wavelength co-point integrated structure. It serves as the strain zero point reference and temperature drift reference of the entire network, achieving co-point measurement to eliminate position errors, that is, the two gratings are at the same point, with a small spacing and offset; including axial spacing less than 1cm Grating and grating, The grating is pre-stretched and then solidified on a negative thermal expansion ceramic substrate (thermal expansion coefficient ), so that the net strain after temperature compensation ≡ 0, to achieve physical strain isolation (zero strain package), only output the reference environmental noise signal, The grating output signal is decoupled to generate a reference strain zero point. The center point of the bottom layer is below the plane position corresponding to the hypotenuse layer terminal and is vertically anchored into the stable bedrock to a preset depth. A short baseline array is deployed on the bedrock surface, and each reference point adopts a dual-wavelength co-point integrated structure to maintain vertical spatial alignment with the hypotenuse layer terminal. The top edge layer serves as the environmental noise capture surface, and its output signal is spatially associated with the monitoring signal of the hypotenuse layer through the projection overlap point; the terminal of the hypotenuse layer strain transmission path is connected to the absolute reference of the bottom edge layer through a vertical anchoring link; the bottom edge layer reference point simultaneously receives the environmental reference signal from the top edge layer and the strain signal from the hypotenuse layer, realizing the coordinated decoupling of the three-source signals.

[0029] S2) Assigning operating wavelengths to top and sloping sensors, and dynamically modifying parameters to ensure accuracy. Strain is extracted from signals, and a tide-wavelength offset mapping table is established to compensate for hydrostatic pressure. Phase difference analysis is used to filter wave interference to suppress tidal interference, enabling monitoring of coastal slope deformation and providing reliable data for slope stability assessment. Specifically, in step S2), the operating wavelengths of the top layer sensor and the hypotenuse layer sensor are assigned, the parameters are dynamically corrected to ensure accuracy, the signals are collected to extract strain, a tide level-wavelength offset mapping table is established to compensate for hydrostatic pressure, and phase difference analysis is used to filter wave interference. The specific steps are as follows: a1. Dual wavelength division of labor The spectral spatial allocation of the operating wavelengths of the top layer sensor array and the slant layer sensor array is performed as follows: (1) Limit the operating wavelength of the top layer sensor array to the first band that is only sensitive to environmental physical quantities ; (2) Limiting the operating wavelength of the bevel layer sensor array to the second band that responds synchronously to mechanical strain and environmental interference ; (3) The working wavelength deployment of the bottom layer sensor array covers the first band and the second band middle; The first band and the second band are separated by a certain distance in the spectral domain to avoid wavelength aliasing; a2. Dynamic correction Since the temperature field, salt spray concentration and geotechnical parameters of the coastal slope have significant time-varying properties, and a large number of experiments have shown that the strain sensitivity of the same batch of FBG sensors has decreased after 3 years of service in the coastal environment. The discreteness is ±9.7% (initial ±1.2%), and the temperature sensitivity The attenuation rate varies from 5% to 18%, so in the following four cases, it is necessary to re-calibrate the environmental coupling factor, strain sensitivity coefficient and corrosion attenuation coefficient dynamically. The dual-wavelength division mechanism and parameter correction processing flow chart are shown in the attached figure. Figure 2 The specific operations are as follows: (1) When a salt spray mutation event occurs, the environment interferes with the bottom layer sensor and the environmental coupling factor is recalculated; when the bottom layer detects (Salt spray mutation event), environmental coupling factors Make corrections; calculate the corrected environmental coupling factor , to eliminate environmental interference, the formula is as follows:

[0030] in, is the change in the baseline environmental noise, that is, the baseline environmental noise signal, The wavelength shift output by the bottom layer sensor is a signal caused purely by environmental factors (temperature / salt spray) and does not contain any mechanical strain components; is the step change threshold, which is determined in coordination with the background noise statistical characteristics of historical monitoring data and the identification results of environmental mutation events; is the reference strain zero point variation under strain and environmental interference, that is, the reference strain zero point signal, which is In the wavelength offset output by the bottom layer sensor, after eliminating environmental interference through the decoupling algorithm, the strain output value should theoretically be a constant zero signal; is the current benchmark value; is the initial calibration value; is the change of initial environmental noise, that is, the initial environmental noise signal; is the initial strain zero-point quantity, that is, the initial strain zero-point signal; (2) When the deformation detected by the slope layer sensor exceeds the long-term drift threshold When the sensor strain (Suspected landslide precursor) Strain sensitivity coefficient Make corrections; calculate the corrected strain sensitivity coefficient The steps are as follows: Apply hydraulic load to the bottom layer , hydraulic load Dynamic adjustment based on real-time inversion of geotechnical elastic modulus E to meet hydraulic load >2 times the maximum static pressure of the tide level, collect and record the ambient wavelength offset of the bottom layer sensor and hybrid wavelength shift First, eliminate the environmental interference and obtain the wavelength change caused by deformation. Then, convert it into the deformation caused by force through the rock and soil elastic modulus E, and then use the hydraulic load Calculate the current strain sensitivity coefficient , the formula is as follows:

[0031] in, is the long-term drift threshold, which is essentially The average annual drift rate of the bottom layer sensor is determined by the following steps: Based on the monitoring system accuracy target (e.g. strain error < 1με within 10 years), derive the upper limit of the wavelength drift rate ; Verified by accelerated aging test Coverage of preset life targets; based on the statistical distribution of drift rate of bottom layer sensors on site, ensure Greater than 95% of the normal drift value of the bottom layer sensor; For the first band The wavelength shift of ambient noise under environmental interference, For the second band Hybrid wavelength shift due to downstrain and environmental disturbances; (3) Caused by the temperature difference between day and night When the temperature is in a stable period, the environmental coupling factor is corrected with a period of 24 hours; the corrected environmental coupling factor is calculated by the ratio of the total change of the environmental interference of the top layer in 24 hours to the total change of the environmental interference of the bottom layer. , the formula is as follows:

[0032] in, is the corrected environmental coupling factor; is the environmental coupling factor before correction; The wavelength measured by the top layer sensor over time The amount of change; for The wavelength measured by the bottom layer sensor changes with time The amount of change; (4) Due to the growth of salt crystals in salt mist, the corrosion attenuation coefficient of the sensor decays by 5-18% annually, resulting in an error in the strain sensitivity coefficient. The corrosion attenuation coefficient and the strain sensitivity coefficient are corrected on an annual basis to maintain the long-term accuracy of the top edge layer sensor and the bottom edge layer sensor to offset the influence of salt crystals. The corrosion attenuation coefficient is corrected by using the ratio of the top edge layer corrosion wavelength change rate to the bottom edge layer reference wavelength change rate. The corrected corrosion attenuation coefficient and strain sensitivity coefficient are calculated using the following formula:

[0033] in, is the corrected corrosion attenuation coefficient; is the corrosion attenuation coefficient before correction; is the absolute value of the wavelength change rate of the top sensor, for The absolute value of the wavelength change rate of the bottom layer sensor, ; is the strain sensitivity coefficient after correction for one cycle; is the strain sensitivity coefficient before correction for one cycle; is the salt spray concentration; is the duration in salinity environment; a3. Collect signals and extract strain (1) Collect wavelength offset of top layer sensor , which is used as a pure ambient noise reference; (2) Collecting wavelength offset of the bevel layer sensor , which is used as a mixed monitoring signal; (3) From the bevel layer sensor In the equation, the environmental interference is removed and then converted into strain through the strain sensitivity coefficient. The strain without considering the tidal interference is extracted according to the following formula:

[0034] in, is the strain without considering the interference of tidal effect; a4. Eliminate tidal interference (1) Hydrostatic pressure compensation For the static water pressure generated by tidal water level changes, a tide-wavelength offset mapping table is first constructed based on the tide height data to calibrate the wavelength offset and equivalent strain corresponding to the tide height data. The equivalent strain is obtained by real-time acquisition of tide level and querying the mapping table, which is then deducted from the measured value of the hypotenuse layer to obtain the true strain after eliminating tidal interference. ; (2) Wave dynamic filtering Real-time strain monitoring signals and tidal theory simulation signals are collected synchronously and decomposed into different frequencies through frequency domain transformation. Through phase difference discrimination, the frequency bands determined to be wave interference are filtered out, and the real deformation signals of low frequencies <0.1Hz and high frequencies >10Hz are retained.

[0035] More specifically, in step a4, the hydrostatic pressure is compensated by looking up the tide level mapping table, and the wave interference is filtered out by phase difference analysis. The specific steps are as follows: (1) Hydrostatic pressure compensation Establish a tide-wavelength offset mapping table: In the static water pressure generated by tidal water level changes, the hydraulic gradient of the simulated tide height data on the bottom layer is determined through the tide height data, and the wavelength offset and equivalent strain are calibrated and generated; the tide height data is collected in real time, and the equivalent strain is generated by looking up the mapping table , deducted from the measured value of the hypotenuse layer, the formula is as follows:

[0036] in, To eliminate the true strain after tidal disturbance; (2) Filtering wave dynamics The bottom layer sensor signal generates two types of interference: pseudo strain noise and spectrum aliasing. Phase difference analysis is used to identify interference. The specific operation is as follows: ①Signal synchronous acquisition: The real-time strain monitoring signal of the slope and the tidal theory simulation signal are collected in parallel; the tidal theory simulation signal is generated through the hydrostatic pressure mapping table, reflecting the ideal strain waveform under the action of pure tidal load; ② Frequency domain transformation processing: Frequency domain analysis is performed on the real-time monitoring signal and the tidal simulation signal respectively, and they are decomposed into spectral components of different frequency components. The frequency domain analysis uses fast spectrum conversion technology with a resolution of not less than 0.01Hz to ensure the distinction between different frequencies. ③Phase consistency judgment: Calculate the phase offset angle of each frequency component: When the phase offset angle between the monitoring signal and the simulation signal in a specific frequency band is less than 30 degrees, the signal in that frequency band is determined to be dominated by wave dynamic interference; when the phase offset angle is greater than 30 degrees, it is retained as a true deformation signal. The phase offset angle is determined by comparing the degree of peak / trough alignment of the same-frequency components of the two signals. ④Interference signal mark: Add filter marks to the frequency bands determined to be wave interference and filter them out; retain the true deformation signals of low-frequency creep signals and high-frequency rupture signals with a phase shift angle greater than 30 degrees.

[0037] S3) To address annual monitoring distortion caused by salt crystal accumulation and material aging, the annual average drift of the top edge layer and the baseline drift of the bottom edge layer are extracted using top edge layer sensors and bottom edge layer sensors, and the annual corrosion attenuation coefficient is calculated to correct the annual monitoring cumulative displacement. Specifically, in step S3), to address the annual monitoring distortion caused by salt crystal accumulation and material aging, the annual average drift of the top edge layer and the baseline drift of the bottom edge layer are extracted using the top edge layer sensor and the bottom edge layer sensor, and the annual corrosion attenuation coefficient is calculated to correct the annual monitoring cumulative displacement. The specific steps are as follows: (1) Extracting the average annual drift of top-edge layer sensors (Take the average annual drift of all sensors in the top layer); (2) Obtaining the baseline drift of the bottom layer sensor ; (3) Calculation of annual corrosion attenuation coefficient The formula is as follows:

[0038] Among them, time For one year, is the salt spray concentration function; (4) The formula for correcting the cumulative displacement of annual monitoring is as follows:

[0039] in, is the corrected cumulative displacement, is the cumulative displacement before correction, is the annual corrosion attenuation coefficient, is the cumulative time, is the dynamic corrosion factor.

[0040] More specifically, the dynamic corrosion factor Obtained by the following steps: ① Temperature compensation processing: For each top edge layer sensor in the top edge layer, the component caused by temperature change is deducted from the wavelength offset output by the sensor to obtain the wavelength offset after temperature compensation; the temperature change component is obtained by multiplying the ambient temperature change at the sensor location by the pre-calibrated temperature sensitivity coefficient; ②Conversion of salt spray deposition: The wavelength offset after temperature compensation is divided by the salt spray sensitivity coefficient of the top edge layer sensor to obtain the salt spray deposition amount at the corresponding moment; the salt spray sensitivity coefficient is obtained in advance through the laboratory salt spray chamber calibration test; ③Calculation of instantaneous rate of change: For each top-edge layer sensor, calculate the difference in salt spray deposition between two adjacent sampling time points; Divide the difference by the corresponding time interval to obtain the instantaneous value of the dynamic corrosion factor of the top edge layer sensor in the current period; ④Spatial fusion processing: The arithmetic average of the instantaneous values ​​of the dynamic corrosion factors of all valid top edge layer sensors at the same moment is taken as the dynamic corrosion factor at that moment; The effective sensor should meet the requirement that the instantaneous value of its dynamic corrosion factor is within the preset reasonable range, and exclude abnormal data caused by biological attachment or mechanical damage; ⑤Abnormal data processing: When the data of a top edge layer sensor is missing, the average value of the three adjacent top edge layer sensors in the area where the top edge layer sensor is located is used as a replacement; When the regional data is missing as a whole, the salt spray concentration change rate data provided by the meteorological station is used as the backup dynamic corrosion factor value.

[0041] S4) Based on the annual corrosion attenuation coefficient and salt spray concentration, the normal operating hours are calculated using a formula to predict the service life of the sensor; Specifically, in step S4), the normal operating hours are calculated based on the annual corrosion attenuation coefficient and the salt spray concentration to predict the service life of the sensor. The specific steps are as follows: When the sensitivity of the top edge layer sensor, bevel layer sensor and bottom edge layer sensor is attenuated to 80% of the initial value (i.e., 20% loss is allowed) due to salt spray deposition (or other environmental factors), the annual corrosion attenuation coefficient and salt spray concentration Calculate the normal working time, the formula is as follows:

[0042] in, The normal working time of the sensor.

[0043] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0044] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A method for collaborative monitoring of coastal slope deformation based on dual wavelength and fiber Bragg grating network, characterized in that: The method comprises the following steps: S1) Deploy sensors on the top, slope, and bottom layers of the coastal slope based on the network topology. Top layer sensors capture environmental disturbances, slope layer sensors capture shear deformation data, and bottom layer sensors establish absolute displacement reference points, building a spatial topology foundation for collaborative monitoring. S2) Assigning operating wavelengths to top and sloping sensors, and dynamically modifying parameters to ensure accuracy. Strain is extracted from signals, and a tide-wavelength offset mapping table is established to compensate for hydrostatic pressure. Phase difference analysis is used to filter wave interference to suppress tidal interference, enabling monitoring of coastal slope deformation and providing reliable data for slope stability assessment. S3) The annual average drift of the top edge layer and the base drift of the bottom edge layer are extracted through the top edge layer sensor and the bottom edge layer sensor, and the annual corrosion attenuation coefficient is calculated to correct the cumulative displacement of the annual monitoring scale; S4) Calculate the normal operating hours based on the annual corrosion attenuation coefficient and salt spray concentration to predict the sensor service life.

2. The method for collaborative monitoring of coastal slope deformation based on dual wavelength and fiber Bragg grating network according to claim 1 is characterized in that: In the step S1), a sensor network topology structure is deployed on the coastal slope, including: A sensor network topology is deployed on the top, slope and bottom layers of the coastal slope. The top layer sensor array is used to capture pure environmental interference signals; the slope layer sensor array is used to capture shear deformation along the principal strain direction of the slope; and the bottom layer sensor array is used to establish an absolute displacement reference point.

3. The method for collaborative monitoring of coastal slope deformation based on dual wavelength and fiber Bragg grating network according to claim 1 is characterized in that: In step S2), the operating wavelengths of the top layer sensor and the oblique layer sensor are assigned, the parameters are dynamically corrected to ensure accuracy, the signals are collected to extract strain, a tide level-wavelength offset mapping table is established to compensate for hydrostatic pressure, and phase difference analysis is used to filter wave interference. The specific steps are as follows: a1. Dual wavelength division of labor The spectral spatial allocation of the operating wavelengths of the top layer sensor array and the slant layer sensor array is performed as follows: (1) Limit the operating wavelength of the top layer sensor array to the first band that is only sensitive to environmental physical quantities ; (2) Limiting the operating wavelength of the bevel layer sensor array to the second band that responds synchronously to mechanical strain and environmental interference ; (3) The working wavelength deployment of the bottom layer sensor array covers the first band and the second band middle; The first band and the second band are separated by a certain distance in the spectral domain to avoid wavelength aliasing; a2. Dynamic correction Recalibrate the environmental coupling factor, strain sensitivity coefficient, and corrosion attenuation coefficient dynamically in the following four situations. The specific operations are as follows: (1) When a salt spray mutation event occurs, the environment interferes with the bottom layer sensor and the environmental coupling factor is recalculated; when the bottom layer sensor detects , environmental coupling factor Correction and calculation of environmental coupling factor , the formula is as follows: ； in, is the step change threshold; is the change in the baseline environmental noise, that is, the baseline environmental noise signal; is the reference strain zero point variation under strain and environmental interference, that is, the reference strain zero point signal; is the current benchmark value; is the initial calibration value; is the change of initial environmental noise, that is, the initial environmental noise signal; is the initial strain zero-point quantity, that is, the initial strain zero-point signal; (2) When the deformation detected by the slope layer sensor exceeds the long-term drift threshold When the sensor strain , the strain sensitivity coefficient Make corrections and calculate the strain sensitivity coefficient The steps are as follows: Apply hydraulic load to the bottom layer , hydraulic load Dynamic adjustment based on real-time inversion of geotechnical elastic modulus E to meet hydraulic load > 2 times the maximum static pressure of the tide level, collect and record the ambient wavelength offset of the bottom layer sensor and hybrid wavelength shift First, eliminate the environmental interference and obtain the wavelength change caused by deformation. Then, convert it into the deformation caused by force through the rock and soil elastic modulus E, and then use the hydraulic load Calculate the strain sensitivity coefficient , the formula is as follows: ； In the formula For the first band The wavelength shift of ambient noise under environmental interference, For the second band Hybrid wavelength shift due to downstrain and environmental disturbances; (3) When the temperature is in a stable period, the environmental coupling factor is corrected with a cycle of 24 hours; the corrected environmental coupling factor is calculated using the ratio of the total change in environmental interference of the top layer sensor over 24 hours to the total change in environmental interference of the bottom layer sensor. , the formula is as follows: ； in, is the corrected environmental coupling factor; is the environmental coupling factor before correction; The wavelength measured by the top layer sensor over time The amount of change; The wavelength measured by the bottom layer sensor over time The amount of change; (4) The corrosion attenuation coefficient and strain sensitivity coefficient are corrected on an annual basis to maintain the long-term accuracy of the top and bottom layer sensors. The corrosion attenuation coefficient is corrected using the ratio of the corrosion wavelength change rate of the top layer sensor to the reference wavelength change rate of the bottom layer sensor. The corrected corrosion attenuation coefficient and strain sensitivity coefficient are calculated using the following formula: ； ; in, is the corrected corrosion attenuation coefficient; is the corrosion attenuation coefficient before correction; is the absolute value of the wavelength change rate of the top sensor, ; is the absolute value of the wavelength change rate of the bottom layer sensor, ; is the strain sensitivity coefficient after correction for one cycle; is the strain sensitivity coefficient before correction for one cycle; is the salt spray concentration; is the duration in salinity environment; a3. Collect signals and extract strain (1) Collect wavelength offset of top layer sensor , which is used as a pure ambient noise reference; (2) Collecting wavelength offset of the bevel layer sensor , which is used as a mixed monitoring signal; (3) From the bevel layer sensor In the equation, the environmental interference is removed and then converted into strain through the strain sensitivity coefficient. The strain without considering the tidal interference is extracted according to the following formula: ； in, is the strain without considering the interference of tidal effect; a4. Eliminate tidal interference (1) Hydrostatic pressure compensation First, a tide-wavelength offset mapping table is built based on the tide height data to calibrate the wavelength offset and equivalent strain corresponding to the tide height data; the tide level is collected in real time and the equivalent strain is obtained by looking up the mapping table. This is then subtracted from the actual measured value of the hypotenuse sensor to obtain the true strain after eliminating tidal interference. ; (2) Wave dynamic filtering Real-time strain monitoring signals and tidal theory simulation signals are collected synchronously and decomposed into different frequencies through frequency domain transformation. Through phase difference discrimination, the frequency bands determined to be wave interference are filtered out, and the real deformation signals of low frequencies <0.1Hz and high frequencies >10Hz are retained.

4. The method for collaborative monitoring of coastal slope deformation based on dual wavelength and fiber Bragg grating network according to claim 3 is characterized in that: In step a4, the hydrostatic pressure is compensated by looking up the mapping table by the tide level, and the wave interference is filtered by phase difference analysis. The specific steps are as follows: (1) Hydrostatic pressure compensation Establish a tide-wavelength offset mapping table: Use tide height data to determine the hydraulic gradient of the bottom layer caused by the simulated tide height data, and calibrate the generated wavelength offset and equivalent strain; collect tide height data in real time, and look up the mapping table to generate the equivalent strain , deducted from the actual measured value of the bevel layer sensor, the formula is as follows: ； in, To eliminate the true strain after tidal disturbance; (2) Filtering wave dynamics The bottom layer sensor signal generates two types of interference: pseudo strain noise and spectrum aliasing. Phase difference analysis is used to identify interference. The specific operation is as follows: ①Signal synchronous acquisition: The real-time strain monitoring signal of the slope and the tidal theory simulation signal are collected in parallel; the tidal theory simulation signal is generated through the hydrostatic pressure mapping table, reflecting the ideal strain waveform under the action of pure tidal load; ② Frequency domain transformation processing: Frequency domain analysis is performed on the real-time monitoring signal and the tidal simulation signal respectively, and they are decomposed into spectral components of different frequency components. The frequency domain analysis uses fast spectrum conversion technology with a resolution of not less than 0.01Hz to ensure the distinction between different frequencies. ③Phase consistency judgment: Calculate the phase offset angle of each frequency component: When the phase offset angle between the monitoring signal and the simulation signal in a specific frequency band is less than 30 degrees, the signal in that frequency band is determined to be dominated by wave dynamic interference; when the phase offset angle is greater than 30 degrees, it is retained as a true deformation signal. The phase offset angle is determined by comparing the degree of peak / trough alignment of the same-frequency components of the two signals. ④Interference signal mark: Add filter marks to the frequency bands determined to be wave interference and filter them out; retain the true deformation signals of low-frequency creep signals and high-frequency rupture signals with a phase shift angle greater than 30 degrees.

5. The method for collaborative monitoring of coastal slope deformation based on dual wavelength and fiber Bragg grating network according to claim 1 is characterized in that: In step S3), the annual average drift of the top edge layer and the baseline drift of the bottom edge layer are extracted by the top edge layer sensor and the bottom edge layer sensor, and the annual corrosion attenuation coefficient is calculated. Then, the annual scale monitoring cumulative displacement is corrected. The specific steps are as follows: (1) Extracting the average annual drift of top-edge layer sensors ; (2) Obtaining the baseline drift of the bottom layer sensor ; (3) Calculation of annual corrosion attenuation coefficient The formula is as follows: ； Among them, time For one year, is the salt spray concentration function; (4) The formula for correcting the cumulative displacement of annual monitoring is as follows: ； in, is the corrected cumulative displacement, is the cumulative displacement before correction, is the annual corrosion attenuation coefficient, is the cumulative time, is the dynamic corrosion factor.

6. The method for collaborative monitoring of coastal slope deformation based on dual wavelength and fiber Bragg grating network according to claim 5 is characterized in that: The dynamic corrosion factor Obtained by the following steps: ① Temperature compensation processing: For each top edge layer sensor in the top edge layer, the component caused by temperature change is deducted from the wavelength offset output by the sensor to obtain the wavelength offset after temperature compensation; the temperature change component is obtained by multiplying the ambient temperature change at the sensor location by the pre-calibrated temperature sensitivity coefficient; ②Conversion of salt spray deposition: The wavelength offset after temperature compensation is divided by the salt spray sensitivity coefficient of the top edge layer sensor to obtain the salt spray deposition amount at the corresponding moment; the salt spray sensitivity coefficient is obtained in advance through the laboratory salt spray chamber calibration test; ③Calculation of instantaneous rate of change: For each top-edge layer sensor, calculate the difference in salt spray deposition between two adjacent sampling time points; Divide the difference by the corresponding time interval to obtain the instantaneous value of the dynamic corrosion factor of the top edge layer sensor in the current period; ④Spatial fusion processing: The arithmetic average of the instantaneous values ​​of the dynamic corrosion factors of all valid top edge layer sensors at the same moment is taken as the dynamic corrosion factor at that moment; The effective sensor should meet the requirement that the instantaneous value of its dynamic corrosion factor is within the preset reasonable range, and exclude abnormal data caused by biological attachment or mechanical damage; ⑤Abnormal data processing: When the data of a top edge layer sensor is missing, the average value of the three adjacent top edge layer sensors in the area where the top edge layer sensor is located is used as a replacement; When the regional data is missing as a whole, the salt spray concentration change rate data provided by the meteorological station is used as the backup dynamic corrosion factor value.

7. The method for collaborative monitoring of coastal slope deformation based on dual wavelength and fiber Bragg grating network according to claim 1, characterized in that: In step S4), the normal working hours are calculated based on the annual corrosion attenuation coefficient and the salt spray concentration to predict the service life of the sensor. The specific steps are as follows: When the sensitivity of the top edge layer sensor, the bevel layer sensor and the bottom edge layer sensor is attenuated to 80% of the initial value due to salt spray deposition, the annual corrosion attenuation coefficient and salt spray concentration Calculate the normal working time, the formula is as follows: ； in, The normal working time of the sensor.

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