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

Abstract

The application discloses a kind of based on dual-wavelength and fiber grating network's coast slope deformation cooperative monitoring method, belong to geotechnical engineering safety monitoring technical field, according to network topology, top edge layer, inclined edge layer and bottom edge layer of coast slope are carried out sensor deployment;Distribute the working wavelength of top edge layer sensor and inclined edge layer sensor, realize the spectrum separation of environmental interference and deformation signal, then dynamically calibrate parameter, collect signal and extract strain, remove the interference of tidal action by hydrostatic pressure compensation and wave filtering, to ensure signal accuracy;Top edge layer sensor and bottom edge layer sensor are carried out annual scale monitoring cumulative displacement correction and sensor service life prediction.The space cooperation of three-layer network and the fusion of dual-wavelength signal, multi-layer cooperation, dynamic correction, accurate monitoring of slope deformation, finally realize high-precision, anti-interference monitoring of coast slope deformation, guarantee the safety of coast slope.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of geotechnical engineering safety monitoring, and particularly relates to a coastal slope deformation cooperative monitoring method based on a dual-wavelength and fiber grating network. BACKGROUND

[0002] The coastal slope deformation monitoring faces severe environmental challenges, and is coupled by multiple factors such as periodic immersion by tides, high salinity mist corrosion, and marine organism attachment, so that the traditional monitoring technology has significant limitations:

[0003] (1) The bottleneck of traditional monitoring technology, the electrical sensor (such as resistance strain gauge, electrolytic inclinometer), generally has electrochemical corrosion failure problem in the coastal environment. The penetration of salt mist causes the insulation resistance between the internal electrodes of the sensor to decrease exponentially; at the same time, the dense attachment of marine organisms on the surface of the sensor will cause the mechanical transmission mechanism to be stuck, which will cause the measurement error of the inclinometer. The satellite positioning technology (such as GPS) is affected by the multi-path effect of sea surface reflection and the loss of satellite signal at low tide, and its vertical positioning accuracy is usually greater than 3 cm, and the data missing rate during heavy rain is as high as more than 40%. The manual inspection method has the defect of time lag, and the precursor response time of slope instability can be shorter than 2 hours, while the conventional inspection cycle is usually 7 days, and the accessibility of the intertidal zone is poor, resulting in a crack detection rate of more than 70% on the rear edge.

[0004] (2) Defects of existing fiber grating (FBG) technology

[0005] Although the FBG sensor has the advantage of anti-electromagnetic interference, there are still three major technical defects in the application of coastal slopes:

[0006] 1. Temperature and strain cross-sensitivity problem: The wavelength shift of a single FBG sensor responds to temperature changes and mechanical strain at the same time, and the physical relationship can be expressed as . The large diurnal temperature difference in the coastal environment will produce a relatively high equivalent strain error; even when the tide rises, the sudden cooling of the sensor surface caused by seawater immersion will further cause more serious measurement distortion.

[0007] 2. Tidal load induced signal drift: The tidal level exerts periodic hydrostatic pressure and wave dynamic load on the slope. The hydrostatic pressure P is transmitted to the sensor through the rock-soil body, producing additional strain (E is the elastic modulus of rock-soil, A is the cross-sectional area of the sensing area), and the high-frequency noise caused by the wave load will all cause serious errors in the measurement data.

[0008] 3. Salt crystal attachment causes long-term wavelength distortion: The deposition of sea salt mist on the surface of the optical fiber will change the refractive index n of the fiber cladding, and according to the Bragg equation (A is the grating period), directly leading to wavelength non-strain offset.

[0009] The current improvement scheme has a fundamental limitation: when using a reference FBG to compensate for the temperature effect, the compensation sensor is also affected by salt spray corrosion, and the residual error is still greater than 8με; although the low-pass filter can suppress the high-frequency noise of the tide, it will filter out the characteristic signal of the slope creep on the order of 0.01Hz; although the salt-proof coating can delay corrosion, the thickness exceeding 200μm will weaken the strain transmission sensitivity by 42%. The existing technology cannot simultaneously solve the three core problems of temperature-strain decoupling, tidal interference suppression and salt mist drift control in the complex environment of the coastal slope, and innovative monitoring methods are urgently needed to break through the technical bottleneck of long-term reliable monitoring. SUMMARY

[0010] In view of the deficiencies in the background art, the purpose of the present application is to provide a coastal slope deformation collaborative monitoring method based on dual-wavelength and fiber grating network. The method deploys a sensor network topology composed of top edge layer, inclined edge layer and bottom edge layer to form a collaborative monitoring architecture: the top edge layer captures pure environmental interference signals, the inclined edge layer captures shear deformation along the main strain direction, and the bottom edge layer establishes an absolute displacement reference. Through a dual-wavelength division mechanism, environmental and mixed signals are separated, parameters are corrected through dynamic calibration, strain is extracted, tidal interference is suppressed through hydrostatic pressure compensation and wave filtering, and annual cumulative drift correction and sensor life prediction are supplemented to realize full-process signal optimization. The method solves key problems such as environmental interference (temperature, salt mist), tidal and wave influence, sensor drift and life evaluation. Through hierarchical monitoring, dual-wavelength reference, dynamic correction and other technical means, the accuracy and long-term stability of slope deformation monitoring are significantly improved, ensuring that potential risks of the slope can be effectively identified in complex coastal environments.

[0011] The technical scheme adopted by the present application is as follows:

[0012] The coastal slope deformation collaborative monitoring method based on dual-wavelength and fiber grating network comprises the following steps:

[0013] S1) According to the network topology structure, sensors are deployed on the top edge layer, inclined edge layer and bottom edge layer of the coastal slope, wherein the top edge layer sensors capture environmental interference, the inclined edge layer sensors capture shear deformation data, and the bottom edge layer sensors establish an absolute displacement reference point, thereby constructing a spatial topology basis for collaborative monitoring;

[0014] S2) Assign the working wavelengths of the top edge layer sensors and the inclined edge layer sensors, and dynamically correct the parameters to ensure accuracy; collect signals to extract strain, establish a tidal level-wavelength offset mapping table to compensate for hydrostatic pressure, and use phase difference analysis to filter wave interference to suppress the interference of tidal action, thereby monitoring the deformation of the coastal slope and providing reliable data for slope stability evaluation.

[0015] S3) Extracting the top edge layer annual average drift and the bottom edge layer reference drift by the top edge layer sensor and the bottom edge layer sensor respectively, calculating the annual corrosion attenuation coefficient, and correcting the annual scale monitoring cumulative displacement;

[0016] S4) According to the annual corrosion attenuation coefficient and the salt fog concentration, the normal working time is calculated to predict the service life of the sensor.

[0017] Preferably, in the step S1), the sensor network topology structure is deployed on the coastal slope, comprising:

[0018] The sensor network topology structure is deployed on the top edge layer, the inclined edge layer and the bottom edge layer of the coastal slope, wherein the top edge layer sensor array is used to capture the pure environmental interference signal; the inclined edge layer sensor array is used to capture the shear deformation along the main strain direction of the slope; and the bottom edge layer sensor array is used to establish an absolute displacement reference point.

[0019] Preferably, in the step S2), the working wavelengths of the top edge layer sensor and the inclined edge layer sensor are allocated, and the parameter accuracy is dynamically corrected to collect signals, extract strain, establish a tide level-wavelength offset mapping table to compensate hydrostatic pressure, and filter wave disturbance by phase difference analysis. The specific steps are as follows:

[0020] a1. Double wavelength division

[0021] The working wavelengths of the top edge layer sensor array and the working wavelengths of the inclined edge layer sensor array are allocated in the spectral space, specifically as follows:

[0022] (1) The working wavelengths of the top edge layer sensor array are limited to a first waveband that is only sensitive to environmental physical quantities ;

[0023] (2) The working wavelengths of the inclined edge layer sensor array are limited to a second waveband that synchronously responds to mechanical strain and environmental interference ;

[0024] (3) The working wavelengths of the bottom edge layer sensor array are deployed to cover the first waveband and the second waveband ;

[0025] The first waveband and the second waveband maintain a certain interval in the spectral domain to avoid wavelength aliasing;

[0026] a2. Dynamic correction

[0027] In the following four cases, the environmental coupling factor, the strain sensitivity coefficient and the corrosion attenuation coefficient are dynamically recalibrated, and the specific operations are as follows:

[0028] (1) When salt spray mutation occurs, the environment interferes with the bottom edge layer sensor, and the environmental coupling factor is recalculated; when the bottom edge layer sensor detects , the environmental coupling factor is corrected, and the environmental coupling factor is calculated, and the formula is as follows:

[0029]

[0030] , wherein is the step change threshold; is the reference environmental noise change, i.e., the reference environmental noise signal; is the reference strain zero point change under strain and environmental disturbance, i.e., the reference strain zero point signal; is the current reference value; is the initial calibration value; is the initial environmental noise change, i.e., the initial environmental noise signal; is the initial strain zero point change, i.e., the initial strain zero point signal;

[0031] (2) When the oblique edge layer sensor detects that the deformation exceeds the long-term drift threshold , i.e., the sensor strain , the strain sensitivity coefficient is corrected, and the strain sensitivity coefficient is calculated, and the steps are as follows:

[0032] A hydraulic load is applied to the bottom edge layer , and the hydraulic load is dynamically adjusted according to the real-time inverted rock-soil elastic modulus E, satisfying the hydraulic load >2 times the maximum static pressure of tidal level, and the environmental wavelength shift and the mixed wavelength shift of the bottom edge layer sensor are collected and recorded; first, the environmental disturbance is eliminated to obtain the wavelength change caused by deformation, which is converted into the deformation amount caused by stress through the rock-soil elastic modulus E, and then the hydraulic load is used to calculate the strain sensitivity coefficient , and the formula is as follows:

[0033]

[0034] , wherein is the environmental noise wavelength shift of the first wave band under environmental disturbance, is the mixed wavelength shift of the second wave band under strain and environmental disturbance;

[0035] (3) When the temperature is in the stable period, the environmental coupling factor is corrected every 24 hours; the ratio of the total change of the environmental disturbance of the top edge layer sensor and the total change of the environmental disturbance of the bottom edge layer sensor is used to calculate the corrected environmental coupling factor , the formula is as follows:

[0036]

[0037] wherein, is the corrected environmental coupling factor; is the uncorrected environmental coupling factor; is the change of the wavelength measured by the top edge layer sensor with time ; is the change of the wavelength measured by the bottom edge layer sensor with time ;

[0038] (4) The corrosion attenuation coefficient and the strain sensitivity coefficient are corrected every year to maintain the long-term accuracy of the top edge layer sensor and the bottom edge layer sensor; the ratio of the corrosion wavelength change rate of the top edge layer sensor and the reference wavelength change rate of the bottom edge layer sensor is used to correct the corrosion attenuation coefficient, and the corrected corrosion attenuation coefficient and the strain sensitivity coefficient are calculated, the formula is as follows:

[0039]

[0040] wherein, is the corrected corrosion attenuation coefficient; is the uncorrected corrosion attenuation coefficient; 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 edge layer sensor, ; is the strain sensitivity coefficient after correction for a period; is the strain sensitivity coefficient before correction for a period; is the salt mist concentration; is the duration in the salt environment;

[0041] a3. Collecting signals to extract strain

[0042] (1) Collect the wavelength offset of the top edge layer sensor , which is used as a pure environmental noise reference;

[0043] (2) Collect the wavelength offset of the inclined edge layer sensor , which is used as a mixed monitoring signal;

[0044] (3) From the wavelength offset of the inclined edge layer sensor In the formula, the strain is the strain without considering the interference of tidal action, and the tidal height is the tidal height data.

[0045]

[0046] In the formula, the strain is the strain without considering the interference of tidal action, and the tidal height is the tidal height data.

[0047] a4. Removing the interference of tidal action

[0048] (1) Static water pressure compensation

[0049] First, according to the tidal height data, a tidal height-wave length offset mapping table is established to calibrate the wavelength offset and equivalent strain corresponding to the tidal height data; the equivalent strain is obtained by searching the mapping table in real time, and the real strain without tidal interference is obtained by deducting the measured value of the inclined edge layer sensor. ;

[0050] (2) Wave power filtering

[0051] The real-time strain monitoring signal and the tidal theoretical simulation signal are simultaneously collected and decomposed into different frequencies through frequency domain transformation; through phase difference discrimination, the frequency band determined as wave interference is filtered, and the real deformation signal of <0.1 Hz low frequency and >10 Hz high frequency is reserved.

[0052] Further preferably, in a4, the static water pressure is compensated by searching the tidal height mapping table, and the wave interference is filtered by phase difference analysis, and the specific steps are as follows:

[0053] (1) Static water pressure compensation

[0054] Establish a tidal height-wave length offset mapping table: through the tidal height data, determine the hydraulic gradient of the simulated tidal height data on the bottom layer, and calibrate the generated wavelength offset and equivalent strain; real-time collection of tidal height data, search the mapping table to generate equivalent strain , deduct from the measured value of the inclined edge layer sensor, and the formula is as follows:

[0055]

[0056] In the formula, the strain is the strain without considering the interference of tidal action, and the tidal height is the tidal height data.

[0057] (2) Filtering wave power filtering

[0058] The bottom layer sensor signal produces two types of interference: pseudo-strain noise and frequency spectrum aliasing; the phase difference analysis method is used to identify the interference, and the specific operation is performed according to the following steps:

[0059] ① Signal synchronous acquisition: ​​

[0060] 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 a hydrostatic pressure mapping table and reflects an ideal strain waveform under the action of pure tidal load;

[0061] ② Frequency domain transformation processing:

[0062] The real-time monitoring signal and the tidal simulation signal are respectively analyzed in the frequency domain, and are decomposed into spectral components of different frequencies; the frequency domain analysis uses fast spectral transformation technology, with a resolution of not less than 0.01 Hz, to ensure the differentiation of different frequencies;

[0063] ③ Phase consistency discrimination:

[0064] The phase offset angle of each frequency component is calculated: when the phase offset angle of the monitoring signal and the simulation signal in a specific frequency band is less than 30 degrees, it is determined that the signal in this frequency band is dominated by wave power interference; when the phase offset angle is greater than 30 degrees, it is retained as the real deformation signal; the phase offset angle is determined by comparing the alignment degree of the wave crests / troughs of the same frequency components of the two signals;

[0065] ④ Interference signal marking:

[0066] The frequency band determined to be wave interference is added with a filter mark and filtered; the real deformation signal of the low-frequency creep signal and the high-frequency rupture signal with a phase offset angle greater than 30 degrees is retained.

[0067] Preferably, in step S3, the top edge layer sensor and the bottom edge layer sensor are used to extract the top edge layer annual drift and the bottom edge layer reference drift, respectively, and after calculating the annual corrosion attenuation coefficient, the annual scale monitoring cumulative displacement is corrected, and the specific steps are as follows:

[0068] (1) Extracting the annual drift of the top edge layer sensor ;

[0069] (2) Obtaining the reference drift of the bottom edge layer sensor ;

[0070] (3) Calculating the annual corrosion attenuation coefficient The formula is as follows:

[0071]

[0072] Wherein, the time is one year, is a salt mist concentration function;

[0073] (4) The formula for correcting the annual scale monitoring cumulative displacement is as follows:

[0074]

[0075] Wherein, is the corrected cumulative displacement, is the uncorrected cumulative displacement, is the annual corrosion decay coefficient, is the cumulative time, is the dynamic corrosion factor.

[0076] More preferably, the dynamic corrosion factor is obtained by the following steps:

[0077] For each roof layer sensor in the roof layer, the temperature change caused component is deducted from the wavelength shift outputted by the sensor to obtain the temperature compensated wavelength shift; the temperature change component is obtained by multiplying the environmental temperature change amount at the position where the sensor is located by the pre-labeled temperature sensitivity coefficient;

[0078] ②Salt fog deposition amount conversion:

[0079] The temperature compensated wavelength shift is divided by the salt fog sensitivity coefficient of the roof layer sensor to obtain the salt fog deposition amount at the corresponding time; the salt fog sensitivity coefficient is obtained by pre-labelling the salt fog chamber test in the laboratory;

[0080] ③Instantaneous change rate calculation:

[0081] For each roof layer sensor, the difference of salt fog deposition amount between adjacent two sampling time points is calculated;

[0082] The difference is divided by the corresponding time interval to obtain the instantaneous value of the dynamic corrosion factor of the roof layer sensor in the current period;

[0083] ④Spatial fusion processing:

[0084] The instantaneous values of the dynamic corrosion factor of all valid roof layer sensors in the roof layer at the same time are arithmetically averaged to obtain the dynamic corrosion factor at the time;

[0085] The valid sensors should meet that the instantaneous value of the dynamic corrosion factor is within a pre-set reasonable range, and the abnormal data caused by biological attachment or mechanical damage is excluded;

[0086] ⑤Abnormal data processing:

[0087] When the data of a certain roof layer sensor is missing, the mean value of the adjacent three roof layer sensors in the area where the roof layer sensor is located is used as a substitute;

[0088] When the overall area data is missing, the salt fog concentration change rate data provided by the weather station is used as a backup dynamic corrosion factor value.

[0089] Preferably, in the step S4), the normal working duration is calculated according to the annual corrosion attenuation coefficient and the salt fog concentration to predict the service life of the sensor, and the specific steps are as follows:

[0090] When the top edge layer sensor, the inclined edge layer sensor and the bottom edge layer sensor are caused by salt fog deposition Sensitivity attenuation to 80% of the initial value, the normal working duration of the sensor is calculated through the annual corrosion attenuation coefficient And the salt fog concentration The formula is as follows:

[0091]

[0092] Among them, The normal working duration of the sensor.

[0093] Compared with the prior art, the present application proposes a coastal slope deformation collaborative monitoring method based on a dual-wavelength and fiber grating network, and the method has the following advantages:

[0094] The present application solves the coupling problem of tide, salt fog and temperature interference in the monitoring of the coastal slope through three technical 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 inclined edge layer accurately senses the strain, realizing physical separation of the interference sources; second, the temperature drift error is compressed by using the division of the λ1 / λ2 wave band and the real-time updating of the environmental coupling factor η; further, the tide interference is suppressed through the static water pressure table compensation and the wave phase difference filtering; finally, the technical bottleneck of millimeter-level resolution and ten-year-level life under the salt fog environment is broken through the real-time correction of the corrosion factor δ and the historical backtracking of the attenuation coefficient β, and reliable monitoring guarantee is provided for the whole life cycle of the coastal major infrastructure. BRIEF DESCRIPTION OF DRAWINGS

[0095] Figure 1 It is a deployment diagram of the three-layer topological structure of the sensor network of the present application;

[0096] Figure 2 It is a dual-wavelength division mechanism and parameter modification process diagram of the present application. DETAILED DESCRIPTION

[0097] The technical solutions in the embodiments of the present application will be further described in detail below with reference to the drawings in the embodiments of the present application. It should be noted that the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0098] To make the inventive objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be further described in detail below with reference to the accompanying drawings: In order to better understand the above-mentioned objectives, features, and advantages of this invention, the advantages of this invention will be further illustrated below by comparing the embodiments with the accompanying drawings and specific implementation methods.

[0099] This invention proposes a method for coordinated monitoring of coastal slope deformation based on dual-wavelength and fiber Bragg grating networks. The steps of this method are described in detail below:

[0100] S1) Based on the network topology, sensors are deployed in the top edge layer, inclined edge layer and bottom edge layer of the coastal slope. The top edge layer sensors capture environmental interference, the inclined edge layer sensors capture shear deformation data, and the bottom edge layer sensors establish absolute displacement reference points to build a spatial topology basis for collaborative monitoring.

[0101] Specifically, in step S1), deploying a sensor network topology on the coastal slope includes:

[0102] A sensor network topology is deployed on the top, sloping, and bottom layers of the coastal slope. The top layer sensor array captures purely environmental disturbance signals (temperature fluctuations / salt spray deposition), providing a dynamic environmental reference for the entire network. The sloping layer sensor array captures shear deformation along the principal strain direction of the slope, minimizing strain transfer loss and ensuring the sensitivity of the slip surface identification. The bottom layer sensor array establishes an absolute displacement reference point, utilizing the stability of the bedrock environment to eliminate long-term drift and eliminating planar position errors through vertical alignment. The deployment diagram of the three-layer sensor network topology is attached. Figure 1 As shown;

[0103] Top edge layer sensor arrangement:

[0104] The top-side sensor is encapsulated on a zero-strain ceramic substrate (thermal expansion coefficient). A rigid substrate is installed above the ground surface at the rear edge of the slope using a support structure, allowing the sensor array to be directly exposed to the atmospheric environment. The array extends horizontally along a direction parallel to the coastline, covering the entire width of the rear edge of the slope. Each sensor is fixed to the surface of the substrate at equal intervals to ensure that it is physically isolated from the surface soil and is in a zero-strain state.

[0105] Sensor arrangement in the slanted layer:

[0106] The starting point of the sensor chain in the inclined layer coincides with the vertical projection of the center point of the top layer. From this point, it extends obliquely towards the toe of the slope with the characteristic dip angle of rock and soil shear. The sensor chain is laid out obliquely through the toe of the slope with the characteristic dip angle of rock and soil shear. The chain path crosses the potential sliding surface area, and measuring points are set according to the preset minimum resolution unit spacing. The terminal extends to the seabed plane corresponding to the toe of the slope.

[0107] Bottom edge layer sensor arrangement:

[0108] The bottom edge layer sensor is a bedrock anchored dual-wavelength FBG, which is a dual-wavelength same-point integrated structure, serving as a full-network strain zero-point reference and temperature drift reference, achieving same-point measurement to eliminate position errors, that is, the two gratings are at the same point, with small spacing and offset; containing a dual-wavelength same-point integrated structure with an axial spacing of less than 1 cm grating and grating, The grating is cured in a negative thermal expansion ceramic substrate (thermal expansion coefficient ) after pre-stretching, so that the net strain ≡0 after temperature compensation, achieving physical isolation of strain (zero strain packaging), and only outputting reference environmental noise signals, The grating output signal generates a reference strain zero point after decoupling; the bottom edge layer center point is anchored vertically into the stable bedrock to a preset depth below the plane position corresponding to the hypotenuse layer terminal; a short baseline array is arranged on the bedrock surface, and each reference point adopts a dual-wavelength same-point integrated structure, which is vertically spatially aligned with the hypotenuse layer terminal;

[0109] The top edge layer serves as an environmental noise capturing surface, and its output signal is correlated with the projection coincidence point of the hypotenuse layer monitoring signal in space; the terminal of the hypotenuse layer strain transmission path is connected to the bottom edge layer absolute reference through a vertical anchor 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 three-source signal cooperative decoupling.

[0110] S2) Assign the working wavelengths of the top edge layer sensors and the hypotenuse layer sensors, and dynamically correct the parameters to ensure accuracy; collect signals to extract strain, establish a tide level-wavelength offset mapping table to compensate for hydrostatic pressure, and use phase difference analysis to filter wave interference to suppress the interference of tidal action, realizing the monitoring of the deformation of the coastal slope and providing reliable data for slope stability evaluation;

[0111] Specifically, in step S2), the working wavelengths of the top edge layer sensors and the hypotenuse layer sensors are assigned, and the parameters are dynamically corrected to ensure accuracy, the signals are collected to extract strain, and 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:

[0112] a1. Dual-wavelength division

[0113] The working wavelengths of the top edge layer sensor array and the working wavelengths of the hypotenuse layer sensor array are spectrally spatially distributed, specifically as follows:

[0114] (1) The working wavelengths of the top edge layer sensor array are limited to a first waveband that is sensitive only to environmental physical quantities;

[0115] (2) The working wavelength of the hypotenuse layer sensor array is limited to the second waveband which synchronously responds to mechanical strain and environmental disturbance ;

[0116] (3) The working wavelength of the base layer sensor array is deployed to cover the first waveband and the second waveband ;

[0117] The first waveband and the second waveband are kept apart in the spectral domain to avoid wavelength aliasing;

[0118] a2. Dynamic correction

[0119] Since the temperature field, salt fog concentration and geotechnical mechanics parameters of the coastal slope have significant time-varying characteristics, and a large number of experiments have proved that the strain sensitivity of the same batch of FBG sensors serving in the coastal environment for 3 years divergence rate is ± 9.7% (initial ± 1.2%), the temperature sensitivity attenuation rate is 5%~18% different, so in the following four cases, the environmental coupling factor, strain sensitivity coefficient and corrosion attenuation coefficient need to be dynamically recalibrated, the dual-wavelength division mechanism and parameter correction process flow chart is shown in the attached Figure 2 , the specific operation is as follows:

[0120] (1) When salt fog mutation event occurs, the environment disturbs the base layer sensor, and the environmental coupling factor is recalculated; when the base layer detects (salt fog mutation event), the environmental coupling factor is corrected; the corrected environmental coupling factor is calculated to eliminate environmental disturbance, the formula is as follows:

[0121]

[0122] , wherein is the reference environmental noise change, that is, the reference environmental noise signal, which is the wavelength shift output by the base layer sensor, which is purely caused by environmental factors (temperature / salt fog) and does not contain any mechanical strain component; is the step change threshold, which is determined according to the statistical characteristics of the background noise of historical monitoring data and the identification results of environmental mutation events; is the reference strain zero point change under strain and environmental disturbance, that is, the reference strain zero point signal, which is the wavelength shift output by the base layer sensor, which is the strain output value after eliminating environmental disturbance by decoupling algorithm, which should be theoretically constant zero signal; is the current reference value; is the initial calibration value; This represents the initial change in ambient noise, i.e., the initial ambient noise signal. This is the initial strain zero-point quantity, i.e., the initial strain zero-point signal;

[0123] (2) When the angled layer sensor detects deformation exceeding the long-term drift threshold When, i.e., the sensor strain (Suspected precursor to landslide) Strain sensitivity coefficient Make corrections; calculate the corrected strain sensitivity coefficient. The steps are as follows:

[0124] Apply hydraulic load to the bottom layer Hydraulic load Dynamically adjust based on the real-time inverted elastic modulus E of the soil and rock to meet hydraulic load requirements. >2 times the maximum hydrostatic pressure at tidal level, collect and record the environmental wavelength shift of the bottom edge sensor. and mixed wavelength shift First, eliminate environmental interference to obtain the wavelength change caused by deformation. Then, convert this change into the deformation caused by force using the elastic modulus E of the soil and rock. Finally, apply hydraulic load. Calculate the current strain sensitivity coefficient The formula is as follows:

[0125]

[0126] in, The long-term drift threshold is essentially... The annual average drift rate of the bottom layer sensor is determined through the following steps: based on the accuracy target of the monitoring system (e.g., strain error <1με within 10 years), the upper limit of the wavelength drift rate is derived. Verification was achieved through accelerated aging experiments. Coverage of the preset lifespan target; based on the statistical distribution of sensor drift rates at the bottom edge layer in the field, ensure... Greater than 95% of the normal drift value of the bottom layer sensor; For the first band Wavelength shift of environmental noise due to environmental interference For the second band Wavelength shift resulting from a combination of strain and environmental disturbances;

[0127] (3) Caused by the temperature difference between day and night The periodic drift is considered, and when the temperature is stable, the environmental coupling factor is corrected with a 24-hour cycle. The corrected environmental coupling factor is calculated using the ratio of the total change in environmental disturbance in the top layer over 24 hours to the total change in environmental disturbance in the bottom layer. The formula is as follows:

[0128]

[0129] wherein, is the modified environmental coupling factor; is the unmodified environmental coupling factor; is the variation of the wavelength measured by the top edge layer sensor over time; is the variation of the wavelength measured by the bottom edge layer sensor over time; is the is the variation of the wavelength measured by the bottom edge layer sensor over time; is the

[0130] (4) The corrosion attenuation coefficient of the sensor caused by the growth of salt crystals in the salt spray is attenuated by 5-18% per year, which causes errors in the strain sensitivity coefficient. The corrosion attenuation coefficient and the strain sensitivity coefficient are corrected every year as a cycle to maintain the long-term accuracy of the top edge layer sensor and the bottom edge layer sensor, which is used to offset the influence of salt crystals. The ratio of the top edge layer corrosion wavelength change rate to the bottom edge layer reference wavelength change rate is used to correct the corrosion attenuation coefficient. The modified corrosion attenuation coefficient and the strain sensitivity coefficient are calculated, and the formula is as follows:

[0131]

[0132] wherein, is the modified corrosion attenuation coefficient; is the unmodified corrosion attenuation coefficient; is the absolute value of the top sensor wavelength change rate, is the absolute value of the bottom edge layer sensor wavelength change rate, ; is the strain sensitivity coefficient after one cycle of correction; is the strain sensitivity coefficient before one cycle of correction; is the salt spray concentration; is the duration in the salinity environment;

[0133] a3. Collecting signals to extract strain

[0134] (1) Collect the wavelength offset of the top edge layer sensor , which is used as a pure environmental noise reference;

[0135] (2) Collect the wavelength offset of the inclined edge layer sensor , which is used as a mixed monitoring signal;

[0136] (3) From the inclined edge layer sensor , remove the environmental interference, and then convert it into strain through the strain sensitivity coefficient. The strain not considering the influence of tides is extracted according to the following operation formula, and the formula is as follows:

[0137]

[0138] wherein, is the strain without considering the interference of tidal action;

[0139] a4. removing the interference of tidal action

[0140] (1) hydrostatic pressure compensation

[0141] The static water pressure generated by the tidal level change is first compensated according to the tidal level data, a tidal level-wavelength offset mapping table is established, the wavelength offset corresponding to the tidal level data is calibrated, and the equivalent strain is obtained; the equivalent strain obtained from the mapping table is collected in real time, and the real strain is obtained by deducting the equivalent strain from the measured value of the inclined side layer ;

[0142] (2) wave dynamic filtering

[0143] The real deformation signal is obtained by filtering the frequency band determined as wave interference through phase difference discrimination, and retaining the low frequency <0.1 Hz and high frequency >10 Hz.

[0144] More specifically, the a4 compensates the static water pressure by the tidal level mapping table, and filters the wave interference by phase difference analysis, and the specific steps are as follows:

[0145] (1) hydrostatic pressure compensation

[0146] The tidal level-wavelength offset mapping table is established: the static water pressure generated by the tidal level change is determined by the tidal level data, the hydraulic gradient of the simulation tidal level data to the bottom layer is determined, and the wavelength offset and the equivalent strain are calibrated; the tidal level data is collected in real time, the equivalent strain is generated by searching the mapping table , and the equivalent strain is deducted from the measured value of the inclined side layer, and the formula is as follows:

[0147]

[0148] wherein, is the real strain after removing the interference of tidal action;

[0149] (2) filtering wave dynamic filtering

[0150] The bottom layer sensor signal generates two types of interference: pseudo-strain noise and frequency spectrum aliasing; the phase difference analysis method is used to identify the interference, and the specific operation is performed according to the following steps:

[0151] ① Signal synchronous acquisition:

[0152] 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 a static water pressure mapping table and reflects the ideal strain waveform under the action of pure tidal load;

[0153] ② Frequency domain transformation processing:

[0154] The real-time monitoring signal and the tidal simulation signal are respectively analyzed in the frequency domain, and are decomposed into spectral components of different frequencies; the frequency domain analysis uses fast spectral transformation technology, with a resolution of not less than 0.01 Hz, to ensure the differentiation of different frequencies;

[0155] ③ Phase consistency discrimination:

[0156] The phase offset angle of each frequency component is calculated: when the phase offset angle of the monitoring signal and the simulation signal in a specific frequency band is less than 30 degrees, it is determined that the signal in the frequency band is dominated by wave power interference; when the phase offset angle is greater than 30 degrees, the real deformation signal is retained; the phase offset angle is determined by comparing the alignment degree of the wave crests / troughs of the same frequency components of the two signals;

[0157] ④ Interference signal marking:

[0158] The frequency band determined to be wave interference is added with a filter mark and filtered; the real deformation signal of the low-frequency creep signal and the high-frequency rupture signal with a phase offset angle greater than 30 degrees is retained.

[0159] S3) For the annual scale monitoring distortion caused by salt crystal accumulation and material aging, the top edge layer sensor and the bottom edge layer sensor are used to extract the top edge layer annual average drift and the bottom edge layer reference drift, and after calculating the annual corrosion attenuation coefficient, the annual scale monitoring cumulative displacement is corrected.

[0160] Specifically, in the step S3), for the annual scale monitoring distortion caused by salt crystal accumulation and material aging, the top edge layer sensor and the bottom edge layer sensor are used to extract the top edge layer annual average drift and the bottom edge layer reference drift, and after calculating the annual corrosion attenuation coefficient, the annual scale monitoring cumulative displacement is corrected, and the specific steps are as follows:

[0161] (1) Extracting the annual average drift of the top edge layer sensor (Taking the average value of the annual average drift of all sensors in the top edge layer);

[0162] (2) Obtaining the reference drift of the bottom edge layer sensor ;

[0163] (3) Calculating the annual corrosion attenuation coefficient The formula is as follows:

[0164]

[0165] Wherein, the time is one year, is a salt fog concentration function;

[0166] (4) The formula for correcting the annual scale monitoring cumulative displacement is as follows:

[0167]

[0168] wherein, is the corrected cumulative displacement, is the uncorrected cumulative displacement, is an annual corrosion attenuation coefficient, is a cumulative time, is a dynamic corrosion factor.

[0169] More specifically, the dynamic corrosion factor is obtained by the following steps:

[0170] ① Temperature compensation processing:

[0171] For each roof edge layer sensor in the roof edge layer, a temperature change caused component is deducted from the wavelength shift output by the sensor to obtain a temperature compensated wavelength shift; the temperature change component is obtained by multiplying the environmental temperature change at the position of the sensor by a pre-labeled temperature sensitivity coefficient;

[0172] ② Salt fog deposition amount conversion:

[0173] The temperature compensated wavelength shift is divided by the salt fog sensitivity coefficient of the roof edge layer sensor to obtain the salt fog deposition amount at the corresponding time; the salt fog sensitivity coefficient is obtained by a laboratory salt fog chamber calibration test in advance;

[0174] ③ Instantaneous change rate calculation:

[0175] For each roof edge layer sensor, the difference in salt fog deposition amount between two adjacent sampling time points is calculated;

[0176] The difference is divided by the corresponding time interval to obtain the instantaneous value of the dynamic corrosion factor of the roof edge layer sensor in the current time period;

[0177] ④ Spatial fusion processing:

[0178] The instantaneous values of the dynamic corrosion factors of all valid roof edge layer sensors of the roof edge layer at the same time are arithmetically averaged to obtain the dynamic corrosion factor at the time;

[0179] Wherein the valid sensor should satisfy that its instantaneous value of the dynamic corrosion factor is within a pre-set reasonable range, and abnormal data caused by biological attachment or mechanical damage is excluded;

[0180] ⑤ Abnormal data processing:

[0181] When the data of a top-layer sensor is missing, the average of the three top-layer sensors adjacent to the top-layer sensor is used to replace the missing data.

[0182] When the data of a region is missing, the data of the salt concentration rate provided by the weather station is used as the backup dynamic corrosion factor.

[0183] S4) According to the annual corrosion attenuation coefficient and the salt concentration, the normal working time is calculated by the formula to predict the service life of the sensor.

[0184] Specifically, in step S4), according to the annual corrosion attenuation coefficient and the salt concentration, the normal working time is calculated to predict the service life of the sensor, and the specific steps are as follows:

[0185] When the sensitivity of the top-layer sensor, the oblique-layer sensor, and the bottom-layer sensor is attenuated to 80% of the initial value (i.e., a loss of 20% is allowed) due to salt deposition (or other environmental factors), the normal working time of the sensor is calculated by the annual corrosion attenuation coefficient and the salt concentration The formula is as follows:

[0186]

[0187] wherein, is the normal working time of the sensor.

[0188] Although the preferred embodiments of the present application have been described, those skilled in the art who are familiar with the basic inventive concept can make additional changes and modifications to the embodiments. Therefore, the appended claims are intended to include the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0189] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for monitoring deformation of a coastal slope based on a dual-wavelength and fiber grating network, characterized in that, The method comprises the following steps: S1) Sensor deployment on the top edge layer, inclined edge layer and bottom edge layer of the coastal slope according to the network topology structure, wherein the top edge layer sensor realizes environmental disturbance capture, the inclined edge layer sensor captures shear deformation data, and the bottom edge layer sensor establishes an absolute displacement reference point, and a spatial topology basis for cooperative monitoring is constructed; The sensor network topology structure deployment on the coastal slope comprises: Deploying the sensor network topology structure on the top edge layer, inclined edge layer and bottom edge layer of the coastal slope, wherein the top edge layer sensor array is used for capturing pure environmental disturbance signals; the inclined edge layer sensor array is used for capturing shear deformation along the main strain direction of the slope; and the bottom edge layer sensor array is used for establishing an absolute displacement reference point; S2) Assigning the working wavelengths of the top edge layer sensor and the inclined edge layer sensor, and then dynamically correcting the parameters to ensure accuracy; collecting signals to extract strain, establishing a tide level-wavelength offset mapping table to compensate for hydrostatic pressure, and using phase difference analysis to filter wave disturbance to suppress the disturbance of tidal action, so as to realize the monitoring of the deformation of the coastal slope and provide reliable data for slope stability evaluation; Assigning the working wavelengths of the top edge layer sensor and the inclined edge layer sensor, and then dynamically correcting the parameters to ensure accuracy, collecting signals to extract strain, establishing a tide level-wavelength offset mapping table to compensate for hydrostatic pressure, and using phase difference analysis to filter wave disturbance, the specific steps are as follows: a1. Double-wavelength division The working wavelengths of the top edge layer sensor array and the inclined edge layer sensor array are spectrally allocated in space, specifically as follows: (1) limiting the operating wavelength of the top edge layer sensor array to a first waveband that is sensitive only to the environmental physical quantity ; (2) limiting the working wavelength of the hypotenuse layer sensor array to a second wavelength band that is synchronous to respond to mechanical strain and environmental interference ; (3) The working wavelength deployment of the bottom edge layer sensor array covers the first waveband and the second waveband ; The first wave band and the second wave band maintain a certain interval in the spectral domain to avoid wavelength aliasing; a2. Dynamic correction In the following four cases, the environmental coupling factor, strain sensitivity coefficient and corrosion attenuation coefficient are dynamically recalibrated, and the specific operations are as follows: (1) When 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 , the environmental coupling factor is corrected, and the environmental coupling factor is calculated, and the formula is as follows: ； wherein, is a step change threshold value; is a reference ambient noise variation, i.e. a reference ambient noise signal; is a reference strain zero point variation under strain and environmental disturbance, i.e. a reference strain zero point signal; is a current reference value; is an initial calibration value; is an initial ambient noise variation, i.e. an initial ambient noise signal; is an initial strain zero point variation, i.e. an initial strain zero point signal; (2) When the hypotenuse layer sensor monitors a deformation exceeding a long-term drift threshold , the sensor strain , the strain sensitivity coefficient is corrected, and the steps for calculating the strain sensitivity coefficient are as follows: Apply hydraulic load on the bottom layer , hydraulic load According to the real-time inversion of rock and soil elastic modulus E dynamic adjustment, meet the hydraulic load Maximum static pressure of 2 tidal range, collect and record the environmental wavelength shift of the bottom layer sensor And mixed wavelength shift First eliminate the environmental interference, get the wavelength change caused by deformation, convert it into the deformation caused by stress through rock and soil elastic modulus E, and then calculate the strain sensitivity coefficient With hydraulic load , the formula is as follows: ； wherein is a first wavelength band is a wavelength shift under environmental noise, is a second wavelength band is a mixed wavelength shift under strain and environmental noise; (3) When the temperature is in the stable period, the environmental coupling factor is corrected with 24 hours as a cycle; the ratio of the total change of environmental disturbance of the top edge layer sensor and the total change of environmental disturbance of the bottom edge layer sensor is used to calculate the corrected environmental coupling factor , the formula is as follows: ； in, This is the corrected environmental coupling factor; The environmental coupling factor before correction; Wavelength measured by the top edge layer sensor over time The change in; Wavelength measured by the bottom layer sensor over time The change in; (4) Correcting the corrosion attenuation coefficient and the strain sensitivity coefficient every year as a cycle to maintain the long-term accuracy of the top edge layer sensor and the bottom edge layer sensor; using the ratio of the corrosion wavelength change rate of the top edge layer sensor to the reference wavelength change rate of the bottom edge layer sensor to correct the corrosion attenuation coefficient, calculating the corrected corrosion attenuation coefficient and the strain sensitivity coefficient, and the formula is as follows: ； wherein, is the corrected corrosion attenuation coefficient; is the uncorrected corrosion attenuation coefficient; is the absolute value of the wavelength change rate of the top edge layer sensor, ; is the absolute value of the wavelength change rate of the bottom edge layer sensor, ; is the corrected strain sensitivity coefficient for one cycle; is the uncorrected strain sensitivity coefficient for one cycle; is the salt mist concentration; is the duration under the salinity environment; a3. Collecting signals to extract strain (1) Collecting the wavelength shift of the top edge layer sensor as a pure environmental noise reference; (2) Collecting the wavelength offset of the hypotenuse layer sensor as a mixed monitoring signal; (3) From the hypotenuse layer sensor In the above, the environmental disturbance is removed, and the strain is converted into strain by the strain sensitivity coefficient. The strain not considering the tidal effect disturbance is extracted according to the following operation formula, and the formula is as follows: ； wherein is the strain without considering the interference of tidal action; a4. Removing the disturbance of tidal action (1) Hydrostatic pressure compensation First, according to the tidal height data, the tidal height-wave length offset mapping table is built, the wavelength offset and equivalent strain corresponding to the tidal height data are calibrated; the equivalent strain is obtained from the mapping table in real time, which is deducted from the measured value of the hypotenuse layer sensor, and the true strain eliminating the tidal interference is obtained ; (2) Wave power filtering Synchronize the real-time strain monitoring signal and the tidal theory simulation signal, and decompose them into different frequencies through frequency domain transformation; through phase difference discrimination, filter the frequency band determined as wave disturbance, and retain the true deformation signal of low frequency <0.1Hz and high frequency >10Hz; S3) Extracting the top edge layer annual drift and the bottom edge layer reference drift through the top edge layer sensor and the bottom edge layer sensor respectively, calculating the annual corrosion attenuation coefficient, and correcting the annual scale monitoring cumulative displacement; The specific steps are as follows: (1) Extracting the top edge layer sensor annual drift ; (2) Obtain the bottom layer sensor reference drift ; (3) Calculate the annual corrosion decay factor The formula is as follows: ； wherein the time is one year, is a salt fog concentration function; (4) The formula for correcting the annual scale monitoring cumulative displacement is as follows: ； wherein, is the corrected cumulative displacement, is the uncorrected cumulative displacement, is the annual corrosion decay factor, is the cumulative time, is the dynamic corrosion factor; S4) According to the annual corrosion attenuation coefficient and the salt fog concentration, the normal working time is calculated to predict the service life of the sensor.

2. The method according to claim 1, wherein, In a4, the static water pressure is compensated by searching the mapping table according to the tide level, and the wave disturbance is filtered by phase difference analysis, and the specific steps are as follows: (1) Hydrostatic pressure compensation Establishing the mapping table of tidal level-wavelength offset: through the tidal level data, the hydraulic gradient of the simulated tidal level data on the bottom layer is determined, and the wavelength offset and equivalent strain are calibrated; the tidal level data is collected in real time, and the equivalent strain is generated by looking up the mapping table Subtracting the measured value from the hypotenuse layer sensor, the formula is as follows: ； wherein Real strain after eliminating tidal interference; (2) Filtering wave power filtering The bottom layer sensor signal generates two types of interference: spurious strain noise and spectral aliasing. Interference is identified using phase difference analysis, and the specific steps are as follows: ①Signal synchronous acquisition: The real-time strain monitoring signal and tidal theory simulation signal of the slope are acquired in parallel; the tidal theory simulation signal is generated by hydrostatic pressure mapping table, reflecting the ideal strain waveform under pure tidal load. ② Frequency domain transformation processing: Frequency domain analysis was performed on the real-time monitoring signal and the tidal simulation signal, decomposing them into spectral components of different frequencies. The frequency domain analysis adopted fast spectrum transform technology with a resolution of no less than 0.01Hz to ensure the distinction between different frequencies. ③ Phase consistency judgment: Calculate the phase offset angle of each frequency component: when the phase offset angle between the monitored signal and the simulated signal in a specific frequency band is less than 30 degrees, it is determined that the signal in that frequency band is dominated by wave dynamic interference; when the phase offset angle is greater than 30 degrees, it is retained as the true deformed signal; the phase offset angle is determined by comparing the alignment degree of the peaks / troughs of the same frequency components of the two signals. ④ Interference signal marking: Add a filter label to the frequency bands identified as wave interference and filter them out; retain the true deformation signals of low-frequency creep signals and high-frequency rupture signals with a phase offset angle greater than 30 degrees. 3.The method according to claim 1, wherein, the dynamic corrosion factor was obtained by the following steps: ① Temperature compensation processing: For each sensor in the top edge layer, the temperature-compensated wavelength shift is obtained by subtracting the component caused by temperature change from its output wavelength shift. The temperature change component is obtained by multiplying the ambient temperature change at the sensor's location by a pre-calibrated temperature sensitivity coefficient. ② Salt spray deposition conversion: The amount of salt fog deposition at the corresponding time is obtained by dividing the temperature-compensated wavelength shift by the salt fog sensitivity coefficient of the top edge layer sensor; the salt fog sensitivity coefficient is obtained in advance through laboratory salt fog chamber calibration test. ③ Calculation 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 time period; ④ Spatial fusion processing: The instantaneous values ​​of the dynamic corrosion factor of all effective top edge layer sensors at the same moment are arithmetically averaged and used as the dynamic corrosion factor at that moment. Among them, the effective sensor should meet the requirement that its dynamic corrosion factor instantaneous value is within a preset reasonable range, and exclude abnormal data caused by biological adhesion or mechanical damage. ⑤ Abnormal data handling: When data from a certain top-edge sensor is missing, the average of the three adjacent top-edge sensors in the same region is used as a substitute. When regional data is missing, the salt spray concentration change rate data provided by the meteorological station is used as a backup dynamic corrosion factor value. 4.The method according to claim 1, wherein, In step S4), the normal operating time is calculated based on the annual corrosion decay coefficient and salt spray concentration to predict the sensor's service life. The specific steps are as follows: When the top edge layer sensor, the bevel edge layer sensor, and the bottom edge layer sensor have their sensitivity attenuated to 80% of the initial value due to salt spray deposition, the annual corrosion attenuation coefficient is calculated by and the salt spray concentration The length of time during which it operates normally is calculated, according to the formula: ； wherein, is the duration of normal operation of the sensor.

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