Strip mine wide-area deformation field monitoring method based on flexible photonic crystal coding

Abstract

The invention discloses a strip mine wide-area deformation field monitoring method based on flexible photonic crystal coding, and belongs to the technical field of strip mine slope safety monitoring. A'sandwich 'heterostructure is adopted, the flexibility, environmental tolerance and long-term stability of the sensor are improved, the problems that a traditional optical fiber sensor is prone to damage and high in cost are solved, and the sensor is suitable for complex working conditions of strip mines. By adopting a roll-to-roll micro-nano imprinting large-scale production process, high-efficiency and low-cost batch production of the sensing belt is realized, which is far lower than that of a traditional fiber grating sensor, and the sensor has economical efficiency of large-scale application. A'spectrum-space 'dual coding mechanism is adopted, high-precision space positioning and temperature self-compensation are realized, measurement errors caused by temperature are reduced, and the anti-interference capability and data reliability of the system are improved. A multi-physics coupling deformation-optical interpretation model and an extended Kalman filtering processing flow are established by using a signal interpretation algorithm, and collaborative decoupling of multiple factors such as strain, temperature and stress is realized.

Description

Technical Field

[0001] This invention belongs to the field of open-pit mine slope safety monitoring technology, and specifically relates to a method for monitoring wide-area deformation fields in open-pit mines based on flexible photonic crystal encoding. Background Technology

[0002] Monitoring surface deformation on open-pit mine slopes is a core technical aspect of preventing geological disasters such as landslides and collapses, and is especially crucial for the safe operation of large-scale projects such as open-pit mines and railway / highway subgrades. Currently, this field mainly relies on the following monitoring technologies, but all of them have inherent technical bottlenecks and cannot meet the urgent needs of modern engineering projects for large-scale, high-density, high-precision, and low-cost monitoring:

[0003] Traditional point-based monitoring technology obtains local deformation information by sparsely deploying monitoring points. It has the inherent defect of "using points to represent the whole area". It cannot capture the precise location of the overall deformation field and potential slip surface of the slope, nor can it achieve effective coverage of the entire mining area. Moreover, it is costly and complex to implement on steep slopes.

[0004] While space-based Earth observation technology can achieve large-scale monitoring, the density of GNSS monitoring points is limited and cannot reflect the detailed deformation of the terraced slope. InSAR is significantly affected by atmospheric delay and vegetation cover, and is prone to signal decoherence in mining disturbance areas. In addition, its revisit cycle of several days to tens of days makes it difficult to meet the needs of real-time early warning.

[0005] While distributed fiber optic sensing technology can achieve continuous measurement, its signals suffer from severe temperature cross-sensitivity, resulting in a significant decrease in measurement accuracy in open-pit mines with large day-night temperature differences. Furthermore, the system is costly, requiring expensive demodulation equipment and point-by-point writing of fiber optic grating sensors, leading to a massive overall investment in kilometer-scale deployment scenarios. In addition, the system is prone to localized damage under harsh conditions such as blasting and mechanical crushing, with difficult fault location, high repair costs, and insufficient ability to identify complex deformation patterns such as bending and shearing.

[0006] These technical deficiencies severely restrict the effectiveness and cost-effectiveness of open-pit mine slope safety monitoring, necessitating the development of new monitoring solutions. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for monitoring wide-area deformation fields in open-pit mines based on flexible photonic crystal encoding.

[0008] The technical solution adopted in this invention is: a flexible photonic crystal sensing strip, the key technical point of which is that it adopts a sandwich heterogeneous structure, including: a protective layer, a photonic crystal sensing layer and a signal transmission layer arranged from top to bottom; the protective layer is composite-encapsulated with the photonic crystal sensing layer by a hot-pressing process; the photonic crystal sensing layer is disposed between the protective layer and the signal transmission layer; the signal transmission layer carries the photonic crystal sensing layer and transmits optical signals.

[0009] In the above scheme, the protective layer is a polytetrafluoroethylene propylene film.

[0010] In the above scheme, the photonic crystal sensing layer uses polydimethylsiloxane as an elastic matrix, in which multiple spectral coding units formed by monodisperse nanospheres are sequentially arranged along the length of the sensing band, and the multiple spectral coding units are periodically arranged according to a preset particle size sequence.

[0011] In the above scheme, each of the spectral coding units is composed of monodisperse nanospheres of a single particle size.

[0012] In the above scheme, each of the spectral coding units further includes a spatial hybrid coding unit composed of nanospheres with mixed particle sizes, and the nanosphere particle sizes used in different coding units are different.

[0013] A method for fabricating a flexible photonic crystal sensing band, the key technical point of which is that, during the formation of the photonic crystal sensing layer, the method for fabricating the spatial hybrid coding unit includes the following steps:

[0014] Step S1: Prepare two or more monodisperse nanosphere suspensions with different particle sizes;

[0015] Step S2: Mix the nanosphere suspensions of different particle sizes according to a preset mixing ratio;

[0016] Step S3: Using an impression roller device with a nanocavity array, the mixed nanospheres are suspended and hydraulically imprinted into the uncured polydimethylsiloxane matrix to form a spatially mixed coding unit with a non-closely packed structure.

[0017] Step S4: Perform optical detection on the formed spatial mixing coding unit to verify whether there are multiple characteristic peaks in its reflection spectrum that correspond to the mixing ratio.

[0018] The signal transmission layer is a composite structure arranged from top to bottom, including:

[0019] Flexible polymer film substrate;

[0020] Polymer optical waveguide integrated on the flexible polymer thin film substrate;

[0021] The periodic wedge-shaped microstructures disposed on the upper surface of the polymer optical waveguide, the microstructures being periodically arranged in an array and having tilted reflective surfaces, are used to enhance the interlayer optical coupling between the photonic crystal sensing layer and the optical waveguide.

[0022] A silicon-based photoconductive sensing chip located below the periodic wedge-shaped microstructure and forming a light-guiding channel;

[0023] And a flexible polyimide substrate that carries the silicon-based photoconductive sensing core.

[0024] A method for monitoring wide-area deformation field in open-pit mines based on flexible photonic crystal sensing strips includes the following steps performed in sequence: Step S1: Deploy flexible photonic crystal sensing strips as described in any one of claims 1-3 along the slope of the open-pit mine to be monitored to form a monitoring network;

[0025] Step S2: Collect reflected light signals covering a wide area of ​​the slope through the monitoring network;

[0026] Step S3: Input the collected reflected light signal into the deformation-optical signal interpretation model for processing, so as to calculate the real deformation data of each monitoring location on the wide-area slope;

[0027] Step S4: Based on the real deformation data, generate a visualized wide-area deformation field distribution map / report to characterize the slope safety status, and output it.

[0028] In the above scheme, the deformation-optical signal interpretation model includes the following steps:

[0029] The reflected light signal returned by the sensor band is collected, and the reflected light signal contains spectral coding and spatial hybrid coding information;

[0030] The reflected light signal is preprocessed to separate noise from the effective component in the signal;

[0031] Extract characteristic optical parameters from the preprocessed signal, wherein the characteristic optical parameters include at least the center wavelength of the characteristic peak of the reflection spectrum;

[0032] Based on the aforementioned characteristic optical parameters, the wavelength shift is calculated using a deformation-optical signal interpretation model. The state variables, including strain, temperature, and wavelength shift, are input into an extended Kalman filter for state prediction and observation correction, so as to calculate the true mechanical strain that eliminates the influence of temperature.

[0033] Based on the actual mechanical strain and the layout parameters of the sensing belt, deformation field data is generated and output.

[0034] In the above scheme, the solution obtains the true mechanical strain that eliminates the influence of temperature, including a temperature self-compensation algorithm, which performs the following steps:

[0035] The temperature self-compensation algorithm utilizes the dual-channel sensing mechanism of the spatial hybrid coding unit to construct a temperature-insensitive parameter; when the temperature changes, the temperature-insensitive parameter remains unchanged, and the true strain is obtained by calculating the parameter.

[0036] The beneficial effects of the present invention are as follows: The flexible photonic crystal sensing strip provided by the present invention adopts a "sandwich" heterostructure. This improvement enhances the flexibility, environmental tolerance and long-term stability of the sensor, and solves the problems of easy damage and high cost of traditional fiber optic sensors. It is suitable for complex working conditions in open-pit mines.

[0037] By adopting roll-to-roll micro-nano imprinting mass production technology, efficient and low-cost mass production of sensor tapes has been achieved, which is far lower than that of traditional fiber Bragg grating sensors, making it economical for large-scale applications.

[0038] By adopting a dual encoding mechanism of "spectral-spatial", high-precision spatial positioning and temperature self-compensation are achieved, which reduces measurement errors caused by temperature and improves the system's anti-interference ability and data reliability.

[0039] A deformation-optical interpretation model and extended Kalman filter processing flow for multi-physics coupling were established using signal interpretation algorithms, achieving coordinated decoupling of multiple factors such as strain, temperature, and stress. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a flowchart of a method for monitoring wide-area deformation fields in open-pit mines based on flexible photonic crystal sensing bands, as described in an embodiment of the present invention.

[0042] Figure 2 This is a schematic diagram of the flexible photonic crystal sensing strip in an embodiment of the present invention;

[0043] Figure 3 This is a block diagram illustrating the principle of the temperature self-compensation algorithm in an embodiment of the present invention.

[0044] Figure 4 This is a schematic diagram of the layout on the slope of an open-pit mine in an embodiment of the present invention. Detailed Implementation

[0045] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the following description is provided in conjunction with the accompanying drawings. Figures 1-4 The present invention will be further described in detail below with reference to specific embodiments.

[0046] This embodiment provides a flexible photonic crystal sensing strip with a sandwich heterogeneous structure, comprising a protective layer, a photonic crystal sensing layer, and a signal transmission layer arranged from top to bottom. The protective layer is composite-encapsulated with the photonic crystal sensing layer via a hot-pressing process. The photonic crystal sensing layer is disposed between the protective layer and the signal transmission layer. The signal transmission layer carries the photonic crystal sensing layer and transmits optical signals. In this embodiment, the upper protective layer is made of FEP roll material with a thickness of 50 μm and a width of 52 cm. The lower signal transmission layer is made of polyimide roll material with a thickness of 100 μm and a width of 50 cm, on which a photoconductive sensing core array has been integrated using standard photolithography.

[0047] In this embodiment, a polytetrafluoroethylene propylene film is selected as the first protective barrier of the sensing strip. Its thickness is 50 μm, and it is sealed with the intermediate functional layer through a hot-pressing process.

[0048] In this embodiment, the photonic crystal sensing layer uses polydimethylsiloxane as an elastic matrix and embeds multiple spectral coding units arranged sequentially along the length of the sensing band. Each spectral coding unit is composed of monodisperse nanospheres of a single particle size. In this embodiment, the monodisperse nanospheres are silica nanospheres with a particle size in the range of 150-300 nm and a dispersion coefficient of less than 5%. The photonic crystal sensing layer employs a spectral coding system, with a coding unit length of 10 cm. Adjacent units are periodically arranged according to a nanosphere particle size sequence of 150 nm, 180 nm, 210 nm, 240 nm, 270 nm, and 300 nm.

[0049] This embodiment can also incorporate spatial hybrid coding units based on monodisperse nanospheres. The method for preparing the spatial hybrid coding units includes the following steps:

[0050] First, in the substrate material preparation stage, suspensions of two nanospheres with different particle sizes (e.g., 200 nm and 250 nm) are prepared using microfluidic technology. The nanospheres are dispersed in an ethanol-water mixed solvent, with the addition of appropriate surfactants (such as SDS or CTAB) to prevent agglomeration. They are then precisely proportioned according to preset mixing ratios (e.g., 1:1, 2:1, 1:2, etc.). Each mixing ratio corresponds to a specific coding sequence, and these ratios are controlled by adjusting the flow rate and time of the liquid supply to ensure the accuracy of the mixing ratio in each coding unit. During the imprinting process, an imprinting roller device with a dual-size nanocavity array on its surface is used. This cavity array corresponds one-to-one with the preset coding unit arrangement. By adjusting the pressure, the mixed nanosphere suspension is filled into the corresponding nanocavities. During the imprinting process, the imprinting pressure is monitored in real time and maintained within the range of 0.1–0.5 MPa and the temperature within the range of 60–80 °C, thereby ensuring that the nanospheres form a stable, non-closely packed structure within the PDMS matrix.

[0051] The second stage is the coding verification phase. After each coding unit is prepared, a bimodal reflectance spectrum is immediately performed to measure the center wavelengths (λ = 540 nm, λ = 674 nm) and intensity ratio (I / I) of the two characteristic peaks. The test data is compared with a preset coding standard; unqualified coding units are automatically marked and recorded. In actual testing, deformation measurement and temperature compensation are achieved by analyzing changes in the bimodal intensity ratio. When the sensing band deforms, the intensity ratio of the two characteristic peaks changes systematically. Using a pre-calibrated ratio-strain relationship curve, the actual mechanical strain value can be directly calculated. Because this ratio is insensitive to temperature changes (temperature coefficient < 0.05% / ℃), a temperature self-compensation function is achieved.

[0052] In this embodiment, the signal transmission layer uses a flexible polymer film as a substrate, on which a polymer optical waveguide is integrated using micro-nano fabrication processes. The upper surface of the optical waveguide has periodic wedge-shaped microstructures. These periodic wedge-shaped microjunctions, formed on the upper surface of the polymer optical waveguide, are periodically arranged wedge-shaped protrusions used to efficiently couple reflected light from the photonic crystal sensing layer into the optical waveguide, thereby improving the optical coupling efficiency with the photonic crystal sensing layer. Above the periodic wedge-shaped microjunctions are a silicon-based optical guide sensing core and flexible polyimide. This embodiment's periodic wedge-shaped micro-shielding structure effectively suppresses external electromagnetic interference while adapting to the irregular curvature of the slope surface.

[0053] This invention improves the positioning accuracy of the system to ±5cm through a dual identification mechanism (spectral coding + spatial hybrid coding); by utilizing the temperature insensitivity of the bimodal intensity ratio, the measurement error caused by temperature is reduced to ±0.2mm; at the same time, the unique spectral characteristics of each coding unit ensure the identifiability of the monitoring point and the reliability of the data.

[0054] In this embodiment, the signal transmission layer uses a flexible polymer film as a substrate, on which a polymer optical waveguide is integrated using micro-nano fabrication processes. The upper surface of the optical waveguide has periodic wedge-shaped microstructures. These periodic wedge-shaped microjunctions, formed on the upper surface of the polymer optical waveguide, are periodically arranged wedge-shaped protrusions used to efficiently couple reflected light from the photonic crystal sensing layer into the optical waveguide, thereby improving the optical coupling efficiency with the photonic crystal sensing layer. Above the periodic wedge-shaped microjunctions are a silicon-based optical guide sensing core and flexible polyimide. This embodiment's periodic wedge-shaped micro-shielding structure effectively suppresses external electromagnetic interference while adapting to the irregular curvature of the slope surface.

[0055] The sensing tape in this embodiment is manufactured using a roll-to-roll micro / nano imprinting process. This process system includes six main steps: unwinding and plasma surface treatment, precision coating, micro / nano imprinting and nanosphere filling, pre-stretching and thermosetting, release and lamination, and rewinding and inspection. The nanoimprinting unit in this embodiment uses a nickel imprinting roller, whose surface is processed with an array of cylindrical nanocavities with a depth of 150 nm and diameters of 150-300 nm using electron beam lithography and electroforming. The cavities are distributed according to a preset coding pattern, achieving a processing accuracy of ±5 nm, ensuring the consistency and accuracy of the coding pattern. The hot pressing process employs a roll-to-roll micro / nano imprinting manufacturing process, which is as follows:

[0056] (1) Unwinding and Plasma Treatment: The PI substrate roll is loaded onto the unwinding device and unwound at a speed of 0.5 m / min. The PI surface is activated by a corona treatment machine to improve the adhesion of PDMS.

[0057] (2) Precision coating: A slit coating head is used, and the base agent and curing agent are mixed at a weight ratio of 10:1. The degassed PDMS mixture is uniformly coated on the PI substrate, and the wet film thickness is controlled at 30μm.

[0058] (3) Micro / Nano Imprinting and Nanosphere Filling: The coated substrate immediately passes through the pressure zone (0.3 MPa) between the imprinting roller and the support roller. The imprinting roller rotates clockwise, and its internal microdroplet jetting system precisely sprays nanosphere suspensions of the corresponding particle size into the nanocavity below it according to a preset program. Under the action of capillary force, the nanospheres self-assemble and fill the cavity, while the PDMS slurry is imprinted with the corresponding negative structure.

[0059] (4) Pre-stretching and heat curing: After imprinting, the strip enters the tension control zone, and the speed difference is controlled to induce a precise 1.5% engineering strain in the strip. Subsequently, the strip passes through a 5-meter-long heating tunnel, which is divided into three zones with temperatures set at 80℃, 100℃, and 120℃ respectively. The strip is cured at 120℃ for about 2 minutes.

[0060] (5) Tension release and composite: After curing, the strip leaves the tension control system, and the elastic PDMS layer rebounds to form a stable prestressed structure. Then, the FEP material layer and the PDMS sensing layer are composited through a pair of hot press rollers (temperature 150℃, pressure 0.5MPa).

[0061] (6) Winding and Inspection: The finished composite sensor tape is wound up. Every 100 meters produced, the reflectance spectrum of the sensor tape is sampled and inspected using an online spectral detection system to ensure coding accuracy and consistent optical performance.

[0062] In this embodiment, the production line operates at a precisely controlled speed of 0.5 m / min, ensuring complete transfer and encoding accuracy of the nanostructure. The imprint roller is processed using electron beam lithography, achieving a surface nanocavity array processing accuracy of ±5 nm. Each imprint roller contains over 10 million nanocavities, ensuring the consistency and accuracy of the encoded pattern. During manufacturing, the system uses machine vision to detect encoding quality in real time, and an online spectral detection system verifies the optical characteristics of each encoding unit. This highly automated production process keeps the unit length production cost of the sensor tape at 8-12 RMB / meter, far lower than the 100-200 RMB / point cost of traditional fiber Bragg grating sensors.

[0063] Example 1:

[0064] This embodiment provides a low-cost method for monitoring wide-area deformation fields in open-pit mines based on flexible photonic crystal sensing strips, comprising the following steps performed in sequence:

[0065] Step S1: Deploy flexible photonic crystal sensor strips along the open-pit mine slope to be monitored, using a trunk line deployment method to form a monitoring network.

[0066] This embodiment employs a physically isolated, dual-redundant backbone network, comprising the following steps: laying a main sensing strip and a parallel redundant sensing strip, spaced 0.3m to 1.0m apart and independently protected by conduits, within separate protective pipes to achieve physical isolation and prevent simultaneous failure of both lines due to the same external force event. IP68-rated explosion-proof / waterproof junction boxes with built-in stress buffer structures are installed at the line joints; maintenance wells with optical testing interfaces are installed every 150m to 250m along the backbone network, each well equipped with a standardized fiber optic distribution frame for convenient daily system maintenance, performance testing, and rapid location and switching of faulty sections. For example, in this embodiment, the main signal junction station is located in a stable zone ≥200m outside the mining area boundary, using a C30 concrete foundation (1.5m × 1.5m × 1.0m). The main trunk line adopts a dual redundancy architecture, laying two parallel armored sensing strips (outer diameter 8mm, compressive strength ≥80kN / m, bending radius ≥150mm), with a parallel spacing of 0.5m, and independently laid using SN8 grade PVC solid wall conduit. The junction box has an IP68 protection rating and a built-in "S"-shaped stainless steel stress buffer structure (capable of withstanding ±5mm displacement). The maintenance manholes are spaced 200m apart and include built-in 19-inch fiber optic patch panels and FC / APC test interfaces.

[0067] The redundant sensing strip used in this embodiment consists of one or more "sensor strips" connected by a splitter. It extends from the junction box of the main line to the slope step area to be monitored. Each branch node is equipped with a smart splitter, for example, this splitter supports 1×N splitting (N is an integer greater than or equal to 2, typically 1×8 in this embodiment), with an insertion loss of no more than 3.5dB and a return loss of no less than 55dB, ensuring efficient and low-noise transmission of the optical signal on the branch link. The branch link length is dynamically adjusted according to the step height, and the formula for calculating the reserved length is:

[0068] L reserve =1.02*L design *(1+αΔT)

[0069] In the formula L design α is the design length of the branch chain; α is the coefficient of thermal expansion of the sensing band (5×10). -6 / ℃); ΔT is the estimated local annual temperature variation range. This design avoids the sensor belt being too tight or too loose due to temperature stress, which could affect monitoring accuracy or damage the sensor belt. The inclination angle of the branch chain is dynamically optimized and adjusted according to the actual geometric characteristics of the step slope to ensure that the fit between the sensor belt and the slope surface reaches more than 90% (preferably ≥95%), maximizing the deformation coordination between the sensor belt and the soil.

[0070] For example, branch nodes are equipped with intelligent optical splitters, supporting 1-to-8 signal distribution with an insertion loss of no more than 3.5 dB. The branch chain length is determined based on the step height, with a 2% temperature expansion margin reserved. In key monitoring areas such as the F5 fault, a high-density grid deployment scheme is adopted, with three parallel branch chains simultaneously led out from one splitter, and the chain spacing strictly controlled at 10 meters to form a dense monitoring network.

[0071] Step S2: Collect reflected light signals covering a wide area of ​​the slope through a monitoring network;

[0072] Step S3: Input the collected reflected light signals into the intelligent interpretation method for processing, so as to calculate the real deformation data of each monitoring location on the wide-area slope;

[0073] The intelligent interpretation method used in this embodiment is as follows:

[0074] Step S3.1: Collect the reflected light signal returned by the sensor band. The reflected light signal contains spectral coding and spatial hybrid coding information.

[0075] The reflected light signal is preprocessed to separate noise from the effective components. For example, a wavelet threshold denoising algorithm is used, which performs a five-level decomposition using the Daubechies wavelet basis function to effectively separate the noise components from the effective signal.

[0076] Step 3.2: Identify the peak values ​​of the reflection spectrum from the preprocessed signal using a Gaussian fitting algorithm. The characteristic optical parameters include at least the center wavelength of the characteristic peak of the reflection spectrum.

[0077] Step 3.3: Based on the aforementioned characteristic optical parameters, calculate the wavelength offset using the deformation-optical signal interpretation model.

[0078] The interpretation model used in this embodiment is:

[0079]

[0080] In the formula, Δλ is the reflection center wavelength offset, λ0 is the initial center wavelength, and K ε K is the strain sensitivity coefficient, ε is the axial strain, and K is the strain sensitivity coefficient. σ K is the stress sensitivity coefficient, σ is the stress component, and K is the stress sensitivity coefficient. T β is the temperature sensitivity coefficient, ΔT is the temperature change, and β is the temperature sensitivity coefficient. i Let φ be the coupling coefficient of the i-th environmental factor. i As an environmental impact factor, ξ noise This represents the system noise term. Model parameters were determined using a hybrid optimization algorithm that combines the global search capability of a genetic algorithm with the local convergence characteristics of the Levenberg-Marquardt algorithm, ensuring the accuracy and stability of parameter calibration.

[0081] Model parameters were determined using a hybrid optimization algorithm that combines the global search capability of a genetic algorithm with the local convergence property of the Levenberg-Marquardt algorithm. The genetic algorithm, with a population size of 50 and 200 generations, achieved global parameter optimization; the LM algorithm then fine-tuned the parameters to ensure accuracy and stability of the calibration. The strain sensitivity coefficient K of the sensing band was measured using a laboratory universal testing machine coupled with a hyperspectral analyzer. ε =1.002, temperature sensitivity coefficient K T =0.085pm / ℃.

[0082] Step S3.4: Intelligent correction and temperature compensation. Based on the state variables including strain, temperature change and wavelength offset, the extended Kalman filter algorithm and temperature self-compensation algorithm are used to perform iterative prediction, correction and compensation, and output the final deformation data after eliminating noise and temperature cross-sensitivity effects.

[0083] The temperature self-compensation algorithm, as the core module of the intelligent interpretation system, together with the Extended Kalman Filter (EKF) processing flow, forms a temperature-insensitive monitoring system. This method employs an improved EKF algorithm for real-time signal processing. State variables including strain, temperature, and wavelength offset are input into the EKF filter for state prediction and observation correction, thereby calculating the true mechanical strain after eliminating the influence of temperature. Specifically:

[0084] Step S3.4.1: System state initialization, initializing the state vector and error covariance matrix containing strain, temperature change, stress and temperature-insensitive parameters;

[0085] During the system initialization phase, the state vector is expanded into a four-dimensional vector containing temperature-related parameters:

[0086]

[0087] In the formula, R0 is an initial temperature-insensitive parameter. Given its corresponding initial uncertainty, this extension lays the mathematical foundation for temperature compensation.

[0088] Step S3.4.2: State prediction, based on the system dynamics model, to make a priori prediction of the system state at the next moment;

[0089]

[0090] In the formula Let f(*) be the prior state estimate at time k, and f(*) be the nonlinear state transition function. k-1 For system control input, F kQ is the Jacobian matrix of the state transition matrix. k-1 Let be the process noise covariance matrix.

[0091] Correcting the predicted state using real-time observation data:

[0092]

[0093] P k|k =(IK k H k )P k|k-1

[0094] In the formula K k H is the Kalman gain matrix. k Let R be the Jacobian matrix of the observation matrix. k To observe the noise covariance matrix, z k Let h(*) be the actual observation vector, and h(*) be the nonlinear observation function.

[0095] Step S3.4.3: Temperature self-compensation calculation: Calculate the temperature insensitive parameter R based on the wavelength shift of the dual-channel reflection spectrum in the spatial hybrid coding unit of the sensing band.

[0096] A dual-channel sensing mechanism is constructed using two nanospheres of different sizes (A: 200 nm, B: 250 nm) in a spatially hybrid coding unit. The wavelength shift law can be described as follows:

[0097] Δλ A / λ 0A =K εA *ε+K TA *ΔT+v1

[0098] Δλ B / λ 0B =K εB *ε+K TB *ΔT+v2

[0099] In the formula, Δλ A and Δλ B λ represents the wavelength offset of the reflection center of nanospheres A and B, respectively; 0A and λ 0B K represents the initial center wavelengths of nanospheres A and B, respectively; εA and K εB These are the sensitivity coefficients for nanospheres A and B, respectively; K TA and K TB ε represents the temperature sensitivity coefficients of nanospheres A and B, respectively; ε is the true axial strain to be measured; ΔT is the change in ambient temperature; v1 and v2 are the observation noises of the two channels, respectively, which follow a Gaussian distribution with a mean of 0.

[0100] Through precise material design and optimization, the temperature-sensitive properties and strain sensitivity of the two types of nanospheres are ensured to meet a specific proportional relationship:

[0101] K TA / K TB ≈K εA / K εB ±δ

[0102] In the formula, δ represents the material parameter matching error, which can be controlled within ±2% through process optimization.

[0103] Based on the above material properties, a temperature-insensitive parameter R is constructed:

[0104] R=(Δλ A / λ 0A ) / (Δλ B / λ 0B )=(K εA *ε+K TA *ΔT) / (K εB *ε+K TB *ΔT)

[0105] Through careful material selection and design,

[0106] K TA / K εA =K TB / K εB =C (constant)

[0107] If the relative effects of temperature change and deformation on the two channels are equal, then the ratio R can be approximated as a function that depends only on the strain ε, i.e.

[0108] R=K εA / K εB

[0109] This result indicates that, under the material design conditions, the value of parameter R depends only on the ratio of the strain sensitivity coefficients of the two types of nanospheres, and not on the temperature change Δ. Completely unrelated. Experiments show that, within a temperature range of -20℃ to +60℃, this algorithm reduces the temperature-induced deformation measurement error from ±2mm in the traditional FBG method to within ±0.2mm.

[0110] Step S3.4.4: State correction. Using the actual strain observations obtained in step S4.3, the prior state prediction in step S4.2 is corrected by combining the Kalman gain to obtain the optimal state estimate.

[0111] Step S3.4.5: Output the final deformation data. Based on the corrected optimal state estimate, output the deformation after eliminating the influence of temperature cross-sensitivity.

[0112] Step S4: Based on real deformation data, generate and output the distribution information of the wide-area deformation field;

[0113] Specifically, by employing a flexible photonic crystal sensing strip with low production cost per unit length, and combining it with the intelligent interpretation method to interpret the reflected light signal, a significant reduction in the unit length cost of the wide-area deformation field monitoring system is achieved.

[0114] Example 2:

[0115] The main difference between this embodiment and Embodiment 1 lies in step S1. Step S1: A flexible photonic crystal sensing strip is deployed along the open-pit mine slope to be monitored. A zigzag anchoring pattern is used to deploy the sensing strip to form a monitoring network. Specifically, this includes:

[0116] The sensor strip is laid out in a zigzag pattern along the slope surface with a preset degree of tortuosity. The degree of tortuosity is the ratio of the actual laying length to the vertical height difference of the slope surface, ranging from 1.2:1 to 2.0:1, preferably 1.5:1.

[0117] Anchor points are set at equal intervals of 3m to 5m along the zigzag path for fixation.

[0118] The spatial coordinates of the anchorage point can be determined by the following parametric equation:

[0119] x = s * n

[0120] y=(s / R)*n*(1-A*sin(π*n / P))

[0121] In the formula, s is the baseline horizontal spacing of anchor points, which can be taken as 4m; R is the design tortuosity, taken as 1.5; n is the anchor point number; A is the path amplitude coefficient, taken as 0.5; and P is the path period parameter, taken as 2. The path generated by this equation can optimize the sensitivity distribution of strain sensing. A shallow trench with a rectangular cross-section is excavated along the planned path to accommodate the sensing strip. Anchor points are achieved using mechanical anchor bolts, which are made of high-strength corrosion-resistant materials (such as φ16mm austenitic stainless steel) with a yield strength of not less than 205MPa. The anchor bolts are arranged at equal intervals of 3m to 5m (preferably 4m). The anchoring depth is calculated using the following formula:

[0122] H anchor =max(D min C*H step )

[0123] In the formula, D min Minimum anchorage depth; C is an empirical coefficient; H step The step height is specified. Anchor holes are drilled using diamond drill bits, with a diameter 4-6 mm larger than the anchor rod diameter. High-performance epoxy resin anchoring agent is injected to ensure that the single-point pull-out resistance after curing is not less than 15 kN.

[0124] The core of this deployment pattern lies in its multi-dimensional deformation sensing capability. When the slope undergoes tensile or compressive deformation along the slope surface, it directly causes axial strain in the sensing strip along the zigzag path, which is then captured. When the slope experiences displacement perpendicular to the slope surface or potential shear slip, it forces bending deformation at the turning points of the zigzag path. This bending modulates the optical signal, generating additional micro-bending losses or changes in strain distribution, thus responding to non-axial deformation. By demodulating the axial strain and bending response at different locations of the sensing strip, the two-dimensional deformation field of the slope surface can be reconstructed.

[0125] For example, in this embodiment, the sensor strip is laid out in a zigzag pattern on the stepped slope, with a path tortuosity ratio of 1.5 to 1. Anchor points are set at 4-meter intervals along the path, using 16-mm diameter stainless steel anchor rods. The anchoring depth is dynamically adjusted according to the step height, with a minimum depth of 0.3 meters. Holes are drilled using a special drill bit, with a diameter of 20 mm and a depth of 350 mm, and high-performance epoxy anchoring agent is injected to ensure that the pull-out resistance at a single point reaches more than 15 kN. After construction, backfilling and compaction are carried out to ensure that the sensor strip is fully adhered to the slope surface.

[0126] Example 3:

[0127] The main difference between this embodiment and Embodiment 1 lies in step S1.

[0128] Step S1: Deploy flexible photonic crystal sensing strips along the open-pit mine slope to be monitored to form a monitoring network.

[0129] For potential slip zones, fault zones, or other geologically vulnerable areas identified through preliminary exploration (such as ground-penetrating radar and microseismic monitoring), a high-density gridded monitoring strategy is implemented. Multiple (e.g., 3-8) parallel and closely adjacent branch sensor chains are simultaneously drawn from one or more branch junction boxes. These branch chains are deployed within the target area at fixed intervals (e.g., 5m to 20m, preferably 10m), forming a high-density sensor grid covering the area. This grid increases the spatial density of monitoring points by an order of magnitude, achieving a "CT scan" of critical areas. It can detect not only the occurrence of deformation with extremely high spatial resolution but also accurately depict the spatial location, geometry (such as dip angle and undulation), expansion direction, and acceleration trend of potential slip surfaces. Through the fusion analysis of data from multiple sensor chains within the grid, early and accurate warnings of local instability precursors can be achieved, providing unprecedented detailed information for disaster prevention and control decisions.

[0130] After the flexible photonic crystal sensing strips of this embodiment are deployed, an initial full-network scan is performed at night when there is no external construction interference. A coherent OFDR (Optical Frequency Domain Reflectometer) is used as the signal demodulation device, with a spatial resolution of 1 cm and a strain measurement range of ±15000 μm / m. The device scans and obtains the initial Rayleigh scattering signal or FBG (Fiber Bragg Grating) reflection spectrum of each sensing strip as a unique reference optical feature (also known as an "optical fingerprint") for subsequent comparison of that sensing unit. The initial value of the center wavelength of the FBG is recorded as λ. B0 The coordinates of each sensor unit, determined by GPS mapping, are stored in the baseline database.

[0131] Data acquisition across the entire network is scheduled to occur at fixed intervals of 2 hours. To eliminate the interference of ambient temperature changes on the measurement results, a special coded sensor capable of simultaneously sensing strain and temperature is employed. By calculating the signal changes output by the sensor and processing them based on a calibrated algorithm model, the mechanical strain value, after eliminating the influence of temperature, can be directly calculated. Subsequently, based on the strain value and preset layout geometric parameters, the absolute deformation of each monitoring point is calculated, thereby generating a distribution map reflecting the deformation field of the entire slope area.

[0132] The calculated deformation data and the original optical data are synchronously stored on an industrial-grade server. The system software platform provides a graphical user interface that can display the deformation curves, spatial distribution cloud maps, and historical deformation trends of key points for each branch chain in real time. The platform supports data querying, backtracking, and exporting based on various conditions such as time, spatial location, and deformation threshold, providing support for in-depth analysis.

[0133] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A flexible photonic crystal sensing band, characterized in that, The structure employs a sandwich heterogeneous design, comprising, from top to bottom, a protective layer, a photonic crystal sensing layer, and a signal transmission layer; the protective layer is composite-encapsulated with the photonic crystal sensing layer via a hot-pressing process; the photonic crystal sensing layer is disposed between the protective layer and the signal transmission layer; and the signal transmission layer carries the photonic crystal sensing layer and transmits optical signals.

2. The flexible photonic crystal sensing strip according to claim 1, characterized in that, The protective layer is a polytetrafluoroethylene propylene film.

3. The flexible photonic crystal sensing strip according to claim 1, characterized in that, The photonic crystal sensing layer uses polydimethylsiloxane as an elastic matrix, in which multiple spectral coding units formed by monodisperse nanospheres are embedded and arranged sequentially along the length of the sensing band, and the multiple spectral coding units are arranged periodically according to a preset particle size sequence.

4. The flexible photonic crystal sensing strip according to claim 3, characterized in that, Each of the spectral coding units is composed of monodisperse nanospheres of a single particle size.

5. A flexible photonic crystal sensing strip according to claim 3, characterized in that, Each of the spectral coding units further includes a spatial hybrid coding unit composed of nanospheres with mixed particle sizes, wherein the nanosphere particle sizes used in different coding units are different.

6. A method for preparing the flexible photonic crystal sensing band as described in claim 5, characterized in that, The method for preparing the spatial hybrid coding unit during the formation of the photonic crystal sensing layer includes the following steps: Step S1: Prepare two or more monodisperse nanosphere suspensions with different particle sizes; Step S2: Mix the nanosphere suspensions of different particle sizes according to a preset mixing ratio; Step S3: Using an impression roller device with a nanocavity array, the mixed nanospheres are suspended and hydraulically imprinted into the uncured polydimethylsiloxane matrix to form a spatially mixed coding unit with a non-closely packed structure. Step S4: Perform optical detection on the formed spatial mixing coding unit to verify whether there are multiple characteristic peaks in its reflection spectrum that correspond to the mixing ratio.

7. The flexible photonic crystal sensing strip according to claim 1, characterized in that, The signal transmission layer is a composite structure arranged from top to bottom, including: Flexible polymer film substrate; Polymer optical waveguide integrated on the flexible polymer thin film substrate; The periodic wedge-shaped microstructures disposed on the upper surface of the polymer optical waveguide, the microstructures being periodically arranged in an array and having tilted reflective surfaces, are used to enhance the interlayer optical coupling between the photonic crystal sensing layer and the optical waveguide. A silicon-based photoconductive sensing chip located below the periodic wedge-shaped microstructure and forming a light-guiding channel; And a flexible polyimide substrate that carries the silicon-based photoconductive sensing core.

8. A method for monitoring wide-area deformation fields in open-pit mines based on flexible photonic crystal sensing bands, characterized in that, The steps are executed in the following order: Step S1: Deploy flexible photonic crystal sensing strips as described in any one of claims 1-3 along the open-pit mine slope to be monitored to form a monitoring network; Step S2: Collect reflected light signals covering a wide area of ​​the slope through the monitoring network; Step S3: Input the collected reflected light signal into the deformation-optical signal interpretation model for processing, so as to calculate the real deformation data of each monitoring location on the wide-area slope; Step S4: Based on the real deformation data, generate a visualized wide-area deformation field distribution map / report to characterize the slope safety status, and output it.

9. The method for monitoring wide-area deformation field in open-pit mines based on flexible photonic crystal encoding as described in claim 8, characterized in that, The deformation-optical signal interpretation model includes the following steps: The reflected light signal returned by the sensor band is collected, and the reflected light signal contains spectral coding and spatial hybrid coding information; The reflected light signal is preprocessed to separate noise from the effective component in the signal; Extract characteristic optical parameters from the preprocessed signal, wherein the characteristic optical parameters include at least the center wavelength of the characteristic peak of the reflection spectrum; Based on the aforementioned characteristic optical parameters, the wavelength shift is calculated using a deformation-optical signal interpretation model. The state variables, including strain, temperature, and wavelength shift, are input into an extended Kalman filter for state prediction and observation correction, so as to calculate the true mechanical strain that eliminates the influence of temperature. Based on the actual mechanical strain and the layout parameters of the sensing belt, deformation field data is generated and output.

10. The method for monitoring wide-area deformation field in open-pit mines based on flexible photonic crystal encoding as described in claim 9, characterized in that: The solution obtained is the true mechanical strain after eliminating the influence of temperature, including a temperature self-compensation algorithm, which performs the following steps: The temperature self-compensation algorithm utilizes the dual-channel sensing mechanism of the spatial hybrid coding unit to construct temperature-insensitive parameters. When the temperature changes, the temperature-insensitive parameter remains unchanged, and the true strain is obtained by calculating the parameter.

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