A settlement monitoring method and system based on Z-shaped guiding optical fiber laying

Abstract

The application discloses a settlement monitoring method and system based on Z-shaped guiding optical fiber layout, and relates to the technical field of road engineering monitoring. A plurality of guiding nodes are arranged in a region to be monitored, and sensing optical fibers pass through the guiding nodes in sequence to form a Z-shaped guiding optical fiber path. Distributed axial strain distribution is continuously collected along the Z-shaped guiding optical fiber path, and distributed differential strain is calculated based on the distributed axial strain distribution. The distributed differential strain is converted into an observation form matched with the guiding nodes to construct a segment-level differential strain observation vector. A forward model is established based on the quantitative relationship between the segment-level differential strain observation vector and a node settlement vector. A plurality of displacement meters are arranged in the region to be monitored, and an anchor point constraint is constructed based on a calibration displacement meter observation vector. The guiding node settlement vector is solved by using a constraint regularization inversion method based on the forward model and the anchor point constraint to obtain a guiding node settlement estimation vector. High-precision and high-robustness settlement curve reconstruction is realized.

Description

Technical Field

[0001] This invention relates to the field of road engineering monitoring technology, and in particular to a settlement monitoring method and system based on Z-shaped directional optical fiber deployment. Background Technology

[0002] The statements in this section are merely background information relating to this disclosure and do not necessarily constitute prior art.

[0003] Distributed fiber optic sensing technology has gained widespread attention and application in geotechnical engineering settlement monitoring due to its advantages such as high precision, long distance, and resistance to electromagnetic interference. This technology, by embedding a single sensing fiber along the structure, can acquire continuous axial strain distribution along the line, providing a rich data foundation for structural health monitoring.

[0004] However, in practical engineering, due to limitations imposed by construction conditions and fiber optic cable protection requirements, optical fibers are mostly laid horizontally and directly along the cable line. In this case, settlement under vertical loads mainly manifests as overall subsidence and limited bending deformation. Horizontal optical fibers buried at a certain depth exhibit relatively weak axial strain response to vertical settlement and are easily affected by factors such as incomplete soil-fiber coupling, local slippage, and environmental noise. This makes it difficult for the strain measured by the optical fiber to directly reflect the true settlement deformation. Existing methods for settlement inversion based on strain integration lack curvature information under single horizontal optical fiber conditions. The inversion problem often presents insufficient information and non-uniqueness, and the inversion results are prone to ill-conditioned amplification and non-physical oscillations, making it difficult to meet engineering accuracy requirements.

[0005] To improve the sensitivity of optical fibers to vertical settlement, some studies have attempted to enhance strain response by pre-setting a polygonal layout based on the vertical drop. However, the lack of systematic geometric mapping models, segment-level observation construction methods, and stability inversion frameworks incorporating external constraints in existing technologies has prevented this approach from becoming an engineeringable monitoring technology. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a settlement monitoring method and system based on Z-shaped directional optical fiber deployment, aiming to effectively improve the accuracy and robustness of settlement inversion and solve the problems of low sensitivity and difficulty in inversion of existing horizontal direct-buried optical fibers in settlement monitoring.

[0007] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: In a first aspect, the present invention provides a settlement monitoring method based on Z-shaped guided optical fiber deployment, comprising: Within the area to be monitored, multiple guide nodes are sequentially set along the preset monitoring direction, and the sensing optical fiber passes through each guide node in sequence to form a Z-shaped guide optical fiber path. Distributed axial strain distribution was continuously acquired along the Z-shaped guide fiber path, and distributed differential strain was calculated based on the distributed axial strain distribution. The distributed differential strain is converted into an observation form that matches the guide node, and a segment-level differential strain observation vector is constructed. A forward model is established based on the quantitative relationship between the segment-level differential strain observation vector and the nodal settlement vector. Multiple displacement gauges are deployed in the area to be monitored, and anchor point constraints are constructed based on the observation vectors of the calibrated displacement gauges participating in the inversion. Based on the forward model and anchor point constraints, the constraint regularization inversion method is used to solve the guide node settlement vector, and the guide node settlement estimation vector is obtained.

[0008] In a further technical solution, the Z-shaped guide fiber path has a fixed horizontal spacing and a preset vertical drop.

[0009] A further technical solution involves constructing segment-level differential strain observation vectors, specifically including: Based on the location of the guide node, the Z-shaped guide fiber path is divided into multiple straight guide segments; Through distance coordinate calibration experiments, the start and end intervals of each straight guide segment on the Brillouin optical time domain analysis distance coordinates were determined; Based on the start and end intervals, a set length of interval is removed from both ends of each straight guide segment to obtain the effective interval; Within the effective range, the representative differential strains of each straight guide segment are combined to form a segment-level differential strain observation vector.

[0010] A further technical solution is that the forward model is represented as follows:

[0011] in, This represents the segmented differential strain observation vector. For geometric mapping matrix, Let be the nodal settlement vector. For the error vector, For monitoring time.

[0012] A further technical solution is that the anchor point constraint is expressed as:

[0013] in, To calibrate the displacement gauge observation vector, To calibrate the interpolation matrix corresponding to the displacement gauge, To guide the settlement vector of the node, To calibrate the displacement gauge observation error vector.

[0014] A further technical solution is that the constraint regularization inversion method constructs a weighted regularization objective function, expressed as:

[0015] in, Let be the settlement vector of the guide node to be solved. For geometric mapping matrix, The strain observation weight matrix is... This represents the segmented differential strain observation vector. For smoothing regularization operator matrix, To smooth out the regularization parameters, The anchor point displacement observation weight matrix, For anchor point constraint weight parameters, To calibrate the interpolation matrix corresponding to the displacement gauge, To calibrate the displacement gauge observation vector, It is a 2-norm.

[0016] A further technical solution involves optimizing the parameters and evaluating the independent accuracy of the guide node settlement estimation vector based on the observation data of the verification displacement gauge.

[0017] Secondly, the present invention provides a settlement monitoring system based on Z-shaped guided optical fiber deployment, comprising: The fiber optic deployment module is configured to: sequentially set multiple guide nodes along a preset monitoring direction within the area to be monitored, and sequentially pass through each guide node to form a Z-shaped guide fiber optic path. The distributed fiber optic strain acquisition module is configured to continuously acquire distributed axial strain distribution along the Z-shaped guide fiber path, and calculate distributed differential strain based on the distributed axial strain distribution. The differential strain observation module is configured to: convert distributed differential strain into an observation form that matches the guide node, and construct segment-level differential strain observation vectors. The mapping model construction module is configured to: establish a forward model based on the quantitative relationship between the segment-level differential strain observation vector and the nodal settlement vector; The constraint construction module is configured to: deploy multiple displacement gauges in the area to be monitored, and construct anchor point constraints based on the observation vectors of the calibrated displacement gauges participating in the inversion; The regularized inversion module is configured to: solve for the guide node settlement vector based on the forward model and anchor point constraints using the constrained regularized inversion method, and obtain the guide node settlement estimation vector.

[0018] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a settlement monitoring method based on Z-shaped directional optical fiber deployment as described in the first aspect.

[0019] Fourthly, the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of a settlement monitoring method based on Z-shaped directional optical fiber deployment as described in the first aspect.

[0020] The above one or more technical solutions have the following beneficial effects: This invention enhances the sensitivity of optical fibers to vertical settlement by introducing a guide node with a preset vertical drop. It also achieves high-precision and robust settlement curve reconstruction by combining segment-level strain construction, geometric mapping modeling, and regularized inversion, thus solving the problems of low sensitivity and difficult inversion in existing horizontally buried optical fibers for settlement monitoring.

[0021] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 This is a flowchart of a settlement monitoring method based on Z-shaped directional optical fiber deployment according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the overall layout of the Z-shaped guiding optical fiber according to an embodiment of the present invention. Detailed Implementation

[0024] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0027] Example 1 like Figure 1 As shown in the figure, this embodiment discloses a settlement monitoring method based on Z-shaped directional optical fiber deployment, which is applicable to distributed monitoring of vertical settlement of structures such as roads, roadbeds, and foundations. The method includes the following steps: S1: In the area to be monitored, multiple guide nodes are set sequentially along the preset monitoring direction, and the sensing optical fiber passes through each guide node in sequence to form a Z-shaped guide optical fiber path. In this embodiment, as Figure 2 As shown, within the monitoring area of ​​the soil or structure to be monitored, multiple guide nodes are sequentially set along a preset monitoring direction, denoted as... ,in This represents the total number of nodes. Among them, For the first One guide node.

[0028] The guide node is made of a rigid structural component, and the material can be metal, engineering plastic, or composite material. The guide node is equipped with an arc-shaped guide groove or a low-friction roller structure for guiding the optical fiber to turn. To avoid excessive bending damage to the optical fiber at the bend, the radius of curvature of the guide groove is preferably not less than 30 mm.

[0029] The optical fiber turns along the guide groove, and the sensing optical fiber passes through each guide node in sequence, and the optical fiber is connected in a straight line between each pair of adjacent guide nodes, thus forming a Z-shaped guide optical fiber path with a fixed horizontal spacing and a preset vertical drop.

[0030] The fixed horizontal spacing is determined by the projected distance between adjacent nodes in the monitoring direction, while the preset vertical drop is achieved by burying adjacent nodes at different depths.

[0031] The geometric characteristics of this deployment method are as follows: when soil settlement occurs, the vertical settlement difference between adjacent nodes changes the initial vertical drop of the fiber optic segment, thus causing a change in the length of the straight segment. Under the guidance constraint and the coordinated deformation of the soil, this length change can be characterized as a change in the axial strain of the fiber optic cable. Therefore, by pre-setting the vertical drop, the originally weak settlement difference can be amplified into an observable axial strain response, improving the sensitivity of the fiber optic cable to vertical settlement.

[0032] S2: Continuously acquire distributed axial strain distribution along the Z-shaped guide fiber path, and calculate distributed differential strain based on the distributed axial strain distribution; In this embodiment, a Brillouin optical time-domain analysis (BOTDA) distributed fiber optic sensing system is used to continuously acquire the axial strain distribution at various times along the Z-shaped guide fiber path, denoted as... ,in These are the distance coordinates along the fiber optic cable. For monitoring time.

[0033] To eliminate the influence of factors such as initial prestress of optical fibers, temperature drift, and system zero drift, a reference time is selected before monitoring begins or in the initial stage of monitoring. As a baseline, the differential strain relative to the baseline at each time point is calculated:

[0034] in, For monitoring time Relative to the reference time The differential strain, For monitoring time Axial strain distribution, Reference time The axial strain distribution.

[0035] Differential strain The incremental change in fiber axial strain during monitoring is characterized and used as input data for subsequent segment-level differential strain construction and settlement inversion calculations, thereby reducing the impact of environmental factors and system drift on the monitoring results.

[0036] S3: Convert the distributed differential strain into an observation form that matches the guide node, and construct a segment-level differential strain observation vector; In this embodiment, to convert the continuous distributed differential strain data acquired by BOTDA into an observation format that matches the discrete guide nodes, a segment-level differential strain observation vector is constructed, which specifically includes the following steps: First, based on the guide node positions set in S1, the entire Z-shaped guide fiber path is divided into... Each guide segment consists of a straight guide segment, and each guide segment corresponds to an optical fiber segment between a pair of adjacent guide nodes.

[0037] Secondly, through the distance coordinate calibration test in S2, the distance coordinate of each straight guide segment in BOTDA was determined. The corresponding start and end intervals are denoted as

[0038] in, Indicates the segment number. and The first The coordinates of the start and end points of the segment on the BOTDA differential strain curve.

[0039] Calibration can be achieved by applying a local perturbation at a known physical location and identifying the response peak on the strain curve to establish the correspondence between the physical fiber segment and the BOTDA distance coordinates.

[0040] Considering the fiber optic bending, local friction, and constraint changes near the guide node, which can easily generate additional strain interference, a length of [missing value] is removed from both ends of each straight guide segment. The effective interval is obtained from the interval:

[0041] Among them, the length of rejection The dimensions of the guide node are determined based on the fiber bending radius, BOTDA spatial resolution, and the influence range of additional strain near the node during calibration testing. Preferably, The effective range should be no less than the spatial resolution of the BOTDA system, and the excluded effective range should avoid local strain anomaly regions at node inflection points. The differential strain data within the effective range are used to characterize the axial strain response of the straight guide segment caused by settlement.

[0042] Within the effective interval, robust statistical methods are used to extract the first... The representative differential strain value of the segment is denoted as To suppress the influence of measurement noise and local outliers, robust statistical methods are preferably truncated means or medians, where the truncated mean is the average of the remaining data after removing a certain proportion of data from both ends of the interval.

[0043] The representative differential strains of each straight guide segment are combined in segment number order to form segment-level differential strain observation vectors. :

[0044] in, For the first The segment represents differential strain.

[0045] The segment-level differential strain observation vector is used to characterize the overall strain increment state of each guide segment and serves as the observation input data for subsequent geometric mapping modeling and settlement inversion calculation.

[0046] S4: Based on the quantitative relationship between the segment-level differential strain observation vector and the nodal settlement vector, a forward model is established; In this embodiment, to establish a quantitative relationship between segment-level differential strain observations and nodal settlement, this invention proposes a mapping model based on Z-shaped guiding geometric features, transforming the settlement inversion problem into a standard linear inverse problem. The specific construction method is as follows: First, define the vertical displacement vector of the guiding node as:

[0047] in, The vertical settlement vector of the guide node. For the first Each guiding node at time The vertical settlement, The total number of guiding nodes, This represents the transpose of a vector.

[0048] For the A straight guide segment, with nodes at both ends and The settlement difference between them is:

[0049] in, For the first The settlement difference between adjacent guide nodes of the segment For the first Each guiding node at time The vertical settlement, For the first Each guiding node at time The vertical settlement, Number the guide segment.

[0050] Based on the geometric layout of the Z-shaped guide fiber in S1, the first The initial horizontal spacing of the straight guide segment is The initial horizontal spacing of the first fiber segment is The initial vertical drop is Then the initial length of this fiber segment is:

[0051] in, For the first The initial length of the optical fiber segment before settlement occurs.

[0052] When soil settlement occurs, the vertical drop of that section becomes The corresponding segment length is:

[0053] in, For the first time after settlement The length of a fiber optic segment.

[0054] Then the axial strain increment of this fiber segment It can be represented as:

[0055] Under the condition of small deformation where the settlement is relatively small compared to the segment length, a first-order linear approximation of the above equation yields the... The relationship between segmental strain and differential settlement between adjacent nodes:

[0056] in, For the first The representative differential strain of a fiber segment, For the first Segment geometric sensitivity coefficient, For the first The difference in settlement between adjacent nodes in a segment.

[0057] The geometric sensitivity coefficient is expressed as follows:

[0058] By combining the strain relationships of each guide segment, a matrix-form forward model can be established between the segment-level differential strain observation vector and the nodal settlement vector:

[0059] in, This represents the segmented differential strain observation vector. For geometric mapping matrix, Let be the nodal settlement vector. For the error vector, For monitoring time.

[0060] Error vector This represents the residual between the segment-level differential strain observations and the forward model predictions, including distributed fiber optic strain measurement noise, soil-fiber coupling error, local disturbances at the guide nodes, and model linearization approximation errors. Its statistical characteristics can be estimated through repeated measurements under steady-state conditions, calibration tests, or the variance of strain fluctuations in each guide segment, and are characterized by the strain observation weight matrix during the inversion process.

[0061] The segment-level differential strain observation vector is:

[0062] for The dimensional geometric mapping matrix, whose dimensional geometric mapping matrix, has a 3D geometric mapping matrix. The line only contains the first The non-zero elements corresponding to the two endpoints of a segment are represented as:

[0063]

[0064] in, The first in the geometric mapping matrix Line 1 Column elements, The first in the geometric mapping matrix Line 1 The elements of the column, the two corresponding to the first The settlement at both ends of the straight guide segment contributes to the differential strain of the segment, and the elements in the remaining columns are 0.

[0065] The forward model establishes a linear mapping relationship between segment-level differential strain observations and nodal settlement, providing a mathematical basis for subsequent introduction of displacement gauge constraints and settlement inversion solutions.

[0066] S5: Deploy multiple displacement gauges in the area to be monitored, and construct anchor point constraints based on the observation vectors of the calibrated displacement gauges participating in the inversion. In this embodiment, to provide an absolute displacement benchmark for settlement inversion and to suppress the overall drift that may occur when inversion is based solely on strain observations, multiple displacement measurement points are set up along the monitoring area, denoted as... ,in The total number of displacement gauges, of which, For the first There are 10 displacement gauge measuring points. The displacement gauges are set on the soil surface or at key locations on the structure to obtain vertical settlement observations at the corresponding locations.

[0067] Based on the different roles of the displacement gauges in the inversion process, the displacement plan is divided into two categories: calibration displacement gauges and verification displacement gauges. Among them, the observation data of calibration displacement gauges are used in subsequent settlement inversion calculations to provide absolute constraints for the nodal settlement solution; the observation data of verification displacement gauges are not used in the inversion solution, but only for independent accuracy verification of the inversion results.

[0068] Assume that each displacement gauge is at time 10:00. The settlement observations constitute the displacement observation vector:

[0069] in, This is the settlement observation vector of the displacement gauge. For the first Each displacement gauge at time Settlement observations For the total number of displacement gauges, This represents the transpose of a vector.

[0070] Since the locations of displacement gauge measuring points do not always perfectly coincide with the locations of guide nodes, an interpolation relationship is constructed based on the relative positions of each displacement gauge measuring point and the adjacent guide node in the monitoring direction to establish the correspondence between displacement gauge observations and node settlement. Displacement Gauge Observation Model Represented as:

[0071] in, For the displacement gauge interpolation matrix, To guide the settlement vector of the node, This is the displacement gauge observation error vector.

[0072] Displacement gauge observation error vector This represents the deviation between the measured settlement value of the displacement gauge and the actual settlement value at the corresponding location. It mainly includes instrument measurement error, installation error, environmental drift, and interpolation approximation error. Its statistical characteristics can be determined based on the nominal accuracy of the displacement gauge, field calibration results, standard deviation of repeated measurements, or observed fluctuations during the steady-state phase, and are characterized in subsequent inversion using the anchor point displacement observation weight matrix.

[0073] matrix The The line represents the first The interpolation relationship between each displacement gauge measuring point and each guide node. When the first... The displacement gauge is located at the first The first guiding node and the first When there are multiple guiding nodes, the observed values ​​are represented by linear interpolation as follows:

[0074] in, For the first Each displacement gauge at time Settlement observations These are interpolation weights, and 0 ≤ ≤ 1, its value is determined by the first The horizontal position of each displacement gauge measuring point relative to two adjacent guide nodes is determined; For the first Each guiding node at time The vertical settlement, For the first Each guiding node at time The vertical settlement.

[0075] When the displacement gauge's measuring point coincides with the location of a guide node, the displacement gauge's observed value can directly correspond to the settlement of that guide node. In this case, the interpolation matrix... The corresponding row is set to 1 only at the corresponding node position, and 0 at the other positions.

[0076] Furthermore, calibrated displacement gauges are selected from all displacement gauge observations to participate in the inversion constraints, and their corresponding observation vectors are denoted as . The corresponding interpolation matrix is Then the anchor point constraint relationship can be expressed as:

[0077] in, To calibrate the displacement gauge observation vector, To calibrate the interpolation matrix corresponding to the displacement gauge, To guide the settlement vector of the node, To calibrate the displacement gauge observation error vector, an anchor-constrained guiding fiber is constructed based on the calibration displacement gauge observation vector used in the inversion.

[0078] The selection of calibration displacement gauges follows the principles of spatial coverage, measurement reliability, and the effectiveness of inversion constraints. Calibration displacement gauges are preferably located at the boundaries of the monitoring area, typical settlement zones, and locations with significant changes in settlement gradient. Measurement points with unstable installations, significant local disturbances, or abnormal measurement data should be avoided. Validation displacement gauges do not participate in inversion constraints and are only used for subsequent independent accuracy evaluation.

[0079] Anchor point constraints are used to introduce absolute settlement reference information in the subsequent inversion process to improve the stability and reliability of the settlement solution results; the verification displacement gauge is used to evaluate the accuracy of the settlement reconstruction results after the inversion is completed.

[0080] S6: Based on the forward model and anchor point constraints, the guide node settlement vector is solved by the constraint regularization inversion method to obtain the guide node settlement estimation vector.

[0081] In this embodiment, based on the geometric mapping forward model and the displacement gauge anchor point constraint relationship, a constraint regularization inversion method is used to solve for the guide node settlement vector. The method simultaneously considers the strain observation fitting accuracy, anchor point displacement constraints, and settlement curve smoothness, constructing a weighted regularization objective function:

[0082] in, Let be the settlement vector of the guide node to be solved. The strain observation weight matrix is... For smoothing regularization operator matrix, To smooth out the regularization parameters, The anchor point displacement observation weight matrix, For anchor point constraint weight parameters, It is a 2-norm.

[0083] The first term is the strain observation fitting term, which minimizes the deviation between the segment-level differential strain calculated from the inverted settlement vector through the forward model and the actual observed differential strain; the second term is the smoothing regularization term, which suppresses noise amplification and non-physical oscillations and ensures the continuity of the settlement curve; the third term is the anchor point displacement constraint term, which minimizes the deviation between the interpolated value of the inverted settlement result at the calibrated displacement gauge position and the measured displacement value, thereby introducing an absolute settlement benchmark.

[0084] By differentiating the above objective function and setting it to zero, the analytical solution for the nodal settlement vector can be obtained:

[0085] in, This is the nodal settlement estimation vector obtained from the inversion. This represents the matrix inversion operation.

[0086] Strain observation weight matrix For diagonal matrices:

[0087] in, For the first Strain observation weights, Based on the noise level determined by the strain measurement in that section, when the noise levels are consistent across all sections, the following approach is taken: .

[0088] Anchor point displacement observation weight matrix It can also be taken as a diagonal matrix:

[0089] in, To calibrate the number of displacement gauges, For the first The observation weight of each calibrated displacement gauge is determined based on the measurement accuracy of the corresponding displacement gauge. When the measurement accuracy of each anchor point is consistent, the weight is taken as follows: .

[0090] Smoothing regularity operator A second-order difference matrix is ​​used to constrain the second-order smoothness of the nodal settlement curves to ensure that the settlement curves are continuous and smooth.

[0091] After obtaining the settlement estimate at the discrete guide node, the node settlement vector is... Spatial interpolation is performed to obtain a continuous settlement distribution curve along the monitoring direction:

[0092] in, For position At the moment The estimated settlement value, Represents the spatial interpolation operator. Spatial coordinates in the monitoring direction.

[0093] Piecewise linear interpolation or cubic spline interpolation is preferred as the interpolation method to obtain a continuous and smooth settlement curve. Through the above-described constraint regularization inversion process, the settlement distribution of the guide node can be solved jointly by segment-level strain observation and anchor point displacement observation.

[0094] In this embodiment, to improve the accuracy and stability of the settlement inversion results, the calibration displacement gauge measurement points and verification displacement gauge measurement points reserved in S5 are used to optimize the parameters and evaluate the independent accuracy of the settlement reconstruction results obtained in S6.

[0095] The observation data of the calibration displacement gauge is not involved in the inversion solution in S6, but is only used for the selection of inversion parameters; the observation data of the verification displacement gauge is neither involved in the inversion solution nor in the selection of parameters, but is only used for independent accuracy verification of the final inversion results.

[0096] Let the location of the calibration point or verification point be... The corresponding measured settlement by the displacement gauge is The continuous settlement curve obtained from S6 is as follows: The inversion error at that measurement point is defined as:

[0097] in, For the measuring point at time Inversion error, To invert the settlement curve at the measuring point location The interpolation result at that point, This corresponds to the measured settlement value of the displacement gauge.

[0098] Under multi-time monitoring conditions, the following statistical indicators are used to evaluate the inversion accuracy: Root mean square error:

[0099] Maximum absolute error:

[0100] in, This represents the total number of data collection moments. The root mean square error, This represents the maximum absolute error.

[0101] To calibrate the displacement gauge Minimization is the primary objective, combined with Constraints are applied to optimize key parameters in the inversion process. These key parameters include: regularization parameter λ and anchor point constraint weights. Length of node influence zone removal And the range of the differential strain statistical window. The range of the differential strain statistical window is determined by the effective interval after removing the influence area of ​​the nodes in each straight guide segment, and is used to extract the truncated mean or median of the segment as a representative differential strain value.

[0102] A grid search method is used to perform combined traversals within a reasonable range of parameters. For each set of parameters, the error index corresponding to the calibration displacement gauge is calculated, and then selected. The parameter combination with the smallest and most stable error variation is selected as the final parameter value. Subsequently, the settlement distribution is recalculated based on the final parameters, and the accuracy of the inversion results is independently evaluated using a verification displacement gauge.

[0103] Through the above parameter optimization and independent verification process, stable and reliable settlement inversion results can be obtained, and the applicability of the method in practical engineering applications can be improved.

[0104] In summary, the present invention has the following beneficial effects: This invention lays out optical fibers in a Z-shaped undulating path along the monitoring direction in a vertical plane, creating a fixed vertical drop between adjacent guide nodes. When soil settlement occurs, the vertical displacement of the nodes directly changes the amplitude of the waveform undulation, thereby causing a change in the slant length of each fiber segment, which is then converted into an axial strain response. Compared with traditional horizontally buried optical fibers, this deployment method geometrically amplifies the minute vertical settlement difference into observable axial strain, solving the technical problem of weak settlement response and difficulty in direct inversion of horizontal optical fibers.

[0105] Based on the geometric characteristics of a Z-shaped fiber optic cable layout, this invention establishes a first-order linear mapping model between the settlement difference between adjacent nodes and the segment-level strain, and provides an analytical expression for the geometric sensitivity coefficient. This mapping relationship reveals the physical essence of settlement inversion: when the fiber segment has an initial vertical drop, a unit settlement difference can produce a stable strain response; while when the segment tends to be horizontal, the sensitivity approaches zero. This theoretical framework provides a clear mathematical foundation for subsequent inversion solutions, transforming the originally information-deficient inversion problem into a solvable problem with clear physical meaning.

[0106] This invention effectively eliminates localized additional strain interference in nodal transition zones through a segment-level strain construction method, and employs robust statistical extraction of representative strain, significantly suppressing the influence of measurement noise and outliers. By introducing multi-point displacement gauge anchor constraints, an absolute benchmark is provided for the inversion, overcoming the overall drift problem inherent in pure strain observation. Combined with second-order difference regularized smoothing priors, a weighted regularized objective function is constructed and an analytical solution is obtained, effectively suppressing noise amplification and non-physical oscillations. Verification at independent validation points shows that the inverted settlement curves agree well with measured values, and both the root mean square error and maximum error are controlled within engineering allowable ranges.

[0107] The Z-shaped deployment of this invention only sets guide nodes at key locations to achieve vertical undulation, while the main optical fiber is still continuously laid along the monitoring direction, forming an engineering deployment scheme of "horizontal main line + local vertical sensitive units". This scheme retains the advantages of long-distance continuous monitoring of distributed optical fibers, and enhances the sensitivity to settlement through local vertical undulation. The setting of guide nodes can be achieved through simple burial depth adjustment without adding additional complex construction techniques, and has good engineering operability and prospects for widespread application.

[0108] Example 2 This embodiment discloses a settlement monitoring system based on Z-shaped guided optical fiber deployment, including: The fiber optic deployment module is configured to: sequentially set multiple guide nodes along a preset monitoring direction within the area to be monitored, and sequentially pass through each guide node to form a Z-shaped guide fiber optic path. The distributed fiber optic strain acquisition module is configured to continuously acquire distributed axial strain distribution along the Z-shaped guide fiber path, and calculate distributed differential strain based on the distributed axial strain distribution. The differential strain observation module is configured to: convert distributed differential strain into an observation form that matches the guide node, and construct segment-level differential strain observation vectors. The mapping model construction module is configured to: establish a forward model based on the quantitative relationship between the segment-level differential strain observation vector and the nodal settlement vector; The constraint construction module is configured to: deploy multiple displacement gauges in the area to be monitored, and construct anchor point constraints based on the observation vectors of the calibrated displacement gauges participating in the inversion; The regularized inversion module is configured to: solve for the guide node settlement vector based on the forward model and anchor point constraints using the constrained regularized inversion method, and obtain the guide node settlement estimation vector.

[0109] In this embodiment, the settlement monitoring system of the present invention integrates innovative Z-shaped directional fiber optic deployment, high-precision BOTDA strain acquisition, multi-point displacement gauge auxiliary constraints, and inversion algorithm, which can effectively improve the sensitivity and inversion accuracy of vertical settlement monitoring and is suitable for distributed settlement monitoring of geotechnical engineering structures such as roads, roadbeds, and foundations.

[0110] Z-type guided fiber optic path: It consists of multiple guide nodes arranged sequentially along the monitoring direction and straight fiber optic segments connecting adjacent nodes; the guide nodes have preset horizontal spacing and vertical drop, which are used to convert vertical settlement difference into fiber optic axial strain.

[0111] BOTDA Distributed Fiber Optic Strain Acquisition System: Connected to a Z-shaped guide fiber path, it is used to continuously acquire the axial strain distribution at various times along the fiber path, and output differential strain data with the reference time before loading as a reference.

[0112] Multi-point displacement gauges: deployed on the soil surface or at key locations of the structure, some displacement gauges serve as anchor points to provide inversion constraints, some displacement gauges serve as calibration points for parameter selection, and the remaining displacement gauges serve as verification points for independent accuracy evaluation.

[0113] The data acquisition and processing system includes a data storage module, a differential strain observation module, a mapping model construction module, a constraint construction module, a regularized inversion module, and an accuracy verification and parameter optimization module. The data storage module stores the strain data output by BOTDA and the settlement data synchronously acquired by the displacement gauges. The differential strain observation module, mapping model construction module, constraint construction module, regularized inversion module, and accuracy verification and parameter optimization module perform segment-level strain construction, geometric mapping modeling, constraint regularization inversion solving, settlement curve reconstruction, and accuracy verification and parameter optimization, respectively.

[0114] Example 3 The purpose of this embodiment is to provide a computing device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the method of Embodiment 1.

[0115] Example 4 The purpose of this embodiment is to provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the method of Embodiment 1.

[0116] The steps and methods involved in the apparatuses of Embodiments 3 and 4 above correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood as including any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and enabling the processor to perform any of the methods in this invention.

[0117] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0118] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0119] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A settlement monitoring method based on Z-shaped guided optical fiber deployment, characterized in that, include: Within the area to be monitored, multiple guide nodes are sequentially set along the preset monitoring direction, and the sensing optical fiber passes through each guide node in sequence to form a Z-shaped guide optical fiber path. Distributed axial strain distribution was continuously acquired along the Z-shaped guide fiber path, and distributed differential strain was calculated based on the distributed axial strain distribution. The distributed differential strain is converted into an observation form that matches the guide node, and a segment-level differential strain observation vector is constructed. A forward model is established based on the quantitative relationship between the segment-level differential strain observation vector and the nodal settlement vector. Multiple displacement gauges are deployed in the area to be monitored, and anchor point constraints are constructed based on the observation vectors of the calibrated displacement gauges participating in the inversion. Based on the forward model and anchor point constraints, the constraint regularization inversion method is used to solve the guide node settlement vector, and the guide node settlement estimation vector is obtained.

2. The settlement monitoring method based on Z-shaped guided optical fiber deployment as described in claim 1, characterized in that, The Z-shaped guide fiber path has a fixed horizontal spacing and a preset vertical drop.

3. The settlement monitoring method based on Z-shaped guided optical fiber deployment as described in claim 1, characterized in that, Constructing segment-level differential strain observation vectors specifically includes: Based on the location of the guide node, the Z-shaped guide fiber path is divided into multiple straight guide segments; Through distance coordinate calibration experiments, the start and end intervals of each straight guide segment on the Brillouin optical time domain analysis distance coordinates were determined; Based on the start and end intervals, a set length of interval is removed from both ends of each straight guide segment to obtain the effective interval; Within the effective range, the representative differential strains of each straight guide segment are combined to form a segment-level differential strain observation vector.

4. The settlement monitoring method based on Z-shaped guided optical fiber deployment as described in claim 1, characterized in that, The forward model is represented as follows: in, This represents the segmented differential strain observation vector. For geometric mapping matrix, Let be the nodal settlement vector. For the error vector, For monitoring time.

5. The settlement monitoring method based on Z-shaped guided optical fiber deployment as described in claim 1, characterized in that, The anchor point constraint is expressed as follows: in, To calibrate the displacement gauge observation vector, To calibrate the interpolation matrix corresponding to the displacement gauge, To guide the settlement vector of the node, To calibrate the displacement gauge observation error vector.

6. The settlement monitoring method based on Z-shaped guided optical fiber deployment as described in claim 1, characterized in that, The constrained regularization inversion method constructs a weighted regularization objective function, expressed as: in, Let be the settlement vector of the guide node to be solved. For geometric mapping matrix, The strain observation weight matrix is... This represents the segmented differential strain observation vector. For smoothing regularization operator matrix, To smooth out the regularization parameters, The anchor point displacement observation weight matrix, For anchor point constraint weight parameters, To calibrate the interpolation matrix corresponding to the displacement gauge, To calibrate the displacement gauge observation vector, It is a 2-norm.

7. The settlement monitoring method based on Z-shaped guided optical fiber deployment as described in claim 1, characterized in that, Based on the observation data of the verification displacement gauge, the parameters of the guide node settlement estimation vector are optimized and the independent accuracy is evaluated.

8. A settlement monitoring system based on Z-shaped guided optical fiber deployment, characterized in that, include: The fiber optic deployment module is configured to: sequentially set multiple guide nodes along a preset monitoring direction within the area to be monitored, and sequentially pass through each guide node to form a Z-shaped guide fiber optic path. The distributed fiber optic strain acquisition module is configured to continuously acquire distributed axial strain distribution along the Z-shaped guide fiber path, and calculate distributed differential strain based on the distributed axial strain distribution. The differential strain observation module is configured to: convert distributed differential strain into an observation form that matches the guide node, and construct segment-level differential strain observation vectors. The mapping model construction module is configured to: establish a forward model based on the quantitative relationship between the segment-level differential strain observation vector and the nodal settlement vector; The constraint construction module is configured to: deploy multiple displacement gauges in the area to be monitored, and construct anchor point constraints based on the observation vectors of the calibrated displacement gauges participating in the inversion; The regularized inversion module is configured to: solve for the guide node settlement vector based on the forward model and anchor point constraints using the constrained regularized inversion method, and obtain the guide node settlement estimation vector.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the settlement monitoring method based on Z-shaped directional fiber optic deployment as described in any one of claims 1-7.

10. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the settlement monitoring method based on Z-shaped directional optical fiber deployment as described in any one of claims 1-7.

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