Multi-dimensional monitoring system and method for tunnel joints based on multi-line distributed optical cable

Abstract

This invention relates to the field of tunnel crack monitoring technology, specifically to a multi-dimensional monitoring system and method for tunnel cracks based on multi-line distributed optical cables. The multi-dimensional monitoring system includes multiple working optical cables, a temperature compensation optical cable, a data acquisition module, and a data analysis module. Multiple working optical cables and temperature compensation optical cables are laid out on both sides of the tunnel crack to be monitored according to a predetermined layout. A distributed fiber optic demodulator, via a fiber optic switch, sequentially connects and drives all working optical cables and temperature compensation optical cables to synchronously acquire and calculate data. Based on the obtained mechanical strain distribution data, the longitudinal opening, vertical settlement, and lateral misalignment are calculated. Based on the calculated multi-dimensional displacements, a more comprehensive and accurate assessment of the health status of the structural crack can be performed, providing richer and more reliable data for tunnel structure safety early warning and maintenance decisions.

Description

Technical Field

[0001] This invention relates to the field of tunnel crack monitoring technology, and in particular to a multi-dimensional monitoring system and method for tunnel cracks based on multi-line distributed optical cables. Background Technology

[0002] During operation, underground engineering structures such as tunnels and subways experience uneven settlement and deformation due to changes in geological conditions, surrounding loads, and material shrinkage and creep. Structural joints (such as expansion joints and settlement joints) are weak points in tunnel structures, and their condition directly reflects the overall safety and health of the structure. Therefore, high-precision, multi-dimensional, and long-term stable automated monitoring of tunnel structural joints is crucial.

[0003] Currently, fiber optic sensing-based monitoring technologies, especially Brillouin optical time-domain analysis, have been applied to structural health monitoring due to their advantages such as resistance to electromagnetic interference, corrosion resistance, distributed measurement, and long-distance monitoring. Existing distributed fiber optic monitoring schemes typically employ a unidirectional, single-path fiber optic cable deployment along the tunnel wall. While this method achieves long-distance strain measurement, the monitoring results are essentially one-dimensional linear strain distributions due to the single sensing path and insufficient spatial information dimension. Faced with potential vertical, lateral, and longitudinal coupled displacements at structural joints, existing technologies lack effective multi-dimensional synchronous monitoring and data decoupling capabilities, making it difficult to comprehensively and accurately assess their true safety status. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-dimensional monitoring system and method for tunnel joints based on multi-line distributed optical cables. Based on the calculated multi-dimensional displacement, the health status of the structural joints can be assessed more comprehensively and accurately.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for multi-dimensional monitoring of tunnel joints based on multi-line distributed optical cables, comprising the following steps:

[0006] On both sides of the tunnel structural joint to be monitored, multiple working optical cables and temperature compensation optical cables are laid out according to the set layout.

[0007] A distributed fiber optic demodulator is used to connect and drive all working optical cables and temperature compensation optical cables in sequence via fiber optic switch to perform synchronous acquisition and calculation.

[0008] Based on the obtained mechanical strain distribution data, the longitudinal opening, vertical settlement, and lateral misalignment were calculated.

[0009] Among them, multiple working optical cables and temperature compensation optical cables are laid on both sides of the tunnel structural joint to be monitored, according to the set layout, including:

[0010] Divide the tunnel structure joint into near-joint zone and far-joint zone on both sides;

[0011] The first working optical cable is laid horizontally parallel to the tunnel axis at the bottom of the side wall close to the inner wall of the tunnel; the second working optical cable is laid horizontally parallel to the tunnel axis at the arch waist close to the inner wall of the tunnel; and the third working optical cable is laid horizontally parallel to the tunnel axis at the center line of the arch top close to the inner wall of the tunnel.

[0012] The optical cable is placed inside the heat-insulating protective tube in a stress-free state to assemble it into a temperature-compensated optical cable, and then fixed to the far-seam area by a bracket.

[0013] The distributed fiber optic demodulator, connected sequentially via fiber optic switch, drives all working optical cables and temperature-compensated optical cables for synchronous data acquisition and calculation, including:

[0014] A distributed fiber optic demodulator is used to sequentially connect the first working optical cable, the second working optical cable, the third working optical cable, and the temperature compensation optical cable via a fiber optic switch.

[0015] The fiber optic switcher is controlled to perform cyclic switching acquisition according to the set acquisition cycle and acquisition sequence.

[0016] The mechanical strain distribution data were obtained by adjusting the original Brillouin frequency drift through strain and temperature.

[0017] The method further includes:

[0018] The original Brillouin frequency drift values ​​collected based on the first working optical cable, the second working optical cable, the third working optical cable, and the temperature-compensated optical cable are respectively assigned corresponding tags. Each tag includes the switcher channel number, timestamp, and optical cable type.

[0019] The method further includes:

[0020] Based on a preset channel space mapping table, each switcher channel number is bound to the physical location of the corresponding optical cable and the designed mileage range.

[0021] The mechanical strain distribution data obtained by strain and temperature adjustment of the collected raw Brillouin frequency drift includes:

[0022] The temperature compensation reference is extracted from the data collected by the temperature compensation optical cable, and differential calculation is performed between it and the corresponding original Brillouin frequency drift collected by the first working optical cable, the second working optical cable, or the third working optical cable.

[0023] Divide the obtained differential calculation result by the corresponding optical cable strain coefficient to obtain the mechanical strain distribution data.

[0024] The longitudinal opening is calculated based on the obtained mechanical strain distribution data, including:

[0025] From the mechanical strain distribution data of the first and third working optical cables, strain distribution curves within a set range on both sides of the structural joint are extracted respectively.

[0026] On each of the strain distribution curves, the strain abrupt change value at the structural joint is identified and calculated, and the joint width change value is calculated based on the effective measurement base distance;

[0027] The longitudinal opening is obtained by averaging the changes in seam width at the top and bottom.

[0028] The vertical settlement was calculated based on the obtained mechanical strain distribution data, including:

[0029] The mechanical strain distribution curves of the first and second working optical cables in the structural joint are extracted, and the bending curvature is calculated based on the identified strain abrupt change values.

[0030] The vertical settlement is obtained by multiplying the curvature by the effective measurement base distance and then dividing by 2.

[0031] The lateral misalignment is calculated based on the obtained mechanical strain distribution data, including:

[0032] Extract the strain abrupt change value of the second working optical cable at the structural joint. At the same time, extract the strain abrupt change values ​​at the corresponding positions from the first and third working optical cables, and calculate the corresponding misalignment dominant factor.

[0033] When the misalignment dominant factor exceeds the set threshold, the lateral misalignment is calculated based on the comprehensive proportional coefficient, the effective measured base distance, and the strain mutation value of the second working optical cable at the structural joint.

[0034] Secondly, the present invention provides a multi-dimensional monitoring system for tunnel joints based on multi-line distributed optical cables, which is applied to a multi-dimensional monitoring method for tunnel joints based on multi-line distributed optical cables as provided in the first aspect. The multi-dimensional monitoring system for tunnel joints based on multi-line distributed optical cables includes multiple working optical cables, a temperature compensation optical cable, a data acquisition module, and a data analysis module.

[0035] Multiple working optical cables and temperature compensation optical cables are respectively laid on both sides of the tunnel structure joint to be monitored according to the set layout method;

[0036] The data acquisition module is used to employ a distributed fiber optic demodulator to sequentially connect and drive all working optical cables and temperature compensation optical cables through a fiber optic switch to perform synchronous acquisition and calculation.

[0037] The data analysis module is used to calculate the longitudinal opening, vertical settlement, and lateral misalignment based on the obtained mechanical strain distribution data.

[0038] This invention discloses a multi-dimensional monitoring system and method for tunnel joints based on multi-line distributed optical cables. The multi-dimensional monitoring system for tunnel joints based on multi-line distributed optical cables includes multiple working optical cables, temperature compensation optical cables, a data acquisition module, and a data analysis module. Multiple working optical cables and temperature compensation optical cables are laid out on both sides of the tunnel joint to be monitored according to a predetermined layout. A distributed fiber optic demodulator is used to sequentially connect and drive all working optical cables and temperature compensation optical cables through an optical fiber switch to perform synchronous acquisition and calculation. Based on the obtained mechanical strain distribution data, the longitudinal opening, vertical settlement, and lateral misalignment are calculated. Based on the calculated multi-dimensional displacement, a more comprehensive and accurate assessment of the health status of the structural joint can be performed, providing richer and more reliable evidence for tunnel structure safety early warning and maintenance decisions. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0040] Figure 1 This is a schematic diagram illustrating the steps of a multi-dimensional monitoring method for tunnel joints based on a multi-line distributed optical cable according to the first embodiment of the present invention.

[0041] Figure 2 This is a flowchart illustrating a multi-dimensional monitoring method for tunnel joints based on a multi-line distributed optical cable, provided by the present invention.

[0042] Figure 3 This is a schematic diagram of the working optical cable layout provided by the present invention.

[0043] Figure 4 This is a schematic diagram of the structure of a tunnel joint multi-dimensional monitoring system based on a multi-line distributed optical cable according to the second embodiment of the present invention.

[0044] Figure 5 This is a schematic diagram of the electronic device of the present invention.

[0045] In the diagram: 101 - Data acquisition module, 102 - Data analysis module. Detailed Implementation

[0046] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0047] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0048] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0049] The first embodiment of this application is as follows:

[0050] Please see Figures 1-3 This invention provides a method for multi-dimensional monitoring of tunnel joints based on multi-line distributed optical cables, comprising the following steps:

[0051] S101. On both sides of the tunnel structural joint to be monitored, multiple working optical cables and temperature compensation optical cables are laid out according to the set layout method.

[0052] Specifically, near-joint zone and far-joint zone are defined on both sides of the structural joint to be monitored in the tunnel. At least three working optical cables are laid within each of these zones. These working optical cables are of the same specification and are laid symmetrically around the structural joint.

[0053] The first working optical cable: This cable is laid horizontally parallel to the tunnel axis, close to the bottom of the sidewall of the tunnel's inner wall, crossing the structural joint. It must be firmly bonded to or embedded in the lining surface to ensure it deforms in tandem with the lining structure. The cable extends at least 5-10 meters to both sides (near the joint area) from the structural joint as the center. It is mainly used to monitor longitudinal opening and vertical settlement. When the structural joint experiences simple longitudinal opening or compression, this horizontal optical cable will directly bear tensile or compressive strain, with its peak strain directly corresponding to the change in joint width. When vertical relative settlement occurs on both sides of the structural joint, the bottom optical cable will be bent and stretched due to the "lever effect." Combined with the strain of the second working optical cable (at the arch), a strain difference can be formed, and the settlement can be accurately calculated using geometric relationships (such as considering the bottom and the second working optical cable as the two sides of a triangle).

[0054] The second working optical cable: This cable is laid horizontally parallel to the tunnel axis at the arch waist of the tunnel wall, crossing the structural joint. It is closely attached to the tunnel wall, located at the arch waist (usually above the arch line, approximately at the center height of the tunnel cross-section), and laid horizontally parallel to the tunnel axis. Its fixing method and coverage area are the same as the first working optical cable. It is mainly used for the coordinated monitoring of vertical settlement and lateral misalignment. During vertical settlement, the bending strain of the second working optical cable differs in magnitude and sign from that of the bottom optical cable. This difference in strain signal is key to calculating the absolute settlement. When the structural joint experiences lateral (horizontal direction perpendicular to the tunnel axis) misalignment, the tunnel cross-section undergoes shear deformation. The optical cable located at the arch waist will therefore experience tensile or compressive strain. If a fourth second working optical cable is symmetrically laid on the other side of the tunnel, the strain signs of the two cables will be opposite, allowing direct calculation of the misalignment by comparison. Even with only one side, the strain mode, combined with the analysis of the top and bottom optical cables, can infer the misalignment.

[0055] The third working optical cable: laid close to the centerline of the tunnel arch, parallel to the tunnel axis, and crossing the structural joint. This cable is primarily used to monitor longitudinal opening and verify overall deformation. Similar to the bottom cable, it is directly sensitive to the longitudinal opening of the structural joint. Comparing the opening measurements at the top and bottom can verify the accuracy of the measurements or reveal more complex torsional deformations. The arch cable, together with the bottom and the second working optical cable, forms a closed "sensing loop." This loop completely "frames" the deformation of the tunnel cross-section; any form of deformation will trigger interpretable strain signals at different locations on this loop, ensuring the completeness and reliability of the three-dimensional displacement calculation.

[0056] Temperature-compensated optical cable deployment: A temperature-compensated optical cable is deployed. This cable is placed in a relaxed, stress-free state (e.g., coiled or wavy) within a dedicated thermally insulated protective tube. This tube is fixed to a stable region of the tunnel wall unaffected by structural joint deformation (i.e., the far-joint zone), and its orientation is parallel to the working optical cable to sense the temperature field under the same environment. It is specifically designed to measure temperature changes, providing a temperature compensation reference for the working optical cable. The relaxed deployment ensures the cable is unaffected by structural mechanical deformation; the thermally insulated tube blocks instantaneous thermal shocks caused by localized sunlight, ventilation, etc., allowing it to sense a more uniform and stable ambient temperature. Because it is the same type and environment as the working optical cable, the Brillouin frequency shift it measures is purely due to temperature changes. Subtracting the data of the temperature-compensated optical cable at the same time from the original measurement data of each working optical cable yields the pure mechanical strain, eliminating the temperature effect.

[0057] S102. A distributed fiber optic demodulator is used to connect and drive all working optical cables and temperature compensation optical cables in sequence through an optical fiber switch to perform synchronous acquisition and calculation.

[0058] Specifically, to achieve centralized acquisition and control of multiple optical cables, a master-slave ring network architecture is adopted, which is the foundation for ensuring the efficient and reliable operation of the system. The core host distributed fiber optic demodulator is responsible for generating laser pulses, receiving and demodulating the backscattered Brillouin light signals returned from all optical cables, and finally outputting the Brillouin frequency shift distributed along the length of the optical cable. A multi-port fiber optic switch is introduced as a key slave device. One "common end" of the switch is connected to the optical output / input port of the demodulator via a lead fiber. The multiple "channel ends" of the switch are connected to the ends of the first working optical cable, the second working optical cable, the third working optical cable, and the temperature compensation optical cable deployed in the tunnel, respectively, via corresponding lead fibers. This "demodulator-switcher-multiple optical cables" architecture allows a single expensive distributed fiber optic demodulator to be shared for use on multiple measurement lines as needed, greatly reducing system costs and making it particularly suitable for tunnel monitoring scenarios with numerous measurement points and long distances.

[0059] The distributed fiber optic demodulator integrates a high-precision clock. It sends control commands to the fiber optic switcher according to a preset acquisition cycle (e.g., every 10 minutes or 1 hour). Within one acquisition cycle, the switcher cycles through channels in a predetermined order (e.g., channel 1 -> channel 2 -> channel 3 -> channel 4). When a channel is activated, the demodulator performs a complete distributed measurement on the fiber optic cable connected to that channel, acquiring the Brillouin frequency drift data for the entire cable. Since the entire cyclic scanning process is completed within a relatively short time (e.g., within a few minutes), and the tunnel's ambient temperature and deformation typically change very little during this period, the data from the four fiber optic cables can be considered to be acquired "quasi-synchronously." This time-series cyclic scanning mechanism maximizes the utilization of hardware resources while ensuring data time consistency.

[0060] After each fiber optic cable measurement is completed, the demodulator or its connected host computer software will automatically tag the data set. This tag must contain at least:

[0061] Switcher channel number: uniquely corresponds to the port of the fiber optic switch, thus uniquely identifying which physical optical cable it is.

[0062] Timestamp: Records the precise time when data was collected.

[0063] Fiber optic cable type: Predefined during system initialization, indicating whether it is a "working fiber optic cable" or a "temperature-compensated fiber optic cable".

[0064] Based on a preset channel-space mapping table, this table binds each switcher channel number to the physical location of the corresponding optical cable (such as "Tunnel A Section X Joint - Bottom", "Tunnel A Section X Joint - Arch - Temperature Compensation") and the designed mileage range.

[0065] The raw Brillouin frequency drift collected needs to be processed before it can be used to calculate displacement.

[0066] First, for any sensing optical cable, the relationship between the measured Brillouin frequency shift Δν_B(z) and the strain Δε(z) and temperature change ΔT(z) is as follows:

[0067] Δν_B(z)=C_ε*Δε(z)+C_T*ΔT(z),

[0068] Where C_ε and C_T are the strain coefficient and temperature coefficient of the optical cable, and z is the length coordinate along the optical cable.

[0069] From the data of the temperature-compensated optical cable, the Brillouin frequency shift Δν_B_temp(z) over its entire length is read. Since the optical cable is isolated from mechanical strain, we have:

[0070] Δν_B_temp(z)=C_T*ΔT(z);

[0071] This formula is a pure representation of the distribution of the ambient temperature field along the tunnel at the current moment.

[0072] For any working optical cable (taking the first working optical cable as an example), we read its original frequency drift data Δν_B_work1(z). Then, we perform the following calculations:

[0073] Δν_B_work1(z)−Δν_B_temp(z)=[C_ε·Δε_mech1(z) + C_T·ΔT(z)] − [C_T·ΔT(z)]= C_ε·Δε_mech1(z);

[0074] Through this simple difference operation, the temperature term C_T*ΔT(z) is precisely canceled out, resulting in a frequency drift that is only related to mechanical strain.

[0075] Dividing the above difference result by the strain coefficient C_ε of the optical cable, we can obtain the mechanical strain distribution data Δε_mech1(z) along the entire length of the working optical cable:

[0076] Δε_mech1(z)=[Δν_B_work1(z)-Δν_B_temp(z)] / C_ε

[0077] Using the mapping table established during initialization, the mechanical strain data of all optical cables are unified into the same spatial coordinate system centered on the structural joint and with the tunnel mileage as the coordinate axis. The processed mechanical strain data, with clear spatial coordinates and optical cable identification, are stored in the database in time series. Each data record clearly points to a specific optical cable at a specific time and location (e.g., "2023-10-27 10:00:00, Tunnel A, Xth joint, bottom horizontal survey line, mechanical strain = X.Xμε").

[0078] S103. Based on the obtained mechanical strain distribution data, calculate the longitudinal opening, vertical settlement, and lateral misalignment.

[0079] Specifically, calculation of longitudinal opening.

[0080] Longitudinal opening refers to the separation or proximity displacement of the two sides of the structural joint along the tunnel axis. When the structural joint opens purely longitudinally, the optical cable laid parallel to the axis across the joint will experience uniform tensile or compressive strain. This strain manifests as a sudden peak at the structural joint location. According to the basic formula in mechanics of materials: Displacement = Average Strain × Measurement Base Distance.

[0081] Calculation process:

[0082] From the mechanical strain data of the first working optical cable (bottom horizontal measuring line) and the third working optical cable (arch top vertical measuring line), the strain distribution curves are extracted within a certain range on both sides of the structural joint (for example, 1 meter on each side of the joint).

[0083] On the strain distribution curve of each optical cable, the strain abrupt change values ​​Δε_bottom (bottom) and Δε_top (top) at the structural joint are identified and calculated. This value represents the relative elongation or shortening rate of the optical cable in that area due to the opening of the joint. The strain distribution curve is extracted by taking a specified range (e.g., 1 meter on each side of the joint) along the length of the optical cable, centered on the structural joint, and plotting the strain as a function of mileage. The strain abrupt change value is identified and calculated by subtracting the strain value at the corresponding position of the structural joint from the average strain value of the adjacent stable sections on both sides of the strain distribution curve to obtain the strain abrupt change value Δε at that position. ΔL_bottom represents the estimated joint width change value based on the bottom optical cable, and ΔL_top represents the estimated joint width change value based on the top optical cable.

[0084] For each optical cable, the estimated slot width variation ΔL can be initially calculated using the following formula:

[0085] ΔL_bottom = Δε_bottom * L_gauge (bottom estimate);

[0086] ΔL_top = Δε_top * L_gauge (top estimate);

[0087] Where L_gauge is the effective measurement base distance, which is usually taken as the total length of the optical cable in the sensitive area on both sides of the structural joint (e.g., 2 meters).

[0088] The final longitudinal opening D_longitudinal is obtained by averaging the estimates from the top and bottom:

[0089] D_longitudinal=(ΔL_bottom+ΔL_top) / 2

[0090] By using the fusion calculation of top and bottom measurement data, errors caused by structural torsion or abnormal local stress on one side of the optical cable can be effectively offset, making the obtained opening amount more representative of the overall behavior of the structure and improving the reliability and representativeness of the results.

[0091] Vertical settlement calculation

[0092] Vertical settlement refers to the vertical relative displacement of one side of a structural joint relative to the other. When uneven settlement occurs, the tunnel lining, essentially a rigid body, rotates, resulting in varying bending strains on horizontal survey lines laid out at different heights. By establishing a geometric transformation model, this strain difference can be converted into vertical displacement.

[0093] Calculation process:

[0094] Extract the mechanical strain distribution curves of the first working optical cable (bottom) and the second working optical cable (arch waist) near the structural joint.

[0095] Similarly, the strain abrupt changes Δε_bottom and Δε_mid at the joint of the two optical cables were identified. Due to the bending caused by settlement, the signs of the strains at these two locations are usually opposite (one side is under tension, the other under compression). The algebraic difference between the two is calculated as Δε_bend = Δε_mid - Δε_bottom. This difference directly reflects the curvature of the cross-section, κ ≈ Δε_bend / H, where H is the vertical distance between the bottom and the second working optical cable.

[0096] The bottom optical cable and the second working optical cable are considered as a virtual sensing beam. The vertical distance H between the two optical cables (referring to the vertical height of the tunnel sidewall from the location where the bottom optical cable is laid to the location where the second working optical cable is laid) is a known fixed parameter.

[0097] According to mechanics of materials, the bending curvature κ of a beam is proportional to the strain gradient, approximately κ≈Δε_bend / H.

[0098] Therefore, the relative rotation angle θ caused by the bending of this "beam" at the seam can be approximated as θ≈κ*L_gauge.

[0099] Finally, the vertical settlement S_vertical can be calculated using this angle and geometric relationship: S_vertical ≈ θ * (H / 2). Combining the above formulas, a simplified calculation formula can be obtained:

[0100] S_vertical ≈ (Δε_bend · L_gauge) / 2.

[0101] This method cleverly transforms vertical displacement, which is difficult to measure directly, into measurable strain differences along horizontal survey lines at different heights. It achieves the conversion from one-dimensional linear strain to two-dimensional displacement through a simple geometric model.

[0102] Calculation of lateral misalignment

[0103] Lateral misalignment refers to the relative shear displacement on both sides of a structural joint in the horizontal plane, perpendicular to the tunnel axis. This deformation will cause distortion of the tunnel cross-section, resulting in strains of opposite signs on symmetrical survey lines located at the same horizontal level but on opposite sides (such as the left and right arch waists).

[0104] Calculation process (taking the ideal case of laying a second working optical cable on both sides as an example):

[0105] Extract the mechanical strain abrupt change values ​​Δε_left and Δε_right of the second working optical cable on the left and the corresponding fourth working optical cable on the right (if deployed) at the structural joint.

[0106] Calculate shear strain: Under transverse misalignment, Δε_left and Δε_right have opposite signs. Calculate the difference between them: Δε_shear = Δε_left - Δε_right. This difference reflects the degree of shear deformation experienced by the cross-section.

[0107] Establish a geometric model and solve it:

[0108] The left and right second working optical cables are regarded as virtual horizontal sensing rods, and their span is the width W of the tunnel.

[0109] Similar to the calculation of vertical settlement, the shear strain difference Δε_shear can be correlated with the shear angle γ of the cross section. The relationship between the shear angle γ and the shear strain difference Δε_shear is: γ ≈ Δε_shear, where Δε_shear is the difference in strain abrupt changes between the left and right second working optical cables. The lateral misalignment D_transverse can be estimated using the following formula:

[0110] D_transverse ≈ γ × L_gauge / 2;

[0111] Where L_gauge is the effective measurement base distance.

[0112] Finally, the lateral misalignment D_transverse can be estimated using the following formula:

[0113] D_transverse≈(Δε_shear*L_gauge*W) / (2*W)=(Δε_shear*L_gauge) / 2

[0114] If only a second working optical cable is deployed on one side, its strain mode can be analyzed, and combined with the strain states of the top and bottom optical cables for joint inference. For example, when lateral misalignment occurs, the second working optical cable on one side will exhibit significant strain, while the strain responses of the first and second working optical cables will be relatively weaker or exhibit different modes. Specifically:

[0115] The abrupt change value Δε_shear_side of mechanical strain at the structural joint is extracted from the second working optical cable (single-sided arch waist). This value is the most direct and sensitive indicator of lateral misalignment. At the same time, the strain abrupt change values ​​Δε_bottom and Δε_top at the corresponding positions are extracted from the first working optical cable (bottom) and the third working optical cable (arch top).

[0116] First, the system determines whether the current deformation is dominated by lateral misalignment. A key criterion is that under pure lateral misalignment, the second working optical cable should exhibit significant strain, while the strain response of the top and bottom optical cables should be relatively weak.

[0117] Calculate a misalignment dominance factor α:

[0118] α=|Δε_shear_side| / (|Δε_bottom|+|Δε_top|+|Δε_shear_side|).

[0119] When α exceeds a set threshold (e.g., 0.7), the lateral misalignment is considered to be the current major deformation.

[0120] Once the lateral misalignment is confirmed as the dominant factor, we establish a simplified computational model. The tunnel cross-section is considered as a rectangular frame with height H (from the top to the bottom) and width W. The lateral misalignment causes the frame to become a parallelogram. The strain Δε_shear_side of the second working optical cable on one side is related to the horizontal displacement at that point (i.e., half the amount of misalignment).

[0121] Based on geometric relationships, the lateral misalignment D_transverse can be estimated as follows:

[0122] D_transverse≈k*Δε_shear_side*L_gauge;

[0123] Here, k is a comprehensive scaling factor calibrated through finite element simulation, used to convert the strain of the single-sided arched optical cable into lateral misalignment. During simulation, a series of known lateral misalignment displacements are applied to the model, and the simulated strain values ​​of the second working optical cable on one side are recorded. The value of k is determined by fitting a curve. This factor implicitly considers the actual shape of the tunnel (not an ideal rectangle) and material properties.

[0124] Multi-level safety thresholds (e.g., normal, warning, alarm, danger) are set for each displacement quantity (especially the composite displacement vector). The composite displacement vector is obtained by vector synthesis of the longitudinal opening, vertical settlement, and lateral misalignment. Its magnitude is the square root of the sum of the squares of the longitudinal opening, vertical settlement, and lateral misalignment, and its direction is determined by the orientation angle of each component in three-dimensional space.

[0125] The calculated displacement is compared with a threshold in real time. Once the "early warning" threshold is exceeded, the system automatically sends an alert to the management personnel via SMS, email, or monitoring platform. If the "alarm" threshold is exceeded, a more urgent response mechanism is activated.

[0126] All displacement data is stored as a time series to form a historical database. By performing time-series analysis on the historical data, the deformation development trend of each structural joint (stable, slow development, or accelerated development) can be clearly displayed. Using machine learning algorithms (such as the LSTM time series prediction model), the displacement amount in the future can be predicted, enabling predictive maintenance and taking intervention measures in advance before the problem becomes serious.

[0127] The second embodiment of this application is as follows:

[0128] Please see Figure 4 This invention provides a multi-dimensional monitoring system for tunnel joints based on multi-line distributed optical cables, applicable to a multi-dimensional monitoring method for tunnel joints based on multi-line distributed optical cables as provided in the first embodiment. The multi-dimensional monitoring system for tunnel joints based on multi-line distributed optical cables includes multiple working optical cables, a temperature compensation optical cable, a data acquisition module, and a data analysis module.

[0129] Multiple working optical cables and temperature compensation optical cables are respectively laid on both sides of the tunnel structure joint to be monitored according to the set layout method;

[0130] The data acquisition module 101 is used to use a distributed fiber optic demodulator to connect and drive all working optical cables and temperature compensation optical cables to perform synchronous acquisition and calculation through a fiber optic switch.

[0131] The data analysis module 102 is used to calculate the longitudinal opening, vertical settlement, and lateral misalignment based on the obtained mechanical strain distribution data.

[0132] Regarding the system in the above embodiments, the specific ways in which each module performs operations have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0133] For the system embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this application according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0134] Accordingly, this application also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the multi-dimensional monitoring method for tunnel gaps based on multi-line distributed optical cables as described above. Figure 5 The diagram shown is a hardware structure diagram of any device with data processing capabilities in a tunnel joint multi-dimensional monitoring system based on multi-line distributed optical cable provided by an embodiment of the present invention, except for... Figure 5 In addition to the processor, memory, and network interface shown, any data processing device in the embodiment may also include other hardware depending on the actual function of the data processing device, which will not be described in detail here.

[0135] Accordingly, this application also provides a computer-readable storage medium storing computer instructions, which, when executed by a processor, implement the multi-dimensional monitoring method for tunnel gaps based on multi-line distributed optical cables as described above. The computer-readable storage medium can be an internal storage unit of any data processing device as described in any of the foregoing embodiments, such as a hard disk or memory. The computer-readable storage medium can also be an external storage device, such as a plug-in hard disk, smart media card (SMC), SD card, flash card, etc., equipped on the device. Furthermore, the computer-readable storage medium can include both internal storage units of any data processing device and external storage devices. The computer-readable storage medium is used to store the computer program and other programs and data required by the data processing device, and can also be used to temporarily store data that has been output or will be output.

[0136] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0137] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A method for multi-dimensional monitoring of tunnel joints based on multi-line distributed optical cables, characterized in that, Includes the following steps: On both sides of the tunnel structural joint to be monitored, multiple working optical cables and temperature compensation optical cables are laid out according to the set layout. A distributed fiber optic demodulator is used to sequentially connect and drive all working optical cables and temperature-compensated optical cables via fiber optic switches for synchronous data acquisition and calculation, including: A distributed fiber optic demodulator is used to sequentially connect the first working optical cable, the second working optical cable, the third working optical cable, and the temperature compensation optical cable via a fiber optic switch. The fiber optic switcher is controlled to perform cyclic switching acquisition according to the set acquisition cycle and acquisition sequence. The temperature compensation reference is extracted from the data collected by the temperature-compensated optical cable, and differential calculation is performed between it and the corresponding original Brillouin frequency drift collected by the first working optical cable, the second working optical cable, or the third working optical cable. Specifically, for any working optical cable, taking the first working optical cable as an example, its original frequency drift data Δν_B_work1(z) is read, and then the following calculation is performed: Δν_B_work1(z)−Δν_B_temp(z)=[C_ε·Δε_mech1(z) + C_T·ΔT(z)] − [C_T·ΔT(z)] = C_ε·Δε_mech1(z); Through this difference operation, the temperature term C_T*ΔT(z) is precisely canceled out, resulting in a frequency shift that is only related to mechanical strain. Divide the obtained differential calculation results by the corresponding optical cable strain coefficient to obtain mechanical strain distribution data; The original Brillouin frequency drift values ​​collected based on the first working optical cable, the second working optical cable, the third working optical cable, and the temperature compensation optical cable are respectively assigned corresponding tags, and each tag includes the switcher channel number, timestamp, and optical cable type; Based on the preset channel space mapping table, each switcher channel number is bound to the physical deployment location and designed mileage range of the corresponding optical cable; Based on the obtained mechanical strain distribution data, the longitudinal opening, vertical settlement, and lateral misalignment were calculated, specifically as follows: ΔL_bottom represents the estimated slot width change based on the bottom optical cable, and ΔL_top represents the estimated slot width change based on the top optical cable; for each optical cable, the estimated slot width change ΔL is initially calculated using the following formula: Bottom estimate ΔL_bottom = Δε_bottom * L_gauge; Top estimate ΔL_top = Δε_top * L_gauge; Where L_gauge is the effective measurement base distance; the estimated values ​​at the top and bottom are averaged to obtain the final longitudinal opening D_longitudinal; Similarly, the strain abrupt changes Δε_bottom and Δε_mid at the joint of the two optical cables are identified, and their algebraic difference Δε_bend = Δε_mid - Δε_bottom is calculated. This difference directly reflects the curvature of the cross-section, where the curvature κ ≈ Δε_bend / H, and H is the vertical distance between the bottom and the second working optical cable, resulting in a simplified calculation formula: S_vertical ≈ (Δε_bend · L_gauge) / 2; For the case of deploying double-sided second working optical cables, extract the mechanical strain abrupt change values ​​Δε_left and Δε_right of the left-side second working optical cable and the corresponding right-side fourth working optical cable at the structural joint, and calculate the difference between them Δε_shear = Δε_left - Δε_right; the lateral misalignment D_transverse is estimated by the following formula: D_transverse≈(Δε_shear*L_gauge*W) / (2*W)=(Δε_shear*L_gauge) / 2; Where L_gauge is the effective measurement base distance; If only a single-sided second working optical cable is deployed, the abrupt change value Δε_shear_side of its mechanical strain at the structural joint is extracted from the second working optical cable. Simultaneously, the strain abrupt change values ​​Δε_bottom and Δε_top at the corresponding positions are extracted from the first and third working optical cables. A misalignment dominance factor α is calculated. When α exceeds a set threshold, the lateral misalignment D_transverse is estimated using geometric relationships as follows: D_transverse≈k*Δε_shear_side*L_gauge; Where k is the comprehensive scaling factor calibrated through finite element simulation.

2. The method for multi-dimensional monitoring of tunnel joints based on multi-line distributed optical cables as described in claim 1, characterized in that, On both sides of the tunnel structural joint to be monitored, multiple working optical cables and temperature compensation optical cables are laid according to the predetermined layout, including: Divide the tunnel structure joint into near-joint zone and far-joint zone on both sides; The first working optical cable is laid horizontally parallel to the tunnel axis at the bottom of the side wall close to the inner wall of the tunnel; the second working optical cable is laid horizontally parallel to the tunnel axis at the arch waist close to the inner wall of the tunnel; and the third working optical cable is laid horizontally parallel to the tunnel axis at the center line of the arch top close to the inner wall of the tunnel. The optical cable is placed inside the heat-insulating protective tube in a stress-free state to assemble it into a temperature-compensated optical cable, and then fixed to the far-seam area by a bracket.

3. A multi-dimensional monitoring system for tunnel joints based on multi-line distributed optical fiber, applied to the multi-dimensional monitoring method for tunnel joints based on multi-line distributed optical fiber as described in claim 1, characterized in that, The tunnel joint multi-dimensional monitoring system based on multi-line distributed optical cable includes multiple working optical cables, temperature compensation optical cables, a data acquisition module, and a data analysis module. Multiple working optical cables and temperature compensation optical cables are respectively laid on both sides of the tunnel structure joint to be monitored according to the set layout method; The data acquisition module is used to employ a distributed fiber optic demodulator to sequentially connect and drive all working optical cables and temperature compensation optical cables through a fiber optic switch to perform synchronous acquisition and calculation. The data analysis module is used to calculate the longitudinal opening, vertical settlement, and lateral misalignment based on the obtained mechanical strain distribution data, specifically: ΔL_bottom represents the estimated slot width change based on the bottom optical cable, and ΔL_top represents the estimated slot width change based on the top optical cable; for each optical cable, the estimated slot width change ΔL is initially calculated using the following formula: Bottom estimate ΔL_bottom = Δε_bottom * L_gauge; Top estimate ΔL_top = Δε_top * L_gauge; Where L_gauge is the effective measurement base distance; the estimated values ​​at the top and bottom are averaged to obtain the final longitudinal opening D_longitudinal; Similarly, the strain abrupt changes Δε_bottom and Δε_mid at the joint of the two optical cables are identified, and their algebraic difference Δε_bend = Δε_mid - Δε_bottom is calculated. This difference directly reflects the curvature of the cross-section, where the curvature κ ≈ Δε_bend / H, and H is the vertical distance between the bottom and the second working optical cable, resulting in a simplified calculation formula: S_vertical ≈ (Δε_bend · L_gauge) / 2; For the case of deploying double-sided second working optical cables, extract the mechanical strain abrupt change values ​​Δε_left and Δε_right of the left-side second working optical cable and the corresponding right-side fourth working optical cable at the structural joint, and calculate the difference between them Δε_shear = Δε_left - Δε_right; the lateral misalignment D_transverse is estimated by the following formula: D_transverse≈(Δε_shear*L_gauge*W) / (2*W)=(Δε_shear*L_gauge) / 2; Where L_gauge is the effective measurement base distance; If only a single-sided second working optical cable is deployed, the abrupt change value Δε_shear_side of its mechanical strain at the structural joint is extracted from the second working optical cable. Simultaneously, the strain abrupt change values ​​Δε_bottom and Δε_top at the corresponding positions are extracted from the first and third working optical cables. A misalignment dominance factor α is calculated. When α exceeds a set threshold, the lateral misalignment D_transverse is estimated using geometric relationships as follows: D_transverse≈k*Δε_shear_side*L_gauge; Where k is the comprehensive scaling factor calibrated through finite element simulation.

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