Buried pipeline weight strain isolation temperature measuring optical cable and depth monitoring method

Abstract

The application discloses a counterweight strain isolation temperature measuring optical cable of a buried pipeline and a buried depth monitoring method. The counterweight structure of the counterweight strain isolation temperature measuring optical cable comprises an arc-shaped shell connected through threads, a rigid support forming a four-corner support with the shell, a counterweight bin arranged in the shell and a rigid counterweight column arranged in the counterweight bin. The buried depth monitoring method calculates a temperature amplitude index and a relative temperature change amplitude mean value through collecting a temperature sequence, screens representative temperature data sequences and eliminates abnormal temperature points, establishes a buried depth-temperature response monitoring model and inversely calculates output results after monitoring. The optical cable is made to sink to the bottom of the pipeline by the self weight of the counterweight structure and is kept stable under water flow disturbance. A flexible anti-skid clamping lining layer is additionally arranged to improve the connection stability of the optical cable and the counterweight structure. An ultra-weak optical fiber Bragg grating array is used to continuously acquire temperature responses along the pipeline. According to the buried depth distribution along the pipeline and the elimination of abnormal temperature points, the interference of the buried depth-temperature response monitoring model is reduced.

Description

Technical Field

[0001] This invention relates to a counterweight strain-isolated temperature-measuring optical cable and a method for monitoring burial depth, specifically to a counterweight strain-isolated temperature-measuring optical cable and a method for monitoring burial depth of a buried pipeline. Background Technology

[0002] Buried water pipelines are an important component of urban infrastructure, playing a vital role in ensuring urban water supply and the safe operation of underground spaces.

[0003] However, existing buried pipelines generally suffer from problems such as missing burial depth information and inconsistencies between actual burial depth and design data. Patent CN223105852U (publication date: July 15, 2025) integrates a controller, battery, communication components, and sensor components into a monitoring float, relying on external detection equipment to collect pipeline environmental parameters and perform low-power continuous burial depth monitoring. However, it cannot monitor environmental parameters of the entire pipeline in real time and causes significant disturbance to the pipeline's internal structure. Patent CN114184155A (publication date: March 15, 2022) monitors the relative displacement between the pipeline and the riverbed using a limiting rod, sliding sleeve, pipeline clamp, cross sliding bracket, and pull-wire displacement gauge, achieving automatic monitoring of the burial depth of pipelines crossing rivers. However, it cannot monitor long distances.

[0004] Meanwhile, in existing pipeline burial depth monitoring schemes, image recognition methods typically require the pipeline to be visible, which limits their applicability in complex external environments or when the pipeline is obscured by mud or water. They are also susceptible to lighting conditions and shooting angles. Electromagnetic detection and ground-penetrating radar methods are widely used in underground pipeline burial depth monitoring, but their monitoring accuracy is easily affected by factors such as pipe material type, soil moisture content, underground obstacles, and surrounding pipelines. Furthermore, they are mostly phased detection methods with limited monitoring range and continuity. Mechanical contact monitoring methods require the installation of limit rods, supports, or displacement sensors around the pipeline, making installation and maintenance complex. They also primarily monitor local measurement points, making it difficult to obtain continuous burial depth distribution along the pipeline. Distributed fiber optic monitoring methods offer continuous sensing advantages and can largely compensate for the above research deficiencies. However, when deployed inside existing underground pipelines, the fiber optic cable is difficult to fix to the bottom of the pipeline and is easily affected by water flow, silt, and operational disturbances, causing it to drift, roll, or partially float, resulting in unstable spatial position and affecting the correspondence between temperature monitoring results and pipeline spatial position. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a counterweight strain-isolated temperature measuring optical cable for buried pipelines that can reduce the influence of internal disturbances and strain in the pipeline, enhance the continuity of temperature monitoring, and improve the stability of the optical cable; the second purpose of this invention is to provide a method for monitoring the burial depth of buried pipelines that can improve the accuracy of burial depth monitoring results and enhance the anti-interference capability of the burial depth-temperature response monitoring model.

[0006] Technical Solution: The buried pipeline counterweight strain isolation temperature measurement optical cable of the present invention includes an optical cable and a counterweight structure spaced outside the optical cable; the counterweight structure includes an arc-shaped shell connected by threads, a rigid support forming four corner supports with the shell, a counterweight chamber set on the inner side of the arc of the shell, and a sliding rigid counterweight column set inside the counterweight chamber. The rigid counterweight column is used to adjust the center of gravity position of the counterweight structure and improve the fit between the optical cable and the buried pipeline; the rigid support is used to form a support contact at the bottom of the pipeline to suppress the optical cable from rolling, drifting or partial suspension, and the lowering angle is unlimited; the shell is used to protect the internal counterweight structure and together with the rigid support forms an external load-bearing frame; the counterweight chamber is used to accommodate the rigid counterweight column and increase the overall weight; the rigid counterweight column is used to increase the weight of the counterweight structure so that the optical cable can sink to the bottom by its own weight, and when the optical cable lands, the counterweight column can slide and sink to the bottom to better fix the optical cable; the optical cable is used to acquire temperature data along the inside of the buried pipeline.

[0007] Preferably, it also includes a flexible anti-slip clamping liner installed between the optical cable mounting groove and the counterweight structure to increase the friction between the liner and the optical cable, and to adapt to optical cables of different diameters through elastic deformation.

[0008] The counterweight structure also includes longitudinally arranged water passage holes on the shell to maintain the flow of water inside the pipe and reduce the obstruction of the counterweight structure to the water flow inside the pipe.

[0009] The optical cable includes an optical fiber, a protective sleeve forming a loose tube structure with the optical fiber, a reinforcing member covering the outside of the protective sleeve, and a waterproof protective sleeve disposed on the outside of the reinforcing member; the counterweight structure also includes screw holes disposed on the housing and bolts for connecting and fixing the housing; the protective sleeve is used to achieve strain isolation; the optical fiber is an ultra-weak fiber Bragg grating array (UWFBG), used to acquire high spatial resolution temperature data under low-cost, long-distance monitoring conditions; the reinforcing member is a GFRP reinforcing member, used to improve the tensile strength and overall stability of the optical cable; the waterproof protective sleeve is a PE protective sleeve, used to improve the abrasion resistance, corrosion resistance and waterproof performance of the optical cable; the bolts are used to maintain a stable connection between the counterweight structure and the optical cable, and the screw holes are used to cooperate with the bolts to achieve a tight connection of the counterweight structure.

[0010] The number of the arc-shaped shells (12) is not less than two.

[0011] The method for monitoring the burial depth of underground pipelines according to the present invention includes the following steps:

[0012] (1) The initial temperature sequence was acquired and demodulated using a demodulator connected to the optical cable. Temperature sequence along the pipeline at different times ;

[0013] (2) Based on the initial temperature sequence Calculate the temperature series relative temperature change And construct a temperature amplitude index ;

[0014] (3) Based on the temperature amplitude index Calculate the average magnitude of relative temperature change. Select representative temperature data sequences ;

[0015] (4) Using the standard score Z-score, representative temperature data sequences were removed. Abnormal temperature points are identified, and burial depth-temperature fitting data is generated.

[0016] (5) Establish a burial depth-temperature response monitoring model, perform inversion monitoring of burial depth along the pipeline and output the burial depth results.

[0017] The temperature sequence acquisition process is as follows:

[0018] (1.1) The counterweight strain isolation temperature measuring optical cable is bound to the high-pressure jet nozzle of the high-pressure cleaning vehicle. It is lowered into the underground pipeline by its own weight through the inspection well. The high-pressure jet nozzle sprays water backward, thereby driving the counterweight strain isolation temperature measuring optical cable and the high-pressure jet nozzle to move forward, thus completing the installation of the counterweight strain isolation temperature measuring optical cable in the underground pipeline. The inspection well is used for the lowering, installation and subsequent maintenance of the counterweight strain isolation temperature measuring optical cable. The underground pipeline is used as the object to be monitored, so that the counterweight strain isolation temperature measuring optical cable is installed along the bottom of the pipeline.

[0019] (1.2) Select optical cable (10) at the initial time The following pipeline temperature data was used as the initial temperature sequence. ;

[0020] (1.3) According to the preset sampling frequency, the temperature sequence along the pipeline at different times is continuously collected and demodulated using a demodulator. The demodulator is a UWFBG demodulator;

[0021] in, Indicates the first along the axial direction of the pipe One measuring point, This indicates the sequence number of the monitored temperature data.

[0022] Phase temperature amplitude index The build process is as follows:

[0023] (2.1) Using the initial temperature sequence Based on this, calculate the first... The first group of temperature monitoring data Relative temperature change values ​​at each measuring point: ;

[0024] (2.2) By analyzing the relative temperature change value The absolute value is processed to obtain the temperature amplitude index. ;

[0025] The representative temperature data sequence The screening process is as follows:

[0026] (3.1) Calculate the first Mean of relative temperature change amplitude of the monitoring data The formula is shown below:

[0027] ,

[0028] in, For the first The first group of monitoring data Temperature amplitude index at each measuring point This indicates the total number of measuring points along the route;

[0029] (3.2) Filter out the average amplitude of relative temperature change The maximum value in ;

[0030] (3.3) will The corresponding number A set of monitored temperature data sequences as representative temperature data sequences ;

[0031] The process for generating the burial depth-temperature fitting data is as follows:

[0032] (4.1) Set a standard score threshold and use the standard score Z-score to calculate the standard score for each measuring point. The corresponding average amplitude of relative temperature change Compared to this group Standard fraction of the overall distribution of monitored temperature data The formula is shown below:

[0033] ,

[0034] ,

[0035] in, For the first The first set of data Standard scores for each test point For the first The average relative temperature change amplitude of the monitoring data. For the first Standard deviation of relative temperature change amplitude of the group Temperature amplitude index This indicates the total number of measuring points along the route;

[0036] (4.2) For representative temperature data series Outlier identification: When the standard score is greater than or equal to the preset standard score threshold, the measurement point is determined to be an abnormal temperature point and removed from the representative temperature data sequence; when the standard score is less than the preset standard score threshold, the measurement point is determined to be a valid temperature measurement point and retained in the representative temperature data sequence.

[0037] (4.3) The representative temperature data sequence after the removal operation is used as the burial depth-temperature fitting data.

[0038] The output process for the burial depth results is as follows:

[0039] (5.1) Select several locations with known burial depths as calibration points, and establish calibration data pairs based on the burial depth-temperature fitting data at the corresponding locations. ;in, For the first Known pipeline burial depth at each calibration point , Temperature response at the corresponding location in the depth-temperature fitting data The numerical value; the burial depth The methods of obtaining data include actual measurements of inspection wells, construction data, and local measurements;

[0040] (5.2) Establish pipeline burial depth With temperature response The quantitative relationship between them, input calibration data pairs A fitting process is performed to generate a burial depth-temperature response monitoring model;

[0041] (5.3) The temperature response of the pipe section to be tested The numerical values ​​are substituted into the burial depth-temperature response monitoring model, and the burial depth D of the corresponding measuring point is calculated by function inversion or numerical solution.

[0042] (5.4) Calculate the continuous burial depth monitoring results of the underground pipeline by sequentially measuring each measuring point along the pipeline.

[0043] The burial depth of the pipeline With temperature response The quantitative relationship between them can be a polynomial function, an exponential function, a power function, a logarithmic function, a machine learning model, or a calibration curve.

[0044] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: 1. Lowering the optical cable into the existing pipeline through the inspection well minimizes construction disturbance and is suitable for long-term online monitoring; 2. Combining the counterweight chamber, rigid counterweight column, rigid support, and shell into an optical cable counterweight structure allows the optical cable inside the buried pipeline to sink to the bottom under its own weight and maintain a relatively stable position under the influence of water flow disturbance; 3. Adding a flexible anti-slip clamping liner improves the connection stability between the optical cable and the counterweight structure, reducing relative slippage and minimizing clamping damage to the outer sheath of the optical cable; 4. The UWFBG temperature-measuring optical fiber used has long-distance, high spatial resolution, and high-precision temperature measurement capabilities, enabling continuous acquisition of temperature response along the pipeline interior, providing a reliable data foundation for burial depth monitoring; 5. Eliminating abnormal temperature points based on the burial depth distribution along the pipeline reduces interference from special locations such as inspection wells on the construction of the burial depth-temperature response monitoring model, improving the stability and reliability of the burial depth monitoring results. Attached Figure Description

[0045] Figure 1 This is a structural diagram of the counterweight strain isolation temperature measurement optical cable of the present invention;

[0046] Figure 2 This is a cross-sectional view of the counterweight strain isolation temperature measuring optical cable of the present invention;

[0047] Figure 3 This is a schematic diagram of the flexible anti-slip clamping liner and counterweight structure of the present invention;

[0048] Figure 4 This is a schematic diagram of the monitoring process of the present invention;

[0049] Figure 5 This is a temperature variation curve along the pipeline of the present invention;

[0050] Figure 6 This is a graph showing the temperature-burial depth fitting results for the burial depth decrease section of the pipeline in this invention.

[0051] Figure 7 This is a temperature-burial depth fitting curve after Z-score threshold filtering according to the present invention. Detailed Implementation

[0052] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0053] Example 1

[0054] In this embodiment, the provided underground pipeline counterweight strain isolation temperature measuring optical cable, such as... Figures 1 to 4 As shown, it includes an optical cable 10, a counterweight structure spaced apart outside the optical cable 10, and a flexible anti-slip clamping liner 11 installed between the optical cable 10 mounting groove and the counterweight structure.

[0055] The optical cable 10 includes an optical fiber 1, a protective sleeve 2 forming a loose tube structure with the optical fiber 1, a reinforcing member 3 covering the outside of the protective sleeve 2, and a waterproof protective sleeve 4 disposed on the outside of the reinforcing member 3. The optical fiber 1 is an ultra-weak fiber Bragg grating array (UWFBG), connected to a demodulator 14, used to acquire and demodulate the temperature data along the inside of the buried pipeline 16. The protective sleeve 4 is used to reduce the impact of external tension, bending, and local compression on the optical fiber 1, thereby achieving strain isolation. The reinforcing member 3 is a GFRP reinforcing member, used to improve the tensile strength and overall stability of the optical cable 10. The waterproof protective sleeve 4 is a PE protective sleeve, used to improve the abrasion resistance, corrosion resistance, and waterproof performance of the optical cable 10.

[0056] The counterweight structure includes a shell 12, rigid supports 5 forming four corner supports with the shell 12, water passage holes 6 on the shell 12, a counterweight chamber 7 inside the shell 12, a rigid counterweight column 8 inside the counterweight chamber 7, screw holes 13 on the shell 12, and bolts 9 for connecting and fixing the shell 12. The counterweight chamber 7 and the rigid counterweight column 8 are used to increase the self-weight of the counterweight structure, so that the optical cable 10 sinks into the underground pipeline 16 through the inspection well 15 and is stably laid at the bottom inside the existing underground pipeline 16. The rigid supports 5 can also be set at the bottom of the counterweight structure to form a stable support at the bottom of the underground pipeline 16, and to suppress the optical cable 10 from rolling, drifting or partially suspending under the disturbance of water flow. The water passage holes 6 are used to ensure the flow of water inside the pipeline and reduce the obstruction of the counterweight structure to the water flow inside the pipe. The bolts 9 cooperate with the screw holes 13 to realize the connection and fastening of the counterweight structure.

[0057] The flexible anti-slip clamping liner 11 is used to cover and clamp the outer surface of the optical cable 10. It adapts to optical cables 10 of different diameters through elastic deformation, and increases the friction between the optical cable 10 and the counterweight structure, thereby reducing the relative slippage between the two.

[0058] In a preferred embodiment, adjacent counterweight structures are arranged at intervals along the length of the optical cable 10. The interval can be set to 1000mm, or it can be adjusted according to the pipe diameter, water flow velocity, optical cable weight, siltation in the pipe and actual deployment requirements, but it is generally adjusted according to the UWFBG monitoring grid pitch. The counterweight strain isolation temperature measuring optical cable used sinks to the bottom of the pipe by its own weight without being fixed to the pipe wall or bottom, and maintains a relatively stable spatial position at the bottom of the pipe.

[0059] Example 2

[0060] In this embodiment, the method for deploying the counterweight strain-isolated temperature-measuring optical cable specifically includes the following steps:

[0061] (1) Determine the starting and ending manholes 15, pipe length, pipe diameter, manhole location and pipe operating status of the underground pipeline 16 to be monitored, and determine the laying length of the optical cable 10 according to the pipe length.

[0062] (2) Install a counterweight structure on the outside of the optical cable 10 at a preset interval, and set a flexible anti-slip clamping liner 11 between the optical cable (10) mounting groove and the counterweight structure, so that the flexible anti-slip clamping liner 11 can fit with the outer surface of the optical cable 10 and be fastened by bolts 9 and screw holes 13, so that a stable connection is formed between the counterweight structure, the optical cable 10 and the flexible anti-slip clamping liner 11.

[0063] (3) The counterweight strain isolation temperature measuring optical cable is bound to the high-pressure jet nozzle of the high-pressure cleaning vehicle. It sinks to the underground pipeline 16 through the inspection well 15 by its own weight. The high-pressure jet nozzle sprays water backward, thereby driving the counterweight strain isolation temperature measuring optical cable and the high-pressure jet nozzle to move forward and lay along the axial direction of the underground pipeline 16. The rigid counterweight column 8 of the counterweight structure of the optical cable 10 sinks to the bottom of the counterweight chamber according to its own weight, lowering the center of gravity of the counterweight strain isolation temperature measuring optical cable. This allows the counterweight strain isolation temperature measuring optical cable to gradually sink to the bottom of the pipeline under the action of gravity, further suppressing the optical cable from rolling, drifting or local suspension, and also improving the strain isolation capability of the optical cable.

[0064] (4) After the optical cable 10 is laid in the underground pipeline 16 to be monitored, one or both ends of the optical cable 10 are led out through the inspection well 15 and connected to the UWFBG demodulator 14 to form an underground pipeline temperature monitoring device.

[0065] (5) Start the UWFBG demodulator 14 to continuously collect the temperature along the inside of the buried pipeline 16 and obtain a pipeline temperature monitoring dataset containing time, spatial location and temperature information. The minimum spatial resolution of the monitoring is 1m, the temperature measurement accuracy is ±0.1℃ and the monitoring frequency is 0.1Hz.

[0066] Example 3

[0067] In this embodiment, the process for adjusting the center of gravity of the counterweight structure using the rigid counterweight column is as follows:

[0068] (1) The center of gravity height of the counterweight strain-isolated temperature measuring optical cable of the immovable rigid counterweight column is set to 110mm. The center of gravity height of the counterweight strain-isolated temperature measuring optical cable corresponding to the rigid counterweight column that sinks to the bottom of the counterweight chamber is 40mm. The total weight of the counterweight strain-isolated temperature measuring optical cable It is 20N.

[0069] (2) Under the action of water flow, the tilt angle of the counterweight strain isolation temperature measuring optical cable for Then, the overturning angle when the center of gravity height is 110mm is The overturning angle when the center of gravity height is 40mm is Actual measurements show the distance the center of gravity of the immovable rigid counterweight column shifts. The distance by which the center of gravity of the movable rigid counterweight column shifts is 0.032m. It is 0.009m.

[0070] (3) Torque The calculation formula is: ;

[0071] (4) When the center of gravity height is 110mm, , This indicates that the torque at this point will drive the optical cable to continue to flip outward, disrupting the relative stability between the optical cable and the pipe.

[0072] When the center of gravity height is 40mm, , This indicates that the torque at this point pulls the optical cable toward the lowest point of the pipe, resisting lateral tipping and improving the relative stability between the optical cable and the pipe.

[0073] Example 4

[0074] In this embodiment, the method for monitoring the burial depth of underground pipelines includes the following steps:

[0075] (1) Obtaining the temperature sequence

[0076] (1.1) Bind the counterweight strain isolation temperature measuring optical cable to the high-pressure jet nozzle of the high-pressure cleaning vehicle. It sinks to the underground pipeline 16 through the inspection well 15 by its own weight. The high-pressure jet nozzle sprays water backward, thereby driving the counterweight strain isolation temperature measuring optical cable and the high-pressure jet nozzle to move forward, thus completing the installation of the counterweight strain isolation temperature measuring optical cable in the underground pipeline.

[0077] (1.2) Select optical cable 10 at the initial time The following pipeline temperature data was used as the initial temperature sequence. ;

[0078] (1.3) According to the preset sampling frequency, the UWFBG demodulator is used to continuously collect and demodulate the temperature sequence along the pipeline at different times. ;

[0079] in, Indicates the first along the axial direction of the pipe One measuring point, This indicates the sequence number of the monitored temperature data.

[0080] (2) Calculate the relative temperature change And construct a temperature amplitude index

[0081] (2.1) Using the initial temperature sequence Based on this, calculate the first... The first group of temperature monitoring data Relative temperature change values ​​at each measuring point: ;

[0082] (2.2) To eliminate the influence of the direction of temperature increase or decrease on the amplitude analysis, the relative temperature change value is analyzed. The absolute value is processed to obtain the temperature amplitude index: ;

[0083] in, For the first The first group of temperature monitoring data The relative temperature change at each measuring point; Indicates the first along the axial direction of the pipe One measuring point, This indicates the sequence number of the monitored temperature data.

[0084] (3) Screening representative temperature data sequences

[0085] (3.1) Calculate the first Mean of relative temperature change amplitude of the monitoring data The formula is shown below:

[0086] ,

[0087] (3.2) Filter out the average amplitude of relative temperature change The maximum value in ;

[0088] (3.3) will The corresponding number A set of monitored temperature data sequences as representative temperature data sequences The representative temperature data sequence It can reflect the state where the temperature response differences along the pipeline are relatively significant during the monitoring period;

[0089] in, Indicates the first along the axial direction of the pipe One measuring point, Indicates the sequence number of the monitored temperature data. For the first The average relative temperature change amplitude of the monitoring data. For the first The first group of monitoring data Temperature amplitude index at each measuring point This indicates the total number of measuring points along the route.

[0090] (4) Generate burial depth-temperature fitting data

[0091] (4.1) Due to the different heat transfer boundary conditions between inspection well 15 and the conventional pipe section, local temperature anomalies are easily formed. In order to reduce the impact of abnormal temperature points of inspection wells on the burial depth monitoring model, a standard score threshold is set and the standard score Z-score is used to calculate the temperature of each measuring point. The corresponding average amplitude of relative temperature change Compared to this group Standard fraction of the overall distribution of monitored temperature data The formula is shown below:

[0092] ,

[0093] ,

[0094] in, For the first The first set of data Standard scores for each test point For the first The average relative temperature change amplitude of the monitoring data. For the first Standard deviation of relative temperature change amplitude of the group Temperature amplitude index This indicates the total number of measuring points along the route;

[0095] (4.2) For representative temperature data series Outlier identification: When the standard score is greater than or equal to the preset standard score threshold, the measurement point is determined to be an abnormal temperature point and removed from the representative temperature data sequence; when the standard score is less than the preset standard score threshold, the measurement point is determined to be a valid temperature measurement point and retained in the representative temperature data sequence.

[0096] (4.3) The representative temperature data sequence after the removal operation is used as the burial depth-temperature fitting data.

[0097] (5) Establish a burial depth-temperature response monitoring model, perform inversion monitoring of burial depth along the pipeline, and output the burial depth results.

[0098] (5.1) Select several locations with known burial depths As a model calibration point; the burial depth The acquisition methods include actual measurements of inspection wells, construction data, and local measurements; and obtaining temperature response data from the depth-temperature fitting data corresponding to each calibration point. And establish calibration data pairs ,in, For the first The known burial depth of the pipeline at each calibration point The temperature response in the depth-temperature fitting data after initial temperature correction, absolute value transformation, and outlier removal at the corresponding location. The value;

[0099] To ensure the fitting effect, the monitoring times with large temperature change amplitude and significant temperature spatial differences along the line are preferred as the temperature sequence. For abnormal temperature points caused by inspection wells, local water flow disturbances or other boundary conditions, the Z-score threshold method is used to identify and remove them, and only the valid temperature data are retained to participate in the model fitting.

[0100] (5.2) Establish pipeline burial depth With temperature response The quantitative relationship between them, input calibration data pairs A fitting process is performed to generate a burial depth-temperature response monitoring model;

[0101] (5.2.1) Set the pipeline burial depth With temperature response The quantitative relationship between them is a rational function in which the numerator is a constant and the denominator is a cubic polynomial: ;

[0102] in, This refers to the temperature response data in the burial depth-temperature fitting data. For the depth of the pipeline, These are the model parameters obtained by fitting the calibration data. This is a temperature response scaling parameter, primarily used to control the overall temperature amplitude of the fitted curve. and These are curve shape correction parameters used to jointly adjust the nonlinear attenuation trend, curve slope, and degree of curvature of the temperature response as the pipeline burial depth changes; the parameters a, b, c, and d are empirical fitting parameters that comprehensively reflect the thermal conductivity of the soil, pipeline material, ambient temperature disturbance, soil cover thickness, and monitoring conditions, and are not respectively equivalent to the thermal conductivity, specific heat capacity, or other single physical parameters of the soil.

[0103] when The unit is , The unit is At that time, in order to ensure that the dimensions of each term in the formula are consistent, the parameters The unit is ,parameter The unit is ,parameter The unit is ,parameter The unit is .

[0104] (5.2.2) In another embodiment, the burial depth of the pipeline With temperature response The quantitative relationship between them can also be established using polynomial functions, exponential functions, power functions, logarithmic functions, machine learning models, or calibration curves;

[0105] By selecting quadratic polynomial functions, cubic polynomial functions, exponential decay functions, power functions, logarithmic functions, rational functions with quadratic denominators, and rational functions with cubic denominators as candidate models, the same calibration data were fitted.

[0106] Each candidate model can be represented as a quadratic polynomial function: cubic polynomial function: Exponential decay function: Power function: Logarithmic function: Rational functions in the quadratic denominator: ; cubic rational function in denominator: ;

[0107] (5.2.3) Using the coefficient of determination The root mean square error (RMSE) and mean absolute error (MAE) were used to compare the candidate models.

[0108] (5.2.4) The results show that the cubic denominator rational function can better describe the nonlinear change law of temperature response gradually decaying and becoming flat as the pipeline burial depth increases. Its coefficient of determination is the highest. Therefore, it is determined as the burial depth-temperature response monitoring model in this embodiment.

[0109] (5.3) The temperature response of the pipe section to be tested The numerical values ​​are substituted into the burial depth-temperature response monitoring model, and the burial depth D of the corresponding measuring point is calculated by function inversion or numerical solution.

[0110] (5.4) Calculate the continuous burial depth monitoring results of the underground pipeline by sequentially calculating the measurement points along the pipeline. When there are multiple real roots in the calculation results, remove the roots that exceed the preset burial depth range, and determine the final predicted burial depth from the remaining real roots by combining the continuity of burial depth of adjacent measurement points, pipeline design slope, known manhole burial depth and pipeline direction. Then, perform inversion on each effective measurement point along the pipeline to obtain the continuous burial depth distribution results along the pipeline.

[0111] Based on the burial depth of each measuring point Based on its spatial location, the system generates a pipeline burial depth distribution curve or burial depth distribution table, and can combine the location of inspection well 15, pipeline direction and pipeline mileage information to form the spatial calibration result of the buried pipeline burial depth.

[0112] Example 5

[0113] In this embodiment, the on-site verification implementation method is as follows:

[0114] A counterweight strain-isolation temperature-measuring optical cable is laid inside an existing underground pipeline 16 with a length of approximately 320m, and led out through an inspection well 15 to connect to a UWFBG demodulator 14. The UWFBG demodulator 14 continuously collects temperature data along the pipeline 16, with the monitoring period covering temperature changes in different seasons, such as... Figure 5 As shown; Figure 5 Using arbitrary temperature data from pipeline monitoring in September and January, a clear temperature gradient can be observed during the cooling process.

[0115] Based on the monitoring results, using the initial temperature as a baseline, the relative temperature change along the pipeline was calculated, and monitoring data sets with larger temperature change amplitudes were selected as modeling data. Subsequently, the Z-score thresholding method was used to remove abnormal temperature response points near manhole 15, and a depth-temperature response monitoring model based on rational functions was established. ,in, , , , , After removing outliers, the fitted model can more accurately represent the correspondence between pipeline burial depth and temperature response. The process of removing outliers using Z-scores for the temperature-burial depth fitting results during the pipeline burial depth decrease segment is as follows: Figure 6 As shown. Data filtered for outliers can significantly improve the burial depth monitoring effect and enable monitoring of the burial depth-temperature response monitoring model based on rational functions, such as... Figure 7 As shown.

[0116] Furthermore, a portion of the pipeline was selected as a verification section. Temperature data along this section was substituted into the burial depth-temperature monitoring model to calculate the burial depth at each measuring point and compared with the measured burial depth. The results of the pipeline burial depth monitoring data are shown in Table 1, with only representative points highlighted. The results show that the pipeline burial depth monitoring results obtained by this method have good consistency with the measured burial depth, enabling continuous monitoring of the burial depth along existing underground pipelines. The implementation results demonstrate that the counterweight strain-isolated temperature-measuring optical cable of this invention can be stably deployed inside the pipeline and can achieve underground pipeline burial depth monitoring based on the temperature response characteristics under natural temperature disturbances.

[0117] Table 1

[0118] Pipe length (m) Relative temperature (°C) Monitoring pipeline burial depth (m) Measured pipeline burial depth (m) relative error 0 19.9 4.20 4.10 -2.44% 5 21.0 3.87 4.05 4.44% 10 21.7 3.80 4.00 5.00% 25 22.4 3.75 3.90 3.77% 30 22.1 3.77 3.87 2.67% 35 22.3 3.75 3.85 2.52% 40 23.0 3.71 3.83 2.99% 45 22.4 3.75 3.8 1.40%

Claims

1. A counterweight strain-isolated temperature-measuring optical cable for buried pipelines, characterized in that, It includes an optical cable (10) and a counterweight structure spaced outside the optical cable (10); the counterweight structure includes an arc-shaped shell (12) connected by threads, a rigid support (5) forming a four-corner support with the shell (12), a counterweight chamber (7) set on the arc-shaped inner side of the shell (12), and a rigid counterweight column (8) set inside the counterweight chamber (7) that can slide; the rigid counterweight column (8) is used to adjust the center of gravity of the counterweight structure and improve the fit between the optical cable (10) and the underground pipeline (16).

2. The counterweight strain-isolated temperature-measuring optical cable for buried pipelines according to claim 1, characterized in that, It also includes a flexible anti-slip clamping liner (11) installed between the optical cable (10) mounting groove and the counterweight structure.

3. The counterweight strain-isolated temperature-measuring optical cable for buried pipelines according to claim 1, characterized in that, The counterweight structure also includes water passage holes (6) arranged longitudinally on the shell (12).

4. The counterweight strain-isolated temperature-measuring optical cable for buried pipelines according to claim 1, characterized in that, The optical cable includes an optical fiber (1), a protective sleeve (2) forming a loose tube structure with the optical fiber (1), a reinforcing member (3) covering the outside of the protective sleeve (2), and a waterproof protective sleeve (4) disposed on the outside of the reinforcing member (3).

5. The counterweight strain-isolated temperature-measuring optical cable for buried pipelines according to claim 1, characterized in that, The number of the arc-shaped shells (12) is not less than two.

6. A method for monitoring the burial depth of underground pipelines, characterized in that, Includes the following steps: (1) The initial temperature sequence is acquired and demodulated using a demodulator (14) connected to the optical cable (10). Temperature sequence along the pipeline at different times ; (2) Based on the initial temperature sequence Calculate the temperature series relative temperature change And construct a temperature amplitude index ; (3) Based on the temperature amplitude index Calculate the average magnitude of relative temperature change. Select representative temperature data sequences ; (4) Using the standard score Z-score, representative temperature data sequences were removed. Abnormal temperature points are identified, and burial depth-temperature fitting data is generated. (5) Establish a burial depth-temperature response monitoring model, perform inversion monitoring of burial depth along the pipeline and output the burial depth results.

7. The method for monitoring the burial depth of underground pipelines according to claim 6, characterized in that, The temperature sequence acquisition process is as follows: (1.1) Bind the counterweight strain isolation temperature measuring optical cable to the high-pressure jet nozzle of the high-pressure cleaning vehicle. It sinks to the underground pipeline (16) through the inspection well (15) by its own weight. The high-pressure jet nozzle sprays water backward, thereby driving the counterweight strain isolation temperature measuring optical cable and the high-pressure jet nozzle to move forward, thus completing the installation of the counterweight strain isolation temperature measuring optical cable in the underground pipeline. (1.2) Select optical cable (10) at the initial time The following pipeline temperature data was used as the initial temperature sequence. ; (1.3) According to the preset sampling frequency, the temperature sequence along the pipeline at different times is continuously collected and demodulated using a demodulator. ; in, Indicates the first along the axial direction of the pipe One measuring point, This indicates the sequence number of the monitored temperature data.

8. The method for monitoring the burial depth of underground pipelines according to claim 6, characterized in that, The phase temperature amplitude index The build process is as follows: (2.1) Using the initial temperature sequence Based on this, calculate the first... The first group of temperature monitoring data Relative temperature change values ​​at each measuring point: ; (2.2) By analyzing the relative temperature change value The absolute value is processed to obtain the temperature amplitude index. ; The representative temperature data sequence The screening process is as follows: (3.1) Calculate the first Mean of relative temperature change amplitude of the monitoring data The formula is shown below: ， in, For the first The first group of monitoring data Temperature amplitude index at each measuring point This indicates the total number of measuring points along the route; (3.2) Filter out the average relative temperature change amplitude The maximum value in ; (3.3) will The corresponding number A set of monitored temperature data sequences as representative temperature data sequences ; The process for generating the burial depth-temperature fitting data is as follows: (4.1) Set a standard score threshold and use the standard score Z-score to calculate the standard score for each measuring point. The corresponding average amplitude of relative temperature change Compared to this group Standard fraction of the overall distribution of monitored temperature data The formula is shown below: ， ， in, For the first The first set of data Standard scores for each test point For the first The average relative temperature change amplitude of the monitoring data. For the first Standard deviation of relative temperature change amplitude of the group Temperature amplitude index This indicates the total number of measuring points along the route; (4.2) For representative temperature data series Outlier identification: When the standard score is greater than or equal to the preset standard score threshold, the measurement point is determined to be an abnormal temperature point and removed from the representative temperature data sequence; when the standard score is less than the preset standard score threshold, the measurement point is determined to be a valid temperature measurement point and retained in the representative temperature data sequence. (4.3) The representative temperature data sequence after the removal operation is used as the burial depth-temperature fitting data.

9. The method for monitoring the burial depth of underground pipelines according to claim 6, characterized in that, The output process for the burial depth results is as follows: (5.1) Select several locations with known burial depths as calibration points, and establish calibration data pairs based on the burial depth-temperature fitting data at the corresponding locations. ;in, For the first Known pipeline burial depth at each calibration point , Temperature response at the corresponding location in the depth-temperature fitting data The value; (5.2) Establish pipeline burial depth Temperature response The quantitative relationship between them, input calibration data pairs A fitting process is performed to generate a burial depth-temperature response monitoring model; (5.3) The temperature response of the pipe section to be tested The numerical values ​​are substituted into the burial depth-temperature response monitoring model, and the burial depth D of the corresponding measuring point is calculated by function inversion or numerical solution. (5.4) Calculate the continuous burial depth monitoring results of the underground pipeline by sequentially measuring each measuring point along the pipeline.

10. The method for monitoring the burial depth of underground pipelines according to claim 9, characterized in that, The burial depth of the pipeline Temperature response The quantitative relationship between them can be a polynomial function, an exponential function, a power function, a logarithmic function, a machine learning model, or a calibration curve.

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