A flexible piezoelectric-based multi-modal pipeline damage early warning system and laying method

Abstract

The application discloses a kind of based on flexible piezoelectricity multimodal pipeline damage early warning system, including pipeline perception layer, by piezoelectric strain / vibration composite sensing cable embedded in pipeline groove is formed, the cable is laid by coaxial cable series connection section, terminal connection pipeline acquisition card;Soil perception layer, by buried in the soil around pipeline micro ground probe module is formed;Edge computing layer;Ground relay station, data and digital signal are received by LoRa / NB-IoT dual-mode communication, by 4G / 5G connection cloud platform, cloud platform connects software terminal and mobile phone mobile terminal;Energy supply module;Early warning decision module triggers hierarchical response.The system is by depth fusion distributed piezoelectric strain sensing (PDSS) and distributed piezoelectric vibration sensing (PDAS) technology and ground subsidence monitoring technology, introduce edge computing architecture, realize all-around, intelligent, fast early warning to pipeline damage.The application also discloses a kind of based on flexible piezoelectricity multimodal pipeline damage early warning system's layout method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pipeline safety monitoring, and particularly relates to a multi-modal pipeline damage early warning system based on flexible piezoelectricity and a laying method. BACKGROUND

[0002] Water, oil and natural gas are indispensable resources for the development of today's national economy and society, and are often transported over long distances through buried pipelines. At present, with the rapid development of urban infrastructure construction, the safe operation of underground pipe networks, as an important lifeline system of the city, is crucial to the normal operation of the city. The length of water supply and drainage pipelines in cities across the country is 201.65 million kilometers, the length of oil pipelines is 46,000 kilometers, and the length of natural gas pipelines is 980,400 kilometers. The ground is very easy to have excessive settlement under the static and dynamic action of overburden soil weight and long-term traffic load, thereby causing pipeline deformation, and in severe cases, leakage. Traditional manual inspection and positioning consume a lot of manpower and resources, and cannot provide real-time feedback on pipeline damage conditions. Often, problems are not addressed until excavation and maintenance, thereby missing the best repair opportunity. Pipeline damage such as corrosion, cracks, deformation and other problems can cause serious safety accidents and economic losses, so it is of great significance to establish an efficient and reliable pipeline damage monitoring and early warning system.

[0003] The main methods of pipe network monitoring are surface detection methods and internal monitoring methods. The surface detection method of the pipe network is relatively mature, such as the ultrasonic method, the magnetic memory method, the ground penetrating radar method, the acoustic emission method, etc. However, these methods are mostly detected by electric sensors, which are easily affected by weather conditions, complex corrosion environment, electromagnetic interference, etc., thereby releasing incorrect alarm signals, resulting in low detection accuracy. In addition, these methods basically belong to offline detection, and cannot perform real-time, online, distributed and long-term monitoring of the pipe network. The detection results are difficult to reflect the true operating conditions of the pipe network, and cannot provide early warning of possible large deformation, leakage and damage accidents of the pipe network.

[0004] The internal monitoring method is mainly based on point sensors (such as strain gauges, extensometers, fiber Bragg grating sensors, etc.). First, the point sensor cannot comprehensively monitor the damage of the pipe network between two sensors; second, each point sensor needs to be connected by two power lines and two signal lines, resulting in excess transmission lines; finally, the current widely studied environmental energy collection technologies such as friction power generation, thermoelectric power generation, and piezoelectric power generation are all for powering the distributed and scattered point sensor network, and these point sensor self-power technologies have great difficulties in cost, stability, and long-term durability. Therefore, researchers have turned their attention to distributed optical fiber sensing technology based on Brillouin optical time domain analysis, which has the advantages of high monitoring accuracy, long sensing distance, and good real-time data, but the glass optical fiber is fragile and easily damaged, the strain measurement range is only 2%, and the demodulator is expensive. The currently studied plastic optical fiber has good flexibility, and the strain measurement range can reach 50%, but due to the limitations of the plastic optical fiber material and the light emission technology of the demodulator, the light intensity decays too quickly in the plastic optical fiber, and it is still in the laboratory research stage.

[0005] In recent years, sensing technology based on piezoelectric effect and electromechanical impedance effect has been confirmed by many experiments, which is a widely applicable engineering detection and monitoring method. Among them, the self-sensing piezoelectric geocable (SPGC) with polyvinylidene fluoride (PVDF) piezoelectric film as the core has the advantages of long sensing distance, large strain measurement range, and wide vibration frequency response range, and becomes a potential technology to realize distributed monitoring of infrastructure. However, there is no related report on SPGC pipeline strain and vibration sensing. Therefore, it is of great significance to develop a pipeline distributed deformation and leakage integrated monitoring and early warning technology based on SPGC. SUMMARY

[0006] In view of the deficiencies in the background art, the technical problem to be solved by the present application is to provide a flexible piezoelectric-based multi-modal pipeline damage early warning system, which realizes omnidirectional, intelligent, and rapid early warning of pipeline damage by deeply integrating distributed piezoelectric strain sensing (PDSS) and distributed piezoelectric vibration sensing (PDAS) technologies with ground subsidence monitoring technology and introducing an edge computing architecture.

[0007] To this end, the present application is implemented by adopting the following technical solutions:

[0008] A flexible piezoelectric-based multi-modal pipeline damage early warning system, characterized in that it comprises:

[0009] A pipeline sensing layer composed of a piezoelectric strain / vibration composite sensing cable pre-buried in a pipe groove, the cable is arranged in segments by coaxial cable series connection, and the end is connected to a pipeline acquisition card;

[0010] a soil perception layer composed of miniaturized underground probe modules embedded in the soil around the pipeline, one every 10 m along the pipeline;

[0011] an edge computing layer including adaptive sampling processors in the pipeline acquisition card and edge computing units in the miniaturized underground probe modules, which respectively process pipeline impedance / voltage signals and soil multi-modal data in real time;

[0012] a ground relay station receiving edge layer data and digital signals of the coaxial cable through LoRa / NB-IoT dual-mode communication, achieving ±1 ms time synchronization through the built-in GPS disciplined clock, and connecting the cloud platform through 4G / 5G, the cloud platform connecting software terminals and mobile phones through the network;

[0013] a power supply module including a solar panel and a lithium iron phosphate battery, and the monitored data and digital signals are transmitted through the lithium iron phosphate battery power supply;

[0014] an early warning decision module based on improved D-S evidence theory to fuse pipeline strain mutation, soil settlement vector and leakage negative pressure wave characteristics, and combined with the seasonal correction factor output by the LSTM network model to trigger a graded response.

[0015] Further, a semicircular groove is arranged on each of the left and right sides of the groove bottom, respectively, for embedding a piezoelectric strain / vibration composite sensing cable and a coaxial cable, the piezoelectric strain / vibration composite sensing cable adopts a three-core coaxial structure, and the piezoelectric strain / vibration composite sensing cable includes:

[0016] a piezoelectric strain / vibration sensing cable core: PVDF piezoelectric film winding, strain measurement range 0-50%, frequency response 0.1-1000Hz;

[0017] a distributed FBG sensing core: directly contacting the pipe wall, crack detection sensitivity 1με;

[0018] a temperature compensation cable core: fully wrapped with metal seamless pipe to isolate mechanical stress;

[0019] the piezoelectric strain / vibration sensing cable core, the distributed FBG sensing core and the temperature compensation cable core are three-core PE sheath, diameter ≤3mm, working temperature -20℃ to 70℃.

[0020] Further, the pipeline acquisition card includes:

[0021] a charge amplifier: amplifying the charge signal of the piezoelectric strain / vibration composite sensing cable;

[0022] an impedance / voltage collector: collecting impedance strain and vibration voltage;

[0023] Adaptive sampling module: when the soil settlement rate ≥1.2mm / d, the sampling rate is increased from 1Hz to 10Hz;

[0024] Circuit switch: control the on-off of impedance or voltage signal;

[0025] Injection molding package shell: fixed at the pipe joint by a metal clamping protector, which includes a collection card protection box, a sealing washer, and two arc-shaped elastic arms, the two ends of the two arc-shaped elastic arms are opposite and fastened by bolts to fix the injection collection card protection box at the pipe interface;

[0026] Wire interface: the wire interface is tightened with a sealing washer to play a waterproof role.

[0027] Further, the miniaturized underground probe module comprises:

[0028] Three-mode sensing unit: magnetostrictive displacement meter, dual-axis MEMS inclinometer, and distributed FBG sensor;

[0029] Edge computing unit: STM32H743VIT6 chip and Kalman filter, outputting settlement rate vector and confidence;

[0030] Self-powered system: geothermal temperature difference generator and lithium titanate battery;

[0031] Communication module: LoRa / NB-IoT dual-mode chip;

[0032] Spiral flow guide fin: provided on the surface of the stainless steel shell to enhance the coupling of the soil body.

[0033] Further, the LSTM network model takes environmental parameters, historical settlement data, and engineering parameters as input and outputs a seasonal correction factor k season ; based on the basic threshold V base and the seasonal correction factor k season determine the final settlement rate threshold V th and grade the warning response according to the cumulative settlement, displacement mutation, and inclination threshold;

[0034] wherein the basic threshold V base is set according to the building safety specification: such as a tunnel V base =2mm / month, the seasonal correction factor k season output by the LSTM network: k season =1.2 in the rainy season and k k season=0.8, final settlement rate threshold V th =V base ×k season .

[0035] Further, the early warning decision module executes the following logic:

[0036] Primary early warning: pipeline impedance change rate >= 15% or soil settlement rate number >= 1.2V th Last for three days, start unmanned aerial vehicle laser scanning retest;

[0037] Secondary early warning: pipeline deflection curve mutation >= 5% or soil cumulative settlement >= design value 80%, ground relay station transmits data to cloud platform through 4G / 5G, cloud platform pushes data to software terminal and mobile phone mobile terminal, and issues warning;

[0038] Tertiary early warning: pipeline voltage waveform appears negative pressure wave or soil inclination >= 0.5°, automatically closes associated road, ground relay station transmits data to cloud platform through 4G / 5G, and cloud platform pushes emergency instructions to software terminal and mobile phone mobile terminal.

[0039] After adopting the above technical scheme, the distributed pipeline monitoring system is adopted, is attached to the groove of the pipeline in any segmented number, and a coaxial cable is used to transmit digital signals, so that the problems that the traditional surface detection technology cannot realize real-time long-term online monitoring, the internal point type monitoring technology cannot realize full coverage monitoring, and the transmission wire is excessive are solved; a piezoelectric strain / vibration composite sensing cable formed by a three-core composite is used to form strain-vibration-temperature three-parameter synchronous sensing capability, a distributed FBG sensing core is arranged outside the piezoelectric strain / vibration composite sensing cable, directly contacts the pipe wall to capture microcracks (sensitivity reaches 1με), and the piezoelectric core is located on the inside to monitor overall vibration (frequency response range 0.1-1000Hz), the price of the impedance / voltage collector is less than 100 yuan, the software platform can control the collection rule through a program to save electricity, and the problem that the distributed sensing technology is high in cost is solved; the impedance-strain curve of the system monitoring the pipeline can obtain the deflection curve of the pipeline, so that the time of pipeline leakage occurrence can be predicted, and the problem that the traditional monitoring data is delayed to cause untimely maintenance is solved; in addition, the system is fast, convenient, safe and reliable in construction.

[0040] The application also provides a laying method of the flexible piezoelectric-based multi-modal pipeline damage early warning system.

[0041] Step 1: pipeline pretreatment: check whether the appearance of the prefabricated pipeline is damaged, fix the to-be-welded pipeline, and mill the end face of the pipeline with a milling cutter;

[0042] Step 2: Hot melt butt joint of pipe: the grooves of two pipe sections are aligned, the heating plate is heated to 220℃±10℃, the heat absorption time is 10-12 times of the pipe wall thickness, the pressure is maintained until the pipe cools down, and after butt joint, the amount of misalignment is checked to be ≤10% of the wall thickness and <3mm;

[0043] Step 3: Piezoelectric strain / vibration composite sensing cable laying: foreign matter in the groove is cleaned and wiped with alcohol, the piezoelectric strain / vibration composite sensing cable and coaxial cable are respectively fixed in the semicircular groove by epoxy resin, a metal clamping protector is installed at the joint, and an injection molding package shell is clamped on the outer wall of the pipe by using an arc-shaped elastic arm;

[0044] Step 4: Soil body probe deployment: a miniaturized underground probe module is buried in a hole with a burial depth of 1.5-3m, the probe axis forms a 45° angle with the radial direction of the pipe, and a synchronous pulse is sent through a ground relay station to calibrate the pipe-soil displacement coupling matrix.

[0045] Further, the temperature difference compensation welding process is used in step 1: FBG sensors are pre-buried on both sides of the weld, the real-time monitoring of the thermal stress attenuation process is carried out until the stress value is stable in the range of ±5με. BRIEF DESCRIPTION OF DRAWINGS

[0046] The present application has the following drawings:

[0047] Figure 1 It is a structural schematic diagram of the flexible piezoelectric-based multi-modal pipeline damage early warning system in the present application;

[0048] Figure 2 It is a partial structural schematic diagram of the piezoelectric strain / vibration composite sensing cable in the present application;

[0049] Figure 3 It is a cross-sectional structural schematic diagram of the pipe, piezoelectric strain / vibration composite sensing cable and temperature compensation cable core in the present application;

[0050] Figure 4 It is a structural schematic diagram of the pipeline acquisition card in the present application;

[0051] Figure 5 It is a layout process schematic diagram of the flexible piezoelectric-based multi-modal pipeline damage early warning system in the present application;

[0052] Figure 6 It is a circuit structure schematic diagram of the miniaturized underground probe module in the present application.

[0053] Reference signs: 1, road surface; 2, roadbed; 3, piezoelectric strain / vibration composite sensing cable; 4, pipeline; 5, pipeline tensile yield; 6, pipeline bending deformation; 7, pipeline shear failure; 8, pipeline confining pressure deformation; 9, pipeline leakage; 10, energy supply module; 11, ground relay station; 12, software terminal; 13, mobile phone mobile terminal; 14, piezoelectric strain / vibration sensing cable core; 15, distributed FBG sensing core; 16, temperature compensation cable core; 17, seamless metal pipe; 18, PE sheath; 19, groove; 20, semicircular groove; 21, coaxial cable; 22, impedance / voltage collector; 23, collection card protection box; 24, sealing washer; 25, arc-shaped elastic arm; 26, bolt; 27, wire interface; 28, interface processing process; 29, pipeline hot melting process; 30, pipeline butt joint process; 31, cable laying process; 32, collection card protection process; 33, milling cutter; 34, heating plate; 35, heating controller; 36, miniaturized underground probe module; 37, magnetostrictive displacement meter; 38, dual-axis MEMS inclinometer; 39, distributed FBG sensor; 40, STM32H743VIT6 chip; 41, Kalman filter; 42, geothermal temperature difference generator; 43, lithium titanate battery; 44, LoRa / NB-IoT dual-mode chip. DETAILED DESCRIPTION

[0054] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined object of the application, the specific embodiments, structures, features and effects according to the present application will be described in detail below in combination with the drawings and preferred embodiments.

[0055] Referring to the drawings shown above, the present application provides a multi-modal pipeline damage early warning system based on flexible piezoelectricity, which comprises:

[0056] The pipeline sensing layer is composed of a piezoelectric strain / vibration composite sensing cable 3 pre-buried in the groove 19 of the pipeline 4, which is laid in series by a coaxial cable 21, and the end is connected to the pipeline collection card;

[0057] The soil sensing layer is composed of a miniaturized underground probe module 36 buried in the soil around the pipeline 4, and one is laid every 10m along the direction of the pipeline 4;

[0058] The edge computing layer includes an adaptive sampling processor in the pipeline collection card and an edge computing unit in the miniaturized underground probe module 36, which respectively processes the pipeline impedance / voltage signal and the soil multi-modal data in real time;

[0059] The ground relay station 11 receives edge layer data and digital signals of the coaxial cable 21 through LoRa / NB-IoT dual-mode communication, realizes ±1ms time synchronization through the built-in GPS domesticated clock, and connects the cloud platform through 4G / 5G. The cloud platform connects the software terminal 12 and the mobile phone mobile terminal 13 through the network;

[0060] The energy supply module 10 includes a solar panel and a lithium iron phosphate battery. The monitored data and digital signals are transmitted through the lithium iron phosphate battery power supply;

[0061] The early warning decision module is based on the improved D-S evidence theory to fuse the characteristics of pipeline strain mutation, soil settlement vector and leakage negative pressure wave, and combines the seasonal correction factor output by the LSTM network model to trigger a graded response.

[0062] Each of the left and right sides of the bottom of the groove 19 is provided with a semicircular groove 20 for embedding a piezoelectric strain / vibration composite sensing cable 3 and a coaxial cable 21, respectively. The piezoelectric strain / vibration composite sensing cable 3 adopts a three-core coaxial structure, and the piezoelectric strain / vibration composite sensing cable 3 comprises:

[0063] The piezoelectric strain / vibration sensing cable core 14 is wound with a PVDF piezoelectric film, and the strain measurement range is 0-50% and the frequency response is 0.1-1000Hz;

[0064] The distributed FBG sensing core 15 directly contacts the pipe wall, and the crack detection sensitivity is 1με;

[0065] The temperature compensation cable core 16 is fully wrapped with a metal seamless pipe 17 to isolate mechanical stress;

[0066] The piezoelectric strain / vibration sensing cable core 14, the distributed FBG sensing core 15 and the temperature compensation cable core 16 are three-core PE sheath 18, and the diameter is ≤3mm and the working temperature is -20℃ to 70℃.

[0067] The pipeline acquisition card comprises:

[0068] Charge amplifier: amplifies the charge signal of the piezoelectric strain / vibration composite sensing cable 3;

[0069] Impedance / voltage collector 22: collects impedance strain and vibration voltage;

[0070] Adaptive sampling module: when the soil settlement rate is ≥1.2mm / d, the sampling rate is increased from 1Hz to 10Hz;

[0071] Circuit switch: controls the on-off of impedance or voltage signals;

[0072] Injection molding package shell: fixed at the pipe 4 joint through a metal clamping protector, which includes a collection card protection box 23, a sealing washer 24, and two arc-shaped elastic arms 25, the two ends of the two arc-shaped elastic arms 25 are opposite and fastened by a bolt 26, and the collection card protection box 23 is fixed at the pipe 4 interface;

[0073] Wire interface 27: the wire interface 27 is screwed with the sealing washer 24 to play a waterproof role.

[0074] The miniaturized underground probe module 36 includes:

[0075] Three-mode sensing unit: magnetostrictive displacement meter 37, dual-axis MEMS inclinometer 38, and distributed FBG sensor 39;

[0076] Edge computing unit: STM32H743VIT6 chip 40 and Kalman filter 41, outputting settlement rate vector and confidence;

[0077] Self-powered system: geothermal temperature difference generator 42 and lithium titanate battery 43;

[0078] Communication module: LoRa / NB-IoT dual-mode chip 44;

[0079] Spiral flow guide fin: provided on the surface of the stainless steel shell to enhance the coupling of the soil body.

[0080] The LSTM network model takes environmental parameters, historical settlement data, and engineering parameters as input, and outputs a seasonal correction factor k season ; Based on the basic threshold V base and the seasonal correction factor k season determine the final settlement rate threshold V th , and according to the cumulative settlement, displacement mutation, and inclination threshold, grade the warning response;

[0081] Wherein, the basic threshold V base is set according to the building safety specification: such as the tunnel V base =2mm / month, the seasonal correction factor k season output by the LSTM network: rainy season k season =1.2, dry season k season =0.8, and the final settlement rate threshold V th =V base ×k season .

[0082] The warning decision module executes the following logic:

[0083] Primary warning: pipeline impedance rate of change ≥ 15% or soil settlement rate number ≥ 1.2V th For three days, start unmanned aerial vehicle laser scanning retest;

[0084] Secondary warning: pipeline deflection curve mutation ≥ 5% or soil cumulative settlement ≥ 80% of the design value, ground relay station 11 transmits data to the cloud platform through 4G / 5G, and the cloud platform pushes data to software terminal 12 and mobile phone mobile terminal 13, and issues a warning;

[0085] Tertiary warning: negative pressure wave appears in pipeline voltage waveform or soil inclination ≥ 0.5°, automatically close associated roads, ground relay station 11 transmits data to the cloud platform through 4G / 5G, and the cloud platform pushes emergency instructions to software terminal 12 and mobile phone mobile terminal 13.

[0086] In this embodiment, a distributed pipeline monitoring system is adopted to be attached in the groove 19 of the pipeline 4 in any number of segments, and a coaxial cable 21 is used to transmit digital signals, solving the problems that traditional surface detection technology cannot realize real-time long-term online monitoring, internal point detection technology cannot realize full-coverage monitoring, and transmission conductors are excessive; a piezoelectric strain / vibration composite sensing cable 3 formed by three cores is used to form strain-vibration-temperature three-parameter synchronous sensing capability, the piezoelectric strain / vibration sensing cable core 14 adopts a PVDF piezoelectric film, the flexible characteristic of which greatly increases the bending fatigue life, and is directly embedded in the semicircular groove 20 to realize curvature self-adaptation; the distributed FBG sensing core 15 is placed outside the piezoelectric strain / vibration composite sensing cable 3 and directly contacts the pipe wall to capture micro-cracks (sensitivity up to 1με), while the piezoelectric strain / vibration sensing cable core 14 is located inside to monitor overall vibration (frequency response range 0.1-1000 Hz); the piezoelectric strain / vibration sensing cable core 14 can sense two parameters of strain and vibration, and the temperature compensation cable core 16 corrects the monitoring data of impedance and voltage; the price of the impedance / voltage collector 22 is less than 100 yuan, the software platform can control the collection rules through the program to save electricity, and the problem of high cost of distributed sensing technology is solved; the impedance-strain curve of the pipeline 4 monitored by the system can obtain the deflection curve of the pipeline 4 to predict the time of pipeline 4 leakage, solving the problem of delayed maintenance caused by the reaction lag of traditional monitoring data; in addition, the system is fast, convenient, safe and reliable in construction; the working temperature of the pipeline 4 is not less than -20℃ and not greater than 70℃, preventing the piezoelectric strain / vibration composite sensing cable 3 from failing due to high and low temperatures, and the PE sheath 18 plays a role in waterproofing and anti-aging of the cable core material; the two arc-shaped elastic arms 25 are wrapped around the pipeline 4 for one turn, the two ends of the two arc-shaped elastic arms 25 are opposite and fastened by the bolts 26, and the injection molding packaging shell is fixed at the interface of the pipeline 4; the magnetostrictive displacement meter 37 has a range of ±50 mm, a resolution of 0.001 mm, and a sampling frequency of 10 Hz; the two-axis MEMS inclinometer 38 has a range of ±30°; the distributed FBG sensor 39 is buried at a depth of 1.5-3 m to avoid the disturbance layer of the shallow backfill soil; the STM32H743VIT6 chip 40 performs wavelet threshold denoising on the optical fiber wavelength drift data, calculates the standard deviation and kurtosis coefficient of the displacement meter data, identifies the mutation event, fuses the optical fiber strain, displacement and inclination data through the Kalman filter 41, and outputs the settlement rate, inclination angle and confidence index; the LSTM network model includes 1. input layer: 30-dimensional features (including time series environmental data and settlement), 2. output layer: hidden layer: 2 layers of LSTM (128 neurons per layer), Dropout rate 0.2, 3. output layer: current season settlement rate threshold, 4.Training data: 10000 sets of historical monitoring data; using underground probe and ground temperature difference (Delta T >= 10 DEG C), through Bi2Te3 thermoelectric material generates electricity, output power >= 2W, charges the lithium titanate battery 43 and stores for self-power supply, the lithium titanate battery 43 cycle life > 10,000 times, supports-30 DEG C low temperature discharge; LoRa / NB-IoT dual-mode chip 44 automatically switches according to signal strength, ensures the success rate of data transmission under complex terrain, LoRa mode: transmission distance 3km (urban area), 20km (suburb), rate 5kbps, NB-IoT mode: support mobile / telecom Band5 / Band8 frequency band, monthly average traffic consumption < 50MB; solar panel is used to collect solar energy to charge and store the lithium iron phosphate battery, and the lithium iron phosphate battery supports-20 DEG C ~ 60 DEG C wide temperature range work, cycle life > 3,000 times.

[0087] The application also provides a laying method of a flexible piezoelectric-based multi-modal pipeline damage early warning system, characterized by comprising the following steps:

[0088] Step 1: pipeline 4 pretreatment: check whether the appearance of the prefabricated pipeline 4 is damaged, fix the pipeline 4 to be welded, and mill the end face of the pipeline 4 with a milling cutter 33;

[0089] Step 2: pipeline 4 hot melt butt joint: the grooves 19 of the two pipeline 4 segments are aligned, the heating plate 34 is controlled by the heating controller 35 to be heated to 220 DEG C plus or minus 10 DEG C, the heat absorption time is 10-12 times the thickness of the pipeline wall, and the pressure is maintained until the pipeline 4 cools down, and the misalignment after butt joint is checked to be less than or equal to 10% of the wall thickness and less than 3mm;

[0090] Step 3: piezoelectric strain / vibration composite sensing cable 3 laying: remove foreign matters in the groove 19 and wipe it clean with alcohol, fix the piezoelectric strain / vibration composite sensing cable 3 and the coaxial cable 21 in the semicircular groove 20 with epoxy resin, install a metal clamping protector at the joint, and clamp the acquisition card protection box 23 on the outer wall of the pipeline 4 by using the arc-shaped elastic arm 25;

[0091] Step 4: soil probe deployment: drill and bury the miniaturized underground probe module 36, the burial depth is 1.5-3m, the probe axis is at an angle of 45 DEG with the radial direction of the pipeline 4, and the pipeline-soil displacement coupling matrix is calibrated by issuing a synchronous pulse from the ground relay station 11.

[0092] The temperature difference compensation welding process is used in step 1: FBG sensors are embedded on both sides of the weld, the thermal stress attenuation process is monitored in real time, and the stress value is stabilized in the range of plus or minus 5με.

Claims

1. A flexible piezoelectric based multi-modal pipeline damage warning system, characterized in that, The pipeline sensing layer is composed of a piezoelectric strain / vibration composite sensing cable embedded in a pipeline groove, which is arranged in series by coaxial cable and connected to a pipeline acquisition card at the end. The soil sensing layer is composed of miniaturized underground probe modules embedded in the soil around the pipeline, with one module arranged every 10 m along the pipeline. The edge computing layer includes an adaptive sampling processor in the pipeline acquisition card and an edge computing unit in the miniaturized underground probe module, which respectively processes pipeline impedance / voltage signals and soil multi-modal data in real time. The ground relay station receives edge layer data and digital signals from the coaxial cable through LoRa / NB-IoT dual-mode communication, implements ±1 ms time synchronization with a built-in GPS disciplined clock, and connects to a cloud platform through 4G / 5G, which connects software terminals and mobile phones through the network. The power supply module includes a solar panel and a lithium iron phosphate battery, and the monitored data and digital signals are transmitted through the lithium iron phosphate battery power supply. The early warning decision module combines the seasonal correction factor output by the LSTM network model to trigger a graded response based on the improved D-S evidence theory fusion of pipeline strain mutation, soil settlement vector, and leakage negative pressure wave characteristics. The groove bottom left and right sides are each provided with a semicircular groove for embedding a piezoelectric strain / vibration composite sensing cable and a coaxial cable, respectively. The LSTM network model takes environmental parameters, historical settlement data and engineering parameters as input and outputs a seasonal correction factor k season ; Based on the base threshold value V base With the seasonal correction factor k season Determine the final settlement rate threshold V th And according to the cumulative settlement of soil, displacement mutation and inclination threshold, the graded early warning response is given. wherein the base threshold V base According to the building safety code, the final settlement rate threshold V th = V base × k season .

2. A flexible piezoelectric based multi-modal pipeline damage warning system as claimed in claim 1, wherein, Tunnel V base = 2 mm / month.

3. A flexible piezoelectric based multi-modal pipeline damage warning system as claimed in claim 2, wherein, Seasonal correction factor k for the rainy season season = 1.2, Seasonal correction factor k for the dry season season = 0.

8.

4. A flexible piezoelectric based multi-modal pipeline damage warning system as claimed in claim 3, wherein, The piezoelectric strain / vibration sensing cable adopts a three-core coaxial structure, and the piezoelectric strain / vibration composite sensing cable includes: A piezoelectric strain / vibration sensing cable core: PVDF piezoelectric film winding, strain measurement range 0-50%, frequency response 0.1-1000Hz; A distributed FBG sensing core: directly contacts the pipe wall, crack detection sensitivity 1με; A temperature compensation cable core: fully wrapped with a metal seamless tube to isolate mechanical stress; The piezoelectric strain / vibration sensing cable core, distributed FBG sensing core, and temperature compensation cable core are covered with a PE jacket, with a diameter ≤3mm and a working temperature of -20℃ to 70℃.

5. A flexible piezoelectric based multi-modal pipeline damage warning system as claimed in claim 4, wherein, The pipeline acquisition card includes: A charge amplifier: amplifies the charge signal of the piezoelectric strain / vibration composite sensing cable; An impedance / voltage collector: collects impedance strain and vibration voltage; An adaptive sampling module: when the soil settlement rate ≥1.2mm / d, the sampling rate is increased from 1Hz to 10Hz; A circuit switch: controls the on-off of impedance or voltage signals; An injection molding package shell: fixed to the pipeline joint by a metal clamping protector, which includes an acquisition card protection box, a sealing gasket, and two arc-shaped elastic arms, with the two ends of the two arc-shaped elastic arms opposite and fastened by bolts to fix the acquisition card protection box at the pipeline interface; A wire interface: the wire interface is tightened with a sealing gasket to play a waterproof role.

6. A flexible piezoelectric based multi-modal pipeline damage warning system as claimed in claim 5, wherein, The miniaturized underground probe module includes: A three-modal sensing unit: magnetostrictive displacement meter, dual-axis MEMS inclinometer, and distributed FBG sensor; An edge computing unit: STM32H743VIT6 chip and Kalman filter, outputting settlement rate vector and confidence; A self-powered system: geothermal temperature difference generator and lithium titanate battery; A communication module: LoRa / NB-IoT dual-mode chip; Spiral guide fin: set on the surface of the stainless steel shell, enhance the coupling of soil.

7. A flexible piezoelectric based multi-modal pipeline damage warning system as claimed in claim 6, wherein, The early warning decision module executes the following logic: Primary warning: pipeline impedance change rate ≥ 15% or soil settlement rate number ≥ 1.2V th For three days, start unmanned aerial vehicle laser scanning retest; Secondary early warning: pipeline deflection curve mutation ≥ 5% or soil cumulative settlement ≥ 80% of the design value, ground relay station transmits data to the cloud platform through 4G / 5G, and the cloud platform pushes data to the software terminal and mobile phone terminal, and issues a warning; Third-level early warning: negative pressure wave appears in pipeline voltage waveform or soil inclination ≥ 0.5°, automatically close the associated road, ground relay station transmits data to the cloud platform through 4G / 5G, and the cloud platform pushes emergency instructions to the software terminal and mobile phone terminal.

8. A method of laying a flexible piezoelectric based multi-modal pipeline damage warning system according to claim 7, characterized in that, Comprising the following steps: Step 1: pipeline pretreatment: check whether there is damage on the appearance of the pipeline, fix the pipe to be welded, and mill the end face of the pipeline with a milling cutter; Step 2: pipeline hot melt butt joint: the grooves of the two pipes are aligned, the heating plate is heated to 220℃±10℃, the heat absorption time is 10-12 times the pipe wall thickness, and the pressure is maintained until the pipeline cools down, and after butt joint, the misalignment amount is checked ≤ 10% of the wall thickness and < 3mm; Step 3: piezoelectric strain / vibration composite sensing cable laying: clean the foreign matter in the groove and wipe it clean with alcohol, fix the piezoelectric strain / vibration composite sensing cable and coaxial cable in the semicircular groove with epoxy resin, install a metal clamping protector at the joint, and clamp the injection molded shell on the outer wall of the pipeline with an arc-shaped elastic arm; Step 4: soil probe deployment: drill and bury the miniaturized underground probe module, the burial depth is 1.5-3m, the probe axis forms a 45° angle with the radial direction of the pipeline, and the pipeline-soil displacement coupling matrix is calibrated through the ground relay station issuing a synchronous pulse.

9. The method of claim 8, wherein the method further comprises: In step 1, the temperature difference compensation welding process is used: FBG sensors are pre-buried on both sides of the weld, real-time monitoring of the thermal stress attenuation process is performed, and the stress value is stable within ± 5με.

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