CN116576790A - Fiber bragg grating integrated monitoring and early warning system for underground engineering grid structure - Google Patents
Fiber bragg grating integrated monitoring and early warning system for underground engineering grid structure Download PDFInfo
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering
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- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
- G08B21/18—Status alarms
- G08B21/182—Level alarms, e.g. alarms responsive to variables exceeding a threshold
Abstract
The invention discloses an integrated monitoring and early warning system of an underground engineering grid structure fiber bragg grating, which comprises a grid structure fiber bragg grating, a fiber bragg grating demodulator, a monitoring terminal and an alarm system, wherein: the fiber bragg grating with the grid structure takes the geogrid as a flexible matrix, and two transmission optical cables are adhered to the geogrid after being arranged and arranged into a grid-shaped structure; the fiber bragg grating engraved on the transmission optical cable is used as a fiber bragg grating sensor, and the fiber bragg grating demodulator is connected with the fiber bragg grating sensor through the transmission optical cable; the fiber bragg grating modulator uploads monitoring data to the monitoring terminal through a network, and the monitoring terminal predicts a possible structural health state change trend according to the monitoring data; and the alarm system judges whether to send out early warning according to the state evaluation result. The early warning system can be used for monitoring potential safety hazards possibly existing in underground engineering in the service period in real time for a long time, and solves the problem that an underground structure monitoring and early warning method is technically imperfect.
Description
Technical Field
The invention belongs to the technical field of underground space safety, relates to a fiber bragg grating monitoring and early warning system, and particularly relates to a grid structure fiber bragg grating monitoring and early warning system suitable for underground engineering.
Background
Urban underground engineering has been rapidly developed in recent years, such as underground tunnels, subways and the like. As an important component of major structural engineering and urban traffic pulse, the healthy service of the urban traffic pulse is critical to the normal operation of the city. However, the underground engineering structure is gradually damaged along with operation, and diseases can occur at any time under the influence of complex load conditions such as temperature, basic deformation, external invasion and the like, so that potential safety hazards occur. The underground engineering structure diseases show frequent and sudden occurrence, so that the construction of a full-time global safety monitoring system for the underground engineering structure is needed to comprehensively and timely master the health conditions of the underground engineering structure in the service period, timely early warning the potential diseases and protecting the safety operation of the underground engineering structure.
At present, the structural monitoring mainly adopts a construction monitoring or third party monitoring mode aiming at the underground engineering construction period, and the safety of the structure and surrounding building structures in the construction process is fed back. However, aiming at the established underground engineering, no mature health monitoring system exists, reasonable and accurate monitoring feedback cannot be carried out on the safety state of the underground structure, particularly the safety state of the underground structure, such as the structural disease induced by fatigue damage under the action of accidental states (such as earthquake, accidental overload, piling, tunnel crossing, karst and the like), after the underground engineering is established, the real-time monitoring performance cannot be ensured, and manual support data cannot be provided for the maintenance work of the underground structure in the operation period, so that the problem of exposure in part of the operation period is difficult to fundamentally solve.
Therefore, the level of safety monitoring technology of underground engineering is improved by utilizing new technology and new method. For traditional electric detection systems, electromagnetic interference is serious on electrified circuit sections, and signals cannot be transmitted remotely. The optical fiber sensor has the advantages of good long-term stability, long-distance signal transmission, electromagnetic interference resistance and the like, gradually replaces an electric sensor with long-term stability which is difficult to ensure, and is widely used in long-term health monitoring in the fields of bridges, tunnels, airports, railways and the like.
Disclosure of Invention
In order to solve the problems in the technical background, the invention provides an integrated monitoring and early warning system for an underground engineering grid structure fiber bragg grating. The early warning system can be used for monitoring potential safety hazards possibly existing in underground engineering in a service period in real time for a long time, and timely early warning and accurately positioning the potential hazards through the visual monitoring terminal, so that the problem of technical imperfection of underground structure monitoring and early warning methods is solved.
The invention aims at realizing the following technical scheme:
the utility model provides an underground works grid structure fiber bragg grating integration monitoring early warning system, includes grid structure fiber bragg grating, fiber bragg grating demodulator, monitoring terminal and alarm system, wherein:
the fiber bragg grating with the grid structure takes the geogrid as a flexible matrix, and two transmission optical cables are arranged into a grid-shaped structure and then adhered to the geogrid;
the transmission optical cable is a single-mode optical fiber, a Bragg grating engraved on the transmission optical cable is used as an optical fiber grating sensor, the optical fiber grating sensors are connected in series at equal intervals to form a long-section monitoring area, and a plurality of optical fiber grating sensors collect ambient temperature and strain information through two transmission optical cables at the same time and accurately position a safe hidden part found by monitoring;
the optical fiber grating demodulator is connected with the optical fiber grating sensor through a transmission optical cable, the light source emits near infrared laser pulses to enter the transmission optical cable, when the laser pulses are transmitted forward along the transmission optical cable, the laser pulses are partially reflected by the grating sensor array connected in series on the transmission optical cable, the reflections back along the same transmission optical cable are detected and analyzed in real time, so that temperature, stress and strain information acquired by the optical fiber grating sensor are acquired and demodulated, the optical fiber grating demodulator is connected with the monitoring terminal through a network, and the acquired temperature, stress and strain information is uploaded, so that potential safety hazards possibly existing in underground engineering during long-term real-time monitoring service are realized;
the monitoring terminal performs abnormal data identification, data smoothing, reliability analysis and trend prediction on the signal data of the fiber bragg grating modulator, intelligently analyzes the health condition of the underground structure according to the processed data, predicts the possible change trend of the health state of the structure, predicts hidden danger factors, accurately positions hidden danger positions according to the arrangement of the fiber bragg grating of the grid structure, and displays the hidden danger positions on the visual monitoring terminal so as to provide manual support data for the maintenance work of the underground structure in the service period;
the alarm system judges whether to send out an early warning according to the state evaluation result, and if the temperature, the temperature difference, the stress or the strain in the monitoring terminal exceeds a preset threshold value, alarm information is timely generated, so that potential safety hazards possibly existing in any position of underground engineering in the service period are monitored in real time for a long time.
A method for monitoring and early warning of a fiber bragg grating with a grid structure by using the system comprises the following steps:
firstly, obtaining internal force, displacement control values and control points based on numerical analysis and calculation, and arranging grid structure fiber gratings at corresponding points in the secondary lining process to monitor underground structure safety state information in real time;
step two, the fiber bragg grating sensor transmits the collected monitoring data to a fiber bragg grating demodulator through a single-mode fiber;
step three, uploading monitoring data to a monitoring terminal by the fiber grating mediator through a network, and intelligently analyzing the structural health condition of the site by the monitoring terminal according to the monitoring data to predict the possible structural health state change trend;
and fourthly, judging whether to send out an early warning according to the state evaluation result by the alarm system, thereby realizing long-term real-time monitoring of potential safety hazards possibly existing at any position of the underground engineering during service.
Compared with the prior art, the invention has the following advantages:
the intelligent monitoring system based on fiber grating sensing introduces a fiber sensing technology into the field of underground engineering structure monitoring aiming at the application environment of underground engineering, and the temperature, stress and strain on any point along the fiber can be accurately measured by adopting a distributed fiber monitoring technology at present, so that the information quantity is large, the achievement is visual, the fiber grating is paved according to a certain network structure, the omnibearing monitoring of the structure safety state can be realized, and the difficulties of missed detection and difficult positioning of the prior monitoring technology are overcome. The invention takes the geogrid commonly used in engineering as a carrier of the fiber bragg grating with the grid structure, and aims to facilitate the arrangement, construction and installation of the fiber bragg grating grid. The fiber grating sensors on the fiber grating grids are connected in series at equal intervals to form a long-section monitoring area, and meanwhile, ambient temperature and strain information are collected, so that potential safety hazards possibly existing in any position of underground engineering in the service period are monitored in real time for a long time.
Drawings
FIG. 1 is a schematic diagram of a fiber grating;
FIG. 2 is a schematic diagram of a fiber grating monitoring and early warning system with a grid structure;
FIG. 3 is a schematic diagram of a fiber grating arrangement of a lattice structure;
fig. 4 is a construction and installation schematic diagram of a fiber grating with a grid structure.
Detailed Description
The following description of the present invention is provided with reference to the accompanying drawings, but is not limited to the following description, and any modifications or equivalent substitutions of the present invention should be included in the scope of the present invention without departing from the spirit and scope of the present invention.
The invention provides an integrated monitoring and early warning system for an underground engineering grid structure fiber bragg grating, which is shown in fig. 1-3, and comprises a grid structure fiber bragg grating, a fiber bragg grating demodulator, a monitoring terminal and an alarm system, wherein:
1. grid structure fiber grating: the temperature, stress and strain of the optical fiber at any point along the line can be accurately measured by adopting the existing distributed optical fiber grating monitoring technology, and the optical fiber grating is paved according to a certain grid structure, so that the omnibearing monitoring of the structural safety state can be realized, and the difficulties of missing measurement and difficult positioning are overcome.
In the invention, the fiber bragg grating with the grid structure takes the geogrid as a flexible matrix, and the two transmission optical cables are adhered to the geogrid after being arranged and arranged into the grid-shaped structure, so that the fiber bragg grating is convenient to install and has the reinforcement and reinforcement effects on the structure, and the grid interval is determined by specific engineering requirements.
In the invention, the transmission optical cable is a common single-mode optical fiber (single-mode silica optical fiber) and is used for transmitting optical signals, and a Bragg grating engraved on the transmission optical cable is used as a monitoring unit, namely an optical fiber grating sensor. The use of a resin material cladding protects the fragile single-mode silica fiber, acting to ensure that the fiber bragg grating sensor can deform in conjunction with the concrete structure and prevent it from being damaged during integration into the geogrid and during installation at the job site. The fiber bragg grating sensors adhered on the geogrid are connected in series at equal intervals to form a long-section monitoring area, and the fiber bragg grating sensors simultaneously acquire ambient temperature and strain information through two transmission optical cables, so that the purpose of collecting structural hidden danger information and accurately positioning safe hidden affected parts found by monitoring is achieved.
In the invention, the fiber grating sensor is a passive temperature and strain multiplexing fiber grating sensor. The fiber grating has the defect of easy breakage due to brittleness, is easy to break in the process of monitoring stress strain, and the resin material cladding can enable the fiber grating to have certain flexibility and can deform together with the structure. The fiber bragg grating sensors are buried in an underground engineering structure along with the fiber bragg grating with a grid structure, and specifically comprise the following components: and pre-burying the underground structure in the secondary lining process, and monitoring the safety state information of the underground structure in real time. When a beam of light is directed onto an optical fiber, the Bragg grating reflects a narrow spectral line, called the Bragg wavelength. The fiber bragg grating sensor takes the offset of the Bragg wavelength as a parameter so as to achieve the purpose of monitoring. That is, when external parameters (deformation, stress, temperature, etc.) change, the bragg grating pitch changes, and the bragg wavelength changes. Therefore, the corresponding physical change amount at the grating can be calculated by measuring the change amount of the Bragg wavelength of the light reflected by the grating.
2. Fiber grating demodulator: the fiber grating demodulator is connected with the fiber grating sensor through a transmission optical cable, the light source emits near infrared laser pulses to enter the transmission optical cable, when the laser pulses are transmitted along the forward direction of the optical fiber, the laser pulses are partially reflected by the grating sensor array connected in series on the optical fiber, the reflections back along the same optical fiber and are detected and analyzed in real time, and therefore temperature, stress and strain information acquired by the fiber grating sensor are acquired and demodulated. And the fiber bragg grating modulator is connected with the monitoring terminal through a network, and the obtained temperature, stress and strain information is uploaded, so that potential safety hazards possibly existing in underground engineering in the service period are monitored in real time for a long time.
3. And (3) monitoring the terminal: and carrying out abnormal data identification, data smoothing processing, reliability analysis and trend prediction processing on the signal data of the fiber bragg grating modulator. According to the processed data, the health condition of the underground structure is intelligently analyzed, the possible change trend of the health state of the structure is predicted, hidden danger factors (aging, cracking, deformation and the like) are predicted, meanwhile, the hidden danger positions are accurately positioned according to the arrangement of the fiber bragg gratings of the grid structure, the hidden danger positions are displayed on a visual monitoring terminal, and manual support data is provided for maintenance work of the underground structure in the service period.
4. And (3) an alarm system: if the temperature, the temperature difference, the stress or the strain in the monitoring terminal exceeds a preset threshold value, alarm information is timely generated.
The invention also provides a method for monitoring and early warning the fiber bragg grating with the grid structure by utilizing the system, which comprises the steps of arranging the fiber bragg grating on the geogrid to form a network structure, arranging the fiber bragg grating with the grid structure in the underground engineering structure, and acquiring monitoring data of the underground engineering structure in real time by a fiber bragg grating sensor. The fiber grating sensor is connected with the fiber grating demodulator through a single mode fiber, and the collected monitoring data is transmitted to the fiber grating demodulator. The fiber bragg grating modulator uploads the original monitoring data to the monitoring terminal through a network and performs unified analysis processing (see fig. 2), and the alarm system judges whether to send out early warning according to the state evaluation result, so that potential safety hazards possibly existing in any position of underground engineering in the service period can be monitored in real time for a long time. The specific scheme is as follows:
(1) Monitoring segment selection
The monitoring position should be mainly selected from regions with obvious adverse geological effects such as soil layer weakness, differential distribution, karst and the like, complex structural system, complex surrounding environment and the like. The monitoring section layout should combine the stress deformation performance of the structure, and the parts with larger or representative internal force and deformation of the structure are selected for monitoring. And obtaining an internal force, a displacement control value and a control point based on numerical analysis and calculation, and then laying a grid structure fiber bragg grating at a corresponding point location for long-term real-time monitoring. The monitoring items can directly or indirectly reflect the actual stress deformation state of the structure, and are used for structural safety evaluation and early warning, wherein the monitoring items comprise strain, stress, leakage, temperature, fatigue and the like.
(2) Arrangement and installation of fiber grating with grid structure
The arrangement mode is specifically as follows: the geogrid cloth is selected as a flexible matrix, the fiber grating sensor with a resin material cladding and a polyimide coating is used as a monitoring unit, and the common single-mode fiber is used as a transmission optical cable. The monitoring unit is fixed on the surface of the flexible matrix by using glue, the monitoring unit is protected by using waterproof glue, the survival rate is further improved, the transmission optical cable is used for threading on the flexible matrix, and finally, the tail fiber led out is protected by using a loose tube at the tail end. The two transmission optical cables are arranged into a grid-like structure, and the geogrid integrated distributed fiber bragg grating sensor can provide strain, stress and temperature information at any position through distributed strain measurement along the optical fibers. The monitoring unit and the transmission optical cable integrated on one geogrid are used as a grid structure fiber bragg grating unit (see fig. 3), and the specific size is determined by specific engineering requirements. The construction and installation method is to pre-embed the fiber grating units of the grid structure into the underground engineering structure, specifically to paste the fiber grating units of the grid structure or fix the fiber grating units of the grid structure on the primary support by using steel nails, reserve the threading openings of the transmission optical cable and construct and pour the secondary lining (see fig. 4, taking an underground tunnel as an example).
(3) Monitoring means and instrument requirements
The fiber grating with the grid structure adopts the existing distributed fiber grating monitoring technology, so that the temperature, stress and strain of the fiber at any point along the line can be accurately measured, and the fiber grating is paved according to a certain grid structure, so that the omnibearing monitoring of the structural safety state can be realized. When a beam of light is directed onto an optical fiber, the Bragg grating reflects a narrow spectral line, called the Bragg wavelength. The fiber bragg grating sensor takes the offset of the Bragg wavelength as a parameter so as to achieve the purpose of monitoring. That is, when external parameters (deformation, stress, temperature, etc.) change, the bragg grating pitch changes, and the bragg wavelength changes. Therefore, the corresponding physical change amount at the grating can be calculated by measuring the change amount of the Bragg wavelength of the light reflected by the grating. Structural health monitoring selects automated monitoring, reduces the influence of manual interference to precision and human cost, and manual monitoring can be assisted in the construction period.
(4) Data acquisition and transmission
The automatic real-time data acquisition is adopted in the operation period, and all the fiber bragg grating sensors are connected with the fiber bragg grating modulator by using the transmission optical cable, so that all the optical path signals are collected and processed in the system. The remote real-time transmission of the monitoring data is realized by erecting a network system, the monitoring data is transmitted to the monitoring terminal through a network, and the dynamic management of the monitoring data is realized.
(5) Data analysis and prediction
And according to the monitoring data, intelligently analyzing the structural health condition of the site, and predicting the possible structural health state change trend. The method specifically comprises the steps of carrying out abnormal data identification, data smoothing processing, reliability analysis and trend prediction on signal data of a monitoring instrument.
(6) State assessment and alarm
And (5) carrying out structural health state assessment and early warning in time according to the data analysis and prediction conditions of the monitoring system. Aiming at the analysis of potential hidden danger signals of underground engineering, typical hidden danger signal characteristics are extracted to establish a typical threat event database, and an artificial intelligent BP neural network is adopted to integrate and correlate each characteristic quantity with a threat event, so that the establishment of the comprehensive database and the threat event alarm are realized. After the site health monitoring system prompts and gives early warning, the early warning is fed back to site maintenance personnel for processing, the monitoring system provides data support for coping measure decision, the underground structure is internally regulated and controlled according to the early warning level, and all maintenance personnel in the underground structure are fully, reasonably and efficiently allocated, so that potential safety hazards are eliminated in time.
Claims (5)
1. The utility model provides an underground works grid structure fiber bragg grating integration monitoring early warning system, its characterized in that integration monitoring early warning system includes grid structure fiber bragg grating, fiber bragg grating demodulator, monitoring terminal and alarm system, wherein:
the fiber bragg grating with the grid structure takes the geogrid as a flexible matrix, and two transmission optical cables are arranged into a grid-shaped structure and then adhered to the geogrid;
the fiber bragg gratings engraved on the transmission optical cables are used as fiber bragg grating sensors, the fiber bragg grating sensors are connected in series at equal intervals to form a long-section monitoring area, and the plurality of fiber bragg grating sensors collect ambient temperature and strain information through the two transmission optical cables at the same time and accurately position the safe hidden parts found by monitoring;
the optical fiber grating demodulator is connected with the optical fiber grating sensor through a transmission optical cable, the light source emits near infrared laser pulses to enter the transmission optical cable, when the laser pulses are transmitted forward along the transmission optical cable, the laser pulses are partially reflected by the grating sensor array connected in series on the transmission optical cable, the reflections back along the same transmission optical cable are detected and analyzed in real time, so that temperature, stress and strain information acquired by the optical fiber grating sensor are acquired and demodulated, the optical fiber grating demodulator is connected with the monitoring terminal through a network, and the acquired temperature, stress and strain information is uploaded, so that potential safety hazards possibly existing in underground engineering during long-term real-time monitoring service are realized;
the monitoring terminal performs abnormal data identification, data smoothing, reliability analysis and trend prediction on the signal data of the fiber bragg grating modulator, intelligently analyzes the health condition of the underground structure according to the processed data, predicts the possible change trend of the health state of the structure, predicts hidden danger factors, accurately positions hidden danger positions according to the arrangement of the fiber bragg grating of the grid structure, and displays the hidden danger positions on the visual monitoring terminal so as to provide manual support data for the maintenance work of the underground structure in the service period;
the alarm system judges whether to send out an early warning according to the state evaluation result, and if the temperature, the temperature difference, the stress or the strain in the monitoring terminal exceeds a preset threshold value, alarm information is timely generated, so that potential safety hazards possibly existing in any position of underground engineering in the service period are monitored in real time for a long time.
2. The underground engineering grid structure fiber grating integrated monitoring and early warning system according to claim 1, wherein the transmission optical cable is a single-mode fiber.
3. The underground engineering grid structure fiber grating integrated monitoring and early warning system according to claim 2, wherein the single mode fiber is a single mode silica fiber.
4. The fiber bragg grating integrated monitoring and early warning system of the underground engineering grid structure according to claim 1, wherein the fiber bragg grating sensor is provided with a resin material cladding and a polyimide coating.
5. A method for monitoring and pre-warning an underground engineering grid structure fiber bragg grating by using the integrated monitoring and pre-warning system as claimed in any one of claims 1 to 4, which is characterized by comprising the following steps:
firstly, obtaining internal force, displacement control values and control points based on numerical analysis and calculation, and arranging grid structure fiber gratings at corresponding points in the secondary lining process to monitor underground structure safety state information in real time;
step two, the fiber bragg grating sensor transmits the collected monitoring data to a fiber bragg grating demodulator through a single-mode fiber;
step three, uploading monitoring data to a monitoring terminal by the fiber grating mediator through a network, and intelligently analyzing the structural health condition of the site by the monitoring terminal according to the monitoring data to predict the possible structural health state change trend;
and fourthly, judging whether to send out an early warning according to the state evaluation result by the alarm system, thereby realizing long-term real-time monitoring of potential safety hazards possibly existing at any position of the underground engineering during service.
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| CN202310550416.XA CN116576790A (en) | 2023-05-16 | 2023-05-16 | Fiber bragg grating integrated monitoring and early warning system for underground engineering grid structure |
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| CN202310550416.XA CN116576790A (en) | 2023-05-16 | 2023-05-16 | Fiber bragg grating integrated monitoring and early warning system for underground engineering grid structure |
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