Distributed fiber based concrete construction quality online monitoring system and method

Abstract

The application discloses a kind of concrete construction quality on-line monitoring system and method based on distributed optical fiber, and the on-line monitoring system includes narrowband light source, first optical fiber coupler, acoustooptic modulator, erbium-doped fiber amplifier, band-pass filter, three-port circulator, sensing fiber array, optical fiber polarization beam splitter, polarization optical fiber coupler, first balanced photodetector, second balanced photodetector, self-coherent mixing unit, data acquisition device, dynamic filter unit, digital demodulation unit, base frequency multiplication combined fading noise identification unit and time-frequency analysis unit, time-frequency analysis unit analyzes the time course change of phase signal after noise elimination, obtains the vibration signal change trend of each point of concrete.The monitoring system of the application uses sensing fiber array arranged in structure, has many measuring points, high sensitivity and phase vibration analysis accuracy of optical fiber sensing system, accurate full-distributed defect identification, good stability and durability, simple implementation.

Description

Technical Field

[0001] This invention relates to an online monitoring technology for concrete pouring construction quality based on distributed optical fiber vibration sensing, which is used for monitoring the construction quality of concrete pouring in civil engineering structures and can realize real-time monitoring of the entire pouring construction process. Background Technology

[0002] In civil engineering and transportation structure construction, concrete pouring is a crucial step, significantly impacting the building's load-bearing capacity, deformation, and seismic performance. Therefore, it significantly influences the overall quality, efficiency, cost, structural safety, and stability of the construction process. Consequently, the quality of concrete pouring during civil engineering construction not only affects structural safety but also the safety of people and property. Monitoring the construction quality is essential to detect defects during the pouring process, such as mud inclusions in pile foundations, diameter reduction, segregation, fractures, voids, and other defects, and to evaluate the pouring quality. Currently, both domestically and internationally, traditional sonic logging methods are primarily used for concrete structure quality inspection. This method generally requires waiting until the concrete has cured after pouring, making it difficult to detect defects early during the pouring process. Furthermore, it is inefficient, labor-intensive, complex, has low resolution, and is expensive. In addition, due to the complex on-site conditions during concrete pouring, there are currently no technical means to directly monitor the concrete pouring process and detect defects early. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an online monitoring system and method for pile foundation construction quality based on distributed optical fiber vibration sensing for monitoring the construction period of concrete structure pouring.

[0004] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0005] An online monitoring system for concrete pouring construction quality based on distributed optical fiber includes a narrowband light source, a first optical fiber coupler, an acousto-optic modulator, an erbium-doped fiber amplifier, a bandpass filter, a three-port circulator, a sensing fiber array, an optical fiber polarization beam splitter, a polarization fiber coupler, a first balanced photodetector, a second balanced photodetector, a self-coherent mixing unit, a data acquisition device, a dynamic filtering unit, a digital demodulation unit, a fundamental frequency harmonic and fading noise identification unit, and a time-frequency analysis unit. The output of the narrowband light source is connected to the first input of the first coupler, and the first output of the first coupler is connected to the acousto-optic... The input and output of the acousto-optic modulator are connected to the input of an erbium-doped fiber amplifier. The output of the amplifier is connected to the input of a bandpass filter. The output of the bandpass filter is connected to the input of a three-port circulator. The reflection end of the three-port circulator is connected to a sensing fiber array. The output of the three-port circulator is connected to the input of a polarization fiber coupler. The second output of the first coupler is connected to the input of a fiber polarization beamsplitter. The first output of the fiber polarization beamsplitter and the first output of the polarization fiber coupler are connected to the input of a first balanced photodetector. The second output of the fiber polarization beamsplitter and the second output of the polarization fiber coupler are connected to the input of a second balanced photodetector. The outputs of the first and second balanced photodetectors are connected to the first and second inputs of the self-coherent mixing unit. A data acquisition device, a dynamic filtering unit, a digital demodulation unit, a fundamental frequency doubling combined fading noise identification unit, and a time-frequency analysis unit are sequentially connected to the output of the self-coherent mixing unit. The sensing fiber array is housed within a cast-in-place concrete structure. The first and second balanced photodetectors convert the detected coherent optical signals into electrical signals. The self-coherent mixing unit converts the first... The electrical signals converted by the balanced photodetector and the second balanced photodetector are cross-correlated and mixed; the dynamic filtering unit divides the signal after mixing by the self-coherent mixing unit into two signals: a base signal and a harmonic signal; the digital demodulation unit demodulates the phase of the two signals divided by the dynamic filtering unit; the base-harmonic combined fading noise identification unit compares and identifies the two demodulation results to eliminate fading noise and other field crosstalk noise in the demodulated signal of the digital demodulation unit; the time-frequency analysis unit analyzes the time history change of the phase signal after noise elimination to obtain the change trend of the vibration signal at each point of the concrete.

[0006] The quality assessment unit analyzes and compares the changes in vibration signals at various points of the concrete during the pouring process, and uses the spectral change trends to assess and identify the quality and defects of the pile foundation.

[0007] This invention relates to an online monitoring system for pile foundation construction quality based on distributed optical fiber vibration sensing. By monitoring the frequency and time history changes of distributed vibration signals at various measuring points of the sensing optical fiber array during the concrete pouring and solidification processes, the system enables the monitoring of concrete structure quality and defect identification during construction.

[0008] This invention relates to an online monitoring system for the construction quality of concrete structures based on distributed fiber optic vibration sensing. For two different fiber optic array deployment methods, two methods and criteria for construction quality monitoring and defect identification and judgment can be adopted respectively. When the entire fiber optic array is completely bound to the reinforcing steel, the system can monitor the time history variation trend of the natural vibration frequency at various points in the reinforcing steel structure to achieve pile foundation construction quality monitoring and defect identification: if the natural frequency of a certain point in the reinforcing steel is at a relatively high frequency during the pouring period, and then its natural frequency first decreases significantly during the initial solidification of the concrete, and then rises and stabilizes at a relatively low frequency, and the frequency trend changes at various points are relatively consistent, then the pile foundation quality is judged to be good; if the natural frequency of individual points does not show a regular change, or its change trend differs significantly from other points, then the reinforcing cage may have quality defects. When the entire sensing fiber array is directly embedded in the concrete, the drift of the natural vibration frequency of each point in the concrete during the pouring and solidification periods can be monitored through the sensing fiber array, thereby enabling construction quality monitoring and defect identification: if the natural frequency of a certain point in the concrete is at a relatively low frequency during the pouring period, but its resonant frequency gradually rises and stabilizes at a relatively high frequency during the initial solidification period of the concrete, then the quality of the pile foundation area where that point is located is determined to be good; if the natural frequency of the concrete does not show a regular change, then it can be determined that there may be quality defects in the concrete.

[0009] This invention relates to an online monitoring system for pile foundation construction quality based on distributed fiber optic vibration sensing. It can further identify pile foundation quality defects by comparing the resonant frequency distribution of various points in the reinforcing steel cage or concrete after the initial setting of the pile foundation concrete. If the resonant frequencies of various points in the reinforcing steel cage or concrete are all distributed within a specific frequency range, it is determined that the quality of each point area of ​​the pile foundation is good. If the resonant frequency of a certain point in the reinforcing steel cage or concrete is significantly different from the vibration frequencies of other points, it can be determined that there may be quality defects in the concrete area where that point is located.

[0010] Compared with the prior art, the beneficial effects of the present invention are:

[0011] This invention's monitoring system obtains the vibration signal variation trends at various points in the concrete. These trends can be used as a basis for judging concrete quality defects, enabling real-time monitoring of the entire pile foundation pouring process. Different defects, such as mud inclusion, diameter reduction, segregation, fracture, and voids, can be identified through varying vibration signal trends. The monitoring system employs a fiber optic sensing array embedded within the structure, featuring numerous measuring points, high sensitivity and phase vibration resolution of the fiber optic sensing system, accurate fully distributed defect identification, good stability and durability, and simple implementation. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a specific structure of the present invention.

[0013] Figure 2 This is a diagram illustrating a specific embodiment of the present invention.

[0014] Figure 3 This is a diagram illustrating a specific embodiment of the present invention. Implementation

[0015] The present invention will be described in detail below with reference to the accompanying drawings, but this should not be construed as limiting the scope of protection of the present invention.

[0016] like Figure 1As shown, the present invention discloses an online monitoring system for pile foundation construction quality based on distributed optical fiber, comprising a narrowband light source 1, a first optical fiber coupler 2, an acousto-optic modulator 3, an erbium-doped fiber amplifier 4, a bandpass filter 5, a three-port circulator 6, a sensing fiber array 7, an optical fiber polarization beam splitter 8, a polarization fiber coupler 9, a first balanced photodetector 10, a second balanced photodetector 11, a self-coherent mixing unit 12, a data acquisition device 13, a dynamic filtering unit 14, a digital demodulation unit 15, a fundamental frequency harmonic and fading noise identification unit 16, a time-frequency analysis unit 17, and a quality assessment unit 18. The system is connected as follows: the output of the narrowband light source 1 is connected to the first input of the first coupler 2; the first output of the first coupler 2 is connected to the input of the acousto-optic modulator 3; the output of the acousto-optic modulator 3 is connected to the input of the erbium-doped fiber amplifier 4; the output of the erbium-doped fiber amplifier 4 is connected to the input of the bandpass filter 5; the output of the bandpass filter 5 is connected to the input of the three-port circulator 6; the reflection end of the three-port circulator 6 is connected to the sensing fiber array 7; the output of the three-port circulator 6 is connected to the input of the polarization fiber coupler 8; and the second output of the first fiber coupler 2 is connected to the fiber polarization beam splitter. The first output of the fiber polarization beam splitter 9 and the first output of the polarization fiber coupler 8 are connected to the input of the first balanced photodetector 10. The second output of the fiber polarization beam splitter 8 and the second output of the polarization fiber coupler 9 are connected to the input of the second balanced photodetector 11. The outputs of the first balanced photodetector 10 and the second balanced photodetector 11 are connected in sequence to the self-coherent mixing unit 12, the data acquisition device 13, the dynamic filtering unit 14, the digital demodulation unit 15, the fundamental frequency harmonic combined fading noise identification unit 16, the time-frequency analysis unit 17, and the quality assessment unit 18.

[0017] The high-coherence light emitted by the narrowband light source 1 enters the first fiber coupler 2 and is split into two paths. One path passes through the acousto-optic modulator 3, which modulates the high-coherence light emitted by the light source 1 into pulsed light. The modulated pulsed light is then amplified by the erbium-doped fiber amplifier 4, which generates ASE noise. The bandpass filter 5 filters out the generated ASE noise, and then the amplified pulsed light enters the three-port circulator 6. The reflective end of the three-port circulator 6 is connected to the sensing fiber array 7. The backscattered light containing vibration information is output from the output end of the three-port circulator 6. The backscattered Rayleigh signal carrying vibration information is split into two paths after passing through the polarization fiber coupler 9, and enters the first balanced photodetector 10 and the second balanced photodetector 11, respectively. The other output light from the first fiber coupler 2, as the local oscillator light, directly enters the fiber polarization beam splitter 8, which splits it into two orthogonally linearly polarized lights, and then enters the first balanced photodetector 10 and the second balanced photodetector 11, respectively. The first balanced photodetector 10 and the second balanced photodetector 11 convert the detected coherent optical signals into electrical signals and perform cross-correlation mixing. The multi-channel data acquisition device 13 simultaneously acquires the output signal from the cross-correlation mixer 12, which is then divided into two signals, a base signal and a harmonic signal, by the dynamic filtering unit 14. The digital demodulation unit 15 demodulates the phase of the two signals respectively. The base-harmonic combined fading noise identification unit 16 compares and identifies the demodulation results of the two signals to eliminate fading noise and other on-site crosstalk noise. The time-frequency analysis unit 17 analyzes the trend of vibration signal changes at various points of the concrete. Finally, the quality assessment unit 18 analyzes and identifies the quality and defects of the pile foundation during the pouring construction process.

[0018] The first and second balanced photodetectors convert the detected polarization coherent light signals into electrical signals, perform autocorrelation mixing, and generate a mixed signal containing the substrate and harmonics.

[0019] After the multi-channel data acquisition and mixing of the signals, the mixed signals are divided into two signals, the base signal and the frequency harmonic signal, by dynamic filtering. The phase of the base signal and the frequency harmonic signal are then demodulated by the digital demodulation unit.

[0020] The fundamental frequency harmonic and fading noise identification unit compares and analyzes the phases of the fundamental and harmonic signals. If the phases of the two signals show the same trend, they are identified as real signals. If there is a significant difference in the phases of the two signals, they are identified as field crosstalk noise. If one signal changes phase while the other does not, it is identified as fading noise. This eliminates fading noise and other field crosstalk noise.

[0021] By analyzing the time history changes of the phase signal after noise removal, the trend of vibration signal change of each point of concrete over time is obtained. The trend of vibration signal change of each point of concrete is analyzed by time-frequency analysis. Finally, the quality and defects of pile foundation during the pouring construction process are analyzed and identified through quality assessment.

[0022] This invention relates to an online monitoring system for the construction quality of concrete structures based on distributed optical fiber vibration sensing. The sensing fiber array 7 can be configured in various ways, such as: (1) bundling the sensing fiber array 7 onto the reinforcing bars in the pile foundation ( Figure 2 (2) The sensing fiber array 7 is directly embedded in the concrete. Figure 3 In this study, by detecting and analyzing the phase changes of backscattered light signals at each point of a distributed fiber optic sensing array 7 caused by external vibrations, the time-frequency variation law of vibration signals during concrete pouring and curing is monitored in real time, and the identification results of pile foundation quality and defects during the pouring construction process are obtained.

Claims

1. An online monitoring system for concrete pouring construction quality based on distributed optical fiber, characterized in that: The system includes a narrowband light source, a first fiber coupler, an acousto-optic modulator, an erbium-doped fiber amplifier, a bandpass filter, a three-port circulator, a sensing fiber array, a fiber polarization beam splitter, a polarization fiber coupler, a first balanced photodetector, a second balanced photodetector, a self-coherent mixer, a data acquisition device, a dynamic filtering unit, a digital demodulation unit, a fundamental frequency doubling and fading noise identification unit, and a time-frequency analysis unit. The output of the narrowband light source is connected to the first input of the first coupler; the first output of the first coupler is connected to the input of the acousto-optic modulator; the output of the acousto-optic modulator is connected to the input of the erbium-doped fiber amplifier; the output of the amplifier is connected to the input of the bandpass filter; the output of the bandpass filter is connected to the input of the three-port circulator; the reflector of the three-port circulator is connected to the sensing fiber array; and the output of the three-port circulator is connected to the polarization fiber coupler. The input terminal of the first coupler is connected to the input terminal of the fiber polarization beamsplitter. The first output terminal of the fiber polarization beamsplitter and the first output terminal of the polarization fiber coupler are connected to the input terminal of the first balanced photodetector. The second output terminal of the fiber polarization beamsplitter and the second output terminal of the polarization fiber coupler are connected to the input terminal of the second balanced photodetector. The output terminals of the first and second balanced photodetectors are connected to the first and second input terminals of the self-coherent mixing unit. The output terminal of the self-coherent mixing unit is sequentially connected to a data acquisition device, a dynamic filtering unit, a digital demodulation unit, a fundamental frequency harmonic fading noise identification unit, and a time-frequency analysis unit. The sensing fiber array is set inside the cast concrete structure. The first and second balanced photodetectors convert the detected coherent optical signals into electrical signals. The self-coherent mixing unit performs cross-correlation mixing on the electrical signals converted by the first balanced photodetector and the second balanced photodetector. The dynamic filtering unit divides the signal after mixing by the self-coherent mixing unit into two signals: a base signal and a frequency multiplier signal. The digital demodulation unit demodulates the phase of the two signals divided by the dynamic filtering unit. The base-frequency multiplier combined fading noise identification unit compares and identifies the two demodulation results to eliminate fading noise and other field crosstalk noise in the demodulated signal of the digital demodulation unit. The time-frequency analysis unit analyzes the time history changes of the phase signal after noise elimination to obtain the trend of vibration signal changes at various points of the concrete.

2. The online monitoring system for concrete pouring construction quality based on distributed optical fiber according to claim 1, characterized in that: The fundamental frequency harmonic fading noise identification unit compares and analyzes the phases of the fundamental and harmonic signals. If the phases of the two signals show the same trend, they are identified as real signals. If there is a significant difference in the phases of the two signals, they are identified as field crosstalk noise. If one signal changes phase while the other does not, it is identified as fading noise, thereby eliminating fading noise and other field crosstalk noise.

3. The online monitoring system for concrete pouring construction quality based on distributed optical fiber as described in claim 1, characterized in that: The sensing fiber array is bundled and deployed on the reinforcing bars in the pile foundation or directly embedded in the concrete.

4. The online monitoring system for concrete pouring construction quality based on distributed optical fiber according to any one of claims 1-3, characterized in that: It also includes a quality assessment unit, which analyzes and compares the changes in vibration signals at various points of the concrete during the pouring process, and uses the spectral change trends to assess and identify the quality and defects of the pile foundation.

5. The online monitoring system for concrete pouring construction quality based on distributed optical fiber according to claim 4, characterized in that: Methods for assessing and identifying pile foundation quality and defects by analyzing spectral variation trends include: When the entire sensing fiber array is directly embedded in the concrete, the drift of the natural vibration frequency of each point in the concrete during the pouring and solidification periods is monitored through the sensing fiber array, thereby enabling construction quality monitoring and defect identification: if the natural frequency of a certain point in the concrete is at a relatively low frequency during the pouring period, but its resonant frequency gradually rises and stabilizes at a relatively high frequency during the initial solidification period of the concrete, then the quality of the pile foundation area where that point is located is determined to be good; if the natural frequency of the concrete does not show a regular change, then it can be determined that there may be quality defects in the concrete.

6. The online monitoring system for concrete pouring construction quality based on distributed optical fiber according to claim 5, characterized in that: Methods for assessing and identifying pile foundation quality and defects based on spectral variation trends also include: By comparing the resonant frequency distribution of various points in the steel reinforcement or concrete after the initial setting of the pile foundation concrete, pile foundation quality defects can be further identified: if the resonant frequencies of various points in the steel reinforcement cage or concrete are all distributed within the natural frequency range of the structure, it is determined that the quality of each point area of ​​the pile foundation is good; if the resonant frequency of a certain point in the steel reinforcement cage or concrete is significantly different from the vibration frequencies of other points, it is determined that there may be quality defects in the concrete area where that point is located.

7. A method for online monitoring of concrete pouring construction quality based on distributed optical fiber, characterized in that: Monitoring is performed using the online monitoring system for concrete pouring construction quality based on distributed optical fiber, as described in any one of claims 1-6.

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