A cast-in-place pile optical fiber monitoring system and method

Abstract

The present invention discloses a cast-in-place pile optical fiber monitoring system, wherein an optical fiber sensor is provided in each monitoring point of the cast-in-place pile, and the optical fiber sensor is installed on the main reinforcement of the cast-in-place pile through a protective fastener, and the optical fiber sensor is also connected to an optical fiber lead-out line, and the optical fiber lead-out line is connected to a detection module. The system realizes the automatic monitoring function of foundation pit deformation, has the advantages of convenient measurement, high measurement efficiency, little influence by the measurement environment, and real-time early warning, realizes the function of intelligent measurement, and makes the measurement informationized; the protective fastener of the present application can effectively protect the optical fiber sensor, prevent the damage to the optical fiber sensor by construction, and has strong practicality. At the same time, the system uses an optical fiber demodulator to realize the monitoring of foundation pits at various construction sites, which solves the problem of small number and high price of optical fiber demodulators, and there is no need to dispatch additional on-site technicians for monitoring, which is convenient for management, greatly improves the monitoring efficiency, and greatly reduces the monitoring cost.

Description

Technical Field

[0001] The invention relates to the field of safety detection equipment, and in particular to a cast-in-place pile optical fiber monitoring system and method. Background Art

[0002] In the process of foundation pit monitoring and early warning, since the environment of many test points is complex and changeable, and this type of detection needs to be carried out online for a long time, sensors with strong anti-interference and corrosion resistance are required. At the same time, people need to be sent to monitor and read and record the measurement data, which is time-consuming and labor-intensive. At present, optical fiber sensors are used for monitoring and early warning of foundation pit cast-in-place piles. However, during the installation of optical fiber sensors, optical fiber sensors are interfered by equipment and human factors, and there is a problem of serious damage to optical fiber sensors. The survival rate of optical fiber sensors is too low, resulting in failure to collect data during measurement. After the collection fails, it is difficult to install the optical fiber sensor again, resulting in a reduction in the number of foundation pit monitoring points and a significant reduction in monitoring data, resulting in a large safety hazard in foundation pit construction.

[0003] Due to the difficulty in power supply and signal transmission of optical fiber sensors in foundation pit monitoring, these sensors currently work in single units. When they are used, the staff can only go to the monitoring point and use a dedicated handheld device to read the data of each sensor one by one, collect relevant status information, and take the obtained information back to the laboratory for analysis, and then get the results. This method cannot achieve the functions of networking and online monitoring and early warning, and the monitoring range is small. In addition, the optical fiber demodulation system is expensive. If each construction site uses this device to read data, the aging speed of the optical fiber demodulation system will be accelerated, affecting its service life, thereby causing a significant increase in the overall monitoring cost. Summary of the invention

[0004] In view of the above problems, the present invention aims to provide an efficient and widely applicable cast-in-place pile optical fiber monitoring system and method.

[0005] To achieve the technical purpose, the solution of the present invention is: a bored pile optical fiber monitoring system, each bored pile monitoring point is provided with an optical fiber sensor, the optical fiber sensor is installed on the main reinforcement of the bored pile through a protective fastener, the optical fiber sensor is also connected to an optical fiber lead-out line, and the optical fiber lead-out line is connected to a detection module.

[0006] Preferably, the protective fastener comprises a movable sleeve and a fastener, wherein the movable sleeve is composed of a rotating shaft, a semi-lunar inner cover and a semi-lunar outer cover, and the semi-lunar outer cover can be opened outward around the rotating shaft;

[0007] One end of the buckle is fixedly connected to the semi-lunar inner cover, and the other end of the buckle can be fixed on the main rib by screw fastening. The optical fiber sensor is bonded to the semi-lunar inner cover and the semi-lunar outer cover by an epoxy resin layer.

[0008] Preferably, magnets with opposite polarities are respectively arranged on the edges of the semi-moon inner cover and the semi-moon outer cover, and the semi-moon inner cover and the semi-moon outer cover are automatically closed by magnetic attraction when they are brought close to each other.

[0009] Preferably, the detection module comprises: a tunable laser for emitting tuned light of a specified wavelength;

[0010] A coupler, used for dividing the tuned light into a first tuned light signal and a second tuned light signal;

[0011] The interferometer includes a signal arm and a reference arm, wherein the signal arm is connected to the optical fiber sensor, the first tuned optical signal enters the optical fiber sensor, and the signal arm receives the back Rayleigh scattered signal; the back Rayleigh scattered signal and the second tuned optical signal generate a beat frequency to obtain a beat frequency optical signal, and the reference arm is used to separate the beat frequency optical signal into P light and S light with orthogonal polarization directions;

[0012] A polarization beam splitter is used to split the P light and S light with orthogonal polarization directions into two beams of light;

[0013] A photoelectric converter, used to convert the P optical signal and the S optical signal into corresponding electrical signal data;

[0014] An acquisition card is used to collect the electrical signal data of each bored pile monitoring point through a data transmission line and store the electrical signal data locally;

[0015] A terminal server, used for receiving and storing electrical signal data;

[0016] A wireless transmitter is used to transmit the collected electrical signal data to a terminal server for storage;

[0017] The optical fiber demodulator is used to analyze the electrical signal data to obtain the Brillouin frequency shift and calculate the strain value at the corresponding position of the distributed optical fiber through the Brillouin scattering principle.

[0018] Preferably, adjacent bored pile monitoring points are electrically connected via a data transmission line, and adjacent bored pile monitoring points share a set of acquisition cards and wireless transmitters.

[0019] A monitoring method, based on a bored pile optical fiber monitoring system, comprises the following specific steps:

[0020] S1, conversion, the tuned light in each bored pile monitoring point passes through the coupler, interferometer, polarization beam splitter and photoelectric converter to generate corresponding electrical signal data;

[0021] S2, collection and transmission, the collection card collects the electrical signal data sent by each bored pile monitoring point, and transmits the electrical signal data to the terminal server through a wireless transmitter;

[0022] The acquisition card sends a designated pulse signal to the designated bored pile monitoring point. After receiving the pulse signal, the bored pile monitoring point sends an electrical signal to the acquisition card. The acquisition card receives the incoming electrical signal. When the time interval of the electrical signal meets the preset requirements, the acquisition card continues to send pulse signals. After receiving the pulse signal, the bored pile monitoring point performs data inspection and monitoring. When the acquisition card collects the preset number of groups, it sends a pulse signal. After receiving the pulse signal, the bored pile monitoring point suspends monitoring.

[0023] The pulse signals used for triggering are different at different bored pile monitoring points;

[0024] S3, analysis, the optical fiber demodulator obtains electrical signal data from the terminal server, and obtains the Brillouin frequency shift by analyzing the electrical signal data. The bending moment and deflection at the corresponding position of the optical fiber sensor can be calculated through the Brillouin scattering principle;

[0025] The calculation formula for the bending moment distribution of cast-in-place piles is as follows:

[0026]

[0027] Where, M(x) is the bending moment of the pile at a certain section; I is the moment of inertia of the pile section; E is the elastic modulus of the pile material; Δε is the strain change of the pile;

[0028] The calculation formula of the pile deflection distribution is as follows:

[0029] IE d (x)=-∫[∫M(x)d(x)]d(x)+Cx+D

[0030] In the formula, y d (x) is the deflection at a certain section; C and D are parameters determined by boundary conditions.

[0031] The beneficial effects of the present invention are as follows: the system realizes the automatic monitoring function of foundation pit deformation, has the advantages of convenient measurement, high measurement efficiency, little influence by the measurement environment, and real-time early warning, realizes the function of intelligent measurement, and makes the measurement informationized; the protective fasteners of the present application can effectively protect the optical fiber sensor, prevent the damage to the optical fiber sensor by construction, and has strong practicality. At the same time, the system uses a fiber optic demodulator to realize the monitoring of foundation pits at various construction sites, solving the problem of small number and high price of fiber optic demodulators, and there is no need to dispatch additional on-site technicians for monitoring, which is convenient for management, greatly improves the monitoring efficiency, and greatly reduces the monitoring cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the present invention;

[0033] Figure 2 is a cross-sectional view of the present invention;

[0034] Figure 3 It is a schematic diagram of the local structure of the present invention;

[0035] Figure 4 It is a partial cross-sectional view of the present invention;

[0036] Figure 5 It is a structural block diagram of the present invention;

[0037] Figure 6 This is a flow chart of data acquisition by the acquisition card of the present invention;. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] like Figure 1-6 As shown, the specific embodiment of the present invention is a bored pile optical fiber monitoring system, each bored pile monitoring point 1 is provided with an optical fiber sensor 2, the optical fiber sensor 2 is installed on the main reinforcement 5 of the bored pile 4 through a protective fastener 3, the optical fiber sensor 2 is also connected to an optical fiber lead-out line 6, and the optical fiber lead-out line 6 is connected to a detection module 7. The optical fiber sensor is a fiber Bragg grating.

[0040] The protective fastener 3 includes a movable sleeve 301 and a fastener 302. The movable sleeve 301 is composed of a rotating shaft 303, a semi-lunar inner cover 304 and a semi-lunar outer cover 305. The semi-lunar outer cover 305 can be opened outward around the rotating shaft 303.

[0041] One end of the fastener 302 is fixedly connected to the semi-lunar inner cover 304 , and the other end of the fastener 302 can be fixed to the main rib 5 by screw fastening. The optical fiber sensor 2 is bonded to the semi-lunar inner cover 304 and the semi-lunar outer cover 305 through the epoxy resin layer 8 .

[0042] Magnets 306 with opposite polarities are respectively arranged on the edges of the semi-moon inner cover 304 and the semi-moon outer cover 305. When the semi-moon inner cover 304 and the semi-moon outer cover 305 are close to each other, they are automatically closed by magnetic attraction.

[0043] The detection module 7 includes: a tunable laser for emitting tuned light of a specified wavelength;

[0044] A coupler, used for dividing the tuned light into a first tuned light signal and a second tuned light signal;

[0045] The interferometer includes a signal arm and a reference arm, wherein the signal arm is connected to the optical fiber sensor, the first tuned optical signal enters the optical fiber sensor, and the signal arm receives the back Rayleigh scattered signal; the back Rayleigh scattered signal and the second tuned optical signal generate a beat frequency to obtain a beat frequency optical signal, and the reference arm is used to separate the beat frequency optical signal into P light and S light with orthogonal polarization directions;

[0046] A polarization beam splitter is used to split the P light and S light with orthogonal polarization directions into two beams of light;

[0047] A photoelectric converter, used to convert the P optical signal and the S optical signal into corresponding electrical signal data;

[0048] An acquisition card is used to collect the electrical signal data of each bored pile monitoring point through a data transmission line and store the electrical signal data locally;

[0049] A terminal server, used for receiving and storing electrical signal data;

[0050] A wireless transmitter is used to transmit the collected electrical signal data to a terminal server for storage;

[0051] The optical fiber demodulator is used to analyze the electrical signal data to obtain the Brillouin frequency shift and calculate the strain value at the corresponding position of the distributed optical fiber through the Brillouin scattering principle.

[0052] To further reduce costs, Figure 5 Only a photoelectric signal conversion system is set in each bored pile monitoring point, and adjacent bored pile monitoring points 1 are electrically connected through a data transmission line 8, and adjacent bored pile monitoring points 1 share a set of acquisition cards 9 and wireless transmitters 10.

[0053] A monitoring method, based on a bored pile optical fiber monitoring system, comprises the following specific steps:

[0054] S1, conversion, the tuned light in each bored pile monitoring point passes through the coupler, interferometer, polarization beam splitter and photoelectric converter to generate corresponding electrical signal data;

[0055] S2, collection and transmission, the collection card collects the electrical signal data sent by each bored pile monitoring point, and transmits the electrical signal data to the terminal server through a wireless transmitter;

[0056] The acquisition card sends a designated pulse signal to the designated bored pile monitoring point. After receiving the pulse signal, the bored pile monitoring point sends an electrical signal to the acquisition card. The acquisition card receives the incoming electrical signal. When the time interval of the electrical signal meets the preset requirements, the acquisition card continues to send pulse signals. After receiving the pulse signal, the bored pile monitoring point performs data inspection and monitoring. When the acquisition card collects the preset number of groups, it sends a pulse signal. After receiving the pulse signal, the bored pile monitoring point suspends monitoring.

[0057] The pulse signals used for triggering are different at different bored pile monitoring points;

[0058] S3, analysis, the optical fiber demodulator obtains electrical signal data from the terminal server, and obtains the Brillouin frequency shift by analyzing the electrical signal data. The bending moment and deflection at the corresponding position of the optical fiber sensor can be calculated through the Brillouin scattering principle;

[0059] The calculation formula for the bending moment distribution of cast-in-place piles is as follows:

[0060]

[0061] Where, M(x) is the bending moment of the pile at a certain section; I is the moment of inertia of the pile section; E is the elastic modulus of the pile material; Δε is the strain change of the pile;

[0062] The calculation formula of the pile deflection distribution is as follows:

[0063] IE d (x)=-∫[∫M(x)d(x)]d(x)+Cx+D

[0064] In the formula, y d (x) is the deflection at a certain section; C and D are parameters determined by boundary conditions.

[0065] When this system is used, 1. The stress and deformation of the cast-in-place piles are automatically and real-time monitored to realize the foundation pit early warning function; 2. The installation of the measuring device protects the optical fiber, and the measurement accuracy is high. 3. Indoor monitoring can be achieved through the wireless transmission device, and a large-scale rapid monitoring function can be achieved, which greatly improves the monitoring efficiency. 4. A fiber optic demodulator realizes the foundation pit monitoring of each construction site, solving the problem of the small number and high price of fiber optic demodulators, with high monitoring efficiency and low monitoring cost.

[0066] The fiber optic sensor used in this application has the advantages of anti-electromagnetic interference, good stability, corrosion resistance, high sensitivity, high resolution, etc. It is suitable for complex environments on construction sites and can be used in series to achieve remote transmission. This system realizes the automatic monitoring function of foundation pit deformation, and has the advantages of convenient measurement, high measurement efficiency, little influence from the measurement environment, and real-time early warning. It realizes the function of intelligent measurement and makes the measurement informationized. The protective fasteners of this application can effectively protect the fiber optic sensor and prevent damage to the fiber optic sensor during construction, and it is highly practical. At the same time, a fiber optic demodulator in this system realizes the monitoring of foundation pits at various construction sites, solving the problem of a small number of fiber optic demodulators and high prices, and there is no need to dispatch additional on-site technicians for monitoring, which is convenient for management, greatly improves monitoring efficiency, and greatly reduces monitoring costs.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any slight modification, equivalent substitution and improvement made to the above embodiment based on the technical essence of the present invention should be included in the protection scope of the technical solution of the present invention.

Claims

1. A monitoring method, Features: A bored pile optical fiber monitoring system is used, which includes an optical fiber sensor disposed in each bored pile monitoring point, the optical fiber sensor being mounted on the main reinforcement of the bored pile through a protective fastener, the optical fiber sensor being also connected to an optical fiber lead-out line, the optical fiber lead-out line being connected to a detection module, the detection module including: a tunable laser for emitting tuned light of a specified wavelength; A coupler, used for dividing the tuned light into a first tuned light signal and a second tuned light signal; The interferometer includes a signal arm and a reference arm, wherein the signal arm is connected to the optical fiber sensor, the first tuned optical signal enters the optical fiber sensor, and the signal arm receives the back Rayleigh scattered signal; the back Rayleigh scattered signal and the second tuned optical signal generate a beat frequency to obtain a beat frequency optical signal, and the reference arm is used to separate the beat frequency optical signal into P light and S light with orthogonal polarization directions; A polarization beam splitter is used to split the P light and S light with orthogonal polarization directions into two beams of light; A photoelectric converter, used to convert the P optical signal and the S optical signal into corresponding electrical signal data; An acquisition card is used to collect the electrical signal data of each bored pile monitoring point through a data transmission line and store the electrical signal data locally; A terminal server, used for receiving and storing electrical signal data; A wireless transmitter is used to transmit the collected electrical signal data to a terminal server for storage; Fiber optic demodulator, used to analyze electrical signal data to obtain Brillouin frequency shift, and calculate the strain value at the corresponding position of the distributed optical fiber through the Brillouin scattering principle; The specific steps are as follows: S1, conversion, the tuned light in each bored pile monitoring point passes through the coupler, interferometer, polarization beam splitter and photoelectric converter to generate corresponding electrical signal data; S2, collection and transmission, the collection card collects the electrical signal data sent by each bored pile monitoring point, and transmits the electrical signal data to the terminal server through a wireless transmitter; The acquisition card sends a designated pulse signal to the designated bored pile monitoring point. After receiving the pulse signal, the bored pile monitoring point sends an electrical signal to the acquisition card. The acquisition card receives the incoming electrical signal. When the time interval of the electrical signal meets the preset requirements, the acquisition card continues to send pulse signals. After receiving the pulse signal, the bored pile monitoring point performs data monitoring. When the acquisition card collects the preset number of groups, it sends a pulse signal. After receiving the pulse signal, the bored pile monitoring point suspends monitoring. The pulse signals used for triggering are different at different bored pile monitoring points; S3, analysis, the optical fiber demodulator obtains electrical signal data from the terminal server, and obtains the Brillouin frequency shift by analyzing the electrical signal data. The bending moment and deflection at the corresponding position of the optical fiber sensor can be calculated through the Brillouin scattering principle; The calculation formula for the bending moment distribution of cast-in-place piles is as follows: Where, M(x) is the bending moment of the pile at a certain section; I is the moment of inertia of the pile section; E is the elastic modulus of the pile material; Δε is the strain change of the pile; The calculation formula of the pile deflection distribution is as follows: IEy d (x)=-∫[∫M(x)d(x)]d(x)+Cx+D In the formula, y d (x) is the deflection at a certain section; C and D are parameters determined by boundary conditions.

2. The monitoring method according to claim 1, Features: The protective fastener comprises a movable sleeve and a fastener, wherein the movable sleeve is composed of a rotating shaft, a semi-lunar inner cover and a semi-lunar outer cover, and the semi-lunar outer cover can be opened outward around the rotating shaft; One end of the buckle is fixedly connected to the semi-lunar inner cover, and the other end of the buckle can be fixed on the main rib by screw fastening. The optical fiber sensor is bonded to the semi-lunar inner cover and the semi-lunar outer cover by an epoxy resin layer.

3. The monitoring method according to claim 2, Features: Magnets with opposite polarities are respectively arranged on the edges of the semi-moon inner cover and the semi-moon outer cover, and the semi-moon inner cover and the semi-moon outer cover are automatically closed by magnetic attraction when they are close to each other.

4. The monitoring method according to claim 1, Features: Adjacent bored pile monitoring points are electrically connected via data transmission lines, and the adjacent bored pile monitoring points share a set of acquisition cards and wireless transmitters.

Images