CN111412893A - Tandem type fiber bragg grating settlement monitoring system and method - Google Patents
Tandem type fiber bragg grating settlement monitoring system and method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C5/00—Measuring height; Measuring distances transverse to line of sight; Levelling between separated points; Surveyors' levels
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
- G01D5/35309—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer
- G01D5/35316—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using a Bragg gratings
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
- G01L11/02—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means
- G01L11/025—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means using a pressure-sensitive optical fibre
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Abstract
The invention provides a tandem type fiber bragg grating settlement monitoring system and a method, which relate to the field of stratum settlement monitoring and comprise a liquid level pool, a datum point settlement instrument, a settlement instrument of a point to be measured, a pipeline, a plug, an optical cable and a fiber bragg grating demodulator, wherein a datum cavity is arranged in the datum point settlement instrument, the reference cavity is provided with an inlet and an outlet, the test cavity is arranged in the settlement gauge of the point to be tested and is provided with a corresponding inlet and an outlet, the fiber bragg grating monitoring mechanisms are respectively arranged in the settlement gauge of the point to be tested and the reference point settlement gauge and are used for monitoring the hydraulic pressure in the reference cavity and the hydraulic pressure in the test cavity respectively in real time, an openable port is reserved at the tail end of the closed space, the gas in the closed cavity can be well discharged, the whole closed space can be ensured to be filled with liquid, and the problems of large construction difficulty and high maintenance cost when the distance between the reference point and the point to be measured is long are solved.
Description
Technical Field
The disclosure relates to the field of stratum settlement monitoring, in particular to a tandem type fiber bragg grating settlement monitoring system and method.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
Formation subsidence is a common geological phenomenon. The stratum settlement is a slow and long-term evolution and development process, and becomes a geological disaster when serious, thus threatening the safety and use of people's lives and properties. Such as overburden and surface subsidence caused by mining, stratum subsidence caused by excessive underground water mining, foundation subsidence caused by urban underground engineering and the like; monitoring is the most effective and the most fundamental measure for preventing and treating ground settlement for a long time and continuously in spite of ground settlement geological disasters; the Fiber Bragg Grating (FBG) settlement meter has the advantages of excellent networking capability, safety, electromagnetic interference resistance, high stability and the like, and is suitable for real-time monitoring of settlement parameters.
The inventor finds that the scheme of measuring the stratum settlement by adopting the fiber bragg grating settlement meter at present has more defects; for example, only the measurement between a reference point and a point to be measured can be realized, when a plurality of measurement points need to be measured, a plurality of reference points need to be arranged, and a plurality of measurement points cannot be measured by sharing one reference point; when the distance between the reference point and the point to be measured is far, the gas is sealed in the sealed cavity due to the fact that the middle snake-shaped hose can fluctuate up and down, so that the whole sealed container cannot be filled with water well, and construction and maintenance difficulty is increased; when the measuring environment is in a low-temperature environment, the used liquid water is easy to freeze to block the coiled pipe, so that the monitoring cannot be performed, and the frozen water is easy to expand and break the coiled pipe, so that the liquid leakage is caused, and the measurement cannot be performed; in addition, when the existing settlement monitoring system is used, sensors of measuring points are mostly required to be ensured to be on the same horizontal plane, so that the number of the sensors connected in series is not large, and long-distance multiple points are required to be measured in a segmented mode; the horizontal plane of the sensor needs to be adjusted through hoisting, so that the construction and maintenance cost is increased; the existing requirement for long-time real-time monitoring of the stratum settlement is difficult to meet.
Disclosure of Invention
The invention aims to provide a tandem type fiber bragg grating settlement monitoring system and a method aiming at the defects in the prior art, an openable port is reserved at the tail end of a closed space, so that gas in a closed cavity can be well discharged, the whole closed space can be ensured to be filled with liquid, and the problems of high construction difficulty and high maintenance cost when the distance between a reference point and a point to be measured is long are solved; the coiled pipe is replaced by the low-temperature-resistant PVC steel wire hose, so that the pressure resistance, the wear resistance and the low-temperature resistance of the series pipeline are improved; the colored antifreeze liquid is used for replacing water, so that the maintainability of the closed space and the engineering environment adaptability are improved.
The first purpose of the present disclosure is to provide a tandem fiber bragg grating settlement monitoring system, which adopts the following technical scheme:
the method comprises the following steps: a liquid level tank containing liquid;
the datum point settlement meter and the liquid level pool are arranged at the datum point position together, a datum cavity and a corresponding fiber grating monitoring mechanism are arranged in the datum point settlement meter, and the fiber grating monitoring mechanism monitors the hydraulic pressure in the datum cavity in real time;
the device comprises a plurality of to-be-measured point settlers and a plurality of fiber bragg grating monitoring mechanisms, wherein the to-be-measured point settlers are respectively and correspondingly arranged at positions of various to-be-measured points;
the fiber grating demodulator is connected with all the fiber grating monitoring mechanisms through optical cables;
the liquid level pool is sequentially connected with the reference cavity and all cavities to be detected in series through pipelines, the liquid level pool is positioned at an outlet of the last cavity to be detected for plugging to form a cavity with a sealed tail end, and the reference cavity, the pipelines and each cavity to be detected are filled with liquid;
the fiber grating demodulator monitors the settlement change of the reference point position and the position to be measured in real time by acquiring the change data of the fiber grating monitoring mechanism.
Furthermore, the liquid contained in the liquid level tank is colored anti-freezing liquid, and the level of the liquid in the liquid level tank is higher than that of the pipeline, the datum point settlement gauge and the to-be-measured point settlement gauge, so that the whole cavity is filled with the liquid.
Further, the reference point settlement gauge and the liquid level pool are jointly installed on a fixed base which does not settle along with the point to be measured, and the reference point settlement gauge and the liquid level pool are used for enabling the hydraulic pressure in the reference cavity to serve as a reference point to judge whether the point to be measured settles or not.
Furthermore, corresponding fiber grating monitoring mechanisms are arranged in the reference point settlement gauge and the settlement gauge to be measured, and when the hydraulic pressure in the cavity to be measured and the hydraulic pressure in the reference cavity are changed, the fiber grating monitoring mechanisms acquire the hydraulic pressure change and send the hydraulic pressure change to the fiber grating demodulator.
Furthermore, the cavity to be measured is provided with an inlet and an outlet, the inlet of the cavity to be measured is communicated with the outlet of the previous cavity to be measured through a pipeline, and the outlet is communicated with the inlet of the next cavity to be measured through a pipeline, so that a series structure is formed in sequence.
Furthermore, an outlet of the last cavity to be tested of the series structure is matched with a plug, the plug is matched with a pipeline, the reference cavity and the cavity to be tested to form a cavity with an opening at one end, the cavity is used for discharging air in the cavity and plugging the tail end of the series structure, and the opening of the cavity is communicated with the liquid level pool.
A second object of the present disclosure is to provide a settlement monitoring method using the tandem fiber grating settlement monitoring system as described above, including the following steps:
installing a liquid level pool and a datum point settlement meter on a datum point, and respectively installing the settlement meters of the points to be measured on all the points to be measured;
the liquid level pool, the reference cavity and all the cavities to be detected are sequentially communicated in series through pipelines, and liquid is poured into the liquid level pool, so that the pipelines, the reference cavity and the cavities to be detected are filled with the liquid level;
after standing, measuring the wavelengths of the fiber bragg grating monitoring mechanisms corresponding to all the settlement instruments through a fiber bragg grating demodulator, using the wavelengths as calibration data, and calculating the liquid level depth of each point to be measured relative to a reference point;
after calibration, the fiber bragg grating demodulator measures the wavelengths of the fiber bragg grating monitoring mechanisms corresponding to all the settlement instruments in real time, and therefore the real-time settlement amount of each point to be measured is obtained.
Furthermore, before the pipeline is arranged, all the fiber bragg grating monitoring mechanisms are connected into the fiber bragg grating demodulator through the optical cable, and when liquid is not introduced, the wavelengths of the fiber bragg grating monitoring mechanisms corresponding to all the settlement instruments are respectively measured and used as initial wavelength data of the fiber bragg grating monitoring mechanisms.
Further, after the pipeline is arranged, liquid in the liquid level pool gradually fills the cavity, and after air in the cavity is completely discharged and the whole cavity is filled with the liquid, the tail end of the cavity is plugged.
Further, the liquid level in the liquid level pool is higher than the pipeline, the reference point settlement gauge and the settlement gauge of the point to be measured.
Compared with the prior art, the utility model has the advantages and positive effects that:
(1) the liquid level pool, the reference point settlement gauge and the settlement gauge to be measured are sequentially connected in series through pipelines, so that the liquid level pool, the reference cavity and the cavity to be measured are communicated, a closed cavity is formed by matching with a plug, liquid is filled in the whole cavity, and smoothness of hydraulic transmission is guaranteed;
the settlement measurement of the multi-point position to be measured is realized by using the hydraulic value of the reference point settlement meter as a reference value and comparing the hydraulic value of the point to be measured with the hydraulic value of the reference value, so that the settlement measurement is simpler to install, the construction cost and the maintenance cost are reduced, and the practicability of engineering application is improved;
(2) the colored anti-freezing solution is stored in the liquid level tank, so that when residual bubbles and leakage points are checked, the anti-freezing solution can generate obvious color difference with the external environment and pipelines, the identification degree is improved, and the checking efficiency is improved; the liquid level pool and the reference point settlement gauge are fixed on a fixed base which does not settle along with the point to be measured, and simultaneously the liquid level of the anti-freezing liquid in the liquid level pool is ensured to be higher than that of the pipeline, the reference point settlement gauge and the point to be measured settlement gauge, so that the anti-freezing liquid is always filled in the whole sealed cavity; the influence of residual liquid in the cavity on the measurement precision is avoided;
(3) compared with the common pipe, the low-temperature-resistant PVC steel wire hose has the advantages of wear resistance, low temperature resistance, strong pressure resistance and the like, and can reduce the risks of rupture and extrusion blockage when being in a severe monitoring environment; and the stable operation of the whole system is ensured.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.
Fig. 1 is a schematic overall structure diagram of a settlement monitoring system in embodiments 1 and 2 of the present disclosure;
fig. 2 is a schematic view of the internal structure of a settlement meter in embodiments 1 and 2 of the present disclosure;
fig. 3 is an appearance structure schematic diagram of a settlement meter in embodiments 1 and 2 of the present disclosure.
In the figure, 1, a stainless steel sleeve, 2, a slotted capillary, 3, a stress fiber grating, 4, a temperature compensation fiber grating, 5, a metal membrane, 6, a liquid inlet, 7, a liquid outlet, 8, a fixed hole, 9, a base, 10 and a sealing cover,
11. the device comprises an optical cable, 12, vent holes, 13, a shell, 14, a fiber bragg grating demodulator, 15, a liquid level pool, 16, a datum point settlement gauge, 17, a pipeline, 18, a settlement gauge of a point to be measured, 19 and a plug.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an", and/or "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof;
for convenience of description, the words "up", "down", "left" and "right" in this disclosure, if any, merely indicate that the directions of movement are consistent with those of the figures themselves, and are not limiting in structure, but merely facilitate the description of the invention and simplify the description, rather than indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present disclosure.
As introduced in the background art, the formation settlement monitoring device in the prior art can only realize the measurement between a reference point and a point to be measured, when a plurality of measurement points need to be measured, a plurality of reference points need to be arranged, and a plurality of measurement points cannot be measured by sharing one reference point; when the distance between the reference point and the point to be measured is far, the gas is sealed in the sealed cavity due to the fact that the middle snake-shaped hose can fluctuate up and down, so that the whole sealed container cannot be filled with water well, construction and maintenance difficulty is increased, and the like; in order to solve the problems, the present disclosure provides a tandem fiber bragg grating settlement monitoring system and method.
Example 1
In an exemplary embodiment of the present disclosure, as shown in fig. 1 to 3, a tandem fiber grating settlement monitoring system is provided.
As shown in fig. 1, the device comprises a liquid level pool 15, a reference point settlement gauge 16, a settlement gauge 18 of a point to be measured, a pipeline 18, a plug 19, an optical cable 11 and a fiber grating demodulator 14;
a reference cavity is arranged in the reference point settlement gauge, the reference cavity is provided with an inlet and an outlet, a test cavity is arranged in the settlement gauge to be measured, the test cavity is provided with a corresponding inlet and a corresponding outlet, and fiber bragg grating monitoring mechanisms are arranged in the settlement gauge to be measured and the reference point settlement gauge respectively and are used for monitoring the hydraulic pressure in the reference cavity and the hydraulic pressure in the test cavity in real time;
the liquid level pool is sequentially connected with the reference point settlement instrument and the plurality of to-be-measured point settlement instruments in series through pipelines, so that the pipelines, the reference cavity and the test cavities are filled with liquid in the liquid level pool, and after all the pipelines, the reference cavity and the test cavities are filled with the liquid, an outlet of the to-be-measured point settlement instrument at the tail end far away from the liquid level pool is plugged by adopting a plug;
all the fiber bragg grating monitoring mechanisms are electrically connected with the fiber bragg grating demodulator, when the height of the settlement gauge of the point to be measured changes relative to the height of the settlement gauge of the reference point, the hydraulic pressure in the cavity to be measured also changes correspondingly, the fiber bragg grating monitoring mechanisms are used for acquiring the hydraulic pressure change, and the height change is reversely deduced according to the hydraulic pressure change in each cavity, so that the settlement amount of the point to be measured is measured.
The liquid level pool, the datum point settlement gauge and the to-be-measured point settlement gauge are sequentially connected in series through pipelines, so that the liquid level pool, the reference cavity and the to-be-measured cavity are communicated, a sealed cavity is formed by matching with the plug, liquid is filled in the whole cavity, all to-be-measured points share one reference liquid level to carry out series remote measurement on settlement, the hydraulic value of the datum point settlement gauge is used as a reference value, the settlement is obtained by comparing the hydraulic value of the to-be-measured point with the hydraulic value of the reference value, the settlement measurement of the multi-point to-be-measured position is realized, the installation is simpler, the construction cost and the maintenance cost are reduced, and the practicability of engineering.
Specifically, colored anti-freezing solution is stored in the liquid level tank; the liquid level pool and the reference point settlement gauge are fixed on a fixed base which does not settle along with the point to be measured, and simultaneously the liquid level of the anti-freezing liquid in the liquid level pool is ensured to be higher than that of the pipeline, the reference point settlement gauge and the point to be measured settlement gauge, so that the anti-freezing liquid is always filled in the whole sealed cavity; the influence of residual liquid in the cavity on the measurement precision is avoided;
in the embodiment, a water tank with the length, width and height of 40cm × 40cm 3540 cm × 80cm is selected as the liquid level pool, and the liquid level of the anti-freezing liquid is kept higher than 30 cm.
The datum point settlement gauge is mainly used for measuring a hydraulic value on the fixed base; the datum point settlement gauge and the liquid level pool are fixed on a fixed base which does not settle along with the point to be measured, and a hydraulic value measured by the datum point settlement gauge is used as a datum point to judge whether the point to be measured settles or not;
it can be understood that an inlet of a reference cavity in the reference point settlement gauge is communicated with the liquid level pool, and an outlet of the reference cavity is sequentially connected in series with the to-be-measured cavity corresponding to each to-be-measured point settlement gauge through a pipeline to form a liquid passage, so that the antifreezing solution is ensured to be smoothly communicated.
The settlement meter of the point to be measured is mainly used for measuring the hydraulic value of the point to be measured relative to the reference position; the settlement meter of the point to be measured is fixed at the position of the point to be measured, and if the point to be measured is settled, the settlement meter and the point to be measured are settled together; a plurality of to-be-measured points are correspondingly provided with a plurality of to-be-measured point settlement instruments and are sequentially connected in series through pipelines, so that the settlement value measurement is carried out by sharing one datum point by the plurality of to-be-measured points;
it can be understood that the inlet of the cavity to be measured corresponding to the settlement gauge of the point to be measured is communicated with the outlet of the cavity to be measured through a pipeline, the outlet of the cavity to be measured is communicated with the inlet of the cavity to be measured, so that series connection is sequentially realized, and the inlet of the cavity to be measured located closest to the settlement gauge of the reference point is communicated with the outlet of the cavity to be measured.
The pipeline is mainly used for communicating the settlement gauge with the liquid level pool to form a communicating relation; in the embodiment, a low-temperature-resistant PVC steel wire hose is adopted, and a liquid level pool, a reference point settlement gauge and a to-be-measured point settlement gauge are sequentially communicated through the low-temperature-resistant PVC steel wire hose; the reference cavity, the cavity to be tested and the low-temperature resistant PVC steel wire hose are matched with plugs to form a cavity together;
compared with the common pipe, the low-temperature-resistant PVC steel wire hose has the advantages of wear resistance, low temperature resistance, strong pressure resistance and the like, and can reduce the risks of rupture and extrusion blockage when being in a severe monitoring environment; the stable operation of the whole system is ensured;
in this embodiment, the inner diameter of the low temperature resistant PVC steel wire hose is 20mm, and the outer diameter is 28 mm.
The sealing plug is mainly used for plugging an outlet of a cavity to be tested in the final settlement meter to be tested in the series structure, and forms a closed cavity together with the low-temperature-resistant PVC steel wire hose, the settlement meter to be tested and the datum point settlement meter;
when the anti-freezing liquid filling device is used, colored anti-freezing liquid needs to be injected into the serial structure, the plug at the tail end of the serial structure is opened, the anti-freezing liquid gradually fills each cavity along the pipeline, and in the process of filling the cavities, gas in the sealed cavity is discharged, so that the gas residue is avoided, and the phenomenon that the colored anti-freezing liquid cannot fill the whole cavity due to the fact that the gas is extruded into the cavities is prevented; the antifreeze liquid is ensured to be filled in the whole cavity, and the monitoring precision is improved;
in this embodiment, an internal thread stainless steel sealing plug with a diameter of 20mm is selected.
The anti-freezing liquid is injected into the cavity to be measured and the reference cavity which are provided with the inlet and the outlet after being connected in series, and the gas in the cavity is exhausted, so that the anti-freezing liquid fills the whole cavity, the long-distance correlation between the reference point and the point to be measured is realized, and the long-distance measurement is realized;
the gas is discharged through the end opening, so that the liquid can be filled in the whole closed cavity from hundreds of meters to kilometers, and the continuous transmission and the mutual correlation of the hydraulic pressure are realized.
The fiber grating monitoring mechanism is connected with the fiber grating demodulator through an optical cable, the optical cable adopts an armored optical cable, and the fiber grating demodulator is connected with the fiber grating monitoring mechanisms corresponding to the reference point settlement meter and the to-be-measured point settlement meter through armored optical fibers, so that optical path communication is realized to demodulate fiber grating signals;
it can be understood that the connection mode of the fiber grating monitoring mechanism and the fiber grating demodulator is not limited to series connection, and can be determined according to actual conditions, and the communication of optical signals can be realized to demodulate the fiber grating signals;
in the embodiment, the optical path communication is realized in a serial connection mode, and an outdoor optical cable with the diameter of 7mm is used as the optical cable.
The fiber grating demodulator is mainly used for demodulating a fiber grating signal on a light path, and calculating the change of hydraulic pressure according to the change of the fiber grating signal so as to calculate a settlement value to be measured; the specific parameters of the fiber grating demodulator can be determined according to actual conditions.
It should be particularly noted that the reference point settlement gauge and the settlement gauge to be measured have the same structure, and mainly include a stainless steel sleeve 1, a grooved capillary 2, a stress fiber grating 3, a temperature compensation fiber grating 4, a metal diaphragm 5, a liquid inlet 6, a liquid outlet 7, a fixing hole 8, a base 9, a sealing cover 10, an armored optical cable 11, a vent hole 12 and a housing 13;
as shown in fig. 2 and 3:
specifically, the stainless steel sleeve is mainly used for fixing the connection between the armored optical cable and the sealing cover and guiding the bare wire part with the fiber bragg grating into the settlement gauge;
in this example, a stainless steel sleeve 15mm in diameter and 25mm in length was used, and the steel sleeve was fixed with epoxy resin 353 ND.
The slotted capillary is mainly used for connecting the stress fiber grating and the metal membrane and transmitting hydraulic pressure applied to the metal membrane to the stress fiber grating; the invention uses a slotted capillary tube with the diameter of 2mm and the length of 15mm to be welded at the center of a metal diaphragm to form a central hard core, and uses epoxy resin adhesive 353ND for fixation.
The stress fiber grating is mainly used for measuring the hydraulic pressure applied to the metal membrane, so that the real-time measurement of the settlement amount is realized; when the stress fiber grating is measured, the stress fiber grating is always kept in a stressed state, and when the hydraulic pressure applied to the metal membrane is changed, the stressed state of the stress fiber grating is also changed.
In this embodiment, the stress fiber grating is a fiber bragg grating.
The temperature compensation fiber grating is mainly used for carrying out temperature compensation on the stress fiber grating, and the test data result is not influenced by temperature change; the temperature light-filling fiber grating is always in an unstressed state during measurement.
The metal membrane is mainly used for measuring hydraulic pressure, when the hydraulic pressure on the membrane changes, the stress and deformation quantity on the metal membrane also change, and the stress and deformation quantity is transmitted to the stress fiber grating through the grooved capillary;
in this embodiment, a beryllium copper sheet with a diameter of 30mm and a thickness of 0.2mm is used as the metal diaphragm, and the joint of the metal diaphragm and the shell is welded by laser sealing.
The liquid inlet is mainly used for connecting a low-temperature-resistant PVC steel wire hose to form a closed cavity so that liquid enters the settlement gauge; the inlet corresponds to the cavity to be measured and the reference cavity;
in this embodiment, the connection is fixed and sealed by using a stainless steel cable tie and epoxy resin adhesive 353ND, so as to ensure non-detachment and sealing.
The liquid outlet is mainly used for connecting a low-temperature-resistant PVC steel wire hose to enable liquid to flow out of the settlement gauge or is used for connecting a sealing plug to form a closed cavity; the outlet of the cavity to be measured and the outlet of the reference cavity correspond to the outlet of the cavity to be measured and the outlet of the reference cavity;
in this embodiment, the connection is fixed and sealed by using a stainless steel cable tie and epoxy resin adhesive 353ND, so as to ensure non-detachment and sealing.
The fixing hole is mainly used for fixing a base of the settlement gauge on a point to be measured or a base to play a role in fixed connection; in the present embodiment, the specification of the fixing hole is M5.
The base is mainly used for connecting the settlement gauge with a point or a base to be measured;
in this example, circular stainless steel having a diameter of 10cm and a thickness of 8mm was used as the base.
The sealing cover is mainly used for fixing the stainless steel sleeve and connecting the shell to protect the internal structure of the settlement gauge;
in this embodiment, the epoxy adhesive 353ND is used for the fixing and packaging.
The armored optical cable is mainly used for connecting the fiber bragg grating in the settlement gauge to ensure smooth light path;
in this embodiment, the armored cable uses an outdoor cable having a diameter of 7 mm.
The vent hole is mainly used for communicating the atmosphere with the interior of the settlement gauge, so that the internal air pressure of the settlement gauge is kept consistent with the external atmospheric pressure, and the measurement error caused by the change of the atmospheric pressure is eliminated;
the diameter of the vent hole is 2mm in this embodiment.
The shell is mainly used for connecting the metal diaphragm and the sealing cover to form a whole and protect the internal structure;
in this example, a stainless steel housing having an inner diameter of 3cm and an outer diameter of 5cm and a length of 1cm was used.
Through increasing air vent, temperature compensation fiber grating, keep sensor measuring accuracy when different atmospheric pressure and temperature environment, through the deformation volume direct action stress fiber grating that new structure acted on the diaphragm with hydraulic pressure simultaneously, increased sensor sensitivity and range, realize wide-range, high accuracy measurement.
Example 2
In another exemplary embodiment of the present disclosure, a method for monitoring sedimentation is provided as shown in fig. 1-3, using the in-line fiber grating sedimentation monitoring system as described in embodiment 1.
And installing a liquid level pool and a settlement gauge. And connecting the optical paths, and measuring the wavelengths of the stress fiber gratings and the temperature compensation fiber gratings of all the settlement instruments when liquid is not introduced through a fiber grating demodulator.
Connecting a liquid level pool and all settlers through a low-temperature-resistant PVC steel wire hose, and pouring colored antifreeze into the liquid level pool; in the embodiment, the liquid level of the liquid level tank is kept higher than 30 cm;
unscrewing the sealing plug at the tail end for discharging air, screwing the sealing plug again when the whole cavity is filled with the anti-freezing solution, standing for 1 hour, and measuring the wavelengths of the stress fiber gratings and the temperature compensation fiber gratings of all the settlement instruments through a fiber grating demodulator to be used as calibration data; calculating the liquid level depth of each point through a formula;
and after calibration, the wavelengths of the stress fiber gratings and the temperature compensation fiber gratings of all the settlement instruments are measured in real time through a fiber grating demodulator, and the real-time settlement amount of each point to be measured is calculated through a formula.
The fiber bragg grating employed in this embodiment is an optical sensor that is inscribed in the center of a standard, single-mode fiber in a spatially varying manner using intense ultraviolet laser. Short wavelength ultraviolet photons have sufficient energy to break the highly stable silica binder, destroy the structure of the fiber and slightly increase its refractive index. Interference between two successive laser beams or between the fiber and its mask produces strong spatial periodic variations in the uv light, which results in a corresponding periodic variation in the refractive index of the fiber. The grating formed in the region of the fiber where this change occurs will become a wavelength selective mirror image: light travels down the fiber and reflects at each slight change, but these reflections produce destructive interference at most wavelengths and continue along the fiber.
Within a particular narrow band of wavelengths, useful interference is generated that travels back along the fiber. Bragg wavelength lambdaBIs determined by the following formula:
λB＝2neffΛ (1-1)
in the formula: n iseffEffective refractive index for laser propagation in the fiber, Λ the period of the Bragg gratingBIs Λ and neffAs a function of (c).
λ when the FBG is not affected by the external force field and the ambient temperature changes △ TBDrift occurs, and the relationship between the amount of drift and the temperature change can be written as
△λB＝λB(α+ζ)△T (1-2)
Wherein α is the thermal expansion coefficient of the FBG material, ζ is the thermo-optic coefficient of the FBG material, and △ T is the temperature variation.
When the ambient temperature is constant, the FBG is subjected to the action of an external force field, lambdaBDrift by an amount of
△λ＝λB(1-Pe)△ (1-3)
Wherein △ is the stress variation, Pe＝neff 2[P2-μ(P1+P2)][ 2 ] represents the effective elasto-optic coefficient of the FBG material, where P1And P2Is the elasto-optic coefficient of the FBG material; μ is the poisson ratio of the FBG material.
λ when strain and temperature act on the FBG at the same timeBDrift by an amount of
△λ＝λB(1-Pe)△+λB(α+ζ)△T (1-4)
In this embodiment, during actual measurement, the liquid level depth of the settlement gauge can be calculated from the wavelength measured by the fiber grating demodulator, and the relationship between the liquid level depth of the settlement gauge and the measured fiber grating wavelength is as follows:
H＝((λ-λ0)-(λT-λT0)*KT)/K (2-1)
wherein lambda is the wavelength of the stress fiber grating after the liquid is introduced into the settlement gauge; lambda [ alpha ]0The wavelength of the stress fiber grating is the wavelength of the stress fiber grating when no liquid is introduced into the settlement gauge; lambda [ alpha ]TThe wavelength of the fiber bragg grating is compensated in a temperature mode after liquid is introduced into the settlement gauge; lambda [ alpha ]T0The wavelength of the temperature compensation fiber grating is the wavelength when no liquid is introduced into the settlement gauge; kTThe compensation factor is a fixed value for eliminating the temperature cross-sensitivity influence of the fiber bragg grating; k is a hydraulic sensitivity coefficient and is a fixed value; h is the liquid level depth.
When the settlement amount is tested, all settlement instruments are subjected to calibration test, namely, when the calibration test is defaulted, the points to be tested are not settled; after the calibration test, the sedimentation amount is measured in real time, and the relation between the liquid level depth and the sedimentation amount is
S＝(Hx-H)-(Hx0-H0) (2-2)
Wherein S is the sedimentation amount; hxThe measured liquid level depth of the settlement gauge of the point to be measured after calibration test; h is the liquid level depth measured by the reference point settlement meter after calibration test; hx0The liquid level depth measured by a settlement meter of the point to be measured during calibration test is obtained; h0The liquid level depth measured by a reference point settlement meter during the calibration test is realized.
Specifically, when the settlement gauge of the point to be measured sinks for 1cm, the fiber bragg grating demodulator measures that the wavelength variation of the stress fiber bragg grating in the settlement gauge of the point to be measured is 30pm, the temperature compensation fiber bragg grating is unchanged, the liquid level depth of the settlement gauge of the point to be measured after settlement is carried out can be obtained through a formula (2-1), the calibrated data and the obtained liquid level depth of the settlement gauge of the point to be measured are substituted into the formula (2-2), and the settlement amount of the point to be measured can be obtained to be 1 cm; the system measurement value is verified to be consistent with the actual sedimentation amount.
The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.
Claims (10)
1. A tandem fiber bragg grating settlement monitoring system is characterized by comprising:
a liquid level tank containing liquid;
the datum point settlement meter and the liquid level pool are arranged at the datum point position together, a datum cavity and a corresponding fiber grating monitoring mechanism are arranged in the datum point settlement meter, and the fiber grating monitoring mechanism monitors the hydraulic pressure in the datum cavity in real time;
the device comprises a plurality of to-be-measured point settlers and a plurality of fiber bragg grating monitoring mechanisms, wherein the to-be-measured point settlers are respectively and correspondingly arranged at positions of various to-be-measured points;
the fiber grating demodulator is connected with all the fiber grating monitoring mechanisms through optical cables;
the liquid level pool is sequentially connected with the reference cavity and all cavities to be detected in series through pipelines, the liquid level pool is positioned at an outlet of the last cavity to be detected for plugging to form a cavity with a sealed tail end, and the reference cavity, the pipelines and each cavity to be detected are filled with liquid;
the fiber grating demodulator monitors the settlement change of the reference point position and the position to be measured in real time by acquiring the change data of the fiber grating monitoring mechanism.
2. The in-line fiber grating settlement monitoring system of claim 1, wherein the liquid contained in the liquid level tank is a colored anti-freezing liquid, and the liquid level of the liquid in the liquid level tank is higher than the level of the pipeline, the reference point settlement gauge and the point settlement gauge, so as to fill the whole cavity with the liquid.
3. The in-line fiber bragg grating settlement monitoring system of claim 1, wherein the reference point settlement gauge and the liquid level tank are mounted together on a fixed base which does not settle with the point to be measured, and are used for making the hydraulic pressure in the reference cavity as a reference point to judge whether the point to be measured settles.
4. The tandem fiber bragg grating settlement monitoring system of claim 1, wherein corresponding fiber bragg grating monitoring mechanisms are arranged in the reference point settlement gauge and the point-to-be-measured settlement gauge, and when the hydraulic pressure in the cavity to be measured and the reference cavity changes, the fiber bragg grating monitoring mechanisms acquire the hydraulic pressure change and send the hydraulic pressure change to the fiber bragg grating demodulator.
5. The in-line fiber grating settlement monitoring system of claim 1, wherein the chamber to be tested has an inlet and an outlet, the inlet of one chamber to be tested is connected to the outlet of the previous chamber to be tested via a pipeline, and the outlet is connected to the inlet of the next chamber to be tested via a pipeline, thereby forming a series structure.
6. The in-line fiber grating settlement monitoring system of claim 5, wherein a plug is fitted at an outlet of a last cavity to be measured of the series structure, the plug cooperates with the pipeline, the reference cavity and the cavity to be measured to form a cavity with an open end for exhausting air in the cavity and plugging a tail end of the series structure, and the open end of the cavity is communicated with the liquid level tank.
7. A sedimentation monitoring method using the in-line fiber grating sedimentation monitoring system according to any one of claims 1 to 6, comprising the steps of:
installing a liquid level pool and a datum point settlement meter on a datum point, and respectively installing the settlement meters of the points to be measured on all the points to be measured;
the liquid level pool, the reference cavity and all the cavities to be detected are sequentially communicated in series through pipelines, and liquid is poured into the liquid level pool, so that the pipelines, the reference cavity and the cavities to be detected are filled with the liquid level;
after standing, measuring the wavelengths of the fiber bragg grating monitoring mechanisms corresponding to all the settlement instruments through a fiber bragg grating demodulator, using the wavelengths as calibration data, and calculating the liquid level depth of each point to be measured relative to a reference point;
after calibration, the fiber bragg grating demodulator measures the wavelengths of the fiber bragg grating monitoring mechanisms corresponding to all the settlement instruments in real time, and therefore the real-time settlement amount of each point to be measured is obtained.
8. The sedimentation monitoring method according to claim 7, wherein before the piping is arranged, all the fiber grating monitoring mechanisms are connected to the fiber grating demodulator through the optical cable, and when no liquid is introduced, the wavelengths of the fiber grating monitoring mechanisms corresponding to all the sedimentation instruments are respectively measured and used as initial wavelength data of the fiber grating monitoring mechanisms.
9. The sedimentation monitoring method according to claim 7, wherein after the piping is arranged, the liquid in the liquid level tank gradually fills the cavity, and after the air in the cavity is completely discharged and the liquid fills the whole cavity, the end of the cavity is blocked.
10. The sedimentation monitoring method according to claim 7, wherein the liquid level in the liquid level tank is higher than the level of the pipeline, the reference point sedimentation meter and the point sedimentation meter to be measured.
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