CN110319862B - A helical structure device for distributed optical fiber sensing among civil engineering - Google Patents
A helical structure device for distributed optical fiber sensing among civil engineering Download PDFInfo
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- CN110319862B CN110319862B CN201910623461.7A CN201910623461A CN110319862B CN 110319862 B CN110319862 B CN 110319862B CN 201910623461 A CN201910623461 A CN 201910623461A CN 110319862 B CN110319862 B CN 110319862B
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- 238000012544 monitoring process Methods 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 8
- 239000002689 soil Substances 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 238000001228 spectrum Methods 0.000 claims description 4
- 238000004804 winding Methods 0.000 claims description 4
- 238000009933 burial Methods 0.000 claims description 2
- 239000003822 epoxy resin Substances 0.000 claims description 2
- 239000003292 glue Substances 0.000 claims description 2
- 229920000647 polyepoxide Polymers 0.000 claims description 2
- 230000003595 spectral effect Effects 0.000 claims description 2
- 230000001360 synchronised effect Effects 0.000 claims description 2
- 230000008602 contraction Effects 0.000 claims 1
- 238000005259 measurement Methods 0.000 abstract description 4
- 238000010276 construction Methods 0.000 description 4
- 238000012423 maintenance Methods 0.000 description 3
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- 238000010586 diagram Methods 0.000 description 2
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- 230000000717 retained effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
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- ZZUFCTLCJUWOSV-UHFFFAOYSA-N furosemide Chemical compound C1=C(Cl)C(S(=O)(=O)N)=CC(C(O)=O)=C1NCC1=CC=CO1 ZZUFCTLCJUWOSV-UHFFFAOYSA-N 0.000 description 1
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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
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
- G02B6/4401—Optical cables
- G02B6/4429—Means specially adapted for strengthening or protecting the cables
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Abstract
The invention discloses a spiral structure device for distributed optical fiber sensing in civil engineering, which consists of an inner pipe body, an outer pipe body, a positioning fixture, a protecting cover, a fixture and a protecting sleeve which are nested and combined. The sensing optical cable is wound into a spiral structure on the surface of the inner tube body, and then is embedded into the outer tube body, and the tube body is packaged by the protecting cover and the protecting sleeve. The optical cable is clamped at the two ends of the tube body by tightly attaching the clamp to the outer side of the protecting cover, so that the optical cable in the tube body obtains a prestress. When large-scale sensing is carried out, a plurality of identical pipe bodies are connected in series at certain intervals by using an optical cable and are embedded into an object to be measured, and strain measurement at each position can be realized through distributed optical fiber strain sensing equipment. The device converts the tensile force that originally vertically produced of sensing optical cable into spiral tightening force to on expanding the whole optical cable in the body on average with the meeting an emergency on the short distance, both effectively increased sensing optical cable's range, also improved measurement accuracy.
Description
Technical Field
The invention belongs to the field of civil engineering monitoring and distributed optical fiber sensing, and particularly relates to a spiral structure device for distributed optical fiber sensing in civil engineering.
Background
In large civil engineering such as highway maintenance, slope monitoring, and various projects such as tunnels, bridges, hydro hubs and the like, due to the action of external loads or environments, the structures can deform to different degrees, namely, large-range or integral uniform and non-uniform deformation, and the deformation is not easy to observe by naked eyes in the initial stage; secondly, local deformation mainly comprising various cracks, wherein the width of the cracks is as small as a few microns and as large as a few tens of centimeters, and the cracks are distributed unevenly. Corresponding methods and means are needed to be adopted for monitoring in engineering, however, due to large difference of engineering environment and complex engineering conditions, monitoring personnel cannot frequently go to the site for monitoring, and the traditional observation means is backward, the information collection amount is seriously insufficient and lagged, and even disasters cannot be predicted.
At present, the distributed optical fiber strain sensing technology is gradually applied to civil engineering monitoring, and the optical fiber is used as a transmission medium on one hand and a sensor on the other hand, so that the parameter change condition of each point on the optical fiber can be accurately positioned. The back brillouin scattering light is sensitive to temperature and strain changes, brillouin frequency shift and temperature and strain are in a linear relation, and the brillouin scattering light is very suitable for real-time monitoring of temperature and strain at any position in a long distance and a large range. At present, optical fibers are laid in two ways, one way is a comprehensive adhesion way, the optical fibers are straightened and then completely adhered to a structure, when a structure body is locally deformed greatly, an optical cable can be directly broken, the maximum strain borne by the optical fibers is 1 to 2 percent, and the maximum strain range in the actual engineering environment cannot be matched; the other is a fixed-point adhesion mode, the optical fiber is fixed on a structure at intervals after being straightened, the fixed-point adhesion mode cannot provide good protection for the optical cable, the optical cable is easy to break in the operation and maintenance period during and after construction, and the space fineness for monitoring the structure and the space resolution of a sensing system are difficult to be considered simultaneously.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the problems, the invention provides a spiral structure device for distributed optical fiber sensing in civil engineering, which is characterized in that the structure of a sensing optical cable is designed by applying a spiral winding mode, the original longitudinal tension of the sensing optical cable is converted into spiral tightening force, the strain on a short distance is averagely expanded to the whole optical cable in a tube body, the range of the sensing optical cable is effectively increased, and the measurement precision is also improved.
The technical scheme is as follows: in order to realize the purpose of the invention, the technical scheme adopted by the invention is as follows: a spiral structure device for distributed optical fiber sensing in civil engineering comprises a sensing optical cable, an inner pipe body and an outer pipe body which are combined in a nested mode, a protecting cover, a clamp and a protecting sleeve. A spiral sliding track is preset on the surface of the inner tube body and used for installing a sensing optical cable.
The sensing optical cable is wound on the surface of the inner tube body to form a spiral structure, the inner tube body wound with the sensing optical cable is embedded into the outer tube body, the length of the inner tube body and the length of the outer tube body can be designed according to the requirement in practical engineering, the lengths are kept consistent, and the diameter of the inner tube body is smaller than that of the outer tube body. The two ends of the outer tube body are respectively covered by the protecting covers, and the purpose is to isolate the inner space of the outer tube body. Protecting cover center below is equipped with the perforation, and the sensing optical cable outside that is located interior body both ends adds respectively is equipped with protective case, and protective case wears out the protecting cover at outer body both ends through the protecting cover hole for the sensing optical cable of wearing out the outer body is protected.
Preferably, the protective sleeve is a rubber tube; the length of the protective sleeve is 5-10 cm.
Preferably, the inner pipe body is a ppr pipe, and the outer pipe body is a pvc pipe; the diameter of the inner pipe body is 2-3cm smaller than that of the outer pipe body.
The spiral sliding track is preset on the surface of the inner pipe body and used for installing the sensing optical cable, and the method comprises the following two modes: the sensing optical cable can freely shuttle in the positioning clamps but cannot transversely slide on the surface of the inner tube body by fixing the positioning clamps with certain sizes on the surface of the inner tube body; or, a smooth spiral groove is polished on the surface of the inner tube body, so that the sensing optical cable can only slide along the preset direction of the groove when being stretched and cannot transversely slide along the surface of the inner tube body.
In large-scale civil engineering such as highway maintenance, slope monitoring, and tunnel, bridge, hydro-junction engineering, the structure can deform to different degrees due to the action of external load or environment, so that the structure needs to be monitored in engineering, and the structure is the measured object. In practice, the device of the present invention is mounted in a structure.
According to the stress conduction mode, the optical cable prestress setting scheme of the device can be two, which respectively correspond to two different outer tube end connection modes:
the protective cover and the protective sleeve at two ends of the outer tube body are not fixed at the protective cover hole, the protective sleeve and the sensing optical cable inside the protective sleeve are clamped by tightly attaching the clamp to the outer side of the protective cover respectively, and the sensing optical cable, the protective sleeve and the clamp can be synchronously stretched outside the outer tube body but cannot be shrunk inside the outer tube body, so that a prestress can be applied to the sensing optical cable inside the outer tube body. When a plurality of the devices are connected in series on one sensing optical cable for use, the strain of the structural body is transmitted to the sensing optical cable in the outer pipe body of two adjacent devices.
Secondly, a protecting cover at one end of the outer tube body and the protecting sleeve are fixed together at a protecting cover hole, and then the protecting sleeve and the sensing optical cable inside the protecting sleeve are clamped by tightly clinging to the outer side of the protecting cover by using a clamp, so that the sensing optical cable and the outer tube body do not slide relatively; the protecting cover and the protecting sleeve at the other end of the outer pipe body are not fixed at the protecting cover hole, the clamp is used for tightly clinging to the outer side of the protecting cover to clamp the protecting sleeve and the sensing optical cable inside the protecting sleeve, the sensing optical cable, the protecting sleeve and the clamp can be synchronously stretched outside the outer pipe body, but cannot be shrunk inside the outer pipe body, and therefore prestress can be applied to the sensing optical cable inside the outer pipe body. In the manufacturing process, the clamp for reserving the unfixed end of the protective sleeve can prevent the sensing optical cable from loosening on the spiral track on the surface of the inner tube body. In the construction process, because the outer pipe body and the structural body are fixed together, the clamp of the unfixed end of the protective sleeve can be removed or retained. After the clamp at the unfixed end of the protective sleeve is removed, the sensing optical cable can be stretched towards the outside of the outer tube body or contracted towards the inside of the outer tube body according to the deformation direction of the structure body, so that the strain in different directions can be measured; after the clamp at the unfixed end of the protective sleeve is reserved, only the strain stretching outwards the outer tube body can be measured, but the integrity of the inner structure of the outer tube body is ensured. When a plurality of the devices are connected in series on one sensing optical cable for use, the strain of the structural body is only transmitted to the sensing optical cable in the outer pipe body of the corresponding device.
A plurality of identical inventive devices may be connected in series on one sensing cable. The number of turns of the inner tube body surface sensing optical cable can be set according to actual requirements. The length, the diameter and the pipe wall thickness of each section of pipe body can be adjusted according to the required measuring range, the spatial resolution and the engineering requirements, and the lengths of all the series pipe bodies can be the same or different.
Has the advantages that: compared with the prior art, the technical scheme of the invention has the following beneficial technical effects:
(1) according to the invention, each section of the tube body is adopted to protect the sensing optical cable, and the small section of the optical cable penetrating out between the tube body and the tube body is protected by the protective sleeve, so that the risk that the optical cable is directly exposed in the structure body and is easy to damage in actual engineering is avoided.
(2) The invention enlarges the original tension-strain bearing range of the optical cable by a plurality of times through the spiral winding structure, thereby greatly improving the measuring range and the service life of the sensing optical cable in the actual engineering.
(3) According to the invention, through two stress conduction modes, when tension is generated, only one section of tube body or the optical cable in two adjacent sections of tube body generates strain, so that the strain of the measured object in a very short distance is conducted to a longer length of the sensing optical cable, and the measurement precision of a strain event is improved.
(4) The invention can conveniently and reliably maintain the prestress of the optical cable during construction.
(5) The invention has simple structure and low manufacturing cost.
Drawings
FIG. 1 is a schematic view of the apparatus of the present invention;
FIG. 2 is a partial block diagram of the apparatus of the present invention;
FIG. 3 is a schematic view of an embodiment of the apparatus of the present invention;
FIG. 4 is a schematic view of a second embodiment of the apparatus of the present invention;
FIG. 5 is a pictorial view of the interior space of the apparatus of the present invention;
FIG. 6 is a schematic diagram of the series use of the apparatus of the present invention;
FIG. 7 is a graph showing the results of field experiments according to the present invention;
FIG. 8 is a partial enlarged view of the results of the field experiments of the present invention;
the optical fiber sensor comprises a first protective sleeve, a first clamp, a first 3-perforated hole, a first 4-protecting cover, a first 5-outer tube, a second 6-inner tube, a 7-positioning clamp, a 8-sensing optical cable, a second 9-protecting cover, a second 10-perforated hole, a second 11-clamp and a second 12-protective sleeve.
Detailed Description
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
The description will be given by taking the slope monitoring in the actual civil engineering as an example. The frame beam on the side slope has the advantages of firm combination with the side slope and convenience for gridding arrangement, so that the frame beam can be an effective support for arranging the optical cable. However, the frame beam is an integral solid structure, and when the optical cable is directly poured into the frame beam, the maximum strain borne by the optical fiber is generally between 1% and 2%, and beyond this limit, the optical cable is very easy to break.
The invention discloses a spiral structure device for distributed optical fiber sensing in civil engineering, which comprises an inner pipe body 6, an outer pipe body 5, a first protecting cover 4, a second protecting cover 9, a positioning clamp 7, a first protecting sleeve 1, a second protecting sleeve 12, a first clamp 2, a second clamp 11 and a sensing optical cable 8, as shown in figure 1. The diameter of the inner pipe body is 40mm, and the length of the inner pipe body is 0.5 m; the diameter of the outer tube is 59mm, and the length of the outer tube is 0.5 m. The first protective sleeve 1 and the second protective sleeve 12 are rubber tubes. The inner pipe body 6 is a ppr pipe, and the outer pipe body 5 is a pvc pipe.
The sensing optical cable 8 is wound on the surface of the inner tube body 6 to form a spiral structure, the inner tube body 6 wound with the sensing optical cable 8 is embedded into the outer tube body 5, and two ends of the outer tube body 5 are respectively covered by the first protective cover 4 and the second protective cover 9, so that the inner space of the outer tube body 5 is isolated. Protecting cover one 4, two 9 center undersets of protecting cover are equipped with and perforate one 3, perforate two 10, and the sensing optical cable 8 that is located 6 both ends of interior body installs protective case one 1, protective case two 12 additional outside, and protective case one 1, protective case two 12 wear out protecting cover one 4, protecting cover two 9 at outer body 5 both ends through perforating one 3, two 10 respectively for the sensing optical cable 8 of outer body 5 is worn out in the protection.
A spiral sliding track is preset for the sensing optical cable 8 by fixing 9 positioning clamps 7 on the surface of the inner tube body 6. Each positioning fixture 7 has a length of 2cm and a height of 8mm, so that the sensing optical cable 8 can freely shuttle in the positioning fixture 7 but cannot transversely slide on the surface of the inner tube body 6. The sensing optical cable 8 passes through the positioning fixture 7 and is spirally wound on the surface of the inner tube body 6, and 9 coils are wound together, so that the length of the wound sensing optical cable 8 is 3 times of that of the inner tube body 6.
According to the stress conduction mode, the optical cable prestress setting scheme of the device can be two, which respectively correspond to two different outer tube end connection modes, and the partial enlarged view of the outer tube end is shown in fig. 2 and is implemented as follows:
in the first embodiment, the first protective sleeve 1, the second protective sleeve 12, the first protective cover 4 and the second protective cover 9 are not fixed at the first through hole 3 and the second through hole 10, and the first protective sleeve 1, the second protective sleeve 12 and the sensing optical cable 8 inside the protective sleeve are clamped outside the first protective sleeve 4 and the second protective cover 9 respectively by using the first clamp 2 and the second clamp 11; the sensing optical cable 8, the first protective sleeve 1 and the first clamp 2 can be synchronously stretched out of the outer tube body 5 but cannot be shrunk into the outer tube body 5, and the sensing optical cable 8, the second protective sleeve 12 and the second clamp 11 can be synchronously stretched out of the outer tube body 5 but cannot be shrunk into the outer tube body 5, so that a prestress can be applied to the sensing optical cable 8 in the outer tube body 5.
When multiple devices of this embodiment are used in series on a single sensor cable, as shown in fig. 3, assuming a strain event point C exists between any two adjacent segments of device A, B, the strain event is a slope tensile deformation event, and due to the simultaneous mobility of the clamps, protective sleeves, and sensor cable at both ends of device A, B, the slope strain will be and will only be transmitted to the sensor cables in devices a and B.
In the second embodiment, the second protective sleeve 12 penetrates out of the second through hole 10 of the second protective cover 9 at one end of the outer tube 5, the second protective cover 9 and the second protective sleeve 12 are fixed by epoxy resin glue at the second through hole 10, and then the second clamp 11 is tightly attached to the second protective cover 9 to clamp the second protective sleeve 12 and the sensing optical cable 8 inside the second protective sleeve, so that the sensing optical cable 8 and the outer tube 5 do not slide relatively. Protecting cover one 4 and protective sleeve one 1 are not fixed in perforation one 3 department, use anchor clamps one 2 to hug closely the protecting cover one 4 outside and clip protective sleeve one 1 and inside sensing optical cable 8, protective sleeve one 1 and anchor clamps one 2 can be synchronous outside body 5 is outer tensile, nevertheless can't contract in outside body 5, just so can exert a prestressing force for the inside sensing optical cable 8 of outer body 5. During the manufacturing process, the first retaining clamp 2 can prevent the sensing optical cable 8 from loosening on the spiral track on the surface of the inner tube body 6. In the construction process, the first clamp 2 can be removed or retained because the outer pipe body 5 and the side slope frame beam are poured together. After the first clamp 2 is removed, the sensing optical cable 8 can be stretched out of the outer tube body 5 or contracted into the outer tube body 5 according to the deformation direction of the frame beam, and strain in different directions can be measured; after the first clamp 2 is reserved, only the strain stretching outwards the outer pipe body 5 can be measured, but the integrity of the structure in the outer pipe body 5 is ensured.
As shown in fig. 4, when a plurality of the same devices of this embodiment are connected in series on a sensing cable, two segments A, B connected adjacently are provided, and the sensing cable at the right end of the device A, B is fixed, i.e. the sensing cable and the outer tube body do not slide relatively; the sensing optical cable, the protective sleeve and the clamp at the left end of the device A, B can synchronously move, namely, the sensing optical cable, the protective sleeve and the clamp can synchronously stretch outwards but cannot contract inwards; assuming that there is a strain event point C between the devices A, B, the strain event is a slope tensile deformation event, and since the sensing cable at the right end of the device a and the outer tube do not slide relative to each other, the clamp, the protection sleeve and the sensing cable at the left end of the device B can move synchronously, the slope strain will be and will only be transmitted to the sensing cable in the device B.
Fig. 5 shows the structure of the inner space of the tube body. FIG. 6 shows a helical structure device E made according to example IIa、Eb、EcAnd the sensing optical cables at the right end of each section of device are fixed and the sensing optical cables at the left end can move freely.
A highway slope monitoring method based on a spiral structure device of distributed optical fiber sensing comprises the following steps:
(1) according to the second embodiment, a three-section helical structure device E connected in series on one sensing optical cable is manufactureda、Eb、Ec；
(2) Connecting the three sections of the spiral structure devices connected in series into a BOTDR system through an optical cable connecting box;
(3) selecting a section of slope body and selecting a position on the section of slope body, and arranging a groove with the length of l and the depth of h at the position; in the embodiment of the method, the length L of the slope body is 1000m, the selected position is 500m of the slope body, the length L of the slot is 2m, and the depth h of the slot is 30 cm;
(4) placing three sections of spiral structure devices connected in series in a groove, filling soil, burying and compacting;
(5) in the burial of EcApplying external load to the soil body of the segment device to displace the surface of the soil body and to Eb、EcThe sensing optical cable between the section devices generates tension and the stress is transmitted to EcStrain is generated on the optical fiber inside the sensing optical cable in the section device;
(6) the strain in the step (5) can change the refractive index of the optical fiber through an elasto-optical effect, and can also change the sound velocity in the optical fiber through the Young modulus, the Poisson ratio and the optical fiber density; sound velocity v in optical fiberaIs represented as follows:
wherein Y is Young's modulus, κ is Poisson's ratio, and ρ is the density of the optical fiber;
obtaining Brillouin spectrum frequency shift v in optical fiber according to sound velocity in optical fiberBNamely:
wherein n is the refractive index of the optical fiber, v is the frequency of the pump light, and c is the speed of light in vacuum;
by the step (5) of said EcOffset quantity delta v of Brillouin spectrum frequency shift in optical fiber of segment deviceBAnd calculating a strain value epsilon generated by the optical fiber in the device, wherein the formula is as follows:
△vB＝(△nε+△Yε+△κε+△ρε)vB(T0,0)ε
wherein v isB(T00) is the Brillouin spectral frequency shift under the condition of no applied strainAmount, T0Represents normal temperature, 0 represents no strain; delta Yε、△κε、△ρε、△nεRespectively performing Taylor expansion first-order terms on Young modulus Y, Poisson ratio kappa, density rho of the optical fiber and refractive index n of the optical fiber at the position of epsilon-0; and finally, obtaining the strain state of the slope body where the external load event occurs by inversion according to the strain value epsilon.
Fig. 7 and 8 show the result of the test using the above test method by the sensing optical cable device designed according to the second embodiment of the present invention, and it is obvious that an external load is generated at 500 m.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (12)
1. A helical structured device for distributed optical fiber sensing in civil engineering is characterized in that: the device comprises an inner tube body (6), an outer tube body (5), a first protective cover (4), a second protective cover (9), a first protective sleeve (1), a second protective sleeve (12), a first clamp (2), a second clamp (11) and a sensing optical cable (8); the lengths of the inner pipe body and the outer pipe body are kept consistent, and the diameter of the inner pipe body (6) is smaller than that of the outer pipe body (5); a spiral sliding track is preset on the surface of the inner tube body (6) and used for installing a sensing optical cable (8); the sensing optical cable (8) is wound on the surface of the inner tube body (6) to form a spiral structure, the inner tube body (6) wound with the sensing optical cable (8) is embedded into the outer tube body (5), and two ends of the outer tube body (5) are respectively covered by a first protective cover (4) and a second protective cover (9); a first through hole (3) and a second through hole (10) are arranged below the centers of the first protective cover (4) and the second protective cover (9); a first protective sleeve (1) and a second protective sleeve (12) are additionally arranged outside the sensing optical cable (8) positioned at the two ends of the inner pipe body (6), and the first protective sleeve (1) and the second protective sleeve (12) respectively penetrate out of the first protective cover (4) and the second protective cover (9) at the two ends of the outer pipe body (5) through the first perforation (3) and the second perforation (10);
the second protecting cover (9) and the second protecting sleeve (12) are fixed at the second through hole (10), and the second protecting cover (12) and the sensing optical cable (8) inside the second protecting cover (9) are clamped by tightly attaching a second clamp (11) to the outer side of the second protecting cover (9), so that the sensing optical cable (8) and the outer pipe body (5) do not slide relatively; protecting cover one (4) and protective sleeve one (1) are not fixed in perforation one (3) department, use anchor clamps one (2) to hug closely the protecting cover one (4) outside and clip protective sleeve one (1) and inside sensing optical cable (8), protective sleeve one (1) and anchor clamps one (2) synchronous outside body (5) are tensile, but unable outside body (5) internal contraction.
2. The helical structural device for distributed optical fiber sensing in civil engineering as claimed in claim 1, wherein: a spiral sliding track is preset on the surface of the inner tube body (6), and a spiral sliding track is preset for the sensing optical cable (8) by fixing a plurality of positioning clamps (7) on the surface of the inner tube body (6); each positioning clamp (7) enables the sensing optical cable (8) to freely shuttle in the positioning clamp (7) but cannot transversely slide on the surface of the inner tube body (6); the sensing optical cable (8) passes through the positioning fixture (7) and is spirally wound on the surface of the inner tube body (6).
3. The helical structural device for distributed optical fiber sensing in civil engineering as claimed in claim 1, wherein: the spiral sliding track is preset on the surface of the inner pipe body (6), namely a smooth spiral groove is polished on the surface of the inner pipe body (6), so that the sensing optical cable (8) can only slide along the preset direction of the groove when being stretched and cannot transversely slide along the surface of the inner pipe body (6).
4. A helical structure device for distributed optical fiber sensing in civil engineering works according to any one of claims 1 to 3, wherein: the protective sleeve I (1) and the protective sleeve II (12) are rubber tubes; the inner pipe body (6) is a ppr pipe, and the outer pipe body (5) is a pvc pipe; and the second protective cover (9) and the second protective sleeve (12) are fixed by epoxy resin glue at the second through hole (10).
5. A helical structure device for distributed optical fiber sensing in civil engineering works according to any one of claims 1 to 3, wherein: when the first clamp (2) is removed, the sensing optical cable (8) stretches outwards the outer pipe body (5) or contracts inwards the outer pipe body (5) according to different deformation directions, and strain in different directions is measured.
6. A helical structure device for distributed optical fiber sensing in civil engineering works according to any one of claims 1 to 3, wherein: a plurality of same devices are connected in series on one sensing optical cable; the number of winding turns of the surface sensing optical cable (8) of the inner tube body (6) is set according to actual requirements; the length, the diameter and the pipe wall thickness of each section of pipe body are adjusted according to the required measuring range, the spatial resolution and the engineering requirement.
7. A helical structured device for distributed optical fiber sensing in civil engineering is characterized in that: the device comprises an inner tube body (6), an outer tube body (5), a first protective cover (4), a second protective cover (9), a first protective sleeve (1), a second protective sleeve (12), a first clamp (2), a second clamp (11) and a sensing optical cable (8); the lengths of the inner pipe body and the outer pipe body are kept consistent, and the diameter of the inner pipe body (6) is smaller than that of the outer pipe body (5); a spiral sliding track is preset on the surface of the inner tube body (6) and used for installing a sensing optical cable (8); the sensing optical cable (8) is wound on the surface of the inner tube body (6) to form a spiral structure, the inner tube body (6) wound with the sensing optical cable (8) is embedded into the outer tube body (5), and two ends of the outer tube body (5) are respectively covered by a first protective cover (4) and a second protective cover (9); a first through hole (3) and a second through hole (10) are arranged below the centers of the first protective cover (4) and the second protective cover (9); a first protective sleeve (1) and a second protective sleeve (12) are additionally arranged outside the sensing optical cable (8) positioned at the two ends of the inner pipe body (6), and the first protective sleeve (1) and the second protective sleeve (12) respectively penetrate out of the first protective cover (4) and the second protective cover (9) at the two ends of the outer pipe body (5) through the first perforation (3) and the second perforation (10);
the protective sleeve I (1), the protective sleeve II (12), the protective cover I (4) and the protective cover II (9) are not fixed at the through hole I (3) and the through hole II (10), the protective sleeve I (1), the protective sleeve II (12) and a sensing optical cable (8) inside the protective sleeve I (1), the protective sleeve II (12) and the protective cover II (9) are clamped outside the protective cover I (4) and the protective cover II (9) respectively by using a clamp I (2) and a clamp II (11), and the sensing optical cable (8), the protective sleeve I (1) and the clamp I (2) synchronously stretch outwards the outer pipe body (5) but cannot shrink inwards the outer pipe body (5); the sensing optical cable (8), the second protective sleeve (12) and the second clamp (11) are synchronously stretched out of the outer tube body (5) but cannot be retracted into the outer tube body (5).
8. The helical structural device for distributed optical fiber sensing in civil engineering as claimed in claim 7, wherein: a spiral sliding track is preset on the surface of the inner tube body (6), and a spiral sliding track is preset for the sensing optical cable (8) by fixing a plurality of positioning clamps (7) on the surface of the inner tube body (6); each positioning clamp (7) enables the sensing optical cable (8) to freely shuttle in the positioning clamp (7) but cannot transversely slide on the surface of the inner tube body (6); the sensing optical cable (8) passes through the positioning fixture (7) and is spirally wound on the surface of the inner tube body (6).
9. The helical structural device for distributed optical fiber sensing in civil engineering as claimed in claim 7, wherein: the spiral sliding track is preset on the surface of the inner pipe body (6), namely a smooth spiral groove is polished on the surface of the inner pipe body (6), so that the sensing optical cable (8) can only slide along the preset direction of the groove when being stretched and cannot transversely slide along the surface of the inner pipe body (6).
10. A helical structure device for distributed optical fiber sensing in civil engineering works according to any one of claims 7 to 9, wherein: the protective sleeve I (1) and the protective sleeve II (12) are rubber tubes; the inner pipe body (6) is a ppr pipe, and the outer pipe body (5) is a pvc pipe.
11. A helical structure device for distributed optical fiber sensing in civil engineering works according to any one of claims 7 to 9, wherein: a plurality of same devices are connected in series on one sensing optical cable; the number of winding turns of the surface sensing optical cable (8) of the inner tube body (6) is set according to actual requirements; the length, the diameter and the pipe wall thickness of each section of pipe body are adjusted according to the required measuring range, the spatial resolution and the engineering requirement.
12. A method for monitoring a highway slope, implemented according to any one of claims 1-3, characterized in that: the method comprises the following steps:
(1) device E for manufacturing three-section spiral structure connected in series on sensing optical cablea、Eb、Ec；
(2) Connecting the three sections of the spiral structure devices connected in series into a BOTDR system through an optical cable connecting box;
(3) selecting a section of slope body and selecting a position on the section of slope body, and arranging a groove with the length of l and the depth of h at the position;
(4) placing three sections of spiral structure devices connected in series in a groove, filling soil, burying and compacting;
(5) in the burial of EcApplying external load to the soil body of the segment device to displace the surface of the soil body and to Eb、EcThe sensing optical cable between the section devices generates tension and the stress is transmitted to EcStrain is generated on the optical fiber inside the sensing optical cable in the section device;
(6) changing the sound velocity in the optical fiber through the strain according to the Young modulus, the Poisson ratio and the optical fiber density; sound velocity v in optical fiberaIs represented as follows:
wherein Y is Young's modulus, κ is Poisson's ratio, and ρ is the density of the optical fiber;
obtaining Brillouin spectrum frequency shift v in optical fiber according to sound velocity in optical fiberBNamely:
wherein n is the refractive index of the optical fiber, v is the frequency of the pump light, and c is the speed of light in vacuum;
by the step (5) of said EcOffset quantity delta v of Brillouin spectrum frequency shift in optical fiber of segment deviceBAnd calculating a strain value epsilon generated by the optical fiber in the device, wherein the formula is as follows:
△vB＝(△nε+△Yε+△κε+△ρε)vB(T0,0)ε
wherein v isB(T00) amount of Brillouin spectral frequency shift under the condition of no strain, T0Represents normal temperature, 0 represents no strain; delta Yε、△κε、△ρε、△nεRespectively performing Taylor expansion first-order terms on Young modulus Y, Poisson ratio kappa, density rho of the optical fiber and refractive index n of the optical fiber at the position of epsilon-0; and finally, obtaining the strain state of the slope body where the external load event occurs by inversion according to the strain value epsilon.
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| CN111637845B (en) * | 2020-05-26 | 2022-01-04 | 河海大学 | Distributed optical fiber torsion measuring device and method |
| CN111637994B (en) * | 2020-05-27 | 2021-08-03 | 南京大学 | Distributed optical fiber sensing device, system and method for measuring stress of power transmission cable |
| CN112414293B (en) * | 2020-10-27 | 2022-04-29 | 西安电子科技大学 | Strain detection method for conduction cooling high-temperature superconducting cable |
| CN115711634B (en) * | 2022-11-16 | 2023-09-19 | 江苏中天科技股份有限公司 | Sensitivity-enhanced sensing optical cable |
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