阅读说明：本技术 一种分布式光纤扭转测量装置、方法 (Distributed optical fiber torsion measuring device and method ) 是由 武鑫 郑东健 刘永涛 晏周 于 2020-05-26 设计创作，主要内容包括：本发明公开了一种分布式光纤扭转测量装置、方法,属于光纤测量技术领域,包括感应棒、传感光纤、光纤数据采集器、分析显示系统,所述感应棒上固连有沿着测斜管导槽上下运动的传动装置,所述传感光纤呈螺旋型分布于所述感应棒的外周面,所述传感光纤的两个自由端均通过光纤耦合器与所述光纤数据采集器连接,所述光纤数据采集器与所述分析显示系统连接。能够实现测斜管导槽扭转角及扭转方向的测量,利用光纤传感单元电绝缘性、化学稳定性以及较好的抗电磁干扰能力,能够避免复杂环境的影响,具有操作简便、易维修的优点,且在保证监测精度的同时降低测扭探头的造价。(The invention discloses a distributed optical fiber torsion measuring device and a distributed optical fiber torsion measuring method, which belong to the technical field of optical fiber measurement and comprise an induction rod, sensing optical fibers, an optical fiber data collector and an analysis display system, wherein a transmission device moving up and down along a guide groove of an inclinometer pipe is fixedly connected to the induction rod, the sensing optical fibers are spirally distributed on the peripheral surface of the induction rod, two free ends of the sensing optical fibers are connected with the optical fiber data collector through optical fiber couplers, and the optical fiber data collector is connected with the analysis display system. The measuring device can realize the measurement of the torsion angle and the torsion direction of the inclinometer pipe guide groove, can avoid the influence of a complex environment by utilizing the electrical insulation property, the chemical stability and the better anti-electromagnetic interference capability of the optical fiber sensing unit, has the advantages of simple and convenient operation and easy maintenance, and reduces the manufacturing cost of the torsion measuring probe while ensuring the monitoring precision.)

1. The utility model provides a measuring device is twistd reverse to distributing type optic fibre, its characterized in that, includes response stick, sensing optical fibre, optic fibre data collection station, analysis display system, the last transmission along deviational survey pipe guide slot up-and-down motion that links firmly of response stick, sensing optical fibre be the spiral type distribute in the outer peripheral face of response stick, two free ends of sensing optical fibre all through optical fiber coupler with optic fibre data collection station connects, optic fibre data collection station with analysis display system connects.

2. The distributed fiber optic twist measurement device of claim 1, wherein said sensing rod has a notch in its outer circumference, said sensing fiber being located in said notch.

3. The distributed fiber optic twist measurement device according to claim 2, wherein the sensing fiber is bonded in the groove on the outer circumferential surface of the sensing rod by a fastening glue.

4. A distributed fibre optic torsion measurement apparatus according to claim 1 wherein the sensing fibre is a tight-buffered single mode fibre.

5. The distributed fiber optic twist measurement device of claim 1, wherein said sensing rod is made of polyurethane material.

6. The distributed optical fiber torsion measuring device according to claim 1, wherein the transmission device comprises two sleeves fixedly sleeved at two ends of the sensing rod respectively, and guide wheel devices for rolling in cooperation with the guide grooves of the inclinometer pipes are fixedly connected to two opposite sides of the sleeves respectively.

7. The distributed optical fiber torsion measuring device according to claim 6, wherein a support rod is fixedly connected to the bottom end sleeve of the sensing rod, a rotating ring is fixedly connected to an end of the support rod away from the bottom end sleeve of the sensing rod, an annular guide groove is formed in the bottom of the top end sleeve of the sensing rod, and the rotating ring is rotatably located in the annular guide groove.

8. The distributed optical fiber torsion measuring apparatus according to claim 7, wherein the supporting rod is a telescopic rod, and a telescopic end of the telescopic rod is fixedly connected with the rotating ring.

9. A distributed fiber optic twist measurement method, comprising:

the sensing optical fiber is spirally distributed on the peripheral surface of the sensing rod, a transmission device is fixedly connected on the sensing rod, and the sensing rod is placed to the bottom in the inclinometer pipe along the guide groove of the inclinometer pipe through the transmission device;

the sensing optical fiber of the sensing rod is accessed into an optical fiber data acquisition unit through a coupler, short pulse light and continuous detection light are injected into two ends of the sensing optical fiber to enable the sensing optical fiber to generate Brillouin scattering, and strain measurement values of various points of the optical fiber are obtained according to the corresponding relation between the frequency shift and the strain of the Brillouin scattering light;

taking the length of the induction rod as a lifting unit to lift the induction rod in the inclinometer, and simultaneously recording the optical fiber strain information of each section of the inclinometer along the way;

according to the strain measurement data of the optical fiber data collector, the optical fiber line strain caused by the torsion of the inclinometer is solved, and according to the change of the geometric relation of the surface optical fiber in the torsion process, the relative torsion angle and the torsion direction of each part of the inclinometer along the way are calculated.

10. A distributed optical fiber torsion measuring method according to claim 9, wherein the relative torsion angle of each part along the way of the inclinometer is calculated by using formula (1) and formula (2):

in the formula: l is the length of the induction rod; r is the radius of the induction rod; Δ l₁、Δl₂Respectively resolving the positive strain value and the negative strain value of the optical fiber sensing unit to obtain deformation quantities;_j(i) for the strain distribution of the strain-varying section of the optical fibre, D_jAnd p is the spatial resolution of PPP-BOTDA, which is the length of the optical fiber strain variation section.

Technical Field

The invention relates to a distributed optical fiber torsion measuring device and method, and belongs to the technical field of optical fiber measurement.

Background

Inclinometers have been widely used in monitoring internal deformation of soil bodies such as building foundation pits, mountain slopes, earth and rockfill dams, and dam plugs. The inclinometer probe is positioned by depending on the guide groove of the inclinometer pipe, the deformation of a rock-soil body is obtained by measuring the deflection of the embedded inclinometer pipe, and the guide pipe is not only a sensitive pipe for the deformation of the soil body, but also a channel for arranging the inclinometer probe, so that the quality of the inclinometer pipe directly influences the reliability of the measurement result of the inclinometer. In actual engineering, the inclinometer is affected by factors such as external force, installation and manufacturing process, embedding mode and the like, so that the distortion phenomenon generally exists, the measurement azimuth angle error of the inclinometer is caused, and the accuracy of data analysis is affected. The international rock-soil mechanics society rock mechanics suggestion and the national rock mechanics test regulations stipulate that: the torsion angle of each 3 m of the inclinometer pipe is not more than 1 degree, and the total length is not more than 5 degrees. Considering the cost of the instrument, the conduit of the actual engineering is usually made of PVC, ABS and other materials, the stability is poor, the torsion deformation is easy to generate, and the torsion angle is difficult to control in a standard range in the engineering application; for deep hole measurement, the influence of the torsion of the pipe-measuring guide groove on inclination measurement tends to be accumulated, so that a torsion meter is needed to measure the torsion degree of the pipe-measuring guide groove so as to correct the monitoring data of a slightly-twisted part, repair measures such as re-embedding of an inclinometry pipe with serious torsion are needed, and the reliability of a monitoring result is ensured.

At present, a torsion measuring device is usually adopted in engineering to obtain the torsion angle distribution of the whole hole of an inclinometer through a fluxgate or an angular displacement sensor, but the torsion measuring instruments are high in manufacturing cost and easy to break down or damage under severe monitoring conditions such as humidity, and particularly the electromagnetic torsion measuring instruments can normally work under the environment without strong magnetic field interference and ferromagnetic substance influence.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides a distributed optical fiber torsion measuring device and method, which have the advantages of strong environmental adaptability, electromagnetic interference resistance, simplicity and convenience in operation, accurate measurement and low cost of a torsion measuring probe.

In order to achieve the purpose, the invention is realized by adopting the following technical scheme:

in a first aspect, the invention provides a distributed optical fiber torsion measuring device, which comprises an induction rod, a sensing optical fiber, an optical fiber data collector and an analysis display system, wherein the induction rod is fixedly connected with a transmission device which moves up and down along a guide groove of an inclinometer tube, the sensing optical fiber is spirally distributed on the peripheral surface of the induction rod, two free ends of the sensing optical fiber are connected with the optical fiber data collector through optical fiber couplers, and the optical fiber data collector is connected with the analysis display system.

With reference to the first aspect, further, the sensing rod has a notch on an outer circumferential surface thereof, and the sensing fiber is located in the notch.

With reference to the first aspect, further, the sensing optical fiber is bonded in the groove on the outer circumferential surface of the sensing rod by a fastening adhesive.

With reference to the first aspect, further, the sensing fiber is a tight-buffered single-mode fiber.

With reference to the first aspect, further, the sensing rod is made of a polyurethane material.

In combination with the first aspect, further, the transmission device includes two sleeves respectively sleeved at two ends of the sensing rod, and two opposite sides of the sleeves are respectively and fixedly connected with guide wheel devices for rolling in cooperation with the guide grooves of the inclinometer tube.

Combine the first aspect, it is further, the bracing piece has been linked firmly on the sleeve of response stick bottom, the bracing piece is kept away from the telescopic one end of response stick bottom has linked firmly a swivel becket, the telescopic bottom in response stick top has seted up annular guide slot, the swivel becket is rotatable to be located in the annular guide slot.

In combination with the first aspect, further, the support rod is a telescopic rod, and a telescopic end of the telescopic rod is fixedly connected with the rotating ring.

In a second aspect, the present invention provides a distributed optical fiber torsion measurement method, including:

the sensing optical fiber is spirally distributed on the peripheral surface of the sensing rod, a transmission device is fixedly connected on the sensing rod, and the sensing rod is placed to the bottom in the inclinometer pipe along the guide groove of the inclinometer pipe through the transmission device;

the sensing optical fiber of the sensing rod is accessed into an optical fiber data acquisition unit through a coupler, short pulse light and continuous detection light are injected into two ends of the sensing optical fiber to enable the sensing optical fiber to generate Brillouin scattering, and strain measurement values of various points of the optical fiber are obtained according to the corresponding relation between the frequency shift and the strain of the Brillouin scattering light;

taking the length of the induction rod as a lifting unit to lift the induction rod in the inclinometer, and simultaneously recording the optical fiber strain information of each section of the inclinometer along the way;

according to the strain measurement data of the optical fiber data collector, the optical fiber line strain caused by the torsion of the inclinometer is solved, and according to the change of the geometric relation of the surface optical fiber in the torsion process, the relative torsion angle and the torsion direction of each part of the inclinometer along the way are calculated.

With reference to the second aspect, further, the relative torsion angle of each part of the inclinometer along the way is calculated by using formula (1) and formula (2):

in the formula: l is the length of the induction rod; r is the radius of the induction rod; Δ l₁、Δl₂Respectively resolving the positive strain value and the negative strain value of the optical fiber sensing unit to obtain deformation quantities;_j(i) for the strain distribution of the strain-varying section of the optical fibre, D_jAnd p is the spatial resolution of PPP-BOTDA, which is the length of the optical fiber strain variation section.

Compared with the prior art, the distributed optical fiber torsion measuring device and the method provided by the embodiment of the invention have the beneficial effects that: the measuring device can realize the measurement of the torsion angle and the torsion direction of the inclinometer pipe guide groove, can avoid the influence of a complex environment by utilizing the electrical insulation property, the chemical stability and the better anti-electromagnetic interference capability of the optical fiber sensing unit, has the advantages of simple and convenient operation and easy maintenance, and reduces the manufacturing cost of the torsion measuring probe while ensuring the monitoring precision.

Drawings

FIG. 1 is a schematic structural diagram of a distributed optical fiber torsion measuring apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of an induction rod and a sensing optical fiber in FIG. 1;

FIG. 3 is a schematic diagram of the structure of the sensing rod, sensing fiber, sleeve, and idler assembly of FIG. 1;

FIG. 4 is a schematic cross-sectional view of FIG. 3 at A;

FIG. 5 is a cross-sectional view of FIG. 3 at B;

FIG. 6 is a schematic view of an assembly structure of a top sleeve, a rotating ring and a support rod of the induction rod of FIG. 1;

FIG. 7 is a schematic view of the assembly of the bottom sleeve and the support rod of the sensing rod of FIG. 1;

fig. 8 is a schematic structural view of the support rod of fig. 1.

The meaning of the reference numerals: a 1-PPP-BOTDA optical fiber data acquisition unit; 2-sensing optical fiber; 3-distributed optical fiber torsion measuring probe; 31-a sensing bar; 32-sensing optical fiber; 33-a sleeve; 331-an annular guide groove; 34-a support bar; 341-telescoping end; 342-a fixed end; 35-a rotating ring; 36-a guide wheel device; 4-an inclinometer pipe; 5-analysis display system.

Detailed Description

The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

As shown in fig. 1 to 8, the distributed optical fiber torsion measurement apparatus provided according to the embodiment of the present invention includes a distributed optical fiber torsion measurement probe 3, a PPP-BOTDA optical fiber data collector 1, and an analysis display system 5, where the distributed optical fiber torsion measurement probe 3 is connected to the PPP-BOTDA optical fiber data collector 1 through an optical fiber coupler, and the PPP-BOTDA optical fiber data collector 1 is connected to the analysis display system 5.

The Pulse-pre-pumping Brillouin time domain analysis technology (PPP-BOTDA for short) is a distributed optical fiber sensing technology based on Brillouin scattering, which injects short Pulse light and continuous detection light into two ends of an optical fiber to generate Brillouin scattering, then obtains a strain measurement value of each point in the axial direction of the optical fiber according to the corresponding relation between the frequency shift and the strain of the Brillouin scattering light, and increases a section of pre-pumping Pulse wave to excite phonons before the measured Pulse light is emitted by changing the form of the pumping light, thereby realizing the improvement of spatial resolution and measuring precision.

The distributed optical fiber torsion measuring probe 3 comprises a sensing rod 31 with grooves on the surface, a sensing optical fiber 32, a sleeve 33 and a guide wheel device 36, the sensing optical fiber 32 is spirally bonded in the grooves on the surface of the sensing rod 31, the sensing optical fiber 32 is in smooth transition at the lower part of the sensing rod 31, the sleeve 33 and the guide wheel device 36 are fixed at two ends of the sensing rod 31, the length of the distributed optical fiber torsion measuring probe 3 is ensured to be constant in the torsion measuring process, meanwhile, the torsion of the sleeve 33 and the guide wheel device 36 is kept consistent, two ends of the sensing optical fiber 32 are connected into a PPP-BOTDA optical fiber data collector 1, when the inclinometer 4 generates torsional deformation, the strain change of each point line of the optical fiber measured by the PPP-BOTDA optical fiber data collector 1 is utilized, and the relative torsion angle and the torsion direction.

The sensing fiber 32 is preferably a tight-buffered single mode fiber, the sensing fiber 32 is adhered to the groove on the outer circumference of the sensing rod 31 by a fastening glue, and the sensing fiber 32 can be increased in length by welding or fiber flange.

The sensing rod 31 is preferably made of polyurethane material with high oxidation stability, flexibility, resilience, wear resistance and skid resistance.

The bottom end sleeve 33 of the induction rod 31 is fixedly connected with a support rod 34, one end of the support rod 34, which is far away from the bottom end sleeve 33 of the induction rod 31, is fixedly connected with a rotating ring 35, the bottom of the top end sleeve 33 of the induction rod 31 is provided with an annular guide groove 331, and the rotating ring 35 is rotatably positioned in the annular guide groove 331. In order to avoid axial deformation of the sensing rod 31 in the process of torsion measurement, which results in an increase of torsion angle error calculated by optical fiber strain data, the upper end of the supporting rod 34 is provided with a rotating ring 35 inserted into the annular guide groove 331, the sleeve 33 at two ends of the sensing rod 31 is twisted relatively by the torsional deformation of the inclinometer tube 4, the supporting rod 34 can keep the axial length of the sensing rod 31 unchanged in the process of torsion, and meanwhile, the rotating ring 35 at the upper end of the supporting rod can slide relatively with the sleeve 33 at the top end, so as to keep the sleeve 33 and the sensing rod 31 twisted uniformly.

The supporting rod 34 is designed to be a telescopic rod, the telescopic end 341 of the telescopic rod is fixedly connected with the rotating ring 35, the fixed end 342 of the telescopic rod is fixedly connected with the bottom sleeve 33 of the sensing rod 31, the telescopic rod is matched with the sensing rods with different lengths to realize the length adjustment of the distributed optical fiber torsion measuring probe 3, and the torsion measuring device can adapt to the torsion measurement of the inclinometer 4 with different geological conditions, depths and precision requirements.

The invention provides a distributed optical fiber torsion measuring method, which specifically comprises the following steps:

according to the depth and measurement accuracy requirements of a to-be-measured guide pipe, a distributed optical fiber torsion measuring probe 3 with a proper length is selected, namely an induction rod 31 with a groove on the surface, a tight-sleeved single-mode optical fiber with a corresponding length is bonded in the groove of the induction rod 31, a sleeve 33 and a guide wheel device 36 are fixed at two ends of the induction rod 31, and the induction rod is placed to the bottom of an inclinometer pipe 4 along a guide groove of the inclinometer pipe 4.

The sensing optical fiber 32 of the distributed optical fiber torque measuring probe 3 is connected to the PPP-BOTDA optical fiber data acquisition unit 1 through a coupler, and the strain information of each section of the inclinometer along the way is lifted and recorded at intervals equal to the length of the probe.

According to the strain measurement data of the PPP-BOTDA optical fiber data collector 1, calculating the optical fiber line strain caused by the torsion of the inclinometer 4, and calculating the relative torsion angle and the torsion direction of each part of the inclinometer 4 along the way, thereby giving the distribution of the full hole torsion angle of the inclinometer 4.

If influenced by the monitoring condition, the length of the sensing optical fiber 32 can be increased by adopting an optical fiber flange, or a plurality of sensing rods 31 are prefabricated, so that the sensing rods 31 with faults can be replaced in time.

In the torsion measuring process, the torsion of the distributed optical fiber torsion measuring probe 3 enables the sensing optical fiber 32 with the surface arranged in a spiral distribution mode to generate strain change, wherein the sensing optical fiber 32 wound in the torsion direction can generate positive strain, otherwise, the sensing optical fiber is negative strain, therefore, the torsion direction can be determined by the positive and negative strain values of the sensing optical fiber 32 at each point, and meanwhile, according to the change of the geometrical relation of the surface optical fiber in the torsion process of the distributed optical fiber torsion measuring probe 3, the relative torsion angle theta of the inclinometer 4 at the position can be calculated as follows:

in the formula: l is the length of the induction rod; r is the radius of the induction rod; Δ l₁、Δl₂And respectively calculating the deformation of the optical fiber sensing unit according to the positive strain value and the negative strain value.

Under normal conditions, when the inclinometer 4 is not subjected to torsional deformation, the optical fiber on the surface of the distributed optical fiber torsion measuring probe 3 is in an initial state, and a torsional strain calculated value is zero; when a certain section of the inclinometer 4 is twisted, the PPP-BOTDA optical fiber data collector 1 monitors that the calculated value of the strain of the part deviates from zero, and the larger the deviation means that the larger the twisting degree of the inclinometer 4 at the part is, the worse the quality is, and error compensation or device repair work can be carried out according to the calculation result of the twisting.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.