CN1300571C - Snake type fiber-optical sensor burying and detecting method and its snake type fibre-optical sensor - Google Patents
Snake type fiber-optical sensor burying and detecting method and its snake type fibre-optical sensor Download PDFInfo
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- CN1300571C CN1300571C CNB2004100730212A CN200410073021A CN1300571C CN 1300571 C CN1300571 C CN 1300571C CN B2004100730212 A CNB2004100730212 A CN B2004100730212A CN 200410073021 A CN200410073021 A CN 200410073021A CN 1300571 C CN1300571 C CN 1300571C
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Abstract
The present invention relates to a method for embedding and testing a snake-shaped optical fiber sensor and the snake-shaped optical fiber sensor thereof. The method comprises the steps of manufacturing the optical fiber sensor and embedding the optical fiber sensor. A heat sealing machine is connected with the optical fiber sensor and transition fibers, and the position of the optical fiber sensor is determined; the initial value of loss is tested, and a loss change curve of an optical fiber testing system is tested after excavation; the deformation and breakage conditions of a rock layer are observed; OTDR test data is processed and managed by a computer program. A sleeve pipe is sheathed on the outer diameter of a nude optical fiber, and protective devices are arranged at both ends. The optical fibers can form a plurality of microbent points which can be used for the deformation of a rock mass whose strength is lower than the strength of hyaline-quartz, the generation and the development of large deformation rock mass cracks and microscopic deformation and macroscopic deformation monitoring, the initial deformation of the rock layer can be captured, even material damage, and accuracy reaches +/-0.01mm. Macroscopic deformation reaches 35 to 50mm and is higher than a test of concrete deformation, and distributed optical fiber detection is realized. The optical fibers are connected with a testing instrument. The present invention has the advantages of convenient use, stable test and high accuracy.
Description
Technical field
The present invention relates to imbedding and method of testing and Fibre Optical Sensor thereof of Fibre Optical Sensor, be specially adapted to flush type microbend fiber sensor and the flush type microbend fiber sensor and the method for testing of low-intensity, large deformation structure monitoring.
Background technology
In recent years, a kind of status monitoring and damage method of estimation-optical fiber smart material and structure of compound substance of novelty studied by some scientific and technological advanced countries, optical fiber sensing system is imbedded building structure form the intelligent building material, promptly imbed Fibre Optical Sensor at the key position of material and structure, survey its internal stress, strain variation in use, operational process, and the distortion, crackle, the layer that produce owing to external loads, fatigue of materials are separated equivalent damage and monitored in real time.Beyond the application of Aero-Space, military affairs, prepare composite, smart material and structure has been applied to the Geotechnical Engineering field in recent years, is used for the observation of structural damage that earthquake causes and destruction, pipeline damage.
1989 Brown Univ USA (Brown University) H people such as (Mendez) detection that Fibre Optical Sensor is used for reinforced concrete structure has at first been proposed, hereafter, the university of the U.S., Britain, Germany, Japan, research institution etc. have dropped into the application of a large amount of strength research microbend fiber sensor in alert and resourceful civil engineering structure.Mendez, Wanser and Voss etc. utilize multimode optical fiber OTDR optical time domain reflection technology (Optical Time Domain Reflectometer is called for short OTDR) to detect crack and slippage; Ansari imbeds optical fiber in the reinforced concrete structure, carries out real-time working state monitoring; Huang Shanglian (1992), Jiang Desheng (1998) have carried out the research of the alert and resourceful civil engineering structure of optical fiber, and are applied in the Geotechnical Engineering; People such as Liu Haowu, Yang Chaohui has proposed novel changing the mechanism-oblique Fibre Optical Sensor form based on the optics and the mechanics principle of crack sensing.Wherein the achievement in research with especially big of the Wei Ermeng of the U.S. (Vermont University) is the most outstanding especially, they are embedded to various Fibre Optical Sensors respectively in covil construction, skyscraper, overpass, interstate highway bridge, railway bridge and the water power dam, stress, strain, structural vibration with detection architecture or interior of building, structural damage degree, internal states such as the generation in crack and development.
Present many Fibre Optical Sensors can be used for the detection of strain, displacement, and maximum detection strain is 1% (or 10
4μ ε) in.In order to adapt to the development of distortion, successively occur based on wound form, bushing type and little curved device of the microbending loss curved Fibre Optical Sensor that declines.
(1) wound form microbend fiber sensor
With reference to shown in Figure 1, adopt multimode optical fiber to be wrapped on the steel cable rope, two ends form with the special gelatin cementation, when steel cable is subjected to the axial stress effect and when being stretched, optical fiber 1 also and then is tightened up together, forms optical fiber micro-bending.On common communications optical fiber 1 (core diameter is 62.5/125 μ m, the coating diameter 0.25mm) wire rope that closely to be wrapped in diameter spirally be 0.9mm is made up of 7 strands of finer wires, protected with epoxy resin then, form the rod shaped structure of diameter 5mm.
(2) bushing type microbend fiber sensor
Structure has a telecommunication optical fiber 1 as shown in Figure 2 in the optical cable, be wrapped on the optical fiber 1 with a polymer fiber spirality, and the outside is fixed by the covering sleeve pipe.When the pressurized of optical cable outside, sleeve pipe has limited the distortion of polymerization spiral fiber, and distortion is applied on the inner optical fiber, forms periodically deforming.When increasing external disturbance, multimode optical fiber just has very high loss.
(3) little curved device sensor
Fig. 3 is an optical fiber micro-bending device sensor synoptic diagram, and little kinking structure is that the castellated plates of Λ is formed by a pair of space periodic, and optical fiber 1 passes in the middle of castellated plates, produces periodic crooked under the effect of castellated plates.When castellated plates was subjected to external disturbance, the little curved degree of optical fiber changed thereupon, thereby caused the change of output intensity.Size by the indirect measurement external disturbance of the variation of test output intensity.
Fig. 4, shown in Figure 5, when nuditing fiber 1 was directly imbedded, rock deformation and fibre loss did not have corresponding relation, can not monitor out rock deformation.The analysis showed that, optical fiber 1 is not out of shape with rock deformation, but destroyed the globality of rock stratum, embed the rock stratum, be difficult to produce effectively little curved, optical fiber 1 collapses in the rock stratum and falls or natural transition does not produce the typical step loss waveform of reflected signal in destroying, and therefore, exists the preparation and the sensing technology problem of optical fiber smart material.
But at present in research optical fiber smart material and configuration aspects, concentrate on and explore Fibre Optical Sensor and imbed that (as buildings, bridge, dam) carries out structural intergrity nondestructive evaluation, internal stress state-detection in reinforced concrete member and the structure, common feature is that optical fiber is used for the structure that the concrete equal strength is higher than the optical fiber quartz glass, the crack deformation failure of permission little (less than 6mm).But, exist low-intensity, a large amount of Geotechnical Engineerings that deflection is big at present, as city underground engineering, Tall Building Foundation, deep basal pit, huge Moderate and Thick Unconsolidated Formation, the thick loess surrouding rock deformation in field such as the exploitation report that also do not have a kind of effective method and device this class material deformation destruction to be detected down with optical fiber.
Summary of the invention
Goal of the invention of the present invention provides a kind of static(al) according to optical fiber and cast material, dynamic interaction, to the flush type microbend fiber sensor that the rock cranny of low-intensity, large deformation material structure aximal deformation value produces and the monitoring of development is used.
Another goal of the invention of the present invention provides a kind of flush type microbend fiber sensor and imbeds and method of testing.
The technical scheme that realizes goal of the invention is to solve like this:
A, Fibre Optical Sensor
Flush type microbend fiber sensor; comprise on the external diameter of optical fiber being with sleeve pipe, and the protective device that is connected the optical fiber two ends, its on the external diameter of nuditing fiber, be connected in series two or two above pipe nipple sleeve pipes; the length of its pipe nipple sleeve pipe is 10～20mm, and diameter is φ 1.4～2.5mm.
Above-mentioned protective device is meant because optical fiber is very thin; in the process of imbedding and testing, appear at the position that has just gone out model meet accident fracture or maloperation fracture easily; the optical fiber that therefore need add one section this position of casing protection, the sleeve pipe of this position, only shielding is called protective device.
B, flush type microbend fiber product sensor are imbedded method
Undertaken by following step successively:
I, choose the optical fiber specification, make the described flush type microbend fiber of claim 1 sensor;
The various materials of test specimen model are made in II, preparation, and test specimen is made and also press design proposal laying flush type microbend fiber sensor between the lamination of the laminate of estimating;
III, lay flush type microbend fiber sensor at laminate, flush type microbend fiber sensor is placed between the lamination of laminate; When making test specimen, firmly evenly, guarantee the survival rate of flush type microbend fiber sensor;
IV, imbed model microbend fiber sensor length perceived model specification and decide, the outer both sides of model respectively stay the length of 0.5～1m in order to connecting, and the two ends, position that optical fiber goes out model install protective device additional;
After V, model are ready, adopt heat sealing machine to connect Fibre Optical Sensor and transition optical fiber, and optical time domain reflectometer OTDR is carried out parameter setting.
The method of testing of C, flush type microbend fiber sensor
Undertaken by following step successively:
I, flush type flush type microbend fiber sensor is imbedded according to claim 1;
II, by local curved method of decreasing, determine the particular location of flush type microbend fiber sensor in the optical fiber testing system;
III, the test of loss initial value, in the digging process of model coal seam, after excavating each time, measuring fiber test macro loss change curve;
The deformation and failure situation observation of IV, model rock stratum;
V, computer programs process OTDR test result.
This sensor is monitored base material crack 0～50cm scope width deformation or destruction.
The present invention compared with prior art has following characteristics:
(1) present existing Fibre Optical Sensor is mainly used in the structure detection of high-strength materials such as concrete, and this sensor can be used for the rock mass deformation monitoring that intensity is lower than hyaline-quartz.
(2) this sensor can be used for the rock cranny generation of aximal deformation value and the monitoring of development, in the practical application, matrix material contacts with sleeve pipe, form bonding, and optical fiber is " freedom " state in sleeve pipe, be out of shape with the collapse distortion that falls of rock stratum, can test rock mass damage on a large scale, the rock stratum formation loss step that falls that collapses.
(3) flush type microbend fiber sensor both can carry out the microdeformation monitoring, can be used for the macroscopic deformation monitoring again.Because the out-of-flatness that sleeve pipe is installed, optical fiber can form a plurality of little curved points, distortion of materials is in case constitute influence to them, this curved slightly point just becomes highstrung microbend fiber sensor, reflect these variations, therefore Fibre Optical Sensor can capture the initial deformation of rock stratum, or even the damage of material, and its degree of accuracy reaches ± 0.01mm.And its macroscopic deformation reaches 35～50mm, far above concrete deformation is tested.
(4) realized the distribution type fiber-optic detection, optical fiber is connected with testing tool, easy to use, stable testing, degree of accuracy height.
(5) rock stratum has tangible sequential in the process collapsing, i.e. development successively, and the fibre loss value falls to having correlativity with collapsing, and can tell the process of distortion and the process that collapses and.Can be used for that the rock stratum, colliery is moved, the scope of the monitoring of coal column stability and testing substrates distortion.
(6) with other detection method contrast, optical fiber detects has high degree of accuracy.
Table 2 accuracy of detection relatively
| Detection Techniques | Sonic detection | Infrared acquisition | Optical fiber detects | The GPS monitoring | |
| Detected object | Concrete porosity | The rock cranny expansion | The concrete crack | Rock mass deformation | The bridge three-D displacement |
| Precision | Greater than 10cm | Can survey | 0.05mm | 0.01mm | 20mm |
Description of drawings
Fig. 1, Fig. 2 are prior art wound form microbend fiber sensor construction synoptic diagram;
Fig. 3 is the little curved device sensor construction synoptic diagram of prior art;
Fig. 4 is the prior art rock stratum structural representation that falls that collapses;
Fig. 5 is that the nature transition of prior art rock stratum destroys structural representation;
Fig. 6 is a flush type microbend fiber sensor construction synoptic diagram;
Fig. 7 is the little kinking structure of a flush type microbend fiber sensor synoptic diagram;
Fig. 8 is a flush type microbend fiber sensor macrobend structural representation;
Fig. 9 is the structural representation of imbedding of flush type microbend fiber sensor;
Figure 10 is the fibre-optical bending synoptic diagram;
Figure 11 arranges and the test macro synoptic diagram for Fibre Optical Sensor;
Figure 12 is the relation curve synoptic diagram of Fibre Optical Sensor loss and advance distance in the 1.2m model recovery process;
Figure 13 is the distribution type fiber-optic test macro synoptic diagram of rock beam distortion;
The loss of Figure 14 OTDR screen shows synoptic diagram.
Embodiment
Accompanying drawing is background technology and embodiments of the invention.
Below in conjunction with accompanying drawing of the present invention summary of the invention is described further:
The present invention is to provide the accompanying drawing of when the laboratory similar material model is tested, gathering.
A, flush type microbend fiber sensor
Flush type microbend fiber sensor; comprise on the external diameter of optical fiber being with sleeve pipe, and the protective device that is connected the optical fiber two ends, its on the external diameter of nuditing fiber, be connected in series two or two above pipe nipple sleeve pipes; the length of its pipe nipple sleeve pipe is 10～20mm, and diameter is φ 1.4～2.5mm.
Above-mentioned protective device is meant because optical fiber is very thin; in the process of imbedding and testing, appear at the position that has just gone out model meet accident fracture or maloperation fracture easily; the optical fiber that therefore need add one section this position of casing protection, the sleeve pipe of this position, only shielding is called protective device.
B, flush type microbend fiber product sensor are imbedded method, are undertaken by following step successively:
I, choose the optical fiber specification, make the described flush type microbend fiber of claim 1 sensor;
The various materials of test specimen model are made in II, preparation, and test specimen is made and also press design proposal laying flush type microbend fiber sensor between the lamination of the laminate of estimating;
III, lay flush type microbend fiber sensor at laminate, flush type microbend fiber sensor is placed between the lamination of laminate; When making test specimen, firmly evenly, guarantee the survival rate of flush type microbend fiber sensor;
IV, imbed model microbend fiber sensor length perceived model specification and decide, the outer both sides of model respectively stay the length of 0.5～1m in order to connecting, and the two ends, position that optical fiber goes out model install protective device additional;
After V, model are ready, adopt heat sealing machine to connect Fibre Optical Sensor and transition optical fiber, and optical time domain reflectometer OTDR is carried out parameter setting.
The method of testing of C, flush type microbend fiber sensor
Undertaken by following step successively:
I, flush type flush type microbend fiber sensor is imbedded according to claim 1;
II, by local curved method of decreasing, determine the particular location of flush type microbend fiber sensor in the optical fiber testing system;
III, the test of loss initial value, in the digging process of model coal seam, after excavating each time, measuring fiber test macro loss change curve;
The deformation and failure situation observation of IV, model rock stratum;
V, computer programs process optical time domain reflectometer OTDR test result.
This sensor is monitored base material crack 0～50cm scope width deformation or destruction.
The model of flush type microbend fiber sensor or on-the-spot rock-soil layer are undertaken by following step successively for the deformation and failure method of testing of rock-soil layer:
I, by local curved method of decreasing, determine the particular location of Fibre Optical Sensor in the optical fiber testing system;
II, the test of loss initial value, in the digging process of model coal seam, after excavating each time, measuring fiber test macro loss change curve;
The deformation and failure situation observation of III, model rock stratum;
IV, computer programs process OTDR test result, optical time domain reflectometer OTDR is the instrument that is used to check fibre loss characteristic, fiber failure, test be the loss of optical fiber testing system along whole process.When the optical fiber of imbedding model deformed, the loss of this place's optical fiber was just higher.Conversely, can judge that optical fiber buries stressed, the damage status of material at place underground, can determine that material is stressed, the position at damage place simultaneously according to the fibre loss result.Parameter setting is mainly according to the length of optical fiber testing system.The optical fiber testing system loss change curve of OTDR test is actually a sets of curves, is carved with one during each test, and what each bar curve all reflected is the length of optical fiber testing system and the loss value of correspondence position.Data file of each test curve formation constantly deposits computing machine in.Computer programs process is according to optical time domain reflectometer OTDR test result, uses the OTDR specific program, reads the loss value of diverse location on each bar test curve on computers, as finds out the loss value of the Fibre Optical Sensor corresponding position of imbedding model.Its processing procedure can be carried out at any time, and test figure has the advantages that to preserve and analyze at any time.And each test constantly reflects is rock deformation situation in the model experiment process, and therefore, the distortion of model rock stratum and loss form certain corresponding relation.
With reference to shown in Figure 6; comprise on the external diameter of optical fiber 1 and be with sleeve pipe 3; an end that also comprises optical fiber 1 is connected with protective device 2; two or two above pipe nipple sleeve pipes 3 are connected in series on the external diameter of optical fiber 1; the length of its pipe nipple sleeve pipe 3 is 10～20mm or 12～18mm or 14～16mm, and diameter is 1.4～2.5mm or 1.6～2.0mm.
Fig. 7, shown in Figure 8, its sensor mechanism are little curved principles, bury injustice naturally underground or are out of shape when inconsistent when sleeve pipe 3, just form the little curved of optical fiber 1 between sleeve pipe 3 and the sleeve pipe 3, and the further distortion of material is inevitable pass through the optical fiber perception because this bends to put slightly; When large deformation appears in material, matrix material contacts with sleeve pipe 3 and forms strong bond, and optical fiber 1 is " freedom " state displacement in sleeve pipe 3, and sleeve pipe 3 has limited the distortion of optical fiber 1, optical fiber 1 forms little curved point in the macroscopic deformation bending, collapsing with the rock stratum drops out existing loss step reflected signal.Optical fiber 1 forms little curved " intersection point " in macrobending.According to the transmission principle of optical fiber, the loss of optical fiber is owing to due to the bending of optical fiber part, conversely, utilize loss to monitor, and just must make optical fiber 1 have high loss to produce.Yet, be not to have crooked local optical fiber 1 just lossy, must be that effective microbend could be lossy, can make optical fiber in distortion, form lossy microbend with sleeve pipe, little bending is to form between sleeve pipe 3 and the sleeve pipe 3, be actually one section optical fiber that bending is very serious, because its distance is very short and very little, so be called little curved " intersection point "
Fig. 9 imbeds structural representation for flush type microbend fiber sensor, and the optical fiber embedment method is the imbedding in the process of laminate, optical fiber 1 is placed between the lamination of laminate.At model rock deformation area arrangements Fibre Optical Sensor, model is imbedded in the process optical fiber 1 is placed between rock beam and coal column, the working seam, place dial gauge at the rock beam middle part, intend observing the distortion and the deflection of rock beam, in the lamination process of material, make it to combine with material, because of Fibre Optical Sensor is imbedded inside, can monitor the variation and the damage of material and inside configuration state.The embedded mode of optical fiber 1 in material is simpler, adopt manual or mechanical paving all can, between the lamination of estimating, imbed optical fiber 1 by design proposal, imbed model optical fiber span length perceived model specification and decide, the outer both sides of model respectively stay the length of 0.5～1m in order to connection.Do not have the effect of temperature when optical fiber is imbedded rock material, its survival rate mainly is subjected to operating influence.
It is the first step that realizes that Geotechnical Engineering optical fiber detects that optical fiber 1 is imbedded.Optical fiber 1 burying underground in Geotechnical Engineering relates to following basic problem:
(1) how optical fiber 1 is imbedded in the Geotechnical Engineering with no damage;
(2) reasonable Arrangement of optical fiber and long-time stability, integrity problem in the structure term of validity;
(3) the Micromechanics problem at Fibre Optical Sensor fiber/ferrule/matrix material three interface.Optical fiber 1 is in two kinds of states in the model experiment process, a kind of is that optical fiber 1 is out of shape mobile status with the rock stratum, and another kind is a not deformation failure state of rock stratum.Select the optical fiber 1 under two kinds of states to adopt the electronic line scanner of the Philip charged sub-probe of XL20 type (EDS) to scan amplification, optical fiber is in the scanning electron microscope enlarged drawing under the model formation damage state, amplifies 350 times, and optical fiber surface is intact, attachment is only arranged, do not have the defective of corrosion.The interval time of model from mating formation to experimentizing is 1 month, and as seen from the figure, lime carbonate (composition accounts for 10%) composition is to not corrosion of optical fiber in the similar material model experiment.
Figure 10 is the fibre-optical bending synoptic diagram, and according to the Simple Calculation Method of bending loss of optical fiber, influential to bending loss is wavelength, bending radius, crooked number and four variablees of angle of bend.Certain test conditions and Fibre Optical Sensor, wavelength X and bending radius r are definite value (r=3.5mm), have only crooked number N and angle of bend θ
NAlong with the variation of the integrally bending radius R of Fibre Optical Sensor and change, Fibre Optical Sensor bending loss calculating formula is T
Total=ζ
1N exp (ζ
2θ
N), according to experimental result, ζ
1=0.0046, ζ
2=0.0526.
Sleeve pipe has played following effect:
1. increase the contact area of fibre diameter and material, reduced the chance of optical fiber, make the bonding of sleeve pipe and material interface firm, help the follow-up distortion of optical fiber the cast material cutting damage;
2. optical fiber has been subjected to protection in sleeve pipe, has reduced the unnecessary deformation bending, and optical fiber can with the needs of adaptation material development of deformation, reach the purpose to the large deformation test along the sleeve pipe slippage again;
3. optical fiber constraint owing to sleeve pipe in the process of distortion forms little curved.Bushing outer surface is selected low-modulus material for use, the inside surface high modulus material consistent with optical fiber.The composition that high modulus material refers to optical fiber is a monox, and its theoretical value is 7.2 * 10
4Mpa, Poisson ratio is 0.17, the high modulus material that internal surface of casing is used is exactly the material with above-mentioned elastic modulus numerical value basically identical
This sensor is applicable to monitoring rock and soil engineering, and especially intensity is lower than in the rock mass deformation monitoring of hyaline-quartz.
1.2 * 0.12m plane stress model experiment
Figure 11 is that 1.2 * 0.12m plane stress model experiment frame Fibre Optical Sensor is arranged and test macro.Experiment material is common river sand, gypsum, chalk powder and mica powder, realizes the simulation of all kinds of rock stratum by proportion design.The model height 50cm that mats formation, geometric similarity is than 100, volume to weight ratio 1.7, working seam thickness 3.5cm.Imbed three layers of Fibre Optical Sensors, No. 3 optical fiber is embedded in the mud stone of model, this layer distance of positions seat earth 40.5cm; No. 2 optical fiber is embedded in the siltstone, apart from seat earth 24cm; No. 1 optical fiber is embedded in the packsand, apart from seat earth 7cm.Test macro fiber lengths 2.178km.
Figure 12 is the graph of relation of Fibre Optical Sensor loss and advance distance in the 1.2m model recovery process, among the figure Fibre Optical Sensor loss value by the damage curve of OTDR test as calculated machine handle gained, horizontal ordinate is the advance distance of model workplace.The advance of the face occurs collapsing and in the rock stratum during to 40cm, and drop height degree 8cm collapses; The advance of the face collapses and drops down onto No. 1 optical fiber (drop height degree 10cm collapses) in the rock stratum during to 50cm; The advance of the face collapses and drops down onto No. 2 optical fiber (drop height degree 16cm collapses) in the rock stratum during to 60cm; The advance of the face is the rock stratum drop height degree 23.5cm that collapses during to 75cm.The deformation process that has reflected the model rock stratum here, with the workplace advance distance.The rock stratum collapse fall before, fibre loss has a local stage that increases, No. 1 fibre loss value increases 15%, No. 2 fibre loss value and increases 13%; Return to initial value again with the further propelling of workplace subsequently, or slightly reduce, but be in steady state (SS) relatively.Fibre Optical Sensor can detect the initial deformation (advance of the face to 20cm) of rock stratum, and the rock depression that traditional displacement method of testing draws is when measuring the present advance of the face to 40cm.Collapsing to be when falling increases rapidly, and No. 1 the fibre loss value increases 1.5 times, and No. 2 the fibre loss value increases 2.17 times.
The analysis showed that the distortion of model rock stratum and fibre loss form certain relation, promptly is positive relation-changing, but the expression of the physical relationship of distortion and fibre loss is difficult to provide.With regard to The above results with enough be used for the monitoring.
The destruction of superincumbent stratum can be typically the form of Figure 13, wrong distance occurs, and optical fiber forms the step loss waveform of reflected signal because the kink distortion appears in the effect of sleeve pipe.
The experiment of 2m model rock beam
Figure 13 is a 2m model experiment situation.Analogue formation height 11.5cm, lift height 1cm, thickness of coal seam 3.5cm.Bury 2 layers of optical fiber in the rock beam underground, No. 1 optical fiber is embedded in apart from seat earth 5cm place, and No. 2 optical fiber is embedded in apart from seat earth 8cm place.Optical fiber testing system is for being connected in series, each Fibre Optical Sensor is cascaded by an optical fiber, and a termination of optical fiber is gone into the OTDR optical time domain reflectometer, because the time domain meter spatial resolution that experiment is used is in the decimeter grade scope, for accurate location, between Fibre Optical Sensor, insert transition optical fiber and tail optical fiber.At the rock beam middle part dial gauge is installed.
To extraction rock beam coal seam (totally 10 excavations) down progressively, both sides, make the span increase of rock beam from model middle part, finally reaching collapses falls.Surperficial deflection with dial gauge test rock beam middle part.
Optical time domain reflectometer screen display optical fiber testing system damage curve is seen Figure 14, and horizontal ordinate is a distance, and the distance between two dotted lines is 50m, according to the position of the curve length of optical fiber testing system as can be seen; Ordinate is fibre loss, and the loss between two dotted lines is 4dB.Be followed successively by model the 1st among the figure from top to bottom and be excavated to system's fibre loss change curve of testing in the 10th digging process, that is to say, excavation is constantly to there being a test damage curve each time.Each bar curve has two steps is all arranged, and the position of two steps is respectively at 1.013km and 1.081km place, and these two positions that the position just in time is a Fibre Optical Sensor are by the size of the step size that changes of loss as can be seen.Span with rock beam increases, and the loss step increases gradually.
Aforementioned showing, flush type microbend fiber sensor had both been realized the microdeformation monitoring, had reached the macroscopic deformation monitoring again.Utilize this kind flush type microbend fiber sensor testing method can carry out the test of rock mass initial deformation and destruction on a large scale, might be applied in the following areas thus.
(1) coal column STABILITY MONITORING
Bury flush type microbend fiber sensor underground in the coal column internal drilling,, can reach judgement, help the Stability Design of coal column coal column stability with elastic-plastic deformation, the destructive process of OTDR at the ground monitoring coal column.
(2) tomography, slope stability safety monitoring
Flush type microbend fiber sensor is installed in the glide plane boring possible in the rock stratum, by the monitoring to the glide plane changing of the relative positions, judges the activation of tomography and the stability of side slope.
(3) anchor pole, anchor cable service property (quality) detect
When anchor pole is installed flush type microbend fiber sensor is wrapped on the anchor pole, the disengaging situation of monitoring anchor pole and anchoring rock stratum reaches the stressed analysis of anchor pole.
(4) influence of formation damage scope detects
Along rockhole flush type microbend fiber sensor is installed,, is reached determining the formation damage scope by detecting the position that the rock stratum, deep begins absciss layer or displacement occurs.Also can be used for determining that formation damage influences the angle, be the research service of face of land movement law.
(5) soil matrix body non-uniform settling monitoring
Soil matrix body non-uniform settling is the principal element that influences building destruction, flush type microbend fiber sensor is installed along the building foundation, utilize the loss of this embedded-type sensor optical fiber when differently curved radius to change, come the non-uniform settling of judgement basis, and EARLY RECOGNITION and discovery.
Flush type microbend fiber sensor is imbedded and method of testing deconditioning mutually outside the analog model in sum, also flush type microbend fiber sensor and test are imbedded in the adaptation scene, also can realize distributed monitoring, fiber arrangement is in xoncrete structure or in the rock stratum or in coal seam or the soil layer, tubular construction stress where, distortion and crack can not be monitored to.
The method of on-the-spot flush type microbend fiber sensor is consistent with the laboratory: promptly according to the character of tested rock stratum, at first make simulation rock stratum test specimen, flush type microbend fiber sensor is packed into wherein with breadboard method; The simulation rock stratum test specimen that to make is then imbedded the expectation test position.
Claims (6)
1, a kind of flush type microbend fiber sensor; comprise the sleeve pipe (3) that is with on the external diameter of optical fiber (1); and the protective device (2) that is connected the optical fiber two ends; two or two above pipe nipple sleeve pipes (3) is characterized in that being connected in series on the external diameter of nuditing fiber (1); the length of its pipe nipple sleeve pipe (3) is 10～20mm, and diameter phi is 1.4～2.5mm.
2, flush type microbend fiber sensor according to claim 1 is characterized in that between said sleeve pipe and the sleeve pipe forming the little curved point of flush type microbend fiber sensor.
3, flush type microbend fiber sensor according to claim 1 is characterized in that said pipe nipple bushing outer surface is a low-modulus material, and inside surface is the high modulus material consistent with optical fiber.
4, a kind of flush type microbend fiber product sensor is imbedded method, it is characterized in that being undertaken by following step successively:
I, choose the optical fiber specification, make the described flush type microbend fiber of claim 1 sensor;
The various materials of test specimen model are made in II, preparation, and test specimen is made and also press design proposal laying flush type microbend fiber sensor between the lamination of the laminate of estimating;
III, lay flush type microbend fiber sensor at laminate, flush type microbend fiber sensor is placed between the lamination of laminate; When making test specimen, firmly evenly, guarantee the survival rate of flush type microbend fiber sensor;
IV, imbed the microbend fiber sensor length perceived model specification of model and decide, the outer both sides of model respectively stay the length of 0.5～1m in order to connecting, and the two ends, position that optical fiber goes out model install protective device additional;
After V, model are ready, adopt heat sealing machine to connect Fibre Optical Sensor and transition optical fiber, and optical time domain reflectometer OTDR is carried out parameter setting.
5, a kind of method of testing to flush type microbend fiber sensor is characterized in that being undertaken by following step successively:
I, the described flush type microbend fiber of claim 1 sensor is imbedded;
II, by local curved method of decreasing, determine the particular location of flush type microbend fiber sensor in the optical fiber testing system;
III, the test of loss initial value, in the digging process of model coal seam, after excavating each time, measuring fiber test macro loss change curve;
The deformation and failure situation observation of IV, model rock stratum;
V, computer programs process are to optical time domain reflectometer OTDR test result.
6, the method for testing of flush type microbend fiber sensor according to claim 5 is characterized in that and can monitor base material crack 0～50cm scope width deformation or destruction with this sensor.
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| CN102252703B (en) * | 2011-06-30 | 2013-04-17 | 重庆大学 | Optical fiber compound sensing module |
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| CN108755616B (en) * | 2018-08-22 | 2024-02-20 | 江苏省水利勘测设计研究院有限公司 | Optical fiber sensor buries protective device |
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| CN111103029B (en) * | 2019-12-26 | 2021-04-30 | 河南理工大学 | Intelligent monitoring device and monitoring method for fiber bragg grating of coal level of coal bunker |
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| CN113588374B (en) * | 2021-08-20 | 2024-02-06 | 华北有色工程勘察院有限公司 | Sensing optical fiber burying device and method in geotechnical engineering similar material model |
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