CN109141271A - Multi-point type optical fiber grating bottom hole strain gauge - Google Patents
Multi-point type optical fiber grating bottom hole strain gauge Download PDFInfo
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- CN109141271A CN109141271A CN201811227177.XA CN201811227177A CN109141271A CN 109141271 A CN109141271 A CN 109141271A CN 201811227177 A CN201811227177 A CN 201811227177A CN 109141271 A CN109141271 A CN 109141271A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
- G01B11/165—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge by means of a grating deformed by the object
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Abstract
The invention discloses a kind of multi-point type optical fiber grating bottom hole strain gauges, including measurement conical section, glue storage cavity body and piston rod portion；Measuring conical section includes fiber Bragg grating strain sensor, plastic hole and binder retaining ring, glue storage cavity body and pin hole, and fiber Bragg grating strain sensor is pasted on conical rubber cap outer wall, and lead is laid in wire lead slot；It is moved by piston rod to glue storage cavity body direction and squeezes out the glue in glue storage cavity body from lower end plastic hole, fiber Bragg grating strain sensor is posted on bellmouth bed rock body, is deformed together with surrounding rock body, obtain strain of rock mass information during stress relieving.The present invention has many advantages, such as that anti-electromagnetic interference capability is strong, good corrosion resistance, precision small in size are high, measurement range is big, number of leads is few, transmission range is long, and structure is simple, size is smaller, Rock Mass Integrality is required low, installation is quick and convenient with measurement procedure, may be implemented to install the bottom hole strain measurement in sub-aperture in Φ 76mm.
Description
Technical field
The present invention relates to geophysics rock mass stress fields of measurement, specifically, being related to a kind of multi-point type optical fiber grating hole
Bottom strain gauge.It is mainly used in the geostress survey field based on set core stress relieving method, function is to use to be laid in circle
Multiple fiber Bragg grating strain sensors with temperature compensation unit on conehead, measuring unit core process is due to caused by stress relieving
The strain of sub-aperture bottom hole and its variation, through hole bottom strain measurement Stress calculation principle and formula find out the Original strata stress around aperture
State.
Background technique
Geostress survey is the mechanics basic parameter for measuring Solid Geophysics phenomenon behind physical mechanism, in underground tunnel
Using very extensive in the Geological Engineerings such as road, railway, highway, mining engineering country rock, high slope and ground excavation.With the mankind couple
The increase of the energy and mineral resources demand and continuing to increase for mining rate, superficial part mineral resources are increasingly reduced, domestic and international mine
Mountain all subsequently enters deep resource development status, and " three high " problem (high-ground stress, High-geotemperature, the height encountered in deep mining
Hydraulic pressure) focus in Rock Mechanics In Deep Mining Engineering research and difficulties (what full sea etc., 2005) will be become.It is accurate to determine deep
The crustal stress spatial-temporal distribution characteristic and rule in development space region are one of necessary ways for solving the above problem and geology work
The research of journey Problem stability and design analysis, the prerequisite for realizing the geotechnical engineering scientification of decision-making, therefore geostress survey is managed
By the research of, method and technique, there is important scientific meaning.
The observation and estimation of MAFIC ROCKS IN DEEP CRUST stress state are an important difficulties of crustal stress actual measurement work, are answered from ground
Power concept proposes that so far, the tens of kinds of detecting earth stress methods that scientists from all over the world propose are sorted out according to its data source, probably may be used
To be divided into five major class: the method based on core, the method based on drilling, Geologic method, geophysical method (or seismology side
Method), method based on the underground space (Hill et al., 1994；Amadei and Stephasson, 1997).On these ground
In method for measuring stress, only over-coring stress relief method and hydraulic fracturing can provide principal stress size and the side of horizontal stress
To remaining earth stress measuring method is only capable of providing principal direction of stress, cannot provide principal stress size.Over-coring stress relief method conduct
A kind of geostress survey common method based on drilling, by monitoring core from parent rock release during strain and change
Shape, and then inverting Original strata stress field.This method can pass through the one-shot measurement in a drilling, so that it may determine that the three-dimensional of rock mass is answered
Power state crosses stress measurement without three holes, is generally acknowledged most effective triaxiality measurement method.
Over-coring stress relief method is grown up based on plane strain overcoring method, and Hast discloses him for the first time within 1958
It is utilized during 1952-1953 in Sweden La Yisiwaer (Laiswall) lead ore and four, Scandinavian Peninsula mining area
The resulting drilling hole stress measurement result of magnetic inductance method crustal stress measurer is pressed, the shock of people is caused.From Hast public affairs in 1958
After its research achievement of cloth, drilling hole stress measuring technique is all developed energetically and developed in countries in the world.By domestic and foreign scholars' many decades
Research, a set of standardized process of measurement has been formed at present, using opposite more square with other test method with measurement process
Just, and measuring device bulking value is smaller, becomes that applicability is most strong and one of the highest earth stress measuring method of reliability.
Different with the physical quantity of measurement according to measuring cell installation, set core stress relieving mensuration can be divided into borehole wall again
Strain measurement method, boring aperture deformation measurement method and three kinds of drilling hole bottom strain measurement method (Cai Meifeng, 2000), pass through prison respectively
The strain of releasing process middle hole wall, aperture deformation and bottom hole strain are surveyed to calculate Original strata stress field.Borehole wall strain measurement method will
Measuring cell resistance strain plate is affixed directly on drilling palisades, or measuring cell resistance strain plate is wrapped in epoxy
It is pasted again in resin-case on drilling palisades, carries out drilling three-dimensional strain measurement, realize that single hole tests resultant stress tensor.The party
Method measurement accuracy is high, but complicated for operation, requires height to tested Rock Mass Integrality, measurement success rate is lower.Boring aperture deformation is surveyed
Amount method principle is that the aperture to drill after stress relieving can change, by recording this knots modification, using some basic theories
Being derived by indicates that the physical mathematics relational expression between each relevant variable is solved, to obtain the measurement side of rock stress
Method.This kind of measuring device has very much, but boring aperture deformation measurement method can only measure plane stress state, is unable to get true
Real three-dimensional stress constraint.
The principle of bottom hole Strain Method is resistance strain plate to be pasted onto the plane of bottom hole position, and then sets of holes release rock
Core stress, measurement strain, to obtain the measurement method of borehole circumference triaxiality.The Typical Representative of this kind of measuring instrument has
" CSIR's door plug " bottom hole strain gauge (Leeman, 1964) that the Leeman in South Africa is developed, Japan Sugawara et al. development
Hemispherical-shaped aperture bottom strain gauge (Sugawara and Obara, 1986) and round taper hole bottom strain gauge (Sugawara etc.,
1999).16 or the 24 foil gauge round taper hole bottom strain gauges-CCBO bottom hole strain that especially Sugawara et al. is developed
Meter, can be by 16 to 24 foil gauge assembled units, can accurately and effectively the surface strain of testing bore holes conical lower portion is in turn
Original strata stress is obtained, testing time, energy and testing expense are effectively reduced.This method advantage is it to Rock Mass Integrality requirement
It is low, the sets of holes core grown is not needed very much, it is advantageous under large ground pressure as long as that section of bottom hole completely uses,
The region especially influenced by disc-shaped core, this method advantage is clearly, it is thus possible in relatively more broken rock mass.
However be measuring cell since existing bottom hole strain gauge is all based on traditional resistive foil gauge, and resistance-type strains
The generally existing interference vulnerable to test environment especially temperature factor in piece measurement, is specifically primarily present following problems:
1. the main strain measurement element of bottom hole deformeter, the resistance value of resistance strain plate is easy the variation by ambient temperature
And nonlinear change is generated, and it is larger non-linear to strain its resistance value to have greatly, thus its is affected by environment larger, moisture resistant
It is poor with anti-interference ability；
2. being lost greatly in transmission process since strain signal is reflected by resistance variations, it is not easy to acquire and pass over long distances
It is defeated, thus it is limited to fathom, and is not suitable for longhole survey.
3. 16 foil gauges need 32 leads, number of leads is more, lead is thick, is not easy to installation and aperture measuring.
In view of the above objective technique reason, it is highly desirable the bottom hole strain based on new sensor technology research and development a new generation
Instrument.
Fiber grating (FBG:Fiber Bragg Grating) sensing technology since being the 1990s it is emerging based on
The sensing technology of optical fiber passive Sensitive Apparatus, due to the wavelength that its sensitive variable parameter is light, because without light source, transmission line
The interference of the factors such as loss, has excellent temperature and strain-responsive characteristic, extensive application prospect, and FBG is to utilize doping
The light sensitivity of (such as germanium, phosphorus) optical fiber, the technology make the doping in extraneous incident photon and fibre core by the method for U-V writing
Particle interaction causes the refractive index of fiber core that axial cyclic or acyclic permanent change occurs, in fibre core
Interior formation space phase grating.The basic principle of FBG sensing as shown in Figure 1, when the incident light beam strikes of a branch of wide range are to FBG,
According to grating theory, in the case where meeting Bragg condition, will be totally reflected, reflectance spectrum is in Bragg wavelengthλ BPlace
There is peak value, and hasλ B=2n effΛ, whereinn effFor the effective refractive index of fibre core, Λ is period (the i.e. grid of variations in refractive index
Away from), the reflectance spectrum and transmitted spectrum characteristic of fiber grating are as shown in Figure 1.
When fiber grating external physical field, (such as ess-strain, temperature) changes, pitch Λ becomes therewith
Change, to change the wavelength of grating back reflected laser.Become according to the wavelength of fiber Bragg grating strain sensor made of this principle
The expression formula changed between strain has:λ B=(1-P ε)ε•λ B, whereinP εFor elasto-optical coefficient, determined by the material of fiber grating.
Therefore, the variation of grating Bragg wavelength in reflection signal is only detectedλ B, can be detected strain variation to be measured.
Fiber Bragg Grating technology also has the advantage that other than having the advantages of general optical fiber sensing technology
1. it is strong antijamming capability, good corrosion resistance, small in size, there are very high reliability and stability；
2. measurement sensitivity is high, high resolution, precision are high, there is good repeatability；
3. dynamic range is big, good linearity, energy self calibration can be used for the absolute measurement to extraneous parameter；
4. multiple sensors can be integrated in an optical fiber, it is reusable, convenient for constituting various forms of fibre optical sensor nets
Network realizes distributed measurement；
5. being convenient for remote monitoring, it can be made into intelligence sensor, be widely used；
6. structure is simple, the service life is long, maintenance, extension and installation easy to repair etc..
The technology has had relatively broad application in geotechnical engineering health monitoring field, but changes in crustal stress and observe
Aspect is related to less, more only based on the stress strain gauge of optical fiber sensing technology, lacks the crustal stress based on the technology
Bottom hole strain monitoring technique study.The above-mentioned characteristic of fiber grating is particularly adapted to the strain of the bottom hole in over-coring stress relief method and surveys
Amount field, thus developed the bottom hole strain measurement technique in detecting earth stress the present invention is based on Fiber Bragg Grating technology, research and develop base
In the multipoint mode bottom hole strain gauge of the fiber Bragg grating strain sensor with temperature compensation unit, realize in over-coring stress relief method
The high-precision detection of bottom hole strain.
Summary of the invention
The present invention is precisely in order to a kind of multi-point type optical fiber grating bottom hole strain gauge for solving above-mentioned technical problem and designing.It is logical
Invention multi-point type optical fiber grating (FBG) bottom hole strain gauge is crossed to carry out the bottom hole strain testing work based on over-coring stress relief method
Make, maximum outside diameter is the cone of 50mm, meets the measurement request in 76mm drilling, and measurement accuracy reaches 0.5%FS.It adopts
Fiber Bragg grating strain sensor with multipoint mode with temperature compensation unit, is fixed in tapered wall, passes through epoxide-resin glue
Sensor is pasted into bottom hole, by Sensor Data Record and is stored in conjunction with aperture fiber Bragg grating (FBG) demodulator, realizes set core stress
Bottom hole strain measurement during releasing.
The technical solution adopted by the present invention to solve the technical problems is:
1, multi-point type optical fiber grating (FBG) bottom hole strain gauge Design of Main Structure
Multi-point type optical fiber grating (FBG) bottom hole strain gauge main structure of the present invention consists of three parts, and is measurement cone respectively
Body portion, glue storage cavity body and piston rod portion.The structure composition schematic diagram of multi-point type optical fiber grating (FBG) bottom hole strain gauge is as schemed
Shown in 2.Measurement conical section includes fiber Bragg grating strain sensor, plastic hole and binder retaining ring, glue storage cavity body and pin hole,
Fiber Bragg grating strain sensor is pasted on conical rubber cap outer wall, and in lower notches, lead is laid in Optical Fiber Winding
In wire lead slot；There is the attachment device with finder, mounting rod in piston rod upper end, and the upper end is equipped with installation positioning pin nail hole and lead
Slot, by rotational installation bar realize mounting rod and the connection of piston rod with separate；It is moved by piston rod to glue storage cavity body direction
Glue in glue storage cavity body is squeezed out and is compacted from lower end plastic hole, fiber Bragg grating strain sensor is posted bellmouth bed rock body
On, it is deformed together with surrounding rock body, obtains strain of rock mass information during stress relieving.
, sensor layout scheme
Fiber Bragg grating strain sensor uses multipoint mode mounting means, as shown in figure 3, totally 8 groups of fiber gratings in measurement cone
Strain transducer, along measurement cone even circumferential distribution, i.e. 45 ° of adjacent spaces, every group has 2 fiber Bragg grating strain sensors,
Its withρThe angle of axis is respectively 0 °, 90 °.
The laying of fiber Bragg grating strain sensor and connection type such as Fig. 4 and Fig. 5: utilize 2 sensor fibres by 16 light
2 groups of fiber grating strain transducer point is connected in series, wherein vertical ρ axis direction is that circumferential fiber Bragg grating strain sensor is
A group, 1 fiber Bragg grating strain sensor of every installation groove winding above it, one circle, then installs next fiber grating and answers
Become sensor；Wherein along the fiber Bragg grating strain sensor of ρ axis direction be B group, each fiber Bragg grating strain sensor according to
From upper and lower part groove, alternately one circle of winding, 2 groups of fiber Bragg grating strain sensors measure circumferential direction ε to wire locations respectively respectivelyθAnd axis
To ερStrain is convenient for data analysis.
, Sensor Temperature Compensation
Fiber Bragg grating strain sensor is the strain transducer with temperature compensation unit, and temperature calibration is with compensation method:
Before fiber Bragg grating strain sensor is mounted on measurement cylinder, fiber Bragg grating strain sensor unit is first placed in thermostatted water
Temperature calibration experiment is carried out in the case of domain, and the experimental data of wavelength with temperature variation is fitted, handled and analyzed, temperature is passed through
Calibration experiment obtains the temperature sensitivity coefficient of strain sensing unit, and then to strain sensing list in set core stress relieving actual measurement
First temperature compensates；There is the temperature-sensitive of a not strained influence inside fiber Bragg grating strain sensor with temperature compensation unit
Grating, it acts as monitoring variation of ambient temperature ΔsT, there is ΔT=(λ t1 -λ t0)/R 1, in formula:λ t0For the primary wave of temperature-sensitive grating
It is long；λ t1Fort 1The wavelength at moment；R 1For the temperature sensitivity of temperature-sensitive grating；Environment temperature ΔTCause fiber grating strain sensor
Device wavelength shift, variation deltaλ sAre as follows: Δλ s=R sΔT, in formulaR sFor the temperature sensitivity of strain sensing unit；By (FBG) demodulator solution
The wavelength recalledλWavelength change caused by temperature is subtracted, finally obtains fiber Bragg grating strain sensor in set core stress relieving
Wavelength in journey are as follows:λ s=λ-Δλ s, whereinλFort 1The fiber Bragg grating strain sensor wavelength that moment wavelength demodulation device demodulates.
The beneficial effects of the present invention are: a kind of multi-point type optical fiber grating bottom hole strain gauge is anti-interference for resistance strain plate
The deficiencies of ability and long distance transmission are lost place, proposes the fiber Bragg grating strain sensor based on multipoint mode with temperature-compensating
Crustal stress bottom hole strain detecting method, and develop fiber grating bottom hole strain gauge.The present invention has anti-electromagnetic interference capability strong, resistance to
The advantages that corrosivity is good, precision small in size is high, measurement range is big, number of leads is few, transmission range is long, and structure is simple, size
Smaller, low to Rock Mass Integrality requirement, installation is quick and convenient with measurement procedure, may be implemented to install the hole in sub-aperture in Φ 76mm
Bottom strain measurement.
Detailed description of the invention
Fig. 1 is the reflectance spectrum and transmitted light spectrogram of grating.
Fig. 2 multi-point type optical fiber grating bottom hole strain gauge structure composition schematic diagram.
Fig. 3 fiber Bragg grating strain sensor mounting means schematic diagram.
Fig. 4 fiber Bragg grating strain sensor layout diagram.
Fig. 5 fiber Bragg grating strain sensor two-expanded view of layout diagram
Fig. 6 is one of set core stress relieving bottom hole Strain Method geostress survey step schematic diagram-set core macropore.
Fig. 7 is the two-installation apertures for covering core stress relieving bottom hole Strain Method geostress survey step schematic diagram.
Fig. 8 is the three-strain transducers installation for covering core stress relieving bottom hole Strain Method geostress survey step schematic diagram.
Fig. 9 is the four-set rock drilling cores for covering core stress relieving bottom hole Strain Method geostress survey step schematic diagram.
Figure 10 is one of multi-point type optical fiber grating bottom hole strain gauge strain testing result.
Figure 11 is the two of multi-point type optical fiber grating bottom hole strain gauge strain testing result.
Specific embodiment
Present invention will be further explained below with reference to the attached drawings and examples.
Referring to fig. 2, multi-point type optical fiber grating (FBG) bottom hole strain gauge structure composition schematic diagram of the present invention, 1 is in figure
Conical rubber cap, 2 be fiber Bragg grating strain sensor, and 3 be plastic emitting aperture, and 4 be Optical Fiber Winding groove, and 5 be binder retaining ring,
6 be glue storage cavity body, and 7 be pin hole, and 8 be piston rod, and 9 be wire lead slot, and 10 be installation positioning pin nail hole.It is measurement cone portion respectively
Divide 8 part 1-5, glue storage cavity body 6 and piston rod.Fiber Bragg grating strain sensor 2 is pasted onto advance on 1 outer wall of conical rubber cap,
In lower notches 4, lead is laid in wire lead slot 9 Optical Fiber Winding；Binder is stored in glue room 6, by piston rod 8 to
Glue in glue storage cavity body 6 is squeezed out and is compacted from lower end plastic hole 3 by the movement of 6 direction of glue storage cavity body, by fiber grating strain sensor
Device 2 is posted on bellmouth bed rock body；8 upper end of piston rod is equipped with installation positioning pin nail hole 10 and wire lead slot 9, passes through rotational installation
Bar realize mounting rod and the connection of piston rod with separate；(4 ~ 12h is generally required) after binder solidification, and fiber grating strain passes
Sensor 2 and bottom hole are securely cementing, take out mounting rod, start to cover core releasing, fiber Bragg grating strain sensor 2 is together with surrounding rock body
Deformation obtains strain of rock mass information during stress relieving.
Fiber Bragg grating strain sensor 2 uses multipoint mode mounting means, and space layout is as shown in figure 3, in measurement cone
Totally 8 groups of fiber Bragg grating strain sensors 2, along measurement cone even circumferential distribution, i.e. 45 ° of adjacent spaces, every group has 2 optical fiber light
Grid strain transducer 2, withρThe angle of axis is respectively 0 °, 90 °.
The multi-point type optical fiber grating bottom hole strain gauge, the connection type of fiber Bragg grating strain sensor (2): be according to
WithρThe angle of axis is divided into two groups of A, B (such as Fig. 4, Fig. 5), divides 2 for 16 fiber Bragg grating strain sensors 2 using 2 sensor fibres
Group is connected in series, wherein verticallyρAxis direction is that circumferential fiber Bragg grating strain sensor is A group, 1 optical fiber light of every installation
One circle of the winding of groove 4 above it of grid strain transducer 2, then installs next fiber Bragg grating strain sensor；Wherein alongρ
The fiber Bragg grating strain sensor 2 of axis direction be B group, each fiber Bragg grating strain sensor 2 according to wire locations respectively from it is upper,
Alternately one circle of winding, 2 groups of fiber Bragg grating strain sensors 2 measure circumferential direction ε to lower recess 4 respectivelyθWith axial ερStrain, convenient for into
The analysis of row data.
The multi-point type optical fiber grating bottom hole strain gauge, fiber Bragg grating strain sensor 2 are with temperature compensation unit
Strain transducer, temperature calibration are with compensation method: before fiber Bragg grating strain sensor 2 is mounted on measurement cylinder, first
Fiber Bragg grating strain sensor Unit 2 is placed in progress temperature calibration experiment in the case of constant temperature waters, wavelength with temperature is changed
Experimental data be fitted, handle and analyze, test to obtain the temperature sensitivity system of strain sensing unit by temperature calibration
Number, and then strain sensing unit temperature is compensated in set core stress relieving actual measurement；Optical fiber light with temperature compensation unit
There is the temperature-sensitive grating of a not strained influence inside grid strain transducer, it acts as monitoring variation of ambient temperature ΔsT, there is ΔT=(λ t1 -λ t0)/R 1, in formula:λ t0For the initial wavelength of temperature-sensitive grating；λ t1Fort 1The wavelength at moment；R 1For the temperature of temperature-sensitive grating
Sensitivity；Environment temperature ΔTCause fiber Bragg grating strain sensor wavelength shift, variation deltaλ sAre as follows: Δλ s=R sΔT, in formulaR sFor the temperature sensitivity of strain sensing unit；The wavelength that (FBG) demodulator is demodulatedλWavelength change caused by temperature is subtracted, finally
Obtain wavelength of fiber Bragg grating strain sensor during covering core stress relieving are as follows:λ s=λ-Δλ s, whereinλFort 1Moment wavelength
The fiber Bragg grating strain sensor wavelength that (FBG) demodulator demodulates.
Embodiment:
Multi-point type optical fiber grating bottom hole strain gauge of the present invention uses for reference the main structure of CCBO bottom hole strain testing instrument, maximum outside diameter
For 50 mm, entire length 100mm.When it carries out set core stress relieving bottom hole strain measurement method measurement crustal stress, measuring process is such as
Shown in Fig. 6-9.A drilling is drilled through at measuring point first to predetermined depth (generally higher than tunnel diameter) (such as Fig. 6), then with spy
Rounding taper bit drilling depth is the aperture (such as Fig. 7) of 280mm or so.5~10 ° of the updip that drills in order to rock powder and mud row
Out.Aperture is cleaned and wiped with clear water, cotton yarn and acetone, it will be clean in hole.
Measurement drilling, sub-aperture pore-forming and preparation it is ready after, by the binder being stirred inject glue room in, will measure
Cone and piston portion are fixed by pin, record the first time initial value of multiple spot fiber Bragg grating strain sensor.With with orientation
Fiber grating bottom hole strain gauge is sent into measurement sub-aperture (such as Fig. 8) by the mounting rod of device.
It after strain gauge is sent to predetermined position, forcibly drives mounting rod and worms, binder is from cavity aperture stream at this time
Into between gaging hole and the hole of element, second of initial value of multiple spot fiber Bragg grating strain sensor is recorded again.
(4 ~ 12h is generally required) after to be bonded dose of solidification, keeps element and bottom hole securely cementing, and record FBG sensor
Angle then takes out direction finder, and sensor fibre is successively pierced by from basket, drilling rod and the tee tube of the rear part, connects aperture
Fiber Bragg grating (FBG) demodulator, and record the final initial value of grating strain transducer.Several minutes of bath, after reading strain is stablized, i.e.,
It can carry out set core and release (such as Fig. 9), the measurement of grating strain transducer is carried out during covering core, set core is read every 0.5cm
Once, record fiber Bragg grating (FBG) demodulator reading, (drilling depth about 100mm to 200mm) stops set core when not changing with drilling depth wait read.
After covering core, the core for having strain gauge is taken out.Planar calibration is carried out, is finally turned survey measurements using special-purpose software
It is changed to crustal stress.
The in vitro Original strata stress test experiments of this set equipment are tested, and application effect is good.Multipoint mode light
Measured and record the strain curve of fine grating (FBG) bottom hole strain gauge.By Figure 10 and 11 it is found that 16 shown in figure are logical
Road signal, steady smooth, strong antijamming capability are very ideal.
The present invention is not limited to above-mentioned preferred forms, anyone obtain under the inspiration of the present invention other it is any with
The identical or similar product of the present invention, is within the scope of the present invention.
Claims (4)
1. a kind of multi-point type optical fiber grating bottom hole strain gauge, including measurement conical section, glue storage cavity body (6) and piston rod (8) portion
Point, there is the attachment device with finder, mounting rod in piston rod (8) upper end, and the upper end is equipped with installation positioning pin nail hole (10) and draws
Wire casing (9), by rotational installation bar realize mounting rod and the connection of piston rod with separate；It is characterized by: measurement conical section
Including fiber Bragg grating strain sensor (2), plastic hole (3) and binder retaining ring (5), glue storage cavity body (6) and pin hole (7), light
Fiber grating strain transducer (2) is pasted on conical rubber cap (1) outer wall, and Optical Fiber Winding is in lower notches (4), lead
It is laid in wire lead slot (9)；It is moved the glue in glue storage cavity body (6) to glue storage cavity body (6) direction from lower end by piston rod (8)
Plastic hole (3) squeezes out, and fiber Bragg grating strain sensor (2) is posted on bellmouth bed rock body, is deformed together with surrounding rock body,
Strain of rock mass information during acquisition stress relieving.
2. multi-point type optical fiber grating bottom hole strain gauge according to claim 1, it is characterised in that: fiber grating strain sensor
Device (2) is using single section multipoint mode mounting means, and totally 8 groups of fiber Bragg grating strain sensors (2), edge measure cone in measurement cone
The distribution of body even circumferential, i.e. 45 ° of adjacent spaces, every group has 2 fiber Bragg grating strain sensors (2), withρThe angle of axis is distinguished
It is 0 °, 90 °.
3. multi-point type optical fiber grating bottom hole strain gauge according to claim 2, it is characterised in that: fiber grating strain sensor
The connection type of device (2): 16 fiber Bragg grating strain sensors (2) point being connected in series for 2 groups using 2 sensor fibres,
It is wherein verticalρAxis direction is that circumferential fiber Bragg grating strain sensor is A group, 1 fiber Bragg grating strain sensor (2) of every installation
One circle of groove (4) winding above it, then installs next fiber Bragg grating strain sensor；Wherein alongρThe light of axis direction
Fiber grating strain transducer (2) is B group, and each fiber Bragg grating strain sensor (2) is recessed from upper and lower part respectively according to wire locations
Alternately one circle of winding, 2 groups of fiber Bragg grating strain sensors (2) measure circumferential direction ε to slot (4) respectivelyθWith axial ερStrain, is convenient for
Data analysis.
4. multi-point type optical fiber grating bottom hole strain gauge according to claim 1,2 or 3, it is characterised in that: fiber grating is answered
Become sensor (2) as the strain transducer with temperature compensation unit, temperature calibration is with compensation method: answering in fiber grating
Become sensor (2) to be mounted on before measurement cylinder, first fiber Bragg grating strain sensor (2) unit is placed in the case of constant temperature waters
Temperature calibration experiment is carried out, the experimental data of wavelength with temperature variation is fitted, handled and analyzed, passes through temperature calibration reality
It tests to obtain the temperature sensitivity coefficient of strain sensing unit, and then to strain sensing unit temperature in set core stress relieving actual measurement
It compensates；There is the temperature-sensitive grating of a not strained influence inside fiber Bragg grating strain sensor with temperature compensation unit,
It acts as monitoring variation of ambient temperature ΔsT, there is ΔT=(λ t1 -λ t0)/R 1, in formula:λ t0For the initial wavelength of temperature-sensitive grating；λ t1
Fort 1The wavelength at moment；R 1For the temperature sensitivity of temperature-sensitive grating；Environment temperature ΔTCause fiber Bragg grating strain sensor wavelength
Change, variation deltaλ sAre as follows: Δλ s=R sΔT, in formulaR sFor the temperature sensitivity of strain sensing unit；(FBG) demodulator is demodulated
WavelengthλWavelength change caused by temperature is subtracted, finally obtains fiber Bragg grating strain sensor cover core stress relieving during
Wavelength are as follows:λ s=λ-Δλ s, whereinλFort 1The fiber Bragg grating strain sensor wavelength that moment wavelength demodulation device demodulates.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
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| CN113670491A (en) * | 2021-08-17 | 2021-11-19 | 中国矿业大学 | Chemical expansion rubber-pushing type hollow capsule geostress meter and method |
| CN115014602A (en) * | 2022-06-16 | 2022-09-06 | 中国地质大学（武汉） | Sensitization type fiber grating hollow inclusion stressometer |
| CN115014602B (en) * | 2022-06-16 | 2023-12-29 | 中国地质大学（武汉） | Method for measuring sensitization type fiber bragg grating hollow inclusion stress meter |
| CN115420251A (en) * | 2022-11-02 | 2022-12-02 | 煤炭科学研究总院有限公司 | Twelve-component small-aperture hole bottom strain gauge |
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