CN101358886B - Fiber Bragg Grating Anchor Rod Measuring Device and Method for Monitoring Anchor Rod Stress Variation - Google Patents

Abstract

The invention discloses an optical fiber grating bolt force measuring device and an application method. Including the connection between the pressure gauge and the oil pipe, the connection between the horizontal pipe and the hydraulic cylinder, the anchor rod inserted into the inner hole of the hydraulic cylinder, the connection between the vertical pipe and the fiber grating sensor, the connection between the cladding and the fiber core in the fiber grating sensor housing, the fiber core is connected to the grating, and the fiber core Both ends are connected to a fiber grating sensor network analyzer and a computer. The application method of the force measuring device, the fiber grating demodulator detects the magnitude of the wavelength change, and converts it into an electrical signal, and the fiber grating sensor network analyzer calculates the stress and strain of the point to be measured and its distribution in the entire point to be measured Status; FBG wavelength demodulation analysis software reads test data; establishes a linear regression model to obtain the stress and strain values of the bolt under external force, with simple structure, low cost, and strong anti-interference ability; multi-parameter sensing measurement. High test accuracy, good stability, long signal transmission distance, widely used in mines or tunnels or slopes and other fields.

Description

The method that grating anchor rod force-measuring device and monitoring anchor stress change

Technical field

The present invention relates to the method that device for measuring force and monitoring anchor stress change, being specifically related to is a kind of grating anchor rod force-measuring device and the method that is applied to monitor the anchor stress variation.

Background technology

Existing mine or tunnel or side slope use anchor pole that rock or soil layer are reinforced, and employed anchor pole monitoring instrument has various ways such as resistance-strain type, steel chord type, flat jack formula by its type of sensor branch ^[1]But there is the requirement that can't satisfy the anchor pole long term monitoring in said method, its reason has two aspects: the work under bad environment of one side anchor pole, require high to the waterproof of sensor, protection against the tide, anticracking, anticorrosion etc., bring difficulty for the long term monitoring of anchor pole, also directly influenced the reliability and the serviceable life of instrument; On the other hand on the monitor signal long-distance transmissions, be difficult to realize automatic data collection and processing, also exist simultaneously complex structure, mounting process loaded down with trivial details, can only disposablely use, be difficult for protection and maintenance, be subjected to the big defective of influence of environment.

Summary of the invention

The purpose of this invention is to provide a kind of simple in structure, easy to operate, grating anchor rod force-measuring device that cost is low.

Another object of the present invention provides the method that the monitoring anchor stress changes.

In order to overcome the deficiencies in the prior art, technical scheme of the present invention is to solve like this: grating anchor rod force-measuring device, comprise a tensimeter, special character of the present invention is that tensimeter is connected with T font oil pipe, the horizontal tube of T font oil pipe is connected with hydraulic jack, anchor pole is inserted in the hydraulic jack endoporus, the vertical tube of T font oil pipe is connected with fiber-optic grating sensor, described fiber-optic grating sensor comprises a housing, be connected with covering in the housing, the covering inner chamber is equipped with a fibre core, and fibre core is connected with two gratings at least at interval, the fibre core two ends are connected on the optical fiber grating sensing network analyser, and the optical fiber grating sensing network analyser is connected with computer.

A kind of device for measuring force is applied to monitor the method that anchor stress changes, and is undertaken by following step:

1) skyhook, at first in rock or soil layer, bore bolthole, and in bolthole;

2), an end that will expose the anchor bar body outside rock or soil layer connects bunk, shell feed plate, hydraulic jack, backing plate successively respectively, is connected to one with nut at last;

3), the fibre core at fiber-optic grating sensor two ends lead-in wire is connected on the optical fiber grating sensing network analyser, the optical fiber grating sensing network analyser is connected with computer;

4), survey the size of its changed wavelength, and convert thereof into electric signal by the fiber grating demodulation device, calculate by the optical fiber grating sensing network analyser each measuring point for the treatment of geodesic structure ess-strain size and in whole structural distribution to be measured;

5), by optic fiber grating wavelength demodulation analysis software read test data;

6), the read test data are set up Linear Regression Model in One Unknown, after the arrangement, promptly draw anchor bar body ess-strain numerical value under external force, when this place's numerical value is in unsafe condition by analysis, unit in charge of construction must take corresponding reinforcement measure, prevents the generation of accident.

The present invention compared with prior art, simple in structure, operation, easy for installation, cost is low, it is except having little, in light weight, corrosion-resistant, the anti-electromagnetic interference (EMI) of ordinary optic fibre size sensor, advantage such as safe and reliable, also have its unique advantage: as the wavelength-modulated type, antijamming capability is strong; Be easy to and the optical fiber coupling, coupling loss is little; Integrate " biography " and " sense " and have stronger multiplexing capacity, be easy to constitute sensing network; Measuring object is extensive, is easy to realize the multiparameter sensing measurement.Reusable, be easy to the protection and the maintenance; can be used for anchor stress is distributed and long term monitoring; and has very high measuring accuracy; long-time stability are good; long distance of signal transmission; a kind of reliable and effective means are provided for the long-term on-line monitoring of bolt supporting quality, are widely used in mine or fields such as tunnel or side slope.

Description of drawings

Fig. 1 is an anchor rod force-measuring device structural representation of the present invention;

Fig. 2 is the dynamometry oil cylinder plan structure synoptic diagram of Fig. 1;

Fig. 3 is the main TV structure synoptic diagram of Fig. 2;

Fig. 4 is the dynamometry oil cylinder piston plan structure synoptic diagram of Fig. 1;

Fig. 5 is the main TV structure synoptic diagram of Fig. 4;

Fig. 6 is the optical fiber grating structure synoptic diagram;

Energy distribution synoptic diagram when Fig. 7 passes through grating for light;

Fig. 8 is the schematic diagram of fiber grating distributed sensor system;

Fig. 9 is optical fiber grating anchor ergometer and stem-winder reading comparison diagram;

Figure 10 is a grating anchor rod force-measuring device burial place synoptic diagram.

Embodiment

Accompanying drawing is embodiments of the invention.

Below in conjunction with accompanying drawing summary of the invention is described further:

With reference to shown in Figure 1, a kind of grating anchor rod force-measuring device, comprise a tensimeter 1, tensimeter 1 is connected with T font oil pipe 2, the horizontal tube of T font oil pipe 2 is connected with hydraulic jack 4, anchor pole is inserted in hydraulic jack 4 endoporus, the vertical tube of T font oil pipe 2 is connected with fiber-optic grating sensor 3, described fiber-optic grating sensor 3 comprises in the housing 5 and is connected with covering 6, covering 6 inner chambers are equipped with a fibre core 7, fibre core 7 is connected with two gratings 8 at least at interval, and fibre core 7 two ends are connected on the optical fiber grating sensing network analyser, and the optical fiber grating sensing network analyser is connected with computer.

Fig. 2, Figure 3 shows that the dynamometry oil cylinder is overlooked, main TV structure synoptic diagram, cylinder body 4-1 inner chamber is provided with the hole 4-2 that inserts anchor rod body, and cylinder body 4-1 inner chamber is filled with hydraulic oil 4-3, and the connection holes 4-4 that establishes on the cylinder body 4-1 is connected with horizontal tube one end of T font oil pipe 2.

Fig. 4, Figure 5 shows that the dynamometry oil cylinder piston is overlooked, main TV structure synoptic diagram, be provided with four spring eye 4-5 on the piston 4-6 at least, spring eye 4-5 is equipped with spring 4-7.

Fig. 6, energy distribution synoptic diagram when Figure 7 shows that optical fiber grating structure synoptic diagram and light by grating, fiber-optic grating sensor 3 comprises in the housing 5 and is connected with covering 6, covering 6 inner chambers are equipped with a fibre core 7, fibre core 7 is connected with two gratings 8 at least at interval, fibre core 7 two ends are connected on the optical fiber grating sensing network analyser, and the optical fiber grating sensing network analyser is connected with computer.

Theory of the fiber optical, fiber grating is a photosensitivity of utilizing doped fiber, make the photon of extraneous incident and the doping particle interaction in the fibre core by certain process (the normally ultraviolet ray to about the fiber-optic illuminated 240nm of Ge magnetic core), cause fiber core refractive index along fiber axis direction periodicity or acyclic permanent change, in fibre core, form the space phase grating.The principle of work of fiber grating can reduce following process: a branch of light beam is gone into the optical fiber grating, will produce effective reflection as long as satisfy Bragg condition, and catoptrical peak wavelength is called bragg wavelengths _B, in the single-mode fiber, bragg wavelength is

λ _B＝2n _effΛ (1)

N in the formula _EffBe the effective refractive index of fibre core, Λ is the space periodic of grating.Reflection or transmission peak wavelength spectrum depend primarily on the effective refractive index n of grating periods lambda and reverse coupled mould _Eff, any physical process that these two parameters are changed all will cause the drift of reflection or transmission peak wavelength.

Cause in the extraneous factor of grating Bragg wave length shift at all, the most direct for the strain parameter, because no matter be that grating is stretched or compress, all certainly will cause the Λ variation, and the elasto-optical effect that had of optical fiber itself makes n _EffAlso the variation with extraneous stress state changes, and this provides basic physical characteristic for adopting optical fiber Bragg raster to make fibre optic strain sensor.Also having a key factor is exactly temperature, and temperature is to λ _BInfluence then be because thermo-optic effect and thermal expansion effects.Ess-strain causes grating Bragg wave length shift

Δλ _Bε＝λ _B(1-P _e)Δε＝K _εΔε　　　　　　　(2)

In the formula: P _eFor the elasto-optical coefficient of optical fiber (to silica fibre, P _e=0.22); Δ ε is the optical fiber axial strain; K ε is for measuring the sensitivity (nm/ μ ε) of strain.The wavelength variable quantity that causes owing to temperature variation

Δλ _Bt＝λ _B(a+ζ)Δt＝K _tΔt　　　　　　　　　　　　(3)

In the formula: α is the thermal expansivity of optical fiber Bragg raster; ξ be fiber grating thermo-optical coeffecient (to silica fibre, α=0.5 * 10 ^-6℃ ^-1, ξ=7 * 10 ^-6℃ ^-1); Kt is for measuring the sensitivity (nm/ ℃) of temperature.

Suppose that strain and temperature cause that respectively the Bragg wavelength change is separate, the Bragg wavelength change can be expressed as when then both changed simultaneously

Δλ _B＝(1-P _e)Δε+λ _B(a+ζ)Δt＝K _sΔε+K _tΔt(4)

By formula (2) as can be known, fiber Bragg grating strain sensor based on this principle is minimum measurement unit with light wavelength, and the detection of at present optic fiber grating wavelength being moved has reached the high resolving power of pm magnitude, thereby it has the highly sensitive characteristics of measuring, and only need detect the accurate position of grating wavelength distribution plan medium wave peak, fluctuation to light intensity is insensitive, has higher antijamming capability than general Fibre Optical Sensor.Because draw, variation that compressive stress can both produce optic fiber grating wavelength to it, so this sensor has excellent distortion matching properties in structure detection, its dynamic range big (reaching 1000 μ ε) and the linearity are good.On the other hand, in strain measurement, for fear of the influence of temperature to measuring, by formula (3) as can be seen, measuring system can adopt the optical fiber grating temperature compensation sensor under the temperature environment of the same race to overcome.

Fig. 8 is the schematic diagram of fiber grating distributed sensor system, the accurate a plurality of optical fiber Bragg rasters that distribute, (λ 1, and λ 2 by different fiber grating reflection optical wavelength, λ n), with treat that geodesic structure is along each measurement point (1,2 of journey, n) corresponding, the distribute ess-strain of each point of geodesic structure is treated in impression along the line respectively, and its catoptrical wavelength is changed.The reflected light that changes spreads out of from measure field through Transmission Fibers, survey the size of its changed wavelength by the optical fiber Bragg raster detuner, and converting thereof into electric signal, the size that is calculated the ess-strain of each measuring point for the treatment of geodesic structure by secondary instrument reaches in whole structural distribution to be measured.

Fig. 9 is optical fiber grating anchor ergometer and stem-winder reading comparison diagram, and horizontal ordinate is the real load that is carried on the optical fiber grating anchor ergometer among the figure, and left side ordinate is the stem-winder reading, and the right ordinate is a fiber grating pressure gauge reading.By data in the table as can be known, data are linear distribution substantially, and set up Linear Regression Model in One Unknown data in the last table are analyzed,

y＝ax+b

A in the formula, b are regression coefficient, and x is institute's imposed load, and unit is KN.Degree of confidence is 95%, and the linear regression analysis result is as shown in table 2.

The linear regression analysis of table 2 experimental data

Table2Linear?regression?analysis?of?experiment?results

By above-mentioned test and data analysis result as can be known:

(1) in the test, the linearity of tensimeter and fiber-optic grating sensor reading is 1 all, illustrates that tensimeter and fiber-optic grating sensor all have the good linearity in afternoon in the morning.

(2) the slope basically identical of the regression curve of fiber-optic grating sensor reading, and pressure gauge reading regression curve slope differs relatively large, illustrates that fiber-optic grating sensor specific pressure table performance is more stable.

(3) tensimeter and fiber-optic grating sensor reading all have a bit of inelastic region at two ends, and the linearity of interlude is very good, and anchor pole is stressed substantially at interlude, do not influence its accurate measurement.

(4) load several times and uninstall process in, the reading of tensimeter and fiber-optic grating sensor all can return initial value substantially, illustrate that tensimeter and fiber-optic grating sensor all work in its elastic range, and is repeated better.

(5) in the test of the morning and afternoon, the fiber-optic grating sensor reading has certain difference, because of the morning, afternoon the temperature difference cause, in single load and unloading test, because the time is shorter, can ignore Temperature Influence, and the morning and afternoon temperature difference bigger, fiber-optic grating sensor there is certain influence, illustrates when optical fiber grating anchor ergometer is applied to field monitoring and must take the temperature compensation measure.

Figure 10 shows that the on-the-spot burial place synoptic diagram of grating anchor rod force-measuring device, beat armature boring 9 at rock or soil layer, skyhook 10 in armature boring 9, then boring 9 in filling cementing agent fixing anchor bar 10, after treating filling cementing agent condensation cure, on an end of the exposed anchor pole 10 of rock or soil layer, connect bunk 11 successively respectively, shell feed plate 12, hydraulic jack 4, backing plate 13, be connected to one with nut 14 at last, the end load of anchor pole acts on the oil cylinder piston 4-6, affact on the hydraulic oil 4-3 by oil cylinder piston 4-6, can calculate the size of oil pressure P under anchor pole end load F effect thus, the oil cylinder piston active area is calculated as follows

S＝πR ²-πr ²(5)

The end load of anchor pole acts on the oil cylinder piston, affacts on the oil by oil cylinder piston, can calculate the size of oil pressure P under anchor pole end load F effect thus,

$P=\frac{F}{S}=\frac{F}{\mathrm{\π}(R^2-r^2)}---\left(6\right)$

Optical fiber grating anchor ergometer is when installation; impacted in work progress for fear of fiber Bragg grating strain sensor; prevent that the fiber grating signal transmssion line is destroyed in work progress; must note protecting the fiber grating signal transmssion line; the fiber grating signal transmssion line is installed in the hidden place of religion, protects the cleaning of optical patchcord head.

Device for measuring force is applied to monitor the method that anchor stress changes, and is undertaken by following step:

1) skyhook, at first in rock or soil layer, bore bolthole, and in bolthole;

2), an end that will expose the anchor bar body outside rock or soil layer is inserted in backing plate, hydraulic jack (4), backing plate successively, is connected to one with nut;

3), fibre core 7 lead-in wire at fiber-optic grating sensor two ends is connected on the optical fiber grating sensing network analyser, the optical fiber grating sensing network analyser is connected with computer;

4), survey the size of its changed wavelength, and convert thereof into electric signal by the fiber grating demodulation device, calculate by the optical fiber grating sensing network analyser each measuring point for the treatment of geodesic structure ess-strain size and in whole structural distribution to be measured;

5), by optic fiber grating wavelength demodulation analysis software read test data;

6), the read test data are set up Linear Regression Model in One Unknown, after the arrangement, promptly draw anchor bar body ess-strain numerical value under external force, when this place's numerical value is in unsafe condition by analysis, unit in charge of construction must take corresponding reinforcement measure, prevents the generation of accident.

In sum, bolt supporting is compared with traditional shed ding support, it has simple in structure, easy to operate, low cost and other advantages, and along with the raising of roadway support technology, bolt supporting has developed into one of a kind of main support form of world's mine laneway and other underground engineering support.The supporting quality of anchor pole is determining the safe in utilization and adjoining rock stability in tunnel, how stability, the security in tunnel is monitored, and takes preventive measures in advance, avoids loss and disaster.

Fiber-optic grating sensor size and package design thereof

Grating is the space phase grating that forms in the fibre core of single-mode fiber with the Ultra-Violet Laser method of writing direct, and grating region length is 2cm, and fiber core 9 μ m, covering external diameter are 125 μ m, and the external diameter behind the band overlay is 250 μ m.Fiber-optic grating sensor physical dimension is 98mm * 36mm * 36mm, two ends band standard FC/PC wire jumper head.

The experiment of optical fiber grating anchor ergometer pressure testing machine loading and unloading:

Be the performance of measuring fiber grating anchor ergometer, optical fiber grating anchor ergometer loaded and unloads experiment with pressure testing machine in the laboratory.The loading equipemtn that experiment is used is a 300KN universal material pressure testing machine, and testing tool is selected P101 type optical fiber grating sensing network analyser for use, and its key technical indexes is: wavelength resolution is _1pm, sweep limit is 1525～1565nm, variable resolution≤1 μ ε is answered in temperature resolution≤0.1 ℃.P101 type optical fiber grating sensing network analyser is connected with computer, by the optic fiber grating wavelength demodulation analysis software read test data of special use.

Utilize per step of pressure testing machine to load 10KN in the experiment to optical fiber grating anchor ergometer, work in its range ability for guaranteeing optical fiber grating anchor ergometer, being loaded into 120KN stops, loaded for 12 steps altogether, after treating that reading is stable, begin unloading from 120KN again, and read the reading in the uninstall process with per step 10KN.

Experiment records data and sees Table 1.

Table 1 pressing machine loading and unloading experimental data

Bolt supporting quality fiber grating monitoring system

A very important advantage of fiber-optic grating sensor is exactly that optical fiber optical grating array combines with wavelength-division multiplex (WDM) Time Division Multiplexing and space division multiplexing (SDM) technology, constitutes the quasi-distributed monitoring system of fiber grating.Arrange optical fiber grating anchor ergometer in local each anchor pole monitoring point such as colliery underworkings, open-off cut and coal column, each optical fiber grating anchor ergometer couples together by the watch-dog on optical fiber and ground, has formed bolt supporting quality fiber grating monitoring system.Utilize this monitoring system can realize the stressing conditions of each monitoring point anchor pole of down-hole is monitored, thereby underworkings supporting quality and coal column stability etc. is made assessment and prediction.

Conclusion

(1) optical fiber grating anchor ergometer is compared with simple manometer and is had higher measuring accuracy.

(2) the optical fiber grating anchor ergometer morning and afternoon experimental result be subjected to Temperature Influence, can adopt certain indemnifying measure to eliminate the influence of temperature on fiber grating anchor ergometer.

(3) optical fiber grating anchor ergometer can be used for the bolt supporting quality is carried out on-line monitoring, does not need engineering technical personnel's field observation.

(4) to be used for bolt supporting quality on-line monitoring be essential safety to optical fiber grating anchor ergometer, satisfies colliery underground monitoring safety anti-explosive requirement.

Claims (2)

1. grating anchor rod force-measuring device, comprise a tensimeter (1), it is characterized in that tensimeter (1) is connected with T font oil pipe (2), the horizontal tube of T font oil pipe (2) is connected with hydraulic jack (4), anchor pole is inserted in hydraulic jack (4) endoporus, the vertical tube of T font oil pipe (2) is connected with fiber-optic grating sensor (3), described fiber-optic grating sensor (3) comprises a housing (5), be connected with covering (6) in the housing (5), covering (6) inner chamber is equipped with a fibre core (7), fibre core (7) is connected with two gratings (8) at least at interval, fibre core (7) two ends are connected on the optical fiber grating sensing network analyser, and the optical fiber grating sensing network analyser is connected with computer.

2. the described device for measuring force of claim 1 is applied to monitor the method that anchor stress changes, and is undertaken by following step:

1) skyhook, at first in rock or soil layer, bore bolthole, and in bolthole;

2), an end that will expose the anchor bar body outside rock or soil layer connects bunk (11), shell feed plate (12), hydraulic jack (4), backing plate (13) successively respectively, is connected to one with nut at last;

3), the fibre core (7) at fiber-optic grating sensor two ends lead-in wire is connected on the optical fiber grating sensing network analyser, the optical fiber grating sensing network analyser is connected with computer;

4), survey the size of its changed wavelength, and convert thereof into electric signal by the fiber grating demodulation device, calculate by the optical fiber grating sensing network analyser each measuring point for the treatment of geodesic structure ess-strain size and in whole structural distribution to be measured;

5), by optic fiber grating wavelength demodulation analysis software read test data;

6), the read test data are set up Linear Regression Model in One Unknown, after the arrangement, promptly draw anchor bar body ess-strain numerical value under external force, when this place's numerical value is in unsafe condition by analysis, unit in charge of construction must take corresponding reinforcement measure, prevents the generation of accident.

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