CN103454020A - Surrounding rock stress on-line monitoring system and method based on fiber bragg grating borehole stress meter - Google Patents

Abstract

The invention relates to a surrounding rock stress on-line monitoring system and method based on a fiber bragg grating borehole stress meter. A plurality of measurement points are arranged on a surrounding rock, the fiber bragg grating borehole stress meter is installed in a surrounding rock wall drill hole, an optical fiber connector is connected with an optical fiber, and the optical fiber is connected to a mining optical cable, is then directly connected to the ground, and is connected with a fiber bragg grating modulator; an optical signal is modulated to a digital signal by the fiber bragg grating modulator, the digital signal is transmitted to a computer, is monitored in real time and is analyzed and processed, and a surrounding rock axial stress and transverse stress analyzing and processing method is provided under the temperature compensation condition according to grating stress characteristics. The surrounding rock stress on-line monitoring system and method have the advantages that equipment is easy to install, long in service life and suitable for popularization and use; power supply is not needed underground, electrical signals and electronic devices do not exist, and therefore the field is safe; because all-optical measurement and optical fiber transmission are adopted, monitoring precision is greatly improved, and effect of electromagnetic interference can be effectively avoided under complex and poor environment; surrounding rock stress monitoring results can be provided in time and guiding of field production and scientific research work is facilitated.

Description

Surrouding rock stress on-line monitoring system and method based on the fiber grating borehole stressmeter

Technical field

The present invention relates to a kind of Stress On-Line system and method, specifically a kind of surrouding rock stress on-line monitoring system and method based on the fiber grating borehole stressmeter.

Background technology

In recent years, the continuous increase with mining depth that improves constantly along with mining technique, the disaster that strata behaviors causes is also more and more serious, as the accidents such as roof collapse, roadway deformation, impulsion pressure frequently occur, cause huge loss to the coal mining of China, had a strong impact on practitioner's life security and mine production.Therefore, as the surrouding rock stress of one of mine safety production important leverage means, monitoring more and more comes into one's own, also more and more higher to the requirement of accuracy, reliability and the on-line monitoring ability of monitoring.If set up an advanced person's surrouding rock stress on-line monitoring early warning system, just can effectively prevent and reduce the generation of ore deposit pressure accident.

Although obtained certain development in manual intelligent monitoring field both at home and abroad at present, existing ore deposit presses monitoring method generally to have following shortcoming: 1, be subject to electromagnetic interference (EMI) and external environmental interference, monitoring accuracy is bad; 2, non-moistureproof, reliability is low, and monitoring efficiency is not high, and the sensing element life-span is short; 3, can't carry out remote monitoring to monitoring, can not realize real time on-line monitoring and long term monitoring.

Summary of the invention

Technical matters: in order to overcome deficiency of the prior art, the invention provides a kind of surrouding rock stress on-line monitoring system and method based on the fiber grating borehole stressmeter, solving current ore deposit presses monitoring to exist: 1, be subject to electromagnetic interference (EMI) and external environmental interference, monitoring accuracy is bad; 2, non-moistureproof, reliability is low, and monitoring efficiency is not high, and the sensing element life-span is short; 3, can't carry out remote monitoring to monitoring, can not realize the problem of real time on-line monitoring and long term monitoring.

Technical scheme: purpose of the present invention is achieved through the following technical solutions:

A kind of surrouding rock stress on-line monitoring based on the fiber grating borehole stressmeter comprises system and method,

Described system comprises: fiber grating borehole stressmeter, fiber connector, optical fiber, optical fiber cable for mine, fiber Bragg grating (FBG) demodulator and computing machine; Afterbody at the fiber grating borehole stressmeter is connected with fiber connector, and fiber connector is connected with the input end of fiber Bragg grating (FBG) demodulator with optical fiber cable for mine by optical fiber, and the output terminal of fiber Bragg grating (FBG) demodulator is connected with computing machine; Include many group fiber gratings in described fiber grating borehole stressmeter, every group of fiber grating is comprised of an axial strain grating, a transverse strain grating and a temperature grating.

Described method realizes through the following steps:

The vertical working wall boring in roadway surrounding rock of A, use drilling machine, bore diameter is than the large 2-4mm of the diameter of fiber grating borehole stressmeter, Anchor Agent is sent into to the boring front end, the fiber grating borehole stressmeter is arranged in boring by horizontal or vertical direction, and with the abundant anchoring of Anchor Agent; Fiber connector is drawn to the outside of boring and is connected with optical fiber, by boring sand-cement slurry sealing of hole; Optical fiber access optical fiber cable for mine, be passed to the ground fiber Bragg grating (FBG) demodulator by light signal, and after demodulation, signal transfers to computer system, and computer system obtains the centre wavelength drift value of axial strain grating, transverse strain grating and temperature grating;

B, the centre wavelength data of axial strain grating and temperature grating are handled as follows to obtain the axial strain amount:

$\left\{\begin{array}{c}\frac{\mathrm{\Δ}{\mathrm{\λ}}_{B_H}}{{\mathrm{\λ}}_{B_H}}=K_{\mathrm{\ϵ}}{\mathrm{\ϵ}}_H+K_T\mathrm{\ΔT}\\ \frac{\mathrm{\Δ}{\mathrm{\λ}}_{B_T}}{{\mathrm{\λ}}_{B_T}}=K_T\mathrm{\ΔT}\end{array}\right.$

In formula,

be respectively the centre wavelength drift value of axial strain grating and temperature grating,

be respectively the initial center wavelength of axial strain grating and temperature grating, ε _hfor the axial strain amount of axial strain grating, K _εfor wave length shift axial sensitivity coefficient under the fiber grating photoelastic effect, K _tfor fiber grating relative temperature sensitivity coefficient, Δ T is temperature variation;

C, obtain the axial strain amount after, obtain the country rock axial stress at one group of axial strain stop position place according to following formula:

σ _H＝Eε _H

In formula, σ _hfor this group stop position place country rock axial stress, the elastic modulus that E is the fiber grating borehole stressmeter;

For the unbalance stress of avoiding fiber grating borehole stressmeter bias to cause, four groups of axial strain gratings, transverse strain grating and temperature grating are calculated to gained country rock axial stress and be weighted on average, obtain revised country rock axial stress:

${{\mathrm{\&sigma;}}_H}^{\text{'}}=\frac{{\mathrm{\&sigma;}}_{H_1}+{\mathrm{\&sigma;}}_{{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">H</figure-callout>}}_2}+{\mathrm{\&sigma;}}_{{\mathrm{<figure-callout\; id="3"\; label="H"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">H</figure-callout>}}_3}+{\mathrm{\&sigma;}}_{{\mathrm{<figure-callout\; id="4"\; label="H"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">H</figure-callout>}}_4}}{4}$

In formula, σ _h' be revised country rock axial stress,

be respectively the country rock axial stress at axial strain stop position place in four groups of fiber gratings;

D, the centre wavelength data of transverse strain grating are handled as follows to obtain level and the perpendicular stress of grating xsect:

$\left\{\begin{array}{c}\frac{\mathrm{\&Delta;}{\mathrm{\&lambda;}}_{\mathrm{Bx}}}{{\mathrm{\&lambda;}}_{B0}}=-\frac{(1+v){\mathrm{<figure-callout\; id="2"\; label="n\; eff"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">n</figure-callout>}}_{\mathrm{eff}}^{}}{2E}\left\{\right[(1-v)p_{11}-v{p}_{12}]{\mathrm{\&sigma;}}_x+[(1-v)p_{12}-v{p}_{11}]{\mathrm{\&sigma;}}_y\\ \frac{\mathrm{\&Delta;}{\mathrm{\&lambda;}}_{\mathrm{By}}}{{\mathrm{\&lambda;}}_{B0}}=-\frac{(1+v){\mathrm{<figure-callout\; id="2"\; label="n\; eff"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">n</figure-callout>}}_{\mathrm{eff}}^{}}{2E}\left\{\right[(1-v)p_{12}-v{p}_{11}]{\mathrm{\&sigma;}}_x+[(1-v)p_{11}-v{p}_{12}\left]{\mathrm{\&sigma;}}_y\right\}\end{array}\right.$

In formula,

be respectively the transverse strain grating in the horizontal direction with the centre wavelength drift value of vertical direction, λ _b0for the initial center wavelength of transverse strain grating, n _efffor the initial effective refractive index of transverse strain grating, the elastic modulus that E is fiber grating, the Poisson's coefficient that ν is fiber grating, p ₁₁, p ₁₂be respectively the horizontal and axial strain optical coefficient of fiber grating, σ _x, σ _ythe level that is respectively grating xsect mid point reaches vertical;

E, obtain the level and perpendicular stress of grating xsect mid point after, in following two formulas, select the same form obtain fiber grating borehole stressmeter boring edge country rock at this group stop position place the radial stress along xsect:

$\left\{\begin{array}{c}{\mathrm{\&sigma;}}_x=\frac{2{\mathrm{\&sigma;}}_V}{\mathrm{\&pi;LD}}\\ {\mathrm{\&sigma;}}_y=-\frac{6{\mathrm{\&sigma;}}_V}{\mathrm{\&pi;LD}}\end{array}\right.$

In formula, σ _vfor this group stop position place country rock radial stress, L is fiber grating length, and D is fibre diameter;

F, the unbalance stress for avoiding fiber grating borehole stressmeter bias to cause, every group of fiber grating calculated value to axisymmetric position is weighted on average, because the fiber grating borehole stressmeter is installed by horizontal or vertical direction, in the grating group calculated value of upright position radially stress be perpendicular stress, in the grating group calculated value of horizontal level radially stress be horizontal stress, can obtain revised country rock horizontal stress and perpendicular stress:

$\left\{\begin{array}{c}{\mathrm{\&sigma;}}_{\mathrm{Vx}}=\frac{{\mathrm{\&sigma;}}_{V1}+{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="3"\; label="V"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">V</figure-callout>}3}}{2}\\ {\mathrm{\&sigma;}}_{\mathrm{Vy}}=\frac{{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">V</figure-callout>}2}+{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="4"\; label="V"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">V</figure-callout>}4}}{2}\end{array}\right.$

In formula, σ _vx, σ _vybe respectively revised stop position place country rock horizontal stress and perpendicular stress, σ _v1, σ _v3be respectively the country rock horizontal stress of two groups of rotational symmetry fiber gratings of horizontal direction, σ _v2, σ _v4be respectively the country rock perpendicular stress of two groups of rotational symmetry fiber gratings of vertical direction.

Beneficial effect, owing to having adopted such scheme, a kind of surrouding rock stress on-line monitoring system and method based on the fiber grating borehole stressmeter, arrange some measuring points at country rock, the fiber grating borehole stressmeter is arranged in the boring of country rock wall, fiber connector is connected with optical fiber, the straight-through ground of optical fiber access optical fiber cable for mine, be connected with fiber Bragg grating (FBG) demodulator, realize that light signal is from down-hole to aboveground transmission; Fiber Bragg grating (FBG) demodulator is monitored and analyzing and processing in real time with light signal being demodulated into to digital signal and transferring to computing machine, and the analysis and processing method of country rock axial stress and transverse stress under the temperature compensation condition is provided according to the grating stress characteristic.Having solved current ore deposit presses monitoring to exist: 1, be subject to electromagnetic interference (EMI) and external environmental interference, monitoring accuracy is bad; 2, non-moistureproof, reliability is low, and monitoring efficiency is not high, and the sensing element life-span is short; 3, can't carry out remote monitoring to monitoring, can not realize the problem of real time on-line monitoring and long term monitoring, reach purpose of the present invention.

Advantage: equipment is installed simple, and long service life, be suitable for generally applying; Down-hole does not need power supply, does not have electric signal and electron device, guarantees site safety; Adopt full photo measure and Optical Fiber Transmission, greatly improved monitoring accuracy, and can effectively avoid the impact of electromagnetic interference (EMI) under complicated rugged surroundings; The surrouding rock stress monitoring result can be provided in time, be beneficial to guide field production and research work.

The accompanying drawing explanation

Fig. 1 is system architecture schematic diagram of the present invention.

Fig. 2 is advance of the face direction measuring point arrangement figure of the present invention.

Fig. 3 is that tunnel of the present invention measuring point is arranged sectional drawing.

Fig. 4 is that system of the present invention forms frame diagram.

In figure, 1 is the fiber grating borehole stressmeter; 2 is fiber connector; 3 is optical fiber; 4 is optical fiber cable for mine; 5 is the light fiber Bragg grating (FBG) demodulator; 6 is computing machine; 7 is country rock; 8 is Anchor Agent; 9 is sand-cement slurry; 10 is workplace; 11 is mining roadway; 12 is advance of the face direction measuring point; 13 is boring; 14 is anchor pole.

Embodiment

Below in conjunction with accompanying drawing, one embodiment of the present of invention are further described:

Embodiment 1: a kind of surrouding rock stress on-line monitoring based on the fiber grating borehole stressmeter comprises system and method,

Described system comprises: fiber grating borehole stressmeter 1, fiber connector 2, optical fiber 3, optical fiber cable for mine 4, fiber Bragg grating (FBG) demodulator 5 and computing machine 6; Afterbody at fiber grating borehole stressmeter 1 is connected with fiber connector 2, and fiber connector 2 is connected with the input end of fiber Bragg grating (FBG) demodulator 5 with optical fiber cable for mine 4 by optical fiber 3, and the output terminal of fiber Bragg grating (FBG) demodulator 5 is connected with computing machine 6; Include 4 groups of fiber gratings in described fiber grating borehole stressmeter 1, every group of fiber grating is comprised of an axial strain grating, a transverse strain grating and a temperature grating.

Described method realizes through the following steps:

The vertical working wall boring in roadway surrounding rock of A, use drilling machine, bore diameter is than the large 2-4mm of the diameter of fiber grating borehole stressmeter, Anchor Agent is sent into to the boring front end, the fiber grating borehole stressmeter is arranged in boring by horizontal or vertical direction, and with the abundant anchoring of Anchor Agent; Fiber connector is drawn to the outside of boring and is connected with optical fiber, by boring sand-cement slurry sealing of hole; Optical fiber access optical fiber cable for mine, be passed to the ground fiber Bragg grating (FBG) demodulator by light signal, and after demodulation, signal transfers to computer system, and computer system obtains the centre wavelength drift value of axial strain grating, transverse strain grating and temperature grating;

B, the centre wavelength data of axial strain grating and temperature grating are handled as follows to obtain the axial strain amount:

$\left\{\begin{array}{c}\frac{\mathrm{\&Delta;}{\mathrm{\&lambda;}}_{B_H}}{{\mathrm{\&lambda;}}_{B_H}}=K_{\mathrm{\&epsiv;}}{\mathrm{\&epsiv;}}_H+K_T\mathrm{\&Delta;T}\\ \frac{\mathrm{\&Delta;}{\mathrm{\&lambda;}}_{B_T}}{{\mathrm{\&lambda;}}_{B_T}}=K_T\mathrm{\&Delta;T}\end{array}\right.$

In formula,

be respectively the centre wavelength drift value of axial strain grating and temperature grating,

be respectively the initial center wavelength of axial strain grating and temperature grating, ε _hfor the axial strain amount of axial strain grating, K _εfor wave length shift axial sensitivity coefficient under the fiber grating photoelastic effect, K _tfor fiber grating relative temperature sensitivity coefficient, Δ T is temperature variation;

C, obtain the axial strain amount after, obtain the country rock axial stress at one group of axial strain stop position place according to following formula:

σ _H＝Eε _H

In formula, σ _hfor this group stop position place country rock axial stress, the elastic modulus that E is the fiber grating borehole stressmeter;

For the unbalance stress of avoiding fiber grating borehole stressmeter bias to cause, four groups of axial strain gratings, transverse strain grating and temperature grating are calculated to gained country rock axial stress and be weighted on average, obtain revised country rock axial stress:

${{\mathrm{\&sigma;}}_H}^{\text{'}}=\frac{{\mathrm{\&sigma;}}_{H_1}+{\mathrm{\&sigma;}}_{{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">H</figure-callout>}}_2}+{\mathrm{\&sigma;}}_{{\mathrm{<figure-callout\; id="3"\; label="H"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">H</figure-callout>}}_3}+{\mathrm{\&sigma;}}_{{\mathrm{<figure-callout\; id="4"\; label="H"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">H</figure-callout>}}_4}}{4}$

In formula, σ _h' be revised country rock axial stress,

be respectively the country rock axial stress at axial strain stop position place in four groups of fiber gratings;

D, the centre wavelength data of transverse strain grating are handled as follows to obtain level and the perpendicular stress of grating xsect:

$\left\{\begin{array}{c}\frac{\mathrm{\&Delta;}{\mathrm{\&lambda;}}_{\mathrm{Bx}}}{{\mathrm{\&lambda;}}_{B0}}=-\frac{(1+v){\mathrm{<figure-callout\; id="2"\; label="n\; eff"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">n</figure-callout>}}_{\mathrm{eff}}^{}}{2E}\left\{\right[(1-v)p_{11}-v{p}_{12}]{\mathrm{\&sigma;}}_x+[(1-v)p_{12}-v{p}_{11}\left]{\mathrm{\&sigma;}}_y\right\}\\ \frac{\mathrm{\&Delta;}{\mathrm{\&lambda;}}_{\mathrm{By}}}{{\mathrm{\&lambda;}}_{B0}}=-\frac{(1+v){\mathrm{<figure-callout\; id="2"\; label="n\; eff"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">n</figure-callout>}}_{\mathrm{eff}}^{}}{2E}\left\{\right[(1-v)p_{12}-v{p}_{11}]{\mathrm{\&sigma;}}_x+[(1-v)p_{11}-v{p}_{12}\left]{\mathrm{\&sigma;}}_y\right\}\end{array}\right.$

In formula,

be respectively the transverse strain grating in the horizontal direction with the centre wavelength drift value of vertical direction, λ _b0for the initial center wavelength of transverse strain grating, n _efffor the initial effective refractive index of transverse strain grating, the elastic modulus that E is fiber grating, the Poisson's coefficient that ν is fiber grating, p ₁₁, p ₁₂be respectively the horizontal and axial strain optical coefficient of fiber grating, σ _x, σ _ythe level that is respectively grating xsect mid point reaches vertical;

E, obtain the level and perpendicular stress of grating xsect mid point after, in following two formulas, select the same form obtain fiber grating borehole stressmeter boring edge country rock at this group stop position place the radial stress along xsect:

$\left\{\begin{array}{c}{\mathrm{\&sigma;}}_x=\frac{2{\mathrm{\&sigma;}}_V}{\mathrm{\&pi;LD}}\\ {\mathrm{\&sigma;}}_y=-\frac{6{\mathrm{\&sigma;}}_V}{\mathrm{\&pi;LD}}\end{array}\right.$

In formula, σ _vfor this group stop position place country rock radial stress, L is fiber grating length, and D is fibre diameter;

F, the unbalance stress for avoiding fiber grating borehole stressmeter bias to cause, every group of fiber grating calculated value to axisymmetric position is weighted on average, because the fiber grating borehole stressmeter is installed by horizontal or vertical direction, in the grating group calculated value of upright position radially stress be perpendicular stress, in the grating group calculated value of horizontal level radially stress be horizontal stress, can obtain revised country rock horizontal stress and perpendicular stress:

$\left\{\begin{array}{c}{\mathrm{\&sigma;}}_{\mathrm{Vx}}=\frac{{\mathrm{\&sigma;}}_{V1}+{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="3"\; label="V"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">V</figure-callout>}3}}{2}\\ {\mathrm{\&sigma;}}_{\mathrm{Vy}}=\frac{{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">V</figure-callout>}2}+{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="4"\; label="V"\; filenames="HDA0000367292980000011.png"\; state="\{\{state\}\}">V</figure-callout>}4}}{2}\end{array}\right.$

In formula, σ _vx, σ _vybe respectively revised stop position place country rock horizontal stress and perpendicular stress, σ _v1, σ _v3be respectively the country rock horizontal stress of two groups of rotational symmetry fiber gratings of horizontal direction, σ _v2, σ _v4be respectively the country rock perpendicular stress of two groups of rotational symmetry fiber gratings of vertical direction.

By above concrete enforcement, the invention provides a kind of surrouding rock stress on-line monitoring system and method based on the fiber grating borehole stressmeter, arrange some measuring points at country rock, the fiber grating borehole stressmeter is arranged in the boring of country rock wall, fiber connector is connected with optical fiber, the straight-through ground of optical fiber access optical fiber cable for mine, be connected with fiber Bragg grating (FBG) demodulator, realizes that light signal is from down-hole to aboveground transmission; Fiber Bragg grating (FBG) demodulator is monitored and analyzing and processing in real time with light signal being demodulated into to digital signal and transferring to computing machine, and the analysis and processing method of country rock axial stress and transverse stress under the temperature compensation condition is provided according to the grating stress characteristic.Its advantage is: equipment is installed simple, and long service life, be suitable for generally applying; Down-hole does not need power supply, does not have electric signal and electron device, guarantees site safety; Adopt full photo measure and Optical Fiber Transmission, greatly improved monitoring accuracy, and can effectively avoid the impact of electromagnetic interference (EMI) under complicated rugged surroundings; The surrouding rock stress monitoring result can be provided in time, be beneficial to guide field production and research work.

Embodiment 2: include 10 groups of fiber gratings in described fiber grating borehole stressmeter 1.Other embodiment 1 are same.

Claims (2)

1. the surrouding rock stress on-line monitoring system based on the fiber grating borehole stressmeter, it is characterized in that: described system comprises: fiber grating borehole stressmeter, fiber connector, optical fiber, optical fiber cable for mine, fiber Bragg grating (FBG) demodulator and computing machine; Afterbody at the fiber grating borehole stressmeter is connected with fiber connector, and fiber connector is connected with the input end of fiber Bragg grating (FBG) demodulator with optical fiber cable for mine by optical fiber, and the output terminal of fiber Bragg grating (FBG) demodulator is connected with computing machine; Include many group fiber gratings in described fiber grating borehole stressmeter, every group of fiber grating is comprised of an axial strain grating, a transverse strain grating and a temperature grating.

2. the method for the surrouding rock stress on-line monitoring system based on the fiber grating borehole stressmeter claimed in claim 1, it is characterized in that: described method realizes through the following steps:

The vertical working wall boring in roadway surrounding rock of A, use drilling machine, bore diameter is than the large 2-4mm of the diameter of fiber grating borehole stressmeter, Anchor Agent is sent into to the boring front end, the fiber grating borehole stressmeter is arranged in boring by horizontal or vertical direction, and with the abundant anchoring of Anchor Agent; Fiber connector is drawn to the outside of boring and is connected with optical fiber, by boring sand-cement slurry sealing of hole; Optical fiber access optical fiber cable for mine, be passed to the ground fiber Bragg grating (FBG) demodulator by light signal, and after demodulation, signal transfers to computer system, and computer system obtains the centre wavelength drift value of axial strain grating, transverse strain grating and temperature grating;

B, the centre wavelength data of axial strain grating and temperature grating are handled as follows to obtain the axial strain amount:

$\left\{\begin{array}{c}\frac{\mathrm{\&Delta;}{\mathrm{\&lambda;}}_{B_H}}{{\mathrm{\&lambda;}}_{B_H}}=K_{\mathrm{\&epsiv;}}{\mathrm{\&epsiv;}}_H+K_T\mathrm{\&Delta;T}\\ \frac{\mathrm{\&Delta;}{\mathrm{\&lambda;}}_{B_T}}{{\mathrm{\&lambda;}}_{B_T}}=K_T\mathrm{\&Delta;T}\end{array}\right.$

In formula,

be respectively the centre wavelength drift value of axial strain grating and temperature grating,

be respectively the initial center wavelength of axial strain grating and temperature grating, ε _hfor the axial strain amount of axial strain grating, K _εfor wave length shift axial sensitivity coefficient under the fiber grating photoelastic effect, K _tfor fiber grating relative temperature sensitivity coefficient, Δ T is temperature variation;

C, obtain the axial strain amount after, obtain the country rock axial stress at one group of axial strain stop position place according to following formula:

σ _H＝Eε _H

In formula, σ _hfor this group stop position place country rock axial stress, the elastic modulus that E is the fiber grating borehole stressmeter;

For the unbalance stress of avoiding fiber grating borehole stressmeter bias to cause, four groups of axial strain gratings, transverse strain grating and temperature grating are calculated to gained country rock axial stress and be weighted on average, obtain revised country rock axial stress:

${{\mathrm{\&sigma;}}_H}^{\text{'}}=\frac{{\mathrm{\&sigma;}}_{H_1}+{\mathrm{\&sigma;}}_{H_2}+{\mathrm{\&sigma;}}_{H_3}+{\mathrm{\&sigma;}}_{H_4}}{4}$

In formula, σ _h' be revised country rock axial stress,

be respectively the country rock axial stress at axial strain stop position place in four groups of fiber gratings;

D, the centre wavelength data of transverse strain grating are handled as follows to obtain level and the perpendicular stress of grating xsect:

$\left\{\begin{array}{c}\frac{\mathrm{\&Delta;}{\mathrm{\&lambda;}}_{\mathrm{Bx}}}{{\mathrm{\&lambda;}}_{B0}}=-\frac{(1+v)n_{\mathrm{eff}}^2}{2E}\left\{\right[(1-v)p_{11}-v{p}_{12}]{\mathrm{\&sigma;}}_x+[(1-v)p_{12}-v{p}_{11}\left]{\mathrm{\&sigma;}}_y\right\}\\ \frac{\mathrm{\&Delta;}{\mathrm{\&lambda;}}_{\mathrm{By}}}{{\mathrm{\&lambda;}}_{B0}}=-\frac{(1+v)n_{\mathrm{eff}}^2}{2E}\left\{\right[(1-v)p_{12}-v{p}_{11}]{\mathrm{\&sigma;}}_x+[(1-v)p_{11}-v{p}_{12}\left]{\mathrm{\&sigma;}}_y\right\}\end{array}\right.$

In formula,

be respectively the transverse strain grating in the horizontal direction with the centre wavelength drift value of vertical direction, λ _b0for the initial center wavelength of transverse strain grating, n _efffor the initial effective refractive index of transverse strain grating, the elastic modulus that E is fiber grating, the Poisson's coefficient that ν is fiber grating, p ₁₁, p ₁₂be respectively the horizontal and axial strain optical coefficient of fiber grating, σ _x, σ _ythe level that is respectively grating xsect mid point reaches vertical;

E, obtain the level and perpendicular stress of grating xsect mid point after, in following two formulas, select the same form obtain fiber grating borehole stressmeter boring edge country rock at this group stop position place the radial stress along xsect:

$\left\{\begin{array}{c}{\mathrm{\&sigma;}}_x=\frac{2{\mathrm{\&sigma;}}_V}{\mathrm{\&pi;LD}}\\ {\mathrm{\&sigma;}}_y=-\frac{6{\mathrm{\&sigma;}}_V}{\mathrm{\&pi;LD}}\end{array}\right.$

In formula, σ _vfor this group stop position place country rock radial stress, L is fiber grating length, and D is fibre diameter;

F, the unbalance stress for avoiding fiber grating borehole stressmeter bias to cause, every group of fiber grating calculated value to axisymmetric position is weighted on average, because the fiber grating borehole stressmeter is installed by horizontal or vertical direction, in the grating group calculated value of upright position radially stress be perpendicular stress, in the grating group calculated value of horizontal level radially stress be horizontal stress, can obtain revised country rock horizontal stress and perpendicular stress:

$\left\{\begin{array}{c}{\mathrm{\&sigma;}}_{\mathrm{Vx}}=\frac{{\mathrm{\&sigma;}}_{V1}+{\mathrm{\&sigma;}}_{V3}}{2}\\ {\mathrm{\&sigma;}}_{\mathrm{Vy}}=\frac{{\mathrm{\&sigma;}}_{V2}+{\mathrm{\&sigma;}}_{V4}}{2}\end{array}\right.$

In formula, σ _vx, σ _vybe respectively revised stop position place country rock horizontal stress and perpendicular stress, σ _v1, σ _v3be respectively the country rock horizontal stress of two groups of rotational symmetry fiber gratings of horizontal direction, σ _v2, σ _v4be respectively the country rock perpendicular stress of two groups of rotational symmetry fiber gratings of vertical direction.

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