JP2009294039A - Structure deformation monitoring method using distribution type optical-fiber sensing system, and device thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for monitoring deformation or behavior of a structure such as a bridge or a building, as well as, a tunnel constructed by an underground drilling work, a base rock, a mountain surface, and to provide a method can monitor deformation over a wide range, especially for a space, such as, a tunnel for a mine where dust is suspended. <P>SOLUTION: In this structure deformation monitoring method that uses a distribution type optical-fiber strain sensing system, lock bolts are piled into a ceiling or a wall surface of an underground surface, or a base rock which is a monitoring object, and a pair of two optical fiber sensors are fixed in the crossed state on the lock bolts. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a method and system for detecting deformation of a structure by a distributed optical fiber sensing system. The present invention is a technique for monitoring deformations and behaviors of structures such as tunnels, bridges, and structures such as tunnels constructed by excavation work in a mine, bedrock, and mountain surface.

The underground space constructed by excavation work in the ground will be deformed or damaged due to excavation during construction work, imbalance in surrounding ground stress distribution due to the passage of time, and it will collapse as they progress There is a case. Therefore, in order to maintain and manage the underground space in a healthy state, improve the safety and efficiency of construction work, and continue to use the underground space safely after construction, always monitor the state and change its state. It is important to detect.

There have been many researches and developments on monitoring methods and systems not only in underground spaces, but also on mountain surfaces and rock masses where there is a risk of landslides. The physical quantities to be monitored are various such as deformation, displacement, strain, stress, vibration, temperature, etc. that occur in the underground space and surrounding rocks, and resistance strain gauges and vibrating wire stress meters are used to measure strain and stress. For measuring displacement and deformation, extensometers based on various measurement principles are used (for example, Non-Patent Documents 1 and 2).

Monitoring using a total station and photogrammetry has the advantage that the three-dimensional coordinates of a target installed at a plurality of measurement points can be measured simultaneously, and the displacement of the measurement point can be obtained from the change in the measured coordinates. Non-patent document 3 is reported in the research on the deformation monitoring of the railway tunnel accompanying the proximity work by the total station, and non-patent document 4 is reported in the research on the deformation measurement of the inner wall of the railway tunnel by the photogrammetry. A system combining a total station and photogrammetry has also been developed (Non-Patent Document 5).

Research has also been conducted on the use of optical fiber sensing systems (Patent Documents 1 and 2). From a system that measures the change in length of an optical fiber based on light interference, or a Bragg grating formed in an optical fiber, There is a fiber Bragg grating (FBG) system that utilizes the property that the frequency of reflected light shifts depending on strain and temperature. These systems measure changes in distance between two points and strain / temperature changes in the grating portion, and are basically point sensors that obtain information on the sensing element portion as in the prior art.

An underground space deformation monitoring system using a distributed optical fiber strain sensing system has also been developed (Non-Patent Document 6). The system includes a strain measurement device (BOTDR: Brillouin Optical Time Domain Reflector) and an optical fiber sensor installed on a measurement target. As a specific example, there is a system in which lock bolts are driven into the ceiling of a mine tunnel, the lock bolts are connected by a single optical fiber sensor, and the deformation of the tunnel is detected by expansion and contraction of the sensor.

JP 2001-66117 A JP 2001-201411 PR “Structural health monitoring ofunderground facilities &#8211; Technological issues and challenges”, S. Bhalla, Y.W. Yang, J. Zhao, C.K.Soh, Tunneling and Underground Space Technology 20, 487-500 (2005). “Monitoring ground deformation intunneling: Current practice in transportation tunnels”, M. J. Kavvadas, EngineeringGeology 79, 93-113 (2005). “Effect of large excavation ondeformation of adjacent MRT tunnels”, J. S. Sharma, A. M. Hefny, J. Zhao and CW. Chan, Tunneling and Underground Space Technology 16, 93-98 (2001). “Tunnel profile measurement by visionmetrology toward application to NATM”, S. Hattori, K. Akimoto, T. Ono, S. Miura, In: Proceeding of SPIE / IS & T 5011, Machine Vision and Applications in Industrial Inspection XI, SantaClara, California, January, 50-58 (2003). “Europeanpractice in geotechnical instrumentation for tunnel cinstruction control”, Tunnels and Tunnelling International 33, 51-53 (2001). “Application of distributed fiber optic strain sensing system to monitoring underground mine deformation”, Naruse, Uehara, Hideki, Deguchi, Kazuhiko Fujihashi, Masatoshi Onishi, R. Espinoza, C. Guzman, C. Pardo, C. Ortega , M. Pinto, IEICE Technical Report, The Institute of Electronics, Information and Communication Engineers, OFT 2006-66 (2007-1), 71-76 (2007).

As described above, various methods for monitoring the underground space have been proposed so far, but each technique has its own drawbacks. Since the techniques of Non-Patent Documents 1 and 2 are measurement at individual points where the sensors are installed, it is necessary to install a large number of sensors in order to perform multi-point monitoring. And wiring to send and receive observation data. Therefore, it is difficult to apply to a case where extensive monitoring is required.

  In the monitoring method based on the optical survey technique such as Non-Patent Documents 3 to 5, when dust floats in the underground space, the measurement light attenuates while reciprocating between the measuring instrument and the target. There is a problem that the monitoring range is limited.

In the method in Non-Patent Document 6, only the vertical and horizontal combined displacements of the ceiling are required, and the sensitivity of the vertical displacement is lower than the horizontal direction, and there is a problem that the deformation cannot be detected depending on the direction of the combined displacement. .

The present invention provides a method and apparatus capable of monitoring deformation over a wide range even in an underground space where dust is floating, using a distributed optical fiber strain sensing system. Furthermore, it aims at providing the computer-readable recording medium which recorded the program for making a computer perform this monitoring method.

The present invention relates to a structural deformation monitoring method using a distributed optical fiber strain sensing system, in which a rock bolt is driven into a ceiling, a wall surface, or a rock in an underground space to be monitored. As shown in FIG. A structure deformation monitoring method characterized in that a pair of optical fiber sensors are fixed to a peg in a structure, and the strain of the optical fiber between adjacent lock bolts is measured by a strain measuring instrument and installed. It is a structure deformation monitoring method and apparatus characterized in that the vertical displacement of the lock bolt is calculated from the length of the optical fiber sensor and the strain at the time.

The structure deformation monitoring method according to claim 1 is a computer-readable recording medium recording a program for causing a computer to execute the program, and a program for causing the computer to execute the monitoring method. .

In the optical fiber multipoint measurement and monitoring system, an error occurs in the strain measurement value when measuring the strain between adjacent rock bolts. For this reason, when calculating the displacement in the vertical direction of the lock bolt, it is necessary to eliminate the influence of the error on the displacement. The present invention relates to a structural deformation monitoring method using a distributed optical fiber strain sensing system, in which a rock bolt is driven into a ceiling, a wall surface, or a rock in an underground space to be monitored, and a pair of optical fibers is paired with the rock bolt. A structure deformation monitoring method characterized in that a sensor is fixed to a rake, wherein the strain of the optical fiber between adjacent lock bolts is measured by a strain measuring instrument, and the length of the optical fiber sensor at the time of installation is measured. The vertical displacement of the rock bolt is calculated from the distortion and the distortion, and the vertical displacement of the rock bolt located at both ends of the monitoring range is measured by a water sink type subsidometer etc. Then, a distortion correction value is calculated based on the distortion, the vertical position, and the length of the optical fiber sensor at the time of installation, and is included in the distortion. Characterized in that it is a structure Deformation monitoring method characterized by correcting the difference.

Further, the present invention is a computer-readable recording medium that records a program for causing a computer to execute the monitoring method, and a program for causing the computer to execute the monitoring method. With this monitoring method, the displacement measurement error can be reduced as compared with the prior art.

According to the present invention, multipoint monitoring can be realized over a wide range even in an underground space where dust is floating. Moreover, the displacement measurement error can be reduced by 40% compared to the prior art by measuring the displacement of the lock bolt as a reference with a water sink type subsidence meter and correcting the strain measurement value with the obtained value.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a flowchart showing a structure deformation monitoring method according to an embodiment of the present invention. The monitoring method is composed of two processes, a “sensor installation process” and a “deformation monitoring process”.

Step S1 is a step of driving a rock bolt into a ceiling or wall surface of an underground space to be monitored or a rock deformation monitoring section.

Step S2 is a step of installing two pairs of optical fiber sensors on the lock bolts as shown in FIG.

Step S3 is a step of measuring the sensor length between adjacent lock bolts, that is, the sensor length at the time of installation.

After completion of the “sensor installation process”, monitoring of the deformation monitoring section is started.

In step S4, the strain of the sensor between adjacent lock bolts is measured using the optical fiber sensor and strain measuring device.

In step S5, it is determined whether to proceed to step S6 for correcting the strain measurement value and further the vertical displacement of the lock bolt using the constraint condition, or not to use the constraint condition, that is, to perform step S7 without performing the correction. To do. If the constraint condition is not used in step S5, in step S7, the vertical displacement of the lock bolt is calculated using the sensor length and the distortion at the time of installation.

If it is determined in step S5 that the constraint condition is to be used, in step S6, the vertical positions of the lock bolts located at both ends of the deformation monitoring section are measured using a water sink type subsidometer or the like, and the vertical relative displacement is measured. To do. A distortion correction value is calculated using the vertical relative displacement and the sensor length and distortion obtained in steps S1 to S4. In step S7, the vertical displacement of the lock bolt is calculated using the corrected distortion obtained by adding the distortion correction value to the distortion.

Next, a process (corresponding to steps S5, S6, and S7) of calculating the displacement in the vertical direction of the lock bolt using the sensor length and strain between the adjacent lock bolts measured in steps S3 and S4 will be described.

Fig. 2 shows how the sensor is installed on the underground rock. A total of n + 1 lock bolts are driven into the underground space, and two pairs of optical fiber sensors are fixed to the lock bolts in a cross, that is, crossed in an x-shape. In the sensor installation method in the present invention, it can be considered that each optical fiber sensor section fixed to the adjacent lock bolt operates as an independent extensometer. By measuring the strains of these 2n sensors, the displacement of the underground space is calculated from the expansion and contraction of each sensor caused by the displacement through the lock bolt. The expansion / contraction of each sensor is obtained as the product of the length of each sensor and the strain measured by an optical fiber sensing system capable of distributed measurement such as BOTDR. Considering Fig. 2 that the lock bolt is driven vertically into the ceiling of the underground space and the lock bolt is displaced integrally with the rock, the vertical displacement is measured, and the lock bolt is If it is considered that it indicates the state of being driven, the displacement in the horizontal direction is calculated. In the following, a case will be described in which a lock bolt is driven into the ceiling in the vertical direction and the displacement in the vertical direction is measured.

i-1番目ロックボルトのセンサ下側固定部とi番目ロックボルトのセンサ上側固定部との間の距離即ちこの部分のセンサ長をl ^LH
_{i-1, i}、それに交差するセンサ長をl ^HL _{i-1, i}とすると、これらの間の幾何学的条件

から、u _{i-1, i}は次のように求められる。

ここでsは、ロックボルト上でのセンサ上側固定部と下側固定部との間の距離であり、すべてのロックボルトにおいて同じであるとする。 As shown in FIG. 2, the lock bolts are numbered 0, 1, 2,..., N from the left end. The left end, that is, the position of the sensor lower fixing part of the 0th lock bolt is the origin O, and the horizontal direction is the x axis and the vertical direction is the z axis. The x-axis and z-axis are given positive signs on the right and upper sides, respectively. The horizontal and vertical coordinates of the sensor's lower fixed part of the i-th lock bolt are x _i and z _i respectively, and the horizontal direction between the i-1th and i-th lock bolts in the initial state immediately after the sensor is installed The relative distance, that is, the driving interval is L _{i-1, i} , and the vertical relative distance is u _{i-1, i} . Then, the following relationship holds between them.

The distance between the sensor lower fixing part of the i-1st lock bolt and the sensor upper fixing part of the i-th lock bolt, that is, the sensor length of this part is ^defined as l ^LH
_{If i-1, i} and the crossing sensor length is l ^HL _{i-1, i} , the geometric condition between them

From this, u _{i−1, i} can be obtained as follows.

Here, s is the distance between the sensor upper fixing portion and the lower fixing portion on the lock bolt, and is the same for all the lock bolts.

になったとする。ここで、ε^LH _{i-1, i}、ε^HL _{i-1, i}は地下空間の変形によってそれぞれのセンサに生じた歪みであり、引張り、圧縮歪みには、それぞれ正、負の符号を与える。次式で表されるロックボルト変位とセンサ長についての幾何学的条件

と数式５より、v_{i-1, i}は次のように求められる。

したがって、i番目ロックボルトの変位後の鉛直座標z_iは、初期状態におけるロックボルトの位置u_{0, i}と鉛直方向変位v_{0, i}との和として、

と算出される。更に、数式４を考慮すると、このロックボルトの鉛直方向変位v_{0, i}は次のように求められる。

以上の解析では、センサの伸縮によって生じるセンサの張力変化によるロックボルトの曲がりは無視できると仮定している。補強用のロックボルトを斜めに打ち込み、それをセンサが設置されるロックボルトに溶接することによって、この仮定をみたすようにセンサを設置できる。 Next, a method for calculating the vertical displacement of the lock bolt from the sensor distortion caused by the deformation of the underground space will be described. The initial state and the state after underground space deformation are shown in FIG. Here, let us consider a case where the rotation generated in the underground space is sufficiently small and the lock bolt can be regarded as being displaced only in the vertical direction. The analysis of the effect of horizontal displacement on vertical displacement measurement will be described later. Due to the deformation of the underground space, a vertical relative displacement v _{i-1, i} occurs between i-1 and the i-th rock bolt, and the length l ^{LH of the} two sensors fixed between them
_{i-1, i} and l ^HL _{i-1, i}

Suppose that Here, ε ^LH _{i−1, i} and ε ^HL _{i−1, i} are strains generated in the respective sensors due to deformation of the underground space, and positive and negative signs are given to tensile and compressive strains, respectively. Geometrical conditions for rock bolt displacement and sensor length expressed by

And v _{i−1, i} can be obtained as follows.

Therefore, the vertical coordinate z _i after displacement of the i-th lock bolt is the sum of the position u _{0, i} of the lock bolt and the vertical displacement v _{0, i} in the initial state,

Is calculated. Further, when considering Equation 4, the vertical displacement v _{0, i} of the lock bolt is obtained as follows.

In the above analysis, it is assumed that the bending of the lock bolt due to the sensor tension change caused by the expansion and contraction of the sensor can be ignored. The sensor can be installed to satisfy this assumption by driving a reinforcing lock bolt diagonally and welding it to the lock bolt on which the sensor is installed.

Compared to the above method, the vertical position of the 0th and nth rock bolts installed at both ends is measured with another system such as a water-filled subsidometer, and this is used as a constraint condition for vertical displacement. Improvement of measurement accuracy and detection capability. As described above, the vertical displacement and coordinates of each rock bolt after deformation of the underground space are calculated as the cumulative relative displacement of the two adjacent lock bolts. The error included in the distortion measurement value is accumulated. In addition, when the entire bedrock in the monitoring range is deformed as a unit, the sensor is not distorted and cannot be detected. Furthermore, even if the reference, that is, the 0th lock bolt is displaced, the displacement cannot be observed. A method for realizing such reduction of accumulated error, detection of integral deformation, and observation of reference position displacement will be described below.

が成り立つことを意味する。歪みの補正値は十分小さいとして、数式１０を１次の項までテーラー展開すると数式１１が得られる。

更に、全ロックボルトについて数式１１の総和を求めると、数式１２が得られる。

ここで、B、Δεを以下のように、

とおくと、数式１２は

と書けるので、この解は

と求められる。ここで、Tは転置ベクトルを示している。したがって、各歪み計測値に対する補正値は次のように求められる。

数式１７で求められた補正値で補正された歪みの値を用いて、各ロックボルトの鉛直方向変位を求める。座標原点である0番目ロックボルトが鉛直方向にA’₀−A ₀だけ変位していることを考慮すると、i番目のロックボルトの鉛直座標z’_iは、

で与えられる。 The position in the initial state and the position after displacement of the sensor lower fixing part of the 0th lock bolt, measured by a water sink-type subsidence meter as described above, are A ₀ and A ′ ₀ , respectively, and the nth lock bolt _Let A _n and A ′ _n be the positions of, respectively. Assuming that the vertical relative displacement of the 0th and nth rock bolts measured by another system is A, A is (A ′ _n −A ′ ₀ ) − (A _n −A ₀ ). The strain measurement value is corrected by using, as a constraint condition, the value of A and the vertical displacement of the nth rock bolt calculated from the strain of each sensor. The correction values for the strain measurement values ε ^LH _{i-1, i} and ε ^HL _{i-1, i} are Δε ^LH _{i-1, i} and Δε ^HL _{i-1, i , respectively.} The function v _{i-1, i} (ε ^LH _{i-1, i} + Δε ^LH _{i-1, i} , ε ^HL _{i-1, i} + Δε ^HL _{i-1, i} ) Considering the constraints

Means that Assuming that the distortion correction value is sufficiently small, Equation 11 is obtained by Taylor expansion of Equation 10 to the first-order term.

Further, when the sum of Expression 11 is obtained for all the lock bolts, Expression 12 is obtained.

Where B and Δε are as follows:

Then, Equation 12 is

This solution is

Is required. Here, T represents a transposed vector. Accordingly, the correction value for each distortion measurement value is obtained as follows.

The vertical displacement of each lock bolt is obtained using the distortion value corrected by the correction value obtained by Expression 17. Considering that the 0th rock bolt, which is the coordinate origin, is displaced by A ′ ₀ −A _{0 in the} vertical direction, the vertical coordinate z ′ _i of the i th lock bolt is

Given in.

Lock bolt vertical displacement measurement error is (1) strain measurement error of optical fiber sensing system, which is a parameter related to sensor strain measurement, and (2) sensor length between adjacent lock bolts and lock bolt, which is a parameter related to sensor installation. It depends on the distance between the sensor fixing parts and (3) the monitoring range which is a parameter related to the monitoring target.

両者の関係は次式で与えられる。

幾何学的条件から与えられる数式３において通常のセンサ設置では、初期状態における、i-1番目とi番目のロックボルト間の水平方向相対距離（打ち込み間隔）L_{i-1, i}は、それらの間の鉛直方向相対距離u_{i-1, i}とロックボルト上でのセンサ固定部間距離sに比べて大きく

じる歪みが小さいことから、数式１９は次のように近似できる。

この結果は、鉛直方向相対変位計測誤差はロックボルト打ち込み間隔の２乗と歪み計測誤差とに比例し、センサ固定部間距離に逆比例することを示している。これは、センサ設置作業の効率化のためにロックボルト打ち込み間隔L_{i-1, i}を長くすること、設置したセンサが障害物にならないようにするためにセンサ固定部間距離sを短くすることは、いずれも相対変位計測精度を低下させることを示している。 First, the relationship between these parameters and the vertical relative displacement measurement error is examined. When using a distributed fiber optic strain sensing system, the entire fiber optic sensor is measured with a single measuring device, so the statistical properties of strain measurement errors are the same regardless of location.

The relationship between the two is given by the following equation.

In the normal sensor installation in Equation 3 given by the geometric condition, in the initial state, the horizontal relative distance (driving interval) L _{i-1, i} between the i-1 and i-th lock bolts is expressed as follows. Is larger than the vertical relative distance u _{i-1, i} between the sensor fixed part distance s on the lock bolt

Since twisting distortion is small, Equation 19 can be approximated as follows.

This result indicates that the vertical relative displacement measurement error is proportional to the square of the lock bolt driving interval and the strain measurement error, and inversely proportional to the distance between the sensor fixing portions. This is to increase the lock bolt driving interval L _{i-1, i} to increase the efficiency of the sensor installation work, and to shorten the distance s between the sensor fixing parts so that the installed sensor does not become an obstacle. Indicates that the relative displacement measurement accuracy is lowered.

で与えられる。ここで、すべてのロックボルト打ち込み間隔、及びセンサ固定部間距離が

される。この場合の即ち補正した歪み計測値の標準偏差は、補正していない場合のσ_vの値より小さくなっている。以上の結果は、ロックボルト鉛直方向変位測誤差が、計測しているロックボルト番号の平方根に比例して増加していくことを示している。 Next, the vertical displacement measurement error is examined. In the following, for the sake of simplicity, it is assumed that all the lock bolts are driven at equal intervals L. Vertical displacement measurement error of i-th lock bolt

Given in. Here, all the lock bolt driving intervals and the distance between sensor fixing parts are

Is done. In this case, that is, the standard deviation of the corrected distortion measurement value is smaller than the value of σ _v when the correction is not performed. The above results indicate that the lock bolt vertical displacement measurement error increases in proportion to the square root of the measured lock bolt number.

数式２４よりv _{i-1, i}は

と求められる。数式２５は数式８と一致していることから、水平方向に変位が生じている場合でも、その影響を受けることなく鉛直方向変位を求めることができることがわかる。 Here, the effect of the horizontal displacement of the lock bolt on the vertical displacement measurement is examined. Consider the case where the i-th lock bolt is displaced in the horizontal direction by x _i to w _i in addition to the vertical relative displacements v _{i−1, i} . An analysis model in this case is shown in FIG. At this time, the length of the two sensors l ^LH
_{i-1, i} and l ^HL _{i-1, i} are l '' ^LH _i-1,
i , l '' ^HL
_{i-1 and i} , and the distortions occurring in the sensors are ε ′ ^LH _{i−1, i} and ε ′ ^HL _{i−1, i.} The following relationship holds.

From Equation 24, v _{i-1, i} is

Is required. Since Expression 25 is consistent with Expression 8, it can be seen that the vertical displacement can be obtained without being affected even when a displacement occurs in the horizontal direction.

の計測値とした。この場合について、図１を用いて本発明の実施例を具体的に示す。 In Non-Patent Document 6, deformation of the ceiling and wall surface of a tunnel is detected by driving a lock bolt into a 200m long section of an underground mine tunnel at intervals of 3m and measuring the strain of one optical fiber sensor installed on it. There have been reports of field trials that tried to. In this simulation, similarly to this report, the lock bolt driving intervals L _{i−1, i} are all the same L, that is, x _i = (i−1) L, and the value of L is 3 m. The total number n + 1 of the lock bolts is 68, that is, n is 67, and the monitoring section is 201 m. Other values were set as follows. The distance s between the upper and lower fixed parts of the sensor was set to 30 cm, which is 1/10 of L. Vertical coordinate z _i (= u _0,
i ) is given by a normal distribution with a standard deviation of 15 cm (1/2 of L) centering on z = 0. Furthermore, the vertical displacement v _{0, i} from the initial state of each lock bolt is given as a normal distribution with a center of 0 and a standard deviation of 1.5 cm (1/200 of L), and is calculated from geometric conditions. The value of the distortion of the sensor was taken as the true value. So

It was set as the measured value. In this case, an embodiment of the present invention will be specifically described with reference to FIG.

In step S1, the lock bolts are driven at intervals of 3 m as described above. In step S2, as shown in FIG. 2, a pair of two optical fiber sensors are installed on the lock bolt. However, as described above, the distance between the sensor upper and lower fixed portions in the lock bolt is set to 30 cm. The solid line in FIG. 5 is a straight line that connects the vertical coordinates (the position of the lower fixed point) of the lock bolt before installation, that is, before displacement.

In step S3, sensor lengths l ^LH _{i-1, i} and l ^HL _{i-1, i} between adjacent lock bolts are measured.

In step S4, sensor strains ε ^LH _{i−1, i} and ε ^HL _{i−1, i} between the respective lock bolts are measured. The displacement given to each lock bolt and the vertical coordinate after the displacement are indicated by a solid line in FIG. 6 and a circle in FIG. When it is determined in step S5 that the constraint condition is not used, in step S7, the vertical displacement of the lock bolt is calculated by Equation 9 using the sensor length and the distortion at the time of installation. The result is the mark ● in FIG.

If it is determined in step S5 that the constraint condition is to be used, the process proceeds to step S6, where the vertical positions of the 0th and nth, that is, the lock bolts installed at both ends are measured with a summit type subsidometer or the like. Measure A. The vertical relative displacement and the sensor lengths l ^LH _{i−1, i} , l ^HL _{i−1, i} , strains ε ^LH _{i−1, i} , ε ^HL _{i−1, i} obtained in steps S1 to S4 17 is calculated, and distortion correction values Δε ^LH _{i−1, i} and Δε ^HL _{i−1, i} are calculated. Corrected strains ε ^LH _{i−1, i} + Δε ^LH _{i−1, i} , ε ^HL _{i−1, i} + Δε ^HL _{i−1, i} obtained by adding the strain correction value to the strain Is substituted into Equation 9 to calculate the vertical displacement of the lock bolt when distortion is corrected.

The vertical displacement of the lock bolt thus obtained is indicated by a circle in FIG. When the constraint condition is not used, the error of the vertical displacement calculated for accumulation of strain measurement error increases, whereas when the constraint condition is used, the error of the lock bolts at both ends Is 0, and it can be seen that the displacement measurement error for each lock bolt is small.

状態及び変位を変えたモニタリングパターンを１０００組作成し、数式２６の計算を繰り

係を求めた結果を図７に示す。解析結果が示すように、変位計測誤差は制約条件の有無にかかわらずセンサの歪み計測誤差に比例していること、又、この例では、補正によって変位計測誤差を４０％程度低減できることを確認した。 Further, in order to evaluate the measurement accuracy, the standard deviation σ ′ _v of the lock bolt vertical direction displacement measurement error is obtained by Expression 26.

Create 1000 sets of monitoring patterns with different states and displacements, and repeat the calculation of Equation 26.

FIG. 7 shows the result of obtaining the relationship. As shown in the analysis results, it was confirmed that the displacement measurement error is proportional to the sensor distortion measurement error regardless of whether there is a constraint condition, and in this example, the displacement measurement error can be reduced by about 40% by correction. .

Industrial applicability

INDUSTRIAL APPLICABILITY The present invention can be used for systems such as tunnels constructed by excavation work in mines, bridges, structures, etc., and systems for monitoring the deformation and behavior of rocks, mountain surfaces, etc. The deformation can be monitored over a wide area even in a mine tunnel. In the present invention, the displacement of the lock bolt as a reference is measured with a water sink type subsidence meter, and the distortion measurement value is corrected based on the obtained value, thereby reducing the displacement measurement error by 40% compared to the prior art. be able to.

It is the flowchart which showed the distributed optical fiber distortion measuring method concerning one Embodiment of this invention. It is a figure which shows installation of the distributed optical fiber sensor of this invention. It is a figure which shows the optical fiber sensor initial installation state of this invention, and the state after a deformation | transformation. It is a figure which shows the analysis model of the influence which the horizontal direction displacement in this invention has on a vertical direction displacement. It is a figure which shows an example of a rock bolt perpendicular direction coordinate. It is a figure which shows an example of the rock bolt vertical direction displacement calculation result in this invention. It is a figure which shows the relationship between the distortion measurement error in this invention, and a displacement measurement error.

Claims (8)

In a structural deformation monitoring method using a distributed optical fiber strain sensing system, a rock bolt is driven into the ceiling, wall surface, or bedrock of the underground space to be monitored, and two pairs of optical fiber sensors are tapped into the rock bolt. The structural deformation monitoring method is characterized in that the strain of the optical fiber between adjacent lock bolts is measured by a strain measuring instrument, and the length of the optical fiber sensor and the strain at the time of installation are measured. A structural deformation monitoring method characterized by calculating a vertical displacement of the lock bolt. In a structural deformation monitoring method using a distributed optical fiber strain sensing system, a rock bolt is driven into the ceiling, wall surface, or bedrock of the underground space to be monitored, and two pairs of optical fiber sensors are tapped into the rock bolt. The structural deformation monitoring method is characterized in that the strain of the optical fiber between adjacent lock bolts is measured by a strain measuring instrument, and the length of the optical fiber sensor and the strain at the time of installation are measured. A structural deformation monitoring device comprising means for calculating the vertical displacement of the lock bolt. The structural deformation monitoring method according to claim 1, wherein the computer-readable recording medium stores a program for causing a computer to execute the monitoring method. The structure deformation monitoring method according to claim 1, wherein the program causes a computer to execute the monitoring method. In a structural deformation monitoring method using a distributed optical fiber strain sensing system, a rock bolt is driven into the ceiling, wall surface, or bedrock of the underground space to be monitored, and two pairs of optical fiber sensors are tapped into the rock bolt. The structural deformation monitoring method is characterized in that the strain of the optical fiber between adjacent lock bolts is measured by a strain measuring instrument, and the length of the optical fiber sensor and the strain at the time of installation are measured. A structural deformation monitoring method characterized by calculating a vertical displacement of the rock bolt, wherein the vertical positions of the rock bolts located at both ends of the monitoring range are measured by a water sink type subsidometer or the like, and the distortion is measured. And the vertical position, the vertical position of the lock bolt at the time of installation, and the length of the optical fiber sensor at the time of installation. Out, structural Deformation monitoring method characterized by correcting the error contained in the strain. In a structural deformation monitoring method using a distributed optical fiber strain sensing system, a rock bolt is driven into the ceiling, wall surface, or bedrock of the underground space to be monitored, and two pairs of optical fiber sensors are tapped into the rock bolt. The structural deformation monitoring method is characterized in that the strain of the optical fiber between adjacent lock bolts is measured by a strain measuring instrument, and the length of the optical fiber sensor and the strain at the time of installation are measured. A structural deformation monitoring method characterized by calculating a vertical displacement of the rock bolt, wherein the vertical positions of the rock bolts located at both ends of the monitoring range are measured by a water sink type subsidometer or the like, and the distortion is measured. And the vertical position, the vertical position of the lock bolt at the time of installation, and the length of the optical fiber sensor at the time of installation. Out, structural Deformation monitoring device having means for correcting the error contained in the strain. 6. The structural deformation monitoring method according to claim 5, wherein the computer-readable recording medium stores a program for causing a computer to execute the monitoring method. The structure deformation monitoring method according to claim 5, wherein the program causes a computer to execute the monitoring method.

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