JP2007114176A - Displacement measurement device and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displacement measurement device and a displacement measurement system inexpensively constructible and capable of accurately measuring three-dimensional displacement of an optional point in the ground, for example, only by an optical fiber sensor of a FBG system (fiber grating method). <P>SOLUTION: This displacement measurement device includes a flexible rod-shaped measurement base body, a pair of first fiber grating parts installed in two positions, which are symmetric to each other in the axial direction of the rod-shaped measurement base body, on the outer circumferential face of the rod-shaped measurement base body, a second fiber grating parts arranged in two positions symmetric in the axial direction of the rod-shaped measurement body in the position turned around the axis of the rod-shaped measurement base body from the installation positions of the first fiber grating parts, a measurement part having optical fibers connecting the first fiber grating parts and the second grating parts together, and fixing apparatuses fixing the optical fibers on both sides of the fiber grating parts. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a displacement measuring device and a displacement measuring system, and more particularly to a displacement measuring system that measures displacement in the ground.

    Conventionally, so-called inclinometers are commonly used for measuring underground displacement.

    However, since displacement measurement by an inclinometer is measurement at regular intervals in the ground, there is a problem that continuous measurement or measurement at an arbitrary point cannot be performed.

    For this reason, a device capable of measuring an arbitrary point using an optical fiber sensor has been proposed separately (Japanese Patent Laid-Open No. 2003-14451).

    Therefore, since the above apparatus uses the OTDR or B-OTDR system, there is a problem that measurement accuracy is poor.

    In contrast to these conventional proposals, an apparatus for improving measurement accuracy using both the optical fiber sensor and the inclinometer has been proposed (Japanese Patent Laid-Open No. 2005-61985), but there is an indication that the cost is high.

In this way, with the above-described conventionally proposed measuring apparatus,
(1) Since the measurement accuracy is not good, if it is desired to improve the measurement accuracy, another measurement device must be prepared, which complicates the measurement device and the measurement system, and other measurement devices. This increases the cost (Japanese Patent Laid-Open No. 2005-61985).
(2) The above-described conventionally proposed measuring device is limited to a two-dimensional displacement measuring device, and if it is desired to measure a so-called three-dimensional displacement, another measuring device must be required.
(3) Although the so-called FBG type optical fiber sensor can be used to improve the measurement accuracy, the FBG type optical fiber sensor can be used to make an apparatus and method (pipe) similar to the conventional B-OTDR type. It has to be configured to measure with a measuring apparatus and method such as a strain gauge, and there is a problem that the apparatus and method cannot grasp differences such as the deformation mode of the ground.
Japanese Patent Laid-Open No. 2005-61985

Thus, the present invention was devised to cope with the above-described conventional problems, and can measure, for example, a three-dimensional displacement at an arbitrary point in the ground with high accuracy using only a so-called FBG type (fiber grating type) optical fiber sensor. In addition, it is an object of the present invention to provide a displacement measuring device and a displacement measuring system that can be configured at a low cost.

The displacement measuring device according to the present invention is:
A flexible rod-shaped measurement substrate;
On the outer peripheral surface of the rod-shaped measurement substrate, a pair of first fiber grating portions installed at two positions that are substantially symmetrical in the axial direction of the rod-shaped measurement substrate, and a rod-shaped measurement from the installation position of the first fiber grating portion A second fiber grating portion installed at two positions that are substantially symmetrical in the axial direction of the rod-shaped measurement substrate at a position rotated about the axis of the substrate;
An optical fiber connecting the first fiber grating part and the second fiber grating part, and a measurement part formed by including:
A fixture for fixing the optical fiber on both sides of the fiber grating part;
It is characterized by having a rod-shaped measurement substrate having
Or
A flexible rod-shaped measurement substrate;
On the outer peripheral surface of the rod-shaped measurement substrate, a pair of first fiber grating portions installed at two positions that are substantially symmetrical in the axial direction of the rod-shaped measurement substrate, and a rod-shaped measurement from the installation position of the first fiber grating portion A second fiber grating portion installed at two positions that are substantially symmetrical in the axial direction of the rod-shaped measurement substrate at a position rotated approximately 90 degrees around the axis of the substrate;
An optical fiber connecting the first fiber grating part and the second fiber grating part, and a measurement part formed by including:
A fixture for fixing the optical fiber on both sides of the fiber grating part;
It is characterized by having a rod-shaped measurement substrate having
Or
The measurement unit has a plurality of fiber grating units installed at positions rotated about the axis of the rod-shaped measurement base from the installation position of the first fiber grating unit toward the installation position of the second fiber grating unit. Configured,
It is characterized by
Or
The measuring unit is configured to be installed in at least two places at an interval in the axial direction of the rod-shaped measuring base,
It is characterized by
Or
A plurality of the rod-shaped measuring bases can be connected in the axial direction, and the optical fibers installed on each of the bar-shaped measuring bases can also be connected to each other.
It is characterized by
Or
The rod-shaped measurement base is provided with an expansion / contraction allowance portion in the axial direction on at least one end side in the axial direction,
It is characterized by
Or
The rod-shaped measuring base is provided with a fitting recess that opens toward the outer side in the axial direction at one end in the axial direction, and a fitting portion that loosely fits into the fitting recess at the other end in the axial direction. An expansion / contraction allowance portion is provided between the insertion portion and the insertion portion.
It is characterized by
Or
In the rod-shaped measurement base, the outer peripheral surface shape of the fitting recess is configured as a bulging portion shape that bulges outward from the outer peripheral surface shape of the rod-shaped measurement base.
It is characterized by
Or
In the rod-shaped measurement base, a holding portion for holding the rod-shaped base in the bore hole is provided on the outer peripheral surface of the fitting recess.
It is characterized by
Or
On the outer peripheral surface of the rod-shaped measurement base, a second measurement unit provided with an expansion / contraction fiber grating unit for measuring an axial expansion / contraction displacement toward the axial direction was formed,
It is characterized by
Or
The rod-shaped measurement base is formed of a cylindrical member, a temperature correction fiber grating portion is installed in the hollow portion, and the temperature correction fiber grating portion is connected to the optical fiber.
It is characterized by
Or
The rod-shaped measurement base is formed of a cylindrical member, and a hollow tube is attached to the outer peripheral surface in the axial direction, and a temperature correction fiber grating portion is installed in the hollow tube, and the temperature correction The fiber grating portion is also connected to the optical fiber,
Or
In the rod-shaped measurement base provided with the expansion / contraction allowance part in the axial direction, the temperature correction of the measurement value was made possible without the installation of the temperature correction fiber grating part.
It is characterized by
Or
The rod-shaped measurement base is composed of a long and flexible rod-shaped member, and a plurality of fiber grating portions connected to the optical fiber at an interval are installed in the axial direction of the rod-shaped measurement base, A fixture for fixing the optical fiber at an interval in the axial direction is attached,
It was possible to form in the same configuration as the state where a plurality of the rod-shaped measurement bases are connected,
It is characterized by
Or
Capture means for capturing measurement data measured by the measurement unit;
A transmission means for transmitting the captured measurement data via a communication network;
Receiving means for receiving the transmitted measurement data;
Position data to be measured in advance is input, drawing means for drawing a pre-displacement image of the measurement position based on the position data,
A post-displacement image rendering means for rendering the post-displacement image of the measurement location based on the measurement data;
It is characterized by comprising.

With the displacement measuring apparatus and displacement measuring system according to the present invention, it is possible to measure, for example, a three-dimensional displacement at an arbitrary point in the ground with high accuracy and low cost, using only a so-called FBG (fiber grating) optical fiber sensor. And has an excellent effect.

    Hereinafter, the present invention will be described based on embodiments shown in the drawings.

    Here, a fiber grating type optical fiber sensor, that is, a sensor principle of a type using a fiber grating as a sensor will be described briefly.

    First, as shown in FIG. 10, a plurality of Bragg diffraction gratings 3 are formed in the core 2 of the optical fiber 1.

    When the incident light 4 is incident on the Bragg diffraction grating 3, reflected light 5 having a frequency proportional to the product of the interval x of the Bragg diffraction grating 3 and the refractive index of the core 2 is generated.

    Thus, when the optical fiber 1 is distorted, the interval x of the Bragg diffraction grating 3 changes, so that the frequency of the reflected light 5 also changes. A sensor using FBG, that is, a fiber grating sensor, calculates strain based on the amount of change.

    The FBG, that is, the fiber grating 6 is formed by forming the Bragg diffraction grating 3 in the core 2 of the optical fiber 1 in the Ge-doped region using the incident light 4 and reflects light having a specific wavelength λ determined by the grating interval x. Has characteristics.

と定義し、ファイバグレーティング６の格子間隔ｘも同じ比率でのびると仮定すれば、温度が一定のもとでは波長も同じ比率

で変化することとなる。
従って、反射光５の波長を計測することで歪み率εが得られることとなる。 Now, when the optical fiber 1 of length L is stretched by ΔL under tension, the strain rate is ε

Assuming that the grating spacing x of the fiber grating 6 also extends at the same ratio, the wavelength is the same ratio under a constant temperature.

Will change.
Therefore, the distortion rate ε can be obtained by measuring the wavelength of the reflected light 5.

    If the fiber grating 6 is attached to the object to be measured, the distortion of the object can be detected as the distortion of the fiber grating.

    Further, since the transmitted light 19 of the fiber grating 6 has a spectrum with a missing reflection component, the same measurement is possible even if the missing wavelength is measured.

  As described above, the fiber grating 6 includes the Bragg diffraction grating 3 in which the refractive index in the core 2 of the optical fiber 1 is periodically changed. The fiber grating wavelength selectivity is applied to strain measurement. It can be said that.

    Further, it is said that about 2000 Bragg diffraction gratings 3 can be arranged per 1 mm in the fiber grating 6 of the fiber grating type optical fiber sensor.

  Next, an embodiment of the present invention will be described with reference to the drawings.

    1 and 2 show the basic configuration of the present invention.

    In the present invention, the bar-shaped measurement base 7 is required to have flexibility, and for example, a flexible columnar or cylindrical metal rod or metal pipe is used. However, the rod-shaped measurement substrate 7 is not limited to such a cylindrical metal rod or a cylindrical metal pipe, and is flexible, and a plurality of fiber gratings 6 are arranged on the outer periphery of the rod-shaped measurement substrate 7. Any member that can be installed on the surface and spaced apart in the axial direction may be used.

    In general, the length of the rod-shaped measurement base 7 is, for example, a length of about 10 m or more corresponding to the depth of the ground 31 to be measured if the displacement of the ground 31 is measured. A plurality of fiber gratings 6 are installed on the outer peripheral surface 7 at predetermined intervals in the axial direction.

FIG. 1 is a diagram in which the outer peripheral surface of a long rod-shaped measurement base body 7 is developed in a planar shape, and the installation state (drawing state) of one optical fiber 1 provided with a plurality of fiber grating portions is planarly shown. It is shown.
As can be understood from FIG. 1, the optical fiber 1 extends from the position of 0 degrees on the upper side of the bar-shaped measurement base 7 in FIG. 1 is passed through the position of 0 degree at the lower end of the rod-shaped measuring base 7 in FIG. 1, and is bent in a substantially semicircular shape so as to be axially upward again from the lower 180-degree angular position of the rod-shaped measuring base 7. It is laid toward the upper side and protrudes upward and outward from a position 180 degrees on the upper side of the rod-shaped measuring base 7. In the meantime, a plurality of first fiber grating portions 9 are attached at a predetermined interval at a position of 0 degrees and a position of 180 degrees.

    Then, the end portion of the projected optical fiber 1 is connected to another optical fiber 1 via a connector 16, and the other connected optical fiber 1 is curved to be on the upper side 90 of the rod-shaped measurement base 7. It is laid down again in a straight line from the position in the axial direction downward in the axial direction, and attached so as to pass through the position 8 at the lower 90 degrees of the rod-shaped measuring base 7 in FIG.

    Thus, the optical fiber 1 that has passed through the lower 90 ° position of the rod-shaped measurement base 7 in FIG. 1 is curved in a substantially semicircular shape, and is again axially upward from the lower position 270 ° of the bar-shaped measurement base. It goes up and lays in a straight line, passes through a position of 270 degrees on the upper side of the rod-shaped measuring base 7 and protrudes outward. In the meantime, a plurality of second fiber grating portions 10 are attached at predetermined intervals at positions of 90 degrees and 270 degrees.

    The projecting end of the optical fiber 1 is connected to another optical fiber 1 through a connector 16, and the other connected optical fiber 1 is bent and provided on the outer peripheral surface of the rod-shaped measurement base 7. The temperature correction fiber grating portion is inserted from the upper end of the hollow tube 17 and laid down to the lower end portion of the hollow tube 17.

    As can be understood from FIGS. 1 and 2, a plurality of first fiber grating portions 9, second fiber grating portions 10, and temperature correction fiber grating portions 12 are connected to form one optical fiber. In the embodiment shown in FIGS. 1 and 2, a total of 40 fiber grating portions are provided at 32 locations and at eight temperature-correcting fiber grating portions 12.

    Then, the actual rod-shaped measurement base 7 is installed in the ground 31 to be measured, for example, as shown in FIG.

    In this embodiment, the length of the rod-shaped measurement base body 7 is about 12 m, the measurement units 11 by the fiber grating units are provided at intervals of about 1.5 m, and the first fiber grating unit 9 and the second fiber are directed in the axial direction. A ring-shaped fixture 8 is attached to each of the two measurement parts 11 and 11 constituted by the grating part 10, and the optical fiber 1 to which a plurality of fiber grating parts are attached is fixed on the outer peripheral surface of the rod-like measurement base 7. And it shall fix to the boring hole 18 in the ground.

    In FIG. 1, the numbers “1” and “16”, “2” and “15”, “3” and “14”, “4” and “13”, “5” and “12”, “ The fiber grating portions indicated by “6” and “11”, “7” and “10”, and “8” and “9” are the first fiber grating portions 9, and the numbers “17”, “32”, “18” ”And“ 31 ”,“ 19 ”and“ 30 ”,“ 20 ”and“ 29 ”,“ 21 ”and“ 28 ”,“ 22 ”and“ 27 ”,“ 23 ”,“ 26 ”, and“ 24 ” The fiber grating portion indicated by “25” is the second fiber grating portion 10.

    That is, the set of first grating portions 9 is installed at two positions that are substantially symmetrical in the axial direction of the rod-shaped measurement base body 7, and the second fiber grating portion 10 is installed at the position where the first fiber grating portion 9 is installed. Further, the rod-shaped measuring base 7 is installed at two positions that are substantially 90 degrees around the axis of the rod-shaped measuring base 7 and are substantially symmetrical in the axial direction of the bar-shaped measuring base.

    The first fiber grating part 9 and the second fiber grating part 10 constitute a measuring part 11.

    Therefore, in this embodiment, eight measuring units 11 are configured at predetermined intervals in the axial direction of the rod-shaped measuring base 7.

    That is, in this embodiment, the eight measurement units 11 are configured by the first fiber grating unit 9 and the second fiber grating unit 10 toward the lower side in the axial direction with an interval of 1.5 m.

    Further, as shown in FIG. 1, eight temperature-correcting fiber grating portions 12 are provided in the hollow tube 17 in a free state with an interval of 1.5 m in the axial direction of the rod-shaped measuring base 7. Thus, the error of the measured value due to the temperature change is corrected.

    By the way, in this embodiment, 40 fiber grating portions are provided in one optical fiber 1, but up to 100 fiber grating portions can be measured in one optical fiber 1.

    Therefore, for example, when it is necessary to measure the displacement at a deep location in the ground, a longer rod-shaped measurement base 7 is used, and the measurement is performed by attaching a number of fiber grating portions within 100 pieces, or the conventional bar-shaped measurement base. A new rod-shaped measuring base 7 is added to 7 to make it long, and the optical fibers 1 and 1 laid on each are also connected to each other via a connector 6, and a large number of fiber grating portions are attached within 100 pieces. It is conceivable to form a single optical fiber 1.

    As can be understood from FIG. 17, it is also possible to connect the optical switch 35 to the FBG light measuring device 20 and connect the optical fiber 1 branched and installed in five systems to the optical switch 35. .

Next, FIGS. 11 and 12 show a mechanism that allows a plurality of rod-shaped measurement base bodies 7 to be connected.
When measuring the displacement in the depth direction of the ground, that is, the displacement in the substantially vertical direction, the borehole 18 is excavated in the depth direction of the ground, and the rod-shaped measurement base body 7 is attached in the borehole 18.
In order to measure the displacement in the depth direction of the ground, that is, the displacement in the substantially vertical direction particularly accurately and accurately, the displacement in the axial direction of the rod-shaped measuring base 7 can freely follow the behavior of the ground. It is necessary to attach the measurement unit 11.

For example, the material of the rod-shaped measurement base 7 may be an elastic coefficient that matches the strength of the ground to be measured. However, it is difficult to use the bar-shaped measurement base 7 made of the above-mentioned materials one by one in a measurement situation where various ground strengths exist, which is not realistic. Therefore, the following mechanism made it possible to accurately measure the displacement in the depth direction of the ground.

Here, it is assumed that the rod-shaped measurement base body 7 to be connected has an underground fixing portion 37 for locking to the inner wall of the boring hole 18 on either end side in the axial direction. Then, it is conceivable that the underground fixed portion 37 is formed in, for example, a substantially short cylindrical shape, and the diameter of the inner hole thereof is formed substantially the same as the diameter of the rod-shaped measurement base body 7. Next, the rod-shaped measurement base 7 and the underground fixing part 37 are integrated by inserting the end of the rod-shaped measurement base 7 into the inner hole of the underground fixing part 37, for example, up to the middle part and fixing both.

As a result, a fitting recess 47 bulging outward is formed on the opening side of the inner hole of the underground fixed portion 37. Accordingly, the outer peripheral surface of the underground fixed portion 37 in which the fitting concave portion 47 is formed is configured to have a shape that bulges outward from the outer peripheral surface of the rod-shaped measurement base body 7.

Further, on the outer peripheral surface of the underground fixed portion 37 in which the fitting concave portion 47 is formed, a holding portion 48 that generates a frictional force necessary for holding and locking the rod-shaped measuring base body 7 on the inner wall of the boring hole 18 is provided. . Here, the holding portion 48 may be processed and formed into an uneven shape, a wave shape, a saw shape, or the like in order to obtain a necessary frictional force.

The holding portion 48 may be formed of a bulging / shrinking member that bulges or shrinks outward. That is, after the rod-shaped measurement base body 7 is inserted and installed in the boring hole 18, the rod-shaped measurement base body 7 can be easily placed in the boring hole 18 by adopting a mechanism that expands the bulging / shrinking member and generates a frictional force. This is because it can be fixed and installed.

By the way, the other axial end portion of the rod-shaped measurement base 7 becomes a fitting portion 49 to be inserted into the fitting recess 47 in the other rod-shaped measurement base 7 to be connected.
FIG. 12 shows a connected state in which the rod-shaped measurement substrate 7 and the other rod-shaped measurement substrate 7 connected to the rod-shaped measurement substrate 7 are connected by fitting. Thus, a gap is formed between the bottom of the fitting recess 47 and the tip of the fitting 49, and the gap serves as an expansion / contraction allowance 36 that allows the rod-shaped measurement base 7 to expand and contract.

Further, the fitting recess 47 and the fitting portion 49 inserted into the fitting recess 47 are formed with temporary fixing bolt holes 46 communicating with both of them on the side surface side, and are fitted when the rod-shaped measuring base body 7 is installed. In order to connect the temporary fixing bolt hole 46 of the recess 47 and the temporary fixing bolt hole 46 of the fitting portion 49, and to insert the plastic bolt 45 or the like into the hole to connect the rod-shaped measurement bases 7 to be connected to each other, It shall be temporarily fixed.

Then, if ground expansion or contraction occurs in the depth direction of the ground after installation, that is, in a substantially vertical direction, the interval between the adjacent rod-shaped measurement bases 7 also expands and contracts, so that the plastic bolt 45 or the like is easily broken. By this breakage, the rod-shaped measurement base 7 can freely expand and contract, and the ground behavior in the depth direction can be accurately measured.

Here, a case is considered where displacement occurs in the depth direction of the ground and the interval between the holding portions 48, 48 in the two connected rod-shaped measurement base bodies 7 changes. Then, due to the function of the expansion / contraction allowance part 36, it is considered that the distance expansion / contraction amount between the adjacent rod-shaped measurement bases 7, 7 becomes equal to the ground expansion / contraction amount. Therefore, the amount of expansion / contraction in the ground depth direction can be accurately measured by measuring the amount of expansion / contraction of the plurality of rod-shaped measurement bases 7 connected together.

A connection structure for measuring the amount of expansion and contraction of the rod-shaped measurement base 7 is shown in FIG. As can be understood from FIG. 11, for example, one extensometer fiber grating portion 38 is installed for two adjacent rod-shaped measurement bases 7, 7. The extensometer fiber grating section 38 is connected to another extensometer fiber grating section 38 by an extensometer fiber 43. The extensometer fiber 43 is laid along the axial direction on the outer peripheral surface of the rod-shaped measurement substrate 7, and is fixed to the rod-shaped measurement substrate 7 by an adhesive portion 41 at a substantially central position in the longitudinal direction of the rod-shaped measurement substrate 7. Here, the configuration of the bonding portion 41 is not limited at all, and fixing with an adhesive, fixing such as binding, and the like are conceivable. Further, the position of the bonding portion 41 is not limited to the substantially central position in the longitudinal direction of the rod-shaped measurement substrate 7, and may be anywhere as long as one bonding portion 41 is formed for one rod-shaped measurement substrate 7. .

The extensometer fiber grating section 38 may be installed at any position as long as it is between the bonding sections 41 and 41 formed on two adjacent rod-shaped measurement bases 7.

Therefore, when displacement occurs in the ground, displacement measurement in the depth direction of the ground is performed as follows.

First, due to the ground expansion and contraction that occurs in a substantially vertical direction, the interval between the connected rod-shaped measurement bases 7 and 7 is expanded and contracted. Then, the stretchable fiber 43 attached and fixed between the connected rod-shaped measurement bases 7 expands and contracts, and the stretchable fiber grating portion 38 connected to the stretchable fiber 43 also expands and contracts. The resulting strain is measured. The extensometer fiber grating portion 38 converts the strain into the amount of expansion and contraction, so that accurate displacement measurement in the depth direction of the ground can be achieved.

On the other hand, the displacement in the horizontal direction of the ground is measured by the first and second fiber grating units installed in the measurement unit 11 as described above.
As already described, the connection between the adjacent bar-shaped measurement bases 7 and 7 is integrated by inserting the fitting portion 49 of the other-side bar-shaped measurement base 7 into the fitting recess 47 of the one-side bar-shaped measurement base 7. Thus, the moment generated in the horizontal direction due to the horizontal displacement of the ground is accurately transmitted to the measurement unit 11 provided on the other rod-shaped measurement base 7 which is connected and integrated. Therefore, the horizontal displacement of the ground can be measured in exactly the same state as in the case where the long integrated rod-shaped measurement base 7 is used.

FIG. 13 shows a cross section taken along line AA of FIG.
The AA cross section corresponds to a cross section of a portion where the first fiber grating portion 9 and the second fiber grating portion 10 are attached to the outer peripheral surface of the rod-shaped measurement base 7 as a bending measurement sensor by bonding or the like. It is shown that the four bonded fiber grating portions 9 and 10 are fused to the rod-shaped measurement base 7 with the heat shrinkable tube 40. And the extensometer fiber 43 is installed in a form along the outer periphery of the heat shrinkable tube 40.

FIG. 14 shows a cross section taken along the line BB of FIG.
The B-B cross section corresponds to a cross section of a portion where the outer peripheral surface of the underground fixing portion 37 is locked to the inner wall of the borehole 18 and the bar-shaped measurement base 7 is fixed to the inner wall of the borehole 18 at this location.
The thickness portion of the underground fixing portion 37 (the portion of the difference between the outer diameter of the underground fixing portion 37 and the inner diameter of the fitting recess 47) is formed as a so-called sleeve portion 44. The sleeve portion 44 is formed with through holes for the first and second fiber grating fibers 42 and the extensometer fiber 43. In the through hole, the fibers 42 and 43 are covered with a hollow tube 17 so as to penetrate the outer periphery.

FIG. 15 is a cross-sectional view taken along the line BB in FIG. 11 and shows a modification of FIG.
Inside the sleeve portion 44, a plurality of existing holes 50 are formed so as to penetrate substantially in a radial direction about the axial center portion of the sleeve portion 44 as a central axis. Here, the number and shape of the plurality of existing holes 50 are not limited in any way, as long as the wiring and installation of the fibers 42 and 43 can be easily performed.

In this way, in the embodiment shown in FIG. 15, by using the existing internal space of the plurality of existing holes 50, it is not necessary to newly provide each fiber wiring and installation through-hole in the sleeve portion 44. The fibers 42 and 43 can be easily installed.

Sensors such as the first fiber grating part 9 and the second fiber grating part 10 as bending measurement sensors are not installed in the sleeve part 44, but the fiber grating part 38 for the extensometer is provided in the sleeve part 44. You may install in the said through-hole.

FIGS. 13 to 15 show the case of a columnar rod-shaped measurement substrate 7 having a circular cross-sectional shape. However, the rod-shaped measurement substrate 7 is not limited to a columnar shape, and a prismatic column such as a square column is used. May be. When the rod-shaped measurement base body 7 is a quadrangular prism, the cross-sectional shape is a quadrangle, and the fiber grating portion and the fiber can be installed along each of the four side surfaces.

  Next, the basic principle of displacement measurement according to the present invention will be described.

ここで、P／EI、およびM／EIは、

となり、上記の式から、ひずみεおよび中立軸ｊからの距離yが求まれば、θとυが求まるから、これが計測原理の公式となる。 The displacement amount v and the angle θ shown in FIG. 3 are determined by the following equation.
That is,

Here, P / EI and M / EI are

From the above equation, if the strain ε and the distance y from the neutral axis j are obtained, θ and υ are obtained, and this is the formula of the measurement principle.

In the above equation, E is Young's modulus, I is the moment of inertia of the cross section, M is the moment, and l is the distance between the displacement measurement points AB.

Further, with reference to FIG. 4 to FIG. 8, as understood from FIG. 8, between the two measurement points A and B at the axial end, the axis is symmetrical (1) and With the fiber gratings 6 and 6 of (2) as a set, the bending strain of the connecting material can be measured from the difference in strain between the fiber gratings 6 and 6. Therefore, the displacement amount and angle of the measurement location are obtained from the measurement principle.

    And by installing this at two or more locations in the axial direction, it becomes possible to measure bending strain at two or more locations in the axial direction, and the relative displacement and relative angle between the measurement points A and B can be determined from the above measurement principle. It can be measured. And since the displacement and angle of each location are obtained, the difference in deformation mode can also be grasped.

    Next, the displacement and angle in one direction (the direction of the fiber grating (1)-(2)) can be measured by the above method as shown in FIG. 8, but this is further measured around the axis of the measurement point AB. Displacement in at least two directions (directions of fiber gratings (1)-(2) and (3)-(4)) by rotating 90 degrees and installing one or more sets (fiber gratings (3) and (4)) And the angle can be measured.

    Further, regarding the displacement in the axial direction, in addition to the measurement by the extensometer installed in the second measuring unit 39, the expansion / contraction in the axial direction of the measurement point A-B is measured from the expansion / contraction strain in the axial direction between the expansion / contraction measurement points A-B. Therefore, three-dimensional displacement measurement can be performed together with the above measurement.

    In addition, since displacement and angle can be measured by the above method, if a plurality of measurement units 11 composed of a plurality of fiber grating units are installed intermittently and continuously in the axial direction, the displacement and angle are accumulated. Therefore, displacement at multiple points (multiple locations) can be measured smoothly.

  The temperature correction fiber grating portion 12 is installed as described above. For example, the temperature correction fiber grating portion 12 is free in the hollow portion of the rod-shaped measurement base 7 formed of a cylindrical metal pipe or the like. It can be installed in any state.

By the way, the displacement measuring device including the rod-shaped measurement base 7 having the expansion / contraction allowance portion 36 shown in FIG. 11 can correct the temperature of the measurement signal without providing the temperature correction fiber grating portion 12 for the following reason. It becomes.

First, when considering a case where a substantially vertical displacement occurs in the ground, the interval between adjacent rod-shaped measurement bases 7 and 7 connected as described above expands and contracts. However, due to the function of the expansion / contraction allowance portion 36, the adjacent rod-shaped measurement bases 7, 7 do not contact each other, and a compression force or a tensile force in a substantially vertical direction is not generated on each bar-shaped measurement base 7.
If it does so, the expansion-contraction of the axial direction of each rod-shaped measurement base | substrate 7 will not generate | occur | produce, but the distortion | strain of the 1st fiber grating part 9 and the 2nd fiber grating part 10 by the said expansion / contraction will not generate | occur | produce. That is, the first fiber grating part 9 and the second fiber grating part 10 are not affected even if a displacement in the substantially vertical direction occurs on the ground.

Therefore, the strain generated in the first fiber grating portion 9 and the second fiber grating portion 10 is caused by the bending of the rod-shaped measurement base 7 caused by the horizontal displacement of the ground, excluding the strain caused by the expansion and contraction of the rod-shaped measurement base 7 in the axial direction. This is a combination of the strain generated and the strain generated by the temperature change.

Of the combined strains, the strain due to bending can be calculated by the equation (5).
That is, in FIG. 8 showing a cross section of the measurement base 7 on which the first fiber grating portion 9 and the second fiber grating portion 10 are installed, the strain detected by the fiber grating portions (1) to (4) at time t1. When ε11, ε21, ε31, ε41 and the average strain thereof is εt1, the strains due to bending among the strains detected by the fiber grating portions (1) to (4) ε'11, ε'21, ε '31, ε'41 can be calculated by the formula.

Also, assuming that the strain detected by each fiber grating portion at time t2 after Δt from time t1 is ε12, ε22, ε32, ε42, and the average of these is εt2, each fiber grating portion ( Among the strains detected in 1) to (4), strains ε′12, ε′22, ε′32, and ε′42 due to bending can be calculated.

On the other hand, the temperature change can be calculated by the equation (7). That, and it calculates by multiplying the temperature correction coefficient α changes in temperature between time t2 from time t1 (the temperature difference) to the difference of the average strain epsilon _ti at each time.

時刻t1から時刻t2の間に変化した温度変化（温度差）Ｋ_１２は以下のように示される。

α：温度校正係数

また、図１に示すように、棒状計測基体７の軸方向上下両端には前記複数のファイバグレーティング部を取り付けた光ファイバ１の端部がコネクタ１６あるいは融着接続を介して連結できるよう配置されており、もって該光ファイバ１の端部が他の光ファイバ１と連結できるよう構成されている。 From the above results, the temperature difference can be calculated and the temperature of the measurement signal can be corrected.
Therefore, even if the temperature correction fiber grating portion 12 is not provided, the temperature correction is performed on the measurement signal of the expansion grating fiber grating portion 38 by calculating the measurement signals of the first fiber grating portion 9 and the second fiber grating portion 10 for bending measurement. Is possible.

Temperature variation (temperature difference) K ₁₂ has changed between the time t2 from time t1 is shown as follows.

α: Temperature calibration coefficient

Further, as shown in FIG. 1, the ends of the optical fiber 1 to which the plurality of fiber grating portions are attached are arranged at the upper and lower ends in the axial direction of the rod-shaped measurement base 7 so that they can be connected via a connector 16 or a fusion connection. Therefore, the end portion of the optical fiber 1 can be connected to another optical fiber 1.

    Therefore, when it is desired to make the rod-shaped measurement substrate 7 shown in FIG. 1 longer or when the length of the rod-shaped measurement substrate 7 itself is a short type on the premise of being connected, for example, a length of about 2 m to 4 m. In some cases, the measurement device can be formed in the same configuration as the long rod-shaped measurement base 7 by connecting and lengthening the optical fibers in the axial direction and connecting the optical fibers together by the connector 16 or fusion connection. .

    Thus, it can be said that the type which can be added is suitable for the measurement in a remote place. In other words, it is not necessary to transport the long rod-shaped measurement base 7 itself, so that it can be said that it is suitable for transportation and transportation.

    In the above-described embodiment, the measurement unit 11 includes the set of the first fiber grating unit 9 and the set of the second fiber grating unit 10, but is not limited to this example. A plurality of, for example, a set of third fiber grating portions, a set of fourth fiber grating portions, and the like are provided at positions rotated around the axis of the rod-shaped measurement base between the fiber grating portion 9 and the second fiber grating portion 10. May be installed. In such a case, detailed three-dimensional measurement is possible.

In the case where simple measurement is sufficient without requiring three-dimensional measurement, the measurement unit 11 may be formed by only one set of the first fiber grating units 9, for example.
Next, the use state of the present invention will be described.

    For example, as shown in FIG. 2, a boring hole 18 is excavated in the ground 31 and, for example, a rod-shaped measuring base 7 provided with eight measuring portions 11 by fiber grating groups attached at intervals of 1.5 m is installed therein. .

    As described above, a plurality of measuring portions 11 are fixed to the rod-shaped measurement base 7 together with the optical fiber 1 with the fixture 8 at every two positions, and a packer or the like provided on the outer periphery of the fixture 8 is expanded to measure the rod-shape. The base body 7 itself is also fixedly installed in the boring hole 18.

Here, the upper end portion of the optical fiber 1 is connected to the FBG light measuring device 20, and the incident light 4 incident through the optical fiber 1 is reflected light for each measurement unit 11 and temperature correction fiber grating unit 12. Returns 5
The FBG light measuring apparatus 20 measures each reflected light 5 and measures a three-dimensional displacement at multipoint positions.

    Thus, the measurement data 32 by the reflected light 5 is taken into the PC 21 and transmitted to the server PC 24 through the communication line network 23 such as the Internet by the transmission unit 22 of the PC 21.

Here, as can be understood from FIG. 16, the server PC 24 includes a receiving unit 25, a transmitting unit 29, a control unit 30, a storage unit 26, and a display unit 31.
In the server PC 24, the measurement data 32 is taken in by the receiving unit 25 and stored in a storage unit 26 such as a hard disk.

    By the way, the position data 33 of the ground 31 whose displacement is to be measured is input in advance to the server PC 24, and the pre-displacement image of the ground 31 whose displacement is to be measured is drawn by the drawing means 27 based on the position data 33. Yes.

Subsequently, the measurement data 32 is taken into the server PC 24, and a post-displacement image of the ground 31 to be measured is drawn and created by the post-displacement image drawing means 28 based on the measurement data 32.
The drawn pre-displacement image and post-displacement image are instantaneously displayed on the display unit 34 such as a display so that the displacement in the ground 31 to be measured can be recognized in detail in real time.

The present invention is not only capable of accurately measuring underground displacement measurement and slip surface detection of landslides, roads and natural slopes, but also used for tunnel interior displacement measurement, preceding displacement measurement, looseness measurement, and bedrock structures. (Slopes, underground cavities, etc.), rock bed slip surface detection, etc.

It is explanatory drawing (the 1) explaining the installation state of the optical fiber by this invention. It is explanatory drawing explaining the use condition of the displacement measuring device by this invention. It is explanatory drawing (the 1) explaining the principle of the measurement by this invention. It is explanatory drawing (the 2) explaining the principle of the measurement by this invention. It is explanatory drawing (the 3) explaining the principle of the measurement by this invention. It is explanatory drawing (the 4) explaining the principle of the measurement by this invention. It is explanatory drawing (the 5) explaining the principle of the measurement by this invention. It is schematic structure explanatory drawing (the 1) explaining the outline of the rod-shaped measurement base | substrate with which the measurement part was formed. It is schematic structure explanatory drawing (the 2) explaining the outline of the rod-shaped measurement base | substrate with which the measurement part was formed. It is explanatory drawing explaining the principle of a fiber grating sensor. It is schematic structure explanatory drawing (the 1) explaining the connection structure of a rod-shaped measurement base | substrate. It is schematic structure explanatory drawing (the 2) explaining the connection structure of a rod-shaped measurement base | substrate. It is an AA part partial sectional view of FIG. FIG. 12 is a partial cross-sectional view (part 1) taken along the line BB of FIG. It is a BB section sectional view of FIG. 1 is a configuration explanatory diagram illustrating a schematic configuration of a measurement system according to the present invention. It is explanatory drawing (the 2) explaining the installation state of the optical fiber by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Core 3 Bragg diffraction grating 4 Incident light 5 Reflected light 6 Fiber grating 7 Rod-shaped measurement base 8 Fixture 9 1st fiber grating part 10 2nd fiber grating part 11 Measurement part 12 Temperature correction fiber grating part 16 Connector 17 Hollow tube 18 Boring hole 19 Transmitted light 20 FBG light measuring device 21 PC
22 Transmitter 23 Communication network 24 Server PC
25 receiving unit 26 storage unit 27 drawing unit 28 post-displacement image drawing unit 29 transmission unit 30 control unit 31 ground 32 measurement data 33 position data 34 display unit 35 optical switch 36 expansion / contraction allowance unit 37 underground fixing unit 38 fiber grating for extensometer Part 39 second measurement part 40 heat shrink tube 41 fiber bonding part 42 for extensometer first and second fiber grating part 43 fiber for extensometer 44 sleeve part 45 plastic bolt 46 temporary fixing bolt hole 47 fitting recess 48 Holding part 49 Insertion part 50 Existing hole

Claims (15)

A flexible rod-shaped measurement substrate;
On the outer peripheral surface of the rod-shaped measurement substrate, a pair of first fiber grating portions installed at two positions that are substantially symmetrical in the axial direction of the rod-shaped measurement substrate, and a rod-shaped measurement from the installation position of the first fiber grating portion A second fiber grating portion installed at two positions that are substantially symmetrical in the axial direction of the rod-shaped measurement substrate at a position rotated about the axis of the substrate;
An optical fiber connecting the first fiber grating part and the second fiber grating part, and a measurement part formed by including:
A fixture for fixing the optical fiber on both sides of the fiber grating part;
A displacement measuring apparatus comprising:
A flexible rod-shaped measurement substrate;
On the outer peripheral surface of the rod-shaped measurement substrate, a pair of first fiber grating portions installed at two positions that are substantially symmetrical in the axial direction of the rod-shaped measurement substrate, and a rod-shaped measurement from the installation position of the first fiber grating portion A second fiber grating portion installed at two positions that are substantially symmetrical in the axial direction of the rod-shaped measurement substrate at a position rotated approximately 90 degrees around the axis of the substrate;
An optical fiber connecting the first fiber grating part and the second fiber grating part, and a measurement part formed by including:
A fixture for fixing the optical fiber on both sides of the fiber grating part;
A displacement measuring apparatus comprising:
The measurement unit has a plurality of fiber grating units installed at positions rotated about the axis of the rod-shaped measurement base from the installation position of the first fiber grating unit toward the installation position of the second fiber grating unit. Configured,
The displacement measuring device according to claim 1 or claim 2, wherein
The measuring unit is configured to be installed in at least two places at an interval in the axial direction of the rod-shaped measuring base,
The displacement measuring apparatus according to claim 1, 2, or 3.
A plurality of the rod-shaped measuring bases can be connected in the axial direction, and the optical fibers installed on each of the bar-shaped measuring bases can also be connected to each other.
The displacement measuring device according to claim 1, 2, 3, or 4.
The rod-shaped measurement base is provided with an extension / contraction permission portion in the axial direction on at least one end side in the axial direction.
The displacement measuring device according to claim 5.
The rod-shaped measuring base is provided with a fitting recess that opens toward the outer side in the axial direction at one end in the axial direction, and a fitting portion that loosely fits into the fitting recess at the other end in the axial direction. An expansion / contraction allowance portion is provided between the insertion portion and the insertion portion.
The displacement measuring device according to claim 5 or 6, characterized by the above.
In the rod-shaped measurement base according to claim 7, the outer peripheral surface shape of the fitting recess is configured as a bulging portion shape that bulges outward from the outer peripheral surface shape of the rod-shaped measurement base.
A displacement measuring device characterized by that.
In the rod-shaped measurement base according to claim 7, a holding portion for holding the rod-shaped base in the borehole is provided on the outer peripheral surface of the fitting recess.
A displacement measuring device characterized by that.
On the outer peripheral surface of the rod-shaped measurement base, a second measurement unit provided with an expansion / contraction fiber grating unit for measuring an axial expansion / contraction displacement toward the axial direction was formed,
The displacement measuring apparatus according to claim 6, 7, 8, or 9.
The rod-shaped measurement base is formed of a cylindrical member, a temperature correction fiber grating portion is installed in the hollow portion, and the temperature correction fiber grating portion is connected to the optical fiber.
The displacement measuring device according to claim 1, 2, 3, 4, or 5.
The rod-shaped measurement base is formed of a cylindrical member, and a hollow tube is attached to the outer peripheral surface in the axial direction, and a temperature correction fiber grating portion is installed in the hollow tube, and the temperature correction The fiber grating part is also connected to the optical fiber,
The displacement measuring device according to claim 1, 2, 3, 4, or 5.
In the rod-shaped measurement base provided with the expansion / contraction allowance part in the axial direction, the temperature correction of the measurement value was made possible without the installation of the temperature correction fiber grating part.
The displacement measuring device according to claim 6, 7, 8, 9, or 10.
The rod-shaped measurement base is composed of a long and flexible rod-shaped member, and a plurality of fiber grating portions connected to the optical fiber at an interval are installed in the axial direction of the rod-shaped measurement base, A fixture for fixing the optical fiber at an interval in the axial direction is attached,
It was possible to form in the same configuration as the state where a plurality of the rod-shaped measurement bases are connected,
(1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), and (10) The displacement measuring device according to claim 12 or claim 13.
Capture means for capturing measurement data measured by the measurement unit;
A transmission means for transmitting the captured measurement data via a communication network;

Receiving means for receiving the transmitted measurement data;
Position data to be measured in advance is input, drawing means for drawing a pre-displacement image of the measurement position based on the position data,
A post-displacement image rendering means for rendering the post-displacement image of the measurement location based on the measurement data;
Displacement measurement system characterized by comprising:

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