JP2004191061A - Measuring device of expansion and contraction of ground - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring device of ground elasticity capable of preventing disconnection of an optical fiber, and measuring a ground change in the shrinking direction of the optical fiber. <P>SOLUTION: This measuring device 1 of expansion and contraction the ground is equipped with a plurality of piles 2A-2D installed at prescribed intervals along a slope of the natural ground, pulleys 3, journaled rotatably on the piles 2A-2D, the optical fiber 4 hooked over between the pulleys 3, making at least one round of the pulleys 3, and a measuring apparatus 6 for measuring an optical loss position generated on the optical fiber 4 by the pulley 3 so as to show the positions of the piles 2A-2D included in a light signal transmitted through the optical fiber 4. In the device, when the piles 2B-2D are moved by being influenced by a slope change, movement of the optical loss position generated on the optical fiber 4 so as to show the positions of the piles 2B-2D is measured by the measuring apparatus 6, to thereby measure elasticity of the ground. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground expansion / contraction measuring device that measures expansion / contraction of ground due to landslide or slope failure using optical fibers.
[0002]
[Prior art]
2. Description of the Related Art In general, various measuring devices are used to grasp changes in the ground due to landslides, slope deformation, and collapse. That is, a measuring device such as an extensometer or an inclinometer is installed in advance at a place where such a change is predicted, and the amount of change in the ground is measured by the extensometer or the amount of ground incline is measured by the inclinometer. I was measuring. In recent years, as such a measuring device, a measuring device using an optical fiber cable as a sensor has been proposed. That is, the optical fiber has a transmission loss characteristic in which the transmission loss of the optical signal increases even when subjected to a slight tensile strain or bending. Therefore, the measuring apparatus has a configuration in which an optical fiber is laid at a place where a change in the ground is expected with a small optical transmission loss, and the optical transmission loss of the optical signal of the optical fiber is measured. In other words, optical fiber laying methods include burying optical fibers below the ground surface, placing piles at predetermined intervals on the ground surface, passing optical fibers over these piles, Had fixed to the stake the part that was in contact with the stake. Therefore, according to such a measuring device, the optical fiber is deformed in conjunction with the change in the ground, and this deformation can be measured as the optical transmission loss of the optical fiber, and the change in the ground that is the cause of the deformation of the optical fiber can be grasped. can do. As a result, according to the measuring device using the optical fiber, a linear observation region formed by laying the optical fiber is secured, so that a large area can be observed with a small number of measuring instruments.
[0003]
In addition to this, a measuring device in which a plurality of detection units having projections are installed at the measurement location, and an optical fiber is disposed around these projections while being wound with a loop diameter that minimizes optical transmission loss (for example, Patent Document 1) is known. In other words, in this measuring device, when the ground is deformed and the distance between certain measurement points is increased and the optical fiber is pulled, the loop diameter of the measurement point decreases, so that optical loss can be caused in the optical fiber. 2. Description of the Related Art A measuring apparatus in which a plurality of optical fibers each having an inherent slack and a loop having the same diameter is installed is known (for example, see Patent Document 2). Therefore, according to this measuring device, all the optical fibers are pulled by the change in the ground, and the loop diameter of the optical fibers from the less loosened to the larger number of the optical fibers is reduced. For this reason, light loss can be caused in the optical fibers that differ stepwise in a certain order, so that the amount of change in the ground can be measured.
[0004]
[Patent Document 1]
Japanese Patent No. 3265413
[Patent Document 2]
JP-A-11-258356
[0005]
[Problems to be solved by the invention]
However, in the above measuring device, since the transmission loss due to bending or tensile strain caused by stretching the optical fiber is measured, when the ground changes greatly, the amount of expansion of the optical fiber increases, There is a problem that the fiber itself is broken. For this reason, in the event that even one of the wires is broken, all the observation areas where the optical fibers are installed cannot be observed. In particular, when a large-scale ground change occurs in a large observation area, the optical fiber may be disconnected at a plurality of locations, and thus there is a disadvantage that it takes time and effort to restore the observation system.
[0006]
On the other hand, the above measuring device measures that the optical fiber has been pulled and deformed due to a change in the ground, so if the ground changes in a direction to shrink the optical fiber due to compression of landslide mass, etc. Will not be deformed. For this reason, the conventional measuring device has a problem that the deformation amount of the ground in the compression direction cannot be measured.
[0007]
Accordingly, an object of the present invention is to solve the conventional problems as described above, and to provide a ground expansion / contraction measuring device capable of preventing disconnection of an optical fiber and measuring ground change in a direction in which the optical fiber is contracted. .
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes a plurality of piles installed at predetermined intervals along a slope of a ground, a pulley rotatably supported by these piles, Measuring an optical fiber passed between the pulleys at least once around the pulley and an optical signal transmitted to the optical fiber, the optical loss position being generated in the optical fiber so as to indicate the position of the pile. And a measuring device for measuring the expansion and contraction of the ground, comprising a measuring device that performs a movement of an optical loss position generated in an optical fiber so as to indicate the position of the pile when the pile moves under the influence of the slope deformation. It is characterized in that the expansion and contraction of the ground is measured by measuring with a measuring instrument.
[0009]
According to the invention of claim 2, a plurality of piles installed at predetermined intervals along the slope of the ground, a pulley rotatably supported by these piles, and at least one round of these pulleys A wire wound between the pulleys, an optical loss generator arranged on these pulleys, and bending the optical fiber by rotation of the pulley when the position of the pile moves to generate optical loss; An apparatus for measuring the expansion and contraction of a ground, comprising an optical fiber disposed through a loss generator and a measuring instrument for measuring an optical signal transmitted to the optical fiber, which is affected by slope deformation. When the pile is moved, by measuring the position of the optical loss generated by the optical loss generator of the pile in the optical fiber by the measuring device, the expansion and contraction of the ground is measured. I do.
[0010]
According to a third aspect of the present invention, in the second aspect, the optical loss generator has two cam mechanisms driven by the rotational force of the pulley to bend different portions of the optical fiber to generate optical loss. One of the cam mechanisms is connected to the pulley via a one-way clutch that transmits only the rightward rotational force from the pulley, and the other cam mechanism transmits only the leftward rotational force from the pulley. Is connected to the pulley via a one-way clutch, and when the pile is moved under the influence of the slope deformation, the pulley is rotated clockwise or counterclockwise with the movement of this pile, and One or the other cam mechanism, to which the rotational force is transmitted by a suitable one-way clutch, bends different portions of the optical fiber to generate light loss.
[0011]
According to a fourth aspect of the present invention, in any one of the first to third aspects, a weight for applying tension to the optical fiber or the wire wound around the pulley is connected to a predetermined portion of the optical fiber or the wire. It is characterized by the following.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing the entire configuration of the measuring device, and FIGS. 2A and 2B are graphs showing the measurement results of optical signals before and after the change of the ground.
[0013]
As shown in FIG. 1, the ground expansion / contraction measuring device 1 is fixedly mounted on the fixed piles 2 </ b> A and the piles 2 </ b> B to 2 </ b> D sequentially at predetermined intervals along the slope, and is pivotally supported by these piles 2 </ b> B to 2 </ b> D. The pulley 3, the one optical fiber 4 wound around the pulleys 3 at least one round, and the optical fiber 4 interposed between the pulleys 3 and 3 apply tension to the pulleys 3. And a measuring instrument 6 connected to one end of the optical fiber 4. The pulley 3 is not provided on the fixed pile 2A on the left side in the figure, and the other end of the optical fiber 4 is fixed to the upper end.
[0014]
That is, as a measurement target of the measuring device 1, for example, a slope of a mountain where slope deformation, that is, a change in the ground is predicted due to occurrence of a landslide or the like, is selected, and a plurality of piles are set along a direction in which the height of the slope increases or decreases. 2A to 2D are arranged in a single row at a predetermined interval from each other. For these piles 2A to 2D, pipe-shaped members having sufficient strength are used, and are firmly fixed to the installation locations in an upright posture. That is, the base of each of the piles 2A to 2D is buried at a sufficient depth to maintain an upright posture and not move from the installation location except for movement due to changes in the ground. Although the piles 2A to 2D are not installed so that all the piles 2A to 2D are aligned in order to avoid obstacles such as trees (not shown) vegetated between the piles 2A to 2D, It is installed so that it moves in a certain direction even if it is irregular. A pulley 3 is pivotally supported on the upper ends of these piles 2 so that the pulley 3 is separated from the sloped ground surface by a predetermined distance. Therefore, the optical fiber 4 can be laid over the pulleys 3 and 3 of the piles 2A to 2D regardless of the unevenness of the ground surface or the plant existing between the piles 2A to 2D, and the ground surface is not affected. , The pulley 3 can be rotated.
[0015]
The pulley 3 is formed in a disk shape having a predetermined diameter, and is rotatably supported at the upper ends of the piles 2B to 2D. The pulley 3 is installed so that its rotation surface is a vertical surface and is oriented in a direction as parallel as possible to a line connecting the adjacent piles 2B to 2D on both sides. The optical fiber 4 is wound around the outer periphery of the pulley 3 so as to make at least one round, and then the optical fiber 4 is stretched between the pulleys 3 and 3 toward the adjacent piles 2B to 2D. . The outer diameter dimension of the pulley 3 is set to a dimension that allows the optical fiber 4 to bend to an extent that causes optical loss and give bending strain. Therefore, the positions of the piles 2B to 2D can be measured in correspondence with the light loss position of the optical fiber 4.
[0016]
As the optical fiber 4, an optical fiber cable having a predetermined optical loss characteristic is used. That is, the core portion of the optical fiber 4 is a transmission portion for transmitting an optical signal, which has an ultra-high transparency, and the outer peripheral portion is colored and covered with a synthetic resin film or the like. The optical fiber 4 is flexible enough to be wound around the pulley 3.
[0017]
A weight 5 for applying tension to the portion of the optical fiber 4 between the piles 2A to 2D is provided on the pile 2D installed at the end of the measurement area. That is, the weight 5 has a predetermined weight enough to apply tension without breaking the optical fiber 4, and its height position occupies a substantially middle height position of the pile 2D. It is connected to the optical fiber 4.
[0018]
The measuring device 6 is a measuring device using an OTDR (Optical Time Domain Reflectometer), and an input / output section of an optical signal is connected to one end of the optical fiber 4. The measuring device is generally known as a device for detecting a fault position of an optical fiber cable, measuring a loss, and measuring a connection loss at a connection point when manufacturing, laying, and maintaining the optical fiber 4. That is, the measuring instrument makes the incident light and the reflected light incident on the optical fiber 4 to be measured by detecting the reflected light returning from the fault point in the optical fiber 4 by inputting the optical pulse for the failure measurement to the optical fiber 4 to be measured. The distance to the position of the obstacle is measured from the time difference. Therefore, since the OTDR is used as the measuring device 6, the measuring device 6 can be a small and inexpensive measuring device, and can easily be transported to a place where the measuring device 1 is installed.
[0019]
Next, the operation of the measuring device 1 will be described. That is, due to the crack deformation at a certain place in the ground, the pile 2C is affected by the slope deformation in the direction approaching the pile 2B as shown by the broken arrow in the drawing, that is, the pile 2C and the pile 2B. When the optical fiber 4 is moved in a direction of contracting the optical fiber 4, the optical fiber 4 is wound around the pulley 3, so that the pulley 3 pivotally supported by the pile 2C moves while rotating. Therefore, the optical transmission loss position indicating the position of the pile 2C on the optical fiber 4 moves in the same direction. That is, since the optical fiber 4 is a continuous single body, the direction and the amount of movement of the optical loss position on the optical fiber 4 can be measured by the measuring device 6 connected to one end of the optical fiber 4. Therefore, the moving direction and the moving amount of the pile 2C affected by the change in the ground can be confirmed from the moving direction and the moving amount. Thereby, it is possible to grasp the position where the displacement occurred in part or the whole of the ground and the amount of change in the ground. That is, as shown in FIG. 2 (A), the measurement result of the signal by the measuring instrument 6 shows that the optical loss position on the optical fiber 4 indicating the position of the pile 2C in this state in the initial state before the ground change. On the other hand, in the state after the ground change, the light loss position showing the position of the pile 2C moved by the ground change has moved to a different position, as shown in FIG. Measured.
[0020]
In addition, in addition to the above, when the height position where the piles 2A to 2D are installed moves up and down, for example, as the piles 2A to 2D are pulled into the landslide slope due to slope deformation, the piles 2A to 2D Even when the length of the optical fiber 4 changes up to 2D, the amount of change can be compensated for by the tension imparting weight 5, so that it is possible to prevent the occurrence of a problem beforehand. That is, when the weight 5 rises or falls, the portion of the optical fiber 4 hanging down from the pulley 3 of the pile 2D supplements the shortage of the optical fiber 4 between the piles, or adds an unnecessary portion. It can be absorbed by adding it to the hanging part. As a result, disconnection of the optical fiber 4 can be prevented while maintaining the tension of the optical fiber 4 between the piles 2A to 2D.
[0021]
According to this embodiment, the optical fiber 4 is previously rotated at least once around the pulleys 3 of each of the piles 2B to 2D so that the position of each of the piles 2B to 2D is represented as an optical loss position on the optical fiber 4. Since the piles 2 </ b> B to 2 </ b> D affected by the slope deformation move since they are hung over the adjacent pulley 3, the piles 2 </ b> B and 2 </ b> D move while maintaining the optical fiber 4 wound around the pulley 3. The movement of 2B to 2D can be measured as the movement of the light loss position. Thereby, the amount of change such as expansion and contraction of the ground can be grasped. On the other hand, since the measurement state after the change as the movement of the light loss position can be set as a new reference measurement state, the measurement apparatus 1 can observe the ground change over the long term in the same area. In addition to this, one end of the optical fiber 4 is fixed to the pile 2A, and the other end is connected to the weight 5 while giving the pile 2D a pre-length, and the middle of these is connected to each pulley 3 of each of the piles 2B to 2D. Since the optical fiber 4 is not fixed to each of the piles 2B to 2D since the optical fiber 4 is fixed to the adjacent pulley 3 after at least one round, disconnection of the optical fiber 4 can be prevented. That is, even if the piles 2B to 2D move due to the slope deformation, the movement in the length direction of the optical fiber 4 itself is not restricted. For this reason, the optical fiber 4 can follow and adapt to the change in the ground shape due to the deformation of the slope, so that disconnection of the optical fiber 4 can be prevented.
[0022]
In addition, since the measuring apparatus 1 uses an optical fiber cable for transmitting an optical signal as a sensor, the measuring apparatus 1 is not affected by electromagnetic noise such as electromagnetic noise due to a surrounding high voltage line or lightning strike. Therefore, the accuracy and reliability of the measurement data are improved, and the measurement performance can be improved. That is, the measuring device 1 is configured so that the light loss position on the single continuous optical fiber 4 moves with the change of the ground, and the displacement of the light loss position is measured by the measurement connected to one end of the optical fiber 4. It is measured with a container. Therefore, a power source and a measuring instrument are not required on site to generate light loss, and the work for installing and maintaining the measuring device 1 can be simplified. On the other hand, glass fiber, which is a main component of the optical fiber 4, is considerably lighter than a copper conductor, which is a main component of a metal cable for transmitting an electric signal, so that the optical fiber 4 can be transported to an observation point. The burden of installation work is reduced.
[0023]
Next, another embodiment of the present invention will be described. As shown in FIG. 3, the measuring device 10 of this embodiment includes a wire 11 wrapped between the pulleys 3 and 3 after at least one round of the pulleys 3 and 3 of each of the piles 2A to 2C, and 2C, the optical fiber is installed through these optical loss generators 12, and when the specific piles 2A to 2C move due to a change in the ground, they move. The optical loss generator 1 of the piles 2A to 2C generates an optical loss in the optical fiber 4 in which the moving direction and the moving amount are specified. Note that members having the same configuration as in the above-described embodiment are denoted by the same reference numerals, and description thereof will be simplified. That is, a pulley 3 is pivotally supported on the upper end of the pile 2A, and the tension 5 is applied to the pile 2A, while the pulley 3 is eliminated from the pile 2D, and the upper end of the pile 2D is removed. , One end of the wire 11 is fixed.
[0024]
The wire 11 is made of a material having a small amount of expansion and contraction due to a temperature change, has a predetermined diameter, and has a sufficient tensile strength. Therefore, the pulleys 3 of the moved piles 2A to 2C can be surely rotated at an angle directly proportional to the amount of movement of the piles 2A to 2C.
[0025]
As shown in FIG. 4, the light loss generator 12 is directly driven by a rotation shaft of the pulley 3, a driving gear 14 having a rotation center connected to the direct connection shaft 13, and driven by the driving gear 14. It has two sets of cam mechanisms 15 and 16, and is housed in a case 17 together with the optical fiber 4. For this reason, the optical loss generator 12 causes one of the cam mechanisms 15 and 16 to bend the optical fiber 4 in accordance with the rotation direction, thereby causing the optical fiber 4 to generate optical loss.
[0026]
That is, the left cam mechanism 15 in the figure has a small-diameter driven gear 19 meshed with the large-diameter driving gear 14 and a rotating shaft (not shown) of the driven gear 19 via a one-way clutch 20 (one-way clutch). The optical fiber 4 is provided so as to be in contact with the cam 21. The cam 21 is formed in a substantially elliptical shape having a protrusion, and is set so that the protrusion of the cam 21 faces upward in an initial state before measurement. When the driven gear 19 rotates clockwise, the one-way clutch 20 does not engage and does not transmit the rotational force to the cam 21 without engaging the clutch, whereas when the driven gear 19 rotates counterclockwise, the clutch engages, The rotation force is transmitted to the cam 21. Therefore, when the pulley 3 and the driving gear 14 rotate clockwise, the driven gear 19 rotates counterclockwise, so that the rotational force is transmitted to the cam 21 by the one-way clutch 21, and the rotated cam 21 bends the optical fiber 4.
[0027]
The right cam mechanism 16 in the drawing is connected to a small-diameter driven gear 23 meshed with a large-diameter driving gear 14 and a rotating shaft (not shown) of the driven gear 23 via a one-way clutch 24 (one-way clutch). The optical fiber 4 is disposed so as to be in contact with the cam 25. The cam 25 is formed in a substantially elliptical shape having a protrusion, and is set so that the protrusion of the cam 25 faces upward in an initial state before measurement. When the driven gear 23 rotates counterclockwise, the one-way clutch 24 idles without engaging the clutch and does not transmit the rotational force to the cam 25. On the other hand, when the driven gear 23 rotates clockwise, the clutch engages. , Is transmitted to the cam 25. Therefore, when the pulley 3 and the driving gear 14 rotate rightward, the driven gear 23 rotates leftward, the rotational force is transmitted to the cam 25 by the one-way clutch 24, and the rotated cam 25 causes the optical fiber 4 to bend.
[0028]
In addition, even if the pulley 3 rotates at a slight rotation angle, one of the cam mechanisms 15 and 16 can be operated in accordance with the rotation direction to the extent that optical loss occurs in the optical fiber 4. That is, the rotation of the driving gear 14 is enlarged according to the gear ratio between the driving gear 14 and the driven gears 19 and 23 and transmitted to the driven gears 19 and 23. Therefore, the cam mechanisms 15 and 16 operate even when the amount of movement of the piles 2A to 2C is small and the rotation angle of the pulley 3 is small. As a result, a slight amount of change in the ground can be measured, so that the detection sensitivity of the measuring device 10 is improved, and high performance can be achieved.
[0029]
Reference numerals 27 and 28 denote springs for applying a predetermined tension to portions of the optical fiber 4 that come into contact with the cams 21 and 25, respectively. That is, the portion of the optical fiber 4 located above the driven gears 19 and 23 is fixed to the case 17, and the portion of the optical fiber 4 located below the driven gears 19 and 23 is connected to the tensioned spring 27. It is fixed to the case 17 via 28. For this reason, when the optical fiber 4 is bent by the rotation of the cams 27 and 28, tension is applied to the optical fiber 4 to prevent the optical fiber 4 from loosening. Along with the bending caused by the cams 27 and 28. On the other hand, when the rotation of the cams 27 and 28 is returned to the original initial state, the optical fiber 4 can be returned from the bent state to the original extended state. In addition to this, the expansion and contraction state of the portion of the optical fiber 4 interposed between the light loss generators 12, 12 of the piles 2A to 2D, that is, the light in the light loss generator 12, The deformation state of the portion of the fiber 4 can be made independent. For this reason, the former part can be slackened so as to have a margin. As a result, even if the distance between the piles 2A to 2D changes due to a change in the ground, disconnection of the optical fiber 4 can be prevented.
[0030]
Reference numeral 29 denotes a winding unit for winding and storing the optical fiber 4 interposed between the two cam mechanisms 15 and 16 by a predetermined length. That is, it is necessary to separate the optical loss positions of the optical fibers 4 from each other by a predetermined distance due to restrictions on measurement performance such as the minimum reading resolution of the measuring device 6. That is, unless a predetermined distance is secured between the two light loss positions, the two cannot be distinguished. For this reason, the optical fiber 4 is accommodated in the winding section 29 by a length corresponding to a necessary distance. Therefore, since a distance is secured between the light loss position by the left cam mechanism 15 on the optical fiber 4 and the light loss position by the right cam mechanism 16, both can be distinguished and measured by the measuring device 6. .
[0031]
Next, the operation of the measuring device 10 will be described. That is, as shown in FIG. 3 again, when the pile 2C moves in the direction approaching the left pile 2B under the influence of the change in the ground, that is, moves in the direction to shrink the optical fiber 4 located on the left side of the pile 2C. In this case, when viewed from the pulley 3 of the pile 2C by this movement, the wire 11 is relatively drawn out from the left side, and the wire 11 is drawn out relatively to the right side. For this reason, the pulley 3 is rotated clockwise, and as shown in FIG. 4 again, the driving gear 14 is clockwise rotated in the same direction. Therefore, both driven gears 19 and 23 are rotated left, but only the left cam 21 is driven to rotate by the operation of the one-way clutches 20 and 24, respectively. That is, when the driven gear 19 is rotated to the left, the one-way clutch 20 is engaged in the left rotation, so that the cam 21 is rotated left along with the driven gear 19. On the other hand, even if the driven gear 23 is rotated to the left, the one-way clutch 24 idles, so that the cam 25 maintains its rotational position.
[0032]
Therefore, only the cam 21 shifts from the rotational position indicated by the imaginary line in the figure to the rotational position indicated by the solid line. As a result, since the protrusion of the cam 21 presses the optical fiber 4 from the side, the optical fiber 4 is bent deeply, and light loss occurs at the bent optical fiber 4. Therefore, the measuring device 6 measures the position on the optical fiber 4 where the optical loss has occurred and the decrease in the optical signal intensity. Therefore, by detecting the position where the optical loss occurs and the decrease in the optical signal intensity, the moving direction and the moving amount of the pile 2C affected by the change in the ground can be confirmed. As a result, it is possible to grasp the position where the displacement has occurred in part or the whole of the ground and the amount of change in the ground. That is, as shown in FIG. 5A, as a result of measuring the optical signal by the measuring device 6, a waveform that linearly falls due to the attenuation phenomenon of the optical signal is obtained before the ground changes. On the other hand, after the change of the ground, as shown in FIG. 3B, a waveform having a stepped portion indicating the light loss position and a decrease in the optical signal intensity is obtained.
[0033]
In the above embodiment, the cams 21 and 25 are formed to have a shape having one protruding portion. However, the present invention is not limited to this, and the protruding portions protruding in a direction opposite to this protruding portion are provided. And a configuration using a cam formed in a shape having two projecting portions may be used. Therefore, according to this configuration, when the pile moves by the same distance due to a change in the ground, as compared with a cam having a single protrusion, the two protrusions that are rotationally driven in conjunction with this movement. The number of deformations of the optical fiber can be doubled by the cam having the above. Therefore, the measurement accuracy of the measurement device 10 can be improved.
[0034]
【The invention's effect】
The present invention is as described above, and according to the first aspect of the present invention, a plurality of piles are installed along a slope at a predetermined interval, and pulleys are pivotally supported on these piles. Since the optical fiber is spanned between the pulleys by making one round, and the optical signal of the optical fiber is measured by the measuring device, the disconnection of the optical fiber can be prevented. That is, when the pile moves due to the deformation of the slope, the pulley supported by the pile moves while being rotated by the optical fiber without pulling or compressing the optical fiber, and the optical loss position showing the position of the pile is changed. Moving. For this reason, the expansion and contraction of the ground can be grasped by measuring the movement of the light loss position with the measuring instrument regardless of the slope deformation that has changed in the tensile direction or the compression direction of the optical fiber.
[0035]
In addition, when the pile moves due to slope deformation, the optical fiber is not fixed to the pile, but is supported by the pile with a pulley interposed, so the movement in the length direction of the optical fiber is not restricted. And no excessive external force is applied to the optical fiber. As a result, disconnection of the optical fiber can be prevented. On the other hand, the measurement state of the optical fiber measured after the slope deformation can be used as a reference state for measuring the subsequent slope deformation. For this reason, long-term repeated measurement at the same measurement location is possible without resetting or adjusting the measuring device.
[0036]
According to the invention of claim 2, a plurality of piles are installed on the slope at predetermined intervals, pulleys are pivotally supported on these piles, these pulleys are rotated at least once, and wires are passed between the pulleys, An optical loss generator is disposed on these pulleys, an optical fiber is disposed through these optical loss generators, and the optical signal loss of the optical fiber is measured by a measuring device. Since the optical fiber is bent by rotation of the pulley of the pile to cause optical loss, disconnection of the optical fiber can be prevented. That is, with the movement of the pile due to the slope deformation, the pulley of the pile is rotated by the wire, and the rotation of the pulley causes the optical loss generator to bend the optical fiber to cause optical loss. For this reason, excessive external force is not applied to the optical fiber, and disconnection of the optical fiber can be prevented.
[0037]
According to the third aspect of the present invention, the optical loss generator has at least two cam mechanisms for deforming the optical fiber, and these cam mechanisms transmit only rotational forces in the opposite directions from the respective pulleys. Since the optical fiber is connected to the pulley through the one-way clutch, not only the slope deformation in the direction in which the optical fiber is pulled but also the slope deformation in the contraction direction can be distinguished and grasped. That is, since the one-way clutch for transmitting the rotational force in the predetermined direction is interposed in the transmission path of the rotational force from the pulley to each cam mechanism, the pile moves due to the slope deformation, and the pile moves according to the moving direction of the pile. When the pulley is rotated clockwise or counterclockwise, the cam mechanism selected by the one-way clutch can be operated according to the rotation direction. Therefore, different portions of the optical fiber can be deformed according to the rotation direction. Therefore, light loss can be generated at different positions on the optical fiber according to the moving direction of the pile, and the measuring device can measure such different light loss positions. As a result, it is possible to perform measurement while distinguishing slope deformation such as pulling or shrinking the optical fiber.
[0038]
According to the invention of claim 4, the weight is connected to a predetermined portion of the optical fiber or the wire, and the tension is applied to the optical fiber or the wire wound around the pulley. The loosening of the interposed optical fiber or wire can be prevented. For this reason, when the pile moves due to the deformation of the slope, the pulley can be rotated by following the pulley at an accurate angle according to the movement amount of the pile. As a result, the accuracy as a measuring device can be improved. In addition to this, the part hanging down by the weight can be secured as an extra length, so if the length of the optical fiber or the wire wound around the pulley is insufficient due to slope deformation, this part is used. Can be replenished. Therefore, disconnection of the optical fiber or wire can be prevented.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the present invention and is an overall configuration diagram of a measuring device.
FIGS. 2A and 2B illustrate a detection state of an optical signal by the measuring instrument according to the embodiment, in which FIG. 2A is a graph showing a state before the ground changes, and FIG. 2B is a graph showing a state after the changes. is there.
FIG. 3 shows another embodiment of the present invention and is an overall configuration diagram of a measuring device.
FIG. 4 is a schematic diagram of an optical loss generator of another embodiment.
5A and 5B illustrate a detection state of an optical signal by a measuring device according to another embodiment, wherein FIG. 5A is a graph showing a state before a change in ground, and FIG. 5B is a graph showing a state after a change. It is.
[Explanation of symbols]
1,10 Measuring device 2 pile
3 Pulley 4 Optical fiber
5 Weight 6 Measuring instrument
11 wire 12 optical loss generator
14 Driving gear 15, 16 Cam mechanism
19,23 driven gear 20,24 one-way clutch
21,25 cam

Claims (4)

A plurality of piles installed at predetermined intervals along the slope of the ground, pulleys rotatably supported on these piles, and these pulleys were wound around the pulleys at least once. A ground expansion / contraction measuring device comprising: an optical fiber; and an optical signal transmitted to the optical fiber, and a measuring device for measuring an optical loss position generated in the optical fiber so as to indicate the position of the pile. hand,
When the pile is moved under the influence of the slope deformation, by measuring the movement of the optical loss position generated in the optical fiber so as to indicate the position of the pile, the expansion and contraction of the ground is measured. A device for measuring the expansion and contraction of the ground, characterized in that: A plurality of piles installed at predetermined intervals along the slope of the ground, pulleys rotatably supported on these piles, and these pulleys were wound around the pulleys at least once. A wire, an optical loss generator that is disposed on these pulleys, and that generates an optical loss by bending the optical fiber by rotation of the pulley when the position of the pile is moved, and passing through these optical loss generators An optical fiber disposed, and a measuring device for ground expansion and contraction comprising a measuring device for measuring an optical signal transmitted to the optical fiber,
When the pile is moved under the influence of the slope deformation, the measuring device measures the position of the optical loss generated by the optical loss generator of the pile in the optical fiber, so that the expansion and contraction of the ground is measured. A device for measuring the expansion and contraction of the ground, characterized in that: The optical loss generator has two cam mechanisms that are driven by the rotational force of the pulley and that bend different portions of the optical fiber to generate optical loss, respectively.
One cam mechanism is connected to the pulley via a one-way clutch that transmits only the right-hand rotational force from the pulley, and the other cam mechanism transmits only the left-hand rotational force from the pulley. Connected to a pulley via a directional clutch,
When the pile is moved under the influence of the slope deformation, the pulley is rotated clockwise or counterclockwise in accordance with the movement of the pile, and the one-way clutch that is adapted to one of these rotation directions transmits torque or 3. The measuring apparatus according to claim 2, wherein the other cam mechanism bends different portions of the optical fiber to generate light loss. The ground expansion / contraction measuring apparatus according to any one of claims 1 to 3, wherein a weight for applying tension to the optical fiber or the wire wound around the pulley is connected to a predetermined portion of the optical fiber or the wire.

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