JP2000292216A - Optical fiber sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the safe monitoring of sign phenomenon of disasters which are micro displacements of unstable strata, rocks, etc., at all times and to enable utilization for preventing disasters such as land slides in cliffs and slopes. SOLUTION: In an optical fiber sensor 4, an optical fiber 6 is integrally displaceably mounted to an object 5 of monitoring such as a rock or the like with a possibility of displacement. An optical fiber 8 on the side of a stable stratum 7, which is a reference side of monitoring, is detachably connected to the optical fiber 6 via optical connectors 9a and 9b to connect the optical fiber 6 on the side of the object 5 of monitoring to an optical time domain reflectometer 10 via the optical fiber 8 on the side of the stable stratum 7. Then the vicinity of the tip of the optical fiber 8 on the side of the stable stratum 7 connected to the optical fiber 6 on the side of the object 5 of monitoring is fixed to the side of the stable stratum 7 by a fixing means 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber sensor for observing the displacement of an object to be monitored, such as an unstable stratum or a rock having a possibility of displacement, with respect to a stable ground on a monitoring reference side.

[0002]

2. Description of the Related Art For example, disaster prevention measures such as rock fall, landslides and rock fall include daily and emergency inspections by staff in charge.
It is common to have a patrol. The purpose of this inspection and patrol is to monitor the presence or absence of signs of disaster, such as the occurrence of cracks on the ground slope or cliffs, or the displacement of rock or specific rock.

[0003]

However, in the above-described inspection and patrol monitoring, it is difficult to constantly monitor the entire wide monitoring area, and there is a possibility that a response may be delayed due to on-site movement. Inspections and patrols themselves are difficult under nighttime conditions, and the inspections and patrols themselves are dangerous.In the event of a wide-area disaster such as an earthquake, there are many dangerous spots that need to be inspected and patroled. There are problems that it is difficult to secure personnel, it is not possible to collect information promptly, it is not possible to enter dangerous places itself, and inspection and patrol are impossible. In recent years, various sensing technologies using optical fibers have been developed and put into practical use, and are being applied to various applications. It is expected that this technology will be applied to constant monitoring of rocks and rocks in the monitoring area. I have. However, there has never been a suitable optical fiber sensor capable of efficiently measuring the displacement, strain, and the like of natural soil and rock, and its development has been demanded.

[0004] The present invention has been made in view of the above-mentioned problems, and can efficiently measure displacement, strain, and the like of earth and sand and rock mass.
It is an object of the present invention to provide an optical fiber sensor capable of constantly monitoring a danger point such as a bedrock collapse or a slope failure to quickly recognize a sign of a disaster and utilizing it for disaster prevention.

[0005]

According to the first aspect of the present invention,
An optical fiber sensor for observing a displacement of a monitoring target such as an unstable stratum having a possibility of collapse or a rock having a possibility of displacement with respect to a stable ground serving as a monitoring reference side, wherein the sensor is integrated with the monitoring target. The optical fiber on the object to be monitored and the optical pulse tester are connected via the optical fiber on the stable ground side by detachably connecting the optical fiber on the stable ground side to the optical fiber attached as displaceable via the optical connector. And an optical fiber sensor, wherein the vicinity of the tip of the stable ground side optical fiber connected to the monitored object side optical fiber is fixed to the stable ground side by fixing means. Means. According to the present invention, the monitoring target is an unstable stratum (that is, a stratum in which landslides are likely to occur), a rock that may be displaced, or the like (that is, a block of rock or rock that is easy to move and may fall). Due to the displacement of the object with respect to the stable ground on the monitoring reference side (that is, the stable rock or hard rock where it is difficult to move, landslide, partial collapse, falling etc. does not occur), the optical fiber on the monitored object side The optical connector connecting the optical fiber on the stable ground side is disconnected. At this time, from the observation result of the return light of the incident light from the optical pulse tester to the optical fiber (for example, the backscattered light of Rayleigh scattered light, etc.), it can be grasped that the optical connector has been disconnected. The displacement of the object to be monitored can be safely monitored from any place.

As is well known, when light is incident on an optical fiber, it is caused by light reflected at a broken portion of the optical fiber or a connector connecting portion, or light scattering (Rayleigh scattering) due to a subtle change in the density of the optical fiber or the like. It is known that the backscattered light returns to the input end of the optical fiber, and the time from when the test light enters the optical fiber from the optical pulse tester (OTDR) to when the return light is received (hereinafter, referred to as “OTDR”). ,
By measuring the “return time”, the disconnection position (distance from the optical pulse tester) can be grasped. In a state where the optical fiber on the monitored object side and the optical fiber on the stable ground side are connected by an optical connector, the disconnection position observed by the optical pulse tester is an optical fiber extending from the optical connector to the monitored object side. Return light such as backscattered light of Rayleigh scattered light generated over the entire length of the optical fiber from the optical pulse tester to the end of the optical fiber and reflected light generated at the end of the optical fiber. However, if the connection between the optical fibers on the monitored object side and the stable ground side by the optical connector is released, the return light from the optical fiber on the monitored object side will not be observed. From the result of the observation of the return light by the device, it can be understood that the connector connection between the optical fibers has been released.

According to a second aspect of the present invention, there is provided an optical fiber for observing a displacement of an object to be monitored, such as an unstable stratum having a possibility of collapse or a rock having a possibility of displacement, with respect to a stable ground which is a monitoring reference side. A sensor unit disposed between the monitored object and the stable ground, a unit body connected to the stable ground side, and a unit attached to the monitored object side so as to be integrally displaceable; and A movable member that is relatively displaceable with respect to the main body, a plurality of optical fiber wiring portions in which optical fibers housed with an extra length secured in the sensor unit are wired, and in cooperation with the movable member. Breaking means for sequentially moving the plurality of optical fiber wiring parts by being driven, and breaking the optical fiber in order from a location far from an optical pulse tester connected to the optical fiber. An optical fiber sensor, characterized in that it comprises the a solution of the above problems. According to the present invention, an unstable stratum (that is, a stratum in which landslides are likely to occur), a rock having a possibility of displacement, or the like (that is, for example,
The surveillance target, which is a block of rock or rock that is easy to move and may fall,
The movable member is displaced by displacement against a stable stratum or stable rock that is difficult to move and is less likely to cause landslide, partial collapse, drop, etc. While sequentially moving the wiring sections, the optical fibers wired in each optical fiber wiring section are sequentially broken from a location far from an optical pulse tester (a so-called OTDR). At this time, the optical pulse tester does not observe return light (backscattered light; reflected light from the tip of the optical fiber or Rayleigh scattered light generated in the optical fiber) from the optical fiber ahead of the cut point. The change of the position (break point) can be grasped, whereby the displacement of the monitored object can be detected even from a place remote from the site.

The breaking of the optical fiber by the breaking means is performed in order from a position far from the optical pulse tester of the optical fiber,
When the break point of the optical fiber moves toward the optical pulse tester with an increase in the displacement of the monitored object, the optical pulse tester stops sequentially observing the return light with a long return time. Can understand. Thereby, it is possible to observe the change of the displacement amount of the monitoring target in real time from the observation result of the return light by the optical pulse tester.

As a method for observing the continuous distribution of the amount of strain in the longitudinal direction of an optical fiber with high accuracy, the frequency shift of Brillouin scattered light, which is one of nonlinear phenomena, depends on the strain of the optical fiber. Have been developed. That is, the wavelength of the Brillouin scattered light, which is one of the backscattered light generated when the test light enters the strained optical fiber, deviates from the wavelength of the test light incident on the optical fiber. Thus, the amount of distortion of the optical fiber can be grasped. Further, the outline of the strain occurrence position of the optical fiber can be ascertained by the time from the entrance of the test light until the Brillouin scattered light is received and observed.

According to a third aspect of the present invention, an object to be monitored is an unstable stratum which is likely to collapse or a rock which is likely to displace existing in a monitoring area by receiving and observing Brillouin scattered light. An optical fiber sensor for observing displacement with respect to a stable ground that is a monitoring reference side, wherein an optical fiber connected to an optical pulse tester is extended along a boundary between the monitoring area and the stable ground. A plurality of longitudinally separated portions of the optical fiber were retained on the stable ground side by an optical fiber retaining member, and the optical fibers between adjacent optical fiber retaining members were connected to the monitored object so as to be integrally displaceable. An optical fiber sensor characterized by the above feature is provided as a means for solving the above problem. According to the present invention, an unstable stratum (that is, a stratum in which landslides are likely to occur) or a rock or the like that is likely to be displaced (that is, for example, a block of rock or rock that is easy to move and may fall) is present in the monitoring area. )
When the object to be monitored is displaced from the stable ground with respect to the stable ground, tension acts on the optical fiber between the optical fiber retaining members, and when elongation strain is applied to the optical fiber, an optical pulse tester (a so-called BOTDR) transmits the optical fiber to the optical fiber. The back scattered light of the Brillouin scattered light in which the incident test light is scattered at the elongational strain occurrence location returns to the optical pulse tester. By measuring the return time of the backscattered Brillouin light to the optical pulse tester, it is possible to grasp the location where the elongation distortion has occurred. Further, by measuring the amount of distortion of the optical fiber from the amount of frequency shift of the Brillouin scattered light observed by the optical pulse tester, the amount of displacement of the monitored object can be grasped. This optical fiber sensor can be installed simply by connecting an appropriate part of the optical fiber laid in the monitoring area to the object to be monitored and allowing the optical fiber to be stretched and distorted by the displacement of the object to be monitored. Is easy. Moreover, since the optical fiber is laid along the boundary between the monitoring area and the stable ground, even if the monitoring area is wide, it is easy to install the optical fiber sensor over the entire length of the boundary, and the entire monitoring area can be installed. Displacement can be monitored. In addition, as the stable ground on the monitoring standard side,
It is not limited to stable geological formations and stable rocks that are difficult to move and hard to cause landslides, partial collapses, falls, etc., and landslides, partial collapses, falls, etc. occur relatively compared to monitored objects Any stratum or rock that is difficult to do is fine.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the optical fiber sensor according to the present invention will be described below with reference to the drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. In this embodiment, an example of application to a monitoring system for landslides, falling rocks, and the like on a slope 2 of a ground 1 will be described.

In FIG. 1 and FIG. 2, an optical fiber sensor 4 includes an optical fiber 6 (optical cable) attached to a monitoring object 5 (rock or rock which has a possibility of collapse) exposed on the slope 2 with an extra length secured. And the like, the optical fiber 8 (optical cable) on the stable ground 7 (stable rock) side, which is the monitoring reference side with less possibility of landslide, is detachably connected via the optical connectors 9a and 9b, thereby providing stable ground. The optical fiber 6 on the monitoring target 5 side and the optical pulse tester 10 (OTDR) are connected via the optical fiber 8 on the 7 side. The surplus length of the optical fiber 6 on the side of the monitoring target 5 is stored in a sensor unit 11 attached to a rock, which is the monitoring target 5 exposed on the slope 2, and the optical connector 9a at the tip pulled out from the sensor unit 11 is stored. Is detachably connected to the tip of the optical fiber 8 on the stable rock side, which is the stable ground 7. In the sensor unit 11, specifically, for example, the extra length of the optical fiber 6 is wound around a reel 11 a attached to a rock as the monitoring target object 5 and absorbed. Sensor unit 11
Then, the optical fiber 6 is stored with a cover (not shown) while ensuring waterproofness. Also, the optical connectors 9a, 9b
Also, waterproofness is secured by a cover or the like.

The optical fiber 8 on the stable ground 7 side is in the vicinity of the tip (optical connector 9b) connected to the optical fiber 6 on the monitored object 5 side by a connector, and is fixed in the vicinity of the monitored object 5 by fixing means 12 (anchor). It is fixed to the stable rock on the stable ground 7 side. The optical fiber 6 on the side of the monitoring target 5 is retained so as not to be pulled out from the sensor unit 11, and between the sensor unit 11 and the fixing means 12, the optical fibers 6, 8 connected by optical connectors 9a, 9b.
Is kept in a straight line.

In FIG. 1, an optical fiber 8 on the stable ground 7 side is connected to an optical fiber 14 (optical cable) on the optical pulse tester 10 via an optical termination box 13 arranged on the stable ground 7 side. ing. Extra length 8a of this optical fiber 8
Is located inside the optical termination box 13 or with the optical termination box 13
Between the two, the curve is absorbed. In the optical termination box 13, the optical fiber 14 on the optical pulse tester 10 side may be branched and connected to a plurality of optical fibers 8 by an optical splitter via a built-in optical coupler. In the optical termination box 13, a plurality of optical fibers drawn from the optical cable 14 on the optical pulse tester 10 side may be directly connected to a plurality of optical fibers 8 without using an optical coupler.

The optical pulse tester 10 inputs test light to the optical fibers 6 and 8 via the optical fiber 14 and receives and observes the return light to monitor the disconnection position of the optical fiber 6 as needed. In a state where the optical fiber 6 on the monitoring object 5 side and the optical fiber 8 on the stable ground side 7 are connected by the optical connectors 9a and 9b, the disconnection position observed by the optical pulse tester 10 is determined by the optical connector 9a. , 9b extending toward the monitored object 5 side. The return time (elapsed time from the entrance of the test light to the reception of the return light) of the return light of the incident light (such as the backscattered light of Rayleigh scattered light) from the optical pulse tester 10 is determined by the optical fiber sensor 4.
If there is no change from the beginning of installation, the length of the optical line from the optical pulse tester 10 to the end of the optical fiber 6 (the distance from the optical pulse tester 10) does not change, and a break occurs in the optical line. Absent. However, if the return time of the return light observed by the optical pulse tester 10 is shorter than the return time of the return light from the end of the optical fiber 6, the light from the optical pulse tester 10 to the end of the optical fiber 6 There will be a break in the middle of the road. This disconnection can be caused by the disconnection of the optical connectors 9a and 9b due to the movement of the monitoring object 5, the poor connection between the optical fibers in the optical termination box 13, and the optical fibers 8 and 14 caused by an artificial or natural disaster. (For example, cutting of the optical fibers 8 and 14 due to civil engineering work or falling rocks). By observing the return light in the optical pulse tester 10, the presence or absence of a failure in the entire optical line of the optical fiber sensor 4 can be monitored at any time, and the disconnection position of the optical line can be specified from the return time of the return light. Recovery work can be performed quickly.

When the monitored object 5 is displaced downward, the optical fiber 6 on the monitored object 5 side is displaced downward integrally with the monitored object 7, and the two optical fibers 6, 8 are moved by the action of the tensile force. The optical connectors 9a and 9b connecting between them are disconnected. At this time, in the optical pulse tester 10, strong Fresnel reflection is observed, return light from the monitored object side optical fiber 6 is not observed, and the monitored object side optical fiber 6 of the stable ground side optical fiber 8 is not observed. By observing the leading end (the end of the optical fiber 8) connected to the connector as the disconnection position, it can be grasped that the connector connection between the optical fibers 6, 8 has been released. As a result, the displacement (eg, downward inclination) of the monitoring target 5 can be monitored even from a place remote from the site, and the predictive phenomena such as the falling of the rock as the monitoring target 5 and the collapse of the bedrock can be grasped. , Can be used for disaster prevention.

According to the optical fiber sensor 4, since the optical fiber 6 is provided so as to be integrally displaceable with respect to the specific object 5 to be monitored, the risk of dropping the object 5 is particularly high. It is possible to individually monitor high-specific rocks and high-risk rocks. In addition, the monitoring object 5
The displacement of the monitoring target 5 can be monitored from a remote place away from the vehicle, and the safety can be secured as compared with a case where a person approaches the monitoring target 5 and directly inspects and patrols, and the optical pulse tester 10 can be used. Since the monitoring can be performed at any time, there is an advantage that a countermeasure can be taken promptly when the displacement of the monitoring target 5 is confirmed. If a plurality of optical fibers 8 connected to the optical fiber 14 are pulled out by the optical termination box 13, the displacement of a plurality of rocks,
Displacements at a plurality of locations of the monitoring target 5 can be monitored collectively.
In this case, for example, the displacement can be comprehensively monitored over a wide range of the slope 2, and a more detailed and effective disaster prevention plan can be established.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. 3 to 6A and 6B. In the drawings, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be simplified. As shown in FIG. 3 and FIG. 4, the optical fiber sensor 20
The sensor units 21a, 21b, and 21c are provided between (a rock or a rock which has a possibility of collapse) and a stable ground 7 (a stable rock) which is a monitoring reference side with a low possibility of a landslide or the like. These sensor units 21a, 21b, 21
The optical fiber 8 on the stable ground 7 side is drawn into c. In the optical termination box 13, the excess length of the optical fiber 8 is stored in a curved manner. The sensor units 21a and 21b are
It is arranged so as to connect the observation object 5 projecting upward from the slope 2 and the stable ground 7 forming the slope 2 above the projecting position of the observation object 5,
On the other hand, the sensor unit 21c is configured such that the observation object 5 and the stable ground 7 forming the slope 2 below the observation object 5 are formed.
And are arranged so as to be connected to each other.

FIGS. 5A and 5B show the sensor unit 2
It is a figure which shows the internal structure of 1a, 21b, (a) is a top view and (b) is a front sectional view. 5A and 5B, the sensor units 21a and 21b are attached to the monitoring ground 5 side so as to be integrally displaceable with the unit body 22 connected to the stable ground 7, and the unit body A movable member 23 capable of being relatively displaced with respect to 22; a plurality of optical fiber wiring portions 25 to which optical fibers 24 housed with the extra length 24a secured in the sensor units 21a and 21b are wired; Breaking means 26 (optical fiber cutting member) for sequentially moving the plurality of optical fiber wiring sections 25 by being driven in conjunction with the movable member 23 to break the optical fiber 8 in the optical fiber wiring section 25. And

The optical fiber 24 is connected to the sensor unit 21.
a and 21b are stored in a curved manner in a case-like module 27 that is removably stored in the module. More specifically, the optical fiber 24 is connected to the reel 27a in the module 27.
And a curved optical fiber wiring portion 25 formed on a plurality of curved walls 27b protruding from the reel 27a in the module 27 so as to be surplus. The length is absorbed. The curved wall 27b is connected to a wiring area 27 provided in the module 27.
c, a plurality of optical fiber wiring portions 25 on the curved wall 27b are respectively provided with slits 27e formed in a bottom plate 27d of the wiring region 27c.
Is crossing. The slit 27e is also formed continuously on each curved wall 27b.

The wiring area bottom plate 27d is formed by raising the bottom from the bottom plate 27f of the module 27.
The movable member 23 is movable in and out of the movable member storage chamber 27g in the movable member storage chamber 27g formed on the lower side of 7d (the middle lower side in FIG. 5B) (FIGS. 5A and 5B). b) It can be moved to the middle and left and right). In the wiring area 27c, a cutter-like breaking means 26 erected on the movable member 23 projects through a slit 27e. The movement of the movable member 23 is made parallel to the slit 27 e by a guide portion 28 provided on the unit main body 22. When the movable member 23 moves, the breaking means 26 also moves in the slit 27e integrally with the movable member 23 to cross each optical fiber wiring portion 25.

The optical fiber 24 wired between the module bottom plate 27f and the wiring region bottom plate 27d is
By wiring to the inclined portion 27h provided between the module bottom plate 27f and the wiring region bottom plate 27d, the wiring is performed while being bent gently without being sharply bent. On the module bottom plate 27f, the optical fiber 24 is stably pressed by a plurality of tongue pieces 27j projecting from the periphery of the reel 27a or from the module side wall 27i near the reel 27a.

The optical fiber 24 is an optical connector 29 (optical connector adapter) attached to the module 27 side.
Is detachably connected to the optical fiber 8 connected to the optical pulse tester 10 via a connector. Optical fiber 8,
The distal end of the connector 24 is connected to the optical connector 29 by optical connector plugs 29a and 29b which can be attached to and detached from the optical connector 29. The optical fiber 24 is stored in a curved state by using a reel 27a or the like so that a sufficient extra length 24b is secured between the storage portions in the optical fiber wiring sections 25. 25m between storage parts to 25
Is secured. In addition, the portion closest to the optical pulse tester 10 is closer to the monitoring target 5 (FIG. 5A,
(B) The wiring is housed in the optical fiber wiring section 25 (center left),
Hereinafter, the portion on the tip (end) side farther from the optical pulse tester 10 is sequentially replaced with the optical fiber storage portion 25 on the stable ground 7 side.
To house the wiring.

In FIG. 5A, reference numeral 30 denotes a guide piece which is provided so as to protrude toward the inner surface of the unit body 22. The module 27 has an optical fiber storage space 31 into which the optical fiber 8 is drawn in the unit main body 22.
It is inserted and stored in the module storage section 32 in the unit body 22 so as to be attached to the guide piece 30 from the side. The module 27 can be easily taken out by pulling it out of the module storage section 32 (see arrow A). The module 27 is taken out of the unit main body 22, and another module 27 is housed. The connection of the optical fiber 8 to the optical connector 29 of the newly housed module 27 is switched to the module 2
7 and the optical fiber 24 in the sensor unit 2
The module 27 housed in 1a, 21b can be easily replaced. The entrance of the optical fiber 8 into the unit body 22 is waterproofed by a waterproof joint 33, and
The unit body 22 is provided with a detachable lid (not shown), so that the sensor units 21a,
Waterproofness is secured inside 1b.

2 and 4, the unit main body 22 of each sensor unit 21a, 21b, 21c is connected to the stable ground 7 by a connecting member 34, and the movable member 23 is connected to the rock which is the object 5 to be monitored 5 by a connecting member 35. Are linked. In FIG. 4, between the connecting piece 22 a projecting from the unit body 22 and the connecting member 34 and between the movable member 23 and the connecting member 35,
Since the sensor units 21a and 21b are rotatably pivoted via the horizontal pins 4a and 35a, the sensor units 21a and 21b can be attached to the monitoring target 5 and the stable ground 7 by adjusting the connection angle by appropriately bending. It can be performed efficiently. In addition, the inclination angles of the sensor units 21a and 21b are changed by changing the connection angles of the connection portions 34a and 35a following the downward displacement of the rock as the monitoring target object 5, and the movable units from the unit main body 22 are moved. Since the direction in which the member 23 is pulled out matches the direction in which the monitoring target 5 is displaced, the movement of the movable member 23 with respect to the unit body 22 is performed smoothly.

The connecting portions 34a and 35a are not limited to the above-described configuration, but may be any configuration that allows the moving direction of the movable member 23 with respect to the unit body 22 to coincide with the displacement direction of the monitored object 5. For example, various configurations such as a universal joint whose connection angle can be changed by approximately 360 degrees can be adopted. In the case of the universal joint, even if the direction of displacement of the monitored object 5 is not a straight movement down the slope 2 but an oblique movement including a displacement in the horizontal direction, a change in the connection angle corresponding thereto causes , Movable member 2 for unit body 22
3 can be made to coincide with the displacement direction of the monitoring target 5. However, the sensor units 21a, 21b, 2
On the 1c side, it is necessary to prevent the vibration applied to the built-in optical fiber 24 and the movement of the optical fiber 8 pulled in from the outside in order to maintain the observation reliability of the return light. Try to keep it down.

The monitored object 5 is displaced downward, and the stable ground 7
When the movable member 23 moves away from the sensor units 21a and 21b, the movable member 23 is displaced integrally with the monitoring target 5 and is pulled out from the sensor units 21a and 21b (FIG. 5).
(A), (b) moving to the left in the middle), initially, the wiring region 27
The breaking means 26 located closest to the stable ground 7 of c moves integrally with the movable member 23 to form a slit 27e.
Is moved to the monitoring object 5 side so as to sequentially cross the plurality of optical fiber wiring sections 25 along, and the optical fibers 24 wired to each optical fiber wiring section 25 are broken (cut). The optical fibers 24 accommodated in the plurality of optical fiber wiring sections 25 are sequentially shifted toward the optical pulse tester 10 from the optical fiber wiring section 25 on the stable ground 7 side to the optical fiber wiring section 25 on the monitored object 5 side. So, initially,
The breaking means 26 located closest to the stable ground 7 in the wiring area 27c moves toward the object 5 to be monitored, so that the optical fiber 24 is sequentially subjected to the optical pulse test from a position near the terminal farthest from the optical pulse tester 10. It breaks toward the part near the container 10. Here, since the return light (backscattered light of Rayleigh scattered light, etc.) observed by the optical pulse tester 10 is not observed from the order farthest from the optical pulse tester 10, the change in the disconnection position (fracture) is determined. The displacement of the monitored object can be grasped even from a place remote from the site.

Optical fiber 24 by optical pulse tester 10
The disconnection position is grasped by measuring the return time of the return light, similarly to the optical fiber sensor 4 of the first embodiment. At the beginning of the installation of the optical fiber sensor 20, the distal end (end) of the optical fiber 24 farthest from the optical pulse tester 10 is detected as a disconnection position. 26 is the optical fiber 2
When the optical fiber 24 is broken, the terminal position of the optical fiber 24 grasped by the optical pulse tester 10 changes (the observed terminal position becomes closer to the optical pulse tester 10), and the monitoring target 5
Can be grasped. The breaking of the optical fiber 24 by the breaking means 26 is performed in order from a location far from the optical pulse tester 10 of the optical fiber 24, and as the displacement amount of the monitoring target 5 increases, the breaking location of the optical fiber 24 is subjected to an optical pulse test. The optical pulse tester 1
By observing the change in the end position of the optical fiber 24 at 0, the displacement amount of the monitoring target 5 can be grasped. Further, in the case where the movement of the monitoring target 5 is continued and the breakage of the optical fiber 24 by the breaker 26 progresses every moment, the light observed by the optical pulse tester 10 with the elapse of time. It is also possible to calculate the moving speed and the like of the monitoring target 5 from the change in the broken position of the fiber 24. Here, the optical fiber 24 has a surplus length 24 of several meters (preferably 2 m or more) between portions housed in the adjacent optical fiber wiring section 25.
By securing b, the difference in the return time of the return light from the optical fiber 24 of each optical fiber wiring section 25 to the optical pulse tester 10 can be ensured. It can be grasped more clearly.

The sensor unit 21c disposed between the rock 5 and the stable ground 7 below the slope 2 of the rock 5 has a unit body 22 connected to the stable ground 7 side.
The movable member 23 is connected to the rock 5 above. FIG.
As shown in (a) and (b), this sensor unit 21
The configuration of c is almost the same as the sensor units 21a and 21b, and the difference from the sensor units 21a and 21b is that
The wiring method of the optical fiber 24 inside, the initial setting position of the movable member 23, the breaking means 26 attached to the movable member 23
a and the like. 6A and 6B, in the sensor unit 21c, initially, the sensor unit 21c
The movable member 23 which is set in a state of protruding from the sensor unit 21 c is pushed into the sensor unit 21 c by the displacement of the rock which is the monitoring target object 5 down the slope 2, and the guide portion 28 is initially provided.
While the breaking means 26a on the side moves toward the optical fiber storage space 31 in the slit 27e, the optical fiber 24 wired to each optical fiber wiring section 25 is connected to the optical pulse tester 10 by the optical pulse tester 10.
Cut from the point farthest away and break it. The wiring of the optical fiber 24 to the plurality of optical fiber wiring sections 25 is performed by arranging a portion far from the optical pulse tester 10 to the optical fiber wiring section 25 closest to the monitoring target 5, and hereinafter, farther from the monitoring target 5. A portion close to the optical pulse tester 10 is sequentially wired to the optical fiber wiring portion 25. Therefore, if the amount of downward displacement of the monitored object 5 is small, the optical fiber 24 wired to the optical fiber wiring section 25 on the monitored object 5 side is cut by the breaking means 26a, and the optical pulse tester of the optical fiber 24 is cut. If only the portion far from 10 is broken and the amount of downward displacement of the monitored object 5 is large, the optical fiber 24 wired to the optical fiber wiring section 25 on the more stable ground 7 side is also broken. Thus, the displacement of the monitoring target 5 can be grasped by changing the end position of the optical fiber 24 observed by the optical pulse tester 10.

According to the optical fiber sensor 20, the position of the monitoring target 5 is grasped in units of the arrangement pitch of the optical fiber wiring portions 25 of the sensor units 21a, 21b, 21c. Is smaller, the displacement of the monitoring target 5 can be grasped in more detail. When the change of the break point of the optical fiber 24 caused by the breaking means 26, 26a is grasped with time, the displacement speed of the monitored object 5 and the state of the displacement (for example, the displacement speed is initially high, but after a certain time elapses, the displacement becomes almost zero) Etc.) can be grasped. Further, in the optical fiber sensor 20, similarly to the optical fiber sensor 4 of the first embodiment, for example, the displacement of the monitoring target 5 such as a rock having a danger of falling can be directly monitored. It can be safely performed from a place away from the object 5. Further, the monitoring target 5 can be constantly monitored, and if a predictive phenomenon of the occurrence of a disaster is observed, a disaster prevention plan can be quickly established. Further, it is also possible to pull out a plurality of optical fibers 8 from the optical termination box 13 and simultaneously monitor a plurality of monitored objects 5 and a plurality of locations of the same monitored object 5 at the same time. Further, in the optical fiber sensor 20, since the module 27 is replaceable, the movable member 23 operates due to an erroneous operation or the like due to some cause such as a collision of a falling rock irrelevant to the drop of the monitored object 5, and Even if the optical fiber 24 of the fiber wiring section 25 is cut, the module 27
Can be easily restored by replacing the. The used sensor units 21a, 21b, 21c can also be reused by replacing the module 27, so that the cost can be reduced.

The sensor unit of the optical fiber sensor 20 and the module and the like which are removably housed in the sensor unit are not limited to the above-described configuration, and it goes without saying that the design can be changed as appropriate. . For example,
As the sensor unit, various configurations such as a configuration in which an optical fiber wiring section is formed by a curved wall provided directly inside the unit main body without housing the module can be adopted. The module is not limited to the configuration having the grooved optical fiber wiring section 25 formed in the curved wall 27b, but may be a configuration in which a gap between the curved walls is an optical fiber wiring section. The breaking means is not limited to a configuration in which the optical fiber is cut by a cutter-shaped member, and various configurations such as a configuration in which the optical fiber is bent and broken can be employed.

Third Embodiment Hereinafter, a third embodiment of the present invention will be described with reference to FIGS. In FIG.
Reference numeral 51 denotes a stable ground (stable rock), which is a monitoring reference side, and 5
Reference numeral 2 denotes an unstable stratum (surface soil layer having a high possibility of landslide or the like) as an object to be monitored, and 53 denotes an optical fiber sensor. The optical cable 55 constituting the optical fiber sensor 53 includes a stable ground exposed portion 54, which is an upper exposed portion of the stable ground 51, and a monitoring region extending along the ground slope below the stable ground exposed portion 54. It is arranged to extend along a substantially horizontally extending boundary with the unstable formation 52 to be formed. In the longitudinal direction of the optical cable 55, a plurality of sensing portions 56a,
56b and 56c are provided continuously. In FIG. 7, the sensing portions 56a, 56b, and 56c are arranged continuously without any gap by being in contact with each other along the longitudinal direction of the optical cable 55, but they may be arranged only at necessary places. is there. Also, the sensing units 56a, 56b,
In 56c, the connection target of the connecting linear body 63a is different.
That is, the connecting linear body 63a of the sensing unit 56a is connected to the anchor driven into the unstable formation 52, and the connecting linear body 63a of the sensing unit 56b is connected to the detection movable body 60 at the tip thereof by the soil at the bottom of the valley 65. The connecting linear member 6 of the sensing portion 56c is made to be able to move integrally with the sensing portion 56c.
3a is connected to the rock 52a on the unstable formation 52. An optical pulse tester 5 capable of observing Brillouin scattered light of light incident on the optical fiber is provided on an optical fiber (mainly, an optical fiber core) housed in the optical cable 55.
7 (BOTDR) is connected.
From which test light can be incident.

FIGS. 8 and 9 show the sensing section 56b. FIG. 8 is a plan view and FIG. 9 is a side sectional view. As shown in FIGS. 8 and 9, the sensing unit 56b
The fixed frame 58 fixed to the stable ground exposed portion 54 near the boundary between the stable ground exposed portion 54 and the unstable formation 52
And a pair of optical fiber retaining members 59, which are optical fiber gripping parts for gripping and fixing two locations separated from each other in the longitudinal direction of the optical cable 55 with a certain separation distance, and connected to the optical cable 55 between the optical fiber retaining members 59. A displacement amplifying unit 64, a connecting linear body 63a connected to the displacement amplifying unit 64, and a cable duct 61 that covers the optical cable 55 and the optical fiber retaining member 59 from outside. The cable duct 61 is fixed to the fixed frame 58 by a fixed component 61a, and is provided so as to cover the entire length of the optical cable 55. A fixed separation distance is secured by fixing the pair of optical fiber retaining members 59 to the fixed frame 58. The fixed frame 58
Is installed as needed.

An end of the connecting linear body 63a facing upward toward the optical cable 55 is wound around a pressure receiving pulley 64a of the displacement amplifying unit 64. On the other hand, a connecting linear body 63b (wire or the like) is attached as a connecting tool via a connecting fitting 62 at a central portion in the longitudinal direction of the optical cable 55 between the pair of optical fiber retaining members 59. The lower end of the connecting linear body 63b pulled down toward the unstable formation 52 is connected to the amplifying pulley 64 of the displacement amplifying unit 64.
It is wound around b.

As shown in FIGS. 8 and 10, the displacement amount amplifying section 64 houses the pressure receiving pulley 64a and the amplifying pulley 64b in a housing 64c fixed to a fixed frame 58 by a fixed component (not shown). It has a structured structure. The pressure receiving pulley 64a and the amplification pulley 64b are integrally rotatably connected by the same shaft 64d supported at a fixed position in the housing 64c. However, the amplification pulley 64
b is larger in diameter than the pressure receiving pulley 64a (for example, 2 to 2).
Therefore, when these pulleys 64a and 64b rotate, the peripheral speed of the outer periphery of the amplification pulley 64b around which the connecting linear body 63b is wound is higher than the peripheral speed of the outer periphery of the pressure receiving pulley 64a. The pressure receiving pulley 64a and the amplification pulley 64b are used to connect the connecting linear bodies 63a, 6
The winding direction of 3b is reversed. 8 and 10
Reference numerals 64e and 64f denote connection linear bodies 63a and 63, respectively.
It is a guide member for guiding b.

The connecting linear body 63b is inserted through a wire hole (not shown) opened in the cable duct 61.
The connecting linear bodies 63a and 63b are connected to the optical cable 55.
Is tensioned so as not to give an elongational strain. The tensioned state of the connecting linear bodies 63a and 63b can be easily obtained by adjusting the length of the connection linear bodies 63a and 63b wound around the pulleys 64a and 64b. The optical cable 55 between the pair of optical fiber retaining members 59 is also stretched with a tension in a range that does not cause slackness and does not give an elongational strain that affects the detection of displacement of the detection movable body 60. Is more preferable in terms of improvement in detection accuracy.

The detection movable body 60 connected to the lower end of the connecting linear body 63a has a plate shape as a whole, and a large number of fixed projections 60a projecting from the lower surface are cut into the earth and sand of the unstable formation 52. , And is displaced integrally with the unstable formation 52. In FIG. 7, the detection movable body 60
Is installed in a valley 65 formed in the unstable formation 52 due to the outflow of the earth and sand, and is displaced integrally with the flow of the earth and sand in the valley 65. The installation location of the detection movable body 60 is not limited to the valley 65, and may be on the unstable formation 52 other than the valley 65. Also, the detection movable body 60
Various configurations can be adopted as long as the configuration can be integrally displaced with the earth and sand of the unstable formation 60. For example, a configuration buried in the earth and sand can also be adopted.

As shown in FIG. 7, the connecting linear members 63a,
Detection movable body 6 connected to optical cable 55 via 63b
The number of 0 is not limited to one, and may be plural. In each of the sensing units 56a, 56b, and 56c, the adjustment of the length of the connecting linear bodies 63a and 63b and the attachment position of the detection movable body 60 to the connecting linear bodies 63a, etc., can be performed. Connection to the target monitoring target such as 52a can be easily performed. A sensing unit 56a,
The connection of the lower end of the connecting linear body 63a of 56c to the unstable formation 52 or the rock 52a is made by a fixed part such as an anchor, but is not limited thereto. The use of 60 and the rock 52a may be connected by binding or the like.

It is known that the unstable stratum 52 causes a small downward displacement before the downward landslide occurs, and this displacement causes a gap between the stable ground exposed portion 54 and the unstable stratum 52. Also, a crack 66 in the middle of the slope of the unstable stratum 52
Occurs. For example, in the sensing unit 56a, when a minute displacement occurs below the unstable formation 52, the connecting linear body 63a connected to the unstable formation 52 is pulled downward. On the other hand, the optical cable 55 disposed on the stable ground exposed portion 54 above the unstable formation 52 does not displace. Accordingly, the tensile force acting from the connecting linear body 63a causes the optical cable 55 between the pair of optical fiber retaining members 59 to exert a tensile force via the connecting linear bodies 63a and 63b and the displacement amplifying unit 64. As a result, stretching strain is applied to the optical cable 55. In the other sensing units 56b and 56c, similarly, the monitoring target 5
The downward displacement of 2, 52a acts as a pulling force from the connecting linear body 64, and acts as a pair of optical fiber retaining members 59.
The optical cable 55 is stretched and distorted. As shown in FIG. 12, the optical cable 55 is made of PVC (polyvinyl chloride).
A single optical fiber core 55 is provided in a resin jacket 55a.
b, and the jacket 55a and the optical fiber core 55
This structure is such that a tensile strength member 55c (Kevlar) is housed between the two members. Here, the optical cable 55 does not have a tension member (formed of a metal wire or the like) which is a general optical cable for outdoor laying, and relies only on the fibrous strength members 55c for tension. Therefore, compared with a general optical cable for outdoor laying, the extension strain is easily applied. As the jacket 55b, one having excellent waterproofness and durability is applied. In addition, the optical cable 55 is not limited to the above-described configuration, and various configurations can be adopted as long as the configuration is easy to apply elongation strain.

Here, the optical fiber of the optical cable 55 is
When Brillouin scattered light (backscattered light of Brillouin scattered light) is detected by entering test light from the optical pulse tester 57,
The extension strain of the optical cable 55 is detected, whereby the displacement of the unstable stratum 52 itself can be detected, and the danger of collapse of the unstable stratum 52 and landslide can be detected. It should be noted that, based on the elapsed time from the entrance of the test light to the optical fiber of the optical cable 55 to the reception of the Brillouin scattered light, the location where the extension distortion of the optical cable 55 has occurred is detected by the sensing units 56a,
Since it can be specified in units of 6b and 56c, it is possible to specify a portion of the unstable formation 52 where the distortion has occurred over the entire monitoring area extending downward from the stable ground exposed portion 54.

For example, in the sensing section 56a, if the installation position of the connecting linear body 63a with respect to the unstable formation 52 is above the crack 66, there is a possibility that partial displacement of the unstable formation 52 may not be detected. Occurs. In order to reliably detect the displacement of the unstable formation 52 over the entire monitoring area, it is more preferable to connect as many sensing units 56a, 56b, 56c as possible to various parts of the unstable formation 52.

The displacement amplifying section 64 includes the connecting linear member 6.
3a by amplifying the displacement amount of the optical fiber retaining member 59.
Because it is transmitted to the optical cable 55 between
The strain measurement accuracy of the optical fiber sensor 53 can be improved. Specifically, when the connecting linear body 63a is displaced in a direction away from the optical cable 55, the pressure receiving pulley 64 is
The unwinding excess length of the connecting linear body 63a secured at a is unwound and the pressure receiving pulley 64a rotates, and the amplification pulley 64b is integrally driven and rotated with the rotation of the pressure receiving pulley 64a. Then, the connecting linear body 63b is wound up, the optical cable 55 is pulled to the side, and an elongation strain is applied. However, since the peripheral speed of the outer peripheral portion of the amplification pulley 64b is higher than that of the pressure receiving pulley 64a, compared to the unwinding amount of the connection linear body 63a from the pressure receiving pulley 64a, the connection linear body 63b by the amplification pulley 64b is formed. The winding amount is larger, and as a result, the displacement of the optical cable 55 due to the tensile force from the connecting linear body 63b is larger than the displacement of the connecting linear body 63a. Thereby, the monitoring objects 52, 5
The displacement amount 2a is amplified by the displacement amount amplifying unit 64 and transmitted to the optical cable 55, and functions more effectively by forming an elongation strain.

For example, the diameter of the outer peripheral portion around which the connecting linear body 63b of the amplification pulley 64b is wound (referred to as the pulley ratio) with respect to the outer peripheral portion around which the connecting linear body 63a of the pressure receiving pulley 64a is wound. If it is twice, at the center in the longitudinal direction of the optical cable 55 between the optical fiber retaining members 59,
A displacement twice as large as the displacement of the monitored objects 52 and 52a is given. Therefore, the pulleys 64a, 64b
If the pulley ratio between them is sufficiently large, the monitoring objects 52, 5
Even if the displacement amount of 2a is minute, the optical fiber retaining member 5
Sufficient elongation strain can be given to the optical cable 55 between the nine, and as a result, the strain measurement accuracy can be improved. Pulley 6
The distortion measurement accuracy can be improved only by adjusting the outer peripheral diameter around which the connecting linear bodies 63a, 63b of 4a, 64b are wound and changing the pulley ratio. Theoretically, if the pulley ratio is n times, the strain measurement accuracy (error) conventionally ± 0.02% can be reduced to 1 / n (for example, if the pulley ratio is twice, the strain measurement accuracy can be reduced). Accuracy (error) is 1/2).

As described above, according to the optical fiber sensor 53 of the present invention, excellent strain measurement accuracy can be obtained.
0.001% (error), which is a general reading resolution of the optical pulse tester 57, can be fully utilized, and a minute displacement of the monitored objects 52, 52a can be detected. 0.0 which is the reading resolution of the optical pulse tester 57
01% (error) is 0.01% in terms of elongation strain of the optical cable 55 secured 2 m between the optical fiber retaining members 59.
mm, and this value corresponds to a displacement amount of 4.47 mm of the moving unit directly connected to the optical cable by the wire without passing through the displacement amount amplifying unit 64. In the optical fiber sensor 53 according to the present invention, the displacement amount of the monitored objects 52 and 52a is amplified by the displacement amount amplifying section 64 and acts on the optical cable 55, so that the displacement amount of the monitored objects 52 and 52a is several mm. However, an elongation strain exceeding the reading resolution of the optical pulse tester 57 can be applied to the optical cable 55, and a minute displacement of the monitored objects 52, 52a can be accurately detected.

By the way, even if the optical fiber in the optical cable 55 has no distortion, the frequency shift of the Brillouin scattered light with respect to the incident light has a temperature dependency of about 1 MHz / ° C. If a change occurs, it is necessary to correct the measurement data. The optical cable 55 may be heated to a temperature of several tens of degrees Celsius or higher than room temperature due to the situation and environment of the installation place, for example, by sunshine or geothermal heat in a volcanic zone. To do so, temperature correction of the measured data of Brillouin scattered light is indispensable. In consideration of this, for example, an optical fiber for temperature correction is housed in the optical cable 55 separately from the optical fiber to which elongation strain is applied, and Raman scattered light of the light incident on the optical fiber for temperature correction is stored. A method of correcting measurement data of Brillouin scattered light from data obtained by receiving and observing the backscattered light by the optical pulse tester is adopted. As an optical fiber for temperature correction, an SM type optical fiber is generally used. The backscattered light of the Raman scattered light observed by the incidence of light on the optical fiber for temperature correction is:
Since the intensity changes depending on the temperature of the temperature correcting optical fiber, the intensity of the backscattered light of the observed Raman scattered light is
It will differ depending on the partial temperature difference of the optical fiber. Then, the intensity ratio between the scattered light intensities of the observed waveforms (OTDR waveforms of Stokes light and anti-Stokes light) is obtained, and the temperature is obtained from a predetermined theoretical formula. In addition, since the optical fiber for temperature correction needs to maintain an unstrained state, for example, the extra length of the optical fiber for temperature correction is placed in a termination box installed at an appropriate place in the middle of the optical cable 55. When the optical cable 55 is stretched and strained, the optical fiber for detecting Brillouin scattered light is stretched while the temperature compensating optical fiber is drawn into the optical cable 55 by the extra length. A configuration or the like in which the distortion-free state is maintained can be adopted.

Therefore, according to the optical fiber sensor 53, by monitoring the Brillouin scattered light, it is possible to detect and monitor the minute displacement of the unstable formation 52 and the rock 52a. And rock 52a
The danger of falling can be detected at an early stage, which can be useful for evacuation of nearby residents. In addition, monitoring can be performed from a remote place away from the monitoring area, and safety of the monitoring operation can be ensured.

In this optical fiber sensor 53, an optical cable 55 extends and extends along a boundary between the stable ground exposed portion 54 and the unstable ground layer 52, and a plurality of sensing portions 56a, 56b extend along the optical cable 55. , 56c can be monitored simultaneously, so that multiple locations can be monitored at the same time, and there is no need to move between multiple inspection points or monitoring points, etc., and the signs of collapse of the unstable stratum 52 and the fall of the rock 52a are detected. If so, measures can be taken quickly. Moreover, from the observation data obtained by the optical pulse tester 57,
Since the presence or absence of displacement at a plurality of locations in a wide monitoring area can be monitored simultaneously, the behavior of the entire monitoring area can be comprehensively grasped, and the concrete collapse range of the unstable stratum 52 can be grasped, and effective measures can be taken. Can be set up.

The optical fiber sensor 53 is an IT fiber sensor.
Compared to a case where many expensive facilities such as V are installed, the cost can be significantly reduced, and a wide range of monitoring can be realized at low cost. In addition, since the optical fiber sensor 53 has no electrical operation parts other than the optical pulse tester 57 and does not have to be affected by an induced current due to lightning strike or the like, the optical pulse tester 57 and its attached instruments, etc. However, if protection is provided so as not to be affected by induced current, monitoring performance will not be impaired even if it is installed in a mountain area where lightning is likely to occur, and the degree of freedom of installation location will be greatly improved. . Optical pulse tester 57
May be connected to the optical cable 55 of the optical fiber sensor 53 installed in another monitoring area adjacent to each other, whereby, for example, it is possible to grasp the deformation behavior of the entire ground and the like, and Can be monitored.

When test light is incident on the optical cable 55 from the optical pulse tester 57, Fresnel reflected light is emitted from portions other than the end of the optical cable 55 separated from the optical pulse tester 57 and a connector connection part in the optical line. If detected, the breakage of the optical cable 55 is detected. Since the position of the break point of the optical cable 55 can be roughly specified by the elapsed time from the incidence of the test light to the reception of the Fresnel reflected light,
For example, an optical cable 55 that has been accidentally cut by construction or the like.
Can be easily found, and the repair work time and the like can be reduced. As described above, according to the optical fiber sensor 53, a failure relating to the optical transmission system can be monitored by performing a test using the optical pulse tester 57 as needed.

The sensing units 56a, 56b, 56c
By a simple measure such as covering the entirety including the connecting linear bodies 63a and 63b and the detection movable body 60 with a cover or the like, a person or an animal accidentally contacts the connecting linear bodies 63a and 63b,
Malfunction can be prevented. Also, the displacement amount amplifying unit 64
Has a structure housed in the housing 64c, so that it can be firmly configured. When a person or a tool comes into contact with the connecting linear bodies 63a and 63b due to construction or the like,
When stretch strain is applied to the optical cable 55 by mistake,
Eliminating the extension strain of the optical cable 55 between the pair of optical fiber retaining members 59 allows easy recovery. Also in this case, the malfunctioning part can be easily specified from the elapsed time from the entrance of the test light to the reception of the Brillouin scattered light.

(Fourth Embodiment) Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG. In the figure, the same components as those in FIG. 7 are denoted by the same reference numerals, and the description thereof will be simplified.

In FIG. 11, in the optical fiber sensor 70 of the present embodiment, the unstable formation layer 52 as a monitoring area and the stable ground exposed portion 54 existing above the unstable formation layer 52 are provided.
The optical cable 55 connected to the optical pulse tester 57 is extended and arranged on the unstable formation 52 along the boundary of the optical pulse tester 57, and the sensing portions 71a, 71b, 71c are continuously provided.
The optical cable 55 is an optical fiber retaining member 72 (wire)
As a result, it is retained on the stable ground exposed portion 54 side.

In the sensing part 71a, a pair of connecting parts 72 connecting the optical fiber retaining member 72 to the optical cable 55 are provided.
A draw-out portion 73 from which the optical cable 55 is drawn out from between a is formed, and a turn-up portion 74 that is bent so that the optical cable 55 is turned up at the end of the draw-out portion 73 is connected to the unstable formation 52 so as to be integrally displaceable. . The connection of the folded portion 74 formed on the optical cable 55 to the unstable formation 52 is shown in FIG.
In the above, the anchor 75 driven into the unstable formation 52
But is not limited to this,
For example, the detection may be performed by coupling to the detection movable body 60 which is made to be able to be integrally displaced by digging into the soil of the unstable formation 52. The draw-out portion 73 is provided with the optical fiber holding members 72 on both sides thereof.
From the connecting portion 72a between the optical fiber 55 and the unstable formation 5
It is preferable that the unstable formation 52 is linearly arranged along the assumed displacement direction until the connection position (anchor 75) to the second formation 2, so that the unstable formation 52 is displaced downward. In addition, the optical cable 55 of the drawer 73 can be efficiently stretched and strained. It is more preferable that the optical cables 55 on both sides from the folded portion 74 extend in parallel with each other along the assumed displacement direction of the unstable formation 52. Note that the connection target of the drawer 73 is other than the anchor 75 driven into the unstable formation 52, for example, the unstable formation 52.
The rock 52a exposed from the surface may be used. In any case, when the optical cable 55 of the drawer 73 (specifically, the optical cable 55 from the folded portion 74 to the two connecting portions 72a) is displaced downward from the unstable formation 52, the displacement amount corresponds to this displacement amount. Is applied.

In the sensing section 71b, a pair of connecting sections 7
The detection movable body 60 connected to the folded portion 76a at the center of the drawing portion 76 from which the optical cable 55 is drawn out from between the spaces 2a is cut into the earth and sand of the unstable stratum 52 so as to be integrally displaceable. In FIG. 11, the detection movable body 60 is installed in a valley 65 extending in the up-down direction of the unstable formation 52.
The detection movable body 60 has a large number of fixed protrusions 60a on the bottom side.
Into the unstable stratum 52, the unstable stratum 5
Since it is installed so as to be integrally displaceable with the earth and sand of No. 2, it is particularly suitable for installation in the valley 65 where the flow of earth and sand is large. The optical cable 55 forming the lead-out portion 76 is drawn toward the bottom of the valley portion 65, and is turned over to the folded portion 76 connected to the detection movable body 60.
a and between the connecting portions 72a on both sides thereof. In FIG. 11, the drawer 76 has a shape in which the central portion of the optical cable 55 between the connecting portions 72a on both sides thereof is pulled down toward the bottom of the valley portion 65 and bent in a “C” shape. Instead, for example, the folded portion 76a may be pulled down to the downstream side of the valley portion 65 from the connecting portion 72a, and the drawn-out portion 76 may extend substantially parallel to the direction of displacement of the earth and sand in the valley portion 65.

In the sensing section 71c, the drawing section 77 connected to the rock 52a is formed by the optical cable 55 drawn from between a pair of anchors 78 driven into the unstable formation 52. Folding part 7 at the tip of this drawer 77
9 is connected to the rock 52a by, for example, connection to the anchor 80 driven into the rock 52a or binding to the rock 52a.

The sensing units 71a, 71b, 7
The drawers 73, 76, and 77 of 1c are not limited to the above-described configuration. For example, a plurality of connection jigs (anchor, detection movable body 60, and the like) that can be displaced integrally with the monitoring target 52, 52a.
It is also possible to adopt a configuration in which an optical cable 55 drawn out from between the connecting portions with the optical fiber retaining member is laid between them. In this case, it is more preferable that the optical cable 55 extends between the connection portion with the optical fiber retaining member and the connection jig in parallel with the displacement direction of the monitoring objects 52 and 52a. Further, it is also possible to lay the optical cable 55 in a zigzag manner between a plurality of connecting portions to which the optical fiber retaining members are connected and the plurality of connecting jigs. Also in this case, it is more preferable that the optical cable 55 has a large number of portions extending in parallel with the displacement direction of the monitored objects 52 and 52a.

The unstable stratum 52 which is a predictive phenomenon such as a landslide.
When a small displacement occurs downward of the sensing unit 71a,
In this case, the anchor 75 is displaced downward integrally with the unstable formation 52, and an elongation strain corresponding to the displacement of the unstable formation 52 is applied to the optical cable lead-out portion 73 connected to the anchor 75. The optical pulse tester 57 observes the backscattered light of the Brillouin scattered light generated in the optical cable lead-out portion 73, thereby detecting the extension strain of the optical cable lead-out portion 73. Here, since the elongation strain applied to the optical cable lead-out portion 73 corresponds to the amount of displacement of the unstable formation 52, the unstable formation is smaller than the sensing portion 56 of the optical fiber sensor 53 shown in the third embodiment. The extension strain of the optical cable 55 given by the displacement amount of the optical cable 52 is remarkably large, so that the sensing unit 71a can secure sufficient detection accuracy (sensitivity) without providing a separate mechanism for amplifying the displacement amount. Even a minute displacement of the stable formation 52 can be detected. However, it goes without saying that a mechanism for amplifying the amount of displacement can be interposed between the folded portion 74 and the anchor 75 to improve the detection accuracy. Further, since the sensing unit 71a has a simple configuration, it is easy to assemble the unstable formation 52 at a target position.
There is an advantage that the workability is excellent because the amount of materials required for assembly is not required to be carried into the site.

In the sensing section 71b, the unstable formation 52
The longitudinal center of the optical cable 55 between the pair of connecting portions 72a to which the optical fiber retaining member 72 is connected is moved downward by the detection movable body 60 integrally moved with the earth and sand of the valley portion 65 along the ground slope. To stretch the optical cable 55 between the connecting portions 72a. The optical pulse tester 57 observes the backscattered light of the Brillouin scattered light generated in the extraction unit 76 of the sensing unit 71b, so that the elongation distortion of the optical cable 55 is detected. Detection movable body 60
More preferably, a mechanism for amplifying the amount of displacement is interposed between the optical cable 55 and the optical cable 55.

The sensing unit 71c directly detects the displacement of the rock 52a. Rock 5 on the unstable formation 52
When a small downward displacement, which is a sign of the fall of 2a, occurs, an elongational strain corresponding to the amount of displacement of the rock 52a is applied to the optical cable lead-out portion 77. Therefore, the test light is incident on the optical cable 55 from the optical pulse tester 56, and the presence or absence of the backscattered light of the Brillouin scattered light generated in the optical cable lead-out portion 77 can be monitored to monitor the displacement of the rock 52a.

The rocks 52a on the unstable formation 52
There is a danger of being displaced or dropped separately from the unstable formation 52 due to reasons such as unstable posture on the weak unstable formation 52. Therefore, even if the optical cable lead-out portion 77 connected to the rock 52a is retained in the unstable formation 52, the monitoring effect is sufficiently exhibited. When the rock 52a is also displaced integrally with the downward displacement of the unstable stratum 52, no abnormality is detected by the sensing 71c. In this case, the sensing unit 71a adjacent to the sensing unit 71c, The displacement of the unstable stratum 52 is detected by 71b, or the optical cable 55 is stretched and distorted by the sensing part 71c between the anchor 78 for retaining the optical cable 55 and the connecting part 72a of the adjacent sensing part 71b. Is detected and unstable formation 5
2 itself is grasped. Also, this sensing unit 7
In 1c, the plurality of rocks 52 on the unstable stratum 52 are routed by routing the optical cable 55 on the unstable stratum 52.
Since the optical cable lead-out portion 77 can be easily connected to a, a plurality of objects to be monitored (such as the rock 52a) scattered in the monitoring area.
Can be efficiently monitored. For example, a plurality of sensing units 71c can be provided between the sensing units 71a and 71b.

According to the optical fiber sensor 70, the lead portions 73, 76, 77 are formed at appropriate positions of the optical cable 55 laid along the boundary between the unstable formation layer 52 and the stable ground exposed portion 54, which is the monitoring region. To be monitored 52, 52a
It is easy to assemble simply by connecting it to the machine, and excellent workability can be obtained. In addition, unstable ground 52 and stable ground 5
For example, there is a curved portion or a bent portion at the boundary between
Even if there is a depression such as a valley 65 in the middle, the optical cable 55 may be curved along the boundary or laid around the depression, and furthermore, the lead portions 73 and 76 formed on the optical cable 55. , 77, the connection between the optical cable 55 and the objects to be monitored 52, 52a can be freely performed. Therefore, the optical fiber sensor 70 can be easily used anywhere regardless of the topography of the monitoring area. There is an advantage that can be constructed. From the return time of the Brillouin scattered light in the optical pulse tester 57, the displacement of the unstable formation 52,
That the rock 52a or the like having caused the displacement can be specified; and
By observing the backscattered light such as Fresnel reflected light and the like, it is possible to easily ascertain the failure point of the optical fiber line system of the optical fiber sensor 70, and the effect is the same as that of the optical fiber sensor of the third embodiment. Also, in the optical fiber sensor 70, the observation data of the Brillouin scattered light is converted into the temperature by using the observation data of the Raman scattered light of the optical fiber for temperature correction incorporated in the optical fiber optical cable 55 so as to maintain the distortion-free state. It is more preferable to correct.

The present invention is not limited to the above embodiment,
For example, it goes without saying that the structure and the like of the optical fiber sensor unit can be changed as appropriate. In addition, as an optical fiber extending along the boundary between the monitoring area and the stable ground,
The invention is not limited to the optical cable, and for example, an optical cord or the like can be adopted. Even in the case of an optical cable, it is also possible to employ an optical cord or the like which is easily deformed only in a portion where an elongation strain is applied in the optical fiber sensor section. In each of the above embodiments, an example of application to a monitoring system for landslides, rockfalls, and the like on a ground slope has been described.However, the present invention is not limited to this, and is used for monitoring displacement of soft ground with respect to stable ground on flat ground, and the like. It is also possible to apply. In the third and fourth embodiments, for example, it is possible to construct an optical fiber sensor by laying an optical cable so as to surround the monitoring area. The optical fiber sensor according to the present invention includes, for example, a determination unit that determines the presence or absence of a displacement of a monitoring target from observation data in an optical pulse tester, and an alarm unit that issues an alarm when the displacement of the monitoring target is detected. Equipped configurations can also be employed.

[0064]

According to the optical fiber sensor of the first aspect of the present invention, the light which is displaced integrally with the monitored object due to the displacement of the monitored object such as an unstable stratum or a rock which may be displaced with respect to the stable ground. By observing the disconnection of the connector between the fiber and the optical fiber on the stable ground side using an optical pulse tester, it is possible to determine the presence or absence of displacement of the monitored object from a safe place away from the monitored object. Can be monitored. This monitoring can always be performed by an optical pulse tester, and furthermore, since the displacement of the monitoring target can be grasped in real time, there is an excellent effect that it can be used for disaster prevention measures against landslides and falling rocks.

According to the optical fiber sensor of the second aspect, the object to be monitored, such as an unstable stratum or a rock that may be displaced, is attached to the object to be monitored so as to be integrally displaceable by the displacement of the object with respect to the stable ground. Movable member is displaced,
As the breaking means displaced in conjunction with this moves the plurality of optical fiber wiring sections sequentially, it breaks the optical fibers wired in each optical fiber wiring section in order from a location far from the optical pulse tester. From the change in the optical fiber break position observed by the optical pulse tester, the amount of displacement of the monitoring target can be easily grasped, and the danger of disasters such as landslides and falling rocks can be grasped in more detail. It has an excellent effect of being able to make more detailed disaster prevention measures.

According to the optical fiber sensor of the third aspect, an elongation strain is applied to the optical fiber extending along the boundary between the monitoring area on the ground slope and the stable ground existing above the monitoring area. By observing the fact by observing the Brillouin scattered light with the optical pulse tester, it is possible to monitor the displacement of the monitoring target.
The connection can be easily performed by connecting the monitoring object at a plurality of locations in the monitoring area so that the strain can be applied by the displacement of the monitoring object. In addition, by connecting the optical fiber to the object to be monitored at a plurality of locations in the monitoring area, it is possible to perform a two-dimensional monitoring of the entire monitoring area, which can be used to formulate a more effective disaster prevention plan. It has an excellent effect.

[Brief description of the drawings]

FIG. 1 is an overall view showing an optical fiber sensor according to a first embodiment of the present invention.

FIG. 2 is an overall view showing the vicinity of a sensor unit of the optical fiber sensor of FIG.

FIG. 3 is a front view showing an optical fiber sensor according to a second embodiment of the present invention.

FIG. 4 is a front view showing the vicinity of a sensor unit of the optical fiber sensor of FIG. 3;

5A and 5B are diagrams showing the inside of the sensor unit of FIG. 4 which is installed above a monitoring target that may fall, wherein FIG. 5A is a plan view and FIG. FIG.

FIGS. 6A and 6B are views showing the inside of a sensor unit installed below a monitoring target that may fall among the sensor units of FIGS. 4A and 4B, wherein FIG. 6A is a plan view and FIG. It is sectional drawing.

FIG. 7 is a perspective view showing an optical fiber sensor according to a third embodiment of the present invention.

FIG. 8 is a plan view showing a sensing unit of the optical fiber sensor of FIG.

FIG. 9 is a side sectional view showing the sensing unit of FIG. 8;

FIG. 10 is a front sectional view showing a displacement amplifying unit provided in the sensing unit of FIG. 8;

FIG. 11 is a perspective view showing an optical fiber sensor according to a fourth embodiment of the present invention.

FIG. 12 is a cross-sectional view illustrating an example of an optical fiber housed in an optical cable constituting the optical fiber sensor according to the third and fourth embodiments.

[Explanation of symbols]

4: Optical fiber sensor, 5: Object to be monitored (rock), 6:
Optical fiber (optical cable), 7: stable ground (stable rock), 8: optical fiber (optical cable), 9a, 9b: optical connector, 10: optical pulse tester (OTDR), 12 ...
Fixing means (anchor), 20 ... optical fiber sensor, 21
a, 21b, 21c: sensor unit, 22: unit body, 23: movable member, 24: optical fiber, 24a, 2
4b: extra length, 25: optical fiber wiring part, 26, 26a ...
Breaking means, 51: stable ground (stable rock), 52: monitored object, unstable stratum (surface soil layer), 52a: monitored object, rock, 53: optical fiber sensor, 55: optical fiber (optical cable), 57 ... Optical pulse tester (BOTDR), 59
... Optical fiber retaining member (optical fiber gripping part), 70 ...
Optical fiber sensor, 72: Optical fiber retaining member (wire), 73, 76, 77: Optical fiber (leading portion) between optical fiber retaining members.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuya Ogata 1440 Misaki, Sakura City, Chiba Prefecture Inside Fujikura Sakura Factory (72) Inventor Katsuo Yasue 102 Nakajima, Oji, Moriyama-ku, Nagoya City, Aichi Prefecture Applied Geological Stock Chubu Branch Office of the Company (72) Inventor Yoshinori Ikeda 102 Nakajima, Oji Seko, Moriyama-ku, Nagoya City, Aichi Prefecture Applied Geological Co., Ltd. Chubu Branch Office F-term (Reference)

Claims (3)

[Claims] An optical fiber for observing a displacement of a monitored object (5), such as an unstable stratum that is likely to collapse or a rock that may be displaced, with respect to a stable ground (7) that is a monitoring reference side. A sensor, wherein the optical fiber (8) on the stable ground side is detachably connected to the optical fiber (6) attached to the monitored object so as to be integrally displaceable via optical connectors (9a, 9b). The optical fiber on the object to be monitored and the optical pulse tester (10) are connected via the optical fiber on the stable ground side, and the vicinity of the tip of the stable ground side optical fiber connected to the optical fiber on the monitored object side An optical fiber sensor (4), wherein the optical fiber sensor is fixed to the stable ground side by a fixing means (12). 2. An optical fiber for observing a displacement of a monitored object (5) such as an unstable stratum having a possibility of collapse or a rock having a possibility of displacement with respect to a stable ground (7) serving as a monitoring reference side. A sensor unit (21a, 21b, 21c) disposed between the monitored object and the stable ground, a unit body (22) connected to the stable ground side, A movable member (23) attached to the unit body so as to be integrally displaceable and capable of being displaced relative to the unit body.
And a plurality of optical fiber wiring portions (25) to which the optical fibers (24) housed with the extra lengths (24a, 24b) secured in the sensor unit are wired, and are driven in conjunction with the movable member. Breaking means (26, 26a) for sequentially moving the plurality of optical fiber wiring portions and breaking the optical fiber in order from a location far from the optical pulse tester (10) connected to the optical fiber. An optical fiber sensor (20), comprising: 3. An unstable stratum (52) and a rock (52) that may exist in the monitoring area and have a possibility of collapse.
a) an optical fiber sensor for observing a displacement of a monitoring object such as a) with respect to a stable ground (51, 54) as a monitoring reference side, wherein an optical pulse is generated along a boundary between the monitoring area and the stable ground. An optical fiber (55) connected to a tester (57) is extended, and a plurality of portions of the optical fiber that are separated from each other in the longitudinal direction are retained on the stable ground side by optical fiber retaining members (59, 72). An optical fiber sensor (53, 70), wherein optical fibers (55, 73, 76, 77) between adjacent optical fiber retaining members are connected to the monitoring object so as to be integrally displaceable.