JP2016065806A - Ground collapse detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground collapse detection system capable of highly accurately detecting ground collapse with deformation of a coated optical fiber.SOLUTION: A ground collapse detection system includes a light source part transmitting an optical signal to a coated optical fiber, a light reception part receiving the optical signal from the coated optical fiber, and an optical fiber cable 16 in which the coated optical fiber transmitting the optical signal is inserted into a metal pipe. The metal pipe has an easy deformation part 28 that is provided in a predetermined range in a longitudinal direction, and easily deforms the metal pipe beyond the predetermined range in a case of receiving external force. The ground collapse detection system detects ground collapse, from fluctuation of the optical signal of the coated optical fiber with deformation in the easy deformation part 28 of the metal pipe in ground collapse.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a ground collapse detection system that includes a light source unit, a light receiving unit, and an optical fiber cable, and detects ground collapse.

  The cut and slope of railways and roads or embankments may collapse due to heavy rain or earthquakes. In addition, the sediment on the riverbed where the bridge piers are installed may be scoured and collapsed by the water flow of the river whose flow velocity has increased due to heavy rain. The collapse of the ground in an environment where such railways and roads are laid may interfere with traffic and may cause a derailment accident in some cases. It is required to detect a collapse of the ground at the time of such a disaster and stop train operation and vehicle traffic to prevent derailment accidents.

  For example, slope disaster prevention management due to heavy rain or earthquake is generally performed by patrol monitoring by personnel. However, there are an enormous number of slopes that should be patroled, and there are limits to monitoring by patrol. In addition, during a disaster such as heavy rain or an earthquake, the patrol itself is dangerous and it is difficult to fully patrol.

  On the other hand, a detection system has been proposed in which a sensor for detecting a collapse is installed on the slope, and the collapse information is automatically transmitted when the slope collapses. Various types of detection systems have been proposed, but detection systems using optical fibers are prominent because of the fact that the sensor itself is an optical fiber cable and can be extended, and there is no influence of lightning or other inductive disturbances. Proposed as a detection system.

  For example, in Patent Document 1 and Patent Document 2, a collapse detection system using an optical fiber has an optical fiber cable inserted through a metal tube on a slope to be monitored, and an optical pulse transmission / reception device is connected thereto Configured. And when the slope collapses and the optical fiber core of the installed optical fiber cable is bent or broken, the backscattered light from that part is analyzed, and fluctuations such as physical quantities such as strain and light loss are Recognize as a fall of the fall is detected.

JP2001-099686 JP2007-155550A

  When detecting ground collapse using an optical fiber cable, in order to improve the reliability of ground collapse detection, it is necessary to reliably deform the optical fiber core wire in the event of ground collapse. There is a need for a means for accelerating deformation of a metal tube that accommodates the optical fiber core.

  In view of such circumstances, the present invention is a ground collapse detection system capable of accurately deforming a metal tube of an optical fiber cable and detecting the collapse of the ground with high accuracy due to the stress generated in the optical fiber core wire associated therewith. The purpose is to provide.

  A ground collapse detection system according to the present invention is a system for detecting ground collapse, wherein a light source unit that transmits an optical signal to an optical fiber core, a light receiver that receives an optical signal from the optical fiber core, and an optical signal And an optical fiber cable inserted into the metal tube, and the metal tube is more easily deformed than the predetermined range when an external force is applied to the predetermined range in the longitudinal direction. An easily deformable portion is provided, and when the ground collapses, the collapse of the ground is detected by the change in the optical signal of the optical fiber core wire accompanying the deformation at the easily deformable portion of the metal tube.

  In the present invention, an optical fiber cable is installed on the ground to be monitored for collapse, and an optical signal transmitted from the light source unit is transmitted through the optical fiber core and received by the light receiving unit. When a ground collapse occurs in the ground, the easily deformable portion of the metal tube of the optical fiber cable that receives the load due to the collapse is easily deformed as compared with the other portions. As a result, stress is generated in the optical fiber core in the metal tube, and the optical fiber core wire is bent or broken, whereby the optical signal to be received in the light receiving unit varies. In this way, the ground collapse detection system according to the present invention detects the occurrence of the bending or breakage of the optical fiber core and the ground collapse due to the fluctuation of the optical signal in the light receiving unit.

  The easily deformable portion in the present invention can be formed in various forms. For example, the easily deformable portion may be formed by the arrangement shape of the optical fiber cable itself in the predetermined range, and a deformation promoting member for promoting the deformation of the metal tube is engaged with the metal tube in the predetermined range. Accordingly, an easily deformable portion may be formed in the metal tube in the predetermined range.

  In the present invention, the easily deformable portion is preferably formed by winding or bending the optical fiber cable at a local portion. By forming the easily deformable part by winding or bending the optical fiber cable, the easily deformable part can be used as an allowance for the displacement of the optical fiber cable at any position in the middle or end in the longitudinal direction of the optical fiber cable. You can also Here, “displacement allowance” means a margin length for allowing bending displacement of the optical fiber cable. When the optical fiber cable receives an external force, the optical fiber cable is within the range of the displacement allowance. By moving according to the external force, it becomes possible to cause bending displacement of the optical fiber cable.

  If such a displacement allowance is not given to the metal tube, the metal tube is difficult to bend and displace, and the optical fiber core wire can be deformed only by cutting by shearing. Since the metal tube is easily bent and displaced even if the load due to the ground collapse does not reach the shear of the metal tube, the optical fiber core wire in the metal tube can be easily Stress can be generated to reliably detect ground collapse.

  In the present invention, the easily deformable portion formed by winding or bending the optical fiber cable suppresses the displacement of the optical fiber cable in a direction perpendicular to a certain plane including the easily deformable portion, and the above-described easy deformable portion. It is preferable to provide a suppressing member that holds the deformed portion in the plane. When such a restraining member is not provided, even if an external force is applied to the optical fiber cable forming the easily deformable portion and a stress is generated, the optical fiber cable is displaced in the perpendicular direction to the easily deformable portion. There may occur a situation where the stress to be applied is dispersed around the easily deformable portion. In the present invention, by providing the suppressing member and retaining the easily deformable portion in the plane, the stress can be applied to the easily deformable portion of the metal tube to reliably promote the deformation of the metal tube.

  In the present invention, the metal tube is engaged with a deformation promoting member for transmitting a load caused by the collapse of the ground to the metal tube to promote the deformation of the metal tube, and is engaged with the deformation promoting member in the metal tube. The mating portion may be formed as an easily deformable portion. Further, when such a deformation promoting member is provided on the metal tube, a margin for displacement outside the predetermined range may be provided.

  In the present invention, the metal tube is preferably provided with a low-strength portion within the range of the easily deformable portion that causes local deformation within the range of the easily deformable portion when an external force is applied. As described above, by providing the low-strength portion within the range of the easily deformable portion, when a load due to ground collapse is applied to the easily deformable portion of the metal tube, stress concentrates on the low-strength portion. Therefore, the metal tube of the optical fiber cable can be more reliably deformed at the position of the low-strength portion, and the reliability of detecting the collapse of the ground due to the occurrence of the stress in the optical fiber core wire can be improved.

  In the present invention, the low-strength portion is preferably formed by caulking the metal tube with the direction of one straight line orthogonal to the axis as the caulking direction. As described above, the caulking structure may be, for example, a flat caulking that caulks the metal tube in a single straight direction perpendicular to the axis of the metal tube, or a diameter direction of the metal tube over the entire circumference. There is a circumferential caulking to reduce the diameter. Of these, when the low-strength portion is formed by circumferential caulking, it is ideal because the strength is constant throughout the entire circumferential direction of the low-strength portion, but in reality it is a perfect circle by shifting the axis. This is often difficult, and it takes time and effort to form a uniform shape. On the other hand, flat caulking is effective in that it can easily form a low-strength portion by simply compressing a metal tube from the outside with a caulking processing device, and also can keep the machining quality constant. is there.

  In the present invention, in the optical fiber cable, when the ground collapses, the pressure receiving member that receives a load due to the collapse is attached so as to be able to transmit the pressure receiving force to the easily deformable portion, thereby promoting the deformation of the optical fiber cable. Is preferred. By providing such a pressure receiving member, it is possible to increase the sensitivity with which the easily deformable portion is deformed by an external force.

  In the present invention, the pressure receiving member is preferably attached to the optical fiber cable at a position where the pressure receiving force can be transmitted to the low strength portion. By providing the pressure receiving member at such a position, it is possible to increase the sensitivity of causing deformation due to an external force in the low-strength portion.

  As described above, in the present invention, since the easily deformable portion that makes the deformation of the metal tube easier than outside the predetermined range is provided in the predetermined range in the longitudinal direction of the metal tube, the optical fiber cable is caused by ground collapse. When the load is received, the easily deformable portion is easily deformed. Along with this, stress is generated in the optical fiber in the metal tube, and the optical fiber is bent or broken. The optical signal to be received in the unit varies. As a result, it is possible to reliably detect the occurrence of the bending or breakage of the optical fiber core and the collapse of the ground due to the fluctuation of the optical signal in the light receiving unit.

(A) is a figure which shows the use condition of 1st embodiment apparatus as a ground collapse detection system, (B) is a figure which shows the state which supported the optical fiber cable with the mooring member. It is a schematic block diagram of the apparatus of the first embodiment. 2 is a schematic configuration diagram showing one of a plurality of detection units included in the apparatus together with an optical fiber cable. It is the figure which showed the state which the easily deformable part of the optical fiber cable in 1st embodiment deform | transforms. It is a figure which shows the lowest part of the easily deformable part of FIG. 4, (A) has shown the state before a deformation | transformation, (C) has shown the state after a deformation | transformation. It is a figure which shows an example of the suppression member provided in the easily deformable part of the optical fiber cable in 1st embodiment. It is a figure which shows the other example of the suppression member provided in the easily deformable part of the optical fiber cable in 1st embodiment. It is a figure which shows the other example of the suppression member provided in the easily deformable part of the optical fiber cable in 1st embodiment, (A) is a front view, (B) is a side view. It is a figure which shows the modification of the easily deformable part of the optical fiber cable in 1st embodiment. It is a figure which shows the low intensity | strength part of the optical fiber cable in 2nd embodiment. (A), (B) is a perspective view which shows an example of the optical fiber cable low intensity | strength part in 3rd embodiment, respectively. It is a figure which shows the cross section of the optical fiber cable low intensity | strength part in 4th embodiment. An example of the pressure receiving member in 5th embodiment is shown, (A) is a front view, (B) is a longitudinal cross-sectional view, (C) is a top view. The other example of the pressure receiving member in 5th embodiment is shown, (A) is a front view, (B) is a longitudinal cross-sectional view, (C) is a top view. It is a figure which shows the usage condition of the pressure receiving member in 5th embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Examples of the detection target in the ground collapse detection system according to the present invention include a sediment collapse on a cut slope and a bank slope, and a collapse caused by scouring a river bed on which bridge piers are installed. Below, the detection system which detects the landslide on the cut slope located in the highland side with respect to a track laying zone | band and the embankment slope located in a lowland side is demonstrated as embodiment of this invention.

<First embodiment>
FIG. 1A is a diagram illustrating a usage state of the apparatus of the present embodiment as a ground collapse detection system, and FIG. 1B is a diagram illustrating a state in which an optical fiber cable is supported by a mooring member described later. 2 is a schematic configuration diagram of the apparatus of the present embodiment, and FIG. 3 is a schematic configuration diagram illustrating one of a plurality of detection units included in the apparatus of FIG. 2 together with an optical fiber cable.

  The apparatus of this embodiment has a ground collapse monitoring device 10 as a monitoring base station installed in a station building or the like, and the ground collapse monitoring device 10 includes a large number of detection units 11 (four detection units 11A and 11B in FIG. 2). , 11C, and 11D), a control device 12 that controls these and determines the output from the detection unit 11, and a display device 13 that displays the result. The control device 12 is connected to a wireless communication device 15 that communicates with the train 14.

  Optical fiber cables 16A, 16B, 16C, and 16D extend from each of the detection units 11A, 11B, 11C, and 11D, and these optical fiber cables 16A, 16B, 16C, and 16D have one trunk cable as a preferred form. It is summarized as 17 and extends toward the slope where landslide should be detected. As described above, since a large number of the detection units 11 are provided, the corresponding number of optical fiber cables 16 are inserted into one trunk cable 17. As shown in FIG. 2, one trunk cable 17 has a plurality of sections (in FIG. 2, for example, section 1, section 2, In contrast, four sections of sections 3 and 4 are shown), and the optical fiber cables 16A, 16B, 16C, and 16D are drawn from the trunk cable 17 so as to be sequentially installed. Further, instead of inserting a plurality of optical fiber cables 16 into the main cable 17, for example, an optical fiber in which a plurality of optical fibers are accommodated in the main cable 17 and the optical fibers are inserted into a metal tube. The cable 16 may be branched from the trunk cable 17 to each section.

  In general, for example, as shown in FIG. 1A, the slope is a cut slope R on one side which is a highland side and a lowland with respect to a flat track laying band Q where the railroad track P is laid. There is an embankment slope S on the other side as a side. The track laying band Q may be a road.

  In the example of FIG. 1 (A), the main cable 17 extends from both sides of the line laying band Q, that is, near the boundary between the line laying band Q and the cut slope R and near the boundary between the embankment slope S. An outgoing optical fiber cable 16 is installed. The line laying band Q is divided into a plurality of sections, for example, section 1, section 2, section 3, and section 4, as seen in FIG. As seen in FIG. 2, the optical fiber cables 16A, 16B, 16C, and 16D drawn from the trunk cable 17 are connected to the ground in each section, that is, section 1, section 2, section 3, and section 4. Are supported by the mooring member 18 and extend over the respective ranges of the sections 1, 2, 3 and 4.

  In the present embodiment, the optical fiber cables 16A, 16B, 16C, 16D are not only cut on the cut slope R side, but also draw the other optical fiber cable 16 from the main line cable 17 so that the section 1, section 2, section 3, By providing the section 4 on the embankment slope S side in the same manner, it is possible to detect landslides on both slopes.

  For example, as shown in FIG. 1B, the anchoring member 18 supports the optical fiber cable 16 in a state in which the optical fiber cable 16 can be moved in the longitudinal direction by a hook portion 18A that can hook the optical fiber cable 16 from the side. It has a pile shape and is driven against the ground at a plurality of positions at intervals in the longitudinal direction. The mooring member 18 only needs to support the optical fiber cable 16 with respect to the ground, and is not limited to the shape shown in FIG.

  As a form of support of the optical fiber cable 16 by the mooring member 18, for example, in addition to the form shown in FIG. The optical fiber cables 16A, 16B, 16C, and 16D are combined as one trunk cable 17 as described above, but are connected to the corresponding detection units 11A, 11B, 11C, and 11D in the station building. ing.

  Each of the optical fiber cables 16A, 16B, 16C, 16D (since each optical fiber cable has the same form, FIG. 3 shows the optical fiber cable 16 and thus the detection unit is also shown as the detection unit 11). As shown in FIG. 2, two optical fiber cores 22A and 22B are inserted into the metal tube 21, and one of the optical transmission paths is the forward path and the other F is the return path. The two optical fiber cores 22A and 22B are connected by appropriate means so as to form a folded loop portion 22C at one end (right end in FIG. 3), and one optical fiber core wire forming the forward path portion at the other end. 22 A is connected to the light source unit 23, and the other optical fiber core wire 22 B forming the return path unit is connected to the light receiving unit 24. A metal tube 21 into which the optical fiber core wires 22A and 22B are inserted has a cap-shaped or box-shaped protective member 25 attached at one end thereof, and the folded loop 22C is protected. The two optical fiber cores 22A and 22B in the metal tube 21 are connected so that one ends thereof form a loop back for convenience of work, but one long and continuous optical fiber core wire is folded back to the forward path portion. You may make it have a return path part. In the present embodiment, the light source unit 23 and the light receiving unit 24 are combined as one detection unit 11. Since the detection unit 11 detects not the degree of change of the optical signal (hereinafter also simply referred to as “light”) but the presence / absence (blocking), compared to OTDR or BOTDR based on measurement of the fluctuation amount of light, Extremely simple configuration and low cost.

  As the material of the metal tube 21, stainless steel, nickel alloy, copper, titanium, aluminum or the like can be used. The optical fiber cable 16 is covered with vinyl chloride resin, polyethylene, nylon, urethane, or the like, or the inside of the metal tube 21 is filled with a resin such as an epoxy resin or a urethane resin or a synthetic oil of a hydrocarbon polymer. be able to.

  In the present embodiment, the other end of the optical fiber cable 16, that is, the end connected to the ground collapse monitoring device 10 provided in the station building, the two optical fiber core wires 22 </ b> A and 22 </ b> B in the metal tube 21 are connected. One of the optical fiber cores 22A is connected to the light source unit 23, and the other optical fiber core wire 22B is connected to the light receiving unit 24. Therefore, in normal times when no landslides have occurred on the slope, the light emitted from the light source section 23 travels through one optical fiber core 22A as the forward path section, passes through the return loop section 22C on one end side, and returns to the return path section. And enters the other optical fiber core wire 22B and is received by the light receiving unit 24.

  Although not shown in FIG. 3, the metal tube 21 is easier to deform the metal tube 21 than outside the predetermined range when an external force is applied to a plurality of predetermined ranges in the longitudinal direction. A deforming portion 28 is provided. FIG. 4 is a view showing a state in which the easily deformable portion 28 is deformed. 5 is a view showing the lowermost part of the easily deformable portion 28 in FIG. 4, where (A) shows a state before deformation, and (C) shows a state after deformation.

  As shown in FIG. 4, the easily deformable portion 28 is formed by winding a predetermined range in the cable longitudinal direction into a substantially circular shape at a plurality of positions in the cable longitudinal direction of the optical fiber cable 16. Thus, by winding a part of the optical fiber cable 16 to form the easily deformable portion 28, the easily deformable portion 28 can be used as a displacement of the optical fiber cable 16. The “displacement” is a margin length for allowing bending displacement of the optical fiber cable. By providing the displacement allowance in advance as in the present embodiment, even if the load from the collapsed earth and sand is a load that does not reach the shear of the metal tube 21, the metal tube 21 is within the range of the easily deformable portion 28. Since it is easily bent and displaced, the optical fiber core wires 22A and 22B in the metal tube 21 can be easily disconnected to reliably detect the collapse of the earth and sand.

  When the earth and sand collapses and the easily deformable portion 28 receives a downward load in FIG. 4 from the earth and sand, the easily deformable portion 28 that has received the load has a substantially circular portion as shown in FIG. The width dimension (lateral dimension in FIG. 4) is deformed to be narrowed. As a result, the easily deformable portion 28 is bent most greatly in the lowermost portion within the range of the easily deformable portion 28.

As can be seen by comparing FIG. 5A showing the lowermost part of the easily deformable portion 28 in FIG. 4 before deformation and FIG. 5B showing the lower part, the lowermost part shown in FIG. The difference between the length (l ₂ + l ₃ ) of the range in the vicinity of the lowermost part after the deformation and the length l ₁ of the range in the vicinity of the lowermost part before the deformation of the lowermost part shown in FIG. That is, the length (l ₂ + l ₃ −l ₁ ) is the length of the movement at the displacement.

  Since the optical fiber core wires 22A and 22B in the metal tube 21 are significantly lower in strength than the metal tube 21 and have brittleness, as shown in FIG. When the lowermost portion of the deformed portion 28 is bent greatly, the optical fiber core wires 22A and 22B are easily bent and disconnected at the lowermost position. That is, when the load is received, the light passing through the optical fiber cores 22A and 22B is blocked, and the collapse of the earth and sand can be reliably detected. In the present embodiment, an example in which both of the optical fiber cores 22A and 22B are disconnected is shown. However, in order to block light, at least one of the optical fiber cores 22A and 22B only needs to be disconnected. .

  In order to reliably deform the metal tube 21 within the range of the easily deformable portion 28, the easily deformable portion 28 is fastened in a plane including the easily deformable portion 28 (a surface parallel to the paper surface in FIG. 4). While maintaining the state where the optical fiber cables 16 are close to each other in the direction perpendicular to the plane, the crossing portion between the optical fiber cables 16 (the uppermost portion of the easily deformable portion 28 in FIG. 4) is maintained. It is preferable to displace the deformation portion 28 in the width direction (lateral direction in FIG. 4). If the optical fiber cables 16 are separated from each other in the perpendicular direction at the intersecting portion, even if the easily deformable portion 28 is displaced in the width direction, the stress to be applied to the easily deformable portion 28 is concentrated on the easily deformable portion 28. Therefore, the easily deformable portion 28 cannot be sufficiently deformed.

  In order to surely displace the easily deformable portion 28 in the width direction of the substantially circular portion, the easily deformable portion 28 is formed at the intersection of the optical fiber cables 16 (the uppermost portion of the easily deformable portion 28 in FIG. 4). And a restraining member having a play that allows displacement (movement) in the longitudinal direction of the optical fiber cable while preventing the optical fiber cables 16 from separating in a direction perpendicular to a plane including Is preferred.

  The suppression member can adopt various forms. FIG. 6 thru | or FIG. 8 (A), (B) is a figure which shows an example of a suppression member, respectively. The restraining member 29 shown in FIG. 6 is configured as a bundling member that bundles the intersecting portions by winding the wire around the intersecting portions of the easily deformable portion 28 a plurality of times. Moreover, the suppressing member 30 shown by FIG. 7 is comprised as a tubular member which penetrated the said cross member. Moreover, the suppressing member 31 shown in FIGS. 8A and 8B is configured as a thin box-shaped member that accommodates the entire easily deformable portion 28. According to these restraining members, the metal tube 21 of the easily deformable portion 28 can be easily deformed by enabling downward displacement while preventing the optical fiber cables 16 from being separated from each other at the intersecting portion in the easily deformable portion 28. .

  In this embodiment, the easily deformable portion 28 shown in FIGS. 4 to 8A and 4B is formed by bending an optical fiber cable so as to form a closed loop when viewed in a direction perpendicular to the paper surface. However, the easily deformable portion 28 is not limited to this, and can be formed in various forms. For example, the easily deformable portion 28 may be formed in a substantially Ω shape as shown in FIG. 9 by bending the optical fiber cable 16, or may be formed in a waveform or the like. Even when the easily deformable portion 28 is formed in these shapes, for example, the entire easily deformable portion 28 is accommodated in a thin box-like restraining member (see FIGS. 8A and 8B), and thus the easily deformable portion 28 is easily deformed. It is preferable that the easily deformable portion 28 is deformed while maintaining the state where the easily deformable portion 28 is held in a plane including the portion 28.

  Moreover, in this embodiment, in order to accelerate the deformation of the easily deformable portion 28 of the optical fiber cable 16 when a landslide occurs, the landslide is received by the pressure receiving member 27 described later, and the received pressure is changed to the easily deformable portion 28. It is also possible to configure to transmit to As seen in FIG. 1, the metal pipe 21 of the optical fiber cable 16 installed in the vicinity of the boundary between the track laying band Q and the embankment slope S has a cable body extending downward along the embankment slope S. A wire 26 is suspended. Specifically, the wire 26 is suspended at the lowermost portion of each easily deformable portion 28 (not shown in FIG. 1). A pressure receiving member 27 that receives the load of collapsible earth and sand is locked and attached to the wire 26 at a plurality of positions in the longitudinal direction of the wire 26. The pressure receiving member 27 is formed with a receiving surface for receiving the flow of collapsible earth and sand, and maintains a posture in which the receiving surface is substantially perpendicular to the inclination direction of the embankment slope S. Therefore, when the earth and sand on the embankment slope S collapses and the pressure receiving member 27 receives a load from the flow of the collapsed earth and sand on the receiving surface, the pressure receiving force generates tension on the wire 26, and this tension is applied to the optical fiber cable 16. It is transmitted to the lowermost part of the easily deformable part 28, and the deformation of the lowermost part of the easily deformable part 28, and hence the disconnection of the optical fiber core wires 22A and 22B is promoted. In other words, the lowermost portion of the easily deformable portion 28 is more sensitive to deformation due to external force than the other portions.

  Further, a weight (not shown) may be engaged with the wire 26 together with the pressure receiving member 27 or instead of the pressure receiving member 27. By holding the weight in this way, when the sediment collapses, the load due to the weight of the weight acts on the wire 26 in the region where the sediment is absent, so that the weight forms a pressure receiving member. The wire 26 is tensioned by the load. As a result, the tension is transmitted to the easily deformable portion 28 of the optical fiber cable 16 and the easily deformable portion 28 is deformed, and the disconnection of the optical fiber core wires 22A and 22B is promoted.

  In the form shown in FIG. 1, the above-described wire 26, pressure receiving member 27, and weight are not provided in the optical fiber cable 16 installed in the vicinity of the boundary between the track laying band Q and the cut slope R. However, when the cut slope R collapses, the optical fiber cable 16 receives the flow of the collapsed soil and deforms. However, for example, when the optical fiber cable 16 is installed on the cut slope R above the position shown in FIG. 1, the wire 26, the pressure receiving member 27, and the weight are attached to the easily deformable portion 28 of the optical fiber cable 16. It is also possible to provide it.

  Further, as still another form of the easily deformable portion 28, for example, a pressing member (not shown) as a deformation promoting member for promoting the deformation of the easily deformable portion 28 may be attached to the optical fiber cable 16. The pressing member has, for example, a substantially ring shape surrounding almost the entire circumference of the lowermost portion of the easily deformable portion 28, and a wedge-shaped pressing portion that protrudes toward the outer peripheral surface of the metal tube 21 is formed on the inner edge thereof. Can be configured. At this time, the pressing member may be fixedly attached to the metal tube 21, or may be attached to be movable within the range of the easily deformable portion 28 in the longitudinal direction of the metal tube 21. Good. By inserting the optical fiber cable 16 into the inner edge of the pressing member, the pressing portion of the pressing member bites into the metal tube 21 at the bottom of the easily deformable portion 28 when a load is applied from the collapsed earth and sand. Thus, the lowermost part can be more reliably deformed. For example, when the wire 26, the pressure receiving member 27, and the weight described above are provided, the wire 26 is suspended from the pressing member, so that when the landslide collapses, the tension is applied to the wire 26. The member moves downward and the pressing portion of the pressing member bites into the metal tube 21 to deform the lowermost portion of the easily deformable portion 28.

  Further, as a further modification of the easily deformable portion 28, the easily deformable portion 28 is not formed by winding or bending of the optical fiber cable 16, but in a plurality of predetermined ranges over the longitudinal direction of the metal tube 21 as described above. By attaching the pressing member and engaging with the metal tube 21, the engaging portion of the metal tube 21 with the pressing member may be formed as the easily deformable portion 28. At this time, the pressing member may be fixedly attached to the metal tube 21 or may be attached to be movable in the longitudinal direction of the metal tube 21.

  As described above, the present invention can also be applied to a ground collapse detection system that detects ground collapse due to scouring a river bed on which bridge piers are installed. In the ground collapse detection system, the above-described wires, pressure receiving members 27 and When a weight is used, the pressure receiving member 27 and the weight are arranged, for example, on the river bed around the pier. When scouring occurs in the riverbed around the bridge pier, the pressure receiving member 27 receives a load from sediment or water flow, or a load due to the weight of the weight in a region where sediment is absent due to the scouring. By acting on the wire 26, a tension corresponding to the load is generated in the wire 26. As a result, the tension is transmitted to the easily deformable portion 28 of the optical fiber cable 16 and the easily deformable portion 28 is deformed, and the disconnection of the optical fiber core wires 22A and 22B is promoted.

  Next, the operation principle of the ground collapse detection system according to the present embodiment will be described. As described above, in normal times when no landslide has occurred, the light emitted from the light source unit 23 is one optical fiber core wire 22A (forward path portion), the return loop portion 22C, and the other optical fiber core wire 22B ( The light-receiving unit 24 receives light after traveling the return path portion. Then, the control device 12 determines that the optical fiber core wires 22A and 22B are not disconnected while the light receiving unit 24 is receiving light, that is, no landslide has occurred in any of the sections 1 to 4, and A signal corresponding to the determination result is transmitted to the display device 13. As a result, the display device 13 displays a determination result that no landslide has occurred.

  On the other hand, for example, when a landslide has occurred in the section 2 of the embankment slope S, the pressure receiving member 27 located in the section 2 flows on the receiving surface of the pressure receiving member 27 as described above. The tension is transmitted to the easily deformable portion 28 of the optical fiber cable 16B in the section 2 through the wire 26 that receives the load from the collapsed sand and sand and generates tension by the pressure received. As a result, as shown in FIG. 4, the easily deformable portion 28 is greatly bent and deformed, and the optical fiber core wires 22 </ b> A and 22 </ b> B in the metal tube 21 are broken and disconnected.

  When the optical fiber cores 22A and 22B are disconnected, the light passing through the optical fiber cores 22A and 22B is blocked (disrupted), so that the light receiving unit 24 of the detection unit 11B corresponding to the section 2 does not receive light. Become. Therefore, the control device 12 determines that the optical fiber cores 22A and 22B are disconnected in the section 2, that is, the landslide has occurred, and transmits a signal corresponding to the determination result to the display device 13 and the wireless communication device 15. . Then, the display device 13 displays that a landslide has occurred in the section 2 of the embankment slope S. Moreover, the radio | wireless communication apparatus 15 transmits the radio signal corresponding to the said determination result toward the train 14, and notifies the crew member of this train 14 of the occurrence of the landslide in the said area. As a result, by appropriately stopping the train 14, it is possible to reliably prevent the train from being damaged due to a landslide. In addition, for roads, it is possible to prevent accidents by stopping traffic of vehicles.

  Here, a case has been described in which a landslide has occurred on the embankment slope S, but even when a landslide has occurred on the cut slope R, the easily deformable portion 28 of the optical fiber cable 16 directly receives a load from the landslide. The operating principle of the ground collapse detection system is the same as in the case of the embankment slope S described above, except for the point that it deforms.

  In this embodiment, since the monitoring area is divided into a plurality of areas and the optical fiber cables are arranged corresponding to each of them, it is possible to immediately detect in which section the disconnection has occurred. In this embodiment, since only the presence or absence of an optical signal is detected, the disconnection position cannot be detected, but since it is possible to detect in which section the disconnection has occurred, the position where the landslide has occurred is thereby determined. Can be easily identified. In addition, in the conventional detection method using backscattered light, landslides are detected based on the amount of change in strain and light loss, so there is ambiguity in the amount of change and threshold setting for setting the detection limit. Since only the presence / absence of an optical signal is detected, a landslide can be reliably detected.

  In addition, the monitoring level can be improved by increasing the number of sections in the area where there is a high possibility of landslides (shortening the section length) and decreasing the number of sections in the area where the possibility is low. Moreover, in this embodiment, since an optical fiber cable should just be replaced | exchanged only about the area where the landslide has occurred, subsequent repair is easy. If a larger number of optical fiber cables than the number of sections are stored in the trunk cable in advance, an extra optical fiber cable can be used as a replacement optical fiber cable, and this point also facilitates repair.

  In the present embodiment, an example in which a plurality of detection units are provided corresponding to each of the optical fiber cables arranged in a plurality of sections is illustrated, but common to each optical fiber cable without using a plurality of detection units. The common detection unit may be sequentially switched and connected to each optical fiber cable. In this way, the cost can be greatly reduced with respect to providing the detection unit.

  Further, in the ground collapse detection system according to the present embodiment, the presence or absence of light received by the light receiving unit, that is, the light is blocked using an optical fiber cable having an optical fiber core wire formed with the forward path part and the return path part. Depending on whether the optical fiber core wire is broken or not, the occurrence of a landslide is detected, but instead of this, for example, bending or breaking of the optical fiber core wire due to stress generated in the optical fiber core wire. Detects landslides by recognizing changes in physical quantities such as strain and light loss as landslides using an optical transceiver (BOTDR or OTDR) that analyzes the backscattered light from the site in the event It is good as well. When performing such detection, it is not essential to fold the optical fiber core wire to form the forward path portion and the return path portion, and the single optical fiber core wire can be used without being folded back.

<Second embodiment>
This embodiment differs from the first embodiment in which the low-strength portion is not provided in that the low-strength portion that has been locally processed to have low strength is provided within the range of the easily deformable portion. ing. In the present embodiment, when the load from the collapsed earth and sand is applied to the easily deformable portion, the stress concentrates on the low strength portion, and the metal tube is reliably deformed at the position of the low strength portion. Hereinafter, the present embodiment will be described focusing on differences from the first embodiment.

  FIG. 10 is a view showing a low strength portion of the optical fiber cable in the second embodiment. In this embodiment, as seen in FIG. 10, the low-strength portion 21 </ b> A is formed at the lowest position of the easily deformable portion 28. The low-strength portion 21 </ b> A is a part that is locally processed to have a lower strength in order to preferentially deform than the other portions when an external force is applied to the metal tube 21. For example, in the example of FIG. 10, the metal tube 21 is crimped (crushed) with the direction of one straight line (hereinafter also referred to as “diameter line”) orthogonal to the axis of the metal tube 21 as the crimping direction. By forming the flat portion, the strength is reduced. Of course, the caulking process is performed in a processing dimension range that does not affect the optical fiber core wires 22A and 22B in the metal tube 21. The low-strength portion can be made by other methods, for example, by thinning the corresponding portion without depending on the caulking process.

  When the easily deformable portion 28 provided with the low-strength portion 21A receives a force from the earth and sand caused by the landslide on the slope as an external force, the easily deformable portion 28 has a substantially circular portion as in the first embodiment. It is displaced so as to narrow the width dimension (lateral dimension in FIG. 10) (see FIG. 4). As a result, the low-strength portion 21A is greatly bent and deformed, and the optical fiber core wires 22A and 22B in the metal tube 21 are broken and disconnected. In this embodiment, since the low-strength portion 21A is provided in the easily deformable portion 28 and stress is concentrated on the low-strength portion 21A, the first embodiment in which the low-strength portion 21A is not provided. Compared with the form, the easily deformable portion 28 can be more reliably deformed, and the reliability of detecting the collapse of earth and sand caused by the disconnection of the optical fiber cores 22A and 22B can be improved.

  In this embodiment, when the wire 26, the pressure receiving member 27, and the weight described in the first embodiment are provided in the easily deformable portion 28, the wire 26 is suspended from the low strength portion 21A of the easily deformable portion 28. Thus, the deformation of the low strength portion 21A can be promoted by causing the tension of the wire 26 caused by the load of the collapsed earth and sand to act on the low strength portion 21A. In this embodiment, the pressing member as the deformation promoting member described in the first embodiment is attached to the position of the low-strength portion 21A of the easily deformable portion 28 and engaged with the low-strength portion 21A. The deformation of the low-strength portion 21A may be further promoted by causing the pressing portion of the pressing member that receives a load from the earth and sand to bite into the low-strength portion 21A.

<Third embodiment>
In this embodiment, the diameter lines in the caulking direction of the plurality of low-strength portions formed on the metal tube of the optical fiber cable are different from each other, and the diameter lines in the caulking direction of all the low-strength portions are in the same direction. It is different from the second embodiment. Hereinafter, the present embodiment will be described based on FIGS. 11A and 11B with a focus on differences from the first and second embodiments.

  The low-strength portion 21A of the metal tube 21 is most easily deformed when a load from the collapsed sand is received in a direction perpendicular to the caulking surface. In other words, when all the low-strength portions 21A are formed by caulking in the same direction, the low-strength portions 21A collapse in a direction having almost no angle with respect to the caulking surface, for example, in a direction parallel to the caulking surface. When a load from earth and sand is received, a situation may occur in which these low-strength portions 21A are not easily deformed. This means that directionality occurs at the circumferential position of the metal tube in the deformability of the low-strength portion 21A of the optical fiber cable 16.

  In order to cope with such a situation, the low-strength portion 21A in the present embodiment is such that the diameter lines in the caulking direction of the low-strength portions 21A at a plurality of positions have an intersection angle when the metal tube 21 is viewed in the longitudinal direction. It is formed to have. For example, in the form shown in FIG. 11A, the low-strength portions 21 </ b> A in which the crossing angle between the diameter lines in the caulking direction forms approximately 90 ° are alternately formed in the longitudinal direction of the metal tube 21. In this way, by providing the low strength portion 21A with different caulking directions, any low strength portion 21A can receive any bending stress due to the load from the collapsed soil at any position in the circumferential direction of the metal tube 21. Since the load can be received in a direction substantially perpendicular to the caulking surface, if these different low-strength portions 21A are both located in the same section of the detection area, the collapsed sediment can be taken from any direction. Even if it is received, the low-strength portion 21A is easily and reliably deformed to disconnect the optical fiber core wires 22A and 22B, and the occurrence of landslide can be reliably detected.

  Moreover, in this embodiment, since the said crossing angle is set large as about 90 degree | times, even if it receives collapsed earth and sand from what direction, in any low intensity | strength part 21A, it is more reliably with respect to a crimping surface. Thus, an external force can be received in a substantially perpendicular direction, and the deformation of the low-strength portion 21A, and thus the disconnection of the optical fiber core wires 22A and 22B can be promoted.

  The positions where the low strength portions 21A having different caulking directions are formed are not limited to the form in which the low strength portions 21A are located apart from each other as shown in FIG. 11A. For example, in the longitudinal direction of the metal tube 21 As shown in FIG. 11B, the low-strength portions 21A having different caulking directions may be adjacent to each other. By setting it as such a structure, even if it is any place of the said several places that receive the load of collapsed earth and sand, any low intensity | strength part 21A in the place which received the said load is a crimping surface. On the other hand, it receives the above load in a substantially right angle direction and reliably deforms.

  In the present embodiment, for the low-strength portions 21A having different caulking directions, the crossing angle between the diameter lines in the caulking direction is approximately 90 °. However, the crossing angle is not limited to this, and may be arbitrarily set. it can. In the present embodiment, two types of low-strength portions 21A having crossing angles are provided. Instead, three or more types of low-strength portions 21A having crossing angles are provided. Also good.

<Fourth embodiment>
In the present embodiment, the stress concentration portion having a lower strength is formed in the range of the low strength portion of the metal tube, such a stress concentration portion is not formed, and the strength of the low strength portion is in the entire range. And different from the second and third embodiments. Hereinafter, the present embodiment will be described based on FIG. 12 with a focus on differences from the first to third embodiments. In FIG. 12, only the metal tube 21 is shown, and the optical fiber core wires 22A and 22B are not shown.

  As described above, in the low-strength portion 21A in the present embodiment, a stress concentration portion for further reducing the strength of the low-strength portion 21A is locally formed within the range of the low-strength portion 21A. In the form shown in FIG. 12, the stress concentration portion 21B has a plurality of notches as cuts extending in a direction perpendicular to the paper surface of FIG. 12 on the crimping surface of the low strength portion 21A. By forming the stress concentration portion 21B in this way, when the low strength portion 21A receives a load from the earth and sand, stress concentrates on each stress concentration portion 21B, so that the deformation of the low strength portion 21A is promoted. The optical fiber core wires 22A and 22B can be disconnected more reliably, and the occurrence of landslide can be detected.

  The shape of the stress concentration portion is not limited to the notch as shown in FIG. 12, and can be formed by, for example, a groove, a concave portion, an unevenness, or the like that extends perpendicular to the paper surface of FIG. 12. For example, the stress concentration portion is formed by forming a machining surface of a caulking tool for forming a low strength portion in a shape corresponding to the stress concentration portion, so that both the low strength portion and the stress concentration portion can be formed by a single caulking process. It becomes possible to form.

<Fifth embodiment>
The present embodiment is characterized by the structure of the pressure receiving member that receives the flow of the collapsed earth and sand. As shown in FIG. 13A, the pressure receiving member 27 in the present embodiment is formed with a pressure receiving body 27A-1 that is driven into the earth and sand of the embankment slope S (see FIG. 1) and receives the flow of the collapsed earth and sand. The portion 27 </ b> A and one locking portion 27 </ b> B that are locked to a cable body such as a wire 26 suspended from the optical fiber cable 16 are integrally formed.

  As shown in FIGS. 13A to 13C, the pressure receiving main body 27A has a plate-like member in the width direction in FIGS. 13A and 13B (left and right in FIGS. 13A and 13B). Direction) to be bent in the thickness direction and to have a loose V-shaped cross section, and the inner concave plate surface is formed as a receiving surface 27A-1 that receives the flow of collapsed earth and sand. Has been. By making the receiving surface 27A-1 concave as described above, the collapsed earth and sand are easily accumulated on the receiving surface 27A-1. 13A and 13C, the pressure receiving main body portion 27A has a pointed tip edge (lower edge in FIGS. 13A and 13C), and the pressure receiving main body portion 27A. Can be embedded in the earth and sand easily (see FIG. 15). At this time, the pressure receiving main body 27A is embedded in the earth and sand in such a posture that the receiving surface 27A-1 is substantially perpendicular to the inclination direction of the embankment slope S, as seen in FIG.

  As often seen in FIG. 13A, one locking portion 27B is formed at the centroid position of the receiving surface 27A-1. As is often seen in FIG. 13C, the locking portion 27B is formed with a locking hole 27B-1 for locking to the end portion of the wire 26 as a rope body. Thus, in this embodiment, since one latching | locking part 27B is provided in the centroid position of receiving surface 27A-1, when receiving surface 27A-1 of the pressure receiving member 27 receives the load from collapsed earth and sand. The tension generated in the wire 26 by the force from the locking portion 27B acts in one direction passing through the centroid.

  Therefore, when a load (pressure) is received from the collapsed earth and sand, the pressure receiving member 27 does not rotate around the locking portion 27B, as shown in FIG. 15, and the load is almost all over the receiving surface 27A-1. It will be received evenly, and will move downward following the collapsed sediment while maintaining the installation posture of the pressure receiving member 27 (see the solid line portion in FIG. 15) in the normal state before the occurrence of the sediment collapse (see two in FIG. 15). (See dotted line position). As a result, the pressure receiving member 27 completely receives the load from the collapsible earth and sand, and a large tension is generated in the wire 26 locked by the locking portion 27B. The tension is applied to the optical fiber cable via the wire 26. 16 is transmitted to the lowermost part of the easily deformable part 28, the lowermost part is bent and deformed, and the optical fiber core wires 22A and 22B are bent and surely disconnected.

  13A to 13C, only one locking portion 27B of the pressure receiving member 27 is provided at the centroid position of the receiving surface 27A-1, but the position of the locking portion 27B is not limited. The number is not limited to this, and can be appropriately designed as long as the resultant tension of the wire 26 passes through the centroid of the receiving surface. For example, in the form shown in FIGS. 14A to 14C, two locking portions 27B are provided on two side edges of the pressure receiving main body portion 27A (edge portions extending in the vertical direction in FIG. 13A). Each side edge is formed by cutting out the side edges (four in total). The center positions of these four locking portions 27B coincide with the centroid of the receiving surface 27A-1.

  In the form of FIGS. 14A to 14C, if the lower end of one wire 26 is branched into four, and they are locked to each of the four locking portions 27B, four locking Since the center positions of the portions 27B coincide with the centroid of the receiving surface 27A-1, when the receiving surface 27A-1 of the pressure receiving member 27 receives a load from the collapsed soil, the force from the locking portion 27B The resultant tension of the wire 26 acts in one direction passing through the centroid. Accordingly, the pressure receiving member 27 moves following the collapsed earth and sand while maintaining the installation position of the pressure receiving member 27 in the normal state, as in the embodiment of FIGS. The lowermost portion of the easily deformable portion 28 of the optical fiber cable 16 is bent and deformed by the tension, and the optical fiber core wires 22A and 22B are bent and surely disconnected.

  As described above, the pressure receiving member 27 does not use the weight of the pressure receiving member 27 itself as a force for deforming the easily deformable portion 28 of the metal tube of the optical fiber cable 16, but the pressure receiving member 27 receives from the collapsed soil. A load is used. Therefore, it is not necessary to increase the weight of the pressure receiving member 27 itself, and the pressure receiving member 27 can be made of a lightweight member, so that the installation work of embedding the pressure receiving member 27 in the earth and sand becomes easy.

  Also, a weight can be used as the pressure receiving member together with the pressure receiving member 27 or in place of the pressure receiving member 27, as described in the first embodiment. In this case, when the load due to the weight of the weight acts on the wire 26, the weight forms a pressure receiving member.

  Although this embodiment demonstrated the example which comprises a pressure receiving member with a plate-shaped member based on FIGS. 12-14, the pressure receiving member should just be a shape which can receive collapsed earth and sand, and is limited to plate shape. For example, it is also possible to comprise a bowl-shaped member. Further, the pressure receiving member may have a mesh or net-like pressure receiving surface for receiving earth and sand. By forming the pressure receiving surface in a mesh or net shape in this way, moisture permeates the pressure receiving surface. For example, rainwater accumulates in the pressure receiving member and the tension generated in the wire by the weight is transmitted to the optical fiber cable. Therefore, it is possible to prevent malfunction. Further, when the load of the member itself is applied to the wire 26 as in the embodiment using the weight described above, the pressure receiving member can be formed by the member.

  Although the already described first to fifth embodiments have been described separately, a plurality of these embodiments can be combined and implemented.

11, 11A, 11B, 11C, 11D Detection unit 16, 16A, 16B, 16C, 16D Optical fiber cable 18 Anchor member 21 Metal tube 21A Low strength portion 21B Stress concentration portion 22A, 22B Optical fiber core wire 22C Folding loop portion 23 Light source Part 24 light receiving part 26 wire (strand body)
27 Pressure-Receiving Member 27A Pressure-Receiving Body 27A-1 Receiving Surface 27B Locking Section 28 Easy Deformable Section 29, 30, 31 Suppressing Member

Claims (8)

In the system to detect ground collapse,
A light source unit that transmits an optical signal to the optical fiber core, a light receiving unit that receives the optical signal from the optical fiber core, and an optical fiber cable in which the optical fiber core that transmits the optical signal is inserted into a metal tube. And
The metal tube is provided with an easily deformable portion that makes deformation of the metal tube easier than outside the predetermined range when an external force is applied to the predetermined range over the longitudinal direction,
A ground collapse detection system that detects a ground collapse based on a change in an optical signal of an optical fiber core wire accompanying a deformation at an easily deformable portion of a metal pipe when the ground collapses.   The ground collapse detection system according to claim 1, wherein the easily deformable portion is formed by winding or bending the optical fiber cable at a local portion.   The easily deformable portion formed by winding or bending the optical fiber cable suppresses the displacement of the optical fiber cable in a direction perpendicular to a certain plane including the easily deformable portion, and the easily deformable portion is The ground collapse detection system according to claim 2, wherein a restraining member that is held in a plane is provided. The metal tube is engaged with a deformation promoting member for transmitting the load due to the collapse of the ground to the metal tube and promoting the deformation of the metal tube,
The ground collapse detection system according to claim 1, wherein a portion of the metal tube that engages with the deformation promoting member is formed as an easily deformable portion.   The metal pipe is provided with a low-strength portion that causes local deformation within the range of the easily deformable portion when an external force is applied within the range of the easily deformable portion. The ground collapse detection system according to one of the four.   6. The ground collapse detection system according to claim 5, wherein the low-strength portion is formed by caulking the metal tube with a straight line direction orthogonal to the axis as a caulking direction.   The optical fiber cable is configured such that when the ground collapses, a pressure receiving member that receives a load due to the collapse is attached so as to be able to transmit the received pressure to the easily deformable portion, and promotes deformation of the optical fiber cable. The ground collapse detection system according to claim 6.   The ground collapse detection system according to claim 7, wherein the pressure receiving member is attached to the optical fiber cable at a position where the pressure receiving force can be transmitted to the low strength portion.

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