JP2006266992A - Device and method for measuring landslide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for measuring landslide capable of preventing torsions from being accumulated in an optical fiber cord, and capable of facilitating maintenance work in a field. <P>SOLUTION: The device is provided with the optical fiber cord 17, and a displacement detecting part including a conversion means for converting a displacement acting via a tension line 20 into a rotational motion, and including a transmission means for transmitting the rotational motion to a winding shaft 15. A holding metal 16 having a holding part not bringing a light transmission loss by the bending in the optical fiber cord is fixed onto the winding shaft, one part of the optical fiber cord is formed into a U-shape, and a tip end thereof is held in the holding part of the holding metal. When the winding shaft is rotated by the displacement acting via the tension line, a parallel portion 17-1 formed into the U-shape in the optical fiber cord is wound onto the winding shaft, without generating the accumulated torsion, to impart the light transmission loss to the optical fiber cord. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a landslide measuring apparatus and method for measuring ground displacement using an optical fiber.

  In recent years, land development has also made rapid progress in mountainous areas. As a result, large-scale embankment work has been carried out on hillside slopes, and landslide disasters have occurred in various places along with natural disasters. In order to prevent these disasters in advance, it is important to monitor landslides during and after construction, and a landslide displacement measurement method that identifies the landslide boundaries in areas where landslides are suspected of being landslides is desired.

  Conventionally, an electric ground extensometer has been mainly used as a device for measuring the displacement of a landslide. On the other hand, a displacement measuring device using an optical fiber capable of constructing a long signal transmission line has been developed because it is resistant to electrical disturbances such as lightning, has excellent corrosion resistance, and has little signal attenuation with respect to distance.

  Patent Document 1 discloses a technique for detecting displacement by utilizing the fact that the number of turns of an optical fiber around a light-attenuating circular curve portion increases or decreases due to displacement and the transmitted light intensity of the optical fiber changes. Specifically, this technique is an optical displacement sensor that measures the amount of displacement using a change in transmitted light intensity due to a change in curvature of an optical fiber. This optical displacement sensor includes an optical non-attenuating circular curve portion and an optical attenuation circular curve portion in which an optical fiber is disposed in a relaxed state and an optical fiber is wound several times around two disks having different diameters. The disc diameter of the light non-attenuating circular curved portion is set to 35 mm or more at which transmitted light is not attenuated, and the disc diameter of the light attenuating circular curved portion is set to 30 mm or less at which transmitted light is attenuated. Furthermore, the number of turns of the optical fiber in the light non-attenuating circular curve portion and the light attenuating circular curve portion is changed by the amount of expansion / contraction of the wiring that is arranged in a tension state and expands / contracts according to the displacement of the displacement detection location. The winding ratio of the optical fiber around the disk is changed.

  A light-attenuating circular curve portion of the optical displacement sensor is shown in FIG. In this example, a part of the optical fiber cord 102 is fixed to the disk 101 constituting the light attenuation circular curve portion 100 and then wound. However, there is a problem that the optical fiber cord 102 is twisted when the optical fiber cord 102 is wound around the disk 101. Further, after the optical displacement sensor including the light attenuation circular curve portion 100 is installed at the measurement site, when the ground attenuation advances and the light attenuation circular curve portion 100 rotates, the twist of the optical fiber cord 102 is accumulated. There was a problem that the optical fiber cord 102 was damaged.

  Patent Document 1 also discloses an optical displacement sensor to which a technique for preventing twisting of the optical fiber cord as described above is applied. This optical displacement sensor uses the fact that an optical fiber cord wound in a coil shape is arranged on the outer periphery of a coil spring, and the optical transmission loss of the optical fiber changes due to the change of the pitch of the coiled optical fiber cord due to the displacement. ing.

  However, in landslide measurement, it is necessary to install a measuring device or perform maintenance outside the mountain. In particular, in a measuring apparatus provided with the optical displacement sensor as described above, it is necessary to replace the optical fiber cord inside the measuring apparatus that has deteriorated during the measurement period on site. However, there is a problem that the operation of winding an optical fiber cord in a coil shape around the outer periphery of the coil spring is practically impossible at the site. Moreover, another measuring device may be added in the middle of the optical fiber cord laid in a long range. In this case, it is necessary to cut the optical fiber once and weld it when the work of adding the measuring device is completed.

  Further, Patent Document 1 discloses an example in which a plurality of optical displacement sensors 200-1, 200-2, 200-3, 200-4 are arranged at each of a plurality of measurement target positions as shown in FIG. Has been. In this example, the disks 201-1, 201-2, 201-3, and 201-4 for rotating the light-attenuating circular curve portion of each optical displacement sensor are mechanically coupled by a wiring 202 such as a wire. That is, one wiring 202 is wound around the disks 201-1 to 201-4 of the optical displacement sensors 200-1 to 200-4 several times in order. For this reason, all the continuous optical displacement sensors may detect the ground displacement due to the ground displacement generated in one measurement section. Therefore, there is a problem that it is difficult to specify the boundary of the landslide in an area where the ground displacement due to the landslide is suspected.

JP 2003-057013 A

  An object of the present invention is to provide a landslide measuring apparatus and a measuring method capable of specifying a boundary of a landslide.

  Another object of the present invention is to provide a landslide measuring apparatus and a measuring method that can prevent the twisting from being accumulated in the optical fiber cord and can facilitate the maintenance work on site.

  According to the first aspect of the present invention, the displacement includes an optical fiber cord, conversion means for converting a displacement acting via a tensile wire into a rotational motion, and a transmission means for transmitting the rotational motion to a winding shaft. A detecting portion, and a holding portion having a shape that does not give an optical transmission loss due to bending to the optical fiber cord is fixed to the winding shaft, and a part of the optical fiber cord is made U-shaped and a tip thereof is When the winding shaft is rotated by a displacement acting on the holding portion and acting through the tension wire, the U-shaped parallel portion of the optical fiber cord does not cause cumulative twisting and the winding shaft A landslide measuring device is provided, characterized in that an optical transmission loss is given to the optical fiber cord.

  In the landslide measuring apparatus according to the first aspect of the present invention, the converting means includes a first gear having the tension wire, a pulley wound around one end of the tension wire, and a rotation shaft concentric with the pulley. The transmission means includes: a second gear meshed with the first gear; and the winding shaft having a rotation axis concentric with the second gear, and the optical fiber cord On the opposite side to the tip of the U-shaped parallel portion, tension is applied in the direction opposite to the winding around the winding shaft by the first spring body via the parallel holding fixture, A rotational force is applied to the gear 1 in a direction opposite to the tensile force due to the tensile wire by a second spring body, a fixture is attached to the other end of the tensile wire, and the U of the optical fiber cord is attached. One of the extended parallel parts is used to hold the parallel part. The displacement detection unit, the parallel holding fixture, and the first and second spring bodies are arranged on the first pile so as to reach the OTDR (Optical Time Domain Reflectometer) through the fixture and the fixture. The second pile is installed at a location away from the first pile, and another fixture is disposed on the second pile, and the light is placed between the fixture and the other fixture. Relative displacement between the first pile and the second pile can be measured by the OTDR in which the extension portion of the fiber cord is installed and the ends of the extension portion are connected.

  According to the third aspect of the present invention, the optical fiber cord, the corrugated leaf spring having a plurality of peaks and valleys, and the optical fiber cord that is provided in a portion of the corrugated leaf spring close to the plurality of peaks are held. A displacement detecting unit including a plurality of holding members for holding the optical fiber cord so as to meander in the expansion and contraction direction of the corrugated spring by the plurality of holding members. The optical fiber cord in between is formed into a substantially semicircular arc shape, and the optical transmission loss of the optical fiber cord is changed by changing the curvature of the substantially semicircular arc shape of the optical fiber cord by expansion and contraction of the wave spring. A landslide measuring device characterized by the above is provided.

  In the landslide measuring apparatus according to the third aspect of the present invention, the holding member is formed of a split cylindrical member, a fixing tool is provided on the corrugated spring, and the optical fiber cord passes through the fixing tool. OTDR (Optical Time Domain Reflectometer) is reached, the displacement detector is placed on the first pile, and a second pile with another fixture is placed at a location away from the first pile. In addition, by laying the optical fiber cord between the fixture and the other fixture, the relative displacement between the first pile and the second pile can be changed via the optical fiber cord. Can be transmitted to the corrugated spring.

  In any of the landslide measuring apparatuses according to the first and third aspects of the present invention, a tensile wire may be installed between the fixture and the another fixture instead of the optical fiber cord.

  According to a sixth aspect of the present invention, a plurality of the landslide measuring devices according to any one of the above are assembled and arranged in series so as not to be mechanically coupled to one optical fiber cord. A landslide measurement method is provided.

  In the landslide measuring apparatus according to claim 1, since the optical fiber cord is substantially U-shaped and the parallel portion thereof is wound around the winding shaft, the optical fiber cord is not subjected to cumulative twisting. Therefore, the durability and safety of the optical fiber cord can be improved. Further, even when a measuring device is added in the middle of an optical fiber laid in a long range, workability is improved because it is not necessary to cut the optical fiber.

  In the landslide measuring apparatus according to claim 3, since the optical fiber cord is held by the holding member provided on the corrugated spring, the optical fiber inside the measuring apparatus that has deteriorated during the measurement period is replaced locally. Even if it exists, the attachment or detachment of the optical fiber cord to the holding member is easy, and the replacement work is simple. Further, even when a measuring device is added in the middle of an optical fiber laid in a long range, workability is improved because it is not necessary to cut the optical fiber.

  According to the sixth aspect of the present invention, when a plurality of landslide measuring devices are assembled and arranged in one optical fiber cord, and the measurement is performed, the portion of the optical fiber cord or the tensile wire installed in each measurement section is mechanically Therefore, there is no problem that the landslide measuring device in another measurement section detects the displacement due to the displacement generated in one measurement section.

  Next, embodiments of the landslide measuring apparatus and method according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a first embodiment of the present invention and shows a basic configuration of a displacement detection unit of a landslide measuring apparatus according to the first aspect of the present invention.

  In FIG. 1, the first pulley 11, the second pulley 12, and the first gear 13 are concentrically combined so as to have the same rotation axis. A second gear 14 is meshed with the first gear 13, and the winding shaft 15 is concentrically attached to the second gear 14 so that the winding shaft 15 has the same rotation axis. A holding metal fitting 16 for holding the optical fiber cord 17 is fixed to the winding shaft 15. The holding portion of the optical fiber cord 17 in the holding fixture 16 has a peripheral shape with a curvature that does not give optical transmission loss due to bending to the optical fiber cord 17. A part of the optical fiber cord 17 is U-shaped, and a U-shaped parallel portion 17-1 is turned around the winding shaft when the winding shaft 16 is rotated by hooking the U-shaped tip side onto the holding portion of the holding metal fitting 16. 16 is wound around.

  The U-shaped parallel portion 17-1 in the optical fiber cord 17 is also maintained in a parallel state by fixing and holding the portion on the opposite side to the tip side with a first fixing bracket (fixing bracket for parallel holding) 18. I try to do it. One of the parallel parts fixed and held is guided to an OTDR (Optical Time Domain Reflectmeter) 35 (see FIG. 2) side through a second fixing bracket (fixing bracket) 19. The other of the fixed and held parallel parts is guided to the next displacement detection unit or is opened if there is no next displacement detection unit.

  To briefly explain an example of the function of OTDR, when an optical signal (light pulse) is incident on an optical fiber cord from OTDR, a local displacement (for example, a straight line portion is deformed into a curve) occurs in the optical fiber cord. The refractive index of that portion changes. As a result, Rayleigh backscattered light is generated and returned to OTDR. Rayleigh backscattered light returns to OTDR after a time proportional to the distance from the incident end of the optical signal to the location where the Rayleigh backscattered light is generated, and the light intensity (light transmission loss) depends on the change in refractive index, that is, the magnitude of displacement. To do. From this, in OTDR, the magnitude | size and position of the displacement which generate | occur | produced in the optical fiber cord can be known from the return time and light intensity of Rayleigh backscattered light.

  A tensile force is applied to the first fixing bracket 18 by the first spring body 21. A tension line 20 is stretched between the first pulley 11 and the second fixing bracket 19, and a tension force is applied to the second pulley 12 by a second spring body 22.

  As described above, the tension wire 20 is fixed to the first pulley 11 and wound around the first pulley 11, thereby converting the displacement of the tension wire 20 into the rotational motion of the first pulley 11. In the present embodiment, a wire is used as the tensile wire 20, but it goes without saying that the same effect can be obtained even if another material such as Invar is used. The reaction force of the tension wire 20 is obtained by the second spring body 22 attached to the second pulley 12 on the same rotation axis as the first pulley 11.

  In any case, the optical fiber cord 17 extending to the OTDR side and the optical fiber 17 extending to the next displacement detection unit side with the first holding metal fitting 18 as a boundary is in a state where no tension acts between them, that is, mechanically. It is made not to be connected to.

  The first pulley 11 is rotated by a first gear 13 fixed to the same rotation shaft as the first pulley 11 and a second gear 14 fixed to a shaft different from the rotation shaft of the first gear 13. This is transmitted as the rotation of the winding shaft 15 fixed to the same rotation shaft as the second gear 14. The rotation speed of the winding shaft 15 per unit displacement length of the tensile wire 20 is determined by the predetermined gear ratio between the first gear 13 and the second gear 14. Specifically, the rotation speed of the winding shaft 15 is set with a gear ratio of about 0.5 to 5.

  In this embodiment, a structure using two gears is used to transmit the rotation of the first pulley 11 to the rotation of the winding shaft 15, but two pulleys and a belt may be used, or two or more pulleys may be used. It goes without saying that the same effect can be obtained even when gears are used. Furthermore, it goes without saying that the first pulley 11, the first gear 13, the second gear 14, and the winding shaft 15 are attached to the chassis or the housing via a bearing using a ball bearing or the like.

  As described above, the winding shaft 15 has a curvature shape that does not give optical transmission loss due to bending to the optical fiber cord 17, specifically, a holding bracket 16 having a circular or semicircular holding portion having a diameter of about 3 cm. Is fixed. A part of the optical fiber cord 17 is U-shaped, and the tip side thereof is hung on the holding metal fitting 16. Further, tension is applied to the optical fiber cord 17 by the first spring body 21 via the first fixing bracket 18. For example, in this embodiment, a tension of 0.2 kgf is applied. In FIG. 1, spring springs are shown as the first and second spring bodies, but the same effect can be obtained with a spring spring or the like.

  When the winding shaft 15 is rotated by the displacement of the tensile wire 20 as described above, the optical fiber cord 17 is wound around the winding shaft 15 by the U-shaped parallel portion 17-1, and the optical fiber cord 17 is cumulatively twisted. Does not occur. When the winding shaft 15 rotates due to the displacement of the tensile wire 20, the parallel portion 17-1 of the optical fiber cord 17 is wound, so that the curvature of the optical fiber cord 17 changes and the refractive index changes. As a result, the optical fiber cord 17 has an optical transmission loss. In the present embodiment, the winding shaft 15 has a diameter of about 10 mm to 20 mm. As the diameter of the winding shaft 15 becomes thinner, the optical transmission loss of the optical fiber cord 17 with respect to the number of windings becomes larger. The optical transmission loss of the optical fiber cord 17 per unit displacement length of the tensile wire 20 is set by the gear ratio and the diameter of the winding shaft 15.

  FIG. 2 shows the configuration of a landslide measuring apparatus using the basic configuration of the displacement detector described in FIG. The basic configuration shown in FIG. 1 is housed in a housing or the like and placed on the first pile 31 installed on the ground slope. A second pile 32 is also installed on the ground slope at a position away from the first pile 31. One of the parallel portions 17-1 of the optical fiber cord 17 led out from the first fixing bracket 18 is fixed on the second fixing bracket 19 connected to one end of the tensile wire 20 and the second pile 32. It is installed between the fixing bracket (another fixing bracket) 33.

  When relative displacement occurs between the first pile 31 and the second pile 32, the installed optical fiber cord 17 is displaced, and the tensile wire 20 connected thereto is displaced, so that the first pulley 11, The first gear 13, the second gear 14, and the winding shaft 15 are rotated so that the parallel portion 17-1 of the optical fiber cord 17 is wound.

  In this embodiment, an optical fiber cord 17 in which an aramid fiber is arranged as a tensile strength body and an optical fiber core wire inside the coating is used. The optical fiber cord 17 is installed with a tension of about 1.5 kgf and is balanced with the tension of the first spring body 21 and the second spring body 22 shown in FIG. However, it goes without saying that the same effect can be obtained even if an optical fiber cord or the like containing a wire is used as the optical fiber cord 17. Further, it goes without saying that the same effect can be obtained even when a wire or an invar line is used separately from the optical fiber cord 17 as means for transmitting the displacement. In this case, a wire or an invar line is installed as a tension line between the second fixing bracket 19 and the third fixing bracket 33, and the optical fiber cord 17 is laid without tension. Of course, the tension wire between the second fixing bracket 19 and the third fixing bracket 33 may be realized by extending the tension wire 20, and in this case, the second fixing bracket 19 is unnecessary. In addition, it goes without saying that the optical fiber cord 17 in the installed or laid part is cured by an installed protective tube not shown here, and in a relaxed state between the installed section and the OTDR 35 and between the measurement sections. It goes without saying that the installed optical fiber cord 17 is also cured by a protective tube. Further, the holding metal fitting 16 and the first and second fixing metal fittings 18 and 19 do not need to be made of metal.

  The optical transmission loss of the optical fiber cord 17 on the winding shaft 15 is measured by an OTDR (optical pulse measuring method) 35 connected to the end of the optical fiber cord 18. An actual measurement example of the optical transmission loss of the optical fiber cord 17 is shown in FIG. Here, the gear ratio of the gear structure (the number of teeth of the first gear 13 / the number of teeth of the second gear 14 in FIG. 1) is five times and the diameter of the winding shaft 15 is 11 mm. As apparent from FIG. 3, the optical transmission loss increases substantially in proportion to the displacement amount of the tensile wire 20, so the displacement amount of the tensile wire 20 from the optical transmission loss, that is, the first pile 31 and the second pile 32. The relative amount of displacement can be known.

  FIG. 4 shows a second embodiment of the present invention, and shows a basic configuration of a displacement detection unit of a landslide measuring apparatus according to the third aspect of the present invention.

  In FIG. 4, the displacement detection unit has an optical fiber cord 17 and a telescopic wave plate spring 41 having a plurality of peaks and valleys, and a portion close to each mountain of the wave plate spring 41 follows the ridgeline. A holding member 42 is provided. The holding member 42 is for holding the optical fiber cord 17. A fixing fitting 36 is also attached to one end side of the corrugated spring 41 so that no tension acts on the optical fiber cord 17 between the fixing fitting 36 and the corrugated spring 41.

  The optical fiber cord 17 meanders in the extending and contracting direction of the wave plate spring 41 by being held by a plurality of holding members 42 fixed to the wave plate spring 41. That is, in the optical fiber cord 17, the portion held by the holding member 42 is a straight line, and is formed in a substantially semicircular arc shape between adjacent holding members 42.

  As shown in FIG. 5, when the corrugated spring 41 is expanded and contracted, the interval between the crests of the corrugated spring 41 changes, so that the curvature of the optical fiber cord 17 having a substantially semicircular arc shape between the holding members 42 changes. The optical fiber cord 17 has a structure that changes the optical transmission loss.

  As shown in FIG. 6, the holding member 42 of the optical fiber cord 17 has a split cylindrical shape, and is fixed to each portion of the corrugated spring 41 near each mountain with an adhesive or the like. The optical fiber cord 17 opens the split of the holding member 42 and is disposed inside the holding member 42. Since the inner diameter of the holding member 42 is set slightly smaller than the outer diameter of the optical fiber cord 17, the optical fiber cord 17 is tightened by the restoring force of the holding member 42. Although the holding member 42 is formed of a plastic material, the same effect can be obtained even when rubber or metal is used. The holding member 42 may also be realized by installing a plurality of substantially C-shaped holding portions at intervals without using a cylindrical member.

  The optical fiber cord 17 between the holding members 42 has a shape that draws a substantially semicircular arc. However, the optical transmission loss of the optical fiber cord 17 varies depending on the expansion / contraction state of the wave spring 41 and the substantially semicircular shape of the optical fiber cord 17. . Therefore, the expansion and contraction state of the corrugated spring 41 and the shape of the substantially semicircular arc of the optical fiber cord 17 are defined using a shaping jig 50 as shown in FIG.

  In FIG. 6, the shaping jig 50 has a plurality of peaks 51, and substantially semi-cylindrical portions 52 are alternately provided at locations corresponding to the valleys between the peaks 51. The substantially semi-cylindrical portion 52 defines the curvature of the substantially semicircular arc shape of the optical fiber cord 17. That is, the optical fiber cord 17 is held by the holding member 42 in a state where the crest 51 of the shaping jig 50 is covered with the corrugated spring 41. At this time, the optical fiber connector 17 between the adjacent holding members 42 is made to follow the substantially semi-cylindrical portion 62. Thereafter, the shaping jig 50 is removed.

  The corrugated spring 41 is made such that the distance between the peaks changes in the range of about 1 cm to 3 cm due to the expansion and contraction thereof. The expansion / contraction amount of the entire corrugated spring 41 can be adjusted by the number of peaks of the corrugated spring 41. The shaping jig 50 is made to have four peaks 51 as an example in FIG. 6, but is made to have the maximum number of peaks assumed for the corrugated spring 41. If such a shaping jig is prepared, any corrugated spring having a maximum number of peaks or less can be handled.

  FIG. 7 shows the configuration of a landslide measuring apparatus using the basic configuration of the displacement detector described in FIG. The displacement detection part shown in FIG. 4 is arrange | positioned on the 1st pile 31 installed on the ground slope, and is cured with the storage box etc. which are not shown here. A second pile 32 is installed on the ground slope away from the first pile 31. A tensile wire is laid between the fixing bracket 36 on the first pile 31 and fixed to the corrugated spring 41 and the fixing bracket (another fixing bracket) 33 disposed on the second pile 32. The tension of the tension wire is obtained by the corrugated spring 41. Specifically, the tension of the tension wire is about 0.5 kgf to 2 kgf.

  In this embodiment, the optical fiber cord 17 held by the holding member 42 attached to the corrugated spring 41 is shared as a tensile wire. However, as described with reference to FIG. However, the same effect can be obtained. In this embodiment, the optical fiber cord 17 uses an optical fiber core wire and an aramid fiber disposed as a tensile body inside the coating. The tension of the tension wire at the erected portion is balanced by the corrugated leaf spring 41 through the fixing bracket 36, and no tension is applied to the portion of the optical fiber cord 17 held by the holding member.

  When relative displacement occurs between the first pile 31 and the second pile 32, the corrugated spring 41 to which the installed optical fiber cord 17 is connected expands and contracts. As described above, when the corrugated leaf spring 41 expands and contracts, the curvature of the optical fiber cord 17 having a substantially semicircular arc shape between the holding members 42 changes, and the optical transmission loss of the optical fiber cord 17 changes. The optical transmission loss amount of the optical fiber cord 17 is measured by the OTDR 35 connected to the end of the optical fiber cord 17. The amount of expansion / contraction of the corrugated spring 41, that is, the relative displacement of the first pile 31 and the second pile 32 can be known from the amount of optical transmission loss.

  FIG. 8 is a diagram showing an example in which the landslide measuring apparatus according to the invention of claim 1 is used, that is, the landslide measuring system according to the invention of claim 6 is configured using the landslide measuring apparatus shown in FIGS. 1 and 2. is there. Of course, the same effect can be obtained even when the landslide measuring apparatus according to the third aspect of the present invention, that is, the landslide measuring apparatus shown in FIGS. 4 and 7 is used.

  This landslide measurement system is characterized in that a plurality of landslide measurement devices are assembled and arranged in one optical fiber cord. As described in FIG. 2, the first landslide measuring device 10 </ b> A is arranged on the first pile 31 installed on the ground slope. A second pile 32 is installed on the ground slope away from the first pile 31. As described with reference to FIG. 1, one of the parallel portions 17-1 of the optical fiber cord 17 in the first landslide measuring apparatus 10 </ b> A is led out to the OTDR 35 side via the first fixing bracket 18 and the second fixing bracket 19. The The derived optical fiber cord 17 is connected to the OTDR 35 via a fixing bracket 33 disposed on the second pile 32. As described above, the optical fiber cord 17 that goes to the OTDR 35 side through the first and second fixtures 18 and 19 and the optical fiber cord 17 that goes to the next landslide measuring device side through the first fixture 18 The tension acting on one side is prevented from acting on the other.

  The other of the parallel portions 17-1 of the optical fiber cord 17 is led out to the next landslide measuring device side through the first fixing bracket 18. In particular, the next second landslide measuring device 10 </ b> B is arranged on the third pile 37 installed on the ground slope away from the first pile 31. Then, one of the parallel portions 17-1 of the optical fiber cord 17 in the second landslide measuring device 10B is led out to the first landslide measuring device 10A side through the first fixing bracket 18 and the second fixing bracket 19. The However, between the 1st pile 31 and the 3rd pile 37, the 4th pile 38 is installed in the place near the 1st pile 31, and the optical fiber cord 17 is put on the 4th pile 38. A fixing bracket 39 for holding is disposed. Thereby, the optical fiber cord 17 between the fourth pile 38 and the first landslide measuring apparatus 10A is in a relaxed state in which no tension acts. The same applies to the third landslide measuring device installed next to the second landslide measuring device 10B and the subsequent steps.

  When the OTDR 35 is displaced in at least one of the plurality of landslide measuring devices assembled to the optical fiber cord 17, the magnitude of the optical transmission loss and the position where the optical fiber loss is generated can be known. Therefore, by assembling a plurality of landslide measuring devices to one optical fiber cord 17, the corresponding measurement section is determined from the position where the optical transmission loss is generated, and two of the corresponding measurement sections are determined from the amount of the optical transmission loss. The relative displacement of the pile can be judged.

  According to the measurement method shown in FIG. 8, the optical fiber cords 17 installed in each measurement section are not mechanically coupled, so one measurement is performed unless a landslide that includes a plurality of measurement sections occurs. There is no problem that the optical displacement sensor in the other measurement section detects the displacement due to the displacement generated in the section. That is, in FIG. 8, the first landslide measuring apparatus 10 </ b> A detects only the relative displacement between the first pile 31 and the second pile 32. The second landslide measuring device 10B does not react to the relative displacement between the first pile 31 and the second pile 32, but only the relative displacement between the third pile 37 and the fourth pile 38. To detect. Therefore, when the boundary of the landslide is specified in an area where the ground displacement due to the landslide is suspected, the measurement section in which the ground displacement due to the landslide is generated can be accurately specified.

  In the embodiment shown in FIG. 8, two piles are used in one measurement section. However, as shown in FIG. 9, the measurement adjacent to the pile (for example, the first pile 31) that fixes the landslide measuring device. Even if a pile (for example, the fourth pile 38) for laying the optical fiber cords in the section is shared, the same effect can be obtained. That is, 10 A of 1st landslide measuring apparatuses detect only the relative displacement between the 1st pile 31 and the 2nd pile 32, and the 2nd landslide measuring apparatus 10B is the 1st pile 31 and the 2nd pile. The relative displacement between the third pile 37 and the first pile 31 is only detected. As described above, in the first landslide measuring apparatus 10A, the optical fiber cord 17 from the second fixing bracket 19 toward the OTDR 35 side and the second landslide measuring apparatus 10B side from the first fixing bracket 18 are used. This is because it is not mechanically coupled to the optical fiber cord 17 toward the front. In this case, referring to FIG. 9, the fixing bracket 39 arranged on the fourth pile 38 is arranged on the first pile 31.

  As is apparent from the above description, according to the landslide measuring apparatus according to the first embodiment, the number of windings of the optical fiber cord 17 on the winding shaft 15 increases or decreases due to ground displacement, and the optical transmission loss changes. When the ground displacement is detected by using the optical fiber cord 17 by winding the parallel portion 17-1 of the substantially U-shaped optical fiber cord 17 around the winding shaft 15, the optical fiber cord 17 is not twisted. The durability and safety of the fiber cord 17 can be secured. In addition, when a measuring device is added in the middle of an optical fiber cord laid in a long range, workability is improved because it is not necessary to cut and weld the optical fiber cord.

  Further, according to the landslide measuring apparatus according to the second embodiment, not only does the cumulative twisting not occur in the optical fiber cord 17, but also a simple configuration by the combination of the corrugated spring and the holding member, the measurement period. Even if it becomes necessary to replace the optical fiber inside the measuring device that has deteriorated inside, replacement work is easy. Further, when a measuring device is added in the middle of an optical fiber cord laid in a long range, it is not necessary to cut and weld the optical fiber cord, so that workability is greatly improved.

  Furthermore, according to the landslide measuring method using the landslide measuring apparatus according to the first and second embodiments, the following effects can be obtained when the landslide boundary is specified in an area where the ground displacement due to the landslide is suspected. . Even if an area where the ground displacement due to landslide is suspected is quite wide, one or a few optical fiber cords are laid in the area, and the landslide measurement according to the first and second embodiments is carried on the optical fiber cord. By assembling and arranging a plurality of devices, it is possible to specify a measurement section in which ground displacement due to landslide has occurred from the position where the optical transmission line loss generated on the optical fiber cord has changed. At this time, since the optical fiber cords (tensile lines) of the portions installed in each measurement section are not mechanically coupled, the displacement detector connected by the displacement generated in one measurement section does not detect the displacement, Only the measurement section where the ground displacement occurs can be specified accurately.

  In areas where landslides are suspected, it is necessary to measure not only the surface displacement but also the underground displacement, pore water pressure, groundwater level, and ground slope by installing appropriate measuring equipment. Therefore, when the area where a landslide is suspected is large, the number of the above-mentioned various measuring devices must be increased. On the other hand, by grasping the landslide area and boundary in advance by the landslide measuring method according to the present invention, it is possible to plan the arrangement of the measuring instruments efficiently, and the economic effect obtained thereby is great. .

FIG. 1 is a diagram showing a basic configuration of a displacement detection unit of a landslide measuring apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram showing a configuration of a landslide measuring apparatus using the basic configuration of the displacement detection unit shown in FIG. FIG. 3 is a diagram showing an actual measurement example of the amount of optical transmission loss generated in the optical fiber cord when the displacement of the tensile wire shown in FIG. 1 acts on the optical fiber cord via the winding shaft. FIG. 4 is a diagram showing a basic configuration of a displacement detector of the landslide measuring apparatus according to the second embodiment of the present invention. FIG. 5 is a diagram showing a change state of the expansion and contraction of the corrugated spring and the curvature of the optical fiber cord in the landslide measuring apparatus shown in FIG. FIG. 6 is a view for explaining the structure of the shaping jig used when assembling the optical fiber cord and the holding member of the optical fiber cord in the landslide measuring apparatus shown in FIG. FIG. 7 is a diagram showing a configuration of a landslide measuring apparatus using the basic configuration of the displacement detector shown in FIG. FIG. 8 is a diagram showing a configuration of a landslide measuring method in which a plurality of landslide measuring apparatuses shown in FIG. 2 are combined. FIG. 9 is a diagram showing a modification of the landslide measurement method shown in FIG. FIG. 10 is a diagram showing the structure of a light-attenuating circular curved portion of an optical fiber that is a part of a conventional optical displacement sensor. FIG. 11 is a diagram showing an example in which the conventional optical displacement sensors shown in FIG. 10 are connected and arranged at a plurality of measurement target positions.

Explanation of symbols

10, 10A, 10B Landslide measuring device 11, 12 First and second pulleys 13, 14 First and second gears 15 Winding shaft 16 Holding bracket 17 Optical fiber cord 17-1 Parallel portion 18, 19 First, Second fixing bracket 20 Tension line 21, 22 First and second spring bodies 31, 32, 37, 38 First, second, third, and fourth piles 33, 36 Fixing bracket 41 Corrugated leaf spring 42 Holding Member 50 Shaping jig 51 Mountain 52 Almost semi-cylindrical part

Claims (6)

A displacement detection unit including an optical fiber cord, a conversion unit that converts a displacement acting via a tensile wire into a rotational motion, and a transmission unit that transmits the rotational motion to a winding shaft;
A holding portion having a shape that does not give optical transmission loss due to bending with respect to the optical fiber cord is fixed to the winding shaft,
A part of the optical fiber cord is U-shaped and its tip is hung on the holding part
When the winding shaft rotates due to the displacement acting through the tension wire, the U-shaped parallel portion of the optical fiber cord is wound around the winding shaft without causing a cumulative twist, and the light Landslide measuring device characterized in that an optical transmission loss is given to the fiber cord. The converting means includes the tension wire, a pulley around which one end of the tension wire is wound, and a first gear having a rotation axis concentric with the pulley,
The transmission means includes a second gear meshed with the first gear, and the winding shaft having a rotation axis concentric with the second gear,
In the U-shaped parallel portion of the optical fiber cord, on the side opposite to the tip, in the direction opposite to the winding around the winding shaft by the first spring body via the parallel holding fixture. Give tension,
A rotational force is applied to the first gear in a direction opposite to the tensile force caused by the tensile wire by the second spring body,
A fixture is attached to the other end of the tensile wire, and one extension portion of the U-shaped parallel portion of the optical fiber cord is connected to the parallel holding fixture and the fixture, and OTDR (Optical Time Domain). To Reflectometer)
The displacement detector, the parallel holding fixture, and the first and second spring bodies are arranged on a first pile,
A second pile is installed at a location away from the first pile, and another fixing tool is disposed on the second pile, and the optical fiber is interposed between the fixing tool and the another fixing tool. 2. The relative displacement between the first pile and the second pile is measured by the OTDR in which the extension portion of the cord is installed and ends of the extension portion are connected. Landslide measuring device described in 1. An optical fiber cord;
A corrugated spring having a plurality of peaks and valleys;
A displacement detector including a plurality of holding members for holding the optical fiber cords, each provided at a portion near the plurality of peaks of the wave spring;
The optical fiber cord is held by the plurality of holding members so as to meander in the expansion / contraction direction of the wave spring, and the optical fiber cord between adjacent holding members is formed in a substantially semicircular arc shape,
A landslide measuring apparatus characterized in that the optical transmission loss of the optical fiber cord is changed by changing the curvature of the substantially semicircular arc shape of the optical fiber cord by expansion and contraction of the corrugated spring. The holding member is composed of a split cylindrical member,
The corrugated spring is provided with a fixture, and the optical fiber cord passes through the fixture to an OTDR (Optical Time Domain Reflectometer).
Placing the displacement detector on the first pile;
By installing a second pile in which another fixing tool is disposed at a location away from the first pile, and by laying the optical fiber cord between the fixing tool and the another fixing tool, The landslide measuring apparatus according to claim 3, wherein a relative displacement between the first pile and the second pile is transmitted to the corrugated spring through the optical fiber cord.   The landslide measuring apparatus according to claim 2 or 4, wherein a tension wire is installed between the fixture and the another fixture instead of the optical fiber cord.   A plurality of landslide measuring devices according to any one of claims 1 to 5, wherein a plurality of landslide measuring devices are assembled and arranged in series so as not to be mechanically coupled to one optical fiber cord.

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