JP3880765B2 - Underground optical fiber sensor and optical fiber sensor system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an underground optical fiber sensor, and more particularly to an optical fiber sensor for measuring deformation in the underground and an optical fiber sensor system thereof.
[0002]
[Prior art]
Conventionally, as a sensor to detect the deformation of the earth structure,
(1) Although there are sensors such as strain gauges and landslide meters attached to long members, they are point-to-point measurement.
[0003]
(2) At present, the optical fiber sensor is used as a method for measuring distortion of a concrete member or deformation on the surface of the embankment.
[0004]
[Problems to be solved by the invention]
However, in the point-to-point measurement of the conventional technique (1) described above, measurement points are independent at each point, and it has not been possible to continuously measure several tens of kilometers.
[0005]
In addition, the optical fiber sensor of the above-described conventional technique (2) is used as a method for measuring distortion of a concrete member or deformation on the surface of the embankment, but in order to measure detailed deformation in the ground. It is currently not used.
[0006]
An object of the present invention is to provide an underground optical fiber sensor and an optical fiber sensor system thereof that can eliminate the above-mentioned problems and can measure detailed deformation in the ground.
[0007]
[Means for Solving the Invention]
In order to achieve the above object, the present invention provides
[1] An underground optical fiber sensor in which a deformation detection sensor for an earth structure using an optical fiber is installed at a measurement point, and the deformation detection sensor for the earth structure easily follows the deformation of the earth. winding an optical fiber on the the tip of the structure is easily sticks to the punch 設時, withdrawn when a force acts in a direction, pile der having a fixing plate provided with withdrawn resistor member so the upper open The pile is placed directly on the measurement point together with the outer pipe, and only the deformation detection sensor of the earth structure is left in the ground and installed.
[0008]
[2] In underground optical fiber sensor according to [1] before SL earth follow easiness I構 Zotai the deformation is characterized by a split hollow rod.
[0009]
[ 3 ] The underground optical fiber sensor according to [1], wherein the structure that easily follows the deformation of the soil is a bellows type structure.
[0010]
[ 4 ] A plurality of earth structure deformation detection sensors using the optical fiber described in [1] above are disposed in the monitoring area, and the monitoring area is detected by comparing with a reference optical fiber. Features.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0012]
FIG. 1 is a layout view of an underground optical fiber sensor showing an embodiment of the present invention.
[0013]
As shown in FIG. 1, a high-rigidity tubular pile 3 such as a steel pipe or FRP pipe on which an optical fiber sensor (optical fiber part) 2 is mounted is driven into an embanked area 1 and an optical fiber 4 is laid. In that case, a reference optical fiber 5 is arranged.
[0014]
In the case of the above-described tubular pile 3 such as a steel pipe or an FRP pipe, here, the optical fiber portion 2 is attached to the inner pipe of the hollow portion 3A inside the tubular pile 3 as shown in FIG. . This is advantageous because even when the tubular pile 3 is driven, the optical fiber portion 2 is not damaged. However, it may be wound around the outer side of the tubular pile 3 so that the optical fiber portion 2 can be easily laid.
[0015]
Therefore, light is introduced from the light source 6 through the first optical coupler 4a to the optical fiber 5 serving as a reference and the optical fiber 4 disposed in the embankment 1 and light is transmitted through both the optical fiber 5 and the optical fiber 4, respectively. The optical waveguide 5 and the optical fiber 4 are converted into electricity by an O / E (optical / electrical) converter 7 via a second optical coupler 4b and demodulated by a passive homodyne demodulator 8. The electrical output state from the optical fiber 5 and the optical fiber 4 is monitored by the measuring device 9.
[0016]
Therefore, for example, when the deformation is in the embankment, the path of the optical fiber 4 is changed. That is, the tubular pile 3 is displaced. Then, the waveguide state of light in the optical fiber 4 changes, and a deviation occurs when compared with the waveguide state of light in the optical fiber 5 serving as a reference. The deviation can be measured by the measuring device 9. it can.
[0017]
In addition, when a destructive deformation occurs inside the embankment, a large change occurs in the optical fiber 4, and when the state of the guided light of the optical fiber 5 becomes large, An alarm may be issued by the alarm device 10 that is linked to the measuring device 9.
[0018]
Depending on how the structure of the optical fiber sensor is to be monitored, the arrangement of various optical fiber sensors may be selected.
[0019]
FIG. 3 is a block diagram of an underground optical fiber sensor showing another embodiment of the present invention, which constitutes a flexible tubular pile.
[0020]
In this embodiment, (1) as shown in FIG. 3A, an optical fiber portion (optical fiber sensor) 12 is wound around a divided hollow FRP rod 11 (about 10 to 20 cm). Also, a fixing plate 14 is provided at the tip of the inner tube so that it can be easily pierced.
[0021]
Further, an optical fiber portion (optical fiber sensor) 12 wound around such a hollow FRP rod 11 is protected by a placement outer tube 13 as shown in FIG. And lay in the ground.
[0022]
(2) Further, as shown in FIG. 3C, an optical fiber portion 22 may be wound around the bellows type tube 21. In this case, it may be protected by the placement outer tube 23 and laid in the ground. In addition, a fixing plate 24 is installed at the tip of the inner tube so as to be easily stuck.
[0023]
As an installation method, a sensor is inserted in a hollow tube that can be placed, and the sensor is placed simultaneously with the outer tube. When the target depth is reached, the outer tube is pulled out while the inner tube sensor remains in the ground.
[0024]
As shown in FIG. 4A, in order to make it difficult for the optical fiber sensor to be pulled out after the optical fiber sensor is installed on the fixing plate 16 of the pile 15, as shown in FIG. It is desirable to provide a pull-out resistance member 16A that opens when the force acts in the pull-out direction.
[0025]
Moreover, according to said description, although the pile was demonstrated as a hollow type, a solid type may be sufficient. In that sense, the pile may be a structure that can easily follow the deformation of the soil.
[0026]
FIG. 5 is a block diagram of an underground optical fiber sensor showing still another embodiment of the present invention.
[0027]
As shown in FIG. 5 (a), the coated optical fiber 31 may be directly laid in the ground, and the deformation in the ground may be detected by the deformation of the core material 32 of the optical fiber 31 and measured. .
[0028]
Furthermore, in order to detect deformation near the ground surface, a sensor in which the optical fiber 35 is simply covered with the resin member 36 as shown in FIG. 5B may be embedded.
[0029]
The configuration of the underground optical fiber sensor system of the present invention will be described below.
[0030]
As shown in FIG. 1, a light source (laser light source) 6 is connected to an optical fiber 4 via a first optical coupler 4a, and this optical fiber 4 is connected to the underground optical fiber sensor shown in FIGS. The underground optical fiber sensor is connected to the second optical coupler 4b via the optical fiber 4 ', and the second optical coupler 4b is connected to the O / E (optical / electrical) converter 7 for conversion. The output of the device 7 is connected to a passive homodyne demodulator 8, for example. A modulation signal generator 40 is provided between the light source (laser light source) 6 and the passive homodyne demodulator 8.
[0031]
The output of the passive homodyne demodulator 8 is connected to a measuring device 9, and the measuring device 9 is connected to an alarm device 10 as appropriate. Here, the reference optical fiber 5 is branched from the first optical coupler 4a and connected to the second optical coupler 4b. Reference numeral 41 denotes a railroad track.
[0032]
Therefore, the laser light output from the laser light source 6 is branched into two by the first optical coupler 4a, one of which is passed through the underground optical fiber sensor 2 via the optical fiber 4, and the second optical coupler. 4b interferes with the other. The output of the second optical coupler 4b is O / E converted by an O / E (optical / electrical) converter 7 and passive homodyne processed by a passive homodyne demodulator 8 for demodulation. The demodulated signal is taken into the measuring device 9, and the underground deformation is detected by comparing the light output via the reference optical fiber 5 with the light output via the underground optical fiber sensor 2. Can do. The output of the modulation signal generator 40 for passive homodyne processing is connected to a light source (laser light source) 6 and a passive homodyne demodulator 8.
[0033]
As described above, according to the present invention, a pile in which a strain sensor using an optical fiber is incorporated is placed in the ground, and a plurality of coated optical fiber sensors are arranged depending on the situation, distance, etc. of the measurement target location. By laying and embedding directly in the ground, it is possible to easily measure the deformation in the ground continuously (for example, several tens of kilometers). Targets are embankments and other earth structures, which are effective for long extensions (railways, roads, etc.).
[0034]
As described above, according to the optical fiber sensor system of the present invention, it is possible to predict a danger in an arbitrary region of a structure having a long extension, such as a railway or a road. In particular, it is difficult to judge visually, etc., and the underground deformation can be easily monitored, and the effect is remarkable even from the viewpoint of disaster prevention.
[0035]
In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and these are not excluded from the scope of the present invention.
[0036]
【The invention's effect】
As described above in detail, according to the present invention, the following effects can be obtained.
[0037]
(A) Detailed deformation in the ground can be measured. In particular, deformation in the ground can be easily measured continuously (for example, several tens of kilometers). Targets are embankments and other earth structures, which are effective for long extensions (railways, roads, etc.).
[0038]
(B) It is possible to measure detailed deformation in the ground in a wide area. It is possible to foresee the danger in any area of long-length structures such as railways and roads. In particular, it is difficult to judge visually, etc., and the underground deformation can be easily monitored, and the effect is remarkable even from the viewpoint of disaster prevention.
[Brief description of the drawings]
FIG. 1 is a layout view of an underground optical fiber sensor showing an embodiment of the present invention.
FIG. 2 is a configuration diagram of an underground optical fiber sensor showing an embodiment of the present invention.
FIG. 3 is a block diagram of an underground optical fiber sensor showing another embodiment of the present invention.
FIG. 4 is a configuration diagram of an underground optical fiber sensor having a pull-out resistance member.
FIG. 5 is a configuration diagram of an underground optical fiber sensor showing still another embodiment of the present invention.
[Explanation of symbols]
1 Filled area 2, 12, 22 Optical fiber sensor (part of optical fiber)
DESCRIPTION OF SYMBOLS 3 High rigidity tubular pile 3A Hollow part 4,4 ', 31,35 Optical fiber 4a 1st optical coupler 4b 2nd optical coupler 5 Optical fiber used as a reference 6 Light source 7 O / E converter 8 Passive homodyne demodulator 9 Measuring apparatus DESCRIPTION OF SYMBOLS 10 Alarm device 11 Divided hollow type FRP rods 13, 23 Outer pipes for placement 14, 16, 24 Fixing plate 15 Pile 16A Pull-out resistance member 21 Bellows type pipe 32 Core material 36 Resin member 40 Modulation signal generator 41 Railway line

Claims (4)

An underground optical fiber sensor in which a deformation detection sensor for soil structure using an optical fiber is installed at a measurement point, the deformation detection sensor for the earth structure is configured to connect an optical fiber to a structure that easily follows the deformation of soil. winding, easily sticks to punch設時 the tip of the structure, but when a force acts in the withdrawn direction, pile der having a fixing plate provided with withdrawn resistor member so the top is opened is,該杭A fiber optic sensor for underground use, which is directly laid on a measurement point together with an outer tube, leaving only the deformation detection sensor of the earth structure in the ground. Underground fiber optic sensor, wherein the ground fiber optic sensor of claim 1, wherein a hollow rod follow ease I構 granulated material is divided into deformation before Symbol soil. 2. The underground optical fiber sensor according to claim 1, wherein the structure that easily follows the deformation of the soil is a bellows type structure.   A ground structure comprising a plurality of earth structure deformation detection sensors using an optical fiber according to claim 1 in the monitoring area, and detecting the deformation of the monitoring area by comparison with a reference optical fiber. Medium-use optical fiber sensor system.

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