JP2000275018A - Method and apparatus for measuring deformation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure a deformation generated to a structure such as a tunnel or the like without requiring manpower. SOLUTION: The method for measuring a deformation includes a process of attaching an optical fiber 2c in a loop to a part to be measured of a structure 1 and a process of measuring a deformation of the fiber 2c on the basis of a scattering light of a light brought into the optical fiber 2c. The deformation generated to the structure such as a tunnel or the like can be accurately measured without requiring manpower. Moreover, even when the part to be measured of the structure is curved, the deformation can be measured without a trouble.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tunnel, steel,
The present invention relates to a method and an apparatus for measuring distortion of a concrete structure or the like.

[0002]

2. Description of the Related Art Tunnels and other structures are distorted by external loads due to external pressure. Therefore, conventionally, an abnormality (deformation, crack, or the like) of the building based on the distortion is mainly visually inspected.

[0003]

However, the visual inspection work not only takes a great deal of time, but also often leads to oversight of abnormal parts. Further, when the structure is a tunnel, there is a time constraint that the inspection must be performed in a time zone when the traffic is small. It is conceivable that a strain gauge is attached to the structure to electrically detect the above abnormality.However, when a crack occurs in the measurement area, the stress acting on itself is released. This makes it impossible to measure distortion. Therefore, the range of use is limited, and the utility is low. An object of the present invention is to provide a distortion measuring method and apparatus capable of accurately measuring distortion generated in a structure such as a tunnel without requiring any manual operation in view of such a situation.

[0004]

According to a first aspect of the present invention, there is provided a method for measuring a strain of a building, comprising the steps of: attaching an optical fiber in a loop to a portion to be measured of the building; Measuring the distortion of the optical fiber based on the scattered light of the light. According to a second invention, in the first invention, the optical fiber is formed in a loop shape in advance, and the loop-shaped optical fiber is attached to the measurement site. The third invention is an apparatus for measuring the strain of a building, which is formed by fixing and arranging a flexible and stretchable sheet material and an optical fiber in a loop on one surface of the sheet material. Strain detection sensor
A strain measurement unit that measures the strain of the strain detection sensor based on the scattered light of light incident on one end of the strain detection sensor, and affixing the back surface of the sheet material to a measurement target portion of the structure. Thereby, the distortion detection sensor is attached to the measured portion. A fourth invention is an apparatus for measuring a strain of a building, wherein the first rod has a tubular shape, a second rod slidably inserted into the first rod, and the first and second rods. A displacement detecting means for electrically detecting a relative displacement of the rod, and first and second mounting members respectively connected to ends of the first and second rods via universal joints; , A second rod is attached to the object to be measured via each of the attaching members. In a fifth aspect based on the fourth aspect, the displacement detecting means is interposed between the first and second rods and is deformed in accordance with a relative displacement of each of the rods; A strain gauge for converting the deformation strain into a corresponding electric signal. In a sixth aspect based on the fourth aspect, a dustproof cover is attached to a boundary between the first and second rods.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of strain measurement using an optical fiber will be briefly described. When laser pulse light is incident from one end of the optical fiber, so-called Brillouin scattered light is generated inside the fiber. Then, after a time corresponding to the distance, the backscattered light returns to one end of the optical fiber.At this time, if the optical fiber is distorted,
As shown in FIG. 8, the frequency (wavelength) of the Brillouin scattered light changes by ΔF.

The distortion of the optical fiber and the frequency shift Δ
A proportional relationship is established with F as illustrated in FIG.
Therefore, it is possible to measure the strain at each position in the longitudinal direction of the optical fiber based on the frequency shift amount ΔF of the scattered light and the propagation time.

The above measurement principle can be applied to the measurement of the distortion generated in the tunnel 1 shown in FIG. That is, if the optical fiber is disposed at the measurement site of the tunnel 1 and the optical fiber is distorted by the distortion generated in the tunnel 1, the frequency shift amount ΔF based on the distortion of the optical fiber is generated in the tunnel 1. It will deal with distortion.

Therefore, a distortion detection sensor 2 as shown in FIG. 2 is disposed at a measured portion of the tunnel 1 (in this example, a top portion where the largest distortion occurs). This sensor 2
Is formed by meandering the optical fiber 2c on a flexible and stretchable sheet material 3, and connects a plurality of straight portions 2a parallel to each other and ends of the straight portions 2a to each other. It has a plurality of loop portions 2b. The sensor 2 is integrally fixed to the surface of the sheet material 3 with an appropriate adhesive. And in this example, the length of each parallel straight part 2a is set to about 300 mm, and the diameter of each loop part 2b is set to about 60 mm.

The sensor 2 is mounted on a peripheral surface of a portion to be measured of the tunnel 1 via a sheet material 3. That is, the entire back surface of the sheet material is attached to the measurement target peripheral surface of the tunnel 1 with an appropriate adhesive (for example, an adhesive such as a silicon-based or epoxy-based adhesive). At the time of the attachment, the sticking position and the sticking posture of the sheet material 3 are set so that the parallel linear portions 2a intersect the line 5 along the peripheral surface of the measurement site.

A site measuring instrument 6 shown in FIG. 2 is provided at an appropriate place near the measuring site. The measuring device 6 receives the laser pulse light at one end of the optical fiber sensor 2 and receives the scattered light of the laser pulse light. Then, based on the above-described measurement principle, the distortion of the measured portion is measured. That is, when distortion occurs in a direction along the longitudinal direction of the tunnel 1 at a position where a portion to be measured of the tunnel 1 is present, distortion occurs at a corresponding position of the sensor 2 via the sheet material 3. Therefore, the measuring device 6 measures the position and magnitude of the distortion based on the propagation time of the laser light and the frequency of the scattered light.

FIG. 3 shows an example of the measurement result.
As shown in the measurement result, when distortion occurs in the measured portion of the tunnel 1, the distortion is measured as the distortion of the sensor 2. This measurement result is transferred from the on-site measuring instrument 6 to a central monitoring device (not shown) via a telephone line or the like.

According to the distortion measuring device of this embodiment using the sensor 2, the position where the distortion occurs can be detected with the accuracy of the arrangement interval of the parallel straight portions 2b. In addition, it is possible to continuously measure a wide area, and there is no hindrance to the measurement even when the measured portion is curved. Further, even when a crack is generated in the portion to be measured due to the strain, the strain can be measured. Of course, this measuring device can also be effectively applied to strain measurement of other structures such as buried pipes.

The same strain measurement as described above can be performed by using the sensor 2 'shown in FIG.
The sensor 2 ′ is formed in advance using a mold 7 as shown in FIG. 5 or a jig that can be temporarily installed so as to have the same shape as the sensor 2. When the sensor 2 'is formed, the optical fiber 2c is fitted into the concave groove 8 of the single frame 7, and then the semicircular groove 8a located at the loop 2b of the optical fiber 2c is filled with an appropriate resin. . And
After the resin is solidified, the optical fiber 2c is taken out from one frame to form the sensor 2 'shown in FIG. 4 in which the resin portion 9 is interposed in the loop portion 2b. The sensor 2 'thus formed is directly adhered to the peripheral surface of the portion to be measured of the tunnel 1 using an adhesive. Of course, this sensor 2 'can also easily follow the arc-shaped peripheral surface of the tunnel 1 or the like.
When a structure that can be grooved, such as a concrete structure, is to be applied, the form 7
The strain measurement can also be performed by forming a groove like the groove 8 and directly bonding the optical fiber 2c into the groove.

FIG. 6 shows another embodiment of the strain measuring apparatus according to the present invention. This strain measuring device fixes a tubular first rod 10, a second rod 11 slidably inserted into the first rod 10, and one end to the first rod 10 via a bracket 12. In addition, a U-shaped spring plate 14 having the other end fixed to the second rod 11 via a bracket 13 and a strain gauge 15 attached to the spring plate 14 are provided.
This constitutes a so-called pie displacement meter.

A mounting member 17 is connected to an end of the first rod 10 via a universal joint 16. Similarly, a mounting member 19 is connected to an end of the second rod 11 via a universal joint 18. Are connected. This strain measuring device is mounted on a measured portion of a concrete structure 20 such as a tunnel through mounting members 17 and 19, and at this time, the mounting direction is set so that the longitudinal direction is along the direction of the strain to be measured. Set. The attachment members 17 and 19 are attached to the building 2 with an adhesive, a screw, or the like.
Fixed to 0.

According to this strain measuring device, when the measured portion of the building 20 is distorted in the left-right direction in FIG. 6, the first rod 10 and the second rod 11 are relatively displaced, and the spring plate 14 is displaced. Bend. As a result, an electrical signal corresponding to the amount of deflection of the spring plate 14 from the strain gauge 15, that is, an electrical signal corresponding to the magnitude of the strain generated at the measured portion of the building 17 is generated, and the strain is measured. .

Since this distortion measuring device is provided with the universal joints 16 and 18, the mounting members 17 and
It is possible to follow the rotation and parallel movement of the portion (marked portion) where the 18 is fixed, and it can be easily attached to a curved surface as shown. In addition, the first
The end of the rod 10 on the side of the second rod 11 includes
The dust-proof cover 20 is fitted, whereby the rod 10,
11 to prevent foreign matter from entering the space.

FIG. 7 shows a comparison result in the case where the strain generated in the same portion to be measured is measured by the optical fiber strain detecting sensor 2 shown in FIG. 2 and the strain gauge 15 shown in FIG. ing. As shown in FIG. 7, the measurement results of the optical fiber strain detection sensor 2 and the strain gauge 15 are:
They are in good agreement with each other.

[0019]

According to the present invention, it is possible to accurately measure the distortion generated in a structure such as a tunnel without requiring any human intervention. Further, even when the measured portion of the structure is curved, the measurement can be performed without any trouble.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a mode of attaching a strain detection sensor to a top peripheral surface of a tunnel.

FIG. 2 is a plan view showing a configuration example of a strain detection sensor applied to the strain measurement device according to the present invention.

FIG. 3 is a graph illustrating a relationship between a distortion occurrence position and a distance measured by the distortion detection sensor of FIG. 2;

FIG. 4 is a plan view showing another example of the distortion detection sensor.

FIG. 5 is a plan view showing a mold for molding the distortion detection sensor of FIG. 4;

FIG. 6 is a side view showing another embodiment of the strain measuring device according to the present invention.

7 is a graph comparing the strain measured by the strain detection sensor of FIG. 2 with the strain measured by the strain gauge shown in FIG. 6;

FIG. 8 is a graph exemplifying a change mode of a frequency (wavelength) of Brillouin scattered light when distortion occurs in an optical fiber.

FIG. 9 is a graph illustrating the relationship between the frequency change of Brillouin scattered light and distortion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tunnel 2, 2 'Distortion detection sensor 2a Linear part 2b Loop part 2c Optical fiber 3 Sheet material 6 Measuring instrument 7 Single frame 8 Concave groove 8a Semicircular groove part 10 1st rod 11 2nd rod 12, 13 Bracket 14 Spring plate 15 Strain gauge 16, 18 Universal joint 17, 19 Mounting member 20 Dustproof cover

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Hironori Nori, 5-717-1, Fukahori-cho, Nagasaki City, Nagasaki Prefecture Inside the Nagasaki Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Taketoshi Yamaura 5-chome, Fukahori-cho, Nagasaki City, Nagasaki Prefecture No. 717 No. 1 in Nagasaki Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Tokio Kai No. 1-1, Akunouramachi, Nagasaki City, Nagasaki Pref. FF32 FF58 GG04 GG08 JJ01 LL02 2F103 CA03 CA07 DA01 EA14 EA17 EA19 EA23 EB02 EB11 EC08 FA02 FA04

Claims (6)

[Claims] 1. A method for measuring distortion of a structure, comprising: a step of attaching an optical fiber in a loop to a site to be measured of the structure; and a method of measuring a scattered light of light incident on the optical fiber. Measuring the strain of the optical fiber. 2. The strain measuring method according to claim 1, wherein the optical fiber is formed in a loop shape in advance, and the looped optical fiber is adhered to the measurement site. . 3. An apparatus for measuring distortion of a building, comprising a sheet material having flexibility and elasticity, and an optical fiber fixedly arranged in a loop on one surface of the sheet material. A strain detection sensor, and a strain measurement unit configured to measure a strain of the strain detection sensor based on scattered light of light incident on one end of the strain detection sensor; A strain measuring device, wherein the strain detection sensor is attached to the measured portion by attaching the strain detecting sensor to a portion to be measured. 4. An apparatus for measuring a strain of a building, comprising: a first tubular rod; a second rod slidably inserted into the first rod; and the first and second rods. A displacement detecting means for electrically detecting a relative displacement of the first and second rods, and first and second attachment members respectively connected to ends of the first and second rods via a universal joint. A strain measuring device, wherein a second rod is attached to the building via each of the attachment members. 5. A spring plate interposed between the first and second rods and deformed in accordance with the relative displacement of each rod, and an electric signal corresponding to the deformation of the spring plate. The strain measurement device according to claim 4, further comprising: a strain gauge configured to convert into a strain gauge. 6. The strain measuring device according to claim 4, wherein a dustproof cover is provided at a boundary between the first and second rods.