JP2000009438A - Method for laying optical fiber sensors for measuring circumferential distortion on tunnel wall surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for laying optical fiber sensors which measure the circumferential distortion on a tunnel wall surface, capable of avoiding an installation border. SOLUTION: (a) Optical fiber strain sensors are alternately laid with intervals X and Y circumferentially on a tunnel wall surface, which is connected into one, (B) the laying is so performed that the intervals X and Y satisfy an equations (1) and (2). Z<X<Y (1), Y+2X=L (2), (L: required value of distortion detection interval, Z: width of part where strain measurement at installation border is not effective).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for laying an optical fiber sensor for measuring strain on a tunnel wall surface of a railway or a road.

[0002]

2. Description of the Related Art A conventional technique is shown in FIGS.

FIG. 2 is an explanatory view of a method for measuring the strain on a tunnel wall using an optical fiber sensor, and FIG. 3 is an explanatory view of a conventional method for measuring the strain on a tunnel wall. (1) In the conventional method for measuring the strain on the tunnel wall shown in FIG.
Two digital transits 21 and 22 are set horizontally at an arbitrary position on the central passageway with a measuring point between them at a distance of 7 to 8 m, and collimation targets 23 attached to the front surfaces of the digital transit 21 and 22 are collimated with each other. The collimation lines are made to coincide with each other, and the collimation targets 23 attached to both ends of the reference scale 24 are collimated with the telescope at the opposite positions, and then collimated with each other.

[0004] In this way, the position coordinates of the two digital transit arbitrarily set are determined.

[0005] By collimating the measuring point 25, the coordinates of the measuring point 25 are determined, and when collimating of all the measuring points 25 is completed,
The coordinates are calculated by the personal computer 26 to calculate the interval between the measurement points.

[0006] This operation is periodically measured at each cross section, and changes in the inner cross section of the tunnel are examined.

There is also a method of examining a change in the cross section of a direct tunnel due to an Invar rule or the like. (2) In the method of directly measuring the strain on the tunnel wall, a normal electric resistance type strain sensor is conventionally used as a strain measuring device, but it is necessary to install as many strain sensors as the number of points to be measured. There are costs. (3) Therefore, use of an optical fiber sensor capable of continuously measuring the strain of the laid portion has been considered.

In the optical fiber sensor, the strain at many points can be measured with one optical fiber, so that the measurement cost can be reduced.

In the method for measuring the strain on the tunnel wall using the optical fiber sensor shown in FIG. 2, the optical fiber 2 is laid on the wall 3 of the tunnel. Therefore, when the wall surface is distorted, the optical fiber is also distorted.

At this time, by detecting the scattering of the pulse light incident from the optical fiber sensor 1, the strain distribution of the optical fiber can be detected.

As shown in FIG. 2, an optical fiber is laid in the circumferential direction of the wall 3 of the tunnel to measure the strain in the circumferential direction. There is a method of measuring the strain in the longitudinal direction by laying in a tunnel, but there is a case where it is required to detect the strain in the circumferential direction for maintenance of the tunnel.

[0012]

The prior art has the following problems. (1) In the conventional method for measuring the strain on the wall surface of a tunnel shown in FIG. 3, it is necessary to use a time interval between trains or to stop vehicles. Therefore, it is not efficient, and it takes time and costs. (2) In the method of directly measuring the distortion of the tunnel wall,
Since it is necessary to install as many strain sensors as the number of points to be measured, the cost is high. (3) In the method of measuring the strain in the circumferential direction by laying the optical fiber sensor in the circumferential direction of the wall surface 3 of the tunnel, it is necessary to lay the optical fiber in the circumferential direction at every certain length to detect the strain. However, at this time, the following problems occur.

The wall of the tunnel generally has a length of 10
It will be built 12 meters each. One unit of the wall thus constructed is referred to as casting.

When the strain on the wall surface of the tunnel is to be measured, since the internal structure is discontinuous at the boundary portion of the casting, the deformation state of the surface is discontinuous.

If the strain is measured at such a portion, it is not possible to obtain a general strain state of the tunnel wall surface. Therefore, it is necessary to lay a strain measuring device avoiding the boundary of the casting.

At this time, it is relatively easy to avoid driving a newly constructed tunnel or the like, but it becomes difficult to determine the boundary of the driving after repairing the surface or the like. Further, when laying the optical fiber on the ceiling of the tunnel, it is necessary to use a work table that can reach the entire wall surface of the tunnel.

Since the work table needs to be moved as the optical fiber is laid, when laying one optical fiber, it is necessary to move the work table by the length thereof, which takes a lot of time. .

An object of the present invention is to provide a method of laying an optical fiber sensor for measuring a circumferential distortion of a tunnel wall surface which can solve these problems.

[0019]

(First Means) A method of laying an optical fiber sensor for measuring a strain in a circumferential direction of a tunnel wall according to the present invention is as follows. Y is laid in the circumferential direction of the tunnel wall and connected to one. (B) The distances X and Y are calculated by the following equations (1) and (2): Z <X <Y (1) Y + 2X = L (2) However, L is a required value of the strain detection interval. Z is laid so as to satisfy the width of the portion where the strain measurement of the casting boundary is not effective. (Second Means) A method for laying an optical fiber sensor for measuring a circumferential strain on a tunnel wall surface according to the present invention is characterized in that, in the first means, the interval X is 1 m ± 0.3 m. And

That is, according to the present invention, in the method of laying the optical fiber strain sensor 1 for detecting the strain in the circumferential direction of the tunnel in the tunnel, the distance X between a pair of adjacent optical fiber sensors is set to about 1 m. It is characterized by.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows a first embodiment of the present invention.

FIG. 1 is an explanatory diagram of a method of laying an optical fiber sensor for measuring a circumferential strain on a tunnel wall according to a first embodiment of the present invention.

In FIG. 1, 1 is an optical fiber strain sensor,
2 is an optical fiber (fixed to the tunnel wall), and 3 is a tunnel wall.

As shown in FIG. 1, the optical fiber strain sensors 1 are laid alternately in the circumferential direction at intervals X and Y, and are connected to one.

Therefore, the operation is as follows.

When the laid optical fiber 2 undergoes elongation strain, its position and the amount of strain can be measured.

However, when the laying position is at the boundary of the driving, the measured distortion amount is not effective. The width Z of the portion where the strain measurement of the casting boundary is not effective is generally about several tens of centimeters.

Therefore, as shown in FIG.
When the optical fibers 2 are laid in parallel at (Z <X <Y), one of the optical fibers 2 parallel at the interval X can avoid the boundary of the driving.

In this case, the measurement interval of the strain is Y at the longest.

Here, if (Y + 2X) is made equal to the required value L of the distortion detection interval, the distortion detection interval becomes L or less at all places, and the requirement of the distortion detection interval can be satisfied.

Further, if X is set to about 1 m, parallel optical fibers are simultaneously laid on the wall surface by using a small work table such as an aerial work vehicle when the optical fiber is laid. Laying work can be efficiently performed.

[0032]

Since the present invention is configured as described above, it has the following effects. (1) When the optical fibers are laid in parallel at the interval X (Z <X <Y), one of the optical fibers 2 parallel at the interval X can avoid the boundary of the driving. (2) If (Y + 2X) is made equal to the required value L of the distortion detection interval, the distortion detection interval becomes L or less at all places, and the requirement of the distortion detection interval can be satisfied. (3) If the interval X is set to about 1 m, parallel optical fibers can be simultaneously laid on the wall surface by using a small work bench such as an aerial work vehicle when laying optical fibers. Therefore, the laying work can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an optical fiber sensor laying method according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a method for measuring a strain on a tunnel wall surface using an optical fiber sensor.

FIG. 3 is an explanatory diagram of a conventional method for measuring the strain on the wall surface of a tunnel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical fiber strain sensor 2 ... Optical fiber 3 ... Tunnel wall 21 ... Digital transit 22 ... Digital transit 23 ... Collimation target 24 ... Standard scale 25 ... Measurement point 26 ... PC etc.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tokio Kai 5-717-1, Fukahori-cho, Nagasaki-city, Nagasaki Prefecture Inside the Nagasaki Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Yoshiaki Inoue 5-chome, Fukahori-cho, Nagasaki-city, Nagasaki Prefecture No. 717 No. 1 Mitsubishi Heavy Industries, Ltd. Nagasaki Research Laboratory (72) Inventor Masazumi Tsukano 1-1, Akunouramachi, Nagasaki-shi, Nagasaki F-term in Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard 2F065 AA65 CC40 FF31 FF44 LL02

Claims (2)

[Claims] 1. A method of laying an optical fiber strain sensor 1 for detecting strain in a circumferential direction of a tunnel in a tunnel, wherein (A) the optical fiber strain sensors are alternately spaced X and Y.
And laid in the circumferential direction of the tunnel wall and connected to one. (B) The distances X and Y are as follows: Z <X <Y (1) Y + 2X = L (2) where L: distortion detection interval The required value of Z: A method of laying an optical fiber sensor for measuring circumferential distortion of a tunnel wall, wherein the width is a width of a portion where the measurement of distortion at a placing boundary is not effective. 2. The method according to claim 1, wherein the distance X is 1 m ± 0.3 m.