JP2003014509A - Optical fiber sensor and setting-up method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an optical fiber sensor mountable on its supports or half steel timbering members on the site to eliminate the complexity of handling the long supports with the optical fiber sensor previously pasted thereto, and mount the sensor also on a portion of the timbering corresponding to the ceiling top after assembling half steel timbering members, thereby allowing the portion corresponding to the ceiling top to be measured. SOLUTION: Magnets 3 are mounted with spacings in the longitudinal direction on an optical fiber 2 to form an optical fiber sensor 1. This sensor is installed in an AGF steel pipe such that the mounting of the sensor 1 on split blocks 5 of a specified length, insertion of the blocks 5 in the AGF steel pipe and joining of the block 5 with a new one are repeated, and a U-shaped timbering is assembled using half steel timbering members. Then the sensor 1 is mounted in the lengthwise direction thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber sensor and a method for installing the optical fiber sensor on an object to be measured.

[0002]

In recent years, the characteristic of being able to detect the distribution in the longitudinal direction of the strain generated in the optical fiber by an external force due to the backscattered light generated in the optical fiber is used to measure the length of the object to be measured. It is used as a sensor for measuring strain, displacement and the like in the vertical direction. As an example using this optical fiber sensor, for example,
In the AGF method that receives and improves and strengthens the ground in front of the face of tunnel excavation, AGF steel pipe and injected material are used, but the state of the ground is due to the displacement of the AGF steel pipe placed in the ground in front of the face. In order to understand
The displacement of the AGF steel pipe is measured using an optical fiber sensor for measuring the steel pipe.

Using this optical fiber sensor, an AGF steel pipe (standard: length 12.5 m, outer diameter 114.3 mm, thickness 6)
When measuring displacement in mm, aluminum pipe (length 1
2.5 m, outer diameter 50 mm, thickness 2 mm) is used as a support, and an optical fiber sensor is attached to this (adhesion is performed so that the optical fiber sensor is integrated with the support). The optical fiber sensor is attached to the AGF steel pipe by inserting and arranging the support to which the fiber sensor is attached into the AGF steel pipe, and filling the inside of the AGF steel pipe with grout.
It was attached to a steel pipe. The support itself is provided with spacers protruding in all directions from the center at a required interval in the longitudinal direction, and the spacer is brought into contact with the inner peripheral surface of the AGF steel pipe to bring the support to a substantially central position. I am trying.

Further, as an application of the optical fiber sensor, the optical fiber sensor is attached to an arc-shaped steel support bar which receives the ground excavated in tunnel excavation work, and the steel support bar is measured to grasp the condition of the natural rock. It is also used to do.
Even when measuring the steel support as the object to be measured, the optical fiber sensor is attached to the flange part of the steel support to attach the optical fiber sensor to the object to be measured (steel support). It was being appreciated.

By the way, when the optical fiber sensor is attached to the AGF steel pipe, the optical fiber sensor is attached to the support by using an adhesive agent or the like. However, it takes time to attach the optical fiber sensor. Before using it in actual construction, it was necessary to attach the optical fiber sensor to the support in advance. Therefore, a support body having a length of 12.5 m, to which the optical fiber sensor is attached, has to be carried into the construction site and handled, which causes a problem that the handling work on the construction site becomes complicated.

On the other hand, even when the above-mentioned steel support structure is measured by an optical fiber sensor, there are the following problems. The optical fiber sensor is attached to the steel support by using an adhesive or the like as in the case of the AGF steel pipe support, but this attachment also requires time. Therefore, the optical fiber sensor is attached to the steel support in advance, and this state is brought to the construction site. In addition, the steel shoring itself is brought into the construction site in a half state, and at the site, the end plate part of the steel shoring of the half section is bolted at the top end (ceiling) of the tunnel face to reverse U We are constructing a letter-shaped support work.
Since the optical fiber sensor is attached to the steel support which is half, it is said that the optical fiber sensor is folded back before approaching the top end at the portion corresponding to the top end of the tunnel face. Therefore, there is a problem that the part corresponding to the top cannot be measured.

As described above, it takes time to attach the optical fiber sensor to a support used to indirectly attach to an object to be measured, such as an AGF steel pipe, or to the object to be measured, such as the steel supporting member. Therefore, it is the current situation that the optical fiber sensor is attached in advance and then the support body and the half steel support work are brought to the site. And
This causes the above-mentioned various problems. Therefore, in view of the above circumstances, the present invention has an object to make it possible to attach the optical fiber sensor to the support body or the half steel supporter in the field, and the optical fiber sensor is attached in advance. Eliminates the complexity of handling a long support, installs the optical fiber sensor after assembling the steel halves of each half, and also arranges the optical fiber sensor in the part corresponding to the top end of the steel stanchion. Then, the purpose is to be able to measure the part corresponding to the top.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems and is characterized in that magnets are attached to an optical fiber at intervals in the longitudinal direction of the optical fiber. To solve the above problems. Another invention is characterized in that a magnet in the above-mentioned optical fiber sensor is magnetically attached to a long magnetic object to be measured, and the optical fiber sensor is attached along the length direction of the object to be measured. A method for installing a fiber sensor, and a method for installing the optical fiber sensor is provided to solve the above problems.

Another aspect of the present invention is to magnetize a magnet in the above optical fiber sensor to a long support which is inserted and arranged inside a long tubular object to be measured and has a magnetized portion, A method for installing an optical fiber sensor, characterized in that an optical fiber sensor is attached along a length direction of a support, and the support is inserted and arranged in the object to be measured. The method for installing the optical fiber sensor is provided. Then, the above problems are solved. In the present invention, the support is a plurality of divided bodies joined together, and the optical fiber sensor is attached while repeating the joining of the divided bodies and the attachment of the optical fiber sensor to the joined divided bodies. It is preferable that the divided bodies are sequentially inserted into the object to be measured.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in detail based on the embodiments shown in FIGS. FIG. 1 shows an optical fiber sensor 1 of the present invention. As shown in the figure, the optical fiber sensor 1 is formed by attaching a plurality of magnets 3 having the same shape over the longitudinal direction of the optical fiber 2, and the magnets 3 are arranged at equal intervals (for example, 10 cm). Are lined up. The magnet 3 is fixed completely without moving with respect to the optical fiber 2,
The optical fiber 2 is attached so as not to cause local distortion. The optical fiber sensor 1 having the magnet 3 has sufficient flexibility and is usually provided so that it can be wound up and handled as a roll body.

Next, the installation of the optical fiber sensor 1 having the above structure will be described. First, when the AGF steel pipe is an object to be measured using this optical fiber sensor 1, FIG.
The support 4 shown in is used. A support is also used for the measurement using the conventional optical fiber sensor of the AGF steel pipe, but in the support 4 shown in FIGS. 2 to 4, a plurality of divided bodies 5 are connected together. The split body 5 is a state in which a prismatic rod (a square pipe made of aluminum, iron or the like can be used) 6 having a length of 1 to 2 m, and two rods at both ends of the rod 6 in each of four directions. Is attached so as to extend over a rebar 7 protruding to a constant length, and to be parallel to the longitudinal direction of the rod 6 and to be hung over the rebar 7 at one end and the rebar 7 at the other end of the rod 6. And a magnetized portion 8 having a long plate shape.
Are arranged parallel to each other on all sides of the rod 6, and the respective magnetized portions 8 are provided at positions closer to the rod 6 side with a certain distance from the projecting end 7a of the reinforcing bar 7. In the divided body 5, the magnetized portions 8 arranged on each of the four sides of the central rod 6 are made of magnetic iron plates and are the portions where the optical fiber sensor 1 is positioned. Further, when the reinforcing bars 7 in the divided body 5 are installed inside the AGF steel pipe in a state where the divided bodies 5 are connected to each other, the rod 6 is located at the center position of the AGF steel pipe A as shown in FIG. In addition, since the magnetized portion 8 is positioned with a certain distance from the projecting end 7a of the reinforcing bar 7 serving as the centerizer to the rod 6 side, the reinforcing bar 7 is As a result, the optical fiber sensor 1 is positioned with respect to the AGF steel pipe A. The distance of the projecting end 7a of the magnetized portion 8 is set such that the optical fiber sensor 1 does not contact the inner surface of the AGF steel pipe A when the magnet 3 attaches the optical fiber sensor 1 to the magnetized portion 8. , And is set so as to approach the inner surface of the AGF steel pipe A.

A plurality of divided bodies 5 each having four magnetized portions 8 are connected to a rod 6 having a required length, and a plurality of divided bodies 5 are joined together to form an integral support body 4.
When the magnets are formed, the magnetized portions 8 are provided so as to be in a continuous state in the joining direction of the divided bodies 5 (see FIG. 3). Further, in joining the divided bodies 5, the rod 6
One end of the rod 6 is the convex portion 9, and the concave portion 10 into which the convex portion 9 can be fitted is the other end of the rod 6, and the rod 6 can be sequentially joined by the concave and convex fitting of the convex portion 9 and the concave portion 10. (See Figure 2). Further, in order to more reliably maintain the connected state of the rod 6, the convex portion 9 of the rod 6 is provided with the bolt mounting hole 11 and the concave portion 10 is provided.
Is provided with a bolt insertion hole 12 corresponding to the bolt attachment hole 11, and the bolt attachment hole 11 and the bolt insertion hole 12 are provided.
By connecting the convex portion 9 and the concave portion 10 with bolts and the like in correspondence with each other, the connection of the divided bodies 5 becomes reliable.

An example of installing two optical fiber sensors 1 on an AGF steel pipe will be described. First, two optical fiber sensors 1 are cross-arranged on the end side of one divided body 5 which is the insertion start end into the AGF steel pipe, and one optical fiber sensor 1 is placed symmetrically with the rod 6 in between. Another set of magnetized parts 8 is attached to the magnetized part 8 via the magnet 3, and the other optical fiber sensor 1 is also symmetrically positioned with the rod 6 in between.
To be attached via the magnet 3. Then, the divided body 5 is inserted into the end portion of the AGF steel pipe. Next, another division body 5 is connected to the division body 5 inserted into the end portion of the AGF steel pipe to fix the connection portion between the convex portion 9 and the concave portion 10 and a new connection body 5 is formed.
On the other hand, in the same manner as in the case of the divided body 5, the magnetized portion 8
The optical fiber sensor 1 is attached to the magnet via the magnet 3 and is again inserted into the AGF steel pipe. By repeating this procedure in order and inserting the divided body 5 to a predetermined length to form the integral support body 4 in the AGF steel pipe, the optical fiber sensor 1 becomes the AGF.
It is inserted and arranged inside the steel pipe. After that, the inside of the AGF steel pipe is filled with grout to be integrated.

When an optical fiber sensor is installed on an AGF steel pipe driven into the ground, the diameter ratio of the strain (strain distribution) measured by the optical fiber sensor 1 is 1.429 (= 114.3).
mm / 80 mm), the strain (strain distribution) of the AGF steel pipe can be obtained. Further, the strain of the AGF steel pipe can be multiplied by the Young's modulus of the steel pipe to obtain the stress of the AGF steel pipe (continuous stress distribution in the longitudinal direction), and the deformation of the AGF steel pipe by integrating the strain ( That is, the displacement of the ground at the portion where the AGF steel pipe is driven can be obtained. Thus, the strain, stress, deformation, etc. of the AGF steel pipe driven into the ground can be continuously measured. Further, since the optical fiber sensor is equipped with a magnet, it can be easily attached to the divided body having the magnetized portion at the construction site, and the divided body is connected and inserted into the AGF steel pipe while attaching the optical fiber sensor. Therefore, it is not necessary to handle a long support as in the conventional case, and the installation of the optical fiber sensor becomes simple.

In the above example, the two optical fiber sensors 1 are attached to the support 4, and as shown in FIG. 5 (a), one optical fiber sensor 1 is located inside the AGF steel pipe A. And the lower optical fiber sensor 1 is disposed on the left c and the right d. Also, A
It is not necessary to arrange the optical fiber sensor 1 vertically or horizontally in the cross-sectional direction along the longitudinal direction of the GF steel pipe A, and as shown in (b), one optical fiber sensor 1 may be provided, for example, on the upper a and lower b. It may be arranged. Further, as shown in (c), one optical fiber sensor 1 may be arranged in a single stroke, for example, top a, bottom b, left c, right d in this order. . When the length of the magnet 3 in the optical fiber sensor 1 to be arranged in the AGF steel pipe is set in advance, the magnet 3 is not attached to the portion protruding from the AGF steel pipe A. Also, the support 4
It is not always necessary to attach the magnet 3 to the portion corresponding to the tip of the.

Next, a case where the above-mentioned optical fiber sensor 1 is installed by using the half steel support 13 as an object to be measured will be described. The half steel support bar 13 has magnetism as a whole, and the optical fiber sensor 1 can be directly attached by magnetically adhering the magnet 3. A half steel support bar 13 to which the fiber sensor 1 is not attached is brought in, and a pair of the half steel support bar 13 is used to assemble the inverted U-shaped support bar first.
Then, the optical fiber sensor 1 is brought into the working place, and the magnets 3 are magnetically attached to the insides of the upper and lower flanges 14 with the webs in between (see FIG. 7), and the optical fiber sensor 1 is assembled into an inverted U shape. Installed along the length of the steel support. The optical fiber sensor 1 of the flange 14
The surface to which is attached is lightly polished if rust is noticeable, and the optical fiber 2 is supported by the steel support 13 even if the magnet 3 is interposed.
Behave as a unit with. A plate 15 for joining is provided at an end portion corresponding to the top end of the tunnel face in each of the half steel supporters 13, but the mounting positions of the optical fiber sensors 1 of the steel supporters 13 are continuous. Notch 16 corresponding to the inside of the flange 14
The optical fiber sensor 1 may be attached to the assembled steel support through the notch 16. In the optical fiber sensor 1, the optical fiber 2 is in a single state except for the mounting portion for the steel support, and after the optical fiber 2 is mounted along the side wall of the tunnel or the like, up to the previously installed ground measuring device. It is fused with the optical fiber for wiring, and the fused portion is placed in the terminal box.

When the optical fiber sensor 1 is directly installed with the steel support bar as the object to be measured, the strain (distribution of strain) measured by the optical fiber sensor 1 is multiplied by the Young's modulus of the steel support bar to be assembled. It is possible to obtain the edge stress (continuous stress distribution along the shape of the steel support) of the specified steel support, as well as the bending stress and the bending moment from the bending strain. You can understand the behavior of the ground supported by. In this way, the distortion, stress, bending moment, etc., of the steel support structure that has been constructed to support the ground by assembling the half steel support structure in the circumferential direction (steel support) It is possible to continuously measure the direction along the shape of the support work. Further, since the optical fiber sensor is provided with the magnet in advance, it can be easily attached to the steel supporting work which has been assembled and constructed in advance at the construction site.

[0018]

According to the present invention described above, since the optical fiber sensor is one in which a magnet is attached to the optical fiber in advance, a support for putting the optical fiber sensor into the AGF steel pipe in advance outside the construction site. It is no longer necessary to attach it to the steel support of the object to be measured, and the optical fiber sensor can be brought to the construction site and attached to the installation location. Then, when the optical fiber sensor is installed inside an object to be measured such as an AGF steel pipe, the supporting body for supporting the optical fiber sensor is formed by connecting the divided bodies, and the optical fiber sensor is attached to the divided body and the divided body is attached. By repeating the splicing and the insertion and placement of the support body into the steel pipe in order, it is not necessary to handle the long object to which the optical fiber sensor is attached in advance in the field. Also, when installing this optical fiber sensor on a steel support that is formed by assembling a half steel support, install the optical fiber sensor so that it passes through the joint part of the half steel support. By attaching it, it becomes possible to measure the strain of the entire assembled steel supporting structure, and it is possible to eliminate unmeasurable points, which is a very practical effect.

[Brief description of drawings]

FIG. 1 shows an example of an optical fiber sensor according to the present invention, in which (a) is an explanatory view showing a cross section along a longitudinal direction,
(B) is an explanatory view showing a state in which an example is viewed from above.

FIG. 2 is an explanatory view showing a support.

FIG. 3 is an explanatory view showing a support in a cross section along a longitudinal direction.

FIG. 4 is an explanatory view showing a support in a cross section in a direction orthogonal to the longitudinal direction.

FIG. 5 is an explanatory diagram showing an arrangement example of optical fiber sensors.

FIG. 6 is an explanatory view showing a state in which an optical fiber sensor is attached to a steel support bar which is made up of a half steel support bar.

FIG. 7 is an explanatory view showing a cross section of a mounting state of the optical fiber sensor with respect to a steel supporting member.

[Explanation of symbols]

1. Optical fiber sensor 2 ... Optical fiber 3 ... Magnet 4 ... Support 5 ... divided body 8 ... Magnetic field 13 ... Steel support

Claims (4)

[Claims] 1. An optical fiber sensor in which magnets are attached to an optical fiber at intervals in the longitudinal direction of the optical fiber. 2. The method according to claim 1 for a long magnetic object to be measured.
A method for installing an optical fiber sensor, wherein a magnet in the optical fiber sensor is magnetically attached, and the optical fiber sensor is attached over the length direction of the object to be measured. 3. A magnet in the optical fiber sensor according to claim 1 is magnetically attached to a long support body which is inserted and arranged inside a long tubular object to be measured and which has a magnetized portion, to thereby obtain an optical fiber. A method of installing an optical fiber sensor, characterized in that a sensor is attached along a length direction of a support, and the support is inserted and arranged in the object to be measured. 4. The optical fiber sensor is attached by repeating the step of joining the divided bodies and the attachment of the optical fiber sensor to the joined divisions. The method for installing an optical fiber sensor according to claim 3, wherein the divided bodies are sequentially inserted into the object to be measured.