Optical fiber installation structure and optical fiber installation method

Abstract

An optical fiber installation structure and an optical fiber installation method are provided that adequately protect optical fibers installed together in a concrete skeleton during construction of the concrete skeleton. [Solution] The optical fiber installation structure 1 comprises a first optical fiber 10 connected to a support material 40 at least partially buried in a concrete body 30, with a protrusion 11 protruding from the main surface 30b of the concrete body 30, and a storage section 20 fixed to at least one of the concrete body 30 and the support material 40 and storing the protrusion 11 in a storage space 20b formed therein, and at least one of the concrete body 30 and the storage section 20 shields the first optical fiber 10 from the external space (hole portion 5a).

Description

[Technical Field]

[0001] The present invention relates to an optical fiber installation structure and an optical fiber installation method. [Background technology]

[0002] Conventionally, the technology of Patent Document 1 listed below has been known as a method for determining the soundness, etc., of concrete structures. Patent Document 1 discloses that a coated optical fiber is attached along the PC steel rods of a reinforcing cage, and then centrifugal molding and curing are performed to manufacture a prefabricated pile. The method described in Patent Document 1 verifies the degree of damage to the structure based on the amount of strain in the optical fiber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-213676 Summary of the Invention [Problem to be solved by the invention]

[0004] After concrete is poured, a portion of the support material embedded in the concrete skeleton may be chipped off. The optical fiber in Patent Document 1 is covered with a coating material such as a resin material or a fiber material, but there is a possibility that the optical fiber may not be adequately protected when the chipping process is carried out. In order to utilize the functions of the optical fiber placed inside the concrete skeleton during the construction of the concrete skeleton, including the concrete pouring and chipping processes, a structure and method for adequately protecting the optical fiber is required.

[0005] An object of the present disclosure is to provide an optical fiber installation structure and an optical fiber installation method that adequately protect optical fibers installed together in a concrete structure during construction of the concrete structure. [Means for solving the problem]

[0006] The gist of the present invention lies in the following [1] to [8].

[0007] [1] An optical fiber installation structure comprising: an optical fiber connected to a support material at least partially embedded within a concrete structure, with a protrusion protruding from a main surface of the concrete structure; and a storage unit fixed to at least one of the concrete structure and the support material, for storing the protrusion within a storage space formed therein, wherein at least one of the concrete structure and the storage unit shields the optical fiber from external space.

[0008] [2] The optical fiber installation structure according to [1], further comprising another optical fiber connected to the protruding portion of the optical fiber within the storage space of the storage section.

[0009] [3] The optical fiber installation structure according to [1] or [2], wherein the storage section has a cylindrical wall section extending toward one side and forming an opening that is open toward the one side, the protruding section of the optical fiber is inserted into the storage space through the opening, and at least a part of the opening and one end of the wall section are covered by a part of the concrete structure.

[0010] [4] The optical fiber installation structure according to [3], further comprising another optical fiber connected to the protruding portion of the optical fiber within the storage space of the storage section, the other optical fiber extending into the external space through the opening.

[0011] [5] The optical fiber installation structure according to any one of [1] to [4], wherein the storage section has a shape that tapers toward the one side.

[0012] [6] An optical fiber installation structure according to any one of [1] to [5], wherein the protrusion protrudes from the main surface of the concrete body that can be exposed after a portion of the concrete body is chipped away, and at least one of the concrete body that can be exposed after a portion of the concrete body is chipped away and the storage section shields the protrusion from external space.

[0013] [7] A method for laying an optical fiber, comprising: an optical fiber placement step of placing an optical fiber together with a support material in a concrete formwork; a body construction step of pouring concrete into the concrete formwork to construct a concrete body so that a protruding portion of the optical fiber protrudes; and a storage step of fixing the protruding portion to at least one of the concrete body and the support material and storing the protruding portion in a storage space of a storage unit, wherein at least one of the concrete body and the storage unit shields the optical fiber from external space during at least one of the body construction step and the storage step.

[0014] [8] The optical fiber installation method according to [7], further comprising a connecting step of connecting another optical fiber to the protruding portion of the optical fiber within the storage space of the storage unit after the optical fiber placement step and before the structure construction step. [Effects of the Invention]

[0015] According to the present disclosure, it is possible to provide an optical fiber installation structure and an optical fiber installation method that appropriately protect optical fibers installed together in a concrete skeleton during construction of the concrete skeleton. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram schematically illustrating a part of an optical fiber installation structure according to an embodiment; [Figure 2] 1 is a diagram illustrating an optical fiber installation structure during a framework construction step of an optical fiber installation method according to an embodiment of the present invention; [Figure 3] 1 is an enlarged view schematically illustrating an optical fiber installation structure according to an embodiment of the present invention; [Figure 4] 1 is a flowchart illustrating an example of an optical fiber laying method according to an embodiment. [Figure 5] 1 is a diagram illustrating an optical fiber installation structure during an optical fiber placement step of an optical fiber installation method according to an embodiment of the present invention; [Figure 6] 1 is a diagram illustrating an optical fiber installation structure during a storage step of an optical fiber installation method according to an embodiment of the present invention; [Figure 7] 1 is a diagram illustrating an optical fiber installation structure during a support material placement step of an optical fiber installation method according to an embodiment of the present invention; [Figure 8] 1 is a diagram illustrating an optical fiber installation structure during a backfilling step of an optical fiber installation method according to an embodiment of the present invention; [Figure 9] 1 is a diagram illustrating an optical fiber installation structure during a drilling step of an optical fiber installation method according to an embodiment of the present invention; [Figure 10] 1 is a diagram illustrating an optical fiber installation structure during a chipping step of an optical fiber installation method according to an embodiment of the present invention; [Figure 11] FIG. 2 is a diagram schematically illustrating an optical fiber installation structure during a second connection step of the optical fiber installation method according to one embodiment. [Figure 12] FIG. 10 is a diagram schematically illustrating an optical fiber installation structure according to a modified example. [Figure 13] FIG. 10 is a diagram schematically illustrating a part of an optical fiber installation structure according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of an optical fiber installation structure and an optical fiber installation method according to the present disclosure will be described in detail with reference to the drawings. An optical fiber installed by the optical fiber installation structure and the optical fiber installation method can measure temperature changes in concrete that constitutes a concrete structure. The optical fiber can also measure strain (stress) of a pile. The optical fiber installation structure and the optical fiber installation method according to the present disclosure are used when installing an optical fiber that is installed during pouring of a concrete structure.

[0018] [Optical fiber installation structure] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that identical or corresponding parts in each drawing are denoted by the same reference numerals, and redundant description will be omitted. In the following description, the X-axis, Y-axis, and Z-axis directions are mutually orthogonal axes in a Cartesian coordinate system in three-dimensional space. The X-axis and Y-axis directions are, for example, horizontal directions. For example, the X-axis direction is a horizontal direction, and the Y-axis direction is a horizontal direction intersecting the X-axis direction. In this embodiment, the positive direction of the X-axis direction is referred to as "rightward," the negative direction of the X-axis direction is referred to as "leftward," and the X-axis direction is referred to as the "left-right direction." In this embodiment, the positive direction of the Y-axis direction is referred to as "forward," the negative direction of the Y-axis direction is referred to as "rearward," and the Y-axis direction is referred to as the "front-to-back direction." The left-to-right direction is an example of a direction intersecting the front-to-back direction. The Z-axis direction is, for example, the up-down direction (vertical direction). In this embodiment, the positive direction of the Z-axis direction is referred to as "upward," and the negative direction of the Z-axis direction is referred to as "downward."

[0019] FIG. 1 is a diagram schematically illustrating a portion of an optical fiber installation structure according to an embodiment. FIG. 2 is a diagram schematically illustrating an optical fiber installation structure during a skeleton construction step of an optical fiber installation method according to an embodiment. The optical fiber installation structure 1 shown in FIGS. 1 and 2 is applied, for example, during the construction of a building 2 including a concrete skeleton 30 and supporting members 40. Hereinafter, the optical fiber installation structure 1 may be simply referred to as the "installation structure 1." The installation structure 1 is a structure for installing optical fibers on supporting members 40 arranged within a concrete skeleton 30 of a concrete formwork 5. The installation structure 1 can be applied to various concrete skeletons, such as surface members, column members, and beam members, in various reinforced concrete structures, such as piles, diaphragm walls, box culverts, bridge piers, and water gates.

[0020] The installation structure 1 includes at least one first optical fiber 10 (an example of an optical fiber) and at least one storage section 20. The installation structure 1 of this embodiment further includes at least one support member 40, at least one second optical fiber 50 (another optical fiber) connectable to the at least one first optical fiber 10, a plurality of fixing members 60, and a measuring instrument 70.

[0021] First, the concrete skeleton 30 and the support material 40 on which the first optical fiber 10 is to be installed will be described. As illustrated in FIG. 2 , the concrete skeleton 30 is constructed within a concrete formwork 5. Hereinafter, the concrete formwork 5 may be simply referred to as the formwork 5. The size, shape, and opening direction of the formwork 5 are appropriately set depending on the specifications of the structure 2 and the construction method of the structure 2. A support material 40 is placed in a hole 5a inside the formwork 5. The support material 40 is a member used to reinforce the structure 2. The support material 40 is, for example, at least a part of a reinforcing bar cage (reinforcing steel). When the support material 40 is a reinforcing bar cage used for a cast-in-place pile, the concrete formwork 5 corresponds to, for example, the ground. When the support material 40 is used for a cast-in-place pile, the concrete skeleton 30 and the support material 40 are integrated to form the cast-in-place pile. The support material 40 is, for example, a steel material. In this case, the support material 40 is arranged in the hole 5a of the formwork 5. The length, thickness, shape, and reinforcement density of the support material 40 are set appropriately according to the specifications of the building 2 and the construction method of the building 2.

[0022] As shown in Figures 1 and 2, the support material 40 is, for example, cage-shaped. The support material 40 is, for example, a reinforcing bar cage, and has, for example, at least one extension portion, an upper frame portion 42 and a lower frame portion 43. The support material 40 of this embodiment has, as at least one extension portion, a plurality of extension portions 41. Each of the plurality of extension portions 41 extends in the vertical direction. The plurality of extension portions 41 is, for example, the main reinforcement of a cast-in-place pile. Each of the plurality of extension portions 41 has an upper end portion 41a and a lower end portion 41b. The plurality of extension portions 41 extend shorter than the vertical length of the hole portion 5a in the formwork 5. The plurality of extension portions 41 extend, for example, longer than the length from the bottom surface of the formwork 5 to a reference plane L. The reference plane L will be described later.

[0023] The upper frame portion 42 is connected to the upper ends 41a of the multiple extending portions 41. The lower frame portion 43 is connected to the lower ends 41b of the multiple extending portions 41. The multiple extending portions 41 are fixed to the upper frame portion 42 and the lower frame portion 43, for example, by welding. The upper frame portion 42 and the lower frame portion 43 are, for example, annular. Note that the shape and number of the upper frame portion 42 and the lower frame portion 43 are not limited as long as they are frame-shaped.

[0024] The concrete structure 30 is poured into a formwork 5 in which the support members 40 are placed. The concrete that constitutes the concrete structure 30 is poured using the same procedure as in the construction of a normal concrete structure, and the concrete is cured. As a result, at least a portion of the support members 40 is embedded in the concrete structure 30. The formwork 5 may then be removed using the same procedure as in the construction of a normal concrete structure. For example, if the support members 40 are cast-in-place piles, the upper region of the concrete structure 30 (the pile head) is a weak concrete structure and may be chipped away. Therefore, the upper portion of the concrete structure 30 immediately after pouring is subject to chipping. The reference plane L is a boundary surface that vertically separates the upper region of the concrete structure 30 that is subject to chipping from the lower region that is not subject to chipping. The reference plane L extends horizontally. It should be noted that chipping refers to at least one of a process of scraping off and a process of cutting away hard material such as concrete.

[0025] Next, the first optical fiber 10 and the second optical fiber 50 will be described. FIG. 3 is an enlarged view schematically illustrating an optical fiber installation structure according to one embodiment. In the example illustrated in FIGS. 1 to 3, one first optical fiber 10 is provided relative to a concrete structure 30 and a support member 40. The first optical fiber 10 and the second optical fiber 50 are examples of optical fiber cables. The first optical fiber 10 and the second optical fiber 50 may be, for example, optical fiber cores, or may be optical fiber cables in the narrow sense that include a plurality of bundled optical fiber cores. One end of the second optical fiber 50 can be connected to a protrusion 11 (described later) that is an end of the first optical fiber 10 installed in the concrete structure 30 by the optical fiber installation method.

[0026] The first optical fiber 10 is connected to at least one support member 40. The first optical fiber 10 is, for example, longer than the vertical length of the hole 5a of the formwork 5. The first optical fiber 10 may have a length equal to or greater than twice the vertical length of the hole 5a of the formwork 5. The first optical fiber 10 has a shape that is folded back near the bottom of the hole 5a of the formwork 5. The first optical fiber 10 has a protrusion 11 that protrudes from a reference plane L (the main surface 30b of the concrete mass 30 after a portion of the concrete mass 30 has been chipped (see FIG. 11)). The protrusion 11 may be the upper end of the first optical fiber 10. If the first optical fiber 10 is folded back inside the hole 5a, the protrusion 11 may be both ends of the first optical fiber 10.

[0027] The first optical fiber 10 is fixed to the support member 40 by a first fixing member 61, which will be described later. The first optical fiber 10 is connected to, for example, two of the multiple extending portions 41. The first optical fiber 10 is connected to, for example, one of the multiple extending portions 41, and is connected to the lower frame portion 43, and is also connected to another extending portion 41 that is located at a position opposite the one extending portion 41 with respect to the center of the lower frame portion 43. The first optical fiber 10 is inserted into the hole 5a of the form 5 together with the support member 40 in a state where it is fixed to the lower frame portion 43. As the support member 40 is inserted into the hole 5a of the form 5, the first optical fiber 10 is fixed sequentially from the bottom to the top of the extending portion 41.

[0028] The second optical fibers 50 shown in FIG. 2 can have one end connected to each protruding portion 11 of the first optical fiber 10, and the other end connected to a measuring instrument 70 (see FIG. 2). In this embodiment, each of a pair of second optical fibers 50 is connected to each protruding portion 11 of the first optical fiber 10. The second optical fibers 50 have a pair of second laid optical fibers 51 and a pair of second inspection optical fibers 52 connectable to the first optical fiber 10. The second laid optical fibers 51 and the second inspection optical fibers 52 are not arranged at the same time. The second laid optical fibers 51 are connected to the first optical fiber 10 before a portion of the concrete body 30 is chipped. The second inspection optical fibers 52 are connected to the first optical fiber 10 after the portion of the concrete body 30 is chipped.

[0029] Fig. 3 is an enlarged view schematically illustrating an optical fiber installation structure according to one embodiment. The storage unit 20 shown in Figs. 2 and 3 stores the protruding portion 11 of the first optical fiber 10. The storage unit 20 is made of, for example, a metal material. The storage unit 20 is made of, for example, a material that is less likely to break and has a small amount of deformation even when it comes into contact with a chipping machine during a chipping process of the concrete body 30. That is, the storage unit 20 has a function of protecting the protruding portion 11 of the stored first optical fiber 10.

[0030] The storage section 20 is fixed to at least one of the concrete body 30 and the support material 40. The storage section 20 is fixed to the support material 40 by, for example, a second fixing member 62 described below. The storage section 20 has a cylindrical wall section 21 that extends downward (to one side) and forms an opening 20a that opens downward. The wall section 21 extends, for example, in the up-down direction and has a cylindrical shape.

[0031] The storage section 20 further has a top cover 22 and a bottom cover 25. The top cover 22 covers the upper end of the wall section 21. The top cover 22 does not have, for example, an opening that penetrates in the vertical direction. The bottom cover 25 covers a portion of the opening 20a of the wall section 21. The top cover 22 may be formed integrally with the wall section 21.

[0032] The bottom cover 25 may be detachably fixed to the wall 21. For example, the bottom cover 25 is fixed to the wall 21 at a position above the lower end of the wall 21 and below the reference plane L. The bottom cover 25 may be fixed to the lower end of the wall 21. The bottom cover 25 has, for example, a first opening 25a and a second opening 25b penetrating in the vertical direction as the opening 20a. The first opening 25a is an opening through which the first optical fiber 10 can be inserted. The second opening 25b is an opening through which the second optical fiber 50 can be inserted. At least a portion of the opening 20a and the lower end 21b (an example of an end on one side) of the wall 21 are covered by a portion of the concrete skeleton 30. That is, the concrete skeleton 30 is located below the lower end 21b of the wall 21, the first opening 25a, and the second opening 25b.

[0033] The storage section 20 defines a storage space 20b therein. The storage space 20b is a space surrounded by a wall section 21, an upper cover section 22, and a bottom cover section 25. The protruding portion 11 of the first optical fiber 10 is stored in the storage space 20b. The protruding portion 11 of the first optical fiber 10 is inserted into the storage space 20b through the opening 20a and arranged therein. The protruding portion 11 of the first optical fiber 10 is wound and stored in the storage space 20b. The protruding portion 11 of the first optical fiber 10 is stored so that its end is located below the storage space 20b.

[0034] The second optical fiber 50 is connected to the first optical fiber 10 in the storage space 20b of the storage unit 20. One end of the second optical fiber 50 is disposed in the storage space 20b through the second opening 25b. The second optical fiber 50 extends to the external space of the storage space 20b (here, the hole 5a) through the second opening 25b.

[0035] The multiple fixing members 60 include multiple first fixing members 61 and multiple second fixing members 62. The multiple first fixing members 61 shown in FIGS. 1 and 2 fix the first optical fiber 10 and the support member 40. The multiple first fixing members 61 may be, for example, bundling wires. The multiple first fixing members 61 are, for example, arranged at intervals of approximately 500 mm to 3000 mm in the multiple extending portions 41, and fix each of the multiple extending portions 41 and the first optical fiber 10. The multiple first fixing members 61 are, for example, arranged between a pair of extending portions 41 in the lower frame portion 43, and fix the lower frame portion 43 and the first optical fiber 10. As a result, the first optical fiber 10 is fixed without bulging (bending) relative to the support member 40. In this way, the first optical fiber 10 is not adhered to the support member 40, but is bundled by the first fixing members 61 so as to follow the support member 40. After the concrete body 30 is poured, the first optical fiber 10, the concrete body 30, and the support material 40 are integrated as the concrete hardens.

[0036] 2 and 3 secure the storage section 20 and the support material 40 together. The second fixing members 62 may be, for example, binding wires. The second fixing members 62 secure, for example, each of the extension sections 41 to the storage section 20. The second fixing members 62 may secure, for example, each of the extension sections 41 to the storage section 20 and the second optical fiber 50. Note that if the storage section 20 and the support material 40 are secured by welding or the like, the installation structure 1 may not include the second fixing members 62.

[0037] The measuring instrument 70 shown in FIG. 2 is a device connectable to the second optical fiber 50. The measuring instrument 70 inputs laser pulse light into the optical fiber strand of the second optical fiber 50 and receives scattered light returning from each position in the longitudinal direction of the optical fiber strand. By inputting laser pulse light into the second optical fiber 50, the measuring instrument 70 can input laser pulse light into the first optical fiber 10 and receive scattered light from the first optical fiber 10. The measuring instrument 70 calculates the strain and temperature at each position in the longitudinal direction of the first optical fiber 10 based on the principle that the intensity and wavelength of the scattered light depend on the strain applied to the optical fiber strand and temperature change. The measuring instrument 70 may calculate at least one of the longitudinal strain distribution and the temperature distribution in the concrete structure 30 based on the strain and temperature at each position in the longitudinal direction of the first optical fiber 10.

[0038] [Optical fiber installation method] Next, an optical fiber laying method will be described with reference to Figs. 4 to 10. Fig. 4 is a flowchart showing an example of an optical fiber laying method according to an embodiment. In an optical fiber laying structure, for example, a preparation process is first carried out as step S11. Fig. 5 is a diagram schematically showing an optical fiber laying structure during the optical fiber arrangement process of an optical fiber laying method according to an embodiment. Fig. 5 may also show a part of the preparation process of step S11. In the preparation process, the hole 5a of the formwork 5 is prepared. The vertical length of the hole 5a is equal to or greater than the vertical length of the support material 40. A reinforcing formwork 80 is placed at the upper end of the hole 5a.

[0039] Subsequently, an optical fiber arranging process is performed in step S12. In the optical fiber arranging process, the first optical fiber 10 is connected to the support material 40. The first optical fiber 10 is fixed to the lower frame portion 43 of the support material 40 by a first fixing member 61. The first optical fiber 10 is fixed to the lower end portions 41b of the two extending portions 41 of the support material 40 by the first fixing member 61.

[0040] Next, a support material placement step is performed as step S13. FIG. 5 may also show a portion of the support material placement step of step S13. In the support material placement step, the support material 40 connected to the first optical fiber 10 is placed in the formwork 5. The support material 40 is inserted into the hole 5a of the formwork 5 while being suspended by a work machine such as a crane (not shown). As the support material 40 is inserted into the hole 5a of the formwork 5, the first optical fiber 10 is guided so as to follow the support material 40. As the support material 40 is inserted (moved), the first optical fiber 10 is guided while being subjected to a tensile force. As the support material 40 is inserted into the hole 5a of the formwork 5, the first optical fiber 10 is inserted into the hole 5a of the formwork 5. When the position of a certain first fixing member 61 that fixes the first optical fiber 10 and the support material 40 reaches a predetermined depth, another first fixing member 61 fixes the first optical fiber 10 and the support material 40. As a result, the first optical fiber 10 is placed in the hole 5a of the form 5 along the support material 40. The support material placement step may be a step included in the optical fiber placement step. That is, in the step including the optical fiber placement step and the support material placement step described above, the first optical fiber 10 is placed in the form 5 together with the support material 40.

[0041] In the support material placement step (step S13), the central and lower end portions 41b of the extending portion 41 of the support material 40, on which the storage portion 20 can be placed, are inserted into the hole 5a, leaving only the upper end portion 41a of the extending portion 41, and then a storage step is performed as step S14. FIG. 6 is a diagram schematically showing an optical fiber installation structure during execution of an optical fiber installation method according to one embodiment. As shown in FIG. 6, in the storage step, for example, the storage portion 20 is fixed to the upper end portion 41a of the extending portion 41 by a second fixing member 62. Next, the protruding portion 11 of the first optical fiber 10 is stored in the storage portion 20. The first optical fiber 10 is stored in the storage space 20b of the storage portion 20 so that the end of the protruding portion 11 is located on the opening 20a side of the storage portion 20. When the storage section 20 is fixed by a method other than welding, such as the second fixing member 62, the storage section 20 may be fixed to the upper end 41 a of the extending section 41 after the protruding section 11 of the first optical fiber 10 is stored in the storage section 20. When the storage section 20 is fixed by welding, fixing the storage section 20 to the upper end 41 a of the extending section 41 before storing the protruding section 11 of the first optical fiber 10 in the storage section 20 can prevent the first optical fiber 10 from being damaged by sparks generated during welding.

[0042] Subsequently, a first splicing step is executed as step S15. The first splicing step may be included in the storing step (step S14). In the first splicing step, a second optical fiber 50 is spliced to the first optical fiber 10 in the storage space 20b of the storage unit 20. Each protrusion 11 of the first optical fiber 10 stored in the storage space 20b of the storage unit 20 is spliced to one end of a pair of second laid optical fibers 51. The spliced portion between the protrusion 11 and one end of the second laid optical fiber 51 is stored in the storage space 20b. After the protrusion 11 and one end of the second laid optical fiber 51 are spliced, the bottom cover 25 is fixed to the wall 21. In this case, the first optical fiber 10 is inserted through the first opening 25a, and the second laid optical fiber 51 is inserted through the second opening 25b. As a result, the storage unit 20 shields the first optical fiber 10 from the external space (hole 5a) in the storage step (step S14) and the first connecting step (step S15). The other end of the second laid optical fiber 51 is connected to the measuring instrument 70. When the first connecting step is completed, the measuring instrument 70 may input laser pulse light to the first optical fiber 10 via the second optical fiber 50 and receive scattered light. As a result, it may be possible to inspect whether the first optical fiber 10 is properly connected to the second optical fiber 50.

[0043] 7 is a diagram schematically illustrating an optical fiber installation structure during the support material placement step of the optical fiber installation method of one embodiment. As shown in FIG. 7, the support material placement step (step S13) continues even during the storage step (step S14) and the first splicing step (step S15). For example, after the storage step (step S14) is completed and the first optical fiber 10 is spliced to the second installed optical fiber 51 in the first splicing step (step S15), the support material 40 is inserted into the hole 5a of the formwork 5 while being suspended by a work machine such as a crane and a guide member 81 (not shown), as shown in FIG. 7. As a result, the first optical fiber 10, the storage unit 20, and the support material 40 are arranged at predetermined positions in the hole 5a of the formwork 5. The storage unit 20 is arranged so that the bottom cover 25 is located at the same level as or below the reference plane L, and so that at least the upper end 21a of the wall 21 is located above the reference plane L.

[0044] Subsequently, in step S16, a skeleton construction process is executed. As shown in FIG. 2, in the skeleton construction process, concrete is poured into the formwork 5, and a concrete skeleton 30 is constructed so that the protruding portion 11 of the first optical fiber 10 protrudes. The concrete is poured from the bottom of the hole 5a of the formwork 5 to above the reference plane L. The concrete is poured, for example, so that a portion of the storage section 20 is exposed. As a result, the storage section 20 and the concrete skeleton 30 shield the first optical fiber 10 from the external space (the hole 5a) in the storage process (step S14), the first connection process (step S15), and the skeleton construction process (step S16). The concrete skeleton 30 includes, for example, a chipping target region 33 above the reference plane L.

[0045] Subsequently, an optical fiber checking process is executed as step S17. In the optical fiber checking process, the measuring instrument 70 may emit laser pulse light to the first optical fiber 10 via the second optical fiber 50 and receive scattered light. This allows the first optical fiber 10 to check the soundness of the concrete body 30 from inside the concrete body 30.

[0046] Subsequently, a backfilling process is performed as step S18. Fig. 8 is a diagram schematically illustrating an optical fiber installation structure during the backfilling process of the optical fiber installation method of one embodiment. As shown in Fig. 8, in the backfilling process, concrete is poured into the hole 5a of the formwork 5. The concrete is poured up to the upper end of the formwork 5. The concrete is poured, for example, so that the storage section 20 is buried. The concrete body 30 includes, for example, a backfilling region 35 above the chipping target region 33. After the backfilling process is performed, the concrete is cured for a predetermined time.

[0047] Subsequently, a cutting step is carried out as step S19. As shown in Fig. 8, in the cutting step, the second laid optical fiber 51 protruding from the hole 5a of the formwork 5 is cut. By cutting the second laid optical fiber 51 in the cutting step, the excavation step (step S20) and the chipping step (step S21) described later can be easily carried out.

[0048] Subsequently, an excavation process is performed as step S20. Fig. 9 is a diagram schematically showing an optical fiber installation structure during the excavation process of the optical fiber installation method of one embodiment. As shown in Fig. 9, in the excavation process, the formwork 5 is excavated down to the reference plane L. In the excavation process, at least a part of the backfilled area 35 of the concrete skeleton 30 that was poured in the backfilling process (step S18) may be chipped off.

[0049] Next, in step S21, a chipping process is performed. FIG. 10 is a diagram schematically illustrating an optical fiber installation structure during the chipping process of the optical fiber installation method of one embodiment. As shown in FIG. 10, in the chipping process, a chipping target area 33 of the concrete skeleton 30 that was cast in the skeleton construction process (step S16) is chipped. The chipping process is so-called pile head chipping. In the chipping process, the concrete skeleton 30 is chipped down to the reference plane L, and the main surface 30b of the concrete skeleton 30 is exposed. By positioning the bottom cover 25 of the storage unit 20 at the same position as or below the reference plane L, even if the concrete skeleton 30 is chipped down to the reference plane L in the chipping process, the first optical fiber 10 is stored in the storage unit 20 and is appropriately protected. The main surface 30b is a plane that is along the reference plane L. During the chipping process, even when the chipping target area 33 of the concrete body 30 around the first optical fiber 10 is chipped by a work machine, the storage section 20 can appropriately protect the first optical fiber 10.

[0050] Next, a removal process is performed as step S22. FIG. 11 is a diagram schematically illustrating an optical fiber installation structure during the second splicing process of the optical fiber installation method of an embodiment. FIG. 11 is a diagram schematically illustrating, for example, an optical fiber installation structure after the removal process of the optical fiber installation method of an embodiment. As shown in FIG. 11, in the removal process, the storage unit 20 is removed from the concrete body 30 and the support material 40. The second fixing member 62 is detached from the upper end 41a of the extension portion 41, so that the storage unit 20 can be removed (detached) from the support material 40. The lower end 21b of the wall portion 21 and the bottom cover portion 25 of the storage unit 20 embedded in the concrete body 30 are removed from the concrete body 30. The storage unit 20 is removed by, for example, pulling it out upward. The storage unit 20 may be pulled out upward while being vibrated, for example. The storage section 20 may be cut along the reference plane L. The timing at which the storage section 20 is removed from the concrete body 30 and the timing at which the storage section 20 is removed from the support material 40 may be simultaneous or different, and the order of these steps does not matter.

[0051] Subsequently, in step S23, a second splicing step is performed. As shown in Fig. 11, in the second splicing step, a second optical fiber 50 is spliced to the first optical fiber 10. Each protrusion 11 of the first optical fiber 10 is connected to one end of a pair of second inspection optical fibers 52. The other end of the second laid optical fiber 51 is connected to a measuring instrument 70.

[0052] Next, a measurement step is executed in step S24. In the measurement step, the measuring instrument 70 may input laser pulse light to the first optical fiber 10 via the second optical fiber 50 and receive scattered light. The measuring instrument 70 measures the intensity and wavelength of the scattered light. The measuring instrument 70, for example, calculates the strain and temperature at each position in the longitudinal direction of the first optical fiber 10. The measuring instrument 70, for example, calculates at least one of the longitudinal strain distribution and the temperature distribution in the concrete body 30 based on the strain and temperature at each position in the longitudinal direction of the first optical fiber 10. This allows the measuring instrument 70 to measure, for example, the wiring direction of the optical fiber in the concrete body 30 (for example, at least one of the vertical direction of the extension portion 41 of the support material 40 and the horizontal direction of the lower frame portion 43). After the measurement step (step S24) is completed, the optical fiber installation method ends.

[0053] Next, the effects of the optical fiber installation structure 1 and the optical fiber installation method according to this embodiment will be described in comparison with the prior art. Conventionally, when pile foundations are used during the construction of a building, measuring at least one of the deformation of the piles themselves and the deformation of the concrete (ground) that occurs during construction can be applied to level management of the building. The level includes the height or horizontal position of each part of the building during construction. It is thought that the accuracy of building predictions and the quality of the building can be improved by reflecting the measured deformation in the prediction and management of the building's level.

[0054] For example, if a building is made of reinforced concrete (RC), installing optical fiber around piles (supporting materials) before pouring concrete can measure temperature changes during pouring, allowing the filling status of the concrete to be understood. Traditionally, measuring instruments such as rebar meters, thermocouples, and strain gauges have been used to measure pile characteristics, including strain (stress) and temperature. However, these instruments can only measure the characteristic of a portion of the pile, and cannot measure the characteristic continuously over the entire length of the pile. While it is possible to measure the strain distribution of the entire pile by distributing a large number of measuring instruments, this method requires thick cables to be wired to the instruments, which can result in cross-sectional defects in the pile and require a lot of wiring work.

[0055] In light of the above-mentioned problems, a method for measuring the above-mentioned feature quantities by wiring an optical fiber together with a pile has been proposed in the past, but the optical fiber is prone to breakage. Here, after concrete is poured, a portion of the support material embedded in the concrete may be chipped off, such as by chipping the pile head. For example, the optical fiber may be covered with a coating material such as a resin material or a fiber material, but when the chipping process described above is performed, the optical fiber may not be adequately protected. A structure and method for adequately protecting the optical fiber is needed to utilize the functions of the optical fiber placed within the concrete skeleton during construction of the concrete skeleton, including the concrete pouring and chipping processes.

[0056] An optical fiber installation structure 1 according to one embodiment includes a first optical fiber 10 connected to a support material 40 at least a portion of which is buried in a concrete skeleton 30, the first optical fiber 10 having a protrusion 11 protruding from a main surface 30b of the concrete skeleton 30, and a storage unit 20 fixed to at least one of the concrete skeleton 30 and the support material 40 and storing the protrusion 11 in a storage space 20b formed therein, and at least one of the concrete skeleton 30 and the storage unit 20 shields the first optical fiber 10 from an external space (hole 5a). For example, the protrusion 11 protrudes from the main surface 30b of the concrete skeleton 30 that may be exposed after a portion of the concrete skeleton 30 is chipped (chipping step: step S21), and at least one of the concrete skeleton 30 and the storage unit 20 that may be exposed after the portion is chipped shields the protrusion 11 of the first optical fiber 10 from the external space.

[0057] In addition, an optical fiber laying method according to one embodiment includes an optical fiber placement process (step S12) of placing the first optical fiber 10 together with a support material 40 in a concrete formwork 5, a structure construction process (steps S16, S20, and S21) of pouring concrete into the concrete formwork 5 and constructing a concrete structure 30 so that the protrusion 11 of the first optical fiber 10 protrudes, and a storage process (step S14) of fixing the protrusion 11 to at least one of the concrete structure 30 and the support material 40 and storing it in the storage space 20b of the storage section 20, and in at least one of the structure construction process and the storage process, at least one of the concrete structure 30 and the storage section 20 shields the first optical fiber 10 from the external space.

[0058] In the optical fiber installation structure 1 and the optical fiber installation method described above, the storage section 20 can protect the protruding portion 11 of the first optical fiber 10 protruding from the main surface 30b of the concrete body 30. Because the first optical fiber 10 can be exposed from the concrete body 30, it can be appropriately connected to the measuring instrument 70. Therefore, before, during, and after pouring concrete, a light beam such as a laser pulse beam can be incident on the first optical fiber 10, and scattered light can be received to measure characteristic quantities including at least one of the strain and temperature at each position in the longitudinal direction of the first optical fiber 10 and the longitudinal strain distribution and temperature distribution in the concrete body 30. Furthermore, even when a task that exposes the main surface 30b of the concrete body 30 is performed, such as a chipping process, the possibility of the first optical fiber 10 being broken can be reduced. Therefore, during construction of the concrete body 30, the first optical fiber 10 that is installed in the concrete body 30 can be appropriately protected.

[0059] The optical fiber installation structure 1 according to one embodiment may further include a second optical fiber 50 connected to the protruding portion 11 of the first optical fiber 10 in the storage space 20b of the storage unit 20. The optical fiber installation method may further include a connecting step (step S15) of connecting a second installed optical fiber 51 to the first optical fiber 10 in the storage space 20b of the storage unit 20 after the optical fiber arranging step and before the skeleton construction step. For example, the second installed optical fiber 51 of the second optical fiber 50 is connected to the protruding portion 11 of the first optical fiber 10 at least one of the timings before pouring concrete, during pouring concrete, and before chipping the concrete skeleton 30. In this case, before pouring concrete, it is possible to inspect whether the first optical fiber 10 is properly positioned in the hole 5a of the formwork 5. Furthermore, it is possible to inspect for abnormalities during concrete pouring. Furthermore, before chipping the concrete body 30, it is possible to inspect the state of the concrete body 30 after the concrete has been poured. For example, after the second laid optical fiber 51 is broken and after chipping the concrete body 30, the second inspection optical fiber 52 of the second optical fiber 50 is connected to the protruding portion 11 of the first optical fiber 10. In this case, it is possible to inspect the state of the concrete body 30 during curing after chipping the concrete body 30. Therefore, it is possible to appropriately use the first optical fiber 10 installed in the concrete body 30 during construction of the concrete body 30.

[0060] In the optical fiber installation structure 1 according to one embodiment, the storage section 20 has a cylindrical wall section 21 that extends downward (one example of one side) and forms an opening 20a that opens downward, and the protruding section 11 of the first optical fiber 10 is inserted into the storage space 20b through the opening 20a (first opening 25a), and at least a part of the opening 20a and the lower end section 21b of the wall section 21 may be covered by a part of the concrete body 30. In this case, even when concrete is poured, intrusion into the storage space 20b of the storage section 20 is suppressed.

[0061] The optical fiber installation structure 1 according to one embodiment further includes another second optical fiber 50 connected to the protruding portion 11 of the first optical fiber 10 in the storage space 20b of the storage unit 20, and the other second optical fiber 50 may extend into the external space (hole 5a) through the opening 20a (second opening 25b). In this case, even if there is a possibility that the second laid optical fiber 51 may be broken due to a chipping process or the like, the first optical fiber 10 arranged in the concrete body 30 can be appropriately protected. Therefore, the first optical fiber 10 can be used before and after the chipping process.

[0062] The present invention can be implemented in various forms, including the above-described embodiment, with various modifications and improvements made based on the knowledge of those skilled in the art. Furthermore, the following modifications can also be constructed by utilizing the technical matters described in the above-described embodiment. The configurations of the respective embodiments may be used in appropriate combination.

[0063] Fig. 12 is a diagram schematically illustrating an optical fiber installation structure according to a modified example. As shown in Fig. 12, in the optical fiber installation structure 1A according to the modified example, the storage section 20A may have a shape that tapers downward (one example of one side). In this case, the storage section 20A extends in the vertical direction so that at least a part of the wall section 21 is aligned with the extending section 41 of the support member 40. That is, as in the example shown in Fig. 12, a part of the wall section 21 in the horizontal direction may be aligned with the extending section 41 in the vertical direction. Also, a part of the wall section 21 in the vertical direction may be aligned with the extending section 41.

[0064] At least a portion of the lower portion of the wall 21 of the storage unit 20A may have an inclined portion 26. The inclined portion 26 extends so that the storage space 20b becomes smaller downward (so that it narrows toward the opening 20a). The opening 20a has a size that allows at least the first optical fiber 10 to be inserted therethrough. In this case, the storage unit 20A may not have a bottom lid 25. The top lid 22 may be detachably fixed to the wall 21. The optical fiber installation structure 1A includes the storage unit 20A having a shape that tapers downward, which makes it easier to pull out the storage unit 20A from the concrete body 30, thereby facilitating the execution of the optical fiber installation method. Furthermore, since the top lid 22 is detachable from the wall 21, workers can directly access the storage space 20b when storing the first optical fiber 10 in the storage space 20b, making it easier to store the first optical fiber 10. Furthermore, when connecting the first optical fiber 10 and the second optical fiber 50, workers can access the inside of the storage space 20b, which makes it easier to connect the first optical fiber 10 and the second optical fiber 50.

[0065] The top cover 22 may also have a check valve that opens only from below toward above. In this configuration, the second optical fiber 50 can extend from within the storage space 20b toward the measuring instrument 70, as in the above-described embodiment, and the influence of concrete, earth and sand, etc. that may accumulate in the storage unit 20 on the first optical fiber 10 and the second optical fiber 50 can be reduced.

[0066] In the above-described embodiment, an example in which one first optical fiber 10 is used as the optical fiber installation structure 1 has been shown, but the number and arrangement location of the first optical fiber 10 are not limited. Fig. 13 is a diagram schematically showing a part of an optical fiber installation structure according to a modified example. As shown in Fig. 13, the optical fiber installation structure 1B may include two first optical fibers 10A and 10B. Both ends of each of the first optical fibers 10A and 10B may be stored in the same storage unit 20 or in different storage units 20.

[0067] The support material 40 is not limited to rebar. A part of the support material 40 may be a steel pipe or the like. The first optical fiber 10 may be fixed only to a steel material (a rod-shaped member such as the support material 40 of this embodiment) provided together with the steel pipe, or may be fixed to both the steel pipe and the steel material. Furthermore, the storage unit 20 does not have to be fixed to the support material 40. In this case, the storage unit 20 may be fixed to the concrete skeleton 30.

[0068] Furthermore, in the above-described embodiment, the optical fiber installation structure 1 includes at least one first optical fiber 10, at least one storage section 20, a support material 40, a second optical fiber 50, a plurality of fixing members 60, and a measuring instrument 70. However, the optical fiber installation structure 1 does not necessarily include at least one of the support material 40, the second optical fiber 50, the plurality of fixing members 60, and the measuring instrument 70. For example, the optical fiber installation structure 1 may include only at least one first optical fiber 10 and at least one storage section 20.

[0069] Furthermore, for example, the optical fiber laying method does not need to perform each of the steps from step S17 to step S23. Even in this case, it is possible to reduce the possibility of the first optical fiber 10 being broken during construction of the concrete body 30. Furthermore, for example, the optical fiber laying method may not perform step S17 (optical fiber checking step), and may instead perform at least one of the steps from step S18 onwards. In this case, for example, the optical fiber laying method may perform at least step S24, thereby confirming the soundness of the concrete body 30. Furthermore, the optical fiber laying method may not perform step S18 (backfilling step), and may instead perform at least one of the steps from step S19 onwards. For example, if the support material 40 is a loading pile or the like used in a pile load test or the like, step S18 (backfilling step) may be necessary or not. Furthermore, the optical fiber laying method may not include step S11. In this case, the optical fiber laying method may start with the optical fiber arrangement step. In the optical fiber laying method, the storing step and the framework construction step may be performed in reverse order, or the storing step and the framework construction step may be performed simultaneously. [Explanation of symbols]

[0070] 1, 1A, 1B...optical fiber installation structure, 2...building, 5...concrete formwork, 5a...hole, 10, 10A, 10B...first optical fiber (an example of an optical fiber), 11...protrusion, 20, 20A...storage section, 20a...opening, 20b...storage space, 21...wall, 21a...upper end, 21b...lower end, 22...upper cover, 25...bottom cover, 25a...first opening, 25b...second opening, 26...inclined portion, 30...concrete body, 30b...main surface, 40...support, 41...extension, 42...upper frame, 43...lower frame, 50...second optical fiber, 51...second installed optical fiber, 52...second inspection optical fiber, 60...fixing member, 61...first fixing member, 62...second fixing member, 70...measuring instrument, L...reference plane.

Claims

1. an optical fiber connected to a support material at least a portion of which is buried in a concrete skeleton, the optical fiber having a protruding portion protruding from a main surface of the concrete skeleton; a storage section fixed to at least one of the concrete skeleton and the support material, and configured to store the protrusion in a storage space formed therein; Equipped with the concrete structure and the storage section shield the optical fiber from an external space; the storage section has a cylindrical wall section that extends toward one side and forms an opening that is open toward the one side, the protruding portion of the optical fiber is inserted into the storage space through the opening, At least a portion of the opening and one end of the wall are covered by a portion of the concrete skeleton. Optical fiber installation structure.

2. 2. The optical fiber installation structure according to claim 1, further comprising another optical fiber connected to the protruding portion of the optical fiber within the storage space of the storage section.

3. and further comprising another optical fiber connected to the protruding portion of the optical fiber within the storage space of the storage section, The other optical fiber extends through the opening into the external space.

2. The optical fiber installation structure according to claim 1.

4. 2. The optical fiber installation structure according to claim 1, wherein the storage section has a shape that tapers toward the one side.

5. The protruding portion protrudes from the main surface of the concrete body that is exposed after at least a portion of the concrete body is chipped, The storage section shields the protrusion from an external space.

3. The optical fiber installation structure according to claim 1 or 2.

6. an optical fiber placement step of placing an optical fiber together with a support material in a concrete formwork; a skeleton construction step of pouring concrete into the concrete formwork to construct a concrete skeleton so that the protruding portion of the optical fiber protrudes; a storage step in which a storage section is fixed to at least one of the concrete body and the support material, and the protrusion is stored in a storage space of the storage section; Including, the concrete structure and the storage section shield the optical fiber from an external space; the storage section has a cylindrical wall section that extends toward one side and forms an opening that is open toward the one side, In the storing step, the protruding portion of the optical fiber is inserted into the storing space through the opening, In the skeleton construction step, the concrete is poured so that at least a portion of the opening of the storage section and one end of the wall section are covered by a portion of the concrete skeleton. How to lay optical fiber.

7. 7. The optical fiber laying method according to claim 6, further comprising a connecting step of connecting another optical fiber to the protruding portion of the optical fiber within the storage space of the storage section after the optical fiber placement step and before the structure construction step.

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