Optical fiber laying structure and optical fiber laying method

Abstract

An optical fiber laying structure 1 comprises: a first optical fiber 10 that is connected to a support material 40 at least partially embedded in a concrete skeleton 30 and has a protrusion 11 protruding from a main surface 30b of the concrete skeleton 30; and a storage part 20 that is fixed to the concrete skeleton 30 and / or the support material 40 and stores the protrusion 11 in a storage space 20b formed therein. The concrete skeleton 30 and / or the storage part 20 shields the first optical fiber 10 from an external space (hole part 5a).

Description

Optical fiber laying structure and optical fiber laying method

[0001] The present disclosure relates to an optical fiber laying structure and an optical fiber laying method.

[0002] Conventionally, as a method for grasping the soundness and the like of a concrete structure, the technique disclosed in the following Patent Document 1 is known. Patent Document 1 discloses manufacturing a prefabricated pile by attaching a coated optical fiber along a PC steel bar of a reinforcing cage, performing centrifugal molding and curing. In the method described in Patent Document 1, the degree of damage to a structure is verified based on the strain amount of the optical fiber.

[0003] Japanese Unexamined Patent Publication No. 2003-213676

[0004] After placing concrete, a part of the support material embedded in the concrete body may be chipped. The optical fiber in the above-mentioned Patent Document 1 is covered with a covering material such as a resin material or a fiber material, but there is a possibility that the optical fiber cannot be appropriately protected when a chipping process is performed. During construction of a concrete body including concrete placing and chipping processes, in order to utilize the function of the optical fiber disposed inside the concrete body, there is a demand for a structure and method that appropriately protects the optical fiber.

[0005] An object of the present disclosure is to provide an optical fiber laying structure and an optical fiber laying method that appropriately protect an optical fiber installed together with a concrete body during construction of the concrete body.

[0006] The gist of the present disclosure resides in the following [1] to [8].[L

[0007] [1] An optical fiber laying structure, comprising: an optical fiber connected to a support material at least partially embedded in a concrete body, with a protruding portion protruding from a main surface of the concrete body; and a storage portion fixed to at least one of the concrete body and the support material, and storing the protruding portion in a storage space formed inside the storage portion, wherein at least one of the concrete body and the storage portion shields the optical fiber from an external space.

[0008] [2] The optical fiber laying 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 unit.

[0009] [3] The optical fiber laying structure according to [1] or [2], wherein the storage section has a cylindrical wall portion that extends toward one side and forms an opening that opens toward the one side, the protruding portion 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 portion are covered by a part of the concrete structure.

[0010] [4] The optical fiber laying 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 unit, wherein the other optical fiber extends into the external space through the opening.

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

[0012] [6] The optical fiber laying structure according to any one of [1] to [5], wherein the protruding portion protrudes from the main surface of the concrete structure which can be exposed after a part of the concrete structure is chipped away, and at least one of the concrete structure which can be exposed after a part of the concrete structure is chipped away and the storage portion shields the protruding portion from the external space.

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

[0014] [8] The optical fiber laying method according to [7], further comprising a connection 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 laying step and before the structure construction step.

[0015] According to this disclosure, it is possible to provide an optical fiber laying structure and an optical fiber laying method that appropriately protect optical fibers installed together with a concrete structure during the construction of the concrete structure.

[0016] This is a schematic diagram showing a part of the optical fiber laying structure of one embodiment. This is a schematic diagram showing the optical fiber laying structure during the frame construction process of the optical fiber laying method of one embodiment. This is an enlarged schematic view showing the optical fiber laying structure of one embodiment. This is a flowchart showing an example of the optical fiber laying method of one embodiment. This is a schematic diagram showing the optical fiber laying structure during the optical fiber placement process of the optical fiber laying method of one embodiment. This is a schematic diagram showing the optical fiber laying structure during the storage process of the optical fiber laying method of one embodiment. This is a schematic diagram showing the optical fiber laying structure during the support material placement process of the optical fiber laying method of one embodiment. This is a schematic diagram showing the optical fiber laying structure during the backfilling process of the optical fiber laying method of one embodiment. This is a schematic diagram showing the optical fiber laying structure during the excavation process of the optical fiber laying method of one embodiment. This is a schematic diagram showing the optical fiber laying structure during the chipping process of the optical fiber laying method of one embodiment. This figure schematically shows the optical fiber laying structure during the second connection step of an optical fiber laying method according to one embodiment. This figure schematically shows the optical fiber laying structure according to a modified example. This figure schematically shows a part of the optical fiber laying structure according to a modified example.

[0017] The embodiments of the optical fiber laying structure and optical fiber laying method according to this disclosure will be described in detail below with reference to the drawings. The optical fiber installed by the optical fiber laying structure and optical fiber laying method can measure the temperature change of the concrete constituting the concrete structure. In addition, the optical fiber can measure the strain (stress) of the pile. The optical fiber laying structure and optical fiber laying method according to this disclosure are used when laying optical fibers installed during the pouring of concrete structures.

[0018] [Laying Structure of Optical Fibers] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are omitted. In the following description, the X-axis direction, Y-axis direction, and Z-axis direction are mutually orthogonal axes in a three-dimensional Cartesian coordinate system. The X-axis direction and Y-axis direction are, for example, horizontal directions. For example, the X-axis direction is a horizontal direction, and the Y-axis direction is a horizontal direction that intersects the X-axis direction. In this embodiment, the positive direction of the X-axis direction is referred to as "right," the negative direction of the X-axis direction is referred to as "left," and the X-axis direction is described 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 "backward," and the Y-axis direction is described as the "front-back direction." The left-right direction is an example of a direction that intersects the front-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 "up," and the negative direction of the Z-axis direction is referred to as "down."

[0019] Figure 1 is a schematic diagram showing a part of the optical fiber laying structure of one embodiment. Figure 2 is a schematic diagram showing the optical fiber laying structure during the frame construction process of the optical fiber laying method of one embodiment. The optical fiber laying structure 1 shown in Figures 1 and 2 is applied, for example, when constructing a building 2 that includes a concrete frame 30 and support members 40. Hereinafter, the optical fiber laying structure 1 may be simply referred to as "laying structure 1". Laying structure 1 is a structure for laying optical fibers to support members 40 placed inside the concrete frame 30 of a concrete formwork 5. Laying structure 1 can be applied, for example, to various concrete frames such as surface members, column members, and beam members in various RC structures such as piles, lintels, box culverts, bridge piers, and sluice gates.

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

[0021] First, the concrete structure 30 and support material 40, which are the targets for laying the first optical fiber 10, will be described. As illustrated in Figure 2, the concrete structure 30 is constructed within the concrete formwork 5. Hereinafter, the concrete formwork 5 may be simply referred to as formwork 5. The size, shape, and orientation of the openings of the formwork 5 are set appropriately according to the specifications of the building 2 and the construction method of the building 2. The support material 40 is placed in the holes 5a inside the formwork 5. The support material 40 is a member used to reinforce the building 2. The support material 40 is, for example, at least a part of a reinforcing cage (reinforcement bars). When the support material 40 is a reinforcing cage used for cast-in-place piles, the concrete formwork 5 corresponds to, for example, the ground. When the support material 40 is used for cast-in-place piles, the concrete structure 30 and the support material 40 are integrated to form a cast-in-place pile. The support material 40 is, for example, steel. In this case, the support material 40 is reinforced in the holes 5a of the formwork 5. The length, thickness, and shape of the support members 40, as well as the density of the reinforcement, 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 member 40 is, for example, cage-shaped. The support member 40 is, for example, a reinforcing cage. The support member 40 has, for example, at least one extended portion, an upper frame portion 42 and a lower frame portion 43. The support member 40 of this embodiment has a plurality of extended portions 41 as at least one extended portion. Each of the plurality of extended portions 41 extends along the vertical direction. The plurality of extended portions 41 are, for example, the main reinforcement of a cast-in-place pile. Each of the plurality of extended portions 41 has an upper end portion 41a and a lower end portion 41b. The plurality of extended portions 41 extend to a length shorter than the vertical length of the hole portion 5a in the formwork 5. The plurality of extended portions 41 extend to a length longer than the length from the bottom surface of the formwork 5 to the 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 extension portions 41. The lower frame portion 43 is connected to the lower ends 41b of the multiple extension portions 41. The multiple extension portions 41 and the upper frame portion 42 and the lower frame portion 43 are fixed together, for example, by welding. The upper frame portion 42 and the lower frame portion 43 are, for example, annular in shape. 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 formwork 5 in which the support members 40 are placed. The pouring of the concrete constituting the concrete structure 30 is carried out in the same procedure as for 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. After that, the formwork 5 may be removed in the same procedure as for the construction of a normal concrete structure. For example, if the support members 40 are cast-in-place piles, the upper part (pile head) of the concrete structure 30 is a weak concrete structure and may be chipped away. Therefore, the upper part of the concrete structure 30 immediately after pouring is subject to chipping. The reference plane L is the boundary surface that separates the upper part of the concrete structure 30 that is subject to chipping from the lower part that is not subject to chipping, in the vertical direction. The reference plane L extends along the horizontal direction. Furthermore, "chipping" refers to at least one of the processes of scraping away or cutting away hard materials such as concrete.

[0025] Next, the first optical fiber 10 and the second optical fiber 50 will be described. Figure 3 is a schematic enlarged view showing an optical fiber laying structure in one embodiment. In the example shown in Figures 1 to 3, in this embodiment, one first optical fiber 10 is provided to the concrete structure 30 and the support material 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 they may be optical fiber cables in the narrow sense that include a bundle of multiple optical fiber cores. One end of the second optical fiber 50 can be connected to the protruding portion 11, which will be described later, which is the end of the first optical fiber 10 laid in the concrete structure 30 in the optical fiber laying 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 also be, for example, 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 in which it is folded back near the bottom of the hole 5a of the formwork 5. The first optical fiber 10 has a protruding portion 11 that protrudes from the reference plane L (the main surface 30b of the concrete structure 30 after a part of the concrete structure 30 has been chipped away (see Figure 11)). The protruding portion 11 may be the upper end of the first optical fiber 10. If the first optical fiber 10 is folded back within the hole 5a, the protruding portion 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 extension portions 41. The first optical fiber 10 is connected to, for example, one of the multiple extension portions 41, and is connected to the lower frame portion 43, and is also connected to another extension portion 41 that is positioned opposite to the said extension 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 formwork 5 together with the support member 40 while fixed to the lower frame portion 43. As the support member 40 is inserted into the hole 5a of the formwork 5, the first optical fiber 10 is fixed sequentially from the lower part to the upper part of the extension portion 41.

[0028] The second optical fiber 50 shown in Figure 2 has one end connected to each protrusion 11 of the first optical fiber 10, and the other end can be connected to the measuring instrument 70 (see Figure 2). In this embodiment, each of a pair of second optical fibers 50 is connected to each protrusion 11 of the first optical fiber 10. The second optical fiber 50 has a pair of second laying optical fibers 51 and a pair of second inspection optical fibers 52 that can be connected to the first optical fiber 10. The second laying optical fibers 51 and the second inspection optical fibers 52 are not laid at the same time. The second laying optical fibers 51 are connected to the first optical fiber 10 before a part of the concrete structure 30 is chipped away. The second inspection optical fibers 52 are connected to the first optical fiber 10 after a part of the concrete structure 30 has been chipped away.

[0029] Figure 3 is a schematic enlarged view showing an optical fiber laying structure according to one embodiment. The storage section 20 shown in Figures 2 and 3 houses the protruding portion 11 of the first optical fiber 10. The storage section 20 is made of, for example, a metal material. The storage section 20 is made of a material that minimizes damage and deformation even when it comes into contact with a chipping machine during the chipping process of the concrete structure 30. In other words, the storage section 20 has the 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 structure 30 and the support member 40. The storage section 20 is fixed to the support member 40, for example, by a second fixing member 62, which will be described later. The storage section 20 has a cylindrical wall portion 21 that extends downward (to one side) and forms an opening 20a that opens downward. The wall portion 21 extends along the vertical direction and has a cylindrical shape.

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

[0032] The bottom cover portion 25 may be detachably fixed to the wall portion 21. The bottom cover portion 25 may be fixed to the wall portion 21, for example, above the lower end of the wall portion 21 and below the reference plane L. The bottom cover portion 25 may also be fixed to the lower end of the wall portion 21. The bottom cover portion 25 has, for example, an opening 20a, which has a first opening 25a and a second opening 25b that penetrate in the vertical direction. 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 part of the opening 20a and the lower end portion 21b of the wall portion 21 (an example of one end) are covered by a part of the concrete structure 30. That is, the concrete structure 30 is located below the lower end portion 21b of the wall portion 21, the first opening 25a, and the second opening 25b.

[0033] The storage section 20 forms a storage space 20b inside it. The storage space 20b is a space surrounded by the wall section 21, the top cover section 22, and the 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 positioned there. The protruding portion 11 of the first optical fiber 10 is wound up and stored within the storage space 20b. The protruding portion 11 of the first optical fiber 10 is stored such that its end is located below the storage space 20b.

[0034] The second optical fiber 50 is connected to the first optical fiber 10 within the storage space 20b of the storage unit 20. One end of the second optical fiber 50 is positioned within the storage space 20b via the second opening 25b. The second optical fiber 50 extends into the external space (in this case, the hole 5a) of the storage space 20b via 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 Figures 1 and 2 fix the first optical fiber 10 to the support material 40. The multiple first fixing members 61 may be, for example, binding wires. The multiple first fixing members 61 are arranged, for example, in multiple extensions 41 at intervals of about 500 mm to 3000 mm, and fix each of the multiple extensions 41 to the first optical fiber 10. The multiple first fixing members 61 are arranged, for example, between a pair of extensions 41 in the lower frame 43, and fix the lower frame 43 to the first optical fiber 10. In this way, the first optical fiber 10 is fixed to the support material 40 without bulging (bending). In this manner, the first optical fiber 10 is not glued to the support material 40, but is bound along the support material 40 by the first fixing members 61. After the concrete structure 30 is poured, the concrete hardens and the first optical fiber 10, the concrete structure 30, and the support material 40 become integrated.

[0036] The multiple second fixing members 62 shown in Figures 2 and 3 fix the storage unit 20 and the support material 40. The multiple second fixing members 62 may be, for example, binding wires. The multiple second fixing members 62 may fix each of the multiple extensions 41 to the storage unit 20. The multiple second fixing members 62 may also fix each of the multiple extensions 41 to the storage unit 20 and the second optical fiber 50. Note that if the storage unit 20 and the support material 40 are fixed by welding or the like, the laying structure 1 does not need to include the second fixing members 62.

[0037] The measuring instrument 70 shown in Figure 2 is a device that can be connected to the second optical fiber 50. The measuring instrument 70 incidents laser pulse light onto the optical fiber strands of the second optical fiber 50 and receives scattered light returning from various positions along the longitudinal direction of the optical fiber strands. By incidenting the laser pulse light onto the second optical fiber 50, the measuring instrument 70 can incident laser pulse light onto the first optical fiber 10 and receive scattered light in the first optical fiber 10. Based on the principle that the intensity and wavelength of the scattered light depend on the strain and temperature changes applied to the optical fiber strands, the measuring instrument 70 calculates the strain and temperature at various positions along the longitudinal direction of the first optical fiber 10. Based on the strain and temperature at various positions along the longitudinal direction of the first optical fiber 10, the measuring instrument 70 may calculate at least one of the longitudinal strain distribution and temperature distribution in the concrete structure 30.

[0038] [Method for Laying Optical Fibers] Next, a method for laying optical fibers will be described using Figures 4 to 10. Figure 4 is a flowchart showing an example of a method for laying optical fibers according to one embodiment. In the optical fiber laying structure, for example, first, a preparation process is performed as step S11. Figure 5 is a schematic diagram showing an optical fiber laying structure during the optical fiber placement process of the optical fiber laying method according to one embodiment. Figure 5 may also show a part of the preparation process of step S11. In the preparation process, the holes 5a of the formwork 5 are prepared. The vertical length of the holes 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 holes 5a.

[0039] Next, as step S12, the optical fiber placement process is performed. In the optical fiber placement 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 the first fixing member 61. The first optical fiber 10 is fixed to the lower end portions 41b of the two extended portions 41 of the support material 40 by the first fixing member 61.

[0040] Next, as step S13, the support material placement process is performed. Figure 5 may also show a part of the support material placement process in step S13. In the support material placement process, a support material 40 to which the first optical fiber 10 is connected is placed inside the formwork 5. The support material 40 is inserted into the hole 5a of the formwork 5 while suspended by a working 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 to follow the support material 40. As the support material 40 is inserted (moves), the first optical fiber 10 is guided while tensile force is applied. 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, the first optical fiber 10 and the support material 40 are fixed by another first fixing member 61. As a result, the first optical fiber 10 is positioned within the hole 5a of the formwork 5 along the support material 40. The support material placement step may be included in the optical fiber placement step. That is, in the process including the optical fiber placement step and the support material placement step described above, the first optical fiber 10 is positioned within the formwork 5 together with the support material 40.

[0041] In the support material placement step (step S13), after the central and lower ends 41b of the extension portion 41 of the support material 40, in which the storage portion 20 can be placed, are inserted into the hole 5a, leaving the upper end 41a of the extension portion 41, the storage step is performed as step S14. Figure 6 is a schematic diagram showing the optical fiber laying structure in the process of laying an optical fiber according to one embodiment. As shown in Figure 6, in the storage step, for example, the storage portion 20 is fixed to the upper end 41a of the extension portion 41 by the second fixing member 62. Subsequently, 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 such that the end of the protruding portion 11 is on the side of the opening 20a of the storage portion 20. Furthermore, if 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 41a of the extension section 41 after the protruding portion 11 of the first optical fiber 10 has been stored inside the storage section 20. If the storage section 20 is fixed by welding, fixing the storage section 20 to the upper end 41a of the extension section 41 before the protruding portion 11 of the first optical fiber 10 is stored inside the storage section 20 can suppress damage to the first optical fiber 10 from sparks generated during welding.

[0042] Next, as step S15, the first connection step is performed. The first connection step may be included in the storage step (step S14). In the first connection step, another second optical fiber 50 is connected to the first optical fiber 10 within the storage space 20b of the storage unit 20. Each protrusion 11 of the first optical fiber 10 stored within the storage space 20b of the storage unit 20 is connected to one end of a pair of second laid optical fibers 51. The connection between the protrusion 11 and one end of the second laid optical fiber 51 is stored within the storage space 20b. After the protrusion 11 and one end of the second laid optical fiber 51 are connected, 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) during the storage process (step S14) and the first connection process (step S15). The other end of the second laid optical fiber 51 is connected to the measuring instrument 70. When the first connection process is completed, the measuring instrument 70 may inject laser pulse light into the first optical fiber 10 via the second optical fiber 50 and receive the scattered light. This allows the instrument to check whether the first optical fiber 10 is properly connected to the second optical fiber 50.

[0043] Figure 7 is a schematic diagram showing the optical fiber laying structure during the support material placement step of an optical fiber laying method according to one embodiment. As shown in Figure 7, the support material placement step (step S13) continues even while the storage step (step S14) and the first connection step (step S15) are being performed. For example, after the storage step (step S14) is completed and the first optical fiber 10 in the first connection step (step S15) is connected to the second laid optical fiber 51, the support material 40 is inserted into the hole 5a of the formwork 5 while being suspended by a working machine such as a crane (not shown) and a guide member 81, as shown in Figure 7. As a result, the first optical fiber 10, the storage unit 20 and the support material 40 are positioned in predetermined locations within the hole 5a of the formwork 5. The storage unit 20 is positioned such that the bottom cover 25 is at the same position as or below the reference plane L, and at least the upper end portion 21a of the wall portion 21 is positioned above the reference plane L.

[0044] Subsequently, as step S16, a frame construction step is performed. As shown in FIG. 2, in the frame construction step, concrete is placed into the formwork 5, and a concrete frame 30 is constructed such that the protruding portion 11 of the first optical fiber 10 protrudes therefrom. The concrete is placed from the bottom of the hole 5a of the formwork 5 to a position above the reference plane L. The concrete is placed, for example, such that a part of the storage portion 20 is exposed. Accordingly, the storage portion 20 and the concrete frame 30 shield the first optical fiber 10 from the external space (the hole 5a) during the storage step (step S14), the first connection step (step S15), and the frame construction step (step S16). The concrete frame 30 includes, for example, a cutting target region 33 above the reference plane L.

[0045] Subsequently, as step S17, an optical fiber confirmation step is performed. In the optical fiber confirmation step, the measuring instrument 70 may inject laser pulse light into the first optical fiber 10 via the second optical fiber 50 and receive scattered light. This allows confirmation of the soundness of the concrete frame 30 inside the concrete frame 30 by means of the first optical fiber 10.

[0046] Subsequently, as step S18, a backfilling step is performed. FIG. 8 is a diagram schematically showing an optical fiber laying structure during execution of the backfilling step of the optical fiber laying method according to one embodiment. As shown in FIG. 8, in the backfilling step, concrete is placed into the hole 5a of the formwork 5. The concrete is placed up to the upper end of the formwork 5. The concrete is placed, for example, such that the storage portion 20 is completely buried. The concrete frame 30 includes, for example, a backfill region 35 above the cutting target region 33. After the backfilling step is performed, the concrete is cured for a predetermined period of time.

[0047] Subsequently, as step S19, a cutting step is performed. 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, an excavation step (step S20) and a chipping step (step S21) described later can be easily performed.

[0048] Next, as step S20, an excavation step is performed. FIG. 9 is a diagram schematically showing an optical fiber laying structure during execution of the excavation step of the optical fiber laying method according to one embodiment. As shown in FIG. 9, in the excavation step, the formwork 5 is excavated to the reference plane L. In the excavation step, at least a part of the backfill region 35 placed in the backfilling step (step S18) in the concrete frame 30 may be chipped off.

[0049] Next, as step S21, a chipping step is performed. FIG. 10 is a diagram schematically showing an optical fiber laying structure during execution of the chipping step of the optical fiber laying method according to one embodiment. As shown in FIG. 10, in the chipping step, the chipping target region 33 placed in the frame construction step (step S16) in the concrete frame 30 is chipped off. The chipping step is so-called pile head chipping. In the chipping step, the concrete frame 30 is chipped to the reference plane L, and the main surface 30b of the concrete frame 30 is exposed. Since the bottom cover portion 25 of the storage portion 20 is located at the same position as or below the reference plane L, even when the concrete frame 30 is chipped to the reference plane L in the chipping step, the first optical fiber 10 is appropriately protected by being stored in the storage portion 20. The main surface 30b is a flat surface along the reference plane L. In the chipping step, even when the chipping target region 33 of the concrete frame 30 around the first optical fiber 10 is chipped by a working machine, the storage portion 20 can appropriately protect the first optical fiber 10.

[0050] Next, as step S22, the removal process is performed. Figure 11 is a schematic diagram showing the optical fiber laying structure during the second connection process of the optical fiber laying method of one embodiment. Figure 11 is a schematic diagram showing the optical fiber laying structure after the removal process of the optical fiber laying method of one embodiment has been performed, for example. As shown in Figure 11, in the removal process, the storage section 20 is removed from the concrete structure 30 and the support material 40. The storage section 20 becomes removable from the support material 40 when the second fixing member 62 is detached from the upper end portion 41a of the extended portion 41. The lower end portion 21b of the wall portion 21 and the bottom cover portion 25 of the storage section 20 embedded in the concrete structure 30 are removed from the concrete structure 30. The storage section 20 is removed, for example, by pulling it upward. The storage section 20 may also be pulled upward while being vibrated, for example. The storage section 20 may be cut along the reference plane L. The timing of the removal of the storage section 20 from the concrete structure 30 and the timing of the removal of the storage section 20 from the support material 40 may be simultaneous or different, and the order of these actions does not matter.

[0051] Next, as step S23, the second connection process is performed. As shown in Figure 11, in the second connection process, another second optical fiber 50 is connected 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 test optical fibers 52. The other end of the second test optical fiber 52 is connected to the measuring instrument 70.

[0052] Next, as step S24, a measurement process is performed. In the measurement process, the measuring instrument 70 may incident laser pulse light onto the first optical fiber 10 via the second optical fiber 50 and receive the scattered light. The measuring instrument 70 measures the intensity and wavelength of the scattered light. The measuring instrument 70 calculates, for example, the strain and temperature at each position in the longitudinal direction of the first optical fiber 10. Based on the strain and temperature at each position in the longitudinal direction of the first optical fiber 10, the measuring instrument 70 calculates, for example, at least one of the longitudinal strain distribution and temperature distribution in the concrete structure 30. This allows the measuring instrument 70 to measure, for example, the wiring direction of the optical fiber in the concrete structure 30 (for example, at least one of the vertical direction of the extended portion 41 in the support material 40 and the horizontal direction of the lower frame portion 43). After the completion of the measurement process (step S24), the optical fiber laying method is terminated.

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

[0054] In the case of reinforced concrete (RC) structures, for example, by installing optical fibers around piles (supporting members) before concrete is poured, the filling status of the concrete can be understood by measuring temperature changes during concrete pouring. Conventionally, characteristic quantities including pile strain (stress) and temperature have been measured using measuring instruments such as rebar gauges, thermocouples, and strain gauges. However, these measuring instruments can only measure these characteristic quantities for a portion of the pile and cannot continuously measure them over the entire length of the pile. Another method that can be considered is to measure the strain distribution of the entire pile by placing a large number of measuring instruments, but the cables wired to the measuring instruments are thick, resulting in a large number of cables being wired, which can cause cross-sectional defects in the pile and increases the amount of wiring work required.

[0055] In light of the above challenges, a method has been proposed to measure the aforementioned feature quantities by wiring optical fibers together with piles; however, optical fibers are prone to breakage. Furthermore, after concrete placement, it is sometimes necessary to chip away at a portion of the support material embedded in the concrete, such as during pile head chipping. For example, optical fibers may be covered with a coating material such as resin or fiber, but this coating may not adequately protect the optical fibers when chipping processes are carried out. Therefore, a structure and method are needed to adequately protect optical fibers during the construction of concrete structures, including concrete placement and chipping processes, in order to utilize the functionality of the optical fibers placed within the concrete structure.

[0056] An optical fiber laying 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 embedded in a concrete structure 30, with a protruding portion 11 protruding from the main surface 30b of the concrete structure 30, and a storage unit 20 fixed to at least one of the concrete structure 30 and the support material 40, which stores the protruding portion 11 in a storage space 20b formed inside, with at least one of the concrete structure 30 and the storage unit 20 shielding the first optical fiber 10 from the external space (hole 5a). For example, the protruding portion 11 protrudes from the main surface 30b of the concrete structure 30, which may be exposed after a portion of the concrete structure 30 is chipped away (chipping process: step S21), and at least one of the concrete structure 30, which may be exposed after a portion is chipped away, and the storage unit 20 shields the protruding portion 11 of the first optical fiber 10 from the external space.

[0057] Furthermore, a method for laying optical fibers according to one embodiment includes an optical fiber placement step (step S12) in which the first optical fiber 10 is placed together with a support material 40 in a concrete formwork 5; a structure construction step (steps S16, S20, and S21) in which concrete is poured into the concrete formwork 5 to construct a concrete structure 30 such that the protruding portion 11 of the first optical fiber 10 protrudes; and a storage step (step S14) in which the protruding portion 11 is fixed to at least one of the concrete structure 30 and the support material 40 and stored in the storage space 20b of the storage unit 20, wherein in at least one of the structure construction step and the storage step, at least one of the concrete structure 30 and the storage unit 20 shields the first optical fiber 10 from the outside space.

[0058] In the optical fiber laying structure 1 and optical fiber laying method described above, the storage unit 20 can protect the protruding portion 11 of the first optical fiber 10 that protrudes from the main surface 30b of the concrete structure 30. Since the first optical fiber 10 can be exposed from the concrete structure 30, it can be properly connected to the measuring instrument 70. For this reason, before, during, and after concrete placement, a light ray such as laser pulse light can be incident on the first optical fiber 10, and the scattered light can be received to measure feature quantities including strain and temperature at each position in the longitudinal direction of the first optical fiber 10, as well as at least one of the longitudinal strain distribution and temperature distribution in the concrete structure 30. Furthermore, even when work is performed that exposes the main surface 30b of the concrete structure 30, such as in a chipping process, the possibility of the first optical fiber 10 being disconnected can be reduced. Therefore, the first optical fiber 10, which is installed together with the concrete structure 30, can be properly protected during the construction of the concrete structure 30.

[0059] In one embodiment of the optical fiber laying structure 1, a second optical fiber 50 may be further provided in the storage space 20b of the storage unit 20, which is connected to the protruding portion 11 of the first optical fiber 10. In the optical fiber laying method, a connection step (step S15) may be further included, after the optical fiber placement step and before the structure construction step, in which a second laid optical fiber 51 is connected to the first optical fiber 10 in the storage space 20b of the storage unit 20. For example, at least one timing before concrete pouring, during concrete pouring, and before chipping of the concrete structure 30, the second laid optical fiber 51 of the second optical fiber 50 is connected to the protruding portion 11 of the first optical fiber 10. In this case, before concrete pouring, it is possible to check whether the first optical fiber 10 is properly positioned in the hole 5a of the formwork 5. Also, during concrete pouring, it is possible to check for abnormalities during concrete pouring. Furthermore, before chipping away at the concrete structure 30, the condition of the concrete structure 30 after the concrete pouring is completed can be inspected. For example, after the second laid optical fiber 51 is broken and after the concrete structure 30 has been chipped away, the second inspection optical fiber 52 of the second optical fiber 50 connects to the protruding portion 11 of the first optical fiber 10. In this case, after chipping away at the concrete structure 30, the condition of the concrete structure 30 while it is curing can be inspected. Therefore, the first optical fiber 10, which is installed together with the concrete structure 30, can be properly utilized during the construction of the concrete structure 30.

[0060] In one embodiment of the optical fiber laying structure 1, the storage section 20 has a cylindrical wall portion 21 that extends downward (one example is one side) and forms an opening 20a that opens downward, and the protruding portion 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 portion 21b of the wall portion 21 may be covered by a part of the concrete structure 30. In this case, even when concrete is poured, intrusion into the storage space 20b of the storage section 20 is suppressed.

[0061] In one embodiment of the optical fiber laying structure 1, the storage space 20b of the storage section 20 further includes another second optical fiber 50 connected to the protruding portion 11 of the first optical fiber 10, 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 will break due to a demolition process or the like, the first optical fiber 10 placed inside the concrete structure 30 can be properly protected. For this reason, the first optical fiber 10 can be used before and after the demolition process.

[0062] This disclosure can be implemented in various forms, including the embodiments described above, with various modifications and improvements based on the knowledge of those skilled in the art. Furthermore, the following modified examples can be constructed using the technical matters described in the embodiments described above. The configurations of each embodiment may be used in appropriate combinations.

[0063] Figure 12 is a schematic diagram showing a modified optical fiber laying structure. As shown in Figure 12, in the modified optical fiber laying structure 1A, the storage section 20A may have a tapered shape as it goes downward (one example). In this case, at least a portion of the wall portion 21 of the storage section 20A extends in the vertical direction along the extended portion 41 of the support material 40. That is, as shown in the example in Figure 12, a portion of the wall portion 21 in the horizontal direction may be along the extended portion 41 in the vertical direction. Also, a portion of the wall portion 21 in the vertical direction may be along the extended portion 41.

[0064] At least a portion of the lower part of the wall portion 21 of the storage section 20A may have an inclined portion 26. The inclined portion 26 extends such that the storage space 20b becomes smaller downwards (narrows toward the opening 20a). The opening 20a is large enough to allow at least the first optical fiber 10 to pass through. In this case, the storage section 20A does not need to have a bottom cover portion 25. The top cover portion 22 may be detachably fixed to the wall portion 21. The optical fiber laying structure 1A includes a storage section 20A that tapers downwards, making it easier to pull the storage section 20A out of the concrete structure 30, thus facilitating the execution of the optical fiber laying method. Furthermore, because the top cover portion 22 is detachably attached to the wall portion 21, when storing the first optical fiber 10 in the storage space 20b, workers can directly access 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, the worker can access the storage space 20b, making it easier to connect the first optical fiber 10 and the second optical fiber 50.

[0065] Furthermore, the top cover portion 22 may have a check valve that opens only from below upward. In this configuration as well, the second optical fiber 50 extends from within the storage space 20b toward the measuring instrument 70, and the influence of concrete, soil, and other materials that may accumulate in the storage portion 20 on the first optical fiber 10 and the second optical fiber 50 can be reduced.

[0066] In the above embodiment, an example of a single first optical fiber 10 was shown as the optical fiber laying structure 1, but the number and placement of the first optical fibers 10 are not limited. Figure 13 is a schematic diagram showing a part of an optical fiber laying structure according to a modified example. As shown in Figure 13, the optical fiber laying structure 1B may include two first optical fibers 10A and 10B. The respective ends of the first optical fibers 10A and 10B may be stored in the same storage unit 20, or they may be stored in different storage units 20.

[0067] The support member 40 is not limited to reinforcing bars. Part of the support member 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 member 40 in this embodiment) provided together with the steel pipe, or it may be fixed to both the steel pipe and the steel material. Also, the storage unit 20 does not have to be fixed to the support member 40. In this case, the storage unit 20 may be fixed to the concrete structure 30.

[0068] Furthermore, in the above-described embodiment, the optical fiber laying structure 1 was shown to include at least one first optical fiber 10, at least one storage unit 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 laying structure 1 does not need to 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 laying structure 1 may include only at least one first optical fiber 10 and at least one storage unit 20.

[0069] Furthermore, for example, the optical fiber laying method does not require that each step from step S17 to step S23 be performed. Even in this case, the possibility of the first optical fiber 10 being disconnected during the construction of the concrete structure 30 can be reduced. Also, for example, in the optical fiber laying method, step S17 (optical fiber verification step) may be omitted, and at least one step from step S18 onwards may be performed. In this case, for example, the soundness of the concrete structure 30 can be confirmed by performing at least step S24 in the optical fiber laying method. Also, in the optical fiber laying method, step S18 (backfilling step) may be omitted, and at least one step from step S19 onwards may be performed. For example, if the support material 40 is a load pile used in load testing of piles, etc., step S18 (backfilling step) may or may not be performed. Furthermore, the optical fiber laying method does not require that step S11 be included. In this case, the optical fiber laying method may start from the optical fiber placement step. Furthermore, the order in which the optical fiber laying process is performed, specifically the storage process and the structural construction process, may be reversed. The storage process and the structural construction process may also be performed simultaneously.

[0070] 1, 1A, 1B... Optical fiber laying structure, 2... Building, 5... Concrete formwork, 5a... Hole, 10, 10A, 10B... First optical fiber (an example of an optical fiber), 11... Protruding part, 20, 20A... Storage part, 20a... Opening, 20b... Storage space, 21... Wall part, 21a... Upper end, 21b... Lower end, 22... Upper cover part, 25... Bottom cover part, 25a... First opening, 25b... Second opening, 26... Inclined part, 30... Concrete frame, 30b... Main surface, 40... Support material, 41... Extended part, 42... Upper frame part, 43... Lower frame part, 50... Second optical fiber, 51... Second laid optical fiber, 52... Second inspection optical fiber, 60... Fixing member, 61... First fixing member, 62... Second fixing member, 70... Measuring instrument, L... Reference surface.

Claims

1. An optical fiber laying structure comprising: an optical fiber connected to a support material, at least a portion of which is embedded within a concrete structure, with a portion protruding from the main surface of the concrete structure; and a storage unit fixed to at least one of the concrete structure and the support material, which houses the protruding portion in a storage space formed inside, wherein the concrete structure and the storage unit shield the optical fiber from the external space, the storage unit has a cylindrical wall portion that extends toward one side and forms an opening toward that side, the protruding portion of the optical fiber is inserted into the storage space through the opening, and at least a portion of the opening and one end of the wall portion are covered by a portion of the concrete structure.

2. The optical fiber laying 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 unit.

3. The optical fiber laying 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 unit, wherein the other optical fiber extends into the external space through the opening.

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

5. The optical fiber laying structure according to claim 1 or 2, wherein the protruding portion protrudes from the main surface of the concrete structure which is exposed after at least a part of the concrete structure is chipped away, and the storage portion shields the protruding portion from the external space.

6. A method for laying optical fibers, comprising: an optical fiber placement step of arranging optical fibers together with support material in a concrete formwork; a structure construction step of pouring concrete into the concrete formwork to construct a concrete structure such that the protruding portion of the optical fiber protrudes; and a storage step of fixing a storage unit to at least one of the concrete structure and support material, and storing the protruding portion in the storage space of the storage unit, wherein the concrete structure and the storage unit shield the optical fiber from the external space; the storage unit has a cylindrical wall portion that extends toward one side and forms an opening that opens toward the one side; in the storage step, the protruding portion of the optical fiber is inserted into the storage space through the opening; and in the structure construction step, concrete is poured such that at least a part of the opening of the storage unit and one end of the wall portion are covered by a part of the concrete structure.

7. The optical fiber laying method according to claim 6, further comprising a connection 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 laying step and before the structure construction step.

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