Scour detection method and scour detection device

Abstract

To provide a scour detection method and a scour detection device capable of being easily installed and detecting scour with high accuracy.SOLUTION: A scour detection method according to one embodiment is the scour detection method for detecting scour around a structure constructed by being buried in sediment H on a water bottom T, and comprises the steps of: supporting a sensor 10 for detecting at least one of temperature and vibration on a support member 12 constituting a part of the structure; embedding the support member 12 in the sediment H around the structure; and detecting, by the sensor 10, at least one of water temperature and vibration around the structure.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a scour detection method and a scour detection device for detecting scouring occurring around a structure. [Background technology]

[0002] Conventionally, various methods and devices for detecting scouring around a structure constructed on the bottom of the water have been known. Japanese Patent Application Laid-Open Publication No. 2016-200416 describes a scouring detection system equipped with multiple detection units that transmit and receive light. An optical fiber cable extends from each detection unit, and the optical fiber is stored in a detection box arranged on each of multiple bridge supports of the bridge. An optical fiber cable extends downward from the detection box along the bridge support, and the lower end of the optical fiber cable is connected to a sinker submerged in the bottom of the water. When scouring occurs around the bridge support, the sinker sinks due to scouring. Specifically, a wire attached to the sinker is wound around a drum, and the rotation of the drum is measured by a rotary encoder to measure the sinking of the sinker due to scouring.

[0003] Japanese Patent No. 4838078 describes a scour measurement device. The scour measurement device includes a position detector placed around a bridge pier buried in the water bottom, a chain that wraps the position detector around the pier, and a receiver placed above the pier. The position detector transmits a transmission signal indicating the water pressure at its own position, and the receiver receives the transmission signal. When scour occurs around the pier, the position detector sinks and detects an increase in water pressure. The position detector transmits a transmission signal associated with the increase in water pressure to the receiver, and the receiver detects the scour.

[0004] Japanese Patent Laid-Open Publication No. 6-74768 describes a riverbed scouring monitoring method. In the riverbed scouring monitoring method, a flowing water sensor and a support pile buried in the ground are used. The flowing water sensor extends from the ground surface to the support pile buried in the ground, and a part of the flowing water sensor is wound around the support pile. The support pile is buried below the bottom of the riverbed. The flowing water sensor is a long structure having an optical fiber, a heating wire, and an electrical insulating material that covers the optical fiber and the heating wire. When scouring occurs, the upper part of the flowing water sensor comes into contact with flowing water. As a result, the temperature of the upper part of the flowing water sensor decreases, and a difference occurs in the temperature distribution of the flowing water sensor. The flowing water sensor detects this difference in temperature distribution, thereby detecting scouring in the riverbed.

[0005] JP 2010-210334 A describes a method for determining scouring of a bridge pier and a system for evaluating the soundness of a bridge pier foundation. The soundness evaluation system comprises a soundness evaluation device attached to each of a plurality of bridge piers, and a display device. The soundness evaluation device comprises a vibration detection unit that detects vibrations of the pier, and a water level detection unit fixed to the upper end of the pier. When scouring occurs, the riverbed around the pier is gouged out, which changes the characteristics of the vibration applied to the pier. The vibration detection unit detects this change in the characteristics of the vibration, thereby detecting scouring. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-200416 A [Patent Document 2] Patent No. 4838078 [Patent Document 3] Japanese Patent Application Publication No. 6-74768 [Patent Document 4] JP 2010-210334 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the above-mentioned scour detection system and scour measurement device, a sensor such as a weight or a position detector connected to the tip of an optical fiber cable is placed on the bottom of the water, and scour is detected by the sinking of the sensor. However, in a method in which a sensor is placed on the bottom of the water and detects the sinking of the bottom of the water, the sensor may not sink even when scour occurs, which can cause a problem that the sensor cannot detect scour with high accuracy.

[0008] In the above-mentioned riverbed scouring monitoring method, a flowing water sensor is used that is buried in the ground, and the flowing water sensor is composed of an optical fiber, a heating wire, and an electrical insulating material that covers the optical fiber and the heating wire. In this riverbed scouring monitoring method, since the above-mentioned special sensor must be manufactured separately from the structure, a problem may occur in that the sensor cannot be easily installed.

[0009] In the above-mentioned bridge pier foundation soundness evaluation system, the vibration detection unit detects scouring by detecting changes in the vibration of the pier. However, the method of detecting changes in the vibration of the pier using a vibration sensor may not be able to obtain minute changes in the vibration of the pier. Therefore, since it may not be possible to accurately detect changes in vibration caused by the occurrence of scouring around the pier, there is room for improvement in the accuracy of scouring detection.

[0010] An object of the present disclosure is to provide a scour detection method and a scour detection device that can be easily installed and that can detect scour with high accuracy. [Means for solving the problem]

[0011] A scouring detection method according to the present disclosure is a scouring detection method for detecting scouring around a structure constructed by being embedded in soil on a water bottom, the method comprising the steps of supporting a sensor for detecting at least one of temperature and vibration on a support member constituting a part of the structure, embedding the support member in the soil around the structure, and detecting at least one of the temperature and vibration of the water around the structure with the sensor, the sensor including an optical fiber cable attached to the support member and a measuring unit having a temperature detection unit and a vibration detection unit, the temperature detection unit detects temperature changes by the optical fiber cable, and the vibration detection unit detects vibrations via the optical fiber cable by distributed acoustic sensing. The optical fiber cable includes a detection optical fiber cable for detecting distortion and a fiber dedicated to temperature measurement, and the fiber dedicated to temperature measurement includes an optical fiber core and a tubular member surrounding the optical fiber core. .

[0012] In this scouring detection method, a support member on which a sensor is supported is embedded in the soil around a structure. When the soil around the structure is gouged out and scouring occurs, a part of the support member embedded in the soil is exposed in water. The sensor of the support member exposed in water detects at least one of the temperature and water flow in the water, thereby detecting the scouring. Therefore, the sensor supported on the support member embedded in the soil detects the exposure to water, thereby enabling highly accurate detection of scouring around the structure. The sensor that detects at least one of temperature and vibration is supported on the support member that constitutes a part of the structure. Therefore, since the sensor supported on the support member that constitutes a part of the structure is embedded in the soil, there is no need to prepare the sensor separately from the structure. In other words, it is sufficient to support the sensor on the support member during the process of preparing the support member for the structure. Therefore, the sensor can be easily installed.

[0013] support An optical fiber cable is attached to the support member, and the optical fiber cable measures at least one of temperature and vibration. Therefore, by attaching a linear optical fiber cable to the support member and running the optical fiber cable around, it is possible to measure temperature or vibration over a wide range with a single optical fiber cable. Therefore, the optical fiber cable can be easily installed, and scouring can be detected over a wide range with high accuracy.

[0014] In the step of embedding the support member, the support member to which the optical fiber cable is attached may be embedded in soil before the foundation of the structure is constructed. In this case, the support member to which the optical fiber cable is attached is embedded in soil before the foundation of the structure is constructed. Therefore, since the support member with the sensor is embedded in soil before the foundation is constructed, it is possible to start detecting scouring from the time of construction of the foundation.

[0015] The optical fiber cable attached to the support member may include a first portion extending in a first direction and a second portion extending in a second direction that is continuous with the first portion and intersects with the first direction. In this case, the optical fiber cable has the first portion extending in the first direction and the second portion extending in a second direction different from the first direction, so that the optical fiber cable can be arranged in a zigzag or spiral shape. Therefore, compared to the case where the optical fiber cable is arranged in a straight line, for example, a longer optical fiber cable can be arranged per unit vertical length of the support member, so that temperature or vibration can be detected with higher position resolution.

[0016] The scour detection device according to the present disclosure is a scour detection device that detects scouring around a structure that is constructed by being embedded in soil on the bottom of a body of water, and includes a sensor that detects at least one of temperature and vibration, and a support member that supports the sensor and constitutes part of the structure, the support member to which the sensor is attached is embedded in the soil around the structure, the sensor includes an optical fiber cable that is attached to the support member, and a measuring unit that has a temperature detection unit and a vibration detection unit, the temperature detection unit detects temperature changes by the optical fiber cable, and the vibration detection unit detects vibrations via the optical fiber cable by distributed acoustic sensing. The optical fiber cable includes a detection optical fiber cable for detecting distortion and a fiber dedicated to temperature measurement, and the fiber dedicated to temperature measurement includes an optical fiber core and a tubular member surrounding the optical fiber core. .

[0017] This scour detection device includes a sensor that detects at least one of temperature and vibration, and detects scouring around a structure buried in the sediment on the bottom of the water by using this sensor. The sensor is supported by a support member, and the support member supporting the sensor is buried in the sediment around the structure. Therefore, when the sediment around the structure is gouged out and scouring occurs, a part of the support member is exposed in the water, and the sensor of the support member exposed in the water detects at least one of the temperature and vibration in the water, thereby detecting the scouring. Therefore, as with the above-mentioned scour detection method, scouring around the structure can be detected with high accuracy. In addition, since the sensor supported by the support member constituting a part of the structure is buried in the sediment, there is no need to prepare a sensor separately from the structure. Therefore, the sensor can be easily installed because it is sufficient to support the support member in the process of preparing the support member for the structure. Effect of the Invention

[0018] According to the present disclosure, installation can be easily performed and scouring can be detected with high accuracy. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a perspective view showing an example of a structure to which a scour detection method and a scour detection device according to an embodiment are applied. [Diagram 2] FIG. 2 is a cross-sectional view showing a structure and a scour detection device. [Diagram 3] FIG. 3 is a cross-sectional view showing a schematic state in which scouring has occurred on the structure shown in FIG. 2. [Figure 4] FIG. 13 is a diagram illustrating an example in which an optical fiber cable is used as a sensor of the scour detection device. [Diagram 5] FIG. 1 is a perspective view showing an example of a structure to which a scour detection method and a scour detection device according to an embodiment are applied. [Figure 6] 1 is a perspective view showing an example of a support structure for a sensor relative to a support member that is a part of a structure; [Figure 7]1(a) and 1(b) are diagrams showing an example of an optical fiber cable attached to a support member. [Figure 8] 1A, 1B, and 1C are cross-sectional views showing examples of a mounting structure for an optical fiber cable to a support member. [Figure 9] 1A, 1B, 1C, and 1D are cross-sectional views showing examples of a mounting structure for an optical fiber cable to a support member. [Figure 10] 1A and 1B are cross-sectional views showing an example of a structure for attaching an optical fiber cable to a support member, and FIG. 1C is a perspective view showing an example of a structure for attaching an optical fiber cable to a support member. [Figure 11] FIG. 1 is a cross-sectional perspective view showing an example of a structure to which a scour detection method and a scour detection device are applied. [Figure 12] 1(a) and 1(b) are cross-sectional perspective views showing an example of a structure to which a scour detection method and a scour detection device are applied. [Figure 13] 1(a) and 1(b) are cross-sectional perspective views showing an example of a structure to which a scour detection method and a scour detection device are applied. [Figure 14] 1 is a perspective view showing a schematic example of a support member for supporting a zigzag optical fiber cable. FIG. [Figure 15] FIG. 1 is a cross-sectional view showing an example of a structure to which a scour detection method and a scour detection device are applied. [Figure 16] FIG. 1 is a cross-sectional view showing an example of a structure to which a scour detection method and a scour detection device are applied. [Figure 17] FIG. 11 is a cross-sectional view showing a scour detection device and a structure according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of a scour detection device and a scour detection method according to the present disclosure will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are given the same reference numerals, and duplicated descriptions are omitted as appropriate. In addition, the drawings may be partially simplified or exaggerated for ease of understanding, and the dimensional ratios and the like are not limited to those shown in the drawings.

[0021] Fig. 1 is a perspective view that typically shows a bridge B, which is an example of a structure to which the scour detection device 1 and the scour detection method according to this embodiment are applied. Fig. 2 is a cross-sectional view that typically shows the scour detection device 1 and the bridge B. As shown in Figs. 1 and 2, the bridge B is, for example, a crossing bridge that crosses an ocean or a river.

[0022] As an example, bridge B is a road bridge constructed above the water surface S of an ocean or river. Bridge B includes a plurality of piers B1 aligned along an extension direction D1 of bridge B, and a main girder B2 spanning the plurality of piers B1 and extending along the extension direction D1. As an example, a road R is provided on the main girder B2. However, railway rails may also be provided on the main girder B2, and the type of bridge B is not particularly limited.

[0023] The lower part of the pier B1 is provided underwater W, and the lower end of the pier B1 is buried in soil H on the water bottom T. The scour detection device 1 detects scouring of the pier B1, which is a structure constructed by being buried in soil H on the water bottom T. The scour detection device 1 detects scouring of the soil H around the pier B1.

[0024] For example, the scour detection device 1 includes a sensor 10 that detects at least one of temperature and vibration. As an example, the sensor 10 includes an optical fiber cable 11 and a measuring instrument 15 to which one end of the optical fiber cable 11 is connected. The measuring instrument 15 includes, for example, a temperature detection unit 16 and a vibration detection unit 17.

[0025] The optical fiber cable 11 is composed of an optical fiber core and a resin coating layer that coats the optical fiber core. The diameter of the optical fiber cable 11 is, for example, about 0.9 mm. For example, the measuring device 15 of the sensor 10 has a temperature detection unit 16 and a vibration detection unit 17, so that the sensor 10 can detect at least one of temperature and vibration.

[0026] The scour detection device 1 includes a support member 12 that supports the sensor 10. The support member 12 is, for example, a member that constitutes a bridge pier B1. For example, an optical fiber cable 11 of the sensor 10 is attached to the support member 12, and the support member 12 to which the optical fiber cable 11 is attached is buried in the soil H around the bridge pier B1. The measuring instrument 15 is provided, for example, on the ground. The optical fiber cable 11 is, for example, a distributed optical fiber sensor, and detects strain, temperature, or vibration occurring around the optical fiber cable 11. The optical fiber cable 11 supported by the support member 12 detects strain, temperature, or vibration in the soil H and underwater W.

[0027] Fig. 3 is a cross-sectional view of the sensor 10 and the pier B1, showing a schematic example of a state in which the sensor 10 detects scouring. As shown in Figs. 2 and 3, in a state in which no scouring occurs, the optical fiber cable 11 supported by the support member 12 is buried in earth and sand H, and the optical fiber cable 11 does not detect strain, temperature, or vibration in the water W. Since the optical fiber cable 11 supported by the support member 12 does not detect strain, temperature, or vibration in the water W in this way, the sensor 10 does not detect scouring of the pier B1.

[0028] On the other hand, when scouring occurs at the pier B1, the soil H around the pier B1 is gouged out and a part of the support member 12 is exposed underwater W. At this time, at least a part of the optical fiber cable 11 detects the distortion, temperature or vibration in the water W. For example, the optical fiber cable 11 measures the vertical distribution of temperature or vibration, detects the position of the water bottom T from the difference in temperature or vibration characteristics between the water W and the soil H, and detects the occurrence of scouring from a change in that position.

[0029] Fig. 4 is a schematic diagram showing the optical fiber cable 11 and the measuring instrument 15 of the sensor 10. As shown in Fig. 4, the measuring instrument 15, for example, repeatedly inputs measuring light K1, which is pulsed light, to the optical fiber cable 11 at a constant period. As described above, as an example, the optical fiber cable 11 is a distributed optical fiber sensor. When the optical fiber cable 11 is a distributed optical fiber sensor, it is possible to grasp detailed distribution of strain, temperature, or vibration. Therefore, temperature detection by the temperature detection unit 16 and vibration detection by the vibration detection unit 17 can be performed with high accuracy.

[0030] The measuring instrument 15 (temperature detection unit 16 and vibration detection unit 17) measures at least one of temperature and vibration by Rayleigh measurement using the optical fiber cable 11, for example. However, the measuring instrument 15 may measure at least one of temperature and vibration by Brillouin measurement using the optical fiber cable 11. When the measuring instrument 15 inputs measurement light K1 to the optical fiber cable 11, backscattered light K2 is generated in the optical fiber cable 11. The spectrum of the backscattered light K2 (intensity per frequency) changes depending on strain, temperature, or vibration.

[0031] The intensity of the backscattered light K2 is smaller than the intensity of the measurement light K1. In the Rayleigh measurement, the change in the spectrum of the backscattered light K2 is measured to detect the temperature and vibration occurring in the optical fiber cable 11. The Rayleigh measurement using the backscattered light K2 has the advantages of being highly accurate and resistant to light loss.

[0032] The optical fiber cable 11 can detect changes in the support member 12 exposed to the water W with an accuracy of, for example, 1 μm of distortion and 0.1° C. of temperature. It is known that at the bottom of the water T, the temperature of the water W is higher than the temperature in the sediment H, and the temperature difference between the temperature of the water W and the temperature in the sediment H is about 0.5° C. Therefore, the temperature detection unit 16 according to this embodiment can detect a temperature change of 0.1° C. using the optical fiber cable 11, and can reliably detect a state in which the support member 12 is exposed to the water W as a result of scouring.

[0033] As an example, the vibration detection unit 17 detects vibrations via the optical fiber cable 11 by distributed acoustic sensing (DAS). The vibration detection unit 17 detects vibrations caused by water flow on the support member 12 exposed underwater W as a result of scouring. The DAS can output a vibration distribution over a length of 50 km at high density at intervals of 0.2 m (20 cm). As an example, the optical fiber cable 11 has a detection unit every 20 cm, and the results of vibration detection at each detection unit are input to the vibration detection unit 17.

[0034] The vibration detection unit 17 detects the vibration by detecting the phase of the backscattered light K2 that changes according to the vibration applied to the optical fiber cable 11. The vibration detection unit 17 may acquire position information of the optical fiber cable 11 by measuring the round trip time of light, which differs depending on the propagation distance of the light to the optical fiber cable 11, and may output a vibration distribution along the optical fiber cable 11 by sampling the measurement signal at each position at a rate of several Hz to 2.5 kHz, for example.

[0035] FIG. 5 is a perspective view showing a schematic example of a support member 12 constituting a part of the pier B1. As shown in FIG. 5, the support member 12 may be, for example, a steel sheet pile. As an example, the support member 12 may be a member used in a sheet pile foundation construction method, which is a sheet pile used for temporary retaining and is joined to the foundation (pier B1). In this case, the steel sheet pile used in the sheet pile foundation construction method can be effectively used as the support member 12 for the optical fiber cable 11. Note that each of the multiple optical fiber cables 11 may be supported by each of the multiple support members 12. In this case, it is possible to more easily identify the position or range where scouring has occurred.

[0036] Fig. 6 is a perspective view showing an example of a support structure of the optical fiber cable 11 relative to the support member 12. As shown in Fig. 6, as an example, the optical fiber cable 11 may include two types of optical fibers. In this example, the optical fiber cable 11 includes a detection optical fiber cable 11b that detects strain (temperature or vibration) and a fiber 11c dedicated to temperature measurement.

[0037] The detection optical fiber cable 11b detects at least one of temperature and vibration as described above via the support member 12. The temperature measurement dedicated fiber 11c includes, for example, an optical fiber core 11d and a tubular member 11f surrounding the optical fiber core 11d. The tubular member 11f is, for example, a steel pipe. As an example, the material of the tubular member 11f is a hard material (for example, SUS: Steel Use Stainless). However, the material of the tubular member 11f is not particularly limited.

[0038] The optical fiber cable 11 (e.g., the detection optical fiber cable 11b and the temperature measurement dedicated fiber 11c) is attached to the support member 12 by, for example, an adhesive 13. For example, a cross section of the support member 12 cut along a plane perpendicular to the longitudinal direction D2 of the support member 12 has a trapezoidal shape. In this case, the support member 12 has a bottom surface 12b constituting a web extending along the longitudinal direction D2, a pair of inclined surfaces 12c constituting flanges extending obliquely from both ends in the width direction of the bottom surface 12b, and a pair of bent portions 12d bent at the end of each inclined surface 12c opposite to the bottom surface 12b.

[0039] For example, the optical fiber cable 11 is attached to the bottom surface 12b of the support member 12 so as to extend along the bottom surface 12b. As an example, the detection optical fiber cable 11b and the temperature measurement dedicated fiber 11c are arranged to be aligned along the width direction of the bottom surface 12b. The optical fiber cable 11 is supported by the support member 12 by applying an adhesive 13 to the optical fiber cable 11 arranged in this manner.

[0040] 7(a) and 7(b) each show a modified example of the configuration of the optical fiber cable 11 and the support member 12. As shown in Fig. 7(a) and 7(b), the optical fiber cable 11 attached to the support member 12 includes a first portion 11A extending in a first direction A1 and a second portion 11B that is continuous with the first portion 11A and extends in a second direction A2 intersecting the first direction A1. For example, the first direction A1 is a vertical direction and the second direction A2 is a horizontal direction. However, the first direction A1 may be a direction other than the vertical direction, and the second direction A2 may be a direction other than the horizontal direction.

[0041] In the example of Fig. 7(a), the optical fiber cable 11 includes a plurality of first portions 11A and a plurality of second portions 11B, and is installed in a zigzag shape (so that the optical fiber cable 11 has a corrugated shape) on the support member 12. In the example of Fig. 7(b), the optical fiber cable 11 is installed on the support member 12 so that the optical fiber cable 11 extends in a spiral shape along the inner surface of the tubular support member 12.

[0042] In the following, various examples of the support structure of the optical fiber cable 11 relative to the support member 12 will be described. As shown in Fig. 8(a), one optical fiber cable 11 may be supported on the bottom surface 12b of the support member 12. As shown in Fig. 8(b), multiple optical fiber cables 11 may be supported by the support member 12.

[0043] For example, the optical fiber cable 11 may be attached to each of the bottom surface 12b and the inclined surface 12c of the support member 12. In these examples, the optical fiber cable 11 is installed on the web or flange of the U-shaped steel sheet pile, and extends in the longitudinal direction of the steel sheet pile (the driving direction, the direction perpendicular to the paper surface of FIG. 8).

[0044] In the example of Fig. 8(a), the optical fiber cable 11 is installed on an inner surface 12f of a support member 12 which is a U-shaped steel sheet pile. However, the optical fiber cable 11 may be installed on an outer surface 12g of the support member 12. One of the inner surface 12f and the outer surface 12g of the support member 12 is a surface (excavation surface) that is exposed during ground excavation. In order to prevent the optical fiber cable 11 from being damaged during this ground excavation, it is preferable that the optical fiber cable 11 is installed on the surface of the support member 12 opposite to the excavation surface.

[0045] 8(c), the support member 12 may include a holding portion 12h that holds the optical fiber cable 11. The holding portion 12h is fixed to, for example, the inclined surface 12c of the support member 12. As an example, the holding portion 12h has an L-shaped member 12j into which the optical fiber cable 11 is inserted, and a resin layer 12k that is filled in the L-shaped member 12j into which the optical fiber cable 11 is inserted. Note that the holding portion 12h may have a U-shaped member instead of the L-shaped member 12j.

[0046] 9(a), 9(b), 9(c), and 9(d) are cross-sectional views showing examples of the support structure of the optical fiber cable 11 relative to the bottom surface 12b of the support member 12. As shown in FIG. 9(a), the support member 12 has a fixing portion 12p that fixes the optical fiber cable 11 to the support member 12.

[0047] The fixing portion 12p has a first resin layer 12q that covers the optical fiber cable 11 on the bottom surface 12b, a glass cloth 12r that covers the first resin layer 12q, and a second resin layer 12s that covers the glass cloth 12r. The glass cloth 12r functions as a protective member that protects the optical fiber cable 11.

[0048] According to this fixing portion 12p, the first resin layer 12q, the glass cloth 12r, and the second resin layer 12s protect the optical fiber cable 11 from external forces, further reducing the possibility of damage to the optical fiber cable 11. As a result, even when the support member 12 is driven into the ground, for example, the optical fiber cable 11 can be made less likely to be damaged.

[0049] 9(b), the support member 12 may include a fixing member 12t that fixes the optical fiber cable 11 to the support member 12. For example, the fixing member 12t includes an adhesive 12v applied to the optical fiber cable 11, a double-sided tape 12w that covers the optical fiber cable 11 and the adhesive 12v, and a cable protection member 12x that is placed on the double-sided tape 12w.

[0050] The adhesive 12v is applied to the optical fiber cable 11 and the bottom surface 12b, so that the optical fiber cable 11 is integrated with the bottom surface 12b. The adhesive 12v may be omitted. The double-sided tape 12w is attached to the optical fiber cable 11 so as to cover the optical fiber cable 11 integrated with the bottom surface 12b.

[0051] The cable protection member 12x is made of aluminum, for example. In this case, the cable protection member 12x is lightweight, and therefore workability can be improved. A V-groove 12y is formed on the surface of the cable protection member 12x that faces the optical fiber cable 11. By covering the optical fiber cable 11 with the V-groove 12y, the optical fiber cable 11 and the raised portions of the double-sided tape 12w are accommodated in the V-groove 12y, resulting in a good fit.

[0052] 9(c), the support member 12 may include an installation member 12z that installs the optical fiber cable 11 on the support member 12. The installation member 12z has a cylindrical member 12b1 that houses the optical fiber cable 11 therein, and an adhesive 12b2 that is injected into the cylindrical member 12b1 that houses the optical fiber cable 11. The installation member 12z may be fixed to the bottom surface 12b by welding, for example, or by adhesion, or may be attached to the bottom surface 12b with double-sided tape or the like.

[0053] The configuration of the installation member that supports the optical fiber cable 11 on the support member 12 is not limited to the installation member 12z described above and can be modified as appropriate. Fig. 9(d) shows an installation member 12b3 according to a modified example. The installation member 12b3 includes a pair of weld beads 12b4 aligned along the width direction of the bottom surface 12b and an adhesive 12b5 filled between the pair of weld beads 12b4.

[0054] Optical fiber cable 11 is disposed between a pair of weld beads 12b4. Optical fiber cable 11 disposed between the pair of weld beads 12b4 is filled with adhesive 12b5. Optical fiber cable 11 is covered with adhesive 12b5 that has been filled between the pair of weld beads 12b4 and hardened, thereby enabling optical fiber cable 11 to be firmly supported on support member 12.

[0055] 10(a), the support member 12 may have an accommodating groove 12b6 that accommodates the optical fiber cable 11. The accommodating groove 12b6 is a V-groove recessed in a V-shape in the bottom surface 12b of the support member 12. The accommodating groove 12b6 may be formed by cutting the bottom surface 12b, or may be formed when the support member 12 is rolled.

[0056] The support member 12 further includes an adhesive 12b7 that is applied to the optical fiber cable 11 accommodated in the accommodating groove 12b6. The optical fiber cable 11 is firmly supported by the support member 12 as the adhesive 12b7 applied to the optical fiber cable 11 accommodated in the accommodating groove 12b6 hardens.

[0057] 10(b), the support member 12 may include a groove support member 12b8 having a groove 12b9 into which the optical fiber cable 11 fits. The groove support member 12b8 is made of aluminum, for example, like the cable protection member 12x described above. The groove support member 12b8 may be fixed to the bottom surface 12b of the support member 12 by welding, by adhesion, or by double-sided tape or the like.

[0058] As in the above-mentioned examples, the optical fiber cable 11 is housed in the groove 12b9 of the groove support member 12b8, and the adhesive 12b7 is applied to the groove 12b9. The adhesive 12b7 filled in the groove 12b9 and the optical fiber cable 11 is cured, so that the optical fiber cable 11 is firmly held to the support member 12.

[0059] 10(c), the support member 12 may include a protective member 12c1 that protects the optical fiber cable 11. The protective member 12c1 is made of, for example, steel. The protective member 12c1 is disposed on the driving direction side of the support member 12 as viewed from the optical fiber cable 11 supported by the support member 12. In other words, the support member 12 is driven into the ground or the like from the side where the protective member 12c1 is provided.

[0060] The protective member 12c1 functions as a resistance reducing member that reduces the resistance of the support member 12 when the support member 12 is driven into the ground or the like. The protective member 12c1 has a tapered surface 12c2 that is inclined so that the thickness of the protective member 12c1 decreases toward the driving direction. When viewed from the side of the support member 12, the tapered surface 12c2 has a triangular shape whose height from the bottom surface 12b decreases toward the driving direction.

[0061] By providing the support member 12 with the above-described protective member 12c1, it is possible to more reliably reduce interference of the optical fiber cable 11 with the ground or the like when driving the support member 12 into the ground or the like. Furthermore, by providing the protective member 12c1 with the tapered surface 12c2, it is possible to reduce resistance when driving the support member 12 into the ground or the like.

[0062] Various examples of the support structure of the optical fiber cable 11 on the support member 12 have been described above with reference to Figures 8 to 10. In this manner, various structures can be adopted as the support structure of the optical fiber cable 11 on the support member 12. Also, the optical fiber cable 11 may be supported on the support member 12 by a combination of two or more of the support structures shown in Figures 8(a), 8(b), 8(c), 9(a), 9(b), 9(c), 9(d), 10(a), 10(b), and 10(c).

[0063] Next, the steps of the scour detection method according to this embodiment will be described. The scour detection method according to this embodiment is executed together with the construction of a structure, not after the construction of the structure. First, as shown in Fig. 6, for example, the optical fiber cable 11 is attached to the support member 12 (step of attaching the optical fiber cable to the support member).

[0064] At this time, the optical fiber cable 11 is attached to the support member 12 by the adhesive 13. Specifically, the optical fiber cable 11 is attached to the bottom surface 12b of the support member 12 so as to extend along the bottom surface 12b. In this manner, the optical fiber cable 11 is supported on the support member 12 (a step of supporting the optical fiber cable on the support member).

[0065] However, the method of supporting the optical fiber cable 11 on the support member 12 is not limited to the above, and may be at least any of the methods shown in Figures 8(a), 8(b), 8(c), 9(a), 9(b), 9(c), 9(d), 10(a), 10(b) and 10(c). As a method of supporting the optical fiber cable 11 on the support member 12, the optical fiber cable 11 may be supported on the support member 12 in a meandering (or spiral) manner so as to have a first portion 11A and a second portion 11B, as shown in Figure 7(a) or 7(b).

[0066] After the optical fiber cable 11 is supported on the support member 12, the support member 12 is embedded in the soil H around a structure (for example, the pier B1 of bridge B) as shown in Fig. 5 (step of embedding the support member). "Soil around the structure" refers to the soil located around the location where the structure is to be constructed, and in this embodiment, the support member 12 is embedded in the soil H adjacent to the portion where the structure is to be constructed. For example, support members 12 to which the optical fiber cable 11 is attached, as well as support members 12 to which the optical fiber cable 11 is not attached, are sequentially driven into the soil H. Thereafter, the foundation of the pier B1 is constructed (step of constructing the foundation of the structure), and bridge B is constructed.

[0067] 2 and 3, a measuring instrument 15 connected to one end of an optical fiber cable 11 is installed, and at least one of the temperature and vibration around the pier B1 is detected by a sensor 10 including the measuring instrument 15 (step of detecting at least one of temperature and vibration). At this time, the measuring instrument 15 detects whether or not the support member 12 is exposed to the water W (step of detecting whether or not it is exposed to the water). Specifically, a temperature detection unit 16 detects the temperature of the support member 12 via the optical fiber cable 11, and a vibration detection unit 17 detects the presence or absence of vibration applied to the support member 12 via the optical fiber cable 11.

[0068] For example, the optical fiber cable 11 measures the vertical distribution of temperature or vibration, detects the position of the water bottom T from the difference in temperature or vibration characteristics between the water W and the sediment H, and detects the occurrence of scouring from a change in that position. At this time, the measuring instrument 15 measures the vertical distribution of temperature or vibration via the optical fiber cable 11, and detects the position of the water bottom T from the difference in temperature or vibration characteristics between the water W and the sediment H. Then, when the measuring instrument 15 determines that the detected position of the water bottom T has not changed, it determines that scouring is not occurring.

[0069] On the other hand, as an example, when scouring occurs and a part of the support member 12 is exposed underwater W, the temperature detection unit 16 detects the temperature of the water transmitted to the support member 12 via the optical fiber cable 11, and the vibration detection unit 17 detects the water flow in the water W as vibration. At this time, the measuring instrument 15 measures the vertical distribution of temperature or vibration via the optical fiber cable 11, and detects the position of the water bottom T from the difference in temperature or vibration characteristics between the water W and the soil H. Then, when the measuring instrument 15 determines that the detected position of the water bottom T has changed, it determines that scouring has occurred. The above-mentioned determination of whether scouring has occurred may be performed constantly or at regular intervals. When performed at regular intervals, it is performed, for example, every few months (or every season).

[0070] Next, the effects of the scour detection method and the scour detection device 1 according to the present embodiment will be described in detail. First, in the conventional scour detection system, a sensor is provided to detect the mechanical operation of unwinding the wire from the drum, so that when used for a long period of time in an environment close to the splash zone of river water or seawater, there is a concern that the drum will not operate and the sinker will not sink, or that the rotary encoder will not measure properly. In contrast, the scour detection method and the scour detection device 1 according to the present embodiment do not have a mechanical operating unit, so that the above problems can be avoided. In addition, the optical fiber of the optical fiber cable 11 itself is highly durable, and the measuring instrument 15 can be placed far away. Furthermore, since there is no need to place an operating unit or a machine that handles electricity in the water W, the scour detection device 1 can be made highly durable.

[0071] Furthermore, in conventional riverbed scouring monitoring methods, a special sensor with a heating wire must be fabricated separately from the structure, which can cause a problem that the sensor cannot be easily installed. Furthermore, there are concerns about failure due to poor insulation of the heating wire, or the impact on the environment due to the application of heat. In contrast, the scouring detection method and scouring detection device 1 according to this embodiment do not require a heating wire, so the above problems do not occur. Furthermore, in the scouring detection method and scouring detection device 1 according to this embodiment, it is possible to measure not only temperature but also vibration with the same sensor, making it possible to detect scouring with high accuracy.

[0072] Also, a conventional scour detection device is known that detects scouring from changes in the vibration frequency of a bridge pier. However, this scour detection device may only be able to detect scouring when scouring has progressed to the extent that the vibration frequency of the bridge pier changes, so there is a problem that it cannot reliably detect signs of scouring (for example, a state in which scouring has occurred without affecting a structure). In contrast, the scour detection method and scour detection device 1 according to this embodiment are capable of detecting scouring even at a stage where minor scouring has occurred, so it is also possible to detect signs of scouring.

[0073] In the scour detection method and scour detection device 1 according to this embodiment, the support member 12 on which the sensor 10 is supported is embedded in the soil H around the pier B1. When the soil H around the pier B1 is gouged out and scouring occurs, the area of ​​the support member 12 that is exposed underwater W changes. A measuring instrument 15 measures the vertical distribution of temperature or vibration via an optical fiber cable 11 supported by the support member 12, detects the position of the water bottom T from the difference in temperature or vibration characteristics between the water W and the soil H, and detects the occurrence of scouring from a change in that position.

[0074] Therefore, the sensor 10 supported on the support member 12 buried in the soil H detects the exposure of the support member 12 to the water W, thereby enabling highly accurate detection of scouring around the pier B1. The sensor 10, which detects at least one of temperature and vibration, is supported on the support member 12 constituting a part of the pier B1. Therefore, since the sensor 10 supported on the support member 12 constituting a part of the pier B1 is buried in the soil H, there is no need to fabricate the sensor separately from the pier B1. In other words, the sensor 10 can be supported on the support member 12 during the process of preparing the support member 12 for the pier B1. Therefore, the sensor 10 can be easily installed together with the construction of the pier B1.

[0075] The sensor 10 may include an optical fiber cable 11 attached to the support member 12. In this case, the optical fiber cable 11 is attached to the support member 12, and detects at least one of strain, temperature, and vibration. Specifically, when the measuring instrument 15 measures strain or temperature using the optical fiber cable 11, it measures the elapsed time from when light is incident on the optical fiber cable 11 until the scattered light returns, and converts the frequency shift of the scattered light into strain or temperature data. When the measuring instrument 15 detects vibration using the optical fiber cable 11, it converts the phase change of the backscattered light into vibration data for pulsed light repeatedly input at a constant period. As described above, the measuring instrument 15 can measure strain, temperature, or vibration using the optical fiber cable 11. By attaching the linear optical fiber cable 11 to the support member 12 and laying the optical fiber cable 11 around, it is possible to measure the change in the backscattered light at a wide range of locations with one optical fiber cable 11, and therefore it is possible to detect strain, temperature, or vibration over a wide range. Therefore, the optical fiber cable 11 can be easily installed, and scouring can be detected over a wide range with high accuracy.

[0076] In the step of embedding the support member 12, the support member 12 to which the optical fiber cable 11 is affixed may be embedded in the soil H before the foundation of the pier B1 is constructed. In this case, the support member 12 to which the optical fiber cable 11 is affixed is embedded in the soil H before the foundation of the pier B1 is constructed. Therefore, since the support member 12 with the sensor 10 is embedded in the soil H before the foundation is constructed, scouring detection can be started from the time of construction of the foundation.

[0077] As shown in FIG. 7(a) and FIG. 7(b), the optical fiber cable 11 attached to the support member 12 may include a first portion 11A extending in a first direction A1 and a second portion 11B extending in a second direction A2 that is continuous with the first portion 11A and intersects with the first direction A1. In this case, the optical fiber cable 11 has the first portion 11A extending in the first direction A1 and the second portion 11B extending in the second direction A2 different from the first direction A1, so that the optical fiber cable 11 can be arranged in a zigzag or spiral shape. Therefore, compared with the case where the optical fiber cable 11 is arranged in a straight line, the optical fiber cable 11 can be arranged in a wider area, so that the strain, temperature, or vibration can be detected with higher accuracy from the optical fiber cable 11 arranged in a wider area. More specifically, by arranging the optical fiber cable 11 in a zigzag or spiral shape, the optical fiber cable 11 can be laid out over a wider range, so that a wider range can be measured and the position resolution of the scour measurement can be improved.

[0078] The above describes the embodiments of the scour detection method and scour detection device according to the present disclosure. However, the scour detection method and scour detection device according to the present disclosure are not limited to the above-mentioned embodiments, and can be modified as appropriate within the scope of the gist described in the claims. In other words, the content and order of the steps of the scour detection method, and the configuration, shape, size, number, material, and arrangement of each part of the scour detection device are not limited to the above-mentioned embodiments, and can be modified as appropriate within the scope of the above-mentioned gist.

[0079] For example, in the above embodiment, an example has been described in which the structure on which the sensor 10 is installed is the pier B1 of the bridge B. However, the structure may be something other than a bridge, and the scour detection method and scour detection device according to the present invention are applicable to various structures. Modified examples of various structures will be described below.

[0080] 11 , the scour detection method and scour detection device 1 according to the modified example may be applied to a steel pipe sheet pile foundation 21. The steel pipe sheet pile foundation 21 includes, for example, a sheet pile well 22 (steel pipe well, partition) configured by arranging a plurality of steel pipe sheet piles 22b in a ring shape in a plan view, and a reinforced concrete foundation plate 23 poured in the internal space of the sheet pile well 22.

[0081] The steel pipe sheet pile foundation 21 is, for example, a bridge foundation in which a pier 24 is constructed on a reinforced concrete foundation slab 23. In this steel pipe sheet pile foundation 21, for example, the optical fiber cable 11 is arranged on at least one of a plurality of steel pipe sheet piles 22b, thereby installing the sensor 10 on the steel pipe sheet pile foundation 21. In this case, as in the above-mentioned case, when the soil H is scoured, the part of the sheet pile well 22 to which the optical fiber cable 11 is attached detects the exposure of the steel pipe sheet pile 22b in the water W, thereby making it possible to detect scouring.

[0082] 12(a) shows a foundation 32 and a sensor 10 of a structure 31 according to a modified example. The foundation 32 is a spread foundation. The foundation 32 includes a footing 33 buried in soil H, and a pier 34 extending upward from the footing 33. For example, a support member 12 supporting an optical fiber cable 11 is buried so as to extend vertically along the footing 33. The optical fiber cable 11 detects exposure of the support member 12 in water W at a position adjacent to the pier 34, and the sensor 10 detects scouring of the structure 31.

[0083] 12(b) shows a caisson foundation 41 and a sensor 10 which are structures according to a modified example. The caisson foundation 41 includes a concrete base 42, a cylindrical side wall 43 extending vertically upward from the concrete base 42, a top plate 44 located at the upper end of the side wall 43, and a pier 45 protruding vertically upward from the top plate 44. For example, a support member 12 on which an optical fiber cable 11 is supported so as to extend vertically along the side wall 43 is buried in soil H. The optical fiber cable 11 detects exposure of the support member 12 to water W at a position adjacent to the side wall 43, and the sensor 10 detects scouring of the caisson foundation 41.

[0084] FIG. 13(a) shows a pile foundation 51 and a sensor 10 which are structures according to a modified example. The pile foundation 51 includes a plurality of foundation piles 52, a footing 53 located at the upper ends of the plurality of foundation piles 52, and a pier 54 extending vertically upward from the footing 53. FIG. 13(b) shows a diaphragm wall foundation 61 and a sensor 10 which are structures according to a modified example. The diaphragm wall foundation 61 includes a diaphragm wall 62, a footing 63 located at the upper end of the diaphragm wall 62, and a pier 64 extending vertically upward from the footing 63. In the pile foundation 51 and the diaphragm wall foundation 61, the optical fiber cable 11 detects the exposure of the support member 12 to the water W at a position adjacent to the footings 53, 63, and the sensor 10 detects the scouring of the pile foundation 51 or the diaphragm wall foundation 61.

[0085] Fig. 14 shows a modified support member 65 that can be installed on, for example, the diaphragm wall foundation 61 of Fig. 13(b). As shown in Fig. 13(b) and Fig. 14, a support member 65 having optical fiber cables 11 arranged in a zigzag pattern may be provided on the side of a diaphragm wall 62. For example, by positioning several meters of optical fiber cables 11 in an area of ​​1 meter in the vertical direction, the position resolution of scour measurement can be improved.

[0086] 15 shows an abutment foundation 71, which is a structure according to a modified example, and a sensor 10. The abutment foundation 71 includes a plurality of pile foundations 72, a body 73 extending upward from the pile foundations 72, and a parapet 74 located at the upper end of the body 73. A main girder 75 is constructed on the parapet 74, for example, via a bearing. In the abutment foundation 71, the optical fiber cable 11 detects exposure of the support member 12 to the water W at a position adjacent to the pile foundation 72, and the sensor 10 detects scouring of the abutment foundation 71.

[0087] 16 shows an offshore wind power foundation 81 and a sensor 10, which are structures according to a modified example. The offshore wind power foundation 81 constitutes a wind power generator 80 installed in the ocean. However, the wind power generator 80 may be installed in water W other than the ocean, such as a lake, a river, a coast, or a harbor.

[0088] The wind power generator 80 includes a tower 82 fixed to an offshore wind foundation 81, a nacelle 83 installed on the top of the tower 82, and blades 84 attached to the nacelle 83. The offshore wind foundation 81 includes a support pile 81b which is a monopile driven into water W, and a transition piece 81c which extends upward from the support pile 81b and is connected to the lower end of the tower 82. Note that the offshore wind foundation 81 may include a gravity type or jacket type foundation instead of the monopile foundation type.

[0089] Scour prevention works 85 are provided around the support piles 81b on the water bottom T, and the scour prevention works 85 prevent scouring of soil H around the support piles 81b on the water bottom T. Furthermore, in the offshore wind foundation 81, the optical fiber cable 11 detects exposure of the support members 12 to the water W at a position adjacent to the support piles 81b, and the sensor 10 detects scouring of the offshore wind foundation 81. In this way, it is possible to use the existing scour prevention works 85 and the sensor 10 in combination.

[0090] Fig. 17 is a cross-sectional view showing a scour detection device 1 according to a further modified example. As shown in Fig. 17, the height of the upper end of the support member 12 may be higher than the height of the water bottom T. For example, in the scour detection device 1 shown in Fig. 17, the measuring instrument 15 measures the behavior in the soil and the behavior in the water over the entire length of the support member 12. The measuring instrument 15 then measures the movement and transition of the boundary between the behavior in the soil and the behavior in the water due to scouring. Therefore, even in the case of the scour detection device 1 according to the modified example, scouring can be detected with high accuracy and signs of scouring can be detected, as in the above-mentioned examples.

[0091] The above describes examples of various structures to which the sensor 10 can be applied. However, the sensor 10 can also be applied to other structures. For example, the optical fiber cable 11 detects the exposure of the support member 12 to the water W in a position adjacent to a port facility, marine facility, or river facility, and the sensor 10 can detect scouring of the port facility, marine facility, or river facility.

[0092] In the above-described embodiment, an example has been described in which the optical fiber cable 11 is supported by the support member 12, which is a steel sheet pile, and the support member 12 is embedded in a position adjacent to a structure. However, the optical fiber cable 11 may be supported by a steel pipe, and the steel pipe supporting the optical fiber cable 11 may be pressed into the vicinity of the foundation.

[0093] Also, the optical fiber cable 11 may be installed directly on the foundation (footing). Furthermore, when a plurality of blocks are constructed in stages, such as a caisson, the optical fiber cable 11 may be installed in the constructed blocks while leaving an excess length, and the construction of the blocks and the installation of the optical fiber cable 11 while leaving an excess length may be repeated. In this manner, the installation method and installation structure of the optical fiber cable 11 can be appropriately changed.

[0094] In the above-described embodiment, an example has been described in which the sensor 10 includes the optical fiber cable 11 affixed to the support member 12. However, the sensor 10 does not have to include the optical fiber cable 11. For example, instead of the optical fiber cable 11, the sensor may include a temperature sensor such as a thermocouple that measures a temperature difference or a vibration sensor. [Explanation of symbols]

[0095] 1...scouring detection device, 10...sensor, 11...optical fiber cable, 11A...first part, 11b...detection optical fiber cable, 11B...second part, 11c...temperature measurement dedicated fiber, 11d...optical fiber core, 11f...tubular member, 12...support member, 12b...bottom surface, 12b1...cylindrical member, 12b2...adhesive, 12b3...installation member, 12b4...weld bead, 12b5...adhesive, 12b6...accommodation groove, 12b7...adhesive, 12b8...groove support member, 1 2b9...groove, 12c...inclined surface, 12c1...protective member, 12c2...tapered surface, 12d...folded portion, 12f...inner surface, 12g...outer surface, 12h...holding portion, 12j...L-shaped member, 12k...resin layer, 12p...fixing portion, 12q...first resin layer, 12r...glass cloth, 12s...second resin layer, 12t...fixing member, 12v...adhesive, 12w...double-sided tape, 12x...cable protection member, 12y...V-groove, 12z...installation member, 13...adhesive, 15...measuring instrument, 16 ...Temperature detection unit, 17...Vibration detection unit, 21...Steel pipe sheet pile foundation, 22...Sheet pile shaft, 22b...Steel pipe sheet pile, 23...Reinforced concrete foundation plate, 24...Pier, 31...Structure, 32...Foundation, 33...Footing, 34...Pier, 41...Caisson foundation, 42...Concrete base plate, 43...Side wall, 44...Top plate, 51...Pile foundation, 52...Foundation pile, 53...Footing, 54...Pier, 61...Diaphragm wall foundation, 62...Diaphragm wall, 63...Footing, 64...Pier, 71...Bridge Pedestal foundation, 72...pile foundation, 73...structure, 74...parapet, 75...main girder, 80...wind turbine, 81...offshore wind foundation, 81b...support pile, 81c...transition piece, 82...tower, 83...nacelle, 84...blade, 85...scour prevention work, A1...first direction, A2...second direction, B...bridge, B1...pier, B2...main girder, D1...extension direction, D2...longitudinal direction, H...soil, K1...measurement light, K2...backscattered light, R...road, S...water surface, T...bottom, W...underwater.

Claims

1. A scouring detection method for detecting scouring around a structure that is constructed by being embedded in soil on the bottom of a body of water, comprising: a step of supporting a sensor for detecting at least one of temperature and vibration on a support member constituting a part of the structure; Embedding the support member in soil surrounding the structure; said sensor detecting at least one of temperature and vibration of water surrounding said structure; Equipped with the sensor includes an optical fiber cable attached to the support member and a measurement unit having a temperature detection unit and a vibration detection unit; The temperature detection unit detects a temperature change through the optical fiber cable, the vibration detection unit detects vibrations through the optical fiber cable by distributed acoustic sensing; The optical fiber cable includes a detection optical fiber cable for detecting strain and a fiber dedicated to temperature measurement, the fiber dedicated to temperature measurement including an optical fiber core and a tubular member surrounding the optical fiber core. Scour detection method.

2. In the step of embedding the support member, the support member to which the optical fiber cable is attached is embedded in the soil before constructing a foundation for the structure. The scour detection method according to claim 1 .

3. The optical fiber cable attached to the support member includes a first portion extending in a first direction and a second portion continuing from the first portion and extending in a second direction intersecting the first direction. The scour detection method according to claim 1 or 2.

4. A scour detection device that detects scouring around a structure that is constructed by being embedded in soil on the bottom of a body of water, A sensor for detecting at least one of temperature and vibration; A support member that supports the sensor and constitutes a part of the structure; Equipped with The support member to which the sensor is attached is buried in soil around the structure, the sensor includes an optical fiber cable attached to the support member and a measurement unit having a temperature detection unit and a vibration detection unit; The temperature detection unit detects a temperature change through the optical fiber cable, the vibration detection unit detects vibrations through the optical fiber cable by distributed acoustic sensing; The optical fiber cable includes a detection optical fiber cable for detecting strain and a fiber dedicated to temperature measurement, the fiber dedicated to temperature measurement including an optical fiber core and a tubular member surrounding the optical fiber core. Scour detection device.

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