JP2019184591A - Detector and method for detection - Google Patents

Abstract

To provide a detector which can precisely detect a flow resistance of a weak layer.SOLUTION: A detector 1a includes: an optical fiber sensor 3 buried in a weak layer 10 alone; and a detector 4 detecting the flow resistance of the weak layer 10 according to a detection signal from the optical fiber sensor 3. Since the optical fiber sensor 3 directly receives the flow resistance of the weak layer 10, the detector can detect the flow resistance more accurately.SELECTED DRAWING: Figure 1

Description

  The present invention particularly relates to a detection apparatus and a detection method for detecting a flow resistance of a soft layer, for example, soft ground.

  In general, the strength of the ground, that is, the hardness of the ground, the tightness, the flow resistance, etc., is determined by the standard penetration test method (JIS A 1219), the mechanical cone penetration test method (JIS A 1220) or the in-situ vane shear test method (JGS). 1411 2012) and the like.

  However, the survey method described above is intended for the ground where a certain degree of strength can be expected, and the measurement is performed for those where the strength (flow resistance) cannot be expected, such as clay-like soft ground having a high water content ratio or waste sludge. It was difficult. On the other hand, for example, a method may be considered in which a strain gauge for measurement is attached to a metal piece whose material properties are known, and the flow resistance of the ground is detected from the expansion and contraction and deformation. However, this detection method is affected by the strength and processing accuracy of the metal piece, the adhesive between the strain gauge and the metal piece is affected by the strength, and because it is an electrical measurement, There are problems such as being affected by the coating agent.

  By the way, in patent document 1, in the underground installation type inclination sensor apparatus using an optical fiber, the underground which arrange | positioned the pile by which the optical fiber which fixed the bottom part to the support layer is fixed in the ground adjacent to embankment. It is described that an installation type inclination sensor device is installed.

JP 2003-14451 A

As described above, it has been difficult to detect the flow resistance of a soft layer such as soft ground or waste sludge by the conventional investigation method.
Further, the invention according to Patent Document 1 described above is configured to monitor the inclination of the adjacent land of the embankment caused by the embankment by an inclination sensor in which an optical fiber is fixed to the plate. It is difficult to detect resistance. That is, in this tilt sensor, since the optical fiber is fixed to the plate, if it is attempted to measure the flow resistance of the soft layer by this tilt sensor, the flow resistance applied to the optical fiber is the flow resistance of the soft layer. Specifically, the flow resistance imparted to the optical fiber is obtained by subtracting the rigidity of the plate from the flow resistance of the soft layer, and the flow resistance of the pure soft layer cannot be detected by the optical fiber, The detection accuracy is significantly lowered. In addition, when the flow resistance of the soft layer is smaller than the rigidity of the plate, the flow resistance of the soft layer is not given to the optical fiber, and there is a possibility that the flow resistance of the soft layer cannot be detected. As described above, in the invention according to Patent Document 1, it is difficult to detect the flow resistance of the soft layer.

  In addition, tremmy pipes may be used when placing and placing earth and sand, underwater concrete, etc. when constructing structures such as landfills, breakwaters, and seawalls in harbor construction. In this case, it is necessary to raise the tremy pipe and sequentially add earth and sand, underwater concrete and the like while maintaining the state where the lower end of the tremy pipe is immersed in the sedimentary ground which is a soft layer. For this reason, at the time of construction, in order to optimize the positional relationship between the lower end of the tremy tube and the sedimentary ground (soft layer) around the tremy tube, it was necessary to always manage the height of the tremy tube.

  For the above-described height management of the tremy tube, various methods such as a visual management method of a diver are employed. However, it is difficult to reduce the cost and appropriately manage the height, and needs to be improved. Therefore, at the time of construction, it was necessary to accurately detect the flow resistance of the sedimentary ground, which is a soft layer around the tremmy pipe, and reflect the result in the height management of the tremy pipe.

  This invention is made | formed in view of this point, and it aims at providing the detection apparatus and detection method which can detect the flow resistance of a soft layer accurately.

(Aspect of the Invention)
The following aspects of the invention exemplify the configuration of the present invention, and will be described in sections to facilitate understanding of various configurations of the present invention. Each section does not limit the technical scope of the present invention, and some of the components of each section are replaced, deleted, or further while referring to the best mode for carrying out the invention. Those to which the above components are added are also included in the technical scope of the present invention.

(1) A detection device for detecting a flow resistance of a soft layer, an optical fiber sensor embedded alone in the soft layer, and a flow resistance of the soft layer based on a detection signal from the optical fiber sensor And a detector for detecting the above-described (1) (corresponding to the invention of claim 1).
In the detection apparatus according to the item (1), for example, an optical fiber sensor embedded alone in the soft layer is slid in a direction orthogonal to the axial direction, and the single optical fiber sensor is driven by the flow resistance of the soft layer. By detecting the flow resistance of the soft layer, the detection accuracy of the optical fiber sensor can be improved.

(2) The detection device according to (1), wherein the optical fiber sensor has a base end side as a restraint end and a tip end side as a free end (corresponding to the invention of claim 2). ).
In the detection device described in the item (2), the installation work of the optical fiber sensor can be facilitated. Further, by ensuring the degree of freedom of displacement of the tip of the optical fiber sensor that is not constrained, it is possible to improve the bending followability of the optical fiber sensor with respect to the flow of the soft layer (relative displacement between the soft layer and the optical fiber sensor).

(3) The detection device according to (1) or (2), further comprising a data logger that stores the flow resistance of the soft layer detected by the detector over time. .
In the detection device according to the item (3), an appropriate flow resistance can be analyzed based on the flow resistance data of the soft layer accumulated by the data logger.

(4) The detection device according to (1), wherein the detector is formed in a rod shape, and the optical fiber sensor projects integrally along an axial direction from an axial end portion of the detector. A detection device (corresponding to the invention of claim 3).
In the detection device according to the item (4), the overall size can be made compact to provide a handy type detection device. As a result, handling of the detection device becomes very good.

(5) The detection apparatus according to (4), wherein the detector is provided with a display unit that displays a flow resistance of the soft layer.
In the detection device according to the item (5), the operator can quickly confirm the flow resistance of the soft layer at the time of detection.

(6) The detection device according to any one of (1) to (3), wherein the optical fiber sensor is supported at a base end side at a lower portion of a tremy tube, and the optical fiber sensor and the detector A detection device (corresponding to the invention of claim 4) for detecting a flow resistance of the deposited ground which is the soft layer deposited on the radially outer side of the tremy tube.
In the detection device described in the item (6), the flow resistance of the sedimentary ground, which is a soft layer, which has started to be deposited on the outer side in the radial direction at the lower part of the tremy tube can be detected by the optical fiber sensor. Based on the result, it is possible to accurately grasp the timing of raising the tremy tube. In short, the detection device described in the item (6) can be applied to the height management of the tremy tube.

(7) A detection method for detecting a flow resistance of a soft layer, wherein an optical fiber sensor is embedded alone in the soft layer, and the optical fiber sensor or the soft layer is disposed in an axial direction of the optical fiber sensor. The detector detects the flow resistance of the soft layer based on a detection signal from the optical fiber sensor by bending the optical fiber sensor while sliding in a direction substantially perpendicular to the optical fiber sensor. A detection method (corresponding to the invention of claim 5).
In the detection method according to item (7), the optical fiber sensor is bent while sliding the optical fiber sensor or the soft layer in a state where the optical fiber sensor is embedded in the soft layer, so that the soft layer is bent by the detector. Can be detected.

  According to the detection device and the detection method of the present invention, the flow resistance of the soft layer can be detected with high accuracy. Moreover, in the detection apparatus which concerns on this invention, the flow resistance of the sedimentary ground which is a soft layer around a tremy pipe can be detected accurately, and the height management of the tremy pipe at the time of construction can be performed appropriately.

1A and 1B show a detection apparatus according to a first embodiment of the present invention. FIG. 1A shows a state before an optical fiber sensor is slid, and FIG. 1B shows a state where an optical fiber sensor is slid. It is a figure which shows the mode of later. FIG. 2 is a diagram illustrating a detection apparatus according to the first embodiment of the present invention, in which a soft layer is slid in a lateral direction. FIG. 3 is a diagram illustrating a detection apparatus according to the first embodiment of the present invention, in which a plurality of optical fiber sensors including detectors are provided and a soft layer is slid in a lateral direction. FIG. 4 is a detection device according to the first embodiment of the present invention and is a diagram for explaining the configuration of the detector. FIG. 5 shows the relationship between the slide distance of the optical fiber sensor and the response strain amount in each sample. FIG. 6 shows the relationship between the response strain amount and each sample in the strain amount stable section in FIG. FIG. 7 shows the viscosity with respect to the response strain amount of the optical fiber sensor. FIG. 8 is a schematic perspective view of a detection apparatus according to the second embodiment of the present invention. FIG. 9 is a schematic view of a detection apparatus according to the third embodiment of the present invention. FIG. 10 is an enlarged view of a portion A in FIG. FIG. 11 shows changes in the wavelength of light obtained from the optical fiber sensor.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to FIGS.
The detection devices 1a, 1b, and 1c according to the first to third embodiments of the present invention can detect, for example, the flow resistance of the soft layer 10 shown in (1) to (6) below. (1) General soft ground. (2) River, lake and marine floating mud. (3) Sedimentary ground around Tremy pipe, especially during and after landfill construction. (4) Waste sludge and deposits and inputs at disposal sites. (5) Cement slurry. (6) Other soft layers having fluidity. In short, the detection devices 1a, 1b, and 1c detect the flow resistance of the soft layer 10 (for example, an adhesive force of 1 kN / m ² or less).

First, the detection apparatus 1a according to the first embodiment of the present invention will be described in detail with reference to FIGS.
As shown in FIG. 1, the detection device 1 a according to the first embodiment is based on an optical fiber sensor 3 embedded alone in the soft layer 10 and a detection signal from the optical fiber sensor 3. A detector 4 that detects the flow resistance of the soft layer 10 and a data logger 5 that stores the flow resistance of the soft layer 10 detected by the detector 4 over time are provided. The optical fiber sensor 3 has a small diameter and flexibility. The optical fiber sensor 3 is installed alone in the soft layer 10. The base end side of the optical fiber sensor 3 is restrained by the sensor fixing portion 8. As described above, the optical fiber sensor 3 has a proximal end that is restrained by the sensor fixing portion 8 and a distal end that is not restrained and is installed at a free end. The optical fiber sensor 3 is connected to a detector 4 in the data logger 5.

  The detector 4 is integrally incorporated in the data logger 5. As shown in FIG. 4, the detector 4 includes a light source unit 15 that supplies light toward the optical fiber sensor 3, a light receiving unit 16 that receives light from the optical fiber sensor 3, and a soft layer from the light receiving unit 16. A detection unit 17 that detects a change in the characteristic of light that changes according to a flow resistance (external input) of 10, and a calculation unit 18 that calculates the flow resistance of the soft layer 10 by a change in the characteristic of light from the detection unit 17. I have. Referring also to FIG. 1, when the flow resistance of the soft layer 10 is applied to the optical fiber sensor 3, the optical fiber sensor 3 is bent by the flow resistance of the soft layer 10, and the detection unit 17 of the detector 4 is bent. Then, the optical fiber sensor 3 is detected based on the light characteristic change detected by the detection unit 17 by the calculation unit 18 by detecting a change in the light characteristic that changes according to the flow resistance (external input) of the soft layer 10. It is possible to detect the flow resistance of the soft layer 10 which is a change in the physical amount applied to the. In addition, the relationship of the viscosity (flow resistance) with respect to the characteristic change of light is previously input into the calculating part 18 (refer FIG. 7). The data logger 5 stores the flow resistance of the soft layer 10 detected by the detector 4 over time. And in the data logger 5, based on the flow resistance of the soft layer 10 from the detector 4, the flow resistance of the soft layer 10 based on the bending condition (elapse of time) of the optical fiber sensor 3 is graphed, etc. The flow resistance (strength) of the soft layer 10 can be analyzed.

Next, a method for detecting the flow resistance of the soft layer 10 using the detection device 1a according to the first embodiment and the operation of the detection device 1a will be described.
As shown in FIG. 1A, the optical fiber sensor 3 is embedded in the soft layer 10. Specifically, the optical fiber sensor 3 is installed so as to be immersed in the soft layer 10 from a direction orthogonal to the surface of the soft layer 10. The optical fiber sensor 3 is installed in the soft layer 10 at its free end without being constrained at its tip. Subsequently, the light from the light source unit 15 of the detector 4 is supplied to the optical fiber sensor 3 as incident light, and the reflected light is received by the light receiving unit 16. Subsequently, as shown in FIG. 1B, the sensor fixing portion 8 is slid in a direction orthogonal to the axial direction of the optical fiber sensor 3. At this time, it is necessary to slide the optical fiber sensor 3 at a substantially constant speed as slowly as possible while suppressing the generation of acceleration. Then, the flow resistance of the soft layer 10 is given to the optical fiber sensor 3, and the optical fiber sensor 3 bends according to the flow resistance of the soft layer 10. Subsequently, the detection unit 17 of the detector 4 in the data logger 5 detects a change in the characteristics of the light received by the light receiving unit 16 and changing according to the bending of the optical fiber sensor 3. The characteristics of light are light intensity, phase, frequency, wavelength, polarization, and the like.

  Subsequently, in the calculation unit 18 of the detector 4, the flow resistance of the soft layer 10 is calculated based on the characteristic change of the light detected by the detection unit 17. Subsequently, the flow resistance of the soft layer 10 calculated by the calculation unit 18 of the detector 4 is stored in the data logger 5 as the optical fiber sensor 3 is bent. Subsequently, in the data logger 5, the flow resistance of the soft layer 10 is sequentially stored as time passes, in other words, according to the bending state of the optical fiber sensor 3. The data logger 5 analyzes the flow resistance (strength) of the soft layer 10 by graphing the flow resistance of the soft layer 10 based on the bending state (elapsed time) of the optical fiber sensor 3. .

  Note that, for example, when the optical fiber sensor 3 is slid, a configuration for measuring the speed may be adopted, and the measurement result may be stored in the data logger 5 with time. In the case of this embodiment, the data logger 5 graphs the speed of the optical fiber sensor 3 in addition to the flow resistance of the soft layer 10 based on the bending state (elapse of time) of the optical fiber sensor 3. The flow resistance of the soft layer 10 is analyzed. In short, in the above-mentioned graph, an accurate soft layer can be obtained by paying attention to a section in which the optical fiber sensor 3 is slid at a substantially constant speed movement, in other words, a section in which the flow resistance changes substantially as time passes. Ten flow resistances can be grasped.

  In the above-described embodiment, the optical fiber sensor 3 is slid. However, as shown in FIG. 2, the optical fiber sensor 3 is embedded in the soft layer 10, and the soft layer 10 is placed in the lateral direction (light The flow resistance may be detected by bending the optical fiber sensor 3 by flowing in a direction substantially orthogonal to the axial direction of the fiber sensor 3.

  Further, as shown in FIG. 3, a plurality of optical fiber sensors 3, 3 are embedded in the soft layer 10, and the soft layer 10 is caused to flow in the lateral direction, whereby each optical fiber sensor 3, 3 is bent. The flow resistance is detected by the detectors 4 and 4. Subsequently, the flow resistance calculated by the detectors 4 and 4 is stored in the data logger 5. The data logger 5 can analyze an appropriate flow resistance based on the flow resistance from the detectors 4 and 4. Thereby, the detection accuracy of the flow resistance of the soft layer 10 can be improved by the embodiment shown in FIG.

  Therefore, the experimental results by the detection apparatus 1a according to the first embodiment will be described below. The sample as the soft layer 10 was made into six clay soils having a water content ratio of 200%, 250%, 300%, 400%, 500%, and 1000%. In addition, it has already been confirmed by experiment that it is difficult to specify the strength (flow resistance) of the viscous soil having a water content ratio of 200% or more by the vane shear test method. Then, the tip portion 10 mm of the optical fiber sensor 3 is inserted into each sample 10, and the optical fiber sensor 3 is slid laterally at a constant speed (10 mm / s) to bend the optical fiber sensor 3. . Then, the bending according to the intensity | strength of each sample 10 arises in the optical fiber sensor 3, and the distortion amount generate | occur | produced at that time is measured. FIG. 5 shows the relationship between the slide distance of the optical fiber sensor 3 and the response strain in each sample 10 (moisture content 200%, 250%, 300%, 400%, 500%, 1000% viscous soil). It is.

  Referring to FIG. 5, it can be seen that the response strain amount of the optical fiber sensor 3 is different for each sample 10. That is, as the water content ratio of each sample 10 decreases, the flow resistance increases. Therefore, the optical fiber sensor 3 is bent, and the strain amount of the optical fiber sensor 3 increases accordingly. In FIG. 5, each sample 10 is divided into a section in which the response strain amount at the initial stage of the slide increases in proportion to the slide amount and a section in which the response strain amount is stabilized thereafter. In the section where the response strain amount is increased in proportion to the slide amount at the initial stage of the slide, the section where the acceleration is applied until the optical fiber sensor 3 starts to slide and the speed becomes constant and the optical fiber sensor 3 It is considered that this is a section from when the bending starts until the bending stabilizes. Since the slide speed is slow (10 mm / s) and the slope at which the response strain rises is on the same line in each sample 10, this section is the section until the deflection of the optical fiber sensor 3 is stabilized. Can be considered.

  On the other hand, it can be seen that in the section in which the subsequent response strain amount is stable, the strain amount changes for each sample 10 at a substantially constant value. FIG. 6 shows the relationship between the amount of response strain in the stable section and each sample 10. Referring to FIG. 6, among the samples 10, those having a water content greater than 500% do not show a difference in strain, but in the samples 10 having a water content of 200 to 500%, the difference in strain is clearly shown. Can be determined. And it turns out that the amount of distortion of optical fiber sensor 3 is so large that a moisture content becomes low, and the detection result of this detecting device 1a is appropriate. It should be noted that even if the soil has a moisture content greater than 500%, the sensor can be changed by changing the fixing position of the optical fiber sensor 3 or the insertion length of the optical fiber sensor 3 or changing the material of the optical fiber sensor 3. It is possible to obtain a difference in strain amount by changing the sensitivity of the part.

Moreover, if the relationship between the water content ratio and the viscosity (flow resistance) of each sample 10 is calculated in advance, a graph of the viscosity with respect to the strain amount of the optical fiber sensor 3 as shown in FIG. 7 can be obtained. This graph may be input to the calculation unit 18 of the detector 4 in advance.
As can be seen from the experimental results, even the soft layer 10 can easily detect the flow resistance (strength) by the detection device 1a according to the first embodiment.

  The detection apparatus 1a according to the first embodiment described above includes the optical fiber sensor 3 embedded alone in the soft layer 10 and the flow of the soft layer 10 based on the detection signal from the optical fiber sensor 3. And a detector 4 for detecting resistance. Thereby, since the flow resistance of the soft layer 10 is directly received by the optical fiber sensor 3, the detection accuracy of the flow resistance can be improved. Further, since the optical fiber sensor 3 is installed in the soft layer 10 at the free end without being constrained at the front end side, the installation work of the optical fiber sensor 3 can be facilitated. In addition, by ensuring the degree of freedom of displacement on the tip side of the optical fiber sensor 3, it is possible to improve the bending followability of the optical fiber sensor 3 with respect to the flow of the soft layer 10.

Next, the detection apparatus 1b according to the second embodiment will be described with reference to FIG. When describing the detection apparatus 1b according to the second embodiment, only differences from the detection apparatus 1a according to the first embodiment will be described.
Secondly, in the detection device 1b according to the embodiment, the detector 4 is formed in a rod shape having a substantially circular cross section. The detector 4 has an outer diameter that can be gripped by an operator. The portion of the detector 4 becomes a portion that is gripped by the operator, and the detector 4 is appropriately formed with a length. An optical fiber sensor 3 extends from one axial end of the detector 4. The optical fiber sensor 3 extends for a predetermined length. This length is appropriately set based on the mode of the soft layer 10. A display unit 25 that displays the flow resistance of the soft layer 10 is formed on the outer surface of the detector 4.

  In the detection apparatus 1b according to the second embodiment, an operator holds the portion of the detector 4 and embeds the optical fiber sensor 3 in the soft layer 10 that has entered the container 20 or the like. Slide along the direction perpendicular to the direction. Then, the value of the flow resistance rises from 0 and is displayed on the display unit 25 while maintaining a substantially constant value. The substantially constant value becomes the flow resistance of the soft layer 10 in the container 20.

  In the detection apparatus 1b according to the second embodiment described above, since the size is a handy type, it is easy to carry and the handling is very good. Moreover, the operator can confirm the flow resistance of the soft layer 10 immediately on the spot at the time of detection. Thus, the detection apparatus 1b according to the second embodiment is effective when simply detecting the flow resistance of the soft layer 10.

Next, a detection apparatus 1c according to a third embodiment will be described with reference to FIGS. When describing the detection apparatus 1c according to the third embodiment, only differences from the detection apparatus 1a according to the first embodiment will be described.
The detection device 1c according to the third embodiment is applied to the height management of the tremy tube 30. A support means 33 that supports the sensor fixing portion 8 of the optical fiber sensor 3 is fixed to the lower portion of the tremy tube 30. The support means 33 includes a cylindrical support main body portion 35 fixed around the lower portion of the tremy tube 30 and an annular support plate portion projecting radially outward from the lower end outer peripheral surface of the support main body portion 35. 36. A plurality of optical fiber sensors 3 are arranged at intervals along the circumferential direction on the support plate 36 via the sensor fixing portion 8. Each optical fiber sensor 3 whose base end side is supported by the support means 33 can come into contact with the deposited ground, which is the soft layer 10, whose distal end portion starts to be deposited on the radially outer side at the lower portion of the tremy tube 30. Placed in position. A plurality of detectors 4 are provided so as to correspond to the respective optical fiber sensors 3. Each detector 4 is integrally incorporated in the data logger 5.

  Then, for example, when liquid sediment (or similar sediment) is introduced from the supply pipe 40 into the tremy pipe 30, the liquid sediment flows out from the lower end of the tremy pipe 30, and the liquid Sediment begins to deposit on the outer periphery of the lower part of the tremy tube 30 as a sedimentary ground that is the soft layer 10. Thereafter, when the liquid soil is continuously introduced into the tremy tube 30, the accumulated ground gradually rises and contacts the tip of each optical fiber sensor 3, and the flow resistance of each optical fiber sensor 3 is increased. The tip begins to bend. Thereafter, the flow resistance of the sedimentary ground is detected by each optical fiber sensor 3 and each detector 4 while the tip of each optical fiber sensor 3 is embedded in the rising sedimentary ground, and the detection result is It is continuously transmitted to the data logger 5 and stored as data. At that time, based on the transition of the flow resistance of the sedimentary ground (soft layer 10) stored in the data logger 5, for example, when the flow resistance of the sedimentary ground is maintained for a predetermined time, the tremy tube 30 is connected to each optical fiber sensor. 3, the bottom end of the tremy tube 30 is raised to a predetermined height while maintaining the state where the lower end of the tremmy tube 30 is immersed in the sedimentary ground. This operation is repeated to complete the sediment input. Thus, by adopting the detection apparatus 1c according to the third embodiment, the height management (cylinder tip height management) of the tremy tube 30 can be performed with high accuracy.

  In addition, the detection apparatus 1c which concerns on 3rd Embodiment is not the objective of detecting the intensity | strength (flow resistance) of accumulation ground itself like the detection apparatus 1a which concerns on 1st Embodiment, but the intensity | strength (flow) of accumulation ground. This is for managing the timing of raising the tremy tube 30 by detecting the transition of the resistance. That is, when the liquid sediment is introduced into the trememy tube 30 from the supply pipe 40 and the liquid sediment flows out from the lower end of the tremy tube 30, the detector 4 causes the tip of the optical fiber sensor 3 to be removed. By detecting the degree of bending (change in light characteristics) and grasping the transition of the flow resistance stored in the data logger 5, the timing for raising the tremy tube 30 is managed.

Then, the experimental result by the detection apparatus 1c which concerns on 3rd Embodiment is demonstrated below.
When the optical fiber sensor 3 attached to the tip of the tremy tube 30 is set in a container filled with water, and then a slurry having a high water content is gently put into the tremy tube 30, the slurry accumulates in the container. Go. When the deposited layer in the container rises and comes into contact with the optical fiber sensor 3, the tip of the optical fiber sensor 3 begins to bend, distortion occurs, the wavelength is sequentially detected by the detector 4, and the transition of the wavelength changes. It will be stored in the data logger 5. The transition of the wavelength of the light obtained from the optical fiber sensor 3 at this time is shown in FIG.

  Referring to FIG. 11, first, since slurry is introduced into water at the start of addition, naturally the flow of water itself occurs, but the optical fiber sensor 3 is not bent and does not react with the flow of water. . Thereafter, as the deposited layer in the container rises, the tip of the optical fiber sensor 3 begins to bend and the sensor starts to react. After that, once the slurry injection is stopped, the optical fiber sensor 3 is embedded in the deposition layer and maintained in a bent state. Therefore, the light wavelength accompanying the strain at the tip of the optical fiber sensor 3 is also maintained at a constant value. . Thereafter, when the tremy tube 30 is pulled up, the bending of the tip of the optical fiber sensor 3 is released, and the wavelength of the light is recovered. Thus, it can be seen that the degree of bending of the tip of the optical fiber sensor 3 changes (changes in light characteristics) so as to follow the change in strength (flow resistance) of the deposited layer.

  As can be seen from the experimental results, in the detection device 1c according to the third embodiment, the detector 4 and the data logger 5 are used to determine the degree of bending of the tip of the optical fiber sensor 3 (change in light characteristics). Transition of the strength (flow resistance) of the sedimentary ground can be detected with high accuracy. And based on this detection result, it becomes possible to manage the timing which raises the tremy tube 30.

  In addition, you may construct | assemble the system which raises / lowers the tremy pipe | tube 30 automatically based on the flow resistance of the accumulation ground (soft layer 10) detected by the detection apparatus 1c which concerns on 3rd Embodiment. Specifically, a lifting device that lifts and lowers the tremy tube 30 is provided, and a control device that controls the driving of the lifting device based on a signal from the data logger 5 is provided. Based on the flow resistance transmitted from the detector 4 to the data logger 5, the signal from the data logger 5 is transmitted to the control device, thereby constructing a system for raising the tremy tube 30 to a predetermined height by the lifting device. May be.

  In the detection apparatus 1c according to the third embodiment described above, the flow resistance of the deposited ground, which is the soft layer 10, deposited around the lower part of the tremy tube 30 by each optical fiber sensor 3 and each detector 4 is obtained. It can be detected with high accuracy. As a result, by grasping the transition of the flow resistance of the sedimentary ground stored in the data logger 5, it is possible to accurately grasp the timing for raising the tremy tube 30. As described above, since the height management of the tremy tube 30 can be accurately performed by the detection device 1c according to the third embodiment, the cost associated with the height management of the tremy tube 30 can be suppressed and accurately controlled. The tremy tube 30 can be raised at a proper timing.

  1a, 1b, 1c detector, 3 optical fiber sensor, 4 detector, 10 soft layer, 30 tremy tube

Claims (5)

A detection device for detecting the flow resistance of a soft layer,
An optical fiber sensor embedded alone in the soft layer;
A detector for detecting a flow resistance of the soft layer based on a detection signal from the optical fiber sensor;
A detection apparatus comprising: The detection device according to claim 1,
The optical fiber sensor is a detection device characterized in that a proximal end side is a restraining end and a distal end side is a free end. The detection device according to claim 1,
The detector is formed in a rod shape,
The optical fiber sensor is configured to project integrally along an axial direction from an axial end of the detector. The detection device according to claim 1 or 2,
The optical fiber sensor has a proximal end supported on the lower part of the tremy tube, and the flow resistance of the deposited ground, which is the soft layer deposited on the radially outer side of the tremy tube, is detected by the optical fiber sensor and the detector. A detection device characterized by: A detection method for detecting the flow resistance of a soft layer,
An optical fiber sensor is embedded alone in the soft layer, and the optical fiber sensor is bent while sliding the optical fiber sensor or the soft layer in a direction substantially perpendicular to the axial direction of the optical fiber sensor. Then, the detector detects the flow resistance of the soft layer based on the detection signal from the optical fiber sensor.

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