JP4024407B2 - Bank breakage monitoring method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bank breakage monitoring method that is effective in preventing the breakage of a river bank.
[0002]
[Prior art]
Various techniques have been studied to detect abnormalities such as levee displacement, collapse, scouring, etc. as early as possible in order to prevent river levee breaching (breakdown), most of which are based on point displacement sensors. However, the monitoring area is limited, and it has not been applied to the dike that does not know where to break.
[0003]
[Problems to be solved by the invention]
The main causes of ruptures known from experience are: (1) When the water level of the river rises and the infiltration line in the levee rises, and water leakage from the vicinity of the slope on the back slope triggers (2) When scouring near the slope of the front slope due to flooding triggers, there are three types of (3) bank breakage due to overflow.
[0004]
Of these, the breach caused by the overflow of (3) is unpredictable and unavoidable, but the breach caused by the causes of (1) and (2) gradually progresses, so it is sure to be sure at an early stage. If it can be detected, it can be repaired before it reaches a complete bank break.
[0005]
Therefore, the present invention is intended to be useful for disaster prevention by accurately detecting the occurrence of abnormalities such as displacement, collapse and scouring of embankments due to water level rise and water leakage.
[0006]
[Means for Solving the Problems]
As a solution to the above problem, the present invention provides the following bank breakage monitoring method. In this method, an optical fiber cable reinforced with a reinforcing material is laid in a zigzag on the slope of the levee with the vicinity of the top edge of the levee and the vicinity of the bottom edge of the laying route, and the apex on the top end side of the optical fiber cable. Is fixed in place with a fiber gripping cleat, and the optical fiber cable at the apex on the slope side and the lower half of the slope is mounted with dispersed weights and directly embedded in the soil. The change in the state of the levee that triggers the breach is detected by observing the change over time with an optical fiber strain measuring instrument.
[0007]
In addition, it is preferable to perform the process for attaching weights to the optical fiber cable, fixing the optical fiber cable at the top end of the levee, and connecting the optical fiber cable halfway.
[0008]
[Action]
The inundation line of the embankment rises due to the increase of rivers, and when the vicinity of the hoshijiri softens, the embankment of the embankment is pushed by water pressure, and the buried weight is displaced. Due to this displacement, a strain change appears in the optical fiber, and the measured value of the strain changes, so that it is possible to know the occurrence and location of the abnormality that causes the bank breakage.
[0009]
In addition, when the river water level rises and the infiltration degree of the surface slope increases, the embankment is pushed by water pressure and the weight changes as described above, so that the location where scouring is likely to occur can be identified. In addition, if the weight is suspended due to scouring or slope failure, the change in strain of the optical fiber increases, so it can also be seen that scouring or slope failure occurred. In addition, as scouring and collapse spread toward the top, the number of weights suspended in the air increases and the strain change region of the optical fiber expands. Since the transparency of water is low during floods, it is not possible to confirm the state of the surface slope that has been submerged in the water by visual observation by a surveillance camera or a patrolman.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 and FIG. 2 show the sensor installation status in the bank breakage monitoring method of the present invention. In the figure, 1 and 2 are monitoring sensors, 11 in FIG. 2 is an optical fiber strain measuring instrument connected to each monitoring sensor, and 12 is a display device for displaying the measurement results. The monitoring sensor 1 is used for monitoring displacement and scouring on the front slope 14 side of the bank 13, and the monitoring sensor 2 is used for monitoring displacement and collapse on the back slope 15 side of the bank 13. Further, the strain measuring instrument 11 and the display device 12 are installed in a remote monitoring center.
[0011]
The bank breakage may be triggered by scouring of the front slope, or it may be triggered by the collapse of the back slope due to water leakage. Monitoring sensors 1 and 2 are installed respectively.
[0012]
As shown in FIG. 2, the monitoring sensors 1 and 2 have an optical fiber cable 3 reinforced with a reinforcing material such as metal or plastic, with the vicinity of the top end 16 and the vicinity of the bottom of the levee 13 at the apex of the laying route. Then, lay in a zigzag, fix the apex on the top end 16 side to the anchor pile 4 driven in that position, and attach a weight 5 to the optical fiber cable 3 placed on the apex on the slope side and the lower half of the slope. Distributed and configured.
[0013]
The top end apex of the optical fiber cable 3 is fixed by attaching the fiber gripping cleat (roller cleat) 6 shown in FIG. 4 to the anchor pile 4 and hanging the optical fiber cable 3 on the pair of rollers 6a and 6a of the cleat. This is performed by a method of clamping the straight cable portion between them with the gripping metal fitting 6b. When the optical fiber cable 3 is fixed to the pile using the anchor pile 4, the distortion measurement accuracy is hardly deteriorated due to the displacement of the apex on the top end side.
[0014]
When the weight 5 is hung from the optical fiber cable 3 with a wire or the like, the load concentrates on one point and there is a risk that the optical fiber will be bent extremely. As shown in FIG. In addition, a through hole 5a is provided in the center of the weight 5, the optical fiber cable 3 is passed through the hole 5a, and the weight is attached by a method of stopping the weight 5 from sliding off with a stopper 7 separately attached to the cable.
[0015]
If it is necessary to connect the optical fiber cable 3 in the installation area, the top end apex is fixed with a double cleat 8 (a combination of two fiber gripping cleats 6) as shown in FIGS. A connecting portion 3a may be provided between the two sets of fiber gripping cleats 6 and 6. If it carries out like this, the connection part 3a can be protected from the load of the weight 5, and it will also become possible to attach the fiber extra length part 3b to a connection part. The connecting portion 3a is housed and protected in the connection box 9 shown in FIG. 5 which also serves as a storage box for the double cleat 8 or in the direct connection type dedicated connection box 10 shown in FIG.
[0016]
If the monitoring sensors 1 and 2 are appropriately displaced and overlapped as shown in FIG. 7 or FIG. 8, the sensor distribution becomes dense and precise monitoring is possible.
[0017]
【The invention's effect】
In the method of the present invention, since the optical fiber with the weight attached is distributed in a plane by zigzag laying and the distortion of each part of the optical fiber is measured, the slope of the levee can be monitored over a wide area, which is a sign of a breach It is possible to accurately detect the occurrence and location of embankment displacement, slope scouring, collapse, etc., and prevent bank breakage. The progress of scouring, which cannot be visually confirmed in muddy flows, can be estimated from strain measurement data, and it is now possible to issue timely warnings for prompt emergency treatment and emergency evacuation of dangerous areas on embankments. It is very useful for disaster prevention.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a monitoring sensor installation situation in the method of the present invention. FIG. 2 is a plan view of the monitoring sensor installation situation. FIG. 3 is a perspective view showing how to attach a weight to a cable. FIG. 5 is a plan view of a double cleat and a junction box used for intermediate connection. FIG. 6 is a plan view showing another example of the double cleat and the junction box. FIG. Figure [Figure 8] Figure showing another example of installation of the monitoring sensor [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 2 Monitoring sensor 3 Optical fiber cable 3a Connection part 3b Extra length part 4 Anchor pile 5 Weight 6 Fiber grip cleat 6a Roller 6b Grasp metal fitting 7 Stopper 8 Double cleat 9, 10 Connection box 11 Optical fiber distortion measuring instrument 12 Display apparatus 13 Embankment 14 Front slope 15 Back slope 16 Top edge

Claims (4)

An optical fiber cable reinforced with a reinforcing material is laid in a zigzag on the slope of the levee, with the vicinity of the top edge of the levee and the vicinity of the bottom edge of the laying route apex, and the apex on the top end side of the optical fiber cable is the fiber gripping cleat. The fiber optic cable at the top of the slope and the lower half of the slope is fixed in place with the weights dispersed and installed directly in the soil. A breach monitoring method that detects changes in the state of a levee that triggers a breach by observing with an optical fiber strain gauge. The breakage according to claim 1, wherein the weight is attached to the optical fiber cable by a method in which a through hole is provided in the center of the weight, the optical fiber cable is passed through the through hole, and the weight is received by a stopper separately attached to the optical fiber cable. Dike monitoring method. The bank breakage monitoring method according to claim 1 or 2, wherein the fixed position fixing of the top end side of the embankment of the optical fiber cable is performed by driving an anchor pile to the cable fixing point and attaching the optical fiber gripping cleat to the anchor pile. Double-cleats some of the fiber grip cleats that fix the vertices top apex of the optical fiber cable, place the fiber optic cable connections between the two sets of cleats, The bank breakage monitoring method according to any one of claims 1 to 3, wherein the bank is provided and the connection portion is protected by the connection box.

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