JP3699708B2 - Water leak occurrence position detection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detecting a leakage occurrence position in a dam facing constructed by laying a surface of a dam body using a water shielding structure such as concrete or asphalt as a water shielding facing material. The present invention is particularly suitable for detecting a leakage occurrence position on a concrete impermeable wall formed on the surface of a rockfill dam.
[0002]
[Prior art]
Conventionally, the construction method of forming a water-impervious layer in the center of the dam body in the rock fill dam has been used, but in recent years, a method of constructing the water-impervious layer as a dam facing on the upstream surface of the dam body has been used. Tend to be used. The reason is that the construction cost can be reduced by the method of constructing the water shielding layer on the upstream surface of the levee body as compared with the method of constructing the water shielding layer at the center of the dam body.
[0003]
Concrete or asphalt is used as the material of the water barrier layer to be constructed on the surface of the levee body, but even if a slight crack occurs in the water barrier layer, water leaks from it, and in the worst case the dam body itself Is expected to be damaged. Therefore, when constructing the impermeable layer on the surface of the levee body, it is necessary to always monitor the soundness of the impermeable layer. In the unlikely event that water leakage is detected in the impermeable layer, it is necessary to lower the stored water level and repair the impermeable layer.
[0004]
As this monitoring technology, a method has been proposed in which a twisted wire with a water-permeable coating is embedded in a water shielding layer, an electric pulse is incident on this twisted wire, and the reflected wave is observed to detect the location of water leakage. (For example, Patent Document 1).
[0005]
Briefly, in this water leak occurrence position detection method, if there is an infiltrated part due to water leak at any part of the water-permeable coating of the twisted wire, a reflected wave is generated when an electric pulse is incident. Therefore, it is possible to detect the water leakage occurrence position by measuring the time relationship between the incident wave and the reflected wave.
[0006]
[Patent Document 1]
Japanese Patent Application No. 2002-244525 (4th page, 5th page, FIG. 4)
[0007]
[Problems to be solved by the invention]
However, the water leak occurrence position detection method proposed above has a problem that the water submerged from the water leak occurrence position diffuses over a wide area in the water-permeable coating with time, and the detection accuracy of the water leak occurrence position is lowered.
[0008]
Therefore, the problem of the present invention is that the leak occurrence position can improve the detection accuracy of the leak occurrence position by suppressing the diffusion of moisture infiltrating the water-permeable coating in the multi-core electric wire of the leak occurrence position detection method described above. It is to provide a detection method.
[0009]
[Means for Solving the Problems]
According to the present invention, at least one set of multi-core electric wires having a water-permeable coating embedded in a water-impervious structure, a pulse generation circuit that outputs electric pulses to the multi-core electric wires, and the multi-core electric wires A reflected wave measuring circuit that receives the reflected wave of the electric pulse from the pulse, and the reflected wave measuring circuit measures an incident wave incident on the multicore electric wire from the pulse generating circuit and a reflected wave generated inside the multicore electric wire And a water leakage occurrence position detection method for detecting a water leakage occurrence position inside the water shielding structure by measuring a time until the generation of a reflected wave with respect to an incident wave, wherein the multi-core electric wire is provided with the water permeable coating. A water leak occurrence position detecting system is provided, wherein the multicore electric wires are separated at each interval by a water shielding coating provided at intervals in the length direction of the multi-core electric wire.
[0010]
In the present water leakage occurrence position detection method, a twisted wire or a Lehel wire is used as the multicore electric wire.
[0011]
In the water leakage occurrence position detection method, the multi-core electric wire has a line extending between the top end and the bottom of the water shielding structure parallel to each other with a predetermined distance in the width direction of the water shielding structure. The switch is connected to the transmission path of the incident wave and the reflected wave that is embedded so as to draw a substantially quadrangular shape and connected to the multicore electric wire, and the switch has two end portions of the multicore electric wire. On the other hand, it is desirable to detect the position of occurrence of water leakage from the two ends of the multi-core electric wire by alternately performing switching connection for connecting either one to the pulse generation circuit and the reflected wave measurement circuit.
[0012]
[Action]
In the water leak occurrence position detection method described above, when a crack or the like occurs in the impermeable structure, water enters the water-permeable coating of the multicore electric wire, so that the characteristic impedance of the multicore electric wire changes at that position. Therefore, a reflected wave having a polarity different from that of the incident wave is generated. Thereby, it becomes possible to identify the water leak generation position along the multicore electric wire by observing the incident wave and the reflected wave and measuring the time interval between them.
[0013]
In particular, it is possible to improve the detection accuracy of the water leakage occurrence position by suppressing the diffusion of moisture infiltrating into the water-permeable coating as a water-permeable coating at intervals with the water-permeable coating in the multicore electric wire.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
With reference to FIGS. 1-5, the principle of the water leak generation | occurrence | production position detection system based on the said proposal is demonstrated. FIG. 1 is a diagram showing a cross section of a dam dam body and a concrete impermeable layer in a concrete surface impermeable rockfill dam. A water shielding layer 20 is constructed on the upstream surface of the dam body 10. At that time, a twisted wire 30 made of a metal wire is embedded in the water shielding layer 20 in a direction parallel to the surface, that is, from the top to the bottom. A plurality of twist lines 30 are installed in parallel with each other at intervals in the width direction of the dam body 10. The installation interval is about several meters to several tens of meters. A pulse generation circuit 31 and an oscilloscope 32 as reflected wave measuring means are connected to the plurality of twist lines 30 on the top end side of the dam dam body 10, respectively. One set of pulse generation circuit 31 and oscilloscope 32 may be connected. The oscilloscope 32 is preferably connected to a storage device for storing the observed waveform.
[0015]
When detecting the water leakage occurrence position, pulses having a width of about 10 nsec are continuously output from the pulse generation circuit 31 to the twist line 30 at intervals of about 10 μsec, and the reflected waveform from the twist line 30 is observed by the oscilloscope 32.
[0016]
FIG. 2 is a diagram illustrating a state of an electric field generated around the twisted wire 30, and electric lines of force are concentrated between two metal wires (core wires) in the twisted wire 30. Therefore, if the dielectric constant fluctuates due to moisture or the like in this region, the characteristic impedance changes, and when a pulse is incident from one end of the twisted wire 30, a reflected wave is generated therefrom, so that water intrusion is detected. It becomes possible.
[0017]
FIG. 3 is a cross-sectional view showing the structure of the twisted wire 30 used in the present invention. The two metal wires 30-1 of the twisted wire 30 are insulated with an insulator 30-2 and are continuous at a predetermined interval, and the characteristic impedance is uniform. Furthermore, in order to make the twist wire 30 into a cable, an outer periphery coating is applied, and a water-permeable coating 30-3 made of a water-permeable tape is wound around the outer periphery coating.
[0018]
A material such as polyester tape or cotton tape is suitable for the material of the water-permeable coating 30-3. On the other hand, as the material of the insulator 30-2, paper tape or the like can be used in addition to polyethylene.
[0019]
FIG. 3 shows a cross-sectional structure of the twist line 30. The twist line 30 used in the embodiment of the present invention described below is improved in the length direction. This will be described later.
[0020]
FIG. 4 is a diagram showing an example in which a reflected wave generation state due to pulse incidence is observed using an oscilloscope 32 in the water leak occurrence position detection method having the configuration of FIG. Further, FIG. 5 shows an enlarged view of a situation where a part of the water shielding layer 20 is cracked and the area where the twisted wire 30 is buried is submerged. When a part of the line of the characteristic impedance Z0 in the twist line 30 is changed to the characteristic impedance Z1 due to water immersion, the reflectance R at that point is expressed by the following equation.
[0021]
R = (Z1-Z0) / (Z1 + Z0)
In the above equation, when water penetrates into the water-permeable coating 30-3 around the twisted wire 30, Z1 <Z0, so the reflectance R is R <0, and the characteristic impedance changes at the point of change. The reflected wave has the opposite polarity to the incident wave. The reflectivity R is R> 0 where the water permeability of the water-permeable coating 30-3 changes from the region soaked with water, so that the reflected wave has the same polarity as the incident wave. In addition, a reflected wave having the same polarity as the incident wave is also generated at the end (open end) of the twisted wire 30. Thereby, the reflected wave at the characteristic impedance change point and the reflected wave at the terminal can be easily identified.
[0022]
Assuming that the propagation speed of the electric pulse propagating through the twist line 30 is approximately 200,000 km / s, for example, if the time from the rising of the incident wave to the rising of the reflected wave is 1 μs, the oscilloscope 32 located at the same location as the pulse generating circuit 31 The distance to the leakage occurrence position is 100 m (20 × 10 ⁷ × 10 ⁻⁶ / 2 = 100). Accordingly, the position of occurrence of water leakage is determined by considering (subtracting) the distance from the oscilloscope 32 to the top of the dam dam body, that is, the end of the twist line 30 from the distance calculated by measuring the time between the incident wave and the reflected wave. Can be specified. As described above, when the oscilloscope 32 is shared by one and the distance from the oscilloscope 32 to the end of each twist line is different for each of the plurality of twist lines, the twist line is considered. A power value should be prepared in advance.
[0023]
FIG. 6 is a diagram for explaining an embodiment of a water leak occurrence position detection method according to the present invention. FIG. 6 is a view of the water shielding layer 20 as seen from the upstream side of the dam, and shows one twisted wire. In FIG. 6, twist wires 30 having a water-permeable coating as described above are embedded in the interior of the water shielding layer 20 made of concrete at intervals of several m to several tens m in a direction parallel to the surface. . That is, one twist line 30 is embedded so as to have a substantially rectangular shape, and the interval between parallel lines facing each other in the width direction of the dam dam body is set to several m to several tens m. Although not shown, according to the length of the dam dam body in the width direction, in the drawing of the twist line 30, twist lines having the same shape are embedded at the same interval on both the left and right sides. Needless to say.
[0024]
The switch 33 shown in FIG. 6 is different from the switch for switching the plurality of twist lines 30 described above, but the function of the switch described above and the switch 33 shown in FIG. The function of the selected switch may be realized by one switch. The function of the switch 33 will be described later.
[0025]
Both ends of the twisted wire 30 are connected to a switch 33 installed on the top end side of the dam dam body. Further, a pulse generation circuit 31 and an oscilloscope 32 are connected to the twist line 30 via a switch 33 on the top end side of the dam dam body. The switch 33 alternately performs an operation of connecting the pulse generation circuit 31 and the oscilloscope 32 to one of the two ends of the twist line 30 by a control signal output from the computer 34. In this case, the terminal portion of the twisted wire 30 that is not connected may be in an open state or a short-circuited state. This is due to the following reason. That is, when the terminal portion is open, the reflected wave from the terminal portion has the same polarity as the incident wave as described above, and it is easy to distinguish the reflected wave from the leakage occurrence position. On the other hand, when the terminal is short-circuited, the reflected wave from there is opposite in polarity to the incident wave, that is, the same polarity as the reflected wave from the position where the water leak occurred, but the distance to the terminal is known in advance so It is not difficult to distinguish the reflected wave from the generation position.
[0026]
The pulse wave incident on the twist line 30 from the pulse generation circuit 31 is reflected at the water leakage generation position on the twist line 30 or the end not connected to the pulse generation circuit 31, and the reflected wave is observed by the oscilloscope 32. . This observation data is recorded in an attached storage device via the computer 34. In particular, the computer 34 controls the switch 33 according to a predetermined procedure so that pulse waves are alternately incident from both ends of the twisted wire 30 and records each reflected wave in the storage device. For example, a pulse wave is first incident from the left end portion of the twist line 30 shown in FIG. 6 and the reflected wave is recorded in the storage device, and then the right end portion of the twist line 30 shown in FIG. The reflected wave is recorded in the storage device.
[0027]
As a result, if there is a water leak occurrence location, first, the measurement and detection of the water leak occurrence position are performed by the counterclockwise path in FIG. 6 on the twist line 30, and then the water leak occurrence position is measured by the clockwise path. Detection is performed. As described above, the measurement accuracy can be improved by measuring and detecting the leakage occurrence position from both ends of the twisted wire 30 at least once.
[0028]
In addition, due to water leakage at a large number of positions, a plurality of portions of the twisted wire 30 may infiltrate and the attenuation of the reflected wave becomes remarkable, and it may be difficult to detect the reflected wave. In such a case, a decrease in detection capability due to attenuation of the reflected wave can be minimized by measuring from the end side of the twist line closer to the water leakage position. The end portion of the twist line that is closer to the water leakage position can be known as the end portion side having a shorter interval between the pulse incident wave and the reflected wave.
[0029]
FIG. 7 shows an example of an improved twist line used in the embodiment of the present invention. In this example, the twisted wire 30 is provided with a water-impervious coating 30-5 having a length of about 3 cm instead of the water-permeable coating 30-3 at intervals of 1 m to limit the range in which moisture diffuses in the twisted wire 30. Yes. The water-impervious coating 30-5 is realized by providing a resin such as an acrylic resin or pitch by a method such as molding, but the same effect can be obtained with other materials having a water-stopping effect such as silicone.
[0030]
In FIG. 7, the thickness of the water-permeable coating 30-5 is the same as the thickness of the water-permeable coating 30-3, but the thickness of the water-permeable coating 30-5 and the water-permeable coating 30-3 are different. The same effect can be obtained. Moreover, even if the installation interval and length of the water-impervious coating 30-5 are different from this example, the same effect can be obtained.
[0031]
FIG. 8 shows a reflected wave measured when water is poured assuming a simulated crack at a point 40 m from the measuring instrument side using a twisted wire having no water-shielding coating as described above. In FIG. 8, six types of reflected waves indicate waveforms before water injection, after 2 minutes, after 4 minutes, after 8 minutes, and after 28 minutes, respectively, from the top. It was confirmed that the reflected wave was generated around the water injection position by water injection from the simulated crack. However, since water infiltrates into the water-permeable coating, the water injection detection section expands with time, so that it is difficult to specify the water injection position.
[0032]
On the other hand, FIG. 9 shows a reflected wave measured when water is poured by assuming a simulated crack at a point 40 m from the measuring instrument side using the twisted wire 30 having the water-impervious coating 30-5 according to the present invention. In FIG. 9, 10 kinds of reflected waves are in order from the top immediately before water injection, 1 minute, 15 minutes, 31 minutes, 45 minutes, 61 minutes, 75 minutes, 91 minutes, and 105 minutes after water injection. The waveforms after 12 minutes are shown. Although a reflected wave is generated at the water injection point (40-41m) immediately after water injection, the amplitude and width of the reflected wave at the water injection point are constant for 2 hours from the start of water injection to the time when water is discharged from the pipe after the end of the experiment. Met. Thereby, the effect of the water-impervious coating 30-5 according to the present invention was confirmed.
[0033]
As described above, the embodiment of the present invention has been described with respect to the case where a twisted wire having two core wires is used as a multi-core electric wire. However, the present invention may use a Reher wire, that is, a parallel two wire instead of the twisted wire. In addition, a multi-core electric wire having three or more core wires may be used. Speaking of the Lecher line, it is well known, and its periphery is covered with a water-permeable coating similar to that described with reference to FIG. 3, and a predetermined length of shielding is provided instead of the water-permeable coating at predetermined intervals. By providing the aqueous coating, it is possible to limit the range in which moisture diffuses in the Reher line.
[0034]
Also in this example, the water that has penetrated into the water-impervious layer 20 soaks into the water-permeable coating, and from the local change in characteristic impedance due to the difference in relative permittivity between air and water, the same principle as described in FIG. It is possible to measure and detect the water leak position.
[0035]
Instead of the oscilloscope 32, other reflected wave measuring means having the same function may be used.
[0036]
Furthermore, the scope of application of the present invention is not limited to the above-described water-impervious layer constructed on the dam body, but can be applied to general water-impervious structures provided in rivers, lakes, and the sea.
[0037]
【The invention's effect】
As is clear from the above description, the water leakage occurrence position detection method according to the present invention is a multi-core electric wire having a water-permeable coating inside a water-impervious structure constructed upstream such as a dam dam body, particularly a twisted wire or a reher This is a method to detect the change as a reflected wave of an electric pulse by detecting the change as the characteristic impedance of the twisted wire or the Rehel wire by installing the wire and infiltrating the water permeable coating with the water that has penetrated due to the occurrence of water leakage. Since the number of water leaks can be quickly and widely grasped by the number, the effect obtained is great.
[0038]
In particular, the detection accuracy of the water leakage occurrence position can be improved by suppressing the diffusion of moisture infiltrating into the water-permeable coating instead of the water-impermeable coating at a certain interval.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the principle of a water leak occurrence position detection method according to the present invention, and is a diagram showing a cross section of a dam dam body and a water shielding layer structure.
FIG. 2 is a diagram for explaining a state of an electric field generated around a twist line used in the present invention.
FIG. 3 is a view showing a cross-sectional structure of a twisted wire having a water-permeable coating used in the present invention.
FIG. 4 is a diagram for explaining a generation state of a pulse incident wave and its reflected wave in a twist line used in the present invention.
FIG. 5 is a diagram for explaining a state of water intrusion to the twisted wire when a crack occurs in the water shielding layer constructed on the dam dam body in FIG. 1;
FIG. 6 is a diagram for explaining an embodiment of a water leak occurrence position detection method according to the present invention.
FIG. 7 is a diagram showing an example of an improved twist line used in the embodiment of the present invention.
8 is a diagram showing an example of a reflected wave obtained when a water injection test is performed using a twist line not having a water-impervious coating shown in FIG.
9 is a diagram showing an example of a reflected wave obtained when a water injection test is performed using the twisted wire according to the present invention having the water-impervious coating shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Dam dam body 20 Water shielding layer 30 Twist wire 30-1 Metal wire 30-2 Insulator 30-3 Water-permeable coating 30-5 Water-permeable coating

Claims (3)

At least one set of multi-core electric wires having a water-permeable coating embedded in a water-impervious structure, a pulse generation circuit for outputting electric pulses to the multi-core electric wires, and the electric pulses from the multi-core electric wires. A reflected wave measuring circuit that receives the reflected wave, the incident wave incident on the multi-core electric wire from the pulse generation circuit and the reflected wave generated inside the multi-core electric wire are measured by the reflected wave measuring circuit, and the reflected to the incident wave is measured A water leakage occurrence position detection method for detecting a water leakage occurrence position inside the water shielding structure by measuring the time until the occurrence of waves,
The water leakage occurrence position detection method according to claim 1, wherein the multi-core electric wires are separated at each interval by a water-impervious coating provided at intervals in the length direction of the multi-core electric wires. In the water leak occurrence position detection system according to claim 1,
The water leak occurrence position detecting method, wherein the multi-core electric wire is a twisted wire or a Lecher wire. 3. The water leakage occurrence position detection method according to claim 1, wherein the multicore electric wire has a line extending between a top end portion and a bottom portion of the water shielding structure separated by a predetermined distance with respect to a width direction of the water shielding structure. Embedded in a substantially square shape that exists in parallel,
A switch is connected to the transmission path of the incident wave and the reflected wave connected to the multicore electric wire,
The switching unit alternately performs switching connection for connecting one of the two ends of the multi-core electric wire to the pulse generation circuit and the reflected wave measurement circuit, thereby A leak detection position detection method characterized by detecting the leak occurrence position from the end.

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