JP2002350276A - Medium fluctuation detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a medium fluctuation detection method capable of detecting generation of water leakage in an early stage over a wide range without arranging a great number of sensors such as water meters inside a bank surface facing. SOLUTION: This medium fluctuation detection method includes a Lecher wire 4 arranged inside a uniform medium, a pulse generation circuit 1 outputting an electric pulse at a predetermined time interval to the Lecher wire 4, and an oscilloscope 2 connected to the Lecher wire 4 and the connection part of the pulse generation circuit 1. The oscilloscope 2 measures an incident wave incident on the Lecher wire 4 from the pulse generation circuit 1 and a reflection wave generated inside the Lecher wire 4 and measures a time from the incident of the incident wave to the generation of the reflection wave. From the measured time, a fluctuation occurring position inside the uniform medium is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a medium fluctuation in a dam facing which is constructed by laying concrete or asphalt as a water-blocking facing material on the surface of a dam embankment.

[0002]

2. Description of the Related Art Conventionally, in rockfill dams, a construction method of forming a water-impervious layer at the center (central portion) of an embankment body has been used. Tend to be used. This is because the construction cost can be reduced as compared with the method in which the impermeable layer is provided at the center of the embankment. When the impermeable layer is installed on the upstream surface of the embankment, it is necessary to constantly monitor the soundness of the impermeable layer. As a countermeasure, a method of installing many pore pressure gauges inside the embankment was used. .

[0003]

However, in the above-mentioned conventional leak detection method using a pore water pressure gauge inside the embankment,
There is a limit to the number of sensors such as pore water pressure gauges that are actually installed inside the embankment, and there is a drawback in that an enormous number is required to specify the leak location.

[0004] Further, it is conceivable to arrange a number of sensors such as a moisture meter inside the facing of the embankment body. However, cables are connected to these sensors, and passing the cables through the facing is performed on concrete or concrete. It is not preferable from the viewpoint of a decrease in the strength of the facing itself made of asphalt, and there is a disadvantage that it is difficult to dispose a large number of sensors necessary for detecting the position where the leakage of the facing occurs.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a medium fluctuation detection system capable of detecting early occurrence of water leakage over a wide area without disposing a large number of sensors such as a moisture meter inside the embankment surface facing. That is.

[0006]

According to the present invention, there is provided a rechel line laid inside a uniform medium, a pulse generating circuit for outputting an electric pulse to the rechel line at predetermined time intervals, and the rechel line. And a reflected wave measuring circuit connected to a connection portion of the pulse generating circuit, wherein the reflected wave measuring circuit detects an incident wave incident on the rechel line from the pulse generating circuit and a reflected wave generated inside the rechel line. Observe and measure the time taken from the incidence of the incident wave to the occurrence of the reflected wave, and detect the position of the occurrence of the change inside the uniform medium from the measured time to obtain a medium change detection method. Can be

Further, according to the present invention, a rechel line laid inside a dam facing, a pulse generation circuit for outputting an electric pulse to the rechel line at predetermined time intervals, the rechel line and the pulse generation circuit Having a reflected wave measurement circuit connected to a connection portion of the circuit, and the reflected wave measurement circuit observes an incident wave incident on the rechel line from the pulse generation circuit and a reflected wave generated inside the rechel line, A medium fluctuation detection method is obtained, in which a time taken from the incidence of the incident wave to the occurrence of a reflected wave of the opposite polarity is measured, and a location where moisture enters the inside of the facing is detected from the measured time. .

Further, according to the present invention, there is provided a medium fluctuation detection system characterized in that a twist line is used instead of the Lechel line.

[0009]

[Function] Since concrete or asphalt is used as a dam facing material constructed on the surface of the embankment, if a slight crack is generated in concrete or asphalt, water leaks therefrom. In the above-described measurement method, when a crack or the like occurs in the dam facing, the amount of water inside the facing increases, so that a change occurs in the characteristic impedance of the Rechel wire arranged in the region where the change in the amount of water occurs. Therefore, a reflected wave having a different polarity from the incident wave is generated. The speed of the electric pulse propagating inside the Lechel wire decreases at the location where water leakage occurs due to an increase in the dielectric constant due to medium fluctuation, but in the region where no water leakage occurs, there is no change in water content, and the speed is constant. By measuring the installation location and the time interval from the incident wave to the reflected wave, it is also possible to specify the position where the water leakage occurs due to the medium fluctuating along the Rechel line.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a medium fluctuation detection system according to the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a section of a concrete facing at the time of completion. Inside the concrete facing, a Lecher wire 4 is installed near the center of the concrete facing 5 in a direction parallel to the surface. . Pulses having a width of about 10 nS are continuously output from the pulse generation circuit 1 at intervals of about 10 μS, and the reflected waveform is constantly monitored by the oscilloscope 2.

FIG. 2 is a diagram showing a state of an electric field generated around the Lechel line. As shown in FIG. 2, since the electric flux lines 10 are concentrated in the middle portion of the rechel line 4, if a change occurs in the dielectric constant in this region, a reflected wave is generated as a change in the characteristic impedance. Using this physical property, a change in the dielectric constant can be detected.

FIG. 3 is a diagram showing an example in which a reflected wave generation state in pulse measurement according to the present invention is observed using an oscilloscope. In FIG. 3, pulse A indicates an incident wave, pulse B indicates a negative-polarity reflected wave, pulse C indicates a terminal reflected wave, and region L indicates a region where the characteristic impedance is reduced.

Here, when water leakage occurs, the amount of water inside the facing increases in the region near the occurrence of water leakage, so that the characteristic impedance of the Rechel wire disposed in the region where the water amount has changed changes. by the way,
For example, when a part of the line having the characteristic impedance Z0 becomes the characteristic impedance Z1, the reflectance R at that point is represented by R = (Z1−Z0) / (Z1 + Z0).

Therefore, a water leak occurs, and the
When the amount of water around the object increases, the characteristic impedance Z
1 is smaller than the characteristic impedance Z0 (Z1 <Z0)
Therefore, the reflectance R becomes smaller than zero (R <0), and the reflected wave at the point of change in the characteristic impedance is a reflected wave having the opposite polarity (minus polarity) to the incident wave. In FIG. 3, it appears as a negative reflected wave B. Therefore, it can be seen that the region where the characteristic impedance has decreased is L in FIG.

Further, the speed of the electric pulse propagating inside the Lechel wire becomes slower at the location where water leakage occurs due to an increase in the dielectric constant due to medium fluctuation, but the region where no water leakage occurs has a constant speed because there is no change in water content. . Therefore, it is also possible to specify the location of the occurrence of water leakage by measuring the installation location of the Rechel line and the time interval from the incident wave to the reflected wave.

FIG. 4 is a cross-sectional view showing the structure of a Rechel line used in the medium fluctuation detection system according to the present invention. The two metal wires 12 of the Recher wire extend at a predetermined interval, and both of the two metal wires are insulated by an insulating material 13.

Next, another embodiment of the present invention will be described with reference to FIG. FIG. 5 is a view showing another embodiment of the present invention. In the present embodiment, a twisted wire 21 is used instead of the Lecher wire in the above-described embodiment, and the twisted wire 21 is connected to the concrete facing 2.
2 It was installed inside. By using the twisted wire 21, it is possible to prevent the occurrence of unnecessary reflected waves due to local fluctuations in characteristic impedance due to the difference in the relative dielectric constant between the aggregate and the cement inside the concrete facing 22.

[0019]

As is apparent from the above description, according to the present invention, the leakage of water due to the occurrence of water leakage is reduced by the characteristic impedance of the lecher wire by arranging the lecher wire inside the facing as a method for detecting water leakage of concrete dam facing. , And a water leak detection system that detects the change as a reflection of an electric pulse is obtained. Therefore, it is possible to detect the early occurrence of water leakage over a wide area without arranging many sensors such as a moisture meter inside the embankment surface facing. That is, the construction cost can be reduced because the structure is simple without installing many sensors as in the related art.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of a concrete facing structure at the time of completion.

FIG. 2 is a diagram showing a state of electric lines of force generated around a Lechel line in the present invention.

FIG. 3 is a diagram showing a state of generation of a reflected wave of a Lechel line according to the present invention.

FIG. 4 is a diagram showing one embodiment of a cross-sectional structure of a Lechel line used in the present invention.

FIG. 5 is a diagram showing a situation where a twist wire used in the present invention is installed inside a concrete facing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pulse generation circuit 2 Oscilloscope 3 Embankment body 4 Lechel wire 5,22 Concrete facing 10 Electric flux lines 11,12 Metal wire 13 Insulation material 21 Twist wire

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Claims (3)

[Claims] 1. A rechel line laid inside a uniform medium, a pulse generating circuit for outputting an electric pulse at predetermined time intervals to the rechel line, and a connection between the rechel line and the pulse generating circuit. And a reflected wave measuring circuit, the reflected wave measuring circuit observes an incident wave incident on the rechel line from the pulse generation circuit and a reflected wave generated inside the rechel line, and detects the incident wave from the incident wave. A medium fluctuation detection method, comprising: measuring a time required until the reflected wave is generated; and detecting a fluctuation occurrence position inside the uniform medium from the measured time. 2. A rechel line laid inside a dam facing, a pulse generating circuit for outputting an electric pulse to the rechel line at predetermined time intervals, and a connection between the lechel line and the pulse generating circuit. And a reflected wave measuring circuit, wherein the reflected wave measuring circuit observes an incident wave incident on the rechel line from the pulse generation circuit and a reflected wave generated inside the rechel line, and from the incident of the incident wave. A medium fluctuation detection method, comprising: measuring a time required for generation of a reflected wave having a reverse polarity; and detecting a location of water entering the inside of the facing from the measured time. 3. The medium fluctuation detecting method according to claim 1, wherein a twisted wire is used instead of the Lechel line.