JPH07294233A - Preventive monitoring method of damage on buried pipe - Google Patents

Abstract

PURPOSE:To prevent a buried pipe from being damaged by the cutter of a drilling machine. CONSTITUTION:A band body 13 is arranged with wires 14 at an appropriate interval such that the wires 14 are conducted in the longitudinal direction of the band body 13 to constitute a long monitoring body 12 which is then buried in the vicinity of an object to be monitored, i.e., a buried pipe 11. A resonance characteristics measuring apparatus 16 for the wire 14 is disposed on one end side of the long monitoring body 12 and an AC monitoring signal is inputted while sweeping the wire 14 from one end side thereof thus measuring the resonance frequency of the wire 14 and monitoring the cut-off of the wire 14 due to damage of the long monitoring body 12 based on a resonance frequency. Since a damage alarm signal of the buried pipe 11 can be delivered at a moment when the cutter of a drilling machine approaches the buried pipe 11, the buried pipe 11 can be protected against damage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for monitoring damage prevention of a buried pipe.

[0002]

2. Description of the Related Art In excavation work, a buried pipe may be damaged by an excavating machine, and various methods have been proposed for monitoring this. As one of the conventional systems for monitoring such damage to the buried pipe, an AC signal for monitoring is injected from the transmitter to the buried pipe to be monitored and received by a receiver installed at a remote position. Then, there is a monitoring method for detecting the occurrence of damage to the buried pipe from the decrease in the received voltage.

This monitoring system is shown in a conceptual explanatory view as shown in FIG. 9, for example. Reference numeral 1 is a transmitter, and in this transmitter 1, a monitoring AC signal is incident on the buried pipe 2.
The monitoring AC signal is, for example, 525 from the range of 500 to 2500 Hz.
A suitable frequency such as Hz or 2025 Hz is selected, and the voltage is appropriately set in the range of, for example, 1.0 to 4.0 V according to the installation environment of the buried pipe and incident.

Reference numeral 3 is a receiver installed at a position appropriately separated from the transmitter 1, for example, at a position of the buried pipe 2 separated by 2 to 3 km, and the monitoring AC signal transmitted from the transmitter 1 is supplied to the receiver 3. It is received at and is monitored by the fluctuation of the received voltage (effective value).

That is, in the excavation work currently being carried out between the transmitter 1 and the receiver 3, if the conductive excavating blade 5 of the excavating machine 4 damages the insulating coating of the buried pipe 2, the damaged portion will be damaged. Is grounded through the excavating blade 5, the impedance of this portion is lowered and the monitoring AC signal leaks into the ground. For this reason, the reception voltage of the monitoring AC signal in the receiver 3 decreases, and thus the damage to the buried pipe 2 can be detected by monitoring the decrease in the reception voltage.

[0006]

Since such a monitoring method detects that the buried pipe has been damaged, it cannot be prevented in advance. Further, it may be difficult to reliably detect damage due to noise caused by the operation of the drainage device 6 and the like. Therefore, an object of the present invention is to reliably prevent damage to the buried pipe by generating a predetermined signal when the excavating blade of the excavating machine approaches the buried pipe.

[0007]

In order to solve the above-mentioned problems, in the present invention, electric wires are first arranged at appropriate intervals in a band, and the electric wires can be energized in the length direction of the band for monitoring. A long body is formed, and the long body for monitoring is buried near the buried pipe to be monitored, for example, at least on the upper side or at least the lateral side, and the resonance characteristic measuring device for the electric wire is provided on one end side of the long body for monitoring. Installed, and measuring the resonance characteristics of the electric wire by injecting a monitoring AC signal while sweeping the frequency from the one end side, and monitoring the cutting of the electric wire due to the damage of the long monitoring object by the resonance frequency. We propose a damage prevention monitoring method for buried pipes.

According to the present invention, in the above-mentioned structure, the electric wire has a structure in which a plurality of channels can be energized in the lengthwise direction of the strip, and an AC signal for monitoring is incident on the electric wire between the electric wire of each channel and the ground to cause a resonance frequency. Or the electric wire has a structure in which a plurality of channels can be energized in the lengthwise direction of the strip, and at least one electric wire of any channel is used as a common line, and the common line and other channels We propose to monitor the resonant frequency by injecting a monitoring AC signal between the wires.

Further, in the present invention, in the structure in which the electric wire has a plurality of channels, the transmission / reception device is configured for each channel, or the transmission / reception device is configured to be common to each channel, and the transmission / reception device is switched at each time as appropriate. It is proposed to sequentially monitor the resonance frequency by injecting the monitoring AC signal into the wire.

In the present invention, in the above constitution,
It is proposed that the end of the wire on the other end of the strip be configured as an open termination, a short termination or a non-reflective termination.

[0011]

In the excavation work, the elongated monitoring body is located at a position where the excavating blade of the excavating machine is likely to advance toward the buried pipe, that is, at least above the buried pipe in the normal case, and the buried pipe. If a protective plate or the like is embedded on the upper side of the and you want to prevent damage from the side, it should be embedded at least on the side in advance. Therefore, in the excavation work, when the digging blade advances toward the buried pipe, the elongated monitoring body is always damaged before the buried pipe is damaged by the digging blade.

Therefore, in the present invention, the resonance characteristic measuring device for the electric wire is installed on one end side of the monitoring long body, and the resonance characteristic is measured by injecting a monitoring AC signal while sweeping the frequency from the one end side to the electric wire. To do.

The electric wire arranged in the lengthwise direction on the monitoring strip acts as a distributed constant circuit for the monitoring AC signal, and in the case where the so-called receiving end is open, it is totally reflected here to generate a standing wave. Then, a resonance phenomenon occurs with respect to the monitoring AC signal having a wavelength corresponding to the line length. That is, a series resonance phenomenon occurs when the line length is an odd multiple of 1/4 of the wavelength λ of the monitoring AC signal.

As described above, the resonance frequency corresponds to the line length from one end side to the open end. Therefore, by measuring the resonance frequency, it is possible to monitor the disconnection of the electric wire due to the damage of the monitoring elongated body. You can That is, when the monitoring long body is damaged and the electric wire is cut, the electric wire length for the monitoring AC signal incident from one end side is shortened to the length from the one end side to the cutting point. By the characteristic measuring device,
The resonance frequency corresponding to this length is measured, whereby it is possible to detect the disconnection of the electric wire, that is, the damage of the monitoring elongated body, calculate the electric wire length up to the cutting point, and specify the position.

Since most of the damage to the buried pipe by the excavating machine is from above, the elongated monitoring body is usually installed corresponding to at least the upper side of the buried pipe to be monitored, so that many damages are caused. Although it can be prevented, it is possible to prevent damage in most cases by installing it even if it corresponds to the side of the buried pipe. In addition, as mentioned above, when a protective plate etc. is buried above the buried pipe and it is desired to prevent damage from the lateral side, it is possible to prevent damage by installing it only on the lateral side. it can.

[0016]

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 is an explanatory view conceptually showing a damage monitoring system for a buried pipe to which the method of the present invention is applied, and FIG. 2 is a schematic view of FIG. 1 and FIG.
FIG. 4 is a resonance characteristic diagram conceptually showing an operation example of the present invention. Reference numeral 11 is a buried pipe to be monitored, reference numeral 12 is a monitoring elongated body, and the monitoring elongated body 12 has a large number of electric wires 14 disposed inside the strip 13 at appropriate intervals. The electric wires 14 are configured so that they can be energized in the lengthwise direction of the strip-shaped body 13. And this monitoring long body 12 is the buried pipe 11
Is buried above a predetermined monitoring section of the buried pipe 11 so as to form a side wall portion 15 corresponding to the lateral direction. The symbol a indicates one end side of the monitoring elongated body 12, and this one end side a
The resonance characteristic measuring device 16 is installed on the ground corresponding to. The resonance characteristic measuring device 16 inputs the monitoring AC signal while sweeping the frequency between the respective electric wires 14 and the ground 17, and measures the amplitude level of the reflected wave to resonate the electric wires which are regarded as a distributed constant circuit. It is configured to measure the characteristics. As the resonance characteristic measuring device 16, for example, a network analyzer or the like can be used.

In the above structure, the end of the electric wire on the other end side b of the monitoring elongated body 12 is an open end, and the resonance characteristic measuring device 16 sweeps the frequency from the one end side a of the electric wire 14 to monitor the AC signal. And the amplitude level of the reflected wave is measured for each frequency. As described above, the monitoring elongated body 1
The electric wire 14 arranged in the length direction of 2 acts as a distributed constant circuit because it has a length that cannot be ignored with respect to the wavelength of the monitoring AC signal, and therefore the incident wave of the monitoring AC signal has the other end b
, A standing wave is generated and a resonance phenomenon occurs with respect to the monitoring AC signal having a wavelength corresponding to the wire length L from the one end side a to the other end side b. That is, as described above, the electric wire 1
When the other end side b of 4 is an open termination, a series resonance phenomenon occurs when the line length is an odd multiple of 1/4 of the wavelength λ of the monitoring AC signal, and this resonance phenomenon is caused by the amplitude level of the reflected wave. Can be measured by sweeping every frequency.

The solid line in FIG. 3 shows the resonance phenomenon appearing in the amplitude level of the reflected wave, omitting the higher harmonic side.
A series resonance occurs at a frequency f ₀ corresponding to, and the amplitude level of the reflected wave at this portion sharply decreases. As described above, when the end of the electric wire 14 on the other end side b is an open termination, series resonance occurs when the line length is an odd multiple of 1/4 of the wavelength λ of the monitoring AC signal. The condition is λ = 4L when only the fundamental wave is shown, and f ₀ = v / λ = v / 4L when this is represented by the frequency f ₀ . Note that v is the propagation speed of the monitoring AC signal in the electric wire.

In such a state, in the excavation work by the excavating machine 18, the excavating blade 19 advances toward the embedded pipe 11, and before the excavating blade 19 reaches the embedded pipe 11, reaches the monitoring elongated body 12 and forms a strip. When the body 13 is damaged, and any part of the electric wire 14 arranged at an appropriate interval is damaged and cut, the electric wire length for the monitoring AC signal incident from the one end side a becomes one end. Cutting point 2 from side a
Since the length l is shortened to 0, the resonance frequency is shifted to the high frequency f ₁ side as shown by the broken line in FIG. Therefore,
By monitoring the deviation of the resonance frequency, the electric wire 14
Can be detected, and thus damage to the monitoring elongated body 12, can also be detected, and on the basis of the offset resonant frequency f ₁ the equation l = v /
The wire length l from 4f ₁ to the cut point can be calculated. Then, from the calculated wire length l, the damaged portion of the monitoring elongated body can be specified.

The other end b of the elongated monitoring body 12 may be an open termination as described above, or may be a short-circuit termination or a non-reflection termination in some cases. In the former case, the resonance when the electric wire 14 is not cut results in a series resonance phenomenon when the line length is an even multiple of 1/4 of the wavelength λ of the monitoring AC signal. Due to the difference between the resonance frequency and the above-described resonance frequency due to cutting, damage to the monitoring elongated body 12 is monitored. In the latter case, since the resonance phenomenon occurs only after the electric wire 14 is cut, it is possible to detect the disconnection of the electric wire at the time when the resonance characteristic appears. The wire length l can be calculated.

FIG. 4 shows a concrete example of the monitoring elongated body 12 as shown in FIG.
2, a large number of electric wires 14 are arranged in parallel over the entire surface of the band-shaped body 13, and the electric wires 14 are concentrically buried around the buried pipe 11 at appropriate intervals. Therefore, in such an embedding method, since the side wall portion 15 is formed together with the upper corresponding portion of the embedding pipe 11, the embedding pipe 11 is formed by the above-described operation not only in the upward direction but also in the laterally advancing drilling blade. The damage to 11 can be prevented. Note that the elongated monitoring body 12 of this embodiment may be embeded by deforming a planar object in an arc shape at the time of embedding, or may be formed in an arc shape with rigidity in advance.

The elongated monitoring body 12 shown in FIG. 5 is formed by forming a strip-shaped body 13 in the shape of a rectangular tube having a notched lower surface and having rigidity, and arranging electric wires 14 in parallel over the entire surface. is doing. The buried pipe 11 is embedded so as to cover the upper side and the lateral side of the buried pipe 11.

4 and 5, the electric wire 14 is provided on the entire surface of the band-shaped body 13, but in addition to this, the electric wire 1 is provided at least at a position corresponding to the upper side (or the lateral side) of the buried pipe 11.
It is also possible to dispose the electric wires on the side wall portion 15 (or the upper side) in the structure in which the four wires are arranged, or to widen the arrangement interval. As a method of burying the buried pipe 11, the buried pipe 11 may be buried in a curved shape or a trough shape as described above, or may be buried in a flat shape on the upper side (or the lateral side) of the buried pipe 11 or the like.

Next, FIG. 6 is a system diagram showing a specific example of the monitoring elongated body 12 and the resonance characteristic measuring device 16. The monitoring elongated body 12 has an entire surface of the belt-shaped body 13 as in the above-mentioned configuration. A plurality of electric wires 14 are arranged in parallel, and each electric wire 14 constitutes an independent channel. Then, the electric wires 21 connected to the respective resonance characteristic measuring devices 16 are connected to the ends of the electric wires 14 on the one end a side of the monitoring elongated body 12. Although the electric wire 21 is drawn as a thick single wire in the drawing, it is a collective electric wire such as a multi-core wire, which is a collection of individual electric wires. On the other hand, the end portion of each electric wire 14 on the other end b side of the elongated monitoring body 12 is an open end, and the resonance characteristic measuring device 16 is provided for each electric wire 14 and independently connected to the electric wires 14 in a plurality of channels. The monitoring AC signal is incident and the reflected wave is received.

The resonance characteristic measuring apparatus 16 shown in FIG. 6 includes a sweeping oscillator 22, a receiver 23, a directional coupler 24, an incident wave signal from the sweeping oscillator 22, and a receiver 23 for monitoring AC signals. And a level measuring device 25 for measuring the amplitude level of the reflected wave from the reflected wave signal. The output signal of the level measuring device 25 is input to a common monitoring device 26 to monitor the resonance frequency described above. There is.

FIG. 7 conceptually shows another example of the method of inputting and receiving the monitoring AC signal in the structure of the monitoring elongated body 12 similar to that of FIG. 6 together with the above-mentioned example. That is, in the method drawn by the solid line, one of the electric wires 14 of the plurality of channels is configured as the common line 14c, and the resonance characteristic measuring device 16 is provided between the common line 14c and the electric wires 14 of the other channels. The connection is made so that a monitoring AC signal is incident between them and a reflected wave is received. Further, in the method shown by the two-dot chain line, as described above, the resonance characteristic measuring device 16 is provided corresponding to all the electric wires 14 of the plurality of channels, and a monitoring AC signal is injected between each electric wire 14 and the ground 17. , A configuration for receiving a reflected wave.

FIG. 8 shows still another example of the method of inputting and receiving the monitoring AC signal in the structure of the elongated monitoring body 12 similar to that of FIG. 6, and in this structure, the resonance characteristic measuring device 16 is The configuration is common to the electric wires 14 of a plurality of channels. That is, the resonance characteristic measuring device 16 has the same structure as that shown in FIG. 6, and the changeover switch circuit 28 is interposed between the common electric wire 27 connected to the directional coupler 24 and each electric wire 14. . In this configuration, the monitoring device 26 controls each element of the resonance characteristic measuring device 16 by the control circuit 29 to monitor the resonance frequency of a certain electric wire 14 by the above-described operation, and then the changeover switch circuit 28.
The resonance frequency of the electric wires 14 of all the channels is monitored by sequentially and continuously performing the operation of switching the electric wires to be connected and monitoring the other electric wires 14 by controlling.

[0028]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, a monitoring elongated body having electric wires arranged in the length direction is buried in advance at least on the upper side or at least on the lateral side along the buried pipe to monitor the excavation. When the excavating blade of the machine comes close to the buried pipe, it is possible to issue a damage warning signal for the buried pipe, and thus it is possible to prevent damage to the buried pipe.

[Brief description of drawings]

FIG. 1 is an explanatory view conceptually showing a configuration example of a buried pipe damage monitoring system to which the method of the present invention is applied.

FIG. 2 is a schematic diagram of FIG.

FIG. 3 conceptually shows an operation example of the present invention in the configuration of FIG.

FIG. 4 is a perspective view showing an embedding example of a monitoring elongated body in the method of the present invention.

FIG. 5 is a perspective view showing another embedding example of the monitoring elongated body in the method of the present invention.

FIG. 6 is a system diagram showing the configuration of a monitoring elongated body and a monitoring AC signal transmitting / receiving apparatus in the method of the present invention as a development of the monitoring elongated body.

FIG. 7 is a system diagram conceptually showing a system of incidence of a monitoring AC signal and reception of a reflected wave in the method of the present invention.

FIG. 8 is a system diagram conceptually showing another example of the method of receiving the monitoring AC signal and the reflected wave in the method of the present invention.

FIG. 9 is a conceptual explanatory diagram showing a configuration example of a conventional buried pipe damage monitoring system.

[Explanation of symbols]

 11 Buried Pipe 12 Long Body for Monitoring 13 Band 14 Electric Wire 14c Common Line 15 Sidewall 16 Resonance Characteristic Measurement Device 17 Earth 18 Excavation Machine 19 Excavation Blade 20 Cutting Point 21 Electric Wire 22 Sweep Oscillator 23 Receiver 24 Directional Coupler 25 Reflected wave level measuring instrument 26 Monitoring device 27 Common electric wire 28 Changeover switch circuit 29 Control circuit

Claims (10)

[Claims] 1. A strip-shaped body is provided with electric wires at appropriate intervals, the electric wire is capable of being energized in the lengthwise direction of the strip-shaped body to form a monitoring elongated body, and the monitoring elongated body is embedded in a monitored object. Resonance of the wire by burying it near the tube and installing the resonance characteristic measuring device of the wire on one end side of the monitoring long body and inputting the monitoring AC signal while sweeping the frequency from the one end side to the wire Damage prevention monitoring method for buried pipe, characterized by measuring characteristics and monitoring disconnection of electric wire due to damage of monitoring long body by resonance frequency 2. The method for monitoring and preventing damage to a buried pipe according to claim 1, wherein the monitoring elongated body is buried near at least an upper side of the buried pipe. 3. The method for monitoring and preventing damage to a buried pipe according to claim 1, wherein the monitoring elongated body is buried near at least a lateral side of the buried pipe. 4. The electric wire is configured so that it can be energized in the lengthwise direction of the strip in a plurality of channels, and a monitoring AC signal is incident on the electric wire between the electric wire of each channel and the ground to measure the resonance frequency. A method for monitoring damage prevention of a buried pipe according to claim 1. 5. The electric wire has a structure in which a plurality of channels can be energized in the lengthwise direction of the band-shaped body, and at least one electric wire of any channel is used as a common line, and this common line and other channels are connected. 4. A method for monitoring damage prevention of a buried pipe according to claim 1, wherein a resonance frequency is measured by injecting a monitoring AC signal between the wires. 6. A method for monitoring damage prevention of a buried pipe according to claim 4, wherein the transmitter / receiver is configured for each channel. 7. The transmitter / receiver is configured to be common to each channel, and is switched at appropriate time intervals to inject a monitoring AC signal into the electric wire of each channel to measure the resonance frequency. Damage prevention monitoring method for the buried pipe described 8. The method for monitoring damage prevention of a buried pipe according to claim 1, wherein the end of the electric wire on the other end side of the strip is an open end. 9. The method for monitoring damage prevention of a buried pipe according to claim 1, wherein an end of the electric wire on the other end side of the strip is configured as a short-circuit termination. 10. The buried pipe damage prevention monitoring method according to claim 1, wherein the end of the electric wire on the other end side of the strip is formed as a non-reflective end.