JP2013044612A - Detection method and device of underground piping damage position - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a search performance of an opening damage position of gas piping buried underground.SOLUTION: In a detection method of an underground piping damage position, sound waves are propagated inside underground piping 10, the sound waves propagated inside the underground piping 10 are received at a plurality of positions on the ground, and a position of an opening damage part 11 generated on the piping 10 is estimated from a reception state of the sound waves. A pattern to be a code is used for the sound waves to be propagated inside the piping, and cross-correlation processing is performed with the received sound. In this case, as the pattern to be the code, pseudo random signals or signals for which a frequency is temporally changed can be used.

Description

  The present invention relates to a method and an apparatus for detecting a buried pipe breakage position, and more particularly, an buried breakup capable of detecting an opening breakage position generated in a gas pipe buried in the ground by exploration on the ground without digging up the pipe. The present invention relates to a method and an apparatus for detecting a broken pipe position.

  It is very important for exploration from the ground without digging the pipes for the location of the opening breakage that occurred in the pipes buried in the ground due to an earthquake or the like. In particular, since the sockets at the ends of the pipes in each household, rather than the thick pipes in the main line, are easily removed, the necessity is high.

  Conventionally, when detecting the opening failure position of a gas pipe, which is a kind of piping, a specific part of the gas piping network is partitioned, and the gas pressure is applied only to the gas piping in this section with nitrogen gas, etc. While discriminating whether or not it was lowered, the sections were sequentially narrowed to estimate the leak position.

  In addition, as an efficient pipe inspection method, sound is generated at the open end of a gas pipe concealed by a covering layer (soil), such as a city gas pipe buried underground, in the gas pipe. The sound wave is propagated, the sound wave propagating in the gas pipe is received at a plurality of positions outside the coating layer, and the spatial distribution of the received sound volume is obtained, and from the obtained received sound volume distribution, the position of the gas pipe or Patent Document 1 proposes a method for estimating an opening breakage position occurring in a gas pipe.

  However, in the measurement method shown in Patent Document 1, the sound wave is remarkably lowered because it propagates through the soil, and a sound wave having a frequency approximate to a sound wave of about several hundred Hz used for measurement (high-frequency sound does not pass through the soil) is around. Because it exists in the environment, it is difficult to extract the sound wave propagated to the pipe.

  Therefore, in order to obtain a high sound volume, in the technique of Patent Document 1, before the inspection work, a method in which different frequencies are propagated in the pipe and the frequency at which the sound volume is maximum is obtained and used for measurement, or the pipe diameter Patent Document 2 proposes a method of using a resonance frequency determined based on the sound speed for measurement.

JP-A-8-271370 JP-A-11-142280 JP-A-6-294793

  However, since the method of Patent Document 2 is a means for amplifying the sound volume propagated in the pipe, its effect is limited. In other words, in practice, the appropriate frequency changes depending on various conditions such as pipe shape (inner diameter and length), buried environment, opening breakage shape (opening size) and position. It is only an optimum value, and cannot cope with changes in the shape and position of the broken opening. Regarding the resonance frequency, it cannot cope with branching of pipes, changes in diameter, changes in opening shape or position.

  Also, in the evaluation of measurement data, it is necessary to extract the sound actually propagated in the pipe from the sound of the surrounding environment, but if the transmitted sound wave is a single frequency selected, it is separated and extracted from the surrounding sound There is a limit to accuracy.

  On the other hand, as similar to the present invention, Patent Document 3 discloses that in nondestructive measurement using acoustic waves of physical properties of the formation, an oscillation source is excited according to a pseudo-random code, and a correlation with an oscillation signal is received by a receiver. It has been proposed to distinguish it from other noises by taking it, but it cannot be used as it is to detect the breakage position of the buried piping.

  The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to be able to cope with various piping conditions, embedded environments, and opening damage situations when detecting the location of embedded piping breakage.

  The present invention propagates a sound wave inside the buried pipe, receives the sound wave propagating inside the buried pipe at a plurality of positions on the ground, and estimates an opening breakage position generated in the pipe from the reception state of the sound wave. This method solves the above-mentioned problem by using a pattern as a code for a sound wave propagated inside a pipe and performing a cross-correlation process with the received sound.

  Here, a pseudo-random signal can be used as the pattern serving as the code.

  Further, as the pattern to be the code, a signal whose frequency is changed with time can be used.

  Further, the signal obtained by changing the frequency with time can be obtained by repeating a pattern in which the frequency is continuously changed within a specific range.

  The present invention also provides a buried pipe for propagating a sound wave inside the buried pipe, receiving the sound wave propagating inside the buried pipe at a plurality of positions on the ground, and estimating an opening breakage position generated in the pipe from the reception state of the sound wave. A method for detecting a broken position, which solves the above problem by using a sound wave having a uniform frequency in a specific range as a sound wave to be propagated inside the pipe.

  Here, the propagation direction of the sound wave can be identified from the phase differences of the received sound waves at a plurality of positions, and the breakage position can be estimated together with the sound pressure distribution.

  The present invention also provides a buried pipe for propagating a sound wave inside the buried pipe, receiving the sound wave propagating inside the buried pipe at a plurality of positions on the ground, and estimating an opening breakage position generated in the pipe from the reception state of the sound wave. A damage position detection device, a means for transmitting a sound wave having a pattern to be a code, a plurality of reception sensors arranged on the ground surface, a cross-correlation processing means for a transmission sound and a reception sound, and a received sound wave In addition, means for recording the position information of the measurement point, means for deriving the propagation direction of the sound wave from the phase difference between the reception sensors arranged at known intervals, means for illustrating the measurement position, sound pressure and propagation direction The above-described problem is solved by a detection device for a buried pipe breakage position.

  According to the present invention, a sound wave having a pattern to be a code is propagated inside the pipe, and a cross-correlation process between the received sound wave and the transmitted sound wave is performed, thereby improving the accuracy of extracting the sound wave actually propagated in the pipe.

  In particular, when a pseudo-random signal is used as the pattern to be the code, the pseudo-random signal is a pattern that does not exist in the surrounding environment, and the extraction accuracy by the correlation process is improved as compared with a single-frequency sound wave.

  Further, when a signal whose frequency is changed with time is used as the pattern to be the code, the time change of the frequency improves the discrimination with the sound of the surrounding environment. Furthermore, since this method is based on a sine wave, for example, an output can be easily obtained when transmitting from a speaker. Here, a pattern in which the frequency is continuously changed in a specific range can be repeated.

  In addition, since the effective frequency differs depending on factors such as tube diameter, soil, and broken opening shape, a satisfactory received signal cannot often be obtained with a single-frequency sound wave. By using a simple frequency, it is possible to perform measurement without adjusting the frequency in advance. For example, a pseudo-random signal has a pattern that can generate a sound wave having a uniform frequency in a specific range, and can use only one type of sound wave to cope with a change in frequency characteristics due to various conditions. Moreover, in the time change of the frequency, if one set whose frequency is changed in a specific range is used as one measurement, it is measured at all frequencies in the changed range.

  Furthermore, by arranging a plurality of receiving means at predetermined positions and confirming the phase of the received signal, the arrival time difference of the sound wave to each receiving means is measured, and the arrival direction of the sound wave is calculated, thereby breaking the opening The location can be easily identified.

  As described above, in the present invention, by using a signal having a pattern that is a sign for a sound wave transmitted into a tube, the accuracy of separating and extracting sound waves used for measurement is improved, and the detection performance of a damaged portion is improved. .

  In addition, as the sound wave to be transmitted into the pipe, a sound wave whose frequency characteristic is uniform in a specific range or a sound wave whose frequency is continuously changed in a specific range is used to adjust an appropriate frequency for each piping condition. The work can be omitted, and it is possible to cope with various opening shapes of the damaged portion.

The figure which shows the whole structure of 1st Embodiment of this invention. The perspective view seen from the bottom which shows an example of the receiving sensor used by the said embodiment Block diagram showing the signal processing system The figure which compares and shows the transmission sound waveform in an example of (A) this invention, and (B) conventional example. The figure which shows the cross correlation processing data example in the conventional case which transmitted the sine wave The figure which shows the example of the cross correlation processing data in the case of an example of this invention which transmitted M series (phase modulation) The figure which similarly shows the other example of cross correlation processing data The figure which shows the cross correlation processing data example in the case of the other example of this invention which transmitted white noise. Diagram showing comparison of frequency spectra of various transmission sound waveforms Diagram showing an example of a frequency sweep according to the present invention The figure which similarly shows an example of the evaluation screen The figure which shows the whole structure of 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In FIG. 1, the state which is exploring the opening breakage position of the piping embed | buried under the ground using the inspection apparatus which concerns on 1st Embodiment of this invention is shown. In this embodiment, a transmitting device (for example, a speaker) 20 is installed instead of a gas meter at the open end of a standing tube (for example, a gas meter tube) 12 connected to the buried piping 10 to be inspected, and is generated by a transmission waveform generator 22. The transmitter 20 is driven by the signal thus transmitted, and a sound wave having a predetermined waveform is transmitted into the buried pipe 10 via the standing pipe 12. Thereafter, a plurality of (three in the figure) receiving sensors (for example, vibrometers) 31, 32, and 33 installed on the buried pipe detect vibrations due to sound waves leaking from the broken opening portion 11. Then, the installation position of the reception sensors 31, 32, 33, the sound pressure and the phase of the received signal are recorded by the reception / analyzer 40, and the opening breakage position is specified by analysis.

  As the transmission waveform generator 22, in addition to a so-called waveform generator whose frequency can be adjusted, a digital audio player can be used when the waveform is fixed.

  As the receiving sensors 31 to 33, for example, a vibrometer composed of an acceleration pickup can be used. This vibrometer can be installed immediately above the pipe 10 confirmed in advance with a piping diagram. Note that the installation surface (bottom surface) of the vibrometer is preferably not a planar structure but a structure having a three-point support protrusion 31a as illustrated in FIG. 2 in order to avoid the influence of road surface unevenness.

  The signal processing system of this embodiment is shown in FIG. Signals from the receiving sensors 31, 32, and 33 are input to the data recording unit 42, and their waveforms and position information are recorded. The output of the data recording unit 42 is sent to the cross-correlation processing unit 44, and the cross-correlation with the transmission waveform generator 22 is taken. Next, the amplitude is detected by the amplitude value detection unit 46, the propagation direction is calculated by the propagation direction calculation unit 48, and displayed on the amplitude value distribution and propagation direction display unit 50. In the calculation of the vibration and propagation direction, the phase difference caused by the difference in position of the reception sensors 31 to 33 is regarded as an active intensity in the acoustic field, and an opening breakage point 11 is calculated from the magnitude and polarity of the active intensity. This can be done by obtaining a vector (size and direction) indicating the position of (see Japanese Patent Application Laid-Open No. 11-248591).

  Hereinafter, a method of using a pseudo random signal as a sound wave to be transmitted into the pipe will be described. As a method of applying the pseudo random signal to the sound wave, there is a method of modulating the amplitude, the phase, and the frequency, and any of them may be used.

  FIG. 4 shows (A) a transmission waveform of a pseudo random signal whose phase is modulated according to the present invention, and (B) a transmission waveform of a single frequency for comparison. The signal received on the ground becomes weak and is synthesized with the sound of the surrounding environment, but the sound wave propagated in the pipe can be extracted with high accuracy by performing correlation processing with the transmission signal. Here, when a sine wave having a single frequency as shown in FIG. 4B is used, a peak is obtained with a shift of one wavelength. Therefore, as shown in FIG. After that, it will be displayed as a continuous wave.

  On the other hand, when a pseudo-random signal subjected to phase modulation by M-sequence, for example, as shown in FIG. 4 (A) is used, a correlation peak is obtained as shown in FIG. 6 (400 Hz example). be able to. In FIG. 6, since the M-sequence code is short, the correlation peak is displayed a plurality of times. In another experiment, FIG. 7 shows an example of a waveform after (A) a raw waveform and (B) correlation processing that have received the same 400 Hz M-sequence signal (phase modulation).

  Even if it is white noise, if it is the output of a waveform generator that generates white noise by turning on and off in the M-sequence pattern, as shown in FIG. 8 (example of long M-sequence code), there is one peak. Therefore, it can be used in the present invention.

  FIG. 9 shows a comparison of power spectra of transmission sound waveforms of (A) sine wave 400 Hz, (B) M series (phase modulation), and (C) white noise.

  Next, a method of using a signal swept by changing the frequency over time as a sound wave to be transmitted into the pipe will be described. A sound wave obtained by repeating the process of continuously changing the frequency in a specific range is used as a transmission sound. By considering one pattern whose frequency is changed with time as one code and performing correlation processing with the received signal, it is possible to extract the sound wave propagated in the pipe with high accuracy. An example in which the average value after sweeping the frequency at 100 to 1000 Hz is subjected to correlation processing is shown in FIG.

  In addition, because the frequency effective for measurement tends to change depending on the piping conditions and the shape of the broken opening, it is effective to use transmission sound that has a uniform frequency component in a specific range, not a single frequency. Become. When the pseudo random signal is used as the transmission sound, a signal having a uniform frequency characteristic in a specific range is selected. On the other hand, when the frequency time change signal is used, since the measurement is performed at all frequencies in the range to be changed, the same effect can be obtained.

  When the sound pressure of the received signal is used as a method for identifying the opening breakage position, the breakage position is identified from the transition of the sound pressure at the measurement point. On the other hand, when the phase of the received signal is used, the arrival direction of the sound wave is calculated from the phase difference of the signals received by a plurality of receiving means arranged at predetermined intervals.

  Hereinafter, the procedure of the present invention will be described with reference to FIG. First, a transmitting device 20 that transmits sound waves, for example, a speaker, is attached to a part of a pipe line to be investigated, for example, a standing pipe 12 that protrudes from the ground like a gas meter installation location. The sound wave generated from the speaker is assumed to be based on a pre-programmed pseudo-random signal or a signal that repeats a frequency-time change with a specific change width. In the pseudo-random signal, it is preferable to use a signal whose frequency component is uniform in a band of 100 to 1000 Hz. When frequency time change is used, the frequency change width is preferably set to 100 to 1000 Hz.

  Vibrometers used as the reception sensors 31 to 33 are installed immediately above the pipes confirmed in advance in the piping diagram.

  As shown in FIG. 3, the received signal is recorded together with the vibration meter installation position information by the data recording unit 42, and the cross-correlation processing unit 44 performs cross-correlation processing with the transmission signal to extract the transmission sound wave component. After that, the amplitude value detection unit 46 and the propagation direction calculation unit 48 calculate the propagation direction of the sound wave from the signal amplitude value and the phase difference between a plurality of vibrometers. For example, the amplitude value distribution and propagation direction display unit 50 displays the sound pressure distribution and the propagation direction on the piping diagram to identify the opening breakage point 11.

  An example of the data display screen is shown in FIG. Data used for the evaluation is the received sound intensity (sound pressure) and the propagation direction of the sound wave at each measurement point. Although it is possible to simply estimate the damaged portion from the difference in sound pressure, the evaluation can be facilitated and the accuracy can be improved by evaluating the propagation direction of the sound wave.

  The change in the sound pressure is considered to be caused not only by the location and size of the breakage but also by the soil, the pavement state, the installation state of the reception sensor, and the like. For this reason, it is an effective means to use the propagation direction of the sound wave, which is a parameter different from the sound pressure change.

  In addition, by confirming the propagation direction of the sound wave at the time of measurement, it can be used as an index for arbitrarily adding a measurement location, and the displacement of the buried pipe position can be confirmed.

  As the vibrometer, a laser Doppler vibrometer can be used in addition to the acceleration pickup.

  A second embodiment of the present invention using a microphone instead of a vibrometer is shown in FIG.

  According to this embodiment, it is possible to perform measurement while moving a single microphone 62 as a reception sensor together with a reception / analyzer 64 that the operator 60 can move.

  In the above-described embodiment, the present invention is applied to detection of an opening breakage point of a gas pipe. However, the application target of the present invention is not limited to this, and an opening breakage point of another buried pipe. It is equally applicable to the detection of.

10 ... Built-in piping 11 ... Broken opening 12 ... Standing pipe
20 ... Transmitter (speaker)
22 ... Transmission waveform generator 31, 32, 33 ... Reception sensor (vibrometer)
40, 64 ... reception / analyzer 42 ... data recording unit 44 ... cross correlation processing unit 46 ... amplitude value detection unit 48 ... propagation direction calculation unit 50 ... amplitude value distribution and propagation direction display unit 60 ... operator 62 ... microphone

Claims (7)

A method for detecting the location of a buried pipe breakage that propagates sound waves inside the buried pipe, receives the sound waves propagating inside the buried pipe at a plurality of positions on the ground, and estimates the opening breakage position in the pipe from the reception status of the sound waves. There,
A method for detecting an embedded pipe breakage position, wherein a pattern that is a sign is used for sound waves propagated inside a pipe, and a cross-correlation process is performed with the received sound.   The method according to claim 1, wherein a pseudo-random signal is used as the pattern serving as the code.   2. The embedded pipe breakage position detection method according to claim 1, wherein a signal whose frequency is changed with time is used as the pattern to be the code.   The embedded pipe breakage position detection method according to claim 3, wherein the signal whose frequency is changed with time is a signal obtained by repeating a pattern in which the frequency is continuously changed within a specific range. A method for detecting the location of a buried pipe breakage that propagates sound waves inside the buried pipe, receives the sound waves propagating inside the buried pipe at a plurality of positions on the ground, and estimates the opening breakage position in the pipe from the reception status of the sound waves. There,
A method of detecting a buried pipe breakage position, wherein a sound wave having a uniform frequency in a specific range is used as a sound wave propagated inside a pipe.   6. The buried pipe breakage position according to claim 1, wherein the propagation direction of the sound wave is specified from the phase difference of the received sound waves at a plurality of positions, and the breakage position is estimated together with the sound pressure distribution. Detection method. A buried pipe breakage position detection device that propagates sound waves inside buried pipes, receives sound waves propagating inside the buried pipes at a plurality of positions on the ground, and estimates the opening breakage position in the pipes from the reception status of the sound waves. There,
Means for transmitting a sound wave having a pattern to be a code;
A plurality of receiving sensors arranged on the ground surface;
Means for cross-correlation processing between transmitted sound and received sound;
Means for recording the position information of the measurement point together with the received sound wave;
Means for deriving the propagation direction of the sound wave from the phase difference between the receiving sensors arranged at a known interval;
Means for illustrating the measurement position, sound pressure and propagation direction;
An apparatus for detecting a position where a buried pipe is broken.