JPS62112055A - Method and device for discriminating kind of buried tube - Google Patents

Abstract

PURPOSE:To accurately and easily discriminate the kind of a buried tube by placing the buried tube in impact vibration, analyzing attenuated vibrations by fast Fourier transform, and taking the pattern analysis of an attenuation factor. CONSTITUTION:The ground is digged so that the buried tube 1 is exposed nearly by length 4d (d = tube diameter). A percussion device 3 consists of a guide body and a percussion rod 5, which is fallen along the guide body 4 to strike the buried tube 1 with the percussion rod 5, thereby placing the buried tube 1 in impact vibration. The outputs of impact vibration detection sensors 6 composed of piezoelectric acceleration converters fitted by adhesion at a position A1 or A2 by or under the percussion position of the percussion rod 5 and at a position B which is the tube diameter (d) away from right below the percussion position are inputted to an arithmetic unit 10 through an amplifier 7, a filter circuit 8, and an AD converting circuit 9. The unit 10 records the input vibration waveform for hundreds of milliseconds, accesses vibration waveform of unit time length, takes a fast Fourier transform analysis and the pattern analysis of the attenuation factor, thereby outputting the results to an analyzing device 11. Consequently, the kind of the tube 1 is decided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for determining the type of buried pipe.

[Conventional technology]

At construction sites such as gas pipe replacement, you may come across buried pipes whose type, ie, whether they are gas pipes or water pipes, is unknown. This is because the diameter and material of the gas pipe and water pipe are the same, but as construction progresses, it is necessary to quickly and accurately determine whether the buried pipe is a gas pipe or a water pipe. Generally, the type of buried pipe is determined by having a skilled engineer strike the buried pipe with a hammer and carefully listening to the impact of the buried pipe.

[Problem that the invention seeks to solve]

Judgments based on human subjectivity lack reliability as they are easily influenced by the surrounding environment and mental and physical state.

Furthermore, as disclosed in, for example, Japanese Unexamined Patent Publication No. 58-223714, there is a method of detecting the presence or absence of liquid inside a container from the outside of the container using ultrasonic waves. This ultrasonic wave method involves injecting f1 sound waves at a fixed angle toward the walls of eight vessels containing liquid, detecting the reflected waves of the incident ultrasonic waves from the walls of the vessels, and detecting the reflected waves from the walls of the vessels. The liquid in the container can be detected from the intensity of the sound waves, and it is thought that this can be applied to determine the type of buried pipe.

However, as buried pipes at construction sites are often buried underground for decades or more, the outside surface of the pipes may be locally corroded or damaged, so they must be placed tightly on a smooth surface. It is extremely difficult to make contact with the ultrasonic transmitter/receiver sensor, and the inner surface of the water pipe is extremely uneven due to adhesion of substances dissolved in the water and progression of corrosion. Since ultrasonic waves are subject to absorption and diffusion effects during both transmission and reception, it is difficult to accurately measure the attenuation intensity of the reflected waves of H3 sound waves.Moreover, in the environment of a construction site, the soil inside the excavation is turned into sludge by groundwater. Due to various impeding factors, such as the fact that measurement work is likely to be carried out under adverse conditions and the influence of vibrations from construction machinery, an apparatus for identifying the type of buried pipe using ultrasonic waves has not been put into practical use.

Therefore, even today, if a person involved in construction work encounters a buried pipe of unknown type during construction, he or she must stop the construction work 11 and wait until the specified procedure is completed, permission is obtained, and the type of buried pipe is investigated. Since the machine had to be held for several days, there was a problem in that it required many people and a great deal of time and money.

The present invention has been made in view of the above-mentioned points, and it is an object of the present invention to provide a method and apparatus for determining the type of buried pipe that can accurately and easily identify the type of buried pipe.

[Means for solving problems]

The method of determining the type of buried pipe of the present invention is to impact the buried pipe 1 that has been excavated and exposed to generate impact vibration in the buried pipe 1, detect the damped vibration generated in the buried pipe 1, and detect the damped vibration. The type of buried pipe 1 is determined from the results of fast Fourier transform analysis and attenuation rate pattern analysis.

The buried pipe type discrimination device of the present invention includes an impact device 3 that impacts the buried pipe 1 to generate viJ shock vibration in the buried pipe 1;
A 'fJ percussion vibration detection sensor 6 detects the damped vibration occurring in the buried pipe 1, and the damped vibration detected by the impact vibration detection sensor 6 is recorded, and the damped vibration is subjected to fast Fourier transform analysis and pattern analysis of the damping rate. It consists of a calculation device 10 and an analysis device 11 that determines the type of buried pipe 1 based on the analysis result by the calculation device 10.

[Effect]

The present invention is designed to determine the type of buried pipe based on the damping characteristics of impact vibrations that are avoided when the buried pipe is hit.

[Embodiment] Hereinafter, the configuration of an embodiment of the present invention will be described with reference to the drawings.

In Figures 1 and 2, 1 is a buried gas or water pipe, and this buried pipe 1 is buried underground 2 at a depth of several tens of centimeters to several meters. When determining the type of buried pipe 1, excavation is performed so that about 4 d or more of the length of buried pipe 1 (d=pipe diameter of buried pipe 1) is exposed.

3 is an impact device that generates impact vibration in the buried pipe 1;
This impact device 3 is composed of a cylindrical guide rest 4 disposed on the central surface of the exposed buried pipe 1, and an impact outer part 5 that is movable inside the guide rest 4. By dropping the impact outside 5 along Tc5u, the impact outside 5 connects to the buried pipe 1.
Did it rain on buried pipe 1? generate vibrations.

6 is a box consisting of a piezoelectric acceleration converter for detecting the vibration of the buried pipe 1] -7 is a vibration detection lens ( ), which is located at a lateral position Δ1 of about 90 degrees or about 180 degrees of the impact position of the above-mentioned impact outside 5. Directly below position 2 (A1 and A2 are selected depending on the burial situation of buried pipe 1 in Ouji Prefecture), and from directly below position 6, pipe diameter d
Two sensors 6, 6 are attached to the position B, which is offset by the same amount.

The hinges 6, 6 are connected to an amplifier 7, as shown in FIG. The data is digitally converted and input to the AII G1 device 10.

This performance device 10 records the input vibration waveform for several hundred milliseconds, and then calls out the vibration waveform of a medium length (for example, 0 to 40 m5ec) from the recording and performs fast Fourier transform. Hereinafter referred to as FFT') analysis and pattern analysis of the attenuation rate are performed and output to the analysis device 11. The analysis operation by this analyzer 11 is performed by shifting the intermediate time length recalled from the above record by a fixed time (
For example, the vibration waveform is shifted by 4 m5 ec (eg, 4 to 44 m5 ec) over the entire recorded vibration waveform.

The analysis device 11 analyzes the output from the arithmetic device 10 to determine the 10 types of buried pipes. The pattern analysis value, the pattern analysis value of the attenuation rate, etc. are recorded in advance.

Further, the analysis results by the analyzer 11 are displayed from the output device 12, for example, by printing, charging display, etc.

Next, the arithmetic device 10 and the analysis device 11 perform FFT analysis of the vibration waveform and pattern analysis of the damping rate to obtain yJ! The effectiveness of determining the type of installed pipe 1 will be explained.

The vibration caused by the forward movement of the impact rod 5 in the buried pipe 1 buried underground 2 is extremely complex, but the vibration waveform caused by the impact 'f1 can be expressed by the following Fourier series, f(t ) = a /2 + Σ (a cos
n ωt+ b, sin n ω t
)n By conducting a two-way analysis of this equation, it can be expressed as a combination of many sinusoidal curves and sinusoidal curves with various amplitudes and vibration numbers, no matter how complex the vibration (:l). , and shows each of these simple harmonics t, L, and the combined natural frequency. Preferably, since vibration is generally composed of several main natural frequencies, Vibration waveform analysis can be done by focusing on these few natural frequencies.

Also, depending on whether the object inside the buried pipe 1 is gas or water, J! I! The vibration damping speed of installed pipe 1 is different.

This is because a phenomenon called attenuation occurs when vibrational energy is transferred from one object to another.For example, a part of the vibrational energy is reflected by the boundary between two objects, but in this case, how much of the vibrational energy is reflected? Whether the light is reflected depends on the ratio of the two materials' densities. When vibration energy attempts to escape from a solid material such as iron into the air, it is completely reflected, but 87% of the vibration energy enters water from iron. is reflected, and the reflected skewer is small compared to the air. Therefore, when a fixed value of vibration energy is given to the buried pipe 1, if the object inside the buried pipe 1 is gas, the vibration Ωj of the buried pipe 1 will continue for a long time, and if it is water, the vibration Ωj of the buried pipe 1 will continue for a long time. Since the vibrations are absorbed by water and attenuated in a short time, it is useful to focus on the attenuation rate of the vibrations of the objects inside the buried pipe 1.

In addition, as we know from FFT analysis, the vibration of the buried pipe 1 due to impact can be overcome by a combination of many simple harmonics, but not all the simple harmonic components are equally absorbed by the water and attenuated. , the natural frequency related to the natural frequency of the water in the buried pipe 1 is attenuated by the chopsticks.

Next, as shown in Figures 4 to 18, we conducted an experiment in which we carried out FTT analysis and pattern analysis of the damping rate of the vibrations of gas pipes and water pipes. The results of experiments on gas pipes are shown in Figs. (B) represents the change in the vibration waveform on the time axis, and (B) !, i F F T shows the natural frequency according to the analysis.

Figure 4 (gas pipes) J3J: and Figure 12 (water pipes),
It shows the situation immediately after being hit, and from this state, the vibration waveform, the damping speed of the vibration waveform, and the static vibration! Comparing IIJ numbers etc.b,
It is very difficult to determine whether it is a gas pipe or a water pipe.

However, the natural frequency used in FFT analysis of vibration waveforms is approximately 0.5.1.5 for gas pipes and water pipes.
．． Since a peak appears at llz at 3.0, it cannot be determined.

Figure 7 (Gas pipe) J3 and Figure 15 (Water pipe)
Excluding the vibration waveform immediately after the impact, the waveform after 12 m5ec has elapsed is shown, and from this state, in the case of a water pipe, 0.5
The maximum natural frequency appears at K11z, and on the other hand, the maximum natural frequency appears at fiz at 3 in the gas pipe ringing, and these maximum natural frequencies determine whether the buried pipe 1 is a gas pipe or a water pipe. Easy to identify.

In addition, in the case of gas pipes, as shown in Fig. 11, 3.
．． While the natural frequency of 0 Hz continues for a long time,
In water pipes, as shown in Figure 15, the natural frequency of 3.0 fiz is absorbed by the water in the pipe and disappears in a shorter time than in gas pipes, resulting in a natural frequency of 0.5 KHz. There are only numbers. Furthermore, in a gas pipe, the vibration waveform due to impact continues even after 120 m5cclJ, whereas in a water pipe, the vibration waveform disappears after approximately 3 On+sec.

Furthermore, Fig. 18 shows the temporal changes in the natural frequencies 0.5KIIZ and 3.0KIIZ obtained by this FFT analysis for gas pipes (indicated by broken lines) and water pipes (indicated by solid lines). The vibration waveform analysis time range is 4 to 52.
When limited to m5ec, it can be seen that the proportion of vibration absorbed by water is greater in 3.0KIIZ.

In other words, the magnitude of the natural frequency at Ilz between 0 and 5 during the same time period is the ratio of 6 water pipes to 10 gas pipes, and approximately 40% absorption fT! r
Also, the magnitude of the natural frequency at llz in 3, O is,
The ratio is about 10 water pipes to 10 gas pipes, which is approximately 90.
% is absorbed. Therefore, by comparing the attenuation rate patterns, it can be easily determined whether the buried pipe 1 is a gas pipe or a water pipe.

As described above, the impact vibration is generated by the impact device 3 on the buried pipe 1 that has been excavated and exposed, and the buried pipe 1 is reduced in capital.
The sensors 6 and 6 detect vibrations of By analyzing and determining the type of buried pipe 1 and displaying the determination result from the output device 12, the type of buried pipe 1, that is, whether it is a gas pipe or a water pipe, is determined.

In addition, the vibration generated in the buried pipe 1 by the impact shaft 5 is affected by the material of the buried pipe 1, corrosion of the pipe wall, etc.), and the influence of differences in the restraint state of the soil around the buried pipe 1. However, these awards were made by generating different impact vibrations using, for example, several types of 100-hit rods 5 of cheap materials and weights, and placing them at two locations on the buried pipe 1. can be almost eliminated by detecting and analyzing different vibration waveforms.

Furthermore, in the above embodiment, a piezoelectric acceleration transducer is used for the impact vibration detection hint 6, but depending on the situation of the buried pipe 1, a condenser microphone can be used instead of the piezoelectric acceleration transducer. By using a microphone, there is no need to bond it to the buried pipe 1, so the measurement point can be freely selected, and a piezoelectric acceleration transducer and amplification are not required, making it inexpensive and compact.

(Effects of the Invention) According to the present invention, when a buried pipe is hit to generate shock and motion, a fast Fourier transform analysis of the damped vibration generated in the buried pipe and a pattern analysis of the damping rate are performed. Since the type of buried pipe can be determined, the amount of t generated in this buried pipe can be determined.
: Based on the capital reduction characteristics of W percussion vibration, pi! The type of installed pipe can be accurately and easily determined.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of the positional relationship between the device and the sensor showing one embodiment of the present invention, and FIG. 3 is a block diagram.
FIGS. 4 to 18 are explanatory diagrams showing experimental results, respectively. 1. Buried pipe, 3. Impact device, 6.., 7. System motion detection sensor, 10. Arithmetic device, 11. Analysis device δ. $3 Figure (B) 4th stanza (A) 5th cut (B) 6th diagram (B) 7th diagram (B) Half 8 Concave q diagram %lO1!1 (A) (A) Hot 13th diagram t4 TtJ 15th page CB) Kanji I-

Claims (2)

[Claims] (1) Excavated and exposed buried pipes are struck to generate shock vibrations in the buried pipes, damped vibrations generated in the buried pipes are detected, and fast Fourier transform analysis of the damped vibrations and pattern analysis of the damping rate are performed. A method for determining the type of buried pipe that determines the type of buried pipe from the results. (2) An impact device that impacts a buried pipe to generate impact vibration in the buried pipe, an impact vibration detection sensor that detects the damped vibration generated in the buried pipe, and an impact vibration detection sensor that detects the damped vibration detected by the impact vibration detection sensor. A type of buried pipe characterized by comprising a calculation device that records the damped vibration and performs a fast Fourier transform analysis and a pattern analysis of the damping rate, and an analysis device that determines the type of buried pipe from the analysis results by this calculation device. discrimination device.