JP2008026162A - Inspection method for inspecting deterioration state of embedded pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection method for inspecting the deterioration state of an embedded pipe capable of inspecting the physical deterioration state caused in the outer or inner part of the embedded pipe to inspect the deterioration state as the whole of the embedded pipe. <P>SOLUTION: An impact is applied to predetermined impact positions 5 of the embedded pipes 1 with respect to the embedded pipe 1 free from cracking and the embedded pipe 1 to be inspected and frequency spectra at paired measuring positions being symmetric positions centering around the impact positions 5 are measured while the deterioration values of the embedded pipes 1 are calculated on the basis the similarity of two frequency spectra obtained with respect to the measuring positions and the deterioration values of both embedded pipes are compared to judge the deterioration state of the embedded pipe 1 to be inspected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inspection method for inspecting a deterioration state of an embedded pipe.

  Reinforced concrete buried pipes are used as sewer pipes and agricultural water pipes. These buried pipes corrode due to the distribution of sewage and agricultural water for many years, the strength of which is reduced, and cracks may occur. In addition, these buried pipelines are often buried around the roadway, and the strength of the buried pipelines deteriorates due to automobile vibration or earthquakes, and cracks may occur. Therefore, there has been a need for a method for inspecting physical deterioration states such as strength deterioration, cracks, and minute cracks in sewage pipes and agricultural water pipes.

  In a diagnostic survey that examines the deterioration of sewage and agricultural water pipelines, generally, the basin to be investigated is divided into element areas, the deterioration levels are ascertained for each element area, and the deterioration levels are ranked for each element area. To do.

  In order to inspect this level of deterioration, conventionally, visual inspection is performed using visual observation or a television camera, or if necessary, the core pipe in the element area is dug out and its physical properties are measured. It was.

  However, when visual inspection is performed without digging the buried pipe, only visible degradation can be detected, and deterioration occurring in the outer circumference of the buried pipe or inside the buried pipe wall cannot be inspected. The condition could not be grasped quantitatively.

  In addition, in order to ensure the accuracy of the collected data obtained by inspecting the deterioration state, it is necessary to dig a large amount of the buried pipe that becomes the core, but when digging, the sewage pipe or the agricultural water pipe is damaged. There was a problem that it took a lot of time and work.

  Therefore, as a method for inspecting such a reinforced concrete buried pipe, for example, it is conceivable to apply the technique described in Patent Document 1 or 2.

  According to the technique according to Patent Document 1, a crack width is obtained by attaching a conductive material to a cracked portion of an object to be measured, measuring a voltage and a current value of the conductive material, and calculating a change in the resistance value. Detect changes.

According to the technique described in Patent Document 2, when a non-penetrating detection hole is formed in a measurement object, fluid is supplied to the fluid conduit to the detection hole, and the fluid penetrates into the measurement object. Cracks are detected by measuring the flow velocity.
JP 2004-170104 A JP 2004-333181 A

  However, the technique described in Patent Document 1 can only be applied to a pipe in which a crack exists, and cannot detect whether or not a crack has occurred.

  Further, in the technique described in Patent Document 2, since it is necessary to provide a detection hole in the measurement object, it is necessary to make a hole in a part of the measurement object, which requires troublesome work. In addition, when the detection hole is provided in the buried pipe, the thickness of the pipe wall in the portion where the detection hole is provided becomes thin, so that the strength of the buried pipe may be deteriorated.

  Moreover, in any method, it was possible to inspect only partly, and it was impossible to grasp the deterioration state of the part other than the part inspected.

  The present invention has been made in view of such circumstances, and an embedded pipe that can inspect a physical deterioration state that has occurred outside or inside and that can inspect the deterioration state of the entire embedded pipe. An object of the present invention is to provide an inspection method for inspecting the deterioration state of the steel.

  The inspection method for inspecting the deterioration state of the buried pipe according to the present invention determines the striking position that gives impact to each of the standard buried pipe to be inspected and the inspection target buried pipe to be inspected. A shock is applied, vibrations are measured at two measurement positions that are symmetrical with the respective striking positions as the center positions, and each pipe is deteriorated based on the similarity of two frequency spectra obtained from these vibrations. A deterioration value of the inspection target buried pipe is determined by calculating a value and comparing these deterioration values.

  In addition, the inspection method for inspecting the deterioration state of the buried pipe according to the present invention is to determine the impact position for giving impact to each of the reference buried pipe to be inspected and the inspection target buried pipe to be inspected. Impact is applied to the position, vibrations are measured at a plurality of pairs of measurement positions at symmetrical positions with the respective striking positions as the center position, and the frequency spectrum similarity for each pair of pairs obtained from these vibrations is measured. On the basis of this, a deterioration value is calculated for each of the tubes, and the deterioration state of the buried pipe to be inspected is determined by comparing these deterioration values.

  According to the present invention, since the degradation state is inspected by measuring the frequency spectrum generated by the impact, it can be evaluated even if the buried pipe is not cracked, and for examining the degraded state in the buried pipe. There is no need to form perforations, and the deterioration state can be easily inspected.

  Moreover, since two frequency spectra are acquired at positions symmetrical to the striking position and the deterioration value is calculated based on the similarity between both frequency spectra, the deterioration state is calculated as a numerical value. It is possible to objectively evaluate the deterioration state, unlike the negative evaluation.

  In addition, the degradation value measurement method is to acquire a degradation value by measuring a frequency spectrum based on an elastic wave due to an impact, and this acoustic wave propagates to the inside of the buried pipe. Since the value reflects the internal state of the buried pipe, it is possible to grasp not only the outside of the buried pipe but also the internal deterioration state.

  In addition, when the frequency spectrum is acquired at a plurality of pairs of measurement positions and the deterioration value is calculated, the similarity value is calculated based on the similarity between the two frequency spectra obtained in each of the plurality of pairs, and a plurality of similarities are calculated. Since the deterioration value is calculated based on the value, the deterioration state is inspected from various directions with respect to one buried pipe, so that a more accurate deterioration state can be grasped.

  According to the inspection method for inspecting the deterioration state of the buried pipe according to the present invention, since the deterioration state is inspected by measuring the frequency spectrum generated by the blow, it can be evaluated even if the buried pipe is not cracked. Moreover, it is not necessary to form a perforation for investigating the deterioration state in the buried pipe, and the deterioration state can be easily inspected.

  Moreover, since two frequency spectra are acquired at positions symmetrical to the striking position and the deterioration value is calculated based on the similarity between both frequency spectra, the deterioration state is calculated as a numerical value. It is possible to objectively evaluate the deterioration state, unlike the negative evaluation.

  In addition, the degradation value measurement method is to acquire a degradation value by measuring a frequency spectrum based on an elastic wave due to an impact, and this acoustic wave propagates to the inside of the buried pipe. Since the value reflects the internal state of the buried pipe, it is possible to grasp not only the outside of the buried pipe but also the internal deterioration state.

  In addition, when the frequency spectrum is acquired at a plurality of pairs of measurement positions and the deterioration value is calculated, the similarity value is calculated based on the similarity between the two frequency spectra obtained in each of the plurality of pairs, and a plurality of similarities are calculated. Since the deterioration value is calculated based on the value, the deterioration state is inspected from various directions with respect to one buried pipe, so that a more accurate deterioration state can be grasped.

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

  The inspection method for inspecting the deterioration state of the buried pipe according to the present invention is applied to, for example, a reinforced concrete buried pipe (for example, a fume pipe) used for a sewer pipe or an agricultural water pipe. In inspecting the buried pipe by the inspection method of the deterioration state of the buried pipe, first, a reference buried pipe as an inspection standard and an inspection target buried pipe to be inspected are prepared.

  Next, the deterioration value which shows the deterioration state of an embedded pipe is measured with the deterioration value measuring method shown below about the reference | standard buried pipe used as a test | inspection reference | standard. The deterioration value of the reference buried pipe is a reference value for determining the deterioration state of the inspection target buried pipe to be inspected. Here, as the reference buried pipe, a normal pipe (hereinafter also referred to as a healthy pipe) having the same kind, shape and size as the inspection target buried pipe having no cracks is selected. It is.

  Next, the deterioration value is measured by the deterioration value measuring method for the inspection target buried pipe to be inspected.

  Next, by comparing the two deterioration values, it is determined whether or not the inspection target buried pipe is deteriorated or the degree of the deterioration. If the degradation value of the buried pipe to be inspected is comparable to the degradation value of the standard buried pipe, it is judged that the degradation has not progressed. If there is a difference between the degradation values, there is degradation (such as cracks). If the difference between the deterioration values is large, it is determined that the deterioration is progressing.

  The degradation value measuring method described above is a method for obtaining a degradation value indicating the degradation state of the buried pipe. Specifically, first, the impact position for impacting the buried pipe is determined, and the impact position is impacted. Vibrations due to impact are measured at two measurement positions that are paired at symmetrical positions with the strike position as the center position, and frequency spectra are obtained from these vibrations, and the two frequency spectra obtained at these two measurement positions are obtained. This is a method of calculating a deterioration value based on the degree of similarity.

  Next, a test example in which the deterioration value of the buried pipe is calculated by the deterioration value measuring method will be specifically described.

  FIG. 1 is an explanatory diagram illustrating an example of a state when an embedded pipe is measured by applying the method for inspecting the deterioration state of the embedded pipe according to the embodiment of the present invention. FIG. 2 is an explanatory diagram for explaining another example showing a state when the buried pipe is measured by applying the method for inspecting the deteriorated state of the buried pipe according to the embodiment of the present invention. In addition, the arrow shown to FIG. 1 and FIG. 2 has shown the striking position and the striking direction.

  First, the buried pipe 1 relating to the measurement of the deterioration value is laid down on the earth and sand 14 laid flat on the ground 15. The earth and sand 14 stably holds the buried pipe 1 and plays a role of confining the buried pipe 1 in the buried pipe 1 itself without propagating the impact applied to the buried pipe 1 to the ground 15. Thereby, when an impact is applied to the buried pipe 1, the influence of the reflected wave from the ground 15 can be eliminated, and a frequency spectrum based on the buried pipe 1 itself can be obtained.

  Next, receivers 2 that receive elastic waves due to the impact are disposed at two positions that are symmetrical with respect to the impact position 5 that gives an impact to the buried pipe 1. Specifically, when the hitting position 5 is located near the center that is equidistant from both ends of the buried pipe 1, it is received at two locations that are symmetrically about the hitting position 5 in the extension direction of the buried pipe 1. A container 2 is arranged (hereinafter, this arrangement is referred to as arrangement 1; see FIG. 1). Alternatively, the receivers 2 may be arranged at two positions that are symmetrical in the circumferential direction of the buried pipe 1 with the hitting position 5 as the center (hereinafter, this arrangement is referred to as arrangement 2; see FIG. 2).

  In addition, the arrangement position of the receiver 2, that is, the measurement position for acquiring the frequency spectrum may be a position that is symmetrical with the hitting position 5 as the center position. The symmetrical position here is a symmetrical position as a physical structure when the hitting position 5 is the center position. In other words, the pair of receivers 2 may be arranged at positions equidistant from the striking position 5 that are diagonal when viewed from the upper surface of the buried pipe with the striking position 5 as the center.

  The receiver 2 uses, for example, a vibration sensor such as an acceleration sensor or an AE sensor (Acoustic Emission Sensor). The receiver 2 may be fixed to the embedded pipe 1 with a tape, an adhesive, or the like, or may be fixed using a holding jig or the like. In addition, when fixing to a place where a pressing jig or the like cannot be used because it cannot be fixed with a tape or an adhesive, it may be simply pressed by hand. In addition, the receiver 2 is not limited to being fixed to the outer peripheral surface of the buried pipe 1, and may be fixed to the inner peripheral surface of the buried pipe 1.

  When the receiver 2 is fixed to the buried pipe 1 that is actually used, it may be corroded by water, acidic water, basic water, etc. flowing through the buried pipe 1, and therefore has excellent corrosion resistance such as stainless steel. It is desirable to use a material in which a casing or the like is formed of a material and an internal circuit is protected.

  Next, an impact is given to the striking position 5 of the buried pipe 1. The impact is applied to the buried pipe 1 by dropping a steel ball or hitting it with a hammer. The striking position 5 may be the inner peripheral surface of the buried pipe 1 or may give an impact from the inside of the buried pipe 1.

  As a method of giving an impact, when an impact is given by dropping a steel ball, the impact is given with a constant force by dropping the steel ball from a predetermined height. Also, when impact is applied by a hammer, the hammer is supported by an elastic body such as a spring, and the elastic body is stretched or stretched to a certain length to release the stored elastic force. Impact as a value. Further, the impact force applied to the buried pipe 1 may be acquired as numerical data by using a commercially available impulse hammer. According to the impulse hammer, the impact force can be acquired as numerical data, and the value can be reflected at the time of analysis.

  In addition, in the case where the buried pipe 1 that is actually used is impacted by these instruments, it may come into contact with water, acidic water, basic water, etc., and as such instruments, corrosion resistance such as stainless steel is used. It is desirable to use a material made of an excellent material.

  Next, an elastic wave due to impact is measured by the receiver 2. The elastic wave is measured by measuring it for a predetermined time from the moment the impact is applied and acquiring it as a vibration signal. If the vibration signal is weak, it may be amplified by an amplifier or the like.

  Next, the frequency spectrum of the buried pipe 1 is calculated from the vibration signals obtained by the two receivers 2 in pairs. Specifically, the vibration signals obtained by the two receivers 2 are subjected to FFT (Fast Fourier Transform) processing, and a frequency spectrum is obtained for each receiver 2. Further, the frequency spectrum is processed as a set of intensities at discrete frequencies.

  FIG. 3 is a spectrum diagram showing a frequency spectrum acquired by the degradation value measuring method according to the embodiment of the present invention. FIG. 4 is an image diagram when the frequency spectrum shown in FIG. 3 is represented as a one-dimensional vector.

  Specifically, the frequency spectrum is divided into a predetermined number of elements for a predetermined frequency range, and is processed as a set of spectral intensities of the divided frequencies. That is, the frequency spectrum is processed as a one-dimensional vector of spectrum intensity. For example, when the frequency of the frequency spectrum is divided by 819, the spectrum intensity corresponding to each of the divided frequencies is a vector component having 819 elements.

と表される。ここで、Ｎは、周波数スペクトルを離散した周波数で分割したときの要素数である。これを細分化することにより、周波数スペクトルに近似させることができる。 Here, when the frequency spectrum obtained by one receiver 2 is represented by a vector X and the frequency spectrum obtained by the other receiver 2 is represented by a vector Y,

It is expressed. Here, N is the number of elements when the frequency spectrum is divided at discrete frequencies. By subdividing this, the frequency spectrum can be approximated.

  Next, the deterioration value of the buried pipe 1 is calculated from the frequency spectra obtained by the two receivers 2.

  In the present embodiment, the Euclidean distance D indicating the distance between the two one-dimensional vectors X and Y in the space expressing the one-dimensional vector is used as the deterioration value. The calculation formula is shown below.

ユークリッド距離Ｄは、２つの１次元ベクトルが類似する程より小さい値をとる。したがって、２つの周波数スペクトルの類似する程、２つの周波数スペクトルを表す２つの１次元ベクトルから算出されるユークリッド距離Ｄはより小さい値をとることとなる。

The Euclidean distance D takes a smaller value as the two one-dimensional vectors are similar. Therefore, the more similar the two frequency spectra, the smaller the Euclidean distance D calculated from two one-dimensional vectors representing the two frequency spectra.

  Since the reference buried pipe has no crack and is a symmetric structure with the hitting position 5 as the center, the frequency spectra obtained at two measurement positions that are symmetrical with respect to the hitting position 5 are similar. Is expected to be high, and the Euclidean distance D is considered to be close to zero.

  On the other hand, the buried pipe to be inspected with cracks has frequencies obtained at two measurement positions that are symmetrical with respect to the striking position 5 due to the presence of irregularly generated cracks. The spectrum is expected to have low similarity, and the Euclidean distance D is considered to be a value far from 0 and larger than the Euclidean distance D obtained for the reference buried pipe.

  That is, the Euclidean distance D is an index indicating a deterioration state with respect to structural changes such as cracks in the buried pipe.

  Therefore, by comparing the Euclidean distance D calculated for the inspection target buried pipe and the Euclidean distance D calculated for the reference buried pipe, the deterioration state of the inspection target buried pipe can be quantitatively grasped. Further, since the deterioration state is calculated as a numerical value, the deterioration state can be objectively evaluated unlike arbitrary evaluation by visual observation.

  The method for calculating the deterioration value is not limited to obtaining a one-dimensional vector from two frequency spectra as described above and obtaining the Euclidean distance D from the two one-dimensional vectors. That is, as a method for calculating the deterioration value, a function that can obtain the similarity from two frequency spectra may be used, and the value of the function may be used as the deterioration value.

  As described above, according to the inspection method for inspecting the deterioration state of the buried pipe according to the present invention, the deterioration value measuring method is for inspecting the deterioration state by measuring the frequency spectrum generated by the blow. It is possible to evaluate even if no crack is generated, and it is not necessary to form perforations for investigating the deterioration state in the buried pipe 1, and the deterioration state can be easily inspected.

  The degradation value measuring method is a method for obtaining a degradation value by measuring a frequency spectrum based on an elastic wave due to an impact, and since this elastic wave propagates to the inside of the buried pipe 1 as well, the degradation value is deteriorated. Since the value reflects the internal state of the buried pipe 1, it is possible to grasp not only the outside of the buried pipe 1 but also the internal deterioration state.

  By the way, in the present embodiment, the frequency spectrum is measured at a pair of measurement positions with the striking position 5 as the central position, but is measured at a plurality of pairs of measurement positions at symmetrical positions with the striking position as the central position. May be. In this case, the similarity value of the frequency spectrum is calculated for each of the paired measurement positions, and the deterioration value for the buried pipe is calculated based on the similarity value obtained for the paired measurement positions (for example, the similarity value Sum as degradation value).

In the case of this method, a similarity value is calculated based on the similarity between two frequency spectra obtained in each of a plurality of pairs, and a deterioration value is calculated based on the plurality of similarity values. Since the deterioration state is inspected with respect to the tube 1 from various directions, a more accurate deterioration state can be grasped <Example>
Specific examples will be described below.

[Measurement target]
As the buried pipe 1 (reference buried pipe and inspection target buried pipe) to be measured in this embodiment, a reinforced concrete fume burying having a nominal diameter (inner diameter) of 250 mm and a length of 2 m based on one type of B type of JIS A5373. A tube was used. In addition, a reinforced concrete fume burial pipe (sound pipe) with no cracks was selected as the standard burial pipe. As the buried pipe to be inspected, the sound pipe was dropped and cracks were introduced.

  FIG. 5 is an explanatory diagram for explaining a method of creating a buried pipe to be inspected, FIG. 5 (A) is a state diagram when dropping a healthy pipe, and FIG. 5 (B) introduces a crack. It is the schematic which shows an inspection object buried pipe. In addition, the arrow in FIG. 5 shows the direction of fall.

  The inspection target buried pipe 11 was created by naturally dropping the healthy pipe 10 from the position of a height H30 cm from the ground 15. Moreover, in order to create a buried pipe having different deterioration states such as the size of the crack 6, a tube dropped once and a tube dropped twice were prepared. Here, the inspection target buried pipe 11 dropped once was “small crack degree”, and the inspection target buried pipe 11 dropped twice was “large crack degree”.

  Table 1 is a table showing the degree of cracking when the buried pipe 1 to be measured is viewed from the outside. The buried pipe 1 having a “small crack degree” had a crack width of 0.05 mm or more and 0.50 mm or less, and the number of cracks was about six. The buried pipe 1 having a “large crack degree” had a crack width of 0.05 mm or more and 0.60 mm or less, and the number of cracks was about nine.

[埋設管への衝撃付与]
基準埋設管または検査対象埋設管への衝撃の付与は、鋼球を落下することにより行った。具体的には、大きさ直径３０ｍｍの鋼球を使用し、測定の対象である埋設管の上面から高さ１０ｃｍの距離から鋼球を落下させた。鋼球を落下させた位置（打撃位置５）は、埋設管の両端から等距離にある中心付近とした。

[Impact on buried pipes]
The impact was applied to the reference buried pipe or the buried pipe to be inspected by dropping a steel ball. Specifically, a steel ball having a diameter of 30 mm was used, and the steel ball was dropped from a distance of 10 cm in height from the upper surface of the buried pipe to be measured. The position where the steel ball was dropped (striking position 5) was near the center that is equidistant from both ends of the buried pipe.

[Elastic wave reception method]
As a receiver for receiving the elastic wave, an acceleration sensor of 0 to 10 kHz was used. The vibration signal acquired by the receiver 2 was amplified by a receiving amplifier (manufactured by RION). The amplified vibration signal was stored in a recording device (Data Logger: NR-500 manufactured by Keyence).

  The receiver 2 is arranged at two predetermined positions equidistant from the hitting position 5, in the arrangement 1 shown in FIG. 1 or the arrangement 2 shown in FIG. 2.

  For the reception of the elastic wave, the measurement was individually performed at the arrangement position of the receiver 2 and the arrangement 1 and the arrangement 2 and the vibration signal was recorded for each arrangement.

[Measurement result]
FIG. 6 is a frequency spectrum of a healthy tube measured with the receiver being placed in FIG. 1, FIG. 6 (A) is a frequency spectrum obtained by one receiver, and FIG. 6 (B) is the other. It is the frequency spectrum obtained by the receiver. FIG. 7 is a frequency spectrum of a buried pipe having a “small crack degree” measured in a state where the receiver is arranged 1. FIG. 7A is a frequency spectrum obtained by one receiver. 7 (B) is a frequency spectrum obtained by the other receiver. FIG. 8 is a frequency spectrum of an embedded pipe having a “large cracking degree” measured in a state where the receiver is arranged 1, and FIG. 8A is a frequency spectrum obtained by one receiver. 8 (B) is a frequency spectrum obtained by the other receiver.

  6 to 8 show the arrangement of the receiver 2 in the arrangement 1 shown in FIG. 1 for the buried pipes shown in Table 1 (“healthy pipe”, “small crack degree”, “large crack degree”). 2 shows a frequency spectrum obtained by performing FFT processing on the vibration signal measured in (1). Moreover, (A) and (B) of each figure have each shown the frequency spectrum obtained by two receivers. Comparing the frequency spectra of FIGS. 6 to 8, it can be seen that the similarity between the frequency spectrum shown in FIG. 6A to FIG. 8A and the frequency spectrum shown in FIG. That is, it is understood that the similarity between the two frequency spectra decreases in the order of the “sound pipe”, the “small crack degree” buried pipe, and the “crack degree large” buried pipe.

  FIG. 9 is a frequency spectrum of a healthy tube measured with the receiver placed in the arrangement 2, FIG. 9A is a frequency spectrum obtained by one receiver, and FIG. 9B is the other. It is the frequency spectrum obtained by the receiver. FIG. 10 is a frequency spectrum of a buried pipe having a “small crack degree” measured in a state where the receiver is arranged 2, and FIG. 10A is a frequency spectrum obtained by one receiver. 10 (B) is a frequency spectrum obtained by the other receiver. FIG. 11 is a frequency spectrum of an embedded pipe having a “large cracking degree” measured with the receiver set to be arranged 2, and FIG. 11A is a frequency spectrum obtained by one receiver. 11 (B) is a frequency spectrum obtained by the other receiver.

  9 to 11, the arrangement of the receiver 2 for the buried pipe to be inspected shown in Table 1 (“healthy pipe”, “small crack degree”, “large crack degree”) is the arrangement 2 shown in FIG. A frequency spectrum obtained by performing FFT processing on the vibration signal measured in the above state is shown. Moreover, (A) and (B) of each figure have each shown the frequency spectrum obtained by two receivers. Comparing the frequency spectra of FIGS. 9 to 11, it can be seen that the similarity between the frequency spectrum shown in FIG. 9A to the frequency spectrum shown in FIG. That is, it is understood that the similarity between the two frequency spectra decreases in the order of the “sound pipe”, the “small crack degree” buried pipe, and the “crack degree large” buried pipe.

[Analysis result]
FIG. 12 is a graph showing the Euclidean distances obtained for the buried pipes of “sound pipe”, “small crack degree”, and “large crack degree” with the receiver arranged as 1. FIG. 13 is a graph showing the Euclidean distances obtained for the buried pipes of “sound pipe”, “small crack degree”, and “large crack degree” with the receiver arranged as 2. 12 and 13 show the Euclidean distance for each measurement performed on each of the “sound pipe”, “small crack degree”, and “large crack degree” buried pipes.

  12 and 13, it can be seen that the Euclidean distance D of the healthy tube is a substantially constant value regardless of the number of measurements. Regardless of the arrangement of the receiver 2, the Euclidean distance D of the buried pipe where cracks are present (“small crack degree”, “large crack degree”) is larger than that of the healthy pipe. That is, even if the arrangement of the receiver 2 is either arrangement 1 or arrangement 2, it is possible to grasp the presence of cracks by comparing the healthy pipe and the inspection target buried pipe with respect to the Euclidean distance D.

  Further, according to FIG. 12, it can be seen that the Euclidean distance of the buried pipe 1 having the “large crack degree” is larger than that of the buried pipe 1 having the “small crack degree”. In other words, it can be seen that if the arrangement of the receiver 2 is set to the arrangement 1, the degree of deterioration of the buried pipe 1 can be evaluated.

  Therefore, when inspecting a buried pipe that is actually buried, by obtaining the Euclidean distance D of the reference healthy pipe in advance, whether there is a crack in the buried pipe to be inspected or The deterioration state of the buried pipe can be determined.

It is explanatory drawing explaining an example which showed the state when applying the inspection method of the deterioration state of the buried pipe which concerns on embodiment of this invention, and measuring a buried pipe. It is explanatory drawing explaining the other example which showed the state when applying the inspection method of the deterioration state of the buried pipe which concerns on embodiment of this invention, and measuring a buried pipe. It is a spectrum figure which shows the frequency spectrum acquired by the degradation value measuring method which concerns on embodiment of this invention. It is an image figure when the frequency spectrum shown in FIG. 3 is represented as a one-dimensional vector. It is explanatory drawing explaining the method of creating an inspection object buried pipe, FIG. 5 (A) is a state diagram when dropping a healthy pipe, and FIG. 5 (B) is an inspection object buried pipe into which a crack is introduced. FIG. FIG. 6A shows the frequency spectrum of a healthy tube measured with the receiver set as the arrangement 1, FIG. 6A shows the frequency spectrum obtained with one receiver, and FIG. 6B shows the frequency spectrum obtained with the other receiver. Frequency spectrum obtained. FIG. 7A shows the frequency spectrum of the buried pipe which is “small crack degree” measured in the state where the receiver is placed in FIG. 1. FIG. 7A is the frequency spectrum obtained by one receiver, and FIG. Is the frequency spectrum obtained with the other receiver. FIG. 8A shows the frequency spectrum of the buried pipe measured with the receiver in the arrangement 1 in the state of “large cracking degree”, and FIG. 8A shows the frequency spectrum obtained by one of the receivers. Is the frequency spectrum obtained with the other receiver. FIG. 9 (A) shows the frequency spectrum of a healthy tube measured with the receiver set to the arrangement 2, FIG. 9 (A) shows the frequency spectrum obtained with one receiver, and FIG. 9 (B) shows the frequency spectrum obtained with the other receiver. Frequency spectrum obtained. FIG. 10A is a frequency spectrum of an embedded pipe having a “small crack degree” measured in a state where the receiver is arranged 2, FIG. 10A is a frequency spectrum obtained by one receiver, and FIG. Is the frequency spectrum obtained with the other receiver. FIG. 11A is a frequency spectrum of an embedded pipe having a “large cracking degree” measured in a state where the receiver is arranged 2. FIG. 11A is a frequency spectrum obtained by one receiver, and FIG. Is the frequency spectrum obtained with the other receiver. It is the graph which showed the Euclidean distance calculated | required about each buried pipe of "a healthy pipe", "a crack degree is small", and a "crack degree is large" in the state which set the receiver as arrangement 1. It is the graph which showed the Euclidean distance calculated | required about each buried pipe of "sound pipe | tube", "crack degree small", and "crack degree large" in the state which set the receiver as arrangement 2.

Explanation of symbols

1 buried pipe 2 receiver 5 hitting position 6 crack 14 earth and sand 15 ground

Claims (2)

  For each pipe of the reference buried pipe to be inspected and the inspection target buried pipe to be inspected, the impact position to which the impact is applied is determined, the impact position is impacted, and the symmetrical position with the impact position as the center position The vibration is measured at each of the two measurement positions, the deterioration values are calculated for each of the tubes based on the similarity between the two frequency spectra obtained from the vibrations, and the deterioration values are compared with each other. A buried pipe deterioration state inspection method characterized by determining a deterioration state of a target buried pipe.   For each pipe of the reference buried pipe to be inspected and the inspection target buried pipe to be inspected, the impact position to which the impact is applied is determined, the impact position is impacted, and the symmetrical position with the impact position as the center position Vibrations are measured at a plurality of pairs of measurement positions, and a deterioration value is calculated for each of the tubes based on the similarity of the frequency spectrum for each pair of the plurality of pairs obtained from the vibrations. A buried pipe deterioration state inspection method, wherein the deterioration state of the inspection target buried pipe is determined by comparison.

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