JP2006105680A - Non-destructive inspection method of concrete structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-destructive inspection method of a concrete structure constituted so as not only to sharply reduce the noise component contained in a detected waveform but also to make the change in the waveform caused by back damage or inside damage clear. <P>SOLUTION: In the non-destructive inspection method of the concrete structure 6 using ultrasonic waves, a transmitter 2 and a receiver 3 are brought into contact with a part or the whole of the water immersion part of the concrete structure 6 and the resonance vibration of the concrete structure 6 is detected by the receiver 3 while allowing transversal ultrasonic waves to enter the concrete structure 6 from the transmitter 2. On the basis of the detected waveform of the receiver 3, the back damage and/or inside damage of the concrete structure 6 is judged. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a nondestructive inspection method for a concrete structure using ultrasonic waves, and more particularly, to a nondestructive inspection method suitable for a back surface damage inspection of a concrete structure for a water channel forming a water channel.

  A nondestructive inspection method for a concrete structure using ultrasonic waves is known (for example, see Patent Documents 1 to 3). The method of generating ultrasonic waves includes the case where a transducer that performs electroacoustic conversion is used, and the generation of compressive strain by applying a momentary impact to a small area on the surface of the measurement unit, and the impact elastic wave ( There are two types when using an elastic wave including an ultrasonic component. In the general ultrasonic flaw detection, the former is often used.

  There are two types of ultrasonic waves: longitudinal waves that cause density changes when propagating within an individual and transverse waves that cause shape changes. When ultrasonic waves are propagated vertically to a target member, longitudinal waves are used. Is common. Further, the transverse wave is classified into an SV wave perpendicular to the transmission surface and a parallel SH wave depending on the direction of vibration.

In longitudinal wave ultrasonic waves, the wavelength is greatly related to the resolution at the time of measurement, and generally, the size that can be numerically resolved is said to be 1/4 to 1 / 2λ (wavelength).
The sound velocity, frequency, and wavelength have the following relationship.
C (sound speed) = f (frequency) · λ (wavelength)
Each solid has its own speed of sound, so increasing the frequency reduces the wavelength and improves resolution.

  However, in the case of admixtures such as concrete, longitudinal waves that use density changes are likely to be reflected due to the influence of aggregates, reinforcing bars, etc., so if the wavelength is reduced, the reflection position of sound waves may not be specified. The sound wave may attenuate and may not reach the bottom surface. On the other hand, since the wavelength of the transverse wave does not relate to the vertical direction, there is an advantage that the thickness of the thin plate can be accurately measured even when an audible frequency (20 kHz or less) having a low frequency is used. Scratches that propagate shape changes such as voids cannot be detected. As for the sound velocity of concrete, longitudinal wave velocity = 4,000 m / sec and transverse wave velocity = 2,000 m / sec are often used as common values. In the current concrete ultrasonic flaw detection, longitudinal wave ultrasonic waves have a frequency of 100 kHz. The one of about ~ 400 kHz is used.

  As a nondestructive inspection method for a concrete structure using ultrasonic waves, a shock elastic wave reflection method and a transverse wave ultrasonic resonance method have been put into practical use. The impact elastic wave reflection method has the same concept as the ultrasonic reflection method used for flaw detection of steel materials, but is different in that measurement is performed using an ultrasonic component included in the impact elastic wave. In addition, in the ultrasonic reflection method using a general electroacoustic transducer, a contact medium such as glycerin paste for bringing the transmitter and the surface of the target member into close contact is required in order to propagate the sound wave energy into the target member. However, in the shock elastic wave reflection method using the ultrasonic component of the shock elastic wave, the transmitter can be used for point contact, so that it is not necessary to use a contact medium.

  When conducting a nondestructive inspection of a concrete structure by the shock elastic wave reflection method, as shown in FIG. 1A, the reference sound speed specific to the target member is checked in advance using the parallel method or the transmission method. It is necessary to keep. In concrete structures, since the transmitted sound speed of ultrasonic waves varies depending on the type of cement and the composition of aggregates, it is desirable to measure the reference sound speed near the measurement point of the target member.

  According to the shock elastic wave reflection method, the thickness of the concrete structure can be measured. As shown in FIG. 1 (B), the thickness measurement by the shock elastic wave reflection method is such that a shock elastic wave is incident from the surface of a concrete structure by striking a transmitter and a reflected wave from the back surface is received by a receiver. This is done by detecting with. That is, the thickness of the concrete structure is calculated from the time to the reflection point obtained by exploring from the inside of the concrete structure based on the reference sound velocity measured in advance.

  Moreover, according to the shock elastic wave reflection method, the back surface damage of the concrete structure can be investigated. As shown in FIG. 1C, in the shock elastic wave reflection method, the reflection of the shock elastic wave is disturbed due to the shape of the back surface. Therefore, the state of the reflected wave (size, shape, etc. of the reflected echo) should be determined. Thus, it is possible to determine the state of the back surface. For example, the damaged part and the degree of damage can be specified by using the detection waveform of the healthy part as a reference waveform and comparing the reference waveform with the detection waveform of each measurement point.

  The transverse wave used in the transverse ultrasonic resonance method is an acoustic wave that exists only in a solid. In the transverse ultrasonic resonance method, a horizontal transverse wave called an SH wave is used, so the wavelength acts only in the horizontal direction, and in the vertical direction. Does not matter. For this reason, the wavelength of the sound wave has no correlation with the depth direction (the direction of propagation and travel), and an arbitrary frequency can be used. Moreover, since density change is not used, there is an advantage that it is not affected by density fluctuations such as fine bubbles and internal small-diameter reinforcing bars.

  Solids have an infinite number of natural frequencies, but this phenomenon is particularly noticeable in composite materials such as concrete structures. When a broadband transverse wave is incident on such a member, a wavelength that is likely to be transmitted propagates depending on the natural frequency of the target member, and information on the invisible part can be easily detected. In addition, the natural frequency of a solid is related to the strength and thickness of the solid, and it can be easily detected because the natural frequency changes at a discontinuous shape such as internal peeling or a decrease in member thickness. It is. However, due to the characteristics of the transverse wave, the shape change of the transverse wave propagates in the fine discontinuous part, so it is necessary to have a certain area, but if it is based on the necessity of repair of the concrete structure, a certain amount of area is required. It may be convenient to detect the damage it has and may be convenient.

  According to the transverse wave ultrasonic resonance method, the thickness of the concrete structure can be measured. As shown in FIG. 2, the thickness measurement by the transverse wave ultrasonic resonance method uses a transmitter from the surface of the concrete structure to propagate wideband ultrasonic waves including low-frequency components, and causes membrane vibration to the concrete structure. generate. This membrane vibration is called resonance vibration, and it is an inspection method for estimating the concrete thickness by capturing this resonance vibration with a receiver.

  Moreover, according to the shock elastic wave reflection method, the back surface damage of the concrete structure can be investigated. In other words, since the above-mentioned resonance frequency changes depending on the thickness of the member, the reference resonance frequency is recorded in the sound part, and the change width of the resonance frequency is compared with the resonance method search result at the measurement point. And the shape of the flaw detection waveform, it is possible to estimate the change in the thickness of the member due to the rear surface damage. The sensor installation interval can be arbitrarily set, and can be changed according to the size of the wound to be detected.

Assuming that the shear wave velocity is 2,000 m / sec, the time to propagate the length of 10 cm is as follows.
10cm ÷ 2,000m / sec = 50μsec
And
The frequency at which one wavelength is 50 μsec is
10cm ÷ 50μsec = 20kHz
It becomes.

Thus, when the member thickness of the healthy part is known, the natural frequency of the target member can be known from the relationship with the member thickness by examining the reference sound velocity in the same manner as the elastic wave reflection method. Knowing the natural frequency and the reference sound speed from these relationships makes it possible to estimate the member thickness and the degree of damage.
WO00 / 13008 JP 2003-329593 A JP 2003-329656 A

  The above shock elastic wave reflection method and shear wave ultrasonic resonance method are useful as non-destructive inspection methods for concrete structures and have been put to practical use in various fields of construction and civil engineering. It is empirically known to contain ingredients. In order to identify a damaged part from such a measurement waveform, not only a considerable experience is required, but also the determination criteria are slightly different for each measurement operator, and there is a problem that the determination results vary.

  In recent years, non-destructive inspection using ultrasonic waves has been proposed for concrete structures for waterways such as concrete pipes (PC pipes), box culverts (3 or 4 faces), and lining concrete. Has been. The purpose is to inspect the backside damage (peripheral damage) of the concrete structure for waterways without excavating the surroundings of the concrete structure for waterways, and if this is possible, the inspection cost of the concrete structure for waterways Can be drastically reduced.

  For example, a transmitter and a receiver are brought into contact with the inner peripheral surface of a waterway concrete structure, and a shock elastic wave or a transverse ultrasonic wave is incident on the waterway concrete structure from the transmitter while a reflected wave of the waterway concrete structure is reflected. It is considered that if the receiver detects resonance vibration and the resonance vibration, it is possible to determine the back damage of the concrete structure for the water channel based on the detected waveform of the receiver. Implementation has been difficult due to the problem that water must be drained and the detection waveform contains many noise components.

The present invention was created for the purpose of solving these problems in view of the above circumstances, and is a non-destructive inspection method for concrete structures using ultrasonic waves, part or all of which is provided. A transmitter and a receiver are brought into contact with the flooded portion of the submerged concrete structure, and a transverse wave ultrasonic wave is incident on the concrete structure from the transmitter, and the resonance vibration of the concrete structure is detected by the receiver. It is characterized in that the back damage and / or internal damage of the concrete structure is determined based on the detection waveform of the container. In this way, in the non-destructive inspection of concrete structures by the transverse ultrasonic resonance method, not only can the noise component contained in the detected waveform be significantly reduced, but also the change in the waveform due to back damage and internal damage can be clarified. it can. This is because water acts as a contact medium, so that transverse ultrasonic waves are efficiently incident on the concrete structure, and the resonance vibration of the concrete structure can be efficiently extracted, and the water that has penetrated the concrete structure itself. The cause is considered to be homogenization. As a result, not only a skilled worker but also a damaged part can be easily determined, and the problem that the determination result varies for each measurement worker can be solved.
Further, the concrete structure is a concrete structure for a water channel forming a water channel, and the transmitter and the receiver are arranged on the inner peripheral surface of the concrete structure for water channel without draining water from the concrete structure for water channel. , And the resonant vibration of the concrete structure for a water channel is detected by the receiver while a transverse wave ultrasonic wave is incident on the concrete structure for a water channel from the transmitter. Based on the detected waveform of the receiver, It is characterized by judging the back damage of the concrete structure. In this way, it is possible not only to inspect the backside damage of the concrete structure for a canal without draining water from the concrete structure for a canal, but also the inspection accuracy compared with the case of inspecting after removing the water from the concrete structure for a canal. Can also be improved.
Further, it is a nondestructive inspection method for a concrete structure using a shock elastic wave containing an ultrasonic component, and a transmitter and a receiver are brought into contact with a flooded portion of a concrete structure partially or entirely submerged, and the transmission is performed. The ultrasonic wave reflected in the concrete structure is detected by the receiver while an impact elastic wave is incident on the concrete structure from the vessel, and based on the detected waveform of the receiver, the back damage of the concrete structure and / or It is characterized by determining internal damage. In this way, in non-destructive inspection of concrete structures by the impact elastic wave reflection method, not only can the noise component contained in the detected waveform be significantly reduced, but also the change in waveform due to backside damage or internal damage can be clarified. it can. This is because water becomes a contact medium, impact elastic waves are efficiently incident on the concrete structure, and reflected waves from the concrete structure can be extracted efficiently, as well as by the water that has penetrated the concrete structure itself. The cause is considered to be homogenization. As a result, not only a skilled worker but also a damaged part can be easily determined, and the problem that the determination result varies for each measurement worker can be solved.
Further, the concrete structure is a concrete structure for a water channel forming a water channel, and the transmitter and the receiver are arranged on the inner peripheral surface of the concrete structure for water channel without draining water from the concrete structure for water channel. The ultrasonic wave reflected in the concrete structure for water channel is detected by the receiver while the impact elastic wave is incident on the concrete structure for water channel from the transmitter, and based on the detection waveform of the receiver. The rear surface damage of the concrete structure for waterways is judged. In this way, it is possible not only to inspect the backside damage of the concrete structure for a canal without draining water from the concrete structure for a canal, but also the inspection accuracy compared with the case of inspecting after removing the water from the concrete structure for a canal. Can also be improved.

As described above, according to the present invention, in the nondestructive inspection of a concrete structure by the transverse ultrasonic resonance method or the impact elastic wave reflection method, not only can the noise component contained in the detected waveform be significantly reduced, Waveform changes due to internal damage can be clarified. Thus, not only a skilled worker but also a damaged part can be easily determined, and the problem that the determination result varies among measurement workers can be solved.
In addition, when the nondestructive inspection method of the present invention is applied to a concrete structure for a waterway, it is possible not only to inspect the back surface damage of the concrete structure for a waterway without draining water from the concrete structure for a waterway, but also to a concrete structure for a waterway. The inspection accuracy can be improved as compared with the case where the inspection is performed by removing water from the object.

  Next, embodiments of the present invention will be described with reference to the drawings. In FIG. 3, reference numeral 1 denotes an ultrasonic inspection apparatus, which is adapted to the transverse ultrasonic resonance method or the impact elastic wave reflection method, and has a transmitter 2 (transmission probe). The receiver 3 (reception probe), the oscilloscope 4 (detection waveform display device), the computer 5 (detection waveform storage device), etc. are connected to be used.

  In the ultrasonic inspection apparatus 1 adapted to the transverse wave ultrasonic resonance method, the transmitter 2 and the receiver 3 are brought into contact with the concrete structure 6, and the transverse wave ultrasonic wave is incident on the concrete structure 6 from the transmitter 2. Resonant vibration of the object 6 is detected by the receiver 3, and based on this detected waveform, damage to the back surface or internal damage of the concrete structure 6 can be determined.

  Further, in the ultrasonic inspection apparatus 1 adapted to the shock elastic wave reflection method, the transmitter 2 and the receiver 3 are brought into contact with the concrete structure 6 and a shock elastic wave is incident on the concrete structure 6 from the transmitter 2. The ultrasonic waves reflected in the concrete structure 6 can be detected by the receiver 3, and based on this detected waveform, the back surface damage and internal damage of the concrete structure 6 can be determined.

  The configuration of the ultrasonic inspection apparatus 1 is not particularly limited as long as it conforms to the transverse wave ultrasonic resonance method or the impact elastic wave reflection method, and the ultrasonic inspection apparatus 1 having a known configuration can be used. .

[Non-destructive inspection method 1 for concrete structures]
As shown in FIG. 4, a non-destructive inspection method 1 for a concrete structure according to the present invention brings a transmitter 2 and a receiver 3 into contact with a submerged portion of a concrete structure 6 partially or entirely submerged, thereby transmitting the transmitter. 2, while the transverse wave ultrasonic wave is incident on the concrete structure 6, the resonance vibration of the concrete structure 6 is detected by the receiver 3, and based on the detected waveform of the receiver 3, damage to the back surface of the concrete structure 6 and / or It is also characterized by determining internal damage.

  According to such a method, in the nondestructive inspection of the concrete structure 6 by the transverse wave ultrasonic resonance method, not only can the noise component contained in the detected waveform be significantly reduced, but also the change in the waveform due to backside damage or internal damage is clarified. can do. This is because water acts as a contact medium, so that the transverse ultrasonic waves are efficiently incident on the concrete structure 6 and the resonance vibration of the concrete structure 6 can be efficiently extracted, and the concrete structure 6 itself penetrates. This is considered to be caused by homogenization by the water. Thereby, even if it is not a skilled worker, not only a damaged part can be determined easily, but the problem that the determination result varies for every measurement worker can be solved.

  Although there is no restriction | limiting in the concrete structure 6 used as the test object of the nondestructive inspection method 1, There are many merits when the concrete structure 6 for waterways, such as a concrete pipe, a box culvert, and lining concrete, is made into a test object. That is, the transmitter 2 and the receiver 3 are brought into contact with the inner peripheral surface of the waterway concrete structure 6 without draining water from the waterway concrete structure 6, and the transverse wave is transmitted from the transmitter 2 to the waterway concrete structure 6. Resonant vibration of the waterway concrete structure 6 is detected by the receiver 3 while the sound wave is incident, and damage to the back surface of the waterway concrete structure 6 is determined based on the detected waveform of the receiver 3. According to such an inspection method, it is possible not only to inspect the back surface damage of the waterway concrete structure 6 without draining water from the waterway concrete structure 6, but also to drain water from the waterway concrete structure 6 and inspect it. Compared to the case, the inspection accuracy can also be improved.

[Non-destructive inspection method 2 for concrete structures]
Further, the nondestructive inspection method 2 for a concrete structure according to the present invention, as shown in FIG. 5, the transmitter 2 and the receiver 3 are brought into contact with the flooded portion of the concrete structure 6 partially or entirely submerged. The ultrasonic wave reflected in the concrete structure 6 is detected by the receiver 3 while the impact elastic wave is incident on the concrete structure 6 from the transmitter 2, and the concrete structure 6 is detected based on the detected waveform of the receiver 3. It is characterized by determining the back surface damage and / or internal damage.

  According to such a method, in the nondestructive inspection of the concrete structure 6 by the shock elastic wave reflection method, not only the noise component included in the detected waveform can be greatly reduced, but also the waveform change due to the back surface damage or internal damage is clarified. can do. This is because water acts as a contact medium and impact elastic waves are efficiently incident on the concrete structure 6 and the reflected waves of the concrete structure 6 can be efficiently extracted, and the concrete structure 6 itself penetrates. This is considered to be caused by homogenization by the water. Thereby, even if it is not a skilled worker, not only a damaged part can be determined easily, but the problem that the determination result varies for every measurement worker can be solved.

  Although there is no restriction | limiting in the concrete structure 6 used as the test object of the nondestructive inspection method 2, There are many merits when the concrete structure 6 for waterways, such as a concrete pipe, a box culvert, and lining concrete, is made into a test object. That is, the transmitter 2 and the receiver 3 are brought into contact with the inner peripheral surface of the waterway concrete structure 6 without draining water from the waterway concrete structure 6, and the impact elasticity of the transmitter 2 to the waterway concrete structure 6 is obtained. While receiving the wave, the ultrasonic wave reflected in the concrete structure for water channel 6 is detected by the receiver 3, and based on the detected waveform of the receiver 3, the rear surface damage of the concrete structure for water channel 6 is determined. According to such an inspection method, it is possible not only to inspect the back surface damage of the waterway concrete structure 6 without draining water from the waterway concrete structure 6, but also to drain water from the waterway concrete structure 6 and inspect it. Compared to the case, the inspection accuracy can also be improved.

[Example]
Using the nondestructive inspection method 1 described above, the back flaw inspection of the concrete pipe 7 shown in FIG. 6 was performed. A plurality of simulated damages as shown in FIG. 7 are formed on the outer peripheral surface (back surface) of the concrete pipe 7, the damage area is about 300 mm × 300 mm to 400 mm × 400 mm, and the damage depth is 20 mm to About 60 mm. Further, as shown in FIG. 8, survey lines A, B, and C were set for each damaged portion, and eight measurement points were set on each of the survey lines A, B, and C.

  The concrete pipe 7 was installed in the water tank, and the water level in the water tank was adjusted so that all the measurement points were submerged. Thereafter, the transmitter 2 and the receiver 3 are brought into contact with the measuring point from the inner peripheral surface of the concrete pipe 7, and the transverse vibration is incident on the concrete pipe 7 from the transmitter 2, and the resonance vibration of the concrete pipe 7 is received by the receiver 3. And the detection waveform of the receiver 3 was recorded. Of the detection waveforms recorded at all 24 measurement points, the detection waveforms at 8 points on the measurement line C are shown in FIGS.

  As shown in FIGS. 9 and 10, according to the nondestructive inspection method 1 of the present invention, not only a detection waveform with a small noise component can be obtained, but also the detection waveform (particularly the amplitude) is clear between the healthy part and the damaged part. Changes appeared. This is because water becomes a contact medium, so that the transverse ultrasonic waves are efficiently incident on the concrete pipe 7 and the resonance vibration of the concrete pipe 7 can be taken out efficiently, and the water that has penetrated the concrete pipe 7 itself. The cause is considered to be homogenization.

  In addition, as shown in FIG. 11, when the detection waveforms at three measurement points (A-5, B-5, C-5) having different damage depths are compared, the amplitude of the detection waveform depends on the damage depth. I understood that it would grow. However, since the amplitude of the detected waveform is thought to correlate with the damage area, it is difficult to formulate the amplitude of the detected waveform and the damage depth, but based on the amplitude of the detected waveform, the degree of damage is ranked in several stages. It seems possible enough to divide.

[Comparative example]
Except that the concrete pipe 7 was not submerged, the back flaw inspection of the concrete pipe 7 was performed under the same conditions as in the above-described example. Of the detection waveforms recorded at all 24 measurement points, the detection waveforms at 8 points on the measurement line C are shown in FIGS. As shown in FIGS. 12 and 13, according to the comparative example, not only a large noise component is included in the detected waveform, but also the amplitude of the detected waveform is small as a whole. Although a slight difference appears in the detected waveform between the healthy part and the damaged part, it is not a clear change as in the above-described embodiment, so it seems difficult to accurately identify the damaged part.

(A)-(C) are explanatory drawings of a shock elastic wave reflection method. It is explanatory drawing of a transverse wave ultrasonic resonance method. It is a block diagram of a nondestructive inspection system. It is explanatory drawing which shows the nondestructive inspection method 1 (transverse wave ultrasonic resonance method) of the concrete structure based on this invention. It is explanatory drawing which shows the nondestructive inspection method 2 (shock elastic wave reflection method) of the concrete structure based on this invention. It is sectional drawing of the concrete pipe used for the Example and the comparative example. It is a side view which shows the damaged part of a concrete pipe. It is a side view which shows the measuring point of a concrete pipe. It is a wave form diagram which shows the measurement result of an Example. It is a wave form diagram which shows the measurement result of an Example. It is a wave form diagram which shows the measurement result of an Example. It is a wave form diagram which shows the measurement result of a comparative example. It is a wave form diagram which shows the measurement result of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic inspection apparatus 2 Transmitter 3 Receiver 4 Oscilloscope 5 Computer 6 Concrete structure 7 Concrete pipe

Claims (4)

  A non-destructive inspection method for a concrete structure using ultrasonic waves, in which a transmitter and a receiver are brought into contact with a flooded portion of a concrete structure partially or entirely submerged, and a transverse wave is transmitted from the transmitter to a concrete structure. Resonance vibration of a concrete structure is detected by the receiver while a sound wave is incident, and the back surface damage and / or internal damage of the concrete structure is determined based on a detection waveform of the receiver. Non-destructive inspection method for structures.   The concrete structure is a waterway concrete structure forming a waterway, and the transmitter and the receiver are brought into contact with the inner peripheral surface of the waterway concrete structure without draining water from the waterway concrete structure. And detecting the resonance vibration of the concrete structure for a water channel with the receiver while making a transverse wave ultrasonic wave incident on the concrete structure for a water channel from the transmitter, and based on the detected waveform of the receiver, the concrete structure for a water channel The non-destructive inspection method for a concrete structure according to claim 1, wherein damage on the back surface of the object is determined.   A non-destructive inspection method for a concrete structure using a shock elastic wave containing an ultrasonic component, wherein a transmitter and a receiver are brought into contact with a flooded portion of a concrete structure partially or entirely submerged, and the transmitter The ultrasonic wave reflected in the concrete structure is detected by the receiver while impact elastic waves are incident on the concrete structure, and the back damage and / or internal damage of the concrete structure is detected based on the detected waveform of the receiver. A non-destructive inspection method for a concrete structure, characterized in that   The concrete structure is a waterway concrete structure forming a waterway, and the transmitter and the receiver are brought into contact with the inner peripheral surface of the waterway concrete structure without draining water from the waterway concrete structure. The ultrasonic wave reflected in the concrete structure for water channel is detected by the receiver while the impact elastic wave is incident on the concrete structure for water channel from the transmitter, and the water channel is detected based on the detected waveform of the receiver. 4. The nondestructive inspection method for a concrete structure according to claim 3, wherein damage on the back surface of the concrete structure is determined.

Images