JP2008039429A - Device and method for nondestructive inspection on reinforced concrete structure by electromagnetic wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more surely detect a reflected-wave signal from a crack, a hollow, or the like in a reinforced concrete structure with rebars embedded therewithin. <P>SOLUTION: The nondestructive inspection device comprises: an inspection device body 1 movable to a plurality of positions on a surface of the reinforced concrete structure 6 with rebars 9 embedded therewithin; an electromagnetic wave irradiation means 2 mounted on the device body for irradiating an electromagnetic wave toward the concrete structure; a wave reception means 3 mounted on the device body for acquiring a reflected-wave signal of the electromagnetic wave irradiated from the electromagnetic wave irradiation means; and a signal processing means 4 for detecting a defect in the concrete structure by signal-processing the reflected-wave signal acquired by the reception means. The reception means acquires a plurality of reflected-wave signals different in position with the movement of the device body. The processing means reduces reflected-wave signal components from the rebars by adding up or averaging the plurality of reflected-wave signals different in position acquired by the reception means to detect defects in the concrete structure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for nondestructive inspection of a reinforced concrete structure in which reinforcing bars are embedded by electromagnetic waves.

  In recent years, there are many accidents due to deterioration of concrete structures, and these urgent inspections and repairs are called out. Such concrete structures include structures such as tunnel walls that basically do not contain reinforcing bars, and reinforced concrete structures such as buildings and bridges. As non-destructive inspection methods for these, various methods such as sounding method, ultrasonic method, electromagnetic wave radar method, laser method, infrared method have been researched and developed. There is nothing.

  In addition, nondestructive inspection methods using radar (electromagnetic waves) have been researched and developed. Radar has the advantage of good operability. However, the conventional grayscale image method is a method in which the grayscale image of the radar reception signal is visually observed to determine whether there is an abnormality, and both reliability and accuracy are low and cannot be recommended.

  The conventional nondestructive inspection using the gray image will be described. When scanning with an electromagnetic wave radar, an electromagnetic wave pulse is transmitted and received at a certain distance, but it is 2 in the depth direction and the scanning direction according to the full-wave rectified waveform obtained by rectifying the received signal obtained at each point. This is a dimensionally shaded image. Then, an inspector visually observes this grayscale image, thereby estimating and diagnosing an abnormality inside the concrete. For reference, reinforced concrete with a 15.9 mm diameter reinforcing bar arranged in a grid pattern over two layers of depth 80 mm and 150 mm in Fig. 27 crosses the other orthogonal reinforcing bars through the center of the adjacent reinforcing bars. A gray image when the radar is scanned is shown. The arc-shaped pattern that appears in the center of the figure (convex upward) is due to the reflected wave from the upper crossing rebar. In this pattern, if the distance between the electromagnetic wave radar and the crossing rebar is close, the arrival time of the reflected wave from the rebar is early and the amplitude of the reflected wave is large, but the arrival time is delayed and the amplitude decreases as the distance increases. This is what happens. Further, an upward convex thin arc-shaped image appears at a deep depth between these arc-shaped images, which is due to a reflected wave from the lower crossing reinforcing bar. Thus, in reinforced concrete, it turns out that the reflected wave from a reinforcing bar is very large. Therefore, even if a crack or the like is present inside, the reflected wave from these is smaller than the reflected wave from the reinforcing bar, and it is extremely difficult to detect the crack from the grayscale image.

Patent Document 1 describes a non-destructive inspection technique for a reinforced concrete structure using electromagnetic waves, which is a conventional technique of the present invention. The cracks around the reinforcing bars are detected by comparing the measured extreme values of reflected waves with sound data. Similarly, Patent Document 2 describes the prior art of the present invention. A concrete structure is nondestructively inspected by pattern matching between an actual received signal and a predicted received signal waveform.
JP-A-2005-331404 JP 2003-207463 A

  The present invention reduces a reflected wave signal from a reinforcing bar by a simple method and non-destructively inspects a reinforced concrete structure in which the reinforcing bar is embedded by using an electromagnetic wave. It is an object of the present invention to provide an apparatus and a method that can detect more reliably.

  In order to solve the above problems, the present invention has the following configuration.

  An inspection apparatus body movable to a plurality of positions on the surface of a reinforced concrete structure in which reinforcing bars are embedded, an electromagnetic wave irradiation means mounted on the inspection apparatus body and radiating electromagnetic waves toward the reinforced concrete structure, The reinforced concrete structure is mounted on the inspection apparatus main body and receives the reflected wave signal of the electromagnetic wave emitted from the electromagnetic wave irradiating means, and the signal processing of the reflected wave signal obtained by the wave receiving means. A signal processing means for detecting a defect, wherein the wave receiving means acquires a plurality of reflected wave signals at different positions as the inspection apparatus body moves, and the signal The processing means adds or averages a plurality of reflected wave signals at different positions acquired by the wave receiving means, thereby obtaining the reinforcing bar. It reduces reflection wave signal component of et, and detects a defect of the reinforced concrete structure from the addition or averaged reflected wave signal.

  The inspection apparatus main body moving step of moving the inspection apparatus main body to a plurality of positions on the surface of the reinforced concrete structure in which the reinforcing bars are embedded, and the electromagnetic wave irradiation means mounted on the inspection apparatus main body toward the reinforced concrete structure An electromagnetic wave irradiation step of irradiating an electromagnetic wave, and a step of acquiring a reflected wave signal of the electromagnetic wave irradiated in the electromagnetic wave irradiation step by a wave receiving means mounted on the inspection device body, wherein the inspection device body is moved. Along with this, a wave receiving step of acquiring a plurality of reflected wave signals at different positions, and a step of detecting defects in the reinforced concrete structure by performing signal processing on the reflected wave signal acquired by the wave receiving step, The reflected wave signal component from the reinforcing bar is reduced by adding or averaging a plurality of reflected wave signals obtained at different positions, and added. Having a signal processing step of detecting a defect of the reinforced concrete structure from the averaged reflected wave signal.

  Moreover, it has the following embodiments.

  The range of movement of the inspection apparatus main body is between a position on the surface closest to the crossing rebar and a position on a surface approximately in the middle between the crossing rebar and the next crossing rebar adjacent thereto, and the signal The processing means (step) detects the defect of the reinforced concrete by adding or averaging a plurality of reflected wave signals having different positions within the moving range.

  The added or averaged reflected wave signal is expressed as a sum of a plurality of reflected wave signals resulting from the structure of the reinforced concrete structure and a crack reflected wave signal from a crack, and the signal processing means (step) includes: A crack is detected by extracting and analyzing the components of the plurality of reflected wave signals and the crack reflected wave signal.

  The plurality of reflected wave signals resulting from the structure of the reinforced concrete structure include at least a surface reflected wave signal that is a reflected wave from the surface of the reinforced concrete structure and a bottom surface that is a reflected wave from the bottom surface of the reinforced concrete structure. A reflected wave signal is included.

  The reinforced concrete structure has one or more surface layers on the surface, and a plurality of reflected wave signals resulting from the structure of the reinforced concrete structure are further reflected from the bottom surfaces of the one or more surface layers. It includes a surface layer bottom surface reflected wave signal which is a wave. Examples of the surface layer include an asphalt surface.

  The plurality of reflected wave signals resulting from the structure of the reinforced concrete structure further include a parallel reinforcing bar reflected wave signal that is a reflected wave from a reinforcing bar parallel to the moving direction of the inspection apparatus main body.

  The surface reflected wave signal is approximated by an average value of the reflected wave signal when scanning the surface of a normal portion where the reflected wave signal from the reinforcing bar parallel to the scanning direction and the reflected wave signal from the defect do not appear. And

  The defects are cracks, cavities, or bottom surface defects.

  By adopting the above configuration, the present invention can reduce the reflected wave signal from the reinforcing bar by a simple method and more reliably detect the reflected wave signal from the defect (crack, cavity, etc.). When the transmission / reception wave position is changed, the arrival time of the reflected wave signal from the crossing rebar changes, so that the reflected wave signals from the crossing rebar having different transmission / reception wave positions have different phases. On the other hand, defects such as cracks often spread to the same depth, and the phase of the reflected wave signal hardly changes even if the transmission / reception wave position is changed. The inventor can simply add (average) a plurality of reflected wave signals at different positions to cancel the reflected wave signal component from the crossing rebar, and the signal from a defect such as a crack is emphasized. I found out. Since it is sufficient to simply add the signals, simple signal processing is sufficient, the apparatus can be simplified and the inspection speed is improved. Moreover, the reflected wave signal from a crossing rebar can be canceled more reliably by setting the scanning range between the point just above the crossing rebar and the point just above the intermediate part between the adjacent crossing rebars.

  An embodiment of the present invention will be described. FIG. 1 is a schematic diagram of an apparatus according to the present embodiment. An electromagnetic wave irradiation means 2 and a wave receiving means 3 are mounted on the inspection apparatus main body 1. The inspection apparatus main body 1 moves on the surface of the reinforced concrete structure 6. There is asphalt 7 on the surface of the reinforced concrete structure 6, and concrete 8 thereunder. Further, reinforcing bars 9 are periodically embedded in the concrete 8. As the inspection apparatus main body 1 moves, the electromagnetic wave irradiation means 2 and the wave receiving means 3 are driven to acquire reflected wave signals from different positions. The signal processing unit 4 adds (averages) the acquired reflected wave signals from different positions, detects a signal from a defect such as a crack, and displays the detection result on the display unit 5.

  When electromagnetic waves are emitted from the transmitter of the electromagnetic wave radar to the reinforced concrete, as shown in Fig. 2, at the normal location, the receiver is observed with three reflected waves superimposed from the concrete surface, the crossed reinforcing bars and the bottom surface. FIG. 2 shows a cross section in the case of a single-layer reinforcing bar, but in the case of a two-layer reinforcing bar, a weak reflected wave from the crossing reinforcing bar in the second layer (lower layer) is also added. Therefore, when a large number of reinforcing bars are arranged in one or two layers like a reinforced concrete, the small reflected wave from the crack is buried in the large reflected wave from the reinforcing bar. It is difficult to detect cracks visually. Therefore, here, pre-processing for effectively removing the reflected wave from the crossing rebar will be described. Now, if the radar is scanned so that it intersects perpendicularly with other orthogonal crossing reinforcing bars through the center of adjacent reinforcing bars, the distance between the radar and the crossing reinforcing reinforcing bars changes, so the arrival of reflected waves from the crossing reinforcing bars Time varies depending on the scanning distance. Therefore, considering that the fundamental reflected waveform of the electromagnetic wave radar is a spindle-shaped vibration waveform, when the received signals in the appropriate section are averaged, the reflected waves from many crossed reinforcing bars whose phases are shifted will be added. The influence of the reflected wave from the crossing rebar can be reduced. Of course, since the reflected waves from the concrete surface and the bottom surface do not disappear even if they are averaged, by averaging the received signals, the sum of these two reflected waves remains as the received signal. Therefore, if there is a crack parallel to the surface to some extent, the reflected wave from this crack will not disappear by the averaging process, so it will be added to the previous two reflected waves. Therefore, if a nondestructive inspection method using a signal propagation model is applied to this average waveform, the crack position and crack depth can be detected accurately. In addition, although it is the area to average, what is necessary is just to set it as a unit from right above a cross rebar to the center with the next cross rebar.

  To confirm the removal of the reflected wave from the crossing rebar, we will perform a simulation to confirm. Consider the case where an electromagnetic wave radar is scanned perpendicularly to a 20 mm diameter reinforcing bar 80 mm deep from the surface. In addition, the waveform of FIG.3 and FIG.4 obtained by experiment was used here as a reflected wave from a concrete surface (henceforth a surface wave) and a basic reflected waveform from a crossing reinforcing bar. In addition, as the intensity and propagation time of the reflected wave from the crossing reinforcing bars, the signal propagation model derived by the inventor was used (Japanese Patent Application No. 2006-132996). For reference, FIG. 5 shows a simulation waveform showing a received signal waveform when the center of the electromagnetic wave radar is placed directly above the crossing rebar (x = 0 mm) and at a position 60 mm and 120 mm away from the crossing rebar. It can be seen that the received signal waveform changes greatly in the latter half of the surface wave. Now, when the waveform obtained by averaging the reception signal waveforms in the section from x = 125 mm directly above the crossed reinforcing bar (x = 0 mm) is as shown by the broken line in FIG. In the figure, surface waves are also drawn together (solid lines), but they are very similar, and it can be seen that the reflected waves from the crossing rebar can be effectively removed by this embodiment. For reference, when the surface wave is subtracted from the received signal at x = 0 mm and x = 60 mm and the above average waveform, the result is as shown in FIG. 7, and the average waveform is not subjected to average value processing (x = 0 mm and 60 mm). B) Compared with the received signal, the influence of the reflected wave from the crossing rebar can be greatly suppressed.

Here, the received signal is modeled on the assumption that a substantially parallel crack has occurred on the concrete surface. If the reflection waveform from the concrete surface is represented by r ₀ (t) and the basic reflection waveform from the medium boundary surface such as a crack is represented by r (t), the average waveform r _ave (t) is modeled by the following equation: it can.

ただし，a_i(i = 0,
1, 2)はそれぞれ表面、クラック、底面からの反射波の一次結合係数を、またT_i(i = 0,
1, 2)はそれら反射波の伝播時間を表す。ここで、表面波の一次結合係数a₀及び伝播時間T₀ は実験により予め求めることができるので、既知とできる。従って、求めるべき未知パラメータは{a₁, a₂, T₁, T₂}となるが、これらは次の評価関数を最小化することにより求められる。

Where a _i (i = 0,
1, 2) is the primary coupling coefficient of the reflected wave from the surface, crack and bottom, respectively, and T _i (i = 0,
1, 2) represents the propagation time of these reflected waves. Here, since the primary coupling coefficient a ₀ and the propagation time T ₀ of the surface wave can be obtained in advance by experiments, they can be known. Therefore, the unknown parameters to be obtained are {a ₁ , a ₂ , T ₁ , T ₂ }, which are obtained by minimizing the following evaluation function.

ここで、r_ave(t)は実際に求められた平均波形である。つまり、実際の平均波形r_ave(t)とモデル波形r^*(t)のパターンマッチング角を最小にするパラメータ{a₁, a₂, T₁, T₂} を求めることにより、クラックの深度を求めようとするものである。なお、（数２）式において、最適なa₁, a₂ はr_ave(t) -a₀r₀(t-T₀)をr(t
- T₁), r(t - T₂)で張られる空間に直交射影することにより，任意のT₁, T₂ に対して解析解

Here, r _ave (t) is an average waveform actually obtained. In other words, by determining the parameters {a ₁ , a ₂ , T ₁ , T ₂ } that minimize the pattern matching angle between the actual average waveform r _ave (t) and the model waveform r ^* (t), the crack depth is reduced. It is what you want. In equation (2), the optimum a ₁ and a ₂ are r _ave (t) -a ₀ r ₀ (tT ₀ ) r (t
-Analytical solution for any T ₁ , T ₂ by orthogonal projection onto the space spanned by T ₁ ), r (t-T ₂ )

が得られるので、（数２）式の最小化はT₁, T₂に対してのみ数値的に行えばよい。なお、（数３）式のr₁，r₂はr₁ = r(t - T₁),r₂ = r(t - T₂) の意である。なお，(・，・) 及び||・||はそれぞれヒルベルト空間の内積及びノルム記号である。上記の最適化により{a^* ₁, a^* ₂ , T^* ₁ , T^* ₂} が得られれば、a^* ₁の大きさを見ることにより、クラックの有無を判断することができる。つまり、a^* ₁はクラックからの反射波の大きさを表すことになるので、(1)a^* ₁ が小さな値であれば、底面以外からの反射波は生じていない（つまり，正常）ことになるが、(2)大きな値であれば、クラックがあり、かつ、そのときの伝播時間T^* ₁によってクラックの深度L^*= [(T^* ₁ - T₀)/2]Vが求まることになる。なお、V (=ｃ／√ε) (ｃ：光速，ε：比誘電率) はコンクリート中の電磁波速度を表す。

Therefore, the minimization of Equation (2) may be performed numerically only for T ₁ and T ₂ . Note that r ₁ and r _{2 in the} equation (3) mean r ₁ = r (t−T ₁ ) and r ₂ = r (t−T ₂ ). (・, ・) And || ・ || are the inner product and norm symbol of Hilbert space, respectively. If {a ^* ₁ , a ^* ₂ , T ^* ₁ , T ^* ₂ } is obtained by the above optimization, the presence or absence of a crack can be determined by looking at the size of a ^* ₁ . In other words, since a ^* ₁ represents the magnitude of the reflected wave from the crack, (1) If a ^* ₁ is a small value, no reflected wave from the bottom surface is generated (that is, normal) (2) If the value is large, there is a crack, and the crack depth L ^* = [(T ^* ₁ -T ₀ ) / 2] V can be obtained from the propagation time T ^* _{1 at} that time become. V (= c / √ε) (c: speed of light, ε: relative dielectric constant) represents the speed of electromagnetic waves in concrete.

Accordingly, a suitable live value gamma provided, determines as normal if a ^* ₁ <γ (thickness of the concrete structure at this time _{^{[(T * 2 - T 0}} ) / 2] V), a * 1 > γ, it is judged as abnormal, and the crack depth and concrete thickness at this time are [(T ^* ₁ -T ₀ ) / 2] V and [(T ^* ₂ -T ₀ ) / 2] V, respectively. It is obtained by.

  Although the case where there is one crack has been described above, the above inspection system can be easily expanded by increasing the number of reflected waves even when there are two or more cracks or when there are cavities. In other words, if there are two cracks, the number of reflected waves should be increased by one, and if there is one cavity, the number of reflected waves from the bottom of the cavity should be increased.

  The experimental results are shown below.

[Example 1] In the case of a floor slab from which asphalt has been removed Here, an expressway floor slab is considered as one of the reinforced concrete structures. Then, firstly, a test body in which a highway floor slab was cut out and then the asphalt portion on the surface was peeled off was considered. A schematic diagram of the test specimen is shown in FIG. Although this specimen is an expressway floor slab, it can be thought of as reinforced concrete in a building because the asphalt has been removed. The thickness of the test specimen is 180 mm, but two layers of upper and lower grid-like reinforcing bars with a reinforcing bar diameter of 15.9 mm are arranged. Note that the depths of the first layer and the second layer are about 70 mm and 140 mm, respectively.

In the figure, the y-axis direction represents the direction in which the vehicle travels, and the x-axis direction represents the direction orthogonal thereto, but the pitch of the first layer rebar is about 250 mm and 320 mm in the y-axis and x-axis directions, respectively. On the other hand, the pitch of the second-layer reinforcing bars is about 125 mm and 160 mm in the y-axis and x-axis directions, respectively. In other words, the pitch of the reinforcing bars in the second layer is half the distance (that is, densely) in the first layer. Furthermore, in the second layer, as shown in Fig. 2 (b), there are places where two reinforcing bars are bundled and arranged to increase the strength in some places (Fig. 1 (a)).
Shows only the arrangement of the first-layer reinforcing bars).

  When the above specimen is scanned by an electromagnetic wave radar with [0mm, 950mm] in the x-axis direction passing through the center of adjacent reinforcing bars in the y-axis direction and perpendicular to the crossing rebar in the x-axis direction The (conventional) B-mode grayscale image is shown in FIG. From the figure, arc-shaped dark and shaded images appear at three locations of 150 mm, 480 mm, and 800 mm, respectively, but it is clear that these are due to the crossing reinforcing bars in the first layer. Between these arc-shaped gray images, another extremely thin arc-shaped gray image is seen fainting downward, and these represent reflected waves from the second-layer crossing rebar. With the conventional gray-scale image viewing method, only this level can be known, and it is difficult to determine whether there are abnormalities such as cracks in the concrete.

Next, in order to remove the influence of the reflected wave from the crossing rebar by the method of this paper, the whole inspection section [0mm, 950mm] is taken as (one section from right above the crossing rebar to the center of the adjacent crossing rebar) It was divided into six sections S1 to S6, the average waveform of the received signal was obtained in each section, and the proposed method was applied to each average waveform. At that time, the waveform shown in FIG. 10 was used as the basic reflection waveform from the crack. Further, as the surface reflected wave that is a reflected wave from the concrete surface, an averaged electromagnetic wave radar reception signal when orthogonal cross scanning with the crossing rebar was used as an approximate solution. As a result, the primary coupling coefficient a ^* ₁ of the reflected wave from the crack was as shown in FIG. The coefficient a ^* ₁ is shown as a representative at the center of each section. Since the threshold value is now γ = 0.05, it can be determined from the figure that S1 to S4 are abnormal and S5 and S6 are normal. Then, in the sections S1 to S4 determined to be abnormal, the crack position and the bottom surface position were determined from T ^* ₁ and T ^* ₂ , and in the sections S5 and S6 determined to be normal, the bottom surface position was determined from T ^* ₂ . Came to show. In the figure, the □ mark and the * mark indicate the position of the crack and the floor slab bottom (that is, the depth), respectively. As the relative dielectric constant of concrete, 8 used for general concrete was adopted.

  From the figure, it can be seen that the thickness of the floor slab measured by this example is almost 180 mm, which is almost the same as the actual value. It can also be seen that inclined cracks occur in the section from S1 to S4 over a depth of 48 mm to 76 mm. In order to verify these diagnostic results, coring was performed near the boundary between sections S2 and S3. A photograph of the inside of the coring hole at this time is shown in FIG. 13. The crack actually observed by coring had an inclination, and the depth of the crack ranged from about 55 mm to 70 mm. Therefore, it can be seen that the position and depth of the crack can be measured with very high accuracy in this embodiment.

  For reference, the received signal waveform after the average processing at the abnormal location S2 and the normal location S6 and the optimum predicted waveform (based on the model) according to the proposed method are shown in FIGS. 14 and 15. It is very similar and the rationality of the method of this embodiment can be confirmed.

[Example 2] In the case of a floor slab in which asphalt has not been peeled Next, an experiment was conducted on a highway floor slab specimen in a state before the asphalt was peeled off. In other words, an inspection experiment was conducted on a floor slab that was essentially a freeway. This is to check whether or not the abnormality diagnosis of the highway floor slab can be accurately performed even when the asphalt is not peeled off. A schematic diagram of the test specimen and the experiment is shown in FIG. The scanning line is the same as in the first embodiment.

  For reference, the gray image at this time is shown in FIG. 17, but since the asphalt thickness is 50 mm, the arc-shaped pattern due to the reflected wave from the crossing reinforcing bars not only recedes toward the deeper depth, The image is lighter than before. For the radar received signal at this time, the scanning range was divided into six sections S1 to S6 as in the first embodiment. Then, the received signal was averaged in each section, and the present embodiment method was applied.

  For reference, the average waveform for the section S1 at this time is shown in FIG. 18, but it can be seen from the first part of the received signal that the waveform is different from the waveform when the asphalt is peeled off (FIGS. 14 and 15). This is because the reflected wave from the boundary surface between asphalt and concrete is newly added to the received signal. Therefore, when diagnosing floor slabs without removing asphalt, if there is a crack, three new reflected waves from the surface, crack, and bottom surface are added to the reflected surface from the interface between asphalt and concrete. It can be seen that the four-reflection model considered must be adopted.

Therefore, for the asphalt-equipped highway floor slab specimen, using the four-reflected wave model, firstly the primary coupling coefficient a ^* ₀ , a of the surface wave, the boundary surface (of asphalt and reinforced concrete), the crack and the reflected wave of the bottom ^* ₁ , a ^* ₂ , a ^* ₃ and propagation times T ^* ₁ , T ^* ₂ , T ^* ₃ were obtained (T ^* ₀ is known). FIG. 19 shows the primary coupling coefficient a ^* ₂ of the reflected wave from the crack in the sections S1 to S6 at this time. If the same threshold value γ = 0.05 as in Example 1 is adopted, in the range from S1 to S4, (the primary coupling coefficient of the reflected wave from the crack) a ^* ₂ is larger than the threshold value. It can be seen that cracks have occurred in the two sections. And for this section, the asphalt thickness, crack and bottom position are calculated from T ^* ₁ , T ^* ₂ and T ^* ₃ respectively, and a ^* _{2 is the} threshold value for the remaining sections S5 and S6. Since it became smaller, it was determined to be normal, and as a result of obtaining the thickness of the asphalt and the position of the bottom surface from T ^* ₁ and T ^* ₃ for this section, it was as shown in FIG. In addition, (triangle | delta) mark in a figure shows the position of the boundary surface of asphalt and concrete, and □ mark and * mark show the position of a crack and a floor slab bottom, respectively, similarly to Example 1. In this case, standard 5 and 8 were adopted as the relative dielectric constant of asphalt and concrete, respectively.

  From the figure, it can be seen that the thickness of the asphalt is not only measured with high accuracy and with high accuracy, but also the crack position and depth can be detected with high accuracy without removing the asphalt (for reference, the asphalt is removed). The maximum difference in crack depth measurement between the case of no peeling and the case of peeling is 4.5 mm). However, the depth of the bottom surface is measured slightly shallower than the actual measurement value of 230 mm, because this depth is near the limit of the exploration depth of the electromagnetic wave radar used in this experiment. From this, it can be seen that in order to perform more accurate measurement / diagnosis up to the position of the bottom without peeling off the asphalt, it is necessary to use an electromagnetic wave radar having a slightly larger exploration depth (that is, greater power).

  Anyway, it was found that the non-destructive inspection results for the highway floor slab specimens with asphalt were almost as accurate as those for the asphalt peeled specimens.

  Here, standard values for the physical properties such as the relative permittivity are used here for convenience, but a measurement result with sufficient accuracy can be obtained. If you want to obtain more reliable measurement values at the site, you can consider coring and analyzing, or measuring the dielectric constant using the reflected waves from the reinforcing bars.

  In the first and second embodiments, an ideal case when scanning with an electromagnetic wave radar was considered, that is, a case where a scan line was scanned in the direction of another crossing reinforcing bar passing through the center of two adjacent reinforcing bars. In the inspection, it is naturally desirable that there are as few restrictions on the scanning line as possible. Therefore, the following is an example when scanning different from that in Examples 1 and 2 is performed.

[Example 3] When the scanning line deviates from the center of the two parallel reinforcing bars As shown in FIG. 21, in the highway floor slab specimen when the asphalt of Example 2 is not peeled off, y = 0 mm is set in the scanning direction. The electromagnetic wave radar was shifted from the center and scanned in parallel with the x-axis at intervals of 20 mm within a range of ± 120 mm directly above the rebar. However, the scanning section in the x-axis direction was commonly set to the previous S3 section (about 160 mm), and the average waveform of the received signal in the section was obtained for each scanning line. When the scanning line is close to the scanning direction reinforcing bar, the reflected wave from the scanning direction reinforcing bar is constantly added to the received signal. Therefore, the reflected wave from the scanning direction reinforcing bar is newly added to the previous reflected wave model. Decided to do. In other words, a five-reflection model that takes into account five reflected waves from the asphalt surface, asphalt bottom, scanning rebar, crack, and floor slab bottom was adopted.

  At this time, the primary coupling coefficient of the reflected wave from the crack obtained by the proposed system is shown in FIG. 22, but in the scanning line close to the scanning direction reinforcing bar, the reflected wave from the scanning direction reinforcing bar is large. The primary coupling coefficient of the reflected wave becomes smaller. The coefficient of the reflected wave from the scanning direction reinforcing bar is shown in FIG. 23. The absolute value of the reflected wave coefficient is large in the vicinity of the scanning direction reinforcing bar. It can be seen that the primary coupling coefficient of the reflected wave from the reinforcing bar decreases rapidly. Conversely, the reflected wave primary coupling coefficient from the crack increases.

  By the way, as in the previous embodiment, the threshold value for the primary coupling coefficient of the reflected wave from the crack is set to 0.05, and the portion where the primary coupling coefficient is larger than this value (determined that there is a crack), the asphalt bottom from the reflected wave arrival time. Then, the depth of the crack and the floor slab bottom was obtained, and the depth of the asphalt bottom and the floor slab bottom was obtained at other points. This result is shown in FIG. 24. As for the depth of the bottom surface of the asphalt and the floor slab, the same measured values as in Example 2 were obtained, and the measured depth of cracks was about 105 mm. Thus, almost the same result as that obtained by scanning the center of the reinforcing bar in the scanning direction is obtained. However, since the reflected wave from the scanning bar is large in the vicinity of the scanning reinforcing bar, cracks are not detected in this area of ± 40 mm. I understand that there is.

  For reference, the same threshold value 0.05 as in the case of cracks was adopted for the reinforcing bar in the scanning direction, and the depth of the reinforcing bar in the scanning direction was obtained at the position of the scanning line with the primary coupling coefficient larger than this threshold value. Is indicated by a thick line in FIG. From the figure, the depth of the reinforcing bar increases as the distance between the radar and the scanning reinforcing bar increases, because the arrival time of the reflected wave from the scanning reinforcing bar is delayed. In addition, this is not a crack but an effect from the scanning direction reinforcing bar, which can be easily identified because the reflected wave primary coupling coefficient is negative.

  From the above, it was found that, when scanning with an electromagnetic wave radar, detection of cracks and measurement of crack depth are possible if they are separated from the reinforcing bars in the scanning direction by about 40 mm or more. Note that the reflection wave coefficient of the crack is lower than the threshold value of 0.05 near the scanning direction reinforcing bar, but when the crack depth is forcibly determined as a crack in the test, it becomes as shown by ◆ and away from the scanning direction reinforcing bar. It can be seen that this is almost the same as the crack depth found in the scanning line. Therefore, it is possible to create a general system in which there is a reflected wave regardless of the presence or absence of the reflected wave from the scanning direction reinforcing bar.

[Embodiment 4] When the scanning line crosses the reinforcing bar diagonally Next, let us consider a case where the radar crosses the reinforcing bar diagonally at a certain angle instead of orthogonal crossing. For reference, here are the non-destructive inspection results for three angles of 10 degrees, 30 degrees, and 60 degrees. However, intersections are an area S ₃ with a crack. At this time, as before, FIG. 25 shows the primary coupling coefficient of the reflected wave from the crack when the proposed system is applied to the average waveform of the received data from 120 mm before the intersection with the reinforcing bar to the intersection. It is. At any angle, the primary coupling coefficient has a value larger than the above-described threshold value of 0.05, and it can be seen that a crack is generated immediately below the scanning line. Here, a four-reflected wave model is adopted, but the depth of the bottom surface of the asphalt, cracks, and concrete bottom surface is obtained from the arrival time of each reflected wave at this time, as shown in FIG.

  As described above, according to Examples 3 and 4, it was found that crack detection and position measurement can be performed with high accuracy even when a considerable degree of freedom is given to the scanning line of the electromagnetic wave radar. In other words, this means that even when the crack is inclined with respect to the concrete surface, it is possible to find a direction in which the reflected wave from the crack can be emphasized, and the crack does not necessarily have to be parallel to the concrete surface. It shows that.

1 is a schematic diagram of an embodiment of the present invention. The figure which shows the propagation path of electromagnetic waves. Waveform of reflected wave from concrete surface. Waveform showing the reflected wave from the reinforcing bar. Waveform at each position when the inspection apparatus body moves on the reinforcing bar (x is the horizontal distance from the reinforcing bar). The graph which shows the difference in the waveform of the reflected wave from the surface, and the average reflected wave. The graph which shows the difference of the waveform of the received reflected wave and the reflected wave from the surface. 1 is a schematic diagram of a test body of Example 1. FIG. FIG. 2 is a B-mode grayscale image that is the conventional technology of Embodiment 1. FIG. Basic reflection waveform from the crack. 3 is a graph showing a primary coupling coefficient of a reflected wave from a crack in Example 1. FIG. 3 is a graph showing measurement results of Example 1. A photo inside the coring. The graph which shows the comparison of the received signal waveform after an average process, and the optimal prediction waveform in abnormal area S2. The graph which shows the comparison of the received signal waveform after an average process, and an optimal prediction waveform in normal area S6. FIG. 3 is a schematic view of a test body of Example 2 and an experiment. FIG. 6 is a B-mode grayscale image that is a conventional technique of Embodiment 2. FIG. The average waveform with respect to area S1 in Example 2. FIG. The graph which shows the primary coupling coefficient in the reflected wave from a crack in Example 2. FIG. 6 is a graph showing measurement results of Example 2. Schematic of the test body and experiment of Example 3. 6 is a graph showing a primary coupling coefficient of a reflected wave from a crack in Example 3. The graph which shows the primary coupling coefficient in the reflected wave from a parallel reinforcing bar in Example 3. FIG. 10 is a graph showing measurement results of Example 3. The graph which shows the primary coupling coefficient in the reflected wave from a reinforcing bar in Example 4. FIG. 10 is a graph showing measurement results of Example 4. B-mode grayscale image of the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inspection apparatus main body 2 Electromagnetic wave irradiation means 3 Wave receiving means 4 Signal processing means 5 Display means 6 Reinforced concrete structure 7 Asphalt 8 Concrete 9 Reinforcing bar

An inspection apparatus main body that moves substantially linearly on the surface of a reinforced concrete structure in which reinforcing bars are embedded, an electromagnetic wave irradiation means that is mounted on the inspection apparatus main body and irradiates electromagnetic waves toward the reinforced concrete structure, and The reinforced concrete structure is mounted on the inspection apparatus main body and receives the reflected wave signal of the electromagnetic wave emitted from the electromagnetic wave irradiating means, and the signal processing of the reflected wave signal obtained by the wave receiving means. A signal processing means for detecting a defect, wherein the moving range of the inspection apparatus main body is a position on the surface closest to the reinforcing bar and another reinforcing bar that is parallel and adjacent to the reinforcing bar. It includes a location on substantially intermediate surface between, between at least, the reception means, with the movement of the inspection apparatus main body, the movement range Obtaining a plurality of reflected wave signals of successive different positions in the inner, the signal processing means, obtained by the wave receiving means, adding or averaging a plurality of the reflected wave signal of successive different positions within the movement range To reduce the reflected wave signal component from the reinforcing bar substantially orthogonal to the moving direction of the inspection apparatus body, and detect a defect substantially parallel to the surface of the reinforced concrete structure from the added or averaged reflected wave signal It is characterized by.

On the surface of the reinforced concrete structure in which the reinforcing bar is embedded, on the surface on the surface closest to the reinforcing bar and on the surface substantially intermediate between another reinforcing bar that is parallel to and adjacent to the reinforcing bar. An electromagnetic wave that radiates electromagnetic waves toward the reinforced concrete structure by an inspection apparatus main body moving step that moves substantially linearly within a movement range that includes at least the position and electromagnetic wave irradiation means mounted on the inspection apparatus main body. an irradiation step, the reflected wave signal of the electromagnetic wave emitted by the electromagnetic wave irradiation step, a step of obtaining the reception means mounted on the test apparatus main body, along with the movement of the inspection apparatus main body, the movement a wave receiving step of acquiring a plurality of reflected wave signals of consecutive different positions within the rebar con by performing signal processing on the reflected wave signal obtained by the wave receiving step A process for detecting a defect in Ried structure, the substantially perpendicular to the moving direction of the inspection apparatus main body by adding or averaging a plurality of the reflected wave signal of successive different positions in the acquired moving range A signal processing step of reducing a reflected wave signal component from the reinforcing bar and detecting a defect substantially parallel to the surface of the reinforced concrete structure from the added or averaged reflected wave signal.

An inspection apparatus main body that moves substantially linearly on the surface of a reinforced concrete structure in which reinforcing bars are embedded, an electromagnetic wave irradiation means that is mounted on the inspection apparatus main body and irradiates electromagnetic waves toward the reinforced concrete structure, and The reinforced concrete structure is mounted on the inspection apparatus main body and receives the reflected wave signal of the electromagnetic wave emitted from the electromagnetic wave irradiating means, and the signal processing of the reflected wave signal obtained by the wave receiving means. A signal processing means for detecting a defect, wherein the moving range of the inspection apparatus main body is a position on the surface closest to the reinforcing bar and another reinforcing bar that is parallel and adjacent to the reinforcing bar. It includes a location on substantially intermediate surface between, between at least, the reception means, with the movement of the inspection apparatus main body, the movement range Obtaining a plurality of reflected wave signals of successive different positions in the inner, the signal processing means, out of the acquired reflected-wave signal by the wave receiving means, and position on the surface closest to the reinforcing bars, parallel to the reinforcing bars By adding or averaging a plurality of reflected wave signals at successive positions between the position on the substantially intermediate surface between the adjacent rebars and substantially perpendicular to the moving direction of the inspection apparatus main body The reflected wave signal component from the reinforcing bar is reduced, and a defect including a plane substantially parallel to the surface of the reinforced concrete structure is detected from the added or averaged reflected wave signal.

On the surface of the reinforced concrete structure in which the reinforcing bar is embedded, on the surface on the surface closest to the reinforcing bar and on the surface substantially intermediate between another reinforcing bar that is parallel to and adjacent to the reinforcing bar. An electromagnetic wave that radiates electromagnetic waves toward the reinforced concrete structure by an inspection apparatus main body moving step that moves substantially linearly within a movement range that includes at least the position and electromagnetic wave irradiation means mounted on the inspection apparatus main body. an irradiation step, the reflected wave signal of the electromagnetic wave emitted by the electromagnetic wave irradiation step, a step of obtaining the reception means mounted on the test apparatus main body, along with the movement of the inspection apparatus main body, the movement a wave receiving step of acquiring a plurality of reflected wave signals of consecutive different positions within the rebar con by performing signal processing on the reflected wave signal obtained by the wave receiving step A process for detecting a defect in Ried structure, among the acquired reflected-wave signal, substantially intermediate surface between the position on the surface closest to the reinforcing bars, and another reinforcing bars adjacent to each other in parallel to the reinforcing bars A reflected wave signal component from the reinforcing bar that is substantially orthogonal to the moving direction of the inspection apparatus main body is reduced by adding or averaging a plurality of reflected wave signals at consecutive different positions between the upper position and the upper position. And a signal processing step of detecting a defect including a plane substantially parallel to the surface of the reinforced concrete structure from the averaged reflected wave signal.

Claims (16)

A main body of the inspection apparatus movable to a plurality of positions on the surface of the reinforced concrete structure in which the reinforcing bars are embedded;
An electromagnetic wave irradiation means mounted on the inspection apparatus main body and radiating an electromagnetic wave toward the reinforced concrete structure;
A wave receiving means mounted on the inspection apparatus body for obtaining a reflected wave signal of the electromagnetic wave emitted from the electromagnetic wave irradiation means;
Signal processing means for detecting defects in the reinforced concrete structure by signal processing the reflected wave signal acquired by the wave receiving means;
A reinforced concrete structure inspection apparatus having
The wave receiving means acquires a plurality of reflected wave signals at different positions as the inspection apparatus body moves.
The signal processing means reduces or reduces a reflected wave signal component from the reinforcing bar by adding or averaging a plurality of reflected wave signals at different positions acquired by the receiving means, and adding or averaging the reflected wave signals from the added or averaged reflected wave signals A reinforced concrete structure inspection apparatus for detecting a defect in the reinforced concrete structure. The range of movement of the inspection apparatus main body is between a position on the surface closest to the reinforcing bar and a position on a surface approximately in the middle between the reinforcing bar and the adjacent reinforcing bar,
The reinforced concrete structure inspection apparatus according to claim 1, wherein the signal processing means adds or averages a plurality of reflected wave signals having different positions within the moving range. The added or averaged reflected wave signal is expressed as a sum of a plurality of reflected wave signals resulting from the structure of the reinforced concrete structure and a crack reflected wave signal from a crack,
3. The reinforced concrete structure according to claim 1, wherein the signal processing means detects cracks by extracting and analyzing the components of the plurality of reflected wave signals and the crack reflected wave signal. Inspection device.   The plurality of reflected wave signals resulting from the structure of the reinforced concrete structure include at least a surface reflected wave signal that is a reflected wave from the surface of the reinforced concrete structure and a bottom surface that is a reflected wave from the bottom surface of the reinforced concrete structure. The reinforced concrete structure inspection apparatus according to claim 3, further comprising a reflected wave signal. The reinforced concrete structure has one or more surface layers on its surface;
The plurality of reflected wave signals resulting from the structure of the reinforced concrete structure further include a surface layer bottom surface reflected wave signal that is a reflected wave from each bottom surface of the one or more surface layers. The reinforced concrete structure inspection device described.   The plurality of reflected wave signals resulting from the structure of the reinforced concrete structure further includes a parallel reinforcing bar reflected wave signal that is a reflected wave from a reinforcing bar parallel to the moving direction of the inspection apparatus main body. Or the reinforced concrete structure inspection apparatus of 5.   The surface reflected wave signal is approximated by an average value of the reflected wave signal when scanning the surface of a normal portion where the reflected wave signal from the reinforcing bar parallel to the scanning direction and the reflected wave signal from the defect do not appear. The reinforced concrete structure inspection apparatus according to any one of claims 4 to 6.   The reinforced concrete structure inspection apparatus according to claim 1, wherein the defect is a crack, a cavity, or a bottom shape defect. An inspection apparatus main body moving step for moving the inspection apparatus main body to a plurality of positions on the surface of the reinforced concrete structure in which the reinforcing bars are embedded;
By the electromagnetic wave irradiation means mounted on the inspection apparatus main body, an electromagnetic wave irradiation step of irradiating the electromagnetic wave toward the reinforced concrete structure,
A step of obtaining a reflected wave signal of the electromagnetic wave irradiated in the electromagnetic wave irradiation step by a wave receiving means mounted on the inspection apparatus body, and a plurality of reflections having different positions as the inspection apparatus body moves. A wave receiving process for acquiring a wave signal;
Detecting a defect in the reinforced concrete structure by performing signal processing on the reflected wave signal acquired by the wave receiving step, and adding or averaging the acquired reflected wave signals at different positions A signal processing step of reducing a reflected wave signal component from the reinforcing bar and detecting a defect of the reinforced concrete structure from the added or averaged reflected wave signal;
A method for inspecting a reinforced concrete structure. The range of movement of the inspection apparatus main body is between a position on the surface closest to the reinforcing bar and a position on a surface approximately in the middle between the reinforcing bar and the adjacent reinforcing bar,
The reinforced concrete structure inspection method according to claim 9, wherein the signal processing step detects a defect of the reinforced concrete by adding or averaging a plurality of reflected wave signals having different positions within the moving range. The added or averaged reflected wave signal is expressed as a sum of a plurality of reflected wave signals resulting from the structure of the reinforced concrete structure and a crack reflected wave signal from a crack,
The reinforced concrete structure according to claim 9 or 10, wherein the signal processing step detects cracks by extracting and analyzing the components of the plurality of reflected wave signals and the crack reflected wave signal. Inspection method.   The plurality of reflected wave signals resulting from the structure of the reinforced concrete structure include at least a surface reflected wave signal that is a reflected wave from the surface of the reinforced concrete structure and a bottom surface that is a reflected wave from the bottom surface of the reinforced concrete structure. The reinforced concrete structure inspection method according to claim 11, further comprising a reflected wave signal. The reinforced concrete structure has one or more surface layers on its surface;
13. The plurality of reflected wave signals resulting from the structure of the reinforced concrete structure further include a surface layer bottom surface reflected wave signal that is a reflected wave from each bottom surface of one or more surface layers. Inspection method for reinforced concrete structures.   The plurality of reflected wave signals resulting from the structure of the reinforced concrete structure further include a parallel reinforcing bar reflected wave signal that is a reflected wave from a reinforcing bar parallel to the moving direction of the inspection apparatus main body. Or the reinforced concrete structure inspection method of 13.   The surface reflected wave signal is approximated by an average value of the reflected wave signal when scanning the surface of a normal portion where the reflected wave signal from the reinforcing bar parallel to the scanning direction and the reflected wave signal from the defect do not appear. The reinforced concrete structure inspection method according to any one of claims 12 to 14.   The reinforced concrete structure inspection method according to claim 9, wherein the defect is a crack, a cavity, or a bottom shape defect.

Images