JP6580856B2 - Detection method, detection apparatus, and program - Google Patents

Description

  The present invention relates to a detection method, a detection device, and a program.

  For example, an ultrasonic method is known as a nondestructive inspection technique for concrete structures. FIG. 31 shows an example of a frequency spectrum of a reinforcing bar reflected wave by the ultrasonic method. This frequency spectrum is data of a reflected wave obtained by measurement by a nondestructive inspection apparatus using an ultrasonic method. The object of measurement is a concrete specimen prepared so that the degree of corrosion of the reinforcing bar is different. As shown in FIG. 31, in the relative comparison of the frequency spectrum of an ultrasonic wave, it turns out that there exists a difference in a frequency characteristic with the corrosion degree of a reinforcing bar. This is considered to be due to the difference in the components of relatively high frequency due to the corrosion of the reinforcing bars and the fine cracks in the concrete near the reinforcing bars caused by the expansion pressure of the corrosion products (rust).

  In addition, an electromagnetic wave method is known as a method for exploring reinforcing steel in concrete. FIG. 32 shows the concept of exploration by the electromagnetic wave method. FIG. 32 shows a general electromagnetic wave method for exploring the internal structure of a concrete structure. The electromagnetic wave method utilizes the property that electromagnetic waves transmitted into concrete are reflected at the boundary with substances having different electrical characteristics (relative permittivity) (for example, reinforcing bars in concrete). That is, the presence of a reflective object (for example, a reinforcing bar in concrete) and the distance to the object are probed from the presence or absence of a reflected electromagnetic wave and the propagation time of the electromagnetic wave reciprocating.

FIG. 33 shows an example of a search result by the electromagnetic wave method. (A) in FIG. 33 shows an example of an image by the electromagnetic wave method (in the case of reinforcing bar search). (B) in FIG. 33 shows a characteristic graph of the reflected wave. More specifically, in FIG. 33B, the downward direction in the vertical direction indicates the distance (depth) from the concrete surface. Further, the horizontal direction (left-right direction from “0” when the center is “0”) indicates a change in the intensity of the electromagnetic wave.
The exploration image (a) in FIG. 33 is created with the electromagnetic wave intensity change level (b) in FIG. In this exploration image, the uppermost part of the hyperbolic pattern convex upward is the position where the reinforcing bar exists.

  The following Non-Patent Document 1 describes contents relating to the above-described ultrasonic method and electromagnetic wave method. Non-Patent Document 2 describes contents related to deterioration prediction of a concrete structure that receives salt damage.

Shigeru Yamaguchi, Hiroshi Irie, Shibutsu Tsutsumi, Yasukatsu Yoshida, Masato Kikuchi, “Non-destructive inspection technology for concrete structures”, NTT Technical Journal, 2006.3, pp. 41-46 Matsushima Manabu, Seki Hiroshi, Yokota Yuu, “Prediction of Deterioration of Concrete Structures Subjected to Salt Damage”, Concrete Engineering Annual Papers, Vol. 24, no. 2, 2002

By the way, the ultrasonic method is an inspection method that reflects structural changes as a principle. Further, the contents of Non-Patent Document 1 are only one result of measuring a concrete specimen prepared by determining the degree of corrosion in advance.
On the other hand, a variety of situations are assumed for structural changes in which actual concrete deteriorates due to corrosion. Therefore, it is assumed that the corrosion deterioration of these various concrete may not be covered by the ultrasonic method.
Furthermore, the inspection using the ultrasonic method is often carried out in a form that directly contacts concrete. When the ultrasonic method is used for underground exploration, the application of the ultrasonic method is limited to a relatively shallow range. This is because ultrasonic waves are greatly attenuated in soil at a depth of a certain level or more compared to electromagnetic waves.
Furthermore, when the ultrasonic method is used for underground exploration, many echoes related to various things such as cavities and large stones other than the object are likely to occur. It is difficult to determine and remove these unwanted object echoes. For this reason, it is sometimes difficult to accurately capture an object in underground inspection using an ultrasonic method.

  On the other hand, when using the electromagnetic wave method for exploring concrete structures, there is a limit to the depth and accuracy that can be measured due to the attenuation of electromagnetic waves and the influence of ambient noise. Although these limits have been studied and improved by the method described in Non-Patent Document 1, they have been limited to utilization in reinforcing bar exploration and cavity exploration. Therefore, with the electromagnetic wave method, it has been considered difficult to detect even the deterioration of infrastructure equipment such as corrosion of reinforcing bars in concrete.

  In view of the above circumstances, an object of the present invention is to provide a detection method, a detection device, and a program that can detect the degree of deterioration of a reinforcing bar using a measurement result by electromagnetic waves.

  One embodiment of the present invention relates to a reflected wave characteristic of a reflection peak of the reflected wave obtained from a measurement result of a reflected wave from the reinforcing bar of an electromagnetic wave transmitted toward the reinforcing bar in the structure, and the past with respect to the reinforcing bar. A comparison step of comparing the reflected wave characteristics recorded in the table, and when there is a change in the reflected wave characteristics in the comparison of the comparison step, the measured reflected wave characteristics or the reflected wave characteristics An estimation step of estimating a degree of deterioration of the reinforcing bar based on a change.

  One aspect of the present invention is the above-described detection method, wherein in the estimation step, the degree of deterioration is estimated based on the measured peak frequency or a change in the peak frequency.

  One aspect of the present invention is the above-described detection method, wherein in the estimation step, the degree of deterioration is estimated based on the measured intensity of the peak or a change in the intensity of the peak.

  One aspect of the present invention is the above-described detection method, in which the amount of change in the reflected wave characteristic is a predetermined value or more, and the change in the reflected wave characteristic is a change in a predetermined direction. In the estimation step, the degree of deterioration is estimated.

  One aspect of the present invention is the above-described detection method, further including a determination step of determining whether maintenance of the reinforcing bar is necessary based on the degree of deterioration estimated in the estimation step.

  One aspect of the present invention is the above-described detection method, wherein a difference between the reflected wave characteristic recorded in the past and the reflected wave characteristic based on a numerical analysis result is within a predetermined range, and is measured. When the difference between the reflected wave characteristic and the reflected wave characteristic based on the numerical analysis result is within a predetermined range, the degree of deterioration is estimated in the estimation step.

  One embodiment of the present invention relates to a reflected wave characteristic of a reflection peak of the reflected wave obtained from a measurement result of a reflected wave from the reinforcing bar of an electromagnetic wave transmitted toward the reinforcing bar in the structure, and the past with respect to the reinforcing bar. A comparison unit that compares the reflected wave characteristics recorded in the comparison unit, and when the reflected wave characteristic is changed in the comparison by the comparison unit, the measured reflected wave characteristic or the reflected wave characteristic And an estimation unit that estimates a degree of deterioration of the reinforcing bar based on a change.

  One embodiment of the present invention is a program for causing a computer to execute any of the detection methods described above.

  According to the present invention, the degree of deterioration of a reinforcing bar can be detected using the measurement result of electromagnetic waves.

The figure which shows an example of the frequency shift of 1st Embodiment. The figure which shows another example of the frequency shift of 1st Embodiment. The flowchart which shows the flow of the detection method of 1st Embodiment. The block diagram which shows the structural example of the detection apparatus of 1st Embodiment. The perspective view which shows the simulation model of 1st Embodiment. The side view which shows the simulation model of 1st Embodiment. The perspective view which expands and shows a part of simulation model of 1st Embodiment. The graph which shows an example of the simulation result of 1st Embodiment. The perspective view which shows the simulation model of 2nd Embodiment. The figure which shows the simulation model of 2nd Embodiment. The figure which shows the input wave used by the simulation of 2nd Embodiment. The figure which shows the input wave used by the simulation of 2nd Embodiment. The graph which shows an example of the simulation result of 2nd Embodiment. The graph which shows an example of the simulation result of 2nd Embodiment. The graph which shows an example of the simulation result of 2nd Embodiment. The block diagram which shows the structural example of the detection apparatus of 2nd Embodiment. The flowchart which shows the flow of the detection method of 2nd Embodiment. The flowchart which shows a part of flow of the detection method of 2nd to 4th embodiment. The perspective view which shows the simulation model of 3rd Embodiment. The perspective view which expands and shows a part of simulation model of 3rd Embodiment. The graph which shows an example of the simulation result of 3rd Embodiment. The graph which shows an example of the simulation result of 3rd Embodiment. The graph which shows an example of the simulation result of 3rd Embodiment. The block diagram which shows the structural example of the detection apparatus of 3rd Embodiment. The perspective view which shows the simulation model of 4th Embodiment. The side view which shows the simulation model of 4th Embodiment. The graph which shows an example of the simulation result of 4th Embodiment. The graph which shows an example of the simulation result of 4th Embodiment. The block diagram which shows the structural example of the detection apparatus of 4th Embodiment. The flowchart which shows a part of flow of the detection method of 4th Embodiment. The graph which shows the frequency spectrum of the rebar reflection wave by an ultrasonic method. The figure which shows the concept of electromagnetic wave investigation. The figure which shows the exploration image by electromagnetic wave investigation.

Hereinafter, a detection method, a detection apparatus, and a program according to an embodiment will be described with reference to the drawings. In the following description, the same reference numerals are given to configurations having the same or similar functions. And those overlapping descriptions may be omitted.
In the present application, a change in frequency that appears in a reflected wave due to deterioration (corrosion) of an object is referred to as “frequency shift”. In the present application, the peak of the reflection intensity of the reflected wave from the object (that is, the peak of the electric field intensity) is referred to as a “reflection peak”. In some cases, the intensity (electric field intensity) of the reflection peak is referred to as “peak intensity”, and the frequency of the reflection peak is referred to as “peak frequency”.

  Each of “reflection peak intensity” and “reflection peak frequency” is an example of “reflected wave characteristics”. The “reflected wave characteristic” in the present application means at least one element for specifying the characteristic of the reflection peak (for example, the shape or position in the frequency spectrum). In the following description, a case where “reflection peak intensity” or “reflection peak frequency” is used as an example of “reflection wave characteristics” will be described. Therefore, the description of “reflection peak intensity” or “reflection peak frequency” in the following description may be read as “reflected wave characteristics”, respectively.

  Further, “measured value” or “measured data” in the present application is used as an expression for distinguishing from a theoretical value such as numerical analysis. For this reason, the “measurement value” and “measurement data” referred to in the present application are not limited to information obtained directly from the measuring device that measures the reflected wave, and the information obtained from the measuring device is subjected to predetermined processing (for example, Fourier transform). It is used to include the values marked with Further, “predetermined” in the present application means that it can be arbitrarily set.

(First embodiment)
First, the first embodiment will be described with reference to FIGS. The first embodiment utilizes the frequency characteristics of the reflected wave at the iron bar in vacuum.

  FIG. 1 shows a frequency shift with a change in the thickness of the iron bar. That is, FIG. 1 shows a frequency shift in the high frequency direction with a decrease in the thickness of the iron bar. Specifically, (a) in FIG. 1 shows the shapes of three iron bars having different thicknesses. Moreover, (b) in FIG. 1 shows the frequency characteristics of the reflected wave of each of the three iron bars of (a) in FIG.

More specifically, (a-0) in FIG. 1 is an ideal antenna, and indicates a wire having a length L [m] and a diameter d ₀ = ₀ mm. (B-0) shows the electric field intensity I [V / m] of reflection of the frequency characteristic corresponding to the wire of (a-0). As shown in (b-0), the electric field intensity I [V / m] of the reflection corresponding to the wire (a-0) has a peak at the frequency f ₀ [MHz]. This frequency f ₀ is given by the following equation.
f ₀ = c / L
c: Speed of light 3.0 × 10 ⁸ [m / sec]
The frequency f ₀ is higher than the frequency f ₁ and the frequency f ₂ described below.

Next, (a-2) in FIG. 1 shows a thick cylindrical iron bar having the same length L [m] as described above but a diameter d ₂ = 10 [mm]. This corresponds to a reinforcing bar before corrosion, for example a reinforcing bar in healthy concrete. (B-2) shows the electric field intensity I [V / m] of the reflection of the frequency characteristic corresponding to the thick iron rod of (a-2). As shown in (b-2), the electric field intensity I [V / m] of reflection corresponding to the thick iron bar in (a-2) peaks at the frequency f ₂ [MHz].
The frequency _{f 2,} to the frequency _{f 0} in the _(b-0), the relationship of f 2 _{<f 0.} This is because, in a cylindrical antenna having a length L [m], when the diameter d of the cylinder increases, the substantial length L in the frequency characteristics increases as the diameter d increases.

Further, (a-1) in FIG. 1 indicates a thin iron rod having a length of L [m] which is the same as that described above, but the diameter of the cylinder is d ₁ = 8 [mm]. This corresponds to a corroded rebar, for example a rebar in degraded concrete. (B-1) shows the electric field intensity I [V / m] of the reflection of the frequency characteristic corresponding to the thin iron bar of (a-1). As shown in (b-1), the electric field intensity I [V / m] of reflection corresponding to the thin iron bar in (a-1) peaks at the frequency f ₁ [MHz].
The frequency _{f 1,} to the frequency _{f 2} at (b-0) the frequency _{f 0} and in _(b-2), a relationship of f _{2 <f} 1 _{<f 0.} This is because the cylinders having the same length L [m] have a diameter d ₂ > d ₁ > d ₀ . That is, the diameter of the thin iron bar shown in (a-1) is between the diameter of the ideal antenna shown in (a-0) and the diameter of the thick iron bar shown in (a-2). For this reason, the peak frequency f ₁ shown in (b-1) is between the other f ₀ and f ₂ in the frequency characteristics. Therefore, when the f ₁ resulting from the measurement processing of the subsequent reinforcing bars is shifted in the high frequency direction with respect to the peak frequency f ₂ in the frequency characteristic of the reflected wave from the healthy reinforcing bars, corrosion of the reinforcing bars is estimated. The

Next, FIG. 2 shows a frequency shift in the lower frequency direction with an increase in the dielectric of the iron bar. Note that the diameters d ₁ and d ₂ and the frequencies f _0, f _{1 and} f ₂ in the description related to FIG. 2 are used for the description of FIG. 2, and the diameters d ₁ , d ₂ and FIG. It does not indicate that the values are the same as the frequencies f _0, f _{1, and} f ₂ .
(A) in FIG. 2 shows the state of the dielectric attached to the iron bar. That is, (a-0), (a-1), and (a-2) in FIG. 2 are three types of iron rods, all having the same thickness, but the state of the dielectric attached to the iron rod Is different. That is, (a-0) in FIG. 2 is one in which a dielectric is not attached to the iron bar, and simulates a healthy state in which there is no rust on the reinforcing bar and no corrosion. Moreover, (a-1) in 2 shows that a dielectric is attached to a part of the periphery of the iron bar, and simulates a state in which a part of the reinforcing bar is corroded. Moreover, (a-2) in FIG. 2 simulates the state in which the entire range of the iron bar is covered with a dielectric, and the reinforcing bars are corroded in the entire range.

On the other hand, (b) in FIG. 2 shows the frequency characteristics of the reflected wave of each of these three types of iron bars. As shown in FIG. 2B, by attaching a dielectric to the iron bar, an electromagnetic wave having a long wavelength (that is, a low frequency) is easily reflected if the iron bar has the same length and the same thickness.
Accordingly, it is assumed that a reflection peak exists at the frequency f ₀ in the frequency characteristic (b-0) of reflection by the iron bar to which no dielectric is attached. In this case, in the frequency characteristic (b-1) of reflection by the iron bar partially attached with a dielectric, a reflection peak exists at the frequency f ₁ (<f ₀ ). In addition, in the frequency characteristic (b-2) of reflection by the iron bar whose entire surface is covered with the dielectric, a reflection peak exists at the frequency f ₂ (<f ₁ <f ₀ ). In this way, the reinforcing bars are covered with rust as corrosion progresses, so that the frequency of the reflection peak shifts in the lower frequency direction.

As described above, in both the change in the thickness of the iron bar shown in FIG. 1 and the change in the ratio covered by the dielectric (rust) shown in FIG. A frequency shift of the reflection peak occurs. For this reason, the degree of corrosion of the reinforcing bars can be estimated by measuring the frequency shift of the reflection peak.
For example, in the corrosion of reinforcing bars, either the frequency shift in the high frequency direction as shown in FIG. 1 or the frequency shift in the low frequency direction as shown in FIG. 2 depending on the state of individual corrosion. Is often dominant. That is, when corrosion occurs in a reinforcing bar, it is rare that the frequency shift in the high frequency direction and the frequency shift in the low frequency direction cancel each other, and in many cases, the frequency shift to either one is detected. be able to.

Next, FIG. 3 shows an example of the processing flow of the detection method of the present embodiment.
In FIG. 1 described above, it has been described that the frequency shift of the reflection peak occurs due to the change in the thickness of the iron bar. Here, it is considered that the frequency shift of the reflection peak occurs because the iron bar becomes substantially thin even when the reinforcing bar is corroded by rust. FIG. 3 is a flowchart showing an example of a method for detecting the corrosion state of a reinforcing bar by utilizing this frequency shift phenomenon.

  In the processing flow shown in FIG. 3, first, information related to a measurement target buried facility (hereinafter, buried facility information) is acquired from a database (DB) (step S101). As a result, specific information of the buried equipment, for example, the type of the equipment to be measured (manhole standard and size) and its position (location and depth), the material to be measured and the surrounding buried medium And numerical information on the dielectric constant, and the position, length, and thickness of the reinforcing bars in the concrete that constitutes the buried equipment. The burying equipment (for example, a structure made of reinforced concrete) is an example of a “structure”.

  Next, the reflection time of the reflected wave with respect to the object (for example, a reinforcing bar) (reciprocation time when the electromagnetic wave propagates and reciprocates) or the peak frequency of the reflected wave is calculated (step S102). This calculation is based on the buried equipment information previously obtained from the DB, thereby obtaining a calculated value of the reflection time or peak frequency of the reflected wave in the buried equipment. For example, the reflection time can be obtained from the position of the object (distance from the observation point) and the propagation speed of the electromagnetic wave. The peak frequency can be obtained from the material (for example, dielectric constant), shape and size of the object. Strictly speaking, the peak frequency can be obtained by electromagnetic analysis of an analysis model in which these are digitized.

  Subsequently, the object is measured using an electromagnetic wave radar device. That is, an electromagnetic wave is transmitted toward the object and a reflected wave from the object part is measured. Thereby, the measurement result (radar inspection information) of the reflected wave from the object is acquired (step S103). That is, data obtained by measuring reflected waves from an actual buried facility is acquired.

  However, this measurement data may include various noises (for example, reflected waves in surrounding structures other than the object). Therefore, based on the calculation time (reflection time) or frequency characteristic (peak frequency) calculated in step S102, the reflection peak related to the object is specified (selected and extracted) from the measurement data (step S104). This identified reflection peak becomes important information for estimating the deterioration of the object in the subsequent process.

Next, with respect to the identified reflection peak, the intensity or frequency of the reflection peak is obtained (step S105). For example, obtaining the frequency of the reflection peak means, for example, obtaining the frequency f ₁ or f ₂ (the peak frequency of the reflected wave from a healthy reinforcing bar or a corroded reinforcing bar) described in FIG.

  Returning to the description of the processing flow in FIG. 3 again, in the next step, the past measurement data (in the past, the intensity or frequency value of the reflection peak obtained in step S105 is measured and recorded for the same object. Comparison is made with the reflection peak intensity or frequency history measured in the past (step S106). That is, as shown in FIG. 1, the frequency shift of the reflection peak appears due to the difference in the diameter of the iron bar, for example, the frequency of the reflection peak measured from the iron bar where corrosion has progressed, and the past when the soundness or corrosion is still slight. The frequency of the obtained reflection peak is compared.

  Next, it is considered that the corrosion of the reinforcing bars follows the relationship of the frequency shift of the reflection peak, and in the above comparison, it is determined whether or not there is a change in the intensity or frequency shift of the reflection peak (step S107). If it is determined in step S107 that there is a reflection peak intensity change or frequency shift (step S107: Yes), the reflection peak intensity change or frequency shift is collated with a theoretical value or a statistical value (step S108). Then, based on the above collation, the state of deterioration of the object (corrosion of reinforcing bars) (that is, the degree of deterioration of the object) is estimated (step S109).

  On the other hand, if the determination in step S107 described above is the opposite result, that is, if there is no intensity change or frequency shift of the reflection peak (step S107: No), there is no progress of deterioration of the object (corrosion of reinforcing bars). Or deterioration cannot be detected (step S110).

  Next, the theoretical / statistical collation in step S108 in FIG. 3 will be described more specifically. For example, in the collation in step S108, when collating the measured intensity change of the reflection peak with the theoretical value, the amount of change calculated in principle or the numerical analysis (electromagnetic field simulation) taken up in the second and later embodiments described later. The measured value measured by the radar technique for the buried equipment to be inspected is checked against the value of the intensity change of the reflection peak in the result.

  That is, in the comparison with the theoretical value, the degree of deterioration of the target object and the intensity value of the reflection peak corresponding to each of the degree of deterioration of the target object are grasped in association with each other by simulation. The degree of deterioration of the target object can be estimated by comparing the measured reflection peak intensity value with the reflection peak intensity value based on the numerical analysis result.

  Instead of the above, in the comparison with the theoretical value, the amount of change in the degree of deterioration of the object and the amount of change in the intensity of the reflection peak corresponding to the amount of change in the degree of deterioration are determined by simulation. May be grasped in association with each other. In this case, the degree of deterioration of the object can be estimated by comparing the amount of change in the intensity of the measured reflection peak with the past with the amount of change in the intensity of the reflection peak based on the numerical analysis result.

  The same applies to the case where the frequency shift of the measured reflection peak is collated with the theoretical value in the collation in step S108.

  On the other hand, in the collation of step S108, when collating the measured intensity change of the reflection peak with the statistical value, first, the measured value is obtained by using the values measured by the radar technique in the past for the buried equipment of the same type and type as a history. Prepare a database that correlates and the degree of deterioration. Then, the measured value of the buried equipment to be checked is checked against the database. Thereby, collation of statistics of Step S108 is performed. Or the measured value measured in the past several times with respect to the same burying equipment is registered as a history database. And it is good also as collation of the statistics of step S108 by comparing the historical database and the newly measured value. Thereby, the degree of deterioration of the object can be estimated.

  Instead of the above, in the comparison with the statistical value, based on the past measurement data, the amount of change in the degree of deterioration of the target object and the reflection peak corresponding to each of the amount of change in the degree of deterioration of the object You may grasp | ascertain by associating the variation | change_quantity of intensity | strength. In this case, the degree of deterioration of the object can be estimated by comparing the amount of change of the measured reflection peak intensity with the past with the amount of change of the intensity of the reflection peak based on past measurement data.

Note that the same applies to the case where the frequency shift of the measured reflection peak is collated with the statistical value in the collation in step S108.
Here, the collation of the statistics uses a database that grasps the numerical value of the same type or the same type of equipment measured by electromagnetic waves in the past and the degree of deterioration. For this reason, it is possible to estimate the degree of finer degradation compared to the theory of numerical calculation such as simulation.

Next, the detection apparatus 100 of this embodiment is demonstrated.
FIG. 4 shows a configuration example of the detection device 100 and peripheral devices. Note that the detection apparatus 100 in FIG. 4 is an apparatus for handling frequency characteristics in the processing flow in FIG. 3 (when estimating deterioration using a frequency shift).

  As illustrated in FIG. 4, the detection apparatus 100 includes a measurement result processing unit 101, a numerical analysis unit 102, a comparison unit 103, and an estimation unit 104.

  The measurement result processing unit 101 receives measurement data to be measured from the measuring instrument 111. The measuring device 111 is a radar device, for example. The measuring device 111 acquires reflected wave data from a measurement target (for example, an embedded object buried in the ground). The measurement result processing unit 101 changes the time response of the reflected wave to the frequency characteristic by performing Fourier transform on the measurement result received from the measuring device 111.

  In addition, the measurement result processing unit 101 acquires embedded facility information related to a measurement target embedded object from the facility DB 112. In the present embodiment, the measurement result processing unit 101 calculates the peak frequency of the reflected wave related to the object based on the embedded facility information. Then, based on the calculated value of the peak frequency, the reflection peak related to the object is specified from the Fourier transformed frequency characteristics. Furthermore, the measurement result processing unit 101 specifies the frequency of the reflection peak from the specified reflection peak. That is, the measurement result processing unit 101 performs the processing from step S101 to step S105 described above.

  The numerical analysis unit 102 acquires embedded facility information from the facility DB 112. The numerical analysis unit 102 constructs a numerical analysis model based on the acquired embedded facility information. The numerical analysis unit 102 performs numerical analysis processing (electromagnetic field analysis simulation) and outputs a numerical analysis result. The numerical analysis result includes, for example, a plurality of degrees of deterioration of the target object, and values of reflection peak frequencies corresponding to the respective degrees of deterioration.

  The comparison unit (comparison determination unit) 103 first compares the result processed by the measurement result processing unit 101 with the result of numerical analysis performed by the numerical analysis unit 102. The comparison unit 103 determines that the numerical analysis model is appropriate when the difference between the result processed by the measurement result processing unit 101 and the numerical analysis result is within a predetermined range.

  Further, the comparison unit 103 can acquire past measurement data (history information) from the history DB 113. For example, the history DB 113 stores a plurality of measured values of past reflected waves related to the same object and the degree of deterioration of the object in the measured values in association with each other.

  The comparison unit 103 acquires past measurement data from the history DB 113. And the comparison part 103 determines the presence or absence of the change regarding a reflection peak by comparing the result which the measurement result process part 101 processed, and the past measurement data acquired from log | history DB113. For example, the comparison unit 103 determines the presence or absence of a frequency shift by comparing the measurement value of the reflection peak frequency from the measurement result processing unit 101 with the value of the reflection peak frequency included in the past measurement data. . That is, the comparison unit 103 performs the processes in steps S106 and S107 described above.

  When the comparison unit 103 determines that there is a change with respect to the reflection peak, the estimation unit 104 determines, for example, the frequency shift of the reflection peak due to deterioration obtained by numerical analysis and the reflection peak of the reflection wave obtained by measurement. The degree of deterioration is estimated based on the frequency. The estimation unit 104 determines the degree of deterioration based on past measurement data acquired from the history DB 113 (reflection peak frequency shift due to deterioration recorded in the past) and the reflection peak frequency of the reflected wave obtained by measurement. May be estimated. That is, the estimation unit 104 performs the processing from step S108 to step S110 described above.

Next, an example of a numerical analysis model by the numerical analysis unit 102 of this embodiment will be described.
5 to 7 show a steel bar model in a vacuum as a simulation model. For example, FIG. 5 shows a perspective view of the analysis model. In this model, there is an iron bar in the vacuum of the analysis space, and the state where there is rust on a part of the iron bar is simulated. The size of the space is 1.4 m × 1.4 m × 0.76 m in XYZ coordinates. In the center of this space, a cylindrical iron rod having a length of 80 cm and a diameter of 1 cm is arranged along the Y axis. The rust range (length in the Y-axis direction) is variably set at the center of the iron bar. An observation point is provided directly above the center of the iron bar (on the positive side of the Z axis). The input wave for analysis is a plane wave substantially parallel to the XY plane, and is set so as to be generated on the plus side of the Z axis and propagate to the minus side. This input wave is substantially the same as the input wave of the second embodiment. A detailed description of this input wave will be given in the second embodiment.

  FIG. 6 shows a side view (YZ plane) of the analysis model. FIG. 6 shows the mesh size in the analysis space in addition to the iron bar in vacuum. As described above with reference to FIG. 5, there are an 80 cm iron bar and rust whose range (length) is variably set at the center of the iron bar. As shown in FIG. 6, this rust is formed on the surface of the iron bar. In addition, the observation point is arranged right above the center of the iron bar (the positive side of the Z axis). The plane of generation of the input wave, which is a plane wave, is set immediately below the observation point (a position slightly smaller than the observation point on the Z axis). The input wave propagates in the negative direction of the Z axis from the generation surface. As the mesh size, a 1 cm mesh is adopted in the vacuum portion of the entire space, and a 1 mm mesh is adopted in the iron bar and its surroundings.

FIG. 7 is an enlarged view of a boundary portion between a portion where rust is provided and a portion where rust is not provided in the analysis model of FIG. As shown in FIG. 7, the 1 mm mesh size described in FIG. 6 is set at the rust portion of the iron bar and the surface of the iron bar. In FIG. 7, the mesh used for the analysis is shown by a cross section of the XY plane. The iron bar is a cylinder with a diameter of 1 cm. For this reason, the 1 mm mesh is divided into 10 equally in the iron bar. The rust on the surface of the iron bar is set to a thickness of 3 mm around the iron bar. In particular, the mesh that hits the layer on the surface of the iron bar is also set to ferric oxide (Fe ₂ O ₃ ) that is rust, not iron.

  FIG. 8 shows a simulation result (Fourier transform of reflected wave) of the analysis model. In the analysis result graph shown in FIG. 8, there are three reflection peaks. The parameter is the difference in the rust range (length in the Y-axis direction). The range of the rust shown in FIG. 8 is 1 cm long (an iron rod with almost no rust), 30 cm (about half of the rust with respect to the iron rod), and 80 cm (the entire surface of the iron bar is covered with rust). There are three types. Due to the difference in the rust range, a frequency shift appears in any of the three reflection peaks. Among these three reflection peaks, the second reflection peak has the largest frequency shift. For this reason, it is considered that the second reflection peak is convenient for estimating the range of rust.

According to the detection method and the detection apparatus as described above, it is possible to detect the degree of deterioration of the object using the measurement result of the electromagnetic wave. That is, the detection method of the present embodiment compares the reflected wave characteristic of the reflected wave of the reflected wave from the object with the reflected wave characteristic recorded in the past with respect to the object, and changes to the reflected wave characteristic. And estimating the degree of deterioration of the object based on the measured reflected wave characteristic or the change in the reflected wave characteristic. As an example, the detection method of the present embodiment compares the measured peak intensity or frequency of the reflected wave with the peak intensity or frequency of the reflected wave recorded in the past, and changes the peak intensity or frequency. And estimating the degree of deterioration of the object based on the value of the peak intensity or frequency of the measured reflected wave or the degree of change in the peak intensity or frequency.
According to such a configuration, the reflection characteristic change of the object can be captured by the electromagnetic wave, and the degree of deterioration of the countermeasure can be detected by nondestructive inspection. That is, according to the detection method and the detection apparatus described above, for example, the state of a corroded reinforcing bar in concrete and the degree of corrosion (ratio of rust) of the reinforcing bar can be detected.

  In addition, as described above, the degree of deterioration of the object may be performed by comparing the measured value with a theoretical value obtained by numerical analysis or the like, or by comparing the measured value with a past statistical value. May be. In addition, whether the verification is performed against the theoretical value or the statistical value, the above verification is performed using the measured peak intensity or frequency value of the reflected wave (that is, the measured value at the new measurement point). ), Or instead based on the intensity of the reflection peak or the degree of change in frequency (that is, the amount of change with respect to the past).

  In the above description, the method and apparatus for estimating the degree of deterioration using either the peak intensity change or the frequency shift of the reflected wave have been described. Instead, the peak frequency intensity change and the frequency shift are described. Both may be used to estimate the degree of deterioration. In the above description, the method and apparatus for estimating the degree of deterioration using either one of collation with a theoretical value or collation with a statistical value has been described. The degree of deterioration may be estimated using both of the comparison with the value. These are the same in the following embodiments.

  In the present embodiment, the degree of deterioration is estimated based on the value of the measured peak frequency of the reflected wave or the degree of change in the peak frequency. Here, when deterioration occurs in the object, the value of the frequency shift often changes more greatly than the intensity change of the reflection peak. For this reason, by estimating the degree of deterioration based on the frequency shift, it is possible to detect the deterioration state of the target object with higher accuracy.

  Moreover, in this embodiment, the reflection peak regarding a target object is specified from the measurement data of the reflected wave measured using the reflection time or peak frequency calculated based on the buried equipment information. According to such a configuration, even if the reflected wave includes noise, the reflection peak related to the object can be specified. In the above description, the method and apparatus for specifying the reflection peak using either the reflection time or the peak frequency have been described. Instead, the reflection peak is specified using both the reflection time and the peak frequency. May be. These are the same in the following embodiments.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. In the second embodiment, analysis of a steel bar model in concrete (intensity change of reflection peak) is utilized.

  9 and 10 show a simulation model of a steel bar in concrete. More specifically, this simulation model has an iron bar (a cylinder with a diameter of 1 cm, a length (inside of an X-axis direction: 1.4 m, a Y-axis direction: 1.4 m, a Z-axis direction: 1.1 m)). Y-axis direction): 80 cm) is a concrete plate (X-axis direction: 1 m, Y-axis direction: 1 m, Z-axis direction: 20 cm). This is an infrastructure facility buried underground, simulating part of reinforced concrete. Moreover, in this model, rust exists in a part of iron bar in concrete. This assumes that the infrastructure facilities have deteriorated and the reinforced concrete rebar is corroded. Furthermore, this rust is modeled so as to surround the periphery of the iron bar, and the range of the rust, that is, the length in the iron bar direction (Y-axis direction) can be changed by a parameter (Y-axis direction: 1 cm to 80 cm, particularly 80 cm). In the case, the entire surface of the iron bar is corroded). Thereby, it is possible to analyze by changing the degree of deterioration (the progress of corrosion of reinforcing bars).

  Here, the point which modeled so that rust may surround the circumference | surroundings of a steel bar is demonstrated in detail. Iron is oxidized from the surface, and when it changes to rust, the volume expands relative to the original iron. In addition, it is considered that the oxidation proceeds faster around the surface than in the iron. For this reason, as shown in FIG. 9, as a model in which the corrosion of oxidation proceeds, a first oxidation point is assumed at the center of the iron bar, and the oxidized range is a model that spreads on the surface of the iron bar. Note that how to set rust around the iron bar in the analysis model will be described in detail in the explanation of the iron bar model in vacuum of the third embodiment described later.

In the model analysis of this embodiment, a plane wave on the XY plane from the upper part of the drawing to the lower side (from the positive direction of the Z axis to the negative direction) is used as a transmission wave (irradiation wave) in the electromagnetic wave (radar) method. To do. The transmission waves used in this electromagnetic field simulation will be described in detail with reference to FIGS.
As for the reception of reflected waves, an observation point is placed as a receiving point for measuring the intensity of electromagnetic waves, at a position corresponding to the center of the analysis space of the concrete plate (positive direction of the Z axis, upper center in FIG. 9). Is done.

  (A) in FIG. 10 shows a front view of the model. Moreover, (b) in FIG. 10 shows a side view of the model. The front view of (a) in FIG. 10 is a cross section of the XZ plane. In this figure, the analysis space is 1.4 m in the horizontal direction (X-axis direction). In this analysis space, there is a concrete plate having a width of 1 m and a thickness of 20 cm. There is a 1 cm diameter iron bar in this concrete plate. And the rust of 3 mm thickness covers the circumference | surroundings of a steel bar. In addition, an observation point is arranged in the center of the concrete plate and directly above the concrete plate (in the Z-axis direction).

  Similarly, (b) in FIG. 10 is a cross section of the YZ plane. In the side view of (b) in FIG. 10, the analysis space is 1.4 m in the Y-axis direction. The concrete board is 1 m in the Y-axis direction. There is an 80cm iron bar in this concrete board. Moreover, there is rust on a part (or all) of the iron bar. This range of rust (length in the Y-axis direction) is variable between 1 cm and 80 cm. From this side view, the observation point is located on the positive side of the Z axis in the center of the concrete plate.

  FIG. 11 shows the conditions of the input wave (plane wave) used in the simulation. The input wave shown in FIG. 11 is a plane wave on the XY plane in a space coordinate system (XYZ coordinate system). And, just as a ground penetrating radar radiates radio waves from the ground to the ground, the input wave (plane wave) is generated in the positive direction of the Z axis (upper side of the space), and in the negative direction (lower side of the space) Propagate to. Here, (a) in FIG. 11 shows the setting and shape of the input wave. As shown in FIG. 11A, the time response of the input wave is a Gaussian pulse having a peak intensity of 1.0 V / m. Further, as shown in FIG. 11B, the frequency characteristic of the input wave is −3 dB at 2 GHz.

  FIG. 12 shows how the input wave is generated and propagated. (A) in FIG. 12 shows how the input wave is generated. The input wave is a plane wave on the XY plane, and it can be seen that it is generated on the positive side of the Z axis, that is, on the upper side of the space. (B) in FIG. 12 shows a situation where the input wave has propagated to the concrete plate in the analysis space. It can be seen that the input wave has propagated in the negative direction of the Z-axis as time elapses from the generation of the input wave (a) in FIG.

  In addition to the input wave described above, the setting conditions in the electromagnetic analysis simulation include material constants of substances constituting the model. Specifically, a uniform dielectric constant and conductivity are set for rust, concrete, and soil used in the fourth embodiment described later. On the other hand, in this analysis, iron is defined and set as a complete conductor because it is much different in conductivity from other substances. Note that these input waves and the setting conditions of the substances constituting the model are used in common in the third and fourth embodiments described later.

Next, the time response of the reflected wave to the iron bar in concrete will be described in detail.
FIG. 13 shows an overall view of the time response of the reflected wave to the iron bar in the concrete. FIG. 13 shows the result of simulation by three-dimensional electromagnetic field analysis using the models shown in FIGS. 9 and 10 described above. This simulation is performed by a time domain difference method (FDTD method: Finite-Difference Time-Domain method). The time-domain difference method is a technique for obtaining an electromagnetic field by solving Maxwell's equations that are spatially and temporally differentiated at each time step. The time domain difference method is applied to an analysis of a model made of a dispersive medium (a substance whose material constant depends on frequency, such as a dielectric constant of a material). In addition, in the time domain difference method, the increase in the required memory with respect to the increase in the analysis model scale is supposed to be suppressed as compared with other algorithms (for example, finite element method (FEM)).

  In the simulation, the time response of the reflected wave is time (unit: nsec) on the horizontal axis and electric field strength (unit: V / m) obtained at the observation point on the vertical axis. In this time response graph, the range of rust is varied between 1 cm and 80 cm. However, in FIG. 13, almost no difference in the response graph can be confirmed in any rust range.

  Here, the strongest reflected wave (0.57 V / m) is observed at the beginning of this time response (about 3 nsec). This reflected wave is considered to be reflected on the concrete surface. The triangles in the time response graph shown in FIG. 13 indicate the reflection time on the concrete surface obtained by calculation based on the design distance of the model. The time of the reflection peak of the strongest reflected wave coincides with the time of the reflection peak of the triangle mark obtained by calculation. Similarly, the reflection time on the iron bar and the concrete back is indicated by asterisks and circles. FIG. 14 shows a graph in which a portion including these reflection times (6 nsec to 8 nsec, a portion surrounded by a broken line) is enlarged.

  FIG. 14 shows an enlarged view of a portion of the time response of the reflected wave to a steel bar in concrete. The vertical axis | shaft of the graph shown in FIG. 14 is reflection peak intensity (a unit is mV / m). In FIG. 14 as well, similar to FIG. 13, the reflection time on the iron bar obtained by calculation is indicated by an asterisk mark. The reflection peak of this iron bar is approximately 6.7 nsec. As for the reflection peak of this iron bar, a slight intensity change due to the difference in the rust range can be confirmed. This intensity change will be described in detail later with reference to FIG. Further, in FIG. 14, as in FIG. 13, the reflection time on the back surface of the concrete is indicated by a circle (about 7.2 nsec). However, in the graph of the analysis result, a reflection peak appears at about 7.3 nsec. As for the intensity of the reflection peak due to the concrete back surface, a change in the peak intensity due to the difference in the rust range can be confirmed somewhat.

  In addition, a circle mark plots the value of desktop calculation on the graph. In this calculation, the circles simply take into account the representative dielectric constant from the speed of light for the distance from the input wave generation to the concrete back and the distance from the back to the observation point specified in the numerical analysis model. Based on the propagation speed, the value obtained for the propagation time is less than 7.2 nsec. On the other hand, the electric field strength graph shown in FIG. 14 represents a reflection peak from a change in electric field strength at an observation point obtained by electromagnetic field analysis. The time of this reflection peak exceeds 7.3 nsec, and there is a difference from the propagation time of the desktop calculation. One factor of this difference is that the dielectric constant having a frequency characteristic set in the analysis is calculated as a representative value at a frequency corresponding to the center of the observed frequency characteristic in the desktop calculation. Another factor is that the analysis assumes an overlap of reflection from various directions in the space, and a peak shift occurs when another electromagnetic wave overlaps a part of the reflection peak of the target concrete back surface. On the other hand, in the desktop calculation, the time is simply calculated by dividing the distance to the object by the velocity of the electromagnetic wave. Due to this difference, it is considered that the reflection arrival time in the desktop calculation is earlier than the reflection peak in the analysis graph.

  FIG. 15 shows the intensity change of the reflection peak with respect to the difference in the rust range. This reflection peak is due to the iron bar (and the back of the concrete) in the concrete. In the graphs shown in FIGS. 15A and 15B, the horizontal axis indicates the ratio of rust (unit is%, for example, 100% is a state in which all of the 80 cm long iron rod is covered with rust). Show. The vertical axis of the graph represents the intensity of the reflection peak (unit: mV / m). As shown to (a) in FIG. 15, when the ratio of rust increases, it turns out that the reflective intensity of a concrete back surface increases a little. Moreover, as shown to (b) in FIG. 15, it can confirm that the intensity | strength of the reflection peak of a iron bar falls, although it is not monotonous, as the ratio of rust increases.

  More specifically, (a) in FIG. 15 is a graph of the intensity of a reflection peak including an electric field intensity of 0 [mV / m]. In addition to the reflection peak due to the iron bar, the reflection peak due to the concrete back surface is also shown. On the other hand, (b) in FIG. 15 is an enlarged view of the location of the reflection peak due to the iron bar in the graph of (a) in FIG. As shown in FIG. 15B, when the rust ratio is 40% or less, the intensity of the reflection peak of the iron bar changes up and down. However, it can be confirmed that the intensity of the reflection peak clearly decreases until the rust ratio reaches 80%, with the rust ratio being 50%. By knowing such a change in the reflection peak of the iron bar, it becomes possible to detect the rust ratio, that is, the corrosion status of the reinforced concrete.

Next, the detection apparatus 200 of 2nd Embodiment is demonstrated.
FIG. 16 shows a configuration example of the detection device 200 and peripheral devices of the present embodiment. In addition, the same code | symbol is attached | subjected to the structure which has the same or similar function as 1st Embodiment. As illustrated in FIG. 16, the detection apparatus 200 includes a measurement result processing unit 201, a numerical analysis unit 202, a comparison unit 203, and an estimation unit 204.

  The measurement result processing unit 201 receives measurement data to be measured from the measuring instrument (radar apparatus) 111. In addition, the measurement result processing unit 201 acquires embedded facility information related to the measurement target embedded object from the facility DB 112. In the present embodiment, the measurement result processing unit 201 calculates the reflection time of the reflected wave related to the object based on the embedded facility information. And based on the calculated reflection time, the reflection peak regarding a target object is specified from the said measurement data. Furthermore, the measurement result processing unit 201 specifies the intensity of the reflection peak from the specified reflection peak. That is, the measurement result processing unit 201 performs processing from step S201 to step S205, which will be described later with reference to FIG.

  The numerical analysis unit 202 acquires embedded facility information from the facility DB 112. The numerical analysis unit 202 constructs a numerical analysis model based on the acquired embedded facility information. The numerical analysis unit 202 performs numerical analysis processing (electromagnetic field analysis simulation) and outputs a numerical analysis result. The numerical analysis result includes, for example, a plurality of degrees of deterioration of the target object and reflection peak intensity values corresponding to the respective degrees of deterioration.

  First, the comparison unit (comparison determination unit) 203 compares the result processed by the measurement result processing unit 201 with the result of numerical analysis performed by the numerical analysis unit 202. The comparison unit 203 determines that the numerical analysis model is appropriate when the difference between the result processed by the measurement result processing unit 201 and the numerical analysis result is within a predetermined range.

  The comparison unit 203 acquires past measurement data from the history DB 113. And the comparison part 203 determines the presence or absence of the change regarding a reflection peak by comparing the result which the measurement result process part 201 processed, and the past measurement data acquired from log | history DB113. For example, the comparison unit 203 compares the measured value of the intensity of the reflection peak from the measurement result processing unit 201 with the value of the peak intensity of the reflection peak included in the past measurement data, thereby determining whether there is a change in peak intensity. Determine. That is, the comparison unit 203 performs the processing of Step S206 and Step S207, which will be described later with reference to FIG.

  In addition, the detection apparatus 200 according to the present embodiment may include a comparison unit (comparison determination unit) 203a having a slightly different function instead of the comparison unit 203. For example, the comparison unit 203a detects the change amount and the change tendency regarding the reflection peak by comparing the result processed by the measurement result processing unit 201 with the past measurement data acquired from the history DB 113. For example, the comparison unit 203a detects a change amount and a change tendency of the reflection peak intensity. That is, the comparison unit 203a performs the processing of step S251 and step S252 described later with reference to FIG.

  When the comparison unit 203 or the comparison unit 203a determines that there is a change with respect to the reflection peak, the estimation unit 204, for example, changes in the intensity of the reflection peak due to deterioration obtained by numerical analysis and the reflected wave obtained by measurement. The degree of deterioration is estimated based on the intensity of the reflection peak. The estimation unit 104 determines the degree of deterioration based on past measurement data acquired from the history DB 113 (reflection peak intensity change due to deterioration recorded in the past) and the reflection peak intensity of the reflected wave obtained by measurement. May be estimated. That is, the estimation unit 204 performs processing from step S208 to step S210, which will be described later with reference to FIG. Note that in one modification, the estimation unit 204 may perform the processing of step S253 and step S254, which will be described later with reference to FIG.

Next, FIG. 17 shows an example of the processing flow of the detection method of this embodiment.
For example, FIG. 17 shows a processing flow for detecting rebar corrosion due to reflected waves. FIG. 17 shows the entire processing flow of this embodiment. In the following description, description of parts common to the processing flow of the first embodiment may be omitted.

  In the detection method of FIG. 17, at the beginning of the process flow, the buried equipment information to be measured is acquired from the equipment DB 112 (step S201). This embedded facility information includes the position (location), depth, shape, size, and the like of the embedded facility to be measured. The buried equipment information corresponds to information such as the depth and position of reinforcing bars in concrete.

  Next, the reflection time of the reflected wave on the object is calculated from the depth and position where the object (for example, a reinforcing bar) is embedded (step S202). That is, the time for the electromagnetic wave transmitted into the concrete to be reflected by the reinforcing bar is calculated. Then, measurement data (radar inspection information) is acquired by the measuring instrument 111 (step S203).

Next, based on the reflection time calculated in step S202, a reflection peak related to the object is specified from the measured measurement data (step S204). That is, reflection peaks due to reinforcing bars in concrete are selected and extracted.
Next, the intensity of the reflection peak at the object identified in step S204 is obtained (step S205). Then, the intensity of the reflection peak is compared with the intensity of the reflection peak of the reflected wave measured and recorded in the past for the same object (step S206). Thereby, it is determined whether or not the intensity of the reflection peak has changed (step S207).

  When there is a change in the intensity of the reflection peak (step S207: Yes), the intensity change of the reflection peak is collated with a theoretical value or a statistical value (step S208). Thereby, the state of deterioration of the object (the degree of deterioration) is estimated (step S209). On the other hand, if there is no change in the intensity of the reflection peak (step S207: No), it is assumed that there is no progress of deterioration of the object or that the deterioration cannot be detected (step S210).

  Here, similarly to the processing flow of FIG. 3, the theoretical / statistical collation in step S208 will be described in a little more detail in the processing flow shown in FIG. The theoretical collation in step S208 is an inspection for the intensity change value of the reflection peak in the numerical analysis (electromagnetic field simulation) results shown in FIGS. 9 to 15 of the second embodiment as described above. It is to collate the measured values measured by radar technology against the target buried equipment. On the other hand, the collation of the statistics in the step S208 means that a plurality of measured values measured in the past with respect to the buried equipment of the same type and type are used as a history, and these measured values and the state of deterioration (degree of deterioration) Prepare a database that is related to each other. And it is set as the collation of the statistics in step S208 to confirm the value which measured the buried equipment to check against the database. Or it is good also as collation of statistics to hold | maintain as a log | history the measured value measured several times in the past with respect to the same burying equipment, and to compare the value of this log | history with the value measured newly.

  FIG. 18 shows a modification of the processing flow of the detection method of the present embodiment. Specifically, FIG. 18 shows a modified example of the processing flow reprinted as (a) in FIG. 18 in a part of the processing flow of FIG. 17 described above. That is, in FIG. 17, the comparison between the new measurement value and the past measurement data (step S206), the determination of the presence or absence of the intensity change of the reflection peak (step S207), the intensity change of the reflection peak and the theory / statistics. The processes up to collation (step S208) and estimation of deterioration (rebar corrosion) situation of the object (step S209) are replaced as follows.

That is, as shown in FIG. 18B, in the processing flow of one modified example, after the comparison between the new measurement value and the past measurement data (step S206), the amount of change in the intensity of the reflection peak is It is determined whether or not the value is equal to or greater than a predetermined value (step S251). If the amount of change in the intensity of the reflection peak is greater than or equal to a predetermined value (step S251: Yes), it is then determined whether or not the intensity change in the reflection peak is a change in a predetermined direction (step S252). In this embodiment, it is determined whether or not the intensity change of the reflection peak is a change in the decreasing direction.
In a specific example, the predetermined value is set to 0.1 mV / m. In this case, in the case of changing from 2.37 mV / m to 2.25 mV / m in FIG. 15B, the amount of change in the intensity of the reflection peak is 0.1 mV / m or more, so that The condition that the value is equal to or greater than the predetermined value is satisfied, and the condition that the intensity change of the reflection peak is a change in the decreasing direction is satisfied.

When the intensity of the reflection peak is a change in the predetermined direction (step S252: Yes), the intensity of the reflection peak is compared with theory / statistics (step S253). The verification of this theory is a comparison between the measured value and the graph (b) in FIG. 15 obtained as a result of the simulation analysis. For example, it can be read from the graph that the ratio of rust when the intensity of the reflection peak is 2.25 mV / m is about 65%. Therefore, the state of deterioration of the object (corrosion of the reinforcing bar) is estimated by this collation (step S254).
On the other hand, if the determination result of either of the previous two determinations (step S251) and (step S252) is “No”, the deterioration of the object (corrosion of the reinforcing bars) cannot be clearly estimated. Alternatively, as shown in FIG. 17 above, it is estimated that there is no progress of deterioration of the object (corrosion of reinforcing bars) (step S210).

The processing flow shown in FIGS. 17 and 18 has been described above in the order of steps. The following is a supplementary explanation of the important items in these steps.
First, in FIG. 18B, the order of the two determinations (step S251) and (step S252) may be reversed. That is, first, it is determined whether or not the intensity change of the reflection peak is a change in a predetermined direction (step S251 ′), and subsequently, it is determined whether or not the change amount of the intensity of the reflection peak is greater than or equal to a predetermined value. (Step S252 ′). When both of these (step S251 ′) and (step S252 ′) are determined to be “Yes”, the process proceeds to the reflection peak intensity and theoretical / statistical collation (step S253). On the other hand, if one of the two determinations is “No”, it is estimated that the deterioration cannot be clearly estimated or the deterioration has not progressed (step S210).

  Next, as in FIG. 17, the theoretical / statistical collation in step S253 will be specifically described in the processing flow shown in FIG. In the collation of the theory in step S253, the buried equipment to be inspected is compared with the intensity change value of the reflection peak in the numerical analysis (electromagnetic field simulation) results shown in FIGS. 9 to 15 of the second embodiment. Compare the measured values against the measured values. On the other hand, in the collation of statistics in step S253, a plurality of measured values measured in the past for the same type or type of buried equipment are recorded, and a large number of records are used as history. This history is recorded in the database in correspondence with the degree of deterioration. The past measurement data recorded in this database is checked against the value measured for the buried equipment to be inspected. Thereby, collation of the statistics of step S253 is performed. Alternatively, it is also possible to leave a measured value measured a plurality of times in the past for the same buried equipment in the history, and compare the value of this history with a newly measured value for statistical comparison. Based on information from a database that associates numerical values measured with electromagnetic waves in the past with the same type or the same type of equipment and the state of deterioration, the reflection peak is more finely compared to the theory of numerical calculations such as simulation. Can be collated (step S253). In addition, also in the subsequent step S254, a more detailed degradation state can be estimated based on a database corresponding to past measurement values remaining in the history and the degradation state.

Next, supplementary explanation will be given for “estimation of deterioration of target object (corrosion of reinforcing bars) by collation” given in step S254 of FIG. 18B. For example, in the case of changing from 2.37 mV / m to 2.25 mV / m, the analysis result is obtained when the intensity of the reflection peak is 2.25 mV / m following the theoretical verification (step S253). As described above, it can be read from the graph (b) in FIG. 15 that the ratio of rust corresponding to the intensity of the reflection peak is about 65%. However, there is a case where the estimation of the deterioration state cannot be determined only by a numerical change by a single simple measurement. Therefore, preferable items are listed below for more accurate determination.
(I) Analysis side: Match the setting conditions before analysis to the on-site environment (match)
(Ii) Measurement side: Calibration / Calibration (iii) Detailed history (iv) Numeric value when sound

  First, since it is a numerical analysis as a matter of course, (i) it is important to set conditions before the analysis. Investigate on-site conditions as much as possible to match the on-site environment of the target equipment. For example, the model size, that is, the length and thickness of concrete, and the length of rebar use the design value of the buried equipment. For the depth of buried equipment, soil, and the like, it is conceivable to use information obtained by processing information at the time of buried installation or data obtained by first measuring by the electromagnetic wave method. The surveyed information is taken into analysis setting conditions, analyzed, and used as an analysis result.

  Further, not only the analysis side, but also (ii) calibration / calibration is required as the measurement side. For example, when the numerical value of the analysis result consistent with the field environment is obtained by the above (i), it is preferable to grasp how the numerical value actually measured for the target corresponds to the numerical value of the analysis result. For example, in this electromagnetic wave method, attention is paid to the amount of temporal change in the intensity of the reflection peak. Therefore, it is preferable to carry out measurement with the passage of time and obtain the relationship between the numerical change and the analysis result. That is, (ii) an example of calibration / calibration is calibration / calibration for grasping numerical changes over time in correspondence with analysis results.

  Furthermore, it is preferable that (iii) there is a detailed history related to the above-mentioned (ii) multiple measurements with time in calibration / calibration. Even the results (FIGS. 13 to 15) of the analysis (FIGS. 9 to 12) that do not reach the analysis results according to the above (i) field environment are not monotonous. Therefore, (iii) It is preferable to confirm in which position in the analysis result the change in the numerical value of the history (a plurality of values measured in the past) is located. Such (iii) detailed history includes (iv) the measurement value at the time of sound before the object deteriorates in order to determine whether there is deterioration in light of the analysis result. It may be preferable.

According to the detection method and the detection apparatus of the second embodiment as described above, the degree of deterioration of the object can be detected using the measurement result by the electromagnetic wave, as in the first embodiment.
Here, as described above with reference to FIGS. 1 and 2, the frequency shift may be shifted in the high frequency direction or in the low frequency direction. For this reason, although not many cases are assumed, when a specific condition is satisfied, an element that shifts in the high frequency direction overlaps with an element that shifts in the low frequency direction, and it may be assumed that the frequency shift cannot be measured.
On the other hand, in the present embodiment, the degree of deterioration is estimated based on the value of the measured peak intensity of the reflected wave or the degree of change in the peak intensity. According to such a configuration, even when the frequency shift cannot be measured, it is possible to reliably detect the state of deterioration of the object.

In the present embodiment, the degree of deterioration is estimated when the amount of change in the reflected wave characteristic is a predetermined value or more and the change in the reflected wave characteristic is a change in a predetermined direction. As an example, when the amount of change in the intensity or frequency of the reflection peak is a predetermined value or more and the change in the intensity or frequency of the reflection peak is a change in a predetermined direction, the degree of deterioration of the object is estimated. The According to such a configuration, for example, the degree of deterioration can be detected with relatively high accuracy even when the tendency of the intensity change of the reflection peak changes midway as described above. That is, in this embodiment, it is determined whether or not the amount of change in the intensity or frequency of the reflection peak is greater than or equal to a predetermined value, and whether or not the change in the intensity or frequency of the reflection peak is a change in a predetermined direction. This guarantees the accuracy in estimating the degree of deterioration.
In the above embodiment, it is determined whether the intensity change of the reflection peak is a predetermined value or more and whether the change is in a predetermined direction. Instead, the frequency shift of the reflection peak is more than the predetermined value. It may be determined whether or not it is a change in a predetermined direction.

(Third embodiment)
The third embodiment will be described with reference to FIGS. The third embodiment utilizes analysis of a steel bar model in vacuum (reflection peak intensity change).

  19 and 20 show a simulation model for a steel bar in a vacuum. Specifically, FIG. 19 shows an overall view of the simulation model. In FIG. 19, the analysis space has a size of 1.4 m × 1.4 m in both the X-axis and Y-axis directions and 1.1 m in the Z-axis direction. In this model, a cylindrical iron rod having a length of 80 cm in the Y-axis direction and a diameter of 1 cm on the XZ plane is arranged in the analysis space. Rust (thickness of 3 mm from the surface of the iron bar) is provided around a part (or all) of the iron bar. This rust range (the length in the Y-axis direction) is variable as a parameter from 1 cm to 80 cm. Furthermore, this model sends plane waves on the XY plane from the upper part (plus direction on the Z axis) to the lower side (minus direction on the Z axis) of the analysis space. And the observation point which receives the reflected wave which the plane wave reflected by the iron bar is arrange | positioned in the center upper part (Z-axis plus direction) of the analysis space (XY plane). An electromagnetic field simulation is performed with a steel bar model in a vacuum as shown in FIG.

  FIG. 20 shows an enlarged part of the simulation model. The enlarged portion of FIG. 20 shows a boundary portion between a portion where rust is provided and a portion where rust is not provided in the periphery (surface) of the iron bar. The shape of this rust is a ring surrounding the circle of the iron bar in the cross section of the XZ plane. In FIG. 20, a rectangular lattice drawn on the XY plane is a mesh for simulation analysis. As shown in FIG. 20, the diameter of the iron bar is 1 cm. Then, rust is covered with a thickness of 3 mm so as to surround the surface of the iron bar. For the part of the iron bar shown in FIG. 19, a mesh size of 1 mm including the periphery is adopted due to the restrictions described later. In FIG. 20, there are ten meshes of 1 mm size in the diametral cross-sectional direction of the iron bar as meshes in the XY cross section inside the iron bar and rust. Moreover, the same mesh for three pieces can be confirmed in rust in the thickness direction.

In the rectangular mesh shown in FIG. 20, the material constants (dielectric constant, conductivity, etc.) of each substance constituting the model are set. In FIG. 20, the material constant of a complete conductor is set for the iron bar. On the other hand, for rust, a dielectric constant and conductivity including frequency characteristics of ferric oxide (Fe ₂ O ₃ ) are set as material constants. In particular, the material constant of Fe ₂ O ₃ is set on the surface of the iron bar that surrounds the rust. Thereby, the surface part of the iron bar is set to be corroded (rusted).

The reason why it is set as described above is because there are the following three restrictions as a model for simulation and the situation regarding the rust of the reinforcing bar.
(1) If the reinforcing bar is cut by 10% in cross-sectional area, a structural problem will occur.
(2) The volume expansion coefficient when iron is oxidized to become rust is 2.5. This numerical value is shown in Non-Patent Document 2, for example.
(3) The minimum mesh size that can be set in the analysis space is 1 mm.
The reason why the minimum mesh size that can be set in the analysis space is 1 mm is as follows. That is, when the mesh size in the analysis space is changed from 10 mm to 1 mm, it is confirmed that there is an influence in the analysis evaluation for the same model with the same size. Even if the mesh size is changed in such a range from 10 mm to 1 mm, the analysis result is converged by making it finer. It has been confirmed by the present inventors that the reflection peak change is sufficiently accurate with a 1 mm mesh size.

  When the above three restrictions are satisfied, the surface of the iron bar is set to be replaced with rust as shown in FIG. This actually means that the surface of the reinforcing bar is corroded and shaved. The mesh with this setting will be explained. In the iron rod model with rust shown in FIG. 20, one layer of mesh that hits the surface of the iron rod is rusted from the iron among the 10 equally divided meshes in the direction of the diameter cross section. It has become. Then, when the reinforcing bar corrodes from the iron of the corresponding mesh 1 layer, the mesh 4 layers outward including the surface mesh of the iron bar, and the volume of 3 meshes are changed to rust. In addition, in the setting of the iron priority listed in the analysis results shown in FIGS. 21 to 23 described later, the mesh has three layers of rust, and the volume does not change and three pieces are rusted.

  This time, the time domain difference (FDTD) method used for electromagnetic field simulation does not handle a single rectangular parallelepiped block made of mesh. Material constants of the substance are set for each of the 12 sides of the rectangular parallelepiped made of the mesh, and this setting is used for analysis. In the above description of changing the iron surface to rust, since it relates to the cross section of the iron bar shown in FIG. 20 on the XY plane, one side of the mesh is referred to as a layer. The part that hits the surface with the original iron bar, or the part newly formed as rust around the iron bar is also a side, but in the above description, it is called a “layer” because it has a shape in the cross section.

Next, the time response of the reflected wave with respect to the iron bar in the vacuum in this embodiment is demonstrated.
FIG. 21 shows an overall view of the time response of the reflected wave with respect to the iron bar in vacuum. In the time response shown in FIG. 21, the horizontal axis represents time (unit: nsec) and the vertical axis represents electric field strength (unit: V / m), as in FIG. 13 of the second embodiment. Also, in this time response graph, the rust surrounding the model iron bar has options of whether the surface of the iron bar is also rust (rust priority) or whether the surface of the iron bar is iron (iron priority). In addition, the range of rust surrounding the iron bar (length 80 cm) is variable to 10 cm, 20 cm, 30 cm, and 40 cm.

  In the graph of FIG. 21, there is a reflection peak (hereinafter referred to as a first reflection peak) of about 0.135 V / m to 0.145 V / m at about 4 nsec. This first reflection peak is the reflection of electromagnetic waves by the iron bar. Then, after about 4 nsec of the first reflection peak, the electric field strength rises every about 3 nsec (from 4.7 nsec to 48 mV / m, 7.8 nsec to 26 mV / m, 10.4 nsec to 14 mV / m, 13. 5 nsec to 11 mV / m, 16.2 nsec to 9 mV / m, etc.). It is presumed that the increase in the electric field intensity is caused by resonating the electric field excited on the iron bar by the irradiated electromagnetic wave and re-radiating the electromagnetic wave from the iron bar. The rising of the electric field strength and the first reflection peak from the iron bar have slightly different peak shapes and rising shapes of the electric field strength due to differences depending on rust priority / iron priority and rust range.

  In the graph of the analysis result shown in FIG. 21, in addition to the case of rust priority as a model setting, the result is also shown for the case of iron priority. The reason why the results of different model settings are combined (arranged) in FIG. 21 and FIG. 22 and FIG. 23 described later is that the numerical value of the analysis result varies depending on the model settings, but the range of rust is changed. This is to show that the tendency of changing the reflection peak that appears sometimes is the same. In other words, this means that it is confirmed that two different settings show the same tendency in this numerical analysis study for various forms of rust.

Here, in order to show in more detail how the difference in intensity of the first reflection peak differs depending on the rust setting, the encircled portion of the broken line in the graph of FIG. 21 is shown in FIG.
In the first reflection peak shown enlarged in FIG. 22, it can be confirmed that the rust priority is higher than the iron priority and the intensity of the reflection peak is higher. For example, when the rust ranges are both 10 cm, the intensity of the iron-priority reflection peak is 0.144 V / m, and the intensity of the rust-priority reflection peak is 0.146 V / m. In addition, regarding the range of rust, there is a tendency that the intensity of the reflection peak decreases as rust expands. For example, with priority on rust, the intensity of the reflection peak is 0.144 V / m, 0.142 V / m, 0.139 V / m, 0.136 V / as the range of rust expands to 10 cm, 20 cm, 30 cm, and 40 cm. It can be read that m decreases. For each of these rust settings (iron priority / rust priority, rust range), the graph of FIG. 23 shows how the electric field strength value of the first reflection peak changes.

  FIG. 23 shows the change in intensity of the reflection peak with respect to the rust range. This model is a horizontal bar in a vacuum. In the graph of FIG. 23, the vertical axis represents the intensity of the reflection peak (V / m), and the horizontal axis represents the range of rust (unit: cm). In the graph of (a) in FIG. 23, the range of the vertical axis is 0 to 0.16 V / m. On the other hand, the graph of (b) in FIG. 23 is an enlarged view of a portion of the range of 0.134 V / m to 0.148 V / m in which the intensity of the reflection peak as a result of analysis changes. As shown in the graph (b) in FIG. 23, it can be seen that the intensity of the reflection peak monotonously decreases as the range of rust increases.

In particular, in the case where rust is given priority, that is, when the position corresponding to the surface of the iron bar is set to the material constants (dielectric constant and conductivity) of rust, the intensity of the reflection peak decreases more significantly in the range of rust. As shown in FIG. 20, the rust priority setting is a grid mesh of 1 mm for analysis on a 1 cm diameter steel bar, and the surface of the iron bar is rusted within the range where there is rust. Material constants (dielectric constant and conductivity). As a result, the thickness of rust is substantially 4 mm. This numerical value of thickness is appropriate for the following reason.
The reason, first, when the iron is ferric oxide by oxidation (Fe 2 _{O 3),} the general inflation rate, there is a point which is 2.5 times. In addition, the numerical value of 2.5 times is a value shown by the nonpatent literature 2, for example. From another viewpoint, it is said that when 10% of the reinforcing steel bars corrode in concrete, problems arise in structural strength. From these two points, in the grid mesh for every 1 mm for analysis, set the grid mesh up to the 3 mm grid mesh around the iron bar to rust, and set the mesh grid side that hits the iron bar surface to the rust material constant. Therefore, the total is substantially 4 mm.

  Here, as shown in the graph of (b) in FIG. 23, the intensity of the reflection peak tends to decrease monotonously as the range of rust increases. Therefore, it is conceivable to utilize this tendency in the inspection. That is, if it can be determined from the measurement data and past history (past measurement data) that the intensity of the reflection peak is reduced, the extent of the rust, that is, the degree of corrosion of the reinforced concrete, depending on the degree to which the intensity decreases. Can be grasped.

Next, the detection apparatus 300 of 3rd Embodiment is demonstrated.
FIG. 24 shows a configuration example of the detection device 300 and peripheral devices of the present embodiment. In addition, the same code | symbol is attached | subjected to the structure which has the same or similar function as 1st and 2nd embodiment. As illustrated in FIG. 24, the detection apparatus 300 includes a measurement result processing unit 201, a numerical analysis unit 202, a comparison unit 303, an estimation unit 204, and a processing necessity determination unit 305.

The comparison unit (comparison determination unit) 303 acquires past measurement data from the history DB 113. And the tendency of the change of a reflection peak is detected by comparing the result processed by the measurement result processing unit 201 with the past measurement data acquired from the history DB 113. For example, the comparison unit 303 determines whether the intensity change of the reflection peak is a change in a predetermined direction. In the present embodiment, the comparison unit 303 determines whether the intensity change of the reflection peak is a change in the decreasing direction. That is, the comparison unit 303 performs a process of step S301 described later with reference to FIG.
In addition, the estimation unit 204 according to the present embodiment performs processing in step S302 and step S303, which will be described later with reference to FIG.

  After estimating the degree of deterioration, the processing necessity determination unit 305 determines whether or not the object needs to be maintained based on the estimated degree of deterioration. That is, the process necessity determination unit 305 performs a process of step S304 described later with reference to FIG. A specific example of processing by the processing necessity determination unit 305 will be described in a processing flow described later.

Next, an example of the processing flow of the detection method of this embodiment is shown.
Here, FIG. 17 and FIG. 18 described in the second embodiment will be referred to again. Note that the processing flow until the intensity change of the reflection peak is detected is substantially the same as that in the second embodiment, and thus the description thereof is omitted here.

  (A) in FIG. 18 is a comparison between new measurement values and past measurement data in FIG. 17 (step S206), determination of presence / absence of reflection peak intensity change (step S207), measurement data and theory / statistics. The process until collation with (step S208) and estimation of deterioration of the object (step S209) is shown.

  In the present embodiment, a comparison between new measurement values and past measurement data (step S206), determination of presence / absence of reflection peak intensity change (step S207), collation between measurement data and theory / statistics (step S208), The processing flow up to the estimation of deterioration of the object (step S209) is replaced as follows.

  That is, as shown in FIG. 18C, in the processing flow of the present embodiment, after comparison between a new measurement value and past measurement data (step S206), first, the intensity change of the reflection peak is changed. It is determined whether or not the change is in a predetermined direction (step S301). In this embodiment, it is determined whether or not the intensity change of the reflection peak is a change in the decreasing direction. If it is determined that the intensity change of the reflection peak is a change in a predetermined direction (step S301: Yes), the intensity of the reflection peak is compared with theory / statistics (step S302).

  Next, based on the result of this collation (step S302), the state of deterioration of the target (rebar corrosion) is estimated (step S303). For example, when the intensity of the reflection peak is 0.138 V / m and the past data is 0.144 V / m, it is determined in step S301 that the intensity of the reflection peak has decreased. In comparison with the theoretical value (step S302) and estimation of the deterioration state of the object (step S303), based on (b) in FIG. 23, for example, the peak intensity is 0.138 V / m and the range of rust is about Estimated to be 35 cm.

Thereafter, in the process flow of (c) in FIG. 18, it is determined whether or not the object needs to be dealt with (maintenance) based on the degree of deterioration estimated in step S303 (step S304). That is, in step S304, it is determined whether or not the estimated degree of deterioration is greater than or equal to a predetermined value. If the estimated degree of deterioration is equal to or greater than a predetermined value, it is determined that countermeasures (maintenance) are necessary. On the other hand, if the estimated degree of deterioration is less than a predetermined value, it is determined that no countermeasure (maintenance) is necessary.
For example, in the graph of (b) in FIG. 23, the intensity of the reflection peak when there is a standard in which the progress is observed at a rust range of 20 cm or less, and maintenance is required at 30 cm or more. Is 0.138 V / m (estimated rust range: about 35 cm), the determination in step S304 is “Yes” that requires maintenance. On the other hand, either the determination of whether or not the intensity of the reflection peak is a change in a predetermined direction (step S301) or the determination whether or not the estimated deterioration progress needs to be dealt with (maintenance) (step S304). However, if “No”, as shown in FIG. 17, it is presumed that there is no progress of deterioration of the object (corrosion of the reinforcing bars) (step S210).

  Here, similarly to FIG. 3 and FIG. 17, the theoretical / statistical collation in step S302 will be described in the processing flow shown in (c) of FIG. In the verification of the theory in step S302, the buried facility to be inspected is inspected with respect to the intensity change value of the reflection peak in the numerical analysis (electromagnetic field simulation) results shown in FIGS. 19 to 23 of the third embodiment. Compare the measured values against the measured values. On the other hand, in the statistical verification in step S302, a plurality of measurement values measured in the past for the same type and type of buried equipment are recorded, and a large number of records are used as histories. This history is recorded in the database in correspondence with the deterioration state. The past measured values recorded in this database are checked against the values measured for the buried equipment to be inspected. Thereby, collation of the statistics of step S302 is performed. Alternatively, it is also possible to leave a measured value measured a plurality of times in the past for the same buried equipment in the history, and compare the value of this history with a newly measured value for statistical comparison. Based on information from a database that associates numerical values measured by radio waves with the same type or the same type of equipment in the past and grasps the state of deterioration, reflection peaks are more finely compared to the theory of numerical calculations such as simulation. Strength change and statistics can be collated (step S302). In addition, in the subsequent step S303, a more detailed degradation state can be estimated based on a database corresponding to past measurement values remaining in the history and the degradation state.

  (C) in FIG. 18 is a step that is not included in the processing flow of (a) or (b) in other FIG. 18, “determining whether or not countermeasures (maintenance) are required for the progress of estimation degradation” ( Step S304). The reason for this is, for example, in FIG. 18B, a theory (numerical analysis) for collating the results of an analysis model including concrete that is relatively close to reality (see FIG. 15). For this reason, a probable judgment is assumed in the theoretical verification. On the other hand, (c) in FIG. 18 is a processing flow (steps S301 to S303) based on a policy of dealing with even a range including a slightly incorrect determination from the analysis result (see FIG. 23) using only the iron bar as a model. ). For this reason, in order to check against a case where an erroneous determination is included, it is determined whether or not it is necessary to deal with (maintenance) the progress of the estimation deterioration in step S304 in (c) in FIG. Provided.

According to the detection method and the detection apparatus of the third embodiment as described above, the degree of deterioration of the object can be detected using the measurement result by the electromagnetic wave, as in the first embodiment.
In the present embodiment, after estimating the degree of deterioration, it is determined based on the estimated degree of deterioration whether or not the object needs maintenance. According to such a configuration, even when a somewhat large error is estimated with respect to the degree of deterioration, it is possible to narrow down the cases where it is necessary to deal with the object in the process of determining the necessity of dealing with the object. . In other words, some errors can be allowed as a result of numerical analysis. For this reason, an analysis model can be simplified (for example, the element of concrete can be omitted). Thereby, the time and cost required for the model construction of numerical analysis etc. can be held down.

Further, in the present embodiment, it is determined whether or not the change in the intensity or frequency of the reflection peak is a change in a predetermined direction, and when the change in the intensity or frequency of the reflection peak is a change in the predetermined direction, Estimate the degree of degradation. According to such a configuration, the deterioration state can be detected with relatively high accuracy. That is, in this embodiment, the accuracy in estimating the degree of deterioration is ensured by determining whether or not the change in the intensity or frequency of the reflection peak is a change in a predetermined direction.
In the above embodiment, it is determined whether the intensity change of the reflection peak is a change in a predetermined direction. Alternatively, it may be determined whether the frequency shift of the reflection peak is a change in a predetermined direction. .

(Fourth embodiment)
The fourth embodiment will be described with reference to FIGS. 25 to 30. The fourth embodiment is intended for a steel bar in concrete including a soil layer. That is, in the fourth embodiment, various conditions such as the depth of the soil layer and the moisture content of the concrete are considered.

FIG. 25 shows a steel bar model in concrete including a soil layer. That is, FIG. 25 is a simulation model in which a soil layer is added to the steel bar model in the concrete shown in FIG. 9 of the second embodiment.
In the simulation model of FIG. 25, the iron rod portion with rust hits the dielectric constant of rust around the portion in the specified range from the center in the cylindrical iron shown in FIGS. 19 and 20 of the third embodiment. The structure is covered with a dielectric.

  The input wave is the same XY plane as the surface of the concrete board. That is, as the input wave, a plane wave that propagates from the upper side to the lower side (from the positive side of the Z axis to the negative side) in FIG. 25 is used. The observation point for receiving the electric field strength in the space is provided above the center of the model (Z axis plus side).

FIG. 26 shows a side view of a steel bar model in concrete including a soil layer. FIG. 26 shows a structure in which a soil layer is added to the upper part of the concrete with respect to the steel bar model in the concrete shown in FIG. 10B of the second embodiment. The concrete thickness (Z-axis direction) is 20 cm. On the other hand, the depth of the soil layer is variable between 5 cm and 15 cm.
In FIG. 26, the description is omitted (also in FIG. 10 above), but the dielectric constant of the concrete in the simulation model of the electromagnetic field analysis is the dielectric constant in the wet state (ε _r : 10.5−frequency 1 GHz). ). The dielectric constant of the soil layer in the simulation model, the dielectric constant of the state where the clay and sand are mixed with water content of 30% (ε _r: 12.8- at frequency 1 GHz) to adopt.
As described above, the electromagnetic field simulation is performed using the iron bar model in the concrete including the soil layer described with reference to FIGS. 25 and 26.

Next, the time response of the reflected wave to the iron bar in the concrete including the soil layer will be described.
FIG. 27 shows the time response of the reflected wave by the iron bar in the concrete including the soil layer. FIG. 27 shows the entire result graph and an enlarged part of it. The time response graph shown in FIG. 27 is obtained when the depth of the soil layer is 5 cm. The model also includes vacuum, soil, concrete, horizontal bar, and rust. Reflections occur at these various boundaries. For this reason, in FIG. 27, the time during which the reflected wave propagates at the main boundary is calculated on the desk and displayed on the time axis on the graph. These are reflections on the soil surface, concrete surface, iron bar, and concrete back surface. In the overall time response shown in FIG. 27, the reflection time on the soil surface calculated on the desktop coincides with the reflection time of the strongest peak (reflection on the ground) of the graph. In the reflection time by the horizontal bar, when the graph of the analysis result is enlarged, the peak is present although it is weak as less than 5 mV / m.

Next, the difference in the intensity change of the reflection peak with respect to the depth of the soil layer will be described.
FIG. 28 shows the intensity of the reflection peak by the iron bar with respect to the depth of the soil layer. That is, FIG. 28 shows analysis results at different soil layer depths. For example, (a) in FIG. 28 shows the intensity of the reflection peak when the depth of the soil layer is 5 cm. Moreover, (b) in FIG. 28 shows the analysis result when the depth of the soil layer is 7.5 cm. In each of graphs (a) and (b) in FIG. 28, the horizontal axis represents the rust ratio [%], and the vertical axis represents the reflection peak intensity [mV / m].

  As can be seen from the two graphs shown in FIGS. 28A and 28B, the intensity value of the reflection peak varies depending on the depth of the soil layer. For example, the intensity of the reflection peak in the soil layer of 5 cm is a value between about 1.0 mV / m and 1.4 mV / m. In addition, the intensity of the reflection peak at the soil layer of 7.5 cm is a value between about 1.6 mV / m and 1.7 mV / m. Also, the change in the intensity of the reflection peak is different. For example, the reflection peak at a soil layer of 5 cm has a maximum value with respect to the rust ratio of 0%, but the reflection peak at the soil layer of 7.5 cm has a maximum value at a rust ratio of around 25%. In other words, depending on how deep the object is buried, how much the intensity of the reflection peak will be in advance by numerical calculation etc. considering this depth, and the rate at which the iron bar rusted Thus, it is necessary to grasp how the intensity of the reflection peak changes.

Table 1 shows the amount of change in the intensity of the reflection peak with respect to the depth of the soil layer. As shown in Table 1, in the model in which only the rust is provided on the iron rod in the concrete explained in the second embodiment, that is, in the model including the soil layer, when compared with the case where the soil layer is 0 cm, Under the influence of attenuation, the amount of change in the intensity of the reflection peak due to the horizontal bar (maximum / minimum difference or rate of change) is decreasing.

  As shown in FIG. 28 and Table 1, as a result of electromagnetic field analysis using a steel bar in a concrete including a soil layer as a model, the intensity change of the reflection peak with respect to the range where the steel bar is covered with rust is the depth of the soil layer. Was shown to be different. Therefore, it is necessary to consider conditions such as the depth at which the object is embedded in the change in the reflection peak obtained as the analysis result.

Next, the detection apparatus 400 of 4th Embodiment is demonstrated.
FIG. 29 shows a configuration example of the detection device 400 and peripheral devices of the present embodiment. In addition, the same code | symbol is attached | subjected to the structure which has the same or similar function as 1st-3rd embodiment. As illustrated in FIG. 29, the detection apparatus 400 includes a measurement result processing unit 201, a numerical analysis unit 202, a first comparison unit 401, a second comparison unit 402, a determination unit 403, and an estimation unit 204.

  The first comparison unit (first comparison determination unit) 401 compares past measurement data from the history DB 113 and the result of numerical analysis performed by the numerical analysis unit 202. In the present embodiment, the numerical analysis unit 202 has a curve (curve shown in FIG. 28, hereinafter referred to as a “reflection curve”) connecting a plurality of numerical analysis results having different degrees of deterioration of the object as a result of the numerical analysis. ) Is output. The first comparison unit 401 compares the reflection peak intensity value of the reflected wave measured in the past with the reflection curve. In other words, the first comparison unit 401 determines whether or not the difference between the reflection peak intensity value of the reflected wave measured in the past and the reflection curve is within a predetermined range. When the difference between the reflection peak intensity value of the reflected wave measured in the past and the reflection curve is within a predetermined range, the first comparison unit 401 determines that the numerical analysis model is appropriate. To do. That is, the first comparison unit 401 performs a process of step S401 described later with reference to FIG.

The second comparison unit (second comparison determination unit) 402 is substantially the same as the comparison unit 203 of the second embodiment. That is, the second comparison unit 402 compares the result processed by the measurement result processing unit 201 with the result of numerical analysis performed by the numerical analysis unit 202. The second comparison unit 402 determines that the numerical analysis model is appropriate when the difference between the result processed by the measurement result processing unit 201 and the numerical analysis result is within a predetermined range.
In the present embodiment, the second comparison unit 402 compares the reflection peak intensity value from the measurement result processing unit 201 with the reflection curve. In other words, the second comparison unit 402 determines whether the difference between the reflection peak intensity value of the newly measured reflected wave and the reflection curve is within a predetermined range. When the difference between the reflection peak intensity value of the newly measured reflected wave and the reflection curve is within a predetermined range, the second comparison unit 402 determines that the numerical analysis model is appropriate. To do. That is, the second comparison unit 402 performs the process of step S402 described later with reference to FIG.

The determination unit 403 receives the comparison result of the first comparison unit 401 and the comparison result of the second comparison unit 402, and determines whether it is possible to estimate deterioration using the newly measured value. That is, the determination unit 403 performs the process of step S403 described later with reference to FIG. The specific processing of the determination unit 403 will be described in detail in the description of the processing flow described later.
In addition, the estimation part 204 of this embodiment performs the process of step S404 mentioned later using FIG.

Next, FIG. 30 shows an example of the processing flow of the detection method of this embodiment.
In the present embodiment, rebar corrosion is detected in consideration of various conditions such as the depth of the soil layer. The processing flow shown in FIG. 30 is a detailed extraction of a part of the characteristic change detection method of FIG. 17 described in the second embodiment. That is, “(a) Degradation status estimation from reflection peak intensity” in FIG. 30 is the same as the four steps (steps S206 to S209) of the processing flow shown in FIG. In the present embodiment, these four steps are replaced with the correspondence of (b) in FIG.

  In the processing flow shown in FIG. 30 (b), it is first determined whether or not the numerical analysis result obtained by the analysis considering various conditions such as the depth of the soil layer and the humidity of the concrete matches the past measurement data. (Step S401). In the present embodiment, as a numerical analysis result, whether or not past measurement data coincides with a “reflection curve” obtained by connecting a plurality of numerical analysis results with different degrees of deterioration (for example, the ratio of rust) by a curve. (That is, whether or not the difference is within a predetermined range). That is, when past measurement data is located on the reflection curve, it is determined that the numerical analysis result matches the past measurement data. If the past data matches the reflection curve obtained by analysis in the determination in step S401 (step S401: Yes), the process proceeds to the next determination (step S402).

  In step S402, it is determined whether or not the intensity of the newly measured reflection peak matches the previously obtained numerical analysis result (that is, whether or not the difference is within a predetermined range). That is, when a new measurement value is positioned on the reflection curve, it is determined that the numerical analysis result matches the new measurement value. If the new measurement value matches the numerical analysis result (step S402: Yes), the process proceeds to the next determination step S403. Note that the order of step S401 and step S402 may be reversed.

  In step S403, it is determined whether or not deterioration can be estimated from the curve obtained by analysis and the measurement result. When all these three determinations are Yes, the state of deterioration (corrosion of reinforcing bars) of the object is estimated (step S404). On the other hand, if any one of the three determinations is “No”, in FIG. 17, it is estimated in step S210 that there is no progress of deterioration of the object (corrosion of the reinforcing bar) or the technique of the present invention is used. Even if used, deterioration cannot be detected and estimated.

Next, supplementary explanation will be given for each step of the processing flow shown in FIG.
First, step S401 (determining whether or not the reflection curve obtained by analysis matches the past measurement data) and step S402 (whether or not the reflection curve obtained by analysis and the newly measured reflection peak intensity match). The two steps of (determination) are supplemented.
An example is shown in FIG. 30, but the obtained analysis result is not a change in which the reflection peak monotonously decreases with respect to the ratio of rust. Therefore, the analysis result and the measured value cannot be simply compared and collated. For this reason, it is preferable to confirm a detailed history (change in values of both past and new measurements). Therefore, in order to confirm the detailed history, the determination is divided into two steps. That is, as shown in (b) in FIG. 30, the first step (step S401) is to determine whether or not past values that have already been measured match the results obtained by analysis. Also, the second step (step S402) is to determine whether or not the newly measured value matches the analysis result.

  Next, it supplements about step S403 (determining whether degradation can be estimated). Here, the conditions regarding the buried equipment to be measured include, for example, the depth of the buried underground, the dielectric constant of the soil, and the state of the reinforcing bars in the concrete constituting the equipment. In this step S403, a graph of deterioration range and reflection peak intensity change is used for determination from the result of numerical analysis based on these setting conditions. In the fourth embodiment, FIG. 27 shows the analysis result, and FIG. 28 shows the intensity change of the reflection peak. In relation to the graphs of these analysis results, it is confirmed where the values of actual buried objects measured by the electromagnetic wave method are located, and whether there have been changes including past measurement values that were in a healthy state.

  Here, a little supplement will be made regarding the processing flow shown in FIG. Even if the above analysis results match the values of the past measurement and the new measurement (that is, even if the determinations in steps S401 and S402 are both “Yes”), there are cases where the estimation of deterioration cannot be performed. In this most frequent example, the measurement value of the reflection peak has not changed to the value at the time of deterioration, that is, the measurement target may remain in a healthy state when collated with the change in the curve obtained by analysis. As another example, there is a case where the new measurement value is different from the past value, but is within a range that cannot be regarded as a change from the accuracy of the measurement. In these cases, the determination (step S403) whether or not the deterioration can be estimated is “No”. In other words, in the present embodiment, a predetermined condition for determining whether or not deterioration can be estimated is set. Then, it is determined whether or not the predetermined condition is satisfied. As a result, when the predetermined condition is not satisfied, a determination result that “degradation cannot be estimated” is output instead of a determination that “no deterioration”.

  As an example of the predetermined condition, when there is a trend change in the reflection curve with an increase in the ratio of rust, a past measurement value or a new measurement value is added to the reflection curve both before and after the trend change. (The difference is within a predetermined range). That is, using the graph of (b) in FIG. 28, for example, when the ratio of rust is about 25%, a trend change is seen in the reflection curve. That is, when the ratio of rust is between 0% and about 25%, the reflection curve is upward. On the other hand, when the ratio of rust exceeds about 25%, the reflection curve is downward for a certain period. It is suitable. For this reason, when the past measurement value and the new measurement value coincide with the reflection curve both before and after the trend change (for example, when the rust ratio is in the range of 0% to about 40%) It is possible to determine that the analysis model is appropriate and “degradation can be estimated”. On the other hand, when there is a tendency change in the reflection curve when the rust ratio is about 25%, for example, when there are past measurement values and new measurement values only in the range of the rust ratio of 0% to 20%. It is difficult to determine whether the reflection curve is appropriate. In this case, it is determined that “deterioration cannot be estimated”.

  In addition, as another example of the predetermined condition, a trend change accompanying an increase in the ratio of rust is present in the reflection curve, and the intensity of the reflection peak is substantially the same at a plurality of points where the ratio of rust is different. The time interval from the measurement to the new measurement is within a predetermined period. For example, with reference to the graph (b) in FIG. 28, in the reflection curve, when the rust ratio is about 50% and when the rust ratio is about 100%, the intensity of the reflection peak is approximately. The same (about 1.65 mV / m). For this reason, in the case where measurement has not been performed for a while since the last measurement period, when the intensity of the newly measured reflection peak is about 1.65 mV / m, the rust ratio is 50%. It is difficult to determine whether it is 100% or not. In this case, it is determined that “deterioration cannot be estimated”. On the other hand, when the time interval from the previous measurement to the new measurement is within a predetermined period, the determination can be made based on the general progress rate of deterioration. In this case, it can be determined that “deterioration can be estimated”.

Finally, a specific process in step S404 (estimation of deterioration status) will be supplemented. By the plurality of determinations up to step S403 immediately before this, the intensity change of the reflection peak capable of estimating the deterioration state is obtained. In step S404, the position where the measured value corresponds to the curve obtained by analysis is collated. Considering that it is preferable to have a detailed history so far, for example, it is assumed that the curve change obtained by the analysis is (b) in FIG. Record of the measurement of 3 degrees as reflection peak intensity in the past (history: 1.686 mV / m-2 years ago, 1.705 mV / m-1 years ago, matching the curve shown in FIG. 28B) 1.702 mV / m-6 months ago). In addition, if the newly measured value is positioned on the curve following the previous measured value (1.671 mV / m-current measurement), the rust ratio (55%) at that position is the estimated degradation status. become. In addition, as a premise that this deterioration state can be estimated, a measurement accuracy of 10 ⁻² mV / m or more is preferable.

According to the apparatus and method of the fourth embodiment as described above, the degree of deterioration of the object can be detected using electromagnetic waves, as in the first embodiment.
In the detection method of the present embodiment, the difference between the reflected wave characteristic recorded in the past and the reflected wave characteristic based on the numerical analysis result is within a predetermined range, and the measured reflected wave characteristic is When the difference from the reflected wave characteristic based on the numerical analysis result is within a predetermined range, the degree of deterioration of the object is estimated. As an example, the difference between the peak intensity or frequency of the reflected wave recorded in the past and the peak intensity or frequency based on the numerical analysis result is within a predetermined range, and the peak of the measured reflected wave is When the difference between the intensity or frequency and the peak intensity or frequency based on the numerical analysis result is within a predetermined range, the degree of deterioration of the object is estimated. According to such a configuration, when the influence of the surrounding embedded medium is large (for example, when soil is included), the suitability of the analysis model can be determined. Thereby, it is possible to detect the deterioration state of the object with relatively high accuracy. That is, in this embodiment, whether or not the difference between the peak intensity or frequency of the reflected wave recorded in the past and the peak intensity or frequency based on the numerical analysis result is within a predetermined range is measured. By determining whether or not the difference between the peak intensity or frequency of the reflected wave and the peak intensity or frequency based on the numerical analysis results is within a predetermined range, the accuracy in estimating the degree of deterioration is ensured. ing.
In the above embodiment, the intensity of the reflection peak is compared with the numerical analysis result (reflection curve). Alternatively, the frequency of the reflection peak may be compared with the numerical analysis result (reflection curve). .

  In the present embodiment, a predetermined condition for determining whether or not deterioration can be estimated is set. Then, it is determined whether or not the predetermined condition is satisfied. As a result, when the predetermined condition is not satisfied, a determination result that “degradation cannot be estimated” is output instead of a determination that “no deterioration”. According to such a configuration, it is possible to ensure the accuracy of estimation of the deterioration of the object.

Although the first to fourth embodiments have been described above, the embodiments are not limited to these. For example, the method and apparatus of the present invention can be realized by a computer and a program, and the program can be recorded on a recording medium or provided through a network. That is, you may make it implement | achieve the detection apparatus 100,200,300,400 in embodiment mentioned above with a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be a program for realizing a part of the above-described functions, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. You may implement | achieve using programmable logic devices, such as FPGA (Field Programmable Gate Array).
The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  100, 200, 300, 400 ... detection device, 101, 201 ... measurement result processing unit, 102, 202 ... numerical analysis unit, 103, 203, 203a, 303 ... comparison unit (comparison determination unit), 104, 204 ... estimation unit 305 ... Processing necessity determination unit 401 ... First comparison unit (first comparison determination unit) 402 ... Second comparison unit (second comparison determination unit) 403 ... Determination unit.

Claims (9)

The reflected wave characteristics of the reflection peak of the reflected wave obtained from the measurement result of the reflected wave from the reinforcing bar of the electromagnetic wave transmitted toward the reinforcing bar in the structure, and the reflected wave recorded in the past with respect to the reinforcing bar A comparison step for comparing the characteristics;
If there is the change in the reflected wave characteristics in comparison of the comparing step, based on the amount of change in the measured pre SL reflected wave characteristics, the estimating step of estimating the degree of deterioration of the reinforcing bars,
Have
In the estimation step,
Based on the history of a plurality of measurement values measured in the past with respect to the reinforcing bars of the same type of reinforcing bar, associates the variation of the previous SL reflected wave characteristic to each of the degree of variation of a plurality of degradation of the reinforcing bar Keep track of
By collating the change amount before SL reflected wave characteristics measured amount of change in the understanding to have that before SL reflected wave characteristics detection method to estimate the degree of deterioration of the reinforcing bar. The reflected wave characteristics of the reflection peak of the reflected wave obtained from the measurement result of the reflected wave from the reinforcing bar of the electromagnetic wave transmitted toward the reinforcing bar in the structure, and the reflected wave recorded in the past with respect to the reinforcing bar A comparison step for comparing the characteristics;
In the comparison in the comparison step, the reflected wave characteristic is changed, and the reflected wave characteristic and the numerical value measured in the past are based on the history of a plurality of measured values measured in the past and newly with respect to the reinforcing bar. The difference between the reflected wave characteristic based on the analysis result is within a predetermined range, and the difference between the newly measured reflected wave characteristic and the reflected wave characteristic based on the numerical analysis result is predetermined. If it is within the range, based on the amount of change in the measured pre SL reflected wave characteristics, the estimating step of estimating the degree of deterioration of the reinforcing bars,
A detection method comprising: The estimated step, based on the amount of change in frequency before SL peaks to estimate the degree of deterioration of the reinforcing bars,
The detection method according to claim 1 or claim 2. The estimated step, based on the amount of change in intensity before SL peaks to estimate the degree of deterioration of the reinforcing bars,
The detection method according to claim 1 or claim 2. In the estimation step, when the amount of change in the reflected wave characteristic is a predetermined value or more and the change in the reflected wave characteristic is a change in a predetermined direction, the degree of deterioration of the reinforcing bar is estimated.
The detection method according to any one of claims 1 to 4. Based on the degree of deterioration of the reinforcing bars estimated in the estimating step, the method further comprises a determination step of determining whether maintenance is required for the reinforcing bars.
The detection method according to any one of claims 1 to 5. The reflected wave characteristics of the reflection peak of the reflected wave obtained from the measurement result of the reflected wave from the reinforcing bar of the electromagnetic wave transmitted toward the reinforcing bar in the structure, and the reflected wave recorded in the past with respect to the reinforcing bar A comparison unit for comparing the characteristics;
If there is a change in the reflected wave characteristics in comparison by the comparison unit, an estimation unit which, based on the amount of change in the measured pre SL reflected wave characteristics, estimates the degree of deterioration of the reinforcing bars,
With
The estimation unit includes
Based on the history of a plurality of measurement values measured in the past with respect to the reinforcing bars of the same type of reinforcing bar, associates the variation of the previous SL reflected wave characteristic to each of the degree of variation of a plurality of degradation of the reinforcing bar Keep track of
By collating the change amount before SL reflected wave characteristics measured amount of change in the understanding to have that before SL reflected wave characteristics, detecting device for estimating the degree of deterioration of the reinforcing bar. The reflected wave characteristics of the reflection peak of the reflected wave obtained from the measurement result of the reflected wave from the reinforcing bar of the electromagnetic wave transmitted toward the reinforcing bar in the structure, and the reflected wave recorded in the past with respect to the reinforcing bar A comparison unit for comparing the characteristics;
In the comparison by the comparison unit, there is a change in the reflected wave characteristics, and the reflected wave characteristics and numerical values measured in the past are based on a history of a plurality of measured values measured in the past and newly with respect to the reinforcing bar. The difference between the reflected wave characteristic based on the analysis result is within a predetermined range, and the difference between the newly measured reflected wave characteristic and the reflected wave characteristic based on the numerical analysis result is predetermined. If it is within the range, an estimation unit which, based on the amount of change in the measured pre SL reflected wave characteristics, estimates the degree of deterioration of the reinforcing bars,
A detection device comprising:   The program for making a computer perform the detection method as described in any one of Claims 1-6.