JP2001289830A - Method for inspecting internal concrete structure part in concrete structure having outer layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for inspecting capable of easily non-destructively inspecting a craze stage or the like of an internal concrete structure part in a concrete structure having an outer layer on a periphery of the structure part. SOLUTION: The method for inspecting the internal concrete structure part in the concrete structure having the outer layer comprises the steps of standing a plurality of waveguide rods, one end of each of which is exposed from the outer layer through the outer layer and the other ends of which are closely fixed to the internal concrete structure part of the structure of a member to be inspected, introducing an ultrasonic pulse of an ultrasonic method into the internal concrete structure part through the rods exposed from the outer layer, receiving the incident ultrasonic pulse, and further detecting an elastic wave generated in the case of plastically deforming or destroying the structure part in an AE method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for inspecting a concrete structure, and more particularly to a method for non-destructively inspecting an internal concrete structure in a concrete structure having an outer layer.

[0002]

2. Description of the Related Art Conventionally, non-destructive inspection methods for concrete structures include visual inspection, inspection by a penetration method, inspection by an ultrasonic method, and acoustic inspection.
Inspection and the like by measuring emission (hereinafter, referred to as “AE method”) are known.

The visual inspection is a method for inspecting the presence or absence of a defect existing on the surface with the naked eye. Although this method depends on the inspection range and the skill level, it is a method that can detect a considerably small surface defect.

Inspection by the penetrating method is a method in which a penetrating liquid is penetrated into a defect existing on the surface of a subject by utilizing a capillary phenomenon, and the defect is detected as an image which can be easily seen with the naked eye. This method includes a fluorescence penetration test and a dye flaw detection test. In the fluorescent penetration test, a penetrating solution containing a fluorescent substance is permeated into a defect of a subject, and the defect is caused to emit yellow-green light by ultraviolet rays to make an image which is easily visible to the naked eye.
On the other hand, the dye flaw detection test uses a penetrating solution containing a red dye and observes a red defect indicating pattern.

In the examination by the ultrasonic method, an ultrasonic pulse is incident on a subject, and the quality of the subject, for example, based on the sound speed of the incident ultrasonic wave in the subject or the amplitude of the received ultrasonic wave, is measured. The strength, the state of cracks, and the like are determined.

[0006] In the inspection by the AE method, an elastic wave (AE) generated when the subject is plastically deformed or broken is detected, and the cracking state of the subject is determined from the rate of occurrence and amplitude of the elastic wave. Is what you do.

[0007]

Here, the visual inspection and the inspection by the penetration method are based on the premise that the concrete surface of a concrete structure as a test object can be observed from the outside. In the inspection by the ultrasonic method, it is necessary to install the ultrasonic oscillator and the oscillator in close contact with the concrete surface of the concrete structure in order to ensure the incidence and reception of the ultrasonic pulse. Have been done. Also, in the inspection by the AE method, it is necessary to install an AE sensor (resonator) in close contact with the concrete surface of the concrete structure in order to reliably detect the generated elastic wave.

Therefore, the concrete surface of the concrete structure has an outer layer covered by another material layer (for example, a cylindrical concrete structure such as an apparatus for desalinating seawater is made of urethane resin, In the case of a concrete structure that is covered with a heat insulating layer such as glass fiber and the outer periphery is further covered with a concrete or steel structural body.) When inspecting the concrete structure existing inside, the outer layer is obstructive. As a matter of course, it is impossible to carry out visual inspection and inspection by the penetration method. Further, in a concrete structure having such an outer layer, since the oscillator and the receiver cannot be installed on the concrete surface of the inner concrete structure, the above-described inspection by the ultrasonic method or the AE method is also difficult. was there.

Accordingly, an object of the present invention is to easily and non-destructively inspect a concrete structure having an outer layer around such a concrete structure, such as a crack state, in the concrete structure existing inside the concrete structure. It is to provide a test method that can be performed.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a concrete structure having an outer layer around a concrete structure, one end of which is exposed from the outer layer through the outer layer. A plurality of waveguide rods whose ends are fixedly adhered to the internal concrete structure portion of the subject are erected, and an oscillator or a receiver is attached to one end of the waveguide rod exposed from the outer layer, thereby obtaining the ultrasonic method. And the AE method can be performed on the internal concrete structure via a waveguide rod.

That is, according to the present invention, the ultrasonic pulse is applied to the internal concrete structure in the ultrasonic method, the ultrasonic pulse is received, and the internal concrete structure in the AE method is plastically deformed or broken. The detection of the elastic waves generated at this time is performed through a plurality of waveguide rods that penetrate the outer layer and are erected in a state of being tightly fixed to the internal concrete structure part as the test object.

Therefore, according to the present invention, a non-destructive inspection by the ultrasonic method and the AE method can be performed on a concrete structure having an outer layer around a concrete structure portion, which has been impossible in the related art. The deterioration state of the internal concrete structure that cannot be directly seen can be easily grasped.

Here, in the inspection by the ultrasonic method using the waveguide rod in the present invention, an ultrasonic pulse is incident on the concrete structure portion and the incident ultrasonic wave is separated by a known distance, as in the prior art. The state of cracks in the concrete structure is determined from the sound speed of the ultrasonic wave in the concrete structure obtained when the vibration is received at the position or the amplitude of the received ultrasonic wave. In addition, at least the effectiveness of the ultrasonic wave incident or received through the waveguide rod, that is, the inspection of the effectiveness of the waveguide rod as a sensor is performed by the ultrasonic method. Since it is not possible to directly grasp the contact state of the waveguide rod with the concrete structure from the outside, it is necessary in the present invention to check whether the waveguide rod is in an appropriate measurement state. This is because the nature occurs.

Inspection of the effectiveness of the waveguide rod as a sensor is performed, for example, immediately after manufacture, to confirm that the waveguide rod is in a state of being tightly fixed to the internal concrete structure of the concrete structure to be tested. At the time point, the ultrasonic pulse is incident using the waveguide rod, and received, the maximum amplitude value of the ultrasonic wave measured at that time as a reference value, at a later date, the same ultrasonic pulse incident, and This can be performed by comparing the maximum amplitude value of the ultrasonic wave measured at the time of receiving the vibration with the reference value.

In the inspection by the AE method, an elastic wave generated from the concrete structure at the time of plant operation or the like is detected through the waveguide rod in the same manner as in the prior art, and the generation rate and amplitude of the elastic wave are detected. Therefore, it is performed for the purpose of grasping the state of cracks in the concrete structure portion, which is the subject, at an early stage.

The above-mentioned waveguide rod, which stands up in a state of being tightly fixed to the concrete structure, efficiently transmits ultrasonic waves incident on or received from the concrete structure via the waveguide. It is important to use a material that does. Therefore, for example, a waveguide rod made of stainless steel, ceramic, or the like having an acoustic impedance close to that of concrete is used. The shape of the waveguide rod is linear so that it can penetrate the outer layer in the shortest possible time. Further, in order to increase the contact area with the concrete structure, it is also preferable to use a truncated conical waveguide rod.

In addition, the structure in which the waveguide rod is erected in a state of being tightly fixed to the internal concrete structure of the concrete structure to be tested is not easily rattled.
In addition, the contact area with the concrete structure is increased. For this purpose, for example, a bulging portion is formed at the end of the waveguide rod, and the bulging portion side is buried in the concrete structure portion, or a nut of the same quality as the waveguide rod is buried in the concrete structure portion, It is preferable to use a structure in which a screw portion formed around the end of the waveguide rod is screwed to the nut.

Further, when the outer layer covering the concrete structure through which the waveguide rod penetrates is made of a material which can easily transmit ultrasonic waves, an acoustic material such as soft rubber is provided between the waveguide rod and the outer layer. A material with low impedance is interposed. this is,
This is to prevent ultrasonic waves that enter the concrete structure via the waveguide rod or are transmitted from the concrete structure from transmitting to the outer layer side.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a cross sectional view of an apparatus (concrete structure) for desalinating seawater, and FIG. 2 is a longitudinal sectional view. The apparatus 1 for desalinating seawater has a thickness of 200 mm,
A plurality of cylindrical concrete segments 2a each having an outer diameter of about 500 cm and a height of about 200 cm are vertically connected to each other to form a cylindrical concrete structure 2 having a height of 50 m, an outer diameter of 500 cm, and an inner diameter of 460 cm, and an outer periphery of the cylindrical concrete structure 2. A heat insulating layer 3 of glass fiber with a thickness of about 150 mm covering the heat insulating layer 3 and a thickness 2 further covering the outer periphery of the heat insulating layer 3
The apparatus has a three-layer structure with a concrete structural body 4 of about 00 mm.

During operation, the inside of the apparatus 1 is exposed to seawater at a temperature of 140 ° C., a pressure of 2 × 10 ⁵ Pa, and a pH of about 2 to ³ , and its use environment becomes extremely severe. Therefore, it is necessary to periodically or irregularly inspect the deterioration state of the apparatus, particularly the deterioration state of the innermost cylindrical concrete structure 2 which is directly affected by temperature, pressure, and the like.

The innermost cylindrical concrete structure 2
Inspection of the state of deterioration is performed using a plurality of waveguide rods 5 erected on the cylindrical concrete structure 2. The waveguide rod 5 is a solid stainless steel rod having a diameter of 20 mm and a length of about 40 cm. As shown in FIG. 1, eight waveguide rods 5 are erected radially at an interval of 45 ° in the same horizontal plane with respect to the cylindrical concrete structure 2. As shown in FIG. 2, the eight waveguide rods 5 are erected in the same horizontal plane in the vertical direction with respect to the cylindrical concrete structure 2 as shown in FIG. 2.
It is performed at intervals of about cm.

The upright structure of the waveguide rod 5 on the cylindrical concrete structure 2 is as shown in FIG. That is, the nut 6 made of stainless steel, which is the same material as the waveguide rod 5,
Is embedded in the cylindrical concrete structure 2 in advance, and the nut 6 has a threaded portion 7 formed on one end 5 a of the waveguide rod 5.
By screwing them together.

The waveguide rod 5 erected on the cylindrical concrete structure 2 penetrates through the heat insulating layer 3 covering the outer periphery of the cylindrical concrete structure 2 and the concrete structural frame 4, and The other end 5b of the waveguide rod 5 is exposed on the surface of the cylindrical concrete structure 2 so as to be exposed.

As shown in FIG. 4, a soft rubber 8 is interposed between the waveguide 5 and the concrete structural body 4 through which the waveguide 5 penetrates. This is for blocking the transmission of the ultrasonic wave between the waveguide rod 5 and the concrete structural body 4.

As described above, the cylindrical concrete structure 2
Next, a method of inspecting the deterioration state of the cylindrical concrete structure portion 2 using the waveguide rod 5 erected in the following will be described. First, the ultrasonic oscillator 10a and the transducer 10b are
The end 5b of the waveguide bar 5 exposed from the surface of the device 1.
Then, grease or other material is used so as to be in close contact with no gap.

The ultrasonic oscillator 10a and the transducer 10
For b, a common one can be used. For example, a piezoelectric sensor in which a piezoelectric element based on barium titanate, zirconic acid, or lead titanate is placed in a case is provided with the above-described oscillator 10a and transducer 10
b can be used. Then, as shown in FIG. 5, an oscillator of an ultrasonic pulse is connected to the oscillator 10a, and the oscillator 10b is connected to the ultrasonic measuring device via a preamplifier.

Then, an ultrasonic pulse is incident on the cylindrical concrete structure 2 from the oscillator 10a via the waveguide rod 5, and the other waveguide rod 5 erected at a position separated by a predetermined distance.
The ultrasonic wave transmitted through the cylindrical concrete structure 2 through the antenna is received by the receiver 10b. Then, the maximum amplitude value of the received ultrasonic wave was determined immediately after the device 1 was manufactured, at a point in time when it was confirmed that each waveguide rod 5 was in a state of being tightly fixed to the cylindrical concrete structure 2 as the test object. The effectiveness of each waveguide 5 as a sensor is checked by comparing it with the maximum amplitude value of the ultrasonic wave measured in the same manner. Also, based on the sound speed of the ultrasonic wave in the cylindrical concrete structure 2 or the amplitude of the received ultrasonic wave, the deterioration state of the cylindrical concrete structure 2 such as cracks is determined based on the same standard as the inspection by the normal ultrasonic method. Is determined.

During the operation of the apparatus 1, an AE sensor 10c (a piezoelectric sensor similar to the ultrasonic oscillator 10a and the transducer 10b used for the inspection in the ultrasonic method) can be used. It is installed at the end 5b of the waveguide bar 5 exposed from the surface. Then, as shown in FIG. 6, an AE measuring device is connected to the AE sensor 10c, and an elastic wave (AE) generated from the cylindrical concrete structure 2 during operation of the device 1 is transmitted through the waveguide rod 5. And detected by the AE sensor 10c. Then, based on the detected rate of occurrence and amplitude of the elastic wave, the occurrence of cracks in the cylindrical concrete structure 2 and the position of occurrence of the cracks are estimated based on the same standard as the inspection by the normal AE method. .

The above inspection is performed on the apparatus 1 regularly or irregularly, whereby the deterioration state of the internal cylindrical concrete structure 2 which cannot be directly seen from the outside is grasped, and the apparatus 1 is sounded. Drive in a proper state.

Although the embodiment of the inspection method according to the present invention has been described above, the present invention is not limited to the above-described embodiment, and the technical idea of the present invention, that is, concrete having an outer layer When inspecting the internal concrete structure of a structure, the ultrasonic pulse is applied to the concrete structure by the ultrasonic method, the ultrasonic pulse is received, and the concrete structure is plastically deformed or destroyed by the AE method. A technology that detects elastic waves generated when performing through a plurality of waveguide rods that are erected while penetrating the outer layer and tightly fixed to the internal concrete structure of the concrete structure to be inspected Various modifications and changes are possible within the spirit of the invention.

For example, the cylindrical concrete structure 2 as a test object and the apparatus (concrete structure) 1 having the cylindrical concrete structure 2 as one of the constituent elements shown in the above embodiment are examples. It's just Therefore, the inspection method according to the present invention is applicable to various concrete structures having an outer layer and which cannot be directly inspected by visual inspection or the like, for example, a foundation portion of a structure, an internal concrete structure portion of a nuclear power plant facility or the like. It can also be implemented.

Further, the material, shape and the like of the waveguide rod 5 shown in the above embodiment are merely examples. Therefore, as the material of the waveguide rod, a material having an acoustic impedance similar to the acoustic impedance of the concrete structure portion to be tested, for example, a material having an acoustic impedance of 0.7 × 10 ⁷ to 10 × 10 ⁷ Pa · s / m is used. In addition, a waveguide rod made of, for example, ceramic, aluminum, titanium, or the like other than stainless steel can be used. Further, the shape of the waveguide rod is not limited to the columnar shape, but may be a prismatic shape, a truncated cone shape, or the like.
Further, it is preferable that the dimensions of the waveguide rod have an end portion having an area where the sensor can be sufficiently installed, and that the length be within 1 m in consideration of attenuation of ultrasonic waves. Further, it is preferable that the interval between the standing waveguide rods is about 2 m.

Further, in the above-described embodiment, the case where the soft rubber 8 is interposed between the waveguide bar 5 and the outer layer (the concrete structural body 4) through which the waveguide bar 5 penetrates has been described. The material is not limited to soft rubber, but may be any material having a small acoustic impedance, for example, a material having an acoustic impedance of 0.3 × 10 ⁷ Pa · s / m or less. Therefore, a styrene resin, an acrylic resin, or the like may be interposed. Also, the outer layer through which the waveguide rod penetrates is made of a material having a small acoustic impedance,
For example, when it is made of a material having an acoustic impedance of 0.3 × 10 ⁷ Pa · s / m or less, it is not necessary to interpose soft rubber or the like.

[0035]

Test Example Next, a basic test for finding the above-described inspection method according to the present invention will be described below.

-Basic test 1- (Specimen) The following materials were used, and the water / cement ratio was 4
Concrete having a slump of 4.5 cm was prepared under the conditions of 9.8%, fine aggregate ratio of 44.7%, and water reducing agent / cement ratio of 0.25%. Cement; Taiheiyo Cement Co., Ltd. Ordinary Portland cement Fine aggregate; Ome-produced crushed sand Coarse aggregate; Ome-produced crushed stone Water reducer; Pozoris Bussan Co., Ltd. 70 water; industrial water

The concrete thus prepared was mixed with D13 (S
D295A) and D10 (SD295A) are poured into a 125 × 200 × 2700 mm formwork arranged as shown in FIG. 7 and, as shown in FIG.
Four stainless steel solid bars (waveguide bars) having a length of 530 mm and a length of 530 mm were erected at predetermined intervals with the lower end 50 mm buried in the concrete poured into the mold.
Then, after being cured in the air at 20 ° C. for 28 days, the four waveguide rods ch1 to ch4 are erected in a tightly fixed state 12
A reinforced concrete specimen of 5 × 200 × 2700 mm was prepared. A notch having a depth of about 20 mm was provided at the center of the lower edge of the reinforced concrete test piece, as shown, to control the position where cracks occurred.

(Loading Method on Specimen) As shown in FIG. 7, two-line loading was carried out on the reinforced concrete specimen using a fatigue tester (EHF-11D30-70L, manufactured by Shimadzu Corporation). Then, bending loading was performed according to the following loading steps. Loading step 0: zero loading weight (test piece: sound) Loading step 1: loading weight 5.9KN (test piece: slightly cracked) Loading step 2: loading weight 10.5KN (test piece: 1/3 of bending strength) Loading step: Crack propagation) Loading step 3: Loading weight of 20.9 KN (specimen: loading of 2/3 of the bending strength, considerably crack propagation) Loading step 4: Loading weight of 31.4 KN (specimen: fracture)

(Installation and Measurement of Piezoelectric Sensor etc. on Specimen) Waveguide rod ch of the reinforced concrete specimen prepared above.
Piezoelectric sensors (R6 manufactured by Nippon Physical Acoustic Corporation) at the tips of 1 to ch4
Was placed in close contact with grease without any gap. The ultrasonic sensor (C-101-HV, manufactured by Nippon Physical Acoustic Corporation) mounted on the piezoelectric sensor installed on the waveguide rod ch1 is a piezoelectric sensor installed on the other waveguide rods ch2 to ch4. The sensors were each connected to a measuring device (MISTRAS, manufactured by Nippon Physical Acoustic Corporation). Then, after performing bending loading according to the above-described loading step, the rise time 20
An nsec, 300 V spike wave is incident through the waveguide rod ch1, and the incident ultrasonic wave is transmitted to another waveguide rod c.
The sound was received via h2 to ch4, and the sound speed of the ultrasonic wave in each reinforced concrete test specimen and the maximum amplitude value of the received ultrasonic wave were measured.

Further, all of the above piezoelectric sensors installed on the waveguide rods ch1 to ch4 were measured using a measuring device (manufactured by Nippon Physical Acoustic Corporation, MISTR:
AS). Then, the elastic waves generated during the loading are applied to the reinforced concrete test specimens during the bending loading in the loading step 1 described above by waveguide rods ch1 to ch.
4 respectively.

(Test Results) On the log-logarithmic graph with the maximum amplitude value of the ultrasonic wave on the vertical axis and the measurement position on the horizontal axis, the above-mentioned ultrasonic method performed on the reinforced concrete specimen after the loading step 0 was performed. Is plotted. FIG. 8 shows the result. In addition, the vertical axis represents the sound speed of the ultrasonic wave, and the horizontal axis represents the loading step.
The measurement data obtained by the above-described ultrasonic method performed on the reinforced concrete test specimens after the bending loading of No. 4 was plotted. FIG. 9 shows the result. The vertical axis represents the maximum amplitude value ratio of the ultrasonic wave [the maximum amplitude value measured after the loading in the loading steps 1 to 4 / the maximum amplitude value measured after the loading step 0 (in a healthy state)], and the horizontal axis represents the loading. The measured data by the above-described ultrasonic method, which were respectively performed on the reinforced concrete test specimens after the bending loading of loading steps 0 to 4, were plotted on the graphs having the steps. Figure 1 shows the results.
0 is shown. Further, the number of AE hits detected on the vertical axis is
The measurement data by the AE method performed on the reinforced concrete test specimen during the bending loading in loading step 1 is plotted on a graph in which the measurement position is plotted on the horizontal axis. The result is shown in FIG. Note that the maximum amplitude value of the ultrasonic wave was as shown in FIG.

-Basic test 2- (Test body) As in the above-described basic test 1, four waveguide rods ch
125 × 20, standing upright with 1 to 4 tightly fixed
A reinforced concrete specimen of 0 × 2700 mm was produced. Then, above the reinforced concrete specimen, FIG.
As shown in Fig. 3, thickness 250mm
And a 50 mm-thick concrete plate separately made of homogeneous concrete.
Note that the concrete plate placed above has a waveguide rod ch1.
In addition, a hole having a diameter of 30 mm through which ~ ch4 penetrates was formed, and the hole was filled with soft rubber. A notch having a depth of about 20 mm was also provided at the center of the lower edge of the reinforced concrete test piece having the outer layer in the same manner as in the above-described basic test 1 to control the crack generation position.

(Test Method and Test Results) The same test as in the above-described basic test 1 was performed on the reinforced concrete test piece having the above outer layer, and measurement data by the ultrasonic method and the AE method were obtained. The sound velocity of the ultrasonic wave on the vertical axis, on the graph taking the loading step on the horizontal axis, by the ultrasonic method respectively performed on the reinforced concrete test specimen having an outer layer after performing bending loading of loading steps 0 to 4 The measurement data was plotted. The result is shown in FIG. Note that FIG.
Corresponds to FIG. 9 of the basic test 1. In addition, the number of AE hits detected on the vertical axis is plotted on the graph with the measurement position on the horizontal axis, and the AE performed on the reinforced concrete specimen having the outer layer in the middle of the bending loading in loading step 1 is shown. The data measured by the method were plotted. The result is shown in FIG. FIG. 15 corresponds to FIG. 11 of the basic test 1.

-Basic test 3- (Test body) As in the above-described basic test 1, four waveguide rods ch
125 × 20, standing upright with 1 to 4 tightly fixed
A reinforced concrete specimen of 0 × 2700 mm was produced. Then, thereafter, only the waveguide rod ch3 was hit with a hammer, so that the waveguide rod ch3 was not tightly fixed to the reinforced concrete test body. Then, as shown in FIG. 16, a glass fiber layer having a thickness of 250 mm was placed above the reinforced concrete test specimen in a state capable of loading, as shown in FIG. A concrete plate was placed. In addition, the concrete plate placed above has a diameter of 3 through which the waveguide rods ch1 to ch4 penetrate.
In addition to drilling a hole of 0 mm, the hole penetrated by the waveguide rods ch1 to ch3 is filled with soft rubber, and the hole penetrated by the waveguide rod ch4 is mortar [cement: 1, standard sand: 2 (weight ratio) ), Water / cement ratio: 0.65]. A notch having a depth of about 20 mm was also provided at the center of the lower edge of the reinforced concrete test piece having the outer layer in the same manner as in the above-described basic test 1 to control the crack generation position.

(Test Method and Test Results) A test similar to the above-described basic test 1 was performed on a reinforced concrete test piece having the above outer layer, and measurement data by an ultrasonic method was obtained. The ultrasonic method performed on the reinforced concrete specimen after the loading step 0 and after the loading step 3 on a log-logarithmic graph with the maximum amplitude value of the ultrasonic wave on the vertical axis and the measurement position on the horizontal axis. Is plotted. The result is shown in FIG. FIG. 17 corresponds to FIG. 8 of the basic test 1.

[Summary of Basic Tests 1 to 3] Based on the test results of the basic test 1, through a waveguide rod that is erected in a state of being tightly fixed to a concrete structure portion as a test object,
Effectively, the ultrasonic pulse is applied to the concrete structure in the ultrasonic method, the received ultrasonic pulse is received, and the elastic wave generated when the concrete structure is plastically deformed or destroyed in the AE method is effective. It turned out to be done. In addition, from the test results of the basic test 2, in the concrete structure having the outer layer, similarly, through the waveguide penetrating the outer layer and standing upright in a state of being tightly fixed to the concrete structure as the test object, It was found that inspection by the ultrasonic method and inspection by the AE method were possible. Further, from the test results of the basic test 3, it was found that the validity of the waveguide as a sensor can be checked from the maximum amplitude value of the ultrasonic wave received through the waveguide.

[0047]

According to the method for inspecting an internal concrete structure in a concrete structure having an outer layer according to the present invention described in detail above, a concrete having an outer layer around a concrete structure which has heretofore been impossible is impossible. Non-destructive inspection of the structure by the ultrasonic method and the AE method becomes possible, and there is an effect that the deterioration state of the internal concrete structure that cannot be directly seen from the outside can be easily grasped.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an apparatus for desalinating seawater.

FIG. 2 is a longitudinal sectional view of an apparatus for desalinating seawater.

FIG. 3 is a partially enlarged cross-sectional view showing a standing structure of a waveguide rod on a cylindrical concrete structure.

FIG. 4 is a partially enlarged sectional view showing a penetrating state of an outer layer of the waveguide rod.

FIG. 5 is a configuration diagram of an inspection by an ultrasonic method using a waveguide rod according to the present invention.

FIG. 6 is a configuration diagram of an inspection by an AE method using a waveguide rod according to the present invention.

FIG. 7 is a conceptual side view showing a reinforced concrete test specimen used in a basic test 1 for finding an inspection method according to the present invention, and a method of loading the test specimen.

FIG. 8 is a view showing the results of a basic test 1.

FIG. 9 is a diagram showing the results of a basic test 1.

FIG. 10 is a diagram showing the results of a basic test 1.

FIG. 11 is a diagram showing the results of a basic test 1.

FIG. 12 is a diagram showing how to obtain a maximum amplitude value of a waveform.

FIG. 13 is a conceptual side view showing a reinforced concrete specimen having an outer layer used in a basic test 2 in which an inspection method according to the present invention was found.

FIG. 14 is a view showing the results of a basic test 2.

FIG. 15 is a view showing a result of a basic test 2.

FIG. 16 is a conceptual side view showing a reinforced concrete specimen having an outer layer used in a basic test 3 in which an inspection method according to the present invention was found.

FIG. 17 is a view showing the results of a basic test 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Desalination apparatus of seawater 2 Cylindrical concrete structure 3 Heat insulation layer by glass fiber 4 Concrete structure frame 5 Waveguide rod 6 Stainless steel nut 7 Screw part 8 Soft rubber 10a Ultrasonic oscillator 10b Ultrasonic wave reception Pendulum 10c AE sensor

Claims (4)

[Claims] 1. A concrete structure having an outer layer around a concrete structure part, one end of which is exposed from the outer layer through the outer layer and the other end closely adheres to the inner concrete structure part of the concrete structure to be tested. A plurality of fixed waveguide rods are erected, and the ultrasonic pulse in the ultrasonic method is incident on the internal concrete structure portion through the waveguide rod exposed from the outer layer, and the ultrasonic pulse received is further received, A method for inspecting an internal concrete structure in a concrete structure having an outer layer, comprising detecting an elastic wave generated when the internal concrete structure undergoes plastic deformation or breakage in the AE method. 2. The effectiveness of the waveguide rod as a sensor is determined by inputting and receiving ultrasonic pulses to an internal concrete structure through the waveguide rod, and measuring the ultrasonic waves measured at that time. The method for inspecting an internal concrete structure in a concrete structure having an outer layer according to claim 1, wherein the judgment is made from the maximum amplitude value. 3. The acoustic impedance of the waveguide rod is:
0.7 × 10 ⁷ to 10 × 10 ⁷ Pa · s / m,
An inspection method for an internal concrete structure in a concrete structure having an outer layer according to claim 1. 4. A member having an acoustic impedance of 0.3 × 10 ⁷ Pa · s / m or less is interposed between the waveguide rod and an outer layer through which the waveguide rod penetrates. One, two
Or the inspection method of the internal concrete structure part in the concrete structure which has an outer layer as described in 3.