JP7291325B2 - Non-Destructive Exploration Method and Apparatus for Internal Corners of Concrete Structures Using Electromagnetic Radar - Google Patents

Description

The present invention relates to a method and apparatus for non-destructive inspection of concrete structures using electromagnetic wave radar, and more particularly to a method and apparatus for non-destructive inspection of internal corners of concrete structures.

A small electromagnetic wave radar device with a short radio wave propagation axis distance between the front surface of the antenna and the center of the antenna (the center of the transmitting antenna and the receiving antenna) is used when searching for an internal corner of a concrete structure.

Conventionally, as a method of exploring the inside of a concrete structure using an electromagnetic wave radar device, there is a method of detecting cracks that occur inside a reinforced concrete structure (Patent Document 1), and a method of detecting corroded parts of reinforcing bars inside a reinforced concrete structure. A method of measuring (Patent Document 2), a method of detecting cracks and cavities in concrete structures (Patent Document 3), and the like have been proposed.

JP 2018-155551 A JP 2009-244076 A JP-A-2008-39429

However, in the conventional method, as shown in FIGS. 7 and 8, since there is a distance between the front surface of the antenna section of the small electromagnetic wave radar device 10 and the radio wave propagation axis at the center of the antenna section, the entrance of the concrete structure 1 is difficult. A measurement dead angle W, which is difficult to detect, occurs in the corner 2, and it is difficult to detect the earthquake-resistant slit (void) 3 and reinforcing bars (buried objects) 4 placed in the inside corner 2.

The present invention has been made in view of the above problems, and uses an electromagnetic wave radar that enables non-destructive exploration of embedded objects or voids placed in internal corners of concrete structures, which have been blind spots in the past. It is an object of the present invention to provide a non-destructive inspection method and apparatus for inside corners of concrete structures.

In order to solve the above problems, a nondestructive exploration method for an internal corner of a concrete structure using an electromagnetic wave radar according to the present invention includes:
In a non-destructive inspection method for an internal corner between a wall surface of a concrete structure and a concrete surface perpendicular thereto using an electromagnetic wave radar,
When radiating electromagnetic waves from an electromagnetic wave radar device to a concrete structure to search for seismic slits in embedded reinforcing bars or gaps located in the internal corners between the wall surface of the concrete structure and the concrete surface perpendicular to it. ,
The internal corner of the concrete structure has a relative dielectric constant of 6 to 9, has a slope that ascends toward the internal corner, and has an acute angle that is the starting point side of the slope when viewed in longitudinal section. Made of granite, which has a wedge-shaped right-angled triangle consisting of a front end, an acute-angled apex on the terminal side of the slope, and a right-angled portion located at the corner of the internal corner, and has no reflector inside . A wedge -shaped electromagnetic wave propagating material is arranged so that the top portion and the right-angled portion are in contact with the wall surface of the concrete structure , and an electromagnetic wave radar device is installed along the slope of the wedge-shaped electromagnetic wave propagating material to the inner corner portion. By running in a direction perpendicular to the direction of the reinforcing bars of the buried object or the direction of the earthquake-resistant slit in the gap , the electromagnetic wave is radiated to the concrete structure so that the electromagnetic wave propagation axis is oblique to the surface of the concrete structure. The main feature is to search for seismic slits in embedded rebars or gaps located in internal corners between the wall of a concrete structure and the concrete surface perpendicular thereto .

Granite has a stable dielectric constant close to that of concrete, does not contain metal inside, and is strong. When a wedge-shaped electromagnetic wave propagating material is made of concrete, its strength is weaker than that of granite. and it becomes difficult to distinguish between gaps.

When the wedge-shaped electromagnetic wave propagating material is made of concrete, the relative permittivity tends to vary depending on the water content, and correction of the relative permittivity becomes complicated. A wedge-shaped electromagnetic wave propagating material made of wood has a significantly different relative dielectric constant from that of a concrete structure.

A hard substance having a dielectric constant of 6 to 9 is a ceramic member having mica as a main component. It is desirable that the wedge-shaped electromagnetic wave propagating material has a dielectric constant of 6-8.

In the present invention, a wedge-shaped electromagnetic wave propagating material having a dielectric constant of 6 to 9, which is almost the same as that of concrete, and having no reflecting objects such as reinforcing bars inside is placed at an internal corner of a concrete structure, and lead is placed on the slope of the concrete structure. By running the electromagnetic wave radar device on the surface of the concrete structure and obliquely radiating the electromagnetic wave to the surface of the concrete structure, the electromagnetic wave propagation axis extending in the direction perpendicular to the antenna radiation surface from the center position of the transmitting antenna and the receiving antenna It is possible to reach inside the inside corner, and compared with the conventional method, there is an effect that the measurement dead angle of the inside corner can be eliminated.

In addition, according to the present invention, the presence or absence of embedded objects and voids in the internal corners of concrete structures, the depth and position thereof can be reliably searched, the search range and search accuracy can be improved, and the work efficiency thereof can be improved. It has an excellent effect of being able to

A diagram showing a method of searching for an earthquake-resistant slit in the internal corner of a concrete structure using the nondestructive exploration device of the present invention using an electromagnetic wave radar. A diagram showing a reflected waveform obtained by the exploration method of FIG. A diagram showing a method of searching for reinforcing bars in an internal corner of a concrete structure using the nondestructive exploration device of the present invention. Explanatory diagram for determining the dielectric constant of a wedge-shaped electromagnetic wave propagating material, Explanatory diagram for determining the dielectric constant of concrete structures, Explanatory diagram for determining the depth and position of an embedded object in a concrete structure using a wedge-shaped electromagnetic wave propagating material, Explanatory diagram showing measurement blind spots for earthquake-resistant slits in internal corners of concrete structures by conventional methods using electromagnetic wave radar, FIG. 10 is an explanatory diagram showing measurement blind spots with respect to reinforcing bars at internal corners of a concrete structure according to a conventional method using an electromagnetic wave radar;

BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described with reference to the drawings. 1 and 2 show a first embodiment according to the present invention. In these figures, reference symbol S denotes a nondestructive exploration device (hereinafter referred to as exploration device), and reference numeral 1 denotes a concrete structure. .

FIG. 1 shows an example of a method for confirming the presence or absence of an earthquake-resistant slit (void) 3 in an internal corner 2 of a concrete structure 1 using the exploration device S. As shown in the figure, exploration The device S includes an electromagnetic wave radar device 10 , a wedge-shaped electromagnetic wave propagating material 20 , and a body controller 30 .

The electromagnetic wave radar device 10 has a transmitting antenna 11 , a receiving antenna 12 and wheels 13 . The transmitting antenna 11 radiates electromagnetic waves to the concrete structure 1 , and the receiving antenna 12 receives reflected waves from embedded objects and voids of the concrete structure 1 . The wheel 13 incorporates a rangefinder (encoder) for measuring the distance traveled from the starting point. The center axis of the transmitting/receiving antennas 11 and 12, that is, the electromagnetic wave propagation axis 14 extends in a direction perpendicular to the antenna radiation surface 15 and is located in the center between the front surface 16 and rear surface 17 of the antenna section.

The wedge-shaped electromagnetic wave propagating material 20 is arranged at the internal corner 2 of the concrete structure 1, and has a slope 21 rising toward the internal corner 2. A right-angled triangle consisting of an acute-angled front end portion 22 on the starting point side of the slope 21, an obtuse-angled top portion 23 on the terminal side of the slope 21, and a right-angled portion 24 arranged at the corner portion of the internal corner portion 2. It has a wedge shape.

The inclination angle α of the slope 21 is based on the angle at which the electromagnetic wave propagation axis 14 passes through the right-angled portion 24 of the wedge-shaped electromagnetic wave propagation material 20 at the position where the front surface 16 of the antenna portion of the electromagnetic wave radar device 10 contacts the top portion 23 . , is determined taking into account the appropriate scanning distance L.

The wedge-shaped electromagnetic wave propagating material 20 has a relative permittivity of 6 to 8, which is close to that of concrete, and has a structure in which there is no reflector such as reinforcing bars inside. For this reason, granite is used as the wedge-shaped electromagnetic wave propagating material body 20 in this embodiment.

The body control unit 30 is connected to the electromagnetic wave radar device 10 via a cable 31, controls the transmitting antenna 11 and the receiving antenna 12 of the electromagnetic wave radar device 10, and receives data (reflected waves, The measurement result is displayed on the display unit 32 based on the measured distance).

When checking the presence or absence of the earthquake-resistant slit (void) 3 in the internal corner 2 of the concrete structure 1 using the exploration device S having the structure described above, first, the wedge-shaped electromagnetic wave propagating material body 20 is inserted into the concrete structure 1. Place in corner 2. Specifically, the wedge-shaped electromagnetic wave propagating material 20 is arranged at the internal corner 2 so that the top 23 and the right-angled portion 24 are in contact with the wall surface 5 of the concrete structure 1 .

Next, the electromagnetic wave radar device 10 is placed at the starting point SP on the slope 21 of the wedge-shaped electromagnetic wave propagating material 20, and scanning is performed while moving on the slope 21 until the front surface 16 of the antenna section of the radar device 10 comes into contact with the wall surface 5. do.

While the electromagnetic wave radar device 10 scans the slope 21 , electromagnetic waves are radiated from the transmitting antenna 11 to the concrete surface 6 through the electromagnetic wave propagation material 20 . The radiated electromagnetic wave is reflected by the boundary surface of (with the air layer of) the earthquake-resistant slit 3 , the receiving antenna 12 receives the reflected wave, and the reflected wave data is transmitted to the main control unit 30 .

Scanning distance data obtained from a rangefinder built into the wheel 13 of the electromagnetic wave radar device 10 is also transmitted to the body control unit 30, and a reflected waveform is displayed on the display unit 32 with the scanning distance on the horizontal axis. FIG. 2 shows a diagram of the reflected waveform. Since the reflected wave reflected by the boundary surface of the earthquake-resistant slit 3 is displayed on the display unit 32, the presence or absence of the earthquake-resistant slit 3 at the internal corner portion 2 can be confirmed.

According to the exploration method using the exploration device S of the present embodiment, by scanning the electromagnetic wave radar device 10 along the slope 21 of the wedge-shaped electromagnetic wave propagating material body 20, electromagnetic waves are generated obliquely to the surface of the concrete structure 1. is radiated, and the electromagnetic wave propagation axis 14 extending in the direction perpendicular to the antenna radiation surface 15 from the central position of the transmitting and receiving antennas 11 and 12 can reach the inside of the internal corner 2, and the blind spot W measured by the conventional method can be cancel.

FIG. 3 shows a second embodiment according to the present invention, which is an example of searching for a reinforcing bar (buried object) 4 placed in an internal corner 2 of a concrete structure 1. As shown in FIG.

As shown in FIG. 3, the electromagnetic wave radar device 10 is placed at the starting point SP (see FIG. 1) on the slope 21 of the wedge-shaped electromagnetic wave propagating material 20, and when scanning is performed while moving on the slope 21, as shown in FIG. In addition, the reinforcing bar 4A, which was in the measurement blind spot W of the internal corner 2 in the conventional method, enters the scanning range, that is, the measuring range, so that the reinforcing bar 4A, which has not been confirmed until now, can be confirmed.

Similarly, as shown by the dotted line in FIG. 3, the wedge-shaped electromagnetic wave propagating material 20 is placed at the inner corner 2 with the top 25 facing down, and the electromagnetic wave radar is detected from the starting point on the slope 21 of the wedge-shaped electromagnetic wave propagating material 20. When the device 10 is scanned downward along the slope 21, the reinforcing bar 4B inside the wall surface 5, which was in the measurement blind spot W of the inside corner 2 in the conventional method, enters the scanning range as shown in FIG. It is possible to confirm the reinforcing bar 4B.

As a result, by using the exploration device S, the conventional measurement blind spot W shown in FIG. The measurement blind spot W1 can be greatly reduced.

4 to 6 show the principle and method of measuring the position and depth of an embedded object in the concrete structure 1 using the wedge-shaped electromagnetic wave propagating material 20. FIG.

The electromagnetic wave radar device 10 is a device that measures the round-trip electromagnetic wave propagation time T from the transmission of the electromagnetic wave to the reception of the reflected wave from the reflecting material. As shown in the formula (1), it is determined by the product of the round-trip electromagnetic wave propagation time T and the electromagnetic wave velocity c/√ε determined by the propagating material. be able to.
D = (1/2)·(c/√ε)·T (1)

Here, c = 3 × 10 ⁸ m/sec, and ε (relative permittivity) is a coefficient that differs depending on the propagating material (air: 1, plastic: 2-3, granite: 6, concrete: 6-8, water: 81 ). Therefore, in order to obtain the depth D of the buried object, it is necessary to obtain in advance the relative dielectric constant ε of the wedge-shaped electromagnetic wave propagating material.

Referring to FIG. 4, the dielectric constant of wedge-shaped electromagnetic wave propagating material 20 is obtained as follows. Electromagnetic wave propagation times t ₁ and t ₂ from transmission of electromagnetic waves at positions P ₁ and P ₂ to reception of reflected waves from the bottom surface of the wedge-shaped electromagnetic wave propagating material 20 are measured using the electromagnetic wave radar device 10 . From the obtained electromagnetic wave propagation times t _{1 and} t ₂ , the relative depth d ₂ -d ₁ of the positions P ₁ and P ₂ is obtained.
d ₂ −d ₁ =(1/2)·(c/√ε _a )·(t ₂ −t ₁ ) (2)

The true value of the relative depth d ₂ -d ₁ can be obtained from the angle α of the electromagnetic wave propagating material and the distance _la between the positions P ₁ and P ₂ .
d ₂ −d ₁ =la _· tan α (3)
(2) Using the equations (3), the dielectric constant _{ε a} of the wedge-shaped propagating material 20 can be obtained from the following equation (4).

Referring to FIG. 5, the relative permittivity of concrete of concrete structure 1 to be scanned is obtained as follows. Using the electromagnetic wave radar device 10, the electromagnetic wave propagation time t ₃ from each transmission of the electromagnetic wave at the position P ₃ directly above the reinforcing bar and the position P ₄ at a distance of l _b therefrom to each reception of the reflected wave from the reinforcing bar, Measure _t4 . Depths _d3 and _d4 are obtained from the obtained electromagnetic wave propagation times _t3 and _t4 .
_d3 = (1/2).(c/ _√εb ).( _t3 ) (5)
d ₄ = (1/2)·(c/√ε _b )·(t ₄ ) (6)

The true value of the depth _d3 can be obtained from the distance _lb between the positions _P3 and _P4 and the depth _d4 at the position _P4 .
( _d3 ) ² = ( _d4 ) ² - ( _lb ) ² (7)
Using the equations (5), (6) and (7), the dielectric constant ε _b of concrete can be obtained from the following equation (8).

Referring to FIG. 6, the position and depth of the reinforcing bar 4 inside the concrete through the wedge-shaped propagating material body 20 are obtained as follows. First, using _the electromagnetic wave radar device 10, the distance l from the starting point to the position _P5 directly above the reinforcing bar is obtained. Measure the electromagnetic wave propagation time _t5 until the reception of the reflected wave from The depth _d5a is obtained from the distance l from the starting point to the position _P5 directly above the reinforcing bar and the inclination angle α of the electromagnetic wave propagating material 20.
_d5a = l·tanα (9)

となり、深度d₅ は、（９）（１２）より
d₅ = d_5a + d_5b (１３)
で求めることができる。 Next, the electromagnetic wave propagation time t _5a is obtained using the dielectric constant ε _a of the wedge-shaped electromagnetic wave propagation material 20 obtained from (4).
_t5a =( _2√εa /c)· _d5a (10)
The propagation time t _5b in concrete is
_t5b = _t5 - _t5a (11)
, the depth d _5b in the concrete is

and the depth d ₅ is from (9)(12)
_d5 = _d5a + _d5b (13)
can be found at

According to the above principle and procedure, the electromagnetic wave radar device 10 scans from the starting point along the slope 21 of the wedge-shaped electromagnetic wave propagating material 20 placed at the internal corner 2, and the reflected wave from the obtained reinforcing bar 4 and the electromagnetic wave propagation The position and depth of the reinforcing bar 4 can be obtained from the time, the inclination angle α, the wedge-shaped electromagnetic wave propagating material 20 and the relative permittivity of the concrete structure 1 .

As described above, according to the non-destructive inspection method using the electromagnetic wave radar device of the present invention, a wedge-shaped electromagnetic wave propagating By placing the material body 20 at the internal corner 2 of the concrete structure 1 and scanning the electromagnetic wave radar device 10 along the slope 21, the electromagnetic wave propagation axis 14 can be made to reach the internal corner 2, Compared to the conventional method, it is possible to eliminate or reduce the measurement dead angle W of the internal corner 2 as shown in FIGS.

As a result, the presence or absence of embedded objects and voids in the internal corner 2 of the concrete structure 1, the depth and position thereof can be reliably searched, the search range and search accuracy can be improved, and the work efficiency can be improved. can.

In the present embodiment, the method for searching the internal corner 2 of the concrete structure 1 has been described, but the method is not limited to this. By using the electromagnetic wave propagating material 20, it is possible to eliminate or reduce measurement blind spots.

Thus, according to the present invention, it has become possible to reliably and efficiently perform exploration work in the internal corners of concrete structures.

INDUSTRIAL APPLICABILITY The present invention can be used as an investigation method and an investigation device for inside corners of concrete structures.

1 Concrete structure 2 Inner corner 3 Seismic slit (void)
4, 4A, 4B Reinforcing bars (buried objects)
5 Wall surface 6 Concrete surface 10 Electromagnetic wave radar device 11 Transmitting antenna 12 Receiving antenna 13 Wheel 14 Electromagnetic wave propagation axis 15 Antenna radiation surface 16 Antenna front surface 17 Antenna rear surface 20 Wedge-shaped electromagnetic wave propagation material body 21 Slope 22 Front end 23 Top 24 Right angle 30 Main control unit 31 Cable 32 Display unit S Searching device SP Starting point L Scanning distance W, W1 Measurement blind spot α Tilt angle

Claims (1)

In a non-destructive inspection method for an internal corner between a wall surface of a concrete structure and a concrete surface perpendicular thereto using an electromagnetic wave radar,
When radiating electromagnetic waves from an electromagnetic wave radar device to a concrete structure to search for seismic slits in embedded reinforcing bars or gaps located in the internal corners between the wall surface of the concrete structure and the concrete surface perpendicular to it. ,
The internal corner of the concrete structure has a relative dielectric constant of 6 to 9, has a slope that ascends toward the internal corner, and has an acute angle that is the starting point side of the slope when viewed in longitudinal section. Made of granite, which has a wedge-shaped right-angled triangle consisting of a front end, an acute-angled apex on the terminal side of the slope, and a right-angled portion located at the corner of the internal corner, and has no reflector inside . A wedge -shaped electromagnetic wave propagating material is arranged so that the top portion and the right-angled portion are in contact with the wall surface of the concrete structure , and an electromagnetic wave radar device is installed along the slope of the wedge-shaped electromagnetic wave propagating material to the inner corner portion. By running in a direction perpendicular to the direction of the reinforcing bars of the buried object or the direction of the earthquake-resistant slit in the gap , the electromagnetic wave is radiated to the concrete structure so that the electromagnetic wave propagation axis is oblique to the surface of the concrete structure. Characterized by searching for seismic slits in the reinforcing bars or gaps of embedded objects located in the internal corners between the wall surface of a concrete structure and the concrete surface perpendicular thereto ,
A non-destructive inspection method for internal corners of concrete structures using electromagnetic wave radar.

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