JP2006300730A - Apparatus for measuring burial depth - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for measuring a burial depth which can avoid a waste of time in operations. <P>SOLUTION: The apparatus 10 comprises a first transmitting/receiving unit 26 and a second transmitting/receiving unit 30. These transmitting/receiving units have a coincide center and comprise transmitting antennas 28A, 32A and receiving antennas 28B, 32B, respectively. The spacing between the second transmitting antenna 32A and the second receiving antenna 32B differs from the spacing between the first transmitting antenna 28A and the first receiving antenna 28B. The first transmitting/receiving unit 26 and the second transmitting/receiving unit 30 move integrally by a unit support section 34. The first transmitting/receiving unit 26 and the second transmitting/receiving unit 30 are switched by a switching section 42 to perform transmission and reception. A signal processing section 50 of an arithmetic and control section 20 determines a reflected wave on the basis of the output signal of each receiving section and outputs it to an operation section 52. The operation section 52, on the basis of the signal of the reflected wave determined by the signal processing section 50, determines the covering depth of a reinforcing rod 18 and the propagation velocity of radio waves in a concrete structure 12 and displays them on a display section 22. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an embedding depth measuring device, and more particularly to an embedding depth measuring device capable of efficiently measuring the cover depth of a reinforcing bar of a concrete structure by nondestructive inspection.

  Conventionally, the electromagnetic radar method, the ultrasonic method, the electromagnetic induction method, the X-ray transmission photography method, etc. are known as methods for measuring the embedment depth of a buried object such as the reinforcing steel cover depth of a concrete structure in a non-destructive manner. .

  The first electromagnetic wave radar method is a method of measuring the cover depth from the time until the electromagnetic wave radiated into the concrete is reflected from the reinforcing bar and returns, but in order to accurately measure the cover depth It is necessary to measure or estimate the propagation speed of radio waves in concrete by another method. For estimating the propagation speed of electromagnetic waves, a method using a reflection pattern shown below is generally used. In other words, when the transmission / reception antenna scans the integrated radar, a crescent-shaped reflection pattern, which is a reflection image from the reinforcing bar, is obtained. The shape (spread state) of this reflection pattern depends on the propagation speed. It is used to estimate the propagation speed. However, since this reflection pattern also depends on the diameter of the reinforcing bar, when the estimation error is included in the reinforcing bar diameter, there is a drawback that an error is also caused in the measurement value of the cover depth.

  The second ultrasonic method is a method of measuring the depth of cover from the time until the elastic wave radiated into the concrete is reflected from the reinforcing bar and returned. In general, since the attenuation of ultrasonic waves is large in concrete, a frequency band of about 20 KHz to 200 KHz is often used as a transmission pulse. However, in the case of a transmission pulse of several tens KHz band, since the wavelength is as long as 10 cm or more, the fog depth cannot be accurately measured. In the case of a transmission pulse of 100 KHz or more, since the mismatch of acoustic impedance on the concrete surface is large and it becomes a burst-like transmission pulse, it is difficult to accurately evaluate the propagation time from the reflected waveform. Sufficient measurement accuracy cannot be obtained. In addition, as in the “electromagnetic wave radar method”, it is necessary to measure or estimate the propagation speed of the ultrasonic wave by some method.

  The third electromagnetic induction method is as follows. That is, when an alternating current is passed through the coil, an alternating magnetic field is generated. This is a method of measuring the cover depth of the reinforcing bar by measuring the magnetic field change (current change) caused by the electromagnetic induction phenomenon when the reinforcing bar approaches. In general, there appears to be a device for measuring the cover depth when the rebar diameter is known. However, if the rebar diameter is unknown, it is necessary to increase the number of measurement data by changing the distance to the rebar, etc., and it is necessary to estimate both the rebar diameter and the cover depth. There is a disadvantage that cannot be obtained.

  Furthermore, the X-ray transmission imaging method is a method of measuring an object depth from a plurality of directions by moving an X-ray source, and measuring the depth of rebar cover from a geometric relationship based on the obtained transmission images. . When the X-ray source can be scanned so as to spatially surround the object as in tomography measurement, the fog depth can be measured with high accuracy. However, when the source can be scanned only in a plane like a wall surface, the resolution in the horizontal direction, which is the scanning direction, is increased, but the resolution in the fog depth direction orthogonal to the scanning direction is not increased.

Therefore, the applicant of the present invention arranges two receiving antennas at different distances from the transmitting antenna, and estimates the propagation speed of the electromagnetic wave in the reinforced concrete based on the reflected waves received by these two receiving antennas. And developed a device that can measure the depth of cover of the reinforcing bars (Patent Document 1).
JP 2004-132744 A

  However, since the apparatus described in Patent Document 1 receives radio waves transmitted by one transmission antenna by two reception antennas having different arrangement distances, the transmission antenna and the two reception antennas are moved together to scan. Even so, the substantial scanning (movement) distance between the two receiving antennas is different, requiring separate calculation processing, and the calculation is troublesome twice. Also, when the images based on the reflected waves received by the two receiving antennas are displayed up and down on the same screen, the effective scanning distance differs, so the position of the image based on the reflected waves from the same reinforcing bar is the scanning direction. Are displayed at different positions. For this reason, when two images of reflected waves from the same reinforcing bar are arranged vertically and displayed, it is easy to misunderstand that the measurer is different, and the reinforcing bars are arranged relatively densely In addition, when there is an electromagnetic wave reflector near the reinforcing bars, it may be difficult to determine whether the images of the reflected waves received by the two receiving antennas are due to the same reinforcing bars.

  The present invention has been made in order to eliminate the above-mentioned drawbacks of the prior art, and aims to avoid the trouble of twice the calculation.

  Another object of the present invention is to make it possible to display images of reflected waves from the same embedded object received by two receiving antennas at the same scanning distance.

  In order to achieve the above object, an embedded depth measuring apparatus according to the present invention includes a first transmission / reception unit including a first transmission unit that transmits a transmission wave and a first reception unit that receives a reflection wave, and a transmission wave. And a second receiving unit that receives the reflected wave, and an interval between the second transmitting unit and the second receiving unit is an interval between the first transmitting unit and the first receiving unit. Unlike the second transmission / reception unit whose center coincides with the center of the first transmission / reception unit, a unit support unit that moves the first transmission / reception unit and the second transmission / reception unit together, and the first transmission / reception unit; Based on the output signal of each receiver, the reflected wave received by the receiver corresponding to the transmitted wave transmitted by each transmitter is obtained based on the output signal of each receiver. A signal processing unit; Based on the intensity of the reflected wave received by each receiving unit obtained by the signal processing unit, a computing unit for obtaining the depth of the embedded object and the propagation speed of the transmitted wave in the inspection medium, and the computation result of the computing unit And a display unit for displaying

  The calculation unit receives a reflected wave of the transmission wave transmitted from the first transmission unit and outputs a signal sequence output from the first reception unit, and a reflected wave of the transmission wave transmitted from the second transmission unit. The cover depth at the top of the embedded object can be obtained based on the signal sequence received and output from the second receiver.

  The present invention thus configured is provided with a plurality of, for example, two sets of transmission / reception units, each of which includes a transmission unit and a reception unit, and by moving these together to scan each transmission / reception unit. The scanning distance can be the same. Therefore, the calculation which calculates | requires the depth of the embedded object based on the reflected wave received in each transmission / reception unit can be performed simply. In addition, when images of reflected waves obtained from each transmission / reception unit are displayed side by side in the vertical direction, images of reflected waves from the same embedded object can be displayed at the same scanning distance, and the judgment of the measurer Even if there are a plurality of buried objects in close proximity, each buried object can be easily identified and recognized. Further, when the cover depth at the top of the buried object is obtained, for example, the cover depth of the reinforcing bar that affects the life of the concrete structure can be easily obtained.

  A preferred embodiment of an embedding depth measuring apparatus according to the present invention will be described in detail with reference to the accompanying drawings. In the following embodiments, the measurement of the depth of rebar covering of a concrete structure will be described as an example.

  FIG. 1 is an explanatory diagram of an embedded depth measuring apparatus according to an embodiment of the present invention. The depth measuring apparatus 10 controls the radar circuit unit 16 and the transmission / reception unit 14 that scans the surface of the concrete structure 12, the transmission circuit 14 is supplied with a transmission wave, and the reflected wave is received. In addition, an arithmetic control unit 20 that obtains the depth of the reinforcing bar (embedded object) 18 based on the reflected wave, that is, a cover depth, and a display unit 22 that displays the embedding depth obtained by the arithmetic control unit 20 are provided. ing.

  The transmission / reception unit 14 includes two sets of transmission / reception units, and four-element antennas are arranged linearly along a scanning direction 24 indicated by arrows. That is, in the transmission / reception unit 14, the first transmission / reception unit 26 is arranged at the center along the scanning direction 24. The first transmission / reception unit 26 includes a first transmission antenna 28A that is a first transmission unit and a first reception antenna 28B that is a first reception unit, which are arranged close to each other so as to be in contact with each other.

  On the other hand, the second transmission / reception unit 30 includes a second transmission antenna 32A as a second transmission unit and a second reception antenna 32B as a second reception unit, and is configured to sandwich the first transmission / reception unit 26. is there. That is, in the second transmitting / receiving unit 30, the second transmitting antenna 32A is disposed on the left side of the first transmitting antenna 28A in FIG. 1, and the second receiving antenna 32B is disposed on the right side of the first receiving antenna 28B. In the case of the embodiment, the distance between the second transmission antenna 32A and the first transmission antenna 28A is equal to the distance between the first reception antenna 28B and the second reception antenna 32B. For this reason, the center of the 1st transmission / reception unit 26 and the 2nd transmission / reception unit 30 corresponds.

  The first transmission / reception unit 26 and the second transmission / reception unit 30 are attached to a unit support portion 34 formed of a traveling carriage. The unit support 34 is provided with a distance sensor 36. The distance sensor 36 detects the distance traveled along the scanning line from a reference point (not shown) by the transmitter / receiver 14 and inputs the detected distance to the arithmetic control unit 20.

  As shown in FIG. 1, the radar circuit unit 16 includes a transmitter 38, a receiver 40, and a switching unit 42. The switching unit 42 includes a pair of antenna switchers 44 and 46. One antenna switch 44 is provided between the first transmission antenna 28A and the second transmission antenna 32A and the transmitter 38, and switches the first transmission antenna 28A and the second transmission antenna 32A to the transmitter 38. Connecting. The other antenna switching unit 46 is provided between the receiver 40 and the first receiving antenna 28B and the second receiving antenna 32B, and switches the first receiving antenna 28B and the second receiving antenna 32B to the receiver 40. Connecting. The transmitter 38 generates a transmission wave composed of radio waves and supplies it to the transmission antennas 28A and 32A via the antenna switch 44. The receiver 40 demodulates the reflected wave (echo) from the reinforcing bar 18 received by the receiving antennas 28B and 32B.

  The calculation control unit 20 includes a radar control unit 48, a signal processing unit 50, a calculation unit 52, and a memory 54. The radar control unit 48 drives the transmitter 38 every predetermined time to output a transmission wave, and controls the switching unit 42 to switch between the first transmission antenna 28A and the second transmission antenna 32A. 38, and the first receiving antenna 28B and the second receiving antenna 32B are switched and connected to the receiver 40 in synchronization therewith. The driving signal for the transmitter 38 output from the radar control unit 48 and the switching control signal for the switching unit 42 are also provided to the signal processing unit 50.

  The signal processing unit 50 inputs a signal according to the intensity of the reflected wave to the calculation unit 52 based on the output signal of the receiver 40. The calculation unit 52 receives an output signal of the distance sensor 36 provided in the transmission / reception unit 14, writes the distance sensor 36 and the output signal of the signal processing unit 50 in correspondence with each other in the memory 54, and details. As will be described later, an image by a reflected wave from the reinforcing bar 18 is generated, and the depth of covering of the reinforcing bar 18 is calculated, output to the display unit 22, displayed, and written in the memory 54.

Measurement of the depth of cover of the reinforcing bar 18 by the depth measuring apparatus 10 thus configured is performed as follows.
First, a means for obtaining the horizontal position of the reinforcing bar 18 will be described. The transmission / reception unit 14 is scanned with the surface of the concrete structure 12 orthogonal to the axis of the reinforcing bar 18. Then, at each position on the scanning line, the first transmitting antenna 28A and the second transmitting antenna 32A are switched and connected to the transmitter 38, and the first receiving antenna 28B and the second receiving antenna 32B are switched in synchronization therewith. The reception data of the first reception antenna 28B and the second reception antenna 32B is continuously collected by the signal processing unit 50 of the calculation control unit 20 and sent to the calculation unit 52. The calculation unit 52 writes the reception data output from the signal processing unit 50 in the memory 54 together with the scanning distance signal from the scanning base point output from the distance sensor 36. Further, the calculation unit 52 generates a B-mode image (vertical cross-sectional image) of the concrete structure 12 based on the data input from the signal processing unit 50 and the distance sensor 36 and displays the image on the display unit 22. Write to memory 54.

  As shown in FIG. 2, the B-mode image of the reflected wave from the reinforcing bar 18 received by the first receiving antenna 28 </ b> B is displayed as a crescent-shaped (inverse hyperbolic pattern) reflected image 56. Similarly, the B-mode image by the reflected wave from the reinforcing bar 18 received by the second receiving antenna 32B is displayed as a crescent-shaped reflected image 58 as shown in FIG. In the embodiment, the display unit 22 displays the reflection image 56 obtained by the first transmission / reception unit 26 and the reflection image 58 obtained by the second transmission / reception unit 30 side by side. The reflected image 56 by the received data of the first receiving antenna 28B of the first transmitting / receiving unit 26 and the reflected image 58 by the received data of the second receiving antenna 32B of the second transmitting / receiving unit 30 correspond to the transmitting antenna 28A, Since 32A is provided and moved together, the reflected images 56 and 58 from the same reinforcing bar 18 of the transmission waves 60 and 62 of the transmission antennas 28A and 32A are displayed at the same traveling (scanning) distance Lx. .

  In these reflected images 56 and 58, the reflected waves 64 and 66 from the top of the reinforcing bar 18 are displayed most shallowly. That is, when the data of the vertex position P (P1, P2) of the crescent moon pattern is obtained, the horizontal point of the reinforcing bar 18 can be specified because the intermediate point of the transmitting antenna and the receiving antenna is directly above the reinforcing bar 18. This may be calculated as the distance Lx from the scanning starting point by counting the moving distance (scanning distance) from the scanning starting point by the distance sensor 36. Waveform data (A mode) 68 of the reflected wave from the reinforcing bar 18 is as shown in FIG. Therefore, since the reflected wave from the top P of the reinforcing bar 18 is maximized except for the sneak wave of the antenna, the calculation unit 52 compares the reception data of the reflection intensity (echo intensity) input from the signal processing unit 50. The reflection time from the rebar top P (the time from when the transmission antenna transmits a transmission wave until the reception antenna receives reflection) can be automatically calculated. As a result, a diagram of the determination result as shown in FIG. 5 is obtained.

When the calculation unit 52 obtains the reflection time 2t _a by the top of the reinforcing bar by the first transmission / reception unit 26 and the reflection time 2t _b by the top of the reinforcing bar by the second transmission / reception unit 30 as described above, the calculation unit 52 The depth P (rebar cover depth) d of the top portion P is obtained.

Center distance of 2x _a between the first transmitting antenna 28A and the first receiving antenna 28B of the first transceiver unit 26, second transmission antenna 32A of the second receiving unit 30 and the center-to-center distance between the second receiving antenna 32B 2x _b (see FIGS. 2 and 3). When the center of the first transmission / reception unit 26 is directly above the reinforcing bar 18, the distance between the center of the first transmission antenna 28 </ _b > A and the top P of the reinforcing bar 18 is Sa, and the center of the second transmission / reception unit 30 is the reinforcing bar 18. If just above the, the distance between the top P of the center of the reinforcing bar 18 of the second transmission antenna 32A and S _b.

At this time, the time until the transmission wave transmission antenna is transmitted is received by the receiving antenna is reflected by the reinforcing bar top (reflection time) 2t _a and x _a, between the S _a, and the reflection time 2t _b and x _b , S _b , when the propagation speed of the radio wave (transmission wave) in the concrete structure 12 is v and the depth of the top portion P of the reinforcing bar 18 is d, the following formulas 1 and 2 are related. is there.

  The propagation speed v of radio waves depends on the relative dielectric constant of the medium (concrete structure 12). However, since the relative dielectric constant of the concrete structure 12 varies depending on the type and amount of aggregate constituting the concrete structure 12, the water content, etc., it cannot be generally known. Therefore, the depth (reinforcement cover depth) d is obtained by solving the above Equations 1 and 2 as simultaneous equations. In this embodiment, an approximate value of the depth d is obtained by the procedure shown in FIG.

を演算する。 First, in Equation 1, it is assumed that d = d ₀ = 0, and a temporary propagation velocity v ′ of the radio wave in the concrete structure 12 is obtained (step 100). That is,

Is calculated.

Next, a temporary propagation velocity v'determined as Equation 4 calculates the assignment to a depth d in the formula 2 (= d _n) (step 102).

Next, it is determined whether or not the convergence condition shown in Formula 8 is satisfied (step 104). In this case, d _n−1 = d ₀ = 0, and d _n is a value obtained by Expression 7. Also, δ differs depending on the accuracy to which the depth d is obtained. For example, when it is desired to obtain the depth d to the accuracy of mm, δ = 0.1 mm.

If the convergence condition is not satisfied in Step 104, the calculation unit 52 substitutes d _n obtained by Expression 7 in Expression 1 and calculates the propagation velocity v ′ again (Step 106).

Further, returning from step 106 to step 102, the propagation velocity v ′ obtained by equation 9 is substituted into equation 2 to calculate _dn , and it is determined whether or not the convergence condition of step 104 is satisfied. If the convergence condition is not satisfied, the processing from step 102 to step 106 is repeated until the convergence condition is satisfied. When the convergence condition is satisfied as described above, the arithmetic unit 52 writes the cover depth d of the reinforcing bar 18 and the propagation velocity v of the radio wave in the concrete structure 12 in the memory 54 and outputs it to the display unit 22. (Step 108).

のように求めることができる。ただし、ｃは真空中における光の速度、ε_ｒはコンクリートの比誘電率、μ_ｒはコンクリートの比透磁率である。したがって、コンクリート構造物１２の比誘電率ε_ｒは、コンクリートの比透磁率μ_ｒがほぼ１であるので、

のように求めることができる。 In addition, the calculating part 52 calculates | requires and outputs the dielectric constant (epsilon) of concrete as needed using the velocity v of the electromagnetic waves calculated | required as mentioned above. That is, the propagation velocity v of the electromagnetic wave in the medium is

Can be obtained as follows. Where c is the speed of light in vacuum, ε _r is the relative permittivity of concrete, and μ _r is the relative permeability of concrete. Therefore, the relative permittivity ε _r of the concrete structure 12 is approximately 1 as the relative permeability μ _{r of the} concrete.

Can be obtained as follows.

  As described above, according to the depth measurement apparatus 10 of the embodiment, by scanning the two sets of transmission / reception units 26 and 30 integrally, there is no difference in the scanning distance between the two units. It is possible to eliminate the trouble of calculating twice. For this reason, the cover depth d of the reinforcing bar 18 can be obtained simply by placing the mouse pointer on the reflected image 56 or the reflected image 58 displayed on the display screen of the display unit 22 and clicking. In addition, when the two reflected images 56 and 58 are displayed side by side on the display unit 22, they are displayed at corresponding positions in the upper and lower directions. In addition, the measurer can easily identify and recognize the target reinforcing bars.

  In the above-described embodiment, the case where electromagnetic waves are used as transmission waves has been described. However, ultrasonic waves may be used as transmission waves. Moreover, in the said embodiment, although the case where the depth of the reinforcing bar 18 was measured was demonstrated, it is applicable also when measuring the depth of other embedded objects, such as piping. And by making it possible to change the distance between the transmitting antenna and the receiving antenna, it is possible to reduce the influence of radio waves that directly go around from the transmitting antenna to the receiving antenna or reflected on the surface of the concrete structure 12. Depth buried objects can be measured.

  Furthermore, although the case where the four-element antennas constituting the transmission / reception unit 14 are arranged linearly along the scanning direction 24 has been described in the above embodiment, other arrangements may be used. For example, as shown in FIG. 7, the first transmission antenna 28A, the first reception antenna 28B, the second transmission antenna 32A, and the second reception antenna 32B may be arranged orthogonal to the scanning direction 24. With such an antenna arrangement, the reinforcing bar 18 can be reliably detected even if a reflector of radio waves is present in the vicinity of the reinforcing bar 18. Further, each antenna may be arranged as shown in FIG. 8, or each antenna may be arranged in a cross shape.

It is explanatory drawing of the buried object depth measuring apparatus which concerns on embodiment of this invention. It is a figure explaining the reflected image by the 1st transmission / reception unit which concerns on embodiment. It is a figure explaining the reflected image by the 2nd transmission / reception unit which concerns on embodiment. It is explanatory drawing of the method of calculating | requiring the reflection time from the top part of the reinforcing bar of embodiment. It is a figure of the determination result by the embedment depth measuring device concerning an embodiment. It is a flowchart explaining the method of calculating | requiring the depth of the reinforcing bar top part of embodiment. It is explanatory drawing of the example which showed other embodiment of the transmission / reception part, and arrange | positioned each antenna so as to be orthogonal to a scanning direction. It is a figure which shows other embodiment of a transmission / reception part.

Explanation of symbols

  10 ......... Depth measuring device, 12 ......... Concrete structure, 14 ......... Transmitter / receiver, 16 ......... Radar circuit, 18 ......... Bed object (rebar), 20 ......... Control unit , 22... Display section, 26... First transmission / reception unit, 28 A... First transmission section (first transmission antenna), 28 B ... First reception section (first reception antenna), 30. ... 2nd transmission / reception unit, 32A ......... 2nd transmission part (2nd transmission antenna), 32B ......... 2nd reception part (2nd reception antenna), 34 ......... Unit support part, 36 ......... Distance sensor 42 ......... Switching unit, 50 ......... Signal processing unit, 52 ......... Calculation unit, 60, 62 ......... Transmission wave, 64, 66 ......... Reflected wave.

Claims (2)

A first transmission / reception unit including a first transmission unit for transmitting a transmission wave and a first reception unit for receiving a reflected wave;
It consists of the 2nd transmission part which transmits a transmission wave, and the 2nd reception part which receives a reflected wave, and the interval of the 2nd transmission part and the 2nd reception part is the 1st transmission part and the 1st reception part. A second transmission / reception unit whose center coincides with the center of the first transmission / reception unit;
A unit support for moving the first transmission / reception unit and the second transmission / reception unit together;
A switching unit that performs transmission / reception by switching between the first transmission / reception unit and the second transmission / reception unit;
A signal processing unit for obtaining a reflected wave received by the receiving unit corresponding to a transmission wave transmitted by each transmitting unit based on an output signal of each receiving unit;
Based on the intensity of the reflected wave received by each receiving unit obtained by the signal processing unit, a computing unit for obtaining the depth of the embedded object and the propagation speed of the transmission wave in the inspection medium;
A display unit for displaying a calculation result of the calculation unit;
An embedded depth measuring device characterized by comprising: In the embedded depth measuring apparatus according to claim 1,
The calculation unit receives a reflected wave of the transmission wave transmitted from the first transmission unit and outputs a signal sequence output from the first reception unit, and a reflected wave of the transmission wave transmitted from the second transmission unit. An embedding depth measuring apparatus that obtains a covering depth at the top of an embedding object based on a signal sequence received and output from the second receiving unit.

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