JP2010169494A - Compression strength measurement method, and compression strength measuring instrument using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compression strength measuring method which enables the calculation of compression strength with accuracy. <P>SOLUTION: The compression strength measurement method includes a step (S100) for installing a transmission probe, at a predetermined position on the predetermined surface of a concrete structure becoming a measuring target; a step (S101) for installing a reception probe, at a first position separated from the predetermined position by a predetermined distance; a step (S102) for producing ultrasonic vibration by the transmission probe and detecting the wave, based on the vibration by the reception probe to measure a first time being a vibration arriving time; a step (S103) for installing the reception probe at a second position separated from the first position by a first distance; a step (S104) for producing the ultrasonic vibration by the transmission probe and detecting the wave, based on the vibration by the reception probe to measure a second time being a vibration arriving time; a step (S105) for calculating the propagation speed of the waves, based on the vibration from the first time, the second time and the first distance; a step (S106) for calculating the compression strength of the concrete structure from the propagation speed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for measuring the compressive strength of a concrete structure and a compressive strength measuring apparatus for measuring the compressive strength of the concrete structure in a nondestructive manner.

  Conventionally, methods such as a rebound hardness method, an ultrasonic method, and an impact elastic wave method are known as methods for measuring the compressive strength of a concrete structure in a nondestructive manner.

  The rebound hardness method is a method of striking the surface of concrete using a test hammer and estimating (measuring) the compressive strength from the rebound hardness. Although this method is simple, only the compressive strength of the concrete in the surface layer can be measured. In addition, there is a problem in accuracy because it is easily affected by the surface condition of the hit location.

  The ultrasonic method is based on the principle that the elastic wave propagation speed increases as the compressive strength of the concrete increases. In applying this ultrasonic method to an actual concrete structure, Two methods are known: the method and the surface method.

  In the transmission method, as shown in FIG. 12, an ultrasonic pulse is transmitted from a transmission probe installed on one surface side of the concrete to be measured, and this ultrasonic pulse is transmitted through the concrete so that the ultrasonic pulse is opposed to the surface. In this method, the propagation speed is obtained by measuring the time required to reach the receiving probe installed on the side and the distance between the two probes, and the compression strength is estimated from this propagation speed.

  In the surface method, as shown in FIG. 13, both a transmission probe and a reception probe are installed on one side of the concrete to be measured, and an ultrasonic pulse transmitted from the transmission probe is received by the reception probe. It is a method of measuring by receiving with a toucher.

As shown in FIG. 14, the impact elastic wave method uses a hammer or the like to strike a concrete surface to be measured, generates an impact elastic wave, and uses two sensors to detect the time difference between the impact elastic wave and the sensor. This is a method of obtaining the propagation velocity using the distance between them and estimating the compressive strength of the concrete from this propagation velocity. This shock elastic wave method is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-12933.
JP 2001-12933 A

  In the above transmission method using ultrasonic waves, the propagation speed of longitudinal waves can be measured correctly. However, since it is necessary to install probes at both ends of the concrete, the places where it can be used are limited.

  Further, in the above surface method using ultrasonic waves, the concrete installation surface of the transmitter / receiver probe has a certain size, so that the transmission position and the reception position on the installation surface are pinpoint positions. Cannot be specified, and the accuracy of the propagation velocity obtained by measurement is problematic. In general, an ultrasonic pulse having a frequency of 500 kHz is used in the measurement. Since the ultrasonic pulse of this frequency has a large attenuation, it is necessary to shorten the distance between the transmitting and receiving probes, and the local propagation. Only the speed can be measured, and the compression strength estimated therefrom is based solely on local information. Further, only the propagation speed of the shallow position from the concrete surface, that is, the concrete surface layer portion can be measured, and the compressive strength of the concrete estimated by the measurement is only the compressive strength based on the information of the surface layer portion.

  Further, in the above-described shock elastic wave method, by hitting the concrete surface with a hammer, in addition to the surface wave, longitudinal waves are also generated. This longitudinal wave is multiple-reflected in the thickness direction of the concrete (FIG. 14). . In addition, since such multiple reflected longitudinal waves may be mode-converted into surface waves, the wave detected by the sensor is not a simple surface wave. It becomes mixed, and it becomes difficult to determine the stat point of the initial movement time used for calculating the propagation speed, so the measurement accuracy of the propagation speed is deteriorated, and the accuracy of estimating the compressive strength of the concrete accompanying it is also lowered.

  The surface wave (Rayleigh wave) generated by hammering is a low frequency of 20 kHz or less, and when converted to wavelength, it is about 100 mm (surface wave velocity is assumed to be 2000 m / s) or more, and the thickness is 100 mm or less. May be difficult to measure.

  In order to measure the compressive strength in the thickness direction, it is necessary to change the wavelength of the surface wave according to the thickness of the concrete to be measured. However, it is very difficult to control the frequency of hitting with a hammer. It is not easy to create a shock elastic wave suitable for the thickness of the object to be measured.

  In the shock elastic wave method, it is common to add and average the results of multiple measurements to improve measurement accuracy, but the impact, hammering speed, force, hitting location, etc. It cannot be fixed, it is difficult to judge the validity of the data, and the accuracy is difficult to guarantee, regardless of the waveform, initial movement time, and the like.

  Also in this shock elastic wave method, since the installation surface of the receiving vibration sensor has a certain extent, pinpoint reception points cannot be specified, and there is a problem in measurement accuracy. . In addition, in the shock elastic wave method, not only the vibration of the concrete but also the vibration due to the sound around the measurement environment may be received, which limits the measurement environment.

  This invention solves the said subject, The invention which concerns on Claim 1 installs a transmission probe in the predetermined position in the predetermined surface of the concrete surface used as a measuring object, and in the said predetermined surface A step of installing a reception probe at a first position separated from the predetermined position by a predetermined distance; a step of generating ultrasonic vibration by the transmission probe; and a wave based on the vibration by the reception probe A step of measuring a first time when the vibration reaches, a step of installing the reception probe at a second position at a first distance from the first position on the predetermined plane, and the transmission probe. Generating ultrasonic vibration; detecting a wave based on the vibration with the receiving probe; measuring a second time when the vibration reaches; the first time; the second time; Wave propagation velocity based on vibration from distance A step of calculating, the step of determining the compressive strength of the concrete structure from the propagation velocity, a compressive strength measuring method characterized by comprising the.

  The invention according to claim 2 is the compressive strength measuring method according to claim 1, wherein the wave is a longitudinal wave.

  The invention according to claim 3 is the compressive strength measuring method according to claim 1, wherein the wave is a surface wave.

According to a fourth aspect of the present invention, there is provided a step of installing a transmission probe with a mode conversion member at a predetermined position on a predetermined surface of a concrete structure to be measured, and a predetermined distance away from the predetermined position on the predetermined surface. A step of installing a reception probe at a first position; a step of generating ultrasonic vibrations by the transmission probe; a surface wave based on the vibrations detected by the reception probe; A step of measuring one hour, a step of installing the reception probe at a second position at a first distance from the first position on the predetermined surface, and a step of generating ultrasonic vibrations by the transmission probe Detecting a surface wave based on the vibration with the receiving probe and measuring a second time when the vibration reaches, and the vibration from the first time, the second time, and the first distance. The surface wave propagation velocity based on A step, a step of determining the compressive strength of the concrete structure from the propagation velocity, a compressive strength measuring method characterized by comprising the.

  The invention according to claim 5 is a compressive strength measuring apparatus characterized in that the compressive strength is obtained by the method according to any one of claims 1 to 4.

  According to the compressive strength measuring method and the compressive strength measuring apparatus using the method of the present invention, both a transmitting probe and a receiving probe are installed on one predetermined surface of a concrete structure to be measured. Therefore, it is possible to perform measurement in a place where the probe cannot be installed on the surface facing the predetermined surface.

  Further, according to the compressive strength measuring method and the compressive strength measuring device using the method of the present invention, the difference between the first time measured at the first position and the second time measured at the second position, and the difference The wave propagation velocity is calculated based on the first distance, which is the distance between the first position and the second position, which can be measured accurately, and the compression strength is obtained from this propagation velocity, so the compression is performed with high accuracy. The strength can be obtained.

  Further, in the embodiment of the present invention in which the surface wave due to the ultrasonic vibration is detected by the receiving probe, the measurement is performed with the surface wave higher than 20 kHz, which corresponds to about 100 mm or less in terms of wavelength. It is also possible to measure the compressive strength of a concrete structure having a thickness of 100 mm or less.

  In addition, in the embodiment of the present invention in which a wave due to ultrasonic vibration is detected by the receiving probe, it is possible to give an accurate vibration to the concrete structure as compared with a hammer hit by a human hand, so that the measurement accuracy is also improved. .

  Further, in the embodiment of the present invention in which the surface wave is detected by the receiving probe, since the energy and amplitude of the surface wave are larger than the longitudinal wave, the distance between the transmitting and receiving probes can be set relatively long, Since the propagation velocity can be measured in a relatively wide range, the compression strength based on a wide range of information can be obtained.

  In addition, in the embodiment of the present invention in which surface waves caused by ultrasonic vibrations are detected by the receiving probe, there is a low possibility of receiving vibrations caused by sounds around the measurement environment, and it is possible to deal with various measurement environments.

  Further, in the embodiment of the present invention in which the surface wave is detected by the receiving probe, the propagation velocity at a relatively deep position from the surface of the concrete structure can be measured, and the compressive strength of the concrete estimated by the measurement is compared. It is possible to obtain the compressive strength based on information at a deep position.

  In order to measure the compressive strength in the thickness direction, it is necessary to change the wavelength of the surface wave according to the thickness of the concrete to be measured. In the embodiment of the invention, the frequency can be controlled more easily and freely than in the case of hammering or the like, and therefore, an appropriate compressive strength measurement is performed using a wave having a frequency suitable for the thickness of the concrete structure to be measured. Can do.

  Further, in the embodiment of the present invention in which vibration is generated by the transmission probe with a mode conversion member and surface waves are detected by the reception probe, multiple reflections of longitudinal waves in the thickness direction of the concrete occur. In addition, since mode conversion from longitudinal waves to surface waves does not occur, the measurement accuracy of the propagation velocity is improved, and the estimation accuracy of the compression strength obtained from this propagation velocity is also improved.

  According to the present invention, it is possible to increase wave energy and reduce distance attenuation by applying multi-frequency surface wave ultrasonic waves by ultrasonic vibration of a transmission probe. Furthermore, since the influence on the frequency change due to the distance attenuation is small, a wider range of measurement is possible. In addition, according to the present invention, it is possible to easily estimate the compressive strength in the plane direction and the thickness direction at a stretch by manufacturing a measuring device that can also be imaged in consideration of parameters such as sensor arrangement, distance, number, and incident frequency. it can.

It is a figure which shows the outline of the structure for enforcing the compressive strength measuring method which concerns on embodiment of this invention. It is a figure which shows the example of a process in the case of enforcing the compressive strength measuring method which concerns on embodiment of this invention. It is a figure which shows the relationship between the propagation speed and compressive strength in a concrete structure. It is a figure which shows the 1st method for calculating | requiring the relationship between a propagation velocity and compressive strength. It is a figure which shows the 2nd method for calculating | requiring the relationship between a propagation velocity and compressive strength. It is a figure which shows the outline of the structure for enforcing the compressive strength measuring method which concerns on other embodiment of this invention. It is a figure which shows the process example in the case of enforcing the compressive strength measuring method which concerns on other embodiment of this invention. It is a figure which shows the outline of the structure for enforcing the compressive strength measuring method which concerns on other embodiment of this invention. It is a figure which shows the outline of the structure for enforcing the compressive strength measuring method which concerns on other embodiment of this invention. It is a figure which shows the outline of the structure for enforcing the compressive strength measuring method which concerns on other embodiment of this invention. It is a figure which shows the result of having measured by the compressive strength measuring method of this invention. It is a figure which shows the outline of the structure for implementing the conventional compressive-strength measuring method. It is a figure which shows the outline of the structure for implementing the conventional compressive-strength measuring method. It is a figure which shows the outline of the structure for implementing the conventional compressive-strength measuring method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an outline of a configuration for carrying out a compressive strength measuring method according to an embodiment of the present invention, and FIG. 2 is a process example in the case of carrying out a compressive strength measuring method according to an embodiment of the present invention. FIG. In FIG. 1, 10 indicates a concrete structure to be measured for compressive strength, 100 is a transmission probe for applying ultrasonic vibration to the concrete structure 10, and 200 is an ultrasonic wave of the concrete structure. It is a receiving probe that detects vibration. In this embodiment, the ultrasonic vibration higher than 20 kHz is used as the vibration that the transmission probe 100 gives to the concrete structure 10. An arbitrary frequency can be used as the vibration frequency of the transmission probe 100 as long as it is higher than 20 kHz, but a frequency band of several tens of kHz to several hundreds of kHz is a realistic frequency for realizing the invention. The receiving probe 200 may be any sensor that receives vibrations in the frequency band of several tens of kHz to several hundreds of kHz. As the transmission probe 100 and the reception probe 200 as described above, those known in the art can be used.

  With reference to FIG. 2, the compressive strength measurement process by the compressive strength measuring method according to the embodiment of the present invention will be described. The compressive strength measuring method of the present invention described below can be implemented as a compressive strength measuring device by those skilled in the art, and the present invention includes such a device.

  In FIG. 2, in step S <b> 100, the transmission probe 100 is installed at a position O on a predetermined surface of the concrete structure 10.

  Next, in step S101, the receiving probe 200 is installed at a position A that is a predetermined distance away from the position O. Although the distance L0 between them can be measured, the installation surface of the concrete structure 10 of the transmission probe 100 and the reception probe 200 has a certain size, so that the installation is performed. Since the pinpoint position of the transmission position and the reception position on the surface cannot be specified, and the accuracy of the propagation speed obtained by the measurement is problematic, in the present invention, the propagation speed is calculated using the distance L0. Not performed.

In the next step S102, ultrasonic vibration is generated in the transmission probe 100, and the time (t ₁ ) until this vibration reaches the reception probe 200 is measured. In the present embodiment, the reception probe 200 reaches the arrival time (t ₁ ) of the wave propagated as a longitudinal wave in the concrete structure 10.
Is detected.

  In the subsequent step S103, the reception probe 200 is installed at a position B that is L1 away from the position A.

Then, in step S104, to generate ultrasonic vibration in the transmitting probe 100, to measure the time (t ₂₎ until the vibration reaches the receiving probe 200. Also at this time, the reception probe 200 detects the arrival time (t ₂ ) of the wave propagated as a longitudinal wave.

In step S105, the propagation velocity V of the longitudinal wave in the concrete structure 10 is set to L1 / (t ₂
-T ₁₎ is calculated by.

  In step S106, the compression strength F is estimated from the propagation velocity V. For this estimation, a correlation diagram between the propagation speed and the compression strength shown in FIG. 3 is used.

  According to the compressive strength measuring method as described above, in order to perform measurement by installing both the transmitting probe 100 and the receiving probe 200 on one predetermined surface of the concrete structure to be measured, the predetermined surface It is also possible to perform measurement at a place where a probe cannot be installed on the surface opposite to.

Further, according to the compressive strength measuring method as described above, the arrival time (t ₁₎ measured at the first position A is measured.
), The difference in arrival time (t ₂ ) measured at the second position B, and the distance L1 that is the distance between the first position A and the second position B that can be accurately measured as the difference. Since the wave propagation velocity V is calculated by L1 / (t ₂ -t ₁ ) and the compression strength F is obtained from this propagation velocity V, the compression strength can be obtained with high accuracy.

  Further, in the embodiment of the present invention in which the surface wave is detected by the receiving probe, since the energy and amplitude of the surface wave are larger than the longitudinal wave, the distance between the transmitting and receiving probes can be set relatively long, Since the sowing rate can be measured in a relatively wide range, the compression strength based on a wide range of information can be obtained.

Further, in the compressive strength measuring method as described above, the ultrasonic vibration higher than 20 kHz is used as the vibration that the transmission probe 100 gives to the concrete structure 10, which is about 1 in terms of wavelength.
Since it corresponds to 00 mm or less, it is possible to measure the compressive strength of a concrete structure having a thickness of 100 mm or less.

  Further, in the compressive strength measuring method as described above, since ultrasonic vibration is generated by the transmission probe 100, it is possible to give more accurate vibration to the concrete structure as compared with manual hammering. Accuracy is also improved.

  Here, a method for deriving the correlation diagram between the propagation speed and the compression strength will be described. FIG. 3 is a diagram showing the relationship between the propagation speed and the compressive strength in a concrete structure. In FIG. 3, what is indicated by a point is an actual measurement value of the propagation velocity and compressive strength, and a line obtained by fitting based on the point of these actual measurement values is a straight line in the figure. In the compressive strength measuring method according to the present invention, a relationship diagram between the propagation speed and the compressive strength as shown in FIG. 3 is prepared in advance, and the compressive strength is obtained from this relationship diagram. There are the following two methods for obtaining.

  FIG. 4 is a diagram showing a first method for obtaining the relationship between the propagation speed and the compressive strength. In this method, a block-shaped concrete structure 10 and a test piece 10 ′ prepared under exactly the same conditions (mixing, aggregate, curing method, etc.) as the concrete structure 10 are prepared. And as shown to FIG. 4 (A), a propagation velocity measurement is calculated | required by the method of this invention using a block-shaped concrete structure, and also as shown to FIG. 4 (B), on the same conditions as the said concrete structure. The test piece 10 ′ thus prepared is subjected to a compressive strength measurement by a destructive test to obtain a compressive strength value, thereby obtaining an actual measurement point in FIG.

  On the other hand, FIG. 5 is a diagram showing a second method for obtaining the relationship between the propagation speed and the compressive strength. In this method, the same test piece 10 is used for both propagation velocity measurement and compression strength measurement. As shown in FIG. 5 (A), an ultrasonic pulse is transmitted from a transmission probe 100 installed on one side of the test piece 10, and the ultrasonic pulse is transmitted through the concrete so that the ultrasonic pulse is on the opposite side. The propagation speed is determined by the time required to reach the receiving probe 200 installed in the test piece. Further, as shown in FIG. 5B, the compressive strength obtained by the destructive test is the same as the test piece used in the propagation speed measurement. Measurement is performed to obtain a compressive strength value, thereby obtaining an actual measurement point in FIG. In either case of FIGS. 4 and 5, a 10 cm × 20 cm cylindrical test specimen is used as the test piece.

  Next, another embodiment of the present invention will be described. FIG. 6 is a diagram showing an outline of a configuration for carrying out a compressive strength measuring method according to another embodiment of the present invention, and FIG. 7 is a case of carrying out a compressive strength measuring method according to another embodiment of the present invention. It is a figure which shows the example of a process.

  In the previous embodiment, the positions where the receiving probe 200 is installed for measurement are two positions A and B, but in this embodiment, the installing positions of the receiving probe 200 are A, B, and C. There are three locations. In this embodiment, there are three locations. However, in the compressive strength measurement method of the present invention, the measurement may be performed at four or more installation positions of the receiving probe 200. In FIG. 6, the same reference numerals as those in FIG. 1 are assigned to the same reference numerals, and the description thereof is omitted.

  With reference to FIG. 7, the measurement process of the compressive strength by the compressive strength measuring method according to the embodiment of the present invention will be described. In FIG. 7, in step S <b> 200, the reception probe 200 is installed at a position A that is a predetermined distance away from the position O.

  In step S201, the reception probe 200 is installed at a position A that is a predetermined distance away from the position O.

In step S202, ultrasonic vibration is generated in the transmission probe 100, and the time (t ₁ ) until this vibration reaches the reception probe 200 is measured. In the present embodiment, the reception probe 200 detects the arrival time (t ₁ ) of a wave that propagates through the concrete structure 10 as a longitudinal wave.

In step S203, the receiving probe 200 is installed at a position B that is L1 away from the position A. In step S204, ultrasonic vibration is generated by the transmission probe 100, and the time (t ₂ ) until this vibration reaches the reception probe 200 is measured.

In step S205, the receiving probe 200 is installed at a position C that is L2 away from the position B. In step S206, ultrasonic vibration is generated by the transmission probe 100, and the time (t ₃ ) until this vibration reaches the reception probe 200 is measured.

In step S207, the propagation velocity V ₁ based on the data of the position A and the position B is calculated by _{L1 / (t 2 -t 1)} , in step S208, in the concrete structure 10 based on the data of the position B and the position C The wave propagation velocity V ₂ is calculated by L2 / (t ₃ -t ₂ ), and the average value V of the propagation velocity is calculated by V = (V ₁ + V ₂ ) / 2 in step S209.

  In step S210, the compression strength F is estimated from the propagation velocity V. For this estimation, a correlation diagram between the propagation speed and the compression strength shown in FIG. 3 is used.

  According to the embodiment as described above, in addition to the same effect as the previous embodiment, the receiving probe 200 is installed at a plurality of positions and data is acquired a plurality of times, so that a more accurate compression strength is obtained. It has the effect of being able to.

  Next, another embodiment of the present invention will be described. FIG. 8 is a diagram showing an outline of a configuration for carrying out a compressive strength measuring method according to another embodiment of the present invention. In the embodiment described with reference to FIGS. 1 and 2, the reception probe 200 detects the longitudinal wave and obtains the propagation speed of the longitudinal wave. However, in the embodiment shown in FIG. Detects surface waves and determines the propagation speed of surface waves. In the compressive strength measurement method of the present embodiment, the compressive strength is obtained by the same process as that described with reference to FIG. When determining the propagation velocity, the following effects can be obtained in addition to the effects similar to those of the previous embodiment by using the surface wave as in the present embodiment.

  First, since the energy and amplitude of a surface wave with a frequency of 500 kHz are larger than the longitudinal wave, according to the compression strength measurement method using the surface wave, the distance between the transmission probe 100 and the reception probe 200 is relatively long. Since the propagation velocity can be measured in a relatively wide range, the compression strength based on a wide range of information can be obtained.

  In addition, in the embodiment of the present invention in which the reception probe 200 detects surface waves due to ultrasonic vibrations, there is a low possibility of receiving vibrations due to sounds around the measurement environment, and it is possible to deal with various measurement environments.

  In the embodiment of the present invention in which the reception probe 200 detects surface waves, the propagation velocity at a relatively deep position from the surface of the concrete structure 10 can be measured, and the compressive strength of the concrete estimated by the measurement is It is possible to obtain the compression strength based on information at a relatively deep position.

Furthermore, in order to measure the compressive strength in the thickness direction, it is necessary to change the wavelength of the surface wave in accordance with the thickness of the concrete to be measured, but the reception probe 200 detects the surface wave due to ultrasonic vibration. In the embodiment of the present invention, the frequency can be controlled more easily and freely than in the case of hammering or the like, so that an appropriate compressive strength measurement is performed using a wave having a frequency suitable for the thickness of the concrete structure to be measured. be able to.

  According to the present invention, the wave energy can be increased and the distance attenuation can be reduced by applying surface wave ultrasonic waves having a high wave number with the ultrasonic vibration of the transmission probe 100. Can do. Furthermore, since the influence on the frequency change due to the distance attenuation is small, a wider range of measurement is possible. In addition, according to the present invention, it is possible to easily estimate the compressive strength in the plane direction and the thickness direction at a stretch by manufacturing a measuring device that can also be imaged in consideration of parameters such as sensor arrangement, distance, number, and incident frequency. it can.

  Next, another embodiment of the present invention will be described. FIG. 9 is a diagram showing an outline of a configuration for carrying out a compressive strength measuring method according to another embodiment of the present invention. In FIG. 9, 101 of the transmission probe 100 indicates the main body of the transmission probe, 102 indicates the mode conversion member, 201 of the reception probe 200 indicates the main body of the reception probe, and 202 indicates the mode conversion. The member is shown.

  In the present embodiment, by providing the transmission probe main body 101 of the transmission probe 100 with the mode conversion member 102, the vibration applied to the concrete structure 10 is not applied from the vertical direction, but as illustrated. Vibration is incident on the concrete structure 10 through the mode conversion member 102 at an oblique angle. As the mode conversion member 102, an elastic material such as rubber or a viscous material such as viscosity is used. If such a mode conversion member 102 is used and the incident angle of vibration is set to be larger than the longitudinal wave critical angle and the transverse wave critical angle, the vibration of the transmission probe main body 101 in the form of surface waves is applied to the concrete structure 10. Can be granted. At this time, theoretically, no longitudinal wave and transverse wave are generated in the concrete structure 10, so that vibration from the transmission probe main body 101 is efficiently input to the concrete structure 10 as surface waves. The Rukoto.

  The receiving probe 200 is also provided with a mode conversion member 202. According to this, a surface wave can be efficiently input to the receiving probe main body 201. Note that it is not essential to provide the mode conversion member 202 on the reception probe 200 side, and the reception probe 200 similar to the embodiment described so far can also be used. FIG. 10 is a diagram showing an outline of a configuration using a reception probe 200 similar to that of the previous embodiment.

  In the embodiment shown in FIG. 9 as well, the compressive strength is obtained by a process similar to the process described in FIG. When obtaining the propagation velocity, by using the transmission probe 100 provided with the mode conversion member 102 as in the present embodiment, in addition to the same effects as the embodiments described so far, the thickness direction of the concrete In this case, multiple reflections due to longitudinal waves do not occur, and mode conversion from longitudinal waves to surface waves does not occur. Therefore, the measurement accuracy of propagation velocity is improved, and the compression strength estimation accuracy obtained from this propagation velocity is improved. Will also improve.

  Next, examples of the present invention will be described. FIG. 11 is a diagram showing the results of measurement by the compressive strength measuring method of the present invention. The propagation speed was obtained by the three methods of the embodiment described in FIG. 1, the embodiment described in FIG. 8, and the embodiment described in FIG. Further, the degree of difference in each propagation speed was determined based on the longitudinal wave propagation speed (4424 m / s) measured by the transmission method. The distance L0 between the transmission probe 100 and the position A was 200 mm. In the system for measuring the examples, the measurement by the conventional surface method could not obtain a result, but according to the method according to the present embodiment, measurement was performed with high sensitivity and accuracy in any of the embodiments. Results were obtained and the effectiveness of the present invention was demonstrated.

  Although various embodiments have been described above, embodiments configured by appropriately combining arbitrary embodiments also fall within the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Concrete structure, 100 ... Transmission probe, 101 ... Transmission probe main-body part, 102 ... Mode conversion member, 200 ... Reception probe, 201 ... Reception Probe body, 202... Mode conversion member

Claims (5)

Installing a transmitting probe at a predetermined position on a predetermined surface of a concrete structure to be measured;
Installing a receiving probe at a first position at a predetermined distance away from the predetermined position on the predetermined surface;
Generating ultrasonic vibrations in the transmission probe;
Detecting a wave based on the vibration with the receiving probe and measuring a first time that the vibration reaches;
Installing the reception probe at a second position separated by a first distance from the first position on the predetermined surface;
Generating ultrasonic vibrations in the transmission probe;
Detecting a wave based on the vibration with the reception probe and measuring a second time for the vibration to reach;
Calculating a wave propagation velocity based on the vibration from the first time, the second time, and the first distance;
And a step of obtaining a compressive strength of the concrete structure from the propagation speed. The compressive strength measuring method according to claim 1, wherein the wave is a longitudinal wave. The compressive strength measuring method according to claim 1, wherein the wave is a surface wave. A step of installing a transmission probe with a mode conversion member at a predetermined position on a predetermined surface of a concrete structure to be measured;
Installing a receiving probe at a first position at a predetermined distance away from the predetermined position on the predetermined surface;
Generating ultrasonic vibrations in the transmission probe;
Detecting a surface wave based on the vibration with the receiving probe and measuring a first time that the vibration reaches;
Installing the reception probe at a second position separated by a first distance from the first position on the predetermined surface;
Generating ultrasonic vibrations in the transmission probe;
Detecting a surface wave based on the vibration with the receiving probe and measuring a second time for the vibration to reach;
Calculating a propagation speed of a surface wave based on the vibration from the first time, the second time, and the first distance;
And a step of obtaining a compressive strength of the concrete structure from the propagation speed. A compressive strength measuring device, wherein the compressive strength is obtained by the method according to any one of claims 1 to 4.

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