JP2000214139A - Method for evaluating physical properties of elastoplastic object by percussion sound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a physical property evaluating method by a percussion sound capable of quantitatively evaluating the properties or conditions of an elastoplastic object by striking the elastoplastic object by a hammer to catch the percussion sound waveform thereof and especially analyzing the vibration characteristics of the initial component thereof. SOLUTION: A steel ball 2 is allowed to fall on a sample S of an elastoplastic object and a percussion sound waveform of the sample is caught by a microphone 3. This waveform is amplified by an amplifier 4 to be recorded on a data recorder 5 and the vibration characteristics thereof are analyzed by a waveform analyzer 6 and the properties or conditions of the elastoplastic object are quantitatively evaluated and displayed corresponding to the analyzed data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating physical properties of an elasto-plastic body, and more particularly, to analyzing the physical properties of the elasto-plastic body by analyzing a percussion sound waveform generated by hitting the elasto-plastic body with a hammer or the like. It is about the method of evaluation.

[0002]

2. Description of the Related Art As an example of the prior art, when a geological survey is to be carried out on a bedrock or when some kind of construction is to be carried out, it is necessary to rationally evaluate the properties and conditions of the bedrock. Therefore, rock mass classification is performed as a means for expressing the properties and conditions of a rock mass exhibiting a complicated aspect in a simple form. Classification factors often used in this rock classification include uniaxial compressive strength, crack spacing, elastic wave velocity, RQD, and slaking characteristics. One of the classification factors using a simple index is the determination of rock strength by hammering. This judgment is made at every stage of rock survey and is used in rock classification in qualitative terms.

[0003]

Since the determination of rock strength by hammering is a simple method on site, there is an advantage that the utility value is extremely high as a qualitative classification element. However, this determination result is not limited to a qualitative expression and is not quantitative, but has a problem that an error due to individual differences occurs depending on the experience and intuition of the determiner. The present invention has been made in view of the above-described situation, and it has been found that the characteristics and conditions of the rock can be quantitatively evaluated by capturing the percussion sound of a hammer as a sound pressure waveform and analyzing its vibration characteristics. And found the present invention.
That is, an object of the present invention is to provide a method for evaluating physical properties of an elasto-plastic body using a percussion sound obtained from quantitative judgment by eliminating individual differences at the time of evaluation.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention percusses an elasto-plastic specimen with a hammer or the like, converts this percussion sound into a waveform signal, and examines the vibration characteristics of this waveform. It is characterized in that the properties of the elasto-plastic body are evaluated by analysis. Further, the characteristic of the material of the elasto-plastic body is evaluated by analyzing the vibration characteristic of the initial component in the waveform signal of the percussion sound.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION When an elasto-plastic material such as a mortar block is hit with a hammer, a percussion sound is generated reflexively. The main generation mechanism of this percussion sound is acoustic radiation due to sudden elasto-plastic deformation at the time of collision between the hammer and the object to be perceived, and acoustic radiation due to free vibration and internal resonance that respectively occur in the hammer and the object to be perceived. Divided. The former component mainly reflects the material properties of the object to be perceived, and the latter component seems to be strongly governed by physical characteristics such as the shape and size and boundary conditions of the hammer and the object to be perceived. Accordingly, the present inventors have conducted intensive studies and analyzed the vibration characteristics of the initial component, focusing on the former component in the waveform of the percussion sound. From the analysis results, we propose a rock evaluation method using percussion sound as one of the quantitative judgment indexes for rock classification.

[0006] The specimen of the elasto-plastic material referred to in the present invention includes other natural minerals or artificial minerals in addition to bedrock, rock and concrete. For example, the properties and conditions of the specimen include, for example, an elastic modulus, a uniaxial compressive strength, a crack interval, a unit volume weight, and the like.

The actual measurement procedure is as shown in FIG.
First, a specimen S such as a rock is percussed by the hammer 2, and the percussion sound generated is captured by the microphone 3 as an electric waveform signal. Next, the waveform signal is amplified by the amplifier 4 or the like, and then the data signal is recorded in the data recorder 5 as a data signal. As reference examples of the collected data signals, waveforms of the Neogene Pliocene sandstone CH class to CM class and D class are shown in FIGS. 12A and 12B, respectively. By analyzing the vibration characteristics of such a waveform with the waveform analyzer 6, it is possible to evaluate the properties and conditions of the specimen S. Output as a number.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a rock is artificially manufactured as a specimen S, placed on a mat 1, and a steel ball 2 is dropped on the surface of the specimen S as a hammer means, and a microphone 3
The percussion sound waveform is captured by the amplifier 4, amplified by the amplifier 4, collected in the data recorder 5, and its vibration characteristics are analyzed by the waveform analyzer 6. This is displayed on the output display 7. Reference numeral 8 denotes an accelerometer installed on the specimen S near the drop point to measure the vertical acceleration.

In FIG. 1, the size is 300 mm × 300 mm.
A sample S of × 200 mm was percussed, and the percussion sound waveform, that is, the change in the time history of the sound pressure and the time history of the vertical acceleration on the surface of the test sample were measured simultaneously. The percussion was performed by dropping four types of steel balls 2 of different sizes from above vertically near the center of the specimen S. Each drop height h was set such that the energy given to the specimen S was constant. As the specimen S, a total of 14 types of cement mortar and cement bentonite mortar (M1 to M7, B
1 to B7). Table 1 shows the component composition of each specimen S. Further, a columnar specimen having the same composition as that of each specimen S was produced. Table 2 shows the physical quantities and mechanical properties obtained from the cylindrical specimen. Table 3 shows the sizes and the like of the four types of steel balls 2.

[0010]

[Table 1]

[0011]

[Table 2]

[0012]

[Table 3]

In this experiment, four types of steel balls 2 were used 10 times each for the above 14 types of test specimens, for a total of 560 (14
(× 4 × 10) It was dropped and percussed. Two examples of the specimens (M7, B4) are shown in FIGS.
3 (e) and FIGS. 3 (a) to 3 (e). 2 and 3
In the figure, (a) is an original sound pressure waveform diagram, and (c) is a power spectrum diagram as a frequency analysis thereof. Also, (b) in the figure is a vertical acceleration waveform diagram on the surface of the test piece, (d)
Is a power spectrum diagram. From these figures, it can be seen that the dominant frequencies of the power spectra of both (c) and (d) are almost the same.

It is considered that the material characteristics of the object to be consulted are mainly reflected in the initial part of the original sound pressure waveform, and as shown in FIG. We paid particular attention to the rising slope. This rising gradient corresponds to the temporal change of sound pressure, and the sound speed of air is about 340.
m / s and the difference between the sound speed of the steel ball 2 of about 5000 m / s,
It is considered that a sound wave initially propagating into the steel ball 2 immediately after the percussion, that is, “sound pressure including material properties of the object to be perceived” appears in an initial portion of the original sound pressure waveform. The rising gradient of the initial part of the original sound pressure waveform as a signal that specifically indicates the material characteristics unique to the object to be consulted is hereinafter referred to as “response sound pressure pulse gradient”.

The frequency analysis was performed on 140 sound pressure waveforms obtained from the experiment using the steel balls shown in FIG.
Power1 and power in order of power
r2, ..., four dominant frequencies were taken. FIG. 4 shows the relationship between the dominant frequency and the response sound pressure pulse gradient.
FIG. 5 shows only the power1 having the highest power among them. As apparent from these figures, it can be said that there is a close relationship between the dominant frequency of the percussion sound and the response sound pressure pulse gradient. Therefore, it is considered that the response sound pressure pulse gradient can be one of the indexes expressing the frequency characteristics of the percussion sound.

In general, the physical properties of a specimen include unit weight, longitudinal wave propagation velocity, static Poisson's ratio, uniaxial compressive strength, elastic modulus, kinetic elastic modulus, and the like. The correlation between each physical property value and the response sound pressure pulse gradient is shown in the graphs of FIG. 6, FIG. 7, and FIG. In the graph, the horizontal axis represents the response sound pressure pulse gradient, and the vertical axis represents each physical property value of the specimen. In the graph, R represents a correlation coefficient. Here, the static Poisson's ratio is a value in a stress state of 1/3 of the uniaxial compressive strength, and the dynamic elastic modulus was calculated using the values of unit weight, longitudinal wave propagation velocity and static Poisson's ratio. As is clear from these graphs, although there is a slight difference in the correlation between each physical property value of the test sample and the response sound pressure pulse gradient, the response sound pressure pulse gradient generally evaluates the physical property value of the test sample. It is considered to be one of the indicators.

The above experimental results were obtained by percussion with the specimen placed on a mat. Then, the specimen was buried in a sandy soil tank instead of on a mat, and a percussion sound experiment with different boundary conditions was attempted. Here, taking the specimen (B4) as an example, a comparison is made between a case where the specimen is placed on a mat and a case where the specimen is embedded in a sandstone tank, and a sound pressure original waveform diagram obtained from both experimental results, Power spectrum diagrams and enlarged views of the initial part of the original sound pressure waveform are shown in (a), (b), and (c) of FIG. 9 and FIG. 10, respectively.

As apparent from these figures, although the initial portions of the original sound pressure waveforms are similar, the subsequent portions greatly change depending on the boundary conditions. Further, it can be seen that the frequency characteristic of the original sound pressure waveform has a difference in the power of the dominant frequency and the sharpness of the peak. On the other hand, it can be said that the response sound pressure pulse gradient has little change and is almost constant.

As described above, by analyzing the rising portion of the original sound pressure waveform of the hammer percussion sound, which is one of the indices of rock classification, the obtained response sound pressure pulse gradient is used as one index, It is possible to quantitatively evaluate the mechanical properties and physical properties of rocks and rocks, and obtain highly reliable objective judgment data with no individual differences as much as possible.

In this embodiment, as the specimen, a mixture of cement mortar or cement bentonite mortar was used, and this was percussed with a steel ball. Also, the same experimental results as above were obtained, and the properties and physical properties of rocks and the like could be accurately and quantitatively evaluated.

[0021]

According to the present invention, when classifying rock, the rock surface is percussed with a hammer and the vibration characteristics of the waveform due to the percussion sound are analyzed, so that the properties and conditions of the rock can be quantitatively determined. It is possible to evaluate, and there is an excellent effect that there is no possibility that there is an individual difference in the determination result as in the related art. In particular, by analyzing the vibration characteristics of the initial component of the percussion sound waveform and obtaining the response sound pressure pulse gradient, and using this as a judgment index, the mechanical properties and physical properties of the rock mass are not affected by the boundary conditions. Quantitative evaluation of the value can be performed accurately. In addition, the rock can be evaluated by a simple procedure, so that it can be widely used when conducting geological surveys and civil engineering work, etc., and even if there is no skilled judge at the site, it is easy to objectively evaluate the basic material properties of the rock it can.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram showing a measuring device according to the present invention.

FIG. 2 shows a waveform diagram of a specimen M7 according to the present embodiment,
(A) is a sound pressure waveform diagram, (c) is a power spectrum diagram, (b) is a vertical acceleration waveform diagram on the surface of the test piece,
(D) is the power spectrum diagram, and (e) is an enlarged view of the initial part of the original sound pressure waveform.

FIG. 3 shows a waveform diagram of a specimen B4 according to the present embodiment,
(A) is an original sound pressure waveform diagram, (c) is a power spectrum diagram, (b) is a vertical acceleration waveform diagram on the surface of the test piece,
(D) is the power spectrum diagram, and (e) is an enlarged view of the initial part of the original sound pressure waveform.

FIG. 4 is a characteristic diagram showing a relationship between a dominant frequency of a sound pressure waveform and a response sound pressure pulse gradient according to the present embodiment.

FIG. 5 is a characteristic diagram showing a relationship between a maximum power dominant frequency of a sound pressure waveform and a response sound pressure pulse gradient according to the present embodiment.

6A and 6B are graphs showing a correlation between each physical property value and a response sound pressure pulse gradient of a specimen according to the present embodiment, wherein FIG. 6A is a graph showing the relationship between the gradient and the unit volume weight, and FIG. FIG. 6 is a relationship diagram between the longitudinal wave propagation velocity and the longitudinal wave velocity.

FIGS. 7A and 7B are graphs showing the correlation between each physical property value and the response sound pressure pulse gradient of the test piece according to the present embodiment, wherein FIG. 7C is a graph showing the relationship between the gradient and the static Poisson's ratio, and FIG. FIG. 4 is a diagram showing the relationship between and uniaxial compressive strength.

FIG. 8 is a graph showing the correlation between each physical property value and the response sound pressure pulse gradient of the specimen according to the present embodiment, wherein (e) is a graph showing the relationship between the gradient and the elastic modulus, and (f) is a graph showing the relationship between the gradient and the elastic modulus. It is a relation diagram of the dynamic elastic coefficient calculated | required.

FIG. 9 shows a waveform diagram of a specimen B4 placed on a mat,
(A) is an original sound pressure waveform diagram, (b) is a sound pressure power spectrum diagram, and (c) is an enlarged view of an initial portion of the original sound pressure waveform.

FIG. 10 shows a waveform diagram of a specimen B4 embedded in a sand tank,
(A) is an original sound pressure waveform diagram, (b) is a sound pressure power spectrum diagram, and (c) is an enlarged view of an initial portion of the original sound pressure waveform.

FIG. 11 is a configuration diagram conceptually illustrating a measurement evaluation device according to the present invention.

FIGS. 12A and 12B show data waveform reference diagrams collected in a data recorder, wherein FIG. 12A is a percussion sound wave diagram of a Neogene Pliocene sandstone CH class to CM class, and FIG. 12B is a percussion sound wave of sandstone D class. FIG.

[Explanation of symbols]

 1 Mat 2 Steel ball (hammer) 3 Microphone 4 Amplifier 5 Data recorder 6 Waveform analyzer 7 Output display 8 Accelerometer S Specimen

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[Procedure amendment]

[Submission date] October 29, 1999 (1999.10.
29)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

[0004]

In order to achieve the above-mentioned object, the present invention percusses an elasto-plastic specimen with a hammer or the like, converts the percussion sound into a waveform signal, and converts the waveform signal into a waveform signal.
The response sound pressure pulse gradient is analyzed by analyzing the vibration characteristics of the initial components.
Then, this response sound pressure pulse gradient is used as a judgment index.
It is characterized by evaluating the physical properties of the elasto-plastic body more .

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

[0021]

According to the present invention, it is possible to evaluate physical properties of an elastoplastic body.
Analysis of the initial component vibration characteristics of the percussion sound waveform
Response sound pressure pulse that specifically suggests unique material properties
Since the slope was obtained and used as a judgment index ,
In addition to the fact that there is no risk of individual differences in the judgment result ,
Regardless of the boundary conditions, the mechanical properties and physical properties of the rock mass ,
For example, unit weight, longitudinal wave velocity, static Poisson's ratio,
Quantitative evaluation of axial compression strength, elastic modulus, dynamic elastic modulus, etc. can be accurately performed. In addition, the rock can be evaluated in a simple procedure, so it can be extensively performed when conducting geological surveys and civil engineering work, and the objective evaluation of the basic material properties of the rock can be easily performed without a skilled judge at the site. it can.

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Claims (2)

[Claims] The present invention is characterized in that a sample of an elasto-plastic body is percussed with a hammer or the like, the percussion sound is converted into a waveform signal, and the characteristics of the elasto-plastic body are evaluated by analyzing the vibration characteristics of the waveform. Method for evaluating physical properties of elasto-plastic body using percussive sound. 2. The physical properties of an elasto-plastic body according to the percussion sound according to claim 1, wherein the material properties of the elasto-plastic body are evaluated by analyzing the vibration characteristics of the initial component of the percussion sound waveform signal. Evaluation method.