JP2535702B2 - Density measurement method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the density of a measurement region based on the harmonic ratio between a harmonic component and a fundamental wave component contained in a response wave obtained by vibrating the measurement region. .

[0002]

2. Description of the Related Art It is important to know the degree of compaction of soil in order to manage the compaction of embankments on roads, residential land development and earth dams. Also, RCD concrete and RC
It is important to know the density of a structure using super-concrete concrete such as CP concrete in order to control the compaction of concrete.

In general, such a compaction degree is often measured on the basis of the density in the measurement region.
As a measurement method of this kind, a sand replacement method has been widely used from the past. However, this method has the disadvantage that the finished surface must be destroyed, which consumes time and labor.

To compensate for this, a nondestructive test method is used for density measurement, and a typical method is the RI method, which measures the density with a γ-ray densitometer. Although the RI method is not strictly a nondestructive test method, it is now often used in combination with the sand replacement method because of its simplicity. However, the RI method has problems such as time required for measurement, management of radioactive substances, and the like, and development of a simpler density measuring method has been desired.

In order to solve such a problem, techniques related to Japanese Patent Application Laid-Open Nos. 62-284813, 63-308110 and 1-226912 have been proposed.
However, each of these proposals has a problem that the measurement accuracy is not sufficient.

For example, in the measuring method according to Japanese Patent Laid-Open No. 62-284813, a small exciter is placed on the target ground and vibrated at an appropriate frequency. At this time, the response wave obtained from the target ground is The second harmonic ratio between the second harmonic component and the fundamental wave component is obtained. The second-order harmonic coefficient thus obtained is compared with the relationship between the second-order harmonic coefficient and the dry density which have already been measured by the experiment, and the density of the embankment, that is, the degree of compaction is measured.

[0007]

However, in the conventional measuring method, the measuring accuracy is not sufficient because of the reasons described in detail below, and moreover, it is possible to sufficiently cope with the automation of the measurement using a computer. There wasn't. In the measurement method using the vibration exciter, if the properties of the measurement area are different, the optimum measurement conditions are also changed. For example, even when the compaction degree of the same embankment is measured, the optimum vibration frequency for measurement and the weight of the exciter change between the case of sand and the case of Dotan.

Even when the compaction degree of the same sand is measured, if the composition of the sand changes, the measurement condition also changes.

However, in the conventional measuring method, no special consideration has been given to such changes in the optimum measuring conditions. Even when the optimum measurement conditions are set, the reliability of the measurement data changes depending on the timing of the response wave picked up as the measurement target from the time when the vibration is applied. That is, the measurement surface of the ground is slightly compacted while being excited by the exciter. This means that if the method of taking measurement items differs depending on the measurement point, the measurement accuracy will deteriorate. However, if the measurement timing is too early, the frequency of the response wave is not stable and the error increases. Therefore, it is necessary to make a different selection for the acquisition of the response wave data, but in the conventional measurement method, no special consideration was given to this aspect.

As described above, in the conventional measuring method, since the change of the optimum measuring condition for each soil to be measured and the consideration of the response wave data are not sufficiently taken into consideration, the compaction degree of the measuring object is There was a problem that it was not always possible to measure accurately.

The present invention has been made in view of such conventional problems, and an object thereof is to provide a density measuring method capable of setting an optimum measuring condition suitable for a measuring region and obtaining a high measuring accuracy. To do.

[0012]

In order to achieve the above-mentioned object, the method of the present invention includes applying a vibration of a predetermined frequency to a measurement region by using an exciter and including the response wave from the measurement region. In the method of measuring the density of the measurement region based on the harmonic ratio of the harmonic component and the fundamental component, the measurement condition setting step of setting the optimum measurement conditions in the measurement region in advance, according to the set optimum measurement conditions, According to the data creation process that creates the correlation data between the harmonic ratio and the density in the measurement region, and the optimum measurement conditions that have been set, the harmonic ratio at any point in the measurement region is obtained, and the calculated harmonic ratio and the correlation By comparing with the data, including a density measurement step of determining the density, the measurement condition setting step, the vibration generator is installed on a predetermined sampling point of the measurement region, The step of determining the optimum weight ratio of the exciter based on the frequency spectrum of the response wave obtained by changing the weight ratio to the vibrating force to generate vibration, and the exciter installed on the sampling point , Vibrating at different frequencies, based on the harmonic ratio and frequency spectrum of each response wave obtained at this time, the step of determining the optimum vibration frequency for the measurement region, and set the exciter to the optimum weight ratio, The vibration of the optimum frequency is applied from the vibration generator to the measurement area, the harmonic ratio of the response wave obtained in time series is calculated from the time when the vibration is applied, and the obtained harmonic ratio is optimal for creating the correlation data. A step of determining a response wave data acquisition timing, and the data creation step,
The weight of the exciter is set to an optimum weight, vibrations of the optimum frequency are generated from the exciter at a plurality of sampling points having different densities, and the response of the optimum acquisition timing obtained at each sampling point The harmonic ratio at each sampling point is obtained from the wave, and the correlation data between the harmonic ratio and the density is created.The density measuring step is performed by setting the vibration exciter to the optimum weight ratio. Add the vibration of the optimum frequency from the shaker to any measurement point in the measurement area,
The harmonic factor is obtained from the response wave at the optimum acquisition timing obtained at this measurement point, and the density at the measurement point is measured.

[0013]

According to the present invention, the vibration of a predetermined frequency is applied to the measurement area by using the exciter. At this time, the density of the measurement region is measured based on the harmonic ratio of the harmonic component and the fundamental wave component included in the response wave from the measurement region.

FIG. 1 shows a series of steps of the present invention. The method of the present invention comprises a measurement condition setting step (step S10) of setting optimum measurement conditions in the measurement region in advance.
And a data creation step (step S20) of creating correlation data between the harmonic ratio and the density in the measurement area according to the set optimum measurement conditions, and the adjustment at any point in the measurement area according to the set optimum measurement conditions. By obtaining the wave coefficient, by collating the obtained harmonic coefficient and the correlation data,
And a density measuring step (step S30) for obtaining the density.

In the present invention, prior to the measurement of the density, the optimum measurement conditions are set according to the object to be measured (step S10).

FIG. 2 shows the details of the measuring condition setting step (step S10). In the measuring condition setting step, the optimum weight ratio of the vibration generator is determined (step S11) and the optimum vibration frequency is determined. Determination step (step S12) and determination step of optimum data acquisition timing of response wave (step S13)
And

Step of setting the optimum weight ratio (step S1
In 1), a vibration generator is installed at a predetermined sampling point in the measurement area, and the ratio of the weight to the vibration force of this vibration generator (hereinafter referred to as the weight ratio) is changed to generate vibrations. The optimum weight ratio of the exciter is determined based on the frequency spectrum of the response wave. That is, if the weight is too small as compared with the oscillating force of the oscillating machine, the oscillating machine will bounce up and roll, resulting in unstable vibration.

Further, if the weight of the exciter is too heavy, the propagation of vibrations to the ground is poor and a clear response waveform cannot be obtained. Therefore, in the present invention, the weight ratio of the exciter is changed to vibrate, and based on the frequency spectrum of the response wave obtained,
The weight ratio is determined so that a response wave with a small noise component can be obtained.

The step of determining the optimum vibration frequency (step S12) is performed by generating a plurality of vibrations having different frequencies from an exciter installed at a predetermined sampling point in the measurement area. Then, the optimum vibration frequency for this measurement region is determined based on the harmonic ratio of the response wave obtained at this time and the frequency spectrum. That is, the vibration frequency is determined so that the response wave contains few noise components and a sufficient harmonic factor is obtained.

In the step of determining the optimum data acquisition timing (step S13), the vibration generator is set to the optimum weight ratio, and the vibration of the optimum frequency is applied from the vibration generator to the measurement region. Then, from the time when this vibration is applied, the harmonic ratio of the response wave obtained in time series is sequentially calculated. And
From the harmonic factors obtained in time series, the optimum response wave data acquisition timing for creating the correlation data between the harmonic factors and the density is determined. That is, if the measurement time of the response wave based on the time when the vibration is applied is constant, the harmonic factor corresponding to the density can be obtained from this response wave. However, in the actual measurement, when the measurement time is short, the frequency of the exciter is not stable, and therefore the response wave includes an error component.
Further, when the time elapses too much, the measurement surface of the measurement object is compacted little by little, and an error component is included. Therefore, it is necessary to measure the response wave as soon as possible after the vibration frequency of the exciter stabilizes after the excitation of the exciter. In the present invention, from the point of time when vibration is applied using the exciter, by calculating the harmonic ratio of the response wave obtained in time series, the data acquisition timing at which the harmonic ratio is stable is determined. It is determined as the optimum response wave data acquisition timing of the correlation data.

As described above, according to the present invention, the optimum weight ratio, the optimum vibration frequency and the optimum data acquisition timing of the exciter are determined according to the measurement area.

After determining such an optimum measurement condition method, the next correlation data creating step (step S20)
At, the correlation data between the harmonic coefficient and the density in the measurement area is created. The correlation data is created by setting the weight of the exciter to an optimum weight ratio and causing the exciter to generate vibrations of an optimum frequency at a plurality of sampling points having different densities. At this time, the harmonic ratio at each sampling point is obtained from each response wave at the optimum data acquisition timing obtained at each sampling point, and correlation data between the harmonic ratio and the density is created. As described above, the correlation data measured under the optimum measurement condition accurately represents the relationship between the density of the measurement target and the harmonic ratio.

Such a series of steps (steps S10, S
After the step 20) is completed, a density measuring step (step S30) for obtaining the actual density is performed. In this measuring step (step S30), the vibration generator is set to the optimum weight ratio, and the frequency of the vibration generated from the vibration generator is set to the optimum frequency. Then, this vibration exciter is installed at an arbitrary point in the measurement region, and the harmonic factor is calculated from the response wave obtained at a predetermined optimum data acquisition timing from the time when vibration is applied to the measurement region. And this harmonic factor
The actual density is measured at an arbitrary measurement point with reference to the correlation data.

As described above, according to the present invention, the density at an arbitrary point of the measuring object can be accurately measured.

That is, the inventor of the present invention, when measuring the density in the measurement area, the three factors of the vibration frequency of the exciter, the weight ratio, and the optimum data acquisition timing from the time when vibration is applied determine the reliability of the measurement data. It was found to be an important factor to do. By setting these at least three elements to optimum values in advance of the measurement of the measurement region, it is possible to accurately measure the density at any point of the measurement target.

[0026]

The preferred embodiment of the present invention will now be described in detail by taking the case of measuring the compaction degree of embankment as an example. here,
The compaction degree is defined as the ratio of the measured density to the maximum dry density of the object.

Measuring Device FIG. 3 shows a preferred embodiment of a compaction degree measuring device to which the present invention is applied. The measuring device of the embodiment is a vibrating machine 10 installed on the ground 100 to be measured. And a transport vehicle 20 that transports the exciter 10 and other measurement equipment.

As shown in FIG. 4, the exciter 10 has three hemispherical contact portions 12 on its bottom surface and is configured to be supported at three points on the target ground 100. A vibration source 14 configured by using an eccentric motor or the like is provided at the center of the exciter 10, and a target ground such as embankment is further provided.
An acceleration wave sensor 16 that detects a response wave from 00 as acceleration is provided. Then, these vibration sources 1
4. The acceleration wave sensor 16 is connected to the measurement circuit in the transport vehicle 20 via the cord 18.

As shown in FIG. 3, the transportation vehicle 20 has an endless circular track 22 driven by an engine and a driving operation section 24, and is formed so that the vibration oscillating machine 10 can be loaded.

Then, using the transport vehicle 20, the exciter 1
0 is transported to an arbitrary measurement point on the target ground 100, and the exciter 10 is installed on the measurement ground 100 at that point. At this time, the exciter 10 has three hemispherical contact parts 12
It will be more stably supported on the target ground 100.

FIG. 5 shows an example of the measuring circuit provided on the transport vehicle 20. The measurement circuit of the embodiment includes a computer 30 and a memory 38 for arithmetic control, a keyboard 32 used as a peripheral device of this computer,
A CRT 34 and a printer 36 are included. Further, this measuring circuit includes a vibration control device 40 that drives the vibration source 14 according to an instruction from the computer 30, a sensor amplifier 42 that amplifies and outputs an acceleration wave detected by the acceleration wave sensor 16, and an output of the sensor amplifier 42 and It also includes a data recorder 44 that stores necessary data, and an FFT analyzer 46 that performs spelltru analysis of acceleration waves.

In this embodiment, the data recorder 44,
The FFT analyzer 46 is formed separately from the arithmetic and control computer 30.
In addition, it can be formed to have the functions of the data recorder 44 and the FFT analyzer 46.

The vibration control device 40 causes the vibration generator 10 to generate vibration of a predetermined frequency in accordance with a command from the computer 30 for arithmetic control, and applies this vibration to the measurement ground 100.

At this time, the acceleration wave from the measurement ground 100 is picked up by the acceleration wave sensor 16 and DC-amplified by the sensor amplifier 42, and then the data recorder 4 is activated.
4 and the spectrum is analyzed by the FFT analyzer 46.

FIG. 9 shows a fundamental vibration waveform generated by the vibration generator 10 and its power spectrum, and FIG. 10 shows an acceleration waveform obtained as a response wave and its power spectrum. As shown in FIG. 9, the response acceleration wave obtained by vibrating the exciter 10 at a fundamental frequency of, for example, 60 Hz is converted into the fundamental vibration of the exciter 10 (shown in FIG. 9). It will be distorted. This strain reflects the strength of the ground, and is related to the fact that the strain amount increases as the degree of compaction increases. The main characteristic of this distorted response acceleration waveform is that it is composed of a fundamental wave and harmonics,
It is that almost no other frequency components are included. That is, in order to know the amount of distortion, it is sufficient to calculate the total amount of harmonic components of the response acceleration wave. FIG. 11 is a linear display of the Fourier spectrum of the response acceleration waveform, in which the level of the third and higher harmonics is small and the distortion component is almost the second harmonic. Therefore, the arithmetic control computer 30 calculates the secondary harmonic coefficient D ₂ defined by the following equation from the spectrum analysis result output from the FFT analyzer 46, and uses this secondary harmonic coefficient D ₂ As described later, the density (compacting degree) of the measurement ground 100 is measured.

Second harmonic factor D ₂ = (second harmonic component / fundamental component) × 100 (%) FIG. 8 shows an example of the correlation data used for the above-mentioned measurement of the compaction degree. This correlation data represents the relationship between the dry density of the target ground 100 and the secondary harmonic coefficient. When measuring the compaction degree, the dry density of the ground is
It is used as an index that indirectly indicates the degree of compaction.

In the present embodiment, such correlation data is measured in advance and written in the correlation data storage unit 60 of the memory 38. Then, the computer 30 for arithmetic control collates the second harmonic ratio of the response acceleration wave obtained as described above with the correlation data as shown in FIG. 8 to determine the dry density at the measurement point, and thus the degree of compaction. Formed to measure.

However, it is not possible to accurately measure the degree of compaction of the target ground 100 by simply obtaining the second-order harmonic rate of the response acceleration wave and collating the second-order harmonic rate with the correlation data. .

That is, the correlation data is formed in advance according to the soil quality of the ground 100 to be measured, and is naturally different when the ground is mountain sand and Dotan, for example. Becomes Therefore, the phase relation data is formed in accordance with each soil property to be measured.

However, sufficient correlation accuracy could not be obtained by simply creating such correlation data for each soil type and measuring the target ground 100.

The present inventor has studied the factors that cause a decrease in the measurement accuracy. As a result, the optimum weight ratio between the oscillating force of the exciter 10 and the weight, the optimum frequency of vibration, and the point of time when vibration is applied. It was found that the three factors of the optimum data acquisition timing of the response acceleration wave of No. 3 differ depending on the soil type, and that setting the at least three factors according to the soil type greatly improves the measurement accuracy.

The feature of the present invention is that each time the soil quality of the target ground 100 changes, the above-mentioned three measurement conditions are set to the optimum conditions in accordance with the soil quality, and as shown in FIG. It is to measure the correlation data between the second harmonic coefficient and the dry density.

The details will be described below.

FIG. 1 shows a series of flowcharts of the compaction degree measuring operation performed in this embodiment.
The measurement of the example is performed by a measurement condition setting step (step S1) of setting optimum measurement conditions according to the soil quality of the target ground 100 in advance.
0), according to the set optimal measurement conditions, the measurement ground 100
In the data creation step (step S20) of creating the correlation data between the secondary harmonic coefficient and the dry density in step S1, the harmonic coefficient at an arbitrary point of the measurement ground 100 is calculated according to the set optimum measurement condition, and the calculated harmonic is calculated. The density measurement step (step S30) for obtaining the dry density (compacting degree) is performed in this order by comparing the wave coefficient with the correlation data.

FIG. 2 shows details of the optimum measurement condition setting step (step S10). In the embodiment, the optimum measurement conditions are set by using the arithmetic and control computer 30 to determine the optimum weight ratio of the exciter 10 (step S11) and the optimum vibration frequency (step S1).
2) The determination of the optimum data acquisition timing of the response acceleration wave (step S13) is performed in this order.

FIG. 6 is a functional block diagram of the arithmetic and control computer 30 for determining the optimum measurement conditions shown in FIG.

Step S11 First, the step (step S11) of setting the ratio of the oscillating force of the oscillating machine 10 to the weight according to the soil condition as the oscillating condition will be described. If the vibration generating force of the vibration generator 10 is too large, the vibration generator 1
Bounce and roll of 0 occur and vibration becomes unstable.
In addition, when the weight of the exciter 10 is too heavy, the propagation of vibration to the ground is poor, and a clear response acceleration waveform cannot be obtained.
As described above, the setting of the ratio of the vibration force to the weight is an extremely important and cautionary item for realizing good measurement.

FIG. 10 shows a response acceleration waveform when the excitation force and the weight are properly set to the soil quality. On the other hand, FIG. 12 shows a response acceleration waveform when the settings are not matched. In FIG. 12A, since the weight of the exciter 10 is too heavy with respect to the soil, the harmonic components are extremely small, the distortion of the waveform is hardly seen, and the compaction degree of these soils cannot be discriminated. FIG. 12B shows a response acceleration waveform when the weight of the exciter 10 is too light with respect to the soil, and there are many frequency components that can be called noise in addition to the harmonic components. This is a sign that elements unrelated to the vibration characteristics of the ground, such as rattling of the exciter 10 on the ground surface, are mixed in.

Therefore, it is necessary to set the weight ratio of the exciter 10 so that the response acceleration wave has the spectral characteristics shown in FIG. In this embodiment, the exciter 10
The exciter 10 is vibrated while changing the ratio of the exciting force to the weight by changing the weight of the exciter. At this time, the response acceleration wave obtained from the acceleration wave sensor 16 is spectrally analyzed by the FFT analyzer 46 and stored in the sampling data storage unit 52. In this embodiment, the exciter 10
The ratio of the exciting force to the weight of the computer is input to the arithmetic and control computer 30 using the keyboard 32, and the input data is F
The data is stored in the sampling data storage unit 52 together with the spectrum analysis data output from the FT analyzer 46, and is displayed as an image on the CRT 34.

Therefore, the operator can determine the vibration exciter 1 from the spectrum analysis image of the response acceleration wave displayed on the CRT 34.
An optimum weight ratio of 0 can be determined. In the present embodiment, the case where only the weight of the vibration generator 10 is changed has been described as an example, but when the vibration force of the vibration generator 10 can also be changed, the weight and the vibration force At least one of them may be controlled to set the ratio of the vibration force to the weight to the optimum ratio.

The optimum weight of the vibrator 10 or the optimum weight ratio of the vibratory force to the weight thus set is
It is written and stored in the optimum measurement condition setting memory 54.

In this example, when the sand and the soil were measured, the optimum ratio between the vibration force and the weight was measured. It was judged appropriate to set 1.16 to 1.0 for tan.

Step S12 Next, the setting of the optimum vibration frequency step S12 of the vibrator 10 will be described. The fundamental frequency (frequency) of the exciter 10 is an important factor not only for determining the excitatory force, but also for grasping the vibration characteristics of the ground together with the weight inside the exciter. FIG. 13 shows a response acceleration waveform in mountain sand, and FIG. 14 shows a waveform obtained by spectrum analysis of the waveform shown in FIG. As shown in FIG. 13, when comparing the response acceleration waveforms when the fundamental vibration frequencies are set to 50 Hz, 60 Hz, and 70 Hz, the lower the frequency is, the larger the distortion rate of the response acceleration waveform is. The lower the frequency, the larger the change in the wave factor,
It was found that the sensitivity to density was improved.

Further, in the spectrum waveform data shown in FIG. 14, when the vibration frequency is 50 Hz, the frequency of 1/2 of the fundamental frequency and its harmonic components are shown. This phenomenon is not seen at 60 Hz and 70 Hz. Also, 60
Although the power value of the fundamental wave increases with the density at Hz and 70 Hz, it reverses at 50 Hz. It is considered that this is because 50 Hz does not match the vibration mode of the ground.

From the above, it is preferable to set the optimum fundamental frequency for mountain sand to 60 Hz in consideration of the measurement sensitivity. Also, for Dotan, the result that 60 Hz is suitable is obtained as in the case of sand.

The series of operations for determining the optimum vibration frequency is performed by operating the keyboard 32 at a plurality of frequencies, for example, 50.
It starts by setting the vibration frequency of Hz, 60 Hz, and 70 Hz. When the vibration frequency is set, the arithmetic and control computer 30 controls the vibration control device 40, and 50 Hz, 60 Hz, 70 Hz using the exciter 10.
The measurement operation is performed at each fundamental frequency. Then, the response acceleration wave obtained by the vibration of each frequency is picked up by using the acceleration wave sensor 16, the frequency spectrum of each response acceleration wave is obtained by the FFT analyzer 46, and this is stored as sampling data which constitutes a part of the memory 38. The set vibration frequency is stored in the section 52, and the CRT 34
, As shown in FIG. Then, the optimum frequency is determined from the frequency spectrum thus stored. The determined optimum frequency is input from the keyboard 32, and is written in the condition setting storage unit 54 forming a part of the memory 38.

Step S13 Next, the step of determining the optimum data acquisition timing (step S13) will be described. In FIG. 15, the weight of the vibration exciter 10 is set to the optimum weight ratio, and the vibration from the vibration exciter 10 to the target ground 1 is set.
This is the data obtained by adding the vibration of the optimum frequency to 00 and calculating the second harmonic ratio of the acceleration wave obtained in time series from the time when the vibration is added. The horizontal axis represents the data acquisition timing from the time when vibration is applied, and the vertical axis represents the second harmonic coefficient. The three characteristic data are measurement data obtained by changing the measurement points.

As is clear from this measurement data, the second harmonic ratio fluctuates greatly during the unstable period after the vibration is reached until the vibration generator 10 reaches the predetermined vibration frequency.

While the vibrator 10 is vibrating, the side surface of the ground is slightly compacted and its properties are changed.
This can be inferred from the timing of data acquisition of the second harmonic rate shown in FIG. This means that if the measurement time is taken differently depending on the measurement point, the measurement accuracy will deteriorate. Such a tendency can be said even if soil conditions and vibration conditions change.

According to FIG. 15, the difference in density can be determined by keeping the measurement conditions constant, but the measured values vary with the passage of time. Therefore, in order to improve the measurement accuracy, it is necessary to perform the measurement as soon as possible after the vibration generator 10 reaches a predetermined vibration frequency and stabilizes after vibration. As described above, it is necessary to select the data acquisition timing for acquiring the data after the vibration.

In this embodiment, in order to select such an optimum data acquisition timing, the weight of the vibration generator 10 is set to an optimum weight ratio, and the vibration of the optimum frequency is applied from the vibration generator 10 to the target ground 100. . Then, the response acceleration waves obtained in time series from the time when this vibration is applied are spectrally analyzed using the FFT analyzer 46, and the harmonic factor calculator 5
When 0, the second harmonic coefficient is calculated in time series. In this way, as shown in FIG. 15, the correlation data between the sampling time of the response acceleration wave and the second harmonic of the sampled response acceleration wave for the measured ground 100 is created, and the correlation data is created. Store in 52. Then, the correlation data obtained in this way is CR
T34, the data is displayed on the data output section of the printer 36, and the optimum data acquisition timing is determined. For example, if the correlation data is obtained as shown by the side point 3 in FIG.
The optimum data acquisition timing will be set to 4 to 8 seconds. Then, the optimum data fetching timing set in this way is input to the arithmetic control computer 30 using the keyboard 32, and the condition setting storage unit 5
4 will be written.

In this embodiment, the operator determines the optimum weight ratio of the exciter 10 with respect to the measured ground 100, the optimum vibration frequency, and the optimum data acquisition timing on the basis of the display of the CRT 34 each time, and the keyboard is selected. Although the case of inputting from 32 is described as an example, the present invention is not limited to this, and the data stored in the sampling data storage unit 52 is provided with the measurement condition setting control unit 56 as shown by the dotted line in FIG. 6, for example. Therefore, the optimum measurement condition may be automatically determined and written in the condition setting storage unit 54.

Step S20 When the series of measurement condition setting steps shown in FIG. 2 is completed in this way, next, as shown in FIG. 1, correlation data between the secondary harmonic coefficient and the dry density for the target ground 100. Is created.

This correlation data is created by the vibration generator 10.
Is set to the optimum weight ratio, and vibration of the optimum frequency is generated from the exciter 10 at a plurality of sampling points having different dry densities (compacting degrees). That is, the weight ratio and the fundamental vibration frequency of the exciter 10 are set to optimum conditions according to the soil quality of the target ground 100. Then, the vibration generator 10 is used to generate vibrations at a plurality of sampling points having different dry densities (compacting degrees). At this time, the response acceleration wave obtained at each sampling point is fetched at the optimum data fetching timing when a predetermined short time has elapsed from the time when vibration was applied, and the second harmonic rate at each sampling point is obtained. Then, the correlation data between the harmonic ratio thus obtained and the dry density (compacting degree) is created.

By the way, even when the vibration oscillating machine 10 is set to such an optimum measuring condition so that harmonics with less noise can be obtained, the measured values vary depending on the flatness and the horizontal degree of the surface on which the vibration oscillating machine 10 is placed. Will occur.

In order to solve such a problem, in the embodiment, the vibration generator 10 is oscillated while slightly rotating at the same point, and the operation of measuring a plurality of times is performed at each sampling point to obtain correlation data. I asked.

FIG. 8 shows the correlation data obtained for Dotan.

This correlation data is created by using three different sampling points whose dry density (compacting degree) is known in advance.

That is, the exciter 10 in which the weight ratio and the vibration frequency are set to the optimum values is first installed at the first sampling point. Then, the vibration generator 10 is slightly rotated at the same point to generate vibration, and measurement is performed 10 times at the same sampling point. In each measurement, the response acceleration wave obtained after vibration is detected using the sensor 16, and this is frequency-analyzed using the FFT analyzer 46, and the harmonic factor calculator 50
To enter. The harmonic factor calculator 50 calculates the secondary harmonic factor from the frequency spectrum of the response acceleration wave obtained at the optimum data acquisition timing, and the correlation data generator 58.
Output to.

Such a series of operations is repeated at the three sampling points whose dry density is known in advance.

The correlation data creating section 58 creates analysis data as shown in FIG. 8 from the data thus obtained. In this case, the variation in measured values at each sampling point is relatively small, and the correlation coefficient is as good as 0.963. The regression line obtained by such a method can be used as a calibration curve for density measurement. That is, in this embodiment, the calibration curve 200 thus obtained is stored in the memory 38 as correlation data between the dry density (compacting degree) and the second harmonic coefficient when Dotan is the measurement target. It is written and stored in the correlation data storage unit 60 that constitutes the unit.

Step S30 In this embodiment, after the optimum measurement conditions are set in accordance with the soil to be measured (step S10) and the correlation data is created (step S20), the target ground 100 is obtained. Density (compacting degree) for any point in
Is measured (step S30).

FIG. 7 shows a functional block diagram of the arithmetic and control computer 30 for executing the step S30. In the present embodiment, in the measurement of the target ground 100, the vibration generator 10 having the weight ratio and the vibration frequency set to the most enemy values is installed on an arbitrary measurement point.
Is performed by vibrating.

This measurement is performed depending on the situation of the measurement point by vibrating the vibration oscillating machine 10 once to perform the measurement operation, and by rotating the vibration oscillating machine 10 little by little at the same time to vibrate. The measurement operation may be repeated a plurality of times. In this embodiment, the latter case will be described below as an example.

That is, the exciter 10 installed at any measurement point is slightly rotated at the same point to vibrate, and a plurality of measurement operations are repeated. The response acceleration obtained by each measurement is FFT. The analyzer 46 analyzes the frequency and inputs it to the harmonic factor calculator 50. Harmonic factor calculator 5
0 calculates the second harmonic rate based on the response acceleration wave obtained at the optimum data acquisition timing after vibration, and the measuring unit 6
Output to 2.

The measuring section 62 averages a plurality of measurement values input in this way, and obtains an average value of the second harmonics at the measurement points. Then, the average value thus obtained is collated with the correlation data 200 between the dry density and the second harmonic coefficient stored in the correlation data storage section 60, and the dryness corresponding to the average second harmonic coefficient is obtained. The density, that is, the degree of compaction is obtained, and this is written and stored in the measurement data storage unit 40.

The compaction degree thus stored in the measurement data storage section 64 is displayed on an output device such as the CRT 34 or the printer 36 as required.

In particular, the apparatus of this embodiment has a keyboard 32
By inputting the measurement point data from, the measurement data storage unit 64 stores both the data regarding the measurement point and the degree of compaction at the measurement point, and outputs this to the CRT 34 and the printer 36 as necessary. Has been formed.

As described above, according to this embodiment, the correlation data stored in the correlation data storage unit 60 is created by repeating the measurement operation a plurality of times at each sampling point, and the actual compaction degree is obtained. It is possible to accurately measure the compaction degree by performing the above measurement based on the average value obtained by repeating the measurement a plurality of times at the measurement point.

The present embodiment is constructed as described above, and its operation will be described below.

In order to apply the density measurement using the exciter 10 to the soil compaction degree control, it is necessary to improve the measurement accuracy and record reliable data.

Therefore, in this embodiment, first, in the measurement condition setting step (step S10) shown in FIG. 1, optimum measurement conditions are set according to the soil quality.

The setting of the measurement conditions is specifically performed according to the flowchart shown in FIG. That is, in step S11, the optimum weight ratio of the vibration exciter 10 is set according to the soil quality.
Then, the optimum vibration frequency of the exciter 10 according to the soil quality is set in step S12. Next, the optimum response acceleration wave data acquisition timing is determined in step S13.

In this way, each step S11, S1
2. The optimum measurement condition determined in S13 according to the soil quality is written and stored in the condition setting storage unit 54.

Further, in the correlation data creating step (step 20) shown in FIG. 1, the correlation data of the dry density and the second harmonic coefficient is prepared in accordance with the soil to be measured, and this is the correlation data storage unit. Stored in 64. Creation of this correlation data is performed under the optimal measurement conditions.

In particular, in order to remove the influence of the unevenness and inclination of the side bottom surface caused by the placement of the vibration oscillating machine 10 and perform accurate measurement, in the present embodiment, the vibration oscillating machine is used at each sampling point as shown in FIG. The calibration curve 200 is created by rotating 10 gradually and measuring a plurality of times. This makes it possible to obtain accurate correlation data with the influence of the setting failure of the vibrator 10 removed.

The measuring apparatus of the present embodiment stores such optimum measurement conditions and correlation data in a plurality of sets for each soil type, and on the menu screen displayed on the CRT 34, the optimum measurement condition corresponding to an arbitrary soil type is stored. It is formed so that measurement conditions and correlation data can be selected.

When actually measuring the target ground 100, the exciter 10 is loaded on the transport vehicle 20 shown in FIG. 3, and the exciter 10 is transported to an arbitrary measurement point. Then, at the measurement point, the vibration exciter 10 is installed on the target ground 100, and the compaction degree is measured.

At this time, since the soil quality of the target ground 100 is known in advance, the operator operates the keyboard 32 to C
The soil type menu screen is displayed on the RT 34 and the corresponding soil type is designated. As a result, the optimum measurement conditions that match the soil quality to be measured are displayed on the CRT 34, and the correlation data that matches the specified soil quality is selected from the measurement data storage unit 64. At this time, the vibration force and vibration frequency of the vibration generator 10 are automatically set to optimum values, and the optimum data acquisition timing is also automatically set. The optimum weight ratio of the vibrator 10 is adjusted each time by the measurer based on the display on the CRT 34.

After setting the measurement conditions in this way,
The vibration generator 10 is slightly rotated at the same measurement point to measure a plurality of times (for example, 3 to 4 times), and the average value of the second harmonics obtained by these measurements is obtained. Then, this average value is compared with the correlation data to determine the corresponding dry density. This dry density indirectly indicates the compaction degree, and the CRT 34 displays both the dry density and the compaction degree at the measurement point.

Further, in the measurement data storage section 64, both the dry density and the compaction degree at the measurement point are stored together with the position data of the measurement point.

In the above examples, the case of measuring the compaction degree of embankment or the like was described as an example, but the present invention is not limited to this, and it is possible to use ultra-compacted concrete such as RCD concrete or RCCP concrete. It can be similarly applied to the measurement of compaction degree.

Further, in the above-described embodiment, the case where the compaction degree is measured based on the second harmonic of the response acceleration wave has been described as an example, but the present invention is not limited to this, and harmonics other than this are not limited thereto. (For example, the harmonic value obtained by dividing the total value of the second and higher harmonic components by the fundamental wave component) can be used.

[0094]

As described above, according to the present invention,
There is an effect that it is possible to obtain a density measuring method capable of quickly and accurately setting optimum measuring conditions suitable for a measuring region and obtaining sufficient measuring accuracy.

[Brief description of drawings]

FIG. 1 is a flow chart of a density measurement process to which the present invention is applied.

FIG. 2 is a detailed flowchart of the measurement condition setting step shown in FIG.

FIG. 3 is an overall explanatory view of a density measuring device of this embodiment.

FIG. 4 is an explanatory diagram of a vibration exciter used in the density measuring device shown in FIG.

FIG. 5 is a block circuit diagram of the density measuring device according to the embodiment.

FIG. 6 is a block diagram of a circuit used for setting measurement conditions and creating correlation data.

FIG. 7 is a block diagram of a measuring circuit used for measuring density.

FIG. 8 is an explanatory diagram of correlation data between a dry density and a second harmonic coefficient for Dotan.

FIG. 9 is an explanatory diagram of a vibration waveform of the exciter and its spectrum.

FIG. 10 is an explanatory diagram of a waveform of a response acceleration wave and its spectrum.

FIG. 11 is an explanatory diagram of a linear spectrum of a response acceleration waveform.

FIG. 12 is an explanatory diagram of a response acceleration waveform and its power spectrum when the weight ratio of the vibration exciter is inappropriate. FIG. 12A shows a case where the weight is too light and FIG. FIG.

FIG. 13 is an explanatory diagram of a response acceleration waveform when mountain sand is measured.

14 is an explanatory diagram of a power spectrum of the response acceleration waveform shown in FIG.

FIG. 15 is an explanatory diagram of changes over time in the second harmonic coefficient.

[Explanation of symbols]

 10 Vibration Generator 16 Acceleration Wave Sensor 30 Computer for Controlling Computer 32 Keyboard 46 FFT Analyzer 50 Harmonic Factor Calculation Unit 54 Setting Condition Storage Unit 58 Correlation Data Creation Unit 60 Correlation Data Storage Unit 62 Measuring Unit 64 Measurement Data Storage Unit 100 Target ground

Claims (1)

(57) [Claims] 1. A vibration of a predetermined frequency is applied to a measurement region by using an exciter, and the vibration of the measurement region is measured based on a harmonic ratio of a harmonic component and a fundamental component included in a response wave from the measurement region. In the method of measuring density, a measurement condition setting step of setting optimum measurement conditions in the measurement region in advance, and data creation to create correlation data between harmonic ratio and density in the measurement region according to the set optimum measurement conditions A density measurement step of obtaining a density by obtaining a harmonic factor at an arbitrary point in the measurement region according to the set optimum measurement condition and comparing the obtained harmonic factor with the correlation data. In the measurement condition setting step, the exciter is installed on a predetermined sampling point in the measurement area, and the weight ratio to the exciter force of the exciter is changed to generate vibration. Determining the optimum weight ratio of the exciter on the basis of the frequency spectrum of the response wave generated, and vibrating the exciter installed on the sampling point at different frequencies, and adjusting each response wave obtained at this time. Based on the wave factor and the frequency spectrum, the step of determining the optimum vibration frequency for the measurement region, the vibration generator is set to the optimum weight ratio, the vibration of the optimum frequency is added to the measurement region from this vibration machine, vibration Calculating the harmonic ratio of the response wave obtained in time series from the time of adding, and determining the optimum response wave data acquisition timing for the creation of the correlation data from the obtained harmonic ratio, In the data creation process, the weight of the exciter is set to an optimum weight, and vibration of the optimum frequency is generated from the exciter at a plurality of sampling points having different densities, and From the response wave of the optimum acquisition timing obtained at the sampling point, the harmonic ratio for each sampling point is obtained, and the correlation data between the harmonic ratio and the density is created. Set the machine to the optimum weight ratio, add the vibration of the optimum frequency from this exciter to any measurement point in the measurement area, and obtain the harmonic ratio from the response wave at the optimum acquisition timing obtained at this measurement point. And a density measuring method characterized by measuring the density at the measuring point.