JP3406539B2 - Active indirect probe - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for nondestructively exploring the structure of the ground or the crust, or the artificial structure such as architecture or civil engineering.

[0002] Mainly for industrial and security reasons, such as location (ground) surveys for civil engineering and construction, reasons for disaster prevention to prevent natural disasters such as earthquakes, reasons for exploring resources such as minerals and hot springs, etc. Therefore, it is highly necessary to explore underground structures. As for the underground structure exploration method, the direct exploration method that directly obtains information on the underground structure by obtaining a sample by boring the ground, and the underground structure is estimated by observing and measuring the physical signal from the underground and analyzing it. The indirect exploration method to do so has been performed conventionally.

Among the above methods, the method for directly exploring the underground can scrutinize the underground, but the exploration depth is 1
Since it is a little over 00m, it is not possible to perform a deep exploration, and it costs a lot of money, so it is not realistic and is usually limited to a narrow range of exploration such as exploration of the underground structure of a construction site.

Compared with the above-mentioned direct exploration method, the indirect exploration method has the advantages that it can economically explore a relatively large area and that it can perform a wide range of exploration from shallow depth to large depth. is doing. The indirect exploration method is generally an active exploration method for exploring an object by adding wave energy such as artificial elastic waves to the exploration target and capturing and analyzing the reflected wave, refraction wave, or excited electromagnetic wave. . As this method, a vibration generator or an explosive as a source of artificial vibration has been conventionally used.

[0005]

The above-mentioned active type indirect probe method generally involves various kinds of large and small noises, which tends to impede the precise detection of the signal, and the large depth of noise. I am not good at exploration. For example, if the object of exploration is the crust of an urban area, its implementation is virtually impossible due to vibration pollution in addition to the reliability of the exploration. Moreover, although the excitation as a wave is large, it is difficult to precisely control the wave to be excited, and from this point also, it is not suitable for precise exploration of an object.

[0006]

SUMMARY OF THE INVENTION The present invention is an active indirect probe.
Solve the above problems of inspection methods and improve the accuracy of exploration
It is configured to let. That is, the present invention is a wave transmission
The wave transmitted from device to the receiving means via the search target
By analyzing the received wave signal.
Rotation axis in non-destructive exploration
One by one due to the rotating motion of the weight that rotates around
Or excite an elastic wave with multiple frequencies as a sine wave
And the rotation of the weight is a GPS satellite.
Precise control by time data (GPS clock) transmitted from
Through a wave transmission device that has means for controlling
Receiving to receive elastic waves transmitted from this wave transmission device
Means and the wave and the receiving means transmitted from the wave transmitter
Synchronize the received wave with the GPS clock
The precise time setting means and the receiving means continuously receive the data.
Noise is reduced by accumulating the received signal of the generated wave
Fourier analysis of the generated wave signal to analyze the state of the exploration target
Is active indirect exploration apparatus characterized by having means for.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is an apparatus configured to steadily transmit (oscillate) precisely controlled waves to obtain information on a search target. The transmitted wave is a sine wave, and by making it a sine wave, the received wave information can be extracted by Fourier transform. That is, if the transmitted wave is a precisely controlled sine wave and the transmission and reception of the wave are accurately synchronized, basically all the responses of the transmission / reception path can be obtained.

[0008] wave originating in because may be a sine wave, the wave may be an electromagnetic wave even acoustic wave
However, when the exploration target is the crust, there is a tendency for the exploration target to be limited, such as the attenuation of electromagnetic waves being significant. Therefore, in the present invention, a device that transmits elastic waves is used as the wave transmission device. To increase the versatility of the device. The acoustic wave transmitter rotates the was eccentric relative to the axis of rotation weight, to originating against an elastic wave having a frequency corresponding to the rotational speed in search object by precisely controlling the rotational speed of the weight that has been configured.

The elastic wave transmitted from the transmitting device passes through the object to be searched and is received by the receiving device, the received wave signal is accurately synchronized with the transmitting side, and the received data is accumulated to reduce the noise power. To improve the S / N ratio. By analyzing the accumulated data, the change in the transfer function of the wave in the exploration target, that is, the change in the way the wave propagates is captured. If the exploration target is, for example, the crust or ground, this transfer function change means that the underground structure has changed, and if the exploration target is an artificial structure, etc., the structure is normal. Various utilization methods are conceivable, such as collecting state data (wave transfer function) in advance and comparing it with the current data to determine whether or not there is an abnormality in the structure and to quantitatively evaluate the abnormality .

[0010]

Embodiments of the present invention will be specifically described below with reference to the drawings. First, the overall configuration of the device of the present invention will be described mainly with reference to FIG. Reference numeral 1 denotes a wave transmission device that transmits an elastic wave (sine wave) as a wave signal, and is a device that transmits a precisely controlled elastic wave by accurately controlling the rotation speed of the weight as described later. .

Reference numeral 2 is a receiving means for receiving the elastic wave transmitted from the wave transmitting device 1 via the object to be searched 3. Reference numeral 4 is a control means for precisely controlling the elastic wave transmitted from the wave transmission device 1 by precisely controlling the rotation speed of the weight of the wave transmission device 1. The control method is, for example, to receive a highly accurate time data (hereinafter referred to as “GPS clock”) transmitted from the GPS satellite 5 and to use a motor for rotating the weight of the wave transmission device 1 by the GPS clock. The rotation speed is precisely controlled to an accuracy of 0.1 μs level. Further, for example, it is also possible to control so as to emit elastic waves of different frequencies by periodically changing the rotation speed of the motor. In this case, in the switching unit 4a, the state of single frequency control is changed to frequency modulation control (hereinafter referred to as "FM control"), and one wave transmission device 1
, The elastic waves of different frequencies are alternately emitted. An FM unit indicated by reference numeral 4b indicates a means for performing FM control.

Reference numeral 7 is a time interval storage type recording apparatus (hereinafter referred to as "TS recording apparatus"), which is a means for adding recordings to reduce noise and save storage capacity by a method described later. Is. Therefore, when the storage capacity has a margin, or when the data capacity is relatively small, the switching unit 6 may bypass the TS recording device 7 and directly output the data to the processing device 8 side.

The processing device 8 is provided with a fast Fourier transform means 15 for performing a Fourier transform on the received wave signal, an internal storage means 9, a comparing means 10, a central processing unit 11, etc.
And a huge amount of data is appropriately stored in the external storage medium 12. 13 is an alarm means connected to the processor 8 and 14 is a CR
The image display means includes a display medium such as T and liquid crystal.

Next, the configuration and operating state of each part will be described in more detail. The configuration of the wave transmission device 1 will be described in detail with reference to FIG. The wave transmission device 1 has a servo motor 1A and a main body 1B, and a weight 1b which rotates in the main body 1B by the servo motor 1A via a rotary shaft 1c in the main body 1B.
Is stored. Also, the main body 1B of the wave transmission device 1
Is fixed to the exploration target 3 and configured so that the elastic wave generated by the wave transmission device is reliably transmitted to the exploration target 3.

In the wave transmission device 1, the weight 1b
Is rotated at a constant rotation speed, a single force F having a magnitude shown by the following formula is applied to the search target 3 as a reaction of the centripetal force applied to the eccentric load M of the weight 1b. F = MR (2πf) ² M: Eccentric load of the weight 1b R: Distance f from the axis of the rotating shaft 1c to the center of gravity of the weight 1b, rotation frequency of the weight 1b

The servomotor 1A for rotating and driving the weight 1b is digitally controlled by a plurality of pulses supplied from the outside, and in the configuration of the present invention, the control means 4 (see FIG. 1).
The rotation is controlled by the pulse output from. For example, if the servo motor 1A is configured to control one rotation with 2000 pulses, 50000 pulses / second may be output to control the rotation of the servo motor 1A at 25 Hz, for example. The control of the rotation frequency of the weight 1b can be precisely performed up to about 1 μHz as described above.

Next, the receiving means 2 receives the elastic wave transmitted from the wave transmitting device 1 and having passed through, reflected or refracted on the object 3 to be searched. In this case, both the wave transmitting device 1 side and the receiving means 2 side receive the GPS clock from the GPS satellite 5 and synchronize the wave on the transmitting side with the wave on the receiving side (see FIG. 1). It should be noted that if the signal from the GPS is constantly received, the time can be obtained with an error of about 0.1 microsecond at any place on the earth, so that the synchronization is relatively easy.

The wave signal received by the receiving means 2 is once input to the TS recording device 7 via the switching unit 6. The TS recording device 7 is configured to save the storage capacity by performing an operation of adding received signals (accumulation of time intervals) at regular time intervals. For example, if recording is added every 100 seconds, the gain of frequencies other than an integral multiple of 1/100 Hz gradually decreases as the number of additions (number of accumulations) increases. That is, in this example, the frequency of the elastic wave transmitted by the wave transmission device 1 is 1/1
If preset to an integral multiple of 00 Hz, noise can be reduced and recording capacity can be reduced without reducing the gain due to the signal. However, for this purpose, it is necessary that the wave transmission device 1 side and the receiving means 2 side are accurately synchronized, and the GPS clock is used for this synchronization.

FIG. 3 shows how the time interval is accumulated. That is, the signal received by the receiving means 2 is divided into certain constant time intervals (100 seconds in the above example) and accumulated so that the heads are aligned. In the figure, N indicates the number of accumulations,
A frequency characteristic of the TS recording apparatus with respect to the number of accumulations is shown on the left side of the downward arrow indicating the number of accumulations, and a diagram showing the observation results corresponding to the same number of accumulations is shown on the right side.

First, when N = 1 (accumulation number 1) in the upper stage, no gain is obtained as a frequency characteristic, and therefore the observation result is almost only noise NZ. In the middle diagram, for example, when N = 100, the waves of the component having a period of an integer fraction of the time division are selectively emphasized, while the waves having other periods are these waves. It becomes smaller by being offset by the phase shift of. As a result, a fairly clear gain can be obtained in the frequency characteristic, so that the noise NZ becomes small and the signal SG becomes considerably clear even in the observation result. By increasing N in this way, only the signal SG finally remains as shown in the lower diagram.

Next, returning to FIG. 1, other components of the apparatus will be described. The observation data recorded by the TS recording device 7 (“observation result” in FIG. 3) is Fourier-transformed by the fast Fourier transform unit 15 of the processing device 8 and wave analysis is performed. For example, when the exploration target 3 is the ground or the deeper crust, the analysis results are sequentially accumulated in the external storage medium 12, and by installing a large number of receiving means, the signals from the receiving means are compared and analyzed comparatively underground. It is used not only for estimating structures but also for monitoring long-term crustal movements.

When the object to be searched is an artificial structure, the analysis data at the time when the structure is completed is stored in the storage means 9 as basic data, and the data continuously received and analyzed thereafter and this basic data are stored. By comparing the data with the comparison means 10, the internal structure and physical properties of the structure are quantitatively grasped, or the presence or absence of abnormality is detected. For example, when the difference between the basic data and the analysis data is equal to or more than a preset threshold value, the alarm unit 13 issues an alarm,
The image is displayed by the image display means 14.

Next, the search accuracy can be further improved by inputting the following data to the storage means.
Here, in order to exert the performance of the device of the present invention, accurate synchronization between the wave transmission side and the wave reception side is required, and high-accuracy exploration is not possible until the wave signal is accurately and continuously received. It will be possible. When this is called the linearity of the measurement system, various factors that disturb this linearity can be considered. For example, various devices, electronic circuits, etc. are interposed between the transmitting side and the receiving side. For example, an amplifier circuit, an electronic circuit such as an A / D conversion circuit, and the like are also factors that impede the linearity. Further, in the seismograph which is the receiving means 2 , there is a problem such as non-linearity when the mechanical operation is converted into the electrical output. In addition, the wave transmission device 1
And connecting different things, such as the search target, impedes the linearity.

Therefore, the characteristics of the electronic circuit such as the amplifier circuit and the A / D conversion circuit (input / output time lag, etc.), or the time lag between the seismograph vibration detection and the electric output, etc. are stored in advance in the processor 8 as correction values. It is input to the means 9 to minimize the influence of the linearity impediment factor on the receiving side during analysis. On the transmitting side, the control signal of the servo motor 1A is processed as the rotation frequency of the weight 1b.
However, since the twist of the rotary shaft 1c, the connection state between the main body 1B and the search target 3, and the like are considered as factors that impede the linearity on the transmission side, the servomotor 1 is installed at the installation location of the wave transmission device 1.
The rotation frequency of A and the frequency of the wave transmitted to the search target 3 are compared, and the comparison result is used as a correction value that is a coupling characteristic between the wave transmission device 1 and the search target 3 and a storage unit of the processing device 8 is provided. It is stored in 9 and used as a correction value at the time of analysis.

The present apparatus is capable of exploring or monitoring various objects depending on the size of the wave transmission device 1 or the number of installed receiving means. FIG. 4 shows another embodiment of the present invention.

In this embodiment, this device is used as a device for long-term monitoring of bridges, tunnels, embankments and the like for transportation. First, the seismograph 16a as a receiving means is attached to the bridge pier 18 of the bridge 17, and the seismograph 16b is attached to the bridge 17
The 16c is located at the bottom of the tunnel 19, the 16d is located at the top of the tunnel 19, and the 16e is located at the slope through which the tunnel 19 penetrates, or near the place where it is desired to predict the occurrence of a landslide due to rainfall or the like. There is. In the configuration shown in the figure, one seismograph is displayed for each observation target in order to clarify the relationship with the observation target.
In the actual configuration, it is desirable to arrange multiple seismometers for each observation target in order to obtain high observation accuracy.

In this configuration, the wave signal transmitted from the wave transmitting device 1 is detected by each seismograph 16a to 16e, and the received wave of each seismograph is synchronized with the transmitted wave and the received wave by the GPS clock of GPS5. Parsed. Initially received data at the position where each seismograph is arranged is stored as basic data in the processing device 8, and the received data received by each seismograph is compared with the corresponding basic data. As a result, on the side of the bridge 17, the detection of defects in the bridge 17, the state of the pier 18, etc. are constantly monitored. Especially after heavy rain, the slope of 16e is collapsed, or stress is generated in the bridge 17 due to partial outflow of the embankment 20 formed on the sedimentary layer 21, displacement of bridge piers due to erosion of the riverbed or cracking. The situation is assumed, and in this case, the received data changes with respect to the basic data, so it is possible to detect the danger in advance.

Similar to the above, for example seismometers 16c, 16d
Thus, the tunnel 19 can be monitored, and the slope of the slope through which the tunnel 19 penetrates can be monitored by 16e. The vibration generated when an automobile or a railroad vehicle passes through bridges and tunnels is received by each seismograph as a large amount of noise, but these noises can be removed by installing the TS recording device.

In the elastic wave transmitting device which is the above-mentioned wave transmitting device 1, since the rotating shaft 1c is arranged in the vertical direction, the elastic wave generated by the rotation of the weight 1b is mainly a P wave and an SH wave to the side of the object 3 to be searched. Although the SH wave is radiated downward, it is also possible to radiate the P wave below the search target 3 by horizontally installing the rotating shaft 1c.

In each of the above-mentioned embodiments, it is of course possible to form one array by a plurality of seismographs as the structure of the receiving means, and arrange a plurality of such arrays to enhance the search accuracy. Further, the array shape can be various configurations such as a square, a rectangle close to a square, or an equilateral triangle. Furthermore, the wave transmission device 1 can also be made compact and movable. However, in this case,
Since a reliable connection (coupling) to the exploration target is an important factor that affects the accuracy of the device, care must be taken to secure the exploration target even when installing it in a new position.

With the above movable wave transmitting device,
For example, in crustal exploration of a mountainous area where the terrain is expected to be complicated, it is possible to appropriately move and set the installation position of the wave transmission device 1 to a relational position where reception of waves by the receiving unit is good. With such complicated terrain,
However, it is possible to effectively carry out crustal exploration in a zone where the installation of seismographs (including an array of a plurality of configurations) as receiving means is restricted.

[0032]

As described above, according to the present invention, it is possible to control the wave which is an elastic wave transmitted from the wave transmitting device with extremely high precision,
It is received by the receiving means via the accurate time fixing means.
Received signal and is synchronized, and the time interval accumulation type recording and Fourier analysis, it is possible to perform analysis of the search target with high reliability from the received signal.

Further, the wave transmitter and the receiver according to the present invention
Any means can be installed in a specific place for a long time
Therefore, the natural structure such as the crust of a specific area, and
Changes over time of artificial structures such as bridges, tunnels, and buildings
It is also possible to monitor the occurrence of abnormalities and abnormalities over a long period of time.
is there.

[Brief description of drawings]

FIG. 1 is a block diagram of an active indirect exploration device showing a configuration example of the present invention.

FIG. 2 is a perspective view of a wave transmission device that transmits elastic waves.

FIG. 3 is a diagram showing a relationship between the number of times of accumulation of received data and an observation result.

FIG. 4 is a cross-sectional view of a structure such as a bridge showing an application example of the present invention and a crust in which the structure is arranged.

[Explanation of symbols]

1 Wave transmission device 1A servo motor 1B wave transmitter main body 1b weight 1c rotating shaft 2 Receiving means 3 exploration target 4 Control means 5 GPS satellites 7 TS recorder 8 processing equipment 15 Fast Fourier transform unit 16a to 16e seismograph (reception means) 17 bridges 18 piers 19 tunnel

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koharu Yamaoka, Furo-cho, Chikusa-ku, Aichi Prefecture Nagoya University Faculty of Science (72) Inventor Takahiro Kunitomo 959-31 Jorinji Temple, Izumi-cho, Toki-shi, Gifu Japan Nuclear Fuel Cycle Development Institute Tono Geoscience Center (72) Inventor Katsuro Ogawa Nagoya University Aichi Prefecture Furo-cho, Nagoya University Faculty of Science (56) Reference JP-A-9-304547 (JP, A) JP-A-10-319128 ( (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01V 1/30 G01N 29/00 G01V 3/12

Claims (2)

(57) [Claims] 1. A received by the receiving means via the search target that originate wave from the wave transmitting device, and in which non-destructively probing exploration target by analyzing the wave signal received, the rotary shaft Of the weight that rotates as the center
Elasticity with one or more frequencies due to rotational motion
Configured to excite a wave as a sine wave, and
Time data transmitted from GPS satellites (GP)
Wave transmission device having means for precise control by S clock)
Is transmitted from this wave transmission device through the
Receiving means for receiving elastic waves and transmission from the wave transmission device
The generated wave and the wave received by the receiving means are stored in the GPS.
And precision time adjustment hand stage to synchronize with the clock, receiving hand
Characterized in that it has a means for analyzing the state of the search target by Fourier analysis of the wave signal with reduced noise by accumulating wave reception signal received in succession by the step
Active indirect locator to. 2. The exploration target is a natural ground or an artificial structure, and the received signal is configured to be analyzed by a processing device. In addition to performing structural analysis of the exploration target, analysis of a signal received for a long period of time is performed. The active indirect exploration device according to claim 1, wherein the active indirect exploration device is configured to monitor a change in the state of the exploration target by comparing the data with the initial analysis data.