JPH11109041A - Measuring system of detector setting position for underground estimation and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a detector at an arbitrary position, by detecting the vibration wave of ground generated at an exciting position on a straight line with a detector, and calculating the known plural distance data of detectors and its vibration characteristics as reference value. SOLUTION: Vibration of an impact wave generated at an exciting position is detected with each detector 2. A difference between the arrival times of vibration waves detected with each detector 2 is found. For instance, in the case where the detector 21 is made the reference of a time difference, a difference between the arrival times in the detector 21, 22 and another time difference between the other detectors 23...2n are found, and the relative position of each detector in which the detector 21 is made reference is established by performing relative comparison with a distance between the known detectors 21, 22 in a calculation means. The relative position of the other detectors, in the case the detector 21 is made reference from relative comparison with the arrival time difference of the vibration wave in the other detectors in the case where the distance between the known detectors 21, 22 and the arrival time difference of the vibration wave are made references, can be accurately measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system and method for accurately measuring the position of an installed detector in an exploration system for estimating an underground structure from the surface wave velocity of the ground. In particular, the present invention relates to a measurement system and a method suitable for measuring a detector installation position on residential ground.

[0002]

2. Description of the Related Art There is known a method of estimating an underground structure by generating a surface wave by an exciter installed on the ground surface and detecting and analyzing the vibration with a plurality of detectors.
For example, Japanese Patent Application Laid-Open No. 63-309887 discloses a method for measuring the thickness and quality of constituent layers such as roads, but the same applies to underground structures such as residential ground. The measuring method itself is described in detail in Japanese Patent Publication No. 2-1249.

[0003]

In the above-mentioned conventional method, the distance D between the installed detectors is fixed, and the phase velocity c of the surface wave is obtained from the delay time τ of the wave between the detectors, where c = D / τ. The underground structure is estimated from the obtained surface wave velocity of the ground. Therefore, the distance between the detectors needs to be set very accurately. However, in actuality, gravel, crushed stones, and the like often exist on the ground such as residential land, and it may be difficult to install the detector while accurately maintaining a desired distance. In particular, as described in JP-A-63-309887, the number of detectors is not always limited to two, and the number of detectors is actually increased to improve the measurement accuracy. Given that measurements are also taken, it is even more difficult to accurately place multiple detectors at a desired distance. As described above, when it is difficult to install a plurality of detectors at a desired distance due to the presence of gravel or crushed stone, etc., the detectors should be slightly shifted back and forth on a straight line from the exciter. I have no choice. However, it is obvious that an error occurs in the obtained speed unless the shifted amount is accurately measured and corrected at the time of speed conversion. For example, in the ground surface of the surface layer having a surface wave velocity of 100 m / s, the frequency is 100 Hz.
In the case of measuring the speed at the distance between two detectors separated by 20 cm, if the distance between the detectors is unavoidably set to 25 cm, the obtained speed will be 80 m / s. Therefore, the distance between the detectors must be measured very accurately.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide a plurality of detectors for detecting ground vibration waves.
Even if there are obstacles such as gravel and crushed stone on the ground surface, it is possible to install the detector at any position, and it is possible to easily and accurately measure the interval between detectors required for analysis An object of the present invention is to provide a measurement system of a detector installation position for structure estimation and a method thereof.

[0005]

In order to achieve the above object, the invention according to claim 1 comprises at least three vibration detectors arranged in a straight line on the ground surface for estimating an underground structure. When installing the detector, the distance between any two of the detectors is known, and the ground vibration wave generated at the excitation position on the straight line is detected by each detector. 2
A calculating means for calculating a relative position of other detectors based on a distance between the detectors and a vibration characteristic thereof, and a measuring system of a detector installation position for estimating an underground structure. is there.

That is, not all distances between the detectors are defined in advance, but only the distance between any two detectors is known and any position where the detectors can be installed without any obstacles or the like is known. And the other detectors are installed at arbitrary positions, and then the surface waves generated at the excitation position are detected by each detector, and the other is detected based on the distance between the two known detectors. The relative position of each detector is calculated from the relationship with the vibration characteristics obtained from the detector.

According to a second aspect of the present invention, in the first aspect, the vibration characteristic between the detectors is an arrival time of a vibration wave generated at a position where the vibration is generated. Is a measurement system of the detector installation position.

According to a third aspect of the present invention, in the first aspect, the vibration characteristic between the detectors is a phase difference according to a frequency component of the spectrum obtained from a spectrum of a wave obtained by the detector. This is a measurement system of a detector installation position for estimating an underground structure.

According to a fourth aspect of the present invention, in order to estimate the underground structure, at least three vibration detectors arranged in a straight line on the ground surface are installed. The distance between the detectors is known, the ground vibration wave generated at the excitation position on the straight line is detected by each detector, and the distance between the two known detectors and its vibration characteristics are used as a reference,
This is a measurement method for estimating an underground structure, characterized by calculating the relative positions of other detectors.

According to a fifth aspect of the present invention, there is provided the detector according to the fourth aspect, wherein the vibration characteristic between the detectors is an arrival time of a vibration wave generated at the excitation position. This is a method of measuring the detector installation position for structure estimation.

[0011] Further, the invention according to claim 6 is based on claim 4.
In, the vibration characteristics between the detectors, the spectrum of the wave obtained by the detector is obtained, and the phase difference according to the frequency component of the spectrum is characterized by the detector installation position for underground structure estimation It is a measurement method.

[0012]

According to the measuring system of the detector installation position according to the first aspect, the distance between any two of the plurality of detectors to be installed is known and the vibration wave generated at the excitation position. Is detected by each detector, and the relative positions of the other detectors are calculated based on the known distance between the two detectors and the vibration characteristics. Therefore, only the distance between any two detectors is calculated. It is known that there is no obstacle such as gravel or crushed stone on the ground surface, and it can be installed at any position where the detector can be installed, but for other detectors it is possible to install the detector at any position ,
Moreover, the relative position of the detector can be accurately measured.

Further, according to the measuring system of the detector installation position according to the second aspect, the arrival time of the vibration wave obtained by each of the installed detectors is obtained by the time difference from the reference detector, and the known arrival time is obtained. The relative positions of the other detectors can be accurately measured from each time difference based on the distance between the detectors.

According to the measuring system of the detector installation position according to the third aspect, the phase difference for each frequency component from the reference detector is determined from the spectrum of the vibration wave obtained by each installed detector. Then, the relative positions of the other detectors can be accurately measured from each phase difference with reference to the distance between the two known detectors.

Further, according to the method for measuring the detector installation position, as described above, the distance between any two detectors is known, and the distance between the known two detectors is determined. To calculate the relative position of the other detectors based on the vibration characteristics of the detectors, the distance between any two detectors is assumed to be known, and there is no obstacle such as gravel or crushed stone on the ground surface. Is installed at any position where it can be installed, but the other detectors can be installed at arbitrary positions, and the relative positions of the detectors can be accurately measured.

According to a fifth aspect of the present invention, as described above, the arrival time of the vibration wave obtained by each installed detector is determined by the time difference from the reference detector. Then, the relative position of the other detector can be accurately measured from each time difference with reference to the distance between the two known detectors.

According to the measuring method of the detector installation position according to the sixth aspect, as described above, the frequency of each frequency component with respect to the reference detector is determined from the spectrum of the vibration wave obtained by each installed detector. The respective phase differences are obtained, and the relative positions of the other detectors can be accurately measured from the respective phase differences with reference to the known distance between the two detectors.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a configuration diagram of a measuring system of a detector installation position for estimating an underground structure according to the present invention.

In FIG. 1, an exciter 1 for generating a surface wave and a detector 2 for detecting a vertical component of the surface wave generated by the exciter 1 (n detectors 21, 22,...,
2n) are arranged on a straight line. In FIG.
The broken line indicates for convenience that the exciter 1 and the detector 2 are arranged in a straight line. In addition, reference numeral 3 denotes a calculating means for analyzing a signal obtained by each detector 2, and details of its operation will be described later.

As the vibration exciter 1, an electromagnetic type is generally used, but any type may be used as long as it applies a vertical vibration to the ground surface, and there is no particular limitation. As a method of generating such a surface wave, for example, simply by hitting the ground surface with wood or the like, the surface wave is generated, so such a means may be used.

As the detector 2, any detector that is generally used for detecting vibration waves can be used. Here, of the n detectors arranged in a straight line on the ground surface, only the detectors 21 and 22 have known distances, and can be detected without obstacles such as gravel and crushed stone on the ground surface. The vessel is installed at a place where it can be installed. And
The other detectors 23,..., 2n are arranged at arbitrary positions that can be installed on this straight line, and the distance between them is arbitrary. That is, not all the inter-detector distances are defined in advance, only the distance between any two detectors is set in advance as a known value at that distance, but the other detectors can be installed at any distance. It can be installed at each position. However, since the minimum distance between the detectors can be accurately measured if the minimum wavelength is equal to or less than の of the shortest wavelength to be detected, the surface wave phase velocity is several tens to at most about 300 m / s on the surface layer such as residential ground. Considering that, the maximum detection frequency is 100Hz
If so, it is desirable that the minimum distance between the detectors be 40 cm or less.

Next, a description will be given of an embodiment of a method for measuring the detector installation position in the above configuration.

First, a shock wave is generated at the excitation position. Note that the excitation position here does not necessarily need to match the excitation position measured to estimate the ground structure,
Any position on the straight line may be used. As a means for generating a shock wave, a vibration exciter 1 is generally used. However, as described above, a shock wave can be easily generated even when hit with wood or the like or a person jumps.

The vibration of the shock wave generated at the excitation position is
It is detected in each of the detectors 2. FIG. 2 shows, for example, a detection waveform in which the shock wave detected by each detector 2 is represented on the time axis. Then, a difference between the arrival times of the vibration waves detected by the respective detectors 2 is obtained. More specifically, for example, when the detector 21 is used as a reference for the time difference, the time difference Δt12 between the arrival times of the vibration waves at the detector 21 and the detector 22 and the detector 21 and the other detectors 2
, .DELTA.t1n with respect to the respective detectors 2, 3,.
By making a relative comparison between the distances 1 and 22, the detector 21
The relative position of each detector with respect to is determined. That is, relative to the known distance between the detectors 21 and 22 and the time difference between the arrival times of the oscillating waves at the detectors 21 and 22, relative to the time difference between the arrival times of the oscillating waves at the other detectors. From the comparison, the relative position of each of the other detectors based on the position of the detector 21 can be accurately measured. More specifically, for example, when the distance between the detectors 21 and 22 is ΔD12 (known),
The distance ΔD13 between the detectors 21 and 23 is given by ΔD13 = ΔD12 × Δt13 / Δt12.

That is, according to such a measuring method, it is possible to accurately measure the position of each detector installed at an arbitrary position where the detector can be installed. As a result, the surface wave velocity of the ground is also reduced. It can be calculated accurately, and the estimation accuracy of the underground structure is improved. Here, the detector 21 has been described as a reference for the difference in the arrival time of the vibration wave.
The same applies to the reference.

Next, another embodiment of the measuring method of the detector installation position will be described.

First, as in the above-described embodiment, a surface wave is generated at the vibration position. In the present embodiment, the surface wave may be swept by using the exciter 1 or may have a single frequency while appropriately changing the frequency, or may be a shock wave as described above.

This surface wave is detected by each detector 2, and the respective detected waveforms are subjected to Fourier transform. FIG. 3 shows a Fourier transform spectrum of a detected waveform detected by the detector. For example, (a) shows a spectrum corresponding to the detector 21, (b) shows a spectrum corresponding to the detector 22,
The gain G and the phase P are represented on the frequency f axis. FIG. 4 shows a phase difference with respect to a frequency component obtained from the cross spectrum of the detectors 21 and 22 in FIG.

When the detector 21 is used as a reference for the phase difference, for example, the phase difference ΔP12 of the vibration wave between the detector 21 and the detector 22 and the phase difference ΔP13 between the detector 21 and the other detectors,. .DELTA.P1n are obtained, and the relative position of each detector with respect to the detector 21 is determined by comparing the known distance between the detectors 21 and 22 in the calculating means 3. That is, the known detector 2
When the distance between 1 and 22 and the phase difference between the vibration waves in the detectors 21 and 22 are used as a reference, the position of the detector 21 is used as a reference from the relative comparison with the phase difference between the vibration waves in the other detectors. In this case, the relative positions of the other detectors can be accurately measured. More specifically, for example, in FIG. 4, the phase difference ΔP12 at the frequency f1
Is φ1, Δt12 in this case is given by Δt12 = φ1 / 2πf1. Similarly, Δt13 is given from the phase difference between the detectors 21 and 23. Therefore, if the distance between the detectors 21 and 22 in this case is ΔD12 (known),
The distance ΔD13 between the detectors 21 and 23 is given by ΔD13 = ΔD12 × Δt13 / Δt12 as before.

That is, even with such a measuring method,
Since it is possible to accurately measure the position of each detector installed at any position where it can be installed, the surface wave velocity of the ground can be calculated accurately, and the estimation accuracy of the underground structure can be improved. improves. In addition, since the output waveform of each detector generally has a so-called waveform distortion (has dispersibility), when the phase difference is obtained from the Fourier transform spectrum,
As shown in FIG. 4, since there is some fluctuation without a perfect straight line, it is particularly desirable in terms of accuracy to determine the positions of the detectors at a plurality of frequencies and average them.

In the embodiment described above,
The known distance is set between the detectors 21 and 22. However, the distance is not necessarily required, and may be between arbitrary detectors.

[0033]

As described above in detail, according to the measuring system of the detector installation position according to the first aspect, the distance between any two of the plurality of detectors to be installed is known. In order to calculate the relative positions of the other detectors based on the known distance between the two detectors and their vibration characteristics, only the distance between any two detectors is known and the gravel is applied to the ground surface. It can be installed at any position where the detector can be installed without obstacles such as stones and crushed stones, but other detectors can be installed at any position. An excellent effect that the relative position can be accurately measured is exhibited.

Further, according to the measuring system of the detector installation position according to the second aspect, the arrival time of the vibration wave obtained by each of the installed detectors is obtained by the time difference from the reference detector, and the known time is calculated. The relative position of another detector can be easily and accurately measured from each time difference based on the distance between the individual detectors.

According to the detector installation position measuring system of the present invention, the phase difference of each frequency component with respect to the reference detector is determined from the spectrum of the vibration wave obtained by each installed detector. The relative positions of the other detectors can be easily and accurately measured from the respective phase differences with reference to the distance between the two known detectors.

According to the measuring method of the detector installation position, the distance between any two of the detectors to be installed is known, and the distance between the known two detectors is determined. To calculate the relative position of the other detectors based on the distance of the detector and its vibration characteristics, the distance between any two detectors is known and there is no obstacle such as gravel or crushed stone on the ground surface. It is installed at any position where the detector can be installed, but for other detectors it is possible to install the detector at any position and it is possible to accurately measure the relative position of the detector It has excellent effects.

According to the measuring method of the detector installation position according to the fifth aspect, as described above, the arrival time of the vibration wave obtained by each installed detector is determined by the time difference from the reference detector. The relative positions of the other detectors can be easily and accurately measured from the respective time differences with reference to the distance between the two known detectors.

According to the measuring method of the detector installation position according to the sixth aspect, as described above, the frequency of each frequency component with respect to the reference detector is determined from the spectrum of the vibration wave obtained by each installed detector. The respective phase differences are obtained, and the relative positions of the other detectors can be easily and accurately measured from the respective phase differences with reference to the distance between the two known detectors.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a measurement system of a detector installation position for estimating an underground structure according to the present invention.

FIG. 2 is an example of a detection waveform detected by each detector.

FIG. 3 is a Fourier transform spectrum of a detected waveform.

FIG. 4 is a diagram illustrating a phase difference with respect to a frequency component obtained from the cross spectrum of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exciter 2, 21, 22, ..., 2n Detector 3 Calculation means

Claims (6)

[Claims] At least three vibration detectors arranged in a straight line on the ground surface for estimating an underground structure, and when installing the detectors, at least two vibration detectors are used. The distance between the two detectors is known, and the ground vibration wave generated at the excitation position on the straight line is detected by each detector, and the other detection is performed based on the known distance between the two detectors and its vibration characteristics. And a calculating means for calculating a relative position of the detector. 2. The system according to claim 1, wherein the vibration characteristic between the detectors is the arrival time of a vibration wave generated at the vibration generating position. . 3. The underground structure estimation according to claim 1, wherein the vibration characteristic between the detectors is a phase difference according to a frequency component of a spectrum obtained from a wave obtained by the detector. System for measuring the installation position of the detector. 4. When at least three vibration detectors arranged in a straight line are installed on the ground surface to estimate an underground structure, a distance between any two of the vibration detectors is known. The ground vibration waves generated at the excitation position on the straight line are detected by the respective detectors, and the relative positions of the other detectors are determined based on the known distance between the two detectors and the vibration characteristics thereof. A method of measuring a detector installation position for estimating an underground structure, which is characterized by being calculated. 5. The method according to claim 4, wherein the vibration characteristic between the detectors is the arrival time of a vibration wave generated at the vibration generating position. . 6. The underground structure estimation according to claim 4, wherein the vibration characteristic between the detectors is a phase difference according to a frequency component of a spectrum obtained from a wave obtained by the detector. Method of measuring the detector installation position for