JP2001356176A - Active indirect prospecting method and device for executing the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prospect the change of an underground structure with a comparatively simple formation economically with high probability. SOLUTION: A vibration sensor 3 is arranged with an offset distance L determined beforehand from an hammering point of a hammer 1 which is an excitation means, and vibration generated by hammering by the hammer 1 propagating through the ground which is a prospecting object OJ is received by the vibration sensor 3, and the wave propagation characteristic under the vibration sensor 3 is recorded and displayed by a data recording-display means 4. The hammering point and the vibration sensor 3 are moved as far as a distance d, keeping the offset distance L, and the wave propagation characteristic under the moved vibration sensor 3 is again recorded and displayed with the same procedure. Respective recorded data are finally combined and displayed as continuous waveform data under the traverse line where the vibration sensor 3 is moved. If fluctuation exists on a part of the continuous waveform data, existence of a buried structure, a fault, a cavity or the like can be estimated by the state of the fluctuation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for nondestructively searching for an object to be searched, in particular, the structure of the ground or the crust or the presence or absence of an underground buried object.

[0002] For example, 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, and reasons for resource exploration such as minerals and hot springs. The need to explore underground structures is high. The underground structure exploration method is a direct exploration method that directly obtains information on the underground structure by drilling the ground to obtain a sample, and the underground structure is estimated by observing and measuring the physical signal from the underground and displaying it. Indirect exploration methods have been used.

[0003] Of the above-mentioned methods, the method of directly exploring the underground allows the underground to be closely inspected, but requires a considerable number of ball rings in the exploration target area, and is very expensive. In addition, since the underground information is the point information of the boring point, it cannot be used as continuous information of the entire exploration target area.

[0004] Compared to such a direct search method, the indirect search method has advantages such as being able to economically search a relatively large area and being able to perform a wide search from a shallow depth to a large depth. have. The indirect search method adds wave energy such as artificial elastic waves to the
An active search method for searching for an object by capturing and displaying a refraction wave or an excitation electromagnetic wave is generally used. As this method, a method using an exciter as a source of artificial vibration or using an explosive has been conventionally adopted.

[0005]

The above-mentioned active indirect exploration method uses an exciter and an explosive, so that the exploration cost is not inexpensive, though not as inexpensive as the direct exploration method. In addition, since such a relatively large vibration is applied to the crust, it is practically impossible in an urban area or a densely populated residential area.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and comprises a relatively simple vibrating means such as a hammer, and a predetermined distance (offset distance) from the vibrating means. ), And means for recording and displaying various waves received by the vibration receiving means and displaying a mutation or abnormality of the underground structure below the vibration receiving means,
While maintaining the offset distance, moving the vibration means and the vibration receiving means to obtain data of the underground structure under each vibration receiving point, and estimating a variation of the horizontal underground structure by continuing these data. The present invention relates to an underground structure exploration method and apparatus characterized by the following.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The vibrating means is, for example, a hammer,
A predetermined distance from the vibration means is set as an offset distance, and a vibration receiving means (vibration receiving sensor) is arranged. In this state, the ground is vibrated by a hammer. By this excitation, a body wave such as a reflected wave and a surface wave propagate, and the vibration receiving means receives these waves. The received waves are displayed in real time,
For example, by outputting a waveform image corresponding to the traveling time of the wave, a traveling image of the wave below the vibration receiving point is obtained.

[0008] By inputting the wave received data, vertical received data at each observation point is obtained. If one piece of vibration data is obtained, secure the offset distance, move the vibration means and the vibration receiving means by a certain distance, perform vibration and vibration again,
Obtain the received data below the receiving point. After sequentially moving while securing the offset distance in this way and obtaining vibration data for each moving point, the individual data are combined and displayed as continuous vibration data, and the vibration means and the vibration means move. Underground structure of the selected route (line), especially underground structure variation (for example, existence of faults, underground buried objects, abnormal geology, etc.)
Is estimated.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 schematically show the method according to the invention. In the figure, reference numeral 1 denotes a hammer as a vibration means, which is configured to vibrate the search target OJ by hitting an iron plate 2 arranged on the search target OJ such as the ground. Reference numeral 3 denotes a vibration sensor as a vibration receiving means, which receives various waves propagating through the search target OJ by the hammer 1.
The vibration sensor 3 is disposed at a predetermined distance (offset distance) L from the hit point of the hammer 1.
The offset distance L is usually set to about 10 to 20 m.

Reference numeral 4 denotes data recording / display means for displaying wave data received by the vibration sensor 3, for example, extracting only a surface wave component from the wave data, or generating waveform data based on the travel time of the wave. Depending on the purpose, such as displaying as, the characteristic of wave propagation in the underground structure below the receiving point is displayed, and data is recorded, or the display result is displayed in real time. Since the data recording / display unit 4 only needs to obtain the received vibration data of the vibration sensor 3, the arrangement such as the setting of the offset distance L is not limited.

In FIG. 2A, a wave caused by the impact of the hammer 1 on the iron plate 2 is received by the vibration sensor 3 located at the offset distance L via the search object OJ. The offset distance L is, for example, 10 m. Object OJ
Wave reaches the vibration sensor 3 as a body wave (a direct wave, a refracted wave, a reflected wave, etc.) and a surface wave. The received vibration data received by the vibration sensor 3 is subjected to display processing by the connected data recording / display means 4 under preset conditions such as, for example, the running time of the wave (detected by the deviation of the receiving time) and the extraction of only the surface wave. Are recorded and displayed as wave propagation characteristics in the vertical direction below the receiving point.

When the excitation and reception in (1) are completed, the excitation point by the hammer 1 and the reception point of the vibration sensor 3 are moved by a fixed distance d while securing the offset distance L as in (2). In the same manner as in the case of (1), excitation and reception are performed, and the wave propagation characteristics in the vertical direction below the second reception point are recorded and displayed. The moving distance d is set to about 1 m, depending on the required analysis accuracy. Also, as a matter of course, the analysis accuracy is improved by setting the movement distance d to be small.

While the offset distance L is secured in this way, the excitation and the reception are sequentially performed as (2), (3),... With the movement distance d, and the wave propagation in the vertical direction below each of the receiving points. Record and display characteristics. By summing (synthesizing) the individual wave propagation characteristics in the vertical direction in the entire travel of the preset survey line in this way, it is possible to grasp (visually recognize) the horizontal wave propagation characteristics of the object to be searched, such as the crust. Then, it is possible to find the variation such as the existence of a fault or underground buried object. As a method of further improving the search accuracy, a method of reciprocating the striking point and the receiving point along the measurement line in addition to setting the moving distance d small may be considered.

In the above operation, since the data recording / display means 4 is not affected by the offset distance L and the moving distance d, for example, the vibration sensor 3 and the data recording / display means 4
By connecting with a relatively long cable, it is possible to reduce the number of movements of the data recording / display means 4 itself, or to enable the search without moving the data recording / display means 4 at all.

FIGS. 3 and 4 show an example of a display result of received data at each receiving point when the object to be searched is the crust, FIG. 3 shows display data at each receiving point, and FIG. 3 shows data obtained by adding (synthesizing) the display data shown in FIG. In this case, the hammer 1 as a hitting means uses a 20-pound (about 9 kg) metal plate (30 cm square,
The measurement was performed by setting a human-powered strike to the thickness of 1 cm), the vibration sensor 3 as one 10 Hz pickup, the offset distance L at 10 m, and the moving distance d at 1 m.

In the display, the waveform of the received wave is imaged and displayed. Hereinafter, the term “waveform” is used as a term including travel time, wavelength, and amplitude. Although the illustrated one is a black and white display (light and shade display), the waveform image can be displayed much more clearly than the illustrated one because it is actually a color display.

In FIG. 3, reference numerals 1 to n denote waveform images at the respective receiving points. However, since it is difficult to understand the meaning of each waveform image, these waveform images are added together. This will be described with reference to FIG. The image of FIG. 4 shows a continuous image at the time of the wave motion immediately below the survey line as a waveform image. Here, as the wave, a body wave such as a P wave, an S wave, a direct wave, a refraction wave, and a reflected wave is first observed, and then a surface wave is observed. Body waves are observed as short-period, short-width, alternating layered waves. Further, the surface wave is observed as a wave having a relatively long period, a wide alternating layer, and a large amplitude. The body wave duration is short, at most on the order of tens of milliseconds, and thereafter cannot be recognized by a subsequent surface wave. On the other hand, the surface wave has a strong power and usually lasts 200 ms or more, depending on the ground conditions.

From the above viewpoint, the body wave (A) shown in FIG.
Is displayed at run time from 25 ms to 75 m at longest
s, and thereafter becomes a surface wave (denoted by B). In this manner, the waveform images 1 to n at the respective receiving points (FIG. 3)
) And summing the waveform images 1 to n to obtain an overall waveform image along the survey line shown in FIG. As described above, the offset distance L10m and the movement distance d1m are set in the entire waveform image shown in the figure.
In addition, since the moving distance d was set to 1 m, the measurement line 0 to 10
Up to m, ten individual images shown in FIG. 3 are arranged.

FIG. 5 is a schematic diagram for more clearly showing the fluctuation state of the waveform image shown in FIG. Incidentally, since the actual output screen is a color display as described above, in the case shown in the figure, portions which are integrally displayed with the same brightness are also clearly displayed (for example, red and blue with the same brightness). From this overall display, as shown in FIG.
At the point P, it can be seen that the waveform image fluctuates rapidly. That is, it is presumed that there is a sudden change in the stratum immediately below this point P, that is, a fault.

As described above, according to the present invention, the state of the underground structure immediately below the survey line, that is, the presence or absence of a mutation such as a fault can be detected in a very small number of base materials and almost in real time. That is, if the underground structure to be explored is uniform in the horizontal direction, the display image of the obtained wave data shows the same pattern in the moving direction of the survey line, that is, in the horizontal direction, If there are structural changes such as faults, cavities, or burial of foreign matter in the underground structure or local unevenness, the waveform image pattern will be disturbed or changed. It is possible.

FIG. 6 schematically shows a method (actually implemented) of estimating the underground structure of the ground which is the OJ to be searched mainly based on the travel time of the reflected wave. In addition, the same alphabet following the hammer 1 and the vibration sensor 3 such as the hammer 1a and the vibration sensor 3a and the hammer 1b and the vibration sensor 1b form a pair via the offset distance L. In this case, the portion where the underground object 5 such as a concrete object is embedded is reflected by the underground object 5, so that the travel time of the reflected wave is shortened. Further, when the hammer 1 strikes from the underground object 5, the reflected wave is reflected at the stratum boundary 6, so that the travel time of the reflected wave becomes longer. Thus, the underground buried object 5
Can be predicted.

FIG. 7 shows an underground structure which was found by actually boring the ground schematically shown in FIG. 6 described above. The foundation was found to be present. It is to be noted that 5 'is an abnormal stratum found outside the current exploration range, and if the exploration range is extended to the range of this abnormal stratum 5', it is considered that the existence of the abnormal stratum 5 'could be naturally estimated.

In the present invention, a manual hammer has been described as an example of the vibration means. However, the vibration means is not limited to a hammer, and a deeper exploration can be performed by using a mechanical vibration means. It is of course possible.

[0024]

As described above, according to the present invention, the object can be searched by the vibrating means, the vibrating means, and the data recording / display means for displaying the received data of the vibrating means. And can be implemented at a much more economical cost than the conventional method.

In addition, since the structure below each receiving point can be displayed directly and in real time in response to wave reception without performing complicated numerical processing such as spectrum calculation, the structure to be searched can be reduced in a short time. Can be explored.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a positional relationship between a vibration unit and a vibration receiving unit according to an embodiment of the present invention.

FIG. 2 is a diagram showing a moving state of a vibration unit and a vibration receiving unit having the positional relationship shown in FIG.

FIG. 3 shows a waveform image of travel time of individual wave propagation at each receiving point.

FIG. 4 is a diagram showing a continuous image obtained by joining the waveform images of the individual wave propagations shown in FIG. 3;

FIG. 5 is a diagram conceptually showing the content of an image of the waveform of the continuous wave shown in FIG.

FIG. 6 is a conceptual diagram showing a method of searching for an underground buried object by displaying a reflected wave.

7 is an underground sectional view showing an actual measurement state of the search target shown in FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hammer (vibration means) 2 Iron plate 3 Vibration sensor (vibration means) 4 Data recording / display means 5 Solidification board d Moving distance between vibration point and vibration point L Offset distance

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[Procedure amendment]

[Submission Date] June 27, 2000 (2006.2
7)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 2

FIG. 5

FIG. 6

FIG. 7

FIG. 3

FIG. 4

Claims (5)

[Claims] 1. A method for receiving a wave oscillated from a vibration means on an object to be searched, such as the earth's crust, by a vibration receiving means and searching for a structure to be searched below the vibration receiving means from the received data. The point is located at a fixed offset distance, the wave oscillated at the excitation point is received at the receiving point, the propagation characteristics of the wave in the search target below the receiving point are recorded and displayed, and the excitation is performed with the offset distance. By sequentially moving the point and the receiving point by a predetermined distance, the propagation characteristics of the wave at the lower part of each receiving point are sequentially recorded and displayed, and the recorded data of the respective receiving points are summed up to thereby move the lower part of the measuring line at the moving receiving point. An active indirect exploration method characterized by displaying continuous recorded data. 2. An apparatus for receiving a wave oscillated from a vibration means on an object to be searched, such as the crust, by a vibration receiving means, and searching for a structure to be searched below the vibration receiving means from the received vibration data. It has vibration receiving means arranged at a fixed offset distance from the vibration means, and data recording / display means for recording / displaying the wave data received by the vibration receiving means. The recorded wave data is recorded and displayed by a predetermined method, and by combining the individual recorded data for each receiving point, continuous recording data below the measuring line at which the receiving point is moved is displayed. Active indirect exploration equipment. 3. The active indirect exploration apparatus according to claim 2, wherein said vibrating means is a hammer. 4. The active indirect exploration apparatus according to claim 2, wherein said data recording and displaying means records and displays the travel time of the received wave. 5. The active indirect exploration apparatus according to claim 2, wherein said data recording / display means records / displays a surface wave among the received waves.