JP2019007873A - Underground survey system and method for underground survey - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an underground exploration system and an exploration method capable of easily and surely exploring the ground even in a steep terrain such as a mountainous area, which is often seen in Japan. An underground exploration system 1 exhibits an artificial earthquake generator 2, a control device 3 for controlling the artificial earthquake generator 2, a plurality of receiving electrodes 5 configured to be installed on the surface of a medium 4, and vibration. [Selection diagram] FIG. 1 comprising a vibration receiver 6 for detecting, a computer 7 for inputting and recording a current detected by a receiving electrode and a vibration detected by the vibration receiver.

Description

  The present invention relates to an underground exploration system and an underground exploration method using seismic waves and seismic currents.

  Conventionally, seismic exploration for exploring underground conditions has been performed by measuring and analyzing physical phenomena generated by the earth and reactions of physical phenomena artificially generated to the earth.

  In such seismic exploration, a geophone is used in contact with the ground surface or the inner wall of a borehole to capture seismic signals (mediated vibrations) generated from various artificial or natural sources. . These explorations have many disadvantages such as complexity, cost, and that the geophones were driven and had to generate seismic waves with a power above a certain value to record the signal. Had.

For example, the following means have been used as means for generating an artificial earthquake, but each has its own problems.
(1) Explosives such as bombs. This is low reproducibility and leads to environmental destruction.

(2) Heavy and large hammer. This is simple in structure and not expensive, and is particularly suitable for small-scale work, but it is difficult to obtain a large output.

(3) Vibroseis car. Since this is an expensive and huge vehicle, it is difficult to use it on a steep terrain such as a mountainous area often found in Japan.

  Furthermore, in seismic exploration, the structure is examined based on the difference in propagation speeds of multiple types of waves included in the generated seismic wave, but the actual analysis is highly difficult and requires accurate measurement of the crustal structure. Often it does not lead to the discovery of resources.

  Patent Document 1 discloses a method for exploring geological structures by combining seismic waves and seismic currents.

US Pat. No. 6,476,608

  An object of the present invention is to provide an underground exploration system and an exploration method capable of exploring the underground easily and reliably even in a steep landform such as a mountainous area often found in Japan.

  In order to solve the above problems, the underground exploration system according to the present invention has the following features.

(1) Artificial earthquake generating device, control device for controlling the artificial earthquake generating device, a plurality of receiving electrodes configured to be installed on the surface of the medium, a geophone for detecting vibration, a current detected by the receiving electrode, and A computer that receives and records vibration detected by the geophone.

(2) In the underground exploration system according to another embodiment, in (1), the artificial earthquake generator preferably includes a gun.

(3) In the underground exploration system according to another embodiment, in (2), the gun preferably includes an air gun.

  The underground exploration method according to the present invention has the following features.

(4) Artificial earthquake generator, control device for controlling the artificial earthquake generator, a plurality of receiving electrodes configured to be installed on the surface of the medium, a geophone for detecting vibration, a current detected by the receiving electrode, and A method of exploring the ground using a computer that receives and records vibrations detected by a geophone, generates an artificial earthquake by operating an artificial earthquake generator, and generates an artificial earthquake at a receiving electrode The seismic current is detected, transmitted to the computer, recorded, and the vibration of the artificial earthquake is detected by the geophone, transmitted to the computer, recorded, and the seismic current and vibration data recorded by the computer are analyzed. Exploring underground structures.

  According to the present invention, it is possible to provide an underground exploration system and an exploration method capable of exploring the underground easily and reliably even in a steep terrain such as a mountainous area often found in Japan. Become.

It is a schematic diagram of an underground exploration system for performing an underground exploration method according to an embodiment of the present invention. It is a block diagram which shows the structure of the computer 7 which records and analyzes a seismic wave and a weak electric current used for this invention. In the underground exploration method concerning an embodiment of the invention, it is a mimetic diagram showing an example of an earthquake generating device which generates an artificial earthquake. It is an example of the flowchart which shows the method of geological exploration of this invention. It is a schematic diagram which shows an example of the geophone which detects the vibration by an artificial earthquake in the underground exploration method which concerns on embodiment of this invention.

  Hereinafter, the underground exploration system 1 and the underground exploration method according to the embodiment will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a conceptual diagram showing an outline of an underground exploration system 1 according to the present embodiment. As shown in FIG. 1, the underground exploration system 1 according to the present embodiment is used for soil where a water source or the like exists in the ground as shown in FIG. 1.

  The underground exploration system 1 according to the present embodiment includes an artificial earthquake generator 2, a control device 3 that controls the artificial earthquake generator 2, and a plurality of media 4 (soil in this embodiment) installed on the surface. A receiving electrode 5, a geophone 6 that detects vibration, and a computer 7 that receives and records the current detected by the receiving electrode 5 and the vibration detected by the geophone 6.

  The artificial earthquake generator 2 in the present embodiment is, for example, a gun as will be described later, and an excavation hole of about several meters at a desired position of the epicenter 10 that generates an artificial earthquake (hereinafter simply referred to as “seismic source position”). Is operated by a person 8 to form 9 and generate vibrations therein. Moreover, it connects to the control part 3 so that it can control from the outside.

  The receiving electrode 5 is an electrode for receiving an earthquake current generated by an artificial earthquake, and a plurality of receiving electrodes 5 can be installed at predetermined intervals in the vicinity of the hypocenter position (excavation hole 9). For example, it is installed so as to have a point symmetric (line symmetric) relationship so that the distance from the epicenter is the same. In the present embodiment, an example in which the receiving electrodes 5 that receive the seismic current are arranged on the four ground surfaces is shown, but the number of arranged receiving electrodes 5 is not limited to this. The distance between the receiving electrodes 5 is 10 m, for example.

  The geophone 6 is a device that receives vibrations of seismic waves generated by an artificial earthquake. For example, a geophone is used as will be described later. As with the receiving electrode 5, it is preferable to arrange a plurality of the geophones 6 at a predetermined interval in the vicinity of the epicenter position, but is not limited thereto.

  A computer 7 is connected so that the seismic current data received by the receiving electrode 5 and the vibration data detected by the geophone 6 can be recorded. In the computer 7, it is possible to record and store the contents and various data operated by the control unit 3 and to analyze them thereafter.

  And one of the features in the present embodiment is the seismic exploration that uses the above system 1 to perform underground exploration using the vibration of the artificial earthquake generated using the artificial earthquake generating device 2; The purpose is to combine with electric exploration for exploring the ground using the seismic current generated by the artificial earthquake.

  Furthermore, as will be described later, it is preferable to use a gun as the artificial earthquake generator 2.

  Next, the exploration method performed using the system 1 according to the present embodiment will be briefly described.

  (Seismic exploration)

  Among seismic exploration that explores underground structures, especially in the field of crustal structure research and resource development, artificial earthquakes are generated, and reflected waves generated from geological boundaries due to differences in acoustic impedance are measured and data Reflection seismic exploration has been carried out.

  Specifically, in seismic reflection surveys, vibrations (elastic waves) that are artificially generated near the surface of the earth travel downward, reflect on the underground boundary where the speed and density change, and then return to the surface again. This is a technique for elucidating the underground structure by capturing the incident with a geophone (seismic meter) 6 and processing and analyzing the recorded records. By processing and analyzing the arrival time and amplitude of the captured reflected wave, the underground velocity structure and geological structure form are revealed.

  As the seismic exploration, methods such as direct wave seismic exploration, refraction wave seismic exploration, and surface wave seismic exploration can be employed in addition to the reflection seismic exploration described above.

(Electrical exploration)

  When an artificial earthquake is generated by the artificial seismic wave generator 2, a P wave and an S wave are generated. Here, the P wave (P-wave) is an abbreviation for Primary wave (Pressure wave) or Pressure wave (Dense wave). The P wave is an elastic wave that oscillates parallel to the traveling direction, and is transmitted through solid, liquid, and gas. The velocity is about 5 to 7 km / s in the bedrock, and is the first seismic wave that reaches when an earthquake occurs.

  S-wave is an abbreviation for Secondary wave (second wave) or Shear wave (twisted wave, bending wave or shear wave). An elastic wave that oscillates at right angles to the direction of travel and travels through solids. The speed is 3-4 km / s in the rock, and it reaches after the P wave, causing a big shake called main motion.

  Seismoelectric effects occur in conjunction with the charge generated at the surface of the water source, referred to as the electrical double layer. When seismic waves penetrate porous rocks, they incite the relative motion between fluid and solid particles. As a result, the electrical double layer on the surface of the water source is disturbed and charges are generated.

  In this way, the generated charge flow is measured as an earthquake current. The specific resistance structure is grasped by measuring the response (normal potential) and analyzing the response. Generally, in the specific resistance structure, a hard ground is distributed at a high specific resistance, and a soft ground or a fault is often distributed at a low specific resistance.

  FIG. 2 is a block diagram showing the internal structure of the control device 3 and the computer 7 used in the system 1 of the present embodiment. The control device 3 includes at least a driver for controlling the artificial earthquake generating device 2 and an operation unit for operating each instrument. The computer 7 includes a recording unit (memory) that stores received data, a processing unit that processes received data, and a display that displays data and the like.

  FIG. 3 is a schematic diagram showing an example of the artificial earthquake generator 2 used in the present embodiment. In the present embodiment, the gun shown in FIG. 2 is used as the artificial earthquake generator 2. The gun shown in FIG. 2 is a type of so-called buffalo gun, which is placed inside a drilling hole provided on the surface of the earth and fired by operating a driver connected to a cord to generate an artificial earthquake. .

In underground exploration using seismic waves as in the present embodiment, for example, the following elements are required as artificial seismic wave generation sources (seismic sources).
(1) A high output is required. This is because the signal body noise ratio (S / N ratio) improves as the output increases.
(2) It is preferable that a high-frequency signal can be generated. This is because the higher the frequency, the shorter the seismic wave and the easier the analysis.

(3) High reproducibility is required. This is because a plurality of measurements are performed at one place, so that it is required to have a certain characteristic as an energy source.

(4) It is desirable that the epicenter signal is clearly defined. It is possible to measure the time of reflection and / or interference of seismic waves using deconvolution (a processing method that amplifies reflection and / or interference) by grasping the exact pattern of wave energy. become.

The buffalo gun shown in FIG. 3 satisfies all of the above elements, and can provide an optimal earthquake source in the underground exploration system 1 according to the present embodiment. Specifically, the buffalo gun has the following features, for example.
(1) In a shallow excavation hole, a sufficient thermal power explosion can be caused, and the environment is hardly affected.
(2) Small and easy to carry. Therefore, it can be suitably used even in steep terrain such as a mountainous area often found in Japan.
(3) Output is stable every time and reproducibility is very high.

  In this embodiment, an example of a buffalo gun has been described as an artificial earthquake generation source. However, the artificial earthquake generation source is not limited to this, and general guns (including air guns) can also be used. .

  FIG. 4 is a flowchart for explaining the underground exploration method according to the present embodiment. To execute the underground exploration method, first, an artificial earthquake is generated by firing (step S1), a weak current is detected at the receiving electrode 5 (step 2A), and a seismic wave is detected by the geophone 6 (step S2B). The obtained data is recorded in the computer 7 (step S3), and finally the computer 7 processes the data. Analyze (step S4). The above steps are repeated as desired to complete the search.

  The geophone 6 has a configuration as shown in FIG. 5, for example. FIG. 5A shows a vertical geophone 6a that detects vertical vibration, and FIG. 5B shows a horizontal geophone 6b that detects horizontal vibration.

  In the geophone 6, a magnet and a coil surrounding the magnet are mounted. When the vibration of the seismic wave reaches the geophone 6, a voltage is generated due to the relative movement between the coil and the ground. The voltage is converted into a digital signal and transmitted to the computer 7 for recording. In addition, in this Embodiment, although the geophone 6 demonstrated the case where it was arrange | positioned in the position different from an epicenter, not only this but you may arrange | position in the same position as an epicenter, You may incorporate directly in the artificial earthquake generator 2. FIG.

  As described above, in the present embodiment, by combining the elastic wave exploration using the vibration of the artificially generated seismic wave and the electric exploration using the seismic current generated by the generation of the seismic wave, It has become possible to explore the ground with a very high probability compared to.

  Moreover, in the present embodiment, since a gun that can be easily carried is used as an artificial earthquake generation source, it is simpler than a method using a huge rock or the like as in the prior art. This is particularly useful in places that are steep and large vehicles cannot enter, such as mountainous areas that are common in Japan.

1 Underground Exploration System 2 Artificial Earthquake Generator 3 Control Device 4 Medium (Soil)
5 receiving electrode 6 geophone 7 computer 8 person 9 excavation hole 10 epicenter

Claims (4)

An artificial earthquake generator,
A control device for controlling the artificial earthquake generator;
A plurality of receiving electrodes configured to be installed on a medium surface;
A geophone that detects vibration;
A computer for recording the current detected by the receiving electrode and the vibration detected by the geophone;
Underground exploration system. The system according to claim 1, wherein the artificial earthquake generator includes a gun. The system of claim 2, wherein the gun includes an air gun. An artificial earthquake generator,
A control device for controlling the artificial earthquake generator;
A plurality of receiving electrodes configured to be installed on a medium surface;
A geophone that detects vibration;
A method of exploring the ground using a computer that records the current detected by the receiving electrode and the vibration detected by the geophone,
Activate the artificial earthquake generator to generate an artificial earthquake,
With the receiving electrode, the seismic current generated by the artificial earthquake is detected, transmitted to the computer, recorded,
With the geophone, the vibration of the artificial earthquake is detected, transmitted to the computer, recorded,
An underground exploration method for exploring underground structures by analyzing the seismic current and the vibration data recorded in the computer.

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