Underground exploration method

Abstract

To provide an underground exploration method capable of enlarging a transmission signal without increasing a measurement cost to improve measurement accuracy, and eliminating adverse effects on the land on which electrodes are embedded.SOLUTION: An underground exploration method for exploring the ground by passing electricity between at least two electrodes embedded in the ground, comprises a step of forming at least two electrode installation holes in the ground, a step of forming a liquid layer in at least one of the electrode installation holes, and a step of embedding at least one electrode in contact with the liquid layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a subsurface exploration method for grasping the ground conditions by measuring the electrical properties of the ground through electrical exploration, electromagnetic exploration, etc. In particular, it relates to a subsurface exploration method capable of reducing the ground resistance between the transmitting electrode used in electrical exploration or electromagnetic exploration and the ground, increasing the transmitted signal, and improving the measurement accuracy.

Background Art

[0002] Conventionally, as a subsurface exploration method for grasping the ground conditions such as the underground structure, state, and the existence of underground resources, there are known subsurface exploration methods such as electrical exploration and electromagnetic exploration that grasp the ground conditions by measuring the electrical properties of the ground, particularly the specific resistance of the substances constituting the strata.

[0003] In electrical exploration, for example, as disclosed in Patent Document 1, at least two electrodes (a transmitting electrode and a receiving electrode) are buried in the ground or brought into contact with the ground surface, and the specific resistance of the ground between the transmitting electrode and the receiving electrode is measured by receiving the transmitted signal (current) transmitted from the transmitting electrode with the receiving electrode.

[0004] In electromagnetic exploration, for example, as disclosed in Patent Document 2, an alternating current is passed through an electric wire connected to a plurality of transmitting electrodes to radiate a transmitted signal (electromagnetic wave) from around the electric wire, and the specific resistance of the ground between the transmitting electrode and the receiving electrode is measured by receiving this transmitted signal with the receiving electrode.

[0005] In this case, if the ground resistance between the transmitting electrode and its grounding surface is large, the transmitted signal will decrease, leading to a decrease in measurement accuracy. Therefore, for example, as disclosed in Patent Document 3, the ground resistance is reduced by spraying a ground resistance reducing agent containing a conductive substance around the transmitting electrode.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, such a ground resistance reducer increases the cost for measurement. Also, when borrowing the location for electrode embedding from a third party, substances that may have an adverse impact on the land cannot be used.

[0008] In view of such a situation, an object of the present invention is to provide a subsurface exploration method that increases the transmission signal without increasing the measurement cost, improves the measurement accuracy, and does not have an adverse impact on the land where the electrodes are embedded.

Means for Solving the Problems

[0009] The present invention was invented to solve the problems in the prior art as described above, and the subsurface exploration method of the present invention includes the following configurations.

[0010] [1] A subsurface exploration method for exploring the subsurface by energizing between at least two electrodes embedded in the subsurface, forming at least two electrode installation holes in the subsurface; forming a liquid layer in at least one of the electrode installation holes; embedding at least one of the electrodes in a state of being in contact with the liquid layer, and having a subsurface exploration method.

[0011] [2] The subsurface exploration method according to [1], wherein the liquid layer contains water.

[0012] [3] The underground exploration method according to [2], wherein the water includes at least any one of groundwater, well water, river water, seawater, and tap water.

[0013] [4] The underground exploration method according to [2] or [3], wherein the water is supplied to the liquid layer in a state where the electrodes are buried in the ground.

[0014] [5] The underground exploration method according to [4], wherein the water is supplied from one tank to a plurality of the liquid layers formed in a plurality of the electrode installation holes in which the plurality of the electrodes are buried.

[0015] [6] The underground exploration method according to any one of [1] to [5], wherein the liquid layer includes at least any one of ammonium sulfate and bentonite.

Advantages of the Invention

[0016] According to the present invention, by forming a liquid layer in an electrode installation hole for burying an electrode and performing underground exploration (such as electrical exploration or electromagnetic exploration) with the electrode in contact with the liquid layer, the ground resistance between the electrode and the ground can be reduced, the transmission signal can be increased, and the measurement accuracy can be improved.

[0017] In addition, by using water such as groundwater, well water, river water, seawater, and tap water as the liquid layer, or by containing ammonium sulfate that is also used as a fertilizer or bentonite that is also used in civil engineering work, the land where the electrode is buried is not adversely affected.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0019] Hereinafter, embodiments (examples) of the present invention will be described in more detail with reference to the drawings. In the present invention, "electrical exploration" means so-called narrow-sense electrical exploration, and refers to exploration methods such as the pole-pole method, pole-dipole method, Schlumberger method, and Wenner method. Further, "electromagnetic exploration" refers to an exploration method using an electromagnetic induction method such as the MT method, CSAMT method, and TDEM method. Further, when referring to "subsurface exploration", it is used in a meaning including electrical exploration and electromagnetic exploration.

[0020] FIG. 1 is a block configuration diagram of a subsurface exploration device for carrying out the subsurface exploration method of the present embodiment, and FIGS. 2 and 3 are schematic diagrams for explaining the process of embedding electrodes in the subsurface exploration method of the present embodiment.

[0021] As shown in FIG. 1, the subsurface exploration device 10 of the present embodiment includes a transmitting electrode 12, a receiving electrode 14, a signal transmitting unit 16 that applies a transmission signal to the transmitting electrode 12, a signal detecting unit 18 that detects a signal received by the receiving electrode 14, and a control unit 20 that controls the signal transmitting unit 16 and the signal detecting unit 18.

[0022] In the present embodiment, the subsurface exploration device 10 is configured to include only two electrodes, the transmitting electrode 12 and the receiving electrode 14, but a plurality of transmitting electrodes 12 and receiving electrodes 14 can also be provided respectively.

[0023] The transmitting electrode 12 and the receiving electrode 14 are not particularly limited as long as they can transmit and receive a transmission signal (current or electromagnetic wave), and known electrode plates, electrode rods, etc. can be used. For example, it is also possible to use a corrugated iron plate or the like. In addition, in order to radiate and detect electromagnetic waves, a configuration in which a plurality of electrodes are connected by electric wires is also included as the transmitting electrode 12 and the receiving electrode 14.

[0024] The signal transmission unit 16 transmits a current or an electromagnetic wave as a transmission signal from the transmitting electrode 12, and the receiving electrode 14 receives the current or electromagnetic wave propagated through the ground between the transmitting electrode 12 and the receiving electrode 14. The current or electromagnetic wave received by the receiving electrode 14 is detected as a signal by the signal detection unit 18.

[0025] The control unit 20 controls the output of the transmission signal transmitted from the signal transmission unit 16 and stores the signal detected by the signal detection unit 18. In addition, it is configured to analyze the ground conditions based on the stored detection signal.

[0026] Note that the data of the detection signal stored in the control unit 20 can be read into an external computer or the like, and this computer can be configured to analyze the ground conditions based on the data of the detection signal.

[0027] The underground exploration device 10 of the present embodiment configured as described above buries the transmitting electrode 12 and the receiving electrode 14 in the ground and energizes between the transmitting electrode 12 and the receiving electrode 14, thereby transmitting a current or an electromagnetic wave from the transmitting electrode 12 to the receiving electrode 14.

[0028] As shown in Fig. 2(a), first, at least two electrode installation holes 30a and 30b are formed in the ground. The sizes of the electrode installation holes 30a and 30b can be appropriately adjusted according to the sizes of the transmitting electrode 12 and the receiving electrode 14, the distance between the electrodes, etc. Note that the depth of the electrode installation holes 30a and 30b is preferably 2m to 3m.

[0029] Next, as shown in Fig. 2(b), place the transmitting electrode 12 and the receiving electrode 14 inside the formed electrode installation holes 30a and 30b, respectively.

[0030] In this state, as shown in Fig. 3(a), supply liquid to the electrode installation hole 30a on which the transmitting electrode 12 is placed to form the liquid layer 32. Here, the liquid for forming the liquid layer 32 preferably contains water. As the water, for example, groundwater, well water, river water, seawater, tap water, etc. can be used. When groundwater or the like is obtained when forming the electrode installation holes 30a and 30b, the liquid layer 32 can also be formed using the groundwater or the like.

[0031] From the viewpoint of not adversely affecting the land where the electrodes are buried, for example, when burying the electrodes in a field or the like, it is preferable to avoid using water containing salts such as seawater.

[0032] Also, when using groundwater, well water, river water, tap water, etc. as the liquid layer 32, the conductivity is low and the transmission signal may not increase as expected. In such a case, it is preferable to mix, for example, ammonium sulfate, bentonite, etc. into the liquid layer 32. Such substances are also used as fertilizers and, for example, when burying the electrodes in a field or the like, they do not adversely affect the land.

[0033] Next, as shown in Fig. 3(b), backfill the electrode installation hole 30a with the transmitting electrode 12 in contact with the liquid layer 32 to bury the transmitting electrode 12. In this case, instead of completely backfilling the electrode installation hole 30a, it is preferable to provide a depression 30a1 that can hold water and supply water to this depression 30a1 regularly so that water can be supplied to the liquid layer 32.

[0034] Alternatively, when embedding the transmission electrode 12, as shown in FIG. 4, a water supply pipe 34 can be provided so that water can be supplied from the outside of the electrode installation hole 30a to the liquid layer 32. A water storage tank 36 is connected to the water supply pipe 34, and it can be configured to arbitrarily supply water from the water storage tank 36 to the liquid layer 32 via the water supply pipe 34.

[0035] In addition, when the underground exploration device 10 is provided with a plurality of transmission electrodes 12 and the transmission electrodes 12 are respectively embedded in a plurality of electrode installation holes 30a, as shown in FIG. 5, a plurality of water supply pipes 34 can be connected to the water storage tank 36, and it can be configured to supply water from one water storage tank 36 to the liquid layer 32 of each electrode installation hole 30a.

Explanation of reference numerals

[0036] 10 Underground exploration device 12 Transmission electrode 14 Receiving electrode 16 Signal transmission unit 18 Signal detection unit 20 Control unit 30a Electrode installation hole 30a1 Depression 30b Electrode installation hole 32 Liquid layer 34 Water supply pipe 36 Water storage tank

Claims

1. A subsurface exploration method for exploring the subsurface by energizing between at least two electrodes buried in the ground, comprising: forming at least two electrode installation holes in the ground; forming a liquid layer in at least one of the electrode installation holes; burying at least one of the electrodes in a state of being in contact with the liquid layer; A subsurface exploration method having the above steps.

2. The subsurface exploration method according to claim 1, wherein the liquid layer contains water.

3. The subsurface exploration method according to claim 2, wherein the water contains at least one of groundwater, well water, river water, seawater, and tap water.

4. The subsurface exploration method according to claim 3, wherein the water is supplied to the liquid layer with the electrode buried in the ground.

5. The subsurface exploration method according to claim 4, wherein the water is supplied from one tank to a plurality of the liquid layers formed in the plurality of the electrode installation holes in which a plurality of the electrodes are buried.

6. The subsurface exploration method according to claim 1, wherein the liquid layer contains at least one of ammonium sulfate and bentonite.

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