JP2001074850A - Electric surveying method using non-polarizing electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an electrode thin, lightweight, easy to handle, excellent in mass-productivity, and relatively inexpensive, excellent in workability in electrode installation, permitting a precise measurement. SOLUTION: Non-polarizing electrodes 44 each having a sheet type electroconductive polymeric gel body jointed with an electrode element are arranged so that the gel bodies are stuck on a ground 46, and the non-polarizing electrodes detect potentials to analyze the ground structure. For example, non- polarizing electrodes having sheet type conductive macromolecular gel bodies jointed with silver/silver-oxide layers of electrode elements are dispersedly arranged along a measurement line as current electrodes C1 and C2 and potential electrodes P1, P2..., so that the electroconductive polymeric gel bodies are stuck on the ground, and alternate DC currents are supplied from the current electrodes and the potential electrodes detect potentials and their variations to find the specific resistance and charging rate, and the ground structure is analyzed based on them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for exploring the electrical properties of ground using a non-polarized electrode, and more particularly, to a method for bonding a sheet-like conductive polymer gel to an electrode element. The present invention relates to an electric prospecting method using a non-polarized electrode.

[0002]

2. Description of the Related Art As one of techniques for exploring an underground structure using physical phenomena, there is an electric exploration method in which measurement is performed by focusing on the electrical properties of the ground. In this electric prospecting method, it is necessary to install an electrode on the ground or rock for supplying current or measuring potential. This type of electrode is usually
Metal electrodes (rods made of stainless steel or copper) are used.

When a metal electrode is driven into the ground, its surface comes into contact with moisture in the ground. Since water in the ground contains electrolyte ions, due to the difference in ionization tendency, the metal ions are slightly dissolved in the ground from the surface of the metal electrode, and electrons remain inside the electrode. Therefore, a positive charge increases in the ground and a negative charge increases in the electrode, and a potential difference (monopolar potential) is generated between the ground and the electrode. The unipolar potential varies greatly depending on the ion concentration of water in the ground, and the ion concentration of water varies from place to place. Further, when a direct current is passed using two metal electrodes, ions move in a wide area in the ground. That is, the cations move to the negative electrode and the anions move to the positive electrode, and accumulate around the electrodes. Then, most of the voltage applied between the two electrodes is distributed around the electrodes (electrochemical polarization). In such a state where polarization occurs, a constant current cannot flow, and a correct potential difference cannot be measured.

[0004] The IP video method which has been recently developed is
It combines the IP (inductive polarization) method and the specific resistance imaging method, and is a method of measuring and analyzing two kinds of physical quantities of specific resistance and charging rate. The IP effect appears remarkably on the ground containing a polarizable substance, and is therefore considered to be effective in estimating the position of a fault crush zone including, for example, clay-rock. Also, due to the high specific resistance or low specific resistance as a whole, it is expected that a detailed structure can be explored if there is a contrast in the charging rate even in the ground where it is difficult to search only with specific resistance. In such an electric survey, if the electrode itself produces a polarization effect, the polarization effect of only the ground cannot be measured. In addition, as an exploration method that requires a non-polarized electrode, the MT method (geomagnetic earth current method: a method of obtaining an electric field induced when electromagnetic waves enter the ground and a specific resistance distribution underground) or a self-potential method is used. is there.

For this reason, non-polarized electrodes which are not polarized when current is supplied and are less affected by the unipolar potential have been devised and used. Conventionally, as a non-polarized electrode, there has been a configuration in which a copper electrode is inserted into a unglazed pot and copper sulfate is injected, but since a liquid is used, and since the unglazed pot has a problem in strength, Extremely difficult to handle. Therefore, recently, a lead-lead chloride electrode has been developed as a non-polarized electrode. This is a structure in which, for example, a lead rod having a spiral shape in the lower half is used, and the periphery of the spiral portion is solidified in a columnar shape with a mixture of gypsum and lead chloride. For example, the diameter is 10 cm and the height is 12 cm. It is the size. There is also a structure using a lead plate instead of a lead bar. In order to install this type of electrodeless polarization, the ground is dug a little, filled with water, buried in a muddy state.

[0006]

However, since such a lead-lead chloride electrode is also heavy (about 1 kg) and difficult to handle, it takes a lot of labor to install a large number of such electrodes. In addition, since the performance decreases when the gypsum dries, it is necessary to make the gypsum ready for use by dipping it in a saline solution before use. It becomes thin and the lead electrode is exposed. Furthermore,
Since lead chloride is quite expensive, electrodes that require large amounts of it are necessarily expensive. In addition, much cost is required for storage of the electrodes and the like, and mass productivity is poor.

[0007] Further, since gypsum is used, the gypsum melts out each time it is used, and the electrode is damaged. Therefore, maintenance is required every three months of use, and the repair takes time. At that time, due to differences in the structure of lead, differences in the composition ratio of gypsum and lead chloride, or differences in the size of the electrodes,
Since the electrode performance is different, individual differences increase due to repair or the like. As a result, the measured values of the electric survey vary.

[0008] An object of the present invention is to provide an electric exploration method in which the work of installing a non-polarized electrode is good, and inexpensive and accurate measurement can be performed.

[0009]

According to the present invention, a plurality of non-polarized electrodes each comprising a sheet-shaped conductive polymer gel joined to an electrode element, such that the conductive polymer gel adheres to the ground. This is an electrical exploration method for analyzing the ground structure by arranging and detecting a potential with the non-polarized electrode.

Typically, the present invention provides a plurality of non-polarized electrodes in which a sheet-like conductive polymer gel is bonded to a silver / silver chloride layer of an electrode element, and the conductive polymer gel is provided on the ground. Distributed along the measurement line as a current electrode and a potential electrode so as to stick to, supply alternating DC from the current electrode,
This is an electrical exploration method in which a specific resistance and a charging rate are obtained by detecting a potential and its change with a potential electrode, and the ground structure is analyzed from the measured values. More preferably, water is sprayed in advance in the vicinity of the electrode installation position on the ground and moistened, non-polarized electrodes are adhered to the moist ground surface, and water is applied to the metal connection between each non-polarized electrode and the electric cable. While maintaining a state in which no permeation occurs, an alternating direct current is supplied from the current electrode, and the potential and its change are detected by the potential electrode.

The conductive polymer gel used as an electrode in the present invention is an elastic hydrogel that can stably transmit electricity by ionic conductivity. This is a form in which a hydrophilic solvent containing an electrolyte neutral salt is held in a three-dimensional polymer network made of a hydrophilic polymer, and has a structure exhibiting high ionic conductivity due to the interaction between the two.

First, as a preliminary experiment, a non-polarized electrode in which a conductive polymer gel is bonded to an electrode element (hereinafter referred to as a “conductive polymer gel electrode”) and a non-polarized electrode having a conventional structure made of lead-lead chloride. A comparison experiment was performed on the effect of the natural potential, the ground resistance, and the polarization with respect to an electrode (hereinafter, referred to as a “lead-lead chloride electrode”). The conductive polymer gel electrode has a thickness of about 1 mm and a diameter of 8 cmφ, and the lead-lead chloride electrode has a thickness of about 5 cm and a diameter of 8 cmφ.

(Natural potential) 3 cm deep and 30 cm in diameter in the soil layer
Make a puddle of the size, set the electrode spacing to 10 cm
Each electrode was set, and a potential difference generated between the electrodes was measured with a digital voltmeter. The measurement results are as follows. Conductive polymer gel electrode Potential difference: 0.37 mV Lead-lead chloride electrode Potential difference: 0.66 mV If there is no individual difference between the electrodes, the spontaneous potential generated between them should be 0 mV. Although a slight potential difference occurred, each was a sufficiently small and stable value. By the way, when the same experiment was performed for the stainless steel electrode and the copper electrode, the influence of the polarization appeared, the fluctuation was large, and the measurement was impossible.

(Grounding Resistance) A measuring instrument of the IP imaging method was used for measuring the grounding resistance. The results are as follows. Conductive polymer gel electrode: ground resistance: 0.4 kΩ Lead-lead chloride electrode: ground resistance: 0.2 kΩ From these results, the ground resistance of the lead-lead chloride electrode is slightly smaller than that of the same diameter. However, since the conductive polymer gel electrode is thin and lightweight, it is sufficiently possible to realize the same or lower ground resistance by increasing the size (diameter).

(Polarization effect) A current value between electrodes of 200 mA,
The effect of polarization was investigated by supplying a pulse-like alternating direct current (a waveform having a section where current does not flow during switching between positive and negative polarities) with a period of 4 seconds and monitoring the current waveform. If the polarization is large, a large amount of electric charge is released after the current is cut off, as in a capacitor. Therefore, a small amount of electric charge indicates that the polarization effect is small. Figure 1 shows the measurement results
Shown in In FIG. 1, a solid line (moving average of two sections of the conductive polymer gel electrode) and a broken line (moving average of two sections of the lead-lead chloride electrode)
From the comparison with the above, it was found that the conductive polymer gel electrode quickly returned to 0, and it was confirmed that the electrode was slightly excellent.

Based on these facts, it was evaluated that the conductive polymer gel electrode can be sufficiently used as a non-polarized electrode instead of the lead-lead chloride electrode in terms of electrical characteristics.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The non-polarized electrode used in the present invention comprises:
As shown in FIG. 2A, a sheet-like conductive polymer gel body 12 is joined to an electrode element 10. A circular resin film 1 with a thickness of about 100 μm and a diameter of about 10 cm 1
On one side of No. 4, a silver / silver chloride coating layer 16 having a thickness of several to several tens of μm is formed. Silver / silver chloride coating layer 16
Can be formed, for example, by applying an ink containing silver / silver chloride and drying by heating. A hole is formed in the center of the hole, and a resin-made hook (male type) 18 coated with silver / silver chloride is inserted into the hole from the side on which the silver / silver chloride coating layer 16 is formed. The electrode element 10 is obtained by fitting and snapping the snap 20. A sheet-shaped conductive polymer gel body 12 is bonded to the surface of the electrode element 10 on which the silver / silver chloride coating layer 16 is formed, to form a non-polarized electrode 22. Actually, in order to make it easy to handle, an easily peelable separate film (not shown) is stuck on the surface of the conductive polymer gel body 12, and it is peeled off at the time of use so as to be placed on the ground surface. It is preferred to configure.

In use, as shown in FIG. 2B, the female button 26 to which the electric cable 24 is connected is electrically connected to the snap 20 by being fitted into the snap 20. Female button 26
Has a metal fitting portion inside and has a structure in which the outside is covered with a resin. However, since the snap 20 is also made of metal, there is a possibility that polarization occurs when the snap portion contacts water. In such a case, if another thin conductive polymer gel sheet 28 is interposed between the snap 20 and the female button 26 and fitted, a waterproof structure can be easily obtained.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the IP imaging method, a specific resistance distribution and a charging rate distribution in the ground are measured. When an electric current is applied to the ground, electric charges are stored inside the ground. When the electric charge is sufficiently accumulated, the electric field becomes a steady state, and when the current is suddenly cut off, a current accompanying the discharge of the electric current flows from that moment. The current that flows through the ground is called a primary current, the current that flows with charging or discharging is called a secondary current, and the potential resulting from each is called a primary potential and a secondary potential. The ratio of the voltage of the discharge to the applied voltage is the charge rate, indicating the IP effect. Note that the specific resistance can be obtained as a ratio between a primary potential and a primary current.

The charging rate was measured with a measuring instrument arrangement as shown in FIG. A hole 30 with a side of 10cm and a depth of 5cm
Were formed, a conductive polymer gel electrode 32 was placed in each hole 30, and a transmitter 34 and a receiver 36 were connected. In addition, assuming a case where the connection portion between the electrode and the electric cable is waterproof and a case where it is not waterproof, a case where the conductive polymer gel electrode 32 is simply installed as shown in FIG. As shown in FIG. 4B, the measurement was also performed when the conductive polymer gel electrode 32 was placed in a submerged state. The measurement was performed using a pulsed alternating DC having a transmission cycle of 4 seconds, and the current value was set to 500 mA. FIG. 5 shows the definition of the time window of the charging rate. FIG. 6 shows changes in the charging rate for each time window. Both the current and potential electrodes are waterproof. Only the current electrode is waterproof. Both the current and potential electrodes are not waterproof (submerged). In addition, the values of the charging rates become smaller in the order of.
The change in the charging rate is larger when changing from the state to than when changing from the state to. This means that it is important to waterproof the current electrode when measuring the charging rate.

Table 1 shows the average values of the charging rates in the above states. The average charging rate here is 1
It is a simple arithmetic average of the values of the charging rates of zero time windows, and the current IP video analysis mainly uses this averaged value. Like the value of the charging rate of each time window, the value of the charging rate changes in the order of. The change in the charging rate is larger when changing from the state to than when changing from the state to. This suggests that the value of the charging rate is such that the current waveform strongly depends on the polarization phenomenon of the electrodes.

[0022]

[Table 1]

From these results, it can be determined that the measurement of the charging rate can be performed with higher accuracy by keeping the current electrode in a waterproof state.

Next, Table 2 shows the values of the spontaneous potential in the state (1). The value of this natural potential represents the DC component of the potential automatically calculated by the receiver. A difference of more than twice in the value of the self-potential was observed between and.
It was confirmed that the change in the value of the self potential was smaller between the states of and. From these facts, it is considered that the value of the spontaneous potential strongly depends on the potential electrode. Therefore, it can be seen that in the measurement of the natural potential, a higher precision measurement is possible by setting the potential electrode in a waterproof state.

[0025]

[Table 2]

From these facts, if the electrodes are not waterproofed, it is necessary to install each electrode so that water does not enter the connection between the electrode and the electric cable as much as possible. If water inevitably enters the connection between the electrode body and the cable, it is necessary to take waterproof measures such as interposing a conductive polymer gel sheet at the electrode connection or covering with a resin or rubber.

The electric exploration by the IP imaging method is performed with the electrode arrangement as shown in FIG. A pair of current electrodes (C ₁ , C ₂ : one is a far electrode) is arranged, and a number of potential electrodes (P ₁ , P ₂ ,..., P _n ) are arranged at equal intervals on a measurement line. A transmitter 40 is connected between the current electrodes, and a receiver 42 is connected to each potential electrode. A conductive polymer gel electrode 44 is used for each electrode. That is, it is a non-polarized electrode in which a sheet-like conductive polymer gel is bonded to the silver / silver chloride layer of the electrode element. A pulse-like alternating direct current is supplied between current electrodes by a transmitter 40, and the potential at each potential electrode is measured by a receiver 42.
Measure and record with. Each electrode is installed by leveling the vicinity of the electrode installation position on the ground 46, moistening it with water, and bringing the conductive polymer gel body into close contact therewith. The measured value at the potential electrode farther from the current electrode represents information on a deeper part of the ground.

From these measurement results, the specific resistance and the charging rate are obtained. The specific resistance is obtained from the ratio of the current to the primary voltage Vp of the potential waveform shown in FIG. 8, and the charging rate is obtained as the ratio of the secondary voltage to the primary voltage. Note in fact, seeking integral value (area indicated by hatching in FIG. 8) and the charging rate apparently used a ratio of the primary potential of the secondary voltage of the predetermined time after the primary current cut t ₁ ~t _2. The apparent charging rate indicates an average value of the charging rate over a wide range inside the ground. Both the specific resistance and the charging rate are analyzed simultaneously as analysis parameters. Appropriate analysis modeling (for example, finite element method) is adopted, and the specific resistance and the charging rate of the element are used as parameters. The algorithm for iterative modification of the model uses the nonlinear least squares method. A specific resistance distribution and a charging rate distribution are drawn and interpreted.

[0029]

According to the present invention, since a non-polarized electrode in which a conductive polymer gel is bonded to an electrode element is used, it is lightweight and relatively inexpensive, has excellent mass productivity, has good storage and transport properties, and has good electrode installation. Workability is extremely good. In addition, the natural potential is sufficiently small and stable, there is no individual difference between the electrodes, and the grounding resistance is small, so that the charging rate can be measured with high accuracy. Therefore, even in the ground where it is difficult to search only by specific resistance due to low specific resistance as a whole, if there is a contrast in charging rate, detailed structure can be searched with high accuracy, for example,
It is possible to effectively and efficiently investigate the estimation of the position of the fault crush zone including clayified rock.

[Brief description of the drawings]

FIG. 1 is a graph showing a difference in polarization effect due to a difference in electrodes.

FIG. 2 is an explanatory view showing an example of a conductive polymer gel electrode.

FIG. 3 is an explanatory view of a measurement device arrangement.

FIG. 4 is an explanatory diagram of an electrode installation situation.

FIG. 5 is an explanatory diagram of a definition of a time window of a charging rate.

FIG. 6 is an explanatory diagram showing a change in a charging rate for each time window due to a difference in a waterproof state.

FIG. 7 is an explanatory diagram of a measurement system of the IP imaging method.

FIG. 8 is an explanatory diagram of a current waveform and primary and secondary potentials.

[Explanation of symbols]

 Reference Signs List 10 electrode element 12 conductive polymer gel body 14 resin film 16 silver / silver chloride coating layer 18 hook 20 snap 22 non-polarized electrode 24 electric cord 26 female button 28 conductive polymer gel sheet

Claims (3)

[Claims] A non-polarized electrode comprising a sheet-shaped conductive polymer gel joined to an electrode element, and a plurality of non-polarized electrodes arranged so that the conductive polymer gel adheres to the ground. An electrical exploration method using a non-polarized electrode, characterized by analyzing a ground structure by detecting a potential by the method. 2. A plurality of non-polarized electrodes in which a sheet-like conductive polymer gel is bonded to a silver / silver chloride layer of an electrode element, and a current is applied so that the conductive polymer gel adheres to the ground. Electrodes and potential electrodes are distributed along the measurement line, alternating DC is supplied from the current electrodes, and the potential and its change are detected by the potential electrodes to determine the specific resistance and the charging rate. An electrical exploration method using a non-polarized electrode, characterized by analyzing the following. 3. Sprinkling water in advance near the electrode installation position on the ground to make it wet, and attaching non-polarized electrodes to the moist ground surface, and attaching the non-polarized electrodes to the metal connection portions between the electric cables and the non-polarized electrodes. 3. The method according to claim 2, wherein an alternating direct current is supplied from the current electrode while the water does not permeate, and the potential and its change are detected by the potential electrode.