KR100429285B1 - Device for monitoring self-potential using non-polarizable electrode and method thereof - Google Patents

Abstract

The present invention relates to an apparatus for measuring natural potential using a non-polarized electrode and a method thereof, and more particularly, a surface of a repair facility constructed by using a homogeneous medium in which an abnormality of the natural potential caused by a leak of a repair facility is used. By continuously measuring in the present invention, the present invention relates to a natural potential measuring device capable of tracking the leakage flow path generated in a section of the hydraulic structure and its method.

Description

Device for measuring natural potential using non-polarized electrode and its method {DEVICE FOR MONITORING SELF-POTENTIAL USING NON-POLARIZABLE ELECTRODE AND METHOD THEREOF}

The present invention relates to an apparatus for measuring natural potential using a non-polarized electrode and a method thereof, and more particularly, a surface of a repair facility constructed by using a homogeneous medium in which an abnormality of the natural potential caused by a leak of a repair facility is used. By continuously measuring in the present invention, the present invention relates to a natural potential measuring device that can track the leakage flow path generated in some sections of the hydraulic structure and method.

In general, the flow of fluid through a porous medium generates a potential, which is called a streaming potential or a self-potential. It is a method of exploring underground ore or groundwater flow by measuring. The magnitude of the natural potential is related to the electrical resistivity, the dielectric constant, the viscosity of the fluid, and the coupling coefficient between the fluid and the medium.

Natural potentials are divided into natural potentials such as electrodynamic potentials due to flow of electrolytes in the strata, diffusion potentials due to contact of electrolytes with different mobility, semi-membrane action of shale and mineralization potentials due to mineralization. It is divided into background potential by mechanical or electrochemical phenomenon and photochemical potential by mineralization. Background potential is usually positive (+) or negative (-) around a few tens of mV, but the photopotential shows relatively large values (a few hundred mV). In addition, very large natural potential values of several thousand mV have been reported when the bedrock resistivity of ten thousand ohm-m is very high in steep terrain.

Although the mechanism of occurrence of natural potential has not yet been clearly identified, it is classified into three types: electrochemical effect, thermoelectric effect, and electrokinetic effect. Among them, research on the mechanism of the electromechanical and thermoelectric effect is ongoing. On the other hand, the mechanism of natural potential generation due to electrochemical effects was mainly used for data analysis of mineralized zone exploration. The difference in oxidation level between the upper and lower conductors, the oxidation degree of groundwater around the conductor, and the potential difference at the reference point far from the oxidation potential around the conductor were compared. The cause is revealed in part by the phenomenon. The thermoelectric effect is known as the Soret effect, in which there is a corresponding potential gradient when there is a temperature gradient in the strata, which occurs because the ions of the electrolyte in the pores and the electrons in the rock matrix generate different thermal diffusions. Known.

Examples of the application of the natural potential method include various geothermal applications (Corwin and Hoover, 1979; Ishido et al., 1997; Apostolopoulos et al., 1997); Morrison, 1977), and geotechnical applications (Ogilvy et al., 1969; Bogoslovsky and Ogilvy, 1977).

Recently in Korea, there are cases applied to various pumping tests and leaky areas of reservoir sugar and dike as a measure of flow potentials generated by electromechanical effects and exploration applied to monolayer fracture zones or aquifers considering electrodynamic effects.

There are two main methods of natural potential used in the field: the method of measuring the absolute potential of a reference point ("fixed-base" survey configuration; total field SP) and the method of measuring the potential difference between certain electrodes ("leapfrog" or "gradient). "survey configuration; gradient SP). At this time, the method of measuring the potential difference between the electrodes at regular intervals means the rate of change of the absolute potential with respect to the reference point (gradient).

Absolute potential measurement method for the reference point is to install one electrode at a distance that is not affected by the irradiation area, set it as a natural potential starting point, and measure the relative potential difference with respect to the reference point while moving the other electrode to each station It is a method of disposition. This method requires long wires from the reference point and has a complicated disadvantage of exploration but relatively high data reliability. On the other hand, in the method of measuring the potential difference between electrodes, the exploration process is quick and easy by keeping the measurement interval of each potential constant, but the reliability of the measurement data is relatively inferior to the reference point method.

Until now, the natural potential method has been used mainly for qualitative analysis, but since the 1980s, theoretical numerical calculations have been attempted based on the flow potential model, which is a kind of thermoelectric or electromechanical effect, and the interpretation of these results is the actual field. It is a trend being applied in (Fitterman, 1983; Sill, 1983). 1 is a diagram illustrating a conventional method for measuring data using the natural potential method in the reservoir and the embankment.

Referring to FIG. 1, in the conventional data measuring method, the reference point electrode P ₁ is set at an outer portion not affected by the reservoir sugar and the adjuvant, and the electrode P moving with respect to the target point A-A '. ₂ ) The data were acquired using the method of measurement, and the acquired data were applied to the quantitative analysis method. This natural potential measurement method was performed by selecting the required channel with existing exploration equipment or high impedance digital multimeter, but when the measurement point is large, such as monitoring with repeated measurement, the time required for measurement is longer. In comparison, there is a problem in that the interpretation is difficult due to the delay effect of the natural potential value.

In order to solve the above problems, it is an object of the present invention to provide a natural potential measuring device and a method using a non-polarized electrode that can simultaneously measure a plurality of measuring points in the same measuring method.

Another object of the present invention is to provide a natural potential measuring apparatus and method using a non-polarized electrode that can increase the precision of the data in the case of monitoring operations, can be monitored in the long term, and also can be quickly processed data.

1 is a view illustrating a conventional method for measuring data using the natural potential method in the reservoir and the sea repellent.

2 is a view showing the configuration of a natural potential measuring device using a non-polarized electrode according to an embodiment of the present invention.

3 is a diagram illustrating a configuration of a signal processing apparatus according to a preferred embodiment of the present invention.

Figure 4 is a flow chart showing a natural potential measurement method according to another embodiment of the present invention.

5 is a diagram showing a configuration of a non-polarized electrode used in the practice of the present invention.

6 is a view showing the configuration of an experimental apparatus for measuring the stability of the non-polarized electrode used in the practice of the present invention.

7 is a view showing a particle size distribution curve for a sample collected by a grid using a soil sample collection auger in order to determine the soil characteristics of the test cloth for testing the non-polarized electrode used in the practice of the present invention.

8 (a) and 8 (b) show the results of comparing the correlation between the underground embedding depth and the temperature of the non-polarized electrode used in the practice of the present invention.

Figure 9 (a), (b) is a view showing the result of comparing the correlation between the buried depth and the soil moisture content of the non-polarized electrode used in the practice of the present invention.

Figure 10 (a), (b) is a view showing the results of exploration of the single-pole array electrical resistivity of the actual repair facility for the experiment of the present invention.

Figure 11 (a), (b) is a comparison of the potential measurement of the natural potential reference point for the change in the tide of the coast where the actual repair facility was carried out the experiment of the present invention.

Figure 12 (a), (b) is a natural potential two-dimensional cross-sectional view measured in the actual repair facility during the experiment of the present invention.

Figure 13 (a), (b) is a change in natural potential at the leak point of the actual repair facility according to the change in the coastal tide during the experiment of the present invention.

In order to achieve the above object, according to a preferred embodiment of the present invention, in the natural potential measurement device for measuring a plurality of measuring points at the same time to monitor the abnormality of the natural potential value caused by the leakage, A reference electrode, a plurality of measuring electrodes provided at a plurality of measuring points for measuring a natural potential, an analog input terminal for receiving analog signals from the plurality of measuring electrodes, and a plurality of analog signals output from the analog input terminals A plurality of multiplexers for selecting one analog signal, a signal processing device for removing noise from the analog signals selected by the plurality of multiplexers, amplifying the analog signal from which the noise is removed, and a reference potential input from the reference electrode And analog output from the signal processing device An analog-digital conversion device for converting a potential difference with the signal into a digital signal, and a predetermined operating program to control the multiplexers to select an analog signal from any measurement electrode among the plurality of measurement electrodes, and A microprocessor for processing the digital signal output from the analog-to-digital converter according to a predetermined format, a storage device for storing the predetermined operating program and the digital signal, and the digital signal processed according to the predetermined format. There is provided a natural potential measurement apparatus using a non-polarized electrode including a communication device for transmitting to the electronic information processing device, and receiving the change information for changing the predetermined operating program. Here, the signal processing apparatus includes a low pass filter for passing only an analog signal of 10 Hz frequency band or less, and a signal amplifying device for amplifying the analog signal output from the low pass filter, wherein the analog-to-digital converter includes: The potential difference between the reference potential input from the reference electrode and the analog signal output from the signal processing apparatus can be converted into a digital signal of at least 16 bits or more.

In addition, the microprocessor sequentially measures the plurality of measurement electrodes at regular measurement time intervals according to a predetermined operating program, and temporarily stores the measured values measured at least two times for each of the plurality of measurement electrodes in the storage device. The average of the measured values may be calculated for each of the plurality of measuring electrodes.

The natural potential measuring device may further include a variable resistor connected to the reference electrode and the analog-digital converter, respectively, and capable of adjusting the reference potential input from the reference electrode.

The natural potential measuring apparatus may further include a display driving driver controlled by the microprocessor and a display apparatus driven by the display driving driver.

According to another preferred embodiment of the present invention, in the natural potential measurement method for measuring a plurality of measurement points at the same time to monitor the abnormality of the natural potential value caused by the leak, the predetermined measurement date, measurement time and measurement time Reading an interval, comparing the measurement date, the measurement time, and the measurement time interval with the current time to determine whether to measure; sequentially measuring potential values of a plurality of measurement electrodes; There is provided a natural potential measurement method using a non-polarized electrode, comprising calculating a difference between respective potential values measured for each measurement electrode and a reference potential value, and storing each potential difference calculated for each of the plurality of measurement electrodes. .

The natural potential measuring method includes converting the measured potential values into a digital signal, sequentially measuring the potential values of the plurality of measurement electrodes by repeating at least two or more times, and calculating each of the plurality of measurement electrodes. The method may further include calculating an average value of the potential difference.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Natural potential measuring device and method

2 is a view showing the configuration of a natural potential measuring apparatus using a non-polarized electrode according to an embodiment of the present invention.

The device used to measure the natural potential is largely divided into the measuring part and the electrode part. In addition to the conventional electric probe that can measure the potential difference between the two electrodes, multimeters with a large impedance of 1 Mohm or more are possible. In the case of the electrode, it is necessary to measure the weak potential that occurs naturally, non-polarizable electrode (non-polarizable electrode or porous pot) was used to minimize the effect of noise caused by the interference between the electrode and the earth. . However, in the case of non-polarized electrode, a metal electrode CCE (copper clad electrode) is sometimes used for long-term monitoring due to limitations such as manufacturing cost and regular replenishment of electrolyte solution.

Against this backdrop, we have built our own multi-channel SP data monitoring system and non-polarized electrode as a device for natural potential measurement. The elements were reviewed and used as basic data in the field application.

Referring to FIG. 2, the natural potential measurement device uses a micro-processor including a DO / DI, a serial port, and a RAM for a control program as a CPU to increase efficiency, and other necessary devices include a separate IC chip. do.

The reference electrode 10 is a non-polarized electrode provided at a predetermined distance from a repair facility in which the measurement electrode is installed. Here, the constant distance is a distance such that it is not affected by the change in natural potential in the repair facility in which the measuring electrode 11 is installed, and the natural potential measured through the reference electrode 10 is measured by the measuring electrode 11. Used to calculate the difference from the potential.

The plurality of measuring electrodes 11a, 11b ... 11n (collectively referred to as 11) are a plurality of non-polarized electrodes provided at a plurality of measuring points for measuring the natural potential of the repair facility.

The plurality of analog input terminals 20a and 20b (collectively referred to as 20) are devices for receiving natural potentials measured from the plurality of measuring electrodes. The measured natural potential is an analog signal and is a low voltage signal within approximately ± 200 mV. The analog input terminal 20 is coupled to the plurality of measurement electrodes 11 by 1: N, where N is the number of the plurality of measurement electrodes 11. In the present invention, the natural potential measuring device is configured to measure the natural potential at a total of 128 points, but in a specific embodiment, the number of measuring electrodes will not be limited to 128 by increasing or decreasing the number of analog input terminals 20. The analog input terminal 20 is coupled 1: n with a plurality of mulplexers 30a, 30b, 30c, 30d, 31a, 31b, 31c, 31d, where n is the number of multiplexers. In the present invention, a total of eight 16-channel multiplexers 30a, 30b, 30c, 30d, 31a, 31b, 31c, and 31d are used. However, in a specific embodiment, the multiplexers 30a and 30b according to the number of channels and the number of measuring electrodes of the multiplexer. , 30c, 30d, 31a, 31b, 31c, 31d) will not be limited to eight.

The multiplexers 30a, 30b, 30c, 30d, 31a, 31b, 31c, and 31d select one analog signal from the plurality of analog signals output from the analog input terminal. The multiplexers 30a, 30b, 30c, 30d, 31a, 31b, 31c, and 31d occupy a large amount of space in the natural potential measuring device, and are 128 channel multiplexers capable of simultaneously measuring 128 electrodes. To this end, a 128-channel multiplexer is implemented by combining eight analog multiplexers (DG506) having 16 channels to select only one of 128 channels. In a specific embodiment, when the number of measuring electrodes increases or decreases, the number of multiplexers may be appropriately increased or decreased.

In particular, it is preferable to remove residual voltages in the multiplexers 30a, 30b, 30c, 30d, 31a, 31b, 31c, and 31d when the next channel is selected after the measurement. . In addition, it is preferable to set the input voltage range of the multiplexers 30a, 30b, 30c, 30d, 31a, 31b, 31c, and 31d to -5 to +5 V in order to prepare for the variety of input voltages.

The signal processing device 40 removes noise from the analog signal selected by the multiplexers 30a, 30b, 30c, 30d, 31a, 31b, 31c, and 31d, and amplifies the analog signal from which the noise is removed. The signal processing device 40 will be described in detail with reference to FIG. 3.

The analog-to-digital converter 50 converts the potential difference between the reference potential input from the reference electrode 10 and the analog signal output from the signal processing apparatus 40 into a digital signal and outputs the digital signal. Normally, the natural potential measured in the field should be able to measure changes of less than 1 mV with a weak potential of about ± 200 mV. Therefore, it is preferable to use a 16-bit ADC (AD7136) having a resolution of 0 to 65,536. Do.

The microprocessor 60 controls the multiplexers 30a, 30b, 30c, 30d, 31a, 31b, 31c, and 31d by a predetermined operating program to output analog signals from any one of the plurality of measurement electrodes. The program which selects and processes the digital signal output from the analog-to-digital converter 50 according to a predetermined format sequentially selects a channel. Preferably, 50 times are measured for each of the plurality of measuring electrodes, and the average value is stored in the memory to be displayed on the screen display device 72. Here, the predetermined format is a format that can store and reproduce the measured natural potential.

The driver 70 controls the driving of the screen display device 72.

The screen display device 72 displays the processing progress or the processing result of the microprocessor 60 under the control of the driver 70. The display device 72 is a CRT or LCD.

The storage device 74 stores a predetermined operating program and a digital signal. Since the data measured in the field should be stored in the memory in the natural potential measurement device, it is preferable to use the memory allocated in the microprocessor 60 for internal programming and to use CMOS SRAM for data storage. The 3 V battery 76 is connected to the SRAM memory so that data is not lost even when the external power supply is cut off.

The serial driver 78 controls the operation of the serial port 78.

The serial port 79 transmits a digital signal processed according to a predetermined format to an external electronic information processing apparatus (for example, a computer) and receives change information for changing the predetermined operating program.

In order to eliminate the effect of the signals measured at the reference electrode and the measuring electrode returning to the natural potential measuring device, the input signal of the natural potential measuring device is connected to the DC 12 V single power supply 92 by + 5V, Use by converting -5V. Preferably, a switching mode power supply is used to supply a stable voltage to the control device against voltage fluctuations.

3 is a diagram illustrating a configuration of a signal processing apparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 3, a signal processing device is a device for processing a signal measured from a non-polarized electrode which is a basis of natural potential measurement, and includes an amplifier circuit and a filter for removing noise from the outside.

A signal with all frequencies from the reference and 128 measuring electrodes is fed into the system. In particular, a signal near 60 Hz is considered to be noise from the AC power supply. A low-pass filter that passes only below the 10 Hz frequency band. Use The signal of the first pass reference point is connected to the In ^- terminal of the ADC and used as the low-level reference voltage of the ADC input signal.The voltage of the electrode to be measured is amplified by using a non-inverting amplifier and then connected to the In ⁺ terminal of the ADC. Connect. By connecting in this way, the potential output from each of the non-polarized electrodes is measured by the reference electrode potential difference and displayed on the LCD or stored in the memory.

Also, in order to increase the accuracy of the measurement, it is possible to arbitrarily adjust the voltage of the Vref of the ADC with a variable resistor in consideration of the site conditions. When the potential difference of the field becomes more than ± 200 mV or less, the voltage of the Vref and the amplifier The gain can be adjusted up to ± 5 V.

4 is a flowchart illustrating a natural potential measuring method according to another exemplary embodiment of the present invention.

The data measurement program of the natural potential measuring device can be written and coded in C-language and embedded in the RAM of the CPU. 4 is a flowchart illustrating a program used in the natural potential measuring device, and the operating program can be independently executed when power is supplied to the natural potential measuring device.

The date, time, and measurement time interval were initially set to the values stored in the RAM, and they can be changed to the computer through the serial communication port to adjust the measurement time interval, download the measured data, and change the time and date.

In step S10, when the power supply of the natural potential measuring device is turned ON, the flow advances to step S12 to read the measurement date, the measurement time and the measurement time interval stored in the memory.

In step S14, it is determined whether to start the measurement by comparing the current time and the measurement date read out, the measurement time and the measurement time interval. As a result of the determination, if it corresponds to the measurement time, the process proceeds to step S16; otherwise, the process proceeds to step S22.

In step S16, the plurality of multiplexers are controlled to sequentially receive the potential values of the plurality of measurement electrodes.

In step S18, the difference between each of the potential values measured for each of the input measurement electrodes and the reference potential value is calculated. The difference (potential difference) between the measured potential value and the reference potential value is preferably converted into a digital signal, and the step S18 is preferably repeated at least two times to calculate the average value of the potential difference.

In step S20, the calculated potential differences for the plurality of measurement electrodes are stored in a memory.

In step S22, if it does not correspond to the measurement time, it displays the current time and waits for input from the user.

In step S24, it is determined whether a command has been input from the user through the communication device. If a command is input from the user, the flow advances to step S26, otherwise, the flow returns to step S14.

In step S26, a command input from the user is analyzed to perform a necessary task. That is, it determines whether the command input by the user is a current time change, a measurement time / measurement time interval change, or a stored measurement value deletion, and performs a corresponding operation.

Nonpolarized Electrode Fabrication and Verification

5 is a diagram showing the configuration of a non-polarized electrode used in the practice of the present invention.

The natural potential is a combination of anomalies from the object to be measured and various types of environmental noise. Therefore, it is very important to select an electrode type for long-term natural potential monitoring. Various studies for the measurement of the natural potential have been found to be relatively useful non-polarized electrode form compared to other types of electrode.

However, although a recent quantitative method for the production of non-polarized electrodes has been suggested from the results of long-term electrode pairs (Perrier et al., 1997), the electrochemical effects cannot be accurately identified.

Petiau and Dupis (1980) presented the results of noise spectrum, temperature coefficient and stability over time for various types of nonpolarized electrodes using long-term observation data. Based on these results, the Ag-AgCl non-polarized electrode is the most stable but Pb-PbCl ₂ non-polarized electrode is proposed as an electrode suitable for field applications. Perrier et al. (1997) tested the stability of electrodes against various types of noise components, such as precipitation, soil moisture content, and change in ground current, over 50 different electrode pairs in Garch, France, over a year. . As a result, it is suggested that the non-polarized electrode suitable for field application is stable in the range of 0.5 mV / month for wet soil and 0.2 mV / month for dry soil.

Corwin and Butler (1989), on the other hand, conducted three years of field and laboratory experiments on three types of electrodes, and found that Cu-CuSO ₄ non-polarized electrodes were shorter than leaded and copper-clad metal electrodes. It was stabilized and suggested to maintain a stable potential value for a long time. However, the non-polarized electrode shows a stable measurement value, but additional work such as replenishment of the electrolyte is required. Therefore, the copper-clad metal electrode undergoes a long period of stabilization for about 3 to 6 months despite the disadvantage that the noise component is large. In this case, it is suggested that the application is possible.

In the present invention, a non-polarized electrode is used based on the results of the research so far, and as shown in FIG. 5, a radius of 3 cm and a height in order to effectively maintain the electrolyte solution and ground the earth during long-term monitoring with a cylindrical acrylic material It was manufactured to a relatively large size of about 20 cm. At this time, in order to minimize the noise that can be generated in the electrode itself, all materials of the electrode fabrication used insulators. The porous medium in contact with the ground was planed to effectively ground the ground, and the material was used with a baking sheet and plasterboard. The electrode was made of the same material as the saturated salt solution and used a diameter of 10 mm, and the electrode and the porous part were separated from each other in contact with each other.

The contents filled in the non-polarized electrode manufactured by using the roasting plate is a saturated salt solution containing a cation such as an electrode. At this time, in order to explorate for a long period of time, a mixture of gel gypsum was used as a rule, but when using a gypsum plate, only saturated salt solution was used. The formulation of the fabric flame solution used in this study was the case of PbCl ₂ water (1ℓ): was produced at a rate of _{NaCl (360g): PbCl 2 (} 15g). On the other hand, the gypsum in the gel state is saturated in the prepared PbCl ₂ solution, the formulation was prepared in a ratio of PbCl ₂ solution (50 mL): gypsum (25 g).

The non-polarized electrode manufactured by using the gypsum board was solidified for 20 days or more by distilled water: gypsum mixing ratio of 1: 2 for the manufacture of the porous gypsum board. It produced by the same compounding ratio as a non-polarized electrode.

Fig. 6 is a diagram showing the configuration of an experimental apparatus for measuring the stability of non-polarized polarity used in the practice of the present invention. In more detail, the apparatus shown in FIG. 6 is an experimental apparatus used for an experiment for analyzing field noise components using non-polarized electrodes.

The natural potential method is one of very small signal-to-noise ratios of the existing physical sensing methods. In the present invention, a long-term monitoring experiment on noise components was performed in the previous stage of field application on the manufactured non-polarized electrode. At this time, the on-site noise factors examined were the environmental noise, such as air temperature, precipitation, soil moisture content, and ground temperature, and produced a test package of 12 × 26 m ² area as shown in FIG. Reviewed.

In the present invention, meteorological factors such as temperature and precipitation were measured using an automatic weather observation system (AWS) installed in the test packaging. On the other hand, TDR (time domain reflectometry) equipment and underground thermometer for soil temperature measurement are installed at depths of 10 m for depth measurement to examine the effect of contact potential. Comparison was made with each other. The TDR equipment used was AQUA-TEL-TDR from Automata, USA. The exposed part of the surface was installed with a separate shading device to block direct sunlight from the sun.

FIG. 7 is a diagram illustrating a particle size distribution curve for a sample collected by a lattice network using a soil sample collection auger to grasp soil characteristics of a test cloth for experimenting with a non-polarized electrode used in the practice of the present invention. Soil samples collected were subjected to hydrometer analysis using the KS F 2302 method with a particle size of 0.074 mm or less.

As a result, the uniformity coefficient (Cu = d ₆₀ / d ₁₀ ) suggested by Fetter (1994) is 391.9, which is classified as a good particle size distribution but poorly sorted sediment, and the effective particle size (d ₁₀ ) Is 0.0059 mm fine silt. The particle size of the soil is 74.1% sand, 15.7% silt and 10.2% clay, which corresponds to SM according to the unified soil classification system.

FIG. 8 is a diagram showing the result of comparing the correlation between the underground embedding depth and the temperature of the non-polarized electrode used in the practice of the present invention.

Temperature effects on nonpolarized electrodes can be derived in a variety of analytical ways (Ives and Janz, 1961), but Morrison et al. (1979) presented a temperature coefficient of approximately +0.5 mV / ° F for Cu-CuSO ₄ nonpolarized electrodes under various experimental conditions. The temperature coefficient showed that the effect of the metal component in the nonpolarized electrode was greater than that of the soil around the electrode, resulting in a slight time delay between the natural potential change due to the heating of the metal rod in the nonpolarized electrode and the soil temperature. Corwin and Butler (1989) measured a temperature coefficient of approximately +1 mV / 。F by measuring the temperature of two electrodes while heating one electrode using a thermometer on a copper-clad metal electrode in a laboratory. This result is about 2 times higher than the non-polarized electrode.

Petiau and Dupis (1980) presented very low temperature coefficients of about -40 μV / ° C and long term stability of about 1 mV / month when using Pb-PbCl ₂ nonpolarized electrodes based on long-term observation data. Very high applicability for the following frequency bands is found.

8 is a result of comparing the ground temperature installed at a depth of 15 cm with the atmospheric temperature and the natural potential for each depth obtained at the same time. The change in the ground temperature over the 30 days showed a delay of about 8 to 11 hours with respect to the change in the atmospheric temperature. When the temperature rises above about 15 ℃, the temperature at the T9 point is higher than the T10 point. It was about three to four times larger. FIG. 8 (a) shows the change in potential of the non-polarized electrode installed at a depth of 10 cm underground, showing a daily change of 2 mV, and the change in potential was almost identical to the change in atmospheric temperature. As the upper part of the electrode is exposed to the atmosphere, it is determined that the conduction effect of the atmospheric temperature is exhibited through the metal component of the electrode.

8 (b) shows a change of less than 1 mV as a potential change of the non-polarized electrode installed at a depth of 20 cm underground, showing a slight change in the ground temperature change with a delay of about 8 to 11 hours. These results indicate that Morrison et al. The temperature coefficient of about +0.5 mV / 。F suggested by (1979) can be applied, but when installed under the surface, the weak effect of less than about 0.5 mV reflects the constant time lag among the change of natural potential of less than 2 mV. It seems to be.

9 is a view showing the results of comparing the correlation between the depth of the underground and the soil moisture content of the non-polarized electrode used in the practice of the present invention.

Morrison et al. (1978, 1979) revealed through the present invention that the most influential factor when measuring the natural potential value using the non-polarized electrode is the effect of soil moisture content around the electrode. This suggests that as the soil moisture content increases by 1%, the potential increases about +1 mV on average, and the electrode installed in the wet soil has a relatively positive value compared to the electrode installed in the dry soil.

In the present invention, the soil moisture was measured at 30 minute intervals by installing TDR equipment in two sections (0 to 23 cm, 23 to 46 cm) at the same location as the non-polarized electrode pairs installed in the test packaging. Unlike conventional methods of measuring capillary pressure head using a conventional tensionometer, this equipment has the advantage of reflecting the transition state of the field, which is used in many recent researches on pollution. (Kim Dong-joo et al., 1999; Park Jae-hyun, 1998). In general, TDR is a device that measures dielectric constant and electrical conductivity by using the characteristic that the spherical electromagnetic wave generated from the waveform generator flows along the transmission line and reflects the electromagnetic wave according to the change of the transmission line. As used in the present invention, the 9-inch long sensor measures the dielectric constant closely related to the moisture content of the surrounding soil, and calculates the measured current as a water content by transmitting a current of 4-20 mA.

9 is a result of comparing the soil moisture content obtained by the depth using the TDR and the natural potential of the non-polarized electrode installed at a depth of 10 cm and 20 cm, respectively. The measured soil moisture content varies about 3% at each location and the upper part is about 15% smaller than the lower part. In addition, the change in soil moisture content showed a time delay effect of about 8 to 11 hours compared to the change in air temperature, which was found to affect the ground temperature change.

In the case of the electrode installed at a depth of 10 cm below the surface of the surface, as shown in FIG. However, the soil moisture content of the electrode installed at 20 cm below the surface of the electrode remains the same. Therefore, the soil moisture content is the main influence when the electrode is buried.

From these results, it can be seen that the main element of the slight deviation of 1 to 2 mV in the non-polarized electrode buried in the ground is the change in soil moisture content.

Example

10 to 13 are views showing the results obtained by applying the present invention to the actual repair structure.

On-site application was carried out for fishery fishermen located in Gunsan, Jeollabuk-do, which is 5.4 km long and 8 m tall. First of all, from the visual inspection of the inside of the seawall, the point where seawater flows into the inside of the seawall at high tide was selected as the field application target. In the field survey, the 60 m section including the seawater inflow point was primarily conducted for unipolar array electrical resistivity exploration and the natural potential monitoring at the same point for 1 hour every 24 hours. After the blocking, the applicability of the natural potential method was evaluated by monitoring the same section.

Figure 10 (a), (b) is a view showing the results of exploration of the single-pole array electrical resistivity of the actual repair facility for the experiment of the present invention. Figure 10 is apparent resistivity are cross-sectional views and two-dimensional resistivity was cross-sectional view in full 60 m interval distance between electrodes with respect to the 3 m, can be deployed electrode 8 to infinity current electrode (C ₁₎ and the potential of the electrode of the single-pole arrangement Resistivity ( P ₁ ) is the result of measuring the input current at 100-200 mA with 450 m distance from both sides.

The apparent resistivity range is very low at 5 ohm-m or less at 3 or more electrode developments, and even in cross-sections obtained by the two-dimensional inversion method, it is less than 1 ohm-m overall at depths of about 6 m or less. Appeared to be saturated. Especially No. 3 to No. In section 5, a very low resistivity band of 0.3 ohm-m appears, which is similar to the average value of seawater, 0.2 ohm-m (Telford et al., 1990), indicating that it is completely saturated by seawater.

The natural potential method applied to this embarker was conducted by fixing the reference point to the same point as the electrode point of unipolar array electrical resistivity survey, and measured the reference point potential before and after the measurement to remove noise from the outside. Was corrected.

Figure 11 (a), (b) is a comparison of the potential measurement of the natural potential reference point with respect to the tide change of the coast where the actual repair facility is carried out the experiment of the present invention.

11 (a) and (b) show the change in natural potential values and tide levels measured at a reference point before and after reinforcement work to prevent seawater inflow over time. The measurement data of was used and the natural potential of the reference point was not affected by tides.

Figure 12 (a), (b) is a two-dimensional cross-sectional view of the natural potential measured in the actual repair facility during the experiment of the present invention.

12 (a) shows a stable change between about 0 to +20 mV over the entire section as a result of the application of the natural potential method before the reinforcement work to prevent seawater inflow. 3 to No. Measurements at four points between 6 show negative anomalies of -20 to -50 mV. This section corresponds to the section where the water leakage occurred during high tide, and it corresponds to the low resistivity band of about 0.3 ohm-m which is indicated as the seawater inflow section in the monopolar array electrical resistivity survey.

Figure 12 (b) shows the results similar to before the reinforcement work in the entire section as a result of applying the natural potential method carried out after the reinforcement work to prevent seawater inflow.

Figure 13 (a), (b) is a natural potential change diagram at the leak point of the actual repair facility according to the change in the coastal tide during the experiment of the present invention.

Figure 13 (a) is No. before reinforcement work. 3 to No. As a result of comparing the natural potential measurement value with the tide change for the four points between 6, the effect of tides as a whole was shown. Also no. 3 and No. The natural potential measurement at 6 points is No. 4 and No. Considering that it is about 20 mV higher than the measured value at 5 points and the change width is relatively small, the No. 4 and No. The inflow of seawater through the five points seems to be even greater.

Figure 13 (b) is No. after reinforcement work. 3 to No. As a result of comparing the time-varying natural potential measurement value with the tide change for the four points between 6, the effect of tides that appeared before the reinforcement work was markedly reduced, and no seawater inflow was observed with the naked eye. The flow potential is reduced due to the blockage of seawater inflow.

As described above, the present invention provides a natural potential measuring apparatus and method using a non-polarized electrode capable of simultaneously measuring a plurality of measuring points by the same measuring method.

In addition, the present invention provides a device and method for measuring the natural potential using a non-polarized electrode that can increase the precision of the data in the case of the monitoring operation, can be monitored in the long term, and also can be quickly processed data.

Claims (8)

In the natural potential measuring device for measuring a plurality of measuring points at the same time to monitor the abnormality of the natural potential value caused by the leakage, Reference electrode; A plurality of measuring electrodes provided at a plurality of measuring points for measuring the natural potential; An analog input terminal receiving an analog signal from the plurality of measurement electrodes; A plurality of multiplexers for selecting one analog signal among a plurality of analog signals output from the analog input terminal; A signal processing device for removing noise from the analog signals selected by the plurality of multiplexers and amplifying the analog signals from which the noise is removed; An analog-digital conversion device for converting a potential difference between a reference potential input from the reference electrode and an analog signal output from the signal processing device into a digital signal; By means of a predetermined operating program, the plurality of multiplexers are controlled to select analog signals from any of the plurality of measuring electrodes, and to process the digital signals output from the analog-digital converter according to a predetermined format. A microprocessor; A storage device for storing the predetermined operating program and the digital signal; A communication device for transmitting the digital signal processed according to the predetermined format to an external electronic information processing device, and receiving change information for changing the predetermined operating program; And And a variable resistor connected to the reference electrode and the analog-to-digital converter, respectively, and capable of adjusting the reference potential input from the reference electrode. The method of claim 1, The signal processing device, A low pass filter for passing only an analog signal of 10 Hz frequency band or less; And Signal amplification device for amplifying the analog signal output from the low pass filter Natural potential measurement device using a non-polarized electrode comprising a. The method of claim 1, The analog-to-digital converter, And a potential difference between the reference potential input from the reference electrode and the analog signal output from the signal processing device into a digital signal of at least 16 bits. delete delete The method of claim 1, A display drive driver controlled by the microprocessor; And A display device driven by the display driving driver Natural potential measurement device using a non-polarized electrode further comprising. delete delete