JP4353480B2 - Electrode switching device - Google Patents

Description

  The present invention relates to an electrode switching device used for electrical exploration of the ground. More specifically, the present invention relates to an electrode switching device that selects a current electrode and a potential electrode used for measurement from among a large number of electrodes installed on the ground, and switches connection with a transmission device or a reception device.

  In the ground electrical exploration method, a pair of current electrodes and a pair of potential electrodes are installed on the ground surface, a transmitter (DC power supply) is connected to the pair of current electrodes, and a receiver (voltmeter) is connected to a pair of potentials. A specific resistance is obtained by measuring a value of a direct current flowing from the current electrode and a potential difference generated between the potential electrodes, and then searching for the ground based on the specific resistance.

  If the distance between the current electrode and the potential electrode (distance between electrodes) is short, the measurement data reflects the resistivity of the shallow formation, and if the distance between the electrodes is long, the measurement data includes the influence of the resistivity of the deep formation. It comes to be. For this reason, it is possible to know the change in the specific resistance in the depth direction by changing the distance between the electrodes. In order to perform such a measurement efficiently, a large number of electrodes are installed in advance along one measurement line, and current electrodes and potential electrodes used for the measurement are selected from the electrodes, and the combinations are sequentially selected. It is being measured while changing to.

  A pair of current electrodes and potential electrodes to be used is selected from among a large number of electrodes installed along one survey line, the connection between the selected current electrode and the transmitter, and the selected potential electrode and the receiver. As an apparatus for operating the connection, for example, there is an electrode switching apparatus disclosed in Japanese Patent Laid-Open No. 2001-21626.

This electrode switching device is shown in FIGS. The electrode switching device has four relay devices corresponding to the two terminals C1 and C2 of the current transmitter (transmitter) and the two terminals P1 and P2 of the potential receiver (receiver). Each relay device has the same number of relays as the number of terminals, in other words, the number of electrodes. By selecting one relay from the relays and turning it on, one of the electrodes can be selected. Is selected and connected to the current transmitter or the potential receiver. And the electrode connected to an electric current transmission part or an electric potential receiving part can be changed one by one by changing the relay which carries out an ON operation one by one.
Japanese Patent Laid-Open No. 2001-216262

  However, in the above-described electrode switching device, it was possible to cope with a single survey line, but it was not compatible with two or more survey lines. For this reason, when measuring a plurality of survey lines, after measuring a single survey line, re-install the electrodes from the survey line where the measurement has been completed to another survey line where the measurement has not been completed, and wiring them. The measurement was repeated and repeated. For this reason, the work efficiency of the measurement was extremely poor.

  An object of this invention is to provide the electrode switching apparatus which can respond to a several survey line.

In order to achieve such an object, the invention described in claim 1 selects a current electrode and a potential electrode used for measurement from electrodes respectively installed at a plurality of measurement points on a survey line, and selects the selected current electrode. In an electrode switching device for connecting a conducting wire that leads to a transmitting device and connecting a conducting wire that leads to a selected potential electrode to a receiving device, a number of connection terminals for connecting the conducting wires are provided corresponding to a plurality of measuring lines, and electrodes of a plurality of measuring lines are provided. A survey line selection unit that selects one survey line to be used for measurement from a plurality of survey lines and switches the connection, and a station selection unit that selects a survey point to be used for measurement and switches the connection. , it provided a survey line selection unit and the station selection unit in series, is shall switch the survey line and stations to be used in combination with the selection of the measurement point by the selection and station selection portion of the survey line by survey line selection unit.

  Therefore, even if there are a plurality of survey lines, the electrodes of the measurement points at each measurement point can be selectively connected to the transmission device or the reception device. A single survey line has a plurality of survey points, and even if there are a plurality of such survey lines, that is, even if many electrodes are installed vertically and horizontally, the survey line to which the electrodes belong and the survey points in the survey line. By specifying the position of the electrode, the electrode can be specified. Therefore, by selecting a survey line by the survey line selection unit and selecting a survey point in the survey line by the survey point selection unit, it is possible to identify the electrode and connect it to the transmission device or the reception device. Further, the increase in the number of survey lines can be accommodated by the increase in the survey line selection unit and the connection terminals for connecting the conductive wires leading to the electrodes.

  Here, as in the electrode switching device according to claim 2, a dual-purpose electrode that serves both as a current electrode and a potential electrode is installed at the measurement point, and the dual-line electrode is used as the line selection unit and the measurement point selection unit. Alternatively, it may be provided in the middle of the path connected to the receiving device, and as in the electrode switching device according to claim 3, the current electrode and the potential electrode are separately installed at the measuring point, and the line selection unit And the point selection unit may be provided in the middle of the path connecting the current electrode to the transmitter and in the middle of the path connecting the potential electrode to the receiver. That is, even when a common electrode is used as the current electrode and the potential electrode or when different electrodes are used, the connection between the electrode and the transmission device or the reception device can be switched.

  According to a fourth aspect of the present invention, in the electrode switching device, the station selection unit selects a station as a far electrode from the stations, and maintains the connection state of the selected far electrode station. Therefore, it can respond to the electrode arrangement of the bipolar method or the triode method which requires a far electrode.

  Furthermore, in the electrode switching device according to the fifth aspect, the station selection unit switches all the stations in order and switches the connection. Therefore, it can respond to the electrode arrangement of the quadrupole method.

  In the invention according to claim 1, since the inventive electrode switching device is configured as described above, it is possible to cope with a plurality of survey lines. Moreover, since the increase in the survey line can be accommodated by the increase in the survey line selection unit and the connection terminal, it is easy to cope with the increase in the survey line. Furthermore, even when the number of survey lines is increased, there is no need to increase the number of measurement point selection units. Therefore, an increase in the number of necessary parts can be suppressed, and the increase in size and weight of the apparatus can be suppressed. .

  Here, as in the electrode switching device according to claim 2, a dual-purpose electrode that serves both as a current electrode and a potential electrode is installed at the measurement point, and the dual-line electrode is used as the line selection unit and the measurement point selection unit. Alternatively, it may be provided in the middle of the path connected to the receiving device, and as in the electrode switching device according to claim 3, the current electrode and the potential electrode are separately installed at the measuring point, and the line selection unit And the point selection unit may be provided in the middle of the path connecting the current electrode to the transmitter and in the middle of the path connecting the potential electrode to the receiver. That is, even when the same electrode is used as the current electrode and the potential electrode, or when separate electrodes are used, the connection between the electrode and the transmission device or the reception device can be switched satisfactorily. For this reason, an electrode switching device with high versatility can be provided.

  Further, in the electrode switching device according to claim 4, the station selection unit selects a station to be a far electrode from the stations, and maintains the connection state of the selected far electrode station. In the case of the triode electrode arrangement, the connection between the electrode and the transmission device or the reception device can be switched.

  Furthermore, in the electrode switching device according to claim 5, since the station selection unit selects all the station points in order and switches the connection, the connection between the electrode and the transmitting device or the receiving device in the case of the electrode arrangement of the quadrupole method Can be switched.

  Hereinafter, the configuration of the present invention will be described in detail based on the best mode shown in the drawings.

  First, a ground exploration device provided with the electrode switching device of the present invention will be described. 1 to 7 show an example of an embodiment of a ground exploration device. The ground exploration apparatus 1 includes a pair of current electrodes 3 and a pair of potential electrodes 4 installed on the ground 2, and a measuring unit 5 that measures a potential difference between the potential electrodes 4 by supplying a current between the current electrodes 3 at a constant period. And a processing unit 6 for determining the resistance and phase difference of the potential difference waveform with respect to the current waveform, the measuring unit 5 performs measurement a plurality of times by changing the frequency of the current cycle, and the processing unit 6 includes the measuring unit 5, the relationship between the frequency and the resistance and the relationship between the frequency and the phase difference are obtained based on the plurality of measurements. The measurement unit 5 and the processing unit 6 are synchronized and controlled by the control unit 28. Further, in the present embodiment, the storage unit 29 that stores the relationship data between the frequency and the resistance for each ground 2 and the relationship data between the frequency and the phase difference, which are obtained in advance, is provided. The measurement target ground 2 is discriminated by comparing the relation data stored in 29 with the obtained relation.

  The ground 2 is provided with a large number of current electrodes 3 and potential electrodes 4 along the measuring line 7, and two (a pair) are selected from the large number of current electrodes 3 and used. Two (a pair) are selected from four and used. For example, 60 measuring points 8 are set for one measuring line 7, and the current electrode 3 and the potential electrode 4 are separately installed at each measuring point 8. The current electrode 3 and the potential electrode 4 at the same measurement point 8 are arranged side by side in a direction orthogonal to the measurement line 7. Each of the electrodes 3 and 4 is connected to each connection terminal 10 of the electrode switching device 9 of the measurement unit 5 by a separate conductor. That is, each of the 60 current electrodes 3 and the 60 potential electrodes 4 is connected to the corresponding connection terminal 10 of the electrode switching device 9 by a multicore cable 11 in which 60 conductors are bundled. The measurement unit 5 performs measurement by sequentially switching the combination of the pair of current electrodes 3 and the pair of potential electrodes 4 to be used from among the installed electrodes 3 and 4. For example, the measurement is performed with a four-pole Dipole-Dipole electrode arrangement. For example, four survey lines 7 are set as the survey lines 7.

  FIG. 3 shows the current electrode 3. The current electrode 3 is a stainless steel electrode, for example, and is inserted from the ground surface to a depth of 30 to 40 cm, for example. The thickness of the current electrode 3 is 15 mm, for example. FIG. 4 shows the potential electrode 4. The potential electrode 4 is, for example, an electrode made of lead, and is inserted from the ground surface to a depth of, for example, 30 to 40 cm. The thickness of the potential electrode 4 is 15 mm, for example. A conductive gel material (earth FC curing agent) 12 is filled around the potential electrode 4 so that polarization hardly occurs.

  The measuring unit 5 includes a transmission device 13, a reception device 14, and an electrode switching device 9 of the present invention. The transmission device 13 can supply a constant current between the terminals 15 at a constant period and adjust the current value and the transmission frequency of the current. The current value can be adjusted in the range of 1 mA to 400 mA, for example, and the transmission frequency can be adjusted in the range of 0.01 Hz to 10 kHz, for example. However, the adjustable range is not limited to these. The transmission device 13 supplies, for example, a sine wave current as a constant current. The current value is appropriately selected according to measurement conditions and the like.

  The reception device 14 includes a current detection circuit 16, a reception amplification circuit 17, and an A / D converter 18. Further, for example, there are four channels as reception channels for receiving signals from the potential electrode 4. For example, four reception amplifier circuits 17 are provided corresponding to the number of reception channels. For example, three (0 dB, 20 dB, 40 dB) A / D converters 18 are provided according to the degree of amplification.

  An example of an embodiment of the electrode switching device 9 of the present invention is shown in FIGS. The electrode switching device 9 selects a current electrode 3 and a potential electrode 4 to be used for measurement from the electrodes respectively installed at a plurality of measurement points 8 on the measurement line 7, and transmits a conductive wire that leads to the selected current electrode 3 to the transmission device. 13, and a lead wire leading to the selected potential electrode 4 is connected to the receiving device 14. The connection terminals 10 for connecting the conducting wires are provided in a number corresponding to the plurality of survey lines 7 so that the electrodes 3 and 4 of the plurality of survey lines 7 can be connected. Further, a survey line selection unit 19 that selects one survey line 7 to be used for measurement from a plurality of survey lines 7 and switches the connection, and a survey point selection unit 20 that selects the survey point 8 to be used for measurement and switches the connection. It has. In the present embodiment, the current electrode 3 and the potential electrode 4 are separately installed at the measurement point 8, and the survey line selection unit 19 and the measurement point selection unit 20 are in the middle of the path connecting the current electrode 3 to the transmission device 13. And the potential electrode 4 are respectively provided in the middle of the path connecting the receiving device 14.

  240 (= 60 × 4) connection terminals 10 for current electrode 3 and connection terminals 10 for potential electrode 4 are provided, and a maximum of four measurement lines 7 (A measurement line 7 to D measurement line 7). Current electrode 3 and potential electrode 4 can be connected. That is, the same number of connection terminals 10 as the number of the measurement points 8 make one set, and the same number of connection terminals 10 as the maximum number of the measurement lines 7 that can be connected are provided. In addition, a maximum of 60 electrodes can be connected to one set of connection terminals 10. Each connecting terminal 10 is connected to one conducting wire of the multi-core cable 11 of each measuring line 7. Here, the current electrode 3 will be described as an example. In each of the measuring lines 7, the conducting wire that leads to the current electrode 3 of the first measuring point 8 leads to the first connecting terminal 10 and the current electrode 3 of the second measuring point 8. The conducting wire leads to the second connecting terminal 10, the conducting wire leading to the current electrode 3 at the nth measuring point 8, the conducting wire leading to the nth connecting terminal 10, the conducting wire leading to the current electrode 3 at the 60th measuring point 8 Each is connected to the 60th connection terminal 10. The same applies to the potential electrode 4.

  The number of connection terminals 10 is not limited to 240. For example, as indicated by broken lines in FIGS. 5 and 6, 120 (60 × 2) connection terminals 10 for expansion are provided for each of the current electrode 3 and the potential electrode 4, and the number of measurement lines 7 is required. It may be possible to increase the number up to 6 according to. Other numbers may also be used.

  The survey line selection unit 19 is provided in the middle of the main line 21 provided as many as the number of the measurement points 8, the branch line 22 that branches each main line 21 into the same number as the number of the measurement lines 7, and the branch line 22. The relay 23 is provided. The branch line 22 is connected to the connection terminal 10. The relays 23 are grouped for each survey line 7 (A group to D group), and the relays 23 of the same group are simultaneously turned on and off. Of the four sets, one set is alternatively selected and turned on. For example, when the A survey line 7 is selected, the A set of relays 23 are all turned on, and the other sets of relays 23 are all turned off. The same applies to the selection of the B survey line 7, the C survey line 7, and the D survey line 7. The survey line selection unit 19 has the same structure for the current electrode 3 and the potential electrode 4.

  The measurement point selection unit 20 for the current electrode 3 shown in FIG. 5 includes two switch circuits 24 in accordance with the number of current electrodes 3 used for measurement. Further, the measuring point selection unit 20 for the potential electrode 4 shown in FIG. 6 includes eight switch circuits 24 corresponding to the number of potential electrodes 4 for the reception channel. The switch circuit 24 is shown in FIG. The switch circuit 24 includes a branch line 26 connecting the terminal 25 and each main line 21, and a relay 27 provided in the middle of each branch line 26. In the present embodiment, since 60 main lines 21 are provided corresponding to the number of measurement points 8, 60 relays 27 are provided. Each relay 27 is alternatively turned on. For example, when the current electrode 3 of the first measuring point 8 is connected to the terminal 25, the relay 27 provided on the branch line 26 connected to the first main line 21 is turned on. The same applies to the case where the current electrodes 3 of the second to 60th measuring points 8 are connected to the terminal 25, and the same applies to the potential electrode 4.

  For example, the current electrode 3 at the first and second measuring points 8 on the A measuring line 7, the potential electrode 4 (1ch) at the third and fourth measuring points 8, and the potential electrode 4 (1ch) at the fifth and sixth measuring points 8 ( 2ch), the potential electrode 4 (3ch) of the seventh and eighth measuring points 8, and the potential electrode 4 (4ch) of the ninth and tenth measuring points 8 are used, the following relays 23 and 27 are used. Turn on. On the current electrode 3 side (transmission device 13 side) in FIG. 5, the first relay 27 of one switch circuit 24 of the point selection unit 20 and the second relay 27 of the other switch circuit 24 are turned on. At the same time, all the relays 23 of the set A of the survey line selection unit 19 are turned on. Further, for the potential electrode 4 side (receiving device 14 side) in FIG. 6, the third relay 27 of one switch circuit 24 of the 1ch of the survey line selection unit 19 and the fourth relay 27, 2ch of the other switch circuit 24 are arranged. The fifth relay 27 of one switch circuit 24, the sixth relay 27 of the other switch circuit 24, the seventh relay 27 of the one switch circuit 24 of 3ch, and the eighth relay 27 of the other switch circuit 24. The 9th relay 27 of one switch circuit 24 of 4ch and the 10th relay 27 of the other switch circuit 24 are turned on, and all the A-group relays 23 of the survey line selection unit 19 are turned on.

  The relays 23 and 27 are switched by the control unit 28.

  The electrode switching device 9 connects the terminal 15 of the transmission device 13 and the terminal 30 of the current detection circuit 16. The electrode switching device 9 connects the potential electrode 4 and the terminal 31 of the reception amplifier circuit 17 of the reception device 14 for each reception channel. The current detection circuit 16 and the reception amplification circuit 17 are connected to the processing unit 6 via three A / D converters 18. A USB terminal is used for the connection.

  The processing unit 6 includes a resistance and phase difference calculation unit 32, a relationship calculation unit 33, and a determination unit 34. In the present embodiment, the processing unit 6 and the control unit 28 are realized by a computer. That is, the resistance and phase difference are calculated by a computer having at least one central processing unit such as a CPU or MPU, an interface for inputting / outputting data, a storage device for storing programs and data, and a predetermined control or calculation program. Means 32, relationship calculation means 33, discrimination means 34, and control unit 28 are realized. That is, the central processing unit performs procedures such as a control program such as an OS stored in the storage device, relationship data between frequency and resistance, a relationship between frequency and phase difference, and a method for discriminating a rock mass based on the relationship. The resistance and phase difference calculation means 32, the relationship calculation means 33, the determination means 34, and the control unit 28 are realized by the prescribed program and required data. Further, an output device 35 such as a display or a printer is connected to the computer. As the computer, for example, a personal computer equipped with a CPU having an operating frequency of 1.4 GHz can be used. As the OS, it is possible to use, for example, Windows (registered trademark) which is generally commercially available and widely used.

  The resistance and phase difference calculation means 32 compares the signal waveform of the current transmitted by the transmitter 13 with the signal waveform of the potential difference between the potential electrodes 4 measured by the measuring unit 5, and the signal of the potential difference with respect to the signal waveform of the current Determine the resistance and phase difference of the waveform. The measuring section 5 changes the current frequency f and repeats the measurement a plurality of times, and the resistance and phase difference calculating means 32 calculates the resistance and the phase difference for each repeated measurement. The calculated resistance R and phase difference θ are transmitted to the relationship calculating means 33 together with the current frequency f.

  The relationship calculation unit 33 obtains the relationship between the frequency f and the resistance R and the relationship between the frequency f and the phase difference θ based on the data supplied from the resistance and phase difference calculation unit 32. An example of the relationship between the frequency f and the resistor R and the relationship between the frequency f and the phase difference θ are shown in FIG. If the measurement unit 5 repeats the measurement with the frequency f changed 10 times, the obtained data (frequency, resistance) is (f1, R1), (f2, R2), (f3, R3),. Since (f10, R10) is obtained, when the resistance R is plotted on the vertical axis and the frequency f is plotted on the horizontal axis, the relationship shown in FIG. 8 is obtained. Similarly, since the obtained data (frequency, phase difference) is (f1, θ1), (f2, θ2), (f3, θ3),..., (F10, θ10), the phase difference θ is plotted on the vertical axis. Is plotted with the frequency f on the horizontal axis, the relationship shown in FIG. 8 is obtained. The resistance graph representing the relationship between the frequency f and the resistance R has a shape with a slope in the middle, and the phase difference graph representing the relationship between the frequency f and the phase difference θ has a mountain shape having a peak at the frequency of the maximum slope of the resistance graph. The shape of the ground 2 changes depending on the situation / moisture content of the ground 2 (FIGS. 9 and 10).

  The relationship between the frequency f and the resistance R and the relationship between the frequency f and the phase difference θ obtained by the relationship calculation unit 33 are output to the determination unit 34. The discriminating means 34 discriminates the ground 2 to be measured based on the relationship between the frequency f and the resistance R and the relationship between the frequency f and the phase difference θ. Here, regarding the relationship between the frequency f and the phase difference θ, the measurement target ground 2 is determined based on the peak frequency of the phase difference. Here, the peak frequency of the phase difference includes the frequency value fmax and the phase difference magnitude θmax at the frequency fmax. The storage means 29 stores relationship data (here, fmax and θmax) between the frequency and the phase difference for each ground, which have been obtained in advance, and the determination means 34 is connected to the relationship data stored in the storage means 29. The measurement target ground 2 is determined by comparison. In addition to this, the measurement target ground 2 is determined based on the relationship between the frequency f and the resistance R. The storage means 29 stores the relationship data between the frequency and the resistance obtained in advance for each ground, and the determination means 34 determines the measurement target ground 2 by comparing with the relationship data stored in the storage means 29. I do. For example, when fmax, θmax, and the relationship between the frequency and the resistance match or approximate, it is determined that the measurement target ground 2 is a sample ground to be compared.

  As the storage means 29, for example, a hard disk, memory, DVD, CD, MO, floppy disk (registered trademark) or the like can be used.

  The ground exploration device 1 is installed at a measurement site, for example. However, it is not always necessary to install all of the ground exploration device 1 at the measurement site. For example, the electrodes 3 and 4 and the measurement unit 5 are installed at the measurement site, and the processing unit 6 and the control unit 28 are installed at a remote site such as a laboratory. They may be installed on the ground and connected using, for example, an electric communication line such as the Internet, a dedicated line, or a wireless communication line. In this case, it is preferable to provide a control unit dedicated to the measurement unit 5 in the measurement unit 5 separately from the control unit 28. The ground exploration device 1 having such a configuration is particularly suitable for use when the ground 2 is monitored over a long period of time. In other words, for example, geological disposal of high-level radioactive waste, storage of underground rocks such as oil and liquefied natural gas, underground power plant, etc. It is particularly suitable for use as a ground exploration device 1 for period monitoring. In addition, it is possible to control equipment installed at the site from a remote place such as a laboratory by remote access, and to understand the groundwater behavior and the like at the site in real time.

  According to the ground exploration apparatus 1, (1) it is possible to measure the electrical characteristics (resistance and phase difference) of the ground with respect to a sine wave applied current having an arbitrary frequency in a wide band (for example, 0.01 Hz to 10 kHz). (2) It corresponds to a maximum of 60 measuring points 8 and can correspond to any combination of electrode arrangements. In addition, for example, a 4-channel receiving circuit is provided, and in the dipole-dipole method, for example, signals at four pairs of four potential electrodes (receiving electrodes) at four locations are measured simultaneously with respect to three pairs of current electrodes (transmitting electrodes). be able to. (3) A series of measurement operations such as switching of the frequency of the current transmitted by the transmission device 13, switching of the relays 23 and 27 of the electrode switching device 9, adjustment of the transmission current level of the transmission device 13 and the reception gain of the reception device 14. Can be automatically performed under computer control. There are effects such as.

  Next, the ground exploration method will be described. In this method, a current is supplied at a constant cycle between a pair of current electrodes 3 installed on the measurement target ground 2 to measure a potential difference between the potential electrodes 4 installed on the measurement target ground 2, and a potential difference waveform with respect to a current waveform is measured. The resistance and phase difference are obtained, measurement is performed a plurality of times by changing the frequency of the current cycle, the relation between the frequency and the resistance and the relation between the frequency and the phase difference are obtained, and the measurement target ground 2 is based on the above two relations. Is to discriminate.

  In the present embodiment, the receiving apparatus 14 has four channels (1ch to 4ch) of receiving channels. However, in order to simplify the explanation and make it easy to understand, the explanation is made without first considering that there are four channels. Then, a case where there are four channels after that will be described. For the same reason, the description will be made without first considering the change of the current electrode 3 and the potential electrode 4 to be used, and then the change of the current electrode 3 and the potential electrode 4 to be used will be considered. .

  For example, when the transmitter 13 of the measuring unit 5 transmits a current at a frequency f1, a sine wave current is caused to flow between the current electrodes 3 at the frequency f1. At the same time, the current is also supplied to the current detection circuit 16 of the receiving device 14 and is output to the resistance and phase difference calculation means 32 of the processing unit 6 through the A / D converter 18 as a voltage signal with the reference resistance.

  When a constant current flows between the current electrodes 3, the potential difference between the potential electrodes 4 changes. The potential difference signal measured by the pair of potential electrodes 4 is supplied to the reception amplification circuit 17 of the reception device 14, amplified, and then output to the resistance and phase difference calculation means 32 of the processing unit 6 through the A / D converter 18. The The measurement unit 5 notifies the control unit 28 that the current signal and the potential difference signal have been output to the processing unit 6.

  The resistance and phase difference calculating means 32 of the processing unit 6 compares the potential difference signal supplied from the receiving device 14 with the constant current signal, and obtains the resistance R1 and the phase difference θ1 of the waveform of the potential difference with respect to the current waveform. Then, the resistance and phase difference calculation unit 32 transmits the obtained resistance R1 and phase difference θ1 to the relationship calculation unit 33 together with the current frequency f1.

  On the other hand, the measurement unit 5 outputs the current signal and the measured potential difference signal to the processing unit 6 and then receives the command of the control unit 28 to change the current frequency (f1 → f2) and repeat the above measurement. . As a result, the measurement current signal with the frequency changed and the measured potential difference signal are supplied to the resistance and phase difference calculation means 32 of the processing unit 6. As a result of performing the above measurement with the current frequency changed to f2, if the resistance calculated by the resistance and phase difference calculation means 32 is R2 and the phase difference is θ2, then f2 is related to data as R2 and θ2. It is transmitted to the calculation means 33.

  When the repeated measurement with the frequency changed by the measuring unit 5 is completed, the relationship calculating means 33 receives the command of the control unit 28 and obtains the relationship between the frequency f and the resistance R and the relationship between the frequency f and the phase difference θ. . For example, when the frequencies are f1, f2,..., F10, and the resistors are R1, R2,..., R10 and the phase differences are θ1, θ2,.

  The relationship between the frequency and the phase difference is shown in FIGS. As shown in FIG. 9, the phase difference graph becomes larger as the soil 2 contains more clay minerals that generate a polarization phenomenon (in order of A → B → C in FIG. 9). Further, as shown in FIG. 10, the peak frequency of the phase difference graph is determined depending on the properties (porosity, mineral arrangement structure), physical properties (for example, moisture content) of the ground 2 including the clay mineral that generates the polarization phenomenon. The value of fmax varies. For this reason, if the kind of the ground 2 changes, the phase difference graph also changes. In addition, the resistance graph indicating the relationship between the frequency and the resistance also changes as the type of the ground 2 changes. Therefore, the ground 2 can be determined by obtaining the relationship as shown in FIG. 8 by measurement.

  In the present embodiment, the relationship between the frequency and the phase difference and the relationship between the frequency and the resistance are obtained in advance for the various sample grounds 2, and these are stored in the storage means 29 as relation data. Accessing the means 29, the stored relational data is compared with the relation between the frequency and phase difference calculated by the relation calculating means 33 and the relation between the frequency and resistance, and the measurement target ground 2 is determined. For example, the measurement target ground 2 is determined based on the peak frequency value fmax of the phase difference graph, the phase difference magnitude θmax at the frequency, and the relationship between the frequency and the resistance. For example, the sample ground 2 whose fmax, θmax, and the relationship between the frequency and the resistance match or approximate is determined as the measurement target ground 2. By doing in this way, highly accurate discrimination can be performed. In particular, since the determination is performed based on two relationships, that is, the relationship between the frequency and the phase difference and the relationship between the frequency and the resistance, it is possible to perform determination with very high accuracy.

  The relationship between the frequency f and the phase difference θ includes (1) a combination of fmax and θmax, (2) only fmax, (3) only θmax, and (4) the shape of the phase difference graph. (5) Only the shape of the phase difference graph is included.

  Therefore, for example, when the accuracy of ground determination is not so high, the ground 2 may be determined based on only one of fmax and θmax. For example, when the purpose is to determine the amount of clay mineral contained in the ground 2, the ground 2 may be determined based on θmax. Further, for example, when the purpose is to discriminate the properties (porosity, mineral arrangement structure), physical properties (eg, moisture content), etc. of the ground 2 containing clay minerals, the ground 2 is based on fmax. It may be determined.

  Further, regarding the relationship between the frequency and the phase difference, the ground 2 may be determined based on the shape of the phase difference graph. For example, the relationship between the frequency and the phase difference is obtained in advance for the various sample grounds 2 to obtain a phase difference graph, and these are stored in the storage means 29 as relationship data. The discriminating means 34 accesses the storage means 29, compares the stored relational data with the relationship between the frequency and the phase difference obtained by the relation calculating means 33 (here, the shape of the phase difference graph), and determines the ground 2 to be measured. Determine. For example, a sample ground whose shape of the phase difference graph matches or approximates is determined as the measurement target ground 2. By doing in this way, highly accurate discrimination can be performed. Similarly, regarding the relationship between the frequency and the resistance, the ground 2 may be determined based on the shape of the resistance graph.

  Further, when determining the ground 2 based on the shape of the resistance and phase difference graph, the DC specific resistance R0, the charge ability m, etc. are obtained by fitting the resistance and phase difference graph, and the determination is performed based on these. good.

  That is, there is a Cole-Cole model (Cole-Cole model; Patron, 1978) as one of equivalent electric circuit models for explaining the spectrum IP (Induced-Polarization) phenomenon of the ground 2. This is mathematically complex and is shown in Equation 1 including four unknowns.

  Here, R0 is a DC specific resistance, m is a chargeability, τ is a relaxation time constant (sec), c is a frequency dependence coefficient, ω is an angular frequency, and i is √ (−1).

  The four unknowns are R0, m, τ, and c in Equation 1, and are mathematically determined as “solutions” that best match the phase difference (and resistance) data observed by the least square method. it can. A physical image is shown in FIG. FIG. 12 is a conceptual diagram of the IP phenomenon seen in the time domain. 12A shows a transmission current waveform, and FIG. 12B shows a reception potential waveform.

  R0 is a specific resistance (= measurement potential / DC current) determined from the potential with respect to DC current. m is an index representing the strength of the charging effect (charge storing property) of the ground 2, and is related to the integral value of the transient response. τ is related to the time length of the polarization phenomenon. When the IP phenomenon is observed in the time domain, the charge accumulated in the ground 2 during the current flow is observed by the current flowing from the ground 2 after the current interruption. This is related to the time waveform of the potential waveform, that is, the “transient response”. c is a coefficient associated with the dominant process of polarization. When the polarization phenomenon is based on a single dominant process, c = 1 (otherwise, c is 1 or less). The dominant processes of the polarization phenomenon include the charge transfer process between the ore and ions in the groundwater, the charge / discharge process of the electric double layer, and the ion diffusion process as the structure of the electric double layer changes (electricity) A double layer is a region with a high ion concentration formed at the interface between mineral particles (solid) and the surrounding groundwater (liquid).

  In the phase difference graph, not only fmax and θmax change due to the moisture content of the ground 2 or the like, but also the mountain-shaped curve shape (thickness and symmetry) of the graph also changes. The IP characteristics can be expressed in more detail as a numerical index from the above four parameters. That is, the above four parameters are obtained, and the measurement target ground 2 can be determined based on the four parameters. For example, the above four parameters are obtained in advance for various sample grounds 2 and stored in the storage means 29 as related data. The determination unit 34 accesses the storage unit 29 and compares the stored relationship data with the relationship between the frequency and the resistance obtained by the relationship calculation unit 33 and the relationship between the frequency and the phase difference (here, the above four parameters). Then, the measurement target ground 2 is determined. For example, the sample ground 2 that matches or approximates the above four parameters is determined as the measurement target ground 2. By doing so, it is possible to perform discrimination with higher accuracy.

  Note that it is also possible to obtain the IP characteristic from the transient response curve measured in the time domain as shown in FIG. However, this case has the following drawbacks. That is, it is quite difficult to measure the transient response as shown in FIG. In addition, it is difficult to accurately correct the frequency characteristics of the measurement system itself. On the other hand, the method of repeating the measurement a plurality of times by changing the frequency of the constant current used for measurement (measurement in the frequency domain) can withstand noise and reliably measure data for each single frequency.

  In the present embodiment, since the receiving device 14 has four receiving channels, the potential difference between four potential electrodes 4 at four locations can be measured simultaneously. Therefore, the four potential difference signals are supplied from the receiving device 14 to the resistor and phase difference calculating unit 32 at a time, and the resistor and phase difference calculating unit 32 calculates the four resistors and phase differences at a time. Then, the calculated resistance and phase difference at the four locations are supplied to the relationship calculating means 33 at a time, and the relationship calculating means 33 calculates the relationship between the frequency and the resistance and the relationship between the frequency and the phase difference at the four locations in parallel. Ask. The obtained relationship between the frequency and resistance and the relationship between the frequency and the phase difference at the four places are supplied to the discriminating means 34 at a time, and the discriminating means 34 discriminates the ground 2 at the four places at a time. As described above, since four reception channels are provided, it is possible to perform processing for four locations at a time, and thus the electric exploration can be completed in a short time.

  Next, a case where measurement is performed by changing the combination of the current electrode 3 and the potential electrode 4 will be described. For example, the measurement is performed in the following order (1) to (3).

(1) First, one measurement line 7 is selected, and measurement is performed by changing the combination of potential electrodes 4 with respect to one combination of current electrodes 3. The potential electrode 4 at the measuring point 8 other than the current electrode 3 is measured by changing its combination (FIG. 13A). The black triangle in FIG. 13 indicates the station 8 that becomes the potential electrode 4, the hatched triangle indicates the station 8 that becomes the current electrode 3, and the white triangle indicates the station 8 that is not used for the measurement. Further, characters such as C1, P1a indicate the terminal 25.

(2) Next, the combination of the current electrodes 3 is changed and the measurement of (1) is repeated. Measurement is performed for all combinations of current electrodes 3. Thereby, the measurement for one survey line 7 is completed. (Fig. 13 (b))

(3) Next, the measurement line 7 is changed and the measurements (1) and (2) are repeated. And it measures about all the measuring lines 7. FIG.

  Table 1 shows the change in the combination of the electrodes 3 and 4 for one survey line 7. The numbers for the electrodes 3 and 4 in Table 1 mean the measuring point 8. For example, the current electrode 3 of number 1 means the current electrode 3 of the first measurement point 8 among the 60 measurement points 8 provided on each measurement line 7, and the potential electrode 4 of number 60 corresponds to each measurement line. 7 represents the potential electrode 4 of the 60th measuring point 8 out of the 60 measuring points 8 provided in 7.

  Of the four survey lines 7, first, the A survey line 7 is measured. For example, in the first measurement, the current electrode 3 at the first and second measurement points 8 is selected, and measurement is performed by changing the combination of the potential electrodes 4 (A in Table 1). Since measurement is performed using four channels, only one channel is used in the eighth measurement.

  Then, after the measurement using the potential electrode 4 of the third to 60th measurement points 8 is completed for the current electrode 3 of the first and second measurement points 8, the current electrode 3 is changed to the first and third measurement points 8. In place of the current electrode 3, measurement is performed using the potential electrode 4 at the second, fourth to 60th measuring points 8 (B in Table 1). Then, after the measurement using the potential electrode 4 at the 2nd to 4th to the 60th measuring points 8 is completed for the current electrode 3 at the 1st and 3rd measuring points 8, the combination of the current electrodes 3 is further changed. Measurement is performed, and all current electrode 3 combinations are measured (C in Table 1). Thereby, the measurement about A measuring line 7 is complete | finished. Next, the same measurement is performed for the B survey line 7 → C survey line 7 → D survey line 7 as well. Thereby, the measurement ends.

  Thus, by measuring about the four measuring lines 7, the relationship between the frequency and the resistance and the relationship between the frequency and the phase difference for the ground 2 can be obtained three-dimensionally. The image is shown in FIG. Although only one survey line 7 is shown in FIG. 14, the spatial distribution of the relationship between the frequency and the resistance in the ground 2 and the relationship between the frequency and the phase difference is obtained by providing a plurality of the survey lines 7. The ground 2 can be explored three-dimensionally. Since the measuring unit 5 automatically switches the relays 23 and 27 of the electrode switching device 9 by computer control, it is possible to perform measurement quickly and to shorten the period required for measurement even if there are many combinations of the electrodes 2 and 3. .

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention.

  For example, in the above description, the electrode arrangement of the four-pole Dipole-Dipole method has been described as an example, but the present invention is not limited to the Dipole-Dipole method, and the Wenner method, Eltran method, and Schramberger method may be used. Further, the electrode arrangement is not limited to the quadrupole method, and may be an electrode arrangement of the bipolar method or the tripolar method.

  In the case of the bipolar method, any one of the 60 current electrodes 3 is fixedly used as a current far electrode, and any one of the 60 potential electrodes 4 is a potential far electrode. It can be considered to be used as a fixed. For example, the 59th current electrode 3 (referred to as the current electrode 3 at the 59th station 8; hereinafter the same) is fixedly used as the far electrode, and the 60th potential electrode 4 (at the 60th station 8). The potential electrode 4 (hereinafter the same) is fixedly used as a potential far electrode. That is, even if the survey line 7 is switched, for example, the 59th current electrode 3 and the 60th potential electrode 4 are always far electrodes. In this case, of the two switch circuits 24 of the point selection unit 20 for the current electrode 3 of the electrode switching device 9, the 59th relay 27 (59th switch) of one switch circuit (for example, the circuit on the C2 terminal 25 side) 24. The relay 27 provided on the branch line 26 connected to the main line 21 is maintained in the ON state, and among the eight switch circuits 24 of the station selection unit 20 for the potential electrode 4, The 60th relay 27 of one switch circuit (for example, the circuit on the P2a, P2b, P2c, P2d terminal 25 side) 24 of 1ch to 4ch is maintained in the ON state.

  In the case of the triode method, it is conceivable that any one of the 60 current electrodes 3 is fixedly used as a current far electrode. For example, the 60th current electrode 3 is fixedly used as a current far electrode. That is, even if the survey line 7 is switched, for example, the 60th current electrode 4 is always a far electrode. In this case, among the two switch circuits 24 of the point selection unit 20 for the current electrode 3 of the electrode switching device 9, the 60th relay 27 of one switch circuit (for example, the circuit on the C2 terminal 25 side) 24 is turned on. To maintain.

  In the above description, the current electrode 3 and the potential electrode 4 are separately provided at the measuring point 8. However, the present invention is not necessarily limited to this configuration, and the current electrode 3 and the potential electrode 4 are also used as the measuring point 8. A dual-purpose electrode may be installed.

  FIG. 11 shows the electrode switching device 9 when the dual-purpose electrode is installed. The line selection unit 19 and the point selection unit 20 of the electrode switching device 9 are provided in the middle of the path connecting the dual-purpose electrode to the transmission device 13 or the reception device 14. That is, in the electrode switching device 9 described above, the line selection unit 19 and the point selection unit 20 are divided into those for the current electrode 3 and those for the potential electrode 4 as shown in FIGS. In the electrode switching device 9 of FIG. 11, the survey line selection unit 19 and the survey point selection unit 20 are made common. The survey line selection unit 19 has the same configuration as the survey line selection unit 19 shown in FIG. The station selection unit 20 includes ten switch circuits 24 in accordance with the total number of current electrodes 3 and potential electrodes 4 used simultaneously for measurement. More specifically, two switch circuits 24 (for the C1 terminal 25 and for the C2 terminal 25) connected to the transmission apparatus 13 and two switch circuits 24 (for the P1a terminal 25 and P2a) connected to 1ch of the reception apparatus 14 are used. Terminal 25), two switch circuits 24 connected to 2ch (for P1b terminal 25 and P2b terminal 25), two switch circuits 24 connected to 3ch (for P1c terminal 25 and P2c terminal 25), connected to 4ch Two switch circuits 24 (for the P1d terminal 25 and for the P2d terminal 25). Each switch circuit 24 is the same as the switch circuit 24 of FIG. Moreover, since the number of electrodes 3 and 4 is halved as a whole by using the dual-purpose electrode, the number of connection terminals 10 is also halved.

  For example, the 1st and 2nd dual-purpose electrodes of the A measuring line 7 are the current electrodes 3, the 3rd and 4th dual-purpose electrodes are the potential electrodes 4 (1ch), and the 5th and 6th dual-purpose electrodes are the potential electrodes 4 (2ch). When the seventh and eighth combined electrodes are used as the potential electrode 4 (3ch) and the ninth and tenth combined electrodes are used as the potential electrode 4 (4ch), the following relays 23 and 27 are turned on. For example, the first relay 27 of the C1 switch circuit 24 (referred to as the switch circuit 24 for the C1 terminal 25, hereinafter the same) of the station selection unit 20, the second relay 27 of the C2 switch circuit 24, and the P1a switch The third relay 27 of the circuit 24, the fourth relay 27 of the P2a switch circuit 24, the fifth relay 27 of the P1b switch circuit 24, the sixth relay 27 of the P2b switch circuit 24, and the P1c switch circuit 24 The seventh relay 27, the eighth relay 27 of the P2c switch circuit 24, the ninth relay 27 of the P1d switch circuit 24, and the tenth relay 27 of the P2d switch circuit 24 are turned on, and a line selection is performed. All the A-group relays 23 of the unit 19 are turned on.

  When the dual-purpose electrode is used, the number of necessary electrodes can be halved, the configuration of the electrode switching device 9 can be simplified, preparation work such as electrode installation can be facilitated, and the electrode switching device 9 The manufacturing cost can be reduced.

  In the above description, four survey lines 7 are set as the survey lines 7. However, the number of survey lines 7 to be set is not limited to four. For example, one, two, three, five or more may be used.

  In the above description, 60 measurement points 8 are provided on one survey line 7, but the number of measurement points 8 provided on one survey line 7 is not limited to 60. The number of connection terminals 10 of the electrode switching device 9, the main line 21, the relays 23 and 27, etc. may be increased or decreased according to the increase or decrease of the number of measurement points 8. If the number is less than the number of connection terminals 10, main lines 21, relays 23, 27, etc., the connection terminals 10, main lines 21, relays 23, 27, etc. corresponding to the measuring points 8 are used, and the remaining connection terminals 10, main lines are used. 21, relays 23, 27, etc. may be left unused.

  Furthermore, in the above description, the ground exploration apparatus 1 includes the determination unit 34. However, the determination unit 34 is omitted, and the relationship between the frequency and the resistance obtained by the relationship calculation unit 33 and the frequency and the phase difference are determined. The relationship may be output to the output device 35.

  Further, in the above description, the ground 2 is determined based on the two relations of the relation between the frequency and the resistance and the relation between the frequency and the phase difference. The ground 2 may be determined based on the relationship. In this case, it is possible to perform measurement quickly by reducing the amount of calculation while maintaining a high degree of discrimination accuracy.

  In the above description, the electrode switching device 9 of the present invention is applied to the ground exploration device 1 and the ground exploration method for determining the ground 2 based on the relationship between the frequency and the resistance and the relationship between the frequency and the phase difference. However, applicable ground exploration devices and ground exploration methods are not limited to these. For example, a ground exploration device and a ground exploration method for determining the ground 2 based on the specific resistance may be used, and other ground exploration devices and ground exploration methods may be used. In other words, a ground exploration device and a ground exploration device that select current electrodes and potential electrodes used for measurement from among a large number of electrodes installed on a plurality of survey lines, and repeat measurement by sequentially switching the combination of the selected electrodes. Any method is applicable.

  Furthermore, you may utilize rock bolts, such as an underground storage cavity, as the electrodes 3 and 4. FIG.

  An experiment was conducted to confirm that the ground 2 can be determined based on the relationship between the frequency and the phase difference. In the experiment, a sample was prepared by adjusting the amount of water to a certain amount of coal ash (2 to 50% in water content) and tightening it. The sample contained many fine particles of clay size. In addition to the phase difference for each frequency, the resistance was also measured.

  The result of the experiment is shown in FIG. 15A is a sample with a moisture content of 2%, (b) is a sample with a moisture content of 6%, (c) is a sample with a moisture content of 10%, (d) is a sample with a moisture content of 15%, (e) Is a result of using a sample with a water content of 20%, (f) using a sample with a water content of 30%, (g) using a sample with a water content of 40%, and (h) using a sample with a water content of 50%. Moreover, in each figure, the downward arrow shows the peak frequency of the phase difference graph.

  As is clear from FIG. 15, it was confirmed that the value of the peak frequency (arrow) (critical frequency fmax) tends to shift to the higher frequency side as the water content increases. In addition, it was confirmed that the phase difference θmax of the peak frequency tends to increase as the water content increases, and that θmax decreases extremely when the water content is less than 10%. Furthermore, it was confirmed that the shape of the phase difference graph varies depending on the moisture content. As a result, it was confirmed that the moisture content of the ground 2 could be determined based on the relationship between the frequency and the phase difference. That is, fmax, θmax, fmax and θmax (two combinations), graph shape, fmax and graph shape (two combinations), θmax and graph shape (two combinations), fmax, θmax and graph shape (three combinations), It was confirmed that the moisture content of the ground 2 can be determined by any of the above. In addition, since the shape of the resistance graph also changes in FIGS. 15A to 15H, it can be confirmed that more accurate discrimination is possible by also determining the shape of the resistance graph.

  An experiment was conducted to confirm that the ground 2 can be determined with high accuracy based on the relationship between the frequency and the phase difference. In the experiment, mudstone samples and sandstone samples were used. For comparison, the specific resistance was also measured.

  The result of the experiment is shown in FIG. FIG. 16A shows a mudstone sample, and FIG. 16B shows a coarse sandstone sample. When the mudstone sample and the sandstone sample were compared, it was found that the difference between the phase difference graphs was larger than that between the specific resistance graphs. As a result, it was confirmed that it was easier to distinguish between the mudstone sample and the sandstone sample by performing the discrimination based on the phase difference graph than by performing the discrimination based on the resistivity graph, and it was possible to discriminate with higher accuracy. . Moreover, since there is a difference between the mudstone sample and the sandstone sample, it was confirmed that the specific resistance graph could be determined with higher accuracy by performing the determination based on both the phase difference graph and the specific resistance graph.

  FIG. 16A shows the DC specific resistance R0 = 195.5, the charge ability m = 0.5620, the relaxation time constant τ = 7.3430E-03, the frequency dependence coefficient c = 0.6324, and (b) DC specific resistance R0 = 374.9, chargeability m = 0.0984, relaxation time constant τ = 0.5747, and frequency dependence coefficient c = 0.1505.

  In addition, the graph of the theoretical value of FIG. 16 was calculated | required as follows. In other words, Equation 1 representing the Cole-Cole model described above has four unknowns R0, m, τ, and c that serve as indices indicating the strength and nature of the IP phenomenon. It can be obtained as the “solution” that best matches the phase difference and resistivity data. A mathematically specific solution is as follows.

  The impedance Z of the theoretical model equivalent to the sample is a function of the frequency ω and model parameters P1, P2,... Pn, and can be expressed by Equation 2 if the measured impedance at the frequency ωi is taken.

  Since Z is a non-linear function, Equation 3 is obtained by linear approximation using the Taylor expansion of a multivariable function.

Here, P ⁰ j is a parameter value of a true equivalent model, Pj is a parameter value given as an initial guess model, and if the difference is ΔPj, Equation 4 is obtained.

Now, Z ⁰ i and Zi are complex numbers, and their absolute values | Z | and the phase angle θ are used to be expressed as Equation 5. Therefore, logarithmic transformation is performed to separate the absolute value and the phase angle. Handle. That is, Equation 6 and Equations 7 and 8.

  At this time, when the number of data is n and the parameter Pj is m (n ≧ m), A constitutes a matrix of 2n rows and m columns. Therefore, if Formula 9, Formula 10, and Formula 11 are used, Formula 12 is expressed.

  In order to stably obtain y from b using the method of least squares, Equation 13 using a regularized general inverse matrix is used.

Here, I is an identity matrix, and λ is a positive constant called a damping factor.

P ⁰ j is obtained from the relationship of equation 14 with yi, and the calculation is repeated until the RMS residual becomes small.

In the analysis of variance of regression analysis, the mean square is obtained by dividing the residual sum of squares (sum of squares) between the observed values (experiment data) and the theoretical values (calculated values using mathematical formulas) by the degrees of freedom. , √ is the root mean square (RMS).
Here, [rho _ai ^f is measured, [rho _ai ^c are calculated values, N is the is the total number of measurements.

It is a block diagram which shows an example of embodiment of the ground exploration apparatus to which the electrode switching apparatus of this invention is applied. It is a block diagram which shows the measurement part of the ground exploration apparatus. It is sectional drawing of the ground which installed the current electrode. It is sectional drawing of the ground which installed the potential electrode. It is an example of embodiment of the electrode switching apparatus of this invention, and is a block diagram of a survey line selection part and a measurement point selection part by the side of a current electrode. It is an example of embodiment of the electrode switching apparatus of this invention, and is a block diagram of the survey line selection part by the side of a potential electrode, and a measurement point selection part. It is a figure which shows the switch circuit of a station selection part. It is a conceptual diagram which shows the relationship between a frequency and resistance, and the relationship between a frequency and a phase difference. It is a figure which shows a mode that a phase difference graph changes with the quantity of the clay mineral contained in the ground. It is a figure which shows a mode that a phase difference graph changes with the moisture content etc. of a ground. It is a block diagram which shows other embodiment of an electrode switching apparatus. The concept of the IP phenomenon seen in the time domain is shown, (a) is a diagram showing a transmission current waveform, and (b) is a diagram showing a reception potential waveform. The concept of the measurement by the spectrum IP method is shown, (a) is a conceptual diagram showing a state in which the current electrode is fixed and the potential electrode is changed in order, and (b) is the change of the current electrode. It is a conceptual diagram which shows a mode that this measurement is repeatedly performed. It is a figure which shows the concept which calculates | requires the relationship between the frequency of a ground, and a phase difference in three dimensions. The result of the experiment to confirm that the ground can be discriminated based on the relationship between the frequency and the phase difference is shown, (a) is a graph showing the result of using a sample having a moisture content of 2%, and (b) is a sample having a moisture content of 6%. (C) is a graph showing the result of using a sample with a water content of 10%, (d) is a graph showing the result of using a sample with a water content of 15%, and (e) is a water content. Graph showing results using 20% sample, (f) graph showing results using 30% moisture sample, (g) graph showing results using 40% moisture sample, (h ) Is a graph showing the results of using a sample having a water content of 50%. The result of the experiment to confirm that the ground can be discriminated with high accuracy based on the relationship between the frequency and the phase difference is shown. (A) is a graph showing the result of using a mudstone sample, (b) is a coarse sandstone sample. It is a graph which shows the result. It is a figure which shows the principle of the conventional electrode switching apparatus. It is a figure which shows the outline of the conventional electrode switching apparatus.

Explanation of symbols

7 Measuring Line 8 Measuring Point 3 Current Electrode 4 Potential Electrode 13 Transmitting Device 14 Receiving Device 9 Electrode Switching Device 10 Connection Terminal 19 Survey Line Selecting Unit 20 Measuring Point Selecting Unit

Claims (5)

Select the current electrode and potential electrode to be used for measurement from the electrodes installed at each of the multiple measuring points on the survey line, connect the lead wire that leads to the selected current electrode to the transmitter, and lead to the selected potential electrode In the electrode switching device for connecting the lead wire to the receiving device, the connection terminals for connecting the lead wires are provided in a number corresponding to the plurality of survey lines so that the electrodes of the plurality of survey lines can be connected and used for measurement from the plurality of survey lines. A survey line selection unit that selects one survey line and switches connection; and a survey point selection unit that selects a survey point used for measurement provided in each of the plurality of survey lines and switches connection, and the survey line selection unit electrode to the survey point is provided and a selection unit in series, wherein to switch between the survey line and stations to be used in combination with the selection of the station selection of the measuring line and by the measuring line selector according to the station selection unit and Cut off Apparatus.   A dual-purpose electrode that serves both as a current electrode and a potential electrode is installed at the measurement point, and the survey line selection unit and the measurement point selection unit are in the middle of a path that connects the dual-purpose electrode to the transmission device or the reception device. The electrode switching device according to claim 1, wherein the electrode switching device is provided.   A current electrode and a potential electrode are separately installed at the station, and the line selection unit and the station selection unit are in the middle of a path connecting the current electrode to the transmitter and the potential electrode is received. The electrode switching device according to claim 1, wherein the electrode switching device is provided in each of the paths connected to the device.   4. The method according to claim 1, wherein the station selection unit selects a station to be a far electrode from the stations and maintains a connection state of the selected far electrode station. 5. The electrode switching device as described.   The electrode switching device according to any one of claims 1 to 3, wherein the station selection unit switches connections by selecting all the station points in order.