JPH0572348A - Differential sensitivity distribution electric image tomographic method - Google Patents

Abstract

PURPOSE:To achieve a prospecting of a medium and a material and an electric conversion of an underground structure cross section into an image from an electric prospecting data even if no apparent ratio resistance is obtained by using a differential type electrode array cubically. CONSTITUTION:A drilling is performed to the upper end 3 of a drilling hole 2 (shaft) from the ground surface 1. A voltage is applied between a positive current electrode 4 and a negative current electrode 6 in the shaft through an ammeter 9 and wires 11 and 12 from a power source 8. On the other hand, a potential difference meter 10 is provided between a positive potential electrode 5 and a negative potential electrode 7 provided on the ground surface 1 through wires 13 and 14. Separately, an arrangement of electrodes of a differential type cubic electrode array observation pattern is made by connecting the electrodes with the wires 15, 16, 17 and 18. Thus, the use of the electrode arrangement of the electrode array observation pattern is used in plurality in a differential sensitivity distribution enables the formation of an electric prospecting sectional image even if no apparent ratio resistance is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is particularly applicable to a differential electrode array which is avoided or omitted because the apparent resistivity cannot be calculated, and is provided on the ground surface and the boring hole (or well). Wells, tunnels, etc. are also used to identify mining, groundwater, civil engineering foundation grounds / rocks, geological structures, etc. based on electrical exploration data acquired by composite three-dimensional electrode arrangement that is also actively arranged in three dimensions. The present invention relates to an electric tomography method for obtaining cross-sectional images by a new differential sensitivity distribution for exploration (inspection) of mediums and materials.

 (Prior Art) In conventional resistivity tomography, reverse analysis is performed only from apparent resistivity data based on an electrode arrangement observation pattern arranged on the surface of the earth or a borehole (or well).

Therefore, in the case of various electrode arrangements where the potential (or potential difference) is zero in the case of a homogeneous medium and the apparent resistivity cannot be calculated, data is avoided or omitted, and the method of forming the cross-sectional image is used. There was no. In electrical exploration of media such as underground, observation patterns with various electrode arrangements including three-dimensional arrangements such as boring holes (or wells), tunnels, and the ground surface are essential. In many cases, it is avoided or omitted when the calculation of the multiplication resistivity cannot be obtained accurately.

(Example) An example of the present invention will be described with reference to FIG. 1 is the ground surface. 2 is a borehole (or well), 3 is the upper end of the borehole, and 4 is a positive current electrode placed in the borehole. 5 is a positive potential electrode placed on the surface of the earth. 6 is a negative current electrode placed in the hole.

Reference numeral 7 is a negative potential electrode placed on the ground surface. (In FIG. 2, the positive current electrode 4 is placed in the boring hole 1 and the positive and negative potential electrodes 5, 7 are placed in the boring hole 2. The negative current electrode 6 is located on the ground surface far from the boring hole 1. In Fig. 3, positive and negative current electrodes 4 and 6 are placed on the ground surface, and positive and negative potential electrodes 5 and 7 are placed in the tunnel.) 8 is a power source and 9 is an ammeter. 10 is a potentiometer. 11, 12, 13 and 14 are electric wires. Reference numerals 15, 16, 17, and 18 are lines showing combinations of electrode arrangements of this differential type three-dimensional electrode array observation pattern. 19 is the lowermost end of the in-hole electrode. (In FIG. 2, 16 and 17 are electrodes at the upper end of the hole, and 18 and 19 are electrodes at the lower end of the hole. In FIG. 3, 16 and 17 are electrodes at the left and right ends of the ground surface, 18, 19 are electrodes at the left end and the right end in the tunnel.) Next, the sensitivity distribution of the differential type three-dimensional electrode array, which is the basic constant forming the electric exploration image of the present patent application, is created as shown in FIG. The description will be given with reference to FIGS. 2 and 3. Fig. 4 shows the case where positive and negative current electrodes are placed at the depths of 30 m and 40 m in the hole, and positive and negative potential electrodes are placed at the surface of 30 m and 50 m. Fig. 5 shows the depth inside the hole 1. This is the case where a positive current electrode is placed at a distance of 31.5 m, a negative current electrode is placed on the ground surface far from hole 1, and positive and negative potential electrodes are placed at depths 7 m and 17 m in hole 2. In Fig. 6, positive and negative current electrodes are placed at 40 m and 60 m on the surface of the earth, and the depth of 32. This is the case where positive and negative potential electrodes are placed at 20 m and 30 m in a 5 m tunnel. The differential sensitivity distribution due to a three-dimensional anomalous conductor. In the figures, negative values indicate forward sensitivity, positive values indicate reverse sensitivity, and large values indicate good sensitivity. Such differential sensitivity distribution is used to form an electrical exploration (inspection) cross-sectional image by using a plurality of electrode arrangement observation patterns or a combination thereof.

(Effects of the Invention) Generally, there are not a few observation electrode arrangements that are three-dimensionally or arranged on the ground surface, which are avoided or omitted because the apparent resistivity cannot be calculated accurately.

The present invention relates to a differential electrical exploration (inspection) imaging (tomography) method based on a newly found method of creating a differential sensitivity distribution. It is possible to use more data than the apparent resistivity data method, which helps improve the reliability of medium cross-section images.

 FIGS. 7, 8 and 9 are examples showing the effect of the invention. In a homogeneous three-dimensional medium having a specific resistance of 100 Ω · m, a single lump structure (sphere) having a specific resistance of 0 Ω · m is shown. 4A, 2B, and 3 are electrical cross-sectional images of electric exploration (inspection) according to the respective methods in the case where is present. Anomalies due to the structure are shown by iso-value lines in the image. The numerical value is the probability of occurrence of an abnormal body (%), which can also identify the reliability of the formed cross-sectional image.

[Brief description of drawings]

 1 to 3 are sectional views showing an embodiment of the present invention. An example will be described with reference to FIG. 1 is the surface of the earth, 2 is a borehole (or well), 3 is the upper end of the borehole, 4 is a current electrode (positive electrode), 5 is a potential electrode (positive electrode), 6 is a current electrode (negative electrode), 7 is a potential electrode (negative electrode) ), 8 is a power supply, 9 is an ammeter, 10 is a potentiometer, 11, 12, 13 and 14 are electric wires, 15, 16, 17 and 18 are combinations of electrode arrangements of this differential type three-dimensional electrode array observation pattern Is a line indicating. Reference numeral 19 is an electrode at the bottom end of the borehole (well). 4 to 6 are examples of differential sensitivity distributions that are basic constants for obtaining differential electrical exploration images (tomography). The vertical axis represents the depth unit (m), and the horizontal axis represents the horizontal distance unit (m). When using one boring hole (or well) at a horizontal distance of 40 m (Fig. 4), when using two boring holes at a horizontal distance of 20 m and 60 m (Fig. 5), and underground depth. This is when using a 32.5 m tunnel and ground surface (Fig. 6). FIGS. 7 to 9 are sectional images showing the effect of the present invention, which are examples corresponding to the systems of FIGS. 1 to 3. This is the case where a single spherical (radius 5 m) abnormal conductor with a specific resistance of 0 Ω · m exists in a homogeneous three-dimensional medium with a specific resistance of 100 Ω · m. The vertical axis represents the depth unit (m), and the horizontal axis represents the horizontal distance unit (m). The center of the structure, which is the object of exploration (inspection), is indicated by a + sign.

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[Procedure amendment]

[Submission date] Hei 4.10.12 (1) Application form As attached. (2) The title of the invention in the description is corrected to “differential sensitivity distribution electric image tomography method”. (3) “3. Detailed description of the invention” on page 1, line 10 of the specification.
Is corrected as “3. Detailed description of the invention”.

Claims (1)

[Claims] 1. Particularly, the differential type electrode array, which is generally avoided or omitted because an apparent resistivity cannot be obtained, is positively and actively used from the standpoint of the electrical survey data and the underground structure cross section. Tomography method for electrically imaging images