JP5350038B2 - Electrical resistivity method - Google Patents

Description

  The present invention relates to an electrical exploration resistivity method that is excellent in workability and economy that can connect a hole electrode disposed in a boring hole with a hole wall.

The electrical exploration resistivity method uses a pair of boreholes provided in the ground, a plurality of electrodes installed at intervals in the vertical direction within each borehole, and an interval at the ground surface between the boreholes. In this method, a current is passed between an arbitrary pair of electrodes and a potential between the other pair of electrodes is measured by the measuring device using a plurality of electrodes and a measuring device. A two-dimensional resistivity distribution or a three-dimensional resistivity distribution can be obtained, and the properties of the ground can be estimated from the two-dimensional resistivity distribution or the three-dimensional resistivity distribution (see, for example, Patent Document 1).
In order to pass a current between the arbitrary pair of electrodes, it is necessary to energize the electrode disposed in the boring hole and the hole wall (ground surface) of the boring hole. When installing multiple electrodes that are spaced apart from each other in the boring hole, water is put into the boring hole so that the electrode and the wall can be energized. Since the water in the hole penetrates the ground through the hole wall, cementation is performed to cover the hole wall with cement, and then water is poured into the borehole or water is poured continuously into the borehole. It was. Or the electrode (for example, refer patent documents 2; 3 grade | etc.) Of the structure which can be crimped | bonded with a hole wall so that it can energize even if there is no water in a boring hole was used.

JP 2005-337746 A JP-A-10-220182 JP 2006-119096 A

However, the cementation process and the continuous water injection into the borehole have a problem that the work is complicated and the work cost is high. In addition, there is a problem that it is difficult to introduce an electrode having a structure capable of being crimped to a hole wall of a boring hole because it is expensive.
The present invention has been made in view of the above problems, and is arranged in the borehole without performing a cumbersome operation such as cementation treatment or continuous water injection into the borehole or using an expensive electrode. An electrical exploration resistivity method with excellent workability and economy that can connect a hole electrode and a hole wall.

In the electrical exploration resistivity method according to the present invention, a plurality of electrodes are installed at a predetermined interval in the vertical direction in a pair of bore holes provided in the ground, and at a predetermined interval on the ground surface between the pair of bore holes. A configuration in which a plurality of electrodes are installed at a predetermined interval in a pair of boring holes provided in the ground or a plurality of electrodes provided in the ground. A measuring device using a configuration in which two measuring holes are installed at predetermined intervals in one boring hole and at a predetermined interval on the ground surface around the boring hole, and the measuring device is between any pair of electrodes measuring the potential measured by the other pair of electrodes with current flow in the electrical prospecting resistivity method, the hole wall holding tube larger metal pipe than the hole diameter the outer diameter of the borehole tube The lower end side of the hole wall holding tube is fitted into the hole of the boring hole from the upper end opening of the boring hole so that the upper end side of the hole wall holding tube protrudes to the ground, and the inner surface and the outer surface of the tube are A perforated pipe with a plurality of holes provided so as to penetrate is inserted from the upper end opening of the hole wall holding pipe and installed in the borehole, and an injection hose with one end connected to the foam storage tank is connected to the other end side. The other end opening of the injection hose is placed above the groundwater level and is injected into the borehole through the injection hose until the foam overflows from the upper end opening of the hole holding pipe. after, the injection hose withdrawn from the perforated pipe, perforated tube current between any pair of electrodes after securing the conduction between the electrode and the borehole hole wall in a plurality of electrodes installed perforated tube So that the cementation process and the Or perform complicated operations such as a continuous water injection into ring bore, without using an expensive electrode, excellent workability and economy, or the electrode and the boring of the perforated inner tube in the borehole Foam Since energization with the hole wall of the hole is ensured, the in-hole electrode and the hole wall are electrically connected by the bubbles injected into the boring hole, and an electric current can flow between any pair of electrodes. The electrical exploration resistivity method with high reliability and high measurement reliability can be realized. Further, since the perforated pipe is used, the bubbles can be evenly distributed over the entire space above the groundwater level in the borehole, so that the in-hole electrode and the hole wall can be more reliably conducted. In addition, the use of foam that is easy to handle and difficult to penetrate the ground through the hole wall realizes a highly reliable electrical exploration resistivity method that can maintain the electrical connection between the in-hole electrode and the hole wall for a long time. it can.

The schematic diagram which shows the measuring method of an electrical exploration specific resistance method (embodiment). (A) is the figure which installed the hole wall holding pipe in the boring hole, (b) is the figure which installed the perforated pipe in the boring hole (embodiment). The figure which shows the state which supplied the electroconductive material in the boring hole (embodiment). The perspective view which shows the state which supplied the electroconductive material in the boring hole (embodiment).

  The measurement by the electric exploration resistivity method can be realized by the electric exploration resistivity measuring apparatus 1 shown in FIG. The electrical exploration resistivity measuring apparatus 1 includes a pair of boring holes 2 provided in the ground, a plurality of in-hole electrodes 3 installed at predetermined intervals in the pair of boring holes 2, and a pair of boring holes. A plurality of ground electrodes 4 installed at predetermined intervals on the ground surface S between the two, a conductive material 5 having a lower fluidity than water, a conductive material supply device 6, a measuring device 7, and a measuring device 7 and a stabilized power supply (not shown) for supplying power to the machine of the conductive material supply device 6.

  As the conductive material 5 having a lower fluidity than water, bubbles 10 are used. The conductive material supply device 6 includes a foam storage tank 9, a pump 11, a hole wall holding pipe 12, a perforated pipe 13, and an injection hose 14 (see FIG. 3). The hole wall holding tube 12 was a metal tube. As the perforated tube 13, a tube made of vinyl chloride having an aperture ratio of 10% was used. The perforated tube 13 is a tube provided with a plurality of holes 15 provided so as to penetrate the inner surface and the outer surface of the tube (see FIG. 4). The measuring device 7 includes a switching box, an ammeter, a voltmeter, and the like for setting a combination of a pair of electrodes for passing a current and a pair of electrodes for measuring a potential.

  With reference to FIG. 2 thru | or FIG. 4 and FIG. 1, how to make the electric exploration specific resistance measuring apparatus 1 for implement | achieving the measuring method by an electric exploration specific resistance method is demonstrated. As shown in FIG. 2A, after forming the borehole 2 from the ground surface S into the ground, the hole wall holding tube 12 is fitted into the borehole 2 from the upper end opening 20 of the borehole 2. This prevents the hole wall 21 on the upper end side of the boring hole 2 from collapsing. For example, using the hole wall holding tube 12 whose outer diameter is slightly larger than the hole diameter of the bore hole 2, the lower end side of the hole wall holding tube 12 is fitted into the bore hole 2 from the upper end opening 20 of the bore hole 2. The upper end side of the hole wall holding tube 12 is projected to the ground. As shown in FIG. 2 (b), the perforated tube 13 is inserted from the lower end side through the upper end opening 23 of the perforated wall holding tube 12, and the perforated tube 13 is installed in the boring hole 2. The upper end of each is protruded upward from the hole wall holding tube 12. The lower end opening 24 of the perforated pipe 13 may be in contact with the hole bottom 25 of the boring hole 2 (see FIG. 2B), or may be installed above the groundwater level W in the boring hole 2. .

  As shown in FIG. 3, the foam outlet 30 of the foam storage tank 9 and the suction port 31 of the pump 11 are connected by a communication hose 32, and one end of the injection hose 14 is connected to the discharge port 33 of the pump 11. Then, the injection hose 14 is put into the perforated tube 13 from the other end side, and the other end opening 35 of the injection hose 14 is grounded at a predetermined position. That is, the other end opening 35 of the injection hose 14 may be installed at a position where the foam 10 can be efficiently filled into the boring hole 2. For example, the other end opening 35 of the injection hose 14 is installed above the groundwater level W so that the foam 10 is filled into the boring hole 2 via the hole 15 of the perforated pipe 13. After the foam 10 is made by putting water and a foaming agent in the foam storage tank 9 and stirring with a stirring device or the like, the pump 11 is driven to send the foam 10 to the injection hose 14. In order to form the stable foam 10, for example, a foaming agent made of an anionic surfactant may be used. The foam 10 injected through the injection hose 14 is supplied into the borehole 2 through at least the plurality of holes 15 of the perforated pipe 13 and the entire space above the groundwater level W in the borehole 2 ( Hereinafter, it is supplied to the whole boring hole space B). The injection of the foam 10 is continued until the foam 10 overflows from the upper end opening 23 of the hole wall holding tube 12 as shown in FIG. After the foam 10 is supplied to the entire bore B space B, the injection hose 14 is extracted from the perforated tube 13.

  As shown in FIG. 1, after the foam 10 is supplied to the whole bore B space B, a plurality of in-hole electrodes 3 are installed in the perforated tube 13 and the ground surface S between the pair of bore holes 2 is provided. A plurality of ground electrodes 4 are installed. For example, by inserting an electrode attachment body such as a rope or a rod to which a plurality of electrodes are attached at predetermined intervals into the perforated tube 13, the plurality of in-hole electrodes 3 are vertically spaced within the borehole 2. It is installed with a gap. A plurality of in-hole electrodes 3 are installed in the pair of boring holes 2, and the other ends of the wires individually connected to the plurality of in-hole electrodes 3 are drawn from the boring holes 2, and the other ends of the wires are Connect to measuring device 7. Moreover, the ground surface S between the pair of boring holes 2 is provided by installing the electrode mounting body on which the plurality of electrodes are mounted at predetermined intervals on the ground surface S between the pair of boring holes 2. Are connected at predetermined intervals, and the other ends of the electric wires, one end of which is individually connected to the plurality of ground electrodes, are connected to the measuring device 7. Thus, the electrical exploration resistivity measuring apparatus 1 as shown in FIG. 1 is completed. In FIG. 1, for simplification of illustration, a plurality of electrode wires and electrode attachments are indicated by a single line x.

  The measuring device 7 allows a current to flow between any pair of electrodes and measures the potential between the other pair of electrodes. In this case, since the conduction between the electrode and the hole wall 22 (the ground surface) is ensured by the foam 10 injected into the borehole 2, an electric current is passed through an arbitrary electrode arranged in the borehole 2, A current can be reliably passed between any pair of electrodes. Then, the measurement result of the potential (specific resistance Ωm) measured by sequentially changing the combination of the pair of electrodes for passing current and the pair of electrodes for measuring the potential by the switching box provided in the measuring device 7. Therefore, it is possible to obtain a two-dimensional resistivity distribution or a three-dimensional resistivity distribution of the ground, and to estimate the properties of the ground from the two-dimensional resistivity distribution or the three-dimensional resistivity distribution.

  According to this embodiment, without performing complicated work such as cementation treatment or continuous water injection into the borehole 2 or using an expensive electrode, the bubbles 10 injected into the borehole 2 can be connected to the electrode. Since the hole wall 22 (ground surface) is energized, an electric current can be reliably passed between any pair of electrodes, and an electrical exploration resistivity method excellent in workability, economy, and measurement reliability can be realized. Further, since the perforated tube 13 is used, the bubbles 10 can be evenly distributed throughout the entire borehole space B, so that the in-hole electrode 3 and the hole wall 22 can be more reliably conducted. In addition, since the foam 10 that is easy to handle and hardly penetrates the ground through the hole wall 22 is used, the workability, economy, and measurement reliability are excellent, and the conductivity between the in-hole electrode 3 and the hole wall 22 is improved. The electric resistivity method that can be maintained for a long time can be realized.

  Even after the foam 10 is supplied to the entire bore B space B, the injection hose 14 is kept inserted in the perforated tube 13, and a plurality of in-hole electrodes are inserted in the perforated tube 13 in which the injection hose 14 is inserted. 3 may be installed. In this way, it is possible to immediately inject additional bubbles when the number of bubbles is reduced during measurement, and it is possible to achieve highly reliable measurement even in the case of long-time measurement.

  As the conductive material 5 having lower fluidity than water, a conductive material 5 such as mousse or gel may be used.

  In the above form, a plurality of electrodes are installed at a predetermined interval in the vertical direction in a pair of bore holes provided in the ground and at a predetermined interval on the ground surface between the pair of bore holes. Although described as an example, the electrode installation configuration is a configuration in which a plurality of electrodes are installed at a predetermined interval in the vertical direction within a pair of bore holes provided in the ground, or a plurality of electrodes are provided on the ground. It is good also as a structure installed at predetermined intervals on the ground surface around the said boring hole, while installing in the one boring hole provided in the upper and lower sides at predetermined intervals.

  The electrical exploration resistivity method of the present invention can determine a two-dimensional resistivity distribution or a three-dimensional resistivity distribution as a judgment material for knowing water veins, cavities, soil density, etc. in the ground. The present invention can also be applied to a case where a two-dimensional resistivity distribution or a three-dimensional resistivity distribution is obtained by forming a borehole laterally or upwardly with respect to a natural ground.

2 boring hole, 3 hole electrode, 4 ground electrode, 5 conductive material, 7 measuring device,
10 foam, 13 perforated pipe, 22 perforated wall, W groundwater level, S ground surface.

Claims (1)

A configuration in which a plurality of electrodes are installed at predetermined intervals in the vertical direction in a pair of boring holes provided in the ground and at a predetermined interval on the ground surface between the pair of boring holes, or a plurality of electrodes A configuration in which the electrodes are vertically arranged in a pair of boring holes provided in the ground with a predetermined interval, or a plurality of electrodes are vertically spaced in a single boring hole provided in the ground The measurement device uses a configuration that is installed at a predetermined interval on the ground surface around the borehole and the measurement device, and the measurement device allows current to flow between any pair of electrodes and the other pair of electrodes. In electrical exploration resistivity method to measure the measured potential,
Using a metal pipe whose outer diameter is larger than the bore diameter of the borehole as a hole wall holding pipe, the lower end side of the hole wall holding pipe is fitted into the borehole hole from the upper end opening of the borehole to hold the hole wall. While projecting the upper end of the tube to the ground,
A perforated pipe having a plurality of holes provided so as to penetrate the inner surface and the outer surface of the pipe is inserted from the upper end opening of the hole wall holding pipe and installed in the borehole,
Put an injection hose, one end of which is connected to the foam storage tank, into the perforated pipe from the other end and install the other end opening of the injection hose above the groundwater level, and the foam overflows from the upper end opening of the hole holding pipe after injecting the foam into the borehole through the injection hose to, of the injection hose withdrawn from the perforated pipe, by installing a plurality of electrodes in the perforated tube of perforated inner tube electrode and the borehole hole wall An electrical exploration resistivity method, characterized in that a current is passed between any pair of electrodes after ensuring electrical continuity with .

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