JP2023070233A - Ground resistivity measurement device and ground resistivity measurement method - Google Patents

Abstract

To propose a ground resistivity measurement device and a ground resistivity measurement method enabling electrodes to be easily installed without being limited in terms of the drilling direction of a measurement hole, and making it possible to measure the resistivity distribution in a desired range with higher accuracy.SOLUTION: A ground resistivity measuring device includes a bag body 2, a plurality of conductors 3 provided in the bag body 2, and a measuring sonde 4 that can be inserted into the bag body 2. The bag body 2 is inflated into a columnar shape by press-fitting a fluid inside. The plurality of conductors 3 face the inner surface and the outer surface of the bag body 2 and are spaced apart in the longitudinal direction of the bag body 2 . The measuring sonde 4 consists of a multicore cable 41 and a plurality of electrodes 42 provided on the multicore cable 41. The tip of the multicore cable 41 is fixed to the tip of the bag body 2 and the multicore cable 41 is guided into the bag body 2 when the bag body 2 is inflated so that the electrode 42 and the conductor 3 are in contact with each other.SELECTED DRAWING: Figure 2

Description

The present invention relates to a soil resistivity measuring device and a soil resistivity measuring method using the same.

In tunnel construction, forward exploration of the ground is carried out by long-distance boring, etc. to grasp the ground condition in advance, and measures are taken to prevent construction troubles such as flooding and collapse. In particular, in the case of shield tunnels, since the excavated surface cannot be visually observed, a boring survey is often conducted from the ground surface before excavation. On the other hand, it is often difficult to secure land for conducting boring surveys in urban areas, and it is sometimes not possible to secure a sufficient number of boring surveys to obtain a detailed understanding of the stratum structure along the entire excavation length.
Therefore, a geophysical exploration method that interpolates information between boring survey points, which is one-dimensional information, and is capable of ascertaining a planar stratum structure is widely used. There are various methods of geophysical exploration, but among them, the electrical exploration method, which grasps the electrical characteristics of the ground, has many uses, including resource development and civil engineering. Resistivity tomography, which is one of the electrical prospecting methods, is a method to grasp the stratum structure by utilizing the property that the resistivity (≒ electrical resistance) changes according to the porosity in the ground.

In the resistivity survey, multiple electrodes are placed on the ground, and alternating DC current is applied to the ground to measure the voltage. By inversely analyzing the obtained measurement data, the resistivity distribution of the ground can be obtained in two dimensions and three dimensions. Electrodes are often installed in resistivity surveys using one of two methods: installation on the ground surface and insertion of electrodes into pre-drilled holes. The method of installing electrodes on the ground surface can adjust the range from which ground information can be obtained according to the electrode installation range, is suitable for obtaining ground information near the electrodes, and is relatively easy to install. On the other hand, the method of installing electrodes in the holes is a method of grasping the resistivity distribution between holes, so it is also called inter-hole tomography. suitable for the occasion.
When grasping the resistivity distribution from the underground space such as the inside of a tunnel hole by inter-hole tomography, the degree of difficulty of electrode installation varies greatly depending on the drilling direction. When facing downward, the electrode can be easily inserted according to gravity, but when facing horizontally or upward, it is necessary to insert the electrode against gravity. become.

For example, in Non-Patent Document 1, as a method of installing a measurement probe in the horizontal direction from a shaft, a measurement probe in which a multi-core cable is tied to a thin PVC pipe is inserted into a measurement hole drilled horizontally and inserted. A method of filling a space between the measurement probe and the ground with a grout material to fix the measurement probe is disclosed.
In addition, in Patent Document 1, as an electrical prospecting method for measuring the resistivity between a plurality of horizontal boreholes, an electrode is sent to the tip of one of the horizontal boreholes with high pressure water and arranged, and the electrodes of the other horizontal boreholes. A method of measuring the resistivity between electrodes using a plurality of electrodes arranged at predetermined intervals in the axial direction is disclosed.
In addition, in Patent Document 2, in order to measure the resistivity of the upper bedrock of an underground facility, an electric wire is connected to a rock bolt driven into the ceiling and used as a current electrode and a potential electrode. A measuring method is disclosed in which a specific resistance value is obtained from the potential difference generated between each potential electrode by flowing water, and the water content state of the surrounding rock is estimated from the specific resistance value.

However, in the measurement method of Non-Patent Document 1, there is a possibility that the resistivity distribution of the ground cannot be accurately measured because the grout material is interposed between the ground to be measured and the electrodes. In addition, it is necessary to bind the multi-core cable and the PVC pipe, and if the length of the measurement hole to be drilled is long, the binding work and the insertion work must be repeated many times, which takes time and effort.
Moreover, in the measuring method of Patent Document 1, since the electrode is fed with high-pressure water, there is a possibility that the pore wall collapses in the case of a soft ground. In addition, there is a possibility that the specific resistance distribution cannot be measured accurately due to the presence of fluid (water other than groundwater used as high-pressure water) between the electrode and the ground.
Further, in the measurement method of Patent Document 2, one rock bolt serves as one electrode, so only the resistivity of the upper ground facing the underground facility can be measured.

Wataru Ogawa, 3 others, ``Visualization of chemical solution injection range by resistivity tomography'', Civil Engineering and Construction Technology Conference Summary, Japan Society of Civil Engineers, pp.205-210, 2011

JP 2017-15436 A JP-A-08-268497

The present invention makes it possible to easily install electrodes without being limited to the drilling direction of the measurement hole, and to measure the specific resistance distribution in the desired range with higher accuracy. The object is to propose an apparatus and a soil resistivity measurement method.

In order to solve the above problems, the soil resistivity measuring device of the present invention includes a bag, a plurality of conductors provided in the bag, and a measuring sonde that can be inserted into the bag. . The bag expands into a cylindrical shape by pressurizing a fluid into the bag, and the plurality of conductors face the inner surface and the outer surface of the bag and are spaced apart in the length direction of the bag. is provided. The measuring sonde comprises a multicore cable and a plurality of electrodes provided on the multicore cable. The tip of the multi-core cable is fixed to the tip of the bag, and when the bag is inflated, the multi-core cable is guided into the bag and the electrodes and the conductors are connected. configured to abut.
Further, the soil resistivity measuring method of the present invention includes a drilling step of forming a measurement hole in the ground, an insertion step of inserting the soil resistivity device into the measurement hole, and a resistivity distribution using the soil resistivity device. and a measuring step of measuring In the inserting step, a fluid is pressurized into the bag to expand the bag into a columnar shape in the measurement hole, thereby guiding the probe for measurement inside the bag, and The electrodes are brought into contact with each other.
According to the soil resistivity measuring device and the soil resistivity measuring method, the conductor provided in the bag is arranged by expanding the bag in the measurement hole, so that the direction of the measurement hole is horizontal to vertically upward. Even if there is, the conductor can be arranged at a desired position while being in contact with the ground without intervening grout or the like. Further, by inflating the bag, the multicore cable is inserted into the bag and the electrodes fixed to the multicore cable come into contact with the conductor. That is, it becomes possible to supply electricity to the ground through the electrodes and conductors.

It is desirable that the proximal end of the bag is provided with a backflow preventing portion for preventing leakage of the fluid pressurized into the bag. In addition, it is desirable that the backflow prevention part can be inserted through the measuring sonde.
Moreover, when the ground to be measured is soft ground (collapsible ground), it is desirable to further include a measuring tube into which the bag can be inserted. The measuring tube is provided with a plurality of second conductors facing the inner surface and the outer surface of the measuring tube. The second conductor contacts the conductor when the bag is inflated.
When a measuring tube is used, in the inserting step, before pressurizing the fluid into the bag, the measuring tube into which the bag can be inserted is inserted into the measuring hole. Then, by pressurizing a fluid into the bag, the bag is expanded within the measurement tube, and the conductor and the second conductor are brought into contact with each other. By doing so, it becomes possible to supply electricity to the ground via the electrode, the conductor and the second conductor.

According to the soil resistivity measuring device and the soil resistivity measuring method of the present invention, it is possible to easily install the electrode without being limited to the drilling direction of the measurement hole, and to achieve a desired range with higher accuracy. It becomes possible to measure the resistivity distribution.

It is a bird's eye view which shows the installation condition of a soil resistivity measuring apparatus. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the soil resistivity measuring apparatus which concerns on 1st embodiment, (a) is an external view at the time of expansion, (b) is sectional drawing at the time of expansion, (c) is an external view at the time of contraction. 4 is an enlarged cross-sectional view showing the relationship between conductors and electrodes; FIG. (a) to (d) are schematic diagrams showing a state in which the measuring sonde passes through the backflow preventing section. It is a figure which shows the procedure of the ground resistivity measuring method of 1st embodiment, Comprising: (a) is a drilling process, (b) is an insertion process, (c) is a measurement process. It is a figure which shows the soil resistivity measuring apparatus which concerns on 2nd embodiment, Comprising: (a) is sectional drawing at the time of contraction, (b) is sectional drawing at the time of expansion. It is a figure which shows the procedure of the soil resistivity measuring method of 2nd embodiment, Comprising: (a) is a drilling process, (b) and (c) are insertion processes, (d) is a measurement process.

<First embodiment>
In the first embodiment, the ground electrical resistivity distribution is measured using the ground resistivity measuring device 1, and the surrounding ground (ground G) of the tunnel T (shield tunnel in this embodiment) is investigated. A case will be described. Fig. 1 shows an example of the installation situation of the soil resistivity measuring device. As shown in FIG. 1, a plurality of soil resistivity measuring devices 1 are installed at intervals from the inside of the tunnel pit in the lateral direction (horizontal) to upward direction with respect to the analysis area (ground G). That is, the soil resistivity measuring device 1 is arranged radially from the tunnel T. As shown in FIG. FIG. 2 shows the soil resistivity measuring device 1 . As shown in FIGS. 2(a) and 2(b), the soil resistivity measuring device 1 includes a bag 2, a plurality of conductors 3, 3, . . . It has an insertable measurement sonde 4 and a backflow prevention part 5 provided at the proximal end of the bag.

The bag body 2 is inflated into a columnar shape by pressurizing air (fluid) into the inside. Moreover, the bag body 2 shrinks in a bellows-like shape as shown in FIG. The bag 2 is made of an insulating material (for example, vinyl chloride resin) that does not conduct electricity, and contributes to the prevention of electric leakage. The bag body 2 is formed by connecting a plurality of soft and flexible tubular members 21, 21, . . . In this embodiment, as shown in FIGS. 2(a) and 2(b), a plurality of cylindrical members 21, 21, . The tip of a cylindrical member 21 provided at the tip of the bag 2 is shielded to prevent leakage of the air pressurized into the bag 2 .

2(a) and 2(b), the plurality of conductors 3, 3, . . . .5 m to 2.0 m). FIG. 3 shows an enlarged view of the soil resistivity measuring device 1. As shown in FIG. The conductor 3 is made of a ring-shaped metal member, and as shown in FIG. face) and the outer surface (surface on the ground side) (exposed). Due to the expansion of the bag 2, the conductor 3 adheres to the hole wall (ground) of the measurement hole in which the bag 2 is installed. In this embodiment, a pair of protective members 31 , 31 are fixed to the outer surface of the bag 2 to sandwich the conductor 3 of the conductor 3 . The protective member 31 is made of rubber and has a height equal to or less than the protruding length of the conductor 3 from the bag body 2 . The protective material 31 protects the conductor 3 from friction with the ground or the like, and functions as a non-slip against the contact surface of the ground or the like. If the conductor 3 does not protrude from the outer surface of the bag 2 or if the length of protrusion from the outer surface of the bag 2 is small, the protective material 31 can be omitted.

The measuring sonde 4 comprises a multicore cable 41 and a plurality of electrodes 42, 42, . . . provided on the multicore cable 41, as shown in FIG.
The multicore cable 41 is configured by bundling a plurality of electric wires (for example, coated copper wires). The multi-core cable 41 should have an appropriate number of cores according to the number of electrodes 42, and preferably has 4 to 40 cores, for example. An electrode 42 is attached to each electric wire. The tip of the multicore cable 41 is fixed to the tip of the bag 2 .
A plurality of electrodes 42, 42, . The spacing between the electrodes 42 is the same as the spacing between the conductors 3 provided in the bag 2 . The electrodes 42 of the present embodiment are made of metal leaf springs and expand and contract in a direction crossing the length direction of the multicore cable 41 . The electrodes 42 are provided so as to protrude sideways (on the side of the conductors 3 of the bag 2) from the side surfaces of the multicore cable 41 so that they come into contact with the conductors 3 when the bag 2 is inflated. It is configured. That is, the electrode 42 contacts the inner surface of the conductor 3 by its own restoring force (see FIG. 3).

The backflow prevention part 5 can be inserted with the measurement sonde 4, and is fixed to the proximal end of the bag body 2 as shown in FIG. 2(b). FIG. 4 shows the backflow prevention part 5. As shown in FIG. As shown in FIG. 4A, the backflow prevention part 5 is composed of a body part 51 made of a cylindrical member and packers (a first packer 52 and a second packer 53) fixed inside the body part 51. Become. The body portion 51 has an inner diameter through which the measuring sonde 4 can be inserted. In this embodiment, the first packer 52 and the second packer 53 are provided with an interval therebetween. The first packer 52 and the second packer 53 are made of expandable and contractible annular members, and are expanded by forcing fluid into them. The inner diameters of the first packer 52 and the second packer 53 when inflated are equal to or less than the outer diameter of the multicore cable 41, and the first packer 52 and the second packer 53 are in close contact with the multicore cable 41 when they are inflated. As shown in FIG. 4B, when the electrode 42 passes through the first packer 52, the backflow prevention unit 5 of the present embodiment expands the second packer 53 to bring it into close contact with the multicore cable 41. In this state, the first packer 52 is contracted. After the electrode 42 passes through the first packer 52, both packers (the first packer 52 and the second packer 53) are inflated and brought into close contact with the multicore cable 41, as shown in FIG. 4(c). Furthermore, when the electrode 42 moves and passes through the second packer 53, as shown in FIG. The packer 53 is contracted. Then, after the electrode 42 passes through the second packer 53, both packers are expanded and brought into close contact with the multicore cable 41 (see FIG. 4A). In this way, by utilizing the backflow prevention part 5 having the packers arranged in two stages, the leakage (backflow) of the air pressurized into the bag body 2 when the measuring sonde 4 is inserted into the bag body 2 can be prevented. To prevent.

The soil resistivity measuring method according to the present embodiment will be described below. The ground resistivity measuring method includes a drilling process, an insertion process, and a measurement process. FIG. 5 shows the soil resistivity measurement method.
The drilling step is a step of forming a measurement hole 6 in the ground, as shown in FIG. 5(a). The measurement hole 6 is formed by drilling the ground from inside the tunnel pit.
The inserting step is a step of inserting the soil resistivity measuring device 1 (bag body 2 ) into the measurement hole 6 . In the insertion step, first, as shown in FIG. At this time, the bag body 2 is in a contracted state (a state in which the conductors 3 are superimposed). Next, as shown in FIG. 5(c), air is forced into the bag 2 to inflate the bag 2 into a cylindrical shape within the measurement hole 6. Next, as shown in FIG. Since the tip of the multicore cable 41 is fixed to the tip of the bag 2, the measuring sonde 4 is guided inside the bag 2 when the bag 2 is inflated. As the multi-core cable 41 is guided inside the bag 2, the conductor 3 provided in the bag 2 and the electrode 42 provided in the multi-core cable 41 come into contact (FIGS. 2B and 2C). 3).
The measurement step is a step of measuring the resistivity distribution with the soil resistivity measuring device 1 . The resistivity distribution is measured by energizing the multi-core cable 41 while the electrodes 42 and the conductor 3 are in contact with each other, thereby transmitting electrical signals necessary for measurement to the ground.

As described above, according to the soil resistivity measuring device 1 of the present embodiment and the soil resistivity measuring method using the soil resistivity measuring device 1, the bag 2 is inflated in the measurement hole 6 to provide Therefore, even if the direction of the measurement hole 6 is horizontal or vertically upward, the conductor 3 can be arranged at a desired position in contact with the ground without intervening grout or the like. can. As described above, according to the soil resistivity measuring device 1 of the present embodiment, since it is not necessary to fill the surroundings of the soil resistivity measuring device 1 with mortar or the like, it is excellent in workability. In addition, since the conductor 3 directly faces the ground G, it is possible to directly measure the resistivity distribution of the ground G, which in turn enables measurement with higher accuracy.
Further, by inflating the bag 2, the multicore cable 41 is guided into the bag 2, and the electrode 42 fixed to the multicore cable 41 contacts the conductor 3. The measuring sonde 4 can be arranged only by pressurizing air into the bag 2. - 特許庁An electrical signal is supplied to the ground via the electrodes and conductors. Therefore, the labor of the work can be reduced as compared with the conventional measuring method.
In addition, the bag body 2 secures the waterproofness necessary for the measurement.
At the proximal end of the bag body 2, a backflow prevention part 5 is provided to prevent leakage of the air pressurized into the bag body 2, so that air leakage is prevented when the measuring sonde 4 is arranged. there is
Since the measuring sonde 4 having the electrodes 42 is used for measuring the specific resistance value, the measurement can be performed without complicated wiring work. Therefore, it is excellent in workability.

<Second embodiment>
In the second embodiment, as in the first embodiment, a plurality of ground resistivity measuring devices 1 are installed at intervals from the inside of the tunnel in the lateral direction (horizontal) to the upward direction with respect to the analysis area. A description will be given of a case in which a survey is conducted by measuring the electrical resistivity distribution of the ground using a ground surface (see FIG. 1). FIG. 6 shows the soil resistivity measuring device 1 of this embodiment. As shown in FIGS. 6(a) and 6(b), the soil resistivity measuring device 1 includes a bag 2, a plurality of conductors 3, 3, . . . It has an insertable measurement sonde 4 , a backflow prevention part 5 provided at the proximal end of the bag, and a measurement tube 7 .

Details of the bag body 2 are the same as those of the bag body 2 described in the first embodiment, so detailed description thereof will be omitted.
The plurality of conductors 3, 3, . The expansion of the bag 2 causes the conductor 3 to adhere to the second conductor 72 of the measuring tube 7 into which the bag 2 is inserted. Since other details of the conductor 3 are the same as those of the conductor 3 described in the first embodiment, detailed description thereof will be omitted.
Further, details of the measurement sonde 4 and the backflow prevention unit 5 are the same as those described in the first embodiment, so detailed descriptions are omitted.

The measurement pipe 7 is a tubular member made of a material that does not conduct electricity and is provided in the measurement hole 6 formed by drilling the ground. are formed by connecting pipes) 71, 71, . The split pipes 71 are connected via a second conductor 72 . That is, the measuring tube 7 is configured by alternately providing a plurality of split tubes 71, 71, . . . and a plurality of second conductors 72, 72, . The split pipe 71 has the same length as the tubular member 21 that constitutes the bag body 2 . Therefore, the second conductors 72 are arranged at the same intervals as the conductors 3 when the bag 2 is inflated. The second conductor 72 is made of a ring-shaped metal member. The second conductor 72 also faces the inner and outer surfaces of the measuring tube 7 and allows electrical conduction in the radial direction of the measuring tube 7 . The second conductor 72 has an inner diameter that contacts the conductor 3 when the bag 2 is inflated.

The soil resistivity measuring method according to the present embodiment will be described below. The ground resistivity measuring method includes a drilling process, an insertion process, and a measurement process. FIG. 7 shows a soil resistivity measurement method.
The drilling step is a step of forming a measurement hole 6 in the ground, as shown in FIG. 7(a). The measurement hole 6 is formed by drilling the ground from inside the tunnel pit.
The insertion step is a step of inserting the soil resistivity measuring device 1 (the bag 2 ) into the measurement hole 6 . In the inserting step, first, the measuring tube 7 is inserted into the measuring hole 6 as shown in FIG. 7(b). When the measuring tube 7 is inserted into the measuring hole 6 , the second conductor 72 contacts the hole wall of the measuring hole 6 . After inserting the measuring tube 7 into the measuring hole 6, the soil resistivity measuring device 1 is set at the proximal end of the measuring tube 7 (the opening of the measuring hole 6), as shown in FIG. 7(c). At this time, the bag body 2 is in a contracted state (a state in which the conductors 3 are superimposed). Next, as shown in FIG. 7(d), air is injected into the bag body 2 to inflate the bag body 2 into a cylindrical shape within the measuring tube 7. Next, as shown in FIG. When the bag 2 expands, the conductor 3 is guided into the measuring tube 7 as the bag 2 expands in the measuring tube 7, and the conductor 3 and the second conductor 72 come into contact with each other. Further, when the bag body 2 expands, the measuring sonde 4 having the tip end of the multicore cable 41 fixed to the tip end of the bag body 2 is guided into the bag body 2 . As the multicore cable 41 is guided inside the bag 2, the conductor 3 provided in the bag 2 and the electrode 42 provided in the multicore cable 41 come into contact (see FIG. 2(b)). .
The measurement step is a step of measuring the resistivity distribution with the soil resistivity measuring device 1 . The resistivity distribution is measured by energizing the multi-core cable 41 while the electrode 42 and the second conductor 72 are in contact with each other via the conductor 3, thereby transmitting an electric signal necessary for measurement to the ground. by

As described above, according to the soil resistivity measuring device 1 of the present embodiment and the soil resistivity measuring method using the soil resistivity measuring device 1, by inserting the measuring tube 7 into the measuring hole 6, the soft ground Even if there is, it is possible to measure the resistivity distribution of the ground while suppressing collapse of the hole wall.
In addition, since the measuring pipe 7 is directly press-fitted into the ground G, there is no need to fill the circumference of the measuring pipe 7 with a filler material, which is excellent in workability. In addition, since the measurement pipe 7 is directly arranged in the ground G, the second conductor 72 directly faces the ground G, and direct measurement of the resistivity distribution of the ground G is possible. Measurement with higher accuracy becomes possible.
In addition, the water cutoff required for measurement is ensured by the measurement tube 7 .
Since the effects of the soil resistivity measuring device 1 and the soil resistivity measuring method of the second embodiment are the same as those shown in the first embodiment, detailed description thereof will be omitted.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the constituent elements described above can be modified as appropriate without departing from the scope of the present invention.
The ground resistivity measuring device 1 may be installed facing the face of the tunnel T, and the installation direction is not limited.
The material constituting the bag body 2 is not limited to vinyl chloride resin as long as it is non-conductive and expandable/contractible by compressed air. may be Alternatively, the hose may be a chemical fiber hose provided with a ring-shaped cross-section retaining member that preferentially expands in the direction of insertion as compressed air is enclosed.
The shape of the conductor 3 is not limited to a ring shape as long as it is possible to ensure the conduction of electricity to the inside and outside of the bag. good too.

In the above embodiment, the case of pressurizing air into the bag body 2 has been described, but the fluid injected into the bag body 2 when inflating the bag body 2 is not limited to air.

1 soil resistivity measuring device 2 bag 3 conductor 4 measurement sonde 41 multicore cable 42 electrode 5 backflow prevention part 51 body part 52 first packer 53 second packer 6 measurement hole 7 measurement tube 72 second conductor T tunnel

Claims (5)

a bag;
a plurality of conductors provided in the bag;
A soil resistivity measuring device comprising a measuring sonde that can be inserted into the bag,
The bag expands into a columnar shape by pressurizing a fluid into the bag,
The plurality of conductors face the inner surface and the outer surface of the bag and are provided at intervals in the length direction of the bag,
The measuring sonde consists of a multicore cable and a plurality of electrodes provided on the multicore cable,
The tip of the multicore cable is fixed to the tip of the bag,
When the bag is inflated, the multi-core cable is guided into the bag, and the electrode and the conductor are configured to abut against each other. Device. 2. The soil resistivity measuring apparatus according to claim 1, wherein a backflow prevention part through which said measuring sonde can be inserted is provided at the base end of said bag. further comprising a measuring tube into which the bag can be inserted;
The measuring tube is provided with a plurality of second conductors facing the inner surface and the outer surface of the measuring tube,
3. The soil specific resistance measuring device according to claim 1, wherein the conductor and the second conductor are configured to come into contact with each other when the bag is inflated. A drilling step of forming a measurement hole in the ground;
an inserting step of inserting the soil resistivity measuring device according to any one of claims 1 to 3 into the measurement hole;
A soil resistivity measuring method comprising a measuring step of measuring a resistivity distribution with the soil resistivity measuring device,
In the inserting step, a fluid is pressurized into the bag to expand the bag into a columnar shape in the measurement hole, thereby guiding the probe for measurement inside the bag, and A soil resistivity measuring method, characterized in that the electrodes are brought into contact with each other. In the inserting step, before pressurizing the fluid into the bag, a measurement tube capable of inserting the bag is inserted into the measurement hole,
The measuring tube is provided with a plurality of second conductors facing the inner surface and the outer surface of the measuring tube,
5. The ground according to claim 4, characterized in that by pressurizing a fluid into the bag, the bag is expanded within the measurement tube, and the conductor and the second conductor are brought into contact with each other. Resistivity measurement method.

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