JP2006119096A - Electrode cable for measuring specific resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To execute a specific resistance tomography method or electric logging even in a bored hole wherein in-hole water is absent. <P>SOLUTION: This electrode cable 1 inserted in the bored hole 2 has: a cable body 3 wherein a large number of conducting wires 6 are bundled; electrodes 4 installed to the cable body 3 at prescribed intervals apart from each other; and a plurality of electroconductive elastic bodies 5 radially spreading in the radial direction of the cable body 3 from the electrodes 4. The number of the bundled conducting wires 6 is equal to the number of the electrodes 4, and the electrode 4 is electrically conducted to the conducting wire 6 different from the other electrode 4. The electroconductive elastic body 5 spreads more largely than a hole diameter of the borehole 2, and contacts with the inner wall face 2a of the bored hole 2 while elastically deformed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrode cable for measuring specific resistance. More specifically, the present invention relates to an electrode cable for measuring specific resistance suitable for performing a specific resistance tomography method and an electric logging on an anhydrous boring hole.

  There are electrical logging and resistivity tomography as measurement means for grasping the rock characteristics and the extent of the drilling affected area of the borehole. In general, electrical logging and resistivity tomography methods insert an electrode for resistivity measurement into a borehole where groundwater exists, and ensure electrical continuity between the electrode and the ground via the borehole water. Measure the resistivity of the ground.

  For example, there is a technique disclosed in Japanese Patent Laid-Open No. 2002-267664 as an electric logging. This technique is an electric logging for a horizontal borehole, and a measuring apparatus for performing the electric logging method is shown in FIGS. An electrode rod 103 having an electrode portion 102 at its tip is extended in the casing rod 101, and the horizontal boring hole 104 is drilled to a predetermined depth in the ground in front of the tunnel face by the rotational driving force applied to the casing rod 101. Next, the mouth of the horizontal boring hole 104 is closed with the mouth cap 105, the inside of the hole is filled with inflow groundwater, and the electric logging measuring device 106 installed in the tunnel mine via the tunnel side end of the electrode rod 103 is used. The electrode part 102 wired in the above is protruded from the tip of the casing rod 101 into the boring hole 104. Thereby, the specific resistance of the ground is measured between the ground electrode 107 connected to the electrical logging measuring device 106, and electrical logging is performed at the position of the electrode portion 102.

Japanese Patent Laid-Open No. 2002-267664

  However, the electrical logging and resistivity tomography methods described above ensure electrical continuity between the ground and the electrode through the borehole water, so that the borehole where no borehole water exists, for example, upward from the tunnel wall in the tunnel For the borehole drilled in the borehole, the hole section above the groundwater surface of the borehole, etc., it was difficult to ensure the electrical connection between the hole wall surface and the electrode, and it was difficult to measure the specific resistance.

  Further, the measuring apparatus shown in FIGS. 7 and 8 has the same problem. That is, the horizontal boring hole 104 is not filled with groundwater when drilling, but the inflowing groundwater is blocked by the mouth cap 105 when measuring the specific resistance so that the horizontal boring hole 104 is filled with groundwater. Since continuity with the hole wall surface is ensured, if groundwater flows out from a crack or the like in the borehole and the borehole 104 cannot be filled with groundwater, the continuity between the electrode portion 102 and the hole wall surface cannot be ensured. It was difficult to measure resistance.

  An object of the present invention is to provide a specific resistance measurement electrode cable capable of ensuring electrical connection between an inner wall surface of a boring hole and an electrode even in a boring hole in which water in the hole does not exist.

  In order to achieve the above object, an electrode cable for measuring resistivity according to claim 1 is inserted into a boring hole, and a cable body in which a large number of conducting wires are bundled, and an electrode attached to the cable body at a predetermined interval. And a plurality of conductive elastic bodies extending radially from the electrode in the radial direction of the cable body, the conductive wires are bundled at least in the same number as the electrodes, and the electrodes are electrically connected to different conductive wires from the other electrodes. The elastic elastic body comes into contact with the inner wall surface of the borehole while being elastically deformed.

  Therefore, when the electrode cable is inserted into the boring hole, the conductive elastic body comes into contact with the inner wall surface of the boring hole, and conducts the electrode and the inner wall surface. A plurality of conductive elastic bodies are provided, radially extending from the electrode and larger than the hole diameter of the borehole unless pressed down, and therefore always contact the inner wall surface of the borehole. Moreover, since the conductive elastic body comes into contact with the inner wall surface of the boring hole while being elastically deformed, good conduction with the inner wall surface can be ensured. In order to insert the electrode cable into the boring hole, for example, the tip of the electrode cable is hooked on the tip of the rod, and the entire rod is inserted into the boring hole. On the other hand, by pulling out the electrode cable together with the rod from the boring hole, the electrode cable can be recovered from the boring hole. The conductive elastic body is in contact with the inner wall surface of the boring hole. However, since the conductive elastic body is provided in a radial manner, the contact with the inner wall surface is small because of partial contact in the circumferential direction of the electrode. . Further, since the conductive elastic body is an elastic body, it is elastically deformed according to the movement of the cable body and the electrode. For these reasons, the resistance force when the electrode cable is inserted into the boring hole or recovered from the boring hole is small. A cable main body in which a large number of conducting wires are bundled is provided with a large number of electrodes. However, since the conducting wires and the electrodes correspond one-to-one, it is possible to select an electrode to be used for measurement by selecting a conducting wire. it can.

  The electrode cable for measuring specific resistance according to claim 2, wherein the conductive elastic body has a plurality of metal springs projecting radially from the electrode, and a metal thread-like member assembly covering at least the tip of the metal spring. It is what has.

  Therefore, conduction between the electrode and the inner wall surface of the boring hole is ensured through the metal spring and the metal thread-like member assembly. The conductive elastic body is in contact with the inner wall surface of the boring hole at its tip, but since at least the tip of the metal spring is covered with the metal thread-like member assembly, the contact area with the inner wall surface of the boring hole is reduced. Can be bigger.

  Furthermore, the electrode cable for measuring specific resistance according to claim 3 is obtained by impregnating a metal thread-like member assembly with salt water. Therefore, in addition to direct contact between the metal thread-like member aggregate and the inner wall surface of the boring hole, conduction between the metal thread-like member aggregate and the inner wall surface of the boring hole is ensured even through salt water. Brine is held in the gap in the metal thread-like member assembly.

  The electrode cable for measuring specific resistance according to claim 1, wherein the cable body is inserted into the boring hole and bundled with a large number of conductors, the electrode is attached to the cable body at a predetermined interval, and the diameter of the cable body from the electrode A plurality of conductive elastic bodies that radiate in the direction are provided, and the conductive wires are bundled at least as many as the electrodes, the electrodes are connected to different conductive wires from the other electrodes, and the conductive elastic bodies are elastically deformed Since contact is made with the inner wall surface of the borehole, electrical connection between the inner wall surface of the borehole and the electrode can be ensured satisfactorily. For this reason, electrical connection between the electrode and the inner wall surface can be easily ensured even for a boring hole in which no water in the hole exists, and electric logging and specific resistance tomography can be performed. In addition, since the resistance force when the electrode cable is inserted into the boring hole or recovered from the boring hole is small, it is easy to install and recover the electrode cable. Also, even if the electrode cable is lengthened, the resistance force at the time of insertion or recovery does not become so large, so that the electrode cable can be lengthened and can cope with deep boring holes.

  Further, in the electrode cable for measuring specific resistance according to claim 2, the conductive elastic body includes a plurality of metal springs projecting radially from the electrode, and a metal thread-like member assembly covering at least the tip of the metal spring. Therefore, the contact area between the conductive elastic body and the inner wall surface of the boring hole can be increased, and better conduction can be ensured.

  Furthermore, in the electrode cable for measuring the specific resistance according to claim 3, since salt water is infiltrated into the metal thread-like member assembly, in addition to direct contact between the metal thread-like member assembly and the inner wall surface of the borehole. Even through salt water, electrical conduction between the metal thread-like member assembly and the inner wall surface of the boring hole can be secured, and even better electrical conduction can be secured.

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

  1 to 3 show an example of an embodiment of an electrode cable for measuring specific resistance according to the present invention. An electrode cable (hereinafter simply referred to as an electrode cable) 1 for measuring a specific resistance is inserted into a boring hole 2 and a cable body 3 in which a large number of conducting wires 6 are bundled, and an electrode attached to the cable body 3 at a predetermined interval. 4 and a plurality of conductive elastic bodies 5 extending radially from the electrode 4 in the radial direction of the cable body 3.

  The same number of conductors 6 as the electrodes 4 are bundled. That is, the cable body 3 is a multi-core cable in which the same number of conductive wires 6 as the electrodes 4 are bundled, and the conductive wires 6 are insulated from the other conductive wires 6. In the present embodiment, 30 electrodes 4 are provided, for example, at intervals of 25 cm, so that the cable body 3 is configured by bundling 30 coated conductors 6. However, the distance between the electrodes 4 is not limited to 25 cm, and may be appropriately determined according to the depth of the boring hole 2 or the like. Further, the number of the electrodes 4 and the number of the conductive wires 6 are not limited to 30, and may be appropriately determined according to the depth of the boring hole 2 or the like. However, the measurement of specific resistance requires at least two electrodes 4 serving as current electrodes and two electrodes 4 serving as potential electrodes.

  The electrode 4 is electrically connected to a conductive wire 6 different from the other electrodes 4. That is, the conducting wire 6 and the electrode 4 have a one-to-one correspondence.

  The conductive elastic body 5 extends larger than the hole diameter of the boring hole 2 and contacts the inner wall surface 2a of the boring hole 2 while being elastically deformed. For example, when the hole diameter of the boring hole 2 is 101 mm, the conductive elastic body 5 preferably spreads at least 160 mm (dimension d in FIG. 3). However, it goes without saying that the size at which the conductive elastic body 5 spreads is not limited to this value.

  In the present embodiment, each electrode 4 has four conductive elastic bodies 5 that spread radially at equal intervals in the radial direction of the cable body 3, in other words, four conductive elastic bodies 5 arranged in a cross shape. Yes. However, the number of the conductive elastic bodies 5 is not limited to four, and may be plural. For example, as shown in FIG. 4, you may have the three electroconductive elastic bodies 5 which spread radially at equal intervals in the radial direction of the cable main body 3, or, as shown in FIG. You may have two electroconductive elastic bodies 5 which spread in the direction radially at equal intervals, in other words, you may have two electroconductive elastic bodies 5 arranged in a straight line, and also 5 or more electroconductive elastic bodies 5 You may have. That is, if each electrode 4 has two or more conductive elastic bodies 5, at least one conductive elastic body 5 can be brought into contact with the inner wall surface 2a of the boring hole 2 to make them conductive. However, since the resistance force and the manufacturing cost when the electrode cable 1 is inserted into the boring hole 2 or recovered from the boring hole 2 are increased in accordance with the increase in the number of the conductive elastic bodies 5, It is preferable to determine the number of conductive elastic bodies 5 in consideration of the magnitude of the resistance force, the manufacturing cost, and the like.

  The conductive elastic body 5 includes, for example, a plurality of metal springs 7 that project radially from the electrode 4 and a metal thread-like member assembly 8 that covers at least the tip of the metal spring 7. The metal spring 7 is, for example, a coil spring. However, the metal spring 7 is not limited to a coil spring, and may be, for example, a leaf spring that bends in the axial direction of the cable body 3. The metal thread-like member assembly 8 is made of, for example, three-dimensionally knitted thread-like aluminum, and for example, a metal scrubber can be used. In the present embodiment, the metal thread-like member assembly 8 covers the vicinity of the base of the metal spring 7. Further, all metal springs 7 are covered with a metal thread-like member assembly 8. By covering the metal spring 7 with the metal thread-like member assembly 8, the contact area with the inner wall surface 2a of the boring hole 2 can be increased, and the contact resistance can be reduced to ensure better conduction. can do.

  The metal thread-like member assembly 8 is soaked with salt water. For this reason, in addition to direct contact between the metal thread-like member assembly 8 and the inner wall surface 2a of the boring hole 2, conduction between the metal thread-like member assembly 8 and the inner wall surface 2a of the boring hole 2 can be achieved even through salt water. It can be ensured, contact resistance can be further reduced, and even better conduction can be ensured. The metal thread-like member assembly 8 can hold salt water in the internal gap, and can maintain good conduction for a long time.

  The electrode cable 1 is used by being inserted into the boring hole 2. In order to insert the electrode cable 1 into the boring hole 2, for example, a rod 9 is used. The rod 9 is, for example, a PVC pipe. The tip of the electrode cable 1 is hooked on the tip of the rod 9 and the rod 9 is inserted into the boring hole 2. In a state before being inserted into the boring hole 2, the conductive elastic body 5 is wider than the hole diameter of the boring hole 2, but since the conductive elastic body 5 is elastically deformed, the electrode cable 1 is inserted into the boring hole 2. be able to. The conductive elastic body 5 spreads in the boring hole 2 and always comes into contact with the inner wall surface 2a. Moreover, since the conductive elastic body 5 is strongly in contact with the inner wall surface 2a of the boring hole 2 by its elastic force, it is possible to ensure good conduction with the inner wall surface 2a. For this reason, the electrode 4 and the inner wall surface 2a of the borehole 2 are also present in the bore section 2 above the groundwater surface of the borehole, or in the borehole 2 where there is no borehole water such as a borehole drilled upward from the tunnel borehole wall. Can be reliably and easily ensured, and electrical logging and specific resistance tomography can be performed.

  In addition, about the boring hole 2 in which the water in a hole does not exist, it is also considered that water is forced into the boring hole 2 to ensure electrical connection between the electrode 4 and the inner wall surface 2a. The natural state will be destroyed, making it difficult to obtain a correct measurement result in the natural state. In the present invention, the specific resistance can be measured as it is with respect to the boring hole 2 in which no water in the hole exists, and a correct measurement result in a natural state can be obtained.

  By inserting the electrode cable 1 to a predetermined depth of the boring hole 2, for example, 30 electrodes 4 can be arranged at intervals of 25 cm and conducted to the inner wall surface 2 a of the boring hole 2.

  On the other hand, the electrode cable 1 can be recovered from the boring hole 2 by pulling out the electrode cable 1 together with the rod 9 from the boring hole 2.

  Although the conductive elastic body 5 is in contact with the inner wall surface 2a of the boring hole 2, the conductive elastic body 5 is provided in a radial manner and is in partial contact with respect to the circumferential direction of the electrode 4. The contact area with 2a is small. Further, since the conductive elastic body 5 is an elastic body, it is elastically deformed according to the movement of the cable body 3 and the electrode 4. Therefore, the resistance force when the electrode cable 1 is inserted into the boring hole 2 or recovered from the boring hole 2 is small, and the electrode cable 1 can be easily inserted and recovered. Moreover, even if the electrode cable 1 is lengthened, the resistance force at the time of insertion or recovery does not increase so much, so that the electrode cable 1 can be lengthened and the deep boring hole 2 can be dealt with.

  A specific resistance measuring device (not shown) is connected to the proximal end of the electrode cable 1. The specific resistance measuring apparatus has, for example, 30 connection terminals, and the conductive wires 6 of the cable body 3 are connected to separate connection terminals one by one. The specific resistance measuring device selects the electrode 4 to be used for measurement by selecting the connection terminal. That is, the specific resistance measuring device selects two connection terminals for supplying current and two connection terminals for measuring potential under computer control, and measures the specific resistance by sequentially switching these combinations.

  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 conductive elastic body 5 is composed of the metal spring 7 and the metal thread-like member assembly 8, but the metal spring 7 allows conduction between the inner wall surface 2 a of the boring hole 2. If it can be secured, the metal thread-like member assembly 8 may be omitted. An example of the conductive elastic body 5 in which the metal thread-like member assembly 8 is omitted is shown in FIG.

  Further, in the above description, all the metal springs 7 are covered with the metal thread-like member aggregate 8, but it is not necessary to cover all the metal springs 7 with the metal thread-like member aggregate 8, and the metal thread-like shape is not necessary. The metal spring 7 covered with the member assembly 8 and the metal spring 7 not covered with the metal thread-like member assembly 8 may be mixed. By omitting the coating of the metal thread-like member aggregate 8 on some of the metal springs 7, the metal thread-like member aggregate is secured while ensuring the conductivity between the conductive elastic body 5 and the inner wall surface 2 a of the boring hole 2. 8 can be used to reduce the manufacturing cost.

  In the above description, the metal thread-like member assembly 8 covers the vicinity of the base of the metal spring 7. However, only the tip of the metal spring 7 may be covered with the metal thread-like member assembly 8. good. Also in this case, the manufacturing cost can be reduced by reducing the amount of the metal thread-like member assembly 8 used while ensuring the conductivity between the conductive elastic body 5 and the inner wall surface 2a of the boring hole 2.

It is a side view of the state which showed an example of embodiment of the electrode cable for specific resistance measurement of this invention, and was inserted in the boring hole. It is a side view of the state before showing an example of embodiment of the electrode cable for specific resistance measurement of this invention, and inserting in a boring hole. It is sectional drawing which follows the III-III line of FIG. FIG. 5 is a cross-sectional view illustrating a first modification of the conductive elastic body and corresponding to FIG. 3. It is sectional drawing corresponding to FIG. 3 which shows the 2nd modification of an electroconductive elastic body. FIG. 10 is a cross-sectional view corresponding to FIG. 3, showing a third modification of the conductive elastic body. It is sectional drawing of the measuring apparatus which implements the conventional electric logging. It is a fragmentary sectional view of the casing rod of the measuring device which performs the conventional electric logging.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrode cable 2 Boring hole 2a Inner wall surface 3 of boring hole 4 Cable main body 4 Electrode 5 Conductive elastic body 6 Conductor 7 Metal spring 8 Metal thread-like member aggregate

Claims (3)

  A cable body inserted into the boring hole and bundled with a large number of conductors; an electrode attached to the cable body at a predetermined interval; and a plurality of conductive elastic bodies extending radially from the electrode in a radial direction of the cable body The conductive wires are bundled at least as many as the electrodes, the electrodes are connected to different conductive wires from the other electrodes, and the conductive elastic body is elastically deformed on the inner wall surface of the boring hole. An electrode cable for measuring specific resistance characterized by contact.   2. The ratio according to claim 1, wherein the conductive elastic body includes a plurality of metal springs projecting radially from the electrode and a metal thread-like member assembly covering at least a tip portion of the metal spring. Electrode cable for resistance measurement.   3. The electrode cable for measuring resistivity according to claim 2, wherein the metal thread-like member aggregate is impregnated with salt water.

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