Probe for measuring ground resistivity

Abstract

An object of the present invention is to provide a probe for measuring the specific resistance of the ground, which can more reliably measure the specific resistance of the ground and improve the durability against friction and the like. 【Means for solving the problem】 The probe 1 for measuring the specific resistance of the ground includes a probe body 20 having a cylinder portion 201 and a columnar portion 202, a push rod 30, a piston portion 40 connected to the lower end of the push rod 30, and an electrode 60 fixed only to the piston portion 40. When the push rod 30 is pushed downward, the piston portion 40 moves downward in the cylinder portion 201, and the tip of the electrode 60 protrudes outward from the side surface of the columnar portion 202.

Description

Technical Field

[0001] The present invention relates to a probe for measuring ground resistivity.

Background Art

[0002] Conventionally, a ground investigation has been carried out to measure the electrical resistivity and determine the ground properties by using a bored hole excavated in the ground. For this measurement of the electrical resistivity, a probe for measuring ground resistivity equipped with electrodes is used.

[0003] This probe for measuring ground resistivity equipped with electrodes needs to bring the electrodes into contact with the wall surface of the bored hole. For example, the invention described in Patent Document 1 is provided with a contact promoting convex portion protruding outward to bring the outer electrode into contact with the hole wall.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] However, when moving inside the bored hole with the electrodes in contact with the wall surface, wear occurs on the convex portion, and there is a problem with the durability of the electrodes.

[0006] In addition, since the wall surface of the bored hole is covered with earth and sand, etc., there are irregularities. For this reason, there is also a problem that the electrodes may not come into contact with the wall surface, and the resistivity of the ground cannot be measured.

Summary of the Invention

Problems to be Solved by the Invention

[0007] Therefore, an object of the present invention is to provide a probe for measuring ground resistivity that allows the electrodes to protrude only when measuring the resistivity of the ground, can more reliably measure the resistivity of the ground, and improves durability.

Means for Solving the Problems

[0008] The probe for measuring ground specific resistance according to claim 1 comprises a hollow rod extending in the vertical direction, a probe body connected to the lower end of the rod, a push rod that can move up and down within the hollow of the rod, a piston portion connected to the lower end of the push rod, and a bendable rod-shaped electrode, a part of which is fixed to the piston portion. The probe body has a cylinder portion in which the piston portion is accommodated so as to be movable up and down, and a columnar portion in which an electrode guide portion for guiding the movement of the electrode is formed inside. When the push rod is pushed downward, the electrode of a desired length is configured to protrude outward from the side surface of the columnar portion.

[0009] The probe for measuring ground specific resistance according to claim 2 comprises a hollow rod extending in the vertical direction, a probe body connected to the lower end of the rod, a push rod that can move up and down within the hollow of the rod, a piston portion connected to the lower end of the push rod, and a bendable rod-shaped electrode, a part of which is fixed to the piston portion. The probe body has a cylinder portion in which the piston portion is accommodated so as to be movable up and down, and a columnar portion in which an electrode guide portion for guiding the movement of the electrode is formed inside. The electrode guide portion penetrates from the upper surface of one side of the columnar portion divided in the left-right direction to the side surface of the other side of the divided columnar portion. When the piston portion is located at the uppermost part of the range in which it moves up and down within the cylinder portion, the tip of the electrode is arranged in front of the side surface of the other side of the divided columnar portion.

[0010] The probe for measuring the ground specific resistance according to claim 3 includes a hollow rod extending in the vertical direction, a probe body connected to the lower end of the rod, a push rod that can move up and down within the hollow of the rod, a piston portion connected to the lower end of the push rod, and a bendable rod-shaped electrode partially fixed to the piston portion. The probe body has a cylinder portion in which the piston portion is accommodated so as to be movable up and down, and a columnar portion in which an electrode guide portion for guiding the movement of the electrode is formed inside. The electrode guide portion penetrates from the upper surface of one of the two divided portions in the left-right direction of the columnar portion to the side surface of the other of the two divided portions. When the push rod is pushed downward, the electrode pops out to the outside from the electrode guide portion, and a restricting portion for restricting the movement of the piston portion is provided in the cylinder portion so that the length by which the electrode pops out is the same as the distance by which the piston portion can move up and down within the cylinder portion.

[0011] The probe for measuring the ground specific resistance according to claim 4 is the probe for measuring the ground specific resistance according to claim 2 or 3, wherein a plurality of the electrode guide portions are provided, each having a curvature radius of 35 mm or more and being curved, and one end portion of each of the plurality of electrode guide portions is arranged in a row in an oblique direction with respect to the vertical direction on the side surface of the columnar portion.

[0012] The probe for measuring the ground specific resistance according to claim 5 is the probe for measuring the ground specific resistance according to claim 2 or 3, wherein a plurality of the electrode guide portions are provided, each having the same curvature radius of 35 mm or more and being curved, and one end portion of each of the plurality of electrode guide portions is arranged in a row in an oblique direction with respect to the vertical direction on the side surface of the columnar portion.

Advantages of the Invention

[0013] The probe for measuring the ground specific resistance according to the present invention can more reliably measure the specific resistance of the ground and improve durability because the electrode pops out only when measuring the specific resistance of the ground.

Brief Description of the Drawings

[0014]

Figure 1

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Figure 9

Mode for Carrying Out the Invention

[0015] A detailed embodiment of the probe for measuring ground resistivity according to the present invention will be described with reference to the drawings.

[0016] The probe 1 for measuring ground specific resistance according to the present invention includes, as shown in FIGS. 1 to 3, a plurality of hollow rods 10 detachably connected in the vertical direction (Y direction), a probe body 20 detachably connected in the vertical direction to the lower end of the lowermost rod 10 among the plurality of rods 10 connected in the vertical direction, a push rod 30 passing through the hollow of the rod 10 and capable of reciprocating in the vertical direction (Y direction) within the hollow of the rod 10, a piston portion 40 connected to the lower end of the push rod 30, a cable 50 passing through the hollow of the rod 10 so as to penetrate the rod 10, and a bendable rod-shaped electrode 60 connected to the tip of the cable 50. A piston portion 40 is attached to the lower end of the push rod 30, and the piston portion 40 moves up and down (slides) in conjunction with the up and down movement of the push rod 30. The cable 50 is accommodated in the hollow of the rod 10 along the push rod 30 without being fixed. The electrode 60 is fixedly attached only to the piston portion 40 and is accommodated in the probe body 20.

[0017] The rod 10 is a hollow cylinder extending in the vertical direction (Y direction), and a plurality of rods 10 can be added in the vertical direction (Y direction). Also, both the upper and lower ends of the rod 10 are open, and the push rod 30 and the cable 50 can penetrate into the hollow of the cylinder.

[0018] The push rod 30 is composed of a plurality of rod-shaped bodies made of metal or resin with an outer diameter smaller than the inner diameter of the hollow of the rod 10. A connecting member for connecting the rod-shaped bodies in the vertical direction (Y direction) is formed on the push rod 30, and the rod-shaped bodies can be added in the vertical direction (Y direction) through this connecting member. Also, a connecting member for connecting to the piston portion 40 is formed on the lowermost rod-shaped body among the rod-shaped bodies added in the vertical direction (Y direction). The connection is performed by fitting, screwing, etc.

[0019] The piston portion 40 is made of an electrically insulating material such as polycarbonate resin and is formed in a cubic or rectangular parallelepiped shape.

[0020] The push rod 30 and the piston portion 40 may be integrally formed. Also, the push rod 30 and the piston portion 40 may be detachably connected. For example, as shown in FIGS. 8 and 9, a screw hole 40a formed in the center of the piston portion 40 and a screw portion 30a formed at the tip of the push rod 30 are screwed together, whereby the push rod 30 and the piston portion 40 are detachably connected.

[0021] Further, the piston portion 40 is provided with a plurality of through holes 40h penetrating from the upper surface to the lower surface in a region excluding the vicinity of the center of the upper surface. One electrode 60 is inserted into one through hole 40h.

[0022] The cable 50 extends to the ground through the hollow of the rod 10. One end on the ground side is connected to a measuring device or a discrimination device (not shown), and the other end (tip) is connected to the electrode 60 via a coaxial connector or the like (not shown). Note that it is desirable to use a coaxial cable for the cable 50.

[0023] The electrode 60 uses a piano wire, a stainless steel spring wire, or the like having high hardness (high strength) and a strong restoring force. When using a piano wire for the electrode, it is desirable to have a diameter of 0.7 mm or more. The electrode 60 has a predetermined length, and one end is fixedly attached near the upper part (upper surface side) of the through hole 40h formed in the piston portion 40 and is housed in the probe body 20. The fixing method may be an adhesive fixing or other general methods. Since the electrode 60 is fixedly attached to the piston portion 40, the electrode 60 also moves in conjunction with the vertical movement of the piston portion 40.

[0024] The probe body 20 includes a cylinder portion 201 having an internal space in which the piston portion 40 can slide in the vertical direction (Y direction), a columnar portion 202 that allows the movement of the electrode 60 while restricting the downward movement of the piston portion 40, and a cone portion 203 that tapers toward the tip. The probe body 20 is made of an electrically insulating material such as polycarbonate resin or glass epoxy resin. Also, the probe body 20 can use a metal material such as stainless steel that is coated or surface-treated with an electrically insulating material. Note that the cylinder portion 201 and the columnar portion 202 may be integrally formed, or the cylinder portion 201 and the columnar portion 202 may be connected by screwing, adhesion, or the like.

[0025] The cylinder portion 201 is open upward and is configured to allow the piston portion 40 to be inserted from above. The cylinder portion 201 has an internal space in which the piston portion 40 can reciprocate in the vertical direction (Y direction) within the cylinder portion 201. The depth within the cylinder portion 201 is preferably 5 mm to 25 mm longer than the maximum distance that the piston portion 40 reciprocates in the vertical direction (Y direction).

[0026] At the bottom of the cylinder portion 201, a waterproof packing 204 made of an insulator is attached. The packing 204 is formed with a plurality of through holes 201h penetrating in the vertical direction (Y direction) so that the electrode 60 can move in the vertical direction (Y direction). The diameter of the through hole 201h is preferably the same as the diameter of the electrode 60 or slightly smaller than the thickness of the electrode 60 in order to block the intrusion of water and mud into the interior of the cylinder portion 201. Also, the packing 204 may be provided not at the bottom of the cylinder portion 201 but between the cylinder portion 201 and the columnar portion 202.

[0027] The columnar portion 202 is formed internally with a plurality of electrode guide portions 205 corresponding to the number of electrodes 60 (4 electrodes are used in the four-electrode method in FIG. 2). One electrode 60 can be inserted into each electrode guide portion 205, and the electrode 60 can move freely within the electrode guide portion 205.

[0028] As shown in FIG. 4, when the electrode guide portion 205 bisects the columnar portion 202 in the left - right direction (X - direction) (the hatching represents the cross - section when bisected), it penetrates through the inside of the columnar portion 202 from the upper surface 202a on one side of the bisection to the side surface 202b on the other side of the bisection. More specifically, assuming that the electrode guide portion 205 bisects the columnar portion 202 with a straight line L passing through the center O1 of the upper surface and the center O2 of the lower surface of the columnar portion 202 without separating the two, an upper - surface - side hole portion 205c is provided on the upper surface 202a on one side of the bisected columnar portion 202, and a side - surface - side hole portion 205d is provided on the side surface 202b on the other side of the bisection (the surface facing the cross - section when bisected). It penetrates through the inside of the columnar portion 202 from the upper - surface - side hole portion 205c to the side - surface - side hole portion 205d. The electrode guide portion 205 is curved within the columnar portion 202 with a predetermined radius of curvature (curved portion 205b), and it is desirable that the radius of curvature is 35 mm or more. Also, the inner diameter of the electrode guide portion 205 should be such that the electrode 60 can move smoothly when inserted and is not easily penetrated by earth and sand.

[0029] Each of the upper-side hole portions 205c and the side-surface hole portions 205d is provided in plurality corresponding to the number of the electrodes 60. The plurality of upper-side hole portions 205c are arranged in a row on the upper surface 202a of one side of the bifurcated columnar portion 202. On the other hand, the plurality of side-surface hole portions 205d (one end portion of the electrode guide portion 205) are arranged at a predetermined interval in a row in an oblique direction with respect to the vertical direction (Y direction) along the side surface 202b of the other side of the bifurcated columnar portion 202. By arranging them obliquely in this way, the radius of curvature can be increased as compared with the case where they are arranged in a row in the vertical direction (Y direction). As a result, the electrode 60 can be moved smoothly, and the risk of damage to the electrode 60 and the electrode guide portion 205 can be reduced. Further, it is more desirable that the radius of curvature of the curved portion 205b is the same for all. That is, it is more desirable that the plurality of electrode guide portions 205 each consist of a straight portion 205a having a different length and a curved portion 205b that curves with the same radius of curvature for all. This is because among those with a small radius of curvature and those with a large radius of curvature, the smaller the radius of curvature, the easier it is for the electrode to be distorted. Therefore, if distortion occurs in even one of the plurality of electrodes, the durability will be lacking. Therefore, by making the radius of curvature of all the curved portions 205b the same, the bending stress generated by the bending acting on each electrode 60 can be made equal, and the durability can be further improved. Note that it is desirable that the side-surface hole portions 205d are arranged so as to be aligned in a row at an angle of 20 degrees to 40 degrees with respect to the vertical direction (Y direction). Further, among the side-surface hole portions 205d (the portions located on the side surface of the columnar portion 202 among the plurality of electrode guide portions 205), the interval between two adjacent electrode guide portions 205 is desirably in the range of 5 mm to 30 mm, and more desirably 10 mm.

[0030] In such a configuration, the electrode 60, one end of which is fixedly attached to the piston portion 40, passes through the through hole formed in the packing 204, is inserted from the upper surface of one of the two divided parts, is guided by the electrode guide portion 205, and is arranged such that the other end reaches in front of the side surface of the columnar portion 202. At this time, as shown in FIG. 3, the piston portion 40 is located at the uppermost position within the range of moving up and down within the cylinder portion 201. Then, when the push rod 30 is pushed downward, the piston portion 40 attached to the lower end of the push rod 30 moves (slides) downward within the cylinder portion 201. Then, as shown in FIG. 5, the electrode 60 fixedly attached to the piston portion 40 also moves downward in conjunction, and the tip of the electrode 60 arranged in front of the side surface side hole portion 205d (side surface of the columnar portion 202) pops out outward from the side surface side hole portion 205d (side surface of the columnar portion 202).

[0031] At this time, the tip of the electrode 60 needs to protrude so that it reaches the inner surface of the excavation hole. Therefore, a restricting portion is provided inside the cylinder portion 201 to limit the movement of the piston portion 40 so that the desired length by which the electrode 60 protrudes is the same as the distance (the vertical distance of the up-and-down movement) that the piston portion 40 can move within the internal space of the cylinder portion 201. For example, as shown in FIG. 6, after providing a screw hole penetrating the wall surface of the cylinder portion 201 and inserting the piston portion 40 into the cylinder portion 201, a screw S is inserted from the outside of the wall surface of the cylinder portion 201 to penetrate the wall surface of the cylinder portion 201, and the tip of the screw S protrudes from the inner wall of the cylinder portion 201 and is screwed, so that the piston portion 40 abuts against the screw S, thereby restricting the movement of the piston portion 40 within the cylinder portion 201 to a predetermined range. The position of the screw hole is determined so that the range in which the piston portion 40 can move up and down is the same as the desired length by which the electrode 60 protrudes. Further, as shown in FIGS. 7 to 9, by forming the upper side inside the cylinder portion 201 so as to surround it, it is also possible to restrict the upward movement of the piston portion 40. Further, a protrusion extending radially outward is provided on the side surface of the push rod 30, a stopper capable of abutting against the protrusion is provided in the hollow of the rod 10, and based on the initial position where the push rod 30 is slid so that the distance by which the push rod 30 can slide downward is the desired length by which the electrode 60 protrudes, a stopper protruding radially inward may be provided at a position corresponding to the desired length by which the electrode 60 protrudes.

[0032] In addition, when the columnar portion 202 is formed hollow, the electrode guide portion 205 may be constituted by a flexible hose or the like having flexibility. In this case, although there is a space into which the electrode 60 can be inserted, it is necessary to be formed so that the piston portion 40 cannot be inserted. For example, stoppers such as protrusions protruding inward from the inner peripheral surface are provided so that the piston portion 40 does not move downward from the upper surface of the columnar portion 202, or the flexible hose or the like needs to be fixedly attached to the upper surface of the columnar portion 202 so as not to shift downward.

[0033] In such a configuration, after a screw weight penetration test (SWS test), the ground resistivity measurement probe 1 according to the present invention is inserted into the boring hole remaining after the test with the cone portion directed vertically downward from the ground. At the depth where the resistivity of the ground is to be measured, the pushing rod is slid downward. Along with the sliding of the pushing rod, the electrode 60 pops out from the probe body 20 and contacts the wall surface of the boring hole. With the electrode 60 in contact with the wall surface of the boring hole, current is passed through to measure the resistivity of the ground. This operation is repeated at a predetermined depth to determine the soil quality for each depth.

Explanation of Reference Numerals

[0034] 1 Ground resistivity measurement probe 10 Rod 20 Probe body 30 Pushing rod 40 Piston portion 60 Electrode 60 Electrode 201 Cylinder portion 202 Columnar portion 205 Electrode guide portion

Claims

1. A hollow rod extending in the vertical direction, A probe body connected to the lower end of the rod, A push rod that can move up and down within the hollow of the rod, A piston portion connected to the lower end of the push rod, A bendable rod-shaped electrode, a part of which is fixed to the piston portion, Comprising, The probe body has a cylinder portion in which the piston portion is accommodated so as to be movable up and down, and a columnar portion in which an electrode guide portion for guiding the movement of the electrode is formed inside, A probe for measuring ground specific resistance, characterized in that when the push rod is pushed downward, the electrode of a desired length protrudes outward from the side surface of the columnar portion.

2. A hollow rod extending in the vertical direction, A probe body connected to the lower end of the rod, A push rod that can move up and down within the hollow of the rod, A piston portion connected to the lower end of the push rod, A bendable rod-shaped electrode, a part of which is fixed to the piston portion, Comprising, The probe body has a cylinder portion in which the piston portion is accommodated so as to be movable up and down, and a columnar portion in which an electrode guide portion for guiding the movement of the electrode is formed inside, When the columnar portion is divided into two in the left-right direction, the electrode guide portion penetrates from the upper surface of one of the divided sides to the side surface of the other of the divided sides, A probe for measuring ground specific resistance, characterized in that when the piston portion is located at the uppermost part of the range in which it moves up and down within the cylinder portion, the tip of the electrode is arranged in front of the side surface of the other of the divided sides.

3. A hollow rod extending in the vertical direction, A probe body connected to the lower end of the rod, A push rod that can move up and down within the hollow of the rod, A piston portion connected to the lower end of the push rod, A bendable rod-shaped electrode, a part of which is fixed to the piston portion, Comprising, The probe body has a cylinder portion in which the piston portion is accommodated so as to be movable up and down, and a columnar portion in which an electrode guide portion for guiding the movement of the electrode is formed inside, When the columnar portion is divided into two in the left-right direction, the electrode guide portion penetrates from the upper surface of one of the divided sides to the side surface of the other of the divided sides, When the push rod is pushed downward, the electrode protrudes outward from the electrode guide portion. A probe for measuring ground specific resistance, wherein a restricting portion for restricting the movement of the piston portion is provided in the cylinder portion so that the length by which the electrode protrudes is the same as the distance by which the piston portion can move up and down within the cylinder portion.

4. A plurality of the electrode guide portions are provided, each of which is curved with a radius of curvature of 35 mm or more. The probe for measuring ground specific resistance according to claim 2 or 3, wherein one end portion of each of the plurality of electrode guide portions is arranged in a row in an oblique direction with respect to the vertical direction on the side surface of the columnar portion.

5. A plurality of the electrode guide portions are provided, each of which is curved with the same radius of curvature of 35 mm or more. The probe for measuring ground specific resistance according to claim 2 or 3, wherein one end portion of each of the plurality of electrode guide portions is arranged in a row in an oblique direction with respect to the vertical direction on the side surface of the columnar portion.

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