JP2008304265A - Excavation position measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excavation position measuring instrument capable of measuring an excavation position sufficiently efficiently and highly accurately regardless of the shape of an excavated hole. <P>SOLUTION: The excavation position measuring instrument 40A, which is used when an excavated hole 80 is formed in the ground by an excavator 10 with a bit member 10d on the tip face 10c, includes a rod 25 to be measured having a prescribed length and a shape with one end fixed to the excavator 10, and with the other end arranged projected from a pit mouth 80a to the outside; a container 35 for storing the rod 25 to be measured; and liquid 50 stored in the container 35, for floating the rod 25 to be measured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an excavation position measuring tool used when forming an excavation hole in the ground by an excavator having a bit member on a tip surface.

  In construction in which a drilling hole is formed in the ground by a boring method or a propulsion method, it may be necessary to appropriately measure the position of the excavator and grasp whether or not the excavator is excavating a predetermined course. For example, when excavating an underground structure where existing structures and the like diverge by a propulsion method, high construction accuracy is required while long-distance construction by the propulsion method is required in recent years. That is, linear management with high measurement accuracy is required.

As a method for measuring the position of the excavator, a method using a measurement system having a plurality of measurement points continuously provided in the excavation hole is known (see Patent Document 1). In this method, the position of the excavator is calculated from the positional relationship between the measurement points. As a method for measuring the shape of a borehole or the like, a method using a measuring device in which a strain gauge or an angular accelerometer is incorporated is known (see Patent Document 2).
JP-A-8-233575 Japanese Patent Laid-Open No. 10-300413

  However, when the measurement system as in Patent Document 1 is used, there is a problem in that work efficiency is lowered because the operation of installing a plurality of measurement points in the excavation hole is required, and the measurement system itself is expensive. On the other hand, when a measuring device incorporating a strain gauge or the like as in Patent Document 2 is used, the measurement accuracy is insufficient, and it cannot be grasped sufficiently early that the excavator has deviated from a predetermined course. .

  As a position measuring means other than the above, there is a measuring instrument using straightness of a laser beam. However, such a measuring device has a sufficiently large diameter of the excavation hole, and when the operator can enter the excavation mine and perform the measurement, or the excavation hole to be formed is linear, the laser beam irradiated from the excavation port reaches the excavator The shape of the excavation hole that can be applied is limited only when it reaches directly.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an excavation position measuring tool capable of measuring an excavation position sufficiently efficiently and with high accuracy regardless of the shape of an excavation hole.

  The excavation position measuring tool of the present invention is used when forming an excavation hole in the ground by an excavator having a bit member on the tip surface, and has a predetermined length and shape, and one end is excavated. A rod to be measured, which is fixed to the machine and arranged so that the other end protrudes outward from the wellhead, a container that accommodates the rod to be measured, and a liquid that is accommodated in the container and floats the rod to be measured; Is provided.

  The rod to be measured included in the excavation position measuring tool of the present invention is arranged so that one end is fixed to the excavator and the other end projects outward from the wellhead. Since the rod to be measured is inserted into the excavation hole in this way, the length and shape are designed according to the shape of the excavation hole to be formed. Measure the position of the end of the rod to be measured that protrudes from the wellhead, and based on this measured value and the known values for the length and shape of the rod to be measured, the position of the end on the excavator side, that is, Calculate the position of the excavator. Therefore, according to the excavation position measuring tool of the present invention, the excavation position can be grasped sufficiently efficiently regardless of the shape of the excavation hole.

  Since only one end of the rod to be measured is fixed to the excavator and floats in the liquid in the container in a so-called cantilever state, the deflection due to the weight of the rod to be measured is sufficiently reduced. Therefore, the excavation position can be calculated with sufficiently high accuracy based on the actual measurement value of the end of the rod to be measured on the wellhead side and the known values of the length and shape of the rod to be measured.

  Furthermore, according to the excavation position measuring tool of the present invention, when the excavation direction of the excavator is deviated from a predetermined direction for some reason, the occurrence of the deviation appears as a change in the position of the end on the wellhead side of the rod to be measured. Therefore, the excavator can be corrected at an early stage.

  In the excavation position measuring tool of the present invention, the container that houses the rod to be measured is preferably a cylindrical member that surrounds the rod to be measured over substantially the entire length. By adopting such a configuration, there is an effect that the liquid filled in the container is difficult to leak. Therefore, the excavation position measuring tool whose container is a cylindrical member is suitable for measuring an excavation position such as an excavation hole formed upward or downward.

  In the excavation position measuring tool of the present invention, the rod to be measured has a portion to be measured whose base end is fixed to the end portion on the wellhead side, and the portion to be measured is located outside the through hole provided in the tubular member. It is preferable to be exposed to. By adopting such a configuration, even when the entire cylindrical member is formed of an opaque material (for example, a stainless steel pipe), the position of the end on the wellhead side of the rod to be measured can be easily measured.

  The excavation position measuring tool of the present invention preferably further includes a stretchable sealing means for sealing a gap between the through hole of the tubular member and the measured portion. By adopting such a configuration, for example, even when applied to an excavation hole formed upward, it is possible to prevent the liquid in the cylindrical member from leaking from the through hole.

  In the excavation position measuring tool of the present invention, the end of the tubular member on the wellhead side is preferably formed of a transparent material. By adopting such a configuration, it is easy to visually monitor the end on the wellhead side of the rod to be measured, and the position of the end on the wellhead side of the rod to be measured even when the measured portion is not provided on the rod to be measured. Can be measured easily.

  In the excavation position measuring tool of the present invention, it is preferable that the rod to be measured is adjusted so that the apparent specific gravity is substantially equal to the specific gravity of the liquid in the container. Thereby, even when a material different from the specific gravity of the liquid is used for a part of the rod to be measured, the rod to be measured can be suspended in the liquid.

  ADVANTAGE OF THE INVENTION According to this invention, the excavation position measuring tool which can measure an excavation position with sufficient efficiency and high precision irrespective of the shape of an excavation hole is provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Here, the case where the excavation position measuring tool according to the present invention is applied to a single-curved excavation hole formed so as to go upward from a wellhead provided in the underground space and then downward is described as an example.

(First embodiment)
FIG. 1 is a cross-sectional view showing a state where the excavator 10 is excavating in the right direction from the left well 80a by the propulsion method. As shown in the figure, an excavation hole 80 having an upwardly convex shape is formed toward the target arrival point 80b. The excavator 10 moves forward by the pressing force from the pipe P1 inserted from the wellhead 80a provided in the upper part of the underground space 50. In FIG. 1, illustration of the excavation position measuring tool and the propulsion method device (for example, a propulsion mount, a muddy water circulation device, etc.) is omitted.

  FIG. 2 is a perspective view showing the excavator 10 and the excavation position measuring tool according to the present embodiment fixed to the excavator 10. The excavator 10 shown in the figure includes a bit member 10d on the front end surface 10c of the front main body portion 10a, and one end of the excavation position measuring tool 40A is fixed to the rear surface 10e of the rear main body portion 10b. The front main body 10a of the excavator 10 can change the angle of the distal end surface 10c by remote control, and thereby the excavation direction of the excavator 10 can be controlled.

  The excavation position measuring tool 40A includes a measured rod 25 having a predetermined length and shape, and a cylindrical member (container) 35 that surrounds the measured rod 25 over substantially the entire length. In this cylindrical member 35, water 50 for suspending the rod 25 to be measured is accommodated. The length and shape of the rod to be measured 25 are designed so as to be accommodated in the cylindrical member 35, and the length and shape of the cylindrical member 35 are designed so as to be accommodated in the pipe P1.

  The excavator-side rod 25a that forms the end of the rod 25 to be measured on the excavator 10 side is made of a stainless steel hollow member, and one end 25b thereof is fixed to the rear surface 10e of the excavator 10. On the other hand, the well side rod 25c that forms the end of the rod 25 to be measured on the well 80a side is made of a stainless steel hollow member, and the base end of the Y-shaped portion to be measured 28 is fixed near the tip.

  A plurality of connecting rods 25d are connected in series between the excavator side rod 25a and the wellhead side rod 25c. Each connecting rod 25d is made of a stainless steel hollow member, and has flange portions 25e at both ends. The rod 25 to be measured can be extended by adding the connecting rod 25d as the excavation hole 80 advances. Thus, the to-be-measured rod 25 having the same curvature as that of the excavation hole 80 is configured by connecting the plurality of connecting rods 25d in series.

  FIG. 3 is a cross-sectional view showing a connecting portion between two connecting rods 25d. As shown in the figure, both ends of each connecting rod 25d are closed by an end plate 25f, and air is sealed inside. The connecting rod 25d is adjusted in thickness at the portion made of stainless steel so that the buoyancy caused by the internal air and its own weight are balanced and floated in the water 50. Similarly to the connecting rod 25d, the overall specific gravity of the excavator side rod 25a and the wellhead side rod 25c is adjusted by adjusting the thickness of the portion made of stainless steel. Thus, the rod 25 to be measured is adjusted so that the apparent specific gravity is equal to the specific gravity of the water 50 as a whole.

  Further, as shown in FIG. 3, the flange portions 25 e of adjacent connecting rods 25 d are fixed at a plurality of locations by bolts 26 and nuts 27. By firmly fixing the flange portions 25e at a plurality of locations, the rod 25 to be measured is maintained in the designed shape. The excavator side rod 25a and the wellhead side rod 25c also have a flange portion 25e for connecting to the adjacent connecting rod 25d, and are connected to the adjacent connecting rod 25d via the flange portion 25e.

  As shown in FIG. 2, the cylindrical member 35 is disposed so as to surround the rod 25 to be measured over substantially the entire length. The cylindrical member 35 accommodates water 50 in the interior thereof and causes the rod 25 to be measured to float.

  The excavator side cylinder portion 35a that forms the end of the tubular member 35 on the excavator 10 side is made of a stainless steel cylindrical member, and one end 35b thereof is fixed to the rear surface 10e of the excavator 10. On the other hand, the well-end-side cylinder portion 35c that forms the end of the tubular member 35 on the well-opening side is formed of a stainless-steel tubular member, and the other end 35e is closed. A through hole 35f for exposing the measured portion 28 having the base end fixed to the measured rod 25 to the outside is provided in the wellhead side cylinder portion 35c.

  Between the excavator side cylinder part 35a and the wellhead side cylinder part 35c, a plurality of connection cylinder parts 35d are connected in series. Each connecting cylinder portion 35d is made of a stainless steel cylindrical member, and is provided with a male screw and a female screw at both ends. By tightening the male screw and the female screw of the adjacent connecting cylinder part 35d, the connecting cylinder parts 35d are connected to each other, and the sealing property of the connecting part 35g is secured. The tubular member 35 can be extended by adding the connecting tubular portion 35d as the excavation hole 80 is advanced. Thus, the cylindrical member 35 which has the curvature similar to the excavation hole 80 is comprised by connecting the some cylinder part 35d for a connection in series.

  The cylindrical member 35 is provided with a manual valve (not shown) for discharging and injecting water into the wellhead side cylinder portion 35c. The tubular member 35 includes a vent valve (not shown) that can be opened and closed by remote operation, and can be opened as necessary during the operation of discharging and injecting water.

  The to-be-measured part 28 has a Y-shape as shown in FIG. That is, the measurement target portion 28 has a base end fixed to the wellhead-side rod 25c, a rod-shaped member 28a inserted into the through hole 35f of the wellhead-side tube portion 35c, and a V-shape exposed outside the wellhead-side tube portion 35c. It consists of member 28b. By exposing the V-shaped member 28b to the outside of the well-end-side cylinder portion 35c, the position of the rod 25 to be measured is directly measured by a measuring instrument using laser light or the like.

  A rubber seal (sealing means) 36 that seals the gap with the rod-shaped member 28a is provided in the through hole 35f into which the rod-shaped member 28a of the measured portion 28 is inserted, and the water 50 in the cylindrical member 35 does not leak. It is like that. Further, since the rubber seal 36 is extendable, the movement of the rod 25 to be measured floating in the cylindrical member 35 can be sufficiently suppressed, and the rod 25 to be measured is maintained in the designed shape. The

  Next, a method for using the excavation position measuring tool 40A according to the present embodiment will be described. FIG. 4 is a perspective view showing an end of the excavation position measuring tool 40A installed in the excavation hole 80 being excavated by the excavator 10 on the side of the pit 80a. For convenience of explanation, the illustration of the wellhead device for the propulsion method is omitted in FIG.

  As shown in FIG. 4, one end P1a of the pipe P1 protrudes from the wellhead 80a, and the end of the excavation position measuring tool 40A on the wellhead 1a side (the wellhead side rod 25c and the wellhead side cylinder portion 35c). Is protruding. Further, the portion to be measured 28 is exposed from the through-hole 35f of the well-end side cylinder portion 35c. The cylindrical member 35 is held by a cylindrical member mount (not shown) provided around the wellhead 80 a and is arranged so that the rod 25 to be measured does not contact the inner surface of the cylindrical member 25. Moreover, the excavator 10 is not influenced by the weight by holding the cylindrical member 35 with a mount. On the other hand, only one end 25b of the rod 25 to be measured is fixed, and is floating in the water 50 in the cylindrical member 35 in a so-called cantilever state. The water 50 accommodated in the cylindrical member 35 also serves as a damper for suppressing the rod 25 to be measured from vibrating due to disturbance.

  In the present embodiment, the positions of three points that are not on a straight line on the measurement target 28 are measured. Specifically, the distance between the measurement points S1 to S3 indicated by X in FIG. 4 and an arbitrary fixed point is measured. The position of the plane including the measurement points S1 to S3 is determined from the actual measurement values. Since the position of this plane is determined based on the position of the portion to be measured 28 that is integrally fixed to the rod 25 to be measured, by using design values for the length and shape of the rod 25 to be measured, The positional relationship between this plane and the excavator 10 located on the one end 25 b side of the rod to be measured 25 can be calculated.

  In calculating the position of the excavator 10 in this way, design values for the length and shape of the rod 25 to be measured are used. The rod 25 to be measured is accommodated in the cylindrical member 35 over substantially the entire length thereof. Since it is floating in the water 50, the deformation due to its own weight is small, and the designed shape is sufficiently maintained. Therefore, the excavation position can be calculated with sufficiently high accuracy based on the actual measurement values of the measurement points S1 to S3 on the measurement target 28 and the design value of the measurement target rod 25.

  FIG. 5A is a schematic cross-sectional view showing a state where the excavator is excavating a predetermined course, and FIG. 5B is a schematic cross-sectional view showing a state where the excavator is deviated from the predetermined course. . 5A and 5B show only the components necessary for the description (excavation hole 80, excavator 10, measured rod 25, and measured portion 28).

  As shown in FIG. 5B, according to the excavation position measuring tool 40A, when the excavation direction of the excavator 10 deviates from a predetermined direction for some reason, the occurrence of the deviation is large in the position of the measured portion 28. Since it appears as a change, the trajectory of the excavator 10 can be corrected early.

  As described above, the excavation position is appropriately measured using the excavation position measuring tool 40A according to the present embodiment, and the trajectory correction of the excavator 10 is performed at an early stage, whereby the deviation of the excavator 10 from the target arrival position is detected. It can be sufficiently suppressed.

  The rod to be measured 25 and the cylindrical member 35 of the excavation position measuring tool 40A can be extended in length by adding the connecting rod 25d and the connecting cylinder part 35d. The newly added connecting rod 25d is mounted between the wellhead side rod 25c and the adjacent connecting rod 25d. Similarly, the newly added connecting cylinder part 35d is mounted between the well-end side cylinder part 35c and the adjacent connecting cylinder part 35d. With such a configuration, even when the excavation of the excavation hole 80 proceeds, the wellhead side rod 25c and the wellhead side cylinder portion 35c can always protrude from the wellhead 80a. Therefore, excavation position measurement can be performed as appropriate.

  The operation for adding the connecting rod 25d and the connecting cylinder portion 35d may be performed as follows. First, the manual valve and the ventilation valve provided on the cylindrical member 35 are opened, and the water 50 in the cylindrical member 35 is discharged. Thereafter, the wellhead side cylinder portion 35c is removed to expose the connecting portion between the wellhead side rod 25c and the adjacent connecting rod 25d. The wellhead side rod 25c is removed, and a connecting rod 25d that is newly added to the adjacent connecting rod 25d that has been connected is mounted. When the addition work of the rod 25 to be measured is completed, the connecting cylinder portion 35d and the well-end side cylinder portion 35c to be newly added are sequentially attached, and the cylindrical member 35 is added. Thereafter, water is poured into the cylindrical member 35 to fill the interior with water, and the work is completed.

  In order to efficiently perform the above-described addition work, it is preferable that the V-shaped member 28b of the measured portion 28 is detachably provided on the rod-shaped member 28a. The shape of the portion to be measured 28 is not limited to a Y shape as long as it is possible to provide three or more measurement points that are exposed outside the cylindrical member 35 and are not in a straight line. A rod-shaped member may be used as the measured portion 28. Moreover, you may provide multiple to-be-measured parts which consist of such a rod-shaped member in the wellhead side rod 25c. What is necessary is just to select about the form of the to-be-measured part 28 according to arrangement | positioning of the wellhead apparatus around the wellhead 80a.

(Second Embodiment)
FIG. 6 is a partial cross-sectional view showing a second embodiment of the excavation position measuring tool according to the present invention. The excavation position measuring tool 40B shown in the figure is different from the excavation position measuring tool 40A according to the first embodiment in the following points. That is, the excavation position measuring tool 40B includes a wellhead side cylinder portion 37c made of a transparent material instead of the stainless steel wellhead side cylinder portion 35c of the excavation position measurement tool 40A. Further, the excavation position measuring tool 40B does not include the measurement target portion 28 exposed to the outside of the wellhead side cylinder portion 37c, and the measurement point S and the measurement line L are provided on the outer surface of the wellhead side rod 25c. It is engraved. In the present embodiment, the position of the measurement point S and the positions of both ends of the line L are measured, and excavation is performed in the same manner as in the first embodiment based on these actually measured values and the design values of the rod 25 to be measured. Calculate the position.

  The excavation position measuring tool 40B according to the present embodiment has an advantage that it is easy to visually monitor the movement of the rod 25 to be measured housed therein. Further, in the present embodiment, since the portion to be measured 28 that protrudes from the well-end-side cylinder portion 35c is not provided, the connecting rod 25d and the connecting cylinder portion 35d can be added more efficiently, and the through hole 35f and the rubber seal 36 can also be dispensed with.

(Third embodiment)
FIG. 7 is a partial cross-sectional view showing a third embodiment of the excavation position measuring tool according to the present invention. The excavation position measuring tool 40C shown in the figure is different from the excavation position measuring tool 40A according to the first embodiment in the following points. That is, the excavation position measuring tool 40C does not include the portion to be measured 28, and the measurement point S and the measurement line L are stamped on the outer surface of the wellhead side rod 25c and the end surface of the wellhead side rod 25c. In addition, the excavation position measuring tool 40C includes a stainless steel well-end side cylinder portion 39c provided with a rubber seal 38 at the open end 39e instead of the well-end side cylinder portion 35c of the excavation position measurement tool 40A. The well side rod 25c is exposed to the outside.

  In the present embodiment, the position of the measurement point S and the positions of both ends of the line L are measured, and excavation is performed in the same manner as in the first embodiment based on these actually measured values and the design values of the rod 25 to be measured. Calculate the position.

  The excavation position measuring tool 40C according to the present embodiment has an advantage that it is easy to visually monitor the movement of the rod 25 to be measured. Moreover, in this embodiment, since the to-be-measured part 28 which protrudes from the well mouth side cylinder part 35c is not provided, the addition work of the connecting rod 25d and the connecting cylinder part 35d can be implemented more efficiently. Further, since the measurement control is exposed to the outside, each position can be directly measured by a measuring instrument using laser light or the like.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, in the above-described embodiment, water is exemplified as the liquid that floats the rod 25 to be measured. However, as long as it does not restrain the movement of the rod 25 to be measured, for example, a liquid or gel that is more viscous than water. May be used. Here, “the movement of the rod 25 to be measured is not restrained” means that the rod 25 to be measured becomes a design value shape after a certain period of time even if the rod 25 to be measured is displaced with respect to the tubular member 35 for some reason. It means that it can be recovered almost.

  Further, the rod 25 to be measured is not limited to a stainless steel hollow member as long as it has sufficient rigidity and the apparent specific gravity is adjusted and floats in the liquid. For example, as shown in FIG. Thus, it may be constituted by the H-shaped steel 45 and the foamed member 46 sandwiched between the upper plate 45a and the lower plate 45b. Further, the apparent specific gravity of the rod to be measured may be adjusted by appropriately selecting the material of the member constituting the rod to be measured 25.

  Furthermore, the cylindrical member 35 is not limited to a cylindrical member made of stainless steel as long as it can be installed in the pipe P1 and can accommodate a liquid therein. For example, it has flexibility. A pipe may be used as the cylindrical member 35. Furthermore, the cross-sectional shape of the cylindrical member 35 is not limited to a circle, and may be an ellipse or a rectangle.

  Further, the connecting means such as the connecting rod 25d is not limited to the one using the flange portion 25e, the bolt 26, and the nut 27 as long as it can sufficiently prevent the occurrence of displacement at the connecting portion. Further, the connecting means such as the connecting cylinder 35d is limited to a male screw and a female screw as long as the sealing of the connecting portion can be sufficiently ensured and the cylindrical member 35 can be formed in a predetermined shape. Not.

  Furthermore, in the said embodiment, although the case where this invention was used with respect to the excavation hole which consists of a single curve formed by a propulsion construction method was illustrated, this invention is an excavation hole which needs to measure an excavation position with high precision. The application is not limited by the excavation method and the shape of the excavation hole. The present invention may be applied to excavation holes formed by, for example, a shield method or a boring method. Further, the excavation hole is not limited to the excavation hole having an upward convex shape, such as the excavation hole 80, the excavation hole having a downward convex shape, the excavation hole curved in the right direction or the left direction, and the excavation hole curved in the upward direction or the downward direction. Alternatively, it can be applied to straight excavation holes.

  When the excavation position measuring tool according to the present invention is applied to an excavation hole formed in a substantially horizontal direction, the rubber seals 36 and 38 are not necessarily provided. In this case, as a container for housing the rod 25 to be measured, a container whose upper side is opened (for example, a container having a U-shaped cross section) may be used instead of the cylindrical member 35. The container having such a shape is not limited to a straight excavation hole as long as the excavation hole is formed in a substantially horizontal direction, and can also be applied to an excavation hole curved in the right direction and / or the left direction.

It is sectional drawing which shows the state in which the excavator is excavating rightward from a wellhead. It is a perspective view which shows the state by which the excavation position measuring tool which concerns on 1st Embodiment of this invention was fixed to the excavator. It is sectional drawing which shows the connection part of a to-be-measured rod. It is a perspective view which shows the edge part by the side of a wellhead of the excavation position measuring tool shown in FIG. (A) is a schematic cross section which shows the state in which the excavator is excavating a predetermined course, (b) is a schematic cross section which shows the state from which the excavator removed from the predetermined course. It is a perspective view which shows the edge part by the side of a wellhead of the excavation position measuring tool which concerns on 2nd Embodiment of this invention. It is a perspective view which shows the edge part by the side of a wellhead of the excavation position measuring tool which concerns on 3rd Embodiment of this invention. It is a perspective view which shows the other suitable form of a to-be-measured rod.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Excavator, 10c ... Front end surface of excavator, 10d ... Bit member, 25 ... Measuring rod, 28 ... Measuring part, 35 ... Cylindrical member (container), 35f ... Through-hole, 36 ... Rubber seal (sealing) Means), 40A, 40B, 40C ... excavation position measuring tool, 50 ... water (liquid), 80 ... excavation hole, 80a ... wellhead.

Claims (6)

An excavation position measuring tool used when forming an excavation hole in the ground by an excavator having a bit member on a tip surface,
A rod to be measured having a predetermined length and shape, one end fixed to the excavator, and the other end arranged to protrude outward from the wellhead,
A container for housing the rod to be measured;
A liquid contained in the container to float the rod to be measured;
An excavation position measuring tool comprising:   The excavation position measuring tool according to claim 1, wherein the container is a cylindrical member that surrounds the rod to be measured over substantially the entire length.   The rod to be measured has a portion to be measured whose base end is fixed to the end on the wellhead side, and the portion to be measured is exposed to the outside from a through hole provided in the cylindrical member. The excavation position measuring tool according to claim 2, wherein:   The excavation position measuring tool according to claim 3, further comprising a stretchable sealing unit that seals a gap between the through hole and the measurement target part.   The excavation position measuring tool according to any one of claims 2 to 4, wherein an end of the tubular member on the wellhead side is formed of a transparent material.   The excavation position measuring tool according to any one of claims 1 to 5, wherein the rod to be measured is adjusted so that an apparent specific gravity is substantially equal to a specific gravity of the liquid.

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