JP7491873B2 - Tunnel survey target and target installation method - Google Patents

Description

The present invention relates to a target for tunnel surveying and a method for installing the target.

In tunnel construction, the safety and quality of the work is ensured by periodically measuring the displacement of the ground and support materials. By periodically measuring the condition of the tunnel, it is possible to predict the condition of the ground in front of the tunnel face and to determine the suitability of the support structure. Such measurements include settlement measurements and internal displacement measurements.
Subsidence measurements and internal displacement measurements (hereinafter simply referred to as "displacement measurements") are carried out by setting up control sections at regular intervals and periodically measuring the coordinates of tunnel survey targets installed at those control sections.
During construction, multiple heavy machinery such as drill jumbos, spraying robots, and backhoes are operating within the limited space inside the tunnel. Therefore, tunnel survey targets that are installed to protrude from the ground may come into contact with the heavy machinery and be damaged. In addition, when tunnels are excavated using the blasting method, the targets may be damaged by the blast wind or flying rocks.
Therefore, damage to the target may be prevented by installing a removable tunnel survey target for measuring displacement only during surveying.
For example, Patent Document 1 discloses a structure comprising a main body having a plumb bob and a prism, and a magnet part that is integrated with the main body and can be fixed to a support structure.
Furthermore, Patent Document 2 discloses a tunnel surveying target that is attached to an anchor embedded in a tunnel wall, the target comprising a bolt that is screwed into the anchor, an outer frame fixed to the tip of the bolt, a target body that is installed in the internal space of the outer frame, and a rotating shaft that is interposed between the outer frame and the target body and that rotatably holds the target body.
On the other hand, attaching and detaching tunnel survey targets installed on the top or shoulder of a tunnel requires work at a height, which is time-consuming.

JP 2004-301642 A JP 2010-217017 A

From this perspective, the objective of the present invention is to propose a target for tunnel surveying and a method for installing the target that can avoid damage caused by contact with heavy machinery, flying objects, etc.

In order to solve the above problems, the tunnel survey target of the present invention comprises an anchor part embedded in the tunnel wall, a plate-shaped main body part having a through hole formed in the center penetrating from the front to the back and attached to the tunnel wall, a prism attached to the main body part, and a bolt having a shaft part passing through the through hole and screwed into the anchor part. The prism is exposed through an opening formed in the side of the main body part, so that it can be seen from the tunnel entrance side. In addition, the side of the main body part where the opening is formed and the side opposite to the through hole are formed with an inclined surface in which the material thickness decreases with distance from the through hole , so that the blast wind or flying objects during blasting are unlikely to come into contact with the prism, and even if it does come into contact with the prism, the impact can be minimized.
According to this tunnel survey target, the plate-shaped main body is installed attached to the tunnel wall, so that the protruding height into the tunnel interior is small, and it is difficult to come into contact with heavy machinery, etc., and also difficult to come into contact with flying objects during blasting, etc. Therefore, construction using heavy machinery, etc., and excavation by blasting can be performed while the tunnel survey target is installed, eliminating the labor required for attaching and detaching the tunnel survey target, and ultimately shortening the construction period. In addition, since the prism is protected by the main body, the prism is unlikely to be damaged even if it comes into contact with heavy machinery or flying objects. In addition, since the main body is fixed to the anchor part via a bolt, it is possible to replace the main body as necessary.

If the main body is shaped like a truncated cone, it is possible to minimize the impact even if a flying object or a falling object comes into contact with the main body.
Furthermore, if a recess (countersink) capable of accommodating the head of the bolt is formed on the surface of the main body facing the tunnel interior, the head of the bolt will not protrude, preventing the bolt from coming into contact with heavy machinery, flying objects, etc.
Furthermore, if the device further includes a stopper member that penetrates the main body and is inserted into the tunnel wall, the survey target can be prevented from rotating for any reason.

The method for installing the tunnel survey target (target installation method) includes a drilling operation for drilling a tunnel wall surface to form an installation hole, and an installation operation for installing the tunnel survey target in the installation hole. The tunnel survey target includes a main body having a prism attached thereto, a bolt penetrating the main body, and an anchor part fixed to one surface of the main body via the bolt. In the installation operation, the head of the bolt is struck to apply a pressing force to the other surface of the main body, thereby forcing the anchor part into the installation hole and bringing one surface of the main body into contact with the tunnel wall.
This target installation method is excellent in workability because the installation of the tunnel survey target can be completed simply by pushing the main body in. In addition, since the prism is attached to the main body, the prism will not be damaged even if the main body is struck.

The tunnel survey target and target installation method of the present invention make it possible to avoid damage caused by contact with heavy machinery, flying objects, etc.

1A is a cross-sectional view of a tunnel in which a tunnel survey target is installed, and FIG. 1B is a longitudinal section of the same tunnel. FIG. 1A is a front view showing a tunnel survey target, FIG. 1B is a cross-sectional view taken along line A-A of FIG. 1A, and FIG. 1C is a cross-sectional view taken along line B-B of FIG. FIG. 2 is a cross-sectional view showing the mounting state of a tunnel survey target.

In this embodiment, a description will be given of a tunnel survey target 2 used to measure internal displacement of a tunnel 1. Fig. 1 shows a tunnel 1 on which a tunnel survey target 2 is installed. Internal displacement measurement is performed by using a total station TS to measure the tunnel survey targets 2 installed on the side walls and top end of the tunnel 1 (wall surface 11 of the tunnel 1) at control cross sections set at regular intervals as the tunnel 1 advances, as shown in Figs. 1(a) and 1(b).
In this embodiment, tunnel survey targets 2 are installed at three locations for each management cross section: near the top end of the tunnel and near the left and right steam locomotives.
The wall 11 of the tunnel 1 is provided with supports such as shotcrete 13 and steel supports 14 , and the tunnel survey target 2 of this embodiment is attached to the surface of the shotcrete 13 .

2 shows the tunnel survey target 2. As shown in Fig. 2(a) to (c), the tunnel survey target 2 of this embodiment includes an anchor portion 3, a main body portion 4, a prism 5, a bolt 6, and a displacement prevention member 7.
2(b), the anchor part 3 is embedded in the wall surface 11 of the tunnel 1. The anchor part 3 is embedded in an installation hole 12 formed by drilling the wall surface 11. The anchor part 3 in this embodiment is made of a tubular member with a female thread on the inner surface, and the bolt 6 can be screwed into it.

The main body 4 is attached to the wall surface 11 of the tunnel 1. The main body 4 is made of a plate-like member. As shown in Figures 2(a) to (c), an inclined surface is formed on the outer periphery of the main body 4, in which the thickness of the member decreases toward the outside. In other words, the main body 4 is in the shape of a truncated pyramid (in this embodiment, in the shape of a quadrangular pyramid).
A through hole 41 for inserting the shaft portion 61 of the bolt 6 is formed in the center of the main body 4. A recess 42 capable of accommodating the head 62 of the bolt 6 is formed in the surface of the main body 4 facing the interior of the tunnel. As shown in Fig. 2(a) , the recess 42 in this embodiment has a circular shape in a front view. The inner diameter of the recess 42 is larger than the width of the head 62 of the bolt 6. As shown in Fig. 2(b) , the recess 42 has a depth equal to or greater than the height of the head 62 of the bolt 6.
2(a) and 2(c), thin-walled portions 43, 43 are formed in the main body 4. The thin-walled portions 43 are formed on the face side and the mouth side of the main body 4, respectively, so as to face each other with the through hole 41 in between. Anti-slip holes 44 penetrate the thin-walled portions 43. In this embodiment, two anti-slip holes 44 are formed in each thin-walled portion 43.

Prism 5 is attached to main body 4 as shown in Figures 2(a) and (c). An opening 45 is formed in the side of main body 4 facing the well mouth (the side facing thin section 43) according to the position of prism 5. Prism 5 is exposed on the well mouth side of main body 4 through opening 45. In other words, prism 5 can be measured by a total station TS installed on the well mouth side.

As shown in FIG. 2(b), the bolt 6 has a shaft 61 and a head 62. The shaft 61 of the bolt 6 passes through the through hole 41 of the main body 4 and is screwed into the anchor part 3. The head 62 of the bolt 6 is engaged with the bottom surface of the recess 42. At this time, the head 62 is contained within the recess 42 without protruding from the surface of the main body 4.

As shown in FIG. 2(c), the anti-slip member 7 is inserted into the wall surface 11 of the tunnel 1 through the anti-slip hole 44 of the main body 4. In this embodiment, the anti-slip member 7 is a U-shaped metal member. The anti-slip member 7 is inserted into the wall surface 11 of the tunnel 1 while being inserted into the anti-slip holes 44, 44 formed in the thin-walled portion 43. The anti-slip member 7 is inserted across the two anti-slip holes 44, 44, thereby fixing the rotation of the main body 4.

Next, a method for installing the tunnel survey target 2 (target installation method) of this embodiment will be described. Each construction stage of the target installation method is shown in Fig. 3. In the target installation method of this embodiment, first, as shown in Fig. 3(a), a wall surface 11 of the tunnel 1 is drilled to form an installation hole 12 (drilling work). Next, as shown in Fig. 3(b) and (c), the tunnel survey target 2 is installed in the installation hole 12 (installation work).
After the installation hole 12 is formed, as shown in FIG. 3B, a capsule 8 containing adhesive is inserted into the installation hole 12. Next, as shown in FIG. 3C, the anchor part 3 is screwed onto the shaft part 61 of the bolt 6 inserted into the through hole 41 of the main body part 4, and the anchor part 3 is pushed into the installation hole 12 to bring the main body part 4 into contact with the tunnel wall surface. At this time, a pressing force is applied to the surface of the tunnel survey target 2 by using a pressing means such as a hammer H. In this embodiment, the head part 62 of the bolt 6 is struck with the hammer H to push the tunnel survey target 2 into the installation hole 12. By directly applying a pressing force to the anchor part 3 via the bolt 6 in this way, the impact on the main body part 4 is minimized, and the damage to the prism 5 is suppressed. When the anchor part 3 is pushed into the installation hole 12, the capsule 8 is broken, causing the adhesive 81 to flow out, and the adhesive 81 is filled in the gap between the installation hole 12 and the anchor part 3. Once the main body 4 is in contact with the wall surface 11, the anti-slip member 7 is inserted through the anti-slip hole 44 and pushed into the wall surface 11 (see FIG. 2). In this way, the main body 4 is fixed at multiple points (the bolt 6 in the center of the main body 4 and the anti-slip member 7) to prevent the main body 4 from rotating. Furthermore, the adhesive 81 hardens to fix the anchor portion 3 in the installation hole 12, and thus the tunnel survey target 2 is fixed to the wall surface 11 of the tunnel 1.

According to the tunnel survey target 2 of this embodiment, the plate-shaped main body 4 is installed in a state of being attached to the wall surface 11 of the tunnel 1, so that the protruding height into the tunnel interior is small. Therefore, it is difficult to come into contact with heavy machinery, etc., and also difficult to come into contact with flying objects during blasting, etc. Therefore, construction using heavy machinery, etc., and excavation by blasting can be performed while the tunnel survey target 2 is installed, and the downtime of construction due to attachment and detachment of the tunnel survey target 2 can be minimized, and the construction period can be shortened.
Because the prism 5 is protected by the main body 4, the prism 5 is unlikely to be damaged even if heavy machinery or flying objects come into contact with the tunnel survey target 2. In addition, because the main body 4 is fixed to the anchor 3 via the bolt 6, it is also possible to replace the main body 4 (prism 5) as necessary. Therefore, even if the prism 5 is damaged, the main body 4 can be replaced using the same anchor 3.
Furthermore, since the main body 4 is shaped like a truncated cone, even if it comes into contact with a flying object or a falling object, the impact can be kept to a minimum.
In addition, since a recess 42 (countersink) capable of accommodating the head 62 of the bolt 6 is formed on the surface of the main body 4 facing the tunnel interior, the amount by which the head 62 of the bolt 6 protrudes from the surface of the main body 4 can be minimized, and the bolt 6 can be prevented from coming into contact with heavy machinery, flying objects, etc. Therefore, the shaft 61 of the bolt 6 will not break due to an impact such as contact with heavy machinery, leaving the broken shaft 61 in the anchor part 3, and the bolt 6 can be detached and the anchor part 3 can be used repeatedly.
Furthermore, by using the anti-slip member 7, rotation of the main body 4 is prevented, so that the vibrations and shocks associated with tunnel construction will not cause the main body 4 to rotate, which will prevent the prism 5 from being able to be measured, or cause the position of the prism 5 to shift.

Although an embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and each of the above-described components can be appropriately modified without departing from the spirit of the present invention.
In the above embodiment, the main body 4 is described as having a truncated cone shape, but the shape of the main body 4 is not limited to this, and it is sufficient that an inclined surface is formed in which the thickness of the member decreases at least toward the face side.
The recess 42 may be formed as required, and may be omitted. The head 62 of the bolt 6 may protrude from the surface of the main body 4.
Moreover, the thin portion 43 may be formed as required.
In the above embodiment, the bolt 6 is struck to force the tunnel survey target 2 into the installation hole 12, but it is also possible to strike the main body 4. Also, in the above embodiment, the head 62 of the bolt 6 is struck directly, but it is also possible to strike the head 62 of the bolt 6 with a protective cover attached.
Furthermore, the method of pushing the tunnel survey target 2 into the installation hole 12 is not limited to striking, and it may be pushed in by human force or a jack, for example.
The anti-slip member 7 may be installed as required.
In the above embodiment, the anchor portion 3 is fixed to the installation hole 12 by adhesive 81, but the method of fixing the anchor portion 3 is not limited thereto, and for example, the anchor portion 3 may be fixed by frictional force between the anchor portion 3 and the inner wall surface of the installation hole 12.
The capsule 8 may be used as needed, and adhesive 81, grout, etc. may be directly injected into the installation hole 12.
The number and arrangement of the tunnel survey targets 2 to be installed on the wall surface 11 of the tunnel 1 are not limited, and may be determined appropriately depending on the excavation method and the behavior of the ground.

REFERENCE SIGNS LIST 1 Tunnel 11 Wall surface 12 Installation hole 2 Tunnel surveying target 3 Anchor portion 4 Main body portion 41 Through hole 42 Recessed portion 43 Thin portion 44 Displacement prevention hole 5 Prism 6 Bolt 61 Shaft portion 62 Head portion 7 Displacement prevention member

Claims (5)

An anchor part embedded in the tunnel wall;
A plate-shaped main body having a through hole formed in the center from the front surface to the back surface and attached to the tunnel wall surface;
A prism attached to the main body;
A bolt having a shaft portion passing through the through hole and screwed into the anchor portion,
The prism is exposed through an opening formed in a side surface of the main body,
A tunnel surveying target, characterized in that the side of the main body on which the opening is formed and the side opposite the through hole have an inclined surface formed thereon, the thickness of which decreases as the distance from the through hole increases. The tunnel survey target according to claim 1, characterized in that the main body is frustum-shaped. 3. The target for tunnel surveying according to claim 1, wherein a recess capable of accommodating a head of the bolt is formed on a surface of the main body. The tunnel survey target according to any one of claims 1 to 3, further comprising a slip-stop member that penetrates the main body and is inserted into the tunnel wall. Drilling work to drill holes in the tunnel wall to form installation holes;
and installing a target for tunnel surveying in the installation hole,
The tunnel survey target includes a main body to which a prism is attached, a bolt penetrating the main body, and an anchor portion fixed to one surface of the main body via the bolt,
The target installation method is characterized in that, in the installation work, the head of the bolt is struck to apply a pressing force to the other surface of the main body portion, thereby forcing the anchor portion into the installation hole and bringing one surface of the main body portion into contact with the tunnel wall surface.

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