JP7672950B2 - Tunnel support joints - Google Patents

Description

The present invention relates to a tunnel support joint that connects tunnel supports.

The NATM method and other methods are used to construct tunnels, and tunnel supports are used as appropriate. Tunnel supports are usually made of steel such as H-shaped steel, and are formed into an arch shape by connecting a pair of steel members divided into two around the circumference of the tunnel at the top of the tunnel, for example.

In order to connect steel materials together, joint plates provided on the end faces of the steel materials are generally butted together and bolted together.
To connect the bolts, workers must do it manually, using a man gauge or similar equipment, which is a drawback to automation and poses the risk of industrial accidents due to the face falling off.

In the past, as described in Patent Document 1, a connecting plate was provided at the upper end of each divided support, and a concave connecting portion was formed on both sides of the first connecting plate, including a circular insertion hole and a locking hole with a width smaller than the diameter of the insertion hole, and a convex connecting portion was protruded on both sides of the second connecting plate, including a shaft with a diameter smaller than the width of the locking hole and a conical locking portion provided at the tip of the shaft, and the locking portion has a bottom with a diameter larger than the width of the locking hole and smaller than the diameter of the insertion hole, and a method of erecting tunnel supports has been proposed in which the locking portion is inserted into the insertion hole, the first connecting plate and the second connecting plate are butted together, the shaft portion is inserted through the insertion hole, and then the first connecting plate and the second connecting plate are moved in parallel to drop the shaft portion into the locking hole, and the concave connecting portion and the convex connecting portion are engaged to connect a pair of divided supports.

Patent Document 2 also discloses a method of connecting steel supports, in which a male joint plate is provided at the top end of one steel support and a female joint plate is provided at the top end of the other steel support, a groove-shaped female connector that opens at the side edge of the female connector plate is formed, a male connector that slidably engages with the female connector is provided on the male connector plate, the male connector is aligned with the opening of the female connector, and the male connector plate and the female connector plate are moved in parallel to slide the male connector along the female connector and insert it to the end of the female connector, thereby connecting one steel support to the other steel support.

According to the construction methods described in Patent Documents 1 and 2, a pair of split supports are connected by engaging the connecting parts provided at the top ends of the pair of split supports, eliminating the need to manually tighten bolts near the top of the tunnel, and the tunnel supports can be easily erected using an erector device, which also increases the safety of the work.

JP 2017-115446 A JP 2018-178452 A

The tunnel support erection method described in Patent Document 1 above requires aligning the convex connecting parts with the locking holes, and the connection methods described in Patent Documents 1 and 2 both involve parallel movement of the connecting plates while they are in contact with each other, which creates frictional forces when the split supports are moved in this way, causing problems when adjusting the erector device when connecting them. In particular, if the connecting plates are tilted or not smooth due to manufacturing errors, this, combined with friction, can cause problems with smooth parallel movement.

In addition, the connecting methods described in Patent Documents 1 and 2 have two convex connecting parts and two locking holes, which are moved in parallel to connect them, so the two convex connecting parts and locking holes must be moved in parallel at the same speed. However, if the erector device is unable to move with such precision, the speed at which one convex connecting part and locking hole part moves may differ from the speed at which the other convex connecting part and locking hole part moves, causing twisting at the connecting part and causing them to compete or interlock, preventing smooth parallel movement or requiring parallel movement in the opposite direction to release the interlocking, which can reduce the efficiency of the connection construction. This can be particularly significant when there are processing errors in the formation of the convex connecting parts and locking holes.

The problem that this invention aims to solve is to provide a tunnel support joint that can be smoothly connected and assembled.

The invention according to claim 1 of the present application is a joint for tunnel supports that butt-fits the end face of one divided support to the end face of the other divided support, comprising one joint plate provided on the end face of one divided support, the other joint plate provided on the end face of the other divided support, a notch having an entrance portion opening on the periphery of the one joint plate and a deep portion that is continuous with the entrance portion and has a diameter larger than the minimum width of the entrance portion, and a connecting shaft protruding from the surface of the other joint plate in the axial direction of the support, the connecting shaft having a rod-shaped base portion provided on the other joint plate and a thin-diameter shaft portion extending from the tip of the rod-shaped base portion. , and a head portion formed at the tip of the thin-diameter shaft portion of the connecting shaft, the diameter of the rod-shaped base portion is larger than the minimum width of the entrance portion and smaller than the diameter of the innermost portion, the diameter of the thin-diameter shaft portion is smaller than the minimum width of the entrance portion, and the diameter of the head portion is larger than the diameter of the innermost portion, the thin-diameter shaft portion is inserted into the entrance portion, the one joint plate and the other joint plate are moved in parallel while being spaced apart from each other, the thin-diameter shaft portion is aligned with the innermost portion, the one joint plate and the other joint plate are butted together, and the rod-shaped base portion is inserted into the innermost portion to connect them.

The invention according to claim 2 of the present application is the tunnel support joint described in claim 1, characterized in that one connecting shaft is provided on the other joint plate.

The invention according to claim 3 of the present application is a tunnel support joint as described in claim 1 or claim 2, characterized in that the tip of the rod-shaped base portion has a gradually smaller diameter toward the thin-diameter shaft portion.

The invention according to claim 4 of the present application is a tunnel support joint according to any one of claims 1 to 3, characterized in that the entrance portion is formed so that the portion connected to the innermost portion has a minimum width and gradually becomes wider toward the periphery of one of the joint plates.

The invention according to claim 5 of the present application is a tunnel support joint according to any one of claims 1 to 4, characterized in that one of the split supports has a web, and the entrance of the notch opens to the periphery of the one joint plate closer to the tunnel mouth than the web.

The invention according to claim 6 of the present application is a tunnel support joint according to any one of claims 1 to 5, characterized in that the connecting shaft is provided with a locking claw that can be inserted and removed from the outer circumferential surface of the rod-shaped base and is biased in the protruding direction, the locking claw has a tapered outer surface that is inclined so that the protruding width from the outer circumferential surface of the rod-shaped base gradually increases from the tip side to the base end side of the connecting shaft when protruding, and the sum of the protruding width of the base end of the tapered outer surface and the diameter of the rod-shaped base is greater than the diameter of the innermost part.

The invention according to claim 7 of the present application is a tunnel support joint according to any one of claims 1 to 6, characterized in that a through hole is formed in one of the joint plates, and a pin is provided in the other joint plate that protrudes from the other joint plate and engages with the through hole.

The invention according to claim 8 of the present application is the tunnel support joint described in claim 7, characterized in that the pin is provided with another locking claw that can be retracted from the outer peripheral surface and is biased in the protruding direction, the other locking claw has a tapered outer surface that is inclined so that the protruding width from the outer peripheral surface gradually increases from the tip side to the base end side of the pin when protruding, and the sum of the protruding width of the base end of the tapered outer surface and the diameter of the pin is larger than the diameter of the through hole.

The invention according to claim 9 of the present application is a tunnel support joint as described in claim 7 or claim 8, characterized in that the length of the pin protruding from the other joint plate is shorter than that of the rod-shaped base.

The notch and rod-shaped base of the present invention allow one joint plate and the other joint plate to move in parallel while being spaced apart, so that no frictional force is generated between the joint plates during the movement of the divided support, making it easy to adjust the erector device, and allowing the support to be smoothly connected and assembled. In particular, even if the joining plates are inclined or not smooth due to manufacturing errors, there is no hindrance to the parallel movement.
In addition, by forming a head at the tip of the thin-diameter shaft portion with a diameter larger than the diameter of the back part of the notch, there is no need to worry about the connecting shaft coming out of the notch when moving one joint plate in parallel with the other joint plate, which increases the stability of the erection of the tunnel support work.

In addition, because only one connecting shaft is provided on the other joint plate, there is no conflict or interlocking that occurs when two or more shafts are provided, allowing for smooth parallel movement.

In addition, the tip of the rod-shaped base gradually becomes smaller toward the thin-diameter shaft portion, making it easier to insert the rod-shaped base into the depth of the notch.

In addition, the inlet portion is narrowest where it is connected to the back portion, and is gradually wider toward the periphery of one of the joint plates, making it easier to insert the thin-diameter shaft portion of the connecting shaft into the back portion of the notch.

In addition, one of the split supports has a web, and the entrance of the notch opens to the periphery of the tunnel entrance side from the web of one of the joint plates, so the small diameter shaft part and the entrance of the notch can be easily aligned visually.

In addition, the connecting shaft is provided with a locking claw that can retract from the outer circumferential surface of the rod-shaped base and is biased in the protruding direction, the locking projection has a tapered outer surface, and the sum of the protruding width of the base end of the tapered outer surface and the diameter of the rod-shaped base is greater than the diameter of the innermost portion, so that when the rod-shaped base is inserted into the innermost portion of the notch, the locking claw retracts and does not get in the way, and after the rod-shaped base is inserted into the innermost portion of the notch, the locking claw protrudes and locks into one of the joint plates, preventing the connecting shaft from slipping out of the notch.

In addition, one of the joint plates has a through hole formed therein, and the other joint plate has a pin protruding from the other joint plate and engaging with the through hole, further strengthening the connection.

In addition, by making the pin shorter than the rod-shaped base, when one joint plate and the other joint plate are moved in parallel while separated from each other, the rod-shaped base prevents one joint plate from coming into contact with the pin, allowing for a smooth connection and preventing damage to the pin.

1 is a perspective view of a tunnel support to which an embodiment of the present invention is applied. This is an oblique view of the connection state of a tunnel support joint in an embodiment of the present invention, viewed from the tunnel entrance side. This is an oblique view of the connection state of a tunnel support joint in an embodiment of the present invention, viewed from the face side. FIG. 2 is a plan cross-sectional view of the connected state of a tunnel support joint according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of one of the divided supports according to an embodiment of the present invention. FIG. 11 is an end view of the other divided support according to the embodiment of the present invention. FIG. 2 is a side view in which a part of the connecting shaft according to the embodiment of the present invention is cut away. FIG. 2 is a perspective view showing a connection procedure of a tunnel support joint according to an embodiment of the present invention. FIG. 2 is a plan view showing a connection procedure of a tunnel support joint according to an embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings. It goes without saying that the present invention is not limited to the embodiment.

Figure 1 is a perspective view of a tunnel support to which the embodiment is applied, Figures 2 and 3 are perspective views of the tunnel support joints of the embodiment in a connected state, Figure 4 is a plan cross-sectional view of the tunnel support joints in a connected state, Figure 5 is a cross-sectional view of one of the divided supports, Figure 6 is an end view of the other divided support, Figure 7 is a side view with a portion of the connecting shaft broken away, and Figures 8 and 9 are a perspective view and a plan view, respectively, showing the connection procedure of the tunnel support joints.

As shown in Fig. 1, a tunnel support 1 is formed in an arch shape by butting together the end faces of a pair of separate supports 2, 3, which are separated in the circumferential direction of the tunnel, near the top of the tunnel. The tunnel support joint of the present invention is applied to the joint of this connection.
As the tunnel excavation progresses, the tunnel supports 1 are erected along the circumferential direction of the tunnel wall at regular intervals in the tunnel axial direction.

As shown in Figs. 2 and 3, the pair of divided supports 2, 3 are made of H-shaped steel members each having a web 20, 30 and a flange 21, 31 perpendicular to both ends of the web 20, 30, and are formed in an arc shape.
In addition, the pair of split supports 2, 3 are arranged so that the webs 20, 30 run along the height direction of the tunnel and the flanges 21, 31 run along the tunnel axis direction.

As shown in FIG. 5, one joint plate 4 is provided on the end face on the upper end side of one of the divided supports 2 so as to be perpendicular to the axial direction of the support.
One of the joint plates 4 is a rectangular steel plate whose height and width are greater than the height of the web 20 and the width of the flange 21 of one of the split supports 2, and are sufficient to cover the end face of one of the split supports 2.

A notch 40 is formed on the wellhead side of one of the joint plates 4 across the web 20 .
The notch 40 has an inlet portion 40a that opens to the peripheral edge of one of the joint plates 4, and a back portion 40b that is continuous with the inlet portion 40a and opens with a diameter d1 that is larger than the minimum width w of the inlet portion 40a.

The inlet portion 40a is provided between guide edges 41 which are formed at a gradual incline so that the distance therebetween narrows inward from the wellhead side peripheral edge of one of the joint plates 4.
The guide edges 41 at the innermost portion from the wellhead side peripheral edge of the inlet portion 40a are formed close to each other, forming the minimum width w of the inlet portion 40a, where it continues to the inner portion 40b. That is, the inlet portion 40a has the minimum width w at the portion that continues to the inner portion 40b, and is formed so as to gradually widen toward the peripheral edge of one of the joint plates 4.

The innermost portion 40b is circular and opens continuously with the entrance portion 40a on the mine mouth side, and the diameter d1 of the circle is larger than the minimum width w of the entrance portion 40a.

In addition, a circular through hole 42 is formed on the face side of one of the joint plates 4, sandwiching the web 20, at a position symmetrical to the inner part 40b of the notch 40.

As shown in Figures 4 and 6, the other joint plate 5 is provided on the end face on the upper end side of the other divided support 3 so as to be perpendicular to the axial direction of the support.
The other joint plate 5 is a steel plate of the same shape and dimensions as the other joint plate 4, and its height and width are greater than the height of the web 30 and the width of the flange 31 of the other split support 3, and are sufficient to cover the end face of the other split support 3.

On the tunnel entrance side across the web 30, a connecting shaft 50 protrudes from the surface of the other joint plate 5 in the support axial direction.
Only one connecting shaft 50 is provided on the other joint plate 5 .
Specifically, the connecting shaft 50 is inserted into a hole formed in the other joint plate 5 and fixed by welding on the back side (FIG. 4). Since the welding between the connecting shaft 50 and the other joint plate 5 is performed on the back side, the surface of the other joint plate 5, which is the connecting surface, is even and can be connected to the surface of one joint plate 4 without any gaps.

The connecting shaft 50 has a circular cross-section and comprises a rod-shaped base 51 fixed to the other joint plate 5, a thin shaft portion 52 extending from the tip of the rod-shaped base 51, and a head 53 formed at the tip of the thin shaft portion 52.
The diameter d2 of the rod-shaped base portion 51 is larger than the minimum width w of the entrance portion 40a of the notch 40 and smaller than the diameter d1 of the innermost portion 40b.

Further, the diameter d3 of the thin shaft portion 52 is smaller than the minimum width w of the entrance portion 40a of the notch 40. That is, the thin shaft portion 52 is formed thinner than the rod-shaped base portion 51. The diameter of the tip portion of the rod-shaped base portion 51 gradually decreases toward the thin shaft portion 52.
The diameter d4 of the head 53 is larger than the diameter d1 of the innermost portion 40b of the notch 40.

As shown in FIG. 7, the rod-shaped base 51 is provided with a locking claw 54 which can protrude from and retract into the outer circumferential surface and is biased in a protruding direction.
A recess 540 having a circular cross section is formed on the outer circumferential surface of the rod-shaped base 51, and a cylindrical locking claw 54 is fitted into the recess 540 so as to be able to appear and disappear but not to come out.

A spring 541 is interposed between the inner end surface of the locking claw 54 and the bottom surface of the recess 540 to bias the recess 540 in the protruding direction.
The locking claw 54 has a tapered outer surface 542 that is inclined so that the width of the projection from the outer circumferential surface of the rod-shaped base portion 51 gradually increases from the tip end side to the base end side of the connecting shaft 50 .

When the locking claw 54 protrudes, the sum of the protruding width w1 of the base end of the tapered outer surface 542 and the diameter d2 of the rod-shaped base 51 is set to be larger than the diameter d1 of the innermost portion 40b of the notch 40.

On the face side sandwiching the web 30 , a pin 55 with a circular cross section is provided on the surface of the other joint plate 5 at a position symmetrical to the connecting shaft 50 and protrudes in the support axial direction.
Specifically, a pin 55 is inserted into a hole formed in the other joint plate 5 and fixed by welding on the back side (FIG. 4). Since the welding between the pin 55 and the other joint plate 5 is performed on the back side, the surface of the other joint plate 5, which is the connecting surface, is even and can be connected to the surface of the one joint plate 4 without any gaps.

A diameter d5 of the pin 55 is slightly smaller than a diameter d6 of the through hole 42 formed in one of the joint plates 4. The tip of the pin 55 is tapered.
The length of the pin 55 is approximately equal to the length of the rod-shaped base 51 of the connecting shaft 50 , and the length by which it protrudes from the surface of the other joint plate 5 is also approximately equal to that of the rod-shaped base 51 .

The pin 55 is provided with another locking claw 56 that can protrude from and retract into the outer circumferential surface and is biased in the protruding direction (FIG. 3). The structure of the other locking claw 56 is similar to that of the locking claw 54 of the connecting shaft 50, and therefore a detailed description thereof will be omitted.
When the other locking claw 56 protrudes, the sum of the protruding width of the base end of the other locking claw 56 and the diameter d5 of the pin 55 is greater than the diameter d6 of the through hole 42.

The erection of the tunnel support 1 will be explained with reference to Figures 8 and 9.
A pair of hands of an erector device (not shown) grasps one of the split supports 2 and the other split support 3, respectively, and the erector device is brought close to the face.
Next, the hand of the erector device is moved to make the axial direction of one split support 2 and the other split support 3 perpendicular to the tunnel axis direction, so that the heights of one split support 2 and the other split support 3 are aligned.

Next, the hand is moved to move one split support 2 and the other split support 3 relative to each other, so that the other joint plate 5 faces the mine mouth side of one joint plate 4, and the thin-diameter shaft portion 52 of the connecting shaft 50 is positioned within the entrance portion 40a of the notch 40 from the peripheral side, as shown in Figure 8 (a) and Figure 9 (a).
The connecting shaft 50 and the entrance portion 40a of the notch 40 are exposed on the tunnel mouth side, that is, the entrance portion 40a of the notch opens onto the periphery of the tunnel mouth side from the web of one of the joint plates 4, so that the thin-diameter shaft portion 52 and the entrance portion 40a of the notch 40 can be easily aligned visually.

Next, as shown in Figure 8 (b) and Figure 9 (b), one of the split supports 3 is moved toward the face relative to the other split support 2, and one of the joint plates 4 and the other joint plate 5 are moved parallel to each other so that the thin-diameter shaft portion 52 of the connecting shaft 50 is positioned within the innermost portion 40b of the notch 40 from the entrance portion 40a.
At this time, since a rod-shaped base portion 51 having a diameter larger than the minimum width w of the inlet portion 40a is provided on the base end side of the thin-diameter shaft portion 52, one joint plate 4 and the other joint plate 5 are moved in parallel while being spaced apart, and the two do not come into contact with each other.

Furthermore, since guide edges 41 are formed on both sides of the entrance portion 40a of the notch 40, the small diameter shaft portion 52 can be reliably inserted through the entrance portion 40a of the notch 40 into the inner portion 40b.
In addition, a head 53 having a diameter d4 larger than the diameter d1 of the innermost portion 40b of the notch 40 is formed at the tip of the thin-diameter shaft portion 52, so that the connecting shaft 50 will not come out of the innermost portion 40b of the notch 40 and is unlikely to come out of the entrance portion 40a of the notch 40.

Next, one of the split supports 3 is moved relative to the other split support 2 in the axial direction of the supports, and one joint plate 4 is butted against the other joint plate 5, as shown in Figure 8 (c) and Figure 9 (c), so that the surface of one joint plate 4 is brought into contact with the surface of the other joint plate 5.

Then, as shown in FIGS. 2 to 4, the rod-shaped base portion 51 of the connecting shaft 50 is inserted into the inner portion 40 b of the notch 40 , and the pin 55 is inserted into the through hole 42 .
At this time, the tip of the rod-shaped base 51 gradually becomes smaller in diameter toward the thin-diameter shaft portion 52, making it easy to insert into the inner portion 40b of the notch 40, and the tip of the pin 55 is tapered, making it easy to insert into the through hole 42.

The locking claw 54 protruding from the outer peripheral surface of the rod-shaped base 51 and the other locking claw 56 protruding from the outer peripheral surface of the pin 55 have tapered outer surfaces 542, so that when passing through the innermost portion 40b of the notch 40 and the through hole 42, the locking claw 54 and the other locking claws 56 collapse against the spring 541 and sink into the recess 540, allowing the rod-shaped base 51 to pass through the innermost portion 40b of the notch 40 and the pin 55 to pass through the through hole 42.
Then, when the locking claw 54 and the other locking claw 56 pass through the inner portion 40b of the notch 40 and the through hole 42, they are pushed by the spring 541 and protrude again, and engage with the back surface of one of the joint plates 4. The locking claw 54 and the other locking claw 56 are engaged with each other, preventing them from coming loose, and the connection can be made stronger.

By engaging the inner part 40b of the notch 40 with the connecting shaft 50 and engaging the through hole 42 with the pin 55, one joint plate 4 and the other joint plate 5 are overlapped and connected, thereby connecting one divided support 2 and the other divided support 3 near the top of the tunnel, and erecting the arch-shaped tunnel support 1.

One joint plate 4 and the other joint plate 5 are connected on both sides of the webs 20, 30, so that one divided support 2 and the other divided support 3 are stably connected and are not easily deformed by the load.

[Other Modifications]
The present invention is not limited to the above-mentioned embodiment, and may also include the following, for example.

In this embodiment, the tunnel supports are H-shaped steel, but they may be steel materials of other shapes. Also, in this embodiment, the supports are arch-shaped, but they may be other shapes.

In this embodiment, the tunnel support joint is used to connect near the top of the tunnel, but it is not limited to this and may also be used to connect tunnel supports at the side or bottom.

In this embodiment, one joint plate is moved parallel to the tunnel axis direction relative to the other joint plate, then moved in the support axis direction to bring them closer together, and the connecting shaft engages with the notch, but it is also possible to move them parallel upward or downward before bringing them closer together. In this case, the notch opens at the lower or upper edge of one joint plate.

In this embodiment, the face side of one joint plate and the other joint plate sandwiching the web is connected by inserting a pin into the through hole, but it is also possible to connect them using clip fittings, etc. Also, instead of inserting a pin into the through hole, if a decrease in safety can be tolerated, a through hole may be provided in one joint plate and the other joint plate and a conventional bolt and nut method may be applied.

In this embodiment, the entrance of the notch is formed to gradually widen toward the periphery of one of the joint plates, but this is not limited to this. The guide edges formed on one of the joint plates may be provided in parallel and continuous with the inner part. In this case, the distance between the parallel guide edges is the minimum width of the entrance.

In this embodiment, the length of the pin protruding from the surface of the other joint plate is substantially equal to the length of the rod-shaped base protruding from the surface of the other joint plate, but is not limited thereto. The length of the pin protruding from the surface of the other joint plate may be shorter than the length of the rod-shaped base protruding from the surface of the other joint plate, that is, the length of the pin protruding from the other joint plate may be shorter than the rod-shaped base.
In this way, when one joint plate and the other joint plate are moved in parallel while separated from each other, the rod-shaped base portion prevents one joint plate from contacting the pin, allowing for a smooth connection and preventing damage to the pin. The rod-shaped base portion may be set to be longer than the pin.

In this embodiment, only one connecting shaft 50 is provided on the other joint plate, so that smooth parallel movement is possible without any conflict or interlocking as occurs when two or more connecting shafts are provided, but this is not limited to this. Multiple connecting shafts may be provided, and in that case, multiple notches may also be provided.

The technical aspects of any embodiment may be applied to other embodiments as examples.

REFERENCE SIGNS LIST 1 Tunnel support 2 One divided support 20 Web 21 Flange 3 Other divided support 30 Web 31 Flange 4 One joint plate 40 Notch 40a Entrance portion 40b Back portion 41 Guide edge 42 Through hole 5 Other joint plate 50 Connecting shaft 51 Rod-shaped base portion 52 Thin-diameter shaft portion 53 Head portion 54 Locking claw 540 Recessed portion 541 Spring 542 Tapered outer surface 55 Pin 56 Other locking claw

Claims (9)

A joint for tunnel supports that connects the end face of one divided support to the end face of the other divided support by butting them together.
One joint plate provided on an end face of one of the divided supports;
The other joint plate provided on the end face of the other divided support;
a notch having an inlet portion that opens to a peripheral edge of the one joint plate and a deep portion that is continuous with the inlet portion and has a diameter larger than the minimum width of the inlet portion;
A connecting shaft protruding from the surface of the other joint plate in the support axial direction,
the connecting shaft includes a rod-shaped base portion provided on the other joint plate, a thin shaft portion extending from a tip of the rod-shaped base portion, and a head portion formed at a tip of the thin shaft portion of the connecting shaft,
a diameter of the rod-shaped base portion is larger than the minimum width of the inlet portion and smaller than the diameter of the innermost portion, a diameter of the thin-diameter shaft portion is smaller than the minimum width of the inlet portion, and a diameter of the head portion is larger than the diameter of the innermost portion;
a first joint plate and a second joint plate arranged in a spaced-apart relationship to each other, the first joint plate and the second joint plate being moved in parallel to each other while being spaced apart from each other, the second joint plate and the third joint plate being butted together, and the rod-shaped base portion being inserted into the second joint portion to connect the first joint plate and the second joint plate. The tunnel support joint according to claim 1, characterized in that one connecting shaft is provided on the other joint plate. A tunnel support joint as described in claim 1 or 2, characterized in that the tip of the rod-shaped base portion has a gradually smaller diameter toward the thin-diameter shaft portion. A tunnel support joint according to any one of claims 1 to 3, characterized in that the entrance section is formed so that the section connected to the innermost section has a minimum width and gradually widens toward the periphery of one of the joint plates. The one of the divided supports has a web,
A tunnel support joint as described in any one of claims 1 to 4, characterized in that the entrance portion of the notch opens to the peripheral edge of the one joint plate on the tunnel entrance side from the web. the connecting shaft is provided with a locking claw that can protrude from and retract into the outer circumferential surface of the rod-shaped base portion and is biased in a protruding direction,
the locking claw has a tapered outer surface that is inclined so that a protruding width from an outer circumferential surface of the rod-shaped base portion gradually increases from a tip end side to a base end side of the connecting shaft,
A tunnel support joint as described in any one of claims 1 to 5, characterized in that the sum of the protruding width of the base end of the tapered outer surface and the diameter of the rod-shaped base portion is greater than the diameter of the innermost portion. A tunnel support joint according to any one of claims 1 to 6, characterized in that a through hole is formed in one joint plate, and a pin is provided in the other joint plate that protrudes from the other joint plate and engages with the through hole. The pin has another locking claw that can protrude from and retract into the outer circumferential surface and is biased in the protruding direction,
the other locking claw has a tapered outer surface that is inclined so that a protruding width from an outer circumferential surface gradually increases from a tip end side to a base end side of the pin when protruding,
A tunnel support joint as described in claim 7, characterized in that the sum of the protruding width of the base end of the tapered outer surface and the diameter of the pin is greater than the diameter of the through hole. The tunnel support joint according to claim 7 or 8, characterized in that the length of the pin protruding from the other joint plate is shorter than the rod-shaped base.

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