JP7517973B2 - Steel support connection structure and steel support erection method - Google Patents

Description

The present invention relates to a steel support connection structure and a steel support erection method for connecting a pair of left and right steel supports at the top end, mainly in the excavation of mountain tunnels.

Traditionally, there have been various construction methods for mountain tunnel construction, each differing in the excavation method, but in any case, the construction procedure generally involves drilling, charging, blasting, removing debris, primary spraying, erecting steel supports, secondary spraying, and driving rock bolts in a sequential and step-by-step manner to carry out excavation and support work.

As shown in Figures 15 and 16, H-shaped steel is usually used for the steel support 50, and a pair of left and right split supports 50A, 50B are erected, divided left and right at the tunnel center line L. The pair of left and right split supports are connected by joints 51 installed at the top end, forming an arch shape that follows the tunnel perimeter.

In the conventional structure of the top joint 51, as shown in FIG. 16, joint plates 52 are fixed to the ends of the H-shaped steel of the left and right split supports 50A and 50B, and the joint plates 52 are butted together and fastened with bolts 53 that penetrate the joint plates 52, 52 integrally at two locations on both sides of the web part w of the H-shaped steel. In the erection work of the steel support, the work of connecting the split supports at the top was done by a worker riding on a man gauge equipped on a spraying machine with an erector device, approaching the vicinity of the face, and tightening the bolts 53 by hand, as shown in FIG. 17. This work requires the worker to tighten the bolts by hand while looking down (or by feeling with his hands) in an unstable condition where the ground has been sprayed with primary concrete but not yet sprayed with secondary concrete, so there is a risk of a serious accident occurring when the surface falls.

For this reason, one-touch quick joints have been developed in recent years, as described in Patent Documents 1 and 2 below. The following Patent Documents 1 and 2 disclose a connection structure for connecting the top ends of a pair of arc-shaped steel supports erected along a tunnel wall, which includes a first top joint plate and a second top joint plate that are provided at the top ends of the pair of steel supports and abut against each other when the pair of steel supports are connected, a female connector recessed in the first top joint plate, and a male connector protruding from the second top joint plate, and the male connector has a rod-shaped male locking member protruding from the second top joint plate, and the female connector includes an opening formed through the first top joint plate and a casing having a storage chamber inside that communicates with the opening and has an insertion opening through which the male locking member can be inserted, and the steel support connection structure is engaged with the male locking member inserted into the storage chamber from the insertion opening.

JP 2018-178451 A JP 2019-163663 A

However, in the connection structures described in Patent Documents 1 and 2, the rod-shaped male connection part is provided protruding from the second top end joint plate toward the opposing first top end joint plate, so in order to insert this male connection part into the female connection part, the steel support must be extended toward the ground by the length of the protruding male connection part, which has the disadvantage of causing an increase in overexcavation. In addition, because the male connection parts are provided at the front and rear of the tunnel axial direction, there is the issue that it is difficult to align the male connection part when inserting it into the female connection part.

The main objective of the present invention is to provide a steel support connection structure and a steel support installation method that eliminate the need for bolt tightening work when erecting steel supports, allowing workers to complete the erection work of steel supports without approaching the steel supports, and that allows steel supports to be connected easily and accurately.

In order to solve the above problems, the present invention relates to a first aspect of the present invention, which is a steel support connection structure for connecting a pair of left and right steel supports to each other at a joint portion at the top end,
The joint portion of the steel support is configured such that a face-side splice member is fixed to the face-side side of the steel support that is installed first, protruding from the edge of the top end, and a mine-mouth-side splice member is fixed to the mine-mouth-side side of the steel support that is installed later, protruding from the edge of the top end, and the portions of the face-side splice member and the mine-mouth-side splice member that protrude from each steel support are overlapped on the side of the steel support on the opposite side.
The face side splice member is provided with a rod-shaped connecting member protruding toward the mouth side, and the steel support and the mouth side splice member are each provided with an opening into which the connecting member is inserted,
A connecting structure for steel support is provided, characterized in that the connecting member is equipped with a pull-out prevention means that prevents the wellhead side connecting member from easily coming out after the opening provided in the wellhead side connecting member is fitted to a predetermined position.

In the invention described in claim 1, the joint structure of the steel support is not provided so that the connecting member protrudes from the top edge of the steel support in the tunnel circumferential direction as in the conventional case, but is provided so that it protrudes from the side of the steel support in the tunnel axial direction, and the opening of the wellhead side attachment member is inserted into the connecting member while the steel support to be installed later is moved in the tunnel axial direction, and the connecting member is connected to the opening. The connecting member is provided with a pull-out prevention means that prevents the wellhead side attachment member from easily coming out after the opening of the wellhead side attachment member is fitted to a predetermined position. In this way, by fitting the opening on the tunnel head side attachment member of the steel support to be installed later to a specified position with the connecting member provided on the face side attachment member of the steel support to be installed first, the tunnel head side attachment member cannot easily come out due to the anti-detachment means provided on the connecting member, so there is no need to tighten bolts when erecting the steel support, and the erection work can be completed by simply operating the steel support erection device without the worker approaching the steel support, and the steel support can be connected easily and accurately.

In the present invention according to claim 2, the fall-off prevention means comprises a rotating member whose tip side is rotatably supported with respect to the protruding direction of the connecting member and whose base end side is pressed by a pressing member in a direction protruding from an outer surface of the connecting member,
A connecting structure for steel support as described in claim 1 is provided, in which when an opening provided in the minehead side attachment member passes through the rotating member, the rotating member rotates against the pressing force of the pressing member to sink inside the connecting member, and after the opening passes through the rotating member, the rotating member rotates due to the pressing force of the pressing member to protrude from the outer surface of the connecting member, thereby preventing the minehead side attachment member from easily coming out.

The invention described in claim 2 above is a first embodiment of the anti-detachment means provided on the connecting member, and is made of a rotating member whose tip side is rotatably supported inside the connecting member with respect to the protruding direction of the connecting member, and whose base end side is pressed outward by a pressing member. When the opening provided in the wellhead side attachment member passes through, this rotating member rotates about the rotation axis against the pressing force of the pressing member, and sinks into the inside of the connecting member. Then, after the opening passes through, it protrudes from the outer surface of the connecting member by rotating about the rotation axis due to the pressing force of the pressing member. As a result, after the opening of the wellhead side attachment member passes through the rotating member, the wellhead side attachment member does not easily come out.

According to a third aspect of the present invention, the fall-off prevention means includes a protruding member having an outer surface that is an inclined surface that protrudes gradually outward from a tip end side toward a base end side with respect to a protruding direction of the connecting member, and the protruding member is pressed outward by a pressing member,
A connecting structure for steel support as described in claim 1 is provided, in which when an opening provided in the minehead side attachment member passes through the protruding member, as the opening moves along the inclined surface, the protruding member gradually sinks into the inside of the connecting member against the pressing force of the pressing member, and after the opening passes through the protruding member, the protruding member protrudes from the outer surface of the connecting member due to the pressing force of the pressing member, thereby preventing the minehead side attachment member from easily coming out.

The invention described in claim 3 above is a second embodiment of the anti-detachment means provided on the connecting member, and is made of a retractable member whose outer surface is an inclined surface that gradually protrudes outward from the tip side toward the base side with respect to the protruding direction of the connecting member, and which is pressed outward by a pressing member. When an opening provided in the wellhead side attachment member passes through, this retractable member gradually retracts into the connecting member against the pressing force of the pressing member as the opening moves along the inclined surface. Then, after the opening has passed through, it protrudes from the outer surface of the connecting member due to the pressing force of the pressing member. This prevents the wellhead side attachment member from easily coming out after the opening of the wellhead side attachment member has passed through the retractable member.

In the present invention according to claim 4, the fall-off prevention means is a stepped portion formed along a circumferential direction of the connecting member and having a lower proximal end side in a protruding direction of the connecting member,
A steel support connection structure as described in claim 1 is provided, in which the peripheral edge of an opening provided in the minehead side attachment member fits into the step portion, preventing the minehead side attachment member from easily coming loose.

The invention described in claim 4 above is a third embodiment of the anti-detachment means provided on the connecting member, and is made of a low step portion formed along the circumferential direction of the connecting member at the base end side in the protruding direction of the connecting member. When the opening provided in the wellhead side attachment member is inserted up to the step portion, the opening and the connecting member become eccentric, and a part of the periphery of the opening fits into the step portion, preventing the wellhead side attachment member from easily coming out.

The present invention according to claim 5 provides a connection structure for a steel support as described in claim 4, in which a notch is formed on the periphery of the opening provided in the wellhead side attachment member, and the diameter of the connection member is larger than the diameter of the opening provided in the wellhead side attachment member.

In the invention described in claim 5, when the anti-detachment means is made of the step portion, a notch is formed on the periphery of the opening in the wellhead side attachment member so that the opening can be enlarged slightly, and the diameter of the connecting member is made larger than the diameter of the opening in the wellhead side attachment member, so that the wellhead side attachment member is more reliably prevented from coming out than when the opening is fitted into the step portion.

As a sixth aspect of the present invention, there is provided a method for erecting a steel support using the connection structure of the steel support according to any one of the first to fifth aspects,
A method for erecting steel supports is provided, characterized in that the connecting member is fitted into an opening provided in the tunnel entrance side attachment member while the steel support to be installed subsequently is pushed in the tunnel axial direction to connect the connecting member.

In the invention described in claim 6 above, the connecting member can be connected by simply fitting the opening provided in the tunnel mouth side attachment member into the connecting member and pushing the steel support to be installed later in the tunnel axial direction, making the erection of the steel support extremely easy.

As explained above in detail, according to the present invention, the bolt tightening work is eliminated when erecting steel supports, the erection work of steel supports can be completed without the worker having to approach the steel supports, and the steel supports can be connected easily and accurately.

A vertical cross-sectional view of a tunnel with steel supports 4 installed. A front view of the steel support 4. The joint portion of the steel support 4 is enlarged. (A) is a front view of the left-side divided support 4A, (B) is a front view of the right-side divided support 4B, and (C) is a front view of the connected state. 4 is a cross-sectional view taken along line IV-IV in FIG. 1A and 1B show a connecting member 10 according to a first embodiment, in which (A) is a cross-sectional view in a natural state, and (B) is a cross-sectional view in a state in which a rotating member 14 is retracted. A cross-sectional view showing the procedure for erecting a steel support equipped with a connecting member 10 according to the first embodiment. 1 shows a connecting member 10 for a second embodiment, where (A) is a top view, (B) is a cross-sectional view taken along line B-B of (A) in its natural state, and (C) is a cross-sectional view taken along line B-B of (A) in the state in which the retractable member 16 is retracted. A cross-sectional view showing the procedure for erecting a steel support equipped with a connecting member 10 relating to a second embodiment. FIG. 11 is a side view showing a connecting member 10 according to a third embodiment. A cross-sectional view showing the procedure for erecting a steel support equipped with a connecting member 10 according to a third embodiment. 13A is a front view of the left-side split support 4A, FIG. 13B is a front view of the right-side split support 4B, and FIG. 13C is a front view of the connected state, showing an enlarged view of the joint portion of the steel support 4 in a modified example of the third embodiment. 13 is a front view showing the relative positional relationship between a connecting member 10 and an opening 11 according to a modified example of the third embodiment. FIG. FIG. 2 is a plan view showing the installation method of steel shoring. FIG. 14 is a front view (view taken along the line XIV-XIV in FIG. 13 ). FIG. 2 is a front view of a conventional steel support 50. 1A and 1B show a joint 51 of a conventional steel support 50, in which (A) is a front view and (B) is an end view. 1 is a vertical cross-sectional view of a tunnel showing the erection work status of a conventional steel support structure 50. FIG.

The following describes in detail the embodiments of the present invention with reference to the drawings.

In the excavation of mountain tunnels, as shown in Figure 1, the primary shotcrete 2 is sprayed against the tunnel excavation surface 1, steel supports 4 are erected near the face 3, and then secondary shotcrete 5 is sprayed on top of the primary shotcrete 2 between the steel supports 4 erected one cycle before. This process is considered to be one cycle, and the tunnel supports are constructed by repeating this cycle. If necessary, multiple rock bolts (not shown) may be installed from the inner surface of the secondary shotcrete 5, penetrating the primary shotcrete 2 and driven into the ground.

As shown in FIG. 2, the steel shoring 4 is an arch-shaped member that is erected along the tunnel excavation surface onto which the primary shotcrete 2 has been sprayed in order to prevent the ground from collapsing, and is installed at regular intervals along the tunnel axis. The steel shoring 4 is formed from H-shaped steel consisting of a web portion w and flange portions f on both ends thereof, and in the example shown in FIG. 2, it is divided into left and right at the upper end (top end), and is formed into an arch shape by connecting the divided arc-shaped left divided shoring 4A and right divided shoring 4B at the upper end joint 8.

As shown in FIG. 3, the structure of the joint section 8 is such that the face-side joint member 6A is fixed to the face-side side of the web section w of the left-side divided support 4A, which is installed first, protruding from the edge of the top end in the tunnel circumferential direction, and the tunnel-mouth-side joint member 6B is fixed to the tunnel-mouth-side side of the web section w of the right-side divided support 4B, which is installed later, protruding from the edge of the top end in the tunnel circumferential direction. The parts of the face-side joint member 6A and the tunnel-mouth-side joint member 6B protruding from each divided support 4A, 4B are overlapped with the web section w of the divided support on the opposite side, with the top ends of the left-side divided support 4A and the right-side divided support 4B butted against each other. As a result, the face-side joint member 6A and the tunnel-mouth-side joint member 6B are arranged on both sides of the web section w across both divided supports 4A, 4B in the joint section 8.

The face-side attachment member 6A and the mouth-side attachment member 6B may be plate materials that cover only the web portion w of the steel support 4 made of H-shaped steel, but as shown in Figures 3 and 4, it is preferable to form them into a U-shaped cross section that covers the web portion w of the steel support 4 and covers approximately half of the flange portion f of the upper and lower portions. Approximately half of the face-side attachment member 6A and the mouth-side attachment member 6B are stacked on the left-side divided support 4A or the right-side divided support 4B, respectively, and approximately the remaining half protrudes from the left-side divided support 4A or the right-side divided support 4B. The face-side attachment member 6A is firmly joined by welding at the overlapping portion with the left-side divided support 4A, and the mouth-side attachment member 6B is firmly joined by welding at the overlapping portion with the right-side divided support 4B.

As shown in Figures 3 and 4, the face-side attachment member 6A is provided with rod-shaped connecting members 10, 10... that protrude toward the mine mouth side, and the steel support 4 and the mine mouth-side attachment member 6B are each provided with openings 11, 11... into which the connecting members 10 are inserted.

To place the connecting member 10 on the face-side attachment member 6A, the connecting member 10 is inserted into an opening provided in the face-side attachment member 6A, and with the tip of the connecting member 10 protruding toward the mine mouth, the base end of the connecting member 10 is welded to the face-side attachment member 6A.

In the illustrated example, a total of four connecting members 10 are arranged, two on each of the part of the face-side splice member 6A that is stacked on the left-side separate support 4A and the part that protrudes from the left-side separate support 4A, but this is not limited to this and any number between 2 and 8 can be arranged. As in the illustrated example, the multiple connecting members 10 are preferably arranged in a row along the longitudinal center line of the face-side splice member 6A, but they may be arranged in multiple rows, or they may be arranged in a row along the transverse direction of the face-side splice member 6A.

As shown in FIG. 5, the connecting member 10 is a rod-shaped member that is long in the protruding direction and has a circular cross section, and the tip of the protruding direction is formed in a tapered shape with a cross section that gradually becomes smaller toward the tip.

The characteristic feature of this connection structure is that the connecting member 10 is provided with a means for preventing the wellhead side abutment member 6B from easily coming out after the opening 11 provided in the wellhead side abutment member 6B is fitted to a predetermined position. The means for preventing the detachment is provided in the middle of the connecting member 10 in the longitudinal direction (projecting direction), and after the opening 11 of the wellhead side abutment member 6B is fitted to a predetermined position in the projecting direction, the means for preventing the detachment prevents the wellhead side abutment member 6B from easily coming out. The means for preventing the detachment is described in detail below.

[First Example of Dislodgement Prevention Means]
5, the first embodiment of the anti-detachment means is configured with a rotating member 14 whose tip side in the protruding direction of the connecting member 10 is rotatably supported by a rotating shaft 12, and whose base end side in the protruding direction of the connecting member 10 is pressed by a pressing member 13 in a direction protruding from the outer surface of the connecting member 10. As shown in FIG. 5, the rotating members 14 are small piece-like, block-like or plate-like members whose outer surface is curved similarly to the outer surface of the connecting member 10, and are fitted in a pair of left and right recesses or openings provided on the side surface of the connecting member 10, and the tip side in the protruding direction of the connecting member 10 is rotatably supported inside the connecting member 10 by the rotating shaft 12 perpendicular to the protruding direction, and the base end side in the protruding direction of the connecting member 10 can appear and disappear from the outer surface of the connecting member 10 by rotating around the rotating shaft 12. As shown in Fig. 5(A), in a natural state, the base end side of the protruding direction of the connecting member 10 is inclined outward with respect to the central axis of the connecting member 10 due to the pressing force of the pressing member 13, and is disposed in a state in which it protrudes a predetermined height from the outer surface of the connecting member 10, and when an external force is applied to the outer surface of the turning member 14, as shown in Fig. 5(B), the turning member 14 rotates about the turning shaft 12 against the pressing force of the pressing member 13, and can be retracted to approximately the same height as the outer surface of the connecting member 10. Note that the end of the turning member 14 on the side where the turning shaft 12 is provided does not protrude from the outer surface of the connecting member 10, and only rotates about the turning shaft 12 installed inside the connecting member 10.

The procedure for connecting the steel supports 4 using the connecting member 10 will be explained with reference to Figure 6. As shown in Figure 6(A), when the right-side separate support 4B is installed following the previously installed left-side separate support 4A, the opening 11 of the tunnel-head side attachment member 6B fixed to the right-side separate support 4B is inserted into the connecting member 10 while the right-side separate support 4B is moved in a direction from the tunnel head side toward the tunnel face side in a direction approximately parallel to the tunnel axis direction. The method for erecting the steel support 4 at this time will be explained in more detail later.

As shown in FIG. 6(B), when the opening 11 provided in the wellhead side attachment member 6B passes through the rotating member 14, the rotating member 14 rotates about the pivot shaft 12 against the pressing force of the pressing member 13, causing the base end side of the connecting member 10 in the protruding direction to sink into the inside of the connecting member 10.

After the opening 11 provided in the wellhead side attachment member 6B passes through the rotating member 14, the rotating member 14 rotates about the pivot axis 12 due to the pressing force of the pressing member 13, causing the base end side of the connecting member 10 in the protruding direction to protrude from the outer surface of the connecting member 10. This prevents the wellhead side attachment member 6B from easily coming out of the connecting member 10.

As described above, in the steel support erection method of the present invention, the connecting member 10 can be connected simply by fitting the opening 11 provided in the tunnel mouth side attachment member 6B into the connecting member 10 and pushing the right side separate support 4B, which is installed afterwards, in the tunnel axial direction, making the erection of the steel support 4 extremely simple.

In addition, by fitting the opening 11 on the wellhead side attachment member 6B of the right side separate support 4B to a specified position with the connecting member 10 provided on the face side attachment member 6A of the left side separate support 4A, which is installed first, the wellhead side attachment member 6B will not easily come out due to the anti-detachment means (rotating member 14) provided on the connecting member 10, so there is no need to tighten bolts when erecting the steel support 4, and the erection work can be completed by operating a spraying machine with an erector device that grips the steel support without a worker getting close to the steel support 4 on a man cage, and the left side separate support 4A and the right side separate support 4B can be connected easily and accurately.

As shown in Figure 5 (A), in order to make it easier to fit the opening 11 of the wellhead side abutment member 6B into the connecting member 10, it is preferable to set the tip of the connecting member 10 so that it protrudes toward the wellhead side beyond the flange portion f of the left-side divided support 4A. In this way, when the right-side divided support 4B, which is to be installed later, is brought close to the left-side divided support 4A, which was installed earlier, the opening 11 of the wellhead side abutment member 6B fixed to the right-side divided support 4B is inserted into the connecting member 10 first, and while being guided by this connecting member 10, the wellhead side abutment member 6B is inserted between the upper and lower flanges f, f of the left-side divided support 4A.

The lengths by which the multiple connecting members 10... protrude from the face-side attachment member 6A toward the mine mouth side may all be approximately the same length, or may be different lengths. When the lengths are different, the connecting members 10, 10 at both ends of the multiple connecting members 10... arranged in a row may be relatively long and the intermediate connecting members 10, 10 may be relatively short, or may be gradually shortened from one end to the other end. If the multiple connecting members 10... were all made to protrude the same length, all of the openings 11... provided in the mine mouth-side attachment member 6B would need to be simultaneously fitted into the connecting members 10..., but if some of them are formed with different lengths, they can be fitted into the openings 11 in stages, making alignment easier.

[Second embodiment of the detachment prevention means]
Next, a second embodiment of the pull-out prevention means will be described. The pull-out prevention means according to the second embodiment is configured as a retractable member 16 whose outer surface is an inclined surface that gradually protrudes outward from the tip side toward the base end side with respect to the protruding direction of the connecting member 10, and is pressed outward by a pressing member 15, as shown in Fig. 7. The retractable member 16 has a substantially cylindrical outer shape as shown in Fig. 7, and is fitted into two recesses provided at opposing positions on the circumferential surface of the connecting member 10 via the pressing member 15, and the end surface on the outer surface side of the connecting member 10 is the above-mentioned inclined surface. In a natural state, the retractable member 16 is arranged in a state in which it is pressed outward by the pressing force of the pressing member 15, as shown in Fig. 7(B), and in this state, the tip side in the protruding direction of the connecting member 10 does not protrude from the outer surface of the connecting member 10, and the base end side in the protruding direction of the connecting member 10 is arranged in a state in which it protrudes from the outer surface of the connecting member 10. In addition, when an external force is applied to the outer surface of the protruding member 16, as shown in Figure 7 (C), the protruding member 16 moves in the depth direction of the recess against the pressing force of the pressing member 15, and the base end side of the connecting member 10 in the protruding direction is recessed to approximately the same height as the outer surface of the connecting member 10.

The procedure for connecting the steel supports 4 using the connecting member 10 will be explained with reference to Figure 8. Similarly, in this embodiment, as shown in Figure 8(A), when the right-side separate support 4B is installed following the previously installed left-side separate support 4A, the opening 11 of the portal-side attachment member 6B fixed to the right-side separate support 4B is inserted into the connecting member 10 while the right-side separate support 4B is moved in a direction approximately parallel to the tunnel axis direction from the portal side toward the face side.

As shown in FIG. 8(B), when the opening 11 provided in the wellhead side attachment member 6B passes through the retractable member 16, as the opening 11 moves along the inclined surface of the outer surface of the retractable member 16, the retractable member 16 gradually sinks into the inside of the connecting member 10 against the pressing force of the pressing member 15.

After the opening 11 provided in the wellhead side attachment member 6B passes through the protruding member 16, the protruding member 16 protrudes from the outer surface of the connecting member 10 due to the pressing force of the pressing member 15. This prevents the wellhead side attachment member 6B from easily coming out of the connecting member 10.

[Third embodiment of the detachment prevention means]
Next, a third embodiment of the pull-out prevention means will be described. As shown in Fig. 9, the pull-out prevention means according to the third embodiment is constituted by a step 17 formed along the circumferential direction of the connecting member 10 at the base end side in the protruding direction of the connecting member 10. In the embodiment shown in Fig. 9(A), the protruding direction base end side of the connecting member 10 is reduced in diameter from the step 17 to its end, and in the embodiment shown in Fig. 9(B), a groove is formed from the step 17 to the base end side in the protruding direction of the connecting member 10, the groove being reduced in diameter by a certain width, specifically, approximately the thickness of the opening 11 of the wellhead side splice member 6B, and the base end side of this groove is formed with the same diameter as the tip end side of the step 17.

The procedure for connecting the steel supports 4 using the connecting member 10 will be explained with reference to Figure 10. Similarly, in this embodiment, as shown in Figure 10(A), when the right-side separate support 4B is installed following the previously installed left-side separate support 4A, the opening 11 of the portal-side attachment member 6B fixed to the right-side separate support 4B is inserted into the connecting member 10 while moving the right-side separate support 4B from the portal side toward the face side in a direction approximately parallel to the tunnel axis.

As shown in FIG. 10(B), when the opening 11 provided in the wellhead side attachment member 6B reaches the step 17, a large gap is created between the opening 11, which has moved along the side of the connecting member 10, and the connecting member 10, which has reduced in diameter at the step 17. This causes the opening 11 to shift in an arbitrary direction, causing the opening 11 and the connecting member 10 to become eccentric. A portion of the periphery of the opening 11 fits into the step 17, preventing the wellhead side attachment member 6B from easily slipping out of the connecting member 10.

As a modified example of this embodiment, as shown in FIG. 11, a notch 18 can be formed on the periphery of the opening 11 provided in the wellhead side abutment member 6B, and the diameter of the connecting member 10 can be made larger than the diameter of the opening 11 provided in the wellhead side abutment member 6B. As a result, when the opening 11 is fitted into the connecting member 10, the peripheral portion of the opening 11, which becomes easily deformed due to the notch 18 formed on the periphery, elastically deforms and expands slightly in diameter, allowing it to be inserted into the connecting member 10, which has a larger diameter than the opening 11, and after the wellhead side abutment member 6B passes through the step portion 17, the elastic deformation of the periphery of the opening 11 is released, and the state in which the periphery of the opening 11 is fitted into the step portion 17 can be reliably maintained.

As another modification, as shown in FIG. 12, at least one of the multiple connecting members 10 and openings 11 is positioned slightly eccentrically with respect to the corresponding opening 11 or connecting member 10, so that the periphery of the opening 11 can be more reliably maintained in a state where it is fitted into the step portion 17, and the wellhead side attachment member 6B will not easily come out of the connecting member 10.

[Erection method of steel support]
Next, the method of erecting the steel support 4 using a spraying machine with an erector device (hereinafter simply referred to as a spraying machine) will be described in detail with reference to Figures 13 and 14.

As shown in Figure 13, the sprayer 20 is positioned at the steel support installation site near the tunnel face. Coordinate data for the tunnel shape and the installation position of the steel support 4 are all input into the controller (computer) in advance.

A total station 21 is installed relative to the spraying machine 20, and at least two reference points 22A, 22B with known coordinates are installed inside the tunnel. The total station 21 sights the two reference points 22A, 22B and based on the distance and angle data obtained, the installation coordinates of the total station 21 are calculated by the resection method. The position coordinates of the total station 21 are checked at appropriate time intervals to check whether any positional deviation has occurred.

Most of the steel supports 4 are connected at the top and are a single arch material. Therefore, as shown in FIG. 14, the left-hand split steel support 4A facing the face is grasped and lifted by the erector device 23A located on the left, and the right-hand split steel support 4B is grasped and lifted by the erector device 23B located on the right. It is desirable to determine the gripping positions of the split steel supports 4A and 4B in advance and to mark the gripping positions. This is because the target to be surveyed by the total station 21 is the sighting targets 25A and 25B provided on the support clamping parts 24A and 24B, and the end coordinates of the steel support 4 are calculated based on the relative positional relationship between these sighting targets 25A and 25B and the leg end of the steel support 4.

The left-side separate steel support 4A is grasped by the erector device 23A and moved to the vicinity of the face, while the right-side separate steel support 4B is grasped by the erector device 23B and moved to the vicinity of the face. The total station 21 measures the collimation targets 25A and 25B provided on the support clamping parts 24A and 24B to determine the coordinates of both ends of the steel support 4, and the steel support 4 is moved to the installation coordinate point and installed.

1...Tunnel excavation surface, 2...Primary sprayed concrete, 3...Face, 4...Steel support, 4A...Left side divided support, 4B...Right side divided support, 5...Secondary sprayed concrete, 6A...Face side joint member, 6B...Tunnel mouth side joint member, 8...Joint, 10...Connecting member, 11...Opening, 12...Pivoting shaft, 13...Pressing member, 14...Pivoting member, 15...Pressing member, 16...Retracting member, 17...Step, 18...Notch

Claims (6)

A steel support connection structure for connecting a pair of left and right steel supports to each other at the joints at the top end,
The joint portion of the steel support is configured such that a face-side splice member is fixed to the face-side side of the steel support that is installed first, protruding from the edge of the top end, and a mine-mouth-side splice member is fixed to the mine-mouth-side side of the steel support that is installed later, protruding from the edge of the top end, and the portions of the face-side splice member and the mine-mouth-side splice member that protrude from each steel support are overlapped on the side of the steel support on the opposite side.
The face side splice member is provided with a rod-shaped connecting member protruding toward the mouth side, and the steel support and the mouth side splice member are each provided with an opening into which the connecting member is inserted,
A connecting structure for steel supports, characterized in that the connecting member is equipped with a pull-out prevention means that prevents the mine mouth side connecting member from easily coming out after the opening provided in the mine mouth side connecting member is engaged to a predetermined position. the fall-off prevention means is made of a rotating member whose tip end side is rotatably supported with respect to the protruding direction of the connecting member and whose base end side is pressed by a pressing member in a direction protruding from an outer surface of the connecting member,
A connecting structure for steel support as described in claim 1, wherein when an opening provided in the minehead side attachment member passes through the rotating member, the rotating member rotates against the pressing force of the pressing member to sink inside the connecting member, and after the opening passes through the rotating member, the rotating member rotates due to the pressing force of the pressing member to protrude from the outer surface of the connecting member, thereby preventing the minehead side attachment member from easily coming out. the fall-off prevention means is a protruding member having an outer surface that is an inclined surface that protrudes gradually outward from a tip end side toward a base end side with respect to a protruding direction of the connecting member, and is pressed outward by a pressing member;
A connecting structure for steel supports as described in claim 1, wherein when an opening provided in the minehead side attachment member passes through the protruding member, as the opening moves along the inclined surface, the protruding member gradually sinks into the interior of the connecting member against the pressing force of the pressing member, and after the opening passes through the protruding member, the protruding member protrudes from the outer surface of the connecting member due to the pressing force of the pressing member, thereby preventing the minehead side attachment member from easily coming out. The fall-off prevention means is a stepped portion formed along a circumferential direction of the connecting member and having a lower proximal end side in a protruding direction of the connecting member,
A steel support connection structure as described in claim 1, wherein the peripheral edge of an opening provided in the mine mouth side attachment member fits into the step portion to prevent the mine mouth side attachment member from easily coming loose. The steel support connection structure according to claim 4, in which a notch is formed on the periphery of the opening in the wellhead side attachment member, and the diameter of the connection member is larger than the diameter of the opening in the wellhead side attachment member. A method for erecting a steel support using the connection structure of the steel support according to any one of claims 1 to 5,
A method for erecting steel supports, characterized in that the connecting member is fitted into an opening provided in the tunnel entrance side attachment member while the steel support to be installed subsequently is pushed in the tunnel axial direction to connect the connecting member.

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