JP7614252B2 - Concrete box for open shield construction - Google Patents

Description

The present invention relates to an open shield method for constructing underground structures such as water supply and sewerage systems and underground tunnels in urban areas, and to the concrete box used for this method.

The open shield method is a highly efficient method that combines the advantages of the open cut method and the shield method. An outline of the method is shown in Figures 13 to 15.

In the figure, 1 is an open shield machine, which is composed of a front section 1a with an open top, consisting of left and right side wall panels and a bottom plate connected to these side wall panels, as shown in Figure 17, and a tail section 1b with an open top, consisting of left and right side panels and a bottom plate similar to the front section 1a.

Sliding retaining plates 6 that extend forward are attached to the left and right cutting edges of the open shield machine 1, and propulsion jacks 3 that extend from the rear end of the front section 1a toward the tail section are arranged in a row facing backward, one above the other.

The open shield machine 1 has a front section 1a and a tail section 1b that fits into the rear end of the front section 1a, forming a bent section 2 at the mating section, making curved construction possible.

In the figure, 1 is the front part, and the ground at the cutting edge in front of the front part is excavated by an excavator 7 placed in front while forming a slope as shown in Figures 18 and 19. The excavated soil is loaded onto a dump truck for transporting the remaining soil placed behind the excavator 7 and transported. As the excavation progresses, the sliding retaining plate 6 is extended forward to prevent loosening of the sloped side of the ground.

The open shield machine 1 is advanced by extending the shield jack 3 attached to the open shield machine 1 by contacting it with the press bar 8 while the excavator 7 is excavating the ground at the face, and advancing it forward by using the thrust reaction force of the open shield machine 1 against the concrete box behind it. As the machine advances, a gap equivalent to the thickness of the shield machine plate is generated in the ground behind the open shield machine 1, so that the gap is filled with backfill injection material 17 as a secondary injection from grout holes previously installed in the concrete box 4.

After the open shield machine has excavated one box length, the shield jack 3 is retracted and the press bar 8 is removed from inside the tail section 1b, creating space to install the concrete box 4. Before installing the concrete box 4 inside the tail section, PC steel rods 14 are inserted and fastened to the rear concrete box 4 that has already been laid and the concrete box 4 further behind it, as shown in Figure 20.

This allows the entire construction box to have an almost integrated structure. Therefore, the thrust reaction force of the open shield machine 1 is smoothly transmitted to the multiple concrete boxes 4 already laid behind it.

After the above work, as shown in FIG. 13, the concrete box 4 is lowered into the tail section by the lifting machine 13 located behind the open shield machine 1 and installed. After installation, the press bar 8 is installed so that it abuts against the front end face of the concrete box 4. Then, the tail clearance (gap) between the installed concrete box 4 and the inner surface of the tail section 1b is filled with backfill injection material 17 as the primary injection. After filling, the open shield machine 1 is excavated again.

The backfilling work on the upper part of the laid concrete box immediately behind the tail section 1b of the open shield machine 1 is carried out in parallel with the excavation work of the open shield machine 1.

The above steps are repeated to bury the concrete box 4 in the ground. The open shield machine 1 is assembled at the starting shaft 10, and then, after cutting the front end in the direction of travel, it is advanced while receiving a thrust reaction force from the bearing wall 12. However, this work, as well as the initial excavation and the work of reaching the destination shaft, are almost the same as those in normal shield construction methods, so details will be omitted.

The concrete box 4 is made of reinforced concrete, and as shown in Figure 16, is a one-piece structure consisting of a left slab 4a, a right slab 4b, a top slab 4c, and a bottom slab 4d. The connecting end faces are smooth so that the thrust reaction force of the open shield machine 1 can be evenly distributed and transmitted to the entire slabs on both sides of the concrete box 4 that it abuts against via the press bar 8. Grout holes 24 are provided. Although not shown, the haunch portion has insertion holes for the PC steel rods 14, into which the PC steel rods are inserted. The front and rear faces are open as openings.

Regarding the concrete box 4, the following patent document proposes a method of connecting concrete boxes that can prevent the concrete boxes from shifting or opening up, without compromising work efficiency or damaging the concrete boxes, even in cases where thrust is applied unevenly to the joint end faces of the concrete boxes, such as in curved construction, and furthermore, allows parts such as metal fittings to be easily removed and reused after thrust is no longer applied to the concrete boxes.
JP 2009-114642 A

As shown in FIG. 17, in this patent document 1, the upper end of an anchor bolt 121 embedded in the outer or inner surface of a concrete box body 4 is screwed to a fixing bracket 120 so that the upright portion 124 of the fixing bracket 120 stands on the surface of the concrete box body 4, and the screw end of a fully threaded bolt 122 is passed through the upright portion 124 to span adjacent concrete boxes 4, and by screwing it in place, the fully threaded bolt 122, the fixing bracket 120, and the anchor bolt 121 are detachably attached to each other, and the two concrete boxes 4 are connected and fixed.

The use of similar connecting fittings (turnbuckles, etc.) to join concrete boxes (box culverts) can also be seen in the following patent documents:
Japanese Utility Model Application Publication No. 49-113221 Japanese Utility Model Application Publication No. 49-113221

These patent documents aim to prevent misalignment and gaps between concrete boxes, but in the case of a so-called "ink bottle type" concrete box, in which the connecting end face of one concrete box is concave and the connecting end face of another concrete box is fitted into each other to connect the concrete boxes, the pressure-receiving area of the mating part for the thrust reaction force is smaller than that of a concrete box with a smooth connecting end face, so the stress acting on that part is large, and the concrete is prone to splitting and cracking at the joint.

Furthermore, in recent years, the use of inro-shaped concrete boxes for open-cut tunnels, which have been increasingly adopted with individual boxes that have earthquake resistance and are flexible, is difficult to install because the thrust reaction force cannot be smoothly transmitted to the concrete box behind the open shield machine in its current state.

However, when fitting the end face of the convex part of another concrete box into the end face of the concave side of the inro-shaped cut-and-cover concrete box, the tip of the end face of the concave part and the tip of the end face of the convex part do not come into contact with each other, and a certain distance is maintained so that a specified joint distance can be secured.

As a result, no consideration is given to the dimensional accuracy in the vertical direction, particularly at the end face of the recess, or the smoothness of the vertical surface. Therefore, depending on the smoothness in the vertical direction and surface unevenness, and the manufacturing accuracy of the steel frame press bar and the recess, etc., it is possible that some parts of the steel frame press bar will not be in contact, causing local stress due to the thrust reaction force to occur and concentrate at the contact points, resulting in cracks or cracks in the concrete at the contact points.

In other words, the thrust reaction force of the open shield machine is not evenly distributed over the entire area where it contacts the recess in the concrete box, increasing the possibility of cracks occurring.

The object of the present invention is to provide a concrete box for open shield construction that can be installed without cracks or breaks on or near the connecting end faces of the concrete box, not only for open shield construction concrete boxes with thin walls and smooth connecting end faces that are used under conditions where a large thrust reaction force is received, but also for ordinary inro-shaped concrete boxes for open excavation and concrete boxes with individual boxes that have flexibility and earthquake resistance.

In order to achieve the above objective, the gist of the present invention described in claim 1 is that a predetermined joint spacing is maintained at the joints on the inner surfaces of the top, side and bottom plates between the concrete boxes, and multiple channel steel members or H-shaped steel members are laid horizontally in the vertical and horizontal directions as connecting members for the joints and fixed with insert bolts.

According to the present invention described in claim 1, multiple channel steel members or H-shaped steel members are laid horizontally as connecting members of the joint between the leading concrete box and multiple concrete boxes laid behind it, maintaining a predetermined joint spacing, and are fixed with insert bolts. Therefore, the thrust reaction force of the open seal machine 1 does not act on the connecting end surface of the concrete box joint, but is transmitted sequentially to the concrete boxes laid behind via the connecting members.

Therefore, even for concrete boxes with relatively thin walls and smooth connecting end surfaces under conditions where a large thrust reaction force is expected to act, or inro-shaped concrete boxes for open-cut construction, there is no need to worry about cracks or breaks in the side wall end surfaces, and because the connecting members are fixed with insert bolts to maintain the specified joint spacing, these concrete boxes can be laid safely and reliably using the open shield machine 1.

As described above, the thrust reaction force caused by the open shield machine's tunneling is not transmitted to the connection end surface of the laid concrete box as in conventional open shield construction methods, but can be transmitted to the laid concrete box via the reaction force transmission members, connection members, and the insert bolts that secure them.

As a result, it is possible to safely and reliably lay concrete boxes or inro-shaped cut-and-cover concrete boxes with smooth connection end faces and relatively thin walls under conditions where a large thrust reaction force is expected to act, without causing cracks or breaks on the end faces of the concrete boxes or in their vicinity, while maintaining the specified joint spacing.

1 is a cross-sectional plan view showing one embodiment of a concrete box for an open shield construction method according to the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. 1 is a vertical cross-sectional side view showing one embodiment of a concrete box for an open shield construction method according to the present invention. FIG. 4 is a view taken along line BB in FIG. 3. FIG. 1 is an enlarged cross-sectional plan view showing one embodiment of a concrete box body for an open shield construction method according to the present invention. 1 is a longitudinal sectional front view showing one embodiment of a concrete box body for an open shield construction method according to the present invention. FIG. FIG. 7 is an enlarged view of part A in FIG. 6 . FIG. 2 is a cross-sectional plan view showing another embodiment of a concrete box for an open shield construction method according to the present invention. FIG. 4 is a longitudinal sectional front view showing another embodiment of a concrete box body for an open shield construction method according to the present invention. FIG. 10 is an enlarged view of part A in FIG. 9 . FIG. 4 is a plan view showing the installation status of the buckling prevention material. FIG. 4 is a front view showing the installation status of the buckling prevention material. FIG. 2 is a perspective view showing the construction status of the open shield method. FIG. 1 is a plan view showing an overview of the open shield method. FIG. 2 is a longitudinal section showing an overview of the open shield method. FIG. 2 is a perspective view of a concrete box for the open shield construction method. FIG. 11 is a vertical sectional side view showing a conventional example.

The following describes an embodiment of the present invention. Figure 1 is a cross-sectional plan view showing one embodiment of a concrete box for the open shield construction method of the present invention, in which 1 is an open shield machine, as previously described.

In the figure, 18 is a reaction force transmission member, 21 is a connection member, and the reaction force transmission member 18 is made up of a planar member that abuts against the rear surface of the push bar 8 (press bar), and a planar member that protrudes rearward from that rear surface and abuts against the inner surface of both side walls of the leading concrete box 29, and is reinforced with ribs.

The planar member that abuts against the inner surface of the leading concrete box 29 has multiple holes through which the fixing bolts 20 pass, and the leading concrete box 29 has an insert 19 embedded in advance, into which the fixing bolts 20 are inserted to fix the reaction force transmission member 18.

The reaction force transmission members 18 are arranged in multiple positions on both sides of the leading concrete box 29 in the vertical direction, and are connected in the vertical direction by bolts or the like.

The reaction force transmission member 18 is fixed so that the front surface of the planar member that abuts against the rear surface of the push bar 8 of the reaction force transmission member 18 is positioned forward of the front side plate end surface of the leading concrete box 29.

When the open shield machine 1 is propelled, the shield jack 3 extends and pushes the push angle 8 backward, causing the rear surface of the push angle 8 to be pressed against the planar member of the reaction force transmission member 18.

Therefore, the thrust reaction force caused by the thrust of the open shield machine 1 is not transmitted to the end faces of the slabs on both sides of the leading concrete box 29, but is transmitted to the inside of the leading concrete box 29 through the fixing bolts 20 and inserts 19 on the inner surface of the leading concrete box 29 via the reaction force transmission member 18.

The concrete box 4 of the present invention maintains a specified joint spacing at the joints on the inner surfaces of the top, side, and bottom plates between the concrete boxes, and multiple channel steel members or H-shaped steel members are hung vertically and horizontally as connecting members 21 at the joints and fixed with insert bolts.

The connecting member 21 has holes for inserting the fixing bolts 20, and is firmly fixed by inserting the fixing bolts 20 into the inserts 19 that are pre-installed at predetermined positions across each side of the inner surface of the concrete box.

Figures 4 to 7 show an example in which a channel steel material is used as the connecting member 21. The thrust reaction force associated with the thrust of the open shield machine 1 is transmitted from inside the leading concrete box 29 to the rear via the reaction force transmission member 18 installed in the leading concrete box 29, the fixing bolts 20 and inserts 19 that secure the reaction force transmission member 18, and then transmitted rearward in sequence via the connecting members 21 that are cross-hung and fixed to each joint section.

As a result, the thrust reaction force is not transmitted to the connection end faces of the joints between the concrete boxes, so there is no risk of cracks or breakage occurring at the connection end faces. In addition, it is possible to safely lay even ingot-shaped cut-and-cover boxes.

In the above figures, the connecting members 21 are installed horizontally at all the joints on the inner surface of the top plate, side plates, and bottom plate, but depending on the magnitude of the thrust reaction force, the number of connecting members 21 installed may be adjusted, or the installation locations of the connecting members may be changed to both side plates and the bottom plate.

Figures 8 to 10 show an example in which H-shaped steel is used as the connection member 22. The mechanism for transmitting the thrust reaction force is the same as when the connection member 21 described above is installed, so a detailed explanation is omitted.

When the thrust reaction force is large and there is a risk of local buckling occurring in the connecting member 22 itself installed at the joint between each concrete box body 4, local buckling can be prevented by holding down the connecting member 22 with a hydraulic jack or a strong support 23, as shown in Figures 11 and 12.

The support can also serve to prevent the box joint from shifting when the open shield machine 1 is excavating.

1...Open shield machine 1a...Front part 1b...Tail part 2...Bent part 3...Propulsion jack (shield jack)
4...Concrete box body 4a...Left side plate 4b...Right side plate 4c...Top plate 4d...Bottom plate 4f...Hunch portion 6...Slide retaining plate 7...Excavator 8...Press bar (press angle)
9: Water stop bar 10: Starting shaft 11: Steel sheet pile 12: Bearing wall 13: Lifting machine 14: PC steel bar 15: Backfill soil 16: Dump truck for removing residual soil 17: Backfill injection material 18: Reaction force transmission member 19: Insert 20: Fixing bolt 21: Connection member (channel steel) 22: Connection member (H-shaped steel)
23...Support (hydraulic jack or strong support)
24...Grout hole 25...Backfilling heavy equipment 27...Connecting bolts and nuts 30...Joint

Claims (1)

A concrete box for open shield construction, characterized in that a specified joint spacing is maintained at the joints on the inner surface between the concrete boxes, and multiple channel steel members or H-shaped steel members are laid horizontally in the vertical and horizontal directions as connecting members for the joints and secured in place with insert bolts.

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