JPH11310918A - Underground diaphragm wall joint structure - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To improve the structural strength and toughness of a joint between elements of a continuous underground wall. SOLUTION: A female joint 30 extending along a wall depth direction on a surface of a partition steel plate 3 of a preceding element 1 on a trailing element side, and a reinforcing bar built in a wall groove 2 between adjacent preceding elements. The male joint 20 fixed to the side end of the horizontal reinforcing bar 11 of the car 10 via the plate 13 is engaged to form a joint between the preceding element and the following element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint structure of an underground continuous wall, and more particularly to a joint structure of a joint between elements of an underground continuous wall which has high structural strength and is tough.

[0002]

2. Description of the Related Art A rigid joint is one type of joint between a preceding element and a following element of an underground diaphragm wall. Conventionally, various structures have been proposed as the joint structure of the rigid joint. FIG. 11 shows a conventional underground continuous wall 5 in a completed state.
It is the fragmentary sectional view which looked at an example of the joint part 53 of No. 0 from the upper part. As shown in the figure, in the ordinary joint structure, a partition steel plate 55 serving as a partition from the succeeding element 52 is attached to an end surface of the reinforcing element cage 54 of the preceding element 51 in the wall width direction. For this reason, integration of the leading element 51 and the trailing element 52 as a concrete wall by the joint 53 is interrupted. Therefore, in order to reliably transmit the bending moment, the in-plane shear force, and the out-of-plane shear force acting on the underground continuous wall 50 at the joint portion 53, a horizontal joint bar penetrating the partition steel plate 55 as shown in FIG. 56 and a shear connector 57 are used. The horizontal joint bar 56 is connected to the horizontal bar 5 of the reinforcing cage 54 of the preceding element 51.
8 is made to protrude from the end face of the partitioning steel plate 55 with a predetermined overlapping length secured, and a lap joint 61 is constituted by the horizontal reinforcing bars 60 of the reinforcing bars 59 of the following elements 52 to be built later in the grooves. In the overlapping portion of the lap joint 61, the horizontal reinforcing bar 60 of the succeeding element 52 is bent,
The reinforcement is arranged inside the horizontal joint bar 56 of the preceding element 51 so as to have a predetermined horizontal separation. The continuity of the horizontal joint bars is maintained through adhesion to the concrete cast in the joint portion 53.

[0003]

After the horizontal joint reinforcement of the preceding element is installed, the reinforcing cage of the succeeding element is installed after the installation of the horizontal joint reinforcement of the preceding element. difficult. For this reason, when the thickness of the underground continuous wall and the concrete strength are relatively small compared to the amount of horizontal joint reinforcement, or when the lap length of the horizontal joint reinforcement is short, the proof strength of the joint part is smaller than that of the general part. Will be lower. It is known that, as shown in FIG. 11, the fracture properties of a joint having such a structure become brittle due to the occurrence of adhesion splitting cracks in gaps between reinforcing bars of the joint. Therefore, in terms of structural design, this type of joint has been designed as a part with low proof stress, and the joint has been placed in a part where the sectional force is relatively small, or devised to reduce the acting sectional force. .

However, based on the lessons learned from the damage caused by the Hyogoken-Nanbu Earthquake, the guidelines for seismic design of various structures were reviewed.
It has become required to have a structural design with excellent seismic performance. Specifically, there has been a demand for a structure capable of improving the toughness of a structural member and avoiding brittle destruction. As one of the toughness indexes of a member against a load, a member toughness factor μ = δu / δy (δ
u: ultimate displacement, δy: yield point displacement), but μ = 8 to 1
It is required that the structure be zero. It is necessary to realize a structure that can meet such design requirements even with an underground continuous wall joint structure.

Accordingly, an object of the present invention is to provide a joint structure of an underground continuous wall which solves the above-mentioned problems of the prior art, enhances structural strength, and forms a joint part having high toughness. It is in.

[0006]

In order to achieve the above object, the present invention provides a first joint member extending along a wall depth direction on a surface of a preceding element on a trailing element side of a partition steel plate. A second joint member fixed via a support plate to a side end of a horizontal reinforcing bar of a reinforcing cage built in a wall groove between the adjacent preceding elements, thereby locking the preceding element and the succeeding element. And a joint portion is formed.

When the rebar cage is built in a wall groove while the second joint member is locked to the first joint member,
It is preferable to adjust the length of the horizontal reinforcing bar of the reinforcing bar cage in the longitudinal direction using an adjustment margin provided in the first joint member.

[0008] Further, when the rebar cage is built in the wall groove while the second joint member is locked to the first joint member, the longitudinal dimension of the horizontal rebar of the rebar cage is adjusted. It is preferable to perform this at a lap joint provided on a part of the horizontal reinforcing bar.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the joint structure of an underground continuous wall according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic plan view showing a state in which a reinforcing cage is installed in a wall groove 2 portion of a succeeding element that has been excavated between the previously constructed preceding elements 1. As shown in FIG. 1, the vertical and horizontal reinforcing bars 11 (horizontal reinforcing bars 1)
1A, vertical reinforcing bars 11B) and lateral reinforcing bars 12 (shear reinforcing bars, stirrups) are assembled in a known shape. On the other hand, as shown in the partial enlarged view of FIG. 3, the end plates 13 as support plate members made of flat steel extending in the wall depth direction are provided on both side ends of the horizontal reinforcing bar 11A of the reinforcing bar cage 10.
Are welded. Further, as shown in FIGS. 1 and 3, a male joint 20 as a second joint member having a tip flange 20a having a substantially T-shape in plan view is welded to an end of the end plate 13. This male joint 20 is shown in FIG.
As shown in (1), a plurality of joint members having the same shape are arranged at predetermined intervals along the wall depth direction of the end plate 13. Further, in order to maintain the shape of the rebar cage 10 and to keep the two male joints 20 arranged side by side apart, shape retaining rods 14 are incorporated at both ends of the rebar cage 10. The shape-retaining rod 14 is screwed or welded at its ends to form two end plates 1.
Attached between three.

On the other hand, the surface of the partitioning steel plate 3 of the preceding element 1 on the trailing element side is provided with a female joint 3 along the wall depth direction.
0 is extended. As shown in FIGS. 1 and 3, the female joint 30 has one end on the short side 30 a side of two trapezoidal steel members having a substantially L-shape in plan view facing each other so that a slit 31 is formed. In this state, one end on the long side 30b side is fixed to the partition steel plate 3, and a slit 31 having a predetermined width is provided at a tip thereof in a box shape extending in the depth direction. In this way, the front end flanges of the male joints 20 provided on both side ends of the reinforcing cage 10 of the succeeding element are connected to the slits 31 of the female joint 30 attached to the partition steel plate of the preceding element 1.
The entire reinforcing rod cage 10 is dropped into the wall groove 2 while being locked so as to be fitted through the groove. In addition, from the viewpoint of ensuring the durability of the completed underground continuous wall, it is preferable that the cover of the female joint 30 has a cover size in accordance with the design specification, and the width of the slit 31 to be formed is also the width of the web 20c of the male joint 20. It is preferable to set the width as narrow as possible. It is preferable that the length of the web 20c be set in accordance with the adjustment margin of the female joint 20.

Hereinafter, various embodiments suitable as the male joint 20 and the female joint 30 will be described with reference to FIGS. FIG. 4 is a schematic plan view showing the shape of the male joint 20 attached to the end plate 13. FIG.
(A) shows the male joint 20 having a T-shaped tip flange shown in FIGS. 1 to 3. In this male joint 20, the width of the front end flange is set substantially equal to the inner dimension of the box of the female joint 30, so that the female joint 30
Is obtained. It is also preferable that the other shape of the male joint 20 be a shape in which a vertex having a triangular wedge shape is formed at the tip as viewed in plan, as shown in FIG. In this case, since the wedge-shaped distal end 20b is locked so as to be securely fitted into the slit position of the female joint 30, the connection of the joint portion can be ensured.
Also, as shown in FIG. 3C, by forming the tip 20b in a circular shape in plan view, it is possible to reduce the clogging when the reinforcing cage 10 is built, and to improve the construction efficiency at the time of building. it can.

FIG. 5 is a schematic plan view showing the shape of the female joint 30 attached to a part of the partition steel plate 3. FIG. FIG. 3A shows a female joint 30 in which a pair of inequilateral L-shaped members shown in FIGS. FIG. 2B shows a modification in which a spacer bar 32 is welded near the slit of the female joint 30. A space is provided between the male joint 20 and the female joint 30 by disposing the space server 32 near the slit along the wall depth direction, and when the mortar is filled into the female joint 30 as described later, The male joint 20 can be completely surrounded by the filled mortar. Further, it is possible to prevent the box from opening when a tensile force acts on the horizontal streaks. In FIG. 4C, a wedge-shaped joint is used in the box of the female joint 30, so that the male joint 20 can be securely locked in the female joint 30. FIG. 5D shows a substantially elliptical female joint 30 that can be surely integrated with the male joint 20 shown in FIG. 4C. By using the female joint 30 and the male joint 20 shown in FIG. 4C, the work of installing the reinforcing cage 10 as the following element can be facilitated. FIG. 3E shows the female joint 3 attached to the partition steel plate 3 via the attachment flange 33.
0 is shown. The male joint 20 can be easily and accurately attached to the partition steel plate 3 by using the attachment flange 33 shown in FIGS. 5 (d) and 5 (e).

Next, a structure for absorbing a dimensional error when the reinforcing cage 10 is installed will be described with reference to FIGS. 6 (a) and 6 (b). The female joint 30 shown in both figures has a shape having an adjustment margin by which the position of the male joint 20 can be freely changed within the range of the long side 30b of the L-shaped member. The rebar basket 10 is manufactured with high precision at a factory. For example, the separation distance between the male joints 20 at both ends is substantially constant at any position. On the other hand, the wall groove 2 constituting each element is likely to vary in the wall longitudinal direction and width due to an excavation error or the like.
For this reason, the distance between the female joints 30 attached to the preceding element 1 facing each other across the wall groove 2 serving as the following element may be different. Further, the partition steel plate 3 may be deformed when the preceding element 1 is constructed. Therefore, an adjustment margin is provided on the long side 30b of the female joint 30 so as to absorb a dimensional error when the rebar cage 10 is built due to an excavation error of the wall groove 2 or the like. At this time, as shown in FIG. 6B, the entire joint inside the female joint 30 is filled with the mortar M, whereby the joint portion can be integrated.

FIGS. 7 to 9 are views showing a joint structure using a female joint 30 having a compact shape without any adjustment with respect to the shape of the female joint having an adjustment margin (see FIGS. 1 to 6). . As shown in FIG. 7, in the present embodiment, the female joint 30 has an annular shape with a part cut away in plan view. In this female joint 30, there is no adjustment margin as shown in FIG. For this reason, in order to absorb a dimensional error when the reinforcing cage 10 is installed, as shown in FIG. 8, a horizontal reinforcing bar 1 extending in the depth direction at the central portion of the reinforcing cage 10 in the longitudinal direction.
A 1A lap joint 35 is provided. The lap joint 35 is configured by superposing horizontal reinforcing bars 11A extending from both sides. By expanding and contracting the lap joint 35 in accordance with the construction error of the wall groove 2 of the succeeding element, the reinforcing cage 10
The dimensional error at the time of building can be absorbed. In the lap joint 35, it is preferable to secure an expansion margin of about 20 to 40 cm.

The female joint 30 and the male joint 2 shown in FIGS.
FIG. 9 is an enlarged view of the zero portion. This female joint 30 has an advantage that it can maintain reliable engagement with the male joint 20 as compared with the one shown in FIG. Regarding the shape, the female joint 30 having a shape corresponding to each drawing in FIG. 5 as shown in each drawing in FIG. 10 can be adopted. Further, a spacer bar (see FIG. 5B) may be attached to the slit position of each female joint 30. In this embodiment, the female joint 30 and the male joint 20 are formed by processing a steel plate specified in a rolled steel material for general structure (JIS G3101), and have predetermined tensile strength and rigidity. Rolled steel material for welded structures (JISG3) as long as it can be joined to the partition steel plate by welding means such as welding
106) etc. can be adopted.

[0016]

As described above, the structural strength of the joint between the elements of the underground continuous wall, which has been a weak point in the past, can be increased to sufficiently secure the seismic performance (dust performance), resulting from construction errors. It is possible to provide a structure in which a dimensional error when the reinforcing cage is built can be tolerated. Thereby, the structure quality of the conventional underground continuous wall can be remarkably improved, and the work of installing the reinforcing steel cage can be made equal to the conventional work.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a joint structure of an underground continuous wall according to the present invention.

FIG. 2 is a side view showing a side shape of the joint structure of the underground continuous wall shown in FIG. 1;

FIG. 3 is a partially enlarged perspective view showing the joint structure of the underground continuous wall shown in FIG. 1 in an enlarged manner.

FIG. 4 is a partial plan view schematically showing a shape example of a male joint.

FIG. 5 is a partial plan view schematically illustrating a shape example of a female joint.

FIG. 6 is a schematic explanatory view showing a dimensional adjustment state of the joint structure by an adjustment margin of the female joint.

FIG. 7 is a plan view showing another embodiment of the joint structure of the underground continuous wall according to the present invention.

FIG. 8 is a side view showing a side shape of the joint structure of the underground continuous wall shown in FIG. 7;

9 is a partially enlarged perspective view showing the joint structure of the underground continuous wall shown in FIG. 7 in an enlarged manner.

FIG. 10 is a partial plan view schematically showing an example of the shape of a female joint.

FIG. 11 is a plan sectional view showing an example of a conventional joint structure of an underground continuous wall.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Leading element 2 Wall groove 3 Partition steel plate 10 Rebar basket 20 Male joint 30 Female joint

Claims (3)

[Claims] 1. A first joint member extending along a wall depth direction on a surface of a partition steel plate of a preceding element on a trailing element side, and is built in a wall groove between adjacent preceding elements. A second joint member fixed to a side end of the horizontal reinforcing bar of the reinforcing cage via a supporting plate is engaged to form a joint portion between the preceding element and the succeeding element. Underground diaphragm wall joint structure. 2. The method according to claim 1, wherein said reinforcing cage is embedded in a wall groove while locking said second joint member to said first joint member.
2. The joint structure of an underground continuous wall according to claim 1, wherein a longitudinal dimension of the horizontal reinforcing bar of the reinforcing bar cage is adjusted by an adjusting margin provided on the first joint member. 3. When the rebar cage is built in a wall groove while locking the second joint member to the first joint member,
2. The joint structure for an underground continuous wall according to claim 1, wherein the dimensional adjustment in the longitudinal direction of the horizontal reinforcing bar of the reinforcing bar is performed by a lap joint portion provided on a part of the horizontal reinforcing bar.