JP3081121B2 - How to join underground diaphragm walls - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining reinforced concrete underground continuous walls constructed by cast-in-place concrete.

[0002]

2. Description of the Related Art A unit wall of an underground continuous wall constructed by repeatedly excavating a trench, laying a reinforcing cage, and placing concrete is usually, for example, as shown in FIG. In the groove on the side, the reinforcing bars 3 that were processed so as to form the joint bars 2a and 2a by projecting the lateral force bars 2 and 2 from the partition plate 1 serving as the joint surface with the trailing wall side were inserted. Then, concrete is cast and the preceding wall 4 is built.

Then, as shown in FIG. 4B, a reinforcing bar cage 5 is erected in the groove on the trailing wall side so as to form an overlapping joint with the protruding lateral force bar, and is inserted into this groove. The trailing wall is constructed by casting concrete, and the trailing wall is integrated with the leading wall 4.

[0004]

However, the conventional joint structure of a reinforced cage of a conventional reinforcing cage is, as shown in FIG. 4 (B), as an example, in order to facilitate the insertion of the reinforcing cage on the trailing wall side. ,
Since all the joint rebars in the rebar basket 5 on the trailing wall are bent so as to be arranged inside the joint rebar on the preceding wall, the following structural defects occur.

That is, as is apparent from FIG. 4 (B), the conventional lap joint structure is subjected to bending near the lap joint of the reinforcing bar cage on the trailing wall side. As shown in FIG. 5 (A), when the external force P is applied to the lap joint portion, a bending crack mc is generated, and further, the shear crack sc and the lower lap joint portion are generated. The adhesion crack fc develops, and the lap joint is broken. In particular, when the amount of reinforcement in the wall is large, the adhesion crack fc is remarkably advanced, and brittle fracture is likely to occur.

To prevent such destruction, it is conceivable to lengthen the lap joint. However, lengthening the lap joint increases the size of the unfilled concrete groove that is left until the subsequent wall is built. Therefore, there are many construction and quality problems. Even if this space is covered with steel, etc.,
This would increase the total weight of the reinforced cage, which is not economical.

[0007] Also, as shown in FIG. 4 (A), there has been proposed a method in which a width stop bar 6 or a reinforcing bar is provided in a bent portion of a reinforcing steel basket on the trailing wall side. It is not a definitive solution.

Accordingly, an object of the present invention is to provide a method of joining an underground continuous wall capable of improving the strength of a lap joint at a joining portion between a leading wall and a trailing wall and preventing the occurrence of brittle fracture. Is to do.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first invention is to construct a trailing wall for a lateral force bar projecting from a joint surface of a leading wall of an underground continuous wall. In the joining method of the underground continuous wall connecting a part of the reinforcing bars erected by the lap joint structure, a reinforcing bar is added to the lateral reinforcing bars on both sides of the preceding wall, and either the lateral reinforcing bars or the reinforcing bars are added. One side is bent inward at the leading wall portion and projected to the trailing wall side to form a lap joint streak, and the other side is fixed with a perforated metal plate projecting to the trailing wall side, and then to the trailing wall side. The horizontal force bars are laid between the joint bars and the perforated metal plate, and then concrete is cast to build a trailing wall.

[0010] In the second invention, a part of a reinforcing bar built in the following wall is connected to a lateral force bar protruding from the joint surface of the leading wall of the underground continuous wall by a lap joint structure. In the joining method of the underground continuous wall, a part of the lateral force bars on both sides of the leading wall is bent inward at the leading wall portion and is projected to the trailing wall side to form a lap joint streak, and the leading wall side remains Fix the perforated metal plate projecting to the trailing wall side to the lateral force bar,
A structure in which the lateral force bars on the trailing wall side are overlapped and the perforated metal plate is erected between the joint streaks and the perforated metal plate as a guide, and then the concrete is cast and the subsequent wall is built. is there.

[0011]

[Function] By bending the lateral force bars or streaks of the preceding wall inward at the preceding wall and projecting to the trailing wall side, it becomes a lap joint muscle, and a perforated metal plate is fixed to the remaining lateral force bars. Since the perforated metal plate serves as a guide when installing the following wall reinforcement, the clearance between the reinforcements at the lap joint part can be reduced by improving the installation accuracy,
When the trailing wall is built, perforated metal plates are embedded on both sides of the joint, so that the strength, rigidity and toughness of the joint are improved.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIGS. 1 to 3, the leading wall 11 has a joining surface of a trailing wall formed by a partition plate 12, and the reinforcing bar cage 13 buried therein has lateral force bars 21 located on both sides. An end of 21 penetrates through the partition plate 12 and protrudes toward the following wall.

Reinforcing bars are added to the portions located on the trailing wall side of the two lateral force bars 21, 21, and the reinforcing bars are bent inward in the preceding wall 11 so that the trailing wall is bent. By projecting to the side, the lap joint streaks 14a, 14a are formed.
The lateral force bars 21, 21 are projected straight to the trailing wall side without being bent, and perforated metal plates 15, 15 for reinforcement are fixed vertically on the outer surface side thereof.

The length of the perforated metal plates 15, 15 protruding toward the trailing wall and the size and shape of the holes 16 provided in parallel with the perforated metal plates 15, 15 are determined by various studies on structural design, workability, and lateral arrangement. The thickness may be determined in consideration of the joining method with the rebar, etc.

The reinforcing bar cage 17 on the trailing wall side is formed so that the lateral force bars 18, 18 on both sides are accommodated in a state of being inscribed between the perforated metal plates 15, 15.

In order to build the trailing wall after the leading wall 11 has been built, the reinforcing cage 17 for the trailing wall is inserted into the excavated groove.

At the time of this insertion, the reinforcing bar cage 17 is attached to both lateral force bars 1.
Insert the ends of 8, 18 between the perforated metal plates 15, 15. Since the perforated metal plates 15 and 15 serve as guides when the reinforcing bar cage 17 is inserted, the accuracy of setting is improved, and the swinging of the reinforcing bar cage 17 when suspended is prevented. For this reason, the interval between the lap joint streaks 14a, 14a protruding from the preceding wall 11 and the trailing wall side lateral force bars 18, 18 can also be reduced in design,
It is possible to build a highly rigid and reliable vertical joint.

As described above, after the reinforcing bar cage 17 is erected, concrete is poured into the groove, so that a succeeding wall can be continuously constructed on the preceding wall 11, and connection of the succeeding wall can be performed. In the part, perforated metal plates 15, 1
5 is reinforced by being buried, and the concrete put into the outer surface side of the perforated metal plates 15 and 15 is integrated with the inner concrete at the portion of the hole 16 and there is no occurrence of peeling or the like.

Next, the test specimens b and c manufactured by using the bonding method of the present invention and the test body a manufactured by using the conventional bonding method shown in FIG. The results of the test are shown in FIGS.

Specimen b using the joining method of the present invention comprises:
The test piece a according to the conventional joining method shown in FIG. 4 was set to the same conditions as the amount of reinforcement, the concrete strength, the interval between the reinforcing bars, and the like.

FIG. 5B shows the state of occurrence of cracks when a load P is applied to the joint of the specimen b using the joining method of the present invention. The bending cracks mc and the bending shear cracks sc progress. However, brittle bond cracking does not occur.

FIG. 6 (A) shows a load-deformation curve. The dotted line in FIG. 6 (A) shows the load when the specimen b of the present invention shown in FIG. The dashed line indicates the load when the conventional test piece a shown in FIG. As a result of the experiment, the test piece b of the present invention greatly exceeded the adhesion crack load of the test piece a, the tensile main bar was considerably yielded, and the bending failure and the bending shear failure occurred almost simultaneously.

For comparison between the joining method of the present invention and the conventional joining method, the loading span was changed and, as shown in FIG. The experiment of the adhesion crack fc of the joint part by applying the concentrated load was performed in the same manner as the experiment described above. In addition,
The drawing shows the case of the test piece of the present invention. In the conventional joining method, as shown in FIG.

FIG. 6B shows the result, and FIG.
Specimen c employing the joining method of the present invention shown in FIG. 5 is much higher in rigidity and strength than the conventional specimen a shown in FIG. 5 (A), and the lower tensile rebar also yields considerably. It was on the verge of bending failure.

From these experimental results, it can be said that the joining method according to the present invention contributes to great improvement in performance such as strength, rigidity and toughness and safety.

The design values of the test specimens in the above experiment are as follows.

Dimensions 400 (length) × 400 (width) × 2500 (length) (mm) Reinforcing bar 12-D19 (SD345) Lap joint length 760 mm (= 40 d) Concrete strength 270 kg / cm ^2- hole metal plate t = 6 mm (SS400) Hole: 70 × 70 mm Pitch 100 mm In the embodiment of the present invention shown in FIGS. 1 to 3, the reinforcing bars 21 are added to the lateral force bars 21 of the preceding wall 11, and the reinforcing bars are added. And the streaks 14, 14 are bent inward in the preceding wall 11 so as to project toward the following wall, and the lap joint streaks 14a,
14a, and the perforated metal plates 15, 15 were fixed to the lateral force bars 21, 21. On the contrary, the horizontal force bars 2, 15 were fixed.
The metal plates 15 and 15 may be fixed in such a manner that the metal plates 1 and 21 are bent inward in the preceding wall 11 so as to protrude toward the following wall to form a lap joint streak, and the streak is straight.

Although not shown in the figure, the use of the streaks is omitted, and a part of the lateral force bars 21, 21 is bent inward in the preceding wall 11 so as to protrude toward the trailing wall, and is connected to the overlapping joint muscle. While leaving the rest straight,
5 may be fixed.

Further, the connection between the perforated metal plates 15, 15 and the rebar is not shown, but may be performed at the preceding wall with the end of the rebar related to this connection, or at the end of the rebar related to this connection. May be projected to the trailing wall portion.

[0031]

As described above, according to the present invention, it is possible to improve the strength, rigidity, and toughness of the joint between the leading wall and the trailing wall of the underground continuous wall, thereby contributing to the improvement of safety. Can be.

Further, since the perforated metal plate is fixed to the lateral force bars of the preceding wall, the insertion of the reinforcing bar cage on the trailing wall side can be performed by using the perforated metal plate as a guide, so that the installation accuracy is increased and the rigidity is high. A reliable joint is obtained.

[Brief description of the drawings]

FIG. 1A is a plan view of a reinforced cage on a preceding wall showing a joining method of the present invention, and FIG. 1B is a front view of the same.

FIG. 2 is a perspective view of the same.

FIG. 3 is a cross-sectional plan view showing a state in which a preceding wall is being constructed by combining a reinforcing steel basket on a trailing wall side with the above.

FIG. 4 (A) is a plan view of a preceding wall-side reinforcing cage showing a conventional joining method, and FIG. 4 (B) is a cross-sectional plan view of a preceding wall building state in which a trailing wall-side reinforcing cage is incorporated therein.

FIG. 5A is a front view showing the occurrence of cracks in a load test of a specimen a using a conventional joining method, and FIGS. 5B and 5C are specimens b and c using the joining method of the present invention. Front view showing the occurrence of cracks in a loading test

FIG. 6A is a graph showing the load of the test piece b shown in FIG. 5B.
FIG. 5B is a chart showing a deformation curve, and FIG. 5B is a chart showing a load-deformation curve of the test piece a shown in FIG. 5A and the test piece c shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Leading wall 12 Partition board 13, 17 Reinforcement cage 14, 18 Lateral force bar 15 Perforated metal plate 16 hole

Continuation of the front page (73) Patent owner 591214804 Matsumura Gumi Co., Ltd. 1-10-20 Higashitenma, Kita-ku, Osaka-shi, Osaka (73) Patent owner 000176785 Mitsubishi Construction Corporation 3-3-1 Nihonbashi Honcho, Chuo-ku, Tokyo No. 6 (72) Inventor Goro Moriguchi 4-17-17 Shimoshinjo, Higashiyodogawa-ku, Osaka (72) Inventor Kenji Kimura 152-101012, 300, Ukimachi, Moriyama-shi (72) Inventor Eiji Uchii Tennoji-ku, Osaka JP-A-61-183518 (JP, A) JP-A-4-353115 (JP, A) JP-A-5-17936 (JP, A) JP-A-5 JP-A-5-148834 (JP, A) JP-A-63-151539 (JP, U) JP-A-47-38414 (JP, Y1) (58) Fields investigated (Int. Cl) . ^7, DB name) E02D 5/02 - 5/20 103

Claims (2)

(57) [Claims] 1. An underground continuous wall connecting a part of a reinforcing bar to be built in a succeeding wall construction with a lap joint structure to a lateral force bar protruding from a joint surface of a preceding wall of the underground continuous wall. In the joining method, a reinforcing bar is added to the lateral force bars on both sides of the preceding wall, and one of the lateral force bars and the reinforcing bar is bent inward at the preceding wall portion and protruded toward the succeeding wall to overlap. Along with the joint muscle,
On the other side, fix a perforated metal plate protruding to the trailing wall side, then lay the lateral force bars on the trailing wall side and erected between the joint streaks and the perforated metal plate, and then cast concrete. A method for joining an underground continuous wall, comprising building a trailing wall. 2. An underground continuous wall connecting a part of a reinforcing bar built in a following wall construction with a lap joint structure to a lateral force bar projecting from a joint surface of a preceding wall of the underground continuous wall. In the joining method, a part of the lateral force bars on both sides of the leading wall is bent inward at the leading wall portion and protruded to the trailing wall side to form a lap joint line, and the remaining lateral force bars on the leading wall side are A perforated metal plate protruding to the trailing wall side is fixed, and then the lateral force bars on the trailing wall side are overlapped and the perforated metal plate is built between the joint streaks and the perforated metal plate as a guide. A method of joining an underground continuous wall, comprising constructing a trailing wall by casting concrete.