JPH11209968A - Joint structure of underground continuous wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the shear resistance and toughness of the joint part between the elements of an underground continuous wall. SOLUTION: A lap joint 35 is formed inside by both horizontal joint reinforcement 13 extended from the reinforcing cage of a leading element 11 in a groove in which an underground continuous wall 1 is to be constructed and horizontal reinforcement 24 extended from the reinforcing cage 23 of a following element 21 built inside the groove while adjoining to the leading element 11. Super high strength concrete 31 mixed with fiber reinforcement 32 is poured into a joint space 30 defined by joint steel plates 12, 22 mounted on the end faces of the reinforcing cages.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint structure for an underground continuous wall, and more particularly to an underground underground joint in which the shear strength and bending toughness of a joint between elements are improved to prevent the joint from being broken. The present invention relates to a joint structure of a continuous wall.

[0002]

2. Description of the Related Art In general, a rigid joint is employed at a joint between a preceding element and a following element of an underground continuous wall. Conventionally, various structures have been proposed as the joint structure of the rigid joint. FIG. 5 is a partial sectional view of an example of the joint 53 of the conventional underground continuous wall 50 in a completed state, as viewed from above. As shown in the figure, in the ordinary joint structure, a joining steel plate 55 serving as a partition from the succeeding element 52 is attached to an end face of the reinforcing element cage 54 of the leading 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. 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 53, FIG.
In this case, a horizontal joint bar 56 and a shear connector 57 penetrating through the joining steel plate 55 are used. The horizontal joint bar 56 is formed by projecting the horizontal bar 58 of the reinforcing bar 54 of the preceding element 51 from the end face of the joining steel plate 55 with a predetermined overlapping length, and is provided with the following element 52 to be built later in the groove. A lap joint 61 is constituted by the horizontal reinforcing bar 60 of the reinforcing bar cage 59. In the overlapped portion of the lap joint 61, the horizontal reinforcing bar 60 of the succeeding element 52 is bent and arranged inside the horizontal joint bar 56 of the preceding element 51 at a predetermined distance.

[0003]

As described above, in the lap joint of the joint portion between the elements of the underground continuous wall, the lap joint is not a lap joint in which the reinforcing bars are integrally bundled, and the separated reinforcing bars are also contained in the stable liquid. Since it is present, clay or the like adheres to the surface of the reinforcing bar, and a sufficient adhesive force cannot be obtained. For this reason, in the design of the joint structure, it is required that the overlap length (la) be sufficiently larger than the overlap length of the concrete member cast in the air. Usually, about 40 times the rebar diameter (φ) (la
= 40φ). However, when a large earthquake or the like occurs and an excessive bending moment or shear force acts on the underground continuous wall as a building foundation, cracks occur at the weak joints, and the cracks increase as the load increases. As shown in FIG. 5, it grows so as to penetrate in the wall thickness direction inside the wall along the horizontal reinforcing bar, and may eventually break from the lap joint due to brittle adhesive split fracture.

[0004] Further, as the length of the lap joint becomes longer,
As the excavation open length of the ground increases, the danger of collapse of the trench wall increases.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, to ensure sufficient shear strength and bending toughness and to maintain the stability of the groove wall underground continuous. It is to provide a wall joint structure.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a horizontal joint bar extending from a reinforcing cage of a preceding element in a trench in which an underground continuous wall is constructed, and a horizontal joint bar adjacent to the preceding element. A lap joint is formed internally by a horizontal reinforcing bar extending from a reinforcing bar cage of a subsequent element built in the groove, and a joint space defined by a joint steel plate attached to an end face of each reinforcing bar cage. It is characterized in that ultra-high-strength concrete mixed with a fiber reinforcing material is poured into the inside.

[0007] Thereby, the proof stress of the joint portion is greatly increased, and it is possible to prevent the joint portion from being broken.

At this time, it is preferable that the joint space is defined by the two opposed joint steel plates and a side steel plate attached to the joint steel plate along the groove wall.

[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. The joint structure 10 of the underground continuous wall 1 shown in FIG.
A subsequent element 21 having a joined steel plate at a position facing the second element 2 at a predetermined distance is shown. The joining steel plate 22 of the succeeding element 21 passes through the horizontal reinforcing bar 24 of the reinforcing cage 23 in the same manner as the preceding element 11 and the reinforcing cage 2
3 are integrally attached. A joint space 30 is formed between the two joined steel plates 12 and 22 to form a lap joint 35 formed by the horizontal joint bars 13 and the horizontal reinforcing bars 24. An ultra-high-strength fiber reinforced concrete 31 is cast in the joint space 30.

The compressive strength of the concrete poured into the joint space 30 is set to be sufficiently higher than that of the wall body.
It is preferable to use ultra-high-strength concrete with fc '= 800 to 1000 kg / cm2 or more. As the ultra-high-strength concrete, it is preferable to use a concrete using a high-performance water reducing agent. In addition, it is preferable to use silica fume concrete in which silica fume is added at a predetermined mixing ratio as a means using an admixture.

Further, short steel fibers 32 as a fiber reinforcing material are mixed at a predetermined mixing rate into the ultra-high strength concrete as a matrix of the fiber reinforced concrete 31.
In the present embodiment, the diameter φf = 0.4 mm and the length Lf = 1
2 mm steel fiber is mixed. In the present invention, the fiber mixing ratio Vf is set to 6% (vol%) in consideration of the improvement of the shear strength and the balance with the compressive strength of the high-strength concrete. As a result, the concrete tensile strength can be increased, and the bond splitting failure caused by the concrete crack can be prevented. In addition, carbon fiber, aramid resin fiber, vinylon resin fiber and the like can be appropriately selected as the fiber reinforcing material to be mixed. By mixing the short steel fibers 32 into the ultra-high-strength concrete 31 in this way, it is possible to improve the toughness, crack dispersibility, and shear strength at the joint.

The wall concrete 14, 27 of each element 11, 21 and the ultra-high strength concrete 3 in the joint space 30
The casting procedure of No. 1 will be described with reference to FIGS. The wall concrete 14 of the preceding element 11 is cast as tremy concrete as in the prior art. Next, as shown in FIG. 2, the reinforcing cage 23 of the succeeding element 21 provided with the joining steel plate 22 at the end is built in the groove. Thereafter, as shown in FIG. 3, the wall concrete 27 of the succeeding element 21 is cast as tremy concrete. At this time, the concrete used for the preceding element 11 and the following element 21 has the same strength. Further, after the wall concretes 14 and 27 of the preceding element 11 and the following element 21 have been cast, the ultra-high strength concrete 31 is cast in the joint space 30.

Since the joint structure 10 has high concrete strength and high crack dispersibility, the length of the joint structure 10 can be made shorter than the conventionally used lap joint, and the excavation open length of the ground can be shortened. Thus, the stability of the groove wall can be improved. In this embodiment, the overlap length (l
a) about 10 times the diameter (φ) of the horizontal reinforcing bar (la = 1
0φ), and the total length Lj of the joint structure 10 can be reduced to about 20 times (20φ) the horizontal rebar diameter (φ).

FIG. 4 shows the structure of the joint space 30 before the concrete of the joint structure 10 is cast. When placing ultra-high-strength concrete, slime adhering to horizontal joint bars (not shown) projecting into the joint space 30 is removed by a joint cleaner (not shown), and is stabilized as necessary. Concrete is poured by replacing the liquid with fresh water. In this case, the side steel plate 3
6, 37 may be provided. Further, steel struts 3 are provided as support members for the joint space 30 at predetermined intervals in the depth direction.
8 may be arranged. Ultra-high-strength concrete mixed with the fiber reinforcing material 32 is poured into the joint space 30 stiffened in order to prevent deformation. Needless to say, the strut 38 is arranged at a position where it does not interfere when a horizontal reinforcing bar (not shown) of the following element is inserted.

[Brief description of the drawings]

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

FIG. 2 is a partial cross-sectional view (part 1) illustrating a procedure for installing the joint structure illustrated in FIG. 1;

FIG. 3 is a partial cross-sectional view (part 2) illustrating a procedure for installing the joint structure illustrated in FIG. 1;

FIG. 4 is a partial plan view showing a configuration example of a joint space.

FIG. 5 is a partial cross-sectional view showing an example of a joint structure of a conventional underground continuous wall.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Underground continuous wall 10 Joint structure 11 Leading element 12,22 Joined steel plate 13 Horizontal joint bar 21 Trailing element 24 Horizontal reinforcing bar 30 Joint space 31 Ultra-high-strength concrete 32 Fiber reinforcement 36,37 Side steel plate

Claims (2)

[Claims] 1. A horizontal joint bar extending from a rebar cage of a preceding element in a trench in which an underground continuous wall is constructed, and a rebar cage of a succeeding element built in the trench adjacent to the preceding element. Lap joints are formed internally by horizontal reinforcing bars extending from the steel bar, and ultra-high-strength concrete mixed with a fiber reinforcing material is poured into a joint space defined by the joining steel plates attached to the end faces of the respective reinforcing cages. A joint structure of an underground continuous wall, characterized in that the joint structure is formed. 2. The ground according to claim 1, wherein said joint space is defined by said two opposed joined steel plates and a side steel plate attached to said joined steel plates along a groove wall. Medium continuous wall joint structure.