JP3637524B2 - Underground continuous wall joint structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a joint structure of underground continuous walls, and more particularly to a joint structure of underground continuous walls that improves shear strength and bending toughness at joints between elements and prevents breakage at joints.
[0002]
[Prior art]
Generally, a rigid joint is employed at the joint between the leading element and the trailing element of the 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 portion 53 of the conventional underground continuous wall 50 in a completed state as viewed from above. As shown in the figure, in a normal joint structure, a joining steel plate 55 serving as a partition from the succeeding element 52 is attached to the end face of the reinforcing bar 54 of the preceding element 51 in the wall width direction. For this reason, the preceding element 51 and the succeeding element 52 are blocked from being integrated as a concrete wall body at the joint portion 53. 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 in the joint portion 53, in FIG. 57 is used. This horizontal joint bar 56 is obtained 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 overlap length, and the rear element 52 to be built into the groove later. A lap joint 61 is constituted by the horizontal reinforcing bar 60 of the reinforcing bar 59. Note that, in the overlapping portion of the lap joint 61, the horizontal reinforcing bar 60 of the succeeding element 52 is bent and arranged at a predetermined distance inside the horizontal joint bar 56 of the preceding element 51.
[0003]
[Problems to be solved by the invention]
In this way, the lap joint of the joint part between the elements of the underground continuous wall is not a lap joint in which the reinforcing bars are bundled together, and the separated reinforcing bars are also placed in the stable liquid, It is in a state where clay or the like is adhered and sufficient adhesion 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 placed in the air. Normally, it is defined to have an overlap length of about 40 times (la = 40φ) the diameter of the reinforcing bar (φ). However, if a large earthquake or the like occurs and an excessive bending moment or shearing force acts on the underground continuous wall as a building foundation, cracks occur in the weak joints. As shown in FIG. 5, it grows so as to penetrate the wall thickness direction inside the wall body along the horizontal rebar, and there is a risk that it will eventually break from the lap joint due to brittle adhesion split fracture.
[0004]
In addition, since the length of the lap joint is increased, the excavation open length of the ground is increased, thereby increasing the risk of the groove wall collapsing.
[0005]
Therefore, the object of the present invention is to solve the problems of the prior art described above, ensure sufficient shear strength and bending toughness, and maintain the stability of the groove wall. To provide a structure.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention was built in a groove adjacent to the preceding element and a horizontal joint extending from the reinforcing bar of the preceding element in the groove in which the underground continuous wall is constructed. A lap joint is formed inside by a horizontal reinforcing bar extending from the reinforcing bar cage of the succeeding element, and a fiber reinforcing material is mixed in the joint space defined by the joining steel plate attached to the end surface of each reinforcing bar cage. It is characterized by placing high-strength concrete.
[0007]
Thereby, the yield strength of the joint portion is significantly increased, and it is possible to prevent the joint portion from being broken.
[0008]
At this time, it is preferable that the joint space is defined by the two opposed bonded steel plates and side steel plates attached to the bonded steel plates along the groove walls.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a joint structure for underground continuous walls according to the present invention will be described with reference to the accompanying drawings.
The joint structure 10 of the underground continuous wall 1 shown in FIG. 1 includes a joined steel plate 12 of a preceding element 11 and a trailing element 21 having a joined steel plate at a position facing the joined steel plate 12 with a predetermined distance. It is shown. The joining steel plate 22 of the trailing element 21 is integrally attached to the reinforcing bar 23 in a state where the horizontal reinforcing bar 24 of the reinforcing bar 23 is penetrated in the same manner as the leading element 11. A joint space 30 constituting a lap joint 35 formed by the horizontal joint bars 13 and the horizontal reinforcing bars 24 is formed between the two bonded steel plates 12 and 22. An ultrahigh strength fiber reinforced concrete 31 is placed in the joint space 30.
[0010]
The compressive strength of the concrete cast in the joint space 30 is preferably sufficiently higher than that of the wall body, and is preferably ultrahigh strength concrete with fc ′ = 800 to 1000 kg / cm 2 or more. It is preferable to use a high-performance water reducing agent as the ultra high strength concrete. Moreover, it is preferable to set it as the silica fume concrete which added the silica fume by the predetermined | prescribed compounding ratio as a means using an admixture.
[0011]
Moreover, in the ultra high strength concrete as a matrix of the fiber reinforced concrete 31, short steel fibers 32 as a fiber reinforcing material are mixed at a predetermined mixing rate. In the present embodiment, a steel fiber having a diameter φf = 0.4 mm and a length Lf = 12 mm is mixed. In the present invention, the fiber mixing rate Vf is set to 6% (volume%) in consideration of the balance between improvement in shear strength and compressive strength of high-strength concrete. Thereby, concrete tensile strength can be enlarged and the adhesion split fracture resulting from a 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.
Thus, by mixing the short steel fibers 32 into the ultra-high-strength concrete 31, it is possible to improve the toughness, crack dispersibility, and shear strength at the joint.
[0012]
The placement procedure of the wall concrete 14 and 27 of each element 11 and 21 and the ultra high strength concrete 31 of the joint space 30 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 steel basket 23 of the succeeding element 21 in which the bonded steel plate 22 is provided at the end is built in the groove. After that, as shown in FIG. 3, the wall concrete 27 of the trailing element 21 is placed as treme concrete. At this time, the same strength is used for the concrete used for the leading element 11 and the trailing element 21. Further, after the wall body concrete 14, 27 of the preceding element 11 and the succeeding element 21 is placed, the ultra high strength concrete 31 is placed in the joint space 30.
[0013]
Since this joint structure 10 has high concrete strength and high crack dispersibility, the length of the joint structure 10 can be made shorter than the conventional lap joint, and the excavation open length of the ground can be shortened. It becomes possible to improve stability. In this embodiment, the overlap length (la) can be expected to be about 10 times the diameter (φ) of the horizontal rebar (la = 10φ), and the total length Lj of the joint structure 10 is about 20 times the horizontal rebar diameter (φ). It is possible to shorten to double (20φ).
[0014]
FIG. 4 shows the structure of the joint space 30 before the concrete of the joint structure 10 is placed. When placing ultra-high-strength concrete, the slime adhering to the horizontal joint bars (not shown) protruding into the joint space 30 is removed by a joint cleaner (not shown) and stable as necessary. Replace the liquid with clean water and cast concrete. In this case, side steel plates 36 and 37 may be provided to ensure the stability of the groove wall. Further, the steel struts 38 may be arranged at predetermined intervals in the depth direction as support members for the joint space 30. In this way, ultra-high-strength concrete in which the fiber reinforcing material 32 is mixed is placed in the joint space 30 stiffened to prevent deformation. Needless to say, the strut 38 is disposed at a position where it does not interfere when a horizontal reinforcing bar (not shown) of the trailing element is inserted.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing an embodiment of a joint structure for underground continuous walls according to the present invention.
FIG. 2 is a partial cross-sectional view showing a construction procedure of the joint structure shown in FIG. 1 (part 1).
FIG. 3 is a partial cross-sectional view (part 2) showing a construction procedure of the joint structure shown 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 Joining steel plate 13 Horizontal joint reinforcement 21 Subsequent element 24 Horizontal reinforcement 30 Joint space 31 Super high-strength concrete 32 Fiber reinforcement 36,37 Side steel plate

Claims (2)

Horizontal joint bars extending from the reinforcing bar cage of the preceding element in the groove where the underground continuous wall is constructed, and horizontal bars extending from the reinforcing bar cage of the succeeding element built in the groove adjacent to the preceding element A lap joint was formed inside with the reinforcing bars, and ultra-high-strength concrete mixed with fiber reinforcements was placed in the joint space defined by the bonded steel plates attached to the end faces of the reinforcing bars. An underground continuous wall joint structure characterized by The joint wall of the underground continuous wall according to claim 1, wherein the joint space is defined by the two opposing joined steel plates and side steel plates attached to the joined steel plates along a groove wall. Construction.

Images