JP7214546B2 - Shear failure prevention structure for diaphragm wall - Google Patents

Description

As a method for constructing RC diaphragm walls, there is a method in which preceding elements are provided in the ground at intervals, and trailing elements are provided between these preceding elements to construct a diaphragm wall. . The connection between the leading element and the trailing element is such that the load (in-plane shear force) can be transmitted to each other (see, for example, Patent Documents 1 to 3), and the case where they are in contact with each other but the load is not applied to each other. In some cases, it is connected to a state in which no transmission is performed.

When the leading and trailing elements are connected to each other so that in-plane shear forces can be transmitted between them, it is conceivable that the joints between the leading and trailing elements are: .
Protrusive streaks and recessed streaks extending in the wall thickness direction (thickness direction of the diaphragm wall) are alternately formed in the wall height direction (vertical direction) on each of the mutually connected end faces of the preceding element and the succeeding element. Then, the concave streak portion of the leading element and the protruding streak portion of the trailing element are fitted, and the protruding streak portion of the leading element and the recessed streak portion of the trailing element are fitted to form a shear key in the joint portion.

Japanese Patent No. 3982327 JP 2010-242318 A JP 2017-179734 A

However, if a shear force greater than the in-plane shear force assumed in the design acts between the leading and trailing elements, cracks will occur at the corners of the recessed streaks of the leading and trailing elements. It is conceivable that cracks may develop along the joint surface of concrete between the leading element and the trailing element toward both elements, causing shear failure at the joint between the leading element and the trailing element.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a diaphragm wall shear failure prevention structure capable of preventing shear failure of a first element (preceding element) and a second element (following element).

In order to achieve the above object, a diaphragm wall shear failure prevention structure according to the present invention is a diaphragm wall in which a first element and a second element made of reinforced concrete are provided adjacent to each other. In the diaphragm wall shear failure prevention structure for preventing shear failure between the first element and the second element via a joint portion with the second element, the first element includes the second element on the side end face, a first ridge protruding in the wall length direction of the wall adjacent to the first element and the second element and extending in the wall thickness direction; are alternately arranged in the wall height direction, and the second element has, on the end face on the first element side, a projection in the wall length direction and a wall thickness direction. Extending second ridges and second ridges recessed in the wall length direction and extending in the wall thickness direction are alternately arranged in the wall height direction. The ridge portion and the second ridge portion are fitted together, the first ridge portion and the second ridge portion are fitted together, and the first element includes the first ridge portion and the second ridge portion. A first reinforcing bar is provided along the unevenness of the first grooved line, and the second element is provided with a second reinforcing bar along the unevenness of the second convex line and the second grooved line. and a plurality of the first reinforcing bars are arranged in the wall height direction, have first bending portions corresponding to the first ridges, and are adjacent to each other in the wall height direction. a portion of the upper first reinforcing bar below the first bent portion and a portion of the lower first reinforcing bar above the first bent portion are arranged at the same height. , the second reinforcing bars are arranged in a plurality in the wall height direction and have second bent portions corresponding to the second ridges; and the second reinforcing bars adjacent in the wall height direction are A portion of the second reinforcing bar on the upper side below the second bent portion and a portion of the second reinforcing bar on the lower side above the second bent portion are arranged at the same height . It is characterized by

In the present invention, since the first element is provided with the first reinforcing bars along the unevenness of the first protruded line and the first recessed line, an in-plane shear force acts between the first element and the second element. It is possible to prevent cracks from occurring in the first element from the first concave streak portion when the first element is formed. Since the second element is provided with the second reinforcing bars along the unevenness of the second protruded line and the second recessed line, when an in-plane shear force acts between the first element and the second element, , the second element can be prevented from being cracked from the second concave streak portion.
As a result, shear failure of the first element and the second element can be prevented when an in-plane shear force acts between the first element and the second element.
In the present invention, the direction in which the first element and the second element of the diaphragm wall are adjacent to each other is defined as the wall length direction, and the thickness direction of the diaphragm wall (thickness direction of the first element and the second element) is defined as the wall length direction. The thickness direction is defined as the wall height direction, and the height direction of the diaphragm wall (height direction of the first element and the second element) is defined as the wall height direction.

Further , the first reinforcing bars can be arranged in the vertical direction without gaps along the unevenness of the first ridge and the first groove in the first element, and the second ridge and the second ridge can be arranged in the second element. The second reinforcing bars can be arranged vertically without gaps along the unevenness of the two grooved portions.

According to the present invention, shear failure of the first element and the second element can be prevented.

(a) is a plan view omitting concrete showing an example of reinforcement bar arrangement for preventing shear failure of a diaphragm wall according to the first embodiment of the present invention; Side view omitting concrete showing an example of reinforcing bar arrangement for preventing shear failure of a continuous wall, (c) is a cross-sectional view along the line AA of (b), (d) is BB of (b) It is a line sectional view. (a) is a plan view omitting concrete showing an example of reinforcement bar arrangement for preventing shear failure of a diaphragm wall according to the second embodiment of the present invention; Side view omitting concrete showing an example of reinforcing bar arrangement for preventing shear failure of a continuous wall. It is a line sectional view. (a) is a plan view omitting concrete showing an example of reinforcement bar arrangement for preventing shear failure of a diaphragm wall according to a first modification of the embodiment of the present invention; (b) is a plan view of the embodiment of the present invention; A side view omitting concrete showing an example of reinforcing bar arrangement for shear failure prevention of a diaphragm wall according to the first modification, (c) is a cross-sectional view along the EE line of (b), (d) is ( b) is a cross-sectional view taken along line FF. (a) is a plan view omitting concrete showing an example of reinforcing bar arrangement for preventing shear failure of a diaphragm wall according to a second modification of the embodiment of the present invention; (b) is a plan view of the embodiment of the present invention; A side view omitting concrete showing an example of reinforcing bar arrangement for preventing shear failure of a diaphragm wall according to the second modification, (c) is a cross-sectional view along the GG line of (b), (d) is ( b) is a cross-sectional view taken along line HH.

(First embodiment)
Hereinafter, a diaphragm wall shear failure prevention structure according to a first embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, a diaphragm wall 1 according to the first embodiment includes a plurality of wall-like elements 2 and 3 which are joined together by abutting their ends. The horizontal direction orthogonal to the wall surface of the diaphragm wall 1 is the wall thickness direction, and the horizontal direction along the wall surface and orthogonal to the wall thickness direction is the wall length direction. shall be the wall height direction or vertical direction.
A plurality of elements 2 and 3 that constitute the diaphragm wall 1 include a preceding element (first element) 2 that is constructed first, and a succeeding element (second element) 3 that is constructed after the preceding element 2. A leading element 2 and a trailing element 3 are arranged in the wall length direction.
Both the preceding element 2 and the succeeding element 3 are constructed by excavating the ground 11 (see FIG. 1).

The preceding element 2 and the succeeding element 3 are RC wall bodies in which vertical reinforcements 22, 32 and horizontal reinforcements 23, 33 are embedded in concrete 21, 31, respectively. The leading element 2 and the trailing element 3 are set to have the same dimensions in the wall thickness direction and the vertical direction, and are arranged so that the respective wall centers are aligned. The leading element 2 and the trailing element 3 are arranged so that their ends in the wall length direction are butted against each other. A joint portion 4 is a portion where the leading element 2 and the trailing element 3 are butted against each other.
In the description of the joint portion 4 below, the side of the wall length direction where the trailing element 3 is arranged with respect to the leading element 2 is defined as the front side, and the leading element 2 is arranged with respect to the trailing element 3. The side on which the wall is located is referred to as the rear side, and the longitudinal direction of the wall is sometimes written as the front-back direction.

As shown in FIG. 1(b), on the front end face of the preceding element 2, there are a concrete concave streak portion 24 (first concave streak portion) and a concrete protruding streak portion 25 (first protruding streak portion) extending in the wall thickness direction. are arranged alternately in the vertical direction to form irregularities. In other words, a plurality of concrete protruding streaks 25 are arranged in the vertical direction, and the concrete recessed streaks 24 are formed between the concrete protruding streaks 25 adjacent to each other in the vertical direction. The plurality of concrete protruding streaks 25 are each formed with the same cross-sectional shape, and the concrete recessed streaks 24 therebetween are also formed with the same cross-sectional shape.

The concrete protruding portion 25 has a triangular cross-sectional shape, and the upper surface is formed as an inclined surface that gradually slopes downward toward the front side, and the lower surface is formed as an inclined surface that gradually slopes upward toward the front side. The front ends are connected to form a corner 251 . The inclined surface of the upper surface of the concrete protrusion 25 is referred to as a first inclined surface 26 and the inclined surface of the lower surface thereof is referred to as a second inclined surface 27 .
The rear ends of the second inclined surfaces 27 of the upper concrete ridges 25 arranged in the vertical direction and the rear ends of the first inclined surfaces 26 of the lower concrete ridges 25 form corners 251 . connected to form The first inclined surfaces 26 and the second inclined surfaces 27 are arranged alternately.
The concrete groove 24 is formed between the first slanted surface 26 and the second slanted surface 27 , and a corner 241 is formed at the connecting portion between the first slanted surface 26 and the second slanted surface 27 .
Both the corner 241 of the concrete concave streak 24 and the corner 251 of the concrete protruding streak 25 are substantially right-angled.

A plurality of first reinforcing bars 28 are arranged along the unevenness of the front end surface of the leading element 2 .
The first reinforcing bar 28 has a first bent portion 281 bent at the same angle as the corner portion 251 of the concrete ridge portion 25 . The first reinforcing bar 28 is arranged such that the first bent portion 281 is located behind the corner portion 251 of the concrete ridge portion 25 . When viewed from the wall thickness direction, the first reinforcing bar 28 has an L shape in which the first bent portion 281 is bent at a substantially right angle, and the upper portion of the first bent portion 281 gradually extends upward and backward. The lower portion of the first bent portion 281 extends obliquely downward and gradually toward the rear side.

The first reinforcing bar 28 is arranged at a height slightly above the corner 251 of the concrete ridge 25 positioned immediately above the concrete ridge 25 whose upper end 282 is positioned on the front side of the first bent portion 281 . The lower end portion 283 is arranged at a height slightly lower than the corner portion 251 of the concrete protruding streak portion 25 positioned immediately below the concrete protruding streak portion 25 positioned on the front side of the first bent portion 281. .
A plurality of first reinforcing bars 28 are arranged in the vertical direction so as to correspond to each of the plurality of concrete ridges 25 arranged in the vertical direction. In the vertically adjacent first reinforcing bars 28, the lower end portion of the upper first reinforcing bar 28 and the upper end portion of the lower first reinforcing bar 28 are arranged at the same height.
The vertically adjacent first reinforcing bars 28, 28 are arranged at positions shifted in the wall thickness direction so as not to interfere with each other.

In this embodiment, vertical reinforcements 22 and horizontal reinforcements 23 are arranged at both end portions of the preceding element 2 in the wall thickness direction, respectively, and vertical reinforcements 22 and horizontal reinforcements 23 are arranged at one end portion in the wall thickness direction. A first reinforcing bar 28 is provided on both sides in the wall thickness direction between the vertical bar 22 and the horizontal bar 23 arranged at the end portion on the other side.

On the rear end surface of the trailing element 3, a plurality of concrete recessed streaks 34 (second recessed streaks) extending in the wall thickness direction and concrete protruding streaks 35 (second protrusive streaks) are arranged alternately in the vertical direction. and unevenness is formed. In other words, a plurality of concrete protruding streaks 35 are arranged in the vertical direction, and the concrete recessed streaks 24 are formed between the concrete protruding streaks 35 adjacent to each other in the vertical direction. The plurality of concrete protruding streaks 35 are formed with the same cross-sectional shape, and the concrete recessed streaks 34 therebetween are also formed with the same cross-sectional shape.

The concrete protruding portion 35 has a triangular cross-sectional shape, and the upper surface is formed to be an inclined surface gradually downward toward the rear side, and the lower surface is formed to be an inclined surface gradually upward toward the rear side. The rear ends of the lower surfaces are connected to form corners 351 . The inclined surface of the upper surface of the concrete ridge 35 is referred to as a third inclined surface 36 , and the inclined surface of the lower surface thereof is referred to as a fourth inclined surface 37 .
The front end of the fourth inclined surface 37 of the upper concrete ridge 35 arranged in the vertical direction and the front end of the third inclined surface 36 of the lower concrete ridge 35 form a corner 351. connected as follows. The third inclined surfaces 36 and the fourth inclined surfaces 37 are arranged alternately.
The concrete groove 34 is formed between the third slanted surface 36 and the fourth slanted surface 37 , and a corner 341 is formed at the connecting portion between the third slanted surface 36 and the fourth slanted surface 37 .
A corner portion 341 of the concrete grooved portion 34 and a corner portion 351 of the concrete convex portion 35 are both substantially right angles.

A plurality of second reinforcing bars 38 are arranged along the unevenness of the rear end surface of the trailing element 3 .
The second reinforcing bar 38 has a second bent portion 381 bent at the same angle as the corner portion 351 of the concrete ridge portion 35 . The second reinforcing bar 38 is arranged so that the second bent portion 381 is positioned in front of the corner portion 351 of the concrete ridge portion 35 . When viewed from the wall thickness direction, the second reinforcing bar 38 has an L shape in which the second bent portion 381 is bent at a substantially right angle, and the upper portion of the second bent portion 381 gradually moves forward toward the upper side. , and the lower portion of the second bent portion 381 extends obliquely downward and gradually toward the front side.

The second reinforcing bar 38 has a height slightly above the corner 351 of the concrete ridge 35 positioned just above the concrete ridge 35 whose upper end 382 is positioned on the rear side of the second bent portion 381 . The lower end portion 383 is arranged at a height slightly lower than the corner portion 351 of the concrete protruding streak portion 35 positioned immediately below the concrete protruding streak portion 35 positioned on the rear side of the second bent portion 381 . ing.
A plurality of second reinforcing bars 38 are arranged in the vertical direction so as to correspond to each of the plurality of concrete ridges 35 arranged in the vertical direction. The second reinforcing bars 38 adjacent to each other in the vertical direction are arranged such that the lower end portion of the second reinforcing bar 38 on the upper side and the upper end portion of the second reinforcing bar 38 on the lower side are at the same height.
The vertically adjacent second reinforcing bars 38, 38 are arranged at positions shifted in the wall thickness direction so as not to interfere with each other.

In this embodiment, vertical reinforcements 32 and horizontal reinforcements 33 are arranged at both end portions of the trailing element 3 in the wall thickness direction, respectively, and vertical reinforcements 32 and horizontal reinforcements 33 are arranged at one end portion in the wall thickness direction. Second reinforcing bars 38 are provided on both sides in the wall thickness direction between 33 and the vertical bars 32 and horizontal bars 33 arranged at the other end portion.
The first reinforcing bar 28 and the second reinforcing bar 38 are arranged at positions opposed to each other in the wall length direction.
The fixing lengths of the first reinforcing bar 28 and the second reinforcing bar 38 are set according to existing standards.

Next, the operation and effects of the diaphragm wall shear failure prevention structure according to the first embodiment described above will be described with reference to the drawings.
In the above-described diaphragm wall shear failure prevention structure according to the first embodiment, since the preceding element 2 is provided with the first reinforcing bars 28 along the unevenness of the concrete protruded streak 25 and the concrete recessed streak 24, the preceding element 2 and the trailing element 3, cracks can be prevented from occurring in the leading element 2 from the concrete groove 24 when an in-plane shear force acts between the trailing element 3 and the leading element 2. - 特許庁
Since the trailing element 3 is provided with the second reinforcing bars 38 along the unevenness of the concrete ridges 35 and concrete grooves 34, an in-plane shear force acts between the leading element 2 and the trailing element 3. It is possible to prevent the trailing element 3 from being cracked from the concrete recessed streak portion 34 when the concrete groove 34 is formed.
As a result, when an in-plane shear force acts between the leading element 2 and the trailing element 3, the leading element 2 and the trailing element 3 can be prevented from shear failure.

In addition, in the present embodiment, the first reinforcing bars 28 adjacent in the vertical direction are arranged such that the lower end portion of the upper first reinforcing bar 28 and the upper end portion of the lower first reinforcing bar 28 are at the same height, The second reinforcing bars 38 adjacent to each other in the vertical direction are arranged such that the lower end portion of the second reinforcing bar 38 on the upper side and the upper end portion of the second reinforcing bar 38 on the lower side are at the same height. As a result, the first reinforcing bars 28 can be arranged in the vertical direction without gaps along the unevenness of the concrete ridges 25 and the concrete grooves 24 in the leading element 2 , and the concrete ridges in the trailing element 3 can be arranged. The second reinforcing bars 38 can be arranged in the vertical direction without gaps along the unevenness of the concave streaks 35 and the concrete grooves 34 .

(Second embodiment)
Next, another embodiment will be described with reference to the accompanying drawings. The same or similar members and portions as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Different configurations are described.
As shown in FIG. 2, in the diaphragm wall shear failure prevention structure according to the second embodiment, compared with the diaphragm wall 1 according to the first embodiment, the first and second elements 2B of the preceding element 2B of the diaphragm wall 1B The second slanted surfaces 26B, 27B and the second and fourth slanted surfaces 36B, 37B of the trailing element 3B are elongated in the vertical direction and the wall length direction. formed large.
In the second embodiment, the upper end portion 282B of the first reinforcing bar 28B is slightly below the corner portion 251B of the concrete ridge portion 25B located above the concrete ridge portion 25B located on the front side of the first bent portion 281B. The lower end portion 283B is located at a height slightly above the corner portion 251B of the concrete protruding portion 25B positioned below the concrete protruding portion 25B positioned on the front side of the first bent portion 281B. are placed. As for the vertically adjacent first reinforcing bars 28B, 28B, the lower end portion of the upper first reinforcing bar 28B and the upper end portion of the lower first reinforcing bar 28B are arranged at the same height.
The second reinforcing bar 38B has a height slightly below the corner 351B of the concrete ridge 35B positioned above the concrete ridge 35B whose upper end 382B is positioned behind the second bent portion 381B. The lower end portion 383B is arranged at a height slightly above the corner portion 351B of the concrete protruding streak portion 35B positioned below the concrete protruding streak portion 35B positioned on the rear side of the second bent portion 381B. . In the vertically adjacent second reinforcing bars 38B, 38B, the lower end portion of the upper second reinforcing bar 38B and the upper end portion of the lower second reinforcing bar 38B overlap.

In the above-described diaphragm wall shear fracture prevention structure according to the second embodiment, the same effects as those of the first embodiment are obtained.

Although the embodiment of the shear failure prevention structure for a diaphragm wall according to the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the scope of the invention.
For example, the shapes of the concrete recessed streak portion 24 and the concrete protruding streak portion 25 of the preceding element 2 and the shapes of the concrete recessed streak portion 34 and the concrete protrusive streak portion 35 of the succeeding element 3 may be other than those described above.
In the above-described embodiment, the corners 341, 351 of the concrete recessed streaks 24, 34 and the corners 251, 351 of the concrete protruding streaks 25, 35 of the diaphragm wall 1 are substantially right angles. As in the diaphragm wall shear failure prevention structure shown, the corners 241C and 251C of the concrete ridges 25C of the leading element 2C of the diaphragm wall 1C and the concrete of the trailing element 3C The corner 341C of 34C and the corner 351C of the concrete ridge 35C may have an obtuse angle.
Also in such a case, the first reinforcing bars 28C and the second reinforcing bars 38C are provided so as to correspond to the corners 351C, 351C of the concrete ridges 25C, 35C.

Moreover, like the shear failure prevention structure of the diaphragm wall shown in FIG. The cross-sectional shape of the portion 34D and the concrete protruding streak portion 35D is trapezoidal. Two 351D may be provided.
Also in such a case, the first reinforcing bar 28D and the second reinforcing bar 38D are provided so as to correspond to the corners 351D, 351D of the concrete ridges 25D, 35D.

Further, in the above-described embodiment, the preceding element 2 has a plurality of first reinforcing bars 28 having one first bent portion 281 arranged in the vertical direction so as to correspond to one concrete ridge portion 25. A first reinforcing bar having a plurality of bent portions may be arranged so as to correspond to the plurality of concrete ridges 25 . Further, in the trailing element 3, a plurality of second reinforcing bars 38 having one second bent portion 381 are arranged in the vertical direction so as to correspond to one concrete ridge portion 35. A second reinforcing bar having a plurality of bent portions may be arranged so as to correspond to the streak portion 35 .

1, 1B-1D Diaphragm wall 2 Leading element (first element)
3 trailing element (second element)
4, 4B-4D Joint part 24, 24C, 24C, 24D Concrete concave streak part (first concave streak part)
25, 25B, 25C, 25D Concrete ridge (first ridge)
26 First inclined surface 27 Second inclined surface 28 First reinforcing bar 34, 34C, 34C, 34D Concrete concave streak (second concave streak)
35, 35B, 35C, 35D Concrete ridges (second ridges)
36 third inclined surface 37 fourth inclined surface 38 second reinforcing bar 281 first bent portion 381 second bent portion

Claims (1)

Shearing of the first element and the second element via the joint part of the first element and the second element in the diaphragm wall in which the first element and the second element made of reinforced concrete are provided adjacently. In the shear failure prevention structure of the diaphragm wall to prevent failure,
The first element includes, on the end face on the side of the second element, a first ridge protruding in the length direction of the wall where the first element and the second element are adjacent and extending in the thickness direction of the wall; First grooves recessed in the length direction and extending in the wall thickness direction are alternately arranged in the wall height direction,
The second element has, on the end face on the first element side, a second protruding portion that protrudes in the wall length direction and extends in the wall thickness direction; and second grooves extending in the direction of the wall are arranged alternately in the wall height direction,
In the joint portion, the first ridge portion and the second ridge portion are fitted, the first ridge portion and the second ridge portion are fitted,
The first element is provided with a first reinforcing bar along the unevenness of the first protruded streak and the first recessed streak,
The second element is provided with a second reinforcing bar along the unevenness of the second protruded streak and the second recessed streak ,
a plurality of the first reinforcing bars arranged in the wall height direction and having a first bent portion corresponding to the first ridge;
The first reinforcing bars adjacent in the wall height direction are a portion below the first bent portion of the first reinforcing bar on the upper side and the first bent portion of the first reinforcing bar on the lower side. are arranged at the same height as the upper part of
a plurality of the second reinforcing bars arranged in the wall height direction and having second bent portions corresponding to the second ridges;
The second reinforcing bars adjacent to each other in the wall height direction are a portion below the second bent portion of the second reinforcing bar on the upper side and the second bent portion of the second reinforcing bar on the lower side. A structure for preventing shear failure of a diaphragm wall, characterized in that the upper part of the diaphragm wall is arranged at the same height .

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