Diaphragm walls and foundation structures

Abstract

To provide an underground continuous wall and a foundation structure capable of being constructed without excessive design and capable of improving construction efficiency.SOLUTION: In an underground continuous wall 1 in which a preceding element 2 and a following element 3 of reinforced concrete construction are provided so as to be adjacent to each other, an isolating material 41 is arranged in a boundary portion 40 of the preceding element and the following element, and a preceding reinforcement 20 arranged in the preceding element is not overlapped with a following reinforcement 30 arranged in the following element.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a diaphragm wall and a foundation structure. [Background technology]

[0002] A reinforced concrete diaphragm wall comprises leading elements constructed at a predetermined interval and trailing elements constructed later to connect adjacent leading elements. One method for connecting the leading and trailing elements is to use a lap joint between the reinforcing bar cages of the leading element and the trailing element to make a structurally integrated wall (see, for example, Patent Document 1). Another method that has been proposed is to cut the connecting surface of the leading element with the trailing element using an excavator or the like, and then pour the concrete of the trailing element to join them. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-97841 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a diaphragm wall is used as the foundation of a building, it is generally constructed so as to surround the entire periphery of the building. For example, if a diaphragm wall is constructed in a rectangular shape in plan view, it will have a very large horizontal rigidity against horizontal forces such as earthquakes. If a diaphragm wall is constructed using the above-mentioned lap joint method and the diaphragm wall and piles are used together as the building foundation, the horizontal rigidity of the diaphragm wall is very large compared to the piles, so most of the horizontal force acting on the building foundation during an earthquake acts on the diaphragm wall, and the load borne by the piles becomes very small. As a result, a large shear force is generated in the diaphragm wall, and wall thickness, reinforcement, and concrete strength that can withstand the force are required, which increases costs and causes problems such as dense reinforcement and reduced construction efficiency. In addition, since the horizontal force borne by the piles is small, only a horizontal force that is too small compared to the horizontal load bearing capacity of the piles is borne, which is also inefficient from that point of view.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an underground diaphragm wall and foundation structure that can be constructed without excessive design and that can improve construction efficiency. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the underground continuous wall of the present invention is characterized in that, in an underground continuous wall in which a leading element and a trailing element made of reinforced concrete are arranged adjacent to each other, an edge cutting material is arranged at the boundary between the leading element and the trailing element, and the leading reinforcing bar arranged in the leading element and the trailing reinforcing bar arranged in the trailing element do not overlap.

[0007] According to this invention, the leading rebar of the leading element and the trailing rebar of the trailing element are cut by the edge cutter. As a result, the friction and adhesion between the leading element and the trailing element are smaller than in the past. In other words, when a horizontal force of a certain level or more acts on the diaphragm wall, deformation (slip) can be caused between the leading element and the trailing element along the surface of the edge cutter, and the stress generated in the diaphragm wall can be reduced. As a result of being able to reduce the stress generated in the diaphragm wall, the amount of reinforcing bars and the diameter of the reinforcing bars can be set to appropriate values ​​without excessive use, and construction efficiency can also be improved.

[0008] The edge cutting material may be a flat or corrugated steel plate. By constructing the edge separation material from a flat steel plate in this way, it can be used as a formwork when pouring the concrete for the leading element, and also has the function of an edge separation material for the following element. In addition, since it is only necessary to install a flat or corrugated steel plate at a predetermined position, construction can be easily performed. In other words, construction efficiency can be improved.

[0009] The foundation structure according to the present invention is characterized by comprising the above-mentioned diaphragm wall formed in a ring shape, and piles disposed inside the diaphragm wall.

[0010] According to this invention, since the diaphragm wall and the piles are used in combination in the foundation structure, the piles can bear a large horizontal force, and the load borne by the diaphragm wall can be reduced. Specifically, when a horizontal force acts on the diaphragm wall, a deformation (slip) occurs along the boundary surface (end surface) between the leading element and the trailing element, since only a flat steel plate-shaped edge cutter is interposed. The stress of the diaphragm wall is relieved by the slip between the leading element and the trailing element. As a result, the horizontal deformation amount of the upper end (top end) of each element of the diaphragm wall increases. When the diaphragm wall and the piles are used in combination in the foundation structure, the pile head displacement increases by the amount of the horizontal deformation of the upper end of the diaphragm wall increases, and the horizontal force borne by the pile also increases. As a result, the load borne by the diaphragm wall is reduced, and the stress of the diaphragm wall can be further reduced. In other words, the horizontal force can be appropriately shared between the diaphragm wall and the piles, and the design of the diaphragm wall and the piles can be optimized without excessive design. In addition, since the stress generated in the diaphragm wall can be reduced, the amount of reinforcement in the diaphragm wall and the size of the reinforcing bars can be reduced, thereby improving construction efficiency. Effect of the Invention

[0011] According to the present invention, it is possible to provide a diaphragm wall and foundation structure that can be constructed without excessive design and that can improve construction efficiency. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic plan view (cross-sectional view) of a diaphragm wall according to the present embodiment. [Diagram 2] 1 is a schematic front view (cross-sectional view) of a diaphragm wall according to the present embodiment. [Diagram 3] FIG. 2 is a diagram showing a construction procedure of a diaphragm wall according to the present embodiment. [Figure 4] FIG. 2 is a schematic diagram of the diaphragm wall according to the present embodiment during deformation. [Diagram 5] This is a schematic plan view of a building foundation (foundation structure) that combines underground diaphragm walls and piles. [Figure 6] FIG. 2 is a schematic front view (sectional view) showing another embodiment of a diaphragm wall. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a diaphragm wall and a foundation structure according to an embodiment of the present invention will be described with reference to Figs.

[0014] As shown in Figs. 1 to 3, a diaphragm wall 1 of this embodiment is constructed by alternately arranging leading elements 2 and trailing elements 3, both made of reinforced concrete, in plan and front views.

[0015] As shown in FIGS. 1 and 2, in the diaphragm wall 1 of this embodiment, a leading element 2 and a trailing element 3 are connected via an edge insulating material 41 .

[0016] The leading element 2 is a wall made of reinforced concrete (RC) with vertical reinforcements 21 and horizontal reinforcements 22 embedded in a wall panel portion 25 made of concrete. The vertical reinforcements 21 are provided over the entire vertical direction of the wall panel portion 25. The horizontal reinforcements 22 are provided over substantially the entire length of the wall panel portion 25 in the wall length direction. In this embodiment, the horizontal reinforcements 22 are provided in two rows spaced apart in the wall thickness direction and in multiple stages spaced apart in the vertical direction. The vertical reinforcements 21 are provided in multiple rows spaced apart in the wall length direction so as to follow the horizontal reinforcements 22 in each row.

[0017] The trailing element 3 is a wall made of reinforced concrete (RC) with vertical reinforcements 31 and horizontal reinforcements 32 embedded in a wall panel portion 35 made of concrete. The vertical reinforcements 31 are provided over the entire vertical direction of the wall panel portion 35. The horizontal reinforcements 32 are provided over substantially the entire length of the wall panel portion 35 in the wall length direction. In this embodiment, the horizontal reinforcements 32 are provided in two rows spaced apart in the wall thickness direction and in multiple stages spaced apart in the vertical direction. The vertical reinforcements 31 are provided in multiple rows spaced apart in the wall length direction so as to follow the horizontal reinforcements 32 in each row.

[0018] The leading element 2 and the trailing element 3 are set to have the same dimensions in the wall thickness direction and the up-down direction, and are arranged so that their wall centers are aligned. The leading element 2 and the trailing element 3 are arranged so that their end faces 2a, 3a in the wall length direction are butted against each other. The part where the leading element 2 and the trailing element 3 are butted against each other is called the boundary portion 40.

[0019] An edge cutting material 41 is disposed at the boundary portion 40. The edge cutting material 41 is formed, for example, of a flat steel plate. The surface of the edge cutting material 41 may be smoothly processed. The edge cutting material 41 cuts the edge between the reinforcing bar (reinforcing bar cage 20) of the leading element 2 and the reinforcing bar (reinforcing bar cage 30) of the following element 3. In other words, the reinforcing bar cage 20 and the reinforcing bar cage 30 do not overlap when viewed from above or from the front.

[0020] Next, a construction procedure for the diaphragm wall 1 will be described with reference to FIG.

[0021] In FIG. 3(a), a predetermined position in the ground is excavated at a location where the leading element 2 to be constructed first is to be installed, and a drilled hole 11 is formed.

[0022] In Fig. 3(b), a reinforcing bar cage 20 with vertical bars 21 and horizontal bars 22 is inserted into the first excavated hole 11. At the same time, a location where the next preceding element 2 is to be installed is excavated at a position a predetermined distance away from the excavated hole 11.

[0023] In FIG. 3(c), concrete is poured into the excavated hole 11 in which the reinforcing bar cage 20 is placed. In this embodiment, concrete is poured after placing an edge cutter 41 on the end face (side face) 2a of the excavated hole 11, which corresponds to the boundary 40 with the following element 3. The edge cutter 41 is a flat steel plate, and is formed in a size that covers the end face 2a. In other words, the edge cutter 41 also functions as part of the formwork material when pouring concrete. Also, excavation of the location where the next leading element 2 is to be installed is completed, and construction of the excavated hole 12 is completed.

[0024] In Fig. 3(d), the excavated hole 11 where the concrete has been poured is cured. At the same time, a reinforcing bar cage 20 is inserted and placed in the adjacent excavated hole 12. Furthermore, excavation is performed at a position a predetermined distance away from the excavated hole 12 where the next preceding element 2 will be installed.

[0025] In Fig. 3(e), curing of the excavated hole 11 in which concrete has been poured continues. Concrete is poured with an edge cutter 41 placed on the end face 2a of the excavated hole 12, which corresponds to the boundary 40 with the following element 3. Furthermore, excavation of the location where the next leading element 2 is to be installed is completed, and construction of the excavated hole 13 is completed.

[0026] In Fig. 3(f), excavation is performed for the trailing element 3 to be installed between the excavated holes 11 and 12, and an excavated hole 14 is formed. At the same time, a reinforcing bar cage 20 is inserted and placed in the excavated hole 13. The portion of the excavated hole 12 where the concrete has been poured is cured.

[0027] In Fig. 3(g), a reinforcing bar cage 30 having vertical bars 31 and horizontal bars 32 is inserted into the excavated hole 14. Concrete is poured with an edge cutter 41 placed on the end face 2a of the excavated hole 13, which corresponds to the boundary 40 with the following element 3.

[0028] In Fig. 3(h), concrete is poured into the excavated hole 14. At this time, the edge cutter 41 has already been placed on the end face 3a of the following element 3, which corresponds to the boundary portion 40. In other words, the edge cutter 41 also functions as a part of the formwork material when pouring the concrete. Also, excavation is performed for the following element 3 to be installed between the excavated hole 12 and the excavated hole 13, and the excavated hole 15 is formed.

[0029] Thereafter, the same procedure is repeated to construct the diaphragm wall 1. Although Fig. 3 illustrates the case where the diaphragm wall 1 is constructed in a straight line, diaphragm walls of other shapes can also be constructed. For example, at the boundary 40 between the leading element 2 and the following element 3, an edge cutting material 41 can be arranged so as to be inclined with respect to the wall thickness direction in a plan view, thereby setting an angle for the diaphragm wall.

[0030] Next, a case where a horizontal force such as an earthquake acts on the diaphragm wall 1 of this embodiment will be described. As shown in Fig. 4, when a horizontal force acts on the diaphragm wall 1, a deformation (shift) occurs along the boundary surface (end surface) between the leading element 2 and the trailing element 3, because only a flat steel plate-shaped edge cutting material 41 is interposed between the boundary surface 40. The stress in the diaphragm wall 1 is alleviated by the shift between the leading element 2 and the trailing element 3 in this way. In this embodiment, each element can deform, so a bending deformation component occurs in addition to shear deformation. As a result, the horizontal deformation of the upper ends (tops) 2b, 3b of the elements 2, 3 of the diaphragm wall 1 increases.

[0031] As shown in FIG. 5, when a diaphragm wall 1 having a rectangular shape in plan view and a plurality of piles 60 arranged inside the diaphragm wall 1 are used together as a building foundation (foundation structure) 50, the amount of horizontal deformation of the upper ends 2b, 3b of the diaphragm wall 1 increases, and the pile head displacement also increases, and the horizontal force borne by the piles 60 also increases. As a result, the load borne by the diaphragm wall 1 decreases, and the stress of the diaphragm wall 1 can be further reduced. In other words, the horizontal force can be appropriately shared between the diaphragm wall 1 and the piles 60, and the design of the diaphragm wall 1 and the piles 60 can be optimized. In addition, since the stress generated in the diaphragm wall 1 can be reduced, the amount of reinforcement and the size of the reinforcing bars of the diaphragm wall 1 can be reduced.

[0032] In the diaphragm wall 1 of this embodiment, the reinforcing bar cage 20 of the leading element 2 and the reinforcing bar cage 30 of the trailing element 3 are separated at their boundary portion 40 by a separation material 41. As a result, the frictional force and adhesive force between the leading element 2 and the trailing element 3 are smaller than in the past. In other words, when a horizontal force of a predetermined value or more acts on the diaphragm wall 1, deformation (displacement) can be caused between the leading element 2 and the trailing element 3 along the separation material 41.

[0033] The building foundation (foundation structure) 50 of this embodiment uses a diaphragm wall 1 and piles 60 in combination. As a result, not only the diaphragm wall 1 but also the piles 60 can bear a large horizontal force, and the load borne by the diaphragm wall 1 can be reduced. In other words, the diaphragm wall 1 can be constructed without excessive design, and construction efficiency can be improved.

[0034] In addition, by configuring the edge separation material 41 with a flat steel plate, it can be used as a formwork when pouring concrete for the leading element 2, and also has the function of an edge separation material 41 with the following element 3. In other words, construction efficiency can be improved.

[0035] In addition, a method has been proposed in which the connecting surface of the leading element with the following element is cut with an excavator or the like, and then the concrete of the following element is poured to join the preceding element. However, in the case of the joint construction method, since the transmission performance of the shear force at the joint surface is uncertain, it is necessary to consider both the case where the walls are regarded as one unit and the case where each element behaves completely independently (no force is transmitted between the elements) assuming that there is a gap at the joint, and to use a condition on the safe side, which is a strict condition in terms of design. On the other hand, in the underground diaphragm wall 1 of this embodiment, although the edge cutting material 41 is interposed, both the leading element 2 and the following element 3 are displaced while in contact with the edge cutting material 41, so there is no need to assume two conditions when designing, as in the case of the joint construction method.

[0036] The above describes the embodiments of the underground diaphragm wall and foundation structure according to the present invention, but the present invention is not limited to the above embodiments and can be modified as appropriate without departing from the spirit of the present invention. For example, in this embodiment, the edge cutting material 41 is a flat steel plate, but for example, an edge cutting material 45 having an uneven shape (wave shape) as shown in FIG. 6 may be used. In addition, in this embodiment, the case where the reinforcing bars are arranged in the form of the reinforcing bar cages 20 and 30 has been described, but the reinforcing bars may be arranged at the construction site. In addition, in this embodiment, the building foundation (foundation structure) 50 is described as being composed of an underground continuous wall 1 having a rectangular shape when viewed from above, and a plurality of piles 60 arranged within the underground continuous wall 1, but the planar shape of the underground continuous wall 1 is arbitrary, and the arrangement of the piles 60 may also be set arbitrarily. [Explanation of symbols]

[0037] 1. Diaphragm wall 2. Preceding element 3. Following elements 20 Reinforced Concrete Cage (Pre-reinforced Concrete) 30 Reinforced Concrete Cage (Trailing Reinforcement) 40 Border 41 Edge cutting material 50 Building Foundations (Foundation Structure) 60 stakes

Claims

1. In a diaphragm wall in which a preceding element and a following element made of reinforced concrete are provided adjacent to each other, An edge separator is provided at a boundary between the leading element and the trailing element, The preceding rebar arranged in the preceding element and the following rebar arranged in the following element do not overlap, The leading element and the trailing element are formed such that the length of the wall plate portion in the up-down direction is greater than the length of the wall plate portion in the width direction, as viewed from the front, An underground continuous wall characterized in that, when a horizontal force equal to or greater than a predetermined value is applied, deformation occurs between the leading element and the trailing element along the edge cutting material.

2. The underground continuous wall according to claim 1 , wherein the edge cutting material is a flat or corrugated steel plate.

3. The underground continuous wall according to claim 1 or 2 formed in a ring shape; and piles disposed inside the diaphragm wall.

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