JP2021121725A - Underground wall pile structure provided with expanded bottom part - Google Patents

Abstract

To provide an underground wall pile structure forming an underground wall pile with high support strength by preventing deterioration of bearing strength of an expanded bottom part of the wall pile with the expanded bottom part.SOLUTION: A cast-in-place underground wall pile structure comprises an expanded bottom part where a lower part of a wall shape body is expanded. The wall shape body is placed along a foundation of a building, the expanded bottom part is formed in an arch shape expanding in a wall thickness direction of a short side of the wall shape body, and underground wall piles are installed correspondingly to arrangement of pillars of the building continuously or intermittently in a lower part of the pillars of the building.SELECTED DRAWING: Figure 1

Description

The present invention relates to an underground wall pile structure. In particular, it relates to an underground wall pile structure used for wall piles that function as foundation piles for building structures.

Conventional underground wall piles have the same wall thickness in the depth direction. After that, construct underground wall piles with different excavation cross-sectional shapes (wall thickness) in the depth direction to secure the bearing capacity at the tip of the foundation, or increase the overall rigidity to reduce the amount of deformation. For this reason, underground wall piles with different wall thicknesses in the depth direction have been developed. Since the water pressure and earth pressure change depending on the depth direction even in the continuous wall for mountain retaining, the wall thickness differs depending on the depth direction.
The following proposals have been made as a conventional example in which a widened portion or a widened portion is provided in the middle.
Patent Document 1 (Japanese Unexamined Patent Publication No. 9-228398) discloses that a bottom-expanded pile (see FIG. 13) having an enlarged pile diameter at the tip portion is used as a foundation pile of a building to increase the bearing capacity. ..
Patent Document 2 (Japanese Unexamined Patent Publication No. 6-336725) discloses an underground wall pile having a bottom-expanded portion. It is disclosed that a horizontally arranged rotary cutter (see FIG. 14) is used as the excavator, and an excavator for excavating the bottom-expanded portion is used by increasing the number of rotary cutters at the bottom of the bottom-expanded portion.
Patent Document 3 (Japanese Unexamined Patent Publication No. 2009-2156) discloses a wall pile having a widened portion and a widened portion in the middle. It is disclosed that an excavator having a kelly bar that can rotate about a vertical direction and a bucket portion attached to a lower end portion of the kelly bar is used.

Japanese Unexamined Patent Publication No. 09-228398 Japanese Unexamined Patent Publication No. 06-336725 Japanese Unexamined Patent Publication No. 2009-002156

Underground wall piles with a flat tip and expanded bottom have the problem that the concrete at the base of the expanded bottom, which is unreinforced, is pulled and bent, causing a decrease in the bearing capacity of the wall pile. The purpose is to form underground wall piles with high bearing capacity.

1. 1. It is a cast-in-place underground wall pile structure with a widened bottom of the wall-like body.
The wall is provided along the foundation of the building,
The expanded bottom portion is formed in an arch shape that extends in the wall thickness direction, which is the short side of the wall-shaped body.
The underground wall pile structure is characterized in that it is continuously or intermittently provided below the building pillar according to the arrangement of the building pillar.
2. It is characterized by being a continuous wall for retaining mountains. Described underground wall pile structure.
3. 3. The bottom-expanded portion is characterized in that it is formed on only one side of the wall-shaped body. Or 2. Described underground wall pile structure.
4. The bottom-expanded portion is characterized in that it is provided intermittently or partially. ~ 3. Underground wall pile structure described in any of.
5. The wall thickness of the wall-shaped body is 150 to 240 cm, and the amount of widening on one side of the widened portion is 55 to 130 cm. ~ 4. Underground wall pile structure described in any of.
6. 1. The bottom expansion angle at which the bottom expansion portion extends from the side surface of the wall-like body is 12 to 20 degrees. ~ 5. Underground wall pile structure described in any of.

1. 1. By forming an underground wall pile structure with a bottom-expanded portion having an arch-shaped bottom surface, a ground reaction force acts along the curved surface of the arch-shaped expanded bottom portion, so that the ground reaction force is higher than that of a flat bottom-expanded portion. Since it is not unevenly distributed, it is possible to form a high bearing capacity underground wall pile in which damage such as cracks is suppressed.
An underground wall pile with a bottom-expanded portion is formed mainly under the place where a high axial force acts, such as the pillar part of the upper skeleton.
By providing the bottom-expanded portion, it is possible to improve the pull-out resistance due to an earthquake.
2. By providing a protrusion on the bottom-expanded portion, the protrusion is projected and buried in the supporting ground, and the shaft of the wall-like body including the bottom-expanded portion is fixed to the supporting ground. Can be strongly supported.
3. 3. Since the protrusion of the bottom-expanded portion is provided in the direction in which the wall-shaped body is extended, the verticality between the wall-shaped body and the bottom-expanded portion having the protrusion is ensured in the underground wall pile provided with the bottom-expanded portion having the protrusion. A wall pile structure can be realized.
4. By providing the bottom-expanded portion asymmetrically, it is possible to form an underground wall pile according to a situation such as being close to an adjacent boundary. For example, it can be used as a retaining wall during underground excavation.
5. The bottom expansion portion can be set between 0 ° and 90 ° or less according to the required bearing capacity. Normally, the minimum overhang of the bottom of the expanded bottom portion is 10 cm, so “0 ° or more” here means 10 cm or more of the bottom overhang length.
6. These bottom-expanded parts are arched along the turning locus of the tip of the cutter by a method of widening excavation by an excavator equipped with a cutter whose shaft rotates and the shaft rotates, and by using a widening excavator. Can be formed.

The figure which shows the example of the arch-shaped bottom expansion wall pile of this invention. An example of an expanded wall pile having an arched bottom is shown. The figure which shows the example of the bottom expansion wall pile which has an arch-shaped bottom surface with a protrusion. The schematic diagram about the rotation angle θ of the bottom expansion part. The figure which shows the example of the bottom expansion angle of the bottom expansion portion. The figure which shows the manufacturing process of the bottom expansion part. The figure which shows the example of the excavation apparatus of the wall pile with the bottom expansion part of this invention. The figure which shows the excavation cutter part. The figure which shows the arrangement example of the wall pile (the grid, the multiple frame). Schematic diagram of the ground reaction force of the expanded bottom. The figure which shows the state which installs the leading element and constructs the leading wall. The figure which shows the state of constructing an underground wall pile. (A) Following excavation state. (B) A state in which a trailing element is installed to form a continuous wall. The figure which shows the independent expansion pile of the prior art example (Patent Document 1). An example of a conventional expanded wall pile.

The present invention is an underground wall pile structure having a bottom-expanded portion in which the lower portion of the wall-shaped body is widened and having an arch-shaped bottom-expanded portion. By making the bottom surface of the bottom expansion part arch-shaped, the ground reaction force acts along the curved surface of the arch shape, so that the ground reaction force etc. that occurs in the flat bottom expansion part is not unevenly distributed, and cracks etc. It will be a high bearing capacity underground wall with suppressed damage. Underground wall piles provided with protrusions in the extending direction of the wall-like body transmit the horizontal stress acting in an earthquake or the like to the supporting ground to increase the resistance.
Underground wall piles with asymmetrical overhangs can be used to construct underground wall piles with expanded bottoms even at adjacent adjacent boundaries. This left-right asymmetry can also be partially provided, such as avoiding underground structures that cannot be widened.
In the underground wall pile extending in the longitudinal direction, the location where the bottom expansion part is to be provided and the size do not have to be uniform, and it is set according to the required yield strength in the concentrated place where high axial force acts such as the pillar part of the upper skeleton. can do.
Further, in the case of an underground wall pile provided with a widening portion in the middle of the wall, the vertical bearing capacity and the pull-out resistance are increased to improve the proof stress at the time of an earthquake. This widening portion can also be partially provided, such as being concentrated in a portion where the pulling force is large, such as a corner of a building.
The underground wall pile of the present invention is a pile that is continuous in the shape of a wall, and is provided not only on the outer circumference of the building but also on the wall pile that does not circulate or on the inner side such as a grid, so that the arrangement of the building pillars can be accommodated. It can also be configured as a continuous wall. Alternatively, the wall pile does not have to have a continuous wall shape (see FIG. 9).

The underground wall pile of the present invention can be used for a foundation support structure such as a wall pile of a building structure such as a building, or a continuous wall for retaining a mountain.
Since the underground wall pile of the present invention exhibits a continuous wall-shaped pile function, a high ground bearing capacity can be secured as compared with the case where a single pile is arranged. Especially in high-rise buildings, a pile structure using underground wall piles is often adopted because the weight of the building also increases. In addition, the stability is improved because the building is supported by a continuous surface. Since the bottom surface of the expanded bottom is curved in an arch shape, the supporting area of the supporting ground can be increased by providing the expanded bottom at the tip of the wall pile without uniformly increasing the building thickness of the wall pile body. Therefore, the load bearing capacity of the underground wall pile is improved. Even if the widened portion is unreinforced, the load is distributed along the arched arch surface, but in a wall pile having a widened portion having a flat surface, the load is unevenly distributed on the surface, so that cracks and the like occur. There is a risk of damage, and there is a limit to the set load bearing capacity compared to the bottom area.
In the present invention, since the shaft of the excavation cutter is rotated like a pendulum, the bottom surface of the expanded bottom portion is arched, so that the area controlled by the wall pile can be increased.
Since the excavation depth of underground pile construction is short, the construction period can be shortened and the construction cost can be reduced.
FIG. 10 shows a schematic description showing the difference in controlling force depending on the shape of the bottom-expanded portion. A ground reaction force acts on the arch-shaped bottom surface in the direction orthogonal to the arch, and a vertical load as the reaction force also acts in the direction orthogonal to the arch-shaped bottom surface. Further, even if the bottom surface is flat, the ground reaction force acts in the orthogonal direction in the same manner. Therefore, the ground reaction force acting on the edge of the flat bottom surface acts on the expanded bottom part where the reinforcement is not arranged, which increases the risk of damage such as cracks. The vertical load of is smaller than the horizontal cross-sectional area of the expanded bottom. On the other hand, since the ground reaction force is concentrated in the wall thickness direction on the arched bottom surface, it is received at the reinforced portion, and the risk of damage is small.

<Underground wall pile>
An example of a wall pile which is an underground wall pile structure of the present invention is shown in FIG.
The wall pile 1 has a wall-shaped body 2 extending long along the foundation of a building and a bottom-expanded portion 3 below the wall-shaped body 2, and the bottom surface of the expanded bottom portion is an arch-shaped bottom surface 34.
Since the bottom surface of the expanded bottom is arched, the load of the superstructure (vertical load, especially compression axial force) can be stably supported, and a large vertical load can be borne compared to the flat bottom surface, which is high. Can exert supportive power. Alternatively, the wall pressure can be reduced. In addition, it is difficult to arrange reinforcement in the part of the bottom that is wider than the wall-shaped part, so if a large load is applied due to an earthquake or the like by making it unreinforced, it will easily crack and be damaged. , It is difficult to enlarge the bottom expansion part. In the present invention, by forming the bottom surface of the bottom-expanded portion into an arch shape, the bottom-expanded portion is stabilized and the load capacity is improved.
As for the reinforcing bars, the braided reinforcing bars along the thickness of the wall-shaped part are inserted into the holes excavated in the ground in the shape of this underground wall pile structure. Reinforcing bars are difficult to arrange in the part extending from the wall-like body, and it is often unreinforced.
This underground wall pile structure is suitable for a wall-shaped foundation structure of a building or a wall pile that also serves as a retaining wall.

FIG. 2 shows a basic example of the shape of the underground wall pile structure.
The underground wall pile structure shown in FIG. 2A is an example of the same overhanging widening underground wall pile structure 11 in which the lower side is provided with the bottom widening portion 3 which is widened to the left and right in the same shape with respect to the extension of the wall-shaped body 2. The bottom surface of the expanded bottom portion is an arched bottom surface 34 having the same angle on the left and right.
The underground wall pile structure shown in FIG. 2B is an example of an underground wall pile structure 12 having a bottom expansion portion 32 with a protrusion having a protrusion 4 below the bottom expansion portion 3.
In the illustrated example, the protrusion 4 is provided immediately below the wall-shaped body 2 with the same width. The mounting direction and size of the protrusion 4 are arbitrary, and the mounting angle can be set in consideration of the lateral pressure due to the characteristics of the ground and the like.

The underground wall pile structure shown in FIG. 2C has an irregularly widened bottom surface 34 having a small overhanging portion 33a and a large overhanging portion 33b having different amounts of protrusions to the left and right from the extending portion 21 of the wall-like body. This is an example of the underground wall pile structure 13 provided with the portion 33.
It is an underground wall pile structure in which the amount of overhang of the expanded bottom is adjusted according to the situation on the left and right.
For example, an underground wall pile structure can be formed as a continuous wall for retaining a mountain. For example, by making the widening portion of a small overhang on the side close to the adjacent boundary, it is possible to approach the adjacent land boundary. The same applies when the buildings are in close proximity.

FIG. 3 shows a cross-sectional view of the underground wall pile structure. FIG. 3 (a) shows a cross section of the underground continuous structure 12 provided with the bottom-expanded portion 32 with a protrusion shown in FIG. 2 (b).
FIG. 3B is a bottom-expanded portion with a protrusion, which is an underground wall pile structure 14 with a one-sided widening protrusion having a one-sided widening portion 35 with a protrusion having an arch-shaped bottom surface 34 having a widening portion provided on only one side. .. It is also effective for the mountain retaining wall near the boundary of the adjacent land. When used for wall piles, it is possible to avoid only the part where there is an underground structure such as an existing pile, and to make an underground wall pile structure in which widening is interrupted, such as not providing a bottom expansion part in that part.

(Arch-shaped expanded bottom)
The angle of inclination that forms the expanded portion of the expanded wall pile is the angle that extends from the outer surface of the wall and is called the expanded angle. The example shown in FIG. 4 is an example created by swinging a cutter having a center of rotation. When the bottom expansion angle is expressed by θ, the swing angle of the cutter is 2θ.
The bottom expansion angle θ is schematically shown in FIG. In the bottom-expanded portion 3 of the underground wall pile structure, the intersection angle between the wall-shaped body represented by a straight line and the widened portion is represented as θ, and the rotation angle of the cutter in which the cutter swings left and right is 2θ.
FIG. 5 shows an example of examining the size of the arched bottom surface of the underground wall pile structure.
This is an example in which a widening width is formed by using a cutter having a rotating shaft, and the size of the arch surface is set by setting the rotation angle θ of the cutter and the shaft length.
In FIG. 5A, when the wall thickness is 2.4 m, the cutter length is 6 m, and θ = 20 degrees, the widening amount is 5 m, and the widening ratio with respect to the wall thickness is 2.08 times.
In FIG. 5B, when the wall thickness is 2.0 m, the cutter length is 6 m, and θ = 12 degrees, the widening amount is 3.5 m, and the widening ratio with respect to the wall thickness is 1.75 times.
In FIG. 5C, when the wall thickness is 2.0 m, the cutter length is 4 m, and θ = 20 degrees, the widening amount is 3.7 m, and the widening ratio with respect to the wall thickness is 1.85 times.
In FIG. 5D, when the wall thickness is 1.5 m, the cutter length is 4 m, and θ = 12 degrees, the widening amount is 2.6 m, and the widening ratio with respect to the wall thickness is 1.73 times.
In the example shown in FIG. 5, 2θ is set to 12 to 20 degrees for the widened portion of the arched bottom that is widened with respect to the wall thickness, the radius of the widened portion is 4 to 6 m, and the widening ratio with respect to the wall thickness is 1.73. It is ~ 2.08 times.
In the excavator that excavates the bottom expansion part, which will be proposed later, the cutter can be rotated left and right by 90 degrees or more due to the structure of the mechanical device. , Up to twice the cutter length is possible. During this period, the amount of widening is set according to the required design strength. In addition, the strength of concrete will be taken into consideration and reflected in the design of the layout of wall piles.
The arch angle (θ) is preferably wall thickness +0 degrees or more and 90 degrees or less, and preferably wall thickness +10 to 60 degrees, and even if the bottom expansion angle is different on the left and right, it is adjusted in this angle range. It should be noted that the arch surface has a wider control angle than the flat surface, so that the yield strength of the wall pile is improved. In an independent footing foundation in which the base of a general foundation (footing) is widened, the length of the footing width that distinguishes between a footing foundation and no footing foundation is the spread angle (one side) of the footing foundation with respect to the central axis of the column. Expressed by, it is about 3.6 degrees. Therefore, when limited to general columns, the length of the base that protrudes outward from the outer peripheral surface of the column is independent without widening up to a widening of about 3.6 degrees in terms of the spreading angle (one side) from the central axis of the pillar. It is evaluated as a pillar. The present invention is different from a normal pillar material in that it is provided with an arch-shaped bottom-expanded portion, but the angle at which the bottom-expanding effect is exerted is 5 degrees or more on one side (that is, 10 degrees or more when the bottom-expanded portions are provided on both sides). ) Is appropriate.
Further, since the management unit in construction is 10 cm, the minimum one-sided overhang length of the expanded bottom portion is 10 cm in practice.

By using the underground wall pile structure for wall piles with such an arch-shaped bottom expansion part, not only the vertical load bearing capacity is improved, but also the resistance to pulling force and pushing force is improved, and excavation is performed for wall piles. The depth can be made shallow, and the thickness of the wall-like body of the wall pile body can be made thin. As a result, the labor required for excavation, the amount of concrete to be cast, and the amount of reinforcing bars can be reduced, and the construction work can be shortened.
In addition, when a wall pile is used as a foundation, it is possible to support a building or the like to which a large vertical load is applied, such as a high-rise building.

<Construction method>
The construction method of the present invention employs a method of placing concrete in a ground gap excavated in the shape of an underground wall pile structure provided with a bottom-expanded portion. FIG. 6 shows an example of the construction method. The construction method shown in this example is an example of constructing a continuous underground wall pile structure by alternately creating a leading wall structure and a trailing wall structure, and shows a process of creating a leading wall structure or a trailing wall structure. ing.
As the first step, excavation of the same width is performed in the vertical direction. This excavation is similar to the usual excavation for a continuous wall without a bottom expansion. In the first step, the vertical excavation hole portion 82 of the excavation hole is formed. As the construction method used in this excavation process, there are excavation methods such as a rotary method and a bucket method.
As the second step, an excavator for expanding the bottom is put into the vertical excavation hole 82. In the present invention, the excavator for bottom expansion is a type in which a cutter having a rotating bit attached to a shaft is rotated in an arm swing shape. The excavator is inserted with the cutter extended in the vertical direction.
As the third step, the cutter attached to the excavator for bottom expansion is rotated in one direction to the left and right to perform widening excavation. In the illustrated example, the left side of the bottom-expanded excavation hole 81 is drilled. Then, the protruding portion hole 83 is formed by performing the bottom expansion excavation above the lowermost end of the vertical excavation hole 82.
As the fourth step, the earth and sand excavated in the width in the previous step is carried out. The method of carrying out excavated soil is the same as before. The fourth step may be performed at the same time as the third step.
As the fifth step, widening excavation on the opposite side is performed. In the illustrated example, the right side of the bottom-expanded excavation hole 81 is drilled.
As the sixth step, the earth and sand produced in the fifth step are carried out. After the earth and sand are carried out, the excavation hole 8 is formed.
As a seventh step, a bottom-expanded excavation hole 81 having an excavated and protruding protrusion hole 83 and an expanded arch-shaped bottom is formed in an excavation hole 8 provided under the vertical excavation hole 82. NS. Reinforcing bars (reinforcing bar cages) are inserted into the space for the underground wall pile structure formed by the excavation holes 8 to cast concrete. After that, it is cured to manufacture a leading or trailing underground wall pile structure.

Since the construction method of the underground wall pile structure shown in FIG. 6 shows an example in which a protrusion is formed from the bottom surface of the bottom expansion portion, the protrusion portion is excavated deeper than the bottom expansion portion in the first step. The length of the protrusion can be adjusted by deepening the excavation in the first step or by changing the height of the arch-shaped bottom expansion excavation in the third step.
The bottom surface of the expanded bottom portion is formed in an arch shape by the rotation of the cutter.
In addition, excavation can be carried out by the usual method of manufacturing an underground wall, which is divided into a leading part and a trailing part, or can be formed continuously.

<Expanded bottom drilling device>
FIG. 7 shows an overall view. FIG. 8 shows the main part of the bottom expansion excavator.
The bottom-expanded excavation is performed using a cutter equipped with a shaft that can rotate and swing into the hole excavated in the vertical direction.
FIG. 7 shows a state in which the bottom expansion excavator 5 is inserted into the excavation hole 8 suspended by a crawler crane.
The bottom-expanding excavator 5 includes a cutter 6 having a shaft 61 around which a bit 62 is attached. The shaft 61 rotates in a swing shape and a shaft rotation to perform widening excavation.

FIG. 8A shows a main part of the bottom expansion excavator 5 in a state of being suspended and inserted in the excavation hole 8.
A cutter 6 is rotatably attached to a support shaft 64 provided at the lower stage of the frame 7.
The frame 7 includes upper and lower horizontal frames 71 and 71, fixed guides 72 and 72 which are left and right vertical frames, and a support shaft 64. A swivel cylinder 65 is installed on the fixed guide 72, and the cutter is rotated. A hydraulic motor 63 is attached to the support shaft, and the cutter 6 is rotationally driven by the hydraulic motor. The frame receives a reaction force by pressing against the excavation hole when the cutter rotates to perform widening excavation.
Three cutters 6, a first cutter 6a, a second cutter 6b, and a third cutter 6c, are installed. Each cutter has a large number of bits 62 attached around a shaft 61 which is a shaft. As shown in FIG. 8B, the bit 62 has a triangular shape and has a stable shape so that the ground to be cut can resist. This bit is spirally attached to the shaft. The shaft rotates and excavates. Although the number of cutters constituting the bottom expansion excavator is described for a 3-piece set in this embodiment, it may be composed of 2 or 1 cutter depending on the bit shape of the cutter body or the like. ..
The shaft is widened and excavated in an arc shape by rotation and rotation.

<Construction example of underground wall pile>
In the construction of the underground wall pile structure having the bottom-expanded portion having the arch-shaped bottom of the present invention, the construction method using the preceding element previously proposed by the present inventors in Japanese Patent Application No. 2016-139669 shall be used. Can be done.
That is, as shown in FIGS. 11 and 12, the prior invention has a partition plate 110 arranged at a boundary between a leading element 100 using a cage reinforcing bar and a trailing element 200 using a cage reinforcing bar, and a partition plate 110. A space formed between the connecting member 120 projecting from the side surface on the trailing element 200 side, the space forming member 150 forming a space around the connecting member 120, and the partition plate 110 and the space forming member 150. It is provided with an end structure 100B of a leading element having a granular body 170 filled therein, and the space forming member can be cut by a ground excavator.
In the present invention, in the preceding excavation, the preceding element of the prior invention is laid in the excavation groove in which the vertical excavation hole 82 is provided with the expanded bottom excavation hole 81 and the preceding excavation is performed, and concrete is poured. The cast concrete does not flow into the space filled with the granular material, and the outer wall plate of the space formed of plastic or the like is maintained in a state where it is easy to cut. Then, the trailing element is laid in the drilling ditch having the expanded bottom drilling hole formed by performing the trailing excavation. In the trailing excavation, the space forming member 150 provided at the end of the leading element 100 is cut, and the space forming member 150 is cut to form a recess 100A at the end of the leading element 100. At this time, when the space forming member 150 is cut, the granular body 170 collapses to the trailing excavation groove D2 side, so that the partition plate 110, the connecting member 120, and the water stop plate are exposed. The granular body 170 is collected together with the earth and sand generated by the excavation of the trailing excavation ditch D2. After that, by placing concrete, an underground wall pile structure having a continuous bottom expansion portion is formed.

1 Wall pile 11 Same overhang widening underground wall pile structure 12 Underground wall pile structure with protrusions 13 Underground wall pile structure with irregular bottom expansion 14 Underground wall pile structure with one-sided widening protrusions

2 Wall-shaped body 21 Extended part of wall-shaped body

3 Expanded bottom
31 Arch expansion part 32 Bottom expansion part with protrusion 33 Deformed widening part 33a Small overhang part 33b Large overhang part

34 Arched bottom 35 Single-sided widening part with protrusions

4 Protrusion 5 Bottom expansion excavator

6 Cutter 6a 1st cutter 6b 2nd cutter 6c 3rd cutter 61 Shaft 62 Bit 63 Hydraulic motor 64 Support shaft 65 Swing cylinder

7 Frame 71 Horizontal frame 72 Fixed guide

8 Excavation hole 81 Expanded bottom excavation hole 82 Vertical excavation hole 83 Projection hole

100 Leading element 100A Recess 100B Leading element end structure 110 Partition plate 120 Connecting member 150 Space forming member 170 Granule 200 Trailing element D2 Trailing excavation groove

Claims (6)

It is a cast-in-place underground wall pile structure with a widened bottom of the wall-like body.
The wall is provided along the foundation of the building,
The expanded bottom portion is formed in an arch shape that extends in the wall thickness direction, which is the short side of the wall-shaped body.
The underground wall pile structure is characterized in that it is continuously or intermittently provided below the building pillar according to the arrangement of the building pillar. The underground wall pile structure according to claim 1, wherein the wall is a continuous wall for retaining a mountain. The underground wall pile structure according to claim 1 or 2, wherein the bottom-expanded portion is formed on only one side of the wall-shaped body. The underground wall pile structure according to any one of claims 1 to 3, wherein the bottom-expanded portion is provided intermittently or partially. The underground wall pile structure according to any one of claims 1 to 4, wherein the wall thickness of the wall-shaped body is 150 to 240 cm, and the amount of widening on one side of the widening portion is 55 to 130 cm. The underground wall pile structure according to any one of claims 1 to 5, wherein the bottom expansion angle at which the bottom expansion portion extends from the side surface of the wall-like body is 12 to 20 degrees.

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