JP2016196734A - Method for creating ground improvement foundation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for creating a ground improvement foundation which can create a ground improvement foundation high in ground improvement performance and having a bearing strength against bending and shear and hard to be removed in the vertical direction.SOLUTION: A method for creating a ground improvement foundation comprises the steps of: boring a vertical hole 110 extending in a prescribed direction in a ground surface; creating improved soil by mixing excavated soil discharged by excavation with a cement-based solidifying agent; filling the vertical hole 110 with the improved soil while reversely turning an auger 200 with a pressing part so that the improved soil is pressed on at least the lower back side and the side face of the vertical hole 110 by the pressing part for compaction; forming a columnar body 310 by solidifying the improved soil in the vertical hole 110; forming an internal hole 320 extending in a prescribed direction from one end of the columnar body 310; filling the internal hole 320 with a metallic core material 330 and cement not containing the excavated soil; and solidifying the cement.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a ground improvement foundation creation method for creating a foundation capable of improving the ground and at the same time being connected to a framework of a building.

  Conventionally, after forming a columnar body for ground improvement in the ground, a foundation was created on the columnar body, and a steel frame was connected to the foundation. In the conventional ground improvement stage, first, an auger is used to dig a vertical hole vertically from the ground surface. A cement-type columnar body is created by putting a cement-type solidifying agent into the vertical hole and solidifying it. In the next foundation creation stage, a foundation using steel frames is constructed on the soil where the columnar bodies are formed.

JP-A-8-184029

  In the conventional method, since it is necessary to make ground improvement and foundation construction into separate processes, it takes time.

  At first glance, it seems that if you put a steel frame in a concrete column for ground improvement, it seems that both the ground improvement and foundation functions can be performed at the same time, but this is not the case. First of all, the columnar body into which concrete has been poured is strengthened by the steel frame. However, since the pressure on the surrounding soil is weak, the consolidation effect is thin and the ground cannot be improved, and the columnar body is vulnerable to vertical omission.

  It is also conceivable to use an improved soil in which excavated soil and cement-based solidifying agent are mixed to form a columnar body by a conventional ground improvement method, and to put the steel frame while the columnar body is soft. However, in reality, the columnar body made by the conventional ground improvement method has a weak pressure effect on the surrounding soil, so that the consolidation effect is thin and the ground improvement cannot be performed, and the vertical stability is weak. Moreover, the bond strength between the improved soil and the steel frame has not been proven empirically.

  Since it is required to perform ground improvement and foundation construction in a short period of time, the present invention provides a ground for creating a ground improvement foundation that has high ground improvement ability and is resistant to bending, shearing and vertical slipping. The purpose is to provide an improved foundation creation method.

  The ground improvement foundation preparation method of the present invention includes a step of excavating a vertical hole extending in a predetermined direction on the ground, a step of mixing the excavated soil discharged by excavation and a cement-based solidifying agent, and an improved soil. , By putting the improved soil into the vertical hole while reversely rotating the auger with the pressing portion, the pressing portion presses and fixes the improved soil to at least the lower back and the side of the vertical hole, and the improved soil in the vertical hole is solidified A step of forming a columnar body, a step of forming an internal hole extending in a predetermined direction from one end of the columnar body, a step of putting a metal core material and cement without excavating soil into the internal hole, Solidifying the cement.

  According to the present invention, when the columnar body is formed with the improved soil, the surrounding soil is compacted and consolidated, so that the frictional force between the cylindrical peripheral surface of the columnar body and the surrounding soil increases, and the vertical force Can be received not only at the lower end but also at the wide peripheral surface. Therefore, it becomes strong against vertical displacement and omission.

  According to the present invention, since the columnar body is created while being compacted toward the surrounding soil, the density can be increased by eliminating water and bubbles. Accordingly, the columnar body is strong against shearing, bending, and the like.

  According to the present invention, since the metal core material is inserted, the entire ground improvement foundation is resistant to bending and shearing. Cement that does not contain excavated soil is placed between the columnar body made of the improved soil and the metal core material, so that it becomes difficult for the metal core material to come out of the columnar body made of the improved soil.

It is a figure which shows the several process of the ground improvement foundation preparation method of this embodiment.

  The ground improvement foundation preparation method of this embodiment is demonstrated referring FIG. In addition, when actually creating a ground improvement foundation, processes other than the processes described in the present specification may be included as appropriate. As shown in FIG. 1A, first, a vertical hole 110 extending in the vertical direction is excavated in the ground 100 by rotating the auger 200 forward.

  When the cylindrical auger shaft 210 of the auger 200 is rotated forward, the conical head 220 pointed downwardly rotates together. Between the auger shaft 210 and the head 220, a truncated cone-shaped relay portion 230 having a diameter that decreases downward is provided. When the head 220 rotates, the first blade 240 and the second blade 250 provided on both sides in the horizontal direction of the head 220 rotate integrally to excavate the ground 100. The excavated excavated soil is transported upward by the spiral transport unit 260 and discharged out of the vertical hole 110.

  Next, the excavated soil discharged by excavation, sand having different particle diameters, and a cement-based solidifying agent are mixed to create improved soil.

  Next, as shown in FIG. 1B, the auger 200 is rotated in the reverse direction, so that the improved soil placed on the spiral transport unit 260 is transported around the head 220 below the vertical hole 110. The first blade 240 of the auger 200 is provided with a lower pressing surface 241 and a first lateral pressing surface 242. The lower pressing surface 241 is an inclined surface with the upper side in front in FIG. 1B and the lower side in the back, and the lowermost end is substantially linear along a horizontal plane. In FIG. 1B, the first lateral pressing surface 242 is a slope with the center side in front and the outer side in the back, and the leftmost end is generally along the vertical direction. The second blade 250 is provided with a second lateral pressing surface 251. In FIG. 1A, the second lateral pressing surface 251 is a slope with the center side in front and the outer side in the back, and the left end is substantially along the vertical direction. FIG. 1B shows a momentary state of the auger 200. In the reverse rotation, the first blade 240 moves forward from the state of FIG. 1B, and the second blade 250 moves backward from the state of FIG. 1B. It is a rotation.

  The newly introduced improved soil is between the improved soil column 300 and the lower pressing surface 241 already existing in the lower back of the vertical hole 110 and between the improved soil already existing on the horizontal inner surface of the vertical hole 110 and the first lateral pressing. It is fed between the improved soil already existing on the surface 242 and on the horizontal inner surface of the vertical hole 110 and the second lateral pressing surface 251 and is compacted by the action of a trowel. When the improved soil is further charged and compacted, the auger 200 is pushed up by the resistance of the improved soil column 300. The improved soil pillar 300 is made to a predetermined height.

  Next, the improved soil column 300 of the vertical hole 110 in FIG. 1B is solidified to form the columnar body 310 shown in FIG. Compared with the conventional case where the columnar body is formed using the auger 200 having no pressing portion, the present embodiment forms the improved soil column 300 of FIG. The columnar body 310 in FIG. 1C has a high density by sufficiently removing moisture and bubbles. Since the columnar body 310 in FIG. 1C has a high density, the pressure with which the outer peripheral curved surface and the surrounding soil are pressed is strong. As a result, the vertical frictional force applied between the outer peripheral curved surface and the surrounding soil is strong and stable even when a force is applied in the vertical direction.

  Next, as shown in FIG. 1D, an internal hole 320 extending vertically downward from the upper end of the columnar body 310 is formed. When viewed in a cross section parallel to the horizontal plane, the diameter of the internal hole 320 is smaller than the diameter of the columnar body 310, and the internal hole 320 is disposed at the approximate center of the columnar body 310. The vertical depth of the internal hole 320 is shallower than the vertical depth of the columnar body 310.

  Next, as shown in FIG. 1E, a long metal core material 330 is put in the internal hole 320, and the longitudinal direction is arranged along the vertical direction. The metallic core member 330 is disposed away from the inner wall of the inner hole 320. Although the core material of this embodiment is H steel, other members long in the vertical direction may be used. Next, cement 340 is put in the internal hole 320 to fill the space between the columnar body 310 and the metal core member 330. The cement 340 placed in the internal hole 320 does not include excavated soil. Thereafter, the cement 340 in the inner hole 320 is solidified. Thereby, the ground improvement foundation 400 is completed.

  According to this embodiment, the composition of the columnar body 310 and the composition of the cement 340 to be put in the internal hole 320 can be determined independently. That is, the composition of the columnar bodies 310 can be determined so as to be suitable for consolidation of the surrounding soil, and can be determined regardless of whether it is suitable for fixing the metal core member 330. On the other hand, the composition of the cement 340 to be put into the inner hole 320 can be determined so as to be suitable for fixing the metal core material 330 and can be determined regardless of whether it is suitable for forming the columnar body 310 for ground improvement. Furthermore, since the columnar body 310 and the cement 340 to be inserted into the internal hole 320 are both cement-based, both are firmly bonded. As a result, the metal core member 330 can be firmly fixed to the columnar body 310.

  The ground improvement foundation 400 created according to the present embodiment has the ability to perform ground improvement and also has a function as a foundation strong against bending and shearing. Therefore, the structure can be simplified and the overall process can be shortened.

  Conventionally, since it was thought that the bonding force between the improved soil and cement was weak, it was not considered to put the cement 340 into the columnar body 310 as in this embodiment. However, according to experiments by the inventors, the columnar body 310 and the cement 340 portion did not separate even when the metal core member 330 portion was pulled with a strong force. At least, this embodiment was able to withstand a stronger force than when the columnar body 310 and the metal core material 330 were directly inserted without using the cement 340.

100 Ground 110 Vertical hole 200 Auger 210 Auger shaft 220 Head 230 Relay portion 240 First blade 241 Lower pressing surface 242 First lateral pressing surface 250 Second blade 251 Second lateral pressing surface 260 Spiral transport unit 300 Improved soil column 310 Columnar 320 Internal hole 330 Metal core 340 Cement

The ground improvement foundation creation method of the present invention creates an improved soil by mixing a step of excavating independent vertical holes extending in a predetermined direction on the ground, and excavated soil discharged by excavation and a cement-based solidifying agent. A process, a substantially cylindrical auger shaft, a helical transport unit that is spirally arranged around the auger shaft and transports the improved soil toward the lower back of the vertical hole at the time of reverse rotation, and below the vertical hole than the auger shaft A substantially frustoconical relay portion that is located at the back and decreases in diameter toward the lower back; a head having a substantially conical diameter that decreases in diameter toward the lower back of the vertical hole along the predetermined direction from the relay portion; by placing the first blade and the modified soil in the vertical hole while the reverse rotation of the auger and a second blade which projects in opposite directions in the direction substantially orthogonal to the predetermined direction from the outer peripheral surface, a second blade Than the bottom of the vertical hole The first blade and the compacting pressing the modified soil beneath the rear of the by Ri vertical hole under the pressing surface of the positioned, against the modified soil on the side surface of the vertical hole by a first transverse pressing surface of the first blade A step of compacting and compacting by pressing the improved soil against the side surface of the second horizontal pressing surface vertical hole of the second blade, and solidifying the improved soil in the vertical hole to form an independent columnar body , A step of forming an internal hole extending in a predetermined direction from one end of the columnar body, a step of putting a core material made of metal H-steel into the internal hole, and a cement not including excavated soil And a step of solidifying the cement.

Claims (1)

Drilling a vertical hole extending in a predetermined direction on the ground;
A step of mixing the excavated soil discharged by excavation with a cement-based solidifying agent to create improved soil;
A step of pressing and compacting the improved soil against at least the lower back and side surfaces of the vertical hole by the pressing portion by inserting the improved soil into the vertical hole while rotating the auger provided with the pressing portion; and
Solidifying the improved soil in the vertical hole to form a columnar body;
Forming an internal hole extending in the predetermined direction from one end of the columnar body;
Putting the metal core material into the internal hole and cement not containing the excavated soil;
Solidifying the cement,
Ground improvement foundation creation method.

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