JP2005083149A - Reinforcement method for foundation and reinforcement structure of foundation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reinforce a foundation of a structure in a short period of construction without a major temporary work. <P>SOLUTION: A foundation part 12 of a pier 10 comprises a footing 14 and a foundation 16 which extends from a lower surface of the footing to the depth of a bearing layer 30. In the ground surrounding the foundation 16, a sheet pile 18 is driven down to the depth of a surface layer 32 to surround the foundation 16. In the ground inside the sheet pile 18, a soil improvement part 20 is provided by improving the soil. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a reinforcing method and a reinforcing structure for reinforcing a foundation of a structure.

  Conventionally, as an earthquake-proof reinforcement method for foundations of existing structures such as bridge piers, there are an additional pile method, a steel pipe sheet pile foundation extension method, and the like (for example, see Non-Patent Document 1).

  In the additional pile construction method, an additional pile is placed around the existing pile, and the existing footing is enlarged to join the enlarged portion and the additional pile. In this method, it is important to integrate the existing footing and the expanded footing. Generally, the side of the existing footing is suspended to connect the reinforcing bars, and the concrete is placed to expand the footing. ing.

In addition, in the steel pipe sheet pile foundation extension method, a steel pipe sheet pile is driven to the depth of the support layer so as to surround the existing footing, the temporary fastening is performed, the inside of the temporary fastening is excavated to the bottom surface of the existing footing, and then the existing footing and steel pipe are The sheet pile is connected with a reinforcing bar or the like, and the concrete is placed integrally with the existing footing.
“Reference Materials for Reinforcement of Existing Road Bridge Foundations”, Japan Road Association, February 2000, p. 3-1 to 3-9

  As mentioned above, any of the above-mentioned reinforcement methods requires concrete to be cast integrally with the existing footing. For this reason, earth retaining work or temporary closing work is required in the case of underwater pier foundations. It takes a lot of time for temporary construction, and the construction period becomes longer. In addition, when reinforcing the foundation of the existing pier, it becomes difficult work under the bridge girder and the construction conditions are severe, and the labor required for the temporary construction is further increased.

  The present invention has been made in view of the above points, and an object of the present invention is to make it possible to reinforce a structure foundation in a short construction period without requiring a large-scale temporary work.

  In order to achieve the above object, the foundation reinforcing method according to the first aspect of the present invention includes a sheet pile placed on the ground on which the foundation of the structure is built so as to surround the existing foundation. It is characterized by applying ground improvement to the ground inside the sheet pile.

  According to the present invention, since the ground improvement is performed on the ground inside the sheet pile placed so as to surround the existing foundation, the ground improvement portion is integrated with the foundation, and the area receiving the resistance force from the ground is increased. A reinforcing effect can be obtained. Thus, since the reinforcement effect is obtained by the ground improvement, large-scale temporary work such as earth retaining work and temporary cut-off work becomes unnecessary, and the construction period can be shortened.

  The invention described in claim 2 is characterized in that, in the foundation reinforcing method according to claim 1, the sheet pile is driven so as to surround the periphery of the upper portion of the existing foundation.

  In this way, it is only necessary to drive the sheet pile to a shallow depth in the upper part of the foundation, so the sheet pile installation work can be easily performed. Moreover, since reinforcement is made at the upper end of the existing foundation, a higher reinforcement effect can be obtained.

  Further, in the foundation reinforcing structure according to the third aspect of the invention, a sheet pile is placed on the ground on which the foundation of the structure is constructed so as to surround the existing foundation, and the ground on the inner side of the sheet pile is formed. It is characterized by ground improvement.

  According to the present invention, the foundation can be reinforced in a short construction period without requiring a large-scale temporary work.

  FIG. 1 is a cross-sectional view showing a foundation reinforcing structure according to an embodiment of the present invention, and FIG. 2 is a plan view thereof. In the present embodiment, as an example, the foundation portion 12 of the pier 10 constructed underwater is reinforced, but the present invention can be widely applied to the case where the foundation of a structure is reinforced regardless of underwater or land. is there.

  As shown in FIGS. 1 and 2, the foundation portion 12 of the pier 10 includes a footing 14 and a foundation 16 that reaches the support layer 30 from the lower surface of the footing. On the ground around the foundation 16, a sheet pile 18 is driven to a depth within the range of the surface layer 32 so as to surround the foundation 16. And the ground improvement is given to the ground inside the sheet pile 18, and the ground improvement part 20 is provided. As the sheet pile 18, various types of sheet piles such as a steel pipe sheet pile, a steel sheet pile, a wood sheet pile, and a concrete sheet pile can be used.

According to the above configuration, the ground improvement part 20 around the upper part of the foundation 16 is integrated with the foundation 16, so that the area where the foundation part 12 receives a resistance force from the ground is increased, thereby improving the seismic performance. . That is, as shown in FIG. 2, when the horizontal force H _Y in the figure the left-right direction acts on the foundation 12, the effective width for receiving the horizontal resistance force displacement direction front of the base portion 12 (hereinafter, front effective that width) increases from the front reinforcement B _0Y to B _Y, also enable subjected to shear resistance in the displacement direction side width (hereinafter, referred to as side effective width) is increased from the previous reinforcement B _0X to B _X. Similarly, when the horizontal force H _X in vertical direction in the drawing to the base portion 12 is applied, the front effective width of the base portion 12 is increased from B _0X before reinforcement to B _X, also side effective width of the reinforcing _Increase from previous _B0Y to _BY . As a result, the horizontal resistance force at the front surface of the base portion 12 and the shear resistance force at the side surface are both increased, and the seismic performance is improved.

  Furthermore, in this embodiment, since the foundation part 12 is reinforced by ground improvement, temporary work is not required and the construction period can be greatly shortened. That is, as described above, in the conventional reinforcing method, the concrete is cast integrally with the footing, and therefore the construction period becomes longer due to temporary construction such as temporary closing and earth retaining, but in this embodiment, Because it is only necessary to improve the ground, such troublesome temporary work can be eliminated.

  Moreover, in this embodiment, since the lower end part of the foundation 16 is driven into the support layer 30 and is firmly supported, a high reinforcing effect can be obtained only by reinforcing the upper part of the foundation 16 with the ground improvement part 20. Therefore, as described above, it is only necessary to place the sheet pile 18 on the upper layer portion of the surface layer 32, and the operation of placing the sheet pile 18 becomes easy. Further, since the length of the sheet pile 18 may be short, it is possible to eliminate the troublesome work of driving the sheet pile 18 to the support layer while connecting the sheet pile 18 in small steps in a work environment where the height under the bridge girder is limited. Is further improved.

  The depth and width (diameter) of the ground improvement portion 20 can be appropriately designed in consideration of the seismic performance required for the base portion 12 and the properties of the ground (strength characteristics of the surface layer 32). If necessary, increasing the width (diameter) of the ground improvement portion 20 can avoid increasing the depth of the ground improvement portion 20 (that is, the placement depth of the sheet pile 18).

  Moreover, in the said embodiment, as shown in FIG. 2, the base part 12 is applied with respect to the horizontal force of any direction by driving the sheet pile 18 circularly and forming the circular ground improvement part 20. As shown in FIG. The front resistance width and the side resistance width are the same, and a stable seismic reinforcement effect can be obtained. However, the shape of the ground improvement portion in the present invention is not limited to a circle, and for example, a ground improvement portion of another shape is provided, such as placing a sheet pile so as to surround the base portion 12 in a rectangular shape to provide a rectangular ground improvement portion. It is also possible to have a configuration in which a portion is provided.

It is sectional drawing which shows the reinforcement structure of the base part which is one Embodiment of this invention. It is a top view which shows the reinforcement structure of the base part of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pier 12 Base part 14 Footing 16 Foundation 18 Sheet pile 20 Ground improvement part 30 Support layer 32 Surface layer

Claims (3)

  A method for reinforcing a foundation, characterized in that a sheet pile is placed on the ground on which the foundation of the structure is built so as to surround the existing foundation, and the ground inside the sheet pile is improved.   The foundation reinforcing method according to claim 1, wherein the sheet pile is driven so as to surround an upper portion of an existing foundation. A foundation reinforcement structure characterized in that a sheet pile is placed on the ground where the foundation of the structure is constructed so as to surround the existing foundation, and the ground inside the sheet pile is improved.

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