JP3673990B2 - Pile foundations for structures built on soft ground that tend to liquefy - Google Patents

Pile foundations for structures built on soft ground that tend to liquefy Download PDF

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Publication number
JP3673990B2
JP3673990B2 JP16871099A JP16871099A JP3673990B2 JP 3673990 B2 JP3673990 B2 JP 3673990B2 JP 16871099 A JP16871099 A JP 16871099A JP 16871099 A JP16871099 A JP 16871099A JP 3673990 B2 JP3673990 B2 JP 3673990B2
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JP
Japan
Prior art keywords
ground
pile
soft
soft ground
liquefy
Prior art date
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Expired - Fee Related
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JP16871099A
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Japanese (ja)
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JP2000319903A (en
Inventor
光夫 野津
Original Assignee
不動建設株式会社
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Priority to JP16871099A priority Critical patent/JP3673990B2/en
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Description

【0001】
【発明が属する技術分野】
本発明は、液状化し易い軟弱地盤上に構築される構造物の杭基礎に関するものである。
【0002】
【従来の技術】
軟弱地盤中に深層混合処理工法で円筒状地盤改良体を形成することは従来公知である(特開昭58−195621号公報参照)。
【0003】
ところで、前記円筒状地盤改良体を地震時に液状化現象が生じ易い軟弱地盤(主として砂質土系軟弱地盤)に形成した場合、地震時に、円筒状地盤改良体の周辺の地盤では過剰間隙水圧が上昇するのに対して、円筒状地盤改良体の内部では地盤土のせん断変形が抑制され、過剰間隙水圧の上昇も抑えられるため、円筒状地盤改良体の内外で水位差が生じ、円筒状地盤改良体に外方から圧縮力が作用することになる。
【0004】
そして、この際、深層混合処理工法で形成された地盤改良体の躯体の強度はそれほど大きくないが、前記円筒状地盤改良体はその形状に基づくアーチ効果で外側からの圧力に抵抗するので、構造破壊を免れ、安定性を保持する。
【0005】
【発明が解決しようとする課題】
本発明が解決しようとする課題(本発明の目的)は、円筒状地盤改良体の前記特性を利用して、液状化し易い軟弱地盤上に構築される構造物の基礎杭の地震時における安定性を確保することにある。
【0006】
【課題を解決するための手段】
前記課題を解決するために、本発明の液状化し易い軟弱地盤上に構築される構造物の杭基礎(以下、本発明の杭基礎という)では、液状化し易い軟弱地盤上に構築される構造物の杭基礎が打設される部所の軟弱地盤土を地表から適宜深度に亙ってリング状に深層混合処理して円筒状地盤改良体の複数個を、互いに離隔して形成し、それぞれの円筒状地盤改良体の内部の軟弱地盤土を貫通して下方の支持地盤に達する基礎杭を打設する。
【0007】
【発明の実施の形態】
本発明の杭基礎の一例を図面に基づいて説明すると、図1において、Aは液状化し易い軟弱地盤、Bは上部支持地盤、Cは下部支持地盤、1は基礎杭、2は円筒状地盤改良体である。
【0008】
図の場合は、基礎杭1は、8本で、4本づつ2列に並んで、軟弱地盤Aと上部支持地盤Bとを貫通して下部支持地盤に達するように打設されており、また、円筒状地盤改良体2は、各基礎杭1の打設部所において軟弱地盤Aの地盤土を地表から軟弱地盤Aの全深度に亙ってリング状に深層混合処理して形成され、各基礎杭1は対応する円筒状地盤改良体2の中心部にそれぞれ位置している。
【0009】
本発明の杭基礎は図示の実施態様に限定されず、例えば、円筒状地盤改良体2がの高さが地表から軟弱地盤Aの中間深度までの場合もあり、また、円筒状地盤改良体2が1個で、その内部に複数本の基礎杭1が打設されている場合もあり、また、円筒状地盤改良体2が複数の場合に、これらが図の場合のように離れていないで、互いに接している場合もあり、また、基礎杭1が図の場合のように下部支持地盤Cで支持される支持杭タイプでなく、上部支持地盤Bで支持される摩擦杭タイプの場合もある。
【0010】
そして、本発明の杭基礎では、基礎杭1が既製杭タイプと場所打ち杭タイプの何れであってもよく、また、基礎杭1の打設と円筒状地盤改良体2の形成は何れが先であってもよい。
【図面の簡単な説明】
【図1】本発明の杭基礎の一例を模式的に示す縦断面図である。
【図2】同じく平面図である。
【符号の説明】
A:軟弱地盤、B:上部支持地盤、C:下部支持地盤、1:基礎杭、2:円筒状地盤改良体。
[0001]
[Technical field to which the invention belongs]
The present invention relates to a pile foundation of a structure constructed on soft ground that is liable to be liquefied.
[0002]
[Prior art]
It is conventionally known that a cylindrical ground improvement body is formed in soft ground by a deep mixing treatment method (see Japanese Patent Application Laid-Open No. 58-195621).
[0003]
By the way, when the cylindrical ground improvement body is formed on a soft ground (mainly sandy soil-based soft ground) where liquefaction is likely to occur during an earthquake, excessive pore water pressure is generated on the ground around the cylindrical ground improvement body during an earthquake. On the other hand, since the shear deformation of the ground soil is suppressed inside the cylindrical ground improvement body and the increase in excess pore water pressure is also suppressed, a water level difference occurs between the inside and outside of the cylindrical ground improvement body. A compressive force acts on the improved body from the outside.
[0004]
And, at this time, the strength of the frame of the ground improvement body formed by the deep mixing treatment method is not so great, but the cylindrical ground improvement body resists pressure from the outside due to the arch effect based on its shape, Escape destruction and maintain stability.
[0005]
[Problems to be solved by the invention]
The problem to be solved by the present invention (object of the present invention) is to use the above-mentioned characteristics of the cylindrical ground improvement body to stabilize the foundation pile of a structure constructed on soft ground that is liable to liquefy at the time of earthquake. Is to ensure.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, in the pile foundation of a structure constructed on the soft ground easily liquefied of the present invention (hereinafter referred to as the pile foundation of the present invention), the structure constructed on the soft ground easily liquefied. The soft ground soil of the place where the pile foundation is placed is deeply mixed in a ring shape from the surface to the appropriate depth to form a plurality of cylindrical ground improvement bodies separated from each other. The foundation pile which penetrates the soft ground soil inside the cylindrical ground improvement body and reaches the lower supporting ground is laid.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
An example of a pile foundation according to the present invention will be described with reference to the drawings. In FIG. 1, A is a soft ground that is easily liquefied, B is an upper support ground, C is a lower support ground, 1 is a foundation pile, and 2 is a cylindrical ground improvement. Is the body.
[0008]
In the case of the figure, the foundation piles 1 are arranged in 8 rows, 4 by 2 in a row, penetrate the soft ground A and the upper support ground B, and reach the lower support ground. The cylindrical ground improvement body 2 is formed by deeply mixing the ground soil of the soft ground A from the ground surface to the entire depth of the soft ground A at the placement site of each foundation pile 1, The foundation pile 1 is located in the center part of the corresponding cylindrical ground improvement body 2, respectively.
[0009]
The pile foundation of the present invention is not limited to the illustrated embodiment. For example, the height of the cylindrical ground improvement body 2 may be from the ground surface to the intermediate depth of the soft ground A, and the cylindrical ground improvement body 2 There is a case where a plurality of foundation piles 1 are driven in the inside, and when there are a plurality of cylindrical ground improvement bodies 2, these are not separated as in the case of the figure. In some cases, the foundation piles 1 are not the support pile type supported by the lower support ground C as shown in the figure, but the friction pile type supported by the upper support ground B. .
[0010]
In the pile foundation of the present invention, the foundation pile 1 may be either a ready-made pile type or a cast-in-place pile type, and the foundation pile 1 is formed and the cylindrical ground improvement body 2 is formed first. It may be.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view schematically showing an example of a pile foundation of the present invention.
FIG. 2 is a plan view of the same.
[Explanation of symbols]
A: Soft ground, B: Upper support ground, C: Lower support ground, 1: Foundation pile, 2: Cylindrical ground improvement body.

Claims (1)

液状化し易い軟弱地盤上に構築される構造物の杭基礎が打設される部所の軟弱地盤土を地表から適宜深度に亙ってリング状に深層混合処理して円筒状地盤改良体の複数個を、互いに離隔して形成し、それぞれの円筒状地盤改良体の内部の軟弱地盤土を貫通して下方の支持地盤に達する基礎杭を打設して成ることを特徴とする液状化し易い軟弱地盤上に構築される構造物の杭基礎。 A plurality of cylindrical ground improvement bodies obtained by subjecting soft ground soil at the place where pile foundations of structures constructed on soft ground that are liable to liquefy to be placed to a ring shape from the surface to the appropriate depth in a ring shape. Soft and easy to liquefy, characterized in that the pieces are formed separately from each other and formed by foundation piles that penetrate the soft ground soil inside each cylindrical ground improvement body and reach the lower support ground Pile foundation for structures built on the ground.
JP16871099A 1999-05-13 1999-05-13 Pile foundations for structures built on soft ground that tend to liquefy Expired - Fee Related JP3673990B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP16871099A JP3673990B2 (en) 1999-05-13 1999-05-13 Pile foundations for structures built on soft ground that tend to liquefy

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP16871099A JP3673990B2 (en) 1999-05-13 1999-05-13 Pile foundations for structures built on soft ground that tend to liquefy

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JP2000319903A JP2000319903A (en) 2000-11-21
JP3673990B2 true JP3673990B2 (en) 2005-07-20

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103556621B (en) * 2013-10-21 2015-05-27 开封大学 Strengthening method for silt foundation

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