JP4707287B2

JP4707287B2 - Basic structure of the structure

Info

Publication number: JP4707287B2
Application number: JP2001288843A
Authority: JP
Inventors: 弘量黄; 信一日比野; 栄二郎溝口; 貴史本目
Original assignee: Tenox Corp
Current assignee: Tenox Corp
Priority date: 2001-09-21
Filing date: 2001-09-21
Publication date: 2011-06-22
Anticipated expiration: 2021-09-21
Also published as: JP2003096796A

Description

【０００１】
【発明の属する技術分野】
本発明は、液状化する可能性がある表層地盤中若しくは軟弱な表層地盤中に建築された構造物の基礎構造に関する。
【０００２】
【従来の技術】
液状化する可能性がある表層地盤中若しくは軟弱な表層地盤中に、原地盤土と固化材が攪拌・混合されて形成された地盤改良体が壁状でかつ平面視で格子状に構築されていると共に、その格子の交点部に上部構造物の荷重を負担する杭が存在する基礎構造が特願平１−２９０８２４号公報で知られている。
【０００３】
しかし、この構造では杭の上部は地盤改良体と一体となっているので、施工性の面から格子状の地盤改良体の格子で囲まれた中心部に杭を配する基礎構造を特許第２６４５８９９号公報は提案している。このように、格子状の地盤改良体の格子で囲まれた中心部に杭を配する基礎構造に関しては特開２０００−１１０１７７号公報でも提案されている。
【０００４】
また、格子状の地盤改良体における格子部の交点部に杭を設ける場合、杭と地盤改良体を接することがないように、交点部の地盤改良体が杭を囲むように構築するようにした基礎構造が特開平１１−２００３８１号公報で提案されている。
【０００５】
しかしながら、これらの杭と併用する地盤改良体は、いずれも壁状でかつ平面視で格子状に構築されたものであった。
【０００６】
一方、当出願人は、壁状でかつ平面視で格子状に構築された構造の地盤改良体よりも壁状改良体にスリットを形成して実質的に複数の壁に分断されている構造とした方が、地震時における壁状の地盤改良体の脆性破壊を防止することができることを特許第２９１８５５０号公報に示した。
【０００７】
【発明が解決しようとする課題】
特開平１−２９０８２４号公報の基礎構造は、格子状の地盤改良体を用いると共に、格子の交点に杭を設けた構造であり、地震時に生じる地盤の揺れを地盤改良体の剛性により押さえる効果があり、その結果、格子状で囲まれた地盤の液状化を防止できる。
【０００８】
しかし、このように液状化を防止できるということは、地盤改良体が地盤の揺れに抵抗していることであり、大きな水平力が格子状に構成された地盤改良体に作用しており、地中梁と地盤改良体が繋がっていると、この大きな水平力が上部構造物に伝達されることになる。従って、上部構造物を設計する際に、この大きな水平力を考慮せねばならないという不利な点があった。
【０００９】
このように、地震動（地震波）による入力を上部構造物へ大きく伝達する構造になっているばかりでなく、地盤改良体に更に大きな水平力が加わると脆性破壊を起こす恐れがなくはない構造であった。
【００１０】
また、上述したその他の公報に提案された地盤構造、即ち、杭を格子状の地盤改良体とは直接接触しない地盤構造でも地盤改良体とその上部のコンクリート部材との間は、特開平１１−２００３８１号公報の第１図に示されているように、一体化されていた。
【００１１】
このように杭と地盤改良体を併用することが開示されている何れの基礎構造も、大きな地震時に地盤改良体にも大きな水平力が加えられることが避けられず、地盤改良体が脆性破壊し易い構造であり、かつ地震動（地震波）による入力を上部構造物へ大きく伝達する構造になっていることには代わりがなかった。
【００１２】
また、先に述べた壁状改良体にスリットを形成して実質的に複数の壁に分断されている構造とした方が、地震時に壁状の地盤改良体の脆性破壊を防止することができることを開示した特許第２９１８５５０号公報においては、杭との関係を開示しなかったし、上部構造物への地震動の入力についても言及しなかった。
【００１３】
本発明の目的は、杭と地盤改良体とを併用して、同時に地震時に壁状の地盤改良体の脆性破壊を防止することができると共に、上部構造物への地震動（地震波）の入力を減少できるようにした構造物の基礎構造を提供することである。
【００１４】
【課題を解決するための手段】
請求項１記載の構造物の基礎構造は、液状化する可能性のある表層地盤中若しくは軟弱な表層地盤中に、原地盤土と固化材が攪拌・混合されて形成された複数の地盤改良体がそれぞれ壁状に構築され、該地盤改良体は平面上少なくとも縦方向と横方向に、互いに接しないように間隙をおいて存在し、かつそれらの地盤改良体の延長線が交差する部分に上部構造物の荷重を負担する杭が前記地盤改良体に接しないように存在し、前記地盤改良体の上部に地中梁が存在し、かつ該地中梁と前記地盤改良体との間に衝撃緩和材または空隙部が存在してなること特徴とするものである。
【００１５】
本発明の構造物の基礎構造においては、杭は壁状に構築された地盤改良体に接しないように配置されていればよい。また、地盤改良体と地中梁との間に存在させる衝撃緩和材としては、地盤改良体と地中梁との間で地震時の衝撃が緩和されて伝達できる緩和材、所謂ダッシュポットであれば良く、具体的には粘土やゴム、あるいは弾性プラスチック等の粘性材料である。
【００１６】
また、この場合、地盤改良体の上部に突起を設け、その上部に粘土やゴムなどの粘性材料を敷く一方、地中梁の下部に突起を設けるとともに地中梁側の突起が地盤改良体や地盤改良体側の突起に直接接しないようにし、かつ地盤改良体側の突起が地中梁や地中梁側の突起に直接接しないようにし、さらに地中梁側の突起と地盤改良体側の突起を千鳥配置にすることにより、地震時の衝撃を粘土やゴムなどの粘性材料を介して緩和する性能を調制できるようにしてもよい。
【００１７】
なお、衝撃緩和材としての粘性材料の粘性度や硬さにより、ダッシュポットによる緩和度を調節することもできる。
【００１８】
また、地震時の衝撃が地中梁と地盤改良体との間で伝達し難くする衝撃緩和材の他の例として、例えば二枚の金属製の板材を使用し、該板材の一枚を地盤改良体の上部に置き、その上に残る１枚の板材を置き、さらにその上に地中梁を設けることにより、板材間の滑りにより地中梁と地盤改良体との間で地震時の衝撃が伝達し難い構造とすればよい。
【００１９】
更に、地中梁と地盤改良体との間に空隙部を設けることにより地中梁と地盤改良体とを互いに分離させた構造とすることである。このように地中梁と地盤改良体とを分離させることにより、地中梁と地盤改良体との間で地震時に加わる衝撃が互いに伝わらない構造とすることができる。
【００２０】
なお、地中梁と地盤改良体との間に空隙部を設ける代わりに衝撃緩和材を設けて、地震時に発生する衝撃を互いに適度に伝達し合えるような構造とすることが、適度に応力分散させる際には好ましい。また、急激に応力分散させる際には空隙部を設ける構造とすることが好ましい。
【００２１】
請求項２記載の構造物の基礎構造は、請求項１記載の構造物の基礎構造において、壁状に構築された地盤改良体として、平面上、縦方向と横方向にそれぞれ配列された地盤改良体が存在し、かつそれらの地盤改良体の延長線が交差する部分に上部構造物の荷重を負担する杭が前記地盤改良体に接しないように存在することを特徴とするものである。
【００２２】
このような位置に杭が配置された構造とすることにより、周辺部に杭を設けることができ、また上部構造物の周辺部に杭を存在させることも、周辺部に地中梁を存在させることも可能になる。
【００２４】
なお、分断された壁状に構築された各地盤改良体の長さが短いと、壁状に構築された地盤改良体の端部側、即ち次の壁状に構築された地盤改良体側に応力が集中し易いが、壁状に構築された地盤改良体の杭に面する側が平面視でＴ字状になっていることで、この応力集中を緩和できる。
【００２５】
【発明の実施の形態】
本発明の構造物の基礎構造を図面を用いながら具体的に説明すると、図１（ａ），（ｂ）は本発明の基礎構造の一例を示したものであり、図１（ａ）に示すように、支持層イの上に非液状化層ロが存在し、最上部に液状化層ハが存在する地盤に基礎構造が設けられている。
【００２６】
このような液状化する可能性がある液状化層（表層地盤）ハ中に、図１（ａ）に示すように、原地盤土と固化材が攪拌・混合されて構築された地盤改良体１（以下「地盤改良体１」という。）が壁状に構築されている。
【００２７】
この地盤改良体１の下端は液状化層ハの下端まで達している。また、この地盤改良体１は、地盤改良体１と杭２の平面的な配置状態を示す図１（ｂ）に示すように、平面上、二方向以上に配列してなり、地盤改良体１同士は互いに間隙ニをおいて存在している。
【００２８】
この間隔ニ内に双方の地盤改良体１に接することなく上部構造物の荷重を負担する杭２を存在させる。この杭２は、図１（ａ）に示すように、支持層イにまで到達させている。
【００２９】
図１（ａ）に示すように、各杭２の上部に作られたフーチング３の相互間に地中梁４が構築される。このようにして地盤改良体１の上部に地中梁４が存在した構造にする。なお、図１（ａ），（ｂ）に示すように地盤改良体１と地中梁４との間に衝撃緩和材５を存在させている。また、図２に示すように、地盤改良体１と地中梁４との間に空隙部６を設けた構造とすることもできる。
【００３０】
このように図１（ａ），（ｂ）に示した衝撃緩和材５を使用した基礎構造と、図２（ａ），（ｂ）に示した空隙部６を設けた基礎構造と、地盤改良体１の上部に地中梁４が地盤改良体１と接着一体化して形成された、比較例の基礎構造（図省略）について、上部構造物に加わる地震による水平加速度がどのような状態になるかを調べた。
【００３１】
その結果、比較例の場合は、上部構造物に加わる加振方向の加速度は、４００ガルとなり、図５（ｂ）に示すようになかなか減少しない。空隙部６を設けた場合は、上部構造物に加わる加振方向の加速度が一瞬３００ガル程度になるが、図５（ａ）に示すように急激に１００ガルまでに低下する。
【００３２】
また、衝撃緩和材５を設けた場合は、上部構造物に加わる加振方向の加速度が一瞬３００ガル程度から４００ガルになるが、徐々に低下して１００ガル程度までに低下する。勿論、これらの低下傾向は使用する衝撃緩和材５の特性によって異なる。
【００３３】
なお、地盤改良体１と地中梁４との間に衝撃緩和材５を存在させた場合、例えば図３に示すように、地盤改良体１の上部に突起７を、地中梁４の下部に突起８をそれぞれ設けるとともに、梁側の突起８を地盤改良体１や地盤改良体１側の突起７に直接接しないようにし、かつ地盤改良体１側の突起７が梁４や梁側の突起８に直接接しないようにし、更に梁側の突起８と地盤改良体１側の突起７を相互に間隔が開いた千鳥配置にし、これらの間に衝撃緩和材５を配置する構造にしても良い。
【００３４】
更に、壁状地盤改良体１と杭２の平面的な配置状況を示す図４（ａ）に見られるように、壁状に構築された地盤改良体１の杭２に面する側が平面視でＴ字状になっている構造としても良い。
【００３５】
この構造の場合でも、地中梁４と地盤改良体１との間に衝撃緩和材５を存在させるか、図２の例のように空隙部６を設けてもよく、また図３のように突起７，８と衝撃緩和材５を存在させた構造にしても良い。
【００３６】
なお、地盤改良体１の杭２に面する側が平面視でＴ字状になっている構造とした場合は、分断された地盤改良体１の長さが短いと、地盤改良体１の端部側、即ち次の地盤改良体１側に応力が集中し易いが、地盤改良体１の杭２に面する側が平面視でＴ字状になっていることで、この応力集中を緩和でき、地盤改良体１が地震時により崩壊し難くすることが可能になる。
【００３７】
最後に、本発明のように、地盤改良体１は、平面上、二方向以上に配列してなり、地盤改良体１同士は互いに間隙をおいて存在した場合に、液状化防止効果が奏せられることを示す。
【００３８】
地盤改良体１が存在せず、単に杭２のみが存在する場合の地震時における過剰間隙水圧比（過剰間隙水圧比とは、通常の地盤状態において地盤深さにおける間隙水圧がある値を示している場合、地震時発生時にその深さにおいて示す間隙水圧から、通常時の間隙水圧を引いた値、即ち過剰間隙水圧を通常時の間隙水圧で割った比率である。過剰間隙水圧が零の場合は、過剰間隙水は存在しなく通常の地盤状態と変わらず、過剰間隙水圧比が１．０になると通常の問隙水圧の２倍の間隙水圧となることを示す。この過剰間隙水圧が大きくなると液状化現象をおこす可能性が高いことを示す。）の加振時からの時間経過と、地盤改良体１が二方向以上に存在し、かつ地盤改良体１同士が互いに間隙をおいて存在した場合の地震時における過剰間隙水圧比の加振時からの時間経過とを図６（ａ），（ｂ）に示す。
【００３９】
それぞれの場合について大型振動台を使用しての液状化実験により過剰間隙水比を求めた。この結果は次のようであった。
【００４０】
図６（ｂ）に実験値を示すように、地盤改良体１が存在せず、単に杭２のみが存在する場合は、過剰間隙水圧比が上昇し、地震時に液状化現象が起こる可能性があることを示したが、地盤改良体１が二方向以上に存在し、かつ地盤改良体１同士が互いに間隙ニをおいて存在した場合は、図６（ａ）に示すように、過剰間隙水圧比の上昇が抑えられ、液状化現象の発生を抑制できることを示した。
【００４１】
このように、本発明の構造物の基礎構造では、液状化現象を起こす地盤の場合でも、液状化現象の発生を抑制できることが立証された。
【００４２】
【発明の効果】
本発明の構造物の基礎構造は次の効果を併せ持つことができる。
▲１▼杭が地盤改良体と独立して設けられているために、杭と地盤改良体とが一体化されている場合に比べて、杭上部にかかる曲げ応力の集中を防止できる。
▲２▼杭が地盤改良体と独立して設けられているために、杭と地盤改良体とが一体化されている場合に比べて施工しやすい。また、杭と地盤改良体とが一体化されている場合は、地盤改良体が未硬化のうちに杭を沈設するなどの特別の作業工程とすることが必要になり、施工に手間がかかり、それ故高価になるが、本発明の場合はそのような施工上の配慮をする必要がない。
▲３▼図５を用いて説明したように、上部構造物の地震時の振動を少なくすることができる。即ち、地震波入力に対して、上部構造物の加速度応答の振幅を小さくできる。言葉を換えると、上部構造物への地震導入力を低減できる。
▲４▼一方、地震動による上部構造物の慣性力を地盤へ逸散させる効果が良くなる。
なお、衝撃緩和材の粘性材料の粘性度や硬さにより、ダッシュポットによる緩和度を調節することができ、上記▲３▼の効果も▲４▼の効果も適度に調節することができる。
【００４３】
また、請求項２に記載したように、壁状に構築された地盤改良体として、平面上、縦方向に配列された地盤改良体と横方向に配列された地盤改良体とが存在し、それらの地盤改良体の延長線が交差する部分に壁状に構築された地盤改良体に接することなく上部構造物の荷重を負担する杭が存在するような配置構造とすることにより、周辺部分に杭を設けることが可能となり、上部構造物の周辺部に杭を存在させることや周辺部に地中梁を存在させることも可能になる。
【００４４】
なお、壁状に構築された地盤改良体の杭に面する側が平面視でＴ字状になっている基礎構造であることがより好ましい。分断された壁状に構築された地盤改良体の長さが短いと、壁状に構築された地盤改良体の端部側、即ち次の壁状に構築された地盤改良体側に応力が集中し易いが、壁状に構築された地盤改良体の杭に面する側が平面視でＴ字状になっていることで、この応力集中を緩和できる。
【図面の簡単な説明】
【図１】本発明の構造物の基礎構造の一例を示す図であり、(a) は深さ方向の配置状態を示す縦断面図、(b) は平面視で杭と地盤改良体の配置構造を示す平面図、(c) は地盤改良体と地中梁の配置状態を(a) の断面方向から見た状態を示す縦断面図である。
【図２】本発明の構造物の基礎構造の他の例を示す図であり、(a) は深さ方向の配置状態を示す縦断面図、(b) は平面視で杭と地盤改良体の配置構造を示す平面図、(c) は地盤改良体と地中梁の配置状態を(a) の断面方向から見た状態を示す縦断面図である。
【図３】本発明の構造物の基礎構造の他の例を示す図であり、(a) は深さ方向の配置状態を示す縦断面図、(b) は平面視で杭と地盤改良体の配置構造を示す平面図、(c) は地盤改良体と地中梁の配置状態を(a) の断面方向から見た状態を示す縦断面図である。
【図４】本発明の構造物の基礎構造の他の例を示す図であり、(a) は深さ方向の配置状態を示す縦断面図、(b) は平面視で杭と地盤改良体の配置構造を示す平面図である。
【図５】（ａ），（ｂ）は、地震時に上部構造物に加わる加振力の応答加速度を示す図である。
【図６】（ａ），（ｂ）は過剰間隙水圧比の時間的変化を示す図である。
【符号の説明】
イ支持層
ロ非液状化層
ハ液状化層
ニ間隙（地盤改良体間の間隙）
１地盤改良体（壁状に構築された地盤改良体）
２杭
３フーチング
４地中梁
５衝撃緩和材
６空隙部
７突起
８突起[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a basic structure of a structure built in a surface layer ground that may be liquefied or in a soft surface layer ground.
[0002]
[Prior art]
The ground improvement body formed by mixing and mixing the original ground soil and solidified material in the surface ground that is liable to liquefy or in the soft surface ground is constructed in a wall shape and in a lattice shape in plan view. In addition, a basic structure in which a pile that bears the load of the upper structure is present at the intersection of the lattice is known from Japanese Patent Application No. 1-290824.
[0003]
However, in this structure, since the upper part of the pile is integrated with the ground improvement body, the foundation structure in which the pile is arranged in the center part surrounded by the lattice of the grid-like ground improvement body from the viewpoint of workability is disclosed in Japanese Patent No. 2645899. No. Gazette proposes. As described above, Japanese Laid-Open Patent Publication No. 2000-110177 has also proposed a foundation structure in which a pile is arranged in a central portion surrounded by a grid of a grid-like ground improvement body.
[0004]
In addition, when a pile is provided at the intersection of the lattice part in the grid-like ground improvement body, the ground improvement body at the intersection part is constructed so as to surround the pile so as not to contact the pile and the ground improvement body. A basic structure is proposed in JP-A-11-200381.
[0005]
However, all of the ground improvement bodies used in combination with these piles were wall-like and constructed in a lattice shape in plan view.
[0006]
On the other hand, the applicant of the present invention has a structure in which a slit is formed in the wall-like improvement body, substantially divided into a plurality of walls, rather than a ground improvement body having a wall-like structure and a grid-like structure in plan view. It has been shown in Japanese Patent No. 2918550 that this can prevent brittle fracture of the wall-shaped ground improvement body at the time of an earthquake.
[0007]
[Problems to be solved by the invention]
The basic structure of JP-A-1-290824 is a structure in which a grid-like ground improvement body is used and a pile is provided at the intersection of the grid, and the effect of suppressing the ground shaking caused by an earthquake by the rigidity of the ground improvement body is effective. As a result, liquefaction of the ground surrounded by the lattice can be prevented.
[0008]
However, the fact that liquefaction can be prevented in this way means that the ground improvement body resists shaking of the ground, and a large horizontal force is acting on the ground improvement body configured in a lattice shape. If the intermediate beam and the ground improvement body are connected, this large horizontal force is transmitted to the superstructure. Therefore, there is a disadvantage that this large horizontal force must be taken into consideration when designing the superstructure.
[0009]
In this way, not only is it structured to transmit the input from seismic motion (earthquake waves) to the superstructure, but it also has a structure that will not cause brittle fracture if a greater horizontal force is applied to the ground improvement body. It was.
[0010]
Further, even in the ground structure proposed in the above-mentioned other publications, that is, the ground structure in which the pile is not in direct contact with the lattice-shaped ground improvement body, the gap between the ground improvement body and the concrete member thereabove is not disclosed in Japanese Patent Laid-Open No. 11- As shown in FIG. 1 of Japanese Patent No. 200381, it was integrated.
[0011]
In any of the foundation structures that are disclosed to use piles and ground improvement bodies in this way, it is inevitable that a large horizontal force will be applied to the ground improvement body during a large earthquake, and the ground improvement body will be brittle. There was no substitute for it being an easy structure and a structure that greatly transmits the input of seismic motion (seismic waves) to the superstructure.
[0012]
In addition, it is possible to prevent brittle fracture of the wall-like ground improvement body at the time of an earthquake by forming a slit in the wall-like improvement body described above and substantially dividing it into a plurality of walls. In Japanese Patent No. 2918550 which disclosed the above, the relationship with the pile was not disclosed, and the input of the earthquake motion to the superstructure was not mentioned.
[0013]
The object of the present invention is to use piles and ground improvement bodies together, and at the same time, can prevent brittle fracture of wall-like ground improvement bodies during earthquakes and reduce the input of earthquake motion (earthquake waves) to the superstructure. It is to provide the basic structure of the structure that can be made.
[0014]
[Means for Solving the Problems]
The basic structure of the structure according to claim 1 is a plurality of ground improvement bodies formed by mixing and mixing the original ground soil and the solidified material in the surface ground that may be liquefied or in the soft surface ground. Are constructed in the shape of a wall, and the ground improvement body is present at least in the vertical and horizontal directions on the plane so as not to contact each other , and the upper part is located at the intersection of the extension lines of the ground improvement bodies. There is a pile that bears the load of the structure so as not to contact the ground improvement body, there is an underground beam above the ground improvement body, and there is an impact between the underground beam and the ground improvement body. It is characterized by the presence of a relaxation material or a void.
[0015]
In the foundation structure of the structure of the present invention, the piles only need to be arranged so as not to contact the ground improvement body constructed in a wall shape. In addition, as an impact mitigating material to be present between the ground improvement body and the underground beam, a so-called dashpot, which is a mitigation material capable of mitigating and transmitting an impact during an earthquake between the ground improvement body and the underground beam. Specifically, it is a viscous material such as clay, rubber, or elastic plastic.
[0016]
Also, in this case, a protrusion is provided on the upper part of the ground improvement body and a viscous material such as clay or rubber is laid on the upper part, while a protrusion is provided on the lower part of the underground beam and the protrusion on the underground beam side is Make sure that the protrusion on the ground improvement body side does not touch directly, and the protrusion on the ground improvement body side does not touch the underground beam or the protrusion on the underground beam side.In addition, the protrusion on the underground beam side and the protrusion on the ground improvement body side A staggered arrangement may be used to regulate the ability to mitigate the impact of an earthquake through a viscous material such as clay or rubber.
[0017]
In addition, the relaxation degree by a dashpot can also be adjusted with the viscosity and hardness of the viscous material as an impact relaxation material.
[0018]
In addition, as another example of an impact mitigating material that makes it difficult for an impact during an earthquake to be transmitted between the underground beam and the ground improvement body, for example, two metal plates are used, and one of the plates is ground. Place the plate on the top of the improved body and place the remaining plate on it, and then install the underground beam on it. The impact between the underground beam and the ground improved body due to the slip between the plates May be a structure that is difficult to transmit.
[0019]
Furthermore, it is set as the structure which isolate | separated the underground beam and the ground improvement body mutually by providing a space | gap part between an underground beam and a ground improvement body. By separating the underground beam and the ground improvement body in this manner, it is possible to achieve a structure in which the impact applied during the earthquake is not transmitted between the underground beam and the ground improvement body.
[0020]
It should be noted that instead of providing a gap between the underground beam and the ground improvement body, an impact mitigating material is provided so that the impact generated during an earthquake can be appropriately transmitted to each other. This is preferable. In addition, it is preferable to have a structure in which a gap is provided when stress is dispersed rapidly.
[0021]
The foundation structure of the structure according to claim 2 is the foundation structure of the structure according to claim 1, wherein the ground improvement body arranged in the shape of a wall is arranged on the plane, in the vertical direction and in the horizontal direction, respectively. The pile which bears the load of a superstructure exists in the part which a body exists and the extension line of those ground improvement bodies cross | intersects, It is characterized by the above-mentioned.
[0022]
By adopting a structure in which piles are arranged in such a position, it is possible to provide piles in the periphery, and it is also possible to have piles in the periphery of the upper structure, or to have underground beams in the periphery It becomes possible.
[0024]
In addition, if the length of the ground improvement body constructed in the divided wall shape is short, the stress is applied to the end side of the ground improvement body constructed in the wall shape, that is, the ground improvement body side constructed in the next wall shape. However, this stress concentration can be alleviated because the side facing the pile of the ground improvement body constructed in a wall shape is T-shaped in plan view.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
The basic structure of the structure of the present invention will be described in detail with reference to the drawings. FIGS. 1A and 1B show an example of the basic structure of the present invention, which is shown in FIG. As described above, the foundation structure is provided on the ground where the non-liquefied layer B exists on the support layer A and the liquefied layer C exists on the top.
[0026]
As shown in FIG. 1 (a), a ground improvement body 1 constructed by mixing and mixing the original ground soil and the solidified material in a liquefied layer (surface layer ground) that can be liquefied as described above. (Hereinafter referred to as “ground improvement body 1”) is constructed in a wall shape.
[0027]
The lower end of the ground improvement body 1 reaches the lower end of the liquefied layer c. Moreover, this ground improvement body 1 is arranged in two or more directions on the plane, as shown in FIG. 1 (b) showing a planar arrangement state of the ground improvement body 1 and the pile 2, and the ground improvement body 1 They exist with a gap between each other.
[0028]
A pile 2 that bears the load of the upper structure without contacting both ground improvement bodies 1 is made to exist within this distance d. As shown in FIG. 1A, the pile 2 reaches the support layer a.
[0029]
As shown in FIG. 1 (a), underground beams 4 are constructed between footings 3 formed on the top of each pile 2. In this way, a structure in which the underground beam 4 exists on the upper portion of the ground improvement body 1 is obtained. In addition, as shown to Fig.1 (a), (b), the impact relaxation material 5 exists between the ground improvement body 1 and the underground beam 4. As shown in FIG. Moreover, as shown in FIG. 2, it can also be set as the structure which provided the space | gap part 6 between the ground improvement body 1 and the underground beam 4. As shown in FIG.
[0030]
Thus, the basic structure using the impact relaxation material 5 shown in FIGS. 1A and 1B, the basic structure provided with the gap 6 shown in FIGS. 2A and 2B, and ground improvement What is the state of horizontal acceleration due to the earthquake applied to the upper structure of the basic structure (not shown) of the comparative example in which the underground beam 4 is formed integrally with the ground improvement body 1 on the upper part of the body 1? I investigated.
[0031]
As a result, in the case of the comparative example, the acceleration in the excitation direction applied to the upper structure is 400 gal, and does not decrease easily as shown in FIG. When the gap 6 is provided, the acceleration in the excitation direction applied to the upper structure is about 300 gal for a moment, but rapidly decreases to 100 gal as shown in FIG.
[0032]
In addition, when the shock absorbing material 5 is provided, the acceleration in the excitation direction applied to the upper structure instantaneously changes from about 300 gal to 400 gal, but gradually decreases to about 100 gal. Of course, these downward trends vary depending on the characteristics of the shock absorbing material 5 to be used.
[0033]
In addition, when the impact relaxation material 5 exists between the ground improvement body 1 and the underground beam 4, for example, as shown in FIG. 3, the protrusion 7 is provided on the upper part of the ground improvement body 1, and the lower part of the underground beam 4 is provided. Are provided so that the projection 8 on the beam side does not directly contact the ground improvement body 1 or the projection 7 on the ground improvement body 1 side, and the projection 7 on the ground improvement body 1 side is provided on the beam 4 or the beam side. The structure is such that the projections 8 on the beam side and the projections 7 on the ground improvement body 1 side are arranged in a staggered manner with a space therebetween, and the shock absorbing material 5 is arranged between them. good.
[0034]
Furthermore, as can be seen in FIG. 4 (a) showing the planar arrangement of the wall-like ground improvement body 1 and the pile 2, the side facing the pile 2 of the ground improvement body 1 constructed in a wall shape is a plan view. It may be a T-shaped structure.
[0035]
Even in the case of this structure, the shock absorbing material 5 may be present between the underground beam 4 and the ground improvement body 1, or the gap 6 may be provided as in the example of FIG. 2, or as shown in FIG. A structure in which the protrusions 7 and 8 and the impact relaxation material 5 are present may be used.
[0036]
In addition, when it is set as the structure where the side which faces the pile 2 of the ground improvement body 1 becomes T shape by planar view, when the length of the divided ground improvement body 1 is short, the edge part of the ground improvement body 1 Although the stress tends to concentrate on the side, that is, the next ground improvement body 1 side, the side facing the pile 2 of the ground improvement body 1 is T-shaped in plan view, so that this stress concentration can be alleviated. It becomes possible to make the improved body 1 less likely to collapse due to an earthquake.
[0037]
Finally, as in the present invention, the ground improvement bodies 1 are arranged in two or more directions on the plane, and when the ground improvement bodies 1 exist with a gap between each other, the effect of preventing liquefaction can be obtained. Indicates that
[0038]
Excess pore water pressure ratio at the time of earthquake when the ground improvement body 1 does not exist and only the pile 2 exists (excess pore water pressure ratio indicates a value with a pore water pressure at the ground depth in a normal ground condition) When the earthquake occurs, it is the value obtained by subtracting the normal pore water pressure from the pore water pressure at the depth when the earthquake occurs, that is, the ratio of the excess pore water pressure divided by the normal pore water pressure. Indicates that there is no excess pore water, which does not change from the normal ground condition, and that when the excess pore water pressure ratio is 1.0, the pore water pressure is twice the normal pore water pressure. This indicates that there is a high possibility of causing a liquefaction phenomenon.) The time elapsed from the time of vibration), the ground improvement body 1 exists in two or more directions, and the ground improvement bodies 1 exist with a gap between each other. Excess gap during an earthquake And the time elapsed from the pressure ratio of the pressure Futoki FIG. 6 (a), the shown (b).
[0039]
In each case, the excess pore water ratio was determined by liquefaction experiments using a large shaking table. The results were as follows.
[0040]
As shown in the experimental values in FIG. 6 (b), when the ground improvement body 1 does not exist and only the pile 2 exists, the excess pore water pressure ratio increases, and liquefaction may occur during an earthquake. In the case where the ground improvement bodies 1 exist in two or more directions and the ground improvement bodies 1 exist with a gap between each other, as shown in FIG. It was shown that the increase in the ratio was suppressed and the occurrence of the liquefaction phenomenon could be suppressed.
[0041]
As described above, it was proved that the occurrence of the liquefaction phenomenon can be suppressed even in the case of the ground causing the liquefaction phenomenon in the basic structure of the structure of the present invention.
[0042]
【The invention's effect】
The basic structure of the structure of the present invention can have the following effects.
(1) Since the pile is provided independently of the ground improvement body, it is possible to prevent the concentration of bending stress applied to the upper part of the pile compared to a case where the pile and the ground improvement body are integrated.
(2) Since the pile is provided independently of the ground improvement body, it is easier to construct than the case where the pile and the ground improvement body are integrated. In addition, when the pile and the ground improvement body are integrated, it is necessary to make a special work process such as setting the pile while the ground improvement body is uncured, and it takes time and labor for the construction. Therefore, it is expensive, but in the case of the present invention, it is not necessary to consider such construction.
{Circle around (3)} As described with reference to FIG. 5, the vibration of the superstructure can be reduced. That is, the amplitude of the acceleration response of the superstructure can be reduced with respect to the seismic wave input. In other words, the earthquake introduction force to the superstructure can be reduced.
(4) On the other hand, the effect of dissipating the inertial force of the superstructure due to earthquake motion to the ground is improved.
Incidentally, the degree of relaxation by the dashpot can be adjusted by the viscosity and hardness of the viscous material of the impact relaxation material, and the effects (3) and (4) can be appropriately adjusted.
[0043]
Further, as described in claim 2, as the ground improvement body constructed in a wall shape, there are a ground improvement body arranged in a vertical direction on a plane and a ground improvement body arranged in a horizontal direction, By placing the piles that bear the load of the superstructure without touching the ground improvement body built in the shape of a wall at the part where the extension lines of the ground improvement body intersect, piles in the surrounding part It is possible to provide piles in the periphery of the superstructure, and it is also possible to have underground beams in the periphery.
[0044]
In addition, it is more preferable that it is a foundation structure in which the side facing the pile of the ground improvement body constructed in a wall shape is T-shaped in a plan view. If the length of the ground improvement body constructed in a divided wall shape is short, stress concentrates on the end side of the ground improvement body constructed in the wall shape, that is, on the ground improvement body side constructed in the next wall shape. Although it is easy, this stress concentration can be relieved by the side facing the pile of the ground improvement body constructed in a wall shape being T-shaped in plan view.
[Brief description of the drawings]
FIG. 1 is a view showing an example of a basic structure of a structure according to the present invention, (a) is a longitudinal sectional view showing an arrangement state in a depth direction, and (b) is an arrangement of piles and ground improvement bodies in a plan view. A plan view showing the structure, (c) is a longitudinal sectional view showing the arrangement of the ground improvement body and the underground beam as viewed from the sectional direction of (a).
FIG. 2 is a view showing another example of the basic structure of the structure of the present invention, wherein (a) is a longitudinal sectional view showing an arrangement state in the depth direction, and (b) is a pile and ground improvement body in plan view. (C) is a longitudinal sectional view showing the arrangement state of the ground improvement body and the underground beam as viewed from the sectional direction of (a).
FIG. 3 is a view showing another example of the foundation structure of the structure of the present invention, (a) is a longitudinal sectional view showing a state of arrangement in the depth direction, and (b) is a pile and ground improvement body in plan view. (C) is a longitudinal sectional view showing the arrangement state of the ground improvement body and the underground beam as viewed from the sectional direction of (a).
FIG. 4 is a view showing another example of the basic structure of the structure of the present invention, wherein (a) is a longitudinal sectional view showing a state of arrangement in the depth direction, and (b) is a pile and ground improvement body in plan view. It is a top view which shows the arrangement structure.
FIGS. 5A and 5B are diagrams showing response acceleration of excitation force applied to an upper structure during an earthquake.
FIGS. 6A and 6B are diagrams showing temporal changes in excess pore water pressure ratio. FIGS.
[Explanation of symbols]
B Support layer B Non-liquefaction layer C Liquefaction layer D Gap (gap between ground improvement bodies)
1 Ground improvement body (Ground improvement body built in the shape of a wall)
2 Pile 3 Footing 4 Underground beam 5 Impact relaxation material 6 Cavity 7 Protrusion 8 Protrusion

Claims

A plurality of ground improvement bodies formed by mixing and mixing the original ground soil and solidified material in the surface ground which may be liquefied or in the soft surface ground, are each constructed in the shape of a wall. Is a pile that bears the load of the upper structure at a portion where the extension lines of the ground improvement bodies intersect with each other at least in the vertical direction and the horizontal direction on the plane so as not to contact each other. It exists so that it may not touch a body, an underground beam exists in the upper part of the above-mentioned ground improvement object, and an impact relaxation material or an air gap part exists between this underground beam and the above-mentioned ground improvement object The basic structure of the structure.

There are ground improvement bodies arranged in the vertical and horizontal directions on the plane, and a pile that bears the load of the upper structure is in contact with the ground improvement body at the intersection of the extension lines of those ground improvement bodies. The foundation structure of the structure according to claim 1, wherein the foundation structure does not exist.