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Experimental study on effects of lateral soil flow on group pile and its application to design procedure

侧向土流对群桩影响的试验研究及其在设计中的应用

基本信息

批准号：
16360234
负责人：
TOWHATA Ikuo
金额：
$ 9.02万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16360234/
关键词：
liquefaction model test lateral pressure group pile ground flow shaking table sandy ground 群杭基礎粘性流体振動台砂地盤横荷重耐震設計

项目摘要

Model tests were conducted on a 1-G shaking table with a variety of group pile which was embedded in a liquefied sloping ground. Different from foregoing group pile tests with 4 or 9 constituent piles, the present study employed 36 or 121 piles in a square configuration.Upon shaking the model with different intensities and frequencies, the bending moment was recorded along the length of piles at several piles. Moreover, lateral ground displacement was studied by using data of embedded displacement transducers as well as distortion of soil markers in the ground surface. Records were taken of acceleration and pore water pressure as well. It was revealed that soil flows in the downslope direction upon liquefaction and large deformation occurs around piles. This large deformation makes it very difficult or even inappropriate to analyze the pile-soil interaction by conventional FEM analysis.The interpretation of bending moment data revealed that the magnitude of bending moment (and consequently the lateral earth pressure) takes the maximum value at the upstream and downstream ends of the pile foundation. This implies that the existence of piles in the upstream direction reduces the earth pressure in the downstream direction, which is called the Shadow Effects, and that, in the downstream end, the ground elevation difference, which is produced by the prevented soil flow by piles, creates significant lateral earth pressure on end piles. The shadow effects vary with the pile spacing ; the narrower spacing makes the shadow effects more remarkable.Finally, a retrofitting measure for existing group foundation was proposed. That is installation of additional piles on upstream and downstream sides of a foundation. The earth pressure due to flow of liquefied soil is borne by those additional piles and the load on the existing and important piles is mitigated. These findings were examined in a numerical model as well in which liquefied sand is modeled as a viscous liquid.

在1-G振动台上进行了液化斜坡地基中各种群桩的模型试验。与以往的4根或9根成桩的群桩试验不同，本试验采用36根或121根成桩的正方形布置，在不同的振动强度和频率下，记录了沿桩长方向沿着多根桩的弯矩。此外，通过埋设位移传感器的数据，以及在地面上的土壤标记的变形，地面侧向位移进行了研究。记录了加速度和孔隙水压力。结果表明，液化后土体沿坡下方向流动，桩周土体发生较大变形。通过对弯矩数据的分析，发现在桩基的上、下游端弯矩值最大，土侧压力值最大。这意味着上游方向的桩的存在降低了下游方向的土压力，这被称为阴影效应，并且在下游端，由桩阻止的土流产生的地面高程差在端桩上产生显著的侧向土压力。阴影效应随桩间距的变化而变化，桩间距越小，阴影效应越显著。最后，提出了既有群基础的加固措施。即在基础的上游侧和下游侧安装额外的桩。由于液化土流动而产生的土压力由这些额外的桩承担，并减轻了现有和重要桩的荷载。这些研究结果进行了检查，以及在一个数值模型中，液化砂模拟为粘性液体。

项目成果

期刊论文数量（20）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Development of Geotechnical Earthquake Engineering in Japan.

日本岩土地震工程的发展。

DOI：
发表时间：
2005
期刊：
Heritage Lecture, XVIth International Conference on Soil Mechanicsand Geotechnical Engineering, Osaka Vol.11
影响因子：
0
作者：
Towhata;Ikuo
通讯作者：
Ikuo

Model test on response of large pile group under lateral flow of liquefied sandy soil ground

液化砂土地基侧流作用下大型群桩响应模型试验

DOI：
发表时间：
2004
期刊：
Proc.Symp.on Behavior and Design of Piles Embedded in Liquefied Ground,Japanese Geotechnical Society
影响因子：
0
作者：
Sesov;V.;Towhata;L.;Gonzalez;M.;Ball;R.;Ishimatsu,S.
通讯作者：
Ishimatsu,S.

Experimental Study on Large Pile Group Response Subjected to Lateral Flow of Liquefied Ground

液化地基侧流作用下大型群桩响应试验研究

DOI：
发表时间：
2005
期刊：
Proc. TC4 Satellite Conference,Int.Conf.Soil Mechanics and Geotechnical Engineering,Osaka Vol.4
影响因子：
0
作者：
Sesov;V.;Towhata;L.;Gonzalez;M.;Ball;R.;Ishimatsu,S.
通讯作者：
Ishimatsu,S.

Experimental Study on Large Pile Group Response Subjected to Lateral Flow of Liquefied Ground.

液化地基侧流作用下大型群桩响应试验研究。