Seismic deformation of composite breakwaters and embankments on saturated sandy ground with reference to torsional cyclic behavior of sand after phase transformation

饱和沙地基上复合防波堤和路堤的地震变形参考沙子相变后扭转循环行为

• 批准号: 13650548
• 负责人: KITA Katsutoshi
• 金额: $ 1.6万
• 依托单位: TOKAI UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13650548/
• 关键词: earthquake; breakwater; embankment; settlement; saturated sand; cyclic plasticity; phase transformation; pore pressure; 水際線構造物; 塑性; 非排水繰返しねじりせん断試験; 砂質土; 繰返しせん断; 間隙水圧; 液状化

In the 1995 Hyogoken-Nambu earthquake, some composite breakwaters in Kobe port experienced over 2.5m settlement due to strong ground shaking. In this study, a series of shaking table tests were conducted on breakwater- and embankment-foundation saturated sandy ground system is centrifugal conditions of 30-g and 50-g with viscous scaling incorporated, in order to clarify the mechanism of such large settlements. The deformation characteristics of the foundation ground were then discussed referring to the results of undrained cyclic torsional shear tests on anisotropically consolidated loose sand. Results obtained from these experiments are summarized as follows:(1) In centrifuge model tests, foundation ground just beneath the main part of a composite breakwater may undergo large axial deformation (vertical compression associated with horizontal extension) during ground shaking, due to the undrained cumulative shear deformation mechanism, which becomes operational once effective stresses … More reach phase transformation states. The vertical compressive strains in the middle and/or lower (deep) layers were larger than those in the shallow layers.(2) Vertical and torsional shear strains developed significantly after the stress paths reached the transformation lines in cyclic torsional shear tests. The vertical strains cumulated, however the strain increments decreased with the number of cyclic shearing. Larger the initial consolidation stress ratio K=σ'_<z0>/σ'<I0*> (σ'_z0> and σ'_<r0> are respectively the initial vertical and horizontal effective stresses), the effective confining stress at phase transformation is larger, leading smaller cumulative vertical strain of sand specimen. According to linear elastic finite element analysis on stresses induced by the self-weight of composite breakwater-foundation ground system, large shear stresses were introduced prior to shaking at the shallow part of the foundation ground. The profiles of vertical compression observed in centrifuge experiments can be explained with the elemental performance.The above-mentioned results indicate the significance of soil behavior after phase transformation, which may have been incorporated to less extent in current analytical schemes. In such analyses, for example, the constitutive parameters may often be determined based on the cyclic shear stress ratio - number of shear repetition relationship governed by pre-phase transformation process. Less

在1995年兵库县南部地震中，科比港的部分复合式防波堤在强烈的地面震动作用下出现了超过2.5m的沉降。本研究针对防波堤-地基及防波堤-地基饱和桑迪地基系统，在30-g及50-g离心力作用下，进行一系列的振动台试验，并加入黏性结垢，以探讨此大沉降的机制。结合各向异性固结松砂的不排水循环扭剪试验结果，探讨了地基变形特性。试验结果表明：（1）在离心模型试验中，复合式防波堤主体下方的地基在地震作用下会发生较大的轴向变形（竖向压缩和水平拉伸），这是由于不排水的累积剪切变形机制，一旦有效应力作用，这种机制就开始起作用 ...更多信息 达到相变状态。中、下层（深层）的垂直压应变大于浅层。(2)在循环扭剪试验中，当应力路径到达转换线后，竖向和扭转剪应变显著发展。随着循环剪切次数的增加，竖向应变逐渐累积，应变增量逐渐减小。初始固结应力比K='_z0&gt;<z0>/'_&lt;I 0 *&gt;（'_z0&gt;和'_z0&gt;<r0>分别为初始竖向和水平有效应力）越大，相变时的有效围压越大，试件竖向累积应变越小。通过对防波堤-地基复合系统自重应力的线弹性有限元分析，发现在地基浅部产生较大的剪应力，并在振动前产生较大的剪应力。离心试验中所观察到的垂直压缩剖面可以用元素特性来解释，上述结果表明了相变后土的特性的重要性，而在目前的分析方案中，这可能在很大程度上被考虑在内。在这种分析中，例如，本构参数通常可以基于由预相变过程控制的循环剪应力比-剪切重复次数关系来确定。少

项目成果

Kita, K. and Yamada, H.: "Centrifuge modeling of seismic settlement of composite breakwaters"Proc. 15th International Conference on Soil Mechanics and Geotechnical Engineering. 2. 1171-1174 (2002)

Kita, K. 和 Yamada, H.：“复合防波堤地震沉降的离心机建模”Proc。

北 勝利, 梶 聡明, 宮下勝也: "盛土-飽和砂地盤系の地震時沈下に関する遠心力載荷実験"土木学会中部支部平成13年度研究発表会講演概要集. 333-334 (2002)

Katsutoshi Kita、Satoshi Kaji、Katsuya Miyashita：“路堤饱和沙地系统地震沉降的离心力加载实验”日本土木工程学会中部分会 2001 年研究报告摘要 333-334 (2002)。

Kita, K., Kaji, T., Miyashita, K. and Ono, S.: "Centrifuge model tests on seismic settlement of embankments on saturated sandy ground"Proc. 37th Annual Congress of Japanese Geotechnical Society (in Japanese). 1813-1814 (2002)

Kita，K.，Kaji，T.，Miyashita，K.和Ono，S.：“饱和沙地基路堤地震沉降的离心模型试验”Proc。

Kita K., Kaji, T. and Miyashita, K.: "Settlement of embankments on saturated sandy ground due to strong shaking in a centrifuge"Proc. Annual Congress of Chubu-branch, Japanese Society of Civil Engineers (in Japanese). 333-334 (2002)

Kita K.、Kaji, T. 和 Miyashita, K.：“由于离心机中的强烈震动而导致饱和沙地上的路堤沉降”Proc。

K.Kita, H.Yamada: "Centrifuge modeling of seismic settlement of composite break waters"Proc.15th International Conference on Soil Mechanics and Geotechnical Engineering. 2. 1171-1174 (2001)

K.Kita，H.Yamada：“复合防波堤地震沉降的离心机模拟”Proc.15th International Conference on Soil Mechanics and Geotechnical Engineering。