Research on the Mechanism of Slope Failures in Partially Saturated Slopes during Earthquakes

部分饱和边坡地震破坏机理研究

基本信息

批准号：
18560487
负责人：
NAKATA Yukio
金额：
$ 1.75万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18560487/
关键词：
earthquake unsaturated soil slope dynamic behavior cyclic test online test degree of saturation residual displacement

项目摘要

Recent large-scale earthquakes, such as the 2004 Niigata Chuetsu Earthquake in Japan, have highlighted the role of antecedent rainfall on the seismic instability of slopes. Days prior to the occurrence of the earthquake, the region was subjected to large amount of rainfall. The saturation of the ground and the increase in water table could have led to decrease in the strength of the soil. These may have contributed to the scale and number of earthquake-induced failure of slopes in the region. Unfortunately, most studies concerning thquake-induced slope failures have focused on extreme conditions : dry slopes or completely saturated slopes. There has not been much quantitative investigation on the effect of degree of saturation on the cyclic shear response of sloping grounds. With the advent of performance-based design, it was believed that considering the effect of degree of saturation of the soil could lead to a more accurate evaluation of soil response during earthquakes.In this rese … More arch, three sets of tests were conducted on soil samples under varying degrees of saturation (S_r) and initial static shear stresses (σs). The samples employed were decomposed granite soils, more popularly referred to as "Masado" in Japan, obtained in Iwakuni City, Yamaguchi Prefecture. Note that only particle sizes smaller than 2 mm were used because of the limitation of testing equipment. The material was silty sand with fines content, F_c=10%. Since the soil water characteristic curve indicated abrupt change in suction from S_1=30%-60%, samples with S_r=30%, 60% and 100% were considered in the tests.Initially, simple shear tests and online pseudo-dynamic earthquake response tests were conducted to analyze the earthquake response characteristics of Masado soils with different inclinations (i.e., different initial shear stress ratios) and initial degree of saturation. Results indicated that the higher the degree of saturation and/or the steeper the slope, the lower the cyclic shear strength, leading to larger residual displacements of slopes. Next, undrained cyclic triaxial tests under different degrees of saturation and initial shear stresses were conducted. The results showed that for unsaturated specimens, large strength degradation typically observed in fully saturated specimens were not observed. Moreover, the combination of initial static shear stress and applied dynamic stress determined the mode of failure (extension or compression) of the specimen.Finally, these experimental results were used in conjunction with pseudo-static slope stability analysis and a modified version of the Newmark sliding block model to estimate the magnitude of seismic-induced displacements of partially saturated embankment slopes under different earthquake loads. Although simplified in nature, the example calculations clearly showed the effect of degree of saturation on the magnitude of seismic-induced displacement of embankments. These illustrated the need in considering the effect of degree saturation on the post-failure behavior of embankments and slopes. Less

最近的大规模地震，例如日本的2004年尼加塔·奇图库（Niigata Chuetsu）地震，强调了降雨对插槽地震不稳定的作用。地震发生前几天，该地区受到大量降雨。地面的饱和度和地下水位的增加可能导致土壤强度降低。这些可能导致了该地区地震诱导的插槽故障的规模和数量。不幸的是，大多数研究涉及Thquake引起的斜率故障的重点是极端条件：干插槽或完全饱和的插槽。饱和度对倾斜地面的环状剪切响应的影响并没有太多的定量投资。随着基于绩效的设计的发展，人们相信，考虑到土壤饱和度的影响可能会导致地震期间对土壤反应的更准确评估。在此问题中……更多的拱门，在不同程度的饱和度（S_R）（S_R）和初始静态剪切应力（σs）下，对土壤样品进行了三组测试。样品是分解的花岗岩土壤，在山口县伊瓦库尼市获得的花岗岩土壤通常称为“马萨多”。请注意，由于测试设备的限制，仅使用小于2 mm的粒度。材料是粉质砂，含量为罚款，F_C = 10％。由于土壤水特征曲线表明任务从S_1 = 30％-60％的突然变化，因此在测试中考虑了S_R = 30％，60％和100％的样本。在本质上，进行简单的剪切测试和在线伪动态地震响应测试，以分析具有不同的包含率的压力和不同程度的均等（I.），以分析与不同的含量分析（I.结果表明，满意度和/或钢筋的斜率越高，环状剪切强度越低，导致散射的残留位移越大。接下来，在不同程度的满意度和初始剪切应力下进行了未排水的循环三轴测试。结果表明，对于不饱和标本，未观察到在完全饱和的样品中通常观察到的较大强度程度。此外，初始静态剪切应力和应用动态应力的组合确定了样品的故障模式（扩展或压缩）。在本文中，这些实验结果与伪静态斜率稳定性分析结合使用，并将其修改后的Newmark Sliding块模型的修改后的隔离式隔离量的变化量的隔离量的幅度估计，以估算隔离型的幅度不同。该示例计算清楚地表明了饱和度对地震诱导的路堤位移大小的影响。这些说明了考虑程度饱和对路堤和斜坡的失败行为的影响的需求。较少的