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A long-term delayed consolidation settlement of naturally deposited soil and its prediction and improvement methods

自然堆积土的长期延迟固结沉降及其预测与改进方法

基本信息

批准号：
16360236
负责人：
ASAOKA Akira
金额：
$ 9.02万
依托单位：
Nagoya University
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-16360236/
关键词：
Clay Soli structure Consolidation Overconsolidation Anisotropy Elasto-plastic constitutive equation

项目摘要

In a naturally deposited clay foundation subject to embankment loading, a delayed settlement can often be observed after the embankment's completion, sometimes also showing acceleration over time. The settlement cannot be always predicted from the laboratory test results even with the undisturbed sample. The prediction of the settlement and the long-term period were always underestimated.In the present study, the compression index ratio Cd Ccr was defined by the ratio of the compression index of the undisturbed sample Cc to remolded sample Ccr, and the in-situ settlement data and the laboratory test results on the about 50 expressways are estimated and classified by the compression index ratio Cd Ccr and sensitivity index St. The mechanism of the large delayed settlement is discussed described by using a soil-water coupled finite deformation analysis with the Supre/subloading Yield Surface Cam-clay model (SYS Cam-clay model). The new findings are as follows :1)The clay, which exhibits a long-term large settlement beyond the prediction, can have high sensitivity St, the value of which is more than 8.0 and high the compression index ratio Cd Ccr, more than 1.5. Through the simulation by the SYS Cam-clay model, the clay is a high degree of initial structure and show fast decay of the structure.2)The in-situ compression behavior was predicted from the laboratory test assuming that both the consolidation yield stresses are the same, and the mechanism of the long-term large settlement was discussed taking the sample disturbance into consideration.3)The occurrence of in-situ secondary/delayed consolidation of clay foundation in Nagashima can be described by using a soil-water coupled finite deformation analysis with the SYS Cam-clay model, and it provide that it is necessary to determine the in-situ initial condition from the laboratory test taking the sample disturbance into consideration.

在承受路堤荷载的自然沉积粘土地基中，路堤完工后通常会观察到延迟沉降，有时还会随时间推移出现加速沉降。即使采用原状土样，也不能根据室内试验结果预测沉降量。在本研究中，压缩指数比Cd Ccr定义为原状样Cc与重塑样Ccr的压缩指数之比，和内-根据近50条高速公路的实测沉降数据和室内试验结果，采用压缩指数比Cd Ccr和敏感指数St对高速公路的沉降进行了估算和分类，采用土-水耦合有限变形分析方法，采用预压/预压屈服面剑桥模型（CAM-clay model），对大滞后沉降的机理进行了探讨。新的发现如下：1）表现出超出预测的长期大沉降的粘土可以具有高敏感性St，其值大于8.0，并且具有高压缩指数比Cd Ccr，大于1.5。通过对试验结果的分析，发现该土具有较高的初始结构性，且结构性衰减较快。2）通过室内试验，在假定两种固结屈服应力相同的条件下，并结合试样扰动对长期大沉降的机理进行了探讨。采用土-水耦合的有限变形分析方法，采用剑桥-粘土模型，可以描述长岛地区粘土地基的延迟固结，并提出了在考虑试样扰动的情况下，通过室内试验确定原位初始条件的必要性。