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Study on the Strain localization behavior of water-saturated clay and the method of prediction

饱和水粘土应变局部化行为及预测方法研究

基本信息

批准号：
07650568
负责人：
OKA Fusao
金额：
$ 1.15万
依托单位：
GIFU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

It has been observed that geomaterials such as sand and clay deformshomogeneously in the early stage of loading and then the shear band occurs as a result of strain localization before failure. These phenomena have been well-known as the occurrence of slip surface and land slides. In order to describe and predict the failure phenomena of ground, it is quite necessary to clarify the mechanism of strain localization. In the present study, was studied a water saturated clay that is a difficult material to study because of the existance of pore water. Based on the experimental observations of shear bands during the undrained plane strain tests performed by multi-axial testing machine, the width and the direction of shear bands were discussed.Then, numerical simulations were carried out using the local and non-local viscoplastic constitutive model with strain softening. In the numerical analysis, the transport of pore water was included using the updated Lgrangian method and Biot'stheory of two phase materials. The following main conclusions were obtained :(1) Strain localization phenomena were numerically simulated by use of Adachi and Oka's viscoplastic constitutive model with strain softening.(2) The significant increase of the pore water pressure was observed along the shear bands. This trend is consistent with the experimentally observed results.(3) The shear bands develops significantly in the clay with small permeability.(4) The width of shear bands can be controlled by the second gradient of viscoplastic volumetric strain. The introduction of second gradient of viscoplastic strain make the material system more conservative.

砂土、粘土等岩土材料在加载初期均质变形，破坏前由于应变局部化而出现剪切带。这些现象被称为滑面和滑坡的发生。为了描述和预测地基的破坏现象，阐明应变局部化的机理是十分必要的。由于孔隙水的存在，饱和水粘土是一种较难研究的材料。根据多轴试验机不排水平面应变试验中剪切带的实验观察，讨论了剪切带的宽度和方向。然后，采用考虑应变软化的局部和非局部粘塑性本构模型进行了数值模拟。在数值分析中，采用更新的Lgrangian方法和Biot的两相材料理论考虑孔隙水的输运。得到以下主要结论：(1)采用Adachi和Oka的考虑应变软化的粘塑性本构模型对应变局部化现象进行了数值模拟。(2)孔隙水压力沿剪切带显著增大。这一趋势与实验观测结果一致。(3)在渗透性较小的黏土中，剪切带发育明显。(4)剪切带宽度可由粘塑性体应变第二梯度控制。黏塑性应变二次梯度的引入使材料体系更加保守。