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Mechanism of shear band formation in Ko-consolidated clayey soil--experimental and theoretical approaches by naked hollow-cylindrical soil specimen--

Ko固结粘土剪切带形成机制--裸空心圆柱土样的实验与理论方法--

基本信息

批准号：
02805057
负责人：
OHTA Hideki
金额：
$ 0.7万
依托单位：
Kanazawa university, Dept. of Civil Engineering
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

The purpose of this research is to give theoretical and experimental bases to capture the failure mechanism of the ground material. The development of localized deformation and its prominence may cause the instability of foundation ground and lead to its failure. Such localized deformation is commonly observed during large deformation of soils, for instance, slip lines observed in the laboratory, the sliding failure of embankment foundation and the fault caused by the orogenic movement. The simulation of shear bands formation may lead to clarify the occurrence mechanism of their phenomena and also make it possible to explain the soil behaviors consistently from the beginning of deformation up to the limit failure state.In this research, the theoretical basis of bifurcation problem is summarized and classified in regard to the formation of shear band. In particular, the mathematical conditions of the formation of shear band under axisymmetric condition discussed relating to the non-coax … More iality of the elasto-plastic constitutive model for Ko-consolidated clay specimen proposed by Sekiguchi and Ohta (1977). As to experimental study, a new shear test equipment is designed and developed to observe the development of shear band with increase of shear strain in the axisymmetric soil specimen. The distinctive features of it are : 1) able to carry out Ko-consolidation, 2) able to measure Ko-value, 3) able to observe the development of shear bands (slip lines), because a rubber membrane is not used (naked specimen like the unconfined compression test specimen), 4)able to estimate parameters in terms of effective stresses, because the pore water pressure can be measured using measurement system of negative pressure with the ceramic disk.It was found in this research that the apparent strain-softening stress strain relation in axisymmetric soil specimen is not an essential phenomenum of material but the consequence of inhomogeneous distribution of stress and strain in the specimen as a boundary-value problem. Less

本研究的目的是为揭示地面材料的破坏机理提供理论和实验依据。局部变形的发展及其突出性可能导致地基失稳，导致地基破坏。这种局部变形常见于土体的大变形中，如室内观测到的滑移线、路堤地基的滑动破坏、造山运动引起的断层等。剪切带形成过程的模拟有助于阐明剪切带现象的发生机理，也可以对土体从变形开始到极限破坏状态的行为作出一致的解释。特别讨论了非同轴…在轴对称条件下形成剪切带的数学条件Sekiguchi和Ohta(1977)提出的Ko固结粘土试件的弹塑性本构模型更符合实际。在试验研究方面，设计并研制了一套新型剪切试验装置，用于观察轴对称土样中剪切带随剪应变的变化规律。它的显著特点是：1)能够进行Ko固结，2)能够测量Ko值，3)能够观察剪切带(滑移线)的发展，因为不使用橡胶膜(像无侧限压缩试件一样的裸试件)，4)能够根据有效应力估计参数，研究发现，轴对称土样的表观应变-软化应力应变关系不是材料的本质现象，而是试件内部应力应变分布不均匀的结果，是一个边值问题。较少