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主应力轴循环旋转下高密实粉土稳定性影响研究

ISSN号：1000-7598
期刊名称：岩土力学
时间：0
页码：2957-2964
分类：TU435[建筑科学—岩土工程;建筑科学—土工工程]
作者机构：[1]河海大学岩土力学与堤坝工程教育部重点实验室,南京210098, [2]河海大学岩土工程科学研究所,南京210098
相关基金：国家自然科学基金资助项目（No.50639010 No.50909039）; 教育部博士点基金新教师基金项目资助（No.200802941019）; 中国博士后科学基金资助项目（No.20080441021）
相关项目：主应力方向旋转及与应力幅值耦合变化路径下粉土多相态性状及临界破坏准则建模研究

关键词：主应力轴循环旋转, 粉土, 高密实度, 相态点, 崩塌状态, 孔压, cyclic principal stress axis rotation, silt, high relative density, phase transformation point, collapse state, pore water pressure

中文摘要：

为研究主应力轴循环旋转对粉土性状影响,对长江入海口高密实饱和粉土进行了主应力轴180°转幅的循环旋转试验。试验发现,等向固结的高密实粉土在恒定动剪应力比的主应力轴循环旋转下能发生孔压达到初始围压水平的液化破坏,但液化前孔压开展会因动应力水平的不同而呈现以渐变相态点和激变相态点区分的3阶段变化形式,或仅以激变相态点区分的两阶段变化形式。试样应变开展则始终呈现由崩塌点区分的两阶段变化形式,且孔压激变相态点与应变崩塌点同步反映了土体结构崩塌状态,崩塌状态时主应变差双向幅值限制在0.2%～0.4%这一较小范围内。试样进行主应力轴旋转达到崩塌时的应力状态与频率无显著关系,可由p′-q空间中一条准不稳定状态线归一化。而以崩塌状态为终点进行归一化的主应力轴循环旋转下孔压振次曲线,可用修正的Seed公式进行较好拟合。

英文摘要：

Hollow cylinder samples tests were performed with high-density saturated silt from the sea entrance of the Yangtze River.The stress paths consisted of undrained cyclic principal stress rotation at the range of 180° with different shear stress ratio and frequency.It is found that isotropic consolidated samples would liquefy after cyclic principal stress axis rotation,which is featured by the excess pore water pressure reached initial effective confining pressure.Before the liquefaction,due to the different shear stress levels the development of pore water pressure was divided into three stages by graded phase transformation point and cataclysmic phase transformation point or two stages by cataclysmic phase transformation point.As for the development of strain components,it was divided into two stages by collapse point.Meanwhile the cataclysmic phase transformation point of pore water pressure and the collapse point of strain occurred simultaneously,which reflected the state of structure collapse.Besides the deviator strains when the collapse state occured were limited within a narrow range of 0.2%-0.4%.The stress state of collapse can be normalized in-space with a line when samples underwent cyclic principal stress axis rotation after isotropic consolidation.Furthermore the development of pore water pressure can be fitted well by modified Seed model in which the collapse state was used as the normalized denominator.

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