长期循环荷载作用下砂土的棘轮应变累积行为及描述方法

项目名称： 长期循环荷载作用下砂土的棘轮应变累积行为及描述方法

项目编号： No.41302219

项目类型： 青年科学基金项目

立项/批准年度： 2014

项目学科： 天文学、地球科学

项目作者： 贾鹏飞

作者单位： 西北大学

项目金额： 25万元

中文摘要： 本项目面向快速轨道交通中的核心问题，以长期循环荷载作用下砂土的棘轮应变累积行为为主要研究内容，通过循环三轴试验研究塑性体应变和偏应变的累积规律，以及由累积塑性体应变和偏应变所确定的塑性应变累积方向(循环剪胀特性)的发展规律，揭示轨道结构基础与土体动力相互作用过程中由于棘轮效应产生不均匀沉降(差异沉降)的物理机制和力学机理；借鉴Suiker循环压密模型和Bochum试验累积模型的优点，采用合适的模式描述循环荷载作用下塑性应变增量的变化规律以及循环流动准则，以期提出一个更加合理的累积模型来描述砂土在长期循环荷载作用下的棘轮应变累积行为；结合循环三轴试验(排水和不排水)、共振柱试验、以及固结压缩试验研究所提模型中弹性(伪弹性)刚度的确定方法，并通过数值方法对多组循环三轴试验结果进行模拟，验证所提模型的预测能力和适用性；为快速轨道交通路基动力沉降分析提供理论依据和技术支持。

中文关键词： 高周循环荷载；砂土；应变累积；棘轮效应；累积模型

英文摘要： The main content of this research is distributed ratcheting stain accumulation behaviour of sands under long-term cyclic loading, which belongs to the core issue in the express rail traffic (e.g. high-speed railway, inner-city railway, city underground railway ect.) engineering. Cyclic triaxial tests will be carried out to study the evolution of accumulated plastic volume strain and deviator strain, and the direction of the plastic strain accumulation (cyclic dilation) will also be studied through cyclic triaxial tests. These studies will help us understand the physical mechanisms of asymmetric settlements (differential settlements) as a result of ratcheting during the dynamic interreaction between the foundation of structures and soils. If the asymmetric settlements are over the allowable limit, the inclination even damage maybe occur. Second, on the basis of Suiker cyclic densification model and Bochum test accumulation model, a more reasonable constitutive model will be proposed, which will use a proper function to describe the change trend of plastic stain increment and the direction of strain accumulation. Finally, a comparison of the measured data with predictions made by the proposed model is given. This research work provides a solid theoretical and thechnical support for the dynamical analysis on settle

英文关键词： high-cyclic loading；sands；strain accumulation；ratcheting；accumulation model