地铁振动下黄土永久变形力学模型的研究

A Mechanical Model of Loess Permanent Deformation under Metro Vibration

以黄土地区地铁项目为背景,首先对地铁荷载长期循环作用下不同类型黄土的动变形特性分别进行了动三轴试验研究,得到了不同类型黄土累积塑性变形的发展规律,并提出了界定黄土临界动应力比的新方法,其次利用颗粒流程序建立了黄土土体动三轴试验的细观模拟模型,考察了其在模拟地铁列车荷载作用下的动力特性,并与前述相应的土工试验结果进行了比较和分析,在上述工作的基础上,基于建立的粘弹性模型-拓展的Burgers模型,推导建立了描述地铁行车荷载长期循环作用下黄土变形特性的力学模型。从而探讨了在土工试验与细观数值模拟有机结合的基础上建立土体力学模型的有效途径。

For subway project in loess area, experimental study of the dynamic strain behavior of different types of loess under metro-induced long-term cyclic loading is carried out by dynamic triaxial apparatus, and the accumula-ted plastic deformation development laws of different types of loess are obtained. In addition, a new definition method for the loess critical dynamic stress ratio is presented. Then, the microscopic numerical simulation model of the loess dynamic triaxial test is implemented by the particle flow code, and the dynamic strain characteristics of the loess under the metro-induced loads are investigated, and the results are analyzed by comparing to the results of the laboratory soil test. After that, the mechanical model for describing the dynamic deformation characteristics of the loess under the long-term cyclic metro-induced loadings is derived based on the extended Burgers four elements viscoelastic model. Our model has been successfully applied in the evaluation of the influence of metro-induced loading on the ancient building of Xi＇an.