Dynamic UH model for sands and its application in FEM
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摘要: 饱和砂土在循环载荷下具有复杂的应力应变关系, 通常表现出液化过程中的大变形以及往返活动性现象. 为简单有效地模拟上述特性, 在超固结UH模型的基础上, 将其扩展为可考虑砂土动力加载下的本构模型. 具体做法有3点: (1)改变屈服面椭圆长短轴之比, 将比值定义为反映应力诱导各向异性转轴斜率的函数; (2)引入旋转硬化规则, 用来反映应力诱导各向异性; (3)建立一个与旋转硬化规则以及临界状态特性相协调的统一硬化参数. 模型预测结果表明, 所提动力模型可简单、有效地用于砂土在动力载荷下应力应变关系的模拟. 最后将该动力UH模型嵌入到有限元软件中, 三维地基的动力加载模拟结果表明, 动力UH模型可方便地应用于岩土工程实践中.
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关键词:
- 循环加载
Abstract: Complex stress-strain relationship is exhibited forsaturated sands under cyclic loading conditions. The large deformation andphenomena of cyclic mobility occur during liquefaction. In order to simulatethe above mechanical behaviors of sands simply and effectively, a dynamicconstitutive model which can be used to describe stress-strain relationshipfor sands under dynamic loading conditions is proposed on the basis of UHmodel for overconsolidated clay. There are three specific revisions in thispaper: (1) Ratio between the length of long axis to that of short axis forellipse yielding surface is defined as the function for slope of rotationalaxis which can be used to reflect stress-induced anisotropy. (2) Rotationalhardening rule is introduced into the proposed model to reflectstress-induced anisotropy. (3) A unified hardening parameter is establishedby coordinating rotational hardening rule and critical state behavior.Comparison between model prediction and test results demonstrates that theproposed model can be conveniently used to simulate stress-strainrelationship under dynamic loading conditions for sands. Dynamicconstitutive model is also embedded into FEM program. Stress-strainrelationship of sands for soils foundation is simulated. Simulated resultshave shown that the proposed model can be applied into geotechnicalengineering practice conveniently.-
Key words:
- cyclic loading
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