摘要
土体在剪切变形过程中产生主应力方向的旋转时,主应变率方向与主应力方向之间存在着非共轴现象,然而,传统的弹塑性本构模型并不能考虑该现象的影响。通过在传统本构模型屈服面的切线方向增加一项非共轴塑性应变率,即可实现对非共轴现象的反映。利用有限元软件ABAQUS的材料子程序接口UMAT,通过显式积分算法和自动分步方法实现了非共轴模型在有限元分析中的应用。首先,对砂土的单剪试验进行数值模拟,预测了主应力方向和主应变率方向之间的关系,所得结论与试验结果较为吻合。然后,针对吸力桶与砂质地基间的相互作用问题进行弹塑性有限元计算,分析了土体主应力方向在剪切变形过程中的旋转规律,以及桶体的端部阻力、侧壁摩擦阻力和顶部阻力在变形过程中的变化规律。最后,检验了非共轴现象对地基承载力计算结果的影响。研究结果表明,所开发的非共轴模型对非共轴现象具有良好的预测能力。
When the direction of soil principal stress rotates during the shearing process,there is a non-coaxial phenomenon between the direction of principal strain rate and the direction of principal stress,but the conventional elastoplastic constitutive model could not take this phenomenon into consideration.In order to reflect the non-coaxial phenomenon,a non-coaxial plastic strain rate term is added on the tangential direction of conventional constitutive model′s yield surface.Based on the material subroutine UMAT of FEM software ABAQUS,the non-coaxial model is numerically implemented into the application of FEM analysis using automatic substepping scheme with explicit integral algorithm.Firstly,a numerical simulation of sand＇s simple shear test is carried out to predict the relationship between the direction of principal stress and the direction of principal strain rate,and the conclusion is in good agreement with the experimental results.Secondly,the problem of interaction between suction bucket and sand foundation is taken into the elasto-plastic FEM analysis,the rotation law of the direction of principal stress and the variation trend of resistance of the bucket＇s top,tip and side walls are researched.And then,the influence of the non-coaxial phenomenon on the numerical result of the foundation＇s bearing capacity is checked.It can be concluded that the non-coaxial model used in this paper has a good predictive ability of the non-coaxial phenomenon.
出处
《海洋工程》
CSCD
北大核心
2012年第2期87-94,共8页
The Ocean Engineering
基金
国家自然科学基金资助项目(51079018)
关键词
非共轴
本构模型
吸力桶
弹塑性
地基承载力
non-coaxial
constitutive model
suction bucket
elasto-plastic
bearing capacity
