摘要
已有试验研究表明,应力主轴循环旋转条件下砂土具有以下基本变形规律:(1)体应变随循环周数的增加而增加,但增加速率随其自身累积值的增加呈递减趋势;(2)剪应力–剪应变关系曲线存在明显的滞回圈,随循环周数的增加,滞回圈由未封闭型转化为封闭型;(3)应力主轴旋转条件下砂土的非共轴流动具有分段特征;(4)中主应力系数对应力主轴循环旋转条件下砂土的变形有重要影响,体应变的累积速率随中主应力系数的增加而增加。基于对上述应力主轴循环旋转条件下砂土的基本变形规律的认识,采用将主应力幅值变化以及应力主轴旋转产生的塑性变形单独加以考虑的办法,建立一个可合理考虑应力主轴循环旋转效应的砂土弹塑性本构模型,并对该模型在包含应力主轴旋转的多种复杂循环应力路径下的有效性进行验证。数值模拟结果与试验结果的对比表明:该模型可较好地考虑应力主轴循环旋转效应,对不同条件下各应变分量及体应变的发展历程能够进行较为合理的模拟,初步验证了该模型良好的适用性及有效性。
The deformation behavior of sands under cyclic rotation of principal stress axes can be concluded as follows based on the current test results. Firstly, the volumetric strain induced is increased with the increase of cycles number, yet its increase rate is lowered with its progressive accumulation. Secondly, the hysteretic loop is produced for the shear stress and strain components. And the unclosed hysteretic loop tends to be closed with the increase of rotation cycle numbers. Thirdly, the obvious non-coaxiality between directions of the plastic strain increment and stress shows segment characteristics. Finally, the effects of the intermediate principal stress parameter are significant, The accumulation rate of the volumetric strain is increased with the increase of the intermediate principal stress parameter under otherwise identical conditions. Based on the above physical fundamentals of sands subjected to cyclic rotation of principal stress axes, a new cyclic elastoplastic constitutive model for saturated sands aiming at describing the deformation behavior of sands due to cyclic rotation of principal stress axes is developed. And its effectiveness under the complex stress paths including cyclic rotation of principal stress axes is verified by comparison of simulation model and test results; and it is shown that the proposed constitutive model is capable of predicting reasonably the developments of strain components and the volumetric strain in various conditions including principal stress axes rotation.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2009年第9期1918-1927,共10页
Chinese Journal of Rock Mechanics and Engineering
基金
国家重点基础研究发展规划(973)课题(2007CB714108)
北京市自然科学基金资助项目(8061003)
关键词
土力学
应力主轴旋转
砂土
弹塑性本构模型
soil mechanics
principal stress axes rotation
sands
elastoplastic constitutive model
