端部效应对土体三轴扭剪试样应力分布的影响

Influences of end-effect on stress of soil specimens in hollow cylinder test

利用ABAQUS模拟6个不同壁厚、不同高度的空心试样的扭剪过程,总结在柱坐标系下六个应力分量及三个主应力的分布规律,并重点对端部效应影响下应力分布不均匀的性质进行分析。结果表明,径向应力σr和中主应力σ2在两端部各约10%的高度范围内,环向应力σθ、轴向应力σz、横截面上的扭剪应力τzθ以及主应力σ1和σ3在两端各约20%的高度范围内受端部效应影响而分布不均匀;试样端部的真实应力与中间段应力相比存在误差,其中端部的σr和σθ相对于中间段会减小,减幅分别约为20%、30%,σz和τzθ产生的误差大小则与试样的厚度成正相关;为减小端部效应的影响,对空心扭剪试样建议的高宽比为2.5,内外径比值为0.8。

ABAQUS is used to simulate 6 different hollow specimens with different wall thickness and height, six stress components and three principal stress in a cylindrical coordinate system were summed up, and the end effect of stress distribution of properties were analyzed. Results showed that, the intermediate principal stress σ2 and radial stress σr within each of the height of about 10% at the ends, circumferential stress τzθ, axial stressσ1 and σ3 of about 20% at each end are under the influence of end effect. There are errors between real stresses of the sample end and middle, the decrease extent of σr and σθ are about 20% , 30%, respectively, and the errors of σz and τzθ are positively correlated with the thickness of the specimen. In order to reduce the effect of end - effects, the ratio of height to width is recommended to be 2.5, the ratio of inner to outer diameter is 0.8.