土体平面应变方向上的主应力

The principal stress of soil in the direction of plane strain

通常认为在土体平面应变的方向上的主应力总是中主应力 ,而文中的试验结果和理论分析表明 :在土体接近破坏时 ,土体平面应变的方向上的主应力是中主应力 ;在保持两个主动主应力比值较小加载时 ,土体平面应变的方向上的主应力一般是小主应力 ;当两个主动主应力减载到应力值或应力水平很低时 ,平面应变方向上的主应力可能变成大主应力 ,并且发生减载屈服。这是由土受力变形的弹塑性性质决定的。

The principal stress of soil in the direction normal to plane strain is usually considered to be the intermediate principal stress,however it is true only when the sample is nearly failed in plane strain condition. In present paper, based on test results and theory analysis, some interacting conclusions are drawn. In the plane strain loading tests where the ratio of major active principal stress to minor one keeps a small constant, the principal stress of soil in the direction normal to plane strain is generally the minor principal stress. In the plane strain tests where active principal stresses decrease to small values, the principal stress of soil in the direction normal to plane strain may become the major principal stress, that indicates the yielding of soil under decreasing load and results from elasto plasticity of soils.