平面应变状态下粘性土破坏时的中主应力公式

从平面应变状态下破坏时金属和无粘性土的中主应力公式出发，针对粘性土提出：在破坏状态下中主应力σ2使(σ1-σ3)莫尔圆和(σ2-σ3)莫尔圆有相同的摩擦发挥度和粘性发挥度。首先，推导出了粘性土的中主应力公式，当c，φ分别取0时，公式分别退化成金属和无粘性土的形式，然后，得到了平面应变和三轴压缩两种应力状态下强度指标的关系。

FORMULA OF INTERMEDIATE PRINCIPAL STRESS AT FAILURE FOR COHERENT SOIL IN PLANE STRAIN STATE

Based on the stress state at failure for coherent and frictional materials in plane strain state,it is hypothesized that the intermediate principal stress,s2,makes the Mohr circles of (s1-s2) and (s2-s3) have the same effect degree of cohesion and friction,and then the intermediate principal stress formula at failure for coherent and frictional materials in plane strain state is obtained. When coherence,c,is equal to zero,the formula becomes the one of frictional materials,and when frictional angle,j,is equal to zero,the formula becomes the one of coherent materials. At last,the relationships of strength indexes in plane strain state and those in triaxial compressive state are gained.