应用Mohr-Coulomb、Lade-Duncan、广义Mises、Matsuoka-Nakai、AC-SMP强度准则，以及平面应变条件和相关联流动法则，建立了平面应变条件下土的强度准则。通过分析不同平面应变条件强度准则，确定最大、最小主应力比随土的内摩擦角的变化规律，分析了各强度准则的适用性。当内摩擦角小于30°时，各强度准则的差异性较小；当内摩擦角大于30°时，各强度准则的差异逐渐增大；内摩擦角较大时，广义Mises平面应变强度准则已不适用于描述土的破坏应力条件。同时，考虑黏聚力的作用，将无黏性土平面应变强度准则推广应用于黏性土，根据黄土的平面应变试验结果对各强度准则进行了初步验证，结果表明：Matsuoka-Nakai强度准则适用于描述砂土的强度，Lade-Duncan、AC-SMP强度准则可以很好地描述黄土的强度。

The strength criterion of soil in plane strain state is set up according to the strength criteria of Mohr-Coulomb, Lade-Duncan, general Mises, Matsuoka-Nakai, AC-SMP, plane strain condition and associated flow rule. The analyses of strength criteria in different plane states are made to determine the variation laws of the ratio of major principal stresses to minor principal stresses with internal friction angle. The applicabilit of every strength criterion is also analyzed. When the friction angle is less than 30°, the differences among different criteria are insignificant; otherwise, the differences become significant gradually. When internal friction angle is large enough, general Mises strength criterion in plane strain is not applicable to describe the failure of soil. Considering the cohesion effect, the strength criterion of cohesionless soil in plane strain state can be applied to cohesive soil and every strength criterion is verified by the plane strain test of loess. The results show that the Matsuoka-Nakai strength criteria is suitable for describing the strength of sand soil , and Lade-Duncan, AC-SMP strength criteria can characterize the strength of loess.