中文摘要：

以热力学和连续介质力学的应力理论为基础，从非饱和土的土骨架平衡方程出发，导出了一系列应力状态变量，目前文献中所使用的应力状态变量都在其中。研究发现：非饱和土的应力状态变量有多种组合形式（5组以上），不是惟一的；大多数应力状态变量与土的孔隙率、饱和度等物性指标孪生相伴；所有应力状态变量都具有应力的量纲，单纯孔隙率或饱和度及其组合都不构成应力状态变量；简化的Bishop有效应力公式和Fredlund倡导的两个应力状态变量都是简化了的应力状态变量，前者忽略了孔隙率的影响，而后者忽略了与孔隙率及饱和度的关联性。在选择应力状态变量时应考虑理论合理、应用方便、逻辑关系正确的原则，还应做一定的验证工作。

英文摘要：

Based on thermodynamics and stress theory of continuum mechanics, a series of stress state variables of unsaturated soils, which covered all stress state variables used in literature, are deduced from the equilibrium equation of soil skeleton. It is shown that there are more than five combinations of stress state variables for unsaturated soils, most of which are related to physical properties such as void ratio and degree of saturation. Stress state variables should have dimensions of stress, while void ratio, degree of saturation and their combination could not be regarded as stress state variables. Both the simplified Bishop＇s effective stress equation and the Fredlund＇s two stress state variables are simplified forms of stress state variables. The influence of void ratio is not included in the simplified Bishop＇s effective stress equation, while the dependence on void ratio and degree of saturation are neglected in the Fredlund＇s two stress state variables. When choosing stress state variables for unsaturated soils, rationality in theory and convenience in application as well as correctness in logic should be taken into account.