与土体稳定有关的工程问题诸如挡土结构物上的土压力、地基承载力以及土坡稳定性都与土的极限平衡状态相关 联。将土体一点（单元）的极限平衡条件推广，给出土体沿滑动面的极限平衡条件，证明了该条件的充分必要性。依据该条件，提出了有限元应力分析与极限平衡结合的有限元极限平衡法及土体稳定的安全系数，并明确了安全系数的物理意义，以评价土工结构的稳定性。随后，列举了该方法在土工结构稳定分析中的一些具有代表性的应用，证明了该法是有效的，可以用于分析岩土工程中的稳定问题。

In the engineering of soils stability, evaluation of earth pressure, foundation bearing capacity and slope stability are all related to limit equilibrium conditions. Limit equilibrium conditions of a soil element are extended to limit equilibrium conditions of a slip surface. Necessary and sufficient conditions required for determining the limit equilibrium state is proven. Based on the extension, a stability method combining limit equilibrium analysis with finite element stress analysis to provide a factor of safety is proposed. And the physical interpretation of the definition of the factor of safety is offered. Then several representative two-dimensional examples about soils stability are analyzed. The results show that the method could be used to analyze the stability of geotechnical structures.