Abstract:Two types of heave-destruction of foundation pit induced by less inserting depth have been summed up;and then the formulas for safety factor of heave-resistant stability calculated through arc-sliding method have been researched. The applicability and localization of calculating formulas of safety factor of heave-resistant stability that are widely applied to design of foundation pits have been analyzed;and four modified formulas,which are more applicable and rational,have been presented. Sensitivity of the new formulas is analyzed. The relation between deformation of deep braced excavation and the value of Ks has been studied by finite element method,through which mutation of excavation deformations is found at some value of Ks. Based on the previous research,it is proven that the deep braced excavation has an optimum inserting ratio and that the formulas have are simple,convenient for application to design and construction of foundation pit.