以岩质边坡倾倒破坏地质过程分析为基础，假定岩体倾倒破坏过程中始终处于力平衡状态以及层面上下缘存在着阻止剪切错动破坏的层间阻力，岩体中某一点应力根据弹性力学原理可以简化为垂直的自重应力和水平的侧应力，将倾倒破坏岩体的力学过程概化为平面应变模型，并基于最大拉应力破坏准则，推导出岩体倾倒折断破坏深度的临界公式。实例计算及讨论表明，倾倒破坏临界深度理论适用范围广，并且考虑了边坡水平应力，计算结果更加符合实际破坏特征。另外，边坡坡角、岩层倾角及厚度对岩体倾倒破坏深度影响具有较大影响，特别是层面倾角50°～70°时边坡最易发生倾倒破坏。

On the basis of geological process analysis in the topple failure of rocky slope, provided that the equilibrium state and interlamination resistance which prevent shearing offset damage do always exist between upper and lower edges of stratum, the stress of some point on rock mass can be simplified to vertical self-weight and horizontal lateral stress. In this way, the formula of the critical depth for topple failure can be deduced by turning the geological and mechanical process into plane strain model and adopting maximum stress failure criterion. Living example and discussion show that the critical depth theory about toppling failure applied widely, conform to actual failure，and also take horizontal stress into account . Besides, the slope and stratum dip angle as well as the thickness have greater influence on rock toppling failure, especial the slope of stratum angle between 50° and 70° is the most likely to topple.