危岩崩塌实际是危岩主控结构面断裂扩展问题。基于主控结构面的断裂力学模型提出了危岩断裂稳定性判定方法，建立了以联合应力强度因子为指标的危岩稳定系数，推导得出危岩主控结构面尖端受力分布形式及计算表达式，提出了危岩主控结构面尖端断裂力学模型，推导得出主控结构面尖端联合应力强度因子计算公式。重庆万州首立山危岩断裂稳定性计算结果表明，计算结果与现场情况较吻合，采用文中的断裂稳定性计算方法比现有的地质灾害防治工程设计规范更加安全、客观、实际。

The collapse of unstable rock is actually the problem of fracture and extension in dominant fissure of unstable rocks. Based on fracture mechanics model of dominant fissure, this paper puts forward a fracture stability determination method for unstable rocks, and establishing stability coefficient by the index of union stress intensity factor. By this method tip stress distribution forms of dominant fissure and its calculation expression are deduced. Fracture mechanism model of tip in dominant fissure for unstable rocks is proposed; and then for this calculation method union stress intensity factor in tips of dominant fissure is deduced. Fracture stability calculation results of unstable rocks in Shouli Mountain, Wanzhou Area, Chongqing show that the calculation results fit well with the field situation, so as to show that the fracture stability calculation method proposed is more security, objective and practical than the existing “specification method”.