危岩是山区主要地质灾害，危岩破坏的本质是主控结构面在荷载作用下的断裂扩展。将主控结构面类比为宏观裂纹，运用断裂力学方法建立了主控结构面尖端断裂扩展方向岩石的联合断裂强度因子计算方法，其为第一类断裂强度因子和第二类断裂强度因子的函数，并结合危岩的断裂韧度，建立了危岩稳定性计算方法。进一步把滑塌式危岩、坠落式危岩和倾倒式危岩的破坏机理统一为压剪断裂及拉剪断裂，据此建立了第一类和第二类断裂强度因子的计算方法。实例分析表明，计算方法显示的危岩稳定状态更为客观、敏感。

Perilous rock is a type of geological disaster in mountainous areas. Research concerning perilous rock ruptures focuses on the expanding of control fissures in perilous rock under load action. Taking the control fissure in perilous rock as one crevice in a sample, a method employing fracture mechanics is established to calculate the union fracture strength factor along the rupture orientation at the terminus of a control fissure in perilous rock. The union fracture strength factor is a function of both the firstand secondtype fracture strength factors. We define the ratio between the fracture tendency of rock and the union fracture strength factor as the stability coefficient of perilous rock. Further, it simplifies the rupture mechanism of sliding, falling, and toppling perilous rock as pressureshear and tensionshear ruptures. We establish methods for calculating the firstand secondtype fracture strength factors. The applications show that the stability status identified by the method is more reasonable and sensitive.

国家自然科学基金资助项目(50678182)；重庆市自然科学基金重点项目(2008BA0015)