In worldwide, the most common triggering factor of rock landslides is extended and intense rainfall. However, different from the soil slope failure caused by softening action of infiltration rainwater, the mechanism of rock landslide in rainfall is not clear. From the view of fracture mechanics, the propagation of cracks on rock slope and the development of sliding surface were researched. Then based on hydraulics formulas and using Sweden arc method, the influence of crack water on stability of rock slope was quantitatively studied. Finally, an example was given to check the theoretical approach. The result shows that the development of sliding surface of rock slope is mainly caused by crack propagation under hydrostatic pressure when the stress intensity factor KI at crack tip is bigger than the toughness index of rock fractures Klc, and the failure of slope is the result of hydraulic action of crack water and the softening of materials on sliding surface when the depth of crack water is bigger than a minimum value hmin.
Among the triggering factors of postearthquake bedrock landslides, rainfall plays an important role. However, with slope variation, the mechanism of its effects on the failure of rock landslides is not dear. Here, from the viewpoint of fracture mechanics, and based on post-earthquake conditions, the mechanisms of crack propagation, water infiltration and development of the sliding surface were investigated. Then, according to the upper boundary theorem, the effects of water infiltrated into fractures on the stability of rock slopes were analyzed quantitatively. Finally, an example is presented to verify the theory. The results show that the propagation and coalescence of cracks and the lubrication of incipient sliding surfaces are the main causes of the failure of post-earthquake rock landslides in response to rainfall.
