Plane sliding failures of bedded rock slopes along the rock level occur frequently and in large-scale. According to the mechanism of bedded sliding

the plane failure is divided into two types

i.e. sliding rupture and hydraulic driving. According to plane rigid model

a sliding rupture landslide instable criterion is set up. The analysis results show that the landslide occurs when slope height is greater than the critical height. Groundwater flow through the passage that consists of the slide face and the trailing edge splay fracture of bedded rock slopes produces static water pressure of splay fracture

flotage and haulage of slide face. The analysis results show that the three water pressures above increase with the increasing of the water height of the splay fracture

and the slope will be instable once the water height of the splay fracture reaches to a critical value.