Yanchishan Hill is located in the east of Jinan city. Because of perennial mining

deformations and slumps have occurred locally within the hillside of Yanchishan. There are lots of factors influencing the stability of the western slope. The potential instability of slope poses damage to the developing district lying near the west of Yanchishan slope. This paper analyses the mechanism controlling the stability of the high slope of Yanchishan using the preferred plane theory. The analytical results indicate that there are 4 sets of preferred planes and 3 groups of preferred isolated bodies dictated by the preferred plane assembling. The slope stability is controlled by the preferred planes and preferred isolated bodies and 5 failure mechanisms is formed. Under the adverse conditions such as intense or prolonged precipitation

the strength of rock mass will decrease and the plastic area will extend. Vertical cracks at the top of slope and the interface between the dredger fill and dioritic rock mass constitute a potential slip surface. Finally

the slope stability is quantitatively evaluated by finite element method

and the evaluation results agree well with what the preferred plane method predicts. It is concluded that the Yanchishan slope is potentially unstable and corresponding treatment measures need to be carried out.