Based on investigation on spot and geological analysis

an unstable rock masses of Xiloudu Hydropower Station may to be failure through two modes: shear-falling and rip-topple is proposed; and a mechanical model for calculation of stability by limit equilibrium theory is established; and the unstable rock masses deformation and failure characteristics are analyzed by numerical simulation. The results show: stability of the unstable rock masses is relatively bad if the failure mode is rip- topple

but is good if shear-falling. Based on stability analysis

the anchor reinforcement force is calculated as 12 306 kN when safety factor is 1.5 and the failure is rip-topple; and some reinforcement measures of the unstable rock masses are put for ward follows: fill hollow of rock and fill in cracks and prestressed anchor cables and anchor bolts combination reinforcement. The results of numerical simulation show that: effect of the reinforcement measures is better.