Based on the investigation data of the reservoir

the mechanical model of slope stability of the right bank dam shoulder is set up; and the computational formulas are deduced for calculating the cross-sectional area of each slip block. Then

slope stability analyses of both definite method and reliability method are carried out by using unbalance thrust force transfer method. The influences of the variability of shear strength parameters and geometric parameters of slip surfaces on slope stability are discussed in the reliability analysis. It is demonstrated that the variability of geometric parameters of slip surfaces has large effect on the reliability index and failure probability. Therefore

it is necessary to pay much attention to the variability of geometric parameters of slip surfaces as well as the variability of slip surface shear strength parameters.