Shear strength parameters have important effect on the slope stability of earth-rock dam. The Mohr failure envelope for rockfill material is obvious nonlinear particularly under the high stress linear and nonlinear shear strength theroies

value of the parameters

analysis method and safety factor criterion of nonlinear shear strength are discussed. The results of 171 sets of triaxial tests of rockfill reveal that the Duncan nonlinear strength theory is better than other models. The slope stability of 261.5 m high Nuozhadu rockfill dam is analyzed with three different shear strength criterions; the safety factors are almost equal and the positions of potential failure surfaces are also similar to each other. So the allowable safety factor base on linear criterion can be applied without any change when using nonlinear shear strength rules.