Abstract: This paper presents the threedimensional numerical analysis results using elastoplastic constitutive model on the stress-deformation in a rock slope under seismic conditions. In the analysis, the Mohr Coulomb failure criterion, the nonlinear time history analytical method as well as the strength reduction theory were used and the stability of the rock slope is evaluated by the sudden displacement as well as the development of a throughout plastic zone in the model. The viscoelastic artificial boundaries were established in the model to absorb the radiational damping effect from the foundations and the effect of the gravitational field of the rock slope and the fracture zone or rock vein on the seismic stability of the rock slope were also considered. The results show that: under the sudden displacement criterion, the dynamic stability factor of safety corresponding to a sudden change in the displacement of the characteristic points along the slope elevation is greater than 1.35; when plastic zone penetration criterion used, the factor of safety increases with the gradual increase of the plastic yield zone. When the factor of safety is low, the plastic yield zone is relatively small; When the safety factor reaches 1.35, a large number of yielded plastic zones appear locally at the toe of slope. With the further development of the locally isolated yielded plastic zones at the excavation slope position gradually grow connected; Slope failure will occur when the factor of safety exceeds 1.5. Combined consideration of sudden change in displacement and the development of a throughout plastic zone in the slope failure consideration, a satisfactory dynamic stability factor of safety should be 1.35.

Key words: viscoelastic artificial boundary, rock slopes, strength reduction method, finite element method, stability