ABSTRACT
Assessment of seismic slope stability traditionally rely on pseudo-static approaches whereby the seismic loads are simplified as static loads and applied to the model. These analyses tend to be conservative and may result in unnecessary and costly countermeasures. In many such cases, the slope will experience some permanent deformation, but it will not fail. Therefore, a more realistic approach is to assess the slope stability using finite element analyses and defining the seismic load in terms of acceleration time histories. The limit state is then defined by acceptable levels of displacements and strains, and satisfactory functionality of the construction possibly affected by the slope movement. In this study, the dynamics module of the finite element software Plaxis 2D has been utilized for the analyses. The conventional Mohr-Coulomb model is employed to characterize the soil’s undrained behavior during the earthquake situation. This model is a linear elastic perfectly plastic material model in which the undrained shear strength is related to the soil’s effective vertical stress. The cyclic shear strength in the model was determined through calculations and specialized cyclic laboratory tests conducted on soil samples from the site. The estimation of shear strength includes the effect of the static shear stress due to gravity, which was confirmed by the lab test results. Nonlinear finite element analyses using this approach have yielded promising results, suggesting that the approach is a more realistic method for assessing seismic slope stability.
