Insights into seismic slope deformation patterns using finite element analysis

Two-dimensional (2D), nonlinear total stress finite-element analyses were performed to investigate the seismic deformation patterns for soil slopes. The numerical parametric analyses consisted of 16 models with soil stiffness and strength parameters selected to isolate the impact of yield acceleration, depth of the sliding mass, natural period of the slope, and the slope angle on the deformation patterns. The results indicate that deeper sliding masses experience notable strain localization at the sliding mass depth, while shallow sliding masses experience more distributed straining throughout the entire soil mass. These factors result in larger displacements for the deep sliding masses relative to shallow sliding masses at small ky, whereas shallow sliding masses experience larger movements at large ky. The numerical simulations also show that an increase in shear wave velocity or decrease in slope height result in smaller displacements, although the effect of shear wave velocity is more significant. Importantly, the slope angle notably affects the resulting displacements and when ky is the same. A steeper slope increases displacements for deep sliding masses but reduces the movements for shallow sliding masses. The deformation patterns in the finite element simulations are inconsistent with the sliding block as-sumptions commonly employed in seismic slope stability analysis and point to the need to develop empirical slope displacement models from finite element simulations. However, this study shows that to capture fully the factors that affect seismic slope displacement the numerical models analyzed must consider a comprehensive set of slope models that vary the depth of the sliding mass, the shear wave velocity, the slope height, and the slope angle in addition to the yield acceleration.