Kinematical Analysis of 3D Seismic Stability of Slopes in Unsaturated and Inhomogeneous Soils Using a Pseudodynamic Method

Earthquakes are recognized as one of the main causes of slope instability. Hence, assessment of slope seismic stability has attracted considerable attention from researchers. However, most studies currently focus on the seismic stability of dry or saturated homogeneous slopes and do not consider the spatial and time effect of the seismic waves. To fill this gap, under the framework of kinematical approach of limit analysis, this paper presents an analytical procedure for assessing the three-dimensional seismic stability of slopes in unsaturated and inhomogeneous soils, in which the variations in suction and effective unit weight profiles of soil were considered, and the soil cohesion was assumed to increase linearly with depth. A pseudodynamic approach was employed to take the dynamic characteristics of seismic waves into account. The expression of the factor of safety (F-s) for the slope was derived by the energy balance equation combined with the gravity increase method, and the minimum of F-s was optimized by a genetic algorithm. The methodology was well demonstrated by comparing the results with previous solutions and numerical simulations. Parametric analysis revealed that the sensitivity of slope stability with earthquake intensity becomes smaller with the increase in infiltration rate, whereas this does not vary with soil inhomogeneity. The enhancement of seismic intensity significantly weakens the influence of suction and soil inhomogeneity on slope stability. The soil amplification factor poses a great impact on F-s, especially for higher horizontal seismic coefficient and infiltration rates, while the effects of the shaking period and wave velocity are very small.