Effect of vertical seismic coefficient on cohesive-frictional soil slope under generalised seismic conditions

In the present work, seismic performance parameters have been reviewed by considering the possible combined action of vertical and horizontal seismic loadings of the ground motion during the earthquakes. Analytical expressions of factor of safety, yield seismic coefficient and permanent seismic displacement of a cohesive-frictional soil slope have been developed by following deterministic sliding block approach in a two-dimensional pseudo-static framework. The slope with a planar failure surface is assumed to follow the Mohr-Coulomb criterion by considering a slice of unit thickness through the slope. For a given range of slope geometrical and soil parameters, the role of vertical seismic coefficient has been analysed in the presence of cohesion to investigate its effect on factor of safety, yield seismic coefficient, and consequently on the permanent seismic displacement of the slope through a set of graphical presentations. The results show that avoidance of vertical seismic component of the ground motion in the stability analysis may lead to severe slope failures. The general expressions proposed herein can be used to carry out a quantitative stability assessment of cohesive- frictional soil slopes during earthquakes in real-life projects.