Critical Slope Profile in Purely Cohesive Soil under Seismic Conditions: An Alternate Stability Criterion

This study explores the efficacy of an alternate stability criterion to investigate the critical stability of purely cohesive soil (ϕ=0°) slopes under seismic excitation. By superseding the traditional stability indices, the present criterion addresses the slope profile required to preserve the critical equilibrium condition with a factor of safety (FS) equal to 1.0. Such a slope profile is termed the critical slope profile (CSP). To derive the CSP, a unified theoretical framework is developed using the stress characteristics method (SCM) and the original pseudodynamic (OPD) approach. The SCM negates the necessity of any presumed failure mechanism in the analysis. The OPD approach captures the realistic behavior of the CSP under seismic incidence. Accordingly, an extensive parametric analysis examines the impact of soil cohesion, surcharge, seismic accelerations, seismic wave velocities, and amplification factors on the potential variability in CSPs. This study highlights the conservatism of the pseudostatic (PS) approach over the OPD approach. Compared to existing solutions, the CSPs in this study exhibit a steeper profile than conventional linear slopes. Such insights help design new slopes and guide practicing engineers in taking preventive measures for unstable slopes. For illustration, a field case study is performed based on the present CSP concept, predicting the stability state of the Narbonne embankment of France.