Simplified Procedure for Coupled Seismic Sliding Movement of Slopes Using Displacement-Based Critical Acceleration

Downward movement of sliding soil mass in earthquake-induced earth slopes may gradually improve the system's stability. Hence, significant change in critical (or yield) acceleration of the slope is anticipated. The existing simplified coupled procedures, however, assume a constant critical acceleration in stick-slip sliding analysis. Fully coupled sliding block analyses with continuously increased critical acceleration were conducted to estimate earthquake-induced permanent displacement of earth slopes. The sliding mass was assumed as a flexible chain moving along the planes with gradually gentler inclinations. The measured data of a slope failure test in a shaking table were used to validate performance of the model. The proposed approach was compared with the previous procedures, which ignored critical acceleration changes due to downward movement of the sliding mass. Accordingly, earth slopes with smaller slip length were more influenced by the downward movement modification, especially in small amounts of initial yield acceleration. A semi-empirical equation is presented based on more than 425,000 modified-coupled analyses of several hundred strong ground motion records. An equation was then developed as a function of acceleration ratio, period ratio, slip length, peak ground velocity, Arias intensity, and earthquake magnitude. Predictions of the developed equation were compared with the available equations, which ignore the role of increased critical acceleration. It is shown that a majority of the previous models predict conservative estimates of seismic permanent displacements compared with that of new equation. The proposed semi-empirical model can be used as an alternative equation of seismic displacement for deterministic and probabilistic evaluations of earthquake-induced landslide hazard.