PARAMETRIC STUDY OF ROCK SLOPES CONSIDERING EARTHQUAKE EFFECTS

To evaluate earthquake effects on rock slopes, pseudostatic and earthquake-induced displacement analyses were performed on plane and wedge type failures. Equations of the pseudostatic factor-of-safety (FS) were derived using the limit equilibrium method and parametric studies performed assuming various earthquake and rock-slope conditions. Relationships between FS and other parameters i.e. dip of failure, discontinuity, surface friction angle, pseudostatic (vertical and horizontal) coefficients, pore pressure, and direction of earthquake force were evaluated. Effects of the wedge factor on wedge stability were also considered. The critical earthquake coefficient (kc), is the pseudostatic horizontal earthquake coefficient when FS equals 1.0, was calculated for both plane and wedge failures. Relationships between kc and other parameters such as static FS, pore pressure, and the additional effect of vertical acceleration beyond the traditional horizontal acceleration, were evaluated. Then, earthquake-induced displacements were determined using double-integration of those parts of the accelerograms that lie above the kc, based on a strong ground motion record from the Loma Prieta earthquake. Results show, as peak acceleration and predominant period increase, and as duration becomes longer, the displacement becomes greater. Regarding pore pressure effects, as pore pressure increases, the static FS decrease, the critical earthquake coefficient is reduced, and the displacement becomes greater