Seismic stability of gentle infinite slopes

Deterministic and probabilistic analyses of the stability of gentle infinite slopes subject to seismically induced excess pore pressures and inertia forces are developed. In the deterministic analysis, classical equations for infinite slope stability are rewritten to explicitly include excess pore pressure and seismic acceleration. Equations for the factor of safety are developed that include these factors. In the probabilistic analysis, the seismic acceleration, excess pore pressure, and effective friction angle are considered random variables. Acceleration peaks are considered Rayleigh distributed. Excess pore pressure is predicted using a model that considers Rayleigh distributed shear stress peaks. The friction angle is modeled with a Beta distribution. Acceleration and pore pressure development within the gentle infinite slope are assumed the same as those in a horizontal deposit of the same average thicknesss. Finite element analyses are performed to investigate the limits of this assumption. Results from both analyses are compared to documented case histories of lateral spreading.