A generalized log-spiral-Rankine limit equilibrium model for seismic earth pressure analysis

A method of slices for estimating seismic earth pressures due to earthquake-induced pseudo-static body forces is presented herein. The method is based on a limit-equilibrium approach, and utilizes a composite logarithmic spiral failure surface along which the Mohr-Coulomb failure criterion is enforced. The model explicitly accounts for the magnitude of earthquake acceleration, the structure's height, the backfill soil properties (e.g., internal friction angle, and cohesion), and the mobilized interface friction angle between the backfill and the earth-retaining structure. Majority of the previous analytical (or semi-analytical) methods neglect the effects of soil's cohesion and/or use simple planar failure surfaces. Parametric studies conducted with the proposed method, as well as a number of prominent others indicate that the aforementioned simplifying assumptions often yield significantly different estimates of seismic earth pressures from the more general model proposed here, and that they may lead to sub-optimal or unsafe designs.

► An analytical model for assessing seismic earth pressures is proposed.
► The effects of inter-particle friction and cohesion of backfill soil are considered.
► The model's predictions are verified against 6 prominent existing analytical models.
► Soil cohesion drastically decreases the resultant active earth-pressure force.
► Soil cohesion considerably increases the resultant passive earth-pressure force.