Seismic Bearing Capacity of Foundation on Cohesionless Soil

The seismic bearing capacity of a strip-surface foundation resting on a Mohr-Coulomb material is evaluated. The upper-bound theorem of the yield design theory is used to obtain an estimate of the ultimate load. The loading parameters consist of a normal and tangential force applied to the foundation and of inertia forces developed within the soil volume. The classical Prandtl-like mechanism is used to show that the reduction in the bearing capacity is mainly caused by the load inclination; the consideration of inertia forces within the soil is only responsible for a decrease in the bearing capacity that is at least an order of magnitude smaller than the one caused by the load inclination. It is therefore concluded that, from a practical engineering standpoint, the soil-inertia forces can be neglected.