Seismic Stability of Seawalls under Earthquake and Tsunami Forces Using a Modified Pseudodynamic Method

Abstract

The 211 Tohoku earthquake demonstrates the significance of seismic aftershocks to examine in the design of marine structures. The seawalls in seismic zones are prone to the joint action of tsunami wave forces and earthquake aftershocks. The existing pseudodynamic method for submerged soils that is used for the determination of inertia forces due to earthquake had the limitations of the violation of boundary condition at the ground surface and assumption of linear amplification in the submerged backfill. All the existing studies on the compound influence of tsunami and earthquake forces on seawalls considered the simple planar failure surface in the submerged backfill for the computation of seismic passive resistance. In the present study, a modified pseudodynamic approach that beats these limitations is used, and the stability of seawall in passive condition under the compound action of the tsunami and seismic aftershocks is evaluated. It has been noticed from the parametric investigation that for sliding stability, the factor of safety reduces from 17.11 to 1.33, with an increase in the ratio of tsunami wave height to the water depth in front of the wall from (i.e., no tsunami) to 1.5. The present study might be helpful for revising design guidelines considering the joint action of tsunami and earthquake on the stability of seawalls.