Pseudo-dynamic approach for active thrust of submerged soils

The proper calculation of dynamic thrust is a key issue in the design of rigid retaining walls in seismically active zones. Although the Mononobe-Okabe approach is widely used in practical applications, the pseudo-dynamic approach has been introduced in recent years, and provides a more realistic representation of an earthquake compared to the pseudo-static approach. Whereas studies in the past have focused on dry backfills, to the authors' knowledge there is no specific literature dedicated to pseudo-dynamic analysis for submerged soils; in certain studies dealing with waterfront areas, the pseudo-dynamic analysis - valid for dry soils - has been incorrectly extended to submerged backfills as well. In this paper, a more rational pseudo-dynamic approach is developed for fully submerged soil under the assumption that a restrained or free water condition exists within the backfill. The results obtained demonstrate that the proposed analysis is perfectly consistent with the widely used pseudo-static approach. The analysis is also extended to account for amplification phenomena. Within a range of practical interest of soil and seismic input parameters, the acting point of the seismic active thrust is found to be very close to a height of H/3 from the base of the wall.