Modified Pseudo-dynamic Method for Seismic Passive Earth Thrust of Submerged Backfill

Abstract

The accurate assessment of seismic earth pressure acting on a retaining wall is an important problem in earthquake geotechnical engineering. The existing calculations of pseudo-dynamic method mainly focus on the dry soil condition. To investigate the seismic passive earth thrust of submerged backfill, a general modified pseudo-dynamic method is established based on the limit equilibrium analysis. The derivation aims at a vertical gravity wall with a planar rupture surface retaining a horizontal, cohesionless and fully submerged backfill. Meanwhile the method assumes that the amplitude of the seismic acceleration increases linearly along the wall and the backfill is divided into two extreme cases of free water and restrained water conditions according to the permeability difference. Through the comparison with the previous work, the trend of seismic passive earth thrust for submerged backfill is basically consistent with that of the dry soil, but the submerged condition has a reducing effect on the passive earth thrust. Then a parametric study is carried out to investigate the influences of soil friction angle, wall friction angle, horizontal seismic action and vertical seismic action on the intensity distribution of seismic passive earth pressure. The results indicate that the passive earth pressure increases with the increase of soil friction angle and wall friction angle, but the impact of soil friction angle is more significant. The horizontal seismic acceleration is still the determining factor affecting the magnitude and distribution of the passive earth pressure rather than the vertical one.