Seismic Earth Pressures behind Retaining Walls: Effects of Rigid-Body Motions

Abstract

The seismic earth pressures behind a retaining wall that bends, rotates about its base, and translates horizontally and vertically are evaluated numerically using an ideally elastic model. The following factors are analyzed: (1) flexural movements of the wall; (2) rotation of the wall at its base; and (3) horizontal and vertical movements of the wall. The following results are obtained: (1) the flexural flexibility of the wall, the horizontal translation, and the rotation at the base have significant effects on the earth pressures behind the wall; and (2) within the range of relative flexibilities of typical retaining walls (relative between wall and backfill), the effects of the horizontal translation are more significant than those of the vertical translation and rotation. Four extreme cases are also analyzed: rigid wall with stiff foundation, rigid wall with soft foundation, flexible wall with stiff foundation, and flexible wall with soft foundation. The seismic pressures behind a rigid wall with a stiff foundation are the largest, and they are the smallest for a flexible wall with a soft foundation. The pressures behind a rigid wall with a soft foundation are affected the most by the horizontal translation of the wall, while the pressures behind a flexible wall with a soft foundation are affected both by the flexural flexibility of the wall and by the horizontal movements.