Micromechanical Modeling of the Seismic Response of Gravity Retaining Walls

Abstract

In this study, the analysis of the seismic response of a soil-retaining wall system is performed based on a three-dimensional microscale framework utilizing the discrete element method (DEM). The proposed method is employed to investigate the seismic response of gravity-type retaining walls with three degrees of freedom. In the simulation, the granular soil deposit is idealized as a collection of spherical soil particles; the retaining wall is simulated as a rigid block composed of clumped particles to yield the physical characteristics of a real-life retaining wall. The model is processed under the gravitational acceleration of 50 g to reduce the total duration of the simulation and dimensions of the model.

The model accounts for the effects of nonlinear soil behavior and possible separation between the retaining wall and soil deposit. The impact of amplitude and frequency of input dynamic excitation on the response of the wall was analyzed under different conditions. The computational approach is able to capture essential dynamic response patterns such as the effect of resonance on amplifying the response and the failure of the wall as it underwent excessive rotation and displacement due to increased earth pressure and inertia forces. In addition, time histories of the resultant lateral thrust on the wall show that its magnitude varies as the wall moves relative to the backfill and its location changes as well. The shape of the failure wedge was also captured from analysis of maximum shear strains developed in the backfill. Under strong ground motion, wall failure was associated with seismic bearing capacity failure near the wall toe due to increased wall pressure.