DEM Analysis and Simplified Calculation of Passive Earth Pressure on Retaining Walls Backfilled with Sand Considering Strain-Softening Behavior

Abstract

Common calculation methods of passive earth pressure, such as the Rankine or Coulomb earth pressure theory, assume that the width of the fill behind the wall is sufficient for the development of the slip surface and that after the passive earth pressure reaches the limit state, its value remains unchanged with the increase of displacement of the retaining wall. Nevertheless, cases with narrow backfill width should be considered when retaining walls must be built close to existing stabilization walls in urban areas or near rock faces in mountainous areas. Furthermore, for sand, especially dense sand, when the displacement of the retaining wall is large, a strain-softening behavior similar to the triaxial test will appear, resulting in a decrease in passive earth pressure. In this regard, a practical model for strain-softening of dense sand is proposed firstly and verified by the discrete element method (DEM) using the Particle Flow Code (PFC-2D) software. Then, based on the sliding surface shape obtained by DEM, a simplified method for determining the passive earth pressure distribution of retaining walls using limit equilibrium analysis was proposed. Finally, the passive earth pressures calculated by the proposed method agree well with those from PFC results, and the effects of the width of the backfill and displacement of retaining wall on the distribution of active earth pressure were discussed.