External stability of reinforced soil walls under seismic conditions

Determination of the external stability of reinforced soil walls under earthquake condition is an important topic of research for geotechnical engineers. In the present paper, a pseudo-dynamic method, which considers the effect of phase difference in both the shear and primary waves travelling through the backfill due to seismic excitation, is considered to obtain the minimum length of the geosynthetic reinforcement to resist direct sliding and overturning failure of the reinforced soil wall. A two-part wedge mechanism is used for determining the external stability of the reinforced soil wall against direct sliding. Reinforced soil walls with cohesionless backfill soil are considered in the present analysis. Results are presented in both graphical and tabular form to show the required length of the geosynthetic reinforcement to maintain the external stability of the reinforced soil wall under seismic conditions. The effects of variation of parameters such as soil friction angle, horizontal and vertical seismic accelerations on the external stability of the reinforced soil wall have been studied. With increase of seismic accelerations in both the horizontal and vertical directions, the external stability of the reinforced soil wall decreases significantly and a greater length of geosynthetic reinforcement is needed to maintain the external stability of the wall. For most practical cases, the minimum length required to resist direct sliding failure is found to govern the design rather than overturning failure under seismic conditions. Comparisons of the present results with available pseudo-static results found in the literature are shown, and the improvements using the proposed pseudo-dynamic approach are highlighted.