Influence of Surcharge and Foundation Soil on the Seismic Stability of Helical Soil-Nail Walls

This study proposes a closed-form solution to estimate the seismic factor of safety of helical soil–nail walls subjected to uniform surcharge. Unlike the existing solutions, the proposed method considers an underlying layer of foundation soil. The backfill and the foundation soil are modelled as a viscoelastic material which enables to incorporate effect of material damping. The study investigates how the amplification of seismic waves in both the foundation and backfill soil influences the stability of the wall. The study also explores the impact of impedance ratio on wall stability as seismic waves propagate through the interface between the foundation soil and backfill. The impact of surcharge magnitude, foundation soil properties, base excitation frequency, and the diameter and spacing of helix in soil nail on the seismic factor of safety are also discussed. It is observed that the helical soil nails provide an enhanced stability to the vertical cuts compared to the conventional soil nails.