Prediction of Seismic Active Earth Pressure Using Curved Failure Surface with Localized Strain

Problem statement: Correct evaluation of the earth pressure against retaining structure during earthquake is essential for the safe and economic design of geotechnical structures. Progressive deformation in the backfill and the assumed shape of failure wedge affect the calculated values of seismic earth pressures. However, no research until now is available that considers both of these two factors in an analysis. Approach: In this study, a new analytical methodology was proposed that took into the account the progressive failure of the backfill soil as well as the shape of the failure wedge. A new formulation was first established taking the failure plane as the combination of a curved lower part and a straight upper part. The localized deformation of the backfill was accounted for in the formulation by utilizing the mobilized friction angle and the peak friction angle depending on the locations along the failure surface. The proposed methodology was validated by comparing the calculated results with the established experimental results. Calculations were also performed for different types of wall with various backfill inclinations. Results: The developed methodology could predict the seismic active earth pressure against retaining structure with reasonable accuracy. It could also realistically predict the active failure domain in the backfill soil at the high excitation level, as compared to the pseudo-static solution provided by the well-known Mononobe-Okabe method. Conclusion/Recommendations: It was observed that the Mononobe-Okabe method underestimates the seismic active earth pressure and overestimates the domain of failure zone in the backfill, especially under intense seismic excitation. The proposed methodology, therefore, can contribute greatly towards the economic earthquake resistant design of geotechnical structures.