Effect of site condition below slip surface on prediction of equivalent seismic loading parameters and sliding displacement

摘要

The effect of seismic site response below the slip surface is commonly ignored in conventional predictive models of sliding displacement of slopes. In this study, the influence of site condition below the critical slip surface (i.e., the bedrock depth below slip surface) on the dynamic response of sliding mass and the seismic sliding displacement is investigated. The equivalent seismic loading time history which represents the average acceleration within the sliding mass is derived for sliding masses with different site conditions (i.e., various depths to the overlying bedrock). The frequency-dependent effects of bedrock depth are emphasized for accurate assessment of the stability of slopes during earthquakes. For the same sliding mass, the equivalent seismic loading parameters and sliding displacements are strongly dependent on the depth to the underlying bedrock. Empirical models are developed for predicting the amplitude and frequency parameters of equivalent seismic loading by introducing the ratio of the depth of sliding mass and bedrock to capture the seismic responses of the sliding mass as well as the full slope site. The performance of existing empirical models for rigid block sliding displacement is examined and simplified modifications are performed to appropriately predict the sliding displacement by including the dynamic response of sites. Two example applications are presented, and the results indicate that the proposed empirical models including the site condition below the slip surface provide a more accurate assessment of dynamic response and sliding displacement of slopes.