One- and two-dimensional seismic analysis of solid-waste landfills

The results from one-dimensional (1D) and two-dimensional (2D) dynamic response analyses are compared to determine the reliability of the common practice of using 1D analysis to evaluate the seismic response of solid-waste landfills. Results indicate that 1D analysis generally provides a reasonably conservative estimate of the seismic loading and earthquake-induced permanent displacement for deep sliding surfaces, such as along the base liner. However, caution is warranted for shallower sliding surfaces, where 2D topographic amplification often results in larger values of seismic loading and permanent displacement than that predicted by 1D analysis. The 1D–2D analysis comparison is not just a function of geometry, but is also dependent on the different numerical formulations typically employed in each procedure (e.g., 1D wave propagation versus 2D finite element). Comparisons of accelerations along the landfill surface indicate that 1D analysis consistently under predicts the maximum horizontal acceleration (MHA) along the slope near the crest of the landfill. However, the seismic loading is shown to vary systematically with normalized cover slope length, with the maximum equivalent acceleration for the full cover slope being about 40% of the peak acceleration at the crest. Based on the results of this study, a simplified procedure is proposed for scaling 1D results to account for 2D topographic amplification and cover slope averaging when evaluating the seismic performance of landfill cover systems.