Seismic Slope Stability Analysis of a Hydraulic Fill Dam

Abstract

This paper presents a seismic slope stability assessment study of an inherently heterogeneous hydraulic fill dam in Texas. Extensive cone penetration soundings conducted at the dam site were interpreted to estimate different dam material properties. Eight sections distributed along the length of the dam were considered for the slope stability assessment to incorporate the effect of variations in material properties on the hydraulic fill dam. The conventional pseudostatic analysis method was modified to account for the differences in the behavior of the dam materials during static and seismic loading conditions. The current state of practice considers the same critical slip surface for both static and pseudostatic analyses. A modified pseudostatic slope stability analysis was performed to identify other possible critical slip surfaces with lower factors of safety values than the critical slip surface obtained from the static stability analysis. A reliability-based approach was then adopted to incorporate the effect of uncertainty on the estimation of shear-strength parameters of the dam materials, and the expected performance during different seismic events was evaluated. Two hypothetical earthquake events were also considered for the postearthquake deformation and serviceability assessment studies. The approach adopted in this research study facilitates identifying the critical sections of a dam that the conventional analysis method may not consider. Hence, this new approach would be integral toward developing guidelines for evaluating the seismic resilience of earthen dams.