Effect of geomaterial variability on seismic response analyses of earthen dams

Abstract

In a recently completed research study, two-dimensional (2D) and three-dimensional (3D) seismic response analyses were performed on a hydraulic fill earthen dam located in north Texas, USA. Analysis results obtained from both methods were compared to study and address the influence of geomaterial variability on the seismic response of heterogeneous earthen dams such as hydraulic fill dams. For evaluating the material variability within the dam, twenty-eight piezocone penetration soundings (CPTu) were conducted along the crest of the dam. These CPTu soundings, along with the available laboratory test results, were utilized to represent various scenarios that depict geomaterial variability within the dam for numerical modeling and seismic response analysis. In the first scenario, limited subsurface investigation information obtained from six CPTu soundings distributed along the dam crest was considered to develop the numerical models. In the second scenario, all the twenty-eight CPTu soundings were utilized to model the same dam using extensive site characterization test results. The first natural frequency, earthquake-induced crest accelerations, and shear stresses of the dam segments were computed from 2D and 3D numerical analyses for both scenarios of site characterization results. Results indicated that a 3D analysis might be more appropriate than a 2D analysis for studying the seismic response of a heterogeneous earthen dam, especially when extensive site characterization information is available to model the dam for numerical analyses. Overall, the findings of this study emphasize the impact of geomaterial variability on seismic response analyses of heterogeneous earthen dams and will enable engineers to assess the conditions that warrant a comprehensive 3D analysis.