Prof Ross W. Boulanger PhD, PE, NAE
Professor and Director, Center for Geotechnical Modeling. University of California at Davis, U.S.A.
Professor Ross W. Boulanger is the Director of the Center for Geotechnical Modeling in the Department of Civil and Environmental Engineering at the University of California, Davis. He received his PhD and MS degrees in Civil Engineering from the University of California at Berkeley, and his BASc degree in Civil Engineering from the University of British Columbia. His research and professional practice are primarily related to liquefaction and its remediation, seismic performance of dams and levees, and seismic soil-pile-structure interaction.
Over the past 25 years, he has produced over 250 publications and served as a technical specialist on over 50 seismic remediation and dam safety projects. His honors include the TK Hsieh Award from the Institution of Civil Engineers, the Ralph B. Peck Award, Norman Medal, Walter L. Huber Civil Engineering Research Prize, and Arthur Casagrande Professional Development Award from the American Society of Civil Engineers (ASCE), and election to the US National Academy of Engineering.
Evaluating Seismic Deformation of Levees Over Soft Clay
Ross W. Boulanger, PhD, PE, Professor, University of California at Davis, Davis, California, USA
Tyler J. Oathes, Graduate Student Researcher, University of California at Davis, Davis, California, USA
Steven Friesen, PE, Water Resources Engineer, California Department of Water Resources, Sacramento, California, USA
Michael W. Driller, PE, Senior Engineer, California Department of Water Resources, Sacramento, California, USA
Evaluating the seismic deformation of levees in California’s Sacramento-San Joaquin Delta requires accounting for a wide range of soil types, including liquefiable sands and silts, soft organics and peats, and soft clays. In some situations, the potential for earthquake-induced strength loss in soft clays of medium or greater sensitivity can be a significant concern and source of uncertainty. This paper describes results of nonlinear dynamic analyses (NDAs) to evaluate how strain-softening, localizations, and strength loss in soft clay of varying sensitivity can affect seismic deformation of a levee. The PM4Silt constitutive model, developed for representing clays and plastic silts in earthquake engineering applications, and its calibration in practice are described. The NDAs examine the effects of levee height, clay layer thickness, clay sensitivity, and input motion characteristics. The analysis results show that strain softening and associated strength loss in the clay layer increased with increasing clay sensitivity but did not necessarily result in increased levee deformations for the conditions examined. Instead, increasing clay sensitivity sometimes reduced levee deformations because strength loss in the clay also caused a reduction in the accelerations that developed at the levee level. The factors influencing the effect of clay sensitivity on seismic deformations, and the implications of these findings for practice, are discussed.