CS3C - Concurrent Session 03C: Numerical Modeling and Remediation Design of a Hydraulic Fill Embankment with Liquefiable Foundation Under Extreme Seismic Loading

Reclamation studied options for the improvement of a legacy dam in Washington with a hydraulic fill core and thick deposits of soft liquefiable sediments in the foundation. Deformations driven by seismic strength loss dominate the risk at this facility. To evaluate potential remediation options, Reclamation used finite difference numerical modeling (FLAC2D) to investigate various options to increase the stability of this structure during seismic loading. Numerous modeling challenges were encountered including unusual bedrock geometry, extreme deformations impacting boundary conditions, and the frequent need for model rezoning. Reclamation overcame these challenges and successfully identified two remediation alternatives, deep soil mixing (DSM) and installation of a new toe shear key. A field test section for the deep soil mixing alternative was successfully implemented.