Numerical Evaluation of Static Liquefaction–Induced Flowslide Causing the Edenville Dam Failure, Michigan

Abstract

This paper re-evaluates the Edenville earth dam that failed in 2020 after a rapid rise in reservoir level caused by prolonged significant rainfall. The dam instability and possibility of static liquefaction–induced flow failure are assessed in the framework of critical state soil mechanics (CSSM). Both undrained loading and drained unloading stress paths are considered for flow liquefaction assessment. Using documented triaxial compression tests, the Norsand constitutive model is calibrated for finite-element numerical models. This study supplements the analyses conducted by an independent forensic team (IFT) in charge of failure investigation. The advances achieved by tailings dam practitioners are leveraged here to study flow liquefaction as recommended by the IFT. Multiple ways are employed to generate reasonable initial field stresses. Simulation of dam construction coupled with steady-state seepage analysis creates an appropriate starting condition for further flow liquefaction assessment. The numerical outputs confirm the result of the IFT’s limit equilibrium analyses for an undrained boundary condition. Stress analyses with a drained boundary condition show that a major stress change with a constant-shear-drained (CSD) stress path develops below the dam crest due to a rising reservoir level. The results of our models with a CSD stress path and drained-to-undrained transition better explain the evolution of the Edenville dam failure. The current study provides a practical approach to earth dam design and evaluation.