Back Analysis of Mount Polley Tailing Dam Failure

The motivation of this research was to verify the findings of Independent Review Panel for the failed perimeter embankment at Mount Polley Tailings Storage Facility. The finite element analysis conducted in industry standard geotechnical softwares indeed confirmed that the foundation of the perimeter embankment would have failed along the weak GLU layer because of excessive shear deformation in the layer. Additionally, the finite element models also highlighted the importance of choosing correct relative stiffness values for various foundation layers for a realistic development of failure mechanisms for stability analyses done using the Strength Reduction technique. This observation is novel and is of considerable practical significance because designers pay little attention to obtaining stiffness parameters for foundation soils and focus more on obtaining realistic shear-strength parameters. A numerical parametric study conducted to investigate potential ways of preventing failure of the perimeter embankment revealed downstream slope flattening to be the most effective solution.