Stability assessment of an earth dam on silt/clay tailings foundation: A case study

This case study describes the design, and construction of an earth dam built on recently sedimented tailings consisting of low strength, low plasticity silt/clay, and variably silty sand. The tailings were encountered within the construction limits of Cell 7 at the 4 km2 Loxahatchee (L-8) Reservoir in western Palm Beach County, Florida. Fully coupled steady state and transient seepage models with slope stability analyses were performed for operational and rapid drawdown conditions, respectively, using both limit equilibrium methods (LEM) and finite element stress-based modeling (FESBM) techniques. In addition, stability calculations utilizing fully coupled stress/pore pressure analysis were performed to analyze rapid drawdown stability during drawdown.

► This case study describes the design of an earth dam built on tailings. ► LEM performed equally as well as FESBM based models. ► Regardless of the type of stability analysis, rapid drawdown governs the design. ► Analyses using DSS test results for tailings indicated unacceptably low FOS values.