Recent failures of upstream-raised tailings storage facilities (TSF) have raised concerns on the stability of these dams, which relies on the strength of tailings, which are loose and normally consolidated rock flour that may exhibit a collapsible structure inducing strong strain-softening in undrained loading.
Standard practice to evaluate global stability of TSFs entails the use of limit equilibrium analyses, which consider either peak or residual undrained shear strength. These procedures do not consider the work input required to drive the softening process that leads to progressive failure, and therefore there is room for numerical deformation models to provide further insight of the liquefaction process.
This presentation describes recent applications of such analyses employing the Hardening Soil Model with Small Strain (HS-Small or HSS) to evaluate triggering of static liquefaction of upstream-raised TSFs. The calibration methodology captures the complete stress path of the softening behavior. The importance of the stiffness parameters that control both the rate of elastic and plastic volumetric strains is disccused.
Focus is placed on the parameters of the non-linear solver and their numerical implications. As an example, a TSF is modelled in PLAXIS 2D® to evaluate its vulnerability to static liquefaction due to an undrained lateral spreading at the foundation. It is shown that this procedure is useful to verify the robustness of the TSF design.
