Quasi-1D Deformation Modelling of a TSF under Undrained Loading

Abstract

The assessment of tailings static liquefaction has become a key topic in recent years. The stability of upstream-raised tailings dams relies on the strength of tailings, which are loose and normally consolidated materials that may exhibit strain-softening during undrained loading. Limit equilibrium analyses do not consider the work input required to drive the softening process that leads to progressive failure, and therefore require that only fully softened strength be considered in the analyses. On the other hand, FEM analysis can capture the complete stress path of the softening behavior, but may lead to geometrically complex and computationally expensive models. This paper describes a simplified procedure to analyze the stability of tailings storage facilities employing a quasi-1D soil column using the constitutive model NorSand. A fully automated script was developed to produce meshes of various heights and characteristics, to reproduce the entire deposition sequence, and to perform push over analyses. The proposed strategy reproduces the main features of tailings behavior along the relevant stress path, estimates the brittleness of tailings at various depths, and produce an assessment of the risk of static liquefaction. It is shown that this procedure is useful to verify the stability of the TSF at screening level, and to provide guidance in the optimization of the dam design.